JPH08101585A - Multi-stage developing device - Google Patents

Abstract

(57) [PROBLEMS] To provide a multi-stage developing device in which improvement of image density and improvement of reproducibility of low-contrast image are compatible. SOLUTION: The amount of the developer held by the second developing roller 5 located on the downstream side is smaller than the amount of the developer held by the first developing roller 4 located on the upstream side in the moving direction of the photoconductor 3. I am less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention supplies a developer by a plurality of developing rollers arranged along the moving direction of an image carrier to visualize an electrostatic latent image formed on the image carrier. The present invention relates to a developing device of an electrostatic recording device, such as a copying machine, a facsimile, or a printer, which forms an image.

[0002]

2. Description of the Related Art Conventionally, as a multi-stage developing device used in a copying machine or the like, first, second and third developing sleeves having a magnet inside and holding a two-component developer composed of a magnetic carrier and a toner have been conventionally used. It is known that the photoconductor is arranged around the photoconductor. However, in this case, the amount of the developer held on the developing sleeve of each developing roller after the developer supplied was regulated was the same between the developing sleeves. On the other hand, the relationship between the image density and the reproducibility of a low-contrast image, which is a halftone image, with respect to the amount of the developer is as shown in FIG. There is a so-called cross relationship,
When the same amount of developer was supplied to each developing sleeve, it was not possible to achieve both improvement in image density and improvement in low-contrast reproducibility.

Further, there is an increasing demand for downsizing of copying machines and the like, which necessitates downsizing of the developing device, and there is known a developing device in which the number of developing rollers facing the photoconductor is reduced from three to two. Has been. FIG. 4 shows this type, but in this case as well, there are the same problems as described above, and the developing roller 4,
In order to convey the developer only on the half surface side on the circumferential surface of 5, it is necessary to provide the third developing roller 4'in the developing device.
It was not possible to reduce the size and cost of a large device.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the prior art, and in the invention described in claim 1, a multi-stage developing device that achieves both improvement in image density and improvement in reproducibility of low-contrast images. The challenge is to provide
In addition to the above, an object of the present invention is to provide a small-sized and low-cost multi-stage developing device.

[0005]

In order to solve the above problems, the present invention provides a developer by a plurality of developing rollers arranged along the moving direction of an image carrier. In a multi-stage developing device for visualizing an electrostatic latent image formed on the image carrier, the amount of developer held by the developer carrier located upstream in the moving direction of the image carrier In addition to the above, the invention according to claim 2 is characterized in that the amount of the developer retained on the developer carrying member located on the downstream side is 25 mm or less and the magnet having 5 poles is provided inside. A certain first developer carrying member and a second developer carrying member provided with a magnet of four poles inside the first developer carrying member arranged downstream of the first developer carrying member in the moving direction of the image carrying member. However, the first and second developer carrying members are also on the opposite sides of the rollers from the image carrying member, Characterized by conveying the serial developer.

[0006]

According to the present invention, the amount of developer held by the downstream developing roller is smaller than the amount of developer held by the upstream developing roller. Can be supplied to improve the image density,
On the other hand, the downstream developing roller that holds a small amount of developer can improve the reproducibility of low-contrast images.

According to the second aspect of the invention, since the diameter of the first developing roller is set to 25 mm or less, even if the number of poles of the magnets of the first and second developing rollers is reduced, the first developing roller and the second developing roller are
The developer can be separated between the developing rollers to reduce the amount of the developer supplied to the second developing roller, and the developer can be conveyed by using both the image carrier side and the opposite side of both rollers. As a result, the developing device can be reduced in size and cost.

[0008]

1 is a schematic structural diagram of a multi-stage developing device showing an embodiment of the present invention. The developing device includes a developing unit 1 and a toner replenishing unit 2.

In the developing unit 1, a first developing roller 4 and a second developing roller 5 are provided from the upstream side of the photoconductor 3 which is an example of an image carrier. Both rollers 4 and 5 respectively have a first sleeve 6 and a second sleeve 7 which rotate on the outer surface and a fixed first magnet 8 which is a magnet inside.
Has a second magnet, and this magnet 8,
By the action of 9, the two-component developer consisting of the magnetic carrier and the toner is adsorbed on and carried by the sleeves 6 and 7.
The electrostatic latent image above is visualized.

A paddle 10 is provided diagonally below the second sleeve 7.
The paddle 10 conveys the developer, which is replenished by the toner replenishing roller 15 of the toner replenishing unit 2 and mixed and stirred by the stirring plate 11 (elliptical plate), to the second sleeve 7.

The developer that has moved from the second sleeve 7 to the first sleeve 6 is regulated to an appropriate amount by the doctor blade 12 and used to visualize the electrostatic latent image on the photoconductor 3. .

On the other hand, the remaining regulated developer passes over the separator 13, while a part of the developer is dropped into the separator 13 during that time, and the lateral stirring screw 14 provided inside the developer horizontally moves the developer. Agitating.

Further, on the upstream side of the first developing roller 4, the first
Further, an inlet seal 15 is provided to prevent the floating toner in the developing unit generated by the rotation of the second sleeves 6 and 7 from scattering outside the developing device.

Next, the flow of the developer will be described with reference to FIG. The developer drawn up by the paddle 10 to the second sleeve 7 is carried from the second sleeve 7 to the first sleeve 6, and is regulated by the doctor 12 above the first sleeve as described above. The first development is performed by the developer on the first sleeve 6 after the regulation. In this case, since sufficient developer can be supplied onto the first sleeve, a high image density (ID) can be achieved by the first development as shown in FIG.

