JP2009069476A - Drive unit, and image forming device equipped with the drive unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive unit capable of preventing the rotational speed i.e. the angular velocity from fluctuating by meshing of mutual gears, and capable of effectively restraining a rotation-driven object such as, a photoreceptor drum in a rotation-driven side from affecting operation, in a gear train that transmits rotation power from a power source. <P>SOLUTION: The rotation power from a power source motor 6 is rotatively transmitted to a rotor, such as, the photoreceptor drum 104 via the gear train comprising an input gear 3, an intermediate gear 2 and a drum gear (output gear) 1. The frequency amplitude due to the fluctuations in the angular velocity in the output gear is set so as to make minimum a phase by meshing of the output gear with the intermediate gear 2 in this side thereof by one, and a phase by meshing thereof with the input gear 3 in this side thereof by two. The output gear and the input gear 3 are also constituted to be movable, under conditions where positions thereof faced to a rotary shaft direction are kept fixed at all times. As a result, the rotational speed i.e. the angular velocity is prevented from being fluctuated by the meshing of the fellow gears in the gear train. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus (hereinafter simply referred to as an “image forming apparatus”) such as a copying machine, a facsimile machine, a printer, and a multifunction machine, and relates to a driving device mounted on the image forming apparatus.

  A drive device that operates an image carrier such as a photosensitive drum or an intermediate transfer member in an image forming apparatus generally includes a gear train that transmits rotation output from a power source such as a motor to the photosensitive drum. . By the way, when the gear train is configured, vibration is generated by the meshing of the gears, and the vibration component may affect the speed of the rotation of the photosensitive drum or the like. When rotational fluctuations occur in the photosensitive drum or the like, there is a problem that the image expands and contracts, causing pitch unevenness (banding) and appearing on the image.

  In order to eliminate the rotation fluctuation of the photosensitive drum caused by the vibration of the gear train, the following techniques including the present applicant have been proposed. For example, when the gear train is composed of three gears of an input gear, an intermediate gear, and an output gear in order from the drive input side, the meshing phase on the input side by the input gear and the intermediate gear, the intermediate gear, and the output gear The output side meshing phase is shifted by 180 ° with a half phase. By doing so, fluctuations in angular velocity at the time of gear rotation are canceled, and fluctuations in rotation on the output side are suppressed (for example, see Patent Documents 1 and 2).

  In particular, in the gear train of a drive device that rotationally drives a photosensitive drum or the like, the meshing length (meshing ratio) is increased by using an inclined gear as a gear, and the meshing vibration is suppressed as much as possible to smoothly rotate. In many cases, a transmission mechanism is employed. When the inclined gear is used, the gear phases of the input gear, the intermediate gear, and the output gear are reduced in order to reduce the rotational fluctuation, that is, the fluctuation of the angular velocity by shifting the meshing phase by 1/2 phase (angle 180 °). There is known a mechanism for adjusting a shaft angle formed in a rotation direction with reference to an intermediate gear. The phase of the gear also changes depending on the width dimension in the direction of the rotation axis with which the inclined gear engages. Focusing on this point, as an alternative technique to the above-described shaft angle adjusting mechanism, a device has been proposed in which the inclined gear is movable in the direction of the rotating shaft and the phase is adjusted by fluctuations in angular velocity due to the meshing frequency. Furthermore, a structure provided with a gear position restricting member that restricts the position of the inclined gear in the rotation axis direction has also been proposed (see, for example, Patent Document 3).

  On the other hand, particularly in the case of a printer or a copying machine, the image carrier such as a photosensitive drum can be replaced when it reaches the end of its life. That is, an image carrier such as a photosensitive drum is unitized together with other process means, and the devices and members in the unit can be exchanged so that the unit can be attached to or detached from the image forming apparatus. In such a case, a structure is required in which a general user can easily attach and detach the unit to and from the image forming apparatus main body.

  Along with further downsizing of the image forming apparatus, there are an increasing number of structures in which the unit is attached to and detached from the image forming apparatus main body from a direction orthogonal to the rotation axis of the photosensitive drum. In this case, as a coupling method for meshing the gears in the gear train, the gears are arranged so that the gears overlap each other when viewed from the unit insertion direction, and the gears are automatically meshed in half in conjunction with the unit insertion operation. It has been known. However, in that case, there are problems such as scratches and dents on the tooth surface of the gear and a reduction in rotational accuracy.

