JPH03200991A - Developing device - Google Patents

Abstract

PURPOSE:To control a toner layer to a toner amount or uniform toner density corresponding to desire density by providing a roller-shaped layer thickness control member which is arranged at a specific interval with a developer carrier and a controller which controls the rotating speed of the layer thickness control member. CONSTITUTION:The control means controls the rotating speed of the layer thickness control roller 12 to control the amount of toner on a developing roller 11. Namely, when the rotating speed of the developing roller 11 is made constant and the rotating speed of the layer thickness controller 12 is increased, the toner layer on the developing roller 11 becomes thin: when the rotating speed of the layer thickness control roller 12 is decreased, a border layer approaches the layer thickness control roller 12 and the thickness of the toner layer on the developing roller 11 becomes thick. The rotating speed of the layer thickness controller 12 is controlled according to copy density to vary the toner amount, and the development density of a latent image on a photosensitive drum 2 is varied. Consequently, the toner layer which has uniform toner density is formed on the developer carrier and an excellent image with invariably stable density is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device for an electrophotographic image forming apparatus such as a copying machine, facsimile machine, or printer.

[Prior art]

A magnetic brush or toner layer of a two-component developer containing a magnetic developer or non-magnetic toner and a magnetic carrier is formed on a developer supply roller placed in contact with the developer, and the layer thickness is controlled to a constant thickness by a layer thickness regulating member. A toner-only layer is formed on a developing roller placed in contact with the magnetic brush of the developer supply roller, and a latent image on a latent image carrier placed in a non-contact manner is transferred to the developing roller. The method of developing the magnetic brush of the developer supply roller to a constant layer thickness by rotating the roller at a constant rotational speed is known, for example, from Japanese Patent Laid-Open No. 5
6-40862, JP 56-126870, JP 60-123859, JP 60-1
No. 40277, JP-A-62-279374,
This is known from Japanese Patent Application Laid-Open No. 62-279375.

In the conventional developing device described above, the layer thickness of the magnetic brush of the developer supply roller is leveled by a roller with a constant rotation speed, but the layer thickness of the magnetic brush of the developer of the developer supply roller is leveled. Adjustment of the toner layer formed on the developing roller is not taken into account. Therefore, when developing a latent image carrier in a non-contact state by toner flying from the developing roller due to the charge of the latent image, the toner density will be low. There was a problem that it could not be controlled accurately.

In addition, in the conventional developing device described above, the layer thickness of the developer on the developer supply roller is kept constant, but the layer thickness of the developer on the developer roller or the developer supply roller is kept constant. The density is not made uniform, so there are problems in some images where the developer is too dense and the image density is capricious, or the density is insufficient and the image density is insufficient. Ta.

[Problem to be solved by the invention]

The present invention solves the above-mentioned conventional problems, regulates the toner layer thickness of a developer carrier, such as a developing roller, which performs a developing action on a latent image carrier, to a uniform layer thickness, and also controls the toner layer thickness according to a desired density. It is an object of the present invention to provide a developing device that can regulate the amount or density of a toner layer to be uniform.

[Means to solve the problem]

The present invention solves the above problem by providing a replenishment developer carrier that forms a magnetic brush for a developer made of a mixture of non-magnetic toner and a magnetic carrier, and a replenishment developer carrier disposed close to the developer carrier and the latent image carrier. In a developing device which has a developer carrier and forms a toner layer on the developer carrier by sliding of a magnetic brush of the replenished developer carrier, roller-like rollers are arranged at predetermined intervals on the developer carrier. The problem was solved by a developing device characterized by being provided with a layer thickness regulating member and a control device for controlling the number of rotations of the layer thickness regulating member.

The present invention further solves the above problem by providing a replenishment developer carrier that forms a magnetic brush for developer made of a mixture of non-magnetic toner and magnetic carrier, and a replenishment developer carrier that is close to each of the replenishment developer carrier and the latent image carrier. In the developing device, the developing device has a developer carrying member disposed and forms a toner layer on the developer carrying member by transferring only non-magnetic toner by sliding of a magnetic brush of the replenishing developer carrying member. A toner layer uniformizing member is provided which extends in the circumferential direction of the body, and whose distance from the surface of the developer carrier gradually narrows in the toner transport direction, with the narrowest distance being set to a predetermined distance. This problem was solved with a unique developing device.

