US3732853A

US3732853A - Electronic fuel injection system having high speed compensation

Info

Publication number: US3732853A
Application number: US00175573A
Authority: US
Inventors: L Wilkinson
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1971-08-27
Filing date: 1971-08-27
Publication date: 1973-05-15
Anticipated expiration: 1990-05-15
Also published as: JPS503450B2; CA964348A; DE2242194A1; JPS4831327A; DE2242194B2; GB1334039A

Abstract

In an internal combustion engine, the inductance of an inductive device is defined in direct relation to the intake pressure of the engine. Further, the inductive device is alternately charged through a first resistive device and discharged through a second resistive device at a trigger frequency which is defined in direct relation to the output speed of the engine. As a result, an action voltage of one polarity is developed as the inductive device is charged and a reaction voltage of opposite polarity is developed as the inductive device is discharged. Fuel is applied to the engine in an amount directly related to the duration of the action voltage as determined in direct relation to the time constant provided by the inductance of the inductive device and the resistance of the first resistive device and as determined in direct relation to the maximum peak of the action voltage. In turn, the maximum peak of the action voltage is inversely related to the minimum peak of the reaction voltage as determined in direct relation to the time constant provided by the inductance of the inductive device and the resistance of the second resistive device and as determined in direct relation to the trigger frequency. The resistances of the first and second resistive devices are selected so that the amount of fuel applied to the engine decreases with increasing output speed and increasing intake pressure after the output speed exceeds a predetermined speed limit.

Description

"United States Patent [1 1 [111 3,732,853

Wilkinson [4 May 15, 1973 [54] ELECTRONIC FUEL INJECTION take pressure of the engine. Further, the inductive SYSTEM HAVING HIGH SPEED device is alternately charged through a first resistive COMPENSATION device and discharged through a second resistive device at a trigger frequency which is defined in direct relation to the output speed of the engine. As a result, [73] Assignee: General Motors Corporation, an action voltage of one polarity is developed as the Detroit, Mich. inductive device is charged and a reaction voltage of o osite olarit is develo ed as the inductive device [22] Flled' 1971 is iischasged. uel is apglied to the engine in an [21] Appl. No.: 175,573 amount directly related to the duration of the action voltage as determined in direct relation to the time III-S. C EA 19 COn-Stant provided the inductance 0f the inductive 51 Int. (:1. ..F02d 5/02 heme and the resistance first 'eslshve devlee 5s 1 Field of Search ..123/32 EA, 119 R, and as determined in direct rehheh the maximum 1 123/140 MP peak of the action voltage. In turn, the maximum peak of the action voltage is inversely related to the [75] Inventor: Lester Wilkinson, Kokomo, Ind.

5 .R f Cited minimum peak of the reaction voltage'as determined in direct relation to the time constant provided by the UNITED STATES PATENTS inductance of the inductive device and the resistance 2 992 640 7/1961 Knapp ..123/32 EA of the i resistive f and as determined in 3:521:606 7 1970 Schmidt ..123 32 EA dheet relahh the mgger freqhehey- The sistances of the first and second resistive devices are primary Examine, Laurence Goodridge selected so that the amount of fuel applied to the en- ";fli5 w. Christen et gine decreases with increasing output speed and increasing intake pressure after the output speed ex- [57] ABSTRACT ceeds a predetermined speed limit. In an internal combustion engine, the inductance of an 3 Claims, 4 Drawing Fi ures inductive device is defined in direct relation to the in- Tl PIGCER- PULSE FORMER Al 1V1 PATENIEOIIAYI 51973 SIIEEI 1 [IF 3 INJECTOR DRIVE CIRCUIT SENSOR PRESSURE TIMING PULSE GENERATOR I INVEN'TOR fiesier M/di nw BY J.

TRIGGER PULSE FORMER PATENTEDHAY15I975 3.732.853

SHEET 2 UF 3 p LP FUEL QUANTITY PULSE LENGTH N N N, N

ENGINE SPEED 1 N VEN TOR.

fiesier [i /X12250 ATORNFY ELECTRONIC FUEL HIJECTION SYSTEM HAVING HIGH SPEED COMPENSATION This invention relates to a fuel supply system for an internal combustion engine. More particularly, the invention relates to an electronic fuel injection system for varying the amount of fuel applied to an engine in response to variations in engine speed and in engine load.

In one well known electronic fuel injection system, fuel is applied to an internal combustion engine in an amount directly related to the duration of control pulses produced by the fuel injection system. The duration of the control pulses is determined-in direct relation to the intake pressure of the engine and the frequency of the control pulses is determined in direct relation to the output speed of the engine. Thus, since the control pulses are produced at a frequency which is directly related to the output speed of the engine, the amount of fuel applied to the engine is inherently a function of engine speed.

