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Field experience Exceptional noise analysis of DF7 locomotive gearbox Cui Yuqin, Jie Sidong (Beijing Erqi Locomotive Works, Beijing's main reason for analysis, and proposed corresponding improvement measures DF7 locomotive gearbox with starter gearbox, auxiliary gearbox static Pressure transmission and diesel engine gearbox, etc. Gear transmission will inevitably produce meshing noise, but the meshing impact noise caused by the different backlash size is abnormal. It should be ruled out through several years of practice and it is considered to solve this kind of problem. The problem can only be solved after the gear is assembled, during the running-in test, at different speeds to determine the sound source position of the noise, and then the gearbox unpacking check to solve the gearbox noise causes many reasons, including the gear processing precision, the box The machining accuracy of the hole, the parallelism of the centerline of the hole, the coaxiality of the front and rear holes, the bearing clearance, the deformation during press-fitting, etc., may cause large noise. The following reasons for the noise generation are as follows: (1) Grinding teeth When the root of the tooth is shallow, the root has a step and is arc-shaped, such as when the step exceeds the base circle, then When the mating gears mesh, the top teeth phenomenon will occur, which will cause more noise. For example, the 6mm and z=52 gears of the static pressure transmission 208 and 209 have obvious indentations at the root arc, resulting in paired gears. There is a wear scar on the top of the gear, and the sound is normal after replacing the gear.
There is no problem in the measurement, but after 2~3h of high-speed running-in, obvious indentation appears on the tooth top or root of the tooth of the gear. The measured base section is 0. 008~0.01mm, and the base of the remaining teeth is qualified. In this way, the noise generated by the imbalance is normal, and the sound is normal after the replacement.
This sub-section overshoot phenomenon is caused by the low precision of the gear during machining and the cumulative error of the gear indexing process.
When grinding teeth, noise is caused by changes in pressure angle. Due to the accuracy error of the grinding wheel corrector, the pressure angle changes. When the tooth pressure angle is too large or too small, as long as the tolerance value of the tooth shape is not exceeded, it is still a good product. For gears with 7-step accuracy, the maximum error value of the tooth profile is 0. 016mm, which will be eliminated step by step during the use process, and will not generate large noise. However, during the machining process, due to problems with the wheel modifier, the tooth will be generated. The shape pressure angle is abnormal, resulting in noise.
This is the case with the 6m, z=62 gear of the 946 starter gearbox, which produces noise during the running-in process and the sound is normal after replacement.
Noise generated by excessive meshing clearance. The gear assembly meshing clearance is generally between 0.2 and 0.4 mm. If the meshing gap is 0.3~0.4mm, the noise will be louder, while at 0.2~0.3mm, the noise will be smaller. When the axial turbulence is large, the noise is relatively Also, the center hole tolerance of the larger box hole is ±0.06mm, and the parallelism error is 0.06mm. Therefore, the machining error of the box body is effectively controlled, and the bearing clearance is appropriately adjusted to reduce the gear meshing gap variation and improve the tooth direction. Contact accuracy can effectively reduce noise.
During the handling process, accidental gear injuries can also cause gear transmission noise.
Through the above analysis of gearbox noise, it is not difficult to see that improving gear machining accuracy, strict assembly quality requirements, and avoiding tooth surface damage are extremely important for reducing gearbox noise. After noise occurs, the running-in test should be carefully carried out to find out The cause of the noise.