JP2014191306A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device which is capable of suppressing a developer from being leaked from between the end of a developing roller and a seal member.SOLUTION: The developing device includes a cartridge frame, a developing roller 72, and a seal member 77 arranged between the developing roller 72 and the cartridge frame, to suppress the developer from being leaked from between the developing roller 72 and the cartridge frame. The developing roller 72 has a shaft member 72B configured so as to rotate and an elastic layer 72C covering the outer periphery of the shaft member 72B. The elastic layer 72C has a first part A covering the intermediate part of the shaft member 72B and a second part B which covers the end of the shaft member 72B and whose thickness is smaller than that of the first part A. The second part B comes into contact with the seal member 77.

Description

  The present invention relates to a developing device constituting an image forming apparatus.

  As a developing device constituting an electrophotographic image forming apparatus such as a printer or a copying machine, a developing roller carrying a developer, a housing supporting the developing roller, and a space between the housing and the end of the developing roller A developing device having a side seal member for sealing is generally known (see, for example, Patent Document 1).

  Here, the developing roller has a structure in which the outer periphery of the metal roller shaft is covered with a conductive rubber roller body, and the developer is carried on the peripheral surface of the rubber roller body. It has become.

JP 2009-63635 A

  By the way, in the developing device described in the above-mentioned Patent Document 1, the peripheral surface of the end portion of the rubber roller body comes into sliding contact with the side seal member as the developing roller rotates, so that frictional heat is applied to the sliding contact portion. Will occur.

  Here, when the rotation speed of the developing roller is increased so as to increase the printing speed of the image forming apparatus, the sliding contact portion between the end peripheral surface of the rubber roller body and the side seal member becomes high temperature due to frictional heat, There is a possibility that a part of the developer carried on the peripheral surface of the roller body melts and leaks from the seal portion of the side seal member.

  SUMMARY An advantage of some aspects of the invention is that it provides a developing device capable of suppressing leakage of developer from between a developing roller and a seal member.

  A developing device according to the present invention for solving the above-described problems is provided between a developing roller and a housing in order to suppress leakage of the developer from the housing, the developing roller, and between the developing roller and the housing. And a seal member disposed on the surface. The developing roller includes a shaft member configured to rotate and an elastic layer covering the outer periphery of the shaft member. The elastic layer has a first portion that covers the intermediate portion of the shaft member, and a second portion that covers the end portion of the shaft member and is thinner than the first portion. The second portion is in contact with the seal member.

  In this developing device, when the developing roller generates frictional heat by sliding contact with the seal member as the developing roller rotates, the frictional heat is generated from the second part having a thickness smaller than that of the first part. Heat is transferred to. As a result, the elastic layer and the seal member of the developing roller are suppressed from being heated to high temperatures due to frictional heat, and toner leakage from between the seal member and the elastic layer is suppressed.

  Here, it is preferable that the boundary between the first portion and the second portion of the elastic layer in the axial direction of the developing roller is disposed outside the printing area of the developing roller. The second portion may have a constant thickness that is continuous in the axial direction of the developing roller. In this case, the contact pressure between the second portion of the elastic layer and the seal member becomes constant, and the leakage of the developer can be further suppressed.

  In addition, the second portion has an inclined portion that gradually decreases in thickness from the inner side to the outer side in the axial direction of the developing roller, and a linear portion that has a constant thickness extending continuously from the inclined portion in the axial direction. Good. Further, it is preferable that the thickness of the second portion gradually decreases from the inner side to the outer side in the axial direction of the developing roller. In this case, since the contact pressure of the developing roller with respect to the photosensitive drum gradually changes from the inner side to the outer side in the axial direction of the developing roller, the influence on the photosensitive drum is less than when the contact pressure changes suddenly.

  Further, the second portion may have a convex portion protruding toward the inside in the radial direction of the developing roller. In this case, since the surface area of the elastic layer in contact with the shaft member is increased, the frictional heat due to the sliding contact between the developing roller and the seal member can be efficiently released.

  According to the developing device of the present invention, it is possible to suppress the leakage of the developer from between the seal member and the developing roller.

1 is a side sectional view showing a schematic configuration of a laser printer including a developing device according to an embodiment of the present invention. FIG. 2 is an exploded perspective view of the developing cartridge shown in FIG. 1. FIG. 3 is a partially enlarged perspective view in the vicinity of a left end portion of the housing illustrated in FIG. 2. (A), (b) is a fragmentary sectional view which shows two different structures of the structure of the edge part of the developing roller shown in FIG. (A), (b) is a fragmentary sectional view which shows two other different structures of the structure of the edge part of the developing roller shown in FIG.

