Dual fuel system

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Drawing sheet — no readable text.

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to control the flow of main and secondary fuels into a

DUAL FUEL SYSTEM mixing chamber to momentarily increase the octane rating of the fuel charge during acceleration, such as by

BACKGROUND OF THE INVENTION mixing in a quantity of alcohol with gasoline in a prede This invention relates to the field of dual fuel systems termined ratio, for example as 1 part alcohol to 10 parts for vehicles with internal combustion engines, and in gasoline.

particular vehicles with engines designed to use gaso U.S. Pat. No. 4,031,864 discloses a multiple fuel sup line as their primary fuel wherein an alternate fuel sys ply system for an internal combustion engine wherein tem can be added to enable use of an alternate fuel by O phase separation of a gasoline-methanol blend in a sin switching back and forth between gasoline and the gle tank is induces by adding a minor amount of water alternate fuel. sufficient to guarantee separation into an upper gasoline Prior art devices of this kind of which the inventor is phase and a lower methanol-water phase. Separate fuel aware include those described in the following United pickups and separate level indicators are provided for States patents. each phase. Either gasoline or methanol can be supplied U.S. Pat. No. 5,228,423 discloses a dual fuel engine 15 to the engine by the vehicle's fuel delivery system. which uses liquid fuel such as gasoline or gaseous fuel U.S. Pat. No. 3,659,574 discloses a natural gas pow such as compressed natural gas, wherein separate intake ered engine having a dual fuel feed apparatus and con passages into the combustion chamber of each cylinder trol whereby the engine can operate on both natural gas and separate fuel supply devices are provided for the and gasoline. Two carburetors are mounted in parallel gaseous fuel and for the liquid fuel. Both intake passages 20 at the intake manifold and a switch mechanism is pro are provided with intake valves, and both intake valves vided to switch between natural gas from one carbure are actuated when the liquid fuel is used but substan tor and gasoline from the other.

tially only one of the intake valves is actuated when the gaseous fuel is used. - SUMMARY OF THE INVENTION U.S. Pat. No. 4,878,475 discloses a dual fuel system 25 The dual fuel system in accordance with the present for internal combustion engines, one fuel such as pro invention provides a number of improvements and ad pane to start the engine, to operate it at idle speed and vantages over the prior art.

to supplement the other fuel during acceleration, and The present invention is adapted for motor vehicles the second such as gasoline to operate the engine at its which come from the factory equipped with an elec normal working speed. Vacuum controlled valves de 30 tronic fuel injection system for use with gasoline as the liver the one fuel such as propane to the carburetor. The fuel. The fuel system in accordance with this invention primary fuel such as gasoline is delivered to the carbu is able to utilize the original equipment electronic con retor by the usual fuel pump. trol module to regulate and deliver an alternate fuel, U.S. Pat. No. 4,606,322 discloses a dual fuel control and supply system for internal combustion engines such 35 such as compressed natural gas to give one example, to the intake manifold and cylinders without modification as diesel, but not necessarily confined to diesel engines, of the throttle body except to add a venturi mixer and an injector pump to deliver the principal liquid fuel under pressure to the cylinders, an electronic control provide a port through the side wall of the venturi unit, and an electrically controllable variable flow regu mixer for the alternate fuel to enter. lator to receive a gaseous alternative fuel and deliver A pilot valve serves as the regulator for the alternate controlled quantities to the cylinders as signalled by the fuel to deliver the properamount of alternate fuel to the electronic control unit. venturi mixer and throttle body as called for by the U.S. Pat. No. 4,594,201 discloses a multi-fuel system original equipment electronic control module which for internal combustion engines, comprising a non-ven senses the demands of the engine for fuel. The pilot turitype of carburetor having a metered inlet and means 45 valve has a through passageway chamber withinlet and for controlling the pressure of each fuel in accordance outlet ports, the opening of such passageway controlled with the stoichiometric ratio of that fuel to assure by a stem valve, a diaphragm to move the stem valve proper fuel/air ratio is delivered to the mixing chamber from a completely closed position to any degree of of the carburetor without requiring any change in either partially open up to fully open, and a pressure regulat the carburetor or engine when a different fuel is used. 50 ing chamber separated by the diaphragm from the U.S. Pat. No. 4,576,137 discloses a gas and a diesel through passageway chamber.

