JPS643260B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic brush developing device using a dry developer in an electronic copying system, in which the developer is stably supplied from a developer hopper to a magnet roll for forming a magnetic brush. The purpose of this is to prevent developer clogging due to malfunction and spillage of developer from the developer tank due to oversupply.

Generally, when a fine powder such as a developer is flowed out of a container, if the outlet is narrow, the internal friction of the fine powder itself will cause bridging or blockage phenomena near the developer outlet or in the path, causing the developer to flow out. There are times when I don't want to do it. Possible causes of such crosslinking and clogging phenomena include the particle size, component composition, and adhesion of the fine powder, the size of the outlet opening of the container, and the applied pressure. Among these, the particle size, component composition, and adhesion of the fine powder are determined by the image quality characteristics of the developer.
Furthermore, there are restrictions on the size of the outflow aperture because the amount of developer supplied must be controlled in accordance with the amount consumed for image formation. For this reason, many magnetic brush developing devices are equipped with a mechanism to mechanically stir the developer in the developer tank in order to ensure a stable supply of developer. There are drawbacks to it.

The present invention provides an apparatus that can solve the above problems at low cost without providing a mechanical movement mechanism. This will be described in detail below along with examples.

In FIG. 1, a magnet roll 3 for forming a magnetic brush is provided, which comprises a fixed sleeve 1 made of a non-magnetic material and a rotatable roller 2 having a large number of magnetic poles. A slit-shaped developer supply port 6 is provided near the magnet roll 3. The slit of the supply port 6 is formed by a magnetic rod 7 and a doctor blade 8 made of a non-magnetic material that limits the amount of developer supplied to the magnet roll 3. This doctor blade 8 is attached to the sleeve 1 in order to limit the amount of developer on the magnet roll 3.
It is supported while maintaining a constant gap width G1. An electromagnet 9 for generating an alternating current magnetic field is provided above the supply port 6, and a toner pressure relief plate 10 is provided below the hopper. To replenish the developer, attach the replenishment port 12 to the container 11 and insert it into the hopper 13.
The shutter 14 is opened, and the hopper 13 is located directly above the exposure area, avoiding the exposure area 15.

Next, the movement of the developer will be explained. When the shutter 14 is opened, the developer flowing out from the container 11 fills the developer tank from below and is stored in the hopper 13. As the developer in the hopper 13 is consumed,
As indicated by an arrow 16, the developer flows through a developer passage 17 to a developer tank. The developer that has reached the developer tank 18 further flows into the developer supply port 6, receives the magnetic action of the magnet roll 3, passes through the gap G1 as the magnet roll 3 rotates, and is transferred to the roller 2 while rotating on the sleeve 1. It moves in the direction of arrow 4, which is opposite to the direction of rotation. The thickness of the developer on the sleeve 1 at this time is the gap width G of the doctor blade 8.
Determined by 1. On the other hand, at the development point 19, the photoreceptor 20 on which the electrostatic latent image has been formed maintains a predetermined gap width G2 with respect to the sleeve 1. The gap width G2 is narrower than the gap width G1 in order to ensure that the photoreceptor 20 comes into contact with the developer.

A part of the developer that has reached the development point 19 is transferred to the photoreceptor 20 due to the electrostatic force of the electrostatic latent image and is used for development, and most of the remaining developer continues to move in the direction of the arrow 5 and returns to the supply port 6. I'll follow you.

Here, the gap width of the supply port 6 is controlled so that the developer returning on the sleeve 1 and the developer trying to flow out from the supply port 6 are balanced, and the developer is supplied according to the amount consumed. Therefore, it is very narrow. Therefore, as described above, the developer near the narrow outlet 6 may undergo crosslinking or blockage if external factors such as temperature and humidity change or excessive pressure is applied, resulting in unstable developer supply. Although it is common knowledge, since the electromagnet 9 is installed in the developer tank, an alternating magnetic field is generated by the electromagnet 9, and the magnetic developer in the developer tank is stirred by the magnetic force.
It is possible to prevent cross-linking and clogging of the developer at the supply port 6 and other parts of the developer tank, thereby stabilizing the supply of the developer. Further, in general, the fluidity characteristics of a magnetic developer are significantly deteriorated due to magnetization of the magnetic developer itself. Therefore, it is possible to prevent the magnetic developer from becoming magnetized by adding a degaussing function that gradually reduces the magnitude of the magnetic force as shown in Figure 3 when the alternating current magnetic field generation mechanism is stopped. Furthermore, the supply of developer can be stabilized.

As is clear from the above embodiments, the present invention has a structure in which an electromagnet that generates an alternating current magnetic field is provided inside the toner replenishment hopper, so that toner agitation can be achieved without a movement mechanism, and furthermore, the crosslinks can be collapsed. The magnetic field generation source can be placed in the most effective position for this purpose, and there is no need for an airtight cover to prevent toner adhesion. Further, the present invention has the effect that it is possible to prevent the magnetic developer from becoming magnetized by adding a demagnetizing function that gradually reduces the magnitude of the magnetic force.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a magnetic brush developing device according to an embodiment of the present invention, FIG. 2 is an enlarged block diagram of the main parts,
FIG. 3 is an explanatory diagram of the degaussing operation. 2...roller, 3...magnet roll, 6...
... Supply port, 9 ... Electromagnet, 11 ... Developer container,
18...Developer tank.

Claims (1)

[Claims] 1. A rotatable magnet roll for forming a magnetic brush that supplies developer to a photoreceptor with an electrostatic latent image;
A hopper that stores the developer and supplies the developer to the magnet roll from a developer supply port provided with a magnetic material rod, and a hopper that is installed within the developer passage path in the hopper and generates an alternating magnetic field. A magnetic brush developing device is provided with an electromagnet having a demagnetizing function by gradually decreasing the magnitude of magnetic force when stopping the magnetic brush.