Patent ID: 8370085

Claim:
A position detecting device, comprising: an ultrasonic wave transmitting device arranged at a part to be detected, plural ultrasonic wave transmitting and receiving devices, each of said transmitting and receiving devices being spaced from the part to be detected, a sonic wave speed calculating device adapted to calculate sonic wave speed of each of said plural ultrasonic wave transmitting and receiving devices and further adapted to calculate sonic wave speed at the part to be detected, said sonic wave speed at the part to be detected depending upon the sonic wave speed of each of said plural ultrasonic wave transmitting and receiving devices, and a distance calculating device adapted to calculate a distance from the ultrasonic wave transmitting device arranged at the part to be detected to a specific ultrasonic wave transmitting and receiving device of said plurality of ultrasonic wave transmitting and receiving devices, depending on a spread time of ultrasonic waves from the ultrasonic wave transmitting device arranged at the part to be detected to the specific ultrasonic wave transmitting and receiving device, and depending on the sonic wave speed at the part to be detected; wherein the plural ultrasonic wave transmitting and receiving devices are arranged at corners of plural imaginary polyhedrons, the part to be detected is contained in one of the plural imaginary polyhedrons, and the sonic wave speed calculating device calculates sonic wave speed at the part to be detected depending on sonic wave speed between the plural ultrasonic wave transmitting and receiving devices arranged at the corners of the one imaginary polyhedron containing the part to be detected.