JP2011150113A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device configured to suppress occurrence of image problem resulting from failure in developer supply, by improving efficiency in developer supply. <P>SOLUTION: The developing device 50 includes: a frame body 50A; a developing roller 3; a supply roller 4; a toner storage chamber 55 laid out below the supply roller 4 within the frame body 50A and storing developer; a stirring conveyance member 6 freely rotatably provided inside the toner storage chamber 55 and used for conveying developer from the toner storage chamber 55 to the supply roller 4; and a partition member 9 which is disposed opposite to an outer peripheral surface of the developing roller 3 and disposed so as to cover an outer peripheral surface of the supply roller 4 from an upstream-side end 9a to a downstream-side end 9b, and which forms an empty space 53 between the outer periphery of the supply roller 4 and the partition member 9 and forms an opening 54 between the outer periphery of the developing roller 3 and the partition member 9, to partition the supply roller 4. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention visualizes an electrostatic latent image formed on an image carrier using an electrophotographic method or an electrostatic recording method using a developing device to form a visible image, and transfers the visible image onto a recording material. The present invention also relates to an image forming apparatus that obtains a permanent image by fixing, and a developing device applied to the image forming apparatus.

  2. Description of the Related Art Conventionally, an in-line image forming apparatus is known in which a plurality of photosensitive drums are arranged in a line in a direction crossing the vertical direction. An image forming apparatus is known in which a plurality of image forming units are disposed below the intermediate transfer belt or the recording material conveyance belt, and a fixing device is disposed above the intermediate transfer belt or the recording material conveyance belt. With this configuration, when the image forming unit includes a photosensitive drum, a developing device, and an exposure device, there is an advantage that each element of the image forming unit is hardly affected by the heat of the fixing device. There exists an invention of patent document 1 as invention regarding such a structure.

  The invention described in Patent Document 1 is an invention itself relating to an image forming apparatus in which a photosensitive drum and a developing device are disposed below an intermediate transfer belt, and a fixing device is disposed above the intermediate transfer belt. The developing device includes a developer storage chamber defined below the inside of the frame and a developing chamber defined above the inside of the frame. The developer storage chamber is provided with a developer transport member that stores the developer and transports the developer to the developer supply body. The developing chamber is provided with a developer carrier for supplying the developer to the photosensitive drum, a developer supplier for supplying the developer to the developer carrier, and the like. Since the developing chamber is disposed above the developer storage chamber, the developer is transported against gravity when supplying the developer from the developer storage chamber to the developing chamber.

  Here, it is assumed that a sponge-like elastic member having a plurality of cells is used on the outer periphery of the developer supply body. In the contact nip, when the cell is crushed at the upstream end portion in the rotation direction of the developer supply body, the developer is discharged from the cell, and the cell is opened at the downstream end portion in the rotation direction of the developer supply body. Then, the developer is sucked into the cell. In such a configuration, when supplying the developer to the developer supply body, the developing is performed at the downstream end of the developer supply body in the rotation direction in the contact nip between the developer supply body and the developer carrier. It is considered that when the developer is conveyed, the developer supply efficiency is improved.

JP 2003-173083 A

  However, in the invention described in Patent Document 1, even if the developer that has entered the space between the developing chamber wall and the developer supply body is supplied to the developer supply body, the developer supply body and the developer carrying body. Before reaching the abutting nip, the developer supply unit may rotate and fall to the floor of the developing chamber. Alternatively, such a developer may return to the developer storage chamber. For this reason, the amount of developer supplied to the developer supply body is insufficient, and image problems such as density unevenness due to poor developer supply may occur.

  In view of the above circumstances, an object of the present invention is to provide a developing device capable of improving the supply efficiency of a developer and suppressing the occurrence of an image problem due to poor supply of the developer.

