JPH09319227A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and surely prevent the leakage of a magnetic developer, without adversely affecting the formation of an image by obtaining the magnetic poles of a magnetic field generating means, with magnetization, at positions within a specific distance from the surface of a developer carrier and providing a seal member inside a developing device. SOLUTION: A developing sleeve 1 as a developer carrier is freely rotatably supported, for instance, driven to rotate counterclockwise at a given speed, so that magnetic toner is held on the periphery of the sleeve 1, to be carried. The developing sleeve 1 is constituted in such a manner that a magnet layer 1b as the magnetic field generating means and an electrode layer 1c for carrying the developer are successively laminated on the outer periphery of a cylindrical dielectric substrate 1a. The magnetic poles of the magnet layer 1b are obtained by the magnetization in the positions within 1mm from the surface of the sleeve 1 and the seal member 4 is provided in the developing device. The magnet layer 1b consists of a mixture of a dielectric material and a magnetic material and in the surface part of the layer 1b, a large number of very small magnetic poles are obtained in a stripe shape by the magnetization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry developing device, and more particularly to a developing device using a one-component magnetic developer.

[0002]

2. Description of the Related Art Generally, in a developing device of a system in which a magnetic field generating means is provided inside a developer carrier to carry a magnetic developer on the surface by a magnetic force and the developer is carried, the developer leaks from both ends of the carrier. Tend. For this reason, a method has been adopted in which seal members are provided at both ends of the transport body to prevent leakage thereof. However, when using the developer transport body in which the magnetic field generating means and the surface portion carrying the developer are integrally formed,
Since the magnetic poles are uniformly magnetized to both ends of the carrier, the magnetic developer is easily moved to both ends by its magnetic force, and it is difficult to prevent the movement by the seal member. If the developer leaks, for example, in the case of a developing device of an electrophotographic copying machine, it contaminates driving parts, bearings, a photoconductor, an optical system or a charger system and other internal components, and seriously impairs the function of the copying machine. It can affect.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and provides a developing device in which leakage of a magnetic developer is easily and reliably prevented without adversely affecting image formation. The purpose is to provide.

[0004]

According to the present invention, in a developing device for supplying a thin layer of magnetic developer to the surface of a latent image carrier, the magnetic field generating means and the surface portion carrying the developer are integrated. Of the magnetic developer is formed on the surface by a magnetic force.The magnetic developer is attracted to the surface by a magnetic force, which is lower than the magnetic force of the image region involved in image formation. A developer carrying member that is carried and conveyed along a predetermined path, and a layer thickness regulating member that regulates the layer thickness of the magnetic developer that is conveyed in contact with or in proximity to the surface of the developer carrying member, And a seal member arranged in a low magnetic force region for preventing leakage of the magnetic developer, wherein the magnetic pole of the magnetic field generating means is magnetized at a position within 1 mm from the surface of the developer carrier. The seal member is provided inside the developing device. Developing apparatus is provided, wherein.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The structure of the present invention will be described below based on specific embodiments. FIG. 1 is a schematic diagram showing a developing device of an electrophotographic copying machine using a one-component magnetic toner as one embodiment of the present invention. In FIG.
A developing sleeve 1 as a developer carrying body is rotatably supported, and is rotatably driven, for example, counterclockwise at a predetermined speed to carry and carry the magnetic toner on its peripheral surface. The developing sleeve 1 is configured by sequentially laminating a magnet layer 1b as a magnetic field generating means and an electrode layer 1c carrying a developer on the outer peripheral surface of a cylindrical conductive substrate 1a. Among them, the magnet layer 1b is formed as follows in order to prevent leakage of the magnetic toner.

The magnet layer 1b of this embodiment is made of a mixture of a dielectric material and a magnetic material. On the surface of the magnet layer 1b, as shown in FIG. It is magnetized in stripes so as to be arranged at intervals of 3 mm or less along the direction. Therefore, as shown in FIG. 1, magnetic poles having different polarities are arranged in the circumferential direction. The both ends of the magnet layer 1b are not magnetized as shown in FIG. In order to easily obtain such a magnetized configuration, the magnetized layer is first magnetized once over the entire peripheral surface, and then, as shown in FIG. Magnetic field generator AG
May be brought close to each other, and the entire periphery of the end may be demagnetized or demagnetized. The magnetic force distribution at the end of the magnet layer 1b obtained in this way is as shown in FIG. In FIG. 4, the vertical axis represents the surface magnetic flux density (magnetic force) Br, and the horizontal axis represents the axial position. In this case, if the area A where the predetermined magnetic force is held is set in the image area, and the area B where the magnetic force starts to decrease and the area C where the magnetic force is almost demagnetized are set in the non-image area, respectively,
The presence of the region does not hinder image formation. Then, the leakage of the developer can be easily prevented without the magnetic developer being forcibly moved toward the end by the magnetic force of the end of the magnet layer 1b as in the related art.

