JP2003015383A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily prevent a photoreceptor and an endless transfer belt from being damaged by eliminating color slippage without causing a difference between the linear velocity of the photoreceptor and that of the endless transfer belt. SOLUTION: In a color image forming device to form a color image by forming an image on one or several photoreceptors and performing intermediate transfer of the image on the endless transfer belt or transferring the image on a recording sheet held on the endless transfer belt, the driving means of the photoreceptor and that of the endless transfer belt are independent, and are controlled so as to synchronize with an independent clock means functioning as a reference. Either the driving means of the photoreceptor or that of the endless transfer belt is set so as to cause a delay or a lead to the independent clock means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention ensures the synchronization of driving between a photoconductor as an image carrier and an endless transfer belt for transferring a toner image thereof to prevent scratches due to misalignment between the photoconductor and the endless transfer belt. The present invention relates to a high-quality, high-durability color image forming apparatus that prevents image deformation such as generation and color shift.

[0002]

2. Description of the Related Art As a system of a color image forming apparatus, an image is formed on one or a plurality of photoconductors, and the image is intermediately transferred to an endless transfer belt, or a recording held on the endless transfer belt. There is one that forms a color image by transferring onto a sheet.

In such a color image forming apparatus, the photoconductor and the transfer belt come into contact and rotate. If the speeds of the photoconductor and the transfer belt do not match, color misregistration or scratches may occur between the photoconductor and the transfer belt, so it is desirable to match the speeds, but in reality, Since the belt also rotates with unevenness in rotation due to various factors, it is difficult to perfectly match it.

In Japanese Patent Laid-Open No. 8-314286, a braking means is provided in the driving means of the intermediate transfer belt, and when a speed difference occurs between the intermediate transfer belt and the photoconductor, the braking means slides the speed difference. Means for absorbing are disclosed.

Further, in Japanese Patent Laid-Open No. 11-352801, a one-way clutch is inserted in the driving means of the intermediate transfer belt to rotate the belt side slowly, and the speed of the photoconductor is set a little higher to endlessly release the one-way clutch. Means for tracking the speed of the pattern transfer belt are disclosed.

However, both methods have complicated mechanisms, and their reliability is questionable.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks of the prior art and prevents color misregistration caused by a difference in linear velocity between the photoconductor and the endless transfer belt.
It is an object of the present invention to provide a highly durable color image forming apparatus capable of obtaining high image quality by preventing scratches on the photoconductor and the intermediate transfer belt.

[0008]

This object is achieved by any of the following technical means (1) to (6).

(1) An image is formed on one or a plurality of photoconductors, and the image is intermediately transferred onto an endless transfer belt, or transferred onto a recording sheet held on the endless transfer belt. In the color image forming apparatus for forming a color image, the driving means for the photoconductor and the driving means for the endless transfer belt are independent, and the driving means for the photoconductor and the driving means for the endless transfer belt are the reference. Is controlled so as to be synchronized with the independent clock means, and one of the drive means for the photoconductor and the drive means for the endless transfer belt is within the torque range used for the independent clock means. The color image forming apparatus is characterized in that the color image forming apparatus is set so that a delay or a lead occurs.

(2) The color image forming apparatus as described in the item (1), wherein the driving means set so that the delay or the advance occurs uses a DC servomotor as a driving source.

(3) The DC servo motor has a current value,
Either the voltage value, the resistance value related to the control gain, the resistance value related to the capacitor value or the control time constant, or the capacitor value,
The color image forming apparatus according to item (2), wherein the color image forming apparatus is shifted in a direction in which a delay or advance occurs within a torque range to be used.

(4) The color image forming apparatus according to item (1), characterized in that the driving means set so as to cause the delay or advance uses a stepping motor as a driving source.

(5) In the stepping motor, any one of the current value, the voltage value, the magnetic material of the motor, the magnetic force setting and the gap between the rotor and the stator causes a delay or advance in the torque range used. The color image forming apparatus according to item (4), which is offset.

(6) The driving means set so as to cause the delay or advance does not cause delay or advance in a state in which the photoconductor is not mounted in the color image forming apparatus, and the photoconductor is The color image forming apparatus according to any one of (1) to (5), wherein the color image forming apparatus is set so that delay or advance occurs in a state where all the color image forming apparatuses are installed. .

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. Note that the description in this section does not limit the technical scope of the claims or the meaning of terms. Further, the following affirmative description in the embodiments of the present invention shows the best mode, and does not limit the meaning or technical scope of the terms of the present invention.

