JP2006064134A - Driving apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep an appropriate parallelism of gears even when a load is applied to the gears of a driving apparatus in the different directions. <P>SOLUTION: The driving apparatus has a driving frame 105 for supporting the rotary shaft 104a of a pinion 104 at the other side of the casing of the apparatus across the pinion 104. When the rotary shaft 104a of the pinion 104 has been tilted by the load, the neighborhood of a fixed position X fixed to the casing of the apparatus deforms, and as a result, the driving frame 105 makes the rotary shaft 104a turn about the fixed position X serving as a fulcrum. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, and a facsimile, and a driving device used in the image forming apparatus.

  As is well known, a drive gear train using gears is often used for driving an image forming apparatus. In particular, in the system that drives the photosensitive drum and the developing roller, the speed unevenness caused by the meshing of the gears is recognized as image quality deterioration called banding on the image (also referred to as pitch unevenness and streaks on the image). Therefore, various countermeasures have been taken conventionally. Further, since the vibration of the meshing also deteriorates the noise level, further improvement is required.

  The transmission error or vibration level generated at the meshing portion of the tooth surface is greatly influenced not only by the accuracy of the gear itself but also by the positional relationship between the meshing gears. Along with the inter-shaft distance (or backlash) of the gear pair, the relative parallelism, that is, the alignment of the rotation axes is a very important factor. Even if the alignment is off by about 0.1 ° to 0.2 °, it will affect the rotation accuracy.

  In general, the drive unit using gears has a structure that ensures static positional accuracy and rigidity in order to guarantee the positional relationship of the gears. Tilt and alignment get out of order. In response to this problem, a method has been proposed in which the shaft is inclined in the opposite direction in advance against the load, or the twist angle of the gear is changed to cancel the influence of the load (for example, patents). Reference 1). This method is very effective as a practical measure for mass-produced products under conditions where the load is stabilized to some extent.

JP 09-080840

  However, the drive system of the image forming apparatus often has a plurality of non-drive gears branched from one drive gear in order to provide various controls and functions and to reduce costs. In such a drive system, when the load on the non-drive side fluctuates, the magnitude and direction of the load applied to the drive gear change, and therefore the inclination amount and direction of the shaft of the drive gear change. In this configuration, when measures are taken to correct the predetermined inclination as described above, the desired performance cannot be obtained when the load changes even though the performance is good in a specific load state. There is.

  An object of the present invention is to keep the parallelism of the rotation shaft of the gear properly even when a load is applied in a different direction with respect to the gear of the drive device.

  In order to achieve the above object, a typical configuration according to the present invention is a drive device having a gear and a drive means for driving the gear, wherein the rotation shaft of the gear is on the opposite side of the device housing with the gear interposed therebetween. When the rotation shaft of the gear is tilted by a load, the support member is deformed in the vicinity of the fixed position fixed to the apparatus housing, and the fixed position is supported at the fulcrum. The rotating shaft is tilted as follows.

  Since the present invention is configured as described above, even when a load is applied in a different direction with respect to the gear of the drive device, the support member is deformed, and in a direction opposite to the inclination of the rotation shaft, Since the rotating shaft is tilted, the parallelism of the rotating shaft of the gear can be maintained appropriately.

  First, a configuration common to embodiments to be described later will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view showing the overall configuration of the image forming apparatus. In this figure, a full color laser beam printer will be described as an example of the image forming apparatus.

(Configuration of image forming apparatus)
A color image forming apparatus 100 shown in FIG. 1 includes four photosensitive drums 1 (1a, 1b, 1c, 1d) arranged in parallel in the vertical direction. The photosensitive drum 1 is rotated counterclockwise by transmission of power from a motor. A charging device 2 (2a, 2b, 2c, 2d) for uniformly charging the surface of the photosensitive drum 1 in order according to the rotation direction, and a laser beam is irradiated around the photosensitive drum 1 based on image information. A scanner unit 3 (3a, 3b, 3c, 3d) for forming an electrostatic latent image on the drum 1, and a developing device 4 (4a, 4b, 4c, 4d) for developing the toner image by attaching toner to the electrostatic latent image ), A transfer roller 12 as an electrostatic transfer device for transferring the toner image on the photosensitive drum 1 to the transfer material S, and a cleaning device 6 (6a, 6) for removing transfer residual toner remaining on the surface of the photosensitive drum 1 after transfer. 6b, 6c, 6d) and the like are provided. Here, the photosensitive drum 1, the charging device 2, the developing device 4, and the cleaning device 6 are integrated into a cartridge to form a process cartridge 7. Hereinafter, the photosensitive drum 1 will be described in detail.

