US3566846A

US3566846A - Electronically controlled fuel injection arrangement for internal combustion engines

Info

Publication number: US3566846A
Application number: US800851A
Authority: US
Inventors: Otto Glockler
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1968-02-23
Filing date: 1969-02-20
Publication date: 1971-03-02
Anticipated expiration: 1988-03-02
Also published as: FR2002456A6; GB1197865A; SE338901B; BE728792A; BR6906583D0

Abstract

A fuel injection arrangement for internal combustion engine in which one monostable multivibrator provides a pulse the duration of which is determined by a temperature-sensing device thermally coupled to the engine. The pulse duration of this monostable multivibrator is also a function of a pressure within the intake manifold of the engine. A second monostable multivibrator with the pulse being controlled by the first multivibrator has a pulse duration determined by a second and separate temperature-sensing device at a different location from the first temperature-sensing device. The quantity of fuel injected is determined by the combination of the pulse durations of the two multivibrator circuits.

Description

C United States Patent 1111 3,5 72 Inventor 01m Glockler 156] References Cited Renningen. Germany UNITED STATES PATENTS

P

2, 3 9 3,203,410 8/1965 Scholl l23/32(E-l) ggf 3 .47U,854 /1969 Eisele etal .Y l23/32(E-l) [73] Assignee Robert Bosch GmbH 3.483.85] l2/l969 Relchardta. .7 l23/32(E l) stuflgart Germany Primary Examiner--- Laurence M. Goodridge [32] Priority Feb. 23. [963 Attorney-Michael S. Striker [33 1 Germany c...4.-. [31] p 16 m 3675 ABSTRACT: A fuel injection arrangement for internal combustion engine in which one monostable multivibrator provides a pulse the duration of which is determined by a tern: [54] AL perature-sensing device thermally coupled to the engine. The COMBUSTION ENGINES pulse duration of this monostable multivibrator is also a func- Cl 6 D tion ofa pressure within the intake manifold of the engine. A aims rawmg second monostable multivibrator with the pulse being con- [52] U.S.Cl...., 123/32, trolled by the first multivibrator has a pulse duration deter- 123/1 19 mined by a second and separate temperature-sensing device at [51 Int. Cl F02d 5/00 a different location from the first temperature-sensing device! Field of Search 123/32, 32 The quantity of fuel injected is determined by the combination (E), 32 (E-l 119 of the pulse durations of the two multivibrator circuits.

PATENTEUMAR 2:971 4 3.568846 SHEU 2 UP 3 FIG. 2

h/J Afr/JIMMY sum 3 or a V PATENTED m 2m:

'INVENTQR Ofio GLOCKLEP his ATTORNEY V ELECTRONICALLY CONTROLLED FUEL llNJECTTON ARRANGEMENT FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION The present invention resides in an arrangement for internal combustion engines used particularly in motor vehicles with intake manifold injection. A first monostable multivibrator is provided which has operating characteristics dependent upon the pressure within the intake manifold. The injection duration of the injection arrangement is made dependent upon the pulse durationof this first monostable multivibrator circuit to control the quantity of fuel injected. A second monostable multivibrator is provided with a pulse duration made dependent upon the pulse duration of the first multivibrator circuit. The beginning of the pulse of the second monostable multivibrator is controlled by the first multivibrator circuit and OR gate applies the pulses for injection from. the two multivibrator circuits.

With the arrangement of the present invention, it is possible to vary the fuel injection duration as a function of different operating parameters. Thus, for example, a resistor with negative temperature coefficient is provided for increasing the quantity of fuel during the cold and heating operating state. This resistor is thermally coupled to the cooling water'of the engine, and influences the pulse duration of the second monostable multivibrator so that the entire injection duration is influenced as desired.

It has been found, however, that it is advantageous when, in accordance with the present invention, the pulse duration of the first multivibrator as well as the pulse duration of the second multivibrator are influenced or affected each by one temperature sensor.

SUMMARY OF THE INVENTION An arrangement for injecting fuel into an internal combustion engine through electromagnetically controlled valves. A first monostable multivibrator provides a pulse having a duration which is dependent upon an operating characteristic of the engine such as the pressure within the intake manifold. A second monostable multivibrator having a pulse which begins upon control from the first monostable multivibrator, has a pulse duration dependent upon that of the first multivibrator. Each of the monostable multivibrator circuits is associated with a temperature-sensing device in the form of a resistor with negative temperature coefficient. The arrangement is such that the temperature-sensing devices affect the duration of the pulses emitted by the monostable multivibrator circuits. The temperature-sensing devices are displaced from each other and are located so that they are influenced and vary with a time constant differing by a factor of five from each other.

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 schematic diagram of the fuel injection arrangement, in accordance with the present invention; and

FIGS. 2 to 6 are graphical representation of parameters and variables applicable to the arrangement of FIG; 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, and in particular to FIG. I, the fuel injection arrangement shown therein is designed for the operation of a four-cylinder internal combustion engine It? with spark plugs 11 connected to a high-voltage ignition arrangement, not shown. An intake manifold 12 branches off to the individual cylinders of the engine it). Electromagnetically actuated injection valves 113 lie directly in the proximity of the inlet valves, not shown, of the internal combustion engine. One such valve 13 is provided for eachone of the individual cylinders. The combined function of the four electromagnetically actuated valves I3 is to serve as the fuel injection arrangement. Fuel under constant pressure is applied to each one of the injection valves 13, through a conducting line 114 leading from a distributor H5. The fuel is sucked or drawn from a storage tank 17, through means of a pump 16, and forced into the distributor 15. The pump 16 can be electrically operated or, driven by the internal combustion engine 10 itself, as shown in the drawing.

Each of the injection valves 13 has one terminal connected to ground potential. The two leftmost injection valves 13, shown in FIG. 1, lead, by way of resistors 18, to the collector of a PNP power transistor 22. The two rightmost injection valves 13 lead, by way of resistors 19 to the collector of the PNP power transistor 23. The emitters of the two transistors 22 and 23 are connected together and to the positive terminal of the battery 25, by way of the conducting path or connection 24. The operating voltage source for the arrangement of the present invention is shown in the form of the battery 25, and the connection 24 leading from the battery is designated as the positive terminal of the latter. A connecting path 26 is connected to the negative terminal of the battery 25, and coupled to ground potential. This connecting path 26 is designated as the negative connection in the arrangement.

The bases of the two power transistors 22 and 23 are connected to the fixed contacts of a mechanically operated switch 27. This switch is a cam-operated unit in which the cam is rotationally driven by the crankshaft of the engine. The movable contact of the switch 27 is connected to the output of the OR gate 28 having an output transistor 2?. With the engine 10 in operation, the cam-driven switch 27 connects alternately the bases of the power transistors 22 and 23 to the output of the OR gate 28. The movable contact of the switch 27 is connected to the junction of tap of a voltage divider comprised of

resistors

108 and 109 in the collector circuit of the transistor 2%. The resistors 106 and R07 within the OR gate 28, serve as the input resistors of this gate. The base of the transistor as is joined to one terminal of each of the

resistors

106 and 107, whereas the emitter of the transistor 29 leads to ground potential. At the input of this OR gate 28, the outputs of two multivibrators are connected. One of these multivibrators is a first monostable multivibrator 32 with two NPN transistors 33 and 34. The second monostable multivibrator resides in the circuit 35 with two

PNP transistors

36 and 37, as well as an NIN transistor 38. The second multivibrator 35 operates in conjunction with a timing network 39 which includes an NPN transistor 40. The pulse duration 72of the second multivibrator 35 is related with the pulse duration T1 of the first multivibrator 32 in accordance with the function T2x b P Ti] 0, the embodiment. Through this particular arrangement, it is possible to realize in an advantageous manner, the desired variation of the injection duration in the form of T X T12 T2 Thus, the injection duration T is the opening duration of the valve 13 of which there are four cylinder engines, and the desired duration of this opening duration is difficult to realize particularly for high rotational speeds of the engine, as previously indicated. The variation in the injection duration may extend over at a ratio of 1:4. The parameter b is, in the embodiment, a function of the temperature of the engine, and is a factor of the pulse duration T2 The voltage of the battery 25, on the other hand, influences the pulse duration TZadditively. Aside from this, a starting arrangement is also provided through which the pulse duration T2is also extended when initiated.

In particular, the circuitry of FIG. It is designed so that the emitter of transistors 33 and 34 are directly connected to ground potential. The base of the transistor 33 is connected to the cathode of the diode 43, and leads, at the same time, to

ground potential by way of resistor 44. The anode of the diode 43 is connected to the junction 45 to which the anodes of the two diodes 46 and 47 are also connected. A resistor 48 is connected between the junction 45 and the positive terminal or connection 24 of the battery. The cathode of the diode 46 leads, by way of the resistor 49, to ground potential. The cathode of the diode 46 is also connected to a capacitor 52 leading to the junction 53 which is connected to the fixed contact of an interrupting switch 55. The junction 53 also leads to the positive connected 24, by way of the resistor 54. The cam 56 which operates or actuates the interrupting switch 55 has two high portions which actuates the switch 55 twice for every revolution of the cam. The cam 56 is mechanically driven by the crankshaft of the engine, and when the switch 55 becomes closed through actuation of this cam, a negative impulse is applied to the junction 53. The applied impulse to this junction, is differentiated through an RC differentiating network consisting of resistor 49 and capacitor 52. As a result of the differentiation, the waveform shown in the drawing results. The diode 46 transmits only the negative half of the waveform when closing the contact 55. This is shown by the voltage relationship u, in FlG. 2 and appearing at the junction 45.

The cathode of the diode 47 is connected to one terminal of the secondary winding 57 of a transformer 58. The other terminal of this secondary winding is connected to the junction 59. A resistor 63 is connected between this junction 59 and the positive connection 24. By varying the potential of the junction 59, the pulse duration T of the multivibrator 32 may be varied multiplicatively as, for example, in dependence of the rotational speed.

The collector of the transistor 33 leads to the positive connection 24, by way of a resistor 64. The collector of this transistor 33 is also joined to the base of the transistor 34 through a resistor 65. The collector of the transistor 34 leads to the positive connection 24, through the series circuit consisting of the primary windings 66 of the transformer 58, and the resistor 67.

Connected to the junction P between the primary winding 66 and the resistor 67, is the cathode of a diode 122. The anode of this diode R22 is connected to the junction S, which is also the junction or tap of a voltage divider consisting of resistors 120 and 121. The resistor 120 is independent of temperature and connected to the positive line or connection 24. The other resistor 121 of the voltage divider leads to the negative connection 26, and is in the form of a thermal conductor or NTC resistor. This latter resistor is in proximity to the motor oil of the engine, so that the resistor reflects the thermal condition of the motor oil. By varying the resistor 121 which is made in the form of an adjustable resistor, the pulse duration T may be varied as a function of the temperature of the motor oil.

The transformer 58 has an adjustable ferromagnetic core 63 which is coupled to a pressure-measuring membrane 72, through a positioning rod 69. The pressure-measuring membrane 72 is designed in the form of an evacuated barometric membrane or device communicating with the suction line or intake manifold 12. At the entrance of the intake manifold 12 is a throttle 73, as provided in conventional arrangements, which is located behind an air filter 74 and is actuated by the gas pedal 75. When the gas pedal 75 is depressed, the throttle 73 is opened, and the vacuum within the intake manifold 12 is decreased. As a result, the ferromagnetic core 68 within the transformer 53 is moved in position so that the pulse duration of the multivibrator 32 is extended and, accordingly, a larger quantity of fuel is injected. if, on the other hand, the throttle 73 is closed, the vacuum within the intake manifold 32 becomes greater and the pressure-measuring membrane device 72 draws or moves the ferromagnetic core 68 in the direction of the arrow shown in the drawing. in this direction, the ferromagnetic core 68 is moved out of or drawn out of the transformer 58, and as a result the inductance of the primary winding is decreased to the extent that the injection duration becomes correspondingly smaller.

The operation of the monostable multivibrator 32, in accordance with FIG. 1, is known in the art and, for this reason, will be described only briefly. Thus, when the interrupting contact 55 is opened, the transistor 33 conducts in its quiescent state, whereas the transistor 34 is turned off. When, now, the switching contact 55 is closed, a negative impulse u, arrives at the junction 45, in the form shown in FIG. 2. This impulse u, cuts off the diode 43 and thereby also the transistor 33. As a result, the transistor 34 is turned on and current flow takes place through the primary winding 66. The current rises exponentially to its maximum value which is determined by the magnitude of the resistance of the coil 66 and the value of the resistors 67. During this rise of the current, an exponentially shaped voltage is induced within the secondary winding 57. It is the function of this induced voltage to maintain the base of transistor 33 at ground potential. After a sufficient time interval of this voltage induced within the secondary winding 57, the base of the transistor 33 becomes again positive, and the transistor is again turned on while, simultaneously, turning the transistor 34 off. This time interval of the induced voltage is dependent upon the inductance of the primary winding 66, and thus is determined by the position of the ferromagnetic core 68.

Accordingly, positive voltage pulses u as shown in FIG. 2, appear at the collector of the transistor 33. The pulses u; are synchronized with the rotational speed of the internal combustion engine 10. The duration T of these pulses is dependent upon the position of the ferromagnetic core 68 and the resistance value of the resistor 121 which is in thermal contact or thermally coupled to the motor oil.

The base of the transistor 36 is directly connected with the collector of the transistor 33. The emitter of the transistor 36 leads to the positive connection 24 by way of an adjustable resistor 76. The collector of the transistor 36 is coupled to the collector of the transistor 37, by way of a capacitor 77. The charging voltage of this capacitor determines essentially the pulse duration of the second multivibrator 35. The collector 36 also leads to the base of the transistor 38, through the diode 78. Specifically, the cathode of the diode 75 is connected to the base of the transistor 38, and leads through a resistor 79, to ground potential.

The emitter of the transistor 37 is connected to the positive supply line 24 through an adjustable resistor 82. Aside from this, the emitter of the transistor 37 is directly connected to the cathode of a diode 83. The anode of this diode 83 leads to the junction 85, by way of an adjustable resistor 84. The anode of the Zener diode 86 is directly connected to the junction 85, whereas the cathode of the Zener diode is connected to the positive supply line 24. A resistor 87 is connected, moreover, between the junction and ground potential.

The base of the transistor 37 leads to the positive supply line 24, by way of a resistor 88. At the same time, the base of this transistor 37 also leads to ground potential, through two resistors 91 and 92 connected in series and having ajunction 93 between them. The junction 93 is directly connected to the cathode of a diode 94 with its anode connected to the junction 95. This junction 95 leads to ground potential through a resistor 96 having a negative temperature coefficient abbreviated as NTC. A resistor 97, furthermore, is connected between the junction 95 and the positive supply line 24. The junction 95 is also connected to the anode of the diode which has its cathode joined to ground potential, by way of a resistor 100. A resistor 103 is connected in parallel with the diode 98. The cathode of the diode 98 is, furthermore, connected to the fixed contact of an operating switch 104. The movable contact of the latter leads directly to the positive supply line 24. The emitter of the transistor 38 is connected directly to ground potential, whereas the collector of this transistor 38 leads to the positive supply line 24, by way of the resistor 135. Aside from this, the collector of the transistor 38 leads to the base of the transistor 29, through the resistor 166 of the OR gate 28. The collector of the transistor 33 also leads to the base of the transistor 29 of the OR gate 213, through the resistor 107.

The collector of the transistor 29 is coupled to the movable contact of the switch 27, and leads to the positive supply line 24, by way of the collector resistor 109.

The anode of the diode 83 is directly connected to the anode of another diode 112, the cathode of which is connected to the collector of a transistor 40. The emitter of this transistor 50 is connected to ground potential, whereas the collector of the transistor Ml leads to the positive supply line 2 through the resistor 113. A resistor 115 is connected between the base of a transistor 40 and ground potential, and the cathode of the diode lid is connected to the junction of the resistor 115 and the base of the transistor M). The anode of the diode 114 is connected to the junction 116 which, in turn, leads to the-positive supply line 24, by way of the resistor 1117. Through the series circuit of a capacitor 118 and resistor 119, the junction 116 is connected to the collector of the transistor 33.

ln operation of the injection arrangement of FIG. 1, a negative impulse 1.4,, as shown in FIG. 2, reaches the junction 45 for each closure of the interrupting switch or contact 55. This negative impulse cuts off the diode 43 as well as the transistor 33 for a time interval T,, as already described above. As a result, positive impulses n as shown in FIG. 2, appear at the collector of the transistor 33, with a time duration T,, where T is a function of the vacuum within the intake manifold12 and the temperature of the motor oil as already described.

The pulses u are applied to the base of the transistor 29 of the OR gate 28, through the resistor 107, and thereby cause the gate to conduct or transmit during the duration of the pulse 14,. During this conducting interval, the collector of the transistor 29 is essentially at the negative potential of the supply line 26 which corresponds to the voltage level 14 in FIG. 2. As a result, a power transistor 22 becomes turned on or conducting when a switch 27 is in the position shown in the drawing, and the two leftmost injection valves 13 become opened. With these injection valves actuated in this manner, fuel is injected in the two left cylinders of the internal combustion engine 10. When the switch 27 is in the position opposite to that shown in the drawing, the two right valves 13 corresponding to the two right cylinders of the engine, become opened.

During the interval of each pulse 14 the transistor 40 is, moreover, maintained in the conducting state, through the RC network consisting of

elements

119 and 118. During this interval the capacitor K18 becomes charged in the manner determined by the plus and minus signs shown in the drawing. The resistor 119 limits the charging current of the capacitor 118, in an advantageous manner. The waveform of the pulses u thereby becomes improved, since the collector potential of the transistor 33 rises more rapidly when the latter is turned off. At the end of a pulse 14 at which time the collector of the transistor 33 becomes again negative, this voltage variation is transmitted to the junction 116, by way of the capacitor 118, and cuts off the diode 114 as well as the transistor 40. Such cutoff is maintained until the capacitor 113 has sufficiently discharged through the resistors 117 and 119, and the transistor it) again becomes conducting or turned on. The cutoff time interval of the transistor 40 in the present embodiment, is approximately 1 msec. This particular value has shown itself to be of advantage in a number of types of internal combustion engines. 7

During the turned-off or cutoff time of a transistor 40, a positive voltage appears at its collector. This positive voltage is designated as u in FlGS. 1 and 2. The pulses u connect directly, in time, with the pulses a For every positive pulse 11 furthermore, the transistor 36 acquires a base potential which lies between the potential of the negative supply line 26 and the positive supply line 24. If, for example, one assumes that the battery 25 has a voltage of 12 volts, and the positive supply line 24 is at the potential of volts for at voltage reference potential, then this base of the transistor has a potential of approximately 6 volts. The emitter of the transistor 36 then acquires a positive potential of approximately -5.4 volts, for example, due to the voltage drop along the emitter-base path of the transistor 36. An essentially constant collector current flows, correspondingly, in the transistor 36 during the time interval T, of the pulses a and this collector current charges linearly the capacitor 77. With such linear charging of the capacitor, the voltage across the capacitor increase linearly with time. Thus, the transistor 36 serves as a constant current source in which the current may be adjusted through the resistor 76. The potential at the left electrode of the capacitor 77 in FIG. 1, is designated as 14 in the waveform diagram of FIG. 2.

When the transistor 33 becomes again conducting at the end of the impulse u the base potential of the transistor 36 transfers essentially to the negative value of, for example, 1 1.5 volts, when referred to the positive supply line 26. This transfer in the base potential of the transistor 36 is in the form of a step function. The collector of this transistor becomes correspondingly more negative also, and the step variation in the collector potential is transmitted to the base of the transistor 38, by way of the capacitor 77 and diode 78. When this step variation in the collector potential of the transistor 36 is thus transmitted to the base of the transistor 38, the latter is turned off, and in particular at the instant coinciding with the end of the pulse a As a result, the positive voltage 14 prevails at the collector of the transistor 38. This positive voltage a is transmitted to the base of the transistor 29 by way of the resistor 106. When the signal u is thus applied to the base of the transistor 29 within the OR gate 28, this transistor 29 is maintained in the conducting state. The two left injection valves ll3 remain, thereby, in the open state, so that the injection duration is extended beyond the pulse interval T of the first multivibrator 32.

The capacitor 77 now becomes discharged through the resistor 82, the transistor 37, and the

transistors

36 and 33. The collector-base path of the transistor 36 is thereby driven in the inverse direction, implying that the current flow is opposite from its normal direction.

A variety of advantages are realized through the second multivibrator circuit 35. The first advantage resides in the feature that the components or elements of the first multivibrator 32, may be designed for shorter pulse time intervals T,. This feature applies particularly to the transformer 58. The second advantage resides in the feature that it is also possible to apply multiplicative or factor corrections with the second multivibrator, in addition to the necessary additive corrections which are applied, for example, for variations in the voltage of the battery 25. The multiplicative or factor corrections are used to compensate, for example, for the variation of the temperature of the internal combustion engine 10. It should be understood, here, that an additive correction is interpreted to vary the injection duration by an essentially fixed correction constant. Thus, for example, the correction constant for lowbattery voltage is 0.3 msec. A pulse duration of T 8 msec. then becomes extended to 8.3 msec., and a pulse duration of T 2 msec. becomes extended to 2.3 msec. A multiplicative correction, on the other hand,'extends the pulse duration T by an essentially predetermined correction factor. Thus, assume, for example, that for low temperatures of internal combustion engine 10, a correction factor of 20 percent is to be applied. A pulse duration of T= 8 msec. is then extended to 9.6 msec., and a pulse duration of T= 2 msec. becomes extended to 2.4

msec.

At high rotational speeds, furthermore, the advantage is realized that injection is accomplished uniformly and reliably for the following reasons:

When a large quantity of fuel is to be injected at high rotational speeds, and only a single multivibrator is provided for the purpose of controlling the injection valves, then this multivibrator has a very large pulse duration in relation to its periodic interval. A pulse then prevails for 8 msec., for example, and a new impulse begins only I msec. at the end of the impulse. As a result of this condition, the multivibrator can sometimes not sufficiently recover during this short time interval, and when this occurs, the following pulse becomes shortened or is lost. Under these conditions, therefore, the injection is irregular.

In accordance with the invention, on the other hand, the total pulse for the injection is composed of two individual pulses to realize an injection with a time duration T. The first single pulse from the multivibrator 32 has the duration or time interval T,, and the single pulse from the multivibrator 35 has the time interval 7",. These individual or single pulses are each shorter than the total pulse of, for example, 4 msec. in duration. If the next injection pulse if to follow after 1 msec., as in the above example, then each one of the two multivibrators has a recovery time of 4 l msec. made available. Through the present invention, therefore, it is possible to realize considerably higher speeds than previously, and still govern the injection process reliably. This situation prevails even though the injection process for all valves is determined by the pulse duration of the first multivibrator.

A further advantage is realized through the timing network 39 in conjunction with the second multivibrator 35. As a result of this timing network 39, the pulse duration T rises above proportionality with increase in the pulse duration T,. Thus, the pulse duration T is thereby given by the function T b X T, a. The constance in this relationship may be further functions in which a is, for example, a function of the battery supply voltage, and l; is a function of the temperature of the engine 10.

Through this arrangement, the advantage is realized that the total injection duration T= T, T has a larger range from maximum to minimum duration, and may be more variable within this range than the pulse duration T,. Such an enlarged variation of the duration parameter is particularly desirable, since the quantity injected may vary in the ratio of 4:1 in internal combustion engines. The variation of the pulse duration over such a range or ratio, is conventionally difficult to achieve.

The aforesaid individual advantages may be achieved in the following manner:

When the transistor 33 is turned off, the transistor 40 is also turned off or cut off and its collector is positive. The collector voltage u of the transistor 40 is traced in FIG. 2. The diode 112 is then cut off, whereas current flows through the diode 83, the resistor 84 and the Zener diode 86. The current flow through these elements raises the emitter and collector current of the transistor 37. The capacitor 77 becomes thereby more rapidly discharged, as long as the transistor 40 remains turned off.

When the transistor 40 becomes again conducting after the expiration of the time interval T,, its collector is approximately the potential of the negative supply line 26. Current flows correspondingly from the junction 85 towards ground by way of the resistor 84, the diode 112 and the transistor 40. The junction 85 is maintained at constant potential by the Zener diode 86. The current flow from this junction results in a voltage drop across the resistor 84 and applies a negative potential to the anode of the diode 83 so that the latter diode is cut off. As a result, the emitter and collector current of the transistor 37 becomes smaller and the capacitor 77 becomes correspondingly slower discharged.

When the capacitor 77 has discharged sufficiently, the base of the transistor 33 becomes again positive after a time interval T In this manner, the transistor becomes again conducting or turned on and the collector of this transistor becomes thereby negative. The OR gate 28, consequently, also no longer receives a positive voltage and the transistor 29 is turned off. The injection process of the two left valves is thereby terminated. The injection process lasts for a total time interval Tcornposcd of the pulse duration T, of the first multivibrator 32, and the pulse duration T of the second multivibrator 35. Thus, T= T, T

FIG. 5 shows the relationship between T, and T for constant engine temperature and constant battery voltage. Within a first region as, for example, between the pulse duration T, of 0 to l msec. (not occurring in the operation of the present arrangement) a linear relationship exists between T, and T These time intervals lie within the pulse duration Y, of the timing network 39. Above this pulse duration, T rises more rapidly than T,.

Through a second multivibrator 35, furthermore, fluctuations in the voltage of the battery 25 and the fluctuations of the temperature of the engine 10 are correspondingly varied with the pulse duration T and thereby also the injection duration T= T, T Aside from this, the starting arrangement is provided for the purpose of enriching the fuel-air mixture automatically when starting. All of these corrections affect the discharge circuit of the capacitor 77. These corrections are described in detail and in sequence in what follows.

CORRECTIONS FOR FLUCTUATIONS OF THE OPERATING VOLTAGE Fluctuations in the operating voltage affect the fuel injection arrangement, since the injection valves 13 will open more rapidly when the applied pulse has a larger magnitude than when it has a smaller magnitude. Since the operating voltage also affects the pulse level, the implication is that when the pulse duration remains constant, more fuel is injected for higher operating voltage than for lower operating voltage.

FIGS. 3 and 4 show voltage functions for different operating voltages U Since the voltage function u, as well as the voltage function u, is dependent upon the operating voltage U,,, the values Il /U and u.,/U,, have been plotted. Thus, the plotted curves are normalized and display percents of the operating voltage.

The curve Ug/U shows the voltage function across the capacitor 77 while charging with constant current. The curve u.,/U shows the voltage prevailing at the collector of the transistor 37 while discharging of the capacitor 77. During the time interval Y,, the transistor 40 is turned off. During this time interval, the diode 112 becomes cut off through the resistor H3, and as a result current can flow through the diode 83, resistor 84, and Zener diode 86. This current flow adds to the current through the resistor 82 and thereby accelerates the discharge of the capacitor 77 during the time interval Y,.

If the operating voltage U,, is increased, the character of the curve u /U is not varied. The current through the diode 83, the resistor 84 and the Zener diode 86, however, increases disproportionately higher, since the voltage at the Zener diode 86 is substantially constant. This function of u /U,, with increased operating voltage is shown in FIGS. 3 and 4 through the broken-line curve. The speed of discharge ofthe capacitor 77 is thus increased during the time interval Y,, and remains constant after the expiration of this interval Y,. With this feature, a decrease in the pulse duration T is realized with increased operating voltage U,,, and hence a decrease in the time interval T. Through this particular decrease in the pulse duration, a same quantity of fuel is injected for highand low operating voltages U FIG. 3 shows the voltage functions for substantially long pulse duration, whereas FIG. 4 shows these functions for shorter pulse durations. In both cases, the extended curves display the function for a predetermined lower operating voltage, whereas the broken-line curves display the function for a predetermined higher operating voltage. In both cases the same decrease AT of the pulse duration is realized. Accordingly, the correction operates in an additive manner. It has been found that such an additive decrease provides optimum results.

HEATING AND CORRECTING FOR FLUCTUATIONS IN THE ENGINE TEMPERATURE When starting in a cold state and during the subsequently following warmer running of the engine, it is necessary to apply a larger quantity of fuel in order to realize satisfactory operation. Thus, it is necessary to provide a fuel-air mixture which contains more fuel. Such a mixture is often designated as a richer mixture. The reason for this requirement ofa larger quantity of fuel resides on the basis of a relatively worse preparation and distribution of the fuel in cold environment than in a warmer operating state of the engine, and in more unfavorable ignitability.

It has been found that to achieve good operating characteristics of the internal combustion engine, it is sufficient to apply to the engine a fivefold quantity of fuel during the heating phase, and to decrease the fuel quantity exponentially with the temperature characteristic of the engine temperature as, for example, the temperature of the cooling water.

in order to meet the requirement for restricting the amount of exhaust emission, it is necessary to satisfy the function of FIG. 6 which is a complex function for regulating the heating quantity. It is also essential for this requirement to provide a second temperature sensor for regulating the fuel quantity.

The temperature sensors must be located in unique positions of the engine, so that their speed of heating differs by a factor of five. The first temperature sensor TF is the one with the short time constant. This temperature sensor can, for example, be mounted on the cylinder head, at the exhaust system, or within the cooling water. This temperature sensor affects the total quantity of fuel by approximately 60 to 80 percent. The temperature sensor TF has a time constant which exceeds that of the sensor TF by a factor of five. This second temperature sensor TF can, for example, be arranged within the oil fluid circuit. The second sensor affects the fuel quantity by approximately 20 to 40 percent.

The NTC resistor 96 with negative temperature coefficient is used as the temperature sensor TF in the present embodiment. This resistor 96 is coupled to the engine or is in thermal contact with the cooling water circuit.

For low temperatures of the engine 10, as for example when starting, this resistor has a high value, and the junction 95 has correspondingly a positive potential as does the junction 93. Accordingly, current flows through the diode 94. The base potential of the transistor 37 thereby becomes more positive. Thus, the resistance resulting from the transistor 37 within the discharge circuit of the capacitor '77, becomes larger. Consequently, the discharge time of the capacitor 77 is extended for low temperatures of the engine 10, and the pulse duration T is correspondingly extended. In order to prevent the injection of too much fuel for very low temperatures, the resistor 100 is provided. When, for such low temperatures the junction 95 becomes more positive than the cathode of the diode 98, current flows through the diode 98 and further increase in the potential of the junction 95 is thereby prevented. Through this simple means, a fuel-air mixture which is too rich is prevented from being formed at very low temperatures. The diode 93 is connected between the tap of the voltage divider consisting of resistors 96 and 97, and the tap of the voltage divider consisting of resistors I00, I03 and 97.

when the internal combustion engine has achieved its operating temperatures as, for example, 80 C., the resistance value of the NTC resistor 96 becomes very small and the diode 94 becomes correspondingly cut off. Above this temperature, the resistor 96 no longer affects the pulse duration T The relationship between resistors 91 and 92 determines this parameter.

The NTC resistor i211 serves as a second temperature sensor TF which is thermally coupled to the oil fluid circuit of the internal combustion engine It This resistor 121 is a component of the voltage divider consisting of resistors 120 and 1121. At the junction S of this voltage divider and between resistors 12d and 1211, one electrode of the diode 122 is connected. The other electrode of this diode 122 is connected to the junction P between the transformer winding 66 and the resistor 67. The transmitting direction of the diode 122 is chosen so that current flow takes place only when the potential of the junction S is higher than the potential of the junction P. The resistance values of the two resistors 124i and 121 are chosen so that when the oil temperature exceeds 0 C., the diode 122 remains continuously cut off. When, however, the temperature of the NTCresistor 121 drops below 0 C., so that this resistor assumes a higher resistance value, the potential of the junction 5 is shifted in the positive direction. The potential of the junction P becomes increasingly more negative with rising collector current, and thereby attains at an earlier time the potential of the junction S. Thus, the lower the oil temperature of the engine, the earlier this potential of the junction P is achieved. If, now, the diode 122 conducts before the unstable state of the circuit is terminated, the time constant for the rise in the collector current becomes increased in a stepwise manner. This again causes an increase in the output pulse duration which increases the more the oil temperature drops below 0 C. I

STARTING CORRECTIONS When starting, the junction 93 is made positive through the starting switch 104, the resistor 103 and the diode 94. As a result, the discharge time of the capacitor 77 becomes increased as described above, and the pulse duration T becomes thereby extended. At the same time, the cathode of the diode 93 acquires the potential of the positive supply line 24. The implication of this arrangement is that the diode remains cut off during the starting process, independent of the temperature of the internal combustion engine 10. Accordingly, a very rich mixture is realized when starting, and the engine 10 starts readily through such a rich mixture. Thus, a larger quantity of fuel is injected so that fuel enrichment is realized when starting.

Through the present invention, therefore, a fuel injection arrangement is realized which also operates very satisfactorily at high operating speeds. Such desired operating characteristics are realized through corrections which are applied in an additive manner and in a multiplicative manner, without the provision that these applied corrections influence each other. Through the use of the present invention, furthermore, it is also possible to achieve the desired adjustment in the pulse duration over a wide region without difficulties.

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 on constructions differing from the types described above.

While the invention has been illustrated and described as embodied in fuel injection arrangement for 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.

I claim:

11. A fuel injection arrangement for internal combustion engines comprising, in combination, first monostable multivibrator means with pulse duration dependent upon an operating characteristic of said engine and determining partially the quantity of fuel being injected; second monostable multivibrator means connected to said first monostable multivibrator means and having a pulse duration dependent upon the pulse duration of said first monostable multivibrator means, the beginning of the pulse duration of said second monostable multivibrator being controlled by said first monostable multivibrator; first temperature-sensing means operatively connected to said first monostable multivibrator means for influencing the pulse duration of said first monostable multivibrator means; and second temperature-sensing means operatively connected to said second monostable multivibrator means for influencing the pulse duration of said second monostable multivibrator means, whereby the quantity of fuel injected is determined by the combined pulse durations of said first and second monostable multivibrator means, said pulse durations being dependent on said operating characteristic of said engine and on temperatures sensed by said first and second temperature-sensing means.

2. The fuel injection arrangement as defined in claim I wherein said first and second temperature-sensing means are subjected to two different temperatures varying with a time constant different from each other by a factor of five.

3. The fuel injection arrangement as defined in claim 2 wherein said first temperature-sensing means is influenced by temperature variations of substantially small time constant, said first temperature-sensing means applying a correction of 60 to 80 percent to the injection duration in which fuel is injected; and wherein said second temperature-sensing means is influenced by temperature variations of substantially longer time constant, said second temperature-sensing means applying a correction to said injection duration within the range of 20 to 40 percent.

4. The fuel injection arrangement as defined in claim 1 wherein said temperature-sensing means are temperature dependent resistors.

5. The fuel injection arrangement as defined in claim 1 wherein the pulse duration of said second monostable multivibrator means exceeds proportionately an increase in the pulse duration of said first monostable multivibrator means within at least a portion of the region of said pulse durations.

6. The fuel injection arrangement as defined in claim 5 wherein the pulse duration of said second monostable multivibrator means is equal to the pulse duration of said first monostable multivibrator means multiplied by a factor b minus a second factor a.

7. The fuel injection arrangement as defined in claim 1 including capacitor means in said second monostable multivibrator means and being charged during the time interval of the pulse duration of said first monostable multivibrator means, said capacitor means being discharged at the end of the pulse duration of said first monostable multivibrator means, the pulse duration of said second monostable multivibrator means being dependent upon the charged voltage on said capacitor means.

8. The fuel injection arrangement as defined in claim 7 including a constant current source for charging said capacitor means.

9. The fuel injection arrangement as defined in claim 8 wherein said constant current source comprises a transistor.

10. The fuel injection arrangement as defined in claim 1 including a timing network controlled by said first monostable multivibrator means; and discharge circuit means in said second monostable multivibrator means influenced by said timing network.

11. The fuel injection arrangement as defined in claim 10 wherein said timing network influences said discharge circuit of said second monostable multivibrator means for rapid discharging within a predetermined time interval at the end of the pulse duration of said first monostable multivibrator means.

12. The fuel injection arrangement as defined in claim 7 including a voltage source connected to said monostable multivibrator means for providing operating voltage; and means for influencing the discharge of said capacitor means as a function of said operating voltage so that the pulse duration of said second monostable multivibrator means is decreased with increase in said operating voltage.

13. The fuel injection arrangement as defined in claim 12 including a timing network controlled by said first monostable multivibrator means; and discharge circuit means in said second monostable multivibrator means influenced by said timing network, said discharge circuit in said second monostable multivibrator means being influenced by the operating voltage of said monostable multivibrator means only when said timing network is operative, said operating voltage for said monostable multivibrator means being applied by a source of voltage.

14. The fuel injection arrangement as defined in claim 13 including a transistor connected to said capacitor means; emitter resistor means connected in series with the emitter of said transistor; voltage-dividing means having a tap connected to the base of said transistor, said voltage-dividing means being connected to said operating voltage of said voltage source; diode means connected to the emitter of said transistor; a Zener diode connected to said diode means and in parallel with said emitter resistor means so that the part of the l discharge current from said capacitor means flowing through said Zener diode increases above a proportionately increase in said operating voltage.

15. The fuel injection arrangement as defined in claim 14 including second resistor means connected between said diode means and said Zener diode.

16. The fuel injection arrangement as defined in claim 7 including means for discharging said capacitor means so that the discharge is a function of the temperature of said engine, whereby the discharged time is decreased with increase in the temperature of said engine.

17. The fuel injection arrangement as defined in claim 16 including a transistor in said means for discharging said capacitor; a source of voltage supply; a voltage divider connected across said source of voltage supply and having a tap connected to the control electrode of said transistor; an auxiliary voltage divider connected across said source of voltage and including a temperature dependent resistor thermally coupled to said engine; a diode connected between a tap of said first voltage divider and a tap of said auxiliary voltage divider so that the conductivity of said transistor decreases below a predetermined temperature of said engine.

18. The fuel injection arrangement as defined in claim 17 including additional voltage-dividing means connected across said source of voltage; and an additional diode connected between a tap of said auxiliary voltage-dividing means and a tap of said additional voltage-dividing means so that said additional diode conducts when said temperature dependent resistor attains a predetermined resistance value at low temperatures, whereby further decrease in the conductivity of said transistor in inhibited.

19. The fuel injection arrangement as defined in claim 7 including discharge circuit means for discharging said capacitor means; and starting switching means operatively connected to said discharge means for increasing the discharge time of said capacitor means when said switching means is in operative closed-circuit state.

20. The fuel injection arrangement as defined in claim 19 including a transistor in said discharge circuit means; a source of operating voltage; a voltage divider connected across said source of operating voltage and having a tap connected to the control electrode of said transistor, and means for connecting said switching means parallel with a portion of said voltagedividing means so that the conductivity of said transistor decreases when said switching means is in operative closedcircuit state.

21. The fuel injection arrangement as defined in claim 18 including starting switching means connected in parallel with a portion of said first voltage-dividing means, said additional diode being nonconductive when said switching is in operative closed-circuit state.

22. The fuel injection arrangement as defined in claim 1 wherein said operating characteristic of said engine is the pressure within the intake manifold of said engine.

23. The fuel injection arrangement as defined in claim 4 wherein said temperature dependent resistor means comprises resistor means with negative temperature coefficient.

24. A fuel injection arrangement for internal combustion engines comprising, in combination, first monostable multivibrator means with pulse duration dependent upon an operating characteristic of said engine and determining partially the quantity of fuel being injected; second monostable multivibrator means connected to said first monostable multivibrator means and having a pulse duration dependent upon the pulse duration of said first monostable multivibrator means, the beginning of the pulse duration of said second monostable multivibrator being controlled by said first monostable multivibrator; first temperature-sensing means operatively connected to said first monostable multivibrator means for influencing the pulse duration of said first monostable multivibrator means; and second temperature-sensing means operatively connected to said second monostable multivibrator means for influencing the pulse duration of said second monostable multivibrator means, whereby the quantity of fuel injected is determined by the pulse durations of said first and second monostable multivibrator means, said first temperature-sensing means being thermally coupled to the cooling water of said internal combustion engine, said second temperature-sensing means being thermally coupled to the oil flow circuit of said engine.

25. A fuel injection arrangement for internal combustion engines comprising, in combination, first monostable multivibrator means with pulse duration dependent upon an operating characteristic of said engine and determining partially the quantity of fuel being injected; second monostable multivibrator means connected to said first monostable multivibrator means and having a pulse-duration dependent upon the pulse duration of said first monostable multivibrator means, the beginning of the pulse duration of said second monostable multivibrator being controlled by said first monostable multivibrator; first temperature-sensing means operatively connected to said first monostable multivibrator means for influencing the pulse duration of said first monostable multivibrator means; and second temperature-sensing means operatively connected to said second monostable multivibrator means for influencing the pulse duration of said second monostable multivibrator means, whereby the quantity of fuel injected is determined by the pulse durations of said first and second monostable multivibrator means, said first temperature-sensing means being arranged on the cylinder head of said internal combustion engine, said second temperature-sensing means being arranged in the oil flow circuit of said engine.

Claims

1. A fuel injection arrangement for internal combustion engines comprising, in combination, first monostable multivibrator means with pulse duration dependent upon an operating characteristic of said engine and determining partially the quantity of fuel being injected; second monostable multivibrator means connected to said first monostable multivibrator means and having a pulse duration dependent upon the pulse duration of said first monostable multivibrator means, the beginning of the pulse duration of Said second monostable multivibrator being controlled by said first monostable multivibrator; first temperature-sensing means operatively connected to said first monostable multivibrator means for influencing the pulse duration of said first monostable multivibrator means; and second temperature-sensing means operatively connected to said second monostable multivibrator means for influencing the pulse duration of said second monostable multivibrator means, whereby the quantity of fuel injected is determined by the combined pulse durations of said first and second monostable multivibrator means, said pulse durations being dependent on said operating characteristic of said engine and on temperatures sensed by said first and second temperature-sensing means.

2. The fuel injection arrangement as defined in claim 1 wherein said first and second temperature-sensing means are subjected to two different temperatures varying with a time constant different from each other by a factor of five.

14. The fuel injection arrangement as defined in claim 13 including a transistor connected to said capacitor means; emitter resistor means connected in series with the emitter of said transistor; voltage-dividing means having a tap connected to the base of said transistor, said voltage-dividing means being connected to said operating voltage of said voltage source; diode means connected to the emitter of said transistor; a Zener diode connected to said diode means and in parallel with said emitter resistor means so that the part of the discharge current from said capacitor means flowing through said Zener diode increases above a proportionately increase in said operating voltage.

20. The fuel injection arrangement as defined in claim 19 including a transistor in said discharge circuit means; a source of operating voltage; a voltage divider connected across said source of operating voltage and having a tap connected to the control electrode of said transistor, and means for connecting said switching means parallel with a portion of said voltage-dividing means so that the conductivity of said transistor decreases when said switching means is in operative closed-circuit state.

25. A fuel injection arrangement for internal combustion engines comprising, in combination, first monostable multivibrator means with pulse duration dependent upon an operating characteristic of said engine and determining partially the quantity of fuel being injected; second monostable multivibrator means connected to said first monostable multivibrator means and having a pulse duration dependent upon the pulse duration of said first monostable multivibrator means, the beginning of the pulse duration of said second monostable multivibrator being controlled by said first monostable multivibrator; first temperature-sensing means operatively connected to said first monostable multivibrator means for influencing the pulse duration of said first monostable multivibrator means; and second temperature-sensing means operatively connected to said second monostable multivibrator means for influencing the pulse duration of said second monostable multivibrator means, whereby the quantity of fuel injected is determined by the pulse durations of said first and second monostable multivibrator means, said first temperature-sensing means being arranged on the cylinder head of said internal combustion engine, said second temperature-sensing means being arranged in the oil flow circuit of said engine.