Here, some other modified examples of the magnetized structure will be described. In FIG. 5, magnetic poles of the same polarity are spirally magnetized, and B and C regions in which the magnetic force has been reduced or disappeared are similarly secured at both ends. The magnetic force distribution in this case is substantially the same as that in the case of the stripe shape. Such a magnetized configuration can be obtained by helically magnetizing while appropriately controlling the magnetic force of the magnetizing means when magnetizing both ends, but this is more effective than the above-described case of magnetizing in a stripe shape. difficult. Therefore, it is more preferable to temporarily magnetize the entire peripheral surface in a spiral shape with the same magnetic force and then erase the magnetic force at both ends from outside by, for example, the above method. This magnetized structure has the effect of suppressing the vibration of the magnetic blade for toner thinning, which will be described later.

FIG. 6 (a) shows the entire surface of the magnet layer 1b except for both ends magnetized to the same polarity (indicated by oblique lines), and is therefore shown in FIG. 6 (b). As described above, the magnetic pole of the opposite polarity is formed on the conductive base 1a side. In this case as well, the magnetic poles of the same polarity may be once magnetized on the entire peripheral surface, and then the both ends may be demagnetized. Specifically, the magnet layer 1
This is possible by using a permanent magnet that generates a magnetic field sufficiently larger than the coercive force of the material constituting b as the magnetic force erasing means, and repeating the operation of moving this closer and slower than the rotation speed of the developing sleeve 1 '. It is.

FIG. 7 (a) shows the end of the peripheral surface of the magnet layer 1b uniformly magnetized with the same polarity, which is slightly closer to the center than the end surface in the non-image area not involved in image formation. The portion E is selectively demagnetized over the entire circumference.
Therefore, the magnetic force distribution in the axial direction is shown in FIG.
As shown in. That is, the magnetic force is locally reduced at a portion E in the non-image area, and a repulsive magnetic field is formed at the portion E. This repulsive magnetic field is effective for preventing the magnetic developer from moving to the end of the developing sleeve 1.

FIG. 8 (a) shows a developing sleeve 1 'which is magnetized in a stripe shape, in which a permanent magnet is brought close to the end of the developing sleeve 1' so that the entire peripheral surface of the end is made to have one polarity, for example, N pole. It is magnetized. In this case, the lines of magnetic force are formed as shown in FIG. 8 (b), and the magnetic force of one polarity on the peripheral surface of the end portion is set to be relatively small, and therefore is the same as that of the magnet layer 1b of another magnetized configuration. This has the effect of preventing leakage of the magnetic developer.

[0011] Returning to FIG. 1, on the magnet layer 1b is a float electrode comprising a number of microelectrodes 1c ₁ is held in an electrically insulated state from each other on the surface portion by a holding member made of a dielectric material The layer 1c is laminated. The electrode layer 1c of this example is thinly laminated so that the layer thickness is within 1 mm. Therefore, the substantially same area as the B and C areas of the magnet layer 1b may be set as the non-image area as the B and C areas on the peripheral surface of the developing sleeve 1.

A hopper 2 that stores toner T and replenishes the peripheral surface of the developing sleeve 1 in an appropriate amount is disposed at an appropriate position near the peripheral surface of the developing sleeve 1 configured as described above. The toner T of this example is a one-component magnetic toner, and has a mean particle size of about 6 μm and a true specific gravity of 1.75 mixed with a magnetic powder in a resin.
It has been adjusted to be.

A doctor blade 3 made of an elastic magnetic material such as an SK material is disposed downstream of the hopper 2 in the rotation direction of the developing sleeve 1. Doctor blade 3
Is brought into contact with the peripheral surface of the developing sleeve 1 by its appropriate pressure contact force, which is a combination of the pressing force set in the holding portion 3a holding one end and the magnetic force of the magnet layer 1b, and is conveyed by the pressure contact portion P. The toner T coming in is pinched, the layer thickness is regulated to form a thin toner layer, and the friction at this time triboelectrically charges the charge necessary for development. In this case, the periphery of both ends of the developing sleeve 1 is configured as follows to prevent the leakage of the magnetic toner T.

