Oil sensor

• US 9,222,822 B2
• Filed: 08/22/2012
• Issued: 12/29/2015
• Est. Priority Date: 09/20/2011
• Status: Active Grant

• Current Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Original Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Inventors: Sinha, Karn R., Davis, Nicholas P.
• Primary Examiner(s): Fitzgerald, John
• Assistant Examiner(s): Eyassu, Marrit
• Application Number:
  US13/591,856
• Publication Number:
  US 20130068015A1
• Time in Patent Office: 1,224 Days
• Field of Search: 733/04.C, 73/530.5, 731/145.5, 732/90.R, 73/191.1, 73/17.3, 733/04.R, 324/654, 324/713, 324/681
• US Class Current: 1/1
• CPC Class Codes: G01F 23/263 by measuring variations in capacitance of capacitors
• CPC Class Codes: G01F 23/266 measuring circuits therefor
• CPC Class Codes: G01F 23/268 mounting arrangements of probes
• CPC Class Codes: G01N 27/028 Circuits therefor measuring impedance per se G01R27/02
• CPC Class Codes: G01N 33/2888 Lubricating oil characteristics, e.g. deterioration lubricating properties G01N33/30

Abstract

A system and method for measuring oil level and quality is provided. The system and method uses an alternating current (AC) to determine oil level, and a lower frequency alternating current, or a direct current (DC), to measure oil quality. The system may comprise a single sensor that is used to measure both oil quality (by providing the lower frequency alternating current or direct current) and oil level (by providing the higher frequency alternating current). Using the lower frequency AC, or DC, enables the resistance of the oil to be determined, which gives an accurate indication of the oil quality.

Claims

1. A method of measuring lubricant level and quality using a lubricant sensor that comprises a plurality of electrodes, the method comprising:

placing the lubricant sensor into a lubricant;

providing a first current, which is AC at a first frequency, (a) between a first electrode and a second electrode of the lubricant sensor and (b) between the first electrode and a third electrode of the lubricant sensor;

measuring, at the first current, between the first and second electrodes, and between the first and third electrodes, capacitance parameters used to determine the capacitance between the first and second electrodes and the capacitance between the first and third electrodes;

determining the level of the lubricant in which the sensor is placed from the measured capacitance parameters by comparing the capacitance between the first and second electrodes with the capacitance between the first and third electrodes;

providing a second current between the first electrode and one of the second and third electrodes, the second current being provided at a different time to the first current and being either;

(i) DC;

or (ii) AC at a second frequency that is lower than the first frequency;

measuring, at the second current and between the first electrode and the one of the second and third electrodes, an impedance or resistance parameter representative of the impedance or resistance between the first electrode and the one of the second and third electrodes; and

determining the quality of the lubricant in which the sensor is placed from the measured impedance or resistance parameter.

2. A method of measuring lubricant level and quality according to claim 1, wherein the second frequency is less than 1 kHz.

3. A method of measuring lubricant level and quality according to claim 1, wherein by placing the lubricant sensor into the lubricant, the third electrode is fully submerged in the lubricant.

4. A method of measuring lubricant level and quality according to claim 3, wherein the second current is provided between the first electrode and the third electrode.

5. A method of measuring lubricant level and quality according to claim 3, wherein:

the second current is provided between the first electrode and the second electrode; and

the determined level of the lubricant in which the sensor is placed is used in combination with the impedance parameter measured between the first electrode and the second electrode to determine the quality of the lubricant in which the sensor is placed.

6. A method of measuring lubricant level and quality according to claim 1, wherein:

the second current is DC; and

the polarity of the DC is reversed each time it is provided compared with the previous time it was provided.

7. A method of measuring lubricant level and quality according to claim 1, wherein:

the lubricant into which the sensor is placed is lubricant in a tank of an engine;

the second current is provided a finite number of times to determine the lubricant quality at one or more specific times between when the engine is switched on and turned off; and

between the finite times when the second current is provided, the first current is provided substantially continuously during engine running to determine lubricant level substantially continuously during the engine running.

8. A method of measuring lubricant level and quality according to claim 7, wherein:

the second current is provided upon start-up and/or shut-down of the engine; and

the first current is provided at substantially all other times of engine operation; and

the engine is a gas turbine engine.

9. A method of measuring lubricant level and quality according to claim 1, wherein:

the first electrode is an elongate electrode having a longitudinal axis and at least one longitudinally extending surface; and

the at least one longitudinally extending surface of the first electrode at least partially surrounds the second electrode and the third electrode.

10. A method of measuring lubricant level and quality according to claim 9, wherein:

the first electrode has a distal end that, in use, extends farthest into the lubricant;

the third electrode is surrounded by a distal end portion of the at least one longitudinally extending surface of the first electrode;

the second electrode is surrounded by substantially the rest of the at least one longitudinally extending surface of the first electrode; and

the second and third electrodes are longitudinally separated by a non-conductive spacer.

11. A system for measuring lubricant level and quality, comprising:

a lubricant sensor comprising a plurality of electrodes, one or more of the electrodes being configured to be at least partially submerged in lubricant in use;

a switching mechanism configured to switch between (a) a first current to be provided between first and second electrodes of the lubricant sensor and between the first electrode and a third electrode of the lubricant sensor, and (b) a second current to be provided between the first electrode and one of the second and third electrodes, the first current being AC at a first frequency, and the second current being either;

(i) DC;

or (ii) AC at a second frequency that is lower than the first frequency;

a lubricant level calculator configured to determine the level of the lubricant in which the sensor is placed by measuring, at the first current, between the first electrode and the second electrode, and between the first electrode and the third electrode, the capacitance between the first electrode and the second electrode and the capacitance between the first electrode and the third electrode, and comparing the measured capacitance between the first electrode and the second electrode with the measured capacitance between the first electrode and the third electrode; and

a lubricant quality calculator configured to determine the quality of the lubricant in which the sensor is placed by measuring, at the second current, an impedance or resistance parameter representative of the impedance or resistance between the first electrode and the one of the second and third electrodes.

12. A system for measuring lubricant level and quality according to claim 11, wherein the switching mechanism contains switching logic to determine when to switch between the first current and the second current.

13. A system for measuring lubricant level and quality according to claim 12, wherein:

the system is for use with a gas turbine engine for use on an aircraft; and

the switching logic determines when to switch between the first current and the second current based on one or more of;

engine rotational speed, throttle angle, flight phase of the aircraft, oil pressure, and weight on landing wheels of the aircraft.

14. A system of measuring lubricant level and quality according to claim 11, wherein:

the first electrode is an elongate electrode having a longitudinal axis and at least one longitudinally extending surface; and

the at least one longitudinally extending surface of the first electrode at least partially surrounds the second electrode and the third electrode.

15. A system of measuring lubricant level and quality according to claim 14, wherein:

the first electrode has a distal end that, in use, extends farthest into the lubricant;

the third electrode is surrounded by a distal end portion of the at least one longitudinally extending surface of the first electrode;

the second electrode is surrounded by substantially the rest of the at least one longitudinally extending surface of the first electrode; and

the second and third electrodes are longitudinally separated by a non-conductive spacer.

16. A system for measuring lubricant level and quality according to claim 11, wherein the second current is DC.