JPS6037607B2 - permanent magnet roll - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a permanent magnet roll for performing magnetic brush development in an electrostatic transfer type electrophotographic copying machine.
This article relates to a permanent magnet roll that is lightweight.

In recent years, there has been a demand for smaller and lighter copying machines, and 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, in the permanent magnet roll shown in FIG. 1, a magnet structure 2 is fixed to a ball 4 and built into a cylindrical sleeve made of a non-magnetic material, but the magnet structure 2 is a cylindrical non-magnetic support. Since the magnet has a structure in which a plurality of integral or split type ferrite bar magnets 5 are arranged around the circumference of the magnet 3, high magnetic properties can be obtained by using anisotropic ferrite magnets as the bar magnets. However, when this diameter is reduced, the magnetic effective cross-sectional area of each bar magnet inevitably becomes smaller, and the magnetic flux density on the sleeve surface cannot be said to be sufficient to form the necessary magnetic brush development. In addition, in the case of the permanent magnet roll shown in FIG. 2, the magnet structure 2 is a ferrite-based cylindrical magnet 6 integrally molded in the ratchet direction by a rubber press method.
Since the shaft 4 is fixed to the magnet 6 and the magnet 6 is isometric, its magnetic properties are lower than those of anisotropic magnets, making it unsuitable for reducing the diameter. is not obtained.

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

That is, this invention fixes an anisotropic ferrite magnet to a shaft, which has a cylindrical body with a hole in the shaft center, has a seamless axial direction, has anisotropic properties in one diameter direction, and has magnetic poles formed 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. In the permanent magnet roll according to the present invention, even if the outer diameter of the sleeve is as small as 30 Yanagi, the magnetic flux density on the surface is about 10 or more, and sufficient magnetic brush development can be performed.

The present invention will be explained 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 forming device has an upper punch 11 and a lower punch 12 made of a ferromagnetic material arranged in the upper and lower open openings of a frame-shaped die 10 made of a non-magnetic material, and furthermore, an upper punch 11 and a lower punch 12 made of a ferromagnetic material are arranged on the outer periphery of each punch in the direction of the upper and lower punches 11 and 12, that is, M in the figure. Electromagnetic coils 13, 13 that form a magnetic field in the direction are fixed. The die 10 is filled with a fine particle magnetic material 15 as a raw material, and a core bar 14 is placed in the center of the die 10 so as to be located at the center of the magnet after the forming is completed, and press forming is performed in a magnetic field. After press molding in a magnetic field in a molding device,
When the pressure is released, the core metal 14 is released due to the spring pack action.
As shown in Fig. 4, it is a prismatic body with a hole in the axial center, has anisotropy in the M direction in the figure, and is a one-piece prismatic anisotropic body with no seam in the axial direction. Sex ferrite magnet 2
1a can be obtained.

Next, the square rod-shaped 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 cylindrically polished using the shaft 22 as a reference. A cylindrical anisotropic ferrite magnet 21 is obtained which is seamless in the direction of the cylinder and has anisotropy in the direction of its diameter. The thus obtained cylindrical anisotropic ferrite magnet 21 can easily have a desired magnetic pole on its outer peripheral surface. For example, as shown in FIG.
To form the magnetic pole of the pole, the electromagnetic coil 16 is wound around the 6
Magnetizing yokes 17 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 properties at each position.

At this time, the magnetic poles of the magnetic brush forming part are N,′ as shown in the figure.
By providing the portion in the S2' portion, that is, in the same direction as the anisotropy direction, the most efficient magnetic pole arrangement can be achieved. Further, in the case of a three-pole arrangement, three magnetizing yokes 17 may be arranged at 90° intervals as shown in FIG. 6, and the number and arrangement of these poles can be arbitrary.

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, so that the two can rotate freely relative to each other. , finished into a permanent magnet roll.

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

By the manufacturing method described above, a diameter of 28 ribs and a hollow part 21b
A cylindrical anisotropic ferrite magnet 21 having a diameter of 10 ribs and a length of 30 ribs was produced.

This cylindrical anisotropic ferrite magnet 21 has a residual magnetic flux density Br=400 in the anisotropic direction and a coercive force Hc of 350 e.
, has a maximum energy product (BH) max: 3.8 MG○e, and after magnetizing into 6 poles and 3 poles respectively by the method shown in Figs. It was inserted into the sleeve 20 on the side of the ship and assembled into a permanent magnet roll. At this time, the magnetic flux distribution on the surface of the sleeve 20 was measured. The results are shown in FIG. 8 (in the case of 6-pole magnetization) and FIG. 9 (in the case of 3-pole magnetization). As is clear from the results, the magnetic flux densities on the sleeve surfaces were all greater than loo, indicating that sufficient magnetic flux density was obtained to form a proper magnetic brush.

Next, using an anisotropic ferrite bar magnet 5 having magnetic properties in the anisotropic direction equivalent to those of the magnet used in this invention,
As shown in FIG. 1, a permanent magnet roll with an external diameter of 3 mm was created using magnet structures arranged around the cylindrical non-magnetic support 3 at 6 locations, as in the embodiment of the present invention. When compared to the above embodiments of the invention, the magnetic flux density on the sleeve surface was more than 5% lower than according to the invention.

Similarly, a permanent magnet roll with an external size of 3 and 300 mm was manufactured using the conventional isotropic ferrite cylindrical magnet 6 by the rubber press method shown in FIG. 2, and compared with the permanent magnet roll according to the present invention. The magnetic flux density on the sleeve surface was more than 20% lower than that of the present invention, and the magnetic flux density was insufficient to form a practically appropriate magnetic brush development.

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

[Brief explanation of drawings]

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. 5 and 6 are explanatory diagrams showing a method for forming magnetic poles of a cylindrical anisotropic ferrite magnet according to the present invention, and FIG.
The figure shows the case of six poles, and FIG. 6 shows the case of three poles. FIG. 7 is a perspective view of a permanent magnet roll according to the present invention. Figures 8 and 9 are graphs showing the magnetic flux distribution on the sleeve, and Figure 8 is a graph showing the magnetic flux distribution on the sleeve.
FIG. 9 shows a case where the magnet shown in FIG. 6 is used. In the figure, 10...Dice, 11...Upper punch,
12... lower punch, 13... electromagnetic coil,
14...Core metal, 15...Fine particle magnetic material,
16... Electromagnetic coil, 17... Magnetizing yoke, 20... Sleeve, 21... Cylindrical anisotropic blower, magnet, 21b. ...Hollow part, 22...Shaft. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9

Claims (1)

[Claims] 1. A magnet structure in which an anisotropic ferrite magnet is fixed to a shaft, having an anisotropy in one 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 roll in which the above-mentioned magnet structure is built in a non-magnetic cylindrical sleeve and is relatively rotatable.