FR2493399A1 - Control of fuel supply in internal combustion engine - has transducer which provides series of signals at predetermined positions of rotary part of engine, through shaping circuit - Google Patents

Abstract

The system includes an electromagnetic device (52) which when energised causes an increase in the amount of fuel supplied by a fuel pump forming part of the system, to an associated engine. A transducer (54) which provides series of signals at predetermined positions of a rotary part of the engine, is provided, the signals being supplied through a shaping circuit (55) to a delay circuit (56) which provides a signal of fixed time length to a second circuit (58) to deenergise the device (52) every time a transducer signal is moved. As the engine speed increases therefore the amount of fuel supplied by the pump decreases and vice versa. The delay circuit is adjustable by the engine operator so that he can exercise some control over the quantity of fuel supplied by the pump. A third circuit (57) provides a continuous signal to de-energise the device if the interval between pulses from transducer becomes excessive.

Description

 The present invention relates to a fuel supply device for supplying fuel to an internal combustion engine of the type comprising a fuel pump for distributing fuel to the engine, a movable element inside the pump, the position of this element determining the flow of fuel supplied to the engine, electromagnetic means for controlling the position of this element, these means, when they are excited, causing the displacement of the element for ac against the flow of fuel supplied to the engine, and electronic control means operating in response to the speed of the motor to control the flow of electric current through the electromagnetic means.

 An example of a pump as defined in the preceding paragraph has been described in British Patent No. 2,037,365. In this case, the movable element is sensitive to a fluid pressure and the electromagnetic means comprise a valve which controls the pressure applied to said element. It is possible to produce complex electronic control means designed for use with this pump and which are part of the device. The control means may take into account various operating parameters of the engine to ensure correct control of the fuel supply of the corresponding engine in order to ensure that the engine operates as efficiently and as economically as possible without the production of a smoke level higher than the maximum level tolerated in the engine exhaust.It is possible that such a device is subject to a breakdown such that it is no longer supplied with fuel to the engine. In such a situation, it is desirable that relatively uncomplicated control means can be brought into service which at least allow the engine to operate without allowing it to operate at excessive speed.

 The object of the present invention is to provide a device of the type specified in a simple and convenient form.

 According to the present invention, in a fuel supply device of the specified type, the electronic control means comprise transducer means for producing signals at predetermined positions of a rotating part of the engine, a first circuit which receives the signals and which produces output signals having an approximately constant duration upon receipt of said signals, a second circuit to which these output signals are applied and which, in the absence of the output signals, energizes the electromagnetic means and other means for set the duration of the output signals.

An example of a fuel supply device according to the invention will now be described with reference to the accompanying drawings in which
Figure 1 is a vertical longitudinal sectional view of a pump forming part of the device;
Figure 2 is a block diagram of electronic control means for controlling the operation of the valve shown in Figure 1;
FIG. 3 is a diagram of the pulses produced in the electronic control means; and
FIG. 4 represents an embodiment of the electronic control means.

 The pump shown in Figure 1 to which reference will be made, comprises a body 10 which is formed in two parts, 11, 12, the part II being provided with pierced tabs 13 so that it can be fixed to the corresponding motor.

 The part 11 carries a rotary drive shaft 14 which, in service, is coupled to a corresponding engine drive member so that the shaft 14 rotates in synchronism with the engine. The drive shaft extends into a chamber 15 of generally cylindrical shape and has a portion 14A of larger diameter in the form of a bowl located inside the chamber. The part of larger diameter is provided with two diametrically opposite slots 16, and it is also hollow. The open end of the larger diameter portion is positioned around a protruding portion 17 formed on the portion 12 of the body. The remainder of the interior surface of the larger diameter portion flares out in the form of a truncated cone for purposes to be described later.

 The drive shaft is also provided with a counter bore 18 and an oil seal 19 is disposed at the outer end of the part II of the body so as to be in abutment against the shaft training. The latter is carried by a plain bearing 20. The shaft is retained against an axial movement by abutment surfaces which are in abutment against the end surfaces of the part of larger diameter of the shaft . In one case, the abutment surface is formed directly by the part 12 of the body while, in the other case, the abutment surface is formed by an annular plate 21 which surrounds the drive shaft and which also serves , end cover for a low pressure fuel supply pump 22. The rotor 22A of this supply pump is carried by the drive shaft and it in turn carries pallets which cooperate with a eccentrically arranged surface formed on a stator ring 22B carried inside the part 17 of the body. The low pressure pump has a fuel inlet port 23 connected to a fuel inlet port 23A formed in a housing attached to the body part. The low pressure pump also has an outlet port 24. A relief valve 25 is provided to ensure that the outlet pressure of the low pressure pump remains within desired limits.

