In the process of heat treatment, heating and cooling of hypoid gear, due to the uneven thermal stress and tissue stress in different parts, the distortion of hypoid gear is difficult to control. Although the heat treatment distortion of hypoid gear is difficult to control, the variation of tooth surface error before and after heat treatment of active and passive teeth is basically the same under the same heat treatment conditions. In order to analyze the variation law of tooth surface error before and after heat treatment, 27 sets of hypoid gears produced in the same batch are selected as samples. The variation of tooth surface error of hypoid gears before and after heat treatment is shown in Figure.

For 27 sets of hypoid gears in this batch, there is an obvious law of heat treatment distortion of hypoid gears. As shown in Fig. (a), the pressure angle error of the convex surface of the main gear of the hypoid gear is significantly increased by about 5 ‘, and the pressure angle error of the concave surface of the driven gear is significantly increased by about 7’; The variation of pressure angle error is large, but after heat treatment of hypoid gear, the pressure angle error tends to be stable, the convex pressure angle error of main gear is basically stable at about 8 ‘, and the concave pressure angle error of driven gear is also basically stable at about 5’.

As shown in Figure (b), the helix angle error of the convex surface of the main tooth of the hypoid gear is significantly reduced by 3 ‘, and the helix angle error of the concave surface of the driven tooth is significantly reduced by about 7’. Combined with the analysis, the pressure angle error after heat treatment is stable at about – 2 ‘, but the spiral angle error of hypoid gear after heat treatment fluctuates obviously, which is roughly distributed in the range of – 8’ ~ – 6 ‘.

Through the heat treatment distortion law of hypoid gear, it is not difficult to find that the influence of pressure angle error on the quality of contact area can be basically ignored. Therefore, the influence of the relative helix angle error of driving and driven teeth on the quality of contact area after heat treatment of hypoid gear is mainly studied.