JP2003057909A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the deterioration of an image by keeping the load fluctuation of an image carrier to an endless belt constant and making the elongation of the endless belt or slide thereof to a driving roller small. SOLUTION: The tooth number of photoreceptor gears 18Y, 18M, 18C and 18B fixed on photoreceptors 3Y, 3M, 3C and 3B is different respectively and set so that it may be smaller in order toward the belt carrying direction of an intermediate transfer belt 2. Assuming that the surface speeds of the photoreceptors 3B, 3C, 3M and 3Y are V1, V2, V3 and V4 respectively, relation between the surface speeds holds V1<V2<V3<V4 because the diameters of the photoreceptors 3B, 3C, 3M and 3Y are the same. Assuming that the carrying speed of the belt 2 is Vb, the relation becomes Vb>V4, that is, Vb is higher than the surface speed V4 of the photoreceptor 3Y near to the driving roller 2B on the most downstream side in the belt carrying direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, and the like.
The present invention relates to a tandem type image forming apparatus having a plurality of image carriers.

[0002]

2. Description of the Related Art An image forming apparatus of this type is disclosed in Japanese Patent Laid-Open No.
As described in JP-A-26887 and Japanese Patent Laid-Open No. 10-78734, the endless belt stretched over a plurality of rollers is in contact with a linearly extending surface of the endless belt and is spaced in the conveying direction of the endless belt. A plurality of image carriers (photoconductors) are provided. A toner image of different colors formed on each image carrier is superposed and transferred onto an endless belt as an intermediate transfer belt, and the superposed toner images are collectively transferred onto a transfer material to obtain a full-color image. ing.
It is also known that the endless belt as the transfer belt conveys the transfer material and superimposes and transfers the toner images of different colors formed on the respective image carriers onto the transfer material. In such an image forming apparatus, each image carrier is rotatably driven by one drive source via a structure such as gear transmission and pulley and timing belt transmission. The endless belt is rotationally driven by a frictional force with one of the plurality of rollers as a driving roller.

[0003]

As described above, in an image forming apparatus such as a tandem type color copying machine or a color printer having a plurality of image carriers, toner of each color formed on each image carrier is used. It is necessary to transfer the images on the transfer material conveyed by the transfer belt or on the intermediate transfer belt in an overlapping manner without positional deviation. However, in the case of a gear that is a rotating body or an image carrier, eccentricity in which the center of rotation is deviated cannot be avoided from the viewpoint of manufacturing accuracy, and therefore speed fluctuations occur. Further, also in the drive roller that drives the endless belt, there is variation in diameter from the viewpoint of manufacturing accuracy, and variation in the transport speed of the endless belt occurs.

In the tandem type, since the endless belts are driven in contact with a plurality of image carriers arranged in parallel, if the speed of each image carrier fluctuates, the load on the endless belt fluctuates. Depending on the magnitude of the surface speed due to the speed fluctuation, the endless belt between the image carriers may be loosened. As a result, there is a problem that the endless belt expands and contracts due to variations in tension, or slips on the driving roller, causing color misregistration and deteriorating the image.

Therefore, an object of the present invention is to provide an image forming apparatus capable of suppressing the image deterioration by making the load fluctuation of the image carrier with respect to the endless belt constant and reducing the expansion and contraction of the endless belt and the slippage with respect to the driving roller. To do.

[0006]

In order to achieve the above object, in the invention described in claim 1, a plurality of image bearing members are arranged in contact with an endless belt stretched around a plurality of rollers. In the image forming apparatus, the plurality of image carriers are driven at different surface speeds.

According to a second aspect of the invention, in the image forming apparatus according to the first aspect, the drive roller for driving the endless belt among the plurality of rollers is the endless belt with respect to the plurality of image carriers. It is provided on the downstream side in the transport direction and has a configuration in which the surface speed of each image carrier is gradually decreased from the side closer to the drive roller to the upstream side.

