ROTARY MEMBER SUPPORT STRUCTURE, TRANSPORT DEVICE, CHARGING DEVICE, AND IMAGE FORMING APPARATUS

Abstract

A rotary member support structure includes: a rotary member including a shaft; a bearing that rotatably supports the shaft of the rotary member; a pressing member that presses the bearing in one direction; and a support that supports the bearing such that the bearing is movable in a pressing direction of the pressing member. When the rotary member is not rotating, the bearing and the pressing member are in contact with each other such that the bearing is rotatable about the shaft.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2017-233292 filed Dec. 5, 2017.

BACKGROUND

Technical Field

The present invention relates to a rotary member support structure, to a transport device, to a charging device, and to an image forming apparatus.

SUMMARY

According to an aspect of the invention, there is provided a rotary member support structure including: a rotary member including a shaft; a bearing that rotatably supports the shaft of the rotary member; a pressing member that presses the bearing in one direction; and a support that supports the bearing such that the bearing is movable in a pressing direction of the pressing member. When the rotary member is not rotating, the bearing and the pressing member are in contact with each other such that the bearing is rotatable about the shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein:

FIG. 1 is a schematic diagram showing the structure of an image forming apparatus;

FIG. 2 is an enlarged schematic diagram showing an output transport path near a fixing device in the image forming apparatus in FIG. 1;

FIG. 3 is a partial schematic cross sectional view showing the structure of a pair of first output rollers in the output transport path in FIG. 2 (the structure includes support structures);

FIG. 4A is a schematic diagram showing a support structure for a driven roller in the pair of output rollers in FIG. 3 in exemplary embodiment 1;

FIG. 4B is a schematic cross-sectional view taken along line IVB-IVB in FIG. 4A;

FIG. 5A is an enlarged schematic diagram showing the support structure for the driven roller in FIG. 4A;

FIG. 5B is a schematic diagram showing a contact state of a protrusion in the support structure in FIG. 5A;

FIG. 6A is a schematic diagram showing a state when the driven roller in the support structure in FIG. 5A is not rotating;

FIG. 6B is a schematic diagram showing a state during rotation of the driven roller in the support structure in FIG. 6A;

FIG. 7A is an exploded perspective view showing the structure of a pressing member including the protrusion in the support structure in FIG. 5A;

FIG. 7B is a schematic cross-sectional view showing the pressing member in FIG. 7A;

FIG. 8A is an enlarged schematic diagram showing a support structure for the driven roller in exemplary embodiment 2;

FIG. 8B is a schematic diagram showing a contact state of a protrusion in the support structure;

FIG. 9A is a schematic diagram showing a state when the driven roller in the support structure in FIG. 8A is not rotating;

FIG. 9B is a schematic diagram showing a state during rotation of the driven roller in the support structure in FIG. 9A;

FIG. 10A is a schematic perspective view showing the structure of the protrusion in the support structure in FIG. 8A;

FIG. 10B is a schematic perspective view showing another example of the structure of the protrusion in the support structure;

FIG. 11A is an enlarged schematic diagram showing a support structure for the driven roller in exemplary embodiment 3;

FIG. 11B is a schematic diagram showing a contact state of a protrusion in the support structure;

FIG. 12A is a schematic diagram showing a state when the driven roller in the support structure in FIG. 11A is not rotating;

FIG. 12B is a schematic diagram showing a state during rotation of the driven roller in the support structure in FIG. 12A;

FIG. 13 is an enlarged schematic diagram showing a support structure for a charging roller in exemplary embodiment 4;

FIG. 14A is a schematic diagram showing a state when the charging roller in the support structure in FIG. 13 is not rotating;

FIG. 14B is a schematic diagram showing a state during rotation of the charging roller in the support structure in FIG. 14A;

FIG. 15A is an enlarged schematic diagram showing a comparative support structure for the driven roller;

FIG. 15B is a schematic diagram showing a contact state between a pressing member and a bearing in the support structure;

FIG. 16A is a schematic diagram showing a state when the driven roller in the support structure in FIG. 15A is not rotating; and

FIG. 16B is a schematic diagram showing a state during rotation of the driven roller in the support structure in FIG. 16A.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention will next be described with reference to the drawings.

EXEMPLARY EMBODIMENT 1

FIGS. 1 and 2 show exemplary embodiment 1 of the invention. FIG. 1 shows the structure of an image forming apparatus 1 according to exemplary embodiment 1. FIG. 2 is an enlarged illustration of an output transport path in the image forming apparatus 1 in FIG. 1.

<General Structure of Image Forming Apparatus>

In the image forming apparatus 1, an image based on the information about an image including letters, photographs, diagrams, etc. is formed using a developer on a recording paper sheet 9 that is an example of a transportation object or a recording medium.

As shown in FIG. 1, the image forming apparatus 1 includes: a housing 10 serving as an apparatus body; an image forming unit 2 that forms a toner image using a toner serving as the developer by, for example, electrophotography and transfers the toner image onto a recording paper sheet 9; a paper feeder 3 that holds a prescribed number of recording paper sheets 9 and feeds a recording paper sheet 9 to a transfer position of the image forming unit 2; and a fixing device 4 that fixes the toner image transferred onto the recording paper sheet 9. The image forming unit 2, the paper feeder 3, and the fixing device 4 are disposed inside the housing 10.

The housing 10 is composed of various members such as structural members and exterior materials. An output tray 11 for placing ejected recording paper sheets 9 with images formed thereon is provided in an upper portion of the housing 10. The output tray 11 is formed as a collecting surface having an inclined surface disposed below a paper outlet 12 of the housing 10 and is configured to collect recording paper sheets 9 ejected from the paper outlet 12.

The image forming unit 2 includes a photoreceptor drum 21 that is a driving drum and rotates in a direction indicated by arrow A and further includes a charging device 22, an exposure device 23, a developing device 24, a transfer device 25, and a cleaning device 26 that are disposed in this order around the photoreceptor drum 21.

The charging device 22 is, for example, a contact charging device that electrically charges the circumferential surface (the outer circumferential surface serving as an image-forming region) of the photoreceptor drum 21 to a prescribed potential with a prescribed polarity. The exposure device 23 irradiates the circumferential surface of the charged photoreceptor drum 21 with light (indicated by a chain double-dashed arrow) in response to image information (signals) inputted in various forms to the image forming apparatus 1 to thereby form an electrostatic latent image. The developing device 24 supplies a charged toner used as a developer to develop the electrostatic latent image on the photoreceptor drum 21, and a toner image is thereby formed. The transfer device 25 is, for example, a contact transfer device that electrostatically transfers the toner image on the photoreceptor drum 21 onto a recording paper sheet 9. The cleaning device 26 cleans the photoreceptor drum 21 by removing undesired substances such as the toner remaining on the circumferential surface of the photoreceptor drum 21.

