JP3475518B2 - Color image forming equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus, and more particularly to a lateral direction (belt width direction) perpendicular to a process direction (belt length direction) of an image bearing belt on which a color toner image is formed. ) To prevent color misregistration, and to suppress edge force (pressing force) due to movement restriction to prevent damage such as cracks and deformation of the image bearing belt and improve life. And a color image forming apparatus.

[0002]

2. Description of the Related Art As a conventional color image forming apparatus, there is an apparatus which uses an endless belt as a photoreceptor for carrying a visible image, an intermediate transfer apparatus, and a transfer medium conveying apparatus.

In such a color image forming apparatus, the belt is driven by a driving roll to convey the belt, so that the degree of freedom in the structure of the image forming apparatus is improved and the apparatus can be made compact. During driving, the speed fluctuations due to the angular velocity fluctuation frequency and geometrical eccentricity on the driving roll formation accuracy are introduced into the belt, which causes an error in the transport amount between the driving roll and the belt, and the lateral direction perpendicular to the process direction. There is a possibility of slippage, meandering and wrinkles.

Therefore, in order to improve the gradation, graininess and hue in the halftone image quality of an image normally required in an office, it is required to drive the belt with high precision.

In particular, the lateral shift and meandering of the belt cause color misregistration when writing is performed by vertical lines that superimpose color toner in the process direction of the belt. Color shift value on vertical lines is at least 50μ
Since it is required to be m or less, it is necessary to regulate the movement of the belt in the lateral direction within a predetermined range, and various belt deviation and meandering control methods have been proposed.

In such a belt deviation and meandering control method, there is a steering system for steering the belt support roll according to the deviation and meandering of the belt. For example, in Japanese Patent Laid-Open No. 3-288167, a drive for driving an endless belt is provided. The belt is supported by a roll and a support roll that supports the roll and a correction roll that adjusts the belt tension.
The deviation or the meandering is detected by detecting with a detection means such as D (charge coupled device), and the rotation center axis of the correction roll is moved based on the output signal of the detection means. I am trying to correct the belt deviation and meandering by adjusting. When moving the rotation center axis of the correction roll, the movement that attempts to move the rotation center axis of the correction roll in a direction perpendicular to the normal direction of the belt wrap angle that is the winding angle of the belt wound around the correction roll The movement in the soft axis direction is called, and the movement in the normal direction of the belt wrap angle is called the movement in the hard axis direction.

[0007]

However, according to the conventional color image forming apparatus, when the central axis of rotation of the correction roll is moved by the steering method, if the moving direction is the soft axis direction, the control gain is increased. Is small and the tension hardly changes. On the other hand, when the moving direction is hard axis, the control gain is large and the tension changes greatly. When the roll separation / contact, the interaction when the registration roll or the fuser roll nips the paper, the change in the nip pressure with the photoconductor at the primary transfer portion, the change in the electrostatic attraction force, etc.), the force component in the lateral direction of the disturbance Depending on the situation, the intermediary transfer belt is slanted or meandered. On the other hand, various systems for controlling the lateral movement of the intermediate transfer belt are conceivable, but the mechanism is complicated and the cost is increased, and the maintenance is difficult. For example, if the edge of the intermediate transfer belt is regulated by a guide, Damages the transfer belt and shortens its life (belt life). Therefore, it is an object of the present invention to provide a color image forming apparatus that prevents the intermediate transfer belt from being damaged and suppresses the shortening of the life.

Another object of the present invention is to provide a color image forming apparatus capable of suppressing the deviation of the belt and the meandering without increasing the cost and preventing the color shift.

[0009]

The present invention achieves the above objects.
Image-bearing carrier supported by multiple rolls to
Color image by superposing multiple color toner images on top of each other.
In a color image forming apparatus for forming an image, the image bearing
The support frame of the holding belt is fixed without a spring member.
Is constant, lateral and belt guide member, the image bearing belt to restrict the movement of the contact with the edge of the image bearing belt to the edge side of the lateral direction of the image bearing belt
Moving means for moving in a direction, the moving amount of the lateral direction of the image bearing belt, said image bearing belt the Berutoga
A movement amount detecting means for detecting the distance from the id member ,
Based on the moving amount detected by the moving amount detecting means,
A calculating means for serial image bearing belt to be deployed calculate the pressing force applied from the belt guide member in accordance with the moving amount, the calculating
Controlling the moving means based on the calculation result of the means
The edge of the image bearing belt to
Always in contact with the id member, to provide a color image forming apparatus characterized by a control means for setting the pressing force in a predetermined range.

