Title:
ARRANGEMENT FOR APPLYING FUEL INJECTION CORRECTIONS AS A FUNCTION OF SPEED, IN INTERNAL COMBUSTION ENGINES
United States Patent 3620196
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.


Inventors:
WESSEL WOLF
Application Number:
05/067851
Publication Date:
11/16/1971
Filing Date:
08/28/1970
Assignee:
ROBERT BOSCH GMBH.
Primary Class:
International Classes:
F02D41/32; (IPC1-7): F02B3/00
Field of Search:
123/32
View Patent Images:
Primary Examiner:
Laurence, Goodridge M.
Assistant Examiner:
Ronald, Cox B.
Attorney, Agent or Firm:
Michael, Striker S.
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 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.

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 and 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 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.

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 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.

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 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.

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

Description:
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 produced through 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.

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. 1 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. 1;

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. 1, 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 provided for 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 terminal 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 18, furthermore, is located directly behind an adjustable throttle flap 10 which may be adjusted or displaced to a foot lever or pedal 19. When the pressure drops within the intake manifold, the armature 16 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 15 has one terminal connected to the base of the input transistor 13 and to a resistor 24. The other terminal 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 30 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 12-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 supplyline 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 J 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 12 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 of the 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 11 become again cut off. The duration of the pulses J 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 Us, shown in FIG. 2, has a function of time, is produced by the control circuit. This control circuit Us is composed exclusively of exponential parts and sections of constant instantaneous values.

The control circuit A includes a first transistor T1 with base connected to the positive voltage supply line 23, through a resistor R1. The series circuit of a capacitor C1 and resistor 39, is connected between the circuit junction G and the base of the transistor T1. 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 T1, a second transistor T2 has its emitter connected to the negative voltage supply line 30, and its base connected to the collector of the transistor T1 through a coupling resistor 40.

Two resistors R4 and R5 are connected in series and between the collector of transistor T2 and the positive voltage supply line 23. The junction between these two resistors R5 and R4 is connected to the cathode of a diode D1. The collector of the transistor T2, furthermore, is connected to a resistor 41 which, in turn, is connected in series with a capacitor C2. One electrode of this capacitor C2 is connected to the base of a third transistor T3. This transistor T3 as well as a fourth transistor T4 are of the PNP-type. The emitters of both of these transistors T3 and T4 are connected to the positive voltage supply line 23. The base of the transistor T3 is connected, through a resistor, R2, to the negative voltage supply line 30. The transistor T3 has, thereby, the tendency to be conducting in the quiescent state of the control circuit, as does the transistor T4. This transistor also has its base connected to the negative voltage supply line 30, through a resistor R3. Both of these transistors form sources of charge through their different internal resistances, and they feed a common storage capacitor C4. The control voltage Us, shown in FIG. 2, appears across this storage capacitor C4. This control voltage is applied to the circuit junction H of the secondary winding 22, through a transistor T5 which operates as an emitter follower.

Two resistors R11 and R12 are arranged between the collector of the transistor T3 and the negative voltage supply line 30. One terminal of a resistor R13 is connected to the junction of the two resistors R11 and R12, whereas the other terminal of the resistor R13 is connected to the anodes of two diodes D4 and D5. The cathode of the diode D4 is connected to one electrode of the capacitor C4, and also to the anode of the diode D1. The cathode of the diode D5, on the other hand, is connected to the junction of two resistors R14 and R15, which form a voltage divider. The anode of a diode D6 is connected directly to the collector of a transistor T3, while the cathode of this diode D6 leads to the negative voltage supply line 30 through a resistor R19. The cathode of the diode D6 is also connected to the base of the transistor T4, through a capacitor C3. Analogous to the transistor T3, a series circuit of two resistors R16 and R17 is connected between the collector of the transistor T4 and the negative voltage supply line 30. A resistor R18 is connected, with one terminal, to the junction of resistors R17 and R16. The other terminal of the resistor R18 is connected to the anodes of two diodes D7 and D8. The cathode of the diode D7 is connected to the cathode of the diode D4, as well as to the base of the transistor T5 and one electrode of the storage capacitor C4. The cathode of the diode D8, on the other hand, is connected directly to the collector of the transistor T3.

The control circuit A, moreover, includes two further voltage dividers of which one divider consists of resistors R6 and R7. The junction of these two resistors R6 and R7 is connected to a further resistor R8, which leads to the anodes of two diodes D2 and D3. The other voltage divider consists of resistors R9 and R10, with the junction between these two resistors is connected to the cathode of a diode D3. The cathode of the diode D2 is connected to the capacitor C4.

