WO2014010111A1

WO2014010111A1 - Image formation device

Info

Publication number: WO2014010111A1
Application number: PCT/JP2012/080823
Authority: WO
Inventors: 弘司半田; 啓城森
Original assignee: ブラザー工業株式会社
Priority date: 2012-07-09
Filing date: 2012-11-29
Publication date: 2014-01-16
Also published as: CN204496163U; JP2014016480A; JP5949240B2

Abstract

Provided is an image formation device capable of stably supplying a developing agent inside a developing cartridge to a photosensitive body. A process cartridge (15) is mounted to a body casing (2), has both a drum cartridge (18) having a photosensitive drum (20), and a developing cartridge (19) having a developing roller (34) and capable of attachment/detachment to/from the drum cartridge (18), and is mounted in a manner such that the developing roller (34) is positioned lower in the vertical direction than a center-axis line (A1) of the photosensitive drum (20). A pressing member (66) on the drum cartridge (18) causes the developing cartridge (19) to be pressed toward the photosensitive drum (20) by a pressing force having a component from the bottom in the vertical direction. As a result, the developing roller (34) is guided to a guiding groove (59) in the drum cartridge (18), and contacts and presses the photosensitive drum (20) by the pressing force having a component from the bottom in the vertical direction.

Description

Image forming apparatus

The present invention relates to an image forming apparatus employing an electrophotographic apparatus.

2. Description of the Related Art As an image forming apparatus employing an electrophotographic method, an image forming apparatus including a photosensitive member on which an electrostatic latent image is formed and a developing device that supplies a developer to the photosensitive member is known.

For example, a laser printer has been proposed that includes a drum cartridge having a photosensitive drum and a developing cartridge that contains toner and is detachable from the drum cartridge (see, for example, Patent Document 1).

In this laser printer, a developing cartridge is disposed on the front upper side of the photosensitive drum in the main body casing, and the developing roller is in contact with the photosensitive drum from the upper front side. The developing cartridge is pressed toward the photosensitive drum by the pressing portion of the drum cartridge.

JP 2006-72285 A

However, in the laser printer described in Patent Document 1, when the developing cartridge is mounted on the drum cartridge, the developing cartridge is pressed against the photosensitive drum by the pressing force from the pressing portion and the weight of the developing cartridge. ing.

Therefore, if the developer in the developing cartridge decreases with use, the developing cartridge's own weight decreases, and the pressing force of the developing cartridge against the photosensitive drum decreases.

If the pressing force of the developing cartridge against the photosensitive drum decreases, the amount of toner supplied to the photosensitive drum may decrease.

Accordingly, an object of the present invention is to provide an image forming apparatus capable of stably supplying the developer in the developing cartridge to the photoreceptor.

(1) In order to solve the above-described problems, an image forming apparatus of the present invention includes an apparatus main body and a process cartridge that can be attached to and detached from the apparatus main body. The process cartridge includes: a photosensitive cartridge having a photosensitive member rotatable; and a developing cartridge detachably attached to the photosensitive member cartridge having a developer carrying member configured to carry the developer. Prepare. The photoconductor cartridge includes a pressing member for pressing the developer cartridge so as to press the developer carrier toward the photoconductor, and a guide unit for guiding the developer carrier toward the photoconductor.

In a state where the process cartridge is mounted on the apparatus main body, the developer carrier is disposed at a position lower in the vertical direction than the rotation axis of the photosensitive member.

According to such a configuration, in a state where the process cartridge is mounted on the apparatus main body, the developing cartridge is pressed toward the photoconductor by the pressing force having a component from the vertically lower side.

Therefore, when the developer in the developing cartridge is consumed, the pressing force by the pressing member increases as the developing cartridge's own weight decreases, and the developer carrying member can be pressed more toward the photosensitive member.

As a result, even when the developer in the developer cartridge is consumed, the developer in the developer cartridge can be stably applied to the photoreceptor without reducing the pressing force of the developer carrier on the photoreceptor. Can be supplied.
(2) The pressing member may be configured to linearly move in a pressing direction toward the photoconductor and in a pressing release direction opposite to the pressing direction.

According to such a configuration, the developing cartridge can be efficiently pressed toward the photoconductor.
(3) Further, the developing cartridge may rotatably have a supply member configured to supply the developer to the developer carrying member. In this case, the supply member may be opposed to the developer carrying member from the opposite side of the photosensitive member.

According to such a configuration, when the developer carrying member is pressed against the photoreceptor, the supply member can suppress the deflection of the developer carrying member due to the reaction force from the photoreceptor.

Therefore, the developer carrying member can be reliably pressed against the photosensitive member.
(4) The supply member may be configured such that a supply bias having the same polarity as the development bias applied to the developer carrying member and having an absolute value larger than the development bias is applied.

According to such a configuration, it is possible to attract the developer charged to the polarity opposite to the polarity of the developing bias to the supplying member by the supplying bias having an absolute value larger than the developing bias.

For this reason, it is possible to prevent the developer or the like charged to a reverse polarity from being supplied to the photoreceptor.
(5) Further, the photosensitive member cartridge is disposed opposite to the photosensitive member, and rotates a transfer member for transferring the developer image carried on the photosensitive member to a transferred member passing between the photosensitive member and the photosensitive member. It may be possible.

According to such a configuration, since the transfer member is brought into contact with the photosensitive member or the member to be transferred, there is a case where the transfer member is soiled by an adherent adhering to the photosensitive member or the member to be transferred.

In this regard, according to the image forming apparatus of the present invention, when the photosensitive member cartridge is maintained, the transfer member can be reliably maintained.
(6) The transfer member may be configured to follow the rotation of the photoreceptor.

According to such a configuration, it is necessary to press the transfer member relatively strongly against the photoconductor in order to cause the transfer member to follow the photoconductor. When the pressing force of the transfer member against the photosensitive member is increased, the transfer member tends to become dirty due to sliding friction with the photosensitive member and the transfer target member.

In this regard, according to the image forming apparatus of the present invention, as described above, since the transfer member is provided in the photosensitive member cartridge, when the photosensitive member cartridge is maintained, the transfer member can be reliably maintained. it can.
(7) Further, the transfer member may be arranged so that a virtual straight line passing through the rotation axis of the transfer member and the rotation axis of the photosensitive member extends in a substantially horizontal direction.