[0010]

According to the color image forming apparatus of the present invention, the belt guide member regulates the lateral movement of the belt by coming into contact with the edge of the image carrying belt. When the image carrying belt rotates, the detecting means detects the amount of lateral movement of the belt, and the calculating means calculates the pressing force applied to the edge based on the amount of movement. The calculated pressing force is compared with the reference pressing force by the calculating means to calculate the difference between the two. According to the difference, the control means, for example, tilts the support roll of the image bearing belt to move the image bearing belt in the lateral direction, and sets the pressing force received from the belt guide member that increases or decreases according to the movement amount to the reference value. To do. As a result, even if a lateral force is applied to the image bearing belt due to a disturbance, the belt guide member prevents the lateral displacement, and since the pressing force is suppressed to a certain value or less, the belt is prevented from being damaged. The life is not reduced.

[0011]

First Embodiment A color image forming apparatus of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of a color image forming apparatus using an intermediate transfer belt. As shown in FIG. 1A, this color image forming apparatus is based on an image input device 1 for scanning an original image and an image signal scanned by the image input device 1 and processed by an image processing device (not shown). And an image output device 8 for printing on a recording sheet.

The image input device 1 includes a lamp 3 for irradiating a document (not shown) placed on a transparent document table 2 with light.
And the reflection mirrors 4 and 5 that reflect the reflected light from the original,
A lens 6 that focuses the reflected light from the mirror 5, and a lens 6
And a charge-coupled device (CCD) 7 on which the light focused by is incident. The charge-coupled device 7 simultaneously separates the incident light into R, G, and B signals and reads them.

The image output device 8 separates the R, G and B signals obtained by the image input device 1 into Y (yellow), M (magenta), C (cyan) and BK (black) and stores them. IPS (Image Proses) not shown
9A of laser light source based on image data obtained by performing image processing with IPS
Oscillates the modulated laser light, and the polygon mirror 9B
An image writing device 9 which is deflected by a mirror, and a mirror 10 which reflects a laser beam emitted from the image writing device 9 in a scanning direction,
The photosensitive drum 11 to which the laser light reflected by the mirror 10 is irradiated and the developing materials of the toners of Y, M, C, and BK are arranged at intervals of 90 degrees in the circumferential direction, and are rotated at the time of development to obtain respective colors. And a developing unit 12 of a rotary type that supplies the corresponding toner to the surface of the photosensitive drum 11, and a charger 13 around the photosensitive drum 11 and a photosensitive member for removing the toner remaining on the photosensitive drum 11. A body cleaner 14 is arranged.

Further, below the photosensitive drum 11, there is provided an intermediate transfer belt device 16 having a polyimide intermediate transfer belt 15 onto which the toner image formed on the drum surface is transferred. As other belt materials, polyethylene terephthalate, polycarbonate, polyimide, and polymer materials such as polyvinylidene fluoride, and metal films such as aluminum and stainless films are used. The intermediate transfer belt 15 is driven by a drive roll 17, and the tension roll 18 and the secondary transfer backup roll 19 are driven.
Supported by. The drive roll 17, the tension roll 18, and the secondary transfer backup roll 19 are configured to rotate an integral number when the intermediate transfer belt 15 makes one revolution.

The intermediate transfer belt device 16 includes a primary transfer corotron 20 provided at a primary transfer point of the intermediate transfer belt 15, a belt cleaner 21 provided adjacent to the drive roll 17, and an optional intermediate transfer belt 15. Belt reference position detection sensor (hereinafter, referred to as sensor) 2 for detecting a reference position mark 15A (described later) provided at the position 2
At the secondary transfer position where the secondary transfer backup roll 19 is located, the recording paper (not shown) supplied from the paper transport device (tray) 23 through the paper supply roll 24 is transferred to the secondary transfer roll. The toner image transferred to the intermediate transfer belt 15 by being nipped by 25 is transferred to the recording paper. The recording paper on which the toner image has been transferred is conveyed to the fixing device 26 and the toner image is fixed.

Around the tension roll 18 is shown in FIG.
As shown in (B), a bearing 28A that is rotatably supported by a frame 28 (29) that serves as a support frame for the intermediate transfer belt 15, and a rotating shaft 18A that is supported by the bearing 28A and rotates.
Is provided with a cam 31 driven by a cam drive motor and a spring 32 stretched between a rotary shaft 18A and a hook 28C provided on the frame 28.

