JP2012022174A - Developing device and image forming apparatus - Google Patents

Abstract

To reduce toner accumulated on a regulating member or developer accumulated on the back side of a regulating member on the upstream side of the developer conveying direction of the developing roller, and to stabilize the amount of developer regulated on the developing roller. By doing so, a sufficient amount of developer is supplied to the nip portion between the developing roller and the photosensitive drum, and the reduction in image density is reduced.
A developer carrying a developer comprising a toner and a magnetic carrier is carried on the surface and rotated, and the toner is supplied to the latent image on the surface of the image carrier at a position facing the image carrier and developed. And a developer regulating member 23c disposed opposite to the surface of the developer carrying body and regulating the thickness of the developer on the surface of the developer carrying body. The problem is solved by installing a rotatable stirring member 23m for stirring the developer on the back side of the developer regulating member on the upstream side of the developer in the developer transport direction.
[Selection] Figure 3

Description

  The present invention relates to a developing device and an image forming apparatus used in an image forming apparatus such as a copying machine, a facsimile machine, and a printer.

  A developing device used in an electrophotographic image forming apparatus includes a magnet having a plurality of fixed magnetic poles, a developing roller that carries a developer including a magnet and a toner and a carrier, and conveys the developer. It is often used in recent years. A regulating member such as a doctor blade that regulates the amount of developer on the developing roller is installed in the vicinity of the developing roller, and this regulating member plays a role of making the amount of developer conveyed by the developing roller constant. As described above, a technique for regulating the amount of developer conveyed by the developing roller to a certain amount by the regulating member is already known.

  However, in the conventional technology that regulates the developer amount on the developing roller by the regulating member, the toner or developer adhered to the tip of the regulating member or the development accumulated on the back side of the regulating member on the upstream side in the developer conveying direction of the developing roller. The developer reduces the amount of developer on the developing roller after passing through the regulating member compared to the initial use, so that a sufficient amount of developer is not supplied to the nip portion between the developing roller and the photosensitive drum, and the developer on the photosensitive drum There is a problem that the image density is lowered due to insufficient amount of the developer.

  In Patent Document 1, in order to remove toner or developer attached to the front and back sides of a doctor blade, an operator enters a cleaning member into a gap between the developing roller and the doctor blade, and the cleaning member is moved along the gap. To remove the toner or developer attached to the doctor blade. However, maintenance by the operator is necessary, and it is difficult to prevent the developer from accumulating on the back side of the doctor blade.

  Therefore, the present invention reduces the amount of developer regulated on the developing roller by reducing the toner or developer adhering to the doctor blade, or the developer accumulated on the back side of the doctor blade on the upstream side in the developer conveying direction of the developing roller. The purpose of this is to supply a sufficient amount of developer to the nip portion between the developing roller and the photosensitive drum, thereby reducing the decrease in image density.

  According to the present invention, according to the present invention, a developer composed of toner and a magnetic carrier is carried on the surface and rotated, and the toner is supplied to the latent image on the surface of the image carrier at a position facing the image carrier. A developing device having a developer carrying member to be developed and a developer regulating member disposed to face the surface of the developer carrying member and regulating the thickness of the developer on the surface of the developer carrying member. This is solved by providing a rotatable stirring member for stirring the developer on the back side of the developer regulating member on the upstream side in the developer transport direction of the developer carrying member.

Moreover, it is preferable that the stirring member includes a shaft portion and a screw portion that spirally extends on the shaft portion.
Further, a developer conveying member that supplies the developer to the developer carrying member while stirring and conveying the developer in the longitudinal direction is provided, and the stirring member is in the same direction as the developer conveying direction of the developer conveying member It is preferable to transport the developer.

The stirring member preferably includes a shaft portion and a blade portion extending linearly outward from the shaft portion in the radial direction.
Further, this problem is solved by the present invention by an image forming apparatus provided with the above-described developing device.

