JP2020034761A - Image carrier, image formation unit, and image formation apparatus - Google Patents

Abstract

To maintain image quality.SOLUTION: A photoreceptor drum 35 of an image formation unit 15 of a color printer 1 includes: a cylindrical drum element tube 50 which extends in an axial direction; a hollow drum gear 52 which is provided on an end part at one direction side in the axial direction of the drum element tube 50 and in which a gear teeth part 62 formed on an outer periphery is engaged with a drive side gear 74 to transmit driving force; a shaft 66 which extends in the axial direction at an inner peripheral side of the drum gear 52; and a disk-like support part 70 which is arranged closer to an engagement start side end 84 side in an engagement portion 82 where the drum gear 52 is engaged with the drive side gear 74 with respect to the axial direction, located between the shaft 66 and the drum gear 52, caused to pass through the shaft 66 and rotatably supports the drum gear 52 with respect to the shaft 66.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an image carrier, an image forming unit, and an image forming apparatus, and is suitably applied to, for example, a gear for driving an image carrier mounted on an electrophotographic image forming apparatus.

  Conventionally, as an image forming apparatus, an exposure head that emits light for exposure emitted from an LED (Light Emitting Diode), which is a light emitting element, irradiates light onto the surface of the photosensitive drum to illuminate the surface of the photosensitive drum. 2. Description of the Related Art A method of printing an image by forming an electrostatic latent image and further developing a toner image by attaching toner to the electrostatic latent image has been widely used. In such an image forming apparatus, a drum gear is inserted and fixed to the inner peripheral side of one end of a drum tube of a photosensitive drum, and the photosensitive drum is rotated by transmitting a driving force from a driving gear to the drum gear. (For example, see Patent Document 1).

  In such a photosensitive drum, if the drum gear is made lighter by making the drum gear hollow, a shaft extending in the axial direction is passed through a bearing portion of the drum gear, so that the drum gear is rotatably supported by the shaft, and the drum gear is rotatable. In the above, it is conceivable that the cylindrical rim portion having teeth formed on the outer peripheral side and the bearing portion are connected to each other by the disk-shaped support portion, so that the rim portion is supported by the disk-shaped support portion.

JP 2009-237139 A

  However, if the weight of the drum gear is reduced by making it hollow, there is a possibility that the image quality is reduced. Specifically, since the rim portion protrudes outward from the axial end of the disc-shaped support portion in a cantilever manner, when the driving force is applied from the driving gear to the drum gear, the deformation of the drum gear Is more likely to occur. When the drum gear is deformed and comes into contact with the drive side gear, the meshing width is reduced, which may cause wear, jitter, and abnormal noise.

  The present invention has been made in consideration of the above points, and has as its object to propose an image carrier, an image forming unit, and an image forming apparatus capable of maintaining image quality.

  In order to solve the above problem, in the image carrier of the present invention, a cylindrical element tube extending in the axial direction, and a gear tooth portion provided at an end of the element tube in one axial direction and formed on the outer periphery are provided. A hollow gear that meshes with the driving gear to transmit the driving force, a shaft that extends along the axial direction on the inner peripheral side of the gear, and a meshing start end of the meshing portion where the gear and the driving gear mesh with each other in the axial direction. And a support portion disposed between the shaft and the gear, penetrated by the shaft, and rotatably supporting the gear with respect to the shaft.

  In the image forming unit of the present invention, the above-described image carrier is provided.

  In the image forming apparatus of the present invention, the above-described image forming unit is provided.

  The present invention provides a meshing start side end portion of a gear from a support portion while supporting the gear start side end portion of a gear that receives a large rotational load at the start of meshing with a drive side gear, thereby making the gear hollow and light. Since the gear overhang portion can be shortened, the deformation of the gear can be suppressed.

  According to the present invention, by supporting the engagement start side end of the gear that is subjected to a large rotational load at the start of engagement with the drive side gear, the gear can be hollowed to reduce the weight, and the gear can be engaged with the gear from the engagement start side. Since the gear overhang to the end can be shortened, deformation of the gear can be suppressed, and thus an image carrier, an image forming unit, and an image forming apparatus capable of maintaining image quality can be realized.

FIG. 2 is a left side view illustrating the configuration of the color printer. FIG. 3 is a left side view illustrating a configuration of an image forming unit. FIG. 2 is a perspective view illustrating a configuration of a photosensitive drum. FIG. 3 is a perspective view illustrating a configuration of a drum gear. FIG. 2 is a plan view illustrating a configuration of a gear engagement unit according to the first embodiment. It is a perspective view showing composition of an engagement part by a 1st embodiment. It is a perspective view showing composition of a gear engagement part by a 2nd embodiment. FIG. 9 is a perspective view illustrating a configuration of a photosensitive drum of a comparative example. It is a top view showing composition of a gear engagement part of a comparative example.

  Hereinafter, embodiments for carrying out the invention (hereinafter, referred to as embodiments) will be described with reference to the drawings.

