Belt transmission is one of the most widely used transmission methods in mechanical design. According to different belt structures, it can be divided into ordinary V-belts, narrow V-belts, combined narrow V-belts, multi wedge belts, ordinary flat belts, trapezoidal tooth synchronous belts, circular arc tooth synchronous belts, etc. The characteristics and application scope of different V-belts are shown below. Appropriate belt types should be selected according to different working conditions during design.
1、 Type classification
.Ordinary V-belt
The transmission ratio i ≤ 10, the applicable belt speed is 20-30m/s, the optimal speed is 20m/s, the two sides of the belt are well attached to the wheel groove, the equivalent friction coefficient is large, the center distance is small, the preload is small, and the transmission power can reach 700kw.
.Narrow V-belt
The transmission ratio i ≤ 10, the limit belt speed is 40-50 m/s, and the optimal speed is 20-25 m/s. In addition to the characteristics of ordinary V-belts, narrow V-belts can withstand greater preload, extend their service life, and increase their transmission power, which can reach 75 Kw for a single belt. The width and diameter of the pulley can be reduced, and the cost can be reduced by 20% - 40% compared with ordinary V-belts. It can completely replace the ordinary V-belt.
.Combined narrow V-belt
Transmission ratio i ≤ 10, belt speed 20-30m/s, belonging to the extension product of narrow V-belts, all V-belts have the same length, good integrity, large lateral stiffness, stable operation, eliminating the vibration of a single belt, especially suitable for parallel shaft transmission vertical to the ground, but the pulley size and processing accuracy are required to be high. At present, only 2-5 belts are combined.
.Polywedge belt
Transmission ratio i ≤ 10, belt speed 20-40m/s, circular belts with equal spacing of 40 degree triangular wedges are evenly distributed on the inner surface of the flat belt, which has the characteristics of both flat belt and combined V-belt. However, compared with the combined V-belt, the transmission power is larger, the efficiency is higher, the speed is faster, the diameter of small pulley can be very small, and it is widely used in machine tools.
.Ordinary flat belt
Transmission ratio i ≤ 5, generally no more than 3, belt speed 15-30m/s, large center distance, low price, but small transmission ratio, low efficiency, cross, half cross and angle transmission with guide wheel, transmission power up to 500kw.
.Trapezoidal tooth and circular arc tooth synchronous belt
It is driven by gear mesh, with accurate transmission ratio, high transmission efficiency, minimum initial tension, minimum bearing pressure, and uniform instantaneous speed. It is generally used in automatic design.
2、 Selection of pulley material
When the belt speed v ≤ 20m/s, HT150 can be used; When v ＞ 25-30 m/s, HT200 can be used; V ≥ 35m/s, when the diameter is large and the power is large, use 35 steel or 40 steel; In case of high speed and small power, engineering plastics can be used; in case of large batch, die-casting aluminum alloy or other alloys can be used.
