JP6131751B2 - Process unit - Google Patents

Description

  The present invention relates to a process unit including a photosensitive drum and a developing roller.

  Conventionally, a process unit used in an electrophotographic image forming apparatus includes a photosensitive drum and a developing roller that supplies a developer to the peripheral surface of the photosensitive drum (for example, Patent Document 1). reference). Specifically, the process unit includes a drum cartridge that supports the photosensitive drum and a developing cartridge that is attached to the drum cartridge. The developing roller has a shaft portion supported by a side wall constituting the developing cartridge via a bearing member.

  In this process unit, the bearing member is disposed inside the both end portions in the axial direction of the photosensitive drum. The bearing member is provided so as not to protrude from the peripheral surface of the developing roller, and does not contact the peripheral surface of the photosensitive drum.

JP 2013-54060 A

  By the way, in the above-described technique, when the diameter of the developing roller is reduced, the bearing member protrudes from the surface of the developing roller and hits the peripheral surface of the photosensitive drum. If the bearing member is designed so as not to hit the peripheral surface of the photosensitive drum, the portion of the shaft portion of the developing roller that is supported by the bearing member may become too thin.

  Therefore, an object of the present invention is to provide a process unit that can reduce the diameter of the developing roller while ensuring the rigidity of the developing roller.

In order to achieve the above object, a process unit according to the present invention includes a photosensitive drum having a substrate having a photosensitive layer formed on the peripheral surface, a developing roller for supplying a developer to the peripheral surface of the photosensitive drum, and a shaft of the developing roller A pair of bearing members that rotatably support both end portions in the direction.
Each bearing member is provided outside the base in the axial direction, and the shortest distance from the rotation axis of the photosensitive drum to the bearing member is smaller than the radius of the photosensitive drum.

  According to the process unit configured in this way, even if the diameter of the developing roller is small, the bearing member that supports the developing roller does not hit the peripheral surface of the photosensitive drum, so both end portions of the shaft portion of the developing roller There is no need to make it extremely thin. Thereby, the diameter of the developing roller can be reduced while ensuring the rigidity of the developing roller.

The process unit described above may further include a drum frame that holds the photosensitive drum, and a developing frame that holds the developing roller via a bearing member.
In this case, the developing frame is smaller in size in the axial direction than the drum frame, and the bearing members are positioned on the inner side of the side walls of the drum frame disposed on both sides in the axial direction of the photosensitive drum. It can be.

  In the above-described process unit, the developing roller is preferably a brush roller having a roller main body and a brush layer in which fibers are implanted on the outer peripheral surface of the roller main body.

  The brush roller, for example, has a smaller repulsive force with the photosensitive drum and a higher developer conveying force than a developing roller with a shaft covered with rubber. The developer can be supplied to the photosensitive drum. And even when using a brush roller with a reduced diameter, the process unit configured in this way does not require extremely narrow ends of the roller body, ensuring the rigidity of the roller body. can do.

  The roller body described above is desirably formed with a uniform thickness at least at a position between the pair of bearing members.

  According to this, the rigidity of the roller body can be ensured.

Further, the process unit described above is provided at both end portions in the axial direction of the developing roller and seal members provided between both end portions in the axial direction of the developing roller and in contact with the surface of the photosensitive drum. Thus, a regulating member configured to regulate the distance between the developing roller and the photosensitive drum may be provided.
In this case, the restricting member can be arranged outside the seal member and inside the end portion of the base in the axial direction.

The process unit described above may include a photosensitive drum gear that rotates integrally with the photosensitive drum, and a developing roller gear that rotates integrally with the developing roller.
In this case, the photosensitive drum gear and the developing roller gear can be directly meshed with each other.

  In the above-described process unit, the developing frame may be detachable from the drum frame.

  According to the present invention, even when the diameter of the developing roller is small, it is not necessary to extremely narrow the shaft portion of the developing roller. Therefore, the developing roller diameter can be reduced while ensuring the rigidity of the developing roller. Can do.

