JP2012252367A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus of an electrophotographic system by which improvement of image quality is expected while improving workability and assemblability of a toner image conveyance unit.SOLUTION: An image forming apparatus is constituted by comprising: a toner image conveyance unit 1 constituted like a belt conveyer in appearance by stretching an intermediate transfer belt 12 over a plurality of rollers pivotally supported by a frame 11a, and providing the frame 11a with a drive motor part 13 which rotates the intermediate transfer belt 12; and a toner image conveyance unit support part 2 which slides the toner image conveyance unit 1 towards inside an apparatus body m1 and by which the toner image conveyance unit 1 can be internally provided to a prescribed position inside the apparatus body ml in an attachable and detachable manner.

Description

  The present invention relates to an electrophotographic image forming apparatus provided with an endless belt for carrying a toner image, and more particularly to an improvement around the belt.

  2. Description of the Related Art Conventionally, there is an image forming apparatus of a type in which a toner image formed on a photoreceptor is primarily transferred to an intermediate transfer belt and the primary transferred toner image is secondarily transferred to a recording sheet. The configuration around the intermediate transfer belt in this type of image forming apparatus will be briefly described. For example, the intermediate transfer drive unit provided on the apparatus main body side and the intermediate transfer drive unit can be attached to and detached from the intermediate transfer drive unit (the transport direction of the toner image transport unit). And an intermediate transfer unit that is detachable from the direction orthogonal to the plan view). The former intermediate transfer drive unit includes a drive motor having a rotation shaft, a drive shaft, and a gear train that reduces the rotational speed of the rotation shaft at a desired reduction ratio and transmits the rotation to the drive shaft. Comprises a drive roller connected to a drive shaft via a coupling (shaft joint), and an intermediate transfer belt hung on the drive roller or the like.

  Among these configurations, the above-described coupling for connecting the driving shaft and the driving roller includes a female side coupling in which a concave portion is formed, and a male side coupling in which a convex portion to be inserted into the concave portion is formed. (For example, see Patent Document 1), a coupling (for example, see Patent Document 2) in which a pin provided on a drive shaft and a V groove provided on a drive roller are engaged. Can be mentioned. In any case, since the intermediate transfer driving unit is provided on the apparatus main body side around the conventional intermediate transfer belt, the toner image conveying unit is necessarily assembled by using a coupling means such as a coupling or a bolt. It was. Further, the assembly of the intermediate transfer drive unit and the toner image transport unit provided on the apparatus main body side requires connecting the shafts and inserting the shaft into the intermediate transfer drive unit. The direction of assembly to the transfer drive unit was naturally the axial direction.

  However, the conventional image forming apparatus described above has the following problems. That is, when the driving force of the drive motor is transmitted by coupling, there has been a problem of joint eccentricity. Further, when the intermediate transfer unit is attached or detached from the top or side of the apparatus main body, the coupling cannot be used to connect the shafts because the conveying direction of the recording material or toner image is the side direction of the main body of the apparatus. Therefore, the problem that the connection mechanism becomes complicated has arisen. Therefore, there is a possibility that the rotation accuracy of the intermediate transfer belt is lowered due to the drive transmission by the coupling and the complicated coupling mechanism, and banding, color misregistration and the like occur. Furthermore, in order to realize high-accuracy belt transfer of the intermediate transfer belt, when the above-described gear train is configured with small module gears (particularly 0.5 modules or less), the smaller the module, the greater the inter-axis accuracy. Therefore, a member for ensuring the accuracy of the drive transfer portion between the intermediate transfer unit side and the intermediate transfer drive unit side is required.

  In addition, when the transfer unit of the pull-out type in the side surface direction (or the upper surface direction) is attached / detached, the gear connecting portion sometimes collides. Therefore, it is difficult to deliver with a small module gear due to strength problems, and a large module may be used, resulting in banding and the like. Similarly, even with a gear train having a meshing frequency of 0.5 mm or less on the image, the accuracy of the drive transfer unit is necessary, and there is a risk of banding, color misregistration, etc. if the accuracy is not achieved. Accordingly, the present invention has been made in view of such circumstances, and an object thereof is to provide an image forming apparatus in which improvement in image quality can be expected while improving workability and assemblability of a toner image transport unit. To do.

