Abstract:
A pressure medium container for a hydraulic motor vehicle brake system. A pressure medium container is provided including a container casing the interior of which can be filled with a pressure medium via a filler pipe and is closed off by a closure cap fixed to the filler pipe. A sealing element made from an elastomeric material is provided between the filler pipe and a bottom of the closure cap. The sealing element has a valve which rests on a support pedestal arranged on the closure cap is closed in a non-actuated initial state and reaches an opened actuated state under the control of differential pressure, whereby a pressure is equalized between an interior of the pressure medium container and an ambient atmosphere. Direction-dependently, the valve has different valve opening resistances.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the U.S. National Phase Application of PCT International Application No. PCT/EP2013/077333, filed Dec. 19, 2013, which claims priority to German Patent Application No. 10 2013 000 041.6, filed Jan. 7, 2013 and 10 2013 005 375.7, filed Mar. 28, 2013, the contents of such applications being incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention concerns a pressure medium container for a hydraulic motor vehicle brake system. 
       BACKGROUND OF THE INVENTION 
       [0003]    Pressure medium containers for hydraulic motor vehicle brake systems are known. Usually such pressure medium containers are mounted in the engine bay directly on the brake master cylinder or at least connected thereto hydraulically via lines. In many vehicle variants, the installation conditions present in the engine bay mean that pressure medium containers are used which are formed more linear than cuboid, because for example front windscreens with a shallow slope angle and at the same time a more compact construction of a brake actuating system mean that pressure medium containers must be arranged below the header tank. 
         [0004]    In order to be able to receive the filling device for vacuum or pressure filling at the neck, such an arrangement means that the filler pipe is usually mounted at the front in the driving direction or on a front end of the pressure medium container. Because of such a decentralized arrangement of the filler pipe however, during driving operation or in transport, frequently during a braking process or when parking on a steep downhill gradient, the filler pipe is regularly flooded with the pressure medium. 
         [0005]    The closing caps of generic containers usually have devices for pressure equalization with the surrounding atmosphere. To prevent the pressure medium from escaping through such a pressure medium equalization device during flooding of the filler pipe, complex systems are provided which are intended to guarantee a venting function and prevent an escape of the fluid, but at the same time these increase the complexity and production cost of the closing cap. 
       SUMMARY OF THE INVENTION 
       [0006]    An aspect of the invention aims to eliminate said disadvantages and offer an improved pressure medium container which is simple and economic to produce and install, wherein a venting function is still reliably guaranteed and at the same time an escape of fluid from the pressure medium container through the closing cap is effectively prevented. 
         [0007]    An aspect of the invention comprises a valve which is arranged resting on a bearing pedestal and having different valve opening resistances depending on direction. In this way the air can still flow in both directions so that a pressure equalization can take place securely, but the pressure medium is largely retained in order not to escape into the environment. 
         [0008]    In an advantageous refinement of the invention, the valve opening resistance may be set higher in the direction of the surrounding atmosphere than in the opposite direction, for example in the direction of a pressure medium chamber inside the pressure medium container. Thus emergence of the pressure medium from the pressure medium container through the valve is effectively prevented, without hindering the intake of pressure medium from the pressure medium container to the brake master cylinder. In a further refinement of the invention, the valve may, particularly simply and effectively, comprise at least one slot in the sealing element of the closing cap so that it can be produced particularly simply and economically and be adaptable to different requirement profiles. 
         [0009]    In an advantageous embodiment, the bearing pedestal for the sealing element may be configured as a tubular profile which extends from a base of the closing cap in the direction of the sealing element and has at least one air passage between an inside and an outside of the tubular profile. Thus a reliable valve function and pressure equalization function can be ensured particularly simply. 
         [0010]    Particularly advantageously, the closing cap may have support means which supports the valve in at least one valve opening direction and hence increases the valve opening resistance in the supported valve opening direction. Thus the desired influencing of the valve opening resistance and its adaptation can be achieved reliably in a particularly efficient manner and without increasing the installation complexity. In a further advantageous refinement, the support means may be arranged on the base of the closing cap and/or be integrated in, preferably molded onto, the closing cap. In this way a functional, highly integrated closing cap is provided which can be produced technologically simply, for example in the injection molding process. No additional components or mounting operations are required. 
