Thermal type expansion valve

An expansion valve for use in a refrigerant circuit that compresses refrigerant supplied thereto from an evaporator and discharges the compressed refrigerant to a condenser, wherein said discharged refrigerant is supplied to the evaporator from the condenser by way of the expansion valve, said expansion valve comprising:

• a valve body having a unitary hollow cylindrical shape and of thermally insulating synthetic resin, wherein a guide passage extends along the axis of the body and is surrounded by thermally insulating synthetic resin, said body having a first passage for introducing the refrigerant to the body, a second passage for supplying the refrigerant from the first passage to said evaporator and a third passage for supplying the refrigerant to the compressor from the adjusting mechanism extending into the guide passage for adjusting a flow rate of the refrigerant supplied to the evaporator, said adjusting mechanism having a restriction for controllably connecting said first passage with said second passage and a valve member for adjusting a degree of the restriction;
• a control mechanism for controlling said adjusting mechanism in accordance with a temperature of the refrigerant supplied to the compressor from the evaporator, wherein said mechanism includes a heat sensitive gas-filled sealed chamber and a diaphragm movable in accordance with changes in pressure in the sensitive chamber, said sensitive chamber being exposed to the ambient atmosphere;
• and
• a metallic valve seat secured to an insulated wall between the first passage and the second passage to prevent the insulated wall from being damaged by contact with the valve member, said metallic valve seat having a hole extending therethrough along the axis to form said restriction;
• and
• a transmitting member for transmitting the temperature of the refrigerant flowing in the third passage to the gas in the sensitive chamber and the movement of the diaphragm to the valve member wherein said control mechanism, and
• wherein said valve body is opposed to the sensitive chamber with respect to the diaphragm and has a pressure chamber communicating with said third passage, and wherein said transmitting member extends through the pressure chamber and the third passage to transmit the heat of the refrigerant in the third passage and the pressure chamber to the gas in the sensitive chamber by way of the diaphragm.