JPH0220990B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a developing device for forming a thin layer of developer on a developer holding member using a dry developer for development.

Prior Art Conventionally, various devices have been proposed and put into practical use as dry developing systems. However, in any of the developing methods, it is extremely difficult to form a thin layer of dry developer, and for this reason, the developing device has been constructed by forming a relatively thick layer. However, nowadays, there is a need to improve the clarity, resolution, etc. of developed images.
It is essential to develop a method for forming a thin layer of dry developer and an apparatus for the same.

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, it is necessary to add a magnetic substance to the developer. (Magnetic material is usually black)
There are problems such as poor color reproduction.

For this reason, methods for forming a thin layer of non-magnetic developer include a method 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 fibers such as velvet is used. A method has been proposed in which the developer is coated on the developing 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.

As a developer thin layer forming method that is completely different from the conventional method described above, the present applicant et al. provided a magnetic particle restraining member opposite to the developer holding member, and the upstream side of the magnetic particle restraining member with respect to the moving direction of the surface of the holding member. A method and apparatus for forming a magnetic brush of magnetic particles by the magnetic force of a magnetic field generating means, and forming a thin layer of non-magnetic developer on a developer holding member using the magnetic brush restrained by a magnetic particle restraining member. has already been proposed.

Purpose of the Invention The present invention improves the above-mentioned developing device, thereby ensuring better binding of magnetic particles and stable and uniform formation of a thin layer of non-magnetic developer with a simple configuration. Or the purpose is to prevent leakage of magnetic particles.

Structure of the Invention The present invention provides a developer supply container having an opening and containing a non-magnetic developer and magnetic particles, and a developer supply container that is provided in the opening and that moves endlessly between the inside and outside of the container, and a non-magnetic developer. a developer holding member that holds and conveys the developer layer and supplies it to the latent image carrier; a developer holding member provided outside the developer holding member with a gap between the developer holding member and the developer holding member;
a first magnetic member for restraining magnetic particles, which is arranged to be tilted downstream in the moving direction of the holding member with respect to a normal line erected on the surface of the holding member; a second magnetic member forming a magnetic brush; and a position upstream in the developer holding member moving direction from a position where the first magnetic member faces the developer holding member, and from a position where the second magnetic member faces the developer holding member. and a magnetic field generating means fixedly arranged inside the developer holding member so as to have a single magnetic pole at a position on the downstream side, and the magnetic field generating means is fixedly arranged inside the developer holding member so that the magnetic particles are guided into the container by the magnetic pole and the first magnetic member. A non-magnetic developer layer is formed on the developer holding member by restraining the developer, and a magnetic brush of magnetic particles formed by the magnetic pole and the second magnetic member causes the non-magnetic developer in the container to leak from the inlet side. This is a developing device that allows the non-magnetic developer to return into the container while preventing this.

According to the present invention, a thin developer layer having a uniform layer thickness and a uniform charge amount can be obtained by using a small amount of magnetic particles and a simple magnetic pole configuration, and the thin developer layer is used for development. When this was done, it became possible to obtain a more stable developed image. Furthermore, the magnetic member of the present invention can prevent developer or magnetic particles from leaking from the lower part of the developing device, and can also prevent developer from leaking or scattering due to mechanical vibration, impact, or rough handling, making it possible to achieve a compact developing device. Equipment is now available.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram showing the basic configuration of the present invention. In FIG. 1, numeral 11 is a cylindrical electrophotographic photoreceptor that moves in the direction of arrow a. This photoreceptor 1
A non-magnetic sleeve 12 which is a developer holding member is provided with a gap between the sleeve 1 and the sleeve 1 . This sleeve 12 rotates in the direction of arrow b as the photoreceptor 11 moves. A fixed magnet 13 is provided within the sleeve 12 as a magnetic field generating means. A hopper 14 serves as a developer supply container, and contains a developer mixture containing a non-magnetic developer 15 and magnetic particles 16 together with the sleeve 12 .

