JPH1124452A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the contact/uncontact of transfer member with the surface of an image carrier, without using an exclusive motor by separating the transfer member from the surface of the image carrier with its rotation, at the time of rotating the image carrier in a second direction. SOLUTION: A transfer roller 11 is supported to enable the contact/uncontact with the surface of a photoreceptor 5 and when it is rotated in the second direction, the transfer roller 11 is separated from the photoreceptor 5 by using this rotation as a drive source. In other words, a cam 38 is attached to the roller shaft 28 of the roller 11 and a one-way clutch 39 is interposed between the cam 38 and the roller shaft 28. When the photoreceptor 5 is rotated in the second direction, after an image forming operation is completed, the rotation of the roller shaft 28 of the roller 11 rotated in the second direction is transmitted to the cam 38 and when this can 38 is turned, it is engaged with an end member 22 on the side of the photoreceptor 5, so that the transfer roller 11 is separated from the surface of the photoreceptor 5, against the workings of springs 33 and 34.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image carrier having a surface on which a toner image is formed while being driven to rotate in a first direction;
A transfer member for transferring the toner image formed on the surface of the image carrier to the transfer material while contacting the surface of the image carrier via the transfer material; and a transfer residual toner adhered to the surface of the image carrier after the transfer of the toner image And a cleaning member for cleaning the surface of the image carrier by removing the image carrier from the surface of the image carrier, wherein the image carrier is rotatable also in a second direction opposite to the first direction. The present invention relates to a forming apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copier, a printer, a facsimile, or a multifunction machine having at least two of these functions, a transfer material positioned between an image carrier and a transfer member is provided. The toner image formed on the surface of the image carrier is transferred to the image carrier. The transfer member abuts on the surface of the image carrier via the transfer material or directly, but if the abutment of both is left for a long time while being maintained even during the non-image forming operation, the image carrier Contact marks of the transfer member remain on the surface, which may cause an abnormal image.
Further, when the transfer member is in contact with the surface of the image carrier for a long time, the transfer member causes permanent distortion, and the deformation causes a transfer failure when the toner image is transferred from the image carrier to the transfer material. There is also. Therefore, it is desirable to separate the transfer member from the surface of the image carrier during the non-image forming operation.

[0003] From such a viewpoint, there has been proposed an image forming apparatus provided with a motor for driving the transfer member in order to move the transfer member toward and away from the surface of the image carrier (Japanese Patent Laid-Open No. 3-107180). reference). According to this configuration, it is possible to prevent the transfer member from staying in contact with the surface of the image carrier for a long period of time, and it is possible to prevent the occurrence of an abnormal image or transfer failure. However, in the image forming apparatus according to this proposal, a motor for moving the transfer member toward and away from the surface of the image carrier is required, which not only complicates the structure of the image forming apparatus but also increases its cost. There are some disadvantages.

[0004]

SUMMARY OF THE INVENTION The present invention has been made based on the above recognition, and an object of the present invention is to move an image carrier member to an image carrier surface without using a dedicated motor. An object of the present invention is to provide an image forming apparatus of the type described at the beginning, which can be brought into contact with and separated from the image forming apparatus.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an image forming apparatus of the type described at the beginning, wherein the transfer member is supported so as to be able to approach and separate from the surface of the image carrier. When the image carrier rotates in the second direction, the image carrier is driven by the rotation to separate the transfer member that has been in contact with the image carrier surface from the image carrier surface, and the image carrier moves in the first direction. An image forming apparatus is proposed in which a transfer member contacting / separating means is provided which, when rotated, is driven by the rotation and makes the transfer member separated from the surface of the image carrier abut on the surface of the image carrier. Claim 1).

At this time, the transfer member contacting / separating means is provided on the transfer member side, and when the image carrier rotates in the second direction, it is driven by the rotation and operates from the retreat position to operate on the image carrier side. When the image carrier is rotated in the first direction, the transfer member is driven by the rotation to return to the retracted position, and the transfer member is brought into contact with the surface of the image carrier. It is advantageous to have a cam to contact (claim 2).

In the image forming apparatus according to the second aspect, when the transfer member contacting / separating means is interposed between the cam and the transfer member, and the image carrier rotates in the first direction. A clutch for transmitting the rotation of the image carrier to the cam so that the cam engages with the image carrier when the image carrier rotates in the second direction without transmitting the rotation of the image carrier to the cam. Is advantageous (claim 3).

Further, in the image forming apparatus according to any one of claims 1 to 3, the transfer member is drivingly connected to the image carrier via a transmission means, and the rotation of the image carrier is transmitted to the transfer member. When the transfer member is rotated and driven, and the transfer member is separated from the surface of the image carrier, it is advantageous to configure the transmission means so that rotation is transmitted from the image carrier to the transfer member. ).

Further, in the image forming apparatus according to the first aspect, the transfer member can be brought into contact with and separated from the surface of the image carrier, and the first member or the second member can be moved in conjunction with the rotation of the image carrier.
The transfer member contacting / separating means includes a cam attached to the transfer roller, and a clutch interposed between the cam and the transfer roller. When the carrier rotates in the first direction, and when the transfer roller rotates in the first direction while abutting on the surface of the image carrier, the cam is held at the retracted position. The image carrier rotates in the second direction without transmitting the rotation to the cam.
It is advantageous if the cam is engaged as a one-way clutch for transmitting the rotation of the transfer roller to the cam so that the cam is engaged with the image carrier and the transfer roller is separated from the surface of the image carrier. Claim 5).

Further, in the image forming apparatus according to claim 5, the transfer roller has a roller body made of an elastic body, and a roller shaft made of a rigid body fixedly supporting the roller body. Advantageously, it is supported on the roller shaft via the one-way clutch (claim 6).

The image forming apparatus according to claim 6, further comprising a pressing member for pressing each end of the roller shaft in the axial direction such that the roller body is pressed against the surface of the image carrier. (Claim 7).

The image forming apparatus according to any one of claims 5 to 7, further comprising a power transmitting means for transmitting the rotation of the image carrier to a transfer roller, so that the image is transferred even when the transfer roller is separated from the surface of the image carrier. It is advantageous to configure the transmission means so that the rotation is transmitted from the carrier to the transfer roller (claim 8).

Further, in the image forming apparatus according to claim 1, the transfer member is wound around a plurality of transfer member pulleys and is capable of coming into contact with and separating from the surface of the image carrier. When the image bearing member rotates in the first direction or the second direction in conjunction with the image carrier and rotates in the first direction while abutting on the surface of the image carrier, it carries and conveys a transfer material onto which the toner image on the surface of the image carrier is transferred. A transfer belt, wherein the transfer member contacting / separating means is provided on a facing pulley of the plurality of transfer member pulleys that faces the image carrier via the transfer belt; and the cam and the facing pulley. And a clutch interposed between the transfer belt and the opposing pulley and the transfer belt rotating in the first direction when the image carrier rotates in the first direction. So that the cam is held in the retracted position. When the rotation of the pulley is not transmitted to the cam, the image carrier rotates in the second direction, and the cam engages with the image carrier when the opposing pulley and the transfer belt rotate in the second direction. Advantageously, the transfer belt is configured as a one-way clutch for transmitting the rotation of the opposing pulley to the cam so that the transfer belt is separated from the surface of the image carrier.

