JP2009288366A - Drive unit and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce unevenness in rotation of a photoreceptor drum in a gear transmission unit for driving a plurality of photoreceptor drums with one driving source. <P>SOLUTION: A drive unit includes a plurality of reduction gears 61 for transmitting the rotation from a motor 600 to a plurality of photoreceptor drum gears 36. The motor 600 includes a motor gear 601 which is composed of a helical gear. The reduction gear 61 includes large gears 611, 612 which are integrally made of two helical gears having the same twisting angles and opposite twisting directions and a small gear 613 composed of a helical gear which is coaxial and integral with the large gears. One of the large gears 611K in the first reduction gear 61K is engaged with the motor gear 601 and the other large gear 612K is engaged with an idle gear 73 located between itself and the second reduction gear 61Y. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus having a plurality of photosensitive drums used in a tandem type color electrophotographic system.

In recent years, tandem color electrophotographic image recording apparatuses have appeared in response to office color orientation. In this type of image forming apparatus, when an image is exposed on a photosensitive drum to form an image, even if slight rotation unevenness occurs in the photosensitive drum due to meshing vibration of the driving gear, the image has uneven pitch, In particular, when a color image is formed, the color tone appears sensitively, which is a problem from the viewpoint of improving the image quality. Conventionally, as a method of reducing the rotation unevenness of the photosensitive drum due to the meshing vibration of the gear, a method of increasing the accuracy of the gear or changing the spur gear to a helical gear is known.
JP-A-10-161477

  However, in the above-described conventional example, the cause of the meshing vibration of the gear is largely due to the change in the spring stiffness of the teeth between the gears due to the change in the number of meshed teeth when the gear meshes. Is attributed. For this reason, simply increasing the gear accuracy as described above does not change the difference in the number of teeth in the meshing state of the gears, so that there is a problem that it is not sufficient for reducing the meshing vibration.

  If the spur gear is changed to a helical gear, the meshing ratio of the gear increases, which is effective against meshing vibration. However, since the driving reaction force is generated in the thrust direction, the gear itself is deformed. The force which tries to incline the shaft that holds the gears acts to deteriorate the meshing state, resulting in an increase in meshing vibration. In addition, there is a problem that a large radial load is applied to the bearing portion of the gear due to a force that tilts the shaft that holds the gear, and wear is accelerated.

  Here, the force to tilt the shaft holding the gear will be described with reference to FIGS. 10 and 11. FIG. 10 is a perspective view showing a driving unit for driving an OPC drum provided in a conventional image forming unit. FIG. 11 is a plan view showing a driving unit for driving an OPC drum provided in a conventional image forming unit. Reference numeral 600 denotes a motor for driving the four OPC drums 31 held by a frame (not shown). Reference numeral 601 denotes a motor gear provided in the motor 600, which is constituted by a helical gear whose twist direction is the right direction. A reduction gear 61K is rotatably held by a frame and a shaft (not shown). The reduction gear 61K is configured integrally with a large gear 611K having the same twist angle as that of the motor gear 601 and having a reverse twist direction, and a small gear 613K having the same number of teeth, modules, and the like on the same axis as the large gear. ing. The small gear 613K provided in the reduction gear 61K meshes with the gear 36K provided in the OPC drum 31K.

  The other reduction gears 61Y, 61M, 61C are the same gears as the reduction gear 61K, and are arranged so as to mesh with 36Y, 36M, 36C provided in each OPC drum 31. 73, 74, and 75 are idle gears for transmitting drive from the reduction gear 61K to the reduction gear 61Y, from the reduction gear 61Y to the reduction gear 61M, and from the reduction gear 61M to the reduction gear 61C. The idle gears 73, 74, 75 are arranged so as to mesh with the large gears 611 of the respective reduction gears 61, and are constituted by helical gears whose twist direction is the right direction.

  As shown in FIG. 11, when attention is paid to the OPC drum 31C, a load torque is present in the gear 36C of the OPC drum 31C. In order to rotate the load torque, power is generated from the motor 600 and torque is generated around the axis of the reduction gear 61C. Torque generated in the reduction gear 61C is transmitted to the reduction gear 61C by a tangential force acting on the meshing pitch circle at the meshing portion with the idle gear 75. When the gear is constituted by a helical gear as described above, the reduction gear 61C has a gear tooth surface that meshes with the direction of the tangential force acting on the meshing portion with the idle gear 75 (the twist angle of the helical gear). ) Is generated and a meshing force is generated between the meshing gears.

  When the reduction gear 61C is viewed, if a thrust force of, for example, 10 N is generated at the meshing portion between the gear 61C and the idle gear 75, a downward thrust force is applied to the reduction gear 61C as shown in FIG. For example, when the rotation center A is the axis, a moment (10 · r (N · m)) is generated by multiplying the distance (r) from the center to the meshing portion by 10N.

  Next, when the reduction gear 61M is viewed, a thrust force of 10N is also generated in the meshing portion of the reduction gear 61M and the idle gear 75. Since the load torque of the OPC drum 36M is generated in addition to the load torque of the OPC drum 36C at the meshing portion of the reduction gear 61M and the idle gear 74, a thrust force of approximately 20 N is generated.

  At this time, the reduction gear 61M receives thrust forces in different directions of the idle gears 75 to 10N and the idle gears 74 to 20N. When viewed from the rotation center A shown on the reduction gear 61M shown in FIG. And a moment (30 · r (N · m)) corresponding to the resultant force of 20N.

