CA1110736A - Fuel injection system with pressure excursion start inhibit - Google Patents
Fuel injection system with pressure excursion start inhibitInfo
- Publication number
- CA1110736A CA1110736A CA307,019A CA307019A CA1110736A CA 1110736 A CA1110736 A CA 1110736A CA 307019 A CA307019 A CA 307019A CA 1110736 A CA1110736 A CA 1110736A
- Authority
- CA
- Canada
- Prior art keywords
- fuel
- pressure
- engine
- injector
- supply
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/04—Introducing corrections for particular operating conditions
- F02D41/06—Introducing corrections for particular operating conditions for engine starting or warming up
- F02D41/062—Introducing corrections for particular operating conditions for engine starting or warming up for starting
- F02D41/065—Introducing corrections for particular operating conditions for engine starting or warming up for starting at hot start or restart
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D2200/00—Input parameters for engine control
- F02D2200/02—Input parameters for engine control the parameters being related to the engine
- F02D2200/06—Fuel or fuel supply system parameters
- F02D2200/0602—Fuel pressure
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
- Fuel-Injection Apparatus (AREA)
Abstract
INVENTION: FUEL INJECTION SYSTEM WITH PRESSURE EXCURSION
START INHIBIT
INVENTOR: EMILE DAVID LONG
ABSTRACT OF THE DISCLOSURE
A fuel injection system for a spark ignition internal combustion engine employs at least one electrically energized injector. The injector connects to a fuel supply line which receives fuel from a source and is maintained at substantially constant pressure during engine operation by an engine powered fuel pressure booster. The injector is energized by a variable width electric pulse generator controlled by a sensor measuring engine operating parameters. A control circuit prevents the injector from providing fuel to the engine during start condi-tions until satisfactory pressure is obtained within the fuel line. The control circuit receives the output of a pressure switch connected to the fuel line and provides a signal that inhibits energization of the injector when the fuel line pressure is below a predetermined value.
START INHIBIT
INVENTOR: EMILE DAVID LONG
ABSTRACT OF THE DISCLOSURE
A fuel injection system for a spark ignition internal combustion engine employs at least one electrically energized injector. The injector connects to a fuel supply line which receives fuel from a source and is maintained at substantially constant pressure during engine operation by an engine powered fuel pressure booster. The injector is energized by a variable width electric pulse generator controlled by a sensor measuring engine operating parameters. A control circuit prevents the injector from providing fuel to the engine during start condi-tions until satisfactory pressure is obtained within the fuel line. The control circuit receives the output of a pressure switch connected to the fuel line and provides a signal that inhibits energization of the injector when the fuel line pressure is below a predetermined value.
Description
..~.
BACKGROUND OF Tt~E INVENTION
_ ld of the Invention This inven-tion relates to fuel injection systems for spark ignited internal cornbustion engines employiny at least one injector fed by a constant pressure fuel supply, and more particularly to l,leans to prevent fuel injection to the system during startiny when the fuel delivery rate provided by the injector would be insufficient to prevent emissions of hiyh leveLs of unburned hydrocarbons.
Prior Art Canadian Patent 1,075,9~7 discloses a form of ~ !
fuel injection system for a spark iyllition internal colnbustion engine employing electrically eneryized fuel injectors disposed at each engine cylinder and connected lS to a common fuel line. Duriny the engine operation the pressure in the fuel line and at the injectors is maintained at a regulated, relatively hiyh value such as 100 psiy by a camshaft driven fuel pressure booster.
The latter is fed from a low pressure fuel su~ply pump.
The regulated, high pressure fuel line insures that the quantity oE fuel provided to a cylinder by an injector will always be at a predetermined value. rrhe injectors are each eneryized into open condition by individual variable width pulse yenerators controlled by sensors which measure engine operating parameters such as manifold vacuum and the like.
~ ecause the pressurized fuel delivery line is located in proximity to the enyine, and the injectors are positioned in iml~lediate proxi1nity to the cylinders, -the fuel within the line becomes ~leated during normal engine operation and expands. During normal engine opera-tion the pressure booster retains regulated fuel pressure independent of the variable fuel density.
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After the engine stops, the booster is no longer operative, with the result that the cooling fuel will contract in volume and cause a drop in pressure in the fuel line. Pressure wave converters employing flexible diaphragms connected to the line on one side and a reference pressure on the opposite side ac~ to adjust auto-matically the high pressure fuel line volume as the pressure decays.
When the engine is restarted the initial fuel pressure may be substantially lower than the normal operating pressure.
Such low fuel pressure will result in a diminution of the fuel charges provided to the cylinders by the injectors during starting.
Since the variable width pulse generators that control the injec-tors as a function of measured engine operating parameters are programmed on the basis of an assumed constant pressure in the fuel line the lowered pressure will result in a decreased fuel flow rate through the injectors during actuation thereof.
If the engine has been allowed to cool to an appreciable degree below its normal operating temperature before restarting is attempted, the diminished fuel charge provided to the cylinders as a result of the drop in fuel line pressure may not inhibit start-ing. The variable width pulse generators are programmed to provide an excessive fuel charge during cold start. ~oreover, at cooler engine starting temperatures the fuel charge tends to accumulate~
providing an air-fuel mixture that may be sufficient for ignition.
In the event that restarting is attempted while the engine is still fully close to operating temperature, however, the reduced fuel charge provided to the engine because of the lowered fuel line pressure may be insufficient tG produce an ignitable air-fuel mixture ~uickly. The unburned hydrocarbons pumped into the exhaust system prior to ignition may substantially raise 3~
pollutants sufficiently to exceed limits imposed by ~vernment regulations.
