JPS6431002A - Detecting device of position of piston of hydropneumatic cylinder - Google Patents

Abstract

PURPOSE:To reduce the cost and also to enable the detection suffering little malfunction, by using a Hall element as a magnetism detecting element. CONSTITUTION:The main body 6 of a sensor wherein a Hall element 7 formed in the shape of a plate is fitted in the center of the lower end part on the surface side of a base plate 8 so that it is parallel to the base plate 8, is fitted on the outer peripheral surface of a cylinder tube 2. When a permanent magnet 5 fitted to a piston 3 approaches the main body 6 of the sensor, deflecting plates 11 and 12 of lines of magnetic force are magnetized, and the respective extension ends of the deflecting plates 11 and 12 facing each other at a short distance with the element 7 held between are magnetized in reverse polarities to each other, so that a magnetic field be formed in the direction wherein they face each other. The lines of force magnetic formed by the magnet 5 pass through the deflecting plates 11 and 12 and pierce the element 7 in the direction being the sensing direction of the element 7 and intersecting the surface of the base plate 8 at the right angle, between the respective extension ends of the deflecting plates, and an output voltage corresponding to the intensity of the lines of magnetic force piercing the element 7 is delivered from the element. This output voltage is compared with a reference voltage set beforehand, and the arrival of the magnet 5 (piston 3) at a prescribed position in the tube 2 can be detected thereby.