Fuel supply systems for internal combustion engines

Claim 2

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, and a summing amplifier to which the three signals are applied, the summing amplifier comparing the three signals and controlling the pump control means, and further including a second summing amplifier which receives an input representing the pump output and also a reference input, and a discriminator coupling the first-mentioned and the second summing amplifiers to the pump control means, the output from the discriminator at any given instant being the output from the summing amplifier which demands the least fuel, so that the second summing amplifier limits the maximum pump output.

Claim 3

A system as claimed in claim 1 including means for limiting the maximum speed of the engine.

Claim 4

A system as claimed in claim 2 in which said means acts by restricting the demand signal to a predetermined level.

Claim 5

A system as claimed in claim 1, including a third summing amplifier to which are fed electrical signals representing a system parameter and a reference, the third amplifier being connected to the pump control means through said discriminator, so that in certain conditions the third amplifier only controls the pump.

Claim 6

A system as claimed in claim 4, including a further amplifier which receives an electrical signal representing a system parameter, and limits the value of said parameter under certain system conditions, and a second discriminator coupling the first and said further amplifier to the pump control means by way of the first-mentioned discriminator, whereby when the first discriminator couples the second discriminator to the pump control means, then the second discriminator couples to the pump control means either the first or said further amplifier.

Claim 7

A system as claimed in claim 4, including an additional amplifier which under certain system conditions modifies said maximum value of said further system parameter, and an additional discriminator coupling the second and additional amplifier to the pump control means by way of the first mentioned discriminator, whereby when the first discriminator couples the additional discriminator to the pump control means, then the additional discriminator couples to the pump control means either the second or said additional amplifier.

Claim 8

A fuel system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, and a summing amplifier to which the three signals are applied, the summing amplifier comparing the three signals and controlling the pump control means, the maximum output of the pump being controlled, but the system includes circuit means having a first state and a second state, said circuit means when in its second state increasing the maximum output of the pump, said circuit means being driven to its second state when the engine speed is below cranking speed and being driven to its first state when the engine speed is above a datum speed, the datum speed being in excess of the cranking speed.

Claim 9

A fuel system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, and a summing amplifier to which the three signals are applied, the summing amplifier comparing the three signals and controlling the pump control means, the maximum output of the pump being controlled, but the system includes circuit means having a first state and a second state, said circuit means when in its second state increasing the maximum output of the pump, said circuit means being driven to its second state when the engine speed is below cranking speed and being driven to its first state when the engine speed is above a datum speed, the datum speed being in excess of the cranking speed.

Claim 10

A system as claimed in claim 7, in which the datum speed at which excess pump output is terminated is set by a bistable circuit forming part of said circuit means and the cranking speed at which excess pump output is permitted again is set by a control circuit which until the engine speed falls to cranking speed holds the bistable circuit in a state to prevent excess pump output.

Claim 11

A system as claimed in claim 8, in which said control circuit becomes operative when the engine speed is above cranking speed, and when operative is capable of holding the bistable circuit in a state to prevent excess pump output, but not of driving the bistable circuit to a state to prevent excess pump output.

Claim 12

A system as claimed in claim 7, in which the circuit means incorporates a bistable circuit switching to the first state at said datum speed, and by virtue of its own differential switching back to the second state at the cranking speed.

Claim 13

A system as claimed in claim 7, in which the engine drives a vehicle having a throttle pedal, said throttle pedal providing said demand signal, said circuit means being driven to its second state only when the engine speed is below cranking speed and the throttle pedal is depressed beyond a predetermined position, and the circuit means being driven to its first state when either the engine speed is above the datum speed, or the pedal is not depressed beyond said predetermined position.

Claim 14

A system as claimed in claim 7, in which excess pump output is permitted only if the engine temperature is below a predetermined value.

Claim 15

A system as claimed in claim 7, including means for maintaining said circuit means in its first state between the datum and cranking speeds even if the supply to the circuit means becomes momentarily disconnected between the datum and cranking speeds.

Claim 16

A system as claimed in claim 13, in which said means includes a capacitor.

Claim 17

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, and a summing amplifier to which the three signals are applied, the summing amplifier comparing the three signals and controlling the pump control means, the maximum pump output being controlled, but the system includes a control network to which an electrical signal dependent on engine speed is applied, said control network serving to modify the maximum pump output for a range of engine speeds.

Claim 18

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, and a summing amplifier to which the three signals are applied, the summing amplifier comparing the three signals and controlling the pump control means, the maximum pump output being controlled, but the system includes a control network to which an electrical signal dependent on engine speed is applied, said control network serving to modify the maximum pump output for a range of engine speeds.

