Sheet conveying apparatus and image forming apparatus
In case a belt member of an endless intermediate transfer belt causes an improper running such as a skewed or zigzag movement, the belt member contacts belt contact detecting portions on both ends of a belt control roller and causes friction thereon. A difference in the frictional forces on the belt contact detecting portions causes a pivoting of a rotary axis of the belt control roller about a roller support member formed by a supporting shaft and a bearing at the center, thereby correcting the belt member in running operation to an appropriate position.
Latest Canon Patents:
- MEDICAL INFORMATION PROCESSING APPARATUS AND COMPUTER-READABLE STORAGE MEDIUM
- SAMPLE PROCESSING CARTRIDGE AND COLLECTION APPARATUS
- CLASSIFICATION METHOD, MICRO FLUID DEVICE, METHOD FOR MANUFACTURING MICRO FLOW CHANNEL, AND METHOD FOR PRODUCING PARTICLE-CONTAINING FLUID
- CULTURE APPARATUS
- SAMPLE PROCESSING APPARATUS, SAMPLE PROCESSING SYSTEM, AND CARTRIDGE
1. Field of the Invention
The present invention relates to an apparatus for guiding a belt, and more particularly a belt guiding apparatus equipped with a control mechanism for preventing a belt skewing. The present invention also relates to a driving apparatus utilizing a belt guiding apparatus equipped with a control mechanism for preventing a belt skewing, a conveying apparatus utilizing such belt guiding apparatus, and an image forming apparatus equipped with such conveying apparatus.
2. Related Background Art
There is known an image forming apparatus for forming a color image, utilizing a belt drive apparatus for driving an endless flat belt, called an intermediate transfer belt. In such image forming apparatus, toner images are formed on plural photosensitive drums serving as image bearing members of plural colors, and, before being transferred onto a recording sheet, at first transferred onto the intermediate transfer belt, and then collectively transferred onto such recording sheet.
Also the belt drive apparatus is employed in a sheet conveying apparatus for conveying a sheet as a recording medium.
Also for monitoring a skew movement of the conveying belt 131, optical belt detection sensors 138 such as photointerruptors are provided on both lateral ends of the belt, and a control apparatus 156 shown in
In such control mechanism for preventing belt skew, the belt adjusting roller 135 is pivoted, as shown in
However, a high-speed running of the conveying belt 131 increases a skewing speed, thus often leading to a breakage or the like in the belt.
Also Japanese Patent Publication No. H6-99055 discloses a belt drive apparatus having a function of correcting a zigzag movement of the belt.
However, such prior belt skew preventing mechanisms are associated with a following drawback that has to be resolved. In case the rotary axis C-C of the belt adjusting roller 135 is angularly displaced as shown in
In consideration of the foregoing, an object of the present invention is to provide a sheet conveying apparatus and an image forming apparatus of a high reliability, capable of preventing an endless flat belt supported by plural conveying rollers, from a skew movement or a zigzag movement in the course of rotation thereof, thereby preventing an abrasion or a damage resulting from mutual friction of the components.
The above-mentioned object can be attained, according to the present invention, by a sheet conveying apparatus including an endless belt for conveying a recording medium sheet, a belt control roller constituting at least one of plural rollers for supporting the belt and serving to correct an improper running of the belt cause by skew and zigzag movements thereof, a roller support member for supporting the belt control roller in an angularly variable manner about a fulcrum at a longitudinal center of the roller, and first and second belt contact detecting portions provided on both end portions of the belt control roller so as to come into contact with and to be subjected to a friction by the belt itself in case of an improper running thereof, wherein the belt control roller causes an angular change of a rotary axis thereof about the roller supporting member according to a difference between the frictional forces of the first and second belt contact detecting portions.
The present invention also provides an image forming apparatus including a sheet conveying apparatus of the above-described constitution and an image forming part for forming an image on a sheet conveyed from the sheet conveying apparatus.
