JP2017040679A - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device, process cartridge, and image forming apparatus in which a developing bias output from a power supply part is satisfactorily applied to a rotary shaft part of a developing roller.SOLUTION: A developing device comprises a first electrode terminal 23m (electrode terminal) that is in slide contact, with an elastic force, directly or indirectly with an outer peripheral surface of a rotary shaft part 23a13 of a first developing roller 23a1 (developing roller) to relay so that a developing bias output from a power supply part 50 is applied to the rotary shaft part 23a13.SELECTED DRAWING: Figure 6

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrophotographic method such as a copying machine, a printer, a facsimile, or a multifunction machine thereof, and a developing device and a process cartridge installed therein, and in particular, developing on a developing roller. The present invention relates to a developing device, a process cartridge, and an image forming apparatus configured to apply a bias.

  2. Description of the Related Art Conventionally, in a developing device installed in an image forming apparatus such as a copying machine or a printer, a technique for performing a developing process by applying a developing bias to a rotating shaft portion of a developing roller carrying a developer is widely known. (For example, refer to Patent Document 1).

  Specifically, the developing device in Patent Document 1 uses a two-component developer, and is a bearing that holds a developing bias output from a power supply unit (bias power supply) so that the rotating shaft portion of the developing roller can rotate. And is applied to the rotating shaft portion of the developing roller.

  In the conventional developing device, the inner peripheral surface of the bearing that rotatably holds the rotating shaft portion of the developing roller is worn over time, so that there is a gap between the rotating shaft portion and the bearing, A foreign matter such as toner may enter between the rotating shaft and the bearing, resulting in a poor contact between the rotating shaft of the developing roller and the bearing, and the developing bias output from the power supply unit is applied to the rotating shaft of the developing roller. There was a problem that it was not applied well to the part. As a result of such application failure (conductivity failure), abnormal images such as density unevenness and white spots have occurred in the toner image formed on the surface of the image carrier (photosensitive drum).

  The present invention has been made to solve the above-described problems. A developing device, a process cartridge, and the like in which a developing bias output from a power supply unit is applied to a rotating shaft portion of a developing roller well over time. Another object is to provide an image forming apparatus.

  The developing device according to the present invention is a developing device that develops a latent image formed on the surface of an image carrier, and faces or abuts the image carrier to carry a developer and is driven to rotate in a predetermined direction. The developing bias output from the power supply unit is applied to the rotating shaft part by directly or indirectly slidingly contacting the developing roller and the outer peripheral surface of the rotating shaft part of the developing roller by an elastic force. And an electrode terminal to be relayed.

  According to the present invention, it is possible to provide a developing device, a process cartridge, and an image forming apparatus in which the developing bias output from the power supply unit can be satisfactorily applied to the rotating shaft portion of the developing roller over time.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic view showing a process cartridge installed in the image forming apparatus. It is an enlarged view which shows a developing device. It is sectional drawing which looked at two developing rollers in a developing device in the longitudinal direction. It is a front view which shows the principal part of the longitudinal direction edge part in a developing device. It is a perspective view which shows the principal part of the longitudinal direction edge part in a developing device. FIG. 4 is an exploded perspective view showing a longitudinal end portion of a first developing roller. FIG. 10 is a perspective view showing a part where a second electrode terminal is installed by removing a part of the parts installed at the end in the longitudinal direction in the developing device. It is sectional drawing which shows the vicinity of the 1st ball bearing in a 1st developing roller. FIG. 10 is a front view illustrating a main part of a longitudinal end portion of a developing device as a first modification. FIG. 10 is a front view illustrating a main part of a longitudinal end portion of a developing device as a second modification.

Embodiment.
Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

First, the overall configuration and operation of the image forming apparatus 1 according to the embodiment will be described with reference to FIG.
The writing units 2A to 2D are devices for writing an electrostatic latent image on the photosensitive drum 21 (image carrier) after the charging process based on image information. The writing units 2A to 2D are optical scanning devices using polygon mirrors 3A to 3D, optical elements 4A to 4D, and the like. An LED array can be used as the writing unit instead of the optical scanning device.
The paper feeding unit 61 stores a recording medium P such as paper, and feeds the recording medium P toward the transfer belt 30 during image formation.

The transfer belt 30 is an endless belt for transferring the toner image formed on the photosensitive drum 21 onto the recording medium P by electrostatically attracting and transporting the recording medium P to the surface thereof. An adsorption roller 64 and a belt cleaner 65 are provided on the outer peripheral surface.
The transfer roller 24 that faces the photosensitive drum 21 via the transfer belt 30 includes a cored bar and a conductive elastic layer that covers the cored bar. The conductive elastic layer of the transfer roller 24 is prepared by blending and dispersing a conductive agent such as carbon black, zinc oxide or tin oxide in an elastic material such as polyurethane rubber or ethylene-propylene-diene polyethylene (EPDM). It is an elastic body whose (volume resistivity) is adjusted to medium resistance.

The fixing unit 66 includes a heating roller 68 and a pressure roller 67, and fixes the toner image on the recording medium P to the recording medium P by pressure and heat.
The four process cartridges 20Y, 20C, 20M, and 20BK arranged in the vertical direction along the transfer belt 30 are for forming toner images of yellow, cyan, magenta, and black, respectively.

On each process cartridge 20Y, 20C, 20M, and 20BK, an agent cartridge 28Y for supplying a carrier (magnetic carrier) and toner (toner particles) of each color (yellow, cyan, magenta, black) to the developing device 23, 28C, 28M, and 28BK are installed.
The process cartridges 20Y, 20C, 20M, and 20BK and the agent cartridges 28Y, 28C, 28M, and 28BK can be attached to and detached from the apparatus main body 1 by opening the transfer belt 30 around the rotation support shaft.

  The image forming apparatus 1 according to the present embodiment is a composite image forming apparatus that functions as a copier and a printer. When functioning as a copying machine, the image information read from the scanner is subjected to various image processing such as A / D conversion, MTF correction, gradation processing, etc., and converted into writing data. In the case of functioning as a printer, image processing is performed on image information in a format such as a page description language or a bitmap transmitted from a computer or the like, and converted into write data.

