JPH0574824B2 - - Google Patents

Description

Detailed Description of the Invention Technical Field The present invention relates to a method for forming a thin layer of a non-magnetic developer on the surface of a developer holding member using a non-magnetic developer and magnetic particles for development. It is related to the device.

BACKGROUND ART Conventionally, various devices have been proposed and put into practical use as a dry developing method. However, in any of the development methods, it is extremely difficult to form a thin layer of dry developer, and for this reason, a developing device has been constructed by forming a relatively thick layer. However, the brightness of the developed image,
At present, there is a demand for improvement in resolution, etc., and it is essential to develop a method for forming a thin layer of a dry developer and an apparatus therefor.

Japanese Patent Application Laid-Open No. 43037/1984 has proposed a method for forming a thin layer of a conventionally known dry developer.
And it has been put into practical use. However, this concerned the formation of a thin layer of magnetic developer. In order to make magnetic developers magnetic, a magnetic material must be added to the developer. (Magnetic material is usually black)
There are problems such as poor color reproduction.

For this reason, as a method for forming a thin layer of non-magnetic developer, there are methods in which soft bristles such as beaver hair are used as a cylindrical brush and the developer is adhered to the brush, and a developer with a surface made of fibers such as velvet is used. A method has been proposed in which the coating is applied to a roller using a doctor blade or the like.

However, when an elastic blade is used as a doctor blade for the above-mentioned fiber brush, it is possible to regulate the amount of developer, but uniform application is not achieved, and the fibers of the brush are simply rubbed by the fiber brush on the developing roller. Since no triboelectric charge is imparted to the developer present in between, fogging and the like are likely to occur.

Purpose of the Invention As a developer thin layer forming method that is completely different from the above-mentioned conventional method, the applicant has provided a magnetic particle restraining member opposite to a developer holding member, and the magnetic particle restraining member A magnetic brush of magnetic particles is formed upstream by the magnetic force of the magnetic field generating means, and a thin layer of non-magnetic developer is formed on the developer holding member by this magnetic brush restrained by the magnetic particle restraining member. A method and apparatus have already been proposed. In this method, it is important that the formed thin layer does not contain magnetic particles, that is, that the magnetic particles are reliably restrained.

The present invention improves the above-mentioned developer thin layer forming device to provide a developer thin layer forming device that can obtain even better magnetic particle restraint properties with a simple configuration without substantially increasing the magnetic force. The purpose is to

Summary of the Invention According to the present invention, there is provided a developer container having an opening and accommodating non-magnetic developer and magnetic particles, and a developer holding member provided in the opening and capable of endless movement between the inside and outside of the opening. a magnetic member disposed on the outside of the developer holding member with a gap between the surface and the surface thereof to restrain the magnetic particles; and a fixed magnetic field generating means provided inside the developer holding member, the fixed magnetic field generating means being provided inside the developer holding member. The means has magnetic poles with different magnetic properties, a portion made of a material with higher magnetic resistance than a substance constituting the magnetic poles is provided between the magnetic poles, and the magnetic member is placed opposite to the portion between the magnetic poles. Since a developer thin layer forming device is provided which is tilted toward the downstream direction of the rotation of the developer holding member, it is possible to reduce the magnetic pressure applied to the developer without increasing the magnetic flux density of the magnetic poles within the developer holding member. It is possible to prevent magnetic particles from leaking out of the developer supply container with a light load without increasing the load.

Example The present invention will be explained in detail below using the figures.

