Fundamentals of Anti-Shudder Durability: Part II - Fluid Effects

Devlin, Mark T.; Li, Shoutian; Tersigni, Samuel H.; Turner, Tu Lai; Jao, Tze‐Chi; Yatsunami, Kenji; Cameron, Timothy M.

doi:10.4271/2003-01-3254

Cited by 22 publications

(9 citation statements)

References 26 publications

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“…For example, Newcomb et al [9] developed a methodology to evaluate worn or damaged friction material plates. Devlin et al [10] investigated the loss of friction control in automatic transmissions, a result of stick-slip and shudder, when samples age. The samples were aged both in a test rig and by oxidation of the oil.…”

Section: Introductionmentioning

confidence: 99%

Lubricant ageing effects on the friction characteristics of wet clutches

Berglund

Marklund

Larsson

2010

Proceedings of the Institution of Mechanical Engineers, Part J:

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The friction characteristics and performance of wet clutches have been investigated by several authors. Studies have also been made to understand the frictional performance during the service life of the clutch system. However, most lifetime studies have been conducted for systems with paper-based friction material so that systems using sintered bronze friction material remain largely unexplored. To study the friction performance of how these systems can vary over time, the friction characteristics for a clutch system using lubricants aged in three different ways were compared. The effects on friction characteristics resulting from oxidation of the lubricant, reduced additive concentration, and ageing under real operating conditions in a wet clutch test rig were studied.The oxidation effects on friction characteristics were examined using a modified waterless turbine oil oxidation stability test on a fully formulated lubricant. Five oxidation time periods from 48 to 408 h were investigated. For each period of oxidation, a friction performance test was run using a pin-on-disc machine.The ageing carried out in a wet clutch test rig is a standard test of a wet clutch systems manufacturer which is used in order to verify that an oil-friction disc combination will last the full service life of the specific application. This test gives a realistic ageing process similar to that in a wet clutch in a field test.Under boundary-lubricated conditions, additives are vital to the performance of wet clutches. Therefore, the effect of reducing the additive concentration in the oil was also studied, in the range of 10 to 100 per cent of the original additive package used in the fully formulated wet clutch lubricant.Results showed that a general friction increase can be observed for oxidation, additive reduction, and test rig ageing. It was also concluded that different methods of simulating the wet clutch ageing process differ and cannot be directly correlated with each other.

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Section: Introductionmentioning

confidence: 99%

Lubricant ageing effects on the friction characteristics of wet clutches

Berglund

Marklund

Larsson

2010

Proceedings of the Institution of Mechanical Engineers, Part J:

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“…The continuous sliding, ATF degradation, surface flattening, and glazing of the friction plates may generate reduction of torque transmission capacity, but also undesirable self-excited vibrations by stick-slip effects, which is named as "shudder " [4]. It has demonstrated that shudder may occur when friction coefficient, , in the clutch plates decreases as the sliding speed, ν, increases, so a positive slope, d/dv, therefore needs to be maintained in curves of friction coefficient versus sliding velocity (μ-ν) to prevent shudder, in particular, in full scale tests since it depends on many factors included in the torque convertor operation [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Influence of oxidation of automatic transmission fluids (ATFs) and sliding distance on friction coefficients of a wet clutch in the running-in stage

et al. 2020

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In this paper, the influence of oxidation of automatic transmission fluids (ATFs) and sliding distance on the friction coefficients of a wet clutch in approached running-in conditions was investigated. The ATFs were oxidized by a laboratory process approaching oxidation occurred in actual ATFs. Oxidation was evaluated by means of increase in carbonyl compounds and depletion of zinc dialkyldithiophosphates (ZDDPs) additives. Also, the changes in kinematic viscosity and viscosity index were evaluated. Pin-on-disk tests were conducted to replicate the actual sliding contact in a wet clutch. The pin specimens were cut from friction material composite plates and the disks were actual steel separators both from an automotive wet clutch. Friction coefficient, μ, was measured at progressive sliding velocity, ν, to obtain μ-ν curves at 26 and 100 ΰC. Three μ-ν tests were consecutively run using the same pair of specimens and oil. The cumulative sliding distance for each μ-ν test generated surface flattening using the oils. The friction coefficients of the wet clutch increased due to the ATFs oxidation meanwhile the dμ/dυ values decreased in most cases. It suggests that ATF oxidation can enhance torque capacity of the wet clutch, but it could reduce anti-shudder property. Progressive sliding distance improved the slopes in the μ-ν results using fresh ATFs meanwhile it generated a slope decrease by using aged ATFs.

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“…JASO established the M349 series standards in the 1990s, which were designed to reproduce conditions seen in the actual CSTCC and to improve the precision of anti-shudder durability testing (Murakami,et al (6); Devlin, et al (10)). Devlin, et al (10), (11) and Li, et al (12) have published a series of papers describing work that they performed on JASO SAE No. 2 and LVFA machines.…”

Section: Introductionmentioning

confidence: 97%

Anti-Shudder Properties of ATFs—An Investigation into Friction Modifying Mechanisms Using VSFT and SAE No. 2 Tests

Zhao

Morina

Neville

et al. 2010

Tribology Transactions

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In recent years, continuous slip torque converter clutches (CSTCCs) have been widely used in automatic transmissions, mainly to improve fuel efficiency. With the adoption of these devices the problem of shudder vibration has arisen. To help alleviate this problem, better anti-shudder characteristics are desired for automatic transmission fluids (ATFs). Positive µ-v curves are well recognized to correlate to the avoidance of shudder. A variable-speed friction tester (VSFT), which combines a low-velocity friction apparatus (LVFA)-type test with the ability to age an oil in situ, was used to determine friction characteristics of four model ATF formulations in a wet clutch tribosystem. The linear-defined multiple parameter spider chart ATF evaluation (LSAE) method was applied to present the ATF's overall friction results including anti-shudder performance and durability (Zhao, et al. (1)). One modified SAE No. 2 test was also used to test the four oils' friction behavior, to compare with the VSFT results. Similar performance rankings have been obtained from those two tests. Both test results and evaluation parameters will be discussed in this article and the response will be linked to the physical parameters defining the posttest surface. The oil absorption ability of post test friction material is shown to be important to the overall friction performance. The environmental scanning electron microscope (ESEM) images and 3D profiling results showed that some surface topographical parameters, such as V vc (void volume of the core) and V vv (void volume of valleys), can be linked with the friction modifying mechanisms in the ATF tests.

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Fundamentals of Anti-Shudder Durability: Part II - Fluid Effects

Cited by 22 publications

References 26 publications

Lubricant ageing effects on the friction characteristics of wet clutches

Lubricant ageing effects on the friction characteristics of wet clutches

Influence of oxidation of automatic transmission fluids (ATFs) and sliding distance on friction coefficients of a wet clutch in the running-in stage

Anti-Shudder Properties of ATFs—An Investigation into Friction Modifying Mechanisms Using VSFT and SAE No. 2 Tests

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