The gearbox system contains gears, drive shafts, bearings and box structure. Among them, the box structure plays a supporting and sealing role in the whole system, and its probability of failure is very low, so in the gearbox, the failure mainly occurs in gears, drive shafts and bearings. According to statistics, gears, shafts and rolling bearings failures account for more than 90% of gearbox failures.
1 Tooth shape error
Tooth shape error refers to the gear tooth shape deviation from the ideal tooth profile, including manufacturing errors, installation errors and errors generated after service. Here mainly refers to the gear shape error generated after the gear is put into use, including plastic deformation of the tooth surface, surface uneven wear and surface fatigue. Broken teeth also cause tooth shape errors, but because the characteristics of their vibration signals are significantly different from these tooth shape errors, it is listed as a separate form of failure to facilitate fault diagnosis.
2 Gear uniform wear
Gear uniform wear mainly refers to the phenomenon of material friction damage that occurs in the meshing process after the gear is put into use, mainly including abrasive uniform wear and corrosion uniform wear. Gear teeth uniform wear will not cause serious tooth error, the characteristics of the vibration signal is also very different, so it is not attributed to tooth error.
3 Shaft misalignment
Shaft misalignment mainly refers to the shaft at both ends of the coupling due to the design, manufacture, installation or use of the process of the problem, so that the shaft system is parallel but not in the centre, resulting in a distribution of gears on the shaft to produce the type of tooth error. Vibration signal and a single gear tooth error is different, the shaft is not in the middle of all the gears on the shaft will produce tooth error and lead to signal modulation phenomenon.
4 Broken teeth
Broken teeth is a more serious gear failure, mainly fatigue broken teeth and overload broken teeth in two forms, most of which are fatigue broken teeth. Broken teeth when its vibration signal impact energy, different from the tooth shape error and gear uniform wear.
5 Box resonance
Box resonance is excited by the impact energy of the gear box box body of the intrinsic frequency and the resonance phenomenon. Box resonance produces a large shock vibration energy, is a very serious failure, generally caused by the external excitation of the box.
6 Mild bending of the shaft
Shafts in gearboxes also frequently fail. When a shaft is mildly bent, it can also cause the gears on that shaft to produce form errors. Unlike single gear tooth error failures, all gears on the shaft will have large tooth errors when the shaft is bent.
7 Shaft severe bending
Severe shaft bending is a more serious form of gearbox failure. When a shaft is severely bent, it generates large impact energy with serious consequences, and its vibration signal is different from that of a mild bend.
8 Shaft unbalance
Shaft imbalance is a typical failure of the shaft in the gearbox. The so-called unbalance, is the shaft due to the existence of eccentricity caused by the unbalance of the vibration, this eccentricity can be due to manufacturing, installation and put into use after the deformation generated. When the shaft imbalance is generated, it will also lead to tooth shape error in gear transmission, but this failure is significantly different from the simple tooth shape error.
9 axial runout
Axial runout mainly occurs in the use of helical gears, when the same shaft has two helical gears involved in meshing at the same time, and the axial direction is not a good positioning and locking device, axial runout phenomenon sometimes occurs, mainly due to its axial force imbalance. Axial runout will seriously affect the accuracy and smoothness of the gear transmission, may also cause the gear tooth end face impact wear, is a more serious failure.
10 bearing fatigue spalling and pitting
Typical faults of rolling bearings in gearboxes are fatigue spalling and pitting of the inner and outer rings and rolling bodies. Shaft rotation, the inner and outer rings and rolling body in the contact process will occur in the mechanical impact, resulting in a large variation of the force known as the impact pulse, rolling bearings in the gear box failure, its energy than the vibration energy generated by the gear is much smaller, and therefore is one of the difficulties in the diagnosis.
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