JPH11119502A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which the color slurring of a toner image superposed on a body to be recorded is prevented by perfectly synchronizing the rotation of respective photoreceptor drums by a simple mechanism. SOLUTION: As to this full-color image forming device; the respective photoreceptor drums 4C, 4M, 4Y, and 4K, and a driving motor are connected by a connecting link 2 with the same phase, and also the outer circumferential length πϕ of the respective drums 4C, 4M, 4Y, and 4K is made equal to an interval (d) between them, and the driving signal of the driving motor is corrected based on the detection value of a rotational speed sensor 23 attached to the drum 4C farthest from the driving motor. Therefore, the rotation of the respective photoreceptor drums 4C, 4M, 4Y, and 4K is synchronized, so that phase and amplitude are matched even though rotational irregularity exists. Thus, the positions of the toner images transferred to a recording paper are aligned in respective colors, so that the color slurring does not appear.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tandem image forming apparatus for forming toner images on a plurality of photosensitive drums and superimposing these toner images on a recording medium to obtain an image. More specifically, image formation that eliminates misalignment of the rotation of each photoreceptor drum (and also the conveyor belt) and achieves high-precision synchronization to prevent misalignment of each image superimposed on the recording medium It concerns the device.

[0002]

2. Description of the Related Art In the case of a tandem-type image forming apparatus used for forming a color image, an image is obtained by superposing toner images formed on a plurality of photosensitive drums on a recording medium. Therefore, if the positions of the toner images are shifted from each other, a color shift occurs, and an image of a correct color cannot be obtained. For this reason, it is necessary to make the rotation state of each photosensitive drum (and further, the traveling state of the conveyor belt) coincide with each other, and adjust the position of each toner image on the recording medium with high accuracy. For this reason, various techniques for synchronizing the rotation status of each photosensitive drum (and the running status of the transport belt) have been conventionally proposed.

For example, Japanese Patent Application Laid-Open No. Sho 62-178982 discloses an example in which a rotary encoder is provided for each photosensitive drum, and a rotation speed detection and a drive motor (servo motor) are provided for each photosensitive drum. motor)
Speed control. In addition, 4-3
Japanese Patent Laid-Open No. 1590 discloses a technique for controlling the phase of rotation unevenness (rotational speed fluctuation) for each photosensitive drum. Alternatively, in the apparatus disclosed in Japanese Utility Model Laid-Open No. 3-14651, each photosensitive drum is driven by a single motor via a worm and a worm wheel provided for each photosensitive drum, and is driven on a worm shaft. The rotation speed of each of the photosensitive drums is adjusted by controlling the speed by providing a rotation speed detecting means in the camera.

[0004]

However, each of the above image forming apparatuses according to the prior art has the following problems.

First, in the case of detecting the rotation speed of each photosensitive drum and controlling the drive based on the rotation speed for each photosensitive drum as disclosed in Japanese Patent Application Laid-Open No. Sho 62-178982 or Japanese Patent Publication No. Hei 4-31590. Detection means (rotary encoders and the like) and control systems are required by the number of drums. For this reason, the whole apparatus becomes very large and complicated. Further, even though the phase control is performed as in Japanese Patent Publication No. 4-31590, since the gear pitch is used as the transmission element for driving from the motor, there is uneven pitch of the meshing. This effect cannot be eliminated unless high-frequency components are controlled with high accuracy and responsiveness. For this reason, the control system becomes very complicated.

Further, in the apparatus having a single drive source using a worm as disclosed in Japanese Patent Publication No. 4-31590, a worm wheel for receiving drive from a worm shaft is provided for each photosensitive drum, so that the machining accuracy is increased. (Eccentricity, tooth profile, etc.). The machining accuracy of the worm wheel also affects the detection of the rotational speed of the worm shaft, and the driving control becomes inaccurate. In addition, the worm mechanism requires a large torque because the drive transmission efficiency is not very good, and also requires a lubricant such as oil.

The present invention has been made to solve the above-mentioned problems of the conventional image forming apparatus. That is, the problem is that the rotation of each photosensitive drum can be completely synchronized with a simple mechanism, and a color shift of a toner image superimposed on a recording medium can be prevented to obtain a high-quality image. It is an object of the present invention to provide an image forming apparatus capable of performing the above.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the invention according to claim 1 comprises a plurality of photosensitive drums and an image forming means for forming a toner image on the surface of each of the photosensitive drums. A single driving unit for rotating each of the photosensitive drums, and forming an image by superimposing a toner image formed on each of the photosensitive drums on a recording medium. A rigid connecting member for connecting each of the photosensitive drums to the driving means;
And a rotation speed detection means for detecting the rotation speed of the photosensitive drum, wherein the rotation speed of each of the photosensitive drums is synchronized by correcting the drive speed of the drive means based on the detection value of the rotation speed detection means. Is specified as a feature.

