Roller for image forming apparatus and method of manufacturing same
An image forming apparatus has a plurality of image bearing bodies in a predetermined sequence, an intermediate transfer medium for running in contact with each of the plurality of image bearing bodies, and a plurality of supporting rollers for driving the intermediate transfer medium. The rollers are manufactured such that a driven coupler is engaged with the roller body in a predetermined orientation with a location of a radius deviation along the circumference of the roller body.
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This application claims the benefit of Korean Patent Application No. 2004-48837 filed Jun. 28, 2004, and Korean Patent Application No. 2005-43735 filed May 24, 2005, in the Korean Intellectual Property Office, the disclosures of which are hereby incorporated by reference. This application is related to U.S. Patent Applications titled “Image Forming Apparatus Having Reduced Image Errors From Driving Unit and Method of Manufacturing Same,” “Image Forming Apparatus Having Reduced Image Errors From Image Bearing Bodies and Method of Manufacturing Same,” and “Image Forming Apparatus Adapted to Overlap Image Errors From Driving Unit and Image Bearing Bodies and Method of Manufacturing Same,” each filed on even date herewith.
BACKGROUND OF THE INVENTION1. Field of the Invention:
The present invention relates to a driving unit for an image forming apparatus, a color image forming apparatus having the same, and a method of manufacturing an image forming apparatus having the driving unit.
2. Description of the Related Art:
Generally, image forming apparatuses are classified into a monochromatic image forming apparatus and a color image forming apparatus. The monochromatic image forming apparatus forms an image in black and white by using only one color developer, while the color image forming apparatus forms a colorful image by using color developers such as magenta, cyan, yellow, and black.
An electrophotographic image forming apparatus forms an electrostatic latent image by scanning a laser beam onto an organic photoconductor (OPC), which is electrified by an electrifying unit to have a predetermined level of electric potential, using a light exposing unit. The electrostatic latent image is developed using a developer and then transferred into a visible image on supplied print paper. In a color image forming apparatus, the electrostatic latent image is developed by using color developers on the organic photoconductors and overlapped images are transferred onto an intermediate transfer medium, such as an Intermediate Transfer Belt (ITB). The color images overlapped on the intermediate transfer medium are transferred onto print paper. Subsequently, the print paper with a color image goes through a series of fixing processes before it is transferred out of the image forming apparatus.
Developers each corresponding to K (black), C (cyan), M (magenta), and Y (yellow) are attached to the electrostatic latent image area of each of the organic photoconductors 16, 17, 18 and 19. The T1 rollers 12, 13, 14 and 15 are set up to correspond to the organic photoconductors 16, 17, 18 and 19 with the belt 10 between the organic photoconductors 16, 17, 18 and 19 and the T1 rollers 12, 13, 14 and 15. Accordingly, the developers attached to the surfaces of the organic photoconductor 16, 17, 18 and 19 are primarily transferred to the surface of the belt 10 by the transferring activity of the T1 rollers 12, 13, 14 and 15. Herein, the respective color images of the organic photoconductors 16, 17, 18 and 19 are transferred onto the belt 10 at predetermined time intervals so that the color developers transferred to the belt 10 can be overlapped in registration into a complete color image. Therefore, the color developers are overlapped on the belt 10 to thereby form a complete color image. Subsequently, the color image on the belt 10 goes through a secondary transferring process between the T2 roller 20 and the belt driving roller 21. Also, the belt driving roller 21 runs the belt 10 at a proper rate.
The belt 10 and the organic photoconductors 16, 17, 18 and 19 are consumption goods with limited life spans, that must periodically be replaced.
A transferring unit including the belt 10 and developing units including each organic photoconductor 16, 17, 18 or 19 are typically set up in a detachable manner along with a predetermined coupling unit and the driving unit for providing power in the image forming apparatus.
When the consumption goods, that is, the transferring unit and the developing units, are replaced, the structure of the coupling unit for performing relative motion of the driving unit, the transferring unit, and the developing units is significant. That is, it is important to connect the transferring unit and the developing units to have the same rotational axis as the driving unit. It is also important to realize highly precise color registration in consideration of the so-called total runout between the transferring unit and the developing unit. This is particularly important in view of manufacturing tolerances in the external circumferential surface of the driving roller of the transferring unit.
Herein, the total runout can be understood to include a phenomenon that the belt 10 rotates at a predetermined rate, but small changes in the instantaneous rotation rate occur due to the manufacturing tolerance of the external circumferential surface of the driving roller. The total runout affects the developing units in the same period through the belt 10. Therefore, it is important to equalize the influence of the total runout on the developing units and improve the quality of a color image.
Additionally, the organic photoconductors and the driving roller may have deviations in their radii if the outer circumferences thereof do not make a perfect circle due to manufacturing tolerances. Such deviations result in errors of a composite color image on the belt as the color image partially stretches or cuts due to the aforementioned deviations in the OPC rollers and the driving roller.
SUMMARY OF THE INVENTIONIt is, therefore, an object of the present invention to provide a roller which enables controlling the orientation of a predetermined radial displacement.
It is another object of the present invention to provide a method of manufacturing a roller which enables controlling the orientation of a predetermined radial displacement.
It is another object of the present invention to provide an improved driving unit of an image forming apparatus which enables minimizing an image error caused due to radial errors in rollers supporting the belt.
It is another object of the present invention to provide an improved image forming apparatus which enables minimizing an image error caused due to a plurality of image bearing bodies.
It is another object of the present invention to provide an improved image forming apparatus which enables minimizing an image error caused due to a plurality of image bearing bodies and belt supporting rollers.
The above aspects and other features of the present invention can substantially be achieved by providing a roller including a roller body having a radial displacement along the direction of its circumference; and a driven coupler engaged with one end of the roller body, for complimentary mating with a driving coupler for driving a driving force. The roller body has a mark formed on a predetermined position for indication of radial displacement.
The driven coupler includes a positioning part for determining a position of engaging with the driving coupler. The roller body is engaged with the driven coupler such that the positioning part maintains a predetermined angle with respect to the mark.
The mark is preferably provided at a predetermined angle with respect to a maximum radial displacement location of the roller body.
According to one aspect of the present invention, an image bearing body for use in an image forming apparatus includes a drum body having a radial displacement along the direction of its circumference; and a driven coupler engaged with one end of the roller body, for complimentary mating with a driving coupler for driving a driving force. The drum body preferably has a mark formed on a predetermined position for indication of the location of maximum radial displacement.
The mark is preferably provided at a predetermined location with respect to a maximum radial displacement location.
The driven coupler preferably includes a positioning part for determining a position of engaging with the driving coupler. The driven coupler may be engaged with the drum body such that the positioning part maintains a predetermined angle with respect to the mark.
The driven coupler preferably includes a non-circular coupling part formed at one end either in concave or convex fashion to receive a driving force in an engagement with the driven coupler. The positioning part may be extended from the coupling part in the direction of the radius of the driven coupler.
According to another aspect of the present invention, a method of manufacturing a roller including a roller body having a radial displacement along the direction of its circumference, and a driven coupler engaged with one end of the roller body, is provided. The method may include the steps of identifying a location of radial displacement of the roller body; and setting the position of the driven coupler with respect to the identified location and engaging the driven coupler with the roller body in said position.
The step of finding the location having a radial displacement preferably includes the steps of finding a point of maximum radial displacement by measuring an end of the roller body; and forming a mark on the roller body for indication of the found point of maximum radial displacement.
The step of engaging the driven coupler preferably includes assembling the driven coupler with the roller body in a manner such that a positioning part of the driven coupler maintains a predetermined angle with respect to the point of maximum radial displacement and that the relative positions of engaging the driven coupler and the driving coupler are determined.
The step of engaging the driven coupler preferably includes the steps of supporting the roller body on a first jig such that the point of maximum radial displacement is positioned at a predetermined angle with respect to a reference coordinate axis; supporting the driven coupler on a second jig such that the driven coupler is positioned at a predetermined angle with respect to the reference coordinate axis; and moving the first and the second jigs relative to each other and thereby engaging the driven coupler with the roller body.
According to yet another aspect of the present invention, a driving unit of an image forming apparatus may include a driving gear for driving a plurality of image bearing bodies which are arranged in a predetermined sequence, and a driving gear for driving a plurality of supporting rollers which support a belt running on the plurality of image bearing bodies. A distance between centers of rotation of at least two of the plurality of driving gears is preferably a positive integral multiple of the length of circumference of one of the supporting rollers.
Each of the distances between the centers of rotation of the plurality of driving gears is preferably a positive integral multiple of the length of the circumference of at least one of the supporting rollers.
One of the supporting rollers may be a driving roller which receives a driving force in engagement with the driving gear.
One of the supporting rollers may be a roller having a radial displacement.
The driving gear preferably includes first through fourth driving gears in a predetermined sequence with respect to the direction of belt running, which satisfy at least one of the following equations:
[Equation Set 1]
L1=l·Sd·(1±0.05)(l=1, 2, 3, . . . ) (1)
L2=m·Sd·(1±0.05)(m=1, 2, 3, . . . ) (2)
L3=n·Sd·(1±0.05)(n=1, 2, 3, . . . ) (3)
L4=o·Sd·(1±0.05)(o=1, 2, 3, . . . ) (4)
L5=p·Sd·(1±0.05)(p=1, 2, 3, . . . ) (5)
L6=q·Sd·(1±0.05)(q=1, 2, 3, . . . ) (6)
-
- where L1 is the distance between the centers of first and second driving gears,
- L2 is the distance between the centers of second and third driving gears,
- L3 is the distance between the centers of third and fourth driving gears,
- L4 is the distance between the centers of first and third driving gears,
- L5 is the distance between the centers of first and fourth driving gears,
- L6 is the distance between the centers of second and fourth driving gears, and
- Sd is the length of the circumference of the one of the supporting rollers.
The driving gears are preferably mounted to satisfy all of the equations in Equation Set 1.
The driving gears are preferably mounted to satisfy L1=L2=L3.
The driving gears are preferably mounted to satisfy L1=L2=L3, and L1, L2, and L3 are positive integer multiples of Sd.
The radius of the supporting rollers is preferably equal to the radius of the image bearing bodies.
A plurality of driving couplers are preferably provided to a center of rotation of each of the plurality of driving gears, to transmit a driving force in engagement with each of the plurality of image bearing bodies.
The driving coupler may include a coupling part configured to have a non-circular section corresponding to each of the driven couplers provided to an end of each image bearing body; and a positioning part provided to a side of the coupling part to determine a position of engagement such that the driving coupler engages with the driven coupler at a fixed posture.
The coupling part may be a coupling recess sunken into an end of the coupling part in a non-circular shape, and the positioning part may be a recess sunken into an inner side of the coupling part to a predetermined depth.
The driven coupler may include a shaft protruding from an end toward the center of rotation, and a shaft hole at a bottom of the coupling recess for engagement with the shaft.
The coupling part may be a coupling protrusion extending from an end in a non-circular shape, and the positioning part may be a protrusion extending from an outer portion of the coupling protrusion.