The paper feeder 3 includes: a paper tray 31 that holds plural recording paper sheets 9 having a prescribed size and a prescribed type and used for image formation, the recording paper sheets 9 being stacked on a sheet stacking plate 32; and a delivery unit 33 that delivers the recording paper sheets 9 held in the paper tray 31 one by one.

The paper tray 31 is attached to the housing 10 such that the paper tray 31 can be pulled out of the housing 10, and plural paper trays 31 may be provided depending on use conditions. The recording paper sheets 9 used are, for example, recording mediums cut into a prescribed size such as plain paper sheets, coated paper sheets, or thick paper sheets.

The fixing device 4 includes a housing 40 having an inlet for a recording paper sheet 9 and a paper outlet and further includes a heating rotary body 41 and a pressurizing rotary body 42 that are disposed inside the housing 40 and rotate while in contact with each other.

As shown in FIGS. 1 and 2 etc., the heating rotary body 41 is a driving rotary body and rotates in a direction indicated by an arrow. The heating rotary body 41 is a fixing member for heating and is in a roller form or a belt-pad form, and the circumferential surface of the heating rotary body 41 is heated to a prescribed temperature by a heater 43. The pressurizing rotary body 42 is a fixing member for pressurization that is in a roller form or a belt-pad form and is disposed so as to be aligned substantially along the axial direction of the heating rotary body 41. The pressurizing rotary body 42 is in contact with the heating rotary body 41 at a prescribed pressure and is rotated by the heating rotary body 41. In the fixing device 4, the contact portion between the heating rotary body 41 and the pressurizing rotary body 42 serves as a fixing treatment section FN through which a recording paper sheet 9 with a non-fixed toner image transferred thereon passes to thereby subject it to prescribed fixing treatment (heating, pressurization, etc.).

<Structure of Transport Path>

In the image forming apparatus 1, as shown by a chain double-dashed line in FIG. 1, a transport path Rt for transportation of a recording paper sheet 9 is provided in the housing 10. The transport path Rt includes a supply transport path Rt1, a relay transport path Rt2, and an output the transport path Rt3.

As shown in FIG. 1, the supply transport path Rt1 connects the delivery unit 33 of the paper feeder 3 to the transfer position (a portion of the photoreceptor drum 21 that faces the transfer device 25) of the image forming unit 2. The supply transport path Rt1 is composed of a pair of transport rollers 34 and unillustrated plural transport guide members.

The pair of transport rollers 34 are composed of so-called resist rollers. The resist rollers in a non-rotating state have the function of correcting the inclination of a transported recording paper sheet 9. The resist rollers start rotating at the timing of transfer, and the rotating resist rollers have the function of feeding a recording paper sheet 9 to the transfer position.

As shown in FIG. 1, the relay transport path Rt2 connects the transfer position of the image forming unit 2 to the fixing treatment section of the fixing device 4. The relay transport path Rt2 is composed of a prescribed guide member 35.

As shown in FIGS. 1 and 2 etc., the output transport path Rt3 connects the fixing treatment section FN of the fixing device 4 to the paper outlet 12. The output transport path Rt3 is composed of a pair of first output rollers 36, a pair of second output rollers 37, plural output guiding members 38 and 39, etc.

The pair of first output rollers 36 is disposed on the paper outlet side of the housing 40 of the fixing device 4 and includes a driving roller 361 and a driven roller 362 that is pressed against the driving roller 361 and driven to rotate by the driving roller 361. The pair of second output rollers 37 is disposed at the paper outlet 12 and includes a driving roller 372 and a driven roller 371 that is in contact with the driving roller 372 and is driven to rotate by the driving roller 372. A support structure for the pair of first output rollers 36 will be described later.

The output guiding members 38 are a pair of members 38a and 38b that face each other so as to form a transport space through which a recording paper sheet 9 subjected to fixation is guided to the pair of first output rollers 36. The output guiding members 39 are a pair of members 39a and 39b that face each other so as to form a transport space through which a recording paper sheet 9 discharged from the pair of first output rollers 36 is guided to the pair of second output rollers 37.

<Image Forming Operation by Image Forming Apparatus>

In the image forming apparatus 1, an image is formed as described below. An image forming operation for forming an image on one side of a recording paper sheet 9 will be described.

First, when an unillustrated controller in the image forming apparatus 1 receives an image formation request, the image forming unit 2, the paper feeder 3, and the fixing device 4 are actuated.

Then, in the image forming unit 2, the photoreceptor drum 21 starts rotating. The charging device 22 charges the circumferential surface of the photoreceptor drum 21 to a predetermined potential with a predetermined polarity (a negative polarity in this embodiment), and then the exposure device 23 exposes the charged circumferential surface of the photoreceptor drum 21 to light according to image information to thereby form an electrostatic latent image having a prescribed pattern. Next, the developing device 24 supplies a toner serving as a developer and charged to a prescribed polarity (a negative polarity in this embodiment) to the electrostatic latent image formed on the circumferential surface of the photoreceptor drum 21 to develop the electrostatic latent image, and the electrostatic latent image is thereby converted to a visible toner image.

Next, in the image forming unit 2, the rotating photoreceptor drum 21 transfers the toner image to the transfer position facing the transfer device 25. The delivery unit 33 of the paper feeder 3 feeds a recording paper sheet 9 to the supply transport path Rt1 according to transfer timing, and the pair of resist rollers 34 in the supply transport path Rt1 delivers the recording paper sheet 9 to the transfer position. Then, in the image forming unit 2, the transfer device 25 transfers the toner image on the photoreceptor drum 21 onto one side of the recording paper sheet 9 through electrostatic action at the transfer position. In the image forming unit 2, after the image transfer, the cleaning device 26 cleans the circumferential surface of the photoreceptor drum 21 and other portions to prepare for the next image forming process.

Next, in the image forming unit 2, the rotational force of the rotating photoreceptor drum 21 causes the recording paper sheet 9 with the toner image transferred thereon to be delivered to the relay transport path Rt2 and transported to the fixing device 4. In the fixing device 4, the recording paper sheet 9 is introduced into the fixing treatment section FN between the heating rotary body 41 and the pressurizing rotary body 42 driven to rotate by the heating rotary body 41. When the recording paper sheet 9 passes through the fixing treatment section FN, the toner image on the recording paper sheet 9 is heated and fused under pressure and is thereby fixed to the recording paper sheet 9.

Finally, the recording paper sheet 9 subjected to fixation is transported through the output transport path Rt3 to the paper outlet 12 of the housing 10 and then ejected and placed in the output tray 11.

In this case, as shown in FIGS. 1 and 2, the recording paper sheet 9 subjected to fixation is guided by the output guiding members 38 and the output guiding members 39 in the output transport path Rt3, held between the pair of first output rollers 36 and then between the pair of second output rollers 37, and transported by the transportation force of the rollers.

