JPH05301652A - Image forming device - Google Patents

Abstract

PURPOSE:To set the meandering speed of an endless belt into the appropirate value so as to prevent the generation of an ill effect such as color dislocation in the lateral direction. CONSTITUTION:The top dead center of a meandering correction cam 63 can be selected among three kinds (POS. A-C), and the bottom dead center is also selected among three kinds (POS. D-F). The respective offset speeds of an intermediate transfer belt 12 in the directions (a, b) are detected on the basis of the detection results of belt end part detecting sensors 72a, 72b. On the basis of these offset speeds, the rotation of a stepping motor 69 is controlled to select the top dead center and bottom dead center positions of the meandering correction cam 63.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image using an endless belt, and more particularly to an image forming apparatus having means for correcting the meandering state of the endless belt.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus of this kind, a color forming a multicolor image by using an intermediate transfer member composed of an endless belt as disclosed in JP-A-63-11967. There is an image forming apparatus. In this color image forming apparatus, image forming units of yellow, magenta, and cyan are arranged in a line on an intermediate transfer belt (endless belt).

In this conventional image forming apparatus, since an image forming unit is provided for each color, the speed of image formation can be increased, and the use of the intermediate transfer belt simplifies the transfer mechanism. For this reason, it has advantages that it can be used for a wide range of recording media, and that it is possible to perform long copying of a size larger than a standard size. As a material of the intermediate transfer belt, a material such as a film having a small mechanical elongation is selected for the purpose of preventing color shift.

By the way, when such an intermediate transfer belt is used, in general, meandering occurs when the belt is driven, and it is necessary to correct this meandering. Conventionally, as a method for correcting the meandering, for example, a method in which the meandering of the belt is suppressed by a roller with a collar and an auxiliary pressure contact roller (JP-A-59-184379), a guide groove provided on the roller and a guide rib provided on the belt are used. There is a method (Japanese Patent Laid-Open No. 2-27383) for suppressing the meandering. However, all of these methods have a problem in that the end portions of the belt or the ribs are subjected to an excessive force due to the force of meandering, which adversely affects the life of the belt. In addition, there is a risk of wrinkles, which naturally limits the selection range (material, size) of the belt.

For this reason, belt end detection sensors are provided at both ends of the intermediate transfer belt, and when one end of the belt that is about to move in one direction is detected, the roller on which the belt is stretched is detected. Among these, one or more rollers (meandering correction rollers) are changed in alignment (position) to move the belt in the opposite direction, and when the other belt end is detected, the position of the rollers is changed in the opposite direction. The method of making it proposed is proposed. After that, by repeating this operation, image formation is performed while the intermediate transfer belt is meandering in a certain range.

However, in this meandering correction method, since the meandering direction of the intermediate transfer belt is changed, when the alignment of the meandering correction roller is changed, the tension of the belt abruptly changes and the belt momentarily expands and contracts. .. Therefore, there is a problem in that color misregistration occurs in the image process direction (paper feed direction). Accordingly, the same applicant as the present applicant has proposed, on the same date as the present application, an image forming apparatus capable of preventing a change in tension of the intermediate transfer belt at the time of changing the meandering direction and preventing color misregistration of an image.

[0007]

However, although this image forming apparatus can prevent color misregistration in the process direction, it has a problem that the meandering speed of the intermediate transfer belt cannot be predicted in advance. In other words, the meandering of the intermediate transfer belt is influenced by the finished state of the belt itself, the alignment (position) of the rollers that stretch the belt, and the rotation direction of the belt. Is extremely difficult to predict quantitatively. Therefore, the amount of change in the alignment of the roller for correcting the meander tends to be excessively set, and in such a case, the meandering speed of the belt becomes too fast, and when the multiple transfer is performed,
For example, when an image transferred by the image forming unit is overlaid with the image by the next image forming unit, there is a problem that a significant color shift occurs between the four image forming units in the lateral direction (width direction). ..

The present invention has been made in view of the above problems, and an object thereof is to provide an image forming apparatus capable of preventing the occurrence of harmful effects such as lateral color misregistration by setting the meandering speed of the endless belt to an appropriate value. To provide.

