Internal-combustion engines – Miscellaneous – Fuels – lubricants and additives
Reexamination Certificate
1999-02-17
2001-07-10
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Miscellaneous
Fuels, lubricants and additives
C123S689000
Reexamination Certificate
active
06257174
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention generally relates to fuel control systems and, more particularly, to a method of determining the percent alcohol content of a fuel used in a motor vehicle capable of operating on more than one type of fuel.
2. Discussion
Environmental and energy independence concerns have stimulated the development of alternative transportation fuels, such as alcohol fuels, for use in automobiles. Alcohol fuels include methanol and ethanol. A flexible fueled vehicle capable of operating on gasoline, or alcohol fuel, or any mixture of the two fuels, is therefore in demand. Modifications to the engine are necessary when operating on different fuels because of the different characteristics of each fuel. For example, an engine operating on ethanol or E85 (a blend of 85% ethanol and 15% gasoline) requires approximately 1.4 times the amount of fuel relative to gasoline at stoichiometry due to a lower energy content of the ethanol.
Air/fuel ratio in internal combustion engine design is typically considered to be the ratio of mass flow rate of air to mass flow rate of fuel inducted by an internal combustion engine to achieve conversion of the fuel into completely oxidized products. The chemically correct ratio corresponding to complete oxidation of the products is called stoichiometric. If the air/fuel ratio is less than stoichiometric, an engine is said to be operating rich, i.e., too much fuel is being burned in proportion to the amount of air to achieve perfect combustion. Likewise, if the air/fuel ratio is greater than stoichiometric, an engine is said to be operating lean, i.e., too much air is being burned in proportion to the amount of fuel to achieve perfect combustion. Alcohol fuels have a lower air/fuel ratio than gasoline at stoichiometric, so that the engine must be compensated for in the rich direction as the percentage of alcohol in the fuel increases.
In a returnless fuel system, once the fuel enters the fuel line, the only exit is through the fuel injectors into the engine. Two particular characteristics of interest related to this one way-in, one way-out system are that there is a delay from the time fuel is added to the tank to the time the new fuel mixture reaches the engine and that the fuel tends to mix in the fuel system such that there is no step change from the old fuel mixture to the new fuel mixture. These characteristics affect how the fuel compensation is controlled in a flexible fueled vehicle after a fueling event. That is, these characteristics must be accounted for regardless of whether the ethanol content of the fuel is being determined by a fuel composition sensor or inferred by an oxygen feedback system.
SUMMARY OF THE INVENTION
It is, therefore, one object of the present invention to provide a system of flexible fuel compensation.
It is another object of the present invention to provide a flexible fuel compensation system for theoretically determining the percent ethanol content of fuel being delivered to the engine at the instance of fueling to insure accurate operating parameters.
It is yet another object of the present invention to provide a flexible fuel compensation system for determining a direction of the percent ethanol content of fuel (i.e., towards 85% ethanol or 0% ethanol) for calculating theoretical values that may be used in an open loop operating condition.
The above and other objects are provided by a method of determining the percent alcohol content of fuel for a flexible fuel control system in a flexible fueled vehicle. According to the present invention, two curves are calculated based on the old fuel mixture's (i.e., the fuel in the tank before a fuel tank fill) ethanol content and two fueling possibilities. An E85 curve is calculated for the possibility that 85% ethanol and 15% gasoline was added to the tank and an E0 curve is calculated for the possibility that 0% ethanol and 100% gasoline was added to the tank. If the inferred ethanol content increases above a positive delta threshold during a closed loop update, the methodology assumes that E85 has been added to the tank. As such, if the vehicle is shut down before a more accurate ethanol content determination is complete, the engine operating parameters follow the inferred ethanol content E85 curve until the system reaches a closed loop operating condition. Conversely, if the inferred ethanol content decreases below a negative delta threshold, the methodology assumes that E0 was added to the tank. Accordingly, if the vehicle is shut down before a more accurate ethanol content determination is complete, the engine operating parameters follow the inferred ethanol content E0 curve until the system reaches a closed loop operating condition.
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Cheng Yi
Huff Shean
Joyce Mary
Kennie Jerry
Nankee, II Robert J.
Calcaterra Mark P.
Chrysler Corporation
Kamen Noah P.
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