  Toner that adheres to the tip of the doctor blade by installing a stirring member that stirs the developer behind the doctor blade on the upstream side in the developer conveyance direction of the developing roller and moves the developer on the back side of the doctor blade by rotating the stirring member Alternatively, the developer and the developer accumulated on the back side of the doctor blade on the upstream side in the transport direction of the developer on the developing roller can be prevented or destroyed. Therefore, the toner or developer adhering to the tip of the doctor blade and the developer accumulated on the back side of the doctor blade are reduced, and the amount of developer regulated by the doctor blade is the original thickness corresponding to the gap between the doctor blade and the developing roller. Therefore, a sufficient amount of developer can be conveyed to the nip portion between the developing roller and the photosensitive drum to reduce a decrease in image density.

1 is a schematic configuration diagram of an image forming apparatus according to the present invention. FIG. 2 is an enlarged view of a process cartridge and an agent cartridge of the image forming apparatus in FIG. 1. FIG. 2 is a schematic cross-sectional view of a developing device installed in a process cartridge. FIG. 4 is a longitudinal sectional view of the developing device when a developer circulation path in the developing device is viewed from the direction of an arrow X in FIG. 3. It is a schematic block diagram of the developing device which shows the state of the developer accumulated on the back side of the doctor blade. It is a figure which shows the developer conveyance amount on the developing roller after passing through a doctor blade when the developing device is provided with a stirring member. It is a schematic perspective view which shows other embodiment of a stirring member.

The image forming apparatus according to the present invention will be described below.
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention. Write units 2 </ b> A to 2 </ b> D are arranged in the apparatus main body 1. The writing units 2A to 2D are devices for writing an electrostatic latent image on the photosensitive drum (image carrier) 21 after the charging process by the charging unit 22 based on image information, and include polygon mirrors 3A to 3D and optical elements. This is an optical scanning device configured to include 4A to 4D and the like. An LED array can be used as the writing unit instead of the optical scanning device.
A paper feeding unit 61 is provided in the lower part of the apparatus main body 1, stores a transfer material P such as recording paper or OHP, and feeds the transfer material P toward the transfer belt 30 during image formation.

A transfer belt 30 is provided in the apparatus main body 1 in the vertical direction. The transfer belt 30 is an endless belt for transferring the toner image formed on the photosensitive drum 21 onto the transfer material P by electrostatically attracting the transfer material P to the surface thereof and transporting it. The suction roller 64 and the belt cleaner 65 are provided on the outer peripheral surface.
A transfer roller 24 is provided to face the photosensitive drum 21 with the transfer belt 30 interposed therebetween, and 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.

A fixing unit 66 is provided on the upper portion of the apparatus main body 1, and includes a heating roller 68 and a pressure roller 67. Fix to the transfer material P.
Four process cartridges 20Y, 20C, 20M, and 20BK are arranged in the vertical direction along the transfer belt 30 to form yellow, cyan, magenta, and black toner images, respectively.

Above each of the process cartridges 20Y, 20C, 20M, and 20BK, an agent as a supply unit that supplies a carrier (magnetic carrier) and toner (toner particles) of each color (yellow, cyan, magenta, black) to the developing device 23. Cartridges 28Y, 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 in this embodiment is a composite image forming apparatus that functions as a copying machine and a printer. When functioning as a copier, the image information read from a scanner (not shown) is subjected to various image processing such as A / D conversion, MTF correction, gradation processing, etc., and converted into write data. . On the other hand, when functioning as a printer, image processing is performed on image information in a format such as a page description language or a bit map 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 3 </ b> A to 3 </ b> D, the optical elements 4 </ b> A to 4 </ b> D, and is irradiated onto each photosensitive drum 21. As a result, toner images corresponding to the exposure light are formed on the photosensitive drums 21 of the process cartridges 20BK, 20M, 20C, and 20Y. The toner image is transferred to the transfer material P.

