JP2012155041A - Image forming apparatus and transferring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress degradation of image quality even when a part of an outer peripheral face is lacking in transferring means for transferring an image having been formed on an image carrier onto a recording medium.SOLUTION: An image forming apparatus of the invention comprises: a photosensitive drum; an exposing device for forming an image on the photosensitive drum; and a transfer drum 21 for transferring the image having been formed on the photosensitive drum by the exposing device onto a sheet. The transfer drum 21 includes: a base part 21A rotatably provided; an elastic layer 21B provided on an outer circumferential face of the base part 21A, having an exposed portion 21C corresponding to a partial lack of an outer circumferential face thereof, and brought into contact with the photosensitive drum under pressure; and a pressing part 61 provided to be rotated with the base part 21A and pressing the photosensitive drum when the exposed portion 21C opposes the photosensitive drum during the rotation of the base part 21A.

Description

  The present invention relates to an image forming apparatus and a transfer apparatus.

  An image forming apparatus for transferring a developed image formed on a photoconductor to a sheet using a transfer drum having an elastic layer and a gripper for gripping the edge of the sheet on the surface as the prior art described in the publication, An image that satisfies L1-L3> L2 where L1 is the distance from the latent image forming position to the transfer position, and L3 is the distance from the leading edge position of the transfer material to the rear end of the elastic layer. There is a forming apparatus (Patent Document 1).

JP 7-271209 A

  An object of the present invention is to suppress deterioration in image quality even when a part of the outer peripheral surface is cut out by a transfer unit that transfers an image formed on an image carrier to a recording medium.

According to the first aspect of the present invention, there is provided an image carrier, an image forming unit for forming an image on the image carrier, and a transfer for transferring an image formed on the image carrier by the image forming unit to a recording medium. The transfer means includes a base portion that is rotatably provided, a notch portion that is provided on an outer periphery of the base portion, and a part of the outer peripheral surface of which is notched, and is in pressure contact with the image carrier. Provided with a peripheral member and a pressing portion that is provided so as to rotate together with the base, and presses the image holding body when the notch faces the image holding body as the base rotates. An image forming apparatus characterized by the above.
2. The image forming apparatus according to claim 1, further comprising a holding member that is provided in the notch and holds the supplied recording material on the outer peripheral surface of the outer peripheral material. It is.
A third aspect of the present invention is the image forming apparatus according to the first or second aspect, wherein the pressing portion exists in a range corresponding to the notch portion in a circumferential direction of the base portion.

According to a fourth aspect of the present invention, when the image forming unit forms an image on the image holding member, the notch portion faces the image holding member as the base portion rotates. The image forming apparatus according to claim 1.
A fifth aspect of the present invention is the image forming apparatus according to any one of the first to fourth aspects, wherein the pressing portion protrudes outward from the outer peripheral surface of the outer peripheral material.
According to a sixth aspect of the present invention, there is provided a base portion that is rotatably provided, and an outer peripheral member that is provided on the outer periphery of the base portion and includes a notch portion in which a part of the outer peripheral surface is notched and is pressed against the image carrier. A holding member that is provided in the notch and holds the supplied recording material on the outer peripheral surface of the outer peripheral material, and is provided so as to rotate together with the base, and the notch as the base rotates. And a pressing unit that presses the image carrier when the unit faces the image carrier.

According to the first aspect of the present invention, as compared with the case where the present configuration is not provided, a part of the outer peripheral surface is notched by the transfer means for transferring the image formed on the image carrier to the recording medium. Even in the case where image quality is present, image quality deterioration can be suppressed.
According to the second aspect of the present invention, the supplied recording material can be more reliably held as compared with the case where the present configuration is not provided.
According to the third aspect of the present invention, image quality deterioration can be further suppressed as compared with the case where the present configuration is not provided.
According to the fourth aspect of the present invention, image quality deterioration that occurs when the image forming unit forms an image on the image holding member can be suppressed as compared with the case where the present configuration is not provided.
According to invention of Claim 5, compared with the case where it does not have this structure, a press part can press an image holding body more reliably.
According to the sixth aspect of the present invention, a part of the outer peripheral surface is notched in the transfer device that transfers the image formed on the image holding member to the recording medium, as compared with the case without this configuration. Even in the case where image quality is present, image quality deterioration can be suppressed.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an exemplary embodiment. It is the schematic for demonstrating the relationship between the paper concerning this Embodiment, a front-end | tip gripper, and a rear-end gripper. It is a schematic block diagram of the front-end | tip gripper which concerns on this Embodiment. It is a schematic block diagram of the rear-end gripper which concerns on this Embodiment. It is a schematic block diagram of the press part which concerns on this Embodiment. The modification of the press part provided in an exposed part is shown. The modification of the press part provided in a front-end | tip gripper is shown.

Hereinafter, this embodiment will be described in detail with reference to the accompanying drawings.
<Overall Configuration of Image Forming Apparatus 1>
First, each configuration of the image forming apparatus 1 to which the exemplary embodiment is applied will be described with reference to FIGS. Here, FIG. 1 is a schematic configuration diagram showing an image forming apparatus 1 to which the exemplary embodiment is applied. FIG. 2 is a schematic diagram for explaining the relationship between the sheet S and the leading edge gripper 23 and the trailing edge gripper 27 according to the present embodiment, and FIG. 2A is viewed from the outside of the image forming apparatus 1. FIG. 2B is a view of the leading edge gripper 23 and the trailing edge gripper 27 for suppressing the sheet S, and FIG. 2B is a drawing of the leading edge gripper 23 and the trailing edge gripper 27 for suppressing the sheet S as viewed from the direction of arrow II in FIG. FIG.

  The image forming apparatus 1 includes an image forming unit 10 on which a toner image is formed, a paper supply unit 40 that supplies and conveys a paper S (recording medium), and holds the supplied paper S and forms an image on the held paper S. The image forming apparatus includes a transfer device 20 that transfers a toner image formed by the unit 10, a fixing device 30 that fixes a toner image on the paper S released from the transfer device 20, and a control unit 100 that controls the entire image forming apparatus 1. Yes. Each component of the image forming apparatus 1 is accommodated in the housing 2, and a paper discharge stacking unit 3 for stacking the sheets S discharged from the fixing device 30 is provided on the top of the housing 2. Yes.

<Configuration of each member>
First, the image forming unit 10 includes a photosensitive drum 11. Further, the image forming unit 10 includes a charging device 12 that charges the photosensitive drum 11, an exposure device 13 that exposes the charged photosensitive drum 11, a rotary developing device 14 that performs development using a developer, and the photosensitive drum 11. A cleaning device 15 is included for cleaning the developer remaining on the top. Each member will be described below.

