Dual fuel method and system

• US 6,591,817 B2
• Filed: 03/21/2001
• Issued: 07/15/2003
• Est. Priority Date: 03/21/2001
• Status: Expired due to Fees

• Current Assignee: Temic Automotive of North America, Incorporated (Continental AG)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Deutsch, Robert W.
• Primary Examiner(s): Kamen, Noah P.
• Application Number:
  US09/813,622
• Publication Number:
  US 20020134362A1
• Time in Patent Office: 846 Days
• Field of Search: 123/27.GE, 123/525, 123/526
• US Class Current: 123/525
• CPC Class Codes: F02D 19/0615 being initiated by automatic means, e.g. based on engine or vehicle operating conditions
• CPC Class Codes: F02D 19/0647 the gaseous fuel being liquefied petroleum gas [LPG], liquefied natural gas [LNG], compressed natural gas [CNG] or dimethyl ether [DME]
• CPC Class Codes: F02D 19/0692 Arrangement of multiple injectors per combustion chamber
• CPC Class Codes: F02M 13/08 Carburettors adapted to use liquid and gaseous fuels, e.g. alternatively
• CPC Class Codes: Y02T 10/30 Use of alternative fuels, e.g. biofuels

Abstract

A special dual fuel method and system is provided to enhance vehicle performance and fuel consumption as well as to accommodate a smooth transition when operating the engine on different fuels, such as gasoline or liquified petroleum gas (LPG). When the engine is operated on a different fuel, a filtered oxygen (O₂) signal is transmitted to an engine control unit (ECU) which can regulate operation of the gasoline shutoff valve and an LPG valve and responds to the filtered O₂ signal and the type of fuel, i.e. mode of operation, selected for the dual fuel engine.

Claims

1. A method for operating a dual fuel system, comprising the steps of:

pumping a first fuel to a first fuel feeding device;

feeding the first fuel from the first fuel feeding device to an engine;

operating the engine with the first fuel in a first fuel mode;

changing the mode of operation of the engine to operate on a second fuel by

stopping the flow of the first fuel to the first fuel feeding device;

preventing the flow of the first fuel from the first fuel feeding device to the engine;

thereafter

opening a valve for feeding the second fuel to a second fuel feeding device;

passing the second fuel to the engine; and

operating the engine on the second fuel in a second fuel mode;

monitoring the oxygen content of exhaust gases emitted from the engine;

generating a filtered signal based upon the monitored oxygen content of the exhaust gases over a finite period of time, the generating of the filtered signal occurring in association with an engine control unit (ECU); and

controlling operation of the valve via the ECU based upon the signal.

2. A method for operating a dual fuel system in accordance with claim 1 including changing the mode operation of the engine from the second fuel mode to the first fuel mode by:

starting the flow of the first fuel to the first fuel feeding device;

closing the valve to stop the flow and feeding of the second fuel to the engine;

feeding the first fuel from the first fuel feeding device to the engine; and

operating the engine on the first fuel.

3. A method for operating a dual fuel system in accordance with claim 1 wherein:

the first fuel feeding device comprises a carburetor with a float bowl; and

the first fuel is pumped by a fuel pump operatively associated with the engine.

4. A method for operating a dual fuel system in accordance with claim 1 wherein:

the first fuel feeding device comprises one or more electronic fuel injectors (EFI) with a rail and fuel line; and

the first fuel is pumped by a fuel pump operatively associated with a first fuel tank.

5. A method for operating a dual fuel system in accordance with claim 1 including opening the valve when the signal decreases upon changing to the second fuel mode.

6. A method for operating a dual fuel system in accordance with claim 1 including closing the valve when the signal increases upon changing to the first the mode.

7. A method for operating a dual fuel system in accordance with claim 1 including:

timing said signal; and

opening the valve in the second fuel mode if the signal does not substantially change for a predetermined period of time.

8. A method for operating a dual fuel system in accordance with claim 1 including:

timing said signal; and

closing the valve in the first fuel mode if the signal does not substantially change for a predetermined period of time.

