平面连杆机构极位夹角定义的探讨

Study of the Definition of the Crank Angle Between the Two Limiting Positions of Planar Linkage Machanisms

急回平面连杆机构实现了机构工作行程的慢速进给和空间行程的快速退回 ,从而提高了生产率。而平面连杆机构的急回特性与其极位夹角θ密切相关。现行的众多教科书中对极位夹角的定义和锐角的取值范围 ,限制了书中所确定的行程速比系数k与极位夹角θ的关系式的通用性。本文对极位夹角θ的新定义解决了这个问题 ,并通过实例说明了其正确性和可行性。

Because of its lower follower speed in the working stroke and the higher follower speed in the return stroke, quick-return planar linkage mechanisms can raise produceing efficiency. The quick-return characteristics of planar linkage mechanisms have closely relationship with its crank angle θ between the two limiting positions. The definition of the angle θ in the present text books restricts the widely use of the formula about the coefficient k of travel speed variation and the θ existed in these books. By using the definition of the θ presented in this paper, this problem is soluted, and the results of two examples show that the definition of θ is right and practicable.