JP2002040774A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the circulating balance of developer within a developing tank by preventing unevenness in distribution of the developer in a horizontal direction by maintaining a better balance of the developer than when the developer is returned to only one direction of an agitating paddle 21 or a carrying spiral 22. SOLUTION: In the device, a guide plate 26 to return the developer that is scraped off from a feeding roll 23 to each of the agitating paddle 21 and the carrying spiral 22 in specified proportions is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for an image forming apparatus such as a copying machine, a printer, and a facsimile. In particular, the present invention relates to a developing device for an image forming apparatus capable of forming an image on a sheet having a large size such as a row A (A0) size and a row A (A1) size of Japanese Industrial Standard.

[0002]

2. Description of the Related Art In a copying machine, an electrostatic latent image is formed on the surface of a photoconductor, which is uniformly charged, by exposing the surface of the photoconductor to a visible toner image. The output image is obtained by transferring the toner image onto the paper. The development of the electrostatic latent image with the toner is performed by a developing device that electrostatically attaches the toner to the surface of the photoconductor. FIG. 6 is a cross-sectional view of the developing device 9 that is usually used.

The developing device 9 includes a developing tank 20 and a developing tank 20.
And a supply roller 28 that supplies the developer in the hopper 27 to the developing tank 20. A stirring paddle 21 is arranged at the bottom of the developing tank 20.
2 are arranged. The stirring paddle 21 is provided with a spiral blade and a radial blade 21a around an axis, and rotates to stir the developer in the developing tank 20 by the function of the radial blade 21a. The developer is supplied to the supply roller 23, and the developer is fed in a lateral direction (a direction perpendicular to the paper surface) by the function of a spiral blade.

[0004] The transport spiral 22 is provided with spiral blades around the axis, and the developer is sent in the reverse direction by the function of the blades. Therefore, the developer can be circulated in the developing tank 20 in cooperation with the stirring paddle 21. At the upper right of the stirring paddle 21, a cylindrical supply roller 23 is arranged in parallel and close contact with the photosensitive drum 7 outside the developing tank 20. The supply roller 23 includes a rotatable cylindrical sleeve, and includes a magnet fixed inside the cylinder. Reference numeral 24a denotes an ear-cutting plate for scraping off excess developer in order to keep the developer attached to the supply roller 23 at a constant thickness, and 24 denotes a regulating plate.

[0005] Above the stirring paddle 21, the stirring paddle 21
A guide plate 26 is disposed between the control plate 24 and the control plate 24. The guide plate 26 is inclined so that the stirring paddle 21 is lowered toward a certain direction. According to the above-described structure, of the developer adhered to the supply roller 23, the excess developer scraped off by the ear splitting plate 24a falls along the guide plate 26 and returns to the stirring paddle 21.

[0006]

When the toner density fluctuates due to a change in charging ability due to the deterioration of the developer or a change in the environment of the apparatus, the amount of the developer scraped off by the ear splitting plate 24a changes. As a result, the circulation balance of the developer is disrupted, and the developer is laterally shifted in the developing tank. In some cases, the developer may overflow from the end of the developing device.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a developing device which can maintain the circulation balance of the developer even when the amount of the scraped developer changes.

[0008]

According to a first aspect of the present invention, there is provided a developing device comprising: a supply roller for supplying a developer to a photoreceptor; and a supply roller arranged in parallel with the supply roller. A first developer transport path, a second developer transport path disposed parallel to the supply roller, and transporting the developer in a direction opposite to the transport direction of the first developer transport path; A guide plate is provided in the developing tank for returning the scraped developer to the first developer transport path and the second developer transport path at a predetermined ratio, respectively.

According to the construction of the developing device, the developer can be returned to the first developer transport path and the second developer transport path at a predetermined ratio by the function of the guide plate.
Therefore, the developer circulation cycle can be shortened and the circulation balance of the developer can be easily maintained as compared with the case where only one of them is returned. Therefore, lateral deviation of the developer can be prevented. Generally, the first developer transport path is provided with a stirring paddle, and the second developer transport path is provided with a transport spiral.

The guide plate may be provided with an extension plate for guiding the developer to the second developer conveying path, and a notch for guiding the developer to the first developer conveying path. You may. Thus, the function of the guide plate of the present invention can be achieved by forming the guide plate in a simple shape.

[0011]

FIG. 1 is a cross-sectional view showing the overall structure of a copying machine employing a developing device according to an embodiment of the present invention. The copier 1 is provided from a paper storage unit 2 for storing roll paper or cut paper, a transport mechanism 3 for feeding paper to the image forming unit 5, an optical system for reading a document, and an optical system. An image forming unit 5 for forming an image based on light and transferring the image to a sheet, a fixing device 6 for fixing the image transferred to the sheet, a document table 11 and the like are provided.

