JPS6095573A - Developing device - Google Patents

Abstract

PURPOSE:To form a magnetic brush securely even by a relatively weak magnetic field generating means, and prevent a developer and magnetic particles from leaking from a developer container by providing a magnetic member to the magnetic field generating means in a developer holding member at the upstream side in the moving direction of the holding member where a magnetic field almost operates. CONSTITUTION:The gap (g) between the magnetic member and holding member is 0.1<=g<=1.5mm., preferably, 0.3<=g<=1.0mm.. Magnetic particles 5 which are present in quantities near the surface of a sleeve 2 circulate as shown by an arrow (c) while forming a magnetic brush at a magnetic pole part by a magnetic field and the rotation of the sleeve 2. Namely, magnetic particles 5 near a magnetic blade strike the blade 6 or a container wall and are moved up by being pressed by particles conveyed from the upstream side and conveyed to the lower part of the container with the assistance of gravitation. Further, flowing magnetic particles before being held on the sleeve 2 are mixed with a nonmagnetic developer and reaches the 1st magnetic pole 7a again.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device that develops a latent image such as an electrostatic latent image using a non-magnetic developer.

Conventionally, various types of dry-component developing devices have been proposed and put into practical use. However, in any of the development methods, it is extremely difficult to form a thin layer of the dry component developer, and for this reason, a developing device has been configured to form a relatively thick layer.

However, as the sharpness and resolution of developed images are becoming more important, it has become essential to develop a method for forming a thin layer of a dry component developer and an apparatus therefor.

As a conventionally known method for forming a thin layer of a dry component developer, Japanese Patent Application Laid-Open No. 54-43037 has been proposed.
And it has been put into practical use. However, this concerned image formation with magnetic developers. Magnetic developers must have a magnetic material added inside them to have magnetism. There are problems such as poor color reproduction of the attached rounding.

For this reason, methods for forming a thin layer of non-magnetic developer (1), methods (1), (1), (1), (4), (4), (4), (4), (1) to (1), (1), (2), (4) a method (4), a method (4) which uses soft hair like beaver hair as a cylindrical brush, and (4) coats the entire surface of the developer with a cylindrical brush made of soft bristles such as beaver's hair, and (4)
A method has been proposed in which a developing roller made of i[# is coated with a doctor blade or the like. However, if an elastic blade is used as a doctor blade for the above-mentioned fiber brush, it is possible to control the amount of developer, but uniform application is not achieved, and only a delicate brush on the developing roller is rubbed. However, since no triboelectric charge is imparted to the developer existing between the fibers of the brush, problems such as ghosts are likely to occur. Furthermore, since the device includes a non-magnetic developer, it is difficult to prevent the developer from leaking from the device.

The present invention eliminates the problems of the conventional method described above, and provides a new developing device that forms a uniform thin layer of developer on the surface of a developer holding member and applies sufficient triboelectric charging. The purpose is A further object of the present invention is to make it possible to prevent the non-magnetic developer from leaking out of the developing device.

A developing device of the present invention that achieves the above object includes a container that stores non-magnetic developer and magnetic particles, a developer holding member that rotatably conveys the non-magnetic developer to a latent image carrier, and a non-magnetic developer of the container. A magnetic particle restraining member disposed on the magnetic developer supply outlet side with a gap formed on the surface of the holding member, and a magnetic field generating member disposed on the opposite side of the magnetic particle restraining member via the holding member. and a magnetic member that is provided on the developer inlet side of the container and forms a magnetic brush, and the magnetic member is arranged on the surface of the holding member in a direction in which the magnetic field of the magnetic field generating means acts. It is provided on the upstream side of the magnetic field generating means with respect to the moving direction, and the gap y with the holding member is set to 0.
．． The developing device is set in the order of 1≦I≦1.5, preferably 0.3≦y≦1.0.