  Similarly, when viewed with the reduction gear 61Y, a large moment (50 · r (N · m)) corresponding to the resultant force of 20N and 30N when viewed from the rotation center A shown on the reduction gear 61Y. Will receive. Further, when viewed from the reduction gear 61K, when viewed from the rotation center A shown on the reduction gear 61K, a large moment (70 · r (N · m)) corresponding to the resultant force of 30N and 40N is received. As a result, the elastic deformation of the gear and the deformation of the support portion of the gear occur. For this reason, the meshing state of the gear is deteriorated, and vibration is generated or feed unevenness is caused.

  On the other hand, in order to reduce the thrust force of the helical gear, it has been considered to use a helical gear having two helical gears whose torsion directions are reversed, but the effect of the helical gear is exhibited. It is necessary to increase the accuracy of gears with opposite torsional directions, and it is also necessary to increase the accuracy of attaching the gears to the shaft, which makes it difficult to use in the field where resin-formed gears such as image forming apparatuses are used. Met.

  Japanese Patent Laid-Open No. 10-161477 proposes a gear body having a structure in which a damping member is sandwiched between two helical gears whose directions of twisting are opposite to each other, but the assembly becomes complicated due to an increase in the number of components. In addition, there is a problem in that cost is increased due to the necessity of a damping material.

  The present invention provides a gear transmission device that drives a plurality of photosensitive drums with a single driving source, and configures a drive gear train without deteriorating the meshing state of the gears that drive the photosensitive drums, thereby reducing the rotational unevenness of the photosensitive drums. An object of the present invention is to provide an image forming apparatus capable of performing stable drive transmission.

In order to solve the above-mentioned problem, the means according to claim 1 of the present invention is the drive source having a plurality of reduction gear mechanisms for transmitting the rotation from the drive source to the plurality of driven gears. Is provided with a drive source gear consisting of a helical gear that transmits the rotation of the drive source to the first reduction gear mechanism, and the reduction gear mechanism has the same twist angle and two opposite twist directions. A large gear portion in which a helical gear is integrated, and a small gear made of a helical gear that is coaxial and integrated with the large gear portion are provided, and among the large gear portion in the first reduction gear mechanism, One large gear meshes with the drive source gear, and the other large gear meshes with an idle gear between the second reduction gear mechanism, thereby transmitting the rotation of the drive source to the reduction gear mechanism. is there.

According to the present invention, the large gear of the reduction gear mechanism is constituted by two adjacent gears (so-called angle gears) having the same twist angle and opposite twist directions (so-called angle gears), and the driven gear and the drive gear are twisted with each other. By engaging with the same gear, the moment to tilt the shaft of the reduction gear mechanism generated by the thrust force acting on each reduction gear mechanism can be minimized. Accordingly, it is possible to reduce the meshing vibration of each gear and drive a stable photosensitive drum without deteriorating the meshing state of each gear.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram illustrating an example of the image forming apparatus 10. In the figure, a sheet tray 100 has sheets 20 stacked therein. The paper stacking plate 102 is rotatable about a support shaft (not shown) in order to stack the paper 20 provided in the paper tray 100. Further, the paper tray 100 is provided with a guide member (not shown) for regulating the stacking position of the sheets 20 so that the stacking position of the sheets 20 is constant with respect to the sheet side surface in the direction orthogonal to the sheet feeding direction and the sheet feeding direction. regulate. The lift-up lever 103 is rotatably provided on a support shaft (not shown) in order to move the paper placing plate 102 up and down. The motor 104 is a drive motor for driving the lift-up lever 103, and is engaged with a support shaft (not shown) of the lift-up lever 103 so as to be able to contact and separate.

  A paper feeding unit 200 that feeds the paper 20 one by one is provided on the feeding side of the paper tray 100. The rise detector 201 detects that the paper 20 has been raised to a certain height. The paper feeding unit 200 includes a pickup roller 202 provided so as to be pressed against the paper 20 raised to a certain height, a feed roller 203 and a retard roller 204 for separating the paper 20 fed by the pickup roller 202 one by one. A pair of rollers is provided. Further, the paper feeding unit 200 is provided with a paper presence / absence detection unit 205 that detects the presence / absence of the paper 20 and a remaining paper amount detection unit 206 that detects the remaining amount of paper.

  The sheet conveying unit 300 conveys the sheet 20 fed out by the sheet feeding unit 200 to the image forming unit 400. The paper sensor 301 detects the fed paper 20. The conveyance roller pairs 302 and 304 convey the fed paper 20. Further, the sheet sensor 303 detects the timing for driving the conveyance roller pair 304, and the writing sensor 305 further detects the timing for conveying the conveyed sheet 20 to the next image forming unit 400.

  The image forming unit 400 includes four toner image forming units 430 arranged in series. The four toner image forming units 430 are the toner image forming units 430 for black toner (K), yellow toner (Y), magenta toner (M), and cyan toner (C) from the right side in the drawing. The image forming unit 400 includes the toner image forming unit 430 and a transfer unit 460 that transfers the toner image formed by the toner image forming unit 430 to the upper surface of the sheet by Coulomb force.

  The toner image forming unit 430 forms an electrostatic latent image on the surface of the charged OPC drum 31, an OPC (Organic Photo Conductor) drum 31 that carries the toner image, a charging roller 432 that charges the surface of the OPC drum 31, and the like. A laser head 433 including an LED array, a developing roller 434 that forms a toner image on the electrostatic latent image by frictional charging, and a toner supply unit 436 that supplies toner. In the drawing, only the toner image forming unit 430K for black toner is shown in detail, and the other parts are shown only in the OPC drums 31Y, 31M, and 31C.