1 is a central sectional view illustrating a schematic configuration of a laser printer including a process unit according to an embodiment of the present invention. It is a figure which shows the state which took out the process unit of the laser printer. Sectional view (a) showing process unit, left side view (b) of photosensitive drum and developing cartridge when brush roller is located at developing position, and photosensitive drum and developing cartridge when brush roller is located at separated position It is a left side view (c). It is II sectional drawing of Fig.3 (a). They are a sectional view (a) showing the drum cartridge when the cam takes the second posture, and a left side view (b). They are a sectional view (a) showing the drum cartridge when the cam takes the first posture, and a left side view (b). It is an expanded sectional view which shows the structure of the cam vicinity in a modification.

  Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, after describing the schematic configuration of the laser printer 1 to which the process unit 6 according to the embodiment is attached and detached, the characteristic portions of the present invention will be described in detail.

  In the following description, the direction will be described with reference to the user when using the laser printer 1. That is, in FIG. 1, the right side toward the paper surface is “front side (front side)”, the left side toward the paper surface is “rear side (back side)”, the back side toward the paper surface is “right side”, and it faces the paper surface. Let the near side be the “left side”. In addition, the vertical direction toward the page is defined as the “vertical direction”.

<Schematic configuration of laser printer>
As shown in FIG. 1, the laser printer 1 includes an apparatus main body 2, a feeder unit 3 for feeding paper S, and an image forming unit 4 for forming an image on the paper S.

  The apparatus main body 2 mainly includes a side frame 21 (shown only on the right side), a top cover 22, and a front cover 23 arranged on the left and right.

  The top cover 22 is configured to be openable and closable up and down with a rotating shaft 22A provided at the rear as a fulcrum. Then, by turning the top cover 22 upward, the mounting opening 2 </ b> A formed in the upper part of the apparatus main body 2 can be opened.

  The front cover 23 is configured to be openable and closable forward and backward with the lower part as a fulcrum. The paper S can be supplied to a paper feed tray 31 described later from an opening that is opened when the front cover 23 is rotated forward.

  The feeder unit 3 is provided with a paper feed tray 31 into which the paper S is placed. Various conveyance mechanisms such as a pickup roller 32 are provided on the rear side of the paper feed tray 31 so that the paper S placed on the paper feed tray 31 can be supplied to the image forming unit 4 one by one.

  The image forming unit 4 includes a scanner unit 5, a process unit 6, and a fixing device 7.

  The scanner unit 5 is provided on the front side in the apparatus main body 2 and includes a laser light emitting unit, a polygon mirror, a lens, a reflecting mirror, and the like (not shown). In the scanner unit 5, a laser beam is irradiated on the surface of a photosensitive drum 61 described later by high-speed scanning.

  The process unit 6 includes a drum cartridge 6A that supports the photosensitive drum 61 and a developing cartridge 6B that stores toner as an example of a developer. In addition to the photosensitive drum 61, the drum cartridge 6A includes a transfer roller 62 that transfers the toner image on the photosensitive drum 61 onto the paper S, and a charger 63. The developing cartridge 6 </ b> B supports a brush roller 64 as an example of a developing roller for supplying toner to the photosensitive drum 61. The detailed configuration of the process unit 6 will be described later.

  As shown in FIG. 2, the process unit 6 is detachably attached to the apparatus main body 2 through a mounting opening 2 </ b> A formed when the drum cartridge 6 </ b> A and the developing cartridge 6 </ b> B are integrated and the top cover 22 is opened. is there.

  Specifically, the side frame 21 is provided with a first guide 21A and a second guide 21B disposed in front of the first guide 21A. The first guide 21 </ b> A and the second guide 21 </ b> B are grooves extending from the edge of the mounting opening 2 </ b> A toward the back of the apparatus main body 2. And the process unit 6 has the 1st boss | hub 101 and the 2nd boss | hub 102 which protrude on the left-right side wall 120 (only right side is shown) of the drum frame 100 mentioned later to the left-right direction outer side. The first boss 101 is provided on the rotation axis of the photosensitive drum 61. The second boss 102 is provided at the front end of the drum frame 100.

  When the process unit 6 is attached to or detached from the apparatus main body 2, the first boss 101 moves along the first guide 21A, and the second boss 102 moves along the second guide 21B. .