The latent image carrier of the present invention is a drum-shaped or belt-shaped part having a photoconductor or an insulating layer, and the magnetic field generating means is a magnetic roller with magnetic poles of the same or different polarity attached in the axial direction. A support member that fixes magnetic objects or multiple rod-shaped magnets.
It is possible to use one that is glued to two. Further, between the rotating developer holding member 1 and 1, it is possible to use a sleeve made of non-magnetic metal such as aluminum, copper, stainless steel, brass, or a synthetic resin material, or an endless belt between resin and the toner holding member 1 m in circumference. In order to improve the transportability and charging characteristics of the material, a roughened surface or an uneven pattern may be provided as necessary. Further, as the magnetic particle restraining member, a blade plate or a wall made of a magnetic material such as iron or a non-magnetic material such as aluminum, steel, or resin may be used. Furthermore, when providing a magnetic member facing the magnetic field generating means in order to form a magnetic blank for preventing the developer from flowing out, a magnetic member other than metal such as iron may be used to oppose the magnetic field generating means in a relationship of opposite polarity. It may also be a magnet. These magnetic members may be attached to the wall of the container facing the magnetic field generating means, or the container itself may be made of a magnetic material such as iron, and the wall of the container facing the magnetic field generating means may be placed close to the developer holding member. It may be configured.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 1 shows a sectional view of a developing device for explaining the developing principle of the present invention.

In the figure, reference numeral 1 denotes an electrophotographic photosensitive drum, which holds a latent image formed by a latent image forming means (not shown) and rotates in the direction of arrow a to pass through a developing position shown in the drawing. A non-magnetic sleeve 2, which is a developer holding member that holds developer, faces the photosensitive drum 1 with a predetermined gap therebetween, and the sleeve 2 rotates in the direction indicated by the arrow. A container 3 made of a non-magnetic material such as resin or aluminum is located above the sleeve 2 and stores a mixture of a non-magnetic developer 4 and magnetic particles 5, and downstream of the container 3 in the rotational direction of the sleeve, A magnetic blade 6, which is a magnetic particle restraining member, is screwed.

On the other hand, on the opposite side of the sleeve 2 to the magnetic blade 6, a magnet 7 is provided as a magnetic field generating means.

The installation position of this magnet is the position of the magnetic pole and the magnetic blade 6.
In reality, by providing a magnetic pole slightly upstream of the position of the magnetic blade 2, the magnetic field created prevents the outflow of magnetic particles and the current fv! Even better results are obtained in terms of uniform application of the agent.

In the above configuration, a magnetic brush 8 is formed by a magnetic field generated between the five magnetic particles in the container 3, the eight poles of the magnet 7, and the magnetic blade 6. As the sleeve 2 rotates, the magnetic particles and non-magnetic developer are stirred and mixed while the magnetic brush 8 is held. In this state, on the magnetic blade side of the container 3, due to the presence of the blade 6, the mixture of non-magnetic developer and magnetic particles is prevented from moving by this blade, moves upward, and circulates in the direction of arrow C.

As a result, the non-magnetic developer is triboelectrically charged by the sleeve 2 or the magnetic particles by mixing with the magnetic particles. The charged developer is uniformly and thinly applied to the surface of the sleeve 2 by mirror force by a magnetic brush 8 formed near the magnetic blade 6, and reaches a position facing the photoreceptor drum.

By the way, the magnetic particles 5 constituting the magnetic brush 8 do not flow onto the sleeve 2 by setting the restraining force due to the magnetic field of the magnet 7 to be greater than the conveying force caused by the frictional force. If there is non-magnetic developer within the area of the magnetic brush 8, the ratio of the magnetic particles of the magnetic brush 8 to this developer remains approximately constant throughout the 20 rotations of the sleeve.

As a result, even if the developer on the sleeve is consumed during development,
Developer is automatically supplied to the area of the magnetic brush 8. Therefore, it is possible to always supply and apply a constant amount of developer onto the sleeve 2.

In the above principle explanation, a magnetic blade is used as the magnetic particle restraining member, but a non-magnetic blade or a wall made of a non-magnetic material such as resin or aluminum constituting the container can also be used as the restraining member. However, in this case, in order to prevent the magnetic particles from flowing out, it is necessary to further reduce the gap between the sleeve and the restraining member when using the magnetic blade. Further, when a magnetic blade is used, it is preferable because magnetic particles can be stably produced by the magnetic field between the blade and the magnetic pole.

