JPS58111067A - Developing device - Google Patents

Abstract

PURPOSE:To perform excellent development by providing a magnetic material provided over the surface of the dielectric layer of a developing sleeve and a magnetic material constituting a developer with different magnetic properties, and thus flying a developer in a gap formed with a photosensitive drum even when a developer layer on the surface of the developing sleeve is made thin. CONSTITUTION:In the external circumferential surface of the external dielectric part 3 of the developing sleeve 1 which incorporates a magnet 5, numbers of magnetic mterials 2 are embedded while insulated from one another. Over the surface of this developing sleeve 1, the developer made of the magnetic material is allowed to fly greatly outward in the radius direction of the developing sleeve 1 through the operation of a magnetic field, and consequently the developer is stuck to the photoreceptor 6 sufficiently. Then, the magnetic force of the magnet 5 in the developing sleeve 1 and the magnetic permeability and saturation density of the magnetic materials 2 are adjusted to obtain the saturation curve of the magnetic material of the developer closer to a square shape than that of the magnetic materials 2 of the developing sleeve 1, thereby obtaining excellent picture quality with a large gap.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device such as a scanner or an electrostatic recording device using a one-component developer.

- A developing device using a component-based developed image includes a developing sleeve in which a large number of magnetic materials are dispersed on the outer circumferential surface, and a magnet provided inside the developing sleeve and having a large number of magnetic poles in which north poles and south poles are arranged alternately. A developer layer, for example, a single layer of toner, is formed on the circumferential surface of the rotating developing sleeve, and the developer layer is brought into contact with a latent image carrier on which an electrostatic latent image has been formed to visualize the latent image. Developing devices are known.

In the above-mentioned known developing device, an attempt has been made to make the developer layer as thick as possible in order to improve the conveyance of the developer. However, in order to improve the development effect, it is better to have a large charging area of the developer, but when the thickness of the developer layer on the developing sleeve is increased, the electric field near the developing sleeve increases and the charge is reduced. There is a problem in that the amount of charge of the developer cannot be increased too much because run-off occurs.

The present invention provides a developing device that can thin the developer layer of a developer carrier, such as a developing sleeve, in order to increase the amount of charge of the developer, and is also suitable even if there is a gap between the latent image carrier and the developer layer. The object of the present invention is to provide a developing device capable of performing development.

The present invention focuses on the phenomenon in which the magnetic material placed in the tap water moves toward the direction of higher magnetic flux density, and the developer made of the magnetic material is moved outward in the radial direction of the developing sleeve by the action of a magnetic field on the circumferential surface of the developing sleeve. The above object has been achieved by creating a developing device that makes it possible to make a jump M and to make the jump as large as possible.

When a magnetic material is magnetized by induction of a magnetic field, a linear range is formed in which the magnetic susceptibility is proportional to the magnetic field until the strength of the magnetic field reaches a predetermined value, and above a predetermined value, the change in magnetic susceptibility decreases and gradually saturates. -h In the linear range, the magnetic material is v(V-
m'), the magnetic body moves toward the direction of higher magnetic flux density.

As shown in Fig. 1, if the magnetic body 12 is placed above the magnetic pole 11, the lines of magnetic force will be concentrated on the magnetic body 12, and the magnetic flux density will change between the part with the magnetic body and the part without it, so the magnetic flux Density becomes uneven.

By providing the magnetic body 12, the same effect as providing a large number of magnetic poles can be obtained using one magnetic pole. Location A in Figure 1
If there is a fine magnetic material such as iron powder in place A or B,
The magnetic material located at location BK receives a force directed downward in the diagram toward the magnetic material 12 having a large magnetic flux density, and the magnetic material located at location BK receives a force directed upward in the diagram. For fine magnetic materials such as iron powder, move the magnetic material 12 in the left and right direction in the figure, or move the magnetic pole 1
If you move 1 to the left or right, the magnetic fields at locations A and H will change, causing the minute magnetic material to jump up and down in the figure.

In FIG. 2, a developer carrier, for example, a developing sleeve 1tl, is arranged so as to include therein a magnet 5 having multiple poles in which north poles and south poles are arranged alternately. The developer sleeve 1 is conveniently formed as a hollow cylinder having an inner conductive part 4 and an outer dielectric part 3 made of non-magnetic material. A large number of magnetic bodies 2 are embedded in the outer peripheral surface of the dielectric part 3 in a mutually insulated state, and the developing sleeve 1 is embedded with the magnetic bodies 2.
The outer periphery is machined into a cylindrical surface while it is buried and installed.

A latent image carrier 6, such as a photosensitive drum, is provided opposite the developing sleeve 1 with a drying gap therebetween.

A tap is formed by a magnet 5 on the outer periphery of the developing sleeve 1, and the magnetic body 2 of the developing sleeve 1 corresponds to the magnetic body 12 in FIG. 1, and the magnet 5 corresponds to the a pole 11 in FIG. A magnetic flux is formed, and the magnetic flux density is formed as a magnetic field with non-uniformity depending on the presence or absence of the magnetic body 2.

Move the developing sleeve 1 in the direction of arrow A, and move the magnet 5 if necessary.
By rotating the developing sleeve 1 in the direction of arrow B, a layer of developer 7, e.g., a removable toner, is formed on the outer circumferential surface of the developing sleeve 1.
The developer is conveyed to a portion facing the photoreceptor 6 and performs a developing action. An abrasive leveling plate 8 whose distal end portion is close to the outer circumferential surface of the developing sleeve l and which regulates the thickness of the developer layer of the developing sleeve l is supported by a support member 9.