FIG. 2 is a perspective view of an intermediate transfer belt device 16 having a tension roll 18 having a roll steering device, and a drive roll 17 for driving the intermediate transfer belt 15 is not shown via a driving force transmission gear 27 or the like. The driving force is transmitted from the motor. A belt can also be used as another means of transmitting driving force. Alternatively, a direct drive system using a motor may be used.

The intermediate transfer belt 15 has a triangular reference position mark 15 on the side of the surface on which the color toner image is transferred.
Have A. In forming the reference position mark 15A, any means such as printing, pasting, and punching may be used. The reference position mark 15A has a predetermined gradient with respect to the lateral direction of the intermediate transfer belt 15, and is detected by a sensor 22 provided near the intermediate transfer belt 15.

The rotating shaft 18A of the tension roll 18 is rotatably supported by frames 28 and 29 provided along both ends of the intermediate transfer belt 15 via bearings 28A and 29A. The bearing 28A, 29A has a frame 28,
With respect to 29, the one that does not impair the rotatability even if the support angle of the rotating shaft 18A changes is used.

Bearing 28A for supporting one end of rotating shaft 18A
Are movably supported in an elliptical direction by an elliptical portion 28B formed on the frame 28. Here, the oval portion 28B may have another shape as long as it can guide the bearing 28A. Further, the rotary shaft 1 protruding from the bearing 28A
A cam 31 driven by a cam driving motor 30 is in contact with 8A. A stepping motor, a DC motor, or the like can be used as the cam driving motor 30.

The cam 31 is constructed so that the cam surface is always in contact with the rotary shaft 18A by a spring 32 stretched between a hook 28C provided on the frame 28 and the rotary shaft 18A. By being driven by the motor 30, the bearing 28A is moved in the oval direction of the oval portion 28B according to the amount of eccentricity.

On the other hand, the other end of the rotary shaft 18A is connected to the frame 29.
It is rotatably supported by a bearing 29A provided on the. A belt guide 29B is fixed to the side surface of the frame 29 on which the tension roll 18 is arranged, and the belt guide 29B is arranged so as to come into contact with the edge of the intermediate transfer belt 15 conveyed along the outer periphery of the tension roll 18. ing.

FIG. 3 shows a belt movement amount control section in the color image forming apparatus of the present invention, which is a sensor 22 for detecting the reference position mark 15A provided on the intermediate transfer belt 15.
Of the belt reference position of the intermediate transfer belt 15 based on the measurement data, and the belt movement amount detection unit 34 for detecting the movement amount of the intermediate transfer belt 15 in the lateral direction based on the measurement data; A correction amount calculation unit 3 that calculates a correction amount in the lateral direction of the intermediate transfer belt 15 on the tension roll 18 based on the movement amount.
5 and a control unit 36 that drives the cam drive motor 30 based on the correction amount calculated by the correction amount calculation unit 35. The correction amount calculation unit 35 stores a memory 35A that stores data representing the relationship between the belt movement amount in the lateral direction and the pressing force that acts on the edge of the intermediate transfer belt, and the memory 3A.
5A, a reading unit 35B for reading data, and a memory 35
A comparison unit 35 that performs a comparison calculation between the data read from A and the belt movement amount detected by the belt movement amount detection unit 34.
It is composed of C.

The operation of the color image forming apparatus of the present invention having the above construction will be described below.

In the color image forming apparatus, when an image forming start is instructed, the laser light source 9A of the image writing apparatus 9 outputs laser light corresponding to the first color image. This laser light is deflected in the scanning direction by the polygon mirror 9B, then reflected by the mirror 10 and irradiated on the photoconductor drum 11 charged by the charger 13, thereby forming an electrostatic latent image. This electrostatic latent image is developed with the corresponding color toner in the developing device unit 12 located in the rotation direction of the photosensitive drum 11. Next, the developed color toner image is conveyed to the primary transfer point where the primary transfer corotron 20 is provided and transferred to the intermediate transfer belt 15.

