KR20040021315A - Developing unit of electrophotographic image forming apparatus and electrophotographic image forming apparatus using it - Google Patents

Abstract

PURPOSE: A developing unit of and an electrophotographic image forming system employing the developing unit are provided to prevent a developing gap from being increased and improve picture quality. CONSTITUTION: A developing unit(130) of an electrophotographic image forming system includes a frame(190), at least one guide rail, at least one developer, and a support(180). The guide rail is provided in the frame and has a sloped part that is sloped toward the center of a photosensitive drum(100). The developer is guided by the guide rail such that a developing roller is located distant from the photosensitive drum by a predetermined distance. The support supports the front end of the developer to prevent the distance between the developing roller and the photosensitive drum from being increased due to the weight of the developer.

Description

Developing unit of an electrophotographic image forming apparatus and an electrophotographic image forming apparatus employing the same

The present invention relates to a developing unit of an electrophotographic image forming apparatus and an electrophotographic image forming apparatus employing the same.

An electrophotographic image forming apparatus such as a dry color laser printer is an apparatus for forming an electrostatic latent image on a photosensitive member and then developing it with powdery toner, and transferring the developed image onto paper via a predetermined transfer medium to form an image. It includes a developing unit including a plurality of developing devices arranged to access the photosensitive member for developing the electrostatic latent image.

1 illustrates an example of a developing unit applied to a conventional electrophotographic image forming apparatus.

As shown, the developer 40Y, 40M, 40C, 40K, which accommodates toners of four colors of Y (yellow), M (magenta), C (cyan), and K (black), has a spring 20. By this, it is elastically biased toward the photosensitive drum 10, and the developing roller 42 provided at its tip is made to access the photosensitive drum 10. FIG.

The developing devices 40Y, 40M, 40C, and 40K are slidably supported by the guide rails 31, 32, 33, 34 of the frame 30, and are buried with toner stored therein. The developing roller 42 which supplies (g) to the surface of the photosensitive drum 10 and is installed coaxially with the developing roller 42 to maintain the developing gap g, and has an outer circumferential surface of the photosensitive drum 10. And a gap holding roller 41 and the like in contact with each other.

The tip side of the guide rails 31, 32, 33, 34 is directed toward the center of the photosensitive drum 10 so that the developing roller 42 can be accessed in a normal direction with respect to the outer circumferential surface of the photosensitive drum 10. It is formed to be inclined. The tip ends of the guide rails 31 and 32 are inclined downward toward the center of the photosensitive drum 10, and the tip ends of the guide rails 33 and 34 are inclined upward toward the center of the photosensitive drum 10. This is to ensure that each developing device 40Y, 40M, 40C, 40K is accessed with a uniform pressing force against the photosensitive drum 10 so that a constant developing gap g is maintained.

However, the developing unit having such a configuration has a problem in that the developing gap g is opened while the developing device sags downward due to its own weight. In other words, the developing devices 40C and 40K mounted on the guide rails 31 and 32 which are inclined downwardly are exposed to light because the gap holding roller 41 is in contact with the photosensitive drum 10 even if it sags due to its own weight. The drum 10 serves as a supporting member that prevents sag due to its own weight, and thus there is no problem in maintaining the developing gap g, but the developing unit 40M mounted on the guide rails 33 and 34 inclined upwardly. (40Y) has a tendency that the gap holding roller 41 is separated from the photosensitive drum 10 due to its own weight, and thus there is a problem that the developing gap g is opened. The developing gap g is a developing parameter which must be kept very precisely and has a significant influence on the quality of the image. However, according to the configuration shown in Fig. 1, even if the spring 20 is pressing each developing unit toward the photosensitive drum 10, the developing gap g is developed for each developing unit by the influence of its own weight depending on the installation position of the developing unit. There is a problem that can not be kept uniform.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a developing unit having a supporting means for preventing sagging due to its own weight and an electrophotographic image forming apparatus employing the same.

1 is a view showing an example of a developing unit of a conventional electrophotographic image forming apparatus.

2 is a view showing an example of an electrophotographic image forming apparatus according to the present invention;

3 is an exploded perspective view showing a first embodiment of a developing unit according to the present invention employed in the electrophotographic image forming apparatus shown in FIG.

4 is a view showing the action by the developing unit shown in FIG.

