US3620196A

US3620196A - Arrangement for applying fuel injection corrections as a function of speed, in internal combustion engines

Info

Publication number: US3620196A
Application number: US67851A
Authority: US
Inventors: Wolf Wessel
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1969-09-04
Filing date: 1970-08-28
Publication date: 1971-11-16
Anticipated expiration: 1988-11-16
Also published as: CH513332A; DE1944878A1; GB1262249A; FR2030872A5

Abstract

An arrangement by which corrections are applied to the pulses which open electromagnetically controlled valves for fuel injection in internal combustion engines. The opening pulses for the valves are generated by a monostable multivibrator to which a control voltage is applied. The multivibrator emits substantially rectangular-shaped pulses, the durations of which are controlled as a function of speed of the engine, through the control voltage. The control voltage has characteristics variable periodically in synchronism with the pulses provided by the monostable multivibrator. A storage capacitor integrates the control voltage, and charging sources connected to the capacitor have different internal resistances. The charging sources are switched and connected to the capacitor in predetermined sequence.

Description

United States Patent [72] Inventor Wolf Wessel Stuttgart, Germany [2]] Appl. No. 67,851 [22] Filed Aug. 28, I970 [45] Patented Nov. 16, 1971 Primary Examiner Laurence M. Goodridge Ass/slant Examiner-Ronald 8. Cox Allornev- Michael S. Striker ABSTRACT:

[73] Assignee Robert Bosch GmbII Stuttgart, Germany [32] Priority Sept. 4, 1969 [33] Germany An arrangement by which corrections are apulses which open electroma plied to the p gnetically controlled injection in internal combustion en valves for fuel gines. The generated by a monostable [54] ARRANGEMENT FOR APPLYING FUEL opening pulses for the valves are INJECTION CORRECTIONS AS A FUNCTION OF SPEED IN INTERNAL COMBUSTION ENGINES multivibrator to which a control voltage is applled. The mul- 20 chilns6mlwing Figs tivibrator emits substantially rectangular-shaped pulses. the

durations of which are controlled as a function of 5 engine. through the control volta characteristics variable periodic ulses provided by the monost emee mhmm .I nsmm da 60 A p m. .B I. O mm r. m O .I m w e h h .mm C V.C sum 3 [52] US. [51] Int. [50] FIeldoISearch..

capacitor integrates the control voltage, and charging sources connected to the capacitor have different internal resist The c [56] References Cited UNITED STATES PATENTS 2,883,976 4/l959 Woodward.

ances. arging sources are switched and connected to the capacitor in predetermined sequence.

PATENTEnuuv 1s l97| SHEET 1 [IF 3 Fig. I

INVENTOR:

h/s ATTORNEY PATENTEDunv 1s l87l SHEEI 2 BF 3 fir INVENTOR.

Wolf wEssEL his ATTOQNEY PATENIEnuuv 16 I97! SHEET 3 0F 3 INVENTOR. Wolf WfiSEL Fig.6

his ATTORNEY BACKGROUND OF THE INVENTION In. fuel injection arrangements of this species, the quantity of fuel injected after each operating cycle of an internal combustion engine is determined by the opening duration of the associated fuel injection valve. This valve admits the fuel under substantially constant pressure. To vary the duration of the pulse applied to the valve, the feedback circuit of the monostable multivibrator includes an electrical energy storage element, which consists of an inductor or choke. The magnitude of the inductor or choke is adjusted or varied in accordance with the pressure prevailing behind the throttle flap within the intake manifold. In order to achieve the application of correction to the pulse duration, which are dependent upon the rotational speed, it is possible to provide for the shortening or extension of the unstable state of the multivibrator through a time-dependent variable control voltage. The feedback provisions of such a multivibrator are otherwise nonvariant. Thus, the duration of the unstable state of the multivibrator may be varied through a control voltage which varies as a function of time. The control voltage is generated at the end of a pulse and is producedthrough a control circuit which has two or more switching transistors.

In one control arrangement of the preceding species known in the art, two storage capacitors are provided in one interconnected chain through resistors. The voltage at the end of the chain is coupled to the emitter-base circuit of the input transistor of the monostable multivibrator. Such coupling is achieved through a resistor. In view of such coupling, it is essential to use relatively large storage capacitors, since the resistors which function in conjunction with the capacitors, can only have substantially small magnitudes. In addition, difficulty is incurred in matching such known control circuit to the speed characteristics of a particular internal combustion engine. Thus, when varying individual resistance values, considerably complex and incomprehensible effects take place upon the characteristics of the control voltage and the duration of the opening pulses for the valves.

