JP2013125212A - Developing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of preventing the fusion of toner due to a temperature rise in a rotary shaft member made of a resin by friction between the rotary shaft member and bearings when a conveying member having the rotary shaft member is used, and an image forming apparatus comprising the developing device.SOLUTION: A developing device 200 comprises rotary shaft temperature rise restraining members 209a and 209b, respectively, which support a first rotary shaft member 202a made of a resin, and have higher thermal conductivity than those of the first rotary shaft member 202a and first bearings 210a and 210b, between the first rotary shaft member 202a and the first bearings 210a and 210b. The developing device 200 comprises rotary shaft temperature rise restraining members 209c and 209d, respectively, which support a second rotary shaft member 203a made of a resin, and have higher thermal conductivity than those of the second rotary shaft member 203a and second bearings 211a and 211b, between the second rotary shaft member 203a and the second bearings 211a and 211b.

Description

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

  2. Description of the Related Art Two-component developers composed of toner and carrier are widely used in electrophotographic image forming apparatuses that are compatible with full color and high image quality. The developing device stirs the two-component developer in the developing tank to generate friction between the toner and the carrier, thereby charging the toner. The charged toner is supplied to the surface of the developing roller, and moves to the electrostatic latent image formed on the surface of the photosensitive drum from the developing roller by an electrostatic attraction force. As a result, a toner image based on the electrostatic latent image is formed on the photosensitive drum.

  In recent years, there has been a demand for speeding up and downsizing of an image forming apparatus, and accordingly, it is necessary to charge the developer quickly and sufficiently, and to quickly transport the developer. As a technique for that purpose, in Patent Document 1, a partition is provided in the developing tank, and the partition is extended along the longitudinal direction of the partition by the partition, and the first developer transport path and the first facing each other with the partition interposed therebetween. The first developer transport path is divided into a second developer transport path, a first communication path and a second communication path that communicate the first developer transport path and the second developer transport path at both ends in the longitudinal direction of the partition wall. A circulation-type developing device has been proposed in which a first auger screw and a second auger screw, which are conveying members for conveying the developer, are provided in the inner and second developer conveying paths.

JP 2009-109741 A

  The first auger screw and the second auger screw in the developing device described in Patent Document 1 are members in which a spiral blade is provided on the side surface of a cylindrical rotary shaft member, and rotate around the axis of the rotary shaft member. Then, the developer is conveyed by the spiral blade. In such an auger screw, conventionally, the rotating shaft member is made of metal and the spiral blade is made of resin. This is because a resin that is easy to process is suitable for a spiral blade having a complicated shape, and a metal is suitable for a rotating shaft member that requires rigidity. However, since the process for fixing the resin-made spiral blade to the metal rotary shaft member is complicated, in recent years, it has been studied to make the rotary shaft member also made of resin.

  The auger screw is rotatably supported by a bearing provided in the developing tank. When the auger screw rotates for transporting the developer, frictional heat is generated between the auger screw and the bearing by friction. When using an auger screw having a metal rotating shaft member, the frictional heat generated between the auger screw and the bearing is quickly diffused throughout the rotating shaft member, and there is little conduction of heat to the toner. Does not occur. In contrast, when using an auger screw having a resin-made rotating shaft member, the frictional heat generated between the auger screw and the bearing is difficult to diffuse throughout the rotating shaft member and concentrates on the toner near the bearing. Heat is conducted. As a result, the toner is fused in the vicinity of the bearing, and the agitation and conveyance of the toner circulated and conveyed by the auger screw are reduced due to friction with the fused toner. Further, when a large amount of toner is fused in the vicinity of the bearing, the rotation of the auger screw is hindered.

  This invention is for solving the subject mentioned above, and when using the conveyance member which has a resin-made rotating shaft member, the temperature of a rotating shaft member rises by friction with a rotating shaft member and a bearing. It is an object of the present invention to provide a developing device capable of preventing toner fusion due to the above and an image forming apparatus including the developing device.

The present invention includes a developer tank having a plurality of walls that form an internal space for containing a developer;
A rotating shaft member made of resin and a spiral blade fixed to the rotating shaft member, and a conveying member that conveys the developer accommodated in the developing tank by rotating;
A bearing fixed to the wall of the developing tank and rotatably supporting the conveying member;
A part of the rotating shaft member supports the rotating shaft member between the rotating shaft member and the bearing, and the other part is provided to be exposed to a space outside the developing tank, and is provided more than the rotating shaft member and the bearing. A developing device comprising: a rotary shaft temperature rise suppression member having high thermal conductivity.

  Moreover, this invention is characterized by the said other part of the said rotating shaft temperature rise suppression member containing a heat sink.

  Further, the present invention is characterized in that the heat radiating plate rotates around the axis of the rotary shaft member in conjunction with the rotation of the rotary shaft member.

  In the invention, it is preferable that the rotating shaft temperature rise suppressing member contains aluminum or copper as a main component.

The present invention also provides an electrophotographic image forming apparatus,
An image forming apparatus comprising the developing device.

  According to the present invention, the frictional heat generated with the rotation of the rotating shaft member is quickly diffused into the space outside the developing tank by the rotating shaft temperature rise suppressing member provided between the rotating shaft member and the bearing. As a result, the temperature rise in the vicinity of the bearing of the rotating shaft member is suppressed, and the toner in contact with this portion can be prevented from fusing.

  Further, according to the present invention, in the rotating shaft temperature rise suppressing member, a portion exposed to the space outside the developing tank includes the heat radiating plate, so that the frictional heat generated with the rotation of the rotating shaft member can be developed. It can be efficiently discharged to a space outside the tank, and heat can be prevented from staying in the developing tank.

  Further, according to the present invention, the heat radiating plate provided in the space outside the developing tank of the rotating shaft temperature rise suppressing member rotates around the axis of the rotating shaft member in conjunction with the rotation of the rotating shaft member. Therefore, the rotating shaft temperature rise suppressing member can be efficiently cooled, and as a result, the frictional heat generated with the rotation of the rotating shaft member can be more efficiently released to the space outside the developing tank. .