After a period of cranking without combustion, the fuel booster or fuel pump will raise the fuel pressure, increas-ing the quantities of injected fuel to a level sufficient for starting of the engine. Further, the time period required for the pressure booster to raise fuel pressure to a level suffl-cient for clean combustion is increased by injection of dimin-ished fuel charge during the starting mode.
SU~ARY OF THE INVENTION
. ~. _ .
The present invention provides a fuel injection system that eliminates the problems arising from the injection of fuel into the cylinders of an engine in insufficient quantities to sustain ignition during starting of the engine. The improved system incorporates means for sensing the fuel pressure in the lines feeding the injector and means for inhibiting the energi~
zation of the injectors during starting until the fuel pressure exceeds a preselected value.
In accordance with one aspect of this invention there is provided in a fuel injection system for a spark ignition engine having a supply of pressuri~ed fuel, an injector valve connected to the supply, sensors for measuring engine operating conditions and an electric circuit for energizing the injector in timed relation to the engine operation for periods controlled by the output of said sensors, the improvement comprising:
means actuated in response to the pressure of the fuel in said supply for inhibiting energization of the injector during start-ing of said engine until the fuel pressure exceeds a preselected minimum pressure.
In accordance with another aspect of this invention there is provided a fuel injection system for a spark ignited internal combustion engine, comprising: a Euel source; a fuel supply line; means powered by the engine for feeding fuel from .
the source to the supply line to maintain a predetermined, operating fuel pressure in the supply line; an injector con-nected to the supply line; sensors connec-ted to the engine to measure Pngine operating parame~erSi an electric circuit connected to the outputs of the sensors and to the engine op-erative to energize the injector at periods occurring in timed relation to the operation of the engine and having durations dependent upon the outputs of said sensors; and means actuated in response to the pressure of the fuel in said supply line for inhibiting energization of the injector during starting of said engine, independent of the output of said electric circuit, unti]. the pressure of said fuel in said supply line exceeds a preselected minimum pressure.
In one embodiment of the invention, described here-in-aEter in more detail, a pressure switch is connected to the fuel line and is set to switch at a pressure which is some substantial portion of the normal fuel pressure; for example, with a system having a normal fuel pressure of 100 psig, the pressure switch may be set to change outputs at 70 psig. A
thermistor supported in proximity to the engine provides the variable width pulse generators with an electrical signal pro-portional to engine temperature. This siynal is also compared to a reference value to derive a signal indicative o~ whether the engine temperature is above a predetermined level, below normal hot engine temperature. The system includes logic which receives the output of -the pressure switch and the temperature signal and acts to prevent $he genera--3a-3~
tion of actuating pulses for the injectors when the pressure is below the level at which the switch actuates and the engine temp-erature is above the comparator level.
In another embodiment of the invention circuitry could be provided for comparing continuous functions of pressure and tem-perature so that the injectors would be inhibited at relatively low engine temperatures if the fuel pressure was very low and at higher temperatures if the fuel pressure was somewhat higher but still below full pressure.
The system prevents the injectors from operating while the engine is being cranked during a hot start until the booster or fuel pump raises the pressure in the fuel line above the required fuel pressure. This will typically only require a few turns of the cranking motor. On continued cranking, the injectors are energized and the fuel flow through the injectors should be sufficient to create a fuel-ai-r mi~ture which will sustain com-bustion, preventing the unburned fuel from being pumped into the engine exhaust.
Other objectives, advantages and applications of the present invention will be made apparent by the following detailed description of a preferred embodiment oE the invention. The description makes reference to the accompanying drawings in which:
FIGURE 1 is a partially schematic, partially block dia gram of a fuel ignition system for an internal combustion engine, forming the prefered embodiment of the invention;
FIGURE 2 is a more detailed schematic diagram of the circuitry of the present invention which measures engine tempera~
ture and fuel line pressure to inhibit fuel injection during high temperature, low pressure starting conditions.
Referring to the dra~ings, FIGURE 1 schematically illus-trates a system for providing fuel under a high~ relatively con-3~
stant pressure to eight fuel injectors or transducers 10 arranged to provide controlled bursts of fuel to the intake valve areas of an eight cylinder internal combustion engine, as well as relevant portions of the ignition system. The injectors 10 may be of any well-known type such as those disclosed in my U.S. Patent 3,~12,718.
Electric signals applied to the injectors 10 through wires 12 open the injectors for controlled periods of time based on measured engine operating conditions, such as manifold vacuum pressurer engine temperature, atmospheric pressure and the like. The quantity of fuel provided by the injector during this signal period is a function of the pressure at the injector.
Fuel is provided to the injectors by a pair of conduits 14 termed fuel rails~ Fuel for feeding the rails is derived from a fuel tank 16. A pump 18 receives fuel from the tank 16 through a one-way valve 17 and operates to feed fuel from the tank through a one-way valve 20. The pump 18 may be electrically powered or driven by the engine in the manner of a conventional automotive fuel pump. It must be capable of pumping fuel at a volumetric rate in excess of the engine requirements at the maximum throttle opening. For a relatively large 8-cyclinder engine this may be in excess of 25 gallons per hour. The outlet pressure of the pump 18 may be substantially lower than the 25-50 pounds per square inch provided by fuel pumps for typical injection fuel systems of the prior art. In a preferred embodiment of the system a 5-10 pound per square inch outlet pressure will suffice. This pressure need not be well regulated and may vary with engine speed. Accord-ingly, the pump 18 should be substantially simpler and lower in cost than fuel pumps used with previous injection systems.
