JP5279559B2 - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device, a process cartridge and an image forming apparatus, wherein the stability of solid density is improved and an image of high quality can be supplied. <P>SOLUTION: In the developing device 4, a developer supply member 20 is rotated, while being brought into contact with a developer carrier 17 through a nip part N and a developer return member 50 is arranged in the vicinity of the downstream side in a rotational direction outside the nip part N, while being adjacent or contact to/with the developer supply member 20. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus that forms an image on a recording material using an electrophotographic system, and more particularly to a developing device and a process cartridge applied to the electrophotographic image forming apparatus.

  Here, the electrophotographic image forming apparatus (hereinafter, also simply referred to as “image forming apparatus”) forms an image on a recording material (recording medium) using an electrophotographic image forming system. Examples of the image forming apparatus include a copying machine, a printer (laser beam printer, LED printer, etc.), a facsimile machine, a word processor, and a multifunction machine (multifunction printer) thereof.

  The developing device is a device for visualizing an electrostatic image on an image carrier such as an electrophotographic photosensitive member using a developer.

  In addition, the process cartridge is a cartridge in which an electrophotographic photosensitive member and a charging unit, a developing unit, or a cleaning unit as a process unit that acts on the electrophotographic photosensitive member are integrated into a cartridge and can be attached to and detached from the image forming apparatus main body. It is a thing. Alternatively, the process cartridge integrally forms an electrophotographic photosensitive member and at least one of charging means, developing means, and cleaning means as process means acting on the electrophotographic photosensitive member, with respect to the image forming apparatus main body. Can be attached and detached. Alternatively, the process cartridge is a cartridge in which the electrophotographic photosensitive member and at least the developing unit are integrated into a cartridge, which can be attached to and detached from the image forming apparatus main body.

  In an image forming apparatus such as a printer using an electrophotographic image forming method (electrophotographic process), an electrophotographic photosensitive member (hereinafter referred to as “photosensitive member”) as an image bearing member is uniformly charged, and the charged photosensitive member. An electrostatic image is formed on the photoreceptor by selectively exposing the body. The electrostatic image formed on the photoconductor is visualized as a toner image with the toner of the developer. The toner image formed on the photoconductor is transferred to a recording material such as recording paper or a plastic sheet, and the toner image is applied to the recording material by applying heat or pressure to the toner image transferred onto the recording material. Image recording is performed by fixing.

  Such an image forming apparatus generally requires replenishment of developer and maintenance of various process means. In order to facilitate the replenishment of the developer and maintenance of various process means, the photosensitive member, the charging means, the developing means, the cleaning means, etc. are collectively assembled into a cartridge, and a process that can be attached to and detached from the image forming apparatus main body. A cartridge has been put into practical use. According to the process cartridge system, an image forming apparatus with excellent usability can be provided.

  In recent years, color image forming apparatuses that form color images using a plurality of color developers have become widespread. As a color image forming apparatus, a photoconductor corresponding to each of image forming operations using a plurality of color developers is arranged in a line along the surface movement direction of a transfer target body onto which a toner image is transferred, so-called An in-line image forming apparatus is known. Some in-line color image forming apparatuses have a plurality of photoconductors arranged in a line in a direction (for example, a horizontal direction) intersecting a vertical direction (gravity direction). The in-line method is a preferable image forming method in that it is easy to meet demands such as an increase in image forming speed and development to a multifunction printer.

  In addition, as an in-line image forming apparatus in which a plurality of photoconductors are arranged in a row in a direction intersecting the vertical direction, the plurality of photoconductors are used as intermediate transfer members as transfer members or recording materials as transfer members. Is disposed below the recording material carrier that transports the recording medium (see Patent Document 1).

  When the photosensitive member is disposed below the intermediate transfer member or the recording material carrier, the fixing device and the developing device (or the exposure device, for example) are arranged in such a manner that the intermediate transfer member or the recording material carrier is sandwiched in the image forming apparatus main body. ) Can be arranged at remote locations. Therefore, there is an advantage that the developing device (or the exposure device) is hardly affected by the heat of the fixing device.

  On the other hand, when the photosensitive member is disposed below the intermediate transfer member or the recording material carrier as described above, the developer is supplied to the developer carrier and the developer supply member against the gravity in the developing device. May need to be done.

