Design of the most popular ordinary V-belt drive

2022-08-18
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Design of ordinary V-belt drive

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Second, the experimental data adopts the database management method to analyze the force and motion characteristics of the belt transmission. First, the force analysis of the belt transmission. When the belt transmission is installed, the belt must be tensioned, that is, it must be tightened on two pulleys with a certain initial tension. At this time, the tension in the transmission belt is equal, which is the initial tension F0 (see Figure 7 – 8a). a) B) Fig. stress of belt transmission a) when it is not working b) when it is working, due to the friction on the contact surface between the belt and the pulley, the side of the belt winding into the driving wheel is further tensioned, and the tension increases from F0 to F1, which is called the tight side; The other side is relaxed, and the tension is reduced from F0 to F2. This side is called loose side (see Figure 7 – 8b). The difference between the pulling forces on both sides is called the effective pulling force, which is expressed in F, that is, f = F1 – F2 (7 – 4). The effective pulling force is the effective circumferential force that the belt drive can transmit. It is not the concentrated force acting on a fixed point, but the sum of the friction generated on the contact surface between the belt and the pulley. When the belt transmission works, the circumferential resistance f generated by the working resistance moment T2 on the driven wheel is f = 2/d2. When it works normally, the effective tension F and the circumferential resistance f are equal. Under certain conditions, the friction force that can be generated on the contact surface between the belt and the pulley has a limit value, that is, the maximum friction force (the maximum effective circumferential force) Fmax. When Fmax ≥ F, the belt transmission can operate normally. If the circumferential resistance to be transmitted exceeds this limit, the drive belt will slip on the pulley. At the beginning of slipping, there is the following relationship between tight edge tension F1 and loose edge tension F2, that is, F1 = F2 EF a (7 – 5), where e – – the base of the natural logarithm (E ≈ 2.718); F – – friction coefficient between belt and rim; A – – the wrap angle (RAD) of the drive belt on the pulley. The above formula is the Euler formula of flexible body friction. Derivation of formula (): take the flat belt as an example to study the relationship between tight side tension and loose side tension when the belt is about to slip on the driving wheel. It is assumed that the belt does not stretch elastically in operation, and the effects of bending, centrifugal force and the quality of the belt are ignored. As shown in Figure 7 – 9, take a micro segment transmission belt DL, and use DN to represent the positive pressure of the micro segment transmission belt of the pulley pair. The tension at one end of the micro segment transmission belt is f, and the molecular motion has obvious relaxation characteristics. The tension at the other end is F + DF, and the friction force is f · DN. F is the friction coefficient between the transmission belt and the pulley (for V-belt, use the equivalent friction coefficient FV, and F is the groove angle of the pulley). Then Design of the most popular ordinary V-belt drive