JP2006337577A - Developing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing apparatus in which a toner layer formed on the surface of a developing sleeve can be made comparatively thin and uniform. <P>SOLUTION: The developing apparatus includes: the developing sleeve 1a holding one-component toner on its surface and rotated around its shaft, thereby conveying held developer to a predetermined developing position; a magnet roll 1b fixedly disposed within the developing sleeve 1a and including a plurality of magnetic poles; and a developing blade 2 disposed upstream of the developing position in the direction A and restricting the amount of developer, held and conveyed by the developing sleeve 1a, by the magnetic force of the magnet roll 1b opposite to it. The leading edge of the developing blade is divided in an upstream leading edge 2a formed upstream in the direction A and a downstream leading edge 2b formed downstream in the direction A. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a developing device provided in an image forming apparatus such as a copying machine or a printer.

  Conventionally, a developing sleeve containing a fixed magnet roll having a plurality of magnetic poles is used as a toner carrying member, and the toner accumulated in the developing container is carried using a magnetic binding force formed on the developing sleeve. A developing device that guides a regulated toner layer to a developing position after layer thickness regulation using a developing blade is known.

  In the jumping development method used in such a developing device, a developer layer is formed on a developing sleeve that is not in contact with the photosensitive drum and an alternating electric field is applied between the two, and the toner on the developing sleeve is exposed to light. The electrostatic latent image is developed by applying an electric field to the body drum and flying between the two.

  In a developing device using one-component toner, a plurality of toners are stacked on the developing sleeve several times to form a toner layer, so that there is a difference in charge amount between the lowermost toner layer and the uppermost toner layer. Will occur. The difference in charge amount tends to increase as the toner layer becomes thicker. Further, when the difference in charge amount increases, the toner in the lowermost layer becomes difficult to develop on the drum and further difficult to separate from the developing sleeve. As a result, it continues to adhere to the developing sleeve and causes overcharging. When this overcharging occurs, there is a problem that unevenness or the like occurs in the toner layer due to long-term driving, affecting the image quality. Further, when the difference in the charge amount between the lowermost layer and the uppermost layer becomes severe, the development performance is deteriorated. Therefore, it is a problem to make the toner layer formed on the surface of the developing sleeve thin.

  8 and 9 show a conventional developing blade. In the developing blade shown in FIG. 8, the width of the developing blade with respect to the conveying direction of the developing sleeve is increased, so that the effect of cutting off the developing blade is enhanced.

Further, as shown in FIG. 9, there is also known a developing blade whose tip is inclined so that the distance from the developing sleeve becomes narrower toward the downstream side. Patent Document 1 is also known as a technique related to the present invention.
JP 10-39622 A

  However, since the developing blade shown in FIG. 8 has a large difference between the distance to the upstream developing sleeve and the distance to the downstream developing sleeve, a large amount of toner enters into this gap, resulting in a sufficient trimming effect. Cannot be obtained, and a thin and uniform toner layer cannot be formed.

  Further, in the developing blade shown in FIG. 9, the distance between the central portion CP of the tip and the developing sleeve is narrow, and the shape of the gap portion is a wedge shape. The amount of toner entering between the blade and the developing sleeve is rather large, and there is a problem that a sufficient trimming effect cannot be obtained and a thin and uniform toner layer cannot be formed.

  An object of the present invention is to provide a developing device capable of making the toner layer formed on the surface of the developing sleeve thinner and more uniform.

  The developing device according to the present invention includes a developing sleeve that carries a single-component developer on its surface and conveys the carried developer to a predetermined developing position by rotating around a shaft, and is fixed inside the developing sleeve. The magnet roll, which is arranged and configured by a plurality of magnetic poles, is disposed upstream of the developing position in the rotation direction of the developing sleeve, and is carried and conveyed by the developing sleeve by the magnetic force of the opposing magnet roll. A developing blade that regulates the amount of the developer, and the developing blade includes an upstream tip formed on the upstream side in the rotation direction of the developing sleeve and a downstream tip formed on the downstream side. The tip is divided into two.