According to a third aspect of the invention, in the image forming apparatus according to the second aspect, the conveying speed of the endless belt is
The configuration is such that the surface velocity of the image carrier on the most downstream side is higher than that of the image carrier.

According to a fourth aspect of the invention, in the image forming apparatus according to the first aspect, the drive roller for driving the endless belt among the plurality of rollers is the endless belt with respect to the plurality of image carriers. It is provided on the upstream side in the transport direction, and has a configuration in which the surface speed of each image carrier is sequentially increased from the side closer to the drive roller to the downstream side.

According to a fifth aspect of the invention, in the image forming apparatus according to the fourth aspect, the conveying speed of the endless belt is
The configuration is such that the surface speed of the image carrier on the most upstream side is slower.

According to a sixth aspect of the present invention, the first to fifth aspects are provided.
In the image forming apparatus according to any one of items 1 to 5, the speed difference between the transport speed of the endless belt and the surface speed of each image carrier is
The configuration is such that it is made larger than the speed fluctuation amount between the transport speed of the endless belt and the surface speed of each image carrier.

According to the invention of claim 7, claims 1 to 6 are provided.
In the image forming apparatus according to any one of 1 to 3, the endless belt is an intermediate transfer belt for sequentially transferring the toner images formed on the image carriers.

According to the invention described in claim 8, claims 1 to 6 are provided.
In the image forming apparatus described in any one of the above ones, the endless belt is a transfer belt that conveys a transfer material for sequentially transferring the toner images formed on the image carriers.

According to the invention of claim 9, claim 7 or 8
In the image forming apparatus described above, the position at which the electrostatic latent image is formed on the image carrier and the position at which the visualized toner image is transferred are shifted by about 180 ° in the rotation direction of the image carrier. The composition is adopted.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described below with reference to FIGS. First, an outline of the configuration and operation of a tandem type color copying machine as an image forming apparatus according to this embodiment will be described with reference to FIG. The color copying machine 1 includes an image forming unit 1 located at the center of the apparatus body.
A, and a sheet feeding section 1B located below the image forming section 1A
And an image reading unit 1C located above the image forming unit 1A. An intermediate transfer belt 2 as an endless belt having a transfer surface (extended surface) extending in the horizontal direction is arranged in the image forming section 1A, and an upper surface of the intermediate transfer belt 2 is in a complementary color relationship with a color separation color. A structure is provided for forming an image of a certain color. That is, the photoconductors (photoreceptor drums) 3Y, 3M, 3C, and 3B as image carriers capable of carrying images of toners of complementary colors (yellow, magenta, cyan, and black) extend the intermediate transfer belt 2. It is placed in contact along the surface.

Each of the photoconductors 3Y, 3M, 3C and 3B is composed of a drum rotatable in the same direction (counterclockwise direction), around which a charging roller 4, an optical writing unit 5 and a developing unit are provided. A unit 6, a primary transfer roller 7, a cleaning unit 8, a charge eliminating lamp 9 and the like are provided.
Similar to the photoconductor 3, the alphabets attached to the respective symbols correspond to the toner colors. Optical writing unit 5
In a single frame for each photoreceptor 3Y, 3M, 3C, 3
The writing structure corresponding to B has a built-in structure. The optical writing unit 5 may be an LD or an LED. Each developing unit 6 contains a color toner.

The intermediate transfer belt 2 includes three supporting rollers 2.
The photoconductors 3Y, 3M, 3C, 3B are wound around A to 2C.
It has a structure capable of moving in the same direction at a position opposed to. A support roller 2C, which is different from the support rollers 2A and 2B that supports the spreading surface, faces the secondary transfer unit 10 with the intermediate transfer belt 2 interposed therebetween. A belt cleaning unit 11 for cleaning the surface of the intermediate transfer belt 2 is provided at a position facing the support roller 2A. Primary transfer roller 7
Through the intermediate transfer belt 2 to the respective photoconductors 3Y, 3M, 3
It is pressed against C and 3B. You may provide three or more support rollers. For example, a support roller for adjusting the deviation of the intermediate transfer belt 2 may be further provided. As for the position of the belt cleaning unit 11, an opposing roller may be provided in addition to the support roller 2A and may be provided at that position. The primary transfer roller 7 may be a non-contact charger.

