JP2008032955A - Drum cleaning unit and image forming apparatus equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drum cleaning unit capable of eliminating jitter failure by achieving the smooth rotation of a photoreceptor drum, and also, capable of forming an image of high quality by uniformly polishing the surface of the photoreceptor drum. <P>SOLUTION: The drum cleaning unit includes a rubbing roller 36 that rotates in contact with the surface of the photoreceptor drum 21, and wherein holding arms 38 that rotatably hold the rubbing roller 36 are rotatably journaled, then, the rubbing roller 36 can come in contact with or separate from the photoreceptor drum 21. A circumferential velocity ratio of the rubbing roller 36 to the photoreceptor drum 21 is set ≤1, and the rotating fulcrum of the holding arm 38 is arranged on a side where a force may work in a direction to make the rubbing roller 36 bite in the photoreceptor drum 21 with the frictional force between the photoreceptor drum 21 and the rubbing roller 36. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a drum cleaning unit including a rubbing roller that rotates in contact with the surface of a photosensitive drum, and an image forming apparatus including the drum cleaning unit.

  Image forming apparatuses such as copying machines, printers, and facsimile machines that employ an electrophotographic system are provided with a drum cleaning unit for scraping off toner (transfer residual toner) remaining on the photosensitive drum after transfer with a cleaning blade. Yes.

In particular, in the photosensitive drum made of amorphous silicon (a-Si), the surface of the photosensitive drum is NOX.
Since the charged product such as the surface adheres to the surface of the photosensitive drum, a rubbing roller that rotates in contact with the surface of the photosensitive drum is provided in the drum cleaning unit, and the charged product that adheres to the surface of the photosensitive drum is polished by the rubbing roller. (See, for example, Patent Documents 1 and 2).
Japanese Patent No. 2529832 Japanese Patent No. 2895191

  By the way, in a drum cleaning unit equipped with a rubbing roller, if the peripheral speed ratio of the rubbing roller to the photosensitive drum is 1 or more, the rubbing roller rotates and drives the photosensitive drum. In other words, there is a problem that jitter is caused due to uneven rotation of the photosensitive drum.

  When the rotation ratio of the photosensitive drum and the rubbing roller is an integral multiple, the same surface of the rubbing roller always polishes the same surface of the photosensitive drum, and the rubbing roller has a polishing ability depending on the surface state. Due to the variation, the surface of the photosensitive drum is not uniformly polished by the rubbing roller, and there is a problem that the surface state of the photosensitive drum is uneven and the image is adversely affected.

  The present invention has been made in view of the above problems, and the object of the present invention is to realize smooth rotation of the photosensitive drum to eliminate jitter defects and to uniformly polish the surface of the photosensitive drum. It is an object of the present invention to provide a drum cleaning unit capable of forming a high quality image and an image forming apparatus including the drum cleaning unit.

  In order to achieve the above object, the invention described in claim 1 is provided with a rubbing roller that rotates in contact with the surface of the photosensitive drum, and a holding arm that rotatably holds the rubbing roller is pivotally supported. Thus, in the drum cleaning unit in which the rubbing roller can be brought into contact with and separated from the photosensitive drum, a peripheral speed ratio of the rubbing roller to the photosensitive drum is set to 1 or less and the holding arm is rotated. The moving fulcrum is arranged on the side where a force acts in a direction in which the rubbing roller bites into the photosensitive drum by the frictional force of the photosensitive drum and the rubbing roller.

  According to a second aspect of the present invention, in the first aspect of the present invention, a rotation ratio between the photosensitive drum and the rubbing roller is a non-integer multiple.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the rotation of the photosensitive drum is transmitted to the rubbing roller through a gear train.

  According to a fourth aspect of the present invention, there is provided a photosensitive drum that forms a latent image, a developing unit that develops the latent image formed on the photosensitive drum as a toner image, and a transfer unit that transfers the toner image onto a transfer material. The drum cleaning unit according to any one of claims 1 to 3, wherein the drum cleaning unit is an image forming apparatus including a drum cleaning unit including a rubbing roller that rotates in contact with the surface of the photosensitive drum. It is characterized by comprising a unit.

