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AssigneeMazda Motor Corporation
InventorsTatsumi Makimae, Yutaka Fujii, Hiroshi Shinagawa
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After it is tightened with a snug torque TA, a bolt is tuned by a total turning angle θS equivalent to the sum of an initial-set turning angle θA and a corrective additional-turning angle (θB+θC). The corrective additional-turning angle (θB+θC) is the sum of a first corrective additional-turning angle θB and a second corrective additional-turning angle θC, the first corrective additional-turning angle θB being to compensate for a situation where a bolt turning angle θ22 corresponding to the snug torque θA on an extension line of the bolt tightening torque properties C2 in a late tightening stage II is different from a bolt turning angle θ11 corresponding to the actual snug torque TA, the second corrective additional-turning angle θC being to compensate for a decrease of an effective bolt axial force that is caused by an existence of the initial tightening stage I.
A bolt tightening method applicable to a bolt having bolt tightening torque properties, in which a torque gradient expressed in terms of the ratio of an additional tightening torque exerted on a bolt to its additional turning angle has a first torque gradient in an initial bolt tightening stage and a second torque gradient in a late bolt tightening stage subsequent to the initial bolt tightening stage, a magnitude of the second torque gradient being greater than that of the first torque gradient, the method comprising the steps of.
A bolt tightening apparatus applicable to a bolt having bolt tightening torque properties, in which a torque gradient expressed in terms of the ratio of an additional tightening torque exerted on a bolt to its additional turning angle has a first torque gradient in an initial bolt tightening stage and a second torque gradient in a late bolt tightening stage subsequent to the initial bolt tightening stage, a magnitude of the second torque gradient being greater than that of the first torque gradient, the apparatus comprising:
Dependencies are inferred from the claim text.