In the operation of the control circuit A, assume that a negative step voltage is applied to the base of transistor T1, through the coupling capacitor C1, 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 T1 remains nonconducting or cut off for as long as coupling capacitor C1 remains to be charged through the resistor R1 to the extent that base current is made available for the transistor T1. During the nonconducting period of the transistor T1 next to the instant of time t=0, the transistor T2 conducts and discharges the storage capacitor C4 through the diode D1, until a residual voltage U0 remains. This residual voltage is determined through the magnitudes of the resistors R4 and R5 which constitute a voltage divider. When the transistor T1 becomes again conducting at the instant of time T1 after the capacitor C3 has again been charged, the transistor T2 becomes cut off. The diode D1 is also then nonconducting, and the discharge of the storage capacitor C4 is terminated. When the transistor T2 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 T3, through the coupling capacitor C2. The transistor T3 remains thereby nonconducting until the capacitor C2 has become charged, through the resistor R2, to the extent that base current again prevails at the transistor T3. This occurs at the instant of time t2. Until this instant of time is attained, the nonconducting transistor T3 has a negative potential applied to its collector through the resistors R11 and R12. As a result, the diode D4 is nonconducting. At the same time, the potential of the circuit junction P between the resistor R18 and the diode D7 is maintained at negative potential, through the diode D8. The diode D7 is thereby also nonconducting. The charging of the storage capacitor C4 result thereafter from the instant of time t1, only through the resistor R8 and the diode D2. The voltage Us across the storage capacitor C4 then tends toward a voltage limit U1, with a time constant T4,1. This time constant is the product of the capacitance of the storage capacitor C4 and the magnitude of the resistor R8. The voltage limit U1 is determined by the voltage divider with the resistors R6 and R7. When the voltage Us has attained the value U1,0 through the voltage-dividing resistors R9 and R10, at the instant of time t1,0, then the diode D3 becomes conducting. In that state of the diode D3, the diode prevents further current flow to the capacitor C4, through the diode D2. The control voltage Us across the storage capacitor C4 remains, thereby, at the value U1,0 until the instant of time t2, at which the transistor T3 is again conducting.

When the transistor T3 becomes again conducting at the instant of time t2, a positive step voltage appears at its collector. This step voltage is transmitted to the base of the transistor T4, through the coupling capacitor C3. The transistor T4 is, thereby, turned off until the instant of time t3. During that interval, the capacitor C3 becomes charged through the resistor R3 to the extent that base current at the transistor T4 again prevails. In the turned-off state of the transistor T4, negative potential is applied to the collector of the transistor through the resistors R16 and R17, so that the diode D7 is also nonconducting.

From the instant of time t2, charging current for the storage capacitor C4 can flow only through the resistor R13 and the diode D4, as well as the resistor R11 and the transistor T3, under the preceding conditions. As a result, the voltage Us across the storage capacitor C4 tends towards a limit U2, with a time constant T4,2. This time constant is approximately the product of the capacitance of the capacitor C4 and the magnitude of resistor R13. The voltage limit U2 is determined by the voltage divider consisting of resistors R11 and R120, in the collector circuit of the transistor T3. When the voltage Us attains the value U2,0, through further increase at the instant of time t2,0, the diode D5 becomes conducting. The voltage U2,0 is determined through the relative magnitudes of the resistors R14 and R15 which constitute a voltage divider. With the diode D5 made conducting, charging current is prevented to the capacitor C4, through the diode D4. From the instant of time t2,0 to the instant of time t3, at which point the transistor T4 is again conducting, because the coupling capacitor C3 has then become sufficiently charged, the voltage Us across the capacitor C4 remains at the constant value U2,0.

From the instant of time T3, charging current can flow to the capacitor C4 through the then conducting transistor T4, through the collector resistor R16, through the resistor R18 and through the diode D7. With such charging of the storage capacitor C4, the voltage Us across the capacitor also increases exponentially. The rate at which the voltage Us rises, is determined by the time constant T4,3 which corresponds to the product of the capacitance of the capacitor C4 and the magnitude of the resistor R18. Similarly to the two preceding exponential sections that were described, the voltage Us tends to a limit value which is not described in FIG. 2, but which is determined by the relative magnitudes of the resistors R16 and R17 constituting a voltage divider in the collector circuit of the transistor T4.

