| 摘要 |
PURPOSE: To quietly actuate a control valve during application of brake by a method wherein a plunger provides a smooth profile surface to feed air in a radial direction passage without the occurrence of turbulence and the generation of noise when air flows to a rear chamber through a hub is damped. CONSTITUTION: To reduce the occurrence of turbulence in a flow of fluid under the ambient pressure of a plunger 52, a light porous material 51, such as polyethylene foam in this case, is arranged in a groove positioned between a spherical surface 62 and a conical surface 60, a portion extending from the end part of the semispherical surface 62 to the start of the conical surface of the plunger 52 and forms a smooth surface. This constitution provides the porous material 51 with a smooth surface extending from the end part of the semispherical surface sheet 62 to the conical surface 60 and absorbs noise by the porous material 51, whereby noise generated by a flow of air to the rear chamber is almost removed at a servo motor. |
