Refrigerating system having a compressor with an internally and externally controlled variable displacement mechanism

Claim 1

A refrigerating system including a refrigerant circuit, comprising a condensor (201), evaporator (203) and compressor (10), the compressor including a compressor housing having a central portion (11), a front end plate (14f) at one end and a rear end plate (14r) at its other end, the housing having a cylinder block (12), a piston (71) slidably fitted within each of said cylinders (70), a drive mechanism (16,20,30) coupled to the pistons to reciprocate the pistons within the cylinders, the drive mechanism including a drive shaft (16) rotatably supported in the housing, a rotor (20) coupled to the drive shaft and rotatable therewith, and coupling means (21,22,31,32,30,50) for drivingly coupling the rotor to the pistons such that the rotary motion of the rotor is converted into reciprocating motion of the pistons, the coupling means including a member (50) having a surface disposed at an incline angle relative to the drive shaft, the incline angle of the member being adjustable to vary the stroke length of the pistons and the capacity of the compressor, the rear end plate (14r) having a suction chamber (141) and a discharge chamber (142), variable displacement control means for controlling angular displacement of said adjustable member, comprising first valve control means (81) for controlling fluid communication between the crank chamber and the suction chamber (141) in response to changes in refrigerant pressure in the compressor, first valve control means comprising a first passageway (814) providing fluid communication between the crank chamber and the suction chamber and first valve means (811) for controlling the opening and closing of the first passageway to vary the capacity of the compressor by adjusting the incline angle, the first valve means comprising a first valve (811b) to directly open and close the first passageway, the variable displacement control means further comprising second valve control means (82) for controlling fluid communication between the crank chamber (13) and the suction chamber (141) in response to a signal generated outside of the compressor, the second valve control means comprising a second passageway (823) providing fluid communication between the crank chamber and the suction chamber and second valve means (821) for controlling the opening and closing of the second passageway to vary the capacity of the compressor by adjusting the incline angle, the second valve means comprising a second valve to directly open and close the second passageway and override the operation of the first valve, characterised by: means for controlling the generation of the signal in response to at least one thermodynamic characteristic related to the evaporator as compared with two distinct boundary values.