SYSTEMS AND METHODS FOR REAL-TIME MONITORING OF ELECTRICAL DISCHARGE ACROSS A TRIBOLOGICAL CONTACT

Abstract

Systems and methods for real-time monitoring of electrical discharge events across a tribological contact are provided. The systems comprise a signal generator, a test device comprising a tribological contact, a reference device and a signal comparator. The systems recognize changes between states where electrical discharge across a tribological contact does or does not occur and produce distinct output signals for each state and, further, may maintain a count of how often such events occur.

Claims

1. A system for detecting electrical discharge events across a tribological contact, said contact comprising at least one fluid, the system comprising: a signal generator configured to generate an input signal; a reference device configured to receive the input signal from the signal generator and produce a first output signal; a test device configured to receive the input signal from the signal generator and produce a second output signal, said test device comprising a tribological contact, said contact comprising at least one fluid; and a signal comparator configured to compare the first and second output signals, said signal comparator being further configured to switch between two states in response to an electrical discharge event across the tribological contact.

2. A system according to claim 1, further comprising a counting device configured to count each time the signal comparator switches between states.

3. A system according to claim 1, wherein the input and/or output signals are selected from voltage or current.

4. A system according to claim 1, wherein the output signals from the test device and the reference device differ from the input signal in a quantity of interest, for example, in relative magnitude and/or phase.

5. A system according to claim 4, wherein under conditions wherein electrical discharge is absent, the output signal from the reference device is greater or less in the quantity of interest compared to the output signal from the test device and wherein under conditions wherein discharge is present, the relationship between the output signal from the reference device and the output signal from the test device changes, for example reverses.

6. A system according to claim 1, wherein the fluid is selected from the group consisting of mineral oil, synthetic oils, such as hydrogenated polyolefins, esters, silicones and fluorocarbons, vegetable oil, air, inert gases and mixtures thereof.

7. A system according to claim 1, wherein the signal comparator is selected from a voltage comparator and a current comparator.

8. A system according to claim 1, wherein the electrical discharge event is triggered by a change in surface roughness or through wear of one or both tribological contact counter surfaces.

9. A system according to claim 1, wherein the electrical discharge event is triggered by deposition of chemical species onto one or both tribological contact counter surfaces.

10. A system according to claim 1, wherein the electrical discharge event is triggered by a change in dielectric strength of the fluid.

11. A system according to claim 1, wherein the electrical discharge event is triggered by a change in conductivity of the fluid.

12. A system according to claim 1, wherein electrical discharge rate across the tribological contact increases with decreasing viscosity of the fluid.

13. A system according to claim 1, wherein the tribological contact is selected from the group consisting of rotating cylinders or spinning ball and disc geometry.

14. A tribological test apparatus comprising the system according to claim 1.

15. A method of detecting electrical discharge events across a tribological contact, said contact comprising at least one fluid, the method comprising the following steps: applying an input signal to a reference device and a test device, said test device comprising a tribological contact, said contact comprising at least one fluid; and applying an output signal from the reference device and an output signal from the test device to a signal comparator, said signal comparator providing an output signal when the relationship between the output signal from the reference device and the output signal from the test device changes, wherein said change is characterized by an electrical discharge event across the tribological contact.

16. A method according to claim 15 further comprising counting each electrical discharge event.

17. A method according to claim 15, wherein the input and/or output signals are selected from voltage or current.

18. A method according to claim 15, wherein the output signals from the test device and the reference device differ from the input signal in a quantity of interest, for example, in relative magnitude and/or phase.

19. A method according to claim 18, wherein under conditions wherein electrical discharge is absent, the output signal from the reference device is greater or less in the quantity of interest compared to the output signal from the test device and wherein under conditions wherein discharge is present, the relationship between the output signal from the reference device and the output signal from the test device changes, for example reverses.

20. A method according to claim 15, wherein the fluid is selected from the group consisting of mineral oil, synthetic oils, such as hydrogenated polyolefins, esters, silicones and fluorocarbons, vegetable oil, air, inert gases and mixtures thereof.

21. A method according to claim 15, wherein the signal comparator is selected from a voltage comparator and a current comparator.

22. A method according to claim 15, wherein the electrical discharge event is triggered by a change in surface roughness or through wear of one or both tribological contact counter surfaces.

23. A method according to claim 15, wherein the electrical discharge event is triggered by deposition of chemical species onto one or both tribological contact counter surfaces.

24. A method according to claim 15, wherein the electrical discharge event is triggered by a change in dielectric strength of the fluid.

25. A method according to claim 15, wherein the electrical discharge event is triggered by a change in conductivity of the fluid.

