GB1567044A - Fuel injection system for internal combustion engine - Google Patents

Description

(54) IMPROVED FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINE (71) We, ALLIED CHEMICAL COR PORTION, a Corporation organized and existing under the laws of the State of New York, United States of America, of Columbia Road and Park Avenue, Morris Township, Morris County, New Jersey, 07960, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to fuel Injection systems for an internal combustion, spark ignited engine including means for modifying the fuel charge supplied to the engine during deceleration.

Fuel injection systems for internal combustion, spark ignited engines have been developed which provide each cylinder with a measured quantity of fuel during each engine cycle. The systems employ sensors for manifold pressure, engine temperature and other engine operating parameters, and control the fuel charge as a function of these parameters. These systems were initially devised to improve the fuel economy and performance of the engine relative to that obtainable with a conventional carburettor and their popularity has increased in the last few yearns because of their ability to minimize engine emission pollutants through accurate control of the fuel-air ratio. The systems typically measure manifold pressure, engine temperature and other parameters, and provide the engine with a sufficient charge of fuel at a desired fuel-air ratio.The fuel charge is provided to the intake system of the engine at intervals bearing a timed relationship to the engine operation, such as once per engine cycle.

The present invention relates to improvements in or modifications of the invention of our copending Patent Application No.

45147/76 (Serial No. 1567041) in which we disclose the fuel injection system wherein the injectors take the form of normally closed, electrically energized, valves that provide fuel to the immediate vicinity of the intake valves externally of the cylinders. In order to maximize the vaporisation of this liquid fuel charge before it is admitted to the cylinder the injection time is preferably controlled to closely follow the closing of the engine intake valve. The charge is then heated by the intake valve to promote vaporization before the engine intake valve to promote vaporization before the engine intake valve opens.

The highly vaporized charge burns more completely.

The fuel injection system thus measures the engine parameters at one instant once per engine cycle and injects a quantity of fuel based upon those measurements. If the engine air flow is substantially constant from cycle to cycle, the injected quantity of fuel should be correct to produce the desired fuel-air ratio, but if the engine air flow varies more than a predtermined amount during an engine cycle, such as during deceleration, the previously injected fuel quantity will cause the fuel-air ratio to vary from a desired optimum.

The difference between the actual injected fuel quantity and the calculated optimum quantity is a function of both the engine speed and the rate of change of engine speed.

At high speeds, relatively little time elapses between the calculation of the desired fuel charge and its passage into the cylinder, but the delay is greater at lower speeds. A rapid deceleration occurring at a lower engine speed may result in an appreciable departure in the injected fuel quantity from the optimum in relation to instantaneous engine air flow. During deceleration, the engine may receive too large a fuel charge and the engine emissions will sharply increase temporarily. Additionally, this overly rich charge will combine will all of the air admitted to the engine cylinder during combustion and if the engine is cquipped with a catalytic converter the exhaust will not contain sufficient uncombined oxygen to allow proPer converter operation, further increasing the emission pollutants.

The present invention provides a fuel injection system for aan internal combustion engine and comprising means for measuring engine manifold pressure and other engine operating parameters and for providing fuel to the engine BS;;I function of the measured parameters, the system including means for sensing the rate of decrease of engine manifold pressure and means for modifying the fuel charge provided to the engine as a continuous function of such rate of decrease of engine manifold pressure while manifold prCSStlrC iS decreasing above a prcdtcmmined rate. l'hus the system modifies the fuel charge in proportion to the rate of deceleration of the engine on a per cycle basis to prevent the supply of an excessive fuel charge which would cause a momentary increase in undesirable engine emissions.

A preferred embodiment of the invention which will subsequently be disclosed in detail, cmploys electromagnetically actuated injectors, which arc actuated once each engine cycle for a period of time determined by an electric pulse generated by a circuit.

