JPS58173807A - Permanent magnet roll - Google Patents

Abstract

PURPOSE:To elevate magnetic property in spite of small diameter, by a method wherein anisotropic ferrite magnet of a cylindrical column being seamless in the axial direction and having anisotropy in one diameter direction and forming poles in radial direction from the axial center is fixed to the shaft. CONSTITUTION:A die 10 is filled with fine magnetic powders 15 and a core 14 is disposed at center portion and press molding is performed in magnetic field. If pressure is released after the press molding, a square rod is bored at the axial center and has anisotropy in M-direction thereby anisotropic ferrite magnet 21(a) of integral square rod type is obtained without seam in the axial direction. The magnet 21(a) is sintered and a shaft 22 is inserted in a hollow portion 21(b) and fixed and then grinding is performed. Thereby a column anisotropic ferrite magnet 21 is obtained in column shape being seamless in the axial direction and having anisotropy in one diameter direction. The magnet 21 is inserted in a cylindrical sleeve 20 and finished into a permanent magnet roll. In this constitution, magnetic property is elevated in spite of small diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a permanent magnet roll for performing magnetic brush printing in electrostatic transfer electrophotographic copying. This invention relates to a permanent magnet roll.

In recent years, small-sized 1! There is a strong demand for smaller diameter permanent magnet rolls, which are the main part of the equipment. However, it has been difficult to reduce the diameter while satisfying the magnetic properties on the surface of the permanent magnet roll.

For example, the permanent magnet roll shown in FIG. ) has a structure in which a plurality of integral or split ferrite bar magnets (5) are arranged in layers in the axial direction on a cylindrical non-magnetic support (3), so an anisotropic ferrite magnet is used as the bar magnet. This makes it possible to obtain high magnetic properties. However, when this diameter is reduced, the magnetic effective cross-sectional area of each bar magnet inevitably becomes smaller, and although the magnetic flux density on the surface of the sleeve (1) is sufficient to form the necessary magnetic brush image, do not have. 'Also, in the case of the permanent magnet roll shown in Fig. 2, the magnet structure (2) has a structure in which the shaft (4) is fixed to a ferrite-based cylindrical magnet (6) that is integrally molded in the axial direction by a rubber press method. Since the magnet (6) is isotropic, its magnetic properties are lower than that of an anisotropic magnet, making it unsuitable for reducing the diameter.
Sufficient magnetic properties cannot be obtained.

In view of the current situation, the present invention provides a permanent magnet roll that has a small diameter but has good magnetic properties.

That is, this invention fixes to a shaft an anisotropic ferrite magnet that has anisotropy in one diameter direction of a cylindrical body with a hole in the shaft center and has no seam in the axial direction, and has magnetic poles at radial positions from the shaft center. The present invention is a permanent magnet roll in which the magnet structure is built into a non-magnetic cylindrical sleeve so that the magnet structure is relatively rotatable.

For example, the permanent magnet roll according to the present invention has a sleeve outer diameter of 30 mm1i! Even if the diameter is small, the magnetic flux density on the surface is 100 OG or more, and sufficient magnetic brush development can be performed.

The present invention will be described below based on examples of manufacturing methods. FIG. 3 is an explanatory diagram of a magnet forming apparatus, FIG. 4 is a perspective view of a molded magnet material, and FIGS. 5 and 6 are explanatory diagrams of a method of forming magnetic poles on a magnet.

The molding device is a frame-shaped die (10) made of non-magnetic material.
An upper bunch (11) and a lower punch (12) made of ferromagnetic material are arranged in the upper and lower open openings of the Coil (13) (13
) is fixed. This die (1o) is filled with a fine particle magnetic material (15) as a raw material, and a core metal (14) is placed in the die (10) so that it will be located at the center of the magnet after molding is completed, and the magnetic field Perform medium press molding.

After press forming in a magnetic field in the molding @ position, when the pressure is released, the core metal (14) can be pulled out due to the springback action, and as shown in Figure 4, it becomes a prismatic body with a hole in the center of the axis. An integrated rectangular rod-shaped anisotropic ferrite magnet (21a) that has anisotropy in the M direction and is seamless in the axial direction.
can be obtained.

Next, the square bar type anisotropic magnet (21a) is sintered, the shaft (22) is inserted and fixed into the hollow part (21b) provided at the center of the shaft, and the square bar is is subjected to cylindrical polishing to obtain a cylindrical anisotropic ferrite magnet (21) that is seamless in the axial direction and has anisotropy in one diameter direction.