  In order to achieve the above technical problem, the image forming apparatus according to the present invention employs the following technical means. That is, in the image forming apparatus according to the first aspect, an endless belt for carrying a toner image is hung on a plurality of rollers pivoted on a frame, and a drive motor unit for rotating the belt includes the frame. A toner image carrying unit provided in the apparatus, and a toner that slides the toner image carrying unit inward from the apparatus main body and detachably installs the toner image carrying unit at a predetermined position inside the apparatus main body. An image transport unit support section, and the drive motor section is disposed on the outer side of the apparatus main body with respect to the toner image transport unit support section in an attaching / detaching direction of the toner image transport unit with respect to the toner image transport unit support section. The image transport unit includes an idle gear that transmits drive from the drive motor unit to drive rollers included in the plurality of rollers. In detaching direction of the toner image carrier unit with respect to the toner image conveyance unit support section, said drive roller, the idle gear, in the order of the motor drive unit, characterized in that disposed on the outward of the apparatus main body.

  An image forming apparatus according to a second aspect is the image forming apparatus according to the first aspect, wherein the toner image transport unit is detachable from the side of the apparatus main body as viewed from the front.

  An image forming apparatus according to a third aspect is the image forming apparatus according to the first or second aspect, wherein the attaching / detaching direction of the toner image transport unit with respect to the toner image transport unit support portion is the same as the rotation direction of the belt. The toner image transport unit support portion and the toner image transport unit are configured.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, the drive motor unit includes a drive motor and a gear train configured by the idle gear that transmits a rotation output of the drive motor to the drive roller. It is characterized by that.

  An image forming apparatus according to a fifth aspect is the image forming apparatus according to the fourth aspect, wherein the gear train is constituted by a gear whose module does not exceed 0.5.

  An image forming apparatus according to a sixth aspect is the image forming apparatus according to the fourth or fifth aspect, wherein the toner image transport unit is configured such that the belt movement pitch with respect to one meshing generated based on a meshing pitch in the gear train and a diameter of the driving roller. Is configured so as not to exceed 0.5 mm.

  An image forming apparatus according to a seventh aspect is the image forming apparatus according to any one of the first to sixth aspects, wherein the toner image conveying unit is slid inward from the apparatus main body to a predetermined position inside the apparatus main body. At the same time as being set, the toner image conveying unit and the apparatus main body are provided with an electrical connection portion capable of electrical connection.

  An image forming apparatus according to an eighth aspect is the image forming apparatus according to any one of the first to seventh aspects, wherein the apparatus main body includes a plurality of image forming units that individually form the toner images of the respective colors, and the plurality of rollers includes: And a primary transfer roller that is pivotally mounted on the frame so as to be opposed to the image forming means with the belt interposed therebetween, and that primarily transfers the toner image of each color onto the belt.

  According to the present invention, an endless belt that carries a toner image is hung on a plurality of rollers that are pivotally mounted on a frame, and a drive motor unit that rotates the belt is provided so that the toner can be seen in a belt conveyor shape in appearance. By configuring the image transport unit, there is no shaft to be connected to the main body of the apparatus, and the necessity of using a coupling is eventually eliminated. Therefore, the risk of banding, color misregistration, etc. due to joint eccentricity can be eliminated. . In addition, a toner image transport unit support that slides the toner image transport unit inward from the main body of the device to provide an interior is provided, eliminating the need for conventional shaft-to-shaft coupling and complicated coupling mechanisms. As a result, the toner image carrying unit can be freely attached to and detached from the apparatus main body (free assembly layout is possible), and an extremely simple assembly operation and desorption operation during maintenance can be performed. In particular, when the assembly direction of the toner image conveying unit with respect to the apparatus main body is set inward from the side surface of the apparatus main body, the space on the front side of the apparatus main body can be effectively used. In addition, the conventional shaft-to-shaft coupling and complicated coupling mechanisms are no longer required, which reduces the gear train that reduces the rotational speed of the rotating shaft at the desired reduction ratio and transmits it to the drive shaft. Even if it is constituted by a gear of a module, a member for ensuring the accuracy of the drive transfer portion as in the prior art can be eliminated.

2 is a perspective view around an intermediate transfer belt of the image forming apparatus according to the exemplary embodiment. FIG. It is a cross-sectional top view of a drive motor part. FIG. 4 is an exploded perspective view around an intermediate transfer belt. It is a partial top view around an electric connection part (drawer connector). 1 is a front view showing an outline of an image forming apparatus according to an embodiment.