In order to avoid the difficulties, the control voltage, in accordance with the present invention, is produced from a circuit which applies self-corrections to the opening pulses as a function of engine speed. At least two charging sources of different internal resistance are provided, in accordance with the present invention, for the storage capacitor. These charging sources are connected to the storage capacitor one after another, so that the previously effective charging source becomes disconnected when the next charging source takes effect.

SUMMARY OF THE INVENTION A control arrangement for the injection of fuel in internal combustion engines. The fuel is injected through an electromagnetically controlled valve which is opened through the application of a pulse. The opening pulses for the valves are generated by a monostable multivibrator which provides substantially rectangular-shaped pulses with durations equal to the opening interval of the fuel injection valves. A control voltage is generated and applied to the multivibrator at a circuit point where the potential influences the ends of the pulses, and thereby the ends of the unstable state of the multivibrator. The control voltage varies the duration of the pulse signals as a function of the speed of the engine. The control voltage, furthermore, has characteristics which vary periodically in synchronism with the pulse signals. A storage capacitor is used for integrating the control voltage, and the capacitor becomes charged through at least two charging sources connected thereto, and having different internal resistances. A switching circuit connected to the charging sources connects one or the other sources to the capacitor. Two capacitors may be used in which case the coupling diodes prevail between them. When such two capacitors are used, that capacitor is operative which has the more positive voltage across it.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is an electrical circuit diagram and shows the components and their interconnections of the control device for internal combustion engines, in accordance with the present invention;

FIG. 2 is a graphical representation as a function of time, of the correction applied to the opening duration for the fuel injection valves, as produced by the circuit diagram of FIG. 1;

FIG. 3 is an electrical circuit diagram of another embodiment of the arrangement of FIG. I;

FIG. 4 is a graphical representation as a function of time of the control voltage generated by the circuit diagram of FIG. 3;

FIG. 5 is still another embodiment of the control arrangement of FIG. 1; and

FIG. 6 is a graphical representation as a function of time of the control voltage generated through the circuit arrangement of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, and in particular to FIG. I, the fuel injection arrangement is adapted to drive a four-cylinder internal combustion engine 1. The spark plugs 2 of this engine are connected to a high-voltage ignition arrangement, not shown. In direct proximity of the inlet valves, not shown, for the engine, are electromagnetically actuated injection valves 4. These valves are arranged so that one valve is providedfor each branch leading from the intake manifold 3. Fuel from a fuel distributor 6, is transmitted to each electromagnetically actuated injection valve 4, through fuel lines 5. A pump 7 driven by an electric motor maintains the pressure of the fuel within the distributor 6 and fuel lines 5 at a pressure of substantially 2 atmospheres.

Each fuel injection valve 4 possesses a magnetizing coil, not shown having one tenninal connected to ground potential. The other terminal of the coil are connected through the circuit lines 8 to resistors 9. Thus, each one of the magnetizing coils of a valve is connected through one line 8 to one resistor 9. The resistors 9 are paired, and each of two pairs of resistors 9 are connected together, at one terminal, and to the collector of one of two

transistors

10 and 11.

These transistors are power transistors which belong to an electronic regulating and control circuit described in greater detail in what follows:

The regulating and control circuit includes, in addition to the

power transistors

10 and 11, a monostable multivibrator 12 for generating electrical pulse signals. This monostable multivibrator in transistorized form, is outlined through a border designated by broken lines. The monostable multivibrator has an input transistor 13 and an output transistor 14, as well as an inductor or ferromagnetic choke 15 for the purpose of serving as a timing element.

The choke or inductor 15 is constructed in the form of a transformer, and has a displaceable armature 16. The armature is, in turn, secured to a displacement rod 17 which is connected to the membrane, not shown, of a pressure sensor 18. The pressure-sensing device 18 is connected with its suction side, to the intake manifold 3 of the internal combustion engine. The pressure sensor l8, furthermore, is located directly behind an adjustable throttle flap I0 which may be adjusted or displaced to a foot lever or pedal 19. When the pressure drops within the intake manifold, the armature I6 is moved in the direction of the arrow shown in the drawing. in this manner, the airgap of the transformer is increased and the inductance of the primary winding 21 of the transformer is decreased when the pressure within the intake manifold 3 drops or is decreased and the armature 16 moves in the direction of the arrow shown.

