JP2672558B2 - Image forming device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to performing a transfer operation while a transfer belt is in contact with a photosensitive member mounted at a predetermined position in an image forming case. The present invention relates to an image forming apparatus.

(Prior Art) In various image forming apparatuses such as copiers, printers, and facsimiles, a toner image is carried on the surface of a photoconductor mounted at a predetermined position in an image forming case, and the surface of the photoconductor is There is a transfer belt arranged so as to be in contact with each other, and the transfer paper held by the transfer belt is sent to a transfer portion formed at a contact portion between the transfer belt and the photoconductor to perform a transfer action. .

In an image forming apparatus using such a transfer belt, the appropriateness of the contact state between the photoconductor and the transfer belt affects the transfer action. For example, if the contact pressure between the two is unbalanced in the belt width direction, a density difference may occur on the image,
This causes a problem such that the transfer belt shifts to one side and an image shift occurs. Therefore, conventionally, various mechanisms have been proposed for making the contact pressure between the photoconductor and the transfer belt uniform. For example, in the apparatus described in Japanese Patent Laid-Open No. 53-120442, the back surface of the transfer belt, which is in contact with the photoconductor, is pressed against a roller arranged so as to be pressed against the photoconductor. However, in such a conventional apparatus, when the roller is temporarily separated from the photoconductor during non-transfer and the roller is pressed against the photoconductor again during the next transfer, a shock due to the roller contact directly occurs on the photoconductor. However, there is a problem in that the image is distorted due to the transmission, and disturbances on the image such as jitter may occur.

(Purpose) Therefore, the present invention is capable of keeping the contact state of the transfer belt at all times constant even when the operation of pressing and separating the transfer belt from the photosensitive member is repeated at the same time. An object of the present invention is to provide an image forming apparatus that can be brought into contact without a shock and can favorably avoid image disturbance such as jitter.

(Structure) In order to achieve the above object, the present invention has a transfer belt arranged so as to be transferred to a photosensitive member mounted at a predetermined position in an image forming case while being in contact with the surface of the photosensitive member. In the image forming apparatus configured to feed the transfer paper held by the transfer belt to the transfer portion formed at the contact portion between the transfer belt and the photosensitive member to perform the transfer action, the position separated from the transfer portion. The backup roller that presses the transfer belt against the surface of the photoconductor so that the photoconductor does not come into pressure contact with the crocodile, and the rotation axis of the backup roller that contacts the image forming case where the photoconductor is mounted to the crocodile And a positioning member attached to the positioning roller for positioning the backup roller.

With such a configuration, when the transfer belt is swung from the non-transfer position to the transfer position, the positioning member provided on the backup roller is brought into contact with the image forming case against the edge of the image forming case. Positioning is performed. As a result, the transfer belt is pressed against the photosensitive belt with a predetermined contact pressure.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 shows a color copying machine as an example of an image forming apparatus to which the present invention is applied. In the figure, an endless transfer belt 1 is stretched over a driving roller 2 and a driven roller 3 and stretched in a substantially horizontal direction. The transfer paper S is sent in the direction of the arrow by the paper feed roller 4 and conveyed on the transfer belt 1.

The document table 5 is provided parallel to the arrangement direction of the transfer belt 1 and is reciprocally driven in the extending direction. When a scanning light is applied to a color image of a document (not shown) on the document table 5, the reflected light is applied onto the photoconductor belt 8 through the converging light transmitter array 6, the filter 7, and the like. The light image is exposed and imaged. As a result, an electrostatic latent image is formed on the surface of the photosensitive belt 8. This is performed for each color separation, and the electrostatic latent images corresponding to the respective colors are formed by switching the toner developing sleeves 9A, 9B, 9C of the respective colors in the rotary developing device 9 to the developing areas. The sleeve visualizes each color toner image.

When the transfer sheet S is carried by the transfer belt 1 and passed through the transfer portion 11, the first visible image on the photoconductor belt 8 is transferred onto the transfer sheet by the transfer charger 12.
During this transfer, the transfer belt 1 is driven in the direction of arrow A, and its moving direction is opposite to the forward direction of the document table 5. The fifth manuscript is designed to be returned after finishing the forward movement. At this time, that is, the rear end of the transfer paper is
After passing through the transfer belt 1, the transfer belt 1 is reversely rotated and the upper belt portion is moved in the direction opposite to the arrow A direction to prepare for the next transfer.

