JP2009156951A - Developing device, process cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a developing device capable of preventing a porous surface layer of a developer supply roller from being clogged with developer; a process cartridge; and an image forming apparatus. <P>SOLUTION: The developing device 1 is provided with a developing roller 2 supplying developer G to an image carrier Z, and the developer supply roller 4 having a sponge layer 41 coming into contact with the developing roller 2 in order to scrape off the developer G on the developing roller 2 while supplying the developer G to the developing roller 2. The device 1 is provided with a developer removing member 7 entering the sponge layer 41 in order to remove the developer with which the sponge layer 41 of the developer supply roller 4 is clogged. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing device, a process cartridge, and an image forming apparatus used for image formation such as a copying machine, a printer, and a FAX.

2. Description of the Related Art Conventionally, developing devices used for image formation such as copying machines, printers, and fax machines are used to develop an electrostatic latent image on an image carrier such as a charged photosensitive drum with a developer containing toner. Yes. The toner image on the image carrier is transferred to a transfer belt, and further transferred from the transfer belt to a sheet. The sheet on which the toner image is transferred is heated and pressurized by the fixing device, and the toner image is fixed on the sheet. Further, the toner remaining on the image carrier and the transfer belt without being transferred is cleaned using a cleaning unit. The above process is repeated and printing is performed continuously.
In general, a developing device is provided with a developing roller adjacent to the image carrier, a developer supply roller adjacent to the developing roller, and a developer stirring member for loosening the developer (for example, Patent Documents). 1 and Patent Document 2).

FIG. 5 schematically shows an example of a conventional developing device. The developing device 1 includes a developing roller 2 that supplies a developer to the image carrier Z, and a regulating member 3 that regulates the developer on the developing roller in order to form a thin layer of the developer on the developing roller 2. Is provided. The developing device 1 includes a developer supply roller 4 disposed in contact with the developing roller 2 to replenish the developing roller 2 with developer, and a developer agitation for loosening the developer G in the developing device. A member 5 is provided.
The developing roller 2 includes a developing sleeve 21 and a magnet 22 provided in the developing sleeve. A rubber layer is formed on the developing sleeve 21, and a sponge layer 41 is formed on the developer supply roller 4 that contacts the developing sleeve 21. The developer supply roller 4 rotates in the same direction as the developing roller 2, and the frictional resistance is increased. Incidentally, the developer remaining on the image carrier Z without being developed returns to the developing device via the developing roller 2 and is scraped off by the developer supplying roller 4. On the other hand, since the developer supply roller 4 is filled with the developer in the sponge layer 41, the developer supply roller 4 supplies the developer to the development roller 2 on the upstream side in the rotation direction of the developer supply roller 4 with respect to the scraped portion. become.

JP 2007-79119 A JP 2007-79322 A

However, in the conventional developing device, the developer enters the sponge layer 41 of the developer supply roller 4 and gradually becomes clogged. When the sponge layer 41 of the developer supply roller 4 is clogged, it becomes impossible to rub off the developer from the development roller 2 or to supply the developer to the development roller 2 accurately. In order to stably supply the toner to the image carrier Z, the developer returning from the developing roller 2 to the developer supplying roller 4 is precisely rubbed off so that the developer does not stay at the contact portion of both members. preferable. When the developer stays, the amount of developer adhering to the developing roller 2 changes or developers with different potentials coexist, and density unevenness occurs after development. In order to suppress the retention of the developer, it is preferable to optimize the material of the sponge itself and the size of the bubbles so that clogging is less likely to occur, but in practice it is difficult to avoid clogging.
When the developer supply roller 4 is clogged with the developer, the sponge does not have the inherent flexibility and is cured. For this reason, when the developing roller 2 and the developer supply roller 4 rotate, the rotational torque becomes large, and a high output of the motor as a driving source is required, and the apparatus becomes large.

  Accordingly, the present invention has been made in view of the above-described problems, and the problem is that a developing device, a process cartridge, and a developing cartridge capable of avoiding clogging of the developer in the porous surface layer of the developer supply roller An object of the present invention is to provide an image forming apparatus.

