US3756205A

US3756205A - Method of and means for engine operation with cylinders selectively unfueled

Info

Publication number: US3756205A
Application number: US00137480A
Authority: US
Inventors: G Frost
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1971-04-26
Filing date: 1971-04-26
Publication date: 1973-09-04
Anticipated expiration: 1990-09-04

Abstract

A method and apparatus for controlling the supply of fuel to selected ones of the cylinders of a multi-cylinder internal combustion engine. The apparatus includes solenoid operated valves which are electrically energized to cause fuel to be supplied to the respective cylinders of the engine. Actuating current pulses are normally applied to all valves to discharge the required amount of fuel for each cylinder power stroke. In accordance with the present invention, an electronic system selectively disables certain of the solenoid operated valves to prevent fuel from being injected so as to cause the associated cylinder to pump air only. This unpowered cylinder operation may be used for any desired purpose, such as to pump air or to reduce the number of cylinders using fuel during idling or low power operation.

Description

llttited States Patent Frost Sept. 4, 1973 SELECTIVELY UNFUELED Primary Examiner-Laurence M. Goodridge Assistant Examiner-Ronald B. Cox Attorney-E. W. Christen and C. R. Meland [57] ABSTRACT A method and apparatus for controlling the supply of fuel to selected ones of the cylinders of a multi-cylinder internal combustion engine. The apparatus includes solenoid operated valves which are electrically energized to cause fuel to be supplied to the respective cylinders of the engine. Actuating current pulses are normally applied to all valves to discharge the required amount of fuel for each cylinder power stroke. In accordance with the present invention, an electronic system selectively disables certain of the solenoid operated valves to prevent fuel from being injected so as to cause the associated cylinder to pump air only. This unpowered cylinder operation may be used for any desired purpose, such as to pump air or to reduce the number of cylinders using fuel during idling or low power operation.

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ATTORNEY PATENTEDSEP 4 ma SHED 5 BF 5 INJECTION PULSE SOURCE INVENTOR. BY George 5. 5505? azmzzaw ATTORNEY V METHOD OF AND MEANS FOR ENGINE OPERATION WITH CYLINDERS SELECTIVELY UNFUELED The present invention relates to a method of and means for operating a multi-cylinder spark ignition internal combustion engine with one or more cylinders in an unpowered condition as desired by the operator, or in response to automatic control.

The spark ignition internal combustion engine, such as is used commonly on automobiles, is normally operated with fuel supplied to each of the engine cylinders. This is not necessarily the optimum operation under all conditions of engine usage. For example, the engine may under some conditions supply insufficient oxygen content in the exhaust gases to reduce unburned hydrocarbon and carbon monoxide emissions to the desired levels. It may thus be desirable to provide and control some form of auxiliary air supply to provide the necessary air for this purpose in the engine exhaust stream passing through a catalytic or other afterburner device. Also, when an engine is operated at idle with a substantially closed throttle, the combustion and cooling conditions are relatively adverse. With a particular engine it may be preferable to operate with less than all cylinders fueled and the throttle more nearly open at idle or low load, so that combustion takes place under more favorable conditions.

The present invention is particularly applicable to a multi-cylinder engine, such as an eight-cylinder fourstroke engine, that operates in conjunction with a catalytic converter. In this application, as described hereafter, the non-fueled cylinder operations may be programmed so as to provide intermittent air supply to the converter through the operation of unfueled power strokes in the engine itself and of the number required for effective converter operation. In accordance with one aspect of the present invention, the catalytic memcry of the catalyst in the converter coacts with the intermittent air supply to provide operation comparable to that obtained with a continuous air supply.

The present invention is further applicable to multicylinder automobile type engines in that the non-fueled piston operations are achieved with minimum roughness imparted to the engine. In brief, the non-fueled piston operations take place as occasional, approximately periodic, cylinder miss events having minimum effect on engine roughness and then only as transitory action. As the number of unpowered strokes is progressively increased, the action corresponds more and more to a periodic unpowered cylinder operating cycle superimposed on the normal power strokes. The approximately equal time spacing of the unpowered cylinder strokes minimizes the effect on engine roughness.

Further in accordance with the present invention, the action is accommodated to a comparatively simple form of electric fuel injection system, namely the type wherein the fuel injectors are energized in two separate groups, rather than individually for each cylinder, although not limited to such a system. This typeof fuel injection has the advantage of simplicity and consequent greater desirability, but it does not permit control of each injector separately from the other injectors in the same group. One aspect of the present invention provides such individual injector action to an extent sufficient to provide comparatively smooth engine operation, good control of the number of unpowered strokes, and generally effective utilization in practical automobile applications.

In yet another aspect of this invention, groups of fuel injection solenoids are sequentially energized under the control of semiconductor switching devices such as transistors which are periodically biased conductive in synchronism with operation of the engine. An electronic control system including other semiconductor switches is provided which is capable of preventing certain of the injector solenoids from being energized under certain conditions of operations. This disabling takes place under the control of a pulse generator which may be controlled by the operator or controlled automatically in response to an operating condition of the engine. The disabling control is arranged such that it is controlled by the pulse generator and by pulses developed by an engine driven pulse generator which also controls the sequence of firing of the groups of solenoid injectors.

IN THE DRAWINGS FIG. 1 is a schematic circuit diagram of one embodiment of a fuel injection system made in accordance with this invention;

FIGS. 2 through 5 are approximate and illustrative voltage waveforms which illustrate graphically the operation of the system shown in FIG. 1;

FIG. 6 is a schematic circuit diagram of an alternative form of the system shown in FIG. 1;

FIGS. 7 through 9 are approximate and illustrative voltage waveforms which graphically illustrate the operation of the system shown in FIG. 6;

FIG. 10 illustrates a modified circuit for the system of FIG. 1;

FIG. 11 is a schematic circuit diagram of still another modified fuel injection system made in accordance with this invention;

FIG. 12 is a schematic circuit diagram of a variable frequency control pulse generator which can be utilized in the various embodiments of this invention;

FIG. 13 illustrates a modified fuel injection system controlled by a pulse counter arrangement; and

FIG. 14 illustrates a modified timing pulse generating arrangement for the system of FIG. 13.

Referring now to the drawings and more particularly to FIG. 1, the reference numeral 10 designates an eight cylinder internal combustion engine for a motor vehicle. The fuel that is supplied to the engine is controlled by eight individual solenoid controlled injector valves actuated by solenoids 10-1, 10-2, 10-3, 10-4, 10-5, 10-6, 10-7, and 10-8, respectively. These injectors are located, for example, at the respective inlet valves for the eight engine cylinders in the order of cylinder firing. Each solenoid, during energization, opens a fuel inlet valve, which discharges fuel from a source at constant pressure (not shown), so that the amount of fuel discharged in the region of each inlet valve is determined by the duration of valve opening, which in turn is controlled by the time duration of energization of the corresponding solenoid.