  The photoconductor drum 1 is configured by applying an organic photoconductive layer (OPC photoconductor) to the outer peripheral surface of an aluminum cylinder having a diameter of 30 mm, for example. The photosensitive drum 1 is rotatably supported at both ends by a support member, and is driven to rotate counterclockwise when a driving force from a driving motor (not shown) is transmitted to one end. .

  As the charging device 2, a contact charging type can be used. The charging member is a conductive roller formed in a roller shape. The roller is brought into contact with the surface of the photosensitive drum 1 and the surface of the photosensitive drum 1 is made uniform by applying a charging bias voltage to the roller. To be charged.

  The scanner unit 3 is arranged in a substantially horizontal direction of the photosensitive drum 1, and image light corresponding to an image signal is rotated at high speed by a scanner motor (not shown) by a laser diode (not shown). 9b, 9c, 9d). The image light reflected by the polygon mirror 9 selectively exposes the surface of the charged photosensitive drum 1 through the imaging lens 10 (10a, 10b, 10c, 10d) to form an electrostatic latent image. It is composed.

  The developing device 4 applies yellow, magenta, cyan, and black toners to the outer periphery of the developing roller 40 that rotates in the clockwise direction in the figure, and imparts a charge to the toner. The developing device 4 develops toner on the photosensitive drum 1 according to the electrostatic latent image by applying a developing bias to the developing roller 40 facing the photosensitive drum 1 on which the electrostatic latent image is formed. .

The electrostatic transfer belt 11 is disposed so as to circulate and move in contact with all the photosensitive drums 1a, 1b, 1c, and 1d. The electrostatic transfer belt 11 is formed of a film-like member having a thickness of about 150 μm and having a volume resistivity of 10 ¹¹ to 10 ¹⁴ Ω · cm. The electrostatic transfer belt 11 is supported by four rollers in the vertical direction, and circulates and moves so that the transfer material S is electrostatically attracted to the outer peripheral surface on the left side in the drawing so that the transfer material S comes into contact with the photosensitive drum 1. . As a result, the transfer material S is conveyed to the transfer position by the electrostatic transfer belt 11, and the toner image on the photosensitive drum 1 is transferred.

  A transfer roller 12 (12a, 12b, 12c, 12d) is arranged in parallel at a position in contact with the inside of the electrostatic transfer belt 11 and facing the four photosensitive drums 1a, 1b, 1c, 1d. A positive charge is applied from the transfer roller 12 to the transfer material S via the electrostatic transfer belt 11, and a negative polarity on the photosensitive drum 1 is applied to a sheet in contact with the photosensitive drum 1 by an electric field generated by the charge. The toner image is transferred.

  The electrostatic transfer belt 11 is a belt having a circumferential length of about 700 mm and a thickness of 150 μm. The electrostatic transfer belt 11 is wound around four rollers of a driving roller 13, driven rollers 14a and 14b, and a tension roller 15, and rotates in the direction of the arrow in the figure. As a result, the above-described electrostatic transfer belt 11 circulates and the toner image is transferred while the transfer material S is conveyed from the driven roller 14a side to the drive roller 13 side.

  The feeding unit 16 feeds and conveys the transfer material S to the image forming unit, and a plurality of transfer materials S are stored in the feeding cassette 17. At the time of image formation, the feeding roller 18 (half-moon roller) and the registration roller pair 19 are driven and rotated according to the image forming operation to separate and feed the transfer material S in the feeding cassette 17 one by one, and at the front end of the transfer material S Struck the registration roller pair 19, stopped once, formed a loop, and synchronized with the rotation of the electrostatic transfer belt 11 and the image writing position, and fed to the electrostatic transfer belt 11 by the registration roller pair 19. .

