GB2120409A

GB2120409A - An apparatus for controlling a fuel pump

Info

Publication number: GB2120409A
Application number: GB08310097A
Authority: GB
Inventors: Anthony John Adey; Alistair John Forster Ritchie
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1982-05-14
Filing date: 1983-04-14
Publication date: 1983-11-30
Also published as: GB8310097D0

Abstract

An apparatus for controlling a fuel pump comprises a governor circuit 15 which provides the normal fuel signal to an actuator control circuit 13 by way of a switch 16. A first memory 20 contains information relating to the required excess fuel quantity against engine temperature for starting the engine and provides another input to the switch. The switch is controlled by a comparator 17 which receives at one input the engine speed signal and at its other input a signal provided by a second memory 18. This contains information relating to the maximum allowed engine speed against engine temperature below which excess fuel can be supplied. For starting the switch selects the output of the first memory for supply to the control circuit 13 but as soon as the engine speed exceeds that determined by the second memory for the engine temperature the switch is latched in its alternative state in which the governor circuit 15 provides the normal fuel signal to the control circuit 13. <IMAGE>

Description

SPECIFICATION An apparatus for controlling a fuel pump The invention relates to an apparatus for controlling the fuel pump of a compression ignition internal combustion engine and of the kind comprising an electrically operated actuator for varying the amount of fuel supplied by the pump and circuit means for controlling the actuator, said circuit means including input means through which signals representing various engine operating parameters and desired operating parameters can be supplied.

In order to start a compression ignition engine it is the usual practice to supply a quantity of fuel in excess of the normal maximum quantity and to continue this supply of fuel until the engine speed has attained a predetermined value which is usually in excess of the normal idling speed of the engine. In order to minimise pollution and to economise on fuel, it is desirable to be able to vary the aforesaid quantity in accordance with the temperature of the engine so that for example, when the engine is not the quantity will only be slightly in excess of the normal maximum amount, the quantity tending to increase the lower the engine temperature.

It may also be desirable to adjust the aforesaid predetermined speed.

The object of the invention is to provide an apparatus of the kind specified in a simple and convenient form.

According to the invention an apparatus of the kind specified includes means for providing a signal representing the temperature of the engine, first memory means in which is stored information representing the speed as a function of temperature, that the engine is to be allowed to attain when excess fuel is being delivered, means for obtaining the fuel quantity signal and speed signal from said memory means using the temperature signal, said fuel quantity signal and said speed signal being used in the circuit means to control said actuator during the engine starting process.

One example of an apparatus in accordance with the invention will now be described with reference to the accompanying block diagram.

Shown in the dotted outline at 10, is a fuel pump for supplying fuel to a compression ignition engine, the pump having a first electromagnetic actuator which controls the amount of fuel supplied by the pump to the associated engine at each injection stroke. Also provided is a second electromagnetic actuator 12 which controls the timing of fuel delivery to the associated engine.

The flow of current to the actuators is controlled by control circuits 13, 14 respectively which use feedback techniques to ensure that the desired amount of fuel and the desired timing of fuel delivery are achieved in accordance with the variations of input signals supplied to the control circuits.

The normal fuel control that is to say the signal which is utilised during normal operation of the engine, is derived from a circuit 1 5. The normal fuel control signal is supplied to the control circuit 13 through a switch 1 6. The circuit 1 5 provides an engine governing function and for this purpose will be supplied with various actual and desired engine operating parameters through input means not shown.The switch is controlled by the output of a comparator 1 7 which receives a signal from a speed transducer not shown and a further signal from a memory means indicated at 1 8. The memory means 1 8 contains stored information representing the speed to which the engine is to be allowed to increase following starting of the engine, during which excess fuel is supplied to the engine. It is desirable that this speed should vary in accordance with the temperature of the engine and therefore the information stored in the memory means 1 8 represents the variation of speed in accordance with engine temperature. The engine temperature signal is provided by a temperature sensor 19 which in the particular example, is responsive to the coolant temperature of the engine.The operation of this portion of the apparatus is such that when the actual speed of the engine exceeds the speed signal provided by the memory means 18, the comparator switches the switch 1 6 such that the signal from the circuit 1 5 is applied to the control circuit 13. When the engine speed is below this value the switch 1 6 connects the input of the control circuit 1 3 with the output of a memory means 20 which also receives a temperature signal from the sensor 1 9.

