Experimental investigation of the cryogenic properties of automatic mechanical transmissions

Abstract

A control variable method was used to study experimentally the properties of automatic mechanical transmission actuators under cryogenic running conditions. Only one temperature variable was changed during the experiment so as to facilitate the comparison between the impacts of the temperature on the execution characteristics of actuators. From a series of cryogenic experiments and data analysis, the cryogenic characteristic curves (e.g. for the clutch, for the throttle, for gear selection and for putting the automatic mechanical transmission into gear) were drawn, providing guidance for subsequent temperature compensation control methods. In addition, given that the phenomenon in which the clutch and the shift gear in the automatic mechanical transmission control system seized up at −40 °C, a cryogenic thawing strategy was then added to the automatic mechanical transmission control system. The results show that this cryogenic thawing strategy can effectively reduce the starting and running resistances of the automatic mechanical transmission at low temperatures, enabling vehicles equipped with the automatic mechanical transmission control system to operate normally at −40 °C and thus enhancing the reliability of these vehicles in low-temperature operation. The present temperature compensation control method and the cryogenic thawing strategy are of great significance for improving the reliability and security of automatic mechanical transmission control at low temperatures.