US3734067A

US3734067A - Fuel injection system for internal combustion engine

Info

Publication number: US3734067A
Application number: US00099139A
Authority: US
Inventors: O Glockler; H Schmid; D Eichler
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1970-01-22
Filing date: 1970-12-17
Publication date: 1973-05-22
Anticipated expiration: 1990-05-22
Also published as: ES387505A1; NL7100812A; BR7100407D0; SU519146A3; AT311125B; CS151076B2; CH519101A; GB1332524A; DE2002667A1; JPS4948890B1; BE761871A; SE367674B; FR2073096A5; PL81427B1; CA930848A; DE2002667B2

Abstract

To extend the time of opening of fuel injection valves during starting, a timing circuit, having a time constant preferably between 5 and 30 seconds, and desirably about 25 seconds, is connected to the electronic control circuit controlling the opening times of the fuel injection valves. The timing circuit provides a decreasing signal to extend the time during which the injection valves are open from the time the starter switch is operated. Preferably, the fuel injection system includes a pulse duration multiplier circuit, having a multiplication factor varying between 1 and 5, and the timing circuit affects the multiplication factor.

Description

United States Patent 1 Glockler et al.

[ 51 May 22, 1973 [54] FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINE [73] Assignee: Robert Bosch G.m.b.H., Stuttgart,

Germany [22] Filed: Dec. 17, 1970 [21] Appl. No.: 99,139

[30] Foreign Application Priority Data 3,628.510 12/1971 Moulds ..123/32 EA 2,981,246 4/1961 Woodward. .......123/32 EA 3,032,025 5/1962 Long ..123/32 EA 3,483,851 12/1969 Reichardt.... 123/32 EA 3,500,803 3/1970 Long ..123/32 EA 3,504,657 4/1970 Eichler et a1 ..l23/32 EA Primary Examiner-Laurence M. Goodridge Assistant Examiner-Cort Flint Attorney-Flynn & Frishauf [57] ABSTRACT To extend the time of opening of fuel injection valves during starting, a timing circuit, having a time constant preferably between 5 and 30 seconds, and desirably about 25 seconds, is connected to the electronic control circuit controlling the opening times of the fuel injection valves. The timing circuit provides a decreasing signal to extend the time during which the injection valves are open from the time the starter switch is operated. Preferably, the fuel injection system includes a pulse duration multiplier circuit, having a multiplication factor varying between 1 and 5, and the timing circuit affects the multiplication factor.

1 1 Claims, 4 Drawing Figures PATENIEUHMTZZESH 3.734067.

INVENTORS Qtto GLOCKLER 1 =t HermcmnSCHMlD 31 n3 Dieter EICHLER their ATTORNEY FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINE Cross-reference to prior patents: U. S. Pat. No. 3,483,851.

The present invention relates to fuel injection systems for internal combustion engines and more particularly to the fuel injection system in which electromagnetically operating in fuel injection valves have the time of opening of the valve controlled in accordance with operating parameters of the engine. A complete operating system of this type is disclosed in U.S. Pat No. 3,483,851, to which reference is hereby made.

Fuel injection systems of the type to which the invention relates have an injection valve which is opened by essentially square electrical pulses occuring synchronously with the rotation of the cam shaft. The pulse duration, corresponding to the opening time of the valve is controlled by a controlsystem in dependence on at least one operating parameter of the internal combustion engine, for example intake manifold pressure (or, rather, vacuum). Other operating parameters may additionally control the opening time, such as temperature of the engine. The amount of fuel injected to each cylinder during the suction stroke thereof, by fuel injection systems of this type, can be accurately matched to the operating conditions of the engine, and specifically to its speed and the load thereon. This has the advantage that the exhaust gases from the internal combustion engine can be minimized, and operating efficiency of the engine increased. Normally, the tuning of the engine, that is the adjustment of the fuel-air mixture is made with respect to the engine at its normal operating temperature, that is, when the engine has operated for some time and has reached a stable temperature as determined by its cooling system. Upon cold starting of an internal combustion engine, ease of start can be insured only when the amount of fuel supplied to the cylinder during the suction stroke is substantially increased, that is, when the engine receives a richer mixture with respect to the mixtures which are necessary and desirable when the engine has reached its normal operating temperature.

