JP2013011709A - Photosensitive drum and image forming apparatus including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photosensitive drum capable of being stably grounded over a long period of time while preventing an occurrence of abrasion and abnormal noise of a shaft.SOLUTION: The photosensitive drum includes a cylindrical photoreceptor, and a flange 21 fitted to an axial opening end thereof, is rotatably supported by a shaft 22 inserted through the flange 21, and is configured by bringing an earth terminal 23A of an earth plate spring 23 that is fixed to an inner end face of the flange 21 into slide contact with the shaft 22. A boss 21A in which the shaft 22 is inserted is projected from the inner end face of the flange 21, and is formed with a U-shaped guide groove 21c that encloses a slide contact part of the earth terminal 23A with the shaft 22 from the periphery. A conductive grease is stored in the U-shaped guide groove 21c.

Description

  The present invention relates to an optical scanning device that exposes and scans an image carrier such as a photosensitive drum, and an image forming apparatus such as a copying machine and a printer including the optical scanning device.

  In an image forming apparatus such as a copying machine or a printer that forms an image on a recording material such as paper by an electrophotographic method, a photosensitive drum whose surface is uniformly charged by a charger is exposed and scanned by an optical scanning device. An electrostatic latent image corresponding to the image information is formed. The electrostatic latent image formed on the photosensitive drum is developed by a developing device using toner as a developer to be visualized as a toner image, and the toner image is transferred onto a recording material. The recording material onto which the toner image has been transferred in this way is conveyed to a fixing device, heated and pressurized by the fixing device, and after being fixed on the toner image, is discharged out of the apparatus, thereby performing a series of image forming operations. Is completed.

  By the way, the photosensitive drum includes a cylindrical photosensitive member and a flange fitted to the opening end in the axial direction thereof, and is rotatably supported by a shaft inserted through the flange. Here, a photoconductive layer is formed on the outer surface of the photoconductor. Since this photoconductive layer must be grounded due to its function, a contact portion of a ground leaf spring fixed to the inner end face of the flange is provided. By making sliding contact with the shaft, the photoconductive layer is grounded from the ground plate spring to the main body frame through the shaft.

  When the said structure is employ | adopted, there exists a problem that abrasion generate | occur | produces in a shaft or an unpleasant noise generate | occur | produces by the sliding contact of the contact part of an earth leaf | plate spring, and a shaft.

  Therefore, Patent Document 1 proposes a configuration in which a small diameter portion is formed at a portion where the ground terminal of the shaft is in sliding contact, and a lubricant such as conductive grease is applied to the small diameter portion.

  In Patent Document 2, a grease guiding protrusion is formed on the inner end surface of the drum flange, and the conductive grease protruding from the sliding contact area between the ground terminal and the shaft is transferred to the sliding contact area by the grease guiding protrusion. A configuration for guiding is proposed.

JP-A-8-095428 Japanese Patent Laying-Open No. 2005-077421

  However, according to the configuration proposed in Patent Document 1, since the small-diameter portion is formed on the shaft, the height of the small-diameter portion (depth to which the lubricant is applied) is reduced due to the strength problem of the small-diameter portion of the shaft. Due to limitations, the amount of lubricant applied is limited.

  Further, according to the configuration proposed in Patent Document 2, the conductive grease that has escaped in the axial direction of the shaft does not return to the sliding contact region between the ground terminal and the shaft, and the conductive grease in the sliding contact region is insufficient. there is a possibility.

  The present invention has been made in view of the above problems, and a purpose thereof is to provide a photosensitive drum capable of stably performing grounding over a long period of time while preventing shaft wear and noise from occurring. An image forming apparatus is provided.

  In order to achieve the above object, the invention described in claim 1 includes a cylindrical photoreceptor and a flange fitted to the axially open end thereof, and is rotatably supported by a shaft inserted through the flange. In a photosensitive drum configured by sliding a ground terminal of a ground leaf spring fixed to the inner end surface of the flange in sliding contact with the shaft, a boss through which the shaft is inserted projects from the inner end surface of the flange, and the boss A U-shaped guide groove surrounding the sliding contact portion of the ground terminal with the shaft from the periphery is formed, and conductive grease is accommodated in the U-shaped guide groove.

  According to a second aspect of the present invention, in the first aspect of the present invention, a grease groove for storing conductive grease is formed in the vicinity of the sliding contact portion of the ground terminal of the shaft.

  An image forming apparatus according to a third aspect includes the photosensitive drum according to the first or second aspect.