Claim 19

A system as claimed in claim 15, in which the control network includes a transistor which is turned on at the predetermined engine speed and when conductive modifies an input to a summing amplifier controlling the maximum pump output.

Claim 20

A system as claimed in claim 15, in which the control network includes a transistor which receives a signal dependent on engine speed and so conducts at a level determined by engine speed, and circuit means selectively connectible to said transistor so as alternatively to increase or decrease the maximum pump output when the transistor conducts.

Claim 21

A system as claimed in claim 15, in which the control network includes a pair of transistors connected as a long tailed pair, one of the transistors receiving an input signal dependent on engine speed and the other transistor modifying the maximum pump output only when the engine speed is in the required range.

Claim 22

A system as claimed in claim 18, including a constant current source in the tail of the long tailed pair for setting a minimum level to which the maximum pump output can be reduced.

Claim 23

A system as claimed in claim 15, including pre-set resistance means for determining the way in which the maximum pump output varies.

Claim 24

A system as claimed in claim 15, in which the maximum pump output is modified below a predetermined engine speed.

Claim 25

A system as claimed in claim 15, in which the maximum pump output is modified above a predetermined engine speed.

Claim 26

A system as claimed in claim 4, in which each summing amplifier is an operational amplifier with resistive feedback and has an inverting input and a non-inverting input, the signals fed to each summing amplifier being in the form of currents fed to the inverting input terminals thereof.

Claim 27

A system as claimed in claim 23, in which the feedback network of each amplifier includes a capacitor for modifying the gain of the amplifier.

Claim 28

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, and a summing amplifier to which the three signals are applied, the summing amplifier comparing the three signals and controlling the pump control means, said pump control means comprising and electro-mechanical actuator coupled to the pump to control the pump output, the system including a drive circuit for controlling the electro-mechanical actuator, said signal producing means comprising first, second and third transducers producing respectively output voltages representing engine speed, pump output and demanded engine speed, said summing amplifier comprising a first operational amplifier having its inverting input connected through resistors to the first, second and third transducers, said first amplifier producing an output dependent on the outputs of the first, second and third transducers, said system also including a second operational amplifier connected as a summing amplifier and having its inverting input connected through a resistor to the second transducer, and a discriminator coupling the amplifier producing the greater output to the drive circuit, the arrangement being such that until a predetermined pump output is attained, the discriminator couples the first amplifier to the drive circuit, but when said predetermined rate of supply of fuel is reached, the discriminator couples the second amplifier to the drive circuit to limit the maximum rate of supply of fuel.

Claim 29

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, and a summing amplifier to which the three signals are applied, the summing amplifier comparing the three signals and controlling the pump control means, said pump control means comprising and electro-mechanical actuator coupled to the pump to control the pump output, the system including a drive circuit for controlling the electro-mechanical actuator, said signal producing means comprising first, second and third transducers producing respectively output voltages representing engine speed, pump output and demanded engine speed, said summing amplifier comprising a first operational amplifier having its inverting input connected through resistors to the first, second and third transducers, said first amplifier producing an output dependent on the outputs of the first, second and third transducers, said system also including a second operational amplifier connected as a summing amplifier and having its inverting input connected through a resistor to the second transducer, and a discriminator coupling the amplifier producing the greater output to the drive circuit, the arrangement being such that until a predetermined pump output is attained, the discriminator couples the first amplifier to the drive circuit, but when said predetermined rate of supply of fuel is reached, the discriminator couples the second amplifier to the drive circuit to limit the maximum rate of supply of fuel.

Claim 30

A system as claimed in claim 25, in which the discriminator comprises a pair of diodes, one coupling each of the amplifiers to the drive circuit, and the resistive feedback paths of the two amplifiers are taken from the input to the drive circuit.

Claim 31

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, and a summing amplifier to which the three signals are applied, the summing amplifier comparing the three signals and controlling the pump control means, said pump control means comprising an actuator, and said signal producinig means comprising a first transducer for measuring engine speed, a second transducer for measuring a demand signal set by an operator and a third transducer for measuring the output of the pump, a control circuit including said summing amplifier for controlling the actuator, said control circuit restricting the output of the pump to a predetermined maximum value, a transistor which receives an input from the first transducer and conducts at a predetermined engine speed and circuit means selectively connectible to said transistor so as alternatively to increase or decrease the maximum pump output when the transistor conducts.

