JP2009251541A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having a simple constitution in which a developing roller is appropriately pressed against a photoreceptor drum, and also, a bias voltage is stably supplied to the developing roller, further, grease for a power supply section is not required. <P>SOLUTION: The image forming apparatus 1 includes: the apparatus body 10; and an electrophotographic process unit 8 that is freely detachably loaded into the apparatus body 10. The process unit 8 includes a photoreceptor drum unit 600 and a developing unit 700. The apparatus body 1 includes: a prescribed loading portion 15 for positioning and loading the process unit 8; and a pair of pressing members 18 and 18 which work the metal developing roller shaft 75 of the developing roller 71 in the loaded developing unit 700, and press the developing roller 71 against the photoreceptor drum 61 in the photoreceptor drum unit 600. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus including an electrophotographic image recording unit, and more particularly to an image forming apparatus in which a developing system is a non-magnetic one-component developing system.

  As an example of the electrophotographic image recording unit (apparatus) as described above, the one disclosed in Patent Document 1 can be cited. The image recording apparatus of Patent Document 1 is an electrophotographic image recording apparatus (image forming apparatus) that employs a cleanerless system, and a process unit including a photosensitive drum unit and a developer unit can be attached to and detached from the apparatus main body. It is configured to be wearable. The photosensitive drum unit and the developing unit are detachably connected to each other, and both units are positioned and attached to a predetermined part of the apparatus main body. In the case of such a cleanerless system image recording apparatus, the developing method is a non-magnetic one-component developing method. For this reason, in the mounted state with respect to the apparatus main body, the developing roller of the developing unit is in contact with the photosensitive drum of the photosensitive drum unit, or the surface of the developing roller is pressed to such an extent that the photosensitive drum is elastically deformed It is necessary to maintain the state. Further, the developing roller is also required to be maintained in a state where it can be supplied with a developing bias voltage from the apparatus main body when mounted on the apparatus main body.

  8 and 9 show an example in which a mechanism for pressing the developing roller against the photosensitive drum and a structure for supplying a developing bias voltage are added to the process unit disclosed in Patent Document 1. FIG. 8 is a schematic longitudinal sectional view of the process unit, and FIG. 9 is a sectional view taken along line FF in FIG. 8 and 9, a predetermined mounting portion 101 is formed that can be detachably mounted from above and below in a state where the photosensitive drum unit 200 and the developing unit 300 are coupled to the apparatus main body 100 of the image forming apparatus. . The photosensitive drum unit 200 and the developing unit 300 are coupled by mutual coupling means (see Patent Document 1) to constitute an image forming process unit 400. The photosensitive drum unit 200 is disposed in the photosensitive drum unit housing 201 so as to rotatably support the photosensitive drum 202, and the brush charger 203 and the memory removal brush 204 are in contact with or close to the peripheral surface of the photosensitive drum 202. And unitized. The developing unit 300 is a unit in which a developing roller 302, a supply roller 303, a toner agitator 304, a toner regulating blade 305 that contacts the developing roller 302, and the like are incorporated in a developing unit unit housing 301 that also serves as a toner container. It is a thing.

  In the coupled state of the photosensitive drum unit 200 and the developing device unit 300, corresponding portions of the photosensitive drum unit housing 201 and the developing device unit housing 301 are opened so that the photosensitive drum 202 and the developing roller 302 are in contact with each other. Further, when the process unit 400 is mounted on the mounting portion 101, a corresponding portion of the photosensitive drum unit housing 201 is opened so that the photosensitive drum 202 contacts the transfer roller 500 installed in the apparatus main body 100. Further, in the photosensitive drum unit housing 201, when the opening / closing lid (see FIG. 1) is closed in this mounted state, the light emitting portion of the exposure unit 501 including the LED head array attached to the opening / closing lid is provided as the photosensitive drum 202. An opening is also formed so as to face the surface. The support shaft 205 of the photosensitive drum 202 protrudes on both sides of the photosensitive drum unit housing 201 and is supported by a positioning recess 102 formed in the wall portion of the mounting portion 101. In this supported state, the photosensitive drum unit 200 is positioned when the process unit 400 is mounted on the mounting portion 101.

