JPS60153070A - Magnetic brush developing roller - Google Patents

Abstract

PURPOSE:To carry a developer uniformly and form an excellent image by arranging a magnetic member consisting of plural parts with different magnetic attenuation effect in the space between a magnet roller and a nonmagnetic sleeve. CONSTITUTION:The magnetic member 12 is extended in the space between the magnet roller 10 and nonmagnetic sleeve 11 to a partial inner circumference. Magnetic charges are induced in the magnetic member 12 with a magnetic field established by the magnet roller 10 and the magnetic field from the magnetic poles of the magnet roller 10 is concentrated on among the induced magnetic charges, so the magnetic attenuating effect occurs to attenuate the intensity of the magnetic field formed on the nonmagnetic sleeve 11. Consequently, proper magnetic fields are formed corresponding to functions at respective positions of the developing roller to carry the developer uniformly and obtain an excellent image.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a magnetic brush that rotatably supports a magnet roller inside a non-magnetic sleeve and develops while conveying magnetic developer on the non-magnetic sleeve by the rotation of the magnet roller. This relates to the developing roller.

Conventional technology Conventionally, a non-magnetic sleeve is arranged around the outer periphery of a magnetic roller, and a magnetic brush made of a magnetic developer such as a two-component magnetic developer made of a magnetic carrier and a toner or a one-component magnetic developer is formed on this non-magnetic sleeve. A magnetic brush development method for developing a latent image has been put into practical use. FIG. 1 is a schematic cross-sectional view showing the configuration of a conventional magnetic brush developing device. A developing roller 2 is disposed opposite a photosensitive drum 1 on which an electrostatic latent image is formed. The developing roller 2 includes a magnet roller 3 which is rotatably supported and magnetized with a large number of magnetic poles having substantially equal magnetization, and a "non-magnetic sleeve 4" which is rotatably supported on the outer periphery of the magnet roller 3. A magnetic brush is formed on the top of this non-magnetic sleeve.A guide plate 8 is placed around the developing roller 2 to stir the developer in the height regulating plate 5, scraper 6 and developing housing 7.
A paddle wheel 9 is provided which cooperates with the roller to supply developer to the developing roller 2. In this example, the non-magnetic sleeve Φ rotates in the direction of the arrow, the magnet roller 3 rotates in the direction of the arrow, and the developer on the non-magnetic sleeve 4 is conveyed in the direction of the arrow A. The developer supplied from the paddle wheel 9 is regulated to a constant thickness by the height regulating plate 5 and then rubbed against the photosensitive drum 1 to develop the electrostatic latent image formed on the photosensitive drum 1. After development, the developer is scraped off by the scraper 6, and new developer is supplied again. In this way, the configuration deviation is always constant because the developer on the non-magnetic sleeve 4 is conveyed at a uniform speed along the circumferential direction of the developing roller 2 as the magnet roller 8 rotates. i! This method has the advantage that a large amount of developer is supplied to the development area and a good image can be formed.

However, the optimal conditions for the magnetic field strength at each part of the developing roller are different, and must be set so that a magnetic field is formed according to the function of each part. For example, at the development position facing the photosensitive drum 1, a strong magnetic field of approximately 800 Gauss is generated on the non-magnetic sleeve 4 in order to cause the developer to stand up in spikes at high density and completely rub against the photosensitive drum. If you don't, you won't be able to do it. On the other hand, it is desirable that the magnetic field does not act at all at the scraping position where the scraper 6 comes into contact. In addition, at the hot height regulation position, 800
If a strong magnetic field on the order of Gauss is formed, it becomes impossible to regulate the height of the developer, and the developer is inconveniently exposed to stress from the B depression regulating plate 5. Therefore, a developer layer of a predetermined thickness cannot be transported. A magnetic field of approximately Further, at the developer supply position facing the paddle wheel 9, a magnetic field strength sufficient to attract the developer in the packet 9a of the paddle wheel 9 is required. Therefore, if a large number of equally magnetized magnet rollers are used, the developer can be conveyed effectively at the development position, but the magnetic force is too large at the scraping position where the scraper comes into contact, the height regulation position, and the developer supply position. Otherwise, stress is applied to the developer, which tends to deteriorate the developer.Furthermore, the stress applied to the developer causes the inconvenience that the toner is fused onto the non-magnetic sleeve 4 and the scraper 5.