  According to the first aspect of the present invention, since the U-shaped guide groove is formed in the boss protruding from the inner end face of the flange, the U-shaped guide groove does not affect the strength of the shaft. By increasing the depth, a large amount of conductive grease can be accommodated in the U-shaped guide groove. Further, since the U-shaped guide groove surrounds the sliding contact portion of the ground terminal with respect to the shaft from the periphery, the conductive grease accommodated in the U-shaped guide groove is difficult to escape in the axial direction. Therefore, a sufficient amount of conductive grease is held in the sliding contact portion between the ground terminal of the ground plate spring and the shaft, and the lubricating action of the conductive grease ensures that the shaft is worn and abnormal noise is generated. In addition to being prevented, grounding of the photoreceptor is stably performed over a long period of time by the conductive action of the conductive grease.

  According to the second aspect of the present invention, when the shaft is inserted into the flange, the conductive grease stored in the grease groove formed in the shaft is scraped out by the ground terminal of the ground plate spring, and the ground terminal and the shaft. Therefore, a sufficient amount of conductive grease is held in the sliding contact portion between the ground terminal of the ground plate spring and the shaft.

  According to the third aspect of the present invention, since the grounding of the photosensitive drum is stably performed over a long period of time, a high quality image can be stably obtained. Further, since the wear of the shaft that rotatably supports the photosensitive drum and the generation of abnormal noise are prevented, the durability of the image forming apparatus can be improved and the noise can be reduced.

1 is a cross-sectional view of an image forming apparatus according to the present invention. 1 is a cross-sectional perspective view of a main part of a photosensitive drum according to the present invention. FIG. 3 is a perspective view of a main part of the photosensitive drum according to the present invention. FIG. 3 is an exploded perspective view of a main part of the photosensitive drum according to the present invention.

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

[Image forming apparatus]
FIG. 1 is a longitudinal sectional view of an image forming apparatus according to the present invention. The illustrated image forming apparatus 1 is a laser printer, and an image forming unit 2 is disposed above the inside of the apparatus main body 1A. A sheet storage unit 3 is disposed in the lower half of the inside.

  The image forming unit 2 forms an image by an electrophotographic system, and includes a rotatable photosensitive drum 4, a charger 5, a developing device 6, a transfer roller 7, and a cleaning device disposed around the photosensitive drum 4. In addition to the device 8, the developing device 6 is provided with a toner hopper 9 for supplying toner as a developer. Next to the image forming unit 2, an optical scanning device (laser scanner unit (LSU)) 10 according to the present invention is arranged.

The paper storage unit 3 includes detachable upper and lower two-stage paper feed cassettes 11 and 12 in which a plurality of paper sheets are stacked and accommodated. 11 and 12 are provided with a pick roller 13 for sequentially taking out the papers from the upper one, a feed roller 14 for feeding out the taken paper one by one and a retard roller 15, respectively. Are arranged with a first transport path S1 from the paper storage section 3 to the image forming section 2 and a second transport path S2 from the image forming section 2 to the paper discharge tray 16, and in the first transport path S1 A registration roller 17 and the transfer roller 7 are provided, and a fixing device 18, a conveyance roller 19, and a paper discharge roller 20 are provided in the second conveyance path S2. The fixing device 18 includes a fixing roller 18a and a pressure roller 18b that rotate in a pressure contact state.

  Next, an image forming operation of the image forming apparatus 1 configured as described above will be described.

  When the image forming operation is started, in the image forming unit 2, the photosensitive drum 4 is rotationally driven in a direction indicated by an arrow (clockwise) in FIG. Uniformly charged. When a laser beam based on an electrical signal transmitted from a personal computer or the like is output from the optical scanning device 10 and the surface of the photosensitive drum 4 is exposed and scanned, an electrostatic latent image corresponding to image information is formed on the photosensitive drum 4. Is formed. The electrostatic latent image formed on the photosensitive drum 4 is developed by the developing device 6 using toner as a developer to be visualized as a toner image.

  By the way, when cassette feeding is performed, the paper stored in, for example, the upper paper feeding cassette 11 of the paper storage unit 3 is picked up from the uppermost one by the pick roller 13, and 1 by the feed roller 14 and the retard roller 15. Each sheet is separated and conveyed to the registration roller 17 through the first conveyance path S1. In the registration roller 17, after the paper is temporarily in a standby state, the paper is supplied to the image forming unit 2 at a predetermined timing synchronized with the toner image on the photosensitive drum 4.

  In the image forming unit 2, the sheet supplied to the transfer nip between the photosensitive drum 4 and the transfer roller 7 is conveyed while being pressed against the photosensitive drum 4 by the transfer roller 7, so that the surface of the sheet is exposed to the photosensitive drum. The toner image on 4 is transferred. Then, the sheet on which the toner image is transferred is conveyed to the fixing device 18 and heated and pressed in the process of passing through the fixing nip between the fixing roller 18a and the pressure roller 18b of the fixing device 18 to form the toner image. Get fixed. The toner remaining on the surface of the photosensitive drum 4 (transfer residual toner) after the transfer of the toner image onto the paper is removed by the cleaning device 8, and the photosensitive drum 4 whose surface has been cleaned is prepared for the next image forming operation.