<First Embodiment>
Hereinafter, embodiments of a developing device according to the present invention will be described in detail with reference to the drawings as appropriate. The developing device of the first embodiment is embodied as a developing cartridge of a laser printer 1 as shown in FIG. First, the laser printer 1 will be schematically described. In the following description, the left direction in FIG. 1 is “front”, the right direction is “rear”, the up and down direction is “up and down”, the front direction is “right”, and the back direction is “left”.

<Schematic configuration of laser printer>
As shown in FIG. 1, a laser printer 1 includes a feeder unit 20 for feeding a sheet S as an example of a recording sheet into a main body casing 10 that is an apparatus main body, a scanner unit 30 that is an exposure unit, A developing unit for transferring the toner image onto the sheet S and a process cartridge 40 constituting the transfer unit and a fixing device 50 for thermally fixing the toner image on the sheet S are mainly provided.

  The main body casing 10 includes a top cover 11 and a front cover 12. The main body casing 10 has an opening 13 on the front side, and has an insertion port 14 for inserting the paper S in a lower part on the front side.

  The lower portion of the front cover 12 is pivotally supported by a rotating shaft 15 provided at the lower front side of the main body casing 10. By rotating about the rotating shaft 15, the front cover 12 is in an upright position indicated by a two-dot chain line. The front side of the main body casing 10 is closed, and the front side of the main body casing 10 is opened at a lying position indicated by a solid line.

  The feeder unit 20 is disposed at a lower portion of the main body casing 10, and includes a paper feed tray 21 on which the paper S is placed and a paper feed mechanism 22 that feeds the paper S on the paper feed tray 21. Yes. The paper feed tray 21 is configured by a mounting table 23 disposed at a lower portion of the main body casing 10 and an upper surface of the front cover 12 opened so as to be continuous with the mounting table 23.

  The paper feed mechanism 22 mainly includes a paper feed roller 24, a separation roller 25, and a separation pad 26. The paper feed roller 24 is disposed above the rear end of the mounting table 23 on the upstream side of the separation roller 25 in the transport direction of the paper S. The separation roller 25 is disposed to face the separation pad 26.

  In the feeder unit 20, the sheet S placed across the upper surface of the front cover 12 opened at the lying position indicated by the solid line and the mounting table 23 of the sheet feeding tray 21 is separated from the separation roller 25 side by the rotation of the sheet feeding roller 24. Sent out. The sheets S sent to the separation roller 25 side are separated one by one between the separation roller 25 and the separation pad 26 and conveyed toward the process cartridge 40.

  The scanner unit 30 is disposed on the front side in the main body casing 10 and includes a laser light emitting unit, a polygon mirror, a lens, a reflecting mirror, and the like (not shown). The scanner unit 30 irradiates a surface of a photosensitive drum 62 described later with a laser beam at high speed scanning.

  The process cartridge 40 is disposed above the sheet feeding mechanism 22 in the vicinity of the central portion on the rear side of the main casing 10. The process cartridge 40 is configured to be detachable from the main body casing 10 and can be taken out from the upper side of the main body casing 10 with the top cover 11 being opened.

  Here, the process cartridge 40 includes a drum unit 60 and a developing cartridge 70 as an example of a developing device. The drum unit 60 includes a unit frame 61, a photosensitive drum 62 provided on the unit frame 61, a charger 63, and a transfer roller 64.

  On the other hand, the developing cartridge 70 includes a cartridge frame 71 as a housing, a developing roller 72, a supply roller 73, a layer thickness regulating blade 74, and a toner hopper 75. The developing cartridge 70 can be attached to and detached from the unit frame 61 of the drum unit 60.

  The developing roller 72 is a member configured to carry toner on its peripheral surface, and is provided so as to be rotatable with respect to the cartridge frame 71 so as to rotate about an axis. The developing roller 72 is in contact with the photosensitive drum 62. On the other hand, the supply roller 73 is a member configured to adhere and carry the toner accommodated in the toner hopper 75 on the peripheral surface, and supply the toner to the peripheral surface of the developing roller 72. It is arranged in parallel with the developing roller 110 along the axial direction of the developing roller 72 in the obliquely lower front. The supply roller 73 is in contact with the developing roller 72.

