| 摘要 |
PROBLEM TO BE SOLVED: To prevent shortening of the life by accelerating abrasion of a sliding surface by making a static ring baked carbon, making a rotary ring silicon nitride sintered body and making a seal effective ratio within a specified range. SOLUTION: A shaft seal mechanism 10 is constituted of a static ring 12 mounted on a casing 2 together with a ring 11 and a rotary ring mounted on an impeller 5 via a retainer. The static ring 12 comes into contact with a rotary ring 13 and seals a coolant going to the center of the rotary shaft 4 from the outside. The static ring 12 is made baked carbon and the rotary ring 13 is made silicon nitride sintered body. The inside diameter of the static ring 12 and the effective seal surface width of the static ring 12 are defined as Di and rp, respectively, rp/Di is difined as a seal effective width ratio, and rp is determined so that the seal effective width ratio may be within a range of 0.07 to 0.22. Thus, generation of missing of solid is prevented, durability is improved and leakage amount can be suppressed.
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