However, due to certain speed dependent fuel delivery phenomena, such as volumetric efficiency, it may be necessary that more or less fuel be applied to the engine in response to variations in engine speed. In order to provide optimum operation for some engines, it has been found that the duration of the control pulses should be shortened at high output speeds and high intake pressures. More specifically, the duration of the control pulses should decrease with increasing engine speed and increasing intake pressure after the engine speed exceeds a predetermined speed limit. The present invention provides an electronic fuel injection system for achieving this desired speed compensation.

According to the invention, an inductive device having an inductance directly related to the intake pressure of the engine is alternately charged through a first resistive device and discharged through a second resistive device at a trigger frequency directly related to the output speed of the engine. As a result, an action voltage having a first polarity is developed when the inductive device is charged and a reaction voltage having a second polarity is developed when the inductive device is discharged. In particular, the first polarity action voltage decreases from a variable maximum peak to a fixed minimum peak as the inductive device is charged in accordance with a first time constant provided by the inductance of the inductive device and the resistance of the first resistive device. Conversely, the second polarity reaction voltage decreases from a fixed maximum peak to a variable minimum peak as the inductive device is discharged in accordance with a second time constant provided by the inductance of the inductive device and the resistance of the second resistive device.

The duration of the control pulses is equal to the duration of the action voltage as determined in direct relation to the first time constant and in direct relation to the maximum peak of the action voltage. Hence, the duration of the control pulses is directly related to the intake pressure of the engine. Further, the maximum peak of the action voltage is inversely related to the minimum peak of the reaction voltage as determined in direct relation to the second time constant and in direct relation to the trigger frequency. Utilizing these relationships, the resistances of the first and second resistive devices are selected such that the duration of the control pulses gradually decreases in response to increases in the output speed of the engine above a predetermined speed limit and further decreases in response to increases in the intake pressure of the engine when the output speed is above the predetermined speed limit.

These and other aspects and advantages of the invention may be best understood by reference to the following detailed description of a preferred embodiment when considered in conjunction with the accompanying drawings.

In the drawings:

FIG. 1 is a schematic diagram of an electronic fuel injection system incorporating the principles of the invention.

FIG. 2 is a graphic diagram of several waveforms useful in explaining the operation of the electronic fuel injection system illustrated in FIG. 1.

FIG. 3 is a graphic diagram of certain speed related engine phenomena useful in explaining the principles of the invention.

FIG. 4 is a graphic diagram of several waveforms useful in explaining the principles of the invention.

Referring to FIG. 1, an internal combustion engine 10 for an automotive vehicle includes a combustion chamber or cylinder 12. A piston '14 is mounted for reciprocation within the cylinder 12. A crankshaft 16 is supported for rotation within the engine 10. A connecting rod 18 is pivotally connected between the piston 14 and the crankshaft 16 for rotating the crankshaft within the engine 10 when the piston 14 is reciprocated within the cylinder 12.

An intake manifold 20 is connected with the cylinder 12 through an intake port 22. An exhaust manifold 24 is connected with the cylinder 12 through an exhaust port 26. An intake valve 28 is slidably mounted within the top of the cylinder 12 in cooperation with the intake port 22 for regulating the entry of combustion ingredients into the cylinder 12 from the intake manifold 20. A spark plug 30 is mounted in the top of the cylinder 12 for igniting the combustion ingredients within the cylinder 12 when the spark plug 30 is energized. An exhaust valve 32 is slidably mounted in the top of the cylinder 12 in cooperation with the exhaust port 26 for regulating the exit of combustionproducts from the cylinder 12 into the exhaust manifold 24. The intake valve 28 and the exhaust valve 32 are driven through a suitable linkage 34 which conventionally includes rocker arms, lifters, and a camshaft.

An electrical power source is provided by the vehicle battery 36. An ignition switch 38 connects the battery 36 between a power line 40 and a ground line 42. When the ignition switch 38 is closed, the battery 36 applies a supply voltage to the power line 40. A conventional ignition circuit 44 is electrically connected to the power line 40 and is mechanically connected with the crankshaft 16 of the engine 10. Further, the ignition circuit 44 is connected through a spark cable 46 to the spark plug 30. In a conventional manner, the ignition circuit 44 energizes the spark plug 30 in synchronization with the rotation of the crankshaft 16 of the engine 10. Hence, the ignition circuit 44 combines with the ignition switch 38 and the spark plug 30 to form an ignition system.

A fuel injector 48 includes a housing 50 having a fixed metering orifice 52. A plunger 54 is supported within the housing 50 for reciprocation between a fully opened position and a fully closed position. In the fully opened position, the forward end of the plunger 54 is opened away from the orifice 52. In the fully closed position, the forward end of the plunger 54 is closed against the orifice 52. A bias spring 56 is seated between the rearward end of the plunger 54 and the housing 50 for normally maintaining the plunger 54 in the fully closed position. A solenoid or winding 58 is electromagnetically coupled with plunger 54 for driving the plunger 54 to the fully opened position against the action of the bias spring 56 when the winding 58 is energized. The bias spring 56 drives the plunger 54 to the fully closed position when the winding 58 is deenergized. The fuel injector 48 is mounted on the intake manifold 20 of the engine for injecting fuel into the intake manifold at a constant flow rate through the metering orifice 52 when the plunger 54 is in the fully opened position. Notwithstanding the illustrated structure, it is to be noted that the fuel injector 48 may be provided by virtually any suitable constant flow rate valve.