  In the developing cartridge 70, the toner accommodated in the toner hopper 75 is agitated by the agitator 76 and then supplied from the peripheral surface of the supply roller 73 to the peripheral surface of the developing roller 72. At this time, the toner is positively frictionally charged between the peripheral surface of the supply roller 73 and the peripheral surface of the developing roller 72. Then, as the developing roller 72 rotates, the toner supplied to the peripheral surface of the developing roller 72 enters between the layer thickness regulating blade 74 and the peripheral surface of the developing roller 72, and is further fixed by being frictionally charged. It is carried on the peripheral surface of the developing roller 72 as a thin layer.

  In the drum unit 60, the surface of the rotating photosensitive drum 62 is uniformly charged by the charger 63 and then exposed by high-speed scanning of the laser beam from the scanner unit 30. 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 62.

  Then, the toner image (development) is formed on the surface of the photosensitive drum 62 by supplying the electrostatic latent image on the surface of the photosensitive drum 62 to the surface of the photosensitive drum 62 by supplying a constant amount of toner from the peripheral surface of the developing roller 72 of the developing cartridge 70. Agent image) is formed. Thereafter, when the sheet S is conveyed between the photosensitive drum 62 and the transfer roller 64, a transfer bias is applied to the transfer roller 64, so that the toner image carried on the surface of the photosensitive drum 62 is transferred to the transfer roller. 64 is transferred onto the paper S.

  The fixing device 50 is disposed above the process cartridge 40 at the upper rear of the main body casing 10. The fixing device 50 mainly includes a heating roller 51 and a pressure roller 52.

  The heating roller 51 is a member that heats the paper S, and a heat source (not shown) such as a halogen lamp is provided therein. On the other hand, the pressure roller 52 is a member that sandwiches and conveys the paper S with the heating roller 51, and is provided obliquely above the heating roller 51.

  In the fixing device 50, the toner image transferred onto the paper S is thermally fixed while the paper S passes between the heating roller 51 and the pressure roller 52. Then, the paper S on which the toner image is thermally fixed by the fixing device 50 is conveyed to the discharge roller 16 disposed on the downstream side of the fixing device 50, and the discharge roller 16 onto the discharge tray 17. Discharged.

<Detailed configuration of developing cartridge>
As shown in FIG. 2, the cartridge frame 71 of the developing cartridge 70 has an opening 71A formed in the rear side wall, and the developing roller 72 and the layer thickness regulating blade 74 are attached so as to block the opening 71A. . Further, in order to prevent the toner in the toner hopper 75 (see FIG. 1) from leaking in the upper, lower, left, and right sides of the opening 71A, a side seal member 77, an upper seal member 78, and a lower film 79 as examples of a seal member are provided. Is provided. In addition, fixing portions 71B for fixing the layer thickness regulating blade 74 are formed at both ends of the upper edge of the opening 71A.

  The layer thickness regulating blade 74 includes a blade body 74A, a blade holder 74B, and a reinforcing plate 74C. The blade main body 74 </ b> A is made of a metal plate such as a stainless steel rope, and a tip portion that contacts the peripheral surface of the developing roller 72 is curved. The blade body 74A regulates the layer thickness of the toner carried on the developing roller 72 to a certain thickness by the curved tip portion contacting the peripheral surface of the developing roller 72 in this way.

  The blade holder 74B has a support portion 74D for supporting the blade body 74A, a reinforcement portion 74E for attaching the reinforcement plate 74C, and an attachment portion 74F for attaching to the two fixing portions 71B of the cartridge frame 71. ing. The reinforcing portion 74E is formed to be bent at a substantially right angle from the upper end of the support portion 74D to the front side. The attachment portions 74F are formed at both ends of the blade holder 74B so as to overlap the two support surfaces 71C of the cartridge frame 71.

  The reinforcing plate 74C has a clamping part 74G for clamping the blade body 74A between the supporting part 74D of the blade holder 74B and a fixing part 74H for fixing to the reinforcing part 74E of the blade holder 74B. . The reinforcing plate 74C is formed such that the sandwiching portion 74G is bent at a substantially right angle from the rear end of the fixing portion 74H to the lower side.

  In the layer thickness regulating blade 74, the blade body 74A is sandwiched between the support portion 74D of the blade holder 74B and the sandwiching portion 74G of the reinforcing plate 74C, and the reinforcing portion 74E of the blade holder 74B and the fixing portion 74H of the reinforcing plate 74C are fastened with screws (not shown). By doing so, an integrated assembly part is obtained. As shown in FIG. 3, the layer thickness regulating blade 74 passes the screw B through the hole H of the attachment portion 74F of the blade holder 74B, and the screw of the screw boss 71D provided in the fixing portion 71B of the cartridge frame 71. The cartridge frame 71 is fixed by screwing into the hole.

