Can drive is by the power of the internal combustion engine by the transmission system, so that the drive wheel to obtain the driving torque Mk, to obtain the driving torque of the drive wheel and then through the tire tread and tire surface to the ground small, backward horizontal force (tangential force), and the ground on the driving force of equal size, the direction of the opposite horizontal rice force Pk, this Pk rice force is to promote the tractor forward driving force (also known as feed for propulsion). When the driving force Pk enough to overcome the front and rear wheels forward rolling resistance and traction resistance with farm equipment, the tractor will move forward. If the driving wheel support off the ground, that is, the driving force Pk equal to zero, the driving wheel can only idle in place, the tractor can not travel; if the rolling resistance and traction resistance and greater than the driving force Pk, the tractor can not travel. This can be seen wheeled tractor is driven by the driving torque drive wheel and the interaction between the ground and achieve, and the driving force to be greater than the rolling resistance and traction resistance and.
1, rolling resistance. Tractor rolling resistance, mainly due to the deformation of the tires and soil, the weight of the tractor, the tires are flattened, the soil is compacted. Wheel in the rolling process, the tire along the round around the direction of contact with the ground on each part of the following was flattened and deformed, and the wheel in front of the higher soil pressed down so that the soil deformation and the formation of wheel ruts, that is, the rolling resistance to hinder the wheel rolling forward. Affect the rolling resistance of many factors, mainly with the ground solid and wet degree on the size of the vertical load and other factors. For the same tractor, if the ground conditions are different, the rolling resistance is also different, such as in the asphalt and cement or dry hard ground rolling resistance is small, tractor traction is large, in the same conditions of use, if the weight added to the tires, the greater the soil deformation in the vertical direction, the greater the rolling resistance. Generally speaking, reduce the deformation of the tire itself and the deformation of the soil in the vertical direction, in favor of reducing the rolling resistance. If the tractor in the soft ground, using low-pressure tires, increase the tire support area, can reduce the soil in the vertical direction of the deformation, reduce rolling resistance, so as to improve traction. As the tractor is mainly used for field operations, more in the soft ground, in order to reduce the soil in the vertical direction of the deformation, so the tractor generally uses the most low-pressure tires, using wider tires is the same reason. In our business should pay attention to the low-pressure tires, wider tires and high-pressure tires in the use of the difference.
2, traction resistance. Traction resistance is the tractor to drive the farm equipment for operation to overcome the resistance, it is equal to the tractor through the connection device to the farm equipment traction force. As traction is equal to drive minus rolling resistance, therefore, increase the driving force and reduce rolling resistance is an effective measure to improve traction.
3, driving force. It is the horizontal reaction force of the road surface on the driving wheel. Therefore, the internal combustion engine through the transmission system to the drive wheel drive torque Mk size, indicating the tractor's driving force Pk also the greater. However, 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 and by the soil conditions, can not increase infinitely, because when the soil reaction force that drive force Pk increased to a certain extent with, the soil is destroyed, the drive wheel serious slippage, drive force Pk can not be increased. We call the maximum reaction force that the soil can produce on the driving wheel "adhesion force". It can be seen that the maximum value of drive force Pk is not only limited by the internal combustion rate, but also limited by the soil adhesion force, which cannot be increased indefinitely.
The adhesion force reflects the ability to generate the maximum driving force between the drive and the soil. Affects the adhesion of many factors, mainly with the ground conditions, tire pressure, size, tread and the size of the vertical load acting on the tire and other factors. For the tractor, in a certain soil conditions, in a certain range to reduce tire pressure, increase the tire support area, improve the grip capacity of the wheel on the soil, increase the attachment weight of the wheel, etc., are conducive to improving the tractor's traction, in the tractor commonly used low-pressure tires, some tractors used wider tires and high tread pattern tires and tractor drive wheel with counterweight iron, are to Increase the tractor's traction, improve the tractor's traction capacity and take measures. But it should be pointed out that the drive wheel with counterweight iron, although can increase the traction, but also increased the soil in the vertical direction of the deformation, increased rolling resistance, so whether to add counterweight iron, but also depending on the specific conditions of use, weighing the total effect of trade-offs.
Tractor drive wheel and the ground between the maximum adhesion capacity and resistance to skid, known as the tractor's adhesion performance. If the adhesion performance is good, skid lighter, the drive torque can be fully utilized, the internal combustion engine can also be fully played, the tractor in the work appears to have strength. If the adhesion performance is poor, slipping serious, the drive torque can not be fully utilized, the ability of the internal combustion engine can not be fully played, the tractor in the work appears to have strength to make out, or the tractor is not much strength. Drive wheel serious slippage, will make the tractor driving speed, production and economy decline, but also accelerate the drive wheel tire wear, in addition to the soil structure will also be damaged.
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