  In order to solve the above-described problems, a developing device of the present invention is supported by a developing device main body, a developer carrying member supported by the developing device main body and rotatably supporting the developer, and supported by the developing device main body. A developer supply body that is in contact with the developer carrying body and is rotatable while supplying the developer carrying body, and is partitioned below the developer supply body inside the developing device main body. A developer storage chamber for storing the developer, a developer transport member that is rotatably provided inside the developer storage chamber, and transports the developer from the developer storage chamber to the developer supply body; and The developer carrying member is disposed so as to face the outer peripheral surface of the developer carrying member, and one end thereof is positioned at a spaced apart position with a predetermined dimension on the outer peripheral surface of the developer carrying member, and the other end is positioned at the uppermost position of the developer supplying member. The rotation direction of the developer supply body is higher than the uppermost position. A partition member positioned on the flow side, forming a gap with the outer peripheral surface of the developer supply body, forming an opening with the outer peripheral surface of the developer carrier, and partitioning the developer supply body; It is characterized by providing.

  According to the present invention, a part of the developer conveyed to the developer supply body by the developer conveying member is guided to the opening through the partition member. Therefore, since the developer that has passed through the uppermost position of the developer supply body and passed through the opening is sucked into the developer supply body, it easily reaches the contact nip between the developer supply body and the developer carrier. be able to. Then, the amount of the developer that adheres to the surface of the developer supply body and returns to the developer storage chamber without reaching the developer carrier by the rotation of the developer supply body is reduced. As a result, the supply efficiency of the developer is improved, and the occurrence of image problems due to poor supply of the developer is suppressed.

1 is a cross-sectional view illustrating a configuration of an image forming apparatus according to Embodiment 1 of the present invention. It is sectional drawing which shows the structure of a developing device. FIG. 2 is an enlarged cross-sectional view illustrating a configuration of a developing device. 3 is an enlarged cross-sectional view illustrating a configuration of a toner retention portion. FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, since the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions, there is no specific description. As long as the scope of the invention is not limited to these, it is not intended.

  FIG. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus 100 according to Embodiment 1 of the present invention. The image forming apparatus 100 is a full-color laser beam printer that employs an inline method and an intermediate transfer method. In the first embodiment, a color image forming apparatus that forms an image of a plurality of colors will be described. However, the present invention is not limited to this configuration, and can be applied to an image forming apparatus that forms a black monochrome image.

  As shown in FIG. 1, an image forming apparatus 100 includes an image forming apparatus main body (hereinafter simply referred to as “apparatus main body”) 100A, and a plurality of image forming units for forming images are formed inside the apparatus main body 100A. SY, SM, SC, and SK are provided. The image forming units SY, SM, SC, and SK include photosensitive drums 1Y, 1M, 1C, and 1K that are “image carriers”, and primary transfer rollers 13Y, 13M, 13C, and 13K that are “primary transfer devices”. including. Here, the image forming apparatus includes an electrophotographic image forming apparatus such as a copying machine, a printer (for example, an LED printer, a laser beam printer, etc.), a facsimile apparatus, and a word processor.

  In the present embodiment, the configurations and operations of the first to fourth image forming units SY to SK are substantially the same except that the colors of the images to be formed are different. Therefore, in the following, unless there is a particular distinction, the subscripts Y, M, C, and K given to the reference numerals to indicate that the element is provided for any color are omitted, and the overall Explained.

  The image forming apparatus 100 includes a plurality of photosensitive drums 1 arranged in parallel as “electrophotographic photosensitive members”, that is, four “image carriers”. The photosensitive drum 1 is a drum-type electrophotographic photosensitive member. The photosensitive drum 1 is rotationally driven by a driving unit (not shown) in the direction of the arrow R1. The photosensitive drum 1 has an organic photoreceptor (OPC) coated on the outer peripheral surface of an aluminum cylinder having a diameter of 24 mm. However, the present invention is not limited to this, and a-Si (amorphous silicon), CdS, Se, or the like may be applied instead of the organic photoreceptor. Further, the photosensitive drum 1 rotates in the direction of the arrow R1 at a process speed of 135 mm / sec.