Claim 32

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, and a summing amplifier to which the three signals are applied, the summing amplifier comparing the three signals and controlling the pump control means, said pump control means comprising an actuator, and said signal producinig means comprising a first transducer for measuring engine speed, a second transducer for measuring a demand signal set by an operator and a third transducer for measuring the output of the pump, a control circuit including said summing amplifier for controlling the actuator, said control circuit restricting the output of the pump to a predetermined maximum value, a transistor which receives an input from the first transducer and conducts at a predetermined engine speed and circuit means selectively connectible to said transistor so as alternatively to increase or decrease the maximum pump output when the transistor conducts.

Claim 33

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, and a summing amplifier to which the three signals are applied, the summing amplifier comparing the three signals and controlling the pump control means, and further including an actuator for controlling the output of the pump, a control circuit including said amplifier for comparing at least two of said signals and providing an output for controlling the actuator and so regulating the output of the pump, said control circuit incorporating means for restricting the maximum pump output, and the system including circuit means having a first state and a second state, said circuit means when in its second state increasing the maximum pump output, said circuit means being driven to its second state when the engine speed is below cranking speed and being driven to its first state when the engine speed is above a datum speed, the datum speed being in excess of the cranking speed.

Claim 34

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, and a summing amplifier to which the three signals are applied, the summing amplifier comparing the three signals and controlling the pump control means, and further including an actuator for controlling the output of the pump, a control circuit including said amplifier for comparing at least two of said signals and providing an output for controlling the actuator and so regulating the output of the pump, said control circuit incorporating means for restricting the maximum pump output, and the system including circuit means having a first state and a second state, said circuit means when in its second state increasing the maximum pump output, said circuit means being driven to its second state when the engine speed is below cranking speed and being driven to its first state when the engine speed is above a datum speed, the datum speed being in excess of the cranking speed.

Claim 35

A system as claimed in claim 28 in which the datum speed at which excess pump output is terminated is set by a bistable circuit forming part of said circuit means, and the cranking speed at which excess pump output is permitted again is set by a control circuit which until the engine speed falls to cranking speed hold the bistable circuit in a state to prevent excess pump output.

Claim 36

A system as claimed in claim 29, in which said control circuit becomes operative when the engine speed is above cranking speed, and when operative is capable of holding the bistable circuit in a state to prevent excess pump output, but not of driving the bistable circuit to a state to prevent excess pump output.

Claim 37

A system as claimed in claim 28, in which the circuit means incorporates a bistable circuit switching to the first state at said datum speed, and by virtue of its own differential switching back to the second state at the cranking speed.

Claim 38

A system as claimed in claim 28, in which the engine drives a vehicle and a throttle pedal is provided to provide said demand signal, said circuit means being driven to its second state only when the engine speed is below cranking speed and the throttle pedal is depressed beyond a predetermined position, and the circuit means being driven to its first state when either of the engine speed is above the datum speed, or the pedal is not depressed beyond said predetermined position.

Claim 39

A system as claimed in claim 28, in which excess pump output is permitted only if the engine temperature is below a predetermined value.

Claim 40

A system as claimed in claim 28, including means for maintaining said circuit means in its first state between the datum and cranking speed, even if the supply to the circuit means becomes momentarily disconnected between the datum and cranking speeds.

Claim 41

A system as claimed in claim 34, in which said means includes a capacitor.

Claim 42

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, a first summing amplifier to which the three signals are applied, the first summing amplifier comparing the three signals and controlling the pump control means, a second summing amplifier which receives an input representing the pump output and also a reference input, and a discriminator coupling the first and second summing amplifiers to the pump control means, the output from the discriminator at any given instant being the output from the summing amplifier which demands the least fuel, so that the second summing amplifier limits the maximum pump output, said discriminator comprising a pair of diodes through which the outputs of the amplifiers are fed to the pump control means, whereby at any given moment one of the diodes will be conducting and will reverse bias the other diode.

Claim 43

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, a first summing amplifier to which the three signals are applied, the first summing amplifier comparing the three signals and controlling the pump control means, a second summing amplifier which receives an input representing the pump output and also a reference input, and a discriminator coupling the first and second summing amplifiers to the pump control means, the output from the discriminator at any given instant being the output from the summing amplifier which demands the least fuel, so that the second summing amplifier limits the maximum pump output, said discriminator comprising a pair of diodes through which the outputs of the amplifiers are fed to the pump control means, whereby at any given moment one of the diodes will be conducting and will reverse bias the other diode.