FIG. 1 is a sectional view of a developing device using a developer thin layer forming device according to the present invention, in which 1 is a cylindrical electrophotographic photoreceptor as a latent image carrier, and a latent image forming means (not shown) forms a latent image. The developing position shown in the figure is moved in the direction of the arrow a. A developer holding member 2 for holding developer is provided with a gap between the photoconductor 1 and the holding member 2 in this embodiment, which is a cylindrical developer holding member (sleeve).
2, but it may also be in the form of a web that moves endlessly. Although the latent image carrier 1 is shown as the photosensitive drum 1, the same applies to this. Along with this movement of the latent image carrier 1, the sleeve 2 is rotated in the direction of arrow b. In order to supply developer to this sleeve 2, a developer supply container 3 is provided on the upper part of the sleeve 2, and a developer supply container 3 is provided with a non-magnetic developer 4 and magnetic particles 5.
Store the mixture. The developer supply container 3 is made of a non-magnetic material such as resin or aluminum.

A fixed magnetic field generating means for generating a fixed magnetic field, that is, a magnet 7 is fixedly provided inside the sleeve 2 . Therefore, only the sleeve 2 rotates.

A regulating blade 6, which is a magnetic particle restraining member, is provided almost above the sleeve 2, and as shown in the figure, it is tilted downstream in the direction of rotation of the sleeve 2, and its tip is bent approximately in the tangential direction of the sleeve surface. ” arrangement. A sealing member 8 is provided on the lower right side of the sleeve 2, which is made of a magnetic material and faces the surface of the sleeve where the S2 pole of the magnet 7 is present through a gap, and chains magnetic particles in this gap to form a non-magnetic This prevents the developer from scattering below the developer container 3.

In the above configuration, the magnetic brush 8 is formed by the action of the magnetic field generated between the magnetic particles in the developer supply container 3, the N pole of the magnet 7, and the regulating plate 6. As the sleeve 2 rotates, the magnetic particles 5 and the non-magnetic developer 4 are stirred and mixed while the magnetic brush is held. In this state, on the regulating blade 6 side of the developer supply container 3, the mixture of the developer 4 and magnetic particles 5 is prevented from moving by the blade 6, rises, and circulates in the direction of arrow C. Exercise. Non-magnetic developer 4
is triboelectrically charged by mixing with the magnetic particles 5 and contacting the sleeve 2, and a portion of the developer in the mixture adheres to the surface of the sleeve 2 due to mirroring force and is influenced by the blade 6. The developer passes through the lower part of the blade 7 without any interference (because the developer is non-magnetic), and the developer is formed as a thin layer on the surface of the sleeve 2.

In the present invention, the regulating blade 6 made of a magnetic material is the magnetic pole N of the fixed magnetic field 7 inside the sleeve 2.
1 and S1 in a horizontal direction. This is because between the poles, the magnetic force component in the normal direction to the surface of the sleeve 2 is reduced, so the pressure of the magnetic particles on the sleeve surface, and therefore the frictional force accompanying the rotation of the sleeve 2, is reduced. Therefore, the carrying force exerted by the sleeve 2 on the magnetic particles can be reduced, and the horizontal components of the magnetic lines of force are focused on the magnetic blade in this region.
Since the magnetic particles can be restrained by this horizontal component, the magnetic particles can be restrained more effectively when the same magnetic force is used.

Furthermore, in the present invention, the magnetic pole S1 and the magnetic pole N
1 (the shaded area in Figure 1) is made of a material with high magnetic resistance. First, we will explain the case where the

FIG. 2 shows the distribution of magnetic lines of force converging on the magnetic blade 6 in such a case. N1
Since the magnetic blade with high magnetic permeability faces the magnetic pole N1 from the outside, the lines of magnetic force coming out from the magnetic pole are concentrated at the tip of the magnetic blade, and after passing through the inside of the blade, enter the S1 pole. However, since the magnetic permeability of permanent magnets, which are generally one of the magnetic field generation sources, is 10 to 100, after the N and S magnetic poles are placed adjacent to each other as shown in Figure 2, the magnetic field lines between the magnetic poles Not everything is as described above, but there are lines of magnetic force that pass through the inside of the magnet and do not come out of the magnet.