  Positioning pins 306 are formed on both outer surfaces of the developer unit housing 301. When the process unit 400 is mounted on the mounting portion 101, it is supported by a positioning recess 103 formed on the wall portion of the mounting portion 101. The In this supported state, the developing unit 300 is positioned when the process unit 400 is mounted on the mounting portion 101. The developing roller 302 is made of conductive butadiene acrylonitrile rubber (NBR) or the like, and is formed integrally with a developing roller shaft 307 made of conductive metal (stainless steel or the like). The developing roller shaft 307 is rotatably supported by the developer unit housing 301 via a bearing 308, and a spacer roller 3071 for restricting the pressing state against the photosensitive drum 202 is rotatably attached to the outside of the bearing 308. A spring-type power feeding piece 309 is attached to one side wall portion of the developing device unit housing 301 and elastically contacts one end portion of the developing roller shaft 307. A part of the power feeding portion piece 309 protrudes outside the side wall portion. A spring-type power supply terminal 105 electrically connected to a bias power source 104 installed in the apparatus main body 100 is attached to the mounting portion 101. When the developing unit 300 is mounted on the mounting portion 101, the power supply terminal 105 and the power supply piece 309 are in elastic contact with each other, whereby a predetermined bias voltage is supplied to the developing roller 302 through the developing roller shaft 307. It is made like that. The supply roller 303 and the toner regulating blade 305 are also supplied with a bias voltage with a similar configuration although not shown.

As shown in FIG. 8, a boss portion 3011 is formed on the wall portion of the developer unit housing 301 opposite to the drum unit 200, and a leaf spring 106 is attached to the mounting portion 101. When the developing device unit 300 is mounted on the mounting portion 101 from above, the leaf spring 106 is elastically deformed by the action of the boss portion 3011, and the developing device unit 300 is moved by the restoring elasticity accompanying the elastic deformation of the leaf spring 106. A pressing force acts on the drum unit 200 side. As a result, the developing roller 302 is pressed against the photosensitive drum 202.
Similarly, Patent Literature 2 and Patent Literature 3 disclose a technique in which a developing roller is pressed against a photosensitive drum by applying a spring force to the developing unit unit housing. Further, in Patent Document 4, a bearing that supports the shaft of the developing roller is held in a unit case including the developing roller and the photosensitive drum so that the elastic force is directed toward the photosensitive drum by a compression spring. Has been disclosed which is elastically pressed against the photosensitive drum.
JP-A-10-293517 JP-A-6-19235 JP 2007-193125 A Japanese Patent Laid-Open No. 5-281854

  As described above, in the process unit 400 shown in FIGS. 8 and 9, the developer unit housing 301 is moved to the photosensitive drum unit 200 side by the spring force of the leaf spring 106 in order to press the developing roller 302 against the photosensitive drum 202. Press to Since the developing unit housing 301 is made of a synthetic resin molded body, the developing unit housing 301 is distorted by the spring force of the leaf spring 106, and the developing roller 302 may not be sufficiently pressed against the photosensitive drum 202. is there. Further, the axial center of the developing roller 302 is positioned slightly higher than the axial center of the photosensitive drum 202, both rotate with each other as indicated by arrows in FIG. 8, and the peripheral speed of the developing roller 302 is set to the photosensitive drum 202. It is set to 1.4 to 1.6 times the peripheral speed. For this reason, during rotation driving, the developing roller 302 may float along the peripheral surface of the photosensitive drum 202 due to distortion of the developer unit housing 301 or swinging with the positioning pin 306 as a fulcrum. . Further, the developer unit housing 301 may be distorted or swung, so that the power feeding piece 309 and the power feeding terminal 105 may be misaligned, and the supply of the bias voltage may not be stable.

The power supply piece 309 is made of a highly conductive material such as phosphor bronze and is configured to elastically contact the end of the developing roller shaft 307. However, the contact friction caused by the rotation of the developing roller shaft 307 Cause mechanical wear or metal noise. For this reason, the conductive grease is applied to the contact portion, but the grease may leak out of the developing unit housing 301 and may contaminate the operator's or serviceman's hand or clothes.
The image forming apparatuses (electrophotographic apparatuses) disclosed in Patent Document 2 and Patent Document 3 are assumed to include the same problems.

  In the case of the process unit disclosed in Patent Document 4, the developing roller is pressed against the photosensitive drum by applying a pressing force to the shaft of the developing roller. However, since the developing roller is supported via a spring receiving portion, a compression spring, and a bearing provided in the unit case, if any distortion occurs in the unit case, the developing roller and the photosensitive drum are There is a concern that the pressing state cannot be obtained. Further, this Patent Document 4 does not suggest any countermeasure against the developing roller trying to float up due to the difference in peripheral speed between the photosensitive drum and the developing roller during rotational driving. Furthermore, there is no mention of the relationship between the supply of the bias voltage to the developing roller and the pressing mechanism of the developing roller.

