JP6525575B2 - Transfer unit and image forming apparatus - Google Patents

Description

  The present invention relates to a transfer unit for transferring a toner image to a transfer belt and an image forming apparatus.

  2. Description of the Related Art Conventionally, in an image forming apparatus using electrophotographic technology, a configuration is known in which an image is formed on a recording medium using a transfer belt. In this case, the toner image formed on the photosensitive drum is transferred onto the transfer belt, and the toner image transferred onto the transfer belt is further transferred onto the recording medium to form an image on the recording medium. Here, when the toner image is transferred onto the transfer belt, the transfer belt is pressed against the photosensitive drum by the transfer roller, whereby the toner image formed on the photosensitive drum is transferred onto the transfer belt. When the photosensitive drum and the transfer roller are disposed to face each other with the transfer belt interposed therebetween, the photosensitive drum may be damaged by the transfer roller pressing the photosensitive drum through the transfer belt. When the photosensitive drum is damaged, an image defect may occur in the image formed on the recording medium.

  In Patent Document 1, the transfer roller is disposed such that the position at which the photosensitive drum presses the transfer belt and the position at which the transfer roller presses the transfer belt deviate in the moving direction of the transfer belt. Since the transfer belt is not pinched by the photosensitive drum and the transfer roller, the photosensitive drum is not pressed by the transfer roller via the transfer roller. This prevents the photosensitive drum from being damaged.

Patent No. 5016146 gazette

However, due to displacement of the position of the transfer roller, contraction of the transfer belt, and the like, the force with which the transfer belt presses the photosensitive drum and the developing roller may increase. When the pressing force of the transfer belt is increased and the transfer belt is wound around the photosensitive drum and the transfer roller, the transfer belt may be wound and wrinkled. When the transfer belt is wound and wrinkled, an image defect may occur in the image formed on the recording medium.
Therefore, an object of the present invention is to prevent the transfer belt from being wound and wrinkled.

In order to achieve the above object, the transfer unit of the present invention is
An endless transfer belt carrying a recording medium onto which a toner image is transferred from an image carrier carrying a toner image or onto which a toner image is transferred;
Contact the inner peripheral surface of the transfer belt at a position away from the area where the image carrier and the outer peripheral surface of the transfer belt contact in the moving direction of the transfer belt, and transfer the toner image from the image carrier to the transfer belt A transfer member for transferring toward the
An elastic member resiliently urging the transfer member so as to press the transfer member against the inner circumferential surface of the transfer belt;
A support member configured to be swingable about a swing shaft and supporting the transfer member ;
A regulating member for regulating the swing of the front Symbol supporting member, can be contacted with said support member for regulating a position of the transfer member to an orientation parallel to the direction in which the transfer member is moved by the elastic member restrainer And a member;
The transfer member, the elastic member, the support member, and the restriction member are all disposed on the inner peripheral surface side of the transfer belt.

Further, in order to achieve the above object, the image forming apparatus of the present invention is
Comprising the transfer unit and the image carrier,
An image is formed on a recording medium by the toner image carried by the image carrier.

  According to the present invention, the transfer belt can be prevented from being wound and wrinkled.

FIG. 1 is a schematic view of an image forming apparatus to which a transfer unit according to a first embodiment is attached. FIG. 2 is a schematic view of a transfer unit according to Embodiment 1. FIG. 2 is a perspective view of a transfer unit according to the first embodiment. FIG. 2 is a cross-sectional view of the transfer unit according to the first embodiment. FIG. 7 is a view showing how the transfer belt is wound in the transfer unit. FIG. 6 is a graph showing the relationship between the force with which the transfer belt presses the transfer roller and the offset amount. FIG. 7 is a graph showing the relationship between the amount of lifting of the transfer belt and the pressing force of the transfer belt. FIG. 5 is a schematic view of a transfer unit according to a second embodiment. FIG. 7 is a perspective view of a transfer unit according to a second embodiment.

  Embodiments of the present invention will be illustrated below with reference to the drawings. However, the dimensions, materials, shapes, relative positions, etc. of the components described in these examples should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions, The scope is not limited to the following embodiments.