FIG. 1 is a sectional view of a color image forming apparatus showing an embodiment of the present invention.

This color image forming apparatus is called a tandem type color image forming apparatus, and includes a plurality of sets of image forming sections 10Y, 10M, 10C and 10K, an endless transfer belt unit 7, a sheet feeding and conveying means and And a fixing unit 24. A document image reading device SC is arranged above the main body A of the image forming apparatus.

Image forming unit 1 for forming a yellow image
0Y is a drum-shaped photoconductor 1Y as a first image carrier.
A charging means 2Y, an exposing means 3Y, a developing means 4Y, a primary transfer roller 5Y as a primary transfer means,
It has a cleaning means 6Y. The image forming unit 10M that forms a magenta image includes a drum-shaped photoreceptor 1M as a first image carrier, a charging unit 2M, an exposing unit 3M, a developing unit 4M, and a primary transfer roller 5 as a primary transfer unit.
M, and a cleaning means 6M. The image forming unit 10C that forms a cyan image includes a drum-shaped photoreceptor 1C as a first image carrier, a charging unit 2C, an exposing unit 3C, and
Developing means 4C, primary transfer roller 5 as primary transfer means
C, and a cleaning means 6C. The image forming unit 10K that forms a black image includes a drum-shaped photoreceptor 1K as a first image carrier, a charging unit 2K, an exposing unit 3K, a developing unit 4K, a primary transfer roller 5K as a primary transfer unit, and a cleaning unit. Have 6K.

The endless transfer belt unit 7 has a semi-conductive endless belt-shaped endless transfer belt 70 as a second image carrier which is wound by a plurality of rollers and is rotatably supported.

Image forming units 10Y, 10M, 10C, 10
The image of each color formed by K is transferred to the primary transfer roller 5Y,
Endless transfer belt 7 that rotates by 5M, 5C, and 5K
0 is sequentially transferred to form a composite color image. The sheet P as a recording medium stored in the sheet cassette 20 is fed by the sheet feeding unit 21, passes through the plurality of intermediate rollers 22A, 22B, 22C, 22D, and the registration roller 23, and then is transferred to the secondary transfer unit 5A. The color image is conveyed and collectively transferred onto the paper P. The sheet P to which the color image is transferred is fixed by the fixing unit 24, sandwiched by the sheet discharge rollers 25, and placed on the sheet discharge tray 26 outside the apparatus.

On the other hand, after the color image is transferred onto the paper P by the secondary transfer means 5A, the residual toner is removed from the endless transfer belt 70 in which the paper P is separated by the curvature by the cleaning means 6A.

During the image forming process, the primary transfer roller 5K is constantly in pressure contact with the photoconductor 1K. Other primary transfer roller 5
Y, 5M and 5C are pressed against the corresponding photoconductors 1Y, 1M and 1C only when forming a color image.

The secondary transfer means 5A is provided with the endless transfer belt 7 only when the sheet P passes therethrough and the secondary transfer is performed.
Press to 0.

FIG. 2 is a perspective view showing a state where the housing 8 is pulled out from the apparatus main body A. FIG. 3 is a sectional view of the housing 8, and FIG. 4 is a perspective view of the housing 8.

The casing 8 is composed of the image forming units 10Y, 10M, 1
0C, 10K and an endless transfer belt unit 7.

Image forming units 10Y, 10M, 10C, 10
The Ks are arranged in a vertical column. Photoconductor 1Y, 1
An endless transfer belt unit 7 is arranged on the left side of M, 1C, 1K in the drawing. Endless transfer belt unit 7
Is an endless transfer belt 70 that is rotatable by winding rollers 71, 72, 73, 74, primary transfer rollers 5Y, 5M,
5C, 5K, and cleaning means 6A.

The housing 8 can be pulled out from the main body A. That is, the front door 101 of the main body A is opened, the housing 8 is grasped, and the front side is pulled out. The housing 8 is a support rail 8 on the left and right.
Guided by 2L and 82R, it slides and is pulled out forward. The image forming unit 10 is operated by pulling out the housing 8.
The Y, 10M, 10C and 10K and the endless transfer belt unit 7 are integrally pulled out from the main body A.

The support rail 82L on the left side of the casing 8 in the drawing is
It is disposed in the space above the fixing unit 24 on the left side of the endless transfer belt 70. The support rail 82R on the right side of the casing 8 in the figure is disposed near the lowermost developing unit 4K. The support rail 82R includes the developing means 4Y, 4M, 4
The C and 4K are arranged at positions where they do not interfere with the operation of attaching and detaching the C and 4K.