  The side seal member 77 prevents the developer from leaking between the outer periphery of both end portions in the axial direction of the developing roller 72 and the cartridge frame 71, and is disposed between the developing roller 72 and the cartridge frame 71. . The side seal member 77 has an arcuate cross-sectional shape that follows the outer peripheral shape of the developing roller 72. The side seal member 77 has a structure in which a sliding contact member that is in sliding contact with the peripheral surface of the developing roller 72 is laminated on a base material made of a sponge material such as urethane foam. The sliding contact member is woven with fibers so as to capture the toner, and the surface is raised to make it fluffy.

  The upper seal member 78 is a member that seals between the cartridge frame 71 and the layer thickness regulating blade 74 along the longitudinal direction of the layer thickness regulating blade 74, and is made of a sponge material such as urethane foam. The upper seal member 78 is sandwiched between the mounting surface 71E and the support portion 74D of the blade holder 74B by being bonded to the mounting surface 71E of the cartridge frame 71.

  The lower film 79 is made of polyethylene terephthalate (PET) or the like. The lower film 79 extends in the left-right direction along the axial direction of the developing roller 72, and a tip portion facing the peripheral surface of the developing roller 72 can be slidably contacted with the peripheral surface of the developing roller 72. The lower film 79 is disposed below the developing roller 72 on the upstream side in the rotation direction of the developing roller 72 with respect to the layer thickness regulating blade 74. The lower film 79 is affixed to the cartridge frame 71 with an adhesive.

<Detailed structure of developing roller>
Next, the cross-sectional structure of the developing roller 72 shown in FIG. 2 will be described in detail with reference to FIG. As shown in FIG. 4A, the developing roller 72 has a rotating shaft member 72B, protrusions 72A protruding from the left and right end surfaces in the axial direction of the shaft member 72B, and an elastic covering the outer periphery of the shaft member 72B. Layer 72C.

  The shaft member 72B is made of a metal material such as an aluminum alloy. In the shaft member 72B, the diameter D1 of the intermediate portion in the axial direction is smaller than the diameter D2 of the end portion in the axial direction. The protrusion 72A of the shaft member 72B is supported by the cartridge frame 71 via a bearing member (not shown). The protrusion 72A is integrally formed of the same material as the shaft member 72B. The elastic layer 72C is made of a conductive elastic material such as urethane rubber or silicon rubber.

  The elastic layer 72C includes a first portion A that covers the axial intermediate portion of the shaft member 72B, and a second portion B that covers the axial end of the shaft member 72B and is thinner than the first portion A. Have As shown in FIG. 4A, the first portion A has a constant thickness continuously in the axial direction. Also, the second part B has a constant thickness continuously in the axial direction.

  The thickness of the second part B is, for example, about half the thickness of the first part A. Further, a part of the second portion B is in contact with the seal member 77. Note that the entire area of the second portion B in the axial direction may contact the seal member 77.

  The boundary between the first part A and the second part B is outside the printing area W of the developing roller 72 and inside the inner end 77 A of the side seal member 77.

<Operation with developing cartridge>
In the developing cartridge 10 embodied as an embodiment of the developing device, as the developing roller 72 rotates, the second portion B of the elastic layer 72C is brought into sliding contact with the seal member 77, whereby the second portion B of the elastic layer 72C. Friction heat is generated between the seal member 77 and the seal member 77. The frictional heat moves from the second portion B to the shaft member 72B having a temperature lower than that of the sliding contact portion between the second portion B and the seal member 77.

  The heat that has moved to the shaft member 72B is released into the atmosphere from the axial end surface of the shaft member 72B, or is transferred to the center of the shaft member 72B. Since the thickness of the second portion B is thinner than the thickness of the first portion A, the frictional heat can be radiated more efficiently than the first portion A. As a result, the seal member 77 and the elastic layer 72C are prevented from being heated due to frictional heat, and the toner is prevented from leaking from between the seal member 77 and the second portion B of the elastic layer 72C.

If the first part A and the second part B have the same thickness, the heat dissipation performance of the second part B does not change, so that the sealing member 77 and the elastic layer 72C are prevented from being heated due to frictional heat. .
However, if the thickness of the first part A is reduced, the first part A is less likely to be elastically deformed when it comes into contact with the photosensitive drum 62, so that the nip region between the developing roller 72 and the photosensitive drum 62 becomes smaller. . However, in the developing roller 72 of the present embodiment, it is possible to prevent the toner from leaking from between the seal member 77 and the second portion B of the elastic layer 72C while securing the nip region.

