JP2009145633A - Drum unit and image forming apparatus including the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drum unit wherein: the number of components can be reduced; the accuracy of a drive train can be improved; power transmission can be smoothly performed from a photoreceptor drum to a cleaning roller; and easiness of assembling a charging unit to a drum unit body can be improved. <P>SOLUTION: The charging unit 40 includes: a charging roller 3a that rotates while abutting on the photoreceptor drum 2a; and a cleaning roller 41 for cleaning the charging roller 3a. In the drum unit 30, the charging unit 40 is configured to be detachable; and the rotation of the photoreceptor drum 2a is transmitted to the cleaning roller 41 through a drum flange gear 34, an idle gear 35 and an cleaning roller-driving gear 44 to rotate the cleaning roller 41. A shaft 33a for rotatably supporting the idle gear 35 is integrally formed on a bearing bush 33 for rotatably supporting the photoreceptor drum 2a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a drum unit in which a charging unit is detachably mounted and an image forming apparatus including the drum unit.

  In an image forming apparatus such as a copying machine or a printer that forms an image on a sheet by electrophotography, a photosensitive drum as an image carrier is uniformly charged by a charging means such as a charging roller, and is then placed on the photosensitive drum. An electrostatic latent image is formed on the photosensitive drum by irradiation with laser light or the like corresponding to the image information. The electrostatic latent image is visualized as a toner image by a developing device, the toner image is transferred onto a sheet by a transfer unit, and the sheet on which the toner image is transferred is conveyed to a fixing device. In the fixing device, the toner image is fixed on the sheet by heat and pressure, and the sheet on which the toner image has been fixed is discharged onto a discharge tray outside the apparatus, and a series of image forming operations is completed.

  By the way, in the image forming apparatus, the photosensitive drum and the charging roller are unitized as a drum unit, the drum unit can be attached to and detached from the apparatus main body, and the charging roller and the cleaning roller for cleaning the unit are unitized as a charging unit. A charging unit that is detachable from a drum unit body is known.

Such a drum unit employs a drive system in which the rotation of the photosensitive drum is transmitted to the cleaning roller through the drum gear, the idle gear, and the cleaning roller driving gear to rotate the cleaning roller.
JP 2001-249604 A Japanese Patent Laid-Open No. 7-077917

  However, in the conventional drum unit that employs the above-described drive system, the shaft for rotatably supporting the idle gear is provided in an independent dedicated member, so that the number of parts increases and the drum gear, the idle gear, and the cleaning roller drive gear are mutually connected. Error in the position accuracy of the motor, and not only the power from the photosensitive drum to the cleaning roller is smoothly transmitted, but also when the charging unit is incorporated into the drum unit body, the cleaning roller drive gear is not meshed with the idle gear well. There was a possibility.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and the object of the present invention is to reduce the number of parts and improve the accuracy of the drive train, smoothly transmit power from the photosensitive drum to the cleaning roller, and the drum unit body of the charging unit. An object of the present invention is to provide a drum unit capable of improving the ease of incorporation into an image forming apparatus and an image forming apparatus including the drum unit.

  In order to achieve the above object, according to the first aspect of the present invention, a charging unit having a charging roller rotating in contact with the photosensitive drum and a cleaning roller for cleaning the charging roller is detachable, and the photosensitive drum is rotated. In a drum unit that is transmitted to the cleaning roller through a drum gear, an idle gear, and a cleaning roller driving gear to rotationally drive the cleaning roller, the idle gear is rotatably supported by a bearing bush that rotatably supports the photosensitive drum. The shaft is integrally formed.

  An image forming apparatus according to a second aspect includes the drum unit according to the first aspect.

  According to the present invention, since the shaft for supporting the idle gear so as to be rotatable is integrally formed with the bearing bush for rotatably supporting the photosensitive drum, the number of parts can be reduced, and the structure can be simplified and the cost can be reduced. The positional accuracy between the drum gear, the idle gear, and the cleaning roller drive gear is improved, and smooth power transmission from the photosensitive drum to the cleaning roller is realized. Further, when the charging unit is assembled into the drum unit main body, the cleaning roller driving gear always meshes smoothly with the idle gear remaining on the drum unit main body side, so that the charging unit can be easily incorporated into the drum unit main body.