In the form of the fuel injection system shown in FIG. 1, the injection solenoids for the first four cylinders in the order of firing, are energized in unison. The injection solenoids for the second four cylinders, in the order of firing, are similarly energized in unison. The fuel thus discharged into each intake port adjacent but upstream the intake valve for each cylinder dwells in this location until the particular cylinder begins an intake stroke. This dwell time can be no more than one crankshaft revolution, since the four cylinders fueled in unison in each case are consecutively fired cylinders. During the intake stroke of each cylinder, the intake valve opens and the piston draws in fuel and air, including the fuel previously discharged from the injector on the prior injection pulse.

The engine is mechanically connected, for example, by a distributor shaft to an engine driven pulse generator designated by reference numeral 12. This pulse generator can take various forms and might, for example, be a cam driven switching device which has a square wave output on line 14 as is illustrated in FIG. 1. It is preferred, however, that the engine driven pulse generator 12 be of the electromagnetic type wherein a pair of magnets having opposite poles on diametrically opposed points in relation to the shaft axis pass a pickup winding so as to induce a voltage in the winding as the distributor shaft rotates. The voltage that is induced in the pickup coil is applied to a differentiating circuit and to a flip-flop to produce the square wave voltage shown in FIG. 1. One specific arrangement for developing the square wave voltage on line 14 is disclosed in U.S. Pat. application Ser. No. 36.055, filed on May I l, l970 and assigned to the assignee of this invention.

The injector solenoids 10-1, 10-2, 10-3 and 10-4 are all connected with conductor 18 which in turn is connected to the positive side of a source of direct voltage 20 through a power supply conductor 22. The opposite side of injector solenoids 10-1, 10-2 and 10-3 are connected to a conductor 24. An NPN transistor 26 has its collector-emitter circuit connected between conductor 24 and ground and therefore between conductor 24 and the negative side of the source of direct current 20. With this arrangement it will be evident that when transistor 26 is biased conductive the injector solenoids 10-1, 10-2 and 10-3 are connected directly across the source of direct current 20 and these solenoids are therefore energized sufficiently to open the injector valves and supply fuel to the respective cylinders of the engine 10.

The injector solenoid 10-4, rather than being directly connected between conductors l8 and 24 is connected in series with a controlled rectifier designated by reference numeral 28. The gate of controlled rectifier 28 is connected to conductor 18 through a capacitor 34. The capacitor 34 is connected across the output terminals of a pulse generator 36 through resistor 38. When the pulse generator 36 charges the capacitor 34 with a voltage of the proper magnitude and with the polarity indicated in FIG. 1, gate current to the controlled rectifier 28 is opposed so as to prevent it from being biased to a conductive condition.

It will be appreciated that when transistor 26 is biased conductive, and assuming capacitor 34 does not have a prior charge preventing gate current to the controlled rectifier 28, the voltage developed at conductor 18 will gate the controlled rectifier 28 conductive through capacitor 34. Under this condition of operation the solenoid 10-4 will be energized in unison with solenoids 10-1, 10-2 and 10-3 each time the transistor 26 is biased conductive.

The conduction of transistor 26 is controlled in synchronism with operation of the pulse generator 12 by the signal on line 14 through a system that will now be described. The signal on line 14 is applied to a Schmitt trigger designated by reference numeral 40 having output terminals A and B. The output terminals A and B are connected with transistors within the Schmitt trigger which are preferably connected in series with resistors of predetermined values, whereby the voltage appearing between each of terminals A and B and ground alternates between high and low levels. In other words, when the voltage at output terminal A is high, the voltage at terminal B is at a lower level, and vice versa. The output terminal A is coupled to the base of an NPN transistor 42 the collector of which is connected with power supply conductor 22 by a resistor 44. The collector of transistor 42 is coupled to the base of NPN transistor 26. It will be appreciated that by the connection of these transistors, transistor 26 will be biased conductive when transistor 42 is nonconductive and transistor 26 will be biased nonconductive when transistor 42 is conductive.

The bias voltage applied to the control transistor 42 is obtained from terminal A of Schmitt trigger 40 and from an output terminal 56 of a transistor blocking oscillator designated by reference numeral 60. The base of transistor 42 is connected to output terminal 56 by

conductors

62 and 64 and resistor 66. It is seen that the output terminals A and B of Schmitt trigger 40 are coupled to the blocking oscillator 60 and this is done through differentiating circuits (not illustrated) whereby the output of Schmitt trigger 40 supplies a series of pulses to the blocking oscillator 60. Each time a pulse is supplied to the blocking oscillator 60 from the Schmitt trigger, the output between junction 56 and ground of the blocking oscillator goes to a low value and this value is maintained for the period of operation of the blocking oscillator. This period of operation is further controlled in response to engine temperature and engine manifold pressure. This is indicated in FIG. 1 by the

lines

67 and 68 which indicate known methods of controlling the pulse period of the blocking oscillator in response to the engine conditions of this type. It should be pointed out here that the output of the blocking oscillator is preferably an NPN transistor connected between output terminal 56 and ground and therefore between conductor 64 and ground.

The energization of injector solenoids 10-5, 10-6, 10-7 and 10-8 is controlled in a similar fashion to the energization of the other injector solenoids by complementary circuit elements which include a power output transistor 70 and an NPN control transistor 74. These transistors are coupled to the power supply by resistor 45 as illustrated and the base of transistor 74 is connected with the B output of Schmitt trigger 40 and to conductor 64 via resistor 76. The injector 10-8 is connected in series with a controlled rectifier 80. A capacitor 86 is connected between the gate of controlled rectifier and line 84, the latter being connected to power supply conductor 22 by conductor 85. The capacitor 86 is charged from pulse generator 36 through resistor 88. This capacitor operates in the same manner as capacitor 34 so as to store the charge from pulse generator 36 and thereby block conduction of controlled rectifier 80 until capacitor 86 is discharged.