A magnetic brush made of magnetic particles 16 is formed near the surface of the sleeve 12 corresponding to the magnetic pole 17 of the magnet 13. When the sleeve 12 is rotated in the direction of arrow b, the magnetic brush circulates in the direction of arrow c near the magnetic pole 17 by appropriately selecting the arrangement position of the magnetic pole 17 and the fluidity and magnetic properties of the magnetic particles 16. A circulation layer 18 is formed.

On the other hand, at a point 19 downstream of the magnetic pole 17 in the rotational direction of the sleeve, a magnetic blade 21 as a magnetic particle restraining member made of a magnetic material is attached to the sleeve 12.
and the distance d from the sleeve 12 at point 19
The sleeve is disposed so as to be inclined downstream in the direction of movement of the sleeve, with an angle δ formed between the normal n of the blade and the center line l of the blade. The magnetic particles 16 are restrained at a point 19 on the surface of the sleeve 12 by a balance between the restraining force based on gravity, magnetic force, and the effect of the presence of the magnetic blade 21, and the conveyance force in the direction of movement of the sleeve 12, and are restrained to some extent. A stationary layer 20 is formed which is movable but mostly immobile. A magnetic particle layer consisting of the circulating layer 18 and the stationary layer 20 is formed on the surface of the sleeve 12. The magnetic particle layer contains a non-magnetic developer 15, and the magnetic particles in the stationary layer 20 are restrained on the sleeve surface by the balance between the restraining force and the conveying force described above, but the developer is non-magnetic. Therefore, it is not restrained by the magnetic field of the magnetic pole 17, but is uniformly and thinly coated on the sleeve surface by the mirror force, is transported as the sleeve rotates, and is developed facing the surface of the photoreceptor 11. served.

In the circulation layer 18, the arrow C
During this circulation, the magnetic brush takes in the non-magnetic developer 15 from the developer layer above the magnetic particle layer and returns to the lower part of the developer supply container 14. Repeat the cycle. The principle of this method for forming a thin layer of developer is detailed in Japanese Patent Application No. 151028/1983 filed by the present applicant, so a detailed explanation will be omitted.

In the figure, an L-shaped magnetic member is provided at the bottom of the container 14, one end of which is connected to the magnetic pole 17 of the magnet 13.
A magnetic brush of magnetic particles is formed by the magnetic field between the magnetic pole 17 and the magnetic member 22, and developer or magnetic particles leak from the magnetic member 22 toward the upstream side in the direction of rotation of the sleeve. It prevents you from doing it. In the region between the magnetic member 22 and the magnetic blade 21, only one magnetic pole N17 is provided as shown in the figure.

Next, the installation position of the magnetic member will be explained.

Figure 2 shows the magnet 1 of the device shown in Figure 1.
3 shows the magnetic flux density distribution on the sleeve surface, and the solid line in Figure 2 is the normal direction on the sleeve surface.
The magnetic flux density distribution in Hθ, and the broken line is an example of the magnetic flux density distribution in the tangential direction Hγ, measured using a Gaussmeter. Second
As can be seen from the figure, the pattern of the components in the normal direction and that in the tangential direction have a nearly orthogonal functional relationship even in actual measurements. Further, the angle θ of the horizontal axis is (+) in the clockwise direction with respect to a vertical line passing through the center O of the sleeve in FIG.

Therefore, the strength and direction of the magnetic force at a certain point on the sleeve is a combination of magnetic fields tangential to the normal direction shown in Figure 2, and if a magnetic member is installed in the direction in which this combined magnetic field acts, it will become a magnetic pole. A reliable magnetic brush is formed with the magnetic member (FIG. 3). Therefore, this magnetic brush can prevent magnetic particles and developer from leaking downward from inside the container 14.

