Aspects Concerning the Dynamics of the Mechanisms with Clearances

Abstract

The clearances in the cinematic links appear due to the long functioning. In the paper we shall make a few considerations of geometric and mechanic type about the clearances in the linkages, linkages planes with rotation joint links. We shall elaborate methods to study the influence of the clearances. Consider a rotational kinematic coupling clearance, the clearance being defined by the distance, difference between the radius of the bearing and the radius of the journal. This relationship between elements is unilateral. Journal's behaviour inside the bearing can be highlighted the value normal reaction force. The journal can have the following phases, phase contact (when there is contact between the bearing and journal, the normal reaction force is zero) flight phase (no contact between end journal bearing at this stage is normal reaction force 0). It is considered the most dangerous phase, recovery phase of flight phase where the contact is restored. In this phase occurs shocks, shocks in turn produce vibration in the mechanism leading to the destruction of the system. The clearance size is directly proportional to magnitude impact and vibration level especially high. To be reduced or even eliminated these shocks, the paper presents a solution. Crank Mechanism with clearance, mechanism considered in this paper applies a force so that maintain contact between the bearing and journal, is considered the center of gravity of the connecting rod the forces and the moment. Based on the relations obtained from equation echililibru and vector equation of the contour goes to the numerical calculation for the engine element is inserted angle value (which defines the initial position of the mechanism), one deduces the angles, which define the position of the mechanism. Any would be their source of appearance, they usually produce unwished effects during the mechanisms functioning.