JP2011075712A - Drum assembly and image forming apparatus including the drum assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a long-life drum assembly in which the uneven wear of a photoreceptor drum is prevented, and to provide an image forming apparatus including the drum assembly. <P>SOLUTION: A drum cleaning unit for the drum assembly includes: a cleaning blade 82 with a forming region slide-contact portion which comes in slide-contact with an image forming region of the photoreceptor drum 50 and a non-forming region slide-contact portion coming in slide-contact with a non-image forming region; and at least two accumulation members 88 which are arranged in the vicinity of the non-forming region slide-contact portion of the cleaning blade 82 and separated from each other in an axial direction of a rotational axis of the photoreceptor drum 50 and form storing sections in cooperation with the non-forming region for temporarily storing the toner particles that are scraped off from the photoreceptor drum 50 by the cleaning blade 82. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine having a plurality of these functions using an electrophotographic system, and more particularly to a drum assembly applied to the image forming apparatus. .

An image forming apparatus using an electrophotographic system includes a drum assembly, and the drum assembly includes a photosensitive drum, a charging unit, an exposure unit, a developing unit, and a cleaning unit.
In this type of image forming apparatus, the charging roller of the charging unit charges the photosensitive drum in advance, and then the exposure unit irradiates the photosensitive drum with light in a desired pattern. Thereby, an electrostatic latent image is formed on the photosensitive drum. The developing roller of the developing unit applies toner particles to the photosensitive drum, and the toner particles adhere to the electrostatic latent image to form a toner image. The toner image is transferred to a sheet directly or indirectly via a transfer belt and fixed.

In order to sequentially transfer a plurality of toner images onto a sheet, it is necessary to clean the photosensitive drum and remove residual toner from the photosensitive drum every time it is transferred once.
Further, in order to discharge the deteriorated toner particles, the developing unit may discharge the deteriorated toner particles to the photosensitive drum. The deteriorated toner particles are removed from the photosensitive drum without being transferred to the paper.

  For this purpose, a drum cleaning unit is provided in the vicinity of the photosensitive drum. Specifically, the drum cleaning unit has a cleaning blade, and the cleaning blade is located on the downstream side of the transfer position with the sheet or transfer belt as seen in the rotation direction of the photosensitive drum. When the edge of the cleaning blade comes into sliding contact with the surface of the photosensitive drum, unnecessary toner particles are scraped off from the photosensitive drum.

In the above configuration, the dimensions of each member have the following relative relationship.
Paper width <Developing roller width <Charging roller width <Cleaning blade width <Photoreceptor drum width The reason that the developing roller width is larger than the paper width is to form a toner image up to the edge of the paper. However, the reason why the charging roller width is large is that if the charging roller width is smaller than the developing roller width, toner particles adhere to both ends of the paper. The reason why the cleaning blade width is larger than the charging roller width is to prevent the charging roller from becoming dirty.
In such a configuration, the photosensitive drum has an image forming area in which toner particles are supplied from the developing roller to form a toner image, and an image non-forming area continuous on both sides of the image forming area.

In the above-described configuration, toner particles having abrasive particles attached to the surface may be used. This is due to the following reason.
Paper-derived components such as paper dust and fillers, and discharge products such as nitrate generated by charging adhere to the surface of the photosensitive drum. These deposits obstruct the charging of the photosensitive drum uniformly by the charging unit, and thus reduce the image quality.
Therefore, in order to scrape off deposits such as paper dust and discharge products, the surface of the photosensitive drum is polished with abrasive particles particularly when a photosensitive drum made of an organic photosensitive member (OPC) is used. It has been broken. As the abrasive particles, for example, particles made of titanium oxide, alumina, or the like are used (see, for example, Patent Document 1).

  In addition, for the purpose of suppressing abnormal noise caused by fine vibration caused by sliding between the photosensitive drum and the cleaning blade, a lubricant such as zinc stearate is added to the toner particles as an external additive. . In this case, in order to collect the lubricant at the edge of the cleaning blade, a toner reservoir member is disposed in the vicinity of the cleaning blade (see, for example, Patent Document 2).

  Conventionally, a corona charging unit has been used as the charging unit. However, since the corona charging unit generates a large amount of ozone, a contact charging method using a charging roller or the like has been widely adopted in recent years. In the contact charging method, a photosensitive member such as a conductive rubber roller or a brush is brought into contact with the photosensitive drum, and the photosensitive drum is uniformly charged by applying a voltage between the charging member and the photosensitive drum. When the contact charging method is adopted, compared with the corona charging unit, the amount of current required for charging is remarkably small, and the amount of ozone generated can be greatly reduced.

JP 2003-167375 A JP 2005-309404 A

As described above, the abrasive particles are supplied to the surface of the photosensitive drum in a state of adhering to the surface of the toner particles. Then, the toner particles with abrasive particles remaining on the photosensitive drum without being transferred to the transfer belt accumulate on the edge of the cleaning blade that is in sliding contact with the photosensitive drum.
The cleaning blade is roughly divided into a forming area sliding contact portion that is in sliding contact with the image forming area of the photosensitive drum and a non-forming area sliding contact portion that is in sliding contact with the image non-forming area of the photosensitive drum. The amount of abrasive particles deposited on the edge of the contact portion is significantly larger than that of the abrasive particles deposited on the edge of the formation region sliding contact portion. This is due to the following reason.