  The present invention has been made in view of the above circumstances, and although it has a simple configuration, the pressing of the developing roller against the photosensitive drum is made appropriate, and the supply of the bias voltage to the developing roller is stabilized. An object of the present invention is to provide an image forming apparatus that eliminates the need for grease in the power feeding portion.

  An image forming apparatus of the present invention is an image forming apparatus including an apparatus main body and an electrophotographic process unit that is detachably mounted in the apparatus main body, the process unit including a photosensitive drum unit, The apparatus main body acts on a predetermined mounting portion for positioning and mounting the process unit, and a metal developing roller shaft of the developing roller in the mounted developing unit unit to move the developing roller to the photosensitive unit. And a pair of pressing members that are pressed against the photosensitive drum of the body drum unit.

  In the present invention, when the developing unit is attached / detached, the pressing member is elastically deformed by the developing roller shaft to allow the attaching / detaching operation, and in the state where the developing unit is attached to the attachment portion, the restoring elasticity The developing roller shaft may be used to elastically press the developing roller against the photosensitive drum. In this case, the developing unit is detachable in the vertical direction with respect to the apparatus main body, and the pressing member includes a columnar base portion and a hook portion whose upper end side is bent, and is attached to the bottom portion of the mounting portion. It is composed of an elastic piece provided in an upright state, and elastic deformation by the developing roller shaft when the developing unit is attached / detached is made by the hook part, and in the mounted state of the developing unit, the restoring elasticity of the columnar base Thus, the developing roller can be elastically pressed against the photosensitive drum, and the floating of the developing roller can be suppressed by the elastic hook action of the hook portion with respect to the developing roller shaft.

  In the present invention, at least one of the pair of pressing members may be made of a conductive member, and a developing bias voltage may be supplied to the pressing member. In this case, the end of the developing roller shaft on the side to which the developing bias voltage is supplied may be supported by a bearing made of a conductive member, and the pressing member may act on the developing roller shaft via the bearing. good.

  According to the image forming apparatus of the present invention, the electrophotographic process unit is positioned and mounted at a predetermined mounting site in the apparatus main body. Since the process unit is detachably mounted, it can be easily removed or replaced during maintenance. When the process unit is mounted on the mounting portion, the pair of pressing members act on the metal developing roller shaft of the developing roller in the mounted developing unit, and the developing roller is the photosensitive drum of the photosensitive drum unit. Pressed against. Accordingly, since the developing roller is directly pressed by the pressing member, the developing roller is not pressed against the photosensitive drum due to the distortion of the developing unit housing as in the case of applying a pressing force to the developing unit housing. There is no concern about stability.

  If the pressing member is configured to be elastically deformed by the developing roller shaft when the developing unit is attached and detached to allow the attaching and detaching operation, the attaching and detaching operation of the developing unit is simplified. In the state in which the developing unit is mounted on the mounting portion, the developing roller is elastically pressed against the photosensitive drum by the developing roller shaft by the restoring elasticity of the pressing member, so that the developing roller is pressed against the photosensitive drum. Is made stable. Further, when the developing unit is detachable in the vertical direction with respect to the apparatus main body, if the pressing member is formed of an elastic piece including a columnar base and a hook portion on the upper end side, The hook portion is elastically deformed by the developing roller shaft when the developing unit is attached or detached. Further, when the developing unit is mounted, the developing roller is elastically pressed against the photosensitive drum by the restoring elasticity of the columnar base, and the floating of the developing roller is suppressed by the elastic hook action of the hook portion with respect to the developing roller shaft. Is done. Therefore, even when there is a difference in peripheral speed between the developing roller and the photosensitive drum, the pressing state of the developing roller against the photosensitive drum is further stabilized.

  When at least one of the pair of pressing members is made of a conductive member and is configured so that the developing bias voltage is supplied to the pressing member, the bias voltage is directly supplied to the developing roller by the pressing member. Therefore, unlike the case where the power supply terminal is provided in the developer unit housing, there is no concern that the position of the contact is displaced due to distortion of the developer unit housing, and a stable bias voltage can be supplied. In this case, if the developing roller shaft is supported by a bearing made of a conductive member and a pressing member configured to be supplied with a developing bias voltage acts on the developing roller shaft via the bearing, the bearing is Through this, a developing bias voltage is supplied to the developing roller. Therefore, since the contact portion between the pressing member and the bearing, which is a voltage supply member, does not involve rotational contact, mechanical wear or metal noise due to contact friction does not occur, and it is not necessary to apply conductive grease to this contact portion. The hands or clothes of the operator or service person are not soiled.

