JPH1124507A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To read out a scale formed on an inner peripheral surface of a transfer belt to directly and accurately calculate a moving amount of a rotary moving portion of the transfer belt including an influence of deformation of the transfer belt itself. And a color copier that can be detected. SOLUTION: In a color copying machine provided with an endless transfer belt 2 wound around supporting rollers 3 to 7,
A scale 10 for detecting the amount of movement of the transfer belt 2 is formed on the inner peripheral surface of the transfer belt 2, and a scale 1 of the transfer belt 2 is formed.
A detector 11 for reading 0 is provided. The drive motor 9 for driving the transfer belt 2 is controlled based on the detection result of the detector 11.

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 such as a copying machine, a printer, and a facsimile, and more particularly, to an image forming apparatus such as a photosensitive belt, a transfer belt, a paper transport belt, a photosensitive drum, and a transfer drum. The present invention relates to an image forming apparatus provided with a rotating body.

[0002]

2. Description of the Related Art In an image forming apparatus provided with a rotating body for forming an image, such as the above-mentioned photoreceptor belt, the position of an image on a transfer member conveyed by the rotation portion or the transfer portion can be precisely adjusted. In order to perform this, it is required to accurately control the moving amount and the moving position of the rotary moving unit of the rotating body. However, if the rotational angular velocity of the rotating body fluctuates for some reason, the moving amount and the moving position of the rotating body of the rotating body also fluctuate, and the rotating member and the transfer material conveyed by the rotating member may be moved. It has been difficult to suppress image position errors with high accuracy.

Conventionally, in order to suppress a position error of an image due to a fluctuation in a moving speed of a rotary moving portion of the rotating body with high accuracy,
A rotary encoder is directly connected to the rotation axis of the drive roller of the endless belt-shaped rotator such as a transfer belt or a paper conveyance belt, or the rotation axis of a cylindrical member such as a photosensitive drum, and the rotation of the rotator detected by the encoder is detected. 2. Description of the Related Art An image forming apparatus that controls a rotation angular velocity of a drive motor that is a driving unit of a rotating body based on an angular velocity is known (for example, Fuji Xerox Technical Report (No. 10, pp. 47-48, pp. 47-48)).
1995) and JP-A-6-175427). This image forming apparatus indirectly controls the amount of movement (movement position) of the rotationally moving portion of the rotator by controlling the rotational angular velocity of the rotator.

[0004]

However, in the above-described conventional image forming apparatus, the rotating shaft of a driving roller of an endless belt-shaped rotating body such as a transfer belt or the rotating shaft of a cylindrical rotating body such as a photosensitive drum is used. Using a directly connected rotary encoder,
Since the rotational angular velocity of the rotating body has been detected, deformation of the rotating body itself (including expansion and contraction in the case of a belt member) such as a transfer belt and a photosensitive drum, eccentricity and coaxial misalignment of the rotating shaft and its bearing, and the like. It was difficult to directly and accurately detect the amount of movement of the rotary moving portion of the rotating body, including the influence of the deformation of the rotating body itself.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to directly and directly control the amount of movement of a rotary moving portion of a rotating body including the influence of deformation of the rotating body used for image formation. An object of the present invention is to provide an image forming apparatus capable of detecting an image accurately.

[0006]

According to a first aspect of the present invention, there is provided an image forming apparatus comprising: a rotator used for image formation; and a driving unit for rotating the rotator. The rotary moving section of the rotating body is provided with a scale for detecting a moving amount of the rotary moving section, and scale reading means for reading the scale on the rotating body is provided.

In the image forming apparatus according to the first aspect, the scale provided in the rotary moving portion of the rotary body used for image formation, which is rotated by the driving means, is directly read by the scale reading means, thereby rotating the rotary body. The amount of movement of the unit is detected.

According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the rotating body comprises an endless belt-shaped rotating body wound around a plurality of support rollers. The scale is formed on the inner peripheral surface of the body.

According to the image forming apparatus of the present invention, the scale on the inner peripheral surface of the endless belt-like rotating body wound around the plurality of support rollers is read by the scale reading means.
The scale reading means can be provided inside the rotating body, which is a space that is relatively clean and does not affect the layout of other members.

According to a third aspect of the present invention, there is provided the image forming apparatus according to the second aspect, wherein the endless belt-shaped rotating member is a transfer belt on which an image is transferred or a transfer belt for transferring a transfer material on which the image is transferred. The reading position by the scale reading means is set near the transfer position where the image is transferred.

