Electricity: motive power systems – Reciprocating or oscillating motor – Energizing winding circuit control
Patent
1991-03-05
1992-06-02
Shoop, Jr., William M.
Electricity: motive power systems
Reciprocating or oscillating motor
Energizing winding circuit control
318138, 318811, 318721, 318686, 622284, 62 6, H02K 3314
Patent
active
051190710
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a compressor constituted by housing an induction motor and a compression element rotated and driven by a rotor of the induction motor in a same casing, and more particularly, to a control method and control apparatus which reduces vibration and noise of the compressor by controlling the driving torque of the induction motor.
BACKGROUND OF THE INVENTION
A compressor control system is known from Japanese Patent Laid-Open No. 60-60286/1985. The control system disclosed in this reference provides a motor output torque in synchronism with the change of a load torque applied in one revolution of a motor rotor for driving a compression element of the compressor. In other words, the control system always detects the load torque during one revolution of the rotor and changes the motor output in such a manner as to correspond to this load torque.
Generally, as a rotating position detector of a compressor motor, a detector which detects the rotating position of the rotor by coupling directly a gear or an encoder to a spindle of the motor and disposing a sensor for detecting pulses at the time of revolution, is known as described in Japanese Patent Laid-Open No. 63-23585/1988.
In accordance with the control system of the compressor having the construction described above, the rotating position of the compressor must always be detected, and there remain problems in that a large number of position detectors are necessary, in that a high level of accuracy is required for this position detection, in that the outputs of the motor must be successively calculated and outputted sequentially, with the result being the control circuit becomes complicated.
In the rotating position detector of the motor having the construction described above, the sensor must be disposed directly inside the compressor and for this reason, the Freon resistance, temperature resistance requirements and pressure resistance of the sensor must be fulfilled and the service life of the sensor cannot be secured sufficiently. Though a sensor having an improved Freon resistance has been developed, a sufficiently long service life cannot yet be secured.
SUMMARY OF THE INVENTION
In view of the problems described above, the present invention is directed to provide a control method which can effect torque control of an induction motor by simple position detection and a simple control system.
It is another object of the present invention to provide a control apparatus of an induction motor for a compressor which does not cause the problems of the Freon resistance, the temperature resistance and the pressure resistance even when using an ordinary general-purpose type sensor.
According to the compressor of the present invention wherein an induction motor and a compression element rotated and driven by a rotor of the induction motor are housed in a same casing, an A.C. power of a pattern having a predetermined change, which is determined in advance so as to correspond to the rotating angle of the compression element, is sequentially supplied to the induction motor from a specific phase position of the A.C. power whenever the rotating angle of the compression element reaches a predetermined angle.
The pattern is set so that the frequency at the phase position corresponding to the rotating angle, at which the driving torque required by the compression element becomes great, is greater than the frequency of one period of the pattern. Furthermore, the pattern is set so that the change of the frequency in one period of the A.C. power supplied to the induction motor becomes continuous.
The compressor which employs the control method of the present invention comprises typical permanent magnets which rotate with a rotating shaft, recesses formed by depressing part of an enclosed casing so as to face the permanent magnets, magnetic detection elements in the recesses for detecting the magnetism of the permanent magnets and a control portion for determining the rotating position of a rotor from the outpu
REFERENCES:
patent: 4401419 (1983-08-01), Rabe
patent: 4474537 (1984-10-01), Dolz
patent: 4604036 (1986-08-01), Sutou et al.
patent: 4879502 (1979-11-01), Endo et al.
patent: 5018357 (1991-05-01), Livingstone et al.
Hayashi Norio
Ogawa Takashi
Takezawa Masaaki
Cabeca John W.
Sanyo Electric Co,. Ltd.
Shoop Jr. William M.
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