PROPORTIONAL CONTROL OF REFRIGERANT AND OTHER FLUIDS
WITH A SILICON MICROMACHINED VALVE

presented at the Appliance Manufacturer Conference & Expo, 
Cincinnati, Ohio, Sept. 11-13, 2000

Kirt R. Williams, Tom A. Kwa, Izzat I. Taher, and Nadim I. Maluf
TRW Automotive/Lucas NovaSensor
1055 Mission Ct., Fremont, California, 94539-8203, USA

ABSTRACT
We have designed, fabricated, and tested a series of silicon microvalves 
that proportionally control the flow of both gases and liquids, and have 
applications in appliances, automobiles, and industrial controls. 
In contrast to other micromachined valves, these are plate valves, 
formed in three layers of silicon. The movable member in the plate valves, 
capable of over 100 mm of motion, travels horizontally past an orifice. 
It is pressure-balanced to allow operation at 13 bar pressure drop. 
Measured flow rates at a 7-bar (~100-psi) pressure drop are 2.5 slm of 
nitrogen, 6.5 slm of helium, 40 ml/min of light oil, and 30 g/min of  
R-134A refrigerant. The design is readily altered so that normally open 
and normally closed valves with various orifice sizes and pressure-handling 
capabilities can be batch-fabricated with the same process on the same wafer. 
In contrast to valves with actuators relying on differential expansion rates, 
this valve is primarily silicon, and is relatively unaffected by 
ambient-temperature fluctuation. These miniature valves are packaged in 
modified TO-8 headers with a volume of about 1 cm^3.  Metal tubes provide 
fluidic connections.