The image forming apparatus according to claim 9, further comprising a transmission means for transmitting the rotation of the image carrier to the opposed pulley, so that the image carrier is maintained even when the transfer belt is separated from the surface of the image carrier. It is advantageous to configure the transmission means so that the rotation is transmitted from the body side to the opposing pulley (claim 10).

Further, in the image forming apparatus according to the first aspect, the transfer member can be brought into contact with or separated from the surface of the image carrier, and the first member or the second member can be moved in conjunction with the rotation of the image carrier.
A transfer drum that winds and transfers a transfer material onto which the toner image on the image carrier surface is transferred when rotating in the first direction while contacting the image carrier surface,
The transfer member contacting / separating means includes a cam attached to the transfer drum, and a clutch interposed between the cam and the transfer drum, wherein the clutch rotates the image carrier in a first direction. When the transfer drum rotates in the first direction in conjunction therewith, the rotation of the transfer drum is not transmitted to the cam so that the cam is held at the retracted position, and the image carrier rotates in the second direction. When the transfer drum rotates in the second direction in conjunction therewith, the rotation of the transfer drum is transmitted to the cam such that the cam engages with the image carrier and the transfer drum separates from the surface of the image carrier. Advantageously, it is configured as a one-way clutch (claim 11).

The image forming apparatus according to claim 11, further comprising a power transmitting means for transmitting the rotation of the image bearing member to the transfer drum, so that the image bearing member can rotate even when the transfer drum is separated from the surface of the image bearing member. It is advantageous to configure the transmission means so that the rotation is transmitted from the body side to the transfer drum (claim 12).

The image forming apparatus according to any one of claims 5 to 12, wherein the cam is engaged with the image carrier and the transfer member is separated from the surface of the image carrier.
Advantageously, when the image carrier rotates in the first direction, the cam returns to the retracted position by the force received from the image carrier side, and the transfer member comes into contact with the surface of the image carrier. .

Further, in the image forming apparatus according to any one of the second to thirteenth aspects, it is advantageous that an engaging groove for engaging an edge of the cam returning to the retracted position is formed on the image carrier side. 14).

The image forming apparatus according to any one of claims 2 to 14, wherein the image bearing member comprises an image bearing drum, and when the image bearing drum rotates in the second direction, the cam is moved. It is advantageous that the transfer member is separated from the surface of the image bearing drum by engaging with an end member fixed to the axial end of the image bearing drum.

The image forming apparatus according to any one of claims 2 to 14, wherein the image carrier is wound around a plurality of image carrier pulleys and is rotated in the first or second direction. The cam is engaged with an image carrier pulley facing the transfer member via the image carrier belt among the plurality of image carrier pulleys so as to separate the transfer member from the surface of the image carrier belt. It is advantageous to configure (claim 16).

Further, in the image forming apparatus according to any one of claims 1 to 16, after the transfer residual toner on the surface of the image carrier is completely removed by the cleaning member, the image carrier rotates in the second direction. It is advantageous if it comprises so that it may carry out (claim 17).

Further, in the image forming apparatus according to the present invention, it is advantageous that the cleaning member is a cleaning blade which presses against the surface of the image carrier to scrape off the transfer residual toner adhered to the surface. Claim 1
8).

Further, in the image forming apparatus according to claim 17 or 18, the image carrier starts to rotate in the second direction, and the transfer member separates from the surface of the image carrier as the image carrier rotates. By the time the image carrier stops rotating, the distance that a point on the image carrier surface moves along the surface is
It is advantageous if the distance between the contact point where the transfer member contacts the image carrier surface and the contact point where the cleaning member contacts the image carrier surface is shorter than the distance along the image carrier surface. 19).

Further, in the image forming apparatus according to any one of claims 1 to 19, an electrostatic latent image is formed on the image carrier, and the electrostatic latent image is visualized as a toner image. It may be configured as a latent image carrier.
0).

Similarly, in the image forming apparatus according to any one of claims 1 to 19, the image carrier may be configured as an intermediate transfer member to which toner is transferred from the latent image carrier. 21).

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic sectional view showing the inside of an image forming apparatus according to an embodiment of the present invention from the front side. An image forming unit 2 is detachably mounted on the main body 1 of the image forming apparatus. . The image forming apparatus shown here is configured as a copying machine, and the copying machine may have functions such as a printer and a facsimile. The image forming unit 2 is attached to and detached from the image forming apparatus main body from the near side of the image forming apparatus main body 1.

FIG. 2 is an enlarged sectional view of the image forming unit 2 and the transfer unit 3 as viewed from the front side. As shown in FIG. 2 and FIG. 1, the image forming unit 2 has a unit case 4. Inside the case 4, a drum-shaped photoconductor 5 as an example of an image carrier and a charging roller 6 as an example of a charging device are rotatably mounted.

At the time of the image forming operation, the photosensitive member 5 is driven to rotate clockwise as indicated by a solid arrow in FIG. 2 by a driving device (not shown). At this time, the photosensitive member surface is neutralized by the neutralizing light L1 to the reference potential. The rotation direction of the photoconductor at this time is the first direction. The charging roller 6 is driven to rotate while being in pressure contact with the surface of the photoreceptor 5, and uniformly charges the surface of the photoreceptor to a predetermined polarity. The surface of the photoconductor 5 charged in this way is irradiated with a light image from a document or a light-modulated laser L2, whereby a predetermined electrostatic latent image is formed on the photoconductor 5.

On the other hand, a developing roller 8 of a developing device 7 is rotatably supported on the unit case 4 as shown in FIG. 2, and a developing agent 9 is formed on a developing case 9 constituted by a part of the unit case 4. The developer D is carried and conveyed on a developing roller 8 which is driven to rotate counterclockwise. When the transported developer reaches between the photoconductor 5 and the developing roller 8, the charged toner in the developer is electrostatically transferred to an electrostatic latent image formed on the photoconductor 5, and the latent image is transferred. Is visualized as a toner image.

The transfer unit 3 has a transfer roller 11, which is an example of a transfer member, a charge eliminator 12, and a holder 13 for holding the same. The transfer roller 11 extends in parallel with the photosensitive member 5. I have. The static eliminator 12 includes a static elimination needle 14 extending in parallel with the photoconductor 5 and a holder 1 for holding the needle.
5 is provided. During the image forming operation, the transfer roller 11 occupies the operating position pressed against the surface of the photoconductor 5 and is driven to rotate counterclockwise.