The circuit employs a capacitor which is charged to a voltage that is a function of the manifold pressure, and upon receipt of a triggering signal, discharges through a resistance. The value of the resistance and the voltage level imposed at the end of the resistance and the voltage level imposed at the end of the resistance opposte to the capacitor, are determined by other engine operating parameters. An injector actuating pulse is generated during the discharge of the capacitor.

To modify the pulse duration as a continuous function of the rate of deceleration of the vehicle, a discharge resistor is shunted by the emitter-collector circuit of a transistor and the state of conduction of the transistor is controlled by the voltage on one end of a capacitor that receives a voltage proportional to the rate of change of the manifold pressure at its other end. As the engine decelerates, the manifold pressure decreases and applies an increasing voltage to the capacitor. The capacitor couples this changing voltage to the base of the transistor, increasing its conduction to effectively decrease the value of the discharge resistance and decrease the discharge time.

In an alternative embodiment of the invention, the manifold pressure is imposed on a diaphragm connected to a movable arm of a potentiometer. A decrease in manifold pressure causes the diaphragm to move and a vent then allows the pressure to equalize across the diaphragm, allowing the diaphragm to return to its original position. The potentiometer signal in combination with a transistor shunts the discharge resistance in the pulse generating circuit.

The duration of the actuating pulse duration to the injectors is thus modified in response to a decreasing manifold pressure signal, thereby decreasing the quantity of fuel provided to the engine during deceleration to prevent transient increases in emission pollutants.

The present invention will become further apparent from the following detailed description of a preferred embodiment of the invention given by way of example with reference to the accompanying drawings, in which: Figure 1 is a partially schematic, partially block diagram of a fuel injection system having a preferred embodiment of the present invention, detailing components associated with a single engine cylinder; Figure 2 is a schematic diagram of the variable width pulse generator used with the system of Figure 1 and incorporating fuel charge modification means for decreasing the injector actuating pulse duration during engine deceleration; and Figure 3 is an illustration of an alternative embodiment of deceleration sensor useful with the system of Figure 1.

Referring to the drawings, Figure 1 illustrates an ignition and fuel injection system associated with a single cylinder 10 of an internal combustion, spark ignited engine for a vehicle, such as that disclosed in the Specification of our copending Patent Application No. 45147/76 (Serial No. 1567041).

A fuel charge admitted to the cylinder 10 through an engine intake valve 12 is ignited at an appropriate time in the engine cycle by a spark plug 14. The spark plug 14 is energized through a distributor 16 having its rotor 17 connected to the secondary circuit of an ignition coil 18. The rotor 17 is driven in timed relation to the engine rotation. The other distributor contacts are connected to spark plugs associated with other engine cylinders (not shown).

The primary circuit of the ignition coil 18 is energized in timed relation to the engine operation by a vehicle battery 20 through breaker points 22. A capacitor 24 shunts the breaker points 22.

The primary circuit of the ignition coil 18 is also connected to a multi-stage counter 26 so that the counter 26 receives an electric pulse each time the breaker points 22 are actuated by the engine. The counter 26 has a plurality of output lines 28 and these are sequentially energized as the counter 26 is advanced by the input pulses from the ignition primary circuit.

One of the counter output lines 28 is provided as a triggering input to a variable width pulse generator 30 and the other counter outputs are provided to similar pulse generators associated with the other engine cylinders (not shown). The variable width pulse generator 30 also receives outputs from a group of engine sensors 32 which may measure engine temperature, and other engine and environmental parameters. The engine sensors 32 provide controlling signals to the pulse generator 30 as a function of these parameters. The variable width pulse generator 30 receives another electrical signal, proportional to the pressure in the engine intake manifold 34, either a vacuum with referance to atmospheric pressure or an absolute pressure, from a pressure sensor 36 associated with the manifold 34.In a preferred embodiment, a differential pressure sensor is used to measure manifold pressure. In alternative embodiments of the invention, the outputs of the sensor 36 may be proportional to the absolute pressure in the manifold 34 as opposed to the differential pressure between the pressure in manifold 34 and atmospheric pressure in normally aspirated engines.

