To solve the problem of the generation of asymmetric thrust by the conventional structure, and to achieve symmetric thrust/current characteristics, with regard to the moving coil linear motor that is applied to compressors including a stirling refrigerator.
Two pieces of annular permanent magnets 8a, 8b magnetized in the radial direction and two pieces of moving coils 9a, 9b facing each permanent magnet are placed in the axial direction and arranged between inside and outside circumferential yokes 7a, 7b. The polarity of the magnetic pole of the permanent magnets 8a, 8b and the current-flowing direction in the moving coils 9a, 9b are set in the reverse direction to each other. Then, an AC voltage is impressed to the moving coils to make the pistons 2 of the compressor perform reciprocating operations. This structure forms a closed magnetic circuit that goes through the moving coils in series. In the annular spaces, the sum of the magnetic flux generated by the conducting current of each coil becomes zero, which generates symmetric electromagnetic thrust of the same magnitude in both directions of compression and expansion.
Yoshihide Komada
Kiyoshi Matsuzaki
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