Control valve for variable displacement compressor

Abstract

To provide a control valve for a variable displacement compressor, which is simple in construction and excellent in controllability. Between a port for introducing refrigerant at discharge pressure Pd 1 delivered from a discharge chamber and a port for allowing refrigerant at discharge pressure Pd 2 to flow out at a controlled flow rate, there are provided a main valve the valve lift of which is varied according to the flow rate of refrigerant passing therethrough, and a solenoid valve that uses a valve element of the main valve as a variable valve seat and supplies to the crankcase the refrigerant at pressure Pc the flow rate of which is controlled according to the size of a gap formed between the variable valve seat and the hollow cylindrical valve element. The main valve not only senses the flow rate but also serves as the valve seat of the solenoid valve, and the solenoid valve controls the small flow rate of refrigerant supplied to the crankcase. Therefore, the control valve is simple in construction, and capable of performing stable flow rate control.

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 set to a first valve lift a lift amount of which is dependent on a flow rate of refrigerant passing therethrough which is discharged from a discharge chamber of the compressor; and    a solenoid valve that is set to a second valve lift by an external signal, and controls a flow rate of refrigerant to be allowed to flow from the discharge chamber to a crankcase according to an amount of change in the first valve lift relative to the second valve lift set thereto.    
   
   
       2 . 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 valve seat formed in a refrigerant passage communicating between a first port to be connected to a discharge chamber of the compressor and a second port to be connected to an outlet port of the compressor, and a valve element that is disposed at a location downstream of the valve seat, in a state urged in a valve-closing direction such that the valve element can be moved to and away from the valve seat; and    a solenoid valve that is disposed coaxially with the main valve, and has a hollow cylindrical body having a hollow portion, one open end opening in the first port, and another open end opening in a third port to be connected to a crankcase of the compressor, the hollow cylindrical body being urged along a same axis as that of the main valve, the valve element of the main valve being regarded as a movable valve seat or a movable valve element and forming a valve portion in cooperation with the hollow cylindrical body.    
   
   
       3 . The control valve according to  claim 2 , wherein the valve element of the main valve is configured such that the valve element has an axially extending piston inserted in a through hole axially formed therethrough, and is movable axially back and forth using the piston as a guide, the valve portion of the solenoid valve being a slide valve configured such that the one end of the hollow cylindrical body is disposed in a manner removably insertable into the through hole.  
   
   
       4 . The control valve according to  claim 2 , wherein the valve element of the main valve is configured such that a hollow cylindrical valve element having a same diameter as the hollow cylindrical body is fitted in a through hole axially formed through the valve element, and the hollow cylindrical valve element is held in an axially recessed guide in a manner movable axially back and forth, whereby the valve element of the main valve is movable axially back and forth, the valve portion of the solenoid valve comprising a hollow cylindrical movable valve seat having a funnel-like shape formed by expanding the one open end of the hollow cylindrical body opening in the first port, and the hollow cylindrical valve element fitted on the valve element of the main valve.  
   
   
       5 . The control valve according to  claim 2 , wherein the valve element of the main valve is configured such that the valve element has an axially extending piston inserted in a through hole axially formed therethrough, and is movable axially back and forth using the piston as a guide, the valve portion of the solenoid valve being a poppet valve configured such that a frustoconical valve element having a frustoconical shape at one end of the hollow cylindrical body is disposed such that the frustoconical valve element can be moved to and away from a rim of the through hole.  
   
   
       6 . The control valve according to  claim 2 , wherein the valve element of the main valve comprises a hollow cylindrical skirt slidably disposed in a valve hole of the main valve and having a slit forming a passage in the main valve, and a hollow cylindrical portion forming a valve seat of the solenoid valve, the skirt and the hollow cylindrical portion being coaxially arranged and formed integrally with each other, the valve portion of the solenoid valve being a poppet valve configured such that a frustoconical portion formed at one end of the hollow cylindrical body is disposed such that the frustoconical portion can be moved to and away from the hollow cylindrical portion.  
   
   
       7 . The control valve according to  claim 6 , wherein the slit formed in the skirt is varied in opening width thereof in a direction in which the valve element of the main valve is lifted.  
   
   
       8 . The control valve according to  claim 2 , wherein the hollow cylindrical body has closed opposite ends and a side provided with holes opening into the first port and the third port, and wherein the valve element of the main valve is configured such that the valve element has the hollow cylindrical body inserted in a through hole axially formed therethrough, and is movable axially back and forth using the hollow cylindrical body as a guide, the valve portion of the solenoid valve being a slide valve formed by the open end opening into the first port and the valve element of the main valve.  
   
   
       9 . The control valve according to  claim 2 , wherein the hollow cylindrical body is held by a body accommodating the main valve and the solenoid valve or by a core of the solenoid provided in the body, in a manner movable axially back and forth, an end of the hollow cylindrical body on a side opposite from the main valve being fixed to a plunger of the solenoid.  
   
   
       10 . The control valve according to  claim 2 , wherein the hollow cylindrical body is held by a body accommodating the main body and the solenoid valve or by a core of the solenoid provided in the body, in a manner movable axially back and forth, an end of the hollow cylindrical body on a side opposite from the main valve being in abutment with a shaft fixed to a plunger of the solenoid.  
   
   
       11 . The control valve according to  claim 2 , wherein the main valve includes damper means for suppressing a sudden motion of the valve element responsive to a sudden change in pressure of refrigerant supplied from the discharge chamber.