Patent ID: 7987671
Filing Date: 2011-08-02
Classification: B60T

Abstract:
1. Brake master cylinder ( 10 ) for a motor vehicle, the master cylinder ( 10 ) comprising a substantially axial body ( 12 ) inside a bore ( 14 ) of which is slideably mounted at least one axial piston ( 16 , 18 ) which is capable of being actuated by a driver of the vehicle between a rear rest position and a forward braking force application position, and which is returned elastically toward its rear rest position, the bore ( 14 ) comprising two seals, front ( 30 , 34 ) and rear ( 32 , 36 ), which are interposed between the piston ( 16 , 18 ) and the bore ( 14 ), the front seal ( 30 , 34 ) delimiting, in the bore ( 14 ), a rear supply chamber ( 38 , 42 ) and a front pressure chamber ( 40 , 44 ), the body ( 12 ) comprising a radial supply duct ( 46 , 52 ) which connects an external hydraulic fluid reservoir to the rear supply chamber ( 38 , 42 ) and which opens out between the two seals ( 30 , 32 , 34 , 36 ), the body ( 12 ) comprising a braking circuit supply hole ( 54 , 56 ) which opens into the front pressure chamber ( 40 , 44 ), the piston comprising a bore ( 58 , 60 ), open to the front, communicating on the one hand with the front pressure chamber ( 40 , 44 ) and on the other hand with the periphery of said piston ( 16 , 18 ) by way of at least one hole ( 62 , 64 ) which, when the piston ( 16 , 18 ) occupies its rear rest position, is arranged between the two seals ( 30 , 32 , 34 , 36 ) so as to open communication between the front pressure chamber ( 40 , 44 ) and the rear supply chamber ( 38 , 42 ) and which, when the piston ( 16 , 18 ) is moved axially forward toward its application position, is capable of passing beyond the front seal ( 30 , 34 ) in order to isolate the front pressure chamber ( 40 , 44 ) from the rear supply chamber ( 38 , 42 ) and thus make it possible to establish a braking pressure in the front pressure chamber ( 40 , 44 ), at least each front seal ( 30 , 34 ) comprising at least one lip, arranged in contact with the periphery of the piston ( 16 , 18 ), which is capable, when the front pressure chamber ( 40 , 44 ) is exposed to a partial vacuum caused by the return of the piston ( 16 , 18 ) from its forward application position to its rest position or else by the activation of a trajectory control device forming part of the braking circuit, of separating from the periphery of the piston ( 16 , 18 ) so as to respectively allow the reservoir to be resupplied by means of the front pressure chamber ( 40 , 44 ) or else the front pressure chamber ( 40 , 44 ) to be resupplied by the reservoir, characterized in that the master cylinder ( 10 ) comprises at least one wide groove ( 66 , 68 ) which is formed in the bore ( 14 ) in front of a groove ( 70 , 72 ) for retaining the front seal ( 30 , 34 ), which extends at least in part around the piston ( 16 , 18 ), and which communicates with said retaining groove ( 70 , 72 ) and the hole ( 62 , 64 ) in the piston, in order to allow the resupply to occur with a high flow rate, and characterized in that, in at least the application position of the piston ( 16 , 18 ), the groove ( 66 , 68 ) is in communication with the front pressure chamber ( 40 , 44 ) only through the hole ( 62 , 64 ).