[Effect]

According to the present invention, a rotatable layer thickness regulation roller is disposed on a developer carrier disposed close to a latent image carrier, and the layer thickness regulation roller uniformly regulates the layer thickness of the developer carrier.
When a relative speed difference occurs between the rotation speed of the layer thickness regulation roller and the rotation speed of the developer carrier, the toner layer that follows the rotation of the layer thickness regulation roller and the toner layer that follows the rotation of the developer carrier boundary layer changes. When the number of rotations of the developer carrier is constant and the number of rotations of the layer thickness regulating roller is increased, the boundary layer approaches the developer carrier, the thickness of the toner layer on the developer carrier becomes thinner, and the layer thickness increases. When the rotational speed of the thickness regulating roller is decreased, the boundary layer approaches the layer thickness regulating roller, and the thickness of the toner layer on the developer carrier tends to increase. Therefore, by controlling the rotation speed of the layer thickness regulating roller, the amount of toner on the developer carrier can be controlled.

According to the present invention, the toner layer formed on the surface of the developer carrier, for example, the developing roller by the magnetic brush of the developer supply roller, is controlled by the starting edge of the layer thickness regulating member or the toner layer uniformizing member. Excess toner is removed.The toner layer whose thickness is regulated to 0 is gradually made thinner by the toner layer equalizing member, and when it leaves the end of the toner layer equalizing member, the toner layer has a predetermined layer thickness. A layer is formed. Furthermore, while the toner layer is being leveled by the toner leveling member, the toner density of the toner layer is also leveled, and after passing through the toner layer leveling member, the surface of the developer carrier has a layer thickness and a toner density that are approximately the same in the circumferential direction and the axial direction. A substantially uniform toner layer is formed.

〔Example〕

The details of the present invention will be explained based on embodiments shown in the drawings.

In FIG. 1, a drum-shaped latent image carrier 2 having an electrophotographic photosensitive layer 1 on its surface, such as a photosensitive drum, is rotatably provided, and a developing bag W is arranged along the moving surface of the photosensitive layer 1.
13, the electrostatic latent image on the latent image carrier 2 is developed.

A developer 4 is accommodated in the casing of the developing device 3 . The developer 4 is formed as a mixture of non-magnetic toner and magnetic carrier, and is replenished from a toner replenishing device 5 when the non-magnetic toner is consumed.

In the casing of the developing device t3, the toner and carrier are stirred and mixed by the stirring device 6, and at this time, the toner is frictionally charged and electrostatically held on the surface of the carrier.

The carrier with the toner held on its surface is attracted by a replenishment developer carrier 7 arranged in contact with the developer, for example a magnet 9 of a developer replenishment roller ruff, and forms a magnetic brush on the surface of the sleeve 8 of the developer replenishment roller ruff. .

The replenishment developer carrier 7 consists of a non-magnetic sleeve 8 and a magnet 9 having a plurality of magnetic poles, and one or both of the sleeve 8 and the magnet 9 is rotated to convey the magnetic brush formed on the sleeve 8. do.

The magnetic brush conveyed along the surface of the sleeve 8 of the developer replenishing roller 7 has its ears cut by a cutting plate 10 and is regulated into a developer layer of a predetermined thickness.

A developer carrier 11, for example a developing roller, is disposed in close proximity to the portion of the sleeve 8 that is away from, for example, the opposite side of, the portion that contacts the developer.

The developing roller 11 has a circumferential surface covered with a conductive material and is disposed close to the photosensitive layer l of the latent image carrier 2.

As shown in FIGS. 1 and 2, a layer thickness regulating roller 12 is arranged at a predetermined distance from the surface of a developer carrier 11, for example a developing roller.

The developer that comes into contact with the replenishment developer carrier 7, for example, the developer replenishment roller, is attracted by magnetic force to form a magnetic brush on the sleeve 8 of the developer replenishment roller 7, and the magnetic brush is conveyed, for example, in the clockwise direction shown by the arrow. Ru. The magnetic brush rubs the surface of the developing roller 11, and the charged toner is transferred to the developing roller 1.
is attracted to the conductive surface of 1. A bias voltage is applied to the developing roller 11 by a power source 15 so as to attract and hold the charged toner. A bias voltage is also applied to the sleeve 8 of the developer supply roller by the power supply 16 as required.