The right side of the photoconductors 1Y, 1M, 1C and 1K of the casing 8 is surrounded by developing means 4Y, 4M, 4C and 4K, and the lower side of the figure is charging means 2Y, 2M, 2C and 2K.
And the cleaning means 6Y, 6M, 6C, 6K and the like, and the left side of the drawing is surrounded by the endless transfer belt 70.

Among them, the photoconductor, the cleaning means, the charging means and the like form one photoconductor unit, and the developing means and the toner replenishing device etc. form one developing unit.

The space above the photoconductor 1Y is shielded by a top plate 83 as an upper shield member fixed to the frame 81 of the housing 8. The bottom plate 84 as a lower shielding member fixed to the frame 81 of the housing 8 protects the endless transfer belt 70 at the time of attachment / detachment, and also serves as an upper guide plate for the paper transport path.

In FIG. 5, the endless transfer belt unit 7 and the developing units 4YU, 4MU, 4CU, 4KU from the housing 8 are shown.
6 is a perspective view of the endless transfer belt unit 7, and FIG. 7 is a perspective view of the housing 8. In FIG. 6, for convenience of explanation, the left half of the endless transfer belt 70 is removed to make it easier to see the inside of the endless transfer belt unit 7.

In a state where the housing 8 is pulled out from the main body A, the endless transfer belt unit 7 is slightly moved to the left in the figure, and then the endless transfer belt unit 7 is gripped and pulled up vertically. The positioning pins 75 planted on the upper portions of both side surfaces of the endless transfer belt unit 7 are moved leftward in the figure along the horizontal groove 85 formed in the housing 8, and then the vertical groove 8 is formed.
Moved vertically upwards along 6.

When the endless transfer belt unit 7 is pulled up, the endless transfer belt unit 7 is fixed by the positioning pin 7
5 moves while being regulated by the horizontal groove 85 and the vertical groove 86, the endless transfer belt 70 contacts the member of the housing 8,
It will not be damaged.

On the inner surface side of the endless transfer belt 70, horizontally supported primary transfer rollers 5Y, 5M, 5C and 5K.
And pressure rollers 76Y, 76M, 76C and 76K are arranged in a column. Primary transfer roller 5Y and pressure roller 7
6Y, a lever 77Y that supports the primary transfer roller 5M and the pressure roller 76M, and a lever 77C that supports the primary transfer roller 5C and the pressure roller 76C.
And are simultaneously swung by the regulation plate 78 to press and release the endless transfer belt 70.

FIG. 8 shows four pairs of photoconductor units 11Y and 1Y.
It is a perspective view of 1M, 11C, and 11K.

After removing the endless transfer belt unit 7 from the housing 8, four sets of photoconductor units 11Y, 11M,
11C and 11K can be taken out respectively. The uppermost photoconductor unit 11Y includes a photoconductor 1Y and a charging unit 2.
Y, cleaning means 6Y. The second-stage photoconductor unit 11M includes a photoconductor 1M, a charging unit 2M, and a cleaning unit 6M. Third-stage photoconductor unit 11C
Is a photoconductor 1C, a charging unit 2C, a cleaning unit 6C
Consists of. The lowermost photoconductor unit 11K is the photoconductor 1
K, charging means 2K, and cleaning means 6K.

When the housing 8 is pulled out from the main body A, the photoconductors 1Y, 1 are driven from the drive shafts AYD, AMD, ACD, AKD which are cantilevered and fixed in the main body A and drive the respective photoconductors.
M, 1C, 1K central holes 1YH, 1MH, 1CH, 1
KH is released, and each photoconductor unit 11Y, 11M, 11
C and 11K are mounted on the supporting bases 87Y, 87M, 87C and 87K, respectively.

In this state, the photoconductor unit 11Y can be slid on the support base 87Y and moved in the direction of the white arrow shown in FIG. 5 so that the endless transfer belt unit 7 can be taken out from the space. it can. Photoconductor unit 11
Similarly, M, 11C, and 11K also have support bases 87M and 87, respectively.
It can be taken out from above C and 87K.