  According to the first aspect of the present invention, since the peripheral speed ratio of the rubbing roller to the photosensitive drum is set to 1 or less, the photosensitive drum is not rotated by the rubbing roller, and the photosensitive drum is rotated by the main motor. Since only the brake component acts on the rotation, smooth rotation of the photosensitive drum is realized, and the problem of jitter failure is solved.

  In addition, since the rotation fulcrum of the holding arm is arranged on the side where the frictional force between the photosensitive drum and the rubbing roller acts in the direction in which the rubbing roller bites into the photosensitive drum, adhesion of charged products or the like to the surface of the photosensitive drum If the amount of friction increases and the frictional resistance of the surface of the photosensitive drum increases, the pressure contact force of the rubbing roller to the photosensitive drum increases, and the polishing ability of the rubbing roller is enhanced. Objects and the like are reliably removed by the rubbing roller.

  According to the second aspect of the present invention, since the rotation ratio between the photosensitive drum and the rubbing roller is a non-integer multiple, the same surface of the rubbing roller does not polish the same surface of the photosensitive drum, and the surface of the photosensitive drum is The surface of the photosensitive drum is uniformly polished by the rubbing roller, and the adverse effect on the image is eliminated, and a high quality image can be stably obtained.

  According to the third aspect of the present invention, since the rotation of the photosensitive drum is transmitted to the rubbing roller via the gear train, the peripheral speed of the rubbing roller relative to the photosensitive drum is determined by the pitch circle diameter (number of teeth) of the gear train. The ratio can be easily set to 1 or less, and the rotation ratio between the photosensitive drum and the rubbing roller can be easily set to a non-integer multiple.

  According to the invention described in claim 4, in the image forming apparatus adopting the electrophotographic system, the effect described in any one of claims 1 to 3 can be obtained, and a high quality image can be obtained stably. .

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a side sectional view of a laser beam printer 1 as an embodiment of an image forming apparatus according to the present invention. The laser beam printer 1 conveys paper along a conveyance path L provided in the apparatus main body 1a. On the other hand, an image is formed on a sheet that is a transfer material based on image data transmitted from a terminal (not shown), and the transport path L passes through the apparatus main body 1a from the front to the rear (in FIG. 1). A horizontal portion L1 extending substantially horizontally (from right to left) and a vertical portion L2 rising substantially vertically from the end of the horizontal portion L1 are formed in a substantially L shape in side view.

  Further, the laser beam printer 1 includes a paper feeding unit 2 provided at a lower portion of the apparatus main body 1a, an image forming unit 3 provided at a substantially central portion in the apparatus main body 1a above the paper feeding unit 2, The fixing device 4 disposed behind the image forming unit 3, the concave paper discharge unit 5 provided on the upper surface of the apparatus main body 1 a above the fixing device 4, the horizontal part L 1 of the transport path L and the paper feed A switchback portion 6 provided between the cassette 7 and the cassette 7 is provided.

  The paper feed unit 2 stores paper and feeds the paper toward the image forming unit 3 and includes the paper feed cassette 7 and the manual feed tray 8.

  Here, the paper feed cassette 7 has a rectangular box shape with an open upper surface, and fulfills the function of feeding sheets (not shown) stacked and accommodated therein one by one. As shown, in the state where it is mounted in the apparatus main body 1a, it is located below the horizontal portion L1 of the transport path L as shown.

  The paper feed cassette 7 includes a lift plate 9 that contacts and separates from the inner bottom surface, a lift plate 10 that moves up and down in conjunction with the contact and separation operation of the lift plate 9, and a front end of the lift plate 9 (paper feeding direction). A lift drive shaft 11 that is attached in the vicinity of the downstream end) and rotates the lift plate 9 in the direction of the arrow in FIG. 1 and a shaft that can rotate in the vicinity of the rear end (upstream end in the sheet feeding direction) of the lift plate 10. A supporting shaft 12 is provided.

