JP2017076019A - Photoreceptor drum driving device and image forming apparatus including the same - Google Patents

Abstract

CONSTITUTION: A photoreceptor drum driving device 100 comprises a drum driving gear 108 and a gear shaft 106 that rotatably supports the drum driving gear. The drum driving gear includes a drive coupling 124 that is integrally formed at its tip portion. The drum driving gear can be swung with respect to the gear shaft so that the drive coupling formed at the tip portion swings.EFFECT: Since even when a drum driving gear and a photoreceptor drum are not concentric with each other, the drum driving gear moves in a tilting manner following the positional displacement, the photoreceptor drum can be accurately rotated without causing a shaking component in the rotation of the photoreceptor drum.SELECTED DRAWING: Figure 7

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive drum driving device and an image forming apparatus including the photosensitive drum driving device. The present invention relates to a forming apparatus.

  2. Description of the Related Art Conventionally, a photosensitive drum included in an image forming apparatus is generally unitized together with a charger and the like and can be attached to and detached from the image forming apparatus main body. Further, such a photosensitive drum is rotated by receiving a rotational driving force from a photosensitive drum driving device (main driving unit) provided on the main body side of the image forming apparatus. A coupling is used as a means for transmitting the rotational driving force from the photosensitive drum driving device to the photosensitive drum. At this time, in order to rotate the photoconductor drum with high accuracy, it is necessary to connect the photoconductor coupling provided on the photoconductor drum and the drive coupling provided on the photoconductor drum driving device concentrically with high accuracy.

  For example, the image forming apparatus disclosed in Patent Document 1 employs the following configuration in order to make the axis of the drum drive gear and the axis of the photosensitive drum concentric (that is, align the coupling position). Yes. That is, in the image forming apparatus disclosed in Patent Document 1, a positioning member having a positioning cylindrical portion and a positioning hole is provided on the main body rear side wall provided in the image forming apparatus main body. On the other hand, a holding cylinder portion is provided on the drum rear side wall of the drum unit. A drum driving gear is supported in the positioning hole of the positioning member, and a holding cylindrical portion of the drum unit is supported in the positioning cylindrical portion. Then, the drum shaft of the photosensitive drum and the drum driving gear are coupled by a coupling.

Japanese Patent Laid-Open No. 2004-294631

  However, in a conventional image forming apparatus such as Patent Document 1, whether or not the axis of the drum drive gear and the axis of the photosensitive drum are concentric depends on the dimensional accuracy of each member. It cannot be said that concentricity can be achieved. For this reason, in the conventional image forming apparatus, if the axis of the drum drive gear and the axis of the photosensitive drum are not concentric and the coupling position is shifted, A shake component appears in the rotation, which may adversely affect image formation.

  Therefore, a main object of the present invention is to provide a novel photosensitive drum driving device and an image forming apparatus including the same.

  Another object of the present invention is to provide a photosensitive drum capable of appropriately rotating the photosensitive drum even when the axis of the drum driving gear and the axis of the photosensitive drum are not concentric. A driving device and an image forming apparatus including the driving device are provided.

  A first aspect of the present invention is a photosensitive drum driving device for rotationally driving a photosensitive drum, wherein a driving coupling fitted to a photosensitive coupling provided on the photosensitive drum is integrally formed at a tip portion. A drum driving gear, and a gear shaft that rotatably supports the drum driving gear, and the drum driving gear is a photosensitive drum driving device in which a tip portion can swing with respect to the gear shaft.

  In the first invention, the photosensitive drum driving device includes a drum driving gear and a gear shaft that rotatably supports the drum driving gear, and applies a rotational driving force to the photosensitive drum. The drum drive gear has a drive coupling formed integrally with the tip portion thereof. This drive coupling is engaged with a photoconductor coupling provided on the photoconductor drum, thereby transmitting the rotation of the drum drive gear to the photoconductor drum. Further, the drum drive gear is swingable (can be tilted) with respect to the gear shaft so that the drive coupling formed at the tip portion can swing. As a result, even if the axis of the drum drive gear and the axis of the photosensitive drum are not concentric, that is, even if the position of the photoconductor coupling with respect to the drive coupling is deviated, the misalignment will occur. The drum drive gear tilts following this. The drum driving gear rotates while maintaining the tilted state, so that the rotational driving force is transmitted to the photosensitive drum without stress.

