PURPOSE: To prevent the generation of an error in a rotation amount of a wheel detected at a given distance even when a wheel is deformed by selecting the length of a distance specifying device, located on a running route to specify a distance range in which a rotation amount of a wheel is detected, to a value being integral number times as long as the outer peripheral length of a wheel.
CONSTITUTION: A gauge 10 for correcting a speed serving as a distance specifying device is mounted on a track 2 and on the inlet side of a wheel device line in an automobile assembly process. The gauge is formed of a long stripform light shield plate, a rectangular notch part 10a opened downward is formed closer to the one end thereof, and the gauge is mounted on a web 2c of a track 2 through brackets 11 and 11. A photo sensor PS located in the vicinity of the drive wheel of a vehicle running on the track 2 is caused to approach the gauge 10, and ON and OFF signals are output. In this case, a period between ON-operation of the photo sensor PS and re-ON-operation, namely, length between the one edge of the gauge 10 and the other edge of the notch part 10a is selected to a value being an integral number times as long as the outer peripheral length of a drive wheel to specify a reference distance L.
TAGUCHI FUJIO
ODA TOMIYOSHI
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