Abnormal vibration of gear shaft under complex working condition

In modern engineering production, many kinds of heavy machinery, such as high-speed rolling mill, heavy-duty operation equipment, special vehicles, large ships, airplanes and so on, adopt gear transmission as a transmission form of power transmission. In addition to the transmission of motion and power, gear transmission has the characteristics of high transmission efficiency, strong working reliability, long service life, accurate transmission ratio, compact structure, wide range of applicable speed and transmission power compared with other transmission devices. Its transmission quality directly affects or determines the quality and performance characteristics of mechanical products. Its transmission quality directly affects or determines the quality and performance of mechanical products.

With the increasing demand of modern enterprises for high-quality products, the requirements of speed and working stability of gear transmission system in mechanical equipment are constantly improving. In the production process, the low-frequency vibration and even instability of key parts of mechanical equipment are often caused by the parameters of gear transmission, the surface quality of gear, the lubrication condition and the slight changes in the process of starting and stopping the machine The stable process will cause many hazards to the mechanical equipment: the speed of the gear drive is forced to reduce, thus affecting the quantity of products; the wear of the gear components leads to the decline of product quality and the increase of unqualified products, in addition, it also increases the workload and cost for the maintenance of the mechanical equipment; it leads to the fatigue damage of the key parts of the gear drive system, and in serious cases, it will cause the broken shaft or design of the rotating machinery Standby fault and other accidents.

This kind of destructive vibration has different characteristics from the normal steady-state vibration. Its frequency and strength are related to the stiffness and damping coefficient of the gear transmission system. In addition, it is also related to the arrangement form of mechanical equipment, mechanical technology and operation mode. The specific form and operation mode of system vibration are related. The specific forms of system vibration are as follows: (1) attenuation vibration. The input torque, the distribution of inertia, the elastic coefficient and the damping coefficient of the transmission shaft have some influence on the amplitude and duration of the torsional vibration; (2) forced vibration. When the natural frequency of the transmission shaft and the response frequency of the external excitation are the same, the transmission system will appear forced vibration; (3) intermittent vibration. In some special working conditions, the torsional vibration of the transmission system also shows the intermittent vibration phenomenon with unstable torsional vibration amplitude and frequency; (4) constant amplitude vibration. When the rotating machinery is running at low speed and no load or at light load, the transmission system may also have equal amplitude vibration with small torsional vibration amplitude.

Among all kinds of heavy mechanical equipment, gear transmission system is widely used to output the power of power equipment, and its dynamic performance has an important impact on the whole mechanical equipment. The vibration and noise of mechanical equipment are mostly caused by the operation of gear transmission system. The operation condition of gear transmission system is very complex, not only the manufacturing accuracy of rotating machinery parts is different, but also the external load conditions are different. In addition, time-varying meshing stiffness, gear transmission error and backlash will also generate internal excitation of the transmission system. Therefore, the requirements of mechanical equipment on the dynamic performance of gear transmission system are more stringent.

In the fields of electric power, energy, transportation, metallurgy and national defense, complex power equipment plays a very important role in national economy and national defense construction. Among them, gear transmission system is the key component of rotating machinery in complex power equipment, and its performance directly affects the overall performance of complex power equipment. From the perspective of mechanical vibration theory, the vibration form of gear transmission mechanism of complex power equipment is mainly torsional vibration, also known as torsional vibration. Because of the frequent occurrence of torsional vibration, the normal operation of rotating machinery is affected and even the mechanical equipment is damaged, resulting in significant economic losses.

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