Research On Characteristics Of The Hydro-Mechanical Continuously Transmission Used On The Unroad Vehicle

Hydro-mechanical Continuously Variable Transmission short for HMCVT, contains double flow of power to achieve CVT, one of which is hydraulic power flow able to control speed variable transmission and the other of which is mechanical power flow. The transmission used in the high-power vehicle on non-road can not only improve its dynamic performance and fuel efficiency, but also reduce the complexity of the actual operation dramatically. The object of this paper is the HMCVT box designed and developed independently. According to the in-depth study of HMCVT comprehensive features, the following work is accomplished:1. The principle of HMCVT is introduced, and the design on the tractor HMCVT of our team is analyzed. With the analytical method, a detailed analysis is taken on, consisted of the speed, torque and the characteristics of power flow&power cycle during the drive of HMCVT.2. Based on the software platform of AMESIM, the model of HMCVT vehicle is established, including the subsystem model of the hydraulic drive system, mechanical drive, engine, gearbox load, wet clutch and so on.3. The continuity of the model is simulated to verify whether the design of HMCVT is able to transmit continuously and meets the geometric nature requirement and analyze reversely the reasons of the hydraulic pressure change during the reflux and shift of the hydraulic power. The dynamic characteristic of variable displacement start acceleration vehicle in pure hydraulic segment and variable throttle acceleration the in hydro-mechanical high-speed segment is simulated, which analyzes the acceleration time impact on the dynamic characteristics of the overall system and offers a selection of the best acceleration time on corresponding load.4. Dynamic characteristics of HMCVT on step load excitation is studied to analyze the relationship between pump displacement, hydraulic system oil volume&the rate of change of the pump displacement, and gearbox output shaft dynamic load factor&the time of dynamic load torque duration. The research on shift characteristics of HMCVT is taken on to analyze the pressure and flow of the wet clutch influence on the quality of the shift.5. The test platform of HMCVT is built, the parts are assembled and debugged, the measurement and control system is developed based on Lab VIEW, and the experimental study on dynamic characteristics of HMCVT is carried on.Through research on the project, a solid foundation for structure optimization design and control strategy in run-time is provided. It is significantly valuable both in theory and in practice to promote the popularity of HMCVT in the vehicle and to improve vehicle dynamics, shift stability, economy and so on.