JPS6059377A - Magnet roll - Google Patents

Abstract

PURPOSE:To obtain a small-sized, small-diameter magnet roll with high performance by using a cylindrical rubber magnet and an anisotropic magnet in combination. CONSTITUTION:Only part of the cylindrical rubber magnet material 10A is so oriented as to have magnetic anisotropy in a circumferential direction as shown by dotted lines, and axial grooves 20 are also formed. Rod-shaped anisotropic rubber magnet materials 21 which are so oriented as to have magnetic anisotropy nearly in parallel to the straight line connecting magnetic poles to be magnetized previously are fitted fixedly in the grooves 20. Then, the magnet material 10A and magnet materials 21 are so magnetized as to the magnetic poles on the circumferential surface. In this case, the part having the magnetic anisotropy is magnetized in its direction to obtain the cylindrical rubber magnet 11 having sufficiently intense magnetic poles N1 and S1 formed facing a photosensitive drum. Magnetic poles N2 and S2 at other parts may be relatively weak. A rectangular shaft body 13 is provided in the center hole 12 of the magnet 11 and one surface of the rectangular shaft body 13 is in specific position relation with the magnetic poles.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnet roll used as a developing roll of an electrostatic copying machine.

In electrostatic copying, a developer is used that is a mixture of toner (pigment (1)) and carrier (magnetic powder), or a developer that has the properties of both pigment and magnetic powder. A magnetic roll is provided inside a magnetic cylindrical sleeve and is attracted to the outer peripheral surface of the sleeve to form a magnetic brush, and a photosensitive drum having an electrostatic latent image previously charged by a charging device using electrostatic development is formed. The most widely used method is the magnetic brush method, which produces a visible image by rubbing.

Conventionally, there has been a magnet roll shown in FIG. 1 as a component of this magnetic brush.

This magnet roll consists of a hollow cylindrical permanent magnet 1 that is a long, seamless piece in the longitudinal direction and is fixed with an adhesive through a cylindrical shaft 2. The cylindrical permanent magnet 1 is made of rubber, chlorinated polyethylene, etc. Rubber magnets, in which magnetic particles such as ferrite particles are extruded and magnetized by mixing a polymeric material such as vinyl chloride with a polymer material such as vinyl chloride, have come to be employed from the viewpoint of reducing the diameter.

In this case, the second method of magnetizing the hollow cylindrical permanent magnet 1 is
As shown in the figure, it is most common to form symmetrical magnetic poles N and S of the same strength at equal intervals on an isotropic magnet. However, in the case of a rubber magnet, magnetizing an isotropic magnet material tends to result in insufficient magnetic pole strength.

In consideration of this point, the present applicant has provided only a part of the old cylindrical rubber magnet 10 in the figure so that at least one of the magnetic poles of the cylindrical rubber magnet is sufficiently strong as shown in FIG. As shown by the dotted line, the magnetic poles are oriented so as to produce magnetic anisotropy in the circumferential direction, and have sufficiently strong magnetic poles N, S, and weak magnetic poles N.
2. It has been proposed to form S, and. On this occasion,
The strong magnetic poles N, , S should be located at the portions that should face the photoreceptor drum.

However, recently there has been a demand for smaller diameter magnet rolls, and even with the configuration shown in FIG. 3, the strength of the magnetic poles may be insufficient. The reason for this is that when only a part of the cylindrical rubber magnet +410 is oriented so as to produce magnetic anisotropy in the circumferential direction as shown by the dotted line in FIG. is weakly oriented in the radial direction, and this causes the magnetic tMNz, St
This is because it has the effect of impeding the passage of magnetic flux between the magnetic poles N and 82.

In view of the above-mentioned points, the present invention aims to orient and magnetize only a part of the magnet so as to produce magnetic anisotropy in the circumferential direction, and to form an axial groove in a part other than the part that is oriented in the circumferential direction. A combination structure of a cylindrical rubber magnet and an isotropic magnet fitted into the axial groove or an anisotropic magnet oriented approximately parallel to the straight line connecting the magnetic poles allows for a compact and high-performance magnet. It seeks to provide Magne/Trolls.

Embodiments of the magnet roll according to the present invention will be described below with reference to the drawings.

FIG. 4 shows a first embodiment of the invention. In this diagram,
Only a part of the cylindrical rubber magnet material 10A with a diameter of 18 mm was oriented so as to produce magnetic anisotropy in the circumferential direction as shown by the dotted line in the figure, and the circumference of the cylindrical rubber magnet material 10A was Groove depth 4m+o in areas other than the oriented part
An axial groove 20 having a groove width of 4111111 is formed in advance.

This axial groove 20 may be formed simultaneously during extrusion molding. In the axial groove 20, a rod-shaped anisotropy with a saturation magnetic flux density of about 2400 Gauss is oriented to have magnetic anisotropy approximately parallel to a straight line connecting the magnetic poles to be magnetized in advance, as shown by the solid line arrow in FIG. The orthogonal rubber magnet material 21 is fitted and fixed. after that,
The cylindrical rubber magnet 10A and the rod-shaped anisotropic rubber magnet material 21 are magnetized so that magnetic poles are formed on their circumferential surfaces. At this time, the parts that have magnetic anisotropy are magnetized along that direction, and as a result, as shown in Figure 4, sufficiently strong magnetic poles N, S,
A cylindrical rubber magnet 11 is formed in a portion facing the photosensitive drum. Magnetic pole N of other parts
2. S2 may be a relatively weak magnetic pole. Note that a square shaft body 1 is provided in the center hole 12 of this cylindrical rubber magnet 11.
3 is provided, and one surface of the square shaft body 13 has a specific positional relationship with respect to the magnetic pole.

