JP2005215439A - Magnetic seal of developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an easy and highly reliable magnetic seal capable of preventing leak of developer using rotation of a developing roller by improving structure of the magnetic seal. <P>SOLUTION: Since a plurality of projection ribs 60b are provided on an internal surface of a seal member 60a of the magnetic seal 60, magnetic flux density at a part where the ribs 60b are provided becomes higher and lines of magnetic force are concentrated. Thus, a capture effect of the developer which is going to leak out is enhanced. Furthermore, the developer captured among the plurality of projection ribs 60b is returned into a development container along the projection ribs 60b in accordance with the rotation of the developing roller 45. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnetic seal, and more particularly to a magnetic seal disposed in a non-contact manner with a developing roller in a developing device for developing an electrostatic latent image into a toner image.

  In an electrophotographic image forming apparatus, a charge is uniformly charged on the surface of a photosensitive drum, and an electrostatic latent image is formed by irradiating the surface of the photosensitive drum with light based on an original image. Thus, a developer is attached to the electrostatic latent image to form a toner image. Then, after the toner image is transferred from the photosensitive drum onto the paper by the transfer device, the toner image on the paper is fixed by the fixing device.

  A developing device in such an image forming apparatus includes a developing container that stores a developer, a developing roller that is rotatably supported in the developing container, and a stirring unit that stirs and conveys the developer stored in the developing container. It has. As a developer used in such a developing device, a one-component magnetic developer made of magnetic toner, a two-component magnetic developer made by mixing a magnetic carrier and toner, and the like are used. The developing roller has a magnet having a plurality of magnetic poles therein, is rotatably supported on both side walls of the developing container via bearings, and is provided so as to face the surface of the photosensitive drum. The developer supplied from the developing container adheres to the surface of the developing roller by the magnetic force of the magnet, and adheres onto the latent image on the photosensitive drum after the layer thickness is regulated to be constant by the layer thickness regulating blade. Here, the excess developer is returned to the developing container by the rotation of the developing roller.

  In such a situation, the developer in the developing container may be transferred to both ends of the developing roller along the surface of the developing roller, leaked to the outside from both ends in the axial direction, and scattered inside the apparatus main body. .

  In order to prevent such leakage of the developer, a seal structure is provided in which an elastic seal member is brought into contact with the outer peripheral surfaces of both end portions of the developing roller. However, in this method, the torque for driving the developing roller is increased, and a load is applied to the motor to shorten the service life. At the same time, both ends are heated to cause problems such as toner sticking.

In view of this, there has also been proposed a magnetic roller provided at both ends of the developing roller. This magnetic seal is provided with a magnetic seal member so as to face the outer peripheral surface of both end portions in the axial direction of the developing roller with a gap. In such a magnetic seal member, the surface facing the developing roller is magnetized, and the outer peripheral surface of the developing roller and the surface of the magnetic seal member are formed by a magnetic brush formed by the rising of the developer formed along the lines of magnetic force. And the developer is prevented from leaking out of the developing container.
JP-A-11-167284

  The magnetic seal as described above forms a magnetic brush by magnetic force, and prevents leakage of developer by this magnetic brush. However, with the recent increase in the speed of image formation, the rotational peripheral speed of the developing roller has increased, and as the developer becomes finer to improve the quality of image formation, conventional magnetic seals can be operated for a long time. May cause the developer to leak.

  An object of the present invention is to provide a magnetic seal that can prevent the leakage of the developer with high reliability by utilizing the rotation of the developing roller by improving the structure of the magnetic seal.

  The magnetic seal of the developing device according to claim 1 is installed at both ends of the developing roller that is rotatably attached to the developing container that accommodates the developer of the image forming apparatus, and from both ends of the developing roller to the outside of the developing container. This is to prevent leakage of toner. The magnetic seal includes a seal portion disposed in the developing container with a predetermined distance from the outer peripheral surface at both end portions in the axial direction of the developing roller, and toner transferred to both end portions of the developing roller. And a plurality of protruding ribs inclined in the rotation direction of the developing roller so as to return to the inside of the container.