  A photosensitive drum 11, which is an example of an image carrier, includes a photosensitive layer 11 </ b> A having a negative charging polarity on its surface and is attached so as to rotate in the direction of arrow A. The charging device 12, the exposure device 13, the rotary developing device 14, and the cleaning device 15 are installed in this order along the arrow A direction around the photosensitive drum 11. Here, the outer diameter of the photosensitive drum 11 is, for example, 30 mm.

The charging device 12, which is an example of an image forming unit, is a contact roller type discharging device in the present embodiment, and is configured to charge the photosensitive drum 11 while rotating together with the photosensitive drum 11.
The exposure device 13 is configured to form an electrostatic latent image by irradiating the charged surface of the photosensitive drum 11, and in the present embodiment, a plurality of LEDs (not shown) and a refractive index distribution type are used. Includes a lens.

The rotary developing device 14 includes a rotating shaft 14A, and yellow (Y), magenta (M), cyan (C), and black (K) developing devices 14Y, 14M, 14C, and 14K installed around the rotating shaft 14A. It has. The rotary developing device 14 is detachably attached to the housing 2. The rotary developing device 14 is configured to rotate in the direction of arrow C about the rotation shaft 14A.
When only a single color image is formed instead of a multicolor image, the rotary developing device 14 may be replaced with a developing device having only a single color developing device (for example, only the black (K) developing device 14K). In the rotary developing device 14, any one of the developing devices 14 </ b> Y, 14 </ b> M, 14 </ b> C, and 14 </ b> K is stopped at a position facing the photosensitive drum 11. The rotary developing device 14 is configured to develop the electrostatic latent image on the photosensitive drum 11 formed by the exposure device 13 using toner. The outer diameter of the rotary developing device 14 is, for example, 100 mm.

  These developing units 14Y, 14M, 14C, and 14K contain a one-component developer that uses magnetic toner or non-magnetic toner alone. Here, in the present embodiment, a one-component developer is used, but a two-component developer including a toner and a carrier may be used. In the following description, the one-component developer is simply referred to as a developer.

  The cleaning device 15 is configured to remove the developer remaining on the surface of the photosensitive drum 11 and deposits other than the developer. The cleaning device 15 of the present embodiment is a blade type cleaner.

  Next, the transfer device 20 will be described. The transfer device 20 includes a transfer drum 21 that transfers the toner image on the photosensitive drum 11 onto the paper S. The transfer device 20 also includes a leading edge gripper 23 that holds the leading edge of the paper S on the transfer drum 21, and a trailing edge gripper 27 that holds the trailing edge of the paper S on the transfer drum 21. Further, the transfer device 20 includes a paper detection sensor 25 that detects the passage of the paper S. Furthermore, the transfer device 20 includes a transfer drum motor M1 (described later) that transfers the transfer drum 21 and a transfer drum gear G1 (described later) that connects the transfer drum motor M1 and the rotation shaft 21D.

  A transfer drum 21 as an example of a transfer unit is disposed to face the photosensitive drum 11 and to be rotatable about a rotation shaft 21D. The transfer device 20 is detachably attached to the housing 2. The transfer drum 21 includes a drum-shaped base portion 21A, an elastic layer 21B formed on the outer peripheral surface of the base portion 21A, and a pressing portion 61 (provided on the outer peripheral surface of the base portion 21A on which the elastic layer 21B is not provided. (See FIG. 5, described later). More specifically, the elastic layer 21B extends along the outer periphery of the drum-shaped base 21A from the elastic layer front end 21BL that is the front end of the paper S in the transport direction to the elastic layer rear end 21BT that is the rear end of the paper S in the transport direction. Stretched. On the other hand, the elastic layer 21B as an example of the outer peripheral material does not cover a part of the outer peripheral surface of the base portion 21A along the axial direction of the base portion 21A (the elastic layer rear end 21BT and the elastic layer front end 21BL). This portion is an exposed portion 21C (notched portion) where the base portion 21A is exposed. And the press part 61 is provided in the exposed part 21C.

  The transfer drum 21 is provided to rotate in the direction of arrow B in synchronization with the rotation of the photosensitive drum 11 in a state where the elastic layer 21B is elastically deformed to form a nip portion with the photosensitive drum 11. Here, the rotating shaft (not shown) of the photosensitive drum 11 and the rotating shaft 21D of the transfer drum 21 are fixed to the image forming apparatus 1, respectively. That is, the distance between the rotation axes of the photosensitive drum 11 and the transfer drum 21 is maintained. Further, the exposed portion 21 </ b> C of the transfer drum 21 is not in contact with the photosensitive drum 11. Further, the outer diameter of the transfer drum 21 is larger than the outer diameter of the photosensitive drum 11, for example, 120 mm.

The base 21A in the present embodiment is a conductive hollow tube, for example, made of metal. On the other hand, the elastic layer 21B is an elastic member having semiconductivity, and is made of rubber such as polyurethane, chloroprene, EPDM (ethylene / propylene rubber), NBR (nitrile rubber) or the like.
Here, a dielectric such as a dielectric sheet is not provided on the outer peripheral surface of the elastic layer 21B. Further, the transfer drum 21 is not provided with a charger such as a corotron for electrostatically attracting the paper S. That is, the transfer drum 21 does not use so-called electrostatic attraction for holding the paper S.
Further, the peripheral length of the transfer drum 21 (more specifically, the peripheral length of the elastic layer 21B) is the maximum length of the image formed on the paper S by the image forming apparatus 1 in the transport direction of the paper S (print Longer than the maximum length).

The base 21A is configured to be applied with a transfer bias composed of a voltage having a polarity opposite to that of toner from a high voltage power source (not shown). The toner constituting the toner image on the photosensitive drum 11 is transferred to the paper S on the elastic layer 21B at the transfer portion Tr.
The transfer portion Tr is an area where the photosensitive drum 11 and the transfer drum 21 face each other, and the toner image on the photosensitive drum 11 is transferred to the sheet S of the elastic layer 21B. An area where the transfer drum 21 can come into contact.