  The transfer unit 460 includes an endless belt 461 that conveys the paper 20, a drive roller 462 that is rotated by a driving unit (not shown) to drive the endless belt 461, and a tension that forms a pair with the drive roller 462 and stretches the endless belt 461. A roller 463, a transfer roller 464 disposed so as to face the toner image forming unit 430 and press-contact with the OPC drum 31, a cleaning blade 465 for scraping and cleaning the toner adhering to the endless belt 461, and the cleaning blade 465. And a toner box 466 for accumulating the toner scraped by the toner.

  The fixing unit 500 fixes the toner image transferred on the paper 20 by the transfer unit 460 to the paper 20 by heat and pressure. The fixing unit 500 includes a halogen lamp 503 serving as a heat source therein, and includes a pair of rollers of an upper roller 501 and a lower roller 502 whose surfaces are formed of an elastic body. Reference numeral 504 denotes a discharge roller pair for discharging the paper 20 fixed by the fixing unit 500. Reference numeral 505 denotes a stacker unit for depositing printed sheets 20.

  FIG. 2 is a perspective view showing a drive unit for driving the OPC drum 31 according to the first embodiment. A motor 600 as a drive source drives four OPC drums 31K, 31Y, 31M, and 31C held in a frame (not shown). A motor gear 601 as a drive source gear is a helical gear provided on the rotating shaft of the motor 600 and having a twist direction leftward. The reduction gear 61K is rotatably held by a frame (not shown) and a shaft, and has two adjacent large gears (both constituting so-called angle gears) 611K and 612K having the same twist angle and opposite twist directions, A small gear 613K having different specifications such as the number of teeth and a module is integrally formed coaxially with the large gears 611K and 612K.

  In the present embodiment, the outer large gear 611K is a right-twisted helical gear, and the inner large gear 612K is a left-twisted helical gear. The outer large gear 611K meshes with the motor gear 601. A small gear 613K provided on the reduction gear 61K meshes with a drum gear 36K provided on the OPC drum 31K. The other reduction gears 61Y, 61M, and 61C are gears having the same shape as the reduction gear 61K. The small gears 613Y, 613M, and 613C are drum gears 36Y, 36M, and 36C provided in the OPC drums 31Y, 31M, and 31C, respectively. It arrange | positions so that it may mesh.

  The idle gear 73 is a helical gear whose torsional direction is the right direction, and transmits the drive from the reduction gear 61K to the reduction gear 61Y. Therefore, the idler gear 73 has a large gear 612K inside the reduction gear 61K and a large gear inside the reduction gear 61Y. It arrange | positions so that it may mesh with 612Y. The idle gear 74 is a helical gear whose torsional direction is the left direction, and transmits the drive from the reduction gear 61Y to the reduction gear 61M. Therefore, the idler gear 74 has a large gear 611Y outside the reduction gear 61Y and a large gear 611M outside the reduction gear 61M. Arranged so as to mesh with each other. The idle gear 75 is a helical gear whose torsional direction is rightward, and transmits the drive from the reduction gear 61M to the reduction gear 61C. Therefore, the idle gear 75 has a large gear 612M inside the reduction gear 61M and a large gear 612C inside the reduction gear 61C. Arranged so as to mesh with each other.

  FIG. 3 is a plan view showing a driving unit for driving the OPC drum 31. FIG. 4 is a side view of the driving unit for driving the OPC drum 31 as seen from the direction of the rotation axis. The rotation center axis of the motor gear 601, the rotation center axis of the reduction gear 61 </ b> K, and the rotation center axis of the idle gear 73 are arranged on the same straight line. Similarly, the rotation center axis of the idle gear 73, the rotation center axis of the reduction gear 61Y, and the rotation center axis of the idle gear 74 are arranged on the same straight line. Similarly, the rotation center axis of the idle gear 74, the rotation center axis of the reduction gear 61M, and the rotation center axis of the idle gear 75 are arranged on the same straight line. Accordingly, the meshing positions of the gears substantially coincide with each other on a straight line connecting the central axes.

  Next, the operation of the image forming apparatus 10 will be described with reference to FIG. In FIG. 1, a paper tray 100 is detachably attached to an image forming apparatus 10, and paper 20 is stacked therein by an operator. When the paper tray 100 is inserted into the image forming apparatus 10, the lift-up lever 103 and the motor 104 are engaged, and a control unit (not shown) drives the motor 104. As the lift-up lever 103 rotates, the tip of the lift-up lever 103 lifts the bottom of the paper stacking plate 102, and the paper 20 stacked on the paper stacking plate 102 rises. When the sheet 20 rises to a height at which the sheet 20 is pressed against the pickup roller 202, the rising detection unit 201 detects the sheet 20, and a control unit (not shown) stops the motor 104 based on the detected information.

  Image data is processed by an image processing unit (not shown), and a print command is sent to a control unit (not shown). A drive motor (not shown) drives the pickup roller 202 to rotate. The paper 20 fed out by the pickup roller 202 is conveyed to the nip position of the roller pair of the feed roller 203 and the retard roller 204 and separated one by one. The paper 20 that has been fed out from the paper feed unit 200 by one sheet is sent to the paper transport unit 300. The fed paper 20 passes through the paper sensor 301 and is sent to the conveyance roller pair 302. A driving unit (not shown) is driven by a control unit (not shown) based on the passage time of the paper sensor 301, and the conveying roller pair 302 sends out the paper.