  In order to solve such problems as gear scratches, the following structure is known in which a coupling connection mechanism is provided on the output gear. In other words, the rotating power from the power source provided in the image forming apparatus main body is transmitted to the output gear via the gear train, and the output gear is rotated together with a coupling mechanism such as a coupling provided on the output gear side. Move along the axial direction. The movement of the output gear can be linked to an operation for opening and closing the apparatus main body cover, the transfer belt unit, and the like. When the output gear is moved, it abuts against the end of a rotating body such as a photosensitive drum, and the output gear is positioned at the abutting position. At the time when the output gear is positioned, the meshing relationship between the gears is established and coupled, and the photosensitive drum or the like can be rotated.

  As is apparent from the several prior arts, it can be seen that it is desirable to construct a gear train using inclined gears in order to rotate an image carrier such as a photosensitive drum with high accuracy. At the same time, it is desirable that the input-side meshing phase of the input gear and the intermediate gear be shifted from the output-side meshing phase of the intermediate gear and the output gear by an angle of 180 ° of ½ phase. is there. Furthermore, in consideration of user convenience, when exchanging the unit composed of the photosensitive drum and the process means, it is preferable to attach and detach the unit from the direction orthogonal to the rotation axis of the photosensitive drum or the like.

Japanese Patent Laid-Open No. 9-26001 JP 2000-328551 A JP 2003-240065 A

  However, adopting a structure in which the unit is inserted and removed from a direction orthogonal to the drum rotation axis or the like raises the following new problem. That is, the advantage of using the inclined gear in the gear train is not fully utilized. Further, when a gear train is configured by the input gear, the intermediate gear, and the output gear, the effect of setting the phase due to the meshing between the input side and the output side to a position shifted by ½ phase cannot be expected so much. The reason is as follows.

  One of the reasons is that when the photosensitive drum or the like rotates, a load or the like by the developing process means influences, and the photosensitive drum or the like undergoes minute vibrations in the direction of the rotation axis or changes in position. Therefore, vibration and position change are given to the phase difference between the input side meshing phase of the input gear and the intermediate gear and the output side meshing phase of the intermediate gear and the output gear. As a result, even if the meshing phase is shifted by ½ phase to cancel the angular velocity fluctuation, an effect sufficient to reduce the angular velocity fluctuation on the output side cannot be obtained.

  Another reason is the above-described structure in which the output gear with coupling is moved along the rotational axis direction and positioned by abutting against the end of a rotating body such as a photosensitive drum. According to this structure, each device such as the photosensitive drum in the unit has a variation in accuracy in the direction of the rotation axis, but this affects 100% of the target of accurately shifting the meshing phase by ½ phase. It is a point that cannot be achieved.

  From the above, the object of the present invention is to prevent fluctuations in rotational speed, that is, angular speed due to the meshing of gears in a gear train that transmits rotational power from a power source, and to be driven to rotate such as a photosensitive drum on the side where the rotation is transmitted. An object of the present invention is to provide a drive device that effectively suppresses the influence on the operation of the body.

  It is another object of the present invention to provide an image forming apparatus that can form a stable high-quality image by suppressing the occurrence of pitch unevenness due to the expansion and contraction of an image by including such a driving device.

  In order to achieve the above object, a typical drive device according to the present invention is a drive device that transmits rotational power from a power source to an output gear as a final gear through a gear train composed of two or more gears. Thus, the phase due to the meshing of the output gear and the previous gear and the phase due to the meshing of the two previous gears and the previous gear have the smallest frequency amplitude due to the fluctuation of the angular speed of the output gear. The output gear and the two previous gears are configured to be movable while maintaining their positions relative to the rotation axis direction constant at all times. It is.

  Further, in a typical image forming apparatus of the present invention having the above drive device, the output gear provided in the drive device is provided to the image carrying body rotated in the image forming apparatus main body, or the image carrying body is provided. The rotation drive body is positioned in the direction of the rotation axis with respect to the rotation drive body to be rotated, and the rotation is transmitted by being engaged.

  According to the driving device of the present invention, it is optimal as a mechanism for transmitting rotational power to an image carrier such as a photosensitive drum or an intermediate transfer member, and the rotational speed, that is, the angular speed fluctuation generated by the meshing of the gears of the gear train. Can be prevented.

  Further, according to the image forming apparatus of the present invention, by using the drive device in the image forming apparatus, it is possible to stably form a high-quality image free from pitch unevenness due to image expansion and contraction.

  Hereinafter, a preferred embodiment of a drive device according to the present invention and an image forming apparatus including the drive device will be described in detail using an electrophotographic printer as a specific example.