The paper detection sensor 25 is disposed to face the outer peripheral surface of the transfer drum 21 and detects the passage of the paper S that is wound around the transfer drum 21 and conveyed. More specifically, the paper detection sensor 25 emits near infrared light toward the outer peripheral surface of the transfer drum 21. Then, the reflected light (near infrared light) from the outer peripheral surface of the transfer drum 21 or the sheet S held on the transfer drum 21 is received. Then, for example, by detecting a change in the amount of reflected light, it is detected that the leading edge and the trailing edge of the paper S have passed.
The sheet detection sensor 25 is provided on the upstream side in the transport direction of the sheet S from the standby position (described later) of the trailing edge gripper 27. In the present embodiment, the paper detection sensor 25 is disposed between the standby position of the trailing edge gripper 27 and a paper feed position Pa (described later).
Further, the paper detection sensor 25 measures the phase of the rotating transfer drum 21 by detecting a mark (not shown) provided on the transfer drum 21.

  The fixing device 30 includes a heating roll 31 having a heating source (not shown) and rotatably arranged, and a pressure roll 32 pressed against the heating roll 31.

  The paper supply unit 40 is provided below the image forming apparatus 1, specifically, below the transfer drum 21. The paper supply unit 40 stores the paper S therein, and the size of the paper S stored in the take-out roll 42. A sheet size sensor (not shown) for detecting the sheet S, a take-out roll 42 for taking out the sheet S from the sheet storage unit 41, a separating roll 43 for separating the closely contacted sheet S, and a transport roll 44 for transporting the sheet S.

Note that the image forming apparatus 1 does not include a member that is placed in contact with the transfer drum 21, for example, a peeling claw, in order to peel the paper S wound around the transfer drum 21. This is because, as will be described in detail later, the wound paper S can be peeled off from the transfer drum 21 by the nip between the transfer drum 21 and the photosensitive drum 11. Since there is no need to provide a peeling claw, the image forming apparatus 1 of the present embodiment can be further downsized.
Here, the above description that the separation claw is not provided does not prevent the provision of a guide member (for example, a sheet conveyance path) that guides the sheet S that has already been peeled from the transfer drum 21 in the conveyance direction to the discharge path 52. Absent. In other words, in the present invention, a paper conveyance path or the like that guides the already peeled paper S provided without contacting the transfer drum 21 downstream of the paper discharge position Pb (described later) in the conveyance direction may be provided.

The controller 100 receives a signal from a user interface (not shown) that receives an instruction from the user. In addition, an image signal is input to the control unit 100 from an image output instruction unit (not shown) provided inside or outside the image forming apparatus 1. Further, the control unit 100 is supplied with a paper S passing signal and a phase signal of the photosensitive drum 11 sent from the paper detection sensor 25.
And the control part 100 outputs a control signal to each following part. That is, by rotating / stopping a photosensitive drum driving unit (not shown) for rotating the photosensitive drum 11, the charging device 12, the exposure device 13, and the rotary developing device 14, the developing position facing the photosensitive drum 11 is reached. A developing device driving unit (not shown) for positioning the target developing devices 14Y, 14M, 14C, and 14K, and a developing bias for setting a developing bias to be supplied to the developing devices 14Y, 14M, 14C, and 14K disposed at the developing position A setting unit (not shown), a transfer drum driving unit (see transfer drum motor M1 and transfer drum gear G1 in FIG. 4) for rotating the transfer drum 21, and a rear end gripper driving unit (see FIG. 4) for rotating the rear end gripper 27. A rear end gripper driving motor M2 and a rear end gripper gear G2), a transfer bias setting unit for setting a transfer bias to be supplied to the transfer drum 21 Not shown), the tip gripper 23, the trailing edge gripper 27, the sheet supply unit 40, and the fixing device 30, the control unit 100 is arranged to output a control signal, respectively.

  Here, in the image forming apparatus 1, the supply path 51 for supplying the paper S from the paper storage unit 41 to the transfer portion Tr and the paper S on which the toner image is transferred are discharged via the fixing device 30. And a discharge path 52 for discharging. In this embodiment, the sheet S supplied toward the transfer drum 21 rotates while being wound around the transfer drum 21 by the leading edge gripper 23 and the trailing edge gripper 27. A path along which S passes is referred to as a rotation path 53.

<Front end gripper 23 and rear end gripper 27>
Next, the configuration of the front end gripper 23 and the rear end gripper 27 will be described with reference to FIGS. 1 to 4. Here, FIG. 3 is a schematic configuration diagram of the front end gripper 23 to which the present embodiment is applied, and FIG. 3A is a view of the opened front end gripper 23 cut along a surface intersecting with the rotation shaft 21D of the transfer drum 21. FIG. 3B is a cross-sectional view of the closed leading end gripper 23 cut along a plane intersecting the rotation shaft 21D of the transfer drum 21. FIG. FIG. 4 is a schematic configuration diagram of the rear end gripper 27 to which the present embodiment is applied. FIG. 4A shows the rear end gripper 27 and the transfer drum 21 that are opened along the rotation shaft 21D of the transfer drum 21. FIG. 4B is a cross-sectional view of the closed rear end gripper 27 and the transfer drum 21 cut along the rotation shaft 21D of the transfer drum 21, and FIG. 4C is a cross-sectional view of FIG. It is the elements on larger scale of the rear end gripper 27 shown in the circle | round | yen in the figure of (a).

First, the front end gripper 23 and the rear end gripper 27 can be opened and closed, respectively. Further, the front end gripper 23 and the rear end gripper 27 can rotate together with the transfer drum 21. The leading edge gripper 23 and the trailing edge gripper 27 are configured to hold the sheet S on the transfer drum 21.
Specifically, as shown in FIG. 2, the leading edge gripper 23 grips the leading end portion (the left end portion of the paper S in FIG. 2) in the transport direction (arrow B) of the paper S on the transfer drum 21, and the paper The trailing edge gripper 27 holds the trailing edge (the edge on the right side of the sheet S in FIG. 2) of the conveying direction (arrow B) of S.
The tip gripper 23 is fixed to the transfer drum 21 (see FIG. 1). One rear end gripper 27 is provided separately from the transfer drum 21 (see FIG. 1), and the position of the rear end gripper 27 with respect to the transfer drum 21 can be changed.
When the leading edge gripper 23 grips the sheet S, the movement of the sheet S in the direction away from the transfer drum 21 is restricted without allowing the sheet S to shift in the transport direction. On the other hand, when the trailing edge gripper 27 holds the paper S, the deviation of the paper S in the transport direction is allowed and the movement in the direction away from the transfer drum 21 is limited.
Hereinafter, detailed configurations of the front end gripper 23 and the rear end gripper 27 will be described.