A fuel pump 60 is connected to the fuel injector 48 by a conduit 62 and to the vehicle fuel tank 64 by a conduit 66 for pumping fuel from the fuel tank 64 to the fuel injector 48. Preferably, the fuel pump 60 is connected to the power line 40 to be electrically driven from the vehicle battery 36. Altemately, the fuel pump 60 could be connected to the crankshaft 16 to be mechanically driven from the engine 10. A pressure regulator 68 is connected to the conduit 62 by a conduit 70 and is connected to the fuel tank 64 by a conduit 72 for defining the pressure of the fuel applied to the fuel injector 48. Thus, the fuel injector 48 combines with the fuel tank 64, the fuel pump 60 and the pressure regulator 68 to form a fuel supply system.

A throttle valve 74 is rotatably mounted within the intake manifold 20 for regulating the flow of air into the intake manifold 20 in accordance with the position of the throttle valve 74. The throttle valve 74 is connected through a suitable linkage 76 with the vehicle accelerator pedal 78. The accelerator pedal 78 is pivotably mounted on a reference surface for movement against the action of a compression spring 79 seated between the accelerator pedal 78 and the reference surface. As the accelerator pedal 78 is depressed, the throttle valve 74 is moved to a more opened position to increase the flow of air into the intake manifold 20. Conversely, as the accelerator pedal 78 is released, the throttle valve 74 is moved to a less opened position to decrease the flow of air into the intake manifold 20.

In operation, fuel and air are combined within the intake manifold 20 to form an air/fuel mixture. The fuel is injected into the intake manifold 20 at a constant flow rate by the fuel injector 48 in response to energization. The precise amount of fuel deposited within the intake manifold 20 is regulated by a fuel control system which Will be described later. The air enters the intake manifold 20 from the air intake system (not shown) which conventionally includes an air filter. The precise amount of air admitted into the intake manifold 20 is determined by the position of the throttle valve 74. As previously described, the position of the accelerator pedal 78 controls the position of the throttle valve 74.

As the piston 14 initially moves downward within the cylinder 12 on the intake stroke, the intake valve 28 is opened away from the intake port 22 and the exhaust valve 32 is closed against the exhaust port 26. Accordingly, combustion ingredients in the form of the air/fuel mixture within the intake manifold 20 are drawn by negative pressure through the intake port 22 into the cylinder 12. As the piston 14 subsequently moves up- Ward within the cylinder 12 on the compression stroke, the intake valve 28 is closed against the intake port 22 so that the air/fuel mixture is compressed between the top of the piston 14 and the top of the cylinder 12. When the piston 14 reaches the end of its upward travel on the compression stroke, the spark plug 30 is energized by the ignition circuit 44 to ignite the air/fuel mixture. The ignition of the air/fuel mixture starts a combustion reaction which drives the piston 14 downward within the cylinder 12 on the power stroke. As the piston 14 again moves upward within the cylinder 12 on the exhaust stroke, the exhaust valve 32 is opened away from the exhaust port 26. As a result, the combustion products in the form of various exhaust gases are pushed by positive pressure out of the cylinder 12 through the exhaust port 26 into the exhaust manifold 24. The exhaust gases pass out of the exhaust manifold 24 into the exhaust system (not shown) which conventionally includes a muffler and an exhaust pipe.

Although the structure and operation of only a single combustion chamber or cylinder 12 has been described, it will be readily appreciated that the illustrated internal combustion engine 10 may include additional cylinders 12 as desired. Similarly, additional fuel injectors 48 may be provided as required. However, as long as the fuel injectors 48 are mounted on the intake manifold 20, the number of additional fuel injectors 48 need not necessarily bear any fixed relation to the number of additional cylinders 12. Altemately, the fuel injector 48 may be directly mounted on the cylinder 12 so as to inject fuel directly into the cylinder 12. In such instance, the number of additional fuel injectors 48 would necessarily equal the number of additional cylinders 12. At this point, it is to be understood that the illustrated internal combustion engine 10, together with all of its associated equipment, is shown only to facilitate a more complete understanding of the inventive electronic control system.

A timing pulse generator 80 is connected with the crankshaft 16 for developing rectangular timing pulses having a frequency which is proportional to and synchronized with the rotating speed of the crankshaft 16. The rectangular timing pulses are applied to a timing line 82. Preferably, the timing pulse generator 80 is some type of inductive speed transducer coupled with a switching circuit. However, the timing pulse generator 80 may be provided by virtually any suitable pulse producing device such as a multiple contact rotary switch.