Now, in the present invention, it is necessary that both the magnetic blade 21 and the magnetic member 22 be arranged in the direction in which the magnetic force acts, and for example, the apparatus shown in FIG. 1 is configured in this way. At this time, since the magnetic blade 21 restrains the magnetic particles, the magnetic member 22 is placed downstream of the magnetic pole N in the rotational direction of the sleeve, and the magnetic member 22 is placed on the developer 15 on the sleeve 12.
It is desirable to provide the sleeve at an angle toward the upstream side so that it is not scraped off the top of the sleeve. In this way, in order to restrain the magnetic particles with the magnetic blade, it is necessary to arrange the magnetic blade between _{ω 1} and _{ω 2} in FIG. Alternatively, it is desirable to arrange it between ω ₄ and ω ₁ . From the viewpoint of circulation and restraint of the magnetic particles 16, it is desirable that the magnetic blade 21 and the magnetic member 22 be on the same side (on the right side in the figure) with respect to a perpendicular line passing through the center O of the sleeve 12. Therefore, as in the case where the magnetic member 22 is placed between ω ₄ and ω ₁ in FIG. 2, the magnetic pole N for the magnetic blade and the magnetic pole S for the magnetic member
When the magnetic poles are different, it is necessary to arrange the two or more magnetic poles completely within half the circumference of the sleeve, and this is only possible with magnets of relatively large diameter, which leads to an increase in the size of the device. invite On the other hand, if the magnetic pole for the magnetic blade and the magnetic pole for the magnetic member are made the same, that is, if the magnetic pole is made one so that the magnetic poles do not alternate between them, a very compact device can be formed. Therefore, in the present invention, the magnetic member 22 is arranged between ω ₂ and _{ω 3} in FIG. 2, and one magnetic pole is present in the region between the magnetic blade and the magnetic member.

FIG. 4 is an explanatory diagram of a developing thin layer forming apparatus to which the present invention is applied. In the figure, members having the same functions as those in FIG. 1 are given the same reference numerals.

In FIG. 4, 11 is a cylindrical electrophotographic photoreceptor that moves in the direction of the arrow a. A non-magnetic developer holding member 12 is provided to hold the developer with a gap between the photoconductor 11 and the holding member 12 has a cylindrical (sleeve) shape in this embodiment, but it can move endlessly. It may also be in the form of a web. The same applies to the electrophotographic photoreceptor 11. Along with this movement of the photoreceptor 11, the developer holding member 12 is moved by the arrow b
Rotate in the direction. A developer supply container 14 is provided to supply developer to the developer holding member 12. The developer supply container 14 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. A magnetic member 22 is formed at the bottom of the developer holding container 14 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 13 is fixedly provided inside the developer holding member 12 . Therefore, only the developer holding member 12 rotates. This magnet 13 has N pole 1
7. It has a magnetic pole of S pole 23.

A magnetic blade 21 made of a magnetic material and serving as a magnetic particle restraining member is arranged near the top of the opening of the developer supply container 14 . This magnetic blade 21 is formed by bending an iron plate, and
It is fixed to 4. This magnetic blade 21
The distance between the tip and the developer holding member 12 is 100~
1000μ, preferably 200-500μ, in this example 300μ. If this spacing is smaller than 100μ,
The drawback is that magnetic particles become clogged and are pushed out of the blade. If it is larger than 1000μ, a large amount of non-magnetic developer will leak out due to vibration, making it impossible to form a thin layer.

By supplying magnetic particles or a mixture containing magnetic particles and non-magnetic developer to the developer supply container of the apparatus having such a configuration, the stationary layer 20 and the circulating layer 18
to form. The mixture forming the magnetic particle layer consisting of the stationary layer 20 and the circulating layer 18 preferably contains about 2 to 70% (by weight) of non-magnetic developer to the magnetic particles, but may also contain only magnetic particles. . The particle size of the magnetic particles is between 30 and 200 microns, preferably between 70 and 150 microns. Each magnetic particle may be made of only a magnetic material, a combination of a magnetic material and a non-magnetic material, or a mixture of two or more types of magnetic particles.

The magnetic particles in the circulation layer 18 form a brush due to the magnetic field generated by the magnetic pole 17, and this brush performs the above-mentioned circulation action in the c direction. A stationary layer 20 is formed between the magnetic blade 21 and the magnetic pole 17, and is bound to the surface of the developer holding member.

By supplying the non-magnetic developer onto the magnetic particle layer, two layers are formed substantially in the vertical direction, that is, on and outside the outer periphery of the developer holding member 12. The developer layer 24 may be formed using a small amount of magnetic particles added to this non-magnetic developer.
Even in this case, the magnetic particle content of the developer layer is smaller than the magnetic particle layer described above. 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 as described above. For example, it is possible to form the two layers by mixing magnetic particles and non-magnetic developer almost uniformly for the entire amount of the magnetic particle layer and developer layer 24. After that, the developer supply container 14 is vibrated or the developer holding member is preliminarily rotated to form two layers due to the difference in specific gravity between the magnetic particles and the non-magnetic developer and the magnetic field of the magnet 13. It's okay.

