JP2001166554A - Tandem type image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that it is difficult to arrange the gear group of a driving system and the shafts of respective gears between supporting parts in the case of driving a photoreceptor drum and a developing device by a single driving motor respectively in the conventional tandem type image forming device where plural image forming units including the photoreceptor drum and the developing device are disposed in a line along a paper carrying path. SOLUTION: By coupling the developing device being one part of the image forming unit with the driving motor through a driving belt stretched on the outside of the supporting members and turnably attaching an idle gear included in the gear group to the output shaft of the driving belt, the number of required gears and shafts thereof arranged between the supporting members is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tandem type image forming apparatus, and more particularly, to a tandem type image forming apparatus in which a plurality of image forming units including a photosensitive drum and a developing device are arranged in a line along a sheet conveying path and supported. The present invention relates to a tandem-type image forming apparatus in which each photosensitive drum is driven by a single photosensitive drum driving source connected to each photosensitive drum via a drive system attached between members.

[0002]

2. Description of the Related Art In a tandem type color image forming apparatus, an image forming unit including a photosensitive drum and a developing device for each of a plurality of different colors is arranged in a line along a sheet conveying path. When paper passes through the paper transport path,
Images corresponding to black, magenta, yellow, and cyan are sequentially transferred to a sheet, and when passing through the last image forming unit, a color image in which four colors are superimposed is formed on the sheet. In the tandem-type color image forming apparatus, since the image is formed in this way, a high-speed color image can be output. There is a possibility that the images of the respective colors are shifted on the paper, and an appropriate output cannot be obtained. For this reason, there are many devices that attempt to obtain high drive accuracy by disposing a separate drive motor for each photosensitive drum. However, providing a separate drive motor increases costs and is not preferable in terms of miniaturization of the device. In order to reduce the cost, it is preferable to drive each photosensitive drum by a single drive motor, and it is necessary to ensure high drive accuracy. Japanese Patent Application Laid-Open No. 7-1995 discloses a technique for ensuring high drive accuracy while driving each photosensitive drum by a single drive motor.
For example, it is disclosed in JP-A-209947. According to the technology described in the above publication, the rotation shaft of a single drive motor and the rotation shaft of each photosensitive drum are connected using a gear. The single drive motor is arranged at the center of four image forming units arranged in a line. The gear attached to the rotation shaft of the single drive motor engages with the photoreceptor gears attached to the rotation shafts of the two photoreceptor drums on both sides to drive the single drive motor. The force is transmitted to both photosensitive drums. The photoreceptor gears of the remaining two photoreceptor drums are connected to the drive motor via photoreceptor photoreceptor gears on both sides of the drive motor and idle gears. If the single drive motor is arranged at the center of the four image forming units in this manner, the number of gears required to connect the rotation shaft of the single drive motor to the rotation shaft of each photosensitive drum is provided. Can be reduced, and various advantages such as suppression of a rotation error can be obtained.

[0003]

