JP2011048306A - Developing device and image forming apparatus provided with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device which can prevent an occurrence of unevenness in image density by suppressing shifting of a magnet roller in the periphery direction by a simple supporting structure and to provide an image forming apparatus provided with the developing device. <P>SOLUTION: A developing roller 43 includes a cylindrical developing sleeve 49 which is supported to be rotated to a developing device housing 290 and a magnetic roller 50 that is coaxially inserted to the developing sleeve 49 and supported inside the developing device housing 290 in a fixed state. The developing sleeve 49 is supported to be rotated by a shaft 51 of the magnetic roller 50 through a bearing member 60 that is fixed to the shaft 51 to be rotated around an axial line of the shaft 51 in one end section in the axial direction of the developing sleeve. The bearing member 60 is composed to be fitted and held to a fitting section 62 formed on the image forming apparatus body 1A along the axial direction for the same. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a developing device and an image forming apparatus provided with the same, and more particularly to a support structure for a developing roller constituting the developing device.

  A developing device provided in the electrophotographic image forming apparatus incorporates a developing roller for carrying a developer (toner) and supplying the toner to the electrostatic latent image on the surface of the photoreceptor. The developing roller includes a developing sleeve and a magnet roller that is coaxially inserted into the developing sleeve. The magnet roller is fixed to the housing of the developing device via a fixed shaft (magnet roller shaft), and the developing sleeve is supported so as to be rotatable around the axis of the magnet roller. Therefore, the developing sleeve is supported via a bearing member with respect to the housing of the developing device, and a rotational driving force is applied to the developing sleeve from the driving source installed in the main body of the image forming apparatus via the drive transmission unit. Configured to be communicated. A typical prior art of such a developing device is disclosed in Japanese Patent Application Laid-Open No. H10-228707.

  In the developing device disclosed in Patent Document 1, as shown in FIG. 2, the magnet roller is developed by supporting the cored bar portion (fixed shaft) by a holder fixed to the developing device main body (housing). It is fixed to the container body. In addition, the developing sleeve pivotally supports a flange member attached to a driving side end portion to which a rotation drive transmission gear is attached to a bearing member attached to the developing device main body, and the rotation drive transmission gear is attached thereto. The flange member attached to the non-driving end is not supported by the developing device body by engaging the shaft formed on the holder. The shaft portion functions in the same manner as the bearing member, and supports the developing sleeve together with the driving-side bearing member so as to be rotatable around the axis of the magnet roller. The shaft portion engages and fixes the non-driving side end portion of the cored bar, and the non-driving side flange member is rotatably engaged and supported on the outer peripheral portion thereof.

  However, in the case of the developing device shown in Patent Document 1, the cored bar portion of the magnet roller is only fixed to the holders whose both ends are fixed to the developing device main body. When this occurs, the vibration is transmitted to the entire developing device, and the vibration is propagated as vibration to the entire process cartridge including the main body of the developing device. As a result, the gap between the photosensitive drum and the magnet roller provided in the process cartridge becomes unstable, and problems such as uneven image density occur.

  FIG. 5 is an enlarged cross-sectional view of a part of another prior art. In this prior art, the developing device 100 includes a developing device housing 101, a developing roller 102 incorporated in the developing device housing 101, and another mechanism (not shown) such as a developer stirring screw. , Configured as a developing unit. The developing device 100 configured as a developing unit is detachably mounted at a predetermined position in the apparatus main body 200 of the electrophotographic image forming apparatus. The developing roller 102 includes a cylindrical developing sleeve 103 and a magnet roller 104 inserted coaxially with the developing sleeve 103.

  The magnet roller 104 is integrally fixed to the magnet roller shaft 105, and the magnet roller shaft 105 is supported in a fixed state on the developing device housing 101. The developing sleeve 103 is integrally mounted with flange members 106 and 107 at both ends thereof, and is supported so as to be rotatable around the axis of the magnet roller shaft 105.

