The increasing demand for EVs are driving design teams to search out innovative fluid management solutions for EV thermal management applications. Unlike internal combustion engines, which have relatively simple cooling systems, EV cooling systems must be able to manage multiple heat sources and sinks, each with specific optimal operating temperatures and flow rates.
The ideal proportional control valve for EV thermal management applications would be a valve that did not require steady-state power to hold a commanded position, would be capable of a true leak-free off state, would have a predictable and repeatable relationship between setting and flow (zero hysteresis), and would include a fail-safe condition when power is lost. Traditional proportional control valves do not share all these attributes. For example, stepper-driven rotary valves are a common extant solution and can achieve near-zero hysteresis and near-zero flow state, but they lack the capacity for a fail-safe mode. Additionally, the stepper motor and controller may add weight and cost to the system, and the rotating shaft seals are prone to leakage, inhibiting consistent performance. A better solution is desirable.
The discrete proportional valve system (DPV) is an innovative alternative that incorporates all the desirable attributes with none of the deficiencies of extant solutions. The DPV relies on a combination of binary (on-off) valves of differing flow coefficients housed in a single manifold to achieve a stepped approximation of linear response. The desired flow rate is achieved by opening and closing the valves in specific combinations.