  From the developing unit, the toner particles also move to the non-image forming area of the photosensitive drum. However, since the non-image forming area is charged, most of the toner particles moved to the non-image forming area return to the developing unit. At this time, the abrasive particles are detached from some of the transferred toner particles, and only the abrasive particles are left on the surface of the non-image forming area of the photosensitive drum. For this reason, the deposition amount of abrasive particles increases at the edge of the non-formation area sliding contact portion of the cleaning blade that is in sliding contact with the image non-formation area.

  As the amount of accumulated abrasive particles increases in this way, the non-image forming area of the photosensitive drum is worn earlier than the image forming area. That is, uneven wear occurs on the photosensitive drum. Uneven wear decreases the sensitivity and pressure resistance, shortens the life of the photosensitive drum, and hinders maintenance costs and resource saving of the drum assembly and the image forming apparatus.

Some image forming apparatuses execute a refresh mode for discharging unnecessary toner particles in a developing unit, in addition to an image forming mode for forming a toner image to be transferred onto a sheet. In the refresh mode, a large amount of toner particles are collected by the drum cleaning unit and washed away by the toner particles, whereby the amount of abrasive particles deposited on the edge of the non-formation region sliding contact portion of the cleaning blade is temporarily reduced.
However, the decrease in the amount of abrasive particles deposited by the refresh mode is temporary, and the amount of abrasive particles deposited at the edge of the non-formed region sliding contact portion immediately increases.

Therefore, it is conceivable to retain toner particles at the edge of the cleaning blade to prevent the abrasive particles from accumulating at the edge. Therefore, for example, as disclosed in Patent Document 1, it is conceivable to arrange the toner reservoir forming member along the cleaning blade.
However, the amount of abrasive particles deposited at the edge of the formation region sliding contact portion is smaller than that at the edge of the non-formation region sliding contact portion, and if toner particles accumulate, the function of polishing the photosensitive drum is degraded. As a result, the image quality of the obtained image is degraded.

  Further, even if the toner reservoir temporarily accumulates the toner particles at the edge of the non-formation area sliding contact portion, the non-formation area sliding contact portion of the non-formation area sliding contact portion is determined based on the difference in the particle size between the toner particles and the abrasive particles. The ratio of abrasive particles at the edge gradually increases. As a result, uneven wear also occurs.

  On the other hand, when the amount of accumulated abrasive particles increases at the edge of the non-formed area sliding contact portion of the cleaning blade, the abrasive particles that have passed through the gap between the edge of the non-formed area sliding contact portion and the photosensitive drum continue to the transfer belt. So that a large amount of abrasive particles adhere to both side portions in the width direction of the transfer belt, so-called whitening phenomenon occurs. When the whitening phenomenon occurs, the non-image forming area of the photosensitive drum is also polished by the transfer belt, and the uneven wear of the photosensitive drum further proceeds.

Further, uneven wear of the photosensitive drum becomes more prominent when the contact charging method is adopted. This is due to the following reason.
In the contact charging method, since discharge occurs between the photosensitive drum and the charging roller, the energy of ions colliding with the photosensitive drum is high, and the surface of the photosensitive drum is likely to deteriorate. The deteriorated surface of the photosensitive drum is easily worn, and is quickly worn by contact with a member such as a cleaning blade or a transfer belt through the abrasive particles.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a long-life drum assembly in which uneven wear of a photosensitive drum is prevented and an image forming apparatus including the drum assembly.

  In order to achieve the above object, according to one aspect of the present invention, a rotation axis, an image formation area on which a toner image to be transferred to a sheet is formed, and the image formation area as viewed in the axial direction of the rotation axis. A photosensitive drum having an image non-formation area continuous on both sides, a charging unit for charging the photosensitive drum, a developing unit for applying toner particles contained in a developer to the photosensitive drum, and the photosensitive drum In a drum assembly of an image forming apparatus including a drum cleaning unit that removes unnecessary toner particles, the drum cleaning unit includes a formation area sliding contact portion that is in sliding contact with the image forming area and a non-formation that is in sliding contact with the non-image forming area. A cleaning blade having an area sliding contact portion and a vicinity of the non-formation area sliding contact portion of the cleaning blade, respectively And a storage part for temporarily storing the toner particles scraped off from the photosensitive drum by the cleaning blade in cooperation with the non-formation area part in the axial direction of the rotating shaft A drum assembly of an image forming apparatus, wherein the drum assembly includes at least two reservoir members that respectively form a plurality of reservoir members.