The surface of the photoconductor 3Y is uniformly charged by the charging roller 4, and an electrostatic latent image is formed on the photoconductor 3Y based on the image information from the image reading section 1C. The electrostatic latent image is visualized as a toner image by the developing unit 6Y containing yellow toner, and the toner image is primarily transferred onto the intermediate transfer belt 2 by the primary transfer roller 7Y. Similar images are formed on the other photoconductors 3M, 3C, and 3B only by different toner colors, and the toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 2 and superposed.
In the present embodiment, the writing position and the transfer position are configured to be 180 degrees out of phase with each other in the rotation direction of the photoconductor 3. With such a positional relationship, there is a speed fluctuation due to the eccentricity of the photoconductor 3, and even if the latent image pitch unevenness occurs at the writing position, the pitch unevenness that occurs when the toner image is transferred is canceled and transferred. It The toner remaining on the photoconductor 3 is removed by the cleaning unit 8, and the potential of the photoconductor 3 is initialized by the charge eliminating lamp 9 after transfer, and the next image forming step is prepared.

The secondary transfer means 10 is a charging drive roller 10.
A, a driven roller 10B, and a transfer belt 10C that is wound around these and moves in the same direction as the intermediate transfer belt 2. Although not shown, the secondary transfer unit 10 has a cleaning unit for cleaning the transfer belt 10C. The secondary transfer means 10 is provided so that the transfer material (paper) can be conveyed to the entrance of the fixing unit 12.
The secondary transfer means 10 may be composed of a roller or a charger. The fixing unit 12 is an endless fixing belt 12A.
And two rollers that support the fixing belt 12A
It has a pressure roller 12B and the like that are in pressure contact with. The sheet that has passed through the fixing unit 12 is selectively fed to a sheet feeding tray 14 and a sheet reversing unit 15 by a sheet passage switching claw 13 provided on the downstream side of the fixing unit 12. Be guided. When the sheet is conveyed toward the sheet discharge tray 14, the sheet is discharged onto the sheet discharge tray 14 by the sheet discharge roller pair 16 and is stacked. The double-sided reversing unit 15 includes a reversing roller 15A and a sending roller 15B.
And a plurality of transport rollers 15C.

The paper feed unit 1B has a plurality of paper feed cassettes 1B1 in which papers are stacked and accommodated, and a paper feed in which the papers accommodated in the paper feed cassettes 1B1 are separated one by one from the top and fed. A roller 1B2, a conveyance roller pair 1B3, a registration roller pair 1B4 located upstream of the secondary transfer position, and the like are provided. The paper fed from the paper feed cassette 1B1 is temporarily stopped by the pair of registration rollers 1B4, and after the skew displacement is corrected, the front end of the toner image on the intermediate transfer belt 2 and the predetermined position of the front end in the transport direction match. The registration roller pair 1B4 sends it to the secondary transfer position at the timing. A manual feed tray 17 is rotatably provided on the right side of the apparatus main body, and the paper stored in the manual feed tray 17 is fed by a paper feed roller 18 and then fed to a paper feed cassette 1B.
The sheet is conveyed toward the registration roller pair 1B4 by a conveyance path that joins the sheet conveyance path from 1.

In the optical writing unit 5, the writing light is controlled by the image information from the image reading section 1C or the image information output from a computer (not shown), and the photoconductor 3 is controlled.
Writing light corresponding to image information is emitted to Y, 3M, 3C, and 3B to form an electrostatic latent image.
The image reading unit 1C is an automatic document feeder (ADF) 1C1.
And a scanner 1C2 having a contact glass (not shown) as a document placing table. The automatic document feeder 1C1 has a calibration capable of reversing the document fed out on the contact glass, and can scan the front and back surfaces of the document. The electrostatic latent image on the photoconductor 3 formed by the optical writing unit 5 is subjected to visible image processing by the developing unit 6 and is primarily transferred to the intermediate transfer belt 2. When the toner images of the respective colors are superimposed and transferred onto the intermediate transfer belt 2, the secondary transfer means 10 collectively and secondarily transfers the toner images onto the sheet. The sheet that has been secondarily transferred is sent to the fixing unit 12, where the unfixed image is fixed by heat and pressure.
The residual toner on the intermediate transfer belt 2 after the secondary transfer is removed by the belt cleaning unit 11.

