JP4653543B2 - Image forming apparatus - Google Patents

Description

The present invention relates to an image forming apparatus including driving and conveying technology xerographic device, the rotation stabilizing KaSo location particularly reducing banding in latent image formation system.

Conventionally, in an electrophotographic apparatus, as an abnormal phenomenon derived from a driving / conveying mechanism, a positional deviation in which an entire image or a part of the image is deviated from a predetermined position, and a banding phenomenon in which a band-like density unevenness occurs periodically or randomly. It is known to occur (see, for example, Patent Documents 1 to 3).
Among the banding phenomenon mentioned above, band-like density unevenness occurs at specific timings due to shocks that occur especially when the leading or trailing edge of the paper passes through the drive / conveyance mechanism or when the two types of drive / conveyance mechanism come in contact with each other. For example, shock jitter.
Although these abnormal phenomena are different in fine factors and time scales, the method of suppressing them is eventually replaced by a method in which the speed of the photosensitive drum and the transfer belt is made constant. A method for stably rotating a rotating body such as a driving roller at a predetermined rotational speed is an important issue.
In general, the methods for stably rotating these rotating bodies at a predetermined rotational speed can be roughly classified into the following two methods.
That is, a first method for increasing the moment of inertia of the rotating body using a flywheel or the like, and a second method for controlling the motor and the rotation adjusting mechanism so that the rotation speed becomes constant based on the rotation state information of the rotating body. Can be broadly classified.
The rotation state information includes information obtained by sequentially detecting rotational speed, acceleration, position, etc. using an encoder, and information in which speed reduction mechanism characteristics such as gear eccentricity are detected and recorded in advance. Feedback control and feedforward control based on these pieces of information are used alone or in combination.
The first method has a feature that the mechanism is simple and highly reliable, but on the other hand, the weight of the entire apparatus is increased, and since a large driving torque is required, a large motor is loaded, so that the entire apparatus is further improved. It has drawbacks such as an increase in size, and is used exclusively in high-end and large machines that do not care about price and size.

The second method has a feature that it can be downsized although it is complicated in structure. The most common method of the second method is to connect a rotary encoder to the shaft of the rotating body, detect the rotational fluctuation of the rotating body from the output of the rotary encoder, and feedback control the rotation of the motor. .
In this method, for example, when the rotational speed of the photosensitive drum is controlled, a rotational fluctuation with a relatively long period of several millimeters or more converted into an image, for example, a positional deviation due to a speed fluctuation caused by gear eccentricity of the speed reduction mechanism is sufficient Can be reduced.
However, for periodic banding and shock jitter, a finer period becomes a problem. The period in which banding is most noticeable is said to be around 1 mm from the sensitivity characteristics of the human eye. Assuming that the linear velocity is 200 mm, this corresponds to a time period of around 5 ms.
In order to reduce this, the time delay required for fluctuation control is at most 1.25 ms, preferably 0.5 ms or less, which is 1/4 of 5 ms per cycle. It was.
There are roughly three factors of the delay in the above control. The first is a delay due to the resolution of the rotary encoder. This occurs because the sensor of the rotary encoder cannot detect the speed fluctuation unless two or more marks are continuously detected.
The second is the delay of the control circuit until the data output from the rotary encoder is detected and judged as a speed fluctuation and a motor speed change command is issued. The third is a mechanical delay from when the torque of the motor is changed by a command from the control circuit to when the speed of the motor is changed and the speed change is transmitted to the drum surface via the gear rotation shaft.
If the high-resolution rotary encoder is used, the first delay can be avoided for the time being although the cost is high. There is also a countermeasure as in Patent Document 1. Since patent document 1 itself has not taken measures against the second and third delays as described in the following drawbacks, it is insufficient as a measure.