<Tip gripper 23>
First, as shown in FIG. 1, the front end gripper 23, which is an example of a holding member, is attached to the exposed portion 21 </ b> C of the transfer drum 21. Specifically, the front end gripper 23 is provided between the elastic layer rear end 21BT and the elastic layer front end 21BL. The leading edge gripper 23 is configured not to contact the photosensitive drum 11 regardless of whether the leading edge gripper 23 is opened or closed, as will be described later.
Also, as shown in FIG. 3A, the leading edge gripper 23 includes an outer member 23a that holds the sheet S from the outer peripheral side (upper side in FIG. 3) of the transfer drum 21 and an inner peripheral side (in FIG. 3). An inner member 23b that holds the sheet S from the lower side and a rotating shaft 23c provided integrally with the outer member 23a. The outer member 23a, the inner member 23b, and the rotating shaft 23c are provided between the elastic layer rear end 21BT and the elastic layer front end 21BL. Then, the outer member 23a rotates about the rotation shaft 23c fixed to the transfer drum 21 between the elastic layer rear end 21BT and the elastic layer front end 21BL, whereby the outer member 23a and the inner member 23b are rotated. The relative position changes, and the tip gripper 23 is configured to open and close. As shown in FIG. 3, the leading edge gripper 23 opens toward the downstream side in the conveyance direction (arrow B) of the paper S.

As shown in FIG. 3A, the outer member 23a of the leading end gripper 23 is provided so as to be able to rotate on the outer peripheral side of the transfer drum 21 with respect to the rotating shaft 23c with the rotating shaft 23c as a center (arrows in FIG. 3). F1 and F2). The outer member 23a includes an outer holding portion 23a1 that suppresses the side on which the image of the sheet S is formed from the outer peripheral side of the transfer drum 21, and the inner member 23b as the outer member 23a rotates around the rotation shaft 23c. And a corner portion 23a3 for pushing. The outer holding portion 23a1 is disposed on the outer peripheral side of the transfer drum 21 with respect to the inner member 23b. On the other hand, the corner 23a3 is arranged on the inner peripheral side of the transfer drum 21 with respect to the inner member 23b.
The outer member 23a is preferably thin in order to avoid contact with the photosensitive drum 11 at the transfer site Tr. The outer member 23a is made of metal such as stainless steel (SUS).

The inner member 23b of the tip gripper 23 is movable by the transfer drum 21 so as to be movable between the outer peripheral side and the inner peripheral side of the transfer drum 21 along a guide member (not shown) (arrows D5 and D6 in FIG. 3A). It is supported. The inner member 23b has an inner restraining portion 23b1 that restrains the side opposite to the side on which the image of the paper S is formed from the inner peripheral side of the transfer drum 21.
The rotating shaft 23c extends parallel to the rotating shaft 21D (see FIG. 1) of the transfer drum 21. Further, it is provided inside the transfer drum 21 and on the outer peripheral side.

  In the present embodiment, as shown in FIG. 3A, there is a gap between the outer holding portion 23a1 and the inner holding portion 23b1 when the tip gripper 23 is open. On the other hand, as shown in FIG. 3B, when the tip gripper 23 is closed, the outer restraining portion 23a1 and the inner restraining portion 23b1 are close to each other so as to eliminate a gap between the outer restraining portion 23a1 and the inner restraining portion 23b1. .

<Rear end gripper 27>
First, as shown in FIG. 4, the rear end gripper 27 is attached so as to straddle the transfer drum 21 in the direction of the rotation shaft 27 </ b> D of the rear end gripper 27. The periphery of the rotary shaft 27D is configured to rotate independently with respect to the transfer drum 21.
Specifically, as shown in FIG. 4, the trailing edge gripper 27 holds a sheet suppression unit 27 a that opposes the outer peripheral surface of the transfer drum 21 and suppresses the movement of the sheet S, and both ends of the sheet suppression unit 27 a. Holding part 27b. And this holding | maintenance part 27b is each connected with rotating shaft 27D. The rear end gripper 27 has a wedge-type push-up member 27 c that moves the sheet suppression unit 27 a along the diameter direction of the transfer drum 21 via the holding unit 27 b.
The rear end gripper 27 is configured to open and close by changing the distance between the sheet suppressing portion 27a and the outer peripheral surface of the transfer drum 21 (arrows D1 and D2 in FIG. 4).

  Further, the rotation shaft 27 </ b> D of the rear end gripper 27 is disposed concentrically with the rotation shaft 21 </ b> D of the transfer drum 21. However, as described above, the transfer drum 21 and the rear end gripper 27 rotate by separate driving. Specifically, the transfer drum 21 is rotationally driven by the transfer drum motor M1 and the transfer drum gear G1, while the rear end gripper 27 is held by the rear end gripper drive motor M2 and the rear end gripper drive motor M2. It is rotationally driven by a rear end gripper gear G2 connecting the portion 27b.

The sheet suppression unit 27a extends parallel to the rotation shaft 21D of the transfer drum 21 and is the maximum width of the sheet S that can be used in the image forming apparatus 1 according to the present embodiment (the sheet S is the transfer drum 21). When arranged on the outer peripheral surface, it is longer than the length in the direction parallel to the rotation axis 21D. Further, since the rear end gripper 27 is in contact with the photosensitive drum 11 at the transfer portion Tr (described later), it is preferable that the rear end gripper 27 is thin.
In addition, it is desirable that the portion of the sheet suppressing portion 27a of the rear end gripper 27 that contacts the photosensitive drum 11 does not have a corner portion. This is to reduce damage to the photosensitive drum 11 caused by the rear end gripper 27 coming into contact with the photosensitive drum 11.
In the present embodiment, the sheet suppression unit 27a is made of a plate-like member. The shape of the sheet suppressing portion 27a of the rear end gripper 27 may be a film shape, a wire shape, a columnar shape, or the like. Moreover, the sheet | seat suppression part 27a consists of resin, such as PET (Polyethylene terephthalate), a polyimide, a fluorine, for example.

  The holding unit 27b includes two members provided at both ends of the sheet suppressing unit 27a, and is provided to face each other with a gap longer than the maximum width of the sheet S that can be used in the image forming apparatus 1. . Each holding portion 27b is provided to be rotatable around the rotation shaft 27D. Further, the holding portion 27 b is provided so as to extend in the diameter direction of the transfer drum 21 and be movable in the radial direction of the transfer drum 21. The holding portion 27b is urged from the outer peripheral side of the transfer drum 21 toward the inner peripheral side by a spring 27e.

