Measuring and testing – Liquid level or depth gauge
Reexamination Certificate
1997-03-17
2003-09-09
Lefkowitz, Edward (Department: 2855)
Measuring and testing
Liquid level or depth gauge
C073S001730, C340S618000
Reexamination Certificate
active
06615656
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns an improved system for determining the quantity of a fuel stored in a tank subject to varying external forces, and particularly to the quantity of gasoline stored in an automobile gas tank.
2. Description of the Related Art
The present invention is an improvement on the invention disclosed in U.S. Pat. No. 5,133,212 to Grills et al., the contents of which are included herein by reference. Grills et al. disclose a weighing system utilizing a plurality of load cells supporting the fuel tank and a reference weight and load cell which, in combination with the tank load cells, corrects automatically for the external forces acting on the tank to give an accurate average measure of the quantity of liquid in the tank. Although this system is quite accurate and finds its best use where the cost of such a system can be justified, such as in measuring the quantity of fuel in an airplane fuel tank, the complexity of such a system is not justified where cost is of relatively greater importance such as in the determination of the amount of fuel in an automotive fuel tank.
Another tank weighing system which does not use load cells is disclosed by Kitagawa et al. in U.S. Pat. No. 4,562,732 where the tank is supported on one side by a torsion bar system. In contrast to Grills et al., although the Kitagawa et al. device is quite complicated and consequently quite expensive, it contains no system for correcting for the roll or pitch motions of the vehicle other than to average the tank readings over an extended period of time.
The external forces acting on an automobile fuel tank due to turning, roll and pitch although significant are much less severe in an automobile than in an airplane. Forces due to pitch generally arise when a vehicle is climbing or descending a hill which in North America rarely exceeds 15 degrees and only occasionally exceeds 5 degrees. Roll angles of more than 5 degrees are similarly uncommon. Even when steep angles are encountered, it is usually only for a short time. This is not generally the case in aircraft, especially high performance military aircraft, where turning pitch and roll related forces are not only greater in magnitude but can last for an extended period of time.
The most common systems of measuring the quantity of fuel in an automobile fuel tank use a variable resistance rheostat which is controlled by a float within the gas tank. This system makes no attempt to correct for external forces acting on the tank or for the angle of the vehicle. Modern gas tanks have a convoluted shape and the level of fuel is frequently a poor indicator of the amount of fuel within the tank. In many implementations, for example, the gage continues to register full even after several gallons have been consumed. Similarly, the gage will usually register empty when there are several gallons remaining. It is then a guessing game for the driver to know how far he can go before running out of gas.
The problem has been compounded with the implementation of a digital fuel gage display where the driver now gets an inaccurate display, with seemingly great precision, of the amount of fuel used and amount remaining in the tank. If, for example, the gage states that 14.5 gallons have been consumed and the driver has the tank filled and notices that it takes 15.3 gallons to fill it he wonders if he is being cheated by the service station or, as a ninimum, he begins to doubt the accuracy of the other gages on the instrument panel. The inaccuracy of the fuel gage is now the most common complaint received by at least one vehicle manufacturer from its customers.
These prior art float systems arc also vulnerable to errors due to fouling of the resistor induced by he necessity to operate the sensing elements in direct contact with the mixture held in the tank. These errors can cause the system to become inoperative or to change its calibration over time. These and other problems associated with the prior art fuel gages are solved by the present invention as disclosed below.
Reference is also made to U.S. Pat. No. 4,890,491 (Vetter et al.) which describes a system for indicating the level of fuel in an automobile tank (
FIG. 4
) which includes a fuel level detector
1
, a detector
24
for detecting the longitudinal inclination of the vehicle, a detector
25
for detecting the transverse inclination of the vehicle and a microcomputer
26
containing a table providing an “immersion characteristic curve”. In operation, the microcomputer
26
receives input from the fuel level detector
1
and inclination detectors
24
,
25
and corrects the level of fuel as measured by the fuel level detector
1
in light of the transverse and longitudinal inclination of the vehicle as measured by the detectors
24
,
25
by the application of the immersion characteristic curve to avoid false readings caused by inclination of the vehicle. Vetter et al. does not take any readings during periods of inclination of the vehicle during operation thereof nor provide a corrected level of liquid.
Reference is also made to U.S. Pat. No. 4,815,323 (Ellinger et al.) which describes a fuel quantity measuring system having ultrasonic transducers for measuring volume of fuel in a tank. In the embodiment shown in
FIG. 1
(but not the embodiment shown in FIG.
2
), the system includes ultrasonic tank sensor units which provide a signal representative of the round-trip time between each sensor to the surface of the full, a processor unit (CPU) which receives the round-trip time (which is proportional to the height level of fuel in the tank) and a display to display the volume of fuel in the tank. In this embodiment, the processor is described as performing height-volume calculations and then correcting for attitude, i.e., the pitch and roll of the vehicle. As such, it is clear that for this embodiment, the measured round-trip time is applied to the height-volume table to obtain a volume corresponding to that round-trip time. This volume estimation is thereafter corrected based on the attitude, i.e., the measured pitch and roll. In the embodiment in Ellinger et al.
FIG. 3
, the tank
12
includes three ultrasonic transducers
14
,
16
,
18
which send a respective signal representative of the round-trip time to the surface of the fuel
10
in respective stillwell
22
each surrounding that transducer to a computer
28
through a multiplexer
34
. Only one transducer is related to fuel level (see
FIG. 2
) and the other two transducers are related to reference purposes and fuel density. The computer
28
has a memory
30
which it appears contains height-volume tables specific to each location of the transducer so that the measured round-trip time representative of the height level of fuel at that sensor location can be converted into a volume measurement. Thus, in this Ellinger et al. embodiment, the height of the level of fuel in the tank at each different location is converted to a volume measurement based on the height-volume tables. However, in this embodiment, there is no disclosure of the converted volume measurements being corrected by an attitude correction factor, i.e., the pitch and roll angles of the vehicle.
OBJECTS AND SUMMARY OF THE INVENTION
The fuel gage of the present invention uses a combination of (i) one or more load cells or fuel level measuring devices, plus in some cases other sensors which measure the pitch or roll angle of the vehicle or the fuel density, to approximately measure the quantity of the fuel in the tank and (ii) a processor and algorithm to correct for the inaccuracies arising from the pitch and roll angles of the vehicle, other external forces or from variations in fuel density. Although several weighing systems are disclosed for illustrative purposes, the invention applies to any method of making an approximate measurement of the fuel quantity and then using analytical techniques to improve on the measurement.
The principle objects of this invention are:
1. To provide a measuring system for determining the quantity o
Breed David S.
Duvall Wilbur E.
Johnson Wendell C.
Sanders William Thomas
Automotive Technologies International Inc.
Cygan Michael
Lefkowitz Edward
Roffe Brian
LandOfFree
Method and apparatus for measuring the quantity of fuel in a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for measuring the quantity of fuel in a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for measuring the quantity of fuel in a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3082763