By the way, in the developing device shown in FIG. 1, since the developer is a non-magnetic developer, there is a problem that it tends to leak from the region d on the side where the sleeve 2 enters the container 3. In order to prevent the developer from leaking from the area d, a magnetic brush is formed between the sleeve and the container on the side where the sleeve enters the container, so that the non-magnetic developer and magnetic brush from the container can be prevented. Prevent particle leakage.

Hereinafter, more detailed embodiments will be described with reference to the drawings.

FIG. 2 shows a sectional view of a developing device showing an embodiment of the present invention. In the drawings, the same members as those shown in FIG. 1 are designated by the same reference numerals.

In the figure, reference numeral 7a denotes a first fixed magnet, which is attached to the fixed shaft 9 in the sleeve and forms a first magnetic pole. confine the magnetic particles within the container. Further, 7b is a second fixed magnet forming a second magnetic pole, and an N magnetic pole having an opposite polarity to the first magnetic pole faces the sleeve 2 side. In this case the second
The magnetic pole does not directly contribute to development, but is provided to collect magnetic particles into the container 3 when they leak out from the container 3 when a strong impact is applied to the equipment, for example during transportation. be. Further, an iron piece 10 as a magnetic member is attached to the inner wall of the container 3 facing the first magnet 7a.

With the above configuration, the magnetic particles 5 present in large quantities near the surface of the sleeve 2 circulate in the direction of the arrow C while forming a magnetic brush at the magnetic poles due to the magnetic field and the rotation of the sleeve 2. That is, the magnetic particles 5 near the magnetic blade hit the blade 6 or the container wall, are further pushed upward by the particles conveyed from the upstream side, and are then conveyed to the lower part of the container without the influence of gravity. . Then, before being further held in IJ-sp 2, the flow of magnetic particles takes in non-magnetic developer,
It reaches the position 1f of the first magnetic pole 7a again.

Therefore, magnetic particles are always circulating in the lower part of the container, forming a magnetic brush 8a between the first magnet 7a and the iron piece 10. The presence of this magnetic brush 8a can prevent the developer 4 in the container 3 from flowing down below this brush 8a. Furthermore, since this magnetic brush 8a is formed regardless of the operation of the developing device, the device itself can produce*! +1/ Prevents leakage of not only developer but also magnetic particles even when not in use. In the present invention, since a magnetic member such as the iron piece 10 is used,
The rotation of the sleeve 2 also has the effect of making the magnetic field generated by the first magnetic pole 7a stronger and more stable.

Next, when the magnetic member is opposed to this first magnetic pole,
The wJ madness of the current acid agent on the sleeve due to the positional relationship between these magnetic poles and the 41-wire member will be explained.

FIG. 3 (5) shows that when an iron piece 10a, which is a magnetic member, is placed downstream of the first magnetic pole (S pole) 7a in the rotational direction of the sleeve,
FIG. 3(B) shows the case where it is placed on the upstream side.

As is clear from FIG. 3(5), when a magnetic member is arranged downstream of the first magnetic pole 7a, the magnetic brushes may be concentrated on the upstream side of the iron piece 10a. As a result, depending on the amount of magnetic particles, fluid circulation as shown by arrow e may occur in the brush on the upstream side of the iron piece 10a. In this case, the developer remaining on the sleeve without being consumed by development and reaching the first magnetic pole is easily scraped off by the flowing magnetic brush. As a result, the scraped developer falls to the lower part of the sleeve, and the developer scatters and contaminates the surrounding area.

In the case of FIG. 3(B), the magnetic brushes are concentrated on the downstream side of the iron piece 10a. Therefore, even if fluid circulation occurs in the magnetic brush, the residual developer on the sleeve can smoothly enter the container. Furthermore, since this magnetic brush is formed based on a strong magnetic field between it and the iron piece,
Even when the sleeve 2 rotates, it does not move together with the sleeve, and the effect of preventing leakage of the developer is stably maintained. □It is preferable that the iron piece 10a be opposed to the first magnetic pole 7a as described above, or that the iron piece 10a be disposed on the upstream side.

