Balancing of a Slider-Crank Mechanism by Using a Counter Mass and a Progressive Spring with Two Rates

摘要

This paper investigates the possibility to individually balance the dynamic forces and moment that are characteristic to the slider-crank mechanism. The unbalanced forces that act on the frame which holds the slider-crank mechanism are known as shaking forces. Likewise, the unbalanced moment that acts on the frame is known as shaking moment. Because both force and moment are unbalanced, they cause vibrations on the entire machine that holds the mechanism. The most common mean of balancing the slider crank mechanism by using a counter mass. This is applied for most of the commercial mechanical devices that use the mechanism. However the nature of the mechanism does not allow perfect balancing in such a way. The different nature of motions that govern the slider and the crank imply that a counter mass can only statically balance the mechanism. Perfect dynamic balancing cannot be achieved this way. In this paper the excitations that act on the mechanism are split by the nature of motion that generates them and balanced accordingly. Therefore two motions are defined. The piston motion and the crank motion. The dynamic force associated to the crank motion is balanced with a dynamically equivalent system. The dynamic force associated with the piston motion is balanced by a progressive spring with two rates.