  Returning to FIG. 1, in the process unit 6, the surface of the rotating photosensitive drum 61 is uniformly charged by the charger 63 and then exposed by high-speed scanning of the laser beam from the scanner unit 5. As a result, the potential of the exposed portion is lowered, and an electrostatic latent image based on the image data is formed on the surface of the photosensitive drum 61.

  Next, toner is supplied to the electrostatic latent image on the photosensitive drum 61 by the brush roller 64, and a toner image is formed on the surface of the photosensitive drum 61. Thereafter, the sheet S is conveyed between the photosensitive drum 61 and the transfer roller 62, whereby the toner image carried on the surface of the photosensitive drum 61 is transferred onto the sheet S.

  The fixing device 7 is disposed above the process unit 6 and mainly includes a heating roller 71 and a pressure roller 72.

The heating roller 71 is a member that heats the sheet S, and a heat source (not shown) such as a halogen lamp is provided inside the heating roller 71.
The pressure roller 72 is a member that sandwiches and conveys the paper S with the heating roller 71, and is provided on the upper rear side of the heating roller 71.

  In the fixing device 7 configured as described above, the toner transferred onto the paper S is thermally fixed while the paper S passes between the heating roller 71 and the pressure roller 72. The sheet S thermally fixed by the fixing device 7 is conveyed to a discharge roller 8 disposed on the downstream side of the fixing device 7, and is discharged from the discharge roller 8 onto a discharge tray 9 formed on the upper surface of the top cover 22. To be discharged.

<Detailed configuration of process unit>
Next, the configuration of the process unit 6 will be described in detail.

  As shown in FIG. 3A, the drum cartridge 6A includes a drum frame 100 as an example of a frame having an opening 110 on the upper side and supporting the photosensitive drum 61 and the like at the rear end. The developing cartridge 6B includes a developing frame 200 that is formed separately from the drum frame 100 and supports the brush roller 64 and the like.

  As shown in FIG. 4, the drum frame 100 is formed in a box shape and can accommodate the developing cartridge 6 </ b> B inside.

  The photosensitive drum 61 has a cylindrical base 611, and a photosensitive layer is applied to the surface of the base 611. The base 611 is formed shorter than the roller main body 641 of the brush roller 64, and both left and right end portions are provided in the axial direction of the brush roller 64, that is, on the inner side in the left-right direction from the side wall 240 of the developing frame 200. Yes.

  In addition, shaft members 612 are fitted into the left and right ends of the photosensitive drum 61. The shaft member 612 is rotatably supported on the side walls 120 of the drum frame 100 disposed on both sides of the photosensitive drum 61 in the left-right direction. The left shaft member 612 is integrally formed with a photosensitive drum gear 61G. When the process unit 6 is mounted on the apparatus main body 2, the photosensitive drum gear 61G is engaged with a gear (not shown) provided on the apparatus main body 2 so that a driving force is input from a driving source.

  The development frame 200 is smaller in the left-right direction than the drum frame 100. Returning to FIG. 3A, the development frame 200 has a toner storage chamber 230 formed in a cylindrical shape, and a development chamber 220 protruding from the rear wall of the toner storage chamber 230. The developing chamber 220 and the toner storage chamber 230 communicate with each other through a communication port 211 formed in a partition wall 210 provided between the developing chamber 220 and the toner storage chamber 230.

  In the developing chamber 220, a brush roller 64, a blade 65, and a stirring member 66 are disposed. A conveying member 67 is disposed in the toner storage chamber 230. The developing chamber 220 and the toner storage chamber 230 can store toner.

  The brush roller 64 includes a cylindrical roller body 641 supported by the developing frame 200 and a brush layer 642 in which fibers are implanted on the outer peripheral surface of the roller body 641.

  As shown in FIG. 4, the brush roller 64 is provided with a regulating member 644, a bearing member 645, and a pressure receiving roller 643 arranged in this order from the inside at both left and right ends of the roller body 641. A seal member 68 is provided between the brush roller 64 and both end portions in the left-right direction and the developing frame 200 to prevent toner from leaking from the gap.