Next, the installation position of the iron piece when the iron piece is provided on the second flow side with respect to the first magnetic pole 7a will be explained in more detail. In FIG. 4, the solid line shows the magnetic flux density distribution on the sleeve surface in the normal direction to the sleeve, and the broken line shows an example of the magnetic flux density distribution in the tangential direction to the sleeve, measured using a Gaussmeter.

As can be seen in Fig. 4, the pattern of the component in the normal direction, that in the tangential direction, and the actual measured value are #'1. geiff is an intersection function relationship. In addition, the angle 0 of the horizontal axis is (f
).

The strength and direction of the magnetic force at a certain point on the sleeve.
1. The combination of the magnetic fields in the normal and tangential directions shown in Figure 4 □
If the iron piece is installed in the direction in which this composite magnetic field acts, a reliable magnetic brush is formed between the first magnetic pole (S pole) and the iron piece (Fig. 5). Therefore, this magnetic brush can prevent magnetic particles and developer from leaking downward from inside the container 3.

By the way, as mentioned above, it is preferable that the iron piece be disposed upstream of the magnetic pole in the direction of rotation of the sleeve.
θ in Figure 4, 〈θ〈θ, θ for the second magnetic pole,
〈θ〈θ. It is preferable to place the

Next, at the position of the iron piece 10 shown in FIG.
The relationship between the gap 9 between the iron piece 10 and the leakage amount M of non-magnetic developer and magnetic particles from the developer container 3 will be explained. This general tendency is that when the gap g is wider than about 0.5 mm, the leakage amount M increases, and even when it is narrower than about 0.51 nIIL, the leakage amount M increases. This is because if the gap is wide, the magnetic brush cannot be formed properly between the sleeve and the iron piece.
This is caused by part of the magnetic brush breaking due to rotation of the sleeve, causing magnetic particles to leak, or developer leaking from gaps between the magnetic brushes. In particular, when the gap g exceeds approximately 1.5 mm, leakage of magnetic particles also increases. When the gap is narrow, especially when the gap I is narrower than 0.1 mm, unused developer remaining on the sleeve may be strongly formed at the tip of the iron piece or between the sleeve and the iron piece due to the rotation of the sleeve. Since the non-magnetic developer is scraped off by the magnetic brush, the non-magnetic developer is not collected into the container, resulting in a situation equivalent to leakage. Gap y
When the distance is narrow, there is almost no leakage of magnetic particles. The relationship between the gap g between the sleeve and the iron piece mentioned above and the leakage amount M does not depend greatly on the developer, magnetic particles, or the surface properties or materials of the sleeve, but rather depends on the strength of the magnetic force generated by the magnet 7a provided inside the sleeve. It has been found that GB stands on the surface of the sleeve with a magnet of about 300 to 1000 Gauss used in a normal electrophotographic device.

An embodiment of the present invention will be explained with reference to FIG.

In the figure, the same members as in FIG. 2 are given the same reference numerals.

In the developing device of this embodiment, the photosensitive drum 1 is
It rotates in the direction at a circumferential speed of 60 mm. 2 has an outer diameter of 32mm and a thickness of Q8t that rotates in the direction of the arrow at a circumferential speed of 66cm/sec.
The sleeve is made of NX stainless steel (808304), and its surface is sandblasted using #600 alundum abrasive grains to reduce the roughness of the circumferential surface to 0.8 μm.
(Rz = ).

10,000, inside the rotating sleeve 2 is a ferrite sintered tie 7.
' The first magnet 7a is fixedly arranged, and its S pole is set at an angle of 30 degrees (as shown in the figure) from the line where the core O of the sleeve 2 and the tip of the blade are curved with respect to the magnetic plate L node 6. It is.

One of the second magnets 7b is located opposite to the iron piece 10, which is a breakable member provided on the sleeve entrance side of the container.