26. A method according to claim 15, wherein electrical discharge rate across the tribological contact increases with decreasing viscosity of the fluid.

27. A method according to claim 15, wherein the tribological contact is selected from the group consisting of rotating cylinders or spinning ball and disc geometry.

28. A system for monitoring operational chemical changes of a fluid, the system comprising: a signal generator configured to generate an input signal; a reference device configured to receive the input signal from the signal generator and produce a first output signal; a test device configured to receive the input signal from the signal generator and produce a second output signal, said test device comprising a tribological contact, said contact comprising at least one fluid; and a signal comparator configured to compare the first and second output signals, said signal comparator further configured to switch between two states in response to an operational chemical change of the fluid.

29. A system according to claim 28, wherein the operational chemical changes of the fluid include degradation of the molecular makeup of the fluid and/or contamination by other materials in contact with the fluid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] FIG. 1 illustrates a system according to one embodiment of the present disclosure.

[0055] FIG. 2 illustrates a system according to another embodiment of the present disclosure.

[0056] FIG. 3 is a flow chart of a method according to one embodiment of the present disclosure.

[0057] FIG. 4 is a flow chart of a method according to another embodiment of the present disclosure.

[0058] FIG. 5 is a flow chart outlining the main operational steps of a method according to one embodiment of the present disclosure.

[0059] FIGS. 6A and 6B are plots of voltage against time showing an example comparator signal output in response to example changing input signals.

[0060] FIG. 7A is circuit diagram of a system according to one embodiment of the present disclosure.

[0061] FIG. 7B is the same circuit diagram as FIG. 7A but illustrating four main elements of a system according to one embodiment of the present disclosure.

[0062] FIG. 8 is a plot of output signal against time.

[0063] FIG. 9 is a plot of electrical discharge rate against time.

[0064] FIG. 10 is a plot of electrical discharge rate against temperature for three test lubricants each having different temperature dependent viscosities.

DETAILED DESCRIPTION

[0065] Throughout this specification, use of the terms comprises or comprising or grammatical variations thereon shall be taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof not specifically mentioned.

[0066] When numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated. All numerical values as used herein are modified by about or approximately the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.

[0067] It must also be noted that, as used in the specification and the appended claims, the singular forms a, an and the include plural referents unless otherwise specified. Thus, for example, reference to electrical discharge may include more than one electrical discharge, and the like.

[0068] While the illustrative embodiments of the disclosure have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the spirit and scope of the disclosure. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all the features of patentable novelty which reside in the present disclosure, including all features which would be treated as equivalents thereof by those skilled in the art to which the disclosure pertains.

[0069] The following definitions are included to provide a clear and consistent understanding of the specification and claims. As used herein, the recited terms have the following meanings. All other terms and phrases used in this specification have their ordinary meanings as one of skill in the art would understand.

[0070] As used herein the term tribological contact refers to a system of opposing, mechanically solid surfaces nominally separated by a gap filled with a fluid, either liquid, gaseous, or mixtures thereof.

[0071] FIG. 1 illustrates a system (1) according to one embodiment of the present disclosure. The system comprises signal generator (2), test device (3) comprising a tribological contact, reference device (4), and signal comparator (5). The signal generator is configured to output a signal (6) which inputs into both the test and reference devices. Each of the test and reference devices are configured to operate on the signal from the signal generator and each outputs a different signal, respectively (7) and (8), based on a quantity of interest, for example different magnitude and/or different phase. The signal comparator is configured to compare the quantity of interest for the two device output signals and outputs (9) one of two states. For example, when the quantity is greater in the reference device, the comparator outputs a different signal to when the quantity is less in the reference device. When an electrical discharge event occurs across the tribological contact in the test device it causes the comparator to switch states, therefore detecting the event.

[0072] FIG. 2 illustrates a system (1) according to another embodiment of the present disclosure. The system comprises signal generator (2), test device (3) comprising a tribological contact, reference device (4), signal comparator (5) and counter (6). The signal generator is configured to output a signal (7) which inputs into both the test and reference devices. Each of the test and reference devices are configured to operate on the signal from the signal generator and each outputs a different signal, respectively (8) and (9), based on a quantity of interest, for example different magnitude and/or different phase. The signal comparator is configured to compare the quantity of interest for the two device output signals and outputs (10) one of two states. For example, when the quantity is greater in the reference device, the comparator outputs a different signal to when the quantity is less in the reference device. When an electrical discharge event occurs across the tribological contact in the test device it causes the comparator to switch states, therefore detecting the event. The counter records how often, that is how many times, during some given test interval, the comparator switches between output states.

