Selection principle of pulley and transmission advantages
The pulley is a part of the disc hub, and the relative size is generally relatively large. The manufacturing process is generally based on casting and forging. Generally, the larger size is designed by casting, and the material is generally cast iron (the casting performance is better), and the cast steel is rarely used (the casting performance of the steel is not good); generally, the smaller size can be designed for forging, the material For steel.
Selection principle
The selection of the various indicators and materials of the pulley is based on the selection principle of reducing the raw materials as much as possible, the process is feasible, and the cost is the lowest on the premise of meeting the requirements for use.
Transmission advantages
The advantages of the pulley drive are: the pulley drive can alleviate the impact of the load; the pulley drive runs smoothly, low noise, and low vibration; the structure of the pulley drive is simple and easy to adjust; the precision of the pulley drive for the manufacture and installation of the pulley is not as strict as the meshing drive; the pulley drive It has the function of overload protection; the adjustment range of the center distance of the two shafts driven by the pulley is large. The disadvantages of the belt drive are: the pulley drive has elastic sliding and slippage, the transmission efficiency is low and the accurate transmission ratio cannot be maintained; when the pulley drive transmits the same large circumferential force, the outline size and the pressure on the shaft are larger than the meshing drive; the pulley drive belt Life is shorter. The diameter and other dimensions of the pulleys of various types of mechanical equipment are all their own
According to the reduction ratio, it is designed according to the working speed and the motor speed. Working speed / motor speed = driving wheel diameter / driven wheel diameter * 0.98 (sliding factor), such as the use of steel belt pulleys, the linear speed is not required to be higher than 40m / s, such as the use of cast iron materials, the linear speed is not required to be higher than 35m / s, conversion ratio of motor speed to pulley diameter, speed ratio = output speed: input speed = load pulley pitch circle diameter: motor pulley pitch circle diameter. The pitch circle diameter is the same as the reference diameter, diameter-2h = pitch circle diameter, h is the groove depth on the reference line, different models of V-belt h are different, YZABCDE, the groove depth on the reference line are h = 1.6 2.75 3.5 4.8 8.1 9.6. The pitch diameter of the pulley is the theoretical diameter of the pitch line position of the pulley, which is a bit like the diameter of the dividing circle of the gear. It is generally expressed by PD, and the outer circle is generally expressed by OD. The conversion formula for different groove pitch circles and outer circles is different, generally we It is easier to measure the outer circle of the pulley and calculate the pitch circle according to the formula. SPZ: OD = PD + 4; SPA: OD = PD + 5.5; SPB: OD = PD + 7; SPC: OD = PD + 9.6. The minimum outer diameter of the pulley of A or SPA is 80mm. If it is smaller than this size, especially at high speed, the belt is prone to delamination and cracks at the bottom. SPZ belt, small wheel is not less than 63mm. At the same time, we must pay attention to the installation method and tension of the belt. If it is too small, it may slip, and if it is too large, the belt and bearings may be damaged.