A series of operations of the color copying machine 1 having the above structure will be described. The original set on the ADF tray of the ADF is sent onto the contact glass and read by the scanner 1C2. The data is transmitted to the optical writing unit 5, and the optical writing unit 5 exposes the photoconductor 3 charged by the charging roller 4 based on the read image data to form an electrostatic latent image. The photoconductor 3 rotates in the direction of the arrow, and the electrostatic latent image is visualized by the developing unit 6. A visible image of a different color is developed on each photoreceptor 3, and the photoreceptors 3Y to 3B are sequentially superposed on the intermediate transfer belt 2 and primarily transferred. On the other hand, the sheet as the transfer material is fed from the sheet feeding section 1B as the paper bank to the registration roller pair 1B4 and stopped and stands by. The sheet is sent out from the registration roller pair 1B4 at the timing at which the image that has been superimposed and primary-transferred on the intermediate transfer belt 2 is conveyed,
The images in which the respective colors are overlapped at the secondary transfer position and the primary transfer is performed are collectively secondarily transferred to the paper. The sheet that has been secondarily transferred is directly attached to the fixing unit 1 by the transfer belt 10C of the second transfer means 10.
It is transported to 2 and enters the fixing part.

The fixed sheet remains as it is in the sheet discharge tray 14
It is either stacked on the sheet or conveyed to the double-sided reversing unit 15. When copying on both sides, it is transported to the lower side after fixing,
It is once sent to the stack portion 15D of the double-sided reversing unit 15. This time, from the trailing edge of the sheet, it is sent to the reversing roller 15A by the delivery roller 15B, and the sheet makes a U-turn and is transported to the registration roller pair 1B4 by the transport roller pair 1B3. The subsequent process is the same as the front side copy.

FIG. 2 shows a schematic structure of driving the photoconductor 3 and the intermediate transfer belt 2. Photoreceptors 3Y, 3M, 3C, 3B
The photoconductor gears 18Y, 18M, 18C and 18B are fixed to. Photoconductor gears 18Y, 18M, 18C, 18
Idler gears 19A, 19B and 19C are arranged between B and form a gear train for transmitting the driving force. In driving the photoconductors 3Y, 3M, 3C, and 3B, the power of the photoconductor drive motor 20 provided on the upstream side of the intermediate transfer belt 2 in the belt conveyance direction is first transmitted from the photoconductor drive gear 21 to the photoconductor gear 18B. Idler gear 119C, photoconductor gear 18C, idler gear 19B, photoconductor gear 18
This is performed by sequentially transmitting M, the idler gear 19A, and the photoconductor gear 18Y.

In this embodiment, the support roller 2B of the intermediate transfer belt 2 serves as a drive roller, and the drive roller gear 22 is fixed to the rotary shaft of the drive roller 2B. In the intermediate transfer belt 2, the power of the drive roller motor 23 is transmitted from the drive roller motor gear 24 to the drive roller gear 22 to rotate the drive roller 2B, whereby the drive roller 2B is rotated.
It is transported by the frictional force with. Photoreceptors 3Y, 3M, 3C, 3
The rotation direction of B and the conveyance direction of the intermediate transfer belt 2 are the arrow directions shown in the figure. In this embodiment, the drive roller 2B is provided downstream of the four photoconductors 3Y, 3M, 3C and 3B in the belt conveyance direction. There is.

