JP5011325B2 - Gear and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a gear for transmitting driving and an image forming apparatus using the gear.

  Conventionally, various rotating members are used in image forming apparatuses such as copying machines, printers, and facsimiles. In order to rotate such a rotating member, it is necessary to transmit the drive to each rotating member from a driving source such as a driving motor (not shown). Therefore, a multi-stage gear is provided from the gear connected to the drive motor that rotates at a high speed in order to increase the reduction ratio, and the rotational speed is reduced until reaching each rotating member.

  For example, as shown in FIG. 9, when a gear 32 is connected to a gear 31 connected to a drive motor (not shown), and further a gear 33 is connected to the gear 32, the gear 31 rotates clockwise (in the direction of the arrow). ), The rotational drive is transmitted to the gear 32 and the gear 33, the gear 32 rotates counterclockwise in the figure (arrow direction), and the gear 33 rotates clockwise in the figure (arrow direction).

  In general, the drive transmitted to the gear is transmitted from one tooth to the rim and web and again transmitted to the next gear by another tooth, or from the web to the rotating shaft as a rotational force via the boss. The As such a gear, a resin gear is often used for reasons such as cost, quietness, and simple lubrication.

  Such resin gears are superior to metal gears in terms of sound absorption and rotation transmission stability in the teeth and rims. However, since the rigidity of the web of the resin gear is lower than that of the metal gear, it tends to be inferior to the metal gear in terms of rotational rigidity. In particular, when a parallel pin is passed through a boss formed on the inner peripheral portion of the web and connected to the rotating shaft, the metal gear is less likely to be bent due to stress concentration, so that the rigidity is less likely to decrease.

  Therefore, a gear having a gear main body and a metal reinforcing member having a mechanical strength larger than that of the gear main body is used. FIG. 10A is an external perspective view showing a gear body and a reinforcing member used in a conventional gear, and FIG. 10B is an external perspective view showing a state in which the conventional gear is assembled. As shown in FIG. 10A, the gear 32 includes a resin gear main body 35 and a metal reinforcing member 36.

  The gear body 35 includes a disc-shaped web 35a, a boss 35b formed on the inner peripheral portion of the web 35a, and teeth such as flat teeth and helical teeth (here, flat teeth) formed on the outer peripheral portion of the web 35a. ) Having a rim 35c. The web 35a is formed thinner than the boss 35b and the rim 35c.

  The reinforcing member 36 is formed in a substantially circular plate shape so as to be fitted into the web 35a of the gear body 35, and a fitting hole 36a as an inner peripheral portion is formed in the central portion of the reinforcing member 36. Is formed with a protrusion 36aa so as to be press-fitted into the outer peripheral surface of the boss 35b. Protrusions 36b are formed on the outer peripheral portion of the reinforcing member 36 at predetermined intervals in the circumferential direction so as to be press-fitted into the inner peripheral surface of the rim 35c. Then, by pressing the reinforcing member 36 into the web 35a of the gear main body 35, the inner peripheral portion and the outer peripheral portion of the reinforcing member 36 are fitted with the boss 35b and the rim 35c of the gear main body 35, as shown in FIG. 10 (b). The gear 32 can be assembled.

  However, when the reinforcing member is fitted into the gear main body in this way, the gear main body may be deformed due to thermal expansion or the like of the reinforcing member, and fluctuations in the rotational transmission force may occur. Therefore, in Patent Document 1, for example, a gear body having a tooth portion in which oblique teeth are formed on the outer peripheral portion of a disk-shaped substrate portion is fixed in contact with at least one side surface of the substrate portion at three contact portions. A method of suppressing deformation caused by transmitting a rotational force while suppressing deformation caused by the reinforcing member is disclosed.

JP 2008-014438 A

  However, if the reinforcing member is screwed to the gear body as in Patent Document 1, the gear body may be deformed due to a decrease in roundness due to the screw hole. Further, when the aforementioned reinforcing member 36 is press-fitted into the gear body 35, the rim 35c is pressed radially outward by the reinforcing member 36 at the press-fitting portion of the protrusion 36b in the rim 35c, as shown in a region S1 of FIG. There is a possibility that the shape and pitch of the teeth are deformed.

  In such a case, even if the gear 32 meshes with one gear (for example, the gear 31 in FIG. 9) with high accuracy, the meshing accuracy with the other gear (for example, the gear 33 in FIG. 9) may decrease. In addition, if the reinforcing member is thermally expanded due to the difference in linear expansion coefficient between the resin gear body and the metal reinforcing member, the screw stopper and press-fit portion of the gear body are pressed and the meshing accuracy is lowered. , It can be a cause of creep rupture.

  On the other hand, in such a gear, it is possible to transmit a load (drive) at a contact point between the resin gear main body and the metal reinforcing member. Therefore, the arrangement of the load contacts is an important issue. If the load contact point is moved away from the center of rotation, the load can be transmitted with a small force and the drive transmission efficiency can be improved, so that the deformation amount of the gear body can be reduced. In particular, the rotational rigidity of the gear body can be increased even in a gear having a web. However, this problem is not disclosed in Patent Document 1.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a gear capable of suppressing deformation of a resin gear main body by a reinforcing member, efficiently transmitting drive, and increasing rotational rigidity, and an image forming apparatus including the gear. The purpose is to provide.