  When the image forming operation is started, the photosensitive drum 1 is uniformly charged by the charging roller 2 as a charging unit that is driven while contacting the photosensitive drum 1 and rotates in the direction of an arrow R2 (see FIG. 2). Is done. The charging roller 2 has a diameter of 10 mm, and has a multilayer structure in which an elastic layer 2b made of urethane rubber as a base layer and a fluorine-based resin as a surface layer is provided around a cored bar 2a that is a stainless cylindrical body (see FIG. 2). ). However, a metal such as aluminum or an aluminum alloy may be used as the material of the core metal 2a, and a rubber material such as NBR, EPDM, or silicone rubber may be used as the base layer of the elastic layer 2b. Further, ether urethane, nylon, or the like may be used as the surface layer of the elastic layer 2b.

  The charging roller 2 is connected to a charging bias power supply device (not shown) which is a charging member voltage application means, and a surface of the photosensitive drum 1 is charged by applying a DC bias as a charging bias. A predetermined dark portion potential is formed on the surface of the photosensitive drum 1. Here, a DC bias is used as the charging bias, but a bias in which an AC component is superimposed on a DC component may be used as the charging bias.

  Thereafter, an electrostatic image is formed on the surface of the photosensitive drum 1 by a laser beam scanner device 7 serving as an exposure device serving as an exposure unit. The laser beam scanner 7 emits a semiconductor laser (not shown) according to an image signal corresponding to an input signal, and a polygon mirror (not shown) rotating the laser beam L (see FIG. 2) at high speed. And passes through an imaging lens group (not shown) to irradiate the photosensitive drum 1. By irradiating the photosensitive drum 1 with laser light, a predetermined bright portion potential is formed on the surface of the photosensitive drum 1.

  Next, the electrostatic image on the surface of the photosensitive drum 1 is visualized as a developer image (toner image) by the developing device 50 as developing means. In the first embodiment, the reversal development method is used as the development method. Therefore, the toner having the same polarity (negative polarity) as the charged charge adheres to the portion (image portion) on the photosensitive drum 1 where the negative charged charge is attenuated.

  Further, the developing device 50 that is a developing means employs a contact developing method in which development is performed in a state where the developing roller 3 is in contact with the photosensitive drum 1 and the developing roller 3 is in “contact” with the photosensitive drum 1. Yes.

  FIG. 2 is a cross-sectional view showing the configuration of the developing device 50. With reference to FIG. 2, the configuration of each member disposed inside the developing device 50 will be described in detail below. The developing device 50 is a device that supplies toner t to the electrostatic image formed on the photosensitive drum 1 and develops it, and includes a frame body 50A that is a “developing device body”.

  Inside the frame 50 </ b> A, a toner storage chamber 55 that is a “developer storage chamber” is defined below, and a development chamber 56 is defined above. The toner storage chamber 55 is a chamber for storing the toner t, and is partitioned below the supply roller 4. A negatively chargeable non-magnetic one-component developer (toner) is stored in the toner storage chamber 55. Further, in the toner storage chamber 55, a stirring transport member 6 that is a “developer transport member” that transports the toner t from the toner storage chamber 55 to the supply roller 4 is rotatably provided. The agitating and conveying member 6 is supported in the toner storage chamber 55 of the frame 50A. The agitating / conveying member 6 rotates in the direction of the arrow R6 in order to loosen the toner t inside the toner storage chamber 55 and convey the toner t to the supply roller 4.

  A partition member 9 is disposed on the outer peripheral surface of the supply roller 4 so as to face the outer peripheral surface of the supply roller 4 and cover the outer peripheral surface to partition the supply roller 4. The upstream end 9 a, which is the “one end” on the upstream side in the rotation direction of the supply roller 4 included in the partition member 9, is positioned at a separation position 3 </ b> L that is separated from the outer peripheral surface of the developing roller 3 by a predetermined size. It faces the outer peripheral surface. The downstream end portion 9b which is the “other end portion” on the downstream side in the rotation direction of the supply roller 4 included in the partition member 9 is the uppermost position 4L of the supply roller 4 or the downstream position in the rotation direction of the supply roller 4 from the uppermost position 4L. Positioned on the side. The partition member 9 forms a gap 53 (see FIG. 3A) with the outer peripheral surface of the supply roller 4, and an opening 54 (see FIG. 3A) with the outer peripheral surface of the developing roller 3. Form. In other words, it can be said that the partition member 9 is formed to be inclined downward from the uppermost position 9L of the partition member 9 toward the separation position 3L.

