JPH027845A - Permanent magnet rotor - Google Patents

Abstract

PURPOSE:To obtain a permanent magnet rotor withstandable against high speed rotation by employing a rear earth permanent magnet mainly composed of rear earth element, transition metal and group IIIb elements. CONSTITUTION:A permanent ring magnet 101 having anisotropy in the radial direction is arranged on the outer circumference of a rotary shaft 102. The rotary shaft 102 and the permanent magnet 101 are solid state jointed 103. The permanent magnet 101 employs a rear earth magnet mainly composed of R(at least one rear earth element including Y), M(at least one transition metal) and X(at least one group IIIb element). A molded magnet 201 is placed in a mold 203 arranged with a soft magnetic shell 202, then a mandrel 204 is pushed out in the direction of an arrow 205 thus radially pressurizing and orienting the magnet.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a permanent magnet rotor for an electric motor without commutating brushes.

[Prior art] Electric motors with permanent magnet rotors are mainly used for OA applications due to the development of semiconductor elements for driving and because they do not have a brush part and are more reliable than commutator-equipped motors with commutator brushes. The fields in which it is used are expanding to the field of large FA electric motors.

A permanent magnet rotor that uses permanent magnets in the conventional rotating magnetic field (
An example of a rotor for an inner rotor is shown in FIG. (a
) is a side view, and (b) is a cross-sectional view.

This is an example in which a radially anisotropic ferrite magnet 402 is adhesively fixed around a rotating shaft 401. As shown in (b), the ferrite magnet is magnetized into four poles.

FIG. 5 shows another conventional example in which a resin-bonded rare earth magnet with radial anisotropy is used as the permanent magnet 501.
It is magnetized with 6 poles.

The above-mentioned permanent magnet rotor has a structure in which it rotates by sequentially exciting drive coils installed on a stator (not shown).

FIG. 6 shows an example of a so-called outer rotor type electric motor in which a stator 601 is installed inside a rotor 602.

A permanent magnet 603 is adhesively fixed inside the rotor 602,
With the Hall IC 605 installed on the circuit board 604,
The rotational position of the permanent magnet 603 is detected, and the drive coil 606 wound around the rotor 601 is rotated in accordance with the permanent magnet position.
The structure is such that the rotor 602 is rotated by selectively applying electricity.

[Problem to be solved by the invention] However, in a rotor using conventional ferrite magnets as permanent magnets, the maximum energy product required as a permanent magnet for a field is approximately 58 GOe or less, which is lower than that of rare earth magnets. (1) Efficiency is low.

(2) In order to obtain a sufficient gap magnetic flux density, the permeance of the magnetic circuit must be increased, resulting in a large permanent magnet rotor.

There was a problem.

Furthermore, although alnico magnets have a larger maximum energy product than ferrite magnets, their coercive force is only about 1.5 kOe, so when used in electric motors, they generate back electromotive force during operation, especially when starting due to starting current. There is a problem that demagnetization occurs due to the addition of a strong back electromotive force.
It wasn't used much.

On the other hand, sintered rare earth magnets have a high energy product,
Since it also has a large coercive force, it is ideal as a permanent magnet rotor magnet, but the raw materials are expensive and the manufacturing process is slow.
An alloy ingot is produced by melting and casting, and then crushed and
After forming magnet powder with a particle size of about μm, it is kneaded with a binder as a forming aid, press-molded in a magnetic field, and this compact is sintered in argon at a temperature of around 1000°C for 1 hour. After that, heat treatment must be performed at a temperature of around 600°C, which poses a problem in that the magnet is complicated and becomes even more expensive. In addition, sintered magnets are
The shrinkage rate during sintering is greatly different between the orientation direction and the direction perpendicular to the orientation direction, resulting in cracking, making it impossible to manufacture thin radially anisotropic ring-shaped magnets.

In addition, resin-bonded rare earth magnets offer shape flexibility and resistance (
It has excellent impact resistance and is easy to manufacture as a radially anisotropic ring-shaped magnet, but because it is a mixture of magnet powder and resin, its magnetic properties are inferior to that of sintered magnets.