The intermediate transfer belt 15 is a photosensitive drum 11.
It is driven by the drive roll 17 so as to rotate in synchronism with, and an image is written on the photosensitive drum 11 when the reference position mark 15A is detected by the sensor 22. The full-color image formed by repeating the above operation for each color and transferring the color toner images multiple times is
By the support roll 19 and the secondary transfer roll 25 at the secondary transfer point, via the recording paper guide chute 33,
It is transferred onto the recording paper 24A supplied by the paper transport roll 24.

FIG. 4 shows the reference position mark 1 provided on the intermediate transfer belt 15 in the above image forming process.
5A shows the process of being detected by the sensor 22, and when the intermediate transfer belt 15 rotates in the belt rotation direction and the reference position mark 15A provided on the belt surface crosses the sensor 22, the sensor 22 is at the center line 37. The length L (L (L) of the reference position mark 15A during n rotation and (n + k) rotation
_A detection signal based on _n and L _{n + k} ) is output to the belt movement amount detection unit 34. Here, n and k are positive integers.

The belt movement amount detecting section 34 calculates the movement amount ΔW per one rotation from the nth rotation to the (n + k) th rotation of the intermediate transfer belt 15 by the crystal clock incorporated based on the detection signal input. Calculate by formula. ΔW = [(L _n −L _{n + k} ) / k] · a a is a proportional constant and is appropriately determined according to the shape and size of the reference position mark 15A.

Next, by dividing the lateral movement amount ΔW of the intermediate transfer belt 15 by the length L _B of the belt cycle, the lateral movement amount WR (walk rate at the reference length of the intermediate transfer belt 15). ). The length L _B of the belt cycle is obtained by the product of the interval time of the detection timing of the reference position mark 15A and the average speed of the intermediate transfer belt 15. As another method, a detection unit such as an encoder may be provided on the drive roll 17 and the like, and the reference length with respect to the length L of one belt cycle may be obtained based on the reference position signal of the detection unit.

FIG. 5 shows the relationship between the sensing difference in one cycle of the intermediate transfer belt 15 and _{(L n -L n + k)} / k and WR, is detected difference _{(L n -L n + k)} / k It is shown that the WR linearly increases as it increases. On the other hand, has a negative as well WR if detected difference _{(L n -L n + k)} / k becomes negative, which means that the movement direction of the intermediate transfer belt 15 is reversed ing.

FIG. 6 shows contact between the WR and the intermediate transfer belt 15.
Is applied to the belt guide 29B shown in FIG.
Shows the relationship of pressure (hereinafter referred to as edge force),
Edge force EF₁~ EF₂Is the allowable range and EF
₀Is the target reference value and EF₃Is the current walk
Rate WR₃Is a calculated value based on. Edge force group
Quasi value EF₀Walk rate reference value WR for₀Currently
Walk rate WR ₃Control to approximate.

5 and 6 are stored in the memory 35A.
Therefore, the amount of belt movement L_n-L _{n + k}To WR₃Is profitable
WR₃Is obtained, WR₃Depending on the edge
Source EF₃Is obtained. This Edge Force EF₃Read by
When read by the output unit 35B, this edge focus
EF₃Is the reference value EF of the edge force₀And comparison section 35
A comparison operation is performed in C. Criteria for this edge force
Value EF₀Depends on the configuration of the device or other conditions
It can be arbitrarily determined.

The calculation result in the comparison section 35C is the edge force correction amount. For example, the edge force data EF ₃ according to WR ₃ in FIG.
It is larger than ₀ , and in such a case, a negative correction amount for reducing the edge force is given and output to the control unit 36 that controls the cam driving motor 30. The control unit 36 generates a pulse according to the correction amount, and the cam driving motor 30
To drive.

FIG. 7 shows a mechanism for adjusting the position of the rotary shaft 18A of the tension roll 18 by the rotation of the cam driving motor 30, and the pulses supplied according to the correction amount of the intermediate transfer belt 15 in the lateral direction. When the cam driving motor 30 rotates on the basis of the above, the cam 31 rotates and moves the rotating shaft 18A of the tension roll 18 in the A direction according to the eccentricity of the cam. For example, the rotating shaft 18A
Is moved in the A direction, the tension roll 18 and the rotating shaft 18A are tilted with the bearing 29A as a fulcrum as shown by the alternate long and short dash line.

When the intermediate transfer belt 15 rotates in this state, when the intermediate transfer belt 15 passes through the tension roll 18 having an inclination, the direction B shown in the figure, that is, the edge of the intermediate transfer belt 15 is removed from the belt guide 29B. Slide away.

