Patent ID: 8925314
Filing Date: 2015-01-06
Classification: B60T

Abstract:
1. Master cylinder for a clutch, actuating or brake system of a vehicle, comprising: a cylinder housing with a piston bore, a piston arranged in the piston bore and having an end side facing a cylinder chamber and at least one afterflow opening leading from a cylindrical piston skirt surface to the cylinder chamber at a distance from the end side, said at least one afterflow opening adjoining an afterflow space in a pressure equalization position of the piston so that in the pressure equalization position hydraulic medium can run on into the cylinder chamber in order to equalize the pressure, and an inner sealing element arranged between the housing and the piston in the area of the piston bore and limiting the cylinder chamber, the afterflow space being arranged between the sealing element and the piston skirt surface on a side of a sealing lip of the sealing element facing away from the cylinder chamber and wherein in the pressure equalization position the at least one afterflow opening is arranged so as to be located opposite an inner surface area of the sealing element limiting the afterflow space; wherein an entire axial length of the piston skirt surface with which the sealing lip interacts has a constant outer radius; wherein the inner sealing element has an axial free end spaced away from a contact portion of the sealing lip that contacts the piston skirt surface, the inner surface area is positioned axially between the axial free end and the contact portion, the inner surface area is spaced radially outward from the piston skirt surface for formation of at least part of the afterflow space therebetween, the sealing lip being configured such that the at least one afterflow opening maybe positioned axially between the axial free end and the contact portion with the at least one afterflow opening being entirely uncovered by the inner sealing element and entirely exposed to the afterflow space; wherein an imaginary smooth annular surface may be constructed which extends axially from the axial free end to the contact portion of the sealing lip, wherein at least a portion of the inner surface area coincides with the imaginary smooth annular surface, the inner surface area including an annular cavity which is recessed with respect to the imaginary smooth annular surface such that the annular cavity forms a continuous groove around a circumference of the inner surface area; and wherein the inner surface area further includes overflow channels recessed with respect to the imaginary smooth annular surface such that the overflow channels extend axially from the annular cavity toward the axial free end.