Study on origin of shudder under slip control of a lock-up clutch in an automatic transmission (part 2) : Relationship between friction characteristics under shudder and adsorption of additives

μ-V characteristics in the process of shudder convergence were measured by introducing slip controlling ATF mixed with shudder preventive additive into a simple device for testing lock-up clutches provided with life-size damper and operating the lock-up clutch under conditions where shudder generated rather easily. Also, combining the above clutch with ATF, the maximum coefficient of friction (μs) in sliding tests and the effect of the time of exposure performed before sliding tests were determined. As a result, it was found that the absorption of shudder preventive additive in the case of sliding under applying pressure to the facing led to the activation, but when the sliding interruption time and that of the lock-up release state exceeded a certain interval, the absorbed additive exfoliated and lost its functionality. In addition, appropriate environmental temperature conditions necessary for the activation of absorbed additive were clarified.