  Generally, the paper 20 is pushed into the pressure contact portion of the conveyance roller pair 302 by delaying the time when the conveyance roller pair 302 starts to rotate from the time when it passes through the paper sensor 301, and the skew of the paper is corrected. The paper 20 sent out from the transport roller pair 302 passes through the paper sensor 303 and is sent to the transport roller pair 304. The transport roller pair 304 is rotated by a driving unit (not shown) from the time when it passes through the paper sensor 303 and feeds the paper 20 without stopping. The sheet 20 sent out by the conveyance roller pair 304 passes through the writing sensor 305 and is sent to the image forming unit 400.

  In the image forming unit 400, image data is irradiated from the laser head 433 to the surface of the OPC drum 31 based on data sent from an image processing unit (not shown). As a result, an electrostatic latent image is formed on the surface of the OPC drum 31 charged by the charging roller 432. The toner supplied from the toner supply unit 436 is formed on the OPC drum 31 as a toner image by the developing roller 434. The toner image carried on the OPC drum 31 is transferred onto the sheet 20 that is electrostatically attracted and conveyed at a pressure contact portion with the transfer roller 464. The endless belt 461 that electrostatically attracts and conveys the paper 20 travels by rotating a drive roller 462 from a drive unit (not shown).

  The OPC drum 31 </ b> K and the endless belt 461 of the toner image forming unit 430 </ b> K are driven in synchronization to transfer the toner image onto the sheet 20 electrostatically attracted to the endless belt 461. The toner images on the OPC drums 31Y, 31M, and 31C are sequentially transferred onto the paper 20 in order.

  The sheet 20 on which the toner image is transferred by the image forming unit 400 is conveyed toward a nip formed by a pair of rollers of an upper roller 501 and a lower roller 502 of the fixing unit 500. The upper roller 501 and the lower roller 502 fuse the toner image onto the sheet with heat and pressure, and the sheet 20 is conveyed toward the discharge roller pair 504. The sheet 20 conveyed by the discharge roller pair 504 is transferred to the stacker unit 505. accumulate.

  Next, the operation of the drive unit of the OPC drum 31 will be described with reference to FIGS. In FIG. 4, the motor gear 601 rotates in the direction indicated by the arrow (clockwise), so that the reduction gear 61K is driven counterclockwise. The small gear 613K provided in the reduction gear 61K meshes with the drum gear 36K, and the OPC drum 31K rotates in the clockwise direction, thereby enabling image formation.

  The reduction gear 61K driven by the motor gear 601 drives the reduction gear 61Y via the idle gear 73. Similarly, the reduction gear 61Y drives the reduction gear 61M via the idle gear 74, and similarly, the reduction gear 61M drives the reduction gear 61C via the idle gear 75. Thereby, each OPC drum 31 is rotated by the motor 600 which is one drive source.

  At this time, since each of the gears is constituted by a helical gear, a force acts in the thrust direction as a driving component force. First, in the reduction gear 61K, as shown in FIG. 3, a right-twisted large gear 611K and a left-twisted motor gear 601 mesh, and a left-twisted large gear 612K and a right-twisted idle gear 73 mesh. The helical gear 611K serving as the driven gear portion and the large gear 612K serving as the driving gear portion have the same helical twisting angle and the opposite twisting directions. Therefore, since the motor gear 601 is driven in the clockwise direction shown in FIG. 4, the thrust force acting on the large gear 611 </ b> K of the reduction gear 61 </ b> K acts on the back side as shown in FIG. 4 at the meshing position with the motor gear 601. The thrust force acting on the large gear 612K also acts on the back side at the meshing position with the idle gear 73.

  Therefore, the moment to tilt the shaft of the reduction gear 61K generated by the thrust force acting on the large gears 611K and 612K drives the difference between the load torque applied to the reduction gear 61K and the load torque applied to the idle gear 73. It is generated as a component of the tooth twist angle.

  Similarly, in the next reduction gears 61Y and 61M, the large gears 612Y and 611M serving as the driven gear portions and the large gears 611Y and 612M serving as the drive gear portions have the same twist angle and the reverse twist directions. The direction in which the thrust force is generated works in the same direction for the driven gear and the driving gear.

  A difference in driving force applied to the gear is generated as a component force corresponding to the torsion angle of the driving helical tooth.

  In the reduction gear 61C at the left end in the figure, there is a driven gear driven from the idle gear 75, but there is no drive gear driven by the reduction gear 61C. Therefore, the moment for tilting the axis of the reduction gear 61C is generated as a component force corresponding to the helical torsion angle of the driving force corresponding to the driving load torque of the drum gear 36C.

  As shown in FIG. 3, torque is generated around the axis of the reduction gear 61C in response to the load torque of the OPC drum 31C, and force is generated at the meshing portion with the idle gear 75 that is a gear for driving the reduction gear 61C. To do. A tangential force acts on the meshing pitch from the load torque to the meshing pitch on the meshing pitch circle. As described above, when the gear is constituted by a helical gear, a component force in the thrust direction of the gear is generated at the twist angle. For example, when the reduction gear 61C is viewed, if a thrust force of, for example, 10 N is generated at the meshing portion between the gear 61C and the idle gear 75, the reduction gear 61C has a downward thrust as viewed from the drawing as shown in FIG. For example, when the rotation center A shown on the reduction gear 61C is used as an axis, the distance (r) from the center to the meshing portion is multiplied by 10N (10 · r (N · m )) Occurs.