By the way, in order to form an image of each color on paper by each image forming unit,
In addition to driving the photosensitive drum, it is necessary to drive the developing device. Although this developing device is also provided for each color, it is preferable that the developing device be driven by a single drive motor similarly to the photosensitive drum in order to reduce costs and downsize the device. In this case, two drive motors are required for the photosensitive drum and the developing device, and a drive motor for driving each photosensitive drum is disposed at the center as in the technique described in the above-mentioned publication. It becomes difficult. Although it is not impossible for a single drive motor to drive all the photosensitive drums and all the developing devices, the photosensitive drum and the developing device have different rotation speeds and drive torques, and the objects to be further driven are different. Since the number of times is doubled, the drive system becomes too complicated, and the cost is rather increased. For this reason, for example, as shown in FIG.
a, 2b, 2c, 2d) and the drive motor 400 for driving each of the developing devices 4 (4a, 4b, 4c, 4d) are composed of the photosensitive drums 2 or the developing drums arranged in a line. It must be arranged at a position deviated from the center of the device 4 along the sheet transport path. If the positions of the single drive motors 200 and 400 for driving the respective photosensitive drums 2 or the respective developing devices 4 are biased with respect to the respective image forming units 1 (1a, 1b, 1c and 1d),
Photosensitive drums 2a to 2d or developing devices 4a to 4d
In this case, a photosensitive drum or a developing device far from the drive motors 200 and 400 is formed. In this case, the required number of gears increases, and the space occupied by the drive system naturally increases. The shaft of each gear in the drive system is supported by a pair of side plates. However, if the distance between the side plates is increased to accommodate a large number of gears between the side plates,
Since the rotation of the gear is likely to be uneven and the image is adversely affected, the space occupied by the drive system cannot be expanded without limitation. Therefore, for example, if the drive system of the photosensitive drum is disposed first between the side plates, it is not possible to provide much space in the space between the side plates.
Further, when the drive system for the developing device is arranged between the side plates, it is difficult to arrange the shafts of the respective gears between the side plates. As a result, all the photosensitive drums and the drive system of each developing device could not be arranged. In order to solve the problems in the conventional technology, the present invention has improved a tandem type image forming apparatus, and some of a plurality of developing devices or photosensitive drums are connected via a gear group. And an output shaft connected to the developing device drive source or the photosensitive drum drive source and a drive input portion of the developing device or the photosensitive drum. And an endless drive belt wound around the outer side between the support members of the gear group, and an idle gear included in the gear group is fixed to a shaft disposed between the output shaft and the support member. By rotatably providing one or both of the fixed shafts of the mold clutch, the number of shafts and gears that need to be disposed between the support members can be reduced, and the arrangement of the shafts and gears between the support members can be efficiently performed. Done While the photosensitive drum and the developing devices driven by each single driving source, it is an object to provide a tandem type image forming apparatus which can maintain the driving accuracy required.

[0004]

According to a first aspect of the present invention, a plurality of image forming units including a photosensitive drum and a developing device are arranged in a line along a sheet transport path. In a tandem type image forming apparatus in which each photosensitive drum is driven by a single photosensitive drum drive source connected to each photosensitive drum via a drive system mounted between support members, each developing device is A drive source for a single developing device for driving, and a part of the developing device or the photosensitive drum is connected to the drive system for the developing device or the photosensitive drum. An endless drive belt wound around the support member between the output shaft and the developing device or the drive input portion of the photosensitive drum is used for the remaining developing device and the photosensitive drum. Said Each developing device or each photosensitive drum is connected to the developing device drive source or the photosensitive drum drive source by using a gear group in a dynamic system, and the idle gear included in the gear group is output to the output unit. A tandem-type image forming apparatus is provided in which one or both of a fixed shaft of a fixed-shaft clutch disposed between a shaft and the support member is rotatably provided. Claim 1
In the invention according to the invention, a plurality of image forming units including the photosensitive drum and the developing device are arranged in a line along the paper transport path, and are connected to each photosensitive drum via a drive system attached between the support members. In a tandem image forming apparatus in which each photosensitive drum is driven by a single photosensitive drum drive source, a gear group is used in the drive system for some of the developing devices or each photosensitive drum. An endless coil wound outside the support member between an output shaft connected to the drive source for the developing device or the drive source for the photosensitive drum and a drive input portion of the developing device or the photosensitive drum. Is used. Further, an idle gear included in the gear group is rotatably provided on one or both of a fixed shaft of a fixed shaft clutch disposed between the output shaft and the support member. For example, when the driving source for the developing device and the developing device farthest from the driving source for the developing device are connected via gears, many gears are required, and it is difficult to ensure the driving accuracy. By connecting via a belt, the number of shafts and gears that need to be arranged between the support members can be reduced, and the required driving accuracy can be relatively easily secured. The idle gear included in the gear group is provided with a separate fixed shaft for attachment between the support members. However, by attaching the fixed shaft to the output shaft or the fixed shaft of the fixed shaft clutch, The number of shafts of each gear can be reduced to prevent each gear from interfering. This makes it possible to efficiently arrange the gear group between the support members while suppressing the number of shafts and gears that need to be arranged between the support members. The required driving accuracy can be maintained while each is driven by a single driving source.

[0005]

Embodiments of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention.
The following embodiments are specific examples of the present invention and do not limit the technical scope of the present invention. FIG. 1 is a diagram showing an entire configuration of a driving system which is a main part of a tandem-type full-color printer according to an embodiment of the present invention.
2 is a diagram in which a drum drive system is extracted from the entire configuration shown in FIG. 1, FIG. 3 is a diagram in which a development drive system is extracted from the entire configuration shown in FIG. 1, and FIG. 4 is a diagram shown in FIG. FIG. 5 illustrates only the characteristic configuration of the entire configuration, FIG. 5 illustrates the characteristic configuration illustrated in FIG. 4 more simply, and FIG. 6 schematically illustrates the overall configuration of the tandem-type full-color printer. Figure,
FIG. 7 is an enlarged view showing a configuration around an image forming unit of the tandem type full-color printer.