On the other hand, the plurality of paper feeders 16 shown in FIG.
Transfer paper P, which is an example of a transfer material, is supplied from a selected one of the paper feeders 17, 18 and 19 to the photoconductor 5 and the transfer roller 11.
Are transported to the transfer area 20 as indicated by the arrow A.
When the transfer paper P passes through the transfer area 20, the toner image formed on the surface of the photoconductor 5 is transferred onto the transfer paper P by the action of the transfer voltage applied to the transfer roller 11. The transfer roller 11 rotates while abutting on the surface of the photoconductor 5 via the transfer paper P.
1, a transfer voltage having a polarity opposite to that of the toner on the photoconductor 5 is applied.

On the other hand, the transfer paper P is separated from the photoreceptor 5 by the action of a discharge generated from the charge eliminating needle 14 of the charge eliminating device 12 toward the surface of the photoreceptor 5. The transfer paper P conveyed in the direction of arrow B leaving the photoconductor 5 passes through the fixing device 121, and at this time, the toner image on the transfer paper is fixed on the transfer paper by the action of heat and pressure. Next, this transfer paper P is
The sheet is discharged onto a tray 122 outside the main body of the image forming apparatus as a copy sheet on which a recording image formed of a toner image is formed.

The toner remaining on the photoreceptor 5 after the transfer of the toner image is removed from the surface of the photoreceptor by a cleaning member 24 of a cleaning device 23 and falls into a cleaning case 25 constituted by a part of the unit case 4. I do.

FIG. 3 is a perspective view showing the photoreceptor 5 and the transfer roller 11 shown in FIGS. 1 and 2. The photoreceptor 5 has an axially deep end and a near end. End members 21 and 22 generally called flanges are fixed, and shaft portions 26 and 27 located at the center of each end member 21 and 22 are rotatably supported by the unit case 4 (FIG. 2). I have.
As described above, in this embodiment, the photoconductor 5 is supported by the image forming apparatus main body via the unit case 4, but the photoconductor 5 can be directly rotatably supported by the image forming apparatus main body.

The transfer roller 11 includes a roller shaft 28 made of a conductive rigid body and a cylindrical roller body 29 made of an elastic body fixedly supported on the roller shaft 28 and positioned in parallel with the photoreceptor 5. The roller body 29 is made of, for example, foam or rubber having a resistivity of about 10 ^{7 to} 10 ⁹ Ωcm. Each end of the roller shaft 28 in the axial direction is supported by slide bearings 30 and 31 respectively rotatably fitted thereto, and these bearings 30 and 31 are formed in the grooves of the holding body 13 as shown in FIG. It is slidably fitted in the accommodating portion 32 in a direction approaching or separating from the photoconductor 5. In addition, each bearing 30, 31 and the accommodation portion 3 of the holding body 13
The compression rollers 33 and 34, which are examples of a pressure member, are press-fitted between the transfer roller 1 and the bottom wall of the transfer roller 1.
The first roller body 29 is pressed against the surface of the photoconductor 5. If the compression springs 33 and 34 are compressed, the transfer roller 11
Can be separated from the surface of the photoconductor 5. In this embodiment, the transfer roller 11 is supported by the main body of the image forming apparatus via the holding member 13. However, the transfer roller 11 can be directly rotatably supported by the main body of the image forming apparatus.

End member 2 fixed to the rear end of photoconductor 5
A gear 35 is formed on a peripheral surface of the photoconductor 5. The gear 35 meshes with a driving gear (not shown) supported on the image forming apparatus main body side, and a motor (not shown) drives the photosensitive member 5 via these gears. Are driven to rotate in a first direction, that is, a direction indicated by a solid arrow in FIGS. 2 and 3. Photoconductor 5
As described later, by the above-described gear and motor,
It is also possible to rotate in a second direction opposite to the first direction, that is to say in the direction indicated by the dashed arrows in FIGS.

A gear 36 is also formed on the peripheral surface of the end member 22 fixed to the front side of the photoreceptor 5.
When the photoreceptor 5 rotates in the first direction as described above during the image forming operation, the rotation is performed by the gears 36 and 3.
The power is transmitted to the transfer roller 11 via a power transmission means composed of the transfer roller 7. At this time, the rotation direction of the transfer roller 11 is a direction in which the surfaces of the transfer roller 11 and the photoconductor 5 move in the same direction at the contact portion between the transfer roller 11 and the photoconductor 5, that is, a forward direction with respect to the rotation direction of the photoconductor 5. Orientation. When the photoconductor 5 rotates in the first direction, the transfer roller 1 rotates in conjunction with the rotation.
The rotation direction of the transfer roller 11 that rotates when the photosensitive member 5 rotates in the first direction and the photosensitive member 5 rotates in the second direction is referred to as the second direction.

As described above, the image forming apparatus according to the present embodiment includes an image carrier composed of the photoreceptor 5 on which a toner image is formed while being rotated in the first direction, and a transfer material composed of the transfer paper P. A transfer member configured as a transfer roller 11 for transferring a toner image formed on the image carrier surface to a transfer material while contacting the image carrier surface via A cleaning member 24 for removing the transfer residual toner adhered from the surface of the image carrier and cleaning the surface of the image carrier.

When the image forming operation is completed, the rotation of the photosensitive member 5 is stopped. That is, the photosensitive member 5 stops immediately after the cleaning member 24 has finished removing the transfer residual toner on the surface of the photosensitive member or after a predetermined time. Here, in the image forming apparatus of the present embodiment, after the transfer residual toner on the surface of the image carrier made of the photoconductor has been removed by the cleaning member 24, the image carrier is rotated in the second direction. Have been. The photoreceptor 5 rotates by a predetermined angle in the second direction indicated by the broken arrow in FIGS. As described above, in the image forming apparatus according to the present embodiment, the image carrier including the photoconductor 5 is also rotatable in the second direction opposite to the above-described first direction.

The cleaning member 24 removes transfer residual toner adhering to the surface of the photosensitive member. When such a cleaning operation is performed, the cleaning member 24 is removed.
May accumulate on the surface of the photoreceptor 5 where toner and paper dust accumulate. If the next image forming operation is carried out while leaving this as it is, cleaning failure occurs on the photoconductor,
The toner image formed next may be stained. In particular, as shown in FIG. 2, when the cleaning member 24 is a cleaning blade that presses the leading edge to the surface of the image carrier to scrape off the untransferred toner adhering to the surface, the portion of the leading edge is used. Easily accumulates toner and paper dust.

Then, after removing the transfer residual toner on the photosensitive member 5 by the cleaning member 24, the photosensitive member 5 is rotated by a predetermined angle in the second direction, and the toner collected on the leading edge of the cleaning member 24 is removed. Paper dust and paper dust are discharged from the edge portion, and the paper dust and toner attached to the photoconductor are removed by the cleaning member 24 at the time of the next image forming operation.

The above configuration itself is conventionally known,
This configuration is also adopted in each embodiment described later.