  In the drum assembly according to the first aspect, the two reservoir members each form a reservoir between the cleaning blade. By storing the toner particles in the storage portion, sliding between the image non-formation region of the photosensitive drum and the cleaning blade is alleviated, and uneven wear and vibration of the cleaning blade or the photosensitive drum are suppressed. Further, uneven wear is suppressed and the life of the cleaning blade and the photosensitive drum is prolonged, so that the replacement frequency of the cleaning blade and the photosensitive drum is reduced, and the maintenance cost of the drum assembly is reduced.

Preferably, the developer includes abrasive particles (claim 2).
In the drum assembly according to the second aspect, the abrasive particles contained in the developer scrape off deposits such as paper-derived components and discharge products on the photosensitive drum, thereby suppressing deterioration in image quality.
In addition, since the toner particles are stored in the storage portion formed by the reservoir member, it is possible to suppress wear of the non-image forming area of the photosensitive drum by the abrasive particles.

The two reservoir members are separated from each other, and the toner particles and the abrasive particles stored in the storage part easily flow out of the storage part. For this reason, it is prevented that the ratio of the abrasive | polishing agent particle | grains in a storage part becomes high, and it is suppressed that the image non-formation area | region of a photoconductive drum is worn by an abrasive | polishing agent particle | grain for a long term.
Further, the two reservoir members are spaced apart from each other, and the toner particles stored in the storage portion are polished by the abrasive particles deposited on the edge of the cleaning blade forming region sliding contact portion in the image forming region of the photosensitive drum. Will not be disturbed.

  Preferably, the developer includes one or more particles selected from the group consisting of titanium oxide, aluminum oxide, and silicon oxide as the abrasive particles.

  In the drum assembly according to claim 3, since the developer includes any one of particles made of titanium oxide, aluminum oxide, and silicon oxide as abrasive particles, the photosensitive drum is reliably polished, and the image quality is deteriorated. Is prevented.

  Preferably, the charging unit includes a charging member that contacts the photosensitive drum.

  In the drum assembly according to the fourth aspect, since the charging unit has a charging member that comes into contact with the photosensitive drum and adopts the contact charging method, the generation amount of ozone is small and the environment is friendly.

  Preferably, the image forming area and the non-image forming area of the photosensitive roller are made of an organic photosensitive material.

  In the drum assembly according to the fifth aspect, the image forming area and the non-image forming area of the photosensitive drum are made of an organic photosensitive material, and are highly versatile and inexpensive.

  Preferably, the upper edge of the reservoir member is connected to a parallel portion parallel to the rotation shaft and an oblique lowering with respect to the parallel portion on the center side of the rotation shaft of the photosensitive drum as viewed in the axial direction of the rotation shaft. And an inclined portion (claim 6).

  In the drum assembly according to the sixth aspect, since the inclined portion is provided on the upper edge of the reservoir member, the toner particles and the like stored in the storage portion are more likely to flow out. For this reason, especially when the developer contains abrasive particles, an increase in the amount of abrasive particles stored in the storage portion is suppressed, and uneven wear of the photosensitive drum is reliably suppressed.

  Preferably, the drum cleaning unit further includes a seal member provided in contact with both ends of the cleaning blade as viewed in the axial direction of the rotary shaft, and the seal member and the reservoir member as viewed in the axial direction of the rotary shaft. There is a gap between the two (claim 7).

  In the drum assembly according to the seventh aspect, since the gap is provided between the reservoir member and the seal member, the toner particles and the like stored in the storage portion are more likely to flow out. For this reason, especially when the developer contains abrasive particles, an increase in the amount of abrasive particles stored in the storage portion is suppressed, and uneven wear of the photosensitive drum is reliably suppressed.

  In order to achieve the above object, according to another aspect of the present invention, an image forming apparatus comprising the drum assembly of the image forming apparatus according to claim 1. (Claim 8).

  In the image forming apparatus according to the eighth aspect, since the photosensitive drum has a long life, the maintenance cost is reduced.

  Preferably, a control unit for controlling the drum assembly is provided, and the control unit is configured to form an image forming mode for forming a toner image to be transferred onto a sheet and only unnecessary toner particles in the developing unit. One operation mode selected from a plurality of operation modes including at least a refresh mode applied to the drum is selectively executed by the drum assembly.

  According to the image forming apparatus of the ninth aspect, even if a large amount of toner particles are supplied to the edge of the cleaning blade and the abrasive particles are accumulated on the edge of the non-formation area sliding contact portion of the cleaning blade by the refresh mode. The accumulated abrasive particles are washed away. For this reason, in this image forming apparatus, the photosensitive drum has a longer life, and the maintenance cost is further reduced.

  According to the present invention, a long-life drum assembly in which uneven wear of a photosensitive drum is prevented and an image forming apparatus including the drum assembly are provided.

