Patent ID: 7536944

Claim:
An air pressure cylinder for positioning control, comprising: a slight-vibration-suppressing mechanism attached to a piston rod of the air pressure cylinder, the air pressure cylinder being configured to stop a piston at a target position by positioning control, wherein the piston is moved by feeding and discharging compressed air to and from a head side pressure chamber and a rod side pressure chamber, and the piston rod penetrates through a rod cover and extends to an exterior of the air pressure cylinder, the slight-vibration-suppressing mechanism comprising: a pair of one-directional sealing members pressed to the piston rod by compressed air and generating a sliding friction for suppressing slight vibrations, an air cell surrounding a periphery of the piston rod between the pair of sealing members and configured to introduce the compressed air acting on the sealing members, and an air flow path for feeding and discharging the compressed air to the air cell, wherein the pair of sealing members includes a first sealing member and a second sealing member and the pair of sealing members is positioned in a direction such that the compressed air in the air cell presses the sealing members against the piston rod, wherein a third sealing member is provided between the rod side pressure chamber and the first sealing member, and the third sealing member seals off the rod side pressure chamber to prevent compressed air from flowing to the first sealing member, and wherein a hole is formed between the third sealing member and the first sealing member, and the hole makes a gap between the piston rod and the rod cover to communicate with an exterior of the rod cover.