  The fixing unit 20 fixes the toner images of a plurality of colors transferred to the transfer material S, and includes a rotating heating roller 21a and a pressure roller 21b that presses and applies heat and pressure to the transfer material S. Consists of. That is, the transfer material S to which the toner image on the photosensitive drum 1 is transferred is conveyed by the fixing roller pair 21 (21a, 21b) when passing through the fixing unit 20, and heat and pressure are applied by the fixing roller pair 21. Given. As a result, the toner images of a plurality of colors are fixed on the surface of the transfer material S.

(Operation of image forming apparatus)
With the above configuration, the image forming apparatus operates as follows during image formation.

  The process cartridges 7a, 7b, 7c, and 7d are sequentially driven in accordance with the printing timing, and the photosensitive drums 1a, 1b, 1c, and 1d are driven to rotate counterclockwise in accordance with the driving. Then, the scanner units 3 corresponding to the respective process cartridges 7 are sequentially driven. By this driving, the charging roller 2 applies a uniform charge to the circumferential surface of the photosensitive drum 1, and the scanner unit 3 exposes the circumferential surface of the photosensitive drum 1 in accordance with the image signal, thereby rotating the circumferential surface of the photosensitive drum 1. An electrostatic latent image is formed on the surface. The developing roller 40 in the developing device 4 forms (develops) a toner image on the circumferential surface of the photosensitive drum 1 by transferring the toner to the low potential portion of the electrostatic latent image.

  When the leading edge of the toner image formed on the circumferential surface of the most upstream photosensitive drum is rotated and conveyed to a point facing the electrostatic transfer belt 11, the image formation start position of the transfer material S is reached at the opposite point. So that the registration roller pair 19 starts rotating so that the transfer material S is fed to the electrostatic transfer belt 11.

  The transfer material S is pressed against the outer periphery of the electrostatic transfer belt 11 so as to be sandwiched between the electrostatic adsorption roller 22 and the electrostatic transfer belt 11, and a voltage is applied between the electrostatic transfer belt 11 and the electrostatic adsorption roller 22. Is applied to induce a charge in the transfer material S, which is a dielectric, and the dielectric layer of the electrostatic transfer belt 11, and the transfer material is electrostatically adsorbed to the outer periphery of the electrostatic transfer belt 11. . As a result, the transfer material S is stably adsorbed to the electrostatic transfer belt 11 and conveyed to the most downstream transfer unit. While being conveyed in this way, the toner image on each photoconductive drum 1 is sequentially transferred to the transfer material S by an electric field formed between each photoconductive drum 1 and the transfer roller 12.

  The transfer material S onto which the four color toner images have been transferred is separated from the electrostatic transfer belt 11 by the curvature of the driving roller 13 of the belt, and is carried into the fixing unit 20. After the toner image is thermally fixed by the fixing unit 20, the transfer material S is discharged out of the main body by the discharge roller pair 23 with the image surface facing down from the discharge unit 24.

  Next, a characteristic configuration of the present invention will be described in detail.

[First Embodiment]
1st Embodiment demonstrates the drive frame (support member) which supports the pinion of the motor which a drive device has.

  FIG. 2 shows a part of a driving device that rotationally drives the photosensitive drum 1 and the like in the process cartridge 7 of the image forming apparatus. In the present embodiment, one drive motor (drive means) 101 supported by a drive frame 105 (details will be described later) includes a gear 102 for rotating the photosensitive drum 1 from a pinion (gear) 104, and development. It directly meshes with the gear 103 that rotationally drives the roller 40. This is because the rotational accuracy of the photosensitive drum 1 is very important in order to suppress banding of the image formed by the image forming apparatus. Therefore, the driving is performed separately from other driving such as driving of the developing roller 40. A driving force is obtained directly from the pinion gear 104 attached to the motor 101. Further, in order to avoid waste of toner on the driving side of the developing roller 40, a method of putting a clutch (not shown) and rotating the developing roller 40 only when necessary is adopted.