The photoconductor gears 18Y, 18M, 18C, and 18B fixed to the photoconductors 3Y, 3M, 3C, and 3B have different numbers of teeth, so that the number of teeth decreases in the direction of belt conveyance of the intermediate transfer belt 2. It is set. That is, the relationship of 18B>18C>18M> 18Y is satisfied. Therefore, if the surface velocities of the photoconductors 3B, 3C, 3M, and 3Y are V1, V2, V3, and V4, respectively, the diameters of the photoconductors 3B, 3C, 3M, and 3Y are the same, so the surface velocity relationship is V1 <V2. <V3 <V4. That is, the speed increases in the direction of belt conveyance of the intermediate transfer belt 2.

When the transport speed of the intermediate transfer belt 2 is Vb, the relationship is Vb> V4, which is faster than the surface speed V4 of the photoconductor 3Y near the drive roller 2B on the most downstream side in the belt transport direction. FIG. 3 shows the photoconductors 3B and 3 in this embodiment.
The relationship between the surface velocities (V1, V2, V3, V4) of C, 3M and 3Y and the transport velocity Vb of the intermediate transfer belt 2 is shown. Each gear (photoreceptor gear 1) which is each drive transmission system
8Y, 18M, 18C, 18B, drive roller gear 22,
The idler gears 19A, 19B, 19C, the drive roller motor gear 24, etc.) have eccentricity about the center of rotation, runout of tooth spaces, and meshing pitch error. The surface speeds of the photoconductors 3Y, 3M, 3C, and 3B and the conveyance speed of the intermediate transfer belt 2 change due to these variations. The variation is Δ
It is represented by V.

In this embodiment, (V1 <V2 described with reference to FIG.
The relationship of <V3 <V4 <Vb) is that each photoconductor 3B, 3C, 3M,
The speed differences are set so as to hold even if the surface speed fluctuation amounts ΔV1 to ΔV4 of 3Y and the conveyance speed fluctuation amount ΔVb of the intermediate transfer belt 2 are included. In other words, each photoconductor 3
Surface speed of Y, 3M, 3C, 3B and intermediate transfer belt 2
The speed difference is set to be larger than the speed fluctuation amount that can assure the transport speed, ie, the speed fluctuation amount within the allowable error range at the manufacturing stage. As a result, the speed fluctuation amount is canceled.
Since the surface speeds of the photoconductors 3B, 3C, 3M, and 3Y are sequentially higher in the belt conveying direction of the intermediate transfer belt 2,
The intermediate transfer belt 2 does not loosen between the photoconductors 3B, 3C, 3M, 3Y, and the surface speed varies due to manufacturing errors of the photoconductors 3Y, 3M, 3C, 3B (intermediate transfer belt 2).
Load fluctuation) does not occur. Further, since the conveyance speed of the intermediate transfer belt 2 is set to be higher than the surface speed of the photoconductor 3Y, variations in the tension of the intermediate transfer belt 2 are suppressed, and slippage with respect to the drive roller 2B is also suppressed. .

Next, a second embodiment will be described with reference to FIGS. The same parts as those in the above-described embodiment are denoted by the same reference numerals, and the explanations on the configuration and the function which have already been made are omitted unless particularly necessary. Further, only a main part will be described (same in other embodiments below). In the present embodiment, FIG.
As shown in, the support roller 2A serves as a drive roller, and the drive roller gear 22 is fixed to the rotation shaft of the drive roller 2A. The power of the drive roller motor 23 is transmitted from the drive roller motor gear 24 to the drive roller gear 22 to rotate the drive roller 2A, so that the intermediate transfer belt 2 is conveyed by a frictional force with the drive roller 2A. The drive configuration of the photoconductors 3Y, 3M, 3C, 3B is the same as the configuration shown in FIG.

