JP2013125250A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of efficiently cooling a photoreceptor drum by an air flow and effectively suppressing toner contamination by releasing toner to the inside or outside of the device together with an air flow with a simple and space-saving configuration.SOLUTION: A slit-shaped ventilation opening 51 is formed over a cleaning device 17 in a unit housing 40a and a second ventilation opening 53 is formed in a charging housing 15a. A partition member 55 is attached to the surface facing a cleaning blade 47 in the charging g housing 15a. The air flow flowing into the charging housing 15a through the first ventilation opening 51 and the second ventilation opening 53 flows downward in the charging housing 15a and cools the surface of a photoreceptor drum 14 and then is discharged to the downstream side in the rotation direction of the photoreceptor drum 14. The air flow moving towards the direction of the cleaning blade 47 is blocked by the partition member 55.

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using an electrophotographic method, and more particularly to a cooling mechanism for a photoconductor as an image carrier.

  In recent years, as the process speed of an image forming apparatus is increased, the temperature of devices and members inside the apparatus tends to increase. In particular, the photosensitive drum as an image carrier has frictional heat generated by friction with a cleaning blade for scraping off residual toner on the surface of the photosensitive drum or a rubbing roller for polishing the surface of the photosensitive drum, or both surfaces. After the toner image on the first surface is fixed by passing through the fixing device during printing, the surface temperature rises due to heat radiation from the paper passing near the photosensitive drum before transferring the image on the second surface.

  When the temperature of the photosensitive drum rises, toner external additives and the like are likely to adhere to the surface of the photosensitive drum, which may cause image defects. In addition, toner and toner external additives aggregate on the edge of the cleaning blade that contacts the photoconductor drum, reducing the cleaning performance, generating blade vibration noise due to increased frictional resistance, rolling up of the cleaning blade, jitter, etc. There is also a problem that this problem occurs.

  Therefore, it is necessary to cool the photosensitive drum. Here, devices and members for image formation are arranged around the photosensitive drum, and toner for developing the electrostatic latent image formed on the photosensitive drum is also present. Therefore, it is important to study the air flow path for cooling the photosensitive drum.

  For example, Patent Literature 1 includes an air duct that communicates from the primary charger cleaning fan to the inside of the primary charger and the outer surface of the housing of the cleaning device via the surface of the photosensitive drum, and the surface of the cleaning blade is A cleaning device cooling means also serving as a part of an air duct is disclosed.

JP 2003-241607 A

  However, in the method of Patent Document 1, in order to cool the cleaning blade itself, an air flow is brought into direct contact with the cleaning blade. For this reason, the toner scattered around the cleaning blade is released into or out of the apparatus together with the air flow, which may cause toner contamination inside or outside the apparatus.

  In view of the above problems, the present invention can efficiently cool a photosensitive drum by an air flow, and can effectively suppress toner contamination caused by the toner being discharged into or out of the apparatus together with the air flow. An object of the present invention is to provide an image forming apparatus having a simple configuration and saving space.

  In order to achieve the above object, the present invention charges an image carrier having a photosensitive layer formed on the surface, and charging the surface of the image carrier by applying a charging bias to the surface of the image carrier in contact or non-contact. A charging device having a charging member to be held, and a charging housing for holding the charging member, and disposed adjacent to the upstream side of the charging device with respect to the rotation direction of the image carrier, and remaining on the surface of the image carrier. In the image forming apparatus having a cleaning device for removing toner, the charging housing is formed with an opening for taking in an air flow from a cooling fan disposed in the image forming apparatus, and the charging housing and the cleaning device A partition member for blocking the air flow is disposed between the charging housing and the partition member. After guiding the peripheral surface, it is characterized by forming a vent passage for discharging the downstream side in the rotation direction of the image bearing member.

  According to the present invention, in the image forming apparatus having the above-described configuration, the opening is formed at one end in the longitudinal direction of the charging housing, and an air flow taken into the charging housing from the opening is formed in the charging housing. It is characterized by being guided along substantially the entire length of the image carrier along the longitudinal direction.