  According to the first invention, even if the axis of the drum drive gear and the axis of the photosensitive drum are not concentric, the photosensitive drum does not generate a shake component without causing a shake component. The body drum can be appropriately rotated with high accuracy. Further, since the drive coupling is formed integrally with the drum drive gear, the number of parts can be reduced, and the configuration of the photosensitive drum drive device can be simplified.

  The second invention is dependent on the first invention, and the drum drive gear is such that only the root portion is in sliding contact with the gear shaft, and the tip portion can swing around the root portion as a fulcrum.

  In the second invention, only the root portion of the drum drive gear is in sliding contact with the gear shaft. That is, the drum drive gear has a sliding contact portion with the gear shaft at the base portion, and a gap is formed between the drum driving gear and the gear shaft at a portion other than the sliding contact portion. As a result, the drum drive gear swings (tilts) appropriately with respect to the gear shaft so that the tip portion swings around the root portion as a fulcrum.

  A third invention is dependent on the first or second invention, and further includes a holding member for positioning the photosensitive drum.

  In the third invention, the photosensitive drum (and thus the entire photosensitive unit) is positioned by the holding member provided in the photosensitive drum driving device, and the photosensitive drum is centered with respect to the drum driving gear.

  According to the third invention, since the photosensitive drum is appropriately positioned, the rotation of the drum driving gear can be smoothly transmitted to the drum shaft of the photosensitive drum, and the photosensitive drum can be rotationally driven with high accuracy. .

  A fourth invention is dependent on the third invention, and the holding member is provided so as to cover the outer peripheral surface of the drum drive gear, and the maximum deflection width of the tip portion of the drum drive gear is regulated by the holding member.

  In 4th invention, a holding member is provided so that the outer peripheral surface of a drum drive gear may be covered. The holding member regulates or adjusts the maximum deflection width (maximum inclination angle) of the tip portion of the drum drive gear. Accordingly, it is possible to appropriately set the maximum swing width of the tip portion of the drum drive gear.

  A fifth invention is an image forming apparatus including the photosensitive drum driving device according to any one of the first to fourth inventions.

  According to the fifth invention, the same effect as the first invention is achieved, and even if the axis of the drum drive gear and the axis of the photosensitive drum are not concentric, the photosensitive drum Therefore, the photosensitive drum can be appropriately rotated with high accuracy without causing a shake component in the rotation.

  According to this invention, even if the axis of the drum drive gear and the axis of the photosensitive drum are not concentric, the photosensitive drum does not generate a vibration component in the rotation of the photosensitive drum. Can be rotated accurately and appropriately. Further, since the drive coupling is formed integrally with the drum drive gear, the number of parts can be reduced, and the configuration of the photosensitive drum drive device can be simplified.

  The above object, other objects, features, and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

1 is a schematic sectional view showing an internal structure of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a perspective view showing a photoreceptor unit provided in the image forming apparatus of FIG. 1. FIG. 3 is a cross-sectional view showing the photoreceptor unit of FIG. 2. It is a fragmentary sectional view which expands and shows the rear side part of FIG. FIG. 2 is a perspective view showing a photosensitive drum driving device provided in the image forming apparatus of FIG. 1. FIG. 6 is a plan view showing the photosensitive drum driving device of FIG. 5. FIG. 6 is an enlarged partial cross-sectional view of a peripheral portion of a drum drive gear of the photosensitive drum drive device of FIG. 5. It is an illustration figure which shows a drum drive gear, Comprising: (A) is a perspective view of a drum drive gear, (B) is sectional drawing of a drum drive gear. It is a fragmentary sectional view which shows a mode that the drum drive gear inclined with respect to the gear shaft. It is an illustration figure which shows the state which connected the photoconductor drum drive device and the photoconductor unit. It is a fragmentary sectional view which expands and shows the connection part of FIG. FIG. 6 is a partial cross-sectional view illustrating a state in which the photosensitive unit is connected to the photosensitive drum driving device in an inclined state. FIG. 5 is a partial cross-sectional view showing, in an enlarged manner, a peripheral portion of a drum driving gear of a photosensitive drum driving device provided in an image forming apparatus according to a second embodiment of the present invention. FIG. 10 is a partial cross-sectional view showing, in an enlarged manner, a peripheral portion of a drum driving gear of a photosensitive drum driving device provided in an image forming apparatus according to a third embodiment of the present invention.