  A flange member 106 on the side to which rotational power for rotating the developing sleeve 103 is transmitted (hereinafter referred to as drive side) is integrally fixed to a gear shaft 108 coaxial with the magnet roller shaft 105, and the gear shaft 108 is The developing device housing 101 is rotatably supported around the axis of the magnet roller shaft 105 through the individual bearing members 109 and 110. A rotation drive transmission gear 111 is fixed to the gear shaft 108, and the rotation of the developing sleeve 103 is achieved by the rotation transmission via the gear 111.

  The drive-side flange member 106 of the developing sleeve 103 is supported by the drive-side end portion 105a of the magnet roller shaft 105 via a sliding contact member 112 having a sealing function, and the non-drive side of the magnet roller shaft 105 ( The end portion 105 b (opposite to the driving side) penetrates the non-driving side flange member 107 and the developing device housing 101 and protrudes outward from the side portion of the developing device housing 101. The non-driving side flange member 107 is supported at the non-driving side end portion 105b of the magnet roller shaft 105 via a sliding contact member 113 having a sealing function as described above.

  The non-driving side end portion 105 b of the magnet roller shaft 105 is fixed to the developing device housing 101 via a magnet roller holding member 114 at a portion that penetrates the developing device housing 101. Then, the developing device 100 configured as a developing device unit is mounted in a predetermined position of the image forming apparatus main body 200 by operating in the direction of the white arrow in FIG.

  A fitting portion (fitting hole) 202 capable of fitting and holding the non-driving side end portion 105b of the magnet roller shaft 105 is formed at a predetermined portion of the main body frame 201 in the image forming apparatus main body 200. The side end portion 105b is fitted and held in the fitting portion 202 during the mounting operation of the developing device 100. Further, the gear 111 establishes a drive transmission system with a drive source (not shown) installed in the image forming apparatus main body 200 when the developing device 100 is mounted at a predetermined position of the image forming apparatus main body 200. It is configured.

  In the case of the developing device 100 shown in FIG. 5, since the non-driving side end portion 105b of the magnet roller shaft 105 is directly held by the main body frame 201, the holding state is stabilized and other mechanism portions (for example, recording paper) The relative position with respect to the transport system etc.) can be maintained with high accuracy. However, since the magnet roller shaft 105 is directly held by the main body frame 201, the circumferential deflection of the magnet roller 104 may increase during the rotation of the developing sleeve 103 via the gear 111. When this circumferential shake becomes large, horizontal streaks or image density unevenness occurs in the image forming process, which causes a reduction in image quality.

Still another prior art is described in Patent Document 2. In this prior art, a holder in which a shaft hole having a D-shaped cross section called a D hole is formed on the side plate of the main body, and one axial end portion of the shaft of the magnet roller is formed in a D-shaped cross section also called a D cut. Then, by inserting and supporting the D-shaped cross section at one axial end of the shaft into the shaft hole of the holder, the axial length of the portion forming the D-shaped cross section of the shaft is shortened, A technique has been proposed in which vibration transmission from the developing unit housing to the magnet roller is prevented, development gap variation between the photosensitive member and the developing roller is prevented, and uneven development density is suppressed.
JP-A-8-137369 JP 2007-140091 A

In the prior art, the shaft of the magnet roller is fixed at both ends, and a bearing is provided. Therefore, the magnet roller is easily affected by the circumferential vibration of the magnet roller, and uneven image density occurs.
SUMMARY OF THE INVENTION An object of the present invention is to provide a developing device and an image forming apparatus provided with the developing device that can prevent the occurrence of uneven image density by suppressing the circumferential fluctuation of the magnet roller with a simple support structure. is there.

The present invention is a developing device that is installed in an electrophotographic image forming apparatus main body and includes a developing device housing and a developing roller incorporated in the developing device housing,
The developing roller is
A cylindrical developing sleeve rotatably supported by the developing device housing;
A magnet roller having a shaft inserted coaxially into the developing sleeve and supported in a fixed state in the developing device housing;
A bearing member fixed to the shaft of the magnet roller,
One end of the developing sleeve in the axial direction is supported on the shaft of the magnet roller so as to be rotatable around the axis of the shaft via a bearing member fixed to the shaft.
The bearing member is a developing device configured to be fitted and held in a fitting portion formed in the main body of the image forming apparatus along an axial direction thereof.

