Optimization Method of Speed Ratio for Power-Shift Transmission of Agricultural Tractor

Abstract

The speed ratio parameters of transmission are crucial factors that affect a vehicle’s power, economy, and comfort. Due to the complex working conditions, multiple working modes, and wide range of speed ratios of agricultural tractors, designing and optimizing speed ratio parameters in power-shift transmissions is a challenging task. This paper proposes a transmission speed ratio optimization method based on the life cycle speed utilization rate of general-purpose agricultural tractors. The speed ratio parameters are optimized and solved using the genetic algorithm, with multi-gear power-shift transmissions in agricultural tractors as the research subject. The optimization results and simulation analysis show that the optimized speed ratio has more and denser gears in the common operating speed range while ensuring the general-purpose agricultural tractors’ use requirements. Compared to commonly used geometric series speed ratios, tractors using the optimized speed ratio parameters in this paper can significantly improve fuel economy. Most importantly, this provides a practical method reference for optimizing speed ratios in multi-gear gearboxes with complex structures.

Optimization of Shifting Quality for Hydrostatic Power-Split Transmission with Single Standard Planetary Gear Set

“…Afterwards, transmission manufacturers began to introduce various concepts of tractor CVTs [8,9], such as the Eccom produced by ZF and the Autopowr produced by John Deere. The above-mentioned transmissions all adopt multi-range technology to achieve continuous speed adjustment [10][11][12], so it is necessary to conduct research to improve the quality of the shift [13][14][15], including changing the gear ratio, the clutch engagement time, and the displacement ratio of the swash plate axial piston units. For tractors with heavy load operations such as plowing as their main operating conditions, while paying attention to their riding comfort we also need to consider issues such as power interruption and clutch damage, all of which are important criteria for evaluating the shifting quality.…”