The output of the pressure sensor 36 is also provided to a differentiator circuit 38 which generates an electric output signal proportional to the rate of change of decreasing manifold pressure and provides such output to the variable width pulse generator 30.

Upon receipt of a triggering pulse on line 28, the variable width pulse generator 30 generates an electric output puLse on line 40 having a duration that is a function of the inputs from sensors 32 and 36 and the differential circuit 38. This signal on line 40 is applied to the coil 42 of an electromagneti ca ly operated injector 44. The injector 44 is connected to a constant pressure fuel source 46 and is preferably disposed so as to dispense fuel to the area of the intake valve 12, externally of the engine cylinder 10. The volume of fuel dispensed by the injector 44 will be proportional to the duration of a pulse received on line 40. The timing of the pulse on line 40 is such that the injector 44 is usually actuated one per engine cycle although it may be actuated more often, par ticular during engine start-up.

This single injector pulse per engine cycle is preferably timed to occur immediately after closing of the intake valve 12 so that the injected charge may be heated to a maximum degree by the intake valve 12 before being admitted to the cylinder.

The system of Figure 1 differs from conventional fuel injection systems primarily in the provision of the circuit 38 for differentiating the output of the pressure sensor 36, and in the provision of a variable width pulse generator 30 that is sensitive to the output of the circuit 38 to decrease the duration of the output pulse on line 40 as a function of the rate of decrease in manifold pressure above a predetermined rate of decrease, i.e. in addition to the normal decrease inherently provided by the pressure sensor 36. This decrease occurs during deceleration of the engine and the resultant diminished fuel charge is thus more closely tailored to the engine requirements during deceleration when the intake valve 12 opens, and the fuel charge is admitted to the cylinder 10, a time interval after the occurrence of the injector pulse.

Figure 2 is a detailed schematic circuit diagram of a preferred form of the variable width pulse generator 30, the pressure sensor 36 and the differential circuit 38.

The triggering pulse to the variable width pulse generator 30, from the counter 26, on line 28, take the form of sharp-edged, negative-going pulses. These pulses are applied to the base of a PNP transistor 48 having its emitter connected to the positive side of the power supply through resistor 50.

The collector of the transistor 48 is connected to one side of a capacitor 52 forming part of a resistance-capacitance circuit. The discharge resistance of the circuit is formed by the series combination of a resistor 54 and an engine sensor 56, part of the sensor group 32 designated in Figure 1, which acts in some respects like a variable resistor, and is schematically designated as such. The sensor 56 is primarily sensitive to engine temperature and may be a thermistor.

The collector of transistor 48 is also connected through a resistor 58 to the variable terminal of a potentiometer 60 having its resistance element connected between the positive terminal of the voltage supply and ground. The position of the variable contact of the potentiometer 60 is controlled by the manifold pressure sensor 36. The sensor 36 is schematically illustrated as a piston 62 movable within a cylinder 64. The manifold 34 is connected to the spring end of the cylinder 54 by a conduit 68. The position of the piston 62 is thus a function of the differential pressure between the manifold 34 and atomspheric pressure. The pressure differential biases the spring 66 toward its compressed condition. The piston 62 is connected to the movable contact of the potentiometer 60 so that the voltage at one side of the capacitor 52 is a function of the manifold differential pressure.

The junction of or the capacitor 52 and the resistor 54 is connected to the base of a sec ond PNP transistor 70 having its emitter connected to the emitter of transistor 48 and its collector connected to ground through a pair of resistors 77 and 78. The mid-point of these two resistors 77 and 78 is connected to a driver amplifier 79 and represents the output of the variable width pulse generator 30.

Considering the operation of the pulse generator 30, a triggering pulse on line 28 takes the form of a negative-going pulse, and in the absence of this triggering pulse the transistor 48 operates in a saturated conduction region. Transistor 70 is similarly conductive at this time so the voltage on capacitor 52 is substantially equal to the emitter voltage of transistor 70. Upon receipt of a negativegoing pulse on line 28, transistor 48 is switched out of conduction, allowing the capacitor 52 to charge to a voltage dependent upon the difference between the emitter voltage of transistor 70 and the voltage provided by the manifold pressure potentiometer 60, through resistor 58.

