US Patent 6918409 Spool and poppet inlet metering valve

Valve structures include a combination of spool valving and poppet valving. A spool function of the structure regulates the flow of a liquid, such as the flow of fuel to a diesel engine. A poppet function provides a low leakage in the valve in a closed or cut-off state. With this combination in a valve, spool clearance can be increased reducing the cost and precision machining/assembly of the components, because the poppet to seat closure provides the sealing function at cut-off. Included are an air-gap flux adjustment to adjust responsiveness to control current, and a force pre-load adjustment.