  In the above configuration, it is preferable that a distance between the downstream tip portion and the developing sleeve is shorter than a distance between the upstream tip portion and the developing sleeve.

  In the above configuration, it is preferable that a distance between the downstream tip portion and the developing sleeve is equal to or less than a half of a distance between the upstream tip portion and the developing sleeve.

  In the above-described configuration, it is preferable that the upstream tip portion is formed with a hole for removing toner staying in a gap between the upstream tip portion and the downstream tip portion.

  In the above configuration, it is preferable that a distance between the upstream tip portion and the downstream tip portion is shorter with respect to the developing sleeve toward the upstream side.

  According to the first aspect of the present invention, the tip of the developing blade is divided into the upstream tip and the downstream tip. Then, the developer carried by the developing sleeve is regulated in layer thickness by the upstream tip portion formed on the downstream side after the layer thickness is regulated by the upstream tip portion. As a result, the width of one tip can be made smaller than that shown in FIG. 8, and a thin and uniform developer layer can be formed on the surface of the developing sleeve. Furthermore, since the upstream tip portion and the downstream tip portion are integrally formed, there is no need to separately arrange the upstream tip portion and the downstream tip portion, and the manufacturing process can be simplified. As a result of the thinner and uniform developer layer, the difference in charge amount between the lowermost layer and the uppermost layer of the developer layer is reduced, and the charge amount of the toner on the thin layer can be made uniform. .

  According to the second aspect of the present invention, since the distance between the downstream tip and the developing sleeve is shorter than the distance between the upstream tip and the developing sleeve, the developer could not be regulated by the upstream tip. As a result of being reliably regulated by the downstream end portion, a thinner and uniform developer layer can be formed on the surface of the developing sleeve.

  According to the third aspect of the present invention, the distance between the downstream tip and the developing sleeve is less than one half of the distance between the upstream tip and the developing sleeve, so that the upstream tip cannot be regulated. As a result of the developer being reliably regulated by the downstream end portion, a thinner and uniform developer layer can be formed on the surface of the developing sleeve.

  According to the fourth aspect of the present invention, the toner staying in the gap between the downstream tip and the upstream tip exits from the hole formed in the upstream tip, so that the toner staying in the gap Can be removed.

  According to the fifth aspect of the present invention, the distance between the upstream tip and the downstream tip decreases from the developing sleeve toward the upstream. Therefore, the developing blade and the developing sleeve as shown in FIG. It is possible to more reliably prevent the developer from entering while being compressed in the gap portion.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic side view mainly showing a mechanical configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus includes a main body unit 200, a sheet post-processing unit 300 disposed on the left side of the main body unit 200, an operation unit 400 for a user to input various operation commands and the like, and an upper part of the main body unit 200. The document reading unit 500 disposed in the document reading unit 500 and the document feeding unit 600 disposed above the document reading unit 500.

  The operation unit 400 includes an operation panel 401, a start key 402, a numeric keypad 403, and the like. The operation panel 401 displays various operation screens and various operation buttons for the user to input various operation commands. The start key 402 is used for the user to input a print execution command and the like, and the ten key 403 is used for inputting the number of copies to be printed.

  The document feeding unit 600 includes a document placement unit 601, a document discharge unit 602, a paper feed roller 603, a document transport unit 604, a contact glass 605, and the like, and the document reading unit 500 includes a scanner 501 and the like. The paper feed roller 603 feeds out the original set on the original placement unit 601, and the original transport unit 604 transports the fed originals one by one on the scanner 501.

  The scanner 501 sequentially reads the conveyed document, and the read document is discharged to the document discharge unit 602. When the scanner 501 reads a document placed on the contact glass 605, the scanner 501 slides in the C direction to read the document.

  The main body 200 includes a plurality of paper feed cassettes 201, a plurality of paper feed rollers 202, a transfer roller 203, an intermediate transfer body roller 204, a photosensitive drum 205, an exposure device 206, and development for each color of yellow, magenta, cyan, and black. Devices 207Y, 207M, 207C, and 207K, a fixing roller 208, a discharge port 209, a discharge tray 210, a recording paper transport unit 211, and the like are provided.