[First embodiment]
Referring to FIG. 1, an image forming apparatus 10 according to an embodiment of the present invention is a multifunction peripheral (MFP) having a copying function, a printer function, a scanner function, a facsimile function, and the like, and is an electrophotographic system. To form a multi-color or single-color image on a sheet (recording medium). As will be described in detail later, the image forming apparatus 10 is provided with a photosensitive unit (process unit) 70 in which the photosensitive drum 36 and the charger 40 are unitized. Further, a photosensitive drum driving device (main driving unit; see FIG. 5) 100 is provided on the main body side of the image forming apparatus 10, and the photosensitive drum 36 and the like receive driving force from the photosensitive drum driving device 100.

  First, the basic configuration of the image forming apparatus 10 will be schematically described. As shown in FIG. 1, the image forming apparatus 10 includes an apparatus main body 12 including an image forming unit 30 and the like, and an image reading apparatus 14 disposed above the apparatus main body 12.

  The image reading device 14 includes a document placing table 16 formed of a transparent material. A document pressing cover 18 is attached above the document placing table 16 through a hinge or the like so as to be freely opened and closed. The document pressing cover 18 is provided with an ADF (automatic document feeder) 24 that automatically feeds the documents placed on the document placing tray 20 one by one to the image reading position 22. Although not shown, an operation unit such as a touch panel and operation buttons for receiving an input operation such as a print instruction by a user is provided on the front side of the document placing table 16.

  The image reading device 14 includes an image reading unit 26 including a light source, a plurality of mirrors, an imaging lens, a line sensor, and the like. The image reading unit 26 exposes the document surface with a light source, and guides the reflected light reflected from the document surface to the imaging lens by a plurality of mirrors. Then, the reflected light is imaged on the light receiving element of the line sensor by the imaging lens. The line sensor detects the luminance and chromaticity of the reflected light imaged on the light receiving element, and generates image data based on the image on the document surface. As the line sensor, a charge coupled device (CCD), a contact image sensor (CIS), or the like is used.

  The apparatus main body 12 includes a control unit (not shown) including a CPU, a memory, and the like, an image forming unit 30, and the like. The control unit transmits a control signal to each part of the image forming apparatus 10 in accordance with an input operation to an operation unit such as a touch panel, and causes the image forming apparatus 10 to execute various operations.

  The image forming unit 30 includes an exposure unit 32, a developing unit 34, a photosensitive drum 36, a cleaner unit 38, a charger 40, an intermediate transfer belt unit 42, a transfer roller 44, a fixing unit 46, and the like, and a paper feed tray 48 or a manual feed. An image is formed on a sheet conveyed from the sheet feed tray 50, and the image-formed sheet is discharged to a sheet discharge tray 52. As image data for forming an image on a sheet, image data read by the image reading unit 26 or image data transmitted from an external computer is used.

  The image data handled in the image forming apparatus 10 corresponds to four color images of black (K), cyan (C), magenta (M), and yellow (Y). For this reason, each of the developing device 34, the photosensitive drum 36, the cleaner unit 38, and the charging device 40 is provided so as to form four types of latent images corresponding to the respective colors, thereby providing four image stations. Composed. Further, the photosensitive drum 36, the cleaner unit 38, and the charger 40 are unitized, and a photosensitive unit 70 is configured by these units. That is, the image forming unit 30 is provided with four photoreceptor units 70 including the photoreceptor drum 36, the cleaner unit 38, the charger 40, and the like. Each of the photoreceptor units 70 can be individually attached and detached from the front side (front side) of the apparatus main body 12. The apparatus main body 12 is fixedly provided with a photosensitive drum driving device (see FIG. 5) 100 on the back side (rear side). When the photoconductor unit 70 is attached to the apparatus main body 12, the photoconductor unit 70 and the photoconductor drum driving device 100 are connected to each other, and each photoconductor drum 36 is rotationally driven by receiving a rotational driving force from the photoconductor drum driving device 100. Is done. Specific configurations of the photosensitive unit 70 and the photosensitive drum driving device 100 will be described later.

  The photosensitive drum 36 is an image carrier in which a photosensitive layer is formed on the surface of a cylindrical substrate 74 having conductivity. The charger 40 is a member that charges the surface of the photosensitive drum 36 to a predetermined potential. It is. Further, the exposure unit 32 is configured as a laser scanning unit (LSU) including a laser emitting portion and a reflection mirror, and exposes the surface of the charged photosensitive drum 36 so that an electrostatic latent image corresponding to image data is obtained. An image is formed on the surface of the photosensitive drum 36. The developing device 34 visualizes the electrostatic latent image formed on the surface of the photosensitive drum 36 with toner of four colors (YMCK). The cleaner unit 38 removes toner remaining on the surface of the photosensitive drum 36 after development and image transfer.