Referring now back to the operation of transistors 42 and 74, it will be appreciated that the output voltages of the Schmitt trigger alternate between high and low levels as the Schmitt trigger is switched by the signal on line 14. Assuming the output voltage on terminal A is at its low value and that the blocking oscillator has been switched to a low output level, the transistor 42 will be biased to a nonconductive state. This corresponds to time T of FIG. 2 where transistor 26 is illustrated biased to a conductive condition. This comes about due to the fact that the nonconductive condition of transistor 42 causes a conductive state for transistor 26 and at time T, a positive voltage will be applied to line 18 due to the conduction of transistor 26. Assuming that controlled rectifier 28 has not been disabled, injector solenoids -1, 10-2, 10-3 and 10-4 will all be energized. This produces injection of fuel to four cylinders of the engine. This injection will continue until a time when the blocking oscillator 60 switches from a low output state to a high output state. When this happens, transistor 42 is biased conductive, with the result that transistor 26 is biased nonconductive thus terminating current flow in the solenoids. This will occur at time T shown in FIG. 2 and will occur in response to the duration of the on period of the blocking oscillator 60 as determined by engine operating conditions.

This same analysis can be applied to the bias voltage applied to control transistor 74. Thus, at time T the blocking oscillator 60 is set by a signal from Schmitt trigger 40 to its low output state and when a low voltage from the Schmitt trigger is simultaneously applied to control transistor 74 it will be biased nonconductive with the result that transistor 70 is biased conductive. At time T therefore, injector solenoids 10-5, 10-6, 10-7 and 10-8 will be energized for a period determined by the pulse duration of blocking oscillator 60 and injection is terminated at time T.,. This has assumed that no blocking signal was applied to disable controlled rectifier 80.

It will be appreciated from the foregoing that the transistors 42 and 74 are alternately biased by Schmitt trigger 40 and by the output of blocking oscillator 60. It will be further appreciated that injection can only occur when the proper simultaneous voltages are applied to transistors 42 and 74 from the blocking oscillator and the Schmitt trigger. It will be further appreciated that the voltage level set by the Schmitt trigger will extend for the entire programmed injection period, for example between times T, and T for transistor 42 and times T through T for transistor 74, thus alternately enabling these transistors when the blocking oscillator has the proper output.

The operation of the controlled

rectifiers

28 and 80, the pulse generator 36, and the associated circuitry is as follows. The pulse generator 36 produces a succession of pulses as illustrated by waveform D, FIG. 1, and at a controllable repetition rate. This generator may be of any desired construction, with a pulse producing capability sufficient to charge both capacitor 34 and capacitor 86 through the

respective resistors

38 and 88 on each pulse to a sufficiently negative voltage. to prevent gate current through the gate electrodes of controlled

rectifiers

28 and 80 to thereby prevent these controlled rectifiers from being biased to a conducting condition. The repetition rate of the pulses is made variable between a minimum repetition rate corresponding to the least number of unfueled piston strokes desired and a maximum repetition rate corresponding to the maximum number of such unfueled strokes. Thus, for example, if the maximum number of unpowered cylinder strokes is to be one-fourth of the total number of cylinder strokes, the repetition rate of the pulse generator 24 is made equal to one pulse per crankshaft rotation. If, for example, the minimum number of controlled unpowered piston strokes is to be one per 12 cylinder strokes, then the minimum repetition rate of the pulse generator 36 is equal to one pulse per three crankshaft rotations.

Various forms of variable repetition rate pulse generators are known to the art and may be used for the pulse generator 36. By way of illustration, a multivibrator may be employed to produce an approximately square wave of frequency determined by the feedback time constant of the circuit. The resulting wave may be differentiated and clamped to produce a series of positive pulses of repetition rate controllable by varying such feedback time constant or the square wave itself may be applied to the capacitors and controlled rectifiers where a predetermined pulse width is desired.

The specific operation of the controlled

rectifiers

28 and 80, the pulse generator 36 and the associated circuitry is as follows. The pulses D, FIG. 1, are applied to the SCR gate electrodes of controlled

rectifiers

28 and 80 in unison, thereby blocking energization of both solenoid 10-4 and solenoid 10-8. The time constants of the

capacitors

34 and 86 and their associated discharge circuits (including resistance 38 and 88) are such that this blocked condition remains for at least one crankshaft rotation. Before such crankshaft rotation is completed, one or the other solenoid 10-4 or 10-8 is energized via the fuel injection pulse generator 12. At that time, the three unblocked injector solenoids of the injector group (10-1, 10-2 and 10-3, or 10-5, 10-6 and 10-7, as the case may be) are actuated so as to supply fuel to their respective cylinders. However, the blocked injector (10-4 or 10-8) does not operate. Its cylinder, on subsequent inlet valve opening, draws in air free of fuel and then discharges the same into the exhaust manifold. Thus the pulse from the pulse generator 36 has the effect of disabling the fuel injection to the first one of injectors 10-4 and 10-8 which would otherwise discharge fuel to its respective cylinder.

When the energized injector solenoids are deenergized, as when transistors 26 or go nonconductive, the current through the same is suddenly decreased, and a momentary voltage appears across the same in the direction tending to continue such current flow. This voltage is applied to capacitor 86 when the solenoids 10-1 to 10-4 are deenergized through a circuit that includes conductor 24, conductor 89, capacitor 86, conductors 84 and 85 and conductor 22 to line 18. When solenoids 10-5 to 10-8 are deenergized, a voltage is supplied to capacitor 34 through a circuit that includes conductor 91, conductor 18, conductor 22 and conductors 85 and 84. The circuit is so designed that the magnitude of this voltage is sufficient, when three or more injector solenoids have a current interruption, to discharge the

capacitor

34 or 86, as the case may be, and reduce the voltage at the corresponding SCR control electrode to a value permitting the same to conduct in the event of an injection pulse. Thus, the effect of actuation and subsequent deenergization of either bank of injector solenoids is to clear the other bank for further injection by reducing the reverse bias charge on a

capacitor

34 or 86. It is pointed out that each controlled rectifier 28 or will be turned off where its associated

transistor

20 or 70 goes nonconductive since at this time there is no voltage applied to its anodecathode circuit. Moreover, the voltages induced in the solenoids when they are switched off tends to reverse bias II the anode-cathode circuit ofa given controlled rectifier.

The operation of the system of FIG. 1 is illustrated in FIGS. 3 to 5, inclusive, for three specific different pulse repetition rates from the generator 36. In FIG. 3, the curve 3a illustrates on a time scale the successive engine cylinder firing operations, with the wide pulses indicating operation of injector solenoids 10-4 and 10-8. The respective firing times are identified by injector solenoid number. Curve 3b, FIG. 3, shows the output pulses from the pulse generator 36. In the particular repetition rate shown in FIG. 3 there is one pulse from generator 36 for each l engine power strokes, as shown. Curve 3c, FIG. 3, shows the actual engine power strokes under the conditions shown. It will be observed that the injector solenoids 10-8 and 10-4 are disabled, in accordance with which first follows each control pulse of curve 3b. It should further be noted that a variable number of power strokes separate the respective non-powered strokes, the number varying from seven to eleven in the illustrated operating condition.