The wedge-type push-up member 27c is provided so as to be rotatable around the rotation shaft 27D together with the holding portion 27b. Further, the wedge-type push-up member 27c is provided to be movable in a direction along the rotation shaft 27D by driving a solenoid (not shown) (arrows E1 and E2 in FIG. 4). The holding portion 27b is configured to move in the diameter direction of the transfer drum 21 when the wedge-type push-up member 27c moves in the direction along the rotation shaft 27D.
More specifically, one end of the wedge-type push-up member 27c has a wedge shape. That is, the width of the transfer drum 21 in the radial direction becomes narrower toward the tip of the wedge-shaped end. In the present embodiment, a pair of wedge-type push-up members 27c are provided on both ends of the rotary shaft 27D with the wedge-type end portions facing each other. Each wedge-type push-up member 27c is disposed so as to extend parallel to the rotation shaft 27D. Further, the wedge-type end portions of the wedge-type push-up member 27c are arranged so as to face the inner peripheral side end portions of the holding portions 27b, respectively.
The wedge-type push-up member 27c rotates around the rotation shaft 27D together with the holding portion 27b, and enters the inner peripheral side of the holding portion 27b when, for example, the sheet suppressing portion 27a stops at a standby position to be described later. Accordingly, the sheet suppression unit 27 a is moved away from the outer peripheral surface of the transfer drum 21. Thus, the rear end gripper 27 is configured to open.

In the present embodiment, as shown in FIG. 4A, when the rear end gripper 27 is opened, the wedge-type push-up member 27c supports the inner peripheral end of the holding portion 27b. In addition, the gap formed between the sheet suppression unit 27a and the elastic layer 21B provided on the outer periphery of the transfer drum 21 is large.
On the other hand, as shown in FIG. 4B, when the rear end gripper 27 is closed, the wedge-type push-up member 27c does not support the inner peripheral side end of the holding portion 27b. A gap formed between the sheet suppressing portion 27a and the elastic layer 21B is small.
4A, when the trailing edge gripper 27 is open, the leading edge gripper 23 holding the sheet S can pass between the sheet suppressing portion 27a and the rotation center of the transfer drum 21. .

<Operation of Image Forming Apparatus 1>
Next, the overall operation of the image forming apparatus 1 will be described with reference to FIGS. 1 and 2. Here, a case where a plurality of color images are formed on one sheet S by the image forming apparatus 1 will be described.

  First, a color material reflected light image of a document read by a document reading device (not shown), and color material image data formed by a personal computer (not shown) or the like are, for example, R (red), G (green). , B (blue) data is input to an image signal processing device (not shown) and subjected to predetermined image processing. The image data subjected to the image processing is converted into color material gradation data of four colors of yellow (Y), magenta (M), cyan (C), and black (K), and is output to the exposure device 13.

With the start of the recording image forming operation, the photosensitive drum 11 and the transfer drum 21 start to rotate in synchronization. At this time, both the front end gripper 23 and the rear end gripper 27 are open.
At this time, the front end gripper 23 rotates together with the transfer drum 21, while the rear end gripper 27 does not rotate together with the transfer drum 21 and is stationary at the standby position (the peripheral speed is zero). Specifically, the rear end gripper 27 is arranged on the outer periphery of the transfer drum 21 as shown in FIG. 1 so as to face the position between the paper feed position Pa and the transfer portion Tr.

  Then, after the photosensitive layer 11 </ b> A of the rotating photosensitive drum 11 is charged by the charging device 12, an electrostatic latent image of the first color (for example, yellow) corresponding to the image information is formed by the exposure device 13. Further, as the transfer drum 21 starts to rotate, the paper detection sensor 25 measures the phase of the transfer drum 21. The measured phase is sent to the control unit 100.

On the other hand, in the rotary developing device 14, a developing device (for example, yellow developing device 14 </ b> Y in the case of yellow) having a color component toner corresponding to the electrostatic latent image formed on the photosensitive drum 11 is used as the photosensitive drum 11. It has been rotated in advance so as to be placed at a position opposite to and stopped.
Then, for example, the electrostatic latent image on the photosensitive drum 11 is developed by the developing device 14 </ b> Y, and a toner image is formed on the photosensitive drum 11. Then, the toner image (here, a yellow toner image) is sent toward the transfer portion Tr facing the transfer device 20 as the photosensitive drum 11 rotates.

  Also, the paper S is supplied in response to the start of the recording image forming operation. Specifically, the paper S taken out from the paper storage unit 41 by the take-out roll 42 is sent out to the supply path 51 using the transport roll 44 through the separation roll 43. Then, the paper detection sensor 25 detects that the front end of the paper S in the transport direction has passed, and sends a detection signal to the control unit 100. The control unit 100 that has received the detection signal, based on the detection signal and phase obtained by the paper detection sensor 25, causes the paper S to reach the paper feed position Pa as the leading edge gripper 23 reaches the paper feed position Pa. To control the conveyance.

  At the paper feed position Pa, the leading edge gripper 23 shifts from an open state to a closed state. Along with this, the end on the leading end side in the transport direction of the sheet S is gripped by the leading end gripper 23. At this time, the rear end gripper 27 is at the outer periphery of the transfer drum 21 and is stationary at the standby position. The leading edge gripper 23 holding the sheet S passes between the stationary trailing edge gripper 27 and the rotation center of the transfer drum 21.

The leading edge gripper 23 that has passed between the trailing edge gripper 27 and the rotation center of the transfer drum 21 passes through the transfer portion Tr while holding the sheet S. The sheet S that has been gripped by the leading edge gripper 23 and passed through the transfer portion Tr is wound around the outer peripheral surface of the transfer drum 21 while being gripped by the leading edge gripper 23, and is conveyed along the rotation path 53 (see FIG. 1). The
Then, after the first color (for example, yellow) electrostatic latent image corresponding to the image information is formed by the exposure device 13, the paper detection sensor 25 detects that the rear end of the paper S in the transport direction has passed. Then, the control unit 100 that has received the signal from the paper detection sensor 25 issues an instruction to the trailing edge gripper 27. Receiving the instruction, the rear end gripper 27 shifts from the open state to the closed state (arrow D1 in FIG. 2B).

  Now, the closed rear end gripper 27 starts to rotate in synchronization with the transfer drum 21. In other words, the sheet S rotates with the transfer drum 21 while the front end gripper 23 grips the leading end in the transport direction and the rear end gripper 27 holds the end. The first (for example, yellow) toner image formed on the photosensitive drum 11 is transferred to the sheet S on the transfer drum 21 at the transfer portion Tr where the photosensitive drum 11 and the transfer drum 21 face each other. The toner remaining on the photosensitive drum 11 after the transfer is removed by a cleaning device 15 (see FIG. 1).