In Patent Document 1, since the gravity component is not taken into consideration as one of the acceleration components applied to the acceleration sensor in the embodiment, the direct detection of the speed / acceleration as in the embodiment cannot be performed (the rotation axis is vertical). It seems possible). For the necessity of taking the gravity component into consideration as one of the acceleration components applied to the acceleration sensor, Patent Document 2 is helpful.
Patent Document 1 discloses an acceleration sensor arranged on a photosensitive drum, which simultaneously acquires speed information and acceleration information of a rotating body to control the speed of the photosensitive drum. Patent Document 1 aims at shock jitter countermeasures, and since speed and acceleration are directly detected by an acceleration sensor, speed fluctuations can be detected in a shorter time than an encoder, and shock jitter can also be handled.
In Patent Document 2, acceleration sensors are arranged at two arbitrary points on a rotating body, and the centrifugal force (radial direction) component and gravity component of acceleration are extracted by calculating the measured values of the two sensors, and the rotating body rotates. A detection method and apparatus for detecting velocity and rotational angular displacement are disclosed.
For the third delay, there is a countermeasure as in Patent Document 3. However, this time, as described in the following drawbacks, since measures are not taken against the first delay and the second delay, the measures are insufficient.
Patent Document 3 connects a rotating body and its drive shaft via an actuator, detects the rotational angular displacement, rotational speed, or acceleration of the rotating body, and determines between the rotating body and its drive shaft according to the detection result. It is disclosed that the rotational phase of the motor is adjusted by an actuator.
JP-A-8-1115012 Japanese Patent No. 2637630 JP 2000-330420 A

However, in Patent Document 1 described above, it takes time because the detection data of the acceleration sensor is temporarily output to a control circuit outside the rotating body and used for control. Further, since the speed of the drive motor is controlled and a delay occurs in the deceleration / transmission mechanism from the motor to the photosensitive drum, it is not sufficient as a countermeasure against shock jitter.
Further, in Patent Document 2 described above, since the circumferential component of acceleration is not extracted, it is not possible to consider the detection of steady circumferential vibration, shock jitter, and the like. Further, in Patent Document 3 described above, since the speed variation is detected by the encoder, the detection time delay is large.
In addition, since the actuator is controlled from the outside of the rotating body, problems such as signal delay and malfunction due to noise in communication means connecting the rotating body and the outside become a problem.
From the above, although there are countermeasures in Patent Documents 1 and 3 for the first delay and the third delay, respectively, there is no countermeasure against the second delay even if the two are combined. Is insufficient.
Accordingly, an object of the present invention is to reduce all delays in consideration of the above-described situation, thereby reducing a relatively fine cycle speed fluctuation such as banding and shock jitter, and obtaining a high-quality image. An object of the present invention is to provide a rotation stabilization device and an image forming apparatus including the rotation stabilization device.

In order to solve the above problems, the invention according to claim 1 is a first rotating body which is a driving roller of a photosensitive drum or a transfer belt, which is disposed on the same axis facing a direction other than the vertical direction. And a second rotating body including a flywheel , the second rotating body is rotationally driven by a motor, the first rotating body and the second rotating body are connected via an actuator, and the first rotation body includes an acceleration sensor, the measuring circuit to measure the acceleration sensor in a second rotational member provided with a actuator control circuit for controlling the drive of the actuator and the actuator, the acceleration sensor of the first rotating member an image forming apparatus is disposed at a position sensitive to the circumferential direction, wherein the measuring circuit, the row calculation of the angular acceleration of the first rotating member based on the acceleration detected by the acceleration sensor The actuator control circuit calculates a phase change amount for reducing the rotational speed fluctuation of the first rotating body based on the angular acceleration calculated by the measurement circuit, and the actuator is controlled by the actuator control circuit. The rotation phase between the first rotating body and the second rotating body is changed based on the instructed phase change amount.

