JP2002196561A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device constituted so that the skew quantity of each color toner image may be reduced by reducing the curved quantity of a belt, the adjustment of a writing position in accordance with a temperature change may not be required, high image quality and high productivity may be accomplished, and also, the life of the belt may be prolonged. SOLUTION: As for the image forming device for successively forming several color toner images on the circulating endless belt in an overlaid state, and then, forming a color image constituted of the fixed toner images on a recording medium, a steering roll 35 whose shaft is made in an inclined state with reference to the endless belt so as to correct tracking is arranged in a position so that Ls>=0.4×Lp may be satisfied, provided that a distance between the steering roll 35 and an image forming position closest to the steering roll 35 is expressed by Ls and a distance between two image forming positions furthest from each other is expressed by Lp.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus used for a copying machine, a printer and the like.

[0002]

2. Description of the Related Art Conventionally, as a full-color electrophotographic image forming apparatus, a multi-transfer type image forming apparatus which forms a color image by multi-transferring a color toner image on a photoreceptor onto a transfer target is generally used. An important issue is how to perform multiple transfer without color misregistration.

In the case of an image forming apparatus using a transfer drum, the diameter of the image forming apparatus is set to be the same as that of the photosensitive drum or an integral multiple of the diameter of the photosensitive drum so that the transfer drum position and the photosensitive drum position are always constant. There is a method of preventing displacement.

However, this method is inferior in high speed because the photosensitive drum is rotated a plurality of times, so that a number of tandem types using an intermediate transfer belt and a plurality of photosensitive drums have been developed.

A multi-developing type using a photoreceptor belt which is relatively unlikely to cause color misregistration is also disclosed, for example, in Japanese Patent Application Laid-Open No. Hei 8-44133.

However, in an image forming apparatus using an endless intermediate transfer belt or a photoreceptor belt stretched over a plurality of rolls, the belt tends to be shifted due to the parallelism error of the rolls, and the toner images of the respective colors are sequentially superimposed. Since the skew amounts of the toner images for the respective colors at the positions where the images are overlapped are different, color misregistration is likely to occur in the multicolor toner image in which the images are superimposed a plurality of times.

As a method for preventing the belt from being shifted,
Japanese Patent Application Laid-Open No. 7-36314 discloses a technique in which a sensor for detecting a belt position is provided, and one end of one of a plurality of rolls is made movable to displace the rolls to correct the parallelism error of the belt. Have been.

However, the disclosed technique requires a sensor for detecting the belt position and a device for displacing the roll, and these become bottlenecks in reducing the cost and size of the entire device.

Further, one of the two rolls at the most distant position where the belt is wound around the plurality of rolls is large, both ends are fixed, the other one is fixed at one end, and the other end is fixed at the other end. A technique for freedom is disclosed in JP-A-11-2997.

According to this technique, the endless belt can maintain a certain degree of parallelism between the rolls.

[0011]

However, the method of inclining the axis of the roll disclosed in Japanese Patent Application Laid-Open Nos. Hei 7-36314 and Hei 11-2997 corrects the deviation and meandering of the belt. Since the belt tension is made uniform in the axial direction, the belt is stable in a state where the belt is skewed to the axis of the roll, and a belt using a material such as polyimide which is easily deformed is curved between the rolls. .

In particular, since the intermediate transfer belt used in a tandem type image forming apparatus has a long belt length, the amount of curvature differs depending on the position of each photoconductor, and the amount of skew generated for each color of the toner image is different. Easy to occur.

FIG. 1 is a schematic view of a tandem type image forming apparatus.

The image forming apparatus shown in FIG. 1 includes an intermediate transfer belt 10 that circulates in the direction of arrow A while carrying a toner image on its surface, and a plurality of rolls that stretch the intermediate transfer belt 10. Circulation movement direction A of transfer belt 10
The four photosensitive drums 12 are arranged in series along the line, and the surface of each photosensitive drum 12
A color toner image up to the color is formed. Further, at a position facing each photosensitive drum 12 with the intermediate transfer belt interposed therebetween,
Each of the transfer devices 13 for primary-transferring the first to fourth color toner images formed on each of the photosensitive drums 12 to form an image on an intermediate transfer belt is provided, and the fourth color toner image is provided. Is formed downstream of the photosensitive drum 12 where
A secondary transfer device 14 is provided for secondary-transferring a plurality of color toner images formed such that toner images of respective colors are sequentially overlapped on the intermediate transfer belt to a recording medium.