In the image forming apparatus according to the third aspect, the scale provided on the transfer belt on which the image is transferred or on the transfer belt for transferring the transfer material onto which the image is transferred can be directly adjusted to the image shift in the final output image. Reading is performed in the vicinity of the transfer position that exerts influence, and the amount of movement of the rotary moving portion of the rotating body can be detected.

According to a fourth aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the rotating body comprises a cylindrical rotating body, wherein the scale is formed on an inner peripheral surface of the cylindrical rotating body. It is characterized by the following.

In the image forming apparatus according to the present invention, the scale on the inner peripheral surface of the cylindrical rotating body is read by the scale reading means, so that the scale reading means is relatively clean and affects the layout of other members. Can be provided inside the rotating body, which is a space that does not affect the rotation.

According to a fifth aspect of the present invention, in the image forming apparatus of the first, second, third or fourth aspect, a control means for controlling a driving source of the driving means based on a reading result of the scale reading means is provided. It is characterized by the following.

According to a fifth aspect of the present invention, the amount of movement of the rotary moving section is detected based on a reading result of a scale reading means for directly reading a scale provided on a rotary moving section which is a final control target of the rotary body. In addition, it is possible to realize complete closed-loop control of the amount of movement of the rotation moving unit of the rotating body, that is, feedback control of the driving source of the driving unit that rotationally drives the rotating body.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a color electrophotographic copying machine (hereinafter, referred to as a "color copying machine") as an image forming apparatus will be described. FIG. 1 is a perspective view showing a schematic configuration of a main part of a color copying machine according to the present embodiment. In this color copying machine, a cylindrical photosensitive drum 20, which is one of the rotating bodies used for image formation, is driven to rotate, and toner images of four colors (cyan, magenta, yellow, and black) are sequentially formed on the outer peripheral surface thereof. Is done. In the transfer unit 1, an endless belt-shaped transfer belt 2, which is another member of the rotating body, is driven to rotate. On the outer peripheral surface of the transfer belt 2, the four-color toner images on the photosensitive drum 20 are sequentially arranged. The images are transferred and superimposed to form a color image. The color image on the transfer belt 2 is transferred to a transfer sheet as a transfer material.

In the above image forming process, if the rotational speed (moving speed in the running direction) of the photosensitive drum 20 and the transfer belt 2 fluctuates, the color image on the transfer belt 2 or on the transfer paper is disturbed. In addition, the transfer belt 2 requires very precise rotational driving.

In the color copying machine shown in FIG. 1, the transfer belt 2 is supported by five support rollers 3, 4, 5, 6, and 7, and a rotation shaft 8 of a drive roller 3 which is one of the support rollers is A drive motor 9 as a drive source is connected.
The driving means for driving the transfer belt 2 to rotate is configured using the driving roller 3 and the driving motor 9. When the drive motor 9 is rotated, the transfer belt 2 rotates and the followable support rollers 4, 5, 6, and 7 rotate. The rotational movement of the transfer belt 2 is caused by the deformation and eccentricity of the five support rollers, the eccentricity of the rotation shaft of each support roller, and the drive motor 9.
The movement amount of the transfer belt 2 in the traveling direction always fluctuates due to the influence of the speed fluctuation.

Generally, a photoreceptor belt used in an image forming apparatus such as a color electrophotographic copying machine or a color printer,
The endless belt-shaped rotator such as a transfer belt and a paper transport belt is structured to be supported by a plurality of support rollers, and a drive motor is connected to a rotation shaft of one of the support rollers. The rotary body is driven to rotate. As the drive motor, a servo motor or a step motor having a built-in rotary encoder is used. In driving such an endless belt-shaped rotating body, the moving amount (rotational position) of the rotating body is not directly detected, but
Since the amount of rotational movement (rotational position) of the drive motor, which is the drive source, is detected and feedback control is performed based on this detection result, even if the rotational position and rotational angular velocity of the drive motor can be precisely controlled, the rotation The amount of body movement (rotational position) and rotational movement speed are not precisely controlled.