The developing unit 4YU mainly including the developing means 4Y facing the photoconductor unit 11Y, the developing unit 4MU mainly including the developing means 4M facing the photoconductor unit 11M, and the developing means 4 facing the photoconductor unit 11C.
C developing unit 4CU, photoconductor unit 1
The developing unit 4KU mainly including the developing unit 4K facing 1K can be taken out from a predetermined storage portion of the housing 8 in the direction of the white arrow shown on the right side in FIG.

When mounting these units, the housing 8 is slid along the support rails 82L and 82R,
It is mounted in the main body A, stopped at a predetermined position, and fixed by a lock lever (not shown). The operation detecting means of the casing 8 detects by a sensor that detects that the casing 8 is attached to the main body A at a predetermined position. Alternatively, the housing operation detecting means detects that the lock lever has completed a predetermined operation.

In the above embodiment, the seamless endless transfer belt 70 has been described, but the present invention is not limited to this, and the endless transfer belt such as a seamless endless belt is described. It is also applicable to.

Now, in the present invention, the photoconductors 1Y, 1
Drive axis AY of drive source AD of M, 1C, 1K drive means
The drive shaft 72D of D, AMD, ACD, AKD and the drive source 72M of the drive means of the endless transfer belt 70 are controlled independently so as to be synchronized with the independent clock means serving as a reference.

As one embodiment of the present invention, one of the drive sources AD and 72M is controlled so as to always rotate in synchronization with the clock means within the torque range used. While the other drive source is D
Using the C servo motor, any one of the current value, the voltage value, and the time constant for the control delay is shifted in the direction in which the delay or advance occurs within the torque range used.

Originally, in the DC servo motor, the current value, the voltage value, the resistance value related to the control gain, the capacitor value and the resistance value related to the control time constant, the capacitor value, etc. should be rotated at a constant speed within a wider torque range. It is normal to optimize.

However, the present invention is characterized in that one of the drive sources is intentionally set to a point that is not optimized.

One of the driving means, for example, the DC servo motor for driving the endless transfer belt 70 is set so as to be synchronized with the independent clock means and not to be delayed or advanced with respect to this clock means. There is. On the other hand, the DC servo motors that drive the photoconductors 1Y, 1M, 1C, and 1K are set so that delay or advance occurs with respect to the independent clock means.

By setting in this way, as shown in the diagram showing the relationship between the torque and the motor rotation speed in FIG. 9, the DC servomotor can set the rotation speed to be equal to the used torque range if the optimum setting is made. However, the DC servo motor that drives the photoconductors 1Y, 1M, 1C, and 1K is set so that delay or advance occurs, and in the operating torque range, a uniform rotation speed is obtained in the middle portion of the torque. Although it is maintained, the rotation speed is set to be low in the high torque area and is set to be high in the low torque area.

With this setting, for example, if the thickness of the endless transfer belt 70 is thick and the endless transfer belt 70 is thick, the surface speed of the belt 70 becomes faster than the surface speed of the photosensitive member, and the endless transfer belt 70 becomes faster. The DC servo motor that drives the pattern transfer belt receives a high torque load, and the photoconductors 1Y, 1M, 1C, 1 have the same characteristics as the uncontrolled motor.
When the endless transfer belt is thin, the surface speed of the belt is slower than the surface speed of the photoconductor, and the DC servo that drives the endless transfer belt 70 is automatically corrected so as to approach the surface speed of K. The motor is subjected to a low torque load, and is automatically corrected to increase the rotation speed so as to approach the surface speed of the photoconductors 1Y, 1M, 1C and 1K, similar to the property of the uncontrolled motor.

As another embodiment, contrary to the above, for example, the photoconductors 1Y, 1M, 1C, 1
The DC servo motor for driving K is set so as to be synchronized with the independent clock means and not to be delayed or advanced with respect to this clock means. On the other hand, the DC servo motor that drives the endless transfer belt 70 is set so that delay or advance occurs with respect to the independent clock means.

By setting in this way, FIG.
As shown in the diagram showing the relationship between the motor rotation speed and the torque, the DC servo motor can maintain the rotation speed uniformly over the operating torque range if the optimum setting is made. The DC servo motor that drives 70 is set to cause delay or advance, and a uniform rotation speed is maintained in the intermediate torque range in the operating torque range.
The rotation speed is set to be low in the high torque area and is set to be high in the low torque area.

