| 摘要 |
PROBLEM TO BE SOLVED: To reduce stress in all regions in a cross direction Z of a tube 10 while preventing stress concentration on the end in the cross direction Z of the tube 10 even when a temperature difference between the tubes 10 is greater. SOLUTION: A rib 223 is provided extending from both ends in the cross direction Z of a tube insertion hole to the outside to increase the peripheral rigidity of the tube insertion hole, and so the tube insertion hole is hard to deform therearound into an approximately circular arc shape. Thus, an elongation difference between the center and the end in the cross direction Z of the tube 10 is smaller to prevent stress concentration on the end of the tube. Both ends in the cross direction Z of the rib 223 are not connected to an inside wall portion 23 and so a face 226 between the rib 223 and the inside wall portion 23 is easily deformable in a longitudinal direction X of the tube. Thus, the deformation of the face 226 absorbs the thermal distortion of the tube 10 to reduce stress in all regions of the tube. COPYRIGHT: (C)2007,JPO&INPIT
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