A fuel pressure booster and regulator generally indicated at 22 receives fuel passed through the one-way valve 20 from pump 18. The booster and regulator is schematically illustrated as comprising a piston 24 movable within a cylinder 26 and biased by a spring 28. The spring biases the piston in a direction as to move the piston 24 to contract the volume of the cylinder 26 in communication with the fuel line 30. This increases the fluid pressure in the fuel line 30. The one~way valve 20 prevents this increase in pressure from forcing a reverse flow to the pump 18. ::
A reset mechanism 32 is schematically illustrated as being connected to the piston 24 to periodically move the piston against the bias of the spring 28 to enlarge the volume of the cylinder 26 in communication with the fuel line 30. The reset mechanism is cocked once each engine cycle by the engine cam shaft 33. This lowers the pressure in the fuel line 30 and allows momentary flow from the pump 18 through the one-way valve 20.
A second one-way valve 34 is connected downstream of the booster and regulator 22. When the piston 24 moves under the bias of the spring 28 to contract the volume of the cylinder 26, the valve allows the resulting high or elevated pressure to communicate with a fuel line 36 that connects to the fuel rails 20 14, thus imposing this higher pressure on the rails. When the ~.
reset mechanism 32 withdraws the piston against the force of the spring 28, allowing the pump 18 to force fuel into the low-pres-sure fuel line 30, the one-way valve 34 prevents backflow in the ~:
high pressure fuel line 36 toward the pressure booster 22 and ~hus maintains the high fluid pressure in the rails 14. In alternative embodiments of the invention a conventional high pressure regu-lated fuel pump could replace the booster and regulator 32.
Optionally, the far ends of the rails are connected together by a fuel line 38 to form a closed circuit. A constant bleed one-way valve 40 connects the fuel. line 38 back to the fuel tank 16.
'73~i A fluid wave regulator or converter 42 is connected to the fluid line immediately upstream of the valve 20. The conver-ter is essentially of -the same type disclosed in my U.S. Patent 3,507,263. Schematically, it comprises an enclosed volume 44 separated from the fluid line by an elastic diaphragm 46. The diaphragm 46 assumes a position wherein the forces on its opposite sides are equal, thus when the line pressure increases, the dia-phragm moves to contract the volume of the chamber 44 and thus pressurize the fluid sealed within that volume. Conversely, when the line pressure Ealls the diaphragm moves to expand the sealed volume. When the diaphragm 46 moves outwardly in response to a lowering in the fluid pressure in the line it effectively pumps a volume of fluid into the line, tending to raise the line pres-sure. Conversely, when the diaphragm contracts in response to an increase in line pressure it increases the flow volume connected to the line and thus tends to decrease the pressure. The conver-ter 42 thus acts as a flow regulator.
When the piston 24 is retracted against the bias of the spring 28 by the unit 32 so that the pressure in the line 30 falls below the outlet pressure of the pump 18, and the flow valve 20 opens, the decrease in pressure at the inlet to the converter 42 causes the diaphragm 46 to expand and supply a volume of fuel which replenishes the chamber 26. In the absence of this device the sharp low pressure wave generated by expansion of the cylinder 26 might vaporize the fuel in the line between the pump and the booster.
A similar regulator or converter 48 is connected to the fuel line immediately downstream of the uni-directional valve 34.
This converter provides a pressurized fuel source to the line during the short interval when the piston 24 is resetting and accordingly the valve 34 is isolating the line 30 from the line 36. The converter 18 also acts as a cushion to minimize the travel of expansion and compression waves through the line 36.
In the preEerred embodiment of the invention a pair of pressure converters 52 and 54 are connected adjacent to the input ends of the fuel rails 14. A second pair of converters 56 and 58 are connected adjacent to the outlet ends of the Euel rails, where they connect to the common fuel line 38. These converters all similarly act to regulate the pressure in the rails by cancelling pressure waves created in the system by injection of fluid from the booster 22 or ejection of fluid through the injectors 10.
FIGURE 1 also illustrates the circuitry for providing electrical power to the coils of the injector valves 10 over lines 12. One of the injectors 10 is illustrated as having a coil 60.
Considering the circuitry that derives the energization pulses for this coil, the ignition system includes a distributor generally indicated at 62 having an arm 64 rotated in timed relation to the engine operation to sequentially move into position with contacts that are connected to the engine spark plugs 66, only one of which is illustrated. The arm 64 is connected to the secondary of an ignition coil, generally indicated at 68, having its primary connected to the vehicle battery 70 through a pair of engine actuated breaker points 72. The breaker points are shunted by a capacitor 74. -The breaker points are also connected to a counter 76 forming part of the injector circuitry~ The counter is advanced by one count each time the breaker points 72 close. The counter 76 has a plurality of output lines 78 which connect to a number of variable width pulse genera-tors 80, only one of which is illus-trated. The various lines 78 are sequentially energi~ed as the counter advances so tha-t each line is energized once each engine cycle.
The variable width pulse generators each receive outputs from a group of engine sensors 82 which measure such operating variables as manifold pressure and the like. Each variable width pulse generator also receives an electrical output from a thermis-tor 82 supported relative to the engine to experience the engine temperature. The thermistor 84 is illustrated separately from the other engine sensors 82 because of its roll in the low pressure, high engine temperature inhibit circuitry.
The output of the variable width pulse generators 80 are provided to gates 86 and the outputs of the gates constitute the lines 12 which energize the injectors 10.