Then a similar process is repeated,
The second-time visible image and the third-time visible image are transferred onto one sheet of transfer paper so as not to be displaced. After the final transfer, the transfer paper S is a charge removal charger.
It advances through a space 13 to a transfer paper fixing system 14 composed of a pair of rollers provided in the transfer paper discharge direction, and is fixed at this portion and then discharged outside the machine. The copying machine according to this embodiment is of a type in which the document table is reciprocally moved in the image forming system including the document table 5 and the converging optical transmission element array 6.

The photoconductor belt 8 and the developing device 9 are an image forming case.
Each of the image forming cases 15 is mounted at a predetermined position inside the image forming case 15, and the image forming case 15 is slidably supported by slide rails 16 and 17 on both sides of the image forming case 15 so that the image forming case 15 can be pulled out from the main body of the apparatus. Further, as shown in FIG. 3, the cover provided on the upper portion of the image forming case 15 is provided with a charging charger 21 for initially charging the photoconductor belt 8 and an eraser 22 for discharging the non-image area. These can be pulled out integrally with the image forming case 15. The photosensitive belt 8 and the developing device 9 are detachably attached to the image forming case 15. As shown in FIG.
The image forming case 15 after the developing device 9 is removed is shown. Further, the photoreceptor belt 8 has three support rollers 8 attached to a pair of foldable support frames 8D and 8E as shown in FIGS.
It is stretched by A, 8B and 8C. As shown in FIGS. 7 and 8, the fan-shaped locking piece 8G is formed by bending the support frames 8D and 8E while standing them up.
The photoconductor belt 8 can be detached by disengaging it from the engagement piece 15G of 15 pieces. When the photoconductor belt 8 is mounted, the photoconductor belt 8 is held at a predetermined position with respect to the image forming case 15 by the locking piece 8G and the engagement piece 15G.

Further, the transfer belt 1 is formed by forming a dielectric film into an endless belt shape, and the driving roller 2 and the driven roller 3 supporting the transfer belt 1 are as shown in FIG. It is supported by frame 1A. The frame 1A is provided so as to be swingable about the support shaft of the drive roller 2 so that the transfer belt 1 can be moved to a transfer position shown by a solid line in FIG. 2 and a non-transfer position shown by a chain line in FIG. It is designed to be rocked to and from the transfer position. In particular, as shown in FIG. 9, an eccentric cam 23A fixed to the swing drive shaft 23 is arranged immediately below the frame 1A, and the frame 1A is attached to the eccentric cam 23A. The driven roller 1B is attached so as to be in contact with each other. By rotating the eccentric cam 23A, the frame 1A is swung up and down via the driven roller 1B. Above driven cam 1B
Is supported by a bearing 1C attached to the frame 1A so as to be slidable in the vertical direction, and the bearing 1C is subjected to a predetermined biasing force directed downward by a coil spring 1D. The transfer belt 1 is adapted to be lowered toward the non-transfer position when performing the above-described backward movement.

Further, a pair of registration rollers 25 is provided directly above the eccentric cam 23A and the driven roller 1B so as to sandwich the upper ridge portion of the transfer belt 1. The upper roller of the registration roller 25 is separated from the transfer belt 1 by a cam means (not shown) after the transfer paper is sent toward the transfer portion 11 and a series of copy cycles is completed, whereby the undecided state is determined. The toner image is not disturbed on the registration roller 25. The upper registration roller 25 is returned to the original position for the next paper feeding operation when the copy cycle is completed.

Furthermore, backup rollers 24A, 24B for supporting the transfer belt 1 by pressing the inner surface of the transfer belt 1 against the inner surface of the transfer belt 11 are disposed in the inner edge regions of the transfer belt 1 on both sides of the transfer portion 11. . Each of these backup rollers 24A, 24BE has a function of supporting the transfer belt 1 so that the surface of the photoconductor belt 8 is pressed against the crocodile, and is arranged slightly apart from the transfer section 11 as described above. The photoconductor belt 8 is arranged at a position where it is not pressed into contact with the crocodile.

Of these both backup rollers 24A, 24B,
The backup roller 24A arranged directly below the developing device 5 is positioned at a predetermined position by a positioning member. That is, as also shown in FIG. 1, a rotary ring 24A2 constituting a positioning member is rotatably attached to both support shafts 24A1 projecting outward from both ends of the backup roller 24A. There is. Each of these rotating rings 24A2 is formed to have a predetermined outer diameter dimension that is slightly smaller than the outer diameter of the backup roller 24A. Meanwhile, the image forming case
A contact piece 15E as a positioning member is provided on the lower edge portion of 15
Is formed so that the lower part thereof is projected to the crocodile, and the rotary plates 24A2 are brought into contact with the horizontal plate portion of the contact piece 15E. Then, the backup roller 24A is positioned in a state where the rotating ring 24A2 and the contact piece 15E are in contact with each other, so that the transfer belt 1 is pressed against the photoconductor belt 8 with a predetermined contact pressure by the crocodile. It has become.