  At the time of image formation, exposure light corresponding to the image information of black, magenta, cyan, and yellow is irradiated from the writing units 2A to 2D to the process cartridges 20BK, 20M, 20C, and 20Y, respectively. That is, exposure light (laser light) emitted from each light source passes through the polygon mirrors 3A to 3D, the optical elements 4A to 4D, and is irradiated onto each photosensitive drum 21. Thus, a toner image corresponding to the exposure light is formed on the photosensitive drum 21 (image carrier) of each process cartridge 20BK, 20M, 20C, 20Y. Then, this toner image is transferred to the recording medium P.

  The recording medium P fed from the paper feeding unit 61 is transported to the position of the transfer belt 30 at the timing of the registration roller 63 and the timing. The suction roller 64 disposed at the transfer position of the transfer belt 30 causes the transfer medium 30 to suck the recording medium P that has been transferred by applying a voltage. The recording medium P that moves as the transfer belt 30 travels in the direction of the arrow sequentially passes through the positions of the process cartridges 20Y, 20C, 20M, and 20BK, and the toner images of the respective colors are superimposed and transferred.

  The recording medium P on which the color toner image is transferred is separated from the transfer belt 30 and reaches the fixing unit 66. The toner image on the recording medium P is fixed on the recording medium P by being heated while being sandwiched between the heating roller 68 and the pressure roller 67. On the other hand, the surface of the transfer belt 30 after the recording medium P is separated reaches the position of the belt cleaner 65, and dirt such as toner adhering to the surface is cleaned.

Next, the process cartridge and the agent cartridge in the image forming apparatus 1 will be described in detail.
The process cartridges 20Y, 20C, 20M, and 20BK have substantially the same structure, and the agent cartridges 28Y, 28C, 28M, and 28BK have substantially the same structure. The alphabet (Y, C, M, BK) is removed for illustration. In addition, the writing unit is illustrated by removing the alphabet (A to D).

As shown in FIG. 2, the process cartridge 20 includes a photosensitive drum 21 as an image carrier, a charging unit 22, a developing device 23 (developing unit), and a cleaning unit 25, and is a premix developing unit. System (development system in which carrier is replenished / discharged as appropriate) is adopted.
The photosensitive drum 21 as an image carrier is a negatively charged organic photosensitive member, and is rotationally driven counterclockwise by a rotation driving mechanism (not shown).

The charging unit 22 is a charging roller having elasticity, in which a medium-resistance foamed urethane layer in which a urethane resin, carbon black as conductive particles, a sulfurizing agent, a foaming agent, and the like are formed in a roller shape on a core metal. The material of the middle resistance layer of the charging unit 22 is urethane, ethylene-propylene-diene polyethylene (EPDM), butadiene acrylonitrile rubber (NBR), silicone rubber, isoprene rubber, etc. It is also possible to use a rubber material in which a conductive material such as the above is dispersed or a foamed material of these materials.
The cleaning unit 25 is provided with a cleaning brush (or cleaning blade) that is in sliding contact with the photosensitive drum 21, and mechanically removes and collects untransferred toner on the photosensitive drum 21.

  In the developing device 23, two developing rollers 23a1 and 23a2 as developer carrying members are arranged in parallel so as to face each other along the traveling direction (rotating direction) of the photosensitive drum 21, and the photosensitive drum 21 and the developing roller are arranged in parallel. A developing area where the photosensitive drum 21 and the magnetic brush are in contact with each other is formed in a portion facing 23a1 and 23a2. In the developing device 23, a developer G (two-component developer) composed of toner T and carrier C is accommodated. The developing device 23 develops the electrostatic latent image formed on the photosensitive drum 21 (forms a toner image). The configuration and operation of the developing device 23 will be described in detail later.

Here, the developing device 23 in the present embodiment is of a premix developing system, and a new carrier C (developer G) is appropriately supplied from the agent cartridge 28 into the developing device 23 and deteriorated. The developer G thus discharged is discharged toward the agent storage container 70 installed outside the developing device 23.
Referring to FIG. 2, the agent cartridge 28 accommodates developer G (toner T and carrier C) to be supplied into the developing device 23 therein. The agent cartridge 28 functions as a toner cartridge that supplies new toner T to the developing device 23, and also functions as a supply unit that supplies new carrier C to the developing device 23. Specifically, the shutter mechanism 80 is opened and closed based on information on the toner concentration (the ratio of the toner in the developer G) detected by a magnetic sensor (not shown) installed in the developing device 23. By performing the operation, the developer G is appropriately supplied from the agent cartridge 28 serving as a supply unit into the developing device 23. In the present embodiment, the mixing ratio (toner concentration) of the toner T with respect to the carrier C in the developer G of the agent cartridge 28 is set to be relatively high.
The supply pipe 29 is for reliably guiding the developer G (toner T and carrier C) supplied from the agent cartridge 28 into the developing device 23. That is, the developer G discharged from the agent cartridge 28 is supplied into the developing device 23 via the supply pipe 29.

Next, an image forming process performed on the photosensitive drum 21 will be described.
Referring to FIG. 2, when the photosensitive drum 21 is driven to rotate counterclockwise, the surface of the photosensitive drum 21 is first uniformly charged at the position of the charging unit 22 (this is a charging process). . Thereafter, the surface of the charged photosensitive drum 21 reaches the irradiation position of the exposure light L, and an exposure process by the writing unit 2 is performed. That is, by selectively removing the charge on the photosensitive drum 21 in accordance with the image information by irradiation with the exposure light L, a difference (potential contrast) from the potential of the non-image portion that has not been irradiated is generated, and electrostatic latent Form an image. In this exposure step, the charge generating material receives light in the photosensitive layer of the photosensitive drum 21 to generate charges, and among these holes, the holes cancel out the charged charges on the surface of the photosensitive drum 21. .

