Capacity Control Valve, Variable Capacity Compressor and Capacity Control System Therefor

Abstract

Provided are a capacity control valve, a variable capacity compressor, and a capacity control system, which control a discharge capacity stably even when a cooling load is small, and reduce the risk of damaging a compressor even in a state when the quantity of a refrigerant is insufficient. The capacity control valve ( 300 ) for the variable capacity compressor includes a solenoid unit ( 300 B), a valve body ( 306 ) on which the pressure of a discharge chamber ( 142 ) of the variable capacity compressor acts in a valve opening direction, and the pressure of a suction pressure area of the variable capacity compressor and the electromagnetic force of the solenoid unit ( 300 B) act in a valve closing direction opposite to the valve opening direction, and a pressure sensitive unit ( 340 ) on which the pressure of the discharge chamber ( 142 ) acts, and which is connected to the valve body ( 306 ) to apply urging force in the valve opening direction on the valve body ( 306 ) according to the pressure of the discharge chamber ( 142 ) when the pressure of the discharge chamber ( 142 ) is lower than a set pressure, and is separated from the valve body ( 306 ) when the pressure of the discharge chamber ( 142 ) is higher than the set pressure.

1 . A capacity control valve, disposed in a communication passage communicating a discharge pressure area with a control pressure chamber in a variable capacity compressor, for regulating a pressure in the control pressure chamber to control a discharge capacity of the variable capacity compressor, the capacity control valve comprising:
 a solenoid unit;   a valve body on which a pressure of the discharge pressure area of the variable capacity compressor acts in a valve opening direction, and a pressure of a suction pressure area of the variable capacity compressor and an electromagnetic force of the solenoid unit acts in a valve closing direction opposite to the valve opening direction; and   a pressure sensitive unit on which the pressure of the discharge chamber acts, and which is connected to the valve body to apply urging force in the valve opening direction on the valve body according to the pressure of the discharge pressure area when the pressure of the discharge pressure area is lower than a set pressure, and is separated from the valve body when the pressure of the discharge pressure area is higher than the set pressure.   
     
     
         2 . The capacity control valve according to  claim 1 , wherein a first pressure receiving area of the valve body on which the pressure of the discharge pressure area acts is equal to or greater than a second pressure receiving area of the valve body on which the pressure of the suction pressure area of the variable capacity compressor acts. 
     
     
         3 . The capacity control valve according to  claim 2 , wherein the pressure sensitive unit is disposed in such a way that the pressure of the discharge pressure area acts on the pressure sensitive unit and the valve body in opposite directions. 
     
     
         4 . The capacity control valve according to  claim 3 , wherein the first pressure receiving area is set, in the pressure sensitive unit, substantially identical to a third pressure receiving area on which the pressure of the discharge pressure area acts. 
     
     
         5 . The capacity control valve according to  claim 1 , wherein the pressure sensitive unit is disposed, in the communication passage, in an area extending between the discharge pressure area and a valve hole of the capacity control valve. 
     
     
         6 . A variable capacity compressor comprising:
 a housing having a discharge chamber as the discharge pressure area, a crank chamber as the control pressure chamber, a suction chamber, and a cylinder bore defined therein;   a piston placed in the cylinder bore;   a drive shaft rotatably supported in the housing;   a conversion mechanism including a swash plate element of a variable tilt angle which converts rotation of the drive shaft to a reciprocal motion of the piston; and   the capacity control valve as set forth in  claim 1 .   
     
     
         7 . A capacity control system for a variable capacity compressor, comprising the capacity control valve as set forth in  claim 1 , external information detecting means which detects external information, control target setting means which sets a control target value based on the external information detected by the external information detecting means, and current regulating means which regulates a current to be supplied to the solenoid unit based on the control target value set by the control target setting means, and controlling a discharge capacity of the variable capacity compressor by regulating the pressure of the control pressure chamber,
 the external information detecting means including discharge pressure detecting means for detecting the pressure of the discharge pressure area,   wherein when the pressure of the discharge pressure area detected by the discharge pressure detecting means is lower than the set pressure, the control target setting means sets a target suction pressure which is a target value of the pressure of the suction pressure area as the control target value, and the current regulating means regulates the current to be supplied to the solenoid unit based on the target suction pressure.   
     
     
         8 . The capacity control system for a variable capacity compressor according to  claim 7 , wherein when the pressure of the discharge pressure area detected by the discharge pressure detecting means is higher than the set pressure, the control target setting means sets the target suction pressure which is the target value of the pressure of the suction pressure area as the control target value, and the current regulating means regulates the current to be supplied to the solenoid unit based on the pressure of the discharge pressure area detected by the discharge pressure detecting means, and the target suction pressure. 
     
     
         9 . The capacity control system for a variable capacity compressor according to  claim 7 , wherein when the pressure of the discharge pressure area detected by the discharge pressure detecting means is higher than the set pressure, the control target setting means sets a target value for the current to be supplied to the solenoid unit as the control target value, and the current regulating means regulates the current to be supplied to the solenoid unit in such a way as to approach the target value of the current.