Therefore, in the color copying machine of the present embodiment, a scale 10 having fine and precise graduations is provided on the inner inner surface of the transfer belt 2 and an optical type detection means for reading the scale 10 is provided. Vessel 1
1 so that the rotational position and the movement amount of the transfer belt 2 can be directly and accurately detected. That is, the transfer belt 2
Deformation and eccentricity of the five support rollers appearing in the rotational movement of
The movement amount (rotational position) of the transfer belt 2 can be accurately detected, including all the effects of the eccentricity of the shaft of each support roller and the speed fluctuation of the drive motor 9. Even if the rotational movement of the transfer belt 2 itself slips, a fine and precise scale 10 is provided on the inner inner surface of the transfer belt 2, and the scale 10
Is read by the detector 11, it is possible to accurately detect the amount of movement (rotational position) of the transfer belt 2 including the slippage.

FIGS. 2A and 2B are a plan view and a sectional view, respectively, showing an example of the configuration of the scale 10. FIG. The scale 10 shown in FIG. 2 is an optically readable scale, in which light reflecting surfaces and non-reflecting surfaces of fine and precise pitch are alternately formed on a plastic sheet in the running direction. The light reflecting surface B and the non-reflecting surface C are formed, for example, by depositing a material having a high reflectivity such as aluminum or nickel on a plastic sheet, and exposing a deposited material to be a non-reflective surface with laser light such as an excimer laser. It can be formed by selective removal. In the configuration example of the scale 10 shown in FIG. 2, the width W in the direction orthogonal to the traveling direction (the direction A in the drawing) is shown.
Was set to about 2 mm, the pitch P of the light reflecting surface B and the non-reflecting surface C in the traveling direction was set to 10 to 20 μm, and the width of the light reflecting surface in the traveling direction was set to about half the pitch.

When the transfer belt 2 rotates, the scale 10 comes into contact with the surface of each of the support rollers 3, 4, 5, 6, and 7, and the scale 10 is damaged. A not-shown step (recess) is provided at a portion facing the scale 10 to avoid damage to the scale 10.

The detector 11 converts the focused beam into a scale 1
It is an optical type that irradiates toward 0 and reads the reflected light from the light reflecting surface of the scale 10. This detector 11
Is provided inside the transfer unit 1 so as to read the scale 10 near the transfer position from the photosensitive drum 20 as shown in FIG. 3 and is fixed to the detector holder 12.

Further, in the color copying machine of this embodiment, a feedback control system shown in FIG. 4 is provided in order to precisely perform feedback control of the traveling position and traveling speed of the transfer belt 2 of the transfer unit 1. The feedback control system includes a detector 11 that reads a fine scale 10 provided on the inner surface of the transfer belt 2 of the transfer unit 1.
A position detection circuit 37 for converting a signal from
And a speed detection circuit 38 for converting the speed signal into a speed signal, and constitutes a feedback control system of a minor loop for negatively feeding back each signal, position signal and speed signal.

In the feedback control system shown in FIG. 4, the mechanism of the transfer unit 1 to be controlled is a drive motor unit 3
5, the mechanical unit 36, the transfer belt 2, and the scale 10 are divided into four blocks, and are expressed as a model connected according to a substitution rule of feedback control. Here, the drive motor unit 35 includes the drive motor 9, the rotation shaft 8, and the support roller 3, and integrally rotates. Mechanical part 3
Reference numeral 6 includes four support rollers 4, 5, 6, and 7, which are connected to the transfer belt 2 by friction, and to which rotation of the drive motor unit 35 is transmitted.

The transfer belt 2 and the scale 10 are integral with each other, and rotate by friction with the motor unit 35. Therefore, the rotational movement of the transfer belt 2 and the scale 10 is accompanied by deformation of the five support rollers 3, 4, 5, 6, and 7, eccentricity, eccentricity of the shaft of each roller, speed fluctuation of the drive motor 9, and the like. Since the light is transmitted to the transfer belt 2 and the scale 10 having fine and precise scales, including all the slips due to the friction with the rollers, the detector 11 can accurately detect the moving amount (rotational position) of the transfer belt 2. it can. That is, the position signal and the speed signal obtained by calculating from the output of the detector 11 are accurate detection results directly detected on the transfer belt 2.

The position control circuit 31 calculates a deviation between an accurate and fine position signal from the position detection circuit 37 and a position command (target position) to accurately calculate a speed command (target speed). Can be output. Further, the speed control circuit 32 calculates a deviation between an accurate speed command (target speed) from the position control circuit 31 and a speed signal from the speed detection circuit 38, and calculates an accurate amount of power supplied to the drive motor 9. The calculated value is output to the power conversion circuit 33 to control the drive motor 9. Therefore, the movement amount (rotational position) of the transfer belt 2 can be feedback-controlled accurately and precisely.