  According to the present invention, in the image forming apparatus having the above configuration, the charging member is a charging roller that rotates in contact with the image carrier, and the charging housing rotates in contact with the surface of the charging roller. A cleaning member for cleaning the charging roller is arranged, and the air flow taken into the charging housing from the opening is combined with the air flow generated by the rotation of the charging roller and the cleaning member. It is characterized by being guided over substantially the entire longitudinal direction of the carrier.

  According to the present invention, in the image forming apparatus configured as described above, the partition member is a polyurethane sheet material attached to an outer surface of the charging housing and having a tip contacting the outer peripheral surface of the image carrier. It is said.

  According to the present invention, in the image forming apparatus configured as described above, the cooling fan is an intake fan that takes in air from outside the image forming apparatus.

  According to the first configuration of the present invention, since the inside of the charging housing is used as an air flow passage for cooling the image carrier, there is no need to separately provide a passage for guiding the air flow to the image carrier. And a compact and space-saving structure. In addition, by arranging a partition member between the charging housing and the cleaning device, the air flow toward the cleaning device is blocked after the image carrier is cooled. Therefore, the toner contamination due to the scattered toner around the cleaning device being discharged together with the air flow into or outside the image forming apparatus can be prevented.

  Further, according to the second configuration of the present invention, in the image forming apparatus having the first configuration, the opening is formed at one end in the longitudinal direction of the charging housing so that the air flow from the cooling fan is generated in the opening. Since it is not necessary to increase the guide duct diameter, the structure is compact and space-saving. Also, since the air flow taken into the charging housing from the opening is guided to substantially the entire longitudinal direction of the image carrier along the longitudinal direction of the charging housing, the entire longitudinal direction of the image carrier is cooled without unevenness. Can do.

  Further, according to the third configuration of the present invention, in the image forming apparatus having the second configuration, the charging roller rotates in contact with the image carrier, and the charging roller rotates by contacting the surface of the charging roller. A cleaning member for cleaning the roller is disposed in the charging housing, and an air flow taken into the charging housing from the opening is blown onto the surface of the image carrier together with an air flow generated by rotation of the charging roller and the cleaning member. The cooling efficiency of the surface of the image carrier can be improved.

  According to the fourth configuration of the present invention, in the image forming apparatus having any one of the first to third configurations, a polyurethane sheet material is used as the partition member, and the leading end of the sheet material is the image carrier. By disposing it in contact with the outer peripheral surface, it is possible to reliably block the air flow toward the cleaning device without damaging the photosensitive layer on the surface of the image carrier.

  According to the fifth configuration of the present invention, in the image forming apparatus having any one of the first to fourth configurations, by using an intake fan that takes in air from the outside of the image forming apparatus as a cooling fan, Cold air outside the image forming apparatus can be used for cooling the surface of the image carrier, and the cooling efficiency of the surface of the image carrier can be further improved.

1 is a schematic configuration diagram illustrating an overall configuration of an image forming apparatus 100 according to an embodiment of the present invention. Side sectional view of a drum unit 40 mounted on the image forming apparatus 100 of the present invention. A perspective view of the vicinity of an end of a drum unit 40 mounted on the image forming apparatus 100 of the present invention. Partial perspective view of the photosensitive drum 14 and the charging device 15 constituting the drum unit 40. FIG. 7 is a partial cross-sectional view showing a path of air flow passing through the drum unit 40 in the image forming apparatus 100 of the present invention. Enlarged view of the drum unit 40 in FIG. 6 is a cross-sectional view of the drum unit 40 of FIG. 6 cut in the axial direction of the photosensitive drum 14 and the charging device 15.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram illustrating the overall configuration of an image forming apparatus 100 according to an embodiment of the present invention, and the right side is illustrated as the front side of the image forming apparatus 100. As shown in FIG. 1, an image forming apparatus 100 (in this case, a monochrome printer) includes a paper feed cassette 2 that accommodates sheets stacked on the lower part of the main body. Above this paper feed cassette 2 is formed a paper transport path 4 that extends substantially horizontally from the front of the main body to the rear of the main body and further extends upward to reach the paper discharge section 3 formed on the upper surface of the main body. A pickup roller 5, a feed roller 6, an intermediate transport roller 7, a registration roller pair 8, an image forming unit 9, a fixing unit 10, and a discharge roller pair 11 are arranged in this order from the upstream side along the transport path. Further, in the image forming apparatus 100, a control unit (CPU) 30 for controlling operations of the above-described rollers, the image forming unit 9, the fixing unit 10, and the like is disposed.