  In the invention, it is preferable that a driven transmission member to which rotational power is transmitted from a driving unit in the image forming apparatus main body is provided at the other axial end of the developing sleeve.

In the present invention, a ring-shaped holding member is attached to the developing device housing,
The bearing member is fitted to a ring-shaped holding member attached to the developing device housing between a fitting portion of the image forming apparatus main body and one axial end portion of the developing sleeve. .

Further, the present invention is characterized in that the bearing member comprises a copper-based sintered oil-impregnated bearing.
According to the present invention, the bearing member is a roller bearing.

The present invention also provides an electrophotographic image forming apparatus,
A developing device constituting the electrophotographic process part is detachably installed at a predetermined position in the apparatus main body,
The developing device comprises the developing device,
In the image forming apparatus, the apparatus main body is formed with a fitting portion that fits and holds the bearing member when the developing device is installed at the predetermined position.

  According to the present invention, the developing device is installed in an electrophotographic image forming apparatus main body to constitute an image forming process unit, and a predetermined image is formed by the image forming process unit. The developing sleeve constituting the developing roller is cylindrical and is rotatably supported by the developing device housing. A magnet roller is inserted into the developing sleeve, and the developer (toner) sucked by the magnetic attraction force of the magnet roller. Is carried on the surface of the developing sleeve. With the rotation of the developing sleeve, the electrostatic latent image formed on the surface of the photosensitive member that is arranged in the vicinity of the developing sleeve and forms the process unit is developed by the developer carried on the surface of the developing sleeve. The developing sleeve is supported on the shaft of the magnet roller at one end in the axial direction so as to be rotatable around the axis of the shaft via a bearing member. The shaft is supported in a fixed state on the developing device housing together with the magnet roller. The bearing member is fitted and held in a fitting portion formed in the image forming apparatus main body along the axial direction thereof.

  As a result, the vibration caused by the rotational power applied to the developing sleeve is propagated to the developing device housing and the image forming apparatus main body via the bearing member, and is thereby dispersed. In other words, the circumferential deflection of the magnet roller is also suppressed. In particular, by suppressing the fluctuation in the circumferential direction, the occurrence of uneven image density during image formation can be prevented, and image formation with excellent image quality can be achieved.

  According to the invention, the rotational power is transmitted to the developing sleeve via the driven transmission member provided at the other end in the axial direction.

  The vibration of the developing sleeve and the magnet roller accompanying the rotation transmission is propagated from the other end portion to one end portion which is the non-driving side. However, since the bearing member fixed to the shaft at one end and rotatably supporting the developing sleeve is fitted and held in the fitting portion formed in the image forming apparatus main body, this shake is suppressed, and the magnet roller Circumferential deflection is also suppressed.

  According to the present invention, the bearing member is fitted and held in a fitting portion formed in the image forming apparatus main body, and is fitted in a ring-shaped holding member attached to the developing device housing. The ring-shaped holding member functions as a magnet roller holding member, the shaft of the magnet roller is stably held, and the action of suppressing the shake becomes more remarkable.

  According to the present invention, since the bearing member is made of a copper-based sintered oil-impregnated bearing or a roller bearing, the gap between the shaft of the magnet roller and the inner peripheral surface of the bearing can be suppressed as much as possible. The shaft of the magnet roller can be held with high accuracy, the magnet roller is stably supported, and the action of suppressing the shake becomes more remarkable. In particular, copper-based sintered oil-impregnated bearings do not require lubrication due to their characteristics, are always maintained in an appropriate lubrication state, and there is no fear of rotation failure or vibration due to running out of lubricating oil.

  According to the present invention, an image is formed by electrophotography. Further, since the developing device constituting the electrophotographic process section is detachably installed at a predetermined position in the apparatus main body, maintenance such as replacement can be easily performed. The developing device is configured as described above. When the developing device is installed at a predetermined position in the apparatus main body of the image forming apparatus, the shaft of the magnet roller is formed on the apparatus main body via a bearing member. Thus, the magnet roller, particularly the circumferential deflection, is suppressed as the developing sleeve rotates. As a result, the occurrence of uneven image density during the image formation is prevented, and high-quality image formation is realized.

