Research and design of micro electric tractor

Liao Yue

Key Words：Research and design of micro electric tractor

1. Introduction

The main function of tractor transmission system is to transmit energy torque to wheels and farm implements. Therefore, it is the basis of tractor driving and working. The power system is composed of transmission system and electric motor. There are many possible structural forms of power system. One of the main ways to solve the problem of torque transmission system design is how to bear the torque of transmission system properly. Compared with other vehicles, tractors have more power output structure, and the continuous torque output is required for traction agricultural machinery operation, which highlights the demand for transmission system control.

2.Overall analysis and design of mechanical transmission

The power transmission of mechanical transmission system of micro electric tractor is pided into two routes. One is the operation route: the power is transmitted to the brake of the power take-off shaft through the transmission shaft, so as to drive the whole power output shaft to rotate and realize the operation requirements. The output shaft of micro electric tractor adopts non independent design, so the front axle drive clutch is added to realize the power control and separation function of real-time operation. The other is the travel route: the power is transmitted to the main clutch, and the power transmission is controlled by the clutch pedal. After the clutch is a torque converter, the torque increaser will decelerate and increase the distance, and the increased torque will be transmitted to the gearbox. The gears with different graduation circle diameters can be meshed through manual shift operation, so as to obtain the speed and torque of the required gear. The devices after the transmission are basically installed on the rear axle of the micro electric tractor, so all the transmission systems behind the transmission can be called the rear axle.

After the transmission of the micro electric tractor is the central transmission on the rear axle. The central transmission further increases the torque and decelerates the power to the differential. The differential transforms the longitudinal power into the transverse power and transmits it to the left and right half shafts. On the half shaft, there is a final transmission reduction gear combination, which further increases the torque and reduces the speed. Finally, the energy is transferred to the left and right driving wheels to drive the micro electric tractor forward.

3.Clutch analysis and design

The main components of clutch are its driving plate, pressure plate and driven plate. The driving plate of clutch is called flywheel, and the driven plate of clutch is often called clutch plate. They are located between the engine and the transmission. When the tractor needs to start or decelerate, pedal the clutch pedal, the oil in the clutch will gush out from the clutch master cylinder, through the driven pipe, directly to the inside of the release pump installed on the clutch housing.

The influx of oil increases the pressure inside the clutch release pump, which makes the piston in the release pump move under pressure. The displacement of the piston will drive the ejector pin, which in turn will push the clutch to move. The fork is connected with the clutch assembly through the release bearing, and the displacement of the plug will move the driven plate of the clutch. Make a certain distance between the driving plate and the driven plate. By controlling the depth of pedal clutch pedal, the piston in clutch pump can be provided with different degrees of pressure. The different displacement distance of the clutch plate driven by the fork determines the degree of power transmission between the driving plate and the driven plate, so as to adjust the speed of the transmission shaft or power output shaft, and realize the ability to control the forward speed and output load of the micro electric tractor.

When the driver presses the pedal lightly, the return spring will automatically act to make the pedal return. At this time, the clutch master cylinder and clutch slave cylinder will lose the external pressure and be pushed by the clutch fork lever. At the same time, the clutch bearing and bearing seat will return to their original position, and the gap between the clutch plate and the flywheel due to opening will disappear. The clutch plate and clutch pressure plate will be pressed on the flywheel again, and the function of transmitting kinetic energy of the clutch will be restored. The driver controls the distance between clutch plate and flywheel by controlling the degree of pedal release, so as to control the degree of power transmission, so as to achieve the effect of tractor speed increase. When the clutch pedal is completely released, the flywheel and clutch plate are in a tight state, and the power will be transmitted to the transmission shaft.

4.Analysis and design of reducer

The reducer of micro electric tractor is the core part of the transmission system of micro electric tractor. Including micro electric tractors, common agricultural vehicles such as trucks, buses, light trucks and heavy trucks basically adopt a set of transmission system design, that is, after the clutch gearbox, the kinetic energy is transmitted to the reducer assembly by the transmission shaft to realize the functions of torque increasing, deceleration and reversing. The reducer assembly is the core part of the rear axle of the micro electric tractor. The design of the reducer assembly will affect the overall design performance of the transmission system of the micro electric tractor. In fact, the reducer assembly can be pided into two parts: the central transmission and the differential. Its internal parts are mainly composed of several types of bevel gears. The reduction function of the reducer mainly depends on the action of a pair of bevel gears with large difference in the diameter of the indexing circle. The driving gear of the bevel gear is a small gear, and the driven gear is a big gear. They are also often referred to as the big and small eight character wheels. The large bevel gear has 39 teeth and the small bevel gear has 7 teeth. Therefore, it is also called big and small eight character wheel.

The transmission output power is transmitted to the driving bevel gear through the transmission shaft, and the driving pinion is meshed with the big gear. Because of the same linear speed, the difference of gear radius leads to the change of angular velocity transmission, which plays the role of deceleration and torque increase. The power is transmitted to the differential inside the reducer housing through the driven big tooth bevel gear.

When the micro electric tractor is running straight, the bevel gear with big teeth of the main reducer will drive the differential housing to rotate. At this time, the planetary gear only rotates in revolution and is not automatic. Therefore, the speed allocated to the left and right half axle gears will be the same. The rotation speed of the rear drive wheel of the micro electric tractor will be the same. When the micro electric tractor needs to turn, the planetary gear inside the differential will also carry on the autobiography in revolution. The function of autobiography mainly depends on the cross axis. The planetary gear will rotate along the axis of the cross shaft, which will lead to the increase of the linear speed of the half shaft gear on the other side of the steering, and the linear speed of the half shaft gear in the steering direction will become slower, thus realizing the speed difference between the two driving wheels of the micro electric tractor and helping the micro electric tractor to turn.

5.Conclusions

Through the analysis and design of the transmission system of the micro electric tractor, the feasibility of developing the small-sized electric tractor by using the switched reluctance motor is verified theoretically. The detailed analysis of various parts and systems of the transmission system is expected to contribute to the mechanical research of pure electric tractor.

References

[1] M N Kornienko, Kornienko M N, Fediakov V V, et al. Electric drive of the generator of the diesel-electric tractor DET-250M2 on the basis of a Field Regulated Reluctance Machine. 2020, 548(3):032039-

[2] Tonghui Li, Bin Xie, Zhen Li, et al. Design and Optimization of a Dual-Input Coupling Powertrain System: A Case Study for Electric Tractors. 2020, 10(5)