  The intermediate transfer belt unit 42 includes an intermediate transfer belt 54, a drive roller 56, a driven roller 58, four intermediate transfer rollers 60, and the like, and is disposed above the photosensitive drum 36. The intermediate transfer belt 54 is provided so as to be in contact with each photosensitive drum 36, and the toner images of the respective colors formed on the respective photosensitive drums 36 are sequentially superimposed on the intermediate transfer belt 54 using the intermediate transfer roller 60. As a result, a multicolor toner image is formed on the intermediate transfer belt 54. Further, a transfer roller 44 is disposed in the vicinity of the driving roller 56, and the toner formed on the intermediate transfer belt 54 by passing the sheet through the nip area between the intermediate transfer belt 54 and the transfer roller 44. The image is transferred to the paper.

  The fixing unit 46 includes a heat roller 62 and a pressure roller 64 and is disposed above the transfer roller 44. The heat roller 62 is set to have a predetermined fixing temperature. When the paper passes through the nip area between the heat roller 62 and the pressure roller 64, the toner image transferred to the paper is melted. The toner image is heat-fixed on the sheet by mixing and pressing.

  In the apparatus main body 12, the first sheet for feeding the sheet from the sheet feeding tray 48 or the manual sheet feeding tray 50 to the sheet discharge tray 52 via the registration roller 68, the transfer roller 44 and the fixing unit 46. A conveyance path S1 is formed. In addition, when performing duplex printing on a sheet, the sheet after the one-side printing is completed and passed through the fixing unit 46 is returned to the first sheet conveyance path S1 on the upstream side of the transfer roller 44 in the sheet conveyance direction. The second paper transport path S2 is formed. In the first paper transport path S1 and the second paper transport path S2, a plurality of transport rollers 66 are provided as appropriate to supplementarily apply a driving force to the paper.

  When single-sided printing (image formation) is performed in the apparatus main body 12, the sheets are guided one by one to the first sheet conveying path S 1 by the sheet feeding tray 48 or the manual sheet feeding tray 50, and the registration rollers 68 are reached by the conveying rollers 66. Be transported. Then, the registration roller 68 conveys the sheet to the transfer roller 44 at a timing when the leading edge of the sheet and the leading edge of the image information on the intermediate transfer belt 54 are aligned, and the toner image is transferred onto the sheet. Thereafter, when the toner passes through the fixing unit 46, the unfixed toner on the paper is melted and fixed by heat, and the paper is discharged onto the paper discharge tray 52 through a conveyance roller (paper discharge roller) 66.

  On the other hand, when performing double-sided printing, when the trailing edge of the paper that has passed through the fixing unit 46 after single-sided printing has reached the paper discharge roller 66 near the paper discharge tray 52, the paper discharge roller 66 is reversed. By rotating, the sheet runs backward and is guided to the second sheet conveyance path S2. The paper guided to the second paper transport path S2 is transported through the second paper transport path S2 by the transport roller 66, and is guided to the first paper transport path S1 on the upstream side of the registration roller 68 in the paper transport direction. At this time, the front and back sides of the sheet are reversed, and thereafter, the sheet passes through the transfer roller 44 and the fixing unit 46, whereby printing is performed on the back side of the sheet.

  Next, the configuration of the photoreceptor unit 70 will be described with reference to FIGS. FIG. 2 is a perspective view showing a state where the photoconductor unit 70 is viewed obliquely from above, and FIG. 3 is a cross-sectional view showing a state where the photoconductor unit 70 is viewed from the side. FIG. 4 is an enlarged partial sectional view showing a rear side portion of the photosensitive unit 70, that is, an end portion on the photosensitive drum driving device 100 side.

  As shown in FIGS. 2 to 4, the photoconductor unit 70 includes a photoconductor drum 36, a cleaner unit 38, a charger 40, and the like, and these are integrally held by a photoconductor unit frame 72 in a predetermined arrangement manner. The The photosensitive unit 70 is detachable from the front side of the apparatus main body 12, and is attached to or detached from the apparatus main body 12 by sliding in the depth direction (front-rear direction) of the apparatus main body 12. To do.

