JP2009271109A - Developing device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the contact state of an image carrier and a developing agent carrier in an image forming device achieving compactness and space saving, thus forming a good image. <P>SOLUTION: This developing device 110 comprises a developing roller 112 which develops the image carrier 111, a pair of bearing members 114 which hold the developing roller 112 permitting rotation identity, a pair of support members 130 which guide the bearing member 114 in the direction for the developing roller to approach/depart from the image carrier, and a spring which presses the developing roller 112 against the image carrier 111. A guide part 131 comprising an inclined face part 151 directed outside is formed on the support member 130 as approaching the image carrier 111. A contact face part 152 contacting the inclined face part 151 is formed on the bearing member 114. The bearing member 114 is energized toward the support member 130 by thrust forces of helical gears 121, 122 driving the image carrier 111 and the developing roller 112. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a developing device and an image forming apparatus, and in particular, a developing roller that develops an image carrier, a pair of bearing members that are disposed at both ends of the developing roller and hold the developing roller rotatably. A developing device including a pair of support members that guide the bearing member so that the developing roller can move in a direction in which the developing roller approaches and separates from the image carrier, and an elastic member that presses the developing roller against the image carrier, and the developing device The present invention relates to an image forming apparatus including

  The developer carrying member used in the electrophotographic apparatus is positioned with a minute gap or in minute contact with the image carrying member. The developer carrier is fixed by completely fixing the developer carrier and the image carrier, or by pressing the developer carrier toward the image carrier. In the electrophotographic apparatus having such a configuration, the driving force for driving the developer carrying member is generally transmitted by a gear.

  In addition, a developer carrying member, which is a rotating member such as a developing roller, is generally driven on one end side in the rotation axis direction. In this case, an image bearing member is driven by a driving force of a gear applied to one side of the developing roller. There may be a difference between the driving side and the non-driving side in the pressing force for special holidays.

  As described above, the developing device supplies the developer to the image carrier, and includes a developer carrier that is rotationally driven by the driving force applied to the gear provided on the shaft portion of the developer carrier. The following are examples of pressing in the direction of the image carrier.

  In Patent Document 1, a bearing that supports the drive side end portion of the sleeve is 0.7 × θ to 1.3 × θ with respect to a straight line L connecting the photosensitive drum and the rotation center of the sleeve (where θ is a gear position). A direction R within a range of −6 degrees to +6 degrees with respect to the straight line L is provided between the support guide section that can be displaced in the direction Q inclined by the pressure angle) and the bearing that supports the non-driving side end of the sleeve. A developing device is described in which the magnet is supported inside the sleeve on the driving side and supported independently of the sleeve on the non-driving side. That is, the developing device according to this example is configured such that the toner carrying member is pressed toward the rotation center of the electrophotographic photosensitive member when the driving force is transmitted to the toner carrying holiday.

Japanese Patent Application Laid-Open No. 2005-228867 discloses a photosensitive unit including a photosensitive drum, a developing unit including a developing housing, a developing roller, and an input gear that transmits a driving force to the developing roller, and the photosensitive unit. An image forming machine comprising: a support shaft that supports the developing unit so as to be swingable; and is detachably mounted on the machine housing so that the input gear meshes with a drive gear disposed on the machine housing. The end of the support shaft on the side opposite to the side where the input gear is disposed and the support portion of the photosensitive unit are a rotation shaft of the photosensitive drum and a rotation shaft of the developing roller. Are configured so as to be capable of relative displacement in a plane substantially parallel to a plane passing through. In other words, the process knit according to this example presses the developing device against the photosensitive member by a pressure spring, presses the bearing of the photosensitive member and the developing roller of the developing device, and positions the photosensitive member and the developing roller. To do.
JP-A-6-75471 Special No. 3385550 gazette

  As described above, the technique disclosed in Patent Document 1 can prevent the image carrier and the developer carrier from being separated by the gear driving force between the image carrier and the developer carrier. Since the urging force from the agent carrier to the image holding member is also suppressed, the urging member cannot be applied to an image forming apparatus that is downsized and space-saving.

