Static analysis of constraint conditions of a rotational-to-linear motion conversion mechanism

Abstract

A Scotch yoke mechanism is often used instead of a slider-crank mechanism to obtain high output power. The kinematics of the Scotch yoke mechanism are characterized by elements translating along two orthogonal axes. This is realized by two slider guides placed in parallel in each direction. As a result, the Scotch yoke mechanism achieves high power transmission with high rigidity. A drawback of this mechanism, however, is that it requires high precision in machining and assembly processes. In this study, an orthogonal double-slider mechanism was developed to solve problems caused by machining and assembly errors. With an L-shaped double slider, the mechanical structure is simple and this mechanism has the advantage of lower driving torque compared with a slider-crank mechanism. The developed mechanism is derived from a Scotch yoke mechanism, but the major difference between them is the arrangement of the sliders and slider guides. This study is the first to investigate the effect of the arrangements of slider guides on the driving characteristics of the mechanism. Through measurements of the force acting on slider guides and their deflection, the effect of the slider configuration was experimentally verified as the number of the slider guides was reduced from the maximum of four. In addition, when the mechanism was used in a water pump, the change in shear force acting on the slider guide in the direction of piston translation was investigated as the number of slider guides was reduced. The deflection of the slider guides for the piston was measured under static conditions. Also, the starting force from a stationary state was measured, revealing that the load acting on the mechanism was reduced by removing one of the slider guides arranged in parallel.