2018-01-1228 Published 0 3 Apr 2018 © 2018 SAE International. All Rights Reserved.Modelling of Power Losses of Transmission Synchronizers in Neutral Position Ye Shen and Zhihong Liu IMS,Technische Universität Darmstadt Stephan Rinderknecht TU Darmstadt Citation: Shen, Y., Liu, Z., and Rinderknecht, S., “Modelling of Power Losses of Transmission Synchronizers in Neutral Position,” SAE Technical Paper 2018-01-1228, 2018, doi:10.4271/2018-01-1228. Abstract Developing an energy-efficient powertrain system is a solution for environment-friendly vehicles. Furthermore, it also enhances the performance of vehicles. In powertrain system, transmission plays an impor - tant role in terms of vehicle dynamic performance and energy consumption. Therefore, a lot of researches have been conducted on modelling power losses inside the transmission. Basically, the power losses in transmission consist of bearing losses, drag torque losses on gear blank that is immersed in the oil and gear mesh losses due to the sliding frictional force on gear flank. According to some experiments in the latest literatures, power losses of synchronizers cannot be neglected, when its shift sleeve is in neutral position. Principally, power losses of synchronizers in neutral position mainly come from load independent drag torque. The drag torque is generated by the shear torque of lubrication in the gap (or gaps) between synchronizer ring and synchronizer cone, which are rotating at different speed. In this paper, a drag torque model of synchro - nizer units in neutral position is built up based on mechanism of tribology lubrication. Several factors are considered in the model, for example, synchronizer geometry (cone angle, face width, etc.) and lubrication factors (viscosity, oil volume, etc.). Furthermore, the power losses of synchronizer under different oil injection methods are considered and separately discussed in the paper. In the end, validations are conducted. The ampli - tude and tendency of simulation results agree well with test data. In the future, the model of synchronizer power losses in neutral position will be further modified and it is planned to apply it into a study case for a manual transmission. Introduction Recently, the use of renewable energy is encouraged to solve the climate-related problem, such as pollution and global warming. Therefore, many efforts have been made in this direction. In the field of vehicle engineering, the main concentration is on innovative powertrain with clean energy, for example, pure-electric vehicle or hybrid electric vehicles. Energy consumption of powertrain is also one of important performance criteria of these new vehicles, besides those of traditional vehicles. For example, many control strate - gies for hybrid electric vehicles are developed based on the efficiency character map of powertrain systems, in order to reduce energy consumption [ 1]. The transmission is one of the most vital components in the powertrain and plays a role in vehicle performance in terms of vehicle dynamic performance and energy consumption. Thus, many researches are conducted in direction of modelling the efficiency of transmis - sions based on the calculation of power losses inside the transmission. Generally, overall transmission power losses  P V are divided into load-dependent power losses and load-indepen - dent power losses [ 2], which are sum of component power losses in transmission. In Equation (1) , PVZP refers to the gear load dependent power losses that are evoked mainly by the friction related mechanical power losses in gear meshing [ 3]. PVZ0 is gear load independent losses, which is due to spinning gear pairs that are bathed in the lubricant oil or surrounded by an oil-air-mixture, like oil churning losses [ 4]. The equa - tions for calculating the power losses of the bearings  P VLP and PVL0 are given out by some manufacturers [ 5]. Sealing losses PVD can be found in ISO standard [6 ]. PP PP PP P VV