Abstract:
In a pump with a pump housing which includes at least one working chamber and a valve bore connected to the working chamber and wherein an inlet valve and an outlet valve are arranged one behind the other, and with a displacement element that is adapted to reciprocate and, by its movement, varies the volume of the working chamber, the valve sea, the closing element and a valve spring of the inlet valve or the outlet valve which presses the closing element against the valve seat, are interconnected to provide a cartridge which can be installed into the valve bore so as to seal, and the cartridges of both valves are installed from the same side into the valve bore and are supported in the installation direction on the pump housing by a step in the valve bore.

Description:
TECHNICAL FIELD 
     The present invention generally relates to pumps and more particularly relates to pumps used in a hydraulic brake slip control system. 
     BACKGROUND OF THE INVENTION 
     In a pump of the above-mentioned type disclosed in German patent application No. 32 48 364, the inlet and outlet valves are configured as spherical seat valves, and the valve seat is respectively provided by a stepped expansion of the valve bore in the pump housing. Structural provisions for a simple manufacture of the valve bore and for an easy assembly and testing of the valves are not disclosed in the said application. The pump includes a piston as a displacement element which is guided and sealed in a cylinder bore that crosses the valve bore and is drivable by an eccentric in the pressure direction and by a spring in the suction direction. 
     German patent application No. 40 27 848 discloses a piston pump wherein the inlet valve and the outlet valve are respectively arranged in a separate stepped bore which is connected to the working chamber by way of a connecting bore. The inlet and outlet vales are provided by different valve inserts which comprise the stationary valve seat, the movable closing element and a valve spring. This prior art piston pump necessitates machining of the stepped bores and the installation of the valve inserts from opposite sides of the pump housing. This has unfavorable effects on manufacturing costs and implies a great restriction of the design possibilities of a constructor, for example, in terms of a structural integration of the pump housing in the housing of a valve block. 
     An object of the present invention is to provide a pump of the above-mentioned type which involves low efforts and expenditure in manufacture and assembly and can easily be integrated into the housing of a hydraulic unit. 
     According to the present invention, this object is achieved because the valve seat, the closing element and a valve spring of the inlet valve or the outlet valve, which spring presses the closing element against the valve seat, are interconnected to form a cartridge which is adapted to be sealedly installed into the valve bore, and the cartridges of both valves can be fitted from the same side into the valve bore and are adapted to be supported on the pump housing in the installation direction by means of a step in the valve bore. If the construction of the pump permits it, the cartridges of both valves may further be supported on each other. Besides, in a particularly simple embodiment of the present invention, the valve seat, the closing element and the valve spring of the inlet valve and outlet valve may be interconnected to form one single cartridge which can be sealedly inserted into the valve bore. 
     It is advantageous in the design of the pump according to the present invention that the valve bore can be fabricated in one single operation and, exactly as the assembly of the valves, can be effected from one side of the pump housing. Also, the assembly of the valves can be carried out in one single operation, provided their cartridges are not spaced from one another. This reduces the manufacturing costs and simplifies the accommodation of the pump in a housing provided for further structural elements. In addition, it is a special advantage that the valves in the preassembled cartridges can be tested prior to their installation so that defects of fabrication can be detected early and installation of defective parts can be avoided. If both valves, i.e., the inlet valve and the outlet valve, are accommodated in one joint cartridge, it is possible to remarkably reduce the number of the valve components and the mounting space required. 
     According to the present invention, the cartridge can be assembled of several parts. The cartridge may include a housing or a housing part made of a material of reduced rigidity, for example, aluminum or free cutting steel, which is connected to a valve seat ring made of a material of higher rigidity, for example, hardened steel. The cartridge may be retained and sealed in the valve bore in different fashions. One favorable type of attachment is caulking the cartridge into the valve bore. Preferably, the cartridge or the cartridges is/are inserted into the valve bore from the high-pressure side end so that the valves, in their closed position, are acted upon by the pump pressure in the installation direction in which they are supported on the pump housing by way of a step in the valve bore. The cartridges may be sealed metallically by correspondingly shaped seat surfaces or by means of ring seals. According to the present invention, a particularly favorable attachment and sealing can be achieved in that the end of the cartridge, which is the rear end when viewed in the installation direction, has a sleeve-type portion, and by pressing a plug into the sleeve-type portion, the latter is expandable and thereby adapted to be attached in the valve bore in operative and sealed engagement therewith. 