≪Printer structure≫
FIG. 1 shows a configuration of a printer main body including a driving device including a gear transmission mechanism of the present embodiment. The optical path of the laser light 101 emitted from the laser light emitting unit 100 swayed in the main scanning direction which is the rotational axis direction of the photosensitive drum (image carrier) 104 by a polygon scanner or the like is adjusted by a mirror 102 or the like. The adjusted laser beam 101 reaches the photosensitive drum 104 mounted as an image carrier in the process cartridge 103. An endless belt (not shown) can be disposed at a position facing the sheet 105 as a transfer material of the photosensitive drum 104 across the sheet 105.

  The photosensitive drum 104 rotates at a set rotational speed, and an image is formed on the surface of the photosensitive drum 104 in the sub-scanning direction (rotating direction of the photosensitive drum 104). That is, an arbitrary image is formed as a latent image by turning on / off the laser beam or controlling the intensity of light emission based on a signal from a data input device (not shown).

  A sheet 105 such as paper (transfer material) to be printed is stacked on a cassette 106, fed by a paper feed roller 107 in accordance with a print signal, and guided to the vicinity of the photosensitive drum 104 through a conveyance path 108. The photosensitive drum 104 which already has a latent image forms a toner image on the photosensitive drum 104 by a predetermined development process. This toner image is transferred onto the paper 105 by the transfer unit 109, and after the toner image is fixed by the fixing device 110, the toner image is discharged to the paper discharge unit 111.

  FIG. 2 shows a process of attaching the process cartridge 103 to the printer main body. The process cartridge 103 is a cartridge in which the photosensitive drum 104 and the developing process means acting on the photosensitive drum 104 are integrally formed, and can be easily attached to and detached from the printer body by the user. At the time of attachment / detachment, the user opens the cartridge cover 112 of the printer main body and is guided by a guide rail (not shown) provided in the printer main body to insert the process cartridge 104.

≪Drive mechanism≫
3A to 3C show a gear train of a gear transmission mechanism as a drive mechanism for transmitting rotational power from the motor 6 as a power source to the photosensitive drum 104. FIG. The gear train includes a motor 6 as a rotational power source, a motor gear 4 fixed to the motor shaft 5, an input gear 3 meshing with the motor gear 4, an intermediate gear 2, a drum gear 1, and the like. The drum gear 1 transmits rotation by engaging with the photosensitive drum 104 as a final gear. The intermediate gear 2 enters between the drum gear 1 and the input gear 3 and meshes with both gears. Therefore, in this embodiment, when the drum gear 1 is an “output gear”, the intermediate gear 2 can be defined as a gear that meshes with the output gear one before.

  As will be described in the first embodiment to be described later, the drum gear 1 is an output gear as a final gear, the gear immediately before the drum gear 1 is the intermediate gear 2, and the gear before the two is the input gear 3. In this case, all of these gears can be formed by inclined gears.

  For reference, at each meshing portion of the gear train of these inclined gears, the speed fluctuation phase of the frequency due to meshing may change depending on the position in the rotation axis direction. For this reason, the drum gear 1 as the output gear may vibrate or change its position in the rotation axis direction due to the axial vibration or position change of the rotating body that occurs during rotation. As a result, the meshing phase on the input side between the input gear 3 and the intermediate gear 2 and the meshing phase on the output side between the intermediate gear 2 and the drum gear 1 that is the output gear may not be synchronized, resulting in a large angular velocity fluctuation. . Further, FIG. 3B shows that the drum gear 1 as an output gear is a driven body, ie, a rotating body, that is, in this case, abuts against the end of the photosensitive drum 104 and is positioned in the rotational axis direction, and at the same time, is coupled to the coupling member. The case where it is matched is shown. In such a case, it is difficult to always keep the relative position in the rotation axis direction of the input gear 3 and the drum gear 1 as the output gear constant.

  Therefore, in the present embodiment, the drum gear 1 and the input gear 3 move in the direction of the rotation axis while keeping the relative position of the input gear 3 and the drum gear 1 (output gear) in the direction of the rotation axis always constant. This is one of the main points.

  By adopting a configuration in which the input / output gears can move relative to each other in this way, the meshing phase on the input side of the input gear 3 and the intermediate gear 2 and the meshing on the output side of the intermediate gear 2 and the drum gear 1 (output gear). Synchronize the phase. As a result, the rotation can be continued with the meshing phases canceling each other, so that the fluctuation amplitude of the angular velocity at the gear meshing frequency, that is, the frequency amplitude can be maintained in a minimum state.