Example 1
Hereinafter, Example 1 of the present invention will be described. In the following embodiments, a full-color image forming apparatus to which four process cartridges can be attached and detached is exemplified as an electrophotographic image forming apparatus (hereinafter, referred to as an image forming apparatus). Here, the number of process cartridges mounted to the image forming apparatus is not limited to this. The number of process cartridges is appropriately set as needed. For example, in the case of an image forming apparatus for forming a monochrome image, the number of process cartridges mounted in the image forming apparatus is one. In the embodiment described below, a printer is illustrated as an image forming apparatus.

<Configuration of Image Forming Apparatus>
FIG. 1 is a schematic view of an image forming apparatus to which a transfer unit according to a first embodiment is attached.
The image forming apparatus 1 is a four-color full-color laser printer using an electrophotographic process, and performs color image formation on a recording medium S. The image forming apparatus 1 is a process cartridge type, and forms an image on the recording medium S by mounting the process cartridge P (PY, PM, PC, PK) on the apparatus main body 2.

The apparatus body 2 includes four process cartridges P (PY · P), a process cartridge PY, a process cartridge PM, a process cartridge PC, and a process cartridge PK.
M, PC, PK) are arranged. Each process cartridge P has the same electrophotographic process mechanism, and the color of the toner (developer) to be charged is different. Further, a rotational drive force is transmitted to the process cartridge P from a drive output portion (not shown) of the apparatus main body 2.

Further, a bias voltage (such as a charging bias or a developing bias) is supplied to the process cartridge P from the apparatus main body 2. The process cartridge P includes photosensitive drums 4 (4 a to 4 d) (image carriers), charging units for charging the photosensitive drums 4, and cleaning units 8 (8 a to 8 d) including cleaning units. Further, the process cartridge P is provided with a developing device 9 (9a to 9d) provided with a developing unit for developing the electrostatic latent image formed on the photosensitive drum 4
Have. The cleaning unit 8 and the developing device 9 are connected to each other. Further, the charging roller 5 is used as the charging means, the cleaning blades 7 (7a to 7d) are used as the cleaning means, and the developing roller 6 is used as the developing means. A more specific configuration of the cartridge will be described later.

  The process cartridge PY contains yellow (Y) toner in a developing frame, and forms (carries) a yellow toner image (developer image) on the surface of the photosensitive drum 4a. The process cartridge PM contains toner of magenta (M) in a developing frame, and forms a magenta toner image on the surface of the photosensitive drum 4b. The process cartridge PC contains cyan (C) toner in the developing frame, and forms a cyan toner image on the surface of the photosensitive drum 4c. The process cartridge PK contains black (K) toner in a developing frame, and forms a black toner image on the surface of the photosensitive drum 4d.

  The apparatus body 2 is provided with a laser scanner unit LB as an exposure unit. The laser scanner unit LB outputs a laser beam corresponding to image information. The laser light passes through the exposure windows 10 (10a to 10d) of the process cartridge P and scans and exposes the surface of the photosensitive drum 4. Further, the apparatus main body 2 is provided with an intermediate transfer belt unit 11 as a transfer member. The intermediate transfer belt unit 11 has a drive roller 13, a tension roller 14, and an assist roller 15, and spans the transfer belt 101 having flexibility. The transfer belt 101 is stretched by a drive roller 13 pressed by a tension spring 50 via a tension roller bearing 61.

  The outer peripheral surface of the photosensitive drum 4 in the process cartridge P is in contact with the outer peripheral surface of the transfer belt 101. The contact portion is a primary transfer portion. Primary transfer rollers 102 (102 a to 102 d) are provided on the inner peripheral surface side of the transfer belt 101 so as to correspond to the photosensitive drums 4. The secondary transfer roller 17 is in contact with the tension roller 14 via the transfer belt 101. The contact portion between the transfer belt 101 and the secondary transfer roller 17 is a secondary transfer portion. Further, the apparatus main body 2 is provided with a feeding unit 18. The feeding unit 18 has a sheet feeding tray 19 and a sheet feeding roller 20 capable of stacking and storing the recording medium S. In the following, the photosensitive drums 4a to 4d are the photosensitive drum 4, the charging rollers 5a to 5d are the charging roller 5, the developing rollers 6a to 6d are the developing roller 6, and the primary transfer rollers 102a to 102d are primary transfer rollers. It describes collectively as 102.