The secondary winding 22 of the transformer has one tenninal connected to the base of the input transistor 13 and to a resistor 24. The other tenninal of the winding 22 is connected to the circuit junction H. A resistor 25 is connected between this circuit junction H and the positive voltage supply line 23. A resistor 26, furthermore, is connected between the negative voltage supply line and the circuit junction H. The negative voltage supply line 30 is also connected to ground potential. The positive and negative

voltage supply lines

23 and 30 are connected to a l2-volt battery, not shown, which supply the electrical energy to the respective terminals.

The

transistors

13 and 14 are both of the NPN-type, and both have their emitters connected to the negative voltage supply line 30. The collector of the input transistor 13 is connected through a resistor 27, to the positive voltage supply line 23. The collector of the transistor 14, on the other hand, leads to the positive supply line 23, through a series circuit consisting of the primary winding 21 of the transformer 15 and a resistor 28 connected in series therewith. The base of the transistor 14 is connected, through a resistor 29, with the collector of the transistor 13. A capacitor 31 used for differentiating purposes is connected between the base of the transistor 13 and the fixed contact 32 of the switch having a movable contact 33 connected to the negative supply line 30. The movable arm of this switch is actuated or operated through a two-lobed cam which is mechanically coupled to the crank shaft 34 of the engine. For each rotation of the crank shaft of the engine, the two-lobed cam 35 becomes closed once and thereby causes the transistor 13 to become nonconducting.

For purposes of charging and discharging the capacitor 31, the switching contact 32 leads to the positive voltage supply line 23, through a resistor 36. Another resistor 24 is connected between the voltage supply line 23 and the other electrode of the capacitor 31. The junction of the capacitor 31 and the resistor 24, is also connected to one terminal of the secondary winding 22.

Before describing further the details of these circuit components of the control arrangement, a description is provided on how the opening duration of the fuel injection valves 4 is determined by the pulse currents J, for each closure of the switching contacts 32,33. The pulse currents .l vary with variations in pressure within the intake manifold 3 and, thereby, the inductance of the primary winding 21.

Directly before the switching arm 33 is actuated to a circuit closure position, the input transistor 13 is in the conducting state, and thereby maintains the output transistor 14 cut off. As soon as the switching arm 33 becomes pressed, however, against the switching contact 32, through the action of the cam 35, the stored charge across the capacitor 31 causes a drop in the base potential of the input transistor 13. The arrangement is such that the base potential of the input transistor 13 becomes thereby dropped below the potential of the negative voltage supply line 30. As a result, the transistor 13 becomes cut off and the multivibrator l2 switches to its unstable operating state. In this unstable state, the transistor 14 conducts. The transistor 14 has then applied to its collector, a current which rises exponentially, This exponentially rising current flows through the primary winding 21 and gives rise to an increasing magnetic field in the core and armature 16 of the transformer. The increase in current occurs more rapidly, the larger the airgap and the smaller the inductance ofthe primary winding 21 resulting from the increase in the airgap.

With such increase or rise in current, a voltage is induced within the secondary winding 22. From the instant that the switching contacts 32 and 33 are closed, this induced voltage becomes reduced exponentially from a maximum value, at a reducing rate determined by the magnitude of the inductance. The induced voltage is of the polarity so that it tends to maintain the input transistor 13 cut off, whereby the positive base potential determined by the

resistors

24,25 and 26 is opposed. Thus, such base potential tends to return the input transistor 13 to its stable state in which it is in the conducting operative state. This situation occurs when the induced voltage in the secondary winding 22 has a magnitude which is smaller than the base potential.

