Control valve for variable displacement compressor

Abstract

To provide a control valve for a variable displacement compressor, which can be realized with a simple construction, while being equipped with the function of a check valve to be disposed at an outlet port of the compressor. The control valve for a variable displacement compressor includes a main valve that sets a cross-sectional area-fixed passage in which the passage cross-sectional area thereof is substantially constant when refrigerant flows between a discharge chamber and an outlet port of the compressor, and closes the cross-sectional area-fixed passage due to inversion of the magnitudes of pressure across the cross-sectional area-fixed passage when the compressor is not in operation, a pilot valve that controls the flow rate of refrigerant flowing from the discharge chamber to a crankcase in a manner interlocked with the differential pressure across the cross-sectional area-fixed passage received by the main valve, and a solenoid that is capable of setting a valve lift of the pilot valve by an external signal. The pilot valve controls the flow rate of refrigerant allowed to flow into the crankcase so as to make constant the differential pressure across the cross-sectional area-fixed passage, to thereby provide control such that the flow rate of refrigerant allowed to flow to the outlet port of the compressor is constant.

1 . A control valve for a variable displacement compressor, for providing control such that a flow rate of refrigerant discharged from the compressor becomes constant, comprising: 
 a main valve that is disposed in a first refrigerant passage formed between a first port communicating with a discharge chamber of the compressor and a second port communicating with an outlet port of the compressor, such that the main valve is lifted in a valve-opening direction to set the first refrigerant passage to a cross-sectional area-fixed passage having a predetermined passage cross-sectional area in response to a flow of refrigerant from the first port to the second port, and closed when a flow rate of the flow of refrigerant is slight or zero;    a pilot valve that is disposed into a second refrigerant passage formed between the first port and a third port communicating with a crankcase of the compressor, for controlling a flow rate of refrigerant flowing from the first port to the third port according to a differential pressure across the cross-sectional area-fixed passage; and    a solenoid that sets the pilot valve to a predetermined valve lift by an external signal.    
   
   
       2 . The control valve according to  claim 1 , wherein the main valve and the pilot valve are lifted in a same lifting direction and arranged on a same axis, and the pilot valve senses the differential pressure generated across the cross-sectional area-fixed passage, based on a change in a flow rate of refrigerant flowing through the main valve, to thereby directly control a lift of the pilot valve.  
   
   
       3 . The control valve according to  claim 2 , wherein the solenoid is arranged on the same axis as the main valve and the pilot valve, and holds the pilot valve in a fully-open state when the solenoid is not energized.  
   
   
       4 . A control valve for a variable displacement compressor, for providing control such that a flow rate of refrigerant discharged from the compressor becomes constant, comprising: 
 a main valve that has a main valve seat formed in a refrigerant passage communicating between a first port connected to a discharge chamber of the compressor and a second port connected to an outlet port of the compressor, and a main valve element that is disposed at a location downstream of the main valve seat, in a state urged in a valve-closing direction such that the main valve element is movable to and away from the main valve seat, and is lifted from the main valve seat in response to a flow of refrigerant from the first port to the second port, for setting the first refrigerant passage to a cross-sectional area-fixed passage having a predetermined passage cross-sectional area;    a pilot valve that has a valve seat formed in a second refrigerant passage communicating between the first port and a third port connected to a crankcase of the compressor, and a valve element disposed at a location upstream of the valve seat in a state urged in a valve-opening direction such that the valve element is movable to and away from the valve seat, and at the same time operates in a manner interlocked with the main valve element when the main valve is set to the cross-sectional area-fixed passage, the pilot valve being arranged on a same axis as the main valve; and    a solenoid disposed on a same axis as the main valve and the pilot valve, for setting the pilot valve to a predetermined valve lift by an external signal.    
   
   
       5 . The control valve according to  claim 4 , wherein the valve element of the pilot valve is formed integrally with a shaft extending through a through hole formed in the main valve element of the main valve, the shaft having a stopper member that stops the main valve element when the main valve element is lifted from the main valve seat in response to the flow of refrigerant from the first port to the second port, to thereby set the main valve to the cross-sectional area-fixed passage.  
   
   
       6 . The control valve according to  claim 5 , wherein the valve element of the pilot valve, the shaft, and a drive shaft of the solenoid are formed integrally with each other.  
   
   
       7 . The control valve according to  claim 5 , wherein the shaft has a protrusion that protrudes radially outward, and closes the through hole of the main valve element when the main valve is closed.  
   
   
       8 . The control valve according to  claim 5 , wherein the valve element of the pilot valve has a guide integrally formed therewith, the guide being formed by axially extending the valve element such that a periphery of the guide is in sliding contact with an inner wall of a valve hole of the pilot valve.  
   
   
       9 . The control valve according to  claim 4 , wherein the main valve element of the main valve has an extended portion that is always positioned within a valve hole of the main valve, and wherein the cross-sectional area-fixed passage which the main valve element is to set is defined between an outer peripheral surface of the extended portion and an inner peripheral surface of a valve hole of the main valve.  
   
   
       10 . The control valve according to  claim 4 , wherein the main valve element of the main valve has a skirt axially slidable in a valve hole of the main valve, the skirt being formed with a slit to thereby form the cross-sectional area-fixed passage which the main valve element is to set.  
   
   
       11 . The control valve according to  claim 4 , wherein the main valve element of the main valve defines the cross-sectional area-fixed passage which the main valve element is to set, between an outer peripheral surface thereof and an inner peripheral surface of a cylinder accommodating the main valve element.  
   
   
       12 . The control valve according to  claim 4 , wherein the pilot valve is a poppet valve disposed such that the poppet valve is movable to and away from the valve seat.  
   
   
       13 . The control valve according to  claim 4 , wherein the pilot valve is a slide valve having a valve hole into which the valve element can be inserted or from which the valve element can be removed.