[0006] A tandem type full-color printer according to this embodiment embodies an image forming apparatus according to the present invention. First, the overall configuration of the tandem-type full-color printer will be schematically described with reference to FIGS. In the main body of the tandem-type full-color printer, four image forming units 1 (1a to 1d) are arranged in a line along a sheet transport path. Each image forming unit 1 (1
a to 1d) are in charge of forming images of four different colors (black, magenta, yellow, and cyan), and all have the same configuration. For example, the image forming unit 1
(1a-1d) are the photosensitive drum 2 (2a-2d), the transfer roller 3 (3a-3d), and the developing device 4 (4a-4)
d), exposure unit 5 (5a-5d), charger 6 (6a-6)
d), a cleaning device 7 (7a to 7d) and the like (for the image forming units 1b to 1d, reference numerals of these elements are partially omitted). The transfer rollers 3a to 3d of the image forming units 1a to 1d,
An endless transfer belt 2 is attached to a driving roller 21, a driven roller 22, and an auxiliary roller
4, the transfer belt 24 is rotated in the direction of arrow Y1 by the drive of the drive roller 21. For each of the image forming units 1a to 1d, the peripheral surface of the transfer belt 24 on the side of each of the image forming units 1a to 1d serves as a sheet conveyance path. A registration roller 25 is provided on the upstream side of the transfer belt 24, and a fixing roller 26 is provided on the downstream side.
7a and 27b, and a paper discharge tray 28 for paper is provided at the upper part of the main body.

The image forming operation of the tandem-type full-color printer having the above-described schematic configuration will be briefly described. First, the paper conveyed from the paper cassette 27a or 27b through the paper feed path 29 as indicated by arrow Y2 is registered. The toner is sent out to the image forming unit 1a by the roller 25 at the image forming timing. The sheet sent from the registration roller 25 is inserted into an opposing portion (hereinafter, a transfer portion) of the image forming unit 1a between the photosensitive drum 2a and the transfer roller 3a with its leading end along the transfer belt 24. Is done. While being conveyed by the transfer belt 24, the toner image (for example, a black image) formed on the surface of the photosensitive drum 2a is first transferred by the developing device 4a to the sheet inserted into the transfer portion of the image forming unit 1a.
The sheet is sequentially conveyed by the transfer belt 24 through the transfer sections of the image forming units 1a to 1d,
The four color toner images are sequentially transferred onto the paper, and a full-color image is formed on the paper. The sheet passing through each of the image forming units 1a to 1d is
After the transfer image is fixed at the position shown in FIG.
The sheet is conveyed as shown in FIG.

Next, the main part of the tandem type full color printer according to the present embodiment will be described in detail. First, reference numerals given to FIGS. 1 to 5 will be described. FIG.
In FIG. 2 and FIG. 2, reference numeral 200 denotes a drive motor for driving the photosensitive drum (an example of a drive source for the photosensitive drum);
Is the rotating shaft of the drive motor 200, 202 (202a to 202a).
02d) is a drive input gear attached to the rotating shaft of each of the photosensitive drums 2a to 2d, and 203 is a gear group for connecting the rotating shaft 201 and the drive input gear 202. 1 and 3, reference numeral 400 denotes a driving motor for driving the developing device (an example of a driving source for the developing device).
401 is the rotation axis of the drive motor 400, 402
(402a to 402d) are drive input gears attached to the respective rotating shafts of the developing devices 4a to 4d, and 403 is the rotating shaft 401 and the drive input gears 402b to 402.
This is a group of gears for connecting the gears d. 1 to 5, reference numeral 300 denotes a side plate (an example of a support member) for supporting the shafts of the respective gears included in the gear group 203 and the gear group 403. An output shaft 405 connected to the gears 4031 to 4036 of the gear group 403 in this order, and 405 is the output shaft 40
4, an extension 404E extending outward between the side plates 300.
An endless drive belt 204 wound between the drive input gear 402a and a rotation shaft (an example of a drive input unit) 4021a of the drive input gear 402a is provided with gears 2031 to 2034 of the gear group 203 on the rotation shaft 201. In this order, the idle gear 204 is connected to the drive input gear 202d via a gear 2035 of the gear group 203.