5 shows a second embodiment of a developing unit according to the present invention;

6 shows a third embodiment of a developing unit according to the present invention;

7 shows a fourth embodiment of a developing unit according to the present invention;

<Description of Symbols for Main Parts of Drawings>

100 ...... Photosensitive drum 130 ...... Developer unit

131 ...... developing roller 132 ...... gap holding roller

133 ...... Bearing member 134 ...... Guide boss

150 ...... Plate spring 160 ...... Protrusion

170 ...... elastic arm 180 ...... support member

181 Mounting seat 190 ...... Frame

191,192,193,194 ...... Guide rail

191a, 192a, 193a, 194a ...... straight section

191b, 192b, 193b, 194b ...... Slope

200 ...... Spring 210 ... Door

In order to achieve the above object, the developing unit of the electronic demonstration type image forming apparatus of the present invention comprises a frame; At least one guide rail provided on the frame and having an inclined portion inclined to face the center of the photosensitive drum; At least one developer guided by the guide rail and installed such that a developing roller is spaced apart from the photosensitive drum by a predetermined distance; The inclined portion of the guide rail supports the tip of the developer installed along the guide rail formed to be inclined upward toward the center of the photosensitive drum to prevent a gap between the developing roller and the photosensitive drum due to its own weight. Means; includes.

In addition, the electronic scanning image forming apparatus according to the present invention includes a charging unit for charging a photosensitive drum, an exposure unit for exposing the charged photosensitive drum to form an electrostatic latent image, and developing the electrostatic latent image with a toner of a predetermined color. An electrophotographic image forming apparatus comprising a developing unit for forming a toner image and a transfer unit for transferring the toner image onto a paper, the developing unit comprising: a frame; At least one guide rail provided on the frame and having an inclined portion inclined to face the center of the photosensitive drum; At least one developer guided by the guide rail and installed such that a developing roller is spaced apart from the photosensitive drum by a predetermined distance; The inclined portion of the guide rail supports the tip of the developer installed along the guide rail formed to be inclined upward toward the center of the photosensitive drum to prevent a gap between the developing roller and the photosensitive drum due to its own weight. Means; includes.

Here, the support means may include an elastic member for providing an elastic force in the direction to cancel the force due to its own weight to the developing device.

In addition, the support means may include a support member rotatably installed on the frame and having a plurality of radially formed seating portions to allow the protrusion protruding laterally to the front end of the developing unit.

According to such a configuration, by supporting the developing device in the direction opposite to the weight of the own weight, the developing gap can be prevented from being opened by the own weight, and further, the image quality can be improved.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 shows an embodiment of an electrophotographic image forming apparatus according to the present invention, FIG. 3 is an exploded perspective view showing a first embodiment of a developing unit according to the present invention employed in FIG. 3 is a view showing the action by the developing unit shown in FIG.

Referring to FIG. 3, the image forming apparatus includes a photosensitive drum 100 as a photosensitive member, a charger 110 for charging the photosensitive drum 100, and a charged photosensitive drum 100 to scan light for electrostatic discharge of a desired image. A developing unit for forming a latent image as a laser scanning unit (LSU) 120 and a latent electrostatic image with powdered toner of four colors of Y (yellow), M (magenta), C (cyan), and K (black). A transfer unit including (130M) 130C, 130Y, and 130K, and a transfer belt 140 that sequentially transfers the images of the four colors developed on the photosensitive drum 100 to be superimposed and transferred onto paper; A fixing unit 150 or the like for fixing an image by heating and pressing paper is provided. Reference numeral 160 denotes a paper cassette, reference numeral 170 denotes a photosensitive drum cleaning unit, and reference numeral 180 denotes a static eliminator.

Here, the developing devices 130M, 130C, 130Y, and 130K for each color, as illustrated in FIGS. 3 and 4, guide rails 191, 192, 193, and 194 of the frame 190. A developing roller 131 slidably supported on the developing body 130, a developing roller 131 which is buried with toner stored in the main body 130a, and supplied to the outer peripheral surface of the photosensitive drum 100 in a non-contact state, and coaxially with the developing roller 131. It is installed to be in close contact with the photosensitive drum 100 includes a gap holding roller 132 to maintain a constant gap between the photosensitive drum 100 and the developing roller 131, the developer main body 130a by the spring 200 The guide rails 191, 192, 193, and 194 are elastically biased in a direction approaching the photosensitive drum 100, that is, the gap holding roller 132 is in close contact with the photosensitive drum 100. Typically, the spring 200 is installed in the opening / closing door 210 of the image forming apparatus. When the door 210 is closed, the spring 200 pushes the developer main body 130a toward the photosensitive drum 100.

