JPH0799743A - Permanent magnet type rotor - Google Patents

Abstract

PURPOSE:To facilitate the elimination of crackings by a method wherein hollow bowl-shaped caps which have a specific thickness and are made of non-magnetic material are attached to both the end parts of a permanent magnet member and a shaft piercing through the permanent magnet member is coaxially fixed with filling material made of thermosetting resin. CONSTITUTION:Caps 5 which are made of non-magnetic material such as aluminum alloy or stainless steel, have a thickness of 0.05-0.5mm and are so formed as to have hollow bowl shapes are pushed onto both the end parts of a permanent magnet member 1 to fix. Adhesive may be required to fix the caps to the permanent magnet member 1. In order to make such caps 5, the restriction by a press is recommended. Then the permanent magnet member 1 is inserted into a mold for injection molding with a shaft 2 and polyacetal resin is injected to fill a gap between the permanent magnet member 1 and the shaft 2 and a filling material layer 3 is formed. As an internal pressure is borne by the caps 5 fixed to both the end parts of the permanent magnet members 1, the pressure strength of the permanent magnet member 1 can be improved. As a result, crackings can be eliminated, so that the reliability can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet type rotor constituting a motor such as a stepping motor, a drainage motor or a circulation pump motor.

[0002]

2. Description of the Related Art As an example of a conventional permanent magnet type rotor,
A structure as shown in FIG. 3 is often used. In FIG. 3, reference numeral 1 denotes a permanent magnet member, which is formed of, for example, an anisotropic ferrite magnet material in a hollow cylindrical shape, and a plurality of magnetic poles extending in the axial direction are provided on the outer circumference at equal intervals in the circumferential direction. Next, reference numeral 2 denotes a shaft, which is provided so as to penetrate the permanent magnet member 1 and is coaxially fixed to the permanent magnet member 1 by a filler 3 made of a thermoplastic resin material.

In order to manufacture the permanent magnet type rotor as described above, for example, the permanent magnet member 1 and the shaft 2 are coaxially inserted and held in an injection molding die, and the permanent magnet member 1 and A means for coaxially fixing the permanent magnet member 1 and the shaft 2 by adopting injection molding of a thermoplastic resin material between the shaft 2 and the filler 3 is adopted.

In this case, the anisotropic ferrite magnet material forming the permanent magnet member 1 is brittle, and there is a small amount of space between the inner peripheral surface of the insert of the injection molding die and the outer peripheral surface of the permanent magnet member 1. Since there is a gap, the permanent magnet member 1 cannot withstand the internal pressure when the thermoplastic resin material is filled at a high pressure.
There is a problem that cracks occur in the.

In order to solve the above problems, there is a proposal that the outer shell layer 4 made of a thermoplastic resin material is also formed on the outer peripheral surface of the permanent magnet member 1 when the filler 3 is injection-molded (for example, (See JP-A-53-146760 and JP-A-61-58454). According to the above-mentioned proposal, since the filling pressure acts on the inner and outer surfaces of the permanent magnet member 1 during injection molding, there is an effect that the generation of the crack can be prevented regardless of the brittle ferrite magnet material. .

[0006]

However, in the case of molding the filler 3 and the outer shell layer 4 on the inner and outer peripheral surfaces of the permanent magnet member 1 as described above, the permanent magnet member 1 is formed in the injection mold. As the positioning support means needs to be devised and the structure of the injection molding die becomes complicated, the manufacturing cost of the injection molding die rises and the manufacturing cost of the permanent magnet type rotor also rises. .

After the injection molding, the permanent magnet member 1
Although it is necessary to remove the outer shell layer 4 on the outer peripheral surface of the magnet, the extra man-hours and time are required for this removal operation, which is a factor of increasing the manufacturing cost of the permanent magnet type rotor.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems existing in the prior art and to provide a highly reliable permanent magnet type rotor in which cracks do not occur in the permanent magnet member as a constituent member. Is.

