| 摘要 |
A timing drive sprocket for a direct injection engine having excellent wear resistance, durability and quiet operation is produced by suppressing wear acceleration at the sprocket tooth surfaces resulting from deterioration of the engine oil, even in a direct injection engine of the kind in which the lubricating oil is likely to deteriorate rapidly. In the timing drive sprocket, a surface hardened layer is formed on at least a tooth surface of the sprocket by a carbonitriding and tempering treatment.
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