[0009]

SUMMARY OF THE INVENTION An image forming apparatus according to the present invention comprises an endless belt, a rotation driving means for applying a predetermined tension to the endless belt to drive the endless belt to rotate, and a meandering for correcting the meandering state of the endless belt. A correction means, a meandering speed detection means for detecting the meandering speed of the endless belt in the lateral direction by the meandering correction means, and a correction degree for adjusting the correction degree by the meandering correction means according to the detection result of the meandering speed detection means. And adjusting means.

In this image forming apparatus, the endless belt is rotationally driven while being given a predetermined tension by the rotational driving means, and accordingly, processing such as image formation is performed. The meandering condition that occurs when the endless belt rotates is corrected by the meandering correcting means. Here, the meandering speed detecting means previously detects the meandering speed of the endless belt in the lateral direction, and the correction degree adjusting means adjusts the correction degree of the meandering state based on the detection result. By performing the adjustment of the correction degree while the apparatus is warming up, the meandering correction is performed at an appropriate speed at the time of image formation, and as a result, it is possible to prevent adverse effects such as color misregistration of the image in the lateral direction.

More specifically, the image forming apparatus according to the present invention includes an endless belt, a plurality of rollers, a rotation driving unit for applying a predetermined tension to the endless belt to rotate the endless belt, and the endless belt. A rotatable meandering correction roller, a pair of belt end portion detection sensors for detecting both ends of the endless belt, and a plurality of top dead center positions and a plurality of top dead center positions respectively arranged at one end of the meandering correction roller shaft. A meandering correction cam having a dead center position, and a meandering correction means for correcting the meandering state of the endless belt, which includes a rotation drive mechanism for rotationally controlling the meandering correction cam based on the detection result of the belt end portion detection sensor, A meandering speed detecting means for detecting the meandering speed in the lateral direction of the endless belt by the meandering correcting means based on the detection result of the belt end part detecting sensor; Correction degree adjusting means for adjusting the degree of correction by the meandering correcting means by switching the respective set positions of the top dead center and the bottom dead center of the meandering correcting cam according to the detection result of the traveling speed detecting means. ..

In this image forming apparatus, the meandering speed of the endless belt is detected based on the detection result of the belt end part detection sensors arranged at both ends of the endless belt, and the rotation of the meandering correction cam is controlled based on the detection result. Then, the set positions of the top dead center and the bottom dead center are switched.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 5 shows the structure of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 11 forms a four-color image by a xerographic process using an intermediate transfer method, and an intermediate transfer belt 12 is arranged at the center of the image forming apparatus 11. This intermediate transfer belt 1
2 is formed by an endless belt, and is stretched in a substantially isosceles triangular shape with the right side in the figure as the apex and the left side in the figure as the bottom side. Two image forming portions 13 and 14 are arranged in parallel on the upper inclined surface 12a of the intermediate transfer belt 12, while two image forming portions 15 and 16 are arranged in parallel on the lower inclined surface 12b. The image forming unit 13 is yellow,
The image forming unit 14 is magenta, the image forming unit 15 is cyan,
The image forming section 16 forms a black color image, respectively.

The image forming units 13 to 16 respectively include photosensitive drums 19Y, 19M, 19C and 19B rotatably mounted on a housing (not shown). These photoconductor drums 19Y, 19M, 19C and 19B rotate at a predetermined speed in the directions indicated by the arrows, and around each of them, the charging corotrons 20Y, 20M, 20C and 20B are arranged counterclockwise in the figure. , Image writing units 21Y, 21M, 21C, 21B, developing units 22Y, 2
2M, 22C, 22B, transfer corotron 23Y, 23
M, 23C, 23B, cleaning devices 24Y, 24
M, 24C and 24B are arranged.

Charging corotron 20Y, 20M, 20C,
20B are photosensitive drums 19Y, 19M, and 19 respectively.
The surface of C and 19B is uniformly charged. The image writing units 21Y, 21M, 21C and 21B are composed of, for example, an image bar, an image scanner, etc., and are disposed on the surfaces of the photosensitive drums 19Y, 19M, 19C and 19B charged by the charging corotrons 20Y, 20M, 20C and 20B. It is designed to form a latent image. Developing device 22Y, 22
M, 22C and 22B are image writing units 21Y and 21M,
The electrostatic latent image formed by 21C and 21B is developed with toner to form a visible image. Transfer Corotron 2
3Y, 23M, 23C, and 23B are developing units 22Y and 22Y, respectively.
The image visualized by 22M, 22C and 22B is electrostatically transferred to the intermediate transfer belt 12. The cleaning devices 24Y, 24M, 24C and 24B remove the toner remaining on the surfaces of the photoconductor drums 19Y, 19M, 19C and 19B after the transfer.

