Rotary compressor

Abstract

A rotary compressor includes a compression mechanism, an electric motor and a controller. The compression mechanism includes a piston and a cylinder having two cylinder chambers. The electric motor is configured to change volumes of the cylinder chambers by eccentrically moving the cylinder and the piston relative to each other. The controller is configured to change an output torque of the electric motor in accordance with a variation in a load torque of the compression mechanism in one turn of rotation.

1 . A rotary compressor, comprising:
 a compression mechanism including a piston and a cylinder having two cylinder chambers;   an electric motor configured to change volumes of the cylinder chambers by eccentrically moving the cylinder and the piston relative to each other; and   a controller configured to change an output torque of the electric motor in accordance with a variation in a load torque of the compression mechanism in one turn of rotation.   
   
   
       2 . The rotary compressor of  claim 1 , wherein
 the cylinder includes an annular cylinder chamber, and   the piston is an annular piston housed in the annular cylinder chamber to partition the annular cylinder chamber into an outer cylinder chamber and an inner cylinder chamber, which form the two cylinder chambers.   
   
   
       3 . The rotary compressor of  claim 2 , wherein
 a volume ratio of the inner cylinder chamber to the outer cylinder chamber is in a range from 0.6 to 1.0.   
   
   
       4 . The rotary compressor of  claim 2 , wherein
 the electric motor is a brushless DC motor.   
   
   
       5 . The rotary compressor of  claim 2 , wherein
 the controller is further configured to change an output torque of the electric motor by changing one of an input current, an input voltage, and an input current phase of the electric motor.   
   
   
       6 . The rotary compressor of  claim 2 , wherein
 the electric motor is coupled to the cylinder in order to move the cylinder relative to the annular piston, and   the annular piston is stationary.   
   
   
       7 . The rotary compressor of  claim 2 , wherein
 the electric motor is coupled to the annular piston in order to move the annular piston relative to the cylinder, and   the cylinder is stationary.   
   
   
       8 . The rotary compressor of  claim 2 , wherein
 the compression mechanism is configured to perform two-stage compression on a fluid, with one of the outer and inner cylinder chambers being a low-stage side and the other one of the outer and inner cylinder chambers being a high-stage side.   
   
   
       9 . The rotary compressor of  claim 8 , wherein
 a volume ratio of the inner cylinder chamber to the outer cylinder chamber is in a range from 0.6 to 0.8.   
   
   
       10 . The rotary compressor of  claim 1 , wherein
 the cylinder includes a low-stage first cylinder and a high-stage second cylinder, with each of the first and second cylinders having one of the two cylinder chambers,   the piston includes a first rotary piston housed in the cylinder chamber of the first cylinder and a second rotary piston housed in the cylinder chamber of the second cylinder, and   the compression mechanism is configured to perform two-stage compression on a fluid in the first and second cylinders by eccentrically moving the first and second rotary pistons with the electric motor.   
   
   
       11 . The rotary compressor of  claim 10 , wherein
 a volume ratio of the cylinder chamber of the second cylinder to the cylinder chamber of the first cylinder is in a range from 0.6 to 0.8.   
   
   
       12 . The rotary compressor of  claim 10 , wherein
 the compression mechanism is configured such that a rotational phase of the first rotary piston in of the first cylinder is shifted 180° from a rotational phase of the second rotary piston in the second cylinder.   
   
   
       13 . The rotary compressor of  claim 3 , wherein
 the electric motor is a brushless DC motor.   
   
   
       14 . The rotary compressor of  claim 3 , wherein
 the controller is further configured to change an output torque of the electric motor by changing one of an input current, an input voltage, and an input current phase of the electric motor.   
   
   
       15 . The rotary compressor of  claim 3 , wherein
 the electric motor is coupled to the cylinder in order to move the cylinder relative to the annular piston, and   the annular piston is stationary.