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

  FIG. 1 is a perspective view of a color laser printer as an embodiment of an image forming apparatus according to the present invention, FIG. 2 is a cross-sectional view showing the internal structure of the color laser printer, and the illustrated color laser printer is shown in FIG. As shown, a rectangular box-shaped apparatus main body 100 is provided, and a front cover 24 that is opened and closed during jam processing is provided on the front surface of the apparatus main body 100, and a paper discharge tray 21 is provided above the apparatus main body 100. Can be opened and closed.

  Next, the internal structure of the color laser printer will be described with reference to FIG. 2. A magenta image forming unit 1M, a cyan image forming unit 1C, a yellow image forming unit 1Y, Black image forming units 1K are arranged in tandem at regular intervals.

  Each of the image forming units 1M, 1C, 1Y, and 1K is provided with photosensitive drums 2a, 2b, 2c, and 2d, and charging rollers 3a, 3b, 3c, and 3d are disposed around the photosensitive drums 2a to 2d. 3d, developing devices 4a, 4b, 4c, 4d, transfer rollers 5a, 5b, 5c, 5d and drum cleaning devices 6a, 6b, 6c, 6d are arranged, respectively.

  Thus, in the color laser printer according to the present embodiment, each of the photosensitive drums 2a to 2d and the charging rollers 3a, 3b, 3c, and 3d in each of the image forming units 1M, 1C, 1Y, and 1K is as described below. Each drum unit 30 is unitized as a drum unit 30 (see FIG. 3), and each drum unit 30 can be attached to and detached from the apparatus main body 100.

  The photosensitive drums 2a to 2d are drum-shaped photosensitive members, and are driven to rotate at a predetermined process speed in a direction indicated by an arrow (clockwise) by a variable speed stepping motor (not shown). The charging rollers 3a to 3d uniformly charge the surfaces of the photosensitive drums 2a to 2d to a predetermined potential by a charging bias applied from a charging bias power source (not shown).

  Further, the developing devices 4a to 4d contain magenta (M) toner, cyan (C) toner, yellow (Y) toner, and black (K) toner, respectively, and are formed on the photosensitive drums 2a to 2d. In addition, the toner of each color is attached to each electrostatic latent image to visualize each electrostatic latent image as a toner image of each color.

  The transfer rollers 5a to 5d are arranged so as to be able to contact the photosensitive drums 2a to 2d via the intermediate transfer belt 7 in the respective primary transfer portions. Here, the intermediate transfer belt 7 is stretched between the secondary transfer counter roller 8 and the tension roller 9 and is disposed on the upper surface side of each of the photosensitive drums 2a to 2d. The roller 8 is disposed so as to be in contact with the secondary transfer roller 10 via the intermediate transfer belt 7 in the secondary transfer portion. A belt cleaning device 11 is provided in the vicinity of the tension roller 9.

  Incidentally, toner containers 12a, 12b, 12c, and 12d for supplying toner to the developing devices 4a to 4d are arranged in a line above the image forming units 1M, 1C, 1Y, and 1K in the apparatus main body 100. It is installed.

  In addition, a laser scanner unit (LSU) 13 is disposed below the image forming units 1M, 1C, 1Y, and 1K in the apparatus main body 100, and a paper feed cassette 14 is detachably attached to the bottom of the main body 100 below the image forming units. is set up. A plurality of sheets (not shown) are stacked and accommodated in the paper feed cassette 14, and a pickup roller 15 for taking out the paper one by one from the paper feed cassette 14 is taken out in the vicinity of the paper feed cassette 14. A feed roller 16 and a retard roller 17 are provided for feeding the fed paper to the transport path L.

