JP4243076B2 - Color image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a color image forming apparatus, and more particularly to an image forming apparatus using a belt for an image carrier such as an intermediate transfer member or a photosensitive member.
[0002]
[Prior art]
Japanese Patent Application Laid-Open No. 2001-183911 discloses a conventional technology of an image forming apparatus using a belt as an image carrier such as an intermediate transfer member or a photosensitive member. Japanese Patent Application Laid-Open No. 2001-183911 describes a method for preventing the deviation by providing a protrusion in the circumferential direction of the end of the belt support roller and abutting the end of the belt as means for regulating the deviation and meandering of the belt. Yes.
[0003]
[Problems to be solved by the invention]
However, in the method described in Japanese Patent Laid-Open No. 2001-183911, the load on the belt end portion causes a problem of damage near the belt end portion, which leads to image deterioration or shortened belt life. was there.
[0004]
SUMMARY OF THE INVENTION An object of the present invention is to provide a belt misalignment prevention mechanism that has a simple configuration and has a small load on the belt end, a long life, and high image quality in an image forming apparatus that uses a belt as an image carrier such as an intermediate transfer member or a photosensitive member. It is to be.
[0005]
[Means for Solving the Problems]
The color image forming apparatus of the present invention includes a photosensitive member driven by a driving device, a plurality of developing units for forming toner images of yellow, magenta, cyan, and black colors on the photosensitive member, and a photosensitive member on the photosensitive member. An intermediate transfer member that transfers the toner images of the respective colors on the surface thereof; and a transfer unit that collectively transfers the toner images of the respective colors onto a recording medium. The intermediate transfer member includes a plurality of belt support rollers. One of the plurality of belt support rollers is a photoconductor side roller provided to face the photoconductor, and the photoconductor is in contact with the photoconductor side roller via the intermediate transfer belt. is wound on the intermediate transfer belt, the reinforcing said driven driven by the driving force of the nip portion in contact with the photosensitive member, the image holding side surface of both end portions along the circumferential direction of the intermediate transfer belt The timber is arranged, with prior SL and projections over the thickness of the intermediate transfer belt at both ends of the photoconductor side roller, and a recessed step in the entire circumferential direction of the photoconductor side roller, and the projection, the concave The step is an insulating material.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0007]
FIG. 2 is an explanatory diagram of a full-color printer that is an image forming apparatus according to the present exemplary embodiment. Although FIG. 2 shows a case where a belt is used for both the intermediate transfer member and the photosensitive member, the intermediate transfer member is a belt and the photosensitive member is a drum, or the intermediate transfer member is a drum and the photosensitive member is a belt. The invention can be applied.
[0008]
In this embodiment, the present invention is applied to the intermediate transfer belt. However, the present invention can also be applied to the photosensitive belt, and can be applied to only the photosensitive belt or to both the intermediate transfer belt and the photosensitive belt.
[0009]
FIG. 2 shows a full-color image forming apparatus that forms a color image by rotating the intermediate transfer belt 1 a plurality of times. In FIG. 2, from right to left, developing units 11a to 11d that develop images of yellow, magenta, cyan, and black, the photosensitive belt 8, the intermediate transfer belt 1, and the recording medium 13 are picked up from the paper cassette 12. 14, a transfer roller 16, a fixing device 17, and a paper transport mechanism that transports the paper via a paper discharge mechanism 18 are arranged in this order.
[0010]
The photosensitive belt 8 is driven in the direction of the arrow by a driving device (not shown). The intermediate transfer belt 1 is driven to be driven by the photosensitive belt 8 by a driving force of a nip (sandwich) portion that contacts the photosensitive belt 8.
[0011]
The intermediate transfer belt 1 is wound around the transfer side roller 6 and the photoreceptor side roller 3, and tension is given by the intermediate transfer belt tension roller 7. The photoreceptor belt 8 is wound around the photoreceptor-side roller 3 with the intermediate transfer belt 1 interposed therebetween.
