Key refers to the key in the mechanical transmission, mainly used as a circumferential fixation between the shaft and the parts on the shaft to transmit torque, and some keys can also achieve axial fixed or axial movement of the parts on the shaft. Such as the coupling of the gear and the shaft in the reducer.
Key classification
The keys are divided into flat keys, semi-circular keys, wedge keys, tangential keys, and splines.
Characteristics of various types of keys
1. Flat key
The sides of the flat key are the working faces, and there is a gap between the upper surface and the bottom of the hub groove. The centering performance is good, and the assembly and disassembly is convenient. The flat keys have three types: ordinary flat keys, guide flat keys, and slide keys.
2. Semi-circular key
The semi-circular keys also have working faces on both sides and have good centering performance. The semi-circular key can be swung in the shaft groove to accommodate the bottom surface of the hub groove, but the keyway has a large weakening on the shaft and is only suitable for light load coupling.
3. Wedge key
The upper and lower sides of the wedge key are the working faces, the upper surface of the key has a slope of 1:100, and the bottom surface of the hub keyway also has a slope of 1:100. When the wedge key is driven into the shaft and the hub groove, the surface thereof generates a large preload force, and the working force mainly transmits the torque by the friction force and can withstand the axial force in one direction. The disadvantage is that it forces the shaft and the hub to be eccentric, and is only suitable for couplings with low centering accuracy, smooth load and low speed. The wedge key is divided into two types: a common wedge key and a hook head wedge key.
4. Tangential key
The tangential key consists of a pair of wedge keys that transmit a large amount of torque and are commonly used in heavy machinery.
5. Spline
The spline is formed by uniformly arranging a plurality of key teeth in the circumferential direction of the shaft and the hub hole, and is called a spline coupling. The spline connection is multi-tooth operation, the working surface is the tooth side, the bearing capacity is high, the neutrality and guiding type are good, the strength of the shaft and the hub is weakened, and the centering precision requirement is high, the load is large and the sliding is frequent. Static coupling and dynamic connection, such as the transmission, the coupling of the sliding gear to the shaft. According to the tooth shape, the spline connection can be divided into: rectangular spline, triangular spline and involute spline.