1 is a schematic configuration diagram of a printer according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a drum assembly applied to the printer of FIG. 1 together with a transfer belt. It is a figure which shows the cross section of the drum cleaning unit which follows the III-III line | wire of FIG. 2 with a photosensitive drum. FIG. 2 is a perspective view schematically showing a cleaning blade, a bracket, and a reservoir member together with a photosensitive drum. It is a schematic block diagram of the control system applied to the printer of FIG. 3 is a graph showing the relationship between the position in the longitudinal direction of the photosensitive drum and the thickness of the photosensitive layer in the printer of FIG. 1 for the initial stage and after the durability test. It is a graph which shows the relationship between the longitudinal direction position of a photoconductive drum and the thickness of a photosensitive layer in the printer of a comparative example about the initial stage and after an endurance test. It is a figure corresponding to FIG. 3 which shows the cross section of the drum cleaning unit to which the reservoir member of the modification is applied with the photosensitive drum. FIG. 5 is a perspective view schematically showing a cleaning blade, a bracket, and a reservoir member of a modified example together with a photosensitive drum. 7 is a graph showing the relationship between the position of the photosensitive drum in the longitudinal direction and the thickness of the photosensitive layer in the printer of FIG. 1 to which the reservoir member of the modification is applied, in the initial stage and after the durability test.

Hereinafter, as an image forming apparatus according to an embodiment of the present disclosure, a printer 10 capable of color printing will be described with reference to the drawings.
FIG. 1 schematically shows the structure of the printer 10. A paper discharge tray 12 is provided at the top of the printer 10, and a paper feed cassette 14 is removably inserted at the bottom of the printer 10. In the paper feed cassette 14, paper P to be used for printing is stored.

  Inside the printer 10, a conveyance path 16 extending from the paper feed cassette 14 to the paper discharge tray 12 is formed. A pickup roller 17, a pair of feed rollers 18, a pair of transport rollers 20, a pair of registration rollers 22, a secondary transfer roller 24, a pair of fixing rollers 26, and a pair of discharge rollers 28 are arranged in this order from the upstream side along the transport path 16. ing.

  The secondary transfer roller 24 partially sandwiches an endless transfer belt 32 together with the drive roller 30, and the secondary transfer roller 24 and the drive roller 30 transfer for transferring the toner image on the transfer belt 32 to the paper P. A nip is formed.

  The transfer belt 32 is also looped around a driven roller 34 that is disposed away from the driving roller 30. A belt cleaning unit 36 is disposed in the vicinity of the driven roller 34, and the belt cleaning unit 36 has a fur brush (rotating brush) 38 that is in sliding contact with the transfer belt 32.

  The fur brush 38 scrapes off unnecessary toner particles from the surface of the transfer belt 32, and the scraped toner particles are temporarily stored in the housing 40 of the belt cleaning unit 36. The stored toner particles are discharged from the housing 40 by the screw pump 42.

  Four drum assemblies 44M, 44Y, 44C, and 44B are arranged along the portion of the transfer belt 32 that extends between the driving roller 30 and the driven roller 34. Note that the four drum assemblies 44M, 44Y, 44C, and 44B are different from each other in magenta, yellow, cyan, or black in the color of the developer to be used, but are the same in configuration. Therefore, hereinafter, the drum assemblies 44M, 44Y, 44C, and 44B are also simply referred to as the drum assembly 44 without being distinguished from each other.

  Although not shown, the four toner containers for supplying toner particles to the drum assembly 44 are accommodated above the drum assembly 44 and the transfer belt 32, that is, above the printer 10. On the other hand, a laser scanning unit 46 is disposed below the drum assembly 44 as an exposure unit for forming an electrostatic latent image in the drum assembly 44.

  The developer is, for example, a two-component developer, and includes positively charged toner particles and a magnetic carrier. Preferably, the developer further includes abrasive particles, and the abrasive particles are used in a state of being attached to the surface of the toner particles. As the abrasive particles, it is preferable to use any one or two or more selected from titanium oxide, aluminum oxide (alumina), and silicon oxide (silica) particles.

FIG. 2 shows an enlarged view of one drum assembly 44 together with a part of the transfer belt 32.
The drum assembly 44 includes a photosensitive drum 50 that is in sliding contact with the outer surface of the transfer belt 32. The photosensitive drum 50 is rotatably installed and is rotated counterclockwise as viewed in FIG. The photoreceptor drum 50 is a so-called OPC drum having a photosensitive layer 52 made of an organic photoreceptor (OPC) on the surface thereof.

Around the photosensitive drum 50, a static eliminator 54, a charging unit 56, a developing unit 58, a primary transfer roller 60, and a drum cleaning unit 62 are arranged.
The static eliminator 54 is made of, for example, an LED, and irradiates light to a predetermined circumferential position of the photosensitive drum 50. The portion of the photosensitive layer 52 irradiated with the light from the static eliminator 54 is neutralized.

The charging unit 56 is preferably a contact charging system, and includes a charging roller 64 and a cleaning roller 66. The charging roller 64 is in contact with the photosensitive drum 50, and the photosensitive layer 52 is charged by applying a voltage between the charging roller 64 and the photosensitive drum 50. The cleaning roller 66 has a brush on the surface, and the brush is cleaned by rubbing the surface of the charging roller 64.
The position where the charging roller 64 contacts the photosensitive drum 50 is located downstream of the circumferential position where the static eliminator 54 emits light, as viewed in the rotational direction of the photosensitive drum 50. The portion of the photosensitive layer 52 that is contacted by the charging roller 64 is uniformly charged.

