JPH0493965A - Developing device - Google Patents

Abstract

PURPOSE:To easily detect the change of the thickness of the toner layer of a toner developing roll caused by an effect of the toner concentration on a magnetic brush and the change of environment by providing a detection means for detecting the thickness of the toner layer of the toner developing roll. CONSTITUTION:The means 5 for detecting the thickness of the toner layer of a 2nd carrier 2 is provided. In the case of detecting the change of the thickness of the toner layer by the means 5 and controlling bias impressed on a 1st carrier 3 in accordance with the change of the thickness of the toner layer, a potential difference between the 2nd carrier 2 and the 1st carrier 3 is adjusted to be in an optimum condition and the toner layer which always has the appropriate thickness is formed on the surface of the 2nd carrier 2. Then, the means 5 for detecting the thickness of the toner layer of the 2nd carrier 2 is provided. In the case of detecting the change of the thickness of the toner layer by the means 5 and controlling the bias impressed on the 2nd carrier 2 in accordance with the change of the thickness of the toner layer, the potential difference between the photosensitive body 1 and the 2nd carrier 2 is adjusted so that toner may be allowed to fly under an optimum condition and development by always using the proper flying bias is accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developing device for developing an electrostatic latent image in an electrophotographic copying device or the like.

[Conventional technology]

As a developing device for developing an electrostatic latent image in an electrophotographic copying machine or the like, there is a known device that non-contact develops an electrostatic latent image on a photoreceptor with a non-magnetic insulating toner (Japanese Patent Application Laid-Open No.
6-40862, JP-A-60-140277, JP-A-60-123859, JP-A-61-45260, etc.).

For example, in Japanese Patent Application Laid-open No. 56-40862, a magnetic brush is formed on a magnetic roller using a two-component developer consisting of a magnetic carrier and a non-magnetic toner, and the magnetic brush is placed on a developing roller close to the magnetic roller. A developing device is described in which only the non-magnetic toner in the magnetic brush is transferred onto the developing roller to form a toner layer on the developing roller, and the developing roller develops the electrostatic latent image on the surface of the photoreceptor. In this developing device, an alternating electric field is formed between the magnetic roller and the developing roller, only the toner is delivered from the magnetic brush to the developing roller, and the toner on the developing roller is caused to fly by the alternating electric field to form an electrostatic latent image on the photoreceptor. Perform non-contact M development.

[Problem to be solved by the invention]

In a developing device that develops an electrostatic latent image in a non-contact state using a developing roll closest to the electrostatic latent image,
In order to obtain a good image, it is necessary to always form a thin toner layer with a uniform thickness on the surface of the developing roll directly involved in development.

However, in this developing device, a magnetic brush is formed on the surface of a developer supply roll (magnet roll) which is a first carrier, and the toner in the magnetic brush is transferred to a toner developing roll which is a second carrier. In a developing device having a configuration in which the toner is transferred, the thickness of the toner layer formed on the toner developing roll varies due to changes in the toner concentration of the magnetic brush and the environment such as temperature and humidity. Therefore, if the thickness of the toner layer is too large, the image tends to be foggy or blurred, and if the thickness is too small, the image tends to lack density.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a developing device that can solve the above-mentioned problems and always produce stable images.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an apparatus for non-contact development of an electrostatic latent image on a photoreceptor with a non-magnetic insulating toner, the apparatus comprising a magnetic carrier and a non-magnetic toner on a first carrier surface. A magnetic brush is formed, a first bias is applied to a first carrier, the magnetic brush is brought into contact with a second carrier close to the first carrier, and only the non-magnetic toner in the magnetic brush is removed. The toner layer is transferred onto the second carrier to form a toner layer on the surface of the second carrier, and a second bias is applied to the second carrier to reduce static on the surface of the photoreceptor near the second carrier. In a developing device that performs development by selectively flying toner in response to an electrolytic latent image, a detection device that is located close to the second carrier and detects the thickness of the toner layer on the surface of the second carrier It is characterized by having a means.

Here, the detection means is provided close to the second carrier on the upstream side of the development area of the photoreceptor and the second carrier.