Various fuel injection arrangements, and particularly gasoline injection arrangements have been proposed in which a temperature sensing device is arranged in heattransfer relationship to the internal combustion engine. The temperature sensor controls the ratio of fuel to air during the operationof the internal combustion engine, and particularly upon starting, that is, effectively in the period when the engine is cold and until it reaches its normal operating temperature. The fuelair ratio is increased until the normal operating temperature is reached. Such an electronic control arrangement has a circuit including an input transistor andan output transistor, and a capacitative, or inductive feedback circuit which forms an energy or charge storage device. The duration of the pulses controlling the opening of the injection valve, or valves is then determined by electrical parameters such as voltages and currents, and stored energy, which change in dependence on operating parameters of the internal combustion engine, such as air temperature, pressure (vacuum) in the intake manifold, and speed, for example. A known control system utilizes a highly temperature-responsive resistance which is in thermal transfer with the engine cooling water, or, respectively, with its cylinder head. The temperature sensitive resistance has either a positive or negative temperature coefficient and is arranged in the collector circuit of the output transistor of a controlled multivibrator in the electronic control system. Other known control systems use a first control multivibrator generating pulses synchronized with the speed of the engine, connected to a multiplication stage which increase the length of the base pulses derived from the control multivibrator by a factor depending on temperature (and, if desired, on other operating parameters) which, together with the base pulse, provides an overall injection pulse to control the injection valves.

Upon investigation of the starting process in large numbers of various types of internal combustion engines, it has been found that they all required a substantially richer mixture upon cold starting and idling, to maintain the engine in operation, and to prevent stalling, or even recurring stalling. The richer mixture is also required to insure good response to sudden increases in fuel mixtures, for example commanded by the vehicle operator. It has been found, however, that only a very short operating period of the motor is required before such a rich mixture is no longer necessary; for example, in some motors the time may be as short as 5 seconds, whereas in others it may be 30 seconds or even longer; in many engines the time after which a substantially enriched mixture is no longer required is in the order of 25 seconds. in that time the excess fuel can be reduced by 50 percent. If,however, the internal combustion engine continues to operate with the enriched starting mixture, even short-time operation under these conditions causes carbon disposits on the spark plugs and misfire, or complete ignition malfunction. Additionally, an excessively high portion of raw fuel will be found in the exhaust of the internal combustion engine. By switch-over of the control arrangement within the time period of from about 5 to about 30 seconds to much lower fuel quantity of the fuel being injected, objectionable exhaust and ignition malfunctions can be avoided.

It is accordingly an object of the present invention to provide a fuel injection system for internal combustion engines in which the fuel-air ratio is decreased upon starting, and then smoothly increased to normal operating values during the time required for the engine from cold start to reach normal idling running conditions, typically within about 5 to 30 seconds or so.

Subject matter of the present invention: Briefly, a timing circuit is provided, preferably controlled by the starter switch, which during the time period required by the engine to reach normal running conditions, after cold start, increases the pulse period of fuel injection pulses applied to fuel injection valves. This time period may be between 5 and 30 seconds, or longer, and preferably is about 20-25 seconds.

A timing circuit which changes the amount of fuel injected, after starting, from a rich mixture to a normal, operating or leaner mixture can be constructed in various ways to operate, for example, electrically, electronically, thermoelectrically or mechanically, and also hydraulically or pneumatically. Change-over of fuel-air ratio from a richer to a leaner mixture may be controlled by the starting switch itself, and may control the amount of mixture smoothly, that is progressively from a richer to a leaner mixture, or in one or more abrupt steps. It is important, however, that the pulse duration controlling the opening of the fuel injection valves varies from a longer opening period, upon starting, to the opening period required by engine normal operation.

