Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1993-04-08
1994-10-25
Skudy, R.
Electrical generator or motor structure
Dynamoelectric
Rotary
310 43, 310261, H02K 2112
Patent
active
053592484
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a brushless motor suitable for use in corrosive atmosphere or liquid, particularly in refrigerant, and more particularly to a rotor for such a brushless motor.
PRIOR ART
The permanent magnet rotor is well known, which generally comprises a yoke formed of a plurality of laminated silicon steel sheets and permanent magnets for field inserted into such a yoke.
Referring to FIG. 8 of the attached drawings, there is shown a permanent magnet rotor 50 of prior art which includes a yoke 51. The yoke 51 is formed of, as mentioned above, a plurality of integrally laminated silicon steel sheets 52 and has along its outer periphery four magnetic poles 53 projecting radially outward. The respective magnetic poles 53 are formed with slots 54 serving to respective field permanent magnets 55.
Now referring to FIG. 9, the above well known permanent magnet rotor 50 is shown in a sectional view. As seen, the permanent magnets 55 are inserted into the respective slots 54 of the yoke 51. These permanent magnets 55 are arranged so that the outer periphery of the permanent magnet rotor 50 are magnetized alternately in different polarities, as shown. Consequently, the permanent magnet rotor 50 has four magnetic poles. Magnetic flux generated from these magnetic poles interacts with electric current flowing through excitation coils (not shown) of the motor to drive the permanent magnet rotor 50.
However, the conventional permanent magnet rotor has been disadvantageous in that the fluid surrounding the permanent magnet rotor tends to permeate through interstices of the laminated steel sheets and comes in contact with the permanent magnets. Particularly in the case of the motor used in the scroll type compressor for the air-conditioner, the permanent magnets of the rotor have inevitably been corroded due to direct contact with the refrigerant resulting in serious problems, for example, a capacity of the motor has been reduced due to demagnetization of the magnets and parts of the equipment have been clogged with magnetic particles separated from the permanent magnets.
Moreover, the permanent magnets in the conventional permanent magnet rotor have usually been mechanically fragile and liable to be damaged during insertion into or bonding onto the yoke.
Accordingly, it is an object of the invention to provide a permanent magnet rotor which can be used without corrosion of permanent magnets and easily manufactured, on one hand, and to provide a method of making such a permanent magnet rotor, on the other hand.
DISCLOSURE OF THE INVENTION
The object set forth above is achieved in accordance with a first aspect of the invention, by a permanent magnet rotor comprising a yoke formed from a plurality of silicon steel sheets and permanent magnets inserted into respective slots axially extending through the yoke wherein the permanent magnets are hermetically covered with respective anticorrosive plates.
The object is also achieved by a method of making this permanent magnet rotor comprising steps of forming a peripheral wall of a mold having a rectangular crosssection from an anticorrosive plate, pouring molten metal of cast type permanent magnet and thereby molding a permanent magnet ingot, hot-rolling the permanent magnet ingot by a rolling mill, simultaneously the ingot being magnetically made anisotropic, into a rolled bar of permanent magnet having a predetermined cross-sectional dimension cutting the rolled bar of permanent magnet into an individual permanent magnet of a predetermined length, and inserting or bonding the individual permanent magnet into or onto the yoke.
The object set forth above is achieved in accordance with a second aspect of the invention by a permanent magnet rotor for brushless motor used in corrosive atmosphere or liquid, wherein a yoke and permanent magnets of the rotor are hermetically covered with a sheet of corrosion resisting material.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view showing an embodiment of permanent magnet rotor cons
REFERENCES:
patent: 4433261 (1984-02-01), Nashiki
patent: 4445062 (1984-04-01), Glaser
patent: 4631435 (1986-12-01), McCarty
patent: 4674178 (1987-06-01), Patel
patent: 4742259 (1988-05-01), Schaefer
patent: 4930201 (1990-06-01), Brown
patent: 4973872 (1990-11-01), Dohogne
patent: 5140210 (1992-08-01), Shirakawa
patent: 5233248 (1993-08-01), Kawamura
Endo Ken-ichi
Koike Yoshikazu
Nagate Takashi
Seto Takeshi
Yamagishi Yoshihiko
Seiko Epson Corporation
Skudy R.
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