         [0011]    Preferably, the support means may be arranged inside the bearing pedestal, wherein the valve function is influenced particularly simply and the response behavior of the valve can be predefined particularly precisely. 
         [0012]    One particularly effective embodiment of the support means provides that this may be formed as a tubular profile which extends from the base of the closing cap in the direction of the sealing element and has at least one air passage between an inside and an outside of the tubular profile. In a further refinement of the invention, on a pressure difference equal to zero between the tubular profile of the support means and the sealing element, a distance may be provided in the direction of the sealing element. In this way, particularly simply, the response behavior of the valve can be defined constructionally, preferably in steps or progressively. 
         [0013]    In a further advantageous embodiment, the support means may be designed cuboid, plate-like, pin-like, conical or otherwise, and be arranged at the side of the slot of the valve on the base of the closing cap. In this way, virtually any arbitrary influence can be exerted on the valve behavior in a particularly simple manner. 
         [0014]    Advantageously, the air equalization and hence the pressure equalization between the interior of the pressure medium container and the surrounding atmosphere can be created particularly simply and economically via a radially running air channel formed in the base of the closing cap and via a recess of a thread connected thereto on the collar of the closing cap. 
         [0015]    Particularly effectively, a degree of increase in the valve opening resistance may be predefined by a support distance from the support means. In this way, by change of a single parameter, the pressure medium container can be adapted to different requirement profiles effectively, precisely and with very little proliferation. 
         [0016]    Particularly advantageously and simply, a pressure difference, which is necessary for opening the valve in at least one valve opening direction, may be predefined constructionally by a ratio of a length of the slot to a thickness of the sealing element in the region of the slot, and hence adapted to widely varying applications. Here a ratio in a range between 4 and 6 is preferred, because this allows a particularly good valve functionality for a generic container. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    Further details, features, advantages and possible applications of the invention arise from the subclaims together with the description with reference to the drawings. Corresponding components and constructional elements as far as possible carry the same reference numerals. The drawings show: 
           [0018]      FIG. 1  a pressure medium container mounted on a tandem brake master cylinder of a hydraulic motor vehicle brake system. 
           [0019]      FIG. 2  a first embodiment of the closing cap of a pressure medium container according to the invention without sealing element. 
           [0020]      FIG. 3  a cross-section view of a filler pipe of the embodiment of the pressure medium container according to the invention with a closing cap according to  FIG. 2 . 
           [0021]      FIG. 4  an embodiment according to the invention of the closing cap with a fitted sealing element. 
           [0022]      FIG. 5  a simplified sketch to depict the valve function according to the invention with the closed valve (a) and opened valve for air inlet (b) and air outlet (c). 
           [0023]      FIG. 6  partial views of some embodiments (a-d) according to the invention of a support means on a closing cap of a pressure medium container. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    
       FIG. 1 
     
         [0025]      FIG. 1  shows a pressure medium container  1  according to the invention with a container housing  2  which is mounted, by means of two push-fit connections  20 , on a tandem brake master cylinder  19  of a hydraulic motor vehicle brake system, and at the same time is hydraulically connected to the pressure chambers (not shown) in the brake master cylinder  19 . However other connections of different design (not shown), for example remote connections by means of flexible or rigid lines, or an indirect connection to a brake master cylinder  19  with the interposition of a further reservoir (not shown), are possible within the invention. The pressure chambers (not shown) of the brake master cylinder  19  are connected hydraulically via brake lines  23  to wheel brakes or brake regulation assemblies. The container housing has a filler pipe  3  which is suitable for filling the pressure medium container and can be closed by a cap  4 , preferably by means of a threaded connection. Further connections, such as for example a bayonet connection or a simple push-fit connection, are also conceivable without leaving the invention. 