Furthermore, a common problem with inner rotor type permanent magnet rotors using any magnets is that when used for high-speed rotating electric machines, the centrifugal force becomes larger than the fixation force of the permanent magnets to the rotating shaft. If this occurs, the permanent magnet may separate from the rotating shaft, resulting in damage to the motor.

Therefore, the present invention aims to solve these problems.
The purpose is to use permanent magnets that include R (where R is at least one rare earth element including Y), M (at least one transition metal), and X (however, III
We provide a permanent magnet rotor at low cost that has a basic composition of at least one type of group B element), can manufacture a yoke at the same time, and does not break even during high-speed rotation because the rotating shaft and magnets are in-phase joined. It's there.

[Means for Solving the Problems] A permanent magnet rotor of the present invention includes a permanent magnet for generating a magnetic field and a yoke made of a soft magnetic material. A rare earth magnet whose basic components are at least one rare earth element (including Y), M (but at least one transition metal), and It is characterized by solid-phase bonding between the magnet and the yoke made of a soft magnetic material. Furthermore, the permanent magnet for the permanent magnet rotor is a radially anisotropic ring-shaped magnet. 1 shows a cross-sectional view of one embodiment of the invention.

Ring-shaped permanent magnet 101 with anisotropy in the radial direction
is installed on the outer periphery of the rotating shaft 102.

Since the joint portion 103 between the rotary shaft and the permanent magnet is a solid state joint, the fixing strength is ten times or more that of conventional fixing strength such as adhesive.

Below, the method for manufacturing a permanent magnet rotor of the present invention will be explained in detail.

Table 1 shows the alloy composition of the magnet produced according to the present invention.

However, the composition of the magnet is not limited to those shown in Table 1, and the rare earth metals include Y, La, Ce, Pr.
SNd, Sm, Eu, Gd% Tb,
Dy, Ho, Er, Tm, Yb, and Lu are listed as candidates, and one type or a combination of two or more of these can be used. The highest magnetic properties are obtained with Pr. Transition metals include Fe, Ni, CU
etc. are listed as candidates, and one or a combination of two or more of these may be used.

Further, small additive elements such as heavy rare earth elements Dy, Tb, etc., Al, Si, Mo, Ga, etc. are effective in improving the coercive force.

Rare earths, transition metals, and boron were weighed to have the composition shown in Table 1, melted and cast in an induction heating furnace, and the resulting cast ingot was crushed to an average particle size of 5 μm (by Fischer subsieve sizer). It was molded into a bulk body with an outer diameter of 50 mm and a height of 40 mm in a graphite mold.

FIG. 2 shows a schematic diagram of the rear extruder.

The magnet molded body 201 is placed in a mold 203 in which a shell 202 made of a soft magnetic material is installed, and a mandrel 204 having an outer diameter of 20 mm is pushed out in the direction of an arrow 205, thereby moving the magnet molded body 201 in the direction opposite to the direction of movement of the mandrel 204 (
The extruded magnet was pressed in the radial direction (rearward) and oriented. The extruded magnet molded body was hot-processed in an atmosphere of 900°C and was solid-phase bonded to the shell, so it was possible to obtain strong adhesion. The processing was performed at an extrusion ratio of approximately 4, which is the cross-sectional area of the magnet before extrusion divided by the cross-sectional area after extrusion.

Cut out the completed ring-shaped magnet and cut it in the r direction (radial direction)
Table 2 shows the results of magnetic measurements in three directions: , U direction (chord direction), and 2 directions (axial direction).

This is an example in which an outer rotor type permanent magnet rotor was obtained by using the rotor as is.

The mandrel uses high-speed tool steel, a material that does not form a solid phase bond with the magnet, but by making the mandrel replaceable and using a high-hardness, soft-magnetic material that has a high diffusion speed, It is also possible to manufacture an inner rotor type permanent magnet rotor by solid phase joining between a mandrel and a magnet.

In this case, the shell is unnecessary, and the mold material can be made of a material that does not readily cause solid phase bonding with the magnet, thereby eliminating the need for external processing.