An injector drive circuit 84 is connected to the power line 40 and to the timing line 82. Further, the injector drive circuit 84 is connected through an injection line 86 to the fuel injector 48. The injector drive circuit 84 is responsive to the timing pulses produced by the timing pulse generator 80 to energize the fuel injector valve 48 in synchronization with the rotating speed or frequency of the crankshaft 16 in much the same manner as the ignition circuit 44 energizes the spark plug 30. The time period for which the fuel injector 48 is energized by the drive circuit 84 is determined by the length or duration of rectangular control pulses produced by a modulator or control pulse generator 88 which will be more fully described later. The control pulses are applied by the control pulse generator 88 to the injector drive circuit 84 over a control line 90 in synchronization with the timing pulses produced by the timing pulse generator 80. In other words, the injector drive circuit 84 is responsive to the coincidence of a timing pulse and a control pulse to energize the fuel injector 48 for the length or duration of the control pulse.

The injector drive circuit 84 may be virtually any amplifier circuit capable of logically executing the desired coincident pulse operation. However, where additional fuel injectors 48 are provided, it may be necessary that the injector drive circuit 84 also select which one or ones of the fuel injectors 48 are to be energized in response to each respective timing pulse. As an example, the fuel injectors 48 may be divided into separate groups which are successively energized in response to successive ones of the timing pulses. Conversely, the timing pulses may be applied to operate a counter circuit or a logic circuit which individually selects the fuel injectors 48 for energization.

The control pulse generator 88 includes a timing network 92, a timing switch 94, a switching circuit 96 and an output switch 98. The timing network 92 includes a control transducer 100, a first control resistor 102 and a second control resistor 104. The control transducer 100 includes an inductor or control winding 106 connected in series with the control resistors 102 and 104 between the power line 40 and the ground line 42. F urther, the control transducer 100 includes a movable magnetizable core 108 which is inductively coupled with the winding 106. The deeper the core 108 is inserted within the winding 106, the greater the inductance of the winding 106. The movable core 108 is mechanically connected through a suitable linkage 110 with a pressure sensor 112. The pressure sensor 112 communicates with the intake manifold of the engine l0'downstream from the throttle valve 74 through a conduit 114 for monitoring the negative pressure or vacuum within the intake manifold 20. The pressure sensor 112 moves the core 108 within the winding 106 of the control transducer 100 to regulate the inductance of the winding 106 in direct relation to the pressure within the intake manifold 20. Therefore, as the pressure within the intake manifold 20 increases in response to opening of the throttle valve 74, the core 108 is inserted deeper within the winding 106 of the control transducer 100 to proportionally increase the inductance of the winding 106.

The timing switch 94 is provided by an NPN junction transistor 116. The emitter electrode of the transistor 116 is connected directly to the ground line 42. The collector electrode of the' transistor 116 is connected directly to a junction 1 18 between the first and second control resistors 102 and 104 in the timing network 92. The base electrode of the transistor 116 is connected through a turnoff diode 120 and a biasing resistor 122 to a junction 124 in the switching circuit 96.

The switching circuit 96 includes a differential switch or amplifier 126 and a buffer switch 128. The differential amplifier 126 includes

NPN junction transistors

129, 130, and 132. The emitter electrode of the transistor 129 is connected directly to the ground line 42. The collector electrode of the transistor 129 is connected to a junction 134 between the emitter electrodes of the

transistors

130 and 132. The base electrode of the transistor 129 is connected to a junction 136 between a temperature compensating diode 138 and a biasing resistor 140 which are connected in series between the power line 40 and the ground line 42. The base electrode of the transistor is connected directly to the junction 118 in the timing network 92. The base electrode of the transistor 132 is connected to a junction 142 between a pair of biasing

resistors

144 and 146 which are connected in series between the power line 40 and the ground line 42. The collector electrode of the transistor 130 is connected directly to the power line 40, the collector electrode of the transistor 132 is connected through a biasing resistor 148 to the power line 40.

The buffer switch 128 includes PNP junction transistor 150 and an NPN junction transistor 152. The emitter electrode of the transistor 150 and the collector electrode of the transistor 152 are connected together directly to the power line 40. The collector electrode of the transistor 150 is connected directly to the base electrode of the transistor 152. The base electrode of the transistor 150 is connected directly to the collector electrode of the transistor 132 in the differential amplifier 126. The emitter electrode of the transistor 152 is connected through a biasing resistor 154 to the junction 124. Further, a biasing resistor 156 is connected between the junction 124 and the ground line 42.

The output switch 98 is provided by an NPN junction transistor 158. The emitter electrode of the transistor 158 is connected directly to the ground line 42. The collector electrode of the transistor 158 is connected through a biasing resistor 160 to the power line 40. In addition, the collector electrode of the transistor 158 is connected directly to the control'line 90. The base electrode of the transistor 158 is connected through a biasing resistor 162 to the input junction 124 in the bistable circuit 96.

