JP4952905B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, or a facsimile machine that multiplex-transfers images.

  Patent Document 1 discloses an image forming apparatus in which a plurality of electrophotographic image holders are arranged to constitute an image forming station, and the pressing of the transfer auxiliary member or the transfer member in the direction of the image carrier is set for each station.

JP-A-6-202430

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that can easily prevent image quality from being deteriorated with respect to an image to be multiplex-transferred.

According to a first aspect of the present invention, there are provided a plurality of image carriers, a plurality of transfer rolls that respectively transfer developer images held by the plurality of image carriers to a moving transfer target member, and the plurality of transfer rolls. A plurality of tracking rolls each provided coaxially; and a contact surface with which the plurality of tracking rolls contact, wherein one of the plurality of transfer rolls is connected to the member to be transferred. The image forming apparatus positions the plurality of transfer rolls such that a press contact width formed between the plurality of transfer rolls is different from a press contact width formed between the other transfer roll and the member to be transferred .

The present invention according to claim 2 is the image forming apparatus according to claim 1 , wherein the plurality of image carriers have substantially the same shape, mechanical characteristics, and electrical characteristics.

The present invention according to claim 3 is the image forming apparatus according to claim 1 , wherein the plurality of transfer rolls have substantially the same shape, mechanical characteristics, and electrical characteristics.

According to a fourth aspect of the present invention, substantially the same constant voltage is applied to each of the plurality of image carriers and the plurality of transfer rolls , or substantially the same constant current is applied to each of the plurality of image carriers. The image forming apparatus according to any one of 3 .

According to a fifth aspect of the present invention , each of the plurality of transfer rolls transfers a developer image to a member to be transferred due to a potential difference between the plurality of image holding members, and the contact surface includes the plurality of images. to electrical resistance between the one of one of the plurality of transfer rolls of the holding member, the electrical resistance between the one of the other other one of the plurality of transfer rolls of said plurality of image carriers 5. The image forming apparatus according to claim 1 , wherein at least one of the plurality of transfer rolls is positioned differently.

According to a sixth aspect of the present invention, when substantially the same constant voltage is applied to each of the plurality of image holding bodies and the plurality of transfer rolls , the contact surface includes the image holding body and the transfer roll. electrical resistance between the rolls, the developer image to form a multicolor image to be smaller in order to be transferred to the transfer member, there the plurality of transfer rolls in the image forming apparatus according to claim 5, wherein positioning each .

According to a seventh aspect of the present invention, in the case where substantially the same constant current is applied to the plurality of image holding bodies and the plurality of transfer rolls , the contact surfaces are the image holding body and the transfer roll. The image forming apparatus according to claim 5 , wherein the plurality of transfer rolls are respectively positioned so that an electrical resistance between the plurality of transfer rolls increases in the order in which the developer images forming a multi-color image are transferred to the transfer target member.

According to an eighth aspect of the present invention, the transferred member is an intermediate transfer belt for moving and transferring the transferred developer image, or a recording medium to be conveyed . The image forming apparatus described .

According to a ninth aspect of the present invention, the contact surface is in a direction substantially orthogonal to the moving direction of the transferred member with respect to a positional relationship between one of the plurality of image holding members and one of the plurality of transfer rolls. position relationship is different as, in other one with another image forming apparatus according to any one of claims 1 to 8 for setting the positional relationship between the one of the plurality of transfer rolls of said plurality of image carriers There is .

According to a tenth aspect of the present invention, the contact surface is substantially parallel to a moving direction of the transfer member with respect to a positional relationship between one of the plurality of image holding members and one of the plurality of transfer rolls. position relationship is different as, in other one with another image forming apparatus according to any one of claims 1 to 9 for setting the positional relationship between the one of the plurality of transfer rolls of said plurality of image carriers is there.