In this image forming apparatus, when a toner image is formed on the surface of each of a plurality of photosensitive drums by an image forming means, the toner images are transferred onto a recording medium and superimposed to form an image. It is formed. Here, each photosensitive drum is rotationally driven by a single driving means via a rigid connecting member. Therefore, when the rotational speed of one of the photosensitive drums is detected by the rotational speed detecting means and the driving speed of the driving means is corrected based on the detected value, the effect of the correction is applied to all the photosensitive drums. . For this reason, the rotations of the photosensitive drums are always synchronized, and the overlapping position of the toner images does not shift.

In this case, as for the connection between each photosensitive drum and the rigid connecting member, a fitting portion may be provided at an eccentric position of the end face of the photosensitive drum itself to connect the photosensitive drum to the rigid connecting member. Alternatively, a rotating member that rotates integrally with the rigid connecting member may be provided, and a fitting portion may be provided at an eccentric position of the rotating member. The rigid connecting member is a member that transmits the force while maintaining a constant shape without being substantially deformed even when receiving the force, and is not necessarily a rigid body in a strict sense. For example, a mechanical element used by a name such as a link, a rod, or an arm corresponds to this.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the photosensitive drums are connected at the same phase position by the rigid connecting member, and the photosensitive drums are connected to each other. It is specified as a feature that the interval and the circumference of the body drums match.

In this image forming apparatus, the connecting positions of the respective photosensitive drums to the rigid connecting member are in the same phase, and the intervals and the circumferential lengths of the respective photosensitive drums are the same. Body drum synchronization is more reliable. That is, even if the rotational speed of a certain photosensitive drum varies, the rotational speed of the other photosensitive drum also varies, and the toner image on each photosensitive drum is transferred to a corresponding position on the recording medium. Therefore, the overlapping position of the toner images does not shift.

According to a third aspect of the present invention, there is provided the image forming apparatus according to the first or second aspect, wherein the transport belt transports the recording medium and passes through each of the photosensitive drums. A drive transmission roller connected to the rigid connection member for transmitting the rotational drive of the drive means to the transport belt, wherein a circumference of the drive transmission roller matches a circumference of each of the photosensitive drums. Is specified as a feature.

In this image forming apparatus, the rotational drive of the drive means is transmitted to the drive transmission roller via the rigid connecting member,
The conveyance belt is driven by the rotation of the drive transmission roller. That is, the transport belt for transporting the recording medium and the respective photosensitive drums are driven by the same drive source (drive means). For this reason, the conveyance of the recording material by the conveyance belt is always synchronized with the rotation of each photosensitive drum, so that the overlapping position of the toner images does not shift.
Here, "the circumference of the drive transmission roller is equal to the circumference of the photoconductor drum" means that the length of the conveyance belt conveyed by one rotation of the drive transmission roller is equal to the circumference of the photoconductor drum. Means equal.

According to a fourth aspect of the present invention, there is provided the image forming apparatus according to the third aspect, wherein the drive transmission roller is connected by the rigid connecting member at the same phase position as each of the photosensitive drums. The distance between the passive position where the transport belt receives the drive from the drive transmission roller and the transfer position where each photosensitive drum is close to the transport belt and closest to the passive position is the distance between each of the photosensitive belts. It is specified as a feature that it matches the circumference of the body drum.

In this image forming apparatus, the connecting position of the drive transmission roller to the rigid connecting member is the same in phase as the connecting position of each photosensitive drum to the rigid connecting member. Since the interval between each transfer position and the position closest to the passive position coincides with the circumferential length of each of the photosensitive drums, the synchronization of each of the photosensitive drums and the transport belt is more reliable. That is, even if the rotational speed fluctuates, the rotational speeds of the respective photosensitive drums and the conveyor belt fluctuate at the same time, and the toner image on each photosensitive drum is transferred to a corresponding position on the recording medium. The superposition position of the toner image does not shift.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the image forming apparatus of the present invention will be described in detail. This embodiment is a tandem-type full-color copying apparatus provided with an image forming system such as a photosensitive drum for each of four colors of cyan, magenta, yellow, and black. In the following description, the four colors are indicated by C, M, Y, and K color symbols, respectively.