  The photoconductor unit frame 72 is made of, for example, a synthetic resin, and includes a front wall portion 72a disposed on the front side of the apparatus main body 12, a rear wall portion 72b disposed on the rear side of the apparatus main body 12, and a front wall portion. 72a and the bottom wall part 72c which connects the lower end parts of the rear wall part 72b.

  The photosensitive drum 36 includes a cylindrical base 74 having a photosensitive layer formed on the surface thereof. A flange 76 is fixedly attached to both ends of the base 74 so that a metal drum shaft 78 is provided so as to penetrate the center of the flange 76. Both end portions of the drum shaft 78 are rotatably supported by first bearings 80 provided on the front wall portion 72 a and the rear wall portion 72 b of the photoconductor unit frame 72, and the base body 74 is rotated with the rotation of the drum shaft 78. Rotate. That is, the photosensitive drum 36 is supported by the front wall portion 72 a and the rear wall portion 72 b of the photosensitive unit frame 72 so as to be rotatable around the drum shaft 78.

  Further, a photoreceptor coupling 82 having external teeth is provided at the rear end portion of the drum shaft 78. The photoconductor coupling 82 is detachably fitted (coupled) with a drive coupling 124 included in a drum drive gear 108 of the photoconductor drum driving device 100 described later, and receives a rotational driving force from the photoconductor drum driving device 100. This is transmitted to the photosensitive drum 36.

  Further, a second bearing 84 is provided at the rear end of the drum shaft 78 between the first bearing 80 and the photoreceptor coupling 82. The second bearing 84 is fitted into the leading end portion of the drum support holder 110 of the photosensitive drum driving device 100 described later when the photosensitive unit 70 is attached to the apparatus main body 12, and the photosensitive member together with the drum support holder 110. This is used for positioning the unit 70 (centering of the photosensitive drum 36).

  Next, the configuration of the photosensitive drum driving device 100 will be described with reference to FIGS. FIG. 5 is a perspective view showing a state where the photosensitive drum driving device 100 is viewed obliquely from above, and FIG. 6 is a plan view showing a state where the photosensitive drum driving device 100 is viewed from above. FIG. 7 is an enlarged partial cross-sectional view showing a peripheral portion of the drum driving gear 108 of the photosensitive drum driving device 100.

  As shown in FIGS. 5 and 6, the photosensitive drum driving apparatus 100 includes a driving apparatus frame 102, a driving motor 104, a gear shaft 106, a drum driving gear 108, a drum support holder 110, and the like. As described above, the photosensitive drum driving device 100 is fixedly provided on the rear side wall of the apparatus main body 12 and applies a rotational driving force to each photosensitive drum 36. For this reason, each of the gear shaft 106, the drum drive gear 108, and the drum support holder 110 is provided so as to correspond to the four photoreceptor drums 36 (photoreceptor units 70). It is held in the arrangement mode.

  The drive device frame 102 is made of, for example, metal, and includes an outer plate 102a disposed on the rear side, and an inner plate 102b disposed at a predetermined interval on the front side of the outer plate 102a.

  A drive motor 104 is provided on the rear surface of the outer plate 102a. The motor shaft of the drive motor 104 is provided so as to protrude from the outer plate 102a to the front side. A gear train such as a gear portion 122 and an idle gear (not shown) of the drum drive gear 108, which will be described in detail later, is accommodated between the outer plate 102a and the inner plate 102b. The rotational driving force from the driving motor 104 is transmitted from the motor shaft to the drum driving gear 108 via an appropriate idle gear, and from the drum driving gear 108 via the coupling (the driving coupling 124 and the photoreceptor coupling 82). Is transmitted to the drum shaft 78 of the photosensitive drum 36.

  In the first embodiment, the photosensitive drum driving device 100 includes two driving motors 104, one driving motor 104 is for black and the other driving motor 104 is for color. That is, one drive motor 104 rotates the photosensitive drum 36 for black, and the other drive motor 104 rotates three photosensitive drums 36 for color (cyan, magenta, and yellow). However, the color drive motor 104 may be provided separately. Further, the rotational driving force from the driving motor 104 is appropriately transmitted to the driving gear 112 for the waste toner screw.

  In the first embodiment, the drum drive gear 108 is swingable with respect to the gear shaft 106 so that the tip portion can swing flexibly with the root portion as a fulcrum. That is, the drum drive gear 108 can be tilted around the entire circumference of the gear shaft 106 so that the tip end portion turns around the root portion.

