Cross-Reference to Related Applications

[0001] This application claims the benefit of U.S. Provisional Application No.

61/819,186, filed on 3 May 2013, which is incorporated herein by reference. Field of the Invention

[0002] The present disclosure relates generally to methods of determining performance properties of a lubricant. More specifically, the present disclosure relates to methods of determining performance properties of a lubricant used in vehicles (e.g., motorcycles).

Background of the Invention [0003] Lubricants may be used in machinery, for example, to provide satisfied friction between moving parts, such as in wet clutches of motorcycles. In some cases, slippage may occur in wet clutches that may hinder the movement of the parts and, therefore, impact the performance of the wet clutches. Lubricants may be configured to prevent the likelihood of slippage and/or affect the performance of wet clutches. [0004] Lubricants may include a mix of oils and other additives. The composition of the lubricant may be selected to define properties which can be used to enhance performance of the machinery. For example, various wet clutches may specify the use of a certain viscosity of lubricant under certain conditions, such as outdoor temperature. In another example, the composition of the lubricant (and/or its additives) may be selected to control friction of the wet clutch.

[0005] Designed experiments may be performed to compare lubricants having various compositions. The experiments may involve performing tests of various lubricants to determine how each lubricant will perform in operation. In some cases, experiments may be conducted to determine properties of different lubricants that may affect the performance of the machinery. For example, tests may be performed to determine the effect of lubricants on friction and wear of wet clutches. The experiments may be performed using apparatuses that simulate the wet clutch and provide controlled conditions for testing. For example, wet friction clutch testing of a lubricant may be performed using a SAE No. 2 clutch friction test machine. Other examples of friction or wet clutch tests are provided in M. Ingram et al., Frictional Properties of Automatic Transmission Fluids: Part I-Measurement of Friction-Sliding Behavior, Tribology Transactions, vol. 54, pp. 145-153 (2011) and M. Ingram et al., Frictional Properties of Automatic Transmission Fluids: Part II-Origins of Friction-Sliding Speed Behavior, Tribology Transactions, vol. 54, pp. 154- 167 (2011).

[0006] Testing of lubricants is often performed to determine if the lubricant satisfies certain performance and/or quality requirements set forth by a standard setting

organization. For example, the Japanese Automotive Standards Organization (JASO) has created a set of performance and quality standards relating to motorcycle engine oils.

Specifically, the JASO T903:2011 Standard sets forth a friction test designed to determine the suitability of lubricants for wet clutch usage.

[0007] Currently, the most common method used to determine whether a lubricant satisfies the requirements of the JASO T903:2011 Standard is to perform a friction test using a SAE No. 2 clutch friction test machine. However, this method suffers from certain

disadvantages, including a lack of repeatability, the requirement for a large sample of the lubricant to be tested (40L per test), and the relatively high expense of performing the test. Accordingly, any method providing for an improvement in lubricant testing, and in particular the testing of frictional and/or wear properties of a lubricant, would be desirable. Summary

[0008] In at least one aspect, the disclosure relates to a method of friction testing a lubricant in a test assembly comprising a lubricant bath with a lubricant therein, a friction plate and a friction arm. The method comprises applying a load to the friction plate with the friction arm, selectively moving the friction plate according to a test operation, and measuring at least one test parameter (e.g., coefficient of friction) during the test operation. The test operation comprises at least one dynamic friction test having a dynamic speed and at least one static friction test having a static speed. The dynamic speed includes increasing from the static speed to a maximum speed and then decreasing from the maximum speed to the static speed. [0009] In another aspect, the disclosure relates to a method of friction testing a lubricant. The method involves providing a test assembly comprising a lubricant bath with a lubricant therein, a friction plate and a friction arm. The method also involves applying a load to the friction plate with the friction arm, selectively moving the friction plate according to a test operation, and measuring at least one test parameter (e.g., coefficient of friction) during the test operation. The test operation includes at least one dynamic friction test having a dynamic speed and at least one static friction test having a static speed. The dynamic speed includes increasing from the static speed to a maximum speed and then decreasing from the maximum speed to the static speed.