First, the general outline of the full-color copying apparatus 1 according to the present embodiment will be described. Full color copier 1
Has the overall configuration shown in FIG. That is, a well-known image reader section IR for reading an image of a document is arranged at the upper part, and a print section PR for printing and reproducing the read image on recording paper is arranged below the image reader section IR.
The image reader section IR is provided with a scanner 98 for irradiating a document with light and obtaining image data based on the reflected light, an image processing section 99 for accumulating the obtained image data and performing necessary data processing. I have.

The printing unit PR includes an endless transport belt 3 for carrying and transporting the recording paper, and photosensitive drums 4C, 4M, 4 for each color arranged along the transport belt 3.
Y, 4K. The transport belt 3
It is stretched by a driving roller 31, a driven roller 32, and a tension roller 33. In the photosensitive drum 4C,
Various devices necessary for image formation, such as a charger 5C, a developing unit 6C, and a cleaner 7C, are provided. A transfer blade 8C is provided on the back side of the transport belt 3. Various devices are similarly arranged on the photosensitive drums 4M, 4Y, and 4K of other colors. PR PR
In addition, each of the photosensitive drums 4C, 4M, 4Y, 4K
, An exposure unit 91 for performing laser exposure based on image data, a control unit 90 for controlling the exposure unit 91, each photosensitive drum 4C,
A fixing device 88 for fixing a toner image to recording paper passing through 4M, 4Y, and 4K, a plurality of paper cassettes 93 to 96 provided for each size of recording paper, and the like are provided.

In the full-color copying apparatus 1, an image is printed on recording paper as follows. That is, when an image of a document is read by the image reader unit IR, the image data is supplied to the print unit PR. Then, in the printing unit PR, each of the photosensitive drums 4C, 4M,
4Y, 4K and the transport belt 3 are rotated synchronously, and the charger 5C and other devices also perform predetermined operations, and the laser beam from the exposure device 91 to each of the photosensitive drums 4C, 4M, 4Y, 4K based on the image data. Is irradiated. At this time, paying attention to one place on the surface of the photosensitive drum 4C, the photosensitive drum 4C is first charged to a predetermined potential by the charging charger 5C, and is subjected to laser exposure from the exposure unit 91 to form an electrostatic latent image. Then, cyan (C) toner is supplied onto the electrostatic latent image by the developing device 6C to form a cyan toner image.

At this time, recording paper of a size suitable for the image to be printed is selected from the paper feed cassettes 93 to 96 and supplied to the conveyor belt 3, and the conveyor belt 3 carries the recording paper and Drums 4C, 4M, 4Y, 4K
The paper is transported in synchronization with the rotation of. Therefore, when the recording paper passes directly below the photosensitive drum 4C, the toner image formed on the surface of the photosensitive drum 4C also passes there. At this time, the toner image on the photosensitive drum 4C is transferred to the recording paper by the action of the transfer blade 8C. When the surface of the photosensitive drum 4C having the toner image applied to the recording paper reaches the cleaner 7C, the residual toner is removed there and is ready for the next image formation.

Similarly, for the other colors, the photosensitive drum 4
Toner images are formed on M, 4Y, and 4K, and are sequentially superimposed thereon as the recording paper is transported. The recording paper on which the four color toner images are superimposed is separated from the transport belt 3 and sent to the fixing device 88. Here, the toner of each color on the recording paper is melted by heating, and fixed on the recording paper as a full color image. Then, the recording paper is discharged, and one print is completed.

Next, details of the transport belt 3 and the photosensitive drums 4C, 4M, 4Y, and 4K, which are features of the present invention in the full-color copying apparatus 1, will be described.
As shown in the front view of FIG. 2 and the plan view of FIG. 3, the full-color copying machine 1 has photoconductor drums 4C, 4M, 4Y,
4K, a drive motor 20 for driving the photosensitive drums 4C, 4M,
A connecting link 2 that connects the 4Y and 4K is provided. The transport belt 3 and each of the photosensitive drums 4C, 4M,
Positions 42C, 42M, 42 where 4Y and 4K are closest to each other
Y and 42K are called nip portions. Each nip portion 42C, 42
M, 42Y, and 42K are positions where the transfer of the toner image by the transfer blade 8C and the like is performed.