Thereafter, the surface of the photosensitive drum 21 on which the latent image is formed reaches a position facing the developing device 23. The electrostatic latent image on the photosensitive drum 21 comes into contact with the magnetic brush on the developing rollers 23a1 and 23a2, and the negatively charged toner T in the magnetic brush is attached and visualized (this is a developing process). .
Specifically, the developer G pumped up by the magnetic force generated by the magnetic poles of the first developing roller 23a1 located on the most upstream side of the developing region is adjusted to an appropriate amount by the doctor blade 23c as a developer regulating member, and then the photosensitive drum 21. Are conveyed to the first development area, which is a portion opposite to the first development area. Then, the carrier C spiked in the first development area rubs the photosensitive drum 21. At this time, the toner T mixed with the carrier C is negatively charged due to friction with the carrier C. On the other hand, the carrier C is positively charged. A predetermined developing bias (about −500 V) is applied to the first developing roller 23a1 from the power supply unit 50 (see FIG. 4). As a result, an electric field is formed between the first developing roller 23a1 and the photosensitive drum 21, and the negatively charged toner T is selectively attached only to the image portion on the photosensitive drum 21 by the electric field, and the toner image. Form.
On the other hand, the developer G carried on the first developing roller 23a1 located on the upstream side of the development area (the first development area and the second development area) passes through the first development area and then downstream of the development area. It is conveyed to a position (delivery part) facing the second developing roller 23a2 located on the side. The developer G carried on the first developing roller 23a1 is transferred (delivered) to the second developing roller 23a2 by the magnetic poles (delivery magnetic poles) of the two developing rollers 23a1 and 23a2 acting at this position. Thereafter, the developer G carried on the second developing roller 23 a 2 is conveyed to a second developing region which is a portion facing the photosensitive drum 21. Then, the carrier C spiked in the second developing area rubs the photosensitive drum 21. A predetermined developing bias (about −500 V) is applied to the second developing roller 23a2 from the power supply unit 50 (see FIG. 4). As a result, an electric field is formed between the second developing roller 23a2 and the photosensitive drum 21, and the negatively charged toner T is selectively attached only to the image portion on the photosensitive drum 21 by the electric field, and the toner image. Form.
As described above, the developing device 23 in the present embodiment is provided with the two developing rollers 23 a 1 and 23 a 2 and performs the developing process by the two developing areas formed between the photosensitive drum 21. Therefore, the development time can be made longer than in the case where the development process is performed by the development area by one development roller. Therefore, even when the developing rollers 23a1 and 23a2 are rotated at a high speed, a sufficient developing time can be secured and a toner image having a good image density can be formed.

Thereafter, the surface of the photosensitive drum 21 on which the toner image is formed reaches a position facing the transfer belt 30 and the transfer roller 24. Then, the toner image on the photosensitive drum 21 is transferred onto the recording medium P conveyed to the facing position in accordance with this timing. At this time, a predetermined voltage is applied to the transfer roller 24.
Thereafter, the recording medium P to which the toner image is transferred passes through the fixing unit 66 and is discharged from the discharge roller 69 to the outside of the apparatus.

On the other hand, toner T (untransferred toner) remaining on the photosensitive drum 21 without being transferred to the recording medium P during the transfer process reaches the portion facing the cleaning unit 25 while adhering to the photosensitive drum 21. The untransferred toner on the photosensitive drum 21 is removed and collected by the cleaning unit 25.
Thereafter, the surface of the photoconductive drum 21 passes through a static elimination unit (not shown), and a series of image forming processes on the photoconductive drum 21 is completed.

Hereinafter, the configuration and operation of the developing device 23 will be described in detail.
Referring to FIG. 3, the developing device 23 includes two developing rollers (a first developing roller 23 a 1 and a second developing roller 23 a 2) as developer carriers, and conveying screws 23 b 1 to 23 b 3 (conveying members). An auger screw), a doctor blade 23c as a developer regulating member, and the like. Further, in the developing device 23, three developer transport portions B1 to B3 that transport the developer G to form a circulation path are formed.

  Each of the two developing rollers 23a1 and 23a2 is formed by a developing mechanism 23a12 and 23a22 formed of a conductive / non-magnetic material such as aluminum, brass, stainless steel, and conductive resin in a cylindrical shape by a rotation driving mechanism described later. It is comprised so that it may rotate. In the developing sleeves 23a12 and 23a22 of the two developing rollers 23a1 and 23a2, a plurality of magnetic poles for carrying the developer G on the peripheral surfaces of the developing sleeves 23a12 and 23a22 as described above are formed, respectively. Magnets 23a11 and 23a21 are fixed. In particular, in the developing region and the vicinity thereof, the carrier C in the developer G rises in a chain shape on the developing sleeves 23a12 and 23a22 so as to follow the normal magnetic field lines emitted from the magnets 23a11 and 23a21. The charged toner T is attached to the carrier C that is spiked in a chain shape to form a magnetic brush. The magnetic brush is transferred in the same direction (clockwise) as the developing sleeves 23a12 and 23a22 by the rotation of the developing sleeves 23a12 and 23a22.

The doctor blade 23c as a developer regulating member is installed so that a minute gap (doctor gap) is formed between the first developing roller 23a1 and the first developing roller 23a1 on the upstream side of the developing region. The amount of developer is regulated to an appropriate amount.
The doctor blade 23c (developer regulating member) is a plate-like member made of a nonmagnetic metal material such as SUS316 or SUSXM7 having a plate thickness of about 2 mm, and is screwed onto the developing case 23k (case member). Yes.
In the present embodiment, as the doctor blade 23c, a magnetic metal plate such as SUS430 having a plate thickness of about 0.3 mm may be used on the surface facing the first developer transport unit B1.

Referring to FIG. 3, the three conveying screws 23 b 1 to 23 b 3 are each formed with a screw portion in a spiral shape on a shaft portion, and the developer G accommodated in the developing device 23 is disposed in the longitudinal direction (FIG. 3), while stirring and mixing.
The first transport screw 23b1 as the first transport member is disposed at a position facing the developing roller 23a1 in the first developer transport section B1, transports the developer G in the horizontal direction, and develops the developing roller. Developer 23a is supplied onto 23a1. In other words, the first developer transport unit B1 faces the developing roller 23a1 and supplies the developer G to the developing roller 23a1 while transporting the developer G in the longitudinal direction (the rotational axis direction of the developing roller 23a1).