The thus obtained cylindrical anisotropic ferrite magnet (
21) can easily form desired magnetic poles on its outer circumferential surface. For example, as shown in FIG. 5, in order to form six magnetic poles, six magnetizing yokes ( 1γ)
are arranged on the outer periphery of the ferrite magnet (21), and the current flowing through the electromagnetic coil (16) is adjusted to form magnetic poles having desired magnetic characteristics at each position. At this time, the magnetic pole of the magnetic brush forming part is the N+' part or the S2' part shown in the figure,
That is, by providing the magnetic poles in the same direction as the anisotropic direction, the most efficient magnetic pole arrangement can be achieved.

In addition, in the case of a three-pole arrangement, as shown in the 6th WJ,
The three magnetizing yokes (11) may be arranged at 90° intervals, or any other number and arrangement of poles may be used.

Next, as shown in FIG. 7, the cylindrical anisotropic ferrite magnet (21) whose magnetic poles have been formed is inserted into a cylindrical sleeve (20) made of a predetermined non-magnetic material, and the two are placed relative to each other. Finished as a rotatable, permanent magnet roll.

Examples according to the present invention will be shown below to clarify its effects.

By the above-mentioned manufacturing method, the straight 9!28 holes and the hollow part (2
1b) i! A cylindrical anisotropic ferrite magnet (21) with a length of 300 m and a length of 300 m was produced. This cylindrical anisotropic ferrite magnet (21) has a residual magnetic flux density f3 r -40009 in the anisotropic direction, a coercive force H (! -350
006, maximum energy product (B H) wax -3,
6MGQe, and by the method shown in FIGS. 5 and 6,
Bond magnetized to 6 poles and 3 poles, external size 30. , long 7!5
It was inserted into a 300mm+ sleeve (20) and assembled into a permanent stone holder. At this time, the magnetic flux distribution on the sleeve (20) surface m was measured. The results are shown in FIG. 9 (for 6-pole magnetization) and FIG. 9 (for 3-pole magnetization).

As is clear from the results, the magnetic flux density on the sleeve surface was 100 OG or more in all cases, indicating that a magnetic flux density sufficient to form a proper magnetic brush was obtained.

Next, as shown in FIG. ) was used to create a permanent magnet roll with an outer diameter of 30w1l as in the embodiment of this invention, and compared with the above embodiment of this invention, it was found that the magnetic flux density on the sleeve surface was 15 than that according to this invention.
It was also lower by more than %.

Similarly, the external shape 30 using the conventional isotropic ferrite cylindrical magnet (6) made by the rubber press method shown in FIG.
When a permanent magnet roll of m. Only an insufficient magnetic flux density was obtained.

As described in detail above, the permanent m5 roll according to the present invention can form a high magnetic flux density on the sleeve surface even if its outer diameter is small, and is extremely effective in realizing a reduction in size and weight of a copying machine.

[Brief explanation of the drawing]

1 and 2 are longitudinal sectional front views of a conventional permanent magnet roll. FIG. 3 is an explanatory diagram of a molding apparatus for manufacturing a magnet structure according to the present invention, and FIG. 4 is a perspective view of the magnet material after molding. 5WA and 6 are explanatory diagrams showing a method for forming magnetic poles of a cylindrical xhotropic ferrite magnet according to the present invention; FIG. 5 shows a case of six poles, and FIG. 6 shows a case of three poles. FIG. 7 is a perspective view of a permanent magnet roll according to the present invention. 8 and 9 are graphs showing the magnetic flux distribution on the sleeve. FIG. 8 shows the case where the magnet shown in FIG. 5 is used, and FIG. 9 shows the case where the magnet shown in FIG. 6 is used. In the figure, 10...Dice, 11...Upper bunch, 12...
... lower bunch, 13 ... electromagnetic coil, 14 ... core metal, 15 ... fine particle magnetic material, 16 ... electromagnetic coil,
17... Magnetizing yoke, 2o... Sleeve, 21...
・Cylindrical anisotropic ferrite magnet, 21b hollow part, 22・
··shaft. Part-2 Figure 8''/Figure 9

Claims (1)

[Claims] 1. Magnet configuration by fixing to the shaft an anisotropic ferrite magnet, which has anisotropy in the diameter direction of a cylindrical body with a hole in the shaft center and seamless in the axial direction, and magnetic poles are formed at radial positions from the shaft center. A permanent magnet o-le having a body and a non-magnetic cylindrical sleeve with the above-mentioned magnet structure built therein so as to be relatively rotatable.