The features of the present invention, which is a means for solving the above problems, are listed below.
The developing device according to the present invention includes a developing roller that supplies a developer to an image carrier, and a porous surface that contacts the developing roller to scrape off the developer on the developing roller while supplying the developer to the developing roller. In a developing device provided with a developer supply roller having a layer, the developer removal that bites into the porous surface layer to remove clogged developer in the porous surface layer of the developer supply roller A member is provided.

  Further, the developing device of the present invention is the developing device according to claim 1, further comprising a blade portion on a front end side of the developer removing member, and the developer removing member presses the developer supply roller. The biting shape is such that the blade tip surface of the blade portion upstream in the rotation direction of the developer supply roller and the blade tip surface of the blade portion downstream in the rotation direction of the developer supply roller are the developer supply roller at the tip of the blade shape. When the angles formed by tangents to the concentric circles are θ1 and θ2, respectively, the shape is such that θ1 <θ2.

Further, the developing device of the present invention is further characterized in that the developer removing member is integrally formed in a developing container for storing the developer.
The developing device of the present invention is further characterized in that the developer removing member is a plate material.
The developing device of the present invention is further characterized in that the developer removing member is a flexible plate spring-like member.
A process cartridge according to the present invention includes any one of the developing devices described above.
An image forming apparatus according to the present invention includes any one of the developing devices described above.

  In the developing device, the process cartridge, and the image forming apparatus as the means for solving the problem, a developer removing member that bites into the porous surface layer is provided in the porous surface layer of the developer supply roller in order to remove the clogged developer. Therefore, the clogging of the developer in the porous surface layer of the developer supply roller can be avoided.

  The best mode for carrying out the present invention will be described below with reference to the drawings. Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims.

  FIG. 1 shows an embodiment of the developing device of the present invention. A rotatable developer stirring member 5 provided inside the developing container 6 of the developing device 1 is provided to loosen the developer G. The rotation direction may be either a clockwise direction or a counterclockwise direction. When the developer G in the developing container is loosened, the developer G moves to the vicinity of the developer supply roller 4 by its own weight. The developer supply roller 4 is a roller coated with a foam material having pores, and has a sponge layer 41 that is a porous surface layer. The developer supply roller 4 is in contact with the developing roller 2 in order to scrape off the developer on the developing roller while supplying the developer to the developing roller 2 that supplies the developer to the image carrier Z. In order to ensure this scrubbing function, the developing roller 2 and the developer supply roller 4 rotate in the same direction. The developing roller 2 is provided with a regulating member 3 for forming a thin layer of developer on the developing roller.

The reason why the sponge layer 41 is formed on the developer supply roller 4 is to allow the developer to sufficiently adhere to the developer supply roller, and also because the developer is caused by the pressure at the contact portion with the development roller 2. This is to prevent deterioration. As the foam material of the developer supply roller 4, a conductive material containing carbon fine particles or an ionic conductive material is used.
During the operation of the developing device 1, a voltage is applied to the electrode 42 at the center of the developer supply roller 4. For example, a DC bias offset in the direction opposite to the developer charging polarity with respect to the developing bias, or a bias in which an AC bias is superimposed on the DC bias offset in the direction opposite to the developer charging polarity with respect to the developing bias. Are applied. Further, for example, an AC bias is superimposed on a DC bias offset in the same direction as the developer charging polarity with respect to the developing bias, or a DC bias offset in the same direction as the developer charging polarity with respect to the developing bias. Bias is applied.

  As the developing roller 2, a roller coated with a rubber layer is used, and a surface coat layer made of a material that is easily charged to a polarity opposite to that of the developer is formed on the surface of the rubber layer. The rubber layer is set to a hardness of 60 degrees or less according to JIS-A in order to prevent developer deterioration due to pressure at the contact portion with the regulating member 3. The surface roughness is set to an arithmetic average roughness Ra of 0.3 to 2.0 μm, and a necessary amount of developer is held on the surface. Further, since the developing roller 2 is applied with a developing bias for forming an electric field with the image carrier Z, the rubber layer is set to a predetermined resistance value. The developing roller 2 rotates counterclockwise in the drawing, and conveys the developer held on the surface to a position facing the regulating member 3 and the image carrier Z.

