JP2013015758A - Development apparatus, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a developer amount inside a development apparatus irrespective of the printing speed of an image forming apparatus.SOLUTION: The development apparatus 23 stores a developer G having a carrier C and a toner T and develops a latent image formed on a photoreceptor 21, and it is provided with: first to third conveyance screws 23b1 to 23b3 which have screw parts on shanks and form a circulation path by conveying the developer G stored in the development apparatus in a longitudinal direction; a developer cartridge 28 for newly supplying the carrier into the development apparatus; and a developer discharge port 23d formed by a partition plate 27 which is a barrier plate of the conveyance path by the first conveyance screw 23b1 for discharging the developer G to the outside when the developer surface of the developer G conveyed by the first conveyance screw 23b1 exceeds a predetermined height. The developer discharge port 23d changes the height of the port according to the amount of the developer G inside the development apparatus.

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile machine, or a multi-function machine thereof, and a developing device and a process cartridge installed therein. The present invention relates to a premix developing type developing device, a process cartridge, and an image forming apparatus that appropriately supply carriers.

  2. Description of the Related Art Conventionally, in image forming apparatuses such as copying machines and printers, a reservoir that moves while being agitated by a screw into a developing device containing a two-component developer composed of toner and a carrier (including cases where an additive or the like is added). A developer discharge part is provided at a predetermined height position on the side wall of the developer housing on the downstream side of the developer movement, and the old carrier is discharged from the discharge part each time a new carrier is appropriately supplied, and the developer characteristic value is constant. A technique for maintaining the same (referred to as premix development system or trickle development system) is already known.

  Further, Patent Document 1 aims to provide a developing device that automatically collects an old developer, maintains the developing characteristics of the developer constant, and does not require a developer replacement operation. A carrier replenishing device and a toner replenishing device are provided separately above or integrally with each other, and a developer discharge portion is provided at a predetermined height position on the side wall of the developing housing on the downstream side of the stored developer moving by stirring by the stirring means. A developing device characterized in that it is provided is disclosed.

  However, in the conventional premix developing type developing device, the volume of the stored developer in the device changes depending on the printing speed of the image forming apparatus, so that the volume of the stored developer in the apparatus changes. There is a problem that the developer is not discharged well at a predetermined height of the developer discharge portion. As described above, there is a problem in that an abnormal image is generated or the developer is increased due to the lack of the desired developer amount and the developer roll is clogged due to clogging in the development gap.

  For example, the technique described in Patent Document 1 also has a problem that when the printing speed of the image forming apparatus is changed, the volume of the developer in the developing device fluctuates and the desired developer amount cannot be maintained. It will be.

  Accordingly, the present invention provides a developing device that can stably discharge the developer regardless of the printing speed and can stabilize the image quality of the output image without causing variations in the amount of developer discharged to the outside. It is an object of the present invention to provide a process cartridge and an image forming apparatus.

  In order to achieve such an object, a developing device according to the present invention is a developing device that contains a developer having a carrier and a toner, and that develops a latent image formed on an image carrier, on a shaft portion. A plurality of conveying members that form a circulation path by conveying the developer contained in the developing device in the longitudinal direction, a supply unit that newly supplies a carrier into the device, and a plurality of In order to discharge the developer to the outside when the developer level of the developer conveyed by one of the conveying members exceeds a predetermined height, the developer is formed on the partition wall of the conveying path by the one conveying member. A discharge portion that includes a developer discharge port that changes the height of the port in accordance with the volume of the developer in the developing device.

  Further, the process cartridge according to the present invention is a process cartridge that is detachably installed on the apparatus main body of the image forming apparatus, and the developing device according to the present invention and the image carrier are integrated. is there.

  An image forming apparatus according to the present invention includes the developing device according to the present invention and an image carrier.

  According to the present invention, the amount of developer in the developing device can be maintained regardless of the printing speed of the image forming apparatus.

1 is an overall configuration diagram illustrating an embodiment of an image forming apparatus. FIG. 2 is an enlarged view showing a basic configuration of a process cartridge. It is sectional drawing which looked at the circulation path in a developing device to the longitudinal direction. FIG. 4 is a cross-sectional view showing a Y1-Y1 cross section of a circulation path in the developing device of FIG. 3. FIG. 6 is a side view of a developer discharge unit. It is sectional drawing of a developer discharge part. FIG. 4 is a circuit diagram illustrating a circuit configuration in a developer discharge unit.