  Next, an embodiment of an electrophotographic image forming apparatus according to the present invention will be described with reference to the accompanying drawings. In the image forming apparatus according to the present embodiment, the photosensitive drum m2, the charging unit for charging the photosensitive drum m2, and the charged photosensitive drum m2 are irradiated with light based on the image data. As shown in FIG. 5, an image forming means (only the photoconductive drum m2 is shown) including an exposure unit for forming an electrostatic latent image and a developing unit using toner to convert the electrostatic latent image into a toner image. A so-called tandem color image forming apparatus, in which four in a horizontal row at a predetermined interval in a front view of the apparatus and a toner image conveying unit 1 described later are arranged to face the upper side of the image forming means, is exemplified. Has been. Since the configuration other than the periphery of the intermediate transfer belt is a known configuration, detailed description thereof will be omitted, and the periphery of the intermediate transfer belt will be described in detail below.

  As shown in FIGS. 1 and 3, the image forming apparatus according to the present embodiment includes a toner image transport unit 1, a toner image transport unit support unit 2, and an electrical connection unit 3. The toner image transport unit 1 includes a roller unit 11, an intermediate transfer belt 12 (an endless belt for carrying a toner image), and a drive motor unit 13.

  The roller unit 11 includes a frame 11a in which plate-like members are arranged to face each other at a predetermined interval, a drive roller 11b that is pivoted on one end side of the frame 11a, and a driven that is pivoted on the other end side. A roller 11c, a primary transfer roller 11d pivotally supported at the same pitch as the arrangement pitch of the photosensitive drum m2 between the driven roller 11c and the driving roller 11b, and a frame 11a connected near the driven roller 11c are connected. The plurality of rollers are arranged so as to have a reverse isosceles trapezoidal shape when viewed from the front, as shown in FIG.

  Further, an overhanging portion 11g that comes into contact with a screwing portion 2f described later is provided on the outer surface of the frame 11a on the driving roller 11b side. An attachment hole 11f that communicates in the longitudinal direction of the frame 11a (the X direction in FIG. 1) is formed in the projecting portion 11g. The overhanging portion 11g on the drive motor portion 13 side does not interfere with a gear train 13c described later. The tie rod 11e is a stepped shaft whose both ends are reduced in diameter. The both ends of the tie rod 11e are fitted to the frame 11a so as to protrude from the outer surface of the frame 11a, and a shaft end portion 11j protruding from the outer surface of the frame 11a is described later. The first slide groove 2b is fitted. The shaft end portion of the drive roller 11b protrudes from the outer surface of the frame 11a, and at one shaft end portion, as shown in FIG. 2, a driven gear 13m, which is a component of a gear train 13c described later, The ball bearing 11k is fitted in order, and the other shaft end is fitted with only the ball bearing 11k. This ball bearing 11k is adapted to be fitted into a second slide groove 2c described later.

The intermediate transfer belt 12 has a well-known configuration and is suspended on the roller unit 11 described above.
As shown in FIG. 2, the drive motor unit 13 includes a gear box 13a, a drive motor 13b, and a gear train 13c. The gear box 13a is formed in a box shape in which a bottom surface and one side surface are opened and a motor mounting hole 13d is formed on a flat surface, the opened side surface is directed inward of the frame 11a, and the opened bottom surface side is directed to the gear box 13a. From the end of the frame 11a in the vicinity of the driven gear 13m toward the frame 11a side, it is screwed to the frame 11a so as to cover the required length range inward of the frame. The drive motor 13b is a well-known motor configured to be capable of high-precision feed control, and the bearing portion 13f of the motor housing 13e is inserted into a motor mounting hole 13d provided in the gear box 13a, so that the motor rotating shaft 13g is inserted. Is protruded into the gear box 13a, and a motor housing 13e is screwed into the gear box 13a and fixed to the gear box 13a.

