| 摘要 |
<p>A universal joint in which cracks are less likely to occur, even if the joint is subjected to repeated excessive loads, in the bottom of the thread of a bolt fixing a bearing cup or a bearing holder to a yoke, and that can bear long term use under condition found, for example, in a drive system for rolls of a rolling machine where a large load acts on the joint. In a block-type universal joint etc. where a bearing cup (3) supporting a trunnion (11) of a cross-shaped shaft (1) through needle rollers (2) is fixed to a yoke (4) with a bolt (5), the bolt (5) is produced by rolling after it is subjected to heat treatment. As a result, fiber flows along the shape of the screw thread are formed and residual compression stress is generated directly under the surface of the bottom of the screw thread, which drastically improves an allowable fatigue limit in comparison with a bolt produced by conventional turning.</p> |
