| 摘要 |
PROBLEM TO BE SOLVED: To provide a vacuum pressure control apparatus in which undershoot of pressure in a vacuum container is prevented without using a heater. SOLUTION: A vacuum pressure control apparatus 8 includes a pilot vacuum proportional open/close valve 18, a pressure sensor 17 and a controller 56. The vacuum proportional open/close valve 18 changes vacuum pressure in a vacuum container by changing an aperture on piping connecting the vacuum container and a vacuum pump and comprises a valve element including an O ring which is abutted with or separated from a valve seat and an air cylinder. The pressure sensor 17 measures the vacuum pressure in the vacuum container. The controller 56 changes an elastic deformation amount of the O ring on the basis of the pressure of the pressure sensor 17 and changes the amount of leakage from the O ring, thereby controlling the pressure in the vacuum container. In the vacuum pressure control apparatus 8, when the pressure in the vacuum container measured by the pressure sensor 17 becomes a fixed or more pressure drop rate, inner pressure of the air cylinder is exhausted. COPYRIGHT: (C)2012,JPO&INPIT |