As long as transistor 13 is cut off or is in the nonconducting state, the conducting transistor 14 maintains the

power transistors

10 or 11 also in the conducting state, through an amplifier 38. However, as soon as transistor 13 returns to its stable conducting state, the

transistor

14, 10 and 1! become again cut off. The duration of the pulses .l which switch the valve 4 to their opening position, extends thereby from the instant or closure of the switch 33 to the instant of time at which the output transistor 14 becomes cut off and the input transistor 13 becomes again conducting. When the inductance of the primary winding 21 decreases with drop in pressure within the intake manifold 3, and the collector current of the transistor 14 rises more rapidly as a result, the induced voltage within the secondary winding 22 also decreases more rapidly. The input transistor 13, at the same time, returns to its conducting state at an earlier instant of time. The valves 4 become thereby closed at an earlier instant of time in this case, than in the preceding case in which a higher inductance and higher pressure prevails.

Through the variation in the inductance of the primary winding 21, as described above, the duration of the opening pulse J for the injection valves becomes matched to the pressure of the internal combustion engine. Experiments during running conditions have shown that the fuel quantity to be injected must be varied as a function of rotational speed, in addition to the magnitude of vacuum pressure. Since the pulse durations which are set as a function of the prevailing pressure, and since these pulse durations are independent of the rotational speed of the engine for any value of the pressure, the regulating and control circuit of FIG. 1 has an additional control circuit A, through which the voltage prevailing between the circuit junction H and the negative voltage supply line 30 become periodically varied in rhythm to the injection processes. A control voltage U,, shown in H6. 2, has a function of time, is produced by the control circuit. This control circuit U, is composed exclusively of exponential parts and sections of constant instantaneous values.

The control circuit A includes a first transistor T with base connected to the positive voltage supply line 23, through a resistor R The series circuit ofa capacitor C and resistor 39, is connected between the circuit junction G and the base of the transistor T,. A resistor 27 is connected between the same circuit junction G and the positive voltage supply line 23. The circuit junction G corresponds to the collector of the transistor 13. Similar to the first switching transistor T,, a second transistor T has its emitter connected to the negative voltage supply line 30, and its base connected to the collector of the transistor T through a coupling resistor 40.

Two resistors R and R are connected in series and between the collector of transistor T and the positive voltage supply line 23. The junction between these two resistors R and R, is connected to the cathode of a diode D The collector of the transistor T furthermore, is connected to a resistor 41 which, in turn, is connected in series with a capacitor C, One electrode of this capacitor C is connected to the base of a third transistor T This transistor T as well as a fourth transistor T, are of the PNP-type. The emitters of both of these transistors T and T are connected to the positive voltage supply line 23. The base of the transistor T is connected, through a resistor, R to the negative voltage supply line 30. The transistor T; has, thereby, the tendency to be conducting in the quiescent state of the control circuit, as does the transistor T,. This transistor also has its base connected to the negative voltage supply line 30, through a resistor R Both of these transistors form source of charge through their different internal resistances, and they feed a common storage capacitor C,. The control voltage U,, shown in FIG. 2, appears across this storage capacitor C This control voltages is applied to the circuit junction H of the secondary winding 22, through a transistor T which operates as an emitter follower.

Two resistors R,, and R,, are arranged between the collector of the transistor T, and the negative voltage supply line 30. One terminal of a resistor R,,, is connected to the junction of the two resistors R,, and R,,, whereas the other terminal of the resistor R,,, is connected to the anodes of two diodes D, and D The cathode of the diode D, is connected to one electrode of the capacitor C,, and also to the anode of the diode D,. The cathode of the diode D,, on the other hand, is connected to the junction of two resistors R,, and R,,, which form a voltage divider. The anode of a diode D is connected directly to the collector of a transistor T while the cathode of this diode D leads to the negative voltage supply line through a resistor -R,,,. The cathode of the diode D is also connected to the base of the transistor T,, through a capacitor C Analogous to the transistor T,,, a series circuit of two resistors R,,, and R,, is connected between the collector of the transistor T, and the negative voltage supply line 30. A resistor R,,, is connected, with one terminal, to the junction of resistors R,, and R,,. The other terminal of the resistor R,,, is connected to the anodes of two diodes D, and D,,. The cathode of the diode D is connected to the cathode of the diode D,, as well as to the base of the transistor T and one electrode of the storage capacitor C,. The cathode of the diode D,,, on the other hand, is connected directly to the collector of the transistor T,,.

