Lucas Industries Public Limited Company

Holset Engineering Company, Limited

Alan P Ogburn

Ian J Harvey

Philip C Franklin

John H Francis

Francis R Draper

The disclosure illustrates a self calibrating control system for a variable area turbocharger incorporating a pneumatic actuator having a limiting position achieved at low actuating pressure levels. The calibration takes place by monitoring the demanded actuator signal. If it stays at a level reflecting a physically limiting position of the actuator for a predetermined time air pressure to the actuator is terminated to positively maintain the actuator in the no air position. A signal reflecting the actual position of the actuator is then substituted in the control system as a new zero pressure condition. This procedure is performed periodically and is aborted if normal control inputs are demanded thus resulting in a minimum disruption to normal control inputs. In addition the system provides for fault indications if the calibration procedure fails to result in a zero pressure calibration within predetermined limits. The system may be used to alternatively or in addition calibrate for a maximum pressure condition.

In use position measuring device calibration

A fuel pumping apparatus for supplying fuel to an engine includes a pumping plunger reciprocable in a cylinder by a cam having cam lobes. Fuel is displaced during inward movement of the plunger during forward rotation of the engine by the leading flanks of the lobes. A valve can be closed during the inward movement of the plunger to allow fuel flow through an outlet to an engine. The valve is electrically controlled by a control system which receives plunger position signals. These signals are arranged to occur substantially half way along the trailing flanks of the lobes instead of as is more usual at the top dead center positions of the plunger, whereby if the engine is rotating in reverse the valve will be open while the plunger is moved inwardly by the trailing flanks of the lobes.

Fuel pumping apparatus

An electronic control system for a solenoid based actuator for a fuel system of an engine includes a switchable transistor connected in a series circuit with a current sensing resistor and the solenoid of the actuator. A power circuit supplies switching pulses to the transistor through an AND gate. A control circuit supplies a control signal to the power circuit and also a trigger signal to a monostable circuit. The monostable circuit supplies an enable signal to the AND gate. The control circuit receives a feedback signal from the sensing resistor and as long as this lies within prescribed limits the control circuit will supply the control signal and the trigger signal. If the feedback signal lies outside the prescribed limits at least the trigger signal will be halted so that after the time period of the monostable circuit has lapsed the transistor will receive no further switching pulses. A fuse is connected in series with the solenoid which will blow in the event that the solenoid remains energized for longer than a prescribed time.

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Cirencester, United Kingdom

Alan P Ogburn