The second transport screw 23b2 as the second transport member is installed in the second developer transport section B2. The second transport screw 23b2 is disposed below the first transport screw 23b1 and at a position facing the developing roller 23a2. Then, the developer G separated from the developing roller 23a2 (the developer G forcibly separated from the developing roller 23a2 by the agent separation pole after the developing step) is conveyed in the horizontal direction. In other words, the second developer transport unit B2 is disposed at a position below the first developer transport unit B1 and facing the developing roller 23a2, and the developer G detached from the developing roller 23a2 is disposed in the longitudinal direction. Transport in the direction.
The first transport screw 23b1 and the second transport screw 23b2 are arranged so that the rotation axis is substantially horizontal, like the developing rollers 23a1 and 23a2 and the photosensitive drum 21.

  The third transport screw 23b3 as the third transport member is installed in the third developer transport section B3. The third conveyance screw 23b3 is disposed obliquely with respect to the horizontal direction so as to linearly connect the downstream side of the conveyance path by the second conveyance screw 23b2 and the upstream side of the conveyance path by the first conveyance screw 23b1. Has been. The third transport screw 23b3 transports the developer G transported by the second transport screw 23b2 to the upstream side of the transport path by the first transport screw 23b1, and from the downstream side of the transport path by the first transport screw 23b1. The developer G circulated through the drop path is transported to the upstream side of the transport path by the first transport screw 23b1. In other words, the third developer transport unit B3 transports the developer G transported by the second developer transport unit B2 to the upstream side of the first developer transport unit B1, and also the first developer transport unit B1. The developer G that has reached the downstream side is transported to the upstream side of the first developer transport section B1.

A transport path (first developer transport section B1) by the first transport screw 23b1, a transport path by the second transport screw 23b2 (second developer transport section B2), and a transport path (first transport by the third transport screw 23b3). 3 developer transport section B3) is isolated from the wall.
The downstream side of the second developer transport unit B2 and the upstream side of the third developer transport unit B3 communicate with each other via the first relay unit. In addition, the downstream side of the third developer transport unit B3 and the upstream side of the first developer transport unit B1 communicate with each other via the second relay unit. In addition, the downstream side of the first developer transport unit B1 and the upstream side of the third developer transport unit B3 communicate with each other via a dropping path.

With such a configuration, a circulation path for circulating the developer G in the longitudinal direction in the developing device 23 is formed by the three developer conveying portions B1 to B3 (conveying screws 23b1 to 23b3).
Note that a magnetic sensor (not shown) as a toner concentration sensor is installed in the third developer conveyance unit B3. Then, based on the toner density information detected by the magnetic sensor, the developer G having a predetermined toner density is supplied from the agent cartridge 28 into the developing device 23. In the present embodiment, the toner concentration of the developer G in the developing device 23 is controlled to be 4 to 7% by weight.

  Here, referring to FIG. 2, a part of the developer G accommodated in the developing device 23 is discharged to the outside (agent storage container 70) on the wall portion of the first developer conveying portion B <b> 1. A discharge port 23d (discharge means) is provided. Specifically, the discharge port 23d is supplied with the developer G into the developing device 23 by the supply means 28 and 29, the developer amount in the device is increased, and the developer surface (upper surface) of the developer conveyed to that position. When the amount exceeds the predetermined height, the excess developer G is discharged toward the agent storage container 70. That is, the excess developer G exceeds the height below the discharge port 23d, is discharged from the discharge port 23d, and gravity falls toward the agent storage container 70 via the discharge path. As described above, the carrier deteriorated by being contaminated by the base resin or the external additive of the toner T is automatically discharged to the outside of the developing unit, so that deterioration of the image quality can be suppressed even over time.

Hereinafter, the configuration and operation of the developing device 23, which is characteristic in the present embodiment, will be described in detail with reference to FIGS.
As described above with reference to FIGS. 2 and 3 and the like, the developing device 23 according to the present embodiment carries the developer G so as to face the photosensitive drum 21 (image carrier) and in a predetermined direction. A first developing roller 23a1 is installed as a developing roller that is driven to rotate.
In detail, referring to FIG. 4, FIG. 5, etc., a coupling shaft 23e as a drive transmission member is installed on the rotation shaft portion 23a13 of the first developing roller 23a1 (developing sleeve 23a12), and this coupling 23e. A rotational driving force is transmitted from the outside by the (drive transmission member), and the rotation shaft portion 23a13 rotates together with the developing sleeve 23a12. The coupling 23e (drive transmission member) is connected to a driving cup installed on the rotation shaft of the developing drive motor installed in the image forming apparatus main body 1 in conjunction with the mounting operation of the developing apparatus 23 to the image forming apparatus main body 1. Mates to ring. Then, the rotational driving force is transmitted from the drive coupling of the development drive motor to the coupling 23e (drive transmission member), and the rotation shaft portion 23a13 is rotationally driven together with the development sleeve 23a12 in a predetermined direction.
Here, the coupling 23e is fixed with a parallel pin 23j inserted through a through hole 23a13a formed in the rotation shaft 23a13 of the first developing roller 23a1 with reference to FIGS. By doing so, it is configured to rotate together with the rotating shaft portion 23a13.

The rotating shaft portion 23a13 is made of a conductive material such as stainless steel, and is press-fitted and bonded to the longitudinal end portion of the cylindrical developing sleeve 23a12 (see FIG. 9 and the like).
The rotating shaft portion 23a1 is rotatably held by the developing case 23k through the first ball bearing 23p.
Further, a first gear 23f as a gear is installed on the rotation shaft portion 23a13 of the first developing roller 23a1. The first gear 23f is a gear for transmitting the rotational driving force transmitted by the coupling 23e (drive transmitting member) to the rotating shaft portion 23a23 (other rotating member) of the second developing roller 23a2. Specifically, when the developing sleeve 23a12 (rotating shaft 23a13) of the first developing roller 23a1 is rotationally driven by the developing drive motor, the idler gear 23h (see FIG. 4, the developing case) meshes with the first gear 23f. Through a stud standing on the side surface of 23k.) Via a second gear 23i (installed on the rotating shaft portion 23a23 of the second developing roller 23a2) that meshes with the idler gear 23h. The force is transmitted, and the developing sleeve 23a22 (rotating shaft portion 23a23) of the second developing roller 23a2 is rotationally driven.

