Helical gear accuracy mainly controls the transmission accuracy between helical gears during operation, such as transmission stability, instantaneous speed fluctuation, etc. When the tooth side clearance of the helical gear under alternating reverse operation reaches the minimum, the accuracy should be improved if there is impact load, so as to reduce the damage to the helical gear caused by impact load.
In the accuracy of helical gears, the tooth profile error has a great impact on the vibration and noise of helical gears, not only in the size of the error value, but also in the shape of the error curve. In the single error of helical gear, the influence of tooth profile error on vibration and noise is more significant. Generally speaking, the greater the tooth profile error, the greater the noise, but the relationship between them is not simply proportional. In this paper, the tooth profile error is used to reflect the accuracy grade of helical gears, and the influence of different Accuracy grades of helical gears on vibration and noise is calculated.
The tooth profile error can be divided into two items, namely, the tooth profile error caused by the tooth profile angle error Δ FFA and involute error Δ FFF is as shown in Figure 1, and the two parts compose the tooth profile error Δ ff 。
The tooth profile error varies with the curvature radius of the tooth profile, that is, the tooth profile error is a function of the curvature radius of the tooth profile Δ ff ( ρ) ， Therefore:
The equivalent base circle radius is R ′ B2, and the expression is:
In fact, when the involute shape error of helical gear is very small, the influence of tooth profile error on tooth profile angle error can be ignored, then:
The influence of helical gear speed on vibration and noise is also obvious. When the speed is increased, the helical gear cycle becomes smaller and the impact force action time becomes shorter, which will act on the helical gear tooth surface for many times. Therefore, the noise of helical gear will inevitably increase at high speed. Fig. 2 is the vibration and noise influence law of helical gear at different revolutions according to the accuracy grade of helical gear divided according to the tooth profile error. It can be seen from the curve change law in the figure that the noise increases gradually with the reduction of accuracy. The noise of grade 0 precision helical gear is the smallest, while the noise of grade 12 precision helical gear is the largest. However, since it is difficult to process grade 0~3 precision helical gears at present, under the same working conditions, the impact of helical gears with different accuracy on the vibration noise will reach more than ten decibels or even tens of decibels, The project selection shall also take into account economic factors while meeting the requirements.