  In the roller main body 641, the portion on the outer side in the left-right direction with respect to the pair of bearing members 645 is thinner than the central portion on the inner side in the left-right direction. That is, the roller body 641 has a uniform thickness between the pair of bearing members 645, more specifically, from a portion inserted through one bearing member 645 to a portion inserted through the other bearing member 645. Is formed. Thus, the rigidity of the roller main body 641 can be ensured by making the thickness of the roller main body 641 uniform at portions other than both ends.

  The outer diameter at the center of the roller body 641 can be set to 4 to 10 mm, and more preferably 6 to 8 mm, for example. As described above, even if the roller body 641 is made thin, the brush roller 64 moves away from the photosensitive drum 61 when rotating in contact with the photosensitive drum 61 as compared with the developing roller having the roller shaft surface coated with rubber. Since the force received is small, the roller body 641 is not easily bent. Further, since the brush roller 64 has a higher toner conveying force than the developing roller described above, the toner can be sufficiently supplied to the photosensitive drum 61 even if the roller body 641 is made thinner.

  The pressure receiving roller 643 is a ring-shaped member provided to receive a force from a cam 310 to be described later, and at both ends of the roller main body 641 so that the roller main body 641 can rotate with respect to the pressure receiving roller 643. The narrowed part is inserted. The pressure receiving roller 643 is formed in such a size that the peripheral surface and the peripheral surface of the roller body 641 are flush with each other. The pressure receiving roller 643 is not necessarily provided, and the roller main body 641 may be formed to have a uniform thickness up to both ends.

  The regulating member 644 is formed in a ring shape, and is fitted to the roller main body 641 in the left-right direction, outside the seal member 68 and inside the end portion of the base 611 of the photosensitive drum 61. The regulating member 644 is configured to regulate the distance between the roller main body 641 and the photosensitive drum 61 by contacting the circumferential surface of the base 611.

  The bearing member 645 is formed in a cylindrical shape, and rotatably supports the roller body 641. The bearing member 645 is inserted into a hole formed in the side wall 240 of the developing frame 200 and supported by a bearing support portion 241 that forms an edge of the hole. That is, both end portions in the axial direction of the brush roller 64 are held by a pair of holding portions H including the bearing members 645 and the bearing support portions 241 provided on the left and right.

  Further, the bearing member 645 has a flange that protrudes radially outward from the side wall 240 of the developing frame 200 and extends along the side wall 240.

  Each bearing member 645 is located outside the base 611 of the photosensitive drum 61 in the left-right direction and inside the side wall 120 of the drum frame 100. Each bearing member 645 protrudes toward the shaft side of the photosensitive drum 61 from the tip of the brush layer 642 of the brush roller 64, and as shown in FIG. 3B, the photosensitive drum 61 and the brush roller are viewed from the left-right direction. It overlaps with the photosensitive drum 61 on a straight line L1 connecting the 64 axes. Specifically, the shortest distance D <b> 2 from the rotation axis of the photosensitive drum 61 to the bearing member 645 is smaller than the radius r of the photosensitive drum 61.

  The bearing support portion 241 that supports the entire circumference of the bearing member 645 is also located on the outer side in the left-right direction of the base 611 of the photosensitive drum 61 and on the inner side of the side wall 120 of the drum frame 100 (see FIG. 4). The roller 64 protrudes from the tip of the brush layer 642 toward the shaft side of the photosensitive drum 61. Specifically, the shortest distance D <b> 1 from the rotation axis of the photosensitive drum 61 to the bearing support portion 241 is smaller than the radius r of the photosensitive drum 61.

  For example, when the bearing member that supports the brush roller 64 is provided on the inner side of both end portions in the axial direction of the photosensitive drum 61, when the diameter of the brush roller 64 is to be reduced, the bearing member is photosensitive. If it is designed so that it does not hit the peripheral surface of the drum 61, both ends of the roller body 641 may become too thin. In the present embodiment, since the bearing member 645 and the bearing support portion 241 are configured as described above, the bearing member 645 and the bearing support portion 241 do not hit the peripheral surface of the photosensitive drum 61. It is not necessary to make the both ends of 641 extremely thin. Thereby, it is possible to reduce the diameter of the brush roller 64 while ensuring the rigidity of the roller body 641.