According to such a configuration, it is possible to prevent the adhering matter adhering to the photoconductor from falling on the transfer member, and to suppress contamination of the transfer member.
(8) Further, the developer carrier may be configured to collect deposits adhering to the peripheral surface of the photoreceptor.

According to such a configuration, the deposit can be collected using the developer carrier without separately providing a configuration for collecting the deposit.

Therefore, the configuration of the image forming apparatus can be simplified.

In addition, as described above, since the pressing force of the developer carrying member against the photosensitive member does not decrease, the deposits can be reliably collected.
(9) The photoconductor cartridge may be integrally provided with a photoconductor support section for supporting the photoconductor and a developing cartridge mounting section on which the developing cartridge can be mounted.

According to such a configuration, the developing cartridge is mounted on the developing cartridge mounting portion of the photosensitive cartridge.

Therefore, the relative arrangement of the photosensitive member and the developing cartridge can be positioned within the photosensitive member cartridge.

As a result, the developing cartridge can be more reliably pressed against the photoreceptor.

According to the image forming apparatus of the present invention, the developer in the developing cartridge can be stably supplied to the photoreceptor.

FIG. 1 is a central sectional view of a printer as an embodiment of an image forming apparatus of the present invention. FIG. 2 is a perspective view of the drum cartridge shown in FIG. 1 as viewed from the left front side. FIG. 3 is an exploded perspective view of the drum cartridge shown in FIG. 2 as viewed from the left rear side. 4 is a central sectional view of the process cartridge shown in FIG. FIG. 5 is a left side view of the process cartridge shown in FIG.

1. Printer As shown in FIG. 1, a printer 1 as an example of an image forming apparatus includes a main body casing 2 as an example of a substantially box-shaped main body.

In addition, the printer 1 includes a sheet feeding unit 3 for feeding a sheet S as an example of a transfer target member and an image forming unit 4 for forming an image on the fed sheet S in the main body casing 2. And.

Regarding the printer 1, when referring to the direction, the direction when it is placed in the horizontal direction is used as a reference, and specifically, the direction of the arrow in the drawing is used as a reference.
(1) Main Body Casing The main body casing 2 is formed with a cartridge opening 5 for attaching / detaching a process cartridge 15 (described later) and a paper opening 6 for introducing the paper S.

The cartridge opening 5 is formed through the upper end of the main casing 2 in the vertical direction.

The paper opening 6 is formed to penetrate in the front-rear direction at the lower end of the front end of the main casing 2.

Further, the main body casing 2 is provided with a top cover 7 at its upper end and a paper feed cover 8 at its front end.

The top cover 7 is provided to be swingable (movable) between a closed position for closing the cartridge opening 5 and an open position for opening the cartridge opening 5 with the rear end as a fulcrum.

The paper feed cover 8 is swingably (moved) between a first position where the paper opening 6 is closed and a second position where the paper opening 6 is opened with the lower end of the paper supply cover 8 as a fulcrum.
(2) Paper Feed Unit The paper feed unit 3 includes a paper placement unit 9 provided at the bottom of the main casing 2.

The paper stacking portion 9 is communicated with the outside of the main casing 2 through the paper opening 6.

The sheet S is stacked on the upper surface of the sheet feed cover 8 while the sheet feed cover 8 is disposed at the second position, and the rear part is loaded on the sheet via the sheet opening 6. Stacked in the placement unit 9.

The paper feeding unit 3 includes a pickup roller 11 disposed on the upper side of the rear end portion of the paper placing unit 9, a paper feeding roller 12 disposed on the rear side of the pickup roller 11, and a rear lower side of the paper feeding roller 12. The sheet feeding pad 13 is disposed opposite to the sheet feeding side, and the sheet feeding path 14 extends continuously upward from the rear end portion of the sheet feeding pad 13.
(3) Image Forming Unit The image forming unit 4 includes a process cartridge 15, a scanner unit 16, and a fixing unit 17.
(3-1) Process Cartridge The process cartridge 15 is configured to be detachable from the main casing 2 and is mounted on the main casing 2 above the rear portion of the paper feed unit 3.

The process cartridge 15 includes a drum cartridge 18 as an example of a photosensitive cartridge configured to be detachable from the main body casing 2, and a developing cartridge 19 configured to be detachable from the drum cartridge 18.

The drum cartridge 18 includes a photosensitive drum 20 as an example of a photosensitive member, a transfer roller 21 as an example of a transfer member, and a scorotron charger 22.

The photosensitive drum 20 is formed in a substantially cylindrical shape that is long in the left-right direction (orthogonal direction), and is provided in the rear portion of the drum cartridge 18. The photosensitive drum 20 can be rotated about its center axis A1 (rotation axis) as a rotation center.

The transfer roller 21 is formed in a substantially cylindrical shape extending in the left-right direction, and can be rotated about its center axis A2 (rotation axis) as a rotation center. Further, the transfer roller 21 is pressed against the photosensitive drum 20 from the rear side.

Specifically, the transfer roller 21 is disposed on the rear side of the photosensitive drum 20 so that the position of the center axis A2 (rotation axis) is slightly lower in the vertical direction than the position of the center axis A1 of the photosensitive drum 20. Yes. The lower end edge of the transfer roller 21 is disposed above the lower end edge of the photosensitive drum 20. Specifically, a virtual line segment L1 connecting the central axis A2 of the transfer roller 21 and the central axis A1 of the photosensitive drum 20 and a virtual straight line (not shown) extending horizontally along the front-rear direction are formed. The acute angle is about 3 °. Therefore, the pressure (transfer pressure) at which the transfer roller 21 is pressed against the photosensitive drum 20 is not affected by the weight of the transfer roller 21.

The scorotron charger 22 is disposed opposite to the front upper side of the photosensitive drum 20 with an interval.

Specifically, the scorotron charger 22 is disposed with a distance in the circumferential direction of the photosensitive drum 20 with respect to the transfer roller 21, and the central axis A 1 of the photosensitive drum 20 and the central axis A 2 of the transfer roller 21 are connected. The angle formed by the imaginary line segment L1 connecting and the imaginary line segment (not shown) connecting the central axis A1 of the photosensitive drum 20 and the charging wire 23 (described later) is arranged to be about 120 °. Has been.

The scorotron charger 22 includes a charging wire 23 and a grid 24.