Then, from the second color, latent image formation (for example, magenta, cyan) before the final color (for example, black), development and transfer are similarly repeated according to the above-described procedure. However, when the toner images of the respective colors are formed, the rotary developing device 14 rotates and the corresponding developing devices 14M and 14C are arranged at the stop positions.
Meanwhile, the sheet S is rotated and conveyed while being wound around the transfer drum 21 by the leading edge gripper 23 and the trailing edge gripper 27, and the toner images of the second and subsequent colors are overlapped each time the sheet S passes the transfer portion Tr. Sequentially transferred. As a result, for example, when full-color image formation is performed, toner images of each color of yellow (Y), magenta (M), and cyan (C) excluding black (K) are multiple-transferred onto the sheet S on the transfer drum 21. Is done.

  When the final color is transferred, unlike the transfer before the final color (for example, black), the leading edge gripper 23 shifts from the closed state to the open state at the transfer site Tr. As a result, the sheet S on which the grip by the leading edge gripper 23 is released and a full-color image is formed is peeled off from the transfer drum 21 at the leading edge in the transport direction of the sheet S by the nip between the elastic layer 21B and the photosensitive drum 11. It enters the discharge path 52 from the paper discharge position Pb.

  Thereafter, as the paper S is transported, the trailing edge gripper 27 that holds the trailing edge of the paper S in the transport direction shifts from a closed state to an open state (see arrow D2 in FIG. 2B). Note that the transition from the closed state to the opened state of the trailing edge gripper 27 is after the electrostatic latent image of the final color (for example, black) corresponding to the image information has already been formed by the exposure device 13. . Then, the rear end gripper 27 in the opened state stops at the standby position.

Then, the rear end in the transport direction of the sheet S released from being held by the rear end gripper 27 is peeled off from the transfer drum 21 and enters the discharge path 52 from the discharge position Pb. The sheet S that has entered the discharge path 52 is sent to the fixing device 30. Then, the toner image on the paper S is fixed by the heating roll 31 and the pressure roll 32 of the fixing device 30.
The sheet S after completion of fixing is discharged out of the image forming apparatus 1 by the transport roll 44 and is stacked on the paper discharge stacking unit 3.

<Pressing part 61>
Here, the pressing portion 61 provided on the transfer drum 21 will be described with reference to FIG. FIG. 5 is a schematic configuration diagram of the pressing portion 61 according to the present embodiment. More specifically, FIG. 5A is a perspective view of the transfer drum 21 provided with the pressing portion 61, and FIG. 5B is a configuration diagram around the pressing portion 61 viewed from the arrow V in FIG. It is. Further, in FIG. 5B, the tip gripper 23 is not shown.

First, as described above, in the transfer drum 21 of the present embodiment, the pressing portion 61 is provided. Further, as shown in FIG. 5B, the pressing portion 61 is provided on the exposed portion 21 </ b> C where the base portion 21 </ b> A of the transfer drum 21 is exposed.
As shown in FIG. 5B, in the conveyance direction of the paper S on the transfer drum 21 (arrow B, the circumferential direction of the base portion 21A), the pressing portion 61 is between the elastic layer front end 21BL and the elastic layer rear end 21BT. In the portion where the elastic layer 21B is not provided.
Further, the outer surface of the pressing portion 61 protrudes from the outer surface of the elastic layer 21B with respect to the rotation shaft 21D (see FIG. 1) (see reference symbol h1). In the present embodiment, the thickness of the pressing portion 61 is made thicker than the elastic layer 21B, thereby forming a shape in which the outer surface of the pressing portion 61 protrudes. Specifically, the pressing part 61 is configured with a dimension that is thicker by h1 than the elastic layer 21B.

  Further, the pressing portion 61 is an exposed portion 21C, which is an end portion on the front side of the image forming apparatus 1 (left front side in FIG. 5A) and the rear side of the image forming apparatus 1 (FIG. 5A). At the end of the right side of the paper). In other words, the pressing portion 61 is provided at a position sandwiching the leading end gripper 23 in the direction along the rotation shaft 21 </ b> D (see FIG. 1) of the transfer drum 21. The pressing portion 61 is provided without being in contact with the tip gripper 23 and does not hinder the operation of the tip gripper 23.

  The pressing portion 61 is made of the same material as that of the elastic layer 21B. Specifically, it is a semiconductive elastic member, for example, made of rubber such as polyurethane, chloroprene, EPDM (ethylene / propylene rubber), NBR (nitrile rubber).

The pressing portion 61 presses the photosensitive drum 11 when passing through the transfer site Tr as the transfer drum 21 rotates. That is, the pressing unit 61 applies a nip pressure to the photosensitive drum 11.
As described above, the tip gripper 23 and the exposed portion 21 </ b> C are configured not to contact the photosensitive drum 11 when passing through the transfer site Tr. Therefore, only the pressing portion 61 applies nip pressure to the photosensitive drum 11 when the exposed portion 21C provided with the tip gripper 23 and the pressing portion 61 passes through the transfer site Tr.
In the present embodiment, when the pressing portion 61 passes through the transfer portion Tr, the area where the pressing portion 61 contacts the photosensitive drum 11 is the elastic layer when the elastic layer 21B passes through the transfer portion Tr. 21B is smaller than the area in contact with the photosensitive drum 11.

  In other words, the nip pressure applied to the photosensitive drum 11 when the pressing portion 61 passes through the transfer portion Tr is equal to the nip pressure applied to the photosensitive drum 11 when the elastic layer 21B passes through the transfer portion Tr. The pressing portion 61 of the present embodiment is configured so as to be substantially equal.

  Specifically, as described above, the outer surface of the pressing portion 61 with respect to the rotating shaft 21D (see FIG. 1) is configured to protrude beyond the outer surface of the elastic layer 21B. Here, by adopting a configuration in which the pressing portion 61 protrudes, the pressing portion 61 comes into contact with the photosensitive drum 11 by contact with the photosensitive drum 11 as compared with the case where the pressing portion 61 does not protrude from the outer surface of the elastic layer 21B. The amount of biting into the drum 11 increases. As a result, the nip pressure applied to the photosensitive drum 11 per unit area increases.

As described above, as the elastic layer rear end 21BT passes through the transfer portion Tr, the member that forms a nip with the photosensitive drum 11 changes from the elastic layer 21B to the pressing portion 61. In the transfer portion Tr, the area where the pressing portion 61 contacts the photosensitive drum 11 is smaller than the area where the elastic layer 21B contacts the photosensitive drum 11, but the nip pressure applied to the photosensitive drum 11 per unit area. The pressing portion 61 is larger than the elastic layer 21B. As a result, when the elastic layer rear end 21BT passes through the transfer site Tr and the member that forms a nip with the photosensitive drum 11 changes from the elastic layer 21B to the pressing portion 61, the nip pressure changes substantially. do not do.
In addition, when the elastic layer tip 21BL passes through the transfer site Tr, the member that forms a nip with the photosensitive drum 11 changes from the pressing portion 61 to the elastic layer 21B. In this case, the nip pressure is substantially changed. do not do.

