| 摘要 |
A pneumatic brake booster (10), in particular for motor vehicles, is described. The pneumatic brake booster (10) has a control valve (22) for controlling a pneumatic pressure difference, a force input element (24) for actuating the control valve (22), a force output element (38) for transmitting the braking force as well as a reaction disk (34) of elastomer material disposed between the force output element (38) and the force input element (24). Disposed between the reaction disk (34) and the force input element (24) and acting upon the reaction disk (34) is a unit (30) for altering the force transmission ratio between the force input element (24) and the force output element (38) in dependence upon the force exerted upon the force input element (24). The unit (30) comprises a displaceable inner piston (50) as well as an outer piston (54), which surrounds the radially outer side of the inner piston (50) and is displaceable relative to the inner piston (50). The inner piston (50) has at the radially outer side or the outer piston (50) at the radially inner side a depression (50') for receiving material particles, which depression (50') is covered by the in each case other piston (50, 52).
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