A toner layer is formed on the surface of the developer roller 11 by the toner detached from the surface of the carrier of the magnetic brush on the sleeve 8 of the developer supply roller.

While the developing roller 11 rotates in the direction of the arrow, the layer is leveled into a uniform layer by the layer thickness regulating roller 12, as shown in FIG. In the illustrated example, both the developing roller 11 and the layer thickness regulating roller 12 are rotated counterclockwise, and their opposing surfaces move in opposite directions.

The amount of toner on the developing roller 11 is controlled by controlling the rotation speed of the layer thickness regulating roller 12 by a control means (not shown). That is, when a relative speed difference occurs between the rotation speed of the layer thickness regulation roller 12 and the rotation number of the developing roller 11, the toner layer and the development roller 1 follow the rotation of the layer thickness regulation roller 12.
There is a tendency for the boundary layer with the toner layer that follows the rotation of No. 1 to fluctuate.

When the number of rotations of the developing roller 11 is constant and the number of rotations of the layer thickness regulating roller 12 is increased, the boundary layer
1, the thickness of the toner layer on the developing roller 11 becomes thinner, and when the number of rotations of the layer thickness regulating roller 12 is reduced, the boundary layer approaches the layer thickness regulating roller 12 and the thickness of the toner layer on the developing roller 11 decreases. becomes thicker.

The thickness of the toner layer of the developing roller 11 is made thinner than the gap between the developing roller 11 and the surface of the photoreceptor drum 2, and development is performed on the photoreceptor drum 2 by flying the charged toner. .

The number of rotations of the layer thickness regulating roller 12 is controlled in accordance with the copy density to change the amount of toner and the development density for the latent image on the photosensitive drum 2.

In FIG. 3 showing another embodiment of the present invention, a drum-shaped latent image carrier 2, for example a photosensitive drum, having an electrophotographic photosensitive layer 1 on its surface is rotatably provided, and a surface on which the photosensitive layer 1 moves The electrostatic latent image on the latent image carrier 2 is developed by a developing device 23 arranged along the line.

A developer 24 is accommodated in the casing of the developing device 23 . The developer 24 includes a non-magnetic toner 25 and a magnetic carrier 2.
Formed as a mixture of 6.

In the casing of the developing device 23, the toner 25 and the carrier 26 are stirred and mixed by the stirring devices 27a, 27b, and 27C, and at this time, the toner 25 is frictionally charged and the carrier 26 is mixed.
electrostatically held on the surface of

The carrier 26 on which the toner 25 is held is attracted by a magnet 29 of a replenishing developer carrier 28, such as a developer replenishing roller 28, whose lower part is in contact with the developer.
A magnetic brush is formed on the surface of the sleeve 30 of the developer supply roller 28.

The developer supply roller 28 consists of a non-magnetic sleeve 30 and a magnet 29 having a plurality of magnetic poles, and one or both of the sleeve 30 and the magnet 29 are rotated to convey a magnetic brush formed on the sleeve 30. .

The magnetic brush conveyed along the surface of the sleeve 30 of the developer replenishing roller 28 has its ears cut by a cutting plate 31 and is regulated into a developer layer of a predetermined thickness.

a position away from the part of the sleeve 30 that comes into contact with the developer;
For example, a developer carrier 32, such as a developing roller, is disposed close to the upper position.

The developing roller 32 has a peripheral surface 33 made of a conductive material,
It is arranged close to the photosensitive layer l of the latent image carrier 2.

As shown in FIGS. 3 and 4, a thin plate-like layer thickness regulating member 34 is disposed at a substantially predetermined distance from the surface of the developer carrier 32, for example, a developing roller.

A toner layer uniformizing member 35 is fixed to the layer thickness regulating member 34 . The toner layer uniformizing member extends over almost the entire length of the developing roller 32, and is attached to the developing roller 3 so that the distance from the surface of the developing roller 32 gradually narrows in the toner conveying direction.
It also extends in the circumferential direction of 2. The narrowest distance between the toner layer equalizing member 35 and the developing roller 32, for example, the distance between the end of the toner equalizing member 35, is set so that the toner layer has a predetermined thickness. It is also possible to form the starting end of the toner layer uniformizing member 35 as the layer thickness regulating member 34 and omit forming the layer thickness regulating member 34 as a separate body.

