| 摘要 |
A pulley comprises a disk and an insert. The insert is fitted into the center of the disk integrally. Linear expansion coefficient of the disk is larger than the same of the insert. A concavity is formed on a periphery surface of the insert so that both side surfaces of the concavity are slanted outwardly, i.e. a distance between the side surfaces become large in proportion to being far from the centerline of the insert. When a slanting angle is defined as an angle between the side surface and a line which is perpendicular to the centerline of the insert on a plane including the centerline of the insert, the slanting angle is set from ten degrees to forty-five degrees, preferably from fifteen degrees to forty-five degrees. The disk is made of synthetic resin such as phenol resin, and the insert is made of metal such as iron.
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