  In supplying the developer to the developer supply member, it is most efficient to transport the toner to a location immediately downstream of the developer supply member in the rotation direction and immediately after the nip portion between the developer carrier and the developer supply member. good. That is, in the developer supply member provided with an elastic layer having a plurality of cells on the outer peripheral portion, immediately after the nip portion, the elastic portion coming out of the nip portion is released from pressure, and the cell opens accordingly. At this time, intake is performed and developer is sucked. Therefore, in order to efficiently hold the developer on the developer supply member, it is preferable to feed the toner directly into the suction portion.

  However, in a developing device that supplies developer against gravity, it is difficult to feed a large amount of toner to the suction portion with a simple configuration. Even if the toner is sent to the vicinity of the suction portion, a part of the toner is sucked, but most of the toner is returned to the toner storage chamber or the like with the rotation of the developer supply member.

  Therefore, Patent Document 1 proposes a technique for supplying the developer at the lower portion of the developer supply member. In Patent Document 1, as shown in FIG. 9 attached to the present application, at the contact portion between the developing roller (developer carrying member) 33 and the supply roller (developer supplying member) 31, the developer supplying member 31 extends from below to above. Rotate. A toner receiving member 30 is provided below the developer supply member 31, and one end of the receiving sheet 32 is attached to the toner receiving member 30, and the receiving sheet 32 is contacted below the developer supplying member 31 with an appropriate linear pressure. I am letting.

  As described above, Patent Document 1 discloses a method in which the receiving sheet 32 is brought into contact with the lower portion of the developing supply member 31. According to this, the receiving sheet 32 prevents the developer attached to the developer supply member 31 from dropping due to gravity, and prevents the developer that can be supplied to the developer carrier 33 from decreasing, thereby reducing the solid density. Is preventing.

JP 2003-173083 A

  However, in the developer supply method as described above, when low printing durability is performed, the amount of developer to be developed is small, so that a large amount of developer that does not circulate between the developer supply member 31 and the receiving sheet 32 is large. May exist.

  That is, although toner is accumulated below the developer supply member 31, consumption of the accumulated developer does not proceed with low printing durability. Therefore, as the developer supply member 31 rotates, the developer is successively supplied to the lower side thereof, the developer aggregates and packs, and an image such as uneven density due to uneven toner supply to the developer supply member 31. It may cause deterioration of quality.

  The present invention has been made in view of such problems, and provides a developing device, a process cartridge, and an image forming apparatus capable of improving solid density stability and supplying a high-quality image. With the goal.

The above object is achieved by a developing device, a process cartridge, and an image forming apparatus according to the present invention. In summary, the present invention, according to one aspect,
A developer carrier for carrying the developer;
A developer supply member for supplying a developer to the developer carrier;
A developer storage chamber disposed below the developer supply member and storing the developer;
A conveyance member that is provided in the developer storage chamber and supplies the developer from the developer storage chamber to the developer supply member;
In a developing device having
The developer supply member rotates in contact with the developer carrying member with a nip portion, and approaches or contacts the developer supply member outside the nip portion and in the vicinity of the downstream side in the rotation direction. And a developer returning member.

  According to another aspect of the present invention, at least the image carrier and the developing device having the above-described configuration that performs development by supplying a developer to the electrostatic latent image formed on the image carrier are integrated. A process cartridge is provided that is configured to be detachable from the main body of the image forming apparatus.

  According to another aspect of the present invention, an image carrier and a developing device having the above-described configuration that performs development by supplying a developer to an electrostatic latent image formed on the image carrier are provided. An image forming apparatus is provided.

  According to another aspect of the present invention, there is provided an image forming apparatus characterized in that the process cartridge having the above-described configuration is detachable.

  According to the present invention, there is provided a developing device, a process cartridge, and an image forming apparatus capable of ensuring supply of a developer to a developer supply member, improving solid density stability, and supplying a high-quality image. Can be provided.

