The gearbox is the core component of the tractor chassis. At present, tractors mainly use fixed shaft gear boxes, which are simple in structure and low in manufacturing cost, but have complex operation processes and high labor intensity for drivers. The gearbox of Dongfanghong LX904 tractor in China has 12 forward gears and 4 reverse gears. Each gear of the main gearbox has a pair of helical gears that mesh with each other. The gear is replaced by a gear shift sleeve. The gearbox of Dongfanghong-C1302 tractor has 6 forward gears and 2 reverse gears, of which the forward gear is shifted by an engaging sleeve and the reverse gear is shifted by a sliding gear. TG series tractors of New Holland Company abroad adopt fixed shaft full power shift gearbox, which is composed of a main gearbox and a pair of gearbox in series, with 24 forward gears, 6 reverse gears and a creeper gear. The T7300 transmission produced by ZF Friedrich shafen is a semi power shift transmission. It includes crawl gear area and 6-speed main transmission area. The creeper gear area has two gears: normal gear and creeper gear, which are manually operated; The six speed main gearbox adopts synchronizer for shifting and is also manually operated. These gearbox layout schemes often arrange different gear pairs on the shaft in turn to achieve multiple transmission ratios. In order to meet the various operating conditions and road conditions required by the tractor, the gearbox often needs a large range of gear selection. In order to achieve the purpose of multi gear, the gearbox generally increases the gear number by adding gear pairs or gearshift mechanisms, which makes the gearbox occupy a larger and larger volume on the tractor. This not only increases the weight of the tractor, but also makes it impossible to simplify the structure of the tractor.
In addition, most of the gears used in the existing gearboxes are ordinary cylindrical gears, which are easy to be damaged due to impact when they are engaged, resulting in inaccurate transmission. The power transmission of the end gear is more stable due to its large coincidence. The end face gear is commonly used in the transmission device of two-phase cross axis or two-phase staggered axis with 90 ° angle or non 90 ° angle, and is mainly used in the end face gear transmission of standard straight teeth or spiral teeth with heavy load and long service life. Because of its excellent performance, the end gear is widely used in helicopters, instruments, fishing reelers and other devices. In the helicopter, the transmission device uses the end gear, which reduces the weight by about 40%. In addition, because of the large coincidence of the end gear, the power transmission is more stable, the vibration and noise are less, and it plays an important role in the torque decomposition. It is proved that face gear has unique advantages in power transmission.
To sum up, this gearbox will abandon the sequential arrangement of traditional cylindrical gears on the shaft and change to a planetary gear train composed of four end face gears and planetary carrier. This combination, coupled with the clutch, brake and other torque transmission devices, can achieve eight transmission ratios, reduce the size of the gearbox, improve the bearing capacity, and transmit power smoothly, effectively solving the problems commonly existing in existing tractors mentioned above. In addition, a planetary gear train is set as the auxiliary transmission, and a 16+8 gear transmission can be formed by using the combination of the two in series to meet the requirements of multiple transmission ratios of the tractor.