  Further, according to the present invention, since the rotation shaft temperature rise suppression member contains aluminum or copper as a main component, the thermal conductivity is high, and thereby, frictional heat generated with the rotation of the rotation shaft member is reduced. It can discharge | emit more efficiently to outside space, and can prevent that a heat | fever retains in a developing tank.

  Further, according to the present invention, the developing device can prevent the toner from fusing in the developing tank, thereby preventing the toner from being stirred and transported from being lowered in the developing tank. Therefore, sufficiently charged toner can be supplied by the developing device, so that a high-quality image can be quickly formed.

1 is a schematic diagram illustrating a configuration of an image forming apparatus 100. FIG. 3 is a schematic diagram illustrating a configuration of a toner cartridge 300. FIG. FIG. 3 is a cross-sectional view of the toner cartridge 300 taken along the line AA shown in FIG. 2 is a schematic diagram illustrating a configuration of a developing device 200. FIG. FIG. 5 is a cross-sectional view of the developing device 200 with the line BB shown in FIG. FIG. 5 is a cross-sectional view of the developing device 200 with a line C-C shown in FIG. It is a perspective view of the rotating shaft temperature rise suppression member 209. It is a figure which shows the heat sink 2092.

  First, the image forming apparatus 100 including the developing device 200 according to the embodiment of the present invention will be described. FIG. 1 is a schematic diagram illustrating a configuration of the image forming apparatus 100. The image forming apparatus 100 is a multifunction device having both a copying function, a printer function, and a facsimile function, and forms a full-color or monochrome image on a recording medium according to transmitted image information. The image forming apparatus 100 has three types of printing modes, ie, a copier mode (copy mode), a printer mode, and a facsimile mode, and an operation input from an operation unit (not shown), a personal computer, a portable terminal device, and an information recording medium A print mode is selected by a control unit (not shown) in response to reception of a print job from an external device using the memory device.

  The image forming apparatus 100 includes a toner image forming unit 20, a transfer unit 30, a fixing unit 40, a recording medium supply unit 50, a discharge unit 60, and a control unit unit (not shown). The toner image forming unit 20 includes photosensitive drums 21b, 21c, 21m, and 21y, charging units 22b, 22c, 22m, and 22y, an exposure unit 23, developing devices 200b, 200c, 200m, and 200y, a cleaning unit 25b, 25c, 25m, 25y, toner cartridges 300b, 300c, 300m, 300y, and toner supply pipes 250b, 250c, 250m, 250y. The transfer unit 30 includes an intermediate transfer belt 31, a driving roller 32, a driven roller 33, intermediate transfer rollers 34 b, 34 c, 34 m and 34 y, a transfer belt cleaning unit 35, and a transfer roller 36.

  The photosensitive drum 21, the charging unit 22, the developing device 200, the cleaning unit 25, the toner cartridge 300, the toner supply pipe 250, and the intermediate transfer roller 34 are black (b), cyan (c), magenta included in the color image information. In order to correspond to the image information of each color of (m) and yellow (y), four each are provided. In this specification, when distinguishing each member provided by four according to each color, an alphabet representing each color is added to the end of a number representing each member as a reference symbol, and when each member is collectively referred to Only numerals representing each member are used as reference numerals.

  The photosensitive drum 21 is supported by a drive unit (not shown) so as to be rotatable about an axis, and includes a conductive substrate (not shown) and a photoconductive layer formed on the surface of the conductive substrate. The conductive substrate can take various shapes, and examples thereof include a cylindrical shape, a columnar shape, and a thin film sheet shape. The photoconductive layer is formed of a material that exhibits conductivity when irradiated with light. As the photosensitive drum 21, for example, a cylindrical member (conductive base) formed of aluminum, and amorphous silicon (a-Si), selenium (Se), and the like formed on the outer peripheral surface of the cylindrical member, Alternatively, a film including a thin film (photoconductive layer) made of an organic optical semiconductor (OPC) can be used.

  The charging unit 22, the developing device 200, and the cleaning unit 25 are arranged in this order around the rotation direction of the photosensitive drum 21, and the charging unit 22 is arranged below the developing device 200 and the cleaning unit 25 in the vertical direction. The

  The charging unit 22 is a device that charges the surface of the photosensitive drum 21 to a predetermined polarity and potential. The charging unit 22 is installed along the longitudinal direction of the photosensitive drum 21 at a position facing the photosensitive drum 21. In the case of the contact charging method, the charging unit 22 is installed in contact with the surface of the photosensitive drum 21. In the case of the non-contact charging method, the charging unit 22 is installed so as to be separated from the surface of the photosensitive drum 21.

  The charging unit 22 is installed around the photosensitive drum 21 together with the developing device 200, the cleaning unit 25, and the like. The charging unit 22 is preferably installed at a position closer to the photosensitive drum 21 than the developing device 200, the cleaning unit 25, and the like. As a result, it is possible to reliably prevent the charging failure of the photosensitive drum 21.

  As the charging unit 22, a brush-type charging device, a roller-type charging device, a corona discharge device, an ion generation device, or the like can be used. The brush type charging device and the roller type charging device are contact charging type charging devices. As the brush type charging device, there are a type using a charging brush and a type using a magnetic brush. The corona discharge device and the ion generator are non-contact charging devices. Corona discharge devices include those using wire-like discharge electrodes, those using sawtooth discharge electrodes, and those using needle-like discharge electrodes.

  The exposure unit 23 is arranged such that light emitted from the exposure unit 23 passes between the charging unit 22 and the developing device 200 and is irradiated on the surface of the photosensitive drum 21. The exposure unit 23 irradiates the charged surface of the photosensitive drums 21b, 21c, 21m, and 21y with laser beams corresponding to the image information of the respective colors, so that each of the photosensitive drums 21b, 21c, 21m, and 21y is exposed. An electrostatic latent image corresponding to the image information of each color is formed on the surface. As the exposure unit 23, for example, a laser scanning unit (LSU) including a laser irradiation unit and a plurality of reflection mirrors can be used. As the exposure unit 23, an LED (Light Emitting Diode) array, a unit in which a liquid crystal shutter and a light source are appropriately combined, or the like may be used.