  The photosensitive layer 52 is irradiated with laser light in a desired pattern from the laser scanning unit 46 downstream of the circumferential position where the charging roller 64 contacts. An electrostatic latent image is formed on the photosensitive layer 52 by the laser light.

The developing unit 58 is disposed on the right side of the photosensitive drum 50 as viewed in FIG.
A stirring screw 70 and a paddle screw 72 are disposed below the housing 68 of the developing unit 58, and the stirring screw 70 and the paddle screw 72 are partially partitioned by a partition plate 74.
A supply roller 76 is disposed obliquely above the paddle screw 72, and a developing roller 78 is disposed obliquely above the supply roller 76. The developing roller 78 is rotated clockwise as viewed in FIG.

The toner particles in the toner container are supplied to the stirring screw 70 side below the housing 68. The supplied toner particles are agitated and mixed with the developer in the housing 68 by the agitating screw 70 and then conveyed to the vicinity of the supplying roller 76 by the paddle screw 72.
The supply roller 76 includes a magnetic member, and the conveyed developer adheres to the supply roller 76 to form a magnetic brush. The toner particles in the developer forming the magnetic brush are supplied to the developing roller 78 by the potential difference between the supply roller 76 and the developing roller 78, and a thin layer of toner particles is formed on the surface of the developing roller 78. Is done.

  The developing roller 78 is disposed in the vicinity of the photosensitive drum 50 downstream of the circumferential position where the laser beam is irradiated from the laser scanning unit 46. As a thin layer of toner particles on the developing roller 78 moves onto the photosensitive layer 52, the electrostatic latent image on the photosensitive layer 52 is developed and a toner image is formed.

  As shown in FIG. 2, the transfer belt 32 is in contact with the upper portion of the photosensitive drum 50, and the primary transfer roller 60 is disposed on the transfer belt 32. The photosensitive drum 50 sandwiches the transfer belt 32 in cooperation with the primary transfer roller 60 downstream of the position where the toner particles are received from the developing roller 78. The primary transfer roller 60 has a polarity opposite to that of the toner particles. By applying a voltage (primary transfer bias), the toner image on the photosensitive layer 52 is transferred to the transfer belt 32.

To the transfer belt 32, the toner images of the respective colors are sequentially transferred from the image forming units 44M, 44C, 44Y, and 44B.
Referring to FIG. 1, the toner image transferred to the transfer belt 32 is transferred onto the paper P at the transfer nip portion by applying a voltage having a polarity opposite to that of the toner particles to the secondary transfer roller 24.

  The toner image transferred onto the paper P is fixed on the paper P by being heated by the fixing roller 26, thereby completing the printing on the paper P. Then, the printed paper P is discharged to the paper discharge tray 12 as it is.

Referring again to FIG. 2, the drum cleaning unit 62 is disposed in the vicinity of the photosensitive drum 50 and is located on the side opposite to the developing unit 58.
The drum cleaning unit 62 includes a housing 80, and the housing 80 has an opening that opens toward the photosensitive drum 50. The drum cleaning unit 62 has a cleaning blade 82 made of, for example, polyurethane rubber, and the cleaning blade 82 has a rectangular plate shape parallel to the axial direction of the rotating shaft of the photosensitive drum 50. The upper edge (edge) of the cleaning blade 82 is in sliding contact with the photosensitive drum 50 and scrapes unnecessary toner particles and the like from the photosensitive drum 50.

More specifically, the upper edge of the cleaning blade 82 is in sliding contact with the photosensitive drum 50 in the counter direction, and the position where the upper edge of the cleaning blade 82 is in sliding contact with the photosensitive drum 50 is viewed in the rotational direction of the photosensitive drum 50. It is downstream of the position where the photosensitive drum 50 contacts the transfer belt 32.
For example, the cleaning blade 82 is disposed so that its short side is substantially vertical, and the lower edge side of the cleaning blade 82 is fixed to the bracket 84 by, for example, thermal welding. The bracket 84 is made of, for example, a galvanized steel plate and has an L-shaped cross-sectional shape. The bracket 84 is fixed to the housing 80 so as to close the lower portion of the opening of the housing 80, and the cleaning blade 82 is supported by the housing 80 via the bracket 84.

  A screw pump 86 is provided at the lower part of the housing 80, and the toner particles accumulated in the lower part of the housing 80 are discharged out of the housing 80 by the screw pump 86 and discarded.

Further, the drum cleaning unit 62 has two reservoir members 88. Referring to FIGS. 2, 3, and 4, the reservoir member 88 has a rectangular plate shape. The reservoir member 88 is made of, for example, PET, and the lower edge side of the reservoir member 88 is bonded and fixed to the bracket 84. Therefore, the reservoir member 88 is disposed in parallel to the cleaning blade 82 with a gap corresponding to the thickness of the bracket 84, and is located on the side opposite to the photosensitive drum 50. In other words, the reservoir member 88 is located farther from the cleaning blade 82 than the photosensitive drum 50 in the radial direction of the photosensitive drum 50.
3 shows a schematic cross section of the cleaning unit 62 along the line III-III in FIG. 2 together with the photosensitive drum 50, and FIG. 4 shows the cleaning blade 82, the bracket 84 and the reservoir member 88 in the photosensitive drum. FIG.

