Belt transmission is a kind of mechanical transmission that uses a flexible belt tensioned on a pulley to transmit motion or power. According to the different transmission principles, there are friction-type belt transmissions driven by the friction between the belt and the pulley, and there are synchronous belt transmissions driven by the meshing of the teeth on the belt and the pulley.
Friction belt drive
Mesh belt drive
1. Classification of belt drive types
According to different uses, there are transmission belts for general industrial use, transmission belts for automobiles, transmission belts for agricultural machinery, and transmission belts for household appliances. Friction-type transmission belts are divided into flat belts, V-belts and special belts (V-ribbed belts, round belts) according to their cross-sectional shapes.
Flat belt drive
There are open transmission, cross transmission and semi-cross transmission, etc., respectively to meet the needs of different relative positions and different rotation directions of the driving shaft and the driven shaft. The flat belt transmission has a simple structure, but it is easy to slip. It is usually used for transmission with a transmission ratio of about 3.
V-belt drive
When the V-belt transmission works, the belt is placed in the corresponding groove on the pulley, and the transmission is realized by the friction between the belt and the two walls of the groove. V-belts are usually used in combination with several, and there are corresponding number of grooves on the pulley. When using a V-belt to drive, the belt and the wheel contact well, the slip is small, the transmission ratio is relatively stable, and the operation is stable. V-belt transmission is suitable for occasions with short center distance and large transmission ratio (about 7), and it can also work well in vertical and inclined transmission. In addition, since several V-belts are used together, one of them will not be damaged without causing accidents.
V-belt drive
Very flexible, the back of the belt can also be used to transmit power. If the containment angle around each driven pulley is large enough, one such belt can be used to simultaneously drive several accessories of the vehicle (alternator, fan, water pump, air-conditioning compressor, power steering pump, etc.). It has 5 types of cross-sections of PH, PJ, PK, PL and PM for selection. Among them, the PK type has been widely used in automobiles in recent years. This belt allows the use of narrower pulleys (diameter dmin≈45mm) than narrow V-belts. In order to be able to transmit the same power, the pre-tightening force of this belt is best to increase by about 20% than the narrow V-belt.
Application range of friction transmission belt:
Belt transmission is suitable for occasions where the transmission power is not large or the precise transmission ratio is not required. In the multi-stage reduction gear, the belt drive is usually configured in the high-speed stage. The power transmitted by an ordinary V-belt generally does not exceed 50-100 kW, and the belt's working speed is 5-35 m/s.
In general machinery, the most widely used is V-belt drive. The cross section of the V-belt is an isosceles trapezoid, and the pulleys are also made into corresponding grooves. During transmission, the V-belt only contacts the two sides of the wheel groove, that is, the two sides of the V-belt are working surfaces, and the bottom surface of the belt does not contact the pulley. According to the friction principle of the groove surface, under the same tension, the V-belt drive can produce greater friction than the flat belt drive. Therefore, the V-belt drive has a stronger transmission capacity and a more compact structure. Therefore, the V-belt drive is more widely used than the flat belt. Much.
2. V belt and V belt wheel
V-belt is a general term for endless transmission belts with trapezoidal cross-section, which can be divided into two categories: special-core V-belts and ordinary V-belts. Compared with flat transmission belts, it has the advantages of easy installation, small footprint, high transmission efficiency and low noise, and it occupies an important position in the entire transmission field. Mainly used in the power transmission of mechanical equipment driven by electric motors and internal combustion engines.
Ordinary V belt
V-belt wheel is a V-belt wheel structure composed of rim, spokes and hub. According to the spoke structure, there are three types: solid pulley, spoke pulley, and spoke pulley. The commonly used materials of V pulley are gray cast iron, steel, aluminum alloy or engineering plastics, among which gray cast iron is the most widely used.
3. Meshing synchronous belt drive
The meshing belt drive is generally also called synchronous belt drive. It transmits movement through the meshing of transverse teeth distributed equidistantly on the inner surface of the transmission belt and corresponding tooth grooves on the pulley. Compared with friction type belt transmission, there is no relative sliding between the pulley and the transmission belt of the synchronous belt transmission, which can ensure a strict transmission ratio. However, synchronous belt transmission has higher requirements for center distance and dimensional stability.
