JP5983064B2 - Rotation drive device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a rotational drive device, and more particularly to a rotational drive device that rotationally drives an image carrier or an intermediate transfer member of an image forming apparatus, and an image forming apparatus including the rotational drive device.

  In an image forming apparatus such as a copying machine or a printing machine, a roller that is a rotating body for conveying an image carrier or a film or sheet is rotationally driven by a rotation driving device using a reduction gear such as a motor and a gear. ing. In this case, in order to prevent color misregistration and color unevenness, it is necessary to control the rotational speed of each rotary drive device with high accuracy. As a factor of the speed unevenness generated in the rotary drive device, there are a gear one rotation cycle, a motor one rotation cycle, a gear one tooth cycle, and the like. One rotation of the gear, one gear tooth component, and the like have been taken to improve the meshing rate and drive stably by using the gear accuracy and helical teeth. Further, with respect to one rotation of the motor, a measure for mounting a high-precision motor is taken.

  However, depending on the accuracy of each component, there is a demerit that the cost of each component increases. Therefore, in order to achieve high-accuracy driving at low cost, for example, in Patent Document 1, a speed detection pattern is provided on a coupling disk that engages with a drive gear, and this speed detection pattern is detected by a detector and detected rotation information. Based on the above, a configuration for controlling the motor has been proposed. Patent Document 2 proposes a configuration for controlling the rotation speed of a motor serving as a drive source based on rotation information detected from an encoder provided on a rotation shaft of a photosensitive drum.

  As described above, the conventional rotational drive device suppresses the above-described speed fluctuation by controlling the motor based on the rotation information detected by the detector, such as the rotation detection pattern of the encoder provided on the component downstream from the motor. ing. However, when performing such control, there are the following problems. If the torsional rigidity of the part from the motor provided with the speed detection pattern or the motor to the speed detection pattern is weak, a delay occurs without following the rotation of the motor. If such a delay occurs, the targeted control cannot be performed. In particular, it is difficult to suppress high frequency fluctuation components such as one rotation of the motor.

  In Patent Document 1, since the coupling provided with the speed detection pattern and the drive gear are engaged via the viscoelastic body, the torsional rigidity of the viscoelastic body portion is low, and the operation of the coupling is delayed. It is difficult to control. Further, in Patent Document 2, since a plurality of parts are interposed from the motor to the encoder, if the torsional rigidity is low, the encoder is delayed and it is difficult to control the target.

  In view of this, Patent Document 3 proposes a configuration in which a traction reduction device that transmits a rotational force by frictional contact between metal members is used as a rotation drive device.

  According to the configuration of Patent Document 3, since the rotational force is transmitted by frictional contact between metal members, there is a merit that the torsional rigidity is high, the occurrence of operation delay is extremely small, and target control can be performed. Since it is a metal member, there is a demilit that the cost is high and the reduction device is large in size.

  An object of the present invention is to provide a rotary drive device that is small in size and low in cost and can suppress rotational unevenness.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a high-quality image forming apparatus free from color misregistration and color unevenness by using a rotary drive device that is small and low in cost and can suppress rotational unevenness.

In order to achieve the above-described object, a rotary drive device according to the present invention is a resin-made second gear that directly meshes with a drive motor having a drive shaft and a first gear formed on the outer peripheral surface of the drive shaft to reduce rotation . comprising a gear, and an encoder attached to the second gear, and an output shaft provided in the rotational center of the second gear, the transmission unit second gear for transmitting the output shaft power from a drive motor The meshing rigidity K1 of the first gear and the second gear is set to be larger than the torsional rigidity K2 of the transmission portion.

According to the present invention, a drive motor having a drive shaft, a second gear made of resin that directly meshes with the first gear formed on the outer peripheral surface of the drive shaft and decelerates the rotation, and the second gear are attached. an encoder was, in the rotary driving device and an output shaft provided in the rotational center of the second gear, the meshing rigidity K1 of the first and second gears, power and power from the drive motor to the output shaft By making it larger than the torsional rigidity K2 of the transmission portion of the transmission gear, the delay of the transmission portion that transmits power to the output shaft occurs before the meshing of the first gear and the second gear. Since the encoder is provided on the second gear, it is difficult to detect the delay of the transmission unit that transmits power to the output shaft, and the rotation unevenness can be suppressed with a small size and low cost. By using it in a rotational drive device for a body or an intermediate transfer body, aiming control can be performed, and high image quality without color misregistration and color unevenness can be obtained.