  The best mode for carrying out the present invention will be described below with reference to the drawings. 1 is a schematic longitudinal sectional view of an embodiment of an image forming apparatus according to the present invention, FIG. 2 is an enlarged view of a portion A in FIG. 1, FIG. 3 is a sectional view taken along line BB in FIG. Is a sectional view taken along the line CC in FIG. 3, FIG. 5 is a sectional view taken along the line DD in FIG. 3, FIG. 6 is the same view as FIG. 3 of another embodiment, and FIG. It is E line arrow sectional drawing.

An image forming apparatus 1 shown in FIG. 1 as an example of an image forming apparatus according to the present invention is a so-called multi-function machine having an electrophotographic image recording unit. In other words, the image forming apparatus has a copying function, a facsimile function, and a printer function, but an image forming apparatus embodied as a copying apparatus, a facsimile apparatus, or a printer apparatus is also targeted. The image forming apparatus 1 shown in the figure includes an automatic document feeder (ADF) 2, an image reading unit 3, an image recording unit 4, and a recording paper supply unit 5 in a stacked state from the top. In the ADF 2, a document placed on the document tray 20 is fed and separated one by one by a pickup roller 21 and a separation unit (a pair of a separation roller and a retard roller) 22, and is curvedly conveyed by each pair of conveyance rollers 23, 24, and 25. It is conveyed along the path 26. On the way, at the reading point 27 of the ADF document, the image is read by a stationary reading / scanning device (described later) 33 and sequentially discharged onto the document discharge tray 29 by the discharge roller pair 28.
In addition, as the separating means 22, many things which consist of a separate roller and a separation pad are also employ | adopted.

  The image reading unit 3 includes an ADF reading unit 31 and a flat plate reading scanning unit (FBS) 32 that are provided in the reading unit housing 30. FIG. 1 shows a state in which the reading scanning device 33 is stationary on the ADF reading unit 31 immediately below the ADF reading point 27 in the reading unit housing 30 and reads the images of the originals sequentially and automatically supplied by the ADF 2. A platen glass 34 is installed at a portion corresponding to the FBS 32 in the reading unit housing 30. When reading an image in the FBS 32, the reading scanning device 33 moves to the FBS 32 in the reading unit housing 30, and is placed downward on the platen glass 34 while reciprocating left and right under the platen glass 34. Read the original image. A series of mechanisms constituting the ADF 2 also serves as a platen cover (document pressing plate), and is installed on the reading unit housing 30 so as to be opened and closed up and down with the back side of the paper surface of FIG. Further, the reading unit housing 30 is installed on the upper end opening of the box-shaped device main body 10 and is vertically moved together with the ADF 2 serving as a platen cover with a hinge pin 35 attached to the upper left side portion of the device main body 10 as a fulcrum. It can be opened and closed.

  The image recording unit 4 shown in the figure includes a cleaner-less system electrophotographic process unit and a fixing unit. The process unit includes a photosensitive drum 61 and a brush charger 62, an exposure unit 63, a developing unit 7, a transfer roller 64, and a memory removing member 65 arranged around the photosensitive drum 61. A fixing device 41 is installed on the downstream side. The image recording unit 4 heats and presses the recording paper on which the toner image is transferred in the process unit in the fixing unit 41, fixes the toner image as a permanent image, and is recorded by the discharge roller pair 42 on the downstream side of the fixing unit 41. The recording paper is configured to be discharged to the discharge tray 43. The charger 62 may be a roller charger or a scorotron charger. The detailed configuration of the process part will be described later.

  The recording paper supply unit 5 includes a recording paper supply cassette 51 that is detachably mounted in a cassette chamber 50 formed in the apparatus main body 10 of the image forming apparatus 1. The insertion / removal direction of the recording paper supply cassette 51 may be a direction along the left-right direction from the side of the apparatus main body, in addition to the direction along the back side from the front side of the apparatus main body 10 (the front side in FIG. 1). Is possible. A front end side wall portion of the recording paper supply cassette 51 in the recording paper supply direction is a recording paper guide wall portion 52. The upper surface of the recording paper guide wall portion 52 is an inclined surface, and a pad base 53 is incorporated in a state where an elastic force is applied upward by a compression spring (not shown) at the center thereof. A frictional separation pad 54 is fixed to. A recording paper supply roller 55 is rotatably installed on the front end side of the recording paper supply cassette 51. The separation pad 54 is elastically pressed against the peripheral surface of the recording paper supply roller 55, and the recording paper 9 is separated and fed out one by one by the recording paper supply roller 55 and the separation pad 54, and enters the apparatus main body 10. A recording paper supply member to be supplied is configured.