According to the eleventh aspect of the present invention, there is provided information acquisition means for acquiring at least one of information relating to environmental changes and information relating to passage of time, and the first position based on information obtained by the information acquisition means. The image forming apparatus according to claim 1, further comprising a control unit that controls to change a positional relationship set by at least one of a relationship setting unit and the second positional relationship setting unit.

  According to the present invention, it is possible to easily prevent the image quality from being deteriorated with respect to an image to be multiplex-transferred.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an outline of an image forming apparatus 10 according to an embodiment of the present invention. The image forming apparatus 10 includes an image forming apparatus main body 12, and, for example, a one-stage sheet feeding unit 14 is disposed below the image forming apparatus main body 12.

  The paper feed unit 14 includes a paper feed cassette 16 that stores recording media such as paper. A pickup roll 18 for picking up paper is disposed in the upper part near the rear end of the paper feed cassette 16, and a feed roll 20 and a retard roll 22 are disposed in front of the pickup roll 18. The feed roll 20 rotates so as to feed the sheet toward the conveyance path 24. The retard roll 22 is brought into pressure contact with the feed roll 20, and can be driven by the rotation of the feed roll 20. The retard roll 22 rotates with the feed roll 20 so as to feed sheets one by one.

  The conveyance path 24 is a sheet path from the feed roll 20 to the discharge port 26, and the conveyance path 24 is in the vicinity of the back side (the left side surface in FIG. 1) of the image forming apparatus main body 12, and will be described later from the sheet feeding unit 14. The fixing device 68 is formed in a substantially vertical direction. A secondary transfer roll 64 and a secondary transfer backup roll 62, which will be described later, are arranged on the upstream side of the fixing device 68 in the conveyance path 24, and the registration roll 28 is located upstream of the secondary transfer roll 64 and the secondary transfer backup roll 62. Is arranged. Further, in the transport path 24, transport rolls 30 a to 30 c that transport the paper from below to above are disposed, and a discharge roll 32 is disposed in the vicinity of the discharge port 26.

  Accordingly, the sheet fed from the sheet feed cassette 16 of the sheet feed unit 14 by the feed roll 20 is turned by the retard roll 22 and only the uppermost sheet is guided to the transport path 24 and is temporarily stopped by the registration roll 28. Then, a toner image is transferred between a secondary transfer roll 64 and a secondary transfer backup roll 62, which will be described later, and the transferred toner image is fixed by the fixing device 68, and the discharge port 32 discharges the discharge port 26. Are discharged to a discharge portion 34 provided at the upper part of the image forming apparatus main body 12.

  In the case of duplex printing, it is returned to the reverse path. That is, the front side of the discharge roll 32 of the transport path 24 is divided into two forks, and a switching device 36 is provided at the divided portion, and a reverse path 38 is formed from the divided portion to the registration roller 28. The reversing path 38 is provided with transport rolls 40a to 40c. In the case of double-sided printing, the switching device 36 is switched to the side that opens the reversing path 38, and the discharge roll 32 is near the rear end of the sheet. Then, the discharge roll 32 is reversed and the sheet is guided to the reverse path 38 and is discharged to the discharge portion 34 through the registration roller 28, between the secondary transfer roll 64 and the secondary transfer backup roll 62, and through the fixing device 68. Is.

  In the image forming apparatus main body 12, for example, four image forming modules 42a to 42d are arranged substantially horizontally. The image forming modules 42a to 42d receive toners of four colors, yellow, magenta, cyan, and black, contained in a toner box (not shown) provided on the upper portion of the image forming apparatus main body 14. Each is to accept. The image forming modules 42a to 42d accommodate image holding bodies 44a to 44d, chargers 46a to 46d, optical writing devices (ROS) 48a to 48d, developing devices 50a to 50d, and primary transfer devices 52a to 52d, respectively. Has been.