  Next, when the reduction gear 61M is viewed, a thrust force of 10N is generated upward in the meshing portion between the reduction gear 61M and the idle gear 75 as viewed in FIG. Further, since the load torque of the OPC drum 31M is generated in addition to the load torque of the OPC drum 31C at the meshing portion of the reduction gear 61M and the idle gear 74, a thrust force of about 20 N is obtained as shown in FIG. Will occur in the direction. At this time, the reduction gear 61M receives thrust forces in the same direction of the idle gears 75 to 10N and the idle gears 74 to 20N. When the rotation center A shown on the reduction gear 61M shown in FIG. And a moment (10 · r (N · m)) corresponding to the difference of 20N.

  Similarly, when viewed with the gear 61Y, only the moment (10 · r (N · m)) corresponding to the difference between 20N and 30N is received when the rotation center A point shown on the reduction gear 61Y is used as an axis. . Further, when viewed with the gear 61K, only the moment (10 · r (N · m)) corresponding to the difference between 30N and 40N is received when the rotation center A point shown on the reduction gear 61K is used as an axis. It becomes. Compared with the conventional explanation shown in FIG. 10, this can minimize the tilting of the gear to cause elastic deformation of the gear and deformation of the support portion of the gear.

  That is, the moment generated by the thrust force acting on each reduction gear 61 is generated as a component force corresponding to the helical torsion angle of the driving force for the driving load torque of the drum gear 36 to be driven. The moment for tilting the shaft of the gear 61 can be minimized. Therefore, the OPC drum 31 can be driven without deteriorating the meshing state of each gear.

  In the first embodiment of the present invention described in detail above, the large gears 611 and 612 of the reduction gear 61 that drives the plurality of OPC drums 31 are adjacent to each other with two gears having the same twist angle and opposite to the twist direction. It is generated by the thrust force acting on each reduction gear 61 by meshing the driven gear part and the driving gear part with a gear having the same twist angle and reverse twist direction. The moment for tilting the axis of the reduction gear 61 to be reduced can be suppressed to the minimum necessary, and the meshing vibration of each gear can be reduced. As a result, for example, it is possible to realize a high-quality image forming apparatus that does not have image unevenness due to meshing vibration of each gear in the color image forming apparatus.

(Second Embodiment)
Next, the structure of 2nd Embodiment is demonstrated according to drawing. The second embodiment differs from the first embodiment in the twisting direction of the motor gear 601 provided in the motor 600 and the position where the motor gear 601 meshes. That is, the twist direction of the motor gear 601 is right twist, and the motor gear 601 is arranged to mesh with the idle gear 74. Since the configuration of the image forming apparatus 10 according to the second embodiment is the same as that of the first embodiment, the description of FIG.

  FIG. 5 is a plan view showing a drive unit for driving the OPC drum 31 according to the second embodiment. The motor 600 drives four OPC drums 31K, 31Y, 31M, and 31C held by a frame (not shown). The motor gear 601 is a helical gear provided in the motor 600 and having a twist direction to the right. The reduction gear 61Y is rotatably held by a frame and a shaft (not shown), and has two adjacent large gears 611Y and 612Y having the same twist angle and opposite twist directions (both forming so-called angle gears), A small gear 613Y having different specifications such as the number of teeth and a module is integrally formed coaxially with the large gears 611Y and 612Y.

  In the present embodiment, the outer large gear 611Y is a right-twisted helical gear, and the inner large gear 612Y is a left-twisted helical gear. The small gear 613Y provided on the reduction gear 61Y meshes with the drum gear 36Y provided on the OPC drum 31Y. The other reduction gears 61K, 61M, and 61C are gears having the same shape as the reduction gear 61Y. The small gears 613K, 613M, and 613C are drum gears 36K, 36M, and 36C provided on the OPC drums 31K, 31M, and 31C, respectively. It arrange | positions so that it may mesh.

  The center idle gear 74 is a helical gear whose twist direction is to the left, and meshes with the motor gear 601. The idle gear 74 is arranged to mesh with the large gear 611Y outside the reduction gear 61Y and the large gear 611M outside the reduction gear 61M in order to transmit driving to the reduction gear 61Y and the reduction gear 61M.

  The right idle gear 73 is a helical gear whose torsional direction is the right direction. In order to transmit drive from the reduction gear 61Y to the reduction gear 61K, the large gear 612Y inside the reduction gear 61Y and the inside of the reduction gear 61K are connected. It arrange | positions so that it may mesh with the large gear 612K.

  The left idle gear 75 is a helical gear whose torsional direction is the right direction. In order to transmit drive from the reduction gear 61M to the reduction gear 61C, the large gear 612M inside the reduction gear 61M and the inside of the reduction gear 61C are connected. It arrange | positions so that it may mesh with the large gear 612C.

  FIG. 6 is a side view of the driving unit for driving the OPC drum 31 as seen from the direction of the rotation axis. The rotation center axis of the idle gear 74, the rotation center axis of the reduction gear 61Y, and the rotation center axis of the idle gear 73 are arranged on the same straight line. Similarly, the rotation center axis of the idle gear 74, the rotation center axis of the reduction gear 61M, and the rotation center axis of the idle gear 75 are arranged on the same straight line. Accordingly, the meshing positions of the gears substantially coincide with each other on a straight line connecting the central axes.

  Next, the operation of the second embodiment will be described. In FIG. 6, the motor gear 601 rotates in the direction indicated by the arrow (counterclockwise), whereby the idle gear 74 is driven clockwise, and the reduction gear 61Y and the reduction gear 61M that engage with the idle gear 74 are driven. When the reduction gear 61Y and the reduction gear 61M are driven, the small gear 613Y and the small gear 613M provided on the reduction gear 61Y and the reduction gear 61M are engaged with the drum gear 36Y and the drum gear 36M, and the OPC drum 31Y and the OPC drum 31M are watchpieces. Image formation becomes possible by rotating in the direction.