  The conveyance path L extending in the vertical direction on the side of the apparatus main body 100 includes a conveyance roller pair 18 that conveys the sheet, and the secondary transfer counter roller 8 and the second transfer opposing roller 8 at a predetermined timing after the sheet is temporarily held. A registration roller pair 19 is provided to be supplied to the secondary transfer portion which is a contact portion with the next transfer roller 10. Next to the conveyance path L, another conveyance path L ′ used for forming an image on both sides of the sheet is formed, and a plurality of conveyance roller pairs 20 are appropriate for this conveyance path L ′. Are provided at regular intervals.

  By the way, the conveyance path L arranged in the vertical direction on one side in the apparatus main body 100 extends to the paper discharge tray 21 provided on the upper surface of the apparatus main body 100, and the fixing device 22 and the discharge path are in the middle. A paper roller pair 23 is provided.

  Next, an image forming operation by the color laser printer having the above configuration will be described with reference to FIG.

  When an image formation start signal is issued, the photosensitive drums 2a to 2d are driven to rotate at a predetermined process speed in the direction of the arrow (clockwise) in FIG. 2 in each of the image forming units 1M, 1C, 1Y, and 1K. The drums 2a to 2d are uniformly charged by the charging rollers 3a to 3d. The laser scanner unit 13 emits a laser beam modulated by a color image signal for each color, irradiates the surface of each photosensitive drum 2a to 2d with the laser beam, and each color is applied to each photosensitive drum 2a to 2d. An electrostatic latent image corresponding to the color image signal is formed.

  First, magenta toner is attached to the electrostatic latent image formed on the photosensitive drum 2a of the magenta image forming unit 1M by the developing device 4a to which a developing bias having the same polarity as the charged polarity of the photosensitive drum 2a is applied. The electrostatic latent image is visualized as a magenta toner image. This magenta toner image is transferred to the primary transfer portion (transfer nip portion) between the photosensitive drum 2a and the transfer roller 5a by the action of the transfer roller 5a to which a primary transfer bias having a polarity opposite to that of the toner is applied. Primary transfer is performed on the intermediate transfer belt 7 which is rotationally driven in the direction.

  The intermediate transfer belt 7 on which the magenta toner image has been primarily transferred as described above moves to the next cyan image forming unit 1C. In the cyan image forming unit 1C as well, the cyan toner image formed on the photosensitive drum 2b is transferred to the magenta toner image on the intermediate transfer belt 7 in the primary transfer portion in the same manner as described above.

  Similarly, yellow and black toners respectively formed on the photosensitive drums 2c and 2d of the yellow and black image forming units 1Y and 1K on the magenta and cyan toner images superimposed and transferred on the intermediate transfer belt 7, respectively. The images are sequentially superimposed at each primary transfer portion, and a full-color toner image is formed on the intermediate transfer belt 7. The transfer residual toner which is not transferred onto the intermediate transfer belt 7 and remains on the photosensitive drums 2a to 2d is removed by the drum cleaning devices 6a to 6d, and the photosensitive drums 2a to 2d are prepared for the next image formation. It is done.

  Then, the pickup from the paper feed cassette 14 is performed in accordance with the timing at which the front end of the full color toner image on the intermediate transfer belt 7 reaches the secondary transfer portion (transfer nip portion) between the secondary transfer counter roller 8 and the secondary transfer roller 10. The sheet fed to the conveyance path L by the roller 15, the feed roller 16 and the retard roller 17 is conveyed to the secondary transfer unit by the registration roller pair 19. Then, a full-color toner image is collectively transferred from the intermediate transfer belt 7 to the sheet conveyed to the secondary transfer unit by the secondary transfer roller 10 to which a secondary transfer bias having a polarity opposite to that of the toner is applied. .

  Thus, the sheet on which the full-color toner image has been transferred is conveyed to the fixing device 22, and the sheet on which the full-color toner image has been fixed by being heated and pressurized and thermally fixed on the surface of the sheet. Then, the paper is discharged onto the paper discharge tray 21 by the paper discharge roller pair 23 to complete a series of image forming operations. The transfer residual toner that is not transferred onto the sheet and remains on the intermediate transfer belt 7 is removed by the belt cleaning device 11, and the intermediate transfer belt 7 is prepared for the next image formation.