[1. First Embodiment]
[1-1. Configuration of Color Printer]
As shown in the left side view of FIG. 1, the color printer 1 is a color electrophotographic printer, and prints a desired color image on a sheet P having a size such as A3 size or A4 size. The color printer 1 has various components arranged inside a printer housing 2 formed in a substantially box shape. In the following, the right end portion in FIG. 1 is defined as the front of the color printer 1, and the vertical direction, the left and right direction, and the front and rear direction when viewed facing the front are defined and described. The color printer 1 is totally controlled by the control unit 3. The control unit 3 is connected to a higher-level device (not shown) such as a personal computer wirelessly or via a wire via a communication processing unit (not shown). When image data representing a color image to be printed is provided from the higher-level device and printing of the color image is instructed from the host device, the control unit 3 executes a printing process for forming a print image on the surface of the paper P.

  At the bottom of the printer housing 2, a paper storage cassette 4 for storing paper P and a paper supply for separating and feeding paper P stored in the paper storage cassette 4 one by one A part 5 is provided. The paper feeding unit 5 is located above the front end of the paper storage cassette 4, and is provided above the front end of the paper storage cassette 4, and is provided above the hopping roller 7 with the center axis directed in the left-right direction. In addition to a plurality of rollers such as the registration rollers 8, a guide for guiding the paper P is provided.

  The paper supply unit 5 rotates the hopping roller 7 and the registration roller 8 and the like under the control of the control unit 3 to separate and take in the papers P stored in the paper storage cassette 4 one by one, and After advancing P forward and upward, it is advanced so as to be folded backward at a position approximately at the center in the vertical direction near the front end in the printer housing 2.

  A transfer belt unit 10 is provided above the paper storage cassette 4 in the printer housing 2 so as to largely cross the printer housing 2 back and forth. In the transfer belt unit 10, rollers 11 each having an elongated cylindrical shape with the central axis directed in the left-right direction are arranged one by one in front and back, and a transfer belt 12 is stretched around the front and rear rollers 11. . The transfer belt 12 has a wide width in the left-right direction and is formed as an endless belt, and runs as the roller 11 rotates. The transfer belt unit 10 runs the transfer belt 12 by rotating the roller 11 based on the control of the control unit 3, and places the sheet P delivered from the sheet feeding unit 5 on the upper surface of the transfer belt 12. Transport in the direction.

  On the other hand, four image forming units 15C, 15M, 15Y and 15K shown in FIG. 2 (hereinafter, collectively referred to as image forming units) are provided above the transfer belt unit 10, that is, above the center of the printer housing 2. Units 15) are arranged in order from the rear side to the front side. That is, the image forming units 15 for each color are arranged in a so-called tandem system. The image forming units 15C, 15M, 15Y and 15K correspond to cyan (C), magenta (M), yellow (Y) and black (K), respectively. The image forming units 15C, 15M, 15Y, and 15K have the same configuration, and differ only in the color of the corresponding toner.

  In the printer housing 2, LED heads 16C, 16M, 16Y and 16K (hereinafter, these are collectively also referred to as LED heads 16) so as to correspond to the image forming units 15C, 15M, 15Y and 15K, respectively. Is provided. The LED head 16 is formed in a rectangular parallelepiped shape elongated in the left-right direction, and a plurality of LEDs are arranged inside the LED head 16 along the left-right direction, and correspond to image data supplied from the control unit 3. Each LED emits light in a light emission pattern. When the image forming unit 15 is mounted on the printer housing 2, the image forming unit 15 is very close to the LED head 16, and exposure processing is performed by light from the LED head 16.

  Further, toner cartridges 18C, 18M, 18Y and 18K (hereinafter collectively referred to as toner cartridge 18) are connected to the upper portions of the image forming units 15C, 15M, 15Y and 15K, respectively. The toner cartridge 18 is a hollow container that is long in the left-right direction, contains toner of each color in the form of powder, and incorporates a predetermined stirring mechanism. In the transfer belt unit 10, transfer rollers 13C, 13M, 13Y, and 13K (hereinafter collectively referred to as a transfer roller 13) are respectively provided at four positions immediately below each image forming unit 15 between the front and rear rollers 11. ) Is provided. That is, each image forming unit 15 sandwiches the upper part of the transfer belt 12 between itself and each transfer roller 13. The transfer roller 13 is configured to be charged.

  The control unit 3 causes the toner from the toner cartridge 18 to be supplied to the image forming unit 15. At the same time, the control unit 3 causes the LED head 16 to emit light so as to form a light emission pattern according to image data supplied from a higher-level device (not shown). In response to this, each image forming unit 15 uses the toner supplied from the toner cartridge 18 to form a toner image according to the light emission pattern of the LED head 16, and transfers the toner image to the paper P (for details, see FIG. See below). As a result, four color toner images corresponding to the image data are sequentially transferred onto the sheet P being conveyed by the transfer belt unit 10.

  A fixing unit 20 is provided behind the transfer belt unit 10, that is, near the upper and lower centers near the rear end of the printer housing 2. The fixing unit 20 includes a heating roller 21 and a pressure roller 22. The heating roller 21 is formed in a cylindrical shape with the central axis directed in the left-right direction, and a heater is provided inside. The pressure roller 22 is formed in the same cylindrical shape as the heating roller 21, and presses the upper surface against the lower surface of the heating roller 21 with a predetermined pressing force. The fixing unit 20 heats the heating roller 21 and rotates the heating roller 21 and the pressure roller 22 in predetermined directions based on the control of the control unit 3. Thus, the fixing unit 20 applies heat and pressure to the paper P delivered from the transfer belt unit 10, that is, the paper P on which the toner images of four colors are superimposed, to fix the toner, and further receives the toner image upward and rearward. hand over.