The control circuit A, moreover, includes two further voltage dividers of which one divider consists of resistors R,, and R The junction of these two resistors R,, and R is connected to a further resistor R,,, which leads to the anodes of two diodes D, and D The other voltage divider consists of resistors R,, and R,,, with the junction between these two resistors is connected to the cathode of a diode D The cathode of the diode D is connected to the capacitor C,.

in the operation of the control circuit A, assume that a negative step voltage is applied to the base of transistor T,, through the coupling capacitor C,, at the instant t=0 denoting the end of an injection pulse, in FIG. 2, from the control multivibrator 12. As a result, the transistor T, remains nonconducting or cut off for as long as coupling capacitor C, remains to be charged through the resistor R, to the extent that base current is made available for the transistor T,. During the nonconducting period of the transistor T, next to the instant of time t=0, the transistor T conducts and discharges the storage capacitor C, through the diode D,, until a residual voltage U remains. This residual voltage is determined through the magnitudes of the resistors R, and R,, which constitute a voltage di vider. When the transistor T, becomes again conducting at the instant of time T, after the capacitor C, has again been charged, the transistor T becomes cut off. The diode D, is also then nonconducting, and the discharge of the storage capacitor C, is terminated. When the transistor T returns to its cutoff or nonconducting state, a positive step voltage appears at the collector of this transistor. This stop voltage is, in turn, transmitted to the base of the transistor T,,, through the coupling capacitor C The transistor T remains thereby nonconducting until the capacitor C, has become charged, through the resistor R to the extent that base current again prevails at the transistor T,. This occurs at the instant of time t,. Until this instant of time is attained, the nonconducting transistor T, has a negative potential applied to its collector through the resistors R,, and R,,. As a result, the diode D, is nonconducting. At the same time, the potential of the circuit junction P between the resistor R,,, and the diode D is maintained at negative potential, through the diode D,,. The diode D is thereby also nonconducting. The charging of the storage capacitor C, result thereafter from the instant of time t,, only through the resistor R,, and the diode D The voltage U,, across the storage capacitor C, then tends toward a voltage limit U,, with a time constant T, This time constant is the product of the capacitance of the storage capacitor C, and the magnitude of the resistor R,,. The voltage limit U, is determined by the voltage divider with the resistors R,, and R When the voltage U, has attained the value U,,, through the voltage-dividing resistors R and R,,, at the instant of time t, then the diode D becomes conducting. In that state of the diode D the diode prevents further current flow to the capacitor C,, through the diode D The control voltage U,, across the storage capacitor C, remains, thereby, at the value U,,, until the instant of time t,, at which the transistor T, is again conducting.

When the transistor T becomes again conducting at the instant of time t,, a positive step voltage appears at its collector. This step voltage is transmitted to the base of the transistor T,, through the coupling capacitor C The transistor T, is, thereby, turned off until the instant of time t,. During that interval, the capacitor C becomes charged through the resistor R to the extent that base current at the transistor T, again prevails. in the tumed-off state of the transistor T,, negative potential is applied to the collector of the transistor through the resistors R,,, and R,,, so that the diode D is also nonconducting.

From the instant of time t,, charging current for the storage capacitor C, can flow only through the resistor R,, and the diode D,, as well as the resistor R,, and the transistor T under the preceding conditions. As a result, the voltage U, across the storage capacitor C, tends towards a limit U,, with a time constant T This time constant is approximately the product of the capacitance of the capacitance of the capacitor C, and the magnitude of resistor R,,. The voltage limit U is determined by the voltage divider consisting of resistors R,, and R,, in the collector circuit of the transistor T When the voltage U, attains the value U through further increase at the instant of time t the diode D, becomes conducting. The voltage U,,, is determined through the relative magnitudes of the resistors R,, and R,, which constitute a voltage divider. With the diode D made conducting, charging current is prevented to the capacitor C,, through the diode D,. From the instant of time t to the instant of time t at which point the transistor T is again conducting, because the coupling capacitor C, has then become sufficiently charged, the voltage U, across the capacitor C, remains at the constant value U,,

From the instant of time T charging current can flow to the capacitor C, through the then conducting transistor T,, through the collector resistor R,,, through the resistor R,,, and through the diode D,. With such charging of the storage capacitor C,, the voltage U, across the capacitor also increases exponentially. The rate at which the voltage U, rises, is determined by the time constant T which corresponds to the product of the capacitance of the capacitor C, and the magnitude of the resistor R,,. Similarly to the two preceding exponential sections that were described, the voltage U,, tends to a limit value which is not described in FIG. 2, but which is determined by the relative magnitudes of the resistors R,,, and R,, constituting a voltage divider in the collector circuit of the transistor T,.

