This paper introduces a pulse-motor-driven expansion valve newly developed with high electronics technology and discusses the problem of its application to heat pump room air conditioners. So far as "inverter" (variable-capacity control device) control heat pump room air conditioners are concerned, the conceivable refrigeration control by this pulse-motor-driven expansion valve has several merits or advantages over the existing refrigerant control method as stated below.

1. SEER will be improved as maximum-efficiency operation of the refrigeration cycle is assured .
2. Injection cooling to the compressor in the system will no longer be necessary since it enables temperature control of the compressor and, consequently, improves the working efficiency of the compressor.
3. The defrosting time will be shortened to half of the present length because the refrigeration cycle is to be controlled by this valve during the defrosting time.
4. The performance reliability of each air conditioner unit will be duly enhanced, as this valve ensures effective settlement of the conventional overheating and overcooling trouble of the compressor.
5. The cost of the heat pump air conditioner will be further reducible since the reversible flow characteristics of this expansion valve assure mechanical simplification of the refrigerating system.

Units: SI