REVERSE FLOW COOLING TYPE MULTISTAGE ROOT TYPE VACUUM PUMP ACCOMPANYING GAS DILUTION

摘要

PURPOSE:To perform enough dilution of reaction gas by using inactive gas as drive gas for an ejector by a method wherein the ejector having a compression function is located on the downstream of an initial stage pump division and in a coupling line for intercoupling the delivery port of a preceding stage pump division and the suction port of a subsequent stage pump division. CONSTITUTION:Gas G10 sucked through a suction port 101 of a first pump division 10 to the interior of a housing is carried as delivery gas to a delivery port 102 through the motion of a rotor. The gas is sucked in an ejector 132 operated by means of drive gas G13 introduced through a drive gas nozzle 133, and is mixed with the gas G13. Since gas having a pressure equal to or higher than an atmospheric pressure is discharged in vacuum, heat insulation expansion of the driven gas occurs to a diffuser part 134 of the ejector 132, and a gas temperature is reduced. Delivery gas diluted by means of the gas G13 flows in a pump division 10 through a coupling line and a part thereof flows therein through a reverse flow line 106 branched from the coupling line, and reverse flow compression is effected by means of gas diluted by the inactive gas.