By the way, if the transfer roller 11 is kept in contact with the surface of the photosensitive member 5 even after the photosensitive member 5 stops,
As described above, contact marks of the transfer roller remain on the surface of the photoreceptor and cause an abnormal image, or cause permanent deformation of the roller body 29 of the transfer roller 11 and cause transfer failure. Become. Therefore, conventionally, during a non-image forming operation after the photosensitive member is stopped, the transfer roller has been driven by a motor such that the transfer roller is separated from the surface of the photosensitive member. However, according to this configuration, the structure of the image forming apparatus is complicated, and the cost is increased.

Therefore, in the image forming apparatus of this embodiment, as described above, the image carrier member composed of the transfer roller 11 is supported so as to be able to contact and separate from the surface of the image carrier composed of the photoreceptor 5. When the image carrier rotates in the second direction, the rotation is used as a drive source to separate the transfer member from the surface of the image carrier, and when the image carrier rotates again in the first direction, the rotation is also performed. A transfer member contacting / separating means for bringing the transfer member into contact with the surface of the image carrier is provided as a driving source. The specific configuration is as follows.

As shown in FIG. 3, a cam 38 is attached to the roller shaft 28 of the transfer roller 11, and a one-way clutch 39 is interposed between the cam 38 and the roller shaft 28. The one-way clutch 39 rotates the photoconductor 5 in the first direction during the image forming operation,
When the transfer roller 11 is rotating in the first direction while abutting on the surface of the photoreceptor, the cam 38 is held at a retracted position that does not hinder the rotation of the photoreceptor 5 as shown in FIGS. As described above, when the rotation of the roller shaft 28 is not transmitted to the cam 38 and the image forming operation is completed and the photosensitive member 5 rotates in the second direction, the transfer roller 1 rotating in the second direction
The rotation of one roller shaft 28 is transmitted to the cam 38. When the cam 38 rotates in this manner, the cam 38 engages with the end member 22 on the side of the photoconductor 5 as shown in FIG. 5, whereby the transfer roller 11 opposes the action of the springs 33 and 34. To separate from the surface of the photoconductor 5. The length from the center of the roller shaft 28 to the tip of the cam 38 is set to be larger than the radius of the transfer roller 11, and the tip of the cam 38 engages with the photoconductor 5 side as shown in FIG. This is because the transfer roller 11 is separated from the photoconductor surface.

As described above, when the transfer roller 11 is separated from the photosensitive member surface, the rotation of the photosensitive member 5 in the second direction is stopped, and the image forming apparatus is operated with the transfer roller 11 separated from the photosensitive member surface. To stop. As described above, since the transfer roller 11 does not come into contact with the surface of the photoconductor when the image forming apparatus is stopped, the contact mark of the transfer roller is left on the surface of the photoconductor, and the local external force on the transfer roller 11 is long. The effect of time action can be prevented from causing permanent distortion.

When the power of the image forming apparatus is turned on and the image forming operation is started, the photosensitive member 5 rotates clockwise in FIG. 5, that is, in the first direction. The rotation of the photoconductor 5 at this time is transmitted to the roller shaft 28 of the transfer roller 11 via the gears 36 and 37, and the roller shaft 28 rotates in the first direction, that is, the counterclockwise direction in FIG. The rotation of the roller shaft 28 at this time is not transmitted to the cam 38,
8 is engaged with the end member 22 integral with the photoreceptor 5,
Due to the frictional force between the two, the cam 38 rotates to the retracted position shown in FIG. As a result, the transfer roller 11 is pressed against the surface of the photoconductor 5 by the pressing action of the springs 33 and 34. In this manner, the transfer roller 11 abuts the photoconductor 5 without any trouble at the start of the image forming operation, and transfers the toner image on the photoconductor surface onto the transfer paper P as described above.

When the cam 38 engages with the end member 22 on the side of the photosensitive member 5 as shown in FIG. 5 and the transfer roller 11 is separated from the surface of the photosensitive member 5, the gear 36 on the side of the photosensitive member 5 The distance between the central axes of the two gears 36 and 37 is set so that the gear 37 and the gear 37 on the side of the transfer roller 11 can be maintained in a state of meshing with each other. Accordingly, the cam 38 can be reliably engaged with the photoconductor by the rotation of the photoconductor 5 in the second direction, and the rotation of the cam 38 is hindered when the rotation of the photoconductor 5 in the first direction starts. The rotation can be transmitted to the transfer roller 11 and rotated.

As described above, the transfer member contacting / separating means is driven by the rotation of the image carrier when the image carrier rotates in the second direction, and transfers the transfer member, which has been in contact with the surface of the image carrier, to the image carrier. When the image carrier is rotated in the first direction while being separated from the body surface, the image carrier is driven by the rotation, and the transfer member that has been separated from the image carrier surface is brought into contact with the image carrier surface. ing.

Further, the transfer member contacting / separating means is provided on the transfer member side, and when the image carrier rotates in the second direction, is driven by the rotation and operates from the retracted position to operate from the image carrier side. By engaging with, the transfer member is separated from the surface of the image carrier, and when the image carrier rotates in the first direction, the image carrier is driven by the rotation to return to the retracted position,
There is a cam 38 for bringing the transfer member into contact with the surface of the image carrier.

Further, the transfer member contacting / separating means is provided between the cam 38 and the transfer member. When the image carrier rotates in the first direction, the rotation of the image carrier is transmitted to the cam 38. When the image carrier rotates in the second direction without transmitting,
A clutch 39 for transmitting the rotation of the image carrier to the cam 38 so that the clutch 8 engages with the image carrier.

Further, the transfer member is drive-coupled to the image carrier via transmission means including gears 36 and 37, and the rotation of the image carrier is transmitted to the transfer member, whereby the transfer member is driven to rotate and the transfer member is rotated. The transmission means is configured to transmit the rotation from the image carrier to the transfer member even when the member is separated from the surface of the image carrier. This ensures that the cam 38 is engaged with the image carrier, and that when the image carrier starts rotating in the first direction, the transfer member is surely rotated in the predetermined direction (first direction). it can.

Further, in the image forming apparatus of the present embodiment, the transfer roller is capable of coming into contact with and separating from the surface of the image carrier and rotating in the first direction or the second direction in conjunction with the rotation of the image carrier. The transfer member contacting / separating means includes a cam 38 attached to the transfer roller 11 and a clutch 39 interposed between the cam 38 and the transfer roller 11, and the clutch is provided with an image bearing member. The body rotates in a first direction, and in conjunction with this, the transfer roller 11
When the image carrier rotates in the second direction, the rotation of the transfer roller 11 is not transmitted to the cam 38 so that the cam 38 is held at the retracted position, and the image carrier rotates in the second direction. Is configured as a one-way clutch 37 that transmits the rotation of the transfer roller 11 to the cam 38 so that the cam 38 engages with the image carrier side and separates the transfer roller 11 from the surface of the image carrier when the roller rotates in the second direction. ing.

Further, in the image forming apparatus of this embodiment,
A transfer roller 11 having a roller body 29 made of an elastic material;
And a roller shaft 28 made of a rigid body for fixedly supporting the roller body 29. The cam 38 is supported by the roller shaft 28 via a one-way clutch 39.

