JPS59231568A - Forming device for thin layer of developer - Google Patents

Abstract

PURPOSE:To prevent securely magnetic particles from leaking under a developer supply container by providing collecting and conveying magnetic poles further on the upstream side of a magnetic pole facing a magnetic body. CONSTITUTION:The collecting and conveying magnetic poles 28 and 30 are provided on the movement-directional upstream side of a developer holding member 12. Consequently, magnetic particles deposited at the part of an enclosure 13-1 are collected by those collecting and conveying magnetic poles 28 and 30 and conveyed through the rotation of the developer holding member 12 to be collected in the developer supply container 13. The magnetic poles 28 and 30 have such magnetic intensities that the surface density of the developer holding member 12 is properly 200-600gauss. Consequently, magnetic particles are prevented securely from leaking, specially, under the developer supply container.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for forming a thin layer of dry developer. Furthermore,
The present invention relates to an apparatus for forming a thin layer of non-magnetic developer.

Conventionally, various apparatuses have been proposed and put into practical use as dry developing systems. However, it is extremely difficult to form a thin layer of dry developer even in the l, However, as there is now a growing demand for improvements in the clarity, resolution, etc. of developed images, it has become essential to develop a method for forming a thin layer of dry developer and an apparatus therefor.

A method of forming a thin layer of a conventionally known dry developer has been proposed in JP-A-54-43037.
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. Because magnetic materials are added internally (magnetic materials are 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 method in which the surface is made of m-fiber such as velvet is used. A method has been proposed in which the film is applied to a developed 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, there is a problem in that fogging and the like are likely to occur.

Mandandan 11 As a new method for forming a thin layer that is completely different from the conventional method described above, the applicant et al. have developed a method of forming a magnetic brush made of magnetic particles on the upstream side of the magnetic particle restraining member with respect to the moving direction of the surface of the developer holding member. A method has already been proposed in which a thin layer of non-magnetic developer is formed on a developer holding member by means of a magnetic brush.

In this developing device, it is necessary to restrain the magnetic particles within the developer supply container. In particular, it is an object of the present invention to provide a developer thin layer forming apparatus having means for ensuring the restraint of magnetic particles in a portion where the developer holding member moves in the direction of entering the developer supply container.

The device of the present invention includes a developer supply container having an opening, a developer holding non-magnetic member provided in the opening and movable endlessly inside and outside the container, and a developer holding member provided inside the holding member. a magnetic particle restraining member provided outside the developer holding member and restraining the magnetic particles in the developer supply container together with the magnetic poles of the fixed magnetic field generating means; A magnetic body provided on the outside of the developer holding member on the upstream side of the magnetic particle restraining member in the direction of movement of the developer holding member; and a magnetic body provided on the inside of the developer holding member substantially opposite to the magnetic body. Further, in the moving direction of the developer holding member, there is a collecting/transporting magnetic pole further upstream of the magnetic pole facing the magnetic body, so that there is no space between the magnetic body and the opposing magnetic pole. The magnetic particles constituting the formed magnetic brush can be prevented from leaking from the lower part of the developer supply container.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram of a method and apparatus for forming a thin layer of nonmagnetic developer according to the present invention.

In FIG. 1, 11 is a cylindrical electrophotographic photoreceptor that moves in the direction of the arrow a. A non-magnetic holding member 12 that holds the developer is provided with a gap between the photoconductor 11 and, in this embodiment, the holding member 12 has a cylindrical shape, but it may also have a web shape that moves endlessly. . The same applies to the electrophotographic photoreceptor 11. Along with this movement of the photoreceptor 11, the developer holding member 12 is rotated in the direction indicated by the arrow. A developer supply container 13 is provided to supply developer to the developer holding member 12 .

The developer supply container 13 has an opening near its lower part, and the developer holding member 12 is provided in the opening. Since a portion of the developer holding member is exposed to the outside through the opening, its surface moves from the inside of the developer supply container to the outside, and then returns to the inside.

An enclosure 13-1 is formed at the lower part of the developer holding container 13 so as to wrap around the lower part of the developer holding member 12 to prevent the developer from leaking to the outside.

