Automotive air conditioner

Abstract

An automotive air conditioner which is capable of efficiently disposing an internal heat exchanger, and enabling the air conditioner to perform an efficient operation. A thermostatic expansion valve is accommodated in a casing directly connected to the refrigerant outlet of an evaporator. The inlet of the expansion valve and a pipe for receiving high-pressure liquid refrigerant are connected to each other within the casing. The outlet of the expansion valve and the refrigerant inlet of the evaporator are connected to each other within the casing. The internal heat exchanger for performing heat exchange between high-pressure refrigerant delivered to the inlet of the expansion valve and low-pressure refrigerant returning to a compressor is connected between the casing and a pipe joint disposed in a firewall.

1 . An automotive air conditioner wherein a thermostatic expansion valve having an inlet to which is connected a pipe for receiving high-pressure refrigerant and an outlet to which is connected a refrigerant inlet pipe of an evaporator is accommodated in a casing directly connected to a refrigerant outlet of said evaporator,
 wherein an internal heat exchanger for performing heat exchange between the high-pressure refrigerant and low-pressure refrigerant returning from said casing to a compressor is connected to said casing, and   wherein a pipe joint for connecting a high-pressure pipe extending from a receiver and a low-pressure pipe extending to said compressor independently of each other is connected to an end of said internal heat exchanger on the side opposite to the side where the casing is connected.   
   
   
       2 . The automotive air conditioner according to  claim 1 , wherein said internal heat exchanger is formed by a double pipe in which a low-pressure return pipe for allowing low-pressure refrigerant to flow to said compressor is coaxially disposed outside a high-pressure forward pipe for allowing the high-pressure refrigerant to flow therethrough. 
   
   
       3 . The automotive air conditioner according to  claim 2 , wherein in the double pipe, heat transfer baffles are arranged between the high-pressure forward pipe and the low-pressure return pipe, whereby the state of the low-pressure return pipe and the high-pressure forward pipe being coaxial with each other is held. 
   
   
       4 . The automotive air conditioner according to  claim 1 , wherein said expansion valve has a back pressure cancelling structure in which an area for a valve element to receive pressure of the high-pressure refrigerant introduced into the inlet of said expansion valve in a valve-opening direction and an area for a shaft operating in unison with the valve element to receive the pressure of the high-pressure refrigerant in a valve-closing direction are made substantially equal to each other, the valve element being provided with a guide for guiding the valve element such that the valve element moves along a valve hole during opening and closing operations of said expansion valve. 
   
   
       5 . The automotive air conditioner according to  claim 1 , wherein said expansion valve is provided with a differential pressure valve for causing refrigerant having been just expanded to bypass to the low-pressure return pipe of said internal heat exchanger when a differential pressure between pressure at the refrigerant inlet of said evaporator and pressure at the refrigerant outlet of said evaporator exceeds a predetermined value. 
   
   
       6 . The automotive air conditioner according to  claim 5 , wherein said differential pressure valve includes a diaphragm for sensing the differential pressure, a hollow cylindrical valve element held in a center of said diaphragm, a spring for urging the hollow cylindrical valve element such that the hollow cylindrical valve element is seated on a valve seat having a flat surface, and an orifice disposed in a refrigerant passage within the hollow cylindrical valve element. 
   
   
       7 . The automotive air conditioner according to  claim 2 , wherein the pipe joint has one end face formed with a first connecting hole in which the low-pressure return pipe of the double pipe is fitted, and a second connecting hole which is coaxially disposed in the first connecting hole, for having the high-pressure forward pipe fitted therein, and another end face having a third connecting hole and a fourth connecting hole arranged in parallel for communication with the first connecting hole and the second connecting hole, respectively. 
   
   
       8 . The automotive air conditioner according to  claim 1 , wherein the pipe joint is disposed in a firewall separating an engine room from a vehicle compartment.