SHAPE MEMORY ALLOY FUEL INJECTOR SMALL PACKAGE INTEGRAL DESIGN

摘要

A shape memory alloy actuator assembly (10) for a fuel injector, having a small package integral design, wherein the response times of the shape memory alloy element (22) is decreased to less than about 1 millisecond by forced, convective heat transfer from the SMA element or elements (22). The forced, convective heat transfer is provided by the circulation of fluid across the SMA element (22) by a metering orifice plate (40), which directs a fluid flow across the SMA element (22) so as to maximize the area of contact between the fuel and the SMA element (22), regardless of whether the fuel injection valve (20) 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. Actuator production costs are reduced by 40 %, whereby side frame rails (30) of the actuator (11) are eliminated, and the spacer and the orifice plate (30) are incorporated into a second wafer (40), which is bonded to the first wafer (42), which includes SMA material (22) and a valve seal island (20).