A fixed magnetic field generating means for generating a fixed magnetic field, that is, a magnet 14 is fixedly provided inside the developer holding member 12 . Since the magnet 14 is fixed, only the developer holding member 12 rotates. This magnet 14 has a magnetic particle restraining magnetic pole 20 and a sealing magnetic pole 21, which will be described later.

A magnetic blade 15 (magnetic particle restraining member) made of a magnetic material is arranged near the top of the opening of the developer supply container 12 . The developer holding member 1
On the opposite side of the magnet 14, there is a magnetic particle restraining magnetic pole 20 of the magnet 14.
However, the position of the magnetic particle restraining magnetic pole 20 is the same as that of the magnetic blade 1.
The developer holding member 12 is disposed at an upstream position in the rotational direction of the developer holding member 12 at an angle θ (5 to 50 degrees) shifted from the position facing the developer holding member 5 . A sealing magnetic pole 21 is provided on the upstream side of the magnetic particle restraining magnetic pole 20 in the moving direction of the developer holding member 12 . Although the seal pole 21 is shown as the pole of magnet 14, it may be a separate magnet.

An iron piece 18 made of a magnetic material is provided on the inner wall of the developer supply container 13 facing the sealing magnetic pole 21, and a magnetic brush formed between these pieces seals the lower part of the container 13 and prevents the circulation of magnetic particles. It also improves. Iron piece 18
In addition to metals such as iron, the magnet may be a magnet that faces the sealing magnetic pole 21 in a reverse polarity relationship. These magnetic members may be attached to the wall of the container 13 facing the sealing magnetic pole 21, or a part of the container itself may be made of a magnetic material such as iron, and the wall of the container facing the sealing magnetic pole 21 may be used to hold the developer. It may be configured close to the member 12.

The base layer 16 is formed by supplying magnetic particles or a mixture containing magnetic particles and a non-magnetic developer to the developer supply container of the apparatus having such a configuration. The mixture forming the base layer preferably contains about 5 to 70% (by weight) of non-magnetic developer based on the magnetic particles, but it may also contain only magnetic particles. The particle size of the magnetic particles is 30-200, preferably 70-
It is 150 microns. Each magnetic particle may be made of only magnetic material or may be a combination of magnetic material and non-magnetic material. The magnetic particles in the base layer 16 form a magnetic brush due to the magnetic field generated by the magnet 14, and this magnetic brush performs the circulating action described below. Magnetic particle restraining magnetic pole 20 and magnetic blade 15
A magnetic brush is also formed in between, which confines the magnetic particles of the base layer 16 within the developer supply container 13.

By supplying the non-magnetic developer onto the base layer 16, two layers, the base layer 16 and the developer layer 17, are formed substantially in the vertical direction, that is, on the outer periphery of the developer holding member 12 and on the outside thereof. be done. The developer layer may be formed by adding a small amount of magnetic particles to this non-magnetic developer, but even in this case, the magnetic particle content of the developer layer is the same as that of the base layer.
Less than 6. Silica particles may be externally added to this non-magnetic developer in order to improve fluidity, and abrasive particles may be externally added in order to polish the photoreceptor 11. The method for forming the two layers is not limited to supplying the two layers in two stages, for example,
A substantially uniform mixture of magnetic particles and non-magnetic developer for the entire amount of the base layer 16 and developer layer 17 is supplied, and then vibration is applied to the developer supply container 13 to mix the magnetic particles and non-magnetic developer. Two layers may be formed due to the difference in specific gravity and the magnetic field of the magnet 14.

Even when a nearly uniform mixture of magnetic particles and non-magnetic developer is supplied without particularly forming two layers,
This is possible as long as it contains a sufficient amount of magnetic particles to form a magnetic brush, but in order to maintain long-term stability of the magnetic brush, it is preferable to use two layers.

When the developer holding member 12 is rotated with the magnetic particles and developer applied in this way, the magnetic particles perform a circular motion as shown by arrow C in FIG. 1 due to the magnetic field and gravity of each magnetic pole. That is, near the outer surface of the developer holding member 12, the magnetic particles in the lower part of the developer supply container 13 rise along the outer periphery of the developer holding member 12 due to the interaction between the magnetic field from the magnet 14 and the rotation of the developer holding member 12. death,
At this time, the nonmagnetic developer and the surface of the developer holding member 12 come into contact, and the nonmagnetic developer in the base layer is electrostatically applied onto the developer holding member 12.