Progressive decrease of the fuel-air ratio to increase the ratio from a high value to a normal operating value can be easily controlled in fuel injection systems having a pair of multivibrators; each providing a valve opening pulse. The first provides a base pulse, which, in turn, triggers a second, which forms a multiplication stage generating a second pulse the time duration of which is that of the base pulse, multiplied by a factor varying between and 5. In such an arrangement, the timing circuit can be directly connected to the multiplication stage to affect the multiplication factor thereof, and to increase this factor upon starting, and then progressively decrease the factor as the time after starting elapses.

The invention will be described by way of example with reference to the accompanying drawings, wherein:

FIG. 1 is a schematic circuit diagram of a fuel injection system in combination with an internal combustion engine;

FIG. 2 is a timing diagram illustrating the effect of the timing circuit;

FIG. 3 is a modified form of timing circuit and FIG. 4 is another embodiment of a timing circuit.

The fuel injection system will be described in connection with a four cylinder engine 11, having spark plugs 12, connected to an ignition system, not shown. Fuel injection valves 14 are located in the inlet manifold stubs 13 leading to the various cylinders from the inlet manifold. The injection valves 14 are placed next to the inlet valves. Each injection valve 14 is supplied with fuel over a line 15 connected to a fuel distribution unit 16. Fuel is pumped into line 15 by a pump 7, driven for example by an electric motor, and supplying fuel under pressure, controlled by a pressure regulator 18 at approximately 3 At (2 At gauge).

Each one of the injection valves 14 has a magnetization winding, or solenoid coil, one end of which is connected to chassis, and the other end of which is connected to a line 19 and over a resistance, 20, each to the electronic fuel supply control circuit. In the example shown, all four valves are simultaneously operated, in synchronism with the rotation of the crank shaft, respectively. An opening pulse I, (FIG. 2), having a time duration which determines the opening time of the valves is applied from an output power stage 22 (FIG. 1) to the fuel injection valve.

The electronic control system, essentially, is formed ofa mono-stable multivibrator 25, an inverter stage 26, a multiplication stage 2, and an OR gate 28 to which the output or power stage 22 is connected. Additionally, and in accordance with the present invention, a timing circuit 30 is provided, connected to the multiplication stage.

Multivibrator 25 includes an input and an

output transistor

31, 32. The base of transistor 32 is connected to the collector of the input transistor 31. The collector of the output transistor 32 is connected to a common positive bus 33 over primary winding 35 of a transformer 36, having a movable core 37. Core 37 is connected over a linkage, schematically indicated by a chain-dotted line 38, to the membrane of a pressure transducer 39. Pressure transducer 39 is sensitive to pressure (or rather, vacuum) in the intake manifold of the internal combustion engine, and is located in the manifold behind air inlet 41, and a throttle valve, the

position of which is controllable by accelerator pedal 40.

Input transistor 31 of the multivibrator 25, under normal operating conditions, is held in conductive state by resistance 43 connecting the base thereof to the positive bus. Additionally, the base is connected by diode 44, to the other winding 45 of transformer 36; the other terminal of winding 45 is connected to the tap point of a voltage divider formed of

resistances

46, 47.

The mono-stable multivibrator 25 changes state in synchronism with the rotation of the engine, for example in synchronism with the crank shaft thereof. A cam 51, applied to the cam shaft of the engine operates a switch 53 which is connected to chassis. The switch contact 54 is connected to a charge resistance 55 and to one electrode of a coupling condenser 56. The other electrode of the condenser is connected over a second charge resistance 57 with the chassis bus 52, and, additionally, over a diode 58 with the base of the input transistor 31.

