Contact and separating device and image forming apparatus

A contact and separating device includes a roller member disposed to be capable of being contacted to an abutted member, a bearing member supporting the roller member and configured to be movable together with the roller member in a contact and separation direction with respect to the abutted member, and a biasing member biasing the roller member toward the abutted member through the bearing member. The contact and separating device further includes a separation member holding the roller member and the abutted member in a separation state where the roller member is separated from the abutted member against a biasing force of the biasing member by engaging with the bearing member in the separation state, and a release member releasing engagement between the bearing member and the separation member by moving the separation member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a contact and separating device that enables contact and separation between an abutted member such as an intermediate transfer belt and a roller member such as a transfer roller, and an image forming apparatus including the contact and separating device.

2. Description of the Related Art

Hitherto, an apparatus using an intermediate transfer belt and a transfer roller is well known as an electrophotographic image forming apparatus. The image forming apparatus is in an unused state for a long period of time until reaching an end user from the shipment thereof. In particular, the apparatus is often placed in a harsh environment such as a high-temperature and humidity environment during the transportation thereof. When the image forming apparatus is not used for a long period of time in such a state, the transfer roller is placed for a long period of time in a state where the transfer roller is pressed and welded into the intermediate transfer belt, and thus there is a concern of an image being disturbed by the attachment of an exuding material to the surface of the intermediate transfer belt.

In addition, the local deformation of the transfer roller may cause defective transfer. For this reason, a shipment configuration may be adopted in which the intermediate transfer belt and the transfer roller are set to be in a light-pressure state or a separation state by interposing a sheet-shaped member between the intermediate transfer belt and the transfer roller or inserting a separation member into the transfer roller side. In addition, as disclosed in JP-A-2006-113283, a configuration is proposed in which separation is released by using a driving gear being transmitted to a secondary transfer outer roller during an initial startup, from the viewpoint of improving serviceability and preventing an operational error due to forgotten removal or the like.

However, in the configuration disclosed in JP-A-2006-113283, the meshing of the driving gear with a transmitted gear of a secondary transfer roller even after release is a precondition, and thus the driving gear meshes with the transmitted gear even in a separation state. For this reason, a sufficient amount of separation cannot be secured between both of the gears, and thus it is difficult to sufficiently separate the secondary transfer roller from the intermediate transfer belt. Accordingly, there is a concern that exudation from the secondary transfer roller onto the surface of the intermediate transfer belt and the local deformation of the secondary transfer roller may not be avoided. In addition, the configuration cannot be adopted in a system in which a secondary transfer outer roller rotates in a driven manner.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided a contact and separating device including a roller member which is disposed so as to be capable of being contacted to and separated from an abutted member, a bearing member which supports the roller member and is movable together with the roller member in a contact and separation direction with respect to the abutted member, a biasing member which biases the roller member toward the abutted member through the bearing member, a separation member which engages with the bearing member in a separation state where the roller member is separated from the abutted member against a biasing force of the biasing member to thereby hold the roller member and the abutted member in the separation state, and a release member which releases engagement between the bearing member and the separation member by moving the separation member by the driving thereof.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, an embodiment of an image forming apparatus100having a contact and separating device45mounted thereto according to the present invention will be described with reference to the accompanying drawings. Meanwhile, the same reference numbers and signs denote the same or corresponding portions through the drawings.FIG. 1is a schematic cross-sectional view showing a schematic configuration of the image forming apparatus100such as a tandem type full color digital printer of an intermediate transfer system in this embodiment.

As shown inFIG. 1, the image forming apparatus100includes an apparatus main body100a. The image forming apparatus100performs an imaging operation based on image information which is input from an external host device (not shown) which is connected to a control unit (not shown) so as to be capable of communicating therewith, and forms a full color image on a recording medium and outputs the image. The external host device means a computer, an image reader, or the like.

The apparatus main body100aincludes image forming portions1Y,1M,1C, and1Bk provided in a central portion within the apparatus main body100a, a paper feeding unit28provided in a lower portion within the apparatus main body100a, a conveyance section52, and an ejection tray6provided in an upper portion of the apparatus main body100a.

An intermediate transfer belt unit9including an endless flexible intermediate transfer belt8is disposed above the image forming portions1Y,1M,1C, and1Bk. The intermediate transfer belt8is stretched so as to be wound around a secondary transfer inner roller7, a tension roller14, and an extension roller15, and rotates at a predetermined speed in a counterclockwise direction (direction of an arrow E) ofFIG. 1by the driving of the secondary transfer inner roller7.