In such an embodiment, by rotating the eccentric cam 23A, the frame 1A is swung in the vertical direction via the driven roller 1B, and accordingly, the transfer belt 1 is shown by the solid line in FIG. It is repeatedly rocked at a predetermined timing between the transfer position and the non-transfer position shown by the chain line in FIG. When the transfer belt 1 is swung from the non-transfer position to the transfer position, the rotation ring of the backup roller 24A with respect to the contact piece 15E of the image forming case 15 is rotated.
24A2 is contacted, which causes the backup roller 24
A is positioned. As a result, the transfer belt 1 is brought into pressure contact with the photosensitive belt 8 at a predetermined contact pressure. After the transfer belt 1 is pressed against the crocodile belt 8 with a predetermined contact pressure, when the eccentric cam 23A is rotationally driven to try to push up the frame 1A excessively, the extra pushing stroke is the driven roller 1B. It is designed to be absorbed by the coil spring 1C attached to the.

Further, in the embodiment shown in FIG. 10, both backup rollers 24A, 24B are integrally attached with the shield case 12A of the transfer charger 12 as a common housing, and the shield case 12A is not shown. It is designed to be moved up and down by the solenoid drive mechanism. And both backup rollers 24A,
Both ends of 24B are brought into contact with the contact pieces 15E of the image forming case 15, so that the positioning operation of the transfer belt 1 is performed in the same manner as in the above embodiment.

Although each of the above embodiments relates to an image forming apparatus having a belt-shaped photoreceptor, the present invention can be similarly applied to an image forming apparatus having a drum-shaped photoreceptor. is there.

(Effect) As described above, in the image forming apparatus according to the present invention, the backup roller that supports the transfer belt so that the surface of the photoconductor is pressed against the crocodile is provided at a position where the photoconductor is not pressed and contacted by the crocodile, and by the positioning member. Since the backup roller is positioned with respect to the image forming case to keep the contact state of the photosensitive belt constant,
Even if the operation of pressing and separating the transfer belt from the photoconductor is repeated, the contact state between the two can be kept constant at the same time, and at the same time, the photoconductor elastically contacts the photoconductor without any shock. Therefore, it is possible to satisfactorily avoid image disturbance such as jitter.

[Brief description of the drawings]

FIG. 1 is an explanatory perspective view showing a backup roller positioning mechanism according to an embodiment of the present invention, and FIG. 2 is a side view showing a color copying machine as an example of an image forming apparatus to which the present invention is applied. FIGS. 3A and 3B are side explanatory views showing an enlarged image forming case and its attached object, FIG. 4 is an enlarged side view showing only the image forming case, and FIGS. FIG. 7 and FIG. 8 are partial side explanatory views showing a procedure for attaching and detaching the photoconductor belt to and from the image forming case, and FIG. 9 is a view showing the image forming case and the transfer belt. FIG. 10 is an enlarged side view showing the swinging mechanism, and FIG. 10 is an explanatory perspective view showing the other embodiment of the present invention. 1 ... Transfer belt, 1A ... Frame, 1B ... Driven roller,
8: Photoconductor belt, 15: Imaging case, 15E: Positioning contact piece, 23A: Eccentric cam, 24: Backup roller, 24A2: Positioning rotary ring.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomonori Fukui 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Ken Ken Saito 1-3-6 Nakamagome, Ota-ku, Tokyo Inside the Ricoh Company (72) Inventor Tomonori Nakahara 1-3-6 Nakamagome, Ota-ku, Tokyo Inside the Ricoh Company (56) References JP-A-1-107280 (JP, A)

Claims (1)

(57) [Claims] 1. A transfer belt is arranged so as to be transferred while being in contact with the surface of the photoconductor mounted on a predetermined position in an image forming case, and is held by the transfer belt. In an image forming apparatus in which a transfer sheet is fed to a transfer portion formed at a contact portion between a transfer belt and a photosensitive member to perform a transfer action, the photosensitive member is separated from the transfer portion so that the photosensitive member is not pressed into contact with the crocodile. A backup roller that presses the transfer belt against the surface of the photoconductor at a predetermined position, and a backup roller that is attached to the rotation shaft of the backup roller so that the image forming case on which the photoconductor is mounted comes into contact with the ware. An image forming apparatus, comprising: a positioning member for positioning.