JP2004102129A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide photoreceptor driving constitution in which color shift is hardly caused in spite of eccentricity etc., of a photoreceptor drum shaft and bounding is hardly caused without a heavy large-diameter flywheel by performing driving control over a small-diameter flywheel to which a photoreceptor drum is connected. <P>SOLUTION: A gear 21 for acceleration is fitted to the rotary shaft 1a of a motor 1 for acceleration and a gear 11 for deceleration is fitted to the rotary shaft 10a for a motor for deceleration. A drum gear 4 is fitted to the rotary shaft 25a of the photoreceptor drum 25 so as to engage with those driving gears 2 and 11, and a flywheel 12 is fitted. The drum rotational angle is detected with the output from an encoder 5. A positive manipulated variable (acceleration) is sent to the motor 1 for acceleration while specified torque is added and a negative manipulated variable (deceleration) is sent to the motor 10 for deceleration while specified reverse torque is added. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL 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 in which a photosensitive drum as an image carrier is rotated by a gear mechanism. The present invention can be applied to OA equipment, FA equipment, and the like.
[0002]
[Prior art]
With an increase in image quality in recent years, when trying to increase the printing resolution, color misregistration and banding have become more conspicuous than in the past.
The color misregistration is a phenomenon in which the printing position of each color is shifted on a transfer paper surface as a recording medium during color printing, and one of the causes is considered to be mechanical eccentricity of the photosensitive drum. As this mechanical countermeasure, there is known a method of increasing the precision by using an advanced processing technique.
Banding is a light and shade pattern in the sub-scanning direction seen on the printed transfer paper surface. One of the causes is considered to be rotation unevenness of the photosensitive drum (a frequency band with high visual sensitivity). As a mechanical countermeasure, a method is known in which a heavy flywheel is attached to a photosensitive drum shaft to increase inertia, thereby removing a light and shade pattern in the sub-scanning direction.
[0003]
With regard to color misregistration, the demand for color misregistration accuracy between the photosensitive drums is becoming more and more severe as the image quality of the tandem-type color image forming apparatus becomes higher. One of the measures for preventing color misregistration is high-precision positioning control. Can be avoided.
FIG. 12 shows a conventional example of a positioning control system. In this figure, the drive transmission has a one-stage configuration, and power is transmitted from the motor shaft to the photosensitive drum shaft via a gear.
A drive gear 19 is attached to a rotation shaft 18a of a drive motor 18 that is a DC motor as a drive source, and a drum gear 4 that meshes with the drive gear 19 is attached to a rotation shaft 25a of the photosensitive drum 25.
When the photosensitive drum 25 rotates, the encoder 5 coaxial with the photosensitive drum 25 also rotates at the same time. As a result, the number of pulses corresponding to the rotation angle of the photosensitive drum 25 is output from the encoder 5, so that the detection device 6 can detect the drum rotation angle by counting the number of pulses.
The control device 7 calculates an operation amount according to the deviation between the drum rotation angle and the target rotation angle, and the driving device 8 generates an applied voltage for flowing a current corresponding to the operation amount to the drive motor 1. In the drive motor 18, a current flows by the applied voltage to generate a rotational torque to rotate the motor shaft 18 a.
[0004]
However, in such a configuration, a backlash element (non-linear element) peculiar to the gear transmission exists, and this is an obstacle to realizing a wide control band.
Therefore, as a simple method for removing the play between the gears caused by the backlash element, there is a method of attaching the brake element 9 on the rotating shaft 25a of the photosensitive drum 25. The control band can be extended to some extent.
[0005]
[Patent Document 1]
Japanese Patent Publication No. 7-95244 [Patent Document 2]
JP-A-9-258830 [Patent Document 3]
JP-A-10-6164 [Patent Document 4]
JP-A-2001-51722
[Problems to be solved by the invention]
However, as shown in FIG. 13 (a), when the gain crossover angular frequency omega _C is relatively low, as the variation of the operation amount I required by the control (t) is shown in FIG. 13 (b) small and whereas requires a positive operation amount, as shown in FIG. 13 (c), when the gain crossover angular frequency set omega _C relatively high in order to widen the control band, the operation required by the control The fluctuation of the amount I (t) greatly changes as shown in FIG. In particular, the amount of operation when decelerating the photosensitive drum 3 becomes zero or a negative amount of operation, so that the braking effect is lost and rattling between the gears occurs again.