A single-color toner image is thereby formed on one side of the recording paper sheet 9, and the single-side image formation operation is completed. When an instruction to perform the image forming operation plural times is issued, the above series of operations is repeated the plural times.

<Support Structure for Pair of First Output Rollers and Transport Device Using the Same>

In the image forming apparatus 1, a support structure shown in FIGS. 3 to 6B etc. is used as the support structure supporting the pair of first output rollers 36 disposed in the output transport path Rt3.

First, as shown in FIG. 3 etc., in the pair of first output rollers 36, a rotary member 5A including a rotating shaft 51 serving as a shaft and roller bodies 53 disposed on the outer circumferential surface of the rotating shaft 51 is used as the driving roller 361. The driving roller 361 in exemplary embodiment 1 is a roller having a structure including the plural roller bodies 53 disposed on the rotating shaft 51 at prescribed intervals.

As shown in FIG. 3 etc., in the pair of first output rollers 36, a rotary member 5B including a rotating shaft 52 serving as a shaft and a roller body 54 disposed on the outer circumferential surface of the rotating shaft 52 is used as the driven roller 362. The driven roller 362 in exemplary embodiment 1 is a roller having a structure including one roller body 54 disposed on the rotating shaft 52.

The pair of first output rollers 36 has a structure in which the rotating shafts 51 and 52 are rotatably supported by prescribed support members 70 through bearings 55 and 56, respectively, such that the roller bodies 53 and 54 of the driving roller 361 and the driven roller 362, respectively, forming the rotary members 5A and 5B rotate while in contact with each other.

The support members 70 are plate members such as synthetic resin plates or metallic plates fixed to prescribed positions.

As shown in FIGS. 1 to 3 etc., the pair of first output rollers 36 forms a transport device 7 that transports a recording paper sheet 9, which is an example of a transportation object. Specifically, the recording paper sheet 9 is transported while sandwiched between the driving roller 361 and the driven roller 362 driven to rotate by the driving roller 361.

As shown in FIG. 3, the driving roller 361 is driven to rotate in a prescribed direction by rotating power transmitted to the rotating shaft 51 from a rotation driving device 77. The rotating power is transmitted from the rotation driving device 77 to the driving roller 361 (to its rotating shaft 51) using an unillustrated rotation transmitting mechanism such as a gear train.

In the driving roller 361 in the above support structure, the bearings 55 rotatably supporting the rotating shaft 51 are fixed to respective stationary attachment members 71 disposed in the support members 70, and the driving roller 361 is thereby attached to the support members 70.

The stationary attachment members 71 include, for example, holes or recesses into which the bearings 55 are partially fitted and members which fix the bearings 55. The bearings 55 are, for example, sliding bearings.

As shown in FIGS. 3 to 5B etc., in the driven roller 362 in the above support structure, the bearings 56 rotatably supporting the rotating shaft 52 are attached to movable attachment members 72 disposed in the support members 70 so as to be movable by a given distance toward the driving roller 361 as shown by double-pointed arrows E1-E2.

Each of the movable attachment members 72 includes a support 73 that supports a corresponding bearing 5 for the driven roller 362 movably with respect to the rotating shaft 51 of the driving roller 361. The supports 73 are attached and fixed to the respective support members 70. The bearings 56 are, for example, sliding bearings. The supports 73 may be formed as portions of the support members 70 and integrated therewith.

In the driven roller 362, the bearings 56 supporting the rotating shaft 52 are supported by the movable attachment members 72 so as to be pressed by respective pressing members 57 in a direction E1 directed toward the rotating shaft 51 of the driving roller 361.

As described above, in the pair of first output rollers 36, the driving roller 361 (the rotary member 5A) is rotatably supported by the support members 70 (their stationary attachment members 71) while the position of the driving roller 361 is fixed. The driven roller 362 (the rotary member 5B) is rotatably supported by the supports 73 (the movable attachment members 72) of the support members 70 so as to be movable toward the driving roller 361 and is also supported by the pressing members 57 through the bearings 56 so as to be pressed in the direction E1 directed toward the rotating shaft 51 of the driving roller 361.

In particular, as shown in FIGS. 3, 4A, and 4C, in the pair of first output rollers 36, the driven roller 362 (the rotary member 5B) employs a support structure 6 including: the bearings 56 that rotatably support the rotating shaft 52; the pressing members 57 that press the respective bearings 56 in the direction E1 directed toward the rotating shaft 51 of the driving roller 361; and the supports 73 that support the respective bearings 56 so as to be movable in the direction E1 in which the bearings 56 are pressed by the pressing members 57.

As shown in FIGS. 4A and 4B, each of the bearings 56 in the support structure 6 includes a plate-shaped body 56a having a substantially rectangular side portion. Each body 56a includes: a bearing hole 56b located at substantially the center and passing through the body 56a; a step portion 56c that is disposed in an upper outer portion of the body 56a and extends in the moving direction E1-E2; and a pressure receiving portion 56d that receives the pressure of a corresponding pressing member 57 on one side.

As shown in FIGS. 4A and 4B, each support 73 in the support structure 6 includes a body 74 having a holding portion 74a that accommodates a corresponding bearing 56 such that upper and lower portions of the bearing 56 are held so as to be movable in the direction E1-E2. The body 74 includes: a lower guiding portion 74b that holds and guides the lower side surface of the bearing 56 when it moves; an upper guiding portion 74c that holds and guides the upper side surface (the step portion 56c) of the bearing 56 when it moves; and an abutting portion 74d against which part of the pressing member 57 abuts to fix the pressing member 57.

As shown in FIGS. 4A and 4B, each of the pressing members 57 in the support structure 6 is composed of a member that can elastically press a corresponding bearing 56 in the direction E1 directed toward the rotating shaft 51 of the driving roller 361. Each of the pressing members 57 in exemplary embodiment 1 includes a coil spring.

Each of the coil springs of the pressing members 57 is disposed between the pressure receiving portion 56d of a corresponding bearing 56 and the abutting portion 74d of a corresponding support 73 and is used such that the bearing 56 is pressed by prescribed pressing force F toward the rotation center (02) of the rotating shaft 52 of the driven roller 362.

As shown in FIG. 4A, in the abutting portion 74d of the support 73 in exemplary embodiment 1, a protrusion holding portion 74e that holds one end of the coil spring used as the pressing member 57 is provided. The protrusion holding portion 74e is fitted into an internal space at the one end of the coil, and the coil spring is thereby held. Since the one end of the coil spring is held by the protrusion holding portion 74e, the position of the coil spring is unlikely to be displaced.

<Problems with Support Structure for Pair of First Output Rollers>

Generally, as exemplified in FIG. 15A, in the support structure 6 for the driven roller 362 of the pair of first output rollers 36, each coil spring included in a corresponding pressing member 57 is disposed such that its end portion opposite to the abutting portion 74d of a corresponding support 73 is pressed against part of a corresponding bearing 56.