The original table 11 is movable, and is connected to the original transport plate 12 when it is moved in the direction of arrow A. The image forming unit 5 includes a photosensitive drum 7, a charger 8 for charging the photosensitive drum 7,
Exposure section 4 for forming an electrostatic latent image, developing device 9 for developing the electrostatic latent image formed on photoconductor drum 7 into a toner image, and cleaner 10 for cleaning residual toner
It is included.

The fixing device 6 includes a fixing roller 64 for heating the sheet, a pressure roller 65 that is in pressure contact with the fixing roller 64,
It has a discharge roller 67 for discharging the paper after fixing. FIG. 2 is a sectional view of the developing device 9 of the copying machine 1. Hereinafter, the structure of the developing device 9 will be described with reference to FIG. The developing device 9 is a unit for developing an electrostatic latent image formed on the photosensitive drum 7 into a toner image using a two-component developer having a toner and a magnetic carrier. The developing device 9 includes a developing tank 20, a hopper 27 that stores toner to be supplied to the developing tank 20, a supply roller 28 that supplies the developer in the hopper 27 to the developing tank 20, and the like.

At the bottom of the developing tank 20, a spiral blade 21b (see FIG. 3) and a radial blade 2
1a is disposed.
On the left side of the stirring paddle 21, a transport spiral 22 having spiral blades around the axis is disposed with a partition plate 29 therebetween. A toner density sensor 25 is provided on the partition plate surface of the developing tank 20 on the left side of the transport spiral 22.
It is attached with the detection surface facing the transport spiral 22.

At the upper right of the stirring paddle 21, a cylindrical supply roller 23 is disposed. The supply roller 23 is arranged in parallel and close contact with the photosensitive drum 7 outside the developing tank 20. The supply roller 23 includes a rotatable cylindrical sleeve, and includes a magnet in which a relative position to the apparatus is fixed. A regulating plate 24 is disposed above and to the left of the supply roller 23 at a constant distance from the peripheral surface of the supply roller 23. The regulating plate 24 is made of a non-magnetic material, for example, aluminum. The regulating plate 24 is a flat regulating portion 24.
a, and a partitioning portion 24b located to the left of the regulating portion 24a and having a bottom having a cross-sectional shape and an upwardly convex mountain shape.

A supply roller 23 is provided at a lower end of the regulating portion 24a.
In order to keep the thickness of the developer adhered to the plate at a constant thickness, an ear-cutting plate 24c for scraping off excess developer is connected. A guide plate 26 for dropping the developer onto the stirring paddle 21 is disposed between the stirring paddle 21 and the regulating plate 24 so as to be inclined downward. Reference numeral 26a denotes an extension plate attached to the guide plate 26 to drop the developer farther than the partition plate 29. The toner density sensor 25 detects the toner content in the developer by detecting the magnetic permeability of the developer flowing and passing through the front surface by the action of the transport spiral 22.

FIG. 3 is a plan view showing the arrangement of the developing tank 20, the conveying spiral 22, the stirring paddle 21, and the supply roller 23 of the developing device 9. In FIG. 3, the regulation plate 24, the guide plate 26, and the hopper 27 are removed. The transport spiral 22, the stirring paddle 21, and the supply roller 23 are arranged in parallel with a certain distance from each other. The partition plate 29 between the transport spiral 22 and the stirring paddle 21 does not exist near both ends of the developing tank 20, and the developer can flow freely.

Next, the operation of the developing device 9 will be described. FIG.
, The developer is supplied from the stirring paddle 21 toward the supply roller 23. The developer is attracted to the peripheral surface of the supply roller 23 by being attracted by the magnetic field of the supply roller 23. The developer adhered to the peripheral surface of the supply roller 23 is scraped off by the spike 24c of the regulating plate 24, and regulated so as not to exceed a desired amount.

The developer, which has been worn away and separated from the supply roller 23, changes its traveling direction along the partition 24b, is supplied to the guide plate 26, flows down on the guide plate 26, and falls. The returned developer is supplied to the supply roller 23 again. On the other hand, the portion of the developing tank 20 where the transport spiral 22 exists (the second developer transport path) is substantially filled with the developer. The developer is transported in the direction D (see FIG. 3) along the axis by the rotation of the transport spiral 22.

Since the stirring paddle 21 is also rotating, the developer is conveyed in the direction B (see FIG. 3) along the axis by the action of the spiral blade 21b. Therefore, the developer is conveyed at one end of the developing tank 20 by the transport spiral 22.
From the stirring paddle 21 to the conveying spiral 22 at the other end, and circulates. This circulation is performed by the stirring paddle 21 and the supply roller 23.
It occurs over almost the entire length.