  In this magnetic seal, a magnetic brush is formed by the rising of the developer by a seal portion composed of a magnetic field generating portion provided at both axial ends of the developing roller. The magnetic brush fills the gap between the outer peripheral surface of the developing roller and the seal portion, and prevents the developer from leaking out of the developing container. Further, since the projecting ribs that are inclined with respect to the rotation direction of the developing roller are provided on the surface of the seal portion, the magnetic force concentrates on the projecting portion, the magnetic lines of force can be concentrated, and a good magnetic brush can be formed. it can. At the same time, the developer that has reached the surface of the magnetic seal is accumulated between the protruding ribs, and the developer accumulated on the surface of the magnetic seal is returned to the developer container along the protruding ribs as the developing roller rotates. Further, the effect of preventing leakage of the developer can be further improved.

  The magnetic seal of the developing device according to claim 2 is the magnetic seal according to claim 1, wherein the seal portion is a sintered alloy member.

  Here, since the seal part is formed by sintering, there is no need to increase the number of parts and the processing cost does not need to be raised, so it is possible to obtain a developer leakage prevention effect with a simple structure at low cost. is there.

  In the magnetic seal of the present invention, in addition to the effect of preventing the developer from leaking from the end of the developing roller by the seal portion, the magnetic force is concentrated by the protruding ribs and the magnetic lines of force can be concentrated, thereby forming a good magnetic brush. At the same time, the developer accumulated by the protruding ribs on the inner peripheral surface of the magnetic seal and the rotation of the developing roller can be used to move the accumulated developer into the developing container. The leakage prevention effect can be improved.

  FIG. 1 is a diagram illustrating a configuration of a main part of a main body of an image forming apparatus in which an embodiment of the present invention is employed. A photoconductive drum 1 is disposed almost at the center of the image forming apparatus. Around the photoconductive drum 1, a charging device 2, an exposure device 3, a developing device 4, a transfer device body 5, a separating device 6, and a cleaning device. 7 is arranged. A fixing device 8 is disposed on the downstream side of the photosensitive drum 1 in the sheet conveyance direction.

  2 and 3 show the developing device of the image forming apparatus according to the embodiment of the present invention. The developing device 4 has a developing container 42 for containing a developer, and screws 43 and 44 for stirring and conveying the developer are rotatably disposed in the developing container 42. Further, a developing roller 45 is rotatably supported at the opening of the developing container 42 so as to face the photosensitive drum 1. The developing roller 45 includes a rotatable non-magnetic roller 45a made of aluminum or the like, and a magnet (fixed magnet) 45b having a plurality of magnetic poles built in the roller 45a. A layer thickness regulating blade 46 that regulates the amount of developer conveyed to the photosensitive drum 1 is disposed above the developing roller 45 at a predetermined distance from the developing roller 45.

  Next, the magnetic seal 60 will be described with reference to FIGS. 2 and 4 to 6. The magnetic seal 60 is formed in an arc shape so as not to contact the developing roller 45 and has an inner surface along the outer peripheral surface of the developing roller, and is disposed at both ends of the developing roller 45. That is, the magnetic seal member 60 is disposed at both ends of the developing roller 45 with a predetermined distance (for example, 0.5 mm) away from the outer peripheral surface of the developing roller 45, and the photosensitive drum 1 is sandwiched between the developing roller 45. On the opposite side, a layer from the lower end edge of the developing container facing the photosensitive drum 1 to the layer thickness regulating blade 46 is disposed. The position of both ends will be described in more detail. The magnetic seal member is positioned so that the magnetic brush is formed along the magnetic lines formed between the both ends of the magnet roller inside the developing roller and the magnetic seal member 60. It is arranged. The magnetic seal member 60 is attached to the developing container 42.

  The magnetic seal 60 includes a seal member 60a and a plurality of protruding ribs 60b formed on the surface of the seal member 60a. The seal member 60 a is a circular arc surface extending along the outer peripheral surface of the developing roller 45. A plurality of protruding ribs 60b are provided on the arc surface. The seal member 60a and the plurality of protruding ribs 60b are integrally formed from an iron-based sintered alloy, a magnetic ferritic stainless steel, or the like, and function as a magnetic force line concentration portion. Since the magnetic lines of force concentrate on the tip end side of the projection rib, it is necessary that the tip end side of the projection rib and the outer peripheral surface of the developing roller be disposed at a predetermined distance. Here, the height of the protruding rib 60b is in the range of 0.2 mm to 0.5 mm, and is inclined with respect to the rotation direction of the developing roller. As shown in FIG. 4, the plurality of protruding ribs 60 b are inclined with respect to the rotation direction of the developing roller 45 so that the upstream side in the rotation direction is located outside the developing container 42 and the downstream side is located inside. . 4B is a cross-sectional view of FIG. 4A, and the magnetic seal member 60 actually has a curvature, but is illustrated as a plane so that the protruding ribs can be easily understood. The width and the inclination angle of the protruding rib are set based on the outer shape and peripheral speed of the developing roller.