Among the plurality of rolls, a roll provided in the vicinity of the photosensitive drum 12 on which the first color toner image is formed is a drive roll 15 for driving the intermediate transfer belt 10, and is a fourth color. Photoconductor drum 1 on which toner image is formed
A roll provided near 2 is a tracking correction roll 16 for correcting the tracking of the intermediate transfer belt 10.

FIG. 2 is a diagram showing a state in which the intermediate transfer belt is skewed and a state in which the angle of a line written on the intermediate transfer bell from the photoconductor changes.

In FIG. 2, the intermediate transfer belt 10 is skewed and curved in the circulating movement direction A. The interval between the image forming positions 17 where the respective color toner images are formed is 211
mm, and the tracking correction roll 16 is disposed at a position 50 mm away from the image forming position 17 where the toner image of the fourth color in the moving direction A of the intermediate transfer belt 10 is formed. The state is inclined by 0.3 mm with respect to the intermediate transfer belt 10.

The dotted line in the figure is the line written on the intermediate transfer belt at the image forming position where the first color toner image is formed.
The angle change after the image forming position where the second color toner image is formed is shown. It has been experimentally confirmed that the amount of curvature of the intermediate transfer belt 10 generally has a quadratic curve. Therefore, the skew amount based on the first color is 0.029 mm for the second color and is skew for the third color. 0.115mm, 4th
The tint is calculated to be 0.258 mm.

FIG. 3 is a diagram showing a deviation between a line written at the image forming position where the first color toner image is formed and a line written at the image forming position where the fourth color toner image is formed. is there.

FIG. 2 shows the skew state of the intermediate transfer belt 10 and the like.
And the description is omitted.

The dotted line shown in FIG. 3 shows the angle change of the line written at the image forming position 17 where the first color toner image is formed at the image forming position 17 where the second and subsequent color toner images are formed. The two-dot chain line represents the line 19 written at the image forming position 17 where the fourth color toner image is formed.

As is clear from FIG. 3, the first color and the fourth color
The maximum color misregistration amount of the color is 0.258 mm, which is the same as the skew amount of the line written at the image forming position 17 where the first color toner image is formed at the image forming position 17 where the fourth color toner image is formed. Becomes

Therefore, a method of detecting the amount of color misregistration and correcting it by using adjusting means such as moving a cylinder mirror when writing an image is disclosed in Japanese Patent Application Laid-Open No. H11-254775.
No. 6,009,045.

FIG. 4 shows an example in which the writing position is adjusted by the adjusting means disclosed in Japanese Patent Application Laid-Open No. H11-254775, and the target value of the color shift amount is corrected to an intermediate value between the maximum value and the minimum value to thereby correct the color shift. FIG. 7 is a diagram showing a situation in which is reduced.

FIG. 2 shows the skew state of the intermediate transfer belt 10 and the like.
And the description is omitted.

As is apparent from FIG.
By tilting 0 by 0.129 mm, the first color and the fourth
The maximum color misregistration amount of the color is 0.129 mm, which is half of the skew of the line written at the image forming position 17 where the first color toner image is formed at the image forming position 17 where the fourth color toner image is formed. Becomes

However, this still does not satisfy the generally required color shift limit of 0.1 mm.

In the disclosed method, if the amount of curvature of the belt is large, the color misregistration may not be corrected by the writing position adjustment, and the color misregistration is corrected each time the amount of curvature changes due to a temperature change. And there is a problem that productivity is reduced.

In view of the above circumstances, the present invention reduces the amount of skew of each color toner image by reducing the amount of curvature of the belt, and eliminates the need to adjust the writing position due to a temperature change, thereby achieving high image quality. It is another object of the present invention to provide an image forming apparatus which has high productivity and has a long belt life.

[0030]

An image forming apparatus according to the present invention, which achieves the above object, has an endless structure which is stretched by a plurality of rolls and circulates through a plurality of image forming positions on the surface of which an image is formed. A plurality of color toner images formed on the endless belt so as to sequentially overlap each other, and the plurality of color toner images are transferred and fixed onto a predetermined recording medium, so that a fixed toner image is formed on the recording medium. In the image forming apparatus that forms a color image, one of the plurality of rolls has a state in which the axis of the roll is inclined with respect to the endless belt, thereby tracking the endless belt. A tracking correction roll to be corrected, wherein the tracking correction roll and an image which is the shortest distance to the tracking correction roll among the plurality of image forming positions. Assuming that the distance between the image forming position and the image forming position is Ls, and the distance between the two image forming positions farthest from the plurality of image forming positions is Lp, the tracking correction roll is Ls ≧ 0.4. -It is characterized by being deployed at a position that satisfies Lp.