In the image forming apparatus of this embodiment, the springs 33 and 34 press the axial ends of the roller shaft 28 so that the roller body 29 of the transfer roller 11 is pressed against the surface of the image carrier. The transfer roller 11 can be pressed against the surface of the photoreceptor 5 with a uniform pressure during the image forming operation, so that a high-quality toner image can be transferred onto the transfer paper P. it can.

Further, the image forming apparatus of this embodiment has a transmission means comprising gears 36 and 37 for transmitting the rotation of the image carrier to the transfer roller 11, and when the transfer roller 11 is separated from the surface of the image carrier. The transmission means is configured so that rotation is transmitted from the image carrier side to the transfer roller 11.

In the image forming apparatus of this embodiment, as described above, the image carrier is moved to the first position with the cam engaged with the image carrier and the transfer member being separated from the surface of the image carrier.
When the cam rotates in the direction of, the cam returns to the retracted position by the force received from the image carrier, and the transfer member contacts the surface of the image carrier. Such a configuration is the same in each embodiment described later.

Further, in the image forming apparatus of the present embodiment, the image carrier is constituted by a drum for carrying a toner image.
That is, when the image bearing member is formed of an image bearing drum, and the image bearing drum rotates in the second direction, the cam 38 engages with the end member 22 fixed to the axial end of the image bearing drum to transfer the image. The member is configured to be separated from the surface of the image bearing drum. This configuration can also be applied to an image forming apparatus described below in which the image carrier includes an image bearing drum.

As shown in FIG. 3, the end member 22 on the photoreceptor side has a plurality of engagement grooves 40 arranged in the circumferential direction thereof.
These engagement grooves 40 are provided at positions facing the tip of the cam 38. Now, the cam 38
As shown in FIG. 5, when the photoconductor 5 starts rotating in the first rotation direction from the state in which the cam 38 is engaged with the end member 22 on the side of the photoconductor 5, the cam 38 is moved by the frictional force with the end member 22. It rotates to the retracted position shown in FIG. At this time, the end member 22
The engaging edge 30A of the distal end of the cam 38 is engaged with one of the engaging grooves 30 formed in the cam 38, whereby the engaging force between the end member 22 and the cam 38 is increased. Can be turned to the retracted position shown in FIG.

As described above, in the image forming apparatus of the present embodiment, the engaging groove 40 is formed on the image carrier side for engaging the cam 38 returning to the retracted position, thereby ensuring that the cam 38 is returned to the retracted position. Can be. This configuration is also applicable to each embodiment described later.

In the image forming apparatus of this embodiment, the transfer residual toner on the surface of the photoreceptor is cleaned by the cleaning member 24.
After the removal, the photoconductor 5 is rotated in the second direction, and the rotation of the photoconductor 5 at this time is used to separate the transfer roller 11 from the surface of the photoconductor. When the photoreceptor 5 rotates in the second direction, the paper dust and toner accumulated at the leading edge of the cleaning member 24 approach the transfer roller 11 together with the photoreceptor 5 while adhering to the surface of the photoreceptor. At this time, assuming that toner or paper dust adhering to the surface of the photoconductor reaches the transfer roller 11 before the transfer roller 11 is completely separated from the photoconductor 5, as shown in FIG. 11 adheres to the surface. If the transfer roller becomes dirty in this manner, there is a possibility that the toner or paper dust that has adhered to the transfer roller 11 will adhere to the back surface of the transfer paper P during the next image forming operation, and will stain the transfer paper.

Therefore, in the image forming apparatus of this embodiment,
After the photoreceptor 5 stops rotating, the photoreceptor 5 starts rotating in the second direction until the transfer roller 11 separates from the surface of the photoreceptor 5 and stops. The rotation angle of the rotating member 5 is set smaller than the angle θ (FIG. 4) formed by the point at which the cleaning member 24 contacts the photosensitive member 5 and the point at which the transfer roller 11 contacts the photosensitive member 5. That is, the image carrier starts to rotate in the second direction, the transfer member separates from the surface of the image carrier with the rotation, and then a point on the surface of the image carrier until the image carrier stops rotating. Is shorter than the distance along the surface of the image carrier from the contact point where the transfer member contacts the image carrier surface to the contact point where the cleaning member contacts the image carrier surface. It is set. This configuration can also be applied to each embodiment described below. According to this configuration, the toner and paper dust accumulated at the leading edge of the cleaning member 24 reach the transfer roller 11 before the photoconductor 5 starts rotating in the second direction and then stops. Therefore, it is possible to prevent the transfer roller from being stained by the toner or paper dust.

In the above-described example, the transfer member is configured as the transfer roller 11, but the transfer member can be brought into contact with and separated from the surface of the image carrier, and can be directly or interposed between the transfer members during the image forming operation. The present invention is also applicable to an image forming apparatus including a transfer brush, a transfer blade, a transfer belt, a transfer drum, and the like, which are in contact with the surface of the image carrier.

FIGS. 6 and 7 show that the transfer member is the transfer belt 4.
FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus including an image forming apparatus; The transfer belt 41 shown here is wound around a plurality of, in the illustrated example, two transfer member pulleys 42 and 43. The center axes 45, 46 of these pulleys 42, 43 are rotatably supported by a common frame 44, and are centered on the center axis 46 of the pulley 43, which is away from the image carrier composed of the drum-shaped photoreceptor 5. , The frame 44 is swingably supported. Further, the free end side of the frame 44 is urged by a pressing member formed of a compression spring 47, so that during the image forming operation, as shown in FIG.
The pulley 42 opposing the surface contacts the photoreceptor surface via the transfer belt 41.

The photosensitive member 5 shown in FIG. 5 and FIG.
A gear (not shown) corresponding to the gear 36 shown in FIG. 3 is integrally provided, and a pulley 42 (hereinafter referred to as an opposed pulley) also facing the photoreceptor 5 is provided with a gear 37 shown in FIG.
(Also not shown) are integrally provided, and the two gears mesh with each other to constitute transmission means for transmitting the rotation of the photoconductor 5 to the opposing pulley 42. Accordingly, when the photoconductor 5 is driven to rotate in the first direction shown by the solid line arrow in FIG. 6 during the image forming operation, this rotation is transmitted to the opposing pulley 42, whereby the transfer belt 41 is similarly moved to the solid line in FIG. It is driven to rotate in the first direction indicated by the arrow.
A cam 38 similar to the cam shown in FIG. 3 is supported on the opposing pulley 42 via a one-way clutch configured similarly to the one-way clutch described above.

During the image forming operation, the photosensitive member 5 rotates in the first direction. At this time, a toner image is formed on the surface of the photosensitive member in exactly the same manner as in the example described above with reference to FIG. . At that time, the transfer belt 41 rotates in the first direction while abutting on the photoconductor surface. On the other hand, a transfer material composed of transfer paper P fed from a paper feeding device (not shown) is fed between the photoconductor 5 and the transfer belt 41 at a predetermined timing. At this time, the transfer voltage applied to the bias roller 48 in contact with the back surface of the transfer belt 41 causes
The toner image on the photoconductor is transferred onto the transfer paper P.

