Abstract:
A pulsation damping capsule including at least one hermetically joint-sealed metal membrane housing made of at least two preferably concave hemispheres, the housing being provided for separating an inner space from a surrounding pressure medium, wherein the hemispheres are connected together along a peripheral seam firmly bonded such that the pulsation damping capsule can be compressed and expanded as an energy accumulator with spring elasticity due to the effect of the pressure medium. A pulsation damping device is provided which is both dimensioned to withstand stresses and is simple to produce, the pulsation damping effect of which can be tailored especially easily to the existing conditions. Further disclosed is a pulsation damping module for housing a plurality of pulsation damping capsules.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the U.S. national phase application of PCT International Application No. PCT/EP2009/051873, filed Feb. 17, 2009, which claims priority to German Patent Application No. 102008 009 834.5, filed Feb. 18, 2008, German Patent Application No. 10 2008 021 524.4, filed Apr. 30, 2008, and German Patent Application No. 10 2008 047 303.0, filed Sep. 16, 2008, the contents of such applications being incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a pulsation damping capsule, in particular for pulsation damping in electronically regulated vehicle brake systems or other types of pulsation damping applications. 
       BACKGROUND OF THE INVENTION 
       [0003]    In particular, electronically regulated vehicle brake systems have a hydraulic assembly comprising a receiving body with electrohydraulic valves, with at least one hydraulic pump, and with channels for connecting the pump to at least one hydraulic consumer, a pulsation damping unit being provided between a pressure medium volume (THZ/container, low pressure accumulator) and a suction side of the pump or between a pressure side of the pump and the hydraulic consumer. Eccentric-driven radial piston pumps are mostly used. Millions of said hydraulic assemblies are in use. 
         [0004]    Each piston displacement during an eccentric revolution can be divided in an extremely simplified manner into a suction stroke (0−n) and into a pressure stroke (n−2n). Because in each case liquid columns are accelerated but also retarded, this leads on the suction side and also on the pressure side to largely sinusoidal instantaneous pressure profiles which can be changed in details as a function of the concrete embodiment or else can be superimposed. In order to compensate for undesired effects of the instantaneous pressure profiles which fluctuate because of their principle, a pulsation damping unit is provided. 
         [0005]    For example, it is known from DE 34 14 558, which is incorporated by reference, to use a diaphragm damper with a metal diaphragm for pulsation damping. Conventional diaphragm dampers with a clamped elastomer diaphragm can suffer from the disadvantage that they are subject to wear, with the result that their effect decreases over the length of the service life. The spring properties are dependent on how quickly the loading takes place (dynamic hardening). As a result, they suffer from nonlinear behavior. 
         [0006]    DE 10 2005 028 562 A1, which is incorporated by reference, has disclosed a braking hydraulic assembly comprising a hermetically closed metal hollow body for damping purposes. 
       SUMMARY OF THE INVENTION 
       [0007]    It is an object of the present invention to provide a pulsation damping apparatus which is dimensioned suitably for the loading, can also be produced simply, is resistant to high pressure and the pulsation damping action of which can be adapted particularly simply to the prevailing boundary conditions. 
