Abstract:
A piston pump, in particular for a hydraulic assembly of an electronically controllable vehicle brake system, includes a cylinder element that has a pressure chamber with an outlet formed on the inside. The piston pump further includes an outlet-restricting element held on the outside of the cylinder element on a component by a first holder.

Description:
This application is a 35 U.S.C. §371 National Stage Application of PCT/EP2011/068639, filed on Oct. 25, 2011, which claims the benefit of priority to Serial No. DE 10 2010 063 322.4, filed on Dec. 17, 2010 in Germany, the disclosures of which are incorporated herein by reference in their entirety. 
     BACKGROUND 
     The disclosure relates to a piston pump, which is intended, in particular, for a vehicle hydraulic brake system, having a cylinder element, inside which a delivery chamber with an outlet is formed. 
     Known piston pumps comprise a cylinder element, in which a delivery chamber is formed. A piston is guided so that it is axially displaceable in the delivery chamber. The piston can be driven to perform a reciprocating stroke movement in an axial direction, which causes fluid to be delivered in a manner known in the art. In order to prevent noise-generating pressure pulses, a damping chamber and a restrictor, which are both arranged outside the cylinder element and often even separately from the piston pump, are usually hydraulically connected to the outlet side of such piston pumps. 
     Such a piston pump is disclosed in DE 103 14 979 B3. In order to prevent noise-generating pressure pulses in the connected hydraulic system, the known piston pump comprises a restrictor, connected downstream of the fluid outlet for damping purposes. Here the restrictor comprises a primary hydraulic filter. The fluid outlet is guided along at least a portion of the circumferential surface of a liner and in the area of this portion the filter and the restrictor are formed in one piece on the circumferential surface of the liner. 
     SUMMARY 
     According to the disclosure a piston pump is created, in particular for a hydraulic assembly of an electronically controlled vehicle brake system, having a cylinder element, inside which a delivery chamber with an outlet is formed. On the cylinder element an outlet-restricting element is mounted on a component by means of a first mount. In other words a component having a first mount for an outlet-restricting element is arranged on the cylinder element according to the disclosure. This outlet-restricting element may more preferably be a restrictor. 
     In an advantageous development of the disclosure the restrictor is embodied as a restrictor plate. The first mount, in which the restrictor plate is then accommodated, may have a bearing surface for this purpose. The restrictor plate can thereby be subjected to defined pre-tensioning. The restrictor plate may also be integrated into this first mount according to the disclosure. Such a first mount is capable of achieving a very precise opening pressure of the restrictor. 
     The restrictor itself is connected to the hydraulic outlet side of an outlet valve of the piston pump, that is to say downstream of the outlet valve of the piston pump in the direction of flow. The restrictor may be arranged in a pump bore or in an outlet duct in the pump housing, and according to the disclosure is held in the first mount. The restrictor serves for damping pressure pulses of the fluid delivered by the piston pump, which the piston pump induces due to its pulsating mode of delivery. 
     In addition a second mount for a spring is also preferably arranged or integrated in the component having the first mount for the outlet-restricting element. In an advantageous development this spring is the outlet valve spring for an outlet valve closing member. The spring rests on the second mount in the component. For this purpose the second mount may comprise a bearing surface. Here the components of the outlet valve of the piston pump, comprising the outlet valve closing member and the spring, are supported by the second mount. 
     In an alternative development the spring is integrated into the second mount. In this case the spring may be caulked into the second mount. The form of the mount varies according to the design of the spring. If the spring is a coil spring, the mount comprises a cup-shaped seat for the coil spring. If the spring is a leaf spring or spiral spring, the seat is of shallow design. 
     In addition a third mount for a hydraulic damper is preferably arranged or integrated into the component. 
     In this case the fluid delivered preferably first flows through an opening of the outlet valve into a damping chamber. The outflow then ensues via further, defined openings on the component according to the disclosure onto said restrictor plate. These openings may be designed with various shapes, in particular circular or slit-shaped. The restrictor plate sags due to the incident flow and the pressure differential, and the fluid can flow out via the further, defined openings. Here, at the same time, the damping volume is sealed off from the outlet, therefore giving a forced flow through the restrictor. 
     The damper forms a hydraulic capacity, which likewise has a forced flow passing through it and thereby exhibits an optimized response, because the restrictor forms a hydraulic resistance for the fluid on the outlet side. 
     An installation space for a hydraulic accumulator is also preferably provided in the component according to the disclosure. The accumulator may form a part of said hydraulic capacity. 
