铰链四杆机构曲柄存在条件的新推证

针对传统的铰链四杆机构曲柄存在条件推证中取曲柄的两个特殊位置进行证明的不足,在总结传统的证明方法基础之上,根据机构中三角形的边角关系,运用余弦定理建立关系式,并通过取三角函数极值,解不等式这一新的推证方法,得到了铰链四杆机构的曲柄存在条件连架杆和机架中必有一杆长度最短;最短杆和最长杆长度之和小于或等于另外两杆长度之和.这种推证方法较传统的推证方法更具严密性,易于理解和接受.

New deduction for grashoff's law in hinged four-bar linkage mechanism

In view of the insufficiency in taking the crank two special positions in traditional deduction for the grashoff's law in hinged four-bar linkage mechanism,based on the traditional method,a new method is given by using the cosine theorem to establish relational expression and solving the inequality according to the triangle corner relations in the organization,grashoff's law is obtained in hinged four-bar linkage mechanism:it must have one shortest bar between the frame and the bar linked with frame;the sum of the shortest and the longest bar's length is less than or equal to the sum of the other two bars' length.Compared with the traditional method,this method is stricter and easy to understand and accept.