Further, the invention according to claim 3 is characterized in that the detection means controls the bias applied to the first carrier according to the change in the thickness of the toner layer on the surface of the second carrier, and and the first carrier can be adjusted.

In addition, the invention according to claim 4 controls the bias applied to the second carrier according to the change in the thickness of the toner layer on the surface of the second carrier by the detection means, and It is characterized in that the potential difference between the carriers can be adjusted.

[For production]

In the above-mentioned developing device, a means for detecting the thickness of the toner layer of the second carrier is provided, the detecting means detects a change in the thickness of the toner layer, and the detecting means detects a change in the thickness of the toner layer. When controlling the bias applied to the first carrier, it is possible to adjust the potential difference between the second carrier and the first carrier to the optimum condition, so that the toner layer always has an appropriate thickness. can be formed on the surface of the second carrier.

Further, a means for detecting the thickness of the toner layer of the second carrier is provided, and the detecting means detects a change in the thickness of the toner layer, and the second carrier is When controlling the bias applied to the body, it is possible to adjust the potential difference between the photoreceptor and the second carrier so that the toner is ejected under optimal conditions, and development can be performed using an appropriate ejecting bias at all times. becomes possible.

〔Example〕

The present invention will be explained in detail below based on the illustrated embodiments.

FIG. 1 is a schematic sectional view of a developing device showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram of a developing method using the same developing device.

1 and 2, a photosensitive drum 1 having a photosensitive layer 1b on its surface is rotatably provided in the direction of the arrow in the figure, and the photosensitive layer 1b of the photosensitive drum 1 moves along the moving surface. A developing device 10 is provided.

Developer supply roll 3 which is the first carrier of the developing device 10
consists of a non-magnetic sleeve and a magnet having a plurality of magnetic poles housed inside the sleeve, at least one of which is rotatable about one axis. This developer supply roll 3 is provided so that its lower right side is immersed in a two-component developer consisting of non-magnetic toner and magnetic carrier, and its left side is in close proximity to the toner developing roll 2, which is a second carrier. .

The toner development roll 2 has a conductive surface and is provided in a positional relationship close to both the developer supply roll 3 and the photoreceptor drum 1.

In Figure 1, reference numeral 4 indicates a cutting member, 5 indicates a toner layer thickness detection means, 6 indicates a developer separating member, 7 indicates a developer stirring roll,
Reference numeral 11 indicates toner hoppers.

In any developing device configured, the magnetic carrier holding the triboelectrically charged toner is attracted by the magnetic force of the magnet of the developer supply roll 3, and a magnetic brush is applied to the surface of the sleeve of the developer supply roll 3. form and rotate clockwise in the figure. After the magnetic brush is cut into a predetermined length by the brush cutting member 4, it comes into contact with the surface of the toner developing roll 2. At this time, a DC voltage V is applied between the developer supply roll 3 and the development roll 2 so that only the non-magnetic toner is attracted to and held on the development roll 2 side.
2 is applied, whereby the non-magnetic toner separates from the magnetic carrier and adheres to the developing roll, forming a toner layer.

The toner developing roll 2 rotates counterclockwise in the figure.
The toner layer on the conductive surface also rotates counterclockwise. The toner layer is thinner than the gap between the developing roll 2 and the photoreceptor 1, and development is performed by applying a DC voltage V to the developing roll 2 so that the toner flies between the two surfaces. That is, in this developing device, non-contact development is performed in which development is performed by selectively flying toner in correspondence with the electrostatic latent image on the surface of the photoreceptor.

Here, reference numeral 5 in the figure is a detection means for detecting the thickness of the toner layer on the surface of the toner developing roll 2. As this detection means, for example, a reflective photosensor is used. A DC voltage is applied to the developer supply roll 3 by a control means (not shown) based on the detected signal. V2 or the DC voltage V applied to the toner developing roll 2 is controlled.