  When the reduction gear 61Y and the reduction gear 61M are driven, the drive is transmitted to the reduction gear 61K and the reduction gear 61C via the idle gear 73 and the idle gear 75. Thereby, each OPC drum 31 is rotated by the motor 600 which is one drive source. At this time, since each gear is a helical gear, a force acts in the thrust direction as a driving component.

  As shown in FIG. 5, in the central idle gear 74 and reduction gear 61Y, the left-twisted idle gear 74 meshes with the right-twisted large gear 611Y. In addition, the idle gear 74 and the reduction gear 61M mesh with the large twisted gear 611M that is twisted to the left and twisted.

  Since the idle gear 74 is driven clockwise as shown in FIG. 6, the thrust force acting on the large gear 611 </ b> Y of the reduction gear 61 </ b> Y acts on the back side when viewed from FIG. 6 at the meshing position with the idle gear 74. In the meshing position with the idle gear 73, it works on the back side. Similarly, the thrust force acting on the large gear 611M of the reduction gear 61M acts on the back side when viewed from FIG. 6 at the meshing position with the idle gear 74, and acts on the back side also at the meshing position with the idle gear 75. .

  Therefore, the moment to tilt the shafts of the reduction gears 61Y and 61M generated by the thrust force acting on the large gears 611Y, 612Y, 611M, and 612M is applied to the load torque applied to the reduction gears 61Y and 61M, the idle gear 73, and the idle gear 75. The difference between the load torques is generated as a component force corresponding to the helical angle of the helical teeth.

  In the reduction gear 61K and the reduction gear 61C at both ends in the figure, there are driven gears driven from the idle gear 73 and the idle gear 75, but there are no gears driven by the reduction gear 61K and the reduction gear 61C. Therefore, the moment to incline the axes of the reduction gear 61K and the reduction gear 61C is generated as a component force corresponding to the helical torsion angle of the driving force for the driving load torque of the drum gear 36K and the drum gear 36C.

  As shown in FIG. 5, torque is generated around the axis of the reduction gear 61C in response to the load torque of the leftmost OPC drum 36C, and the meshing portion with the idle gear 74 serving as a gear for driving the reduction gear 61C is generated. Force is generated. A tangential force acts on the meshing pitch from the load torque to the meshing pitch on the meshing pitch circle. As described above, when the gear is constituted by a helical gear, a component force in the thrust direction of the gear is generated at the twist angle. For example, when the reduction gear 61C is viewed, if a thrust force of, for example, 10 N is generated at the meshing portion of the reduction gear 61C and the idle gear 74, the reduction gear 61C is downwardly viewed from the drawing as shown in FIG. When a thrust force is generated and the center of rotation A shown on the reduction gear 61C is used as an axis, the moment (10 · r (N · m) is obtained by multiplying the distance (r) from the center to the meshing portion by 10N. )) Occurs.

  Next, when the reduction gear 61M is viewed, a thrust force of 10N is generated upward in the meshing portion between the reduction gear 61M and the idle gear 75 as seen in the figure. Since the load torque of the OPC drum 31M is generated in addition to the load torque of the OPC drum 31C at the meshing portion of the reduction gear 61M and the idle gear 74, a thrust force of approximately 20N is generated upward as seen in the figure. Will be. At this time, the reduction gear 61M receives thrust forces in the same direction of the idle gears 75 to 10N and the idle gears 74 to 20N, and 10N when the rotation center A shown on the reduction gear 61M shown in FIG. And a moment (10 · r (N · m)) corresponding to the difference of 20N. Similarly, the reduction gears 61Y and 61K receive a moment (10 · r (N · m)) when the axis of rotation A is the axis.

  As described above, the idle gear 74 drives the reduction gear 61Y and the reduction gear 61M, and the load torque applied to the reduction gear 61Y and the reduction gear 61M is distributed by distributing the downstream load of the reduction gear 61Y and the reduction gear 61M. And the force applied to the teeth of the large gears 611 and 612 of the reduction gear 61 can be reduced. Further, as in the first embodiment, the thrust force by the helical gear can be reduced. For this reason, the deterioration of the meshing state of the gear due to the elastic deformation of the reduction gear 61 can be suppressed.

  In the second embodiment of the present invention described in detail above, the reduction gear 61Y and the reduction gear 61M are driven by the idle gear 74, and the load on the downstream side of the reduction gear 61Y and the reduction gear 61M is distributed, thereby reducing the reduction gear. The force applied to the teeth of the 61 large gears 611 and 612 and the thrust force generated by the helical gears can be reduced. For this reason, it is not necessary to increase the tooth width more than necessary or to arrange reinforcing ribs on the large gears 611 and 612 of the reduction gear 61 in order to ensure the strength. Therefore, it is possible to provide a drive device that is inexpensive and has little vibration. As a result, it is possible to realize a high-quality image forming apparatus that is small and inexpensive and has no image unevenness.

(Third embodiment)
Next, the structure of 3rd Embodiment is demonstrated according to drawing. The third embodiment differs from the second embodiment in the twist direction of the motor gear 601 provided in the motor 600 for driving the OPC drum 31 and the idle gear 74 that meshes with the motor gear 601. That is, the twist direction of the motor gear 601 is configured by left twist. The idle gear 74 is composed of two idle gears 74-1 and 74-2 that have the same twist angle and opposite twist directions. Since the configuration of the image forming apparatus 10 according to the third embodiment is the same as that of the first embodiment, the description of FIG. 1 is cited.