  Hereinafter, a configuration according to the present invention will be described in detail based on the embodiment shown in FIGS.

(Image forming device)
FIG. 1 is an overall configuration diagram showing an embodiment of an image forming apparatus according to the present invention. Hereinafter, the configuration and operation of the entire image forming apparatus will be described.

  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, and are polygon mirrors 3A to 3D and 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 feed unit 61 stores a transfer material S such as recording paper or OHP, and feeds the transfer material S 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 by electrostatically attracting the transfer material S to the surface thereof and transferring the toner image onto the transfer material S. A suction 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 transfer material S to the transfer material S 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 yellow, cyan, magenta, and black toner images, respectively.

  On each of the process cartridges 20Y, 20C, 20M, and 20BK, a carrier (magnetic carrier) C and toner (toner particles) T of each color (yellow, cyan, magenta, black) are supplied as supply means. Agent cartridges (toner 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 according to the present embodiment is a composite image forming apparatus that functions as a copying machine 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 black, magenta, cyan, and yellow image information 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. The toner image is transferred to the transfer material S.

  The transfer material S fed from the paper feed unit 61 by the paper feed roller 62 is conveyed 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 feeding position of the transfer belt 30 causes the transfer belt 30 to suck the material to be transferred S fed by voltage application. The transfer material S 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 transfer material S 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 S is fixed on the transfer material S 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 S is separated reaches the position of the belt cleaner 65, and dirt such as toner adhering to the surface is cleaned.

(Developer / Process cartridge)
Next, the basic configuration of 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. Therefore, in FIG. The alphabet (Y, C, M, BK) is removed for illustration. In addition, the writing unit is illustrated by removing the alphabet (A to D).

  FIG. 2 is an enlarged view showing the process cartridge 20 and the toner cartridge 28 installed in the image forming apparatus. As shown in FIG. 2, the process cartridge 20 includes a photosensitive drum 21 serving as an image carrier, a charging unit 22, a developing device 23, and a cleaning unit 25. A development system that replenishes and discharges appropriately 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.

  The developing device 23 is arranged so that two developing rollers 23a1 and 23a2 (hereinafter also collectively referred to as developing roller 23a) as developer carriers are located close to the photosensitive drum 21, and the opposite portions of both are provided. A developing area where the photosensitive drum 21 and the magnetic brush come into contact with each other is formed. 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 later.

  Here, the developing device 23 according to the present embodiment is of a premix developing type, 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.

  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 is performed based on information on the toner density (the ratio of the toner T in the developer G) detected by the magnetic sensor 26 (see FIG. 3) installed in the developing device 23. As a result, the developer G is appropriately supplied from the agent cartridge 28 serving as the supply means into the developing device 23.

  In this 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 serving as a supply means 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. As shown in FIG. 2, when the photosensitive drum 21 is rotated 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 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 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 on the developing rollers 23a1 and 23a2, and the negatively charged toner T in the magnetic brush is attached and visualized.

  Specifically, the developer G pumped up by the magnetic force generated by the magnetic poles of the upper developing roller 23a1 is adjusted to an appropriate amount by the doctor blade 23c, and then the developing region (the two developing rollers 23a1, 23a2 and 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 due to friction with the carrier C.

  On the other hand, 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 S 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 S 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, the toner T (untransferred toner) remaining on the photosensitive drum 21 without being transferred to the transfer material S during the transfer process reaches the 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.

  3 is a cross-sectional view of the circulation path in the developing device 23 as viewed from the direction of the arrow X shown in FIG. 2 in the longitudinal direction. The flow of the developer G will be described with reference to FIG.

  The developing device 23 includes developing rollers 23a1 and 23a2 as developer carriers, conveying screws 23b1 to 23b3 (auger screws) as conveying members, a doctor blade 23c, and the like.

  The developing roller 23a is configured such that a 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).

  In the sleeve of the developing roller 23a, 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 G on the developing roller 23a to an appropriate amount.