[0073] FIG. 3 illustrates a method according one embodiment of the present disclosure. Identical input signals (1) and (2) are applied to test device (3) comprising a tribological contact and reference device (4). The test device outputs signal (5) and the reference device outputs signal (6) which are both then applied to the signal comparator (7), which outputs signal (8).

[0074] FIG. 4 illustrates a method according to another embodiment of the present disclosure. Identical input signals (1) and (2) are applied to test device (3) comprising a tribological contact and reference device (4). The test device outputs signal (5) and the reference device outputs signal (6) which are both then applied to the signal comparator (7), which outputs signal (8) which is subsequently counted by the counter (9).

[0075] FIG. 5 is a flow chart outlining the main operational steps of a method according to one embodiment of the present disclosure. In step 1, a controlled voltage V.sub.IN is divided between a reference device and a test device that comprises know electrical elements and a tribological contact. In step 2, the reference device outputs a voltage V.sub.REF and the test device outputs a voltage V.sub.CON. In step 3, under conditions where discharge across the tribological contact does not occur, there is a known relationship between V.sub.REF and V.sub.CON, for example, V.sub.REF<V.sub.CON. Under conditions where discharge is present, this relationship is reversed, for example, V.sub.REF>V.sub.CON. In step 4, the relationship between V.sub.REF and V.sub.CON is evaluated by an independently powered high impedance measurement device that outputs a voltage Vo that changes between a high and low state depending on the chosen relationship between V.sub.REF and V.sub.CON. In step 5, a counter enumerates the number of times a state change occurs.

[0076] FIGS. 6A and 6B illustrate the behaviour of the different signals during operation of a method according to one embodiment of the present disclosure. In FIG. 6A, V.sub.IN is inputted to a reference device and a test device that includes a tribological contact. The reference voltage, V.sub.REF, is set at a constant value and V.sub.CON changes with time. In this example, V.sub.CON is shown to oscillate periodically for illustration purposes. In FIG. 6B, V.sub.O is the output voltage for detecting a state change. In this example, when V.sub.CON>V.sub.REF, V.sub.O is 0V and when V.sub.CON<V.sub.REF, the electrical state has changed and V.sub.O switches to about 5V.

[0077] FIG. 7A illustrates a system according to one embodiment of the present disclosure. Illustrated is a circuit schematic of the principle electrical elements of the system indicating where important input/output voltages are provided/measured.

[0078] FIG. 7B illustrates the same system as FIG. 7A but also highlights the four main elements. 1) Reference device; 2) Test Device, including a variable resistor (Rx) for setting measurement thresholds for detecting state changes in the tribological contact; 3) Signal comparator that outputs V.sub.O when the relationship between V.sub.REF and V.sub.CON changes and 4) A counting device.

[0079] FIG. 8 is a plot of output signal from signal comparator against time and illustrating low-level noise and large, sharp features that are electrical discharge events across a tribological contact.

[0080] FIG. 9 are plots of electrical discharge event rate against time for three tests of a lubricant Sample A under fixed tribological conditions. The experiments were performed with a spinning ball and disc geometry. Initially, the discharge event rates may be relatively high, however over time these stabilize.

[0081] FIG. 10 are plots of electrical discharge event rate against temperature for three different test lubricants, Samples A, B, C, which have different temperature-dependent viscosities. The experiments were performed using a spinning ball and disc geometry. Temperature was varied while all other tribological controls were fixed. The results indicate that in each case, as the viscosity of the lubricant decreases, the discharge event rate increases due to the conductive surfaces becoming closer together. It may be seen that discharge event rates over more than two orders of magnitude are resolved.

Certain Embodiments

[0082] Certain embodiments of systems and methods according to the present disclosure are presented in the following paragraphs.

[0083] Embodiment 1 provides a system for detecting electrical discharge events across a tribological contact, said contact comprising at least one fluid, the system comprising:

[0084] a signal generator configured to generate an input signal;

[0085] a reference device configured to receive the input signal from the signal generator and produce a first output signal;

[0086] a test device configured to receive the input signal from the signal generator and produce a second output signal, said test device comprising a tribological contact; and

[0087] a signal comparator configured to compare the first and second output signals, said signal comparator being further configured to switch between two states in response to an electrical discharge event across the tribological contact.

[0088] Embodiment 2 provides a system for measuring the frequency of electrical discharge events across a tribological contact, said contact comprising at least one fluid, the system comprising:

[0089] a signal generator configured to generate an input signal;

[0090] a reference device configured to receive the input signal from the signal generator and produce a first output signal;

[0091] a test device configured to receive the input signal from the signal generator and produce a second output signal, said test device comprising a tribological contact;

[0092] a signal comparator configured to compare the first and second output signals, said signal comparator further configured to switch between two states in response to an electrical discharge event across the tribological contact; and

[0093] a counting device configured to count each time the signal comparator switches between states.

