Patent Number: 6,490,227

Title: Device and method for detecting position of movable body by using ultrasonic waves

Abstract: An ultrasonic sensor is located in the bottom of a lift cylinder of a forklift and emits ultrasonic waves toward a piston in the cylinder. A controller controls the ultrasonic sensor to consecutively emit ultrasonic waves that have different amplitudes at predetermined intervals. The ultrasonic waves are emitted in order of smallness of amplitude. The controller computes the distance between the ultrasonic sensor and the piston based on a period from when the ultrasonic sensor emits one of the ultrasonic waves to when the ultrasonic sensor receives the ultrasonic wave that is reflected by the piston. As a result, the range of the detectable distances is extended.

Inventors: Nagai; Katsumi (Kariya, JP), Yagita; Yasunobu (Toyohashi, JP)

Assignee: Kabushiki Kaisha Toyoda Jidoshokki Seisakusho

International Classification: B66F 9/20 (20060101); G01S 15/10 (20060101); G01S 15/00 (20060101); G01S 15/88 (20060101); G01S 015/88 (); F15B 015/28 ()

Expiration Date: 12/03/2011