  In order to achieve the above object, the present invention is for transmitting a drive, and a boss portion into which a rotation shaft is fitted in a central portion, a concentric circle formed in the outer peripheral direction of the boss, and a tooth portion on the outer peripheral portion. A gear having a rim portion having a resin gear body integrally formed with a rim portion and a thin web portion connecting between the boss portion and the rim portion; and a reinforcing member attached to the gear body. In the inner peripheral portion of the rim portion, a protrusion is formed at a predetermined interval in the circumferential direction and toward the radial center side, and the reinforcing member is formed in a substantially circular flat plate shape, A fitting hole is formed in the central portion of the reinforcing member, and the reinforcing member is attached to the gear body by fitting the fitting hole and the boss. The outer diameter of the reinforcing member is larger than the inner diameter of the rim portion. And the outer peripheral surface of the reinforcing member is not in contact with the rim portion. In the outer peripheral portion of the reinforcing member, a position facing the protruding portion can contact the protruding portion in the circumferential direction, but a predetermined gap is provided between the protruding portion in the radial direction. Is provided, and a notch portion is formed in which contact is restricted.

  According to the present invention, in the gear configured as described above, the projecting portion and the notch portion are extended in the radial direction, and the notch portion is a constant surface in the circumferential direction with respect to a side surface portion of the projecting portion. It is formed so that it can contact.

  According to the present invention, in the gear configured as described above, the projecting portion and the notch portion are formed in a substantially rectangular shape having the radial direction as a longitudinal direction when viewed in a direction perpendicular to the gear body. .

  According to the present invention, in the gear configured as described above, the gear transmits power to at least one of an image carrier, a toner carrier, and a toner supply member disposed in the image forming unit. It is characterized by.

  The present invention is also an image forming apparatus including the gear having the above-described configuration.

  According to the first configuration of the present invention, the inner circumferential portion of the rim portion of the gear body is formed with a protruding portion that is spaced apart at a predetermined interval in the circumferential direction and toward the radial center, and the reinforcing member is a substantially circular flat plate. And the reinforcing member is mounted on the gear body by fitting the fitting hole with the inner peripheral portion of the reinforcing member and the boss portion. The outer diameter of the reinforcing member is smaller than the inner diameter of the rim portion, and the outer peripheral surface of the reinforcing member is configured not to contact the rim portion. Although it is possible to make contact in the circumferential direction, a notch portion can be formed in which a predetermined gap is provided between the protruding portion and the contact portion in the radial direction to restrict contact.

  Thereby, since a reinforcement member is not made to contact | abut to the rim | limb part and protrusion part of a gear main body in radial direction, the deformation | transformation of a gear main body by press injection of a reinforcement member, thermal expansion, etc. can be prevented. In addition, since the notch can contact the protrusion in the circumferential direction, the rotation drive can be transmitted at the outer periphery of the gear body far from the rotation center, and the drive can be transmitted efficiently and rotated. Stiffness can also be increased. Therefore, deformation of the resin gear main body due to the reinforcing member can be suppressed, the drive can be transmitted efficiently, and the rotational rigidity of the gear can be increased.

  According to the second configuration of the present invention, in the gear having the first configuration, the protruding portion and the cutout portion are extended in the radial direction, and the cutout portion is formed with respect to the side surface portion of the protruding portion. It is possible to transmit the drive more reliably by forming it so as to be able to contact with a certain surface in the circumferential direction.

  Further, according to the third configuration of the present invention, in the gear of the second configuration, the protruding portion and the cutout portion are formed in a substantially rectangular shape having a radial direction as a longitudinal direction when viewed in a direction perpendicular to the gear body. By forming it, it is possible to transmit the drive more reliably and to secure a sufficient radial gap.

  According to the fourth configuration of the present invention, in the gear having any one of the first to third configurations, the gears are arranged on the image carrier, the toner carrier, and the toner supply member disposed in the image forming unit. By using a gear for transmitting the drive to at least one, it is possible to achieve sufficiently high-accuracy drive transmission even in an image forming unit that requires higher-precision meshing.

  Further, according to the fifth configuration of the present invention, it is possible to perform image formation in which image unevenness is suppressed by using the image forming apparatus including the gear having any one of the first to fourth configurations. It becomes.

1 is a schematic diagram showing the configuration of a tandem color image forming apparatus equipped with a gear according to a first embodiment of the present invention. External appearance perspective view which shows arrangement | positioning in the image formation part of the gear of this embodiment External perspective view showing a gear body and a reinforcing member used in the gear of the present embodiment External perspective view showing the assembled state of the gear of the present embodiment The partial expanded side view which shows the structure of the rib and notch part periphery in the gearwheel of this embodiment The external appearance perspective view which shows the connection state of the gearwheel of this embodiment The partial expanded side view which shows the structure of the rib of a gearwheel and notch part periphery which concerns on 2nd Embodiment of this invention. The partial expanded side view which shows the structure of the rib of a gearwheel and the notch part periphery which concerns on 3rd Embodiment of this invention. Side view showing the connected state of a conventional gear FIG. 10A is a perspective view showing a conventional gear, FIG. 10A is an external perspective view showing a gear body and a reinforcing member used in the gear, and FIG. 10B is an external perspective view showing a state in which the gear is assembled. Figure The partial expansion perspective view which shows the state by which the reinforcement member was press-fitted in the outer peripheral part of the conventional gear body

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of a tandem color image forming apparatus equipped with a gear according to the first embodiment of the present invention. In the main body of the image forming apparatus 100, four image forming portions Pa, Pb, Pc, and Pd are sequentially arranged from the upstream side in the transport direction (the right side in FIG. 1). These image forming portions Pa to Pd are provided corresponding to images of four different colors (black, magenta, cyan, and yellow), and black, magenta, and cyan are respectively obtained by charging, exposure, development, and transfer processes. And yellow images are sequentially formed.