  Depending on the relationship between the load torque of the photosensitive drum 1 and the developing roller 40 and the reduction gear ratio of the drive gear train, the load applied to the pinion 104 of the motor when a clutch (hereinafter referred to as a developing clutch) (not shown) is turned on and off. The direction of changes. That is, when the developing clutch is disengaged and only the photosensitive drum 1 is rotated, the motor pinion 104 receives a reaction force from the gear 102 of the photosensitive drum 1. For this reason, an upward load is applied to the pinion 104 of the motor and its rotating shaft. On the other hand, when the developing clutch is engaged and the photosensitive drum 1 and the developing roller 40 are also rotated, the motor pinion 104 is strongly influenced by the gear 103 on the developing roller 40 side. Therefore, a downward load is applied to the pinion 104 of the motor.

  When full color printing is performed, the photosensitive drums 1 and the developing rollers 40 in all the process cartridges 7 are rotated. For this reason, a downward load is applied to the pinions 104 of all the motors 101. In the case of mono-color printing, the developing roller 40 of only the black process cartridge 7 is rotated, and the developing rollers 40 of the other process cartridges 7 are not rotated. Therefore, a downward load is applied only to the pinion 104 of the motor 101, and an upward load is applied to the pinion 104 of the motor 101 corresponding to other colors. Thus, the direction of the force applied to the pinion 104 of the motor changes depending on the print mode.

(Drive frame 105A)
A case where the drive frame 105A is used as one configuration of the drive frame 105 will be described. As shown in FIGS. 2 and 3, the drive frame 105 </ b> A is configured by bending a plate-like member and supports the drive motor 101. Here, as shown in FIG. 3, the drive frame 105 </ b> A pivotally supports the rotation shaft of the drive motor 101 at a position opposite to the housing 107 with the pinion 104 of the drive motor 101 interposed therebetween. Further, the drive frame 105A is continuously and integrally configured from a position where the drive motor 101 is pivotally supported to a casing 107 on the opposite side of the pinion 104 with the pinion 104 interposed therebetween. The drive frame 105A is fixed to the housing 107 by screws 106a and 106b at the fixed position X. Here, the housing 107 in the present embodiment indicates the housing of the driving device, but may be the same as the housing of the process cartridge 7.

  A notch 105a is formed in the center of the plate-like drive frame 105A in the vicinity of the fixed position X of the drive frame 105A with the housing 107. For this reason, in the vicinity of the fixed position X of the drive frame 105A, it is configured to be easily elastically deformed.

  The state of the drive frame 105A when only the gear 102 of the photosensitive drum 1 is driven and the gear 103 of the developing device 4 is not driven will be described with reference to FIGS. This is the state of the color process cartridge during monocolor printing. FIG. 3 is a side sectional view of a part of the drive device for the process cartridge 7 shown in FIG.

  When the developing clutch is disengaged and the pinion 104 of the drive motor 101 is driven, an upward load F is applied by the reaction force from the gear 102 of the photosensitive drum 1. Then, due to the rigidity of the mounting portion of the motor 101 and the clearance between the bearings 108a and 108b and the shaft in the motor shaft support portion, the rotation shaft 104a of the motor pinion has the mounting portion of the driving motor 101 of the driving frame 105A as a fulcrum. It tries to tilt so that the tip of the pinion rotating shaft 104a faces upward.

  As described above, the drive frame 105A is formed with the notch 105a in the vicinity of the fixing position X with the housing 107. For this reason, the periphery of the notch 105a is easily elastically deformed, and the portion of the drive frame 105A ahead of the fixed position X is displaced upward with the fixed position X as a fulcrum.

  Here, since the portion ahead of the fixed position X of the drive frame 105A is not given elasticity, the original shape is maintained. As a result, the entire drive frame 105A also tends to tilt with the fixed position X as a fulcrum. At this time, the direction in which the drive frame 105A tends to tilt is a direction that cancels the tilt of the rotation shaft 104a of the pinion, specifically, a direction in which the mounting portion of the drive motor 101 of the drive frame 105A is tilted toward the housing 107. It is.

  In this way, the shape of the drive frame 105A is optimized so that the inclination of the pinion rotation shaft 104a and the inclination of the portion ahead of the fixed position X of the drive frame 105A are approximately equal. Therefore, when the load F is applied in the upward direction, as indicated by a two-dot chain line in FIG. 3, the pinion 104 only moves upward, and the pinion rotation shaft 104a does not substantially tilt.