[0007]
A method of further strengthening the brakes to suppress rattling is also conceivable, but there are concerns about the durability of the teeth against the brakes, noise, and overload of the motor, resulting in conflicts with energy savings and cost reductions. 3 tends to increase the rotation unevenness.
Looking at banding, on the other hand, various disturbance components (= load torque) are mixed in the photosensitive drum 3, but when there is an impulse-type disturbance, the photosensitive drum 3 has a high-frequency component exceeding the control band. It is difficult to remove this by control, and requires a mechanical filter such as a flywheel as a means other than control.
For example, when positioning accuracy does not matter much like a conventional monochrome machine with a relatively low speed, a heavy flywheel with a large diameter is used to suppress rotation unevenness in the banding band without relying on control. The photosensitive drum could be rotated.
[0008]
However, the drum rotation speed has increased due to recent demands for improvement in printing speed and reduction in the diameter of the photosensitive drum, and the frequency component of disturbance that causes rotation unevenness has been increasing in frequency. It is starting to play.
Generally, when a feedback control system is considered as shown in FIG. 14A, the disturbance suppression effect by the control is effective in a low frequency range lower than the control band, and as shown in FIG. In addition, the disturbance suppression effect of the flywheel is effective in a high frequency range higher than the control band.
[0009]
The present invention has been made in view of such a problem, and by performing drive control of a small-diameter flywheel to which a photosensitive drum is connected, color misregistration occurs even when the photosensitive drum shaft is eccentric. It is an object of the present invention to provide an image forming apparatus having a photosensitive drum driving configuration that is difficult and does not easily cause banding even without a heavy large-diameter flywheel.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a drum gear is provided so as to rotate synchronously with the photosensitive drum around the rotation axis of the photosensitive drum, and is provided so as to mesh with the drum gear. An image forming apparatus that rotates the photosensitive drum by rotating a driving gear provided by a driving source, a flywheel is provided together with the drum gear, and an acceleration motor driven by an acceleration motor is provided as the driving gear. Two driving gears, a gear and a reduction gear driven by a reduction motor, are provided. The acceleration motor generates a rotational force along the rotation direction of the photosensitive drum, and the reduction motor is These accelerating motor and decelerating motor generate a rotational force in a direction opposite to the rotational direction of the photosensitive drum, and based on information of the rotational angle detecting means of the photosensitive drum. Therefore adopts a configuration that controls the rotation speed of the photosensitive drum at a constant speed.
[0011]
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, a predetermined torque is generated in the acceleration motor, a predetermined reverse torque is generated in the deceleration motor, and control is performed. Among the torques, the torque required for accelerating the photosensitive drum is additionally generated by the acceleration motor, and the torque necessary for decelerating the photosensitive drum is additionally generated by the deceleration motor. .
[0012]
According to a third aspect of the present invention, in the image forming apparatus of the first aspect, the drum gear and the flywheel are integrally formed.
[0013]
According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, an intermediate gear is provided between the drum gear and each of the drive gears.
[0014]
According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, when an outer diameter of the drum gear is d1, an outer diameter of each of the intermediate shaft gears is d2, and an outer diameter of the drive gear is d3, The configuration satisfies the relationship d1>d2> d3.
[0015]
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, a configuration is adopted in which a helical gear is used for a rotational force transmitting portion.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. The same parts as those in the prior art are denoted by the same reference numerals.
First, an outline of the configuration of a tandem-type color copying machine as an image forming apparatus according to the present embodiment will be described with reference to FIG. The color copying machine 20 includes image forming apparatuses 21C, 21Y, 21M, and 21BK that form images for each color in accordance with a document image, and a transfer apparatus 22 that is arranged to face the image forming apparatuses 21C, 21Y, 21M, and 21BK. A manual feed tray 23 as a sheet-like medium supply unit for supplying various sheet-like media (recording media) to a transfer area where the image forming apparatuses 21C, 21Y, 21M, and 21BK and the transfer device 22 face each other; , 24, a manual feed tray 23, a registration roller pair 30 for supplying the sheet-like medium conveyed from the paper feed cassettes 24, 24 at the timing of image formation by the image forming apparatuses 21C, 21Y, 21M, 21BK, and transfer. The image forming apparatus includes a fixing device 1 that fixes the sheet-shaped medium after the transfer in the area.
