US3820198A

US3820198A - Switching circuitry for sequential fuel injection

Info

Publication number: US3820198A
Application number: US00265047A
Authority: US
Inventors: B Scofield
Original assignee: International Harverster Corp
Current assignee: Navistar International Corp
Priority date: 1972-06-21
Filing date: 1972-06-21
Publication date: 1974-06-28
Anticipated expiration: 1991-06-28
Also published as: FR2189639A1; GB1436013A; CA993979A; FR2189639B1; JPS4950328A; DE2331264A1; DE2331264B2; IT985675B

Abstract

SWITCHING CIRCUITRY FOR SEQUENTIAL FUEL INJECTION IN WHICH TRANSISTOR DRIVER STAGES FOR INJECTOR VALVE ACTUATORS ARE COUPLED TO AND GATE MEANS HAVING INPUTS TO WHICH TIMING SIGNALS ARE APPLIED FROM FLIP-FLOP MEANS AND HAVING ADDITIONAL INPUTS TO WHICH CONTROL SIGNALS ARE APPLIED FROM A SEQUENCING CIRCUIT, PREFERABLY COMPRISING A DIGITAL COUNTER AND DECODER GATES FOR DEVELOPING THE CONTROL SIGNALS. THE CONTROL SIGNALS HAVE A DURATION SUFFICIENT TO ALLOW THE TIMING SIGNALS TO EFFECT OPENING OF THE INJECTOR VALVES FOR NEARLY 180 DEGREES OF CRANKSHAFT ROTATION, IN TIMED RELATION TO THE INTAKE STROKES. IN ONE EMBODIMENT, DESIGNED FOR A FOUR CYLINDER ENGINE, A SINGLE TIMING FLIPFLOP IS USED WHILE IN OTHER EMBODIMENTS, DESIGNED FOR EIGHT CYLINDER ENGINES, TWO FLIP-FLOPS ARE USED IN A MANNER TO PERMIT OVERLAP OF THE TIMES OF OPENING OF THE FUEL INJECTION VALVES. ADDITIONAL FEATURES RELATE TO THE APPLICATION OF PRE AND POST BIAS SIGNALS IN COMBINATION WITH A SHORT DURATION VALVE OPENING PULSE IN A MANNER TO PERMIT RAPID AND ACCURATE CONTROL OF THE OPENING AND CLOSING OF THE INJECTOR VALVES.

Description

United States Patent [191 Scot'ield June 28, 1974 SWITCHING CIRCUITRY FOR SEQUENTIAL FUEL INJECTION [75] Inventor: Bruce A. Scofield, Fort Wayne, Ind.

[73] Assignee: International Harvester Company,

Chicago, Ill.

[22] Filed: June 21, 1972 [21] Appl. No.: 265,047

[52] US. Cl. 123/32 EA, 317/123, 123/119, 123/139 AW, 123/140 MC [51] Int. Cl. F02m 51/06 [58] Field of Search 123/32 EA, 119 R [56] References Cited UNITED STATES PATENTS 2,815,009 12/1957 Pribble 123/32 EA 3,612,009 10/1971 Kamazuka et al 123/32 EA 3,612,011 10/1971 MonpetiLf. 123/32 EA 3,621,826 ll/1971 Chrestensen 123/148 E Primary ExaminerLaurence M. Goodridge Attorney, Agent, or FirmFrederick J. Krubel; Floyd B. Harman [57 ABSTRACT Switching circuitry for sequential fuel injection in which transistor driver stages for injector valve actuators are coupled to AND gate means having inputs to which timing signals are applied from flip-flop means and having additional inputs to which control signals are applied from a sequencing circuit, preferably comprising a digital counter and decoder gates for developing the control signals. The control signals have a duration sufficient to allow the timing signals to effect opening of the injector valves for nearly 180 degrees of crankshaft rotation, in timed relation to the intake strokes. In one embodiment, designed for a four cylinder engine, a single timing flip-flop is used while in other embodiments, designed for eight cylinder engines, two flip-flops are used in a manner to permit overlap of the times of opening of the fuel injection valves. Additional features relate to the application of pre and post bias signals in combination with a short duration valve opening pulse in a manner to permit rapid and accurate control of the opening and closing of the injector valves.

17 Claims 11 Drawing Figures COMPUTER TIMER SEQUENCE 38W CIRCUIT *25 I i 1 l 1 AIR 1 DRIVER 324 J IEMP CIRCUIT IO\, 11111 F UEL TANK PATENTED H m 3820.198

SHEET 1 OF 9 FIG 3 3 i 89 COMPUTER TIMER 1 SEQUENCE 38 CIRCUIT *25 I l I I AIR i DRIVER J24 TEMP CIRCUIT /O\ 35 1/1/1111 FUEL TANK FIG 2 2-B/T f [30 COUNTER 53 l I l I 129 DECODER -52 54 I Q55 DELAY FLIP MV FLOP 4a 49 50 5/ AND D w AND ;Q, V08 47 DR L07? L13)? LDR 45 57 SHKU 2 (IF 9 PATENTEDJUH28 I974 MTENTEI] JUN 2 8 I974 SHEET 3 BF 9 PATENTEDJUII28 I974 SHEET 9, [IF 9 I I I I I I I f'llll'lulllllllllIlII-lllllll 1 SWITCHING CIRCUITRY FOR SEQUENTIAL FUEL INJECTION This invention relates to switching circuitry for sequential fuel injection control and more particularly to circuitry which is highly efficient and reliable in operation and which permits very accurate control of the timing of opening and closing of sequentially operated fuel injector valves and thereby highly accurate control of the amounts of fuel injected.