FIG. 4 is like FIG. 3 but for the condition of one pulse from generator 36 for each five cylinder power strokes. The curves 4a, 4b and 4c have the same significance as curves 3a, 3b and 30, respectively, except that they pertain to the different repetition rate of pulse generator 36. In this case, the number of power strokes between successive non-power strokes varies from seven to three in the illustrated operating condition. Again, the non-power strokes are distributed randomly between solenoid injector 10-4 and solenoid injector 10-8.

FIG. 5 is like FIGS. 3 and 4 but for the condition of one pulse from generator 36 for each 20 cylinder power strokes. The

curves

5a, 5b and 50 have the same significance as curves 3a, 3b and 30, respectively, except that they pertain to the different repetition rate of the pulse generator 36. In this instance, the number of power strokes between successive non-power strokes shown is nineteen and the non-power strokes are distributed between solenoid injector -4 and solenoid injector 10-8.

The overall action of the structure and circuitry above described with respect to FIGS. 1-5 is to provide engine operation in the usual fashion except that there is normally one unpowered piston operation for each pulse from the pulse generator 36. Normally, the greater the repetition rate of this generator, the greater the number of such unpowered operations. A maximum occurs when both injector solenoid 10-4 and injector solenoid 10-8 are disabled at all times, that is, the number of pulses from generator 36 exceeds the number of possible operations of injector solenoids 10-4 and 10-8. The system thus makes possible the discharge of air into the exhaust manifold at any selected rate, up to approximately one-third of the total amount of spent air-fuel mixture discharged into the exhaust manifold or one-fourth of the total engine displacement. Moreover, until the maximum is reached, there is a substantially direct relation between the repetition rate of the pulse generator 36 and the number of unpowered cylinder operations per second.

In one application of the present invention, a catalytic afterburner is used to oxidize the unburned exhaust gas constituents. With the pulse generator 36 in operation at a predetermined pulse repetition rate, solenoids 10-4 and 10-8 are periodically disabled. The corresponding engine cylinders are not supplied with fuel from time to time and then draw in air and discharge the same into the exhaust manifold and then into a catalytic converter. Converter 15 preferably is of a type that does not require an instantaneous supply of oxygen, but rather has some oxygen storage capability. Thus, when injector solenoids 10-4 and 10-8 are disabled from time to time, the resultant momentary discharge into the catalytic converter is remembered" and serves to supply oxygen for subsequent periods of no air supply.

FIG. 6 is a diagram showing another form of the present invention which is a modification of FIG. 1. The reference numerals in FIG. 6 identify parts like similarly identified parts on FIG. 1 and FIG. 6 does not illustrate the entire system of FIG. 1. It is to be understood that

transistors

26 and 70, shown in FIG. 6, are controlled by a system that is identical with the one shown in FIG. 1. In the construction of FIG. 6, the respective controlled rectifiers 28 and each control the current flow to two injector solenoids. That is, controlled rectifier 28, when disabled (nonconducting), blocks current flow through both injector solenoid 10-2 and injector solenoid 10-4 and controlled rectifier 80, when nonconducting, blocks current flow through injector solenoid 10-6 and injector solenoid 10-8.

FIGS. 7-9 are similar to FIGS. 35, respectively, but illustrate the operation of the system of FIG. 6 rather than FIG. 1. As will be noted from FIGS. 7-9, the event of each control pulse from the pulse generator 36 causes two injector solenoids to be blocked on the next fuel-injecting pulse. That is, either injectors 10-2 and 10-4 as a pair are blocked or injectors 10-6 and 10-8 as a pair are blocked, depending on which pair would otherwise first be energized. Since the cylinder power strokes are determined by the spark timing, however, the times of the unfueled power strokes are spaced as shown in FIGS. 7-9. In the extreme case when the repetition rate of the pulses from generator 36 is sufficient to block each of injectors 10-2, 10-4, 10-6 and 10-8, the engine operates on four cylinders with an equal time period between successive power strokes and therefore minimum roughness for the four cylinder operating condition.

Referring now more particularly to FIG. 10, a disabling circuit which is a modification of the one shown in FIG. 1 is illustrated. In FIG. 10, the same reference numerals have been used as were used in FIG. 1 to identify equivalent circuit elements in each embodiment and FIG. 10 illustrates only a portion of FIG. 1, it being understood that the remainder of the system would be identical with that shown in FIG. 1.

In FIG. 10, the controlled

rectifiers

28 and 80 rather than being disabled by the pulse generator 36 and associated

capacitors

34 and 86 are disabled by an NPN transistor designated by reference numeral 90 and controlled by pulse generator 36 through the flip-flop 102. The NPN transistor 90 has its collector connected with a conductor 97, which in turn is connected to junctions 92 and 94. The junction 92 is connected between the resistor 93 and a diode 96 whereas the junction 94 is connected between the resistor 95 and diode 98. It is seen that the

diodes

96 and 98 are connected with the gates of controlled

rectifiers

28 and 80. The cathodes of controlled

rectifiers

28 and 80 are connected with a conductor 100 which in turn is connected with the emitter of transistor 90.

From the foregoing it will be appreciated that when

transistor

26 or 70 is conductive, the associated controlled

rectifier

28 or 80 will be gated conductive through circuits that include, respectively, resistor 93 and diode 96 and resistor 95 and diode 98. This has assumed that the transistor 90 is biased nonconductive.

Whenever the transistor 90 is biased conductive (saturated), its collector-emitter path shunts the gatecathode circuits of both controlled

rectifiers

28 and 80 and thereby prevents the controlled rectifiers from being gated to a conductive condition. This disables the associated solenoid valve (104 or -8) to prevent fuel from being injected.

The conduction of transistor 90 is again controlled by pulse generator 36 connected with a differentiator (not illustrated) which feeds pulses to a flip-flop designated by reference numeral 102, each such pulse shifting the flip-flop to a condition that makes transistor 90 conductive. The flip-flop 102 remains in this condition until restored to the rest condition by the second subsequent actuation of Schmitt trigger 40. This is accomplished by pulser 105 which, in known manner, produces a restore pulse momentarily on line 107 when it is conditioned by a first disable pulse from pulse generator 36 and then actuated by the next subsequent pulse on line 14, which (as shown in FIG. 1) actuates Schmitt trigger 40. The restore pulse is slightly delayed so as to hold flip-flop 102 in condition to maintain conduction of the transistor 90 for a short time on the immediately following pulse on line 14 so as to preclude conduction of controlled rectifier 28 or controlled rectifier 80, as the case may be, for an initial short time when conduction is otherwise called for.

