| 摘要 |
PURPOSE: An inner diameter of a crank shaft gear is expanded to eliminate an unnecessary part, thereby decreasing weight and improving energy efficiency. CONSTITUTION: A crank shaft gear(20) is fixed in a gear mounting end of a crank shaft by a key. A tooth(20b) is formed in outer circumference of the crank shaft gear(20) to fix a timing belt. A mounting hole(20c) is formed in inside of the crank shaft gear(20) to mount with the gear mounting end. A key groove(20a) is formed in the mounting hole(20c) to insert the key. A vertical end portion(24) is formed in the mounting hole(20c), and an expansion end(22) is formed from the vertical end portion(24) toward outside to reduce weight of the crank shaft gear(20).
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