  Further, the developing device 50 includes a developing blade 5 that is a “developer regulating unit” that regulates the toner t supplied by the supply roller 4 and forms a thin layer of developer on the surface of the developing roller 3.

  Further, the frame 50A supports the developing roller 3 as a “developer carrying member” that is rotatable while carrying the toner t as the “developer”. The developing roller 3 carries the toner t while carrying it, and contacts the toner t with the photosensitive drum 1 to develop the electrostatic image. The frame body 50 </ b> A is in contact with the developing roller 3, and supports a supply roller 4 that is a rotatable “developer supply body” while supplying the toner t to the developing roller 3. The supply roller 4 is formed of a porous and elastic member such as a sponge. The supply roller 4 is disposed inside the developing chamber 56, approximately half of the developing roller 3 is disposed outside the developing chamber 56, and the remaining approximately half of the developing roller 3 is disposed inside the developing chamber 56. .

  The developing roller 3 rotates in the direction of arrow R3 at a peripheral speed of 160 mm / sec, and contacts the photosensitive drum 1 with a predetermined contact pressure. The developing roller 3 has a diameter of 16 mm, and has a multilayer structure in which an elastic layer 3b made of urethane rubber as a base layer and carbon as a surface layer is provided around a stainless steel core 3a. Thus, the length of the elastic layer 3b in the longitudinal direction is 230 mm. However, the present invention is not limited to this, and a metal cylinder such as aluminum or aluminum alloy is used as the core metal 3a, and the base layer of the elastic layer 3b is made of a rubber material such as NBR, EPDM, silicone rubber, urethane rubber or the like. Also good. The surface layer of the elastic layer 3b may be made of ether urethane or nylon. Further, a DC developing bias of −300 V is applied to the developing roller 3 by a developing bias power supply device (not shown) as developing bias applying means.

  Next, the supply roller 4 is a roller for supplying and collecting the toner t with respect to the developing roller 3. The supply roller 4 is an elastic roller made of an elastic foam, and rotates in the direction of arrow R4 at a peripheral speed of 160 mm / sec. Further, the supply roller 4 is arranged so that the intrusion amount with respect to the developing roller 3 is 1.5 mm. The supply roller 4 is a sponge roller having a diameter of 16 mm and a urethane foam provided as an elastic layer 4b around a stainless steel core 4a. The length of the elastic layer 4b in the longitudinal direction is 230 mm. However, the present invention is not limited to this, and a metal cylindrical body such as aluminum or aluminum alloy may be used as the cored bar 4a.

  Next, the developing blade 5 is a blade that regulates the layer thickness of the toner t on the developing roller 3 and is provided so as to pressurize the developing roller 3. The developing blade 5 was an elastic regulating member made of a thin plate made of SUS having a leaf spring shape with a thickness of 0.1 mm. However, it is not limited to this, and a metal thin plate such as phosphor bronze or aluminum may be used. The surface of the developing blade 5 may be coated with a thin film such as polyamide elastomer, urethane rubber or urethane resin as an insulating layer. Further, a DC blade bias of −500 V is applied to the developing blade 5 by a blade bias power supply device (not shown) as a regulating member bias applying unit. The toner t supplied onto the developing roller 3 by the supply roller 4 is regulated in layer thickness by the developing blade 5 and applied to form a thin layer of toner t on the developing roller 3. Further, the toner t is given sufficient electric charge for development by friction with the surfaces of the developing roller 3 and the developing blade 5 at this time.

