| 摘要 |
<p>Silent pneumatic brake servo comprising a shell (10) with an axis of symmetry (X-X') sealingly divided by a movable wall structure (12, 20) into a front chamber (14) permanently linked to a vacuum source, and a rear chamber (16) selectively linked to the front chamber (14) or the outer air by a three-way valve (36) actuated by a plunger (28) sliding in a bore (26) of the movable wall (12, 20) and secured to an axial control rod (30) acted on by a return spring (68) housed in an annular space (32) between the control rod (30) and a rear tubular part (22) of the movable wall structure (12, 20) projecting outside of the shell (10), the three-way valve (36) being arranged in said rear tubular part (22) and including a valve element (36) cooperating through a first annular surface (A) with a first valve seat (28a) formed on the plunger (28) and through a second annular surface (B) with a second valve seat (20a) formed on the movable wall (20). According to the invention, the first (A) and second (B) annular surfaces are located in different annular planes, the first (A) and second (B) annular surfaces being linked by a surface (C) with a generally truncated shape for guiding moving air downstream of the first valve seat (28a) when it is remote from the first annular surface (A).</p> |
