Clutch engagement judder and stick—slip are investigated analytically and numerically to examine the influencing factors on these phenomena. Models are developed for a four degree-of- freedom (4DOF) torsional system with slipping clutch and for a powertrain with automatic transmission system. Stability analysis is performed to demonstrate that clutch judder is dependent on the slope of the friction coefficient and the analysis is verified with numerical simulations. An algorithm for modelling stick—slip is developed and is used in numerical simulations which show that the likelihood of stick—slip is increased by clutch pressure fluctuations, judder approaching engagement, and external torque fluctuations. Numerical simulations for second to third gear up shifts demonstrate that the likelihood of stick—slip to occur from clutch engagement is increased by clutch applied pressure fluctuations, judder approaching engagement, and external torque fluctuations and that the likelihood of stick—slip occurr...

Analysis and simulation of clutch engagement judder and stick-slip in automotive powertrain systems:

A finite element model has been developed to investigate the engagement of rough, grooved, paper-based permeable wet clutches. The finite element (Galerkin) approach was used to discretize the modified Reynolds and force balance equations, and the solution domain geometry was described using an isoparametric formulation. Surface roughness effects were modeled via the Patir and Cheng (1978) average flow model, while asperity load sharing was calculated using the Greenwood and Williamson (1966) approach. The finite element model developed was used to investigate the effects of applied load, friction material permeability, and groove size on the engagement characteristics of wet clutches (i.e., torque, pressure, engagement time, and film thickness). The results indicate that the applied load, friction material permeability, and groove width significantly influence the engagement characteristics. Higher facing pressures increase peak torque and decrease engagement time. Higher permeability of the friction material significantly decreases engagement time but dramatically increases peak torque. Wider grooves decrease the peak torque and increase the engagement time. Groove depth does not significantly affect engagement characteristics for this model.

Finite Element Modeling of Engagement of Rough and Grooved Wet Clutches

The tribological behaviour of paper friction plates for wet clutch application investigated on SAE#II and pin-on-disk test rigs

A simple mathematical model for the engagement of rough, permeable, grooved wet clutches has been developed and used to determine the effect of various input parameters (applied load, grooved area, and friction material permeability) on engagement The model includes the effects of surface roughness according to Patir and Cheng (1978), friction material permeability according to Natsumeda and Miyoshi (1994) and Beavars and Joseph (1967), and grooving in the friction material according to a new approximation The approach reduces the system ofReynolds and force balance equations to a single, first-order differential equation in film thickness and time A line searching algorithm, exploiting the low computational cost of function evaluations for the new model, is used to find the set of input parameter combinations yielding the same engagement characteristics This set of design points is presented as an engagement isosurface in the parameter space (F app , Φ, A red ) The isosurface implicitly gives information about engagement time, and it shows regions in which the desired engagement characteristics cannot be achieved The input parameters are classified as those affecting the transient portion of engagement and those affecting the steady-state portion

Analytical and Numerical Modeling of Engagement of Rough, Permeable, Grooved Wet Clutches

For a wet clutch in an automatic transmission to operate efficiently and smoothly, it is essential that the friction in the clutch contact be high over the whole sliding speed range and also increase with sliding speed. This is achieved by careful design, both of the friction disc material and morphology and of the automatic transmission fluid. This article describes the development and use of a new test rig, based on a mini-traction machine (MTM), to measure the impact on wet clutch friction versus sliding speed properties of a range of additive solutions as well as a fully formulated automatic transmission fluid (ATF). It is found that most organic friction modifiers reduce friction at low sliding speed, whereas succinimide dispersants and some sulfonate detergent additives raise friction over the whole speed range. Overbased and neutral detergents give almost identical friction curves, indicating that, although a calcium carbonate film is deposited on the steel ball when overbased detergent is present,...

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Frictional Properties of Automatic Transmission Fluids: Part II-Origins of Friction-Sliding Speed Behavior

The coefficient of friction of paper-based facing for a wet clutch was determined under a variety of sliding conditions. It is important to investigate the transitional friction characteristics of ...

Friction Characteristics of a Paper-Based Facing for a Wet Clutch Under a Variety of Sliding Conditions

In analyzing the crack problems under the contact loading condition, the pressure distribution on the contact region is usually assumed to be distributed elliptically. However, the existence of the cracks may require some modifications of the well-known Hertz's theory which expresses the relationship between the distribution of the contact pressure, the contact width, the total load of the indentation and the radius of curvature of the indenter. In this paper, a computational method for the cracks in a half-plane under the contact loading condition is developed with consideration to effect of the cracks on the contact pressure distribution. In this method, the continuous dislocations model is employed. From the results of the numerical calculations, it is concluded that when the crack is not small and is located near the contact area, Hertz's theory does not give a sufficiently accurate contact pressure distribution. Presented as a Society of Tribologists and Lubrication Engineers paper at the STLE/ASME T...

Effect of Cracks on the Contact Pressure Distribution

In this study, contoured nanostripe (CNS) surfaces were fabricated and their friction properties were examined. First, shot blasting was carried out on stainless steel substrates to form shallowly and deeply dented substrates, which had random asperities. Next, multilayer films of Ag and Cu were deposited on each substrate, which was then polished to form contoured nanogrooves. The friction properties of the CNS surfaces were evaluated under lubricating conditions using a ball-on-plate-type reciprocating friction tester. Random asperities coated with Ag or Cu were also evaluated as reference. An Al2O3 ball was used as the counter specimen. The CNS surfaces were found to have low friction coefficients. In particular, the surface fabricated on the deeply dented substrate showed the highest durability, and CNS patterns clearly remained on this surface after the friction tests.

Hironobu Ito

Papers

Friction Characteristics of a Paper-Based Facing for a Wet Clutch Under a Variety of Sliding Conditions

Effect of Cracks on the Contact Pressure Distribution

Fabrication and Lubrication Properties of Contoured Nanostripe Surfaces

Estimation on Wear Damage Process of Poly-Vinyl-Alcohol Gel Surface with Particle Analysis

Mechanism of Negative Pressure Generation in the Sliding Process of Paper-based Wet Frictional Material