  Thereafter, a thin layer of toner t on the developing roller 3 is conveyed to a developing region (developing nip) N1 in contact with the photosensitive drum 1 and the developing roller 3 as the developing roller 3 rotates. It is used for development in contact with the body drum 1. That is, in order to form a developing electric field between the photosensitive drum 1 and the developing roller 3, a developing bias power supply device (not shown) is connected, and the toner t on the developing roller 3 is photosensitive by the action of the developing electric field. Transfer to the body drum 1. The toner t forms a toner image corresponding to the electrostatic image on the surface of the photosensitive drum 1, and visualizes the electrostatic image.

  A part of the toner t carried on the surface of the developing roller 3 is conveyed while being carried to the developing nip N1, but does not contribute to the development and is further carried on the surface of the developing roller 3. It moves and is scraped off from the surface of the developing roller 3 by rubbing with the supply roller 4. A part of the toner t scraped off is supplied to the surface of the developing roller 3 again by the supply roller 4 together with the toner t newly supplied to the surface of the supply roller 4, and the rest is transferred to the inside of the toner storage chamber 55. Returned.

  Further, a blowout prevention sheet 10 is attached to the frame 50 </ b> A of the developing device 50 in order to prevent the toner t from scattering from the developing roller 3 at a position facing the surface of the developing roller 3. The position of the blowout prevention sheet 10 is located downstream of the developing nip N1 where the developing roller 3 is in contact with the photosensitive drum 1 in the rotation direction of the developing roller 3.

  Here, referring back to FIG. 1, the configuration of the image forming apparatus 100 will be further described. The intermediate transfer belt 12 that is an “intermediate transfer member” is in contact with all the photosensitive drums 1 and moves in the direction of the arrow R12. The intermediate transfer belt 12 is formed of an endless belt and is stretched around a plurality of support members. On the inner peripheral surface side of the intermediate transfer belt 12, four primary transfer rollers 13 </ b> Y to 13 </ b> K as “primary transfer units” are arranged in parallel so as to face the respective photosensitive drums 1. The primary transfer rollers 13Y to 13K press the intermediate transfer belt 12 toward the photosensitive drum 1, and the intermediate transfer belt 12 and the photosensitive drum 1 come into contact with each other to form a nip at the primary transfer portion N3. A primary transfer bias is applied to the primary transfer roller 13 by a primary transfer bias power supply device (not shown). As a result, the toner image on the photosensitive drum 1 is transferred onto the intermediate transfer belt 12.

  On the outer peripheral surface side of the intermediate transfer belt 12, a secondary transfer roller 14 as a secondary transfer unit is disposed at a position facing the secondary transfer counter roller 15. The secondary transfer roller 14 is in pressure contact with the secondary transfer counter roller 15 via the intermediate transfer belt 12, and forms a nip at the secondary transfer portion N4 where the intermediate transfer belt 12 and the secondary transfer roller 14 are in contact with each other. A secondary transfer bias is applied to the secondary transfer roller 14 by a secondary transfer bias power supply device (not shown). As a result, the toner image on the intermediate transfer belt 12 is transferred to the recording material P.

  During full-color image formation in this embodiment, charging, exposure, development, and primary transfer processes are sequentially performed in the first to fourth image forming units SY, SM, SC, and SK, and each color is formed on the intermediate transfer belt 12. The toner images are superimposed. Thereafter, the toner images on the intermediate transfer belt 12 are collectively transferred to the recording material P by the action of the secondary transfer roller 14.

  Thereafter, the unfixed toner image carried on the recording material P is subjected to heating by a fixing unit (heat roller) provided in the fixing device 16 and pressurization by the pressing unit, so that a permanent image is formed on the recording material P. It is fixed.

  Further, the transfer residual toner on the photosensitive drum 1 after the primary transfer of the toner image is removed by the cleaning device 8 including a blade-like cleaning unit. Further, the transfer residual toner on the intermediate transfer belt 12 that has finished the secondary transfer of the toner image is removed by an intermediate transfer belt cleaning device 17 having a cleaning means on the blade. In preparation for the subsequent image forming operation.

