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AssigneeRobert Bosch GmbH
InventorsJoan Simon Barcardit, Fernando Sacristan, Bruno Berthomieu
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The invention provides a pneumatic servomotor for an assisted braking of a motor vehicle, of the type comprising a unidirectional clutch device, which includes a coaxial sleeve (58), sliding on a plunger (46), and axial-locking means, which are capable of locking said sleeve (58) in an end front axial position, in which it locks the piston (22) independently of the control rod (38), when an input force is applied at a given speed on the control rod (38) integral with the plunger (46), characterised in that the unidirectional clutch device comprises damping means, made of an elastomeric material and interposed between a stop-forming transverse intermediate face (59) of the plunger (46) and an opposite transverse face (76) of the sleeve (58), so as to permit, once the input force is released and when the locking means no longer lock the sleeve (58), the noiseless return of the sleeve (58) to its rear rest position.
Pneumatic servomotor (10) for an assisted braking of a motor vehicle, of the type comprising a rigid casing (12), in which a transverse partition wall (14) is movable, thus defining in an airtight manner a front chamber (16) under a first engine negative pressure (P1), and a rear chamber (18) under a second pressure (P2), varying between the engine negative pressure and the atmospheric pressure (Pa);
Pneumatic servomotor (10) according to the preceding claim, characterised in that the sleeve (58) has a tubular shape, with an inner diameter corresponding to the diameter of a front section of the plunger (46), and in that the opposite transverse face of the sleeve is formed by the annular rear face (76) of the sleeve (58).
Servomotor (10) according to the preceding claim, characterised in that the stop-forming intermediate face of the plunger consists of a transverse annular front face (59), borne by a shoulder-forming rear section (49) of the plunger (46), whereas a rear face of said rear section bears the rear annular seat (48) of the valve (50).
Servomotor (10) according to the preceding claim, characterised in that the elastomeric damping means comprise a ring-type joint (78), which is fastened on the annular front face (59) of the shoulder-forming section (49) of the plunger (46).
Servomotor (10) according to the preceding claim, characterised in that the ring-type joint (78) comprises at least a rear annular section (80) and a lip-forming truncated-cone-shaped front section (82), the taper of which is directed backwards, and which is intended to decelerate the sleeve (58) in the course of its return to the rest position, before it actually bears against the rear annular section (80).
Servomotor (10) according to any one of the preceding claims, characterised in that the axial-locking means for the sleeve (58) comprise a substantially annular key (60), which surrounds the sleeve (58) with a given clearance and which is capable of being driven by the moving piston (22), when the input force is applied at the determined speed, so as to rock about a generally transverse axis, in such a way that it may cooperate with the periphery of the sleeve (58) and stop the latter.
Servomotor (10) according to the preceding claim, characterised in that the key (60) comprises at least one branch, which is substantially radially directed and traversed by the sleeve (58), and having locking means intended to cooperate with the periphery of the sleeve (58) so as to lock it.
Servomotor (10) according to the preceding claim, characterised in that the key (60) is received within a cavity (62), traversing the piston (22) perpendicularly to the axis of the latter, and in which it is capable of rocking to take its locking position for the sleeve (58), and in that the key is resiliently returned by a compression spring (67), arranged between the front transverse wall (68) of the cavity and a front face of an upper part (64) of its branch, so as to resume its rest position, in which its branch rests, by its upper part (64), on the rear transverse wall of the cavity while, in the opposite direction, the lower part (70) of the branch bears on a support (72) integral with the casing (12) of the servomotor (10).
Dependencies are inferred from the claim text.