In the recording paper supply cassette 51, there are provided a push-up plate 57 that can swing up and down with a hinge pin 56 as a fulcrum and an end guide 58 that can adjust the position of the rear end of the recording paper 9. The push-up plate 57 is in a state in which elasticity is applied upward by the compression spring 59 with the hinge pin 56 as a fulcrum. In the recording paper supply cassette 51, other illustrations and explanations are omitted, but additional members necessary for the recording paper supply cassette 51, for example, side guides for regulating the width direction of the recording paper, or end guides and side guides A positioning part is also provided.
Note that an optional cassette (not shown) may be arranged below the recording paper supply cassette 51 to constitute a multi-cassette system having two or more stages.

  In the apparatus main body 10, a curved recording paper transport path 11 is formed which is continuous with the recording paper supply member (separation pad 54 and recording paper supply roller 55) of the mounted recording paper supply cassette 51. In the middle of the transport path 11, a transport roller pair 12 and a registration roller pair 13 are installed. The recording paper 9 separated and fed one by one by the recording paper supply members 54 and 55 from the recording paper supply cassette 51 is conveyed by these roller pairs 12 and 13, and a nip portion between the photosensitive drum 61 and the transfer roller 64. It is configured to be introduced. A jam access cover (maintenance open / close cover) 14 is mounted behind the recording paper guide wall 52 with a conveyance path 11 ′ for recording paper from the lower cassette interposed therebetween. A hinge pin 141 is attached to the right side wall of the main body 10 so as to be openable and closable. When a recording paper jam occurs in the recording paper transport path 11 (11 '), the nip of the transport roller pair 12 is released by opening the jam access cover 14, thereby enabling the jam recording paper to be taken out.

  The process unit will be further described in detail. The photosensitive drum 61, the brush charger 62, the memory removing member 65, and other incidental members (such as a scooping sheet) are collectively assembled in a photosensitive drum unit housing 60 that is resin-molded to constitute the photosensitive drum unit 600. . The photosensitive drum 61 is rotatably supported by the photosensitive drum unit housing 60 via a support shaft 611. The developing unit 7 incorporates a developing roller 71, a supply roller 72, a toner stirrer 73, a toner regulating blade 74, and other incidental members (toner seal member, etc.) in a resin-molded developing unit unit housing 70. The unit 700 is configured. The developing roller 71, the supply roller 72, and the toner agitator 73 are rotatably accommodated in the developing unit unit housing 70. The developing unit housing 70 also serves as a non-magnetic one-component toner container, and a toner sensor (photoelectric sensor) that detects the presence or absence of the toner is attached to the outside of the developer unit housing 70, although not shown. The toner regulating blade 74 is in contact with the peripheral surface of the developing roller 71 and regulates the amount of toner adhering to the developing roller 71. The photosensitive drum unit 600 and the developing unit 700 are coupled by mutual coupling means (see Patent Document 1) to constitute an image forming process unit 8. In this coupled state, corresponding portions of the photosensitive drum unit housing 60 and the developing unit housing 70 are opened so that the photosensitive drum 61 and the developing roller 71 are in contact with each other.

  The process unit 8 can be detachably attached to a predetermined attachment part 15 formed in the apparatus main body 10 from above and below. An opening / closing lid 16 is attached to the upper part of the unit accommodating space constituting the mounting portion 15 so as to be opened and closed with the hinge pin 161 as a fulcrum. The opening / closing lid 16 can be opened and closed by opening the reading unit housing 30 of the image reading unit 3 upward with the hinge pin 35 as a fulcrum. Accordingly, by opening the reading unit housing 30 and the opening / closing lid 16, the process unit 8 can be attached to and detached from the mounting portion 15. The exposure unit 63 constituting the process unit is unitized with an LED head array, and is attached to the back surface of the opening / closing lid 16. When the open / close lid 16 is closed, the light emitting part of the exposure device 63 is positioned so as to face a predetermined part of the photosensitive drum 61 in the photosensitive drum unit 600 attached to the attachment part 15. Further, the transfer roller 64 constituting the process unit is installed in a state where a part thereof is exposed at the bottom 150 of the attachment part 15 constituting a part of the recording paper transport path 11, and the photosensitive drum unit 600 is attached to the attachment part 15. When it is done, it is brought into contact with or close to the photosensitive drum 61. Accordingly, portions corresponding to the exposure device 63 and the transfer roller 64 of the photosensitive drum unit housing 60 are opened.