1 is a schematic cross-sectional view of an embodiment of an image forming apparatus according to the present invention. 1 is a schematic configuration diagram of an embodiment of a developing device and a process cartridge according to the present invention. It is a cross-sectional enlarged view for explaining the operation of the toner return member of one embodiment. 5 is a schematic configuration diagram of a process cartridge in Comparative Example 1. FIG. FIG. 10 is a schematic configuration diagram of a process cartridge in Comparative Example 2. FIG. 5 is a schematic configuration diagram of another embodiment of a developing device and a process cartridge according to the present invention. It is a top view of the toner return member of other examples. It is a cross-sectional enlarged view for explaining the operation of the toner return member of another embodiment. It is a schematic block diagram of the conventional developing device and process cartridge.

  Hereinafter, a developing device, a process cartridge, and an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Example 1
A first embodiment of the present invention will be described with reference to FIGS.

[Image forming apparatus]
First, the overall configuration of an electrophotographic image forming apparatus (image forming apparatus) according to the present invention will be described.

  FIG. 1 is a schematic cross-sectional view of an image forming apparatus 100 of the present embodiment. The image forming apparatus 100 of this embodiment is a full-color laser printer that employs an inline method and an intermediate transfer method. The image forming apparatus 100 can form a full-color image on a recording material (for example, recording paper, plastic sheet, cloth, etc.) according to the image information. The image information is input to the image forming apparatus main body 100A from an image reading apparatus connected to the image forming apparatus main body 100A or a host device such as a personal computer connected to the image forming apparatus main body 100A so as to be communicable.

  The image forming apparatus 100 includes, as a plurality of image forming units, first, second, and third images for forming yellow (Y), magenta (M), cyan (C), and black (K) images, respectively. And fourth image forming units SY, SM, SC, and SK. In the present embodiment, the first to fourth image forming units SY, SM, SC, and SK are arranged in a line in a direction that intersects the vertical direction.

  In the present embodiment, the configurations and operations of the first to fourth image forming units SY, SM, SC, and SK are substantially the same except that the colors of 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 they are elements provided for any color are omitted, and generally explain.

  In other words, in this embodiment, the image forming apparatus 100 includes four drum-type electrophotographic photosensitive members, that is, the photosensitive drums 1 arranged in parallel in a direction intersecting the vertical direction as a plurality of image carriers. . The photosensitive drum 1 is rotationally driven by a driving means (drive source) (not shown) in the direction indicated by an arrow A (clockwise). Around the photosensitive drum 1, a charging roller 2 as a charging means for uniformly charging the surface of the photosensitive drum 1, a laser is irradiated based on image information, and an electrostatic image (electrostatic) is formed on the photosensitive drum 1. A scanner unit (exposure device) 3 is disposed as exposure means for forming a (latent image). Further, around the photosensitive drum 1, a developing unit (developing device) 4 as developing means for developing an electrostatic image as a toner image, toner remaining on the surface of the photosensitive drum 1 after transfer (transfer residual toner) A cleaning member 6 is disposed as a cleaning means for removing water. Further, an intermediate transfer belt 5 as an intermediate transfer body for transferring the toner image on the photosensitive drum 1 to the recording material 12 is disposed opposite to the four photosensitive drums 1.

  In this embodiment, the developing unit 4 uses a non-magnetic one-component developer toner as the developer. In this embodiment, the developing unit 4 performs reverse development by bringing a developing roller (described later) as a developer carrying member into contact with the photosensitive drum 1. In other words, in this embodiment, the developing unit 4 is a portion where the charge is attenuated due to the exposure of the toner charged to the same polarity as the charging polarity of the photosensitive drum 1 (negative polarity in this embodiment) on the photosensitive drum 1 ( The electrostatic image is developed by being attached to the image portion and the exposure portion).

  In this embodiment, the photosensitive drum 1 and the charging roller 2, the developing unit 4 and the cleaning member 6 as process means acting on the photosensitive drum 1 are integrated, that is, integrated into a cartridge, A process cartridge 7 is formed. The process cartridge 7 can be attached to and detached from the image forming apparatus 100 via mounting means such as a mounting guide and a positioning member provided in the image forming apparatus main body 100A. In this embodiment, the process cartridges 7 for the respective colors all have the same shape, and each of the process cartridges 7 for each color has yellow (Y), magenta (M), cyan (C), and blank ( K) toner of each color is accommodated.

