JP2001319810A - Magnet roller and developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnet roller which has a broad peak magnetic force width for a specific pole in a magnetized pattern and a stable peak position and a developing device using the roller. SOLUTION: The magnet roller 20 is provided with four bar-like magnet pieces 22A-22D which are magnetized to respectively have N1 pole, S1 pole, N2 pole, and S2 pole on the outer periphery of the roller 20 and have fan-shaped cross sections. In the roller 20, a flat section 22K extended in the lengthwise direction is formed on the outer periphery of the magnet piece 22B having the specific pole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnet roller and a developing device used in a copying machine using a magnetic toner, such as a laser printer.

[0002]

2. Description of the Related Art Conventionally, in a copying machine such as an electrophotographic copying machine or a laser printer, an electrostatic latent image is formed on a photosensitive drum, and a magnetic toner is attached to the electrostatic latent image by a developing device. This is transferred to a storage medium such as paper and developed. FIG. 5 is a diagram showing a configuration of a conventional developing device 40. The developing device 40 includes a rotating cylindrical sleeve 51. As shown in FIG.
A developing roller 50 provided with a cylindrical magnet roller 52 having a predetermined magnetic force pattern magnetized therein,
In accordance with the magnetic force pattern, the magnetic toner T stored in the developing container 53 is sucked onto the surface of the sleeve 51 and conveyed. After the magnetic toner T is formed into a uniform thin layer by the layering blade 54, The magnetic toner T is adhered on the electrostatic latent image.
Thereafter, the magnetic toner T remaining on the surface of the sleeve 1 is separated from the sleeve 51 and collected.

[0003] The magnet roller 52 is shown in FIG.
As shown in FIG. 6, after a cylindrical roll body 52A made of a ferrite-based bonded magnet using ferrite magnetic powder such as St ferrite or Ba ferrite is integrally formed with a metal shaft 52B, FIG. As shown in the figure, a predetermined magnetization pattern is magnetized in the circumferential direction of the roll main body 52A. Since various patterns are required for the magnetic force pattern depending on the specifications of the copying machine, for example, as shown in FIGS. 7A and 7B, the magnetic pole on the outer peripheral side is previously attached to the N pole or the S pole. A lamination type magnet roller 62 that forms a roll body 62A by laminating a plurality of side surfaces of a magnetized bar-shaped magnet piece 62P having a fan-shaped cross-sectional shape to the outer periphery of a metal or resin shaft 62B. Are often used. FIG.
Is a diagram showing an example of a magnetic force pattern formed in the circumferential direction of these magnet rollers 52 and 62. The magnetic force pattern has a peak value near the center of each of the magnetic poles N1, S1, N2 and S2. The magnitude of the peak magnetic force width, that is, the width (pole width) of the region where the magnitude of the magnetic force is maintained within 50 G of the peak value before and after the peak value of the magnetic force is generally 10 degrees in angle. ° to 16 °.

[0004]

Incidentally, the magnet rollers 52 and 62 are formed of magnet rollers in order to allow a tolerance for the assembly accuracy of the developing device 40, for example, the set position of the layering blade 54. In some cases, a specific pole having a peak magnetic width of 20 ° or more is required. However, in both the conventional integral molding type and the lamination type magnet roller, if the normal magnetization method is used to widen the peak magnetic force width of the magnetic force, the magnetization method becomes complicated, and equipment is required. There were problems such as an increase in size and a time required for the magnetization step. Further, there are problems that the peak position becomes unstable and the magnitude of the magnetic force in the longitudinal direction is not uniform.

The present invention has been made in view of the conventional problems, and has a wide peak magnetic force width of a specific pole of a magnetization pattern.
It is another object of the present invention to provide a magnet roller having a stable peak position and a developing device using the same.

[0006]

According to a first aspect of the present invention, there is provided a magnet roller provided with a flat portion extending in a length direction on an outer peripheral side of at least one specific pole of a magnetization pattern.

According to a second aspect of the present invention, there is provided a magnet roller wherein at least one of the magnet pieces of the magnet roller is constituted by arranging a plurality of magnet pieces in a circumferential direction on an outer peripheral portion of a cylindrical shaft. A flat portion extending in the length direction is provided on the outer peripheral side of the magnet piece.

According to a third aspect of the present invention, the magnet roller having the flat portion has a parallel orientation.

According to a fourth aspect of the present invention, there is provided a magnet roller formed by molding the magnetic material or the magnet piece by dispersing a magnetic powder of a magnetic ferrite or a rare earth alloy in a resin binder.