The gates 86 are controlled by an injection inhibit circuit 8~. Only a single injection inhibit circuit services the gates 86 associated with each of the variable width pulse genera-tors 80. The injection inhibit circuit 88 has inputs from the thermistor 84 and from a pressure switch 90 connected to the fuel line 14. The switch 90 preferably closes when the pressure in the line 14 is above a predetermined Lraction of normal oepratiny line pressure. In the case of the preferred embodiment, the normal 20 operating line pressure may be 100 psi and the switch 90 may close when the pressure exceeds 65 psi. The injection inhibit circuit 88 can, alternatively, be provided with an input from the pressure switch 90 solely, making it operative in response to pressure of ; the fuel in line 14 to inhibit energization of the injector during starting of the engine until the fuel pressure exceeds a preselec-ted minimum pressure in the order of about 65 psi.
The injection inhibit circuit 88 processes the output of the switch 90 and of the thermistor 84 to control the gate 86u The control is such that the gate 86 passes output pulses from the generator 80 to the injector coil 60 as long as the pressure switch is closed. When the pressure switch is open, indicating a pres-_g_ sure in the line 14 of less than 65 psi, the gate 86 still passesinjector signals if the output of the thermistor 84 is such as to indicate that the temperature of the engine is below a predeter-mined value. In the preferred embodiment of the invention this value may be approximately 150F as compared to a normal engine operating temperature of about 200F.
When the pressure in the line 14 is less than 65 psi and the engine temperature is above 150F the gate 86 is energized by the circuit 88 to prevent the application of firing pulses from the generator 80 to the coil 60. This condition occurs when the engine is being restarted a relatively short period of time after it stopped while at or near operating temperature; i.e., within 5-20 minutes or thereabouts, depending upon the ambient temperature.
Were the injectors not to be inhibited during this time the reduced ~uel quantity that they would provide to the cylinders as a result of the lowered pressure in the line 14 would likely not result in a rich enough fuel/air ratio to achieve ignition and the unburned hydrocarbon vapors would be pumped out of the engine exhaust.
FIGURE 2 illustrates the circuitry of the injection inhibit device 88 and its associated components in greater detail.
The thermistor 84 is connected in series with a resis-tance 100 between a positive voltage provided by a power supply and ground so that the two act as a voltage divider. The mid-p~int of this voltage divider, which experiences a voltage depen-dent upon the resistance of the thermistor 84, is applied to one terminal of an operational amplifier 102 connected to a comparator mode. The reference input to the comparator 102 is provided by a voltage divider consisting of the series combination of two resis-tances 104 and 106. One end of resistance 104 is connected to -~ 30 ground and one end of resistance 106 is connected to a positive reference voltage. Resistance 104 is shunted by the pressure ~10--switch 90 which is closed when the pressure in line 12 exceeds the predetermined pressure such as 65 psig. When the pressure is in : excess of that value the switch 90 is closed and the comparator ln2 cannot provide a high output, independent of the resistance of the thermistor 84~ However, when the pressure is above 65 psi, so that the switch 90 is open, and the engine temperature and thus the thermistor temperature are above a predetermined value, such as 150F, the voltage at the connection between the thermistor 84 : and the resistance 100 will exceed the reference voltage and will provide an output from the comparator 102. This voltage is applied to the gates 86, one for each engine cylinder, through a plurality of isolating diodes 106. When the gates are activated by outputs from the comparator 102 the output pulses from the variable width pulse generators 80 are applied to the coils 60 of the i.njector 10. When the fuel line pressure is below the predetermined value and the engine temperature is above the comparator value, the output of the comparator 102 ~ill be such ~ha~ the gates 86 will block pulses from the variable width generators from being applied to the injectors.
~ 30 .,~.
BACKGROUND OF Tt~E INVENTION
_ ld of the Invention This inven-tion relates to fuel injection systems for spark ignited internal cornbustion engines employiny at least one injector fed by a constant pressure fuel supply, and more particularly to l,leans to prevent fuel injection to the system during startiny when the fuel delivery rate provided by the injector would be insufficient to prevent emissions of hiyh leveLs of unburned hydrocarbons.
Prior Art Canadian Patent 1,075,9~7 discloses a form of ~ !
fuel injection system for a spark iyllition internal colnbustion engine employing electrically eneryized fuel injectors disposed at each engine cylinder and connected lS to a common fuel line. Duriny the engine operation the pressure in the fuel line and at the injectors is maintained at a regulated, relatively hiyh value such as 100 psiy by a camshaft driven fuel pressure booster.
The latter is fed from a low pressure fuel su~ply pump.
The regulated, high pressure fuel line insures that the quantity oE fuel provided to a cylinder by an injector will always be at a predetermined value. rrhe injectors are each eneryized into open condition by individual variable width pulse yenerators controlled by sensors which measure engine operating parameters such as manifold vacuum and the like.
~ ecause the pressurized fuel delivery line is located in proximity to the enyine, and the injectors are positioned in iml~lediate proxi1nity to the cylinders, -the fuel within the line becomes ~leated during normal engine operation and expands. During normal engine opera-tion the pressure booster retains regulated fuel pressure independent of the variable fuel density.
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3~ .
After the engine stops, the booster is no longer operative, with the result that the cooling fuel will contract in volume and cause a drop in pressure in the fuel line. Pressure wave converters employing flexible diaphragms connected to the line on one side and a reference pressure on the opposite side ac~ to adjust auto-matically the high pressure fuel line volume as the pressure decays.
When the engine is restarted the initial fuel pressure may be substantially lower than the normal operating pressure.
Such low fuel pressure will result in a diminution of the fuel charges provided to the cylinders by the injectors during starting.
Since the variable width pulse generators that control the injec-tors as a function of measured engine operating parameters are programmed on the basis of an assumed constant pressure in the fuel line the lowered pressure will result in a decreased fuel flow rate through the injectors during actuation thereof.