By setting in this way, there is play between the drive source AD and the connecting portions of the central holes 1YH, 1MH, 1CH, 1KH which are the rotation axes of the photoconductors 1Y, 1M, 1C, 1K. , When the surface speed of the photoconductor becomes faster than the surface speed of the endless transfer belt, the photoconductors 1Y, 1M, 1
The DC servomotor driving C and 1K receives a high torque load, and is automatically corrected to decrease the rotational speed until it matches the surface speed of the endless transfer belt 70, similar to the nature of an uncontrolled motor. When the surface speed of the body 1Y, 1M, 1C, 1K becomes slower than the surface speed of the endless transfer belt, the DC servo motor driving the photoconductors 1Y, 1M, 1C, 1K receives a low torque load, Similar to the nature of an uncontrolled motor, it is automatically corrected to increase the rotation speed until it matches the surface speed of the endless transfer belt 70.

As another embodiment of the present invention, a stepping motor is used as the drive source instead of the DC servo motor, and in this case, either the current value or the voltage value is delayed. Both the setting that does not cause the advance and the setting that shifts in the direction in which the delay or the advance occurs are used.

That is, as one embodiment of the present invention,
One drive source is controlled so that it always rotates in synchronization with the clock means in the torque range to be used, while the other drive source uses a stepping motor and lags in the normal torque range. It is set to step out to the leading side.

Originally, in the stepping motor, the current value, the voltage value, the magnetic material of the motor, the magnetic force setting, the gap between the rotor and the stator, etc. are optimized so as to rotate at a constant speed in a wider torque range. Is normal.

However, the present invention is characterized in that one drive source is intentionally set in a state where it is not optimized.

One of the driving sources, for example, a stepping motor for driving the endless transfer belt 70 is set so as to be synchronized with the independent clock means and not to be delayed or advanced with respect to this clock means. is there. On the other hand, the stepping motors that drive the photoconductors 1Y, 1M, 1C, and 1K are set so as to step out to the delay side or the advance side with respect to the independent clock means.

With this setting, as in the case of the DC servo motor, the stepping motor can maintain the number of revolutions uniformly over the operating torque range if the optimum setting is made. 1Y, 1M, 1C, 1
The stepping motor that drives K is set so that delay or advance occurs, and in the operating torque range, a uniform rotation speed is maintained in the middle part of the torque, but in the high torque region, step out to the delay side occurs, In the low torque region, it is set so as to step out to the leading side.

With this setting, for example, if the endless transfer belt 70 is thick and the endless transfer belt 70 is thick, the surface speed of the endless transfer belt 70 becomes faster than the surface speed of the photosensitive member, and thus the endless transfer belt 70 has a higher surface speed. The stepping motor that drives the transfer belt 70 receives a high torque load, and is automatically corrected to decrease the rotation speed until the surface speed of the photoconductors 1Y, 1M, 1C, and 1K matches.
If it is thin, the surface speed of the belt 70 becomes slower than the surface speed of the photoconductor, and the stepping motor that drives the endless transfer belt receives a low torque load, and the surface of the photoconductor 1Y, 1M, 1C, 1K It is automatically corrected to increase the rotation speed until it matches the speed.

Contrary to the above, for example, the stepping motor for driving the photoconductors 1Y, 1M, 1C and 1K is synchronized with the independent clock means and is delayed or advanced with respect to this clock means. It is set not to occur. On the other hand, the stepping motor that drives the endless transfer belt 70 is set so that delay or advance occurs with respect to the independent clock means.

With this setting, the optimum setting allows the stepping motor to maintain a uniform rotation speed over the range of torque used, but the stepping motor driving the endless transfer belt 70 does With a setting that causes a delay or advance, in the operating torque range, a uniform rotation speed is maintained in the middle torque area, but the rotation speed is reduced in the high torque area and increased in the low torque area. It has been set.

With this setting, there is play between the drive source AD and the connecting portions of the central holes 1YH, 1MH, 1CH, 1KH which are the rotation axes of the photoconductors 1Y, 1M, 1C, 1K. When the surface speed of the photoconductors 1Y, 1M, 1C, 1K becomes faster than the surface speed of the endless transfer belt 70, the stepping motors that drive the photoconductors 1Y, 1M, 1C, 1K receive a high torque load and are uncontrolled. Similarly to the property of the motor, the surface speed of the photoconductors 1Y, 1M, 1C, and 1K is automatically corrected to decrease the rotation speed so as to approach the surface speed of the endless transfer belt 70. When the speed is slower than the speed, the photoconductors 1Y, 1
The stepping motors that drive M, 1C, and 1K receive a low torque load, and automatically rotate in the direction of increasing the rotation speed so as to approach the surface speed of the endless transfer belt 70, similar to the nature of an uncontrolled motor. Will be fixed.