BACKGROUND OF THE INVENTION Sequential fuel injection systems have heretofore been proposed using one solenoid operated valve for each cylinder to allow flow of a controlled amount of fuel during each intake stroke, with the amount of fuel being controlled by controlling the duration of electrical pulses applied through a distributor or the like used to allocate the application of the pulses to the valves in accordance with the firing order of the engine. Such distributors have not been entirely satisfactory and reli able in operation. For example, with a distributor in which a rotating contact has sliding engagement with commutator segments, there are problems with arcing, high contact resistance and wear, interfering with proper performance and necessitating frequent servicmg.

SUMMARY OF THE INVENTION This invention was evolved with the general object of overcoming the disadvantages of prior art systems and of providing a system permitting highly efficient, accurate and reliable control of the application of control signals to injector valve actuators.

A more specific object of the invention is to provide sequencing circuitry using solid state devices and integrated circuits for maximum reliability coupled with low cost.

Another object of the invention is to provide a system permitting sequential operation of injector valves and permitting opening of the valves through substantially 180 degrees of crankshaft rotation.

A further object of the invention is to provide a sys tem permitting control of operating current for rapid and accurate opening and closing of injector valves.

The systems of this invention may be used, for example, in controlling injection of fuel in an internal combustion engine provided with a solenoid-operated injector valve for each cylinder. The injector valves may be coupled to a header in which the fuel may be maintained at a substantially constant pressure and each injector valve may, for example, be arranged to inject fuel into the intake manifold just ahead of the intake valve for the associated cylinder. By controlling the duration of the time interval in which each injector valve is opened, the amount of fuel supplied is thereby controlled.

In accordance with this invention, the injector valve actuators are coupled to AND gates having first inputs to which timing signals are applied from flip-flop means and having second inputs to which control signals are applied from a sequencing circuit. Each control signal may have a duration of approximately 180 degrees of crankshaft rotation, synchronized with the opening of the intake valve, and each timing signal may have a duration variable from a relatively small angle to an angle approaching 180 degrees, to pennit a wide variation in the amount of fuel supplied during each cycle.

The sequencing means preferably comprises a plurality of flip-flops forming a digital counter arranged to count a predetermined number of pulses equal to the number of cylinders and decoder gate means coupled to the flip-flopsfor developing the sequencing signals.

In a system designed for a four cylinder engine, the digital counter may have two flip-flops while the timer flip-flop means may comprise a single flip-flop arranged to develop a single series of timing signals which are applied to the first inputs of all of the gate means. In a system designed for an eight cylinder engine, the flip-flop means comprises first and second flip-flops arranged to develop first and second series of timing signals in phase displaced relation, one series being applied to the second inputs of one group of four gates and the other series being applied to the second inputs of a second group of four gates. The beginnings of the timing signals of the first series may be displaced degrees crankshaft rotation from the beginnings of the second series of timing signals. With the two flip-flops and the division of the gates into two groups, the times of openings of the injector valve means can overlap and each valve can be opened for up todegrees of crankshaft rotation.

The two flip-flops may be controlled by two timers, using two alternative circuit arrangements. In one arrangement, the two timers are triggered alternately by signals in 90 degree phase relation and each timer controls one of the flip-flops. In another arrangement, the timers are connected in cascade with a first timer being triggered by pulses having a 90 degree phase difference from one pulse to the next and the second timer is triggered from the first timer, with a third flip-flop being used for alternately controlling the two flip-flops from the second timer.

Additional important features of the invention relate to the application of pre and post bias signals in combination with a short duration valve opening pulse in a manner such as to permit rapid and accurate control of the times of opening and closing of the injector valves.

This invention contemplates other objects, features and advantages which will become more fully apparent from the following detailed description taken in conjunction with the accompanying drawings. BREIF DE- SCRIPT ION OF THE DRAWINGS FIG. I is a schematic diagram of a sequential fuel injection system for a four cylinder engine, incorporating switching circuitry according to the invention;

FIG. 2 is a block diagram of sequence and driver circuits of the system of FIG. 1;

FIG. 3 is a circuit diagram of counter, decoder, gating and driver circuitry shown in block form in FIG. 2;

FIG. 4 is a wave form diagram for explanation of the circuitry of FIGS. 2 and 3;

FIG. 5 is a schematic diagram of one preferred form of switching circuitry for an eight cylinder engine;

FIG. 6 is a wave form diagram for explanation of the operation of the circuitry of FIG. 5;

FIG. 7 is a schematic diagram of another preferred form of system designed for an eight cylinder engine;

FIG. 8 is a schematic diagram of a third form of system designed for an eight cylinder engine;

FIG. 9 is a wave form diagram for explanation of the operation of the systems of FIGS. 7 and 8;

FIG. 10 is a circuit diagram of a driver stage used in the systems of FIGS. 5, 7 and 8; and

FIG. 11 is a circuit diagram of an electronic switch and a monostable multivibrator used in the system of FIG. 8.

Reference numeral 10 generally designates a sequential fuel injection system designed for a four cylinder engine, incorporating switching circuitry constructed in accordance with the principles of the invention. An individual solenoid-operated injection nozzle or valve is provided for each cylinder of an engine and each valve is opened once during every revolution of the engine cam shaft, or once during every other revolution of the drive shaft, in the case of a four cycle engine. In the system 10, designed for a four-cylinder engine, there are four injection valves, 11-14, FIG. 2, which may be mounted on an intake manifold 15 of an engine 16 in the manner as shown diagrammatically in FIG. 1. As also shown in FIG. 1, the injection valves are connected to a header 18 which is connected through a filter 19 to the outlet of a pump 20 having an inlet connected to a fuel tank 21. A pressure regulator 22 is provided between the header 18 in the fuel tank 21 to maintain the pressure in the header at a substantially constant valve which may be on the order of 40 PSIG, by way of example.