The charging wire 23 is stretched so as to extend in the left-right direction, and is opposed to the front upper side of the photosensitive drum 20 with an interval.

The grid 24 is formed in a substantially U shape in a side view opened toward the front upper side, and is provided so as to surround the charging wire 23 from the lower rear side.

The developing cartridge 19 is disposed on the lower front side of the photosensitive drum 20 and includes a developing frame 25.

In the developing frame 25, a toner storage chamber 26 and a developing chamber 27 are formed side by side. The toner storage chamber 26 and the developing chamber 27 are formed to have substantially the same volume, and communicate with each other through a communication port 28.

The toner storage chamber 26 stores toner (developer), and an agitator 29 is provided at a substantially central portion in the front-rear and vertical directions. That is, the agitator 29 is disposed below the photosensitive drum 20.

In the developing chamber 27, a supply roller groove 30, a developing roller facing surface 31, and a lower film attaching surface 32 are formed on the inner surface (upper surface) of the lower wall.

The supply roller groove 30 has a substantially semicircular shape along the peripheral surface of a supply roller 33 (described later), and is formed so as to be recessed downward in the rearward direction.

The developing roller facing surface 31 has a substantially arc shape along the peripheral surface of the developing roller 34 (described later), and is formed so as to continuously extend from the rear end portion of the supply roller groove 30 to the rear upper side.

The lower film attaching surface 32 is formed so as to continuously extend rearward from the rear end portion of the developing roller facing surface 31. That is, the lower film attaching surface 32 is disposed above the developing roller facing surface 31.

Further, the lower film attaching surface 32 is disposed to face the lower portion of the photosensitive drum 20 with a space in the vertical direction, and overlaps the central axis A1 of the photosensitive drum 20 when projected in the vertical direction. Are arranged as follows.

Further, the developing chamber 27 is provided with a supply roller 33 as an example of a supply member, a development roller 34 as an example of a developer carrier, a layer thickness regulating blade 35, and a lower film 36.

The supply roller 33 is formed in a substantially cylindrical shape extending in the left-right direction, and is provided in the front portion of the developing chamber 27 so that the lower portion thereof is disposed in the supply roller groove 30. The supply roller 33 can rotate around its central axis. The supply roller 33 is disposed on the rear side of the toner storage chamber 26, and is disposed at substantially the same height as the toner storage chamber 26 in the vertical direction (slightly above the toner storage chamber 26).

The developing roller 34 is formed in a substantially cylindrical shape extending in the left-right direction, and is provided in the rear portion of the developing chamber 27 so that the circumferential surface in the lower portion thereof and the developing roller facing surface 31 face each other with a space therebetween. It has been. The horizontal length of the developing roller 34 is longer than the horizontal length of the supply roller 33. The developing roller 34 can rotate around its center axis.

The developing roller 34 is provided so as to come into contact with the supply roller 33 from the upper rear side, and its upper and rear portions are exposed from the developing chamber 27, and contact the photosensitive drum 20 from the lower front side. Yes. That is, the developing roller 34 is disposed on the upper rear side of the supply roller 33, and is disposed on the front lower side of the photosensitive drum 20 at a position lower than the central axis A <b> 1 of the photosensitive drum 20 in the vertical direction. The central axis of the supply roller 33, the central axis of the developing roller 34, and the central axis A1 of the photosensitive drum 20 are positioned on substantially the same straight line along the radial direction of the photosensitive drum 20.

Further, the developing roller 34 is arranged with a gap in the circumferential direction of the photosensitive drum 20 with respect to the scorotron charger 22, and a virtual line segment connecting the central axis A <b> 1 of the photosensitive drum 20 and the charging wire 23. (Not shown) and an imaginary line segment (not shown) connecting the central axis A1 of the photosensitive drum 20 and the central axis of the developing roller 34 are arranged so that the angle of the angle is about 120 °. ing. That is, the developing roller 34, the scorotron charger 22, and the transfer roller 21 are arranged at substantially equal intervals in the circumferential direction of the photosensitive drum 20.

The upper end portion of the layer thickness regulating blade 35 is fixed to the rear end portion of the upper wall of the developing chamber 27, and the lower end portion thereof is in contact with the developing roller 34 from the front side.

The rear portion of the lower film 36 is fixed to the lower film attaching surface 32, and the front end thereof is in contact with the peripheral surface of the developing roller 34 on the upper side of the developing roller facing surface 31.
(3-2) Scanner Unit The scanner unit 16 is disposed on the front side of the process cartridge 15 so as to face the photosensitive drum 20 with a space in the front-rear direction.

The scanner unit 16 emits a laser beam L toward the photosensitive drum 20 based on the image data to expose the peripheral surface of the photosensitive drum 20.

Specifically, the laser beam L is emitted rearward from the scanner unit 16 and exposes the peripheral surface at the front end of the photosensitive drum 20. That is, the exposure point at which the photosensitive drum 20 is exposed (the peripheral surface at the front end portion of the photosensitive drum 20) is opposite to the nip portion where the photosensitive drum 20 and the transfer roller 21 are in contact with the central axis A1 of the photosensitive drum 20. Is set to the side.

At this time, the developing cartridge 19 is arranged below the emission locus of the laser beam L, and the scorotron charger 22 is arranged above the emission locus of the laser beam L.

A guide portion 37 for guiding the attachment / detachment of the process cartridge 15 is provided on the inner side surface of the main body casing 2 between the scanner unit 16 and the photosensitive drum 20. When the process cartridge 15 is detached from the main casing 2, the process cartridge 15 is guided by the guide portion 37, so that the developing cartridge 19 attached to the drum cartridge 18 has a lower emission locus of the laser beam L. Pass from the top to the top.

At this time, the various rollers (transfer roller 21, supply roller 33 and developing roller 34) provided in the process cartridge 15 also pass the emission locus of the laser beam L from the lower side to the upper side.
(3-3) Fixing Unit The fixing unit 17 is disposed above the rear portion of the drum cartridge 18. Specifically, the fixing unit 17 includes a heating roller 38 disposed on the upper side of the scorotron charger 22 and a pressure roller 39 pressed against the heating roller 38 from the rear upper side.

