| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a method and an apparatus for adjusting the gas circulating amount of a vacuum exhaust device capable of easily adjusting the circulating flow rate of the gas returned to a vacuum chamber through a gas flow rate circulating line even if the difference pressure of a gas circulating line part is not more than the operation pressure (50 kPa) of a gas flowmeter. SOLUTION: In the method for adjusting the gas circulating amount of the vacuum exhaust device equipped with the vacuum chamber 1 for introducing gas, a first vacuum pump 5 for reducing the pressure in the vacuum chamber 1 to a desired pressure, a second vacuum pump 7 reducing the back pressure of the first vacuum pump 5 to allowable back pressure or less, and a gas circulating line 8 for again returning a part of the gas discharged from the first vacuum pump 5 into the vacuum chamber 1, the relation of formula: Q2 =C×(Pd-Pc) (wherein, Q2 is the circulating flow rate of the gas returned to the vacuum chamber 1 through the gas circulating line 8, Pc is the pressure in the vacuum chamber, Pd is the pressure of the upstream part of the gas circulating line and C is the conductance of the gas circulating line) is used to change the effective exhaust speed of the second vacuum pump 7 and the difference pressure Pd-Pc of the gas circulating line is adjusted to adjust the gas circulating flow rate Q2 .</p> |