1 is a schematic configuration diagram of an image forming apparatus according to the present invention. FIG. 3 is a perspective view illustrating a configuration of a rotation driving device according to the present invention and an application form as a driving unit of an intermediate transfer member. The enlarged view which shows the structure of the rotational drive apparatus which concerns on this invention. The figure which shows the evaluation result of the frequency response characteristic in a general rotary drive device. The figure which shows the evaluation result of the frequency response characteristic in the rotary drive device to which this invention is applied. (A) is a front view which describes one form of the gearwheel used as the characteristic part in the rotary drive device which concerns on this invention, (b) is a fragmentary sectional view of (a). (A) is a front view which describes another form of the gearwheel used as the characteristic part in the rotary drive device which concerns on this invention, (b) is a fragmentary sectional view of (a). (A) is a front view which describes another form of the gearwheel used as the characteristic part in the rotary drive device which concerns on this invention, (b) is (a) partial sectional drawing. FIG. 6 is a perspective view showing another configuration of the rotational drive device according to the present invention and an application form as a drive unit of the image carrier.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In the present embodiment, the present invention is applied to an electrophotographic color copier (hereinafter referred to as a “copier”) which is a form of an image forming apparatus. Note that the copying machine according to the embodiment is a so-called tandem image forming apparatus that employs a dry two-component developing system using a dry two-component developer. The image forming apparatus is not limited to a copying machine, but includes a so-called multi-function machine having a plurality of functions such as a printer, a facsimile, or a printer, a facsimile, and a copying machine.

  FIG. 1 is a schematic configuration diagram of an image forming unit in the copying machine 100 according to the present embodiment. The copying machine 100 receives image data as image information from an image reading unit (not shown) and performs image forming processing. The copying machine 100 includes yellow (hereinafter abbreviated as “Y”), magenta (hereinafter abbreviated as “M”), cyan (hereinafter abbreviated as “C”), and black (hereinafter “Bk”). The photosensitive drums 1Y, 1M, 1C, and 1Bk, which are image carriers as four rotating bodies for each color, are arranged in parallel. These photosensitive drums 1Y, 1M, 1C, and 1Bk are intermediate transfer belts 5 that are endless belt-like intermediate transfer members supported by a plurality of rotatable rollers 30 and 31 including an intermediate transfer drive roller 28 that is a drive roller. Are arranged side by side along the belt movement direction. Around the photosensitive drums 1Y, 1M, 1C, and 1Bk, chargers 2Y, 2M, 2C, and 2Bk as charging means, developing devices 9Y, 9M, 9C, and 9Bk corresponding to the respective colors, and cleaning devices 4Y, 4M, and 4B, respectively. Members used in the electrophotographic process, such as 4C and 4Bk, and static elimination lamps 3Y, 3M, 3C, and 3Bk serving as static elimination means, are arranged in the order of the processes.

  When a full-color image is formed by the copying machine 100 according to this embodiment, the photosensitive drum 1Y is uniformly rotated by the charger 2Y while being driven to rotate in the direction of the arrow in the drawing by a rotation driving device 20 for the photosensitive drum described later. After charging, a Y electrostatic latent image is formed on the photosensitive drum 1Y by irradiation with a light beam LY from an optical writing device (not shown). This Y electrostatic latent image is developed with Y toner in the developer by the developing device 9Y. During development, a predetermined developing bias is applied between the developing roller 10Y provided in the developing device 9Y and the photosensitive drum 1Y, and the Y toner on the developing roller 10Y is applied to the Y electrostatic latent image portion on the photosensitive drum 1Y. Electrostatic adsorption.

  The Y toner image developed and formed in this way is conveyed to a primary transfer position where the photosensitive drum 1Y and the intermediate transfer belt 5 come into contact with the rotation of the photosensitive drum 1Y. At the primary transfer position, a predetermined bias voltage is applied to the back surface of the intermediate transfer belt 5 by a primary transfer roller 6Y serving as a primary transfer unit. The Y toner image on the photosensitive drum 1Y is drawn toward the intermediate transfer belt 5 by the primary transfer electric field generated by this bias application, and is primarily transferred onto the intermediate transfer belt 5.

  Similarly, M toner images, C toner images, and Bk toner images are formed on the photosensitive drums 1M, 1C, and 1Bk by the developing rollers 10M, 10C, and 10Bk provided in the developing devices 9M, 9C, and 9Bk. The M toner image, the C toner image, and the Bk toner image are sequentially overlapped by applying a predetermined bias voltage to the Y toner image on the intermediate transfer belt 5 by the primary transfer rollers 6M, 6C, and 6Bk, respectively. Primary transfer is performed.

