Method and device for monitoring oil oxidation in real time by measuring fluorescence

• US 7,391,035 B2
• Filed: 04/18/2006
• Issued: 06/24/2008
• Est. Priority Date: 02/14/2006
• Status: Expired due to Fees

• Current Assignee: Korea Advanced Institute of Science and Technology
• Original Assignee: Korea Advanced Institute of Science and Technology
• Inventors: Yoon, Eui Sung, Han, Hung Gu, Makarenko, Vladimir, Kong, Hosung, Markova, Lyubov, Semenyuk, Mikhail
• Primary Examiner(s): Porta; David P.
• Assistant Examiner(s): Baker; David S
• Application Number:
  US11/407,404
• Publication Number:
  US 20070187617A1
• Time in Patent Office: 798 Days
• Field of Search: 250/364, 250/432, 250/461.1, 356/70
• US Class Current: 250/461.1
• CPC Class Codes: G01N 2021/6421 Measuring at two or more wavelengths
• CPC Class Codes: G01N 21/6408 with measurement of decay time, time resolved fluorescence
• CPC Class Codes: G01N 21/645 Specially adapted constructive features of fluorimeters
• CPC Class Codes: G01N 21/8507 Probe photometers, i.e. with optical measuring part dipped into fluid sample
• CPC Class Codes: G01N 33/2888 Lubricating oil characteristics, e.g. deterioration lubricating properties G01N33/30

Abstract

There is provided a method and a device of monitoring oil oxidation in real time. The method of the present invention comprises the steps of: irradiating ultraviolet light into oil to be monitored; measuring fluorescence emission intensity of the oil in red, green and blue wavelength bands; determining one value measured in a relatively long wavelength band and the other value measured in a relatively short wavelength band among the fluorescence emission intensity measured in the red, green and blue wavelength bands; calculating a fluorescence emission ratio which is defined as a ratio of the value measured in the relatively long wavelength band to the value measured in the relatively short wavelength band; and monitoring a change in the fluorescence emission ratio. It is then determined whether the fluorescence emission ratio reaches a predetermined critical magnitude. When the fluorescence emission ratio reaches the critical magnitude, the necessity of replacing the oil with new one is indicated.

Claims

1. A method of monitoring the oxidation of a lubricant in real time, comprising the steps of:

(a) irradiating a lubricant to be monitored with an ultraviolet light;

(b) measuring a fluorescence emission intensity from the lubricant in red, green and blue wavelength bands;

(c) determining a first value of fluorescence intensity measured in the green wavelength band of 470 nm to 550 nm and a second value of fluorescence intensity measured in the blue wavelength band of 430 nm to 470 nm among the fluorescence emission intensity measured in the red, green and blue wavelength bands;

(d) calculating a fluorescence emission ratio by taking a ratio of the first value measured in the green wavelength band to the second value measured in the blue wavelength band;

(e) monitoring a change in the fluorescence emission ratio in course of oxidation of the lubricant;

(f) determining whether the fluorescence emission ratio reaches a predetermined critical magnitude; and

(g) indicating the necessity of replacing the lubricant when the fluorescence emission ratio reaches the critical magnitude.

2. A device of monitoring the oxidation of a lubricant in real time, comprising:

a housing mounted to a wall of a unit containing a lubricant to be monitored;

a transparent optical window disposed in the housing, the optical window having a boundary surface configured to be in contact with the lubricant;

a UV diode provided inside the housing for irradiating an ultraviolet light into the lubricant through the optical window;

a color sensor provided inside the housing for detecting a fluorescence light emission of the lubricant, the fluorescence light emission passing through the optical window in red, green and blue wavelength bands, and measuring a fluorescence emission intensity; and

a control portion for determining a first value of fluorescence intensity measured in the green wavelength band of 470 nm to 550 nm and a second value of fluorescence intensity measured in the blue wavelength band of 430 nm to 470 nm among the fluorescence emission intensity measured in the red, green and blue wavelength bands by the color sensor, the control portion being configured to calculate a ratio of the first value measured in the green wavelength band to the second value measured in the blue wavelength band, the control portion further being configured to monitor a change in the ratio;

wherein a thickness of the optical window is calculated from the following ecluation;

3. The device of claim 2, wherein a first optical fiber connected to the UV diode is provided inside the housing, the first optical fiber being configured to transmit the ultraviolet light from the UV diode to the optical window.

4. The device of claim 3, wherein a ball lens is provided between the UV diode and an end of the first optical fiber, the ball lens being configured to focus the ultraviolet light from the UV diode on the end of the first optical fiber.

5. The device of claim 2, wherein at least one second optical fiber connected to the color sensor is provided inside the housing, the second optical fiber being configured to transmit the fluorescence light emission of the lubricant to the color sensor, the fluorescence light emission passing through the optical window.

6. The device of claim 2, wherein an oleophobic material is coated on the boundary surface of the optical window for preventing an adherence of contaminants to the boundary surface.

7. The device of claim 6, wherein the oleophobic material is fluorosilane polymer carried in hydrofluoroether solvent.

8. The device of claim 2, wherein the device further comprises a displaying means electrically connected to the control portion,

and wherein the control portion determines whether the ratio of the first value measured in the green wavelength band to the second value measured in the blue wavelength band reaches a predetermined critical magnitude,

if the ratio reaches the critical magnitude, the control portion operates the displaying means to indicate the necessity of replacing the lubricant.