JP2527322B2 - Method for manufacturing magnet for ring-shaped rotor of DC motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnet rotor made of magnetic powder for a DC motor, which can be magnetized by shifting the magnetic center plane in the rotation axis direction from the geometric center plane. The present invention relates to a method for manufacturing a magnet for a rotor of a motor.

2. Description of the Related Art and Related Problems FIG. 5 is a longitudinal sectional view showing the right half of an example of a conventional magnet rotor type brushless DC motor.

A stator core 3 is press-fitted and fixed to the outer side of the tubular boss portion 2 of the fixed frame 1. A bearing 4 is provided inside the boss 2.
The rotating shaft 5 is supported by. A cup-shaped rotor frame 6 is press-fitted and fixed to the rotating shaft 5. A rotor magnet 8 that faces the stator core 3 with a gap 7 is fixed inside the rotor frame 6.

In such a structure, the core 3 that generates torque
The electromagnetic attractive force between the magnet 8 and the magnet 8 changes as the magnetic resistance between the two changes according to the rotational position. In order to minimize the vibration in the axial direction caused by this fluctuation, it is necessary to match the axial centers X and X ′ of the core 3 and the magnet 8.

However, in the case of a brushless motor, since the hall element 9 is provided for detecting the position of the rotor magnet 8 and the speed detecting element 10 is provided for detecting the speed of the rotor magnet 8, the center planes X and X'may not necessarily match. Can not.

In that case, there is a problem that axial noise is generated due to the electromagnetic attraction force and rotational noise is generated.

As a means for solving such a problem, the present inventor has noticed that it is effective to match the magnetic center plane of the rotor magnet having the maximum air gap magnetic flux density with the center plane of the stator core in the direction of the rotation axis. Anisotropy with strength in the axial direction is given in advance, and the magnetic center plane is displaced by a desired amount from the geometrical center plane in the axial direction by magnetization, so that the axial position of the rotor magnet is deviated. Provided is a method of manufacturing a ring-shaped magnet material for a rotor of a DC motor, the magnetic center plane of which coincides with the center plane of a stator core.

Means for Solving the Problems The present invention is directed to a ring-shaped rotor magnet of a mold material, which is in contact with at least one side surface of a side surface of a ring-shaped rotor magnet of a DC motor facing a space and a side surface opposite to the side surface. The magnetic reluctance per unit cross-sectional area in the radial direction of the portion at the position corresponding to the magnetic center plane deviated from the geometrical center plane in the rotational axis direction Magnetic powder is filled in a space surrounded by the mold material that has been made smaller and a pressure material that applies pressure in parallel with the side surface, and the magnetic material is pressure-molded by the pressure material and at the same time the mold material A method for manufacturing a ring-shaped rotor magnet for a DC motor, characterized by magnetizing in a radial direction through the magnet to impart anisotropy, once removing the magnetization, and finally magnetizing. The above problems have been solved by the method.

Action A portion (hereinafter referred to as "intermediate required portion") located at a position corresponding to the magnetic center plane deviated from the geometrical center plane of the ring-shaped rotor magnet of the die material in the direction of the rotation axis is more permeable than other portions. When the magnetic powder is magnetized in the radial direction during pressure molding of the magnetic powder, the portion of the magnetic powder facing the intermediate required portion is magnetized more strongly than the other magnetic powder portions, and the axial direction is increased. A radial anisotropy with strength and weakness is obtained. Therefore, once the magnetization due to this magnetization is demagnetized, a link-shaped rotor magnet material is obtained.

If the die material is formed in a ring shape, a ring-shaped magnet material can be obtained. Therefore, if magnetized by a normal magnetizing method so that N and S magnetic poles with a predetermined number of poles appear inside this magnet material, the axial direction According to the anisotropy, the intermediate required portion is magnetized more strongly than the other portions,
A finished rotor magnet having a magnetic center plane deviated from the geometrical axial center plane is obtained.

If the material and the axial position of the intermediate required portion can be changed, the amount of deviation of the magnetic center plane can be changed.

Embodiments FIGS. 1 and 2 show a molding apparatus for shifting the magnetic center plane Xm (see FIG. 4) of the outer rotor type magnet 8 made of magnetic powder to a required axial position.

 The magnet 8 is formed in a ring shape.

To briefly explain this molding apparatus, a cylindrical base 11 and an annular base 12 are fixed concentrically and with their upper surfaces flush with each other on a fixed base (not shown). A bush 13 having an outer peripheral surface flush with the cylindrical base 11 is fitted on the upper end of the cylindrical base 11. A bush 14 facing the bush 13 is fitted in the center hole of the annular base 12.

This forming apparatus includes a lower punch 15 that moves up and down along the outer periphery of the cylindrical base 11 and an upper punch 16 that contacts the upper end surfaces of the bushes 13 and 14.
As a pressurizing material, magnetic powder 17 such as ferrite filled between both bushes 13 and 14, which is a mold material, is pressed and solidified into a ring shape.

