| 摘要 |
PROBLEM TO BE SOLVED: To miniaturize a driving gear of a hold mechanism holding a workpiece of a lathe, moreover hold the workpiece highly accurately even in cutting work. SOLUTION: A hybrid hydraulically-driven unit 10 integrally formed with a hydraulic cylinder 11, piston pump 12, motor 13, etc., is provided in a chuck inside, a clamp arm 2a, 2b is associated to operate by a reciprocating motion of a draw bar. A chuck control part 20, receiving a detection signal from a pressure sensor 17 detecting an oil pressure in an oil feed pipe 18b and a linear scale 16 detecting a position of a piston 11b in a cylinder, controls the direction of rotation and the speed of the motor 13 through a motor drive part 21. By suitably changing a moving speed of the clamp arm 2a, 2b, shortening of clamp action can be attained, and by controlling the flow of oil so as to fixedly maintain an oil pressure during the clamping of a workpiece W, its vibration can be suppressed, and high work accuracy can be attained.
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