  The developing device 200 is a device that forms a toner image on the photosensitive drum 21 by developing the electrostatic latent image formed on the photosensitive drum 21 with toner. A toner supply pipe 250 that is a cylindrical member is connected to the upper part of the developing device 200 in the vertical direction. Details of the developing device 200 will be described later.

  The toner cartridge 300 is disposed vertically above the developing device 200 and stores unused toner. A toner supply pipe 250 is connected to the lower part of the toner cartridge 300 in the vertical direction. The toner cartridge 300 supplies toner to the developing device 200 via the toner supply pipe 250. Details of the toner cartridge 300 will be described later.

  The cleaning unit 25 is a member that removes the toner remaining on the surface of the photosensitive drum 21 after the toner image is transferred from the photosensitive drum 21 to the intermediate transfer belt 31 and cleans the surface of the photosensitive drum 21. . As the cleaning unit 25, for example, a plate-like member for scraping off toner and a container-like member for collecting the scraped toner are used.

  According to the toner image forming unit 20, the surface of the photosensitive drum 21 that is uniformly charged by the charging unit 22 is irradiated with laser light corresponding to image information from the exposure unit 23 to form an electrostatic latent image. . A toner image is formed by supplying toner from the developing device 200 to the electrostatic latent image on the photosensitive drum 21. This toner image is transferred to an intermediate transfer belt 31 described later. After the toner image is transferred to the intermediate transfer belt 31, the toner remaining on the surface of the photosensitive drum 21 is removed by the cleaning unit 25.

  The intermediate transfer belt 31 is an endless belt-like member that is disposed above the photosensitive drum 21 in the vertical direction. The intermediate transfer belt 31 is stretched by the driving roller 32 and the driven roller 33 to form a loop-shaped path, and moves in the direction of the arrow A4.

  The drive roller 32 is provided so as to be rotatable around its axis by a drive unit (not shown). The drive roller 32 moves the intermediate transfer belt 31 in the direction of the arrow A4 by its rotation. The driven roller 33 is provided so as to be able to rotate following the rotation of the driving roller 32, and generates a certain tension on the intermediate transfer belt 31 so that the intermediate transfer belt 31 does not loosen.

  The intermediate transfer roller 34 is provided in pressure contact with the photosensitive drum 21 via the intermediate transfer belt 31 and rotatable about its axis by a drive unit (not shown). As the intermediate transfer roller 34, for example, a metal (for example, stainless steel) roller having a diameter of 8 mm to 10 mm on which a conductive elastic member is formed can be used. The intermediate transfer roller 34 is connected to a power source (not shown) for applying a transfer bias, and has a function of transferring the toner image on the surface of the photosensitive drum 21 to the intermediate transfer belt 31.

  The transfer roller 36 is provided in pressure contact with the drive roller 32 via the intermediate transfer belt 31 and is rotatable about an axis by a drive unit (not shown). At the pressure contact portion (transfer nip portion) between the transfer roller 36 and the drive roller 32, the toner image carried and conveyed by the intermediate transfer belt 31 is transferred to a recording medium fed from a recording medium supply unit 50 described later. The

  The transfer belt cleaning unit 35 is provided so as to face the driven roller 33 through the intermediate transfer belt 31 and to be in contact with the toner image carrying surface of the intermediate transfer belt 31. The transfer belt cleaning unit 35 is provided for removing and collecting the toner on the surface of the intermediate transfer belt 31 after the toner image is transferred to the recording medium. If toner remains on the intermediate transfer belt 31 after the toner image is transferred to the recording medium, the residual toner may adhere to the transfer roller 36 due to the movement of the intermediate transfer belt 31. When toner adheres to the transfer roller 36, the toner contaminates the back surface of the recording medium to be transferred next.

  According to the transfer unit 30, when the intermediate transfer belt 31 moves while being in contact with the photosensitive drum 21, a transfer bias having a polarity opposite to the charging polarity of the toner on the surface of the photosensitive drum 21 is applied to the intermediate transfer roller 34. The toner image formed on the surface of the photosensitive drum 21 is transferred onto the intermediate transfer belt 31. The toner images of the respective colors respectively formed on the photosensitive drum 21y, the photosensitive drum 21m, the photosensitive drum 21c, and the photosensitive drum 21b are sequentially transferred onto the intermediate transfer belt 31 in this order, thereby transferring full color. A toner image is formed. The toner image transferred to the intermediate transfer belt 31 is conveyed to the transfer nip portion by the movement of the intermediate transfer belt 31, and transferred to the recording medium at the transfer nip portion. The recording medium on which the toner image is transferred is conveyed to a fixing unit 40 described later.

  The recording medium supply unit 50 includes a paper feed box 51, pickup rollers 52 a and 52 b, transport rollers 53 a and 53 b, registration rollers 54, and a paper feed tray 55. The paper feed box 51 is a container-like member that is provided in the lower part of the image forming apparatus 100 in the vertical direction and stores a recording medium inside the image forming apparatus 100. The paper feed tray 55 is a tray-like member that is provided on the outer wall surface of the image forming apparatus 100 and stores a recording medium outside the image forming apparatus 100. Examples of the recording medium include plain paper, color copy paper, overhead projector sheet, and postcard.

  The pickup roller 52a is a member that takes out recording media stored in the paper feed box 51 one by one and feeds it to the paper transport path A1. The transport rollers 53a are a pair of roller-like members provided so as to be in pressure contact with each other, and transport the recording medium toward the registration rollers 54 in the paper transport path A1. The pickup roller 52b is a member that takes out the recording medium stored in the paper feed tray 55 one by one and feeds it to the paper transport path A2. The transport rollers 53b are a pair of roller-like members provided so as to be in pressure contact with each other, and transport the recording medium toward the registration rollers 54 in the paper transport path A2.