  The support shaft 611 of the photosensitive drum 61 protrudes on both sides of the drum unit housing 60 and is supported by a positioning recess 152 formed in the wall portion 151 of the mounting portion 15. In this supported state, the photosensitive drum unit 600 is positioned when the process unit 8 is mounted on the mounting portion 15. Positioning pins 701 and 702 are formed on both outer surfaces of the developer unit housing 70. When the process unit 8 is mounted on the mounting portion 15, a positioning recess 153 formed on the wall portion 151 of the mounting portion 15 is formed. Supported by In this supported state, the developing unit 700 is positioned when the process unit 8 is mounted on the mounting portion 15. A compression coil spring 162 is attached to the lower surface of the opening / closing lid 16. When the opening / closing lid 16 is closed, the compression coil spring 162 is located between the opening / closing lid 16 and the top surface of the drum unit housing 60 and the developer unit housing 70. It is compressed with. Due to the reaction force of the compression coil spring 162 accompanying this compression, the photosensitive drum unit 600 and the developer unit 700 are stably positioned and held at the predetermined mounting portion 15.

  A drive transmission gear (not shown) for rotating the photosensitive drum 61 and the charger 62 is mounted on the outer side of the photosensitive drum unit housing 60. When the photosensitive drum unit 600 is mounted on the mounting portion 15, the drive transmission gear is connected to a drive system (not shown) mounted on the mounting portion 15. In addition, a bias voltage receiving contact (not shown) for the photosensitive drum 61, the charger 62, and the memory removing member 65 is also provided on the outer side of the photosensitive drum unit housing 60. Accordingly, when the photosensitive drum unit 600 is mounted on the mounting portion 15, the photosensitive drum unit 600 is electrically connected to a bias voltage supply contact (not shown) mounted on the mounting portion 15.

  The developing roller 71 is made of conductive NBR or the like, and is integrally formed on a developing roller shaft 75 made of conductive metal (stainless steel or the like). The developing roller shaft 75 is rotatably supported by the developing unit housing 70 via a resin or metal bearing 751, and a spacer roller 752 that regulates the pressing state with respect to the photosensitive drum 61 is rotatable outside the bearing 752. Installed. A gear 753 is attached to one end of the developing roller shaft 75, and the gear 753 meshes with a small-diameter gear of a driven transmission two-stage gear 703 attached to the outer side of the developer unit housing 70 via a stud 702. Yes. The stud 702 also serves as the positioning pin described above. As shown in FIG. 5, gears 722 and 732 are attached to one end portions of the shafts 721 and 731 of the supply roller 72 and the stirrer 73 (the same side as one end portion of the developing roller shaft 75). The gear 722 of the supply roller 72 meshes with the small diameter gear of the driven transmission two-stage gear 703. A two-stage idler gear 704 that meshes with the small-diameter gear of the driven transmission two-stage gear 703 is attached to the outside of the developing unit housing 70, and the gear 732 of the stirrer 73 meshes with the small-diameter gear of the two-stage idler gear 704. Yes. The apparatus main body 10 is provided with a drive transmission gear 17. When the developing unit 700 is mounted on the mounting portion 15, the large-diameter gear of the driven transmission second gear 703 meshes with the drive transmission gear 17. Thereby, rotational drive transmission in the respective arrow directions shown in FIG. 2 is made from a drive source (not shown) to the developing roller 71, the supply roller 72, and the stirrer 73.

  A pair of pressing members 18 and 18 that act on both end portions of the developing roller shaft 75 when the developing device unit 700 is mounted are provided on the bottom 150 of the predetermined mounting portion 15 in an upright state. The pressing member 18 is made of a conductive elastic member, includes a columnar base portion 181 and a hook portion 182 whose upper end is bent, and the columnar base portion 181 is fixed to the bottom portion 150 of the mounting portion 15 with screws 183. . The pressing member 18 in the illustrated example is formed by bending, for example, a SUS bar or plate material. One pressing member 18 (the right pressing member 18 in FIG. 3) is installed in the apparatus main body 10. The developing roller bias power supply 19 is electrically connected.

