Linear electric compressor and refrigerant circuit

Abstract

A refrigerant circuit includes a linear electric compressor including a housing with a cylinder bore, a pair of end plates, a valve unit, a piston, an urging device for urging the piston, a coil generating electromagnetic force and a permanent magnet. The permanent magnet cooperates with the urging device and the coil to reciprocate the piston in the cylinder bore. The piston further includes a piston rod and the urging device is provided around the piston rod and a pair of piston heads integrally formed at opposite ends of the piston rod. The diameter of the piston rod is smaller than that of the piston head. The permanent magnet is provided on the piston head and the coil surrounds the piston head. The housing further includes a seat located between the pair of piston heads and the urging device is provided between the seat and each of the piston head.

1 . A linear electric compressor comprising:
 a housing having formed therein a cylinder bore;   a pair of end plates joined to opposite ends of the housing;   a valve unit provided between the cylinder bore and the end plate, wherein a compression chamber is located on the cylinder bore side of the valve unit and a discharge chamber or a suction chamber is located on the end plate side of the valve unit;   a piston reciprocally-slidably received in the cylinder bore, wherein the piston and the valve unit cooperate to form the compression chamber in the cylinder bore;   an urging device for urging the piston in the direction for the piston to reciprocate;   a coil provided in the housing and generating electromagnetic force; and   a permanent magnet provided in the piston, the permanent magnet cooperate with the urging device and the coil to reciprocate the piston in the cylinder bore,   wherein the piston includes:   a piston rod; and   a pair of piston heads integrally formed at opposite ends of the piston rod, the piston heads are slidable in the cylinder bore, wherein the diameter of the piston rod is smaller than that of the piston head, wherein the permanent magnet is provided on the piston head and the coil surrounds the piston head; wherein the housing includes:   a seat located between the pair of piston heads, wherein the urging device is provided around the piston rod between the seat and each of the piston head.   
     
     
         2 . The linear electric compressor according to  claim 1 , wherein the housing includes:
 a cylinder block having formed therein the cylinder bore; and   a shell housing the cylinder block, wherein the coil is provided between the shell and the cylinder block.   
     
     
         3 . The linear electric compressor according to  claim 2 , wherein the piston has a suction passage provided between the pair of piston heads, the linear electric compressor further comprising:
 an intermediate chamber provided in any one of the cylinder block and the shell, or between the cylinder block and the shell, the intermediate chamber communicates with the suction passage, wherein the discharge chamber is located on the end plate side of the valve unit; wherein the piston head includes a suction valve unit between the compression chamber and the suction passage, wherein the intermediate chamber forms the suction chamber.   
     
     
         4 . The linear electric compressor according to  claim 1 , wherein the housing further comprises an accommodation hole which is coaxial with the cylinder bore and has the same diameter as that of the cylinder bore, wherein the urging device is disposed between the cylinder rod and the accommodation hole. 
     
     
         5 . The linear electric compressor according to  claim 4 , wherein the seat protrudes from inner surface of the housing into the accommodation hole so as to receive the end of the urging device. 
     
     
         6 . A refrigerant circuit comprising:
 the linear electric compressor according to;   a condenser;   an expansion valve;   an evaporator;   a plurality of tubes connecting above components and through which refrigerant gas flows;   a power supply supplying electric power to the coil of the linear electric compressor;   a detecting device detecting a state quantity of the linear electric compressor; and   a control device controlling the electric power that the power supply supplies, based on the state of quantity detected by the detecting device.   
     
     
         7 . The refrigerant circuit according to  claim 6 , wherein the state of quantity is a physical quantity influenced by a position of the piston of the linear electric compressor. 
     
     
         8 . The refrigerant circuit according to  claim 7 , wherein the physical quantity is a pressure difference between first pressure at first position and second pressure at second position in the refrigerant circuit that is located downstream of the first position. 
     
     
         9 . The refrigerant circuit according to  claim 8 , wherein the detecting device is provided in the tube, wherein the detecting device including:
 a spool that is movable based on the pressure difference;   a moving permanent magnet fixed to the spool; and   a magnetic force detecting device detecting magnetic flux density of the moving permanent magnet.   
     
     
         10 . The refrigerant circuit according to  claim 9 , wherein the first and the second positions are provided in the tube located between the discharge chamber and the condenser, wherein a throttle is provided between the first and the second positions. 
     
     
         11 . The refrigerant circuit according to  claim 9 , wherein a bend is provided between the first and the second positions. 
     
     
         12 . The refrigerant circuit according to  claim 7 , wherein the detecting device detects a position of the piston directly.