ラビリンスシール空気圧シリンダにおける摩擦力の算定

Abstract

This paper concerns the friction force of a pneumatic cylinder with a metal seal of labyrinth structure as the piston seal. One major problem in the most widely rubber-sealed pneumatic cylinder used is that friction force greatly affects its performance because the driving force is relatively low, specifically when performing tracking control of the piston to an arbitrary position. On the other hand, a labyrinth-sealed pneumatic cylinder, which was developed for the purpose of reducing friction force, is capable of realizing quick and precise operation. In addition, it excels in terms of resistance to heat and wear, although a labyrinth seal causes deterioration of the damping capacity of a system due to low friction and air leakage from clearance at the seal. The labyrinth-sealed pneumatic cylinder has received little attention because of its disadvantages and so its dynamic properties are not elucidated enough for many practical applications.This paper, in the first place, conducts measurements in order to investigate the behavior of the dynamic and static friction forces acting on the sliding parts in a labyrinth-sealed pneumatic cylinder, as well as its performance at low speed, from the viewpoint of stick-slip occurrence. Comparing with a rubber-sealed pneumatic cylinder, its fundamental disposition is examined and grasped empirically. Furthermore, applying hydrodynamic lubrication theory to the labyrinth seal, the pressure of the lubricant film formed on the seal surface is numerically calculated. The dynamic friction force generated by the lubricant film is estimated from the pressure distribution obtained. The numerical results are verified by referring to the measurement results, showing that the dynamic friction force can be approximately computed by this numerical approach.