Determining quality of lubricating oils in use

• US 7,370,514 B2
• Filed: 04/14/2005
• Issued: 05/13/2008
• Est. Priority Date: 04/14/2005
• Status: Expired due to Fees

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Schneider, Eric West, Rogers, Michael William, Halalay, Ion C.
• Primary Examiner(s): Williams; Hezron
• Assistant Examiner(s): West; Paul M
• Application Number:
  US11/106,309
• Publication Number:
  US 20060232267A1
• Time in Patent Office: 1,125 Days
• Field of Search: 73/530.5
• US Class Current: 73/53.05
• CPC Class Codes: G01N 33/2888 Lubricating oil characteristics, e.g. deterioration lubricating properties G01N33/30

Abstract

Resistivity ρ values of a lubricating oil are repeatedly determined at a predetermined temperature (range) as it is in use in a working mechanism such as a vehicle engine. Such accumulated properties over operating time of the working lubricant can be plotted graphically to display a curve with, for example, a first portion where dρ/dt>0, a maximum ρ_max at a time t₁ where dρ/dt=0, a second portion where dρ/dt<0, a minimum ρ_min at a time t₂ where dρ/dt again is zero, and a third portion where dρ/dt>0. Furthermore, there can exist another time t₃, where dρ/dt exhibits a discontinuous change (increase) with time. Characteristics of the ρ vs. t curve, including, the values of t₁, t₂, t₃, ρ_max, ρ_min, and the ratio ρ_max/ρ_min can be compared with like data on like lubricant oils in estimating the remaining useful life of the present operating lubricant oil.

Claims

1. A method of determining remaining useful life of a quantity of oil in use in fluid lubrication of an operating mechanism, the method comprising:

repeatedly determining resistivity (ρ

) values of the oil at an predetermined oil temperature during operating time intervals of the mechanism;

recording a resistivity-time ρ

(t) history of the oil such that, as successive resistivity values starting with an initial value are accumulated with elapsed operating time, a continuous ρ

(t) linear curve is formulated that includes;

(1) a first portion with a slope of dρ

/dt>

0 up to a first time t₁ during which values of ρ

increase and (2) a maxima at t₁ where dρ

/dt=0 with a corresponding ρ

_max,

comparing, from time to time, the then existing portion of the ρ

(t) curve with like predetermined data on a like or functionally comparable oil composition;

using the comparison to predict the remaining useful life of the oil;

continuing to record a resistivity-time ρ

(t) history of the oil so that a continuous ρ

(t) linear curve is formulated that further includes;

(3) a second portion with a slope of dρ

/dt<

0 during which values of ρ

decrease up to a second time t₂, (4) a minima at t₂ where dρ

/dt=0 with a corresponding ρ

_min, and (5) a third portion where dρ

/dt>

0 ;

continuing to compare, from time to time, the then existing portions of the ρ

(t) curve with like predetermined data on a like or functionally comparable oil composition and using the comparison to predict the remaining useful life of the oil;

continuing to record a resistivity-time ρ

(t) history of the oil in the third portion of the ρ

(t) curve until time t₃ when there is a sudden increase in the value of the time derivative of the resistivity indicating that the useful life of the oil has been depleted; and

then

generating a signal indicating that the useful life of the oil has been depleted.

2. A method as recited in claim 1 in which the oil comprises a mineral-based oil derived from petroleum.

3. A method as recited in claim 1 in which the oil comprises a synthetic oil comprising carbon-based and/or silicon-based materials.

4. A method as recited in claim 1 in which the mechanism is a hydrocarbon fueled engine.

5. A method as recited in claim 1 in which the oil in the mechanism operates at temperatures above about 100°

C.

6. A method as recited in claim 1 in which t₂/t₁ is about 10 or greater.

7. A method as recited in claim 1 in which t₁ is used to predict remaining useful life of the oil.

8. A method as recited in claim 1 in which t₁ and t₂ are used to predict the remaining useful life of the oil.

9. A method as recited in claim 1 in which ρ

_max is used to predict remaining useful life of the oil.

10. A method as recited in claim 1 in which ρ

_min and/or ρ

_max are used to predict remaining useful life of the oil.

11. A method as recited in claim 1 in which the ratio ρ

_max/ρ

_min is used to predict remaining useful life of the oil.

12. A method as recited in claim 1 in which the oil is contained in an impedance sensor with a known resistivity constant, and the sensor is powered with an input voltage by an AC frequency generator in a time varying electric field at frequencies in the range of about 100 MHz to 0.1 Hz;

the sensor output current and phase angle between the output current and input voltage are detected;

the impedance amplitude, resistance and reactance of the sensor-oil combination are determined from the input voltage, output current and phase angle; and

the electrical resistivity of the oil at the predetermined temperature is determined from the determined resistance and sensor resistivity constant.

13. A method of determining remaining useful life of a quantity of oil in use in fluid lubrication of an operating mechanism, the method comprising:

repeatedly determining resistivity (ρ

) values of the oil at a predetermined oil temperature under a time-varying electric field during operating time intervals of the mechanism;

recording a resistivity-time ρ

(t) history of the oil such that, as successive resistivity values starting with an initial value are accumulated with elapsed operating time, a continuous ρ

(t) linear curve is formulated that includes;

(1) a first portion with a slope of dρ

/dt>

0 up to a first time t₁ during which values of ρ

increase, (2) a maxima at t₁ where dρ

/dt=0 with a corresponding ρ

_max, (3) a second portion with a slope of dρ

/dt<

0 during which values of ρ

decrease up to a second time t₂, (4) a minima at t₂ where dρ

/dt=0 with a corresponding ρ

_min, and (5) a third portion where dρ

/dt>

0 ;

comparing, from time to time, the then existing portions of the ρ

(t) curve with like predetermined data on a like or functionally comparable oil composition;

repeatedly using the comparison to predict the remaining useful life of the oil;

continuing to record a resistivity-time ρ

(t) history of the oil in the third portion of the ρ

(t) curve until time t₃ when there is a sudden increase in the value of the time derivative of the resistivity indicating that the useful life of the oil has been depleted; and

then

generating a signal indicating that the useful life of the oil has been depleted.

14. A method as recited in claim 13 in which the oil is a mineral-based oil derived from petroleum.

15. A method as recited in claim 13 in which the oil is a synthetic oil comprising carbon-based and/or silicon-based materials.

16. A method as recited in claim 13 in which the mechanism is a hydrocarbon fueled engine.

17. A method as recited in claim 13 in which the oil in the mechanism operates at temperatures above about 100°

C.

18. A method as recited in claim 13 in which t₁ and t₂ are used to predict the remaining useful life of the oil.

19. A method as recited in claim 13 in which ρ

_min and/or ρ

_max are used to predict remaining useful life of the oil.

20. A method as recited in claim 13 in which the ratio ρ

_max/ρ

_min is used to predict remaining useful life of the oil.

21. A method as recited in claim 13 in which the oil is contained in an impedance sensor with a known resistivity constant, and the sensor is powered with an input voltage by an AC frequency generator in a time varying electric field at frequencies in the range of about 100 MHz to 0.1 Hz;

the sensor output current and phase angle between the output current and input voltage are detected;

the impedance amplitude, resistance and reactance of the sensor-oil combination are determined from the input voltage, output current and phase angle; and

the electrical resistivity of the oil at the predetermined temperature is determined from the determined resistance and sensor resistivity constant.