  The three conveying screws 23b1 to 23b3 agitate and mix the developer G accommodated in the developing device 23 while circulating it in the longitudinal direction (the direction perpendicular to the paper surface of FIG. 2).

  The first conveyance screw 23b1 (first conveyance member) is disposed at a position substantially opposite to the developing roller 23a1, and conveys the developer G in the horizontal direction (conveyance in the left direction indicated by the white arrow in FIG. 3). At the same time, the developer G is supplied onto the developing roller 23a.

  The second conveying screw 23b2 (second conveying member) is disposed below the first conveying screw 23b1 and at a position substantially opposite to the developing roller 23a2, and the developer G (developing step) separated from the developing roller 23a. The developer G) forcibly separated from the developing roller 23a later by the agent separation pole is conveyed in the horizontal direction (conveyance in the left direction indicated by the white arrow in FIG. 3).

  The first transport screw 23b1 and the second transport screw 23b2 are arranged so that the rotation shaft is substantially horizontal, like the developing roller 23a and the photosensitive drum 21.

  The third transport screw 23b3 (third transport member) 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 (conveyed upward to the right as indicated by the white arrow in FIG. 3).

  In addition, the conveyance path by the 1st conveyance screw 23b1, the conveyance path by the 2nd conveyance screw 23b2, and the conveyance path by the 3rd conveyance screw 23b3 are isolated by the wall part.

  The downstream side of the conveyance path by the second conveyance screw 23b2 and the upstream side of the conveyance path by the third conveyance screw 23b3 communicate with each other via the first relay portion 23g. Further, the downstream side of the conveyance path by the third conveyance screw 23b3 and the upstream side of the conveyance path by the first conveyance screw 23b1 are communicated with each other through the second relay portion 23h. Further, the downstream side of the conveyance path by the first conveyance screw 23b1 and the upstream side of the conveyance path by the third conveyance screw 23b3 communicate with each other via the fall path 23f.

  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 transport screws 23b1 to 23b3. Here, when the developing device 23 is operated, the developer G accommodated in the device flows in a state as indicated by the oblique lines in FIG.

  In the transport path of the first transport screw 23b1, the developer surface of the developer G on the downstream side is lower than the upstream agent surface. A part of the developer G being transported is supplied to the developing roller 23a. It is because it has been.

  That is, the developer G that has not been supplied to the developing roller 23a moves to the upstream side of the third conveying screw 23b3 via the dropping path 23f. A magnetic sensor 26 as a toner concentration sensor is installed in the conveyance path by the third conveyance screw 23b3.

  Then, based on the toner density information detected by the magnetic sensor 26, the developer G having a predetermined toner density is supplied from the agent cartridge 28 serving as a supply unit into the developing device 23.

  2 and 3, in the transport path by the first transport screw 23 b 1, a discharge unit (development) that discharges a part of the developer G accommodated in the developing device 23 to the outside (agent storage container 70). A developer discharge port (also referred to as a discharge port) 23d is provided as a developer discharge unit).

  Specifically, the discharge port 23d is provided with a developer surface (upper surface) of the developer G which is supplied to the developing device 23 by the supply means 28 and 29 and the developer amount in the device increases and is conveyed to that position. ) Exceeds a predetermined height, the excess developer G is discharged toward the agent storage container 70.

  That is, the excess developer G exceeds the lower portion of the discharge port 23 d, is discharged from the discharge port 23 d, and gravity falls toward the agent storage container 70 via the discharge path 71.

  As described above, the carrier C deteriorated by being contaminated with the base resin of the toner T or the external additive is automatically discharged to the outside of the developing device 23, so that deterioration of the image quality can be suppressed even over time.

(Developer discharge part)
4 is a cross-sectional view showing a Y1-Y1 cross section of the circulation path in the developing device 23 of FIG. A partition plate 27 is provided near the developer interface of the wall on the back side of the downstream housing along the developer agitating screw 23b1, and when the amount of developer inside exceeds a predetermined amount, the developer in excess G overflows from a hole (developer discharge port) 23 d provided in the partition plate 27, and the overflowed developer G falls and is transported to a discharge screw 23 n that is transported to a discharge path 71.