Momentary deactivation or nonconduction of controlled

rectifiers

28 or 80, as the case may be, is held for the balance of the time injection is called for by the delayed disable voltage applied to their respective control electrodes from blocking oscillator 60 via conductor 62, FIG. 1. The capacitor 111 and resistor 113 delay the blocking voltage buildup on the control electrodes of these controlled rectifiers for a time sufficient to cause these electrodes to lose control under normal conduction by these controlled rectifiers in response to conduction periods of

transistors

26 and 70. The time delay is slightly less than the delay of the restore pulse in line 107, so that when controlled

rectifier

28 or 80 is nonconductive at the inception of an injection period, it is held in that condition to the termination of that injection period.

The

diodes

96 and 98 serve to prevent the saturation voltage of transistor 90 from gating controlled

rectifiers

28 and 80 on when transistor 90 is fully conductive. Zener diodes could be used for this purpose if desired.

FIG. 11 is a schematic circuit diagram ofa fuel injection system incorporating another modification of the present invention. In the system of FIG. 11, the reference numeral 200 has been used to identify a fuel injection pulse generator. The block 200 represents the control system shown in FIG. 1 which triggers

transistors

26 and 70 on" and off". These transistors are connected with

lines

234 and 242 so that pulses of positive voltage, designated by the letters B and C in FIG. 11, are sequentially applied to

lines

234 and 242. In other words, in the system of FIG. 11 the

transistors

26 and 70, with their associated input network, would be connected between a source of direct current and

conductors

234 and 242 to apply the direct current pulses to

lines

234 and 242 in synchronism with the engine.

In the arrangement of FIG. 11, the injector solenoids 10-1, 10-2 and 10-3 are energized from source 202 through the collector-emitter path of transistor 201. Similarly, injector solenoid 10-4 is energized from source 202 through the collector-emitter path of transistor 204, injector solenoids 10-5, 10-6 and 10-7 are energized through the collector-emitter space path of transistor 206 and injector solenoid 10-8 is energized through the collector-emitter space path of transistor 208. The bases of transistors 201 and.204 are connected via

resistances

210 and 212, respectively, to line 242. As described above, line 242 has a positive voltage pulse on alternate crankshaft rotations, indicated diagrammatically at 0, 2, 4, 6, etc., in curve B, FIG. 11. The bases of

transistors

206 and 208 are connected via

resistances

214 and 216, respectively, to line 234 of fuel injection pulse generator 200 which has a positive voltage pulse on the intermediate alternate crankshaft rotations as shown in curve C, FIG. 11.

Under unimpeded operation of the transistors '204 and 208, the system of FIG. 11 energizes solenoids 10-1, 10-2, 10-3 and 10-4 in unison on the even numbered rotations of the crankshaft, and energizes solenoids 10-5, 10-6, 10-7 and 10-8 in unison on the odd numbered rotations of the crankshaft. As above described, the fuel injection pulse generator 200 produces pulses of correct duration to inject the proper amount of fuel on each cylinder operating cycle so that the engine operates as desired.

In the circuitry of FIG. 11, each of the injector solenoids 10-4 and 10-8 is selectively disabled through the action of the

corresponding capacitor

218 and 220, re spectively. As shown, these capacitors are connected between the base of the

corresponding transistor

204 or 206, respectively, and ground and are both connected to the output of pulse generator 224. Additionally, the collector-emitter paths of transistors 222 and 226 are connected across

capacitors

218 and 220, re spectively. The base of the transistor 222 is connected through resistance 228 to ground and via diode 232 and capacitor 230 to the output terminal 234 of the fuel injection pulse generator 200. Similarly, the base of transistor 226 is connected by resistance 236 to ground and via diode 240 and capacitor 238 to the other output terminal 242 of the fuel injection pulse generator 14.

The above described circuitry operates as follows. When the pulse generator 224 produces a pulse, as shown in waveform D, the same is applied to the

capacitors

218 and 220 in parallel. The pulse is of negative polarity, as indicated by waveform D. The circuit constants are chosen to cause these capacitors to be charged sufficiently to preclude injector solenoid energization by

transistors

204 and 208 in the event of operating pulses on lines 2 42 and 234. Injector solenoids 10-4 and 10-8 are thus temporarily disabled. When the first injector operating pulse occurs, the corresponding injector 10-4 or 10-8, as the case may be, remains deenergized so that the corresponding engine cylinder is not fueled on its next power stroke. The same injector operating pulse, however, serves to discharge the

opposite capacitor

220 or 228 as the case may be via the capacitor 238, rectifier 240 and resistance 236 in the case of capacitor 220 and the capacitor 230, rectifier 232 and resistance 228 in the case of capacitor 218. Thus each pulse of the pulse generator 224 gives rise to one miss" of injector -4 or injector 10-8, depending on the timing of the pulse, except of course when the pulse repetition rate is so great that both injectors 10-4 and 10-8 are disabled.

More particularly, the action of the capacitor 238, rectifier 240 and resistance 236 in discharging capacitor 220 is as follows. Assume that capacitor 220 has a negative charge due to a prior pulse from source 224.

The transistor 226 does not conduct to drain off this charge with no forward biasing pulse from the pulse generator 200. Thus, when the transistor 208 is disabled and there is substantial charge on capacitor 220 at the instant a pulse occurs on line 242 even at low engine speed. Since the voltage across capacitor 238 does not instantaneously change when the pulse occurs on line 242, and since the rectifier 240 is poled in a direction to carry charging current to capacitor 238 when the positive pulse appears on line 242, the positive pulse at line 242 appears as a positive pulse across resistance 236 and at the base-emitter of transistor 226, rendering the collector-emitter circuit path of transistor 226 conductive. The values of capacitor 238, resistance 236 and the characteristics of transistor 226 are so chosen in relation to the negative charge existing on the capacitor 220 that this action serves to leave a charge on capacitor 220 such that transistor 208 becomes conductive when a positive pulse subsequently appears on line 234. In other words, transistor 208 is now conditioned for action in response to a pulse on line 234. The net action, therefore, is for the positive pulse from generator 200, appearing on line 242, to discharge the capacitor 220 if it has been previously charged from pulse generator 224. After this action has occurred, the residual charge on capacitor 238 drains off via resistance 244.

In the case of capacitor 218, the event of a positive pulse on line 234 changes the charge if it be a negative value blocking the conduction of transistor 204 to a value that permits such conduction when a subsequent pulse on line 242 occurs. This discharge of capacitor 218 occurs through the collector-emitter space path of transistor 222 which is made conducting by the positive voltage appearing on its base when the pulse occurs on line 234. This positive pulse is communicated to the base of transistor 222 by capacitor 230 and diode 232. Capacitor 230 subsequently discharges through the resistance 246.

