There are three kinds of belt drives: flat belt, triangular belt and synchronous toothed belt. All three kinds of belts have national standards. However, due to the large changes in transmission ratio and power, there is no fully corresponding national standard or national standard, which can not cover all contents, but the national standard determines the selection scope, use conditions, design methods and other contents.
For example, the national standard stipulates that there are seven types of V-belts: O, a, B, C, D, e and F, and the corresponding pulley groove angles are 34 °, 36 ° and 38 °. At the same time, it specifies the minimum diameter of the small pulley corresponding to each pulley groove angle of each type of V-belt, but the large pulley is not specified. The groove angle of the pulley is divided into 34 degrees, 36 degrees and 38 degrees. The specific selection shall be based on the groove type and reference diameter of the pulley; The groove angle of the belt pulley is related to the diameter of the belt pulley. The recommended groove angle degrees of the groove angle of different types of belt pulley in different diameter ranges are as follows: the O-type belt pulley is 34 degrees when the diameter range of the belt pulley is 50mm ~ 71mm; 36 degrees at 71mm ~ 90mm and 38 degrees at > 90mm; Type a pulley is 34 degrees when the pulley diameter ranges from 71mm to 100mm and 36 degrees when the pulley diameter ranges from 100mm to 125mm; > 38 ° at 125mm; B-type pulley is 34 degrees when the pulley diameter ranges from 125mm to 160mm; 36 degrees for 160mm ~ 200mm and 38 degrees for > 200mm; C-type pulley is 34 degrees when the pulley diameter ranges from 200mm to 250mm, 36 degrees when 250mm to 315mm, and 38 degrees when > 315mm; When the diameter range of D-type pulley is 355mm ~ 450mm, it is 36 degrees, and when the diameter range is > 450mm, it is 38 degrees; Type E is 36 degrees when it is 500mm ~ 630mm and 38 degrees when it is > 630mm.
The models of V-belt include: ordinary o a B C D E 3V 5V 8V, ordinary reinforced ax BX CX DX ex 3vx 5vx 8vx, narrow V-belt SPZ spa SPB SPC, strong narrow V-belt XPA XPB XPC; Each model of the triangular belt specifies the section size of the triangular belt. The section size of type a triangular belt is: the top width is 13mm and the thickness is 8mm; The section size of B-type triangular belt is: the top width is 17mm and the thickness is 10.5mm; The section size of C-shaped triangular belt is: the top width is 22mm and the thickness is 13.5mm; The section size of D-shaped triangular belt is: the top width is 21.5mm and the thickness is 19mm; The section size of E-shaped triangular belt is: the top width is 38mm and the thickness is 25.5mm. Corresponding dimensions (width height): O (10 6), a (12.5 9), B (16.5 11), C (22 14), D (21.5 19), e (38 25.5).
The diameter and other dimensions of the pulley are matched according to the reduction ratio and designed according to the working speed and the speed of the motor. Working speed / motor speed {{0}} driven pulley diameter / driving pulley diameter 0.98 (sliding coefficient). If steel pulley is used, the linear speed shall not be higher than 40m / s. if cast iron pulley is used, the linear speed shall not be higher than 35m / s. The conversion ratio between motor speed and pulley diameter, speed ratio = output speed: input speed = load pulley pitch diameter: motor pulley pitch diameter. The pitch diameter is the same as the reference diameter. Diameter - 2H = pitch diameter, h is the groove depth on the reference line, and H is different for different models of V-belt. Y Z a B C D E, the groove depth on the reference line is h = 1.6 2.75 3.5 4.8 8.1 9.6 respectively. Pulley pitch diameter is the theoretical diameter of pulley pitch line position, which is a bit like the indexing circle diameter of gear It is generally expressed by PD, and the outer circle is generally expressed by OD The conversion formulas of pitch circle and outer circle of different groove types are different. Generally, we can easily measure the outer circle of the pulley and calculate the pitch circle according to the formula SPZ:OD=PD plus 4; SPA:OD=PD plus 5.5; SPB:OD=PD plus 7; SPC:OD=PD plus 9.6. The minimum outer diameter of the pulley of a or spa is 80mm. If it is less than this size, especially at high speed, the belt is prone to delamination and cracks at the bottom. SPZ belt, small wheel not less than 63mm. At the same time, pay attention to the installation method and tension of the belt. If it is too small, it is easy to slip, and if it is too large, it is easy to damage the belt and bearing.
In addition, ISO 1081-1995, a standard similar to the national standard, specifies the selection and design specifications of belt drive, triangular belt, triangular Ribbed belt and grooved pulley. There are five types of pulleys: SPZ, spa, SPB, SPC and SPD.