  The image carriers 44a to 44d are, for example, roll-shaped photoconductors, and have substantially the same shape, mechanical characteristics, and electrical characteristics, and are arranged substantially horizontally. The chargers 46a to 46d uniformly charge the image carriers 44a to 44d. The optical writing devices 48a to 48d are arranged below the image forming modules 42a to 42d, respectively, and emit scanning light toward the charged image carriers 44a to 44d, whereby latent images are formed on the image carriers 44a to 44d, respectively. Form. The developing devices 50a to 50d are toners in which latent images formed on the image carriers 44a to 44d are visualized by toners of four colors of yellow, yellow, magenta, cyan, and black, respectively. Make a statue. The primary transfer devices 52a to 52d are, for example, roll-shaped transfer devices having elasticity, and have substantially the same shape, mechanical characteristics, and electrical characteristics.

  An intermediate transfer belt 54 runs between the image carriers 44a to 44d and the primary transfer devices 52a to 52d. The intermediate transfer belt 54 is made of an endless belt-like resin film using, for example, polyimide or polyamide, and includes a drive roll 56, primary transfer devices 52a to 52d, a support roll 58, tension rolls 60a and 60b, and a secondary transfer backup roll. 62 is rotatably stretched (supported) with a predetermined tension, and is rotated by the driving force of the driving roll 56. Accordingly, the primary transfer devices 52 a to 52 d are pressed against the image carriers 44 a to 44 d via the intermediate transfer belt 54, so that the toner images on the image carriers 44 a to 44 d are transferred onto the intermediate transfer belt 54. Here, the transfer voltages of the primary transfer devices 52a to 52c are optimized so that the transfer voltage increases in the order of transfer to the intermediate transfer belt 54 (described later with reference to FIG. 2 and the like).

  The secondary transfer backup roll 62 is in pressure contact with the secondary transfer roll 64 via (interposing) the intermediate transfer belt 54, and transfers the toner image on the intermediate transfer belt 54 to the paper supplied from the paper supply unit 14. I have to do it. That is, the secondary transfer position is between the secondary transfer roll 64 and the secondary transfer backup roll 62, and the secondary transfer roll 64 is primary to the intermediate transfer belt 54 with the assistance of the secondary transfer backup roll 62. The transferred toner image is secondarily transferred onto the paper at the secondary transfer position. In addition, a predetermined potential difference is generated between the secondary transfer roll 64 and the secondary transfer backup roll 62. For example, when the secondary transfer roll 64 is set to a high voltage, the secondary transfer backup is performed. The roll 62 is connected to a ground (GND) or the like.

  Further, a cleaning device 66 is pressed against the drive roll 56 via an intermediate transfer belt 54. The cleaning device 66 secondarily transfers the toner image primarily transferred to the intermediate transfer belt 54 to a sheet, and then cleans the toner remaining on the intermediate transfer belt 54.

  A fixing device 68 is disposed above the secondary transfer position. The fixing device 68 includes a heating roll 70 and a pressure roll 72, and fixes the toner image secondarily transferred to the sheet by the secondary transfer roll 64 and the secondary transfer backup roll 62 to the sheet by heat and pressure. Then, it is conveyed toward the discharge roll 32.

  Further, a power supply unit 74, a control unit 76, and a temperature / humidity sensor 78 are accommodated in the image forming apparatus main body 12. The power supply unit 74 applies a predetermined voltage to each unit constituting the image forming apparatus 10 and has a constant current circuit (not shown). The control unit 76 includes a CPU (not shown) and the like, and controls each unit constituting the image forming apparatus 10. For example, the control unit 76 performs time management by the CPU, and controls the power source unit 74 so that substantially the same constant current flows between the primary transfer devices 52a to 52d and the image holding members 44a to 44d. The temperature / humidity sensor 78 detects the temperature and humidity (change in environment) in the image forming apparatus main body 12 and outputs the detected temperature and humidity to the control unit 76.