In the sheet conveying apparatus of the present invention, in case the flat belt causes an improper running such as a skew or zigzag movement, the both lateral ends of the belt itself contact either one, or alternately contact both, of the first and second belt contact detecting portions, provided on both end portions of the belt control roller, and the belt control roller moves with an angular change in the rotary axis thereof according to the difference of the frictional forces in such contacts, thereby correcting the belt, in an improper running, to a running in a proper position. It is thus rendered possible to prevent the abrasion resulting from the friction between the components such as the belt itself and the roller bearing.
Also in the image forming apparatus of the present invention, particularly in case the flat belt is utilized as an intermediate transfer belt, a sheet conveying apparatus having the above-described function allows to suppress a displacement of the intermediate transfer belt in the running thereof, whereby an exact and stable image transfer is made possible onto the surface of such belt.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following, the sheet conveying apparatus and the image forming apparatus of the present invention will be explained by respective preferred embodiments, with reference to the accompanying drawings. Embodiments will be given in an ink jet recording apparatus and a sheet conveying apparatus to be equipped therein, as a specific example of the image forming apparatus capable of evidently reflecting the purport of the present invention.
Referring to
The sheet feeding part 2 is provided with a pressure plate 21 for supporting a stack of sheets P in a cassette body 23, and a sheet feed roller, which is rotatably supported and serves to pick up and advance the sheets P one by one by a frictional force, to the exterior of the cassette. The pressure plate 21 is pivotably supported, at a rear end portion thereof in a sheet advancing direction, in the cassette body 23 by a rotary shaft. A pressure spring 24 mounted on the bottom side of the pressure plate 21 urges an uppermost sheet P toward the sheet feed roller 22. Also in a part of the pressure plate 21 opposed to the sheet feed roller 22, there is provided a separation pad of a material of a high friction coefficient, such as artificial leather, in order to avoid so-called superposed advancing, in which plural sheets P are advanced in a superposed state.
The cassette body 23 is further provided with a separating finger, which covers one of the corners of the sheet P, for enabling separation of a single sheet P, and a release cam for releasing the contact of the pressure plate 21 and the sheet feed roller 22 (both members being omitted from the illustration). In a stand-by state, the release cam presses the pressure plate 21 down to a predetermined position, whereby the pressure plate 21 is separated to a position not in contact with the sheet feed roller 22.
A driving power from a drive roller 34 is transmitted, for example through gears, to the sheet feed roller 22 and the release cam. Thus the pressure plate 21, upon being released from the release cam, is lifted to bring the sheet P in contact with the sheet feed roller 22, which is rotated to pick up the uppermost sheet P to initiate the sheet feeding. The sheet P is separated by the separating finger one by one and is advanced to the conveying belt 3. The sheet feed roller 22 rotates until the sheet P is advanced to the conveying belt 3, whereupon the stand-by state is resumed in which the sheets P are separated from the sheet feed roller 22 and the driving power from the drive roller 34 is turned off. Also a sheet feed roller 90 of a manual-insert sheet feed device feeds a sheet P, set on a manual insertion tray 91, to the conveying belt 3 in response to a record command signal.
The sheet P, conveyed from the sheet feed part 2, impinges, at a leading end thereof, on a nip of a pair of registration rollers 44 positioned in front of the conveying belt 3, and is stopped in a state forming a loop of a predetermined amount, thereby being corrected from an eventual skewed position. Then, in response to a print start command signal from a main controller (not shown) in the main body of the apparatus, the registration rollers 44 start to rotate to advance the sheet P to the conveying belt 3.
A platen 30 supports a belt member 31 of the conveying belt 3 in a flat state from the inner side, thereby inhibiting a downward displacement thereof. The platen 30 serves to assist that the sheet P on the belt member 31 is advanced to appropriate positions corresponding to respective color recording heads 7 (Y, M, C, K) of the image recording part (image forming part). Also in a position opposed to the idler roller 32, an attraction roller 33 is provided in contact with the belt member 31, so as to be rotated by the movement thereof. The attraction roller 33 is pressed to the belt member 31 by a spring (not shown), thereby guiding the sheet P to the recording head. Also at an upstream side of the conveying belt 3, there are provided an upper guide 27 and a lower guide 28 for guiding the sheet P to the registration rollers 44. At a downstream side of the idler roller 32, in the conveying direction of the recording sheet, a recording head 7 is provided as recording means for recording an image according to image information.
