| 摘要 |
PURPOSE:To make the minimal travel of a feed screw attainable as well as to make fine positioning performable at high speed, by controlling pressure in a static pressure pad being opposed to a static pressure thrust bearing in addition to positioning by means of a motor and the feed screw. CONSTITUTION:When a controller 111 outputs a control signal He1 to a motor driving device 112 and drives a DC motor 110, a table 101 travels and this travel is fed back to the controller 111, and when the table 101 becomes below a minimum positioning value at the motor to the desired value, the control signal He1 is turned to zero, stopping the motor. Next, the controller 111 outputs a control signal Hc2 of a difference between the desired value and the table position to a servoamplifier 115, and when the signal HC2 is amplified and outputted to a servo valve 116, the valve 116 distributes supplied pressure PS to pockets 107a and 107b at both sides of a static pressure thrust bearing 107 at a pressure differential in proportion to the output so that the table travels to the pocket side where pressure is low, and the travel value is fed back to the controller, and when it travels up to the desired value, it is held at the supplied pressure. |