The circuit of FIG. 11 operates to give generally the same blocking action of solenoid injectors 10-4 and 10-8 as the circuit of FIG. 1. The diagrams of FIGS. 3-5 apply to the action of the circuit of FIG. 12 in the same respect as they do to the action of the circuit of FIG. 1.

If desired, solenoid injector 10-2 may be connected in parallel with solenoid injector 10-4, FIG. 11, and injector solenoid 10-6 may be connected in parallel with injector solenoid 10-8. In this case, the circuit action is substantially as described above with regard to FIG. 6 and FIGS. 79 inclusive. That is, the occurrence of a negative pulse from generator 224 will then cause two subsequent unfueled cylinder power strokes.

FIG. 12 shows a system for controlling the output frequency of the disabling pulse generators of FIGS. 1, 6, 10 or 1 1 by an engine throttle control as used on a vehicle so as to automatically vary the non-powered strokes in accord with throttle position. There is shown at 300 a conventional operator foot pedal with is depressed for increased engine power and released to decrease engine power. This pedal is pinned at 301 to the link 302 which is pivoted at 304 to arm 306a of crank 306. The crank 306 is unitary with the shaft 308 which is supported by suitable bearings (not shown) for rotation about a fixed axis. The other arm 306b of crank 306 is pivoted at 310 to the link 312. At 314 the link 312 is pivoted to the crank am 316 which in turn is mounted on the shaft of the throttle valve 318 so as to open and close throttle valve 318 and thereby vary the air flow to the engine 10 through the inlet pipe 320. Throttle return spring 322 urges the throttle to closed position. Thus when the foot pedal 300 is depressed, the throttle valve 318 is opened against the bias of spring 322 to admit more air to the engine and increase the engine power.

The crank 306 is unitary with and thus rotates the shaft 308. This shaft also carries a potentiometer contact arm shown diagrammatically at 324. This arm makes electrical contact with the fixed resistance element 326 as shown. The shaft 308 and hence the arm 324 are grounded as indicated. The line 328 is connected to one end of the resistance element 326 so as to provide increasing resistance in relation to the ground terminal as the foot pedal is depressed. This resistance is connected to a suitable pulse generating circuit 340 so as to produce pulses having repetition rate that decreases as the resistance increases in response to foot pedal depression. The specific circuit illustrated in FIG. 12 is of the type shown and described at pages 337338 of the General Electric Transistor Manual (7th Ed., 1964), which is one of the various circuits that can be used for pulse generator 36, FIGS. 1, 6 and 10, or pulse generator 224, FIG. 11. This circuit includes a pair of transistors 333 and 335 connected as a bistable multivibrator and a unijunction transistor 337 connected to control the time period from one condition to the other, all as described in the above manual. The output of this circuit is a substantially rectangular wave, as shown at E, FIG. 12. This is differentiated by capacitor 330 and resistance 332 to produce the alternate positive and negative pulses as shown at F, FIG. 12. The negative pulses are blocked by diode 334, FIG. 10, so as to produce the positive pulses, as indicated at G, which is the desired output of pulse generator 36, FIGS. 1, 6 and 10. The repetition rate of these pulses is determined by the frequency of the wave E, which in turn depends on the value of resistance 326 in the circuit and hence the position of the throttle control pedal 300.

If negative pulses are desired, as in the case of the apparatus of FIG. 11, the diode 334 is reversed so as to block the positive pulses, thus providing the outputt waveform D of pulse generator 224, FIG. 11.

The relation between the pulse repetition rate and the throttle position may be selected by appropriately tapering the fixed resistance element 326. Beyond a predetermined throttle position, for example, it may be desirable to run the engine with all cylinder operations fueled which can be done by terminating resistance 326 as at 326a, FIG. 12, and thus disabling the pulse generator.

The apparatus of FIG. 12, when used with that of FIGS. 1, 6, 10 or 11, or the equivalent, provides an increased rate of unfueled cylinder operation as the foot pedal 300 is released and the throttle closes. It is thus useful where it is desired either to have progressively fewer cylinders fueled as the throttle pedal is released so as to keep those cylinders operating under the most favorable and eff cient conditions of combustion or to have progressively greater proportion of air in the exhaust system as the throttle pedal is released.

FIG. 13 is a modified arrangement for disabling certain of the fuel injectors in timed relation to engine operation. It is to be understood that the pulse generating arrangement of FIG. 13 can be substituted for the pulse generator 36 of FIGS. 1, 6 and 10 or generator 224, FIG. 11. For convenience of illustration, the pulse generating arrangement is disclosed as controlling the system of FIG. 10 and in this regard the transistor 90 is shown in FIG. 13 connected with

conductors

97 and 100, it being understood that this transistor will control the fuel injection system of FIG. 10.

In FIG. 13, the reference numeral 400 is used to designate a source of fuel injection pulses which occur, for example, at time periods T, and T shown in FIG. 2. This source of pulses can be obtained as one example from the input line 14 to the Schmitt trigger 40 where they are differentiated and connected with suitable diodes to eliminate the unwanted pulses. In other words, a differentiator (not shown) is connected to conductor 14 and provides a series of pulses shown in FIG. 13 which occur at the beginning of each injection period.

The conductor 402 which has injection or timing pulses applied thereto is connected with a switch designated by reference numeral 404. This switch is closed whenever it is desired to disable certain of the fuel injector solenoids and the switch can be operated, or ex ample, through linkage connected with accelerator pedal 300 such that the switch only closes over a predetermined range of movement of accelerator pedal 300. Alternatively, the switch 404 could be closed over a predetermined range of speed of the engine by a centrifugal device (not illustrated) which would respond to engine speed.

When switch 404 is closed, the system of FIG. 13 is set to provide a controlled disabling of certain fuel injectors of the system. Thus, when switch 404 is closed, injection pulses are applied to a conductor 406. The conductor 406 feeds pulses to a pulse counter which is generally designated by reference numeral 416. Although the counter 416 can take a wide variety of forms, it is disclosed specifically herein as what is known in the art as a storage counter. This type of counter is disclosed at pages 706-713 of the book entitled Pulse, Digital and Switching Waveforms, Millman and Taub, McGraw-Hill Book Company (1965). This counter includes capacitors 418 and 420 and diodes 422 and 424. When a series of pulses is applied to the storage counter 416 the capacitor 420 is progressively charged stepwise by each pulse input to the counter so that the voltage attained by capacitor 420 is a function of the number of pulses that have been applied to the counter.