  Therefore, as shown in FIG. 3A, a lever (not shown) operates in conjunction with the operation of opening the cartridge cover 112. As a result, the drum gear 1 that transmits the rotation to the photosensitive drum 104 in the process cartridge 103 is located at the retracted position in the rotation axis direction, so that the process cartridge 103 can be inserted.

  Subsequently, as shown in FIG. 3B, the lever (not shown) operates in conjunction with the operation of closing the cartridge cover 112. As a result, the drum gear 1 moves toward the photosensitive drum indicated by the arrow in the direction of the rotation axis. A claw portion (projection) 7 provided on the drum gear 1 by the movement of the drum gear 1 and a claw portion (projection) 8 provided at the end of the photosensitive drum 104 in the process cartridge 103 in the rotation axis direction are engaged. Match. In this state, the rotation can be transmitted to the photosensitive drum 104.

  4A and 4B show the meshing state of the input gear 3 and the intermediate gear 2 on the inlet side, and the meshing state of the intermediate gear 2 and the drum gear 1 on the output side. That is, the state where the meshing state of the input gear 3 and the intermediate gear 2 changes as the gear rotates is shown, and the portion indicated by the symbol p in the figure is the meshing point.

  The gear tooth portion is slightly deformed by the load applied to the tooth, but the state of receiving the load continuously changes depending on the meshing state, so that the angular velocity varies in the rotation direction. The same applies to the meshing state of the intermediate gear 2 and the drum gear 1.

  5A, the phase of the meshing portion B between the input gear 3 and the intermediate gear 2 and the meshing portion A between the intermediate gear 2 and the drum gear 1 shown in FIG. It is a graph showing a state typically. FIG. 5B shows the phase of the meshing portion B of the input gear 3 and the intermediate gear 2 and the meshing portion A of the intermediate gear 2 and the drum gear 1 shown in FIG. )) Is schematically shown in the offset state where the two phases of the meshing portions A and B cancel each other. The symbol e shown in FIGS. 5A and 5B represents the change in the angular velocity at the meshing portion B between the input gear 3 and the intermediate gear 2, and the symbol f is the meshing portion A between the intermediate gear 2 and the drum gear 1. This represents the change in the angular velocity. Symbol g represents a change in angular velocity of the drum gear 1 with respect to the input gear 3 when they are combined. As shown in FIG. 5A, in the same phase state, the angular velocity amplitude is amplified and the rotation unevenness of the drum gear 1 is increased. On the other hand, as shown in FIG. 5B, when the phases cancel each other, the angular velocity amplitude is canceled out, and the change in angular velocity at the meshing frequency of the drum gear 1 can be made substantially constant. .

  Focusing on the above, in the present embodiment, (1) the gear train is constituted by an inclined gear in order to rotate the drum gear 1 with high accuracy. (2) As shown in FIG. 5B, the meshing phase on the input side of the input gear 3 and the intermediate gear 2 and the meshing phase on the output side of the intermediate gear 2 and the drum gear 1 are approximately ½ phase. Shift and arrange. Thereby, the fluctuations in the angular velocity are canceled each other, and the fluctuation amplitude of the angular velocity at the gear meshing frequency of the drum gear 1 on the output side is set to be minimum. In the case of this embodiment, even in the case where the drum gear 1 that is the output gear moves in the direction of the rotation axis, the meshing phase on the input side and the meshing phase on the output side are shifted by 180 ° of approximately ½ phase. Deploy. As a result, it is possible to maintain a state in which fluctuations in angular velocity cancel each other.

<< First Embodiment >>
6 and 7 show the driving apparatus according to the first embodiment.

  In FIG. 6, the drive device includes a motor gear 4 that is fixed to the motor shaft 5 and a motor gear 4 that is fixed to the motor shaft 5, and an intermediate gear that is fixed at both ends to the motor mounting plate 21 and the drive side plate 25. An intermediate gear shaft 22 and a drum gear unit 30 serving as twelve rotation shafts are provided. In the drum gear unit 30, the input gear shaft 33 is fixed to the two side plates 31 and 32 at both ends. Further, the input gear 13 is rotatably provided on the input gear shaft 33. The bosses 11a and 11b protrude from both ends of the drum gear 11 by being pivotally supported by the two side plates 31 and 32, and the bosses 11a and 11b. Are supported by bearings 34a and 34b.

  The motor gear 4, the input gear 13, the intermediate gear 12, and the drum gear 11 are all formed as inclined gears and constitute a gear train.