The support structure 6 shown in FIG. 15A is a comparative support structure 60. Both ends of the coil spring serving as the pressing member 57 are assumed to be parallel to each other and have a substantially flat annular shape, unless otherwise specifically stated. Symbol L1 for a chain dashed line in FIG. 15A etc. represents a virtual straight line (virtual line) connecting the rotation center 02 of the driven roller 362 to the rotation center 01 of the driving roller 361. Symbol L2 for a chain dashed line represents the direction (the axial line) of the rotating shaft 52 of the driven roller 362.

In the comparative support structure 60, the coil spring serving as the pressing member 57 is disposed such that a central portion 57a of an end of the coil spring that is pressed against part of the bearing 56 substantially coincides with a position P1 at which the virtual line L1 intersects a pressure receiving surface 56e of the bearing 56 and is in contact with the pressure receiving surface 56e. FIG. 15B shows a portion 57b in which an end portion of the coil spring serving as the pressing member 57 is in contact with the pressure receiving surface 56e of the bearing 56 and also shows the state of the portion 57b. In this support structure 60, the coil spring serving as the pressing member 57 is attached on the assumption that the pressing force F of the coil spring acts toward the rotation center 02 of the rotating shaft 52.

As shown in FIG. 15A, in this support structure 60, when the driving roller 361 is rotated in a direction indicated by a chain double-dashed arrow at its operating timing, the driven roller 362 is driven to rotate in a rotation direction C indicated by a chain double-dashed arrow.

In this case, as shown in FIG. 15A, a rotational force (moment) Mr and a rotational drag force (moment) Mb are generated and act on the bearing 56. The rotational force Mr urges the bearing 56 to rotate in the rotation direction C through the frictional force such as the sliding force between the bearing 56 and the rotating shaft 52 of the driven roller 362. The rotational drag force Mb is caused by the pressing member 57 pressed against the bearing 56 and urges the bearing 56 to rest against the rotational force Mr.

In fact, in the support structure 60, the coil springs serving as the pressing members 57 may have different pressing characteristics (may have their own unique pressing characteristics) depending on the attachment states of the coil springs, their individual differences, etc. In this case, as shown FIGS. 16A and 16B, each bearing 56 may rotate about the rotating shaft 52 and come to rest while in contact with part of the holding portion 74a of the support 73 and inclined within a movable space in the support 73.

FIG. 16A shows a state (J1) in which the bearing 56 slides within the holding portion 74a of the support 73 in a direction opposite to the rotation direction C of the driven roller 362 and is thereby inclined and at rest. FIG. 16B shows a state (J2) in which the bearing 56 slides within the holding portion 74a of the support 73 in the rotation direction C of the driven roller 362 and is thereby inclined and at rest.

In this support structure 60, during rotation of the driven roller 362, the sliding friction between the bearing 56 and the rotating shaft 52 may change instantaneously, and the rotational force Mr may increase or decrease. Specifically, when a reduction in the sliding friction occurs, the rotational force Mr decreases. In this case, the rotational force Mr can be substantially equal to the rotational drag force Mb (Mr≅Mb).

When these forces are substantially equal to each other, the bearing 56 is unstable and can easily rotate about the rotating shaft 52 during rotation of the driven roller 362. Therefore, the bearing 56 rotates back and forth repeatedly between the above two states (J1 and J2).

Therefore, in the support structure 60, the bearing 56 repeatedly collides with portions of the support 73, and this causes unwanted noise and vibration. When a transport device 7 is formed using this support structure 60, unwanted noise and vibration are generated during transfer of a recording paper sheet 9 by the transport device 7.

<Detailed Structure of Support Structure for Pair of First Output Rollers>

Accordingly, in exemplary embodiment 1, as the support structure 6 that supports the driven roller 362 of the pair of first output rollers 36, a support structure 6A shown in FIGS. 4A and 5A is employed. In the support structure 6A, when the driven roller 362 serving as the rotary member is not rotating, the bearing 56 and the pressing member 57 are in contact with each other while the bearing 56 is rotatable about the rotating shaft 52.

The state in which the bearing 56 is rotatable is an unstable state. Specifically, for example, when the driven roller 362 is not rotating, the bearing 56 can easily rotate about the rotating shaft 52 in the rotation direction C of the driven roller 362 (or its rotating shaft 52) and also in a direction opposite to the rotation direction C, as shown in FIG. 6A. Symbol L1 for a chain dashed line in FIG. 6A represents a virtual line connecting the rotation center 02 of the driven roller 362 to the rotation center 01 of the driving roller 361, as does the virtual line L1 described above.

In the support structure 6A for the driven roller 362 in exemplary embodiment 1, each pressing member 57 has a protrusion 81, and the protrusion 81 is in contact with a corresponding bearing 56. When the driven roller 362 is not rotating, the bearing 56 can rotate about the rotating shaft 52.

Moreover, in the support structure 6A for the driven roller 362, during rotation of the driven roller 362, the bearing 56 is held in a state in which it is rotated in the rotation direction C of the driven roller 362, as shown in FIG. 6B.

The phrase “the bearing 56 is held in a state in which it is rotated in the rotation direction C of the driven roller 362” means that, for example, the bearing 56 rotated in the rotation direction C of the driven roller 362 comes into contact with part of the holding portion 74a of the support 73 and is thereby inclined and at rest and the inclined state is maintained during the rotation of the driven roller 362, as shown in FIG. 6B. The phrase also encompasses the following case.

Specifically, during the rotation of the driven roller 362 in the rotation direction C, the bearing 56 is brought to the inclined state described above. Then the bearing 56 in the inclined state slightly rotates continuously back and forth in the rotation direction C of the driven roller 362 and its reverse rotation direction. In other words, in this state, during the rotation of the driven roller 362 in the rotation direction C, the bearing 56 is prevented from rotating in the reverse rotation direction beyond the position at which the bearing 56 is unstable and rotatable when the driven roller 362 is not rotating (FIG. 6A).

The protrusion 81 disposed in the pressing member 57 is formed as a structural member having a spherical surface portion that comes in to contact with the pressure receiving surface 56e of the pressure receiving portion 56d of the bearing 56.

As shown in FIG. 5B, the protrusion 81 formed as the spherical surface-shaped structural member is in point contact with the pressure receiving surface 56e of the pressure receiving portion 56d of the bearing 56. This allows the bearing 56 to be easily rotatable when the driven roller 362 is not rotating.

Symbol 81a in FIG. 5B represents a portion of the protrusion 81 that is in contact with the bearing 56. The contact portion 81a substantially corresponds to the apex of the spherical surface-shaped protrusion 81. A chain dashed line L2 in FIG. 5B indicates the direction (axial line) of the rotating shaft 52 of the driven roller 362 as described above.