A trigger pulse former 164 is connected between the timing line 82 and the junction 124 of the control pulse generator 88 for developing negative trigger pulses or voltage spikes in response to the rectangular timing pulses produced by the timing pulse generator 80. More specifically, the trigger pulse former 164 provides a trigger pulse in coincidence with the initiation of each of the timing pulses on the timing line 82. Thus, the trigger pulses have the same frequency as the timing pulses. The trigger pulse former 164 may be provided by a simple RC differentiator or any other suitable trigger pulse forming circuit. Together, the trigger pulse former 164 and the timing pulse generator 80 comprise a timing apparatus for producing trigger pulses having a trigger frequency proportional to the output speed of the engine 10.

Referring to FIGS. 1 and 2, the timing network 92 produces a control signal A across the winding 106 of the control transducer 100. As will be more fully described later, the control signal A includes an action voltage A, having a positive polarity and a reaction voltage A having a negative polarity. In the switching circuit 96, the transistor 129 combines with the diode 138 and the resistor 140 to provide a constant current sink for the differential amplifier 126 at the junction 134. Further, the

resistors

144 and 146 form a voltage divider network for providing a reference voltage at the junction 142. The reference voltage is substantially constant at a reference level L, determined by the ratio of the

resistances

144 and 146.

In the conventional manner, the differential switch or amplifier 126 is operable between first and second states. More particularly, the differential amplifier 126 switches to the second state when the voltage at the junction 118 exceeds the voltage at the junction 142 and switches to the first state when the voltage at the junction 142 exceeds the voltage at the junction 118. Hence, the differential amplifier 126 switches from the first state to the second state when the amplitude of the control signal A across the winding 106 initially increases above a reference level L, and switches from the second state to the first state when the amplitude of the control signal A subsequently decreases to the reference level L,. The reference level L, is approxi mately equal to the reference level L, as shifted in accordance with the resistance ratio of the first and second control resistors 102 and 104.

In the first state of the switching circuit 96, the transistor 132 is rendered fully conductive and the transistor 130 is rendered fully nonconductive. With the transistor 132 turned on, the transistors 150 and 152 in the buffer switch 128 are rendered fully conductive through the biasing action of the resistor 148 and the transistors 128 and 132. in the second state of the switching circuit 96, the transistor 130 is rendered fully conductive and the transistor 132 is rendered fully nonconductive. With the transistor 132 turned off, the transistors 150 and 152 in the buffer switch 128 are rendered fully nonconductive through the biasing action of the resistor 148.

Before time t,, it is assumed that the differentia amplifier 126 is in the first state. As a result, the transistor 132 is turned on to turn on the buffer switch 128. With the buffer switch transistors 150 and 152 turned on, the timing switch transistor 116 is rendered fully conductive through the biasing action of the

resistors

122, 154, and 156. With the transistor 1 16 turned on, the control junction 118 in the timing network 92 is effectively clamped to the ground line 42 through the transistor 116. Thus, the transistor 1 16 effectively places a short circuit across the first resistor 104 and the control winding 106 of the timing network 92. Further, with the buffer switch 128 turned on, the output switch transistor 158 is rendered fully conductive through the biasing action of the resistors 154, 156, and 162. With the transistor 158 turned on, the control line 90 is effectively connected to the ground line 42 through the transistor 158. Hence, before time 1,, no control pulses C are developed on the control line 90 as shown in FIG. 2.

As previously described, the trigger pulse former 164 applies negative trigger pulses to the junction 124 of the control pulse generator 88 at a trigger frequency defined in direct relation to the speed of the engine 10. Assuming a trigger pulse arrives at the junction 124 at time t,, it instantaneously renders both the timing switch transistor 116 and the output switch transistor 158 fully nonconductive. With the transistor 158' turned off, the control line 90 is unclamped from the ground line 42. Thus, at time t,, a control pulse C is initiated on the control line 90 as shown in FIG. 2. The voltage level ofthe control pulse C is determined by the supply voltage on the power line 40 and the resistance of the biasing resistor 160.

Further, with the timing switch transistor 116 turned off, the junction 118 is unclamped from the ground line 42. As a result, the winding 106 of the control transducer 100 charges through the first and second control resistors 102 and 104 to develop the action voltage A, across the inductor 106. Initially, at time t,, the action voltage A, or charging voltage instantaneously increases to a maximum positive polarity peak above the reference level L,. Subsequently, the action voltage A, gradually decreases in accordance with a first L/R time constant provided by the inductance of the winding 106 and the combined resistances of the first and second control resistors 102 and 104. At time t the action voltage A, decreases to a minimum positive polarity peak equal to the reference level L,.