1 is a schematic diagram illustrating a configuration of an image forming apparatus 1 including a developing device according to an embodiment of the present invention. 3 is a schematic longitudinal sectional view of the developing device 29. FIG. FIG. 3 is a partially broken partial longitudinal sectional side view showing a state where the developing device 29 is installed in the apparatus main body 1A of the image forming apparatus 1. FIG. 4 is a partially broken exploded longitudinal side view of a developing roller 43 constituting the developing device 29. FIG. 10 is a partially broken partial longitudinal side view showing a state in which a conventional developing device 100 is installed in an apparatus main body 200 of an image forming apparatus.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus 1 including a developing device according to an embodiment of the present invention. The configuration shown in FIG. 1 is an example that is described in a simplified manner centering on main components of the image forming apparatus 1 of the present embodiment, and the configuration of the image forming apparatus including the developing device according to the present invention is not limited in any way. Not what you want.

  The image forming apparatus 1 shown in FIG. 1 includes a plurality of photosensitive members that serve as electrostatic latent image carriers (in this embodiment, four for yellow image, for magenta image, for cyan image, and for black image). 1 is a tandem color image forming apparatus that can form a color image. Such an image forming apparatus 1 is based on image data transmitted from various terminal devices such as a PC (Personal Computer) connected via a network or image data read by a document reading device such as a scanner. The printer has a printer function for forming a color image on a recording paper P as a transfer material (recording medium).

  As shown in FIG. 1, the image forming apparatus 1 of the present embodiment includes an image forming station unit (Y, M, C, Bk) 3 as an image forming process unit having a function of forming an image on the intermediate transfer belt 2. A secondary transfer station unit 4 having a function of transferring the toner image formed on the intermediate transfer belt 2 to the recording paper P in the image forming station unit 3 and a fixing unit having a function of fixing the recording image transferred to the recording paper P. The apparatus 5, a paper transport unit 7 having a function of transporting the recording paper P from a supply tray (paper feed cassette) 6 on which the recording paper P is placed to the secondary transfer station unit 4 and the fixing device 5. A belt cleaner 8 for removing untransferred toner from the intermediate transfer belt 2 is provided.

  The image forming station unit 3 includes four image forming stations 9, 10, 11, and 12 for yellow (Y) images, magenta (M) images, cyan (C) images, and black (Bk) images, respectively. Has been. A yellow image forming station 9, a magenta image forming station 10, a cyan image forming station 11, and a black image forming station 12 are arranged in this order along the traveling direction of the intermediate transfer belt 2 (the direction of the arrow 2A). In each of the image forming stations 9, 10, 11, and 12, toner bottles 13, 14, 15, and 16 that store toner of a color corresponding to each developing device are installed. The toner corresponding to each developing device is supplied by the means.

  These image forming stations 9, 10, 11, and 12 for each color have substantially the same configuration, and yellow, magenta, cyan, and black images are generated based on image data corresponding to each color. Then, the image is formed on the intermediate transfer belt 2 so as to overlap with the toner of four colors, and is transferred onto the recording paper P as a transfer material (recording medium) by the secondary transfer station unit 4. . Then, a full color image is formed on the recording paper P by heating and pressurizing the toner image on the recording paper P with the fixing device 5.

  Each of the image forming stations 9, 10, 11, and 12 includes photosensitive drums 17, 18, 19, and 20 serving as latent image carriers on which electrostatic latent images are formed. 19 and 20 are circumferentially charged units 21, 22, 23, 24, signal light optical paths 25, 26, 27, 28, developing devices 29, 30, 31, 32, a transfer unit (primary transfer roller) 33. , 34, 35, and 36, and photoreceptor cleaners 37, 38, 39, and 40, respectively.

  The photosensitive drums 17, 18, 19, and 20 have a substantially cylindrical drum shape having a photosensitive material such as OPC (Organic Photoconductor) on the surface, and are disposed above the exposure unit 41 and driven. By means 42 and control means (not shown), it is controlled to rotate in a predetermined direction (directions of arrows 17A, 18A, 19A, 20A in the figure). Transfer devices 33, 34, 35, and 36 including primary transfer rollers are disposed close to the respective photosensitive drums 17, 18, 19, and 20 with the intermediate transfer belt 2 interposed therebetween.