  The paper feed cassette 2 is provided with a paper stacking plate 12 that is rotatably supported with respect to the paper feed cassette 2 by a rotation fulcrum 12a provided at the rear end in the paper transport direction. The paper stacked on the paper 12 is pressed by the pickup roller 5. A retard roller 13 is disposed in front of the paper feed cassette 2 so as to be in pressure contact with the feed roller 6. When a plurality of sheets are simultaneously fed by the pickup roller 5, these feed rollers 6 are fed. The paper is rolled by the roller 6 and the retard roller 13 so that only the uppermost sheet is conveyed.

  Then, the paper rolled by the feed roller 6 and the retard roller 13 is conveyed to the registration roller pair 8 by changing the conveyance direction to the rear of the apparatus by the intermediate conveyance roller 7, and the timing is adjusted by the registration roller pair 8. Are supplied to the image forming unit 9.

  The image forming unit 9 forms a predetermined toner image on a sheet by an electrophotographic process. The photosensitive drum 14 is an image carrier that is pivotally supported in a clockwise direction in FIG. Above the charging drum 15, the developing device 16, the cleaning device 17, the transfer roller 18 disposed so as to face the photosensitive drum 14 across the sheet conveyance path 4, and the photosensitive drum 14. The exposure apparatus (LSU) 19 is arranged. A toner container 20 for supplying toner to the developing device 16 is disposed above the developing device 16. A cooling fan 31 that cools the exposure device 19 by sucking air from the outside of the image forming apparatus 100 is disposed in the vicinity of the exposure device 19.

  In this embodiment, the photosensitive drum 14 is an amorphous silicon (a-Si) photosensitive member, and an a-Si photoconductive layer is formed as a photosensitive layer on a conductive substrate (cylinder) such as aluminum, A surface protective layer made of an inorganic insulator or an inorganic semiconductor such as a-Si based SiC, SiN, SiO, SiON, SiCN or the like is laminated on the upper surface. The photosensitive drum 14, the charging device 15, and the cleaning device 17 are unitized. A unit composed of the photosensitive drum 14, the charging device 15, and the cleaning device 17 is hereinafter referred to as a drum unit 40 (see FIG. 2).

  When image data is input from a host device such as a personal computer, first, the surface of the photosensitive drum 14 is uniformly charged by the charging device 15. Next, an electrostatic latent image based on the image data input on the photosensitive drum 14 is formed by the laser beam from the exposure device (LSU) 19. Further, the developing device 16 attaches toner to the electrostatic latent image and forms a toner image on the surface of the photosensitive drum 14. The toner image formed on the surface of the photoconductive drum 14 is transferred by the transfer roller 18 to the paper supplied to the nip portion (transfer position) between the photoconductive drum 14 and the transfer roller 18.

  The sheet on which the toner image has been transferred is separated from the photosensitive drum 14 and conveyed toward the fixing unit 10. The fixing unit 10 is disposed on the downstream side of the image forming unit 9 in the paper conveyance direction, and the sheet on which the toner image is transferred in the image forming unit 9 includes a heating roller 22 provided in the fixing unit 10 and the heating roller 22. The toner image heated and pressed by the pressure roller 23 pressed against the heating roller 22 is fixed to the toner image transferred to the paper. The paper on which the image is formed in the image forming unit 9 and the fixing unit 10 is discharged to the paper discharge unit 3 by the discharge roller pair 11.