The feedback control system shown in FIG. 4 can be constituted by an analog circuit or a digital circuit. For example, the position detection circuit 35 and the speed detection circuit 3
6. The position control circuit 31 and the speed control circuit 32 are composed of an operational amplifier, a counter, an A / D converter, a D / A converter, etc., which can be used to obtain high-speed, high-accuracy, and highly-reliable arithmetic operations. can do. Further, the power conversion circuit 33 can be configured by a general transistor such as a bipolar transistor (such as silicon) and an FET transistor.

In the color copying machine of the present embodiment, a driving mechanism 40 as a driving means of the photosensitive drum 20 is provided.
A gear 23 connected to a rotating shaft 22 that supports the photosensitive drum 20; a gear 24 that meshes with the gear 23;
4 is configured using a drum drive motor 21 as a drive source connected to a drive shaft 25. When the drum drive motor 21 is rotated at an arbitrary rotation speed, the photosensitive drum 2
The number 0 is increased / decreased by the gear ratio of the two gears 23 and 24 to rotate. Generally, the photosensitive drum 20 rotates at a speed lower than the rotation speed of the drum drive motor 21.

Generally, as the drum drive motor 21, a servo motor or a step motor having a built-in rotary encoder is used. As described above, the photoconductor drum 20 requires extremely precise driving. However, in these general photoconductor drum driving, the rotation position of the photoconductor drum is not detected, but the drum position is detected. Because the rotational position of the drive motor is detected and feedback-controlled, the rotational position and speed of the photosensitive drum are controlled precisely even if the rotational position and speed of the drum drive motor are precise. Absent.

Therefore, in the color copying machine of the present embodiment,
As shown in FIG. 5, a scale 26 on which fine and precise graduations are formed is provided on an inner inner surface of an outer peripheral portion which is a rotationally moving portion of the photosensitive drum 20, and a detector as scale reading means for reading the scale 26 is provided. 27,
The amount of movement of the outer peripheral surface of the photosensitive drum 20 can be directly and accurately detected. Therefore, the outer peripheral surface of the photosensitive drum 20 includes all effects such as eccentricity and speed fluctuation of the rotating shafts 22 and 25, gears 23 and 24, the drum drive motor 21, and the like, and deformation and eccentricity of the photosensitive drum 20 itself. The moving position and moving speed of the camera can be detected accurately and precisely.

The scale 26 is an optically readable scale similar to the scale 10 shown in FIGS. 2 (a) and 2 (b), and has a light reflecting surface and a non-reflecting surface of fine and precise pitch. They are formed alternately in the running direction.

The detector 27 is the same as the detector 1 described above.
Irradiate the focused beam toward scale 10 as in 1
It is of an optical type that reads light reflected from the light reflecting surface of the scale 10. As shown in FIG. 6, the detector 27 is fixed to a detector holder 28 attached to the center of a pipe-shaped fixed shaft 29 provided at the center of the photosensitive drum 20. The wiring to the detector 27 is performed through a fixed shaft 29.

Further, in the color copying machine of the present embodiment, a feedback control system shown in FIG. 7 is provided in order to precisely perform feedback control of the traveling position and traveling speed of the photosensitive drum 20. This feedback control system
A position detection circuit 46 for converting a signal from a detector 27 for reading a fine scale 26 provided on the inner surface of the inside of the photosensitive drum 20 into a position signal; and a speed detection circuit 47 for converting the signal into a speed signal. A feedback control system of a minor loop for negatively feeding back the signal, the position signal, and the speed signal is configured.

In the feedback control system shown in FIG. 7, the drive mechanism 40 for the photosensitive drum 20 to be controlled is divided into four blocks of a drive motor 21, a gear section 44, a photosensitive drum 20, and a scale 26. Are expressed as models connected in accordance with the permutation rule. Here, the gear unit 44 includes a drive shaft 25 and a gear 24 directly connected to the drive motor 21, and a rotating shaft 22 and a gear 23 directly connected to the photosensitive drum 20. The gear 24 and the gear 23 are engaged with each other, and the rotation of the drive motor 21 is transmitted to the photosensitive drum 20.