Even when a nearly uniform mixture of magnetic particles and non-magnetic developer is supplied without particularly forming two layers, as long as it contains enough magnetic particles to form a sufficient magnetic particle layer, Although it is possible,
In order to maintain long-term stability of the magnetic particle layer, it is preferable to use two layers.

When the developer holding member 12 is rotated with magnetic particles and non-magnetic developer applied in this way, the magnetic particles are moved by the magnetic field and gravity of the magnetic pole 17 and the frictional force due to the surface of the developer holding member, as shown in FIG. Perform a circular motion as shown by arrow c. At this time, the nonmagnetic developer and the surface of the developer holding member 12 come into contact with each other, and the nonmagnetic developer in the circulating 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. By insulating the magnetic particles with resin or the like, reducing the triboelectric charge from the magnetic particles, and allowing the developer holding member 12 to receive the necessary charge, it is possible to prevent the effects of deterioration of the magnetic particles and to prevent the developer holding member 12 from being affected by deterioration. Stable developer application.

On the other hand, the frictionally charged developer is transferred to the magnetic blade 2.
1 and the surface of the developer holding member 12, the surface of the developer holding member 12 is uniformly and thinly coated with the action of mirror force, and the surface of the developer holding member 12 is placed on the surface of the developer supplying container 14. It exits to the outside and faces the surface of the photoreceptor 11 for development.

A voltage is applied between the electrophotographic photoreceptor 11 and the developer holding member 12 by a bias power supply 25 . The bias power source 25 may be an alternating current or a direct current, but it is preferably one in which alternating current and direct current are superimposed. In this case, the preferred developing method is the method described in Japanese Patent Publication No. 58-32375. Of course, contact development may also be used. The developer provided during development is supplied from the circulation layer 18 to the developer holding member 12, and the insufficient amount in the circulation layer 18 is supplied from the developer layer 24 by the above-mentioned circulation movement.

In the case of a two-layer structure, the magnetic particle layer consisting of a stationary layer and a circulating layer is formed near the outer surface of the developer holding member 12 from the beginning, and the developer layer 24 does not contain any magnetic particles or Since the amount is small, the state of the magnetic particle layer remains almost constant and does not change even if the operation continues for a long time. In this sense, the magnetic particles within the magnetic particle layer are part of the development apparatus rather than the developer or part thereof.

Based on this example, a φ20 aluminum sleeve whose surface was subjected to irregular sandblasting with alundum abrasive grains was used as the developer holding member 12. However, regular blasting with glass beads, etching, extruding, sandpaper,
The surface may be roughened by anodic oxidation or the like. As the magnetic field generating means 13, a bipolar magnet having an N pole and an S pole as shown in FIG. 4 was used, with the N pole positioned at π=95°.

The magnet shown in FIG. 4 has a maximum surface magnetic flux density of about 500 gauss, but it is preferable to increase this strength even more when using a developer, particularly a developer with slightly poor fluidity. Visual observation revealed that in a magnet with a surface magnetic flux density of approximately 800 Gauss, the circulation in the direction c in Figure 4 was approximately doubled.

The magnetic blade 21 is made of a 1.2 mm thick iron plate with chemical nickel plating. SPC steel plates, silicon steel plates, permalloy, etc., which are commonly used industrially, are preferable as materials for iron plates. Further, these magnetic bodies may be magnetized so as to strengthen the magnetic field in the tangential direction. In Figure 4, θ=35°, δ=85°, 250μ between blade and sleeve
And so. δ = 90°, that is, the tangential direction of the sleeve is fine, but if the mechanical precision is poor, the magnetic blade may hit the sleeve against the belly, and this tendency is even more pronounced when δ>90°, and in this case, the magnetic particles undesirable in terms of restraint. On the other hand, the magnetic member 22 is a 1 mm thick iron plate arranged at an angle of 30 degrees with respect to the normal direction of the sleeve with a distance of 1.5 mm from the sleeve 12. As a result, neither leakage of the developer nor scraping of the developer on the sleeve 12 occurred.