  On the other hand, in the case of double-sided printing in which images are formed on both sides of a sheet, the sheet that has passed through the fixing unit 10 is once conveyed in the direction of the discharge roller pair 11 and a part of the sheet is fed out onto the sheet discharge unit 3. Then, by rotating the discharge roller pair 11 in reverse and switching the conveyance direction of the branching section 24, the paper is distributed from the rear end of the sheet to the reverse conveyance path 25 (switchback), and the registration roller pair in the state where the image surface is reversed. 8 is transported again. Then, the next image formed on the photosensitive drum 14 is transferred by the transfer roller 18 onto the surface on which the image of the paper is not formed, conveyed to the fixing unit 10, and the toner image is fixed. 11 is discharged to the paper discharge unit 3.

  The toner remaining on the surface of the photosensitive drum 14 after the transfer is removed by the cleaning device 17. The photosensitive drum 14 is charged again by the charging device 15 and image formation is performed in the same manner.

  2 is a side sectional view of the drum unit 40, FIG. 3 is a perspective view of the vicinity of the end of the drum unit 40, and FIG. 4 is a partial perspective view of the photosensitive drum 14 and the charging device 15 constituting the drum unit 40. The drum unit 40 mounted in the image forming apparatus 100 of the present invention will be described in detail with reference to FIGS.

  As shown in FIGS. 2 and 3, the drum unit 40 includes a photosensitive drum 14, a charging device 15, and a cleaning device 17 in a unit housing 40a. The unit housing 40a also serves as the housing of the cleaning device 17 and supports the photosensitive drum 14 rotatably.

  The charging device 15 includes a charging roller 41 that contacts the photosensitive drum 14 and applies a charging bias to the drum surface, and a charging cleaning roller 43 for cleaning the charging roller 41 in the charging housing 15a. . The charging roller 41 is made of conductive rubber and is disposed so as to contact the photosensitive drum 14. When the photosensitive drum 14 rotates in the clockwise direction in FIG. 2, the charging roller 41 that contacts the surface of the photosensitive drum 14 is rotated in the counterclockwise direction in FIG. At this time, the surface of the photosensitive drum 14 is uniformly charged by applying a predetermined voltage to the charging roller 41. Further, as the charging roller 41 rotates, the charging cleaning roller 43 that contacts the charging roller 41 is driven to rotate in the clockwise direction in FIG. 2 to remove foreign matter attached to the surface of the charging roller 41. The charging device 15 is detachable from the drum unit 40.

  The cleaning device 17 includes a rubbing roller 45, a cleaning blade 47, a supply roller 49, and a collection spiral 50. The rubbing roller 45 is in pressure contact with the photosensitive drum 14 at a predetermined pressure, and is rotated in the same direction on the contact surface with the photosensitive drum 14 by a drum cleaning motor (not shown). Residual toner on the surface of the photosensitive drum 14 is removed and the photosensitive layer on the surface of the photosensitive drum 14 is rubbed and polished using the residual toner. The toner supplied from the developing device 16 is a toner containing an abrasive (abrasive toner). The polishing toner not only adheres to the electrostatic latent image on the photosensitive drum 14 to form a toner image, but also polishes the surface of the photosensitive drum 14 using residual toner that has not been transferred by the transfer roller 18. Used to do.

  The linear velocity of the rubbing roller 45 is controlled to be faster (1.2 times here) than the linear velocity of the photosensitive drum 14. Examples of the rubbing roller 45 include a structure in which a foam layer made of EPDM rubber and having an Asker C hardness of 55 ° is formed as a roller body around a metal shaft.

  The material of the roller body is not limited to EPDM rubber, but may be a rubber or foamed rubber body of another material, and those having an Asker C hardness of 10 to 90 ° are preferably used. In addition, Asker C is one of durometers (spring type hardness testers) defined in the Japan Rubber Association standard, and is a measuring instrument for measuring hardness. Asker C hardness refers to the hardness measured with the above measuring instrument, and the larger the value, the harder the material.