When the negative-going pulse to the base of transistor 48 termiantes, the transistor 48 immediately becomes conductive again and the voltage at the base of transistor 70 goes sharply positve by an amount proportional to the charge on the capacitor 52, turning off transistor 70. Capacitor 52 then begins to discharge through resistor 54 and the equivalent resistance provided by the device 56.

This discharge continues until the voltage across capacitor 52 reaches the emitter voltage of transistor 70 to turn on and to clamp the voltage on capacitor 52 to a value substantially equal to the emitter voltage of transistor 70.

The time during which transistor 70 is turned off is therefore dependent upon the variable voltage provided by the potentiometer 60, which controls the voltage to which the capacitor 52 charges during the off time of transistor 48, and to the variable resistance provided by the device 56 in combination with resistor 54, which controls the rate at which the capacitor 52 discharges after the transistor 48 becomes conductive.

This time is modified by the differentiator circuit 38 which takes the form of a resistor 71 and a capacitor 72 connected between the variable contact of the potentiometer 60 and the base of an NPN transistor 74. The emitter-collector circuit of transistor 74 shunts resistor 54. The base of transistor 74 is connected to ground through a resistance 76.

The capacitor 72 acts to differentiate the voltage across the movable contact of the potentiometer 60 so as to provide a signal to the base of transistor 74 when a decreasing change occurs in manifold differential pressure above a predetermined rate of change in pressure. As the manifold differential pressure decreases, during deceleration of the engine, the voltage applied to capacitor 72 increases, and the transistor 74 is rendered more conductive, decreasing the effective resistance in the discharge path of capacitor 52 and shortening the time required for the capacitor 52 to discharge. This effectively decreases the injector pulse time during engine deceleration.If the deceleration is suddenly terminated and the engine is accelerated, the resultant change of voltage will cause the capacitor 72 to discharge through potentiometer 60 and thus terminate the pulse shortening effect immediately.

In another embodiment of the present invention, a separate mechanical device may be used in place of the manifold pressure sensor 36 and the differentiator 38 as illustrated in Figures 1 and 2. The device, generally indicated at 80, comprises a closed housing 82 having an elastic diaphragm 84 dividing it into a pair of compartments 86 and 88.

The diaphragm 84 is biased in the direction of compartment 88 by a compression spring 90. A conduit 92 connects the chamber 88 to the engine intake manifold 34. The chambers 86 and 88 are connected by a vent device 94 which by-passes the diaphragm 84 and has a restriction 96 which controls the rate of air flow between the chambers 86 and 88.

The diaphragm 84 is connected to the movable contact of a potentiometer 98 connected between the positive terminal of the power supply and ground. The movable contact of the potentiometer 98 is connected to the base of a transistor 100 which is the equivalent of transistor 74 in Figure 2, having its emitter-collector circuit shunting the resistor 54 in the discharge path of the R-C circuit.

When the manifold pressure decreases, the pressure in chamber 88 is decreased and the diaphragm 84 is moved toward chamber 88, expanding the spring 90. This causes a movement of the movable contact of the potentiometer 98, and increases the voltage at the base of NPN transistor 100, increasing its conductivity, and decreasing the effective resistance of the discharge path of the R-C circuit. Thus, the duration of a pulse generated by the circuit 36 is decreased. The effect is transient, however, because the decrease in pressure in chamber 86 causes air to bleed through the by-pass 94 and restriction 96, into the chamber 88, and thus restore the pressure balance on the diaphragm 84. An increase in manifold pressure, resulting from an acceleration of the vehicle, tends to increase the resistance of the emittercollector path of transistor 100, restoring the normal discharge path of the R-C circuit and the normal duration of the injector pulse.