         [0008]    The object is achieved in principle by virtue of the fact that a hydraulic branch which is afflicted by pulsation is assigned a defined elasticity which makes it possible to accumulate pressure medium. According to one further independent solution of the problem, a preassembled pulsation damping module is proposed containing a bundle with a plurality of identical pulsation damping capsules. The pulsation damping capsule advantageously has a quasilinear, elastic behavior within a predefined functional pressure range which can reach, for example, as far as approximately 60 bar. Above this predefined functional range, the pulsation damping capsule behaves neutrally as it were, by there being a quasiconstant behavior. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The invention is best understood from the following detailed description when read in connection with the accompanying drawings. Included in the drawings is the following figures: 
           [0010]      FIG. 1  diagrammatically and partially shows an electrohydraulic vehicle brake system, 
           [0011]      FIG. 2  shows a pulsation damping capsule in section in the unloaded state and on an enlarged scale, 
           [0012]      FIG. 3  shows a pulsation damping capsule as in  FIG. 1 , but in the loaded state, 
           [0013]      FIG. 4  shows another embodiment of the pulsation damping capsule in section, 
           [0014]      FIG. 5  shows another embodiment of the pulsation damping capsule with structuring, on an enlarged scale and in section, 
           [0015]      FIG. 6  shows a perspective view of the pulsation damper capsule according to  FIG. 5  on a reduced scale, 
           [0016]      FIG. 7  partially shows a pulsation damping capsule as in  FIG. 5 ; with clarification of mechanical stresses, 
           [0017]      FIG. 8  shows a partial section through a hydraulic receiving body with a pulsation damping chamber and a plurality of inserted pulsation damping capsules, 
           [0018]      FIG. 9  shows a diagram for forming an assembled combination (stack) of a plurality of pulsation damping capsules with the use of holding means, 
           [0019]      FIG. 10  shows a perspective view of a combination of a plurality of pulsation damping capsules, 
           [0020]      FIG. 11  shows a perspective view of a combination of a plurality of pulsation damping capsules with modified holding means, 
           [0021]      FIG. 12  shows a perspective view of a combination of a plurality of pulsation damping capsules with modified holding means, 
           [0022]      FIG. 13  shows a perspective view of a combination of a plurality of pulsation damping capsules with modified holding means, and 
           [0023]      FIGS. 14 ,  15  in each case diagrammatically (and not to scale) show further embodiments of a pulsation damping capsule in section, and 
           [0024]      FIG. 16  shows a partially diagrammatic comparison of the requirements and the actual pressure volume behavior of different embodiments of pulsation damping capsules. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    In a very diagrammatically simplified manner and with the omission of details and electrohydraulic valves,  FIG. 1  illustrates an electronically regulated vehicle brake system  1  having a motor/pump assembly  2  with a pump P, comprising a pressure medium inlet E and a pressure medium outlet A, a damping apparatus  3  being provided in connection with the pressure medium outlet A, containing a plurality of damping means  4 ,  5 ,  6 ,  7 ,  8  connected in a cascade with the participation of at least one damping chamber. As diagrammatically illustrated, the pressure medium outlet A can be connected to a main cylinder  9  (THZ) or to a wheel brake  10  depending on the required function. The damping means  4 - 8  are arranged in principle together with the pump P in a common receiving body  35 . The different damping means  4 ,  5 ,  6 ,  7 ,  8  which are shown symbolically by pictograms comprise by way of example one or more damping chambers, orifices and a symbolically illustrated elasticity  4 ,  5  containing one or more pulsation damping capsules  11 ,  11 ′,  11 ″ or pulsation damping cells which have such a compressibility that a defined hydraulic volume can be received within a damper chamber. 
         [0026]      FIG. 2  shows in detail a pulsation damping capsule  11  for use within a hydraulically loaded pulsation damping chamber  12 . The pulsation damping capsule  11  comprises a metal diaphragm housing  15  which is joined in a hermetically sealed manner from two, preferably concave, half shells  13 ,  14 . Although the half shells are formed without the removal of material, a hardenable, stainless metal material is advantageously used, such as, in particular, spring steel of the type 1.4568 with a wall thickness of only approximately a few tenths of a millimeter (by way of example a wall thickness of approximately 0.1 mm). The thin diaphragm which is formed produces a fatigue-resistant, hermetically sealed inner space  16  which is separated from the surrounding pressure means of the pulsation damping chamber  12 , which pressure means usually pulsates at a low frequency (excitation frequency approximately less than 33 Hz). 