At time the differential amplifier 126 switches from the first state to the second state as the action voltage A, rises above the reference level L,. In the second-state, the transistor 130 is turned on and the transistor 132 is turned off to turn off the buffer switch 128. With the buffer switch transistors 150 and 152 turned off, the output switch transistor 158 and the timing switch transistor 116 remain turned off. At time 2 the differential amplifier 126 switches from the second state to the first state. With the differential amplifier 126 in the first state, the transistor 130 is turned off and the transistor 132 is turned on to turn on the buffer switch 128. With the buffer switch transistors 150 and 152 turned on, the timing switch transistor 116 and the output switch transistor 158 are turned on. With the output switch transistor 158 turned on, the control line is effectively clamped to the ground line 42. Hence, at time 1 the control pulse C is terminated on the control line 90 as shown in FIG. 2.

Further, with the control switch transistor 116 turned on at time 2 the junction 118 is effectively connected to the ground line 42. As a result, the control winding 106 of the control transducer discharges through the second control resistor 104 and the transistor 116 to develop the negative polarity reaction voltage A across the winding 106. Initially, at time 1 the reaction voltage A or discharging voltage instantaneously increases to a maximum negative peak. Subsequently, the reaction voltage A decreases in accordance with a second L/R time constant provided by the inductance of the control winding 102 and the resistance of the second control resistor 104. At time t the reaction voltage A reaches a minimum negative polarity peak as a negative trigger pulse next arrives at the junction 124 to again initiate the action voltage A,. Consequently, at time t,,, another control pulse C is initiated on the control line 90 and the operation of the control pulse generator 88 is as previously described.

It will now be appreciated that the duration of the control pulses C is equal to the duration of the action voltage A, as determined in direct relation to the first L/R time constant provided by the inductance of the control winding 106 and the total resistance of the first and second control resistors 102 and 104. Further, since the inductance of the control Winding 106 is directly related to the negative pressure in the intake manifold 20, the duration of the control pulses C is directly related to the intake pressure of the engine 10. Thus, as the intake pressure of the engine 10 increases, the duration of the control pulses C also increases. Of course, the duration of the control pulses C may additionally be determined as a function of several other engine operating parameters, such as engine temperature or battery voltage. As previously described, the fuel injector 46 is energized to apply fuel to the engine 10 for the duration of the control pulses C.

The frequency of the control pulses C is defined by the frequency of the trigger pulses applied at the junction 124 of the control pulse generator 88. Hence, the

frequency of the control pulses C is directly related to the output speed of the engine 10. As a result, the amount of fuel applied to the engine 10 is inherently a function of engine output speed. However, due to certain speed related fuel delivery phenomena, such as volumetric efficiency, it is necessary that the normal fuel quantity be changed in response to variations in the output speed of the engine 10. The effects of these fuel delivery phenomena may be best understood by reference to FIG. 3, which illustrates a set of typical fuel demand curves D,D assuming the engine 10 includes eight cylinders. The fuel demand curves D,D., each represent a graph of engine fuel quantity versus engine output speed at different constant intake pressures. Specifically, the intake pressure corresponding to the fuel demand curve D, is relatively low while the intake pressure corresponding to the fuel demand curve D is relatively high. Since the quantity of fuel delivered to the engine 10 is directly related to the duration of the control pulses C, the ordinate of the graph also repre-sents the duration of the control pulses C.

In general, the fuel demand curves D,D each exhibit one transition point at approximately the same lower speed limit N and another transition point at approximately the same upper speed limit N Below the lower speed limit N the fuel demand curves D,D., are each relatively constant at different minimum levels. Between the lower speed limit N, and the upper speed limit N the fuel demand curves D,D each gradually increase from the different minimum levels to different maximum levels. Above the upper speed limit N the fuel demand curves D,-D., decrease with increasing engine output speed. Further, above the upper speed limit N the fuel demand curves D,D., decrease with increasing engine intake pressure. Hence, the fuel demand curve D, exhibits the least decrease while the fuel demand curve D, exhibits the most decrease.

In order to achieve optimum operation of the engine 10, the fuel demand curves D,-D indicate that the amount of fuel normally applied to the engine 10 must be compensated for variations in the output speed of the engine 10. More specifically, an increasing amount of extra fuel should be added to the normal fuel quantity in response to increasing output speed between the lower speed limit N and the upper speed limit N That is, the normal duration of the control pulses C, as determined by the intake pressure of the engine 10, should be extended by a percentage which increases with increasing engine speed between the lower speed limit N and the upper speed limit N Alternately, when the speed of the engine is below the lower speed limit N a constant minimum amount of fuel should be added to the normal fuel quantity. In other words, the normal duration of the control pulses C, as determined by the intake pressure of the engine 10, should be increased by a constant minimum percentage when the engine speed is below the lower speed limit N An electronic fuel injection system for providing this desired speed compensation as illustrated in copending U. S. Pat. application Ser. No. 158,800.