In fact, the term “point contact” also encompasses the case in which the shape of the contact portion 81a is a dot-like shape (a small circular shape) with a certain diameter (width) w1 on condition that shape of the contact portion 81a is maintained in the above-described rotatable state as shown in FIG. 5B. The pressure receiving surface 56e of the pressure receiving portion 56d of the bearing 56 is a flat surface. However, the pressure receiving surface 56e may be a curved surface with a small curvature so long as the point contact with the protrusion 81 can be maintained.

As shown in FIGS. 7A and 7B, the pressing member 57 provided with the protrusion 81 includes a coil spring 571 having a first end 571a to which a component 85 having the protrusion 81 is attached.

The component 85 having the protrusion 81 has an attachment recess 85c into which the first end 571a of the coil spring 571 is fitted. The protrusion 81 may be integrated with the component 85, or the protrusion 81 formed separately may be later integrated with the component 85.

The pressing member 57 provided with the protrusion 81 is disposed such that the protrusion 81 is pressed toward the rotation center 02 of the rotating shaft 52 of the driven roller 362. Specifically, as shown in FIG. 6A, the pressing member 57 is disposed such that its pressing force F acts toward the rotation center 02 of the rotating shaft 52.

In this case, the coil spring 571 serving as the pressing member 57 may be attached such that a second end 571b of the coil spring 571 is fitted onto and held by the protrusion holding portion 74e (FIG. 4A) provided in the abutting portion 74d of the support 73.

<Operational Advantages of Support Structure for Pair of First Output Rollers>

As shown in FIGS. 5A and 6A, in the support structure 6A supporting the driven roller 362 of the pair of first output rollers, when the driven roller 362 is not rotating (is in a non-rotating state), the bearing 56 is in point contact with the protrusion 81 disposed in the pressing member 57.

In the support structure 6A in this state, the bearing 56 is rotatable about the rotating shaft 52 within the movable space in the holding portion 74a of the support 73. In this case, only the pressing force F exerted by the pressing member 57 and directed to the rotation center 02 of the rotating shaft 52 acts on the bearing 56. Therefore, the bearing 56 is in an unstable state in which it can easily rotate about the rotating shaft 52 in the rotation direction C of the driven roller 362 and also in the reverse rotation direction.

As shown in FIG. 6B, in the support structure 6A, when the driven roller 362 is rotating during, for example, transportation of a recording paper sheet 9 (during rotation of the driven roller 362), the rotational force Mr in the rotation direction C of the driven roller 362 acts on the bearing 56, as described above for the comparative support structure 60.

Therefore, in the support structure 6A, the bearing 56 that is rotatable when the driven roller 362 is not rotating is maintained in a state in which the bearing 56 is rotated in the rotation direction C of the driven roller 362 within the movable space in the holding portion 74a of the support 73.

Specifically, as shown in FIG. 6B, the bearing 56 in this case is rotated in the rotation direction C of the driven roller 362 within the movable space in the holding portion 74a of the support 73. Then part (a corner) of the bearing 56 comes into contact with part of the holding portion 74a, and the bearing 56 comes to rest, so that the bearing 56 is slightly inclined.

Also in this support structure 6A, during rotation of the driven roller 362, the sliding friction between the bearing 56 and the rotating shaft 52 may change instantaneously, and the rotational force Mr may increase or decrease, as described above for the comparative support structure 60. Specifically, when a reduction in the sliding friction occurs, the rotational force Mr decreases. In this case, the rotational force Mr and the rotational drag force Mb may become substantially equal to each other (Mr≅Mb).

However, in the support structure 6A, the protrusion 81 in the pressing member 57 is in point contact with the bearing 56. Since the pressing member 57 is disposed such that its pressing force F acts toward the rotation center 02 of the rotating shaft 52, the vector of the load generated by the protrusion 81 is directed toward the rotation center 02 of the rotating shaft 52. Therefore, in the support structure 6A, the rotational drag force (moment) Mb itself that is caused by the pressing member 57 pressed against the bearing 56 and urges the bearing 56 to rest against the rotational force Mr is unlikely to be generated.

Therefore, in the support structure 6A, the rotational drag force Mb is unlikely to increase to a level comparable to the rotational force Mr, and the relation between the rotational force Mr and the rotational drag force Mb is easily maintained such that the rotational force Mr is larger than the rotational drag force Mb (Mr>Mb).

In this support structure 6A, during rotation of the driven roller 362 (and the driving roller 361), the bearing 56 is easily maintained in a state in which it is rotated in the rotation direction C of the driven roller 362 within the holding portion 74a of the support 73. In this case, the bearing 56 is prevented from rotating in the reverse rotation direction opposite to the rotation direction C beyond the position at which the bearing 56 is in the rotatable state when the driven roller 362 is not rotating and from rotating back and forth repeatedly around the above position.

Therefore, in the support structure 6A, generation of noise and vibration caused by repeated rotation of the bearing 56 within the movable space in the support 73 can be prevented or reduced, as described above for the comparative support structure 60.

In the support structure 6A, the generation of noise and vibration that occurs during rotation of the driven roller 362 in the comparative support structure 60 is prevented or reduced. Therefore, in a transport device 7 produced using the support structures 6A, a recording paper sheet 9 can be smoothly transported without generation of noise and vibration.

In the structural example shown in exemplary embodiment 1, the protrusion 81 in point contact with the pressure receiving portion 56d of the bearing 56 is a structural component having a spherical surface shape. However, this structural example is not a limitation. For example, the protrusion 81 may be a structural component in which the portion in contact with the pressure receiving portion 56d of the bearing 56 has a cone shape or a pyramid shape.

In the support structure 6 in which the protrusion 81 in point contact with the bearing 56 is used, even when the driven roller 362 is rotated in the rotation direction C and the reverse rotation direction in a switchable manner, the bearing 56 is rotated in the direction of rotation of the driven roller 362 (the rotation direction C or the reverse rotation direction).

In the support structure 6A, even when the driven roller 362 is rotated in the forward and reverse directions in a switchable manner, the generation of noise and vibration caused by repeated rotation of the bearing 56 as described above is prevented.

EXEMPLARY EMBODIMENT 2

FIGS. 8A and 8B show a support structure 6B for the driven roller 362 in exemplary embodiment 2.

The support structure 6B according to exemplary embodiment 2 has the same structure as the support structure 6A according to exemplary embodiment 1 except that the protrusion 81 is replaced with a protrusion 82 having a different structure. Therefore, in the support structure 6B, the same components as the support structure 6A are denoted by the same symbols in FIGS. 8A and 8B and subsequent figures, and their description will be omitted in principle.

As shown in FIGS. 8A and 8B, in the support structure 6B, the protrusion disposed in the pressing member 57 is a protrusion 82 in line contact along the axial line L2 of the rotating shaft 52 with the pressure receiving surface 56e of the pressure receiving portion 56d of the bearing 56. Therefore, as shown in FIGS. 8A, 8B, and 9A, when the driven roller 362 is not rotating, the bearing 56 is rotatable about the rotating shaft 52.