WHAT WE CLAIM IS: 1. A fuel injection system for an internal combustion engine and comprising means for measuring engine manifold pressure and other engine operating parameters and for providing fuel to the engine as a function of the measured parameters, the system including means for sensing the rate of decrease of engine manifold pressure and means for modifying the fuel charge provided to the engine as a continuous function of such rate of decrease of engine manifold pressure while manifold pressure is decreasing above a predetermined rate.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. generator 30, a triggering pulse on line 28 takes the form of a negative-going pulse, and in the absence of this triggering pulse the transistor 48 operates in a saturated conduction region. Transistor 70 is similarly conductive at this time so the voltage on capacitor 52 is substantially equal to the emitter voltage of transistor 70. Upon receipt of a negativegoing pulse on line 28, transistor 48 is switched out of conduction, allowing the capacitor 52 to charge to a voltage dependent upon the difference between the emitter voltage of transistor 70 and the voltage provided by the manifold pressure potentiometer 60, through resistor 58. When the negative-going pulse to the base of transistor 48 termiantes, the transistor 48 immediately becomes conductive again and the voltage at the base of transistor 70 goes sharply positve by an amount proportional to the charge on the capacitor 52, turning off transistor 70. Capacitor 52 then begins to discharge through resistor 54 and the equivalent resistance provided by the device 56. This discharge continues until the voltage across capacitor 52 reaches the emitter voltage of transistor 70 to turn on and to clamp the voltage on capacitor 52 to a value substantially equal to the emitter voltage of transistor 70. The time during which transistor 70 is turned off is therefore dependent upon the variable voltage provided by the potentiometer 60, which controls the voltage to which the capacitor 52 charges during the off time of transistor 48, and to the variable resistance provided by the device 56 in combination with resistor 54, which controls the rate at which the capacitor 52 discharges after the transistor 48 becomes conductive. This time is modified by the differentiator circuit 38 which takes the form of a resistor 71 and a capacitor 72 connected between the variable contact of the potentiometer 60 and the base of an NPN transistor 74. The emitter-collector circuit of transistor 74 shunts resistor 54. The base of transistor 74 is connected to ground through a resistance 76. The capacitor 72 acts to differentiate the voltage across the movable contact of the potentiometer 60 so as to provide a signal to the base of transistor 74 when a decreasing change occurs in manifold differential pressure above a predetermined rate of change in pressure. As the manifold differential pressure decreases, during deceleration of the engine, the voltage applied to capacitor 72 increases, and the transistor 74 is rendered more conductive, decreasing the effective resistance in the discharge path of capacitor 52 and shortening the time required for the capacitor 52 to discharge. This effectively decreases the injector pulse time during engine deceleration.If the deceleration is suddenly terminated and the engine is accelerated, the resultant change of voltage will cause the capacitor 72 to discharge through potentiometer 60 and thus terminate the pulse shortening effect immediately. In another embodiment of the present invention, a separate mechanical device may be used in place of the manifold pressure sensor 36 and the differentiator 38 as illustrated in Figures 1 and 2. The device, generally indicated at 80, comprises a closed housing 82 having an elastic diaphragm 84 dividing it into a pair of compartments 86 and 88. The diaphragm 84 is biased in the direction of compartment 88 by a compression spring 90. A conduit 92 connects the chamber 88 to the engine intake manifold 34. The chambers 86 and 88 are connected by a vent device 94 which by-passes the diaphragm 84 and has a restriction 96 which controls the rate of air flow between the chambers 86 and 88. The diaphragm 84 is connected to the movable contact of a potentiometer 98 connected between the positive terminal of the power supply and ground. The movable contact of the potentiometer 98 is connected to the base of a transistor 100 which is the equivalent of transistor 74 in Figure 2, having its emitter-collector circuit shunting the resistor 54 in the discharge path of the R-C circuit. When the manifold pressure decreases, the pressure in chamber 88 is decreased and the diaphragm 84 is moved toward chamber 88, expanding the spring 90. This causes a movement of the movable contact of the potentiometer 98, and increases the voltage at the base of NPN transistor 100, increasing its conductivity, and decreasing the effective resistance of the discharge path of the R-C circuit. Thus, the duration of a pulse generated by the circuit 36 is decreased. The effect is transient, however, because the decrease in pressure in chamber 86 causes air to bleed through the by-pass 94 and restriction 96, into the chamber 88, and thus restore the pressure balance on the diaphragm 84.An increase in manifold pressure, resulting from an acceleration of the vehicle, tends to increase the resistance of the emittercollector path of transistor 100, restoring the normal discharge path of the R-C circuit and the normal duration of the injector pulse. WHAT WE CLAIM IS:

1. A fuel injection system for an internal combustion engine and comprising means for measuring engine manifold pressure and other engine operating parameters and for providing fuel to the engine as a function of the measured parameters, the system including means for sensing the rate of decrease of engine manifold pressure and means for modifying the fuel charge provided to the engine as a continuous function of such rate of decrease of engine manifold pressure while manifold pressure is decreasing above a predetermined rate.

2. A fuel injection system according to

claim 1, wherein the means for modifying the fuel charge provided to the engine is adapted to vary the fuel charge as a direct function of the rate of change of decreasing engine manifold pressure.

3. A fuel injection system according to claim 1 or 2, which includes a source of pressurized fuel, an electrically actuated injector means, and means for generating an electric pulse operative to actuate the injector having a duration which is a function of the engine parameters at intervals occurring in timed relation to the operating of the engine, said means for modifying the fuel charge provided to the engine as a continuous function of the rate of change of decreasing engine manifold pressure comprising means for decreasing the duration of an injector actuating pulse as a function of the rate of change of manifold vacuum.

4. A fuel injection system according to claim 3, wherein the means for generating a pulse having a duration proportional to the engine parameters includes a circuit having a resistance and a capacitance, and the means for decreasing the pulse duration as a function of rate of change of manifold pressure includes means for modifying one of the parameters of the resistance-capacitance circuit as a continuous function of the rate of decrease of engine manifold pressure.

5. A fuel injection system according to claim 4, wherein the means for modifying one of the parameters of the circuit as a continuous function of the rate of decrease of manifold pressure includes a variable resistance transistor shunting the resistance component of the circuit, and means for decreasing the resistance of the variable resistance element as a function of the rate of decrease of manifold pressure by means of a capacitor connected to the transistor for receiving an electrical signal proportional to the rate of change of decreasing manifold pressure.

6. A fuel injection system of claim 4 or 5, wherein said means for measuring engine manifold pressure comprises a potentiometer having a movable element which changes position as a function of manifold pressure, the circuit employing a capacitance and a resistance including means for charging said capacitance to a voltage which is a function of manifold pressure.

7. A fuel injection system for an internal combustion spark ignited engine having a cylinder and intake valve for the cylinder, said fuel injection system comprising a source of fuel; and electromagnetically actuated fuel injector connected to said source of fuel, and disposed to inject said fuel, when actuated, adjacent the intake valve externally of the engine cylinder; means for measuring a plurality of engine operating parameters including the engine manifold pressure; and means for generating an electric pulse for actuating said injector, in timed relation to the operation of the engine, the duration of said pulse being a function of said measured engine parameters and an inverse function of the rate of decrease in manifold pressure.

8. A fuel injection system according to claim 7, wherein the pulse generating means includes a resistance-capacitance circuit including connections for charging the capacitor to a voltage inversely proportional to manifold pressure and transistor means for decreasing the value of the resistance in said circuit as a continuous function of the rate of decrease in manifold pressure and a capacitor connected to receive the manifold pressure signal and connected to the base of said transistor means.

9. A fuel injection system for an internal combustion engine constructed and arranged to operate substantially as herein described with reference to or as illustrated in Figures 1 and 2 of the accompanying drawings.

10. A system according to claim 9 when modified substantially as herein described with reference to and as illustrated in Figure 3 of the accompanying drawings.

11. An internal combustion engine including a fuel injection system according to any preceding claims.