  In addition, although Patent Document 2 is intended to prevent printing failure due to the shafts of the photosensitive member and the developing roller not being parallel due to the gear driving force, it cannot prevent separation of the photosensitive member and the developing roller.

  Accordingly, the present invention can improve the contact state between the image carrier value and the developer carrier in an image forming apparatus that is miniaturized and saves space, and can thereby form a good image. PROBLEM TO BE SOLVED To provide a developing device and an image forming apparatus

  According to a first aspect of the present invention, there is provided a developing roller that develops the image carrier, a pair of bearing members that are disposed at both ends of the developing roller and rotatably hold the developing roller, and the developing roller includes the bearing member. In the developing device, comprising: a pair of support members that are movably guided in a direction of approaching and separating from the image carrier; and an elastic member that presses the developing roller against the image carrier, at least one of the pair of support members The support member is formed with a guide portion having an inclined surface portion facing outward as it approaches the image carrier, and the bearing member held by the support portion on which the guide portion is formed has an inclined surface portion on the guide portion. The developing device further includes a biasing unit that biases the bearing member toward the support portion on which the guide portion is formed, while forming a contact surface portion to be contacted.

  According to a second aspect of the present invention, in the developing device according to the first aspect, the developing roller is driven by a helical gear that generates a thrust force by meshing, and the helical gear is used as the biasing means. Features.

  According to a third aspect of the present invention, in the developing device according to the first or second aspect, a lubricant is applied between the guide portion of the support member and the bearing.

  According to a fourth aspect of the present invention, in the developing device according to any one of the first to third aspects, the support member and the bearing member are made of a synthetic resin, and a convex portion is formed on a contact surface portion of the bearing member. The guide portion is in contact with the tip of the convex portion.

  According to a fifth aspect of the present invention, in the developing device according to any one of the first to fourth aspects, a shaft hole portion into which the shaft portion of the developing roller is inserted is formed in the bearing member. A chamfering process is performed on at least a corner portion of the inner end portion of the portion on the support member side.

  According to a sixth aspect of the present invention, in the developing device according to any one of the first to fifth aspects, the pair of support members are configured to be detachable from the image forming apparatus main body, and an image carrier is provided on the support member. The process cartridge is configured as a process cartridge that is held and detachably attached to the image forming apparatus.

  A seventh aspect of the present invention is an image forming apparatus comprising the developing device according to any one of the first to sixth aspects.

  According to the developing device and the image forming apparatus of the present invention, the contact state between the image carrier value and the developer carrier can be made favorable, and as a result, a good image can be formed. is there.

  Embodiments as the best mode for carrying out the present invention will be described below with reference to the drawings.

  The image forming apparatus according to the embodiment will be described below. FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment. This example is a color electrophotographic apparatus. The image forming apparatus 1 includes an image forming unit 6, that is, a black image forming unit 6K, a cyan image forming unit 6C, and a magenta image forming unit at a substantially central portion of the machine frame. 6M and yellow image forming units 6Y are arranged side by side. In each of the image forming units 6K, 6C, 6M, and 6Y, an image carrier 6a including a photosensitive drum is disposed.

  Above the image forming unit 6, an exposure device 5 for forming a latent image on the image carrier 6a is disposed. Below the image forming unit 6, the transfer belt 3 is supported by support rollers provided on the left and right sides and arranged in the left-right direction. The transfer belt 3 is rotationally driven in the counterclockwise direction. The support roller provided on the right side of the transfer belt 3 is provided with a second transfer device 11 that transfers the toner image onto a recording medium as a sheet-like medium. An intermediate transfer member cleaning device 14 is disposed at a position downstream of the second transfer device 11 and upstream of the black image forming unit 6K in the rotation direction of the transfer belt 3.