The injection valves 11-14 are connected to a driver circuit 24 controlled from a sequence circuit 25. The sequence circuit 25 receives control and triggering signals from a distributor 26 and an ignition coil 27 of the engine and controls the time intervals in which the valves 11-14 may be energized, to synchronize the injection of fuel in relation to the intake strokes of the respective cylinders. The sequence circuit 25 is also connected through

lines

29 and 30 to a timer 31 which is controlled from a computer 32.

Computer 32 controls the timer 31 and through the

sequenceand driver circuits

25 and 24 the time duration of each opening of each injection valve is controlled, the control being a function of the prevailing operating conditions at the time of injection. In the illustrated arrangement, the computer 32 receives pulses from the ignition coil 27 to develop a speed signal and is connected to

switches

33 and 34 mounted on a throttle 35 of the engine 16, switch 33 being operated when the throttle is closed and switch 34 being operated which the throttle in wide open. Computer 32 is also connected to a sensor 36 which senses intake manifold absolute pressure, to a sensor 37 which senses coolant temperature and to a sensor 38 which senses air temperature, as diagrammatically illustrated. The computer 32 may also contain circuitry for sensing acceleration and also the rate of change of intake manifold absolute pressure. In response to such sensed operating conditions, the computer 32 may develop an analog voltage output which controls the duration of a pulse generated by timer 3] and applied to the sequence circuit through line 29, the beginning of each pulse being determined by a triggering signal applied through line 30. It should be understood that the timer 31 and computer 32 are not, by themselves, part of the present invention, and, so far as concerns the switching circuitry of this invention, any suitable means could be employed to generate a timing signal or pulse of controllable duration. By way of example, the duration of the timing signal or pulse may typically be on the order of from 2 and 12 milliseconds.

Referring now to FIG. 2, the solenoids of the injection valves 11-14 are connected between ground and outputs of four driver stages 41-44 connected to a power supply terminal 45 to which battery voltage of on the order or twelve volts may be supplied. Inputs of the driver stages 41-44 are connected to the outputs of four AND gates 47-50 having inputs connected to gether into the output of a flip-flop 51 and having additional inputs connected through a decoder 52 to outputs of a tw0-bit counter 53. Inputs of the flip-flop 51 and of the counter 53 are connected to the output of a delay monostable multivibrator 54 having an input connected through a line 55 to the ignition coil 27. An additional input of the counter 53 is connected to the output of a second monostable delay multivibrator 56 having an input connected through a line 57 to the distributor 26.

In the general operation of the system, signals responsive to ignition pulses are applied through the delay multivibrator 54 to the counter 53 to advance the count thereof and also to the flip-flop 51 which is then placed in a set condition, a signal being then applied through line 30 to the timer 31 to initiate operation thereof. Timer 31 then generates a pulse of controlled length at the termination of which a signal on line 29 resets the flip-flop 51. When the flip-flop 51 is set, a signal is applied through one of the AND gates 47-50, depending upon the condition of the counter 52, .to one of the driver stages 41-44, to energize one of the injection valves 11-14 for a time interval corresponding to the timing pulse applied from the timer 31. The signal applied from the distributor 26 through the delay multivibrator 56 to the counter 53 is for the purpose of correlating the operation of the counter 53 to the firing sequence of the engine.

Referring to FIG. 3, the driver stages 41-44 include power transistors 61-64 having emitters connected to the injection valves 11-14 and having collectors connected through resistors 65-68 to the power supply terminal 45. The bases of the transistors 61-64 are connected through resistors 69-72 to the power supply terminal 45 and to the collectors of transistors 73-76 the emitters of which are connected to ground and the bases of which are connected through resistors 77-80 to a line 81 which is connected through a resistor 82 to ground and which is also connected to an emitter of a transistor 83 the collector of which is connected to the power supply terminal 45 and the base of which is connected through a resistor 84 to the output of the flipflop 51. The bases of the transistors 61-64 are additionally connected to the collectors of transistors 85-88 and also to the collectors of transistors 89-92.

The bases of transistors 85-92 are connected through resistors 93-100 to outputs of two flip-flops 101 and 102, together forming the counter 53. A reset output of flip-flop 101, on line 103 is connected to

resistors

93 and 99 and also to an input line of flip-flop 102. A set output of flip-flop 101 on line 104, is conected to

resistors

94 and 96. A reset output of flip-flop 102, on line 105 is connected to

resistors

97 and 98. A set output of flip-flop 102, on line 106, is connected to resistors and 100. A set input of both flip-flops 101 and 102 is connected through a line 108 to the output of the delay multivibrator 56. A triggering input of flip-flop 101 is connected through a capacitor 109 to the output of the delay multivibrator 54. Power supply terminals for both flip-flops 101 and 102 are connected to the junction between two resistors 111 and 112, connected between ground and the power supply terminal 45.

FIG. 4 graphically illustrates the operation of the circuitry of FIG. 3. The top four representations, numbered: l, 2", 3 and 4 indicate the intake, compression power and exhaust strokes for the engine cylinders corresponding to injection valves 11-14. It is noted that these numbers do not correspond directly to the conventional numbering of engine cylinders from front to rear. With an engine having a l,- 3, 4, 2 firing order, the

numbers

1, 2, 3 and 4 in FIG. 4 may respectively correspond to the

numbers

3, 4, 2 and l cylinders, numbered from front to rear in the engine.

Wave form 116 indicates the signal applied from the distributor 26 through the line 57 to the input of delay multivibrator 56. This signal is in the form of an ignition pulse applied to the front cylinder, corresponding to the injection valve 13, being approximately coincident with the start of the power stroke of that cylinder which is the number 3 cylinder using the designation of FIG. 4. Wave form 117 indicates the signal developed at the output of the delay multivibrator 56 which is applied through the line 108 to the set inputs of both flipflops 101 and 102. The signal is in the form of a short pulse having a trailing negative-going edge delayed by certain time interval after the triggering pulse applied from the distributor. When the trailing negative-going edge is applied to the set inputs of the flip-flops 101 and 102, it insures that they will be placed in a set condition, if not already in that condition.