The upper image forming portions 13 and 14 are supported by the frame 17 except for the transfer corotrons 23Y and 23M, and the image forming portions 15 and 16 are supported by the frame 18 except for the transfer corotrons 23C and 23B, which are unitized respectively. Has been done. The frames 17 and 18 can be pulled out to the right side (direction of arrow A) in the figure along rails 25 and 26 provided on the main body. Intermediate transfer belt 12
Is rotated in a clockwise direction in the drawing at a constant speed by a driving roller 28 that rotates around a shaft portion 27 connected to a driving motor (not shown). Shaft 2
7 further supports the ends of the three frames 29 to 31. The position of the central frame 29 is fixed by shafts 54 and 55. Ends of the upper frame 30 and the lower frame 31 are supported by shafts 27 via bearings and are rotatable. Rollers 32, 34, and 35 are attached to the upper frame 30, respectively. The rollers 3 are respectively provided on the lower frame 31.
3, 35, 36 are attached. A roller 38 is attached to the tip of the central frame 29. The intermediate transfer belt 12 is stretched between the rollers 32 to 38 and the driving roller 28. Further, a tension applying roller 39 is provided inside the intermediate transfer belt 12,
As a result, an appropriate tension is applied to the intermediate transfer belt 12.

A meandering correction roller 40 is arranged between the roller 38 and the roller 32 to correct the meandering state of the intermediate transfer belt 12 caused by the rotation as described later. An intermediate transfer belt cleaning unit 41 is provided outside the intermediate transfer belt 12 so as to face the roller 38, and cleans the surface of the intermediate transfer belt 12 after transfer. In addition, in the upper frame 30,
The transfer corotrons 23Y and 23M are attached so as to correspond to the positions when the photoconductor drums 19Y and 19M are attached. On the other hand, transfer corotrons 23C and 23B are attached to the lower frame 31 so as to correspond to the positions when the above-described photosensitive drums 19C and 19B are attached.

A paper feed tray 42 is disposed below the image forming units 15 and 16, and recording paper 43 is stacked. The paper 43 is taken out one by one by the paper feed roller 44, and then conveyed by the conveyance roller 46 along the conveyance path 45. When the sheet 43 conveyed by the conveying roller 46 reaches the position of the registration roller 47, its progress is temporarily stopped, and the conveying timing is adjusted so as to be synchronized with the rotation of the intermediate transfer belt 12. A transfer corotron 48 is disposed at the lower end of the intermediate transfer belt 12 so as to face the roller 33 attached to the lower frame 31. Paper 4
3 is fed between the transfer corotron 48 and the intermediate transfer belt 12. The image transferred onto the intermediate transfer belt 12 by the photosensitive drums 19Y, 19M, 19C and 19B is transferred onto the paper 53 by the transfer corotron 48.
It is designed to be transferred by. The paper 43 on which the image is transferred is sent to the fixing unit 50 by the carrying unit 49. The fixing unit 50 is composed of a heating roller 51 and a pressing roller 52, and transfers the transferred image onto the paper 43.
It is designed to heat-fix. The paper 43 on which the image has been fixed is discharged by a discharge roller 53 to a discharge unit (not shown).

Next, the overall operation of the image forming apparatus 11 will be described.

In the image forming apparatus 11, the drive roller 28 is rotated by the drive of a drive motor (not shown), and the intermediate transfer belt 12 is rotated in the clockwise direction in the figure at a predetermined speed. On the other hand, in the image forming unit 13, an image is formed on the surface of the photoconductor drum 19Y by the image writing unit 21Y, this image is developed by the yellow toner in the developing unit 22Y, and then this developed image is further developed. Is transferred to the intermediate transfer belt 12 by the transfer corotron 22Y. Thereafter, similarly, images of magenta in the image forming unit 14, cyan in the image forming unit 15, and black in the image forming unit 16 are sequentially transferred to the intermediate transfer belt 12. This intermediate transfer belt 1
Simultaneously with the transfer of the image to the sheet 2, the paper 43 is sent from the paper feed tray 42 to the conveyance path 45 by the paper feed roller 44, and the arrival timing at the transfer portion is adjusted by the registration roller 47. The paper 43 whose timing is adjusted is
The image is fed between the transfer corotron 48 and the intermediate transfer belt 12, and the above-described four color images are transferred. The sheet 43 on which the image is transferred is conveyed to the fixing unit 50 by the conveying device 49, and the heating roller 5 is conveyed in the fixing unit 50.
The image is heat-fixed by passing between 1 and the pressing roller 52. The paper 43 on which the image is fixed is discharged by a discharge roller 53 to a discharge tray (not shown). on the other hand,
After the image is transferred onto the paper 43, the intermediate transfer belt cleaning unit 41 scrapes off the residual toner on the surface of the intermediate transfer belt 12.