  The toner image having four colors superimposed on the intermediate transfer belt 5 is a secondary transfer roller serving as a secondary transfer unit disposed opposite to the roller 31 with the intermediate transfer belt 5 interposed therebetween as the intermediate transfer belt 5 rotates. 7 and the intermediate transfer belt 5 are conveyed to a secondary transfer position. To this secondary transfer position, a transfer sheet P as a recording medium is conveyed from a paper feeding unit at a predetermined timing by a registration roller (not shown). At this secondary transfer position, a predetermined bias voltage is applied to the back surface of the transfer paper P by the secondary transfer roller 7, and the secondary transfer electric field generated by the bias application and the contact pressure at the secondary transfer position are applied. The toner image on the intermediate transfer belt 5 is secondarily transferred onto the transfer paper P at once. Thereafter, the transfer paper P onto which the toner image has been secondarily transferred is subjected to a fixing process by the fixing roller pair 8 constituting the fixing device, and then discharged outside the device.

  Next, the configuration of the rotary drive device 20 that is one embodiment of the present invention will be described with reference to FIGS. In this embodiment, the rotation driving device 20 is used as the rotation driving unit of the intermediate transfer belt 5. The rotation driving device 20 applies the rotational driving force of an intermediate transfer driving motor 21 as a driving source to the intermediate transfer belt 5 shown in FIG. 2 wound around the roller via an intermediate transfer driving roller 28 serving as a driving roller. To communicate.

  The outer peripheral surface of the drive shaft 22 of the intermediate transfer motor 21 is geared to form a motor gear 22A, and the driving force of the intermediate transfer motor 21 is transmitted from the motor gear 22A to the intermediate transfer gear 23 that is a gear. As shown in FIG. 3, the intermediate transfer gear 23 can rotate integrally with the output shaft 27 via a parallel pin 26 that is press-fitted so as to penetrate the output shaft 27, and the driving force from the intermediate transfer gear 23. Is transmitted to the output shaft 27. The output shaft 27 and the intermediate transfer driving roller 28 are integrated so that their rotation centers coincide with each other, and the intermediate transfer belt 5 (see FIGS. 1 and 2) is driven via the intermediate transfer driving roller 28. It is configured.

  A disk-shaped encoder 24 is attached to the intermediate transfer gear 23. An encoder sensor 25 that constitutes rotation information detection means is arranged on the outer peripheral side of the encoder 24, and detects rotation information of the encoder 24. The intermediate transfer drive motor 21 and the encoder sensor 25 are electrically connected to the control unit 200. The control unit 200 is configured by a known computer, and the rotation unevenness of the intermediate transfer belt 5 is suppressed by feedback controlling the rotation of the intermediate transfer drive motor 21 based on the rotation information from the encoder sensor 25. .

  When performing feedback control, the torsional rigidity of each component to which the driving force from the intermediate transfer drive motor 21 to the component (here, the intermediate transfer gear 23) to which the encoder 24 is attached is important. If the torsional rigidity is low, a delay occurs in the rotation of the encoder 24 with respect to the rotation of the intermediate transfer drive motor 21, so that it is difficult to perform feedback control as intended. If the torsional rigidity is low, the resonance of the rotating system occurs at a low frequency. When performing feedback control, control is generally performed at a frequency lower than the resonance point. Therefore, the lower the resonance frequency, the higher the frequency of the feedback control, the narrower the control area, and the difficult the target control is. It becomes. As a result, there is a concern that rotation unevenness occurs in the intermediate transfer belt 5 and problems in image formation such as color misregistration and color unevenness occur.

  When feedback control is performed in this way, the torsional rigidity and resonance frequency of the mechanical component that transmits the driving force are very important. There is a frequency response characteristic evaluation as an evaluation method for examining at what frequency the resonance frequency is generated. In general, this is an evaluation in which the amplitude is variably given to the drive motor from 1 Hz to 1000 Hz, encoder rotation information is detected, and the response to the rotation of the drive motor is observed. An example of the evaluation result is shown in FIG.

