This paper presents recent developments relating to the capacity control of rotary type compressors. The basic design theory and its practical application, as outlined in this paper, will provide effective capacity control in rotary type compressors. Because of their light weight, small size and low level of noise, we have seen a recent increase in the use of rotary type compressors in automotive air-conditioners. The major drawback to the use of rotary type compressors has been the fact that refrigerating capacity increases in proportion to an increase in engine speed. When running at a high speed the cooling capacity is increased to such an extent that there is an overcooling of the compartment which causes an overload of the condenser. A solution is needed that eliminates the major drawbacks without sacrificing the light weight, small size and low level of noise of rotary type compressors. We focused our attention on the speed dependent refrigerant flow in the suction stroke. The ultimate purpose of our research was to develop a compressor which would combine the characteristics of little loss of refrigerating capacity at low speed operation and effective suppression of refrigerating capacity at high speed operation. The result of our research has made it possible to eliminate the factors which have previously hindered the realization of capacity control in compressors, and the final rotary type compressor design turned out to have ideal capacity control characteristics.
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