Therefore, as shown in FIG. 8, the intermediate transfer belt 15 moves from the belt guide 29B to an excessive edge force E.
Even if F _E is received, the edge force can be decreased while converging by adjusting the inclination of the tension roll 18 to approach the target reference value EF ₀ .

As described above, when the intermediate transfer belt 15 is always in contact with the belt guide 29B and a predetermined edge force is generated, even if the intermediate transfer belt 15 receives a disturbance, the occurrence of deviation or meandering is suppressed. To be done.
In this embodiment, the width of the intermediate transfer belt 15 is 300 to 50.
Under the conditions of ₀ mm and a thickness of 50 to 300 μm, the control target value EF ₀ of the edge force was set to 6N and 2 to 10N was set as the allowable range EF _{1 to} EF ₂ .

When the walk rate WR is measured in the above operation, the movement amount ΔW cannot be measured if the edge of the intermediate transfer belt 15 is already in contact with the belt guide 29B. Therefore, by rotating the intermediate transfer belt 15 in the reverse direction, the intermediate transfer belt 15 is separated from the belt guide 29B, and the intermediate transfer belt 15 is again rotated in the forward direction. By doing so, the walk rate WR can be obtained.

Further, the reference position mark 15A is detected by the sensor 22 during the reverse rotation of the intermediate transfer belt 15, and the movement amounts ΔW and W are detected based on the detection differences L _n and L _{n + k} at this time.
You may ask for R.

As described above, the operation of correcting the deviation or meandering of the intermediate transfer belt 15 by detecting the reference position mark 15A by the sensor 22 rotates only the intermediate transfer belt 15 when the main switch of the color image forming apparatus is turned on. Alternatively, only the intermediate transfer belt 15 may be rotated at the end of the preheating operation. The above operation is shown in the flowchart of FIG.

FIG. 10 is a perspective view showing another embodiment of the intermediate transfer belt device 16 in the color image forming apparatus of the present invention. The rotating shaft 18A of the tension roll 18 has a bearing 37 and a supporting shaft 38 as a center. The arm 39 is supported by an arm 39 that is steered to the front, and the arm 39 tilts the rotary shaft 18A when the rotary roller 40 provided on the rear surface abuts and moves in the AB direction. The configuration of the other parts is common, and therefore the description is omitted.

As described above, by appropriately controlling the edge force applied from the intermediate transfer belt 15 to the belt guide 29B, the intermediate transfer belt 15 is prevented from cracking or being deformed, and the life of the intermediate transfer belt 15 is shortened. Can be prevented. Further, the stability of the intermediate transfer belt 15 against disturbance is improved.

[0044]

Second Embodiment FIG. 11 shows a color image forming apparatus in which a photosensitive belt 40 is driven by a driving roll 41 and a tension roll 42 instead of the photosensitive drum 11 in the first embodiment. Overlapping description of portions having the same configurations and functions as those of the first embodiment will be omitted. In this color image forming apparatus, the intermediate transfer belt device 16 having the roll steering device described in the first embodiment can be applied.

[0045]

Third Embodiment FIG. 12 shows that a multicolor toner image is formed by superposing toner images of respective colors on a photosensitive belt 40 driven by a driving roll 41 and a tension roll 42.
1 illustrates a color image forming apparatus that is configured to transfer onto a recording sheet at once. The description of the other parts having the same structures as those of the first and second embodiments will be omitted. In this color image forming apparatus, the intermediate transfer belt device 16 having a roll steering device can be applied to the tension roll 18.

In this way, the difference in the detection length of the reference position mark 15A provided on the intermediate transfer belt 15 L _n -L
By calculating _{n + k} to obtain the walk rate WR and controlling the edge force obtained based on this walk rate WR, the life of the intermediate transfer belt 15 is prevented from being shortened and the quality of the transferred image is improved. Can be realized.

In the first to third embodiments, when the shaft is moved to tilt the tension roll 18,
The moving direction of the shaft is not limited to the direction described in the embodiment.

[0048]

As described above, according to the color image forming apparatus of the present invention, the pressing force received by the image bearing belt from the belt guide is moved in the lateral direction to the predetermined pressing force. The color image quality can be improved by improving the rotational stability of the intermediate transfer belt against disturbance, preventing the belt life from decreasing, and suppressing the belt deviation and meandering without increasing the cost.

[Brief description of drawings]

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

FIG. 2 is a perspective view showing an intermediate transfer belt device having a roll steering device.