If the engine has been allowed to cool to an appreciable degree below its normal operating temperature before restarting is attempted, the diminished fuel charge provided to the cylinders as a result of the drop in fuel line pressure may not inhibit start-ing. The variable width pulse generators are programmed to provide an excessive fuel charge during cold start. ~oreover, at cooler engine starting temperatures the fuel charge tends to accumulate~
providing an air-fuel mixture that may be sufficient for ignition.
In the event that restarting is attempted while the engine is still fully close to operating temperature, however, the reduced fuel charge provided to the engine because of the lowered fuel line pressure may be insufficient tG produce an ignitable air-fuel mixture ~uickly. The unburned hydrocarbons pumped into the exhaust system prior to ignition may substantially raise 3~
pollutants sufficiently to exceed limits imposed by ~vernment regulations.
After a period of cranking without combustion, the fuel booster or fuel pump will raise the fuel pressure, increas-ing the quantities of injected fuel to a level sufficient for starting of the engine. Further, the time period required for the pressure booster to raise fuel pressure to a level suffl-cient for clean combustion is increased by injection of dimin-ished fuel charge during the starting mode.
SU~ARY OF THE INVENTION
. ~. _ .
The present invention provides a fuel injection system that eliminates the problems arising from the injection of fuel into the cylinders of an engine in insufficient quantities to sustain ignition during starting of the engine. The improved system incorporates means for sensing the fuel pressure in the lines feeding the injector and means for inhibiting the energi~
zation of the injectors during starting until the fuel pressure exceeds a preselected value.
In accordance with one aspect of this invention there is provided in a fuel injection system for a spark ignition engine having a supply of pressuri~ed fuel, an injector valve connected to the supply, sensors for measuring engine operating conditions and an electric circuit for energizing the injector in timed relation to the engine operation for periods controlled by the output of said sensors, the improvement comprising:
means actuated in response to the pressure of the fuel in said supply for inhibiting energization of the injector during start-ing of said engine until the fuel pressure exceeds a preselected minimum pressure.
In accordance with another aspect of this invention there is provided a fuel injection system for a spark ignited internal combustion engine, comprising: a Euel source; a fuel supply line; means powered by the engine for feeding fuel from .
the source to the supply line to maintain a predetermined, operating fuel pressure in the supply line; an injector con-nected to the supply line; sensors connec-ted to the engine to measure Pngine operating parame~erSi an electric circuit connected to the outputs of the sensors and to the engine op-erative to energize the injector at periods occurring in timed relation to the operation of the engine and having durations dependent upon the outputs of said sensors; and means actuated in response to the pressure of the fuel in said supply line for inhibiting energization of the injector during starting of said engine, independent of the output of said electric circuit, unti]. the pressure of said fuel in said supply line exceeds a preselected minimum pressure.
In one embodiment of the invention, described here-in-aEter in more detail, a pressure switch is connected to the fuel line and is set to switch at a pressure which is some substantial portion of the normal fuel pressure; for example, with a system having a normal fuel pressure of 100 psig, the pressure switch may be set to change outputs at 70 psig. A
thermistor supported in proximity to the engine provides the variable width pulse generators with an electrical signal pro-portional to engine temperature. This siynal is also compared to a reference value to derive a signal indicative o~ whether the engine temperature is above a predetermined level, below normal hot engine temperature. The system includes logic which receives the output of -the pressure switch and the temperature signal and acts to prevent $he genera--3a-3~
tion of actuating pulses for the injectors when the pressure is below the level at which the switch actuates and the engine temp-erature is above the comparator level.
In another embodiment of the invention circuitry could be provided for comparing continuous functions of pressure and tem-perature so that the injectors would be inhibited at relatively low engine temperatures if the fuel pressure was very low and at higher temperatures if the fuel pressure was somewhat higher but still below full pressure.
The system prevents the injectors from operating while the engine is being cranked during a hot start until the booster or fuel pump raises the pressure in the fuel line above the required fuel pressure. This will typically only require a few turns of the cranking motor. On continued cranking, the injectors are energized and the fuel flow through the injectors should be sufficient to create a fuel-ai-r mi~ture which will sustain com-bustion, preventing the unburned fuel from being pumped into the engine exhaust.
Other objectives, advantages and applications of the present invention will be made apparent by the following detailed description of a preferred embodiment oE the invention. The description makes reference to the accompanying drawings in which:
FIGURE 1 is a partially schematic, partially block dia gram of a fuel ignition system for an internal combustion engine, forming the prefered embodiment of the invention;
FIGURE 2 is a more detailed schematic diagram of the circuitry of the present invention which measures engine tempera~
ture and fuel line pressure to inhibit fuel injection during high temperature, low pressure starting conditions.
Referring to the dra~ings, FIGURE 1 schematically illus-trates a system for providing fuel under a high~ relatively con-3~
stant pressure to eight fuel injectors or transducers 10 arranged to provide controlled bursts of fuel to the intake valve areas of an eight cylinder internal combustion engine, as well as relevant portions of the ignition system. The injectors 10 may be of any well-known type such as those disclosed in my U.S. Patent 3,~12,718.
Electric signals applied to the injectors 10 through wires 12 open the injectors for controlled periods of time based on measured engine operating conditions, such as manifold vacuum pressurer engine temperature, atmospheric pressure and the like. The quantity of fuel provided by the injector during this signal period is a function of the pressure at the injector.