  The two side plates 31 and 32 of the drum gear unit 30 are provided with through holes 31a and 32a into which the intermediate gear shaft 22 is fitted. Further, a drum gear shaft 24 having one end fixed to the motor mounting plate 21 is fitted at the center of the drum gear 11 and is supported so as to be movable in the direction of the rotation axis. Therefore, the drum gear unit 30 can be moved in the rotation axis direction while being regulated by the intermediate gear shaft 22 and the drum gear shaft 24. The movement of the drum gear unit 30 in the rotation axis direction moves in the tooth trace direction while maintaining the relationship between the meshing state of the input gear 13 with the intermediate gear 12 and the meshing state of the drum gear 11 with respect to the intermediate gear 12. .

  In the first embodiment, when the drive device is driven to rotate, the input gear 13 and the drum gear 11 are each urged toward the side plate by the force acting in the direction of the rotation axis of the inclined gear. In the case of the first embodiment, when rotating in the rotation direction shown in FIG. In a state where the input gear 13 and the drum gear 11 are moved toward the rotation axis during rotation, the meshing phase on the input side of the input gear 13 and the intermediate gear 12 and the output of the intermediate gear 12 and the drum gear 11 as described above. The side meshing phase is made to cancel the fluctuation of the mutual angular velocity. Therefore, it is arranged in the best state shifted by almost ½ phase (angle 180 °).

  That is, in the state shown in FIGS. 6 and 7, the relationship between the phase of the meshing portion B between the input gear 13 and the intermediate gear 12 and the phase of the meshing portion A between the intermediate gear 12 and the drum gear 11 is approximately ½. The phase is shifted by 180 °. At that time, as shown in FIG. 5B, the angular velocity changes at the meshing frequency of the gear of the drum gear 11 are made substantially constant by canceling the amplitudes of the mutual angular velocities.

  Of the bosses 11a and 11b protruding from both ends of the drum gear 11, a plurality of claw-shaped projections are formed at the end of the boss 11b on the photosensitive drum 104 side to engage the photosensitive drum 44 and transmit the rotation. 35 is provided. A hemispherical projection 36 is provided for aligning the center of rotation of the drum gear 11 and the center of rotation of the photosensitive drum 44.

≪Movement of drum gear unit≫
Therefore, as shown in FIG. 7, when the user closes the cartridge cover or the like, the drum gear unit 30 moves toward the photosensitive drum 44 along the rotation axis direction in conjunction with the operation. The movement of the drum gear unit 30 causes the hemispherical protrusion 36 to fit into the cylindrical portion 46 of the photosensitive drum, so that the axis is automatically centered. At the same time, the tip of the hemispherical protrusion 36 is the bottom surface of the cylindrical portion. Positioning in the direction of the rotation axis by hitting 47. In this manner, the plurality of claw-shaped projections 35 of the drum gear 11 and the claw-shaped portion 45 provided at the axial end of the photosensitive drum 44 are coupled to each other.

  Note that the drum gear unit 30 has a state in which the phase of the meshing portion B between the input gear 13 and the intermediate gear 12 and the phase of the meshing portion A between the intermediate gear 12 and the drum gear 11 cancel each other's fluctuations in angular velocity. It is moved and positioned in the axial direction while being held. As a result, the drum gear 11 can rotate so that the fluctuation of the angular velocity becomes substantially constant. Note that the positioning of the drum gear 11 is not limited to abutting against the end of the photosensitive drum, and a structure in which the drum gear 11 is positioned with respect to the rotating body that drives the endless belt is also possible.

  In the first embodiment, as shown in FIG. 8, the springs 37 and 38 can be mounted so as to apply a preload in the direction of the inclined gears of the gear train, thereby achieving the effect of gear shifting. Can be further enhanced.

  In addition, according to the first embodiment, the process cartridge including the photosensitive drum 44 is mounted on the printer body, and the rotational power from the motor 6 is generated with the photosensitive drum 44 and the drum gear 11 engaged with the claw-shaped portion. introduce. Then, the photosensitive drum 44 rotates, and the photosensitive drum 44 vibrates in the direction of the rotation axis although it is minute due to the influence of the load by the developing process means or the like. However, with the configuration and operation of the above-described embodiment, it is possible to perform rotation while maintaining the best state in which the fluctuation amplitude of the angular velocity at the meshing frequency of the drum gear 11 is minimized.

  In addition, according to the first embodiment, when the process cartridge is mounted on the printer body, even if the positional accuracy of the photosensitive drum 44 varies in the rotation axis direction, it is not affected.

<< Second Embodiment >>
Next, FIGS. 9 to 11 show a second embodiment according to the driving apparatus of the present invention.