Further, the photosensitive drum 20 and the scale 26 are integrated, and the rotation of the drive motor 21 is transmitted. Accordingly, the rotational movement of the photosensitive drum 20 and the scale 26 includes not only the eccentricity and deformation of the photosensitive drum 20 but also the rotation of the shaft 22,
The photosensitive drum 20 and the fine and precise scale 2 including the eccentricity of the gear 25, the eccentricity of the gears 23 and 24, the speed change due to meshing, and the speed change of the drive motor 21 are all included.
6, the detector 27 is connected to the photosensitive drum 20
The amount of movement of the outer peripheral surface can be accurately detected. That is, the position signal and the speed signal obtained by calculating from the output (movement amount) of the detector 26 are accurate detection results of directly detecting the photosensitive drum 20.

The position control circuit 41 calculates a deviation between a fine and precise position signal from the position detection circuit 46 and a position command (target position) to accurately calculate a speed command (target speed). Can be output. Further, the speed control circuit 42 calculates a deviation between an accurate speed command (target speed) from the position control circuit 41 and a speed signal from the speed detection circuit 47, and calculates an accurate amount of power supplied to the drive motor 20. The calculated value is output to the power conversion circuit 43 to control the drive motor 20. Therefore, the amount of movement (rotational position) of the outer peripheral surface of the photosensitive drum 20 can be feedback-controlled accurately and precisely.

The feedback control system of FIG. 7 can be constituted by an analog circuit or a digital circuit, similarly to the feedback control system of FIG. For example, the position detection circuit 46, the speed detection circuit 47, the position control circuit 41, and the speed control circuit 42 are operational amplifiers, counters, and A / D converters that can be used to obtain high-speed, high-accuracy, and highly-reliable arithmetic operations. , A D / A converter, and the like. Further, the power conversion circuit 43 can be configured by a general transistor such as a bipolar transistor (such as silicon) and an FET transistor.

As described above, according to the present embodiment, the transfer belt 2
Even when the moving speed of the transfer belt 2 fluctuates due to its own deformation or the eccentricity of the rotating shaft of the supporting roller and the bearing, the moving amount (moving position) of the transfer belt 2 including the influence is directly and accurately determined. Can be detected. Further, even when the moving speed of the outer peripheral surface of the photosensitive drum 20 fluctuates due to the deformation of the photosensitive drum 20 itself and the eccentricity of the rotation shaft and the bearing of the support roller thereof, the influence of the photosensitive drum 20 including the influence is also included. The amount of movement of the outer peripheral surface can be directly and accurately detected.

According to the present embodiment, the transfer belt 2
Based on the detection result of the movement amount of the outer peripheral surface of the photosensitive drum 20 and the movement position of the outer peripheral surface of the transfer belt 2 and the photosensitive drum 20, complete closed loop control is realized, and the rotation of the transfer belt 2 and the photosensitive drum 20 is realized. Since all the influences of the driving system can be suppressed and the rotational drive of the transfer belt 2 and the photosensitive drum 20 can be accurately controlled, the color shift of the color image caused by the fluctuation of the moving speed of the transfer belt 2 and the photosensitive drum 20 can be reduced. Can be prevented.

According to the present embodiment, the scale 1
The detectors 11 and 27 for reading 0 and 26 are provided inside the transfer belt 2 and the photosensitive drum 20 which are relatively clean and do not affect the layout of other members. The reading accuracy of 26 is improved, and there is no layout interference with other members.

Further, according to the present embodiment, the amount of movement of the transfer belt 2 near the transfer position which directly affects the color shift in the final output color image is detected, and the speed of the transfer belt 2 is controlled. Since it can be used, deterioration of image quality such as color shift can be more reliably prevented.

In the above embodiment, the scale 10 and the scale 10 are provided on the inner inner surfaces of both the transfer belt 2 and the photosensitive drum 20.
26, and detectors 11 and 27 and a feedback control system are provided corresponding to each scale, but one of the transfer belt 2 and the photosensitive drum 20 which requires more precise and accurate rotational drive control. A scale may be provided, and a detector and a feedback control system may be provided corresponding to the scale.