Fuel is provided to the injectors by a pair of conduits 14 termed fuel rails~ Fuel for feeding the rails is derived from a fuel tank 16. A pump 18 receives fuel from the tank 16 through a one-way valve 17 and operates to feed fuel from the tank through a one-way valve 20. The pump 18 may be electrically powered or driven by the engine in the manner of a conventional automotive fuel pump. It must be capable of pumping fuel at a volumetric rate in excess of the engine requirements at the maximum throttle opening. For a relatively large 8-cyclinder engine this may be in excess of 25 gallons per hour. The outlet pressure of the pump 18 may be substantially lower than the 25-50 pounds per square inch provided by fuel pumps for typical injection fuel systems of the prior art. In a preferred embodiment of the system a 5-10 pound per square inch outlet pressure will suffice. This pressure need not be well regulated and may vary with engine speed. Accord-ingly, the pump 18 should be substantially simpler and lower in cost than fuel pumps used with previous injection systems.
A fuel pressure booster and regulator generally indicated at 22 receives fuel passed through the one-way valve 20 from pump 18. The booster and regulator is schematically illustrated as comprising a piston 24 movable within a cylinder 26 and biased by a spring 28. The spring biases the piston in a direction as to move the piston 24 to contract the volume of the cylinder 26 in communication with the fuel line 30. This increases the fluid pressure in the fuel line 30. The one~way valve 20 prevents this increase in pressure from forcing a reverse flow to the pump 18. ::
A reset mechanism 32 is schematically illustrated as being connected to the piston 24 to periodically move the piston against the bias of the spring 28 to enlarge the volume of the cylinder 26 in communication with the fuel line 30. The reset mechanism is cocked once each engine cycle by the engine cam shaft 33. This lowers the pressure in the fuel line 30 and allows momentary flow from the pump 18 through the one-way valve 20.
A second one-way valve 34 is connected downstream of the booster and regulator 22. When the piston 24 moves under the bias of the spring 28 to contract the volume of the cylinder 26, the valve allows the resulting high or elevated pressure to communicate with a fuel line 36 that connects to the fuel rails 20 14, thus imposing this higher pressure on the rails. When the ~.
reset mechanism 32 withdraws the piston against the force of the spring 28, allowing the pump 18 to force fuel into the low-pres-sure fuel line 30, the one-way valve 34 prevents backflow in the ~:
high pressure fuel line 36 toward the pressure booster 22 and ~hus maintains the high fluid pressure in the rails 14. In alternative embodiments of the invention a conventional high pressure regu-lated fuel pump could replace the booster and regulator 32.
Optionally, the far ends of the rails are connected together by a fuel line 38 to form a closed circuit. A constant bleed one-way valve 40 connects the fuel. line 38 back to the fuel tank 16.
'73~i A fluid wave regulator or converter 42 is connected to the fluid line immediately upstream of the valve 20. The conver-ter is essentially of -the same type disclosed in my U.S. Patent 3,507,263. Schematically, it comprises an enclosed volume 44 separated from the fluid line by an elastic diaphragm 46. The diaphragm 46 assumes a position wherein the forces on its opposite sides are equal, thus when the line pressure increases, the dia-phragm moves to contract the volume of the chamber 44 and thus pressurize the fluid sealed within that volume. Conversely, when the line pressure Ealls the diaphragm moves to expand the sealed volume. When the diaphragm 46 moves outwardly in response to a lowering in the fluid pressure in the line it effectively pumps a volume of fluid into the line, tending to raise the line pres-sure. Conversely, when the diaphragm contracts in response to an increase in line pressure it increases the flow volume connected to the line and thus tends to decrease the pressure. The conver-ter 42 thus acts as a flow regulator.
When the piston 24 is retracted against the bias of the spring 28 by the unit 32 so that the pressure in the line 30 falls below the outlet pressure of the pump 18, and the flow valve 20 opens, the decrease in pressure at the inlet to the converter 42 causes the diaphragm 46 to expand and supply a volume of fuel which replenishes the chamber 26. In the absence of this device the sharp low pressure wave generated by expansion of the cylinder 26 might vaporize the fuel in the line between the pump and the booster.
A similar regulator or converter 48 is connected to the fuel line immediately downstream of the uni-directional valve 34.
This converter provides a pressurized fuel source to the line during the short interval when the piston 24 is resetting and accordingly the valve 34 is isolating the line 30 from the line 36. The converter 18 also acts as a cushion to minimize the travel of expansion and compression waves through the line 36.
In the preEerred embodiment of the invention a pair of pressure converters 52 and 54 are connected adjacent to the input ends of the fuel rails 14. A second pair of converters 56 and 58 are connected adjacent to the outlet ends of the Euel rails, where they connect to the common fuel line 38. These converters all similarly act to regulate the pressure in the rails by cancelling pressure waves created in the system by injection of fluid from the booster 22 or ejection of fluid through the injectors 10.
FIGURE 1 also illustrates the circuitry for providing electrical power to the coils of the injector valves 10 over lines 12. One of the injectors 10 is illustrated as having a coil 60.
Considering the circuitry that derives the energization pulses for this coil, the ignition system includes a distributor generally indicated at 62 having an arm 64 rotated in timed relation to the engine operation to sequentially move into position with contacts that are connected to the engine spark plugs 66, only one of which is illustrated. The arm 64 is connected to the secondary of an ignition coil, generally indicated at 68, having its primary connected to the vehicle battery 70 through a pair of engine actuated breaker points 72. The breaker points are shunted by a capacitor 74. -The breaker points are also connected to a counter 76 forming part of the injector circuitry~ The counter is advanced by one count each time the breaker points 72 close. The counter 76 has a plurality of output lines 78 which connect to a number of variable width pulse genera-tors 80, only one of which is illus-trated. The various lines 78 are sequentially energi~ed as the counter advances so tha-t each line is energized once each engine cycle.
The variable width pulse generators each receive outputs from a group of engine sensors 82 which measure such operating variables as manifold pressure and the like. Each variable width pulse generator also receives an electrical output from a thermis-tor 82 supported relative to the engine to experience the engine temperature. The thermistor 84 is illustrated separately from the other engine sensors 82 because of its roll in the low pressure, high engine temperature inhibit circuitry.