FIG. 1 shows a concrete structure of a meandering correcting mechanism 60 including the meandering correcting roller 40.

One end of the shaft 40a of the meandering correction roller 40 is rotatably supported at a roller fulcrum 61. On the other hand, a cam follower 62 is attached to the other end of the shaft 40 a of the meandering correction roller 40. The cam follower 62 is adapted to follow the rotation of the meandering correction cam 63. The meandering correction cam 63 is attached to the meandering correcting shaft 64.

The cam shape of the meandering correction cam 63 is, for example, as shown in FIG. The top dead center of the meandering correction cam 63 can be set at three positions (POS.A to C), and the bottom dead center can be set at three positions (POS.D to F).

Cams 70a and 70b for detection switches are attached to one end of the meandering correction shaft 64. Cam 7
0a and 70b are provided with convex portions at positions different from each other by 180 degrees, and a top dead center detection switch 71a and a bottom dead center detection switch 71b are arranged at positions facing the cams 70a and 70b. Top dead center detection switch 7
1a is for detecting whether the meandering correction roller 40 is at the top dead center. The bottom dead center detection switch 71b is for detecting whether the meandering correction roller 40 is at the bottom dead center. In this embodiment, as shown in the figure, when the meandering correction roller 40 is at the position of the top dead center, the convex portion of the cam 70a moves upward, and as a result, the top dead center detection switch 71.
a turns on. On the other hand, when the meandering correction roller 40 is at the bottom dead center position, the convex portion of the cam 70b moves upward, and as a result, the bottom dead center detection switch 71b is turned on.

Discs with slits 65a and 65b are attached near the other end of the meandering correction shaft 64. The slit of the disc with slit 65a has a top dead center position detection sensor 66a.
It is detected by. On the other hand, the slit of the disk with slit 65b is detected by the bottom dead center position detection sensor 66b. The top dead center position detection sensor 66a and the bottom dead center position detection sensor 66b are used to set the initialization position from among the above-mentioned three types of top dead center and bottom dead center. Here, the “initialization position” is the position (PO) at which the deviation of the intermediate transfer belt 12 is most generated at both the top dead center and the bottom dead center in this embodiment.
S. It is set to A, D).

A gear 67 is attached to the other end of the meandering correction shaft 64, and the rotational force of the stepping motor 69 is transmitted to the gear 67 via the gear 68. The stepping motor 69, together with the top dead center position detection sensor 66a and the bottom dead center position detection sensor 66b, is for searching the initialization position of each of the top dead center and the bottom dead center in the meandering correction cam 63. The stepping motor 69 rotates in the R direction (clockwise direction) in the figure to search for the initialization position of the top dead center of the meandering correction cam 63, and when the top dead center position detection sensor 66a detects the slit of the disc 65a with slits. It is supposed to stop at the same time.
On the other hand, when the stepping motor 69 recognizes the bottom dead center, the stepping motor 69 rotates in the L direction (counterclockwise direction) in the figure to search for the initialization position of the bottom dead center of the meandering correction cam 63, and the bottom dead center is reached. The position detection sensor 66b detects the slit of the disk with slit 65b and stops at the same time.

Belt end detection sensors 72a and 72b are provided on both sides of the intermediate transfer belt 12 in the width direction, respectively, so that either one end of the intermediate transfer belt 12 can be detected when the belt is meandering. Based on these detection signals, the meandering correction roller 40 switches the meandering correction direction.

FIG. 3 shows the construction of the meandering correction control section of the image forming apparatus 11.

