Interference fit is achieved by making the inner diameter of the hardware accessories ring gear slightly smaller than the outer diameter of the shaft, heating the hardware accessories ring gear or cooling the shaft during assembly to change its size, and then assembling it. After returning to normal temperature, a tight fit is formed between the hardware accessories ring gear and the shaft. The advantage of this assembly method is that it can provide higher connection strength and stability. Since there is no relative motion gap between the hardware accessories ring gear and the shaft, the torque can be effectively transmitted during the transmission process, reducing the vibration and impact caused by the gap, thereby improving the stability of the transmission. For example, in some high-precision machine tool transmission systems, the hardware accessories ring gear and the shaft with interference fit can ensure the transmission accuracy and effectively guarantee the processing accuracy.
The key to interference fit is the control of the interference amount. The appropriate interference amount can generate sufficient friction between the hardware accessories ring gear and the shaft to transmit the required torque. If the interference amount is too small, the hardware accessories ring gear and the shaft may become loose, resulting in unstable transmission and even slippage, affecting the normal operation of the equipment. On the contrary, if the interference is too large, the hardware accessories ring gear and the shaft will be subjected to excessive stress, which may cause deformation of the hardware accessories ring gear, shaft breakage and other problems, and will also reduce the transmission stability. Therefore, during the design and assembly process, it is necessary to accurately calculate and control the interference according to the material, size and transmission requirements of the hardware accessories ring gear and the shaft to ensure the stability and reliability of the transmission.
The installation and removal of interference fit is relatively complicated and requires special equipment and processes. If the operation is improper during the installation process, such as uneven heating and too fast assembly speed, it may cause local deformation of the hardware accessories ring gear or the shaft, affecting the fit accuracy and thus reducing the transmission stability. Similarly, during disassembly, if the method is incorrect, the surface of the hardware accessories ring gear and the shaft may be damaged, affecting the transmission performance after reassembly. Therefore, it is crucial to strictly follow the standardized installation and disassembly process to ensure the transmission stability of the interference fit.
The key connection is to machine keyways on the hardware accessories ring gear and the shaft respectively, and connect the two through the key to achieve torque transmission. The advantages of key connection are simple structure, convenient installation and disassembly, and the ability to compensate for the coaxiality error between the hardware accessories ring gear and the shaft to a certain extent. Since the key can limit the relative rotation between the hardware accessories ring gear and the shaft, the torque can be accurately transmitted during the transmission process to ensure the accuracy of the transmission. Key connection has been widely used in some equipment that does not require particularly high transmission accuracy but requires frequent disassembly and maintenance.
Different types and sizes of keys have different effects on transmission stability. Common keys include flat keys, semicircular keys, wedge keys, etc. Flat keys have a simple structure, good centering, and can effectively transmit torque, but cannot withstand axial forces. Semicircular keys are suitable for the connection between tapered shafts and hubs, and have good centering accuracy. Wedge keys can withstand unidirectional axial forces, but due to the wedging effect, they may cause eccentricity between the shaft and the hub. In addition, the size of the key also needs to be reasonably selected according to the size of the hardware accessories ring gear and the shaft and the size of the transmission torque. If the size of the key is too small, it may be sheared or worn during the transmission process, affecting the transmission stability; if the size of the key is too large, it will increase the processing cost and weight of the hardware accessories ring gear and the shaft.
The matching accuracy between the key and the keyway will also affect the transmission stability. If the matching clearance is too large, there will be relative shaking between the hardware accessories ring gear and the shaft, resulting in unstable transmission, noise and vibration. On the contrary, if the matching is too tight, it may cause installation difficulties and even damage the key and keyway. Therefore, when processing the keyway and selecting the key, it is necessary to strictly control the matching accuracy to ensure the stability and reliability of the transmission.
Interference fit and key connection each have their advantages and disadvantages. In practical applications, it is necessary to select the appropriate assembly method according to specific working conditions and requirements. For occasions with high requirements for transmission accuracy and stability, large loads and no need for frequent disassembly, interference fit is a more appropriate choice; while for occasions with high requirements for installation and disassembly convenience and relatively low transmission accuracy requirements, key connection is more suitable. In some special cases, a combination of interference fit and key connection can also be used to give full play to the advantages of both and improve transmission stability.