  A paper discharge unit 24 is disposed above and behind the fixing unit 20. The paper discharge unit 24 is configured by a combination of a plurality of rollers (not shown) with the central axis directed in the left-right direction, a guide for guiding the paper, and the like. The paper discharge unit 24 conveys the paper P delivered from the fixing unit 20 to the rear and upper direction and then folds it forward by appropriately rotating each roller under the control of the control unit 3. The sheet is discharged to a discharge tray 2T formed on the upper surface.

  As described above, when executing the printing process, the color printer 1 causes the LED head 16 to emit light, thereby forming a toner image by the image forming unit 15 of each color, and sequentially transferring the toner image to the paper P.

[1-2. Configuration of Image Forming Unit]
Next, the configuration of the image forming unit 15 will be described. As shown in FIG. 2, the image forming unit 15 closes most of its outer periphery with a frame 31 and forms a relatively large space therein.

  A photoreceptor drum 35 is provided near the center below the image forming unit 15. The photoconductor drum 35 is formed in a cylindrical shape with the shaft 66 directed in the left-right direction, and is supported by the frame 31 so as to be rotatable around the shaft 66. Incidentally, the photosensitive drum 35 rotates in the direction of the arrow R1 when a driving force is transmitted from a motor (not shown).

  The portion of the frame 31 that is to be the lower surface of the photosensitive drum 35 is open over a relatively wide range. Therefore, when the image forming unit 15 is mounted on the printer housing 2 (FIG. 1), the lower surface of the photosensitive drum 35 contacts the transfer belt 12 or the paper P placed on the transfer belt 12. In a portion of the frame 31 directly above the photosensitive drum 35, an elongated exposure hole is formed in the left-right direction.

  A charging roller 36 having a cylindrical shape smaller in diameter than the photosensitive drum 35 is provided above and behind the photosensitive drum 35. The charging roller 36 is made of, for example, a semiconductive elastic material, and its peripheral side surface is in contact with the peripheral side surface 35S of the photosensitive drum 35, and the contact portion of the peripheral side surface 35S is uniformly charged. Let it.

  Above the front of the photoconductor drum 35, a cylindrical developing roller 38 having a smaller diameter than the photoconductor drum 35 is provided. The developing roller 38 is made of semiconductive urethane rubber whose electric resistance is appropriately adjusted by adding a conductive substance such as carbon to urethane rubber, and can be charged. The developing roller 38 has a peripheral side surface abutting on a peripheral side surface 35S of the photosensitive drum 35 on the rear side and a cylindrical supply roller 39 having a diameter slightly smaller than the developing roller 38 on the front side. The sides are in contact. The supply roller 39 is made of, for example, a semiconductive foamed silicone sponge.

  A thin plate-like developing blade 40 is provided above and behind the developing roller 38. The developing blade 40 is made of a metal such as stainless steel or phosphor bronze, or a rubber material such as silicon rubber. The developing blade 40 has a rear upper end fixed in the frame 31 and forms a slight gap between the front lower end and the peripheral side surface of the developing roller 38.

  Further, spacers 45 are provided on both left and right sides above the photosensitive drum 35. The size of the spacer 45, the mounting position with respect to the frame 31, and the like are optimized, and the lower surface of the LED head 16 is brought into contact with the upper surface of the spacer 45 so that the distance between the peripheral side surface of the photosensitive drum 35 and the LED head 16 is increased. To the desired length.

  In this configuration, when printing an image on the paper P, the image forming unit 15 rotates the photosensitive drum 35 in the direction of the arrow R <b> 1 under the control of the control unit 3, and performs charging roller 36, developing roller 38, and supply roller 39. Is rotated in the direction of arrow R2 to further charge the charging roller 36 and the developing roller 38.

  First, the rear upper portion of the peripheral surface 35S of the photosensitive drum 35 is uniformly charged by the charging roller 36, and the charged portion reaches the vicinity of the upper end by rotating in the direction of the arrow R1 to face the LED head 16. At this time, the peripheral side surface 35S of the photoconductor drum 35 is exposed by irradiating the LED head 16 with light having a light emission pattern corresponding to the image data, and an electrostatic latent image corresponding to the image data is formed.

  On the other hand, the developing roller 38 rotating in the direction of the arrow R2 has the toner supplied from the toner cartridge 18 adhered to the peripheral surface by the supply roller 39, and then excess toner is scraped off by the developing blade 40. The toner is deposited in a uniform thin film.

  The photoreceptor drum 35 further rotates in the direction of arrow R1 so that the toner formed in a thin film on the peripheral side surface of the developing roller 38 near the front end contacting the developing roller 38 according to the electrostatic latent image. Only the contact point is attached to the peripheral side surface 35S. As a result, a toner image corresponding to the image data is formed on the peripheral side surface 35S of the photosensitive drum 35. Incidentally, at this time, the toner image formed on the peripheral side surface 35S is only the component of one color (that is, any one of cyan, magenta, yellow, and black) that the image forming unit 15 is responsible for among the images to be finally printed. Is displayed.