  Further, the paper feed unit 2 includes a pickup roller 13 that takes out the paper in the paper feed cassette 7 one by one, a feed roller 14 that sends out the taken paper to the horizontal part L1 of the transport path L, a retard roller 15, and a plurality of rollers. Pick-up rollers 16, 17, and 18, and a pickup that picks up the paper placed on the manual feed tray 8 in addition to the registration rollers 19 that supply the image forming unit 3 to the image forming unit 3 at a predetermined timing after temporarily waiting the fed paper. A roller 20 is provided.

  The image forming unit 3 forms an image on a sheet supplied from the sheet feeding unit 2, and is an image carrier that is rotatably disposed at a substantially central portion in the front-rear direction of the horizontal portion L 1 of the transport path L. Photosensitive drum 21, primary charger 22, developing device 23, transfer roller 24 and cleaning unit 25 according to the present invention, laser scanner unit (LSU) 26 disposed above them, toner A hopper 27 and the like are provided. In the present embodiment, the photosensitive drum 21 uses an amorphous silicon (a-Si) photosensitive member.

  The fixing device 4 is for fixing the toner image transferred onto the paper in the image forming unit 3 to the paper, and includes a heating roller 28 and a pressure roller 29 that rotate while being pressed against each other. Yes.

  Further, the paper discharge unit 5 is for discharging the paper on which the toner image has been fixed in the fixing unit 4 to the outside of the apparatus main body 1a, and is provided in the middle of the vertical portion L2 of the transport path L. And a paper discharge roller 31 provided at the end of the vertical portion L2 and a paper discharge tray 32 for stacking paper discharged outside the apparatus main body 1a.

  The switchback unit 6 is used when an image is formed on both sides of a sheet. The switchback unit 6 is provided at another position on another conveyance path L ′ disposed below the vertical portion L1 of the conveyance path L and its proper position. A plurality of transport rollers 33 are provided.

  Next, an image forming operation of the laser beam printer 1 having the above configuration will be described.

  For example, when a print start signal is transmitted to the laser beam printer 1 from a terminal such as a personal computer (personal computer), in the image forming unit 3, the photosensitive drum 21 is driven in the direction indicated by the arrow (clockwise) in FIG. ) And the surface thereof is uniformly charged to a predetermined potential by the primary charger 22. When a laser beam based on the image data transmitted from the terminal is output from the laser scanner unit 26 and irradiated onto the photosensitive drum 21, an electrostatic latent image is formed on the photosensitive drum 21. Then, the electrostatic latent image on the photosensitive drum 21 is developed by the developing device 23 using toner as a developer to be visualized as a toner image.

  At the same time, in the paper feeding unit 5, for example, the sheets stored in the paper feeding cassette 7 are picked up one by one from the uppermost one by the pickup roller 13, and the feed roller 14, the retard roller 15, and the paper feeding rollers 16, 17. , 18 are sent to the horizontal portion L1 of the conveying path L, and after being temporarily put into a standby state by the registration roller 19, are supplied to the image forming portion 3 at a predetermined timing synchronized with the toner image on the photosensitive drum 21. . In the paper feed cassette 7, the lift plate 9 is rotated in a direction away from the inner bottom surface, thereby raising the elevating plate 10 to a predetermined height position corresponding to the number of sheets stacked thereon, The uppermost one of the sheets stacked on the elevating plate 10 is picked up by the pickup roller 13. Further, when an image is formed on the paper loaded on the manual feed tray 8, the paper is taken out one by one by the pickup roller 20, and sent to the horizontal portion L1 of the transport path L by the paper feed rollers 16 and 18. .