When the internal combustion engine operates very slowly, the duration between the end of one opening pulse and the end of a subsequent opening pulse is larger than the interval between time t=0 to t3, shown in FIG. 2. The end of the next opening pulse, therefore, becomes determined through the control voltage Us beginning with the portion T4,3 at the instant t3. For this case a very low rotational speed of the engine, the end of the subsequent opening pulse is represented through the time instant t4. A new period begins at that instant of time, in which the control voltage runs in the same manner as between the time instant to to the instant t4. This situation applies for as long as the low rotational speed is maintained. The higher the rotational speed, however, the closer the time instant t4 moves to the instant t1. The spacing of the time instant t1 from the instant t=0, 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 Us, 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. 1, a second storage capacitor C5 is used for the arrangement of FIG. 3. This capacitor C5 produces the decreasing characteristics at the beginning of the control voltage curve shown in FIG. 4.

This second storage capacitor C5 is connected, through a diode D11 to the base of a transistor T5 operating in the form of an emitter follower. The capacitor C5, thereby, functions as a parallel component to the capacitor C4 which is connected to the base of this transistor T5, through an additional diode D13. In addition to both of the voltages which are dependent on charging state of the capacitors C4 and C5, a third voltage may be applied to the transistor T5 to the diode D12. This third voltage is taken or tapped from the junction of two resistors R22 and R23 forming a voltage divider. Through the decoupling function of diodes D11 and D12 and D13, that one of the three voltages is used to control the transistor T5, which has the most positive potential.

In operation of the circuitry, the diode D9 which is connected to the collector of transistor T1, becomes nonconducting as soon as the transistor T1 becomes nonconducting as soon as the transistor T1 becomes nonconducting at the instant of time t=0, at the end of an opening pulse, through the capacitor C1. The capacitor C5 can then charge exponentially, through the diode D10, in accordance with FIG. 4. The capacitor can then become charged to a maximum value of U3 which is determined through the relative magnitudes of the two resistors R19 and R20 which form a voltage divider. By choosing sufficiently small resistances for the voltage-dividing resistors R19 and R20, it is possible to achieve that during the charging process of the capacitor C5, very rapid voltage changes take place which are already larger than the rapidly dropping residual voltage across the discharging capacitor C4 from the instant of time t=0. This time instant is shown in FIG. 4 by t0,1. From this instant of time, the control voltage Us is determined by the electrode of the second storage capacitor C5, with the larger positive potential.

The turned off state of the transistor T1 is maintained until the time instant t1, as described in the preceding embodiment. At this time instant t1, the capacitor C1 has discharged to the extent that sufficient current can flow through the emitter-base path of the transistor T1 so as to make this transistor again conducting. The conducting transistor T1 then short circuits the voltage-dividing resistor R20, through the diode D9 which also conducts. In this manner, the diode D10 is nonconducting and the second storage capacitor can discharge, from the time instant t1, through the parallel resistor R21. This discharge process takes place with a time constant T5.1 which depends upon the capacitance value of the capacitor C5 and the magnitude of the resistor R21. From the instant of time t1,1 the voltage across the capacitor C5 drops below the value U4,0 which is determined by the voltage-dividing resistors R22 and R23. As a result, the control voltage maintains this voltage value from the time instant t1,1.

In accordance with the description of the first embodiment, the storage capacitor C4 becomes charged, through the resistor R8 and the diode D2, from the instant of time t1. The voltage across the storage capacitor then attains the set value U4,0, which is established by the resistors R22 and R23 forming a voltage divider. This voltage value across the storage capacitor is attained at the instant of time t1,2.

From that same instant of time, the voltage across the capacitor C4 remains positive in comparison with the voltage across the capacitor C5. In this manner, the control voltage Us at the transistor T5 is functionally determined through the diode D13 which is now conducting.

With the embodiment of the control arrangement of FIG. 5, it is shown how the control voltage characteristic Us, shown in FIG. 6, is obtained with a single storage capacitor C6. This functional curve of Us 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 Us, 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 T1 which is connected, through a capacitor C1, to the collector of the input transistor 13 of the multivibrator 12. Such interconnection of the transistor T1 is accomplished through a coupling resistor 35, not shown in FIG. 5. At the same time, the base of the transistor T1 is connected to the positive voltage supply line 23, through a resistor R1. The collector of transistor T1 is connected to one terminal of a resistor R31, whereas the other terminal of this resistor is connected also to the positive voltage supply line 23. Another resistor R32 is connected between the same voltage supply line 23 and the base of the transistor T6. A capacitor C7 is connected between the collector of transistor T1 and the base of transistor T6. In the quiescent state of the circuit, the transistor T6 is maintained in the conducting state. The collector of the transistor T6 is connected to a voltage divider formed by resistors R40 and R41 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 T6. The cathode of a diode D24 is also connected to this collector of transistor T6. The anode of the diode D24 is, on the other hand, connected to the junction of two resistors R37 and R38 which are connected in series and between the positive and negative voltage supply lines 23 and 30, respectively. One terminal of the resistor R39, furthermore, is connected to the anode of the diode D24.

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.