JPH0332791B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic brush developing device used in developing dry electrophotography.

Structure of a conventional example and its problems FIG. 1 shows a conventional magnetic brush developing device.

In FIG. 1, 1 is a hopper for storing developer, 2 is a magnet roll, and 3 is a latent image carrier. Conventionally, in this type of magnetic brush developing device, a latent image carrier 3 is brought close to a magnet roll 2 equipped with a hopper 1 for storing developer, and the latent image carrier 3 is attached to the developer supplied from the hopper 1. The structure is such that development is performed by touching the film. Development point A in Figure 1
In this case, if the electrostatic force from the electrostatic latent image on the latent image carrier 3 applied to the developer is stronger than the magnetic force from the magnet roll 2, the developer adheres to the latent image and becomes visible.

In the configuration shown in FIG. 1, it is extremely difficult to control the electrostatic force and magnetic force applied to the developer, and to control the strength of the sliding contact of the magnetic brush that brings the developer into contact with the latent image carrier 3. Specifically, the distance between the latent image carrier 3 and the magnet roll 2 at the development point A, the thickness of the magnetic brush formed with developer on the sleeve of the magnet roll 2, and the distance between the latent image carrier 3 and the magnet roll 2 are determined. The main controlling factors are the time of contact with the agent (development time), the relative speed between the latent image carrier 3 and the magnetic brush, that is, the conveyance speed of the latent image carrier 3 and the rotational speed of the magnet roll. The smaller the distance between the image carrier 3 and the magnet roll 2, the thicker the magnetic brush, the longer the developing time, and the higher the rotation speed of the magnet roll 2, the better the developing characteristics will be. It is something that can be done.

However, in the conventional magnetic brush developing device, when the operation starts, the developer accumulated in the contact portion B between the latent image carrier 3 and the magnetic brush containing the developer obstructs the movement of the latent image carrier 3. In order to prevent this, conventional methods have been to use mechanical or magnetic force to circulate the developer accumulated in the contact portion B to the hopper, or to periodically close the gap between the magnet roll 2 and the latent image carrier 3. Special methods such as spreading the developer and flushing it away in the direction of arrow A had to be taken.

Purpose of the Invention The present invention eliminates the drawbacks of the above-mentioned conventional examples, and while satisfying the conditions for obtaining good development characteristics, does not require the complicated method of the above-mentioned conventional structure, and can be reliably and inexpensively developed. The object of the present invention is to provide a magnetic brush developing device that can achieve the above object.

Structure of the Invention In order to achieve the above object, the present invention rotates a cylindrical sleeve made of a non-magnetic material and a magnet roller having a plurality of magnetic poles provided inside the sleeve. A magnetic developer is supplied onto the sleeve to form a magnetic brush on the sleeve surface, and a roller having a plurality of protrusions formed on the cylindrical surface that guides the latent image carrier to the vicinity of the sleeve is attached to the roller. By arranging it facing the sleeve, the latent image can be visualized uniformly.

DESCRIPTION OF EMBODIMENTS The configuration of an embodiment of the present invention will be described below with reference to the drawings.

In FIG. 2, 11 is a hopper that stores the developer 12, and 13 is a magnet consisting of a fixed sleeve 14 made of a non-magnetic material and a rotatable magnet roll 15 having a large number of magnetic poles housed in the sleeve 14. 1 is a roller, 16 is a latent image carrier, 17 is an introduction guide for conveying the latent image carrier 16 to the development point A, 1
8 faces the magnet roller 13 and is located at the development point A.
opposing guide rollers forming a developing gap a;
A doctor blade 19 controls the amount of developer supplied from the hopper 11.