  Further, the boundary between the first portion A and the second portion B of the elastic layer 72 </ b> C in the axial direction of the developing roller 72 is set outside the printing area W of the developing roller 72. Therefore, the contact pressure between the developing roller 72 and the photosensitive drum 62 is constant in the printing area, and does not affect printing. The second portion B has a constant thickness that is continuous in the axial direction of the developing roller 72. Therefore, the contact pressure between the second portion B of the elastic layer 72C and the seal member 77 is constant, and the leakage of the developer can be further suppressed.

  The developing cartridge 10 according to the embodiment of the developing device according to the present invention has been described above. However, the developing device according to the present invention is not limited to the developing cartridge 10 according to the embodiment, and the configuration thereof may be changed as appropriate. Can do.

Second Embodiment
FIG. 4B shows a second embodiment. The first portion A of the elastic layer 72C has a constant thickness continuously in the axial direction. The second portion B includes a straight portion 80 having a constant thickness continuously in the axial direction, and an inclined portion 81 positioned between the first portion A and the straight portion 80. The straight portion 80 is disposed at the end portion of the developing roller 72 in the axial direction. The inclined portion 81 is continuous with the straight portion 80. Further, the second portion B is in contact with the seal member 77. Specifically, a part of the linear portion 80 and the inclined portion 81 is in contact with the seal member 77.

  According to such a configuration, the contact pressure of the developing roller 72 with respect to the photosensitive drum 62 gradually changes from the inner side to the outer side in the axial direction of the developing roller 72. There is little influence on 62.

<Third Embodiment>
FIG. 5A shows a third embodiment. The thickness of the second portion B of the elastic layer 72C gradually decreases from the inner side to the outer side of the developing roller 72 in the axial direction. The second part B is inclined about 5 ° with respect to the first part A. Further, a part of the second part B is in contact with the seal member 77.

  According to such a configuration, the contact pressure of the developing roller 72 with respect to the photosensitive drum 62 gradually changes from the inner side to the outer side in the axial direction of the developing roller 72. There is little influence on 62.

<Fourth embodiment>
FIG. 5B shows a third embodiment. The second portion B of the elastic layer 72C has a flat surface portion 72H that is thinner than the first portion A, and a convex portion 72J that protrudes from the flat surface portion 72H toward the inside in the radial direction of the developing roller 72. Two protrusions 72J are provided in the axial direction of the developing roller 72, and the radially inner end of the developing roller 72 is located at substantially the same position as the radially inner end of the first portion A.

  According to such a configuration, the surface area of the elastic layer 72C in contact with the shaft member 72B is increased, so that frictional heat due to the sliding contact between the developing roller 72 and the seal member 77 can be efficiently released.

<Modification>
Here, the material of the shaft member 72B of the developing roller 72 shown in FIGS. 4 (a) and 4 (b) and FIGS. 5 (a) and 5 (b) is not limited to a metal material. It is possible to change to an appropriate synthetic resin material having rigidity and conductivity. However, the material of the shaft member 72B must be a material having better thermal conductivity than the elastic layer 72C.

  Further, the developing device of the present invention is not limited to the monochrome printer shown in FIG. 1, but can be applied to a color printer, a copying machine, a multifunction machine, and the like.

1 Laser Printer 40 Process Cartridge 70 Developer Cartridge 71 Cartridge Frame (Housing)
72 Developing roller 72A Protruding portion 72B Shaft member 72C Elastic layer 77 Side seal member (seal member)
A 1st part B 2nd part

Claims (6)

A housing,
A developing roller having a shaft member configured to rotate, and an elastic layer covering an outer periphery of the shaft member;
A seal member disposed between the developing roller and the housing in order to prevent the developer from leaking between the developing roller and the housing;
The elastic layer has a first portion that covers an intermediate portion of the shaft member, and a second portion that covers an end portion of the shaft member and is thinner than the first portion,
The developing device, wherein the second portion is in contact with the seal member.   The developing device according to claim 1, wherein a boundary between the first portion and the second portion is outside a printing area of the developing roller.   The developing device according to claim 1, wherein the second portion has a constant thickness that is continuous in an axial direction of the developing roller.   The second portion includes an inclined portion having a thickness that gradually decreases from the inner side to the outer side in the axial direction, and a linear portion having a constant thickness extending continuously from the inclined portion in the axial direction. The developing device according to claim 1, wherein   The developing device according to claim 1, wherein the second portion has a thickness that gradually decreases from an inner side to an outer side in the axial direction. 3. The developing device according to claim 1, wherein the second portion has a convex portion protruding toward a radially inner side of the developing roller.

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