     When the pump has a damping chamber which succeeds the outlet valve, it is favorable that the cartridge is installed from the damping chamber. To fix the cartridge or the cartridges in the installation position, a compression spring can be used which is mounted into the damping chamber and is supported on the end of the cartridge that projects into the damping chamber. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a radial piston pump configured according to the present invention. 
     FIG. 2 is a partial cross-sectional view of a radial piston pump of the present invention which is incorporated into the housing of a hydraulic unit. 
     FIGS. 3 to  7  show partial cross-sectional views of the radial piston pump according to FIG. 2 with different embodiments of the cartridges which form the inlet and outlet valves. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The radial piston pump  1  shown in FIG. 1 includes a pump housing  2  with a central bearing bore  3  in which a drive shaft  4  is pivotally mounted by way of a ball bearing  5 . Provided on the drive shaft  4  is an eccentric  6  which drives two pistons  8 ,  9  by way of a needle bearing  7 . The pistons  8 ,  9  are guided in cylinder bores  10 ,  11  arranged in a radial direction relative to the bearing bore  3 . The radially outward bore ends are closed by plugs  12 ,  13 . Between the pistons  8 ,  9  and the plugs  12 ,  13 , the cylinder bores  10 ,  11  respectively form a working chamber  14 ,  15  which is penetrated by a valve bore  16 ,  17  that is in parallel or vertical to the bearing bore  3 . The working chamber  14  houses a compression spring  18  which urges the piston  8  against the needle bearing  7  and effects the suction stroke of the piston  8 . The compression spring  18  is guided on a pivot  19  of the plug  12  which extends into the working chamber  14 . The suction stroke of the piston  9  is effected by a resilient coupling ring  20  which is supported on the needle bearing  7  and presses the piston  9  against said&#39;s outside ring. 
     An inlet valve E is arranged in the valve bore  16  between the working chamber  14  and the bore portion  21  leading to a low-pressure chamber, and an outlet valve A is interposed between the working chamber  14  and a bore portion  23  which leads to a high-pressure chamber. Both valves E, A are equally configured as cartridges  22 ,  24  and comprise a sleeve-shaped housing  25  having a bore which forms a valve seat  26  and includes a valve ball  27 , a valve spring  28  and a valve plate  29  with a spring guide pin. The valve plate  29  is secured by caulking in the bore of housing  25  and has at its edge segment-shaped recesses for the provision of pressure fluid passages. At its end which is the rear end in the installation direction, the cylindrical peripheral surface of the housing  25  has a collar  30  of a slightly larger diameter which is supported in an axial direction on a correspondingly shaped step of the valve bore  16 . 
     To be able to install the inlet valve E from the same side as the outlet valve A into the valve bore  16 , the housing  25  of the cartridge  24  and the bore portion  23  of the valve bore  16  have a correspondingly larger diameter. During the assembly, the cartridges  22 ,  24  are one after the other pressed into the bore portion  21  or  23 , and the collar  30  digs with its front edge into the bore step and provides a metallic sealing of the housing  25  in the pump housing  2 . 