[0010] Finally, in another aspect, the disclosure relates to a method of friction testing a lubricant. The method involves providing a test assembly including a lubricant bath with a lubricant therein, a friction plate and a friction arm. The method also involves applying a load to the friction plate with the friction arm, selectively moving the friction plate according to a test operation, and measuring at least one test parameter (e.g., coefficient of friction) during the test operation. The test operation includes at least one dynamic friction test having a dynamic speed and at least one static friction test having a static speed. The dynamic speed includes increasing from the static speed to a maximum speed and then decreasing from the maximum speed to the static speed. The method also involves determining a static friction index and a dynamic friction index from the measured test parameter(s), and identifying the lubricant from the static friction index and the dynamic friction index.

Brief Description of the Drawings

[0011] So that the above recited features and advantages of the disclosure may be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to the embodiments thereof that are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are, therefore, not to be considered limiting of its scope. The figures are not necessarily to scale, and certain features and certain views of the figures may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness. [0012] Figure 1 is a schematic diagram depicting a test assembly for friction testing lubricants in accordance with the present disclosure; [0013] Figure 2 is a detailed view of a friction assembly comprising a lubricant bath, a friction plate, and a friction arm for friction testing lubricants in accordance with the present disclosure;

[0014] Figure 3 is a schematic diagram depicting a friction plate with a test pad for friction testing lubricants in accordance with the present disclosure;

[0015] Figures 4A-4B are schematic diagrams depicting a test pad before and after friction testing lubricants, respectively, in accordance with the present disclosure;

[0016] Figure 5A-5E are graphs depicting various friction tests in accordance with the present disclosure; [0017] Figure 6 is a graph depicting an example test cycle of a friction test in accordance with the present disclosure;

[0018] Figures 7 is a graph depicting a friction coefficient for various lubricants in accordance with the present disclosure;

[0019] Figure 8 is a graph depicting fluid mapping in accordance with the present disclosure; and

[0020] Figures 9 is a flow chart depicting a method of friction testing lubricants in accordance with the present disclosure.

Detailed Description

[0021] The description that follows includes exemplary apparatuses, methods, techniques, and instruction sequences that embody techniques of the inventive subject matter.

However, it is understood that the described embodiments may be practiced without these specific details.

[0022] The disclosure relates to methods for determining a property of a lubricant, such as a frictional property of a lubricant. These methods may involve the use of a test assembly to friction test lubricants. The test assembly may apply friction and heat to the test lubricant in one or more test cycles of a friction test, such as a wet clutch friction test. Each test cycle may involve one or more test parameters, such as constant or variable speed, lubricant temperature, lubricant viscosity, lubricant composition, load, and the like. Each test cycle may also involve a static friction test and a dynamic friction test. The static friction test may be performed by moving the friction plate at a constant static speed. The dynamic friction test may be performed by increasing the speed and then decreasing the speed of the friction plate. Additives may optionally be added during one or more test cycles of the friction test. The test cycles may be analyzed and test strips examined to evaluate the lubricant. The analysis may be used, for example, to identify the lubricant, evaluate lubricant properties (e.g., viscosity, composition, friction coefficient, etc.), determine other test parameters and/or fluid properties, and determine if a lubricant satisfies certain performance and quality standards set forth by a standard setting organization, such as JASO.

[0023] Further, the methods of the present disclosure may involve the use of a test assembly as described herein to perform a friction test, such as a dynamic friction test or static friction test, on a lubricant in accordance with the testing procedures set forth in an applicable JASO standard, such as JASO T903:2011.

[0024] Figure 1 illustrates a test assembly 100 usable for simulating a clutch and evaluating a lubricant in accordance with the methods disclosed herein. The test assembly 100 comprises a base 102, a friction assembly 104 and a processing unit 106. The friction assembly 104 is supported on the base 102. The base 102 has mechanisms, such as gears or motors, to selectively operate the friction assembly 104 for friction testing the lubricant in a desired test operation. For example, the base 102 may have mechanisms for applying force (or load), torque (e.g., rotation), power, heat and/or other means to operate the friction assembly 104.

