The Main Factors Affecting the Driving of Four-wheel Drive Tractors

The rolling resistance of 4WD tractors is mainly due to the deformation of tires and soil. Under the weight of the 4x4 tractor, the tires are flattened and the soil is compacted. During the rolling process of the wheel, the various parts of the tire in contact with the ground in the circumferential direction are then flattened and deformed, and the soil pressure in front of the wheel is downward and the soil is deformed to form a wheel rut, that is, the rolling resistance prevents the wheel from rolling forward. There are many factors affecting rolling resistance, mainly related to factors such as ground firmness and the degree of moisture in vertical loads. For the same four-wheel drive tractor, if the ground conditions are different, its rolling resistance is also different. For example, when driving on asphalt cement or dry hard ground, the rolling resistance is small, and the four-wheel drive tractor has large traction. The added weight is larger, the deformation of the soil in the vertical direction is also larger, and the rolling resistance is also larger. Generally speaking, reducing the deformation of the tire itself and the deformation of the soil in the vertical direction is beneficial to reduce the rolling resistance. If the four-wheel drive tractor runs 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 the rolling resistance, and thus improve the traction. Because the four-wheel drive tractor is mainly used for field operations, and mostly runs on the soft ground to reduce the deformation of the soil in the vertical direction, the four-wheel drive tractor generally uses lower air pressure tires, and the use of widened tires is also the same reason. In our operation, we should pay attention to the difference between low-pressure tires, widened tires and high-pressure tires in use.

Traction resistance is the resistance that the tractor drives the agricultural machinery to overcome, which is equal to the traction force of the tractor through the agricultural machinery through the connecting device. Since traction is equal to driving minus rolling resistance, increasing driving force and reducing rolling resistance are effective measures to improve traction. It is the horizontal reaction force of the road surface to the driving wheels. Therefore, the driving torque Mk of the internal combustion engine is transmitted to the driving wheels through the transmission system, indicating that the driving force Pk of the tractor is also large. But since Mk is determined by the power of the internal combustion engine, then 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 soil reaction force, that is, the driving force Pk, increases to a certain level, the soil will be damaged, the driving wheel will slip severely, and the driving force Pk cannot be increased any more. We call the greater force the soil can exert on the drive wheel "adhesion". It can be seen that the larger value of the driving force Pk is not only limited by the rotation speed of the internal combustion engine, but also limited by the soil adhesion, so it is impossible to increase indefinitely. Reflects the drive's ability to generate a large driving force between the drive and the soil. There are many factors that affect adhesion, mainly related to ground conditions, tire pressure, size, pattern, and the vertical load on the tire. For tractors, under certain soil conditions, reducing the tire pressure within a certain range, increasing the tire support area, improving the grip of the wheels on the soil, and increasing the weight of the wheels are all conducive to improving the adhesion of the tractor. Low-pressure tires Widely used in tractors, some tractors use widened tires and high-pattern tires, and add counterweight iron to the tractor driving wheels, which is to increase the adhesion of the tractor, improve the traction capacity of the tractor and take measures. However, it should be pointed out that adding a counterweight iron to the driving wheel can increase the adhesion, but it will also increase the deformation of the soil in the vertical direction and increase the rolling resistance. Therefore, whether to add a counterweight iron depends on the specific use. situation, the overall effect of the trade-off.