  Photosensitive drums (image carriers) 1a, 1b, 1c, and 1d that carry visible images (toner images) of the respective colors are disposed in the image forming portions Pa to Pd, and these photosensitive drums 1a. The toner image formed on ˜1d is conveyed by a conveying belt 50 that moves adjacent to each image forming unit while rotating counterclockwise (arrow direction) in FIG. 1 by a driving means (not shown). The image is sequentially transferred onto the paper P, and further fixed on the paper P in the fixing unit 7 and then discharged from the apparatus main body. An image forming process for each of the photosensitive drums 1a to 1d is executed while rotating the photosensitive drums 1a to 1d clockwise in FIG.

  The paper P on which the toner image is transferred is accommodated in a paper cassette 16 at the lower part of the apparatus, and is conveyed to the image forming portions Pa to Pd via the paper feed roller 12a and the registration roller pair 12b. A sheet made of dielectric resin is used for the conveyance belt 50, and a belt in which the flange portions are overlapped and joined to each other to form an endless shape, or a belt without a seam (seamless) is used. A cleaning blade 19 for removing toner adhering to the conveyance belt 50 is disposed on the upstream side of the driven roller 10.

  Next, the image forming units Pa to Pd will be described. Chargers 2a, 2b, 2c and 2d for charging the photosensitive drums 1a to 1d and image information on the photosensitive drums 1a to 1d are arranged around and above the rotatable photosensitive drums 1a to 1d. LED heads 4a, 4b, 4c, and 4d for individually exposing, developing units (developing means) 3a, 3b, 3c, and 3d for forming toner images on the photosensitive drums 1a to 1d, and photosensitive drums 1a to 1d. Cleaning portions 5a, 5b, 5c and 5d for removing the developer (toner) remaining on the top are provided.

  When the start of image formation is input by the user, first, the surfaces of the photosensitive drums 1a to 1d are uniformly charged by the chargers 2a to 2d, and then light is irradiated by the LED heads 4a to 4d. An electrostatic latent image corresponding to the image signal is formed on ˜1d. The developing units 3a to 3d include a developing roller 21 (toner carrier, see FIG. 2) disposed to face the photosensitive drums 1a to 1d. Each of the developing units 3a to 3d is filled with a predetermined amount of black, magenta, cyan, and yellow toner by a replenishing device (not shown).

  This toner is, for example, a positive magnetic toner, which is supplied onto the photosensitive drums 1a to 1d from the developing roller 21 of the developing units 3a to 3d and electrostatically adheres to the toner from the LED heads 4a to 4d. A toner image corresponding to the electrostatic latent image formed by exposure is formed. The drive transmission of the photosensitive drums 1a to 1d and the developing units 3a to 3d will be described later.

  Then, after an electric field is applied to the conveying belt 50 at a predetermined transfer voltage, the magenta, cyan, yellow, and black toner images on the photosensitive drums 1a to 1d are conveyed to the conveying belt 50 by the transfer rollers 6a to 6d. Is transferred onto the sheet P. These four color images are formed with a predetermined positional relationship predetermined for forming a predetermined full-color image. Thereafter, the toner remaining on the surfaces of the photosensitive drums 1a to 1d is removed by the cleaning units 5a to 5d in preparation for the subsequent formation of a new electrostatic latent image.

  The conveyance belt 50 is stretched over the driven roller 10 and the drive roller 11. When the conveyance belt 50 starts to rotate counterclockwise with the rotation of the drive roller 11 by a drive motor (not shown), the paper P is loaded. The images are conveyed from the registration roller pair 12b to the image forming portions Pa to Pd at a predetermined timing, and the images are sequentially transferred onto the paper P at the nip portion with the conveying belt 50 in each image forming portion, thereby forming a full color image. The paper P on which the toner image is transferred is conveyed to the fixing unit 7.

  The sheet P conveyed to the fixing unit 7 is heated and pressurized when passing through the nip portion (fixing nip portion) of the pair of fixing rollers 13 to fix the toner image on the surface of the sheet P, and a predetermined full-color image is formed. It is formed. The paper P on which the full color image is formed is discharged to the discharge tray 17 by the discharge roller 15.

  FIG. 2 is an external perspective view showing the arrangement of the gears of the present embodiment in the image forming unit. Since the configurations of the photosensitive drums 1a to 1d and the developing units 3a to 3d in the respective colors of cyan, magenta, yellow, and black are exactly the same, only the photosensitive drum 1a and the developing unit 3a are shown in FIG. Hereinafter, gears applied to the photosensitive drum 1a and the developing unit 3a will be described.

  As shown in FIG. 2, the developing unit 3 a is provided with a developing roller 21 and a magnetic roller (toner supply member) 22 disposed opposite to the developing roller 21 on the side opposite to the photosensitive drum 1 a. . Toner adheres to the surface of the magnetic roller 22 by magnetic force. Further, the developing roller 22 rotates counterclockwise and the magnetic roller 23 rotates clockwise with respect to the photosensitive drum 1a rotating clockwise in the drawing.