That is, the heating roller 38 is disposed in the vicinity of the upper end portion (open end portion) of the grid 24 of the scorotron charger 22.
(4) Image Forming Operation The toner in the toner storage chamber 26 of the developing cartridge 19 is supplied to the supply roller 33 through the communication port 28 by the rotation of the agitator 29, and further supplied to the developing roller 34. Between 33 and the developing roller 34, it is triboelectrically charged to the positive polarity.

The toner supplied to the developing roller 34 is regulated by the layer thickness regulating blade 35 as the developing roller 34 rotates, and is carried on the surface of the developing roller 34 as a thin layer having a constant thickness.

On the other hand, the surface of the photosensitive drum 20 is uniformly charged by the scorotron charger 22 and then exposed by the scanner unit 16. Thereby, an electrostatic latent image based on the image data is formed on the peripheral surface of the photosensitive drum 20. The toner carried on the developing roller 34 is supplied to the electrostatic latent image on the circumferential surface of the photosensitive drum 20, so that a toner image (developer image) is carried on the circumferential surface of the photosensitive drum 20.

The sheets S stacked on the sheet loading unit 9 are sent between the sheet feeding roller 12 and the sheet feeding pad 13 by the rotation of the pickup roller 11 and are turned one by one by the rotation of the sheet feeding roller 12. After that, the paper S that has been squeezed is conveyed to the paper feed path 14 by the rotation of the paper feed roller 12 and is fed sheet by sheet at a predetermined timing (photosensitive drum 20 (described later) and transfer roller 21 ( (To be described later).

Then, the sheet S is conveyed between the photosensitive drum 20 and the transfer roller 21 from the lower side to the upper side. At this time, the toner image is transferred onto the paper S to form an image.

The sheet S is heated and pressed when it passes between the heating roller 38 and the pressure roller 39. At this time, the image is thermally fixed on the paper S.

Thereafter, the paper S is conveyed toward the paper discharge roller 40, and is discharged onto a paper discharge tray 41 formed on the upper surface of the main casing 2 by the paper discharge roller 40.

In this way, the paper S is fed from the paper placement unit 9, passes between the photosensitive drum 20 and the transfer roller 21 (nip portion), and then passes between the heating roller 38 and the pressure roller 39. After that, the paper is transported through a substantially C-shaped transport path in side view so that the paper is discharged onto the paper discharge tray 41. 2. Drum Cartridge As shown in FIGS. 2 and 3, the drum cartridge 18 includes a drum frame 51 and a pressing member 66.

In the following description of the drum cartridge 18, when referring to the direction, the side on which the photosensitive drum 20 is disposed is the rear side of the drum cartridge 18, and the side on which the scorotron charger 22 is disposed is the upper side. . That is, the up / down / front / rear direction with respect to the drum cartridge 18 is slightly different from the up / down / front / rear direction with respect to the printer 1, and the drum cartridge 18 has a rear side above the printer 1. The printer 1 is mounted so that the front upper side and the lower side are the rear lower side of the printer 1.
(1) Drum Frame The drum frame 51 includes a base frame 52 and a cover frame 53. (1-1) Base Frame The base frame 52 is formed in a bottomed frame shape having a substantially rectangular shape in plan view with the upper side open. The base frame 52 includes a pair of left and right side walls 54, a lower wall 55, a rear wall 57, and a front wall 56.

The side wall 54 is formed in a substantially flat plate shape that is long in the front-rear direction. The side wall 54 is integrally provided with a rear portion 60 constituting the rear half and a front portion 61 constituting the front half thereof. Further, the side wall 54 is formed with a drum shaft insertion hole 58 and a guide groove 59 as an example of a guide portion.

The rear portion 60 is formed in a substantially rectangular shape in side view extending in the vertical direction.

The front part 61 is formed in a substantially rectangular shape in side view extending continuously from the lower end of the rear part 60 to the front side.

The drum shaft insertion hole 58 is formed in a substantially circular shape in a side view at the center of the rear portion 60 in the front-rear direction. The inner diameter of the drum shaft insertion hole 58 is slightly larger (substantially the same diameter) than the outer diameter of the drum shaft 80 of the photosensitive drum 20. The drum shaft insertion holes 58 of the side walls 54 coincide with each other when projected in the left-right direction.

The guide groove 59 is formed in a substantially U shape in a side view opened to the front side so as to be cut out from the front end edge of the rear side portion 60 toward the rear side at the lower end portion of the rear side portion 60. The guide groove 59 extends along the pressing direction of the pressing member 66 (described later) against the developing cartridge 19 (see FIGS. 4 and 5). Further, the lower surface of the guide groove 59 is continuous with the upper surface of the front portion 61. The groove width of the guide groove 59 is wider (substantially the same width) than the outer diameter of the collar member 117 (described later). Note that the guide grooves 59 of the side walls 54 coincide with each other when projected in the left-right direction.

As shown in FIG. 3, the lower wall 55 is formed in a substantially flat plate shape that is long in the left-right direction so as to be installed between the lower ends of the side walls 54. Note that the rear end portion of the lower wall 55 is disposed below the photosensitive drum 20.

The rear wall 57 is disposed on the rear side of the rear end portion of the lower wall 55 with a space therebetween, and is formed in a substantially flat plate shape that is long in the left-right direction so as to be installed between the rear end portions of the both side walls 54. Yes. In addition, between the rear wall 57 and the lower wall 55 is a paper feed opening 74 for allowing the paper S going between the photosensitive drum 20 and the transfer roller 21 to pass (see FIG. 4).

Also, a transfer roller support 70 is provided on the rear wall 57. The rear wall 57 has a drum gear exposure opening 72 formed therein.

The transfer roller support portion 70 is formed in a substantially partial cylindrical shape extending in the left-right direction so as to bulge from the rear wall 57 to the rear side. The transfer roller support portion 70 is closed at both ends in the left-right direction and is opened toward the upper side and the front side. The left end portion of the transfer roller support portion 70 is disposed on the inner side (right side) in the left-right direction than the left side wall 54. The right end portion of the transfer roller support portion 70 is disposed on the inner side (left side) in the left-right direction than the right side wall 54.

Further, one transfer roller shaft guide portion 71 is provided at each of both end portions of the transfer roller support portion 70 in the left-right direction.