  The gear train 13c includes a drive gear 13h fitted to the motor rotation shaft 13g, and a first idle gear 13j that is supported by an idle shaft 13i that protrudes from the rear side of the gear box 13a and meshes with the drive gear 13h. The second idle gear 13k that is pivotally supported by the idle shaft 13i and is integrally formed with the first idle gear 13j, and the driven gear 13m that is meshed with the second idle gear 13k are two-stage decelerated. It is configured. These gear modules are 0.3 (from the viewpoint of ensuring smooth movement of the intermediate transfer belt 12 and high-precision belt feeding, it is preferable that the module does not exceed 0.5). The number of teeth of each gear is adjusted so that the transmission ratio is 12. As described above, the toner image conveying unit 1 configured in a belt-conveyor-like appearance has a rotation output of the motor rotation shaft 13g that causes the drive gear 13h, the first idle gear 13j, the second idle gear 13k, and the driven gear 13m. The intermediate transfer belt 12 is transmitted to the drive roller 11b and is laid on a plurality of rollers such as the drive roller 11b, the driven roller 11c, and the primary transfer roller 11d.

  The toner image transport unit support portion 2 is formed with a first slide groove 2b having a substantially U-shaped side view, into which the shaft end portion 11j of the tie rod 11e can be inserted, over a required length, and the first slide groove 2b. A pair of guide rails 2a (a right-handed guide rail, a left-hand guide rail) in which a substantially U-shaped second slide groove 2c fitted to the ball bearing 11k is formed over the required length. (Guide rail) Further, the guide rail 2a is provided with a screwing portion 2f for fixing the toner image conveying unit 1 to the toner image conveying unit support portion 2. The screwing portion 2f includes a side wall portion 2d formed at a position corresponding to the projecting portion 11g, and a nut 2e embedded in a position corresponding to the attachment hole 11f in the side wall portion 2d. The As shown in FIG. 3, the pair of guide rails 2a formed in this way is in the side direction of the apparatus main body m1 (X direction in FIG. 1, and the front-rear direction (front and back) of the apparatus main body m1 is Y in FIG. Direction), the first slide groove 2b and the second slide groove 2c extend in the apparatus main body m1 so as to be horizontally opposed to each other, and the drive motor unit 13 is located at the outermost position in the apparatus main body m1. It is so decorated.

  As shown in FIG. 4, the electrical connection unit 3 includes either the male or female connector 3 a provided on the machine frame (or the toner image transport unit support unit 2) of the apparatus main body m 1, and the toner image transport unit 1. The drawer connector is formed of one connector 3a and the other connector 3b that can be fitted and removed in conjunction with the sliding operation of the toner image transport unit 1.

  The electrical connection unit 3 sets the toner image transport unit 1 on the toner image transport unit support unit 2 and, at the same time, a component that requires electric power in the toner image transport unit 1, such as a drive motor 13b and a primary transfer roller 11d. The apparatus main body m1 is electrically connected.

  Instead of the drawer connector, the electrical connection portion may be constituted by a terminal made of a leaf spring and a terminal pressed against the terminal made of the leaf spring. In this case, since the terminal made of a leaf spring may be bent and damaged by an external force, it is preferable to provide the terminal on the toner image transport unit support 2 or the machine frame of the apparatus main body m1.

  Next, a series of mounting operations of the toner image transport unit 1 in the image forming apparatus according to the present embodiment configured as described above will be described. First, the shaft end portion 11j of the tie rod 11e is hooked on the first slide groove 2b, and the toner image transport unit 1 is slid from the side surface of the apparatus main body m1 toward the inside of the apparatus main body m1. When the toner image transport unit 1 is slid inward of the apparatus main body m1 and the ball bearing 11k reaches the entrance of the second slide groove 2c, the ball bearing 11k is hooked on the second slide groove 2c, and the toner image transport unit 1 is extended. Push until the part 11g contacts the side wall part 2d. With this push-off operation, the toner image transport unit 1 reaches a predetermined position inside the apparatus main body m1, and at the same time, either the toner image transport unit support 2 or the male or female connector 3a provided on the machine frame of the apparatus main body m1 The other connector 3b provided in the toner image conveying unit 1 is fitted, and the toner image conveying unit 1 and the apparatus main body m1 are electrically connected.