The guide rails 191, 192, 193, and 194 may include a guide boss 134 provided in the developing body main body 130a and a bearing member 133 rotatably supporting the rotation shaft of the developing roller 131. Where it is slidably supported, the inclined portion 191b formed to be inclined toward the central axis 101 of the linear portions 191a, 192a, 193a, 194a and the photosensitive drum 100 which extend in the horizontal direction. 192b, 193b, and 194b. The straight portions 191a, 192a, 193a, and 194a are portions for guiding the guide boss 134 to move horizontally, and the inclined portions 191b, 192b, 193b, and 194b are front ends of the developing unit 130a. It is a part for guiding the bearing member 133 on the developing shaft 131 rotating shaft located at the side to move in the radial direction of the photosensitive drum 100. Therefore, the bearing member 133 is restricted to move only in the radial direction of the photosensitive drum 100 on the inclined portions 191b, 192b, 193b and 194b while rotatably supporting the developing roller 131 shaft. . Since the gap holding roller 132 is provided coaxially with the bearing member 133, the gap holding roller 132 also has a radial direction of the photosensitive drum 100, that is, a direction toward the central axis 101 thereof. It moves and is in close contact with the photosensitive drum 100. As a result, since the developing roller 131 moved by the bearing member 133 moves only in the axial direction with respect to the photosensitive drum 100, the gap holding roller 132 is in close contact with the photosensitive drum 100 and the pressure applied thereto is reduced. It only acts in the radial direction of the drum 100. In this case, since the pressure of the gap holding roller 132 does not act at all in the tangential direction, the gap holding roller 132 does not slip in the tangential direction.

The inclined portions 193b and 194b of the two guide rails 193 and 194 formed at the bottom thereof are formed to be inclined upwardly toward the central axis 101 of the photosensitive drum 100. The inclined portions 193b and 194b or the leaf springs 150 are provided adjacent thereto. The leaf spring 150 imparts an elastic force to the bearing member 133 in a direction opposite to the direction of action of the self-weight of the two developing devices 130C and 130M mounted below, i.e., to cancel the force due to the self-weight.

Referring to FIG. 4, since the two developing devices 130K and 130Y positioned above are inserted and guided into the inclined portions 191b and 192b in which the bearing member 133 is inclined downward, the developing devices 130K and 130Y are provided. The force acts in a direction approaching the photosensitive drum 100 by its own weight, and since the gap holding roller 132 is in contact with the photosensitive drum 100, the developing gap g is maintained unchanged.

Since the two developing devices 130C and 130M positioned below are inserted and guided into the inclined portions 193b and 194b in which the bearing member 133 is inclined upward, the force is caused by the weight of the developing devices 130C and 130M. It acts in the direction away from the photosensitive drum 100 and tends to open the developing gap g. However, according to the developing unit according to the present invention, since the pressing force (F) is applied to the bearing member 133 by the elastic force of the leaf spring 150 to offset the influence of its own weight, the gap holding roller 132 and the photosensitive drum 100 It is possible to maintain the developing gap g without being spaced apart. As such, by supporting the developing devices 130C and 130M with the leaf springs 150, the developing gap g can be maintained regardless of the installation positions of the developing devices 130K, 130Y, 130C, and 130M. When forming an image, a development image can be obtained by removing the development deviation between colors due to the difference in the development gap g.

5 is a view showing a second embodiment of a developing unit according to the present invention employed in FIG. As shown, protrusions 160 protruding toward the frame 190 are formed on the side surfaces of the developing devices 130C and 130M, such as the guide boss 134, and the leaf springs 150 are formed on the protrusions 160. It is installed to support. At this time, the protrusion 160 is preferably installed adjacent to the front end of the developing unit (130C) (130M) preferably, it is preferable that is formed to be inserted into the guide rails (193, 194), the guide rail (193) It may be formed irrespective of 194.

The elastic member for supporting the developing devices 130C and 130M does not necessarily need to be a leaf spring 150, as shown in FIG. 6 showing a third embodiment of the developing unit according to the present invention employed in FIG. Likewise, the elastic arm 170 may be formed integrally with the guide rails 193 and 194. The guide rails 191, 192, 193, and 194 are formed integrally with the frame 190 or are made of a separate plastic material and then coupled to the frame 190. The elastic arm 160 may be integrally formed to allow the springs to act on the rails 193 and 194. The elastic arm 160 supports the bearing member 133 or the protrusion 160 to prevent the developing gap from being opened due to the weight of the developing devices 130C and 130M. As such, when the elastic member is integrally formed with the guide rail, component cost and assembly cost can be reduced.

7 shows a fourth embodiment of a developing unit according to the present invention.