Also in this support structure 6B, as in the support structure 6A according to exemplary embodiment 1, during rotation of the driven roller 362, the bearing 56 is held in a state in which it is rotated in the rotation direction C of the driven roller 362, as shown in FIG. 9B.

The protrusion 82 is formed as a structural component in which its portion coming into contact with the pressure receiving surface 56e of the bearing 56 can be in line contact along the axial line L2 of the rotating shaft 52. As shown in FIG. 10A, the protrusion 82 is formed as, for example, a horizontally extending triangular prism-shaped structural component having an edge line 82a that comes into contact with the bearing 56.

As shown in FIG. 8B, the protrusion 82 having the portion capable of line contact comes into line contact with the pressure receiving surface 56e of the pressure receiving portion 56d of the bearing 56.

In this case, when the driven roller 362 is not rotating, the bearing 56 can be easily brought to the above-described rotatable state. When the protrusion 82 in line contact along the axial line L2 of the rotating shaft 52 is used, the bearing 56 is further prevented from being inclined accidentally in a direction intersecting the axial line L2, as compared to the case when the protrusion 81 in point contact is used. Therefore, the posture of the bearing 56 in the direction of the axial line L2 is stabilized.

The term “line contact” encompasses the case in which the contact portion 82a of the protrusion 82 has a continuous or discontinuous rectangular shape with a certain width w2 on condition that the bearing 56 is maintained in the above-described rotatable state, as shown in FIG. 8B. In this case, the width w2 is shorter than the length k1 of the contact portion 82a along the axial line L2 of the rotating shaft 52 (w2<k1).

The pressing member 57 provided with the protrusion 82 includes a coil spring 571 having an end to which a component 85 having the protrusion 82 is attached (e.g., FIG. 8A), as is the pressing member 57 provided with the protrusion 81 (FIGS. 7A and 7B).

<Operational Advantages of Support Structure for Pair of First Output Rollers>

As shown in FIGS. 8A, 8B, and 9A, in the support structure 6B supporting the driven roller 362, when the driven roller 362 is not rotating, the bearing 56 is in line-contact with the protrusion 82 in the pressing member 57.

In the support structure 6B in this case, as in the support structure 6A, the bearing 56 is rotatable about the rotating shaft 52 within the movable space in the holding portion 74a of the support 73. In this case, the bearing 56 is in an unstable state in which it can easily rotate in the rotation direction C of the driven roller 362 and also in the reverse rotation direction. However, the posture of the bearings 56 along the axial line L2 of the rotating shaft 52 is in a stable state.

As shown in FIG. 9B, in the support structure 6B, when the driven roller 362 is rotating, the rotational force Mr in the rotation direction C of the driven roller 362 acts on the bearing 56, and therefore the bearing 56 is held in a state in which it is rotated in the rotation direction C of the driven roller 362 within the movable space in the holding portion 74a of the support 73.

Specifically, as shown in FIG. 9B, the bearing 56 in this case is rotated in the rotation direction C of the driven roller 362 within the movable space in the holding portion 74a of the support 73. Then part (a corner) of the bearing 56 comes into contact with part of the holding portion 74a, and the bearing 56 comes to rest, so that the bearing 56 is slightly inclined.

In this the support structure 6B, as in the support structure 6A, during rotation of the driven roller 362, the sliding friction between the bearing 56 and the rotating shaft 52 may change instantaneously, and the rotational force Mr may increase or decrease. For example, the rotational force Mr and the rotational drag force Mb may become substantially equal to each other (Mr≅Mb).

However, in the support structure 6B, the protrusion 82 in the pressing member 57 is in line contact with the bearing 56. Since the pressing member 57 is disposed such that its pressing force F acts toward the rotation center 02 of the rotating shaft 52, the vector of the load generated by the protrusion 82 is directed toward the rotation center 02 of the rotating shaft 52. Therefore, in the support structure 6B, as in the support structure 6A, the rotational drag force Mb itself that is caused by the pressing member 57 pressed against the bearing 56 and urges the bearing 56 to rest against the rotational force Mr is unlikely to be generated.

Therefore, also in the support structure 6B, as in the support structure 6A, the rotational drag force Mb is unlikely to increase to a level comparable to the rotational force Mr, and the relation between the rotational force Mr and the rotational drag force Mb is easily maintained such that the rotational force Mr is larger than the rotational drag force Mb (Mr>Mb).

Also in this support structure 6B, during rotation of the driven roller 362, the bearing 56 is easily maintained in a state in which it is rotated in the rotation direction C of the driven roller 362 within the holding portion 74a of the support 73. In this case, the bearing 56 is prevented from rotating in the reverse rotation direction opposite to the rotation direction C beyond the position at which the bearing 56 is in the rotatable state when the driven roller 362 is not rotating and from rotating back and forth repeatedly around the above position.

Therefore, also in this support structure 6B, as in the support structure 6A, generation of noise and vibration caused by repeated rotation of the bearing 56 within the movable space in the support 73 can be prevented or reduced.

In exemplary embodiment 2, the protrusion 82 in line contact may be, for example, a structural body including a semicylindrical member having an apex portion (ridge line) 82b extending substantially linearly in a lengthwise direction, as shown in FIG. 10B. This structural body may be disposed such that the apex portion 82b comes into contact with the bearing 56.

In this case, the apex portion 82b of the protrusion 82 is less worn due to contact with the bearing 56 than the protrusion 82 of the structural body shown in FIG. 10A, and the bearing 56 can be maintained in a desirable state for a long time.

EXEMPLARY EMBODIMENT 3

FIG. 11 shows a support structure 6C for the driven roller 362 in exemplary embodiment 3.

The support structure 6C according to exemplary embodiment 3 has the same structure as the support structure 6A according to exemplary embodiment 1 except that the protrusion 81 is disposed in the bearing 56. Therefore, in the support structure 6C, the same components as the support structure 6A are denoted by the same symbols in FIGS. 11A and 11B and subsequent figures, and their description will be omitted in principle.

In the support structure 6C, the protrusion disposed in the bearing 56 is a protrusion 83 that comes into point contact with one end of a coil spring serving as the pressing member 57, as shown in FIGS. 11A and 11B. Therefore, as shown in FIGS. 11A, 11B, and 12A, when the driven roller 362 is not rotating, the bearing 56 is rotatable about the rotating shaft 52.

Also in this support structure 6C, as in the support structure 6A according to exemplary embodiment 1, during rotation of the driven roller 362, the bearing 56 is held in a state in which it is rotated in the rotation direction C of the driven roller 362, as shown in FIG. 12B.

The protrusion 83 disposed in the bearing 56 is formed as a structural component in which its portion coming into contact with one end of the pressing member 57 has a spherical surface shape, as is the protrusion 81 in the support structure 6A. In this case, the pressing member 57 is formed as, for example, a coil spring 571 to which a component 85 having a flat surface serving as a portion 85a to be in contact with the protrusion 83 is attached to the one end.