  FIG. 3A is an enlarged cross-sectional view showing the configuration of the developing device 50. With reference to FIG. 3A, a mechanism for supplying toner t to the supply roller 4 which is a feature of the present invention will be described. The toner t is discharged when the cells on the outer periphery of the supply roller 4 are crushed by the rotation of the supply roller 4. Thereafter, the supply roller 4 is opened to open the cell. At that time, the air is sucked toward the cell and the toner t is sucked. That is, with reference to the rotation direction of the supply roller 4 in the contact nip N2 between the supply roller 4 and the developing roller 3, the toner t is discharged upstream (this position is referred to as “toner discharge portion C”), and the downstream side The toner t is sucked (this position is referred to as “toner sucking portion D”).

  In this embodiment, a partition member 9 is provided on the supply roller 4. When the partition member 9 is based on the rotation direction of the supply roller 4, the rotation of the supply roller 4 from the vicinity of the downstream side portion of the contact nip N <b> 2 between the developing roller 3 and the supply roller 4 is more directly above the rotation center of the supply roller 4. It is arranged on the downstream side in the direction. Further, the partition member 9 does not contact the supply roller 4 and is provided with a gap. In this embodiment, the gap is 0.5 mm.

  FIG. 3B is an enlarged cross-sectional view showing the configuration of the developing device 50. The movement of the toner t downstream of the contact roller nip N2 between the supply roller 4 and the developing roller 3 in the rotation direction of the supply roller 4, that is, in the vicinity of the toner suction portion D will be described with reference to FIG. In FIG. 3B, an arrow indicating the air flow in the vicinity of the toner suction portion D is shown.

  In the vicinity of the supply roller 4, when the supply roller 4 itself rotates, the flow of air or toner t in the direction of the arrow A1 enters the gap 53 (see FIG. 3A) between the partition member 9 and the supply roller 4. Has occurred. On the other hand, in the contact nip N2 between the supply roller 4 and the developing roller 3, a compression movement occurs on the upstream side in the rotation direction, and an opening movement occurs on the downstream side in the rotation direction. In the toner discharge portion C, air and toner t are discharged. In the toner suction portion D on the downstream side, air and toner t are sucked. Therefore, the flow of air and toner t above the partition member 9 is as indicated by an arrow A2, and the flow is such that the toner t is positively sent to the supply roller 4.

  As the agitating / conveying member 6 (see FIG. 2) in the toner storage chamber 55 rotates, the toner t is sent from the toner storage chamber 55 to above the partition member 9 as indicated by a dotted line T. Then, after dropping to the vicinity of the surface of the developing roller 3, the toner t is sent to the toner suction portion D by the rotation of the developing roller 3 and the flow of air. Then, the toner t is actively sucked in the toner sucking portion D, and the toner is efficiently supplied to the supply roller 4.

  Further, since the partition member 9 is located immediately above the rotation center of the supply roller 4 to the vicinity of the toner suction portion D, the toner t conveyed by the stirring conveyance member 6 enters the contact nip N2 between the supply roller 4 and the developing roller 3. I fall down. The toner t adheres to the surface of the supply roller 4 and is returned to the toner storage chamber 55 by the rotation of the supply roller 4, and the toner supply to the supply roller 4 is further efficiently realized. .

  By the way, when the gap 53 between the partition member 9 and the supply roller 4 becomes wide, the air flow between the partition member 9 and the supply roller 4 flows not only in the direction of the arrow A1 but also in the direction toward the toner suction portion D that is the reverse direction. Occurs, and efficient suction of the toner t is hindered. Therefore, the gap between the partition member 9 and the supply roller 4 is preferably 2 mm or less at most. Note that the gap 53 between the partition member 9 and the supply roller 4 is set to be slightly wider on the upstream end 9 a side, but this is to allow the toner to smoothly flow into the gap 53. Is. However, the gap 53 may have a uniform width over the entire length of the partition member 9. Alternatively, as shown in FIG. 3A, it may be set wider on the downstream end portion 9b side.

