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Overview: Elastic sliding is caused by the elastic deformation of the belt and the difference in pulling force (effective pulling force). It cannot be avoided.
Slippage is due to the full sliding caused by overload, which can be avoided by using mediation center distance, increasing the tensioning device, and reducing load. Although slipping can make the drive fail, it also protects other parts of the belt drive from damage.
1 . elastic sliding
The transmission belt is an elastic body, and elastic deformation occurs after being pulled. Since the tight edges and the loose edges have different pulling forces, the elastic deformation is also different. As shown in Fig. 7-12, when the tight edge is wound around the driving wheel at point a, its tensile force is F 1 . At this time, the belt's linear velocity v is equal to the driving wheel's peripheral velocity v 1 . In the driving wheel, when the belt moves from point a to point b, the tension of the belt decreases from F 1 to F 2 and the elastic elongation decreases from δ 1 to δ 2 , indicating that the belt is bypassing the pulley. During the process, the belt is contracted rearward with respect to the wheel (δ 1 - δ 2 ), and local relative sliding occurs between the belt and the pulley wheel surface, resulting in the belt speed being gradually smaller than the peripheral speed of the driving wheel. Similarly, in the driven wheel, when the belt moves from point c to point d, the pulling force gradually increases, the belt is gradually elongated, and forward relative slipping occurs along the wheel surface, so that the belt speed v is gradually greater than the peripheral speed of the driven wheel. v 2. This sliding between the belt and the pulley due to the elastic deformation of the belt is called an elastic sliding of the belt.
The result of elastic sliding is:
1) The transmission ratio of the belt is not stable;
2) Reduced transmission efficiency;
3) Causes belt wear and belt temperature rise and reduces belt life.
The elastic sliding of the belt is caused by the difference in the pulling force of the belt and the elastic deformation of the belt, and the elastic deformation is related to the elastic modulus of the belt. The use of a belt material having a large elastic modulus can reduce the elastic sliding, but because of the friction type belt transmission It is through the difference in the tension of the elastic belt that the load is transmitted. Therefore, the elastic sliding is an inherent characteristic of the belt drive during normal operation. It cannot be completely eliminated.
2 . Slippery
Under normal conditions, the elastic sliding of the belt does not occur over the entire contact arc. The contact arc can be divided into two parts: relative sliding (gliding arc) and non-relative sliding (quiet arc). The corresponding central angles of the two arcs are called the sliding angle and the static angle, respectively. The static arc is always located at the beginning of the belt winding upper and driven wheels, and the sliding arc is located at the contact arc of the belt away from the main and driven wheels. When the belt does not transmit load, the sliding angle is zero. The elastic sliding only occurs on the sliding arc of the belt. As the load increases, the sliding angle gradually increases, and the static angle gradually decreases. When the slip angle increases to the pulley wrap angle, the limit state is reached and the effective pull of the belt drive reaches the maximum (critical) value. If the working load continues to increase, there will be a significant relative slip between the belt and the pulley, ie slippage. Since the wrap angle on the big wheel is always larger than the wrap angle on the small wheel, slipping always occurs first on the small pulley.