  In the image forming unit 3, the sheet supplied to the transfer nip between the photosensitive drum 21 and the transfer roller 24 is conveyed while being pressed against the photosensitive drum 21 by the transfer roller 24, thereby its surface (transfer surface). ) Is transferred to the toner image on the photosensitive drum 21. The sheet onto which the toner image has been transferred is conveyed to the fixing device 4, and is heated and pressed in the process of being sandwiched and conveyed between the heating roller 28 and the pressure roller 29 in the fixing device 4. Get fixed. Incidentally, the toner (transfer residual toner) remaining on the surface of the photosensitive drum 21 and the charged product after the transfer of the toner image onto the paper is removed by the drum cleaning unit 25.

  Thus, the sheet on which the toner image is fixed on the surface by the fixing device 4 is conveyed upward by the conveying roller 30 along the vertical portion L2 of the conveying path L, and is provided on the upper portion of the apparatus main body 1a by the paper discharge roller 31. The paper is discharged and stacked on the discharged paper discharge tray 32.

  The above is a series of operations when an image is formed on one side of a sheet. When an image is formed on both sides of a sheet, a sheet on which a toner image is fixed on one side by a fixing device 4 is conveyed by a conveyance roller 30. After the sheet is fed to the vertical portion L2 of the conveyance path L, the sheet is switched back by feeding the conveyance roller 30 in the reverse direction to be fed to another conveyance path L ′. Then, the paper is transported forward (to the right in FIG. 1) along the transport path L ′ by a plurality of transport rollers 33 provided in the transport path L ′, and the paper is transported by the paper feed rollers 16, 17, 18. When the sheet is fed again to the horizontal portion L1 of the conveyance path L, the front and back of the sheet are reversed, and thereafter, the toner image on the photosensitive drum 21 is transferred to the surface of the sheet (the other side on which no image is formed) by the same operation as described above. ) And the toner image is fixed on the paper in the fixing device 4, images are formed on both sides of the paper. The sheet on which images are formed on both sides in this way is conveyed upward along the vertical portion L2 of the conveyance path L by the conveyance roller 30 and is discharged to the discharge tray 32 by the discharge roller 31 as described above.

  Next, details of the drum cleaning unit 25 according to the present invention will be described with reference to FIGS.

  2 is a side sectional view of the drum cleaning unit according to the present invention, FIG. 3 is a partial perspective view showing the configuration of the driving system of the rubbing roller of the drum cleaning unit, and FIG. 4 is the configuration of the driving system of the rubbing roller. FIG.

  In the housing 34 of the drum cleaning unit 25 shown in FIG. 2, as shown in FIG. 3, a plate-shaped cleaning blade 35 that contacts the outer peripheral surface including the image area of the photosensitive drum 21, and the surface of the photosensitive drum 21. A rubbing roller 36 that contacts and rotates is housed.

The rubbing roller 36 is rotatably arranged along the length direction of the photosensitive drum 21, and both axial ends of the rotation shaft 37 are rotatably supported by the lower end portion of the holding arm 38 (see FIG. Shows only one holding arm 38). Here, each holding arm 38 is supported so as to be swingable in the vertical direction around a fulcrum O ₁ (see FIG. 4) which is an intermediate portion thereof, and is made of metal as a biasing means on both sides of its upper end portion. A coil spring 39 and a rectangular plate-like elastic body 40 are provided.

The coil spring 39, the direction it is intended to rotate in the counterclockwise direction in FIG. 4 the holding arm 38 around the fulcrum O _1, that is, the rubbing roller 36 is axially supported by the holding arm 38 of the photosensitive drum 21 It is biased in the direction of pressing against the outer peripheral surface. On the other hand, as shown in FIG. 2, the elastic body 40 is interposed between the holding arm 38 and the housing 34, and the urging force in the direction opposite to the urging force of the coil spring 39, that is, a rubbing roller. The biasing force in the direction of separating 36 from the outer peripheral surface of the photosensitive drum 21 is applied to the holding arm 38, and the spring constant thereof is set higher than that of the coil spring 39. The elastic body 40 is made of rubber or urethane foam having a higher rebound resilience than the surface material of the rubbing roller 36 (for example, urethane rubber or silicon rubber).