  FIG. 4 is a cross-sectional view showing the configuration of the toner retention part B. As shown in FIG. 4, a toner retention portion B that is a “developer retention region” where toner t is retained is provided inside the frame 50 </ b> A (shaded portion in FIG. 4). The toner staying part B is an area surrounded by the inner wall surface 11 of the frame 50A, the developing roller 3, the partition member 9, the virtual horizontal plane H, the virtual plane I, and the blowout prevention sheet 10. The virtual horizontal plane H is a plane extending from the uppermost point of the partition member 9 to the inner wall surface 11 of the frame 50A in the horizontal direction. The virtual surface I is a plane extending from the lowest point of the partition member 9 to the developing roller 3 in the circumferential direction of the partition member 9. The blowing prevention sheet 10 that is a “blowing prevention member” is a sheet that is attached to the opening 50 a of the frame body 50 </ b> A and prevents the toner t inside the developing chamber 56 from blowing out from between the opening 50 a and the developing roller 3. The toner t inside the toner retention portion B is guided between the supply roller 4 and the developing roller 3 through the opening 54 (see FIGS. 3A and 3B).

  The agitating / conveying member 6 (see FIG. 2) conveys the toner t between the supply roller 4 and the developing roller 3 via the toner retention part B. Here, the toner amount that is the “developer amount” that moves during one cycle in which the stirring and conveying member 6 rotates will be described. During one cycle in which the agitation transport member 6 rotates, the amount of toner that can be stored in the toner retention portion B is “supply roller 4” in the contact nip N 2 that is the “contact portion” of the supply roller 4 and the developing roller 3. Is set to be larger than the amount of toner sucked by the supply roller 4 at the downstream end in the rotation direction. Further, during one cycle in which the agitating / conveying member 6 rotates, the amount of toner that the agitating / conveying member 6 conveys to the toner staying portion B is “the end on the downstream side in the rotation direction of the supply roller 4” of the contact nip N2. Is set to be larger than the amount of toner sucked by the supply roller 4 in the toner sucking portion D. As a result, the amount of toner that can stay in the toner retaining portion B is 1.5 g, and the amount of toner that is sucked into the supply roller 4 by the toner suction portion D is 0.25 g per second. Further, the stirring and conveying member 6 rotates every second, and the amount of toner that the stirring and conveying member 6 conveys to the toner staying portion B per time is 1 g.

  At the time of image formation, the agitating / conveying member 6 in the toner storage chamber 55 rotates, so that the toner t pumped up to the toner retention part B is temporarily stored in the toner retention part B. Then, the toner t stored in the toner retention part B is successively sucked into the supply roller 4 and conveyed to the toner discharge part C. Then, the toner t is discharged from the toner discharge portion C and applied to the developing roller 3. Then, the layer thickness is regulated by the developing blade 5, and the developing roller 3 is in an optimum toner coat state, and is developed in contact with the photosensitive drum 1.

  The solid density followability was evaluated with the configuration of this example. The evaluation condition is that the image forming apparatus is left at 25 ° C. and 50% Rh for one day to adjust to the environment, and after printing 100 horizontal line images with an image ratio of 5% on A4 size paper, a solid black image Were continuously output, and the image density of the first sheet was compared with the image density of the third sheet. The concentration was measured using a spectrodensitometer 500 manufactured by X-Rite. As a result, the difference between the image density of the first sheet and the image density of the third sheet was less than 0.2.

  According to the developing device 50 of the embodiment, a part of the toner t conveyed to the supply roller 4 by the agitating and conveying member 6 passes through the partition member 9 and is guided to the opening 54 (see FIG. 3A). The Accordingly, the toner t that has passed through the uppermost position 4L of the supply roller 4 and passed through the opening 54 formed at the upstream end 9a does not adhere to the supply roller 4 but the contact nip N2 between the supply roller 4 and the developing roller 3. Can be easily reached. The amount of toner t that adheres to the supply roller 4 and returns to the toner storage chamber 55 without reaching the developing roller 3 due to the rotation of the supply roller 4 is reduced. As a result, the supply efficiency of the toner t is improved, and the occurrence of an image problem due to the supply failure of the toner t is suppressed.