In addition, the fuel demand curves D,-D., indicate that the extra fuel applied to the engine 10 should be reduced at relatively high output speeds and high intake pressures. In particular, the extra fuel applied to the engine 10 should decrease with increasing output speed and increasing intake pressure when the output speed of the engine 10 is above the upper speed limit N,,. The present invention provides an electronic fuel injection system for achieving this additional speed compensation. Specifically, the control pulse generator 88 operates in a speed compensation mode to shorten the duration of the control pulses C by a percentage which increases with increasing engine output speed and increasing engine intake pressure when the output speed of the engine 10 exceeds the upper speed limit N As previously described, the duration of thecontrol pulses C is defined by the duration of the action voltage A, as determined in direct relation to the first L/R time constant provided by the inductance of the control winding 106 and the combined resistances of the first and second control resistors 102 and 104. However, the duration of the action voltage A, is also directly related to the maximum positive peak of the action voltage A,. In turn, the maximum positive peak of the action voltage A, is inversely related to the minimum negative peak of the reaction voltage A That is, as the minimum negative peak of the reaction voltage A increases, the maximum positive peak of the action voltage A, proportionally decreases. The minimum negative peak of the reaction voltage A is directly related to the trigger frequency at which the trigger pulses are applied to the control pulse generator 88 as determined in direct relation to the output speed of the engine 10. Moreover, the minimum negative peak of the reaction voltage A is directly related to the second L/R time constant provided by the inductance of the control winding 106 and the resistance of the second control resistor 104. Of course, the first and second L/R time constants are directly related to the inductance of the control winding 106 as determined in direct relation to the intake pressure of the engine 10.

Utilizing these relationships between the action voltage A, and the reaction voltage A the duration of the control pulses C produced by the control pulse generator 88 may be controlled by varying the resistances of the first and second control resistors 102 and 104. Thus, variation of the resistance of both the first and second control resistors 102 and 104 alters both the first and second L/R time constants while variation of the resistance of only the second control resistor 104 alters only the duration of the second L/R time constant. In this manner, it is possible to condition the timing network 92 such that the duration of the control pulses C produced by the control pulse generator 88 increases with increasing engine speed when the output speed of the engine 10 is above the upper speed limit N, and also decreases with increasing intake pressure when the output speed of the engine 10 is above the upper speed limit N This result is dramatically demonstrated by the waveforms of FIG. 4.

In FIG. 4a, the intake pressure of the engine 10 corresponds to the fuel demand curve D of FIG. 3 while the output speed of the engine 10 corresponds to an engine speed N, which is shown in FIG. 3. The engine speed N, is greater than the upper speed limit N Under these conditions, the maximum positive peak of the action voltage A, is above the reference level L, by a magnitude M,. The magnitude M, is determined in inverse relation to the intake pressure of the engine 10 acting through the second L/R time constant and in inverse relation to the output speed of the engine 10 acting through the frequency of the trigger pulses. The resultant duration of the control pulses C is given by the time period T as defined by the duration of the action voltage A In FIG 4b, the intake pressure of the engine corresponds to the fuel demand curve 1);, of FIG. 3 while the output speed of the engine 10 corresponds to the engine speed N which is shown in FIG. 3. Under these conditions, the maximum positive peak of the action voltage A is above the reference level L by a magnitude M Since the engine speed N is greater than the engine speed N the magnitude M is smaller than the magnitude M due to the inverse relation between the maximum positive peak of the action voltage A and the output speed of the engine 10 acting through the frequency of the trigger pulses. Hence, as the output speed of the engine 10 increases above the upper speed limit N the maximum positive peak of the action voltage A decreases. The resultant duration of the control pulses C is given by the time period T which is correspondingly less than the time period T Accordingly, the amount of fuel applied to the engine 10 decreases with increasing engine output speed above the upper speed limit N In FIG. 40, the intake pressure of the engine 10 corresponds to the fuel demand curve D of FIG. 3 while the output speed of the engine 10 corresponds to the engine speed N which is shown in FIG. 3. Under these conditions, the maximum positive peak of the action voltage A is above the reference level L, by a magnitude M Since the intake pressure corresponding to the fuel demand curve D is greater than the intake pressure corresponding to the fuel demand curve D the magnitude M is smaller than the magnitude M due to the inverse relation between the maximum positive peak of the action voltage A and the intake pressure of the engine 10. Thus, as the intake pressure of the engine 10 increases when the engine output speed is above the upper speed limit N the maximum positive peak of the action voltage A decreases. The resultant duration of the control pulses C is given by the time period T which is correspondingly less then the time period T Consequently, the amount of fuel applied to the engine 10 decreases with increasing intake pressure when the output speed of the engine 10 is above the upper speed limit N It will now be appreciated that the present invention provides a simple but effective technique for decreasing the amount of fuel applied to an internal combustion engine with increasing engine speed and increasing intake pressure when the engine speed is above a predetermined speed limit. However, it is to be understood that the illustrated embodiment of the invention is shown for demonstrative purposes only and that various alterations and modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention.