  The intermediate transfer belt 5 formed of an endless belt as an intermediate transfer member abuts on all the photosensitive drums 1 and circulates (rotates) in the direction of arrow B (counterclockwise) in the figure. The intermediate transfer belt 5 is wound around a driving roller 51, a secondary transfer counter roller 52, and a driven roller 53 as a plurality of support members.

  On the inner peripheral surface side of the intermediate transfer belt 5, four primary transfer rollers 8 as primary transfer means are arranged in parallel so as to face the respective photosensitive drums 1. The primary transfer roller 8 presses the intermediate transfer belt 5 toward the photosensitive drum 1 to form a primary transfer portion N1 where the intermediate transfer belt 5 and the photosensitive drum 1 abut. A bias having a polarity opposite to the normal charging polarity of the toner is applied to the primary transfer roller 8 from a primary transfer bias power source (high voltage power source) as a primary transfer bias applying unit (not shown). As a result, the toner image on the photosensitive drum 1 is transferred (primary transfer) onto the intermediate transfer belt 5.

  A secondary transfer roller 9 as a secondary transfer unit is disposed at a position facing the secondary transfer counter roller 52 on the outer peripheral surface side of the intermediate transfer belt 5. The secondary transfer roller 9 is pressed against the secondary transfer counter roller 52 via the intermediate transfer belt 5 to form a secondary transfer portion N2 where the intermediate transfer belt 5 and the secondary transfer roller 9 come into contact. A bias having a polarity opposite to the normal charging polarity of the toner is applied to the secondary transfer roller 9 from a secondary transfer bias power source (high voltage power source) as a secondary transfer bias applying unit (not shown). As a result, the toner image on the intermediate transfer belt 5 is transferred (secondary transfer) to the recording material 12.

  More specifically, at the time of image formation, first, the surface of the photosensitive drum 1 is uniformly charged by the charging roller 2. Next, the surface of the charged photosensitive drum 1 is scanned and exposed by laser light corresponding to the image information emitted from the scanner unit 3, and an electrostatic image according to the image information is formed on the photosensitive drum 1. Next, the electrostatic image formed on the photosensitive drum 1 is developed as a toner image by the developing unit 4. The toner image formed on the photosensitive drum 1 is transferred (primary transfer) onto the intermediate transfer belt 5 by the action of the primary transfer roller 8.

  For example, when forming a full-color image, the above-described process is sequentially performed in the first to fourth image forming units SY, SM, SC, and SK, and the toner images of the respective colors are next superimposed on the intermediate transfer belt 5. The primary transfer.

  Thereafter, the recording material 12 is conveyed to the secondary transfer portion N2 in synchronization with the movement of the intermediate transfer belt 5. The four color toner images on the intermediate transfer belt 5 are secondarily transferred onto the recording material 12 collectively by the action of the secondary transfer roller 9 that is in contact with the intermediate transfer belt 5 via the recording material 12.

  The recording material 12 onto which the toner image has been transferred is conveyed to a fixing device 10 as a fixing unit. The toner image is fixed on the recording material 12 by applying heat and pressure to the recording material 12 in the fixing device 10.

  Further, the primary transfer residual toner remaining on the photosensitive drum 1 after the primary transfer process is removed and collected by the cleaning member 6. The secondary transfer residual toner remaining on the intermediate transfer belt 5 after the secondary transfer process is cleaned by the intermediate transfer belt cleaning device 11.

  Note that the image forming apparatus 100 can form a single-color or multi-color image using only one desired image forming unit or using only some (not all) image forming units. It is like that.

[Process cartridge]
Next, the overall configuration of the process cartridge 7 mounted on the image forming apparatus 100 of the present embodiment will be described.

  FIG. 2 is a schematic cross-sectional view (main cross-sectional view) of the process cartridge 7 of this embodiment viewed along the longitudinal direction (rotational axis direction) of the photosensitive drum 1.

  In the present embodiment, the configuration and operation of the process cartridge 7 for each color are substantially the same except for the type (color) of the developer stored therein.

  The process cartridge 7 is configured by integrating a photosensitive unit 13 including the photosensitive drum 1 and the developing unit 4 including a developing roller 17 and the like.