  The state of the drive frame 105A when driving both the gear 102 of the photosensitive drum 1 and the gear 103 of the developing device 4 will be described with reference to FIG. The state of the black process cartridge corresponds to this state regardless of the color process cartridge at the time of full color printing and at the time of full color printing or mono color printing.

  When the developing clutch is engaged and the pinion 104 of the drive motor 101 is driven, a downward load F is applied by reaction forces from the gear 102 of the photosensitive drum 1 and the gear 103 of the developing roller 40. Then, due to the rigidity of the mounting portion of the motor 101 and the clearance between the bearings 108a and 108b and the shaft in the motor shaft support portion, the pinion rotating shaft 104a tilts downward with the mounting portion of the drive motor 101 of the drive frame 105A as a fulcrum. Try this.

  Here, in the same manner as described above, with the fixed position X between the housing 107 and the drive frame 105A as a fulcrum, the entire drive frame 105A cancels the inclination of the rotation shaft 104a of the pinion (specifically, the drive frame 105A By attempting to incline the mounting portion of the drive motor 101 in the direction away from the housing 107 side, the pinion rotation shaft 104a is not substantially inclined.

  In this embodiment, the direction allowing the elastic deformation in the drive frame 105A is the circumferential direction of the gears 102 and 103. Thus, it is preferable that the direction allowing elastic deformation is the circumferential direction of the gear. This will be described.

  FIG. 5 is a front view of a part of the drive device shown in FIG. 2 and shows the state of the drive gear train (the gears 102 and 103 and the pinion 104). FIG. 6 is an enlarged view of the vicinity of the engagement of the drive gear of FIG. As shown in FIG. 6, the position of the shaft slightly moves in the circumferential direction of the gear, but hardly affects the distance between the shafts of each drive gear train. For this reason, even when the load F is applied to the pinion 104, the drive device can maintain the desired drive performance.

  The configuration for allowing elastic deformation of the drive frame 105A in the circumferential direction of the gears 102 and 103 varies depending on the material of the drive frame 105A. For example, when the support member is formed of a sheet metal like the drive frame 105A, the sheet metal portion raised from the housing 107 by bending the drive frame 105A meshes with the gears 102 and 103 and the pinion 104 as shown in FIG. What is necessary is just to comprise so as to be orthogonal to a tangent.

(Drive frame 105B)
A case where the drive frame 105B is used as one configuration of the drive frame 105 will be described. FIG. 7 is a perspective view of the drive frame 105B, and FIG. 8 is a side sectional view of the drive frame 105B. As shown in FIGS. 7 and 8, the drive frame 105B is provided with a portion that is elastically deformed in contact with the housing 107 even at a position other than the fixed position X that is fixed to the housing 107 by screws 106a and 106b. It is a configuration.

  The drive frame 105B is configured by bending a plate-like metal member so as to cover the upper side of the position where the gear 102 and the gear 103 mesh with the pinion 104 in the circumferential direction. As described above, it is preferable that the drive frame 105B is also elastically deformed in the circumferential direction of the gears 102 and 103. Therefore, as shown in FIG. The gears 102 and 103 and the pinion 104 are configured to be orthogonal to the tangent line.

  The drive frame 105B is formed with a notch 105a and a notch 105b at two locations where the plate-like member is bent. Specifically, first, a notch 105a is formed in the center of the plate-like drive frame 105B in the vicinity of the fixed position X where the drive frame 105B is fixed to the housing 107. A notch 105b is formed in the center of the plate-like drive frame 105B near the contact position Y where the drive frame 105B contacts the housing 107 on the opposite side of the fixed position X across the pinion 104. For this reason, the elastic deformation is likely to occur near the fixed position X of the drive frame 105B (a part in the figure) and near the contact position Y (b part in the figure).

  Further, a notch 107a is formed on the housing 107 side. That is, as shown in FIGS. 7 and 8, the drive frame 105B bends in the vicinity of the contact position Y, and the notch portion 107a is provided in the portion where the drive frame 105B rises from the housing 107, so that the b portion of the drive frame 105B It is configured to be able to enter when elastically deformed. In this way, the presence of the notch 107a allows the drive frame 105B to be deformed when it is deformed to tilt with the fixed position X as a fulcrum.