  Next, the copying operation of this image forming apparatus will be described. When copying is started, the transfer material P in the paper feed unit 61 is fed by the rotation of the paper feed roller 62. The fed material P to be transferred abuts against the registration roller 63 and temporarily stops. At this time, bending is formed and the skew of the material P to be transferred is corrected. Next, the transfer material P is conveyed to the position of the transfer belt 30 in time. The suction roller 64 disposed at the feeding position of the transfer belt 30 causes the transfer belt 30 to suck the material to be transferred P fed by voltage application. The transfer material 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 transferred onto the transfer material P in an overlapping manner. The

  The material P to 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 transfer material P is fixed on the transfer material 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 transfer material 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 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).

Next, the process cartridge 20 and the agent cartridge 28 installed in the apparatus main body 1 will be described.
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 as a developing unit, and a cleaning unit 25.・ A premix development system that can discharge properly is adopted. The photoreceptor drum 21 is a negatively charged organic photoreceptor, and is rotationally driven counterclockwise by a rotation drive 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 includes urethane, ethylene-propylene-diene polyethylene (EPDM), butadiene acrylonitrile rubber (NBR), silicone rubber, isoprene rubber, etc., carbon black and metal oxide for resistance adjustment. 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 disposed so as to be close to the photosensitive drum 21, and the photosensitive drum 21 and the magnetic brush are in contact with each other at both opposing portions. A development area is formed. The developing device 23 contains a developer G (two-component developer) composed of toner T and carrier C, and the developing device 23 develops an electrostatic latent image formed on the photosensitive drum 21. That is, a toner image is formed. The configuration and operation of the developing device 23 will be described in detail later.

  Here, the developing device 23 in the present embodiment employs the premix developing method as described above, and a new carrier C or developer G is appropriately supplied from the agent cartridge 28 into the developing device 23. The deteriorated developer G is discharged toward the agent storage container 70 installed outside the developing device 23.

  As shown in FIG. 2, the agent cartridge 28 contains 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 opening / closing operation of the shutter mechanism 80 based on the toner density information, which is the ratio of the toner T in the developer G, detected by the magnetic sensor 26 (see FIG. 4) installed in the developing device 23. Then, the developer G is appropriately supplied from the agent cartridge 28 as supply means toward 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) 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 through 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. Thereafter, the surface of the charged photosensitive drum 21 reaches the irradiation position of the exposure light L, and the 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 generation 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 by the developer G on the developing rollers 23a1 and 23a2, and the negatively charged toner T in the magnetic brush is attached and visualized.
In detail, the developer G pumped up by the magnetic force of the magnetic pole of the upper developing roller 23a1 is a doctor blade installed facing the developing roller 23a1, and the developer thickness on the surface of the developing roller 23a1 is determined. After being adjusted to an appropriate amount by the doctor blade 23c to be regulated, it is conveyed to a developing region (a region where the two developing rollers 23a1, 23a2 and the photosensitive drum 21 are opposed to each other) that is a portion facing the photosensitive drum 21. The carrier C spiked in the development area rubs the photosensitive drum 21. At this time, the toner T mixed with the carrier C is negatively charged by friction with the carrier C, whereas the carrier C is positively charged. A predetermined developing bias is applied to the developing rollers 23a1 and 23a2 from a power supply unit (not shown). As a result, an electric field is formed between the developing rollers 23a1 and 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.

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 transfer material P conveyed to the opposite position in accordance with this timing. At this time, a predetermined voltage is applied to the transfer roller 24.
Thereafter, the transfer material P onto which the toner image has been transferred passes through the fixing unit 66 to fix the toner image, and is discharged from the discharge roller 69 to the outside of the apparatus.