  The photoconductor unit 13 has a cleaning frame 14 as a frame that supports various elements in the photoconductor unit 13. The photosensitive drum 1 is rotatably attached to the cleaning frame 14 via a bearing (not shown). The photosensitive drum 1 is rotationally driven in the direction of the arrow A (clockwise) in accordance with the image forming operation by transmitting the driving force of a driving motor (not shown) as a driving means (driving source) to the photosensitive unit 13. Is done. In this embodiment, the photosensitive drum 1 which is the center of the image forming process is an organic photosensitive drum in which an outer surface of an aluminum cylinder is coated with a functional undercoat layer, a carrier generation layer, and a carrier transfer layer in this order. 1 is used.

  Further, the cleaning unit 6 and the charging roller 2 are disposed in the photosensitive unit 13 so as to come into contact with the peripheral surface of the photosensitive drum 1. The transfer residual toner removed from the surface of the photosensitive drum 1 by the cleaning member 6 falls and is stored in the cleaning frame 14.

  The charging roller 2 as charging means is driven to rotate by bringing the roller portion of conductive rubber into pressure contact with the photosensitive drum 1.

  Here, as a charging process, a predetermined DC voltage is applied to the core of the charging roller 2 with respect to the photosensitive drum 1, whereby a uniform dark portion potential (Vd) is applied to the surface of the photosensitive drum 1. Is formed. The spot pattern of the laser beam emitted in accordance with the image data by the laser beam from the scanner unit 3 described above exposes the photosensitive drum 1, and the exposed portion is charged on the surface by the carrier from the carrier generation layer. Disappears and the potential drops. As a result, an electrostatic latent image is formed on the photosensitive drum 1 with a predetermined light portion potential (Vl) at an exposed portion and a predetermined dark portion potential (Vd) at an unexposed portion.

  On the other hand, the developing unit 4 includes a developing roller 17 as a developer carrying member for carrying a developer (toner) 80 and a toner supply roller 20 as a developer supplying member that supplies toner to the developing roller 17. Have. Further, the developing unit 4 is disposed below the toner supply roller 20 in the gravity direction, and includes a developer storage chamber that stores the toner 80, that is, a toner storage chamber 18.

  Further, as will be described in detail later, the toner supply roller 20 rotates while being in contact with the developing roller 17 and the nip portion N. Further, in the developing unit 4 of the present embodiment, the developer returning member, that is, the toner returning member 50 constituting the characteristic part of the present invention is outside the nip portion N and near the downstream side in the rotation direction of the toner supply roller 20. The toner supply roller 20 is disposed close to or in contact with the toner supply roller 20.

  A stirring and conveying member 22 is provided in the toner storage chamber 18. The agitating / conveying member 22 agitates the toner stored in the toner storage chamber 18 and also conveys the toner in the direction of arrow G in the figure toward the upper portion of the toner supply roller 20.

  The developing blade 21 is in contact with the developing roller 17 at a counter, and regulates the coating amount of the toner supplied by the toner supply roller 20 and applies a charge. The developing blade 21 is made of a thin plate-like member, forms contact pressure by utilizing the spring elasticity of the thin plate, and the surface thereof is in contact with the toner and the developing roller 17. The toner is triboelectrically charged by rubbing between the developing blade 21 and the developing roller 17 to be charged, and at the same time the layer thickness is regulated. In this embodiment, a predetermined voltage is applied to the developing blade 21 from a blade bias power source (not shown) to stabilize the toner coat.

  The developing roller 17 and the photosensitive drum 1 rotate so that the surfaces of the developing roller 17 and the photosensitive drum 1 move in the same direction (in this embodiment, the direction from the bottom to the top) in the facing portion (contact portion).

  In the present embodiment, the developing roller 17 is disposed in contact with the photosensitive drum 1, but the developing roller 17 is disposed close to the photosensitive drum 1 at a predetermined interval. May be.

  In this embodiment, a toner charged negatively by frictional charging with respect to a predetermined DC bias applied to the developing roller 17 has a bright portion potential portion in a developing portion where the toner contacts the photosensitive drum 1 from the potential difference. The electrostatic latent image is visualized by transferring only to.

