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Why helical gears are used in the manufacture of reducer

2018/10/25 18:41:59 Viewers:
The main disadvantage of spur gears is that they generate vibration. Whether it is due to design, manufacture or deformation reasons, at the same time along the entire tooth surface may occur some changes in the shape of the involute. This will lead to a regular stimulus per tooth, which is usually very strong. The resulting vibration not only causes large loads on the gears but also causes noise. Another disadvantage is that the additional strength sometimes obtained by the engagement of two pairs of teeth in contact time cannot be utilized, because the stress is limited by the condition of the single tooth engagement in the cycle.

Helical gears can be seen as cylindrical gears with a set of flake gears misplaced so that each piece of contact is at different parts of the tooth profile, resulting in the compensation of each flake gear error, which is very effective due to the elasticity of the teeth, thus resulting in such a result that the error is less than 10 mm. The teeth of the gear can make the errors equalize, so it can run as smoothly as the teeth within 1 mm under load. Because at any instant, about half the time (assuming the degree of coincidence is about 1.5) there will be two teeth engaged, which brings additional benefits in terms of strength. Therefore, the stress can be established on the basis of 1.5 times the width of the tooth, not the width of the tooth.

It is difficult and inexpensive to manufacture and assemble a large number of thin spur gears, so they are made into gears that are connected together and the teeth are in the direction of helix. Helical gears are not like spur gears, which cause bad axial forces. But the benefits of vibration and strength far outweigh the disadvantages of axial thrust and slightly increased manufacturing costs. Therefore, helical gears are chosen instead of spur gears in the manufacture of reducers. For example, there are four series: R series coaxial helical gear reducer, K series helical bevel gear reducer, S series helical gear worm gear reducer, F series parallel shaft helical gear reducer.

Note 1:

What is spur gear: spur gear is the gear parallel to the rotating shaft. We only discuss the theory of parallel-axis gear transmission, so any cross-section perpendicular to the two gear shafts is exactly the same.