  A waste toner collecting container 15 is disposed below the transfer belt 3, and a paper feeding cassette 8 for loading and storing the recording medium S is disposed below the waste toner collecting container 15. The recording medium S fed by the paper feeding device 9 that separates and feeds the recording medium S passes between the transfer belt 3 and the second transfer device 11 and is guided to the fixing device 12 to the recording medium S. The toner image is heat-fixed.

  Next, the image forming unit 6 will be described. FIG. 2 is a schematic sectional view showing the configuration of the image forming unit. The toner hopper unit 6b integrated with the developing device 16 corresponds to a black image forming unit 6K, a cyan image forming unit 6C, a magenta image forming unit 6M, and a yellow image forming unit 6Y as a fine colored powder. Four different color toners (black, cyan, magenta, yellow) are filled.

  A developing roller 6h as a developer carrier for supplying toner to the image carrier 6a and an image developed with the toner are transferred around an image bearing member (photosensitive drum in this example) 6a which is a latent image holding means. Cleaning blade 6c for scraping off residual toner after primary transfer to the belt, charging roller 6d in contact with image carrier 68, toner transport screw 6e for transporting scraped toner horizontally, toner transport screw The toner from 6e is pumped up by the toner conveying belt 6f and collected in the waste toner collecting section 6g.

  The process up to the formation of electrophotography will be described. In FIG. 2, the image carrier 6a is rotated in the direction indicated by an arrow 20 by a driving device (not shown here), and the photosensitive layer on the surface thereof is charged to a uniform high potential by the charging roller 6d and initialized. The

  In this way, the photosensitive layer of the image carrier 6a charged to a uniform high potential is selectively exposed based on the image data by the scanning exposure light from the exposure device 5, and the low potential portion where the potential is attenuated by this exposure. And an electrostatic latent image formed by the initialization and the high potential portion.

  Next, when the low potential portion (or high potential portion) of the electrostatic latent image comes to the contact position from the developing roller 6h having the toner thin layer formed on the surface, the toner is transferred to form (develop) the toner image. . After the primary transfer, the cleaning blade 6C in contact with the image carrier 6a cleans the toner remaining on the surface of the image carrier 6a to prepare for the next toner image formation.

  The description will be continued with reference to FIG. A first transfer roller 3 a is installed at a position where the image forming unit 6 is in contact with the transfer belt 3, and a potential difference is applied between the image carrier (photosensitive drum) 6 a and the transfer belt 3 by applying a high potential to the first transfer roller 3 a. To transfer the toner image formed on the surface of the image carrier (photosensitive drum 6a).

  Each of the image forming units 6K, 6C, 6M, and 6Y sequentially transfers the toner images for each color onto the transfer belt 3, and a plurality of color toner images are formed on the transfer belt 3 by superimposing the single color toner images. .

  Next, the recording medium S such as a sheet or an OHP sheet is timed from the sheet feeding device 9 and the sheet conveying device (counter roller) 10 to the second transfer position (the second transfer device 11 and the transfer belt 3 face each other). The single color or color toner image formed on the surface of the transfer belt 3 is applied to the second transfer device 11 by applying a high potential to the potential difference between the transfer belt 3 and the second transfer device 11. Then, the toner image formed on the surface of the transfer belt 3 is transferred onto the recording medium 7.

  The recording medium S to which the toner image has been transferred is peeled off from the transfer belt 3, the toner image is melted and fixed on the recording medium S by the fixing device 12, and the upper surface of the image forming apparatus 1 is discharged by the paper discharge device (counter roller) 13. Paper is ejected to the paper tray.

  Excess toner remaining on the surface of the transfer belt 3 after the toner image is transferred to the recording medium 7 is cleaned by the intermediate transfer body cleaning device 14 and recovered in a waste toner recovery container 15. The cleaned transfer belt 3 prepares for the transfer of the next toner image.