  A cleaning blade 47 is fixed in a state in which the surface of the photosensitive drum 14 is in contact with the photosensitive drum 14 on the downstream side of the contact surface with the rubbing roller 45 in the rotation direction. As the cleaning blade 47, for example, a polyurethane rubber blade having a JIS hardness of 78 ° is used, and is attached at a predetermined angle with respect to the tangential direction of the photosensitive member at the contact point. The material, hardness and dimensions of the cleaning blade 47, the amount of biting into the photosensitive drum 14, the pressure contact force and the like are appropriately set according to the specifications of the photosensitive drum 1a. The JIS hardness refers to the hardness specified by Japanese Industrial Standards (JIS).

  In order to cause toner to adhere to the entire outer peripheral surface of the rubbing roller 45, not only the residual toner on the surface of the photosensitive drum 14 but also the toner from the supply roller 49 that rotates while contacting the rubbing roller 45. Is supplied. Residual toner removed from the surface of the photosensitive drum 14 by the rubbing roller 45 and the cleaning blade 47 is discharged to the outside of the cleaning device 17 as the collection spiral 50 rotates.

  A slit-like first ventilation port 51 is formed in the unit housing 40 a above the cleaning device 17, and a window-like second ventilation port 53 is formed in the charging housing 15 a. A partition member 55 made of a polyurethane sheet material is attached to the surface of the charging housing 15a facing the cleaning blade 47. The tip of the partition member 55 is in contact with the surface of the photosensitive drum 14.

  5 is a partial cross-sectional view showing a path of air flow passing through the drum unit 40 in the image forming apparatus 100 of the present invention, FIG. 6 is an enlarged view of the drum unit 40 in FIG. 5, and FIG. 7 is a drum unit 40 in FIG. FIG. 6 is a cross-sectional view (a cross-sectional view taken along the line AA ′ in FIG. 5) in which the charging device 15 and the photosensitive drum 14 are cut in the axial direction. The cooling mechanism for the surface of the photosensitive drum 14 in the image forming apparatus 100 of the present invention will be described using FIGS. 5 to 7 with reference to FIGS. 1 to 4 as necessary. In addition, the black arrow of FIGS. 5-7 shows the flow path of an airflow.

  As shown in FIGS. 5 and 6, a part of the air flow sucked from the outside of the image forming apparatus 100 by the cooling fan 31 is guided toward the drum unit 40 by the duct 60 inside the image forming apparatus 100, and is unit housing. The air passes through the first ventilation port 51 formed in 40a and the second ventilation port 53 formed in the charging housing 15a in order, and flows into the charging housing 15a. The air flow that has flowed into the charging housing 15 a flows downward in the charging housing 15 a and reaches the surface of the photosensitive drum 14. Then, the surface of the photosensitive drum 14 is cooled by removing heat from the surface of the photosensitive drum 14 by the air flow.

  At this time, as shown in FIG. 7, the airflow flowing into the charging housing 15a from the second ventilation port 53 flows downward while spreading in the longitudinal direction of the charging housing 15a, and contacts the entire axial direction of the photosensitive drum 14. To do. Therefore, the entire surface of the photosensitive drum 14 can be cooled without unevenness.

  Thereafter, the air flow passes through a gap 61 between the photosensitive drum 14 and the charging housing 15a, and is discharged downstream in the rotation direction of the photosensitive drum 14. Further, since the partition member 55 is attached to the surface of the charging housing 15a facing the cleaning blade 47 so as to be in contact with the surface of the photosensitive drum 14, the air flow toward the cleaning blade 47 is blocked.

  According to the configuration of the present embodiment, by using the inside of the charging housing 15a as an air flow path for cooling the photosensitive drum 14, there is no need to separately provide a path for guiding the air flow to the photosensitive drum 14. The number of points can be reduced and the structure can be made compact and space-saving.

  Further, by arranging the partition member 55 between the charging housing 15a and the cleaning blade 47, the air flow toward the cleaning blade 47 is blocked after the photosensitive drum 14 is cooled. Therefore, toner contamination caused by the toner adhering to the periphery of the cleaning blade 47 being discharged into or out of the image forming apparatus 100 together with the airflow can be prevented.