The drive motor 20 is connected to the photosensitive drums 4C, 4C.
Of M, 4Y, and 4K, it is located further downstream of photosensitive drum 4K, which is the most downstream in the traveling direction of the recording paper. The drive motor 20 is provided with a drive wheel 21 that rotates integrally with the drive shaft. The drive wheel 21 is provided with a locking portion 25 to which one end of the link 2 is attached. A driven wheel 22 is provided at a position further upstream of the photosensitive drum 4C, which is the most upstream in the traveling direction of the recording sheet, among the photosensitive drums 4C, 4M, 4Y, and 4K. The driven wheel 22 is provided with a locking portion 26 to which the other end of the link 2 is attached. Further, the photosensitive drums 4C, 4M, 4Y, and 4K are also provided with locking portions 41C, 41M, 41Y, and 41K to which the connecting link 2 is attached. Each locking part (25, 26, 41C, 41M, 4
1Y, 41K) are provided at the same radius from the respective rotation axes.

The connecting link 2 is a straight rod that does not expand or contract or bend, and has a drive wheel 2 at both ends.
1 and the locking portions 25 and 26 of the driven wheel 22. And four places between both ends are the locking portions 41C, 41M, 4 of the photosensitive drums 4C, 4M, 4Y, 4K.
Locked to 1Y, 41K. Here the link 2
Are the locking parts (25, 26, 41C, 41M, 41Y,
41K) have the same phase (angular position) in each wheel 21 and 22 and each photosensitive drum 4C, 4
M, 4Y and 4K are connected to form a link mechanism.
That is, the drive wheel 20 is driven by the drive motor 20.
Is rotated to the photosensitive drums 4C, 4M, 4Y, and 4K (and the driven wheel 22) via the connecting link 2, and these are rotated at the same rotation speed while maintaining the same phase. It is configured so that During this rotation, the connecting link 2 is, of course, kept parallel to the upper side of the transport belt 3, that is, the transport path of the recording paper.

As shown in FIG. 4, the locking portion 41C (the other locking portions are the same) is formed on the side surface of the drum wheel 43 which rotates integrally with the photosensitive drum 4C. A small diameter portion 44 is formed. A hole is formed in each locking portion of the connecting link 2 and is fitted and locked in the small diameter portion 44. In the locked state, the drum wheel 43 and the connecting link 2 are rotatable.

Referring back to FIGS. 2 and 3, each of the photosensitive drums 4C, 4M, 4Y, and 4K has the same outer diameter φ. Further, each of the photosensitive drums 4C, 4M, 4Y, 4
The distance d (distance between nip portions) between adjacent ones of K is also the same. Furthermore, there is a relationship between the outer diameter φ and the interval d such that d = πφ. That is, each of the photosensitive drums 4C, 4C
The outer peripheral lengths and intervals of M, 4Y, and 4K are equal.

The photosensitive drums 4C, 4M, 4Y, 4
K, photosensitive drum 4C farthest from drive motor 20
Is provided with a rotation speed sensor 23. further,
A driver circuit 24 for obtaining rotation speed information from the rotation speed sensor 23 and supplying a drive signal to the drive motor 20
Is provided. The driver circuit 24 has a function of correcting a drive signal to the drive motor 20 in accordance with information from the rotation speed sensor 23 to reduce rotation unevenness, that is, time variation of the rotation speed.

In the full-color copying apparatus 1 constructed as described above, when copying an image on recording paper, the drive motor 20 is rotated by a drive signal from the driver circuit 24 and the rotation is performed via the link 2. The light is transmitted to the photosensitive drums 4C, 4M, 4Y, and 4K. Therefore, each of the photosensitive drums 4C, 4M, 4Y, and 4K rotates. And
The rotation speed of the photosensitive drum 4C is detected by the rotation speed sensor 23 and is notified to the driver circuit 24. Thus, the driver circuit 24 performs drive control for suppressing rotation unevenness. However, even with this control, rotation unevenness cannot always be completely eliminated, and some rotation unevenness may remain.
Since this rotation unevenness is caused by the axial accuracy (so-called wheel balance) of the drive wheel 21 and the photosensitive drums 4C, 4M, 4Y, 4K, etc., the same rotation unevenness is repeated at the same cycle as these rotation cycles. The Rukoto.

