SUBCONTRACTABLE POWER TRANSFER WITH SELECTIVE AUTOMATIC AND POWER-REGULATED SUPPORT

摘要

The invention relates to a pneumatic servomotor for an assisted braking, comprising a rigid casing (1) in which a moving airtight partition wall (2) defines a front chamber (3) and a rear chamber (4), a pneumatic piston (5) travelling with the moving partition wall (2), a plunger (8), housed within the piston (5) and driven by a control rod (7) and controlling the state of a three-way valve (9), force-transmitting means (10, 13, 17, 18, 31), adapted for receiving and transmitting at least one assistance force (Fa), exerted by a front face (51) of the piston (5) when the valve (9) puts the rear chamber (4) under a second pressure (Pa), the plunger (8) including a front section (81) comprising retaining means (18, 31) intended to tie down the front section (81) of the plunger (8) to the pneumatic piston (5).According to the invention, the retaining means comprise a unidirectional clutch device (31, 18) for the driving of the force-transmitting means (10, 13, 17), independently of the control rod (7) and of the rear section of the plunger (8) when they are biased by the pneumatic piston (5), as a result of the actuation of the control rod (7), the speed of which is higher than a predetermined value.