  In the apparatus main body 2, a fixing unit 21, a discharge unit 22, and a discharge tray 23 are provided. The toner image is fixed on the recording medium S by the fixing unit provided in the fixing unit 21, and the recording medium S on which the toner image is fixed is discharged to the discharge tray 23. Although the image forming apparatus 1 is configured to form an image with the removable process cartridge P having the cleaning unit 8 including the charging unit and the cleaning and the photosensitive drum 4, the configuration is other than that. It is also good. For example, the image forming apparatus 1 may be configured to form an image by mounting on the apparatus main body 2 a removable process cartridge P having at least one photosensitive drum 4 and one or more charging means. In the image forming apparatus 1 in FIG. 1, the transfer unit 100 (FIG. 2) is omitted.

<Image formation operation>
The operation for forming a full color image is as follows. First, the photosensitive drum 4 in the process cartridge P is rotationally driven at a predetermined speed. The transfer belt 101 is also rotationally driven at a speed corresponding to the rotational speed of the photosensitive drum 4. In addition, the laser scanner unit LB is also driven. In synchronization with the driving of the laser scanner unit LB, the charging roller 5 uniformly charges the surface of the photosensitive drum 4 to a predetermined polarity and potential. The laser scanner unit LB scans and exposes the surface of the photosensitive drum 4 with laser light according to the image signal of each color.

  Thereby, an electrostatic latent image corresponding to the image signal of the corresponding color is formed on the surface of each photosensitive drum 4. The formed electrostatic latent image is developed by the developing roller 6 rotationally driven at a predetermined speed. By such an electrophotographic image forming process, a yellow toner image corresponding to the yellow component of the full color image is formed on the photosensitive drum 4a of the process cartridge PY. Then, the toner image is primarily transferred onto the transfer belt 101.

  Similarly, a magenta toner image corresponding to the magenta component of the full color image is formed on the photosensitive drum 4b of the process cartridge PM. Then, the toner image is superimposed on the yellow toner image that has already been transferred onto the transfer belt 101, and is primarily transferred. Similarly, a cyan toner image corresponding to the cyan component of the full color image is formed on the photosensitive drum 4c of the process cartridge PC. Then, the toner image is superimposed on the yellow toner image and the magenta toner image already transferred on the transfer belt 101 and primarily transferred.

  Similarly, on the photosensitive drum 4d of the process cartridge PK, a black toner image corresponding to the black component of the full color image is formed. Then, the toner image is superimposed on the yellow toner image, the magenta toner image, and the cyan toner image already transferred on the transfer belt 101, and is primarily transferred. Thus, a full-color unfixed toner image of four colors of yellow, magenta, cyan and black is formed on the transfer belt 101.

  On the other hand, the recording medium S is separated one by one at a predetermined control timing and fed from the paper feed tray 19. The recording medium S is conveyed to a secondary transfer portion which is a contact portion between the secondary transfer roller 17 and the transfer belt 101 at a predetermined control timing. The image forming apparatus 1 performs conveyance of the recording medium S to the secondary transfer portion and transfer of the toner image to the transfer belt 101 in parallel. Thereafter, the recording medium S on which the toner image is transferred at the secondary transfer portion is heated while being pressed by the fixing unit 21. Thus, the toner image is fixed on the recording medium S. The recording medium S on which the toner image is fixed is discharged to the discharge tray 23.

<Transfer unit>
FIG. 2 is a schematic view of a transfer unit according to the first embodiment. FIG. 3 is a perspective view of the transfer unit according to the first embodiment. FIG. 4 is a cross-sectional view of the transfer unit according to the first embodiment. In the first embodiment, the transfer unit 100 includes a transfer belt 101, a primary transfer roller 102 as a transfer member, a pressing mechanism 103, and a regulating member 106. The transfer belt 101 is an endless belt, and when the outer peripheral surface 101A of the transfer belt 101 contacts the outer peripheral surface 4A of the photosensitive drum 4, the toner image formed on the outer peripheral surface 4A of the photosensitive drum 4 is The image is transferred to the outer peripheral surface 101A of the transfer belt 101.