[0012]
In order to form an image, the photosensitive layer of the photosensitive belt 8 is charged by the charging device 9, and a laser beam corresponding to the image information is irradiated from the optical unit 10 to the photosensitive layer of the photosensitive belt 8, thereby forming an electrostatic latent image. Form. As described above, the developing units 11a to 11d are filled with toners of different colors, and any one of them forms a toner image corresponding to the latent image on the photosensitive belt 8. The toner image on the photosensitive belt 8 is once transferred onto the intermediate transfer belt 1. The above process is performed a plurality of times for different color developing devices, and different color toner images are superimposed on the intermediate transfer belt 1 to form a color image.
[0013]
The recording media 13 stored in the paper cassette 12 are fed out one by one by the pickup roller 14 and the skew is corrected by the registration roller 15. Immediately before the leading edge of the recording medium 13 reaches between the transfer roller 16 and the intermediate transfer belt 1, a retracting means (not shown) presses the transfer roller 16 against the intermediate transfer belt 1 and presses the recording medium 13 against the intermediate transfer belt 1. . At this time, a voltage is applied to the transfer roller 16 to transfer the toner image on the intermediate transfer belt 1 to the recording medium 13. Thereafter, the recording medium 13 reaches the fixing device 17, and the toner image on the recording medium 13 is fixed by the fixing device 17 by heat and pressure, and is discharged by the paper discharge mechanism 18. The residual image toner remaining on the intermediate transfer belt 1 after the image transfer is brought into contact with the intermediate transfer belt 1 by a retracting means 19 (not shown) to remove the residual toner.
[0014]
FIG. 1 is a cross-sectional view showing a structure for shifting the intermediate transfer belt unit of this embodiment. Belt reinforcing members 2 a and 2 b are provided at both ends of the intermediate transfer belt 1, and a protrusion 4 for preventing the belt from slipping at both ends of the belt 3 on the photosensitive member side of the belt support roller and a concave step 5 on the inner side of the protrusion. It is provided over the entire direction.
[0015]
The intermediate transfer belt 1 is prevented from being offset by abutting the end portion against the offset protrusion 4. At this time, a load is generated at the end of the intermediate transfer belt 1 on the side in contact with the protrusion due to the contact with the offset protrusion 4 and the offset force. The intermediate transfer belt 1 can reduce damages such as wear, cracks, breakage, buckling and the like due to the above-described loads by the reinforcing members 2a and 2b.
[0016]
Since tension is applied to the intermediate transfer belt 1, if there is no concave step 5 on the photoconductor side roller 3 of the belt support roller, the intermediate transfer belt 1 has a step corresponding to the thickness of the reinforcing member 2b. Therefore, the intermediate transfer belt 1 is subjected to a bendable load, which may cause damage to the intermediate transfer belt 1. Further, when a step is generated on the image holding side surface (reinforcing member 2a installation side) of the intermediate transfer belt 1, the image is transferred from the photosensitive belt 8 to the intermediate transfer belt 1 or from the intermediate transfer belt 1 to the recording medium 13. Prevents uniform transfer during image transfer.
[0017]
The reinforcing member 2a and the reinforcing member 2b disposed on the intermediate transfer belt 1 preferably have the same width. However, if the cross-sectional areas of the reinforcing member 2a and the reinforcing member 2b are the same within the manufacturing error range, the widths are different. May be. In the case where the widths are different, it is preferable to reduce the width of the reinforcing member 2a disposed on the image holding side surface of the intermediate transfer belt 1 in FIG.
[0018]
As in the full color printer of this embodiment, the step formed on the intermediate transfer belt 1 can be reduced by installing the concave step 5 on the photoconductor side roller 3, thereby reducing the aforementioned bending load. . In addition, since the level difference generated on the image holding side surface can be reduced, image disturbance can be suppressed.
[0019]
In order to transfer an image from the photosensitive belt 8 to the intermediate transfer belt 1, it is necessary to have a potential difference of about 0.3 kV to 2 kV between the photosensitive belt 8 and the intermediate transfer belt 1. Since the offset protrusion 4 is close to the photosensitive belt 8, it becomes difficult to provide a desired potential difference between the photosensitive belt 8 and the intermediate transfer belt 1 when discharging is performed between the photosensitive belt 8 and the offset protrusion 4. .