OBJECTS OF THE INVENTION An object of the present invention is to provide a magnetic brush developing roller that can eliminate the above-mentioned drawbacks, can form a magnetic field on a non-magnetic sleeve according to each part of the developing roller, and can smoothly transport developer. It is in.

Summary of the Invention The present invention provides a magnetic brush developing roller in which a magnetic roller is rotatably supported inside a non-magnetic sleeve, and the magnetic developer on the non-magnetic sleeve is conveyed and developed by the rotation of the magnetic roller. This is characterized in that a magnetic member consisting of a plurality of parts having different magnetic damping effects is disposed in the space between the non-magnetic sleeve and the magnetic sleeve.

Embodiment FIG. 2 is a diagrammatic sectional view showing the structure of an example of a magnetic brush developing roller according to the present invention. A plurality of magnet rollers 10 having substantially equal magnetization are rotatably supported, and a non-magnetic sleeve 11 is provided around the outer periphery of the magnet roller 10.
Rotatably supported. And magnet roller 10
The developer on the non-magnetic sleeve is conveyed uniformly in the circumferential direction by rotating both the sleeve and the non-magnetic sleeve in the direction of the arrow. In this example, the magnetic member 12 is made to extend over a partial circumference within the space between the magnet roller 10 and the non-magnetic sleeve 11. When the magnetic member 12 is disposed around the magnet roller 10, induced magnetic charges are induced in the magnetic member 12 by the magnetic field emitted from the magnet roller 10, and the magnetic field emitted from the magnetic poles of the magnet roller 10 is concentrated between the induced magnetic charge and the magnetic member 12. Therefore, a magnetic damping effect occurs that damps the strength of the magnetic field formed on the non-magnetic sleeve II. This magnetic damping effect can be changed by changing the magnetic permeability and thickness of the magnetic member 12 provided. For example, "magnetic member 1
There is a characteristic that as the thickness of the non-magnetic sleeve 2 increases, the strength of the magnetic field formed on the non-magnetic sleeve 11 becomes weaker. As the side slope of this magnetic member, magnetic materials such as soft iron, silicon steel plate, permalloy, sendite, nickel, ferritic or martensitic stainless steel, or magnetic substances such as ferrite and magnetite are sintered and used in the form of a plate. It is also possible to do so. In this example, by utilizing this magnetic damping effect, silicon steel plates are laminated and the thickness of each portion of the magnetic member 12 is changed by changing the number of laminated sheets. In FIG. 2, the portion facing the scraper 13 is formed thickest to increase the amount of magnetic attenuation. Next, the part facing the paddle wheel 14 is made slightly thin enough to suction and convey the developer supplied from the paddle wheel 14, and the part facing the height regulating plate 15 is made the thinnest. The configuration is such that the magnetic member 12 does not extend to the portion facing the drum 16.

With this configuration, even in a magnetic brush developing roller that rotates a uniformly magnetized magnet roller 10 to convey developer, the developing roller can be changed by simply changing the thickness of each part of the magnetic member 12 disposed. It is possible to form an appropriate magnetic field depending on the function of each position. In FIG. 3, a soft iron plate is used as the magnetic part side 12 and processed so that the thickness changes for each part. In this way, the same effect can be achieved even if a single magnetic plate is used and the thickness is changed for each part by cutting.

FIG. 4 is a diagrammatic sectional view showing the structure of a modified example of the magnetic brush developing roller according to the invention. In this example, magnetic member 2
0, a mesh-like magnetic material or a magnetic porous plate with different opening diameters and opening densities is used. If an opening is provided in the magnetic member 20, as is the case, the lines of magnetic force from the magnet roller 10 on the inside pass through the opening 20a and are formed on the non-magnetic sleeve ll on the outer periphery.
It is Noh. For example, to increase the amount of magnetic attenuation, the aperture area ratio may be decreased, and to decrease the amount of magnetic attenuation, the aperture area ratio may be increased. In this row, ・Scraper 13
No opening is formed in the portion facing the paddle wheel 14 to maximize magnetic attenuation, and a small diameter opening 20a is formed in the portion facing the paddle wheel 14.