  Further, since the charging device 15 includes a charging roller 41 that rotates in contact with the photosensitive drum 14 and a charging cleaning roller 43 that rotates in contact with the charging roller 41, the charging device 15 particularly has a process speed (photosensitive drum circumference). In a high-speed machine with a high speed, the charging roller 41 and the charging cleaning roller 43 also rotate at a high speed. Therefore, the photosensitive drum is formed by superimposing the air flow generated by the high-speed rotation of the charging roller 41 and the charging cleaning roller 43 on the air flow flowing into the charging housing 15a through the first ventilation port 51 and the second ventilation port 53. The cooling efficiency of the surface of the photosensitive drum 14 can be improved by spraying on the 14 surface.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, instead of the contact charging type charging device 15 using the charging roller 41 as shown in FIG. 2, a corona charging type charging device including a corona wire and a grid may be used. The cooling fan 31 is not limited to a fan for cooling the exposure device 19, and may be a device that cools other devices and members inside the image forming apparatus 100 as long as it is an intake fan that takes in external air. good.

  Further, the image forming apparatus of the present invention is not limited to the monochrome printer as shown in FIG. 1, and may be other image forming apparatuses such as monochrome and color copiers, color printers, facsimiles and the like.

  The present invention can be used in an image forming apparatus including an image carrier such as a photosensitive drum and a charging device that charges the image carrier. By utilizing the present invention, the housing of the charging device can be used as a passage for guiding the air flow to the image carrier, and the air flow toward the cleaning blade can be blocked. Therefore, it is possible to provide an image forming apparatus that is compact and space-saving and that can prevent toner contamination inside or outside the apparatus.

14 Photosensitive drum (image carrier)
DESCRIPTION OF SYMBOLS 15 Charging device 15a Charging housing 16 Developing device 17 Cleaning device 31 Cooling fan (intake fan)
40 drum unit 41 charging roller (charging member)
43 Development cleaning roller (cleaning member)
45 Rubbing roller 47 Cleaning blade 51 First ventilation port 53 Second ventilation port (opening)
55 Partition member 60 Duct 100 Image forming apparatus

Claims (5)

An image carrier having a photosensitive layer formed on the surface;
A charging device having a charging member that charges the surface of the image carrier by applying a charging bias in contact or non-contact to the surface of the image carrier, and a charging housing that holds the charging member;
A cleaning device disposed adjacent to the upstream side of the charging device with respect to the rotation direction of the image carrier, and removing residual toner on the surface of the image carrier;
In an image forming apparatus having
The charging housing is formed with an opening for taking in an air flow from a cooling fan arranged in the image forming apparatus, and a partition member for blocking the air flow is arranged between the charging housing and the cleaning device. And
The charging housing and the partition member form an air passage that guides the air flow from the cooling fan to the outer peripheral surface of the image carrier and then discharges the air to the downstream side in the rotation direction of the image carrier. Image forming apparatus.   The opening is formed at one end in the longitudinal direction of the charging housing, and the air flow taken into the charging housing from the opening is substantially in the longitudinal direction of the image carrier along the longitudinal direction of the charging housing. The image forming apparatus according to claim 1, wherein the image forming apparatus is guided to the entire area.   The charging member is a charging roller that rotates in contact with the image carrier, and a cleaning member that cleans the charging roller by rotating in contact with the surface of the charging roller is disposed in the charging housing. The air flow taken into the charging housing from the opening is guided to substantially the entire longitudinal direction of the image carrier together with the air flow generated by the rotation of the charging roller and the cleaning member. The image forming apparatus according to claim 2.   4. The partition member according to claim 1, wherein the partition member is a polyurethane sheet material attached to an outer surface of the charging housing and having a tip contacting the outer peripheral surface of the image carrier. The image forming apparatus described.   The image forming apparatus according to claim 1, wherein the cooling fan is an intake fan that takes in air from the outside of the image forming apparatus.