Thermostatic expansion valve for refrigeration or heat-pump circuits with thermally controlled safely function

Abstract

The invention relates to a thermostatic expansion valve having a valve element ( 33 ) which, for the throughflow of the refrigerant, closes and moves in the opening direction a valve seat ( 32 ) of a passage opening ( 29 ) arranged between the supply opening ( 27 ) and the discharge opening ( 31 ), and which is assigned to a first actuating element ( 36 ), the first actuating element ( 36 ) comprising a chamber ( 38 ) which is delimited with a first active face ( 37 ) and which contains a control charge ( 41 ), wherein an actuating element ( 46 ) is provided, which is thermally activated independently of the high pressure, the actuating movement of which actuating element ( 46 ) is coupled in terms of movement to the first active face ( 37 ) of the first actuating element ( 36 ) when a temperature-dependent actuating movement of the thermally activatable actuating element ( 46 ) acts counter to the actuating movement of the first active face ( 37 ) of the first actuating element ( 36 ), with a temperature threshold value of the thermally activatable actuating element ( 46 ) for an actuating movement being set to an identical value as the MOT (maximum operation temperature) of the control charge ( 41 ) of the first actuating element ( 36 ), which control charge ( 41 ) has a fluid density which lies below its critical density.

1 . Thermostatic expansion valve for regulating a high pressure of a refrigeration or heat-pump circuit which is operatable both transcritically and also subcritically, having a valve housing in which, at the input side, a high pressure prevails in a supply opening, and at the output side, a low pressure prevails at a discharge opening, having a valve element which, for the throughflow of the refrigerant, closes and moves in the opening direction a valve seat of a passage opening arranged between the supply opening and the discharge opening, and which is assigned to a first actuating element, the first actuating element comprising a chamber which is delimited with a first active face and which contains a control charge, characterized in that an actuating element is provided, which is thermally activated independently of the high pressure, the actuating movement of which actuating element is coupled in terms of movement to the first active face of the first actuating element when a temperature-dependent actuating movement of the thermally activatable actuating element acts counter to the actuating movement of the first active face of the first actuating element, with a temperature threshold value of the thermally activatable actuating element for an actuating movement being set to an identical value as the MOT (maximum operation temperature) of the control charge of the first actuating element, which control charge has a fluid density which lies below its critical density. 
   
   
       2 . Valve according to  claim 1 , characterized in that a detachable mechanical coupling is provided between the first actuating element and the thermally activatable actuating element, and the thermally activatable actuating element engages on a first active face of the first actuating element or on a valve element which is connected to the first actuating element. 
   
   
       3 . Valve according to  claim 1 , characterized in that the chamber is embodied in the manner of a diaphragm or bellows and is thermally conductive in order to absorb the temperature of the high-pressure-side refrigerant. 
   
   
       4 . Valve according to  claim 1 , characterized in that the critical temperature of the control charge of the first actuating element lies above the critical temperature of the refrigerant. 
   
   
       5 . Valve according to  claim 1 , characterized in that the temperature-independent force of the thermally activatable actuating element corresponds to the increase of the control charge of the first actuating element in the superheated state. 
   
   
       6 . Valve according to  claim 1 , characterized in that the thermally activatable actuating element is embodied in the form of bimetal elements which are stacked one on top of the other. 
   
   
       7 . Valve according to  claim 1 , characterized in that the thermally activatable actuating element is embodied in the form of a spring element which is composed of a shape-memory alloy. 
   
   
       8 . Valve according to  claim 1 , characterized in that the thermally activatable actuating element is embodied in the form of a filled, bellows-like spring element. 
   
   
       9 . Valve according to  claim 8 , characterized in that the thermally activatable actuating element is embodied in the form of a hydraulically filled bellows-like spring element. 
   
   
       10 . Valve according to  claim 7 , characterized in that the thermally activatable actuating element is preloaded by a pressure-independent device. 
   
   
       11 . Valve according to  claim 10 , characterized in that the preload of the thermally activatable actuating element is set by means of the pressure-independent device to a temperature threshold value at which the thermal safety function comes into action. 
   
   
       12 . Valve according to  claim 10 , characterized in that the pressure-independent device is adjustable. 
   
   
       13 . Valve according to  claim 1 , characterized in that the chamber or an inner contour of the chamber is guided by a sleeve or webs. 
   
   
       14 . Valve according to  claim 1 , characterized in that, in a rest position of the valve element, a predefined minimum passage opening between the valve element and the valve seat is opened, which minimum passage opening is externally adjusted during assembly. 
   
   
       15 . Transcritical or subcritical refrigeration or heat-pump circuit having an inner heat exchanger, characterized in that an expansion valve according to one of the preceding claims is provided.