  On the other hand, a drum gear G1 is attached to one end of the photosensitive drum 21 in the axial direction, and a large-diameter side gear G2 of large and small different-diameter idle gears G2 and G3 meshed with the drum gear G1. is doing.

On the fulcrum O ₁ of the holding arm 38, large and small diameter fulcrum gears G4 and G5 are coaxially arranged, and the large-diameter side gear G4 meshes with the small-diameter side idle gear G3. Yes. The small-diameter side arm fulcrum gear G5 meshes with a rubbing roller gear G6 that is attached to the rotating shaft 37 of the rubbing roller 36. Here, in the present embodiment, the number of teeth of the gears G1, G2, G3, G4, G5, and G6 is set to 35, 14, 12, 16, 12, and 13, respectively.

Thus, when a rotational driving force from a main motor (not shown) as a driving source is transmitted to the drum gear G1, the photosensitive drum 21 is rotated clockwise (in the direction of arrow a in FIG. 4) at a predetermined speed (process speed). The rotation is increased and decelerated through the gears G2, G3, G4, G5 and G6 in order and transmitted to the rubbing roller 36. The rubbing roller 36 is counterclockwise at a predetermined speed (the arrow in FIG. 4). b direction) is driven to rotate, charge products of the NO _X or the like adhering to the outer peripheral surface of the photosensitive drum 21 is scraped off by the abrasive action of the rubbing roller 36. Incidentally, the toner (residual toner) remaining on the outer peripheral surface of the photosensitive drum 21 after the toner image transfer is scraped off by the cleaning blade 35.

  In this embodiment, since the number of teeth of the gears G1, G2, G3, G4, G5, and G6 is set as described above, the peripheral speed ratio of the rubbing roller 36 to the photosensitive drum 21 is 0.69 and 1 The photosensitive drum 21 is not driven to rotate by the rubbing roller 36, and the photosensitive drum 21 is driven to rotate by the main motor, and only the brake component acts on the rotation. The rotation is realized and the problem of jitter failure is solved.

  In this embodiment, the rotation ratio between the photosensitive drum 21 and the rubbing roller 36 is 1: 1.73, which is a non-integer multiple. Therefore, the same surface of the rubbing roller 36 is the same surface of the photosensitive drum 21. The surface of the photosensitive drum 21 is evenly polished by the rubbing roller 36 so that the surface state of the photosensitive drum 21 is uniform over the entire circumference, and the adverse effect on the image is eliminated. Can be obtained stably.

  Thus, in this embodiment, the rotation of the photosensitive drum 21 is transmitted to the rubbing roller 36 via the gear trains G1 to G6, so that the sliding is performed according to the pitch circle diameter (number of teeth) of the gear trains G1 to G6. The peripheral speed ratio of the rubbing roller 36 to the photosensitive drum 21 can be easily set to 1 or less, and the rotation ratio of the photosensitive drum 21 and the rubbing roller 36 can be easily set to a non-integer multiple.

Incidentally, as shown in FIG. 4, the drum gear G1 (photosensitive drum 21) is rotationally driven in the clockwise direction (arrow a direction), and the rubbing roller gear G6 (rubbing roller 36) is rotated counterclockwise (arrow b direction). When driven, an upward frictional resistance force F is generated between the photosensitive drum 21 and the rubbing roller 36 in FIG. Therefore, it acts frictional resistance force F in the axial center O ₂ of the rubbing roller 36, in this embodiment, the fulcrum O ₁ of the holding arm 38, the shaft center O ₂ of the rubbing roller 36 in FIG. 4 And the straight line N ₁ connecting the fulcrum O ₁ of the holding arm 38 and the axial center O ₂ of the rubbing roller 36, the axial center O ₂ of the rubbing roller 36, and the axial center O of the photosensitive drum 21. _{Since the} angle θ formed by the straight line N ₂ connecting ₃ is larger than 90 ° (θ> 90 °), the distance between the fulcrum O ₁ of the holding arm 38 and the axial center O ₂ of the rubbing roller 36 is X When the component force of the frictional resistance force F (component force in the direction perpendicular to the straight line L ₁ ) is F ₁ , the rubbing roller 36 has the following formula:
M = F ₁ × X
Is applied to the rubbing roller 36 in the direction of biting into the photosensitive drum 21. As a result, when the adhesion amount of the charged product or the like on the surface of the photosensitive drum 21 increases and the frictional resistance force F on the surface of the photosensitive drum 21 increases, the pressure contact force of the rubbing roller 36 to the photosensitive drum 21 increases. The polishing ability of the rubbing roller 36 is enhanced, and the charged products and the like adhering to the surface of the photosensitive drum 21 are surely removed by the rubbing roller 36.