9. A method for operating a dual fuel system in accordance with claim 1 wherein:

said first fuel and said second fuel are selected from the group consisting of a liquid fuel, gasoline, petro, a gaseous fuel, liquefied petroleum gas (LPG), and compressed natural gas (CNG); and

said first fuel is different than said second fuel.

10. A method for operating a dual fuel system, comprising the steps of:

pumping gasoline to a carburetor with a fuel pump;

feeding gasoline from the carburetor to an engine;

operating the engine on gasoline in a gasoline mode;

detecting and monitoring the oxygen content of exhaust gases emitted from the engine;

generating a signal based upon the detected oxygen content of the exhaust gases;

determining a mean or average value of the signal for a preselected period of time;

filtering the signal to produce a filtered signal corresponding to the means or average value of the signal, the filtering occurring in association with an engine control unit (ECU);

controlling operation of an LPG valve with the ECU;

changing the mode of operation of the engine from gasoline to liquified petroleum gas (LPG);

establishing a reference filtered signal when the mode of operation of the engine is changed from gasoline to LPG;

closing a gasoline valve to stop the flow of gasoline to the carburetor;

waiting until the gasoline substantially empties from a float bowl of the carburetor;

thereafter

opening the LPG valve to access the liquified petroleum gas (LPG);

vaporizing the liquified petroleum gas (LPG);

feeding the vaporized LPG to the engine; and

operating the engine on vaporized LPG in the LPG mode.

11. A method for operating a dual fuel system in accordance with claim 10 including opening the LPG valve in the LPG mode when the filtered signal decreases to a threshold value below the reference filtered signal.

12. A method for operating a dual fuel system in accordance with claim 10 including:

operating a timer in cooperation with the ECU to generate a timing signal if the filtered signal does not decrease to a threshold value below the reference filtered signal for a predetermined period of time; and

opening the LPG valve in the LPG mode in response to the timing signal.

13. A method for operating a dual fuel system in accordance with claim 10 including changing the operation of the engine from the LPG mode to the gasoline mode by:

opening the gasoline valve;

further pumping gasoline to the carburetor;

waiting until the gasoline substantially fills the float bowl of the carburetor;

thereafter

closing the LPG valve and stopping the flow, vaporization and feeding of LPG to the engine;

feeding gasoline from the carburetor to the engine; and

operating the engine on gasoline.

14. A method for operating a dual fuel system in accordance with claim 13 including closing the LPG valve in the gasoline mode when the filtered signal increases to a threshold value above the reference filtered signal.

15. A method for operating a dual fuel system in accordance with claim 13 including:

operating a timer in cooperation with the ECU to generate a timing signal if the filtered signal does not increase to a threshold value above the reference filtered signal for a predetermined period of time; and

closing the LPG valve in the gasoline mode in response to the timing signal.

16. A method for operating a dual fuel system, comprising the steps of:

pumping a first fuel to a first electronic fuel injector (EFI) system comprising one or more electronic fuel injectors (EFI) with a fuel feeding device comprising a fuel line and a rail, and a fuel pump operatively associated with a gasoline tank;

injecting the first fuel from the first EFI system to the engine;

operating the engine with the first fuel in a first fuel mode;

sensing and monitoring the oxygen content of exhaust gases emitted from the engine;

generating a signal based upon the sensed oxygen content of the exhaust gases;

determining a mean or average value of the signal for a preselected period of time;

filtering the signal to produce a filtered signal corresponding to the mean or average value of the signal, the filtering occurring in association with an engine control unit (ECU);

controlling operation of a second fuel valve with the ECU;

changing the mode of operation of the engine from the first fuel to the second fuel;

establishing a reference filtered signal when the mode of operation of the engine is changed from the first fuel to the second fuel;

stopping the flow of the first fuel from the gasoline tank;

opening the second fuel valve to access the second fuel to a second EFI system;

injecting the second fuel from the second EFI system to the engine; and

operating the engine with the second fuel in the second fuel mode.