  Thereafter, the photosensitive drum 35 further rotates in the direction of arrow R1, thereby causing the toner image to reach near the lower end. At this time, the control unit 3 causes the transfer belt unit 10 (FIG. 1) to cause the sheet P to reach the lower side of the image forming unit 15 and also charges the transfer roller 13 to the opposite characteristic to the toner. Therefore, the image forming unit 15 sandwiches the sheet P between the portion of the photosensitive drum 35 where the toner image is formed and the charged transfer roller 13, and transfers the toner image to the sheet P. . Incidentally, if the toner remains on the peripheral side surface 35S of the photosensitive drum 35 after the transfer of the toner image onto the paper P, the toner is removed by a cleaning device (not shown).

  Thus, the image forming unit 15 causes the LED head 16 to face the vicinity of the photosensitive drum 35, and forms a toner image on the peripheral side surface 35S by the exposure action of the LED head 16.

[1-3. Configuration of Photoconductor Drum]
As shown in FIG. 3, the photoconductor drum 35 is configured around a drum base tube 50, which is a main body part, in which a photosensitive layer is coated on a cylindrical aluminum tube, and is arranged in a longitudinal direction ( A drum gear 52 is provided at a left end, which is an end in one direction (axial direction), and a flange 54 having no gear teeth is provided at a right end, which is an end in the other direction. The drum gear 52 and the flange 54 are fixed to the inner peripheral surface of the drum tube 50 with an adhesive. 3 and 6, the shaft 66 is not shown and is omitted. The photosensitive drum 35 is rotated by a driving force transmitted from a driving gear 74 (FIGS. 5 and 6) via the drum gear 52.

[1-4. Configuration of Drum Gear]
As shown in FIGS. 4 and 6, the drum gear 52 is a hollow helical gear. This helical gear is a so-called helical gear, in which the teeth are formed in a spiral shape around the outer periphery of the cylinder. The color printer 1 uses the helical drum gear 52 to set the engagement ratio of the drum gear 52 higher than other types of gears, suppresses speed unevenness (jitter), and obtains a stable image. Like that.

  The drum gear 52 includes a tooth portion 56 and a photoconductor fixing portion 58. The tooth portion 56 includes an inner peripheral rim portion 60 and an outer peripheral gear tooth portion 62, and is formed on the drum gear 52 on the left side, which is one side in the axial direction. The rim portion 60 has a cylindrical shape having a predetermined thickness, and an inner peripheral surface thereof is in contact with an outer peripheral surface of the disk-shaped support portion 70. The outer peripheral surface of the rim portion 60 forms the tooth bottom of the tooth portion 56. The gear tooth portion 62 has a plurality of drum gear tooth profiles 64 formed on the outer peripheral side of the rim portion 60 and extending obliquely with respect to the axial direction. The axial width of the gear tooth portion 62 of the drum gear 52 is the drum gear tooth width L shown in FIG. In this embodiment, the drum gear tooth width L is about 20 [mm]. The photosensitive member fixing portion 58 as a fixing portion is formed integrally with the tooth portion 56 so as to be adjacent to the right side, which is the other side of the tooth portion 56. The photosensitive member fixing portion 58 has a surface that can be bonded to the inner wall surface of the drum tube 50 of the photosensitive drum 35 formed on the outer peripheral surface, and the outer peripheral surface is fitted to the inner wall surface of the drum tube 50. , Is fixed to the drum tube 50.

  The weight of the drum gear 52 is reduced by using a resin gear. Further, the drum gear 52 is formed by injection molding, and the accuracy of the drum gear tooth profile 64 is ensured by designing the rim portion 60 to have a small thickness. Here, if the rim portion 60 has a large thickness, sink occurs during molding, so that the drum gear tooth profile 64 is likely to be deformed. Therefore, in order to prevent the deformation of the drum gear tooth profile 64, the rim portion 60 is required to be thin. However, when the rim portion 60 becomes thinner, the accuracy of the shape of the drum gear tooth profile 64 is secured, but the strength tends to decrease.

  A shaft 66 shown in FIG. 5 as a rotation axis is provided along the left-right direction which is the axial direction at the rotation center of the photosensitive drum 35, and a bearing 68 of the drum gear 52 is rotatable about the shaft 66. It is supported by. The bearing 68 and the rim 60 of the drum gear 52 are connected to each other by a disc-shaped support 70.

  As shown in FIG. 5, the disc-shaped support portion 70 has a shaft that is thinner than the drum gear tooth width L of the drum gear 52, specifically, 1.5 to 2 [mm], and in this embodiment, about 2 [mm]. It has a disk shape having a width in the direction, and is formed by resin molding, and a hole through which the bearing 68 penetrates is formed in the center. The disk-shaped support portion 70 has an outer peripheral surface that comes into contact with the inner peripheral surface of the rim portion 60 that is the inner periphery of the outer cylinder, and an inner peripheral surface of the hole that comes into contact with the outer peripheral surface of the bearing portion 68 that is the outer periphery of the inner cylinder. Thereby, the rim portion 60 is supported from the inside, and the deformation of the rim portion 60 is prevented.

[1-5. Configuration of Gear Engaging Section]
As shown in FIG. 5, a gear engaging portion 72, which is an engaging portion between the drum gear 52 and the driving gear 74, is provided behind the drum gear 52 at a driving side which meshes with the drum gear 52 and transmits a driving force to the drum gear 52. A gear 74 is provided. The drive-side gear 74 is a helical gear, like the drum gear 52, and is formed so as to have an axial width substantially equal to the drum gear tooth width L. The driving gear 74 is rotatably supported by a driving gear shaft 80 extending in the left-right direction. The drive-side gear 74 has a drive-side gear tooth portion 76 formed on the outer periphery thereof, and the drive-side gear tooth portion 76 extends in a direction inclined with respect to the axial direction in a direction opposite to the drum gear tooth profile 64. A plurality of gear teeth 78 are formed on the outer peripheral surface.