A secondary transfer outer roller20as a roller member and a contact and separating device45including the secondary transfer outer roller20are disposed on the opposite side to the secondary transfer inner roller7with the intermediate transfer belt8interposed therebetween. The secondary transfer outer roller20constitutes a transfer roller that transfers an image to a recording medium P from the intermediate transfer belt8.

The contact and separating device45includes the secondary transfer outer roller20as a roller member, a bearing member22, a transfer coil spring21as a biasing member, a separation member24(seeFIG. 2), and a release member25(seeFIG. 2). The release member25moves the separation member24by being driven to thereby release engagement between the bearing member22and the separation member24.

The secondary transfer outer roller20is disposed so as to be capable of being contacted to and separated from the intermediate transfer belt8as an abutted member. In addition, a secondary transfer portion17is formed by an abutting portion (nip portion) between the intermediate transfer belt8, which is wound around the secondary transfer inner roller7, and the secondary transfer outer roller20which is pressed and welded into the intermediate transfer belt.

The image forming portions1Y,1M,1C, and1Bk forming an image in the intermediate transfer belt8as an abutted member are disposed in a row at predetermined intervals along a belt rotation direction on the lower side of the intermediate transfer belt8. Each of the image forming portions1Y to1Bk is constituted by an electrophotographic process mechanism of a laser exposure system. Each of the image forming portions1Y to1Bk includes a photoconductive drum18which rotates at a predetermined speed in a clockwise direction of an arrow.

A charging roller19charging the photoconductive drum18, a developing unit26, a primary transfer roller16, and a drum cleaner device27are disposed in the vicinity of each of the photoconductive drums18. Meanwhile, in this embodiment, the abutted member according to the present invention is applied to the intermediate transfer belt8, and the roller member is applied to the secondary transfer outer roller20. However, the present invention is not limited to this configuration, and it is also possible to apply the abutted member according to the present invention to the photoconductive drum18and to apply the roller member to the charging roller19.

Each primary transfer roller16is disposed on the inner side of the intermediate transfer belt8, and is pressed and welded into the photoconductive drum18opposed thereto through a descending side belt portion of the intermediate transfer belt8. A primary transfer portion29is constituted by an abutting portion between each photoconductive drum18and the intermediate transfer belt8.

A laser exposure unit32corresponding to the photoconductive drum18of each image forming portion is disposed below the image forming portions1Y,1M,1C, and1Bk. The laser exposure unit32is constituted by a laser emitting portion, which performs light emission corresponding to a time-series electrical digital pixel signal of given image information, a polygon mirror, a reflecting mirror, and the like.

In addition, the paper feeding unit28includes a paper feeding cassette1in which recording media P having various sizes are loaded and accommodated, and a paper feeding roller2which is disposed corresponding to the paper feeding cassette1.

The above-described control unit (not shown) causes each of the image forming portions1Y,1M,1C, and1Bk to perform imaging, on the basis of a color separation image signal which is input from the external host device. Thus, the image forming portions1Y,1M,1C, and1Bk form yellow, magenta, cyan, and black color toner images at a predetermined control timing on the surfaces of the rotating photoconductive drums18. Meanwhile, the electrophotographic imaging principle and process of forming a toner image in the photoconductive drum18are well known, and thus the description thereof will be omitted.

The primary transfer portion29sequentially transfers the toner images formed on the surfaces of the photoconductive drums of the image forming portions in an overlapping manner to the outer surface of the intermediate transfer belt8, which rotates in a forward direction with respect to the rotation direction of the photoconductive drum18and at a speed corresponding to the rotational speed of the photoconductive drum18. Thus, unfixed full color toner images, due to the above-described four toner images being superposed on the surface of the intermediate transfer belt8, are synthesized.

On the other hand, the paper feeding roller2corresponding to the paper feeding cassette1rotates at a predetermined paper-feeding timing. Thus, one recording medium P loaded and accommodated in the paper feeding cassette1is separated and fed, and is then conveyed to a registration roller34via a vertical conveyance path33of a conveyance section52.

The registration roller34timing-conveys the recording medium P so that a tip portion of the recording medium P reaches the secondary transfer portion17in accordance with a timing when a tip of the full color toner image on the rotating intermediate transfer belt8reaches the secondary transfer portion17. Thus, the secondary transfer of the full color toner images on the intermediate transfer belt8is sequentially performed on the surface of the recording medium P collectively by the secondary transfer portion17.