The sheet P advanced by the registration rollers 44 is conveyed by the idler roller 32 and the attraction roller 33, and the leading end of thus conveyed sheet P is detected by a PR sensor lever (not shown) thereby determining a recording position on the sheet P.
The recording head 7 is constituted of an ink jet recording head of line type, in which plural nozzles are arrayed along a direction orthogonal to the conveying direction of the sheet P. In a sequential order from the upstream side in the conveying direction of the sheet P, recording heads of respective colors 7K (black), 7C (cyan), 7M (magenta) and 7Y (yellow) are arranged with predetermined gaps therebetween. These recording heads 7K, 7C, 7M and 7Y are supported by mounting on a head holder 7A. These recording heads execute a heating of ink to induce a film boiling therein, thereby discharging the ink from the nozzles of the recording heads utilizing a pressure change caused by a growth or a contraction of a bubble generated by such film boiling, and thus forming an image on the sheet P. The recording head 7 is made adjustable as to a distance (gap) between the nozzle face and the sheet P in the course of a recording operation. In a non-operating state, the recording head 7 is lifted and a cap 8 slides to cover the nozzle face of the recording head 7, thereby preventing the ink from solidification.
The sheet discharge part 4 is constituted of a sheet discharge roller 41 and a spur 42. The sheet P after image recording by the recording head 7 is pinched and conveyed by the sheet discharge roller 41 and the spur 42, thus being discharged to a sheet discharge tray 43. The sheet discharge roller 41 is driven by a driving power transmitted from the drive roller 34 through transmission means. The spur 42, in order to run on the printed surface after recording, has a small contact area with the sheet P, thereby not smearing or perturbing the image recorded on the sheet P even in contact with the printed surface after recording.
As shown in
The belt control roller 35 is a principal member of a belt running adjusting mechanism featuring the present invention, and exerts a function as a tension roller for providing the belt member 31 with an appropriate tension, and a function of correcting an improper running in the belt member 31, such as a skew movement or a zigzag movement. The belt control roller 35 is rotatably supported, at both ends thereof, by a control roller frame 71 which is provided in the frame 39 of the apparatus so as to be capable of a rocking motion.
Now referring to
Also as shown in
Also compression springs 75 are provided as urging means between both ends of the control roller frame 71 and the frame 39, thus urging the belt control roller 35 toward a stationary position where the rotary axis thereof becomes parallel to the rotary axes of the drive roller 34 and the idler roller 32. The compression springs 75 serve to regulate, in a zigzag movement control to be explained later, a magnitude of the frictional forces generated by the belt contact detecting portions 70a, 70b for displacing the belt control roller 35. However, the compression springs 75 are not essential in the zigzag movement control.
The drawings illustrate an example in which the belt member 31 is wound by a wrap angle of about 180° on the belt control roller. However, such wrap angle is not restrictive, and a same control theory is applicable also in case of a wrap angle of about 90° as shown in
In case of a belt wrap angle of 180°, as shown in
By employing a ball bearing in the bearing 74 for the supporting shaft 73, the control roller frame 71, which supports the belt member 31 of a width of 350 mm under a tension of 4 kgf (39.2 N), can be controlled by a force F of 10 kgf (98 N) which is a component in the rotating plane of the frictional force generated in the belt contact detecting portions. As the moving force F is variable depending on the tension, the resistance in the bearing, the belt width and so on, it is important to optimize the frictional forces in the belt contact detecting portions 70. In consideration of the durability, the friction in the belt contact detecting portions 70 is preferably made smaller, so that the force F required for the displacement should be made as small as possible.
