Dual fuel injection system and a method of controlling such a system

• US 5,379,740 A
• Filed: 07/09/1993
• Issued: 01/10/1995
• Est. Priority Date: 11/20/1990
• Status: Expired due to Term

• Current Assignee: The Energy Research and Development Corporation
• Original Assignee: Biocom LLC
• Inventors: Moore, Christopher P., Kavarnos, Manos
• Primary Examiner(s): Nelli, Raymond A.
• Application Number:
  US08/050,465
• Time in Patent Office: 550 Days
• Field of Search: 123/478, 123/301, 123/27 GE, 123/525, 123/501, 123/575, 123/526, 123/1 A
• US Class Current: 123/478
• CPC Class Codes: F02B 1/04 with fuel-air mixture admission into cylinder
• CPC Class Codes: F02B 2201/0622 Liquid and liquefied gas
• CPC Class Codes: F02D 19/0605 to adjust the fuel pressure or temperature
• CPC Class Codes: F02D 19/061 by controlling fuel injectors
• CPC Class Codes: F02D 19/0628 Determining the fuel pressure, temperature or flow, the fuel tank fill level or a valve position
• 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 19/066 Retrofit of secondary fuel supply systems; Conversion of engines to operate on multiple fuels
• CPC Class Codes: F02D 19/0684 High pressure fuel injection systems; Details on pumps, rails or the arrangement of valves in the fuel supply and return systems
• CPC Class Codes: F02D 19/0694 operating with a plurality of fuels
• CPC Class Codes: F02D 41/0025 Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
• CPC Class Codes: F02D 41/345 Controlling injection timing F02D41/365 takes precedence
• CPC Class Codes: F02M 21/0287 characterised by the transition from liquid to gaseous phase F02M21/06 takes precedence; Injection in liquid phase; Cooling and low temperature storage
• CPC Class Codes: F02M 43/00 Fuel-injection apparatus operating simultaneously on two or more fuels, or on a liquid fuel and another liquid, e.g. the other liquid being an anti-knock additive
• CPC Class Codes: Y02T 10/30 Use of alternative fuels, e.g. biofuels
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A dual fuel injection arrangement for an internal combustion engine. Fuel is injected into the inlet manifold ducts to each engine cylinder via injectors. An arrangement of valves allows selected supply of either a first fuel or a second fuel to the injectors via inlet fuel rail and branch lines. Excess fuel is returned to each supply by way of return line (11). Electronic control units determine injection timing for the selected fuel dependent upon engine parameters for the first fuel and upon an adjusted timing for the second fuel where the adjustment takes account of the different characteristics of the second fuel compared with the first fuel. In particular there is disclosed an arrangement where the first fuel is gasoline and the second fuel is a liquified gas.

Claims

1. A dual fuel injection arrangement for use in an internal combustion engine comprising (a) at least one injector for injecting fuel into an inlet manifold of the engine, (b) a single fuel rail system capable of supplying one of a first fuel and a second fuel to the at least one injector, (c) a first control unit using engine parameters and demand parameters for the first fuel to determine injector timing for the first fuel, and (d) a second control unit using supply characteristics of the second fuel to convert injection timing for the first fuel from the first control unit into injector timing for the second fuel.

2. A dual fuel injection arrangement as in claim 1 wherein the supply characteristics are composition and pressure of the second fuel.

3. A dual fuel injection arrangement as in claim 1 wherein the first fuel is petrol and the second fuel is LPG supplied at a higher pressure than the first fuel.

4. A dual fuel injection arrangement as in claim 1 wherein the single fuel rail system comprises an inlet rail directed towards the at least one injector, an outlet rail extending from the at least one injector, and the at least one injector is a flow-through injector.

5. A dual fuel injection arrangement as in claim 1 wherein the at least one injector is a bottom feed injector.

6. A dual fuel injection arrangement as in claim 4 wherein the inlet rail has a first fuel inlet and a second fuel inlet, the outlet rail has a first fuel outlet and a second fuel outlet, a solenoid valve is present on each of the second fuel inlet and the first fuel outlet, a non-return valve is present on each of the first fuel inlet and the second fuel outlet, and the second fuel is supplied at a higher pressure than the first fuel.

7. A dual fuel injection arrangement as in claim 1 wherein the single fuel rail system has a sufficiently low heat-capacity construction so as to permit cooling by circulating flow of each of the first fuel and the second fuel.

8. A dual fuel injection arrangement as in claim 6 further comprising a fuel system for the second fuel having a tank for holding the second fuel, a fuel pump for raising the pressure of the second fuel to a fixed differential above vapor pressure of the second fuel when in the tank, a fuel line from the pump to the second fuel inlet, a return fuel line from the second fuel outlet to the tank, and a fuel regulator in the return fuel line.

9. A dual fuel injection arrangement as in claim 8 wherein the fuel regulator is incorporated in the non-return valve in the second fuel outlet.

10. A method for controlling fuel injection in an internal combustion engine operating on one of a first fuel and a second fuel injected through at least one injector comprising steps of (a) determining injection timing for the first fuel and (b) converting the injection timing for the first fuel into injection timing for the second fuel using a composition and pressure of the second fuel.

11. A method as in claim 10 further comprising steps of (c) determining a maximum difference between the injection timing for the first fuel and injection timing for the second fuel, commencing an injection pulse for the first fuel, and, after at least the maximum difference between the injection timing for the first fuel and the injection timing for the second fuel, starting an injection pulse for the second fuel.

12. A method as in claim 11 further comprising steps of (e) determining duration of the injection pulse for the first fuel, (f) calculating a duration of the injection pulse for the second fuel using the duration of the injection pulse for the first fuel, and then (g) conducting the injection pulse for the second fuel for the duration calculated.

13. A method as in claim 10 wherein determining injection timing for the first fuel is performed by a microprocessor utilizing a look-up table.

14. A method as in claim 10 wherein determining injection timing for the first fuel is performed by a microprocessor utilizing a calculation based on duration of pulse time for the first fuel and energy characteristics of the second fuel and pressure of the second fuel.

15. A method of providing, in an internal combustion engine operating on one of a first fuel and a second fuel, an injection-pulse time for the second fuel comprising steps of:

(a) determining maximum first-fuel-injection-pulse time for the first fuel, (b) determining maximum second-fuel-injection-pulse time for the second fuel, (c) determining difference between the maximum first fuel injection pulse time and the maximum second fuel injection pulse time, (d) starting the first fuel injection pulse, (e) starting the second fuel injection pulse after the first fuel injection pulse following a period of time at least equal to the difference between the maximum first fuel injection pulse time and the maximum second fuel injection pulse time, (f) determining the first fuel injection pulse time after the first fuel injection pulse ends, and (g) calculating the second fuel injection pulse time using the first fuel injection pulse time, and (h) ending the second fuel injection pulse after the second fuel injection pulse time ends.

16. A method as in claim 15 wherein the first fuel is petrol and the second fuel is liquid petroleum gas.

17. A method as in claim 15 wherein calculation of the second fuel injection pulse time is performed by a microprocessor utilizing a look-up table.

18. A method as in claim 15 wherein calculating the second fuel injection pulse time is performed by a microprocessor utilizing a formula.