         [0027]    The half shells  13 ,  14  are connected to one another along a circumferential seam  17  with a material to material fit in such a way that a pulsating pressure means brings about an elastic compression or expansion of the pulsation damping capsule  11 , under the action of which the inner space  16  is reduced in size or enlarged. As a result, the pulsation damping chamber  12  which is filled with at least one pulsation damping capsule serves to achieve a largely linearly growing pressure means volume uptake V up to approximately a maximum of 400 mm 3  with a rising pressure means pressure p a  within a predefined pressure working range according to  FIG. 16 . To this end, an overview of the different targets and the different, concrete measured results (actual) with quadruple, sextuple or octuple arrangements (stacks) of the pulsation damping capsules can be gathered from  FIG. 16 . The predefined pressure working range, in other words the operating damping range, always extends as far as approximately 60 bar pressure means pressure p a . Because, however, the pressure means pressure p a  generated within vehicle brake systems can grow as far as above approximately 200 bar, a constant volume uptake is required above the defined, upper limit of the provided pressure working range, without overshoots being able to cause irreversible damage. This is achieved substantially by virtue of the fact that a further volume uptake is ended in a defined manner by an integrated stop function. 
         [0028]    Each half shell  13 ,  14  is preferably configured in a bowl-like manner with a diaphragm-like bottom  18 ,  19  and with a wall  20 ,  21  which is angled away approximately at a right angle from the bottom  18 ,  19 . In each case two identically shaped half shells  13 ,  14  are laid with their wall  20 ,  21  onto one another immediately directly, and mirror-symmetrically end to end. According to  FIG. 2 , the circumferential seam  17  which forms the outer circumference is provided for the hermetic material to material connection of the half shells  13 ,  14 . As can be seen, the circumferential seam  17  does not protrude substantially in the radial direction beyond the wall  20 ,  21 , but rather is inserted substantially completely smoothly into the course of the wall  20 ,  21 . 
         [0029]    The refinement according to  FIG. 4  differs from the preceding proposal in that each half shell  22 ,  23  has an integrally formed flange section  24 ,  25  which is angled away substantially at a right angle from the wall  20 ,  21  and such that it points radially to the outside. The circumferential seam  17  is placed from the radial outside between the two separate flange sections  24 ,  25 . As a result of this measure, the welded seam is placed in a particularly protected manner with regard to alternating loading and, in particular, damaging tensile loadings. Furthermore, it can be seen from  FIG. 4  and from the further  FIGS. 5-13  that the half shells  22 ,  23  are provided, particularly in the region of the base  18 ,  19 , with a profiling, in particular with a rotationally symmetrical, wave-shaped profiling. In contrast to the embodiments according to  FIGS. 4 to 8 , the wave shape of the profiling can be configured according to a modified embodiment according to  FIG. 14  in such a way that they nestle as far as possible in one another ( FIG. 14 ) for the largely complete compression of a pulsation damping capsule  11 . To this end, in each case one wave crest Wb of an upper half shell  13  is assigned a wave crest wb of a lower half shell  14  and vice versa (wave troughs WT/wt). A further special feature comprises the fact that the half shells  13 ,  14 ;  22 ,  23  can have different diameters, with the result that in each case one of the half shells  13 ,  14 ;  22 ,  23  is as it were inserted into a half shell of greater diameter and, as a result, is as it were preliminarily positioned for a production process, without a separate holding apparatus. In a comparable manner with the embodiment according to  FIG. 4 , this results in placing of the circumferential seam  17  which is particularly suitable for loading. The wall  20 ,  21  is oriented uniformly and is angled off at a right angle from the bottom  18 ,  19 , and is provided with an axially directed circumferential seam  17 . This design has the advantage that the uniformly angled away wall  20 ,  21  makes it possible to insert a pulsation damping capsule fixedly into a hole  36  of corresponding dimensions by means of a resilient clamping action, the circumferential seam being protected against damage by a pressing in operation. Radial pressure means recirculation is made possible by it being possible for separate channels to be provided in the hole  36  from the receiving body  35 . 