  According to the present invention, based on the phase change amount instructed from the actuator control circuit, the rotation between the first rotating body and the second rotating body in order to reduce the rotational speed fluctuation of the first rotating body. By changing the phase, it is possible to reduce the rotational speed fluctuation of the first rotating body without delay even when a sudden rotational speed fluctuation occurs in a short time such as shock jitter.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic view of a rotation stabilizing device having a first rotating body and a second rotating body as viewed from the side. FIG. 2 is a schematic view of the second rotating body (flywheel) viewed from the first rotating body side. FIG. 3 is a block diagram showing the flow of information from the acceleration sensor to the actuator. However, in FIG. 2, the acceleration sensor arranged on the first rotating body is also displayed in order to grasp the positional relationship with the arrangement on the second rotating body.
As shown in FIG. 1, in the rotation stabilization device of the present embodiment, a first rotating body 1 and a second rotating body 2 are arranged on the same shaft 11. The first rotator 1 and the second rotator 2 are connected to each other by an appropriate method via the actuators 4 and the pins 8 arranged at two locations on the second rotator 2, and the pins 8 are not provided. For example, the first rotator 1 and the second rotator 2 are independently rotatable.
Further, the second rotating body 2 is connected to the motor 10 via the gear 9. Accordingly, the first rotating body 1 obtains a rotational driving force from the motor 10 via the gear 9, the second rotating body 2, the actuator 4 and the pin 8.
On the first rotating body 1, two-dimensional acceleration sensors 3 are arranged at two positions opposite to each other by 180 degrees across the rotation center of the first rotating body 1. Although not shown, a signal line extends to the measurement circuit 5 from the two-dimensional acceleration sensor 3.
Similarly, although not shown, signal lines also extend between the measurement circuit 5 and the actuator 4 arranged on the second rotating body 2 and between the measurement circuit 5 and the wireless communication circuit 6.
All of these obtain electric power from the outside of the second rotating body 2 via the power feeding mechanism 12. The power feeding mechanism 12 uses a power feeding method using an orthodox brush. However, a power feeding method using electromagnetic induction can also be used.

The acceleration sensor 3 can also be provided in the second rotating body 2. In this way, the configuration on the first rotating body 1 side can be simplified, which is effective when the first rotating body 1 used as the photosensitive drum needs to be replaced.
Further, the second rotating body 2 can be provided with a measurement circuit 5 of an acceleration sensor 3 and an actuator actuator control circuit 13 of the actuator 4 which will be described later. By removing the measurement circuit 5 from the first rotating body 1, the moment of inertia of the first rotating body 1 is reduced accordingly, so that the rotation phase can be easily changed.
For example, the acceleration sensor 3 is disposed at a position in contact with the first rotating body 1 of the actuator 4 disposed on the second rotating body 2. Alternatively, the acceleration of the first rotating body 1 is estimated from the acceleration of the second rotating body 2 and the operation of the actuator 4.
An inertia moment of 1/10 or more that of the first rotating body 1 can be applied to the second rotating body 2. Even when the torsional rigidity of the shaft 11 or the drive speed reduction mechanism from the second rotating body 2 to the motor is weak or when the moment of inertia is significantly smaller than that of the rotated body (first rotating body 1), the second rotation Using the moment of inertia of the body 2 as a scaffold, the phase of the first rotating body 1 by the actuator 4 can be changed.
Thereby, it can be used with a smaller moment of inertia than the method of stabilizing the rotation with the flywheel alone.
Note that the value of the inertia moment of 1/10 is merely an example, and the present invention is not limited to this value. However, if the value is smaller than this value, only the rotational speed of the second rotating body 2 changes, and the first In some cases, the rotational speed of the rotating body 1 cannot be adjusted.

FIG. 3 is a block diagram showing the flow of information from the acceleration sensor 3 to the actuator 4. In FIG. 3, a measurement circuit 5 of the acceleration sensor 3 and an actuator control circuit 13 of the actuator 4 are shown.
Based on the acceleration detected by the acceleration sensor 3, the measurement circuit 5 identifies the angular acceleration, angular velocity, and angle of the first rotating body 1 and the second rotating body 2.
The specified angular acceleration information is directly sent to the actuator control circuit 13. The actuator control circuit 13 calculates the amount of force to be applied by the actuator 4 or the amount of displacement, and sends a control signal to the actuator 4.
The information on the angular velocity and the angle is transmitted to the main body side wireless communication circuit 14 via the wireless communication circuit 6 and used for motor speed control and the like. Further, when other elements such as a transfer belt (not shown) are driven with respect to the first rotating body 1, not only the rotational speed fluctuation of the first rotating body 1 is suppressed, but also the transfer belt. In consideration of the thickness deviation profile, it is necessary to control the rotation speed of the first rotating body 1 so as to keep the transfer belt speed constant.
However, in such a case, speed correction information is transmitted from the main body side to the actuator control circuit 13 in advance or in real time through the wireless communication circuits 14 and 6. The actuator control circuit 13 determines the amount of force or displacement to be applied by the actuator 4 by combining the angular acceleration information and the speed correction information.
The processing as described above does not require immediacy of information transmission as much as the case where the actuator 4 is controlled based on the angular acceleration information, so that a delay in the wireless communication circuits 14 and 6 can be allowed.

