| 摘要 |
A roots pump (10) has a housing (11), a plurality of rotary shafts (22,25), a rotor (28-37), a confluent passage (49,51,52,53) and a closed space (P1,P2). The housing (11) forms therein a pump chamber (17,18,19,20,21). The rotary shafts (22,25) are supported on the housing in parallel relation to each other. The rotor (28-37) is mounted on each of the rotary shafts (22,25), and the rotors (28-37) on any adjacent rotary shafts (22,25) are in engagement with each other. A set of the engaged rotors (28-37) is accommodated in the pump chamber (17,18,19,20,21). The confluent passage (49,51,52,53) is formed along one crossing line of paired imaginary swept peripheral surfaces (59,60) in one-to-one correspondence with the paired and engaged rotors (28-37). The closed space (P1,P2) is formed in one-to-one correspondence with each of the paired rotors (28-37) between the paired rotors (28-37) and paired peripheral wall surfaces (59,60) which form the pump chamber (17,18,19,20,21). The closed space (P1,P2) initially joins the confluent passage (49,51,52,53) from a terminal end thereof with rotation of the paired rotors (28-37). <IMAGE> |