  As shown in FIG. 3A, the brush roller 64 held by the developing frame 200 is exposed at the rear part from the developing frame 200, and the exposed part can come into contact with the photosensitive drum 61. Yes.

  The blade 65 is a member for regulating the amount of toner carried by the brush roller 64, and is provided so that the tip thereof enters the brush layer 642 of the brush roller 64. The stirring member 66 is a member for uniformly supplying the toner to the brush roller 64 while stirring the toner in the developing chamber 220. The conveyance member 67 is a member for conveying the toner in the toner storage chamber 230 from the communication port 211 to the development chamber 220 side. The shaft portion 671 is rotatably supported by the development frame 200, and the diameter from the shaft portion 671 is increased. The sheet member 672 extends in the direction.

  As shown in FIG. 3B, the developing cartridge 6B has a brush roller gear 64G as an example of a developing roller gear, a stirring member gear 66G, an intermediate gear G1, and a conveying member gear 67G on the left side surface. A gear train including is provided.

  The brush roller gear 64 </ b> G is a gear that rotates integrally with the brush roller 64, and is fixed to the left end portion of the brush roller 64. The stirring member gear 66G is a gear that rotates integrally with the stirring member 66 and is fixed to the left end of the stirring member 66. The stirring member gear 66G meshes with the brush roller gear 64G. The intermediate gear G1 is a gear rotatably supported on the side wall 240 of the developing frame 200, and meshes with the stirring member gear 66G. The conveyance member gear 67 </ b> G is a gear that rotates integrally with the conveyance member 67, and is fixed to the left end portion of the conveyance member 67. The conveying member gear 67G meshes with the intermediate gear G1.

  The developer cartridge 6B configured as described above moves along the first guide groove 121 and the second guide groove 122 formed on the side wall 120 of the drum frame 100 as shown in FIG. It can be attached to and detached from the drum cartridge 6A. Further, the developing cartridge 6B is attached to the drum cartridge 6A from a first position close to the photosensitive drum 61 as shown in FIG. 3B and a first position as shown in FIG. 3C. Is movable to a second position away from the photosensitive drum 61.

  Specifically, the first guide groove 121 formed in the drum frame 100 is a groove with which the pressure receiving rollers 643 provided at both ends of the brush roller 64 are engaged, as shown in FIG. The first guide groove 121 is formed in a substantially U shape that opens upward, and extends downward from the upper end of the side wall 120 to a position obliquely below the front side of the photosensitive drum 61.

  The second guide groove 122 is a groove with which the shaft portion 671 of the transport member 67 is engaged. The second guide groove 122 is formed in a substantially U shape that opens upward, and extends substantially in front of the first guide groove 121 in parallel with the first guide groove 121.

  The lower portion of the first guide groove 121 is wider than the outer diameter of the pressure receiving roller 643, and the lower portion of the second guide groove 122 is wider than the outer diameter of the shaft portion 671 of the conveying member 67. It has become. Thereby, the developing cartridge 6B can move between the first position and the second position.

  Further, the brush roller 64 is configured such that the brush layer 642 can come into contact with the peripheral surface of the photosensitive drum 61 when the pressure receiving roller 643 moves back and forth in the first guide groove 121 along the bottom surface of the first guide groove 121. It is possible to move between a development position (position in FIG. 3B) and a separation position (position in FIG. 3C) where the brush layer 642 is separated from the peripheral surface of the photosensitive drum 61.

  When the brush roller 64 is located at the development position, the brush roller gear 64G is located at a connection position (position shown in FIG. 3B) that meshes with a photosensitive drum gear 61G described later, and when the brush roller 64 is located at a separation position. The cutting position (the position shown in FIG. 3C) deviated from the photosensitive drum gear 61G is set.

  As shown in FIG. 5B, the process unit 6 further includes a moving mechanism 300 for moving the developing cartridge 6B between the first position and the second position.