[0025] The processing unit 106 is operatively coupled to the friction assembly 104 to receive data therefrom, and to generate outputs as desired. An example output 108 generated by the processing unit 106 is depicted as a friction graph. An average friction may be measured at various static and/or dynamic test conditions under various forces, speeds, lubricant temperatures, lubricant compositions and other test parameters. The friction graph may be generated by performing one or more cycles in a desired

configuration of a test operation and analyzed in accordance with embodiments of the disclosure as will be described more fully herein. [0026] The test assembly 100 is an example configuration intended to provide a simulated environment similar to that of a clutch in which the lubricant may be used. An example of a suitable test assembly capable of performing the methods disclosed herein is a mini- traction machine (MTM) with a low-load beam attachment, which is commercially available from PCS INSTRUMENTS™ (see: www.pcs-instruments.com).

[0027] Figure 2 shows a detailed view of an example configuration of a friction assembly 204 which may be the same as the friction assembly 104 of Figure 1. The friction assembly 204 comprises a lubricant bath 210, a friction plate 212, and a friction arm 214. The lubricant bath 210 is configured to receive a lubricant 209 for testing. The lubricant bath 210 may receive a desired amount of lubricant 209. For example, 30 mL of lubricant 209 may be tested in a given test operation. Lubricant 209 may be any suitable lubricant, including a lubricant intended for use in a four-stroke cycle motorcycle gasoline engine.

[0028] The friction plate 212 is positionable in the lubricant bath 210. Figure 3 shows the friction plate 212 in greater detail. As shown in this view, the friction plate 212 is an elliptical plate having a flat testing surface 311 with a test strip 315 along a periphery thereof. Friction plates suitable for use in the test assembly include any friction plate capable of performing a friction test, such as a dynamic friction test or static friction test, on a lubricant in accordance with the desired testing operation. For example, a suitable friction plate may include any friction plate satisfying the specifications set forth in the applicable JASO standard, such as a friction plate having part number 141-D1G26-00, which is commercially available from Chuoseiko Co., Ltd. ( in accordance with JASO T903:2011). The test strip 315 may be, for example, any paper or carbon fiber-based friction material that may absorb a portion of the lubricant 209 and may receive a load. The paper may be, for example, a friction material commercially available from FCC™ (see: http://www.fcc -netxojp/en technical/fTicdori.htnil)

[0029] Figures 4A and 4B depict an example test strip 315 before and after testing, respectively. As shown in Figure 4B, the test strip 315 has a detectable change thereto as a result of testing. Microscopic techniques may be used to examine visual changes in the test strip. A visual examination using, for example, a surface profilometer may be performed on the test plate, the test arm, and/or the test strip to detect, for example, wear, surface roughness, tribofilm formation, etc. [0030] Referring to Figures 2-4, a friction arm 214 is disposable into the lubricant bath 210. A force F may be applied to the friction arm 214 to press the friction arm 214 against the friction plate 212 and test strip 315. The force may be, for example, about 0.5-8 MPa (7N) contact pressure. The friction plate 212 may be rotated at a speed S as the force is applied to the friction arm 214. The speed may be varied, for example, from about 0.0010 m/s to about 3.6 m/s, and/or from about 3.6 m/s to about 0.0010 m/s. The friction assembly 204 may also be provided with a heat source 216 to apply heat to the lubricant during testing.

[0031] While Figures 2 and 3 depict the friction assembly 204 as including a circular lubricant bath 210 with a friction arm 214 applying a force to a circular test strip 315 positioned on the friction plate 212, the friction assembly 204 may be any device capable of applying heat at a given temperature, movement of the friction plate 212 at a given speed S, and a force F at a given load on friction arm 214. The friction arm 214 is depicted as having a ball (e.g., a steel ball) at an end thereof positionable in frictional engagement with the friction plate 212 and test strip 315, but any shaped friction arm may be provided to establish the desired frictional contact. The friction plate 212 may be rotated as shown, or moved in a desired path (e.g., back and forth) to achieve the desired speed.