  Specifically, as shown in FIG. 7, the outer plate 102a is provided with a gear shaft 106 by caulking or the like so as to protrude to the front side (photosensitive unit 70 side). The gear shaft 106 is a metal fixed shaft formed in a substantially cylindrical shape, and supports the drum drive gear 108 rotatably. An annular flange portion 106 a that protrudes outward is formed at the base portion of the gear shaft 106. The axial direction length of the collar part 106a is 5 mm, for example. A ground terminal 114 is attached to the tip of the gear shaft 106.

  As can be seen from FIG. 8, the drum drive gear 108 includes a boss portion 120, a gear portion 122, and a drive coupling (coupling portion) 124, which are integrally formed of synthetic resin or the like. The boss portion 120 is formed in a substantially cylindrical shape, and a disc-shaped gear portion 122 is formed at the root portion (rear side end portion). Further, a drive coupling 124 having internal teeth is formed at the tip portion (front side end portion) of the boss portion 120. That is, the drive coupling 124 is integrally formed at the tip portion of the drum drive gear 108. As described above, the drive coupling 124 is detachably fitted to the photoreceptor coupling 82 attached to the drum shaft 78 of the photoreceptor drum 36.

  Further, the boss portion 120 of the drum driving gear 108 is formed with a shaft hole 126 that is a cylindrical space that opens toward the rear side. By inserting the gear shaft 106 into the shaft hole 126, the drum drive gear 108 is rotatably supported by the gear shaft 106.

  At this time, the shaft hole 126 of the drum drive gear 108 is in sliding contact with the flange portion 106a of the gear shaft 106, and is not slidably in contact with the outer peripheral surface of the gear shaft 106 other than the flange portion 106a. That is, the drum drive gear 108 has a sliding contact portion with the gear shaft 106 only at the root portion, and a gap 128 is formed between the shaft hole 126 and the gear shaft 106 in a portion other than the sliding contact portion. The The diameter of the shaft hole 126 is set to be slightly smaller than the outer diameter of the flange portion 106 a of the gear shaft 106, and the shaft hole 126 of the drum drive gear 108 and the flange portion 106 a of the gear shaft 106 are Make a sliding contact with a slight backlash in the radial direction.

  In this way, by reducing the axial length of the sliding contact portion between the shaft hole 126 and the gear shaft 106, the drum driving gear 108 is moved relative to the gear shaft 106 while ensuring the rotational accuracy of the drum driving gear 108. It can be swung (tilted). That is, the drum drive gear 108 can swing (tilt) around the entire circumference of the gear shaft 106 in the radial direction about the gear shaft 106. In this first embodiment, the sliding contact portion between the shaft hole 126 and the gear shaft 106 is provided at the root portion of the drum drive gear 108. Therefore, the drum drive gear 108 has a tip portion (that is, a drive cup) with the root portion as a fulcrum. The ring 124) swings so as to swing.

  Returning to FIG. 7, the drum drive gear 108 as described above has a rear side portion including the gear portion 122 accommodated between the outer plate 102 a and the inner plate 102 b, and a front side portion including the drive coupling 124. The portion is disposed so as to protrude from the inner plate 102b to the front side. A drum support holder 110 is provided on the inner plate 102b so as to cover the protruding portion of the drum drive gear 108 from the inner plate 102b.

  The drum support holder 110 is a holding member for positioning the photosensitive drum 36, and is formed of, for example, synthetic resin. Specifically, the drum support holder 110 is formed in a substantially cylindrical shape whose inner peripheral surface is gradually reduced in diameter in accordance with the outer surface shape of the drum drive gear 108. The drum support holder 110 is fixed to the inner plate 102 b so that its axis is concentric with the axis of the gear shaft 106. The drum support holder 110 supports the rear side end portion of the drum shaft 78 of the photosensitive drum 36 at the front end portion thereof via the second bearing 84 (see FIG. 11). As a result, the photosensitive drum 36 (and thus the entire photosensitive unit 70) is positioned, and the gear shaft 106, the drum driving gear 108, and the drum shaft 78 of the photosensitive drum 36 are properly centered. That is, in the first embodiment, the photosensitive unit 70 is positioned by the drum support holder 110 provided in the photosensitive drum driving device 100.