The capacitor 420 is connected with the emitter E of a unijunction transistor designated by reference numeral 426. One of the base electrodes B, of the unijunction transistor is connected with resistor 428 and with a conductor 430 which is connected to the set terminal of a flip-flop designated by reference numeral 432. The base electrode B of the unijunction transistor is connected in series with a resistor 434 and this resistor is connected in series with a resistor 436. The resistor 436 is connected in series with a source of direct current 438, the negative terminal of which is connected to one side of resistor 428 so that the voltage of direct current source 438 is applied across the base electrodes of the unijunction transistor and the magnitude of this voltage is controlled by adjusting variable resistor 436. The resistor 436 and direct current source 438 provide a means for adjusting the firing point of the counter and hence the number of counts before actuation. It is hereinafter termed a counter control which is designated in FIG. 13 by reference numeral 440.

The unijunction transistor in this circuit operates as a variable voltage discharge switch in that the unijunction transistor will conduct between its emitter E and base B to discharge capacitor 420 through resistor 428 whenever it attains a predetermined net space-path voltage. This net space-path voltage is determined by the charge on capacitor 420 and the setting of resistance 436. This means that the counter 416 will develop a voltage across resistor 428 which is applied to flip-flop 432 whenever a predetermined number of pulses have been applied to the counter 416.

Resistor 436 controls the firing point of the counter 416. It can be adjusted so that the counter can be set to be actuated for different predetermined number of counts. It is known that the voltage at which the unijunction transistor will conduct between emitter E and base B, is a function of the voltage applied across the base terminals B and 13,. This voltage is adjustable by varying resistor 436. Thus, the counter control 440 can be adjusted to vary the number of counts required before a pulse of voltage is developed across resistor 428. It will, of course, be appreciated by those skilled in the art that the variable voltage applied to base electrodes B and B, could be provided by other means, for example a tachometer generator driven by the engine where it is desired to vary the number of counts as a function of engine speed. In addition, it will be appreciated by those skilled in the art that the number of counts for counter 416 could be varied by any other suitable automatic programming means which is capable of varying the voltage between base electrodes B and B,.

The summarize the operation of the system of FIG. 13 as thus far described, it is seen that whenever switch 404 is closed the injection pulses are sequentially applied to the counter 416. When the counter 416 has accepted the predetermined count it develops a voltage across resistor 428 which is applied to flip-flop 432. The output of flip-flop 432 is applied to a conductor 442 and is of such a polarity as to bias transistor conductive. As previously pointed out in conjunction with FIG. 10, this will result in certain of the fuel injector solenoids to be disabled to prevent fuel injection by these injectors.

When the counter 416 attains its predetermined count the capacitor 420 discharges as pointed out above. The discharge of capacitor 420 automatically resets the counter 416 for a new counting cycle and the counter will again count the .pulses applied to line 406 providing switch 404 is still closed to initiate another disable event.

The flip-flop 432 has a reset terminal R that is connected to conductor 406 by a conductor 435. Each time a pulse from source 400 is applied to the R terminal of flip-flop 432, the flip-flop is reset (if it is in the set state) to a state where transistor 90 is biased nonconductive with the result that the fuel injectors are no longer disabled. The periodic application of injection pulses to reset terminal R while counter 416 is counting does not change the state of flip-flop 432 after the flipflop has been shifted from its set state to its reset state by the first reset pulse. Therefore, the transistor 90 remains biased non-conductive so that fuel injection is not inhibited as the counter 416 is counting.

When the counter 416 attains its predetermined count, the flip-flop 432 changes to its set state since a pulse is applied to set terminal S from the counter. Transistor 90 is now biased conductive to prevent fuel injection by certain of the injectors. This disabling of certain fuel injectors (for example, 10-4 or 10-8) continues until the flip-flop 432 is reset by the next pulse on line 434 from pulse source 400.

From the foregoing it will be appreciated that as long as switch 404 is closed, certain of the fuel injectors will be periodically disabled at the end of each counting cycle of counter 416. The rate of disabling will be a function of crankshaft revolutions and the setting of the counter control 440.

Referring now more particularly to FIG. 14, a modified source of pulses which could be substituted for the pulse source 400 in FIG. 13 is illustrated. In FIG. 14 a pulse generator 500 is provided which includes permanent magnet 502, a pickup coil 504 and a toothed wheel 506 which is connected with the distributor shaft and therefore rotates in synchronism with the crankshaft of the engine. The pulse generator 500 can be of a type shown in the U.S. Patent to Falge No. 3,254,427 which illustrates in detail the toothed wheel, permanent magnet and pickup coil. This pulse generator can also be used to control the ignition system of the engine and an alternating voltage is induced in pickup coil 504. This voltage is rectified by a diode 508 and the pulse output is then applied to a monostable multivibrator 510 to provide the short square wave pulses designated by reference numeral 512 in FIG. 14. The pulses 512 would then be applied to counter 416 and reset terminal R of flip-flop 432 in FIG. 13. When using the system of FIG. 14, actual power pulses are counted since the pulses 512 determine the point in time at which a spark plug is fired. It, of course, will be appreciated that whether the pulses are fuel injection pulses or ignition timing pulses, they are in each case developed in synchronism with rotation of the crankshaft of the engine and occur at predetermined angular positions of the crankshaft.

In the foregoing description, the fuel injection system is of the type having two banks of injectors with the injectors of each bank energized in unison. The invention is equally applicable to systems wherein the injectors are energized in more than two banks, or. are individually energized. In such instance, the reset lines 89 and 91, FIG. 1, for example, would each be connected to the solenoid for a cylinder that is not subject to blocking by a controlled rectifier, such as solenoids 10-2 and 10-6, respectively.

The particular cylinders selected for disabling of the fuel injection should be a group having uniform time spacings of their power strokes, such as the fourth and eighth in an eight-cylinder engine, or the second, fourth, sixth and eighth in such an engine. It will be understood, of course, that modifications and alternative constructions may be made without departing from the true spirit and scope of the present invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a multi-cylinder internal combustion engine-having a first cylinder that executes power strokes during the first half of a crankshaft rotation period and a second cylinder that executes power strokes during the second half of said crankshaft rotation period, and fuel intake valves for the cylinders, respectively;

electrically energizable fuel injectors for said cylinders, respectively, and adapted when energized to discharge fuel adjacent the fuel intake valves, respectively, for induction into the cylinders; voltage pulse developing means synchronized with operation of said engine operable to energize the fuel injectors for the first cylinder momentarily during the first half of crankshaft rotation and to energize the fuel injector for the second cylinder momentarily during the second half of crankshaft rotation;

first and second electrically controlled disabling means effective to disable the fuel injectors, respectively, said disabling means being actuated in unison and in response to a predetermined control event whereby a fuel injector is disabled in the event a disabling means is energized at the time of occurrence of a pulse from said voltage pulse developing means;

and means effective when one injector has been deenergized to reset the other for undisabled injection.

