| 摘要 |
PURPOSE:To reduce an intake air sound without sacrificing responsiveness of a booster by forming a recesss-projection surface on an inside surface of a cylindrical part of a shell, and reducing a collision sound generated when pressure fluid flowing in a voltage transforming chamber collides with the inside surface of the cylindrical part. CONSTITUTION:A synthetic resin annular member 35 is pressed in and fixed to an inside surface of a cylindrical part 2a formed on a rear shell 2. Plural annular grooves 35a extending in the circumferential direction are formed on an inner peripheral surface of the annular member 35, and a recess-projection surface is formed. The annular grooves 35a may be formed in the parallel direction or even in the oblique direction, or may be formed even in a grid shape. When a brake pedal is stepped down and pressure fluid is introduced to a voltage transforming chamber D through a voltage transforming passage 21, since it collides with the recess-projection surface in the cylindrical part 2a of the rear shell 2, a collision sound is reduced, and an intake air sound is reduced. Since flowing resistance of the pressure fluid becomes smaller than when a sound absorbing material is arranged in a pressure passage, a sacrifice of responsiveness is also reduced. |