The recording medium P having passed through the secondary transfer portion17is separated from the surface of the intermediate transfer belt, is guided to the vertical guide35of the conveyance section52, and is then introduced into a fixing nip portion N of the fixing unit36. The full color toner images are melted and mixed, and are then fixed as fixed images onto the surface of the recording medium P by the fixing unit36. The recording medium P having left the fixing unit36passes through a conveyance path37as a full color image formation, and is then discharged onto the ejection tray6by a paper ejection roller5.

The surface of the intermediate transfer belt8after the recording medium P is separated by the secondary transfer portion17is cleaned by a belt cleaning unit (not shown), which is disposed so as to face the tension roller14, upon the removal of residual attachments such as a secondary toner failed to be transferred, and is repeatedly used for imaging.

On the other hand, in a case of two-sided image formation, the conveyance path of the recording medium is switched by a switching member10. The recording medium is conveyed by a reversing roller11, is switch-back conveyed immediately after a back end of the recording medium passes through a bifurcation point, and is guided to a two-sided conveyance path12. Then, the recording medium is conveyed again to the secondary transfer portion17by conveyance rollers38and13and a conveyance roller39during duplex printing. After an image is formed on the rear surface of the recording medium, the recording medium passes through the fixing unit36and is finally discharged onto the ejection tray6, thereby terminating a series of image forming operations.

A drive source51rotating the conveyance rollers38and13is disposed in the apparatus main body100a. The drive source51is connected to a rotation axis of the release member25through a transmission mechanism, not shown in the drawing, so as to be also capable of rotating the release member25, to be described later, in addition to the rotation of the rollers. Accordingly, since the drive source51of the conveyance rollers38and13can be shared, it is possible to simplify the configuration without having to separately provide a drive source of the release member25.

Next, a configuration in the vicinity of the transfer roller according to this embodiment will be described with reference toFIGS. 2A and 2BtoFIG. 5. Meanwhile,FIGS. 2A and 2Bshow the contact and separating device45according to this embodiment.FIG. 2Ais a schematic diagram showing a separation state of the contact and separating device45, andFIG. 2Bis a configuration diagram showing a separation release state of the contact and separating device45.FIG. 3is a configuration diagram showing a separation release operation of the bearing member22according to this embodiment, andFIGS. 4A to 4CandFIGS. 5A and 5Bare perspective views showing the bearing member22by a different viewing angle.

That is, as shown inFIGS. 2A and 2B, bearing supporting portions46aand46bare provided on the apparatus main body100aside, and the bearing supporting portions46aand46bsupport the bearing member22so as to be capable of being contacted to and separated from the intermediate transfer belt8as an abutted member. In a state where the bearing member22supports the secondary transfer outer roller20, the bearing member22is configured to be movable together with the secondary transfer outer roller20in a contact and separation direction (direction of an arrow W ofFIG. 2A) with respect to the intermediate transfer belt8.

The secondary transfer outer roller20supported by the bearing member22is biased by the transfer coil spring21as a biasing portion so as to have a predetermined abutting pressure against the intermediate transfer belt (abutted member)8and the secondary transfer inner roller7. In this manner, the transfer coil spring21biases the secondary transfer outer roller20toward the intermediate transfer belt8through the bearing member22.

Meanwhile, the secondary transfer outer roller20is configured using an iron metal cored bar (not shown) as a cored bar and a semiconductive sponge (not shown) consisting primarily of an NBR Hydrin rubber as an elastic layer.

As shown inFIGS. 2A and 2BandFIG. 3, one end and the other end of the transfer coil spring21are supported between a boss22ain the bearing member22and a boss (not shown) which protrudes from a bearing surface (not shown) of the bearing supporting portion46b. Thus, the transfer coil spring21of which the upper and lower ends are fixedly held biases the secondary transfer outer roller20of which the rotation axis20ais supported by a bearing concave portion22dformed in an upper portion of the bearing member22toward the intermediate transfer belt8. The bearing member22is disposed so as to be slidable only in the contact and separation direction (direction of the arrow W) in portions constituting the bearing surfaces of the bearing supporting portions46aand46b, and is constrained by the bearing supporting portions46aand46bin other directions.

As shown inFIG. 3, the bearing member22includes a circular guiding portion22bwhich rotatably guides and supports the separation member24in an end on the opposite side to the bearing concave portion22d, that is, in a portion on the opposite side to a pressure direction (biasing direction) X of the bearing member22. Further, the bearing member22includes a bearing side engagement portion22c.

