Abstract: A shape memory alloy actuator assembly for a fuel injector, having a small package integral design, wherein the response times of the shape memory alloy element is decreased to less than about 1 millisecond by forced, convective heat transfer from the SMA element or elements. The forced, convective heat transfer is provided by the circulation of fluid across the SMA element by a metering orifice plate, which directs a fluid flow across the SMA element so as to maximize the area of contact between the fuel and the SMA element, regardless of whether the fuel injection valve is opened or closed. Use of forced convective heat transfer in accordance with the present invention allows greater power input levels than previously possible without resulting in an over-temperature condition of the SMA alloy, as well as constant response times.

Abstract: An improved method and apparatus for opening and closing a high performance shape memory alloy (SMA) fuel injector that minimizes performance variations due to changes in ambient temperature. When opening the injector to commence fuel injection, a relatively high voltage is applied to an SMA element of the injector to quickly heat the element to its high temperature state, quickly opening the valve. The current level is monitored as a measure of the element resistivity, and when the determined resistivity indicates that the high temperature state transition is complete, the voltage is reduced to a hold value, sufficient to continue resistivity measurement. When the determined resistivity indicates that the element is beginning to transition back to the ambient temperature state, the high voltage is re-applied to begin a new control cycle. To close the injector, the electric heating is discontinued, and fuel circulating through the injector cools the element to its ambient temperature state.

Abstract: A shape memory alloy actuator assembly for a fuel injector, wherein the response times of the shape memory alloy element is decreased to less than about 1 millisecond by forced, convective heat transfer from the SMA element or elements. The forced, convective heat transfer is provided by the circulation of fluid across the SMA element by a metering orifice plate, which directs a fluid flow across the SMA element so as to maximize the area of contact between the fuel and the SMA element, regardless of whether the fuel injection valve is opened or closed. Use of forced convective heat transfer in accordance with the present invention allows greater power input levels than previously possible without resulting in an over-temperature condition of the SMA alloy, as well as constant response times.

Abstract: A fuel system including a fuel nozzle is disclosed. The fuel nozzle is adapted to receive pulsed pressurized fuel from a source and includes a valve seat assembly having a valve seat body with a longitudinally extending passage. The passage of the valve seat body has a valve seat extending thereabout and interfaces with a downstream opening valve element which is disposed within the longitudinally extending passage and operates to move into and out of sealing engagement with the valve seat to regulate the flow of pressurized fuel though the passage. The valve element has a spherically configured upstream surface for sealing engagement with the valve seat which includes an annular drag groove extending thereabout. The drag groove functions to increase viscous drag force, in the downstream opening direction, which is imparted on the valve element by fuel flow over the spherical upstream surface. The nozzle also has an annular, fuel directing orifice disc which is disposed downstream of the valve seat.