[0094] Embodiment 3 provides a system for monitoring operational chemical changes of a fluid, the system comprising:

[0095] a signal generator configured to generate an input signal;

[0096] a reference device configured to receive the input signal from the signal generator and produce a first output signal;

[0097] a test device configured to receive the input signal from the signal generator and produce a second output signal, said test device comprising a tribological contact, said contact comprising at least one fluid; and

[0098] a signal comparator configured to compare the first and second output signals, said signal comparator further configured to switch between two states in response to an operational chemical change of the fluid.

[0099] Embodiment 4 provides a method of detecting electrical discharge events across a tribological contact, said contact comprising at least one fluid, the method comprising the following steps:

[0100] applying an input signal to a reference device and a test device, said test device comprising a tribological contact; and

[0101] applying an output signal from the reference device and an output signal from the test device to a signal comparator, said signal comparator providing an output signal when the relationship between the output signal from the reference device and the output signal from the test device changes, wherein said change is characterized by an electrical discharge event across the tribological contact.

[0102] Embodiment 5 provides a method of measuring the frequency of electrical discharge events between a tribological contact, said contact comprising at least one fluid, the method comprising the following steps:

[0103] applying an input signal to a reference device and a test device; said test device comprising a tribological contact;

[0104] applying an output signal from the reference device and an output signal from the test device to a signal comparator, said signal comparator providing an output signal when the relationship between the output signal from the reference device and the output signal from the test device changes, wherein said change is characterized by an electrical discharge event across the tribological contact; and

[0105] counting each electrical discharge event.

[0106] Embodiment 6 provides a system according to any one of embodiments 1 to 3 or a method according to any one of embodiments 5 or 6, wherein the input and/or output signals are selected from voltage or current.

[0107] Embodiment 7 provides a system according to any one of embodiments 1 to 3 or 6, or a method according to any one of embodiments 4 to 6, wherein the output signals from the reference device and from the test device differ from the input signal in a quantity of interest, for example, in relative magnitude or phase.

[0108] Embodiment 8 provides a system or method according to embodiment 7, wherein under conditions wherein electrical discharge is absent, the output signal from the reference device is greater or less in the quantity of interest compared to the output signal from the test device and wherein under conditions wherein discharge is present, the relationship between the output signal from the reference device and the output signal from the test device changes, for example reverses.

[0109] Embodiment 9 provides a system according to any one of embodiments 1 to 3 or 6 to 8 or a method according to any one of embodiments 4 to 8, wherein the fluid is selected from the group consisting of mineral oil, synthetic oils, such as hydrogenated polyolefins, esters, silicones and fluorocarbons, vegetable oil, air and inert gases.

[0110] Embodiment 10 provides a system according to any one of embodiments 1 to 3 or 6 to 9 or a method according to any one of embodiments 4 to 9, wherein the signal comparator is selected from a voltage comparator and a current comparator.

[0111] Embodiment 11 provides a system according to any one of embodiments 1 to 3 or 6 to 10 or a method according to any one of embodiments 4 to 10, wherein the electrical discharge event is triggered by a change in surface roughness of one or both tribological contact counter surfaces.

[0112] Embodiment 12 provides a system according to any one of embodiments 1 to 3 or 6 to 10 or a method according to any one of embodiments 4 to 10, wherein the electrical discharge event is triggered by deposition of chemical species onto one or both tribological contact counter surfaces.

[0113] Embodiment 13 provides a system according to any one of embodiments 1 to 3 or 6 to 10 or a method according to any one of embodiments 4 to 10, wherein the electrical discharge event is triggered by a change in dielectric strength of the fluid.

[0114] Embodiment 14 provides a system according to any one of embodiments 1 to 3 or 6 to 10 or a method according to any one of embodiments 4 to 10, wherein the electrical discharge event is triggered by a change in conductivity of the fluid.

[0115] Embodiment 15 provides a system according to embodiment 3, wherein the operational chemical changes of the fluid include degradation of the molecular makeup of the fluid and/or contamination by other materials in contact with the fluid.

[0116] Embodiment 16 provides a tribological test apparatus comprising the system according to any one of embodiments 1 to 3 or 6 to 14.

[0117] All patents, patent applications and other documents cited herein are fully incorporated by reference to the extent such disclosure is not inconsistent with this disclosure and for all jurisdictions in which such incorporation is permitted.