[0009]

In order to achieve the above object, in the present invention, a permanent magnet member is formed of a sintered magnet material in a hollow cylindrical shape and provided with a plurality of magnetic poles extending in the axial direction on the outer circumference. A non-magnetic material with a thickness of 0.05
A technical means was adopted in which a cap formed in the shape of a hollow bowl of ~ 0.5 mm was fitted, and the shaft that penetrates the permanent magnet member was fixed coaxially with the permanent magnet member by a filler made of a thermoplastic resin material. .

In the present invention, the thickness of the cap is 0.05 mm
If it is less than 1, it is not preferable because the effect of improving the pressure resistance of the permanent magnet member during injection molding cannot be expected. On the other hand, if the thickness of the cap exceeds 0.5 mm, the magnetic gap between the outer peripheral surface of the permanent magnet member and the inner peripheral surface of the stator becomes large when assembled as a motor, resulting in deterioration of the motor characteristics.

[0011]

With the above construction, it is possible to improve the pressure resistance of the permanent magnet member during injection molding of the filler and prevent the occurrence of cracks due to internal pressure.

[0012]

FIG. 1 is a diagram showing an embodiment of the present invention,
(A) shows a partially sectional front view, (b) shows an end face, and the same portions are denoted by the same reference numerals as those in FIG. In FIG. 1, the permanent magnet member 1 is formed of, for example, an anisotropic Sr ferrite magnet material into a hollow cylindrical shape having an outer diameter of 19 mm, an inner diameter of 6 mm, and an axial length of 30 mm, and N and S magnetic poles are provided on the outer peripheral surface at symmetrical positions. It is a thing. Next, the shaft 2 is processed to have an outer diameter of 3 mm and an axial length of 70 mm by a mild steel round bar, for example, and is coaxially fixed to the permanent magnet member 1 via a filler 3 made of, for example, polyacetal resin.

Reference numeral 5 denotes a cap, which is an aluminum alloy,
With non-magnetic material such as stainless steel, thickness of 0.1mm
The outer diameter is 19.2 mm, the inner diameter at the end is 11 mm, and the length is 5 mm in the axial direction. In this case, an adhesive may be used together. In order to form such a cap 5, it is preferable to use a drawing means by pressing.

To form the permanent magnet type rotor as described above, the caps 5 are fixed to both ends of the permanent magnet member 1, and the permanent magnet member 1 is inserted into the injection molding die together with the shaft 2 and positioned and held. For example, the filling material 3 may be molded by injection-filling a polyacetal resin. The internal pressure at the time of injection molding is the cap 5 fixed to both ends of the permanent magnet member 1.
The pressure resistance of the permanent magnet member 1 is improved, and the occurrence of cracks can be prevented.

FIG. 2 is a longitudinal sectional view of an essential part showing an example of means for molding the filler 3 in the embodiment of the present invention. In FIG. 2, the injection molding die 10 is composed of a movable die 11 and a fixed die 12. That is, the fixed die 12 is provided on the fixed plate 14 provided on the lower plate 13, and the movable die 11 is provided on the fixed die 12.

The movable mold 11 comprises mold plates 15 and 16, and nozzle ports 17 are formed in these mold plates 15 and 16. The sprue 18 communicating with the nozzle port 17 has a template 15,
It is provided so as to communicate with the runner 19 formed in 16. The runner 19 communicates with a vertical gate 20 formed at a corresponding position of the template 16, and the gate 20
Communicates with a cavity 21 having a ring-shaped cross section.

Next, in the fixed mold 12, there is provided an accommodating portion 22 having a circular cross section so that the cap 5 can accommodate and retain the permanent magnet members 1 fitted at both ends thereof, and the accommodating portion 22 is provided at the center thereof. A cavity 21 is formed between the shaft 21 and the held shaft 2. A lower punch 23 is provided in a fixed plate 14 below the fixed mold 12 so as to be vertically movable, and holds the upper and lower ends of the shaft 2 in cooperation with the mold plates 15 and 16. Reference numeral 24 is a rod, which is connected so as to drive the lower punch 23.