Here, as described above, the connecting portion 2 and the engaging portions 41C, 41 of the photosensitive drums 4C, 4M, 4Y, 4K are connected.
Since M, 41Y, and 41K maintain the same phase, the rotations of the photosensitive drums 4C, 4M, 4Y, and 4K are synchronized. For this reason, even if there is some unevenness in the rotation of each drive motor 20, the photosensitive drums 4C, 4M, 4Y, 4K
The rotation unevenness is complete. In other words, the phase and amplitude of the rotation unevenness are changed for all the photosensitive drums 4C, 4M,
The same applies to 4Y and 4K.

This, and each photosensitive drum 4C, 4M,
When the outer peripheral lengths πφ of 4Y and 4K are equal to the interval d, the following result is obtained when the toner images of the respective colors are superimposed on the recording paper. That is, when the recording sheet passes through the most upstream cyan nip portion 42C and receives the transfer of the cyan toner image, even if there is a slight displacement due to rotational unevenness in the transfer position, the magenta recording sheet continues thereafter. , The photosensitive drums 4C, 4M, 4Y, and 4K make exactly one rotation during that time, and the same rotation unevenness occurs. For this reason, the magenta toner image is transferred with the same positional shift as the cyan toner image. The same applies to the subsequent two color toner images. Therefore, the misregistration is uniform for each color and does not appear as a misregistration.

As described in detail above, in the full-color copying apparatus 1 according to the present embodiment, each photosensitive drum 4
C, 4M, 4Y, and 4K are provided with a connecting link 2 for connecting the photosensitive drums 4C, 4M, 4Y, and 4K in the same phase.
Since the outer peripheral length πφ of 4K is equal to the interval d, and the drive signal of the drive motor 20 is corrected based on the detection value of the rotation speed sensor 23 attached to the photosensitive drum 4C, each photosensitive drum 4C, The rotations of 4M, 4Y, and 4K are synchronized, and even if there is uneven rotation, the phases and amplitudes are uniform. This realizes a full-color copying apparatus 1 in which the positions of the toner images transferred onto the recording paper are uniform for each color and do not appear as a color shift.

In this case, the drive motor 20, the rotational speed sensor 23, or the driver circuit 24 need only be a single set, and the above-described effects are achieved without any particular complication of the device configuration and the control system. In addition, since the drive motor 20 and the photosensitive drums 4C, 4M, 4Y, and 4K are connected by a link mechanism using the connecting link 2, it is not necessary to consider a high-frequency mesh pitch unevenness unlike the case of using a gear or the like. . Also, unlike the case where a worm is used, the machining accuracy required for each rotating member is an accuracy of a normal level, and the driving torque is not excessive.

In the full-color copying machine 1, the rotation speed sensor 23 is mounted on the photosensitive drum 4C.
It may be attached to another photosensitive drum (4M, 4Y, 4K). However, detecting the rotation speed with the photosensitive drum 4C farthest from the drive motor 20 is the most effective in suppressing the rotation unevenness. Also, this does not prevent attachment of the rotation speed sensor to two or more photosensitive drums. Further, the driven wheel 22 in the full-color copying apparatus 1 is for stabilizing the movement of the connecting link 2, but is not an essential component and can be omitted if the connecting link 2 has sufficiently high rigidity.

Next, a modification of the full-color copying apparatus 1 will be described. The modified example shown in FIG. 5 employs a connecting link 26 including a triangular portion instead of the linear connecting link 2, and the position of the drive motor 20 and the like is changed accordingly. In this modification, the connecting link 26 has a very high rigidity because it includes a triangular portion, and a configuration without using a driven wheel is possible.

In the modification shown in FIG. 6, the drive motor 20
This is not only responsible for driving the photosensitive drums 4C, 4M, 4Y, 4K, but also for driving the transport belt 3. To this end, a drive transmission roller 34 that transmits the driving force in contact with the peripheral edge of the drive roller 31 of the transport belt 3 is provided. The rotation of the drive motor 20 is controlled by the drive transmission roller 3 as well as the photosensitive drums 4C, 4M, 4Y, and 4K.
4, a non-linear connecting link 27 is employed. Here, the locking portion 3 of the drive transmission roller 34
5 is another locking part (25, 26, 41C, 41M, 41
Y, 41K) and at the same rotational radius.

Further, the outer diameter φ ₂ of the drive transmission roller 34
Is the outer diameter φ _{1 of} each photosensitive drum 4C, 4M, 4Y, 4K.
Is equal to Further, the point 36 at which the conveyor belt 3 is substantially driven by the drive roller 31 and the nip portions 42C, 42
The distance d ₂ between the nip portion 42K, which is the most downstream of the M, 42Y, and 42K, is equal to the distance between the nip portions 42C, 42M, and 42K.
Y, equal to the distance d ₁ between 42K. As described above, πφ ₁
And d ₁ are equal, so that all of πφ ₁ , πφ ₂ , d ₁ and d ₂ are eventually equal to each other.