So long as switch 53 is in the position shown in the figure, that is, is open, then condenser 56 can charge over the two

resistances

55 and 57, each connected to a

respective supply bus

33, 52, to the operating voltage of the system. When switch 53 is pressed against the contact 54 by the control cam 51, the positively charged electrode of condenser 56 is connected to the negative potential, or chassis; the base of transistor 31 will receive a strongly negative pulse and transistor 31 will block. This brings the output transistor 32 into conductive condition. The collector current flowing over primary winding 35 of transformer 36 induces a voltage in the winding 45 which can further control input transistor 31 to remain conductive, the duration of the blocking voltage depending on the pressure (or rather vacuum) within the intake manifold of the internal combustion engine. If the pressure is substantially below atmospheric pressure, due to closed or almost closed position of the valve, the pressure transducer 39 will lift the core 37 in the direction indicated by the arrow, thus increasing the air gap in the transformer 36, so that the inductivity of the primary winding 35 is substantially decreased. Since the input transistor 31, due to the low induced voltages will rapidly return to its ordinary, conductive condition, the output transistor 32 will be blocked. Thus, the base pulse I, appearing at the collector of the output transistor will have only a very short duration, for example. 1.2 msec., however, if pedal 40 is operated and the valve in the intake line is open, the pressure behind the valve flap will deviate only little from that of ordinary atmospheric pressure, even at high speed. This causes the iron core 37 to be lifted only slightly, increasing the inductivity of primary winding 35 and causing only slow rise of the collector current from transistor 32 in the primary winding. This increases the pulse period of the base pulse I, to about 4.2 msec.

In the example illustrated, each base pulse I is transmitted from the output transistor 32 to an inverter state 26 and then to a multiplying stage 27. The multiplying stage 27 generates an extension pulse I, following immediately after the base pulse 1,. The duration of the extension pulse I, bears a relationship to the base pulse in that it is a multiplied value of the length of the base pulse. The multiplication factor can be determined in know manner (see the above referred to patent) in dependence on various operating conditions and parameters of the internal combustion engine, for example cooling water temperature.

The multiplying stage includes a storage condenser 60, a charging transistor 61 and a discharge transistor 62. A switching transistor 63 has its emitter directly connected to the chassis bus 52. The base thereof is connected to a resistance 64, which in turn connects to the chassis bus 52, and to one electrode of storage condenser 60. Storage condenser 60 is connected, in turn, to the collector of the charging transistor 61. The discharge transistor 62 has its base connected to the tap point of a voltage divider formed of

resistances

65, 66 connected across the

supply buses

52, 53. The emitter of transistor 62 is connected over a resistance 67 to the positive bus 33. The charging transistor 61 has its collector connected through the other electrode of charging condenser 60. Transistor 61 is connected as an emitter follower, since its emitter is connected over emitter resistance 69 to the positive bus 33; its base is connected to a junction X, which directly connects to the collector of transistor 70 of the inverter stage 26. Junction X, and hence the collector of transistor 70 is connected over a resistance 73 to positive bus 33. The base of the invertor transistor 70 is connected over the resistance 72 with the collector of output transistor 32; and, over a resistance 71 to the chassis bus 52.

Junction X, and hence the collector of transistor 70 is connected over a coupling resistance 76 to a transistor 75, forming part of the OR Gate 28. The base of transistor 75 additionally is connected over resistance 77 to chassis bus 52. The second coupling resistance 78 connects the base of the OR Gate transistor 75 with the collector of switching transistor 63 forming part of the multiplying stage 27. The collector of transistor 75 is connected to the common positive line 33 by means of a resistance 79. Its emitter is connected to the chassis bus 52 over resistance 80. The base of npn transistor 81 is connected to the emitter of transistor 75, and forms, together with transistor 82 the output power stage 22.

Operation: the circuit so far described is known in principle, and its general operation can therefore be described briefly. When the internal combustion engine rotates, cam 51, upon each revolution, closes switch 53 and the normally conductive input transistor 31 will block. This causes generation of the base pulse 1, the duration of which will depend on the speed of rotation of the engine and the position of the flap of the valve as commanded by pedal 40. During the time of this base pulse 1,, the normally conductive transistor 70 of stage 26 will block, so that transistor 75, forming part of the OR Gate 28 will become conductive over the coupling resistance 76. This causes conduction of transistor 81 and of power transistor 82. Collector potential of charging transistor 61, just like the collector potential of the inverter transistor 70, which will be conductive, will be approximately at the same value as that of chassis, line 52. The voltage U across the storage condenser 60 will be effectively zero.