An exciting coil 20 is held between the annular base 12 and a support ring 19 fixed to the lower part of the annular base 12 with bolts 18. When a current is applied to the coil 20 at the same time as the pressure molding, the magnetic powder 17 is magnetized in the direction of the magnetic path a.

The intermediate portions 13a, 14a of the bushes 13, 14 are located at a position corresponding to the desired magnetic center plane Xm of the magnet material, and are made of a steel material having a higher magnetic permeability than the upper and lower portions 13b, 14b.

The intermediate portions 13a and 14a are formed of, for example, hot die alloy tool steel SKD (saturation magnetic flux density 13,000 to 15,000 gauss). Further, the upper and lower parts 13b, 14b are, for example, alloy tool steel SKS for impact resistant tools (saturation magnetic flux density 8,000-
10,000 Gauss).

In such a configuration, the portion of the magnetic powder 17 in contact with the intermediate portions 13a, 14a by the energization is magnetized more strongly in the radial direction than the portion in contact with the other portions, and the degree of radial anisotropy in the axial direction. Different magnetic materials. After demagnetizing the magnetization of the ring-shaped magnetic body once, it is magnetized again by a conventional magnetizing method so that N and S magnetic poles appear on the inner surface thereof, whereby a desired completed rotor magnet 8 is obtained.

FIG. 3 shows an embodiment of a molding apparatus for an inner rotor type magnet.

Since the inner rotor magnet has a small center hole into which the rotary shaft is press-fitted, the exciting coil 2 is also used for the upper punch 16a in FIG.
0a is provided so that the coils 20 and 20a are simultaneously energized and magnetized in the directions of the magnetic paths a and b. The bush 14 is provided with a material 14a having a high magnetic permeability, and the bush 13 is omitted.

In the embodiment of FIG. 3, the intermediate portion 13 of the push 13, 14
Instead of forming a and 14a with a material having a higher magnetic permeability than the upper and lower portions 13b and 14b, a thin layer of a non-magnetic material or a layer of a low magnetic permeability material may be provided in the intermediate portions 13b and 14b.

FIG. 4 shows the distribution of the air gap magnetic flux density of a rotor magnet in which the rotor magnet material of the present invention is re-magnetized to provide N and S magnetic poles on the side surface facing the air gap. In this case, even if a uniform magnetizing force is applied in the axial direction, the portion in contact with the intermediate portions 13a and 14a has particularly strong anisotropy compared to the other portions, so that this portion 13
The magnetic flux density of the portion in contact with a and 14a is high, and the magnetic center plane of the whole is biased to the Xm position.

EFFECTS OF THE INVENTION The present invention is a part of a forming device that forms a magnetic path when a magnetic powder is pressed to form a ring-shaped rotor magnet material and the magnet is magnetized to give radial anisotropy. It is possible to change the distribution of the air gap magnetic flux density in the rotating shaft direction of the magnet without increasing the stroke by a relatively simple method of changing the magnetic resistance of the There is an effect that it is easy to shift it from the center plane to match it with the center plane of the stator core, which facilitates the design of reducing the rotation noise without reducing the torque of the motor. The effect of being able to obtain various rotary magnet materials with different magnetic center planes with the same molding device if the parts with different magnetic fields are made replaceable There is a fruit.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a main part of a molding apparatus used for carrying out the present invention. FIG. 2 is a partially enlarged sectional view of FIG. FIG. 3 is a longitudinal sectional view of a main part of another molding apparatus used for carrying out the present invention. FIG. 4 is a distribution diagram of air gap magnetic flux density of a rotary magnet having a biased magnetic center plane according to the present invention. FIG. 5 is a vertical sectional view showing the right half of a conventional magnet rotor type DC motor. 7 ... Air gap, 8 ... Rotor magnet, 13,14 ... Mold material, 15, 16 ... Pressurizing material, 17 ... Magnetic powder

Claims (2)

(57) [Claims] 1. A geometrical shape of a die material in contact with at least one side surface of a ring-shaped rotor magnet of a DC motor facing a space and a side surface opposite to the side surface in a direction of a rotation axis of the ring-shaped rotor magnet. The gold having the magnetic resistance per unit cross-sectional area in the radial direction of the portion at the position corresponding to the magnetic center plane deviated from the center plane smaller than the magnetic resistance per unit cross-sectional area in the radial direction of the portion other than the above portion. A magnetic powder is filled in a space surrounded by a mold material and a pressure material that applies pressure in parallel with the side surface, and the magnetic powder is pressure-molded by the pressure material and at the same time magnetized in a radial direction through the mold material. A magnet for the ring-shaped rotor of a DC motor, wherein the magnetism is finally removed after the magnetization is removed once. 2. The magnetic permeability of the portion of the die material at a position corresponding to the magnetic center plane deviated from the geometric center plane of the ring-shaped rotor magnet in the direction of the rotation axis of the ring-shaped rotor magnet is the material of the portion other than the portion. The method for manufacturing a magnet for a ring-shaped rotor of a DC motor according to claim 1, wherein the magnet has a magnetic permeability higher than the magnetic permeability of.