In this modification, when the drive motor 20 is rotated to copy an image on a recording sheet, the photosensitive drums 4C, 4M, 4Y, and 4K (and the driven wheel 2) are rotated.
2) Not only that, the drive transmission roller 34 also rotates in synchronization with this. Therefore, each of the photosensitive drums 4C, 4M, 4
As Y and 4K rotate, the transport belt 3 runs. Here, since φ ₁ and φ ₂ are equal, the peripheral speed of rotation of each of the photosensitive drums 4C, 4M, 4Y, and 4K and the conveying belt 3
Running speed. Furthermore, the phase and the amplitude of the rotation unevenness (including the running unevenness of the conveyor belt 3 and the same hereinafter) are the same for all the photosensitive drums 4C, 4M, 4Y, 4K and the conveyor belt 3.

For this reason, even if there is some rotation unevenness when the recording sheet passes through the cyan nip portion 42C at the most upstream side and receives the transfer of the cyan toner image, the rotation unevenness is not affected by the photosensitive drum 4C. And the conveyor belt 3, the position of the toner image transferred onto the recording paper does not deviate from the correct position. Similarly, the toner image after magenta is transferred to a correct position without being shifted. Therefore, no color shift occurs in the image on the recording paper.

Here, instead of providing the position 36 at which the conveyor belt 3 substantially receives the drive from the drive motor 20 further downstream of the most downstream nip 42K, the position 36 is further upstream of the most upstream nip 42C. May be provided.

It should be noted that the present embodiment and its modifications are merely examples, and do not limit the present invention in any way. Therefore, naturally, the present invention can be variously modified and modified without departing from the gist thereof.

[0042]

As is apparent from the above description, according to the present invention, the rotation of each photosensitive drum can be completely synchronized with a simple mechanism, and the toner image has a color shift on the recording medium. An image forming apparatus that can obtain a high-quality image because it prevents the images from being superimposed on each other has been provided.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an overall configuration of a tandem-type full-color copying apparatus.

FIG. 2 is a front view showing details around a photosensitive drum.

FIG. 3 is a plan view showing details around a photosensitive drum.

FIG. 4 is an enlarged view showing a locking portion.

FIG. 5 is a front view showing details around a photosensitive drum according to a modified example.

FIG. 6 is a front view showing details around a photosensitive drum according to another modification.

[Explanation of symbols]

 2, 26, 27 Connecting link 3 Conveying belt 4C, 4M, 4Y, 4K Photoconductor drum 5C Charging charger 6C Developing device 20 Drive motor 23 Rotation speed sensor 34 Drive transmission roller 91 Exposure device

Claims (4)

[Claims] An image forming means for forming a toner image on a surface of each of the photosensitive drums; and a single driving means for rotating and driving each of the photosensitive drums.
In an image forming apparatus that forms an image by superposing a toner image formed on each of the photosensitive drums on a recording medium, a rigid connecting member that connects each of the photosensitive drums with the driving unit; Rotation speed detecting means provided on one of the body drums for detecting the rotation speed of the photosensitive drums, and correcting the drive speed of the drive means based on the detection value of the rotation speed detection means to rotate each of the photosensitive drums An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein each of the photosensitive drums is connected at the same phase position by the rigid connecting member, and an interval and a circumferential length of each of the photosensitive drums are different. An image forming apparatus, which is identical. 3. The image forming apparatus according to claim 1, wherein the driving unit is connected to the transport belt that transports the recording medium and passes through each of the photosensitive drums, and the rigid connecting member. And a drive transmitting roller for transmitting the rotational drive of the photosensitive drum to the transport belt, wherein a peripheral length of the drive transmitting roller matches a peripheral length of each of the photosensitive drums. 4. The image forming apparatus according to claim 3, wherein the drive transmission roller is connected to the respective photosensitive drums at the same phase position by the rigid connection member.
The distance between the passive position where the transport belt receives the drive from the drive transmission roller and the transfer position where each photosensitive drum is close to the transport belt and closest to the passive position is the distance between each of the photosensitive drums. An image forming apparatus, wherein the peripheral length of the image forming apparatus is equal to the circumference of the image forming apparatus.