Wave form 118 is that of the signal applied through line 55 to the delay multivibrator 54 from the ignition coil 27, this signal being in the form of an ignition pulse developed at a time approximately coincident with the start of every power stroke.

Wave form 119 is that of the signal developed at the output of the delay multivibrator 54 which is applied through the capacitor 109 to the triggering signal input to the flip-flop 101. This signal was in the form of a series of pulses having negative-going trailing edges delayed by short time interval after the applied ignition pulses. Such trailing edges cause the flip-flop 101 to change its state from one state to the other.

Wave form 120 is that of the set output line 104 of the flip-flop 101 which is caused to go high by the first illustrated pulse wave form 119, low" by the second, again high by the third, again low by the fourth and again high by the fifth. It is noted that the trailing edge of the pulse of wave form 117 occurs after the trailing edge of the first illustrated pulse of wave form 119 and since flip-flop 101 is already in a set condition, the pulses of wave form 117 have no effect. However, if during starting conditions, for example, the flip-flops 101 and 102 were not in set conditions when the first pulse of wave form 117 is applied, the first pulse would then operate to inusre placing both flip-flops in a set condition at this point of the operation.

Wave form 121 is that of a signal at the reset output line 103 of the flip-flop 101 while wave forms 122 and 123 are of the signals at the set and reset

output lines

106 and 105 of the flip-flop 102. It will be noted that the flip-flop 102 is shifted from one state to the other in response to negative-going portions of the signal applied thereto from the reset line 103 of the flip-flop 101, indicated by wave form 121.

Wave form 124 is that of the signal at the output of the flip-flop 51 which is shifted low by the negativegoing trailing edges of the pulses from delay multivibrator 54 (wave form 119) and which is shifted high by a signal applied from timer 3] through line 29, it being noted that the operation of the timer 31 is initiated when the flip-flop 51 is shifted low, by a signal applied through line 30.

Wave forms 125-128 are those of the signals applied to the

injection valves

11, 12, 13 and 14, which are in the form of positive pulses during the respective intake strokes of the cylinders with which valves 11-14 are associated. It is noted that during the first 180 degrees of engine rotation, the signals applied from the

reset output lines

103 and 105 of the flip-flops 101 and 102, wave forms 121 and 123, are low. Such signals are applied through the

resistors

93 and 97 to the bases of transistors and 89 which are cut off. The timing signal signal, wave form 124, is also low during part of the first 180 degrees of engine rotation and this signal is applied through the transistor 83, operative as an emitterfollower, to the line 81 and from line 81 through the resistor 77 to the base of transistor 73, which is thus also cut off. With all three

transistors

73, 85 and 89 cut off, the potential of the base of the transistor 61 rises toward the potential of the power supply terminal 45, being limited only by the flow of base-emitter current through the resistor 69, and the driver transistor 61 conducts heavily through the injection valve 11, so long as the timing signal, wave form 124, is low.

During the first l80 degrees of engine rotation, high signals are applied to the bases of

transistors

86, 87 and 88, and also 92, which are rendered conductive to place the potentials of the bases of the

driver transistors

62, 63 and 64 at values close to ground potential. The

driver transistors

62, 63 and 64 are thus nonconductive, and no card is applied to the

injection valves

12, 13 and 14.

During the next 180 degrees of engine rotation, the signals applied to the bases of

transistors

86 and 90 are both low, and the driver transistor 62 is rendered conductive for the duration of the timing signal from flipfiop 51 (wave form 124). At this time, the inputs to

transistors

85, 87 and 88 are high preventing conduction of the

transistors

61, 63 and 64.

in a similar fashion, the

driver transistors

63 and 64 are rendered conductive during the third and fourth 180 degree intervals of engine rotation, for time intervals equal to the duration of the timing signal from flipflop 51. It is noted that the wave forms 125-128, as illustrated, are rectangular pulses but in actual operation, the wave forms are distorted due to the inductance of the solenoid actuators and due to inertial effects. Because of such inductance and inertial effects,

the actual opening of the injection valve is delayed to take place after the leading edge of the applied pulse and likewise, the actual closing of the valve may be delayed. However, the actual time of opening of each in- 60 jection valve and thereby the amountof fuel injected areproportional to the duration of the timing pulse, to within close limits of accuracy.

It is also noted that each injection valve may be opened throughout nearly degrees of crankshaft rotation which is important in that the required instantaneous rate of flow through each injection valve or nozzle, during the time it is opened, under maximum total flow of conditions, is reduced since the valve is open for a longer time interval. The requirements as to design and construction of the valve are not nearly as stringent as they would be if the valve had to be opened for short periods of time with a correspondingly higher required instantaneous rate of flow. Also, variations in opening and closing times of the valves, as well as varia tions in the accuracy of generation of the timing signals, have a reduced effect on overall accuracy. By way of example, the system may be designed for a 6 millisecond maximum pulse length, for operation and up to 5,000 RPM.