The meandering correction control section has a CPU (central processing unit) 80. The CPU 80 is connected to each unit of the device via a bus line 81. Of these, R
A program for controlling the meandering correction operation and the correction degree adjustment operation is stored in the OM (read only memory) 82. The input port 83 is a detection signal output from the top dead center position detection sensor 66a, the bottom dead center position detection sensor 66b, the top dead center detection switch 71a, the bottom dead center detection switch 71b, and the belt end detection sensors 72a and 72b. Is sent to the CPU 80 through the bus line 81. The CPU 80 receives these detection signals,
Various control signals are sent to the bus line 81. The output port 84 is an interface for sending the control signal sent from the CPU 80 to the stepping motor 69.

The CPU 80 has, as shown in Table 1 below, offset directions of the intermediate transfer belt 12, time t required for each offset, and positions of the meandering correction cam 63 (POS.A to F). ) Is stored a matrix showing an appropriate relationship with. The CPU 80 uses the intermediate transfer belt 12
The time t required for deviation in both directions is measured, and the rotation of the stepping motor 69 is controlled based on the measured data. Thereby, the respective positions of the top dead center and the bottom dead center of the meandering correction cam 63 are switched, so that the intermediate transfer belt 12
The meandering speed of is set to an appropriate value.

[0032]

[Table 1]

Next, the operation of adjusting the meandering correction degree will be described. Here, it is assumed that the entire device is energized when the meandering correction cam 63 is at the position of the top dead center. That is, the top dead center detection switch 71a and the bottom dead center detection switch 71b respectively detect whether the meandering correction cam 63 is at the top dead center or the bottom dead center. Here, the top dead center detection switch 71a is turned on. Then, the detection signal is sent to the CPU 80. The CPU 80 receiving this detection signal appropriately rotates the stepping motor 69 in the counterclockwise direction in FIG. 1 in order to detect the initialization position of the top dead center of the meandering correction cam 63. The rotating force of the stepping motor 69 is the gear 6
The rotation is transmitted to the meandering correction shaft 64 and the disk with slit 65a via 8, 67, and this rotation is detected by the top dead center position detection sensor 6.
6a is detected. When the top dead center position detection sensor 66a is turned on and the detection signal is received, the CPU 80 stops the driving of the stepping motor 69. As a result, the meandering correction cam 63 is set to the initialization position (POS.A) at the top dead center. If the bottom dead center detection switch 71b is turned on when the device is energized, the CPU 80 appropriately rotates the steering motor 69 counterclockwise and stops it when the bottom dead center position detection sensor 66b is turned on. .. As a result, the meandering correction cam 63 is moved to the bottom dead center initialization position (POS.
D) will be set.

Next, the CPU 80 drives a drive motor (not shown) to rotate the intermediate transfer belt 12. here,
Since the intermediate transfer belt 12 approaches in the direction of arrow a in FIG. 1, one end of the intermediate transfer belt 12 has a belt end detecting sensor 72.
detected by b. Upon receiving the detection signal from the belt end portion detection sensor 72b, the CPU 80 starts counting by the built-in timer, and at the same time, the stepping motor 6
9 is driven, and the meandering correction cam 63 is rotated until the initialization position of the bottom dead center is reached. As a result, the intermediate transfer belt 12
Starts to shift in the direction b, which is opposite to the direction a in the figure. When the other end portion of the intermediate transfer belt 12 is detected by the belt end portion detection sensor 72a, the CPU 80
Ends the counting, and calculates the deviation time t in one direction (b direction) based on the counted value. At the same time, CPU8
In the case of 0, the next counting is started, and the offset time t in the a direction is similarly obtained.

Here, the CPU 80 compares the measured offset time t with the matrix (Table 1) stored internally for each direction and prepares for the next offset in the same direction. For example, let's say that we are now offsetting in the direction of arrow a, and
The data (measurement time) when the direction is offset is t ₁ <t <t ₂
It was. In this case, the belt end detection sensor 72
At the same time that b detects one end of the intermediate transfer belt 12, the CPU 80 sets P as the bottom dead center of the meandering correction cam 63.
OS. E is selected, the stepping motor 69 is driven to move the meandering correction cam 63 to a predetermined angle (θ ₁
Rotate + θ + θ ₄ ) clockwise. Then a
If the data when the direction is offset is t ≧ t ₂ ,
At the same time that the belt end detection sensor 72a detects the other end of the intermediate transfer belt 12, the CPU 80 determines that the POS. A is selected and the stepping motor 69 is driven to rotate the meandering correction cam 63 in the counterclockwise direction by a predetermined angle (θ ₄ + θ + θ ₁ ) in FIG. The amount of rotation of the meandering correction cam 63 is stored in the CPU 80 for each rotation direction, and subsequent operations are performed based on this stored data.

