Communications: electrical – Land vehicle alarms or indicators – Internal alarm or indicator responsive to a condition of the...
Reexamination Certificate
1999-07-27
2001-06-26
Wu, Daniel J. (Department: 2736)
Communications: electrical
Land vehicle alarms or indicators
Internal alarm or indicator responsive to a condition of the...
C340S618000, C340S936000, C701S096000, C701S103000
Reexamination Certificate
active
06252499
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to fuel supply indicators for motor vehicle fuel tanks which include a fuel consumption detector to measure the fuel consumption of an internal combustion engine.
Conventional motor vehicle fuel tanks include a fuel level detector for a fuel supply indicator. The fuel level detector is a lever or dip tube sensor with a float that rises and falls with the fuel level. This reciprocating motion varies a resistance by way of a contact bridge or linkage and consequently varies a current in a circuit, and the current is measured by an instrument which is used to indicate fuel level or fuel supply. The scale of the instrument in the circuit is calibrated in fuel volume. However, one disadvantage of this arrangement is that the fuel supply indication depends also on the inclination of the vehicle, so that a faulty fuel supply indication may result if the vehicle is inclined. Also, with a multichamber fuel tank, a plurality of lever or dip tube sensors is required, with a corresponding increase in cost. Moreover, these sensors only provide indications with gaps of up to five liters.
U.S. Pat. Nos. 4,307,452 and 4,546,648 disclose arrangements for measuring the consumption of fuel by an internal combustion engine but those arrangements provide no indication of the fill level of a fuel tank.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a fuel supply indicator arrangement for a motor vehicle fuel tank which overcomes disadvantages of the prior art.
Another object of the invention is to provide a fuel supply indicator arrangement producing an improved fuel supply indication which is more reliable in every operating condition of the vehicle.
These and other objects of the invention are attained by providing a fuel supply indicator which includes an end position switch arrangement having at least one end position switch located above a fuel withdrawal point in a fuel tank at a height corresponding to a predetermined fill level, the end position switch arrangement having a configuration such that it provides an end position switch signal dependent upon whether or not an end position switch is immersed in the fuel, along with an electric circuit that computes a value for the fuel supply indicator from a fuel consumption signal combined with each end position switch signal.
This arrangement has the advantage that an exact and reliable indication of the current fuel supply in the fuel tank is obtained in a simple and economical manner. The fuel supply indicator according to the invention is essentially independent of any rated volume of the fuel tank. Instead, the end position switch arrangement, with one or more end position switches, defines fixed points at which the fill level of the fuel tank is reliably indicated. Between these fixed points, the fuel consumption signal is used to provide an accurate fuel supply indication, since that signal is used to determine a volume of fuel withdrawn over time.
In order to provide the vehicle driver with information regarding current operating parameters of a motor vehicle in especially advantageous manner, an indicating instrument is provided that is connected to the electric circuit to display a value representing the fuel consumption and/or a value representing the fuel supply.
In an especially preferred embodiment, the electric circuit is an electronic circuit, in particular a microprocessor or a data processing device.
For an empty fuel tank warning, the end position switch arrangement includes an end position switch for indicating “Empty”, which is located at a first height above the fuel withdrawal point which corresponds to a minimal fill level of the fuel tank. This ensures that, even with an “Empty” indication, a certain volume of fuel will remain available for operation of the engine.
Preferably, the end position switch for the “Empty” indication is mounted on a fuel withdrawal unit in the fuel tank.
For a reserve warning indication, the end position switch arrangement includes a “Reserve” end position switch for a reserve indication, located at a second height above the fuel withdrawal point corresponding to a fill level of the fuel tank at or below which a reserve warning signal, such as for example a reserve warning light, is activated.
Desirably, the end position switch for the “Reserve” indication may be mounted on a fuel withdrawal unit in the fuel tank.
For an indication of a full fuel tank, the end position switch arrangement includes “Full” end position switch for a “Full” indication, located at a third height above the fuel withdrawal point corresponding to a maximum fill level of the fuel tank.
In a preferred embodiment the end position switch for the “Full” indication is located on a quick vent nipple in the fuel tank so that the end position switch for the “Full” indication is always at a defined distance from a component which causes termination of operation of a filling nozzle. Thus, in each operating condition, a reliable “Full” indication is always assured.
For example, in the case of fuel tanks having several compartments, the end position switch arrangement includes one additional end position switch located at a fourth height above the fuel withdrawal point which is between the first and third heights.
Preferably, the first height is lower than the second height and the second height is lower than the third height.
A simple and dependable construction is achieved by providing a holder for each end position switch welded into the fuel tank.
To further enhance the accuracy of the fuel supply indication, a fuel flow volume measuring device, such as a through flow meter which emits a fuel fill signal to the electric circuit corresponding to the quantity of fuel that has flowed through the nozzle, is provided in a filling nozzle of the fuel tank and the electric circuit calculates the value for the fuel supply indication taking account of the fuel fill signal.
A further improvement in accuracy of the fuel supply indication when the vehicle is inclined is achieved by providing an inclination sensor that ascertains an angle of inclination of the vehicle, or of the direction of gravity, and provides a corresponding inclination signal to the electric circuit, and an electric circuit which calculates the value of the fuel supply indication taking account of the inclination signal.
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Gerdtz Uwe
Schmidtchen Jörg
Baker & Botts L.L.P.
Nguyen Tai T.
Volkswagen AG
Wu Daniel J.
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