It is noted that FIG. 2 illustrates the functional operations performed, whereas FIG. 3 illustrates the implementation of such functions in an actual circuit. in FIG. 2, the function of the decoder 52, illustrated in block form, is to produce a number of outputs in sequence, the number being equal to the number of engine cylinders, and the function of the illustrated AND gates 47-50 is to combine such outputs of the decoder 52 with the output of the timing flip-flop 51. In the actual circuit of FIG. 3, these functions are implemented by using three input NOR gates for each of the driver transistors 61-64. For example,

transistors

73, 85 and 89 and associated circuit elements form a three input NOR gate for the driver transistor 61, requiring three low inputs to produce a high output at the base of driver transistor 61. In a strict sense, there is no AND gate as such as that there is no individual circuit in which all inputs must have the same value to make the output equal to any of the inputs. However, in a broader sense, the functional operations are nevertheless performed, in that the

transistors

85 and 89 perform a decoding function, allowing the collectors thereof to go toward high only when the flip-flops 101 and 102 are in prescribed states, and through the common connection of the collectors of

transistors

85, 89 with the collector of the transistor 73, an AND function is performed in that the decoding function must be performedand the timing flip-flop 51 must be in a certain state in order to make the output have a certain value. It will be understood that other types of logic circuit elements might be used to implement the prescribed functionsand that reference herein to AND and OR gates is intended in a functional sense and not as limiting the invention to particular circuits for implementation of the prescribed functions.

Referring now to FIG. 5, reference numeral 130 generally designates another preferred type of system, designed for use with an eight cylinder engine. As shown, eight injection valves 131-138 are connected between a voltage supply terminal 140 and output terminals of eight driver stages 141-148 having additional terminals connected to ground. Two timing flip-

flops

149 and 150 are provided, an output of the flip-flop 149 being connected to inputs of one group of four AND

gates

151, 153, 155 and 157 and an output of the flip-flop 150 being connected to inputs of a second group of four AND

gates

152, 154, 156 and 158, the outputs of the AND Gates 151-158 being respectively connected to inputs of the driver stages 141-148.

Additional inputs of the AND gates 151-158 are connected to outputs of eight OR gates 161-168 having inputs connected to lines 171-178 which are connected to outputs of an octal decoder 179, which is connected to athree bit counter 180. As shown, the inputs of OR I gate 161 are connected to

lines

171 and 172, the inputs of OR gate 163 are connected to lines 173 and 174, the

inputs of OR gate 165 are connected to lines and 176, and the inputs of OR gate 167 are connected to

lines

177 and 178. Similarly, the inputs of OR gate 162 are connected to

lines

172 and 173, the inputs of OR gate 1 are connected to lines 174 and 175, the inputs of OR gate 166 are connected to

lines

176 and 177 and the inputs of OR gate 168 are connected to

lines

178 and 171. The three bit counter 180 is connected through

lines

181 and 182 to an exitation and conditioning circuit 183 controlled from an engine firing sensor 184. The exitation and conditioning circuit 183 may include delay monostable multivibrators similar to the

multivibrators

54 and 56 of the circuit of FIG. 2 while the engine firing sensor 184 may include connections to a distributor and ignition coil of the engine, as described above in connection with FIGS. 1 and 2. It will be understood, however, that other forms of circuits may be employed for applying synchronizing signals to the three bit counter 180.

The flip-

flops

149 and 150 have set inputs connected to lines 185 and 186, line 185 being connected through four diodes 187 to the

lines

171, 173, 175 and 177 and the line 186 being connected through four diodes 188 to

lines

172, 174, 176 and 178. The diodes 187 and the diodes 188 form two OR gates, applying triggering signals to the flip-

flops

149 and 150 in response to prescribed changes in state of the signals on the lines 171-178. Such triggering signals are also applied to an A timer 189 and a B timer 190 which after controlled time intervals, apply reset signals to the flip-

flops

149 and 150.

Timers

189 and 190 are connected to a line 191 which may be connected to a computer operative in the same manner as the computer 32, described above in connection with FIG. 1.

FIG. 6 illustrates the operation of the system 130 of FIG. 5. The top eight diagrams are of the intake, compression, power and exhaust strokes of the eight cylinders of the engine. numbered 1 through 8 and respectively corresponding to the injection valves 131-138. The numbering of the representations corresponds to the order of firing and not to the position of the engine cylinders. With an engine having a l, 8, 4, 3, 6, 5, 7, 2 firing order, the numbers 1-8 in FIG. 6 may respec tively correspond to

cylinder locations

6, 5, 7, 2, 1, 8, 4 and 3.

Wave forms 201-208 are of the signals on lines 171-178, respectively, these signals being progressively or sequentially low during one complete cycle, corresponding to two turns of the engine crankshaft, each of the signals being low for 90 degrees of crankshaft rotation.

Wave forms 211-218 are of the signals at the outputs of the OR gate 161-168, each of such signals being low during two consecutive low signals on the lines 171-178, and being thus low for 180 degrees of crankshaft rotation.

Wave forms 219 and 220 are of the signals at the outputs of the flip-flops 149 and 1511, applied to the AND

gates

151, 153, 155 and 157 and the AND

gates

152, 154, 156 and 158. When any one of the

lines

171, 173, 175 or 177 goes low, a signal is applied through one of the diodes 187 to the flip-flop 149 to cause the output thereof to go low and at the same time, the operation of the A timer 189 is initiated from the same signal, applied from line 185. After a certain time interval, determined by the voltage applied on line 191, the A timer 189 applies a reset signal to the flip-flop 149 causing the output thereof to again go high. Similarly, the flipflop 150 is triggered to a set condition when anyone of the signals on

lines

172, 174, 176 or 178 goes low and is reset after a certain time interval by a signal applied from the B timer 180.

