Fuel gauge for an automotive vehicle

• US 4,531,407 A
• Filed: 12/19/1983
• Issued: 07/30/1985
• Est. Priority Date: 10/16/1980
• Status: Expired due to Fees

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Kobayashi, Hiroshi
• Primary Examiner(s): Frankfort, Charles E.
• Assistant Examiner(s): Schuster, David R.
• Application Number:
  US06/563,273
• Time in Patent Office: 589 Days
• Field of Search: 340/620, 361/284, 361/286, 324/61 P, 73/304 G, 364/509
• US Class Current: 73/304.00C
• CPC Class Codes: G01F 23/263 by measuring variations in capacitance of capacitors

Abstract

A fuel gauge includes a stationary capacitor located within a fuel tank in such a manner as to be partially immersed in the fuel so that the capacitance of the capacitor varies with the level of fuel. A measuring device determines the capacitance of the capacitor to measure the level of the fuel or the amount of fuel remaining within the tank.

Claims

1. A fuel gauge for an automotive vehicle, comprising:

(a) a tank containing fuel;

(b) first and second conductive elements forming a capacitor, the first and second conductive elements being so arranged as to form therebetween a gap to be insulated from each other, the capacitor being located within the fuel tank so as to admit fuel into the gap thereof, whereby the capacitance of the capacitor varies with the position of the surface of the fuel, the gap of the capacitor being of a predetermined size allowing water droplets to fall out of the gap within a predetermined time period; and

(c) a structural means for reducing inaccuracies in fuel measurement due to temporary presence of water droplets within said gap of said capacitor, including

timing means comprising an arrangement of said conductive elements and the gap therebetween for defining said time period for a water droplet to pass through said gap, and

a measuring means electrically connected to the capacitor for determining a time-averaged capacitance of the capacitor over a time duration in excess of said time period, thereby to reduce effects of a temporary presence of water droplets within said gap.

2. A fuel gauge as defined in claim 1, wherein the gap of the capacitor is 2.5 to 4 mm when the fuel is regular gasoline.

3. A fuel gauge as defined in claim 2, wherein the measuring device determines the time-averaged capacitance of the capacitor over a period of one minute.

4. A fuel gauge for an automotive vehicle, comprising:

(a) a tank containing fuel;

(b) first and second conductive elements forming a capacitor, the first and second conductive elements being so arranged as to form therebetween a gap to be insulated from each other, the capacitor being located within the fuel tank so as to admit fuel into the gap thereof, whereby the capacitance of the capacitor varies with the position of the surface of the fuel, the gap of the capacitor being of a predetermined size allowing water droplets to fall out of the gap within a predetermined time period;

(c) means, including the capacitor, for producing pulses at a frequency which depends on the capacitance of the capacitor; and

(d) means for counting the pulses from the pulse producing means during a preset length of time in excess of said predetermined time period and producing, in accordance with the number of the counted pulses, a signal which depends on the frequency of the pulses and thus on the position of the surface of the fuel,

whereby effects of water droplets on fuel measurements are reduced.

5. A fuel gauge as defined in claim 4, wherein the first and second conductive elements are made up of parallelly arranged first and second flat plates.

6. A fuel gauge as defined in claim 4, wherein the first and second conductive elements are made up of concentrically arranged inner and outer cylinders.

7. A fuel gauge as defined in claim 4, wherein the gap of the capacitor is 2.5 to 4 mm in the case where the fuel is regular gasoline.

8. A fuel gauge as defined in claim 4, wherein the capacitor and the remainder of the means for producing pulses are connected by means of relatively short leads.

9. A fuel gauge as defined in claim 8, wherein the preset length of time is one minute.

10. A fuel gauge as defined in claim 4, further comprising means for displaying the signal dependent on the frequency of the pulses.

11. A fuel gauge as defined in claim 4, wherein the means for producing pulses comprises an astable multivibrator including the capacitor and producing primary pulses at a frequency which depends on the capacitance of the capacitor, and a frequency divider reducing the frequency of the primary pulses and producing secondary pulses at a frequency lower than and proportional to the frequency of the primary pulses, the pulses produced by the means for producing pulses comprising said secondary pulses.

12. A fuel gauge as recited in claim 4, wherein the counting means comprises a counter connected to the means for producing pulses for counting the pulses therefrom, and a resetting circuit connected to the counter for resetting the counter periodically.

13. A fuel gauge as recited in claim 4, wherein the counting means repeats the counting operation.

14. A fuel gauge for an automotive vehicle comprising:

a capacitor disposed within a fuel tank and arranged to admit fuel to a gap between capacitive plates thereof,

pulse producing means incorporating said capacitor for producing a plurality of pulses at a frequency determined by the capacitor;

dividing means connected to said pulse producing means and receiving said plurality of pulses therefrom for producing an output pulse train at a reduced frequency,

counting means connected to said dividing means for counting pulses in said output pulse train during a fixed time period thereby to provide a count representative of the pulses produced by said pulse producing means and of a time average capacitance of said capacitor during said fixed time period;

means for reducing the effects of foreign material in the fuel tank on fuel measurement including timing means for providing passage of a particle of the foreign material through the gap between said capacitive plates in a time duration substantially shorter than said fixed time period;

indicating means connected to said counting means for providing an indication of the time averaged capacitance of said capacitor during said fixed time period; and

a fixed time period resetting means, connected to said counting means, for repeatedly resetting said counting means at time instants separated from one another by said fixed time period,

whereby time averaged indications representative of said capacitance of said capacitor are obtained over time periods substantially longer than said time duration and thus effects of said foreign material on the indicated capacitance and hence fuel measurements are reduced.

15. A fuel gauge for an automotive vehicle, comprising:

(a) a tank containing fuel;

(b) first and second conductive elements forming a capacitor disposed in the tank, the first and second conductive elements defining a vertically-extending gap therebetween and being electrically insulated from each other via the gap, the capacitor defining an opening at the bottom of the gap so that the fuel can enter and leave the gap via the opening, whereby the capacitance of the capacitor varies with the level of the fuel or the amount of the fuel remaining in the tank, the gap having a predetermined size and magnitude determining a time duration during which a water droplet remains within the gap, thereby determining a time period during which a water droplet affects the capacitance of the capacitor; and

(c) a measuring device electrically connected to the capacitor for determining an average value of the capacitance of the capacitor over a predetermined timing interval and thereby measuring the level of the fuel or the amount of the fuel remaining in the tank, said measuring device operative for determining said timing interval to be longer by a predetermined value than said time duration such that the effects of water droplets on the capacitance and hence on the measurement of the level of the fuel or the amount of the fuel remaining in the tank can be negligible.