As shown in FIG. 2, the tandem-type full-color printer according to the present embodiment has a gear group (part of the drive system) in which the four photosensitive drums 2a to 2d are mounted between the side plates 300. ) 203 is the same as the conventional one in that it is driven only by the drive motor 200 connected to the drive input gears 202a to 202d of the respective photosensitive drums 2a to 2d. More specifically, of the four photosensitive drums 1a to 1d, the drive input gear 202a of the photosensitive drum 1a includes a rotation shaft 201 of the drive motor 200 and gears 2036, 2037, 2038, and 20.
39, 2040 and 2041 are connected in this order. The drive input gear 20 of the photosensitive drum 1b
2b is a rotary shaft 201 of the drive motor 200 and gears 2031, 2032, 2042, 2043, 2044,
2045 are connected in this order. The drive input gear 202c of the photosensitive drum 1b is connected to the rotation shaft 201 of the drive motor 200 and the gears 2031 and 203.
2, 2033, 2034, 2046, and 2047 are connected in this order. The photosensitive drum 1d
Of the drive input gear 202d is
The reference numeral 2033, the idle gear 204, and the gear 2035 are connected in this order.

On the other hand, the tandem type full-color printer according to the present embodiment is different from the conventional one in that the developing devices 4a to 4d are driven only by the drive motor 400 as shown in FIGS. The developing device 4a (an example of a part of the developing device) is
For the remaining developing devices 4b to 4d, the drive belt 300 wound around the outer side between the side plates 300 is connected to the output shaft 404 connected to the output shaft 404 and the drive input rotary shaft 4021a of the developing device 4a. , The gear group 203, 40
3, each of the developing devices 4a
4d and the drive motor 400, and the idle gear 204 included in the gear group 203 of the gear groups 203 and 403 is rotatably provided on the output shaft 404. In the tandem-type full-color printer according to the present embodiment, each of the developing devices 4a to 4d is driven only by the drive motor 400. The drive motor 400 is separate from the drive motor 200. In order to make the distance between the two drive motors 200, 400 and each driven body substantially equal, the drive motors 200, 400
400 is not arranged at the center of each of the image forming units 1a to 1d, but is arranged at a position deviated from the center, for example, as shown in FIG. Therefore, the developing device 4a of the four developing devices 4a to 4d is considerably far from the drive motor 400. As for the three developing devices 4b to 4d whose distances from the drive motor 400 are relatively short, similarly to the drive system of the photosensitive drums 1a to 1d, each of the developing devices 4b to 4d
The drive input gears 402b to 402d are connected to the drive motor 400 via gears. More specifically,
As shown in FIG. 3, the drive input gear 40 of the developing device 4b
2b is a rotary shaft 401 of the drive motor 400 and gears 4037, 4038, 4039, 4040, 4041.
4042, 4043, 4044, and 4045 are connected in this order. The drive input gear 402c of the developing device 4c is connected to the rotating shaft 401 of the drive motor 400.
And gears 4037, 4038, 4039, 4046, 4
047 are connected in this order. The drive input gear 402d of the drive input gear 4d of the developing device 4d is
The rotating shaft of the drive motor 400 and the gears 4037, 40
38, 4039, 4046, 4048, 4049, 40
50 are connected in this order.