That is, based on the signal from the detection means, a control means (not shown) controls the DC voltage v2 applied to the developer supply roll 3, that is, the potential difference between the toner development roll 2 and the developer supply roll 3, and controls the toner development. The thickness of the toner layer formed on the surface of the roll 2 is adjusted to an appropriate value, so that the electrostatic latent image on the photoreceptor 1 is always developed with the appropriate toner layer thickness. Alternatively, a direct current voltage V applied to the toner developing roll 2 by a control means (not shown) based on a signal from the detection means, that is, a potential difference between the photoreceptor 1 and the toner developing roll, is used to control the change in toner thickness. The electrostatic latent image on the photoreceptor 1 is developed by always applying an appropriate flight bias according to the change in the thickness of the toner layer.

It is also possible to simultaneously control both the DC voltage v2 applied to the developer supply roll 3 and the DC voltage V applied to the toner development roll 2 based on the signal from the detection means, and in this case, , it becomes possible to develop an electrostatic latent image with an appropriate toner layer thickness and with an appropriate flight bias, and it becomes possible to always provide a stable image.

〔Effect of the invention〕

As explained above, according to the present invention, by providing a detection means for detecting the thickness of the toner layer of the toner developing roll, which is the second carrier, The resulting change in the thickness of the toner layer on the toner developing roll can be easily detected.

Then, the change in the thickness of the toner layer is detected by this detection means, and the bias applied to the developer supply roll, which is the first carrier, is controlled according to the change in the thickness of the toner layer, so that the toner is developed. It becomes possible to adjust the potential difference between the roll and the developer supply roll to the optimum condition, and it becomes possible to always form a toner layer of an appropriate thickness on the surface of the toner development roll, so that the toner layer always has an appropriate thickness. The electrostatic latent image on the photoreceptor can then be developed, making it possible to provide a stable image.

Further, a means for detecting the thickness of the toner layer of the toner developing roll is provided, the detecting means detects a change in the thickness of the toner layer, and a voltage is applied to the toner developing roll in accordance with the change in the thickness of the toner layer. By controlling the bias, it is possible to adjust the potential difference between the photoconductor and the toner developing roll so that the toner flies under optimal conditions, and provides an appropriate flight bias according to changes in the thickness of the toner layer. The electrostatic latent image on the photoreceptor can be developed, making it possible to provide a stable image.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a developing device showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram of a developing method using the same developing device. 1... Photoreceptor, 2... Toner developing roll (second
), 3... developer supply roll (first carrier), 4... ear cutting member, 5... toner layer thickness detection means, 6... development agent separation member, 7...
Developer stirring roll, 11...toner hopper
illusion

Claims (1)

[Scope of Claims] 1. A device for non-contact development of an electrostatic latent image on a photoreceptor with non-magnetic insulating toner, which comprises a magnetic brush made of a magnetic carrier and non-magnetic toner on a first carrier surface. A first bias is applied to the first carrier, the magnetic brush is brought into contact with a second carrier close to the first carrier, and only the non-magnetic toner in the magnetic brush is transferred to the second carrier. The toner is transferred onto the carrier to form a toner layer on the surface of the second carrier, and a second bias is applied to the second carrier to form an electrostatic latent image on the surface of the photoconductor near the second carrier. In response to this, in a developing device that performs development by selectively flying toner, a detection means for detecting the thickness of the toner layer on the surface of the second carrier is provided in the vicinity of the second carrier. A developing device characterized by: 2. In the developing device according to claim 1, the detection means for detecting the thickness of the toner layer on the surface of the second carrier is located on the upstream side of the developing area of the photoreceptor and the second carrier. A developing device characterized in that it is provided in close proximity to. 3. In the developing device according to claims 1 and 2, the second
A detection means for detecting the thickness of the toner layer on the surface of the second carrier controls the bias applied to the first carrier according to the change in the thickness of the toner layer on the surface of the second carrier. A developing device characterized in that a potential difference between a carrier and a first carrier can be adjusted. 4. In the developing device according to claims 1 and 2, the second
A detection means for detecting the thickness of the toner layer on the surface of the second carrier controls the bias applied to the second carrier according to changes in the thickness of the toner layer on the surface of the second carrier, and A developing device characterized in that the potential difference between the second carriers can be adjusted.