JPH10336928A - Rotor magnet for motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotor magnet for motor which is prevented from coming off from coating layers even when the magnet is broken. SOLUTION: In a rotor magnet for motor which is formed in such a way that a connecting body 20 in the hollow section of an annular magnet 1 and a shaft 21 positioned to the center axis of the magnet 1 are integrally formed with the magnet 1, while the magnet 1 is placed in an injection molding machine, thin coating layers 3 which confine the magnet 1 inside are formed by elongating the cross-sectional upper and lower ends of the connecting body 20 so as to cover the upper and lower surfaces of the magnet 1. Therefore, the magnet 1 does not come off from the coating layers 3 even when the magnet 1 is partially broken.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a kind of rotor magnet for an electric motor.

[0002]

2. Description of the Related Art Many synchronous motors or asynchronous motors using permanent magnets have a rotor magnet for the motor.
As shown in FIGS. 1 and 2, the rotor magnet of the electric motor is:
After the magnet 1 is sintered and manufactured into an annular shape, the magnet 1 is placed in an injection molding machine, and integrated with a shaft 21 at the center axis position and a connecting body 20 having a substantially I-shaped cross section using a dedicated mold. The connecting member 20 is formed by injection molding.
And the rotor magnet 1 of the electric motor is prevented from being separated. The rotor magnet 1 of the electric motor has its stator 4
It is used to achieve the operation of the motor by the action of attraction and repulsion generated between the magnetic poles (see FIG. 3).

The rotor magnet of the electric motor having the above structure has the following disadvantages. 1. Since the magnet 1 is manufactured by sintering, the magnet 1 is easily broken, and is placed in an injection molding machine with its surface exposed, and when the molding process proceeds, the magnet 1 bursts due to the large pressure of the injection molding. Easy, the defect rate of the rotor magnet product of the motor increases, and the defect rate is generally 1/100.
It was about 5 to 35. Of defective products, those that can be confirmed with the naked eye or those that were found to be defective during product testing can be removed, but many of the defective products are
Structural molecules are destroyed to a considerable extent by residual stress generated inside during injection molding, and they cannot be removed because they are normal in appearance. A withdrawal situation has occurred. See also FIG. When the detached portion is attracted to the stator 4, the rotor magnet of the electric motor can no longer be operated smoothly, and the defective product which is not apparent on the surface is crushed after a certain period of time from shipment. Not only did manufacturers lose their reputation as they caused electric motor failures, they also suffered from routine repairs and parts replacements, and the associated expenses increased. 2. Also, when the rotor magnet product of the motor, which is not defective at the time of molding, is subjected to improper collision or vibration during transportation or use, the magnet is crushed due to the characteristic that it is manufactured by sintering and has high hardness but brittle. Easy and unusable.
Therefore, great care was required during transportation and use.

[0004] In order to solve the above problems, a kind of so-called "molded plastic magneto" structure has already been developed in the industry. It is made by mixing materials such as magnet powder and nylon into raw materials, and is molded by an injection molding machine.
It has the drawback that the product is relatively flexible because it contains a very small amount of nylon, has good toughness and adsorptivity, and is easily fractured due to the high hardness of the rotor magnet of the well-known motor and its brittle structure. It was a great improvement. However, the unit price is high, the manufacturing process is relatively complicated, and most of the components are made into magnet powder, so it becomes a kind of abrasive substance for the barrel and screw of the injection molding machine, so the barrel And the wear rate of the screw is about 4 to 6 times higher than that of glass fiber reinforced plastic,
Further, the manufacturing cost is high, and it is at least 8 to 10 times as large as the cost of using a sintered magnet before that. Thus, in reality, many manufacturers have not yet adopted this molded plastic magneto structure. In addition, because this structure joins nylon,
The lines of magnetic force were reduced by about one-third compared to traditional sintered magnets, and were not ideal products.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a kind of rotor magnet for an electric motor, which comprises a step of forming a rotor magnet of a known electric motor using a sintered magnet. By adopting a new mold, the shaft is molded and at the same time the plastic is completely covered around the magnet, so that the magnet can be permanently made of plastic even by the molding pressure and unreasonable collision and vibration when using the product. It is assumed that the electric motor can be operated normally by restricting the inside of the coating layer to prevent its rupture and detachment thereby.

[0006]

According to the first aspect of the present invention, an annular magnet 1 is placed in an injection molding machine and is located on the connecting member 20 of the hollow portion of the magnet 1 and on the center axis of the magnet 1. Axis 2
1 is a rotor magnet of an electric motor provided so as to be integrated with the magnet, and the upper end and the lower end of the cross section of the connecting body 20 are magnets 1.
The magnet 1 is stretched so as to cover the upper, lower, and side surfaces of the magnet 1
Is formed so as not to be separated from the coating layer 3 even if a part of the magnet is crushed.
The rotor magnet of the motor is used.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a rotor magnet of an electric motor in which a shaft 21 and a connecting body 20 are provided on a center axis of an annular magnet 1 as shown in FIGS. Articulated body 2
The upper and lower ends of the cross section 0 are stretched so as to cover the upper, lower, and side surfaces of the magnet 1 to form a thin coating layer 3.

[0008]

The excellent features of the present invention are as follows. 1. Since the magnet 1 is completely covered with the coating layer 3, even if a rupture is formed inside the magnet due to release of pressure applied during molding or residual stress after molding, or vibration or collision received during use, the magnet 1 is covered with the coating layer 3. 3, the vehicle can be operated forever without leaving the vehicle. 2. The present invention can be carried out merely by manufacturing a mold capable of forming a new coating layer 3, and the cost is small compared with the cost for removing or replacing a known defective product. It can be manufactured at a lower cost than plastic magneto products. 3. Since the thickness of the coating layer 3 covering the magnet 1 is very small, the influence on the magnetic field lines is very small, and the coating layer 3 is superior to the molded plastic magneto product in the influence on the magnetic field lines. If it is desired to increase the lines of magnetic force, the current of the motor coil may be increased. As can be seen from the above description, the rotor magnet of the electric motor of the present invention has a low defect rate, requires only investment for mold repair in terms of manufacturing cost, and is operated by bursting the magnet in use. It is not disabled and is very practical for consumers.

[Brief description of the drawings]

FIG. 1 is a perspective view of a rotor magnet of a known electric motor.

FIG. 2 is a sectional view of a rotor magnet of a known motor.

FIG. 3 is a plan view of a rotor magnet of a known electric motor.

FIG. 4 is a plan view of a known motor when a rotor magnet is crushed.

FIG. 5 is a perspective view of a rotor magnet of the electric motor of the present invention.

FIG. 6 is a sectional view of a rotor magnet of the electric motor of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnet 20 Connecting body 21 Bottom plate 3 Coating layer 4 Stator

Claims (1)

[Claims] 1. An annular magnet 1 is placed in an injection molding machine, and a connecting member 20 in a hollow portion of the magnet 1 and a shaft 21 located on a central axis of the magnet 1 are provided so as to be integral with the magnet. In the rotor magnet of the electric motor, the upper end and the lower end of the cross section of the connecting body 20 are extended so as to cover the upper surface, the lower surface, and the side surface of the magnet 1, and the thin coating layer 3 for limiting the magnet 1 to the inside is formed. A rotor magnet for an electric motor, wherein the magnet does not separate from the coating layer 3 even if a part of the magnet is crushed.