The measurement circuit 5 performs the following processing. It is assumed that the first rotating body 1 has a rotation axis that does not face the vertical direction. The first rotating body 1 has a constant load and continues to rotate at a constant angular velocity unless a force fluctuation is applied via the second rotating body 2. At this time, the sum of gravity acceleration and centrifugal force is detected from the two two-dimensional acceleration sensors 3.
If the two acceleration sensors 3 are provided with independent coordinate systems, and the polar coordinates are 90 degrees in the direction in which the centrifugal force is applied, one centrifugal force is equal to both acceleration sensors in a 90 degree direction with a constant amount. Added as an acceleration component.
The other gravitational acceleration is equally applied to both acceleration sensors by a certain amount, but the direction applied to the acceleration sensor depends on the angle of the first rotating body 1 and is 180 between the two acceleration sensors. Varies.
Therefore, if the accelerations detected by the two acceleration sensors 3 are averaged, the centrifugal force can be detected, and if the difference between the accelerations detected by the two acceleration sensors 3 is divided by 2, the direction and magnitude of the gravitational acceleration are obtained. Can be detected.
Further, even if the acceleration sensor 3 is treated as a one-dimensional acceleration sensor and only the component in the 90-degree direction (and 180-degree direction) of the acceleration sensor 3 is extracted, the centrifugal force can be similarly detected on average.
Further, if the difference is taken, an amount of acceleration that varies depending only on the angle of the first rotating body 1 is detected, so that the direction of the gravitational acceleration can be specified on the assumption that the rotational direction is known. The angular velocity of the first rotating body 1 can be specified from the centrifugal force, and the angle of the first rotating body 1 can be specified from the direction of gravitational acceleration.
When a change in force is applied to the first rotating body 1 via the load of the first rotating body 1 or the second rotating body 2, angular acceleration is generated in the first rotating body 1. At the same time, acceleration in the translational direction may occur on the rotation shaft 11 of the first rotating body 1.
In the acceleration sensor 3, only the acceleration component in the circumferential direction is extracted by each of the two acceleration sensors, and the already detected gravity acceleration component is subtracted therefrom. Furthermore, the angular acceleration can be specified by averaging two acceleration sensors.
In addition, when the rotating shaft 11 of the first rotating body 1 is oriented in the vertical direction, the angle of the first rotating body 1 cannot be specified from the detection data of the acceleration sensor 3. In this case, another means for specifying the angle such as an encoder is required.

The actuator control circuit 13 roughly performs the following processing. The actuator control circuit 13 basically generates a control signal to the actuator 4 so that acceleration is applied in the opposite direction from the angular acceleration information specified by the measurement circuit 5.
Taking the piezo actuator as an example and describing the actuator very simply, it is only necessary to convert the angular acceleration information of the digital signal into a voltage waveform. As the time delay from the occurrence of the speed fluctuation of the first rotating body 1 increases, it is necessary to emphasize the rise of the waveform. Further, since the range of the displacement of the actuator 4 is limited, it is necessary to adjust so as to maintain the center position of the range of displacement as much as possible.
Further, when there is speed correction information transmitted from the main body through the wireless communication circuits 14 and 6, the amount of force to be applied by the actuator 4 or the amount of displacement is determined in consideration of the information.
As a result of examining a method for shortening all the first to third delays described above, if there is a problem that speed fluctuation occurs in a rotating body such as a photosensitive drum or a driving roller of a transfer belt, the rotating body (Drive roller) or an object (flywheel) that rotates coaxially with its rotating body is also arranged from speed fluctuation detection to rotation fluctuation correcting actuators and their control mechanisms.
If only the power supply and simple signals (start / stop signal, speed correction information, etc.) are exchanged from outside the rotating body, and all the operations from speed fluctuation detection to rotation fluctuation correction by the actuator are completed only within the rotating body , All of the first to third delays are reduced. Therefore, it is understood that a relatively fine cycle speed fluctuation such as shock jitter can be reduced.
The separated circumferential acceleration, centrifugal force, and gravitational acceleration (directions) correspond to the angular acceleration, angular velocity, and angle of the first rotating body 1, respectively, and by obtaining these comprehensive information, the acceleration sensor 1 A wider range of rotation control than in the case of a single unit, for example, simultaneous reduction of speed fluctuation and shock jitter of one cycle component of the drum can be easily achieved.