  FIG. 7 is a perspective view showing a drive unit for driving the OPC drum 31 according to the third embodiment, and FIG. 8 is a plan view showing the drive unit for driving the OPC drum 31 in the same manner. The motor 600 drives four OPC drums 31K, 31Y, 31M, and 31C held by a frame (not shown). The motor gear 601 is provided in the motor 600 and is a helical gear whose twist direction is the left direction. The reduction gear 61Y is rotatably held by a frame and a shaft (not shown), and is coaxial with two adjacent large gears 611Y and 612Y having the same twist angle and opposite to the twist direction (both forming so-called angle gears). A small gear 613Y having different specifications such as the number of teeth and a module is integrally formed on the top.

  In the present embodiment, the outer large gear 611Y is a right-twisted helical gear, and the inner large gear 612Y is a left-twisted helical gear. The small gear 613Y provided on the reduction gear 61Y meshes with the drum gear 36Y provided on the OPC drum 31Y. The other reduction gears 61K, 61M, and 61C are gears having the same shape as the reduction gear 61Y. The small gears 613K, 613M, and 613C are drum gears 36K, 36M, and 36C provided on the OPC drums 31K, 31M, and 31C, respectively. It arrange | positions so that it may mesh.

  The idle gear 74 is composed of an idle gear 74-1 and an idle gear 74-2 which are two helical gears having the same twist angle and opposite twist directions. A right-twisted gear 74-1 and the motor gear 601 mesh with each other. Further, since the idle gear 74 transmits drive to the reduction gear 61Y and the reduction gear 61M, the left-twisted gear 74-2 meshes with the right-twisted large gear 611Y of the reduction gear 61Y. -2 and the right-handed large gear 611M of the reduction gear 61M are arranged to mesh with each other.

  The idle gear 73 is a helical gear whose torsional direction is the right direction, and transmits the drive from the reduction gear 61Y to the reduction gear 61K. Therefore, the idler gear 73 has a large gear 612Y inside the reduction gear 61Y and a large gear 612K inside the reduction gear 61K. Arranged so as to mesh with each other.

  The idle gear 75 is a helical gear whose torsional direction is rightward, and transmits the drive from the reduction gear 61M to the reduction gear 61C. Therefore, the idle gear 75 has a large gear 612M inside the reduction gear 61M and a large gear 612C inside the reduction gear 61C. Arranged so as to mesh with each other.

  FIG. 9 is a side view of a driving unit for driving the OPC drum 31 as viewed from the direction of the rotation axis. The rotation center axis of the idle gear 74, the rotation center axis of the reduction gear 61Y, and the rotation center axis of the idle gear 73 are arranged on the same straight line. Similarly, the rotation center axis of the idle gear 74, the rotation center axis of the reduction gear 61M, and the rotation center axis of the idle gear 75 are arranged on the same straight line. Accordingly, the meshing positions of the gears substantially coincide with each other on a straight line connecting the central axes.

  Next, the operation of the third embodiment will be described. In FIG. 9, when the motor gear 601 rotates in the direction of the arrow shown in the figure (counterclockwise), the right-twisted idle gear 74-1 that meshes with the motor gear 601 is driven in the clockwise direction. When the right-twisted idle gear 74-1 is driven, the reduction gear 61Y and the reduction gear 61M that mesh with the left-twisted idle gear 74-2 are driven. When the reduction gear 61Y and the reduction gear 61M are driven, the small gear 613Y and the small gear 613M provided on the reduction gear 61Y and the reduction gear 61M are engaged with the drum gear 36Y and the drum gear 36M, and the OPC drum 31Y and the OPC drum 31M are watchpieces. Image formation becomes possible by rotating in the direction.

  When the reduction gear 61Y and the reduction gear 61M are driven, the drive is transmitted to the reduction gear 61K and the reduction gear 61C via the idle gear 73 and the idle gear 75. Thereby, each OPC drum 31 is rotated by the motor 600 which is one drive source. At this time, since each gear is a helical gear, a force acts in the thrust direction as a driving component.

  At the meshing position of the right-twisted idle gear 74-1 and the motor gear 601 of the central idle gear 74, the thrust force acting on the idle gear 74 when viewed in FIG. Also in the meshing position of the idle gear 74-2 and the reduction gear 61Y and the idle gear 74-2 and the reduction gear 61M, it works in the forward direction as seen from FIG. Therefore, the moment to tilt the idle gear 74 shaft generated by the thrust force acting on the idle gear 74 is reduced as compared with the configuration of the second embodiment.

  Further, by dividing the idle gear 74-1 portion that meshes with the idler gear 74 and the idle gear 74-2 portion that meshes with the reduction gears 61Y and 61M, the number of meshes of the teeth of the idle gear 74 is reduced. Therefore, the life of the idle gear 74 can be extended.

  As in the second embodiment, as shown in FIG. 9, when the idle gear 74 is driven clockwise, the thrust force acting on the large gear 611Y of the reduction gear 61Y is the same as that of the idle gear 74-2. 9, it works on the back side as viewed from FIG. 9, and also works on the back side in the meshing position with the idle gear 73. Similarly, the thrust force acting on the large gear 611M of the reduction gear 61M acts on the back side when viewed from FIG. 9 at the meshing position with the idle gear 74-2, and on the back side also at the meshing position with the idle gear 75. To work.