The rotation directions of the photoconductors 3Y, 3M, 3C and 3B and the conveying direction of the intermediate transfer belt 2 are the directions of the arrows shown in the figure.
In the present embodiment, the drive roller 2A of the intermediate transfer belt 2 is 4
The photoconductors 3Y, 3M, 3C, and 3B are provided on the upstream side in the belt conveyance direction. Similar to the first embodiment, the photoconductor gears 18Y, 18M, 18C, and 18B fixed to the photoconductors 3Y, 3M, 3C, and 3B have different numbers of teeth, and face the belt transfer direction of the intermediate transfer belt 2. It is set to decrease in order. Ie 1
The relationship of 8B>18C>18M> 18Y is satisfied.
Therefore, assuming that the surface speeds of the photoconductors 3B, 3C, 3M, and 3Y are V1, V2, V3, and V4, respectively, the photoconductors 3B, 3
Since the diameters of C, 3M, and 3Y are the same, the surface velocity relationship is V1.
<V2 <V3 <V4. That is, the speed increases in the direction of belt conveyance of the intermediate transfer belt 2.

When the conveyance speed of the intermediate transfer belt 2 is Vb, the relationship is Vb <V1, which is slower than the surface speed V1 of the photoconductor 3B near the drive roller 2A on the most upstream side in the belt conveyance direction. FIG. 5 shows each of the photoconductors 3B in this embodiment.
3C, 3M, 3Y surface velocity (V1, V2, V3, V4),
3 shows the relationship of the transport speed Vb of the intermediate transfer belt 2. Each gear (photoreceptor gear 1) which is each drive transmission system
8Y, 18M, 18C, 18B, drive roller gear 22,
The idler gears 19A, 19B, 19C, the drive roller motor gear 24, etc.) have eccentricity about the center of rotation, runout of tooth spaces, and meshing pitch error. Due to these variations, the surface speeds of the photoconductors 3Y, 3M, 3C, and 3B and the transport speed of the intermediate transfer belt 2 vary, and the variation amount is ΔV.
It is represented by.

In this embodiment, (Vb <V1 described with reference to FIG.
The relationship of <V2 <V3 <V4) is that each of the photoconductors 3B, 3C, 3M,
The surface speed fluctuations ΔV1 to V4 of 3Y and the conveyance speed fluctuation ΔVb of the intermediate transfer belt 2 are included so that the speed difference is satisfied. In other words, the photoconductors 3Y, 3
The speed difference is made larger than the speed fluctuation amount that can guarantee the surface speed of M, 3C, and 3B and the transport speed of the intermediate transfer belt 2, that is, the speed fluctuation amount within the allowable error range in the manufacturing stage. As a result, the speed fluctuation amount is canceled. The photoconductors 3 are moved toward the belt transfer direction of the intermediate transfer belt 2.
Since the surface speeds of B, 3C, 3M, and 3Y are sequentially higher, the intermediate transfer belt 2 does not loosen between the photoconductors 3B, 3C, 3M, and 3Y, and the manufacturing error of the photoconductors 3Y, 3M, 3C, and 3B, etc. Does not cause variations in surface speed (load fluctuations on the intermediate transfer belt 2). Further, since the conveyance speed of the intermediate transfer belt 2 is set to be smaller than the surface speed of the photoconductor 3B, the variation of the tension of the intermediate transfer belt 2 is suppressed, and the sliding of the intermediate transfer belt 2 with respect to the drive roller 2A is also suppressed. It

Next, a third embodiment will be described with reference to FIG. Although the endless belt is the intermediate transfer belt in both the first and second embodiments, in the present embodiment, the endless belt sequentially transfers the toner image on the photosensitive drum while conveying the sheet as the transfer material. An example of a transfer belt is shown. In this embodiment, the photoconductors 3Y, 3M, 3C,
3B is rotated in the clockwise direction, and the charging roller 4 and the like are arranged correspondingly. Codes LY, LM, LC, L
B indicates the exposure light from the optical writing unit 5. The transfer belt 30 has a structure in which the transfer belt 30 is wound around three supporting rollers 30A to 30C and is movable in the same direction at positions facing the photoconductors 3Y, 3M, 3C, and 3B. A belt cleaning unit 31 that cleans the surface of the transfer belt 30 is provided at a position opposite to a support roller 30C that is different from the support rollers 30A and 30B that support the spreading surface that contacts the photoconductors 3Y, 3M, 3C, and 3B. Has been. Inside the transfer belt 30, the transfer roller 32 is pressed against the photoconductors 3Y, 3M, 3C, and 3B via the transfer belt 30.