Next, the positional relationship between the image carriers 44a to 44d and the primary transfer devices 52a to 52d will be described in detail.
As described above, the image carriers 44a to 44d and the primary transfer devices 52a to 52d have substantially the same shape, mechanical characteristics, and electrical characteristics. Therefore, taking the positional relationship between the image carrier 44b and the primary transfer device 52b and the positional relationship between the image carrier 44c and the primary transfer device 52c as examples, the positional relationship between the image carriers 44a to 44d and the primary transfer devices 52a to 52d. Will be explained.

  FIG. 2 shows the positional relationship of the primary transfer devices 52b and 52c with respect to the image carriers 44b and 44c, respectively. At both ends of the primary transfer devices 52b and 52c, tracking rolls 80b and 80c having smaller outer diameters than the primary transfer devices 52b and 52c are provided coaxially with the primary transfer devices 52b and 52c, respectively. The tracking roll 80b determines the position of the primary transfer device 52b with respect to the image holding body 44b by coming into contact with a contact surface 82 described later from above. The tracking roll 80c determines the position of the primary transfer device 52c with respect to the image carrier 44c by coming into contact with the contact surface 82 from above on the downstream side of the tracking roll 80b in the rotation direction of the intermediate transfer belt 54.

The contact surfaces 82 are respectively formed on the inner sides of the both side surfaces of the image forming apparatus main body 12, and the rotation direction of the intermediate transfer belt 54 with respect to the primary transfer devices 52a to 52c that transfer the toner images forming the multi-color image. A step is provided between each of them so that the downstream side becomes higher in order. Further, as described above, the image holding bodies 44a to 44d are arranged substantially horizontally. For example, since the primary transfer device 52c is positioned higher than the primary transfer device 52b, the primary transfer device 52b is larger than the pressure contact width b in which the primary transfer device 52b is pressed against the image carrier 44b via the intermediate transfer belt 54. The pressure contact width c at which 52c is pressed against the image carrier 44c via the intermediate transfer belt 54 becomes narrower. That is, the primary transfer devices 52 a to 52 c have different amounts of biting into the image holding members 44 a to 44 c due to a plurality of steps provided on the contact surface 82, and press in order toward the downstream side in the rotation direction of the intermediate transfer belt 54. The width is smaller.
The primary transfer device 52d transfers a black toner image that does not form a multi-color image onto a sheet, so there is no need to improve transferability due to toner superposition. For example, the amount of biting into the image carrier 44d is primary transfer. It is the same as the device 52a.

As described above, substantially the same constant current flows between the primary transfer devices 52b and 52c and the image carriers 44b and 44c. On the other hand, since the pressure contact width c is narrower than the pressure contact width b, the intermediate transfer belt 54 and the image holding member 44b are held by the intermediate transfer belt 54 rather than the electrical resistance generated between the primary transfer device 52b and the image holding member 44b by the intermediate transfer belt 54. The electric resistance generated between the body 44c and the body 44c is large. Therefore, even if substantially the same constant current flows between the primary transfer device 52b and the image carrier 44b and between the primary transfer device 52c and the image carrier 44c, the transfer roll 52c and the image carrier 44c The transfer voltage generated between the transfer roller 52b and the image carrier 44b is higher than the transfer voltage generated between the transfer roller 52b and the image holding member 44b.
In other words, even if substantially the same constant current flows between the primary transfer devices 52a to 52c and the image holding members 44a to 44c, the intermediate transfer belt 54 between the primary transfer devices 52a to 52c and the image holding members 44a to 44c. Are set by the tracking rolls 80a to 80c and the contact surface 82, respectively, so that the toner images forming the multi-color image are transferred to the intermediate transfer belt 54 in the order of transfer to the primary transfer device. The electric resistance between each of 52a to 52c and the image holding members 44a to 44c is increased, and the transfer voltage is increased in the order of transfer of the toner images forming the multi-color image.