According to yet another aspect of the present invention, an image forming apparatus preferably includes a plurality of image bearing bodies arranged in a predetermined sequence; an intermediate transfer medium running in contact with each of the plurality of image bearing bodies; and a plurality of supporting rollers for driving the intermediate transfer medium. A distance between centers of rotation of at least two image bearing bodies is a positive integral multiple of the length of the circumference of at least one of the supporting rollers.
The image bearing bodies preferably include first to fourth image bearing bodies which are arranged in a predetermined sequence with reference to the direction in which the intermediate transfer medium runs, and the first to fourth image bearing bodies preferably satisfy at least one of the following equations:
[Equation Set 1]
L1=l·Sd·(1±0.05)(l=1, 2, 3, . . . ) (1)
L2=m·Sd·(1±0.05)(m=1, 2, 3, . . . ) (2)
L3=n·Sd·(1±0.05)(n=1, 2, 3, . . . ) (3)
L4=o·Sd·(1±0.05)(o=1, 2, 3, . . . ) (4)
L5=p·Sd·(1±0.05)(p=1, 2, 3, . . . ) (5)
L6=q·Sd·(1±0.05)(q=1, 2, 3, . . . ) (6)
-
- where L1 is the distance between the centers of first and second driving gears,
- L2 is the distance between the centers of second and third driving gears,
- L3 is the distance between the centers of third and fourth driving gears,
- L4 is the distance between the centers of first and third driving gears,
- L5 is the distance between the centers of first and fourth driving gears,
- L6 is the distance between the centers of second and fourth driving gears, and
- Sd is the length of circumference of the one of the supporting rollers.
The image bearing bodies are preferably mounted to satisfy all of the equations in Equation Set 1.
The image bearing bodies are preferably mounted to satisfy L1=L2=L3.
The image bearing bodies are preferably mounted to satisfy L1=L2=L3, and L1, L2 and L3 are positive integer multiples of Sd.
The plurality of supporting rollers preferably include a driving roller for driving the intermediate transfer medium while being rotated with a driving force transmitted thereto, and an idle roller being passive-rotated while supporting the intermediate transfer medium. Sd defines the length of circumference of a supporting roller.
A driving unit is preferably provided for driving the image bearing bodies and the supporting rollers.
The driving unit preferably includes a first driving unit for driving the plurality of image bearing bodies at the same time; and a second driving unit for driving one of the plurality of supporting rollers independently.
The first driving unit preferably includes a plurality of driving gears provided to correspond to each of the plurality of image bearing bodies, and rotated in association with each other; and a first driving motor for providing a driving force to drive the plurality of driving gears at the same time.
The second driving unit preferably includes a second driving motor; and one driving gear engaged with one of the supporting rollers, and driven by the second driving motor.
Each of the driving gears and each of the image bearing bodies preferably include at their corresponding ends, a driving coupler and a driven coupler for complimentary mating with the driving coupler.
The driving and the driven couplers preferably include coupling parts at their ends provided in a non-circular section and complimentarily mated with each other; and positioning parts extended from a side of each of the coupling parts to a predetermined configuration to determine a posture of engagement of the driving and driven couplers.
The image bearing bodies have a radial displacement in which the radius of the image bearing body varies, and also have intervals A1, A2, A3 and A4 having a predetermined location of maximum radial displacement, and the first to fourth image bearing bodies may be mounted to satisfy one of the following equations:
[Equation Set 2]
{2π·l+(α2−α1)}·Ro·(1±0.05)=L1, (l=0, 1, 2, . . . ), (Ro=Ro1=Ro2) {circle around (1)}
{2π·m+(α3−α1)}·Ro·(1±0.05)=L1+L2, (m=0, 1, 2, . . . ), (Ro=Ro1=Ro3) {circle around (2)}
{2π·n+(α4−α1)}·Ro·(1±0.05)=L1+L2+L3, (n=0, 1, 2, . . . ), (Ro=Ro1=Ro4) {circle around (3)}
-
- where α1 is the angle, which is measured from the transfer starting location of the first image bearing body to the center of the interval Al, in the direction of reverse rotation of the first image bearing bodies,
- α2 is the angle, which is measured from the transfer starting location of the second image bearing body to the center of the interval A2, in the direction of reverse rotation of the second image bearing bodies,
- α3 is the angle, which is measured from the transfer starting location of the third image bearing body to the center of the interval A3, in the direction of reverse rotation of the third image bearing bodies,
- α4 is the angle, which is measured from the transfer starting location of the fourth image bearing body to the center of the interval A4, in the direction of reverse rotation of the fourth image bearing bodies, and
- Ro1, Ro2, Ro3 and Ro4 are radii of the first through fourth image bearing bodies.
The image bearing bodies preferably satisfy L1=L2=L3.
The image bearing bodies preferably satisfy L1=L2=L3, while L1, L2 and L3 are positive integer multiples of Sd.
A driving unit is preferably provided for driving the image bearing bodies and the supporting rollers, and each of the image bearing bodies preferably have at one end a driven coupler for receiving a driving force in engagement with the driving unit.
The driven couplers preferably each include a positioning part for determining a position of engagement with respect to the driving unit. The driven couplers may be engaged such that the intervals A1, A2, A3 and A4 of the respective image bearing bodies are formed at a predetermined angle with respect to the positioning parts.
The driving unit preferably includes a first driving unit for driving the first through fourth image bearing bodies at the same time; and a second driving unit for driving the supporting rollers independently.
The first driving unit preferably includes a plurality of driving gears provided to correspond to the plurality of image bearing bodies, respectively, rotating altogether in association with each other, and each having a driven coupler at one end to engage with the driven coupler; and a first driving motor for providing a driving force to drive the plurality of driving gears at the same time.
The first and second image bearing bodies are preferably mounted to satisfy the first equation of the equations 2-1, and satisfy α1=α2.
The first and third image bearing bodies are preferably mounted to satisfy the third equation of the equations 2-1, and satisfy α1=α3.
The first and fourth image bearing bodies are preferably mounted to satisfy the third equation of the equations 2-1, and satisfy α1=α4.
The first to fourth image bearing bodies are preferably mounted to satisfy all of the equations 2-1, and satisfy α1=α2=α3=α4.
The image bearing bodies have a radial displacement in which the radius of the image bearing body varies, and also have intervals A1, A2, A3 and A4 having a predetermined locations of maximum radial displacement, and at least two of the first through fourth image bearing bodies are mounted to satisfy one of the following equations:
[Equation Set 3]
{2π·l+(α2−α1)}·Ro·(1±0.05)=L1, (l=0, 1, 2, . . . ), (Ro=Ro1=Ro2) {circle around (1)}
{2π·m+(α3−α2)}·Ro·(1±0.05)=L2, (m=0, 1, 2, . . . ), (Ro=Ro2=Ro3) {circle around (2)}
{2π·n+(α4−α3)}·Ro·(1±0.05)=L3, (n=0, 1, 2, . . . ), (Ro=Ro3=Ro4) {circle around (3)}
-
- where α1 is the angle of center of the interval A1, measured from the transfer starting location of the first image bearing body in the direction of reverse rotation of the image bearing bodies,
- α2 is the angle of center of the interval A2, measured from the transfer starting location of the second image bearing body in the direction of reverse rotation of the image bearing bodies,
- α3 is the angle of center of the interval A3, measured from the transfer starting location of the third image bearing body in the direction of reverse rotation of the image bearing bodies,
- α4 is the angle of center of the interval A4, measured from the transfer starting location of the fourth image bearing body in the direction of reverse rotation of the image bearing bodies, and
- Ro1, Ro2, Ro3 and Ro4 are radii of the first to fourth image bearing bodies.
The image bearing bodies preferably satisfy L1=L2=L3.
The image bearing bodies preferably satisfy L1=L2=L3, while L1, L2 and L3 may be positive integral multiples of Sd.
The image bearing bodies are preferably mounted to satisfy all of the equations 2-2, and satisfy α1=α2=α3=α4.
The image bearing bodies each have a radial displacement in which the radius of the image bearing body varies, and an interval A having a maximum radial displacement at a predetermined location, wherein, when one of the supporting rollers has a radial displacement in which the radius varies, and an interval B having a maximum radial displacement, and with reference to a predetermined (X, Y) coordinate system based on the center of rotation of the supporting rollers and the image bearing rollers, the image bearing bodies and the supporting rollers are mounted to satisfy one of the following equations:
[Equation Set 4]
Rd·θd=(2π·l+θox)·Rox·(1±0.05)
(l=1, 2, 3, . . . ), (x=1, 2, 3, . . . ), Rd=z·Rox,(z=2, 3, 4, 5, . . . ) {circle around (1)}
Rd·θd=Rox·θox(1±0.05)
Rd=θox, (x=1, 2, 3, . . . ) {circle around (2)}
(2π·h+θd)·Rd=Rox·θox(1±0.05)
(h=1,2,3, . . . ), (x=1, 2, 3, . . . ), Rox=k·Rd, (k=2, 3, 4, 5, . . . ) {circle around (3)}
-
- where, θd is the angle of the center of the interval B in the direction of reverse rotation of the supporting rollers along the axis +X of the (X, Y) coordinate system,
- θox is the angle measured from the axis +Y of the (x)th image bearing body in the running direction of the intermediate transfer medium to the center of the interval A in the reverse rotational direction of the image bearing body,
- Rox is the radius of the (x)th image bearing body, and
- Rd is the radius of the supporting rollers.
The axis +X is preferably defined to be parallel with reference to the running direction of the intermediate transfer medium, such that when the center of the interval B is positioned on the axis +X, the speed change of intermediate transfer medium reaches a maximum.
When the radius of the supporting rollers is larger than the radius of the image bearing bodies by interger multiples, the integer being 2 or more, the image bearing bodies and the supporting rollers are preferably arranged to satisfy the first equation of the Equation Set 3.
When the radius of the image bearing bodies equals the radius of the supporting rollers, the image bearing bodies and the supporting rollers are preferably arranged to satisfy the second equation of Equation Set 3.
When the radius of the image bearing bodies is larger than the radius of the supporting rollers by an integer multiple, the integer being 2 or more, the image bearing bodies and the supporting rollers are preferably arranged to satisfy the third equation of Equation Set 3.
A first driving unit is preferably provided for driving the image bearing bodies at the same time, and a second driving unit is preferably provided for driving one of the supporting rollers.
The image bearing bodies each preferably include a drum body, a driven coupler engaged with one end of the drum body to receive a driving force in connection with the first driving unit.
The drum body of each of the image bearing bodies preferably have a mark for indicating the maximum radial displacement interval A.
The driven coupler of each of the image bearing bodies preferably include a positioning part for determining a position of engagement with the first driving unit, and the image bearing bodies and the driven couplers are preferably engaged such that the positioning part is positioned at a predetermined angle with respect to the mark.
The supporting rollers each preferably include a roller body, and a driven coupler engaged with one end of the roller body to receive a driving force from the second driving unit.
The driven coupler of each of the supporting rollers preferably include a positioning part to determine a position of engagement with respect to the second driving unit, and the roller body is preferably provided with a mark for indicating the interval B at a predetermined angle with respect to the positioning part.
The image bearing bodies preferably have identical radii.
The image bearing bodies are preferably arranged to satisfy L1=L2=L3.
