| 摘要 |
PURPOSE:To enlarge flow passage area at opening a pressure valve by constituting a pressure valve for changeover of communicating condition between variable pressure chambers in a shell and a pressure fluid source out of a first and a second pressure valves. CONSTITUTION:In a brake booster device, a valve body 6 provided by slidably penetrating a rear shell 2, is provided with a valve mechanism 23 to change over fluid circuits between constant pressure chambers A, C and variable pressure chambers B, D on a atmospheric air passage 17. In the valve mechanism 23, a constant pressure valve 36 as a first valve body 35 energized on the front side with an annular first valve seat 33 formed on the stepped part of the valve body 6 at opening of a constant pressure passage 16 to the atmospheric passage 17 and a spring 34, and seated on the first valve seat 33, is provided. Further, a first pressure valve 40 composed of a second valve body 38 fitted on the outer circumferential part on rear side of a valve plunger 31 and a second valve seat 39a formed on the inner circumferential face of a large diameter part of a movable member 39, and a second pressure valve 44 composed of a third valve seat 42 formed on the member 39 and the valve body 35 seated on there, are provided. |