[0017]
Each of the image forming devices 21C, 21Y, 21M, and 21BK performs development of each color of cyan, yellow, magenta, and black, and uses different toner colors. The configuration of 21C will be described as a representative of each of the image forming apparatuses 21C, 21Y, 21M, and 21BK. The image forming device 21C includes a photosensitive drum 25C as an image carrier, a charging device 27C, a developing device 26C, a cleaning device 28C, and the like which are sequentially arranged in the rotation direction A of the photosensitive drum 25C. This is a known configuration that receives exposure light 29C with the developing device 26C.
[0018]
Next, the drive configuration of the photosensitive drum 25 will be described with reference to FIG. In the present embodiment, the drive transmission has a single-stage configuration, and power is transmitted from the motor shaft to the photosensitive drum shaft via a gear.
An acceleration gear 2 is attached to a rotation shaft 1a of an acceleration motor 1 which is a DC motor as a drive source, and is positioned as an auxiliary gear on a rotation shaft 10a of a deceleration motor which is also a DC motor as a drive source. The reduction gear 11 is attached. The drum gear 4 and the flywheel 12 are attached to the rotating shaft 25a of the photosensitive drum 25 so as to mesh with the driving gears 2 and 11.
It is preferable that the drum gear 4 and the flywheel 12 are provided integrally to suppress the twist (resonance) on the photosensitive drum shaft 25a. Here, the term “integrally” means both the case where the drum gear 4 and the flywheel 12 as separate bodies are tightly joined and the case where they are integrally formed.
It is desirable to use helical gears (for example, helical gears) for the drive gears 2 and 11 and the drum gear 4 in order to suppress unevenness in transmission of rotational force (the same applies to other embodiments described below).
[0019]
An encoder 5 is attached as a rotation angle detector to the rotation shaft 25a of the photosensitive drum 25, and its output is converted into rotation angle information by a detection device 6, and an operation amount is controlled by a control device 7 based on the information. After the calculation, the driving device 8 drives each of the motors 1 and 10.
When the photosensitive drum 25 rotates, the encoder 5 coaxial with the photosensitive drum 25 also rotates at the same time. As a result, the number of pulses corresponding to the rotation angle of the photosensitive drum 25 is output from the encoder 5, so that the detection device 6 can detect the drum rotation angle by counting the number of pulses.
The control device 7 calculates an operation amount according to the deviation between the drum rotation angle and the target rotation angle, and the drive device 8 generates an applied voltage necessary for a current flowing through the acceleration motor 1 and the deceleration motor 10 from the operation amount. I do.
[0020]
At this time, as shown in FIG. 2, for the positive operation amount I (t) (= acceleration), a predetermined torque is added and sent to the acceleration motor 1, and the negative operation amount I (t) (= deceleration) Is sent to the deceleration motor 10 after adding a predetermined reverse torque. In addition, the predetermined torque is a pressurization of a rotational force required to eliminate backlash caused by a backlash element between gears, and as shown in FIG. 3, the acceleration motor 1 and the deceleration motor 10 By applying an opposing rotational force to the motor, play is prevented. That is, the meshing shown in FIG. 4 occurs on the acceleration motor 1 side, and the meshing shown in FIG. 5 occurs on the deceleration motor 10 side.
As described above, the rotation of the photosensitive drum shaft 25a is controlled by the rotational force generated by the current flowing through the acceleration motor 1 and the rotational force generated by the current flowing through the deceleration motor 10.
[0021]
The reduction mechanism will be described in more detail. The relationship between the acceleration gear 2, the reduction gear 11, which is a motor-side gear, and the drum gear 4, which is a photosensitive drum-side gear, can be represented by a model as shown in FIG. .
