Patent ID: 7836690

Claim:
A positioning control mechanism for a double-acting air cylinder comprising: a double-acting main cylinder having a first pressure chamber and a second pressure chamber on both sides of a piston in that the piston is reciprocated by air supplied to or exhausted from the pressure chambers; a length measurement sensor for measuring an acting position of the piston along the entire stroke of the piston; an air supply section having an air source; a main air circuit interposed between the air supply section and the main cylinder; and a controller for electrically controlling the main air circuit, wherein the main air circuit includes a first air flow path and a second air flow path connecting between the air supply section and the first and second pressure chambers of the main cylinder, respectively; to the first air flow path, a two-port supply solenoid valve is connected to intersect the first air flow path, while a two-port exhaust solenoid valve is connected at a position nearer to the first pressure chamber than the supply solenoid valve to intersect the first air flow path between the first pressure chamber and the atmosphere; and the second air flow path is configured to supply air at a set pressure to the second pressure chamber from the air supply section during the reciprocating of the piston while maintaining the state of the second pressure chamber restricted to the atmosphere, and wherein the controller includes inputting means electrically connected to the length measurement sensor and the solenoid valves for inputting a target acting position of the piston; and the controller is configured to move the piston to the target acting position and stop it at the position by on-off controlling the solenoid valves on the basis of the compared results between target position information inputted by the inputting means and measured position information measured by the length measurement sensor: when the piston is advanced, the supply solenoid valve is turned on so as to communicate the air supply section with the first pressure chamber while the exhaust solenoid valve is turned off so as to shut the first pressure chamber off the atmosphere, when the piston is backed, the supply solenoid valve is turned off so as to shut the air supply section off the first pressure chamber while the exhaust solenoid valve is turned on so as to open the first pressure chamber to the atmosphere, and when the piston is stopped at the target position and maintained at the stopped position, both the supply solenoid valve and the exhaust solenoid valve are turned off so as to confine air within the first pressure chamber.