  The registration rollers 54 are a pair of roller-like members provided so as to come into pressure contact with each other, and the toner image carried on the intermediate transfer belt 31 is conveyed to the transfer nip portion of the recording medium fed from the conveyance rollers 53a and 53b. In synchronization with this, the sheet is fed to the transfer nip portion.

  According to the recording medium supply unit 50, the recording medium is transferred from the paper feed box 51 or the paper feed tray 55 to the transfer nip portion in synchronization with the toner image carried on the intermediate transfer belt 31 being conveyed to the transfer nip portion. The toner image is transferred to the recording medium.

  The fixing unit 40 includes a heating roller 41 and a pressure roller 42. The heating roller 41 is controlled to have a predetermined fixing temperature. The pressure roller 42 is a roller that is in pressure contact with the heating roller 41. The heating roller 41 nips the recording medium together with the pressure roller 42 while heating, thereby melting and fixing the toner constituting the toner image on the recording medium. The recording medium on which the toner image is fixed is conveyed to a discharge unit 60 described later.

  The discharge unit 60 includes a conveyance roller 61, a discharge roller 62, and a discharge tray 63. The conveyance roller 61 is a pair of roller-like members provided so as to be in pressure contact with each other in the vertical direction above the fixing unit 40. The conveyance roller 61 conveys the recording medium on which the image is fixed toward the discharge roller 62.

  The discharge roller 62 is a pair of roller-like members provided so as to be in pressure contact with each other. In the case of single-sided printing, the discharge roller 62 discharges the recording medium on which single-sided printing has been completed to the discharge tray 63. In the case of duplex printing, the discharge roller 62 conveys the recording medium on which single-sided printing has been completed to the registration roller 54 via the paper conveyance path A <b> 3, and discharges the recording medium on which duplex printing has been completed to the discharge tray 63. The discharge tray 63 is provided on the upper surface in the vertical direction of the image forming apparatus 100 and stores a recording medium on which an image is fixed.

  Image forming apparatus 100 includes a control unit (not shown). The control unit unit is provided, for example, at an upper part in the vertical direction in the internal space of the image forming apparatus 100 and includes a storage unit, a calculation unit, and a control unit. The storage unit stores various setting values via an operation panel (not shown) arranged on the upper surface in the vertical direction of the image forming apparatus 100, detection results from sensors (not shown) arranged at various locations inside the image forming apparatus 100, external devices, and the like. The image information from is input. A program for executing various processes is written in the storage unit. Examples of the various processes include a recording medium determination process, an adhesion amount control process, and a fixing condition control process.

  As the storage unit, those commonly used in this field can be used, and examples thereof include a read only memory (ROM), a random access memory (RAM), and a hard disk drive (HDD). As the external device, an electric or electronic device that can form or acquire image information and can be electrically connected to the image forming apparatus 100 can be used. For example, a computer, a digital camera, a television receiver, a video recorder DVD (Digital Versatile Disc) recorder, HDDVD (High-Definition Digital Versatile Disc) recorder, Blu-ray disc recorder, facsimile apparatus, portable terminal apparatus, and the like.

  The calculation unit retrieves various data (image formation command, detection result, image information, etc.) written in the storage unit and various processing programs, and performs various determinations. The control unit performs operation control by sending a control signal to each device provided in the image forming apparatus 100 according to the determination result of the calculation unit.

  The control unit and the calculation unit include a processing circuit realized by a microcomputer, a microprocessor, or the like provided with a central processing unit (CPU). The control unit unit includes a main power source together with the processing circuit, and the power source supplies power not only to the control unit unit but also to each device provided in the image forming apparatus 100.

  FIG. 2 is a schematic diagram illustrating the configuration of the toner cartridge 300. FIG. 3 is a cross-sectional view of the toner cartridge 300 taken along line AA shown in FIG. The toner cartridge 300 is a device that supplies toner to the developing device 200 via the toner supply pipe 250. The toner cartridge 300 includes a toner storage container 301, a toner scooping member 302, a toner discharge member 303, and a toner discharge container 304.

  The toner storage container 301 is a container-like member having a substantially semi-cylindrical internal space. In the internal space, the toner scooping member 302 is rotatably supported, and unused toner is stored. The toner discharge container 304 is a container-like member having a substantially semi-cylindrical internal space provided along the longitudinal direction of the toner storage container 301, and supports the toner discharge member 303 rotatably in the internal space. The internal space of the toner storage container 301 and the internal space of the toner discharge container 304 communicate with each other via a communication port 305 formed along the longitudinal direction of the toner storage container 301. The toner discharge container 304 has a discharge port 306 formed in the lower part in the vertical direction. A toner supply pipe 250 is connected to the toner discharge container 304 at a discharge port 306.

  The toner scooping member 302 includes a rotation shaft 302a, a base body 302b, and a sliding portion 302c. The rotation shaft 302 a is a columnar member that extends along the longitudinal direction of the toner container 301. The base 302b is a plate-like member extending along the longitudinal direction of the toner container 301, and is attached to the rotating shaft 302a at the center in the width direction and the thickness direction. The sliding portion 302c is a flexible member attached to both ends in the width direction of the base body 302b, and is formed of, for example, polyethylene terephthalate (PET). In the toner pumping member 302, the base body 302b rotates as the rotary shaft 302a rotates about the axis thereof, and as a result, the sliding portions 302c provided at both ends in the width direction of the base body 302b are formed in the toner container 301. By rubbing the wall surface, the toner in the toner container 301 is pumped up to the toner discharge container 304.

  The toner discharge member 303 is a member that conveys the toner in the toner discharge container 304 toward the discharge port 306. The toner discharge member 303 is an auger screw-like member including a toner discharge rotation shaft 303a and a toner discharge blade 303b provided around the toner discharge rotation shaft 303a.

  According to the toner cartridge 300, unused toner in the toner container 301 is pumped up to the toner discharge container 304 by the toner pumping member 302. The toner drawn up in the toner discharge container 304 is conveyed to the discharge port 306 by the toner discharge member 303. The toner conveyed to the discharge port 306 is discharged from the discharge port 306 to the outside of the toner discharge container 304 and supplied to the developing device 200 via the toner supply pipe 250.