  The chargers 21, 22, 23, and 24 are scorotron type charging means for uniformly charging the surfaces of the photosensitive drums 17, 18, 19, and 20 to a predetermined potential. 19 and 20 are arranged close to the outer peripheral surface. The exposure unit 41 irradiates the surface of the photosensitive drums 17, 18, 19, and 20 charged by the chargers 21, 22, 23, and 24 with laser light based on the image data output from the image processing unit. By performing exposure, the potential of the exposed portion is lowered, and an electrostatic latent image corresponding to image data is written and formed on the surface.

  The exposure unit 41 receives light corresponding to the corresponding image data by inputting image data corresponding to yellow, magenta, cyan, or black according to each of the image forming stations 9, 10, 11, and 12. Light is emitted to the optical paths 25, 26, 27, and 28, and electrostatic latent images are formed on the surfaces of the photosensitive drums 17, 18, 19, and 20. As the exposure unit 41, a laser scanning unit (LSU) including a laser irradiation unit and a reflection mirror, and a writing device (for example, an optical writing head) in which light emitting elements such as EL and LED are arranged in an array are used. Can do.

  The developing devices 29, 30, 31, and 32 have developing rollers 43, 44, 45, and 46 that are developer carriers that carry toner. The developing rollers 43, 44, 45, 46 are configured to convey the toner to a developing area where the toner can move to the photosensitive drums 17, 18, 19, 20. In this embodiment, the developing devices 29, 30, 31, and 32 are formed on the surfaces of the photosensitive drums 17, 18, 19, and 20 by an exposure unit 41 using a two-component developer containing toner and a carrier. The formed electrostatic latent image is reversed and developed with the toner to form a toner image (visible image).

  The developing devices 29, 30, 31, and 32 include developer tanks 290, 300, 310, and 320 that store a two-component developer including each color toner and a carrier. The developer tanks 290, 300, 310, and 320 constitute a developing device housing in which the developing rollers 43, 44, 45, and 46 and other developing mechanisms described later are incorporated and supported. , 11, and 12, a yellow, magenta, cyan, or black developer is accommodated. This developer contains toner charged to the same polarity as the surface potential charged to the photosensitive drums 17, 18, 19, and 20. Here, the polarity of the surface potential charged on the photosensitive drums 17, 18, 19, and 20 and the charging polarity of the toner to be used are both negative (minus) polarity.

  The transfer devices 33, 34, 35, and 36 transfer the toner images on the photosensitive drums 17, 18, 19, and 20 onto the intermediate transfer belt 2. , A positive polarity) bias voltage is applied to the primary transfer roller. The photoconductor cleaners 37, 38, 39, and 40 remove and collect toner remaining on the outer peripheral surfaces of the photoconductor drums 17, 18, 19, and 20 after image transfer to the intermediate transfer belt 2. The cleaning blade is made of urethane rubber and comes into contact with the surfaces of the photosensitive drums 17, 18, 19, and 20.

  The intermediate transfer belt 2 is made of semiconductive polyimide, is stretched over the driving roller 2a and the driven roller 2b, and rotates in the direction of the arrow 2A by the rotation of the driving roller 2a. The intermediate transfer belt 2 is formed by superimposing toner images formed on the surfaces of the photosensitive drums 17, 18, 19, and 20 in the image forming stations 9, 10, 11, and 12 for each color so as to overlap each other. And a toner image composed of four color toners. As the intermediate transfer belt 2 rotates in the direction of the arrow 2A, the four color toner images are conveyed to the secondary transfer station unit 4. In the secondary transfer station unit 4, the secondary transfer roller 4 a comes into pressure contact with the intermediate transfer belt 2 through the recording paper P that is conveyed in synchronization with the conveyance of the toner image. At this time, a positive potential for attracting toner is applied to the secondary transfer roller 4a, and the toner image on the intermediate transfer belt 2 is transferred to the recording paper P.