The image bearing bodies each have a radial displacement in which the radius of the image bearing body varies, and an interval A having a maximum radial displacement at a predetermined location, wherein when, one of the supporting rollers has a radial displacement in which the radius varies, and an interval B having a maximum radial displacement, and with reference to a predetermined (X, Y) coordinate system based on the center of rotation of the supporting rollers and the image bearing rollers, the image bearing bodies and the supporting rollers are mounted to satisfy one of the following equations:
[Equation Set 4]
Rd·θd=(2π·l+θox)·Rox·(1±0.05)
(l=1, 2, 3, . . . ), (x=1, 2, 3, . . . ), Rd=z·Rox, (z=2, 3, 4, 5, . . . ) {circle around (1)}
Rd·θd=Rox·θox·(1±0.05)
Rd=θox, (x=1, 2, 3, . . . ) {circle around (2)}
(2π·h+θd)·Rd=Rox·θox·(1±0.05)
(h=1, 2, 3, . . . ), (x=1, 2, 3, . . . ), Rox=k·Rd, (k=2, 3, 4, 5, . . . ) {circle around (3)}
-
- where, θd is the angle of center of the interval B in the direction of reverse rotation of the supporting rollers along the axis +X of the (X, Y) coordinate system,
- θox is the angle measured from the axis +Y of the (x)th image bearing body in the running direction of the intermediate transfer medium to the center of the interval A in the reverse rotational direction of the image bearing body,
- Rox is the radius of the (x)th image bearing body, and
- Rd is the radius of the supporting rollers.
The axis +X is preferably defined to be parallel with reference to the running direction of the intermediate transfer medium, such thatwhen the center of the interval B is positioned on the axis +X, the speed change of intermediate transfer medium reaches a maximum.
When the radius of the supporting rollers is larger than the radius of the image bearing bodies by an integer multiple, the integer being 2 or more, the image bearing bodies and the supporting rollers are preferably arranged to satisfy the first equation of Equation Set 3.
When the radius of the image bearing bodies equals the radius of the supporting rollers, the image bearing bodies and the supporting rollers may be arranged to satisfy the second equation of Equation Set 3.
When the radius of the image bearing bodies is larger than the radius of the supporting rollers by an integer multiple, the integer being 2 or more, the image bearing bodies and the supporting rollers are preferably arranged to satisfy the third equation of the Equation set 3.
The image bearing bodies are preferably mounted to satisfy L1=L2=L3.
The image bearing bodies preferably satisfy L1=L2=L3, while L1, L2 and L3 are a positive integer multiple of Sd.
A driving unit is preferably provided for driving the image bearing bodies and the supporting rollers, and the image bearing bodies each preferably have a driven coupler at one end to receive a driving force in connection with the driving unit.
The driven couplers each preferably have a positioning part for determining a position of engagement with the driving unit, and the driven couplers are preferably engaged such that the intervals A1, A2, A3 and A4 of the respective image bearing bodies are formed at a predetermined angle with respect to the positioning parts.
The driving unit preferably includes a first driving unit for driving the first to fourth image bearing bodies at the same time; and a second driving unit for driving the supporting rollers independently.
The first driving unit preferably includes a plurality of driving gears provided to correspond to the plurality of image bearing bodies, respectively, rotating altogether in association with each other, and each having a driven coupler at one end to engage with the driven coupler; and a first driving motor for providing a driving force to drive the plurality of driving gears at the same time.
The first and second image bearing bodies are preferably mounted to satisfy the first equation of equations 2-1, and satisfy α1=α2.
The first and third image bearing bodies are preferably mounted to satisfy the third equation of equations 2-1, and satisfy α1=α3.
The first and fourth image bearing bodies are preferably mounted to satisfy the third equation of equations 2-1, and satisfy α1=α4.
The first to fourth image bearing bodies are preferably mounted to satisfy all of the equations 2-1, and satisfy α1=α2=α3=α4.
According to yet another aspect of the present invention, an image forming apparatus preferably includes a plurality of image bearing bodies arranged in a predetermined sequence, and having a radial displacement, and also having an interval A having a maximum radial displacement; an intermediate transfer medium running in contact with each of the plurality of image bearing bodies; and a plurality of supporting rollers for guiding the running of the transfer medium while supporting the transfer medium, and having a radial displacement in which the radius varies, and also having an interval B having a maximum radial displacement, wherein, with reference to a predetermined (X, Y) coordinate system based on the center of rotation of the supporting rollers and the image bearing rollers, the image bearing bodies and the supporting rollers are mounted to satisfy one of the following equations:
[Equation Set 4]
Rd·θd=(2π·l+θox)·Rox(1±0.05)
(l=1, 2, 3, . . . ), (x=1, 2, 3, . . . ), Rd=z·Rox, (z=2, 3, 4, 5, . . . ) {circle around (1)}
Rd·θd=Rox·θox·(1±0.05)
Rd=θox, (x=1, 2, 3, . . . ) {circle around (2)}
(2π·h+θd)·Rd=Rox·θox·(1±0.05)
(h=1, 2, 3, . . . ), (x=1, 2, 3, . . . ), Rox=k·Rd, (k=2, 3, 4, 5, . . . ) {circle around (3)}
-
- where, θd is the angle of center of the interval B in the direction of reverse rotation of the supporting rollers along the axis +X of the (X, Y) coordinate system,
- θox is the angle measured from the axis +Y of the (x)th image bearing body in the running direction of the intermediate transfer medium to the center of the interval A in the reverse rotational direction of the image bearing body,
- Rox is the radius of the (x)th image bearing body, and
- Rd is the radius of the supporting rollers.
The axis +X is preferably defined to be parallel with reference to the running direction of the intermediate transfer medium, such thatwhen the center of the interval B is positioned on the axis +X, the speed change of intermediate transfer medium reaches a maximum.
When the radius of the supporting rollers is larger than the radius of the image bearing bodies by an integer multiple, the integer being 2 or more, the image bearing bodies and the supporting rollers are preferably arranged to satisfy the first equation of Equation Set 3.
When the radius of the image bearing bodies equal the radius of the supporting rollers, the image bearing bodies and the supporting rollers are preferably arranged to satisfy the second equation of Equation Set 3.
When the radius of the image bearing bodies is larger than the radius of the supporting rollers by an integer multiple, the integer being 2 or more, the image bearing bodies and the supporting rollers are preferably arranged to satisfy the third equation of Equation Set 3.
A driving unit is preferably provided for driving the image bearing bodies and the supporting rollers, and the image bearing bodies each preferably have a driven coupler at one end to receive a driving force in connection with the driving unit.
The driven couplers each preferably have a positioning part for determining a position of engagement with the driving unit, and the driven couplers are preferably engaged such that the intervals A1, A2, A3 and A4 of the respective image bearing bodies are formed at a predetermined angle with respect to the positioning parts.
The first driving unit preferably includes a plurality of driving gears provided to correspond to the plurality of image bearing bodies, respectively, rotating altogether in association with each other, and each having a driven coupler at one end to engage with the driven coupler; and a first driving motor for providing a driving force to drive the plurality of driving gears at the same time.
The second driving unit preferably includes a driving gear provided to correspond to the supporting rollers, and having a driving coupler at one end for engagement with the driven coupler which is provided at an end of each of the supporting rollers; and a second driving motor for driving the driving gear.
BRIEF DESCRIPTION OF THE DRAWINGSThe above aspects and features of the present invention will be more apparent by describing certain embodiments of the present invention with reference to the accompanying drawings, in which:
It should be understood that throughout the drawings, like reference numbers are used to depict like elements features and structure.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTSCertain exemplary embodiments of the present invention will now be described in greater detail with reference to the accompanying drawings.
The matters defined in the description such as a detailed construction and elements are provided to assist in a comprehensive understanding of the invention. Thus, it should be apparent to those of ordinary skill in the art that various changes and modifications can be made to the exemplary embodiments described herein without departing from the scope and spirit of the invention. Also, descriptions of well-known functions or constructions are omitted for clarity and consiceness in describing exemplary embodiments of the present invention.
Referring to
In the embodiment illustrated in
Additionally, in this particular example of an exemplary embodiment of the present invention, the respective OPCs 30, 40, 50, 60 sequentially transfer the black, cyan, magenta and yellow color images onto the belt 70 as an overlay of a color image along the running direction of the belt 70 (The OPCs 30, 40, 50, 60 rotate in a clockwise direction in this example).
It will be understood that the following described features of an exemplary embodiment of the present invention are equally applicable to other situations such as when there are more or fewer than four OPCs 30, 40, 50, 60 employed. One of ordinary skill in the art will also understand that the respective OPCs 30, 40, 50, 60 can be arranged along the running direction of the belt 70, in a different sequence from that which is described herein.
Developing units 26, 27, 28, 29 for the respective colors are disposed near, and preferably below the OPCs 30, 40, 50, 60, to form images in each color on the outer circumference of the OPCs 30, 40, 50, 60. Any suitable generally-known structures can be applied as the developing units 26, 27, 28, 29, and one will appreciate that the present invention is not limited to the structures of the developing units 26, 27, 28, 29 described with reference to the exemplary embodiment.
The belt 70 is supported by the driving roller 80, the supporting roller 91 and a plurality of T1 rollers 93 to run in a predetermined direction. The belt 70 is run by the rotational force of the driving roller 80 and receives color images from each of the OPCs 30, 40, 50, 60 in an overlaying manner. As a result, a full color image is formed and then transferred onto a printing medium 97 which is passed between the belt 70 and the T2 roller 95. The driving roller 80 is connected with the driving unit 100 and receives the driving force from the driving unit 100 to move the belt 70. The supporting roller 91 may be elastically biased toward the belt 70 so as to support the belt 70 with a constant tension.
Referring to
The frame 110 includes a front frame 111 and a rear frame 112 coupled in substantially parallel relation with each other.
The first driving part 101 includes a first driving motor 121 installed on the frame 110, first main gears, that is, first through fourth driving gears 123, 124, 125, 126 for each of the colors corresponding to the OPCs 30, 40, 50, 60, and first driving couplers 133, 134, 135, 136 provided at the rotational axes of the first through fourth driving gears 123, 124, 125, 126, respectively. The first through fourth driving gears 123, 124, 125, 126 are arranged at predetermined intervals, and disposed to rotate between the frames 111 and 112. Reference numeral 122 of
The first through fourth driving couplers 133, 134, 135, 136 of each color are rotated together with the driving gears 123, 124, 125, 126. The first through fourth driving couplers 133, 134, 135, 136 are constructed such that each is engaged with a driven coupler at one end of each OPC 30, 40, 50, 60 to transmit driving force. The driving couplers 133, 134, 135, 136 and driven couplers will be described in greater detail below.
The second driving part 103 includes a second driving motor 141 installed on the frame 110, a second main gear, that is, a fifth driving gear 143 rotatably placed between the frames 111 and 112 and rotated by the second driving motor 141, and a fifth driving coupler 145 provided at the rotational axis of the fifth driving gear 143. The fifth driving gear 143 is preferably driven separately from the first through fourth driving gears 123, 124, 125, 126. The fifth driving coupler 145 is rotated together with the fifth driving gear 143, and is configured such that it is complimentarily engaged with the driven coupler at the driving roller 80 to transmit the driving force. In the exemplary embodiment, all of the first through fifth driving couplers 133, 134, 135, 136 and 145 are shown to have identical coupling structures. In addition, other structures of the OPCs 30, 40, 50, 60, and in particular, the structure of the driven couplers can be understood to be substantially identical in this embodiment. Accordingly, for the sake of brevity, only the K color OPC 30 and the first driving coupler 133 will be described as a representative example of the others. Similarly, description of the first driven coupler 133 can appropriately replace that of the fifth driving coupler 145 corresponding to the driving roller 80.