  When the fitting between the shaft end portion 11j of the tie rod 11e and the first slide groove 2b, the fitting between the ball bearing 11k and the second slide groove 2c, and the electrical connection are completed, the protruding portion 11g is formed. A fixing bolt is screwed onto a nut 2e embedded in the side wall 2d through the attachment hole 11f, and the toner image transport unit 1 is fixed to the toner image transport unit support section 2. At this time, the primary transfer roller 11d and the photosensitive drum m2 are vertically opposed to each other with the intermediate transfer belt 12 interposed therebetween. As described above, in the image forming apparatus according to this embodiment, the shaft end portion 11j of the tie rod 11e and the first slide groove 2b are fitted, and the ball bearing 11k and the second slide groove 2c are fitted to each other in the vertical direction. And the overhanging portion 11g and the side wall portion 2d are in contact with each other, thereby positioning in the horizontal direction. When the fixing of the toner image conveying unit 1 and the toner image conveying unit support 2 is completed, an outer panel (not shown) is attached to the machine frame of the apparatus main body m1, and a series of attaching operations is completed.

  According to the image forming apparatus according to this embodiment, the toner image transport unit 1 is configured by including the drive motor unit 13 that rotates the intermediate transfer belt 12, and the apparatus main body m1 side, the toner image transport unit 1, and the like. Since no coupling is required for connection, banding and color misregistration caused by joint eccentricity can be eliminated. Further, since the gear train 13c is configured by using gears of small modules (0.3 in this embodiment), further image quality can be improved by smooth movement of the intermediate transfer belt 12 and high-precision belt feeding. Improvement can be expected. In addition, since the toner image transport unit support portion 2 that slides the toner image transport unit 1 toward the inside of the apparatus main body m1 to provide an interior is provided to eliminate the conventional shaft-to-axis connection operation, the apparatus main body is eliminated. The assembly direction of the toner image conveying unit 1 with respect to m1 is not limited, a free assembly layout is possible, and an extremely simple assembly operation and a detachment operation during maintenance can be performed. Since the assembly direction of the toner image transport unit 1 is inward from the side surface of the apparatus main body m1, the space on the front side of the apparatus main body m1 can be effectively used.

  Conventionally, since the speed reduction mechanism including the gear train 13c and the drive motor 13b are incorporated in the apparatus main body m1, the assembly is not very easy. However, in the present embodiment, the gear train 13c and Since the drive motor 13b is incorporated in the toner image transport unit 1, the highly accurate toner image transport unit 1 can be assembled very easily. In the present exemplary embodiment, the toner image transport unit 1 and the toner image transport unit support unit 2 are configured so that the drive motor unit 13 is located outside the apparatus main body m1, and the toner image transport unit 1 is configured. Since there is no dead space that is used only during the setting, it is possible to contribute to further downsizing of the image forming apparatus.

  Further, in the present embodiment, the attaching / detaching direction of the toner image transport unit 1 with respect to the toner image transport unit support 2 and the rotation direction of the intermediate transfer belt 12 are the same direction (X direction in FIG. 1). Since the toner image transport unit 1 and the toner image transport unit support portion 2 are configured, when the toner image transport unit 1 is set, it is engaged with an image forming unit disposed on the apparatus body m1 side such as the photosensitive drum m2. However, it can be done safely and easily without accidents. In addition, since the ball bearing 11k is used as a locking member and the vertical and horizontal positions of the driving roller 11b are determined via the ball bearing 11k, the apparatus main body m1 can be incorporated with high accuracy. it can. Further, since the drawer connector is also fitted and detached simultaneously with the fitting and unloading of the toner image carrying unit support 2 and the toner image carrying unit 1, the electrical connection between the toner image carrying unit 1 and the apparatus main body m1 is turned on and off. Assembling and maintenance workability can be improved.

  The image forming apparatus according to the present embodiment has been described above. However, the above-described embodiment shows an example of a preferred embodiment of the present invention, and the present invention is not limited thereto. Various modifications can be made without departing from the scope of the invention. For example, in the present embodiment, in order to further improve the image quality, the gear train 13c is configured as one solution for satisfying smooth movement of the intermediate transfer belt 12 and high-precision belt feeding. Although the gear module is made as small as possible (0.3), as another solution, an intermediate transfer belt for one meshing of the drive gear 13h and the gear meshing with the drive gear 13h is used. The gear train 13c and the drive roller 11b (diameter thereof) may be adjusted so that the moving pitch of 12 does not exceed 0.5 mm. In this embodiment, the rotational output of the drive motor 13b is transmitted to the drive roller 11b via the gear train 13c. However, the drive motor 13b that directly drives the drive roller 11b is used without using the gear train 13c. It is good.