  Next, an operation when a load is applied to the drive frame 105B will be described. As shown in FIG. 8, when an upward load F is applied to the pinion 104 of the motor 101, the rotation of the pinion depends on the rigidity of the mounting portion of the motor 101 and the clearance between the bearings 108a and 108b and the shaft in the motor shaft support portion. The shaft 104a tends to tilt upward with the mounting portion of the drive motor 101 of the drive frame 105A as a fulcrum. Here, as described above, with the fixed position X as a fulcrum, the drive frame 105B as a whole tends to tilt in a direction that cancels the tilt of the pinion rotation shaft 104a, so that the pinion rotation shaft 104a does not substantially tilt. .

  In the configuration of the drive frame 105B, since the motor 101 is supported at the top and bottom in FIG. 8, there is an advantage that the initial position accuracy of the mounting portion of the motor 101 can be more easily ensured than the configuration of the drive frame 105A.

(Drive frame 105C)
A case where the drive frame 105C is used as one configuration of the drive frame 105 will be described. FIG. 9 is a side sectional view of the drive frame 105C.

  As shown in FIG. 9, the drive frame 105C has a contact position Y that contacts the housing 107 at the end (upper side in the figure) opposite to the fixed position X of the drive frame 105C by screws 106a and 106b. A vibration damping member 115 is interposed between the contact position Y and the housing 107.

  The vibration damping member 115 is preferably a viscoelastic body having excellent damping characteristics. The reason is as follows. When the drive gear train is driven, the frame 105 or the like that supports the drive gear train may vibrate slightly and affect the rotation accuracy. When damping vibration, of course, it is efficient to dampen a region where vibration is large, but in this configuration, the vicinity of the contact position Y in the figure is easy to identify as the vibration region, so a damping member is attached to this portion . Thereby, the vibration of the drive device including the gear can be effectively suppressed.

(Drive frame 105D)
A case where the drive frame 105D is used as one configuration of the drive frame 105 will be described. As shown in FIG. 10, the drive frame 105 </ b> D has a configuration in which a resin molded part is used as a part of the drive frame 105 </ b> D, and copes with the limit of bending accuracy in the sheet metal frame.

  In the figure, the a and b portions are elastically deformed regions. Similarly to the above example, when an upward load F is applied, the rotation shaft 104a of the pinion is caused by the rigidity of the mounting portion of the motor 101 of the drive frame 105D and the clearance between the bearings 108a and 108b and the shaft in the motor shaft support portion. The drive frame 105D tends to tilt upward with the mounting portion of the drive motor 101 as a fulcrum.

  Here, for the same reason as described above, the rotation axis 104a of the pinion does not substantially tilt as shown by the two-dot chain line in FIG. In this configuration, by making a resin part, that is, a mold, the parallelism between the mounting surface at the fixing position X of the drive frame 105D and the housing 107 and the surface of the mounting portion of the motor 101 is made more accurate than the sheet metal frame. be able to.

[Second Embodiment]
2nd Embodiment demonstrates the supporting member which supports the intermediate gear which a drive device has. Constituent elements similar to those of the above-described embodiment are denoted by the same reference numerals and description thereof is omitted.

  FIG. 10 is a top sectional view of an intermediate gear included in the drive device. The intermediate gear of the present embodiment will be described in which the rotation direction is switched between the forward direction (clockwise) and the reverse direction (counterclockwise).

  As shown in FIGS. 11 to 13, the drive device of this embodiment includes a drive transmission gear 109 that meshes with a pinion 104 of a motor 101, a gear 112 that is coaxial with the drive transmission gear 109 and serves as a drive input side, and a gear An intermediate gear 110 that meshes with 112, and a gear 113 that serves as an output side of meshing drive with the intermediate gear 110.

  As shown in FIGS. 12 and 13, the rotation shaft 111 of the intermediate gear 110 receives the resultant force of the reaction force of the input side gear 112 and the output side gear 113, and the rotation direction is switched between forward and reverse. It can be seen that the direction of the force changes downward (FIG. 12) or upward (FIG. 13).