 In the part 12 of the body is formed a cylindrical bore 26 in which is fixed a sleeve 27. The sleeve 27 houses a distributor member 28 movable axially and angularly which projects into the chamber 15 and includes an enlarged head part located at the inside the room. A bore 29 extending transversely is formed in the head part, a bore in which are housed two reciprocating pump plungers 30.

The bore 29 communicates with a blind passage 31 which is formed in one distributor member and which is closed by a plug at its end located inside the head portion. The passage communicates with a pair of diametrically opposite longitudinal slots 32 formed in the periphery of the distributor member and also with a single longitudinal slot 33 also formed in the periphery of the distributor member. The slot 33 can communicate successively with a series of outlet orifices 34 formed in the sleeve and passing through the part 12 of the body.

The orifices 34 communicate with outlet orifices 35 and with the respective injection nozzles of the corresponding engine. The slots 32 are aligned successively with inlet ports 37 which are formed in the sleeve and which extend inwards from a circumferential groove 38 which communicates with the outlet port 24 of the low pump. pressure via an all-or-nothing control valve 30 which is controlled by a solenoid device 40.

 An annular cam ring 41 surrounds the head portion of the distributor member 28, a ring on the inner peripheral surface of which pairs of diametrically opposite cam bosses are formed. In the particular example shown, the ring has three pairs of cam bosses since the device is intended to supply fuel to a six-cylinder engine. The cam ring 41 can be moved angularly around the axis of rotation of the distributor member by a device controlled by a fluid pressure designated by the general reference 42 and connected to the cam ring by a stud 43 disposed radially.

 Two cam follower members, each of which has a roller 44 carried in a shoe 45, are each positioned on the outer end of a respective plunger.

The cam follower members are retained axially with respect to the distributor member by a pair of side plates 46, 47 which are fixed to the side faces of the head portion of the distributor member. The side plates have an annular shape and have outwardly extending portions which are housed in the slots 16 formed in the drive shaft. The circumferential lateral faces of the shoes are provided with circumferentially extending projections 49 whose outer surfaces have a decreasing or frustoconical section so as to cooperate with the frustoconical surface formed on the internal surface of the part of larger diameter of the shaft d 'in tratment.

 In service, when fuel is supplied to bore 29, when a groove 32 is aligned with an inlet passage 37, the plungers 30 are moved outward by the pressure of the fuel, and as they move erect, they communicate a movement of outward movement to the shoes 45 and the rollers 44. The outward movement is limited by the abutment of the frustoconical surfaces formed on the shoes and on the shaft and, by moving axially the dispensing member, the extent of the outward movement of the hooves can be modified. Thus, one can control the quantity of fuel supplied to the bore 29 and this in turn determines the quantity of fuel supplied by the outlet orifices 34 when the plungers 30 are moved inward by a pair of bosses. cam.

 The axial position of the dispensing member is changed hydraulically and this is obtained by modifying the pressure prevailing inside a chamber 50 delimited by the end of the bore 26 formed in the part 12 of the body. The end of the bore 26 is closed by a shutter member and fuel under pressure is introduced into the chamber 50 via a throttled orifice 51 carried by the sleeve 27. The orifice 51 communicates with the outlet 24 of the pump 20 and the fuel can escape from the chamber 50, so that the pressure prevailing in the chamber can be controlled, by a valve 52 with electromagnetic control. by a helical compression spring 53 mounted inside the bore 18, the spring acting between the drive shaft and the distributor member and serving to push the distributor member against the action of fuel under pressure contained in chamber 50.

 A transducer 54 is disposed inside the chamber 50 and it has a part which rotates with the distributor member. The transducer 54 provides an indication of the speed of rotation of the distributor member and, for the purposes of the usual control device, it provides an indication of the axial adjustment of the distributor member.

 As shown in FIG. 2 which will now be referred to, the signal produced by the transducer 54 is applied to a circuit 55 for transforming the signal into a signal with a rectangular waveform, or conforming circuit and output signal of this circuit is applied to two delay circuits 56, 57. The output signals of circuits 56 and 57 are applied to a current supply circuit 58 whose output signal is an electric current which is applied to the winding of the valve 52.