Meanwhile, being consumables, the OPCs 30, 40, 50, 60 have limited lifespans that expire when used more than a predetermined number of times. The OPCs 30, 40, 50, 60 may be separately installed, or in an alternative example, formed integrally with the developing units 26, 27, 28, 29 and removably placed in the image forming apparatus body 25.
The OPCs 30, 40, 50, 60 are rotated by the driving force transmitted from the driving unit 100. The OPCs 30, 40, 50, 60 are each joined with a passive-driven coupling structure for complimentary mating with the first through fourth driving couplers 133, 134, 135, 136 so that the OPCs 30, 40, 50, 60 receive driving force from the driving unit 100 when mounted in the image forming apparatus body 25. Since the respective OPCs 30, 40, 50, 60 can have essentially the same structure, only the K color OPC 30 for forming an image in black (K) as shown in
Referring to
In an exemplary embodiment, one end of the driven coupler 33 is press-fit to an end of the drum body 31. At the other end, the driven coupler 33 is provided with a coupling part 33a with non-circular cross section, and a positioning part 33b protruding from a side of the coupling part 33a with a predetermined shape. The coupling part 33a is mated with the first driving coupler 133, shown in
The first driven coupler 33 preferably also includes a shaft 33c protruding along the rotational axis of the coupling part 33a. The shaft 33c is coupled to the shaft hole 133c, shown in
The first driving coupler 133 preferably also includes a coupling part 133a sunken from the end in a non-circular configuration, a positioning part 133b sunken from an inner side of the coupling part 133a, and a shaft hole 133c. The coupling part 133a is configured in correspondence with the coupling part 33a of the driven coupler 33, and the positioning part 133b is configured in correspondence with the positioning part 33b of the driven coupler 33.
As shown in
The roller body 81 of the driving roller 80 has a predetermined radius Rd, and a circumference of Sd=2π·Rd. The circumference ‘Sd’ of the driving roller 80 may be the same or different than the circumference of the OPCs 30, 40, 50, 60, and the detailed operation and effect of each case will be explained below.
The first through fourth driving couplers 133, 134, 135, 136 and the driven coupler 33 are preferably configured in an opposing manner. More specifically, as shown in
In other words, the driven coupler 233 is preferably formed in a concave manner in the end of the OPC 30, while the end of the driving coupler 330 corresponding to the driven coupler 233 is preferably configured in a convex manner. The exemplary embodiment of
Although not shown, the structure of the coupler as shown in
Meanwhile, the bodies of the rollers such as OPCs 30, 40, 50, 60 or the driving roller 80 are typically mass-produced using a metal molding process, as is known in the art. An important aspect in mass-producing roller bodies, that is, in the mass-production of the drum bodies, is to achieve a perfect circle along the outer circumference. However, perfect circles have yet to be achieved, andthere are always tolerances or errors during processing, which result in the drum body having an imperfect cross section. This will now be explained in greater detail with reference to the organic photoconductor 30 as a representative example.
As described above, an operator needs to know the interval A in order to control any influence of the roller body 31 cause by radial displacement δo. To this end, as shown in
As described above, by marking the interval A, the operator can regulate the relative orientation between the centers of the positioning part 33b of the driven coupler 33 and the interval A during assembly of the driven coupler 33 with respect to the drum body 31. In other words, as shown in
A variety of methods can be employed to align the positioning part 33b with the mark 31a. For example, as shown in
Next, as shown in
In another example, a structure is separately prepared in which the drum body 31 is rotatably supported on the first jig 241. In this case, separate detecting equipment such as a mark sensor or a monitor detects whether the mark 31a is positioned on the +x axis while the drum body 31 is rotated. Accordingly, when the mark 31a is detected to be positioned on the +x axis, the drum body 31 is stationed, and coupled with the driven coupler 33 such that the positioning part 33b is oriented with respect to the mark 31a.
The OPC 30, after being assembled in the manner as described above, can be positioned in the center of the interval A, which is −45 degrees from the positioning part 33b. Accordingly, in consideration of the fact that the interval A is located in correspondence with the positioning part 33b, it is possible to minimize the generation of image errors due to deviations in the radius of the OPC drum at interval A by controlling the positions of the OPCs during assembling and installing.
Although it has been described above that the drum body 31 is assembled with the driven coupler 33 with reference to the interval A having the maximum radial displacement +δo as an example, it will be appreciated that the initial position of the positioning part 33b can also be set with reference to other intervals, such as an interval having −δo, or δo=0.
In the manner described above, it should also be understood that the other color OPCs 40, 50, 60 each have an interval A that can be oriented −45 degrees away from the positioning parts 33b.
The driving roller 80 also has a runout as a result of manufacturing processes, and as shown in
Meanwhile, the maximum and minimum radial displacements ±δd of the driving roller 80 influences the speed of the belt 70. In other words, the tangential speed maximizes to Vdmax in the center of the interval B of the driving roller 80. Accordingly, when the interval B and the belt 70 contact tightly to the driving roller 80 and therefore, the positions of force application are aligned with each other, that is, when the direction of the tangential speed Vdmax runs parallel with the +y axis as shown in an imaginary line of
Methods according to exemplary embodiments of the present invention to improve image errors caused due to the radial displacement Ad of the driving roller 80 will be explained below. In the following explanation, it is assumed that the OPCs 30, 40, 50, 60 and the supporting roller 91 are free from the runout, and therefore, the radial displacement of the OPCs 30, 40, 50, 60 is δo=0. Accordingly, it is assumed that the radial displacement δd of the driving roller 80 is the only influence on the image being transferred onto the belt 70. As the first step to minimize image errors, the influence of the driving roller 80 is minimized and one example of doing so will be described below.
First, as described above with reference to
[Equation Set 1]
L1=l·Sd·(1±0.05)(l=1, 2, 3, . . . ) (1)
L2=m·Sd·(1±0.05)(m=1, 2, 3, . . . ) (2)
L3=n·Sd·(1±0.05)(n=1, 2, 3, . . . ) (3)
L4=o·Sd·(1±0.05)(o=1, 2, 3, . . . ) (4)
L5=p·Sd·(1±0.05)(p=1, 2, 3, . . . ) (5)
L6=q·Sd·(1±0.05)(q=1, 2, 3, . . . ) (6)
Referring to
Driving couplers 133, 134, 135, 136 are provided to the respective driving gears 123, 124, 125, 126, and the OPCs 30, 40, 50, 60 are rotatably engaged with the driving couplers 133, 134, 135, 136. Accordingly, the centers C1, C2, C3, C4 are aligned with the center of rotation of each of the OPCs 30, 40, 50, 60. Accordingly, it can be understood that the OPCs 30, 40, 50, 60 are arranged to satisfy at least one of the equations 1. Of course, L1 refers to the distance between the centers C1, C2 of the K color OPC 30 and the C color OPC 40, L2 refers to the distance between the centers C2, C3 of the C color OPC 40 and the M color OPC 50, L3 refers to the distance between the centers C3, C4 of the M color OPC 50 and the Y color OPC 60, L4 refers to the distance between the centers C1, C3 of the K color OPC 30 and the M color OPC 50, L5 refers to the distance between the centers C1, C4 of the K color OPC 30 and the Y color OPC 40, and L6 refers to the distance between the centers C2, C4 of the C color OPC 40 and the Y color OPC 60.
Accordingly, by setting the image forming apparatus system to satisfy at least one of the equations in Equation Set 1, image errors due to variations in the radius of the driving roller 80 can be reduced.
Image errors occur frequently on the image on the belt 70 due to the interval B of the driving roller 80 when the OPCs 30, 40, 50, 60 are arranged to satisfy none of the equations 1, and this will be described in detail below. In the following three examples, the radius Rd of the driving roller 80 and the radius Ro of the OPCs 30, 40, 50, 60 are mainly considered.
With reference to
When the length of the image transferred by each image bearing body is short enough, that is, when the location F1 where the K image transfer ends, and the location F2 where the C image starts transfer, are aligned with each other, the interval of C image transfer is not influenced by the interval B. Therefore, no image error due to the interval B does not occur in the C image. In other words, the K image transfer ends before the belt 70 moves by the distance of 1 Sd, and the C image transfer starts. Because the location F3 where the C image transfer ends, is positioned before the belt 70 moves from the location F0 by the distance of Sd+Rd·θd, no image error occurs in the C image.
Next, when it is assumed that the M image transfer location F4 is the same as the location F3, an image error Rme occurs in the M image due to the interval B at the location which is a predetermined distance away from the location F4. Because the distance L4 is not an integer multiple of Sd, the M image transfer start location F4 is positioned after one rotational cycle of the driving roller 80 and the running of the belt 80 as much as t1 from the location f1 where the second rotational cycle of the driving roller 80 starts. When the respective color image transfer intervals are represented in a unit image area P1, the M image error Rme occurs at different locations from the starting line SL of the unit image area P1. In other words, two image errors Rke, Rme appear in the unit image area P1 at a distance apart from one another by Rd·θd−t1.
According to the same principle, the location F5 where the M image transfer ends, and the location F6 where the Y image transfer starts, are positioned before the belt 70 is run as much as 2Sd, that is, before the driving roller 80 completes a second rotational cycle. Accordingly, an image error Rye due to the interval B also occurs in the Y image. Here, because the Y image transfer start location F6 is positioned a predetermined distance (t2) from the location f2 where the second rotational cycle of the driving roller 80 starts, the center of the Y image error Rye occurs away from the starting line SL by t2+Rd·θd.
As explained above, when Rd>Ro, there may be a color image such as a C image, which is not influenced by the interval B of the driving roller 80 because the OPC rollers complete revolutions more often than the larger driving roller. Accordingly, a color OPC 40 which corresponds to the error-free color image, needs not be considered, but at least two of the respectively-spaced image errors Rke, Rme, Rye should be aligned with each other to reduce the frequency of image error occurrence within the unit image area P1. In the following description, a method of aligning the K and M image errors Rke, Rme will be described as one example of the present invention.
In order to align the two image errors Rke, Rme, the system is realized to satisfy the fourth equation of the equation set 1. That is, a distance between the centers C1, C3 of the two OPCs 30, 50 may be set to L4=o·Sd(o=1, 2, 3, . . . ). To this end, as indicated by an imaginary line in
Accordingly, as the system is set as described above, if the K image starts to be transferred, the center of the K image error Rke occurs away from the starting line SL as much as Rd·θd. The C image is free from an image error as mentioned above with reference to
Meanwhile, as shown in
Of course, the Y image error Rye can also be aligned with the other image errors, by establishing the system to satisfy the fourth and third equations of Equation Set 1, or by establishing the system to satisfy the fourth and fifth equations of Equation Set 1. The principle according to which K, M, Y image errors Rke, Rme, Rye are overlapped by satisfying the above conditions, can be easily understood from the above-mentioned process of aligning the two image errors. Therefore, a detailed description thereof will be omitted for the sake of brevity.