  Simplify the transport path from the paper feed (paper feed device 9) to the paper discharge (paper discharge device 13) of the recording medium 7 as much as possible and increase the radius of curvature of the transport path to prevent paper jamming during transport. In addition, reliability can be improved. In addition, it is possible to easily perform a removal processing operation when a paper jam occurs, and it is also possible to cope with a color electrophotographic apparatus of a multi-recording medium type that also uses cardboard or the like.

  In this embodiment, the recording medium conveyance path from the paper supply (paper supply device 9) to the paper discharge (paper discharge device 13) is formed in a substantially arc shape, and the transfer belt 3, the image forming unit 6, and the exposure device 5 are connected to each other. By arranging it inside the recording medium conveyance path, the space inside the machine frame is effectively utilized to reduce the size, simplify the conveyance path, and discharge the recording medium 7 with the image surface facing downward.

  This configuration simplifies the transport path, and because most of the structural units are arranged on the inner side of the transport path, the transport path becomes closer to the machine frame and the transport path can be easily opened. This also simplifies the operation for eliminating paper jams.

  When the recording medium S is discharged on the image forming apparatus 1 with the image surface facing downward, the recording medium S stacked on the image forming apparatus 1 is removed from the upper side to the lower side when taken out so that the image surface side faces upward. Has the advantage of stacking in order of printing.

  Since the right side in FIG. 1 is configured to be the front facing the operator, it is easier to perform the clearing operation when a paper jam occurs. The image forming unit 6, which is a consumable item, has a configuration in which the upper part (the paper discharge tray 2) of the image forming apparatus 1 is opened by holding the exposure device 5 around the upper left shaft 1a, and is replaced from the front by the operator. With a front access configuration that allows all operations to be performed from the front, a color electrophotographic apparatus can be realized regardless of installation location.

  The image forming unit 6 is referred to as a process cartridge when configured as a unit that can be attached to and detached from the image forming apparatus such as the image forming apparatus 1. The process cartridge includes at least an image carrier and a developing device.

  Next, the developing device according to the embodiment will be described. FIG. 3 is a schematic sectional view showing a developing device according to the embodiment, FIG. 4 is an exploded perspective view showing a schematic configuration of the developing device according to the embodiment, and FIG. 5 is a diagram showing the developing device according to the embodiment. ) Is a cross-sectional view, FIG. 6B is a schematic view showing a thrust force on the bearing member, and FIG. 6 is a cross-sectional view showing the bearing member of the developing device.

  As shown in FIGS. 3 and 4, the developing device 110 (corresponding to the image forming unit 6 in FIG. 2) includes an image carrier 111 (same image carrier 6a), a developing roller 112 (same developing roller 6h), and two of them. And a support member 130 that holds the two on both sides. Helical gears 121 and 122 are attached to the image carrier 111 and the developing roller 112, respectively, so that the driving force is transmitted. Both ends of the developing roller 112 are held by a bearing member 114, the bearing member 114 is slidably held by a guide portion 131 formed on the support member 130, and is urged toward the image carrier 111 by a spring 115. As a result, the entire developing unit 140 (the developing device 16) including the toner hopper 141 is urged toward the image carrier 111.

  A boss 116 is formed on the bearing member 114, and one end of the spring 115 is fitted, and a boss 132 is also formed on the support member 130 side, and the other end of the spring 115 is fitted. Has been. The support member 130 is formed with a guide portion 131 of the bearing member 114, and the bearing member 114 is urged by the spring 115 in the support member 130, and can freely move in the direction in which the image carrier 111 is contacted / separated. Can be moved by sliding.

  Further, the guide part 131 guides the bearing member 114 so as not to move in the vertical direction with respect to the pressing direction of the spring 4, and the developing part 140 receives a certain load by the pressing force of the spring 115 against the developing roller 112. The contact with the image carrier 111 is always maintained.

  Further, in the guide member 131, the surface of the support member 130 that contacts the bearing member 114 is inclined toward the outside as the image carrier 111 approaches the contact surface of the bearing member 114, as shown in FIG. As shown in FIGS. 5 and 6, a contact surface portion 152 that contacts the inclined surface portion 151 of the guide portion is formed on the bearing member 114. The inclined state of the inclined surface portion 151 does not appear in FIG.