In FIG. 3 to which we will now refer, the signal produced by the transducer 54 is represented by a curve 54A, the output signal from the conforming circuit 55 by a curve 55A, the output signal from the delay circuit 56 by a curve 56A and the current flowing in the winding of the valve 52 by a curve 52A.

 It can be seen that the signal produced by the transducer is of an intermittent nature and not continuous.

This is essential for the operation of the control device. The output signal from the shaping circuit 55 is, as is to be expected, constituted by a series of pulses separated by an interval TI which decreases when the speed of rotation of the distributor member increases. The output signal from the delay circuit 56 is a pulse of duration T2, the pulse being triggered by the front edge of the pulse produced by the conforming circuit. The duration of the pulses produced by the delay circuit 56 is variable in terms of time as will be explained. When a pulse is produced by the circuit 56, the circuit 58 interrupts the supply of current to the winding of the valve 52 and , since the valve is biased by a spring towards the closed position, the pressure in the chamber 50 increases so that the distributor member is moved to reduce the amount of fuel supplied to the engine. If, for example, there is an increase in the motor speed, the time interval TI becomes smaller and, therefore, the time difference between the pulses TI and T2 becomes smaller so that the flow of average current flowing in the solenoid noise winding of the valve 52 is reduced. This has the effect of increasing the pressure prevailing in the chamber 50 so that the motor speed is controlled. If, on the other hand, the engine speed decreases, the difference in time between the pulses T7 and T2 becomes larger so that an increased fuel flow is supplied to the engine. Similarly, if the length of the T2 pulse is changed as will be explained, the time difference between the T1 and T2 pulses can be changed so as to control the amount of fuel supplied to the engine.

 In Figure 2, there is shown an additional delay circuit 57 and the latter applies a continuous signal to the circuit 58 to prevent the application of current to the solenoid of the valve 52 in the case where the time-interval between the pulses produced by the shaping cir cir exceeds a predetermined value. This time interval is, for example, greater than the longest time interval which can be obtained for example when the engine is idling. The delay circuit 57 therefore prevents operation of the circuit in the event that the transducer signals cease to be applied. In FIG. 4 to which reference will now be made, the electronic control means shown include first and second terminals 59, 60 intended to be connected respectively to the positive terminal and to the negative terminal of a direct current source such as, for example, an accumulator. One terminal of the transducer is connected to the negative supply line while the other terminal of the transducer is connected to one. terminal of a capacitor 61, the other terminal of which is connected to the junction of a pair of resistors 62, 63 connected in series between the positive and negative supply lines. In addition, the junction of the resistors is connected to the inverting input terminal of a comparator 64, the non-inverting input terminal of which is connected to the negative supply line via a resistor 65. , a reaction resistor 66 is provided which is connected between the output of comparator 64 and the non-inverting input terminal of this latter Zen. The output terminal of comparator 64 is connected to the positive line via a resistor 67, to the anode of a diode 68 and to the inverting input terminal of a comparator 69. The cathode of the diode 68 is connected, via a resistor 70, to the output terminal of comparator 69 and to one of the plates of a capacitor 71, the other plate of which is connected to the negative line. The cathode of the diode is also connected to the negative line via a resistor 72 and a capacitor 73 connected in parallel.

 The output of comparator 69 is connected to the inverting input terminal of a comparator 74. The non-inverting input terminals of comparators 69 and 74 are connected to the positive supply line via a resistor 75 and to the negative supply line via a pair of resistors 76, 77, connected in series. The value of the resistor 77 can be modified, as will be explained.

 The output terminal of comparator 74 is connected to the base terminal of a transistor 78 whose collector is connected to the positive supply line and whose emitter is connected to the negative supply line via the winding of the valve 52. In addition, the base terminal of the transistor 78 is connected to the positive supply line via a resistor 79 and it is also connected to the cathode of a Zener diode 80 whose anode is connected to the negative supply line.

 The comparator 64, in combination with the cooperating resistors, constitutes the conforming circuit and the values of the resistors are chosen such that if no signal appears at the output of the comparator 64, as is the case when the engine is stopped or when the connections with the transducer are broken, the capacitor 73 is discharged via the resistor 72 and the capacitor 71 is discharged via the resistors 70 and 72 in series. In this case, the output signal of the comparator 74 is at a low level and the transistor 78 is in a non-conductive state so that no current flows in the winding of the valve 52.

