JP2006003736A - Developing device, process cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain displacement of a doctor gap by reducing the pressure of developer on a restricting member. <P>SOLUTION: The developing device 14Y includes: a developer carrier 141 for holding developer thereon and conveying it to a developing area located opposite a latent image carrier 12Y; the restricting member 146 disposed opposite the developer carrier 141 and adapted to form a developer restricting section S for regulating the thickness of the developer layer held on the developer carrier; and a development casing 144 for supporting at least the restricting member 146. The developing device 14Y develops a latent image on the latent image carrier 12Y. In the developing device 14Y, a receiving member 147 projecting from the development casing 144 toward the inside of the casing 144 and serving as a developer receiving face is disposed upstream of the restricting member 146 in the direction of the movement of the developer carrier 141. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a developing device that carries a developer and develops a latent image on a latent image carrier, a process cartridge that includes the developing device and the latent image carrier, and an image forming apparatus that includes these.

  2. Description of the Related Art Image forming apparatuses using an electrophotographic recording system such as a copying machine, a printer, a facsimile machine, and a composite machine of these are widely known. In these image forming apparatuses, a developer is supplied to a drum-shaped or belt-shaped photoconductor serving as a latent image carrier, and the latent image formed on the surface of the photoconductor is developed. A process cartridge integrated with a casing is mounted.

  The developing device includes a developer screw such as a developer screw or a paddle as an agent conveying member that conveys the developer while stirring the developer in the axial direction of the photosensitive member, a developer carrying member such as a developing roller or a developing sleeve that supplies the developer to the photosensitive member, and a developing device. A doctor blade is provided as an agent regulating member. These developer carrier and doctor blade extend in the axial direction of the photoreceptor.

  Although depending on the positional relationship with the developer carrier, the doctor blade is disposed, for example, below the developer carrier B so as to face the developer carrier as indicated by reference numeral A in FIG. A constant gap (doctor gap) is formed between the tip and the surface of the developer carrying member, and the layer thickness of the developer carried on the developer carrying member is made constant.

  The developer carrier has a plurality of magnets for carrying the developer, but the magnetic force of the developer carrier facing the doctor blade is higher than that of other parts. This is because if the developer is not sufficiently held in the area near the doctor gap, the developer carrier is regulated by the doctor blade when there is some replenishment to the developer carrier in accordance with the pitch of the conveying screw. This is because the density varies, and the density unevenness of the conveying screw pitch occurs in the image.

  In Patent Document 1, a doctor blade is supported by a plurality of nodes of a developing device. However, Patent Document 2 discloses a configuration in which a vibration isolating member is disposed between a doctor blade and a casing.

JP 09-190075 A JP 2001-51501 A

  In the developing device, a doctor gap is formed between the surface of the developer carrying member and the doctor blade, and the developer in the device is collected around the doctor blade. For this reason, when regulating the developer layer thickness on the developer carrier, the agent pressure is generated by the resistance between the agent and the doctor blade, causing the doctor blade to be deformed, and as a result, the layer thickness is determined. The doctor gap changes. Further, if the magnetic force of the developer carrying member facing the doctor blade is increased as compared with other parts, the agent pressure increases, which also causes a doctor gap variation. Such a change in the doctor gap becomes unevenness of the developer in the longitudinal direction of the developer carrying member, and becomes a variation of the developer supplied to the photosensitive member, leading to manifestation as unevenness of image density.

In Patent Document 1, since the doctor blade is supported by a plurality of nodes of the developing device, it is possible to reduce the deformation at the time of attachment by adjusting the nodes, but the influence of the agent pressure during the operation of the developing device. Since the developer directly presses the doctor plate, there is a problem that it is difficult to avoid the pressing action that leads to the displacement of the doctor gap.
In Patent Document 2, a vibration isolating member is disposed on the doctor blade, but this is intended to reduce vibration, and it is inevitable that the doctor blade vibrates due to the influence of the agent pressure. It is only possible to prevent the propagation of vibration to the casing, and not to prevent the displacement of the doctor gap due to the agent pressure.
It is an object of the present invention to provide a developing device and a process cartridge that can reduce the developer pressure applied to the regulating member, suppress the displacement of the doctor gap, and extremely reduce the variation of the developer supplied to the latent image carrier. And its purpose.
The present invention provides an image forming apparatus capable of reducing the developer pressure applied to the regulating member to reduce the variation of the developer on the latent image carrier due to the displacement of the doctor gap and obtaining a good image without uneven image density. The purpose is to do.

In order to achieve the above object, in the present invention, a developer carrying member that carries a developer and transports it to a developing region facing the latent image carrying member, and a developer carrying member are disposed opposite to each other. In a developing device that develops a latent image on a latent image carrier, the regulating member includes a regulating member that forms a developer regulating portion that regulates the layer thickness of the carried developer and a developing casing that supports at least the regulating member. A receiving member that protrudes from the casing toward the inside of the developing casing and serves as a developer receiving surface is provided upstream of the member in the moving direction of the developer carrying member.
A process cartridge according to the present invention includes the developing device, and an image forming apparatus according to the present invention includes the process cartridge.