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

Next, the configuration and operation of the developing device 23 will be described in detail.
3 is a schematic cross-sectional view of the developing device 23 installed in the process cartridge 20, and FIG. 4 is a drawing of the developer circulating path in the developing device 23 in the longitudinal direction of the developing device as viewed from the direction of the arrow X in FIG. It is sectional drawing.
As shown in FIG. 3, the developing device 23 includes a developing roller 23a1, 23a2 as a developer carrying member, a conveying screw 23b1, 23b2, 23b3 as a developer conveying member, a doctor blade 23c as a developer regulating member, and a developer. It is comprised with the discharge screw 23n etc. which discharge | emit. Further, in the developing device 23, three developer conveying portions B1, B2, and B3 that convey the developer G and form a developer circulation path are formed.

  The developing rollers 23a1 and 23a2 are configured such that an outer sleeve formed of a nonmagnetic material such as aluminum, brass, stainless steel, or conductive resin in a cylindrical shape is rotated clockwise by a rotation driving mechanism (not shown). ing. In the sleeves of the developing rollers 23a1 and 23a2, a magnet for forming a magnetic field is fixed so as to cause the developer G to rise on the peripheral surface of the sleeve. The carrier C in the developer G rises in a chain shape on the sleeve so as to follow the normal magnetic field lines emitted from the magnet. 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 sleeve by the rotation of the sleeve.

The doctor blade 23c is installed on the upstream side of the developing area, and regulates the developer on the first developing roller 23a1 to an appropriate amount.
The three transport screws 23b1, 23b2, and 23b3 are each composed of a shaft portion and a screw portion that is formed in a spiral shape on the shaft portion. Stir and mix while circulating in the vertical direction.

  The first conveying screw 23b1 as the first conveying member is disposed in the first developer conveying portion B1 at a position facing the developing roller 23a1, and the developer G is moved leftward as indicated by the white arrow in FIG. While being transported in the horizontal direction, the developer 23a is supplied onto the developing roller 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 (rotational axis direction of the developing roller 23a1).

The second transport screw 23b2 as the second transport member is disposed in the second developer transport section B2 at a position below the first transport screw 23b1 and facing the developing roller 23a2. The second transport screw 23b2 transports the developer G forcibly separated from the developing roller 23a2 by the agent separation pole of the magnet after the development process in the horizontal direction in the left direction indicated by the white arrow in FIG. 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 located on the side of the second developer transport section B2. As shown in FIG. 4, the third transport screw 23b3 is arranged in the horizontal direction so as to linearly connect the downstream side of the transport path by the second transport screw 23b2 and the upstream side of the transport path by the first transport member 23b1. It is arrange | positioned diagonally with respect to it. 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 member 23b1, and from the downstream side of the transport path by the first transport screw 23b1. The developer G circulated through the drop path 23f is transported to the upstream side of the transport path by the first transport member 23b1 (the transport is obliquely upward to the right indicated by the white arrow in FIG. 4). 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 by a wall section.

  As shown in FIG. 4, 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 23g. Further, the downstream side of the third developer transport unit B3 and the upstream side of the first developer transport unit B1 are communicated with each other via the second relay unit 23h. In addition, the downstream side of the first developer transport unit B1 and the upstream side of the third developer transport unit B3 are communicated with each other through a drop path 23f.

  With such a configuration, a developer 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 and the conveying screws 23b1 to 23b3. Here, when the developing device 23 is operated, the developer accommodated in the device flows in a state as indicated by the oblique lines in FIG. Here, in the first developer conveying section B1, the developer surface on the downstream side is lower than the upstream agent surface. Part of the developer being conveyed is supplied to the developing roller 23a1. It is because it has been. Then, the developer that has not been supplied to the developing roller 23a1 moves to the upstream side of the third developer conveying portion B3 via the dropping path 23f.

  Note that a magnetic sensor 26 as a toner concentration sensor is installed in the third developer conveying portion B3. Then, based on the toner density information detected by the magnetic sensor 26, a developer G having a predetermined toner density is supplied from the agent cartridge 28 serving as a supply unit into the developing device 23. In the present embodiment, the toner density of the developer G in the developing device 23 is controlled to be 5 to 10% by weight.

