A four-wheel drive tractor can be driven by the power of an internal combustion engine through the transmission system, allowing the drive wheels to obtain a driving torque Mk. The drive wheels that obtain the driving torque will apply a small backward horizontal force to the ground through the tire pattern and tire surface, and the ground will face a horizontal force Pk that is opposite to the driving force in the same direction. This Pk reaction force is the power that drives the tractor forward. When the driving force Pk is sufficient to overcome the forward rolling force of the front and rear wheels and the traction force of the agricultural tool, the bulldozer will move forward. The driving of a four-wheel drive tractor is achieved through the interaction between the driving torque of the driving wheels and the ground, with the driving force greater than the sum of rolling force and traction force. Let's analyze the main factors that affect the driving of four-wheel drive tractors.
Rolling resistance: The rolling force of a four-wheel drive tractor is mainly caused by the deformation of the tires and soil. Under the heavy pressure of the garbage truck, the tires are flattened and the soil is compacted. During the rolling process of the wheel, the various parts of the tire that come into contact with the ground along the circumference are compressed and deformed. The front of the wheel is pressed higher than the soil, causing the soil to be pressed down. The soil deforms and forms a wheel track, which generates a rolling force that hinders the wheel from rolling forward. There are many factors that affect rolling force, mainly related to the firmness and humidity of the ground caused by vertical loads. For the same garbage truck, if the ground conditions are different, its rolling force will also be different.
Traction: Traction is the force that a four-wheel drive tractor needs to overcome when driving agricultural machinery. As traction is equal to the driving force minus the rolling force, it is equal to the traction force transmitted by the towing machine to the agricultural machinery through the connecting device. Increasing driving force and reducing rolling force are effective measures to improve traction.
Driving force: refers to the reaction force of the road surface on the driving wheel. Therefore, the driving torque Mk transmitted by the internal combustion engine through the transmission system to the driving wheels indicates that the driving force Pk of the tractor is also greater. But Pk is also limited by the power of the internal combustion engine, as Mk is determined by the power of the internal combustion engine. At the same time, Pk is limited by soil conditions, so it cannot be infinitely increased, because when the soil reaction force, i.e. the driving force Pk, increases to a certain extent, the soil is damaged, the driving wheel slips severely, and the driving force Pk cannot be increased anymore. We refer to the reaction force that the soil can generate on the driving wheels as "adhesion". It can be seen that the driving force Pk of four-wheel drive tractors is not only limited by the internal combustion engine rate, but also by the soil adhesion, and cannot be infinitely increased.
Adhesion: It reflects the ability of driving force to generate driving force between the driving force and the soil. There are many factors that affect adhesion, mainly related to ground conditions, tire pressure, size, pattern, and the vertical load borne by the tire. For four-wheel drive tractors, under certain soil conditions, reducing tire pressure, increasing tire bearing area, improving wheel grip capacity on soil, and increasing wheel attachment weight are all beneficial for improving the adhesion of the trailer within a certain range.