Fuel systems for engines

Claim 2

A fuel system for an engine, comprising in combination a pump supply fuel to the engine, an actuator controlling the pump, and an electronic governor for controlling the actuator, said governor receiving electrical signals representing engine speed and at least one further engine parameter, the speed signal being obtained using a transducer producing an a.c. output at a frequency proportional to engine speed, a pump circuit for converting said signal to a d.c. signal, first, second and third supply lines, an operational amplifier having an inverting input terminal and a non-inverting input terminal, said amplifier being powered by the first and second supply lines and having its noninverting input terminal connected to the third supply line, and said pump circuit including a capacitor across which is developed a voltage proportional to the frequency of the a.c. output, said capacitor being connected across the inverting input and output terminals of said operational amplifier, a resistor across the capacitor, a second capacitor and a diode in series between an input terminal and the inverting input terminal, and a second diode coupling the junction of the second capacitor and first diode to the third supply line.

Claim 3

A circuit as claimed in claim 1 including a resistor coupling the inverting input terminal of the amplifier to the second line.

Claim 4

A system as claimed in claim 1 including in addition a further pump circuit providing an input to the operational amplifier or directly to the governor whereby said d.c. signal increases from zero to a maximum level at a minimum engine speed and then decreases substantially linearly to zero at a maximum engine speed.

Claim 5

A system as claimed in claim 1 in which the operational amplifier is biased so that it produces a maximum output at low engine speeds, falling to zero near a maximum engine speed.

Claim 6

A system as claimed in any one of claim 1 including a shaping circuit between the transducer and the first mentioned pump circuit, the shaping circuit converting the output from the transducer to substantially square wave form.

Claim 7

A system as claimed in claim 5, including a pair of supply lines providing power to the governor, said shaping circuit producing a square wave output having an amplitude proportional to the voltage between said supply lines.

Claim 8

A system as claimed in claim 6 including means modifying said amplitude to compensate for temperature dependance of components in the pump circuit.

Claim 9

A system as claimed in any one of claim 6 in which the shaping circuit includes first and second transistors connected as a long tailed pair with a constant current source in the tail, the first transistor having its base connected to the transducer, and the second transistor having a collector-base cross coupling with a third transistor providing the output from the pulse shaping circuit.

Claim 10

A system as claimed in any one of claim 5 in which the shaping circuit includes switching components producing a second square wave output out of phase with the first output, and the capacitor across the operational amplifier is common to two pump circuits driven by the two outputs from the shaping circuit.

Claim 11

An electronic pump circuit in which a voltage dependent on the frequency of an a.c. input is developed across a capacitor connected across the input and output terminals of an operational amplifier, including first, second and third supply lines, the amplifier being powered by the first and second lines and having its non-inverting input terminal connected to the third line, and the pump circuit Including, in addition to the capacitor between the output terminal and the inverting input terminal of the amplifier, a resistor across the capacitor, a second capacitor and a diode in series between an input terminal and the inverting input terminal, and a second diode coupling the junction of the second capacitor and first diode to the third line.

Claim 12

An electronic pump circuit in which a voltage dependent on the frequency of an a.c. input is developed across a capacitor connected across the input and output terminals of an operational amplifier, including first, second and third supply lines, the amplifier being powered by the first and second lines and having its non-inverting input terminal connected to the third line, and the pump circuit Including, in addition to the capacitor between the output terminal and the inverting input terminal of the amplifier, a resistor across the capacitor, a second capacitor and a diode in series between an input terminal and the inverting input terminal, and a second diode coupling the junction of the second capacitor and first diode to the third line.

Claim 13

A circuit as claimed in claim 10 including a resistor coupling the inverting input terminal of the amplifier to the second line.

Claim 14

A circuit as claimed in claim 10 in combination with a conventional pump circuit providing a further input to the amplifier, whereby with increasing frequency the output of the amplifier rises from zero to a maximum value and then decreases with further increase in frequency towards zero.

Claim 15

A fuel system for a compression-ignition engine, comprising in combination a pump for supplying fuel to the engine, an electro-mechanical actuator controlling the pump, and an electronic governor for controlling the actuator, said governor receiving electrical signals from three transducers representing demand, pump output and engine speed, the governor including three power supply lines, the third line being kept at a specified proportion of the potential between the first and second lines, the speed signal being obtained using a transducer producing an a.c. output at a frequency proportional to engine speed, a signal-shaping circuit to which said a.c. output is applied, said signal-shaping circuit producing a square wave output whose amplitude is substantially proportional to the potential between the first two supply lines, and a pump circuit for converting said square wave output to a d.c. signal which at least over the working speed range decreases in magnitude relative to the third supply line with increasing speed, said d.c. signal being applied to the governor, said pump circuit including a capacitor across which is developed a voltage proportional to the frequency of the said a.c. output, said capacitor being connected across the input and output terminals of an operational amplifier.

Claim 16

A fuel system for a compression-ignition engine, comprising in combination a pump for supplying fuel to the engine, an electro-mechanical actuator controlling the pump, and an electronic governor for controlling the actuator, said governor receiving electrical signals from three transducers representing demand, pump output and engine speed, the governor including three power supply lines, the third line being kept at a specified proportion of the potential between the first and second lines, the speed signal being obtained using a transducer producing an a.c. output at a frequency proportional to engine speed, a signal-shaping circuit to which said a.c. output is applied, said signal-shaping circuit producing a square wave output whose amplitude is substantially proportional to the potential between the first two supply lines, and a pump circuit for converting said square wave output to a d.c. signal which at least over the working speed range decreases in magnitude relative to the third supply line with increasing speed, said d.c. signal being applied to the governor, said pump circuit including a capacitor across which is developed a voltage proportional to the frequency of the said a.c. output, said capacitor being connected across the input and output terminals of an operational amplifier.