Patent ID: 6585494
Filing Date: 2003-07-01
Classification: F04B,F25B

Abstract:
A variable-capacity control system for use with a refrigeration cycle that uses carbon dioxide as a coolant, said system comprising:a variable-capacity compressor having an intake side and being operable to compress the coolant, said variable-capacity compressor comprising a cylinder block, a drive shaft provided inside said cylinder block, a drive swash plate, a plurality of cylinders provided within said cylinder block, a plurality of pistons slidably provided at said cylinders, compression spaces defined by said cylinders and said pistons, a crank case formed on a non-compression space side of said pistons, an intake chamber, an outlet chamber and a variable-capacity mechanism; a radiator operable to cool the compressed coolant; an expansion device operable to expand the cooled coolant and having an outlet side; an evaporator operable to evaporate the expanded coolant; a low pressure line extending from the outlet side of said expansion device to the intake side of said variable-capacity compressor; and a pressure sensor operable to detect pressure of coolant in said low pressure line, wherein said drive swash plate is operable to rotate together with said drive shaft and has a variable angle of inclination relative to said drive shaft, wherein each of said cylinders has an axis parallel to said drive shaft, wherein said pistons are operable to reciprocally move within said cylinders as said drive swash plate rotates, wherein said intake chamber is arranged to communicate with the compression spaces during an intake phase of said pistons, wherein said outlet chamber is arranged to communicate with the compression spaces during a compression phase of said pistons, wherein said variable-capacity mechanism comprises an electromagnetic coil operable to generate an electromagnetic force, a plunger operable to slidably insert into said electromagnetic coil as a result of the electromagnetic force, a valve element operable to move between a first position and a second position as a result of movement of said plunger, a spring operable to apply a force to said valve element along a direction opposite to a plunger moving direction, a pair of low pressure chambers located at two ends of said valve element to communicate with said intake chamber, a pressure adjustment chamber arranged to communicate with said crank case, a high pressure chamber arranged to communicate with said outlet chamber, a low pressure side communicating port provided between said pressure adjustment chamber and said low pressure chamber, and a high pressure side communicating port provided between said pressure adjustment chamber and said high pressure chamber, wherein said valve element comprises an opening/closing portion, a small diameter portion and a sliding portion, wherein said pressure adjustment chamber is formed around said opening/closing portion, wherein said high pressure chamber is formed around said small diameter portion, wherein said low pressure side communicating port is operable to close or open via one end of said opening/closing portion, wherein said high pressure side communicating port is operable to open or close via another end of said opening/closing portion, wherein when said valve element is in the first position, a fluid communication is established between said pressure adjustment chamber and said low pressure chamber and a fluid communication is not establish between said pressure adjustment chamber and said high pressure chamber, wherein when said valve element is in the second position, a fluid communication is not established between said pressure adjustment chamber and said low pressure chamber and a fluid communication is established between said pressure adjustment chamber and said high pressure chamber, and wherein said electromagnetic coil is operable to place said valve element in the first position when a coolant pressure detected by said pressure sensor is equal to or higher than a target pressure, and to place said valve element in the second position when a coolant pressure detected by said pressure sensor is lower than the target pressure.