The output of the variable width pulse generators 80 are provided to gates 86 and the outputs of the gates constitute the lines 12 which energize the injectors 10.
The gates 86 are controlled by an injection inhibit circuit 8~. Only a single injection inhibit circuit services the gates 86 associated with each of the variable width pulse genera-tors 80. The injection inhibit circuit 88 has inputs from the thermistor 84 and from a pressure switch 90 connected to the fuel line 14. The switch 90 preferably closes when the pressure in the line 14 is above a predetermined Lraction of normal oepratiny line pressure. In the case of the preferred embodiment, the normal 20 operating line pressure may be 100 psi and the switch 90 may close when the pressure exceeds 65 psi. The injection inhibit circuit 88 can, alternatively, be provided with an input from the pressure switch 90 solely, making it operative in response to pressure of ; the fuel in line 14 to inhibit energization of the injector during starting of the engine until the fuel pressure exceeds a preselec-ted minimum pressure in the order of about 65 psi.
The injection inhibit circuit 88 processes the output of the switch 90 and of the thermistor 84 to control the gate 86u The control is such that the gate 86 passes output pulses from the generator 80 to the injector coil 60 as long as the pressure switch is closed. When the pressure switch is open, indicating a pres-_g_ sure in the line 14 of less than 65 psi, the gate 86 still passesinjector signals if the output of the thermistor 84 is such as to indicate that the temperature of the engine is below a predeter-mined value. In the preferred embodiment of the invention this value may be approximately 150F as compared to a normal engine operating temperature of about 200F.
When the pressure in the line 14 is less than 65 psi and the engine temperature is above 150F the gate 86 is energized by the circuit 88 to prevent the application of firing pulses from the generator 80 to the coil 60. This condition occurs when the engine is being restarted a relatively short period of time after it stopped while at or near operating temperature; i.e., within 5-20 minutes or thereabouts, depending upon the ambient temperature.
Were the injectors not to be inhibited during this time the reduced ~uel quantity that they would provide to the cylinders as a result of the lowered pressure in the line 14 would likely not result in a rich enough fuel/air ratio to achieve ignition and the unburned hydrocarbon vapors would be pumped out of the engine exhaust.
FIGURE 2 illustrates the circuitry of the injection inhibit device 88 and its associated components in greater detail.
The thermistor 84 is connected in series with a resis-tance 100 between a positive voltage provided by a power supply and ground so that the two act as a voltage divider. The mid-p~int of this voltage divider, which experiences a voltage depen-dent upon the resistance of the thermistor 84, is applied to one terminal of an operational amplifier 102 connected to a comparator mode. The reference input to the comparator 102 is provided by a voltage divider consisting of the series combination of two resis-tances 104 and 106. One end of resistance 104 is connected to -~ 30 ground and one end of resistance 106 is connected to a positive reference voltage. Resistance 104 is shunted by the pressure ~10--switch 90 which is closed when the pressure in line 12 exceeds the predetermined pressure such as 65 psig. When the pressure is in : excess of that value the switch 90 is closed and the comparator ln2 cannot provide a high output, independent of the resistance of the thermistor 84~ However, when the pressure is above 65 psi, so that the switch 90 is open, and the engine temperature and thus the thermistor temperature are above a predetermined value, such as 150F, the voltage at the connection between the thermistor 84 : and the resistance 100 will exceed the reference voltage and will provide an output from the comparator 102. This voltage is applied to the gates 86, one for each engine cylinder, through a plurality of isolating diodes 106. When the gates are activated by outputs from the comparator 102 the output pulses from the variable width pulse generators 80 are applied to the coils 60 of the i.njector 10. When the fuel line pressure is below the predetermined value and the engine temperature is above the comparator value, the output of the comparator 102 ~ill be such ~ha~ the gates 86 will block pulses from the variable width generators from being applied to the injectors.
~ 30 .,~.
Claims (9)
1. In a fuel injection system for a spark ignition engine having a supply of pressurized fuel, an injector valve connected to the supply, sensors for measuring engine operating conditions and an electric circuit for energizing the injector in timed relation to the engine operation for periods controlled by the output of said sensors, the improvement comprising: means actuated in response to the pressure of the fuel in said supply for inhibiting energization of the injector during starting of said engine until the fuel pressure exceeds a preselected minimum pressure.
2. The fuel injection system of claim 1 wherein said means for sensing engine operating conditions includes means for sensing engine temperature and said means for inhibiting energi-zation of the injector during starting is disenabled in response to engine temperature below a preselected value, said means for inhibiting energization of the injector being connected to the output of said temperature sensor.
3. The fuel injection system of claim 2 wherein said means for inhibiting energization of the injector during starting includes a pressure transducer connected to the fuel supply having a first output when the pressure in said supply is above a pre-determined pressure, which is below the pressure in said supply during normal engine operation, and a second output when the pressure in said supply is below said predetermined pressure.
4. The fuel injection system of claim 3 wherein said means for inhibiting energization of the injector during starting includes means for generating an electric signal having a property which is a function of engine temperature, and comparator means for receiving said electric signal and a reference signal, the comparator having a first output when the electric signal is greater than the reference signal and a second output when the electric signal is less than the reference signal.
5. The fuel injection system of claim 2 wherein said means for inhibiting energization of the fuel injector during starting acts to inhibit energization of said injector when the pressure in the fuel source is below a predetermined pressure, which predetermined temperature is below the normal, warmed up, operating temperature of the engine.