  The upper edge of the reservoir member 88 is located above the upper edge of the cleaning blade 82, and the reservoir member 88 faces a part of the cleaning blade 82 with a gap. The gap between the reservoir member 88 and the cleaning blade 82 opens upward, and opens toward both sides as viewed in the axial direction of the rotating shaft of the photosensitive drum 50. The gap constitutes a storage unit 90 that temporarily stores toner particles scraped off by the cleaning blade 82, and the toner particles and the like stored in the storage unit 90 gradually flow out from the opening of the gap.

Here, as shown in FIG. 3, the photosensitive drum 50 is roughly divided into an image forming area and an image non-forming area when viewed in the axial direction of the rotation axis of the photosensitive drum 50. The image forming area is an area where a toner image to be transferred to the paper P is formed, and the width of the image forming area is equal to the width of the paper P. The non-image forming area is connected to both sides of the image forming area and is located at both ends of the photosensitive drum 50.
Note that the width of the image forming area changes according to the width of the paper P. The width of the paper P is the width of the maximum paper that can be printed by the printer 10 or the paper that is most frequently used by the printer 10. This refers to the width, and generally refers to the width of A4 size paper.

  The cleaning blade 82 includes a formation region sliding contact portion that is in sliding contact with the image forming region of the photosensitive drum 50 as viewed in the axial direction of the rotation axis of the photosensitive drum 50, that is, the longitudinal direction of the cleaning blade 82, and the photosensitive member. The drum 50 is roughly classified into a non-formation area sliding contact portion that is in sliding contact with an image non-formation area of the drum 50. The non-formation area sliding contact portion is connected to the formation area sliding contact portion and is located at both ends of the cleaning blade 82.

The reservoir members 88 are respectively disposed so as to face the non-formation region sliding contact portion of the cleaning blade 82.
Here, the image forming area (paper width) <the width of the developing roller 70 <the width of the charging roller 64 <the width of the cleaning blade 82, and the reservoir member 88 is preferably in the axial direction of the rotating shaft of the photosensitive drum 50. As a result, they are located outside the image forming area and inside the width of the developing roller 70, respectively.
A seal member 92 made of, for example, a felt material is disposed in the vicinity of both ends of the cleaning blade 62. A gap G is provided between the seal member 92 and the reservoir member 88 as a preferred mode. The gap G is, for example, in the range of 1.0 mm to 5.0 mm, and preferably in the range of 1.5 mm to 2.5 mm.

FIG. 5 is a block diagram schematically showing the configuration of the control system in the printer 10.
The printer 10 includes a control unit 94, and the control unit 94 includes an MPU (microprocessor), a memory, a storage device, and the like. A communication unit 96 and operation keys 98 are connected to the control unit 94.

  The control unit 94 can execute the program stored in the storage device, and executes printing or the like based on the command received from the personal computer via the communication unit 96 or the command from the user using the operation key 98 according to the program. To do.

  Specifically, the control unit 94 is a group of rollers provided along the transport path 16, that is, a pickup roller 17, a paper feed roller pair 18, a transport roller pair 20, a registration roller pair 22, and a secondary transfer roller 24. The rotation of the fixing roller pair 26 and the discharge roller pair 28 is controlled, and the travel of the transfer belt 32 is controlled.

  The control unit 94 controls the operation of the laser scanning unit 46 and also controls the operation of the drum assembly 44, that is, the photosensitive drum 50, the charging unit 56, the developing unit 58, and the primary transfer roller 60.

Here, there are at least two modes of control executed by the control unit 94: an image forming mode and a refresh mode.
The image forming mode is a mode for printing on the paper P. In the image forming mode, the control unit 94 operates the entire drum assembly 44 to form a toner image on the photosensitive drum 50 and transfers the formed toner image onto the paper P via the transfer belt 32.

On the other hand, in the refresh mode, the control unit 94 discharges the deteriorated toner particles by a predetermined amount from the developing unit 58 to the photosensitive drum 50, and collects and discharges the discharged toner particles by the drum cleaning unit 62. For example, the discharge amount of the toner particles is appropriately set based on the past printing rate.
In the refresh mode, since a toner image to be transferred to the paper P is not formed, a reverse bias is applied to the primary transfer roller 60 so that toner particles do not adhere from the photosensitive drum 50 to the transfer belt 32.
When a predetermined amount of deteriorated toner particles is discharged, abrasive particles adhering to the surface of the toner particles are also discharged together.