 When a pulse train is applied to the shaping circuit and a pulse appears at the output of the comparator 64, the capacitor 73 is charged via the resistor 67 and the diode 68 and the comparator 69 is switched from so that its output signal falls to a low level, thereby discharging the capacitor 71 and causing, as in the previous case, the fall to a low level of the output signal of the comparator 74.

When the output signal of comparator 64 goes to a low level, the output signal of comparator 69 goes to a high level, which allows capacitor 71 to be charged by capacitor 73, through resistor 70 The output signal from comparator 76 remains at a low level until the voltage across the capacitor 71 reaches a value such that it exceeds the voltage at the junction of resistors 75 and 76. When this voltage is exceeded, the output signal of comparator 74 goes to a high level so that transistor 78 is turned on to allow current to flow through the valve winding. When the next signal is produced by the transducer, the signal from comparator 64 output goes to a high level and comparator 69 output signal goes to a low level again discharging the capacitor 71 and allowing the capacitor 73 to charge so that the process is repeated.

The length of the time interval T2 can be modified by adjusting the resistor 77 and, advantageously, this adjustment is associated with operator control.

 The operation of the delay circuit 57 will now be described. The time constant of the capacitor 73 and of the resistor 72 is such that the voltage across the terminals of the capacitor 73 is approximately constant at the minimum speed of the motor. The capacitor 73 is charged by the current pulses which flow through the resistor 67 and the diode 68 and discharged mainly by the resistor 72 and partly by the resistor 70 when the output signal of the comparator 69 is at a low level .

 When the frequency of the input pulses decreases, the charge rate of the capacitor 73 decreases and its average voltage decreases. Consequently, at a low frequency of the input pulses, the voltage across the capacitor 73 drops to a value which is lower than the voltage at the junction of the resistors 75 and 76 so that the comparator 74 does not go to a high level.

 The purpose of the Zener 80 diode is to ensure that an approximately constant voltage is applied across the valve winding despite variations in source voltage. The fact that the non-inverting input terminal of comparator 69 is connected to the non-inverting input terminal of comparator 74 has no influence on the operation of the circuit and, if desired, separate biasing means can be used.

 The Zener diode also performs another function when the output of comparator 74 drops to a low level. In this situation, the transistor 78 attempts to go into the non-conducting state. Due to the inductive nature of the winding of the valve 52, when the transistor attempts to go into the nonconductive state, the voltage at the emitter of the transistor becomes negative due to the counterelectromotive force. The base of the transistor is also made negative, but the Zener diode 80 then acts as a normal diode to limit the negative excursion of the base of the transistor and therefore limits the counter-electromotive force generated at the terminals of the winding. of the valve.

 In the circuit produced in practice shown in FIG. 4, the time interval T2 varies, in fact, slightly as a function of the speed of the motor. This is due to the fact that the width of the pulse produced by the shaping circuit varies as a function of speed. The time variation is however short compared to tervalle time line T2 so that its effect can be overlooked. If desired, however, the shaping circuit can be modified to provide an output pulse of constant length.

 The device as described only takes account of the speed of the motor and acts so as to ensure that the safety speed of the motor is not exceeded. The degree of control is, therefore, less than that which would be obtained by means of the more complex control arrangement.

Claims (2)

IEVENDICATIONS 1) A fuel supply device for supplying fuel to an internal combustion engine, comprising a fuel pump (10) for distributing fuel to the engine, a movable element (28) inside the pump, the position of this element determining the flow of fuel supplied to the engine, electromagnetic means (52) for controlling the position of this element, these means, when they are excited, causing the displacement of the element to increase the flow of fuel supplied to the motor, and electronic control means operating in response to the speed of the motor for controlling the flow of electric current in the electromagnetic means, characterized in that the electronic control means comprises transducer means (54) for producing signals at predetermined positions of a rotating part (28) of the motor, a first circuit (56) which receives the signals and which produces output signals having an approximate duration ximatively constant on reception of said signals, a second circuit (58) to which these output signals are applied and which, in the absence of the output signals, excites the electromagnetic means, and other means (77) for regulating the duration output signals. 2) Fuel supply device according to claim 1, characterized in that it comprises a third circuit (57) which receives the signals from the transducer means (54) and which supplies a signal to the second circuit (58) to prevent the energizing the electromagnetic means (52) in the case where the time interval between the signals produced by the transducer means exceeds a predetermined value or in the case where said signals cease.