The transfer roller shaft guide portion 71 extends in a direction connecting the front upper side and the rear lower side, and is formed in a substantially rectangular tube shape in which both ends in the extending direction are opened. A guide opening 73 is formed through the inner wall of the transfer roller shaft guide portion 71 in the left-right direction. The guide opening 73 extends in a direction connecting the front upper side and the rear lower side. The opening width of the guide opening 73 (the length in the direction perpendicular to the horizontal direction and the extending direction of the guide opening 73) is slightly wider (substantially the same width) than the outer diameter of the transfer roller shaft 86 (described later). is there.

The drum gear exposure opening 72 is formed in a substantially rectangular shape in rear view so as to penetrate the rear wall 57 between the left end portion of the transfer roller support portion 70 and the left side wall 54.

The front wall 56 is formed in a substantially flat plate shape that is long in the left-right direction so as to continuously extend from the front end portion of the lower wall 55 and to be spanned between the front end portions of the side walls 54. The front wall 56 includes a pressing member accommodating portion 69.

The pressing member accommodating portions 69 are provided one on each of the left and right sides of the front wall 56, extend from the lower end portion of the front wall 56 to the rear side, and are formed in a substantially rectangular tube shape with the front end portion opened.

A portion of the base frame 52 between the rear portions 60 of the side walls 54 on the front side of the transfer roller support portion 70 is a drum support portion as an example of a photoconductor support portion for supporting the photosensitive drum 20. 101 is partitioned.

In addition, the developing cartridge 19 can be mounted on a portion of the base frame 52 that is in front of the drum support portion 101 (a portion that is partitioned by the lower wall 55, the front wall 56, and the front portions 61 of the side walls 54). The developing cartridge mounting section 102 is an example of a developing unit mounting section.
(1-2) Cover Frame The cover frame 53 is disposed above the rear end portion of the base frame 52. The cover frame 53 is formed in a substantially rectangular tube shape that extends in the left-right direction and opens toward the lower side and the front side. The cover frame 53 includes a pair of left and right side walls 91, an upper wall 92, and a rear wall 93.

The side wall 91 is formed in a substantially flat plate shape extending in the vertical direction. In addition, a drum shaft insertion hole 94 is formed in the side wall 91.

The drum shaft insertion hole 94 is formed in a substantially circular shape in a side view at the lower end portion of the side wall 91. The inner diameter of the drum shaft insertion hole 94 is slightly larger (substantially the same diameter) than the outer diameter of the drum shaft 80 of the photosensitive drum 20. The drum shaft insertion holes 94 of the side walls 91 coincide with each other when projected in the left-right direction.

As shown in FIGS. 3 and 4, the upper wall 92 is formed in a substantially rectangular tube shape that extends in the left-right direction and is opened toward the lower side so as to be installed between the upper ends of the side walls 91. Yes. The scorotron charger 22 is supported inside the upper wall 92.

The rear wall 93 continuously extends from the rear end portion of the upper wall 92 to the lower rear side, and is formed in a substantially flat plate shape that is long in the left-right direction so as to be installed between the rear end portions of the side walls 91. . A paper discharge opening 121 is formed in the rear wall 93.

The paper discharge opening 121 is formed in a substantially rectangular shape when viewed from the rear in the left-right direction at the center in the vertical direction of the rear wall 93. The paper discharge opening 121 is used for passing the paper S that has passed between the photosensitive drum 20 and the transfer roller 21 toward the fixing unit 17.
(2) Press member The press member 66 is provided with the main-body part 110 and the spring member 111, as shown in FIG.

The main body 110 is formed in a substantially rectangular tube shape with the rear end closed, and is housed in the pressing member housing 69 of the front wall 56 so as to be slidable in the front-rear direction. A bulging portion 112 is integrally provided on the rear end surface of the main body portion 110.

The bulging portion 112 is formed in a substantially circular arc shape in sectional view that bulges from the substantially central portion of the rear end surface of the main body portion 110 toward the rear side.

The spring member 111 is a compression coil spring extending in the front-rear direction. The rear end portion of the spring member 111 is in contact with the inner surface (front surface) of the rear end portion of the main body 110 from the front side. The front end portion of the spring member 111 is in contact with the rear surface of the front wall 56 from the rear side. Thereby, the main-body part 110 is always urged | biased by the urging | biasing force of the spring member 111 toward the back side.
(3) Transfer Roller and Photosensitive Drum As shown in FIG. 3, the transfer roller 21 and the photosensitive drum 20 are supported on the drum cartridge 18.

The transfer roller 21 includes a transfer roller shaft 86, a roller body 85, a transfer roller bearing 87, and a transfer roller electrode 88.

The roller body 85 is disposed between the two transfer roller shaft guide portions 71. The roller body 85 is formed in a substantially cylindrical shape extending in the left-right direction from conductive rubber or sponge. The inner diameter of the roller body 85 is substantially the same as the outer diameter of the transfer roller shaft 86.

The transfer roller shaft 86 is inserted into the roller body 85 so as not to be relatively rotatable. The transfer roller shaft 86 is formed in a substantially cylindrical shape extending in the left-right direction from the metal. The transfer roller shaft 86 is longer in the left-right direction than the roller body 85, and both left and right end portions protrude from the roller body 85. The left and right end portions of the transfer roller shaft 86 protrude into the corresponding transfer roller shaft guide portion 71 through the guide opening 73 of the corresponding transfer roller shaft guide portion 71, respectively. The transfer roller shaft 86 is supported in the guide opening 73 so as to be relatively rotatable, and is movable in a direction connecting the front upper side and the rear lower side along the extending direction of the guide opening 73.

The transfer roller bearing 87 is provided at the left end portion of the transfer roller shaft 86. The transfer roller bearing 87 is made of an insulating hard resin and has a substantially cylindrical shape extending in the left-right direction. The inner diameter of the transfer roller bearing 87 is slightly larger (substantially the same diameter) than the outer diameter of the transfer roller shaft 86. The transfer roller bearing 87 is externally fitted to the transfer roller shaft 86 so as to be rotatable relative to the transfer roller shaft guide portion 71 on the left side (fitted from the outside in the radial direction of the transfer roller shaft 86).

