The linear MEMS variable reluctance stepper actuator for fuel metering valves

This work describes the development of the linear MEMS variable reluctance (VR) stepper actuator for engine fuel valves. The work includes the design of the valve actuated by the linear MEMS VR stepper actuator and a novel fabrication procedure that allows the valve to be integrated with the actuator. The operation of the actuator is demonstrated and the force performance is measured.;The planar 4-phase actuator is integrated with the hole-in-the-wall valve. The linear MEMS VR stepper actuator can act as a high-force, long-throw, low-power actuator that meets the requirements of the fuel-flexible portable engine application.;It was shown that several unique design rules need to be considered for a planar actuator. First, the leakage flux between tooth faces and flux guide faces are not negligible. Therefore one needs to pay close attention to the saturation of the soft magnet driven by the additional leakage fluxes. Second, the between-phase flux leakage can be significantly large so that it may create competing force in the adjacent phase that degrades the performance of the actuator. Lastly, the force formula for a macro VR actuator should be adjusted for a planar actuator bringing the leakage flux between the tooth faces into account.;We demonstrated a simple and cost-saving process flow to integrate the actuator with the valve. It was shown that a dry film resist can be used to integrate the hole-in-the-wall process and the consecutive process to form molds for soft magnet parts. NiFe parts were cut out of a 100 mum thick film using wire-EDM and placed into the molds.;It was demonstrated that the magnetization of NiFe parts saturates around B = 1.0T. Some flux guide design showed choking of the magnetic flux due to saturation. The operation of the actuator needs to be designed taking the saturation into account. The machining tolerance of NiFe parts may result in large variation in air gap width, therefore affect the force output of the actuator by large.;The next generation actuator design was proposed to overcome fabrication limitations. The proposed design has 200 mum thick magnet parts to meet the force requirement.