  The photosensitive drum 205 is uniformly charged by a charging device (not shown) while rotating in the direction of the arrow. The exposure device 206 converts the modulation signal generated based on the image data of the document read by the document reading unit 500 into a laser beam and outputs it, and forms an electrostatic latent image on the photosensitive drum 205 for each color. The developing devices 207Y, 207M, 207C, and 207K supply each color developer to the photosensitive drum 205 to form a toner image for each color.

  The intermediate transfer body roller 204 transfers the toner images of each color from the photosensitive drum 205 and forms a color toner image on the intermediate transfer body roller 204.

  On the other hand, the paper feeding roller 202 pulls out the recording paper from the paper feeding cassette 201 in which the recording paper is stored, and the recording paper transport unit 211 transports the drawn recording paper to the transfer roller 203. The transfer roller 203 transfers the toner image on the intermediate transfer roller 204 to the conveyed recording paper. The recording paper to which the toner image has been transferred is conveyed to the fixing roller 208 by the recording paper conveyance unit 211, and the fixing roller 208 heats and transfers the transferred toner image to the recording paper. Thereafter, the recording paper is conveyed to the discharge port 209 by the recording paper conveyance unit 211 and is carried into the paper post-processing unit 300. The recording paper is also discharged to the discharge tray 210 as necessary.

  The paper post-processing unit 300 includes a carry-in port 301, a recording paper transport unit 302, a carry-out port 303, a stack tray 304, and the like. The recording paper transport unit 302 sequentially transports the recording paper carried into the carry-in port 301 from the discharge port 209 and finally ejects the recording paper from the carry-out port 303 to the stack tray 304. The stack tray 304 is configured to move up and down in the direction of the arrow in accordance with the number of recording sheets stacked from the carry-out port 303.

  FIG. 2 is a cross-sectional view showing the configuration of the developing devices 207Y to 207K. Since the developing devices 207Y to 207K have the same configuration, only the developing device 207Y will be described. In the present embodiment, the developing device 207Y is a jumping type developing device that uses one-component toner. The developing device 207 </ b> Y includes a developing roller 1, a developing blade 2, stirring screws 31 and 32, and a developing container 6. The developing roller 1 is disposed at a position facing the photosensitive drum 205, and includes a developing sleeve 1a and a magnet roll 1b. The developing sleeve 1a is a cylindrical member having a hollow inside, and is disposed so as to be rotatable counterclockwise (A direction) about an axis 1c.

  The magnet roll 1b is a cylindrical member that is fixedly disposed in the hollow portion of the developing sleeve 1a. The magnet roll 1b includes an S pole (blade pole) disposed at a position facing the developing blade 2, and an N pole disposed at a position (development position P) where the distance from the photosensitive drum 205 is the shortest, An S pole disposed on the downstream side in the A direction of the developing sleeve 1a with respect to the N pole. In the developing sleeve 1a, toner is adhered to the peripheral surface by the magnetic force of these permanent magnets.

  The developing blade 2 is made of a magnetic material such as SUS, for example, and forms a thin toner layer on the peripheral surface of the developing sleeve 1a by regulating the toner adhering to the peripheral surface of the developing sleeve 1a. The toner carried on the peripheral surface of the developing sleeve 1 a is not only regulated by the distance between the developing sleeve 1 a and the regulating blade 2 but also the magnetic force generated between the tip of the developing blade 2 and the blade pole facing the developing blade 2. As a result, a thin toner layer having a thickness of several tens of microns is formed on the peripheral surface of the developing sleeve 1a.

  FIG. 3 is a perspective view schematically showing the relationship between the developing blade 2 and the developing roller 1. As shown in FIG. 3, the developing blade 2 is long in the longitudinal direction of the developing roller 1, and is arranged above the blade pole of the magnet roll 1b with a certain distance from the peripheral surface of the developing sleeve 1a. Has been. The developing blade 2 has an upstream tip 2a disposed on the upstream side in the A direction and a downstream tip 2b disposed on the downstream in the A direction with respect to the upstream tip 2a. It is divided into and. Therefore, a gap 2c is formed between the upstream tip portion 2a and the downstream tip portion 2b.