         [0026]    Furthermore, the pressure medium container  1  may have fill level sensors  21  and further auxiliary devices (not shown). Pneumatic brake servo  22  is assigned to the brake master cylinder  19 , but the invention may also be implemented with an electrohydraulic, combined or further force-amplifying devices (not shown). 
         [0027]    
       FIG. 2 
     
         [0028]      FIG. 2  shows a first embodiment of a closing cap  4  of a pressure medium container  1  according to the invention. The closing cap  4  is formed substantially pot-like with a base  11  and a peripheral collar on which a thread  24  is arranged. The thread  24  serves for fixing of the closing cap  4  to the filler pipe  3  and corresponds with a thread (not shown) on the filler pipe  3 . For the sake of better understanding of the structure of the closing cap  4 , no sealing element is shown here. In order to allow a pressure equalization with the surrounding atmosphere after mounting of the closing cap  4  on the filler pipe  3 , the closing cap  4  has an air channel  16  which is let into the base  11  of the closing cap  4  and is connected to a recess  17  in the thread  24 . Preferably, both the air channel  16  and the recess  17  may be formed as a groove, but further embodiments are also possible within the same invention, for example as a tubular channel let into the closing cap or a simple opening through the closing cap. 
         [0029]    To support the sealing element  5 , not shown here, a bearing pedestal  6  is provided, the function of which will be discussed in more detail below. The bearing pedestal  6  is here formed as a tubular profile  10  which extends from the base  11  of the closing cap  4  in the direction of the sealing element  5  (not shown here), wherein between the radial inside and outside of the tubular profile, an air passage  12  is provided in order to connect the interior of the bearing pedestal  6  pneumatically to the air channel  16 , and thus allow a pressure equalization when the sealing element  5  rests on the bearing pedestal. 
         [0030]    The closing cap  4  furthermore has a support means  8  for supporting a valve  7  integrated in the sealing element  5 . In the embodiment shown here, the support means  8  is configured as a tubular profile  13  which extends from the base  11  of the closing cap  4  in the direction of the sealing element  5  (not shown here) and is arranged inside the bearing pedestal  6 . Between the inside and outside of the tubular profile  13 , an air passage  14  is provided in order to connect the interior of the tubular profile  13  pneumatically to the interior of the bearing pedestal  6 , and thus allow a pressure equalization when the sealing element  5  rests on the tubular profile  13 . Such a construction allows the closing cap  4  to be produced in a technologically particularly efficient manner, since most construction elements are designed substantially rotationally symmetrical and undercuts are largely avoided. 
         [0031]    As an alternative to the embodiment of the support means  8  shown, further embodiments are permissible within the invention which will be described in more detail below. 
         [0032]    
       FIG. 3 
     
         [0033]      FIG. 3  shows a section through the container housing  2  in the region of the filler pipe  3 . An embodiment of the closing cap  4 , already described in  FIG. 2 , is mounted on the filler pipe  3 . A sealing element  5  made of an elastic and preferably elastomer material is clamped between the base  11  and the filler pipe  3 . In its center, the sealing element  5  has a largely planar, flat valve face  26  with a preferably constant thickness D. In the middle of the valve face  26 , a valve  7  is arranged which in the embodiment shown here is formed as a slot  9 . 