  14 to 16 are cross-sectional views when the rotating shaft 111 of the intermediate gear 110 receives an upward force as shown in FIG. In either case, (a) shows a state in which no drive is applied, and (b) shows a state in which the drive is applied and an upward load F is applied to the rotary shaft 111 of the intermediate gear. 14 and 15 are explanatory diagrams for comparison with the present embodiment, and only FIG. 16 shows the present embodiment.

When only one side of the rotation shaft 111 of the intermediate gear is directly supported by the housing 107, the load F is inclined upward by θ ₁ as shown in FIG. If this inclination becomes misalignment, when the photosensitive drum 1 is attached to the rotation shaft of the gear 113 on the output side, the photosensitive drum 1 may not rotate with a desired rotational accuracy. In this case, banding may occur during image formation or noise may be deteriorated.

As a countermeasure against this, as shown in FIG. 15, it is common to reinforce so that both sides of the rotating shaft 111 of the intermediate gear 110 are supported by a sheet metal frame 114 or the like. Thereby, the inclination of the shaft can be suppressed from θ ₁ , but the inclination θ ₂ still remains due to the rigidity of the sheet metal frame 114 and the rigidity of the portion where the rotating shaft 111 of the intermediate gear 110 is attached to the housing 107.

  Therefore, in the present embodiment, as shown in FIG. 16, the end 111b of the rotating shaft 111 opposite to the end 111a of the rotating shaft 111 of the intermediate gear 110 shown in FIGS. 14 and 15 is connected to the drive frame 105E. Is supported by.

  The drive frame 105E has a notch 105a at the fixed position X, as in the above-described embodiment. For this reason, the frame shape is optimized so that the deformation of each part of the drive frame 105E cancels the inclination of the shaft. Thus, the tilt of the rotating shaft 111 can be suppressed by the same operation as that of the drive frame 105A of the above-described embodiment. In the configuration of the drive frame 105E of the present embodiment, the center position of the rotating shaft 111 moves in the circumferential direction by δ, but since this value is about 0.1 mm, there is almost no problem.

  In the description of the present embodiment, the configuration is the same as that of the drive frame 105A described in the first embodiment, but any configuration of the drive frames 105B to 105D may be adopted.

  An example is shown and the advantage from another viewpoint of the drive device in the above-mentioned embodiment is explained. FIG. 17 shows the transfer characteristics of the drive unit. The horizontal axis represents frequency, and the vertical axis represents vibration transmission rate, that is, gain.

In general, in the resonance region, the output accuracy deteriorates with respect to the input accuracy of rotation. At a frequency lower than that region, gain = 1, that is, the input itself is transmitted, and at a frequency higher than resonance, gain <1, that is, accuracy. Tend to improve. F ₁ is the resonance frequency of the drive frame when adjustment of the rigidity of the drive frame is not performed, f ₂ is the resonance frequency of the drive frame when adjustment of the rigidity of the drive frame is performed, and f _z is in the use state This is the vibration frequency of the drive frame.

  FIG. 18 shows the rotational speed unevenness characteristics of the gear 102 that drives the photosensitive drum 1. The horizontal axis represents frequency, and the vertical axis represents rotational speed unevenness. When the rotation speed unevenness of the gear 102 driving the photosensitive drum 1, that is, the photosensitive drum 1, is deteriorated, it is recognized as banding in the image. Note that fz is the vibration frequency of the drive frame in use.

  A curve A in FIG. 17 indicates that the rigidity of the drive frame that supports the pinion 104 or the intermediate gear 110 is not adjusted. In this case, since the gear meshing frequency is included in the resonance region, the rotational speed unevenness is deteriorated, resulting in a result a as shown in FIG.

  On the other hand, a curve B in FIG. 17 is obtained by optimizing the rigidity of the drive frame. Specifically, the resonance region was shifted to the low frequency side by slightly reducing the rigidity. In this case, since the gear meshing frequency is deviated from the resonance region to the high frequency side, the rotational speed unevenness is improved to be 0.5% or less as indicated by b in FIG. 18, and is not recognized as banding in the image. Can be suppressed to the level. In FIG. 18, when b is seen, it is clearly improved as compared with a.