As soon as the base pulse 1,, starts, the base potential of the charging transistor 61 will reach a voltage value which is somewhat intermediate the voltage of the positive line 33 and of chassis bus 52, due to the base current of OR Gate transistor 75 flowing over resistance 73. Charging transistor 61 can thus supply a constant charging current for storage condenser 60. During the period of the base pulse I voltage U on the storage condenser 60 will rise linearly, as indicated in FIG. 2 in the time period between t, to t At point t the base pulse 1,, terminates. As soon as inverter stage transistor becomes conductive, that is, at the termination of the base pulse, the collector thereof will receive a strongly negative potential and therefore also the collector of charging transistor 61. Thus, the charge on the storage condenser 60 will cause switching transistor 63 to block, by applying a strongly negative potential to its base. This blocking period will be for such a time until a charge has dissipated over discharge transistor 62. Transistor 62 insures that the discharge current will have a constant value. As seen in FIG. 2, the discharge period will extend from time t to time t;,, at which point the switching transistor 63 will again become conductive. During this blocked condition of switching transistor 63, OR gate transistor is kept conductive over the second coupling resistance 78 and the collector resistance 68. Thus, the pulse I, is added to the pulse I so that a combined opening pulse 1, is provided, the time duration of which controls the amount of fuel being injected.

The factor f (T,,/T,,) has a variable value, varying between zero and 5, when the internal combustion engine is at operating temperature; according to practical experience, f l. T, is the duration of the extension pulse 1,, and T, is the duration of the base pulse 1,, of the first multivibrator 25.

It is desired to supply more fuel to the internal combustion engine immediately after starting, than the amount of fuel which would be necessary after continued operation. To provide such additional fuel, in accordance with the invention, timing circuit 30 is provided which electronically increases the above referred extension factor f of multiplier stage 27 during the time period until the engine reaches normal operating equilibrium, typically about 20-25 sec. The multiplying factor is substantially increased initially, and progressively decreases to the value proper for continuous operation of the engine during the period for which the timing circuit is set. Thereafter, the factor f is maintained. Thus, the extension of the pulse by a multiplying factor is solely dependent on time and not on any other operating or ambient parameter of the engine.

The timing circuit 30 has two

npn transistors

85, 86. During normal operation, both transistors are blocked and, to keep them blocked, the base of the first transistor 85 is connected over a resistance 88 to the chassis bus 52; the emitter of transistor 86 is directly connected to chassis'bus 52, and its space to the emitter of transistor 85 and, further, over a resistance 87 to chassis bus 52. A condenser 89 interconnects tthe collector of transistor 86 to the base of transistor 85; the condenser has a value of about 3 pF. Resistance 90 connects the collector of transistor 86 to the positive bus 33, and resistance 93 is the collector resistance for transistor 85. A limiting resistance 91, in series with a diode 92 connects from the connector of transistor 86 to junction X of the inverter stage'26, and thus with the collector of transistor 70 and the base of charging transistor 61. The base of the first timing circuit transistor 85 is connected over a resistance 94 with starter switch 96 which, in turn, has one terminal connected to positive bus 33. The other terminal of starter switch 96 is connected with a point P at the end of the solenoid winding 97 of the usual starter relay, not further shown. Upon operation of switch 96, winding 97 is energized and starts the starter motor. A diode is connected between resistance 94 and the base of transistor 85, and a resistance 98 connects between the diode 94 and resistance 94 to the chassis bus 52.

To start the engine, starter switch 96 is closed. First transistor 85, over resistance 94 and diode 95, will have base current applied and will become conductive, simultaneously causing transistor 86 to become conductive. The condenser 89, before starting, charged to approximately full operating voltage, now discharges since, in conductive condition, the second transistor 86 has a collector voltage which is close to that of the chassis bus 52. Since resistance 91 is also almost at chassis voltage, a substantially higher charging current will flow through charging transistor 61 as soon as transistor 70 changes to blocked condition at the next base pulse 1,. During starting, a series of extension pulse I, result, causing a corresponding increase of the injection periods, to facilitate starting of the engine. In a practical example, factorf= at a base pulse time of 2.5 msec., so that a total pulse of duration T, of msec. is provided for each fuel injection.