The transfer roller electrode 88 is provided at the right end of the transfer roller shaft 86. The transfer roller electrode 88 is formed in a semi-cylindrical shape extending from the conductive hard resin in the left-right direction and opened toward the front side. The inner diameter of the transfer roller electrode 88 is slightly larger than the outer diameter of the transfer roller shaft 86 (substantially the same diameter). The transfer roller electrode 88 is externally fitted (fitted from the outside in the radial direction of the transfer roller shaft 86) so as to be relatively rotatable from the rear side with respect to the transfer roller shaft 86 in the right transfer roller shaft guide portion 71. .

The photosensitive drum 20 includes a drum body 81, a flange member 82, a drum gear 83, and a drum shaft 80.

The drum body 81 is disposed in the drum support portion 101 on the front side of the transfer roller 21. The drum body 81 includes a metal base tube formed in a substantially cylindrical shape extending in the left-right direction, and a resin photosensitive layer that covers the surface of the base tube.

The flange member 82 is fitted to the right end portion of the drum main body 81 so as not to be relatively rotatable. The flange member 82 is formed in a substantially disc shape having a thickness in the left-right direction. Further, an insertion hole (not shown) through which the drum shaft 80 is inserted is formed through the flange member 82 in the central portion in the radial direction.

The drum gear 83 is fitted to the left end portion of the drum main body 81 so as not to rotate relative to the left side wall 54 of the base frame 52 and the left end portion of the transfer roller support portion 70. The drum gear 83 is formed in a substantially disc shape having a thickness in the left-right direction, and has gear teeth on its peripheral surface. Further, the drum gear 83 is formed with a through hole (not shown) through which the drum shaft 80 is inserted in the central portion in the radial direction. The rear lower end of the drum gear 83 is exposed to the rear lower side through the drum gear exposure opening 72.

The drum shaft 80 is inserted into the drum main body 81 along the central axis A1 of the photosensitive drum 20. The drum shaft 80 is formed in a substantially cylindrical shape extending from the metal in the left-right direction. The drum shaft 80 is longer than the drum body 81 in the left-right direction. The left and right end portions of the drum shaft 80 are rotatably inserted into the drum shaft insertion holes 58 of the base frame 52 and the drum shaft insertion holes 94 of the cover frame 53.
3. Developing Cartridge As shown in FIGS. 4 and 5, the developing cartridge 19 includes the developing frame 25 and a drive unit 44 disposed on the left side of the developing frame 25. A power supply unit (not shown) for supplying power to the developing cartridge 19 is provided on the right side of the developing frame 25.

The developing frame 25 is formed in a substantially box shape extending in the left-right direction. The developing roller 34 described above is supported at the rear end of the developing frame 25.

The developing roller 34 includes a metal rotating shaft (hereinafter referred to as a developing roller shaft 45) extending in the left-right direction. The left and right ends of the developing roller shaft 45 protrude outward in the left and right direction so as to penetrate the left and right side walls of the developing frame 25. A substantially cylindrical collar member 117 is fitted on the end portion of the developing roller shaft 45 in the left-right direction so as to be relatively rotatable (fitted from the outside in the radial direction of the developing roller shaft 45).

The drive unit 44 includes a development coupling 118 as shown in FIG.

The developing coupling 118 is disposed at the approximate center of the developing cartridge 19 in the front-rear direction. The development coupling 118 is formed in a substantially cylindrical shape extending in the left-right direction, and is rotatably supported on the left wall of the development frame 25. A coupling recess 116 is formed on the left surface of the development coupling 118.

The coupling recess 116 is formed in a substantially elongated hole shape in a side view extending in the radial direction of the development coupling 118 so as to be recessed from the left surface of the development coupling 118 to the right side. A coupling convex portion (not shown) of a main body coupling (not shown) provided in the main body casing 2 is fitted into the coupling concave portion 116 so as to be able to transmit drive.

Note that gear teeth (not shown) are formed on the peripheral surface of the right end portion of the development coupling 118. The development coupling 118 is connected to the supply roller 33, the development roller 34, and the agitator 29 via a gear train (not shown) so as to be able to transmit driving.
4). As shown in FIG. 4, when the developing cartridge 19 is mounted on the developing cartridge mounting portion 102 of the drum cartridge 18, the developing cartridge 19 bulges the pressing member 66 at its front end. While being in contact with the portion 112 from the rear side, the developing roller 34 is in contact with the photosensitive drum 20 from the front side.

Thereby, the developing cartridge 19 is pressed rearward toward the photosensitive drum 20 by the urging force of the pressing member 66.

Further, as shown in FIG. 5, the color member 117 of the developing cartridge 19 is fitted in the guide groove 59 of the drum cartridge 18. Thus, the developing roller 34 is guided toward the photosensitive drum 20 by the guide groove 59 and is pressed against the photosensitive drum 20 from the front side.
4). As shown in FIG. 1, when the process cartridge 15 is mounted in the main casing 2, the rear side of the main casing 2 is the rear side of the main casing 2 and the front side of the main casing 2 is the front side of the main casing 2. The front lower side, the upper side thereof faces the front upper side of the main body casing 2, and the lower side faces the rear lower side of the main body casing 2. As a result, the developing roller 34 is disposed at a lower position in the vertical direction than the central axis A1 of the photosensitive drum 20. Further, the main body 110 of the pressing member 66 can slide in the direction connecting the front lower side and the rear upper side of the main body casing 2 in the pressing member accommodating portion 69. The main body 110 is urged toward the rear upper side of the main body casing 2 by the urging force of the spring member 111. The guide groove 59 extends in the same direction as the direction connecting the front lower side and the rear upper side of the main body casing 2, that is, the direction in which the main body 110 is urged by the spring member 111. Accordingly, the pressing member 66 presses the developing cartridge 19 toward the photosensitive drum 20 with a pressing force having a vertically upward component. As a result, the developing roller 34 is guided by the guide groove 59 and is brought into pressure contact with the photosensitive drum 20 with a pressing force having a vertically upward component. On the other hand, the substantially rectangular tube-shaped transfer roller shaft guide portion 71 and the guide opening 73 of the transfer roller shaft guide portion 71 extend in the front-rear direction of the main casing 2. A metal urging member (not shown) provided in the main body casing 2 is provided on each of the transfer roller bearing 87 and the transfer roller electrode 88 of the transfer roller 21 via the rear end portion of the transfer roller shaft guide portion 71. It abuts from the rear side.

Thereby, the transfer roller 21 is pressed to the front side toward the photosensitive drum 20 by a biasing force of a biasing member (not shown).