When the internal combustion engine operates very slowly, the duration between the ends of one opening pulse and the end of a subsequent opening pulse is larger than the interval between time F0 to t shown in FIG. 2. The end of the next opening pulse, therefore, becomes determined through the control voltage U,, beginning with the portion T, at the instant t,. For this case a very low rotational speed of the engine, the end of the subsequent opening pulse is represented through the time instant t,. A new period begins at that instant of time, in which the control voltage runs in the same manner as between the time instant t to the instant t,. This situation applies for as long as the low rotational speed is maintained. The higher the rotational speed, however, the closer the time instant t, moves to the instant t,. The spacing of the time instant t, from the instant t#), at which point the period begins. is chosen to be so small that it is smaller than the shortest period of injection which prevails at maximum rotational speed.

The curve shown in FIG. 2 as a function of time and representing the control voltage U,, has exclusively the increasing tendency and to thereby deliver longer injection pulses with rise in engine speed, when all other parameters and conditions remain the same. For this reason, a modified control arrangement is shown in FIG. 3, which can be used in place of the control circuit A in FIG. 1. This arrangement of FIG. 3 can then provide a control voltage which has an increasing function as well as decreasing characteristics. The control voltage curve of the arrangement of FIG. 3 is shown in FIG. 4 as a function of time. Components in the control arrangement of FIG. 3 which are the same as those in the control circuit A in FIG. 1, are denoted by the same reference numeral. In addition to the circuit configuration of FIG. I, a second storage capacitor C is used for the arrangement of FIG. 3. This capacitor C produces the decreasing charac teristics at the beginning of the control voltage curve shown in FIG. 4.

This second storage capacitor C, is connected, through a diode D,, to the base ofa transistor T operating in the form of an emitter follower. The capacitor C thereby, functions as a parallel component to the capacitor C which is connected to the base of this transistor T through an additional diode D,;,. In addition to both of the voltages which are dependent on charging state of the capacitors C, and C,,, a third voltage may be applied to the transistor T to the diode D This third voltage is taken or tapped from the junction of two resistors R and R forming a voltage divider. Through the decoupling function of diodes D,, and D and D that one of the three voltages is used to control the transistor T,,, which has the most positive potential.

In operation of the circuitry, the diode D,, which is connected to the collector of transistor T,, becomes nonconducting as soon as the transistor T, becomes nonconducting as soon as the transistor T, becomes nonconducting at the instant of time t=0, at the end of an opening pulse, through the capacitor C,. The capacitor C,, can then charge exponentially, through the diode D,,,, in accordance with FIG. 4. The capacitor can then become charged to a maximum value of U, which is determined through the relative magnitudes of the two resistors R and R which form a voltage divider. By choosing sufficiently small resistances for the voltage-dividing resistors R,, and R it is possible to achieve that during the charging process of the capacitor C,, very rapid voltage changes take place which are already larger than the rapidly dropping residual voltage across the discharging capacitor C from the instant of time t=0. This time instant is shown in FIG. 4 by t From this instant of time, the control voltage U, is determined by the electrode of the second storage capacitor C,, with the larger positive potential.

The turned-off state of the transistor T, is maintained until the time instant t,, as described in the preceding embodiment. At this time instant t,, the capacitor C, has discharged to the extent that sufficient current can flow through the emitterbase path of the transistor T, so as to make this transistor again conducting. The conducting transistor T, then short circuits the voltage-dividing resistor R through the diode D which also conducts. In this manner, the diode D is nonconductlng and the second storage capacitor can discharge, from the time instant t,, through the parallel resistor R This discharge process takes place with a time constant T,., which depends upon the capacitance value of the capacitor C,, and the magnitude of the resistor R From the instant of time t, the voltage across the capacitor C, drops below the value U which is determined by the voltage-dividing resistors R and R As a result, the control voltage maintains this voltage value from the time instant t,

In accordance with the description of the first embodiment, the storage capacitor C becomes charged, through the resistor R, and the diode D from the instant of time t,. The voltage across the storage capacitor then attains the set value U., which is established by the resistors R and R forming a voltage divider. This voltage value across the storage capacitor is attained at the instant of time t,,,.