The photoconductors 3Y, 3M, 3C and 3B and the transfer belt 30 are rotated and conveyed in the arrow direction. The paper is sent onto the transfer belt 30 by the registration roller pair 33,
The sheet passes through the photoconductors 3Y, 3M, 3C and 3B while being electrostatically attached to the transfer belt 30. Photoconductor 3Y, 3
The drive configuration of M, 3C, and 3B and the drive configuration of the transfer belt 30 are the same as those shown in FIGS. Photoconductor 3
Also in the present embodiment in which the images on Y, 3M, 3C, and 3B are directly transferred onto the paper, the surface speed of the photoconductors 3Y, 3M, 3C, and 3B and the transfer belt are the same as in the first and second embodiments. The conveyance speed of 30 can be adjusted, and a similar image shift suppressing function can be obtained. Also in this embodiment, the writing position and the transfer position are set to 1 in the rotation direction of the photoconductor 3.
It is configured at a position shifted in phase by 80 °. With such a positional relationship, there is a speed fluctuation due to the eccentricity of the photoconductor 3, and even if the latent image pitch unevenness occurs at the writing position, the pitch unevenness that occurs when the toner image is transferred is canceled and transferred. It

[0035]

According to the first aspect of the invention, in the image forming apparatus in which the plurality of image carriers are arranged in contact with the endless belt stretched by the plurality of rollers, the plurality of image carriers are provided. Since the bodies are driven at different surface velocities, the speed of multiple image carriers is increased or decreased in sequence, so that the endless belt can be accurately conveyed without causing slack between the image carriers. Therefore, it is possible to obtain a good image with no color shift.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the drive roller for driving the endless belt among the plurality of rollers is endless with respect to the plurality of image carriers. The endless belt is provided on the downstream side in the conveying direction of the belt, and the surface speed of each image carrier is gradually decreased from the side closer to the drive roller to the upstream side. It is transported accurately,
A good image without color shift can be obtained.

According to the invention of claim 3, in the image forming apparatus of claim 2, the conveying speed of the endless belt is set to be higher than the surface speed of the most downstream image carrier. The slack of the endless belt can be eliminated with high precision, and the color shift can be suppressed with high precision.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, the drive roller for driving the endless belt among the plurality of rollers is endless with respect to the plurality of image carriers. The endless belt is provided on the upstream side in the conveying direction of the belt, and the surface speed of each image carrier is gradually increased from the side closer to the drive roller to the downstream side, so that the endless belt does not loosen between the image carriers. It is transported accurately,
A good image without color shift can be obtained.

According to the invention of claim 5, in the image forming apparatus of claim 4, the conveying speed of the endless belt is set lower than the surface speed of the most upstream image carrier. The slack of the endless belt can be eliminated with high precision, and the color shift can be suppressed with high precision.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the speed difference between the conveying speed of the endless belt and the surface speed of each of the image carriers is calculated as follows. Since the configuration is made to be larger than the normal speed fluctuation amount between the conveying speed of the endless belt and the surface speed of each image carrier, the endless belt is surely conveyed accurately without slack between the image carriers. It is possible to obtain a good image without color shift.

According to the seventh aspect of the invention, in the image forming apparatus according to any one of the first to sixth aspects, the endless belt sequentially transfers the toner images formed on the respective image carriers. Since it is configured as an intermediate transfer belt of
In the structure having the intermediate transfer belt, the slack of the intermediate transfer belt can be eliminated and the color shift can be suppressed.

According to the eighth aspect of the invention, in the image forming apparatus according to any one of the first to sixth aspects, the endless belt sequentially transfers the toner images formed on the respective image carriers. Since the transfer belt is configured to convey the transfer material, the slack of the transfer belt can be eliminated and the color misregistration can be suppressed in the configuration in which the toner image on the image carrier is directly transferred to the transfer material. .

