| 摘要 |
PROBLEM TO BE SOLVED: To measure the amount of an extension due to an abrasion of a link highly accurately in a short time, by detecting a rotational angle of a comparator sprocket corresponding to a rotation of a reference sprocket. SOLUTION: A reference sprocket wheel 2 is rotated by an electric motor 6. Meshing teeth 2g are sequentially meshed with rollers 10, thereby raising a mechanism part M which in turn drives a comparator sprocket 3 at a position spaced a distance L0 . At this time, if there is no extension in a link chain 33e, rotational phases of the wheels 2, 3 agree. However, if the chain 33e is extended byΔL1 , the rollers 10 to be meshed with meshing teeth 3g are raised byΔL1 , and the rotation of the wheel 3 is delayed by a rotational angleΔθ1 corresponding to the amount of the extensionΔL1 . The delay is detected at a measuring hole 4 of a rotational position detection sensor 8, whereby an absolute rotational angleθ1 is detected at a rotational angle detecting sensor 7. When the wheel 2 is further rotated once and the chain 33e is extended by an extension amountΔL2 , similarly the wheel 3 is delayed by a rotational angleθ2 and an absolute rotational angleθ2 at the second time is detected at the rotational angle detecting sensor 7. The extension amount of the chain 33e is calculated based on the rotational anglesθ1 andθ2 .
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