  In FIG. 4, the horizontal axis represents frequency and the vertical axis represents Gain (dB). As can be seen from FIG. 4, there is a portion surrounded by an ellipse having a large Gain (dB) in a mountain shape. This is the resonance point. If the resonance point can be set to a high frequency, the frequency of feedback control can be increased, and rotation unevenness can be further suppressed. Even if the resonance point cannot be raised, the frequency of feedback control can be increased to some extent if the way of raising Gain (dB) at the resonance point (increase rate) can be reduced. That is, in order to perform feedback control as intended, two measures are required, such as increasing the resonance frequency and reducing the increase in Gain (dB) at the resonance point (decreasing the increase rate).

  Here, the torsional rigidity from the intermediate transfer drive motor 21 to the encoder 24 in the configuration shown in FIGS. 2 and 3 is considered as follows.

  The torsional rigidity K1 of the meshing portion A between the motor gear 22A and the intermediate transfer gear 23 cut by the drive shaft 22 of the intermediate transfer motor 21, and the parallel pin 26 press-fitted into the output shaft 27 and the parallel pin 26 of the intermediate transfer gear 23 are received. An example of the torsional rigidity K2 at the portion 23B is given. That is, the intermediate transfer gear 23 has two torsional rigidity, that is, a gear meshing portion and a transmission portion B to the output shaft 27. In other words, the intermediate transfer gear 23 has a tooth portion 23A constituting a meshing portion A with the motor gear 22A on the outer peripheral surface thereof, and a transmission portion in which the parallel pin 26 is press-fitted into the output shaft 27 on the rotation center side. It has a receiving portion 23B.

  Next, the evaluation results obtained by changing the torsional rigidity K1 and K2 at these portions are shown in FIG.

  There are three evaluation conditions: K1> K2, K1≈K2, and K1 <K2. FIG. 5 shows the evaluation results when K1 is fixed and K2 is changed. The resonance point may be K1 <K2, K1≈K2, and K1> K2. This is a result corresponding to the torsional rigidity of K2. On the other hand, the smallest increase in Gain (dB) at the resonance point is K1> K2. This is because the encoder 24 provided in the intermediate transfer gear 23 is disposed downstream of K1 and upstream of K2 in the two torsional rigidity K1 and K2. That is, when viewed from the encoder 24, the motor gear 22A and the intermediate transfer gear 23 are driven to transmit and rotate, so that if the torsional rigidity here is weak, it will come out strongly as a resonance, but the parallel pin 26 and the intermediate transfer gear 23 will receive. Since the transmission of the portion 23B is at a downstream position when viewed from the encoder 24, resonance here does not occur strongly in the encoder 24. From this evaluation result, the resonance point does not change so much, and the gain (dB) at the time of resonance is best when K1> K2. Therefore, in the feedback control by the control means 200, K1> K2. The relationship will be the best.

  The shape (characteristic configuration of the present application) of the intermediate transfer gear 23 for K1> K2 is shown in FIGS. 6, 7, and 8A and 8B, respectively.

6 (a) and 6 (b), the thickness t of the receiving portion 23B of the parallel pin 26 of the intermediate transfer gear 23 is formed thinner than the thickness t1 of other portions. Thereby, the torsional rigidity K2 at the receiving portion 23B of the parallel pin 26 of the intermediate transfer gear 23 can be lowered, and K1> K2.
In the intermediate transfer gear 23 shown in FIGS. 7A and 7B, the thickness t <b> 2 of the web 23 </ b> C is thicker than the thickness t of the receiving portion 23 </ b> B of the parallel pin 26. As a result, the torsional rigidity K1 of the meshing portion A of the intermediate transfer gear 23 can be increased, and K1> K2.
In the intermediate transfer gear 23 shown in FIGS. 8A and 8B, the wall thickness t3 of the rim 23D (tooth bottom) of the intermediate transfer gear 23 is made thicker than the wall thickness t of the receiving portion 23B of the parallel pin 26. Yes. As a result, the torsional rigidity K1 of the meshing portion A of the intermediate transfer gear 26 can be increased, and K1> K2.
6 to 8, the method for increasing the torsional rigidity K1 and the method for decreasing the torsional rigidity K2 are individually described. However, the intermediate transfer gear 23 may be formed by combining these methods.

  By adopting the above-described torsional rigidity, the frequency of feedback control of the intermediate transfer drive motor 21 can be increased, and rotation unevenness can be suppressed. Examples of the material of the intermediate transfer gear 23 include metals and resins. In the case of resin, there is a concern that the accuracy may deteriorate if the thickness is not uniform, but high accuracy can be achieved even with a non-uniform thickness by a molding technique such as compression molding.