         [0030]    As has been explained briefly, an application in an electronically regulated vehicle brake system requires in principle a particularly adapted pressure/volume uptake behavior of the damping apparatus  3 . In this context, it can be required that a volume uptake in relation to the prevailing pressure initially increases linearly as the pressure increases, and that this volume uptake remains constant above a predefined volume uptake. For this purpose, each pulsation damping capsule  11  has at least one integrated means which is suitable for limiting the extent of an elastic compression. In other words, the integrated means which can be defined by the shape of the shells themselves, that is to say without separate components, ensures that no further compression of the pulsation damping capsule/cell occurs, with the result that deformation and volume uptake are limited mechanically (kept constant) above defined pressures. 
         [0031]    According to one preferred variant, the integrated means is configured as an integrated stop means, each inner space-side bottom  18 ,  19  being configured for forming the integrated stop means in the meaning of a stop face  26 ,  27 . The outlay on apparatus and production technology is minimized by the bottom  18 ,  19  fulfilling as it were a double function which comprises the fact that not only a hermetic inner space boundary, but also a limiting of the volume uptake is achieved by immediately direct, metallic contact of the adjacent bottoms  18 ,  19 . 
         [0032]    In a modification of an immediately direct stop function of two immediately directly adjacent bottoms  18 ,  19 , there can be provision according to another preferred solution for an incompressible medium to be provided as integrated means and, additionally to this, a compressible filling element  28 , for example made from elastomer material, in the inner space  16  of the damping capsule  11 , which filling element  28  can likewise have a structuring, preferably wave crests and wave troughs, congruently with respect to an adjacent, structured bottom, in particular structured in a wave shape. If a completely incompressible filling element  28  or a completely incompressible medium is provided, the inner space  16  should be filled only partially with it, in order that there is compressibility for volume accumulation in another way. If, in contrast, there is a compressible filling of an elasticity which is preset in a defined manner, the inner space  16  can certainly be filled completely. 
         [0033]    In order to set the predefined pressure/volume behavior, and also in order to avoid an impermissible deformation or loading of the half shells  13 ,  14 ;  22 ,  23 , an unstructured filling element  28  for supporting the wall  20 ,  21  can bear substantially completely against the half shells  13 ,  14 ;  22 ,  23  in this region. Further faces of the filling element  28  are provided at a spacing from the bottom  19 ,  20 , with the result that the bottom  19 ,  20  can compress elastically as it were. The stop faces  29 ,  30  on the filling element  28  which are assigned to the stop faces  26 ,  27  serve to limit this elastic deformation. 
         [0034]    In principle, the filling element  28  can have one or more recesses  31  which in principle are configured as a through hole parallel to the longitudinal axis, in order for it to be possible to assist a medium uptake or a deformation of the filling element  28  itself. The filling element  28  is advantageously configured metallically, from rubber or plastic, and is preassembled as an insert between the half shells  13 ,  14 ;  22 ,  23 . This can be effected by the filling element  28  being stitched or fastened fixedly to a half shell  13 ,  14 ;  22 ,  23  in such a way that rattling noise is avoided. The same is otherwise also true for pulsation damping capsules  11  which are adjacent to one another, and for the ratio between pulsation damping capsules  11  and receiving body  35 . 
         [0035]    The result tendentially of the given capsule construction is that the edge region makes comparatively low volume uptake possible, whereas maximum elastic deformation predominantly occurs in the center of the bottom of the half shells. The following measures serve to improve the entire volume uptake as a result of an improvement in the edge-side elasticity. To this end, in one embodiment of a pulsation damping capsule  11  with a filling element  28 ′ of wave-shaped structure according to  FIG. 15 , said filling element  28 ′ is configured such that it is segmented into at least two parts  28   a ,  28   b  which can be displaced parallel to one another, in such a way that tolerances of adjacent components, in particular tolerances in the wave structure of adjacent components and/or during the elastic compression operation of the bottoms  18 ,  19 , can be compensated for. A further advantage comprises the fact that the edge-side decoupling (omission of the clamping of the filling element  28 ′, which clamping is fixed on the edge side) brings about a significantly increased volume uptake. As a result, the concrete illustration also differs from the above-described embodiments as a result of the bottoms  18 ,  19  of wave-shaped structure with the use of a spacing element placed in between, namely a cylindrical ring  36  which in principle can be formed either from metal material or, in the sense of a further spring element, from elastomer material, which further increases the volume uptake of the pulsation damping capsule  11 . The entire structure can be joined together by two welded circumferential seams. Play is provided in the radial direction between the outer circumference of the filling element  28 ′ or its parts  28   a ,  28   b  and the ring  36 , with the result that the filling element  28 ′ can be adapted to the bottoms  18 ,  19  for optimum support. 