  Thus, the sheet having the toner image fixed on the surface thereof by the fixing device 18 is transported toward the paper discharge roller 20 by the transport roller 19 through the second transport path S2, and is transported to the paper discharge tray 16 by the paper discharge roller 20. This completes a series of image forming operations.

[Photosensitive drum]
Next, a characteristic configuration of the photosensitive drum 4 according to the present invention will be described with reference to FIGS.

  2 is a cross-sectional perspective view of the main part of the photosensitive drum according to the present invention, FIG. 3 is a perspective view of the main part of the photosensitive drum, and FIG. 4 is an exploded perspective view of the main part of the photosensitive drum.

  The photosensitive drum 4 is configured by fitting a flange 21 (only one is shown in FIGS. 2 to 4) to the inner peripheral portion of the axially open end of the cylindrical photosensitive member 4A. Both shafts 22 are rotatably supported by shafts 22 inserted through both flanges 21, and both ends in the axial direction of the shafts 22 are fixed to a body frame (not shown) made of conductive metal (sheet metal).

  The photoreceptor 4A is formed by forming a photoconductive layer on the outer surface of a cylindrical base tube made of a conductive metal such as aluminum and coating the surface with an insulating protective film made of a transparent resin. .

  The flange 21 is integrally formed in a substantially cylindrical shape with an insulating resin, and a plurality (six in the illustrated example) of arcuate fittings are provided on the outer periphery of one end portion (inner end side end portion) in the axial direction. A piece 21a is formed. Then, as shown in FIG. 2, the flange 21 is fitted to one end in the axial direction of the photoconductor 4A by fitting the plurality of fitting pieces 21a to the inner periphery of the open end of the photoconductor 4A.

  Furthermore, a boss 21A is integrally formed at the center of the flange 21, and a circular shaft hole 21b through which the shaft 22 communicates is formed at the center of the boss 21A. Here, the boss 21A protrudes long in the axial direction on the inner end face of the flange 21, and U-shaped guide grooves 21c with one end cut out are formed at two opposite positions of the boss 21A. . Further, cylindrical fixing pins 21d are projected in the axial direction at four locations on the inner end face of the flange 21, and a gear 21e for receiving a driving force from a driving mechanism (not shown) is provided on the outer end face of the flange 21. Are integrally formed.

  By the way, a ground plate spring 23 made of a conductive metal plate having a spring property is fixed to the inner end face of the flange 21. The ground leaf spring 23 is obtained by punching a thin plate of copper, SUS, or the like into a substantially circular shape. As shown in FIG. 4, a large circular hole 23a is formed at the center thereof, and four surroundings are formed around it. A small circular hole 23b is formed. Further, locking claws 23c having pointed tips are provided projecting radially outward at six locations on the outer periphery of the ground leaf spring 23.

  Further, a belt-like ground terminal 23A extends obliquely inward (in the center) in the radial direction from two opposite locations on the outer periphery of the ground leaf spring 23, and its tip is bent in a V shape. The contact portion 23d is configured.

  Thus, the ground leaf spring 23 has the boss 21A of the flange 21 fitted in the circular hole 23a formed therein, and the fixing pin 21d protruding from the inner end face of the flange 21 is inserted into the four circular holes 23b. The fixing pin 21d is fixed to the inner end surface of the flange 21 by heat fusion or caulking. At this time, the two ground terminals 23 </ b> A of the ground plate spring 23 have contact portions 23 d at their tips facing the inside of the U-shaped guide groove 21 c formed in the boss 21 </ b> A of the flange 21. The six latching claws 23c projecting into the inner surface of the photosensitive member 4A are bitten into the inner peripheral surface of the elementary tube, and thereby the conduction between the photosensitive member 4A and the ground plate spring 23 is established.

  By the way, the shaft 22 made of a conductive metal is passed through the shaft hole 21b formed in the boss 21A of the flange 21 as shown in FIGS. 2 and 3, and thus the shaft 22 passes through the boss 21A of the flange 21. 2 and 3, the contact portion 23d provided at the tip of the two ground terminals 23A of the ground leaf spring 23 is in sliding contact with the outer periphery of the shaft 22, as shown in FIGS. The periphery of the flange 21 is covered with a U-shaped guide groove 21c formed in the boss 21A of the flange 21. Here, conductive grease is accommodated in each of the two U-shaped guide grooves 21 c formed on the boss 21 </ b> A of the flange 21. Further, a small-diameter grease groove 22a is formed over the entire circumference of a part of the outer periphery of the shaft 22 (a part close to the sliding contact portion of the contact portion 23d of the ground terminal 23A with the shaft 22). Conductive grease is stored in 22a.