  However, in the configuration in which one hole is provided as the developer discharge port 23d at a predetermined height position on the side wall of the developing housing as in the developing device 23 shown in FIG. 4, for example, the printing speed of the image forming apparatus is slow, that is, When the rotation speed of the developer stirring screw of the developing device decreases, the volume P of the developer G in the developing device decreases accordingly, and the developer G is not discharged from the developer discharge port 23d.

  That is, since the amount of the developer G required to overflow from the developer discharge port 23d increases, the amount of developer in the developing device increases with respect to a desired amount of the initial printing speed, and the developer carrier 23a. There is a possibility that the developer G is clogged in the gap between the image carrier 21 and the image carrier 21, and problems such as motor lock may occur.

  Conversely, for example, when the printing speed of the image forming apparatus is increased, that is, when the rotation speed of the stirring screw of the developing device is increased, the volume P of the developer G in the developing device is increased accordingly. The discharge amount from the discharge port 23d increases, and the developer amount in the developing device decreases with respect to the developer amount at the initial printing speed. For this reason, a sufficient amount of the developer G is not held on the developer carrier 23a, and there is a possibility that the density unevenness of the screw pitch appears in the image.

  Therefore, the developing device 23 according to the present embodiment accommodates the developer G having the carrier C and the toner T in order to eliminate the above-described problems, and also on the image carrier (photosensitive drum 21). A developing device (developing device 23) for developing a latent image to be formed, wherein a screw portion is formed on a shaft portion, and a developer G accommodated in the device is conveyed in a longitudinal direction so as to pass through a circulation path. A plurality of transport members to be formed (first to third transport screws 23b1 to 23b3), supply means (agent cartridge 28, supply pipe 29) for newly supplying the carrier C into the apparatus, and one of the plurality of transport members When the surface of the developer G transported by one transport member (first transport screw 23b1) exceeds a predetermined height, the partition wall of the transport path by the one transport member in order to discharge the developer G to the outside (Partition Discharging portion formed on 27) and (developer outlet 23d), provided with a discharge unit is to be able to change the height of the mouth in response to the bulk of the developer G in the developing device.

  FIG. 5 is an enlarged configuration diagram of the partition plate and the developer discharge portion in the developing device according to the present embodiment. 6 is a cross-sectional configuration diagram of the partition plate and the developer discharge portion shown in FIG. Note that the configuration other than the partition plate and the developer discharge portion of the developing device according to the present embodiment may be the same as the above-described developing device (FIGS. 2 to 4).

  The partition plate 27 of the developing device 23 according to the present embodiment is provided with three outlets 23d (denoted as holes 23d1, 23d2, and 23d3) as developer discharging portions, and the holes are opened at different heights. ing. In addition, the number of the discharge ports 23d and the arrangement positions thereof are not limited to the example shown in FIG. Further, it is preferable that the partition plate 27 is detachably installed with respect to the developing device 23 as shown in FIG. Thereby, it is also possible to replace the partition plate 27 with a different number of outlets 23d and different heights.

  In the present embodiment, the hole 23d1 is a volume P1 of the developer G defined by the number of rotations of the developing device when the printing speed of the image forming apparatus is 70 pages per minute (ppm). Is provided at such a height that makes it suitable for a developing device. Similarly, the hole 23d2 is a hole having a height suitable for 90 ppm, and 23d3 is a suitable developer amount at 120 ppm.

  Further, a coil L around which an electric wire is wound is provided around the outlet side of each outlet 23d. By adopting such a configuration, as will be described later, it is made to function as an electromagnet when energized. The coils L are L1, L2, and L3, respectively, according to the height of each discharge port 23d.

  For example, if the volume of the developer G in the developing device when the rotation speed of the developing device 23 is 120 ppm is P3, the developer G is discharged from the hole 23d3. The developer G is also discharged from the holes 23d1 and 23d2.

  Therefore, as shown in FIG. 7, the developer discharge portion of the developing device 23 according to the present embodiment includes coils SW1, SW2, and SW2 that switch the energization state of the coils L1, L2, and L3 provided around the discharge ports 23d. , SW3.

  Specifically, the print speed setting of the image forming apparatus (that is, the rotation speed of the developing device) is detected, and among the switches SW1, SW2, and SW3 to be switched, when the print speed is 120 ppm, the switches SW1 and SW2 are connected, The coils L1 and L2 are excited so that a magnetic field is generated.