The developer on the first sleeve 6 after the first development is moved to the second sleeve 7 by the action of the magnets 8 and 9 in the first and second developing rollers 4 and 5, respectively. The one that remains on the first sleeve 6 is separated. Due to this separation, a developer amount smaller than the developer amount supplied on the first sleeve 6 is sent to the second sleeve 7, and as a result, in the second development by the second developing sleeve 7. As is clear from FIG. 3, low cost and highly reproducible development can be performed.

In order to separate such a developer, a two-component developer composed of a magnetic carrier and a toner is used to provide a developing device having the first and second developing rollers having magnets therein, as in the present embodiment. In the above, the influence of the size of the developing roller and the number of poles of the magnet inside the developing roller is
When the diameter of the developing roller is 25 mm or less, the developer is separated even when the number of magnet poles in the first developing roller 4 is 5 and the number of magnet poles in the second developing roller 5 is 4. When the diameter of the first developing roller is 25 mm or more, the above separation can be performed by increasing the number of magnet poles in the first and second developing rollers 4 and 5, but in this case, the cost of the developing device increases. At the same time, heat generation and torque increase due to eddy current occur. According to the present invention, it is possible to provide a highly reliable developing device in which such a phenomenon does not occur.

In the above embodiments, the case where the two-component developer consisting of the magnetic carrier and the toner is conveyed by the developing roller having the magnet inside has been described.
The present invention is not limited to such a case, for example, when a one-component developer made of magnetic toner is used to convey the developer by a developing roller having a magnet inside, or from an upstream developing roller to a downstream developing roller. The present invention can also be applied to the case of electrically separating the toner supplied to the device.

[0018]

As described above, according to the present invention, in the invention of claim 1, the amount of developer held on the downstream developing roller is smaller than that on the upstream developing roller, so that the image density is improved. It is possible to improve the reproducibility of the contrast image as well as increase the contrast. In the invention of claim 2,
In addition to the above effects, it is possible to achieve downsizing and cost reduction of the multi-stage developing device.

[Brief description of drawings]

FIG. 1 is a sectional view of a multi-stage developing device showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the developer flow.

FIG. 3 is a curve diagram showing low image reproducibility and image density with respect to the amount of developer on the developing sleeve.

FIG. 4 is a schematic diagram showing a developer flow in an example of a conventional multi-stage developing device.

[Explanation of symbols]

 3 Photoreceptor (Image Carrier) 4 First Developing Roller (Multiple Developing Rollers) 5 Second Developing Roller (Multiple Developing Rollers) 8 First Magnet (Magnet) 9 Second Magnet (Magnet)

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[Procedure amendment]

[Submission date] November 10, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

[0005]

In order to solve the above-mentioned problems, the present invention has a plurality of developer carrying members arranged along the moving direction of the image carrying member . Stirrer
The developer supplied from the material is regulated and
The developer conveyed and further supplied to the developer carrier is
In a multi-stage developing device regulated by a regulating member to visualize an electrostatic latent image formed on the image carrier, the electrostatic latent image formed on the image carrier is visualized. In the multi-stage developing device, the amount of the developer held by the developer carrier located on the downstream side is smaller than the amount of the developer held by the developer carrier located on the upstream side in the moving direction of the image carrier. According to the invention of claim 2, in addition to the above,
1st with diameter of 25mm or less with magnet of 5 poles inside
A developer carrier, and a second developer carrier having a magnet with four poles inside thereof, which is disposed on the downstream side of the first developer carrier in the moving direction of the image carrier. The first and second developer carrying members are also characterized in that they carry the developer on the opposite sides of the rollers to the image carrying member.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

The developer moved from the second sleeve 7 to the first sleeve 6 is a doctor blade 1 as a regulating member.
It is regulated to an appropriate amount by 2 and used to visualize the electrostatic latent image on the photoconductor 3.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

Next, the flow of the developer will be described with reference to FIG. The developer mixed and stirred by the stirring plate 11 is the paddle 1
It is conveyed to the second sleeve 7 while being stirred by 0,
When the developer is the second sleeve of the separator 13 shown in FIG.
The developer is regulated by the regulation part formed on the lower part on the 7 side.
Received and transported. Then, the developer carried to the second sleeve 7 is carried from the second sleeve 7 to the first sleeve 6, and is regulated by the doctor 12 above the first sleeve as described above. The first development is performed by the developer on the first sleeve 6 after the regulation. In this case, since sufficient developer can be supplied onto the first sleeve, a high image density (ID) can be achieved by the first development as shown in FIG.

Claims (2)

[Claims] 1. A multi-stage developing device for supplying a developer by a plurality of developing rollers arranged along a moving direction of an image carrier to visualize an electrostatic latent image formed on the image carrier. In the above, the amount of the developer held by the developer carrier located on the downstream side is smaller than the amount of the developer held by the developer carrier located on the upstream side in the moving direction of the image carrier. And multi-stage developing device. 2. A diameter of 25 mm with a 5-pole magnet inside.
A first developer carrying member, which will be described below, and 4 inside the first developer carrying member arranged downstream of the first developer carrying member in the moving direction of the image carrying member.
A second developer carrying member having a polar magnet, and
2. The multi-stage developing device according to claim 1, wherein the second developer carrier also conveys the developer on the opposite side surfaces of the rollers to the carrier.