FIG. 4 is a schematic view showing a first arrangement example of the acceleration sensors. FIG. 5 is a schematic view showing a second arrangement example of the acceleration sensors. FIG. 6 is a schematic view showing a third arrangement example of the acceleration sensors.
FIG. 7 is a schematic view showing a fourth arrangement example of the acceleration sensors. FIG. 8 is a schematic view showing a fifth arrangement example of the acceleration sensors. FIG. 9 is a schematic view showing a sixth arrangement example of the acceleration sensors.
4 to 9, as an acceleration sensor, a one-dimensional, two-dimensional or three-dimensional acceleration sensor 3a, 3b is used as a rotating body (first rotating body 1) or a rotation drive shaft (not shown). ) Install in one place above, preferably two places.
It is also conceivable that acceleration sensors having different dimensions, for example, one-dimensional sensor 3a and two-dimensional sensor 3b are arranged one by one. In the one-dimensional sensor 3a and the two-dimensional sensor 3b, the direction in which the acceleration sensor is sensitive is aligned on a plane perpendicular to the axis of the rotated body.
Although not shown, when there is only one acceleration sensor, it is arranged at a position other than the center of rotation of the rotating body or the rotation drive shaft. At this time, in the case of a one-dimensional acceleration sensor, the direction in which the acceleration sensor has sensitivity is aligned with the direction in which the circumferential acceleration of the rotated body is applied.
In the case of a three-dimensional acceleration sensor, it can be handled in the same manner as a two-dimensional acceleration sensor by ignoring the axial acceleration of the rotated body. Of course, the detection of the acceleration in the axial direction of the rotated body for another purpose is not limited at all.
In addition to the circumferential acceleration that has a one-to-one correspondence with the angular acceleration, the acceleration sensor also includes gravitational acceleration. If the angular acceleration is large and the circumferential acceleration applied to the acceleration sensor is sufficiently larger than the gravitational acceleration, gravity can be ignored.
The direction of the gravitational acceleration applied to the two-dimensional sensor 3b changes in synchronization with the rotation cycle, and the gravitational acceleration applied to the one-dimensional acceleration sensor 3a increases or decreases in synchronization with the rotation cycle. The gravitational acceleration component can be removed to some extent.

When the acceleration sensors are installed at two locations, the installation positions can be arbitrarily determined. However, as an arrangement that can easily calculate the angular acceleration, angular velocity, and angle of the rotated body from the detection data, FIG. 4 to FIG. The arrangement as shown is conceivable.
4 to 9, the acceleration sensors 3a and 3b are indicated by block arrows. The direction of the arrow indicates the direction in which the acceleration sensors 3a and 3b have sensitivity, the two-directional arrows in a straight line form the one-dimensional acceleration sensor 3a, and the four-directional arrows indicate the two-dimensional acceleration sensor 3b.
If there are two acceleration sensors, the gravitational acceleration and the other acceleration can be completely separated as shown in Patent Document 2. In Patent Document 2, centrifugal force and gravity are separated, but the present invention focuses on separating circumferential acceleration from gravity.
Therefore, one of the two acceleration sensors 3a and 3b is disposed at a place other than the center of rotation, and is disposed so as to have sensitivity at least in the circumferential direction. The remaining one acceleration sensor 3b or 3a is also arranged at a place other than the center of rotation so as to have sensitivity at least in the circumferential direction (FIGS. 4, 6, 7, and 9) or rotation. It arrange | positions in the center (FIG. 5, FIG. 8).