[0020]
In the color printer of this embodiment, the detent protrusion 4 is formed of an insulating material having a volume resistance of 100 kΩ · cm or more and a surface resistance of 100 kΩ / □ or more. As a result, the discharge between the photosensitive belt 8 and the detent protrusion 4 can be suppressed, and it becomes easy to provide a desired potential difference between the photosensitive belt 8 and the intermediate transfer belt 1, and a uniform image can be obtained. Can transfer. By forming the concave step 5 from the insulating material having the above-described resistance value, the creeping distance from the photoreceptor belt 8 can be further increased, and discharge can be further suppressed.
[0021]
For reinforcement of the intermediate transfer belt 1, it is desirable to install both of the reinforcing members 2a and 2b. However, only one of them may be installed, and if only the reinforcing member 2a that is easy to install is used, the configuration can be made cheaper. it can. When only the reinforcing member 2b is configured, a step on the image holding side surface can be further suppressed, and a configuration in which a uniform image can be easily obtained can be achieved. When both the reinforcing members 2a and 2b are installed, the manufacturing cost can be reduced by forming the reinforcing members 2a and 2b integrally, rather than configuring them separately.
[0022]
The detent protrusion 4 and the concave step 5 are preferably installed on all of the plurality of belt support rollers, but may be installed only on one belt support roller. When the rollers on which the detent protrusion 4 and the concave step 5 are installed are limited, it is better to preferentially install the roller having the largest contact area between the intermediate transfer belt 1 and the detent protrusion 4 in other words, the roller having the largest diameter.
[0023]
【The invention's effect】
In the full color printer of the present invention, the load on the belt end is reduced while the belt end is regulated by the belt end and the detent protrusion, so that an image forming apparatus with high image quality and long life can be realized with a simple configuration. .
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an intermediate transfer belt shift prevention mechanism of an image forming apparatus according to an embodiment.
FIG. 2 is an explanatory diagram of a full-color printer according to an embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Intermediate transfer belt, 2a, 2b ... Reinforcement member, 3 ... Photoconductor side roller, 4 ... Detent protrusion, 5 ... Concave step, 6 ... Transfer side roller, 7 ... Belt tension roller, 8 ... Photoconductor belt, 9 ... Charging device, 10 ... optical unit, 11a to 11d ... developing unit, 12 ... paper cassette, 13 ... recording medium, 14 ... pickup roller, 15 ... registration roller, 16 ... transfer roller, 17 ... fixing device, 18 ... paper discharge mechanism , 19 ... cleaning means, 20 ... image forming apparatus.

Claims (3)

A photosensitive member driven by a driving device; a plurality of developing units for forming toner images of yellow, magenta, cyan, and black on the photosensitive member; and the toner images of the respective colors on the photosensitive member on the surface thereof. In a color image forming apparatus provided with an intermediate transfer member that transfers images in a superimposed manner and a transfer unit that collectively transfers the toner images of each color onto a recording medium, the intermediate transfer member is hung on a plurality of belt support rollers. An intermediate transfer belt, wherein one of the plurality of belt support rollers is a photoconductor side roller provided facing the photoconductor, and the photoconductor is wound around the photoconductor side roller via the intermediate transfer belt. is, the intermediate transfer belt, the photosensitive member is driven driven by the driving force of the nip portion in contact with the reinforcing portion to the intermediate transfer circumferential ends the image holding side surface of the along the belt It was placed, and the projection of more than the thickness of the intermediate transfer belt at both ends of the front Symbol photoreceptor side roller, and a recessed step in the entire circumferential direction of the photoconductor side roller, and the projection, the concave stepped Is a color image forming apparatus characterized by being an insulating material.   2. The color image forming apparatus according to claim 1, wherein the reinforcing member is also disposed on an image holding side rear surface of the intermediate transfer belt.   3. The color image forming apparatus according to claim 2, wherein the width of the reinforcing member on the image holding side surface is narrower than the width of the reinforcing member on the back surface of the image holding side.

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