  The toner supply roller 20 is disposed with a predetermined contact portion (nip portion) N formed on the peripheral surface of the developing roller 17 at the opposed portion, and rotates in the direction of the arrow E (counterclockwise) in the drawing. The toner supply roller 20 is an elastic sponge roller in which a foam layer is formed on the outer periphery of a conductive metal core. The toner supply roller 20 and the developing roller 17 are in contact with each other with a predetermined intrusion amount, that is, in FIG. The contact portion N rotates so as to move in the opposite directions. With this operation, the toner supply roller 20 supplies toner to the developing roller 17 and the toner remaining on the developing roller 17 is peeled off. Yes.

  In carrying the toner by the toner supply roller 20, it is important to include a large amount of toner in the sponge cell. For this purpose, as described above, the toner is directly supplied to the toner suction portion of the toner supply roller 20. Is the most efficient.

  In this embodiment, both the developing roller 17 and the toner supply roller 20 have an outer diameter of 20 mm, and the amount of penetration of the toner supply roller 20 into the developing roller 17, that is, the toner supply roller 20 is recessed by the developing roller 17. The indentation amount ΔE is set to 1.5 mm.

  Hereinafter, the toner return member, which is a feature of the present invention, will be described with reference to FIG.

  In this embodiment, FIG. 3 is an enlarged schematic cross-sectional view of the vicinity of the toner suction portion of the toner supply roller 20, and shows the movement of the toner conveyed from the stirring and conveying member 22 to the toner supply roller 20.

  It is most efficient that the toner is conveyed by the agitating and conveying member 22 toward the toner suction portion M of the toner supply roller 20. Therefore, in this embodiment, by installing the toner return member 50, the toner conveyed near the toner suction portion is efficiently taken into the toner supply roller 20, and the toner conveyance amount to the developing roller 17 by the toner supply roller 20 is achieved. Is to increase.

  The characteristics of the toner return member 50, which is a characteristic of this embodiment, will be described.

  Part of the toner conveyed by the agitating / conveying member 22 in the vicinity of the toner suction portion along the path indicated by the arrow G in the drawing is taken into the suction portion M, and most of the toner is conveyed in the direction of the arrow F1 in the drawing. The operation of the toner return member 50 is to circulate the toner that is not taken in by the toner supply roller 20 in the vicinity of the toner suction portion M but bounces in the direction of the arrow F1 in the drawing, and takes the toner near the toner suction portion M again. It is to create F (circulation that combines F1, F2, and F3). As a result, the toner reservoir J can be formed in the toner suction portion M, and the toner once transported by the stirring and transporting member 22 can be efficiently taken into the toner suction portion M of the toner supply roller 20. .

  The toner returning member 50 is disposed outside the nip portion N and in the vicinity of or in contact with the toner supply roller 20 near the downstream side in the rotation direction of the toner supply roller 20. In this embodiment, the toner supply roller 20 is disposed in a non-contact manner and in the immediate vicinity. This is because, when the toner return member 50 enters the toner supply roller 20 with a predetermined pressure, the toner contained in the toner supply roller 20 is removed before the nip N between the toner supply roller 20 and the toner return member 50. This is because it exhales. Further, if the toner return member 50 is too far from the toner supply roller 20, the toner flowing in the direction of the arrow F1 cannot be sufficiently blocked, and the amount of rebound is reduced. The distance between the toner return member 50 and the toner supply roller 20 is preferably 2 mm or less (0 mm or more), and more preferably 1 mm or less (0 mm or more). In this example, it was set to 0.5 mm. Further, the toner return surface H of the toner return member 50 is between the suction part M and the K point where the difference in height between the toner suction part M on the toner supply roller 20 and the toner supply roller 20 is the largest. It is desirable. If it is within the K point, the toner can be easily fed to the vicinity of the suction portion, and the toner pool J is easily formed.

  As described above, in the present invention, the toner supply to the toner supply roller 20 can be efficiently performed by disposing the toner return member 50 at an appropriate position. Therefore, it is possible to provide a developing device, a process cartridge, and an image forming apparatus that can improve the stability of solid density and supply a high-quality image.

[Comparative Example 1]
A schematic cross-sectional view of Comparative Example 1 is shown in FIG. As shown in FIG. 4, the developing device 7A is not provided with the toner return member 50. Other configurations are the same as those in the first embodiment.