  The belt cleaner unit 8 removes and collects toner remaining on the outer peripheral surface of the intermediate transfer belt 2 after image transfer onto the recording paper P as a transfer material, and is a photoreceptor cleaner 37, 38, 39. , 40, it is made of urethane rubber and has a cleaning blade that contacts the intermediate transfer belt 2. The paper transport unit 7 includes a registration roller pair 7a for controlling the transport timing of the recording paper P fed one by one from the supply tray 6 by the separation paper feed roller 6a, a paper guide 7b for defining a paper transport path, and a paper transport A roller pair 7c is provided, and the recording paper P is conveyed and introduced into the secondary transfer station unit 4 at a timing so that the four-color toner image on the intermediate transfer belt 2 is transferred onto the recording paper P. The fixing device 5 includes a heating roller 5a and a pressure roller 5b, and conveys the recording paper P to the nip portion between both rollers 5a and 5b, thereby thermocompression bonding the toner image transferred onto the recording paper P. A toner image is fixed on the recording paper P as a permanent image.

  In the image forming apparatus 1 configured as described above, the recording paper P conveyed by the paper conveying unit 7 passes through the position where the intermediate transfer belt 2 and the secondary transfer roller 4a are opposed to each other, and the secondary transfer roller. The four color toner images on the intermediate transfer belt 2 are collectively transferred onto the recording paper P by the action of the transfer electric field 4a. As a result, four color toner images are formed on the recording paper P. The recording paper P as a transfer material onto which the toner image has been transferred in this manner is sent to a paper discharge tray (not shown) after the fixing device 5 performs fixing processing of the toner image.

  Next, the configuration of the developing device of this embodiment will be described with reference to the drawings. FIG. 2 is a schematic longitudinal sectional view of the developing device 29 of the yellow image forming station 9 in FIG. 3 is a partially cutaway sectional view showing a state in which the developing device 29 is installed in the apparatus main body 1A of the image forming apparatus 1. FIG. 4 is a partially broken exploded longitudinal side view of the developing roller 43 constituting the developing device 29. It is. Since the other developing devices 30, 31, and 32 are similarly configured, the configuration of the developing device 29 for yellow image formation will be described here, and the description of the other developing devices 30, 31, and 32 will be omitted. .

  The developing device 29 is configured as a developing unit by incorporating and supporting the developing roller 43 and the developer stirring and conveying screws 47 and 48 in a developer tank 290 (hereinafter referred to as a developing device housing 290) as a developing device housing. The The developer agitating and conveying screws 47 and 48 function to agitate and convey the two-component developer (toner and carrier) accommodated in the developing device housing 290 and supply it to the developing roller 43. The developing roller 43 is rotatably supported by the developing device housing 290, is inserted coaxially into the cylinder of the developing sleeve 49, and is fixedly supported in the developing device housing 290. And a magnet roller 50 to be operated.

  The developing roller 43 is disposed in an opening 291 formed in the developing device housing 290 such that the developing sleeve 49 is close to the surface of the photosensitive drum 17 with a predetermined small gap. A two-component developer is accommodated in the developing device housing 290, and toner for replenishment is replenished from the toner bottle 13 (see FIG. 1) to the agitating portion by the developer agitating and conveying screws 47 and 48. After stirring and mixing with the developer, the stirred developer is sucked and conveyed onto the surface of the developing sleeve 49 by the magnetic force of the magnet roller 50. Thereafter, a desired developer layer thickness is set by a developer layer thickness regulating plate (doctor blade) (not shown), and the electrostatic latent image on the photosensitive drum 17 is rubbed with the toner, whereby the electrostatic latent image is made of toner. Visualized.