  The primary transfer roller 102 presses the inner peripheral surface 101 B of the transfer belt 101 so as to press the outer peripheral surface 101 A of the transfer belt 101 against the outer peripheral surface 4 A of the photosensitive drum 4 and applies a voltage to the photosensitive drum 4. It also plays a role. Here, an area of the transfer belt 101 in contact with the primary transfer roller 102 is referred to as an area J, and an area of the transfer belt 101 in contact with the photosensitive drums 4 is referred to as an area K. The area J and the area K are separated in the L direction which is the moving direction of the transfer belt 101. In the first embodiment, the primary transfer roller 102 is made of metal.

The pressing mechanism 103 elastically biases the primary transfer roller 102 so as to press the primary transfer roller 102 against the inner circumferential surface 101 B of the transfer belt 101. The pressing mechanism 103 has a bearing 104 and an elastic member 105. The bearing 104 rotatably supports the primary transfer roller 102. Further, the elastic member 105 presses the bearing 104 in the M direction in which the primary transfer roller 102 presses the inner circumferential surface 101 B of the transfer belt 101. In the first embodiment, the elastic member 105 applies a biasing force in a direction (M direction in the first embodiment) orthogonal to the surface of the transfer belt 101 at a position R where the primary transfer roller 102 presses the transfer belt 101. It is a spring to give.

  The bearing 104 is supported so as to be pivotable about the pivot shaft 104A. The bearing 104 abuts the swing shaft 104A in the direction opposite to the L direction by the abutment portion 108 (second abutment member), whereby the movement (displacement) of the swing shaft 104A in the L direction is restricted. In the bearing 104, the abutment member 109 (third abutment member) abuts on the end 104B which is the end of the bearing 104 in the direction opposite to the L direction in the same direction as the L direction. The movement of the rocking shaft 104A in the opposite direction is restricted.

  The movement of the swinging shaft 104A in the M direction is restricted by the abutment portion 107 (first abutment member) abutting the swinging shaft 104A in the direction opposite to the M direction. Further, since the abutment portion 110 (fourth abutment member) abuts on the rocking shaft 104A in the M direction, the movement of the rocking shaft 104A in the direction opposite to the M direction is restricted. Since the movement of the swing shaft 104A in the direction opposite to the L direction and the L direction is restricted, the movement of the bearing 104 in the direction opposite to the L direction and the L direction is restricted. Further, as described above, the movement of the swing shaft 104A in the direction opposite to the M direction and the M direction is restricted. Accordingly, the rocking shaft 104A is rotatably supported at that position without being vertically (horizontally) displaced (positioned), and the bearing 104 can rock about the rocking shaft 104A. it can.

  Further, the transfer unit 100 has a regulating member 106. The regulating member 106 can regulate the movement of the primary transfer roller 102 in the M direction at a predetermined position. The restricting member 106 restricts the transfer roller 102 from being pressed further at a predetermined position. In the first embodiment, the restricting member 106 abuts on the downstream side of the swinging shaft 104A in the L direction in a direction opposite to the M direction with the controlled portion 104C provided on the bearing 104.

  Here, the predetermined position is the position of the primary transfer roller 102 such that the transfer belt 101 is not curled. When the transfer belt 101 is expanded by use, the transfer belt may move more than necessary in the M direction. In this case, the transfer belt 101 is wound around the primary transfer roller 102, and there is a possibility that the transfer belt 101 may be curled depending on the pressing force of the primary transfer roller 102.

Here, the pressing force of the tension spring 50 for pressing the driving roller 13 is referred to as pressing force F1 (not shown), and the force for pressing back the primary transfer roller 102 generated by the tension T1 of the transfer belt 101 is referred to as repulsive force F2. Further, a force for urging the primary transfer roller 102 by the elastic member 105 via the bearing 104 is defined as a biasing force F3, and an angle of winding of the transfer belt 101 onto the primary transfer roller 102 is an angle θ1 (see FIG. 2). . Let the winding angle of the transfer belt 101 around the tension roller 14 be an angle θ2 (not shown). In this case, the repulsive force F2 can be expressed by the following equation.
F2 = 2 (F1 / 2 sin (θ2 / 2)) sin (θ1 / 2)
When F3> F2, the bearing 104 abuts against the regulating member 106. When F3 <F2, the bearing 104 is separated from the regulating member 106.

