A new method to evaluate the overall anti-shudder property of automatic transmission fluids – multiple parameters spider chart evaluation

Zhao, Hongyuan; Neville, Anne; Morina, Ardian; Durham, John; Vickerman, Richard

doi:10.1243/13506501jet375

Cited by 18 publications

(10 citation statements)

References 27 publications

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“…A value greater than 1 for either of these two ratios indicates a negative gradient of the m-v relationship. Zhao et al 6 developed the concept of the friction ratios with five additional parameters, some of which were based on the m-v relationship. Also the durability aspects and the frictional changes with time were taken into account.…”

Section: Introductionmentioning

confidence: 99%

Prediction of driveline vibrations caused by ageing the limited slip coupling

Berglund

Marklund

Lundh

et al. 2016

Proceedings of the Institution of Mechanical Engineers, Part D:

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The prediction of the wet-clutch service life still remains a challenge for scientists and engineers. Previous research has shown the significance of the wet-clutch friction characteristics on the driveline dynamics. To avoid driveline vibrations an increasing friction coefficient with increasing sliding speed is desirable. Consequently, prediction of the occurrence of driveline vibrations relies on a detailed knowledge of how the friction characteristics are affected by wet-clutch degradation, as well as an understanding of the driveline dynamics. Wet clutches are used in both automatic transmissions and all-wheel-drive systems in cars, where they are referred to as limited slip couplings by manufacturers. Wet clutches used in automatic transmissions are subjected to high slip levels, but for very limited time periods. In all-wheel-drive systems, where the limited slip coupling can be used to control the torque transfer to, for example, the rear wheels, the slip levels are low but continuous. Most wet-clutch research has been performed for clutches in automatic transmissions and not for clutches used in all-wheel-drive systems. Thus, a simulation model was developed to evaluate how different operating conditions of the limited slip coupling influence degradation of the friction characteristics and the tendencies towards driveline vibrations. First, the changes in the friction characteristics with the time of ageing are simulated. The friction characteristics after ageing are used as the input to a simplified driveline model, which is used to evaluate the occurrence of vibrations. It is shown how the developed simulation model can be used as an efficient tool for engineers. The developed simulation model can be used to predict how the operating conditions for the limited slip coupling influence degradation of the friction characteristics.

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Section: Introductionmentioning

confidence: 99%

Prediction of driveline vibrations caused by ageing the limited slip coupling

Berglund

Marklund

Lundh

et al. 2016

Proceedings of the Institution of Mechanical Engineers, Part D:

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show abstract

“…Zhao et al [8] then introduced new methods and parameters to be used to evaluate the μ−v relationship. The friction versus velocity curve was analysed not only on the principle of friction coefficient ratios, but a more systematic approach to analyse the whole curve was used.…”

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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“…2 test and therefore contribute to the better overall lubrication and lower overall friction as in the left side of Eq. [1]. Three oil formulations (II.2, II.3, and II.4) with friction modifiers showed obviously lower average µ in SAE No.…”

Section: Lubrication Comparison Between Vsft and Sae No 2 Testsmentioning

confidence: 90%

“…Three specific temperatures (40, 90, 120 • C), three specific plate surface pressures (273, 683, 1,044 kPa), and 14 specific rotational speeds (1,2,4,8,16,24,30,40,70, 80, 100, 135, 170, 235 rpm) were used in the test procedure ( Table 3). The bulk fluid temperature was controlled to be within ±3 • C of the set point throughout the entire test.…”

Section: Clutch Plate In Sae No 2 Testmentioning

confidence: 99%

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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A new method to evaluate the overall anti-shudder property of automatic transmission fluids – multiple parameters spider chart evaluation

Cited by 18 publications

References 27 publications

Prediction of driveline vibrations caused by ageing the limited slip coupling

Prediction of driveline vibrations caused by ageing the limited slip coupling

Lubricant ageing effects on the friction characteristics of wet clutches

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

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