  The magnet roller 50 is integrally fixed to the magnet roller shaft 51, and the magnet roller shaft 51 is supported in a fixed state on the developing device housing 290. Flange members 52 and 53 are integrally attached to both ends of the developing sleeve 49 and are supported so as to be rotatable around the axis of the magnet roller shaft 51. A flange member 52 on the side (hereinafter referred to as drive side) to which rotational power for rotating the developing sleeve 49 is integrally fixed to a gear shaft 54 coaxial with the magnet roller shaft 51, and the gear shaft 54 is It is supported by the developing device housing 290 via two bearing members 55 and 56 so as to be rotatable around the axis of the magnet roller shaft 51. Of the two bearing members 55, 56, the bearing member 55 located on the side of the developing device housing 290 is a developing gap (DSD) adjusting bearing and is formed on the side wall of the developing device housing 290. Mounted on the holding portion, the end portion of the gear shaft 54 is rotatably supported. Although the bearing members 55 and 56 are not shown in detail, the bearing members 55 and 56 are each composed of an inner ring portion, an outer ring portion, and a sliding portion interposed therebetween, and the inner ring portion is integrally fixed to the gear shaft 54. Then, the outer ring portion is integrally fixed to the developing device housing 290.

  A rotational drive transmission gear 57 as a driven transmission member is fixed to the gear shaft 54. The rotational drive transmission gear 57 is positioned at a predetermined position of the gear shaft 54 by a C ring or E ring 58, and the rotational drive transmission gear of the photosensitive drum 17 (see FIG. 1) is transmitted. (Not shown). By engaging the rotation drive transmission gear 57 with the rotation drive transmission gear of the photosensitive drum 17, a drive transmission system with the drive means 42 using a motor as a drive source is established, and the developing sleeve 49 is connected to the magnet roller 50. Configured to rotate around an axis.

  A driving side flange member 52 of the developing sleeve 49 is supported on a driving side end 51a of the magnet roller shaft 51 via a sliding contact member 59 having a sealing function. Further, a bearing member 60 made of a copper-based sintered oil-impregnated bearing or a roller bearing is fixed to the non-driving side (opposite side to the driving side) end portion 51 b, and the developing sleeve 49 is fixed to the bearing member 60. A non-drive side flange member 53 is fitted.

  The developing sleeve 49 is rotatably supported around the axis of the magnet roller shaft 51 by such a supporting relationship of the driving side flange member 52 and the non-driving side flange member 53 of the developing sleeve 49 with respect to the magnet roller shaft 51. The bearing member 60 is fitted into a ring-shaped holding member 61 attached to the non-driving side side wall portion of the developing device housing 290. The ring-shaped holding member 61 positions the developing roller 43 relative to the developing device housing 290. Then, the non-driving side end 51 b of the magnet roller shaft 51 and the bearing member 60 are projected outwardly through the non-driving side sidewall of the developing device housing 290.

  The developing device 29 configured as a developing unit in this manner is operated along the white arrow direction (the axial direction of the magnet roller shaft 51) in FIG. 3 and is mounted at a predetermined position of the image forming apparatus main body 1A. . A block shape having a fitting hole (fitting portion) 62 capable of fitting and holding the bearing member 60 together with the non-driving side end portion 51b of the magnet roller shaft 51 at a predetermined portion of the main body frame 1B in the image forming apparatus main body 1A. The fitting base 63 is formed, and the bearing member 60 is fitted and held in the fitting hole 62 when the developing device 29 is mounted.

  Further, when the developing device 29 is mounted at a predetermined position of the image forming apparatus main body 1A, the gear 57 has a drive transmission system with the driving means 42 installed in the image forming apparatus main body 1A. It is configured to be established via a rotational drive transmission gear (not shown). The ring-shaped holding member 61 also functions as a spacer for maintaining the relative position between the fitting base 63 and the developing device housing 290 in the mounted state of the developing device 29.

  A positioning hole 64 is formed in the fitting base 63, and a positioning pin 292 parallel to the axis of the magnet roller shaft 51 is provided on the non-driving side wall of the developing device housing 290. During the mounting operation of the developing device 29, the fitting of the positioning pin 292 to the positioning hole 64 and the fitting of the bearing member 60 to the fitting hole 62 are performed in the image forming apparatus main body 1A of the developing device 29. Proper positioning installation with respect to a predetermined position is made.