[Comparative Example 2]
In Comparative Example 2, as in Comparative Example 1, as shown in FIG. 5, the developing device 7 </ b> A is not provided with the toner return member 50. Further, in the second comparative example, as described in the background art with reference to FIG. 9, the toner receiving member 30 is provided below the developer supply member (toner supply roller) 20, and the toner receiving member 30 has the receiving sheet. One end of 32 was attached. Further, the receiving sheet 32 is configured to contact the lower portion of the toner supply roller 20 with an appropriate linear pressure. Other configurations are the same as those in the first embodiment.

[Experiment]
The following two experiments were conducted on the configurations of the above-described embodiment of the present invention and the comparative examples 1 and 2.

(1) Solid density follow-up evaluation As a comparison of toner supply ability, solid density follow-up evaluation was performed to measure the amount of density decrease when high-printing printing was continued.

Evaluation was performed after the image forming apparatus was left in an evaluation environment at 25.0 ° C. and 50% Rh for one day to adjust to the environment, and after printing 100 sheets. In the printing test for 100 sheets, a horizontal line recorded image having an image ratio of 5% is continuously fed. Thereafter, three solid black images were output continuously, and the following evaluation was performed using a spectrodensitometer 500 manufactured by X-Rite based on the density difference between the output front and rear ends of the third solid black image. The print test and evaluation image were output in a single color.
◯: The density difference between the leading edge and the trailing edge of the paper in a solid black image is less than 0.2. Δ: The density difference between the leading edge and the trailing edge of the paper in a solid black image is less than 0.2 to 0.3. In a solid black image, the density difference between the leading edge and the trailing edge of the paper is 0.3 or more. (2) Presence / absence of toner packing Evaluation of toner packing is performed by disassembling a durable image forming apparatus, We investigated and evaluated whether there was any.
○: No toner packing Δ: Toner aggregation occurs ×: Toner packing occurs As a durability condition, 5000 sheets were printed intermittently in an environment of 32.5 ° C. and 80% Rh. Intermittent paper passing means that the next printing is performed after waiting after printing.

  In addition, toner aggregation indicates a state in which toner is present in the developing chamber at a high density although not packed.

(Experimental result)
Table 1 shows the settings of the examples and the evaluation results thereof.

  First, the superiority of the present invention over Comparative Example 2 which is a prior art will be described.

  In the present invention, a toner pool is formed in the toner suction portion M on the toner supply roller 20 to efficiently supply the toner. As a result, the toner supply roller 20 can sufficiently hold the toner, and a solid density followability can be ensured as in the second comparative example. Further, since the receiving sheet 32 of Comparative Example 2 is not used, toner is not packed in principle, and toner supply unevenness due to packing does not occur.

  Next, the superiority of the present invention over Comparative Example 1 will be described.

  In Comparative Example 1, although the toner can be transported to the toner suction portion M by the stirring and transporting member 22, the toner that has not yet been taken in by the toner supply roller 20 as the toner supply roller 20 rotates rotates in the toner storage chamber 18. It will be returned to. For this reason, it is difficult to sufficiently include toner in the toner supply roller 20, leading to insufficient supply of toner to the developing roller 17.

  Further, since the toner packing does not use the receiving sheet 32 according to the comparative example 2, it does not occur in principle.

Example 2
Next, a second embodiment of the developing device according to the present invention will be described with reference to FIG. FIG. 6 is a schematic cross-sectional view of the developing device 4 showing the characteristics of the second embodiment.

  In this embodiment, the image forming apparatus to which the developing device is applied is the same as that described in the first embodiment, and a description thereof will be omitted. Further, the developing device of the present embodiment has the same configuration as the developing device of the first embodiment described above, and members having the same configuration and function are denoted by the same reference numerals. The description of the above is used, and the re-explanation here is omitted.

  A characteristic of the developing device in this embodiment is that the sheet 70 as a toner return member is brought into contact with the toner supply roller 20 with a light pressure to perform the toner return operation.

  Next, the operation of the toner return member 70 which is a feature of the second embodiment will be described in detail.

  The toner return member 70 is composed of a sheet, and is provided so as to cover the toner suction portion M of the toner supply roller 20 as shown in FIG. One end of the toner return member 70 is fixed to the inner wall of the developing container 18, and the opposite side is in contact with the toner supply roller 20 in the forward direction and with light pressure. The light pressure indicates the degree to which the toner contained in the toner supply roller 20 is not ejected before the contact portion. In this embodiment, the sheet 70 is made of PET.

