Hughes Microelectronics Limited

Ranco Inc.

David M Walker

Alastair K Stevenson

Albert L Fowler

Alan G Henderson

Robert F Purssell

Alan Pelczyk

Alfred J Woollard

A displacement-measuring transducer has a laminar member displaceable, for example under control of a vacuum actuator, within a housing containing respective pairs of coils spaced part in the displacement direction of the laminar member, which is provided with two apertures spaced apart in the said direction, such that the coupling between the coils of each pair is dependent upon the position of said apertures and, therefore, on the displacement of the laminar member.

Displacement measuring transducer

A displacement transducer suitable for monitoring the angular rotation of an internal combustion engine is provided. The transducer comprises a rotary disc having a castellated periphery and mounted for rotation with the engine. First and second coils are mounted such that upon operation of the engine the castellations of the disc interrupt the inductive coupling therebetween. The first coil is fed with an oscillatory electrical signal which induces in the second coil an output signal of a first peak amplitude during the interruptions produced by the castellations and of a second peak amplitude during periods between the interruptions. Thresholding circuitry responsive to the output signal produces a control signal which is indicative of the commencement and cessation of the interruptions. In accordance with one disclosed embodiment, the threshold circuitry includes a pair of inverters sharing the same thermal environment. The first inverter is capacitively coupled to receive the output signal from the second coil, and the second inverter, which has its output connected to its input in a feedback arrangement, provides bias through a resistive coupling to the first inverter to compensate for temperature drifts, whereby the first inverter switches output signal states when its input signal passes through a preselected voltage level.

Position sensing transducer

A spark timing control circuit for an internal combustion engine, includes a speed band selector circuit which responds to an electrical signal indicative of engine speed and provides an output signal indicative of which of a plurality of speed bands is occupied by the engine speed. Spark timing information for each speed band is stored in a memory as a first word in units of angular rotation of the engine for the heaviest engine operating load, and a second and third words indicative of the slope of straight line approximations to the curve of engine load plotted against advance in said angle units. A build up circuit responds to an electrical signal indicative of the engine operating load and computes from the second and third words a build up word which is added to the first word in an accumulator so as to derive an accumulated word in said angle units indicative of the desired spark timing. A residue angle counter, clocked by angle clock pulses from a clock converts the accumulated word into a corresponding time delay which is used to control the timing of the occurrence of spark ignition.

Spark timing control circuit for controlling the timing of spark

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Freuchie, United Kingdom

David M Walker