The developer that comes into contact with the replenishment developer carrier 28, for example, the developer replenishment roller, is attracted by magnetic force and is transferred to the developer replenishment roller 2.
A magnetic brush is formed on the sleeve 30 of No. 8, and the magnetic brush is conveyed, for example, in the clockwise direction shown by the arrow. The magnetic brush rubs the surface of the developer carrier 32, for example the developing roller, and only the charged toner is separated from the carrier surface and attracted to the conductive surface 33 of the developing roller 32. Developing roller 3
A bias voltage is applied to 2 by a direct current type [36 and an alternating current power source 37] so as to attract and hold the charged toner. A bias voltage is also applied to the sleeve 30 of the developer replenishing roller 28 by the DC power supply 38 as necessary.

Toner dislodged from the surface of the magnetic brush carrier on sleeve 30 of developer supply roller 28 forms a toner layer on surface 33 of developer roller 32 . The residual developer on the sleeve 30 of the developer supply roller 28 is removed by the return plate 39.
is returned to the casing.

While the developing roller 32 rotates in the direction of the arrow, the layer thickness is regulated by the layer thickness regulating roller 34 as shown in FIGS. 3 and 4, and the toner layer is leveled into a uniform layer by the toner equalizing member 35. Thickness and toner density are made uniform.

The thickness of the toner layer of the developing roller 32 is made thinner than the gap between the surface 33 of the developing roller 32 and the surface l of the photoconductor drum 20, and the charged toner generates vibrations and flies in the gap, thereby causing the charged toner to fly away from the photoconductor. Development is performed on the drum 2.

〔effect〕

According to the present invention, the toner layer is made to have a uniform layer thickness by the layer thickness regulating roller disposed close to the developer carrier, and the amount of toner can be controlled by controlling the rotation speed of the layer thickness regulating roller, thereby adjusting the copy density. could be done easily.

According to the present invention, stable and good images with desired density can be obtained.

According to the present invention, a toner layer with uniform layer thickness and toner density can be formed on the developer carrier by the toner layer thickness equalizing member disposed close to the developer carrier, and the toner layer with a stable and good density can be formed on the developer carrier. Images can be provided.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a developing device according to the present invention, FIG. 2 is a partially enlarged view, FIG. 3 is a sectional view of a developing device of another embodiment, and FIG.
The figure is a partially enlarged view of FIG. 3. 2...Latent image carrier 3...Developing device 4...Developer 7...Replenishment developer carrier 8...Sleeve 9...Magnet 11...Developer carrier I
2...N thickness regulating roller 23...Developing device 24
...Developer 28...Replenishment developer carrier 29...Magnet 31...Sleeve 32...
・Developer carrier 35...toner layer thickness uniformity member Fig. 1

Claims (3)

[Claims] (1) A replenishment developer carrier forming a magnetic brush for developer made of a mixture of non-magnetic toner and magnetic carrier, and a developer carrier disposed close to each of the replenishment developer carrier and the latent image carrier. In the developing device which forms a toner layer on the developer carrier by sliding of the magnetic brush of the replenished developer carrier, the roller-shaped layer thickness regulating member is arranged at a predetermined interval on the developer carrier. and a control device for controlling the number of rotations of the layer thickness regulating member. (2) The developing device according to claim 1, wherein the layer thickness regulating member is disposed upstream of a developing area with respect to the latent image carrier. (3) A replenishment developer carrier forming a magnetic brush of developer made of a mixture of non-magnetic toner and magnetic carrier, and a developer carrier disposed close to each of the replenishment developer carrier and the latent image carrier. In a developing device that forms a toner layer on the developer carrier by transferring only non-magnetic toner by sliding of a magnetic brush of the replenishing developer carrier, the developer carrier extends in the circumferential direction of the developer carrier. A developing device further comprising a toner layer uniformizing member whose distance from the surface of the developer carrier gradually narrows in the toner transport direction, and whose narrowest distance is set to a predetermined distance.