  The second developing roller 23a2 and the first developing roller 23a1 are arranged side by side so as to face each other along the traveling direction of the photosensitive drum 21, and carry the developer G and rotate in a predetermined direction. The rotation shaft portion 23a23 of the second developing roller 23a2 is rotatably held by the developing case 23k via the second ball bearing 23q. The second developing roller 23a2 is configured in substantially the same manner as the first developing roller 23a1 except for the configuration of the magnetic poles of the magnet and members installed on the rotating shaft portion.

Here, referring to FIGS. 4 to 7, the developing device 23 in the present embodiment is in sliding contact with the outer peripheral surface of the rotation shaft portion 23 a 13 of the first developing roller 23 a 1 indirectly by an elastic force, A first electrode terminal 23m is provided as an electrode terminal (plate terminal) that relays the developing bias output from the power supply unit 50 so as to be applied to the rotary shaft portion 23a13.
Specifically, the first electrode terminal 23m is formed so as to come into contact with the rotation shaft portion 23a13 of the first developing roller 23a1 through the conductive sleeve 23g. The conductive sleeve 23g is a substantially cylindrical member formed of a metal material, and is in close contact with the rotary shaft portion 23a13 with reference to FIG. 5 to FIG. The formed engaging portion 23g1 is configured to engage with the parallel pin 23j inserted through the through hole 23a13a of the rotating shaft portion 23a13 and rotate together with the rotating shaft portion 23a13. Further, the other end in the longitudinal direction of the conductive sleeve 23g is positioned by the bush 23t press-fitted into the rotary shaft portion 23a13, and the conductive sleeve 23g moves in the longitudinal direction so that the engagement with the parallel pin 23j is not released. It is configured as follows.

On the other hand, the first electrode terminal 23m is formed of a metal material having a spring property such as phosphor bronze or stainless steel with reference to FIGS. A plate-like member (plate spring) of about ˜1 mm, which is fixed and held on the developing case 23k by a fixing screw (not shown). A contact portion 23m4 is formed on one end side of the first electrode terminal 23m, and the contact portion 23m4 is connected to a contact terminal installed in the image forming apparatus main body 1 so that the power supply unit of the image forming apparatus main body 1 is connected. A desired developing bias is applied from 50 to the first electrode terminal 23m through the contact portion 23m4 (and the contact terminal).
The other end side of the first electrode terminal 23m is formed so as to sandwich the rotating shaft portion 23a13 (conductive sleeve 23g). Specifically, the other end side of the first electrode terminal 23m is formed in a substantially U shape so that two first arm portions 23m1 having elastic force (plate spring force) are formed. The first sleeve 23g and the conductive sleeve 23g (rotating shaft portion 23a13) are electrically connected to each other by contacting the conductive sleeve 23g with the elastic force at the tip of the portion 23m1. Then, the developing bias output from the power supply unit 50 is applied to the rotation shaft portion 23a13 (developing sleeve 23a12) of the first developing roller 23a1 through the first electrode terminal 23m.

Thus, in this embodiment, even if the tip of the first electrode terminal 23m (or the conductive sleeve 23g) is worn over time due to the sliding contact with the conductive sleeve 23g (rotating shaft portion 23a13), A state in which the first electrode terminal 23m is in contact with the conductive sleeve 23g by an elastic force (plate spring force) without a gap or toner entering between the conductive sleeve 23g and the first electrode terminal 23m. Since it can always be maintained, it is possible to prevent poor contact (conductive failure) between the conductive sleeve 23g and the first electrode terminal 23m. Therefore, the developing bias output from the power supply unit 50 is always applied satisfactorily to the rotating shaft portion 23a13 of the first developing roller 23a1, and the toner image formed on the surface of the photosensitive drum 21 has density unevenness or A problem that an abnormal image such as a white spot is generated can be prevented in advance.
In particular, of the two developing rollers 23a1 and 23a2, the first developing roller 23a1 is able to rotate the rotating shaft portion 23a13 because the rotational driving force is directly transmitted (input) from the outside and easily vibrates during the rotational driving. Even if an attempt is made to apply the developing bias to the rotary shaft portion 23a13 via the bearing held on the inner surface, the inner peripheral surface of the bearing is worn over time, and contact failure is likely to occur. Therefore, the bias application mechanism using the first electrode terminal 23m in the present embodiment is useful.
In addition, since the bias applying mechanism using the first electrode terminal 23m in the present embodiment has a simple configuration as described above, the developing device 23 is not increased in size and cost.

Here, in the present embodiment, the first electrode terminal 23m (electrode terminal) contacts the conductive sleeve 23g and indirectly contacts the rotating shaft portion 23a13 in the vicinity of the coupling 23e (drive transmission member). It is arranged like this.
In the developing roller 23a1 of the two-component developing system composed of a magnet 23a11 that is fixed non-rotatingly and a developing sleeve 23a12 (rotating shaft 23a13) that rotates together with the coupling 23e, the developing sleeve 23a12 on which the developer G is carried is supported. In order to bring the electrode terminal 23m into contact with the rotating shaft portion 23a13 not bearing the developer G instead of the outer peripheral surface, the electrode terminal 23m is inevitably disposed in the vicinity of the coupling 23e. The position in the vicinity of the coupling 23e is particularly susceptible to vibration during rotational driving as described above. Therefore, the bias application mechanism using the first electrode terminal 23m in the present embodiment is useful.
In the present embodiment, the first electrode terminal 23m is not in direct contact with the rotating shaft portion 23a13, but the first electrode terminal 23m is connected to the rotating shaft portion 23a13 via the conductive sleeve 23g. Indirect contact. Such a configuration is a case where the material of the rotary shaft portion 23a13 is limited due to the press-fit adhesion processing with the developing sleeve 23a12, and the first electrode terminal 23m is directly brought into contact with the first sleeve 23m12. This is useful when the wear of the one electrode terminal 23m or the rotating shaft portion 23a13 is accelerated. That is, the conductive sleeve 23g has the main functions of conduction with the first electrode terminal 23m and fitting with the rotating shaft portion 23a13, so that the degree of freedom of selection of materials and shapes is increased. It becomes easy to form what is suitable for the bias application mechanism of the invention.