[0032] Figures 5A-5E show various graphs 500A-E depicting test operations that may be performed using the test assembly 100 and/or friction assembly 104, 204. As shown by the graphs 500A-E, one or more test cycles may be performed during a test operation. The graphs 500A-E depict co-efficient of friction (y-axis) versus time (x-axis) for Cl-CN number of test cycles performed on a lubricant in a test operation. The test operation may be performed, for example, by measuring a coefficient of friction (COF) generated as an output 108 using the test assembly 100 and friction assembly 104, 204 of Figures 1 and 2. One or more variables, such as speed, duration, load, lubricant composition, lubricant viscosity, lubricant temperature and/or other test parameters of the test operation, may be selectively varied as desired.

[0033] As shown in Figure 5A, a series of test cycles Cl-CN are performed at times tl-tN. Each test cycle Cl-CN for a lubricant includes a dynamic friction test Dl-N and a static friction test Stl-N performed at the same dynamic and static speeds S, force F, and lubricant temperature T. A dynamic friction curve 520 and a static friction curve 522 are generated at each cycle.

[0034] As shown in Figure 5B, a series of test cycles Cl-CN are performed at times tl-tN. Each test cycle Cl-CN for a lubricant includes a dynamic friction test Dl-DN and a static friction test Stl-StN performed at the same dynamic and static speeds S and force F, but at a varied lubricant temperature ΔΤ.

[0035] As shown in Figure 5C, a series of test cycles Cl-CN are performed at times tl-tN. Each test cycle Cl-CN for a lubricant includes a dynamic friction test Dl-DN and a static friction test Stl-StN performed at the same dynamic and static speeds S and lubricant temperature T, but at a varied force AF. [0036] As shown in Figure 5D, a series of test cycles Cl-CN are performed at times tl-tN. Each test cycle Cl-CN for a lubricant includes a dynamic friction test Dl-DN and a static friction test Stl-StN performed at the same dynamic and static speeds S, force F, and lubricant temperature T, but with an additive A added during the test operation. In some cases, the lubricant can be varied by providing a lubricant with different additives. [0037] As shown in Figure 5E, a series of test cycles Cl-CN are performed at times tl-tN. Each test cycle Cl-CN for a lubricant includes a dynamic friction test Dl-DN and a static friction test Stl-StN performed at varied dynamic and static speeds AS, varied lubricant temperature AT, and varied force AF, and with an additive A added during the test operation. In some cases, the lubricant can be varied by providing a lubricant with different additives.

[0038] As demonstrated by Figures 5A-5E, various operating parameters, such as lubricant temperature, viscosity, speed, composition of the lubricant, and/or force, may be kept constant or varied as desired. Variations may be used to alter the curves generated during the test cycle. Desired combinations of curves may be used to simulate various conditions and/or to evaluate the lubricant. The speed may be selectively varied in one or more cycles by selectively stepping up and down the speed. In another example, a series of about 300 repeat cycles may be performed in 30 steps at a first speed and 30 steps at a second speed.

[0039] The test operation may be performed, for example, at a lubricant temperature T of about 100° C with an applied pressure (or force F) of about 0.785 MPa on a friction plate with a radius of about 57.4 mm at a max speed (S) of about 1800 rpms for a duration of 1000 cycles. Furthermore, the test operation may be performed, for example, to satisfy the applicable friction testing procedures set forth by JASO with respect to motorcycle engine oils. Specifically, the test operation may be performed to satisfy the friction testing procedures set forth in the JASO T903 :2011 Standard.

[0040] Figure 6 is a graph 600 depicting cycle CI of Figures 5A-5E in greater detail.