  When the photosensitive drum 1a, the developing roller 21, and the magnetic roller 22 rotate and a bias is applied to the magnetic roller 22 and the developing roller 21 from a power source (not shown), the toner attached to the surface of the magnetic roller 22 in the developing unit 3a is Due to the potential difference between the magnetic roller 22 and the developing roller 21, it moves to the surface of the developing roller 21. The toner moved to the surface of the developing roller 21 moves to the surface of the photosensitive drum 1a due to a potential difference between the developing roller 21 and the photosensitive drum 1a. As a result, a toner image is formed on the photosensitive drum 1a as described above.

  The photosensitive drum 1a is driven by a drive motor (not shown) or the like, and the drive from the drive motor is transmitted via a first gear 41 provided on the rotating shaft of the photosensitive drum 1a. ing. A second gear (gear) 42 is provided on the rotation shaft of the developing roller 21, and a third gear 43 is provided on the rotation shaft of the magnetic roller 22. The second gear 42 is connected to the first gear 41, and the third gear is provided. 43 is connected to the second gear 42.

  When the first gear 41 rotates clockwise in the figure, the second gear 42 to which the drive is transmitted from the first gear 41 rotates counterclockwise, and when the second gear 42 rotates counterclockwise, the second gear The third gear 43 to which the drive is transmitted from 42 rotates in the clockwise direction. Thus, the rotational drive (drive) received by the first gear 41 is transmitted to the second gear 42 and the third gear 43. Here, since the first gear 41 and the third gear 43 have the same configuration as the gear shown as a conventional example in FIG. 9, the configuration of the second gear 42 will be described below.

  3 is an external perspective view showing a gear body and a reinforcing member used in the gear of the present embodiment, FIG. 4 is an external perspective view showing a state where the gear of the present embodiment is assembled, and FIG. FIG. 6 is an enlarged side view showing a configuration around a rib and a notch in the gear of the present embodiment, and FIG. 6 is an external perspective view showing a connected state of the gear of the present embodiment. Portions common to those in FIG. 2 are denoted by common reference numerals and description thereof is omitted.

  As shown in FIG. 3, the second gear 42 includes a resin gear body 45 and a metal reinforcing member 46. The gear main body 45 is formed of a substantially disk shape as a substrate portion and has a thin-walled web (web portion) 45a, and a boss (boss portion) 45b is formed on the inner peripheral portion of the web 45a. A rotating shaft (not shown) of the developing roller 21 (see FIG. 2) is fitted into the boss portion 45b.

  As will be described later, a protrusion 46aa formed on the inner periphery of the reinforcing member 46 is press-fitted into the outer peripheral surface of the boss 45b. When the boss 45b and the protrusion 46aa are fitted together, 4, the reinforcing member 46 is fixed (mounted) to the gear body 45. On the other hand, as shown in FIG. 3, a rim (rim portion) 45c having spur teeth (tooth portions) is formed on the outer peripheral portion of the web 45a, and a predetermined amount in the circumferential direction is formed on the inner portion of the rim 45c. A rib (protruding portion) 45d protrudes from the first interval (predetermined interval) toward the radial center.

  The rib 45d is formed along the web 45a and protrudes from the web 45a in the vertical direction. The rib 45d is formed in a substantially flat rectangular shape with the radial direction as the longitudinal direction, that is, a substantially rectangular shape with the radial direction as the longitudinal direction when viewed in a direction perpendicular to the web 45a (a direction perpendicular to the gear body 45). Has been. Here, twelve ribs 45d are formed at substantially equal intervals in the circumferential direction.

  The metal reinforcing member 46 has a substantially circular plate shape, and the outer diameter thereof is smaller than the inner diameter of the rim 45 c of the gear body 45. Further, a predetermined first gap C (see FIG. 5) is formed in the radial direction between the outer peripheral surface of the reinforcing member 46 and the inner peripheral surface of the rim 45c. The surface does not come into contact with the rim 45c in the radial direction. In addition, the outer diameter of the reinforcing member 46 is set to such a length that the outer peripheral surface of the reinforcing member 46 does not contact the rim 46 in the radial direction even if the reinforcing member 46 is thermally expanded.

  A fitting hole 46a as an inner peripheral portion is formed at the center of the reinforcing member 46, and protrusions 46aa are formed in the fitting hole 46a at predetermined second intervals in the circumferential direction. The protrusion 46aa is press-fitted into the outer peripheral surface of the boss 45b of the gear body 45. When the protrusion 46aa is press-fitted into the outer peripheral surface of the boss 45b, the boss 45d and the fitting hole 46a are fitted together, and the reinforcing member 46 is fixed to the gear body 45. Thus, only the inner peripheral part of the reinforcing member 46 is fitted and fitted to the boss 45b of the gear body 45, and the outer peripheral surface of the reinforcing member 46 is not in contact with the inner peripheral part of the rim 45c.

  A cutout portion 46 c is formed along the radial direction at a position facing the rib 45 d formed on the gear body 45 on the outer peripheral portion of the reinforcing member 46. The notch 46c is formed in a substantially rectangular shape along the radial direction when viewed in the direction perpendicular to the reinforcing member 46 (in FIG. 4, the direction perpendicular to the gear body 45) and having the radial direction as the longitudinal direction. . The circumferential length (width) of the notch 46c can be substantially the same as the width of the rib 45d, and the notch 46c can contact the rib 45d in the circumferential direction.

