Research on the shift strategy of HMCVT based on the physical parameters and shift time

• This paper focuses on the shift strategy of a typical working condition of HMCVT.
• Shift quality can be improved greatly by the optimization of physical parameters and shift time.
• The optimization scheme based on physical parameters and shift time can be obtained.

This paper focuses on the shift strategy of HMCVT (Hydro-Mechanical Continuously Variable Transmission). A kinetic model for HMCVT is deduced on the basis of transmission theory, and the ITI simulation model is used to study the shift strategy based on the physical parameters and shift time. There are 4 typical working conditions in the continuous shift process, and the shift process from Fi(N) to Fi+1(P) and from F(H) to F1(P) play decisive roles in the shift quality. Simulations are performed to analyze the shift strategy based on the physical parameters and shift time under the working conditions of F2(N)→F3(P) and F(H)→F1(P), which are the most typical conditions. Speed drop amplitude, dynamic load coefficient, maximum degree of shock, and shift time are regarded as evaluation indexes; physical parameters (engine rotating speed, load torque, main circuit pressure, speed valve flow rate) and shift time (switch time of clutches) are considered as the influencing factors of shift quality; the orthogonal test method (including the range method and the variance analysis method) is used to solve the control strategy problems by simulation study and experimental verification. The results show that there are some differences in the shift strategy based on the physical parameters and shift time of the two typical conditions. In the shift process from F2(N) to F3(P), the shift strategy based on the physical parameters is the lower engine rotating speed, smaller load torque and main circuit pressure, and larger speed valve flow rate, the shift strategy based on the shift time is that switch L6 and L7 firstly, then disengage L1 and L3, engage L2 and L4 lastly. In the shift process from F(H) to F1(P), the shift strategy based on the physical parameters is the lower engine rotating speed, smaller main circuit pressure, and larger load torque and speed valve flow rate, the shift strategy based on the shift time is that switch L2 and L8 at first, then engage L4, L5 successively.