dual fuel engine, wherein the engine has an electronic A pilot control port opens to the pressure regulating governor circuit adapted to receive both a speed signal chamber, and a branch alternate fuel line with a pres representing the actual speed of the engine and a set sure regulator to reduce the pressure of the compressed speed signal representing a predetermined command 55 natural gas or other alternate fuel to a desired pilot speed of the engine, electric actuators to actuate a diesel control pressure is connected to the pilot control port. fuel injection pump and a gaseous fuel regulating valve A separate electronic fuel injector is secured to the pilot in response to the signal from the electronic governor valve in communication with the pilot control port to circuit, with a switching control circuit to switch opera control the amount of the alternate fuel at the pilot tion between diesel fuel and gaseous fuel. control pressure which enters the pressure regulating U.S. Pat. No. 4,531,497 discloses a natural gas adap chamber in response to signals received from the origi tor system for automobiles which normally run on gaso nal equipment electronic control module. line, including a compressor driven by the vehicle's When more of the alternate fuel is allowed to enter engine to compress low pressure natural gas up to a the pressure regulating chamber, the diaphragm is higher pressure, and an air mixing delivery system for 65 forced to flex in the direction of the through passage delivering the compressed natural gas to the carburetor. way chamber which moves the stem valve in the direc U.S. Pat. No. 4,354,477 discloses a multi-fuel carbure tion which opens the through passageway wider, thus tor with a rotary mixing valve which has multiple vanes allowing a greater amount of the alternate fuel to flow

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through to the venturimixer, throttle body, intake man The ignition switch 7 must also be in its contacts ifold and cylinders. closed position to complete a circuit from the battery 3 When the electronic control module senses decreased to the solenoid valve 3.

demand for fuel, it signals the electronic fuel injector When solenoid valve 3 is in its valve closed position, affixed to the pilot valve to let less of the alternate fuel gasoline is then supplied to the engine from the gasoline at the pilot control pressure to enter the pressure regu supply tank 9.

lating chamber. The diaphragm then relaxes toward its An electronic control module 10 which controls the at rest position bringing the stem valve toward a nar gasoline electronic fuel injector 11 is switched to con rower opening of the through passageway thereby de trol the amount of gasoline being delivered to the en livering less of the alternate fuel to the engine. 10 gine when fuel selector switch 5 is switched to its posi No other system known to the prior art is able to use tion to open contacts 6. At such time movable contacts an alternate fuel such as compressed natural gas in a 12 and 13 are switched from stationary contacts 14 and motor vehicle originally equipped for operation on 15 to stationary contacts 16 and 17, thereby completing gasoline which for all practical purposes makes use of a circuit across electronic fuel injector 11 to regulate the same sensing and control equipment for delivering 15 the amount of gasoline fuel to the engine. the right amount of alternate fuel to the engine as used At such time, movable contact 18 is switched from for delivering the right amount of gasoline to the engine stationary contact 19 to stationary contact 20 which when switched to that mode. The result is that the completes a circuit across temperature sensor 21 and the electronic control module 10. This sensor is provided to engine is able to operate just as well on the alternate fuel sense as on gasoline, and a minimum of additional parts is perature the temperature of the engine and feed such tem needed. signal to the electronic control module 10. The switching mechanism to switch between gaso This enables the electronic control module 10 to in turn energize the electronic fuel injector 11 to make proper line and the alternate fuel is also simplified in this inven adjustments tion, requiring only a relay to switch the electronic 25 delivered to regarding the amount of gasoline fuel being the engine when it is operating on that fuel.

control module from the electronic fuel injector for The sensor 21 is not required when the engine is gasoline to the one provided at the pilot valve for the switched alternate fuel, and vice versa. The switching mechanism compressedfornatural operation to the alternate fuel such as gas. At such time, movable contact at the same time opens a solenoid valve for flow of the 18 is switched to stationary alternate fuel from its supply tank when in that mode, 30 a circuit across a fixed 180contact 19 which completes ohm resistor 22 and the and closes such valve to stop the flow of alternate fuel electronic control module 10 for use during operation from the supply tank when switched to the gasoline of the engine on such alternate fuel which can flow mode. In addition, the switching mechanism cuts out a through temperature sensor circuit when switched to the alter resistor 22thevaries now open solenoid valve 3. The fixed ohm nate fuel mode, and reconnects it when switched to the 35 ture sensor 21 iswith used the engine on which the tempera for operation in the gasoline gasoline mode. mode. The resistance of the resistor 22 should be that Other features, improvements and advantages of this which simulates the resistance which the sensor 21 invention will become apparent from the more detailed would provide at normal operating temperature of the description which follows and by reference to the ac vehicle.

companying drawing. A heat exchange 23 is provided adjacent the alternate BRIEF DESCRIPTION OF THE DRAWING fuel line to pre-heat the alternate fuel as it passes to the pressure regulator 24. Such pre-heating provides pro