  Here, as shown in FIG. 5, the circumferential length (width) of the notch 46c is set to be slightly larger than the width of the rib 45d, and the downstream end surface (side surface) 45da in the rotational direction of the rib 45d and A slight space is provided between the upstream end surface (side surface portion) 45db and the downstream end surface 46ca and the downstream end surface 46cb in the rotational direction of the notch 46c.

  When the reinforcing member 46 is attached to the gear body 45, either the downstream side or upstream side end surface 46ca, 46cb of the notch 46c is in contact with the downstream side or upstream side end surface 45da, 45db of the rib 45d. The reinforcing member 46 can be attached to the gear body by aligning the positions of the notch 46c and the rib 45d. In this case, the notch 46c is in contact with the downstream and upstream end faces 45da and 45db of the rib 45d from the beginning of assembly on a constant surface in the circumferential direction.

  In addition, the reinforcing member 46 is mounted on the gear body so that the positions of the notch 46c and the rib 45d are aligned so that the rib 45d is positioned at the downstream side of the notch 46c and at the approximate center of the upstream end faces 46ca and 46cb. You can also In this case, at the beginning of assembly, neither the downstream side of the notch 46c nor the downstream end surfaces 46ca and 46cb are in contact with the downstream and upstream end surfaces 45da and 45db of the rib 45d in the circumferential direction.

  However, when the second gear 42 rotates and the rotational drive is transmitted between the first and third gears 41 and 43 (see FIGS. 2 and 6), the resin gear main body 45 is twisted in the circumferential direction. However, since the reinforcing member 46 having higher rigidity than the gear body 45 is difficult to twist, the downstream or upstream end faces 46ca and 46cb of the notch 46 abut against the downstream or upstream end faces 46ca and 46cb of the rib 46c. Is possible.

  In addition, when the second gear 42 rotates, which of the downstream end portions 46ca and 46cb of the notch 46c abuts on the rib 45d depends on the rotational speed of the second gear 42, the gear body 45, and the reinforcing member. It differs depending on the difference in rigidity from 46.

  Thus, when the second gear 42 rotates due to the contact between the notch 46c and the rib 45d in the circumferential direction, the rib 45d of the gear body 45 rotates from the rib 45d to the reinforcing member 46, and from the reinforcing member 46 to the rib 45d again. Drive can be transmitted.

  The radial length of the notch 46c is a predetermined second gap (predetermined gap) D in the radial direction between the bottom 46cc of the notch 46c and the tip 45dc of the rib 45d (see FIG. 5). Is set to such a length as to form. Further, the length is set such that the cutout portion 46c does not contact the rib 45d in the radial direction even if the reinforcing member 46 is thermally expanded. Thereby, even if the reinforcing member 46 is attached to the gear main body 45 or the reinforcing member 46 is thermally expanded after being attached, the notched portion 46c and the rib 45d are not brought into contact with each other in the radial direction.

  Then, by aligning the positions of the rib 45d and the notch 46c and press-fitting the protrusion 46aa formed on the inner peripheral portion of the reinforcing member 46 to the outer peripheral surface of the boss 45b, as shown in FIG. The second gear 42 can be assembled by attaching the reinforcing member 46 to the gear body 45. Further, as shown in FIG. 6, the second gear 42 can be connected to the first gear 41 and the third gear 43.

  When one tooth of the second gear 42 meshes with the first gear 41 in the region S2 of FIG. 6 and the rotation drive is transmitted from the first gear 41 to rotate the second gear 42, the gear in the second gear 42 is rotated. Rotational drive is transmitted from the rib 45d of the main body 45 to the reinforcing member 46 via the notch 46c, and from the reinforcing member 46 to the rib 45d again via the notch 46c. In the region S <b> 3, the other teeth of the second gear 42 mesh with the third gear 43, and the drive can be transmitted from the second gear 42 to the third gear 43.

  Further, as shown in FIG. 5 described above, a predetermined first gap C is provided in the radial direction between the outer peripheral surface of the reinforcing member 46 and the rim 45c, and the leading end 45dc and the notch 46c of the rib 45d. A predetermined second gap D is provided in the radial direction between the bottom portion 46 cc of the base plate 46 cc. Therefore, when the second gear 42 is assembled as shown in FIG. 4, the inner peripheral portion of the reinforcing member 46 is press-fitted into the outer peripheral surface of the boss 45b of the gear body 45, but as shown in FIG. Neither the part where the notch 46c is formed nor the notch 46c is in contact with the rim 45c and the rib 45b.

  Thus, even if the reinforcing member 46 is mounted on the gear body 45, the rib 45d and the rim 45c do not come into contact with the reinforcing member 46 and are not pressed radially outward (hatched arrows in FIG. 5). It is possible to suppress the deformation in the radial direction of the web 45a that greatly affects the transmission of the web. Further, even when the reinforcing member 46 is thermally expanded radially outward when the second gear 42 is rotated, the rib 45d and the rim 45c and the notch 46c do not contact in the radial direction. It is also possible to suppress deformation in the radial direction of the gear body 45 due to thermal expansion.