  It should be noted that the material need not be PET if it can be contacted with light pressure, and there is no problem even if it is composed of other materials as long as the same action can be obtained.

  Further, the ceiling portion 70a of the toner return member 70 is provided with a plurality of round holes 70b as shown in FIG. 7, so that the toner can pass so as not to greatly impede the toner supply from the stirring and conveying member 22. ing.

  The toner that has passed through the ceiling portion 70a falls near the toner suction portion M. Although a part of the toner is taken into the suction part M as shown in FIG. 8, most of the toner is conveyed in the F1 direction. Therefore, the toner conveyed to the toner return member 70 collides and rises along the surface of the toner return member 70 (F2), and returns again to the vicinity of the suction portion M (F3). Then, a toner reservoir J is formed, and it becomes possible to supply toner to the suction portion as in the first embodiment.

  The operation different from that of the first embodiment is that the toner returning member 70 is in contact with the surface of the toner supply roller, so that the toner that has flowed through the circulation of F1 can be returned to the suction portion M more efficiently. .

  As described above, by using the toner return member 70 according to the second embodiment, the toner conveyed from the stirring and conveying member 22 can be efficiently held on the toner supply roller. Accordingly, it is possible to provide a developing device, a process cartridge, and an image forming apparatus capable of improving the solid density stability and supplying a high-quality image.

  In addition, about the structure of the Example of this invention, the experiment similar to the content described in Example 1 was conducted. The result is as described above, and the same effect as in Example 1 is obtained.

  The first and second embodiments have been described above.

  In the above-described embodiments, an image forming apparatus capable of forming a color image is illustrated, but the present invention is not limited to this, and an image forming apparatus capable of forming a monochrome image may be used. The same effect can be obtained by applying the principle of the present invention to the developing device in such an image forming apparatus.

  In the above-described embodiments, the printer is exemplified as the image forming apparatus, but the present invention is not limited to this. For example, another image forming apparatus such as a copying machine or a facsimile machine, or another image forming apparatus such as a composite machine combining these functions, or a recording material carrier is used and is supported on the recording material carrier. An image forming apparatus that sequentially superimposes and transfers the toner images of the respective colors on the recording material may be used. The same effect can be obtained by applying the present invention to the developing device in such an image forming apparatus.

1 Photosensitive drum (image carrier)
2 Charging roller (charging means)
3 Scanner unit (exposure means, exposure device)
4. Developing unit (developing means, developing device)
5 Intermediate transfer belt (intermediate transfer member)
6 Cleaning member 7 Process cartridge 13 Photosensitive unit 14 Cleaning frame 15 Developing chamber 17 Developing roller (developer carrier)
18 Toner storage chamber (developer storage chamber, developer container)
20 Toner supply roller (developer supply member)
21 Developing blade 22 Agitating and conveying member 50, 70 Toner returning member (developer returning member)
80 Toner (Developer)
DESCRIPTION OF SYMBOLS 100 Image forming apparatus 100A Image forming apparatus main body

Claims (5)

A developer carrier for carrying the developer;
A developer supply member for supplying a developer to the developer carrier;
A developer storage chamber disposed below the developer supply member and storing the developer;
A conveyance member that is provided in the developer storage chamber and supplies the developer from the developer storage chamber to the developer supply member;
In a developing device having
The developer supply member rotates in contact with the developer carrying member with a nip portion, and approaches or contacts the developer supply member outside the nip portion and in the vicinity of the downstream side in the rotation direction. And a developer returning member.   The developing device according to claim 1, wherein the developer supply member includes a foam layer having a plurality of cells, and the developer is conveyed by the foam layer.   3. At least the image carrier and the developing device according to claim 1 or 2 for performing development by supplying a developer to the electrostatic latent image formed on the image carrier. A process cartridge characterized in that it is configured to be detachable.   An image forming apparatus comprising: an image bearing member; and a developing device according to claim 1 for performing development by supplying a developer to the electrostatic latent image formed on the image bearing member. .   An image forming apparatus, wherein the process cartridge according to claim 3 is detachable.

Images