The magnetic flux density on the sleeve surface of the second magnet 7b had a peak value of 650 Gauss in the presence of the iron piece 10, and 400 Gauss when the iron piece 10 was removed. At this time, the positional relationship between the magnetic pole of the second magnet and the iron piece 10 is such that the iron piece is installed on the upstream side of the magnetic pole and approximately in the direction in which the second magnetic pole acts.
Further, the distance between the sleeve 2 and the iron piece was set to 0.811. Also, the thickness of the iron piece is 0.5 m.

The magnetic blade 6 is made of iron, and its surface is nickel-plated to prevent rust. The gap between the blade 6 and the surface of the sleeve 2 was set to 200 μm.

The magnetic particles 5 have a particle size of 70 to 100μ and a diameter of 5Q.
100g of emu/g spherical 7E2ite (manufactured by TDK)
Using. On the other hand, the non-magnetic developer 4 contains 100 parts of polyester resin, 3 parts of steel phthalocyanine pigment, 5 parts of negative charge control agent (alkyl salicylic acid metal chain), and 0.5% of silica. 200 g of externally added cyan-colored powder having an average particle size of 12 μm and being negatively (to) positively charged was prepared. Then, after thoroughly mixing the non-magnetic developer and the magnetic particles, they are placed in the container 3. The mixture of non-magnetic developer and magnetic particles in the container 3 can be observed, especially when the developer is running low, as the magnetic particles move in circulation as they are transported by the sleeve under a magnetic field. Ta.

In the developing device having the above structure, as the sleeve rotated, a thin layer of about 80 μm thick consisting only of the non-magnetic developer was formed on the surface of the sleeve 2. When the charging potential of this developer layer was measured by the four-off method, it was found to be -7 μc.
It was confirmed that the battery was uniformly charged at a potential of /g.

On the surface of the photosensitive drum 1 facing the sleeve 2, a charge pattern of +600V in the dark area and 1150V in the bright area is formed as an electrostatic latent image, and the distance between the sleeve surface and the photosensitive drum is set at 30V.
It was set to 0 μm. Then, power supply E is applied to the above sleeve.
The frequency is 800Hz, and the peak-to-peak value is 1.4.
By applying a voltage of kV with a center value of +300v,
8-32375, it was possible to obtain a high-quality developed image free from uneven development, ghost images, and fog. Of course, the present invention can also be applied to a developing device that performs development by bringing a developer layer into contact with a photosensitive drum.

Now, regarding the mixture in container 3, the magnetic particles were hardly consumed and only the non-magnetic developer was consumed for development. Also, lIM, e! Function remained unchanged until the developer was almost consumed. After the developer has been consumed, the developing device is removed from the main body, and the leakage of the developer or magnetic particles in the lower part of the sleeve 2 is measured using a leak meter. The results are shown in FIG. 7. If A
, as shown by the till line, the gap y is 1.51111
When it exceeds 151M, the leakage of magnetic particles increases. Furthermore, if the gap y is less than 0.1 mg, the amount of leakage M increases because the developer on the sleeve is scraped off. Therefore, the gap y must be set to 0.1≦g≦15. Furthermore, considering the contact between the iron piece and the sleeve due to eccentricity of the sleeve and the practically allowable leakage Jt of 1 m, it is preferable that 0.3≦I≦1.01I111. Curve 8 in the figure is a non-magnetic developer containing 100 parts of stereo//butadiene copolymer resin, 5 parts of copper phthalocyanine pigment, powder with an average particle size of 10μ, and 0.6% colloidal silica.
The results obtained using the external addition of , show the same tendency as the curve. Curve C in the figure is obtained by applying chemical nickel plating to the sleeve shown in the example of curve A, and exhibits the same tendency as curve 9A1B.

Compared to the case shown in Fig. 1, in which the magnetic field is applied only to the position of the magnetic blade, it is confirmed that the magnetic member of the present invention clearly exhibits the leakage prevention effect of the magnetic brush. .