A drive gear (not shown) provided in the main body casing 2 is meshed with the drum gear 83. Further, a coupling convex portion (not shown) of a main body coupling (not shown) provided in the main body casing 2 is fitted into the coupling concave portion 116.
5. Drum Cleaning by Cleanerless Method (1) Supply of Power When the above-described image forming operation is performed, a supply bias of, for example, +400 V is applied to the supply roller 33.

Further, for example, a developing bias of +300 V is applied to the developing roller 34.

In addition, a predetermined voltage is applied to the charging wire 23 and the grid 24 of the scorotron charger 22, and the surface of the photosensitive drum 20 is charged with, for example, a charging potential of +630 V before being exposed by the scanner unit 16. .

The charged potential on the surface of the photosensitive drum 20 becomes lower than the potential of the developing bias when exposed by the scanner unit 16. That is, the charging potential of the surface of the photosensitive drum 20 where the electrostatic latent image is formed is equal to or lower than the potential of the developing bias.

Further, a negative transfer bias is applied to the transfer roller electrode 88 of the transfer roller 21 via a biasing member (not shown), and, for example, −15 μA is provided between the photosensitive drum 20 and the transfer roller 21. A transfer current flows.

The transfer bias is controlled so as to keep the transfer current constant.
(2) Driving of process cartridge When the above-described image forming operation is performed, the photosensitive drum 20 is rotated clockwise in a left side view.

Further, when the photosensitive drum 20 is rotated clockwise in the left side view, the transfer roller 21 is rotated counterclockwise in the left side view following the rotation of the photosensitive drum 20.

Further, a driving force is input to the development coupling 118 via a main body coupling (not shown), and the supply roller 33 and the development roller 34 are rotated counterclockwise as viewed from the left side. The peripheral speed of the developing roller 34 is, for example, 1.35 to 1.65 times, preferably 1.5 times the peripheral speed of the photosensitive drum 20.
(3) Cleaning of Photosensitive Drum In the above-described image forming operation, when a toner image is transferred onto the paper S, a toner with poor charging remains on the peripheral surface of the photosensitive drum 20, or an external additive (for toner) Silica) and paper dust may adhere.

The adhering matter adhering to the peripheral surface of the photosensitive drum 20 is opposed to the developing roller 34 as the photosensitive drum 20 rotates.

Then, the adhering matter is removed from the peripheral surface of the photosensitive drum 20 by rubbing against the developing roller 34 and developing bias, and is electrostatically held on the peripheral surface of the developing roller 34. At the same time, toner is supplied to the electrostatic latent image on the photosensitive drum 20 as described above.

The adhering matter held on the peripheral surface of the developing roller 34 is then opposed to the supply roller 33 as the developing roller 34 rotates, and is electrostatically held on the peripheral surface of the supply roller 33 by the supply bias.

In this manner, the deposits attached to the peripheral surface of the photosensitive drum 20 are removed.
6). Operation and Effect (1) According to the printer 1, as shown in FIG. 1, the developing cartridge 19 is a component from the vertically lower side toward the photosensitive drum 20 in a state where the process cartridge 15 is mounted on the main casing 2. It is pressed by the pressing force having.

Therefore, when the toner in the developing cartridge 19 is consumed, the pressing force by the pressing member 66 increases as the weight of the developing cartridge 19 decreases, and the developing roller 34 can be pressed further toward the photosensitive drum 20. it can.

As a result, even when the toner in the developing cartridge 19 is consumed, the toner in the developing cartridge 19 is stabilized against the photosensitive drum 20 without reducing the pressing force of the developing roller 34 against the photosensitive drum 20. Can be supplied.

Further, when the developing cartridge 19 reaches the end of the use period, the toner in the developing cartridge 19 tends to be filmed on the surface of the photosensitive drum 20 due to deterioration with time.

However, according to the printer 1, as described above, when the toner in the developing cartridge 19 is consumed and the developing cartridge 19 reaches the end of the use period, the pressing force of the developing roller 34 against the photosensitive drum 20 is reduced. Become stronger.

Therefore, when the developing cartridge 19 reaches the end of the usage period, the surface of the photosensitive drum 20 can be more reliably cleaned by the developing roller 34.

As a result, deterioration in image quality can be suppressed over the usage period of the developing cartridge 19.
(2) Also, according to the printer 1, as shown in FIG. 4, the pressing member 66 includes a rear side (pressing direction) toward the photosensitive drum 20 and a front side (press releasing direction) opposite to the rear side. ) And linear movement.

Therefore, the developing cartridge 19 can be efficiently pressed toward the photosensitive drum 20.
(3) Also, according to the printer 1, as shown in FIG. 4, the supply roller 33 is opposed to the developing roller 34 from the front lower side (opposite side of the photosensitive drum 20).

Therefore, when the developing roller 34 is pressed against the photosensitive drum 20, the supply roller 33 can suppress the deflection of the developing roller 34 due to the reaction force from the photosensitive drum 20.

As a result, the developing roller 34 can be reliably pressed against the photosensitive drum 20.
(4) Further, according to the printer 1, the supply bias (+ 400V) having the same polarity as the development bias (+ 300V) applied to the development roller 34 and having an absolute value larger than the development bias is applied to the supply roller 33. Has been.

Therefore, it is possible to attract toner charged to a polarity opposite to the polarity of the developing bias to the supply roller 33 by the supply bias having an absolute value larger than that of the developing bias.

As a result, it is possible to suppress the toner charged to the reverse polarity from being supplied to the photosensitive drum 20.
(5) According to the printer 1, the drum cartridge 18 includes the transfer roller 21 as shown in FIG. 3.

Therefore, since the transfer roller 21 is in contact with the photosensitive drum 20 and the paper S, the transfer roller 21 may be contaminated by poorly charged toner remaining on the photosensitive drum 20 or paper dust adhering to the paper S.

In this respect, according to the printer 1, when the drum cartridge 18 is maintained, the transfer roller 21 can be reliably maintained.
(6) Further, according to the printer 1, as shown in FIG. 3, the transfer roller 21 is configured to follow the rotation of the photosensitive drum 20.

Therefore, it is necessary to press the transfer roller 21 relatively strongly against the photosensitive drum 20 in order to cause the transfer roller 21 to follow the photosensitive drum 20. When the pressing force of the transfer roller 21 against the photosensitive drum 20 increases, the transfer roller 21 tends to become dirty due to sliding friction with the photosensitive drum 20 and the paper S.