  4 and 2, a part of the developer G accommodated in the developing device 23 is discharged to the external agent storage container 70 on the wall portion of the first developer conveying portion B1. A discharge port 23d1 is provided. Specifically, the discharge port 23d1 is supplied with the developer G into the developing device 23 by the supply means 28 and 29, the amount of the developer in the device increases, and the developer surface (upper surface) exceeds the predetermined height. When this occurs, 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 23 d 1, is discharged from the discharge port 23 d 1, and is conveyed toward the agent storage container 70 via the discharge path 71. 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.

Although not shown in FIGS. 2 and 4, etc., as shown in FIG. 3, a discharge screw for conveying the developer discharged from the discharge port 23d1 in the discharge path 71 in the horizontal direction is provided. 23n is installed.
In the present embodiment, the outer diameters of the developing rollers 23a1 and 23a2 are 30 mm, the linear velocity on the outer peripheral surface of the developing rollers 23a1 and 23a2 is 748 mm / second, the linear velocity on the outer peripheral surface of the photosensitive drum 21, and the material to be transferred. The process linear velocity, which is the conveyance speed of P, is set to 440 mm / second, and the rotation speeds of the conveyance screws 23b1, 23b2, and 23b3 are set to about 500 to 600 rpm.

  In such a developing device, the developer flow in the vicinity of the doctor blade 23c may stay, the developer may be condensed, and the amount of developer supplied onto the developing roller 23a1 may be reduced. FIG. 5 is a schematic cross-sectional view taken along the line Y1-Y1 in FIG. 4 and shows a state in which the developer 27 has condensed and accumulated on the back side of the doctor blade where the developer flow tends to stay. Since the conveying force due to the rotation of the developing roller 23a1 is small in the upper layer portion of the developing roller 23a1 on the back side of the doctor blade, the developer is difficult to move. Then, the developer aggregates and accumulates due to a rise in temperature of the developing device, and when printing is repeated, the developer accumulates and develops in the accumulated developer, so that the developer roller 23a1 develops before passing through the doctor blade. The amount of developer to be transported is reduced. Although not shown in the drawing, the developer also aggregates at the tip of the doctor blade, the gap between the doctor blade 23c and the developing roller 23a1 becomes narrow, and the amount of developer conveyed by the developing roller 23a1 before passing through the doctor blade is reduced. It will be reduced.

  Therefore, in the present invention, a rotatable stirring member 23m is installed in the vicinity of the doctor blade 23c to stir the developer. As shown in FIG. 3, the developer is placed on the back side of the doctor blade 23c in the vicinity of the transport screw 23b1 where the developer flow tends to stay, and upstream of the developer roller 23a1 in the developer transport direction. A rotatable stirring member 23m is provided for stirring. The stirring member 23m is formed of a shaft portion and a screw portion extending spirally on the shaft portion, similarly to the transport screw, and the drive of the transport screw is transmitted to the stirring member via a gear (not shown). Has been rotated. In addition, the stirring member 23m is disposed in the developing device so that the rotation axis is substantially horizontal, similarly to the first transport screw 23b1 and the second transport screw 23b2.

  By rotating and stirring the developer on the back side of the doctor blade 23c by rotating the stirring member 23m, it is possible to prevent or collapse the developer on the back side of the doctor blade on the upstream side in the developer transport direction of the developing roller. Further, since the stirring member 23m has a spiral screw portion, in addition to the movement of the developer in the longitudinal direction of the stirring member 23m, the developer can be moved in the radial direction. Thereby, the flow of the developer near the tip of the doctor blade 23c can also be fluidized, and the aggregation of the developer at the tip of the doctor blade 23c can be avoided.