  The drum support holder 110 also functions as a regulating member that regulates (adjusts) the maximum deflection width of the tip portion of the drum driving gear 108. In the first embodiment, restriction ribs (protrusions) 110a extending in the axial direction with respect to the inner peripheral surface of the drum support holder 110 are arranged at predetermined intervals in the circumferential direction at a position corresponding to the tip portion of the drum drive gear 108. Is done. Then, by appropriately setting the distance between the top of the restriction rib 110a and the outer peripheral surface of the drum drive gear 108, the maximum deflection width (maximum tilt angle) of the tip portion of the drum drive gear 108 is set. However, the shape and arrangement position of the regulating rib 110a can be changed as appropriate. For example, the restriction rib 110a may be an annular protrusion or the like extending in the circumferential direction, or may be disposed at a position corresponding to a portion other than the tip portion of the drum drive gear 108. Further, for example, instead of providing the regulating rib 110a, the diameter of the entire inner peripheral surface of the drum support holder 110 may be reduced.

  FIG. 9 is a partial cross-sectional view showing a state where the drum drive gear 108 is inclined with respect to the gear shaft 106. As described above, the drum drive gear 108 can swing such that the tip portion swings around the root portion as a fulcrum. Further, the maximum deflection width of the tip portion of the drum drive gear 108 is regulated by the drum support holder 110, and the drum drive gear 108 can be tilted until the outer peripheral surface thereof abuts on the top of the regulation rib 110a. The maximum tiltable angle of the drum drive gear 108 with respect to the gear shaft 106 is set to 0.5 degrees, for example.

  In the image forming apparatus 10 as described above, as shown in FIGS. 10 and 11, when the photosensitive unit 70 is attached to the apparatus main body 12, the photosensitive drum driving device 100 and the photosensitive unit 70 are connected. The Specifically, the photoreceptor coupling 82 is fitted to the drive coupling 124, and the second bearing 84 attached to the drum shaft 78 of the photoreceptor drum 36 is attached to the tip portion of the drum support holder 110. The photosensitive drum 36 is positioned by the drum support holder 110 and the second bearing 84. The rotational driving force from the driving motor 104 is transmitted to the drum shaft 78 of the photosensitive drum 36 via the drum driving gear 108, whereby the photosensitive drum 36 is rotationally driven in a predetermined direction.

  At this time, the photosensitive drum 36 is appropriately positioned by the drum support holder 110 and the photosensitive drum 36 is centered with respect to the drum driving gear 108, so that the rotation of the drum driving gear 108 is smoothly transmitted to the drum shaft 78. In addition, the photosensitive drum 36 can be rotated with high accuracy.

  However, no matter how precisely the members constituting the image forming apparatus 10 are manufactured, it is impossible to completely eliminate manufacturing errors (dimensional errors) such as processing errors and assembly errors. For this reason, when the photosensitive unit 70 is mounted on the apparatus main body 12, the axis of the drum drive gear 108 and the axis of the photosensitive drum 36 may not be concentric.

  On the other hand, in the first embodiment, the drum drive gear 108 is swingable with respect to the gear shaft 106 so that the drive coupling 124 formed at the front end portion swings. Therefore, as shown in FIG. 12, even if the shaft center of the drum drive gear 108 and the shaft center of the photosensitive drum 36 are not concentric, that is, the photosensitive member coupling with respect to the driving coupling 124. Even if the position of 82 is displaced, the drum driving gear 108 tilts following the displacement. The drum driving gear 108 rotates while maintaining the tilted state, so that the rotational driving force can be transmitted to the photosensitive drum 36 without stress. That is, the photosensitive drum 36 can rotate smoothly without causing a shake component even when the axial center thereof is not concentric with the axial center of the drum drive gear 108.

  As described above, according to the first embodiment, since the drum drive gear 108 can swing with respect to the gear shaft 106, the axis of the drum drive gear 108 and the axis of the photosensitive drum 36 are aligned. Even if they are not concentric, the photosensitive drum 36 can be rotated accurately and appropriately without causing a shake component in the rotation of the photosensitive drum 36.

  Further, since the drive coupling 124 is integrally formed with the drum drive gear 108, the number of parts can be reduced, and the configuration of the photosensitive drum drive device 100 can be simplified.

[Second Embodiment]
Next, an image forming apparatus 10 according to a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, the configurations of the gear shaft 106 and the drum drive gear 108 provided in the photosensitive drum driving device 100 are different from those in the first embodiment. Since the other portions are the same, the description overlapping with the first embodiment described above will be omitted or simplified.