Here, it is preferable that the tracking correction roll is a steering roll whose angle is adjusted during the circulating movement of the endless belt.

The tracking correction roll is
It is preferable that the tension roller is fixedly adjusted in advance so that tracking of the endless belt is corrected.

In addition, the image forming apparatus further includes a plurality of image forming members provided on the plurality of image forming positions and having a surface on which a toner image is formed, and the endless belt is provided at each of the plurality of image forming positions. In a preferred embodiment, the intermediate transfer belt receives a transfer of a toner image from the belt.

Further, in a preferred embodiment, the endless belt is a photoreceptor belt which forms an electrostatic latent image on the surface by receiving exposure light at each of the plurality of image forming positions.

[0035]

Embodiments of the present invention will be described below.

FIG. 5 is a schematic configuration diagram showing a first embodiment of the image forming apparatus of the present invention.

The image forming apparatus shown in FIG. 5 includes an intermediate transfer belt 21 that circulates in the direction of arrow A while carrying a toner image on the surface, a plurality of rolls 33 that stretch the intermediate transfer belt 21, and an intermediate transfer belt. Drive roll 3 for driving 21
4 and steering roll 3 to correct tracking
5 are provided.

Here, a steering roll whose angle is adjusted during the circulating movement of the intermediate transfer belt 21 is used as the tracking correction roll, but is fixed in advance so that the tracking of the intermediate transfer belt 21 is corrected. Alternatively, a tension roll whose angle has been adjusted may be used.

Arrow A in which the intermediate transfer belt 21 circulates
Along the direction, four photoconductor drums 22 that form a toner image on the surface are arranged in series, and each photoconductor drum 22 is uniformly charged by a charger 23, and the surface of each charged photoconductor drum 22 is charged. The exposure device 24 irradiates exposure light to form an electrostatic latent image, and the electrostatic latent image on the surface of each photoconductor drum 22 is developed by a developing device 25 with a toner of each color to form a toner image. The unit 26 primarily transfers the toner image formed on the surface of each photosensitive drum 22 to the intermediate transfer belt 21.

Therefore, the image forming position on the intermediate transfer belt 21 in the present embodiment is a position where the toner image formed on the surface of each photosensitive drum 22 is primarily transferred by the primary transfer device 26.

The toner image on the intermediate transfer belt 21 is transferred to the recording medium 31 conveyed from the paper feed tray 30 by the secondary transfer device 29, and the fixing device 32 transfers the unfixed toner image transferred onto the recording medium 31. Is fixed on the recording medium 31.

FIG. 6 is a diagram showing an arrangement position of the tracking correction roll.

In FIG. 6, an intermediate transfer belt 21 circulating in the direction of arrow A while carrying a toner image on the surface thereof,
A plurality of rolls 33 on which the intermediate transfer belt 21 is stretched; and four photosensitive drums 22 arranged in series along the direction of arrow A in which the intermediate transfer belt 21 circulates and form different color toner images on the surface. Each photosensitive drum 1 is located at a position facing each photosensitive drum 22 and the intermediate transfer belt 21.
A primary transfer device 26 for superimposing and primary transferring each color toner image formed on the intermediate transfer belt 21 on the intermediate transfer belt 21 is provided. Downstream of the four photosensitive drums 22 in the direction of arrow A,
A secondary transfer unit 29 is provided for secondary-transferring a plurality of color toner images on the intermediate transfer belt 21 onto which the respective color toner images are superimposed and transferred onto a recording medium (not shown). Arrows A of four photosensitive drums 22 among the plurality of rolls 33
A drive roll 34 for driving the intermediate transfer belt 21 is provided near the photoconductor drum 22 of the first color, which is the most upstream in the direction, and is located on the side of the photoconductor drum 12 of the fourth color, which is the most downstream in the direction of arrow A. Is provided with a steering roll 35 for correcting the tracking of the intermediate transfer belt 21.

With respect to the distance Lp from the image forming position where the first color toner image is formed on the intermediate transfer belt 21 to the image forming position where the fourth color toner image is formed farthest,
Until the distance Ls from the image forming position where the toner image of the fourth color, which is the shortest distance from the position where the steering roll 35 is installed, is 0.4 times or more, the steering roll 35 is moved to the fourth color. It is provided at a position distant from the position where the toner image is formed.

