ENGINEERING FOR RURAL DEVELOPMENT Jelgava, 23.-25.05.2018. 1955 TRANSMISSIONS WITH THREE POWER-FLOWS FOR TRUCKS AND TRACTORS Konstantin Salamandra Mechanical Engineering Research Institute of the Russian Academy of Sciences, Russia ksalamandra@yandex.ru Abstract. Trucks, agricultural machinery and tractors are equipped with transmissions consisting of main 3- speed or 4-speed gearbox with fixed axles of gears and a planetary splitter and/or a planetary range change unit. These planetary gear sets reduce the rotation speed or work in direct gear depending on the driving conditions of the machine. The splitter and range change unit are also providing up to 4 times extension of the number of gear ratios realized by transmission. If the planetary gear set in such transmissions will work as differential drive, it will allow increasing the number of gear ratios in the combined planetary-layshaft transmissions and the number of operating regimes of the tractor consequently. As a result, the gears with fixed axles can work separately in one-stream operation mode of the planetary gear set (reducer or direct gear) and in a two-stream mode - in parallel with other layshaft gears, when the planetary gear set is working as a differential drive. It was shown that combined two-stream planetary-layshaft transmissions consist of simple gear trains, have high efficiency and provide more overall gear ratios, if compared with transmissions consisted of the gear trains of one type. Two planetary gear sets operating as differential drives increase the number of parallel power-flows to three, which allow further improvements of the functionality of transmissions. In addition, if in two-stream transmissions 50- 60 % of the input power is transmitted along the paths, then in three-stream transmissions this percentage is reduced by a factor of 1.5 or 2. The purpose of the paper is to analyse structural schemes of planetary-layshaft transmissions with three power-flows, to determine their general characteristics and to develop a method for synthesis of the kinematic diagrams of these transmissions. Keywords: transmission, synthesis, planetary gear, gear with fixed axle, multi-stream. Introduction The best way to reduce the fuel consumption and improve the automotive efficiency is to reduce the speed range of the internal combustion engine used [1-3]. In order to maintain the required operating speed range of the automobile, it is necessary to increase the number of overall gear ratios in the transmission. Trucks, agricultural machinery and tractors are equipped with transmissions consisting of main 3-speed or 4-speed gearbox with fixed axles of gears and a planetary splitter and/or a planetary range change unit [4; 5]. These planetary gear sets reduce the rotation speed or work in direct gear depending on the driving conditions of the machine. The splitter and range change unit are also providing up to 4 times extension of the number of gear ratios realized by transmission. As it is known [4-7], the planetary gear set consists of three members and in dependence on their linkages has the following three operating modes. 1. Differential drive – converts the motion of two input members into the motion of one output member (summing gear) or the motion of one input member into the motion of two output members (differential gear). 2. Reducer or multiplier – when one member is fixed. 3. Blocked, rotates as a single unit with direct gear, when any two members are connected with each other. In the transmissions of trucks and tractors, the planetary gear of the splitter or the additional gear operates only in modes 2 and 3. Mode 1 is used in planetary transmissions and in hybrids to divide or sum up the power flows of the internal combustion engine and electric motor [4; 5; 8; 9]. In [10] it is shown that the use of the planetary gear set as a differential drive in transmissions with fixed axles of gears makes it possible to obtain simple transmissions designs, which have high efficiency and a greater number of speeds than transmissions consisting of single type of gears. A greater number of speeds is achieved by changing the mode of operation of the planetary gear set and gears with fixed axles, which allows the latter to work both separately in the one-stream mode of operation of the planetary gear set (reducer or multiplier) and in parallel with other layshaft gears in two-stream mode. Using the terminology [11], the obtained transmissions are called two-stream by the number of parallel power-flows from the input shaft to the output one. A method for the synthesis of kinematic diagrams was developed in [10], with the help of which a group of new designs of two- stream transmissions were obtained [10]. DOI: 10.22616/ERDev2018.17.N010