The positional relationship between the primary transfer devices 52a to 52c and the image holders 44a to 44c is set in advance so that the transfer voltage is optimized in the order of transfer. Further, the height (or inclination) of the step of the contact surface 82 is adjusted by the control of the control unit 76 according to the detection result of the temperature / humidity sensor 78 or the operation time of the image forming apparatus 10. Also good.
Further, the contact surface 82 is not limited to a step provided between the primary transfer devices 52a to 52c, and a necessary and sufficient transfer voltage is generated in the order in which the toner images forming the multi-color image are transferred. For example, a step is provided only between the primary transfer device 52b and the primary transfer device 52c, and the positional relationship between the primary transfer devices 52a to 52c and the image carriers 44a to 44c is upstream of the intermediate transfer belt 54. It may be divided into two, a side and a downstream side.

FIG. 3 shows a first modification of the positional relationship of the primary transfer devices 52b and 52c with respect to the image carriers 44b and 44c, respectively.
In the first modification of the positional relationship of the primary transfer devices 52b and 52c with respect to the image carriers 44b and 44c, the contact surfaces 82 are respectively formed on the inner sides of the both side surfaces of the image forming apparatus main body 12, and are used for intermediate transfer. The downstream side in the rotation direction of the belt 54 is inclined so as to increase in the order in which the toner images forming the multi-color image are transferred. Accordingly, since the primary transfer device 52c is positioned at a higher position than the primary transfer device 52b, the primary transfer device 52b is larger than the pressure contact width b in which the primary transfer device 52b is pressed against the image carrier 44b via the intermediate transfer belt 54. The pressure contact width c at which 52c is pressed against the image carrier 44c via the intermediate transfer belt 54 becomes narrower.
That is, even if substantially the same constant current is passed between the primary transfer devices 52a to 52c and the image holding members 44a to 44c, the positional relationship between the primary transfer devices 52a to 52c and the image holding members 44a to 44c is The primary transfer devices 52a to 52c and the image holding members 44a to 44c are set in the order in which the toner images forming the multi-color image are transferred to the intermediate transfer belt 54 by being set by the tracking rolls 80a to 80c and the contact surface 82, respectively. The electric resistance between them increases, and the transfer voltage increases in the order of transfer of the toner images forming the multicolor image.

FIG. 4 shows a second modification of the positional relationship of the primary transfer devices 52b and 52c with respect to the image carriers 44b and 44c, respectively.
In the second modification of the positional relationship of the primary transfer devices 52b and 52c with respect to the image carriers 44b and 44c, the primary transfer devices 52b and 52c are respectively positioned with respect to the image forming apparatus main body 12 by an elastic member 84 such as a spring. It is set and pressed in a direction substantially orthogonal to the rotation direction of the intermediate transfer belt 54. Further, the primary transfer devices 52 b and 52 c are disposed in substantially the same direction in a direction substantially orthogonal to the rotation direction of the intermediate transfer belt 54, and are in pressure contact with the intermediate transfer belt 54 in substantially the same manner. The primary transfer device 52b is disposed so as to be displaced in the rotational direction of the intermediate transfer belt 54 from a position facing the image holding body 44b, and a deviation width from a position facing the image holding body 44b is set as an offset b. . The primary transfer device 52c is disposed so as to be displaced in the rotation direction of the intermediate transfer belt 54 from a position facing the image holding body 44c, and a displacement width from the position facing the image holding body 44c is longer than the offset b. Offset c.

As described above, substantially the same constant current flows between the primary transfer devices 52b and 52c and the image carriers 44b and 44c. On the other hand, the offset c, which is the flow path length of the constant current intermediate transfer belt 54, is longer than the offset b. The electrical resistance generated between the primary transfer device 52c and the image carrier 44c by the transfer belt 54 is large. Therefore, even if substantially the same constant current flows between the primary transfer device 52b and the image carrier 44b and between the primary transfer device 52c and the image carrier 44c, the transfer roll 52c and the image carrier 44c The transfer voltage generated between the transfer roller 52b and the image carrier 44b is higher than the transfer voltage generated between the transfer roller 52b and the image holding member 44b. The primary transfer devices 52a and 52d are also arranged so as to be displaced from the positions facing the image carriers 44a and 44d in the rotation direction of the intermediate transfer belt 54, respectively. In the primary transfer devices 52a to 52c, the deviation widths (offsets a to c) from the positions facing the image holding members 44a to 44c are increased in the order in which the toner images forming the multi-color image are transferred to the intermediate transfer belt 54. Yes. The offsets a to c are the flow path lengths of the intermediate transfer belt 54 having a constant current that flows between the primary transfer devices 52a to 52c and the image carriers 44a to 44c, respectively.
Since the primary transfer device 52d transfers a black toner image that does not form a multi-color image onto a sheet as described above, there is no need to improve transferability due to toner superimposition, for example, an offset with respect to the image carrier 44d. d is the same as that of the primary transfer device 52a.