  Further, the drive side gear 74 has a left end located on the left side of the left end of the teeth 56 of the drum gear 52 and a right end located on the left side of the right end of the teeth 56 of the drum gear 52. That is, the driving gear 74 is not meshed from the right end to the left end of the tooth portion 56 of the drum gear 52, and is arranged at a position slightly shifted leftward with respect to the drum gear 52. For this reason, the meshing portion 82 where the drive gear 74 and the drum gear 52 mesh with each other is in a leftward range of the drum gear 52. The axial width of the meshing portion 82 is the meshing portion width M. In the present embodiment, the engagement portion width M is about 18 [mm].

  In such a configuration, when the driving gear 74 rotates in the driving gear rotation direction r1, the driving gear 74 and the drum gear 52 are separated from each other at the left end of the gear tooth portion 62 by the inclination of the tooth trace of the drum gear tooth profile 64 with respect to the axial direction. Contact starts from the engagement start side end portion 84 shown in FIG. 6 at the start of a certain engagement, and as the drum gear 52 rotates in the drum gear rotation direction r2, the engagement end side end portion 86 (the right end portion of the gear tooth portion 62) at the end of engagement. 6), the contact surface between the drive gear 74 and the drum gear 52 increases. In other words, the meshing width at which the drive gear 74 and the drum gear 52 mesh increases from the mesh start end 84 to the mesh end 86 as the rotation of the drive gear 74 and the drum gear 52 progresses. Thus, the meshing portion width M is obtained. Therefore, the force applied to the gear tooth portion 62 is concentrated on the engagement start side end portion 84 at the time of the start of the engagement, and the root of the drum gear tooth profile 64, which is the root, is easily deformed. If the deformation of the tooth root of the drum gear tooth profile 64 becomes large, a meshing abnormality occurs, and vibration and abnormal noise occur. On the other hand, when the engagement end side end portion 86 of the gear tooth portion 62 comes into contact with the drive side gear tooth portion 76, the engagement width is increased and the force is dispersed, so that the gear tooth portion is compared with the engagement start side end portion 84. The deformation of 62 is unlikely to occur.

[1-6. Arrangement of disk-shaped support]
As shown in FIG. 5, in the gear engaging portion 72, a distance A between gear end support portions, which is a distance from the left end of the gear tooth portion 62 of the drum gear 52 to the left end of the disc-shaped support portion 70, is: It is set to less than half the drum gear tooth width L. That is, in the gear engaging portion 72, the disc-shaped support portion 70 is disposed at a position where the relationship of the distance A between the gear end support portions and the drum gear tooth width L / 2 holds. More specifically, the distance A between the gear end support portions is about half the drum gear tooth width L / 2. Further, in the gear engaging portion 72, the distance between the center of the gear end support portion, which is the distance from the left end of the gear tooth portion 62 of the drum gear 52 to the center in the axial direction of the disc-shaped support portion 70, is also the gear end support. Like the end-to-end distance A, the width is set to less than half of the drum gear tooth width L.

  Further, in the gear engaging portion 72, the distance A1 between the engaging portion end portion supporting portion ends, which is the distance from the left end portion of the engaging portion 82 to the left end portion of the disc-shaped supporting portion 70, is less than half of the engaging portion width M. Is set. That is, in the gear engaging portion 72, the disc-shaped support portion 70 is disposed at a position where the relationship A1 <engagement portion width M / 2 holds between the engagement portion end portion support end portions. Specifically, the distance A1 between the end portions of the engagement portion and the support portion is approximately half the width of the engagement portion width M / 2. Further, in the gear engaging portion 72, the distance between the center of the meshing portion end portion support portion, which is the distance from the left end portion of the meshing portion 82 to the center portion in the axial direction of the disk-shaped support portion 70, is also equal to the meshing portion end portion support portion end. It is set to less than half of the meshing portion width M in the same manner as the inter-unit distance A1.

[1-7. Effects]
8 in which members corresponding to those in FIG. 3 have the same reference numerals, and FIG. 9 in which members corresponding to those in FIG. Are respectively shown. The disc-shaped support portion 270 of the comparative example is different from the disc-shaped support portion 70 (FIG. 5) of the present embodiment in that the right side of the engagement end side 86, that is, the drum gear 52 is fitted to the drum tube 50. It is disposed on the drum insertion direction side, which is the direction of movement of the drum gear 52 during the operation. Hereinafter, a left direction opposite to the drum insertion direction is also referred to as a drum detachment direction.

  Specifically, the distance A between the gear end support portions in the gear engaging portion 272 is equal to or more than half the drum gear tooth width L. That is, in the gear engaging portion 272, the disc-shaped support portion 270 is disposed at a position where the relationship of gear end support portion end distance A ≧ drum gear tooth width L / 2 holds. In the gear engaging portion 272, the distance A1 between the end portions of the engagement portion and the support portion is equal to or more than half of the width M of the engagement portion. That is, in the gear engaging portion 272, the disc-shaped support portion 270 is disposed at a position where the relationship A1 ≧ meshed portion width M / 2 holds.