The bearing supporting portion46ais provided with a supporting portion side engagement portion46c, which prevents a separation side engagement portion47(seeFIG. 3) from rotating in a predetermined direction (clockwise direction ofFIG. 2A) by engaging with a first engagement portion24a. That is, the first engagement portion24aregulates the rotation of the separation member24in a direction of the predetermined position in the separation state by engaging with a supporting portion side engagement portion46cprovided in a bearing supporting portion46asupporting the bearing member22to be movable in the contact and separation direction.

The bearing side engagement portion22cengages with a second engagement portion24cin a separation state, and allows the separation side engagement portion47to rotate in a predetermined direction (clockwise direction ofFIG. 2A) when the engagement between the first engagement portion24aand the supporting portion side engagement portion46cis released. The engagement between the bearing side engagement portion22cand the second engagement portion24cof the separation side engagement portion47is released when the separation side engagement portion47rotates to be set to be located at a predetermined position (position ofFIG. 2B), thereby causing the bearing member22to be movable toward the intermediate transfer belt8.

The circular guiding portion22bincludes a portion having a circular inner circumference and a linear notch portion22fextending to the opposite side to the pressure direction from the circular portion. A boundary portion between the circular portion and the notch portion22fof the circular guiding portion22bis formed as a chamfer or an inclined portion of a corner R. In addition, the bearing supporting portion46b(seeFIGS. 2A and 2B) holds the separation member24which is rotatable on an axis parallel to the secondary transfer outer roller20, in the vicinity of the circular guiding portion22bof the bearing member22.

The bearing member22includes the above-described notch portion22fwhich is formed adjacent to the bearing side engagement portion22c. When the separation side engagement portion47including the first engagement portion24aand the second engagement portion24crotates to be set to be located at a predetermined position (position shown inFIG. 2B), the notch portion22fallows the second engagement portion24cto escape in the opposite direction to the pressure direction X of the transfer coil spring21. The second engagement portion24chas an inclined portion that connects the circular guiding portion22band the notch portion22fat the chamfer or the corner R.

Further, the bearing member22includes a regulation portion22g(FIG. 3) which regulates the rotation of the separation side engagement portion47at a predetermined position. A flat portion22hformed to be bent from the bearing concave portion22dis provided with a longitudinal through hole portion22ewhich passes through the front and back of the bearing member22. The diameters of the circular guiding portion22bof the bearing member22and the second engagement portion24cof the separation member24are set so that a fitting relationship is established to be [JIS fitting of approximately H10/f10, H9/f9, and H8/f8].

The release member25, which rotates independently of the rotation of the secondary transfer outer roller20, is placed at a position facing the separation member24. As shown inFIG. 3toFIGS. 5A and 5B, the separation member24engages with the bearing member22in a separation state where the secondary transfer outer roller20is separated from the intermediate transfer belt8against a biasing force of the transfer coil spring21to thereby hold the secondary transfer outer roller20and the intermediate transfer belt8in the separation state. The separation member24moves to a position where a release state is maintained, regardless of the driving of the release member25, by releasing the engagement with the bearing member22by the release member25.

As described above, the release member25is driven by the drive source51which rotates the conveyance rollers38and13, causes a claw-shaped releasing engagement portion25arotating in the counterclockwise direction ofFIG. 2Ato engage with a released engagement portion24b, and rotates the separation member24in the release direction (clockwise direction ofFIG. 2A). A pair of releasing engagement portions25ais configured to protrude in two directions perpendicular to the rotation center.

The separation member24includes the separation side engagement portion47, having the first engagement portion24aand the second engagement portion24c, which is rotatably supported together with the released engagement portion24bby the bearing supporting portions46aand46b. The separation member24includes a shaft43capable of passing through the circular guiding portion22b, in the center thereof. The shaft43of the separation member24is rotatably supported by the bearing supporting portions46aand46bsides.

The first engagement portion24ais a member, having flexibility, which extends in the form of an arc so as to be directed in a counterclockwise direction from one end (right ends ofFIG. 2AandFIG. 3) of the second engagement portion24c. More specifically, the first engagement portion24ais configured to be capable of being elastically deformed such that the first engagement portion24amoves over the supporting portion side engagement portion46cand releases the engagement with the supporting portion side engagement portion46cin response to the separation member24rotated by the release member25in the separation state. The second engagement portion24cprotrudes in a radial direction from the axial central portion of the shaft43. The separation member24includes the released engagement portion24bwhich protrudes in the form of an arm downward from the end of the shaft43and which engages with the claw-shaped releasing engagement portion25a.