In FIG. 6A, a case is considered where the driving gear 301 and the driven gear 302 mesh with each other. At this time, in an ideal case where the surface roughness of the teeth is not considered, the transmission characteristics between the driving side gear 301 and the driven side gear 302 include the backlash element due to the parallel coupling of the tooth spring strength K and the viscous friction coefficient D. B can be expressed by being connected in series.
At this time, it can be considered that these parameters are equivalently converted around the drive axis, and equivalently converted around the driven axis. Here, it is assumed that these parameters are equivalently converted around the driven axis. Zx, Jx, and Dx indicate the number of teeth, the moment of inertia, and the viscous friction coefficient of each gear, and Tx, ωx, and θx indicate torque, angular velocity, and angle, respectively. The suffix 1 indicates the driving side and the suffix 2 indicates the driven side.
[0022]
When the drive torque T ₁ of the drive shaft and the load torque T ₂ of the driven shaft are input and the angle θ ₁ of the drive shaft and the angle θ _{2 of the} driven shaft are output, the transfer function is shown in the block diagram of FIG. Can be indicated by
[0023]
Here, the operation of FIG. 7 will be described. Note the reduction ratio is set to _{i = Z} 1 / Z _2. The drive shaft torque T ₁ generated by the drive motor or the like is converted into a drive shaft angular velocity ω ₁ by a transfer function 201, and converted to an angle θ ₁ by a pure integration 202.
Similarly, the driven shaft torque T ₂ is converted into the driven shaft angular velocity ω ₂ by the transfer function 203, and is converted into the angle θ ₂ by the pure integration 204. Further, a torque is generated from an angle difference (θ ₁ · i−θ ₂ ) between the drive shaft and the driven shaft via a dead zone function 205 representing a backlash and a transfer function 206.
The generated torque acts on the driven shaft, and the drive shaft receives the reaction. When the reduction ratio i is considered, it is necessary to multiply the driven side torque by i (207) from the driven side torque and to multiply the driven side angle by i (208) from the driven side angle. .
[0024]
In this operation, a problem in control is that there is a dead zone 205 (= play) due to the backlash of the gears. In the case of the configuration shown in FIG. It has characteristics as shown in b). The gist of the present invention is that a wide range of control is achieved by sandwiching the photosensitive drum-side gear 4 using two motor-side gears 2 and 11 and performing a linear operation as shown in FIG. 8C avoiding these two dead zones. It is to realize a band, and also to suppress a high-frequency disturbance outside the control band by rotating the flywheel 12.
In addition, when a wide control band is realized by the high gain feedback, the frequency band of the disturbance that can be suppressed by the control extends to a high frequency range, so that the range of disturbance removal by the flywheel 12 moves to a high frequency range. 12 has a secondary effect of reducing the diameter.
[0025]
Next, a second embodiment will be described with reference to FIG. The same parts as those in the above-described embodiment are denoted by the same reference numerals, and the description of the configuration and function already described is omitted unless otherwise required, and only the main part will be described (the same in other embodiments below).
The present embodiment is characterized in that the drive transmission has a two-stage configuration and power is transmitted from the motor shaft to the photosensitive drum shaft via the intermediate shaft to the photosensitive drum shaft.
An acceleration gear 2 is attached to a rotating shaft 1a of the acceleration motor 1, and a two-stage intermediate gear 13 is attached to an intermediate shaft 16 in the vicinity thereof. A reduction gear 11 is attached to a rotation shaft 10a of the reduction motor 10, and a two-stage intermediate gear 14 is attached to an intermediate shaft 17 near the rotation shaft 10a.
A drum gear 15 is attached to the rotating shaft 25a of the photosensitive drum 25 so as to mesh with the small diameter portions 13a, 14a of the intermediate gears 13, 14.
[0026]
An encoder 5 as a rotation angle detector is attached to the rotation shaft 25a, and its output is converted into rotation angle information by a detection device 6, and an operation amount is calculated by the control device 7 based on the information. The driving devices 8 drive the motors 1 and 10.