  In this example, the helical gears 121 and 122 attached to the image carrier 111 and the developing roller 112 generate a thrust force that urges the developing roller 112 in the direction of arrow A in FIG. Are arranged as follows. Then, the thrust force A acting on the bearing member 114 is transmitted to the bearing member 114 via the shaft portion 112a, and as shown in FIG. 6B, the inclined surface portion 151 of the support member 130 is perpendicular to the inclined surface portion 151. Is divided into a component force Av in a certain direction and a component force Al in a direction along the inclined surface portion 151, and the bearing member 114 is urged by the component force Al along the inclined surface portion 151 to press the developing roller 112 toward the image carrier 111. . As a result, the image carrier 111 and the developing roller 112 are constantly in constant contact, and a developer (not shown) is stably supplied from the developing roller 112 to the image carrier 111.

  In addition, since the guide portion 131 that holds the bearing member 114 is formed with the inclined surface portion 151 in a direction that expands outward toward the image carrier 111, when the bearing member 114 is urged by the spring 115. Since the bearing member 114 does not get caught by the inclined surface portion 151 and the urging force of the spring 115 acts directly as the urging force of the developing roller 112, the spring 115 does not become larger than necessary, and a small developing device and image A forming apparatus can be realized. For example, an urging means such as a spring member that generates a force for pressing the bearing member 114 may be provided separately, and the image carrier 111 and the developing roller 112 may be connected by a gear such as a spur gear that does not generate a thrust force. Good.

  In this example, a lubricant such as grease or oil is provided between the inclined surface portion 151 and the contact surface portion 152 in order to minimize friction between the inclined surface portion 151 of the support member 130 and the contact surface portion 152 of the bearing member 114. The bearing member 114 and the support member 130 are preferably made of synthetic resin having a small friction coefficient. Further, in order to reduce the frictional force between the bearing member 114 and the support member 130, a rectangular shape formed along the long side portion in the sliding direction as the contact surface portion of the bearing member 114 as shown in FIG. A protrusion 114 a is formed, and the surface of the protrusion 114 a can be used as a contact surface portion that contacts the inclined surface portion 151.

  Further, as shown in FIG. 6, it is preferable to provide a chamfered portion 154 at the hole end portion on the contact surface portion 152 side of the bearing hole portion 153 that supports the shaft 112 a of the developing roller 112 in the bearing member 114. By forming the chamfered portion 154, wear powder generated with the passage of time due to sliding between the shaft 112a of the developing roller 112 and the bearing hole portion 153 can be accumulated in the chamfered portion 154. An increase in frictional force due to powder entering between the inclined surface portion 151 of the support member 130 and the contact surface portion 152 of the bearing member 114 can be prevented.

  The formation of the chamfered portion 154 in the bearing hole portion 153 in the bearing member 114 prevents the occurrence of minute burrs 153a (see FIG. 8) at the end portion of the bearing hole portion 153 generated when the bearing member 114 is molded. Thus, an increase in frictional force between the bearing member 114 and the support member 130 due to the burr 153a can be prevented.

  Further, the shape of the bearing hole 153 in the bearing member 114 can be modified as follows. 9, 10 and 11 are cross-sectional views showing modifications of the bearing hole in the bearing member. In the example shown in FIG. 9, the chamfered portion 154a has a round shape. According to this example, similarly to the example shown in FIG. 6, the wear powder prevents the wear powder from entering between the inclined surface portion 151 of the support member 130 and the contact surface portion 152 of the bearing member 114 and an increase in frictional force due to burrs. can do.

  Furthermore, what is shown in FIG. 10 is a bag-like bearing hole 155 that receives the shaft 112a of the developing roller 112 of the bearing member 114. In this example, since the wear powder generated in the bearing hole 155 is not discharged to the inclined surface portion 151 side, the wear powder enters between the inclined surface portion 151 of the support member 130 and the contact surface portion 152 of the bearing member 114. The increase of frictional force due to burrs can be prevented. If the bearing hole portion 153 of the bearing member 114 is formed in a bag shape, the shaft 112b of the developing roller 112 can be formed in a shape not provided with a step as shown in FIG.