FIG. 3 is an explanatory diagram showing an operation of the color image forming apparatus of the present invention.

FIG. 4 is an explanatory diagram showing a detection operation of the reference position mark 15A in the color image forming apparatus of the present invention.

FIG. 5 is a reference position mark 15A detected by a sensor 22.
It is an explanatory view showing a sensing length relationship of the difference L _n -L _n + _k and WR of.

FIG. 6 is an explanatory diagram showing a relationship between WR and edge force.

FIG. 7 is an explanatory diagram showing the operation of the roll steering device.

FIG. 8 is an explanatory diagram showing a state of edge force control based on an operation of a roll steering device.

FIG. 9 is a flowchart showing a process of edge force control by the roll steering device.

FIG. 10 is a perspective view showing a modified example of the roll steering device.

FIG. 11 is an explanatory diagram showing another embodiment of the color image forming apparatus of the present invention.

FIG. 12 is an explanatory diagram showing another embodiment of the color image forming apparatus of the present invention.

[Explanation of symbols]

1 image input device, 2 document table, 3 lamps, 4 ...
5 reflection mirror 6 lens, 7 charge coupled device, 8 image output device, 9 image writing device 9A laser light source, 9B polygon mirror 10 reflection mirror, 11 photoconductor drum 12 developing device unit, 13 charger 14 photoconductor cleaner, 15 Intermediate transfer belt,
15A Reference position mark 16 Intermediate transfer belt device, 17 Drive roll 18 Tension roll, 19 Support roll, 20
Primary transfer corotron 21 Belt cleaner, 22 Belt reference position detection sensor 23 Paper transport device, 24 Paper supply roll, 25
Secondary transfer roll 26 Fixing device, 27 Driving force transmission gear, 28.2.
9 frame 28A bearing, 28B oval portion, 28C hook 29A bearing, 29B belt guide 30 cam drive motor, 31 cam, 32 tension spring 33 recording paper guide chute, 34 belt movement amount detection unit 35 correction amount calculation unit, 35A memory , 35B Read-out part 35C Comparison part, 36 Control part 37 Bearing, 38 Support shaft, 39 Arm, 40
Rotating roller

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masakazu Kobayashi Masakazu Kobayashi 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd.Ebina Business Office (72) Kimito Omori 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd.Ebina Co., Ltd. On-site (72) Inventor Jun-ichi Murakami 2274 Hongo, Ebina-shi, Kanagawa Fuji Zerox Co., Ltd. On-site Ebina (56) References JP-A-4-159911 (JP, A) JP-A-6-64773 (JP, A) ) JP-A-6-254012 (JP, A) JP-A-6-40590 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/01-15/01 117 G03G 15 / 16 G03G 21/00 350-352 G03G 21/16

Claims (3)

(57) [Claims] 1. A color image forming apparatus for forming a color image by superposing a plurality of color toner images on an image carrying belt supported by a plurality of rolls, wherein a spring member is interposed in a supporting frame of the image carrying belt.
A belt guide member that is fixed without contacting the edge of the image bearing belt and restricts the movement of the image bearing belt toward the edge side in the lateral direction, and a moving unit that moves the image bearing belt in the lateral direction.
And the lateral movement amount of the image bearing belt,
A moving amount detecting means for detecting the lifting belt to be apart from the belt guide member, the movement amount detecting means before <br/> Kizo carrier belt on the basis of the movement amount detected in response to the amount of movement calculating means for exiting calculate the pressing force applied from the belt guide member, controlling the moving means based on the calculation result of the calculating means
The edge of the image bearing belt by
A color image forming apparatus comprising: a control unit that constantly contacts the belt guide member and sets the pressing force within a predetermined range. 2. The calculation means is a memory that stores the relationship between the movement amount and the pressing force, a reading means that reads the pressing force according to the movement amount from the memory, and a reading means that is read from the memory. The control unit includes a comparing unit that calculates the difference by comparing the pressing force with the reference pressing force, and the control unit tilts the support roll of the image supporting belt based on the difference to move the image supporting belt to the lateral direction. The color image forming apparatus according to claim 1, further comprising a tilting unit that moves in a direction. 3. The color image forming apparatus according to claim 2, wherein the tilting unit includes a cam roller rotated by a motor, and a bearing unit tilted by the cam roller with one point of the center axis of the support roll as a fulcrum.