  In the present embodiment, the shaft end portion 11j of the tie rod 11e and the ball bearing 11k are used as the locking members. However, the present invention is not limited to this, and other rollers constituting the roller portion, tie rods other than those described above, Alternatively, a boss may be projected from the frame 11a to serve as a locking member. In the present embodiment, an example of a so-called intermediate transfer type image forming apparatus in which a toner image is secondarily transferred using the intermediate transfer belt 12 is illustrated, but the present invention is not limited to this, and the toner image is formed on the belt. It is also applicable to a so-called direct transfer type image forming apparatus in which the toner is developed and transferred directly from the belt onto a recording sheet.

  DESCRIPTION OF SYMBOLS 1 ... Toner image conveyance unit 11 ... Roller part 11a ... Frame 11b ... Drive roller 11c ... Driven roller 11d ... Primary transfer roller 11e ... Tie rod 11f ... Mounting hole 11g ... Overhang part 11j ... Shaft end part 11k ... Ball bearing 12 ... Intermediate transfer belt 13 ... Drive motor unit 13a ... Gear box 13b ... Drive motor 13c ... Gear train 13d ... Motor mounting hole 13e ... Motor housing 13f ... Bearing part 13g ... Motor rotating shaft 13h ... Drive gear 13i ... Idle shaft 13j ... No. DESCRIPTION OF SYMBOLS 1 idle gear 13k ... 2nd idle gear 13m ... driven gear 2 ... toner image conveyance unit support part 2a ... guide rail 2b ... 1st slide groove 2c ... 2nd slide groove 2d ... side wall part 2e ... nut 2f ... screw fixing part 3 ... Electrical connection 3a ... One connector 3b... The other connector m1... Device main body m2.

JP-A-10-307447 (5th page, FIG. 4) Japanese Patent Laying-Open No. 2005-309060 (page 6, FIG. 1)

Claims (8)

A toner image carrying unit in which an endless belt carrying a toner image is hung on a plurality of rollers pivoted on a frame, and a drive motor unit for rotating the belt is provided on the frame;
A toner image transport unit support section that slides the toner image transport unit inward from the apparatus main body, and detachably installs the toner image transport unit at a predetermined position inside the apparatus main body;
The drive motor unit is disposed on the outer side of the apparatus main body with respect to the toner image transport unit support unit in a direction in which the toner image transport unit is attached to or detached from the plurality of rollers.
The toner image transport unit includes an idle gear that transmits driving from the drive motor unit to drive rollers included in the plurality of rollers.
The image forming apparatus is characterized in that the drive roller, the idle gear, and the motor drive unit are arranged in the order of the drive roller, the idle gear, and the motor drive unit in the attaching / detaching direction of the toner image transport unit with respect to the toner image transport unit support unit. apparatus.   The image forming apparatus according to claim 1, wherein the toner image transport unit is attached to and detached from the side of the apparatus main body as viewed from the front of the apparatus.   The toner image transport unit support section and the toner image transport unit are configured so that the attaching / detaching direction of the toner image transport unit with respect to the toner image transport unit support section is the same as the rotation direction of the belt. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 1, wherein the drive motor unit includes a drive motor and a gear train including the idle gear that transmits a rotation output of the drive motor to the drive roller.   The image forming apparatus according to claim 4, wherein the gear train includes a gear whose module does not exceed 0.5.   The toner image conveying unit is configured such that a moving pitch of the belt with respect to one meshing generated based on a meshing pitch in the gear train and a diameter of the driving roller does not exceed 0.5 mm. The image forming apparatus according to claim 4 or 5.   The toner image conveying unit is slid inward from the apparatus main body and set at a predetermined position inside the apparatus main body, and at the same time, the electrical connection between the toner image conveying unit and the apparatus main body is established. The image forming apparatus according to claim 1, further comprising a possible electrical connection portion. The apparatus main body includes a plurality of image forming units that individually form the toner images of the respective colors,
The plurality of rollers include a primary transfer roller that is pivotally mounted on the frame so as to be opposed to the image forming unit with the belt interposed therebetween, and that primarily transfers the toner images of each color onto the belt. The image forming apparatus according to any one of claims 1 to 7.

Images