In small tooth difference of inner meshed transmission, there were a few pairs of tooth faces which were apart from each other for a small gap beside the contact point generated by two meshed teeth.

在少齿差内啮合传动中，存在多对接近啮合的小间隙齿面于理论啮合点左右，轮齿受力产生的微小变形使得某些对齿面相互接触进入啮合状态。

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The initial contact of helical gear teeth is a point, which changes into a line as the teeth come into more engagement.

斜齿轮轮齿的初始接触是一点，当齿进入更多的啮合时，它就变成线。

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