In other words, even if substantially the same constant current flows between the primary transfer devices 52a to 52c and the image holding members 44a to 44c, the intermediate transfer belt 54 between the primary transfer devices 52a to 52c and the image holding members 44a to 44c. Are set with respect to the image forming apparatus main body 12, respectively, so that the toner images forming the multi-color image are transferred to the intermediate transfer belt 54 in the order of transfer to the primary transfer apparatuses 52a to 52c. The electric resistance between the image carriers 44a to 44c is increased, and the transfer voltage is increased in the order of transfer of the toner images forming the multi-color image.
Further, since the positional relationship in the direction substantially parallel to the intermediate transfer belt 54 of the primary transfer devices 52a to 52d is set with respect to the image carriers 44a to 44d, the primary transfer devices 52a to 52d are rigid bodies such as metals. Also good.

FIG. 5 shows a third modification of the positional relationship of the primary transfer devices 52b and 52c with respect to the image carriers 44b and 44c, respectively.
In the third modification of the positional relationship of the primary transfer devices 52b and 52c with respect to the image carriers 44b and 44c, the primary transfer devices 52a to 52d are, for example, blade-like (or film-like) transfer devices having elasticity, The shape, mechanical characteristics, and electrical characteristics are substantially the same.
Further, the primary transfer device 52b is disposed so as to be displaced in the rotation direction of the intermediate transfer belt 54 from a position facing the image holding body 44b, and a deviation width from a position facing the image holding body 44b is set as an offset b. ing. The primary transfer device 52c is disposed so as to be displaced in the rotation direction of the intermediate transfer belt 54 from a position facing the image holding body 44c, and a displacement width from the position facing the image holding body 44c is longer than the offset b. Offset c.

  In other words, even if substantially the same constant current flows between the primary transfer devices 52a to 52c and the image holding members 44a to 44c, the intermediate transfer belt 54 between the primary transfer devices 52a to 52c and the image holding members 44a to 44c. Are set with respect to the image forming apparatus main body 12, respectively, so that the toner images forming the multi-color image are transferred to the intermediate transfer belt 54 in the order of transfer to the primary transfer apparatuses 52a to 52c. The electric resistance between the image carriers 44a to 44c is increased, and the transfer voltage is increased in the order of transfer of the toner images forming the multi-color image.

  In the above embodiment, in the image forming apparatus 10 according to the present invention, the control unit 76 sets the power supply unit 74 so that a constant current flows between the primary transfer devices 52a to 52d and the image holding members 44a to 44d. Although the case of controlling has been described as an example, the present invention is not limited to this. For example, when the control unit 76 controls the power supply unit 74 so that substantially the same constant voltage is applied between the primary transfer devices 52a to 52d and the image holding members 44a to 44d, the rotation of the intermediate transfer belt 54 is performed. By inclining the contact surface 82 so that the height on the downstream side in the direction becomes lower in the order of forming the multi-color image, the electrical resistance between the primary transfer devices 52a to 52c and the image carriers 44a to 44c is multiplexed. You may make it reduce in order of the transfer of the toner image which forms a color image.

