1. Rolling resistance. The rolling resistance of the tractor is mainly due to the deformation of the tire and the soil. Under the weight of the tractor, the tire is flattened and the soil is compacted. During the rolling process of the wheel, the various parts of the tire that are in contact with the ground along the circumferential direction are successively flattened and deformed, and the soil that is higher than the front of the wheel is pressed down to deform the soil and form a rut, which hinders the wheel from moving forward. rolling resistance of rolling. There are many factors that affect rolling resistance, mainly related to factors such as the firmness of the ground and the magnitude of the vertical load of the degree of moisture. For the same tractor, if the ground conditions are different, its rolling resistance is also different. For example, if the rolling resistance is small when driving on asphalt and cement or dry and hard ground, the tractor’s traction will be large. The greater the weight, the greater the vertical deformation of the soil and the greater the rolling resistance. Generally speaking, reducing the deformation of the tire itself and the deformation in the vertical direction of the soil is beneficial to reduce rolling resistance. If the tractor is running on soft ground, using low-pressure tires and increasing the tire support area can reduce the deformation of the soil in the vertical direction, reduce rolling resistance, and improve traction. Since tractors are mainly used for field operations and mostly run on soft ground, in order to reduce the deformation of the soil in the vertical direction, the lowest pressure tires generally used by tractors are also used for the same reason. In our operation, we should pay attention to the difference in the use of low-pressure tires, widened tires and high-pressure tires.
2. Traction resistance. Traction resistance is the resistance to be overcome by the tractor to drive the agricultural implements to work, and it is equal to the traction force that the tractor transmits to the agricultural implements through the connecting device. Since traction equals drive minus rolling resistance, increasing drive and reducing rolling resistance are effective measures to improve traction.
3. Driving force. It is the horizontal reaction force of the road against the drive wheels. Therefore, the magnitude of the driving torque Mk transmitted from the internal combustion engine to the driving wheels through the transmission system indicates that the driving force Pk of the tractor is also greater. But since Mk is determined by the power of the internal combustion engine, Pk is also limited by the power of the internal combustion engine. At the same time, Pk is limited by soil conditions and cannot be increased indefinitely, because when the reaction force of the soil, that is, the driving force Pk increases to a certain extent, the soil is destroyed, the driving wheel slips severely, and the driving force Pk cannot be increased any more. We call the maximum reaction force that the soil can produce on the driving wheel "adhesion". It can be seen that the maximum value of the driving force Pk is not only limited by the internal combustion probability, but also limited by the soil adhesion, and cannot increase infinitely.
Adhesion reflects the ability of the drive to generate maximum drive force with the soil. There are many factors that affect adhesion, mainly related to ground conditions, tire pressure, size, pattern and the size of the vertical load acting on the tire. For tractors, under certain soil conditions, reducing the tire pressure within a certain range, increasing the tire support area, improving the gripping ability of the wheels on the soil, increasing the attachment weight of the wheels, etc., are all conducive to improving the attachment of the tractor. Focus on low-pressure tires are generally used on tractors, and some tractors use widened tires and high-pattern tires, and add counterweight iron to tractor driving wheels, all of which are measures taken to increase the adhesion of the tractor and improve the traction capacity of the tractor. . However, it should be pointed out that adding counterweight iron to the drive wheel can increase the adhesion, but it also increases the deformation of the soil in the vertical direction and increases the rolling resistance. Therefore, whether to add counterweight iron depends on the specific use conditions and weigh the overall The effect is traded off.
The maximum adhesion and the ability to resist slipping between the tractor's driving wheel and the ground are called the tractor's adhesion performance. If the adhesion performance is good and the skidding is light, the driving torque can be fully utilized, the capacity of the internal combustion engine can also be fully exerted, and the tractor will appear vigorous when working. If the adhesion performance is poor and the slippage is severe, the driving torque cannot be fully utilized, and the capacity of the internal combustion engine cannot be fully utilized, and the tractor seems to be struggling when it is working, or the tractor does not have much strength. Severe slipping of the driving wheels will reduce the tractor's driving speed, reduce production and economy, and also accelerate the wear of the driving wheel tires, and the soil structure will also be destroyed.