MEASURING METHOD FOR DEGREE OF DEGRADATION OF LUBRICATING OIL, AND MEASURING DEVICE THEREFOR, AS WELL AS LUBRICATING OIL MONITORING SYSTEM IN MACHINE AND DEVICE

• US 20120229152A1
• Filed: 11/22/2010
• Published: 09/13/2012
• Est. Priority Date: 11/25/2009
• Status: Active Grant

• Current Assignee: Idemitsu Kosan Company Limited
• Original Assignee: Idemitsu Kosan Company Limited
• Inventors: Katafuchi, Tadashi
• Granted Patent: US 9,007,073 B2
• Time in Patent Office: Days
• US Class Current: 324/672
• CPC Class Codes: G01N 27/414 Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS
• CPC Class Codes: G01N 33/2876 Total acid number

Abstract

Provided are a method of measuring a degree of degradation of a lubricating oil and a measuring device therefor, in which (a) acidity is measured through use of an ISFET of hydrogen ion sensitive type and (b) dielectric constants or electrostatic capacitances at two or more different frequencies are obtained, to thereby determine a degradation state of the lubricating oil based on the acidity and a plurality of values of the dielectric constants or the electrostatic capacitances. Accordingly, the degree of degradation of the lubricating oil can be measured easily and precisely and a degradation mechanism of the lubricating oil can be predicted.

Claims

1. A method of measuring a degree of degradation of a lubricating oil, the method comprising:

(a) measuring an acidity of a lubricating oil with an ISFET sensitive to hydrogen ions and (b) measuring a dielectric constant or electrostatic capacitance of the lubricating oil at two or more different frequencies, to determine a degradation state of the lubricating oil based on the acidity and the dielectric constants or the electrostatic capacitances.

2. The method of claim 1, further comprising:

monitoring the acidity measured in (a) and determining that the lubricating oil is degraded when the acidity reaches a set value; and

predicting a degradation mechanism of the lubricating oil based on a rate of a change in dielectric constant or electrostatic capacitance with respect to a frequency between the two or more different frequencies, the rate being obtained from the dielectric constants or the electrostatic capacitances in (b).

3. The method of claim 1, the measuring comprises:

applying a constant voltage between a drain and a source of the ISFET and measuring a current flowing between the drain and the source;

or

applying a constant current to flow between the drain and the source and measuring a voltage between the drain and the source.

4. The method of claim 3, wherein the measuring (a) comprises:

applying different voltages between the drain and the source and measuring a difference of currents between the drain and the source at respective voltage values;

or

applying different currents to flow between the drain and the source and measuring a difference of voltages between the drain and the source at respective current values.

5. The method of claim 1, wherein at least one frequency (H₁) of the two or more different frequencies in (b) is 100 Hz or less, and another frequency (H₂) is more than (H₁) and 10,000 Hz or less.

6. The method of claim 5, further comprising:

measuring a dielectric constant (ε

₁) or an electrostatic capacitance (C₁) at the frequency (H₁) and a dielectric constant (ε

₂) or an electrostatic capacitance (C₂) at the frequency (H₂), and determining a degradation state of the lubricating oil based on a rate of a change in dielectric constant with respect to the frequency [(ε

₁-ε

₂)/(H₂−

H₁)] or a rate of a change in electrostatic capacitance with respect to the frequency [(C₁-C₂)/(H₂−

H₁)].

11. The method of claim 5, wherein H₁ is in a range of 5 to 80 Hz.

12. The method of claim 5, wherein H₁ is in a range of 10 to 60 Hz.

13. The method of claim 5, wherein H₂ is greater than H₁ and 1,000 Hz or less.

14. The method of claim 5, wherein H₂ is greater than H₁ and 500 Hz or less.

15. The method of claim 5, wherein H₂ is greater than H₁ and 200 Hz or less.

7. A device comprising:

(A) an acidity measuring part comprising an ISFET sensitive to hydrogen ions and i) a circuit, which applies a constant voltage between a drain and a source of the ISFET and measures a current flowing between the drain and the source, or ii) a circuit, which applies a constant current to flow between the drain and the source and measures a voltage between the drain and the source; and

(B) an electrostatic capacitance measuring part comprising a pair of electrodes, an AC power source, which applies an AC voltage between the pair of electrodes under control of a frequency to a region of 100 Hz or less, and an electrostatic capacitance measuring circuit, which measures an electrostatic capacitance between the pair of electrodes.

8. The device of claim 7, further comprising:

a dielectric constant calculating part comprising a dielectric constant calculating circuit, which calculates a dielectric constant based on an electrostatic capacitance measured value obtained in the electrostatic capacitance measuring part.

9. A lubricating oil monitoring system comprising the device of claim 7.

10. The device of claim 7, being suitable for measuring a degree of degradation of a lubricating oil.