Next, the operation of the above embodiment will be explained. When the magnet roll 15 of the magnet roller 13 rotates, the developer on the fixed sleeve 14 forms a magnetic brush by the action of its magnetic force.
The developer rotates on the fixed sleeve 14 and moves in a direction opposite to the direction of rotation of the magnet roll 15 (indicated by an arrow in FIG. 2). Therefore, as the magnet roll 15 rotates, the developer is supplied from the hopper 11 onto the magnet roller 13, forms a magnetic brush on the fixed sleeve 14, and moves to the development point A. In this case, the amount of developer sent out from the hopper 11 is the same as that between the doctor blade 19 and the fixed sleeve 1.
Gap b with 4 (doctor blade gap)
However, the width of this gap b must be determined so that the latent image carrier 16 surely comes into contact with the developer at the development point A. In this embodiment, the gap b is larger than the developing gap a. At the development point A, an opposing guide roller 18 is provided opposite the magnet roller 13 to form a development gap a. It is structured so that it is guided so as to be located at a predetermined distance from the network roll 13. When the latent image carrier 16 on which the electrostatic latent image has been formed is conveyed by the introduction guide 17 and comes into contact with the developer, the developer is charged with the opposite polarity to the latent image, so the latent image portion is exposed to the developer. The agent is attached and visualized.

By the way, the gap b between the doctor blade 19 and the magnet roller 13 is caused by the difference between the opposing guide roller 18 and the magnet roller 1 due to the developer supply conditions.
Since it is larger than the developing gap a formed by 3, if you continue to operate the developing device in this state,
Hopper 1 is larger than the amount of developer passing through development point A.
The amount of developer supplied from 1 becomes larger, and the developer gradually accumulates in a portion B in front of the development point A. In this embodiment, as shown in FIG. 3, the cylindrical surface of the opposing guide roller 18 is grooved with a plurality of protrusions, so that the developer can pass through the recess 20 on the cylindrical surface. Therefore, it is possible to prevent the developer from staying in the B section. Furthermore, at the development point A, the positional relationship between the magnet roller 13 and the latent image carrier 16 is maintained by the convex portion 21 on the cylindrical surface of the opposing guide roller 18, so that development characteristics equal to the development gap a can be obtained. be able to.

Effects of the Invention The present invention has the above-described configuration, and the design specifications that directly affect the development characteristics, such as the rotation speed of the developing gap a, the doctor blade gap b, and the magnet roller 13, are shown in FIG. It can be determined from the viewpoint of development characteristics without being restricted by the factor of retention of developer in the area. In addition, it is possible to eliminate problems caused by developer retention such as scattering of developer and failure of the latent image carrier to run in the developing section, which is a major advantage in improving the uniformity of quality and reliability of the device. has.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of a conventional magnetic brush developing device, FIG. 2 is a side sectional view of a magnetic brush developing device according to an embodiment of the present invention, and FIG. 3 is a developing section used in the magnetic brush developing device of the present invention. FIG. 3 is a plan view showing the arrangement of rollers in FIG. 11...Hopper, 12...Developing section, 13...
Magnetic roller, 14... Fixed sleeve, 15
... Magnet roll, 16 ... Latent image carrier, 17 ...
Introduction guide, 18... Opposing guide roller, 19...
...Doctor Blade.

Claims (1)

[Claims] 1. A fixed sleeve formed in a cylindrical shape made of a non-magnetic material and fixed, a magnet roll having a large number of magnetic poles and rotatably attached and housed within the fixed sleeve, and a developer stored therein; A hopper is attached to a position where the developer contacts the fixed sleeve, and a hopper is formed on a part of the hopper, and the rotation of the magnetic roll causes the developer to be transferred onto the fixed sleeve in a direction opposite to the direction of rotation. A doctor blade is rotatably attached to a position facing the sleeve to control the supply amount of the developer so that the developer is moved as a magnetic brush. The developer is made to pass through the concave portion, and the distance between the tip of the protrusion and the sleeve is smaller than the distance between the sleeve and the doctor blade, so that the latent image carrier is aligned with the magnetic brush. A magnetic brush developing device equipped with opposing guide rollers that move in the direction.