  FIG. 4 is an enlarged view of the developing sleeve 1a and the tip portion of the developing blade 2. FIG. As shown in FIG. 4, the distance between the upstream tip 2a and the peripheral surface of the developing sleeve 1a is Da, and the distance between the downstream tip 2b and the peripheral surface of the developing sleeve 1a is Db. In the present embodiment, Da ≧ Db, and more preferably Da ≧ 1/2 Db. The width W1 of the upstream tip 2a, the width W2 of the downstream tip 2b, and the width W3 of the gap 2c preferably have a relationship of W1: W2: W3 = 1: 1: 0.5, Preferably they are 2 mm, 2 mm, and 1 mm.

  Further, since the surface on the developing sleeve 1a side of the upstream tip 2a and the downstream tip 2b is parallel to the horizontal direction, the distance between the developing sleeve 1a, the upstream tip 2a, and the downstream tip 2b is A. As a result of widening in the direction, a thin and uniform toner layer can be formed without weakening the ear cutting effect as in the developing blade shown in FIG.

  The toner container 6 shown in FIG. 2 has a wall 6b formed at the center. A stirring screw 31 is disposed in the toner container 6 on the left side of the wall 6b, and a stirring screw 32 is disposed in the toner container 6 on the right side of the wall 6b.

  The stirring screws 31 and 32 are spiral members that are long in the longitudinal direction of the developing roller 1. In FIG. 2, hatched portions of the stirring screws 31 and 32 indicate cross sections of the stirring screws 31 and 32, and circles 31 a and 32 b indicate spiral wings of the stirring screws 31 and 32. An opening 6a is formed above the toner container 6, and a container (not shown) for storing toner is disposed above the opening 6a. The stirring screw 32 is supplied with toner from the container through the opening 6a. The agitating screw 32 rotates to triboelectrically charge the toner, and supplies the charged toner to the agitating screw 31 side through openings (not shown) provided at two locations on the front and rear sides of the wall 6b. To do. The stirring screw 31 rotates to supply toner to the developing sleeve 1a. The stirring screw 31 collects the toner separated from the developing sleeve 1 a and supplies it to the stirring screw 32.

  The toner supplied to the peripheral surface of the developing sleeve 1a is conveyed to the position of the developing blade 2. At this time, since the developing sleeve 1a rotates counterclockwise, a part of the toner passes between the developing blade 2 and the developing sleeve 1a, and the remaining toner does not pass through the side of the developing blade 2. Regulated by. Since the developing sleeve 1a rotates continuously, toner is continuously supplied to the peripheral surface of the developing sleeve 1a. The toner that is not regulated by the developing blade 2 is collected on the side surface of the developing blade 2.

  Next, the operation of the developing blade 2 will be described with reference to FIG. In FIG. 4, white circles schematically show toner particles. The toner supplied from the stirring screw 31 to the peripheral surface of the developing sleeve 1a is conveyed to the position of the developing blade 2 when the developing sleeve 1a rotates in the A direction. Here, the toner adheres to the peripheral surface of the developing sleeve 1a in a whisker-like shape by a magnetic field from the developing sleeve 1a. A toner layer is formed on the peripheral surface of the developing sleeve 1 a by a regulating action by the upstream tip 2 a and a regulating action by a magnetic field generated between the developing sleeve 1 a and the developing blade 2.

  When the toner layer is conveyed to the downstream tip 2b, it is further regulated by the downstream tip 2b in the same manner as the upstream tip 2a. Thus, since the toner layer is formed by regulating the toner in two stages, a thin and uniform toner layer can be formed on the peripheral surface of the developing sleeve 1a. When the toner particles constituting the toner layer regulated by the downstream end 2b are transported to the development position P shown in FIG. 2, they fly by an alternating electric field applied between the photosensitive drum 205 and the development roller 1. Then, the electrostatic latent image on the photosensitive drum 205 is developed.