The form of the time switch 30 is so selected that, after opening of the starter switch 96, and for a period of time of approximately seconds, prolongation factorf of multiplication circuit 27 is held substantially above the value necessary for constant operation. Under normal operation, this value is approximately f, is equal to I It is regulated from its high initial value off 5 progressively to the operating value off I. As soon as the button of switch 96 is released, both

transistors

85, 86 have the tendency to return to their initial blocked condition, so that the capacitor 89 which is discharged after closing, upon opening of the switch, will revert to its normal, fully charged condition. This requires a charging current indicated by I FIG. 1, which, essentially, is formed by the quotient of the sum of the emitter-base voltages of the transistors, 85, 86, as well as of the resistance 88. This charging current is substantially constant. As a result, the voltage at the collector of transistor 86 rises linearly and, only after the predetermined time period of, for example, 20 seconds, will reach a value in which diode 92 transfers to blocked condition. The voltage, rising in positive direction on the base of the charge in transistor 61 will cause a decrease in the charging current for the charge in condenser 60 developed by transistor 61. As is clearly apparent from the circuit diagram, FIG. 1, and the foregoing explanation, the timing period of the timing circuit and thus the extension, or multiplication factor (f) is dependent only on the electrical values of the timing circuit. The timing period is independent of any other effects, or operating or ambient parameters.

As a result, voltage U, across condenser 60 will rise more slowly, after releasing switch 96 upon occurrence of the next base pulse l,,, than in the preceding base pulses. Assuming the impulse length of the base pulse is to remain constant, the discharge time is also correspondingly decreased and the prolongation factor f decreases. As seen in FIG. 2, the base pulse starting at time will cause a pulse terminating at time r corresponding to a normal value of a multiplication factor which is approximately equal to I. This will occur after a predetermined period of time, in the example after about 20 seconds, with a sufficient time lag to enable steady state operation of the internal combustion engine after starting. The scale in FIG. 2, indicative of time values, is highly compressed for illustration.

In actual operation, an idling speed of about 600 rpm, corresponding to 10 rpsec. would cause, during these 20 seconds, approximately 200 injections cycles, the time duration of the various individual injections of fuel decreasing with progressive decrease of the prolongation factor f.

The circuit 30 shown in FIG. 1 is a preferred embodiment, having the advantage that the time period of delay, in this case 20 seconds, is independent of the speed of the engine, and the pulse duration of the base pulses I FIG. 3 illustrates a timing circuit which is much simpler and, in principle consists of a transistor Tr having its emitter connected to the chassis bus 52, a collector resistance R,, and a condenser C interconnecting the collector and the base. A pair of base resistances R and R are further provided. Resistance R interconnects the base with the negative bus 52. Resistance R forms a connection of the base of the transistor T to the connecting point P between the winding 97 of the starting relays and of starting switch 96. In order to avoid overloading the base junction of the transistor T, by voltage peaks which could arise after starting upon opening of switch 96, a bypass diode D is provided between junction point P and the negative bus 52. The output is again coupled from the collector over resistance 91 and diode 92 to junction X.

FIG. 4 illustrates a timing circuit which is only slightly different from that of FIG. 1. It differs essentially in that the collector resistance 90 of transistor 86 is missing. This enables decrease of the capacity of the condenser 89, interconnected between the base of transistor and the collector of transistor 86, to about one tenth of the value required for the condenser in accordance with FIG. 1. A typical value would be 0.3 uF. The timing provided by the circuit of FIG. 4 is approximately 20 seconds; in contrast to the circuit of FIG. 1 it is, however, speed dependent and further dependent on the length of the base pulse s I,,, since, for discharge of the condenser 89, a balancing current is only available if the transistor 70, forming part of the inverter stage is blocked during a base pulse 1,.