The transfer paper separated from the photoreceptor 5 is subsequently carried on a transfer belt 41 and conveyed to a fixing device (not shown), where the transferred toner image is fixed on the transfer paper P. The transfer residual toner adhered to the photoconductor 5 is removed by the cleaning member 24. At this time, the opposed pulley 4
The second rotation is not transmitted to the cam 38.

Here, when the removal of the transfer residual toner on the photosensitive member 5 is completed, the photosensitive member is driven to rotate by a predetermined amount in the second direction indicated by the broken line arrow in FIG. The transfer belt 41 rotates in the direction indicated by the arrow
Rotate in the second direction indicated by the dashed arrow. The rotation of the opposing pulley 42 is transmitted to a cam 38, which rotates and engages with an end member (not shown) of the photoconductor 5 as shown in FIG. Separate.

When the photosensitive member 5 resumes rotation in the first direction, the cam 38 returns to the retracted position shown in FIG. 6 by the force received from the photosensitive member side, and the transfer belt 41 comes into contact with the photosensitive member surface, and A forming operation is performed.

As described above, in the image forming apparatus shown in FIGS. 6 and 7, the transfer member is wound around the plurality of transfer member pulleys 42 and 43, and the surface of the image carrier made of the photosensitive member 5 is formed. When the image carrier rotates in the first direction or the second direction in conjunction with the rotation of the image carrier and rotates in the first direction while contacting the surface of the image carrier, the toner image on the surface of the image carrier is And a transfer belt 41 that carries and conveys a transfer material made of transfer paper P to which the image is transferred. The transfer member contacting / separating means is an image bearing member via the transfer belt 41 among the plurality of transfer member pulleys 42 and 43. The cam includes a cam 38 attached to an opposing pulley 42 facing the body, and a clutch interposed between the cam 38 and the opposing pulley 42.
When the image carrier rotates in the first direction and the opposing pulley and the transfer belt rotate in the first direction in conjunction therewith, the rotation of the opposing pulley 42 is controlled so that the cam 38 is held at the retracted position. 38, the image carrier rotates in the second direction, and in conjunction therewith, when the opposing pulley 42 and the transfer belt 41 rotate in the second direction, the cam 38 engages with the image carrier and transfers the image. It is configured as a one-way clutch that transmits the rotation of the opposing pulley 42 to the cam 38 so that the belt 41 is separated from the surface of the image carrier.

The other structure is the same as that shown in FIGS. 1 to 5, and the rotation on the image carrier side is
Transfer means comprising a gear for transmitting to the transfer belt 41
There is no change in the point that the transmission means is configured so that the rotation is transmitted from the image carrier side to the opposing pulley 42 even when is separated from the image carrier surface. With this configuration, the cam can be reliably engaged with the photoconductor 5 side, and the opposing pulley 42, and thus the transfer belt 41, can be surely rotated in the first direction when the photoconductor 5 rotates in the first direction. it can.

FIG. 8 shows an embodiment in which the transfer member is configured as a transfer drum 49. During the image forming operation, a transfer material made of transfer paper is wound around and held by the transfer drum 49. The image bearing member including the transfer drum 49 and the drum-shaped photoconductor 5 has the gear 3 described with reference to FIG.
Gears (not shown in FIG. 8) similar to the gears 6 and 37 are fixed, and mesh with each other to constitute transmission means for transmitting the rotation of the photoconductor 5 to the transfer drum 49. Transfer drum 4
9 is supported so as to be able to contact and separate from the photoconductor 5.

During the image forming operation, the photosensitive member 5 rotates in a first direction indicated by a solid arrow, and in conjunction therewith, the transfer drum 4 rotates.
9 is also driven to rotate in the first direction indicated by the solid arrow while being in contact with the surface of the photoconductor 5. Thereby, the transfer drum 4
The transfer paper held on the surface of No. 9 is conveyed. A toner image is formed on the surface of the photoreceptor 5 in the same manner as in the embodiment described above, and the toner image is formed by a corona discharger or roller (not shown) provided inside the transfer drum 49. Is transferred onto the transfer paper by applying the voltage of. In this example, toner images of different colors can be sequentially formed on the photoreceptor 5 and sequentially transferred onto transfer paper. After the transfer of the toner image, the transfer paper is separated from the transfer drum 49 and transported to the fixing device.

A cam (not shown) similar to the above-described cam is supported on the transfer drum 49 via a one-way clutch similar to the above-described clutch.

The transfer residual toner adhering to the surface of the photosensitive member after the transfer of each toner image is removed by a cleaning member not shown in FIG. After the photoconductor cleaning operation is completed, the photoconductor 5 rotates by a predetermined angle in the second direction indicated by the dashed arrow. As a result, the transfer drum 49 rotates in the second direction shown by the broken line, and this rotation is transmitted to the cam, and the cam which has occupied the retracted position until then rotates and engages with the photoreceptor 5 to transfer. The drum 49 is separated from the photoconductor 5.

When the photosensitive member 5 starts rotating in the first direction, the cam returns to the retracted position, and the transfer drum 49 moves to the photosensitive member 5.
Abut.

As described above, in the image forming apparatus shown in FIG. 8, the transfer member can be brought into contact with and separated from the surface of the image bearing member composed of the photosensitive member 5, and the transfer member can be moved in conjunction with the rotation of the image bearing member. When rotating in one direction or the second direction and rotating in the first direction while abutting on the surface of the image carrier, a transfer material made of a transfer paper on which the toner image on the surface of the image carrier is transferred is wound around the surface and conveyed. The transfer member contacting / separating means includes a transfer drum 49, and a cam provided on the transfer drum 49, and a clutch interposed between the cam and the transfer drum 49. Rotates in the first direction, and when the transfer drum 49 rotates in the first direction in conjunction therewith, the rotation of the transfer drum 49 is not transmitted to the cam so that the cam is held at the retracted position. Rotates in the second direction, and in conjunction with this, the transfer drum When 9 is rotated in the second direction, the cam is configured to transfer drum 49 engages the image carrier-side is separated from the image bearing member surface, the rotation of the transfer drum as a one-way clutch for transmitting the cam. The other configuration is the same as that shown in FIGS. 1 to 5 and has a transmission unit for transmitting the rotation of the image carrier to the transfer drum,
Even when the transfer drum is separated from the surface of the image carrier, the transmission means is configured so that the rotation is transmitted to the transfer drum 49 from the image carrier side.