When the belt member 31 has an effective width L equal to or smaller than a length Lμ of the belt control roller 35, and when a zigzag movement is generated as shown in
In an embodiment shown in
As explained in the foregoing, the zigzag movement control of the present embodiment can correct the displacement of the belt member 31 by a force, of which magnitude always corresponds to the positional displacement of the belt member 31. Also in case the frictional durability is lowered between the belt member 31 and the belt contact detecting portions 70a, 70b, the slope of the line becomes smaller, thereby expanding a control impossible range, since the control is not possible unless a force exceeding a pivoting resistance of the supporting shaft 73 is obtained. Such situation can however be avoided by selecting the distance Lμ between the belt contact detecting portions 70a, 70b in anticipation of such situation.
Now reference is made to
In the belt control roller 35 in a state without a zigzag movement, the belt member comes into contact with the belt control roller 35 at a point A0, and remains in contact to a point B0 wherein the belt member leaves the roller. In such case, there is not generated a force for displacing the belt member in a direction orthogonal to the conveying direction.
When the belt member is skewed to the left side, the belt member runs, as shown in
On the other hand, when the belt member skews to the right, a frictional force Fb acts from the belt member 31 to the belt contact detecting portion 70b, thereby shifting the belt control roller 35 to a position 35B shown in
Thus, the belt member 31, in an eventual zigzag movement, can always be returned to the normal position.
It is thus possible to achieve a control by a small difference in the friction, utilizing a frictional force generated in either of the belt contact detecting portions 70a, 70b provided on both ends of the belt control roller or utilizing a difference in the frictional forces generated in both detection portions, and to realize a stabilized conveying operation for the recording sheet P, under a constant monitoring of the skew in the belt 3 and a stable rotation of the belt member 31.
The base layer 62 constituting the belt member 31 is formed by winding a sheet (20 μm) constituted of a thermal plastic resin and a thermosetting resin by plural turns (5 turns), followed by thermal fusing, thereby obtaining a sheet of a thickness of 100 μm. Then a thermosetting surface material is wound also in plural turns and thermally fused to complete the belt. During such process, electrodes 60 are formed, in the state of the base layer sheet, in predetermined positions thereon, whereby such electrodes are provided in a position predetermined within the thickness of the belt. The electrodes may be formed by printing a conductive paint, or by depositing a conductive resin and executing thermal fusion collectively. Such laminate structure improves uniformity of the belt after formation and secures a stable precision.
A voltage of about 0.5-10 kV is applied to the power supply brushes 36 which is in contact with the belt member 31, thereby generating an attractive force in the belt member 31 in the recording positions below the recording heads 7. The power supply brushes 36 are connected to a high-voltage source (not shown) for generating a predetermined high voltage. At the sheet discharge, the charge of the electrodes 60 is eliminated by the charge eliminating brush 37 whereby the attractive force is lost and the sheet is separated and advanced to the sheet discharge part 4.
The present invention is not limited to the embodiments described above, but may also be realized in other embodiments or in modifications or variations of such embodiments within an extent not departing from the scope of the invention.
This application claims priority from Japanese Patent Application No. 2005-167502 filed on Jun. 7, 2005, which is hereby incorporated by reference herein.
Claims
1. A sheet conveying apparatus comprising:
- an endless belt for conveying a recording medium sheet;
- a belt control roller which constitutes at least one of plural rollers supporting the belt and serves to correct an improper running of the belt caused by a skew or zigzag movement thereof;
- a roller support member for supporting the belt control roller in an angularly variable manner about a fulcrum at a longitudinal center of the roller; and
- first and second belt contact detecting portions provided on both end portions of the belt control roller so as to come into contact with and to be subjected to a friction by the belt itself in case of an improper running thereof;
- wherein the belt control roller causes an angular change of a rotary axis thereof about the roller supporting member as a fulcrum according to a difference between the frictional forces of the first and second belt contact detecting portions.
2. A sheet conveying apparatus according to claim 1, wherein the first and second belt contact detecting portions are provided at a same distance with respect to the roller support member.
3. A sheet conveying apparatus according to claim 1, further comprising urging means which urges a rotary axis of the belt control roller toward a base position where the rotary axis becomes parallel to those of the plural rollers.
4. An image forming apparatus comprising a sheet conveying apparatus according to claim 1, and an image forming part for recording an image on a sheet conveyed by the sheet conveying apparatus.
