| 摘要 |
PURPOSE:To give compressive residual stress to a sliding surface of a pulley and thereby aim at a distinct improvement in its service life, by machining a surface- hardenable steel material into a pulley form, hardening it through heat treatment, grinding it, and shot-peening it with fine steel balls being above the specified hardness each. CONSTITUTION:CrMo alloyed steel equivalent to SCM2 is machined into a pulley form at the input or output side for a belt driving type stepless transmission, then, this rough section is hardened and annealed, besides heat treatment, and ground up into a final form as a pulley. And, using cast steel balls of Hv 600- 800 in hardness by way of example, shot-peening treatment takes place under the treatment condition of 0.3-0.35mm. in arc height and more than 95% in coverage. Thus, in each sliding surface of both pulleys 1 and 2, a hardness drop of up to about 0.1mm. in depth from a surface to be produced by grinding and a drop in compressive residual stress are harder than the hardness by hardening, annealing and heat treatment owing to shot-peening treatment using cast steel balls and, what is more, the compressive residual stress also can be made higher than the state of hardening, annealing and heat treatment. |