Claim 44

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, a first summing amplifier to which the three signals are applied, the first summing amplifier comparing the three signals and controlling the pump control means, a second summing amplifier which receives an input representing the pump output and also a reference input, and a discriminator coupling the first and second summing amplifiers to the pump control means, the output from the discriminator at any given instant being the output from the summing amplifier which demands the least fuel, so that the second summing amplifier limits the maximum pump output, each of said summing amplifiers having a resistive feedback path taken from the input to said pump control means.

Claim 45

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, a first summing amplifier to which the three signals are applied, the first summing amplifier comparing the three signals and controlling the pump control means, a second summing amplifier which receives an input representing the pump output and also a reference input, and a discriminator coupling the first and second summing amplifiers to the pump control means, the output from the discriminator at any given instant being the output from the summing amplifier which demands the least fuel, so that the second summing amplifier limits the maximum pump output, each of said summing amplifiers having a resistive feedback path taken from the input to said pump control means.

Claim 46

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, a first summing amplifier to which are fed said second electrical signal and said demand signal, the first summing amplifier comparing the signals and producing an output for controlling the pump control means, a second summing amplifier to which are fed electrical signals representing a further system parameter and a reference, and a discriminator coupling the first and second summing amplifiers to the pump control means, the output from the discriminator at any given instant being the output from the summing amplifier which demands the least fuel, so that the second summing amplifier limits the maximum value of said further system parameter, the system further including a further amplifier which receives an electrical signal representing a system parameter, and limits the value of said parameter under certain system conditions, and a second discriminator coupling the first and said further amplifier to the pump control means by way of the firstmentioned discriminator, whereby when the first discriminator couples the second discriminator to the pump control means, then the second discriminator couples to the pump control means either the first or said further amplifier.

Claim 47

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, a first summing amplifier to which are fed said second electrical signal and said demand signal, the first summing amplifier comparing the signals and producing an output for controlling the pump control means, a second summing amplifier to which are fed electrical signals representing a further system parameter and a reference, and a discriminator coupling the first and second summing amplifiers to the pump control means, the output from the discriminator at any given instant being the output from the summing amplifier which demands the least fuel, so that the second summing amplifier limits the maximum value of said further system parameter, the system further including a further amplifier which receives an electrical signal representing a system parameter, and limits the value of said parameter under certain system conditions, and a second discriminator coupling the first and said further amplifier to the pump control means by way of the firstmentioned discriminator, whereby when the first discriminator couples the second discriminator to the pump control means, then the second discriminator couples to the pump control means either the first or said further amplifier.

Claim 48

A fuel supply system for an engine comprising in combination a pump for a supplying fuel to the engine, pump control means for controlling the output of the pump, a first summing amplifier to which are fed said second electrical signal and said demand signal, the first summing amplifier comparing the signals and producing an output for controlling the pump control means, a second summing amplifier to which are fed electrical signals representing a further system parameter and a reference, and a discriminator coupling the first and second summing amplifiers to the pump control means, the output from the discriminator at any given instant being the output from the summing amplifier which demands the least fuel, so that the second summing amplifier limits the maximum value of said further system parameter, the system further including an additional amplifier which under certain system conditions modifies said maximum value of said further system parameter, and an additional discriminator coupling the second and additional amplifier to the pump control means by way of the first mentioned discriminator, whereby when the first discriminator couples the additional discriminator to the pump control means, then the additional discriminator couples to the pump control means either the second or said additional amplifier.

Claim 49

A fuel supply system for an engine comprising in combination a pump for a supplying fuel to the engine, pump control means for controlling the output of the pump, a first summing amplifier to which are fed said second electrical signal and said demand signal, the first summing amplifier comparing the signals and producing an output for controlling the pump control means, a second summing amplifier to which are fed electrical signals representing a further system parameter and a reference, and a discriminator coupling the first and second summing amplifiers to the pump control means, the output from the discriminator at any given instant being the output from the summing amplifier which demands the least fuel, so that the second summing amplifier limits the maximum value of said further system parameter, the system further including an additional amplifier which under certain system conditions modifies said maximum value of said further system parameter, and an additional discriminator coupling the second and additional amplifier to the pump control means by way of the first mentioned discriminator, whereby when the first discriminator couples the additional discriminator to the pump control means, then the additional discriminator couples to the pump control means either the second or said additional amplifier.

Claim 50

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, a summing amplifier to which the three signals are applied, the summing amplifier comparing the three signals and controlling the pump control means, a second summing amplifier which receives an input representing the pump output and also a reference input, a discriminator coupling the first-mentioned and the second summing amplifiers to the pump control means, the output from the discriminator at any given instant being the output from the summing amplifier which demands the least fuel, so that the second summing amplifier limits the maximum pump output, the system further including a control network to which an electrical signal dependent on engine speed is applied, said control network including a transistor which is turned on at a predetermined engine speed and when conductive modifies the input to said second summing amplifier so as to modify the maximum pump output.