The circuit operates entirely automatically and independently of any controls required by the operator of the vehicle of which the engine may form a part; it provides for reliable starting, even upon cold engine conditions.

We claim:

1. Fuel injection system for internal combustion engines having means controlling the injection of fuel comprising at least one electrically operated fuel injection valve;

electrical means synchronized with the rotation of the engine generating electrical pulses, connected to said valve, to open the valve;

control means including means generating a base pulse (I,,) having a determined pulse length and a multiplying stage generating an extension pulse (1,), said extension pulse being longer than said base pulse length by a multiplying factor (f) of from 1 to 5 and controlled by an operating parameter of the engine connected to said electrical means and controlling the length of said pulses;

an electrical starting control means including a starter switch;

a timing circuit having a fixed predetermined timing period regardless of engine temperature and connected to said starting control means (30) to start the timing period upon actuation of said starter switch and connected in circuit with said control means to affect the multiplying factor of said multiplying stage and to increase the multiplying factor during said fixed predetermined timing period upon starting to thereby prolong the pulses upon starting of the engine.

2. System according to claim 1, wherein the timing circuit has a timing period in the order of from about -3O seconds.

3. System according to claim 1, wherein the timing circuit has a timing period in the order of about -25 seconds.

4. System according to claim 3, wherein the starter switch is interconnected with said timing circuit to apply a voltage to said circuit during operation of the starter switch.

5. System according to claim 1, wherein said timing circuit provides a variable control signal to said control means to continuously reduce the duration of the extension pulses generated by the multiplication stage from a prolonged period immediately upon starting, until the pulse duration is determined solely by said operating parameters when said predetermined period has elapsed.

6. System according to claim 1, wherein said timing circuit comprises a transistor (T means holding said transistor in blocked condition;

means (R3) interconnecting the starter switch with the base of the transistor;

and a capacitor (C) connected in the transistor circuit between the collector and another electrode thereof.

7. System according to claim 1, wherein a source of supply (33, 52) is provided;

said timing circuit comprises first and second transistors (85, 86) of similar conductivity type;

a resistance (87 interconnecting the emitter of one transistor (85) to one supply source terminal (52) and a resistance (93) interconnecting the collector of said one transistor (85) to the other supply source terminal (33);

a base resistance (88) connected from the base parallel to the emitter resistance (87) to the respective terminal of the supply source and holding said one of said transistors (85) in'normally blocked state;

means (94, 95) interconnecting the base of said normally blocked transistor (85) to the starter switch (96); and

a capacitor (89) connected with one terminal to said switch-transistor interconnection means, the other terminal of said capacitor being connected to the collector electrode of the other transistor (86).

8. System according to claim 7, wherein said multiplying stage has a charging transistor (61) and a capacitor (60) having one terminal connected, in series, with the emitter-collector path of the charging transistor (61);

a discharge transistor (62) connected to the other terminal of the capacitor (60);

and means interconnecting the collector of said second transistor (86) of the timing circuit (30) to the base of the charging transistor (61) to increase the charging current to said charging transistor, and thus the pulse length of said extension pulse, upon conduction of said second transistor (86), as determined by the state of conduction of said first transistor 9. System according to claim 1, wherein said timing circuit comprises a capacitor (89); a constant current supply circuit, and switching means being connected to affect a charge on the capacitor (89) upon closing of the starter switch and means applying a current in dependence on the change of charge of said capacitor (89) to said multiplying stage and affecting the multiplying factor thereof.

10. System according to claim 1, wherein said control means comprises a first capacitor (60); means (61, 62) controlling the charging rate of said first capacitor; and said timing circuit (30) includes switching means (85, 86; T,) and a further capacitor (89; C), said switching means interconnecting said further capacitor with said first capacitor (60) to affect the change of charge on the total capacitance in circuit with said control means upon operation of said switching means as determined by operation of the starter switch (96).