According to a fifth aspect of the present invention, there is provided the developing device according to the first aspect.
4. A magnet roller comprising:

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1A and 1B are diagrams showing a configuration of a developing roller according to the present embodiment.
(A) is a front view, and (b) is a sectional view taken along line AA of (a). The developing roller 10 has a cylindrical sleeve 11 made of a non-magnetic material, a holding portion 12 fitted to both ends of the sleeve 11 to fix the sleeve 11, and is coaxially disposed inside the sleeve 11. A cylindrical magnet roller 2 magnetized in a previously designed magnetic force pattern;
0. The holding portion 12 is provided on the outer sleeve 1.
Step 12 whose diameter on one side is smaller by the thickness of sleeve 11
a stepped cylinder having a, at the center of its outer end face,
A cylindrical shaft 12b protruding outward is provided, a circular concave portion 12c is provided at the center of the inner short surface, and both ends of the sleeve 11 are fixed at a fixed portion 12d provided at the step portion 12a. , Is fixed to the holding portion 12 with an adhesive or the like.

As shown in FIG. 2, the magnet roller 20 has a cylindrical shaft 2 made of metal or resin.
1 and a roller main body 22 magnetized in a predetermined magnetic force pattern provided on an outer peripheral portion of the shaft 21. Both end portions 21 a of the shaft 21 are held, for example, via a bearing 13 by a holding portion. 12 (see FIG. 1B). The roller body 22 of the magnet roller 20 has a length corresponding to the length of the shaft 21 along the circumferential direction of the outer peripheral portion of the shaft 21. The four bar-shaped magnet pieces 22 </ b> A to 22 </ b> A extending in the direction and having a fan-shaped cross section.
22D is formed by bonding the side surfaces of adjacent magnet pieces together. In the present embodiment, each of the magnet pieces 22A to 22A
As 2D, a magnetic powder obtained by making a ferrite-based sintered magnet such as St ferrite or Ba ferrite into a fine powder is combined with a binder (binder) such as a thermoplastic resin such as nylon, polyethylene or EVA (ethylene-vinyl acetate copolymer). )
After the resin magnet composition dispersed in the above was molded by injection molding or the like, a ferrite bond magnet magnetized such that the magnetic poles on the outer peripheral side became predetermined magnetic poles was used.

In the present embodiment, the sectional shape of the magnet piece 22B constituting the layer regulating pole (S1 pole), which is a specific pole, is different from the other magnet pieces 22A, 22C, 22D, and the inner circumferential side is Although it is arc-shaped, a flat portion 22K is formed on the outer peripheral side. The magnet piece 22B is formed so that the magnetic powder is oriented uniformly in a magnetic field in which the direction of the applied magnetic field is perpendicular to the surface to be the flat portion 22K, without the magnetic force lines being concentrated at one place in the outer peripheral portion. That is, a flat portion 22K having a width W extending in the length direction is provided on a part of the outer periphery of the bar-shaped magnet piece whose cross-sectional shape is formed into a fan shape by milling or the like after performing so-called parallel orientation. Thus obtained. In addition, the orientation method of the magnet pieces is shown in FIG.
As shown in (b), there is a concentrated orientation in which the magnetic powder is oriented and molded so that the magnetic force lines in the magnet piece 22B are directed toward the center of the outer peripheral portion. In the present embodiment, the peak magnetic force width is wider. A parallel orientation is adopted that can be made and the magnetic pole position after magnetization is easily stabilized.

FIG. 4 is a sectional view of the flat portion 22K of the magnet piece 22B having a diameter of φ16 mm and a width W of φ16 mm manufactured as described above.
FIG. 4 is a schematic diagram illustrating an example of a magnetic force pattern of the magnet roller 20 where = 4.3 mm. The peak magnetic force width of the magnet piece 22B having the flat portion 22K was about 30 °, and a peak magnetic force width wider than the conventional peak magnetic force width of 10 ° to 16 ° could be obtained. The peak magnetic force width is wider as the width W of the formed flat portion 22K is larger, and practically, for example, when the diameter is φ16 mm, W = 2.5
By setting it to 力 8.0 mm, it is possible to obtain a peak magnetic force width of a width of 20 ° to 40 °. The flat portion 22 necessary to secure a peak magnetic force width of 20 ° or more is used.
The size of the width W of K is appropriately determined by the diameter of the magnet roller 20, the size of the magnet piece 22B, the material forming the magnet piece 22B, and the like.