In the first embodiment, the repulsive force F2 for the transfer belt 101 to press the primary transfer roller 102 and the biasing force F3 for the elastic member 105 to bias the primary transfer roller 102 via the bearing 104 are balanced. Therefore, the repulsive force F2 does not become larger than the biasing force F3. Further, by providing the regulating member 106, the primary transfer roller 102 is prevented from moving more than necessary in the M direction. As a result, the transfer belt 101 is wound around the primary transfer roller 102, so that the transfer belt 101 can be prevented from being wound and wrinkled.

<Relationship between offset amount, transfer belt displacement amount, and transfer belt tension>
FIG. 5 is a view showing how the transfer belt is wound in the transfer unit. Here, the roller diameter and the distance between the rollers are defined as follows. The radius of the photosensitive drum 4a and the photosensitive drum 4b is a radius R1, the radius of the primary transfer roller 102a is a radius R2, and the distance between the center of the photosensitive drum 4a and the center of the photosensitive drum 4b is an inter-drum distance Lst. . Further, the distance in the L direction between the center of the photosensitive drum 4a and the center of the primary transfer roller 102a is an offset distance La, and the distance in the L direction between the center of the photosensitive drum 4b and the center of the primary transfer roller 102a is a distance Lb Do.

  Here, the state of the transfer belt 101 when the primary transfer roller 102a is not in contact with the transfer belt 101 and the transfer belt 101 is not bent between the photosensitive drum 4a and the photosensitive drum 4b is referred to as a reference state. Do. The amount of displacement of the transfer belt 101 in the M direction from the reference state is taken as a lifting amount Lup. Further, a central angle of the primary transfer roller 102 corresponding to a portion on the outer peripheral surface of the primary transfer roller 102a in contact with the transfer belt 101 and in the L direction on the photosensitive drum 4a side with respect to the center of the primary transfer roller 102a. As a central angle α. A central angle of the primary transfer roller 102 corresponding to a portion on the outer peripheral surface of the primary transfer roller 102a that is in contact with the transfer belt 101 and in the L direction on the photosensitive drum 4b side of the center of the primary transfer roller 102a. Let it be the angle β.

The central angle α can be derived as follows.
α = 90- (atan (La / (R1 + R2-Lup)) + acos ((R1) / (R1 + R2) * (√ ((R1 + R2-Lup)) ^ 2 + La ^ 2)))
Further, the central angle β can be derived as follows.
β = 90- (atan (Lb / (R1 + R2-Lup)) + acos ((R1) / (R1 + R2) * (√ ((R1 + R2-Lup)) ^ 2 + Lb ^ 2)))
The winding angle θ1 is θ1 = (α + β) / 2.

<Relationship between the pressing force of the transfer belt against the transfer roller and the offset distance>
FIG. 6 is a diagram showing the relationship between the force with which the transfer belt presses the transfer roller and the offset amount in the related art. Conventionally, the photosensitive drum and the bearing of the transfer roller offset are fixed, and the bearing of the transfer roller is not supported by the elastic member. Here, the force of the transfer belt 101 to push back the primary transfer roller 102 by the tension of the transfer belt 101 is referred to as a repulsive force F2. Further, a force that causes the elastic member 105 to bias the primary transfer roller 102 in the M direction via the bearing 104 is defined as a biasing force F3. In FIG. 6, the horizontal axis is the offset distance La, and the vertical axis is the repulsive force F2. FIG. 6 is a graph showing the results of changing the lifting amount Lup between 0.25 and 1.25.

  As shown in FIG. 6, when the bearing of the transfer roller is fixed as in the prior art, it is understood that the repulsive force F2 becomes larger as the offset distance La becomes smaller. Therefore, in the related art, the transfer belt may be pressed against the transfer roller with a pressing force more than necessary, which may cause the transfer belt to be curled. However, in the first embodiment, when the repulsive force F2 becomes larger than the biasing force F3 for biasing the primary transfer roller 102 by the resilient member 105, the primary transfer roller 102 elastically supported by the resilient member 105 is in the M direction. It is pushed back in the opposite direction. Since the repulsive force F2 and the biasing force F3 are balanced, the force (repulsive force F2) with which the transfer belt 101 presses the primary transfer roller 102 is greater than the force with which the elastic member 105 biases the primary transfer roller 102 (biasing force F3). It does not become large. Thereby, the transfer belt 101 can be prevented from being wound around the primary transfer roller 102.