With the above structure, the housing portion 2 of the fixed die 12
2 in which the permanent magnet member 1 is housed (in this case, it is preferable that the housing part 22 of the portion of the cap 5 is slightly escaped so as not to contact the cap 5), the shaft 2 is inserted, and the movable mold 11 is combined. For example, if polyacetal resin is injected at a temperature of 100 to 180 ° C. at a pressure of 40 to 70 kg / cm ² from the nozzle port 17 and is injected and filled into the cavity 21 through the sprue 18, runner 19 and gate 20, The filler 3 shown in FIG. 1 is molded, and the permanent magnet member 1 and the shaft 2 are integrally bonded and fixed.

After the polyacetal resin filled in the cavity 21 is cooled and solidified, the movable die 11 is moved upward, the rod 24 is pushed up and the lower punch 23 is raised to push the molding assembly from the fixed die 12. Can be issued. After that, the lower punch 23 is returned to the original position, the permanent magnet member 1 to which the cap 5 is fixed and the shaft 2 are inserted, the movable die 11 is united on the fixed die 12, and the next molding cycle is performed.

The obtained molded assembly is magnetized in a predetermined manner on the basis of a reference portion or a reference mark provided in advance on the shaft 2 or the permanent magnet member 1 to complete a permanent magnet type rotor.

A pressure resistance test was conducted on the permanent magnet member 1 having the above-mentioned structure. As a result, 272 kg / cm ² and 310 kg / cm ² were obtained for the caps 5 each having the above-mentioned dimensions made of aluminum alloy and SUS304. It was confirmed that these were improved 1.8 times and 2.1 times, respectively, with respect to 150 kg / cm ² in the conventional one shown in FIG.

In this embodiment, an example in which magnetic poles of N and S2 poles are provided on the outer circumference of the permanent magnet member 1 has been described.
The same effect can be expected even if the number of poles is four or more. Further, as a sintered magnet material for forming the permanent magnet member 1, Sr
Not only ferrite magnet materials other than ferrite but also rare earth magnet materials can be used.

[0023]

EFFECTS OF THE INVENTION Since the present invention has the structure and operation as described above, the following effects can be obtained. (1) Since the pressure resistance of the permanent magnet member is improved, the occurrence of cracks can be prevented and the reliability can be improved. (2) The structure of the injection mold for molding the filling material for fixing the shaft is simple, and the mold can be manufactured easily and the manufacturing cost can be reduced. (3) Since it is not necessary to form an outer shell layer on the permanent magnet member,
It eliminates the need for post-processing removal work after injection molding, and can reduce manufacturing costs. (4) Since the thickness of the permanent magnet member in the diametrical direction can be set to the minimum required to secure the magnet characteristics, the weight of the rotor as a whole can be reduced.

[Brief description of drawings]

1A and 1B are views showing an embodiment of the present invention, in which FIG. 1A is a partially sectional front view and FIG. 1B is an end face.

FIG. 2 is a longitudinal sectional view of an essential part showing an example of means for molding the filler 3 in the embodiment of the present invention.

FIG. 3 is a vertical sectional view showing an example of a conventional permanent magnet type rotor.

[Explanation of symbols]

 1 Permanent magnet member 3 Filler 5 Cap

Claims (1)

[Claims] 1. A non-magnetic material having a thickness of 0.05 to 0.5 mm at both ends of a permanent magnet member formed of a sintered magnet material in a hollow cylindrical shape and provided with a plurality of magnetic poles extending in the axial direction on the outer circumference.
A permanent magnet rotor, wherein a hollow bowl-shaped cap is fitted, and a shaft penetrating the permanent magnet member is fixed coaxially with the permanent magnet member by a filler made of a thermoplastic resin material.