As described above, according to the present embodiment, the four bar-shaped magnets having a fan-shaped cross section and whose outer magnetic poles are magnetized to the N1, S1, N2, and S2 poles, respectively. In the magnet roller 20 having the pieces 22A to 22D, a flat portion 22K extending in the length direction is formed on the outer peripheral side of the magnet piece 22B of the specific pole, so that the peak magnetic force width is as wide as 20 ° or more and the magnetic pole position is increased. The magnet roller 20 having the stable specific pole (S1 pole) can be obtained. Further, since the developing device using the magnet roller 20 includes the magnet roller 20 having the layer regulating pole (S1 pole) having a wide peak magnetic force width, the allowable width of the set position of the layering blade 54 is simple. And the manufacturing process of the developing device can be simplified.

In the above-described embodiment, the bonding type magnet roller 20 has been described. However, in the case of an integrally formed magnet roller, a flat portion extending in the length direction is formed, so that the same as in the above-described example is obtained. In addition, a specific pole having a wide peak magnetic force width and a stable magnetic pole position can be obtained. In the above example, each magnet piece 22
A to 22D are formed of ferrite-based bond magnets. However, when high magnetic force is required, for example, as in a small magnet roller, Sm-Fe-N is used as the magnetic powder forming the bond magnet. The magnet pieces 22A to 22D may be manufactured using a rare earth-based bonded magnet using magnetic powder of a rare earth alloy such as an alloy or an Sm-Co alloy.
In addition, the flat portion 22K may be formed by milling or the like after molding, either in a laminated type magnet roller or an integrally molded magnet roller, or may be a mold having a flat portion in the outer peripheral portion in advance. Alternatively, it may be formed by using it. In the above example, the specific pole is the layer regulating pole. However, the present invention is not limited to this. The position and number of the specific pole are appropriately determined according to the specifications of the developing device.

[0017]

As described above, according to the first aspect of the present invention, the flat portion extending in the length direction is provided on the outer peripheral side of at least one specific pole of the magnetization pattern.
With a simple configuration, it is possible to obtain a magnet roller having a specific pole having a wide peak magnetic force width.

According to the second aspect of the present invention, among the magnet pieces of the magnet roller configured by arranging a plurality of magnet pieces along the circumferential direction on the outer peripheral portion of the cylindrical shaft,
Since a flat portion extending in the length direction is provided on the outer peripheral side of at least one magnet piece, it is possible to obtain a bonding type magnet roller having a specific pole having a wide peak magnetic force width.

According to the third aspect of the present invention, since the magnet pieces having the flat portions are used in parallel orientation, the peak magnetic force width can be further increased.

According to the fourth aspect of the present invention, the magnetic material or the magnet piece is constituted by a bonded magnet formed by molding a magnet composition in which a magnetic powder of a magnetic ferrite or a rare earth alloy is dispersed in a resin binder. The flat portion can be easily formed by milling or molding.

According to a fifth aspect of the present invention, there is provided the developing device according to the first aspect.
Since it was equipped with the magnet roller described in any one of 4 above,
For example, it is possible to allow a margin in the assembling accuracy of the developing device such as the allowable width of the setting position of the stratification blade, and to simplify the manufacturing process of the developing device.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a developing roller according to an exemplary embodiment.

FIG. 2 is a diagram showing a configuration of a magnet roller according to the embodiment.

FIG. 3 is a diagram showing a method of magnetizing a magnet piece.

FIG. 4 is a diagram showing a magnetization pattern of the magnet roller according to the embodiment.

FIG. 5 is a diagram illustrating a configuration of a conventional developing device.

FIG. 6 is a diagram showing a configuration of a conventional integrated magnet roller.

FIG. 7 is a diagram illustrating a configuration of a conventional laminated magnet roller.

FIG. 8 is a diagram showing a magnetization pattern of a conventional magnet roller.

[Explanation of symbols]

10 developing roller, 11 sleeve, 12 holder, 1
2a Step, 12b Developing roller shaft, 12c
Recess, 12d fixed part, 13 bearing, 20 magnet roller, 21 shaft of magnet roller,
22 magnet roller body, 22A to 22D magnet pieces, 22K flat part.

Claims (5)

[Claims] 1. A magnet roller in which a predetermined magnetization pattern is formed in a circumferential direction of a cylindrical magnetic body, a flat portion extending in a length direction is provided on an outer peripheral side of at least one specific pole of the magnetization pattern. A magnet roller. 2. A magnet roller comprising a plurality of magnet pieces arranged in a circumferential direction on an outer peripheral portion of a columnar shaft. The magnet roller according to claim 1, further comprising a flat portion extending in a length direction. 3. A magnet piece having a flat portion which is parallel-oriented.
The magnet roller according to the above. 4. The magnetic material or magnet piece according to claim 1, wherein the magnet composition is formed by dispersing magnetic powder of magnetic ferrite or a rare earth alloy in a resin binder. The described magnet roller. 5. A developing device comprising the magnet roller according to claim 1.