Hereinafter, a description will be made with a focus on the operation of the contact and separating device45according to this embodiment which has the above-described configuration.

First, the secondary transfer outer roller20is in a separation state where the secondary transfer outer roller is moved to the opposite side to the pressure direction X up to a light-pressure position or a non-contact position with respect to the intermediate transfer belt8and is held (FIG. 2A). In this separation state, the circular guiding portion22bof the bearing member22and the second engagement portion24cof the separation member24are substantially coaxially located, and the separation member24rotates so that a linear portion of the second engagement portion24cis substantially perpendicular to the pressure direction.

For this reason, the bearing side engagement portion22cof the bearing member22engages with the second engagement portion24cto thereby hold the separation member24so as not to rotate over a separation holding state, and the rotation of the first engagement portion24aof the separation member24in the release direction of the separation member24is regulated by the supporting portion side engagement portion46c. Thus, the engagement between the bearing side engagement portion22cand the second engagement portion24cis maintained to thereby hold the separation state.

In the above-described separation state, for example, when the image forming apparatus100which is carried in a packed state is set to be in an ordinary usage state and then the release member25rotates upon the driving of the drive source51by the application of a main power supply or the like, the following state is set.

That is, the claw-shaped releasing engagement portion25aabuts against the arm-shaped released engagement portion24bof the separation member24by the relatively slow rotation of the release member25in the counterclockwise direction ofFIG. 2A. Thus, the separation member24is pushed in the release direction (clockwise direction ofFIG. 2A) through the released engagement portion24b, and the first engagement portion24amoves over the supporting portion side engagement portion46cby the flexibility thereof. Then, a balance between the engagement of the bearing side engagement portion22cwith the second engagement portion24cand the biasing force of the transfer coil spring21is lost, and the separation member24rotates in a clockwise direction in a manner that the notch portion22fpasses through the second engagement portion24c.

At this time, the linear portion of the second engagement portion24crotates up to an angle which is substantially parallel to the pressure direction (direction of an arrow X ofFIG. 3) of the secondary transfer outer roller20. Thus, the bearing member22moves in the pressure direction in a manner that the notch portion22fpasses through the second engagement portion24c, and thus the separation state is released (seeFIG. 2B). That is, as shown inFIG. 3, when the separation member24rotates up to the vicinity of the superposition of an inclined portion24don an inclined portion22iof the bearing member22, the separation member24rotates without abutting against the release member25by the biasing force of the transfer coil spring21when the notch portion22fpasses through the second engagement portion24c.

At this time, even when the release member25continuously rotates in a state where the separation is released, the separation member24is set to be located at a position where the separation member does not come into contact with the release member25. As described above, a separation release timing is consistent with the time of applying a power supply after the setting to the ordinary usage state, and thus it is possible to reliably prevent the occurrence of a paper jam and a defective image due to user's forgetting to remove a transfer pressure release member or the like as in the related art. In addition, there is no influence on the imaging operation due to the separation release operation. Thus, an ordinary usage state where the secondary transfer outer roller20abuts against the intermediate transfer belt8is set.

According to this embodiment described above, when the image forming apparatus100is not used for a long period of time from packing to conveyance, the secondary transfer outer roller20is separated from the intermediate transfer belt8by a simple configuration, and thus it is possible to reliably suppress a pressurizing force therebetween. In addition, the separation state can be automatically released by the rotating release member25by low torque without damaging the facing component, and thus it is possible to prevent disadvantages such as exudation (weeping) from the secondary transfer outer roller20and the occurrence of a defective image.

That is, a state where a regular transfer pressure is automatically applied can be set during an initial rotation at the time of applying a power supply, and thus it is possible to reliably prevent the occurrence of a paper jam and a defective image due to user's forgetting to remove the transfer pressure release member. In this manner, an arbitrary amount of separation is secured regardless of whether or not a roller member such as the secondary transfer outer roller20is a driving component or a driven component, and thus it is possible to solve the problems of exudation onto the surface of the intermediate transfer belt and the local deformation of the secondary transfer outer roller20.

Next, reference will be made toFIGS. 6Aand,6B andFIG. 7to describe a second embodiment in which a configuration of the contact and separating device45in the first embodiment is partially changed.FIGS. 6A and 6Bshow a contact and separating device in this embodiment.FIG. 6Ais a configuration diagram showing a separation state of the contact and separating device, andFIG. 6Bis a configuration diagram showing a separation release state of the contact and separating device.FIG. 7is a configuration diagram showing a separation state of the contact and separating device in this embodiment by a different viewing angle. Meanwhile, in the second embodiment, the same components as in the first embodiment will be denoted by the same reference numerals and signs, and the description thereof will be omitted.