In the present embodiment, as described above, the first electrode terminal 23m is a plate-like member formed so as to sandwich the rotating shaft portion 23a13. Thus, by forming the first electrode terminal 23m so as to sandwich the rotating shaft portion 23a13, the contact of the first electrode terminal 23m with the rotating shaft portion 23a13 is further enhanced, and the above-described effects of the present invention are further enhanced. It will surely be demonstrated.
In the present embodiment, referring to FIGS. 6 and 7, etc., the first electrode terminal 23m is formed with a conductive brush 23m2 at a portion in contact with the rotating shaft portion 23a13. As the conductive brush 23m2, for example, a resin fiber such as polyester, nylon, rayon, acrylic, vinylon, vinyl chloride or the like mixed with a conductivity-imparting agent such as carbon and having a small friction coefficient is preferable. In this way, the conductive brush 23m2 is provided at the tip of the first electrode terminal 23m, and this is brought into contact with the rotary shaft portion 23a13, whereby wear due to the sliding contact between the first electrode terminal 23m and the rotary shaft portion 23a13. Can be reduced.

  Here, in the present embodiment, the developing bias output from the power supply unit 50 is also applied to the rotation shaft portion 23a23 (developing sleeve 23a22) of the second developing roller 23a2 via the first electrode terminal 23m. Has been. Specifically, the first electrode terminal 23m is in sliding contact with the end surface of the rotating shaft portion 23a23 of the second developing roller 23a2 by an elastic force, and the developing bias output from the power supply unit 50 is the rotating shaft of the second developing roller 23a2. It relays so that it may be applied to part 23a23.

  Specifically, referring to FIG. 6, FIG. 7 and the like, the first electrode terminal 23m extends to the end side in the longitudinal direction (a direction that coincides with the rotation axis direction of the second developing roller 23a2). In addition, a second arm portion 23m3 is formed. Then, due to the elastic force of the second arm portion 23m3, the end of the second arm portion 23m3 comes into contact with the end surface of the rotation shaft portion 23a23 of the second developing roller 23a2, so that the first electrode terminal 23m and the second developing roller The rotating shaft portion 23a13 of 23a2 is electrically connected. The developing bias output from the power supply unit 50 is applied to the rotating shaft portion 23a23 (developing sleeve 23a22) of the second developing roller 23a2 via the first electrode terminal 23m.

Thus, in this embodiment, even if the tip of the first electrode terminal 23m (or the rotation shaft portion 23a23) is worn over time due to sliding contact with the rotation shaft portion 23a23 of the second developing roller 23a2, A state in which the first electrode terminal 23m is in contact with the rotation shaft portion 23a23 by elastic force (plate spring force) without a gap or toner entering between the rotation shaft portion 23a23 and the first electrode terminal 23m. Since it can always be maintained, it is possible to prevent a contact failure (conduction failure) between the rotating shaft portion 23a23 and the first electrode terminal 23m. Accordingly, the developing bias output from the power supply unit 50 is always applied satisfactorily to the rotating shaft 23a23 of the second developing roller 23a2, and the toner image formed on the surface of the photosensitive drum 21 has density unevenness due to improper application. A problem that an abnormal image such as a white spot is generated can be prevented in advance.
In particular, of the two developing rollers 23a1 and 23a2, the second developing roller 23a2 is different from the first developing roller 23a1 because the rotational driving force is not directly input from the outside and the coupling 23e is not installed. The first electrode terminal 23m can be brought into contact with the end surface of the shaft portion 23a23. Since the end surface of the rotating shaft portion 23a23 is closer to the center of rotation, the linear velocity of rotation in the circumferential direction is reduced, the frictional resistance with the first electrode terminal 23m is reduced, and wear is reduced. Contact failure (conductivity failure) between the portion 23a23 and the first electrode terminal 23m is further less likely to occur.

  Note that the tip of the second arm 23m3 in the first electrode terminal 23m (the portion that is in contact with the end surface of the rotation shaft 23a23 of the second developing roller 23a2) is conductive like the tip of the first arm 23m1. It can also be formed with a sex brush. Thereby, wear due to sliding contact between the first electrode terminal 23m and the rotary shaft portion 23a23 can be reduced.

Here, referring to FIG. 4 and the like, the developing device 23 according to the present embodiment applies the developing bias to the two developing rollers 23a1 and 23a2 separately from the first electrode terminal 23m. A terminal 23n is provided. In other words, as the path for applying the developing bias to the developing rollers 23a1 and 23a2, the second electrode terminal 23n for complementing the first path is used in addition to the first path using the first electrode terminal 23m. A second path (which is based on a bias application mechanism of a different type from the first path) is formed.
Specifically, as shown in FIGS. 8 and 9, the developing bias output from the power supply unit 50 is applied to the rotating shaft portion 23a13 of the first developing roller 23a1 via the first ball bearing 23p (deep groove ball bearing 23p1). In addition, a second electrode terminal 23n that relays the second developing roller 23a2 so as to be applied to the rotating shaft portion 23a23 via the second ball bearing 23q (deep groove ball bearing) is provided.

Specifically, referring to FIG. 9 and the like, the first ball bearing 23p that rotatably holds the first developing roller 23a1 in the developing case 23k includes a deep groove ball bearing 23p1, a bearing case 23p2, a sealing material 23p3, and the like. Bearing unit. In the first ball bearing 23p, a deep groove ball bearing 23p1 and a seal material 23p3 are press-fitted in a bearing case 23p2 formed of a resin material or the like, and the inner ring 23p12 of the deep groove ball bearing 23p1 is a rotating shaft portion 23a13. And the bush 23t (fitted to the rotating shaft 23a13), the position in the longitudinal direction (the left-right direction in FIG. 9) is determined. In addition, the inner ring 23p12 of the deep groove ball bearing 23p1 is sandwiched by the bush 23t between the step of the rotary shaft portion 23a13 with a certain amount of pressure and thus the inner ring 23p12 is held by the rotary shaft portion 23a13. On the other hand, it is possible to reduce a problem that the inner peripheral surface is worn due to relative rotation.
The deep groove ball bearing 23p1 is a known one and includes an outer ring 23p11, an inner ring 23p12, a ball 23p13 (rolling element), and the like. These members 23p11, 23p12, and 23p13 are all made of a metal material, and the gap between them is filled with conductive grease, and a good conduction path is formed from the outer ring 23p11 to the inner ring 23p12 through the ball 23p13. It is comprised so that. Although not shown, a seal member is provided on the end face of the deep groove ball bearing 23p1, and is formed so that foreign matter such as toner does not enter inside.
With such a configuration, when a developing bias is input from the second electrode terminal 23n contacting the outer ring 23p11 of the deep groove ball bearing 23p1, the developing bias is applied to the rotating shaft portion 23a13 via the ball 23p13 and the inner ring 23p12. Will be.
Further, the sealing material 23p3 is a known sealing material such as a G seal, and is configured so that foreign matters such as toner floating inside the developing device 23 are not mixed into the first ball bearing 23p.
The second ball bearing 23q that rotatably holds the second developing roller 23a2 in the developing case 23k is configured in the same manner as the first ball bearing 23p.