FIG. 7 is a diagram showing a skew state of the intermediate transfer belt and a state of a change in the angle of a line written on the intermediate transfer bell from the photosensitive member of the first color.

In FIG. 7, the distance between the image forming positions 36 where the toner images are formed is 211 mm, and the image forming position 36 where the first color toner image is formed on the intermediate transfer belt 21 is moved from the image forming position 36 to the fourth color plane. The distance Lp to the image forming position 36 where the toner image is formed is 633 mm. Further, the steering roll 35 is arranged such that the shaft 37 of the steering roll is inclined by 0.3 mm with respect to the axes of the other rolls, and the distance from the image forming position 36 where the fourth color toner image is formed to the shaft 37 of the steering roll. Ls is 253.2 mm away from the image forming position 36 where the toner image of the first color is formed, and the distance 633 mm from the image forming position 36 where the toner image of the fourth color plane farthest is formed. The distance 253.2 mm from the position where the steering roll 35 is installed to the image forming position 36 where the fourth color toner image which is the shortest distance is formed is 0.4 times.
The dotted line indicates the image forming position 3 where the first color toner image is formed.
6 shows the angle change of the line written in 6 at the image forming position 36 where the toner images of the second and subsequent colors are formed.

Since it has been experimentally confirmed that the amount of curvature of the belt is generally a quadratic curve, the skew amount based on the first color is 0.017 mm for the second color and 0 for the third color. 0.068 mm, and the fourth color is 0.153 mm.

FIG. 8 is a diagram showing the deviation between the line written in the first color and the line written in the fourth color.

The dotted line shown in FIG. 8 shows the angle change of the line written at the image forming position 36 where the first color toner image is formed at the image forming position 36 where the second and subsequent color toner images are formed. The two-dot chain line indicates the line 38 written at the image forming position 36 where the fourth color toner image is formed.
The skew state of the intermediate transfer belt 21 is the same as that shown in FIG.

Referring to FIG. 8, reference is made to JP-A-11-25475.
The writing position is adjusted by the adjusting means disclosed in Japanese Patent Application Laid-Open No. 7-107, and the target value of the color shift amount is corrected to an intermediate value between the maximum value and the minimum value to reduce the color shift.

As is apparent from FIG. 8, by tilting the writing position by 0.077 mm at the maximum, the first color and the fourth
The maximum color misregistration amount of the color is 0.077 mm, which is half the skew amount of the fourth color based on the first color, and can satisfy the generally required color registration limit of 0.1 mm. In addition, since the amount of color misregistration is reduced and reduced, the amount of change in the skew amount is small even if there is a temperature change, so that readjustment due to the change is unnecessary.

In this embodiment, the case where the image forming position where the toner image of the fourth color is formed is the shortest distance with respect to the tracking correction roll, however, the first correction is performed with respect to the tracking correction roll. The present invention can be similarly applied to the case where the image forming position where the color toner image is formed is the shortest distance.

FIG. 9 shows the first tracking correction roll.
FIG. 7 is a diagram illustrating a case where the photoconductor is arranged near a photoconductor drum of a color;

The same components as those shown in FIG. 6 are denoted by the same reference numerals, and only the differences will be described.

A steering roll 35 is disposed on the side of the photosensitive drum 22 of the first color, and a driving roll 36 for driving the intermediate transfer belt 21 is connected to the photosensitive drum 22 of the fourth color.
It is provided on the side.

The steering roller 35 is installed at a distance Lp from the position where the first color toner image is formed on the intermediate transfer belt 21 to the position where the fourth color toner image is formed farthest. The steering roll 35 is separated from the position where the first color toner image is formed until the distance Ls from the position where the first color toner image is formed at the shortest distance to the position where the first color toner image is formed is 0.4 times or more. In this case, the relative relationship between the skew state of the intermediate transfer belt 21 and the angle change of the line written at the image forming position where the first color toner image is formed is illustrated in FIG. 7 and the relationship between the line written in the first color and the line written in the fourth color is the same as that shown in FIG.

By arranging a plurality of rolls 33 including the steering roll 35 in this way, the width of the image forming apparatus can be suppressed even when a long belt is used.

FIG. 10 is a diagram showing an example in which a tension roll as a tracking correction roll is fixedly arranged near the photosensitive drum of the first color.

