短语词组短语oil passage slot 油通道缝隙oil guiding slot 导油沟piston oil slot 活塞油槽Oil -returning slot 回油槽;机油泵驱动齿轮pinion with oil slot 油槽齿轮轴errors of distributing oil slot 分配油槽误差double slot oil piston ring 双槽油环 返回 oil slot