In this particular embodiment, the transfer intervals of each of the color OPCs 30, 40, 50, 60 are randomly set, and also the starting and ending points of color images are randomly set for the convenience of explanation. Accordingly, one will appreciate that the above particular case should not be construed as limiting. Various examples are possible under the condition of Rd>Ro, and the number of image errors of a unit image area can variously change. It is only clear that, regardless of the number of image errors, at least two image errors should aligned with each other by satisfying at least one of the equations in Equation Set 1 to reduce the total number of occurrences of image errors due to variations in the radius of the driving roller 80.
Furthermore, although
A second example of the first step will now be described. As shown in
Referring first to
Additionally, because the distance L2 between the centers C2, C3 of the C and M OPCs 40, 50 is longer than Sd as much as t3, the M image starts to be transferred onto the belt 70 when the belt 70 moves from the location F3 where the C image transfer ends, by t3=Rd·45°. The location F4 is at a distance 2t3 from the starting point f2 of the second rotational cycle of the driving roller 80. Accordingly, when considering the fact that the center of the M image error Rme due to the interval B occurs at a distance that the belt 70 is run from the location f2 by Rd·θd, the actual center of the M image error Rme occurs away from the starting line SL of the M unit image area P1 by m3=Rd·θd−2t3=m1−2Rd·45°=Rd(θd−90°)=Rd·45°. As a result, the M image error Rme occurs at a different location of the unit image area P1 from the K and C image errors Rke, Rce.
Referring to
In the following second example of the first step, it will be exemplified that the system is set to satisfy all of the equations of Equation Set 1. Referring to
Next, because the C image transfer start point F2 meets the location F1, and the location f1 also meets the location F1, the center of the C image error Rce occurring in the C image due to the interval B is positioned at the location F1, that is, at a distance from the starting line SL of the C image by m1=Rd·θd. As a result, the K and C image errors Rke, Rce are overlapped at the same location.
Furthermore, because L1=L2=1Sd, the M image transfer start point F4 is positioned at the same location as the C image transfer end location F3, and as the starting point f2 of the third rotational cycle of the driving roller 80. Because the center of the M image error Rme due to the interval B is at a m1=Rd·θd distance from the SL location, which is identical to the location F3, the K and C image errors Rke, Rce can be superimposed at the same location.
Additionally, because L1=L2=L3=Sd, the Y image transfer start point F6 is at the same location as the M image transfer end location F5, and as the start point f3 of the fourth rotational cycle of the driving roller 80. Accordingly, the center of the Y image error Rye due to the interval B occurs at the location F6, that is, at a distance from the starting line SL of the unit image area P1 as much as m1=Rd·θd. Because the Y image error Rye occurs at the same location as the overlap of the K, C and M image errors Rke, Rce, Rme, the number of image errors of unit image area P1 can be greatly reduced, and as a result, the image quality improves.
The third example of the first step where Rd<Ro will now be described.
When the K image is transferred onto the belt 70 at the K image transfer starting point F0, the starting point f0 of the first rotation of the driving roller 80 meets the location F0. Accordingly, the center of the first K image error Rke1 due to the interval B occurs at a distance where the belt 70 is run from the unit image transfer starting line SL as much as M1=Rd·θd. Since the K image transfer is completed by one rotation of the OPC 30, the driving roller 80 rotates twice during the transfer of the K image. Accordingly, the second K image error Rke2 occurs at a distance where the belt 70 is run from the center of the first K image error Rke1 as much as 1Sd=2π·Rd. That is, two K image errors Rke1, Rke2 occur in one unit image area P1 due to the interval B, and the center of the second K image error Rke2 occurs away from the SL as much as Sd+m1.
Meanwhile, because the distance between the centers C1, C2 of the two OPCs 30, 40 is L1=1Sd+t3, the C image transfer starts at a location F2 where the belt 70 is run by the interval of t3 from the starting point f1 of the second rotation of the driving roller 80. Accordingly, the center of the first C image error Rce1, which is caused due to the interval B in the second rotation of the driving roller 80, appears at a location where the belt 70 is moved from the location f1 as much as m1. As a result, the center of the first C image error Rce1 occurs away from the starting line SL of the C image transfer by m2=m1−t3. For the convenience of explanation, the distance corresponding to the interval t3 is defined to be the length of circumference when the driving roller 80 rotates by 45°. Accordingly, m2=Rd·θd−Rd·45°=Rd(θd−45°). As a result, the center of the first C image error Rce1 is at a different location from the centers of the two K image errors Rke1, Rke2 in the unit image area P1.
The second C image error Rce2 is caused due to the interval B while the C image is transferred and during the third rotation of the driving roller 80. The center of the second C image error Rce2 appears at a distance where the belt 80 is moved from the center of the C image error Rce1 by the interval of Sd. Accordingly, the center of the second C image error Rce2 is at a distance from the starting line SL of the C unit image P1 by m2+Sd=Rd(θd−45°)+2πRd=Rd·(2π+90°).
Because the distance between centers C2 and C3 of the C color OPC 40 and the M color OPC 50 is L2=Sd+t3, the transfer of the M image starts from the point F4. The transfer staring point F4 of the M color image is away from the point F0 by 2Sd+2t3, that is, away from the point f2 by 2t3. Accordingly, the center of the first M color image error Rme1 caused due to the interval B in the unit image area P1 is positioned away from the point f2 by m1=Rd·θd. Accordingly, the distance between the center of the image error Rme1 and the SL of the unit image area P1 during the M image transfer is m3=m1−2t3=Rd·θd−2Rd·45°=Rd·(θd−90°). The center of the second M color image error Rme2 caused due to the interval B occurs away from the center of the image error Rme1 at a position where the belt 70 is moved by a distance of Sd. Accordingly, the second M color image error Rme2 occurs away from the SL of the M color image by m3+Sd=Rd·(θd−90°)+2π·Rd=Rd·(2π+45°). Accordingly, the two M color image errors Rme1 and Rme2 occur at different locations from the K and C color image errors Rke1, Rke2, Rme 1 and Rme2.
Referring to
As described above, the number of image errors can be reduced thief the pair of color image errors occurring in the image area P1 are aligned with each other. Therefore, the image quality is improved.
Hereinafter, a method of aligning the two C and Y color image errors (Rce1, Rce2)(Rye1, Rye2) with each other will now be described with reference to
When the K color image is transferred from the point F0 in the state of
The first and the second C color image errors (Rce1)(Rce2) occur at the same location during the transfer of the C color image as shown in
The first M color image error (Rme1) occurs away from the point F4 at a distance where the belt 70 is moved by a distance of m3=m1−2t3=Rd·θd−2Rd·45°=Rd·(θd−90°). The center of the second M color image error Rme2 occurs away from the point F4 at a distance where the belt 70 is moved by a distance of m3+Sd=Rd·(θd−90°)+2π·Rd=Rd·(2π+45°).
Since the center C4 of the Y color OPC 60 is distanced away from the center C2 by a distance of 3Sd, the point F6 from which the Y color image is transferred is located a distance where the belt 70 is moved from the point F2 from which the C color mage is transferred by three times the circumference of Sd (3Sd). Then, the point F6 is distanced away from the point f4 by t3, and the center of the first Y color image error Rye1 occurs away from the point f4 by m1 due to the interval B. Accordingly, since the center of the first Y color image error Rye1 occurs from the point F6, that is, from the transfer starting line (SL) of the Y color image, at a distance where the belt 70 is moved by m4=m1−t3=Rd·θd−Rd·45°=Rd·(θd-−45°)=m2, the two image errors (Rce1, Rye1) are aligned with each other in the unit image area P1. Also, the center of the second Y color image error Rye2 occurs away from the point F6 at a distance where the belt 70 is moved by m4+Sd=m2+Sd=Rd·(θd−45°)+2π·Rd=Rd·(2π+90°). Accordingly, the second C image error (Rce2) and the second Y image error (Rye2) of the unit image area P1 are positioned away from the SL by the same distance and therefore, are aligned with each other.
As described above, in the full color image area P1 where the images are transferred to the belt 70 through all of the four OPCs 30-60, there are six image errors including the overlay of image errors (Rke1, Rye1)(Rke2, Rye2), which is 2 errors less than the 8 image errors occurring in the construction of
In the above embodiment explained with reference to
Also, in the description of an exemplary embodiment of the present invention using the Equation Set 1, the method of minimizing the occurrence of image errors caused due to the runout of the driving roller 80 is highlighted. However, this should not be considered as limiting. If an image error occurs due to a runout of the supporting roller 91, the occurrence of the image error can be minimized by using the above method and Equation Set 1 making any of the lengths L1-L6 equal to an integer multiple of the circumference of the supporting roller 91.
That is, the system is arranged to satisfy at least one of the equations in Equation Set 1 with respect to one of the driving roller 80 or the supporting roller 91 based on which has a greater radial displacement and greater effects on the image. On the other hand, with respect to the other roller, the runout can be minimized through a post-process such as precision machining, and the frequency of the image error occurrence caused by the supporting rollers of the belt 70 can be reduced.
As described above with reference to
Also, an electrostatic latent image is formed by scanning the surface of the OPC 30 with laser beams emitted from a laser scanning unit 31. During this procedure of forming the latent image, the interval A has increasing tangential speed Vmax. Accordingly, the interval A may have a decreasing amount of laser scan and increasing scan areas. The electrostatic latent image formed on the OPC 30 passes through the developing roller 33 so that toner particles are attracted from the developing roller 33 to the electrostatic latent image. Therefore, a visible image is obtained. During this procedure, however, the interval A passes in contact with the developing roller 33 more rapidly, and also, the amount of laser energy scanned onto the electrostatic latent image is less. As a result, less developer is attracted to the electrostatic image, and the developer attracted to the electrostatic image blurs due to the faster tangential speed. In summary, the visible image obtained on the surface of the OPC 30 through a series of procedures such as charging, laser scanning, and developing has an image error such as image blurring, image stretch, and image cut, in the interval A.
As described above, the visible image is formed on the surface of the OPC 30, but has an image error in the interval A prior to being transferred to the belt 70. The visible image which is transferred to the belt 70 may have an image error due to the interval A. As described above, the image error occurs due to the interval A caused by the runout of the OPC 30, 40, 50, 60, independently from the runout of the driving roller 80 as described above. Because one image error occurs in each OPC 30, 40, 50, 60 due to the runout of the OPCs 30, 40, 50, 60, a full color image may have a great number of image errors. For example, if each OPC 30, 40, 50, 60 is designed to rotate two times to form a unit image, two image errors may occur in each OPC 30, 40, 50, 60. As a result, a full color image has total eight image errors due to variations in radius of the OPCs 30, 40, 50, 60.
Meanwhile, the center of the interval A, which causes the image error to occur, can be arranged at a predetermined position with respect to the positioning part 33b of the driven coupler 33 as explained with reference to
Hereinafter, an image error occurring when the images are formed by using the respective OPCs 30, 40, 50, 60, each being mounted to have the center of the interval A positioned at a predetermined angle with respect to the positioning part 33b, will be described. Additionally, a method of reducing the number of image errors and an effect thereof according to an embodiment of the present invention will be described.
