This article shall explore the characteristics of hydro-mechanical transmission in power shift. Based on the double brakesoverlapping, the adjustment of the displacement ratio of variable-displacement hydraulic component is considered, andthen a new full power shift method is proposed. Models respectively for speed, torque, and power in the power shiftprocess are built. The ideal power shift timing is deduced, with the ratio between speed of fixed-displacement hydrauliccomponent and input speed being the criterion. By combining theoretical analysis and experimental studies, it shows thatin power shift process by regulating the displacement ratio of variable-displacement hydraulic component, the interchange between high- and low-pressure sides in closed hydraulic circuit can be completed, and power transition can bethus realized. A new full power shift method is put forward, in which the shift process is divided into five stages: currentrange, prior stable stage, power transition stage, post stable stage, and target range. Experiments on full power shift process prove that the full power shift method is not only feasible but also can remove the rotational speed fluctuation inpower shift process and realize normal full power transmission of output power.
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