In the above embodiment, the scales 10 and 2 are provided on the inner peripheral surfaces of both the transfer belt 2 and the photosensitive drum 20.
However, when contamination of the outer space such as the transfer belt or interference with other members in the layout does not cause a problem, the image formation on the outer peripheral surfaces of the transfer belt 2 and the photosensitive drum 20 is hindered. Scales 10 and 26 may be provided at the ends that do not exist.

In the above embodiment, the optically readable scales 10 and 26 and the optical detectors 11 and 12 are used.
7, the present invention can be applied to the case where a scale and a detector of another reading method are used. For example, a magnetically readable scale and a magnetic detector can be used.

[0046]

According to the first to fifth aspects of the present invention, the moving speed of the rotary moving portion of the rotating body changes due to the deformation of the rotating body itself and the eccentricity of the rotating shaft and the bearing supporting the rotating body. Even in the case where the rotation is performed, there is an effect that the movement amount of the rotary moving portion of the rotating body including the influence can be directly and accurately detected.

In particular, according to the second or fourth aspect of the present invention, the scale reading means can be provided in a space which is relatively clean and does not affect the layout of other members. There is an effect that the accuracy is improved and there is no interference in layout with other members.

In particular, according to the third aspect of the present invention, the movement amount of the rotary moving portion of the rotating body near the transfer position which directly affects image quality such as image shift in the final output image is detected. However, since it can be used for controlling the speed of the rotary moving unit, there is an effect that deterioration in image quality such as image shift can be more reliably prevented.

In particular, according to the fifth aspect of the present invention, by realizing complete closed-loop control for the amount of movement of the rotary moving portion of the rotating body, deformation of the rotating body itself, a rotating shaft for supporting the rotating body and This has the effect of suppressing all effects of the rotary drive system of the rotating body, such as eccentricity of the bearing, and accurately controlling the amount of movement of the rotary moving part of the rotating body.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic configuration of a color copying machine according to an embodiment of the present invention.

FIG. 2A is a plan view of a scale provided on a transfer belt and a photosensitive drum of the color copying machine. (B) is a sectional view of the same scale.

FIG. 3 is an explanatory diagram illustrating a mounting position of a detector that reads a scale on a transfer belt.

FIG. 4 is a block diagram of a feedback control system that performs rotational drive control of the transfer belt.

FIG. 5 is an explanatory diagram showing a scale on a photosensitive drum and its detector.

FIG. 6 is an explanatory diagram showing a mounting position of a detector that reads a scale on a photosensitive drum.

FIG. 7 is a block diagram of a feedback control system that performs rotation drive control of the photosensitive drum.

[Explanation of symbols]

 Reference Signs List 1 transfer unit 2 transfer belt 3 drive roller (support roller) 4, 5, 6, 7 support roller 8 rotation shaft 9 drive motor 10 scale 11 detector 12 detector holder 20 photosensitive drum 21 drum drive motor 22 rotation shaft (drum) Axis) 23, 24 Gear 25 Drive shaft 26 Scale 27 Detector 28 Detector holder 29 Fixed shaft 31, 41 Position control circuit 32, 42 Speed control circuit 33, 43 Power conversion circuit 35 Drive motor section 36 Mechanical section 37, 46 Position Detection circuit 38, 48 Speed detection circuit 40 Photoconductor drive mechanism 44 Gear section

Claims (5)

[Claims] An image forming apparatus comprising: a rotator used for image formation; and a driving unit for driving the rotator to rotate.
An image forming apparatus, wherein a scale for detecting the amount of movement of the rotary moving unit is provided in the rotary moving unit of the rotary body, and scale reading means for reading the scale on the rotary body is provided. 2. The image forming apparatus according to claim 1, further comprising an endless belt-shaped rotator wound around a plurality of support rollers as said rotator, wherein an inner peripheral surface of said endless belt-shaped rotator is provided. An image forming apparatus comprising the scale formed thereon. 3. The image forming apparatus according to claim 2, wherein the endless belt-shaped rotator is a transfer belt on which an image is transferred or a transfer belt for transferring a transfer material on which the image is transferred.
An image forming apparatus, wherein a reading position of the scale reading means is set near a transfer position where the image is transferred. 4. The image forming apparatus according to claim 1, wherein said rotating body comprises a cylindrical rotating body, wherein said scale is formed on an inner peripheral surface of said cylindrical rotating body. Image forming device. 5. The image forming apparatus according to claim 1, further comprising control means for controlling a driving source of said driving means based on a reading result of said scale reading means. Image forming device.