         [0034]    An air chamber  18  is delimited between the base  11  and the sealing element  5  and is connected to the surrounding atmosphere via the air channel  16  and the recess  17 . The sealing element lies with the radially outer region of the valve face  26  on the bearing pedestal  6 . As already described above, the bearing pedestal  6  is formed by a tubular profile  10  which comprises an air passage  12 . The tubular profile  10  extends from the base  11  of the closing cap  4  to the sealing element  5  in the region of its flat valve face  26 , and lies against this so that the interior of the bearing pedestal  4  with the sealing element  5  delimits a type of air chamber, which is pneumatically connected via the air passage  12  to the air channel  16  and hence to the surrounding atmosphere so that on both sides of the valve disc  26 , a pressure difference can be built up between the pressure of the surrounding atmosphere and a pressure in the interior of the pressure medium container  1 . At a specifically defined pressure difference, the valve face begins to deform and the valve  7  opens. The valve  7  can open in two valve opening directions. A valve opening direction opposite to the base  11  is active when a pressure inside the pressure medium container  1  is lower than the pressure of the surrounding atmosphere (container vacuum). In this case, due to the pressure difference, air enters the interior of the pressure medium container  1  from the interior of the bearing pedestal  6  or the surrounding atmosphere. Conversely, a valve opening direction towards the base  11  is active when a pressure inside the pressure medium container  1  is higher than a pressure of the surrounding atmosphere (container positive pressure). In this case, due to the pressure difference, air escapes from the interior of the pressure medium container  1  into the interior of the bearing pedestal  6  or into the surrounding atmosphere. Because the interior of the bearing pedestal  6 , as described above, is permanently connected to the surrounding atmosphere, in this way the pressure equalization between the surrounding atmosphere and the interior of the pressure medium container  1  can take place at any time. 
         [0035]    The support means  8  is arranged inside the tubular profile  10  of the bearing pedestal  6 . In the exemplary embodiment shown, the support means is configured tubular, similarly to the bearing pedestal  6 , with a tubular profile  13  which extends from the base  11  of the closing cap  4  in the direction of the sealing element  5 , so that it further supports the valve face  26  in one direction, preventing a deformation of the valve face  26  in the direction of the base  11  and thus increasing the valve opening resistance of the valve  7  on the emergence of air from the pressure medium container  1 . 
         [0036]    Furthermore the sealing element  5  may have a roll membrane  25  in order for example to prevent undesirable transverse stresses in the valve face  26 , and thus always reliably ensure stable and calculable valve functions of the valve  7  at all pressure differences. 
         [0037]    
       FIG. 4 
     
         [0038]      FIG. 4  shows an embodiment according to the invention of the closing cap  4  with inset sealing element  5  in a view from below in the direction towards the base of the sealing cap  4 . This view illustrates one possible fundamental embodiment of the sealing element  5 . As can be seen, in its radial center the sealing element  5  comprises the round valve face  26  which is surrounded by the roll membrane  25  and has a valve  7  in the center. In the exemplary embodiment shown, the valve  7  is formed as a straight slot  9  with a slot length L. The ratio of the thickness D, already described, of the sealing element  5  in the region of the valve face  26  to the slot length L is decisive for the response behavior of the valve  7 , namely the minimum pressure difference required for the valve to open. Preferably, the ratio L/D has a value between 4 and 6, wherein further value ranges are also functionally possible. 
         [0039]    As well as the embodiment of the valve  7  shown with a single straight slot  9 , within the invention further embodiments are possible, for example a cross slot, a wavy or curved slot, or further slot forms. 
         [0040]    Furthermore, the picture shows the recess  17  in the region of the thread  24  on the collar of the closing cap  4 , through which pressure equalization to the surrounding atmosphere takes place. 
         [0041]    
       FIG. 5 
     
         [0042]      FIG. 5  depicts diagrammatically a greatly simplified working principle of the valve  7 , not to scale, as already described above. Reference should be made to  FIGS. 1 to 4  for the elements not shown in this figure but already mentioned. 
         [0043]    View a) shows the valve  7  with a balanced pressure ratio, or a pressure difference equal to zero. This constitutes for example a generally desired ideal state or a normal state with the vehicle parked, or a brake system momentarily not in operation. The sealing element  5  lies with its valve face  26  both on the bearing pedestal  6  and on the support means  8 , the valve face  26  is flat and not curved, the valve  7  is closed and the slot  9  is closed. 
         [0044]    View b) shows the valve under a negative pressure difference or container vacuum. 