     The valve bore  17  is subdivided by two steps into three portions  31 ,  32 ,  33  of different diameters. Portion  31  has the smallest diameter and is positioned on the low-pressure side. A cartridge  34  which comprises an inlet valve E and an outlet valve A is inserted into portion  32  which extends through the working chamber  15 . Cartridge  34  includes a sleeve-shaped housing  35  which abuts with a frontal sealing edge on the step leading to portion  31 . The housing  35  is caulked in the pump housing  2  at the step leading to portion  33 . Housing  35  has a bore  36  stepped several times which, at one end, provides a valve seat  37  for a valve ball  38  of the inlet valve E. At a distance from valve ball  38 , a hardened valve seat ring  39  is pressed into the bore  36  which is closable by a valve ball  40  and, along with it, forms outlet valve A. A valve spring  41  is compressed between the valve ball  38  and the valve seat ring  39 . A second valve spring  42  is supported on the valve ball  40  and a spring plate  43  attached in the bore  36 . In-between the valve ball  38  and the valve seat ring  39 , the bore  36  is connected to the working chamber  15  by way of a plurality of radial bores  44 . 
     FIGS. 2 to  7  show a portion of a housing  45  of a hydraulic unit for a brake slip control system. The portion of the housing  45  comprises a piston pump  46  and a damping chamber  47  which is used to dampen the pulsation of the high-pressure side delivery flow of the piston pump  46 . The damping chamber  47  which is provided by a cylindrical housing bore is closed outwardly by a cover  48  retained by a circlip  49 . A valve bore  50  leads from the damping chamber  47  to a working chamber  51  of the piston pump  46  and from there further on to a low-pressure port. The working chamber  51  is formed by a housing bore  52  which is vertical relative to the valve bore  50  and is closed outwardly by a plug  53  caulked with the housing  45 . A piston  54  slides in the inwardly disposed portion of the housing bore  52  which is movable by an eccentric drive (not shown in detail) similarly as the piston  9  of the radial piston pump  1  shown in FIG.  1 . The inlet valve E and the outlet valve A are installed as a prefabricated cartridge through the damping chamber  47  into the valve bore  50  prior to the assembly of the cover  48 . 
     The cartridge  55  is set up of four cylindrical sleeves  56 ,  57 ,  58 ,  59  in the embodiment of FIG.  2 . The sleeves  56  and  58  are made up of hardened steel, and each forms a valve seat for a valve ball  60 ,  61 . The sleeves  57  and  59  are made of aluminum and have equal dimensions. They include recesses on their frontal ends into which the sleeves  56 ,  58  with correspondingly shaped portions, or a spring plate  62 , are inserted. The sleeves  57 ,  59  include a plurality of radial bores  63  in their middle. The diameter of the longitudinal bore of the sleeves  57 ,  59  is larger than that of the valve ball  60 ,  61  to permit flow of the pressure fluid around the valve balls  60 ,  61  when the valves are open. Valve springs  64 ,  65  urge the valve balls  60 ,  61  against the valve seats. The cartridge  55  is fixed in its installation position by caulking the end of the sleeve  59  which faces the damping chamber  47 . Sealing in the valve bore  50  is effected by a sealing edge of the sleeve  56  which is pressed on a bore step, and by a ring seal  66  arranged in a groove in the peripheral surface of the sleeve  58 . 
     FIG. 3 shows another embodiment of a cartridge  71  composed of four sleeves  67 ,  68 ,  69 ,  70 . The sleeves  67 ,  69  again are made of hardened steel and the sleeves  68 ,  70  are made of aluminum or free cutting steel. Two sleeves  67 ,  68  and  69 ,  70  each form the housing of an inlet or outlet valve with a valve ball  60  or  61  and valve spring  64  or  65  arranged therein. To seal the cartridge  71  in relation to the valve bore  50 , in turn, there is provision of a sealing edge on the sleeve  67  and a ring seal  66 , and the annular groove to accommodate the ring seal  66  is formed by the peripheral surface of the sleeve  69  and the end surface of the sleeves  68  and  70 . The cartridge  71  is retained in an axial direction by a compression spring  72  arranged in the damping chamber  47 . Spring  72  is supported on the end of the sleeve  70  which projects into the damping chamber  47  and urges the cartridge  71  with its sleeve  67  against the step  73  in the valve bore  50 . 