The same components as those shown in FIG. 6 are denoted by the same reference numerals, and only the differences will be described.

The tension roll 43 and the intermediate transfer belt 2
1 is provided on the photosensitive drum 22 side of the first color.

The tension roll 43 prevents the tracking of the intermediate transfer belt 21, bites into the photosensitive drum 22 side to apply a large tension to the intermediate transfer belt 21, and the intermediate transfer belt 21
The difference is that the angle of winding around is increased.

In this case, the distance Lp from the image forming position where the toner image of the first color is formed on the intermediate transfer belt 21 to the image forming position where the toner image of the fourth color surface is formed farthest is formed. Then, until the distance Ls from the position where the tension roll 43 is installed to the image forming position where the shortest distance toner image of the first color is formed becomes 0.4 times or more, the tension roll 43 is moved to the first position. Since it is provided at a position apart from the position where the color toner image is formed, the same effect as that shown in FIG. 9 can be obtained. Also,
Similarly, the width of the image forming apparatus can be reduced.

Next, a second embodiment of the image forming apparatus of the present invention will be described.

FIG. 11 is a schematic structural view of an image forming apparatus using a photosensitive belt according to the present embodiment.

The image forming apparatus shown in FIG. 11 includes a photosensitive belt 40 circulating in the direction of arrow A while carrying a toner image on its surface, a plurality of rolls 41 over which the photosensitive belt 40 is stretched, and a photosensitive belt. There is a drive roll 42 for driving the photoconductor 40 and a tension roll 43 for correcting the tracking of the photoreceptor belt 40. Image forming positions 44 where toner images of respective colors are formed from four toner image forming units 45 arranged in series at equal intervals on the photoreceptor belt 40.
There is. As the photoreceptor belt 40 circulates,
At each image forming position 44, each color toner image is sequentially superimposed from each toner image forming means 45, and a multicolor toner image is formed on the photoreceptor belt.

Here, the toner image forming means 45 comprises a charger, an exposure device, and a developing device, and the configuration thereof will be described later.

Downstream of the four toner image forming means 45 in the direction of arrow A, there is provided a transfer device 46 for transferring the multicolor toner images on the photosensitive belt 40 to a recording medium.

A tension roll 43 is provided for a distance Lp from the position where the first color toner image is formed on the photosensitive belt 40 to the position where the fourth color surface toner image is formed farthest. Until the distance Ls from the position at which the first color toner image at the shortest distance is formed becomes 0.4 times or more.
It is provided at a position distant from the position where the color toner image is formed.

In this case, the skew state of the photosensitive belt,
The state of the angle change of the line written on the photoreceptor bell from the color toner image forming means, and the deviation between the line written in the first color and the line written in the fourth color will be described with reference to FIGS. This is the same as that in the first embodiment.

Therefore, the writing position is set to a maximum of 0.07
By inclining by 7 mm, the maximum color shift amount of the first color and the fourth color is 0.077 mm, which is half of the skew amount of the fourth color based on the first color, and is 0% of the generally required color registration limit. .1 mm.

Further, since the amount of color misregistration is reduced and reduced, the amount of change in the skew amount is small even if there is a temperature change, so that re-adjustment due to the change is unnecessary.

FIG. 12 is a diagram showing the structure of the toner image forming means.

The four toner image forming means 45 form toner images of different colors on the photoreceptor belt 40, but only the toner colors used in the developing device 49 are different. Only the image forming unit 45 will be described.

The toner image forming means 45 shown in FIG.
There is a charger 47 for uniformly charging the photosensitive belt 40, and the photosensitive belt 40 charged by the charger 41 is provided.
Exposure light is emitted from the exposure device 48 to form an electrostatic latent image, and the developing device 49 develops the electrostatic latent image with color toner to form a color toner image on the photoreceptor belt 40.

Therefore, the image forming position 50 in the present embodiment is a position where the charged photosensitive belt 40 is irradiated with exposure light from the exposure device 48.

[0076]

As described above, according to the image forming apparatus of the present invention, as compared with the case where the tracking correction roll is disposed near the image forming position where the toner image is formed on the belt. Therefore, the amount of skew caused by the bending of the belt can be reduced to less than half, so that the writing position adjustment for preventing color misregistration is only a little necessary, and it is not necessary to readjust the writing position due to a temperature change. Since the degree of freedom of the roll interval spanning the image forming area, which affects the image quality, is increased, it is possible to provide an image forming apparatus with good image quality, low cost, and long life.

