triangular belts is commonly known as V-belt, belt drive is a flexible transmission, with the following characteristics: simple structure, suitable for the occasion of a large center distance between the two axles, elastic tape, can buffer vibration, smooth transmission without noise, overload can produce slippage, can prevent the damage of weak parts, play a safe and protective role, but The accurate transmission ratio can not be maintained; the transmission belt needs to be tightened on the pulley, and the pressure on the shaft and bearing is larger.

Standard V-belts are all made into jointless rings, and their cross-sections consist of a strong layer 1, a stretching layer 2, a compression layer 3 and a cladding layer 4, as shown in Figure 1. The stretching and compressing layers are composed of rubber, the cladding layer is composed of rubber canvas, and the strong layer is the main body to bear the load. It is divided into cord structure (composed of rubber cord fabric) and cord structure (composed of rubber cord). The cord structure has high tensile strength, and this structure is commonly used in V belts for general use. Wire rope structure is relatively soft, bending fatigue strength is better, but the tensile strength is low, often used in small load, small diameter pulley and high speed occasions. When the V-belt is bent and wound on the pulley under the specified tension, the outer layer is lengthened and the inner layer is compressed and shortened. There is a neutral layer of constant length between the two layers. The surface formed along the neutral layer is called the nodal plane, as shown in Figure 2. The width of the joint surface is called BP. The circumference of the nodal plane is the reference length Ld of the belt.

V has two widths: the reference width and the effective width. Generally, there are two kinds of V-bands used in machinery: common V-band and narrow V-band, common V-band is the reference width system, narrow V-band both have. Common V-belt models have Y, Z, A, B, C, D and E; narrow V-belt with SPZ, SPA, SPB and SPC of base width, narrow V-belt with 9N, 15N and 25N of effective width (3V, 5V, 8V respectively); common reinforced AX BX CX DX EX 3VX 5VX 8VX X X, strong narrow V-belt XPA XPB; corresponding pulley groove angles have three 34, 36, 3 V 8 degrees. These numbers and letters come first in the code name and are used to determine the ***’s specifications (width, angle, height, etc.). After the model is determined is the length of the determination, such as SPB-3800 (reference width narrow V-band, SPB type, reference length 3800), 5V 1500 (5V is the effective width of narrow V-band 15N, effective length 1500).

The material of V-belt wheel can be gray cast iron, steel, aluminum alloy or engineering plastics, and gray cast iron is the most widely used. When the belt speed V is less than 25m/s, HT150 and HT200 are used when the belt speed V is more than 25~30m/s. The belt wheel with higher speed can be made of ductile iron or cast steel, and also can be made of steel plate stamped and welded. Small power transmission can be made of cast aluminum or engineering plastics.

The degree of tension of the belt drive has a great influence on its transmission capacity, life span and shaft pressure. The initial tension of V-belt drive can be measured by the load G perpendicular to the belt at the center of the two tangent points between the belt and the pulley, resulting in a deflection of 1.6 mm per 100 mm span. At this time, the initial tension F0 of the belt is suitable (i.e. the total deflection y =1.6a/100).

For the ordinary V belt drive, the vertical force G applied to the center of the span is calculated according to the following formula:

Newly installed with G = (1.5F0 Delta F0) /16

G = (1.3F0 Delta F0) /16 after operation

Minimum limit G = (F0 Delta F0) /16

After a period of work, the belt drive will relax due to plastic deformation, so that the initial tension decreases and transmission capacity decreases. At this time, under the specified load G, the total deflection y becomes larger and needs to be re-tensioned. Correct installation and maintenance is an effective measure to ensure the normal operation of belt drive and prolong the service life of belt.

1. when the parallel shaft is driven, the axes of the pulleys must be kept parallel. The grooves of V-belt drive’s main and driven wheels must be adjusted in the same plane, and the error must not exceed 20’. Otherwise, the distortion of V-belt will cause premature wear on both sides.

2. don’t force it into a suit when you bring it. The center distance should be reduced first, the belt should be sleeved on the pulley, and then the center distance should be gradually increased until the test force G meets the required deflection y = 1.6a/100.

3. The belt drive should be checked regularly and adjusted in time. The damaged V-belts should be replaced in time. The new and old V-belts, common V-belts, hexagonal belts and V-belts of different specifications can not be used together.

4. belt transmission must install safety shield. In this way, it can not only prevent strangulation, but also prevent dust, oil and other sundries from splashing onto the belt to affect the transmission.