  Thus, by setting the twist rigidity relationship in the rotational drive device 20 that rotationally drives the intermediate transfer belt 5 to K1> K2, the frequency of feedback control of the intermediate transfer drive motor 21 can be increased, and rotation unevenness is suppressed. can do. As a result, color misregistration and color unevenness caused by rotation unevenness of the intermediate transfer belt 5 can be suppressed, and a high-quality color copying machine (image forming apparatus) can be provided. That is, since the rotation driving device 20 according to the present invention is used as the rotation driving unit of the intermediate transfer belt 5, the speed fluctuation of the intermediate transfer belt 5 is extremely reduced, and the image forming apparatus has high image quality without color misregistration and color unevenness. Can be provided.

  FIG. 9 shows an embodiment in which the rotation drive unit 30 having the characteristic configuration of the present invention is used for the rotation drive unit of the photosensitive drum shown in FIG. In this embodiment, an example applied to one photoconductor drum 1Y will be described as a representative. However, in the case of a color image forming apparatus, since four color photoconductor drums are provided, the other photoconductor drums 1M, 1C, 1Bk are provided. Also, the same rotational drive device 30 is used for rotational driving.

  The rotational drive device 30 used for rotationally driving the photosensitive drum 1Y transmits the rotational driving force of a drum drive motor 31 as a drive source to the photosensitive drum 1Y.

  The outer peripheral surface of the drive shaft 32 of the drum drive motor 31 is geared to form a motor gear 32A, and the driving force of the drum drive motor 31 is transmitted from the motor gear 32A to the drum gear 33 that is a gear. As in FIG. 3, the drum gear 33 can rotate integrally with the output shaft 37 via a parallel pin 36 that is press-fitted through the output shaft 37, and transmits the driving force from the drum gear 33 to the output shaft 37. Is configured to do. The output shaft 37 and the drum shaft 39 are arranged on the same rotation center line, and are configured to rotate at the same rotation center. A coupling 38 is mounted between the output shaft 37 and the drum shaft 39, and both the shafts are connected to each other so that a driving force is transmitted to the photosensitive drum 1Y via the drum shaft 37. ing.

  A disc-shaped encoder 34 is attached to the drum gear 33. An encoder sensor 35 that constitutes rotation information detection means is arranged on the outer peripheral side of the encoder 34, and detects rotation information of the encoder 34. The drum drive motor 31 and the encoder sensor 35 are electrically connected to the control means 300. The control means 300 is constituted by a known computer, and controls the rotation of the drum drive motor 31 based on the rotation information from the encoder sensor 35, thereby suppressing the rotation unevenness of the photosensitive drum 1Y.

  Similar to the intermediate transfer gear 23 described in the previous embodiment, the drum gear 33 has a tooth portion 33A serving as a gear meshing portion B on the outer peripheral surface of the drum gear 33, and is parallel to the output shaft 37 on the rotation center side. It has the transmission part 33B in which the pin 36 was press-fit. The relationship between the gear meshing rigidity K1 and the torsional rigidity K2 of the receiving portion 33B of the parallel pin 36 is K1> K2. Examples of the shape of the drum gear 33 include the forms shown in FIGS. Since the detailed shape is the same as that of the intermediate transfer gear 23, it is omitted here.

  Thus, by setting the relationship of torsional rigidity in the rotational drive device 30 that rotationally drives the photosensitive drum 1Y to K1> K2, the frequency of feedback control of the drum drive motor 31 can be increased, and rotation unevenness is suppressed. be able to. Thereby, it is possible to suppress color misregistration and color unevenness due to rotation unevenness of the photosensitive drum 1Y, and it is possible to provide a high-quality color copying machine (image forming apparatus). That is, since the rotation driving device 30 according to the present invention is used as the rotation driving unit of each photosensitive drum, the speed fluctuation of each photosensitive drum is extremely reduced, and a high-quality image forming apparatus free from color misregistration and color unevenness. Can be provided.

  As in the above embodiment, the meshing rigidity K1 of the gears 23 and 33 is made larger than the torsional rigidity K2 of the transmission portions 23B and 33B that transmit the power from the drive motors 21 and 31 to the output shafts 27 and 37. Thus, the delay of the transmission portions 23B and 33B that transmit power to the output shafts 27 and 37 occurs before the meshing of the gears 23 and 33. Since the encoders 24 and 34 are provided on the gears 23 and 33, the delays 23B and 33B of the transmission unit that transmits power to the output shafts 27 and 37 are difficult to detect, so that aim control can be performed and rotation unevenness can be performed. Therefore, it is possible to provide the rotational drive devices 20 and 30 with a small amount of rotation.