<Relationship between Lifting Amount Lup and Repulsive Force F2>
FIG. 7 is a graph showing the relationship between the amount by which the transfer belt is lifted and the pressing force of the transfer belt in the related art. FIG. 7 is a graph in which the horizontal axis is the lifting amount Lup, the vertical axis is the repulsive force F2, and the offset distance La is changed between 6.5 and 8.5. As shown in FIG. 7, conventionally, the repulsive force F2 increases as the lifting amount Lup increases. That is, in the related art, when the lifting amount Lup is increased due to component tolerance or the like, the repulsive force F2 may be increased more than necessary. As in the case where the offset distance La is reduced, there is a possibility that the transfer belt may have a curl due to the increase of the lifting amount Lup. In the first embodiment, even if the lifting amount Lup is increased, the repulsive force F2 does not become larger than the biasing force F3 of the elastic member 105. This can prevent the transfer belt 101 from being curled.

(Example 2)
A second embodiment of the present invention will be described. In the second embodiment, parts having the same functions as in the first embodiment are given the same reference numerals, and the description thereof is omitted.
FIG. 8 is a schematic view of a transfer unit according to the second embodiment. FIG. 9 is a perspective view of the transfer unit according to the second embodiment.
In the second embodiment, the bearing 204 has a regulated portion 204C on the opposite side of the support portion 204B that supports the primary transfer roller 102 with the swinging shaft 204A interposed therebetween. The movement of the primary transfer roller 102 in the M direction can be restricted at a predetermined position by causing the regulated portion 204C to abut the regulating member 206 in the M direction. Here, as in the first embodiment, the predetermined position is the position of the primary transfer roller 102 that prevents the transfer belt 101 from being curled. Further, as in the first embodiment, the rocking shaft 204A is rotatably supported by the elastic member 105, the abutting portion 107, the abutting portion 108, and the abutting member 109.

  As described above, in each embodiment, in the transfer unit in which the photosensitive drum and the transfer roller are offset, the pressing mechanism elastically supports the transfer roller so that the transfer roller presses the inner peripheral surface of the transfer belt. doing. Since the force with which the transfer belt presses the transfer roller and the force with which the pressing mechanism biases the transfer roller are balanced, a pressing force larger than the biasing force of the pressing mechanism is not applied to the transfer belt. This prevents the transfer belt from being wound around the transfer roller, and prevents the transfer belt from being wound around and wrinkled.

  Also, in each embodiment, the force with which the transfer belt presses the transfer roller and the force with which the pressing mechanism biases the transfer roller are balanced, so a pressing force larger than the biasing force of the pressing mechanism is applied to the transfer roller. Will not join. Therefore, it is possible to prevent the transfer roller from being bent in the rotational axis direction of the transfer roller due to the pressing force of the transfer belt. Thus, the toner image can be favorably transferred from the photosensitive drum to the transfer belt.

  Further, in each embodiment, since the pressing force larger than the biasing force of the pressing mechanism is not applied to the transfer roller, the diameter of the transfer roller can be reduced. By reducing the diameter of the transfer roller, the distance (Lab in FIG. 5) between the position where the transfer roller presses the transfer belt and the position where the photosensitive drum presses the transfer belt can be reduced. Thus, the toner image can be favorably transferred from the photosensitive drum to the transfer belt.

  In each embodiment, the swing shaft of the bearing of the pressing mechanism is disposed upstream of the position where the transfer roller presses the transfer belt in the moving direction of the transfer belt. Thus, the pressing mechanism can absorb the force acting on the transfer roller by the drive of the transfer belt, and it is possible to prevent the force more than necessary from being applied to the transfer roller.

In each embodiment, the regulating member can regulate the movement of the transfer roller in the direction in which the transfer roller presses the transfer belt at a predetermined position. As a result, when the length of the transfer belt is extended, it is possible to prevent the transfer roller from moving more than necessary in the direction in which the transfer roller presses the transfer belt. The transfer belt can be prevented from being wound around the transfer roller, and the transfer belt can be prevented from being wound around and wrinkled. Further, when the tension of the transfer belt is released to transport the image forming apparatus, it is possible to prevent the transfer roller from floating in the direction of pressing the transfer belt.