Further, the DC servo motor and the stepping motor do not cause delay or advance in a state where the photoconductors 1Y, 1M, 1C and 1K are not installed in the color image forming apparatus, and the photoconductors 1Y, 1M, It is desirable to set such that delay or advance occurs when 1C and 1K are all installed in the apparatus.

[0064]

According to the present invention, there is no difference in the linear velocity between the photoconductor and the endless transfer belt, the color shift of the transferred image is eliminated, and the scratches on the photoconductor and the endless transfer belt can be easily prevented. Became.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an example of an embodiment of the present invention.

FIG. 2 is a perspective view showing a state in which a housing is pulled out from a main body of the image forming apparatus.

FIG. 3 is a cross-sectional view of a housing that houses an image forming unit.

FIG. 4 is a perspective view of a housing containing an image forming unit.

FIG. 5 is an exploded cross-sectional view of a housing in which a photoconductor unit is mounted, an endless transfer belt unit, and a developing unit.

FIG. 6 is a perspective view of an endless transfer belt unit.

FIG. 7 is a perspective view of a housing.

FIG. 8 is a perspective view of four photoconductor units.

FIG. 9 is a relationship between a torque and a motor rotation speed, which shows a state in which a difference in rotation speed between a DC servo motor driving an endless transfer belt and a DC servo motor driving a photoconductor is automatically absorbed in a use torque range. FIG.

FIG. 10 is a graph showing a relationship between a torque and a motor rotation speed, which indicates a state in which a difference in rotation speed between a DC servo motor driving a photoconductor and a DC servo motor driving an endless transfer belt is automatically absorbed. It is a diagram showing.

[Explanation of symbols]

1Y, 1M, 1C, 1K photoconductor 1YH, 1MH, 1CH, 1KH Center hole of photoconductor 2Y, 2M, 2C, 2K charging means 3Y, 3M, 3C, 3K exposure means 4Y, 4M, 4C, 4K developing means 4YU, 4MU, 4CU, 4KU Development unit 5A Secondary transfer means 5Y, 5M, 5C, 5K Primary transfer roller 6A, 6Y, 6M, 6C, 6K Cleaning means 7 Endless transfer belt unit 8 housing 10Y, 10M, 10C, 10K Image forming unit 11Y, 11M, 11C, 11K Photoconductor unit 70 Endless transfer belt 81 frames 82L, 82R support rail 83 Top plate 84 Bottom plate 101 front door A Image forming device body AD, 72M drive source AYD, AMD, ACD, AKD, 72D drive shaft

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 21/00 350 G03G 21/00 382

Claims (6)

[Claims] 1. An image is formed on one or a plurality of photoconductors and the image is intermediately transferred onto an endless transfer belt, or
Alternatively, in a color image forming apparatus that forms a color image by transferring onto a recording sheet held on the endless transfer belt, the driving means for the photoconductor and the driving means for the endless transfer belt are independent of each other. The driving means of the photoconductor and the driving means of the endless transfer belt are controlled so as to be synchronized with an independent clock means serving as a reference, and either one of the driving means of the photoconductor and the driving means of the endless transfer belt is controlled. The color image forming apparatus is characterized in that the driving means is set with respect to the independent clock means so that delay or advance occurs within a torque range used. 2. The color image forming apparatus according to claim 1, wherein the drive means set so that the delay or advance uses a DC servo motor as a drive source. 3. The DC servo motor is characterized in that any one of a current value, a voltage value, a resistance value relating to a control gain, a resistance value relating to a capacitor value and a control time constant, and a capacitor value is delayed or advanced within a torque range to be used. The color image forming apparatus according to claim 2, wherein the color image forming apparatus is shifted in a direction in which the color image is generated. 4. The color image forming apparatus according to claim 1, wherein the drive unit set so that the delay or advance occurs uses a stepping motor as a drive source. 5. In the stepping motor, any one of a current value, a voltage value, a magnetic material of the motor, a magnetic force setting and a gap between a rotor and a stator is in a direction in which a delay or advance occurs in a torque range to be used. The color image forming apparatus according to claim 4, wherein the color image forming apparatus is shifted. 6. The drive means set so that the delay or advance does not occur when the photoconductor is not mounted in the color image forming apparatus, and the photoconductor is The color image forming apparatus according to any one of claims 1 to 5, wherein the color image forming apparatus is set so that delay or advance occurs in a state where all the color image forming apparatuses are installed.