Claim 51

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, a summing amplifier to which the three signals are applied, the summing amplifier comparing the three signals and controlling the pump control means, a second summing amplifier which receives an input representing the pump output and also a reference input, a discriminator coupling the first-mentioned and the second summing amplifiers to the pump control means, the output from the discriminator at any given instant being the output from the summing amplifier which demands the least fuel, so that the second summing amplifier limits the maximum pump output, the system further including a control network to which an electrical signal dependent on engine speed is applied, said control network including a transistor which is turned on at a predetermined engine speed and when conductive modifies the input to said second summing amplifier so as to modify the maximum pump output.

Claim 52

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, and a summing amplifier to which the three signals are applied, the summing amplifier comparing the three signals and controlling the pump control means, the maximum pump output being controlled but is modified in accordance with the pressure of the air.

Claim 53

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, and a summing amplifier to which the three signals are applied, the summing amplifier comparing the three signals and controlling the pump control means, the maximum pump output being controlled but is modified in accordance with the pressure of the air.

Claim 54

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, and a summing amplifier to which the three signals are applied, the summing amplifier comparing the three signals and controlling the pump control means, said summing amplifier being in operational amplifier with resistive feedback and has an inverting input and a non-inverting input, and all the signals fed to said summing amplifier being in the form of currents fed to the inverting input.

Claim 55

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, and a summing amplifier to which the three signals are applied, the summing amplifier comparing the three signals and controlling the pump control means, said summing amplifier being in operational amplifier with resistive feedback and has an inverting input and a non-inverting input, and all the signals fed to said summing amplifier being in the form of currents fed to the inverting input.

Claim 56

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, and a summing amplifier to which the three signals are applied, the summing amplifier comparing the three signals and controlling the pump control means, said control means comprising an actuator, said summing amplifier forming part of an electronic governor for controlling the actuator, and a feedback circuit associated with the summing amplifier, said feedback circuit including a capacitor and a resistor in series.

Claim 57

A fuel supply system for an engine, comprising in combination a pump for supplying fuel to the engine, pump control means for controlling the output of the pump, means for producing a first electrical signal representing the pump output, means for producing a second electrical signal representing engine speed, means for producing a demand signal representing the required engine speed, and a summing amplifier to which the three signals are applied, the summing amplifier comparing the three signals and controlling the pump control means, said control means comprising an actuator, said summing amplifier forming part of an electronic governor for controlling the actuator, and a feedback circuit associated with the summing amplifier, said feedback circuit including a capacitor and a resistor in series.

Claim 58

A fuel supply system for an engine, comprising in combination a pump supplying fuel to the engine, an actuator for controlling the output of the pump, a first transducer for measuring engine speed, a second transducer for measuring a demand signal set by an operator, a third transducer for measuring the output of the pump, a control circuit operable in accordance with the outputs from the transducer for controlling the actuator, said control circuit restricting the output of the pump to a predetermined maximum level, and a control network which receives an input from the first transducer and provides an input to the control circuit for a range of engine speed so that the maximum pump output is modified for said range of speed, said control network including transistors connected as a long tailed pair, and a constant current source in the tail of the long tailed pair for setting a minimum level to which the maximum pump output can be reduced, one of said transistors in the long tailed pair receiving an input signal dependent on engine speed and the other transistor in the long tailed pair modifying the maximum pump output only when the engine speed is in the required range.

Claim 59

A fuel supply system for an engine, comprising in combination a pump supplying fuel to the engine, an actuator for controlling the output of the pump, a first transducer for measuring engine speed, a second transducer for measuring a demand signal set by an operator, a third transducer for measuring the output of the pump, a control circuit operable in accordance with the outputs from the transducer for controlling the actuator, said control circuit restricting the output of the pump to a predetermined maximum level, and a control network which receives an input from the first transducer and provides an input to the control circuit for a range of engine speed so that the maximum pump output is modified for said range of speed, said control network including transistors connected as a long tailed pair, and a constant current source in the tail of the long tailed pair for setting a minimum level to which the maximum pump output can be reduced, one of said transistors in the long tailed pair receiving an input signal dependent on engine speed and the other transistor in the long tailed pair modifying the maximum pump output only when the engine speed is in the required range.

Claim 60

A system as claimed in claim 43 in which the maximum pump output is modified below a predetermined engine speed.