In this embodiment, when the outer diameter of the drum gear 15 which is a photosensitive drum shaft gear is d1, the outer diameter of each of the intermediate gears 13 and 14 is d2, and the outer diameter of each of the motor shaft gears 2 and 11 is d3, The relationship between the outer diameters of the gears is set to satisfy d1>d2> d3. This is suitable for control on inertial load.
[0027]
Next, a third embodiment will be described with reference to FIG.
This embodiment is a modification of the second embodiment, in which a speed reducer 18 provided integrally with the acceleration motor 1 and a speed reducer 19 provided integrally with the speed reduction motor 10 each function as an intermediate gear. Doubles. The details of the operation are the same as those of the above-described embodiments, and a description thereof will be omitted.
[0028]
【The invention's effect】
According to the first aspect of the present invention, the drum gear is provided so as to rotate synchronously with the photosensitive drum around the rotation axis of the photosensitive drum, and the drive gear provided to mesh with the drum gear is driven. An image forming apparatus that rotates the photosensitive drum by rotating the photosensitive drum, a flywheel is provided together with the drum gear, and the driving gear includes an acceleration gear driven by an acceleration motor; And two driving gears of a reduction gear driven by the motor are provided. The acceleration motor generates a rotational force along the rotation direction of the photosensitive drum, and the reduction motor is rotated in the rotation direction of the photosensitive drum. A rotational force is generated to oppose the photosensitive drum, and the photosensitive drum is driven by the acceleration motor and the deceleration motor based on information of the rotation angle detecting means of the photosensitive drum. The rotation speed of the motor is controlled to a constant speed, so that the gear teeth on the acceleration motor side and the gear teeth on the photosensitive drum shaft seem to be in close contact with each other, and the gear teeth on the reduction motor side Since the gear teeth of the gear on the body drum shaft side seem to be in close contact, the backlash element of the gear is apparently eliminated, and highly responsive feedback control by the gear reduction mechanism becomes possible.
Further, by rotating the flywheel on the photosensitive drum shaft, high-frequency disturbance outside the control band can be suppressed. Furthermore, if feedback control with high responsiveness is realized, the frequency band of disturbance that can be suppressed by the control extends to the high frequency range, and the range of disturbance removal by the flywheel moves to the high frequency range, so the flywheel diameter can be reduced. Is obtained. As described above, since the rotation unevenness is reduced from the low frequency to the high frequency range, and the photosensitive drum can be rotated at a constant rotation speed by driving a small output motor, high image quality, power saving, and reduction in size and weight can be achieved.
[0029]
According to the second aspect of the invention, in the image forming apparatus according to the first aspect, the acceleration motor generates a predetermined torque, the deceleration motor generates a predetermined reverse torque, and Of the control torque, the torque required for acceleration of the photosensitive drum is additionally generated by the acceleration motor, and the torque required for deceleration of the photosensitive drum is additionally generated by the deceleration motor. By applying rotational force between the gears, the gear teeth on the acceleration motor side and the gear teeth on the photosensitive drum shaft seem to be in close contact, and the gear teeth on the reduction motor side and the photosensitive drum shaft Since the teeth of the gears on the side seem to be in close contact, the backlash element is apparently eliminated, and feedback control with high responsiveness is possible.
[0030]
According to the third aspect of the present invention, in the image forming apparatus according to the first aspect, the drum gear and the flywheel are integrally formed, so that the gear on the photosensitive drum shaft and the flywheel are formed. Can be prevented, and a highly rigid mechanism suitable for broadband control can be provided.
[0031]
According to the fourth aspect of the invention, in the image forming apparatus according to the first aspect, an intermediate gear is provided between the drum gear and each of the drive gears, so that a large reduction ratio can be set. Therefore, the size and weight of each motor can be reduced, and the diameter of the photosensitive drum shaft side gear can be reduced while maintaining a large reduction ratio, thereby contributing to downsizing of the image forming apparatus.
[0032]
According to a fifth aspect of the present invention, in the image forming apparatus of the fourth aspect, the outer diameter of the drum gear is d1, the outer diameter of each intermediate shaft gear is d2, and the outer diameter of the drive gear is d3. At this time, since the configuration is such that the relationship of d1>d2> d3 is satisfied, the inertia toward the drive can be suppressed to be small, so that feedback control with high responsiveness can be realized.