  In the second embodiment, the goal is to reduce the number of parts by arranging gears more effectively. That is, as shown in FIGS. 9 and 10, it has an input gear shaft 67 that is cantilevered on the motor mounting plate 68 and serves as the rotational shaft of the input gear 53, and the intermediate gear shaft 67 that is the rotational shaft of the intermediate gear 52. Is fixed to support the motor mounting plate 68 and the side plate 69. Also, bosses 51a and 51b projecting from both ends of the drum gear 51 are rotatably supported on the motor mounting plate 68 and the side plate 69 by bearings 64a and 64b. Among the bosses 51a and 51b protruding from both ends of the drum gear 51, a plurality of claw-shaped projections 35 are provided at the end of the boss 11b on the photosensitive drum 104 side to engage the photosensitive drum 44 and transmit the rotation. It has been. Further, a hemispherical projection 36 for aligning the rotation axis of the drum gear 51 and the rotation axis of the photosensitive drum 44 is provided.

  With the above configuration, when the user performs an operation to close the cartridge cover or the like, the drum gear 51 moves to the photosensitive drum 44 side along the rotation axis direction in conjunction with the operation, as shown in FIG. By the movement of the drum gear 51, the hemispherical projection 36 is fitted into the cylindrical portion 46 of the photosensitive drum 44 and centering is performed, and at the same time, the tip of the hemispherical projection 36 abuts against the bottom surface 47 of the cylindrical portion. Positioned in the direction of the rotation axis. A plurality of claw-shaped projections 35 of the drum gear 51 and a claw-shaped portion 45 provided at the axial end of the photosensitive drum 44 are coupled to each other.

  In conjunction with the user opening the cartridge cover or the like, the drum gear 51 moves toward the motor 6 along the rotation axis direction, and the coupling engagement by the claw-shaped portion is separated. Thereby, the user can easily remove the process cartridge from the printer body.

  Even in the present embodiment, inclined gears are used for the motor gear 4, the input gear 53, the intermediate gear 52, and the drum gear 51 that constitute a series of gear trains. The twisting direction of the inclined teeth of the input gear 53 and the drum gear 51 is an axial force acting in the direction of the rotation axis of the input gear 53 when a load is applied to the drum gear 51 and the motor shaft 5 is rotated in the direction indicated by the arrow in FIG. And the axial force acting in the direction of the rotation axis of the drum gear 51 are set to face each other. Further, the torsional direction of the inclined teeth of the input gear 53 is rightward, and the torsional direction of the inclined teeth of the drum gear 51 is leftward. Further, the twisted direction of the inclined teeth of the intermediate gear 52 is configured such that the leftward region 52 a meshing with the input gear 53 and the rightward region 52 b meshing with the drum gear 51 are integrated.

  In addition, each of the input gear 53 and the drum gear 51 is provided with protrusions 71 and 73 having concentric and coaxial circular surfaces on the opposite surfaces facing each other and having a smooth surface by an annular shape when viewed from the direction of the rotation axis. The axis centers are arranged so that the circular shapes intersect.

  In the state where the input gear 53 and the drum gear 51 are close to each other in the rotational axis direction when being rotated, as described above, the meshing phase on the input side of the input gear 53 and the intermediate gear 52, the intermediate gear 52, and the drum gear 51 The output side meshing phase cancels out the fluctuations of the mutual angular velocities. In other words, they are arranged in the best state shifted by an angle of 180 ° with almost ½ phase so as to cancel each other. That is, in the state shown in FIG. 10, the relationship between the phase of the meshing portion B between the input gear 53 and the intermediate gear 52 and the phase of the meshing portion A between the intermediate gear 52 and the drum gear 51 are shifted by almost ½ phase. Deploy. As shown in FIG. 5B, the amplitudes of the angular velocities of each other are canceled and the fluctuations of the angular velocities at the meshing frequency of the drum gear 51 are maintained to be substantially constant.

  In FIG. 10, when the gear train rotates, the input gear 53 and the drum gear 51 face each other in the rotational axis direction due to the action of the axially acting force received by the inclined gear, and the annular protrusions 71 and 73 are mutually connected. Rotate while touching each other. Even when the drum gear 51 moves in the axial direction, the input gear 53 moves while keeping the contact between the annular projections 71 and 73 in the axial direction.

  As a result, according to the second embodiment, the phase of the meshing portion B between the input gear 53 and the intermediate gear 52 and the phase of the meshing portion A between the intermediate gear 52 and the drum gear 51 cancel each other's angular velocity fluctuations. Can be maintained. Therefore, the drum gear 51 can rotate so that the fluctuation of the angular velocity at the gear meshing frequency becomes substantially constant.