  When the thickness t of the transmission portion that transmits power to the output shafts 27 and 37 is made thinner than the other thickness t1, the transmission portion 23B that transmits power from the drive motors 21 and 31 to the output shafts 27 and 37, The torsional rigidity K2 of 33B can be made smaller than the meshing rigidity K1 of the gears 23 and 33. Thereby, the delay of the transmission parts 23B and 33B occurs before the meshing of the gears. Since the encoders 24 and 34 are provided on the gears 23 and 33, the delay of the transmission portions 23B and 33B that transmit power to the output shafts 27 and 37 is difficult to be detected. Therefore, it is possible to provide a rotational drive device with less.

  By making the web wall thickness t2 of each gear 23, 33 thicker than the wall thickness t1 of the transmission portions 23B, 33B that transmit power to the output shafts 27, 37, the gear thickness is greater than the torsional rigidity K2 of the transmission portions 23B, 33B. The meshing rigidity K1 can be increased. Thereby, the delay of the transmission parts 23B and 33B occurs before the meshing of the gears. Since the encoders 24 and 34 are provided on the gears 23 and 33, the delay of the transmission unit that transmits power to the output shafts 27 and 37 is difficult to be detected. A drive device can be provided.

  By making the rim wall thickness t3 of each gear 23, 33 thicker than the wall thickness t of the transmission parts 23B, 33B that transmit power to the output shafts 27, 37, the torsional rigidity K2 of the transmission parts 23B, 33B is increased. The meshing rigidity K1 can be increased. Thereby, the delay of the transmission parts 23B and 33B occurs before the meshing of the gears. Since the encoders 24 and 34 are provided on the gears 23 and 33, the delay of the transmission parts 23B and 33B is difficult to be detected, so that the target drive can be controlled and the rotation driving devices 20 and 30 with little rotation unevenness are provided. can do.

  As described in the above embodiment, by integrating the output shaft 27 and the drive shaft of the intermediate transfer drive roller 28 that drives the intermediate transfer belt 5, the coupling member can be eliminated, and the speed generated in the coupling portion. A variation factor can be eliminated, and a high-quality image forming apparatus with less color misregistration and color unevenness can be provided.

1 (Y, M, C, K) image carrier 5 intermediate transfer member 20, 30 rotation drive device 21, 31 drive motor 22, 32 drive shaft 23, 33 gear 23A, 33A tooth portion 23B, 33B transmission portion 24, 34 Encoder 27, 37 Output shaft 28 Drive roller 100 Image forming apparatus K1 Gear meshing rigidity K2 Torsional rigidity of transmission part t Thickness of transmission part t1 Thickness of other parts t2 Web thickness t3 Rim thickness

JP 2010-102247 A JP 2000-231305 A JP 2002-171779 gazette

Claims (7)

A drive motor having a drive shaft, a second gear made of resin that directly meshes with the first gear formed on the outer peripheral surface of the drive shaft and decelerates rotation, and an encoder attached to the second gear; In the rotation drive device comprising an output shaft provided at the rotation center of the second gear,
The second gear has a transmission unit that transmits power from the drive motor to the output shaft,
The rotational drive device characterized in that the meshing rigidity K1 of the first gear and the second gear is set to be larger than the torsional rigidity K2 of the transmission portion. 2. The rotary drive device according to claim 1, wherein the second gear is formed such that the thickness of the transmission portion is thinner than the thickness of other portions. The rotary drive device according to claim 1 or 2, wherein the second gear is formed with a web thickness larger than a thickness of the transmission portion. 4. The rotary drive device according to claim 1, wherein the second gear is formed with a rim thickness larger than a thickness of the transmission portion. 5. An image carrier on which a toner image is formed, and a rotation drive device that rotationally drives the image carrier;
An image forming apparatus comprising the rotation drive device according to claim 1 as the rotation drive device. In an image forming apparatus comprising: an image carrier on which a toner image is formed; and an intermediate transfer member onto which the toner image formed on the image carrier is transferred.
An image forming apparatus comprising the rotation drive device according to claim 1 as the rotation drive device.   The image forming apparatus according to claim 6, wherein an output shaft provided in the rotation driving device and a driving shaft of a driving roller for driving the intermediate transfer member are integrated.

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