It can be seen that the magnetic properties in the r direction in Table 2 are the highest, indicating radial orientation due to backward extrusion. In the manufacturing method of this example, the shell is a yoke shown in FIG. 6 (Example 2). An alloy having the composition shown in Table 1 is weighed, melted in an induction heating furnace,
After casting, the obtained cast ingot is crushed to an average particle size of 5 μm, mixed with Daiflon, and wet-processed to reduce the outer diameter to φ10.
It was temporarily formed into a ring shape with a diameter of 0 mm, an inner diameter of 40 mm, and a thickness of 30 mm. A soft magnetic cylinder 301 made of pure iron or the like is placed inside this, and a 5us cylinder coated with boron nitride is placed on the outside.
After inserting a pipe 302 made of 304 with a thickness of 2 mm, deaerate the pipe, close both ends of the pipe, and press in the atmosphere with an extruder shown in Fig. 3 until the thickness of the vibrator 302 becomes 10% of the original thickness. did. Next, the pipe was removed and its magnetic properties were measured. The results are shown in Table 3.

If we can obtain a gap magnetic flux density that satisfies the characteristics of the electric motor,
It is also possible to leave the outer 5us304 on the outer periphery for protection without removing it. Also, the outer pipe material may be made of magnetic material as long as the thickness is sufficiently thin.

Table 3 It can be seen that a magnet with high in-plane anisotropy and high magnetic properties in the r direction and the U direction was produced. This magnet is used as the inner rotor type permanent magnet rotor shown in Figure 1, and the cylinder used when extruding the shaft is used as it is, so there is no need to process the connection between the shaft and the permanent magnet, resulting in a highly productive permanent magnet rotor. It became. Since the shaft and the permanent magnet are solid-phase welded, high adhesion strength is obtained, and a permanent magnet rotor that does not break even during high-speed rotation can be obtained.

(Example 3) An alloy having the composition shown in Table 4 was prepared using a vacuum melt spinning device for producing amorphous alloys to a thickness of 30 μm.
A quenched thin piece of about m size is made, and this thin piece is hot pressed.
After bulking, by performing the backward extrusion process described in Example 1, it was possible to obtain a permanent magnet rotor in which radially oriented permanent magnets were solid-phase joined to the yoke.

Table 4 [Effects of the Invention] According to the present invention, a permanent magnet with radial anisotropy (including in-plane anisotropy) can be manufactured integrally with a yoke by extrusion processing, and the joint portion is formed in a solid phase. Because of the bonded structure, a permanent magnet rotor can be obtained that will not break even when used in a high-speed rotating electric motor, especially in the case of an inner rotor type rotor.

Furthermore, since the step of joining the permanent magnets and the yoke is not necessary, the permanent magnet rotor can be manufactured at low cost and with high productivity.

Mold 204...Mandrel Arrow　　　301... Soft magnetic cylinder Pipe 401... Rotating shaft ferrite magnet Resin bonded rare earth magnet Stator 602...Rotor Permanent magnet 604...Circuit board Hall IC606...Drive coil

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the permanent magnet rotor of the present invention. FIG.
Schematic diagram of the backward extruder. FIG. 3 is a schematic diagram of the extruder. FIGS. 4(a) and 4(b) are schematic diagrams of a conventional permanent magnet rotor, with (a) being a side view and (b) being a sectional view. FIG. 5 is a schematic diagram of another conventional permanent magnet rotor. FIG. 6 is a sectional view of the outer rotor type electric motor. 101...Ring-shaped permanent magnet 102...Rotating shaft 103...Joint part 201...
Magnetic molded body 202...Shell and above Applicant Seiko Epson Co., Ltd. agent Patent attorney Kisanbe Meiki and 1 other person Figure (α) Figure 4 Figure 5 jIZ Figure 3 Ryo 4 circuit gravestone 60" 3 vermilion Yu lamb stone grounder map

Claims (3)

[Claims] (1) In a permanent magnet rotor composed of a permanent magnet for generating a magnetic field and a yoke made of a soft magnetic material, the permanent magnets are R (where R is at least one rare earth element including Y), M ( However, at least one of the transition metals),
A permanent magnet rotor characterized in that a rare earth magnet having a basic component of and X (at least one of group IIIb elements) is used. (2) The permanent magnet rotor according to claim 1, wherein the permanent magnet and the yoke made of the soft magnetic material are solid phase joined. (3) The permanent magnet rotor according to claim 1, wherein the permanent magnet is a radially anisotropic ring-shaped magnet.