In principle, the above measurement operation is performed only once during the warm-up of the apparatus, and during normal operation, the rotation amount is controlled based on the measurement data. In order to increase the reliability, the rotation amount may be determined from the measurement results of a plurality of times, that is, the position of the meandering correction cam 63 (POS.A to F) may be selected.

As described above, in the image forming apparatus of this embodiment,
The meandering speed of the intermediate transfer belt 12 is preliminarily measured during the warm-up of the apparatus, and the meandering correction cam 63 rotation amount is determined based on the measurement result to set the meandering speed of the intermediate transfer belt 12 to an appropriate value. Therefore, even if the apparatus is operated and the image forming operation is started, the color misregistration in the lateral direction can be minimized.

The present invention has been described with reference to the examples.
The present invention is not limited to the above embodiments, but can be variously modified without departing from the scope of the invention. For example, although the endless belt is described as the intermediate transfer belt in the above-described embodiments, it can be applied to other fixing belts used in the fixing device, the photoconductor belt, the paper electrostatic attraction belt, etc. It can prevent the occurrence.

[0039]

As described above, according to the image forming apparatus of the first and second aspects, the meandering speed of the endless belt in the lateral direction is detected, and the correction degree by the meandering correction means is determined according to the detection result. I adjusted it, so
The meandering correction is performed at an appropriate speed, and it is possible to prevent the occurrence of adverse effects such as color misregistration of images in the lateral direction.

[Brief description of drawings]

FIG. 1 is a perspective view illustrating a configuration of a meandering correction unit of an image forming apparatus according to an exemplary embodiment of the present invention.

FIG. 2 is a front view for explaining initialization positions of the top dead center and the bottom dead center of the meandering correction cam in the image forming apparatus of FIG.

3 is a block diagram illustrating a configuration of a control unit in the image forming apparatus in FIG.

FIG. 4 is a cross-sectional view showing the configuration of the entire image forming apparatus.

[Explanation of symbols]

11 ... Image forming device, 12 ... Intermediate transfer belt, 60 ... Meandering correction mechanism, 62 ... Cam follower, 63 ... Meandering correction cam, 64 ... Meandering correction shaft, 66a ... Top dead center position detection sensor, 66b ... Bottom dead center position detection Sensor, 69 ... Stepping motor, 70a ... Top dead center detection switch, 71b ... Bottom dead center detection switch, 72a, 72b ... Belt end detection sensor, 80 ... CPU (central processing unit)

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[Procedure amendment]

[Submission date] February 19, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location G03G 15/20 21/00 119

Claims (2)

[Claims] 1. An endless belt, a rotation driving unit that applies a predetermined tension to the endless belt to rotate the endless belt, a meandering correction unit that corrects a meandering state of the endless belt, and the endless belt by the meandering correction unit. An image characterized by including a meandering speed detecting means for detecting the meandering speed in the lateral direction and a correction degree adjusting means for adjusting the correction degree by the meandering correcting means according to the detection result of the meandering speed detecting means. Forming equipment. 2. An endless belt, a rotation driving means including a plurality of rollers, for applying a predetermined tension to the endless belt to drive the endless belt to rotate, a meandering correction roller rotatable together with the endless belt, and both ends of the endless belt. A pair of belt end detecting sensors for detecting a portion, a meandering correction cam which is disposed at one end of the shaft of the meandering correcting roller and has a plurality of top dead center positions and bottom dead center positions, respectively, and the belt. Based on the detection result of the belt end portion detection sensor, including a rotation driving mechanism that controls rotation of the meandering correction cam based on the detection result of the end portion detection sensor, and a meandering correction unit that corrects the meandering state of the endless belt, A meandering speed detecting means for detecting the meandering speed of the endless belt in the lateral direction by the meandering correcting means, and the meandering speed detecting means according to the detection result of the meandering speed detecting means. By switching the dead point and the bottom dead center respectively set position on the corrected cam, the image forming apparatus characterized by comprising a modified adjusting means for adjusting a correction degree of the meandering correction means.