  The moving mechanism 300 includes a cam 310, a first gear 320 and a swing member 330 (only the left side is shown) provided on the left and right side walls 120 of the drum frame 100, and a connecting shaft 340 for connecting the left and right swing members 330, respectively. The second gear 350 that can rotate integrally with the connecting shaft 340 is mainly provided.

  The cam 310 is an example of a working member, and is housed in a housing portion formed as a recess in the side wall 120 of the drum frame 100 and is rotatably supported by the side wall 120 as shown in FIG. . Specifically, the side wall 120 of the drum frame 100 includes support walls 123 as an example of a pair of support portions disposed on the left and right sides of the cam 310, and the pair of support walls 123 extends in the left-right direction. The shaft 313 is rotatably supported. The shaft 313 is a member that defines the rotation axis of the cam 310, and is fixed to the cam 310 and integrated with the cam 310. Thus, the cam 310 can be stably supported by supporting the shaft 313 with both ends.

  Further, as shown in FIG. 5A, the cam 310 is located on the opposite side of the photosensitive drum 61 with the brush roller 64 interposed therebetween, that is, on the pressure receiving roller 643 at positions corresponding to both ends of the brush roller 64 in the axial direction. It is located in the front and faces the pressure receiving roller 643.

  The cam 310 has a first action part 311 and a second action part 312 closer to the rotation axis of the cam 310 than the first action part 311 on the circumferential surface. The first action unit 311 is a surface that positions the brush roller 64 at the development position when facing the pressure receiving roller 643 (see FIG. 6). The second action unit 312 is a surface that allows the brush roller 64 to move from the development position to the separation position when facing the pressure receiving roller 643.

  The cam 310 rotates with respect to the side wall 120 of the drum frame 100, so that the first action portion 311 faces the photosensitive drum 61 side (the posture shown in FIG. 6A) and the second action portion. It is possible to take the second posture (the posture of FIG. 5A) in which 312 faces the photosensitive drum 61 side. When the cam 310 takes the first posture (when the brush roller 64 is located at the developing position), the shortest distance D3 between the first action portion 311 and the rotation axis of the photosensitive drum 61 (see FIG. 6A). ) Is the shortest distance D4 between the second action portion 312 and the rotation axis of the photosensitive drum 61 when the cam 310 takes the second posture (when the brush roller 64 is located at the separation position) (FIG. 5A). (See below).

  As shown in FIG. 5B, the first gear 320 is a gear fixed to the shaft 313 and is provided so as to be rotatable integrally with the cam 310.

  The swing member 330 is formed in a substantially fan shape centering on the connecting shaft 340, and gear teeth that mesh with the first gear 320 are formed on the peripheral surface thereof. Further, the side wall 120 of the drum frame 100 is provided with stoppers 360 that can come into contact with the swing member 330 on both sides in the rotational direction of the swing member 330. Thereby, the range in which the swing member 330 can be rotated is determined.

  The swing member 330 is configured such that when the cam 310 takes the first posture, the swing member 330 assumes the posture most tilted to the front, and when the cam 310 takes the second posture, the swing member 330 takes the posture most tilted to the rear. ing.

  The second gear 350 is provided so as to mesh with a third gear 370 provided in the apparatus main body 2 when the process unit 6 is attached to the apparatus main body 2.

  The third gear 370 is connected to a drive source (not shown) provided in the apparatus main body 2. The rotation of the third gear 370 is controlled by a control device (not shown). Specifically, the third gear 370 rotates by a predetermined amount counterclockwise in FIG. 5 when printing is started, and rotates by a predetermined amount clockwise in FIG. 5 after printing is finished. ing.

Next, the operation of the process unit 6 configured as described above will be described.
When the process unit 6 is not attached to the apparatus main body 2, the cam 310 is in the second posture as shown in FIG. 5A, and the second action portions 312 are provided at both ends of the brush roller 64. It faces the received pressure roller 643. Thereby, the brush roller 64 is located in the separation position by its own weight.