  That is, in the gear engaging portion 272, the disc-shaped support portion 270 is not engaged with the engagement start side end portion 84 of the gear tooth portion 62 but is engaged with the engagement end side end portion 86, specifically, the engagement of the disc-shaped support portion 270 is started. The end on the side end portion 84 side (left side) is provided closer to the meshing end side end portion 86 (right side) than the center portion of the meshing portion 82 and the center portion of the gear tooth portion 62 which is the gear formation region. ing. For this reason, in the gear engaging portion 272, the rim portion 60 and the gear tooth portion 62 are cantilevered from the end on the engagement start side end portion 84 side of the disc-shaped support portion 270 to the engagement start side end portion 84 side (leftward). ). A portion of the teeth 56 of the drum gear 252 that protrudes from the end on the engagement start side end 84 side of the disc-shaped support portion 270 toward the engagement start side end 84 and is not supported by the disc-shaped support portion 270 is geared. It is also referred to as an outlet 290. The length of the gear overhang 290 along the axial direction is the distance A between the gear end support portions.

  Since the rim portion 60 is formed thin and the inside of the hollow is not supported by the disk-shaped support portion 270, the gear overhang portion 290 is easily deformed when a force is applied from the outside. For this reason, when a driving force is applied from the driving gear 74 to the drum gear 252, there is a possibility that the drum gear 252 is deformed due to the rotational load, particularly at the engagement start side end portion 84 side of the gear projection 290 of the tooth portion 56. is there. If the drum gear 252 is deformed and the contact with the drive-side gear 74 is made one-sided, the meshing width becomes small, which may cause abrasion, jitter or abnormal noise.

  On the other hand, the gear engaging portion 72 (FIG. 5) according to the present embodiment is a disk that supports the outer peripheral surface of the bearing portion 68 and the inner peripheral surface of the rim portion 60 in the hollow drum gear 52 provided on the photosensitive drum 35. The gear-shaped support part 70 is not the end-of-mesh end 86 of the gear tooth part 62 but the end of the gear start side 84, specifically, the end of the disc-shaped support 70 that is closer to the mesh start-side end 84. The gear teeth 62 are provided closer to the engagement start end 84 (left side) than the center. In other words, the disk-shaped support portion 70 is provided on the gear tooth portion 62 of the drum gear 52 at an upstream side meshing with the gear tooth portion 62 from the center.

  Further, the gear engaging portion 72 is provided such that the end of the disc-shaped support portion 70 on the side of the engagement start side 84 is closer to the engagement start side end 84 (left side) than the center of the engagement portion 82. In other words, the disc-shaped support portion 70 is provided upstream of the center of the engagement portion 82 where the drum gear 52 meshes with the driving gear 74 from the center.

  For this reason, the length of the gear overhanging portion 90 along the axial direction of the gear engaging portion 72 can be significantly shorter than the length of the gear overhanging portion 290 (FIG. 9). For this reason, the gear engaging portion 72 can increase the rigidity of the gear projecting portion 90 of the rim portion 60, particularly on the side of the engagement start side end portion 84, by the disc-shaped support portion 70. Thus, when a driving force is applied from the driving gear 74 to the drum gear 52 and a rotational load is applied to the gear engaging portion 72, the gear engaging portion 72 is deformed particularly toward the engagement start side end portion 84 of the gear projection 90 of the drum gear 52. The occurrence can be suppressed. Thus, the gear engaging portion 72 can suppress the one-sided contact peculiar to the helical gear, can increase the mesh width, and can smoothly mesh. Thus, the gear engaging portion 72 can prevent the occurrence of uneven wear, jitter and abnormal noise.

  Providing the position of the disc-shaped support portion 70 on the upstream side meshing with the center of the gear teeth 62 of the drum gear 52 and on the upstream side meshing with the center of the meshing portion 82 as described above can be achieved by using the hollow and lightweight drum gear 52. In the state where the strength of the drum gear tooth profile 64 tends to decrease because the accuracy of the drum gear tooth profile 64 is secured by forming the rim portion 60 to be thin, the meshing start side of the rim portion 60 in the gear overhang portion 90. This is not a mere design matter because it has a special action and effect that the rigidity of the end portion 84 can be increased.

  Here, the disc-shaped support portion 70 is moved to a position where the end of the disc-shaped support portion 70 on the engagement start side end portion 84 side is aligned with the end of the gear tooth portion 62 of the rim portion 60 on the engagement start side end portion 84 side. Is closer to the engagement start side end portion 84 side, the rigidity of the end portion of the rim portion 60 on the engagement start side end portion 84 side can be maximized. On the other hand, the closer the disc-shaped support portion 70 is from the engagement start side end portion 84 side of the gear teeth portion 62 of the rim portion 60 to the engagement end side end portion 86 side, the closer the engagement start side end portion 84 of the rim portion 60 is. Is lower, but the strength at the engagement end side end 86 side is higher. However, when the engagement end side end portion 86 of the gear tooth portion 62 comes into contact with the drive side gear tooth portion 76, the engagement width is large, and the force is dispersed. For this reason, in the gear tooth portion 62, since the engagement end side end portion 86 side is less likely to be deformed than the engagement start side end portion 84 side, the strength of the end portion of the rim portion 60 on the engagement end side end portion 86 side is reduced. The need for reinforcement is low. For this reason, in the gear engaging portion 72, it is preferable to arrange the disc-shaped support portion 70 as close to the engagement start side end portion 84 of the rim portion 60 as possible.