From that same instant of time, the voltage across the capacitor C. remains positive in comparison with the voltage across the capacitor C,,. In this manner, the control voltage U, at the transistor T is functionally determined through the diode D,,, which is now conducting.

With the embodiment of the control arrangement of FIG. 5, it is shown how the control voltage characteristic U,, shown in FIG. 6, is obtained with a single storage capacitor C,,. This functional curve of U, in FIG. 6, has increasing as well as decreasing sections.

The circuit arrangement shown in FIG. 5 is used for generating the characteristic of the control voltage U,, shown in FIG. 6. This circuit of FIG. 5 takes the place of the circuit bordered by broken lines in FIG. 1, at the base of the circuit junction H of the secondary winding of the transformer 15. This circuit of FIG. 5, includes an input transistor T, which is connected, through a capacitor C,, to the collector of the input transistor 13 of the multivibrator 12. Such interconnection of the transistor T, is accomplished through a coupling resistor 35, not shown in FIG. 5. At the same time, the base of the transistor T, is connected to the positive voltage supply line 23, through a resistor R,. The collector of transistor T, is connected to one tenninal of a resistor R whereas the other terminal of this resistor is connected also to the positive voltage supply line 23. Another resistor R is connected between the same voltage supply line 23 and the base of the transistor T A capacitor C is connected between the collector of transistor T, and the base of transistor T In the quiescent state of the circuit, the transistor T is maintained in the conducting state. The collector of the transistor T is connected to a voltage divider formed by resistors R and R connected in series. This series connected combination of resistors is further connected between the positive voltage supply line 23 and the collector of the transistor T The cathode of a diode D is also connected to this collector of transistor T,,. The anode of the diode D is, on the other hand, connected to the junction of two resistors R and R which are connected in series and between the positive and negative

voltage supply lines

23 and 30, respectively. One terminal of the resistor R furthermore, is connected to the anode ofthe diode D It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in an arrangement for applying fuel injection corrections as a function of speed, in internal combustion engines, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

1. A fuel injection control arrangement for an internal combustion engine comprising, in combination, electromagnetically controlled fuel injection valve means; monostable multivibrator means connected to said valve means and applying pulse signals to said valve means, the duration of said pulse signals determining opening time interval of said valve means; control voltage-generating means connected to said monostable multivibrator means for generating a control voltage to vary said duration of said pulse signals as a function of the speed of said engine, said control voltage having a characteristics variable periodically in synchronism with said pulse signals; storage capacitor means in said control voltagegenerating means for integrating said control voltage as a a function of time; at least two charging sources connected to said capacitor means and having different internal resistances; and switching means connected to said charging sources for connecting said sources in predetermined sequence to said capacitor means.

2. The arrangement as defined in claim I, wherein said monostable multivibrator means has an input transistor and an output transistor.

3. The arrangement as defined in claim 1, wherein said pulse signals are rectangular-shaped pulses.

4. The arrangement as defined in claim 1, wherein said switching means disconnects in sequence from said capacitor means the source previously connected to said capacitor means upon connecting to said capacitor means the subsequent one of said sources.

5. The arrangement as defined in claim 1 including a diode connected between each source of said storage capacitor means.

6. The arrangement as defined in claim 5 including discharge means connected to said storage capacitor means and comprising a discharge diode; and a transistor with emitter-collector path connected in series with said discharge diode.

7. The arrangement as defined in claim 6 including voltage limiting means connected to said storage capacitor means for limiting the voltage across said capacitor means, said voltagelimiting means comprising a clipping diode; voltage-dividing means connected to said clipping diode and cooperating with said diode for limiting the charging voltage of said capacitor means.

8. The arrangement as defined in claim 7 including a first auxiliary diode connected between said capacitor means and said clipping diode; resistor means connected to the junction of said clipping diode and said first auxiliary diode for limiting the charging current to said capacitor means; second voltagedividing means connected to said resistor means and applying to said resistor means a voltage greater than the voltage applied by said first-mentioned voltage dividing means to said clipping diode.

9. The arrangement as defined in claim 5 including a first auxiliary resistor and a second auxiliary resistor connected in series, said series connected auxiliary resistors being connected to the collector of said transistor, the junction of said first and second auxiliary resistors being connected to said discharge diode so that the discharge rate of said capacitor means is determined by said second auxiliary resistor.