In the embodiment described above, the image carrier is constituted by an image carrier drum for carrying a toner image. However, as shown in FIG. 9, the image carrier comprises a plurality of image carrier pulleys 51, The present invention can also be applied to a case where the image bearing belt 50 is wound around 52 and 53 and rotates in the above-described first or second direction. In this case, one of the pulleys 51, 52, 53 of the plurality of image carriers is
Is opposed to a transfer member including, for example, the transfer roller 11 via the image carrying belt 50, and a cam (not shown) is supported on a roller shaft of the transfer roller 11 via a one-way clutch (not shown). Also in this case, a toner image is formed on the image bearing belt 50 that rotates in the first direction indicated by the solid arrow similarly to the above-described embodiment, and meshes with a gear fixed to the pulley 51 and this gear, and The image holding belt 50 is moved by the gear fixed to the transfer roller 11.
Is transmitted to the transfer roller 11, and the toner image formed on the image carrying belt is formed on the transfer paper P conveyed between the two. When the transfer residual toner adhered to the image carrying belt is completely removed by a cleaning member (not shown), the image carrying belt 50 is moved to the second position indicated by the broken arrow.
, Whereby the transfer roller 11 also rotates in the second direction indicated by the dashed arrow. At this time, the rotation is transmitted to the cam via the one-way clutch. The transfer roller 11 is rotated and engaged with the pulley 51, and the transfer roller 11 is separated from the image carrying belt 50. With the rotation of the image carrying belt 50 in the first direction, the cam returns to the retracted position by the force received from the pulley 51,
The transfer roller 11 comes into contact with the image carrying belt 50. As described above, in this example, the image carrier is wound around a plurality of image carrier pulleys, and is formed of an image carrier belt that rotates in the first or second direction, and a plurality of cams attached to the transfer member are provided. Among the image carrier pulleys 51, 52, 53, the image carrier pulley 5 facing the transfer member via the image carrier belt 50.
1 to separate the transfer member from the surface of the image bearing belt. Other configurations and operations are the same as those of the embodiments described above.

In each of the embodiments described above, the image carrier is formed as a latent image carrier on which an electrostatic latent image is formed and the electrostatic latent image is visualized as a toner image. On the other hand, in the example shown in FIG. 10, the image carrier is configured as an intermediate transfer member to which the toner is transferred from the latent image carrier, and the present invention can be applied to such an image forming apparatus.

In the example shown in FIG. 10, toner images of different colors are sequentially formed on the surface of a latent image carrier composed of a drum-shaped photoreceptor 5, and these toner images are wound around a plurality of pulleys. The toner image is sequentially primary-transferred onto the intermediate transfer member 54, and the superimposed toner image is secondarily transferred onto the transfer paper P by the transfer member including the transfer roller 11. As the intermediate transfer member 54 and the transfer roller 11, the image forming apparatus can be configured by adopting the respective configurations described above.

In the example described above, one cam 38 is used, but a plurality of cams may be used. For example, another cam may be provided on the other end side of the roller shaft 28 shown in FIG. 3 via a one-way clutch.

After the surface of the image carrier has been cleaned by the cleaning member, the image carrier is rotated in the second direction to separate the transfer member from the surface of the image carrier. The transfer member may be separated from the image carrier by rotating the body in the second direction.

The present invention can be widely applied to image forming apparatuses other than copying machines.

[0085]

According to the first to twenty-first aspects of the present invention, the transfer member can be prevented from constantly abutting on the image carrier, leaving traces of the transfer member on the surface of the image carrier, or permanent transfer to the transfer member. Distortion can be prevented. Moreover, when the image carrier rotates in the second direction, the transfer member is separated from the image carrier by using the rotation operation, and when the image carrier rotates in the first direction, the rotation is used. Then, since the transfer member is brought into contact with the surface of the image carrier, a dedicated driving device for moving the transfer member toward and away from the surface of the image carrier is not required, and the cost of the image forming apparatus can be reduced.

According to the image forming apparatus of the present invention, the transfer roller can be brought into contact with the surface of the image carrier with a uniform pressure.

Further, according to the configuration of the eighth, tenth and twelfth aspects, when the transfer member is more reliably separated from the surface of the image carrier and the image carrier starts to rotate in the first direction, The transfer member can be more reliably brought into contact with the surface of the image carrier.

According to the structure described in claim 14, when the image carrier starts to rotate in the first direction, the cam can be more reliably returned to the retracted position.

According to the constructions of the seventeenth and eighteenth aspects, the time required to rotate the image carrier in the second direction in order to remove the toner and paper dust accumulated on the cleaning member is utilized. It can be separated from the image carrier surface.

According to the configuration of the nineteenth aspect, it is possible to prevent a problem that toner and paper dust accumulated in the cleaning member adhere to the transfer member.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the overall configuration of an image forming apparatus.

FIG. 2 is an enlarged sectional view showing a part of FIG. 1;

FIG. 3 is a perspective view illustrating relative positions of a photoconductor, a transfer roller, and a cam.

FIG. 4 is an explanatory diagram showing a position of a cam when the photoconductor is rotating in a first direction.

FIG. 5 is an explanatory diagram illustrating a state in which a cam is engaged with a photoconductor and a transfer roller is separated from the photoconductor;

FIG. 6 is an explanatory diagram illustrating an image forming apparatus in which a transfer member includes a transfer belt.

FIG. 7 is an explanatory view showing a state in which the cam shown in FIG. 6 is engaged with the photoconductor and the transfer belt is separated from the surface of the photoconductor.

FIG. 8 is a schematic explanatory view of an image forming apparatus in which a transfer member includes a transfer drum.

FIG. 9 is a schematic explanatory view showing an example in which a photoconductor is constituted by a belt.

FIG. 10 is an explanatory view schematically showing an image forming apparatus of a type in which a toner image on a photosensitive member is transferred to an intermediate transfer member.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 transfer roller 22 end member 24 cleaning member 28 roller shaft 29 roller body 38 cam 39 one-way clutch 40 engagement groove 41 transfer belt 42 pulley 43 pulley 49 transfer drum 50 image carrying drum 51 pulley 52 pulley 52 pulley 53 pulley 54 intermediate transfer body

Claims (21)