  At this time, a compression spring (not shown) or the like is mounted as an elastic member between the motor mounting plate 68 and the input gear 53 on the input gear shaft 5, and preload is applied to bias the input gear 53 and the drum gear 51. Can be reliably brought into contact with each other.

  Further, applying a lubricating oil material such as grease to the surface where the annular projections 71 and 73 are in sliding contact with each other has an effect of minimizing the influence on wear and vibration transmitted through contact.

  A process cartridge including a photosensitive drum 44 and the like is mounted on the printer main body, and rotational power from the motor 6 is transmitted with the photosensitive drum 44 and the drum gear 51 engaged with the claw-shaped portions. As a result, the photosensitive drum 44 rotates, and the photosensitive drum 44 vibrates along the rotation axis direction, although it is slightly affected by the load of the developing process means or the like acting on the photosensitive drum 44. Even in such a case, it is possible to perform rotation while maintaining the best state in which the fluctuation amplitude of the angular velocity of the drum gear 51 is minimized.

  In any of the first and second embodiments, the intermediate gear can be configured with a multi-stage gear. As shown in FIG. 12, in the case of the second embodiment, if the intermediate gear is constituted by the multi-stage gear 54, a gear train for decelerating or increasing the speed becomes unnecessary, which further contributes to downsizing of the apparatus and further reduces the cost. It is valid. At that time, the phases at the meshing portions A and B may be set so that the fluctuation amplitude of the angular velocity at the meshing frequency of the gear is minimized according to the tooth profile module and the number of teeth.

  Here, FIGS. 13A and 13B are graphs schematically showing the meshing state when the intermediate gear shown in FIG. 12 is a multi-stage gear. Here, an example in which the number of teeth of the large gear of the intermediate gear 54 is twice that of the small gear is taken as an example. Symbols e and e 'in this figure represent changes in angular velocity at the meshing portion B between the input gear 53 and the large gear portion of the intermediate 54 gear, and symbols f and f' represent the small gear portion of the intermediate gear 54 and the drum gear. The change of the angular velocity in the meshing part A with 51 is shown. Symbols g and g ′ represent changes in the angular velocity of the drum gear 51 with respect to the input gear 53 when they are combined. FIG. 13A shows a state in which the fluctuation amplitude L of the angular velocity of the drum gear 51 with respect to the input gear 53 is maximized in the angular velocity fluctuation amplitude at the gear meshing frequency in this drive system. FIG. 13B shows a state in which the angular velocity fluctuation amplitude L ′ of the drum gear 51 with respect to the input gear 53 is the smallest in the angular velocity fluctuation amplitude at the gear meshing frequency in this drive system. That is, a favorable result can be realized by setting the phase of the meshing portion so as to be in the meshing phase state shown in FIG.

  As described above, in each of the above-described embodiments, the direction of the force applied in the axial direction of the output gear at the time of rotation transmission is opposed to the direction of the force applied in the axial direction of the gear connected immediately before the output gear. . In addition, the annular protrusion provided in the tooth width direction of the output gear and the annular protrusion provided in the gear tooth width direction that is two immediately before the output gear face each other so that they slide and rotate while in contact with each other. Constitute. As a result, the number of parts can be reduced, and the effect to be targeted can be prevented from being halved by the accumulated error, and the cost can be reduced. Further, by making the intermediate gear 2 immediately before meshing with the drum gear 1 that is an output gear into a multi-stage gear, there is no need for a gear train for decelerating or increasing the speed, which is effective for downsizing the apparatus. Reduces costs.

  As mentioned above, although several embodiment was described about this invention, this invention is not limited to those embodiment, In the range which does not deviate from the main point of this invention, other embodiment, an application example, and a modified example , And combinations thereof are also possible.