  As described above, when the process unit 8 is mounted on the mounting portion 15 from above, both end portions of the developing roller shaft 75 are caused to act on the hook portions 182 and 182 of the pressing members 18 and 18 to thereby form the columnar base portions 181 and 181. Is bent by elastic deformation. When both end portions of the developing roller shaft 75 get over the bent portions of the hook portions 182 and 182, the columnar base portions 181 and 181 try to return to the original state, and the developing roller shaft 75 is moved by the restoring elasticity to develop the developing roller shaft 75. The pressing force against the photosensitive drum 61 acts on 71. When the process unit 8 (developer unit 700) is completely attached to the attachment portion 15, the developing roller shaft 75 is lifted by the elastic hook action of the hook portions 182 and 182, and the developing roller 71 floats. Is suppressed. Further, the developing roller 71 is maintained in an electrically connected state with the developing roller bias power source 19 via the pressing member 18 and the developing roller shaft 75. The process unit 8 is taken out by an operation opposite to that described above. During this operation, the columnar base portion 181 of the pressing member 18 is bent by the action of the developing roller shaft 75 against the hook portion 182, and can be taken out. Although not shown, the supply roller 72 and the regulation blade 74 are supplied with respective bias voltages by the same configuration as described above.

  An image forming process for the recording paper 9 by the image forming apparatus 1 having the above configuration will be briefly described. Image information read by the image reading unit 3 or image information transmitted from an external terminal such as a facsimile or a personal computer is applied to the surface of the photosensitive drum 61 uniformly charged by the charger 62 by the exposure device 63. Written as optical information. Thereby, an electrostatic latent image based on the optical information is formed on the surface of the photosensitive drum 61. This electrostatic latent image is developed by the developing device 7 as a toner image as the photosensitive drum 61 rotates, and reaches a nip portion with the transfer device 64. From the recording paper supply cassette 51, the recording paper 9 is separated one by one by the recording paper supply members 54 and 55, fed out, and conveyed along the curved conveyance path 11 by the conveyance roller pair 12 to reach the registration roller pair 13. . The recording paper 9 is registered so as to be synchronized with the toner image by the registration roller pair 13 and is introduced into the nip portion between the photosensitive drum 61 and the transfer roller 64, and the toner image is sequentially transferred onto the recording paper 9. The toner image transferred to the recording paper 9 is fixed as a permanent image by the fixing device 41, and the recording paper 9 on which the permanent image is formed is discharged and accumulated on the discharge tray 43 by the discharge roller pair 42. A small amount of toner remains on the surface of the photosensitive drum 61 that has passed through the transfer portion, and this residual toner is disturbed by the memory removing member 62 to which a predetermined bias voltage is applied. Dispersed on the surface. This residual toner is collected by the developing unit 7 without affecting the formation of the electrostatic latent image in the subsequent exposure process.

  In the image forming process described above, the developing roller 71 is constantly pressed against the photosensitive drum 61 by the pair of pressing members 18 and 18. Since this pressing action is directly applied to the developing roller shaft 75, even if the developer unit housing 70 is distorted by some external force, it is not affected by this, and the developing roller 71 is properly applied to the photosensitive drum 61. The pressing state is maintained. Further, as described above, the axis of the developing roller 71 is positioned slightly higher than the axis of the photosensitive drum 61, and both rotate with each other as indicated by the arrows in FIG. Is set to 1.4 to 1.6 times the peripheral speed of the photosensitive drum 61. Therefore, at the time of rotational driving, the developing roller 71 tends to float along the peripheral surface of the photosensitive drum 61 with distortion of the developing unit unit housing 70 or swinging with the positioning pins 701 and 702 as fulcrums. However, the elastic hooking action of the hook portions 182 and 182 suppresses the floating of the developing roller 71 and the proper pressing state of the developing roller 71 against the photosensitive drum 61 is more stably maintained. Furthermore, since the bias voltage for the developing roller is supplied through the pressing member 18, the bias voltage can be stably supplied without causing a positional shift between the contacts as in the conventional case.

