US 6,318,641 B1 · Shape memory alloy fuel injector small package integral design

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. Actuator production costs are reduced by 40%, whereby side fame rails of the actuator are eliminated, and the spacer and the orifice plate are incorporated into a second wafer, which is bonded to the first wafer, which includes SMA material and a valve seal island.

Claims24

Dependent claims

A shape memory alloy fuel injector having forced convective heat transfer and having a small package integral design, comprising:

an actuator assembly including an actuator wafer containing a valve and at least one shape memory alloy element in contact with the valve, the shape memory alloy element further having a characteristic phase change transition temperature wherein the shape memory alloy element and the valve have a first position at a temperature below the transition temperature and a second position at a temperature above the transition temperature, and wherein the width and length of the actuator assembly are substantially dictated by the width and length of the shape memory alloy element;
and
a metering orifice plate comprising an orifice wafer bonded to said actuator wafer and including
a flow metering orifice which is blocked by the valve at either the first position or second position of the shape memory alloy element and the valve, thereby providing a metered flow of fluid through the fuel injector;
at least one inlet flow path and at least one outlet flow path, wherein the at least one inlet flow path and the at least one outlet flow path direct a flow of fluid independent from the metered flow of fluid across the shape memory alloy element, thereby providing a thermal boundary layer between the shape memory alloy element and the bulk flow of fluid that results in an enhanced convective heat transfer rate from the shape memory alloy element.

2 more elements

Dependencies are inferred from the claim text.

Shape memory alloy fuel injector small package integral design

Life of this patent

Shape memory alloy fuel injector small package integral design

Life of this patent

Abstract

Claims24