  According to the above configuration, the photosensitive drum 35 of the image forming unit 15 of the color printer 1 is provided at a cylindrical drum tube 50 extending in the axial direction and an end of the drum tube 50 in one axial direction. The outer peripheral gear teeth 62 mesh with the driving gear 74 to transmit the driving force, the hollow drum gear 52, the shaft 66 extending in the axial direction on the inner peripheral side of the drum gear 52, and the axial direction. The engagement portion 82 as an engagement portion where the drum gear 52 and the driving gear 74 mesh with each other is disposed closer to the engagement start side end portion 84 side, is located between the shaft 66 and the drum gear 52, and is penetrated by the shaft 66. And a disk-shaped support portion 70 for rotatably supporting the drum gear 52.

  Accordingly, the photosensitive drum 35 supports the engagement start side end portion 84 of the drum gear 52 to which a large rotational load is applied at the start of engagement with the drive-side gear 74, thereby making the drum gear 52 hollow and reducing the weight thereof while maintaining the disk shape. Since the gear projecting portion 90 from the support portion 70 to the engagement start side end portion 84 of the drum gear 52 can be shortened, the deformation of the drum gear 52 can be suppressed.

[2. Second Embodiment]
[2-1. Configuration of Color Printer]
A color printer 101 (FIG. 1) according to the second embodiment replaces the image forming unit 15 (image forming units 15C, 15M, 15Y and 15K) in comparison with the color printer 1 according to the first embodiment. 2 is different in that it has an image forming unit 115 (image forming units 115C, 115M, 115Y, and 115K) shown in FIG. The image forming unit 115 is different from the image forming unit 15 according to the first embodiment in having a gear engaging portion 172 (FIG. 7) instead of the gear engaging portion 72, but is different in the other respects. Are similarly configured.

[2-2. Configuration of Gear Engaging Section]
As shown in FIG. 7 in which members corresponding to those in FIG. 5 are denoted by the same reference numerals, the gear engaging portion 172 according to the second embodiment is different from the gear engaging portion 72 according to the first embodiment in comparison with the gear engaging portion 72 according to the first embodiment. Although it differs in having a drive side gear 174 in place of the drive side gear 74, other points are configured similarly. The drive-side gear 174 has a left end located on the right side of the left end of the teeth 56 of the drum gear 52, and a right end located on the right side of the right end of the teeth 56 of the drum gear 52. That is, the driving gear 174 is not meshed from the right end to the left end of the tooth portion 56 of the drum gear 52, and is located at a position slightly shifted rightward with respect to the drum gear 52. For this reason, the meshing portion 182 where the drive gear 174 and the drum gear 52 mesh with each other is in a rightward range of the drum gear 52.

  In the gear engaging portion 172, similarly to the gear engaging portion 72 (FIG. 5), the distance A between the gear end supporting portions is set to be less than half the drum gear tooth width L. That is, in the gear engaging portion 172, the disc-shaped support portion 70 is disposed at a position where the relationship A between the gear end portion support end portions and the drum gear tooth width L / 2 holds.

  In the gear engaging portion 172, similarly to the gear engaging portion 72 (FIG. 5), the distance A1 between the engaging portion end support portions is set to be less than half of the engaging portion width M. That is, in the gear engaging portion 172, the disc-shaped support portion 70 is disposed at a position where the relationship A1 <engaged portion width M / 2 is satisfied.

  As described above, the meshing portion 182 is not formed at the left end of the tooth portion 56 of the drum gear 52, and when the meshing portion 182 is shifted to the right with respect to the tooth portion 56 of the drum gear 52, the meshing portion 182 is formed. Also on the left side, the driving gear 174 does not contact the drum gear 52, so that no rotational load is applied from the driving gear 174 to the drum gear 52. For this reason, the gear engaging portion 172 has the disc-shaped support portion 70 provided at least at the meshing upstream side of the center of the meshing portion 182.

  In other respects, the gear engaging portion 172 of the image forming unit 115 of the color printer 101 according to the second embodiment is different from the gear engaging portion 72 of the image forming unit 15 of the color printer 1 according to the first embodiment. The same operation and effect as described above can be obtained.

[3. Other Embodiments]
In the above-described embodiment, the case where the helical gear is used for the drum gear 52 has been described. The present invention is not limited to this, and various gears such as spur gears may be used for the drum gear 52. However, in the case of the helical gear, the driving gear 74 gradually meshes from one end in the axial direction of the drum gear 52 toward the other end, and when the gear 74 meshes with only one end, a large rotational load is applied to the drum gear 52. , The effect of the present invention is remarkably exhibited.

  In the above-described embodiment, the case where the drum gear 52 is made of resin has been described. The present invention is not limited to this, and the drum gear 52 may be formed of various materials such as metal.

  Further, in the above-described embodiment, the case where the drum gear 52 and the flange 54 are fixed to the inside of the drum tube 50 with the adhesive has been described. The present invention is not limited to this, and the drum gear 52 and the flange 54 may be pressed into the inside of the drum tube 50, or may be fixed using another component.

  Further, in the above-described embodiment, the case where the engagement start side end 84 is the left end of the drum gear 52 and the engagement end side end 86 is the right end of the drum gear 52 has been described. The present invention is not limited to this, and when the inclination of the tooth traces of the drum gear 52 and the drive-side gear 74 is opposite, the engagement start side end and the engagement end side end are reversed left and right. The condition for setting the right and left may be reversed.

