| 摘要 |
A Roots pump rotates a plurality of rotors (23-32) by a pair of rotary shafts (19, 20) to draw gas. Each rotary shaft (19, 20) extends through a rear housing member (14) of the Roots pump. A plurality of stoppers (67, 68, 72) are located on each rotary shaft (19, 20) to integrally rotate with the corresponding rotary shaft (19, 20), and prevent oil from entering a fifth pump chamber (43) of the Roots pump. Stoppers (67, 68, 72) have a circumferential surface (671, 681, 721), respectively. Annular oil chambers (70, 71, 73) collect oil. The oil chambers (70, 71, 73) are located about an axis (191, 201) of the rotary shaft (19, 20) to surround the circumferential surface (671, 681, 721) of the stopper (67, 68, 72). This effectively prevents oil from entering the pump chamber (43) of the Roots pump. <IMAGE> |