2. In combination, a multi-cylinder internal combustion engine having cylinders that execute power strokes in sequence, fuel intake valves for the cylinders, respectively, and a fuel intake manifold defining passages for the intake of airfuel mixture to said cylinders, respectively;

electrically energizable fuel injectors for said cylinders, respectively, and adapted when energized to discharge fuel to said intake manifold adjacent the fuel intake valves, respectively; pulse developing means synchronized with operation of said engine for energizing the fuel injectors, said pulse developing means being effective to alternately energize sequentially each of two fuel injectors at differing times in the engine operating cycle;

and electrical control means effective to disable in unison said two fuel injectors, said control means being actuated on a predetermined control event and being restored to inactive condition in response to a change in voltage of said pulse developing means, whereby said predetermined control event is effective to interrupt fuel for a limited time less than a complete engine operating cycle when said control event has occurred at the time a pulse is developed by said pulse developing means.

3. A fuel injection system for controlling the supply of fuel to an internal combustion engine comprising;

a plurality of electrically energizable fuel injectors for controlling the injection of fuel to said engine; means for developing a series of voltage pulses in timed relation with operation of said engine; means for applying said pulses sequentially to first and second fuel injectors whereby said fuel injectors are alternately energized in sequence to inject fuel into said engine under one condition of operation;

first and second electrically controlled disabling means connected, respectively, with said first and second fuel injectors for preventing the injection of fuel by a respective fuel injector when a disabling means is actuated;

a source of disabling control pulses;

means connecting said source of disabling control pulses to said first and second disabling means whereby said electrically controlled disabling means are energized in unison to prevent energization of an injector that has a voltage pulse applied thereto;

and means responsive to said voltage pulses for resetting said disabling control means.

4. A fuel injection system for an internal combustion engine comprising;

first and second fuel injectors each having a solenoid which when energized sufficiently opens a fuel injector valve to supply fuel to an internal combustion engine;

a source of direct current;

first and second semiconductor switch means connected, respectively, with said source of direct current and with said first and second solenoids for energizing said solenoids when a respective semiconductor switch means is biased to a conductive c0ndition;

means operable in timed relation with said engine for alternately biasing said first and second semiconductor switch means conductive for predetermined lengths of time;

third and fourth semiconductor switch means connected, respectively, in series with said first and second fuel injector solenoids;

means for causing said third and fourth semiconductor switch means to be biased alternately conductive, respectively, as said first and second semiconductor switch means are biased alternately conductive;

and control means coupled to said third and fourth semiconductor switch means for simultaneously and periodically preventing said third and fourth semiconductor switch means from being biased conductive, whereby each associated fuel injector solenoid is prevented from being energized when a respective first or second semiconductor switch means is biased conductive.

Claims

1. In combination, a multi-cylinder internal combustion engine having a first cylinder that executes power strokes during the first half of a crankshaft rotation period and a second cylinder that executes power strokes during the second half of said crankshaft rotation period, and fuel intake valves for the cylinders, respectively; electrically energizable fuel injectors for said cylinders, respectively, and adapted when energized to discharge fuel adjacent the fuel intake valves, respectively, for induction into the cylinders; voltage pulse developing means synchronized with operation of said engine operable to energize the fuel injectors for the first cylinder momentarily during the first half of crankshaft rotation and to energize the fuel injector for the second cylinder momentarily during the second half of crankshaft rotation; first and second electrically controlled disabling means effective to disable the fuel injectors, respectively, said disabling means being actuated in unison and in response to a predetermined control event whereby a fuel injector is disabled in the event a disablinG means is energized at the time of occurrence of a pulse from said voltage pulse developing means; and means effective when one injector has been deenergized to reset the other for undisabled injection.

2. In combination, a multi-cylinder internal combustion engine having cylinders that execute power strokes in sequence, fuel intake valves for the cylinders, respectively, and a fuel intake manifold defining passages for the intake of air-fuel mixture to said cylinders, respectively; electrically energizable fuel injectors for said cylinders, respectively, and adapted when energized to discharge fuel to said intake manifold adjacent the fuel intake valves, respectively; pulse developing means synchronized with operation of said engine for energizing the fuel injectors, said pulse developing means being effective to alternately energize sequentially each of two fuel injectors at differing times in the engine operating cycle; and electrical control means effective to disable in unison said two fuel injectors, said control means being actuated on a predetermined control event and being restored to inactive condition in response to a change in voltage of said pulse developing means, whereby said predetermined control event is effective to interrupt fuel for a limited time less than a complete engine operating cycle when said control event has occurred at the time a pulse is developed by said pulse developing means.

3. A fuel injection system for controlling the supply of fuel to an internal combustion engine comprising; a plurality of electrically energizable fuel injectors for controlling the injection of fuel to said engine; means for developing a series of voltage pulses in timed relation with operation of said engine; means for applying said pulses sequentially to first and second fuel injectors whereby said fuel injectors are alternately energized in sequence to inject fuel into said engine under one condition of operation; first and second electrically controlled disabling means connected, respectively, with said first and second fuel injectors for preventing the injection of fuel by a respective fuel injector when a disabling means is actuated; a source of disabling control pulses; means connecting said source of disabling control pulses to said first and second disabling means whereby said electrically controlled disabling means are energized in unison to prevent energization of an injector that has a voltage pulse applied thereto; and means responsive to said voltage pulses for resetting said disabling control means.

4. A fuel injection system for an internal combustion engine comprising; first and second fuel injectors each having a solenoid which when energized sufficiently opens a fuel injector valve to supply fuel to an internal combustion engine; a source of direct current; first and second semiconductor switch means connected, respectively, with said source of direct current and with said first and second solenoids for energizing said solenoids when a respective semiconductor switch means is biased to a conductive condition; means operable in timed relation with said engine for alternately biasing said first and second semiconductor switch means conductive for predetermined lengths of time; third and fourth semiconductor switch means connected, respectively, in series with said first and second fuel injector solenoids; means for causing said third and fourth semiconductor switch means to be biased alternately conductive, respectively, as said first and second semiconductor switch means are biased alternately conductive; and control means coupled to said third and fourth semiconductor switch means for simultaneously and periodically preventing said third and fourth semiconductor switch means from being biased conductive, whereby each associated fuel injector solenoid is prevented from being energized when a respective first or second semiconductor switch means is biased coNductive.