Experimental Results of a Novel Electronic Expansion Valve

In modern vehicles, a large number of electric motors and solenoid valves are installed, which perform a wide variety of regulation and control tasks. Especially in refrigeration circuits, motor or magnetically driven valves for thermal management of passenger compartments or electrical components such as batteries are necessary. The advantage of these actuator types lies in the acceptable price/performance ratio. Disadvantages often are the weight of the actuators as well as the noise during switching.

There is the development of actuators for refrigerant valves based on a pre-stressed wire element made of a shape memory alloy (SMA), that meets an acceptable price/performance ratio especially. Shape memory alloys are also known as "smart materials" and have the property of being able to switch frictionlessly and completely noiseless between two different phases with two different crystal structures. Additionally “smart materials” have both actuator and sensor properties. The SMA element in the surrounding refrigerant is activated by means of electrical current with the help of Ohm's resistance. The SMA drives are used in the climate circuit as a switching valve or with appropriate resistance or position-based control as a proportional valve. The great advantages of these developments lie in economical, silent, lightweight drives with position feedback due to the integrated sensor properties of the SMA elements.