| 摘要 |
<p>PCT No. PCT/JP90/00287 Sec. 371 Date Feb. 28, 1991 Sec. 102(e) Date Feb. 28, 1991 PCT Filed Mar. 6, 1990.A piston cylinder device having a piston stroke measurement includes a cylinder tube (1) having an inner tube (2) made of a nonmagnetic material and an outer tube (3) formed on the outer peripheral surface of the inner tube and made of a fiber-reinforced resin material. A piston (76) fixed to a rod (75) is disposed slidably inside the cylinder tube. A stroke detector is composed of a position indicating magnet (80) disposed in the piston and an elongated sensor (81) disposed in the cylinder tube. The elongated sensor includes a thin elongated pipe (82) extending along the cylinder tube between both of its ends and holds at least one magnetostriction line (87) having a large magnetostriction coefficient, a driving coil (84) wound on at least one of the ends of the thin elongated pipe. A pulsed input current to the drive coil causes magnetostriction phenomenon on the magnetostriction line generating an ultrasonic wave. A detecting coil (86) wound on the thin elongated pipe in a predetermined length separately from the driving coil induces a detection signal generated by reverse magnetostriction when the ultrasonic wave passes by the position of the magnetostriction line corresponding to the position indicating magnet. Also, at least one pin-like magnet (20A, 42A) for correcting a measurement error due to a temperature change of the stroke detector, and disposed at a position adjacent to the detecting coil (86) and more inward in the axial direction than both ends of the detection coil are fixed to both ends of the cylinder tube (1).</p> |
