JPH03118575A - developing device - Google Patents

Abstract

PURPOSE:To control the copy density without toner scattering by providing a roller-shaped layer thickness control member which is arranged at a specific interval to a developer carrier and a controller which controls the rotating speed of the layer thickness control member. CONSTITUTION:When the rotating speed of a doctor roller 5 is low and the relative speed difference from a sleeve 4 is small, friction is small, and the triboelectric charge quantity of toner becomes small, but when the relative speed difference from the sleeve 4 becomes large by increasing the rotating speed of the doctor roller 5, the friction increases, so that the triboelectric charge quantity of the toner becomes large. Assuming that the latent image conditions of a photosensitive drum 1 are equal, the sticking quantity of toner can be increased by increasing the rotating speed of the doctor roller 5, but decreased by decreasing the rotating speed. Namely, the amount of toner sticking on a latent image on the photosensitive drum 1, i.e. copy density can be controlled by controlling the rotating speed of the doctor roller 5.

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 developing device is conventionally known in which a magnetic brush of a two-component developer containing non-magnetic toner and a magnetic carrier is formed on a developing roller, and a latent image on a photoreceptor is developed by the magnetic brush of the developing roller.

In such a developing device, a layer thickness regulating member regulates the magnetic brush layer of the developing roller into a uniform thin layer, and the toner on the magnetic brush is attracted by the charge of the photoreceptor to perform development. When the toner charge amount of the magnetic brush is low, the adhesion force to the carrier becomes weak, and the amount of toner adhering to the latent image increases, resulting in a dense copy. There is a tendency that the amount of toner that is attracted and adhered due to the charge decreases, resulting in a lower copy density.

Conventional developing devices detect copy density and replenish toner when the density becomes low. When the toner concentration of the refilled developing device increases in this way, the amount of toner scattering increases as shown in FIG. 3, and when the toner concentration exceeds 4 wt%, the amount of toner scattering increases rapidly. Therefore, there is a problem in that the copy density decreases and when toner is replenished, toner scattering increases.

[Problem to be solved by the invention]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and provide a developing device that can control copy density without causing toner scattering.

[Means to solve the problem]

The present invention solves the above problem by having a developer carrier that forms a magnetic brush of a developer made of a mixture of non-magnetic toner and a magnetic carrier, and carrying a latent image by sliding the magnetic brush of the developer carrier. In a developing device for developing a latent image of a body, a roller-like layer thickness regulating member arranged at a predetermined interval on a developer carrier and a control device controlling the rotation speed of the layer thickness regulating member are provided. This problem was solved with a unique developing device.

[Effect]

According to the present invention, a roller-shaped developing member, such as a doctor roller, is arranged in close proximity to a developer carrier, such as a developing roller. When the doctor roller and the rotating sleeve of the developing roller are rotated so that their opposing surfaces move in opposite directions, the doctor roller comes into contact with the magnetic brush on the surface of the sleeve of the developing roller and removes excess developer. death,
Level the developer layer on the sleeve, ie the magnetic brush layer, into a uniform layer. At this time, friction occurs between the doctor roller and the developer toner. The larger the relative speed difference between the doctor roller and the sleeve, the larger the I2 friction, which increases the amount of charge on the toner, and the smaller the relative speed difference, the smaller the friction and the amount of charge on the toner. .

When increasing the amount of developed toner for the latent image on a latent image carrier, such as a photosensitive drum, to increase the copy density, the rotation speed of the sleeve is constant, so the rotation speed of the doctor roller is reduced, and the amount of charge on the toner increases. Try to make it smaller,
When it is desired to lower the copy density, the rotational speed of the doctor roller is increased to increase the amount of charge on the toner.

If the relationship between the copy density and the rotation speed of the doctor roller is set in advance, the copy density can be controlled by controlling the rotation speed of the doctor roller according to the copy density.

The amount of charge on the toner is easily affected by temperature and humidity; as the temperature and humidity increase, the amount of charge decreases, and as the temperature and humidity decrease, the amount of charge tends to increase. Therefore, if a temperature and humidity detection member (one or both of a temperature detection member and a humidity detection member, or both are integrated) is provided in the developing device, and the number of rotations of the doctor roller is controlled according to the detection signal. more effective.

〔Example〕

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

1 and 2, a latent image carrier 1, for example, a photoreceptor drum, is rotatably provided, and a developing device 2 disposed along a moving surface of the photoreceptor drum 1 drives the photoreceptor drum 1.
An electrostatic latent image is developed.