The three developing devices 4b to 4d correspond to three colors of magenta, yellow and cyan.
When monochrome printing is performed, these developing devices 4b to 4d
There is no need to drive. For this reason, a clutch is provided between the gear 4037 and the gear 4038. By turning on and off the clutch, the operation for monochrome printing and the operation for color printing are switched. With respect to these three developing devices 3b to 3d, the developing device 4a which is far from the drive motor 400
Are connected to the drive motor 400 via the drive belt 405. As shown in FIG. 1, FIG. 3, and FIG.
1,4032,4033,4034,4035,403
6, the output shaft 404 is connected. One end of the output shaft 404 is disposed outside between the side plates 300, and an extension 404 </ b> E of the output shaft 404 outside the side plate 300 has an endless drive belt 4.
05 is wound. The drive belt 405 is connected to a rotary shaft 402 of a drive input gear 402a of the developing device 4a.
1a, the gears 4031 to 403
6, the rotation shaft 40 of the drive input gear 202a of the developing device 4a via the output shaft 404 and the drive belt 405.
The driving force of the driving motor 400 is transmitted to 21a.
As described above, the output shaft 404 is provided outside the side plate 300.
Between the drive shaft 405 and the rotating shaft 4021a.
Is wound and the developing device 4a is driven by the driving motor 400, so that a number of shafts and gears necessary for connecting the developing device 4a and the driving motor 400 by gears are provided between the side plates 300. There is no need to arrange them, and the gear group 203,
Mutual interference when arranging 403 can be suppressed. Considering that about nine gears are required to drive the developing device 4b closer to the drive motor 400 than the developing device 4a as described above, the developing device 4a is driven by the drive belt 405. Drive motor 4
The number of shafts and gears that need not be arranged between the side plates 300 by being connected to 00 is significantly reduced. Also,
Since a large number of gears are not used to drive the developing device 4a farthest from the drive motor 400, good drive accuracy is ensured even if the drive motor 400 is not arranged at the center of the image forming unit 1. can do.
The drive error caused by the drive belt 405 is considerably smaller than the case where errors are accumulated over a large number of gears. Further, only the developing device 4a is connected to the drive belt 40.
5, the developing device 4a may be farthest from the drive motor 400,
There is also a reason that the developing device 4a corresponds to black and may be used alone during black and white printing. As described above, the developing device 4a and the developing device 4b
If the connection system is different for 〜4d, it is easy to switch between monochrome printing and color printing.

In the tandem type full-color printer according to the present embodiment, the gear group 2 is provided between the side plates 300.
03 and 403, the drive motor 200 and the drive input gear 402 of the photosensitive drum 4a.
The idle gear 204 of the group of gears used to connect the drive belt 405 d is rotatably provided on the output shaft 404 that rotates to drive the drive belt 405. Only the gear 4036 shown in FIGS. 1, 3, 4, and 5 is originally attached to the output shaft 404. The gear 4036 is fixedly attached to the output shaft 404, and as shown in FIG. 4, the driving force transmitted from the drive motor 401 via the gears 4031 to 4035 is transmitted to the output shaft 404. 404 to rotate the output shaft 404. As described above, the idle gear 204 receives the driving force from the driving motor 200 via the gears 2031 to 2034, and
The drive signal is transmitted to the drive input gear 202d via the main input 35 (see mainly FIG. 4). The idle gear 204
Conventionally, a separate fixed shaft is disposed between the side plates 300 and is provided rotatably with respect to the fixed shaft. However, as described above, a number of gears including the gear groups 203 and 403 are connected to the side plate 3.
00, if the idle gear 204 is provided on a separate fixed shaft, the gear groups 203, 40
There is a possibility that some interference of the gears included in No. 3 may be unavoidable. This is achieved by using the drive belt 405 to drive the side plate 3.
This is a problem that can occur even when the number of required images is reduced during the 00 hours. Therefore, as briefly shown in FIGS. 4 and 5, the idle gear 204 is rotatably provided on the output shaft 404 to which the gear 4036 is fixedly attached. As a result, the output shaft 404 also serves as the shaft of the idle gear 204, so that the number of shafts required between the side plates 300 can be reduced, and interference of the gears between the side plates 300 can be suppressed. . Furthermore, when the rotation direction of the idle gear 204 and the output shaft 404 are made to be the same, the relative circumference of the idle gear 204 and its shaft is smaller than when the idle gear 204 is mounted on a fixed shaft. The speed difference is reduced, and wear of the idle gear can be reduced. As described above, in the copying machine according to the present embodiment, the plurality of image forming units including the photosensitive drums and the developing devices are arranged in a line along the paper transport path, and the drive system mounted between the support members. In a tandem type image forming apparatus in which each photosensitive drum is driven by a single photosensitive drum drive source connected to each photosensitive drum via a photoconductive drum, one of the developing devices includes a gear group in the drive system. Is not used, and an endless drive wound outside the support member around an output shaft connected to a single developing device drive source for driving each developing device and a drive input portion of the developing device. Since a belt is used and an idle gear included in the gear group is rotatably provided on the output shaft, the number of shafts and gears that need to be arranged between the support members is reduced while the number of shafts and gears between the support members is reduced. The said gear The becomes possible to efficiently arranged, while the photosensitive drum and the developing units and was driven by a respective single drive source, it is possible to keep the driving accuracy required.