1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment. It is a schematic sectional drawing which shows the structure of an image forming unit. 1 is a schematic cross-sectional view illustrating a developing device according to an embodiment. 1 is an exploded perspective view showing a schematic configuration of a developing device according to an embodiment. FIG. 2 is a diagram illustrating a developing device according to an embodiment, where (a) is a cross-sectional view and (b) is a schematic diagram illustrating a thrust force applied to a bearing member. It is sectional drawing which shows the bearing member of a developing device. It is a perspective view which shows the modification of the bearing member of a developing device. It is sectional drawing which shows the burr | flash at the time of manufacture of the bearing member of a developing device. It is sectional drawing which shows the modification of the bearing hole part in a bearing member. It is sectional drawing which shows the modification of the bearing hole part in a bearing member. It is sectional drawing which shows the modification of the bearing hole part in a bearing member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 1a Shaft 2 Discharge tray 3 Transfer belt 3a 1st transfer roller 4 Spring 5 Exposure device 6 Image forming unit 6c Cleaning blade 6a Image carrier 6b Toner hopper 6d Charging roller 6e Toner transport screw 6f Toner transport belt 6g Waste Toner recovery unit 6h Developing roller 6K, 6C, M, 6Y Image forming unit 7 Recording medium 8 Paper feed cassette 9 Paper feed device 10 Paper transport device 11 Second transfer device 12 Fixing device 13 Paper discharge device 14 Intermediate transfer member cleaning device 15 Waste toner collecting container 16 Developing device 20 Arrow 68 Image carrier 110 Developing device 111 Image carrier 112a Shaft 112 Developing roller 112a Shaft 112b Shaft 114 Bearing member 114a Protruding portion 115 Spring 116 Boss 121, 122 Helical gear 130 Support member 131 Guide part 132 Boss 140 Developing part 141 G Hoppa portion 151 inclined surface 152 contact surface 153 bearing hole portions 153a burr 154 chamfered portion 154a chamfer 155 bearing hole portion A thrust force Al component force Av component force S recording medium

Claims (7)

A developing roller that develops the image carrier, a pair of bearing members that are disposed at both ends of the developing roller and rotatably hold the developing roller, and the developing roller approaches and separates the bearing member from the image carrier. In a developing device comprising a pair of support members that are movably guided in a direction to move, and an elastic member that presses the developing roller against the image carrier,
At least one support member of the pair of support members is formed with a guide portion having an inclined surface portion facing outward as it approaches the image carrier, and the bearing member is held by the support portion in which the guide portion is formed. And a biasing means for biasing the bearing member toward the support portion on which the guide portion is formed while forming a contact surface portion that contacts the inclined surface portion of the guide portion.   2. The developing device according to claim 1, wherein the developing roller is driven by a helical gear that generates a thrust force by meshing, and the helical gear is used as the biasing means.   The developing device according to claim 1, wherein a lubricant is applied between the guide portion of the support member and the bearing.   The support member and the bearing member are made of synthetic resin, a convex portion is formed on a contact surface portion of the bearing member, and a tip portion of the convex portion is in contact with the guide portion. Item 4. The developing device according to any one of Items 1 to 3   The bearing member has a shaft hole portion into which the shaft portion of the developing roller is inserted, and at least a corner portion on the support member side of the inner end portion of the shaft hole portion is chamfered. The developing device according to claim 1, wherein the developing device includes:   The pair of support members are configured to be detachable from the main body of the image forming apparatus, and an image carrier is held on the support member and is configured as a process cartridge that can be attached to and detached from the image forming apparatus as a unit. 6. The developing device according to claim 1, wherein An image forming apparatus comprising the developing device according to claim 1.