3. The effect of hobbing on noise
For the gear tooth shape, the final machining process is a gear for shaving. The hobbing process is a crucial process, because the shaving process is a conformal cutting, the forced cutting ability of the gear is small, and the short cycle of the gear The error has certain corrections, such as: tooth shape, tooth direction error, spiral wave error and tooth surface roughness, but there is no correction ability for long period error, and there may be a new increase in error, such as: public normal Length variation, weekly error, weekly cumulative error, etc. Therefore, special attention should be paid to the hobbing process. The following points should be controlled by hand: (1) Ensure that the end face of the hobbing fixture is jumped and the full runout is no more than 0.005 mm; ensure the diameter and verticality of the hobbing fixture; The parallelism of the compression pad and the concentricity of the thread. (2) Ensure the transmission accuracy of the worm gear of the gear hobbing machine; the verticality of the small column; the accuracy of the tip and the matching precision of the tip and the thimble hole. (3) To ensure the accuracy of the installation of the tooth blank, the dirt on the parts, the dirt on the backing plate and the pressure plate should be cleaned before the tooth blank is installed, in particular, the iron filings and the parts cannot be bumped. (4) Reasonable selection of cutting speed and feed rate; it is absolutely accurate when calculating the differential hanging wheel and the split tooth hanging wheel. (5) The hob should be centered and the file should be accurate. In particular, the gear with a small number of teeth and the gear with a large modulus should be centered by the hob, so that the teeth of the rolled teeth are symmetric on both sides, and the cutting of the sides is the same, the angle of the root is the same, and the length of the involute of the tooth profile is the same. It is equal. Since the weekly difference, the cumulative error of the circumference, and the variation of the length of the common normal line have a great influence on the noise, it is important to ensure the accuracy of the gear after the hobbing.
4. The influence of the contact spots of the gear on the noise
The ideal contact spot of the gear during the meshing process is between 50% and 80% in the height direction of the middle of the toothed shape, and the top of the tooth and the root of the tooth are not in contact; the contact of the tooth in the middle of the tooth is between 60% and -85%. During the period, the two ends are not in contact, and the shape of the tooth surface contact is like a jujube nucleus, and such contact speckle noise is low. However, it has been found from many years of practice that many gears with lower noise have a certain difference between the contact spot and the ideal state. The contact spots of most noise-qualified gears are not very regular, which is the result of better accuracy of other gears. However, any gear contact spots with low noise must be consistent with the ideal spot; any gear with high noise has irregular contact spots. When the contact spots of the gears appear to be disconnected in the middle; a "Z"-shaped contact occurs; a concave phenomenon occurs; a contact shape appears in a meandering manner; or a contact at the top of the tooth or the root; a single-sided contact of the gear; a flaw in the tooth surface Wait, it will produce higher noise. Therefore, in the manufacturing process of the gear, the above irregular contact spots should be avoided, thereby achieving the purpose of reducing noise.
Conclusion
The above is only the analysis carried out from the gear processing and manufacturing. However, there are still many factors affecting the gear noise, and there are influencing factors in all aspects of the production process, the transportation process, and the assembly process. Therefore, as long as we control every link, it can play a role in reducing noise.
About the author: Shiyan City Car Tooth Auto Parts Co., Ltd. Xie Xuhui
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