Next, the operation will be described.
First, the image forming operation will be briefly described. At the time of image formation, the photosensitive drum 1 is charged by the charging device 2 and is exposed to light from the exposure device 3 to form a latent image on the surface of the photosensitive drum 1. The latent image is developed by the developing device 4, and the developer image is transferred by the transfer device 5 to a sheet conveyed from a paper feed cassette (not shown). Next, the paper is separated from the photosensitive drum 1 by the separation device 6, and the toner image on the paper is fixed by heating and pressurization by the fixing device 8 and discharged. The residual developer remaining on the photosensitive drum 1 is cleaned by the cleaning device 7 and discarded in a waste toner container (not shown).

  Next, the operation in the developing device will be described. The developer in the developing container 42 of the developing device 4 is conveyed while being stirred by the rotation of the stirring screws 43 and 44, and adheres to the surface of the developing roller 45 by receiving the magnetic force of the magnet 45 b in the developing roller 45. The developer adhering to the surface of the developing roller 45 is conveyed to a position facing the photosensitive drum 1 by the rotation of the developing roller. At this time, the thickness of the toner layer on the developing roller 45 is regulated by the layer thickness regulating blade 46 disposed at a predetermined distance from the developing roller 45, and the amount of toner conveyed to the photosensitive drum 1 is controlled. .

In the development processing as described above, the developer may be transferred to both ends of the developing roller 45, and the developer may leak out of the developing container 42. However, since the magnetic seals 60 are disposed at both ends of the developing roller 45, a magnetic field is generated between the developing roller 45 and the seal member 60a of the magnetic seal 60, and the magnetic developer is magnetically brushed along the lines of magnetic force. Form. Such a magnetic brush fills the gap between the outer peripheral surface of the developing roller 45 and the surface of the seal member 60a, thereby preventing the developer from leaking out of the developing container.
In addition, since the plurality of protruding ribs 60b are provided on the inner surface of the seal member 60a, the magnetic flux density in the portion where the ribs 60b are provided increases, and the lines of magnetic force concentrate. For this reason, it is possible to increase the effect of capturing the developer to be leaked. Further, the developer trapped between the plurality of protruding ribs 60b is returned to the developing container along the protruding ribs 60b as the developing roller 45 rotates. When no protruding rib is provided, magnetic lines of force concentrate on the edge of the cross section of the magnetic seal, and toner stagnates in that portion and adheres to the developing roller. The situation can be avoided.

  For this reason, the sealing effect of the magnetic seal can be further improved.

1 is a configuration diagram of a main part of an image forming apparatus main body including a developing device according to an embodiment of the present invention. 1 is a plan sectional view of a developing device according to an embodiment of the present invention. 1 is a front sectional view of a developing device according to an embodiment of the present invention. It is a block diagram of the magnetic seal | sticker in the image development apparatus concerning embodiment of this invention. It is a perspective view of the magnetic seal in the developing device concerning the embodiment of the present invention. It is a front sectional view of a magnetic seal in a developing device concerning an embodiment of the present invention.

Explanation of symbols

1 photosensitive drum 4 developing device 42 developing container 45 developing roller 45b magnet 46 layer thickness regulating blade 60 magnetic seal 60a inner surface of magnetic seal 60b protruding rib on inner surface of magnetic seal

Claims (2)

A magnet for preventing leakage of toner from both ends of the developing roller to the outside of the developing container, which is installed at both ends of the developing roller rotatably attached to the developing container for containing the developer of the image forming apparatus. A seal,
A seal portion disposed in the developing container with a predetermined distance from the outer peripheral surface at both axial ends of the developing roller;
A plurality of protruding ribs provided on the surface of the seal portion and inclined with respect to the rotation direction of the developing roller so that the toner transferred to both end portions of the developing roller returns into the developing container;
Magnetic seal of developing device equipped with The magnetic seal according to claim 1, wherein the seal portion is a sintered alloy member.
The magnetic seal according to claim 1.

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