That is, in this embodiment, as shown inFIGS. 6A and 6BandFIG. 7, a separation member30is rotatably fitted to a circular guiding portion22bprovided in a bearing member22having the same configuration as that in the first embodiment. A shaft43of the separation member30is rotatably supported by bearing supporting portions46aand46bsides.

The bearing supporting portion46ais provided with a supporting portion side engagement portion46c(seeFIG. 2A) which prevents a separation side engagement portion47from rotating in a predetermined direction (clockwise direction ofFIG. 6A) by engaging with a first engagement portion30a.

The bearing side engagement portion22cengages with a second engagement portion30cin a separation state, and allows the separation side engagement portion47to rotate in a predetermined direction (clockwise direction ofFIG. 6A) when engagement between the first engagement portion30aand the supporting portion side engagement portion46cis released. The engagement between the bearing side engagement portion22cand the second engagement portion30cof the separation side engagement portion47is released when the separation side engagement portion47rotates to be set to be located at a predetermined position (position ofFIG. 6B), thereby causing the bearing member22to be movable toward an intermediate transfer belt8. In addition, the bearing supporting portion46b(seeFIG. 2) holds the separation member30which is rotatable on an axis parallel to the secondary transfer outer roller20in the vicinity of the circular guiding portion22bof the bearing member22.

When the separation side engagement portion47including the first engagement portion30aand the second engagement portion30crotates to be set to be located at a predetermined position (position ofFIG. 6B), a notch portion22fof the bearing member22allows the second engagement portion30cto escape in the opposite direction to a pressure direction X of a transfer coil spring21. The second engagement portion30chas an inclined portion that connects the circular guiding portion22band the notch portion22fat a chamfer or a corner R.

The diameters of the circular guiding portion22bof the bearing member22and the second engagement portion30cof the separation member30are set so that a fitting relationship is established to be [JIS fitting of approximately H10/f10, H9/f9, and H8/f8].

A release member31, which rotates independently of the rotation of the secondary transfer outer roller20, is placed at a position facing the separation member30. As shown inFIGS. 6A and 6BandFIG. 7, the separation member30engages with the bearing member22in a separation state where the secondary transfer outer roller20is separated from the intermediate transfer belt8against a biasing force of the transfer coil spring21to thereby hold the secondary transfer outer roller20and the intermediate transfer belt8in the separation state. The separation member30moves to a position where a release state is maintained, regardless of the driving of the release member31, by releasing the engagement with the bearing member22by the release member31.

The gear-shaped release member31is driven by a drive source51(seeFIG. 1) which rotates conveyance rollers38and13. A tooth portion31aas a releasing engagement portion which rotates in a counterclockwise direction ofFIGS. 6A and 6Bis caused to engage with a chipped tooth gear portion30bto thereby rotate the separation member30in a release direction (clockwise direction ofFIG. 2A). As described above, the release member31of this embodiment is configured to have a gear shape, and the tooth portion31aof the release member31constitutes a releasing engagement portion. In this embodiment, the chipped tooth gear portion30bof the separation member30which meshes with the tooth portion31aconstitutes a released engagement portion.

The separation member30in this embodiment includes the separation side engagement portion47, having the first engagement portion30aand the second engagement portion30c, which is rotatably supported together with the chipped tooth gear portion30bas a released engagement portion by the bearing supporting portions46aand46b. The separation member30includes a shaft43capable of passing through the circular guiding portion22b, in the center thereof. The shaft43is rotatably supported by the bearing supporting portions46aand46bsides.

The first engagement portion30a, having flexibility, extends in the form of an arc so as to be directed in a counterclockwise direction from one end of the second engagement portion30c. The second engagement portion30cprotrudes in a radial direction from the axial central portion of the shaft43. The separation member30includes the chipped tooth gear portion30bas a released engagement portion. The chipped tooth gear portion protrudes in the form of an arm downward from the end of the shaft43and engages with the tooth portion31aof the release member31. In other words, the releasing engagement portion according to the present invention is configured as the tooth portion31aof the release member31having a gear shape, and the released engagement portion is configured as the chipped tooth gear portion30bof the separation member30which meshes with the tooth portion31a.