According to a ninth aspect of the invention, in the image forming apparatus according to the seventh or eighth aspect, the position where an electrostatic latent image is formed on the image carrier and the visualized toner image are transferred. Since the position is deviated by about 180 ° in the rotation direction of the image carrier, a good image can be obtained even if the rotation of the image carrier is eccentric.

[Brief description of drawings]

FIG. 1 is a schematic front view of a color copying machine as an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a driving configuration of a photoconductor and an intermediate transfer belt.

FIG. 3 is a graph showing the relationship between the surface speed of the photoconductor and the conveyance speed of the intermediate transfer belt.

FIG. 4 is a diagram showing a driving configuration of a photoconductor and an intermediate transfer belt according to a second embodiment.

FIG. 5 is a diagram showing the surface speed of the photosensitive member according to the second embodiment,
6 is a graph showing the relationship of the conveyance speed of the intermediate transfer belt.

FIG. 6 is a diagram showing a relationship between a photoconductor and a transfer belt according to a third embodiment.

[Explanation of symbols]

2A, 2B, 2C Support rollers as rollers 2 Intermediate transfer belt as an endless belt 3Y, 3M, 3C, 3B Photoreceptor as image carrier 2B Support roller as driving roller 30 Transfer belt as an endless belt

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H030 AA01 AB02 AD16 BB02 BB42                       BB43 BB53 BB63 BB71                 2H035 CA07 CB01 CG01                 2H071 CA02 DA09 DA15 DA26 DA31                       EA18                 2H076 AB05 AB18 AB42 EA01                 2H200 FA17 FA20 GA12 GA23 GA29                       GA33 GA34 GA47 GA49 GB02                       GB22 GB25 HA02 HA12 HA28                       HB03 HB12 JA02 JB06 JB16                       JB20 JB49 JC03 JC07 JC12                       JC19 LA07 LA19 LA25 LA29                       LA30 PA11

Claims (9)

[Claims] 1. An image forming apparatus in which a plurality of image carriers are arranged in contact with an endless belt stretched around a plurality of rollers, wherein the plurality of image carriers are driven at different surface speeds. An image forming apparatus characterized by. 2. The image forming apparatus according to claim 1, wherein a drive roller for driving the endless belt among the plurality of rollers is provided on a downstream side of the plurality of image carriers in a conveying direction of the endless belt. The image forming apparatus is characterized in that the surface speed of each image carrier is gradually decreased from the side closer to the drive roller to the upstream side. 3. The image forming apparatus according to claim 2, wherein the conveying speed of the endless belt is higher than the surface speed of the most downstream image carrier. 4. The image forming apparatus according to claim 1, wherein a drive roller for driving the endless belt among the plurality of rollers is provided on an upstream side of the plurality of image carriers in a conveying direction of the endless belt. The image forming apparatus is characterized in that the surface speed of each image carrier is sequentially increased from the side closer to the drive roller to the downstream side. 5. The image forming apparatus according to claim 4, wherein the conveying speed of the endless belt is lower than the surface speed of the most upstream side image carrier. 6. The image forming apparatus according to claim 1, wherein the speed difference between the conveying speed of the endless belt and the surface speed of each of the image carriers is calculated by comparing the conveying speed of the endless belt with the conveying speed of the endless belt. An image forming apparatus characterized in that it is larger than a speed fluctuation amount between surface velocities of an image carrier. 7. The image forming apparatus according to claim 1, wherein the endless belt is an intermediate transfer belt for sequentially transferring the toner images formed on the image carriers. A characteristic image forming apparatus. 8. The image forming apparatus according to claim 1, wherein the endless belt conveys a transfer material for sequentially transferring the toner images formed on the image carriers. And an image forming apparatus. 9. The image forming apparatus according to claim 7, wherein the position where the electrostatic latent image is formed on the image carrier and the position where the visualized toner image is transferred are the rotation of the image carrier. An image forming apparatus characterized by being shifted by about 180 ° in a direction.