As shown in FIG. 11B, the protrusion 83 formed as the spherical surface-shaped structural body comes into point contact with the one end of the coil spring 571 serving as the pressing member 57 (the flat portion 85a of the component 85). In this manner, when the driven roller 362 is not rotating, the bearing 56 can be easily brought to the above-described rotatable state.

Symbol 83a in FIG. 11B represents a portion of the protrusion 83 that is in contact with the one end of the coil spring 571 serving as the pressing member 57. The contact portion 83a substantially corresponds to the apex of the spherical surface-shaped protrusion 83.

In the support structure 6C, as in the support structure 6A, the pressing member 57 is disposed so as to be pressed toward the rotation center 02 of the rotating shaft 52 of the driven roller 362. Specifically, as shown in FIG. 12A, the pressing member 57 is disposed such that its pressing force F acts toward the rotation center 02 of the rotating shaft 52.

<Operational Advantages of Support Structure for Pair of First Output Rollers>

As shown in FIGS. 11A, 11B, and 12A, in this support structure 6C, when the driven roller 362 is not rotating, the protrusion 83 disposed in the bearing 56 is in point contact with the one end of the pressing member 57.

In the support structure 6C in this case, substantially as in the support structure 6A, the bearing 56 is rotatable about the rotating shaft 52 within the movable space in the holding portion 74a of the support 73. In this case, the bearing 56 is in an unstable state in which it can easily rotate in the rotation direction C of the driven roller 362 and also in the reverse rotation direction. However, the posture of the bearing 56 along the axial line L2 of the rotating shaft 52 is in a stable state.

As shown in FIG. 12B, in the support structure 6C, when the driven roller 362 is rotating, the rotational force Mr in the rotation direction C of the driven roller 362 acts on the bearing 56. Therefore, the bearings 56 is held in a state in which it is rotatable in the rotation direction C of the driven roller 362 within the movable space in the holding portion 74a of the support 73.

Specifically, as shown in FIG. 12B, the bearing 56 in this case is rotated in the rotation direction C of the driven roller 362 within the movable space in the holding portion 74a of the support 73. Then part (a corner) of the bearing 56 comes into contact with part of the holding portion 74a, and the bearing 56 comes to rest, so that the bearing 56 is slightly inclined.

In the support structure 6C, as in the support structure 6A etc., during rotation of the driven roller 362, the sliding friction between the bearing 56 and the rotating shaft 52 may change instantaneously, and the rotational force Mr may increase or decrease. Therefore, for example, the rotational force Mr and the rotational drag force Mb may become substantially equal to each other (Mr≅Mb).

However, in this support structure 6C, the protrusion 83 in the bearing 56 is in point contact with the pressing member 57. Since the pressing member 57 is disposed such that its pressing force F acts toward the rotation center 02 of the rotating shaft 52, the vector of the load generated by the protrusion 83 is directed toward the rotation center 02 of the rotating shaft 52. Therefore, in the support structure 6C, the rotational drag force Mb itself that is caused by the pressing member 57 pressed against the bearing 56 and acts against the rotational force Mr is unlikely to be generated.

Therefore, also in the support structure 6C, because of substantially the same reason as in the support structure 6A etc., the rotational drag force Mb is unlikely to increase to a level comparable to the rotational force Mr, and the relation between the rotational force Mr and the rotational drag force Mb is easily maintained such that the rotational force Mr is larger than the rotational drag force Mb (Mr>Mb).

Also in this support structure 6C, during rotation of the driven roller 362, the bearing 56 is easily maintained in a state in which it is rotated in the rotation direction C of the driven roller 362 within the holding portion 74a of the support 73. In this case, the bearing 56 is prevented from rotating in the reverse rotation direction opposite to the rotation direction C beyond the position at which the bearing 56 is in the rotatable state when the driven roller 362 is not rotating and from rotating back and forth repeatedly around the above position.

Therefore, also in the support structure 6C, substantially as in the support structure 6A, generation of noise and vibration caused by repeated rotation of the bearing 56 within the movable space in the support 73 can be prevented or reduced.

In exemplary embodiment 3, the protrusion 83 in point contact may be, for example, a different structural member such as that described in exemplary embodiment 1.

In exemplary embodiment 3, the protrusion 82 in line contact as exemplified in exemplary embodiment 2 may be used instead of the protrusion 83 in point contact.

EXEMPLARY EMBODIMENT 4

FIG. 13 shows a support structure 6D for a charging roller 220 in exemplary embodiment 4 and the charging device 22 using the support structure 6D.

This support structure 6D supports the charging roller 220 in the charging device 22 of the image forming unit 2. For example, the support structure 6A according to exemplary embodiment 1 (FIGS. 4A, 4B, 5A, 5B, etc.) is used as the support structure 6D.

The charging roller 220 is a rotary member 5C including, for example: a rotating shaft 221 to which a charging voltage is supplied; and a roller body 222 disposed on the rotating shaft 221 and having a multilayer structure including an elastic layer, a surface layer, etc. The charging roller 220 is in contact with the circumferential surface of the photoreceptor drum 21 rotating in the direction of arrow A and is driven to rotate by the photoreceptor drum 21 in a direction indicated by chain double-dashed arrow D, and the circumferential surface of the photoreceptor drum 21 is thereby charged.

A chain dashed line L3 in FIG. 13 etc. represents a virtual straight line (virtual line) connecting the rotation center 03 of the photoreceptor drum 21 to the rotation center 04 of the charging roller 220. A double-pointed arrow denoted by symbols E3 and E4 indicates moving directions when the support 73 movably supports the bearing 56 of the charging roller 220.

As shown in FIG. 13, in the support structure 6D supporting the charging roller 220, substantially as in the support structure 6A according to exemplary embodiment 1, the protrusion 81 disposed in the pressing member 57 is in point contact with the pressure receiving surface 56e of the pressure receiving portion 56d of the bearing 56 (see, for example, FIG. 6B). In this case, as shown in FIG. 14A, when the charging roller 220 is not rotating, the bearing 56 is rotatable about the rotating shaft 221.

As shown in FIG. 14B, also in this support structure 6D, substantially as in the support structure 6A according to exemplary embodiment 1, when the charging roller 220 is rotating, the bearing 56 is maintained in a state in which it is rotated in the rotation direction D of the charging roller 220.

<Operational Advantages of Support Structure for Charging Roller>

As shown in FIGS. 13 and 14A, in the support structure 6D for the charging roller 220, when the charging roller 220 is not rotating, the bearing 56 is in point contact with the protrusion 81 disposed in the pressing member 57.

In the support structure 6D in this case, as in the support structure 6A, the bearing 56 is rotatable about the rotating shaft 221 within the movable space in the holding portion 74a of the support 73.