  According to the present invention, only the periphery of the layer thickness regulating portion of the regulating member is exposed to the pressing of the developer, and the other areas are concealed by the receiving member, so that the developer pressure on the regulating member is reduced and the doctor Gap displacement can be suppressed, and variations in the developer supplied to the latent image carrier can be extremely reduced.

  According to the present invention, since the developer pressure applied to the regulating member is reduced and the variation of the developer on the latent image carrier due to the displacement of the doctor gap is reduced, a good image without image density unevenness can be obtained.

  Hereinafter, an embodiment of an image forming apparatus to which the present invention is applied will be described with reference to the drawings. In the following embodiment, an electrophotographic printer capable of forming a full-color image is illustrated.

  In the printer shown in FIG. 1, image forming apparatuses 10Y (yellow), 10C (cyan), 10M (magenta), and 10K (black) for four colors as process cartridges are formed on the apparatus main body 1 side. The image forming station is detachable and includes an optical unit 20, an intermediate transfer body unit 30, a paper feeding unit 40, a fixing unit 50, and the like as exposure means capable of irradiating laser light.

  The image forming apparatuses 10Y, 10C, 10M, and 10K have the same structure, and the photosensitive drums 12Y, 12C, 12M, and 12K as latent image carriers are charged, and the photosensitive drums are charged as process means that act on the photosensitive drums. The charging devices 13Y, 13C, 13M, and 13K, and cleaning devices 15Y, 15C, 15M, and 15K that remove the developer remaining on the photosensitive drum are integrally configured, and formed on each photosensitive drum. The developing devices 14Y, 14C, 14M, and 14K for developing the latent images are connected.

  The intermediate transfer body unit 30 includes a transfer belt 31 as an intermediate transfer body, a plurality of (here, three) rollers 32, 33, and 34 that rotatably support the transfer belt 31, and toner formed on each photosensitive drum 12. A primary transfer roller 35 for transferring the image onto the transfer belt 31 and a secondary transfer roller 36 for transferring the toner image transferred onto the transfer belt 31 onto the recording paper P are provided.

  The paper supply unit 40 includes a paper supply roller 43 and a registration roller 44 that convey the recording paper P from the paper supply cassette 41 or the manual paper supply tray 42 to the secondary transfer region. The fixing unit 50 includes a fixing roller 51 and a pressure roller 52, and has a known configuration in which fixing is performed by applying heat and pressure to the toner image on the recording paper P.

  In such a configuration, first, in the first color yellow image forming device 10Y, the photosensitive drum 12Y is uniformly charged by the charging device 13Y, and then the latent image is developed by the laser light emitted from the optical unit 20. 14 is developed to form a toner image.

  The toner image formed on the photosensitive drum 12 is transferred onto the transfer belt 31 by the action of the primary transfer roller 35. The photosensitive drum 12Y after the primary transfer is cleaned by the cleaning device 15Y to prepare for the next image formation. The residual toner collected by the cleaning device 15Y is stored in a waste toner collection bottle 16 installed in the take-out direction of the image forming device 10Y (the rotation axis direction of the photosensitive drum). The waste toner collection bottle 16 is detachable from the image forming apparatus main body 1 so that it can be replaced when the storage amount is full. A similar image forming process is performed in each of the image forming apparatuses 10C, 10M, and 10K for C, M, and K to form toner images of the respective colors, which are sequentially transferred to the previously formed toner images.

  On the other hand, the toner image formed on the transfer belt 31 is transferred to the recording paper P conveyed from the paper feed cassette 41 or the manual paper feed tray 42 to the secondary transfer region by the action of the secondary transfer roller 36. . The recording paper P to which the toner image has been transferred is conveyed to the fixing unit 50, where the toner image is fixed at the nip portion between the fixing roller 51 and the pressure roller 52 of the fixing unit 50, and the discharge roller 55 discharges the upper part of the apparatus. The paper is discharged to the paper tray 56.

  On the upper part of the apparatus main body 1, toner bolts Y1, C1, M1, and K1, each storing toner to be supplied to a toner supply port 145, which will be described later, are detachably mounted from the apparatus main body 1 separately from each image forming apparatus. Yes.

  Next, the configuration of the image forming device and the developing device will be described. Each apparatus configuration is the same except that the color of the supplied toner as the developer is different, and therefore the image forming apparatus 10Y will be described below as an example.

  The charging device 13Y provided in the image forming device 10Y includes a charging roller 131 and a cleaning roller 132 that cleans the surface of the charging roller 131. The cleaning device 15Y includes a cleaning brush 151 and a cleaning blade 152 that are in contact with the surface of the photosensitive drum, and a toner recovery coil 153 that transports the toner scraped off by the cleaning brush 151 and the cleaning blade 152 toward the waste toner recovery bottle 16. It has.