  FIG. 4 is a schematic diagram illustrating the configuration of the developing device 200. FIG. 5 is a cross-sectional view of the developing device 200 with the line BB shown in FIG. FIG. 6 is a cross-sectional view of the developing device 200 in which the line CC shown in FIG.

  The developing device 200 is a device that develops an electrostatic latent image formed on the surface of the photosensitive drum 21 by supplying toner to the surface of the photosensitive drum 21. The developing device 200 includes a developing tank 201, a first conveying member 202, a second conveying member 203, a developing roller 204, a developing tank cover 205, a doctor blade 206, a partition wall 207, and a toner concentration detection sensor 208. , And rotation shaft temperature rise suppression members 209a to 209d. When the rotation shaft temperature increase suppression members 209a to 209d are not distinguished, they are collectively referred to as the rotation axis temperature increase suppression member 209.

  The developing tank 201 is a member in which an internal space is formed by the side wall portions 201a and 201b and the bottom wall portion 201c, and stores the developer in the internal space. The side wall parts 201a and 201b and the bottom wall part 201c may be integrally formed, or may be separate members. The developing tank 201 is made of a resin material such as polyethylene, polypropylene, high impact polystyrene, and ABS resin (acrylonitrile-butadiene-styrene copolymer synthetic resin). The developer used in the present invention may be a one-component developer composed only of toner or a two-component developer containing toner and carrier.

  The developing tank 201 is provided with a developing tank cover 205 above the vertical direction, and a first conveying member 202, a second conveying member 203, a developing roller 204, a doctor blade 206, and a partition wall 207 are provided in the internal space. In addition, a toner concentration detection sensor 208 is provided at a lower portion (bottom portion) in the vertical direction of the developing tank 201. The developing tank 201 has an opening between the photosensitive drum 21 and the developing roller 204.

The length _{L 1} in the longitudinal direction of the developer tank 201 is about 200Mm～400mm. The length _{L 2} in the width direction of the developer tank 201 is about 25Mm～80mm.

  The developing roller 204 includes a magnet roller, carries the developer in the developing tank 201 on the surface, and supplies toner contained in the carried developer to the photosensitive drum 21. A power supply (not shown) is connected to the developing roller 204, and a developing bias voltage is applied. The toner carried on the developing roller 204 moves to the photosensitive drum 21 in the vicinity of the photosensitive drum 21 by electrostatic force due to the developing bias voltage.

  The doctor blade 206 is a plate-like member extending in the axial direction of the developing roller 204, and is provided so that one end in the width direction is fixed to the developing tank 201 and the other end has a gap with respect to the surface of the developing roller 204. It is done. The doctor blade 206 is provided with a gap with respect to the surface of the developing roller 204, thereby regulating the amount of developer carried on the developing roller 204 to a predetermined amount. As the material of the doctor blade 206, stainless steel, aluminum, synthetic resin, or the like can be used.

  The partition wall 207 is a member that extends along the longitudinal direction of the developing tank 201 at a substantially central portion in the width direction of the developing tank 201. The partition wall 207 is provided between the bottom wall portion 201 c of the developing tank 201 and the developing tank cover 205, and is provided so that both end portions in the longitudinal direction are separated from the side wall portions 201 a and 201 b of the developing tank 201. The partition 207 divides the internal space of the developing tank 201 into a first conveyance path P, a second conveyance path Q, a first communication path R, and a second communication path S.

  The second transport path Q is a substantially semi-cylindrical space extending along the longitudinal direction of the partition wall 207 and is a space facing the developing roller 204. The first transport path P is a substantially semi-cylindrical space extending along the longitudinal direction of the partition wall 207 and is a space facing the second transport path Q across the partition wall 207. The first communication path R is a space that communicates the first transport path P and the second transport path Q on the longitudinal end 207a side of the partition wall 207. The second communication path S is a space that communicates the first transport path P and the second transport path Q on the side of the other end 207 b in the longitudinal direction of the partition wall 207.

  The developing tank cover 205 is detachably provided above the developing tank 201 in the vertical direction, and has a supply port 205a. A toner supply pipe 250 is connected to the developing tank cover 205 at a supply port 205a. The supply port 205a is an opening in which an opening for supplying toner to the developing tank 201 is formed. The toner contained in the toner cartridge 300 passes through the toner supply pipe 250 and the opening, and then the developing tank 201. Supplied in.

  The supply port 205a is provided in the vicinity of the second communication path S in the vertical direction above the first transport path P. More specifically, the opening formed in the supply port portion 205 a is provided so as to face the first transport path P and be at the same position as the second communication path S in the longitudinal direction of the partition wall 207.

  The first transport member 202 is provided in the first transport path P. The first conveying member 202 conveys the developer in the developing tank 201 from the other end 207b in the longitudinal direction of the partition wall 207 toward the one end 207a in the longitudinal direction. Hereinafter, the developer conveyance direction by the first conveyance member 202 is referred to as a conveyance direction X.

  The first conveying member 202 is an auger screw-like member including a first rotating shaft member 202a, a first spiral blade 202b, a first gear 202c, and first developer stopper plates 202d and 202e. The first rotating shaft member 202a is a columnar member having a diameter of 4 mm to 10 mm, and is connected to the first gear 202c at the downstream end in the transport direction X.

  The first rotating shaft member 202a has a downstream end portion in the transport direction X inserted and fixed to the rotating shaft temperature rise suppressing member 209a, and a side wall of the developing tank 201 together with a rotating cylinder 2091 described later of the rotating shaft temperature rising suppressing member 209a. The first bearing 210a which is a radial bearing fixed to the portion 201a is inserted. The first rotating shaft member 202a is inserted and fixed to the rotating shaft temperature rise suppressing member 209b, and the upstream end in the transport direction X of the rotating shaft temperature rising suppressing member 209b, together with a rotating cylinder 2091 described later, is connected to the developing tank 201. Is inserted into a first bearing 210b which is a radial bearing fixed to the side wall portion 201b. In this way, the first rotating shaft member 202a is supported by the two rotating shaft temperature increase suppressing members 209a and 209b and the two first bearings 210a and 210b so as to be rotatable about the axis.