Also in this embodiment, the drive source51of the conveyance rollers38and13is shared, and the release member31can rotate independently of the rotation of the secondary transfer outer roller20, and thus it is possible to simplify the configuration without having to separately provide a drive source of the release member31.

Hereinafter, a description will be made with a focus on the operation of the contact and separating device45according to this embodiment which has the above-described configuration.

First, the secondary transfer outer roller20is in a separation state where the secondary transfer outer roller is moved to the opposite side to the pressure direction X up to a light-pressure position or a non-contact position with respect to the intermediate transfer belt8and is held (FIG. 6A). In this separation state, the circular guiding portion22bof the bearing member22and the second engagement portion30cof the separation member30are substantially coaxially located, and the separation member24rotates so that a linear portion of the second engagement portion30cis substantially perpendicular to the pressure direction.

For this reason, the bearing side engagement portion22cof the bearing member22engages with the second engagement portion30cto thereby hold the separation member30so as not to rotate over a separation holding state. In addition, the rotation of the first engagement portion30aof the separation member30in the release direction of the separation member30is regulated by the supporting portion side engagement portion46c(seeFIG. 2). Thus, the engagement between the bearing side engagement portion22cand the second engagement portion30cis maintained to thereby hold the separation state.

In the above-described separation state, for example, when the image forming apparatus100which is carried in a packed state is set to be in an ordinary usage state and then the release member31rotates upon the driving of the drive source51by the application of a main power supply or the like, the following state is set.

That is, the tooth portion31arotates while meshing with the chipped tooth gear portion30bof the separation member30by the relatively slow rotation of the release member31in the counterclockwise direction ofFIG. 6A. Thus, the separation member30rotates in the release direction (clockwise direction ofFIG. 6A) through the chipped tooth gear portion30b, and the first engagement portion30acrosses over the supporting portion side engagement portion46cby the flexibility thereof. Accordingly, a balance between the engagement of the bearing side engagement portion22cwith the second engagement portion30cand the biasing force of the transfer coil spring21is lost, and the separation member30rotates in a clockwise direction in a manner that the notch portion22fpasses through the second engagement portion30c.

At this time, when the linear portion of the second engagement portion30crotates up to an angle which is substantially parallel to the pressure direction (direction of an arrow X ofFIG. 6B) of the secondary transfer outer roller20, the bearing member22moves in the pressure direction in a manner that the notch portion22fpasses through the second engagement portion30c. Thus, as shown inFIG. 6B, the separation state is released. That is, as shown inFIG. 6B, when the separation member30rotates up to the vicinity of the superposition of an inclined portion30don an inclined portion22iof the bearing member22, the notch portion22fpasses through the second engagement portion30c. The separation member30rotates without abutting against the release member31by the biasing force of the transfer coil spring21at that time.

At this time, even when the release member31continuously rotates in a state where the separation is released, the separation member30is set to be located at a position where the separation member does not come into contact with the release member31.

Also in this embodiment described above, substantially the same effects as in the first embodiment can be obtained.

Next, a third embodiment to which the present invention is applied will be described with reference toFIG. 8andFIGS. 9A and 9B.FIG. 8is a configuration diagram showing a separation state of a contact and separating device in this embodiment.FIG. 9Ais a cross-sectional view showing a state of engagement in a separation state in this embodiment, andFIG. 9Bis a configuration diagram showing a separation release state of the contact and separating device. Meanwhile, also in this embodiment, the same components as in the first embodiment will be denoted by the same reference numerals and signs, and the description thereof will be omitted.

In this embodiment, a bearing member40includes a boss40j,a bearing concave portion40d, a through hole portion40e, and a flat portion40hwhich are the same as those of the bearing member22of the first embodiment, but does not include portions equivalent to the circular guiding portion22b, the bearing side engagement portion22c, and the like and a member equivalent to the separation member24.

That is, in this embodiment, a separation side engagement portion48having a first curved surface41acentered on a rotation center49is provided as a component that holds and releases the bearing member40in a separation state. Further, a bearing side engagement portion50having a second curved portion40ais provided. The second curved portion engages with the first curved surface41ain a separation state and is curved so as to allow the rotation of the separation side engagement portion48.

The separation side engagement portion48includes a separation member41. The separation member has the first curved surface41aprovided on the upper side from the rotation center49and a released engagement portion41bextending downward from the rotation center49. On the other hand, the bearing side engagement portion50having the second curved portion40ais provided at a position facing the separation member41in the bearing member40.