  The developing device 14Y carries a toner of a two-component developer and carries a developing sleeve 141 as a developer carrying member that is conveyed by rotating counterclockwise in FIG. 2 to a developing region facing the photosensitive drum 12Y. A doctor as a regulating member that is disposed opposite to the developing sleeve 141 and forms a doctor gap S as a developer regulating portion that regulates the layer thickness of the toner carried on the surface of the developing sleeve 141 with the surface of the developing sleeve 141. The blade 146 and the developer stored in the developing device 14Y and the replenishment toner supplied from the toner replenishing port 145 are agitated and guided to the developing sleeve while being reciprocated in the axial direction of the photosensitive drum 12Y. Conveying screws 142 and 143, and a developing casing 144 that stores and supports these members are provided. The doctor blade 146 is supported so as to be sandwiched between the developing casings 144.

  A plurality of magnets (not shown) are arranged inside the developing sleeve 141. The distribution of the magnetic force in the normal direction by these magnets is indicated by reference signs P1 to P5 in FIG. In this embodiment, there is P5 as an opposite pole of the doctor blade 146, P1: 105 mT, P2: 95 mT, P3: 45 mT, P4: 45 mT, and P5: 84 mT.

  A receiving member 147 supported by the developing casing 144 is provided upstream of the doctor blade 146 in the moving direction of the developing sleeve 141. The developing sleeve 141, the doctor blade 146, and the receiving member 147 are extended in the axial direction of the photosensitive drum. The receiving member 147 has a substantially right triangle shape, and protrudes from the casing toward the space 148 where the toner is pumped up and stays by the conveying screw 143 inside the developing casing 144. Specifically, the top of the right triangle protrudes so as to be located toward the surface of the developing sleeve 141 and is adjacent to the doctor blade 146. The receiving member 147 is provided with a toner receiving surface 147 a that moves from the space portion 148 toward the doctor blade 146. The top of the receiving member 147 is substantially the same as or somewhat lower than the tip of the doctor blade 146.

  According to the developing device 14Y having such a configuration, the receiving member 147 is provided around the layer thickness regulating portion of the doctor blade 146 in the space portion 148 where the toner stays and flows toward the doctor blade 146. Other than that, it is concealed by the receiving member 147. As a result, the toner pressure applied to the doctor gap S is reduced, and the displacement of the doctor gap S is suppressed, so that the variation in the toner supplied to the photosensitive drum 12Y is extremely reduced.

  The receiving member 147 is provided on the back side of the doctor blade 146. However, if a gap is formed between the back side of the doctor blade 146 and the receiving member 147, toner may accumulate between the two, and the doctor cap S can be narrowed. For this reason, a gap S1 is provided in advance between the back side of the doctor blade 146 and the receiving member 147, and a plate-like elastic member 150 serving as a seal member is inserted into the gap S1, thereby interposing this. It is possible to prevent toner accumulation and agent dropping with respect to the gap.

  Further, in this embodiment, each toner bottle can be attached to and detached from each image forming apparatus individually from the apparatus main body 1, so that each toner bottle and each image forming apparatus can be exchanged individually, so that unnecessary replacement is possible. It is possible to reduce the user's expense when replacing parts. Further, since the number of times of opening / closing and taking in / out of other parts of the apparatus is reduced, it is possible to prevent toner scattering and improve maintainability.

  A toner having a sphericity of 0.93 or more can be used as the toner used in this embodiment. In other words, it is known to reduce the toner particle size in order to improve the image quality of the image, but in the case of reducing the particle size, the conventional pulverized toner has a particle size distribution that is broad. There is a characteristic that it is difficult. Therefore, it is possible to achieve high image quality by increasing the circularity of the toner by a polymerization method or the like and by making the particle size distribution sharp. The method has become commonplace. However, when the circularity of the toner is increased, the toner approaches a spherical shape, so that cleaning with the cleaning device 15Y becomes very difficult. However, in this embodiment, since the receiving member 147 is provided, the photosensitive drum due to the displacement of the doctor gap S is provided. Since there is no variation in the amount of toner supplied to 12Y, the cleaning performance can be maintained even when spherical toner obtained by polymerization or the like is used.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a configuration of a developing device as a main part of the present invention and a process cartridge including the developing device. FIG. 3 is an enlarged view showing a configuration of the developing device shown in FIG. 2. It is an enlarged view showing a configuration of a conventional developing device.

Explanation of symbols

10Y, 10C, 10M, 10K Process cartridge 12Y, 12C, 12M, 12K Latent image carrier 14Y, 14C, 14M, 14K Developing device 144 Developing casing 146 Restricting member 147 Receiving member 147a Receiving surface 150 Sealing member S Developer restricting portion S1 Gap

Claims (4)

A developer carrying member that carries the developer and transports it to a development area facing the latent image carrying member, and is disposed opposite to the developer carrying member, and regulates the layer thickness of the developer carried on the developer carrying member. In a developing device for developing a latent image on the latent image carrier, comprising: a regulating member that forms a developer regulating portion to be developed; and a developing casing that supports at least the regulating member.
A receiving member that protrudes from the casing toward the inside of the developing casing and serves as a receiving surface for the developer is provided upstream of the regulating member in the moving direction of the developer carrying member. Development device. The developing device according to claim 1,
A developing device, wherein a gap is provided between the regulating member and the receiving portion, and a seal member is interposed in the gap. A latent image carrier;
A process cartridge comprising the developing device according to claim 1. An image forming apparatus comprising the process cartridge according to claim 3.

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