6 and 7 show another embodiment. In this embodiment, the end of the developing roller shaft 75 to which the developing bias voltage is supplied is supported by a bearing 751 made of a conductive member, and the pressing member 18 is connected to the developing roller shaft via the conductive bearing 751. 75 to act on. The conductive bearing 751 is preferably made of a copper-based sintered alloy. As shown in FIG. 6, the mounting portion with respect to the developing unit unit housing 70 extends outward from the mounting unit 70, supports the spacer roller 752 rotatably, and further extends to the installation position of the pressing member 18. . When the developing unit 700 is attached to the attachment portion 15, the pressing member 18 acts to press the developing roller 71 against the photosensitive drum 61 via the bearing 751 and the developing roller shaft 75. In this case, the developing roller shaft 75 is rotatably supported by the developing device unit housing 70 by the bearing 751, but the bearing 751 does not rotate, so that the working portion of the pressing member 18 against the developing roller shaft 75 is rubbed by rotation. Does not occur. Therefore, there is no mechanical wear or metallic noise at this portion, and no grease application is required. The developing roller bias voltage is stably supplied to the developing roller 71 from the bias power source 19 through the pressing member 18, the bearing 751, and the developing roller shaft 75 in the same manner as described above.
Since other configurations are the same as described above, common portions are denoted by the same reference numerals, and descriptions thereof are omitted.

  In the embodiment, the example in which the process unit 8 is attached to and detached from the apparatus main body 10 from above and below has been described. However, the process unit 8 is configured to be attached and detached by sliding from the side of the apparatus main body 10. Also good. In this case, the pressing structure of the developing roller shaft 75 and the pressing member 18 is configured by forming both ends of the developing roller shaft 75 into a tapered shape and the pressing member 18 as an eccentric ring member that receives the tapered portion. It is possible. The pressing structure between the developing roller shaft 75 and the pressing member 18 is a structure in which the developing roller shaft 75 of the developing roller 71 can receive a pressing action in a state where the developing unit 700 is mounted on the predetermined mounting portion 15. Other structures can also be used. Further, although the process unit 8 is exemplified by the photosensitive drum unit 600 and the developing unit 700 that are detachable from each other, the units 600 and 700 may be integrated. As an image forming apparatus, an image forming apparatus having an image recording unit using a cleanerless electrophotographic method has been described. However, a cleaning system may be used, and a developing method is not limited to a non-magnetic one-component method, but a two-component method. Also good.

1 is a schematic longitudinal sectional view of an embodiment of an image forming apparatus according to the present invention. It is an enlarged view of the A section in FIG. FIG. 3 is a cross-sectional view taken along line B-B in FIG. 2. It is CC sectional view taken on the line in FIG. It is DD sectional view taken on the line in FIG. It is a figure similar to FIG. 3 of other embodiment. It is the EE arrow directional cross-sectional view in FIG. It is a schematic longitudinal cross-sectional view of the conventional process unit. FIG. 9 is a cross-sectional view taken along line FF in FIG. 8.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Apparatus main body 15 Mounting part 150 Bottom part of mounting part 18 Pressing member 181 Columnar base 182 Hook part 600 Photosensitive drum unit 71 Developing roller 75 Developing roller shaft 751 Bearing 7 Developing unit 700 Developing unit 8 Process unit

Claims (5)

An image forming apparatus comprising an apparatus main body and an electrophotographic process unit detachably mounted in the apparatus main body,
The process unit includes a photosensitive drum unit and a developing unit, and the apparatus main body includes a predetermined mounting portion for positioning and mounting the process unit, and a metal developing roller of a developing roller in the mounted developing unit. An image forming apparatus comprising: a pair of pressing members that act on a shaft to press a developing roller against a photosensitive drum of the photosensitive drum unit. The image forming apparatus according to claim 1.
The pressing member is elastically deformed by the developing roller shaft when the developing unit is attached / detached to allow the attaching / detaching operation, and when the developing unit is mounted on the mounting portion, the developing roller shaft is restored by the restoring elasticity. The image forming apparatus is configured to elastically press the developing roller against the photosensitive drum. The image forming apparatus according to claim 2.
The developing unit is detachable in the vertical direction with respect to the apparatus main body, and the pressing member is composed of an elastic piece provided in a standing state at the bottom of the mounting portion, and the elastic piece is a columnar base. And a hook portion whose upper end is bent, and the elastic deformation by the developing roller shaft when the developing device unit is attached and detached is made by the hook portion, and when the developing device unit is mounted, the restoring elasticity of the columnar base portion The image forming apparatus is configured such that the developing roller is elastically pressed against the photosensitive drum and the floating of the developing roller is suppressed by an elastic hook action of the hook portion with respect to the developing roller shaft. The image forming apparatus according to any one of claims 1 to 3,
An image forming apparatus, wherein at least one of the pair of pressing members is made of a conductive member, and a developing bias voltage is supplied to the pressing member. The image forming apparatus according to claim 4.
An end of the developing roller shaft to which a developing bias voltage is supplied is supported by a bearing made of a conductive member, and the pressing member is configured to act on the developing roller shaft via the bearing. An image forming apparatus.

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