1 is a side view illustrating an outline of an image forming apparatus according to an embodiment of the present invention. FIG. 4 is a side view illustrating the positional relationship of the primary transfer device with respect to each image carrier. FIG. 10 is a side view illustrating a first modification of the positional relationship of the primary transfer device with respect to each image carrier. FIG. 10 is a side view illustrating a second modification of the positional relationship of the primary transfer device with respect to each image carrier. FIG. 10 is a side view illustrating a third modification of the positional relationship of the primary transfer device with respect to each image carrier.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 44a-44d Image holding body 52a-52d Primary transfer apparatus 54 Intermediate transfer belt 74 Power supply part 76 Control part 78 Temperature / humidity sensor 80a-80d Tracking roll 82 Contact surface

Claims (11)

A plurality of image carriers;
A plurality of transfer rolls that respectively transfer the developer images held by the plurality of image holding members to a moving transfer target member;
A plurality of tracking rolls each provided coaxially with the plurality of transfer rolls;
A contact surface with which the plurality of tracking rolls contact;
Have
The contact surface has a pressure contact width formed between one of the plurality of transfer rolls and the member to be transferred, and a pressure contact width formed between the other one of the plurality of transfer rolls and the member to be transferred. An image forming apparatus that positions the plurality of transfer rolls differently .   The image forming apparatus according to claim 1, wherein the plurality of image carriers have substantially the same shape, mechanical characteristics, and electrical characteristics. The image forming apparatus according to claim 1, wherein the plurality of transfer rolls have substantially the same shape, mechanical characteristics, and electrical characteristics. 4. The image forming apparatus according to claim 1, wherein substantially the same constant voltage is applied to each of the plurality of image carriers and the plurality of transfer rolls , or substantially the same constant current is applied to each of the plurality of image carriers. The plurality of transfer rolls transfer a developer image to a member to be transferred due to a potential difference between the plurality of image carriers and the contact surface includes one of the plurality of image carriers and the plurality of transfer members. to electrical resistance between the one of the rolls, such that the electrical resistance between the one of the other other one of the plurality of transfer rolls of said plurality of image carriers are different, the plurality of transfer rolls The image forming apparatus according to claim 1, wherein at least one of the first and second positions is positioned . When substantially the same constant voltage is applied to each of the plurality of image carriers and the plurality of transfer rolls , the contact surface has an electrical resistance between the image carrier and the transfer rolls , The image forming apparatus according to claim 5, wherein the plurality of transfer rolls are respectively positioned so that a developer image forming a multi-color image becomes smaller in order of transfer to a transfer target member. When substantially the same constant current is applied to each of the plurality of image carriers and the plurality of transfer rolls , the contact surface has multiple electrical resistances between the image carrier and the transfer rolls. The image forming apparatus according to claim 5, wherein each of the plurality of transfer rolls is positioned so as to increase in order of transferring a developer image forming a color image to a member to be transferred.   The image forming apparatus according to claim 1, wherein the member to be transferred is an intermediate transfer belt for moving and transferring the transferred developer image, or a recording medium to be conveyed. The contact surface is different from the positional relationship between one of the plurality of image carriers and one of the plurality of transfer rolls so that the positional relationship in a direction substantially perpendicular to the moving direction of the transferred member is different. a plurality of other one and said plurality of transfer rolls other one to the image forming apparatus according to any one of claims 1 to 8 to set the positional relationship of the image carrier. The contact surface is different from the positional relationship between one of the plurality of image carriers and one of the plurality of transfer rolls so that the positional relationship in a direction substantially parallel to the moving direction of the transferred member is different. a plurality of other one and said plurality of transfer rolls other one to the image forming apparatus according to any one of claims 1 to 9 for setting the positional relationship of the image carrier. Information acquisition means for acquiring at least one of information on environmental changes and information on the passage of time;
Control means for controlling to change the positional relationship set by at least one of the first positional relationship setting unit and the second positional relationship setting unit based on the information acquired by the information acquisition unit ;
The image forming apparatus according to claim 1, further comprising:

Images