According to the present invention, two acceleration sensors are arranged on the first rotating body 1 or the second rotating body 2 in a direction sensitive to at least the circumferential acceleration of these rotating bodies, and By extracting the components of gravitational acceleration and rotational angular acceleration from the detection amount of the acceleration sensor, and further detecting the rotational angle of the rotating body from the magnitude and direction of the gravitational acceleration, the first rotating body 1 or the second rotating body. Two angles and angular acceleration can be detected simultaneously.
Each of the two acceleration sensors is a two-dimensional acceleration sensor 3b, and by detecting the radial acceleration, that is, the centrifugal force simultaneously with the circumferential acceleration of the first rotating body 1 or the second rotating body 2, rotation is achieved. In addition to body angle and angular acceleration, angular velocity can be detected simultaneously. In this case, the rotational axis direction of the rotating body is not matched with the direction of the gravitational acceleration.
The calculation method for separating the gravitational acceleration component and the circumferential acceleration component from the acceleration detected by the acceleration sensor 3a or 3b is basically the same as the method for separating the gravitational acceleration component and the centrifugal force component in Patent Document 2, but the components are different. Since the idea does not change, I will omit the explanation here. Of course, if it is a two-dimensional or three-dimensional acceleration sensor, the centrifugal force can also be separated simultaneously.
The actuators 4 (FIGS. 1 to 3) are arranged at two positions that are 180 degrees opposite to each other with the rotation center of the first rotating body 1 or the second rotating body 2 interposed therebetween. Each actuator 4 displaces the pin 8 linearly along the circumferential direction of the second rotating body 2 as indicated by an arrow in FIG. The direction of displacement is also 180 degrees different between the two actuators 4.
Since the pin 8 is connected to the first rotating body 1, the actuator 4 can change the relative angle, that is, the phase of the first rotating body 1 with respect to the second rotating body 2 by displacing the pin position. it can.

The type of actuator used in the present invention is not particularly limited, but a piezo element is particularly excellent because it has a quick response, a strong force, and a minute displacement can be accurately reproduced. Other candidates include electromagnetic actuators such as voice coils, gel actuators, electrostatic actuators, and magnetostrictive elements.
If the first rotating body 1 described above is used as a driving roller for a photosensitive drum or a transfer belt, when the first rotating body 1 is a photosensitive drum, fluctuations in the rotational speed of the photosensitive drum are reduced. Further, when the first rotating body 1 is a driving roller for the transfer belt, fluctuations in the speed of the transfer belt can be reduced. In general, an image forming apparatus including a rotation stabilizing device that can reduce banding and shock jitter can be obtained.
The present invention can also be applied to plain paper copying machines, plain paper facsimiles, page printers, and the like, and to artificial celestial body vibration control devices that generate pseudo gravity by centrifugal force.

It is a schematic diagram which shows the rotation stabilization apparatus which has a 1st rotary body and a 2nd rotary body. It is the schematic diagram which looked at the 2nd rotary body from the 1st rotary body side. It is a block diagram which shows the flow of the information from an acceleration sensor to an actuator. It is the schematic which shows the 1st example of arrangement | positioning of an acceleration sensor. It is the schematic which shows the 2nd example of arrangement | positioning of an acceleration sensor. It is the schematic which shows the 3rd example of arrangement | positioning of an acceleration sensor. It is the schematic which shows the 4th example of arrangement | positioning of an acceleration sensor. It is the schematic which shows the 5th example of arrangement | positioning of an acceleration sensor. It is the schematic which shows the 6th example of arrangement | positioning of an acceleration sensor.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... 1st rotary body (drive roller), 2 ... 2nd rotary body (flywheel 7), 3 ... Acceleration sensor, 3a ... One-dimensional acceleration sensor, 3b ... Two-dimensional acceleration sensor, 4 ... Actuator, 5 ... Acceleration sensor measurement / control circuit, 6 ... wireless communication circuit, 8 ... pin, 9 ... gear, 10 ... motor, 11 ... shaft, 12 ... power feeding mechanism, 13 ... actuator control circuit, 14 ... main body side wireless communication circuit

Claims (1)

A second rotating body including a first rotating body and a flywheel, which are driving rollers of a photosensitive drum or a transfer belt , arranged on the same axis facing a direction other than the vertical direction ;
The second rotating body is rotationally driven by a motor,
The first rotating body and the second rotating body are connected via an actuator,
The first rotating body includes an acceleration sensor ,
Measuring circuit to measure the acceleration sensor in a second rotational member provided with a actuator control circuit for controlling the drive of the actuator and the actuator,
The acceleration sensor is an image forming apparatus disposed at a position having sensitivity in the circumferential direction of the first rotating body ,
The measurement circuit calculates the angular acceleration of the first rotating body based on the acceleration detected by the acceleration sensor,
The actuator control circuit calculates a phase change amount for reducing the rotational speed fluctuation of the first rotating body based on the angular acceleration calculated by the measurement circuit,
The image forming apparatus, wherein the actuator changes a rotation phase between the first rotating body and the second rotating body based on a phase change amount instructed by the actuator control circuit.

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