  Thus, the developer on the back side of the doctor blade 23c is forcibly moved by the stirring of the developer by the stirring member 23m to prevent or collapse the developer, and the original developing roller 23a1 and the doctor blade The predetermined gap of 23c can be ensured, and the function of regulating the developer amount of the doctor blade 23c can be stably maintained.

  FIG. 6 is a diagram showing the developer conveyance amount on the developing roller 23a1 after passing through the doctor blade 23c when the developing device is provided with the stirring member 23m and when it is not provided. Without the stirring member 23m, as described above, the developer agglomerates and accumulates at the front and back sides of the doctor blade, and when the number of printed sheets increases, the developer conveyance amount on the developing roller after passing through the doctor blade is reduced. On the other hand, when the stirring member 23m is installed, the developer agglomeration is prevented by the above-described stirring effect of the developer. Therefore, even if the number of printed sheets is increased, it is possible to suppress the reduction of the developer conveyance amount.

  The agitating member 23m is configured to convey the developer in the same direction as the developer conveying direction of the first conveying screw 23b1 that supplies the developer to the developing roller 23a1 while agitating and conveying the developer in the longitudinal direction. In this case, it is possible to compensate for a decrease in the amount of developer that occurs on the downstream side of the first conveying screw 23b1. That is, since the developer is supplied to the developing roller 23a1 from the upstream side of the first transport screw 23b1, the amount of developer tends to decrease on the downstream side of the first transport screw 23b1, but the first transport is performed by the stirring member 23m. By transporting the developer in the same direction as the screw 23b1 and supplying the developer to the downstream side of the first transport screw 23b1, the amount of developer on the downstream side of the first transport screw 23b1 can be increased.

  FIG. 7 is a schematic perspective view showing another embodiment of the stirring member. As illustrated, the stirring member 23m is composed of a shaft portion and a blade portion extending linearly outward from the shaft portion in the radial direction, and is configured in a paddle shape. In this paddle-shaped stirring member 23m, the action of moving the developer in the radial direction is larger than that of the screw-shaped stirring member, so that the developer on the back side of the doctor blade 23c and in the vicinity of the tip can be moved more actively. It is possible to prevent or break down the developer accumulated at the location.

  As mentioned above, although this invention was demonstrated by the example of illustration, this invention is not limited to this. For example, the shape, size (area), and number of the developing roller and the conveying screw can be set as appropriate. Further, the image forming method of the image forming apparatus is also arbitrary.

1. Image forming device body (device body)
20, 20Y, 20C, 20M, 20BK Process cartridge 21 Photosensitive drum (image carrier)
23 Developing device (developing part)
23a1, 23a2 Development roller (developer carrier)
23b1 first conveying screw (first developer conveying member)
23b2 Second conveying screw (second developer conveying member)
23b3 third conveying screw (third developer conveying member)
23c Doctor blade (developer regulating member)
23m stirring member

Japanese Patent No. 3955797

Claims (5)

A developer carrier comprising a toner and a magnetic carrier carried on the surface, rotated, and supplied with a toner to a latent image on the surface of the image carrier at a position facing the image carrier, and the developer carrier; In a developing device having a developer regulating member disposed opposite to the surface of the developer carrying body and regulating the thickness of the developer on the surface of the developer carrying body,
A developing device, characterized in that a stirring member that is rotatable to stir the developer is installed on the back side of the developer regulating member on the upstream side of the developer carrying member in the developer transport direction.   The developing device according to claim 1, wherein the stirring member includes a shaft portion and a screw portion extending spirally on the shaft portion.   A developer conveying member that supplies the developer to the developer carrying member while stirring and conveying the developer in the longitudinal direction is provided, and the stirring member develops in the same direction as the developer conveying direction of the developer conveying member. The developing device according to claim 1, wherein the developer is conveyed.   The developing device according to claim 1, wherein the stirring member includes a shaft portion and a blade portion extending linearly outward from the shaft portion in the radial direction.   An image forming apparatus comprising the developing device according to claim 1.

Images