[0033]
According to the sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, a helical gear is used for a rotational force transmitting portion. Fluctuations in rotation unevenness can be suppressed smaller than when gears are used.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a drive configuration of a photosensitive drum according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a command current waveform according to the first embodiment.
FIG. 3 is a diagram showing a relationship between an acceleration torque and a deceleration torque for a drum gear.
FIG. 4 is an enlarged view of a tooth portion showing a meshing state of an acceleration gear and a drum gear in FIG. 3;
FIG. 5 is an enlarged view of a tooth portion showing a meshing state of a reduction gear and a drum gear in FIG. 3;
FIG. 6 is a diagram showing a physical model of a gear reduction mechanism.
FIG. 7 is a block diagram in FIG. 6;
8A and 8B are diagrams showing output characteristics, FIG. 8A is a diagram showing transmission characteristics on the acceleration motor side, FIG. 8B is a diagram showing transmission characteristics on the deceleration motor side, and FIG. It is a figure showing a characteristic.
FIG. 9 is a schematic configuration diagram of a color copying machine as an image forming apparatus.
FIG. 10 is a diagram illustrating a drive configuration of a photosensitive drum according to a second embodiment.
FIG. 11 is a diagram illustrating a drive configuration of a photosensitive drum according to a third embodiment.
FIG. 12 is a diagram illustrating a driving configuration of a conventional photosensitive drum.
13A and 13B are diagrams showing a command current waveform in the related art, wherein FIG. 13A is a diagram showing gain characteristics during open loop of a low gain control system, and FIG. 13B is a diagram showing a command current waveform to a drive motor during low gain control. (C) is a diagram showing a gain characteristic at the time of open loop of the high gain control system, and (d) is a diagram showing a command current waveform to the drive motor at the time of high gain control.
14A and 14B are diagrams illustrating a disturbance suppression effect, wherein FIG. 14A is a diagram illustrating an effect by feedback control, and FIG. 14B is a diagram illustrating an effect by a flywheel.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Acceleration motor 2 Acceleration gear 4 Drum gear 10 Reduction gear 11 Reduction gear 12 Flywheels 13 and 14 Intermediate gear 25 Photoconductor drum 25a Rotating shaft

Claims (6)

A drum gear is provided so as to rotate synchronously with the photosensitive drum around the rotation axis of the photosensitive drum, and a drive gear provided to mesh with the drum gear is driven to rotate by a drive source to thereby rotate the photosensitive member. In an image forming apparatus that rotates a drum,
A flywheel is provided together with the drum gear, and two driving gears, an acceleration gear driven by an acceleration motor and a reduction gear driven by a reduction motor, are provided as the driving gears. A motor generates a rotational force along the rotation direction of the photosensitive drum, the deceleration motor generates a rotation force against the rotation direction of the photosensitive drum, and a rotation angle of the photosensitive drum. An image forming apparatus, wherein the rotation speed of the photosensitive drum is controlled to a constant speed by the acceleration motor and the deceleration motor based on information of a detection unit. The image forming apparatus according to claim 1,
A predetermined torque is generated in the acceleration motor, a predetermined reverse torque is generated in the deceleration motor, and a torque required for accelerating the photosensitive drum out of the control torque is used for the acceleration. An image forming apparatus, wherein an additional torque is generated by a motor, and a torque required to decelerate the photosensitive drum is additionally generated by the deceleration motor. The image forming apparatus according to claim 1,
An image forming apparatus, wherein the drum gear and the flywheel are formed integrally. The image forming apparatus according to claim 1,
An image forming apparatus, wherein an intermediate gear is provided between the drum gear and each of the drive gears. The image forming apparatus according to claim 4,
An image forming apparatus which satisfies a relationship of d1>d2> d3, where d1 is an outer diameter of the drum gear, d2 is an outer diameter of each intermediate shaft gear, and d3 is an outer diameter of the drive gear. The image forming apparatus according to claim 1, wherein
An image forming apparatus using a helical gear for a rotational force transmitting portion.

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