In this case, depending on the circumferential speed of the sleeve 2, the magnetic properties of the magnetic particles, the properties of the sleeve surface, etc., the magnetic particles 5 may pass through the regulating blade 6 and reach the developing section, causing scattering of magnetic particles on the copied image. This may lead to poor image quality due to the occurrence of electric discharge between the passing magnetic particles and the photoreceptor. In order to prevent such leakage of magnetic particles through the passage, it is effective to increase the strength of the restraining magnetic poles. The pressure on 2 also increases, leading to a decrease in developer fluidity. When using a pressure fixing developer,
This pressure increase causes the developer to fuse to the sleeve 2. Further, due to this increase in pressure, the frictional force between the non-magnetic developer and the sleeve increases, so that an excessive triboelectric charge is imparted, and the non-magnetic developer is transferred to the sleeve 2 downstream of the regulating blade 6.
Although it is applied as a thin layer on the sleeve 2, the amount of charge is too large, and the electrostatic mirroring force acting between it and the sleeve 2 may become too large. In this case, even if the thin developer layer faces the photoreceptor 1 in the developing section, it becomes difficult for the developer to separate from the sleeve surface, resulting in problems such as image unevenness being likely to occur.

FIG. 3 is a magnetic force line distribution diagram when a magnetic resistance material higher than that of the magnetic pole constituent material is provided between the N and S magnetic poles according to the present invention. By arranging both magnetic poles N1 and S1 apart, the lines of magnetic force forming a closed loop inside the magnet shown in Fig. 2 are also converged on the magnetic blade with high magnetic permeability, thereby increasing the effect of preventing leakage of magnetic particles. I can do it.

Similar effects can be obtained by using a non-magnetic material such as aluminum or copper as the high magnetic resistance material, or by using air as a non-magnetic material with a gap between the magnetic poles N1 and S1.

The magnetic permeability of non-magnetic materials and air is approximately 1, while magnetic materials such as iron placed close to the outside have a permeability of 1000 to 1.
10,000, it is possible to concentrate the lines of magnetic force more than when they are occupied by magnetic material.

As shown in FIG. 4, it is also possible to use as the magnetic field generating means a plurality of plastic magnets or ferrite magnets 10 attached to a shaft 9 through gaps.

Effects of the Invention As explained above, by interposing a high magnetic resistance material between the N and S magnetic poles of the fixed magnetic field generating means inside the developer holding member and spacing the NS poles apart, lines of magnetic force are concentrated on the magnetic blade. can be increased.

This makes it possible to prevent magnetic particles from leaking out of the developer supply container with a relatively weak magnetic pole.

If desired, a multicolor developing device capable of using a pressure fixing developer and capable of high-flux copying may be provided.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the developer thin layer forming apparatus according to the present invention, FIGS. 2 and 3 are cross-sectional views showing the distribution of magnetic lines of force near the magnetic blade, and FIG. 4 is a cross-sectional view of the developer thin layer forming apparatus according to the present invention. Another example of a fixed magnetic field generating means that can be used is shown below. Explanation of symbols: 1...Photoreceptor, 2...Developer holding member, 3...Developer supply container, 4...Nonmagnetic developer, 5...Magnetic particles, 6...Magnetic particle restraining member,
7...Fixed magnetic field generating means.

Claims (1)

[Scope of Claims] 1. A developer container having an opening and accommodating non-magnetic developer and magnetic particles, and a developer holding member provided in the opening and capable of endlessly moving between the inside and outside of the opening. , a magnetic member provided on the outside of the developer holding member with a gap between it and the surface thereof to restrain magnetic particles, and a fixed magnetic field generating means provided inside the developer holding member, the fixed magnetic field generating means has magnetic poles with different polarities, and between the magnetic poles is provided a part made of a material with higher magnetic resistance than the material constituting the magnetic poles,
A developer thin layer forming device characterized in that the magnetic member is disposed so as to face the portion between the magnetic poles and tilted toward the rotational downstream direction of the developer holding member. 2. The developer thin layer forming apparatus according to claim 1, wherein the high magnetic resistance material is air.