What is claimed is:

1. In an internal combustion engine exhibiting a variable intake pressure and a variable output speed, the combination comprising: a timing network including an inductor and first and second resistors for alternately providing an action voltage and a reaction voltage of opposite polarity; transducer means for defining the inductance of the inductor as a direct function of the intake pressure of the engine; charging means for charging the inductor through the first and second resistors when triggered to terminate the reaction voltage and to initiate the action voltage which substantially instantaneously increases to a variable maximum peak and which subsequently gradually decreases in accordance with a first time constant provided by the inductance of the inductor and the combined resistances of the first and second resistors to a fixed minimum peak when the reaction voltage is next initiated; discharging means for discharging the inductor through the second resistor when the action voltage reaches the fixed minimum peak to ter-minate the action voltage and to initiate the reaction voltage which substantially instantaneously increases to a fixed maximum peak and which subsequently gradually decreases in accordance with a second time constant provided by the inductance of the inductor and the resistance of the second resistor to a variable minimum peak when the action voltage is next initiated; timing means for triggering the charging means at a trigger frequency determined as a direct function of the output speed of the engine; and fuel supply means for applying fuel to the engine in an amount directly related to the duration of the action voltage as determined in direct relation to the first time constant and the maximum peak of the action voltage which is inversely related to the minimum peak of the reaction voltage as determined in direct relation to the second time constant and the trigger frequency; the resistances of the first and second resistors selected such that the amount of fuel applied to the engine decreases with increasing output speed and increasing intake pressure when the output speed is above a predetermined speed limit.

2. In an internal combustion engine exhibiting a variable intake pressure and a variable output speed; the combination comprising: a timing network including the series connection of an inductor and first and second resistors for alternately providing an action voltage and a reaction voltage of opposite polarity; means for defining the inductance of the inductor in direct relation to the intake pressure of the engine; means for producing control pulses each initiated when the action voltage initially increases above a reference level and each terminated when the action voltage subsequently decreases to the reference level; means for producing trigger pulses having a trigger frequency defined in direct relation to the output speed of the engine; means for charging the inductor through the first and second resistors in response to the occurrence of each of the trigger pulses to terminate the reaction voltage and initiate the action voltage which substantially instantaneously increases to a variable maximum peak above the reference level and which subsequently gradually decreases in accordance with a first time constant provided by the inductance of the inductor and the combined resistances of the first and second resistors to a fixed minimum peak at the reference level when the action voltage is next initiated; means for discharging the inductor through the second resistor in response to the termination of each of the control pulses to terminate the action voltage and to initiate the reaction voltage which substantially instantaneously increases to a fixed maximum peak and which subsequently gradually decreases in accordance with a second time constant provided by the inductance of the inductor and the resistance of the second resistor to a variable minimum peak when the reaction voltage is next initiated; and means for applying fuel to the engine in an amount directly related to the duration of the control pulses as determined in direct relation to the first time constant and the maximum peak of the action voltage which is inversely related to the minimum peak of the reaction voltage as determined in direct relation to the second time constant and the trigger frequency, the resistances of the first and second resistors selected such that the amount of fuel applied to the engine decreases with increasing output speed when the output speed is above a predetermined speed limit and decreases with increasing intake pressure when the output speed is above the predetermined speed limit.

3. In an internal combustion engine exhibiting a variable intake pressure and a variable output speed, the combination comprising: a timing network including an inductor and a pair of resistors for providing a control signal including an action voltage and a reaction voltage of opposite polarity; means for defining the inductance of the inductor in direct relation to the intake pressure of the engine; means including a switching circuit operable from a first state to a second state to initiate a control pulse as the action voltage increases above a reference level and operable from the second state to the first state to terminate the control pulse as the action voltage decreases to the reference level; means for producing trigger pulses having a trigger frequency defined in direct relation to the output speed of the engine; means including a switching device operable from a first condition to a second condition in response to the occurrence of each of the trigger pulses and operable from the second condition to the first condition in response to operation of the switching circuit from the first state to the second state, the switching device connected with the timing network to charge the inductor through the pair of resistors when in the second condition to terminate the reaction voltage and to initiate the action voltage which substantially instantaneously increases to a variable maximum peak above the reference level and which subsequently gradually decreases in accordance with a first L/R time constant provided by the inductance of the inductor and the combined resistances of the pair of resistors to a fixed minimum peak when the reaction voltage is next initiated, and the switching device connected with the timing network to discharge the inductor through one of the pair of resistors when in the first condition to terminate the action voltage and to initiate the reaction voltage which substantially instantaneously increases to a fixed maximum peak and which subsequently gradually decreases in accordance with a second L/R time constant provided by the inductance of the inductor and the resistance of the one of the pair of resistors to a variable minimum peak when the action voltage is next initiated; and means for applying fuel to the engine in an amount directly related to the duration of the control pulses as determined in direct relation to the first time constant and the maximum peak of the action voltage which is inversely related to the minimum peak of the reaction voltage as determined in direct relation to the second time constant and the trigger frequency; the resistances of the pair of resistors selected such that the amount of fuel applied to the engine decreases with increasing output speed and with increasing intake pressure when the output speed exceeds a predetermined speed limit.