On the other hand, the second electrode terminal 23n is formed of a metal material such as phosphor bronze or stainless steel and has a thickness of about 0.1 to 1 mm with reference to FIGS. And is fixed and held on the developing case 23k by a fixing screw 51. A contact portion 23n1 is formed on one end side of the second electrode terminal 23n, and the contact portion 23n1 is connected to a contact terminal installed in the image forming apparatus main body 1 so that the power supply portion of the image forming apparatus main body 1 is connected. A desired developing bias is applied from 50 to the second electrode terminal 23n through the contact portion 23n1 (and the contact terminal).
The main surface of the second electrode terminal 23n is formed so as to be in surface contact with the outer ring 23p11 of the first ball bearing 23p (deep groove ball bearing 23p1) and the outer ring of the second ball bearing 23q (deep groove ball bearing). Has been. The developing bias output from the power supply unit 50 is transferred from the first ball bearing 23p (deep groove ball bearing 23p1) to the rotating shaft 23a13 (developing sleeve 23a12) of the first developing roller 23a1 via the second electrode terminal 23n. It is applied and applied from the second ball bearing 23q (deep groove ball bearing) to the rotating shaft 23a23 (developing sleeve 23a22) of the second developing roller 23a2.
In the present embodiment, the second electrode terminal 23n presses the first ball bearing 23p and the second ball bearing 23q from the end in the longitudinal direction so that the first ball bearing 23p and the second ball bearing 23q It also functions as a presser plate (regulating member) that restricts the thrust movement toward the longitudinal end.

  As described above, in the present embodiment, as a path for applying the developing bias to the developing rollers 23a1 and 23a2, the second path using the second electrode terminal 23n in addition to the first path using the first electrode terminal 23m. Therefore, even if a conduction failure occurs in any of the paths, it is possible to reliably apply the developing bias to the developing rollers 23a1 and 23a2. In addition, since the first path and the second path are formed by different bias application mechanisms, continuity failure does not occur at the same timing due to the same phenomenon.

In the present embodiment, the conductive sleeve 23g and the first gear 23f are configured as separate members.
On the other hand, as a first modification, as shown in FIG. 10, a sleeve portion 23f1 as a conductive sleeve is formed integrally with the first gear 23f, and the first electrode terminal 23m is coupled to the coupling 23e (drive transmission). Member) and the first gear 23f may be disposed so as to contact the sleeve portion 23f1 (conductive sleeve). In that case, the first gear 23f in which the sleeve portion 23f1 is integrated is formed of a conductive material such as a conductive resin material or a metal material.
And even if it is a case where it comprises in this way, the effect similar to the thing of this Embodiment can be acquired.

Moreover, in this Embodiment, it comprised so that the 1st electrode terminal 23m might contact | abut indirectly to the rotating shaft part 23a13 via the electroconductive sleeve 23g.
On the other hand, as a second modification, as shown in FIG. 11, the first electrode terminal 23m may be configured to directly contact the rotating shaft portion 23a13 without the conductive sleeve 23g. In that case, it is preferable to restrict the thrust movement of the first gear 23f by installing a retaining ring 23s such as an E ring so that the first gear 23f does not move toward the end in the longitudinal direction.
And even if it is a case where it comprises in this way, the effect similar to the thing of this Embodiment can be acquired. In particular, when the restrictions on the material and shape of the rotating shaft portion 23a13 are not a problem as described above, the number of parts can be reduced by performing such a configuration.

As described above, in the present embodiment, the output from the power supply unit 50 is brought into sliding contact with the outer peripheral surface of the rotation shaft portion 23a13 of the first developing roller 23a1 (developing roller) directly or indirectly by elastic force. A first electrode terminal 23m (electrode terminal) that relays the developed developing bias so as to be applied to the rotary shaft portion 23a13 is provided.
As a result, the developing bias output from the power supply unit 50 can be satisfactorily applied to the rotating shaft 23a13 of the first developing roller 23a1 over time.

  In the present embodiment, the present invention is applied to the developing device 23 in which two developing rollers 23a1 and 23a2 are installed. However, the present invention is also applied to a developing device in which one or more developing rollers are installed. Of course, the present invention can be applied. Even in this case, as in the present embodiment, the electrode terminal is brought into contact with the outer peripheral surface of the rotating shaft portion of the developing roller to which the rotational driving force is input from the outside by an elastic force, thereby The same effects as those can be obtained.

In the present embodiment, the present invention is applied to the premix developing type developing device 23. However, the developing device is not a premix developing type (a developing device in which toner is supplied instead of a two-component developer). For example, the developing device disclosed in Japanese Patent Application Laid-Open No. 2007-241149 is also applicable to the present invention.
Further, in the present embodiment, the present invention is applied to the developing device 23 in which three developer conveying units B1 to B3 are installed. However, the development in which two or less developer conveying units or four or more developer conveying units are installed. The present invention can also be applied to an apparatus.
Further, in the present embodiment, the developing device in which the upstream developing roller 23a1 is disposed above the downstream developing roller 23a2 and the doctor blade 23c is disposed to face the upstream developing roller 23a1. The present invention was applied to 23. On the other hand, the present invention is also applied to a developing device in which the upstream developing roller is installed below the downstream developing roller and the doctor blade is installed so as to face the upstream developing roller. Can be applied.
Even in those cases, the same effects as in the present embodiment can be obtained.

