Position detecting device and industrial vehicle having the position detecting device

摘要

A position detecting device which detects a position of a piston rod based on the time for an ultrasonic wave to be emitted from a sensor (11) toward a lower surface of the piston (6) in a hydraulic cylinder (5), reflected by the surface of the piston and received by the ultrasonic wave sensor. The temperature of the oil is detected by a temperature sensor (18), a microcomputer (17) sets a strength of either the ultrasonic wave emitted from the ultrasonic wave sensor, or the reception level threshold in accordance with the temperature of the oil. Accordingly, even if the viscosity of the oil changes due to temperature, the ultrasonic wave transmission and reception levels make it possible to accurately detect the position of a movable member of the hydraulic cylinder.