SA E TECHNICAL PAPER SERIES ATF Characteristics Required for the Latest Automatic Transmissions Ryo Ashi kawa, Toshitaka Naruse, and Hideo Kurashina Mitsubishi Motors Corp. Tohru Matsuoka, Takao Adachi, and Takeo Nakayama Mitsubishi Oil Co., Ltd. The Engineering Society Fuels and Lubricants EA =For Advancing Mobility Meeting and Exposition w~and Sea Air and Space@ INTERNATIONAL Philadelphia, Pennsylvania October 18-21,1993 400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (41 2)776-4841 Fax:(412)776-5760 Downloaded from SAE International by Imperial College London, Thursday, August 09, 2018Downloaded from SAE International by Imperial College London, Thursday, August 09, 2018ATF Characteristics Required for the Latest Automatic Transmissions Ryo Ashikawa, Toshitaka Naruse, and Hideo Kurashina Mitsubishi Motors Corp. Tohru Matsuoka, Takao Adachi, and Takeo Nakayama Mitsubishi Oil Co., Ltd. ABSTRACT This paper examines the anti-shudder property of automatic transmission fluid (ATF) in terms of evaluation criteria and durability. The anti-shudder property is required for precise slip control around the clutch in that kind of automatic transmission, applicatio~ls which are currerltly increasing. To evaluate anti-shudder properties, friction characteristics are measured by modified Low Velocity Friction Apparatus (LVFA), and the data are compared with those from the actual vehicle. The ar~alysis confirms that the occurrence of shudder on the vehicle is closely related to the ratio of the static friction coefficient to the dynamic one measured by modified LVFA. INTRODUCTION Over 70% of compact cars running on Japanese highways today are equipped with automatic transmissions. This implies that improvement in fuel economy in automatic transmission is an essential requirement for the industry, since such vehicles are considered to consume nearly 10% more fuel than those equipped with manual transmissions. It is well known that tlie poor fuel economy of vehicles with automatic transmissions results mainly from the slippage in the torque converter, which is particularly noticeable at low-speeds. 1 I It is a common practice to improve fuel economy in the conventio~~al automatic trarismissions by locki~ig-up the torque co~lverter i11 the engine-speed range where the torque converter is operated virtually as the complete coupling range. Large-sized springs are installed within the converter to absorb the crankshaft speed fluctuation when tlie clutcli is locked-up. With conventional automatic tra~lsmissions, it is not practical to achieve lock-up in the low speed range where the required slippage occurs to convert the input torque. In this case, the fluctuation in the output-shaft speed is larger, due to poor absorptio~i of the crankshaft speed fluctuation in the torque converter. Thus, consequent slip- loss under urban cruise has been left to further improvement. 111 due co~isideration of such a condition, we have employed a new lock-up clutch-control system i11 automatic transmissions, which provides a minimal slip to the lock-up clutch of the torque co~lverter by electronic control in order to absorb the fluctuation in the output-shaft speed, while minimizing the slip-loss of the torque converter at low-speeds, so tliat tlie fuel economy in urban driving can be improved. 1) This system, however, is susceptible to shudder and consequently requires ATF and friction materials which provide the suitable friction characteristics. This paper is to i~ltroduce tlie methods of evaluating the anti-shudder property and the durability of ATF in this system. OUTLINE OF LOCK-UP CLUTCH AND CONTRIBUTION TO FUEL ECONOMY SHUT-OFF MECHANISM FOR OUTPUT-SHAFT FLUCTUATION - tlie revolution of tlie crankshaft in the engine fluctuates minutely due to the combustion condition and the inertia of the maill moving parts in tlie engine. Theoretically, if an ATF arid fiict