1 is a longitudinal sectional view showing a configuration of an embodiment of an image forming apparatus main body according to the present invention. FIG. 3 is a longitudinal sectional view showing a state in which a process cartridge is mounted on the image forming apparatus. FIGS. 3A to 3C are views of the gear transmission mechanism shown from the motor to the photosensitive drum as viewed from above, the gear transmission mechanism as shown from the motor to the photosensitive drum as viewed from above, and the motor to the photosensitive drum. The figure which looked at the gear transmission mechanism shown in to from the direction of a rotating shaft. FIGS. 1A and 1B are views showing how the meshing state of the input gear and the intermediate gear changes as the gear rotates. FIGS. 3A and 3B are graphs showing the case where the phases of the meshing part B and the meshing part A shown in FIG. 3C are the same, and the phases of the meshing part B and the meshing part A are the same. The graph which contrasts the case of a phase, and the case where the phase is mutually canceled by shifting 1/2 phase. The figure which shows the drive device by 1st Embodiment seeing from an upper surface. The figure which shows the state which the drum gear and the photosensitive drum engaged in the drive device by the said 1st Embodiment seeing from the upper surface. The figure which shows the state which provided the spring which provides a preload in the shift | offset | difference direction of an input gear and a drum gear in the drive device by the said 1st Embodiment. The figure seen from the upper surface in the drive device by a 2nd embodiment. The figure which shows the drive device by the 2nd Embodiment seeing from a rotating shaft direction. The figure which shows the state which the drum gear and the photosensitive drum engaged in the drive device by the said 2nd Embodiment seeing from the upper surface. The figure which shows the case where the intermediate | middle gear is comprised with a multistage gear in the drive device of the said 2nd Embodiment. FIGS. 9A and 9B are graphs showing a case where the fluctuation velocity of the angular velocity is maximized in the state of the phase between the meshing portion B and the meshing portion A when the intermediate gear shown in FIG. 12 is a multi-stage gear. And a graph showing the case where the fluctuation amplitude of the same angular velocity is minimized.

Explanation of symbols

1, 11, 51 Drum gear 2, 12, 52 Intermediate gear 3, 13, 53 Input gear 4 Motor gear 5 Motor shaft 6 Motor 7, 35 Drum gear claw (projection)
8, 45 Photosensitive drum claw (protrusion)
11a, 11b, 51a, 51b Drum gear boss 21, 68 Motor mounting plate 22, 67 Intermediate gear shaft 24 Drum gear shaft 25, 69 Drive side plate 30 Drum gear unit 31, 32 Side plate 31a, 32a Through hole 33, 66 Input gear shaft 34a , 34b, 64a, 64b Bearing 36 Hemispherical projection 37, 38 Spring 44 Photosensitive drum 46 Cylindrical portion 47 Bottom surface of cylindrical portion 52a Torsional leftward region of helical gear of intermediate gear 52b Torsional rightward region of helical gear of intermediate gear 54 Multistage gear 71 Drum gear annular protrusion 73 Input gear annular protrusion 100 Laser light emitting portion 101 Laser light 102 Mirror 103 Process cartridge 104 Photosensitive drum 105 Sheet (transfer material)
106 cassette 107 paper feed roller 108 transport path 109 transfer unit 110 fixing unit 111 paper discharge unit 112 cartridge cover

Claims (8)

A drive device that transmits rotational power from a power source to an output gear that is a final gear through a gear train composed of two or more gears,
The phase amplitude resulting from the meshing of the output gear with the previous gear and the phase resulting from the meshing of the second previous gear with the previous gear minimize the frequency amplitude due to the change in angular velocity of the output gear. Is set to
The drive device, wherein the output gear and the two previous gears are configured to be movable in a state where their positions relative to the rotation axis direction are always kept constant.   2. The drive device according to claim 1, wherein the output gear and the two previous gears are configured to be able to constantly maintain a relative position in a rotation axis direction while acting with each other.   The direction of the force acting on the rotation shaft of the output gear at the time of rotation transmission is opposite to the direction of the force acting on the rotation shaft direction of the two preceding gears, and an annular shape provided in the tooth width direction of the output gear The drive device according to claim 2, wherein the projection and the annular projection provided in the tooth width direction of the two gears in front of each other face each other and slide in contact with each other.   4. The drive device according to claim 1, wherein the output gear, the one-early gear, and the two-early gear are bevel gears. 5.   5. The drive device according to claim 1, wherein the two gears before are input gears that receive rotational power from the power source. 6.   The drive device according to any one of claims 1 to 5, wherein the previous gear is a multistage gear as an intermediate gear.   The drive device according to any one of claims 1 to 6 is mounted, and the output gear provided in the drive device is provided to or rotates with respect to an image carrier provided in a main body of the image forming apparatus. An image forming apparatus characterized in that rotation is transmitted by positioning and engaging in a rotational axis direction with respect to a driving body for rotating the body.   When the driving body is a rotating body that drives an endless belt facing the image carrier with the transfer material interposed therebetween, the output gear is positioned and engaged with the rotating body in the rotation axis direction. The image forming apparatus according to claim 7, wherein the image forming apparatus is rotated and transmitted.