[Brief description of the drawings]

FIG. 1 is a schematic view of a tandem type image forming apparatus.

FIG. 2 is a diagram illustrating a skew state of the intermediate transfer belt and a state of an angle change of a line written on the intermediate transfer bell from the photoconductor of the first color.

FIG. 3 is a diagram illustrating a shift between a line written in a first color and a line written in a fourth color;

FIG. 4 is a diagram showing a situation in which a writing position is adjusted and a target value of a color shift amount is corrected to an intermediate value between a maximum value and a minimum value to reduce color shift.

FIG. 5 is a schematic configuration diagram illustrating a first embodiment of the image forming apparatus of the present invention.

FIG. 6 is a diagram showing an arrangement position of a tracking correction roll.

FIG. 7 is a diagram illustrating a skew state of the intermediate transfer belt and a state of a change in the angle of a line written on the intermediate transfer bell from the photoconductor of the first color.

FIG. 8 is a diagram illustrating a shift between a line written in a first color and a line written in a fourth color;

FIG. 9 is a diagram illustrating an example in which a tracking correction roll is disposed near a photoconductor of a first color.

FIG. 10 is a diagram illustrating an example in which a tracking correction roll is disposed near a photoconductor of a first color.

FIG. 11 is a schematic configuration diagram of an image forming apparatus using a photosensitive belt according to the present embodiment.

FIG. 12 is a diagram showing an arrangement position of a tracking correction roll.

[Explanation of symbols]

 10, 21 Intermediate transfer belt 12, 22 Photoconductor drum 13 Transfer device 14, 46 Secondary transfer device 15, 34, 42 Drive roll 16 Tracking correction roll 17, 36, 44 Image forming position 18 Tracking correction roll shaft 19 , 38 Written line 20 Writing position 23, 47 Charger 24, 48 Exposure device 25, 49 Developing device 26 Primary transfer device 29 Secondary transfer device 30 Feed tray 31 Recording medium 32 Fixing device 33, 41 Roll 35 Steering roll 37 shaft of steering roll 40 photoreceptor belt 43 tension roll 45 toner image forming means

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Takahiko Tatsuzaki 2274 Hongo, Ebina-shi, Kanagawa Fuji Xerox Co., Ltd. Institution (72) Inventor Teruyo Tatsuzaki 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd. Masahiro Takahashi 2274 Hongo, Ebina-city, Kanagawa Prefecture Fuji Xerox Co., Ltd. BB53 BB 63 BB71 2H032 AA15 BA01 BA09 2H035 CA05 CB06 CF02 3F049 AA02 BB07 BB11 EA21 LA02 LA07 LB01

Claims (5)

[Claims] An endless belt stretched by a plurality of rolls and circulating through a plurality of image forming positions on the surface of which an image is formed, and a plurality of color toner images sequentially overlap the endless belt. An image forming apparatus is formed to form a color image composed of a fixed toner image on the recording medium by transferring and fixing the toner images of the plurality of colors on a predetermined recording medium. One of the rolls is a tracking correction roll that corrects the tracking of the endless belt by taking a state in which the axis of the roll is inclined with respect to the endless belt, and the tracking correction roll; The distance between the shortest distance image forming position with respect to the tracking correction roll among the plurality of image forming positions is Ls, and the distance between the plurality of image forming positions is Wherein the distance between two image forming positions which are apart from each other is Lp, the tracking correction roll is disposed at a position satisfying Ls ≧ 0.4 · Lp. Forming equipment. 2. The image forming apparatus according to claim 1, wherein the tracking correction roll is a steering roll whose angle is adjusted during the circulating movement of the endless belt. 3. The image forming apparatus according to claim 1, wherein the tracking correction roll is a tension roll fixedly adjusted in advance so that tracking of the endless belt is corrected. 4. The image forming apparatus according to claim 1, further comprising a plurality of image forming members provided at the plurality of image forming positions, the surface of which is formed with a toner image, wherein the endless belt is provided at each of the plurality of image forming positions. 2. The image forming apparatus according to claim 1, wherein the intermediate transfer belt receives a toner image from the intermediate transfer belt. 5. The belt according to claim 1, wherein the endless belt is a photoreceptor belt having a surface on which an electrostatic latent image is formed by receiving exposure light at each of the plurality of image forming positions. Image forming device.