Further, in the present embodiment, the present invention is applied to the developing device 23 of the two-component developing system. The present invention can also be applied to a one-component developing type developing apparatus using the above. In that case, in addition to the non-contact type in which the developing roller is opposed to the photosensitive drum (image carrier) with a slight gap, the developing roller is in contact with the photosensitive drum (image carrier). Of course, the present invention can be applied to the above.
Even in those cases, the same effects as in the present embodiment can be obtained.

Further, in the present embodiment, the present invention is applied to an image forming apparatus in which a part of the image forming unit is configured by the process cartridge 20. However, the application of the present invention is not limited to this, and the present invention can naturally be applied to an image forming apparatus in which the image forming unit is not formed into a process cartridge. Specifically, the present invention can naturally be applied even when the developing device 23 is configured as a unit that is detachably attached to the image forming apparatus main body.
In the present application, the “process cartridge” refers to a charging unit that charges the image carrier, a developing unit (developing device) that develops a latent image formed on the image carrier, and a cleaning on the image carrier. It is defined as a unit in which at least one of the cleaning units and the image carrier are integrated and installed detachably with respect to the image forming apparatus main body.

  It should be noted that the present invention is not limited to the present embodiment, and it is obvious that the present embodiment can be modified as appropriate within the scope of the technical idea of the present invention, other than suggested in the present embodiment. is there. In addition, the number, position, shape, and the like of the constituent members are not limited to the present embodiment, and the number, position, shape, and the like suitable for implementing the present invention can be achieved.

1 image forming apparatus (image forming apparatus main body),
20, 20Y, 20C, 20M, 20BK Process cartridge,
21 Photosensitive drum (image carrier),
23 Development device,
23a1 first developing roller (developing roller),
23a11 magnet,
23a12 Development sleeve,
23a13 Rotating shaft (drive shaft),
23a13a through hole,
23a2 second developing roller,
23a23 rotating shaft,
23c Doctor blade (developer regulating member),
23e coupling (drive transmission member),
23f 1st gear (gear),
23f1 sleeve (conductive sleeve),
23g conductive sleeve,
23g1 engaging portion,
23h idler gear,
23i 2nd gear,
23j parallel pins,
23k development case,
23m first electrode terminal (electrode terminal),
23m1 first arm,
23m2 conductive brush (contact part),
23m3 second arm,
23n second electrode terminal (presser plate),
23p first ball bearing,
23p1 deep groove ball bearings,
23p2 bearing case,
23p3 sealing material,
23p11 outer ring, 23p12 inner ring, 23p13 ball,
23q 2nd ball bearing,
23s retaining ring,
23t bush,
50 power supply,
51 fixing screws,
G developer (two-component developer), T toner, C carrier.

Japanese Patent No. 5428908

Claims (9)

A developing device for developing a latent image formed on the surface of an image carrier,
A developing roller which faces or abuts the image carrier and carries a developer and is driven to rotate in a predetermined direction;
An electrode terminal that is directly or indirectly slidably brought into contact with the outer peripheral surface of the rotating shaft portion of the developing roller by an elastic force and relays the developing bias output from the power supply unit to the rotating shaft portion. ,
A developing device comprising: A drive transmission member installed on the rotation shaft portion of the developing roller, wherein a rotation driving force is transmitted from the outside to rotate the rotation shaft portion;
The developing device according to claim 1, wherein the electrode terminal is disposed so as to directly or indirectly contact the rotating shaft portion in the vicinity of the drive transmission member.   The said electrode terminal is a plate-shaped member formed so that the said rotating shaft part may be pinched | interposed, Comprising: The part contact | abutted to the said rotating shaft part was formed with the electroconductive brush. 2. The developing device according to 2.   The developing device according to claim 1, wherein the electrode terminal is formed so as to abut on the rotating shaft portion via a conductive sleeve. A drive transmission member installed on the rotary shaft portion of the developing roller, wherein a rotational driving force is transmitted from the outside to rotate the rotary shaft portion;
A gear installed on the rotating shaft of the developing roller for transmitting the rotational driving force transmitted by the drive transmitting member to another rotating member;
With
The conductive sleeve is formed integrally with the gear;
The developing device according to claim 4, wherein the electrode terminal is disposed so as to contact the conductive sleeve between the drive transmission member and the gear. A second developing roller, which is arranged in parallel with the first developing roller as the developing roller so as to face each other along the traveling direction of the image carrier, and carries a developer and rotates in a predetermined direction;
A drive transmission member installed on the rotary shaft portion of the first developing roller to transmit a rotational driving force from the outside to rotate the rotary shaft portion;
A gear that is installed on the rotation shaft portion of the first developing roller and transmits the rotation driving force transmitted by the drive transmission member to the rotation shaft portion of the second developing roller;
A first ball bearing for rotatably holding the first developing roller;
A second ball bearing for rotatably holding the second developing roller;
The developing bias output from the power supply unit is applied to the rotating shaft portion of the first developing roller through the first ball bearing, and the rotating shaft of the second developing roller through the second ball bearing. A second electrode terminal that is relayed to be applied to the portion;
The developing device according to claim 1, further comprising: A second developing roller, which is arranged in parallel with the first developing roller as the developing roller so as to face each other along the traveling direction of the image carrier, and carries a developer and rotates in a predetermined direction;
A drive transmission member installed on the rotary shaft portion of the first developing roller to transmit a rotational driving force from the outside to rotate the rotary shaft portion;
A gear that is installed on the rotation shaft portion of the first developing roller and transmits the rotation driving force transmitted by the drive transmission member to the rotation shaft portion of the second developing roller;
A second gear, which is installed on a rotation shaft portion of the second developing roller, to which a rotational driving force transmitted from the gear of the first developing roller via an idler gear is transmitted;
With
The electrode terminal is in sliding contact with the end surface of the rotating shaft portion of the second developing roller by an elastic force so that the developing bias output from the power supply unit is applied to the rotating shaft portion of the second developing roller. The developing device according to claim 1, wherein the developing device is relayed to each other. A process cartridge that is detachably installed on the main body of the image forming apparatus,
8. A process cartridge, wherein the developing device according to claim 1 and the image carrier are integrated.   An image forming apparatus comprising the developing device according to claim 1 and the image carrier.

Images