The description will mainly focus on the interval A of the respective OPCs 30, 40, 50, 60 which has radial displacement +δo. However, the like definition can be applied to an area having −δo. Because the image error becomes more problematic in the area having +δo than in the area having −δo, the description will be made mainly about the area having +δo.
For the convenience of the following exemplary explanation, it is assumed that the driving roller 80 and the supporting roller 91 form complete circles which have no runouts. It is also assumed that variations in speed of the belt 70 due to a radial displacement difference of the driving roller 80 and the supporting roller 91does not occur, and that the belt 70 runs at a constant speed.
As shown in
As shown in
As shown in
Referring to
Referring to
Referring to
An example of the above will be described in greater detail with reference to
The first graph of
The second graph of
The third graph of
The fourth graph of
As shown in
In
In addition, in the foregoing description, it was assumed that all of the OPC's have the same radius. Of course, as one of ordinary skill in the art will appreciate, the principles described above could also be applied if the OPC drums are not all of equal radius. For example, rather than controlling the distance between rotation centers of OPCs, the same effect can be obtained by controlling the distance between contact points of the OPCs. That is, each OPC has a contact point on the belt 70. By controlling the length between contact points of OPCs along the belt, image errors caused by radius deviations in the OPCs can be overlapped, and thereby reduced. In such a scenario, because the radii are not equal, the length between centers of rotation may not necessarily be equal to the length along the belt between contact points.
If the position of each radial displacement +δof OPCs 30 to 60 is aligned based on the initial transfer point of each OPC 30, 40, 50, 60, that is, if each OPC 30, 40, 50 is adjusted and arranged to generate each image error Oce, Ome, Oye shifted by a certain distance, only a single overlapped Ote of four color image errors is generated. As shown in the fifth graph of
The fifth graph of
Accordingly, description will now be made with reference to
[Equation Set 2]
{2π·l+(α2−α1)}·Ro·(1 ±0.05)=L1, (l=0 , 1, 2, . . . ),(Ro=Ro1=Ro2) {circle around (1)}
{2π·m+(α3−α1)}·Ro·(1±0.05)=L1+L2, (m=0, 1, 2, . . . ), (Ro=Ro1=Ro3) (2)
{2π·n+(α4−α1)}·Ro·(1±0.05)=L1+L2+L3, (n=0, 1, 2, . . . ), (Ro=Ro1=Ro4) {circle around (3)}
In
The K color image is transferred to the K unit image Pk in the state of
Ro·α1+L1=Ro·α2, (Ro=Ro1=Ro2) (1)
Because the distance of L1 is within one rotational circumference length 2π·Ro of the OPC 30, that is, L1<2π·Ro, the equation (1) may be generalized as follows:
Ro·α1+L1=Ro·(α2+2π·l), (l=0, 1, 2, . . . ) (2)
The above equation (2) can be rewritten as follows:
{2π·l+(α2−α1)}·Ro=L1, (l=0, 1, 2, . . . ) (3)
The above equation (3) corresponds to the first equation of Equation Set 2. If two OPCs 30, 40 are arranged to satisfy equation (3), the image errors Oke, Oce by the intervals A1, A2 of K color and C color OPC 30, 40 are superimposed at the same position. More specifically, when setting each OPCs 30, 40 in the image forming apparatus, the K color OPC 30 is preferably first set as the S1 and Ro values are set. Then, if a certain α1 value of the K color OPC 30 is substituted using the first equation of the equations 2, α2 of the C color OPC 40 can be obtained. Therefore, if the C color OPC 40 is properly arranged along axes X and Y based on the obtained α2, the image errors Oke, Oce can be superimposed.
Additionally, as shown in
Ro·α1+L1+L2=Ro·(α3+2π·m), (m=0, 1, 2, . . . ), (Ro=Ro1=Ro3) (4)
Rewriting the above equation (4), the second equation of the Equation Set 2 can be derived as follows:
{2π·m+(α3−α1)}·Ro=L1+L2, (m=0, 1, 2, . . . ), (Ro=Ro1=Ro3) (5)
In order to align the K color image error Oke with the Y color image error Oye generated in the unit image Py by the interval A4 of the Y OPC 60 as shown in
Roα1+L1+L2+L3=Ro·(α4+2π·n), (n=0, 1, 2, . . . ), (Ro=Ro1=Ro4) (6)
The above equation (6) can be rewritten as:
{2π·n+(α4−α1)}·Ro=L1+L2+L3, (n=0, 1, 2, . . . ), (Ro=Ro1=Ro4) (7)
Equation (7) rewritten from the equation (6) corresponds to the third equation of the Equation Set 2.
The aforementioned conditions of Equation Set 2 can be used to control the installation position of OPCs 40, 50, 60 so that image errors generated by one of the OPCs 40, 50, 60 can be superimposed on the K color image error Oke generated by the interval A1 of the K OPC 30.
Additionally, contrary to the Equation Set 2, in order to superimpose the image error generated in at least neighboring OPCs 30, 40, 50, 60, the image forming apparatus needs be set to meet at least one of the following equations.
[Equation Set 3]
{2π·l+(α2−α1)}·Ro·(1±0.05)=L1, (l=0, 1, 2, . . . ), (Ro=Ro1=Ro2) {circle around (1)}
{2π·m+(α3−α2)}·Ro·(1±0.05)=L2, (m=0, 1, 2, . . . ), (Ro=Ro2=Ro3) {circle around (2)}
{2π·n+(α4−α3)}·Ro·(1±0.05)=L3, (n=0, 1, 2, . . . ), (Ro=Ro3=Ro4) {circle around (3)}
where, the equation {circle around (1)} of the Equation Set 3 corresponds to the first equation of the Equation Set 2. The equations represent the conditions to align the image errors Oke, Oce generated by the two neighboring OPCs 30, 40. Of course the above equations refer to a distance between centers of rotation of the OPCs. Alternatively, the distance between points of contact on the belt 70 of each OPC could be controlled with respect to the orientation of the OPC rollers.
The second equation of the Equation Set 3 represents conditions to align the image errors Oce, Ome generated by the interval A2, A3 of the C and M color OPCs 30, 40, and the method of overlapping image errors of the two OPCs 30, 40 can be easily comprehended through the aforementioned method. In other words, if α2 value of the C color OPC 40 is set with set L2 value and Ro value, α3 value of the M color OPC 50 can be obtained through equation {circle around (2)} of the Equation Set 3. Accordingly, by setting the M color OPC 50 based on α3 value, the two image errors Oce, Ome can be superimposed.
Equation {circle around (3)} of the Equation Set 3 represents conditions to superimpose the image errors Ome, Oye generated by the intervals A3, A4 of the M and Y color OPCs 50, 60. At this time, the image errors Ome, Oye of the two OPCs 50, 60 can be superimposed in the same manner as that explained in
In preferred embodiments of the present invention, the distances between the centers C1, C2, C3, C4 of each OPC 30, 40, 50, 60 are identically set as L1=L2=L3. Therefore, the Equation Set 2 can be rewritten as follows:
[Equation Set 4]
{2π·l+(α2−α1)}·Ro·(1±0.05)=L1, (l=0, 1, 2, . . . ), (Ro=Ro1=Ro2) (1)
{2π·m+(α3−α1)}·Ro·(1±0.05)=2L1, (m=0, 1, 2, . . . ), (Ro=Ro1=Ro2=Ro3) (2)
{2π·n+(α4−α1)}·Ro·(1±0.05)=3L1, (n=0, 1, 2, . . . ), (Ro=Ro1=Ro2=Ro3=Ro4) (3)
In the same manner as described with reference to
In this case, L1, Ro and the maximum radial displacement location on the reference OPC, that is, the location of the interval A1 (α1) are obtained. In this embodiment, the K color OPC 30 is preferably set as the reference OPC. Additionally, the maximum radial displacement locations (α2, α3 and α4) of the other OPCS 40, 50, 60 are obtained to satisfy equations 2 and 3, and the respective OPCs 40, 50, 60 are mounted accordingly. In order for visual confirmation of the radial displacement locations, the positioning part 33b of the driven coupler may be fastened in the factory to have a predetermined interval (for example, 45°) with respect to the respective radial displacement locations, as shown in
After the maximum radial displacement locations (α2, α3 and α4) of the other OPCS 40, 50, 60 are determined with respect to the location α1 of the reference OPC 30, the OPCs 30, 40, 50, 60 can be mounted in the image forming apparatus through at least two methods, which will now be described in more detail.
As a first method, as described above, the respective OPCs 30, 40, 50, 60 are mounted such that the positioning part 33b of the driven coupler is positioned at a predetermined angle with respect to the maximum radial displacement +δo. One of the OPCs, namely, OPC 30 is connected to the driving coupler 133 as shown in
A second method for setting the OPCs is to use a jig. For example, as shown in
Meanwhile, the reference drums 330, 340, 350, 360 are rotatably inserted in adjusting holes 313 formed at predetermined intervals on the jig frame 310. In addition, the jig frame 310 has fixing members 320 corresponding to the respective reference drums 330, 340, 350, 360. The plurality of fixing members 320 are fastened to the jig frame 310 in a threaded manner such that one end of each is contacted with the reference drums 330, 340, 350, 360 being inserted in the adjusting holes 313. Therefore, as the fixing member 320 is rotated toward the reference drums 330, 340, 350, 360, the one end is tightly contacted with the reference drums 330, 340, 350, 360, thereby immovably fixing the reference drums 330, 340, 350, 360. On the other hand, as the fixing member 320 is rotated away from the reference drums 330, 340, 350, 360, the reference drums 330, 340, 350, 360 and the fixing member 320 are separated from each other so that the reference drums 330, 340, 350, 360 are rotatable within the adjusting holes 313.
Using the jig device 300, the positions of the reference drums 330, 340, 350, 360, instead of the OPCs 30, 40, 50, 60 mounted in the driving unit 100, can be controlled and fixed to satisfy any of the equations in Equation Set 2 or 3.
In order to control reference positions of the reference drums 330, 340, 350, 360, the first method described above can be used. In other words, α1 of a predetermined reference drum, for example, the reference drum 330 is detected and α2, α3 and α4 of the other reference drums 340, 350, 360 are obtained with respect to α1. Based on the obtained α2, α3 and α4, the positions of the respective reference drums 330, 340, 350, 360 are controlled and fixed in order using the predetermined detecting device.
After the reference positions of the reference drums 330, 340, 350, 360 are determined, the jig device 300 and the driving unit 100 are approached to each other and the driven couplers 333, 343, 353, 363 of the position-controlled reference drums 330, 340, 350, 360 are coupled with the driving couplers 133-136. Since the driven couplers 333, 343, 353, 363 are fixed, the driving couplers 133-136 appropriately rotate to be connected with the driven couplers 333, 343, 353, 363. After the driving couplers 133-136 are position-controlled and coupled with the driven couplers 333, 343, 353, 363, the jig device 300 and the driving unit 10 are moved relative to the reference drums 330, 340, 350, 360 along an axial direction of the reference drums 330, 340, 350, 360 so as to separate the driving couplers 133-136 from the driven couplers 333, 343, 353, 363. Here, the driving unit 100 may be moved by a dedicated moving jig and connected with the jig device 300 or alternatively, the jig device 300 may be moved toward the image forming apparatus, with the driving unit 100 being mounted to the image forming apparatus, thereby controlling the driving couplers 133-136 of the driving unit 100.