  Such adjustment of vibration characteristics is generally made in the shape of gears and rotating shafts, and there are restrictions on the shape of parts to ensure the accuracy of each part. In this configuration, the rigidity of the drive frame is adjusted. The vibration characteristics of the drive unit can be optimized relatively easily only by performing.

[Other Embodiments]
In the above-described embodiment, the gear adjacent to the gear supported by the drive frame 105 is a gear attached to the rotation shaft of the photosensitive drum. However, for any means in the image forming apparatus that rotates. Can be used. For example, the developing roller 40, the charging device 2, the cleaning device 6 and the like.

1 is a side sectional view showing a schematic configuration of an image forming apparatus. The perspective view which shows schematic structure of the drive device and drive frame 105A of 1st Embodiment. The sectional side view which shows a mode that the drive frame 105A deform | transforms when the load F is applied from the bottom to the pinion 104 which the drive frame 105A supports. The sectional side view which shows a mode that the drive frame 105A deform | transforms when the load F is applied to the pinion 104 which the drive frame 105A supports from the top. The top view which shows the drive gear train of a drive device. The enlarged view which shows the state which the pinion 104 displaces in a drive gear train. The perspective view which shows schematic structure of the drive frame 105B. The sectional side view which shows a mode that the drive frame 105B deform | transforms when the load F is applied to the pinion 104 which the drive frame 105B supports from the bottom. The sectional side view which shows a mode that the drive frame 105C deform | transforms when the load F is applied from the bottom to the pinion 104 which the drive frame 105C supports. The sectional side view which shows a mode that the drive frame 105D deform | transforms when the load F is applied to the pinion 104 which the drive frame 105D supports from the bottom. The sectional side view which shows schematic structure of the drive device of 2nd Embodiment. FIG. 4 is an explanatory diagram showing a rotation direction of the intermediate gear 110 and a direction in which a load F is applied. FIG. 4 is an explanatory diagram showing a rotation direction of the intermediate gear 110 and a direction in which a load F is applied. The figure which shows the structure which supported the rotating shaft 111 in the housing | casing as a reference example. The figure which shows the structure which pivotally supported the rotating shaft 111 on the housing | casing as a reference example, and the both ends of the rotating shaft 111. The sectional side view which shows the structure of the drive frame 105E. The figure which shows the transfer characteristic of the drive device at the time of implementing this invention. The figure which shows the characteristic of the rotational speed nonuniformity of a drive device at the time of implementing this invention, and a frequency.

Explanation of symbols

F: Load,
DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum (image carrier), 100 ... Image forming apparatus,
101 ... drive motor (drive means),
102 ... gear, 103 ... gear, 104 ... pinion (gear), 104a ... rotating shaft,
105… Drive frame (support member),
105A: Drive frame (support member), 105B: Drive frame (support member),
105C: Drive frame (support member), 105D: Drive frame (support member),
105E ... Drive frame (support member),
105a ... notch, 105b ... notch,
107… Case,
110 ... intermediate gear, 111 ... rotating shaft, 112 ... gear, 113 ... gear,
115 ... vibration damping member,

Claims (5)

In a driving device having a gear and a driving means for driving the gear,
A support member for supporting the rotation shaft of the gear on the opposite side of the device housing with the gear interposed therebetween;
When the rotation axis of the gear is tilted by a load,
The drive device according to claim 1, wherein the support member tilts the rotation shaft about the fixed position when the vicinity of the fixed position fixed to the apparatus housing is deformed. The drive device according to claim 1,
The gear is a pinion of the driving means. The drive device according to claim 1,
The drive device according to claim 1, wherein the gear is an intermediate gear whose rotation direction is switched according to a drive direction of the drive means. The drive device according to claim 1,
The drive device according to claim 1, wherein a vibration damping member is interposed between the support member and the apparatus housing at a position different from the fixed position. In an image forming apparatus having an image carrier and a driving device for driving the image carrier,
5. The image forming apparatus according to claim 1, wherein the driving apparatus is a driving apparatus according to claim 1.

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