By the way, in the present invention, the number of magnetic poles provided inside the sleeve does not need to be limited to two, the first and second magnetic poles. Second
As shown in the figure, one magnetic pole may form two magnetic brushes 880. In addition, when using a magnetic member, if the container is a magnetic material, the magnetic blade 6 of the embodiment of the present invention
And it becomes possible to configure the iron piece 10 with the wall of the container,
This piece of iron can replace a portion of the container with an axially convex portion of the sleeve.

Also, the shape of the iron piece facing the sleeve is not limited to the embodiment.
A planar member such as a round bar may be used.

By the way, although the case where the N pole is used as the second magnetic pole has been exemplified, it goes without saying that the S pole may also be used. Further, as for the magnetic particle restraining member, although a blade plate made of a magnetic material is illustrated, a wall or a plate-like member made of a non-magnetic material such as synthetic resin, aluminum, brass, stainless steel, etc. may also be used. However, when using a non-magnetic material, the first magnet 7a
Since no magnetic field is generated between the sushi and the sushi, the type of rice crackers created by the magnetic particles inside the container is different, and this E-like material tends to flow out downstream of the container. However, this point can also be solved by setting the gap between the sleeve and the restraining member made of the bowl magnetic material to be approximately equal to or smaller than the diameter of the magnetic particles. Furthermore,
In addition to attaching the restraining member separately from the container, a part of the container may be used as the restraining member. And furthermore,
The bias during development is not limited to alternating voltage, and direct current voltage is also effective. The present invention can be applied to contact development as well as non-contact development.

Although a non-magnetic developer was used in this example, it has significantly weaker magnetism than magnetic particles, and a magnetic developer can also be used if it is capable of triboelectric charging. Further, although the present invention is applied to a developing device that applies non-magnetic developer by circulating magnetic particles, the present invention is not limited to this, and the present invention is not limited to this, but it can also be applied to a developing device in which a magnetic brush is formed to prevent leakage of developer from a developer container. For example, it can be applied to a developing device using a one-component magnetic anti-monitoring agent in which the developer itself has magnetism.

As described above, in the present invention, a magnetic member is provided upstream of the magnetic field generating means in the developer holding member in the moving direction of the holding member, and is installed in the direction in which the magnetic field acts, thereby eliminating the conventional magnetic brush formation. A magnetic brush can be reliably formed even for a relatively weak magnetic field generating means that has not been sufficiently developed, and leakage of the developer and magnetic particles from the inside of the developer container can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a developing device for explaining the principle of the present invention.
Figure 2 is a sectional view of a developing device to which the present invention is applied, and Figure 3 (
- and Fig. 3 03) are explanatory diagrams showing the state of the magnetic brush due to the relationship between the magnet and the magnetic member, Fig. 4 is a magnetic flux density distribution diagram on the sleeve surface, and Fig. 5 is a partial cross section of an embodiment of the present invention. Figure 6 is a cross section of a developing device showing another embodiment of the present invention.
FIG. 7 is a graph showing the amount of leakage of developer or magnetic particles measured. In the figure, 2 is a sleeve which is a developer holding member, 3 is a container, 4 is a non-magnetic developer, 5 is a magnetic particle, 6 is a magnetic blade which is a magnetic particle restraining member, 7, -7a, 7bi&
The stone 10φ10a represents an iron piece which is a magnetic member. prisoner rq -1-1 -120

Claims (2)

[Claims] (1) A container for storing non-magnetic developer and magnetic particles, a developer holding member for rotationally conveying the non-magnetic developer to the latent image carrier, and a developer holding member located on the non-magnetic developer supply outlet side of the container. , a magnetic particle restraining member disposed with a gap formed on the surface of the holding member; a magnetic field generating means disposed on the opposite side of the magnetic particle restraining member with the holding member interposed therebetween; and a developer inlet of the container. a magnetic member provided on the side and forming a magnetic brush, and the magnetic member is arranged on the surface of the holding member in a direction in which the magnetic field of the magnetic field generating means acts, and in a direction in which the holding member moves. The developing device is characterized in that a holder is also provided on the upstream side, and a gap I with the holding member is set to 0.1<J+<:1.5 vtt. (2) The above gap I is 0.3<,! i'< 1.0 mx
The developing device according to claim 1, wherein the developing device is set to .