  When the process unit 6 is mounted on the apparatus main body 2, the photosensitive drum gear 61 </ b> G meshes with a gear (not shown) provided on the apparatus main body 2, and the second gear 350 of the moving mechanism 300 is the third gear provided on the apparatus main body 2. Engage with the gear 370.

  When a printing instruction is input to the laser printer 1, first, the third gear 370 rotates a predetermined amount counterclockwise in FIG. As a result, the swinging member 330 swings forward, and the first gear 320 engaged therewith rotates counterclockwise in FIG. At this time, the cam 310 also rotates together with the first gear 320 toward the first posture. As a result, as shown in FIG. 6A, the portion of the cam 310 that faces the pressure receiving roller 643 is switched from the second action portion 312 to the first action portion 311, and the roller body 641 is pushed up toward the photosensitive drum 61. Therefore, the brush roller 64 moves to the development position. When the brush roller 64 moves to the developing position, the developing cartridge 6B moves to the second position, and the brush roller gear 64G moves to the connecting position and meshes with the photosensitive drum gear 61G.

  When printing is started, driving force is input to the photosensitive drum gear 61G, and the photosensitive drum 61 rotates. Further, when the photosensitive drum gear 61G rotates, the driving force from the driving source is also transmitted to the brush roller gear 64G meshing with the photosensitive drum gear 61G, the stirring member gear 66G connected to the brush roller gear 64G, and the conveying member gear 67G. Then, the brush roller 64, the stirring member 66, and the conveying member 67 also start to rotate.

  As described above, the brush roller gear 64G meshes with the photosensitive drum 61, so that the driving force can be transmitted to the photosensitive drum 61 and each gear provided in the developing cartridge 6B through one path. The configuration can be simplified compared to the configuration in which the driving force is separately transmitted to the developing cartridge 6B.

  Further, since the surface of the brush roller 64 is a brush layer 642 composed of a plurality of fibers, the force generated between the brush roller 64 and the photosensitive drum 61 when the brush roller 64 rotates while contacting the photosensitive drum 61. Although not constant, in the present embodiment, the brush roller 64 is held at the development position by the cam 310 supported by the drum frame 100, so that the brush roller 64 is biased toward the development position by a spring or the like. As compared with the above, the brush roller 64 can be stably held.

  When printing is completed, the third gear 370 rotates a predetermined amount clockwise in FIG. At this time, the swinging member 330 swings backward, and the cam 310 rotates clockwise in FIG. 6 toward the second posture. As a result, as shown in FIG. 5A, the portion of the cam 310 that faces the pressure receiving roller 643 is switched from the first action part 311 to the second action part 312, so that the brush roller 64 moves to the separated position by its own weight. Moving. As the brush roller 64 moves to the separation position in this way, the developing cartridge 6B moves to the second position, and the brush roller gear 64G is disengaged from the photosensitive drum gear 61G.

  As described above, when printing is not performed, the brush roller 64 is positioned at a separated position away from the photosensitive drum 61, so that the fibers constituting the brush layer 642 of the brush roller 64 can be prevented from becoming hazy. The life of the brush roller 64 can be extended. When printing is not being performed, the brush roller gear 64G is disengaged from the photosensitive drum gear 61G, so that the driving force from the drive source cannot be transmitted to the brush roller gear 64G. As a result, when printing is not being performed, the brush roller 64 does not rotate, so that deterioration of the brush roller 64 and toner due to rotation of the brush roller 64 can be reduced.

  Further, in the present embodiment, the brush roller 64 is provided between the developing position and the separation position with a simple configuration by providing the brush roller 64 with a cam 310 that can contact from the side opposite to the photosensitive drum 61. Can be made.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. About a concrete structure, it can change suitably in the range which does not deviate from the meaning of this invention. In the following description, components that are substantially the same as those in the above-described embodiment are given the same reference numerals, and descriptions thereof are omitted.

  In the embodiment, both the bearing member 645 constituting the holding portion H and the bearing support portion 241 of the developing frame 200 protrude toward the shaft side of the photosensitive drum 61 from the tip of the brush layer 642 of the brush roller 64. The configuration of the process unit 6 is not limited to this. For example, the bearing support portion 241 of the developing frame 200 does not support the entire circumference of the bearing member 645 and is formed in a C shape that opens to the photosensitive drum 61 side, and only the bearing member 645 of the holding portion H is The brush roller 64 may protrude from the tip of the brush layer 642 toward the shaft side of the photosensitive drum 61.