Wave forms 221-228 are of the signals at the outputs of the AND gates 151-158. It will be-noted that the signal at the output of the AND gate 151 is low when both the signal applied from OR gate 161 (wave form 211) and the signal at the output of the flip-flop 149 (wave form 219) are low. Similarly, thesignal at the output of I the AND gate 152 (wave form 222) is low when both the output of the OR gate 162 (wave form 212) and the output of the flip-flop 150 (wave form 220) are low. It will be noted that through the division of the circuitry into two groups and through the use of the two flipflops 149 and two

timers

189 and 190, the output signalscan overlap. Thus, the end of the low portion of the signal applied to the driver 141 can occur after the beginning of the low portion of the signal applied to driver 142. The driver circuits, described hereinafter in connection with FIG. 10, are arranged to energize the respective injection valves when the inputs thereof are low. The reset signal applied to each of the flip-

flops

149 and 150 from the

respective timer

189 or 190 may occur at any point from substantially less than 90 degrees of crankshaft rotation to nearly 180 degrees, following the triggering of the flip-flop to its set condition and thus the injection of fuel into each cylinder of the engine may occur throughout corresponding time intervals.

Referring now to FIG. 7, reference numeral 230 generally designates another type of system according to the invention designed for an eight cylinder engine. The system 230 is similar to the system 130 of FIG. 5, incorporating the eight injection valves 131-138, drivers 141-148, flip-

flops

149 and 150, AND gates 151-158, OR gaes 161-168, octal decoder 179, three bit counter 180, exitation and conditioning circuit 183, engine firing sensors 184 and

diodes

187 and 188, connected in the same manner as shown in FIG. and as described above.

In the circuit 230, reset inputs of flip-

flops

149 and 150 are connected to outputs of a pair of AND

gates

231 and 232 having inputs connected to reset and set outputs of a flip-flop 234, which has set and reset inputs connected to the outputs of a pair of

gates

235 and 236 having inputs connected to the lines 185 and 186. A and

B timers

237 and 238 are provided which are operated sequentially, the A timer 237 being triggered by a signal from the exitation and conditioning circuit 183 each time that a delayed ignition pulse or clock signal is applied from the exitation and conditioning circuit 183 to the three bit counter 180. The B timer 238 is triggered from the A timer 237 when the A timer 237 times out. The output of the timer 237 is connected to inputs of the

gates

235 and 236 while the output of timer 238 is connected to inputs of both AND

gates

231 and 232.

The operation of the system 230 is similar to that of the system 130 of FIG. 5 with respect to the generation of the wave forms 201-208 and 211-218, illustrated in FIG. 6. The differences in operation are illustrated by wave forms in the upper part of FIG. 9. Referring thereto, wave form 241 is that of the signal at the output of the A timer 237 which goes high in response to signals applied from the exitation and conditioning circuit 183, approximately coincident with each clock signal applied to the counter 180 to change the state thereof. The output of timer 237 remains high for a controllable time interval controlled by a signal from a computer, applied on line 240. When the output of the timer 237 goes low it triggers the B timer 238 so that the output of timer 238 goes high and also, through one or the other of the

gates

235 or 236, the flip-flop 234 is triggered from one state to the other. When the signal on any one of the

lines

171, 173, 175 or 177 is low, the negative-going part of the output signal of timer 237 triggers the flip-flop 234 to a set condition. Similarly, when the signal on any one of the

lines

172, 174, 176 or 178 is low, the negative-going portion of the signal output of the timer 237 triggers the flip-flop 234 to a reset condition. After a controllable length of time following triggering of the timer 238, the output signal thereof goes low, wave form 242 being that of the output of the timer 238.

Wave forms 243 and 244 are those of the outputs of flip-

flops

149 and 150 while wave form 246 is that of the set output of flip-flop 234 which is applied to the V gate 232. The reset output of flip-flop 234 is of opposite phase and is applied to the gate 231.

In the operation as detected, flip-flop 149 is triggered each time that any one of the signals on

lines

171, 173, 175 or 177 goes low. It is triggered to a set condition in which the output thereof, shown by wave form 243 is low and it remains low until the output of the counter 238 goes low while at the same time the reset output of the flip-flop 234 is low. Thus, the output of flip-flop 149 is low for a time interval equal to the time interval of operation of the timer 237 plus the time interval of operation of the timer 238. In a similar fashion, the flipflop 150 is triggered each time that any one of the signals on the

lines

172, 174, 176 or 178 goes low and the output of flip-flop 150 remains in a low condition until the output of the B timer 238 goes low while at the same time, the flip-flop 234 is in a set condition. Thus, the flip-flop 150 remains in a set condition, with its output low for a time interval equal to the sum of the time intervals of operation of the

timers

237 and 238. Accordingly, the time intervals of operation of the

flipflops

149 and 150 may overlap as illustrated. This will be the case when the output signals, applied to the injection valves, are to have durations of greater than degrees of crankshaft rotation. The circuitry operates in the same manner, however, when the output signals, applied to the injection valves, have a duration of less than 90 degrees of crankshaft rotation.

Wave forms 251-258 are those of the signals applied to the driver stages 141-148 with the circuit of FIG. 7. Wave form 251, for example, represents a combination of the wave form 243 at the output of the flip-flop 149 with the wave form 211 (FIG. 6) at the output of the OR gate 161.

Referring to FIG. 8, reference numeral 260 generally designates another type of system designed for an eight cylinder engine. This system is similar in many respects to the system of FIG. 5 and the system 230 of FIG. 7, incorporating injection valves 131-138, driver circuits 141-148, flip-

flops

149 and 150, gates 151-158, gates 161-168, an octal decoder 179, a counter 180, an exitation and conditioning circuit 183 and an engine firing sensor 184, operative in generally the same manner as the same circuits shown in FIG. 5. It also incorporates

gates

231 and 232, a flip-flop 234,

gates

235 and 246 and

timers

237 and 238 operative in the same manner as described above in connection with FIG. 7. It is here noted that the system of FIG. 8 could altematively utilize alternately operating timers such as the

timers

189 and 190 of FIG. 5.