  The regulating member 3 is a metal leaf spring such as stainless steel or phosphor bronze. The free end side of the regulating member 3 is in contact with the surface of the developing roller 2 with a predetermined pressure. The developer passing through the pressing portion is thinned and charged by frictional charging. Further, the regulating member 3 has a DC bias offset in the same direction as the developer charging polarity with respect to the developing bias in order to assist frictional charging, or in the same direction as the developer charging polarity with respect to the developing bias. A bias obtained by superimposing an AC bias on the offset DC bias is applied.

  The image carrier Z rotates in the clockwise direction in the figure, and the developing roller 2 rotates in the opposite direction to the image carrier Z. The developer thinned by the regulating member 3 is conveyed to a position facing the image carrier Z, and a latent image formed by the developing bias applied to the developing roller 2 and the electrostatic latent image on the image carrier. In accordance with the electric field, it moves to the surface of the image carrier Z and development is performed. The developer left on the developing roller without being developed on the image carrier returns to the inside of the developing container 6. In the figure, the image carrier Z and the developing roller 2 are arranged in contact with each other, but they may be arranged in a non-contact manner.

  Since the developer easily clogs the sponge layer 41, a developer removing member 7 that bites into the sponge layer 41 is provided on the periphery of the developer supply roller 4 in order to remove the clogged developer. . The tip end side of the developer removing member 7 is formed in a blade shape, and the developer removing member 7 has a blade portion 7a. The developer removing member 7 is fixed to the developing container 6. Note that the developer removing member 7 may be provided integrally with the developing container 6.

  FIG. 2 shows the positional relationship between the developer supply roller 4 and the developer removing member 7. As shown in this figure, the blade portion 7 a of the developer removing member 7 bites into the developer supply roller 4. A slight roundness is formed at the tip of the blade portion 7 a so as not to cut the sponge layer 41. The difference in radius between the circle (two-dot chain line in the figure) that is concentric with the developer supply roller 4 and passes through the tip of the blade portion 7a and the outer peripheral surface of the developer supply roller 4 is the depth of biting of the blade portion 7a. L. The biting depth L is appropriately selected depending on the form of the developer removing member 7 and the shape of the blade portion 7a.

When the developer removing member 7 presses the developer supply roller 4, the biting shape is such that the blade surface 7 a 1 of the blade portion 7 a on the upstream side in the rotation direction of the developer supply roller 4 and the downstream side in the rotation direction of the developer supply roller 4. When the angle formed by the blade edge surface 7a2 of the blade portion 7a and the tangent to the concentric circle of the developer supply roller 4 at the tip of the blade portion 7a is the entry angle θ1 and the escape angle θ2, respectively, θ1 <θ2. .
Here, when the entry angle θ1 increases, the sponge layer 41 cannot be gently compressed when the sponge layer 41 of the developer supply roller 4 is compressed, so that the pushing resistance increases, and the amount of developer scraped off. Will increase. However, in this case, the developer is easily clogged in the space S between the developer removing member 7, the inner wall of the developer container 6, and the developer supply roller 4, and the developer separated from the developing roller 2 (described in FIG. 1). Falls out of the developing container 6. Therefore, the developer clogging in the developing container can be prevented by reducing the angle of entry angle θ1. Therefore, it is preferable to set the entry angle θ1 within a certain range, but this range may be set as appropriate including other factors such as the biting depth L.

Further, since the developer supply roller 4 is partially compressed by the developer removing member 7, the gradient of displacement returning from the compressed portion to the original shape increases as the escape angle θ2 increases, so that the original shape is restored. Increases the resilience of time. Therefore, the developer with a larger escape angle θ2 is more likely to peel off the developer on the surface of the developer supply roller 4. Therefore, the escape angle θ2 is preferably set to a certain angle or more, but this may be appropriately set including other factors such as the biting depth L.
Generally speaking, the blade portion 7a may be shaped so that θ1 <θ2.