  Therefore, the moment to tilt the shafts of the reduction gears 61Y and 61M generated by the thrust force acting on the large gears 611Y, 612Y, 611M, and 612M is applied to the load torque applied to the reduction gears 61Y and 61M, the idle gear 73, and the idle gear 75. The difference between the load torques is generated as a component force corresponding to the helical angle of the helical teeth.

  In the reduction gear 61K and the reduction gear 61C at both ends in the figure, there are driven gears driven from the idle gear 73 and the idle gear 75, but there are no gears driven by the reduction gear 61K and the reduction gear 61C. Therefore, the moment to incline the axes of the reduction gear 61K and the reduction gear 61C is generated as a component force corresponding to the helical torsion angle of the driving force for the driving load torque of the drum gear 36K and the drum gear 36C.

  As shown in FIG. 8, the moment about the rotation center A point caused by the thrust force on the reduction gears 61K, 61Y, 61M, 61C is the same as that described in FIG. 5 of the second embodiment. Therefore, the description of the second embodiment is cited.

  As described above, the reduction gear 61Y and the reduction gear 61M are driven by the idle gear 74-2, and the load torque applied to the reduction gear 61Y and the reduction gear 61M is distributed by distributing the downstream load of the reduction gear 61Y and the reduction gear 61M. And the force applied to the teeth of the large gears 611 and 612 of the reduction gear 61 can be reduced. Furthermore, the thrust force by the helical gear can be reduced as in the first embodiment. For this reason, the deterioration of the meshing state of the gear due to the elastic deformation of the reduction gear 61 can be suppressed.

  As described above in detail, in the third embodiment, the idle gear 74 is formed by integrally forming two gears having opposite torsional directions, and a gear portion that meshes with the motor gear 601 and a gear portion that meshes with the reduction gear 61. Therefore, the number of meshing of the teeth of the idle gear 74 where the driving torque is concentrated can be reduced, and it is possible to provide a driving device with a long life and little vibration. As a result, it is possible to realize a high-quality image forming apparatus that has no long-lasting image unevenness.

  The present invention relates to a drive device using gears, and more particularly to a drive device suitable for use in a photosensitive drum in an image forming apparatus such as a copying machine or a printer that requires high accuracy.

1 is a schematic diagram illustrating an example of an image forming apparatus according to the present invention. It is a perspective view which shows the drive part for driving the OPC drum of 1st Embodiment. It is a top view which similarly shows the drive part for driving an OPC drum. It is the side view which looked at the drive part for similarly driving an OPC drum from the direction of a rotating shaft. It is a top view which shows the drive part for driving the OPC drum of 2nd Embodiment. It is the side view which looked at the drive part for similarly driving an OPC drum from the direction of a rotating shaft. It is a perspective view which shows the drive part for driving the OPC drum of 3rd Embodiment. It is a top view which similarly shows the drive part for driving an OPC drum. It is the side view which looked at the drive part for similarly driving an OPC drum from the direction of a rotating shaft. It is a perspective view which shows the drive part for driving the conventional OPC drum. It is a top view which shows the drive part for driving the conventional OPC drum.

Explanation of symbols

31 OPC drum 36 Drum gear 61 Reduction gear 73, 74, 75 Idle gear 600 Motor 601 Motor gear 611, 612 Large gear 613 Small gear

Claims (9)

In a drive device having a plurality of reduction gear mechanisms for transmitting rotation from a drive source to a plurality of driven gears,
The reduction gear mechanism includes a large gear portion in which two helical gears having the same twist angle and opposite twist directions are integrated, and a helical gear that is coaxially integrated with the large gear portion. A small gear,
The drive source is provided with a drive source gear composed of a helical gear that transmits the rotation of the drive source to a first reduction gear mechanism of the plurality of reduction gear mechanisms,
Of the large gears in the first reduction gear mechanism, one large gear meshes with the drive source gear, and the other large gear meshes with an idle gear between the second reduction gear mechanism. A drive device characterized in that the rotation of the drive source is transmitted to the plurality of reduction gear mechanisms. The drive device according to claim 1,
The drive device according to claim 1, wherein a rotation center axis of the drive source gear, a rotation center axis of the first reduction gear mechanism, and a rotation center axis of the idle gear are in a straight line. The drive device according to claim 1,
The direction of the thrust force generated by the engagement of the one large gear with the drive source gear and the direction of the thrust force generated by the engagement of the other large gear with the idle gear are the same. The drive device characterized. The drive device according to any one of claims 1 to 3,
The plurality of reduction gear mechanisms are connected in series via the idle gear,
Of the large gears in the second reduction gear mechanism, one large gear meshes with the idle gear, and the other large gear meshes with the idle gear between the third reduction gear mechanism. The drive device characterized. The drive device according to any one of claims 1 to 3,
A plurality of the first reduction gear mechanisms are provided on both sides of the drive source via first idle gears,
Of the large gear portions in the first reduction gear mechanism, one large gear meshes with the first idle gear, thereby transmitting the rotation of the drive source to the plurality of first reduction gear mechanisms. A drive device characterized by that. The drive device according to claim 5, wherein
The first idle gear comprises an idle gear in which two helical gears having the same twist angle and opposite twist directions are integrated.
One of the idle gears meshes with the drive source gear, and the other idle gear meshes with one large gear of the large gear portion of the first reduction gear mechanism. In the drive device according to any one of claims 1 to 6,
Furthermore, the small gear is a mechanism for transmitting the rotation of the plurality of reduction gear mechanisms to the plurality of driven gears by meshing with the driven gear. The drive device according to claim 7, wherein
The driving device, wherein the plurality of driven gears are gears for driving a photosensitive drum. An image forming apparatus comprising the driving device according to claim 1.

Images