In this embodiment, the non-magnetic developer is charged by friction with the magnetic particles or the developer holding member 12, but preferably there is an oxide film on the surface of the magnetic particles or an oxide film at the same electrostatic level as the non-magnetic developer. The developer holding member 1 is insulated with resin, etc., to reduce tripoding from magnetic particles, and to transfer the necessary charge to the developer holding member 1.
2, it is possible to prevent the influence of deterioration of the magnetic particles and to stabilize the application of the developer to the developer holding member 12.

The magnetic particles rise as the developer holding member 12 rotates, but due to the magnetic field formed between the magnetic blade 15 and the magnetic particle restraining magnetic pole 20, the gap between the surface of the developer holding member 12 and the tip of the magnetic blade 15 is reduced. be prevented from passing through. Therefore, the magnetic particles in this part are pushed by the magnetic particles sent one after another, rotate and reverse as shown by arrow C in FIG. 1, and then slowly fall due to gravity. During this falling, the non-magnetic developer at the lower part of the developer layer 17 is taken in and returned to the lower part of the developer supply container 13, and this process is repeated.

On the other hand, since the triboelectrically charged developer is non-magnetic, it can pass through without being restrained by the magnetic field that exists in the gap between the tip of the magnetic blade 15 and the surface of the developer holding member 12, and is developed by the magnetic brush section formed on the magnetic blade section. The surface of the developer holding member 12 is coated uniformly and thinly with the action of mirror force, and the developer supply container 13 that rests on the surface of the developer holding member 12 comes out and faces the surface of the photoreceptor 11 for development. be done.

FIG. 2 shows the action of the sealing magnetic pole 21. The sealing magnetic pole 21 forms a magnetic brush between it and the sealing magnetic body 18 provided at a position opposite to the lower part of the opening in the developer container. In order to consider the effect of this magnetic brush, first consider the case where the magnetic body 18 does not exist. In the initial state, the magnetic particles perform a circular motion as shown by the arrow 24. In this state, the magnetic particles are sufficiently attached to the sealing magnetic pole 21.
Since a sufficient magnetic brush is formed, the lower part of the developer holding member 12 is completely sealed by the magnetic brush, and the non-magnetic developer does not flow out or scatter from there. However, as the cumulative number of rotations of the developer holding member 12 increases, many of the magnetic particles are drawn up and remain near the magnetic particle restraining magnetic pole 20. Therefore, the magnetic particles present in the seal magnetic pole 21 part gradually decrease.
'ru. Therefore, the magnetic particle circulation loop 24 in the initial state eventually changes as shown by 2B.

As a result, the non-magnetic developer accumulates at the bottom of the container 13, and since there is no magnetic brush that performs a sealing action in this state, the non-magnetic developer flows out due to vibrations inside the machine and vibrations of the developing device itself. This is inconvenient because it scatters. It is preferable to prevent such reduction of magnetic particles at the sealing portion and achieve complete sealing, and this action is performed by the magnetic body 18 provided opposite the sealing magnetic pole 21. Due to the presence of the magnetic material 18, the developer does not flow out or scatter from the lower part of the developer supply container 13 even after long-term use. Of course, no scattering or leakage occurs even when the developing device is attached or detached. The optimum magnetic flux density of the sealing magnetic pole is not uniquely determined by the physical properties such as the saturation magnetization particle size distribution of the magnetic particles, the particle size of the non-magnetic developer, and the addition of triplets, as well as the shape and distance of the magnetic material facing the sealing magnetic pole. When a plate-shaped magnetic material is used, the gap with the surface of the developer holding member 12 is set to 0.5 to 12, and magnetic particles with a saturation magnetization of 100 enu/g are used, the magnetic field is 200 to 600 Gauss.

