Master cylinder

Abstract

A master cylinder, for a clutch, actuating or brake system, comprising a cylinder housing with a piston bore, a piston in the piston bore with an end side facing a cylinder chamber and an afterflow opening leading from a piston skirt surface through a piston wall to the cylinder chamber at a distance from the end side, adjoining an afterflow space in a pressure equalization position of the piston where, in the pressure equalization position, hydraulic medium runs into the cylinder chamber to equalize the pressure, and an inner sealing element, arranged between the housing and the piston, limits the cylinder chamber, the afterflow space 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, in the pressure equalization position, the afterflow opening is located opposite an inner surface of the sealing element.

1 . Master cylinder, in particular 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 piston skirt surface through a piston wall to the cylinder chamber at a distance from the end side, said 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 sealing element being insertable into the cylinder housing from an outer opening thereof and an insert fixing the sealing element in place is insertable into the cylinder housing. 
     
     
         2 . Master cylinder as defined in  claim 1 , wherein the cylinder housing has a bore lying adjacent to the outer opening and reaching as far as a base of a receiving groove, the sealing element being insertable through said bore. 
     
     
         3 . Master cylinder as defined in  claim 1 , wherein the bore lying adjacent to the outer opening has at least one cross sectional surface corresponding to a cross sectional surface of the base of the groove. 
     
     
         4 . Master cylinder as defined in  claim 1 , wherein the piston at least in part extends in said insert and is guided by said insert. 
     
     
         5 . Master cylinder as defined in  claim 4 , wherein the insert forms a groove wall in the state inserted into the cylinder housing. 
     
     
         6 . Master cylinder as defined in  claim 5 , wherein an additional groove wall not formed by the insert is provided in the cylinder housing. 
     
     
         7 . Master cylinder as defined in  claim 3 , wherein the base of the groove is provided in the cylinder housing. 
     
     
         8 . Master cylinder as defined in  claim 1 , wherein it interacts with a regulated clutch or brake system. 
     
     
         9 . Master cylinder as defined in  claim 1 , wherein it is actuatable by hand and by foot. 
     
     
         10 . Master cylinder as defined in  claims 1  wherein, 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 of the sealing element limiting the afterflow space. 
     
     
         11 . Master cylinder as defined in  claim 10 , wherein the sealing element has inner surface areas extending at a distance from the piston skirt surface for the formation of the afterflow space. 
     
     
         12 . Master cylinder as defined in  claim 11 , wherein the inner surface areas form a cavity extending around the piston skirt surface. 
     
     
         13 . Master cylinder as defined in  claim 12 , wherein the inner surface areas form overflow channels leading to a side of the sealing element facing away from the cylinder chamber. 
     
     
         14 . Master cylinder as defined in  claim 13 , wherein the overflow channels extend approximately parallel or spirally or helically in relation to a direction of movement of the piston. 
     
     
         15 . Master cylinder as defined in  claim 10 , wherein the afterflow space lies adjacent to a supply recess located between the piston skirt surface and the piston bore. 
     
     
         16 . Master cylinder as defined in  claim 15 , wherein the supply recess varies in a radial direction towards the afterflow space. 
     
     
         17 . Master cylinder as defined in  claim 15 , wherein the supply recess communicates with a supply channel. 
     
     
         18 . Master cylinder as defined in  claim 10 , wherein the sealing element has an annular base member. 
     
     
         19 . Master cylinder as defined in  claim 18 , wherein a supporting lip located radially outwards extends from the annular base member in the direction of the cylinder chamber. 
     
     
         20 . Master cylinder as defined in  claim 18 , wherein proceeding from the base member a sealing lip located radially inwards extends in the direction of the cylinder chamber. 
     
     
         21 . Master cylinder as defined in  claim 20 , wherein the sealing lip located radially inwards is of a flexible design. 
     
     
         22 . Master cylinder as defined in  claim 20 , wherein the sealing lip abuts on the piston skirt surface radially inwards with elastic pretensioning. 
     
     
         23 . Master cylinder as defined in  claim 18 , wherein the afterflow space arranged between the sealing element and the piston skirt surface extends in the area of the base member. 
     
     
         24 . Master cylinder as defined in  claim 20 , wherein the afterflow space extends as far as the sealing lip. 
     
     
         25 . Master cylinder as defined in  claim 20 , wherein the sealing lip has such a pretensioning that it allows hydraulic medium to flow through from the afterflow space to the cylinder chamber by at least partially lifting away from the piston skirt surface in the case of any underpressure in the cylinder chamber. 
     
     
         26 . Master cylinder as defined in  claim 1 , wherein the piston is positioned in a closed position with the afterflow openings at such a distance from the pressure equalization position that the afterflow openings are covered by a sealing surface of the inner sealing lip. 
     
     
         27 . Master cylinder as defined in  claim 1 , wherein in a pressure position the piston is displaced to such an extent in the direction of the cylinder chamber that the afterflow openings are located on a side of the sealing lip facing the cylinder chamber. 
     
     
         28 . Master cylinder as defined in  claim 27 , wherein when the piston is in the pressure position a gap is present between an inner surface of the cylinder chamber and the piston skirt surface and separates an annular chamber of the cylinder chamber adjoining the sealing element from a variable volume area of the cylinder chamber. 
     
     
         29 . Master cylinder as defined in  claim 28 , wherein the gap between the inner surface of the cylinder chamber and the piston skirt surface is minimal in all the positions of the piston between the pressure position and the closed position. 
     
     
         30 . Sealing element for a master cylinder, in particular 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 piston skirt surface through a piston wall to the cylinder chamber at a distance from the end side, said 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 sealing element being designed in accordance with  claim 2 .