Fuel pumping apparatus

Claim 1

A fuel pumping apparatus for supplying fuel to an internal combustion engine comprising an injection pump operable in use in timed relationship with an associated engine, fluid pressure operable means for adjusting the timing of delivery of fuel by the apparatus comprising a member against a surface of which fluid under pressure can act, and resilient means opposing the movement of the member by said fluid pressure, a low pressure fuel supply pump for supplying fuel to the injection pump, an adjustable throttle for varying the quantity of fuel supplied to the injection pump, a transducer associated with the throttle valve for providing a first signal indicative of the effective flow area of the throttle valve throughout the range of movement thereof, an electrical circuit which receives said first signal, a second signal indicative of the speed of operation of the apparatus and a third signal indicative of the fuel pressure upstream of the metering valve and from which is determined a fourth signal representing the amount of fuel supplied to the injection pump, means responsive to at least said second and fourth signals for providing a fifth signal to vary the timing of delivery of fuel by the apparatus, an error amplifier to which said fifth signal is supplied, a further transducer for providing a sixth signal representative of the position of said fluid pressure operable means, said sixth signal being supplied to said error amplifier, an actuator responsive to the output of said error amplifier for controlling the pressure applied to said fluid pressure operable means, said actuator controlling the size of a restrictor through which fluid under pressure from a source is applied to said surface, said source of fluid pressure being said low pressure fuel supply pump and including a branch passage from downstream of said restrictor and through which fuel is supplied to the injection pump under the control of said throttle valve.