     The housing of the cartridge  74  shown in the FIG. 4 embodiment is only composed of two sleeves  75 ,  76 , each having a stepped sleeve bore to form a valve seat. On its frontal end, the sleeve  75  with a sealing edge  77  is supported on the step  73  of the valve bore  50  and sealed metallically. Its sleeve bore is connected to the working chamber  51  by radial bores  78 . Sleeve  76  engages with a projection into a recess of the sleeve  75  and may thereby be operatively connected to the sleeve  75  to provide a structural unit already prior to its installation into the valve bore  50 . The valve spring  64  is compressed between the valve ball  60  and the sleeve  76 . The valve spring  65  is compressed between the valve ball  61  and a spring plate  62  attached in the bore of the sleeve. A ring seal  66  is again provided to seal the sleeve  76  in relation to the valve bore  50 . In this embodiment, too, the cartridge  74  is fixed in its installation position by a compression spring  72  placed in the damping chamber  47 . 
     The cartridge  78  of the embodiment of FIG. 5 differs from the cartridge  74  merely by the fact that the ring seal  66  and the associated ring seal groove in the sleeve  79 , which is the rear one in the installation direction, are eliminated, with the result of a smaller axial overall length. To achieve a sufficient sealing on the high-pressure side, the outside diameter of the sleeve  79  and the associated portion of the valve bore  50  have a transition fit. A small leakage which is still possible to occur in this arrangement is tolerable. The cartridge  78  is pressed against the step  73  of the valve bore  50  by a compression spring  80  which is supported on a ring  81  caulked into the valve bore  50 . 
     In the embodiment shown in FIG. 6, the housing of the cartridge  82  is made up of one single sleeve  83  which accommodates the inlet valve E and the outlet valve A. To this end, sleeve  83  comprises a sleeve bore  86  which expands in steps forming two valve seats  84 ,  85  from the low-pressure side to the high-pressure side The mid-portion of the bore  86  is connected to the working chamber  51  by way of a transverse bore  87 . Associated with the valve seat  84  is a valve plate  88 , and associated with the valve seat  85  is a valve ball  89 . Compressed between the valve plate  88  and the valve ball  89  is a weak valve spring  90 , and a more potential valve spring  92  is compressed between the valve ball  89  and the plug  91  which is pressed into the end of the sleeve bore  86  close to the damping chamber  47 . On the low-pressure side, the sleeve  83  can be sealed in the valve bore  50  by means of a ring seal  93  (top half of drawing) or also metallically without a ring seal (bottom half of drawing). The sealing on the high-pressure side is carried out by pressing the plug  91  into the sleeve bore  86 , and in doing so, the sleeve portion encompassing the plug  91  is slightly expanded and urged metallically so as to seal against the wall of the valve bore  50 . In addition, the cartridge  82  is operatively attached in the valve bore  50  by pressing in of the plug  91 . Due to the axial force component which acts upon the sleeve  83  when the plug  91  is pressed in, further, a metallic sealing is achieved between the low-pressure side end surface of the sleeve  83  and the plug  73  of the valve bore  50 . The plug  91  can be pressed in either with stop (bottom half of drawing) or without stop (top half of drawing). 
     The embodiment of FIG. 7 distinguishes from the embodiment of FIG. 6 only by the differing configuration of the plug  94  which, in contrast to plug  91 , has a neck portion  95  in which the valve spring  92  is guided. 
     Above all, the embodiments described are characterized by a simple manufacture, preassembly, and installation of the inlet and outlet valves into the housing. Both valves may be installed from one side of the housing, so that the design of the pump housing is also simplified. The valves configured as cartridges require only a small mounting space and can extend into the working chamber, whereby the clearance volume of the working chamber is decreased and the self-venting of the pump is improved. The cartridge configuration further permits ease of testing the complete valve unit prior to the installation It is further especially appropriate for a simple and durable metallic sealing in the pump housing. Still further, as show especially the one-part and two-part cartridge housing designs, the number of the component parts and, thus, the costs incurred for manufacture and assembly of the valves may be reduced.