OIL-DEGRADATION DETECTING APPARATUS

• US 20090315574A1
• Filed: 06/18/2008
• Published: 12/24/2009
• Est. Priority Date: 06/19/2007
• Status: Active Grant

• Current Assignee: Mitsubishi Heavy Industries, Ltd.
• Original Assignee: Mitsubishi Heavy Industries, Ltd.
• Inventors: Akiyama, Yo, Kaga, Junichi, Yano, Akihiko, Deguchi, Yoshihiro, Yamaura, Taketoshi
• Granted Patent: US 8,421,486 B2
• Time in Patent Office: Days
• US Class Current: 324/698
• CPC Class Codes: G01N 2011/0066 electrical properties
• CPC Class Codes: G01N 27/02 by investigating impedance
• CPC Class Codes: G01N 33/2888 Lubricating oil characteristics, e.g. deterioration lubricating properties G01N33/30

Abstract

An oil-degradation detecting apparatus that can more accurately judge oil degradation and a mechanical system having a rotating part or a sliding part and including the oil-degradation detecting apparatus are provided. Two plates (21, 22) are disposed in an oil flow path (11) so as to be parallel to each other, an ammeter (24) measures a current that flows when an AC voltage is applied between the two plates (21, 22), a voltmeter measures the voltage between the plates (21, 22), and a signal processor (processor) (31) determines the electrical conductivity and the dielectric constant of the oil (10) based on the measurement results from the ammeter (24) and the voltmeter (25) and judges degradation of the oil (10) based on the electrical conductivity and the dielectric constant.

Claims

1. An oil-degradation detecting apparatus comprising:

two plates disposed so as to be parallel to each other in a path in which oil flows;

an ammeter measuring the current that flows when an AC voltage is applied between the two plates;

a voltmeter measuring the voltage between the plates when the AC voltage is applied to the two plates; and

a processor determining the electrical conductivity and the dielectric constant of the oil based on measurement results from the ammeter and the voltmeter and judging degradation of the oil based on the electrical conductivity and the dielectric constant.

2. The oil-degradation detecting apparatus according to claim 1, wherein

the ammeter measures a current;

the voltmeter measures a voltage; and

the processor determines the complex impedance between the two plates and the phase difference between the current and the voltage based on the measurement results from the ammeter and the voltmeter, determines the electrical conductivity of the oil by assuming the real part of the reciprocal of the complex impedance as the resistance component between the two plates, and determines the dielectric constant of the oil by assuming the imaginary part of the reciprocal of the complex impedance[0] as the capacitance component between the two plates.

3. The oil-degradation detecting apparatus according to claim 1, wherein the processor stores the respective acceptable ranges of the electrical conductivity of the oil and the dielectric constant of the oil and judges the oil to be degraded when either the electrical conductivity of the oil or the dielectric constant of the oil is outside the acceptable range thereof.

4. The oil-degradation detecting apparatus according to claim 1, wherein the processor stores a table that relates the electrical conductivity of the oil and the dielectric constant of the oil with causes of oil degradation and identifies the cause of the oil degradation by referring to this table.

5. The oil-degradation detecting apparatus according to claim 1, wherein the measurement is performed while varying the frequency of the AC voltage applied to the two plates.

6. The oil-degradation detecting apparatus according to claim 1, wherein the waveform of the AC voltage applied to the two plates is a sine wave, a square wave, a triangle wave, a sawtooth wave, or a reverse sawtooth wave.

7. The oil-degradation detecting apparatus according to claim 1, further comprising:

a viscometer disposed in the oil flow path and measuring the viscosity of the oil, wherein

the processor judges degradation of the oil by additionally using the measurement result from the viscometer.

8. The oil-degradation detecting apparatus according to claim 1, further comprising:

a moisture meter provided in the oil flow path and measuring the moisture of the oil, wherein

the processor judges degradation of the oil by additionally using the measurement result from the moisture meter.

9. The oil-degradation detecting apparatus according to claim 1, further comprising:

an informing unit reporting the result of the judgment of degradation of the oil by the processor.

10. The oil-degradation detecting apparatus according to claim 1, further comprising:

a partial changing unit that replaces part of the oil with oil of good quality when the processor judges the oil to be degraded.

11. A mechanical system including a rotating part or a sliding part, comprising the oil-degradation detecting apparatus according to claim 1.