  As shown in FIG. 3, when the developing device 29 is installed at a predetermined position in the image forming apparatus main body 1A, the developing roller 43 is in contact with the fitting hole 62 of the bearing member 60 fixed to the magnet roller shaft 51. It is fixed to the main body frame 1B by fitting and holding. Accordingly, the vibration due to the rotational power applied to the developing sleeve 49 is propagated to the developing device housing 290 and the image forming apparatus main body 1A via the bearing member 60 and is dispersed thereby. The vibration is suppressed, and consequently the vibration of the magnet roller 50 in the circumferential direction is also suppressed.

  According to the comparison test of the present inventors, in the case of the developing device 100 having the conventional configuration shown in FIG. 5, the circumferential deflection of the magnet roller 104 was 0.05 mm. On the other hand, in the case of the developing device 29 of this embodiment configured as shown in FIG. 3, the circumferential deflection of the magnet roller 50 was 0.02 mm. Thus, in the developing device 29 of the present embodiment, it was found that the deflection in the circumferential direction of the magnet roller 50 accompanying the rotation of the developing sleeve 49 is extremely small. Further, the developing device 29 of the present embodiment shown in FIG. 3 and the developing device 100 of the conventional configuration shown in FIG. 5 are incorporated by remodeling a color multifunction machine MX-7001N manufactured by Sharp Corporation, and loaded with A4 size recording paper. A printing test of 100,000 sheets was conducted after passing the paper. The diameter of each magnet roller was 30 mm. As a result, in the case of a color multifunction machine using the conventional developing device 100, a horizontal stripe having a width of 5 mm was generated at a pitch of 30 mm. However, in the case of a color multi-function machine using the developing device 29 of the present embodiment, a high-quality image with no horizontal stripes and no uneven image density was obtained. Thus, it has been found that the image quality can be improved by reducing the circumferential deflection of the magnet roller 50.

  In the above-described embodiment, the tandem color image forming apparatus is illustrated, but other color image forming apparatuses and monochrome image forming apparatuses may be used. Further, although a developing device using a two-component developer is exemplified as the developing device, a developing type developing device using a non-magnetic one component may be used. Further, an example in which the developing device can be detachably installed as a developing unit on the main body of the image forming apparatus has been described. However, a process cartridge (process unit) in which a photosensitive drum, a charger, and a photosensitive member cleaning unit are also incorporated. ).

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 1A Image forming apparatus main body 29, 30, 31, 32 Developing device 290, 300, 310, 320 Developing device housing 42 Driving means 43, 44, 45, 46 Developing roller 49 Developing sleeve 50 Magnet roller 51 Magnet roller shaft 57 Driven transmission member 60 Bearing member 61 Ring-shaped holding member 62 Fitting portion

Claims (6)

A developing device installed in an electrophotographic image forming apparatus main body and including a developing device housing and a developing roller incorporated in the developing device housing,
The developing roller is
A cylindrical developing sleeve rotatably supported by the developing device housing;
A magnet roller having a shaft inserted coaxially into the developing sleeve and supported in a fixed state in the developing device housing;
A bearing member fixed to the shaft of the magnet roller,
One end of the developing sleeve in the axial direction is supported on the shaft of the magnet roller so as to be rotatable around the axis of the shaft via a bearing member fixed to the shaft.
The developing device according to claim 1, wherein the bearing member is configured to be fitted and held in a fitting portion formed in the image forming apparatus main body along an axial direction thereof.   The developing device according to claim 1, wherein a driven transmission member to which rotational power is transmitted from a driving unit in the image forming apparatus main body is provided at the other axial end of the developing sleeve. . A ring-shaped holding member is attached to the developing device housing,
The bearing member is fitted to a ring-shaped holding member attached to the developing device housing between a fitting portion of the image forming apparatus main body and one axial end portion of the developing sleeve. The developing device according to claim 1 or 2.   The developing device according to claim 1, wherein the bearing member is a copper-based sintered oil-impregnated bearing.   The developing device according to claim 1, wherein the bearing member is a roller bearing. An electrophotographic image forming apparatus,
A developing device constituting the electrophotographic process part is detachably installed at a predetermined position in the apparatus main body,
The developing device comprises the developing device according to any one of claims 1 to 5,
An image forming apparatus, wherein the apparatus main body is formed with a fitting portion that fits and holds the bearing member when the developing device is installed at the predetermined position.

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