         [0045]    Such a situation results for example from suction processes when the pressure medium flows out of the pressure medium container  1  into the brake master cylinder  19  or is extracted by the brake master cylinder  19 . A container vacuum causes a highly undesirable increase in suction resistance which could negatively affect the brake functions. Therefore in the case of a container vacuum, a particularly spontaneous response of the valve  7  at a pressure difference as low as possible is desirable, so that a container vacuum can be equalized as quickly as possible. 
         [0046]    As clearly evident from view b), under a container vacuum the entire valve surface  26  curves away from the base  11  so that the valve  7  opens rapidly even under a relatively low pressure difference, and the slot  9  can be expanded relatively widely. 
         [0047]    View c) shows the valve under a positive pressure difference or container positive pressure. Such a situation may arise for example when the pressure medium in the pressure medium container  1  sloshes in the direction of the filler pipe  3  because of vehicle movements, or when the vehicle is tilted greatly forward relative to the horizontal, or when the temperature of the pressure medium increases relatively quickly. 
         [0048]    Under a container positive pressure, there is an increased risk that the usually flammable pressure medium will escape from the pressure medium container  1 . It is essential to avoid or at least hinder this. 
         [0049]    Due to the supporting effect of the support means  8 , a curvature of the entire valve face  26  is prevented so that the valve face  26  only deforms within the support distance S for the valve  7 . Because the support distance S is substantially smaller than the bearing distance A, the region of the valve face  26  exposed to the pressure difference for the valve effect is substantially smaller than in the case of a container vacuum. A greater pressure difference is required to open the valve, the response behavior of the valve  7  is delayed, and the valve opening resistance is increased. 
         [0050]    By defining the support distance S, a degree of a relative increase of the valve opening resistance under container positive pressure can be defined constructionally. It is also possible to change the height of the support means  8  relative to the height of the bearing pedestal  6 , so that a gap remains between the support means  8  and the valve face  26  under a balanced pressure ratio (see  FIG. 5   a ). Thus e.g. a stepped response behavior of the valve can be achieved—a fine response under a low pressure difference initially, followed by a strong progressive rise in the valve opening resistance under higher pressure differences. 
         [0051]    
       FIG. 6 
     
         [0052]      FIG. 6  shows as an example four further possible embodiments according to the invention of a support means  8 . The embodiment of the support means  8  in view a, like the embodiment already described in  FIG. 2 , is configured as a tubular profile but has four air passages  14  distributed around the periphery instead of just one. Evidently another number of air passages is possible within the invention. 
         [0053]    The embodiment of the support means  8  in view b is formed from two cubes  15  or plates which are arranged parallel to each other and each laterally offset to the slot  9  on the base  11 . A further embodiment with just one plate would also be conceivable. 
         [0054]    The support means  8  in view c are designed as pin-like protrusions or bumps. The embodiment shown has four pin-like support means  8  which are each arranged laterally offset to the slot  9  on the base  11 . Evidently other numbers of pin-like support means  8  are possible within the invention, wherein a plurality of such support means  8  may be arranged in a circle next to each other on the base  11  of the closing cap  4 . 
         [0055]    In contrast to the embodiment in  FIG. 6   c , the support means  8  in view d has a conical form. 
         [0056]    Preferably, all embodiments described of support means and bearing pedestals are integrated in the closing cap or designed integrally therewith. 
       LIST OF REFERENCE SIGNS 
       [0000]    
       
           1  Pressure medium container 
           2  Container housing 
           3  Filler pipe 
           4  Closing cap 
           5  Sealing element 
           6  Bearing pedestal 
           7  Valve 
           8  Support means 
           9  Slot 
           10  Tubular profile 
           11  Base of closing cap 
           12  Air passage 
           13  Tubular profile 
           14  Air passage 
           15  Cube 
           16  Air channel 
           17  Recess 
           18  Air chamber 
           19  Brake master cylinder 
           20  Push-fit connection 
           21  Fill level sensors 
           22  Brake servo 
           23  Brake line 
           24  Thread 
           25  Roller membrane 
           26  Valve face 
         D Thickness of sealing element 
         L Length of slot 
         A Bearing distance 
         S Support distance