FIG. 6 is a graph showing the relationship between the axial position (longitudinal position) of the rotation axis of the photosensitive drum 50 and the thickness of the photosensitive layer 52 in the initial stage and after the durability test. And the conditions of an endurance test are shown below.
Experimental machine: FS-C5300DN remodeling machine manufactured by Kyocera Mita Co., Ltd. Environmental temperature: 23 ° C
Environmental humidity: 65% RH
Paper transport speed: 160 mm / s
Photosensitive drum: φ30mm
Photosensitive layer: Positively charged single layer OPC (initial film thickness 40 μm)
Charging roller: φ12mm (Epichlorohydrin rubber)
Charging applied voltage: 1.2 kVdc
Static eliminator: LED method Photosensitive layer surface potential: + 400V
Number of printed sheets: 200,000 Abrasive particles: Titanium oxide (addition amount 0.5% by mass)
Reserving member: PET film (thickness 100 μm)
Gap G: 2 mm

FIG. 7 shows the relationship between the longitudinal position of the photosensitive drum and the thickness of the photosensitive layer in the comparative printer having the same configuration as the printer 10 except that the reservoir member 88 is not provided. It is a graph shown about.
The conditions of the durability test were the same as in FIG. 6, but the durability test was stopped when the number of printed sheets reached 170,000 due to abrasion of the photosensitive layer.

  Comparing FIG. 6 and FIG. 7, it can be seen that the printer 10 suppresses uneven wear of the photosensitive drum 50 compared to the printer of the comparative example.

  In the drum assembly 44 described above, the two reservoir members 88 form the storage portions 90 between the cleaning blades 82. By storing the toner particles in the storage unit 90, the sliding between the image non-formation region of the photosensitive drum 50 and the cleaning blade 82 is alleviated, and uneven cleaning and vibration of the cleaning blade 82 or the photosensitive drum 50 are generated. It is suppressed. Further, uneven wear is suppressed and the life of the cleaning blade 82 and the photosensitive drum 50 is prolonged, so that the replacement frequency of the cleaning blade 82 and the photosensitive drum 50 is reduced, and the maintenance cost of the drum assembly 44 is reduced.

In the drum assembly 44 described above, the abrasive particles contained in the developer scrape off deposits such as paper-derived components and discharge products on the photosensitive drum 50, thereby suppressing deterioration in image quality.
Further, since the toner particles are stored in the storage portion 90 formed by the reservoir member 88, the abrasion of the non-image forming area of the photosensitive drum 50 by the abrasive particles is suppressed.

The two reservoir members 88 are separated from each other, and the toner particles and the abrasive particles stored in the storage unit 90 easily flow out of the storage unit 90. For this reason, the proportion of the abrasive particles in the reservoir 90 is prevented from gradually increasing with time, and the non-image-forming region of the photosensitive drum 50 is prevented from being worn by the abrasive particles over a long period of time. The
Further, the two reservoir members 88 are separated from each other, and the polishing of the image forming area of the photosensitive drum 50 by the abrasive particles deposited on the edge of the forming area sliding contact portion of the cleaning blade 82 is stored in the storage section 90. The toner particles are not hindered.

  In the drum assembly 44 described above, since the developer includes any one of particles made of titanium oxide, aluminum oxide, and silicon oxide as abrasive particles, the photosensitive drum 50 is reliably polished, and the image quality is deteriorated. Is prevented.

  In the drum assembly 44 described above, since the charging unit 56 includes the charging roller 64 and adopts the contact charging method, the generation amount of ozone is small and it is environmentally friendly.

  In the drum assembly 44 described above, the image forming area and the image non-forming area of the photosensitive drum 50 are made of an organic photosensitive material, and are highly versatile and inexpensive.

In the drum assembly 44 described above, by providing the gap G between the reservoir member 88 and the seal member 92, the toner particles and the like stored in the storage unit 90 are more likely to flow out. For this reason, especially when the developer contains abrasive particles, an increase in the amount of abrasive particles stored in the storage unit 90 is suppressed, and uneven wear of the photosensitive drum 50 is reliably suppressed.
In the printer 10 described above, since the photosensitive drum 50 has a long life, the maintenance cost is reduced.

  Further, according to the printer 10 described above, a large amount of toner particles are supplied to the upper edge (edge) of the cleaning blade 82 in the refresh mode, and the polishing is accumulated on the edge of the non-formation area sliding portion of the cleaning blade 82. Agent particles are washed away. For this reason, in the printer 10, the photosensitive drum 50 has a longer life, and the maintenance cost is further reduced.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the claims.

For example, in the embodiment described above, the reservoir member 88 has a rectangular shape, but the shape of the reservoir member is not limited to a rectangle. 8 and 9 show a reservoir member 100 having a preferred shape, and the reservoir member 100 has a part of the upper edge cut away.
More specifically, the upper edge of the reservoir member 100 includes a parallel portion 102 that is parallel to the axis of the rotation axis of the photosensitive drum 50, and a slantingly inclined portion 104 that continues to the parallel portion 102. The inclined portion 104 is continuous with the parallel portion 102 on the center side in the axial direction of the rotation axis of the photosensitive drum 50.

