High speed driving method and apparatus of pressure cylinder

The present invention relates to high speed driving method and mechanism of a pressure cylinder which is suitably utilized when a work is pressurized at an end of a stroke like a gun cylinder for spot welding. A pressure cylinder is connected to an air pressure source through a servo valve, the servo valve is controlled as an on/off switching valve by a control section in an advancing working step of a piston rod, and at the time of backward stroke of the piston rod, an operation position of the piston rod is detected by a position detector to feedback a detection signal to the control section, the servo valve is controlled by the control section such that a deviation between the operation position and a preset stopping position is eliminated, the piston rod is stopped at an intermediate stopping position, and a state in which substantially the same pressures are supplied to pressure chambers formed on opposite sides of the piston is maintained.