  Next, details of the configuration of the drum unit according to the present invention will be described with reference to FIGS. The color laser printer shown in FIGS. 1 and 2 is provided with four drum units 30. Since these drum units 30 have the same configuration, only the magenta drum unit 30 will be described below.

  3 is a perspective view of the drum unit, FIG. 4 is a partial perspective view of the end of the drum unit, FIG. 5 is a partial perspective view showing the configuration of the cleaning roller drive system by removing the frame at the end of the drum unit, and FIG. 7 is a perspective view of the charging unit, FIG. 8 is an enlarged detail view of part A of FIG. 7, FIG. 9 is a perspective view of the drum unit main body with the charging unit removed, and FIG. 10 shows a state in which the charging unit is incorporated in the drum unit main body. It is a fragmentary perspective view.

  As shown in FIG. 9, the drum unit 30 shown in FIG. 3 is configured by detachably mounting the charging unit 40 shown in FIG. 7 on a drum unit main body 31 including the photosensitive drum 2a. Here, as shown in FIG. 9, the drum unit main body 31 is configured to rotatably support the photosensitive drum 2a by a frame 32, and a space for accommodating the charging unit 40 is provided below the photosensitive drum 2a. The frame 32 is formed with a substantially rectangular insertion port 32a for inserting the charging unit 40 in the axial direction of the photosensitive drum 2a (the arrow direction in FIG. 9).

  Incidentally, as shown in FIG. 5, both ends of the photosensitive drum 2a in the axial direction are supported by resin bearing bushes 33 (only one is shown in FIG. 5). As shown in FIGS. A drum flange gear 34 is bound to one end (the left end in the figure) of the drum 2a, and a drum gear 37 is bound to the outside thereof.

  On the other hand, as shown in FIG. 7, the charging unit 40 rotates a charging roller 3a, which rotates in contact with the photosensitive drum 2a, and a cleaning roller 41 for cleaning the charging roller 3a in parallel with each other on a frame 42. As shown in FIG. 8, a cleaning roller drive gear 44 is attached to one end of the rotating shaft 43 of the cleaning roller 41 (left end in FIG. 8). The cleaning roller 41 is configured to have a weak rotational transmission force such as a brush, so that the charging roller 3a is not removed from the driven rotation of the photosensitive drum 2a.

  Thus, as shown in FIG. 5, the drum gear 34 attached to the end of the photosensitive drum 2a meshes with the cleaning roller drive gear 44 via the idle gear 35. Then, as shown in FIG. 6, a holding bracket 33A is formed integrally with the bearing bush 33, and a shaft 33a for rotatably supporting the idle gear 35 is integrally projected from the holding bracket 33A. . Accordingly, the idle gear 35 is rotatably supported by a shaft 33a formed integrally with a resin bearing bush 33 that rotatably supports the photosensitive drum 2a. As shown in FIG. These parts remain on the drum unit main body 31 side even after being removed from the drum unit main body 31. 3 to 5, reference numeral 36 denotes a gear cover.

  In the drum unit 30 having the above configuration, when the rotational power of a motor (not shown) is input to the drum gear 37, the photosensitive drum 2a is rotated at a predetermined speed, and the charging roller 3a that contacts the photosensitive drum 2a is provided. Following rotation, the photosensitive drum 2a is uniformly charged to a predetermined potential. At the same time, the rotation of the photosensitive drum 2a is transmitted from the drum flange gear 34 through the idle gear 35 to the cleaning roller drive gear 44, whereby the cleaning roller 41 is driven to rotate, and the charging roller 3a that contacts the cleaning roller 41. The surface is cleaned by the cleaning roller 41, and high charging performance is maintained.