  As a result, the coils L1 and L2 hold the developer G as electromagnets, so that the developer G is not clogged and discharged from the hole 23d1 and the hole 23d2, and only from the hole 23d3 having the desired hole height. Emissions are made.

  Similarly, for example, when the printing speed is 90 ppm, the switch SW2 cuts off the current to the coil L2, and the coils L1 and L3 are excited to prevent the developer G from being discharged from other than the hole 23d2. .

  As described above, since the developer G is discharged from the height of the hole suitable for the printing speed, the amount of the developer is always stabilized to an appropriate amount, and an abnormality occurs in the developing device and the printed image. This can be eliminated.

  Further, as shown in FIG. 6, each of the holes 23 d 1 to 23 d 3 preferably has inclined portions 23 k 1 to 23 k 3 that are inclined in the developer G discharging direction. Thereby, the discharge of the developer G is assisted and the discharge is performed smoothly.

  According to the developing device according to the present embodiment described above, the developer discharge portion that adjusts the height of the opening of the developer discharge portion in accordance with the printing speed of the image forming device is provided, thereby increasing the printing speed of the image forming device. The excess developer is stably discharged out of the apparatus in accordance with the bulk of the developer amount in the combined developing device, and the developer amount in the developing device can always be kept within a specified range. Further, by using the process cartridge and the image forming apparatus provided with the developing device, the process cartridge and the image forming apparatus having the above effects can be obtained.

  The above-described embodiment is a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention.

1. Image forming device (device main body)
2A to 2D Writing unit 3A to 3D Polygon mirror 4A to 4D Optical element 20, 20Y, 20C, 20M, 20BK Process cartridge 21 Photosensitive drum (image carrier)
22 Charging unit 23 Developing device 23a1, 23a2 Developing roller (developer carrier)
23b1 first conveying screw (first conveying member)
23b2 Second conveying screw (second conveying member)
23b3 Third conveying screw (third conveying member)
23c Doctor blade,
23d Developer outlet (discharge part)
23d1 to 23d3 Hole 23f Drop path 23g First relay portion 23h Second relay portion 23k1 to 23k3 Inclined surface 23n Discharge screw 24 Transfer roller 25 Cleaning portion 26 Magnetic sensor 27 Partition plates 28, 28Y, 28C, 28M, 28BK Agent cartridge ( Supply means)
29 Supply pipe (supply means)
30 Transfer belt 61 Paper feed section 62 Paper feed roller 63 Registration roller 64 Adsorption roller 65 Belt cleaner 66 Fixing section 67 Pressure roller 68 Heating roller 69 Discharge roller 70 Agent storage container 71 Discharge path 80 Shutter mechanism C Carrier G Developer (2 Component developer)
L Exposure light L1 to L3 Coils P, P1 to P3 Bulk S Transfer material SW Switch T Toner

Japanese Patent Publication No. 2-21591

Claims (9)

A developing device that contains a developer having a carrier and toner and that develops a latent image formed on an image carrier,
A plurality of conveying members that form a circulation path by forming a screw portion on the shaft portion and conveying the developer contained in the apparatus in the longitudinal direction;
Supply means for supplying a new carrier into the developing device;
In order to discharge the developer to the outside when the developer level of the developer conveyed by one of the plurality of conveying members exceeds a predetermined height, a partition of a conveying path by the one conveying member A formed discharge portion, and
2. The developing device according to claim 1, wherein the discharge unit includes a developer discharge port that changes a height of the port corresponding to a volume of the developer in the developing device.   The developing device according to claim 1, wherein a plurality of the developer discharge ports are provided in accordance with a volume of the developer in the developing device.   The developing device according to claim 2, wherein the developer discharge port is switched by exciting a coil provided around the plurality of developer discharge ports.   The developing device according to claim 1, wherein the developer discharge port includes an inclined portion that is inclined in a developer discharge direction.   The developing device according to claim 1, wherein the discharge unit is detachably attached to the developing device.   The developing device according to claim 1, wherein the discharge unit is formed on a downstream side of a conveyance path by the one conveyance member.   The developing device according to claim 1, wherein the supply unit newly supplies toner together with the carrier into the developing device. 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