FIG. 10 is a graph showing the relationship between the longitudinal position of the photosensitive drum 50 and the thickness of the photosensitive layer 52 in the printer 10 to which the reservoir member 100 is applied, in the initial stage and after the durability test. The conditions for the durability test are the same as in FIG.
As is apparent from FIG. 10, when the reservoir member 100 is used, uneven wear of the photosensitive drum 50 is further suppressed as compared with the case where the reservoir member 88 is used. This is due to the following reason.

  When the reservoir member 100 is used, by providing the inclined portion 104 at the upper edge of the reservoir member 100, the toner particles and the like stored in the storage portion 90 are more likely to flow out. For this reason, especially when the developer contains abrasive particles, an increase in the amount of abrasive particles stored in the storage unit 90 is suppressed, and uneven wear of the photosensitive drum 50 is reliably suppressed.

  In the above-described embodiment, the toner image is transferred from the photosensitive drum 50 to the transfer belt 32. However, the toner image may be directly transferred from the photosensitive drum 50 to the paper P.

  Further, in the above-described embodiment, the developer includes abrasive particles as a preferable aspect, but the developer may not include abrasive particles. In this case, the toner particles stored in the storage unit 90 suppress the occurrence of uneven wear and vibration of the cleaning blade 82 or the photosensitive drum 50.

  Furthermore, in the above-described embodiment, an example in which the image forming apparatus is embodied in the printer 10 is shown. However, the present invention is naturally applicable to a multifunction machine, a copier, a facsimile machine, or the like.

  The present invention has been described above with specific embodiments. However, the present invention is not limited to these descriptions, and a configuration obtained by appropriately combining configurations described as different embodiments is also a technique of the present invention. A configuration obtained by appropriately combining a conventionally known technique with the configuration obtained in this manner is also included in the technical scope of the present invention.

10 Printer (image forming device)
32 transfer belt 44 drum assembly 50 photosensitive drum 52 photosensitive layer 58 developing unit 62 drum cleaning unit 64 charging roller 80 housing 82 cleaning blade 88 reservoir member 92 seal member 94 control unit 100 reservoir member 102 parallel portion 104 inclined portion

Claims (9)

A photosensitive drum having a rotating shaft, an image forming region on which a toner image to be transferred to a sheet is formed, and an image non-forming region connected to both sides of the image forming region in the axial direction of the rotating shaft;
A charging unit for charging the photosensitive drum;
A developing unit for applying toner particles contained in a developer to the photosensitive drum;
In a drum assembly of an image forming apparatus comprising a drum cleaning unit that removes unnecessary toner particles from the photosensitive drum,
The drum cleaning unit includes:
A cleaning blade having a forming area sliding contact portion that is in sliding contact with the image forming area and a non-forming area sliding contact portion that is in sliding contact with the non-image forming area;
The cleaning blade is disposed in the vicinity of the non-formation region sliding contact portion, and is spaced apart from each other in the axial direction of the rotation shaft. The cleaning blade cooperates with the non-formation region portion from the photosensitive drum. A drum assembly of an image forming apparatus, comprising: at least two reservoir members that respectively form storage portions that temporarily store the scraped toner particles. The drum assembly of the image forming apparatus according to claim 1,
The drum assembly of an image forming apparatus, wherein the developer includes abrasive particles. The drum assembly of the image forming apparatus according to claim 1 or 2,
The drum assembly of an image forming apparatus, wherein the developer includes one or more particles selected from the group consisting of titanium oxide, aluminum oxide, and silicon oxide as the abrasive particles. The drum assembly of the image forming apparatus according to any one of claims 1 to 3,
The drum assembly of an image forming apparatus, wherein the charging unit includes a charging member in contact with the photosensitive drum. The drum assembly of the image forming apparatus according to any one of claims 1 to 4,
The drum assembly of an image forming apparatus, wherein an image forming area and an image non-forming area of the photosensitive roller are made of an organic photosensitive material. The drum assembly of the image forming apparatus according to any one of claims 1 to 5,
The upper edge of the reservoir member includes a parallel portion parallel to the rotation shaft, and an inclined portion connected obliquely downward with respect to the parallel portion on the center side of the rotation shaft of the photosensitive drum as viewed in the axial direction of the rotation shaft. A drum assembly of an image forming apparatus. The drum assembly of the image forming apparatus according to any one of claims 1 to 6,
The drum cleaning unit further includes a seal member provided in contact with both ends of the cleaning blade as viewed in the axial direction of the rotating shaft,
A drum assembly of an image forming apparatus, wherein a gap is provided between the seal member and the reservoir member when viewed in the axial direction of the rotation shaft.   An image forming apparatus comprising the drum assembly of the image forming apparatus according to claim 1. The image forming apparatus according to claim 8.
A control unit for controlling the drum assembly;
The control unit is
Selected from a plurality of operation modes including at least an image forming mode for forming a toner image to be transferred onto a sheet and a refresh mode for applying only unnecessary toner particles in the developing unit to the photosensitive drum. An image forming apparatus that causes the drum assembly to selectively execute one operation mode.

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