A feature of the embodiment of the present invention is that, as shown in FIG. 2, an extension plate 26a is attached to a guide plate 26 for dropping the developer to drop the developer farther than the partition plate 29. That is. FIG. 4 is a plan view showing the guide plate 26 with the extension plate 26a. The extension plates 26a are arranged in plural at a constant pitch u and have a U-shaped cross section. The extension plate 26a is an x-direction downstream end 26b of the guide plate 26.
Than the distance y. Extension plate 26
The horizontal length of a is indicated by z.

With such a configuration, the supply roller 2
When the developer separated from 3 flows on the guide plate 26,
The developer entering the extension plate 26a passes through the partition plate 29,
The developer drops into the second developer transport path where the transport spiral 22 exists. The developer is transported in a direction D (see FIG. 3) along the axis by the rotation of the transport spiral 22.
The developer that has not entered the extension plate 26a is
Falls toward the first developer conveying path in which is present. Therefore, the developer is moved in the direction B along the axis (see FIG. 3) by the action of the spiral blade 21b of the stirring paddle 21.
Transported to

As described above, the developer separated from the supply roller 23 is divided into two parts, and is conveyed and circulated in the opposite direction, so that the first developer in which the stirring paddle 21 is present as in the related art is used. The stirring efficiency of the developer increases as compared with the case where the developer drops toward the transport path. Therefore, the bias of the toner can be quickly eliminated, which can contribute to prevention of image quality deterioration. In addition, since the cross section of the extension plate 26a has a U-shape, the developer does not come out of the extension plate 26a while falling. Therefore, the falling ratio can be accurately maintained.

The length z in the horizontal direction of the extension plate 26a
And the pitch u of the extension plate 26a can be set according to the developer conveying speed ratio of the stirring paddle 21 and the conveying spiral 22. For example, if both transport speeds are the same,
The length z may be set to １ ／ of the pitch u. The embodiments of the present invention have been described above, but the embodiments of the present invention are not limited to the above embodiments. For example, as shown in FIG. 5, a notch 26c may be formed in the guide plate 26.
According to this shape, the developer is also transferred to the second developer transport path and the stirring paddle 2 where the transport spiral 22 exists.
1 can be distributed to the first developer conveying path in which it exists, and can be dropped. Adjust the length of the notched portion 26c and the uncut portion 26d by adjusting the stirring paddle 2
It can be adjusted in accordance with the developer transport speed ratio of 1 and the transport spiral 22.

The above is an example of the embodiment of the present invention, and various design changes can be made within the scope of the present invention.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an overall configuration of a copier employing a developing device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a developing device according to one embodiment of the present invention.

FIG. 3 is a plan view showing an arrangement of a developing tank, a conveying spiral, a stirring paddle, and a supply roller of the developing device.

4A is a plan view showing a guide plate 26 with an extension plate 26a, and FIG. 4B is a cross-sectional view.

FIG. 5 is a plan view showing a guide plate 26 having a notch 26c.

FIG. 6 is a cross-sectional view of a developing device 9 that is normally used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Copier 9 Developing device 20 Developing tank 21 Stirring paddle 21a Radial blade 21b Spiral blade 26a Extension plate 26 Guide plate 26c Notch

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Hiroyuki Ueda, Inventor Hiroyuki Ueda 1-2-2, Tamazuki, Chuo-ku, Osaka-shi, Osaka Inside Kyocera Mita Co., Ltd. No. 28 Kyocera Mita Corporation F term (reference) 2H077 AA37 AB02 AB03 AB14 AB15 AB18 AC02 AC16 AD06 AD32 BA08 DA10 DA42 DA52

Claims (4)

[Claims] 1. A supply roller for supplying a developer to a photoreceptor, a first developer conveyance path arranged in parallel with the supply roller, and a distance from the first developer conveyance path in parallel with the supply roller. A second developer transport path that transports the developer in a direction opposite to the transport direction of the first developer transport path; and removes the developer scraped from the supply roller with the first developer. A developing device comprising: a developing tank provided with a guide plate for returning the carrier to the transport path and the second developer transport path at a predetermined ratio. 2. The apparatus according to claim 1, wherein the first developer transport path includes a spiral blade and a radial blade around a rotation axis.
By rotating, while stirring the developer in the developing tank by the function of the blade in the radial direction and supplying it to the supply roller, a stirring paddle that sends the developer in the horizontal direction by the function of the spiral blade is arranged. In the second developer transport path, a transport spiral for disposing the developer in a lateral direction opposite to the above by rotating and being installed in parallel with the stirring paddle and circulating the developer in the developer tank is disposed. The developing device according to claim 1, wherein: 3. The developing device according to claim 1, wherein the guide plate is provided with an extension plate for guiding the developer to a second developer conveying path. 4. The developing device according to claim 1, wherein the guide plate has a notch for guiding the developer to the first developer conveying path.