  The first bearings 210a and 210b are sliding bearings formed from a resin material having a low frictional resistance (for example, a resin material such as polyethylene, polypropylene, high-impact polystyrene, or ABS resin impregnated or coated with silicon oil). . The first bearing 210 a is a substantially cylindrical member provided in a hole 201 aa formed in the side wall 201 a of the developing tank 201. The first bearing 210b is a substantially cylindrical member provided in a hole 201ba formed in the side wall 201b of the developing tank 201.

A first spiral blade 202b that is a member that spirally surrounds the side surface is provided on the side surface of the first rotating shaft member 202a. The outer diameter L3 of the first spiral blade 202b is 12 mm to ₃₀ mm. Further, a disk-shaped first developer stopper plate 202d is provided on the side surface of the first rotating shaft member 202a between the downstream end portion in the transport direction X of the first spiral blade 202b and the first bearing 210a. A disc-shaped first developer stopper plate 202e is provided between the upstream end in the transport direction X of the one spiral blade 202b and the first bearing 210b. The first developer stopper plates 202d and 202e are members that prevent the developer from entering between the first bearings 210a and 210b and the first rotary shaft member 202a.

  The first rotating shaft member 202a, the first spiral blade 202b, the first gear 202c, and the first developer stopper plates 202d and 202e are formed of a resin material such as polyethylene, polypropylene, high-impact polystyrene, or ABS resin, for example. . The first rotary shaft member 202a, the first spiral blade 202b, the first gear 202c, and the first developer stopper plates 202d and 202e are preferably integrally formed from the same material.

  The first conveying member 202 is rotated at 150 rpm to 400 rpm around the axis of the first rotating shaft member 202a via the first gear 202c by a rotation driving source such as a motor (not shown) provided in the image forming apparatus 100. To do. Accordingly, the first spiral blade 202b rotates around the axis of the first rotating shaft member 202a. As a result, the developer stored in the first transport path P is transported downstream in the transport direction X. The As described above, the supply port portion 205a of the developing tank cover 205 is formed in the vicinity of the second communication path S above the first conveyance path P in the vertical direction. First, it is supplied to the first transport path P, and then transported to the downstream side in the transport direction X of the first transport path P by the first transport member 202.

  The second transport member 203 is provided in the second transport path Q. The second transport member 203 transports the developer in the developing tank 201 from the longitudinal direction one end 207a side of the partition wall 207 toward the longitudinal other end 207b side. Hereinafter, the developer conveyance direction by the second conveyance member 203 is referred to as a conveyance direction Y.

  The second conveying member 203 is an auger screw-like member including a second rotating shaft member 203a, a second spiral blade 203b, a second gear 203c, and second developer stopper plates 203d and 203e. The second rotating shaft member 203a is a columnar member having a diameter of 4 mm to 10 mm, and is connected to the second gear 203c at the upstream end in the transport direction Y.

  The second rotation shaft member 203a has an upstream end in the transport direction Y inserted and fixed to the rotation shaft temperature rise suppression member 209c, and a side wall of the developing tank 201 together with a later-described rotation cylinder 2091 of the rotation shaft temperature increase suppression member 209c. The second bearing 211a which is a radial bearing fixed to the portion 201a is inserted. Further, the second rotation shaft member 203a has a downstream end portion in the transport direction Y inserted and fixed in the rotation shaft temperature rise suppression member 209d, and together with a later-described rotating cylinder 2091 of the rotation shaft temperature increase suppression member 209d, the developing tank 201. Is inserted into a second bearing 211b which is a radial bearing fixed to the side wall portion 201b. In this way, the second rotating shaft member 203a is supported by the two rotating shaft temperature increase suppressing members 209c and 209d and the two second bearings 211a and 211b so as to be rotatable around the axis.

  The second bearings 211a and 211b are sliding bearings formed from a resin material having a low frictional resistance (for example, a resin material such as polyethylene, polypropylene, high-impact polystyrene, or ABS resin impregnated or coated with silicon oil). . The second bearing 211 a is a substantially cylindrical member provided in a hole 201 ab formed in the side wall 201 a of the developing tank 201. The second bearing 211b is a substantially cylindrical member provided in a hole 201bb formed in the side wall 201b of the developing tank 201.

A second spiral blade 203b that is a member that spirally surrounds the side surface is provided on the side surface of the second rotating shaft member 203a. Outer diameter _{L 4} of the second spiral blade 203b is 12Mm～30mm. Further, a disc-shaped second developer stopper plate 203d is provided on the side surface of the second rotating shaft member 203a between the upstream end portion in the transport direction Y of the second spiral blade 203b and the second bearing 211a. A disc-shaped second developer stopper plate 203e is provided between the downstream end portion in the transport direction Y of the two spiral blades 203b and the second bearing 211b. The second developer stopper plates 203d and 203e are members that prevent the developer from entering between the second bearings 211a and 211b and the second rotary shaft member 203a.

  The second rotating shaft member 203a, the second spiral blade 203b, the second gear 203c, and the second developer stopper plates 203d and 203e are formed of a resin material such as polyethylene, polypropylene, high impact polystyrene, and ABS resin, for example. . The second rotating shaft member 203a, the second spiral blade 203b, the second gear 203c, and the second developer stopper plates 203d and 203e are preferably integrally formed from the same material.

  The second conveying member 203 is rotated at 150 rpm to 400 rpm around the axis of the second rotating shaft member 203a via the second gear 203c by a rotation driving source such as a motor (not shown) provided in the image forming apparatus 100. To do. Accordingly, the second spiral blade 203b rotates around the axis of the second rotating shaft member 203a. As a result, the developer stored in the second transport path Q is transported downstream in the transport direction Y. The

  FIG. 7 is a perspective view of the rotating shaft temperature rise suppression member 209 provided in the developing device 200. The rotating shaft temperature rise suppression member 209 includes a rotating cylinder 2091 and four heat radiating plates 2092.