In this regard, as described above, since the transfer roller 21 is provided in the drum cartridge 18, the transfer roller 21 can be reliably maintained when the drum cartridge 18 is maintained.
(7) Also, according to the printer 1, as shown in FIG. 1, the transfer roller 21 has a virtual line segment L1 passing through the central axis A2 of the main casing 2 and the central axis A1 of the photosensitive drum 20. Are arranged so as to extend in a substantially horizontal direction.

For this reason, it is possible to prevent the adhering matter adhering to the photosensitive drum 20 from falling on the transfer roller 21, and to suppress the contamination of the transfer roller 21.
(8) Also, according to the printer 1, the developing roller 34 collects deposits that adhere to the peripheral surface of the photosensitive drum 20.

Therefore, the deposit can be collected using the developing roller 34 without providing a separate configuration for collecting the deposit.

As a result, the configuration of the printer 1 can be simplified.

In addition, as described above, since the pressing force of the developing roller 34 against the photosensitive drum 20 does not decrease, the deposits can be reliably collected.
(9) According to the printer 1, the developing cartridge 19 is mounted on the developing cartridge mounting portion 102 of the drum cartridge 18 as shown in FIGS. 3 and 4.

Therefore, the relative arrangement of the photosensitive drum 20 and the developing cartridge 19 can be positioned in the drum cartridge 18.

As a result, the developing cartridge 19 can be more reliably pressed against the photosensitive drum 20.
7). Modification The printer 1 described above is an embodiment of the image forming apparatus of the present invention, and the present invention is not limited to the above-described embodiment.

The image forming apparatus of the present invention can be configured as a color printer in addition to the above-described monochrome printer.

When the image forming apparatus is configured as a color printer, the image forming apparatus includes a direct tandem type color printer including a plurality of photosensitive members and a recording medium conveying member, a plurality of photosensitive members, an intermediate transfer member, and a transfer member. It can be configured as an intermediate transfer type tandem color printer.

Further, the developing cartridge 19 can be configured such that a toner cartridge that contains toner is detachably attached to a frame having the developing roller 34.

In addition to the above-described photosensitive drum 20, for example, a photosensitive belt can be used as the photosensitive member.

Further, as the developer carrying member, for example, a developing sleeve, a developing belt, a brush-like roller, etc. can be applied in addition to the developing roller 34 described above.

In addition to the supply roller 33 described above, for example, a supply sleeve, a supply belt, a brush-like roller, or the like can be applied as the supply member.

Further, instead of the agitator 29 described above, for example, a conveying member such as an auger screw or a conveying belt can be applied.

Further, as the transfer member, in addition to the transfer roller 21 described above, for example, a contact type transfer member such as a transfer belt, a transfer brush, a transfer blade, a film type transfer device, or a non-contact type such as a corotron type is used. A transfer member or the like can also be applied.

Further, instead of the above scorotron charger 22, for example, a non-contact charger such as a corotron charger, a sawtooth discharge member, or a contact charger such as a charging roller may be applied. it can.

Further, instead of the scanner unit 16 described above, an exposure member such as an LED unit can be applied.

Furthermore, the image forming apparatus of the present invention can also be configured as a multi-function machine equipped with an image reading unit and the like.

DESCRIPTION OF SYMBOLS 1 Printer 2 Main body casing 15 Process cartridge 18 Drum cartridge 19 Developing cartridge 20 Photosensitive drum 21 Transfer roller 33 Supply roller 34 Developing roller 59 Guide groove 66 Pressing member 101 Drum support part 102 Developing cartridge mounting part A1 Central axis A2 Central axis L1 line segment S paper

Claims

An apparatus body (2);
A process cartridge (15) detachably attached to the apparatus main body,
The process cartridge (15)
A photoreceptor cartridge (18) having a photoreceptor (20) rotatably;
A developer carrying body (34) configured to carry a developer rotatably, and including a developing cartridge (19) detachable from the photosensitive cartridge (18);
The photoreceptor cartridge (18)
A pressing member (66) for pressing the developer cartridge (19) so as to press the developer carrier (34) toward the photoreceptor (20);
A guide portion (59) for guiding the developer carrier (34) toward the photoreceptor (20),
In a state where the process cartridge (15) is mounted on the apparatus main body (2), the developer carrier (34) is positioned lower in the vertical direction than the rotation axis (A1) of the photosensitive member (20). An image forming apparatus (1), wherein
The pressing member (66) is configured to linearly move in a pressing direction toward the photoconductor (20) and in a pressing release direction opposite to the pressing direction. Item 2. The image forming apparatus (1) according to Item 1.
The developer cartridge (19) has a supply member (33) configured to supply a developer to the developer carrier (34), and is rotatable.
2. The image forming apparatus according to claim 1, wherein the supply member is opposed to the developer carrying member from the opposite side of the photoconductor. 1).
The supply member (33) is configured to be supplied with a supply bias having the same polarity as the development bias applied to the developer carrier (34) and having an absolute value larger than the development bias. The image forming apparatus (1) according to claim 3, characterized in that:
The photoconductor cartridge (18) is disposed opposite to the photoconductor (20) and is carried on the photoconductor (20) on a transfer member (S) passing between the photoconductor (20). The image forming apparatus (1) according to claim 1, wherein a transfer member (21) for transferring the developed developer image is rotatably provided.
The image forming apparatus (1) according to claim 5, wherein the transfer member (21) is configured to follow the rotation of the photoconductor (20).
The transfer member (21) is disposed such that a virtual straight line (L1) passing through the rotation axis (A2) of the transfer member (21) and the rotation axis (A1) of the photoconductor (20) extends in a substantially horizontal direction. The image forming apparatus (1) according to claim 5 or 6, characterized in that:
The image forming apparatus (1) according to claim 1, wherein the developer carrying member (34) is configured to collect deposits attached to a peripheral surface of the photosensitive member (20). ).
The photoreceptor cartridge (18)
A photoreceptor support (101) for supporting the photoreceptor (20);
The image forming apparatus (1) according to claim 1, wherein the image forming apparatus (1) is provided integrally with a developing cartridge mounting portion (102) to which the developing cartridge (19) can be mounted.