  Further, the rib 45d and the notch 46c abut in the circumferential direction from the beginning of assembly or by the rotation of the second gear 42 (the white arrow in FIG. 5), and it is possible to transmit the rotational drive therebetween. Become. As a result, the drive is transmitted at the outer peripheral portion of the web 45a far from the rotation center, that is, the load contact can be moved away from the rotation center, so that the load (drive) can be transmitted with a small force, and the drive is efficiently performed. Can be transmitted. Moreover, the deformation | transformation by the load from the 1st and 3rd gearwheels 41 and 43 (refer FIG. 6) can be suppressed, and the rotational rigidity of the 2nd gearwheel 42 can also be improved.

  Therefore, the second gear 42 suppresses deformation of the resin gear main body 45 by the reinforcing member 46, efficiently transmits driving between the first and third gears 41, 43 and increases rotational rigidity. Can do.

  Further, by attaching the metal reinforcing member 46 heavier than the resin to the gear main body 45, the overall weight of the second gear 42 is increased and the inertial force can be increased. Such inertial force varies depending on the metal type of the reinforcing member 46. Accordingly, the material of the reinforcing member 46 can be appropriately set in consideration of ease of molding, strength (rigidity), inertial force, and the like. For example, iron, steel, SUS (stainless steel), SECC (electrogalvanized) Steel plate) or the like can be used.

  The number, arrangement, and circumferential length of the ribs 45d are the rotational drive transmission accuracy and transmission efficiency with the reinforcing member 46, the strength of the ribs 45d, the ease of forming the gear body 45, or the notches in the reinforcing member 46. It can be appropriately set in consideration of the ease of forming the portion 46c, the strength, and the like.

  Further, the radial length of the rib 45d is not particularly limited as long as the rib 45d can contact the notch 46c in the circumferential direction and can transmit the rotational drive therebetween. However, if the radial length of the rib 45d is increased, the contact area with the notch 46c is increased and the transmission accuracy and efficiency of the rotational drive are improved. On the other hand, the notch 46c is also elongated in the radial direction. Therefore, the strength of the reinforcing member 46 may be reduced.

  On the other hand, if the radial length of the rib 45d is shortened, the cutout portion 46c can be shortened in the radial direction, so that the strength of the reinforcing member 46 is increased while the contact area with the cutout portion 46d is small. Therefore, there is a risk that the transmission accuracy and transmission efficiency of the rotational drive will be reduced. Therefore, for example, the radial length of the rib 45d can be appropriately set in consideration of such a viewpoint, and for example, the radial length of the rib 45d can be set to be longer than the circumferential length.

  Further, the outer diameter of the reinforcing member 46 is smaller than the inner diameter of the rim 45c of the gear body 45 and does not contact the rim 45c in the radial direction, and the notch 46c can contact the rib 45d in the circumferential direction. If there is no particular limitation. Here, if the outer diameter of the reinforcing member 46 is too small, the first gap C (see FIG. 5) becomes large, and the contact surface (rotation drive transmission portion) between the notch 46c and the rib 45d becomes large. Since it moves to the center side in the radial direction, the accuracy and efficiency of rotational drive transmission may be reduced. In addition, the rib 45d needs to be formed long in the radial direction.

  On the other hand, if the outer diameter of the reinforcing member 46 is too large, the first gap C is reduced, and the reinforcing member 46 comes into contact with the rim 45c due to thermal expansion of the reinforcing member 46, and the gear body 46 may be deformed. . Therefore, for example, the outer diameter of the reinforcing member 46 can be appropriately set in consideration of such a viewpoint.

  Further, here, as shown in FIG. 5 described above, a slight space is provided between the downstream and upstream end faces 45da and 45db of the rib 45d and the downstream and downstream end faces 46ca and 46cb of the notch 46c. Therefore, the press-fitting of the notch 46c into the rib 45d can be further avoided, and the influence of the thermal expansion in the circumferential direction can be reduced.

  However, when the reinforcing member 46 is attached to the gear body 45, both the downstream end surface 45da and the upstream end surface 45db of the rib 45d abut against the downstream end and upstream end portions 46ca and 46cb of the notch 46c (press-fit). Even in this case, the effect of such contact on the accuracy of rotational drive transmission between the rib 45d and the notch 46c is small. Further, even if the reinforcing member 46 is thermally expanded in the circumferential direction after such mounting, the influence on the rotational drive transmission accuracy is also small.

  Therefore, here, a slight space is provided in the circumferential direction between the rib 45d and the notch 36c. However, such a space is not particularly required, and both the downstream end surface 45db and the upstream end surface 45dc of the rib 45d are provided. Can be configured to contact the downstream side and upstream side end surfaces 45db and 45dc of the notch 46c.

  Here, if the width of the notch 46c is too larger than the width of the rib 45d, the circumferential space between the rib 45d becomes large, and even if the second gear 42 rotates, the notch 46c and the rib 45d. May not be in contact with each other and drive may not be stably transmitted between the two. Therefore, for example, the width of the notch 45d can be appropriately set in consideration of such a viewpoint and the relationship between the rotation of the notch 46c and the rib 45d in the circumferential direction.

  In addition, the radial length of the notch 46c is appropriately set so that the second gap D (see FIG. 5) is formed between the notch 46c and the rib 45d according to the radial length of the rib 45d. Can be set. If the second gap D is too small, the notches 46c and the ribs 45d may come into contact with each other in the circumferential direction due to thermal expansion or the like. If the second gap D is too large, the strength of the reinforcing member 46 is affected, and space is wasted. There is also a fear. Therefore, for example, in consideration of such a viewpoint, the radial length of the notch 46c and the second gap D can be appropriately set.

