The basic components of the planetary gear transmission system are the sun gear, the planetary gear rack and the ring gear. According to the specific structure of the planetary gear reducer, there are many different classification methods. In short, one can distinguish between the first reduction, the second reduction, the third reduction and the fourth reduction. The sun gear of the reducer above the two-stage reduction adopts a floating connection method. The failure mechanism has many similarities with signal transmission paths and modes. Its movement form and self structure are more complicated.
Therefore, analyze the first-order planetary gear reducer as an example. In the first-stage planetary gear reducer, the sun gear is usually fixed on the drive shaft, and a plurality of planetary gears respectively mesh with the sun gear and the ring gear, and output power or movement through the planetary gear carrier. The main defects of the gear train are corrosion, tooth wear and tooth fracture. Common gear failures occur when 10% of gear surfaces are worn, 31% are pitted, 41% of teeth are broken, and 18% of other gears are worn. After a period of gear wear, it is difficult to find the initial tooth surface wear.
Only when the wear reaches a certain vibration signal, the gear meshing frequency and harmonic amplitude increase significantly. The cyclic stress of gear transmission generally exceeds the fatigue limit of the gear material, and cracks gradually appear at the root of the gear, causing tooth cracks. Gear fault vibration signals usually use gear meshing frequency and harmonics as carrier frequency, and gear shaft rotation frequency and dual frequency as modulation frequency. Therefore, the modulation bandwidth is very high. The carrier frequency of the planetary gear is the gear meshing frequency or multiplier, and the modulation frequency is the characteristic frequency of the faulty gear or the multiplier.
The design method of planetary gear reducer The size, weight and carrying capacity of planetary reducer depend on the choice of transmission parameters. The design problem is to determine the number of pinions for a given gear ratio and input torque, the number of teeth per gear, the module and the width of the gear. Due to the special structure of the planetary reducer, the number of teeth of each gear cannot be selected arbitrarily, and must be strictly calculated according to certain matching conditions.
The traditional design method is to first select the number of planetary gears, and then match the teeth according to the matching conditions. The results of this approach are not unique. According to the structure layout and the experience defined by the designer, a set of tooth number schemes can be selected, and then selected according to parameters such as the strength calculation model and the tooth width. When determining the structural parameters, a large number of calculations must be performed to obtain a solution that meets the performance requirements and has a reasonable size. Therefore, it is of practical value to use computers to find better design schemes.
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