The developing device 2 has a developer carrier, for example a developing roller,
The developing roller consists of a non-magnetic sleeve 3 and a magnet 4 having a plurality of magnetic poles, and the sleeve 3 is rotated. A roller type layer thickness regulating member 5, for example a doctor roller, is arranged adjacent to the sleeve 3.

A developer 6 is housed in the casing of the developing device 2 . The developer 1 is formed as a mixture of non-magnetic toner and magnetic carrier.

In the casing of the developing device 2, the toner of the developer 6 and the carrier are stirred and mixed by the stirring bag w7, and at this time the toner is triboelectrically charged and electrostatically held on the surface of the carrier.

The carrier with the toner retained on its surface is attracted by the magnet 4 of the developing roller placed in contact with the developer 6, forming a magnetic brush on the surface of the sleeve 3.

As the sleeve 3 rotates, the magnetic brush formed on the sleeve 3 is conveyed.

The magnetic brush conveyed along the surface of the sleeve 3 of the developing roller comes into contact with the doctor roller 5, and the doctor roller 5
By rotating the magnetic brush, the layer thickness of the magnetic brush is made uniform in a known manner. The developer removed by the doctor roller 5 is sent by the lateral conveyance device 1o and returned into the casing.

The sleeve 3 of the developing roller is arranged close to the photoreceptor drum 1, and the electrostatic latent image on the photoreceptor drum 1 is developed by the sliding friction of the magnetic brush of the sleeve 3. When the non-magnetic toner is consumed by development, toner 9 is replenished from toner supply device 8 .

The sleeve 3 of the developing roller and the doctor roller 5 are rotated and driven so that opposing surfaces thereof rotate in opposite directions. Therefore, in the illustrated example, both the sleeve 3 and the doctor roller 5 are rotated counterclockwise.

When the number of rotations of the doctor roller 5 is constant as in the conventional case, the layer thickness of the developer is only regulated, and changes in the toner charge amount due to friction between the doctor roller 5 and the toner in the developer are not taken into account. When the rotational speed of the doctor roller 5 is low and the relative speed difference with the sleeve 4 is small, there is less friction and the amount of frictional electrification of the toner is small. When the speed difference becomes large, the Pj friction becomes large, and the amount of frictional electrification of the toner becomes large.

Assuming that the latent image conditions of the photosensitive drum 1 are the same, lowering the rotation speed of the doctor roller 5 will increase the amount of toner adhesion, and increasing the rotation speed of the doctor roller 5 will reduce the amount of toner adhesion. That is, by controlling the number of rotations of the doctor roller 5, the amount of toner attached to the latent image on the photosensitive drum 1, that is, the copy density can be controlled.

Since the amount of charge on the toner is affected by temperature and humidity, it is more reliable to provide a temperature and humidity detection member 11 in the casing of the developing device 2, and to control the rotation speed of the doctor roller 5 by a control device (not shown) according to the detection signal. This enables accurate copy density control without unnecessarily replenishing a large number of toners to the developing device.

〔effect〕

According to the present invention, it has become possible to reliably control the copy density without causing toner scattering by a simple method of controlling the rotation speed of the roller-like layer thickness regulating member. The rotation speed of the roller-like layer thickness regulating member is controlled according to the detection signal of the temperature and humidity detection member.
1, it became possible to more accurately control the toner charge amount and copy density.

[Brief Description of the Drawings] Figure 1 is a sectional view of the main parts of the developing device according to the present invention,
The figure is a sectional view of the developing device, and FIG. 3 is a diagram showing the relationship between toner concentration and toner scattering amount. 1...Latent image carrier 2...Developing device 3...Sleeve 4...Magnet 5...Layer thickness regulating member
6...Developer 1 Figure 3 Wt('/,) Tocho-1 friend

Claims (3)

[Claims] (1) It has a developer carrier that forms a magnetic brush of a developer made of a mixture of non-magnetic toner and magnetic carrier, and the latent image on the latent image carrier is developed by the rubbing of the magnetic brush of the developer carrier. A developing device comprising: a roller-shaped layer thickness regulating member disposed at a predetermined interval on a developer carrier; and a control device controlling the number of rotations of the layer thickness regulating member. (2) Claim 1 characterized in that the layer thickness regulating member is arranged upstream of a developing area with respect to the latent image carrier.
The developing device described in . (3) The rotation speed of the layer thickness regulating member is controlled according to a detection signal from at least one of a temperature detection member and a humidity detection member provided in the developing device. Developing device.