         [0036]    In a further modification of a pulsation damping capsule  11 , there can be provision for the inner space  16  to be provided with a vacuum, with an air or gas filling, or with a liquid for the purpose of configuring the predefined pressure/volume behavior. 
         [0037]    Further embodiments of the invention comprise a plurality of identically configured pulsation damping capsules  11 ,  11 ′,  11 ″ being arranged together within a pulsation damping chamber  12 . Here, it is particularly advantageous as an alternative to loose placing of the individual pulsation damping capsules  11 ,  11 ′,  11 ″ within the pulsation damping chamber  12  if a grouping or bundling of a plurality of identical pulsation damping capsules  11 ,  11 ′,  11 ″ is provided, with the result that as it were only a preassembled module is to be inserted into the pulsation damping chamber  12 , and that each bundle has at least one holding means  32  which is provided for the directed securing and placing of the pulsation damping capsules  11 ,  11 ′,  11 ″. It is a basic concept of an arrangement planned in this way to provide a defined spacing between the pulsation damping capsules  11 ,  11 ′,  11 ″, which spacing improves ventilation of the brake system. The unit can be formed with the addition of a hole closure for pulsation damping chamber  12  as in  FIG. 8 . 
         [0038]    Each holding means  32  is arranged integrally with or separately from the pulsation damping capsules  11 ,  11 ′,  11 ″. It is generally possible that the holding means  32  is connected with a material to material fit and/or nonpositively to one or to a plurality of pulsation damping capsules  11 ,  11 ′,  11 ″. Each holding means  32  ensures a cohesion between the pulsation damping capsules  11 ,  11 ′,  11 ″ which are joined together. In this context, it is possible to configure each holding means  32  as a metallic binding which is made from sheet metal and/or wire and is guided overall around all the cells to be bundled. 
         [0039]    A gradual modification of this principle comprises the fact that holding means  32  comprise largely strip-shaped sheet metal material with a plurality of receptacles  33  which act, in particular, on the flange section  24  of the pulsation damping capsules  11 ,  11 ′,  11 ″, as is apparent from  FIGS. 11 and 12 . In this way, it is ensured that the individual pulsation damping capsules  11 ,  11 ′,  11 ″ are arranged at a defined spacing from one another, which simplifies a ventilation and a downstream pressure means filling of a receiving body  35 . 
         [0040]    Furthermore, it is conceivable that each holding means  32  is provided as a tubular body which is slotted to as great an extent as possible and has receptacles  34  which act radially on the outside for the pulsation damping capsules  11 ,  11 ′,  11 ″, with the result that the latter are placed in a defined manner at a predefined regular spacing from one another. Holding means  34  of this type can advantageously be configured from elastic plastic material, in order to make elastic assembly or dismantling possible, as is apparent from  FIGS. 9 and 10 . 
         [0041]    It is advantageous in principle to provide a plurality of identically configured holding means  32 , in order to achieve an economical effect of quantity. 
         [0042]    In a further refinement of the present basic concept of a modular adaptation of a damping characteristic, it can be appropriate and required to add an additional spring element, such as, in particular, an individual half shell, to one or more pulsation damping capsules  11 ,  11 ′,  11 ″, without departing from the essence of the invention. It goes without saying that this separate half shell, just like the remaining pulsation damping capsules  11 ,  11 ′,  11 ″, may be a constituent part of a preassembled grouping which can be handled with one hand, for simplifying the assembly in the receiving body  35 . 
         [0043]    Although the invention has primarily been explained using the example of an application in an electronically regulated vehicle brake system, other types of applications are possible without departing from the core concept of the invention.