The driving couplers 133-136, after being connected and separated with respect to the driven couplers 333, 343, 353, 363, are then coupled with the driven coupler 33 of the OPCs 30, 40, 50, 60. Since positions of the driving couplers 133-136 are fixed, the OPCs 30, 40, 50, 60 can be set to satisfy Equations 2 and 3.
Accordingly, by using the jig device 300, assembling time is saved in bulk production and radial displacement control of the OPCs is facilitated.
When the radii Ro of the respective OPCs 30, 40, 50, 60 are all the same and the distances between centers of the OPCs 30, 40, 50, 60 are all the same (L1=L2=L3=2π·Rox (x=1, 2, 3, . . . )), α2, α3 and α4 all have the same value. Therefore, as shown in
To summarize, i) The OPCs 30,40, 50, 60 and the driving rollers 80 respectively have runouts. In order to advantageously control the frequency of image errors occurring due to +δo and +δd by the runout, the OPCs and the driving rollers are constructed so that the positioning parts 33b and 83b of the driven couplers 33 and 83 are positioned at certain locations with respect to +δo and +δd.
ii) An embodiment and the effect thereof have been described, with the embodiment satisfying the conditions of the Equation Set 1 so that at least two of the image errors (Rke, Rce, Rme, Rye) by the runout of at least one of the driving roller 80 and the supporting roller 91 overlap at the same relative location. Here, the image errors generated in the image area of the corresponding OPC can be overlapped according to relative sizes of the radius Rd of the driving roller 80 and the radius Ro of the OPC and regardless of the number of image errors generated in a unit image.
iii) Hereinbefore, Equation Set 2 and the Equation Set 3 have respectively been described as conditions of superimposition of at least two of the image errors (Oke, Oce, Ome, Oye) generated by the runout of the OPCs 30, 40, 50, 60, without regard to the runout of the driving roller 80 and the supporting roller 91. More specifically, in order to superimpose any one image error of the other OPCs 40, 50, 60 with respect to the predetermined OPC 30, the system is set up to satisfy at least one condition of Equation Set 2 or 3. In order to superimpose the image errors of at least two neighboring OPCs, the system is set up to satisfy at least one condition of the Equation Set 3. Equation Sets 2 and 3 can be generally applied without considering the relative sizes of L1, L2 and L3, which are distances between the centers of the OPCs 30, 40, 50, 60. When L1=L2=L3, the system is set up, generally, on condition of Equation Set 4. In other words, since the product is substantially manufactured to satisfy L1=L2=L3, considering relations in assembly and size with other various parts, frequency of the image error occurrence can be effectively reduced by applying any of Equation Sets 2-4.
As a third step for reducing the frequency of the image error occurrence, a method for superimposing the image error by the runout of at least one of the supporting roller 91 and the driving roller 80 corresponding to the image error by the runout of the respective OPCs 30, 40, 50, 60 will now be described.
As described in
Referring to
[Equation Set 5]
Rd·θd=(2π·l+θox)·Rox·(1±0.05)
(l=1, 2, 3, . . . ), (x=1, 2, 3, . . . ) and Rd=z·Rox,(z=2, 3, 4, 5, . . . ) {circle around (1)}
Rd·θd=Rox·θox (1±0.05)
Rd=θox, (x=1, 2, 3, . . . ) {circle around (2)}
(2πh+θd)Rd=Rox·θox(1±0.05)
(h=1, 2, 3, . . . ), (x=1, 2, 3, . . . ) and Rox=k·Rd, (k=2, 3, 4, 5, . . . ) {circle around (3)}
That is, if the system is set up to satisfy at least one of the equations from Equation Set 5, the image errors occurring due to the radial displacements of the driving roller 80 and the OPCs 30, 40, 50, 60 are superimposed at the same position on the belt 70, and accordingly, the image error appears only at the superimposed location of the image.
First, a case wherein Rox<Rd will be described on the assumption that δo=δd.
According to the first equation of Equation Set 5, the image errors by the driving roller 80 and the objective OPC can be superimposed when the radius Rd of the driving roller 80 is larger than the radius Rox of the OPC of interest by integer multiples equal to or greater than 2.
This will now be described in greater detail with reference to
When Rd=2Ro1, and the driving roller 80 rotates once, the OPC 30 rotates twice. It is assumed for purposes of this example that a unit image is formed by two cycles of rotation of the OPC 30. Accordingly, one image error caused by the interval B of the driving roller 80 and two image errors caused by the interval A1 of the OPC 30 occur within one unit image area.
Hereinbelow, a method of aligning the image error caused by the interval B of the driving roller 80 with one of the two image errors caused by the interval A1 of the OPC 30 by resetting the system to satisfy the first equation of Equation Set 5 will be described with reference to
More specifically, referring to
While the driving roller 80 rotates by one cycle, the OPC 30 rotates by two cycles. Therefore, two image errors, that is, first and second image errors Oke1 and Oke2, casued by the interval A1 are generated within the unit image area.
A center of the first image error Oke1 occurs at a distance Rox·Θox=Ro1·Θo1=Ro1·315° away from SL. Since the second image error Oke2 occurs at a distance 2π·Ro1 away from the first image error Oke1, the second image error Oke2 is distanced away from SL by 2π·Ro1+Ro1·Θo1=(2π+Θo1)·Ro1.
Therefore, in order to align one of the first and second image errors Oke1 and Oke2 caused by the interval A1 of the OPC 30 with the image error Rke caused by the interval B of the driving roller 80 at the same position, the distance Rd·θd from SL to Rke should be the same as the distance Rox·θox=Ro1·θo1 from SL to the first image error Oke1, or as the distance (2π+θo1)·Ro1 from SL to the second image error Oke2.
To generalize the above conditions, the first equation of Equation Set 5 can be obtained as follows.
Rd·θd=(2π·l+θox)·Rox (l=1, 2, 3, . . . ), (x=1, 2, 3, . . . ) and Rd=z·Rox, (z=2, 3, 4, 5, . . . ) {circle around (1)}
By applying Rd=2Ro1 to the first equation of the equations 3, the OPC 30 and the driving roller 80 are mounted to satisfy Θol=2·Θd−2π. Because Θd=315°, Θol=630°·2π=270° is satisfied. That is, when the driving roller 80 is initially positioned at a position moved by 315° clockwise on the +X axis with respect to the interval B, according to the first equation of Equation Set 5, the interval A1 of the OPC 30 can be disposed at a position moved by 270° with respect to the +Y axis as shown in
When the OPC 30 and the driving roller 80 are mounted to satisfy the first equation of the equations 3, the image errors Oke2 and Rke are superimposed at the same distance, that is, by Rd·θd=Rd·315°=(2π+θo1)·Ro1=(2π+270°)·Ro1 away from SL. Therefore, only a single overlay Te1 of superimposed image errors Oke2 and Rke and a non-superimposed image error Oke1 occur in the K color image.
As described above, when the first OPC 30 and the driving roller 80 are arranged so that the image errors thereof are superimposed, one of the image errors occurring in the interval A2 of the neighboring OPC 40 can be superimposed with the image error by the driving roller 80. In other words, as shown in
Since the distance between the neighboring OPCs 30 and 40 is not considered herein, the image error Rke of the driving roller 80 and the other image errors Oke1 and Oce1 are not necessarily superimposed. In order to superimpose the image errors Oke1 and Oke2 caused by the interval A1 with the image errors Oce1 and Oce2 caused by the interval A2, the OPCs 30 and 40 are arranged to satisfy the first equation of the Equation Set 2. To explain it in greater detail, the OPCs 30 and 40 have already been positioned to satisfy the first equation of Equation Set 3. Therefore, as shown in
As can be appreciated from the above description, when the radius of the driving roller 80 is bigger than the radius of the objective OPC by an integer multiple equal to or greater than two, one of the plurality of image errors generated by the OPC of interest can be superimposed with the image error caused by the driving roller 80 by setting up the system to satisfy the first equation of Equation Set 5. In the other plurality of OPCs as well, one of the image errors caused by the corresponding OPCs can be superimposed with the image error caused by the driving roller 80 by setting up the system to satisfy the first equation of Equation Set 5.
When the system is set up to satisfy the first equation of Equation Set 2, the image errors generated by the two OPCs 30 and 40 can be overlapped. Thus, the image errors generated by the OPCs 30 and 40 of interest can be reduced.
It has been illustrated that the image error Rke due to the driving roller 80 and the image error due to the two OPCs 30 and 40 are overlapped, by way of example of the OPCs 30 and 40. It should be understood, however, that if at least one of the plurality of the OPCs 30 through 60 can be selected and set to satisfy the first equation of Equation Set 5, the same effect can be obtained to reduce the image error generated due to the selected OPC.
It has been illustrated that the first equation of Equation Set 5 and the first equation of Equation Sets 2 and 3 can be satisfied at the same time by way of example. It should be understood that the same effect can be obtained from the OPC of interest when the respective OPCs 30 through 60 satisfy at least one of the equations from Equations Set 2, while also satisfying the first equation of Equation Set 5. These scenarios can be understood from the above description, and will not be described in detail for the sake of brevity.
Now a scenario in which the size of the driving roller and the OPC rollers are equal (Rd=Rox) will be described. It is assumed, for purposes of this example, that the radius deviations of the driving roller and the OPC rollers are equal, that is, δD=δo.
Referring to
As a result, the distance between the centers of the first image errors Rke1 and Oke1 is d1=Ro1·θo1−Rd·θd. Likewise, the distance between the centers of the second image errors Rke2 and Oke2 is d1=Ro1··θo1−Rd·θd.
As Rd=Ro, when the OPC 30 and the driving roller 80 are set to satisfy the condition d1=0, that is, the condition Ro1·θo1−Rd·θd, the image errors Oke2 and Oke2 of the OPC 30 can be overlapped with the image errors Rke1 and the Rke2 of the driving roller 80, respectively. As illustrated in
While the OPC 30 is set for the driving roller 80 to satisfy the second condition of Equation Set 5, if one of the neighboring OPCs 40, 50, 60 is set to satisfy one of the conditions of Equation Set 2 or 3, the image error due to the OPC of interest can be overlapped with respect to the overlapping error Te3 and Te4. A detailed description thereof has been provided above in reference to
Now a scenario in which the OPC rollers are larger than the driving roller (Rd<Rox) will be described. Again, it is assumed for purposes of this exemplary description that the radius deviations of the OPCs and the driving roller are equal, that is, δD=δo. As Rd<Rox, the driving roller 80 has a shorter rotational cycle than the OPCs 30, 40, 50, 60 in view of the rotational cycle over a unit of time. As a result, the image error caused by imperfections in the driving roller 80 occur more often than caused by the OPC in the unit image area. The number of image errors can be reduced as a whole by overlapping one of the plurality of the image errors of the driving roller 80 in the unit image area, with the image error of the OPC of interest. To this end, the system is set up to satisfy the third equation of Equation Set 5. An embodiment of the present invention exemplifies that the radius Rox of the OPC of interest is two times (c=2) longer than the radius Rd of the driving roller 80. Suppose that the unit image of a certain color is formed by four rotations of the driving roller 80, and correspondingly two rotations of the OPC roller. Hence, the unit image area has six image errors in total caused by the driving roller and the particular OPC roller, including four image errors caused by the driving roller 80 and two image errors caused by the OPC.