As shown in FIGS. 9 (a) and 9 (b), the doctor blade 3 has its side end 3c in the B and C regions of the above-mentioned magnet layer 1b on the peripheral surface of the developing sleeve 1. In the areas B and C where the magnetic force set in the non-image area corresponding to the above-mentioned area does not decrease or act, the magnetic force is provided so as to abut or approach the developing sleeve 1. A sealing member 4 for preventing the toner T from leaking from the doctor blade 3 is also brought into contact with the developing sleeve 1 in the non-image areas B and C. That is, the doctor blade side end portion 3c and the seal member 4 overlap each other in the non-image areas B and C on the peripheral surface of the developing sleeve 1. The doctor blade 3 of the present embodiment is provided so that the side end 3c is inclined with respect to the circumferential direction of the developing sleeve 1, and the developing sleeve 1 is mainly disposed in the B region where the magnetic force is decreasing in the B and C regions. It is in sliding contact with the peripheral surface.
In this way, by overlapping the doctor blade 3 and the seal member 4 in the region where the magnetic force at both ends of the developing sleeve 1 is reduced or does not act, leakage of the magnetic toner T can be reliably prevented.

In FIG. 1, at an appropriate position on the downstream side of the above-mentioned doctor blade 3 near the peripheral surface of the developing sleeve 1,
For example, on the side opposite to the position where the doctor blade 3 is disposed as in the present embodiment, the endless photosensitive belt 5 rotatably disposed and the developing sleeve 1 come into rolling contact, and the developing sleeve 1
The thin toner layer T ₁ carried on the surface is supplied to the surface of the photoreceptor belt 5. The photoreceptor belt 5 is formed by laminating a photoconductive layer made of a photoconductive substance on a belt-shaped conductive base, and after forming an electrostatic latent image through uniform charging and image exposure processes in appropriate places. , reaches the arrangement position D of the developing device of the present invention, wherein the receiving a supply of the toner thin layer T _1, an electrostatic latent image is visualized.

[0016]

As described above in detail, according to the present invention, by providing the region where the magnetic force is reduced or does not act on the surface of the side end portion of the developer transport body provided with the magnetic field generating means in the developer transport direction, The movement of the magnetic developer toward the side end portion is suppressed, and the leakage of the magnetic developer from the side end portion can be easily prevented. Therefore, by setting the side end area as a non-image area and overlapping the layer thickness regulating member and the seal member in this area, leakage of the magnetic developer can be reliably prevented without adversely affecting image formation. Can be. It should be noted that the present invention is not limited to the above specific embodiments, and it is needless to say that various modifications can be made within the technical scope of the present invention. For example, the developer transporting body may be a developing sleeve having no float electrode layer or a developing sleeve having a normally magnetized magnet layer instead of a finely magnetized type.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory view showing a magnetized configuration of a magnet layer in one embodiment of the present invention.

FIG. 3 is a perspective view showing a method for manufacturing a magnet layer according to one embodiment of the present invention.

FIG. 4 is a graph showing a magnetic force distribution of a magnet layer in one example of the present invention.

FIG. 5 is an explanatory view showing a modification of the magnetizing configuration.

FIGS. 6A and 6B are explanatory views showing other modified examples of the magnetized configuration, respectively.

FIGS. 7A and 7B are an explanatory view showing still another modified example of the magnetized configuration and a graph showing the magnetic force distribution thereof.

8A and 8B are an explanatory view and a perspective view showing still another modified example of the magnetized configuration.

FIG. 9A and FIG. 9B are explanatory views respectively showing a configuration around a developing sleeve side end portion of one embodiment of the present invention.

[Explanation of symbols]

 1: Development sleeve 1b: Magnet layer 3: Doctor blade 4: Seal member

Front page continuation (72) Inventor Hiromi Ogiyama 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (1)

[Claims] 1. In a developing device for supplying a magnetic developer in a thin layer onto the surface of a latent image carrier, a magnetic field generating means and a surface portion carrying the developer are integrally formed, and the developer on the surface is formed. A low magnetic force region having a lower magnetic force than the magnetic force of the image region involved in image formation is set at the side end portion with respect to the conveying direction, and the magnetic developer is attracted to the surface by the magnetic force and carried and conveyed along a predetermined path. A developer carrier, a layer thickness regulating member that regulates the layer thickness of the magnetic developer that is conveyed in contact with or close to the surface of the developer carrier, and a magnetic developer disposed in the low magnetic force region. A seal member for preventing leakage of the magnetic field, the magnetic pole of the magnetic field generating means is magnetized at a position within 1 mm from the surface of the developer carrier, and the seal member is provided inside the developing device. Developing device.