Due to the phenomenon shown in FIG. 1, the layer of toner 7 formed as a thin J- layer on the outer circumferential surface of the developing sleeve L by the leveling plate 8 causes the developing sleeve to rotate 10 times and the magnet 5 to rotate as the case may be.
Due to the 0 rotation, the magnetic toner is transferred to the developing sleeve 10.
It is transported to a position facing the photoreceptor 6 while jumping in the radial direction. Even if there is a certain gap between the surface of the developer layer of the developing sleeve l and the photoreceptor 6 due to the jumping of the toner particles, the toner particles 7 with a true charge are easily moved and attached to the photoreceptor 6 due to the frictional electrification. I can make it.

In order to make the developer sufficiently adhere to the photoreceptor 6 even in a relatively wide gap, it is necessary to make the jumping phenomenon of the developer noticeable.

For this purpose, it is necessary to increase the interaction between the developer, that is, the powdery magnetic material, and the magnetic field formed by the magnetic material in the developing sleeve. The magnetic field due to the magnetic material of the developing sleeve is formed by the relationship between the magnetic field of the magnet 5 in the developing sleeve 1 and the magnetic material 2, so either increase the magnetic force of the magnet or increase the magnetic permeability μ and saturation s flux of the magnetic material. By increasing the density Bs'z or by changing the squareness ratio of the saturation curve of the magnetic material, the strength of the magnetic field produced by the magnetic material of the developing sleeve relative to the developer can be changed. On the other hand, by increasing the magnetic permeability μ and saturation magnetic flux density Bs of the magnetic material constituting the developer, or by making the squareness ratio of the saturation curve close to 1, that is, close to square, the developer and One method is to increase the interaction with the magnetic field.

Since the magnetic material in the developing sleeve is fixed, when the coercive force He is large, the area surrounded by the hysteresis loop becomes large, causing energy loss when one developing sleeve rotates to form a rotating magnetic field. On the other hand, since the developer can move freely to some extent, energy loss is not a problem even if the hysteresis loop is large to some extent. However, if the magnetic permeability μ and saturation magnetic flux density Bs of the developer are too large, the influence of the magnetic field due to the magnetic material of the developing sleeve will be weakened, and the result will be the same as if a uniform developer layer was provided around the developing sleeve. Put it away. Therefore, it is necessary that the magnetic permeability μ and saturation magnetic flux density Bs of the developer be small to some extent.

For the above reasons, in order for the developer to cause a large jump phenomenon, as shown in Figure 3, assuming that the magnetic material constituting the developer has the properties shown by the saturation curve A, the strength of the magnetic field that magnetizes the developer must be In the range of Ho, the magnetic field strength H and the workpiece density B
It is desirable that the relationship shown by straight line B holds true between the two, and that a magnetic material having properties that prevents the a-flux density from reaching a saturated state is embedded in the developing sleeve. As an example of such a preferable state, the magnetic material of the developing sleeve may be soft iron or permalloy, and the magnetic material of the developer may be iron tetroxide tH. The material should be selected in consideration of the magnetic field suitable for development. In this way, in the developing device according to the present invention, the thickness of the developer layer is set to about 20 μm, and the development gap % is 0.
Good image quality was obtained at 2 (1,3 IIJ).As a result, the thickness of the developer layer 't''0-
Compared to the case where the surface of the developer layer is brought into contact with the surface of the photoreceptor when the developer layer is about 5M, the present invention allows the developer layer to be made very thin, and moreover, good image quality can be obtained with a large development gap. .

The same effect can be obtained even if the magnet 5 in the example of FIG. 2 is omitted, the magnet 5 and the magnetic material of the developing sleeve are integrated, and the $ pole is embedded in the developing sleeve.

[Brief explanation of the drawing]

Fig. 1 is a detailed explanatory diagram of the present invention, Fig. 2 is an explanatory diagram of a developing device according to the present invention, and Fig. 3 is a diagram showing the relationship between the canning curves of the magnetic material of the developing sleeve and the magnetic material of the developer. It is. 1...Developing sleeve (developer carrier) 2...Magnetic material 3...Dielectric material 5...Magnet 6...Photoreceptor (latent image carrier) Agent Patent attorney Takeshi Ito Moxibustion- '. ,'l1. l' Figure 3

Claims (4)

[Claims] (1) It has a LiB stone and a developer carrier that moves relative to the magnet, a dielectric layer is formed on the surface of the developer carrier, and fine particles are formed on the surface of the dielectric layer in a mutually insulated state. In a developing device that forms a developer layer on the surface of a developer carrier and develops a latent image at a development position, it faces an electrostatic latent image carrier and develops a latent image. is arranged so that a gap is formed between the electrostatic latent image carrier and the developer layer, and the magnetic material of the developing sleeve and the magnetic material constituting the developer have different magnetic properties. A developing device characterized by being formed as follows. (2) The magnetic properties of the magnetic body are adjusted by the squareness ratio of the saturation curve of the magnetic body, so that the magnetic body constituting the developer is formed closer to a square shape than the magnetic body of the developer carrier. A developing device according to claim 1. (3) The magnetic properties of the magnetic material are adjusted by the magnetic permeability and saturation magnetic flux density of the magnetic material, and the magnetic permeability and saturation a flux density of the magnetic material of the developer carrier are set to be higher than those of the magnetic material constituting the developer. The developing device according to claim 1, characterized in that the developing device is selected from a large number of people. (4) The magnet and the magnetic material of the developer carrier are integrated,
In place of the eight stones mentioned above, magnetic poles are provided in the dielectric layer of the developer carrier.
The developing device according to claim 1, characterized in that the developing device has a cross-section.