  In the above, the embodiment in which the present invention is applied to a laser beam printer has been described. However, the present invention can be similarly applied to other arbitrary image forming apparatuses such as a copying machine and a facsimile machine in addition to a printer. Of course.

1 is a side sectional view of an image forming apparatus (laser beam printer) according to the present invention. It is a sectional side view of the drum cleaning unit which concerns on this invention. It is a fragmentary perspective view which shows the structure of the drive system of the rubbing roller of the drum cleaning unit which concerns on this invention. It is a side view which shows the structure of the drive system of the rubbing roller of the drum cleaning unit which concerns on this invention.

Explanation of symbols

1 Laser beam printer (image forming device)
DESCRIPTION OF SYMBOLS 1a Device main body 2 Paper feed part 3 Image forming part 4 Fixing device 5 Paper discharge part 6 Switchback part 7 Paper feed tray 8 Manual feed tray 9 Lift plate 10 Lifting plate 11 Lift drive shaft 12 Shaft 13 Pickup roller 14 Feed roller 15 Retard roller 16 to 18 Paper feed roller 19 Registration roller 20 Pickup roller 21 Photosensitive drum 22 Primary charger 23 Developing device 24 Transfer roller 25 Drum cleaning unit 26 Laser scanner unit (LSU)
27 Toner hopper 28 Heating roller (heating member)
29 Pressure roller (pressure member)
30 Conveying roller 31 Discharging roller 32 Discharging tray 33 Conveying roller 34 Housing 35 Cleaning blade 36 Rub roller 37 Rub roller rotating shaft 38 Coil spring 40 Elastic body F Friction resistance force F ₁ Friction resistance force L, L 'Conveying path L1 Conveying path horizontal part L2 Conveying path vertical part O ₁ Holding arm fulcrum O ₂ Abrasion roller shaft center O ₃ Photosensitive drum shaft center G1 Drum gear G2, G3 Idle gear G4, G5 Arm fulcrum gear G6 rubbing roller gear

Claims (4)

A rubbing roller that rotates in contact with the surface of the photosensitive drum is provided, and a holding arm that rotatably holds the rubbing roller is pivotally supported to thereby rotate the rubbing roller with respect to the photosensitive drum. In the drum cleaning unit that can be contacted and separated,
The circumferential speed ratio of the rubbing roller to the photosensitive drum is set to less than 1, and the rubbing roller bites into the photosensitive drum by the frictional force of the photosensitive drum and the rubbing roller with respect to the rotation fulcrum of the holding arm. The drum cleaning unit is arranged on the side where the force acts on the drum cleaning unit.   2. The drum cleaning unit according to claim 1, wherein a rotation ratio between the photosensitive drum and the rubbing roller is a non-integer multiple.   3. The drum cleaning unit according to claim 1, wherein the rotation of the photosensitive drum is transmitted to the rubbing roller via a gear train. A photosensitive drum that forms a latent image, a developing unit that develops the latent image formed on the photosensitive drum as a toner image, a transfer unit that transfers the toner image onto a transfer material, and a surface that contacts the surface of the photosensitive drum In the image forming apparatus configured to include a drum cleaning unit provided with a rotating rubbing roller,
An image forming apparatus comprising the drum cleaning unit according to claim 1.

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