  In the above-described embodiment, the cam 310 is exemplified as an action member configured to move the brush roller 64 between the development position and the separation position. However, as illustrated in FIG. , And an arm 380 movable by the cam 310 may be included.

  The arm 380 in this embodiment is provided between the roller main body 641 of the brush roller 64 and the cam 310 and is supported by the drum frame 100 so as to be swingable. The arm 380 extends upward from the swing shaft supported by the drum frame 100. When the cam 310 is in the first posture (see the solid line), the arm 380 has its tip oscillating upward by the first action portion 311 coming into contact with the lower side, and pushes up the roller body 641 to the photosensitive drum 61 side. . As a result, the brush roller 64 moves to the development position. In addition, when the cam 310 is in the second posture (see the two-dot chain line), the arm 380 moves in a direction away from the photosensitive drum 61 when the second action unit 312 contacts. Thereby, the brush roller 64 moves to the separation position by its own weight.

  In the above-described embodiment, the shaft 313 that regulates the rotation of the cam 310 is integral with the cam 310 and is rotatably supported by the pair of support walls 123 of the drum frame 100. However, the configuration of the shaft is not limited thereto. . For example, the shaft may be formed integrally with the pair of support walls 123 so as to be supported by each support wall 123, and the cam 310 may be rotatably supported by this shaft.

  In the embodiment, the brush roller 64 in which the brush layer 642 can come into contact with the peripheral surface of the photosensitive drum 61 is illustrated as an example of the developing roller. A developing roller configured to supply toner to the photosensitive drum by a potential difference between the surface of the photosensitive drum and the photosensitive drum (so-called “jumping development”) may be employed.

6 Process Unit 61 Photosensitive Drum 61G Photosensitive Drum Gear 64 Brush Roller 64G Brush Roller Gear 68 Seal Member 100 Drum Frame 123 Support Wall 200 Development Frame 310 Cam 311 First Action Part 312 Second Action Part 313 Shaft 380 Arm 641 Roller Body 642 Brush Layer 644 Restriction member 645 Bearing member

Claims (7)

A photosensitive drum having a substrate having a photosensitive layer formed on the peripheral surface;
A developing roller for supplying a developer to the peripheral surface of the photosensitive drum;
A pair of bearing members that rotatably support both ends in the axial direction of the developing roller,
Each of the bearing members is provided outside the base in the axial direction,
The process unit, wherein a shortest distance from a rotation axis of the photosensitive drum to the bearing member is smaller than a radius of the photosensitive drum. A drum frame for holding the photosensitive drum;
A developing frame that holds the developing roller via the bearing member;
The developing frame is smaller in size in the axial direction than the drum frame,
2. The process unit according to claim 1, wherein the bearing member is located inside a side wall of the drum frame disposed on both sides of the photosensitive drum in the axial direction.   3. The process unit according to claim 2, wherein the developing roller is a brush roller having a roller body and a brush layer in which fibers are implanted on the outer peripheral surface of the roller body.   The process unit according to claim 3, wherein the roller body is formed with a uniform thickness at least at a position between the pair of bearing members. A seal member provided between both end portions of the developing roller in the axial direction and the developing frame;
A regulating member provided at both ends in the axial direction of the developing roller and configured to regulate a distance between the developing roller and the photosensitive drum by contacting the surface of the photosensitive drum;
The said restriction member is arrange | positioned in the said axial direction on the outer side rather than the said sealing member, and the inner side rather than the edge part of the said base | substrate. The described process unit. A photosensitive drum gear that rotates integrally with the photosensitive drum;
A developing roller gear that rotates integrally with the developing roller,
6. The process unit according to claim 2, wherein the photosensitive drum gear and the developing roller gear are directly meshed with each other.   The process unit according to claim 2, wherein the developing frame is detachable from the drum frame.

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