  Here, the toner staying at the downstream end 2b stays in the gap 2c. However, the staying toner can be taken out by adopting the developing blade as shown in FIGS. become.

  5 to 7 are drawings of the developing blade 2 and the developing sleeve 1a viewed from the B direction shown in FIG. 5-7, the dotted line drawn in the developing blade 2 has shown the ceiling surface of the gap | interval 2c. Further, the hatching shown in FIG. 7 shows a cross section of the housing of the developing device 207Y. In the case of FIG. 5, a plurality of, for example, four holes 21 to 24 are formed on the side surface of the developing blade 2. These holes 21 to 24 are connected to the gap 2c. Therefore, the toner staying in the gap 2c is pushed up to the ceiling surface side as the staying amount in the gap 2c increases, and is eventually collected in the toner container 6 through the holes 21-24.

  In the case of FIG. 6, holes 25 and 26 are formed in the left and right positions on the side surface of the developing blade 2. The holes 25 and 26 are connected to the gap 2c. Accordingly, the toner staying in the gap 2c moves toward the holes 25 and 26 as the amount of staying toner increases, and is eventually collected in the toner container 6 through the holes 25 and 26.

  In the case of FIG. 7, the left end of the developing blade 2 is attached to the housing H with a certain interval. The developing blade 2 is attached to the housing H by a fixing member 27. Therefore, the toner staying in the gap 2 c is collected in the toner container 6 from the left end of the developing blade 2. In this case, the toner staying in the gap 2c can be removed by a simplified configuration in which the developing blade 2 is attached to the housing H at a constant interval.

1 is a schematic side view mainly showing a mechanical configuration of an image forming apparatus according to an embodiment of the present invention. It is sectional drawing which shows the structure of a developing device. It is the perspective view which showed typically the relationship between a developing blade and a developing roller. 2 is an enlarged view of a developing sleeve and a tip portion of a developing blade. FIG. 4 is a drawing of the developing blade 2 and the developing sleeve 1a as viewed from the B direction shown in FIG. FIG. 4 is a drawing of the developing blade 2 and the developing sleeve 1a as viewed from the B direction shown in FIG. 3. FIG. 4 is a drawing of the developing blade 2 and the developing sleeve 1a as viewed from the B direction shown in FIG. 2 is a diagram illustrating a conventional developing blade. 2 is a diagram illustrating a conventional developing blade.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing roller 1a Developing sleeve 1b Magnet roll 1c Axle 2 Developing blade 2a Upstream tip 2b Downstream tip 2c Gap 6 Toner container 6a Opening 6b Walls 21, 22, 23, 24, 25, 26 Hole 27 Fixing member 31 Stir screw 32 Stir screw 32a yen

Claims (5)

A developing sleeve that carries a single-component developer on the surface and conveys the carried developer to a predetermined development position by rotating around a shaft;
A magnet roll which is fixedly arranged inside the developing sleeve and is constituted by a plurality of magnetic poles;
A developing blade that is disposed upstream of the developing position in the rotation direction of the developing sleeve, and that regulates the amount of developer carried and conveyed by the developing sleeve by a magnetic force with an opposing magnet roll;
The developing device is characterized in that the tip of the developing blade is divided into two parts, an upstream tip formed on the upstream side in the rotation direction of the developing sleeve and a downstream tip formed on the downstream side. .   The developing device according to claim 1, wherein a distance between the downstream tip portion and the developing sleeve is shorter than a distance between the upstream tip portion and the developing sleeve.   3. The developing device according to claim 1, wherein a distance between the downstream tip portion and the developing sleeve is equal to or less than a half of a distance between the upstream tip portion and the developing sleeve.   4. The hole according to claim 1, wherein the upstream tip has a hole for removing toner remaining in a gap between the upstream tip and the downstream tip. The developing device described.   5. The developing device according to claim 1, wherein the upstream tip and the downstream tip both have a distance from the developing sleeve that decreases toward the upstream side. 6.

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