The system 260 differs from the previously described systems in that

electronic switches

261 and 262 are provided, switch 261 being connected between the power supply terminal 140 and the upper terminals of

injection valves

131, 133, 135 and 137 while switch 262 is connected between the power supply terminal 140 and the upper terminals of injection valves 132,

134, 136 and 138.

Switches

261 and 262 are operated by monostable

stable multivibrators

263 and 264, controlled from the flip-

flops

149 and 150. In operation,

. the switch 261 is closed by the monostable multivibrator 263 during a short initial portion of each output signal from the flip-flop 149 and since one of the driver stages 141, 143, 145 or 147 is then operative, full operating current is applied to one of the

injection valves

131, 133, 135 or 137. After a short time interval, however, switch 261 is opened but thereafter current continues to flow through resistance means within the switch 261 to maintain the operative injection valve opening until the flip-flop 149 is reset. The continued current flow is referred to herein as the post bias current and is substantially less than the full operating current required to drive the injection valve to an open condition, while being sufficient to maintain the injection valve open. With this feature, the change in current flow required to close the valve is reduced, and the time of closing is more rapid and more accurately controlled.

Another feature of the system 260 is in the application of a pre-bias current to the injection valves, ahead of the opening times thereof. In accordance with this feature, eight diodes 271-278 are provided for applying signals to the driver stages 141-148 during 90 degree time intervals in advance of the respective opening times of the injection valves. Diodes 271-278 are respectively connected between the inputs of driver stages 141-148 and the lines 178 and 171-177.

The operation of the system of FIG. 8 is shown in the lower portion of FIG. 9. Wave forms 281-288 are those of the signals applied to the inputs of the driver stages 141-148 in the system of FIG. 8, representing combinations of the signals developed at the outputs of the gates 151-158 (wave forms 251-258 in FIG. 9) and the signals on the lines 178 and 171-177 (wave forms 208 and 201-207, respectively, FIG. 6).

Wave forms 291-298 represent the current flow through the respective injection valves 131-138, using the system of FIG. 8. During the initial portion of the signal applied to the driver 141, for example, the current flow is limited to a comparativley small value by resistance means within the switch 261, and the current, referred to as the pre-bias current is insufficient to open the injection valve 131. However, when the switch 261 is closed for a short time interval, a large operating current is applied to the injection valve 131 to drive the valve fully open. The current thereafter continues to flow through the injection valve 131, through the resistance means of the switch 261, and this postbias current, although equal to the pre-bias current, is sufficient to keep the valve open since once the valve is open, the current required to keep it open is smaller than that required to initially drive it to an open condition. Each valve is kept open for a time interval dependent upon the control signal applied to the timers.

FIG. 10 illustrates the circuit of the driver stage 141, it being understood that the other driver stages 142-148 may have the same circuit. The signal input to the driver stage 141 is applied to the base of a transistor 300, the base being also connected through a resistor 301 to a power supply terminal 302 which may be at plus five volts relative to ground, for example. The emitter of transistor 300 is connected to ground while the connector thereof is connected through a resistor 303 to a power supply terminal 304 which may be at plus 12 to 14 volts relative to ground. The collector of transistor 300 is also connected to the base of a power transistor 305, the emitter of which is connected to ground and the collector of which is connected to output terminal 306, connected to the injection valve 131.

FIG. 11 shows the circuits of the switch 261 and the monostable multivibrator 263, it being understood that the switch 262 and monostable multivibrator 264 may have the same circuits. An output terminal 307, connected to terminals of the

valves

131, 133, and 137 is connected to the collector of a transistor 308, the emitter of which is connected to a power supply terminal 309 which may be at plus 12 to 14 volts relative to ground, for example. A resistor 310 is connected in parallel with the transistor 308, between

terminals

307 and 309. The resistor 310 has a value such as to maintain the proper pre and post bias currents. The base of transistor 308 is connected through a resistor 311 to the terminal 309 and is also connected through a resistor 312 to the collector of a transistor 313 the emitter of which is grounded and the base of which is connected through a resistor 314 to a circuit point 315 which forms the output terminal of the monostable multivibrator 263. Circuit point 315 is connected through a resistor 316 to a power supply terminal 317 which may be at plus 10 volts relative to ground, for example. Circuit point 315 is also connected to the collector of a transistor 318 the emitter of which is grounded and the base of which is connected through a fixed resistor 319 and an adjustable resistor 320 to the terminal 317. The base of transistor 318 is also connected through a capacitor 321 to the collector of a transistor 322, the collector being also connected through a resistor 323 to a power supply terminal 324 which may be at plus five volts relative to ground. The emitter of the transistor 322 is grounded while the base thereof is connected through a resistor 325 to the circuit point 315 and also through a capacitor 326 to the output of the flip-flop 149.

In operation, the transistor 318 is normally conducting and the collector thereof being at a low potential, the base of the transistor 313 is also at a low potential, preventing conduction thereof and also preventing conduction of the transistor 308. When a positivegoing signal is applied through the capacitor 326 to the base of the transistor 322, the transistor 322 conducts and the transistor 318 is cut off through the signal applied through capacitor 321 from the collector of the transistor 322. With transistor 318 cut off, the transistor 313 is rendered conductive and the transistor 308 is also rendered conductive to present virtually a short circuit between the

terminals

307 and 308, thus permitting full operating current to be applied to the injection valve. After a certain time interval, the charge of 13 the capacitor 321 is changed through current flow through the

resistors

319 and 320 to pennit the transistor 318 to conduct whereupon the transistor 322 is cut off and likewise

transistors

313 and 308 are cut off. The time of operation of the multivibrator 263 is adjustable by adjustment of the resistor 320.

