| 摘要 |
The thermostatic expansion valve capsule is shown mounted in a cavity in a receiver of a widely used device. The exterior of the valve body utilizes two or three O-ring seals to achieve the proper connections in the installation. The temperature responsive charge in the head chamber above the diaphragm controls the movement of the valve in accordance with the temperature of the returning refrigerant, liquid or vapor, coming from the evaporator in an automotive air conditioning system. It is necessary to keep control in accordance with that temperature and, therefore, the temperature of the refrigerant leaving the expansion valve must not influence the head chamber temperature. Thermal conduction between the valve portion and the head portion of the valve body is minimized by undercutting the valve body and flow of refrigerant from the higher pressure in the outlet of the valve to the lower pressure under the diaphragm is minimized by providing a deliberate bleed or bypass so the very cold refrigerant cannot reach the chamber under the diaphragm. In the three O-ring version this communicates with the undercut which, in turn, vents to the suction throttling valve outlet pressure through a conduit in the receiver body. In the two O-ring version that conduit is plugged and the upper O-ring is omitted so the undercut is at the same pressure as the space outside the diaphragm head chamber which is evaporator outlet pressure. |
