Patent ID: 8905409

Claim:
A stroke detection device for a pair of front forks of a motorcycle which detects a variation in length with respect to a reference length of front forks, in which each of the front forks includes a tubular inner tube and a tubular outer tube, one end of the inner tube is inserted into the outer tube through an opening at the other end of the outer tube such that each of the inner tube and the outer tube is movable in a direction along a center line thereof, and one end of the outer tube is coupled to an axle of a front wheel of the motorcycle and the other end of the inner tube is coupled to a bracket, or one end of the outer tube is coupled to the bracket, and the other end of the inner tube is coupled to the axle of the front wheel of the motorcycle, the stroke detection device comprising: a stem shaft which is formed of a conductor in a shape of a cylinder coupled to the bracket, in which a center line of the cylinder is located to be coincident with a steering center line of handlebars of the motorcycle, and the center line of the cylinder is located in parallel to the center lines of the inner tubes and the outer tubes of the front forks coupled to the bracket, and which is mounted in a vehicle frame of the motorcycle so as to be rotatable about the steering center line of the handlebars as a rotation center and serves as a steering center axis of the handlebars; and a coil which is formed of a conductor and whose center line is located to be coincident with the center line of the cylinder of the stem shaft or in parallel to the center line of the cylinder of the stem shaft so as to be movable in a direction along the center line of the cylinder of the stem shaft with movement in a direction along the center line of the inner tube and the outer tube, wherein a variation in inductance of the coil based on change in length in which the coil entering the cylinder of the stem shaft through a lower end opening of the cylinder of the stem shaft and the cylinder of the stem shaft overlap each other is output as a value for obtaining the variation in length with respect to the reference length of the front forks.