Referring to FIG. 7, protrusions 160 protruding toward the frame 190, such as guide bosses 134, are formed on side surfaces of the developing devices 130C and 130M. The protruding portion 160 is preferably formed to be inserted into the guide rails 193 and 194, and preferably formed as close to the front end of the developing devices 130C and 130M as possible. The protrusion 160 is supported by the support member 180. The support member 180 is formed with a plurality of seating portions 181 radially to allow the protrusion 160 to be seated thereon, and is installed to be rotated in the frame 190. The support member 180 is preferably installed such that the center of rotation 182 is located directly below the position where the protrusion 160 is positioned when the gap holding roller 132 is in contact with the photosensitive drum 100.

According to such a configuration, when the developing devices 130C and 130M are mounted with the guide rails 193 and 194, the protrusions 160 come into contact with the support member 180 to slide while the support member 180 is rotated. do. Then, when the gap holding roller 132 is in contact with the photosensitive drum 100, the protrusion 160 is seated in one of the plurality of seating portion (181). Therefore, even if the developing devices 130C and 130M installed below have a tendency to open the developing gap g due to their own weight, since the support member 180 supports the protruding portion 160, the developing gap g is increased. It doesn't happen.

As described above, according to the developing unit and the electrophotographic image forming apparatus employing the same according to the present invention, the following effects can be obtained.

First, it is possible to prevent the developing gap from being opened due to its own weight in a state in which the developing unit is pressed toward the center of the photosensitive drum, thereby maintaining a constant developing gap regardless of the installation position of the developing unit.

Second, in the case of a color image forming apparatus using a plurality of developing devices, the development deviation between colors due to the difference in the developing gap according to the installation position of the developing device can be eliminated, so that the image can be improved in quality.

It is to be understood that the invention is not limited to that described above and illustrated in the drawings, and that more modifications and variations are possible within the scope of the following claims.

Claims (12)

frame; At least one guide rail provided on the frame and having an inclined portion formed to be inclined toward the center of the photosensitive drum at a front end side thereof; At least one developer guided by the guide rail and installed such that a developing roller is spaced apart from the photosensitive drum by a predetermined distance; The inclined portion of the guide rail supports the tip of the developer installed along the guide rail formed to be inclined upward toward the center of the photosensitive drum to prevent a gap between the developing roller and the photosensitive drum due to its own weight. And a developing unit of the electrophotographic image forming apparatus. The method of claim 1, wherein the support means, And an elastic member for imparting an elastic force to the developing device in a direction to cancel the force due to its own weight. The method of claim 2, The front end of the developing unit is provided with a protrusion protruding to the side, The developing member of the electrophotographic image forming apparatus, wherein the elastic member imparts an elastic force to the protrusion. The method of claim 3, And the protrusion is inserted into the guide rail and slides along the guide rail. The method of claim 2, The guide rail, the bearing member fitted to the end of the rotary shaft of the developing roller and the guide boss provided in the developing machine is inserted and supported to be slidable, respectively, And the elastic member imparts an elastic force to the bearing member. The method according to claim 4 or 5, The elastic member is a developing unit of the electrophotographic image forming apparatus, characterized in that formed integrally with the guide rail. The method of claim 1, The front end of the developing unit is provided with a protrusion protruding to the side, The support means, And a support member rotatably installed in the frame, the support member having a plurality of seating parts radially formed to allow the protrusions to be seated thereon. The method of claim 7, wherein And the protrusion is inserted into the guide rail and slides along the guide rail. A charging unit for charging a photosensitive drum, an exposure unit for exposing the charged photosensitive drum to form an electrostatic latent image, a developing unit for developing the electrostatic latent image with toner of a predetermined color to form a toner image, and the toner image In the electrophotographic image forming apparatus comprising a transfer unit to transfer to the, the developing unit, frame; At least one guide rail provided on the frame and having an inclined portion formed to be inclined toward the center of the photosensitive drum at a front end side thereof; At least one developer guided by the guide rail and installed such that a developing roller is spaced apart from the photosensitive drum by a predetermined distance; The inclined portion of the guide rail supports the tip of the developer installed along the guide rail formed to be inclined upward toward the center of the photosensitive drum to prevent a gap between the developing roller and the photosensitive drum due to its own weight. Electrophotographic image forming apparatus comprising; means. The method of claim 9, wherein the support means, And an elastic member for imparting an elastic force in a direction in which the force for self weight is canceled in the developing device. The method of claim 10, The front end of the developing unit is provided with a protrusion protruding to the side, And the elastic member imparts an elastic force to the protrusion. The method of claim 9, The front end of the developing unit is provided with a protrusion protruding to the side, The support means, And a support member rotatably installed in the frame, the support member having a plurality of radially formed seating portions to allow the protrusions to be seated thereon.