In this example, the magnetic particles have a particle size of 100 mm.
~80μ (150/200 mesh) iron particles (maximum magnetization 190emu/g) are used as a non-magnetic developer.
Consisting of 100 parts of styrene/butadiene copolymer resin and 5 parts of copper phthalocyanine pigment, average particle size 10μ
When using a blue toner with 0.6% colloidal silica added to the toner powder, the coating thickness on the sleeve was approximately 50 to 100 μm, and the tribocharge amount of the toner on the sleeve measured by the blow-off method was +
A good coating of 10 μc/g was obtained.

The thin layer forming apparatus of this example was manufactured by Canon Inc.
-10 type copying machine, the bias power supply 25 has a frequency of 1600 Hz, a peak-to-peak value of 1300 V AC voltage and -300 V DC voltage superimposed, and the distance between the sleeve 12 and the OPC photoreceptor 11 is adjusted.
When development was carried out at a setting of 250 μm, a good blue image was obtained.

Although a non-magnetic developer was used in this example,
A magnetic developer can also be used as long as it has significantly weaker magnetism than magnetic particles and can be tribocharged.

Effects of the Invention According to the present invention, in a developing device using magnetic particles with a simple configuration, it is possible to obtain magnetic particle restraint and stable and uniform circulation. As a result, a thin developer layer having a uniform layer thickness and a uniform and sufficient amount of charge was obtained using a small amount of magnetic particles.

Further, in the present invention, since the magnetic particle restraining member is arranged to be inclined toward the downstream side in the moving direction of the developer holding member,
The magnetic field in the tangential direction can be made stronger than the magnetic field in the normal direction on the developer holding member, and blocking of the developer at the magnetic particle restraining member, fusion of the developer, leakage of the magnetic particles, etc. can be prevented. Therefore, the present invention is also suitable for a developing device using toner for pressure fixing.

Furthermore, in the present invention, since it is sufficient to dispose one magnetic pole between the magnetic particle restraining member and the magnetic member, a small diameter magnet can be used, and a compact developing device can be obtained.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the principle of the present invention, Fig. 2 is a graph of the magnetic force distribution of the magnet used in the present invention, Fig. 3 is an explanatory diagram of the arrangement of magnetic members, and Fig. 4 is an example device of the present invention. FIG. In the figure, 11...photoreceptor, 12...sleeve,
13...Magnet, 14...Developer supply container, 15
...Nonmagnetic developer, 16...Magnetic particles, 17,23...
Magnetic pole, 18... circulation layer, 20... stationary layer, 21... magnetic blade, 22... magnetic member, 25... power source.

Claims (1)

[Scope of Claims] 1. A developer supply container having an opening and containing a non-magnetic developer and magnetic particles; a developer holding member that holds and conveys the developer layer and supplies it to the latent image carrier; and a developer holding member provided outside the developer holding member with a gap between the developer holding member and the developer holding member, and a normal line erected to the surface of the holding member. a first magnetic member for restraining magnetic particles, which is inclined toward the downstream side in the moving direction of the holding member; and a second magnetic member, which is provided on the developer inlet side of the container and forms a magnetic brush for the magnetic particles. and a single magnetic member at a position that is upstream in the developer holding member movement direction from a position where the first magnetic member faces the developer holding member and downstream from a position where the second magnetic member faces. a magnetic field generating means fixedly disposed inside the developer holding member so as to have a magnetic pole, and the magnetic particles are restrained in the container by the magnetic pole and the first magnetic member and placed on the developer holding member. A non-magnetic developer layer is formed on the container, and a magnetic brush of magnetic particles formed by the magnetic pole and the second magnetic member prevents the non-magnetic developer from leaking from the inlet side. A developing device that allows return to the container. 2. The developing device according to claim 1, wherein the first magnetic member and the second magnetic member are opposed to the developer holding member at an upward movement position. 3. Claim 1, wherein a DC voltage or a voltage having an AC component is applied to the developer holding member.
The developing device according to item 1 or 2.