What is claimed is:

1. A fuel injection control system for an engine including at least one group of four cylinders and fuel injection valve means associated with each cylinder for injection of fuel for flow into each cylinder during the intake stroke thereof, and electrically energizable actuator means for each of said fuel injection valve means, said control system comprising sequencing means for supplying sequencing signals in synchronized relation to the intake strokes of the engine and further comprising for each group of four cylinders: four driver stages respectively coupled to the four actuator means of said group, each of said four driver stages including transistor means arranged to controllably conduct current through the associated actuator means, four AND gate means having outputs respectively coupled to said four driver stages, flip-flop means triggered to a first state at approximately the beginnings of the intake strokes of said four cylinders and to a second state at controlled times varying from substantially less than 90 degrees to substantially greater than 90 degrees following the beginnings of the intake strokes of said four cylinders, means coupling said flip-flop means to inputs of all of said four gate means to apply a series of four timing signals thereto during each 720 degrees of engine rotation, and means responsive to sequencing signals from said sequencing means to supply four control signals to additional inputs of said four gate means, each of said four control signals having a duration of approximately 180 degrees of engine rotation and being generally coextensive with the intake stroke of one of said four cylinders, said control system being arranged for control of an eight cylinder engine having two groups of four cylinders, and said flip-flop means for said two groups being operative to develop first and second series of timing signals in 90 degree phase displaced relation.

2. In a system as defined in claim 1, means for applying control signals from said sequencing means to said flip-flop means to trigger said flipflop means to said first stage thereof.

3. In a system as defined in claim 1, said sequencing means comprising a plurality of flip-flops forming a digital counter and arranged to count a predetermined number of pulses equal to the number of cylinders, and decoder gate means coupled to said flip-flops.

4. In a system as defined in claim 3, means for applying triggering pulses both to said flip-flop means for determining the starting times of said timing signals and to said counter to advance the count thereof.

5. In a system as defined in claim 1, wherein said engine is an eight cylinder engine having two groups of four cylinders, said flip-flop means for said two groups being operative to develop first and second series of timing signals in 90 degree phase displaced relation.

6. In a system as defined in claim 1, said sequencing means being operativeto develop eight control signals in sequence during the progressive firing of all eight cylinders and eight OR gates each responsive to consecutive control signals for applying signals to said additional inputs of said AND gate means.

7. In a system as defined in claim 1, said sequencing means being operative to develop control signals in sequence during the progressive firing of all eight cylinders, first OR gate means for setting the first flip-flop means associated with one group of four cylinders in response to alternate ones of said control signals from said sequencing means, and second OR gate means for setting the flip-flop means for the other group of four engine cylinders in response to the remaining ones of said control signals from said sequencing means.

8. In a system as defined in claim 1, first and second timers for controlling the triggering to said second state of said flip-flop means for the two groups of cylinders.

9. In a system as defined in claim 8, said first and second timers being connected in cascade, a third flip-flop operated in synchronized relation to said first and second series of timing signals, and means controlled by said third flip-flop for alternately controlling said first and second flip-flops from said second timer.

10. In a system as defined in claim 9, means applying signals from said first timer to said third flip-flop to alternately change said third flip-flop from one state to the other.

11. A fuel injection control system for an engine including a plurality of cylinders and fuel injection valve means associated with each cylinder for injection of fuel for flow into each cylinder during the intake stroke thereof, and electrically energizable actuator means for each of said fuel injection valve means, said control system comprising: a driver stage for each of said actuator means, said driver stage including transistors means arranged to controllably conduct current through said actuator means, means associated with said driver stages for initially applying a pre-bias current to each of said actuator means and subsequently applying a larger operating current thereto, said pre-bias current being insufficient to cause opening of the associated valve means while being sufficient to allow rapid opening thereof in response to said larger operating current, and said pre-bias current being applied for a substantial time interval in advance of application of said larger operating current to pre-condition said actuator means for rapid opening in response to application of said larger operating current.

12. In a system as defined in claim 11, means associated with said driver stages for applying after application of said larger operating current a smaller post-bias current sufficient to maintain the associated valve means in an open condition while being small enough 14. A fuel injection control system for an engine including a plurality of cylinders and fuel injection valve means associated with each cylinder for injection of fuel for flow into each cylinder during the intake stroke thereof, and electrically energizable actuator means for each of said fuel injection valve means, said control system comprising: a driver stage for each of said actuator means, each driver stage including transistor means arranged to controllably conduct current through said actuator means, power supply means having first and second terminals, said transistor means including a first transistor associated with a plurality of said driver stages for connection of said first power supply tenninal to one terminal of a plurality of said actuator means, and a plurality of additional transistors respectively associated with said plurality of driver stages for connecting the other terminals of said plurality of said actuator means to said second power supply terminal, means for applying timing signals to said plurality of additional transistors for conduction thereof, means oper ative during each timing signal for rendering said first transistor highly conductive for a short time interval, and resistance means connected in parallel relation to said first transistor.

15. In a system as defined in claim 14, each of said additional transistors being rendered conductive for a substantial time interval in advance of said short time interval of conduction of said first transistor, said resistance means having a value such as to establish a prebias current insufficient to cause opening of the associated valve means while being sufficient to allow rapid opening thereof in response to conduction of said first transistor.

16. In a system as defined in claim 15, each of said additional transistors being also conductive for a substantial time interval following said short time interval, said resistance means having a value such as to establish a post-bias current sufficient to maintain the associated valve means in an open condition while being small enough for rapid closing thereof in response to termination of conduction of the associated one of said additional transistors.

17. In a system as defined in claim 14, each of said additional transistors being conductive for a substantial time interval following said short time interval, said resistance means having a value such as to establish a post-bias current sufficient to maintainthe associated valve means in an open condition while being small enough for rapid closing thereof in response to termination of conduction of the associated one of said additional transistors.