  Further, here, the rib 45d and the notch 46c extend in the radial direction, and the downstream and upstream end faces 46ca of the notch 46c with respect to the downstream and upstream end faces 45da and 45db of the rib 45d, Since 46cb can be contacted by its contact surface (a constant surface), rotation drive can be transmitted more reliably between the rib 45 and the notch 46c.

  Further, since the rib 45d and the notch 46c are formed in a substantially rectangular shape, these contact surfaces are arranged along the radial direction, and are rotationally driven in a direction perpendicular to the contact surface (substantially parallel to the tangential direction). Can communicate. Thereby, rotational drive can be transmitted more reliably and efficiently. In addition, the predetermined gap D can be more sufficiently secured in the radial direction. However, the shapes of the ribs 45d and the notches 46c are not particularly limited to the above.

  FIG. 7 is a partially enlarged side view showing the configuration around the ribs and notches of the gear according to the second embodiment of the present invention. Portions common to FIGS. 1 to 6 are denoted by common reference numerals, and description thereof is omitted. In this embodiment, as shown in FIG. 7, chamfering is performed on both ends in the circumferential direction of the tip 45dc of the rib 45d and the bottom 46cc of the notch 46c, and the shape of the rib 45d and the notch 46c is changed to the web 45a. Is formed in a substantially U shape when viewed in the vertical direction (perpendicular to the gear body 45). Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  According to the present embodiment, the circumferential ends of the distal end portion 45dc of the rib 45d can be brought into contact with the downstream side and the upstream end surfaces 45da and 45db of the rib 45d while the notch portion 46c can be brought into contact with a certain surface in the circumferential direction. It is possible to avoid contact with the downstream side and upstream side end surfaces 46ca and 46cb of the notch 46c. Thus, both end portions in the circumferential direction of the tip 45dc of the rib 45d can be prevented from coming into contact with the notch 46c in the circumferential direction and scraped, so that generation of foreign matter, deformation, wear, and the like can be prevented.

  FIG. 8 is a partially enlarged side view showing the structure around the ribs and notches of the gear according to the third embodiment of the present invention. Portions common to FIGS. 1 to 6 are denoted by common reference numerals, and description thereof is omitted. In the present embodiment, as shown in FIG. 8, the ribs 45d and the cutouts 46c become narrower toward the center in the radial direction so that the downstream and upstream end faces 45da and 45db and the cutouts 46c of the ribs 45d become smaller. The upstream and downstream end faces 46ca and 46cb are inclined, and the ribs 45d and the notches 46c are formed in a substantially trapezoidal shape when viewed in a direction perpendicular to the web 45a (a direction perpendicular to the gear body 45). .

  According to this embodiment, the notch 46c can be brought into contact with the downstream side and the upstream side end surfaces 45da and 45db of the rib 45d by a certain surface in the circumferential direction. In the present embodiment, the contact surface between the rib 45d and the notch 46c is not substantially parallel to the radial direction, and therefore the transmission direction of the rotational drive is not perpendicular to the radial direction. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  In each of the above embodiments, the downstream side and upstream side end surfaces 46ca and 46cb of the notch 46c can be brought into contact with the downstream side and upstream side end surfaces 45da and 45db of the rib 45d on a constant surface in the circumferential direction. It is possible to abut not only by surface contact but also by line contact. Here, the second gear 42 disposed on the developing roller 21 of the image forming unit Pa has been described, but the developing roller 21 exactly the same as the image forming unit Pa is also disposed on each of the image forming units Pb to Pd. The developing roller 21 is also provided with a gear having the same configuration as the second gear 42.

  In addition, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in the above embodiments, spur teeth are formed on the rim 45c of the gear body 45 of the second gear 42. However, the shape of the teeth is not particularly limited, and in addition, a helical is formed on the rim 45c. You can also The gear body 45 may be a two-stage gear.

  Further, in each of the above embodiments, the rib 45d is formed on the rim 45c of the gear main body 45, and the notch 46c is formed on the outer peripheral portion of the reinforcing member 46. In addition to these, on the outer peripheral surface of the boss 45b of the gear main body 45. A rib 45d similar to the above and a notch 46c similar to the above can be formed in the fitting hole 46a in the inner peripheral portion of the reinforcing member 46 in place of the protrusion 46aa. In such a case, a notch portion 46c formed in the inner peripheral portion of the reinforcing member 46 is press-fitted into the side surface portion of the rib 45d formed in the boss 45b, thereby providing a predetermined distance in the radial direction between the two. The reinforcing member 46 can be attached to the gear main body 45 while being mounted.

  In each of the above-described embodiments, the first gear 41 for driving the photosensitive drums 1a to 1d, the second gear 42 for driving the developing roller 21, and the magnetic roller disposed in the image forming units Pa to Pd. Since the present invention is applied to the second gear 42 among the third gears 43 for driving the motor 22, sufficiently high-accuracy drive transmission is performed even in the image forming portions Pa to Pd that require higher-precision meshing. Image unevenness can be suppressed.