5. A belt guiding apparatus comprising:
- a roller maintained in contact with and driven by a moving belt;
- a support member for rotatably supporting the roller;
- support means which pivotably supports the support member in such a manner that the roller can change a direction of a rotary axis thereof;
- a first friction member so provided as to pivot integrally with the support member and receiving, from the belt, a frictional force which becomes larger as the belt is displaced from a predetermined position to a first lateral direction; and
- a second friction member so provided as to pivot integrally with the support member and receiving, from the belt, a frictional force which becomes larger as the belt is displaced from the predetermined position to a second lateral direction opposite to the first lateral direction;
- wherein the support member pivots together with the first and second friction members, by the frictional force which the first or second friction member receives from the belt, to change the direction of the rotary axis of the roller thereby correcting the displacement of the belt.
6. A belt guiding apparatus according to claim 5, wherein the first and second friction members are unrotatably fixed to the support member.
7. A belt guiding apparatus according to claim 5, wherein the first friction member has a larger contact area with the belt when the belt is displaced from the predetermined position to the first lateral direction.
8. A belt guiding apparatus according to claim 5, wherein the second friction member has a larger contact area with the belt when the belt is displaced from the predetermined position to the second lateral direction.
9. A belt guiding apparatus according to claim 5, wherein the first and second friction members are positioned at lateral sides of the roller.
10. A belt guiding apparatus according to claim 5, wherein a rotation center of the support member is positioned at a longitudinal center of the roller.
11. A belt guiding apparatus according to claim 5, wherein a distance from the rotary center of the support member to the first friction member is equal to a distance from the rotary center of the support member to the second friction member.
12. A belt guiding apparatus according to claim 5, wherein a distance from the first friction member to the second friction member is equal to or larger than a width of the belt.
13. A belt guiding apparatus according to claim 5, wherein a distance from the first friction member to the second friction member is equal to or smaller than a width of the belt.
14. A recording medium conveying apparatus comprising:
- a belt for conveying a recording medium;
- plural rollers for supporting the belt;
- a control roller maintained in contact with and driven by the moving belt;
- a support member for rotatably supporting the control roller;
- support means which pivotably supports the support member in such a manner that the control roller can change a direction of a rotary axis thereof;
- a first friction member so provided as to pivot integrally with the support member and receiving, from the belt, a frictional force which becomes larger as the belt is displaced from a predetermined position to a first lateral direction; and
- a second friction member so provided as to pivot integrally with the support member and receiving, from the belt, a frictional force which becomes larger as the belt is displaced from the predetermined position to a second lateral direction opposite to the first lateral direction;
- wherein the support member pivots together with the first and second friction members, by the frictional force which the first or second friction member receives from the belt, to change the direction of the rotary axis of the roller thereby correcting the displacement of the belt.
15. An image forming apparatus comprising:
- a belt for conveying a recording medium;
- plural rollers for supporting the belt;
- recording means which records an image on the recording medium conveyed by the belt;
- a control roller maintained in contact with and driven by the moving belt;
- a support member for rotatably supporting the control roller;
- support means which pivotably supports the support member in such a manner that the control roller can change a direction of a rotary axis thereof;
- a first friction member so provided as to pivot integrally with the support member and receiving, from the belt, a frictional force which becomes larger as the belt is displaced from a predetermined position to a first lateral direction; and
- a second friction member so provided as to pivot integrally with the support member and receiving, from the belt, a frictional force which becomes larger as the belt is displaced from the predetermined position to a second lateral direction opposite to the first lateral direction;
- wherein the support member pivots together with the first and second friction members, by the frictional force which the first or second friction member receives from the belt, to change the direction of the rotary axis of the roller thereby correcting the displacement of the belt.
Type: Application
Filed: May 23, 2006
Publication Date: Dec 21, 2006
Applicant: Canon Kabushiki Kaisha (Tokyo)
Inventors: Tadashi Matsumoto (Tokyo), Yoshiharu Iwanaga (Tokyo)
Application Number: 11/438,305
International Classification: B65H 5/00 (20060101);