The memory means 20 contains information relative to the variation of excess fuel required to be supplied to the engine in accordance with the engine temperature. As previously stated in general, the amount of excess fuel to be supplied to the engine will increase as the temperature reduces. It is essential to ensure that if the engine speed should during operation, fall below the speed signal provided by the memory means 18, excess fuel should not be supplied and hence the switch 1 6 is a latching switch and once it has been set by the output of the comparator 1 7, its state cannot be changed until the engine has been stopped.

A similar form of circuit is utilized to supply a signal to the control circuit 14 there being provided memory means 21 and 22 which correspond in terms of timing, to the memories 20 and 1 8 respectively. A switch 23 corresponds to the switch 16 and again it is of the latching variety. A circuit 24 is provided to control the normal timing variation, this corresponding to the circuit 1 5.

An additional memory means 25 is provided and this contains stored information relating to the normal idling speed of the engine. When the engine has been started but is still cold, it is often desirable to increase the idling speed to obtain satisfactory running of the engine and therefore the memory means 25 contains information relative to the desired variation of the idling speed in accordance with temperature. All the memory means are supplied with signals from the temperature sensor 19. In addition, variation of the normal timing of fuel delivery in accordance with temperature may be provided this being obtained by applying the temperature signal from the sensor 1 9 to the circuit 24 either directly or through an additional memory means.

A further facility may be provided to indicate to the operator of the engine, an excess engine temperature and for this purpose a comparator 26 is provided, the output of which controls a warning device 27. The comparator receives the temperature signal from the sensor 1 9 and a reference signal so that once the engine temperature exceeds a predetermined value as determined by the reference signal, the warning device will be rendered operative.

Conveniently the temperature sensor is a wide range thermistor.

As described the various memory means are individual items they may however be part of the Read Only memory of a microprocessor based engine control system.

Claims

1. An apparatus controlling the fuel pump of a compression ignition internal combustion engine of the kind having an electrically controlled actuator for varying the amount of fuel supplied by the pump and circuit means for controlling the actuator, said circuit means including input means through which signals representing various engine operating parameters and desired operating parameters can be supplied, means for providing a signal representing the temperature of the engine, first memory means in which is stored information representing the amount of excess fuel to be supplied to the engine in accordance with the engine temperature, second memory means in which is stored information representing the speed as a function of temperature, that the engine is to be allowed to attain when excess fuel is being delivered, means for obtaining the fuel quantity signal and speed signal from said memory means using the temperature signal, said fuel quantity signal and said speed signal being used in the circuit means to control said actuator during the engine starting process.

2. An apparatus according to Claim 1 including a switch having a first input connected to a governor circuit and a second input connected to the output of said first memory means, a comparator the output of which is used to control the setting of said switch, said comparator having a first input connected to an engine speed sensing means and a second input connected to the output of said second memory means the arrangement being such that when the speed signal provided by said second memory means is greater than the actual speed signal which switch is set so that the output of said first memory means is passed to the output of said switch for use as the signal controlling the amount of fuel supplied by the pump, said switch being moved to its alternative setting when the actual speed signal increase above the speed signal provided by said second memory means so that signal controlling the amount of fuel supplied by the pump is the signal provided by the governor circuit.

3. An apparatus according to Claim 1 in which said switch latches in its alternative state.

4. An apparatus according to any one of Claims 1-3 in which the means for providing a signal representing the temperature of the engine is a wide range thermistor.

5. An apparatus according to any of Claims 1-4 including means for adjusting the timing of delivery of fuel for starting purposes.

6. An apparatus according to any one of Claims 1-5 including a further comparator responsive to said engine temperature signal and to a reference signal, and a warning device controlled by said comparator, said warning device being rendered operative if said engine temperature signal exceeds a predetermined value.

7. An apparatus for controlling the fuel pump of an compression ignition engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawing.