US3741171A - Timing circuit for opening fuel injection valves - Google Patents

Abstract

A fuel-injection arrangement for internal combustion engines with electromagnetically actuated fuel-injection valves and intake manifold. A monostable multivibrator provides output pulses having a duration dependent on at least one operating parameter of the engine, such as the suction pressure within the manifold behind the throttle valve. A pulse-extending stage connected to the monostable multivibrator emits an extending pulse adjoining each pulse from the multivibrator and having a duration which depends on the duration of the preceding pulse from the multivibrator. A second monostable multivibrator has an unstable state duration beginning with the extending pulse and lasting for a fraction of the duration of the extending pulse. A compensating network connected to the pulse-extending stage influences the duration of the extending pulse by either increasing or decreasing the duration of the extending pulse.

Description

United States Patent 1 Dautel TIMING CIRCUIT FOR OPENING FUEL-INJECTION VALVES [75] Inventor: Wolfgang Dautel, Esslingen,

[21] Appl. No.: 168,137

[30] Foreign Application Priority Data Aug. 8, 1970 Germany P 20 39 486.9

[52] U.S. CL... 123/32 EA, 123/119 R, 123/140 MP [51] Int. Cl. F0211 5/00 [58] Field of Search 123/32 R, 32 EA,

123/32 AE,119 R [56] References Cited I UNITED STATES PATENTS 3/1970 5/1961 Zechnall et a1 133 32 EA lnoue 123/119 R June 26, 1973 Primary Examiner-Laurence M. Goodridge AttorneyMichael S. Striker [5 7] ABSTRACT A fuel-injection arrangement for internal combustion engines with electromagnetically actuated fuelinjection valves and intake manifold. A monostable multivibrator provides output pulses having a duration dependent on at least one operating parameter of the engine, such as the suction pressure within the manifold behind the throttle valve. A pulse-extending stage connected to the monostable multivibrator emits an extending pulse adjoining each pulse from the multivibrator and having a duration which depends on the duration of the preceding pulse from the multivibrator. A second monostable multivibrator has an unstable state duration beginning with the extending pulse and lasting for a fraction of the duration of the extending pulse. A compensating network connected to the pulseextending stage influences the duration of the extending pulse by either increasing or decreasing the duration of the extending pulse.

8 Claims, 2 Drawing Figures 26 52 77 as "2 i TIMING CIRCUIT FOR OPENING FUEL-INJECTION VALVES BACKGROUND OF THE INVENTION The present invention relates to a fuel-injection arrangement for an internal combustion engine which is equipped in particular with intake manifold injection. A control arrangement determines the opening duration of at least one electromagnetically actuated fuelinjection valve. This control arrangement is preferably constructed of a monostable multivibrator having output pulses with duration made dependent on at least one operating parameter of the engine. Such a parameter is preferably the suction pressure within the intake manifold prevailing behing the throttle valve. An electronic pulse-extending stage is connected to the monostable multivibrator and provides an output pulse adjoining the pulse emitted by the multivibrator. The duration of the pulse from the pulse extender is dependent upon the duration of the output pulse from the monostable multivibrator immediately beforehand. A second monostable multivibrator whichis connected to the first multivibrator has an unstable state which be gins with the pulse from the extending stage and has a duration which is a fraction of the pulse from the extended stage.

In fuel-injection arrangements of the above species, the quantity of fuel injected can be made particularly precise in relation to the speed and load of the engine, for every suction cycle in a cylinder of the engine. This has the advantage above all that injurious exhaust gases from the engine may be held at a minimum. In order to fit the opening duration of the injection valves to the prevailing operating condition, the fuel-injection arrangements known in the art use different devices which provide the required electrical information as a function of the operating conditions, for the control purposes. These devices, however, cannot be massfabricated while maintaining the required narrow tolerances at economical costs. The present. invention, therefore, has as its basic object to provide an arrangement through which the tolerances of the individual devices as well as the tolerances of the engine are compensated through a correcting or compensation control device. This correction is superimposed so that-the magnitude of the opening duration is either shortened or extended and remains constant over the entire speed range. This is made so that too large an influence is avoided at high speeds or high suction pressure. To provide the desired correction, an adjustable voltage divider is provided in conjunction with the fuelinjection arrangement. This adjustable voltage divider SUMMARYv OF THE INVENTION A fuel-injection arrangement used for internal combustion engines provided with intake suction manifold and electromagnetically actuated injection valves. A first monostable multivibrator provides output pulses having a duration made dependent on at least one operating parameter of the engine, such as the suction pressure within the intake manifold behind the throttle valve. A pulse-stretching or extending stage is connected to the first monostable multivibrator and emits an extending pulse adjoining immediately the pulse from the first monostable multivibrator. The duration of the extending pulse is made dependent upon the preceding output pulse from the first monostable multivibrator. A second monostable multivibrator is connected to the first monostable multivibrator and has an unstable state duration which begins with the extending pulse and lasts for a fraction of the duration of this extending pulse. A compensating network is connected to the first monostable multivibrator and the pulseextending stage for influencing the duration of the extending pulse.

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 of the fuelinjection arrangement for an internal combustion engine, in accordance with the present invention;

FIG. 2 is a pulse-timing diagram of pulses prevailing in the circuit shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, and in particular to FIG. 1, the fuel-injection arrangement shown therein is intended for operating a four-cylinder internal combustion engine 11. The sparkplugs 12 of this engine are connected to a high-voltage ignition arrangement, not

shown. An electromagnetically actuated injection valve 14 is provided for each cylinder branch leading from the intake manifold 13. These valves 14 are located directly in proximity of the individual cylinders of the internal combustion engine, and in particular in proximity to the inlet valves, not shown. Fuel from a distributor 16'is transmitted to each injection valve through a fuel line 15. The fuel pressure within the distributor l6 and the fuel lines 15 is maintained at approximately 3 atm. through means of an electrically motor-driven pump 17 and a pressure regulator 18.

Each injection valve 14 possesses an electromagnetic coil, not shown. One end of each coil is connected to ground potential, whereas the other end of each coil is connected through one of the interconnecting lines 19, with one of the four resistors 20. In the embodiment shown, all injection valves are simultaneously operated in synchronous manner relative to the crankshaft rotations of the engine to actuate them to their open positions. This occurs through the application of an electrical opening pulse 1,. The duration of this pulse determines the duration of the fuel injection period. The power stage 22 is used for actuating the injection valves, and is described in further detail below.

The electronic control arrangement controls as'an essential part, a monostable multivibrator 25, an inverting stage 26, a pulse-extending stage 27 connected to the stage 26, and an OR gate 28 to which the power stage 22 is connected. A correction circuit or compensation circuit 30 is, furthermore, provided.

The monostable means 25, have a multivibrator includes an input transistor 31 and an output transistor 32 having its base connected to the collector of the transistor 31. From the collector of the output transistor 32, leads a series circuit to the positivesupply line 33, through a primary winding 35 of a transformer 36, and a resistor 34. The transformer 36 has an adjustable core- 37. The core 37 of this transformer is mechanically'coupled, through linkage 38, with the membrane (not shown) of a pressure sensor 39. This pressure sensor 39 is connected to the intake manifold 13 of the engine, and is located after the throttle valve 41 which is actuated by the accelerator, when viewed in the direction of intake in the manifold 13.

The input transistor 31 of the multivibrator 35 is maintained conducting in its inoperative state, through a resistor 43 which is connected between the base of I this transistor and the positive supply line 33. A diode 44 is, furthermore, connected between the base of transistor 31 and the primarywinding 35 of the transformer 36. The other terminal of this primary winding of the transformer is connected to the junction of two resistom 46 and 47 which serve as a voltage divider.

The crankshaft 50 of the engineis coupled to a triggering means cam 51-comprising a which actuates a switching arm 53 connected to the negative voltage supply line 52 of a power supply not further shown. The actuation of the switching arm 53 produces pulses J, for switching the multivibrator 25 to its unstable state, in a synchronous manner relative to the crankshaft rotations. A charging resistor 55 is connected to the fixed contact 54 associated with the switching arm 53, and

one electrode ofa coupling capacitor 56 is connected to the junction of the terminal 54 and the resistor 55. The other electrode of this capacitor 56 leads to the negative voltage supply line 52 through a resistor 57. At the same time, a diode 58 is connectedbetween the base of transistor 31 and the junction of the capacitor 56 and resistor 57. As long as the switching arm 53 is in the open position shown in FIG. 1, the capacitor 56 can chargethrough the two resistors 55 and 57 and acquire the voltage determined from that prevailing across voltage supply ines 52 and 33. When the switching arm 53 is actuated by the'cam 51 so that it becomes pressed against contact 54, the positively charged electrode of the capacitor 56 becomes connected with negative potential. As aresult, the base of the input transistor 31 strongly acquires negative potential so that the transistor 31 becomes turned off and the output transistor 32 becomes turned on.

The collector current of the output transistor 32 which flows through the primary winding 35, induces a voltage within the secondary winding 45, so that the input transistor 31 is further held turned off. The duration of the time during which the transistor 31 is thus turned off, is thereby determined by the pressure prevailing within the intake manifold 13 of the engine. When this pressure drops considerably below the outer atmospheric pressure when the throttle valve 41 is either closed or almost closed, then the pressure sensor 39 lifts the core 37 in the direction of the arrow in the drawing, and increases thereby the air gap in the transformer 36. The inductance of the primary winding 35 is thereby considerably decreased. In view of such decreased induced voltage, the input transistor 31 then turns rapidly to its initial conducting state, and the output transistor 32 becomes turned off anew. The pulse 1,, appearing at the collector of the output transistor 32 has, thereby, a short duration of approximately 1.2 msec.

When, however, the accelerator or gas pedal 40 is depressed and the throttle valve 41 is thereby moved into its open position, the air pressure behind the throttle valve is only slightly below that of the outer atmospheric air, even when the speed of the engine is substantially high. Since under these circumstances the core 37 can only be lifted slightly, the primary winding 35 has a substantially high inductance, and this leads to a slow rise of the collector current in the primary winding 35. The pulse J has an accompanying larger pulse duration, thereby, of approximately 4.2 msec.

In the embodiment shown, the pulse J,, is taken from the inverting stage 26 of the output transistor 32, and is applied to the pulse-stretching or extending stage 27. This stage 27 produces directly an extended pulse J, connected to the pulse J,,. The duration of the pulse J, is larger than the duration of thepulse J by an adjustable factor. This factor can be made dependent on different operating conditions of the engine, as shown in the art. Such operating conditions of the engine can be, for example, the cooling water temperature.

in particular, the pulse stretcher 27 contains a storage capacitor 60, a charging transistor 61, a discharging resistance ineans have in form of a transistor 62, and a switching transistor 63 which has its. emitter directly connected to the minus voltage supply line 52. The base of this transistor is .connected through a resistor 64 to this minus voltage supply line, and at the same time, to one electrode of the capacitor 60, through a diode 83. The collector of the switching transistor 63 is connected with its base to the collector of the transistor 62, through the diode 83. The base of the discharge transistor 62, on the other hand, is connected to the junction of two resistors 65 and 66 forming a voltage divider. The emitter of transistor 62 leads 'to the posi tive supply line 33 through a resistor 67. 1 t

The collector of the charging transistor 61 is connected'to the other electrode of the storing capacitor 60. This transistor is connected as an emitter follower, since its emitter leads to the positive supply line 33 through the resistor 69, and its base is directly connected to the collector of the inverting'transistor 70 of the inverting stage 26. A resistor 73 is connected between the collector of the transistor 70 and the positive supply line 33. A resistor 71, furthermore, is connected between the base of transistor 70 and the voltage supply line 52. A resistor 72 is connected between the collector of the output transistor 32 and the base of transistor 70.

The collector of the transistor 70 leads to the base of transistor 75, through a resistor 76. The transistor 75 belongs to an OR gate 28. A resistor 77 is connected between the base of the transistor 75 and the negative supply line 52. A coupling resistor 78 is, furthermore, connected between the base of this transistor 75 and the collector of the transistor 63. A resistor 68 is connected between the junction of resistor 78 and the collector of transistor 63, and the positive supply line 33. The collector of transistor 75 leads to the positive supply line 33 through a resistor 79, whereas a resistor 80 is connected between the emitter of transistor 75 and the negative supply line 52. The base of a transistor 81 is directly coupled to the emitter of transistor 75. This transistor 81 is of the npn type, and forms a power stage 22 together with the pnp power transistor 80.

The principle of the circuit described thus far is known in the art. The operation of this circuit can, therefore, be described as follows: When the engine operates the switching arm 53 and closes it through the cam 51 during each rotation of the crankshaft, the input transistor 31 becomes turned off, and the pulse J,, is generated in the manner described above. The duration of this pulse depends upon the rotational speed of the engine and the throttle valve position. During the interval or duration of this pulse, the transistor 70 of the AND gate 26 is turned off, so that the transistor 75 belonging to the OR gate 28 becomes conducting through the first coupling resistor 76. As a result, the transistor 81 and the power transistor 82 are also turned on. In the initial state or inthe inoperative state, the collector potential of the charging transistor 61, as well as the collector potential of the conducting inverting transistor 70 are substantially at the potential of the negative supply line 52. The voltage U across the storage capacitor 60 is then substantially zero. As soon as a pulse 1,, begins, however, the base potential of the charging transistor 61 acquires a magnitude which is intermediate the voltage between the line 33 and the negative line 52, in view of the base current flowing through the resistor 73 of the OR stage 75. The charging transistor 61, consequently,can deliver a constant charging current for the storage capacitor 60. Within the duration of the pulse J,,, the voltage U, rises across the capacitor60 in a linear manner, as shown in FIG. 2. This linearizing votlage takes place from the instant of time t, to the terminal instant 2 of the pulse 1,. However, as soon as the end of this pulse is reached and the inverting transistor 70 becomes again conducting, the collector of this transistor receives a substantially large negative potential, as does also the collector of the charging transistor 61. As a result, the charge accumulated in the meantime on the capacitor 60 causes the base of the switching transistor 63 to be also strongly negative, so that the transistor 63 becomes turned off until the charge disappears through the discharge transistor 62. v

Under the conditions determined by FIG. 2, the discharge process takes place from the instant of time until the instant t During this time interval the switching transistor 63 is again conducting. Since the OR transistor 75 can be held turned on through the second coupling resistor 78 and the collector resistor 68 while the switching transistor 63 is turned off, an extended pulse .1, becomes joined to the pulse J,,. These two pulses together form a pulse J, which determines the opening duration of the fuel injection valves, and therefore the quantity of fuel injected.

As shown in the lower parts of FIG. 2, the discharge of storage capacitor 60 occurs during the interval of the extended pulse 1,, in a manner which is not constant, and the discharge takes place through the transistor 62. The correcting or compensation circuit 30 provides that for the entireengine speed range as well as load range, the extended pulse is compensated or corrected so that it remains constant. In particular, the compensation arrangement 30 has a monostable stage which has a constant time interval of approximately 1 millisecond. The monostable stage consists of a transistor 85 which is of the npn type and has its base connected to the negative supply line 52, through a resistor 86. The base of this transistor is also connected to the cathode of a diode 87, while the anode of this diode leads to the positive supply line 33 through a resistor 88. This resistor 88 maintains the transistor 85 conducting during its initial or inoperative state. In order that the transistor is switched to its unstable, nonconducting state through the pulse 1,, provided by the multivibrator 25, the base of transistor 85 leads to the collector of the, input transistor 31 of the multivibrator 35, through a resistor 89 and capacitor 90. The time constant of this series RC circuit is approximately 1 millisecond. A voltagedivider is, furthermore, provided within the circuit 30. This voltage divider forming part of an adjustment means consists of fixed resistors 91 and 92, and a potentiometer 93 between them.

The movable contact 94 of the potentiometer is connected to the anodes of two diodes 96 and 97, through a resistor 95 which serves as a limiting resistor. The diode 96leads to the positive supply line 33 through a resistor 98, and to the collector of transistor 85. The cathode of the-other diode 97 is connected to the emitter of the discharge transistor 62 of the pulse-extension stage 27. During the correcting or compensation interval T, which adjoins directly the time instant t the switching transistor 85 is turned off. Since the diode 96 is then also non-conducting, auxiliary current can be applied to the collector of transistor 62, through the diode 97. This transistor 62 provides an essentially larger discharge current from the capacitor 60 during the time interval T,. The discharge current of the capacitor 60 determines substantiallythe duration T, of the stretched or extended pulse of the stage 27. Since the auxiliary current flows only for l millisecond as a result of the time interval T, determined by the capacitor 90, the injection duration can be varied only by the amount attained during theduration T The broken line in FIG.12 represents the function of the capacitor voltage U across the storage capacitor 60. This capacitor voltage is determined by the position of the movable contact 94 of the potentiometer 93 when it is substantially near the negative potential. In this case, an extension of the injection duration occurs. The dash-dot line c is applicable, when the movable contact 94 of the potentiometer is near the positive potential, whereby a shortening of the injection duration can be achieved. The solid line b in FIG. 2 is applicable for the center position of the contact 94, at which time the compensating or correcting arrangement 30 is ineffective.

The particular advantage of the compensating or correcting arrangement described above resides in the condition that the correction or compensation is independent of the operating conditions as, for example, speed, manifold pressure, etc. Thus, the fuel injection duration is independent of these operating conditions. IN a simple manner, the influence of the additional equipment, for example the manifold pressure sensor becomes compensated through the present invention. The pressure sensor 39 can be considered as representing numerous other elements which can be compensated against their manufacturing tolerances through the correcting arrangement 30, and as a result the fuelinjection arrangement can be compensated through installation of the present invention, in an electrical manner.

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

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended 1. In a fuel-injection system for an internal combustion engine of the type including at least one electrically controlled fuel-injection valve having an electrical input, an arrangement for generating electrical valveopening pulses, comprising in combination triggering means for generating triggering signals synchronized with engine rotation; monostable means having an input connected to said triggering means and having an output connected to said electrical input of said valve, and operating upon receipt of a triggering signal for generating a first valve-opening pulse having a duration dependent upon at least one variable engine operating condition; and pulse-extending means having an input connected to said monstable means and having an output connected to said electrical input of said valve, and operative upon termination of said first pulse for generatin'g a second pulse having a duration dependent upon the duration of said first pulse and forming with said first pulse a longer composite valve-opening pulse, said pulse-extending means including timing means for determining the duration of said second pulse, said timing means comprising an energy-storing timing component so connected to said monostable means as to undergo a first change of stored energy during said first pulse and an opposite second change of stored energy which commencesupon termination in said first pulse and whose completion results in termination of said second pulse,- resistance means connected to said timing component and having a value causing said second energy change to ordinarily proceed at a first rate, and compensating means connected to said pulse-extending means and automatically operative after termination of said first pulse and'during an initial portion of said second energy change, for causing said second energy change to proceed during said portion thereof at a different second rate, and thereafter at said first rate upon fixed time period independent of the durationof said first pulse.

5. An arrangement as defined in claim 1, wherein said timing component is a timing capacitor, and wherein said compensating means comprises means operative for establishing a flow of current through said capacitor during said initial portion of said second energy change superimposed upon the component of capacitor current determined by the RC-time-constant of said capacitor and said resistance means.

6. An arrangement as defined in claim 2, wherein said selecting meanscomprises adjustable voltage divider means so connected to said pulse-extending means as to be capable of changing said second rate.

7. An arrangement as defined in claim 1, said engine having an air intake passage and a throttle valve 10- cated in said passage, and wherein said engine operating condition is the pressure prevailing in said passage downstream of said valve.

8. An arrangement as defined in calim 1, wherein said timing component is a timing capacitor, and wherein said compensating means includes a timing circuit connected to said monostable means and commencing operation upon termination of said first pulse and comprising a switching circuit including a switching transistor for initiatingoperation of said compen' sating means upon termination of said first pulse and for terminating operation of said compensating means in dependence upon operation of said timing circuit, and wherein said compensating means further includes adjusting means for changing said second rate, said adjusting means comprising an adjustable voltage divider having a mid-tap, further including a diode having one electrode connected to said mid-tap and another electrode connected to said timing component for carrying current between said mid-tap and said timing component, and another diode having one electrode connected to said mid-tap and another electrode connected to the collector of said switching transistor.

18 l III

Claims (8)

1. In a fuel-injection system for an internal combustion engine of the type including at least one electrically controlled fuelinjection valve having an electrical input, an arrangement for generating electrical valve-opening pulses, comprising in combination triggering means for generating triggering signals synchronized with engine rotation; monostable means having an input connected to said triggering means and having an output connected to said electrical input of said valve, and operating upon receipt of a triggering signal for generating a first valveopening pulse having a duration dependent upon at least one variable engine operating condition; and pulse-extending means having an input connected to said monstabLe means and having an output connected to said electrical input of said valve, and operative upon termination of said first pulse for generating a second pulse having a duration dependent upon the duration of said first pulse and forming with said first pulse a longer composite valve-opening pulse, said pulse-extending means including timing means for determining the duration of said second pulse, said timing means comprising an energy-storing timing component so connected to said monostable means as to undergo a first change of stored energy during said first pulse and an opposite second change of stored energy which commences upon termination In said first pulse and whose completion results in termination of said second pulse, resistance means connected to said timing component and having a value causing said second energy change to ordinarily proceed at a first rate, and compensating means connected to said pulse-extending means and automatically operative after termination of said first pulse and during an initial portion of said second energy change, for causing said second energy change to proceed during said portion thereof at a different second rate, and thereafter at said first rate upon termination of operation of said compensating means.

2. An arrangement as defined in claim 1, wherein said compensating means comprises adjusting means for selectably changing said second rate.

3. An arrangement as defined in claim 1, wherein said initial portion of said second energy change commences at the time of termination of said first pulse.

4. An arrangement as defined in claim 1, wherein said compensating means includes a timing circuit for maintaining said compensating means operative for a fixed time period independent of the duration of said first pulse.

5. An arrangement as defined in claim 1, wherein said timing component is a timing capacitor, and wherein said compensating means comprises means operative for establishing a flow of current through said capacitor during said initial portion of said second energy change superimposed upon the component of capacitor current determined by the RC-time-constant of said capacitor and said resistance means.

6. An arrangement as defined in claim 2, wherein said selecting means comprises adjustable voltage divider means so connected to said pulse-extending means as to be capable of changing said second rate.

7. An arrangement as defined in claim 1, said engine having an air intake passage and a throttle valve located in said passage, and wherein said engine operating condition is the pressure prevailing in said passage downstream of said valve.

8. An arrangement as defined in calim 1, wherein said timing component is a timing capacitor, and wherein said compensating means includes a timing circuit connected to said monostable means and commencing operation upon termination of said first pulse and comprising a switching circuit including a switching transistor for initiating operation of said compensating means upon termination of said first pulse and for terminating operation of said compensating means in dependence upon operation of said timing circuit, and wherein said compensating means further includes adjusting means for changing said second rate, said adjusting means comprising an adjustable voltage divider having a mid-tap, further including a diode having one electrode connected to said mid-tap and another electrode connected to said timing component for carrying current between said mid-tap and said timing component, and another diode having one electrode connected to said mid-tap and another electrode connected to the collector of said switching transistor.

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