As shown in FIG. 14B, in the support structure 6D, when the charging roller 220 is rotating, the rotational force Mr in the rotation direction D of the charging roller 220 acts on the bearing 56. Therefore, the bearing 56 is held in a state in which it is rotatable in the rotation direction D within the movable space in the holding portion 74a of the support 73.

Specifically, as shown in FIG. 14B, the bearing 56 in this case is rotated in the rotation direction D of the charging roller 220 within the movable space in the holding portion 74a of the support 73. Then part (a corner) of the bearing 56 comes into contact with part of the holding portion 74a, and the bearing 56 comes to rest, so that the bearing 56 is slightly inclined.

Also in the support structure 6D, as in the support structure 6A, during rotation of the charging roller 220, the sliding friction between the bearing 56 and the rotating shaft 221 may change instantaneously, and the rotational force Mr may increase or decrease. For example, the rotational force Mr and the rotational drag force Mb may become substantially equal to each other (Mr≅Mb).

However, in the support structure 6D, because of the same reason as in the support structure 6A, the rotational drag force Mb is unlikely to increase to a level comparable to the rotational force Mr, and the relation between the rotational force Mr and the rotational drag force Mb is easily maintained such that the rotational force Mr is larger than the rotational drag force Mb (Mr>Mb).

Also in this support structure 6D, during rotation of the charging roller 220, the bearing 56 is easily maintained in a state in which it is rotated in the rotation direction D of the charging roller 220 within the holding portion 74a of the support 73. In this case, the bearing 56 is prevented from rotating in the reverse rotation direction opposite to the rotation direction C beyond the position at which the bearing 56 is in the rotatable state when the charging roller 220 is not rotating and from rotating back and forth repeatedly around the above position.

Therefore, also in the support structure 6D, as in the support structure 6A, generation of noise and vibration caused by repeated rotation of the bearing 56 within the movable space in the support 73 can be prevented or reduced.

In the support structure 6D, the generation of noise and vibration during rotation of the charging roller 220 is prevented or reduced. Therefore, in the charging device 22 formed using the support structure 6D, charging can be performed desirably without generation of noise and vibration.

OTHER EXEMPLARY EMBODIMENTS

In the structural examples shown in exemplary embodiments 1 to 3, one of the support structures 6A to 6C is used as the structure for supporting the driven roller 362 (the rotary member 5B) of the pair of first output rollers 36. However, any of them may be used as a structure for supporting the driving roller 361 (the rotary member 5A) of the pair of first output rollers 36.

In the pair of first output rollers 36, the driving roller 361 may be replaced with an elastic roller having the function of correcting curl of a recording paper sheet 9. The elastic roller is, for example, a continuous single roller such as the driven roller 362, and an elastic body is used as its roller body.

Each of the support structures 6A to 6C exemplified in exemplary embodiments 1 to 3 can be used for a transport device including a pair of transport rollers (rotary members) that are in pressure contact with each other and are rotated and transport a recording paper sheet 9 held therebetween. Specifically, each of the support structures 6A to 6C can be used as a support structure for at least one of the pair of transport rollers.

Each of the support structure 6A to 6C exemplified in exemplary embodiments 1 to 3 can be used as the support structure 6D for the charging roller 220 in the charging device 22 of the image forming unit 2 exemplified in exemplary embodiment 4, but this is not a limitation. Each of the support structures 6A to 6C may be used as the support structure for a different rotary member. Examples of such a rotary member include a transfer roller and fixing roller.

Each of the support structures 6A to 6C may be used as the support structure for a pressing roller pressed against a portion of an endless belt that is not supported by a support roller. In this case, a rotary member in contact with the pressing roller is a portion of the rotating belt that is not supported by the support roller.

Moreover, an image forming apparatus including the rotary member using one of the support structures 6A to 6D and the transport device 7 or the charging device 22 is not limited to the apparatus forming a monochrome image using a single-color toner as exemplified in exemplary embodiments 1 to 4. Image forming apparatuses of different types may be used.

Examples of the image forming apparatuses of different types include: an image forming apparatus that forms a multicolor image using a combination of plural color toners; and an image forming apparatus that forms an image by jetting ink droplets.

The rotary member and the transport device 7 that use any of the support structures 6A to 6C may be a rotary member and a transport device of an apparatus other than the image forming apparatus.

The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.

Claims

1. A rotary member support structure comprising:

a rotary member including a shaft;

a bearing that rotatably supports the shaft of the rotary member;

a pressing member that presses the bearing in one direction; and

a support that supports the bearing such that the bearing is movable in a pressing direction of the pressing member,

wherein, when the rotary member is not rotating, the bearing and the pressing member are in contact with each other such that the bearing is rotatable about the shaft.

2. A rotary member support structure comprising:

a rotary member including a shaft;

a bearing that rotatably supports the shaft of the rotary member;

a pressing member that presses the bearing in one direction; and

a support that supports the bearing such that the bearing is movable in a pressing direction of the pressing member,

wherein a first one of the bearing and the pressing member has a protrusion, and a second one of the bearing and the pressing member is in contact with the protrusion,

and wherein, when the rotary member is not rotating, the bearing is rotatable about the shaft.

3. The rotary member support structure according to claim 1, wherein, during rotation of the rotary member, the bearing is maintained in a state in which the bearing is rotatable in a rotation direction of the rotary member.

4. The rotary member support structure according to claim 2, wherein, during rotation of the rotary member, the bearing is maintained in a state in which the bearing is rotatable in a rotation direction of the rotary member.

5. The rotary member support structure according to claim 1, wherein the pressing member is disposed so as to press the bearing toward the rotation center of the shaft of the rotary member.

6. The rotary member support structure according to claim 2, wherein the pressing member is disposed so as to press the bearing toward the rotation center of the shaft of the rotary member.

7. The rotary member support structure according to claim 1, wherein the bearing and the pressing member are in point contact with each other or in line contact with each other along an axial line of the shaft.

8. The rotary member support structure according to claim 2, wherein the protrusion and the second one of the bearing and the pressing member are in point contact with each other or in line contact with each other along an axial line of the shaft.

9. The rotary member support structure according to claim 2, wherein the protrusion is disposed in the pressing member.

10. The rotary member support structure according to claim 9, wherein the pressing member is a coil spring in which a component having the protrusion is attached to one end thereof.

11. A transport device comprising:

a pair of transport rotary members that transport a transportation object held therebetween; and

the rotary member support structure according to claim 1, the rotary member support structure supporting at least one of the pair of transport rotary members.

12. A charging device comprising:

a charging rotary member; and

the rotary member support structure according to claim 1, the rotary member support structure supporting the charging rotary member.

13. An image forming apparatus comprising the rotary member support structure according to claim 1.

14. An image forming apparatus comprising the transport device according to claim 11.

15. An image forming apparatus comprising the charging device according to claim 12.