Referring to
The OPC 30 is positioned at θo1=45° away from the +Y axis in the counterclockwise direction. To transfer the K unit image area, the OPC 30 rotates two times. Thus, two image errors Oke1 and Oke2 due to the interval A1 occur with the distance 2π·Ro1 therebetween in the K unit image area as illustrated in
As a result, to overlap the two image errors Oke1 and Rke1, the distance from Po1 to the image errors Oke1 and Rke1 should be identical. While the driving roller 80 is set in advance, it is required to satisfy the condition Rd·θd=Ro1·(45°+67.5°). The third equation of Equation Set 5 can be satisfied by setting the OPC 30 to position at 112.5° from +Y of the interval A1 in the counterclockwise direction, as illustrated in
The image errors caused by other OPCs can be further reduced by setting the other OPCs to be in phase with the first OPC. That is, the OPC of interest can be set to satisfy at least one of the conditions of Equation Sets 2-4 while also satisfying the conditions of Equation Set 5. In this situation, at least one of the image errors due to the driving roller 80 can overlap with the image error of the OPC, and at the same time, the image errors occurring due to the OPCs can overlap with each other. Therefore, the number of the image errors can be reduced still more.
The following is an explanation as to how to overlap the image error of the driving error 80 with at least one of the image errors of at least two OPCs at the same location within the unit image. In this exemplary embodiment of the present invention, it is exemplified that all the image errors of the plurality of the OPCs 30, 40, 50, 60 are overlapped, and that the overlapping error of the OPCs 30, 40, 50, 60 is also advantageously overlapped with the image error of the driving roller 80. Note that the radiuses of the OPCs 30, 40, 50, 60 in this example are identical.
Firstly, referring to
As discussed previously, the respective OPCs 30, 40, 50, 60 have radial displacement due to runout. Intervals A1, A2, A3, and A4 of the OPCs 30, 40, 50, 60 cause image errors. To overlap the image errors due the intervals A1, A2, A3, and A4, as shown in
Two image errors occur from each of the respective OPCs 30, 40, 50, 60, and the centers of the first image errors Oke1, Oce1, Ome1, Oye1 caused by the OPCs 30, 40, 50, 60 are positioned away from the starting line SL by a distance of Ro·270°, as illustrated in
The overlapping errors Ote1 and Ote2 caused by the OPCs 30, 40, 50, 60 may appear at different positions from the overlapping error Rte due to the driving roller 80 as mentioned above. When the overlapping error Rte is overlapped with one of the overlapping errors Ote1 and Ote2 by the OPCs 30, 40, 50, 60, the number of the image errors in the unit image area can be reduced further. To this end, it is set to satisfy the first equation of Equation Set 5 in
As for the scenario when Rd=2Ro, when the system is set to satisfy the first equation of Equation Set 5 in addition to all of the conditions of Equation Set 1 and Equation Sets 2-4, the unit image area has only the first overlapping error Ote1 caused by the OPCs 30, 40, 50, 60 and only the overlapping error Te5 of the second overlapping error Ote2 caused by the OPCs 30, 40, 50, 60 and the overlapping error Rte caused by the driving roller 80, as illustrated in
When Rd=Rox, Equation Set 1, Equation Sets 2-4, and Equation Set 5 are all satisfied. In this case, the radii of the OPCs 30, 40, 50, 60 are identical Rox=Ro. Referring to
The OPCs 30, 40, 50, 60 are installed to satisfy the condition of Equation Set 2. In more detail, the OPCs 30, 40, 50, 60 are installed such that the intervals A1, A2, A3, and A4 of the respective OPCs 30, 40, 50, 60 are positioned at the same angle from the transfer start point Po1, Po2, Po3, and Po4 in the counterclockwise direction, that is, at the phase α1=α2=α3=α4. For further understanding of an exemplary embodiment of the present invention, α1-α4 are set to 315° and it is assumed that one rotation of the OPCs 30, 40, 50, 60 creates the color unit images. Referring to
The system of
Accordingly, the image errors due to the interval B of the driving roller 80 overlap with the image errors due to the intervals A1, A2, A3, and A4 of the respective OPCs 30, 40, 50, 60. Meanwhile, as shown in
Thirdly, referring to
The distance between the centers C1, C2, C3, and C4 of the OPCs 30, 40, 50, 60 is L1=L2=L3=2×2π·Rd=2Sd. Accordingly, when the driving roller 80 rotates two times, the respective OPCs 30, 40, 50, 60 make one rotation. Suppose that two rotations of the driving roller 80 create the unit image of a certain color, the interval B of the driving roller 80 produces two effects on the color unit image areas, as illustrated in
The distances between the centers C1, C2, C3, and C4 of the OPCs 30, 40, 50, 60, as defined in the first and second equations of Equation Set 2, are L1=L2=L3=2π·Ro. Since α1=α2=α3=α4=θo1, the centers of the image errors Oke Oce, Ome, Oye due to the intervals A1, A2, A3, and A4 of the OPCs 30, 40, 50, 60 are distanced from SL by Ro·θo1 in the unit image area, as illustrated in
The system of
In the exemplary embodiments of the present invention, it has been described that the image errors mainly result from the runouts of the OPCs 30, 40, 50, 60, which substantially transfer the image onto the belt 70, and the runout of the driving roller 80, which drives the belt 70, without consideration of the effect on the supporting roller 91. Thus, the effect of the supporting roller 91 is not explained herein. It is to be understood that the driving roller 80 and the supporting roller (driven roller) 91 are interchangeable in the relationship.
Also, as indicated in the above equation sets, one will understand that almost the same effect can be obtained within an error range of ±0.05.
As set forth above, the roller and the roller manufacturing method according to embodiments of the present invention are assembled such that the positioning part of the driven coupler is positioned at a certain angle in relation with the maximum radial displacement of the roller body (drum body). Hence, it is possible to control the effect on the radial displacement of the roller.
The driving unit of the image forming apparatus according to embodiments of the present invention can control the alignment of the OPCs based on a criterion, to thus control the effect from radius deviations of the belt supporting roller and/or effects from the radius deviations of the OPCs.
Furthermore, the image forming apparatus controls the locations of the image errors occurring due to runout of the driving roller and reduces the number of image errors in the final overlapping image. Therefore, the image quality can be enhanced and the reliability of the product is increased.
In particular, the frequency of image errors due to runouts of the driving roller and/or the OPCs can be decreased even without consideration of the radii of the OPCs and the driving roller.
The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. Also, the description of the embodiments of the present invention is intended to be illustrative, and not to limit the scope of the claims, and many alternatives, modifications, and variations will be apparent to those skilled in the art.
Claims
1. A roller comprising:
- a roller body having a deviation in its radius along the direction of circumference; and
- a driven coupler engaged with one end of the roller body, for complimentary mating with a driving coupler and receiving a driving force from the driving coupler,
- wherein the roller body has a mark formed on a predetermined position for indicating a location of the deviation.
2. The roller of claim 1, wherein the driven coupler comprises a positioning part for determining a position of engaging with the driving coupler, and
- the roller body is engaged with the driven coupler such that the positioning part maintains a predetermined set angle with respect to the mark.
3. The roller of claim 1, wherein the mark is provided at a predetermined angle with respect to a maximum radius deviation location of the roller body.
4. An image bearing body for use in an image forming apparatus, comprising:
- a drum body having a deviation in its radius along the direction of circumference; and
- a driven coupler engaged with one end of the roller body, for complimentary mating with a driving coupler and receiving a driving force from the driving coupler,
- wherein the drum body has a mark formed on a predetermined position for indicating a location of the deviation.
5. The image bearing body of claim 4, wherein the mark is provided at a predetermined location with respect to a maximum radius deviation location.
6. The image bearing body of claim 4, wherein the driven coupler comprises a positioning part for determining a position of engaging with the driving coupler, and
- the driven coupler is engaged with the drum body such that the positioning part maintains a predetermined angle with respect to the mark.
7. The image bearing body of claim 6, wherein the driven coupler comprises a non-circular coupling part formed at one end either in concave or convex fashion to receive a driving force in an engagement with the driven coupler, and
- the positioning part is extended from the coupling part in a radial direction of the driven coupler.
8. A method of manufacturing a roller comprising a roller body having a deviation in its radius along the direction of its circumference, and a driven coupler engaged with one end of the roller body, the method comprising the steps of:
- finding an interval of the roller body having a radius deviation; and
- setting the posture of the driven coupler with respect to the found interval and engaging the driven coupler with the roller body in said posture.
9. The method of claim 8, wherein said step of finding an interval comprises finding a location of maximum radius deviation.
10. The method of claim 9, wherein the step of finding the interval having a maximum radius deviation comprises the steps of:
- finding a point of maximum radius deviation by measuring an end of the roller body; and
- forming a mark on the roller body for indicating the found point of maximum radius deviation.
11. The method of claim 9, wherein the step of engaging the driven coupler comprises assembling the driven coupler with the roller body in a manner such that a positioning part of the driven coupler maintains a predetermined angle with respect to the point of maximum radius deviation and that the relative positions of engaging the driven coupler and the driving coupler are determined.
12. The method of claim 9, wherein the step of engaging the driven coupler comprises the steps of:
- supporting the roller body on a first jig such that the point of maximum radius deviation is positioned at a predetermined angle with respect to a reference coordinate axis;
- supporting the driven coupler on a second jig such that the driven coupler is positioned at a predetermined angle with respect to the reference coordinate axis; and
- moving at least one of the first and the second jigs to engage the driven coupler with the roller body.
13. A jig for assembling one or more rollers for use in an image forming apparatus, the one or more rollers each comprising a roller body having a radius deviation along a circumference and a driven coupler adapted to receive a driving force, the jig comprising:
- a first receiving portion adapted to receive at least one roller body; and
- a second receiving portion adapted to receive at least one corresponding driven coupler in a predetermined orientation with respect to the at least one roller body radius deviation.
14. The jig of claim 13, wherein at least one of the first and second receiving portions are adapted to move with respect to the other in order to engage the at least one roller body to the at least one corresponding driven coupler in the predetermined orientation.
15. The jig of claim 13, wherein the second receiving portion comprises at least one mating part adapted for complimentary mating with a non-circular coupling part of the at least one driven coupler.
16. The jig of claim 15, wherein the mating part has a positioning part and the coupling part has a complimentary positioning part for determining the predetermined orientation.
17. The jig of claim 13, wherein one of the mating part and the coupling part are concave, and the other of the mating part and the coupling part are convex.
Type: Application
Filed: Jun 28, 2005
Publication Date: Dec 29, 2005
Applicant:
Inventors: Hyun-Soo Kim (Yongin-si), Geun-Yong Park (Suwon-si), Seock-deock Hong (Suwon-si)
Application Number: 11/167,605