In the first embodiment, the cylindrical rubber magnet material 1 OA
The weakly oriented portion in the radial direction is removed by forming an axial groove 2 (n), so that the straight line connecting the axial groove 20 to the magnetic pole N2.S has magnetic anisotropy approximately in the line IL. Since the oriented rod-shaped anisotropic rubber magnet material 21 is fitted, the magnetic flux can flow better between the magnetic poles N2.S and N2.S compared to the configuration shown in FIG. 3, and the magnetization shown in FIG. The surface magnetic flux density B of the magnetic pole S can be increased like a pattern.For example, in the configuration shown in FIG.
In the first embodiment, the current was 0 Gauss, but it is improved to 1200 Gauss. As a result, the demand for further miniaturization (smaller diameter) cannot be satisfied.

In the first embodiment, the groove depth of the axial groove 20 is 4 mm with respect to the diameter of 18 mm of the cylindrical rubber magnet material 10A.
Although the groove width was set to 4+nm, it was found from experiments that the strength of the magnetic pole S1 could be improved if both the groove depth and the groove width were 2111111 mm or more. That is, the diameter is D, the groove depth is Cd,
If ti width is Cur, Cd/D≧]/9 big C
If w/D≧1/9, the strength of the magnetic poles can be increased.

FIG. 6 shows a second embodiment of the invention. In this figure, a rod-shaped isotropic rubber magnet material 31 is used instead of the rod-shaped anisotropic rubber magnet material, and is fitted and fixed into the axial groove 20 of the cylindrical rubber magnet material 10A.

Here, the saturation magnetic flux density of the rod-shaped isotropic rubber magnet material 31 is, for example, about 1500 force. Alternatively, the cylindrical rubber magnet material 10A and the rod-shaped isotropic rubber magnet material 31 are magnetized so that magnetic poles are formed on the circumferential surface. In the second case, the portions with magnetic anisotropy are magnetized along that direction, and as a result, as shown in Figure 6, sufficiently strong magnetic poles N,, S, are located in the portions that should face the photoreceptor drum. A cylindrical rubber magnet is obtained. Magnetic pole N2 of other parts. S.

There is no problem even if the magnetic pole is relatively weak.

” In the second embodiment, 111 rubber magnet 4.
1. The portion of the OA that is weakly oriented in the radial direction is removed by forming the axial groove 20, and the rod-shaped isotropic rubber magnet material 31 is fitted into the axial groove 20.
This rod-shaped isotropic rubber magnet T4'A3] is smoothly magnetized in the final magnetization direction, and compared to the configuration shown in FIG. It is possible to improve the passage and also increase the surface magnetic flux density of the magnetic pole S1.

In the fi52 embodiment as well, if Cd/D≧1/9 and Cw/D≧1/9, the strength of the magnetic pole can be increased.

In the above-mentioned Embodiment 3 and Embodiment 12, materials other than rubber magnets can be used as the magnet material fitted into the axial groove 20 of the cylindrical rubber magnet material 10A. For example, a rod-shaped ferrite sintered body can also be used. However, since machining is difficult in this case, the surface of the ferrite sintered body is drawn into the axial groove 20.

As explained above, according to the present invention, only a portion is oriented and magnetized in the circumferential direction [this magnetic anisotropy is produced], and a portion other than the portion oriented in the circumferential direction is oriented and magnetized in the axial direction. The structure is a combination of a cylindrical rubber magnet with a groove formed therein, and an isotropic magnet fitted into the axial groove, or an anisotropic magnet oriented approximately parallel to the straight line connecting the magnetic poles. A high-performance magnetic roll can be obtained with a small diameter).

[Brief explanation of the drawing]

Figure 1 is a perspective view of a conventional magneso roll;
The figure is a sectional view of the same side, Figure 3 is a side sectional view of a cylindrical rubber magnet material showing the direction of magnetic anisotropy in a magnet roll previously proposed by the present applicant, and Figure 4 is a side sectional view of the magnetic roll according to the present invention. A side sectional view showing the first embodiment of the magnet roll, FIG.
A graph showing the magnetization pattern of the embodiment, Figure f56 is a side sectional view showing the second embodiment of the present invention. j, 0, 10 A...Cylindrical rubber magnet 4/4.1
1... Cylindrical rubber magnet, 20... Axial groove, 2j.
... Rod-shaped anisotropic rubber magnet material, 31... Rod-shaped 1 is a bicarbonate rubber magnet material. Takashi Murai, patent attorney and agent for patent applicant TDC Co., Ltd.

Claims (1)

[Claims] (1) Only a portion is oriented and magnetized to produce magnetic anisotropy in the circumferential direction to form magnetic poles on the circumferential surface, and axial grooves are formed in areas other than the portion oriented in the circumferential direction. It is characterized by comprising a cylindrical comb magnet formed by a comb magnet, and an anisotropic magnetic field oriented substantially parallel to a straight line connecting isotropic or serious magnetic poles fitted into the axial groove. magnetic roll.