  The inner diameter of the rotary cylinder 2091 is the same as or slightly larger than the diameter of the rotary shaft member (first rotary shaft member 202a or second rotary shaft member 203a), and the outer diameter is a bearing (first bearing 210a, 210b or second shaft). It is a cylindrical member that is the same as or slightly smaller than the inner diameter of the bearings 211a, 211b). The end of the rotating shaft member is inserted and fixed in the rotating cylinder 2091 and is supported by the bearing together with the rotating shaft member. Since the rotating cylinder 2091 is fixed to the end of the rotating shaft member, it rotates around the axis of the rotating shaft member in conjunction with the rotation of the rotating shaft member.

  The rotating cylinder 2091 is provided to extend from the inner wall surface of the developing tank 201 to a space outside the developing tank 201, and a part of the rotating cylinder 2091 is exposed to the space outside the developing tank 201. Four heat radiating plates 2092 are provided in a portion of the rotating cylinder 2091 exposed to the space outside the developing tank 201.

  Each heat radiating plate 2092 is a rectangular or square plate-like member, and is fixed to the outer peripheral surface of the rotating cylinder 2091. Each heat sink 2092 has, for example, a thickness of 0.5 mm to 2.0 mm, a width of 5.0 mm to 15.0 mm, and a length of 5.0 mm to 15.0 mm.

  In the present embodiment, each heat radiating plate 2092 is provided such that its main surface is parallel to the axis of the rotating cylinder 2091 and is perpendicular to the outer peripheral surface of the rotating cylinder 2091. Further, each heat radiating plate 2092 is provided such that the width direction coincides with the axial direction of the rotating cylinder 2091 and the longitudinal direction coincides with the direction perpendicular to the axial line of the rotating cylinder 2091. Further, the four heat radiating plates 2092 are provided at equal intervals in the circumferential direction of the rotating cylinder 2091 so that the main surfaces of the two adjacent heat radiating plates 2092 are vertical. In addition, the number of the heat sinks 2092 is not limited to four, may be three or less, and may be five or more.

  The rotating cylinder 2091 and the heat radiating plate 2092 are more than the corresponding rotating shaft member (first rotating shaft member 202a or second rotating shaft member 203a) and the corresponding bearing (first bearing 210a, 210b or second bearing 211a, 211b). It is formed from a material with high thermal conductivity. As described above, the rotary shaft member and the bearing of the present embodiment are formed of a resin material such as polyethylene, polypropylene, high impact polystyrene, and ABS resin. Therefore, the rotary cylinder 2091 and the heat radiating plate 2092 of the present embodiment include these It is formed from a material having a higher thermal conductivity than the resin material. For example, these resin materials may be formed from a material in which metal powder having high thermal conductivity such as aluminum or copper is dispersed, or may be formed from a single metal such as aluminum or copper. It may be formed from an alloy containing any of these metals. In order to increase the thermal conductivity, it is preferably formed from a material mainly composed of these metals. Here, the main component means a component having the largest mass ratio in the material.

  A toner concentration detection sensor 208 shown in FIG. 4 is mounted at the bottom of the developing tank 201 below the second transport member 203 in the vertical direction so that the sensor surface is exposed to the second transport path Q. The toner concentration detection sensor 208 is electrically connected to a toner concentration control unit (not shown).

  The toner density control unit performs control to rotate the toner discharge member 303 and supply the toner into the developing tank 201 in accordance with the toner density detection result detected by the toner density detection sensor 208. More specifically, the toner density control unit determines whether or not the toner density detection result by the toner density detection sensor 208 is lower than a predetermined setting value. A control signal is sent to the driving section to rotate the toner discharging member 303 for a predetermined period.

  A power source (not shown) is connected to the toner concentration detection sensor 208. The power supply applies to the toner concentration detection sensor 208 a drive voltage for driving the toner concentration detection sensor 208 and a control voltage for outputting the toner concentration detection result to the toner concentration control unit. Application of a voltage to the toner concentration detection sensor 208 by the power supply is controlled by a control unit (not shown).

  As the toner concentration detection sensor 208, a general toner concentration detection sensor can be used. For example, a transmitted light detection sensor, a reflected light detection sensor, a magnetic permeability detection sensor, or the like can be used. Among these toner concentration detection sensors, it is preferable to use a magnetic permeability detection sensor. Examples of the magnetic permeability detection sensor include TS-L (trade name, manufactured by TDK Corporation), TS-A (trade name, manufactured by TDK Corporation), TS-K (trade name, manufactured by TDK Corporation), and the like. It is done.

  According to the developing device 200 configured as described above, the developer is in the order of the first conveyance path P, the first communication path R, the second conveyance path Q, and the second communication path S in the developing tank 201. It is circulated and conveyed. A part of the circulated developer is carried on the surface of the developing roller 204 in the second conveyance path Q, and the toner in the carried developer moves to the photosensitive drum 21 and is sequentially consumed. Is done. When the toner concentration detection sensor 208 detects that a predetermined amount of toner has been consumed, unused toner is supplied from the toner cartridge 300 into the first conveyance path P. The supplied toner is diffused in the already stored developer while being conveyed in the first conveyance path P.

  When the developer is circulated in this way, the first conveying member 202 is rotated, and accordingly, the two rotating cylinders 2091 fixed to the first rotating shaft member 202a and the two first bearings corresponding thereto. Friction is generated between 210a and 210b, and frictional heat is generated. Similarly, friction is generated between the two rotating cylinders 2091 fixed to the second rotating shaft member 203a and the two second bearings 211a and 211b corresponding to the two rotating cylinders 2091, thereby generating frictional heat. The generated frictional heat has a rotating cylinder whose heat conductivity is higher than that of the rotating shaft member (first rotating shaft member 202a or second rotating shaft member 203a) and bearing (first bearing 210a, 210b or second bearing 211a, 211b). It moves to the part exposed to the space outside the developing tank 201 of 2091, and further moves to the heat sink 2092 provided in that part. The heat radiating plate 2092 radiates heat to the space outside the developing tank 201.