11. System according to claim 10, wherein said switching means comprises at least one transistor connected to be normally blocked, and to become conductive upon operation of said starter switch (96);

said transistor being interconnected with said further capacitor (89) to provide a discharge path for said further capacitor (89) upon change of said transistor to conductive state, and to extend the time during which said means controlling the charge rate of said first capacitor (60) provides charging current.

Claims

1. Fuel injection system for internal combustion engines having means controlling the injection of fuel comprising at least one electrically operated fuel injection valve; electrical means synchronized with the rotation of the engine generating electrical pulses, connected to said valve, to open the valve; control means including means generating a base pulse (In) having a determined pulse length and a multiplying stage generating an extension pulse (Iv), said extension pulse being longer than said base pulse length by a multiplying factor (f) of from 1 to 5 and controlled by an operating parameter of the engine connected to said electrical means and controlling the length of said pulses; an electrical starting control means including a starter switch; a timing circuit having a fixed predetermined timing period regardless of engine temperature and connected to said starting control means (30) to start the timing period upon actuation of said starter switch and connected in circuit with said control means to affect the multiplying factor of said multiplying sate and to increase the multiplying factor during said fixed predetermined timing period upon starting to thereby prolong the pulses upon starting of the engine.

2. System according to claim 1, wherein the timing circuit has a timing period in the order of from about 5-30 seconds.

3. System according to claim 1, wherein the timing circuit has a timing period in the order of about 20-25 seconds.

6. System according to claim 1, wherein said timing circuit comprises a transistor (Tr); means holding said transistor in blocked condition; means (R3) interconnecting the starter switch wiTh the base of the transistor; and a capacitor (C) connected in the transistor circuit between the collector and another electrode thereof.

7. System according to claim 1, wherein a source of supply (33, 52) is provided; said timing circuit comprises first and second transistors (85, 86) of similar conductivity type; a resistance (87) interconnecting the emitter of one transistor (85) to one supply source terminal (52) and a resistance (93) interconnecting the collector of said one transistor (85) to the other supply source terminal (33); a base resistance (88) connected from the base parallel to the emitter resistance (87) to the respective terminal of the supply source and holding said one of said transistors (85) in normally blocked state; means (94, 95) interconnecting the base of said normally blocked transistor (85) to the starter switch (96); and a capacitor (89) connected with one terminal to said switch-transistor interconnection means, the other terminal of said capacitor being connected to the collector electrode of the other transistor (86).

8. System according to claim 7, wherein said multiplying stage has a charging transistor (61) and a capacitor (60) having one terminal connected, in series, with the emitter-collector path of the charging transistor (61); a discharge transistor (62) connected to the other terminal of the capacitor (60); and means interconnecting the collector of said second transistor (86) of the timing circuit (30) to the base of the charging transistor (61) to increase the charging current to said charging transistor, and thus the pulse length of said extension pulse, upon conduction of said second transistor (86), as determined by the state of conduction of said first transistor (85).

9. System according to claim 1, wherein said timing circuit comprises a capacitor (89); a constant current supply circuit, and switching means being connected to affect a charge on the capacitor (89) upon closing of the starter switch (96); and means applying a current in dependence on the change of charge of said capacitor (89) to said multiplying stage and affecting the multiplying factor thereof.

10. System according to claim 1, wherein said control means comprises a first capacitor (60); means (61, 62) controlling the charging rate of said first capacitor; and said timing circuit (30) includes switching means (85, 86; Tr) and a further capacitor (89; C), said switching means interconnecting said further capacitor with said first capacitor (60) to affect the change of charge on the total capacitance in circuit with said control means upon operation of said switching means as determined by operation of the starter switch (96).

11. System according to claim 10, wherein said switching means comprises at least one transistor connected to be normally blocked, and to become conductive upon operation of said starter switch (96); said transistor being interconnected with said further capacitor (89) to provide a discharge path for said further capacitor (89) upon change of said transistor to conductive state, and to extend the time during which said means controlling the charge rate of said first capacitor (60) provides charging current.