| abstract |
A vacuum pressure control apparatus includes a vacuum proportional opening and closing valve 18 which is disposed on a pipe connecting a vacuum chamber 11 and a vacuum pump 19 and changes its opening to control the vacuum pressure in the vacuum chamber 11 , and a pressure sensor 17 which measures the current vacuum pressure in the chamber 11 . The vacuum proportional opening and closing valve 18 has a valve seat 36 and a valve member 33 provided with an O-ring 35 which is made contact with or separate from the valve seat 36 . The vacuum pressure control apparatus configured as above controls the pressure in the chamber 11 by changing an elastic deformation amount of the O-ring 35 which is in contact with the valve seat 36 and thereby changing the flow quantity of gas leaking between the valve seat 36 and the O-ring 35. |