The magnetic body 18 and the sealing magnetic pole 21 facing it are effective in preventing leakage and scattering of non-magnetic developer as described above, but a part of the magnetic brush formed between them, especially the developer holding member 12 A part of the upstream side in the rotational direction separates from the magnetic binding force and breaks off when the developer holding member rotates 12 times,
It has been found that there is a problem with deposits on the lower enclosure 13-1 of the developer supply container 13. This tends to occur when strong vibrations are applied to the developing device, and when magnetic particles, non-magnetic developer, or a mixture thereof is supplied to the developer supply container 13, the seal magnetic pole 21 and the magnetic material Magnetic particles may enter the enclosure 13-1 before a magnetic brush is sufficiently formed between the enclosure 13-1 and the enclosure 13-1. This phenomenon becomes particularly noticeable when the developer has high fluidity. The accumulated developer may leak and scatter as shown by arrow d in FIG. As shown in FIG. 3, the device according to the present invention has collecting/transporting magnetic poles 28 and 30 on the upstream side in the moving direction of the developer holding member 12, so that the developer is not deposited on the enclosure 13-1. The magnetic particles are collected by the collection/transport poles 28 and 30, transported by the rotation of the developer holding member 12, and collected into the developer supply container 13. Collection/transport magnetic pole 28.3
The strength of o is 20 at the surface density of the developer holding member 12.
0 to 600 Gauss is suitable. In this embodiment, a case where a two-pole structure of 28.3° was used as the collecting/transporting magnetic pole was shown, but it may be an l-pole or three or more poles. However, using multiple poles has a more reliable effect than using one pole.

The developing method used here is JP-A-55-1865.
The method described in 6 is preferred. A voltage is applied between the electrophotographic photoreceptor 11 and the developer holding member 12 by a bias power supply 19 . The bias power supply 19 may be an alternating current or a direct current, but preferably one in which alternating current and direct current are superimposed. The developer provided by the development is supplied from the base layer 16 to the developer holding member 12, and the insufficient amount in the base layer 16 is supplied from the developer layer 17 by the above-mentioned circulation movement.

In the case of a two-layer structure, the base layer 16 is formed near the outer surface of the developer holding member 12 from the beginning, and the developer layer 17 either does not contain any magnetic particles or contains magnetic particles unavoidably as the device is used. Since the amount is small enough to compensate for the loss of magnetic particles that occurs during operation, the state of the magnetic brush in the base layer 16 remains approximately constant and does not change even if the operation continues for a long period of time. In this sense, the magnetic particles in base layer 16 are part of the development apparatus rather than the developer material or part thereof.

The image density does not depend on the weight ratio of the magnetic particles in the developer and the developer that actually formed the image in the above example
Consistent and good images were obtained.

At the same time, environmental tests have confirmed that the developing device has low environmental dependence.

In the above explanation, a magnetic blade made of a magnetic material such as iron is used as the regulating member, but a non-magnetic blade made of a non-magnetic material such as aluminum, copper, or resin or a non-magnetic material such as resin or aluminum constituting the container is used. The wall of the body can also be used as this regulating member. However, in this case, in order to prevent the outflow of magnetic particles, it is necessary to make the gap between the sleeve and the regulating member even smaller than when using a magnetic blade. Further, when a magnetic blade is used, it is preferable because a magnetic brush can be stably formed at the developer outlet by the magnetic field between the blade and the magnetic pole.

As described above, according to the present invention, leakage of magnetic particles is reliably prevented, particularly in the lower part of the developer supply container 13.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a developer thin layer forming apparatus that does not use the present invention. 2 is a cross-sectional view showing the circulation of magnetic particles in the apparatus of FIG. 1; FIG. 3 is a cross-sectional view of the developer thin layer forming apparatus according to the present invention; Explanation of symbols 11: Electrophotographic photoreceptor 12: Developer Holding member 13: Developer supply container 14: Fixed magnetic field generating means 15: Magnetic particle restraining member 16: Base layer 17: Non-magnetic developer layer 20: Magnetic particle restraining magnetic pole 21: Seal magnetic pole 28.30: Collection/transport magnetic pole

Claims (1)

[Scope of Claims] A developer supply container having an opening; a developer holding non-magnetic member provided in the opening and movable endlessly inside and outside the container; and a fixing member provided inside the holding member. a magnetic field generating means; a magnetic particle restraining member provided on the outside of the developer holding member and restraining the magnetic particles inside the developer supply container together with the magnetic poles of the fixed magnetic field generating means; , a magnetic body provided outside the developer holding member on the upstream side in the moving direction of the developer holding member; a magnetic pole provided substantially opposite to the magnetic body inside the developer holding member; and a developer. A developer thin layer forming device comprising a collecting/transporting magnetic pole further upstream of the magnetic pole facing the magnetic body in the moving direction of the holding member.