FIG. 1 is a section view of the venturi mixer, throttle tection against freezing the control valve and regulator body and gasoline electronic fuel injector positioned in due to impurities in the expanding gas. Heat is provided registration therewith connected to the gasoline supply 45 by engine coolant passing through the shell of the heat tank, and a section view of the pilot valve and alternate exchanger, or by some other heat source such as an fuel electronic fuel injector affixed thereto, showing its electrical heater or exhaust gas.

connection to the alternate fuel tank, the electronic Pressure of the alternate fuel is the supply tank is control module and other electronic components shown about 2500 pounds per square inch (psi). The regulator in block form and schematically. SO 24 reduces the pressure in the alternate fuel supply line DESCRIPTION OF PREFERRED EMBODIMENT to between 100 psi to 200 psi. The alternate fuel supply line 4 branches after passing

A dual fuel system for internal combustion engines in through regulator 24 to direct a portion of the alternate accordance with this invention enables the engine to fuel through branch line 25, a secondary regulator 26 run on the usual gasoline fuel, and when desired to run 55 and then to pilot control port 27. The secondary regula on an alternate fuel such as compressed natural gas by tor 26 reduces the alternate fuel pressure to 30 psi. Fuel throwing a switch. from this branch fuel line 25 after passing through sec The invention includes a pressurized storage tank 1 ondary regulator 26 and being reduced to 30 psi is also having a fill port 2 to receive an alternate fuel supply connected to supply idle fuel.

such as compressed natural gas. A solenoid valve 3 The main branch of alternate fuel supply line 4 leads opens and closes the alternate fuel supply line 4 from the to primary port 28 of pilot control valve 29. The pilot pressurized storage tank 1, the solenoid valve 3 being control valve 29 controls flow of the alternate fuel to controlled by the fuel selector switch 5. When the the engine using the fuel injector signal from electronic switch 5 is in its position to close contacts 6, the sole control module 10, normally installed at the factory for noid valve 3 is energized and moves to its valve open 65 engines originally equipped with electronic fuel injec position. When switch 5 is moved to its position to open tion.

contacts 6, the solenoid valve 3 is not energized and When fuel selector switch 5 is switched to open sole moves to its normally biased valve closed position. noid valve 3 and thereby switch operation of the engine

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from gasoline to the alternate fuel supply, movable body 38. An electronic valve 42 narrows and widens contacts 12 and 13 are switched to stationary contacts this auxiliary air supply passageway 41 as signaled by 14 and 15 thereby interrupting the circuit to gasoline the electronic control module 10 to which it is con fuel injector 11 and completing a circuit between the nected. This is important during idle because the throt electronic control module 10 and alternate fuel injectors tle plate 43 is closed. If auxiliary passageway 41 does 30, located in the bonnet of the pilot control valve 29. not allow fresh air to flow not mixed with any fuel, the As the electronic control module 10 calls for fuel, the engine will run poorly regardless of the throttle opening alternate fuel injectors 30 are turned on and off at a rate when operating on alternate fuel. This passage must determined by the electronic control module 10 based bypass the venturi mixer 37 to allow fresh air to be on the requirements of the engine at that particular time. 10 added to the air/fuel mixture allowing the electronic When the electronic control module 10 calls for more control module 10 to control the idle speed and provide fuel at the alternate fuel injectors 30, secondary fuel at additional mixture control at wider throttle openings 30 psi from branch alternate fuel supply line 25 flows when operating on alternate fuel.

into the chamber of the pilot control valve 29 at its I claim:

bonnet side. This causes pressure to build up against the 15 1. A dual fuel system for an internal combustion en diaphragm 31 which in turn displaces the spool 32 until gine, comprising an internal combustion engine having it uncovers primary port 28 allowing primary fuel at an existing electronic fuel injection system to provide between 100 to 250 psi to flow through the pilot control gasoline fuel for operation thereof, said existing elec valve 29. tronic fuel injection system including an existing elec The spool 32 continues to open thereby widening the tronic control module to sense fuel demand conditions opening of port 28 allowing more of the alternate fuel to of said engine and transmit control signals responsive flow through the pilot control valve 29 to the engine. thereto, a throttle body having a throat, a throttle As more primary fuel at 100 to 250 psi flows through therein, a venturi member having a passageway in com port 28, pressure on the port 28 side of the diaphragm munication with said throat of said throttle body and increases until it equalizes the pressure on the bonnet 25 upstream therefrom, a gasoline electronic fuel injector side of the pilot control valve. At such point, the spool to receive said control signals from said electronic con 32 and the amount which it has opened port 28 remains trol module in registration with said throat of said throt fixed until either more of the alternate fuel is called for tle body and connected to a supply of gasoline fuel, a or less. temperature sensor to sense the temperature of said When less fuel is called for by the electronic control 30 engine connected in circuit with said electronic control module 10, the duty cycle portion of the signal of the module for transmission of engine temperature signals alternate fuel injectors 30 in the bonnet of the pilot thereto, an alternate electronic fuel injection system to control valve 29 decreases. Thus, as less secondary fuel deliver an alternate fuel to operate said engine, said is called for at pilot control port 27, pressure on the alternate electronic fuel injection system including al bonnet side of the pilot control valve 29 decreases al 35 ternate electronic fuel injection means for connection to lowing pressure of primary alternate fuel through port said existing electronic control module to receive said 28 on the opposite side of the diaphragm 31 to move the control signals therefrom when connected thereto, al spool 32 in the direction which closes port 28 thereby ternate fuel regulating means operably associated with reducing flow of primary alternate fuel through the said alternate fuel to said engine for operation thereof pilot control valve. on said alternate fuel, including a supply of said alter A coil compression spring 33 biases the spool 32 to nate fuel, and fuel selection switch means to switch the position where it completely closes port 28 when operation of said engine from said existing electronic the engine is turned off or switched to operate on gaso fuel injection system which provides gasoline fuel for line. operation thereof to said alternate electronic fuel injec An output adjustment valve 34 is provided which can 45 tion system which provides an alternate fuel for opera be rotated by a screw driver to narrow or widen the tion of said engine and vice versa wherein said alternate primary flow passageway through the pilot control fuel regulating means includes a pilot control valve, said valve 29. pilot control valve having a diaphragm member sepa A pilot pressure adjustment valve 35, rotatable by a rating a primary flow passageway on one side thereof screw driver, is provided to narrow or widen the pilot 50 and a control pressure chamber on the opposite side pressure passageway. thereof, a flow inlet port opening to said control pres An idle compensation adjustment valve 36, rotatable sure chamber, a primary flow inlet port opening to said by a screw driver, is provided to narrow or widen the primary flow passageway at one end thereof and a pri idle fuel passageway. mary flow outlet port opening to said primary flow These adjustment valves 34, 35 and 36 are adjusted at 55 passageway at the other end thereof, a control valve initial set up only and do not require further adjustment member provided in said primary flow passageway for normal use. The electronic control module 10 makes between said inlet port and said outlet port movable all air/fuel adjustments as called for by the engine dur between a valve open and a valve closed position ad ing normal operation. justable to any position therebetween in response to Primary alternate fuel flows from-the pilot control movement of said diaphragm.

valve 29 to a venturi mixer 37 mounted on top of the 2. A dual fuel system for an internal combustion en throttle body 38 inside of the original equipment air gine as set forth in claim 1, wherein said alternate elec filter 39. The venturi mixer 37 allows unrestricted air tronic fuel injection means comprises an alternate fuel flow to the engine while in the gasoline fuel mode and electronic fuel injector to receive said control signals mixes alternate fuel with air when in the alternate fuel 65 from said electronic control module, said alternate fuel mode. electronic fuel injector including a through passage A tube 40 is inserted through the venturi mixer 37 to way, an inlet opening to said through passageway, an the auxiliary air supply passageway 41 in the throttle outlet opening to said through passageway and closure