In the developing device 1 of the above-described embodiment, the developer removal member 7 that bites into the sponge layer 41 is provided in the sponge layer 41 of the developer supply roller 4 in order to remove the clogged developer. The clogging of the developer in the sponge layer 41 of the agent supply roller 4 can be avoided.
In addition, the developing device 1 according to the above-described embodiment is incorporated in the image forming apparatus. For example, the developing device 1 can be incorporated as a process cartridge in which the developing device and the image carrier are integrated.

In the above-described embodiment, the form using the block-like member as the developer removing member 7 has been described. However, any form that can prevent clogging of the sponge layer 41 may be used, and the developer of the above-described embodiment. The shape of the removing member 7 is not limited.
For example, as shown in FIG. 3, a form in which the developer removing member 7 of the plate material is fixedly attached in the developing container may be used. As a fixing method, a method of fastening with bolts is used in FIG. With such a configuration, the developer removing member 7 can be easily replaced. In the case of the developer removing member 7, the corner portion of the back surface on the front end side of the plate material becomes the blade portion 7a.

For example, as shown in FIG. 4, a plate spring-like developer removing member 7 thinner than the plate material of FIG. 3 may be provided. As the material of the developer removing member 7, various materials such as resin and metal can be used. To make it thinner, metals are preferred. The developer removing member 7 is bent and the back surface of the thin plate comes into contact with the sponge layer 41. The tip of the developer removing member 7 bites into the sponge layer 41 while being minute. This portion becomes the blade portion 7a.
With such a configuration, even when the developer removing member 7 is first attached to the developing container 6 in the assembling process of the developing device, the developer removing member 7 has flexibility. Parts can be assembled or removed in a later process.

FIG. 1 is an explanatory view showing an embodiment of the developing device of the present invention. FIG. 2 is an explanatory diagram illustrating details of a contact portion between the developer supply roller and the developer removing member. FIG. 3 is an explanatory view showing a modification of the developer removing member of FIG. FIG. 4 is an explanatory view showing a modification of the developer removing member of FIG. FIG. 5 is an explanatory view showing a conventional developing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing apparatus 2 Developing roller 21 Developing sleeve 22 Magnet 3 Restriction member 4 Developer supply roller 41 Sponge layer 42 Electrode 5 Developer stirring member 6 Developer container 7 Developer removing member 7a Blade portion 7a1, 7a2 Blade edge surface G Developer L Depth S Space Z Image carrier θ1 Entry angle θ2 Escape angle

Claims (7)

A developing roller for supplying a developer to the image carrier, and a developer supplying roller having a porous surface layer in contact with the developing roller for scraping off the developer on the developing roller while supplying the developer to the developing roller In a developing device provided with
A developing device, wherein a developer removing member that bites into the porous surface layer in order to remove clogged developer is provided in the porous surface layer of the developer supply roller. The developing device according to claim 1,
A blade portion is provided on the tip side of the developer removing member,
The biting shape when the developer removing member presses the developer supply roller is:
The blade edge surface of the blade portion on the upstream side in the rotation direction of the developer supply roller and the blade edge surface of the blade portion on the downstream side in the rotation direction of the developer supply roller are tangent to the concentric circle of the developer supply roller at the tip of the blade shape. A developing device characterized in that when the angles are θ1 and θ2, respectively, θ1 <θ2. In the developing device according to claim 1 or 2,
The developing device according to claim 1, wherein the developer removing member is integrally formed with a developing container for containing the developer. In the developing device according to claim 1 or 2,
The developing device, wherein the developer removing member is a plate material. In the developing device according to claim 1 or 2,
The developer removing member is a plate spring-like member having flexibility. A process cartridge comprising the developing device according to claim 1. An image forming apparatus comprising the developing device according to claim 1.

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