Cycle CI has the dynamic friction test Dl starting at time tl and static friction test Stl starting at time tSt. The dynamic friction curve 520 is generated by moving the friction plate 212 (Figure 2) at a dynamic speed as indicated by speed curve 624. The dynamic speed of rotation increases from about zero (or the static speed) at a time tl to a maximum speed Smax at time tmax, and then decreases back to about zero at a time tSt. As shown, the dynamic speed increases and decreases at a constant rate. The dynamic speed may be, for example, increasing to a maximum speed Smax of about 4 m/s. As shown by the static friction curve 522, the static friction test Stl starts at time tSt and is performed at a static speed near zero (e.g., at about 0.004 m/s) until time tf.

[0041] Figure 7 is graph 700 depicting static friction curves 726A-E for identifying various lubricants, namely Oil A-E. The graph 700 plots coefficient of friction (COF) (y-axis) versus cycle (Cl-CN) (c-axis) for each static friction test performed during a test operation. As shown by this graph, various lubricants have various static friction curves 726A-E. This graph demonstrates that lubricants may be identifiable by their static friction curves. This graph also demonstrates that about 300 test cycles may be performed using the test operation.

[0042] Figure 8 is a graph 800 depicting a friction map for identifying various lubricants according to JASO T903:2011 specifications. The friction map 828A, B plots a known static friction index SI (y-axis) versus a known dynamic friction index DI (x-axis) for given lubricants. Lubricants can be plotted by their static and dynamic indices for identification. Lubricants that fall within friction map 828A may be identified as a given lubricant X; lubricants that fall within friction map 828B may be identified as a given lubricant Y. [0043] Static friction index (SFI) may be calculated according to the JASO industry specification (JASO T903:2011) as follows:

SFI = 1 + ^fe(s) - ^fe(B) Eq. (l) where, μ8(8) is the average static friction coefficient of test oil, μ8(Α) is the average static friction coefficient of high friction reference oil (JAFRE-A11), μ8(Β) is the average static friction coefficient of low friction reference oil (JAFRE-B 11).

[0044] The dynamic friction index (DFI) may be calculated according to the JASO industry specification (JASO T903:2011) as follows:

DFI = 1 + *f ;-^ ^B > Eq. (2) where, μd(S) is the average dynamic friction coefficient of test oil, μd(A) is the average dynamic friction coefficient of high friction reference oil (JAFRE-A11), μd(B) is the average dynamic friction coefficient of low friction reference oil (JAFRE-B 11).

[0045] Figure 9 depicts a method 900 of testing a lubricant. The method involves 950 - providing a test assembly comprising a lubricant bath with a lubricant therein, a friction plate and a friction arm, and 952 - applying a load to the friction plate with the friction arm and selectively moving the friction plate according to a test operation. The test operation includes at least one dynamic friction test having a dynamic speed and at least one static friction test having a static speed. The dynamic speed includes increasing from the static speed to a maximum speed and then decreasing from the maximum speed to the static speed. The method also involves 954 - measuring at least one test parameter during the test operation. The test parameter comprises a coefficient of friction.

[0046] The method may also involve 956 - determining a static friction index and a dynamic friction index from the measured at least one test parameter, 958 - identifying the lubricant from the static friction index and the dynamic friction index, and/or 960 - examining a test strip positioned on the friction plate during the test operation. An additive may optionally be provided either by adding an additive, or providing a lubricant with a different additive. The method may be performed in any order, and repeated as desired. [0047] While the embodiments are described with reference to various implementations and exploitations, it will be understood that these embodiments are illustrative and that the scope of the inventive subject matter is not limited to them. Many variations, modifications, additions and improvements are possible. For example, one or more test cycles with various combinations of constant and/or variable test parameters (e.g., temperature, load, speed, composition, etc.) may be provided.

[0048] Plural instances may be provided for components, operations or structures described herein as a single instance. In general, structures and functionality presented as separate components in the exemplary configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements may fall within the scope of the inventive subject matter.