Now, the present embodiment will be described in comparison with two cases adopting a configuration different from the present embodiment.
First, the present embodiment will be described in comparison with the case where the pressing portion 61 is not provided on the transfer drum 21 unlike the present embodiment.
First, a case where the pressing portion 61 is not provided on the transfer drum 21 will be described. In this case, when the exposed portion 21C passes through the transfer portion Tr, no nip pressure is applied to the photosensitive drum 11 (the tip gripper 23 and the exposed portion 21C do not contact the photosensitive drum 11 and the photosensitive drum No nip pressure is applied to 11). On the other hand, the elastic layer 21B applies a nip pressure to the photosensitive drum 11 when the elastic layer 21B passes through the transfer site Tr. For this reason, as the transfer drum 21 rotates, the applied nip pressure changes when the exposed portion 21C passes through the transfer site Tr and when the elastic layer 21B passes through the transfer site Tr. Therefore, as the transfer drum 21 rotates, the amount of deflection of the photosensitive drum 11 changes when the exposed portion 21C passes through the transfer portion Tr and when the elastic layer 21B passes through the transfer portion Tr.

The change in the deflection amount of the photosensitive drum 11 affects the quality of the image formed on the paper S by the image forming apparatus 1 in the present embodiment. Specifically, the change in the amount of deflection of the photosensitive drum 11 affects the electrostatic latent image formed when the exposure device 13 irradiates the surface of the photosensitive drum 11.
That is, when the exposure device 13 irradiates the surface of the photosensitive drum 11 (writes), if the deflection amount of the photosensitive drum 11 changes, the surface of the photosensitive drum 11 moves, and so-called focus misalignment is caused. Get up. In particular, when a gradient index lens having a shallow depth of focus is used, the influence of the focus position shift is large. When the electrostatic latent image formed when the focus position shift occurs is developed and transferred to the paper S, the image quality of the image formed on the paper S deteriorates. For example, this leads to an increase in the density fluctuation of the highlight portion of the image formed on the paper S and a deterioration in the reproducibility of the thin line.

  Next, this embodiment will be described. In the present embodiment, the pressing portion 61 is provided on the exposed portion 21C as described above. The pressing portion 61 applies a nip pressure to the photosensitive drum 11. As a result, fluctuations in the nip pressure that occur when the exposed portion 21C passes through the transfer site Tr are suppressed, and as a result, image quality deterioration is suppressed.

Second, unlike the present embodiment, the present embodiment will be described in comparison with a case where the pressing portion 61 does not protrude from the elastic layer 21B. Here, the description will be made assuming that the pressing portion 61 is made of the same material as that of the elastic layer 21B.
First, the case where the pressing part 61 does not protrude from the elastic layer 21B will be described. In this case, as the transfer drum 21 rotates, the nip pressure applied to the photosensitive drum 11 changes when the pressing portion 61 passes through the transfer site Tr and when the elastic layer 21B passes through the transfer site Tr. To do.
More specifically, as described above, the distance between the rotation axes of the photosensitive drum 11 and the transfer drum 21 is maintained. Therefore, the amount of biting into the photosensitive drum 11 in the pressing portion 61 is equal to the amount of biting into the photosensitive drum 11 in the elastic layer 21B. Accordingly, the pressing force of the pressing portion 61 and the elastic layer 21B per unit area is equal. On the other hand, when the pressing part 61 passes through the transfer part Tr, the area where the pressing part 61 contacts the photosensitive drum 11 is such that the elastic layer 21B passes through the transfer part Tr when the elastic layer 21B passes through the transfer part Tr. It is smaller than the area in contact with. Accordingly, the nip pressure of the pressing portion 61 with respect to the photosensitive drum 11 becomes smaller than the nip pressure of the elastic layer 21 </ b> B with respect to the photosensitive drum 11. The fluctuation of the nip pressure with respect to the photosensitive drum 11 deteriorates the image quality as described above.

  On the other hand, in this Embodiment, the amount of bite becomes large because the press part 61 protrudes rather than the elastic layer 21B. Therefore, the force with which the pressing portion 61 presses the photosensitive drum 11 per unit area is larger than the force with which the elastic layer 21B presses the photosensitive drum 11 per unit area. Therefore, fluctuations in the nip pressure when the exposed portion 21C passes through the transfer site Tr are further suppressed, and as a result, image quality deterioration is suppressed.

  When the pressing portion 61 receives a nip pressure as it passes through the transfer portion Tr, the pressing portion 61 expands and contracts in the diameter direction of the transfer drum 21 and extends in the transport direction (arrow B) of the paper S. In the present embodiment, the pressing portion 61 only needs to exist from the elastic layer front end 21BL to the elastic layer rear end 21BT when receiving the nip pressure as it passes through the transfer site Tr. Therefore, in a state where the pressing portion 61 is not affected by the nip pressure (a state in which the pressing portion 61 is not elastically deformed), between the pressing portion 61 and the elastic layer front end 21BL or between the pressing portion 61 and the elastic layer rear end 21BT. The pressing portion 61 may be formed with a dimension that forms a gap.

<Modification>
Here, a modified example of the pressing portion 61 will be described with reference to FIGS. 6 and 7. FIG. 6 shows a modification of the pressing portion 61 provided in the exposed portion 21C. More specifically, FIGS. 6A to 6C show first to third modifications, respectively. FIG. 7 shows a modification of the pressing portion 61 provided in the tip gripper 23. More specifically, FIG. 7A is a perspective view of the transfer drum 21 provided with the pressing portion 61, and FIG. 7B is a configuration diagram around the pressing portion 61 as viewed from the arrow VII in FIG. 7A. It is. In FIG. 7A, the tip gripper 23 is closed, and in FIG. 7B, the tip gripper 23 is open.

<Modification 1>
First, as shown in FIG. 6A, an example in which the height of the base 21A is changed will be described as a first modification. In the first modification, a portion that becomes the exposed portion 21C in the base portion 21A is different from the above-described embodiment. That is, the outer surface of the base portion 21A that becomes the exposed portion 21C with respect to the rotation shaft 21D (see FIG. 1) protrudes from the outer surface of the base portion 21A in other portions (see reference symbol h1). In this example, the pressing portion 61 and the elastic layer 21B have the same thickness.
Accordingly, the outer surface of the pressing portion 61 with respect to the rotation shaft 21D (see FIG. 1) protrudes from the outer surface of the elastic layer 21B (see the symbol h1).