  The photosensitive drum 4 having the ground structure as described above rotates around the shaft 22 when the driving force is input from a driving mechanism (not shown) to the gear 21e formed on the one flange 21, and the electrophotographic process. However, the rotation of the photosensitive drum 4 causes the ground leaf spring 23 to rotate together, and the contact portions 23 d of the two ground terminals 23 </ b> A are in sliding contact with the outer periphery of the shaft 22. At this time, since the conductive grease is accommodated in the U-shaped guide groove 21c formed in the boss 21A of the flange 21, as described above, the contact point of the ground terminal 21A surrounded by the U-shaped guide groove 21c. Conductive grease is held in the sliding contact portion of the portion 21d with the shaft 22, and the lubricating action of the conductive grease reliably prevents the shaft 22 from being worn and generating abnormal noise. Further, the photoconductive layer of the photoreceptor 4 is securely grounded by the conductive action of the conductive grease. That is, the charge of the photoconductive layer of the photoreceptor 4A is transmitted from the ground leaf spring 23 to the main body frame (not shown) through the conductive grease and the shaft 22, and finally discharged to the ground.

  As described above, in the present embodiment, since the U-shaped guide groove 21c is formed in the boss 21A protruding from the inner end face of the flange 21, the U-shaped guide groove 21c does not affect the strength of the shaft 22, By increasing the depth of the U-shaped guide groove 21c, a large amount of conductive grease can be accommodated in the U-shaped guide groove 21c. Further, since the U-shaped guide groove 21c surrounds the sliding contact portion of the contact portion 23d of the ground terminal 23A to the shaft 22 from the periphery, the conductive grease accommodated in the U-shaped guide groove 21c is difficult to escape in the axial direction. For this reason, a sufficient amount of conductive grease is held at the sliding contact portion between the ground terminal 23A of the ground plate spring 23 and the shaft 22, and the lubrication action of the conductive grease causes the shaft 22 to be worn or abnormal. Occurrence is reliably prevented, and grounding of the photoreceptor 4A is stably performed over a long period of time by the conductive action of the conductive grease.

  In the present embodiment, when the shaft 22 is inserted into the flange 21, the conductive grease stored in the grease groove 22 a formed in the shaft 22 is scraped out by the ground terminal 23 </ b> A of the ground plate spring 23. Since it is supplied to the sliding contact portion between the ground terminal 23 </ b> A and the shaft 22, a sufficient amount of conductive grease is held at the sliding contact portion between the ground terminal 23 </ b> A and the shaft 22 of the ground leaf spring 23. An effect that a sufficient amount of conductive grease is held at the sliding contact portion between the ground terminal 23A and the shaft 22 is obtained.

  As described above, since the grounding of the photosensitive drum 4 is stably performed over a long period of time, a high-quality image can be stably obtained in the image forming apparatus 1 shown in FIG. 1, and the photosensitive drum 4 can be freely rotated. Therefore, the wear of the shaft 22 that is supported and the generation of abnormal noise are prevented, so that the durability of the image forming apparatus 1 is improved and the noise is reduced.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 1A Image forming apparatus main body 2 Image forming part 3 Paper storage part 4 Photosensitive drum 4A Photoreceptor 5 Charger 6 Developing device 7 Transfer roller 8 Cleaning device 9 Toner hopper 10 Optical scanning device 11, 12 Paper feed cassette 13 Pick Roller 14 Feed roller 15 Retard roller 16 Discharge tray 17 Registration roller 18 Fixing device 18a Fixing roller 18b Pressure roller 19 Conveying roller 20 Discharge roller 21 Flange 21A Flange boss 21a Flange fitting piece 21b Flange shaft hole 21c Boss U-shaped guide groove 21d Flange fixing pin 21e Flange gear 22 Shaft 22a Shaft grease groove 23 Ground plate spring 23A Ground plate spring ground terminal 23a Ground plate spring circular hole 23b Ground plate bar Circular hole 23c earth plate contact portion S1 first conveyance path S2 second conveying path claws 23d earth terminal of spring

Claims (3)

In order to achieve the above object, the invention described in claim 1 includes a cylindrical photoreceptor and a flange fitted to the axially open end thereof, and is rotatably supported by a shaft inserted through the flange. In the photosensitive drum constituted by sliding the ground terminal of the ground leaf spring fixed to the inner end surface of the flange to the shaft,
A boss through which the shaft is inserted protrudes from the inner end face of the flange, and a U-shaped guide groove is formed around the slidable contact portion of the ground terminal with the shaft, and the U-shaped guide groove is formed in the boss. A photosensitive drum containing conductive grease.   2. The photosensitive drum according to claim 1, wherein a grease groove for storing conductive grease is formed in the vicinity of a sliding contact portion of the ground terminal of the shaft. An image forming apparatus comprising the photosensitive drum according to claim 1.

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