  In each embodiment, a transfer roller made of metal is used as the transfer roller. Conventionally, in a transfer unit in which the photosensitive drum and the transfer roller are offset, a transfer roller in which a portion for pressing the transfer belt has a sponge shape has been used. However, by using a metal transfer roller which does not use a sponge, the manufacturing cost of the transfer roller can be reduced. In addition, it is also possible to employ a non-rotational transfer member without being limited to the transfer roller as the transfer member. Further, although the intermediate transfer belt has been described as the transfer belt, the present invention is also applicable to a transfer belt carrying a recording medium.

4 photosensitive drum, 100 transfer unit, 101 transfer belt, outer peripheral surface 101A,
101B inner circumferential surface, 102 transfer roller, 103 pressing mechanism, J area, K area,
L direction

Claims (12)

An endless transfer belt carrying a recording medium onto which a toner image is transferred from an image carrier carrying a toner image or onto which a toner image is transferred;
Contact the inner peripheral surface of the transfer belt at a position away from the area where the image carrier and the outer peripheral surface of the transfer belt contact in the moving direction of the transfer belt, and transfer the toner image from the image carrier to the transfer belt A transfer member for transferring toward the
An elastic member resiliently urging the transfer member so as to press the transfer member against the inner circumferential surface of the transfer belt;
A support member configured to be swingable about a swing shaft and supporting the transfer member ;
A regulating member for regulating the swing of the front Symbol supporting member, can be contacted with said support member for regulating a position of the transfer member to an orientation parallel to the direction in which the transfer member is moved by the elastic member restrainer And a member;
A transfer unit characterized in that the transfer member, the elastic member, the support member, and the restriction member are all disposed on the inner peripheral surface side of the transfer belt.   The transfer unit according to claim 1, wherein the transfer member is a transfer roller rotatable about an axis.   The transfer unit according to claim 2, wherein the elastic member elastically biases the support member such that the transfer roller presses the inner circumferential surface.   4. The image forming apparatus according to claim 1, wherein the swing shaft is disposed upstream of a position at which the transfer member presses the inner circumferential surface in the movement direction of the transfer belt. Transfer unit as described.   The transfer according to any one of claims 1 to 4, wherein the contact between the restriction member and the support member suppresses the occurrence of winding wrinkles of the transfer belt due to the contact with the image carrier. unit. The restricting member is in the direction in which the transfer member is pressed against the inner peripheral surface side by the elastic member, according to claim 1, wherein the transfer member is characterized in that the regulating at a constant position Tokoro so as not to be further pressed The transfer unit according to any one of items 1 to 4.   The control member is characterized in that the transfer member strikes the support member in the direction opposite to the direction in which the inner peripheral surface is pressed on the downstream side of the swinging axis in the movement direction. The transfer unit according to any one of 6. The support member has a regulated portion on the opposite side to a support portion that supports the transfer member with the swinging shaft interposed therebetween,
The said control member abuts on the said to-be-controlled part of the said supporting member which operate | moves so that the said transcription | transfer member may face the direction which presses the said internal peripheral surface, The said control member is any one Transfer unit. A first abutment in which the elastic member strikes the rocking shaft in a direction opposite to a direction in which the elastic member presses the supporting member so as to restrict movement of the rocking shaft in a direction in which the elastic member presses the supporting member. and the member, so as to restrict movement of the pivot shaft in the direction of movement, and a second abutting member abuts on the pivot shaft in a direction toward the moving direction and the pair opposite direction definitive and the moving direction In order to restrict the movement of the rocking shaft, a third abutment member which abuts the support member in the movement direction, and the rocking shaft in the direction opposite to the direction in which the elastic member presses the support member The rocking shaft is positioned by a fourth abutment member that abuts against the rocking shaft in a direction in which the elastic member presses the support member so as to restrict movement. One of eight The transfer unit according to claim.   10. The elastic member according to claim 1, wherein the elastic member is a spring that applies an urging force in a direction perpendicular to the surface of the transfer belt at a position where the transfer member presses the transfer belt. Transfer unit as described.   The transfer unit according to any one of claims 1 to 10, wherein the transfer member is made of metal. A transfer unit according to any one of claims 1 to 11 and the image carrier,
An image forming apparatus, wherein an image is formed on a recording medium by the toner image carried by the image carrier.

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