  In addition, it is possible to control the circulation of the toner t and air to the supply roller 4 by providing the partition member 9 at the upper part of the supply roller 4, and the suction force of the toner t of the supply roller 4 is utilized to the maximum. The toner can be supplied to the supply roller 4.

  Further, when the toner staying portion B is secured above the partition member 9, the developing roller 3 and the frame body 50 </ b> A, the toner t is stored in the toner staying portion B, so that it is supplied between the supply roller 4 and the developing roller 3. The amount of toner t to be increased can be increased.

  Further, the stirring / conveying member 6 has a toner retention portion B that is larger than the amount of toner sucked by the suction portion D in the contact nip N2 between the supply roller 4 and the developing roller 3 per time when the stirring / conveying member 6 rotates once. A large amount of toner is conveyed. In addition, the supply roller 4 can stay in the toner retention portion B more than the amount of toner sucked in the suction portion D in the contact nip N2 of the supply roller 4 and the developing roller 3 per time when the agitating and conveying member 6 makes one rotation. A large amount of toner is set. As a result, the toner t is always retained in the toner retaining portion B, and the supply roller 4 can always suck the toner t.

3 Development roller (developer carrier)
4 Supply roller (developer supply body)
6 Stirring conveying member (developer conveying member)
9 Partition member 50 Developing device 50A Frame (Developing device main body)
54 Opening 55 Toner storage chamber (developer storage chamber)

Claims (5)

A developing device main body;
A developer carrying member supported by the developing device main body and rotatable while carrying the developer;
A developer supply body that is supported by the developing device main body and is in contact with the developer carrier, and is rotatable while supplying the developer to the developer carrier;
A developer storage chamber that is partitioned below the developer supply body in the main body of the developing device and stores the developer;
A developer conveying member that is rotatably provided inside the developer accommodating chamber and conveys the developer from the developer accommodating chamber to the developer supply body;
The developer carrying member is disposed opposite to the outer peripheral surface, one end portion is positioned at a spaced position spaced apart from the outer peripheral surface of the developer carrying member by a predetermined size, and the other end portion is the uppermost position of the developer supplying member. Alternatively, the developer supply body is positioned downstream of the uppermost position in the rotation direction of the developer supply body, and a gap is formed between the developer supply body and the outer peripheral surface of the developer carrier. A partition member that forms an opening and partitions the developer supply body;
A developing device comprising: Inside the developing device main body, an inner wall surface of the developing device main body, the developer carrier, the partition member, a virtual horizontal plane extending from the uppermost point of the partition member to the inner wall surface of the developing device body in the horizontal direction, A virtual plane extending from the lowest point of the partition member to the developer carrying member in the circumferential direction of the partition member, attached to the opening of the developing device main body, the opening of the developing device main body, and the developer carrying member Surrounded by a blowout prevention member that prevents the developer from blowing out between, a developer retention region for retaining the developer is provided,
2. The developing device according to claim 1, wherein the developer inside the developer retention region is guided between the developer supply body and the developer carrier through the opening. The developer supply body is formed of a porous and elastic member,
The developer transport member transports the developer between the developer supply body and the developer carrier through the developer staying area,
During one cycle in which the developer conveying member rotates,
The amount of developer that can be stored in the developer retention area is determined by the developer supply at the downstream end of the developer supply body in the rotational direction of the contact portion between the developer supply body and the developer carrier. More than the amount of developer that the body inhales,
The amount of developer conveyed by the developer conveying member to the developer retention region is an end portion on the downstream side in the rotation direction of the developer supply body among contact portions of the developer supply body and the developer carrier. The developing device according to claim 2, wherein the amount of developer sucked by the developer supply body is larger.   4. The developing device according to claim 1, wherein the partition member is formed to be inclined downward from the uppermost position of the partition member toward the separation position. 5. . An image carrier;
The developing device according to any one of claims 1 to 4, wherein a developer is supplied to the electrostatic image formed on the image carrier and developed.
An image forming apparatus comprising:

Images