[Claims] An image carrier having a toner image formed on the surface thereof while being driven to rotate in a first direction, and a toner image formed on the image carrier surface while being in contact with the image carrier surface via a transfer material A transfer member for transferring the toner image onto the transfer material, and a cleaning member for removing the transfer residual toner adhered to the surface of the image carrier after transferring the toner image from the image carrier surface and cleaning the image carrier surface. An image forming apparatus wherein the image carrier is rotatable also in a second direction opposite to the first direction, while supporting the transfer member so as to be able to approach and separate from a surface of the image carrier; When the image carrier rotates in the second direction,
When the image carrier rotates in a first direction, the transfer member driven by the rotation of the image carrier separates from the surface of the image carrier, and is driven by the rotation. An image forming apparatus provided with a transfer member contacting / separating means for contacting the transfer member separated from the image carrier with the surface of the image carrier. 2. The image forming apparatus according to claim 1, wherein the transfer member contacting / separating means is provided on the transfer member side, and when the image carrier rotates in a second direction, is driven by the rotation and operates from a retracted position to move to the image carrier side. The engagement causes the transfer member to be separated from the surface of the image carrier, and when the image carrier rotates in the first direction, the image carrier is driven by the rotation to return to the retracted position, and the transfer member contacts the surface of the image carrier. The image forming apparatus according to claim 1, further comprising a cam that is in contact with the image forming apparatus. 3. The transfer member contacting / separating means is interposed between the cam and the transfer member. When the image carrier rotates in a first direction, the rotation of the image carrier is not transmitted to the cam. The image according to claim 2, further comprising a clutch for transmitting rotation of the image carrier to the cam so that the cam engages with the image carrier when the image carrier rotates in the second direction. Forming equipment. 4. A transfer member is drivingly connected to an image carrier via a transmission means, and rotation of the image carrier is transmitted to the transfer member to rotate the transfer member. The transmission means is configured such that rotation is transmitted from the image carrier to the transfer member even when the transfer member is separated from the transfer member.
An image forming apparatus according to any one of claims 1 to 3. 5. The image forming apparatus according to claim 1, wherein the transfer member includes a transfer roller that is capable of coming into contact with and separating from the surface of the image carrier and that rotates in a first direction or a second direction in conjunction with rotation of the image carrier. The separating means includes a cam attached to the transfer roller, and a clutch interposed between the cam and the transfer roller, wherein the clutch rotates the image carrier in a first direction. When the transfer roller rotates in the first direction while being in contact with the surface of the image carrier, the rotation of the transfer roller is not transmitted to the cam so that the cam is held at the retracted position, and the image carrier is moved When the transfer roller rotates in the second direction in conjunction with this, when the transfer roller rotates in the second direction, the cam is engaged with the image carrier and the transfer roller is separated from the surface of the image carrier. Claims configured as a one-way clutch that transmits rotation to the cam Item 2. The image forming apparatus according to Item 1. 6. The transfer roller has a roller body made of an elastic body, and a roller shaft made of a rigid body fixedly supporting the roller body, and the cam is supported by the roller shaft via the one-way clutch. The image forming apparatus according to claim 5. 7. The image forming apparatus according to claim 6, further comprising a pressing member that presses each end of the roller shaft in the axial direction such that the roller body comes into pressure contact with the surface of the image carrier. 8. A transmission device for transmitting rotation of the image carrier to a transfer roller, wherein the rotation is transmitted from the image carrier to the transfer roller even when the transfer roller is separated from the surface of the image carrier. The image forming apparatus according to claim 5, wherein the image forming apparatus comprises a transmission unit. 9. The transfer member is wound around a plurality of transfer member pulleys and is detachable from the surface of the image carrier, and is moved in the first direction or the second direction in conjunction with the rotation of the image carrier. A transfer belt that carries and conveys a transfer material onto which the toner image on the image carrier is transferred when rotating and rotating in the first direction while abutting on the surface of the image carrier; A cam attached to an opposing pulley facing the image carrier via the transfer belt among the plurality of transfer member pulleys; and a clutch interposed between the cam and the opposing pulley. When the image carrier rotates in the first direction and the opposing pulley and the transfer belt rotate in the first direction in conjunction therewith, the clutch is opposed so that the cam is held at the retracted position. The rotation of the pulley is not transmitted to the cam, and the image carrier When the opposing pulley and the transfer belt rotate in the second direction in conjunction with this, the cam engages with the image carrier and the transfer belt separates from the image carrier surface. The image forming apparatus according to claim 1, wherein the image forming apparatus is configured as a one-way clutch that transmits rotation of a pulley to a cam. 10. A transmission means for transmitting the rotation of the image carrier to the opposing pulley, wherein the rotation is transmitted from the image carrier to the opposing pulley even when the transfer belt is separated from the surface of the image carrier. 10. The power transmission device according to claim 9, wherein:
An image forming apparatus according to claim 1. 11. The transfer member is detachable from the surface of the image carrier, and rotates in a first direction or a second direction in conjunction with rotation of the image carrier, and contacts the surface of the image carrier. First
A transfer material onto which a toner image on the surface of the image carrier is transferred when the toner image is transferred in the direction of rotation, and a transfer member contacting / separating means provided on the transfer drum; And a clutch interposed between the transfer drum and the transfer drum. The clutch is provided when the image bearing member rotates in a first direction and the transfer drum rotates in a first direction in conjunction with the rotation. When the rotation of the transfer drum is not transmitted to the cam so that the cam is held at the retracted position, the image carrier rotates in the second direction, and when the transfer drum rotates in the second direction in conjunction with the rotation, The image forming apparatus according to claim 1, wherein the image forming apparatus is configured as a one-way clutch that transmits rotation of the transfer drum to the cam so that the cam engages with the image carrier and the transfer drum separates from the surface of the image carrier. 12. A transfer device for transmitting rotation of the image carrier to the transfer drum, wherein the rotation is transmitted from the image carrier to the transfer drum even when the transfer drum is separated from the surface of the image carrier. 2. The power transmission device according to claim 1,
2. The image forming apparatus according to 1. 13. When the image carrier rotates in a first direction in a state where the cam is engaged with the image carrier and the transfer member is separated from the surface of the image carrier, the cam receives from the image carrier. The image forming apparatus according to claim 5, wherein the transfer member returns to the retracted position by force, and the transfer member contacts the surface of the image carrier. 14. An image bearing member, wherein an engagement groove with which an edge of the cam returning to the retracted position is engaged is formed on the image carrier side.
The image forming apparatus according to any one of the above. 15. The image bearing member comprises an image bearing drum, and when the image bearing drum rotates in a second direction, the cam engages with an end member fixed to an axial end of the image bearing drum. The image forming apparatus according to claim 2, wherein the transfer member is separated from the surface of the image bearing drum. 16. The image carrier comprises an image carrier belt that is wound around a plurality of image carrier pulleys and rotates in a first or second direction, and wherein the cam includes the plurality of image carrier pulleys. 15. The image forming apparatus according to claim 2, wherein the transfer member is separated from the surface of the image carrying belt by engaging with a pulley for the image carrier facing the transfer member via the image carrying belt. 17. The image forming apparatus according to claim 1, wherein the image carrier rotates in the second direction after the transfer residual toner on the surface of the image carrier has been removed by the cleaning member. 18. The image forming apparatus according to claim 17, wherein the cleaning member is a cleaning blade that presses against the surface of the image carrier to scrape off the untransferred toner attached to the surface. 19. The image carrier according to claim 1, wherein said image carrier starts to rotate in a second direction, the transfer member separates from the surface of the image carrier with the rotation, and then the image carrier stops rotating. The distance along which the point on the surface moves along the surface is the distance along the surface of the image carrier from the contact point where the transfer member contacts the image carrier surface to the contact point where the cleaning member contacts the image carrier surface. 18. It is set shorter than
Or the image forming apparatus according to 18. 20. The latent image carrier according to claim 1, wherein the image carrier is formed with an electrostatic latent image, and the electrostatic latent image is visualized as a toner image. An image forming apparatus according to claim 1. 21. The image forming apparatus according to claim 1, wherein said image bearing member is configured as an intermediate transfer member to which toner is transferred from a latent image bearing member.