<Modification 2>
Next, as shown in FIG. 6B, an example in which the material of the pressing portion 61 is changed will be described as a second modification. In the second modification, the pressing portion 61 and the elastic layer 21B are formed of different materials. Specifically, the pressing portion 61 is made of a material having a hardness higher than that of the elastic layer 21B. Accordingly, the nip pressure applied to the photosensitive drum 11 when the pressing portion 61 passes through the transfer portion Tr, and the nip pressure applied to the photosensitive drum 11 when the elastic layer 21B passes through the transfer portion Tr. Almost equal. In this example, the pressing portion 61 is formed with the same thickness as the elastic layer 21B, and is configured so as not to protrude from the outer surface of the elastic layer 21B.
In other words, the pressing portion 61 may be formed of a material different from that of the elastic layer 21B, and the outer surface of the pressing portion 61 may protrude from the outer surface of the elastic layer 21B.

<Modification 3>
Next, as shown in FIG. 6C, an example in which the pressing portion 61 is formed integrally with another member will be described as a third modification. In the above-described embodiment, the pressing portion 61 and the elastic layer 21B have been described as separate bodies. However, the present invention is not limited to this, and as shown in FIG. You may form as one.

<Modification 4>
Next, as shown in FIGS. 7A and 7B, an example in which the pressing portion 61 is provided on the tip gripper 23 will be described.
In each of the above-described examples, the configuration in which the pressing portion 61 is fixed to the drum-shaped base portion 21A has been described. However, the configuration is not limited thereto. The pressing portion 61 may be configured to press the photosensitive drum 11 when the pressing portion 61 faces the photosensitive drum 11 as the transfer drum 21 rotates (when passing through the transfer portion Tr). . Therefore, as shown in FIGS. 7A and 7B, the pressing portion 61 may be provided in a place other than the drum-shaped base portion 21 </ b> A, for example, the tip gripper 23.

  In this example, a pressing portion 61 is provided on the outer member 23 a of the tip gripper 23. Therefore, with the operation of the outer member 23a, the pressing portion 61 moves relative to the base portion 21A. Then, as shown in FIG. 7B, in a state where the front end gripper 23 is closed, the pressing portion 61 exists in a place where the elastic layer 21B is not provided between the elastic layer front end 21BL and the elastic layer rear end 21BT. Is configured to do.

Further, as shown in FIG. 7A, the pressing portion 61 is an exposed portion 21C, and from the end of the image forming apparatus 1 on the front side (the left front side in FIG. 7A), the image forming apparatus. 1 is formed so as to exist over an end portion on the rear side (right rear side in FIG. 1A). For this reason, when the pressing portion 61 passes through the transfer portion Tr, the area where the pressing portion 61 contacts the photosensitive drum 11 is such that the elastic layer 21B passes through the transfer portion Tr when the elastic layer 21B passes through the transfer portion Tr. Is almost equal to the area in contact with
In this example, the pressing portion 61 is made of the same material (same hardness) as the elastic layer 21B, and the outer surface of the pressing portion 61 and the elastic layer 21B with respect to the rotating shaft 21D (see FIG. 1) is on the same surface. You may arrange in. Further, as shown in FIG. 7B, both ends of the elastic layer 21B in the paper transport direction (elastic layer front end 21BL, elastic layer rear end 21BT) and both ends of the pressing portion 61 in the paper transport direction are connected to the front gripper 23. You may form along the rotation direction (arrow F1 and F2 of Fig.3 (a)) of the outer side member 23a. This makes it easier to open and close the tip gripper 23.

  In this example, unlike the example shown in FIG. 5, in the configuration in which the pressing portions 61 are provided at both ends of the transfer drum 21 (on both sides of the tip gripper 23) in the direction along the rotation shaft 21 </ b> D (see FIG. 1) of the transfer drum 21. Absent. Therefore, it is possible to reduce the size of the transfer drum 21 in the direction along the rotation shaft 21D (see FIG. 1).

  In the above description, it has been described that the front end gripper 23 does not contact the photoconductive drum 11 when passing through the transfer site Tr. However, the present invention is not limited to this, and the front end gripper 23 contacts the photoconductive drum 11. It may be. In this case, when the exposed portion 21 </ b> C provided with the front end gripper 23 passes through the transfer site Tr, the pressing portion 61 and the front end gripper 23 apply nip pressure to the photosensitive drum 11.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Housing, 3 ... Discharge stacking part, 10 ... Image forming part, 11 ... Photosensitive drum, 12 ... Charging device, 13 ... Exposure device, 14 ... Rotary developing device, 15 ... Cleaning device, DESCRIPTION OF SYMBOLS 20 ... Transfer device, 21 ... Transfer drum, 21A ... Base part, 21B ... Elastic layer, 21C ... Exposed part, 23 ... Front end gripper, 25 ... Paper detection sensor, 27 ... Rear end gripper, 30 ... Fixing device, 40 ... Paper supply , 41... Paper storage unit, 51... Supply path, 52... Discharge path, 61.

Claims (6)

An image carrier,
Image forming means for forming an image on the image carrier;
Transfer means for transferring an image formed on the image carrier by the image forming means to a recording medium, and the transfer means,
A base provided rotatably,
An outer peripheral material provided on an outer periphery of the base portion, and provided with a notched portion in which a part of the outer peripheral surface is notched and pressed against the image carrier;
And a pressing portion that presses the image holding body when the notch is opposed to the image holding body as the base rotates. Image forming apparatus.   The image forming apparatus according to claim 1, further comprising a holding member that is provided in the notch and holds the supplied recording material on the outer peripheral surface of the outer peripheral material.   The image forming apparatus according to claim 1, wherein the pressing portion is present in a range corresponding to the notch portion in a circumferential direction of the base portion.   4. When the image forming unit forms an image on the image holding member, the notch portion faces the image holding member as the base portion rotates. 2. An image forming apparatus according to item 1.   The image forming apparatus according to claim 1, wherein the pressing portion protrudes outward from the outer peripheral surface of the outer peripheral material. A base provided rotatably,
An outer peripheral material provided on the outer periphery of the base portion, and provided with a notched portion in which a part of the outer peripheral surface is notched and pressed against the image carrier;
A holding member that is provided in the notch and holds the supplied recording material on the outer peripheral surface of the outer peripheral material;
A transfer device, which is provided so as to rotate together with the base portion, and includes a pressing portion that presses the image holding body when the cutout portion faces the image holding body as the base portion rotates.

Images