6. The fuel injection system of claim 1 in which said means for inhibiting energization of the injector during starting includes a thermistor connected to the engine to provide an elec-trical signal having a characteristic which is a function of engine temperature and a pressure switch connected to said supply of fuel.
7. A fuel injection system for a spark ignited internal combustion engine, comprising: a fuel source; a fuel supply line;
means powered by the engine for feeding fuel from the source to the supply line to maintain a predetermined, operating fuel pres-sure in the supply line; an injector connected to the supply line;
sensors connected to the engine to measure engine operating para-meters; an electric circuit connected to the outputs of the sensors and to the engine operative to energize the injector at periods occurring in timed relation to the operation of the engine and having durations dependent upon the outputs of said sensors; and means actuated in response to the pressure of the fuel in said supply line for inhibiting energization of the injector during starting of said engine, independent of the output of said elec-tric circuit, until the pressure of said fuel in said supply line exceeds a preselected minimum pressure.
means powered by the engine for feeding fuel from the source to the supply line to maintain a predetermined, operating fuel pres-sure in the supply line; an injector connected to the supply line;
sensors connected to the engine to measure engine operating para-meters; an electric circuit connected to the outputs of the sensors and to the engine operative to energize the injector at periods occurring in timed relation to the operation of the engine and having durations dependent upon the outputs of said sensors; and means actuated in response to the pressure of the fuel in said supply line for inhibiting energization of the injector during starting of said engine, independent of the output of said elec-tric circuit, until the pressure of said fuel in said supply line exceeds a preselected minimum pressure.
8. The fuel injection system of claim 7 wherein said means for inhibiting energization of the injector during starting includes a pressure sensor connected to the fuel supply, a temper-ature sensor connected to the engine and said means for inhibiting energization of the injector is disenabled in response to engine temperature below a preselected value, said means for inhibiting energization of said injector being connected to the output of said temperature sensor.
9. The fuel injection system of claim 7 wherein said means for inhibiting energization of the injector upon obtainment of conditions relatively low pressure in the fuel supply and high engine temperature acts to inhibit operation of the injector when pressure in the fuel supply is below a pressure which is itself below said operating pressure of the supply, and the engine temperature is above a predetermined temperature, which predeter-mined temperature is below the normal engine operating temperature after warm up.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US81406177A | 1977-07-08 | 1977-07-08 | |
| US814,061 | 1977-07-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1110736A true CA1110736A (en) | 1981-10-13 |
Family
ID=25214092
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA307,019A Expired CA1110736A (en) | 1977-07-08 | 1978-07-07 | Fuel injection system with pressure excursion start inhibit |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS5419021A (en) |
| CA (1) | CA1110736A (en) |
| DE (1) | DE2829810A1 (en) |
| ES (1) | ES471306A1 (en) |
| FR (1) | FR2396872A1 (en) |
| GB (1) | GB1591783A (en) |
| IT (1) | IT7868613A0 (en) |
| SE (1) | SE7807309L (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5652533A (en) * | 1979-10-04 | 1981-05-11 | Nissan Motor Co Ltd | Injection timing selecting device |
| JPS5891338A (en) * | 1981-11-24 | 1983-05-31 | Honda Motor Co Ltd | Electronic fuel injection control device for multicylinder internal-combustion engine |
| US4691680A (en) * | 1986-05-22 | 1987-09-08 | Brunswick Corporation | Starting-enrichment control for a fuel-injected engine |
| GB8613465D0 (en) * | 1986-06-04 | 1986-07-09 | Lucas Ind Plc | Fuel pumping apparatus |
| FR2692937B1 (en) * | 1992-06-30 | 1995-07-07 | Renault | FUEL INJECTION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE. |
| FR2711734B1 (en) * | 1993-10-29 | 1995-11-24 | Renault | Method of controlling an internal combustion engine fuel pump. |
| DE10301236B4 (en) * | 2003-01-15 | 2017-08-17 | Robert Bosch Gmbh | Method for starting an internal combustion engine, in particular an internal combustion engine with direct injection |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3385278A (en) * | 1966-10-11 | 1968-05-28 | Sentinel Distributors | Electronic actuator for an engine protective system |
| US3646917A (en) * | 1970-06-16 | 1972-03-07 | Bendix Corp | Auxiliary circuit for electronic fuel control systems to facilitate cold starting |
| FR2119239A5 (en) * | 1970-12-24 | 1972-08-04 | Sopromi Soc Proc Modern Inject | |
| US3705571A (en) * | 1971-03-17 | 1972-12-12 | Bendix Corp | Hot start auxiliary circuit for electronic fuel control system |
-
1978
- 1978-05-19 GB GB20868/78A patent/GB1591783A/en not_active Expired
- 1978-06-28 SE SE7807309A patent/SE7807309L/en unknown
- 1978-06-29 JP JP7917678A patent/JPS5419021A/en active Pending
- 1978-06-30 ES ES471306A patent/ES471306A1/en not_active Expired
- 1978-07-06 DE DE19782829810 patent/DE2829810A1/en not_active Withdrawn
- 1978-07-07 CA CA307,019A patent/CA1110736A/en not_active Expired
- 1978-07-07 FR FR7820402A patent/FR2396872A1/en active Pending
- 1978-07-07 IT IT7868613A patent/IT7868613A0/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| IT7868613A0 (en) | 1978-07-07 |
| JPS5419021A (en) | 1979-02-13 |
| GB1591783A (en) | 1981-06-24 |
| DE2829810A1 (en) | 1979-01-25 |
| FR2396872A1 (en) | 1979-02-02 |
| ES471306A1 (en) | 1979-10-01 |
| SE7807309L (en) | 1979-01-09 |
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| MKEX | Expiry |