  In particular, since the present invention is applied to the second gear 42 that is used in the image forming portions Pa to Pd and has a small number of teeth and easily causes rotation unevenness, it is more effective. Furthermore, if the present invention is applied to the first gear 41 and the third gear 43 having a small number of teeth as in the case of the second gear 42, it is possible to transmit rotational drive with higher accuracy. However, the gear of the present invention is not particularly limited to the gear used for the image forming portions Pa to Pd, and can be applied to other gears.

  In each of the above embodiments, for example, a direct transfer tandem image forming apparatus for color printing has been described. However, the present invention can be applied to other image forming apparatuses and is not particularly limited. For example, the present invention can be applied to an intermediate transfer tandem image forming apparatus, a color copying machine, a monochrome printer for monochrome printing, a monochrome copying machine, and the like. Further, the present invention can be applied to drive transmission of precision equipment, electronic equipment, etc. other than the image forming apparatus.

  The present invention is for transmitting a drive, a boss portion into which a rotation shaft is fitted in a central portion, a rim portion formed concentrically in the outer peripheral direction of the boss and having a tooth portion on the outer peripheral portion, and the boss A gear having a resin-made gear main body integrally formed with a thin web portion that connects between the rim portion and the rim portion, and a reinforcing member attached to the gear main body, wherein the rim portion In the inner circumferential portion, a projecting portion is formed at a predetermined interval in the circumferential direction and toward the radial center, and the reinforcing member is formed in a substantially circular flat plate shape, and the central portion of the reinforcing member is A fitting hole is formed, and the reinforcing member is attached to the gear body by fitting the fitting hole and the boss, and the outer diameter of the reinforcing member is smaller than the inner diameter of the rim portion and the reinforcing member The outer peripheral surface does not come into contact with the rim portion, and the outer peripheral portion of the reinforcing member In the position facing the protruding portion, it is possible to contact the protruding portion in the circumferential direction, but in the radial direction, a predetermined gap is provided between the protruding portion and the protruding portion. Is formed with a notch that is restricted.

  As a result, it is possible to prevent deformation of the gear body due to press-fitting of the reinforcing member, thermal expansion, etc., and to transmit rotational drive at the outer peripheral portion of the gear body, thereby suppressing deformation of the resin gear body by the reinforcing member. Thus, the drive can be efficiently transmitted and the rotational rigidity of the gear can be increased. In addition, the projecting part and the notch part extend in the radial direction, and the notch part is formed so as to be able to come into contact with the side surface part of the projecting part on a constant surface in the circumferential direction. Can be transmitted.

  Further, by forming the protrusion and the notch in a substantially rectangular shape with the radial direction as the longitudinal direction when viewed perpendicularly to the gear body, the drive is transmitted more reliably and the radial gap is further increased. It is possible to ensure sufficient. Further, by using a gear as a gear for transmitting drive to at least one of an image carrier, a toner carrier, and a toner supply member disposed in the image forming unit, a higher-precision mesh is required. Even in the image forming section, the drive transmission with sufficiently high accuracy can be achieved. Further, by using the image forming apparatus including the gear, it is possible to perform image formation in which image unevenness is suppressed.

Pa to Pd Image forming section 1a to 1d Photosensitive drum (image carrier)
3a to 3d Developing unit (developing device)
21 Developing roller (toner carrier)
22 Magnetic roller (toner supply member)
41 First gear 42 Second gear (gear)
43 3rd gear 45 Gear body 45a Web (web part)
45b Boss (boss part)
45c Rim (rim part)
45d rib (protrusion)
45da downstream end face (side face)
45db upstream end face (side face)
45dc distal end 46 reinforcing member 46a fitting hole 46aa protrusion 46c notch 46ca downstream end face 46cb upstream end face 46cc bottom 100 image forming apparatus

Claims (5)

A boss part for transmitting a drive, a boss part into which a rotation shaft is fitted in a central part, a rim part concentrically formed in the outer peripheral direction of the boss and having a tooth part on the outer peripheral part, the boss part and the rim A gear having a resin-made gear body integrally formed with a thin-walled web portion connecting between the parts, and a reinforcing member attached to the gear body,
A projecting portion is formed on the inner peripheral portion of the rim portion at a predetermined interval in the circumferential direction and toward the radial center.
The reinforcing member has a substantially circular flat plate shape,
A fitting hole is formed in the central portion of the reinforcing member, and the reinforcing member is attached to the gear body by fitting the fitting hole and the boss.
The outer diameter of the reinforcing member is smaller than the inner diameter of the rim portion and the outer peripheral surface of the reinforcing member does not contact the rim portion,
In the outer peripheral portion of the reinforcing member, a position facing the protruding portion can contact the protruding portion in the circumferential direction, but a predetermined gap is provided between the protruding portion in the radial direction. A gear having a notch portion that is provided and is restricted from abutting.   The projecting portion and the notch portion are extended in the radial direction, and the notch portion is formed so as to be able to contact a side surface portion of the projecting portion with a certain surface in the circumferential direction. The gear according to claim 1.   3. The gear according to claim 2, wherein the protrusion and the notch are formed in a substantially rectangular shape having the radial direction as a longitudinal direction when viewed in a direction perpendicular to the gear body.   4. The gear according to claim 1, wherein the gear is for transmitting driving to at least one of an image carrier, a toner carrier, and a toner supply member disposed in the image forming unit. The gear according to Crab.   An image forming apparatus comprising the gear according to claim 1.

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