10. The arrangement as defined in claim 1, wherein at least of said charging sources comprises a transistor; a diode connected to said transistor and said charging capacitor means; and coupling capacitor means connected to said transistor.

11. The arrangement as defined in claim 10, wherein said diode is connected between said coupling capacitor means and the collector of said transistor.

12. The arrangement as defined in claim 10, including a first resistor and a second resistor connected in series and to the collector of said transistor; and a third resistor connected in series with said diode and to the junction of said first and second resistors.

13. The arrangement as defined in claim 12 including voltage-dividing means; and a first auxiliary diode connected between the junction of said third resistor and said diode and said voltage-dividing means.

14. The arrangement as defined in claim 13 including an auxiliary transistor; and a coupling capacitor connected between the base of said auxiliary transistor and the collector of said transistor.

15. The arrangement as defined in claim 14 including a second auxiliary diode connected between said auxiliary transistor and said storage capacitor means; and a third auxillary diode wlth anode connected to the anode of said second auxiliary diode, the cathode of said third auxiliary diode being connected to the collector of said transistor.

16 The arrangement as defined in claim 1 including a transistor emitter-follower with base connected to said storage capacitor means, the emitter of said emitter follower being connected to said monostable multivibrator at a circuit junction where the potential influences the end of the unstable state of said multivibrator and the ends of said pulse signals.

17. The arrangement as defined in claim 16 including a source of operating voltage; and a first resistor connected between the emitter of said emitter-follower and said source of operating voltage.

18. The arrangement as defined in claim 16 including a resistor connected between the emitter of said emitter-follower and said circuit junction in said multivibrator.

19. The arrangement as defined in claim I, wherein said storage capacitor means comprises two storage capacitors; and a diode connected between said two storage capacitors for the coupling said storage capacitors, the storage capacitor having the more positive voltage being operative and the other capacitor being inoperative.

20. The arrangement as defined in claim 19, including an emitter-follower transistor with base connected to said diode.

t i I! l

Claims

1. A fuel injection control arrangement for an internal combustion engine comprising, in combination, electromagnetically controlled fuel injection valve means; monostable multivibrator means connected to said valve means and applying pulse signals to said valve means, the duration of said pulse signals determining opening time interval of said valve means; control voltagegenerating means connected to said monostable multivibrator means for generating a control voltage to vary said duration of said pulse signals as a function of the speed of said engine, said control voltage having a characteristics variable periodically in synchronism with said pulse signals; storage capacitor means in said control voltage-generating means for integrating said control voltage as a a function of time; at least two charging sources connected to said capacitor means and having different internal resistances; and switching means connected to said charging sources for connecting said sources in predetermined sequence to said capacitor means.

2. The arrangement as defined in claim 1, wherein said monostable multivibrator means has an input transistor and an output transistor.

5. The arrangement as defined in claim 1 including a diode connected between each source and said storage capacitor means.

7. The arrangement as defined in claim 6 including voltage limiting means connected to said storage capacitor means for limiting the voltage across said capacitor means, said voltage-limiting means comprising a clipping diode; voltage-dividing means connected to said clipping diode and cooperating with said diode for limiting the charging voltage of said capacitOr means.

8. The arrangement as defined in claim 7 including a first auxiliary diode connected between said capacitor means and said clipping diode; resistor means connected to the junction of said clipping diode and said first auxiliary diode for limiting the charging current to said capacitor means; second voltage-dividing means connected to said resistor means and applying to said resistor means a voltage greater than the voltage applied by said first-mentioned voltage dividing means to said clipping diode.

15. The arrangement as defined in claim 14 including a second auxiliary diode connected between said auxiliary transistor and said storage capacitor means; and a third auxiliary diode with anode connected to the anode of said second auxiliary diode, the cathode of said third auxiliary diode being connected to the collector of said transistor. 16 The arrangement as defined in claim 1 including a transistor emitter-follower with base connected to said storage capacitor means, the emitter of said emitter follower being connected to said monostable multivibrator at a circuit junction where the potential influences the end of the unstable state of said multivibrator and the ends of said pulse signals.

19. The arrangement as defined in claim 1, wherein said storage capacitor means comprises two storage capacitors; and a diode connected between said two storage capacitors for the coupling said storage capacitors, the storage capacitor having the more positive voltage being operative and the other capacitor being inoperative.