In addition, a release member42having the same configuration as that of the release member25ofFIG. 2is provided at a position facing the separation member41on the opposite side to the bearing member40so as to be rotatable by the driving of a drive source51(seeFIG. 1). The release member42has a pair of claw-shaped releasing engagement portions42athat protrude in two directions perpendicular to a rotation center.

An abutting pressure against the intermediate transfer belt8is applied to a secondary transfer outer roller20supported by the bearing concave portion40d, by a transfer coil spring21(seeFIG. 2A) through the bearing member40. Bearing supporting portions46aand46b(seeFIG. 2A) support the separation member41having an arc center of the first curved surface41acoaxially with an arc center of the second curved portion40awhen the bearing member40is moved until reaching the separation state ofFIG. 8.

In the contact and separating device45of this embodiment, the relation of (outer diameter of the second curved portion40a) ≦(inner diameter of the first curved surface41a) is established. In this embodiment, a release member42is placed on an axis of a conveyance roller13.

Hereinafter, a description will be made with a focus on the operation of the contact and separating device45according to this embodiment which has the above-described configuration.

First, the secondary transfer outer roller20is in a separation state where the secondary transfer outer roller is moved to the opposite side to the pressure direction X up to a light-pressure position or a non-contact position with respect to the intermediate transfer belt8and is held (FIG. 8). In this separation state, the separation member41rotates at the positions shown inFIG. 8andFIGS. 9A and 9Bto thereby cause the first curved surface41ato engage with the second curved portion40aof the bearing member40. Thus, the engagement between the bearing side engagement portion22cand the second engagement portion30cis maintained to thereby hold the separation state.

In the above-described separation state, when the release member42rotates upon the driving of the drive source51by the application of a main power supply or the like, the following state is set. That is, the releasing engagement portion42apushes the released engagement portion41bby the relatively slow rotation of the release member42in a counterclockwise direction ofFIG. 8. Thus, the separation member41rotates in the release direction (clockwise direction ofFIG. 8), and the first curved surface41ais separated from the second curved portion40ato thereby release the separation state, and thus a state shown inFIG. 9Bis set.

At this time, even when the release member42continuously rotates in a state where the separation is released, the bearing member40is set to be located at a position where the bearing member does not come into contact with the release member42, and thus an ordinary usage state where the secondary transfer outer roller20abuts against the intermediate transfer belt8is set. When the separation is released, the amount of rotation of the separation member41is regulated by collision between the second curved portion40aand the first curved surface41a.

Also in this embodiment described above, substantially the same effects as in the first embodiment can be obtained.

Meanwhile, the first to third embodiments described above illustrate an example of the intermediate transfer belt unit9having the intermediate transfer belt8. However, the present invention is not limited thereto, and can also be applied to a configuration of a direct transfer system that directly performs transfer to a recording medium from a photoconductive drum without going through the intermediate transfer belt8. Further, it is possible to apply the present invention to a configuration including a primary transfer roller in an image forming apparatus having only a monochrome configuration.

In the first to third embodiments, four image forming portions1Y,1M,1C, and1Bk are used as process cartridges which are detachable from the apparatus main body100a. However, the number of units is not limited thereto, and can be appropriately set on an as-needed basis.

In addition, the first to third embodiments illustrate a photoconductive drum, and a charging unit, a developing unit, and a cleaning unit as process units acting on the photoconductive drum, which are formed integrally with each other, as a process cartridge detachable from the apparatus main body100a, but the present invention is not limited thereto. For example, it is also possible to configure a process cartridge in which a photoconductive drum is formed integrally with any one of a charging unit, a developing unit, and a cleaning unit.

Further, the first to third embodiments illustrate a configuration in which the process cartridge including the photoconductive drum is detachable from the apparatus main body100a,but the present invention is not limited thereto. For example, an image forming apparatus in which a photoconductive drum and process units are embedded or an image forming apparatus in which a photoconductive drum and process units are detachable may be configured.

In addition, the first to third embodiments illustrate a printer as the image forming apparatus100, but the present invention is not limited thereto. For example, other image forming apparatuses such as a copier and a facsimile machine, or other image forming apparatuses such as a multifunction machine having a combination of these functions may be used. Alternatively, an image forming apparatus may be used which uses a recording medium support and sequentially transfers various colors of toner images to a recording medium supported by the recording medium support in an overlapping manner.

This application claims the benefit of Japanese Patent Application No. 2013-144165, filed on Jul. 10, 2013, which is hereby incorporated by reference herein in its entirety.