17. A method for operating a dual fuel system in accordance with claim 16 including opening the second fuel valve in the second fuel mode when the filtered signal decreases to a threshold value below the reference filtered signal.

18. A method for operating a dual fuel system in accordance with claim 16 including:

operating a timer in cooperation with the ECU to generate a timing signal if the filtered signal does not decrease to a threshold value below the filtered signal for a predetermined period of time; and

opening the second fuel valve in the second fuel mode in response to the timing signal.

19. A method for operating a dual fuel system in a vehicle in accordance with claim 16 including changing the operation of the engine from the second fuel mode to the first fuel mode by:

starting the flow of the first fuel from the gasoline tank;

further pumping the first fuel to the first EFI system;

closing the second fuel valve and stopping the flow and feeding of the second fuel to the engine;

feeding the first fuel from the first EFI system to the engine; and

operating the engine with the first fuel.

20. A method for operating a dual fuel system in accordance with claim 19 including closing the second fuel valve in the first fuel mode when the filtered signal increases to a threshold value above the reference filtered signal.

21. A method for operating a dual fuel system in accordance with claim 19 including:

operating a timer in cooperation with the ECU to generate a timing signal if the filtered signal fails to increase to a threshold value above the reference filtered signal for a predetermined period of time; and

closing the second fuel valve in the first fuel mode in response to the timing signal.

22. A method for operating a dual fuel system in accordance with claim 16 wherein:

the first fuel and the second fuel are selected from the group consisting of a liquid fuel, gasoline, petro, a gaseous fuel, liquefied petroleum gas, and compressed natural gas (CNG); and

the first fuel is different than the second fuel.

23. A dual fuel system, comprising:

a dual fuel engine powered by two different fuels including a first fuel comprising gasoline and a second fuel, and said engine being operable in a gasoline mode and in a second fuel mode;

an intake manifold connected to said engine for passing fuel to said engine;

a carburetor having a float bowl and a valve communicating with said intake manifold for feeding gasoline to said engine when said engine is operating in the gasoline mode;

a gasoline tank for storing and containing gasoline;

a fuel pump for pumping gasoline from said gasoline tank to said carburetor when said engine is operating in the gasoline mode;

a gasoline valve for controlling the flow of gasoline to said carburetor;

a control valve communicating with said air filter and said intake manifold for passing filtered air from said filter to said gasoline flowing into said intake manifold at an air fuel ratio regulated by said valve of said carburetor;

a one-way valve for permitting flow and passage of filtered air from said air filter to said air valve but preventing the flow of the second fuel to said air filter;

a second fuel tank for storing and containing the second fuel;

a second fuel valve for controlling the flow of the second fuel from the second fuel tank to said control valve;

said control valve being operable to permit flow and passing of the second fuel to said intake manifold when said engine is operating in the second fuel mode;

an engine control unit (ECU) operatively associated with said engine, control valve, and second fuel valve for controlling the performance of said engine, control valve, and second fuel valve; and

a mode selection switch connected to said ECU to select when the engine is operated in the gasoline mode or the second fuel mode.

24. A dual fuel system in accordance with claim 23 wherein:

said second fuel comprises liquified petroleum gas (LPG);

said second fuel valve comprises an LPG valve; and

a regulator and vaporizer are connected to said LPG valve for regulating and vaporizing the LPG when said engine is operating in the second fuel mode.

25. A dual fuel system in accordance with claim 23 wherein:

the second fuel comprises compressed natural gas (CNG); and

said second fuel tank comprises a CNG tank.

26. A dual fuel system in accordance with claim 23 including:

an exhaust pipe communicating with said engine for discharging the exhaust gases;

a catalytic converter for minimizing emission of pollutants from the exhaust gases into the atmosphere; and

an O₂ sensor communicating with said ECU for sensing the oxygen content in the exhaust gases.

27. A dual fuel system in accordance with claim 23 wherein said control valve comprises a dual air valve and a pulse width modulation valve.