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means to open, close and vary the opening of said 10. A dual system for an internal combustion engine through passageway responsive to said control signals comprising an electronic control module to sense fuel from said electronic control module, said inlet of said demand of said engine and transmit control signals re through passageway of said alternate fuel electronic sponsive thereto, an electronic fuel injector connected fuel injector being positioned in registration with said to receive said control signals from said electronic con control flow inlet port opening to said control pressure trol module, a pilot control valve, said pilot control chamber, said outlet of said through passageway of said valve having a movable member separating a primary alternate fuel electronic fuel injector being positioned to flow passageway on one side thereof and a control open to said control pressure chamber. pressure chamber on the opposite side thereof, a control 3. A dual fuel system for an internal combustion en 10 flow inlet port opening to said control pressure cham gine as set forth in claim 1, wherein said fuel selection ber, a primary flow inlet port opening to said primary switch means includes an electrical switching circuit to flow passageway at one end thereof and a primary flow switch operation of said internal combustion engine outlet port opening to said primary flow passageway at from one of said fuels to the other, comprising a power the other end thereof, a control valve member provided source, a first circuit connected between said electronic 15 in said primary flow passageway between said inlet port control module and said gasoline electronic fuel injec and said outlet port movable between a valve open and tor for operation of said engine on said gasoline fuel, a valve closed position adjustable to any position therebe second circuit connected between said electronic con tween in response to movement of said movable mem trol module and said alternate fuel electronic fuel injec 20 ber, a pressurized fuel supply tank to receive a supply of tor for operation of said engine on said alternate fuel, pressurized gaseous fuel, a first fuel line leading from and a switching component connected between said said pressurized fuel supply tank to said primary flow power source and said first and second circuits to opera inlet port of said pilot control valve, a second fuel line tively connect either one of said circuits to said power leading from said primary flow outlet port of said pilot source and disconnect the other. control valve to fuel entrance means to a manifold lead 4. A dual fuel system for an internal combustion en 25 ing to combustion chambers of the cylinders of said gine as set forth in claim 3, including a pressurized engine, including said fuel entrance means, said elec alternate fuel supply tank, an alternate fuel line leading tronic fuel injector including a through passageway, an from said alternate fuel supply tank to said primary flow inlet opening to said through passageway of said fuel inlet port of said pilot control valve, a solenoid valve in 30 injector, an outlet opening to said through passageway said alternate fuel line to open and close said fuel line, of said fuel injector, fuel injector closure means to open, said solenoid valve being connected in said second cir close and vary the opening of said through passageway cuit. of said fuel injector responsive to said control signals 5. A dual fuel system for an internal combustion en from said electronic control module, said inlet of said gine as set forth in claim 3, wherein said temperature 35 through passageway of said fuel injector being posi sensor is connected in said first circuit, being thereby tioned in registration with said control flow inlet port connected and operative when said engine is switched opening to said control pressure chamber, said outlet of for operation on gasoline, being disconnected and inop said through passageway of said fuel injector being erative when said engine is switched for operation on positioned to open to said control pressure chamber, a said alternate fuel. first fuel pressure regulator in said first fuel line to re 6. A dual fuel system for an internal combustion en duce fuel pressure therein to a range which includes one gine as set forth in claim 5, including a fixed resistor, hundred pounds per square inch, a third fuel line lead said fixed resistor being connected in said second cir ing from said first fuel line on the downstream side of cuit, said fixed resistor having a resistance to simulate said first fuel pressure regulator to said control flow that which said temperature sensor impresses on said 45 inlet port opening to said control pressure chamber of first circuit at normal operating temperature of said said pilot control valve, a second fuel pressure regulator engine. in said third fuel line to reduce fuel pressure therein to 7. A dual fuel system for an internal combustion en a range which includes thirty pounds per square inch. gine as set forth in claim 4, including a heat exchanger 11. A dual fuel system for an internal combustion positioned relative to said alternate fuel line to preheat 50 engine as set forth in claim 10, wherein said entrance said alternate fuel as it flows in said line from said alter means to a manifold leading to combustion chambers of nate fuel supply tank to said venturi member and said the cylinders of said engine comprise a venturi mixer throttle body. having a venturi passageway therethrough, a throttle 8. A dual fuel system for an internal combustion en body having a through passageway in registration with gine as set forth in claim 4, including a first alternate 55 said venturi passageway and downstream therefrom. fuel pressure regulator in said alternate fuel line to re 12. A dual fuel system for an internal combustion duce alternate fuel pressure therein to a range which engine as set forth in claim 11, including an air passage includes one hundred pounds per square inch. way through said venturi mixer and said throttle body, 9. A dual fuel system for an internal combustion en having an air intake which opens at one end to receive gine as set forth in claim 8, including a branch alternate a flow of ambient air into said air passageway and an air fuel line leading from said alternate fuel line on the outlet which opens at the other end to said through downstream side of said first alternate fuel pressure passageway of said throttle body.

regulator to said control flow inlet port opening to said 13. A dual fuel system for an internal combustion control pressure chamber of said pilot control valve, a engine as set forth in claim 10, including an output second alternate fuel pressure regulator in said branch 65 adjustment valve movable between an open and closed alternate fuel line to reduce alternate fuel pressure position and positioned to vary the cross-sectional therein to a range which includes thirty pounds per opening of said primary flow passageway of said pilot square inch. control valve.

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14. A dual fuel system for an internal combustion engine as set forth in claim 10, including an idle com engine as set forth in claim 10, including a pilot pressure pensation adjustment valve movable between an open adjustment valve movable between an open and closed and closed position and positioned to vary the cross-sec position and positioned to vary the cross-sectional tional opening of an idle fuel passageway of said pilot opening of the outlet port from said control pressure chamber of said pilot control valve, including said out control valve, including said idle fuel passageway let port thereof. thereof.

15. A dual fuel system for an internal combustion