  Briefly, in the second embodiment, instead of forming the flange portion 106 a on the gear shaft 106, a protrusion 130 is formed on the root portion of the drum drive gear 108. The protrusion 130 is formed in an annular shape that protrudes radially inward from the inner peripheral surface of the shaft hole 126 and extends in the circumferential direction. The protrusion 130 serves as a sliding contact portion with the gear shaft 106, and a gap 128 is formed between the shaft hole 126 and the gear shaft 106 at a portion other than the protrusion 130. As a result, the drum drive gear 108 can swing the drum drive gear 108 with respect to the gear shaft 106 so that the tip portion can swing with the root portion as a fulcrum.

  In the second embodiment, the same effect as in the first embodiment is obtained, and even if the axis of the drum driving gear 108 and the axis of the photosensitive drum 36 are not concentric, the photosensitive member is used. The photosensitive drum 36 can be appropriately rotated with high accuracy without causing a vibration component in the rotation of the drum 36.

[Third embodiment]
Next, an image forming apparatus 10 according to a third embodiment of the present invention will be described with reference to FIG. In the third embodiment, the axial position of the sliding contact portion serving as a fulcrum when the drum drive gear 108 included in the photosensitive drum driving device 100 is swung is shifted from the root portion. And different. Since the other portions are the same, the description overlapping with the first embodiment described above will be omitted or simplified.

  Briefly, in the third embodiment, the flange portion 106a formed on the gear shaft 106 is formed not at the root portion but at a substantially central portion in the axial direction. As a result, the drum drive gear 108 can swing the drum drive gear 108 with respect to the gear shaft 106 so that the tip end portion thereof swings with its substantially central portion as a fulcrum.

  In the third embodiment, the same effect as in the first embodiment can be obtained, and even if the axis of the drum drive gear 108 and the axis of the photosensitive drum 36 are not concentric, the photosensitive member can be used. The photosensitive drum 36 can be appropriately rotated with high accuracy without causing a vibration component in the rotation of the drum 36.

  However, if the axial position of the sliding contact portion serving as a fulcrum when the drum drive gear 108 swings and the axial position of the gear portion 122 deviate, the gear portion 122 easily swings in the radial direction, and an idle gear or the like. There is a risk of problems with the meshing. For this reason, it is preferable that the axial position of the sliding contact portion serving as a fulcrum when the drum drive gear 108 swings and the axial position of the gear portion 122 are substantially the same position. That is, it is preferable that the flange portion 106 a or the protrusion portion 130 is disposed at substantially the same axial position as the gear portion 122.

  In each of the above-described embodiments, the image forming apparatus 10 is exemplified by a multi-function machine in which a copier, a facsimile, a printer, and the like are combined. However, the image forming apparatus 10 may be any one of a copier, a facsimile, a printer, or the like. A multifunction machine combining at least two of these may be used.

  Further, the specific numerical values and materials such as the dimensions mentioned above are merely examples, and can be appropriately changed according to the needs such as product specifications.

DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus 12 ... Apparatus main body 14 ... Image reading apparatus 26 ... Image reading part 30 ... Image forming part 36 ... Photoconductor drum 70 ... Photoconductor unit 72 ... Photoconductor unit frame 78 ... Drum shaft 82 ... Photoconductor coupling DESCRIPTION OF SYMBOLS 100 ... Photosensitive drum drive device 102 ... Drive device frame 106 ... Gear shaft 108 ... Drum drive gear 110 ... Drum support holder (holding member)
120 ... Boss part 122 ... Gear part 124 ... Drive coupling 126 ... Shaft hole

Claims (5)

A photosensitive drum driving device for rotationally driving a photosensitive drum,
A drum drive gear in which a drive coupling fitted to a photoconductor coupling provided on the photoconductor drum is integrally formed at a tip portion; and a gear shaft that rotatably supports the drum drive gear;
The drum driving gear is a photosensitive drum driving device in which the tip portion can swing with respect to the gear shaft.   2. The photosensitive drum driving device according to claim 1, wherein only the root portion of the drum driving gear is in sliding contact with the gear shaft, and the tip portion is swingable with the root portion as a fulcrum.   The photosensitive drum driving device according to claim 1, further comprising a holding member for positioning the photosensitive drum. The holding member is provided so as to cover an outer peripheral surface of the drum drive gear,
The photosensitive drum driving device according to claim 3, wherein a maximum deflection width of a tip portion of the drum driving gear is regulated by the holding member.   An image forming apparatus comprising the photosensitive drum driving device according to claim 1.

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