  Further, in the above-described embodiment, the relationship that the distance A between the gear end support portions is smaller than the tooth width L / 2 of the drum gear, and the relationship that the distance A1 between the mesh portion end support portions is less than the mesh width M / 2. The case where the disc-shaped support portion 70 is arranged at a position where both of the above are satisfied has been described. The present invention is not limited to this, and it is sufficient that the disc-shaped support portion 70 is disposed at a position where at least the relationship A1 <engagement portion width M / 2 holds.

  Further, in the first embodiment described above, the case where the present invention is applied to the photosensitive drum 35 in the image forming unit 15 of each color arranged in series in the front-rear direction in the tandem type color printer 1 will be described. Was. The present invention is not limited to this, and may be applied to a photosensitive drum mounted on a color printer of various other types such as a four-cycle type. The same applies to the second embodiment.

  Further, in the above-described first embodiment, the present invention is applied to the color printer 1. However, the present invention is not limited to this, and if the apparatus has the photosensitive drum 35 like the color printer 1, a facsimile, MFP (Multi Function Printer) The present invention may be applied to apparatuses such as a multifunction peripheral) and a copying machine. The same applies to the second embodiment.

  Further, in the first embodiment described above, the image carrier is formed by the drum tube 50 as the tube, the drum gear 52 as the gear, the shaft 66 as the shaft, and the disk-shaped support portion 70 as the support portion. A case where the photosensitive drum 35 as a body is formed, the image forming unit 15 as an image forming unit having the image carrier is formed, and the color printer 1 as an image forming apparatus having the image forming unit is formed. Was mentioned. The present invention is not limited to this, and the tube, the gear, the shaft, and the support portion having other various configurations constitute an image carrier, and also constitute an image forming unit having the image carrier, Further, an image forming apparatus having this image forming unit may be configured.

  INDUSTRIAL APPLICABILITY The present invention is applicable to, for example, a photosensitive drum mounted on an electrophotographic printer.

  DESCRIPTION OF SYMBOLS 1 ... Color printer, 2 ... Printer housing, 2T ... Discharge tray, 3 ... Control part, 4 ... Paper storage cassette, 5 ... Paper supply part, 7 ... Hopping roller, 8 ... Registration roller Reference numeral 10: transfer belt unit, 11: roller, 12: transfer belt, 13: transfer roller, 15: image forming unit, 16: LED head, 18: toner cartridge, 20: fixing unit, Reference numeral 21: heating roller, 22: pressure roller, 24: paper discharge section, 31: frame, 35, 235: photosensitive drum, 35S: peripheral surface, 36: charging roller, 38: development Roller, 39 Supply roller, 40 Development blade, 50 Drum tube, 52, 252 Drum gear, 54 Flange, 56 Tooth portion, 58 Photoconductor fixing portion, 60 Rim, 6 ... gear teeth, 64 ... drum gear teeth, 66 ... shaft, 68 ... bearings, 70, 270 ... disk-shaped support, 72, 172, 272 ... gear engaging parts, 74, 174 ... Driving gear, 76: Driving gear teeth, 78: Driving gear tooth, 80: Driving gear shaft, 82, 182: Meshing portion, 84: Meshing start side end, 86: Meshing End side end, 90, 290: Gear overhang, A: Distance between gear end support end, L: Drum gear tooth width, A1: Distance between mesh part end support end, M ... Meshing portion width, r1... Drive side gear rotation direction, r2... Drum gear rotation direction.

Claims (11)

A cylindrical base tube extending in the axial direction;
A hollow gear that is provided at one end in the axial direction of the raw tube and has a gear tooth portion formed on the outer periphery that meshes with a driving gear to transmit driving force,
A shaft extending along the axial direction on the inner peripheral side of the gear;
In the axial direction, the gear and the drive-side gear are disposed closer to the engagement start side end in the meshing portion where the gear meshes with the drive side gear, located between the shaft and the gear, penetrated by the shaft, and with respect to the shaft. And a support portion rotatably supporting the gear. 2. The image carrier according to claim 1, wherein the support portion is disposed closer to the one side in the axial direction of the engagement portion. 3. In the axial direction, a distance from an end of the engagement portion on the engagement start side to an end of the support portion on the engagement start side is less than half a width of the engagement portion. 3. The image bearing member according to claim 1 or 2. 4. The image according to claim 3, wherein a distance from an end of the engagement portion on the engagement start side to a center of the support portion in the axial direction is less than half a width of the engagement portion. Carrier. In the axial direction, a distance from an end on the engagement start side of the gear tooth portion to an end on the engagement start side of the support portion is less than half a width of the gear tooth portion. The image carrier according to any one of claims 1 to 4, wherein The distance from the end of the gear tooth portion on the engagement start side to the center of the support portion in the axial direction is less than half the width of the gear tooth portion. Image carrier. The image carrier according to any one of claims 1 to 6, wherein the gear is a helical gear. The image carrier according to any one of claims 1 to 7, wherein the gear is formed by resin molding. The image carrier according to any one of claims 1 to 8, wherein the width of the support portion in the axial direction is smaller than the width of the gear teeth of the gear.   An image forming unit comprising the image carrier according to claim 1.   An image forming apparatus comprising the image forming unit according to claim 10.

Images