  That is, the frictional heat generated with the rotation of the rotating shaft member (the first rotating shaft member 202a or the second rotating shaft member 203a) is the rotating shaft temperature rise suppressing member 209 configured by the rotating cylinder 2091 and the heat radiating plate 2092. As a result, it quickly diffuses into the space outside the developing tank 201. As a result, the temperature rise of the rotating shaft member in the vicinity of the bearing (the first bearing 210a, 210b or the second bearing 211a, 211b) is suppressed, and the toner that contacts this part is prevented from fusing. Can do.

  Moreover, in this embodiment, since the rotating shaft temperature rise suppression member 209 includes the heat sink 2092, the surface area can be increased. As a result, the rotating shaft temperature rise suppression member 209 can efficiently release the generated frictional heat to the space outside the developing tank 201 and prevent the heat from staying in the developing tank 201. it can.

  Further, in this embodiment, the material of the rotary shaft temperature rise suppression member 209 includes aluminum or copper as a main component, and thus has high thermal conductivity, whereby the generated frictional heat is efficiently transferred to the space outside the developing tank 201. It is possible to release the heat and prevent the heat from staying in the developing tank 201.

  In the present embodiment, since the rotating cylinder 2091 is fixed to the rotating shaft member (the first rotating shaft member 202a or the second rotating shaft member 203a), the axis of the rotating shaft member is interlocked with the rotation of the rotating shaft member. The rotating cylinder 2091 also rotates around. And since the heat sink 2092 is being fixed to the rotating cylinder 2091, the heat sink 2092 also rotates around the axis line of a rotating shaft member. Thereby, the heat radiating plate 2092 can be efficiently cooled, and as a result, the frictional heat generated with the rotation of the rotating shaft member can be more efficiently released to the space outside the developing tank 201.

  In the present embodiment, each heat radiating plate 2092 is provided such that the main surface is parallel to the axis of the rotary cylinder 2091. However, in another embodiment of the present invention, the main surface is provided with the rotary cylinder. You may incline with respect to the axis of 2091. FIG. 8 shows a heat radiating plate 2093 having a main surface that is inclined with respect to the axis of the rotating cylinder 2091.

  The main surface of the heat sink 2093 is inclined at an inclination angle θ with respect to the axis of the rotating cylinder 2091. The inclination angle θ is an angle larger than 0 ° and smaller than 90 °, for example, 45 °. When the rotating cylinder 2091 rotates in the rotating direction G in conjunction with the rotation of the rotating shaft member (the first rotating shaft member 202a or the second rotating shaft member 203a), the heat radiating plate 2093 moves in the rotating direction G together with the rotating cylinder 2091. Configured to rotate. Thereby, the heat radiating plate 2093 can send air from the end 2091a on the side farther from the developing tank 201 to the end 2091b on the closer side of the rotating cylinder 2091. As a result, the developing tank 201 can be cooled from the outside, and heat can be prevented from staying in the developing tank 201. When the heat sink 2093 is provided instead of the heat sink 2092, not only the rotary shaft temperature rise suppression member 209 fixed to one end of the rotary shaft member but also the rotary shaft lift fixed to the other end of the rotary shaft member. The temperature suppressing member 209 is preferably configured similarly. As a result, the effect of cooling the developing tank 201 from the outside can be further enhanced, and the reaction force generated by sending air is fixed to one end of the rotating shaft member and the other end of the rotating shaft member. Since the rotating cylinders 2091 fixed to the parts are in opposite directions, it is possible to prevent the rotating shaft members fixed to the two rotating cylinders 2091 from shifting in the axial direction.

  As described above, the developing device 200 including the rotation shaft temperature rise suppression member 209 can prevent heat from staying in the developing tank 201 and can prevent toner fusion in the developing tank 201. It is possible to prevent the toner from being stirred and transported in the tank 201 from being lowered. Therefore, the image forming apparatus 100 including the developing device 200 can supply the toner sufficiently charged by the developing device 200 to the photosensitive drum 21, so that a high-quality image can be quickly formed. Become.

DESCRIPTION OF SYMBOLS 20 Toner image formation part 30 Transfer part 40 Fixing part 50 Recording medium supply part 60 Ejection part 100 Image forming apparatus 200, 200b, 200c, 200m, 200y Developing device 201 Developing tank 201a, 201b Side wall part 201c Bottom wall part 202 1st conveyance Member 202a first rotating shaft member 202b first spiral blade 202c first gear 202d, 202e first developer stopper plate 203 second transport member 203a second rotating shaft member 203b second spiral blade 203c second gear 203d, 203e second Developer stop plate 204 Developing roller 205 Developing tank cover 205a Supply port 206 Doctor blade 207 Partition 208 Toner density detection sensor 209, 209a, 209b, 209c, 209d Rotating shaft temperature rise suppression member 2091 Rotating cylinder 2092, 2093 21 0b First bearing 211a, 211b Second bearing 250, 250b, 250c, 250m, 250y Toner supply pipe 300, 300b, 300c, 300m, 300y Toner cartridge

Claims (5)

A developing tank having a plurality of walls forming an internal space for containing the developer;
A rotating shaft member made of resin and a spiral blade fixed to the rotating shaft member, and a conveying member that conveys the developer accommodated in the developing tank by rotating;
A bearing fixed to the wall of the developing tank and rotatably supporting the conveying member;
A part of the rotating shaft member supports the rotating shaft member between the rotating shaft member and the bearing, and the other part is provided to be exposed to a space outside the developing tank, and is provided more than the rotating shaft member and the bearing. A developing device comprising: a rotating shaft temperature rise suppression member having high thermal conductivity.   The developing device according to claim 1, wherein the other part of the rotation shaft temperature increase suppression member includes a heat radiating plate.   The developing device according to claim 2, wherein the heat radiating plate rotates around an axis of the rotating shaft member in conjunction with rotation of the rotating shaft member.   The developing device according to claim 1, wherein the rotation shaft temperature rise suppression member includes aluminum or copper as a main component. In an electrophotographic image forming apparatus,
An image forming apparatus comprising the developing device according to claim 1.

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