[0013]

In the above embodiment, the idle gear 20
4 was rotatably attached to the output shaft 404. Although only the gear 4036 was attached to the output shaft 404 in addition to the idle gear 204, for example, if it is necessary to output driving force from the output shaft 404 to another system, the output shaft 404 The idle gear 204 and the gear 403
6, a gear for outputting the driving force from the output shaft 404 may be fixedly attached. The gear groups 203 and 403 include the idle gear 204.
There are other idle gears. These idle gears may be rotatably mounted on a fixed shaft of a fixed shaft clutch disposed between the side plates 300, for example. If the fixed shaft of the fixed shaft clutch and the fixed shaft of the idle gear are not separately provided, the side plate 300
The space between them can be used efficiently. If each idle gear is rotatably attached to the output shaft and the fixed shaft of the fixed shaft type clutch, the space between the side plates can be secured most, but either one may be used. In the above-described embodiment, the developing device 4a farthest from the driving motor 400 is driven by using the driving belt 405. However, another developing device, for example, the developing device 4b may be driven by the driving belt 405. . If another belt can be arranged, both may be driven by a drive belt. Further, instead of driving the developing device 4a using the drive belt 405, a part of the photosensitive drums 2a to 2d, for example, the photosensitive drum 2a is driven by using a drive belt for the drive motor 200. Alternatively, other devices (the photosensitive drums 2b to 2d and the developing devices 4a to 4d) may be connected to the drive motors 200 and 400 using a group of gears. In the above embodiment, the present invention is applied to a tandem-type full-color printer. However, the present invention is not limited to this, and the present invention can be applied to other tandem-type image forming apparatuses, such as a copying machine. Is possible.

[0014]

As described above, according to the image forming apparatus of the first aspect, a gear group is used in a drive system for some of a plurality of developing devices or photosensitive drums. An endless drive belt wound outside the support member between an output shaft connected to the drive source for the developing device or the photosensitive drum and a drive input portion of the developing device or the photosensitive drum. Is used for the drive system, and the idle gear included in the gear group is rotatably provided on one or both of the fixed shaft of the fixed shaft clutch disposed between the output shaft and the support member. The arrangement of the gears between the support members is efficiently performed while suppressing the number of shafts and gears that need to be arranged between the support members, and each photosensitive drum and each developing device are controlled by a single drive source. Necessary while driving It can be kept driving accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an overall configuration of a drive system that is a main part of a tandem-type full-color printer according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a drum drive system extracted from the entire configuration shown in FIG. 1;

FIG. 3 is a diagram in which a development drive system in the entire configuration shown in FIG. 1 is extracted.

FIG. 4 is a diagram in which only a characteristic configuration is extracted from the entire configuration shown in FIG. 1;

FIG. 5 is a diagram more simply showing the characteristic configuration shown in FIG. 4;

FIG. 6 is a view schematically showing an entire configuration of the tandem type full-color printer.

FIG. 7 is an enlarged view showing a configuration around an image forming unit of the tandem type full color printer.

FIG. 8 is a diagram illustrating a problem in a conventional tandem image forming apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image forming unit 2 photosensitive drum 4 developing device 200, 400 drive motor 203, 403 gear group 204 idle gear 300 side plate 404 output shaft 405 drive belt

Claims (1)

[Claims] A plurality of image forming units including a photosensitive drum and a developing device are arranged in a line along a paper transport path, and are connected to each photosensitive drum via a drive system attached between support members. A single tandem image forming apparatus for driving each photosensitive drum by a single photosensitive drum drive source provided with a single developing device drive source for driving each developing device. For the developing device or the photosensitive drum, the support member is provided in the drive system, the developing device drive source or an output shaft connected to the photosensitive drum, and the developing device or the drive input portion of the photosensitive drum. Using an endless drive belt wound around the outside between
For the remaining developing device and the photosensitive drum,
A gear group is used in the drive system to connect each developing device or each photosensitive drum to the developing device drive source or the photosensitive drum drive source. A tandem-type image forming apparatus, which is rotatably provided on one or both of a fixed shaft of a fixed shaft clutch disposed between an output shaft and the support member.