Next, a large diameter opening 2 is provided in the portion facing the height regulating plate 15.
0a to minimize the tm magnetic attenuation. With this configuration, the magnetic member 20 can be made of a relatively thin plate-like material, and by simply forming the openings 20a with different opening area ratios by performing etching or electroforming on this, the magnetic member 20 can be magnetically formed in each part. Since the amount of attenuation can be changed and the space between the magnet roller 10 and the non-magnetic sleeve 11 can be made smaller, there is an advantage that the developing roller can be made smaller.

FIG. 5 is a diagrammatic sectional view showing the structure of another modification of the magnetic brush developing roller according to the present invention. In this example, a magnetic wire is used as the magnetic member 30, the magnetic wire is stretched in the longitudinal direction of the developing roller, and the wire spacing is changed for each part. With this configuration, it is possible to similarly change the opening area ratio, and it is possible to exhibit a magnetic damping effect depending on each position of the developing roller.

FIG. 6 is a perspective view showing an example of the external configuration of the magnetic member according to the present invention. In this example, the magnetic member 40 is made of a cylindrical magnetic material, and an opening ΦOa is formed at a position facing the photosensitive drum, and a small-diameter opening 40b is formed at a developer supply position. In other parts, the thickness of the magnetic material or the aperture ratio is changed. With this configuration, the magnetic member 40 can be fixed at both ends, making it easy to arrange the magnetic member 40.

Although the above-mentioned embodiments have been described using a two-component magnetic developer, the magnetic brush developing roller of the present invention is also effective when using a two-component magnetic developer. That is, even when using a -component magnetic developer, it is necessary to form an appropriate magnetic field on the non-magnetic sleeve at the development position and the height regulation position.

Furthermore, in the above-mentioned embodiment, the magnetic field of the magnet roller is attenuated at the position facing the scraper, the developer supply position, and the height regulation position, but the magnetic field is not limited to these positions. The position at which the magnetic field is attenuated and the amount of attenuation should be set in consideration of the amount of charge on the developing roller, the conveyance speed and rotational speed of the developing roller, and the like. Further, in the above-described embodiments, the magnetic member is constructed as a single piece, but it may be constructed as a plurality of separate pieces.

Further, in the above-described embodiment, the magnetic roller and the non-magnetic sleeve are both rotated to convey the developer, but the same effect can be achieved even if only the magnetic roller is rotated and conveyed. It is. In this case, a configuration may be adopted in which magnetic members having different amounts of magnetic attenuation are fixed for each portion on the inner surface of the fixed non-magnetic sleeve.

DETAILED DESCRIPTION OF THE INVENTION As described in detail, according to the present invention, an appropriate magnetic field can be formed on the non-magnetic sleeve according to the function of each position of the developing roller, and the developer can be conveyed uniformly, thereby preventing deterioration of the developer. This makes it possible to extend the service life and form good images.

In particular, the space between the magnet roller and the non-magnetic sleeve can be reduced by using a mesh-like magnetic member or a magnetic perforated plate with a different opening area ratio for each part as a magnetic member that exhibits a magnetic damping effect. This makes it possible to downsize the developing roller.

[Brief explanation of drawings]

The first sentence is a diagrammatic sectional view showing the configuration of a conventional developing device; FIG. 2 is a diagrammatic sectional view showing the configuration of an example of a magnetic brush developing roller according to the present invention; FIGS. Magnetic brush development according to the invention 11...
Non-magnetic sleeve, 12, 30.40... Magnetic member, 13... Scraper, ■4... Paddle wheel, 15... Height regulation &
, 16... Photosensitive drum J Figure 1, Figure 2, Figure 3

Claims (1)

[Claims] L A magnetic brush developing roller in which a magnetic roller is rotatably supported inside a non-magnetic sleeve, and the magnetic developer on the non-magnetic sleeve is conveyed and developed by the rotation of the magnetic roller. A magnetic brush developing roller characterized in that a magnetic member consisting of a plurality of parts having different magnetic damping effects is disposed in a space between the roller and the non-magnetic sleeve. λ The magnetic brush developing roller according to claim 1, wherein the magnetic member is constructed of a magnetic member having a different thickness for each portion. & The magnetic brush developing roller according to claim 1, wherein the magnetic brush is constructed of a magnetic member using a mesh or a perforated plate and having a different opening diameter and/or opening soundness for each part. .