  As described above, in the present embodiment, the shaft 33a for rotatably supporting the idle gear 35 is integrally formed with the bearing bush 33 for rotatably supporting the photosensitive drum 2a. Therefore, the number of parts is reduced. In addition to simplification and cost reduction, the positional accuracy between the drum flange gear 34, the idle gear 35, and the cleaning roller drive gear 44 is improved, and smooth power transmission from the photosensitive drum 2a to the cleaning roller 41 is realized. An effect is obtained.

  The charging unit 40 shown in FIG. 7 is attached to and detached from the drum unit main body 31 shown in FIG. 9 as described above, but the charging unit 40 once detached from the drum unit main body 31 is the drum unit main body 31 shown in FIG. This is inserted into the drum unit main body 31 through the opening 32 a formed in the frame 32 in the direction of the arrow shown in the figure. FIG. 10 shows a state in the middle of assembling the charging unit 40 into the drum unit main body 31.

  Thus, in the present embodiment, the shaft 33a that rotatably supports the idle gear 35 is formed integrally with the bearing bush 33 as described above, so that the drum gear 34, the idle gear 35, and the cleaning roller drive gear 44 are separated. As a result of the mutual positional accuracy being improved, when the charging unit 40 is assembled into the drum unit main body 31, the cleaning roller drive gear 44 always meshes smoothly with the idle gear 35 remaining on the drum unit main body 31 side. The ease of incorporation into the drum unit main body 31 is improved.

  Although the present invention has been described with respect to the embodiment in which the present invention is applied to a color laser printer and a drum unit provided therein, the present invention is similarly applied to a monochrome image forming apparatus and a drum unit provided therein. Of course, it is possible.

1 is a perspective view of a color laser printer according to the present invention. It is sectional drawing which shows the internal structure of the color laser printer which concerns on this invention. It is a perspective view of the drum unit concerning the present invention. It is a fragmentary perspective view of the drum unit end part concerning the present invention. It is a fragmentary perspective view which removes the flame | frame of the drum unit end part which concerns on this invention, and shows the structure of a cleaning roller drive system. It is a perspective view of a bearing bush. It is a perspective view of the charging unit of the drum unit according to the present invention. It is the A section enlarged detail drawing of FIG. It is a perspective view of the drum unit main body from which the charging unit is removed. It is a fragmentary perspective view which shows the state which incorporates a charging unit in a drum unit main body.

Explanation of symbols

1M Magenta image forming unit 1C Cyan image forming unit 1Y Yellow image forming unit 1K Black image forming unit 2a to 2d Photosensitive drum 3a to 3d Charging roller 4a to 4d Developing device 5a to 5d Transfer roller 6a to 6d Drum cleaning device 7 Intermediate transfer belt 8 Secondary transfer counter roller 9 Tension roller 10 Secondary transfer roller 11 Belt cleaning device 12a to 12d Toner container 13 Laser scanner unit (LSU)
DESCRIPTION OF SYMBOLS 14 Paper feed cassette 15 Pickup roller 16 Feed roller 17 Retard roller 18 Conveyance roller pair 19 Registration roller pair 20 Conveyance roller pair 21 Paper discharge tray 22 Fixing device 23 Paper discharge roller pair 24 Front cover 30 Drum unit 31 Drum unit main body 32 Drum unit frame 32a Frame opening 33 Bearing bush 33A Bearing bush holding bracket 33a Bearing bush shaft 34 Drum flange gear 35 Idle gear 36 Gear cover 37 Drum gear 40 Charging unit 41 Cleaning roller 42 Charging unit frame 43 Cleaning roller rotating shaft 44 Cleaning roller drive Gear 100 Image forming apparatus body L, L 'Conveyance path

Claims (2)

A charging unit including a charging roller that rotates in contact with the photosensitive drum and a cleaning roller that cleans the charging roller is detachable, and the photosensitive drum rotates through the drum gear, the idle gear, and the cleaning roller driving gear to the cleaning roller. In the drum unit that transmits and rotationally drives the cleaning roller,
A drum unit, wherein a shaft for rotatably supporting the idle gear is integrally formed with a bearing bush for rotatably supporting the photosensitive drum. An image forming apparatus comprising the drum unit according to claim 1.

Images