     Spacers in the form of thin feet to compensate for tolerances of the installation space of the component and to form the outlet bore may optionally be arranged downstream of the restrictor. 
     The component together with at least the one mount is preferably formed as an injection molded part or as a turned metal part or as a cold-formed part. 
     The design of the piston pump according to the disclosure having the component with the first mount for the outlet-restricting element; and the further advantageous mounts, which are arranged in this component or integrated into this component, affords the advantage that multiple functions are accommodated in just one component. Tolerances between the functions can be minimized through a correspondingly precise forming of this one single component. 
     The component serves, in particular, for the hydraulic connection between the outlet valve, which constitutes the separation from the delivery chamber, and an outlet bore. Here this hydraulic connection between the outlet valve and the outlet bore may, at no significant additional cost, at the same time have a compressible volume. 
     The piston pump according to the disclosure in particular comprises a pump cylinder, which is accommodated in a hydraulic unit. The pump cylinder forms a cylinder element within the meaning of the disclosure and as delivery chamber comprises a cylindrical recess, in which a piston is guided so that it is axial displaceable. 
     The piston pump according to the disclosure is intended, in particular, as a pump in a brake system of a vehicle and is used for controlling the pressure in wheel brake cylinders. Such brake systems are commonly known to include wheel slip control (ABS or ASR), a traction control system (TCS), a brake system serving as a steering aid (FDR), an electro-hydraulic brake system (EHB) and/or an electronic stability program (ESP). In such brake systems the pump serves for returning brake fluid from wheel brake cylinders into a brake master cylinder and/or for delivering brake fluid from a reservoir into wheel brake cylinders. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the solution according to the disclosure are explained in more detail below with reference to the schematic drawings attached, of which: 
         FIG. 1  shows a longitudinal section of a piston pump with a first exemplary embodiment of a component according to the disclosure having a seat for a coil spring, 
         FIG. 2  shows a longitudinal section of a piston pump with a second exemplary embodiment of a component according to the disclosure having a seat for a spiral spring, 
         FIG. 3  shows an oblique top view of the component according to  FIG. 1 , 
         FIG. 4  shows the section IV-IV in  FIG. 3 , 
         FIG. 5  shows and oblique view of the component according to  FIG. 1  from below, 
         FIG. 6  shows a view according to  FIG. 5  with outlet-restricting element, 
         FIG. 7  shows an oblique top view of a variant of the component according to  FIG. 1  and 
         FIG. 8  shows the section VIII-VIII in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
     The piston pump  10  is represented in  FIG. 1 . The piston pump  10  comprises a piston  12 , which is capable of a reciprocating movement its in axial direction. This is done by means of an eccentric drive (not shown). The piston  12  comprises an axial bore  14  and multiple radial bores  16 . A guide element  18 , which has a passage opening  20  and which guides the piston  12  in a cylinder element  22 , is arranged on the piston  12 . The cylinder element  22  is formed with a substantially tubular shape in a pump housing  11 . An inlet valve  24  is arranged at the end of the guide element  18  remote from the piston  12 . The inlet valve  24  comprises a cage  26 , a return spring  28  and a closing member in the form of a plate  30 . The cage  26  is fixed to the guide element  16 . The plate  30  closes and opens the passage opening  20  in the guide element  18 . The inlet valve  24  is thereby arranged inside the cylinder element  22  in a delivery chamber  32 , in which furthermore a piston return spring  34  is also arranged. 
     In addition, the piston pump  10  comprises an outlet valve  36 , which is arranged on the end face of the cylinder element  22  remote from the piston  12 . The outlet valve  36  comprises a valve member  39 , which is pressed against a valve seat  41  formed in this end face by a valve spring  62  in the form of a spiral spring. 
     A component  38  bearing on the cylinder element  22  and having a first mount  40  in the form of a perforated annular disk for at least one outlet-restricting element  42  is arranged on the side of the end face remote from the delivery chamber  32 . The outlet-restricting element  42  is designed as a restrictor plate. 
     In addition, a second mount  44  for supporting the valve spring  62  of the outlet valve  36  is formed or integrated on the component  38 . The second mount  44  comprises an annular support or bearing surface for the valve spring  62 . The valve spring  62  may optionally also be caulked into the second mount  44 . The mount  44  can easily be adapted to the shape of the valve spring  62  to be used. For the valve spring  62 , here designed as a coil spring, the mount  44  is of cup-shaped design. 
     An additional or further space  48  for the installation of a hydraulic accumulator (not illustrated further) is provided axially behind the component  38  in a cap-shaped closure element  46  adjoining the cylinder element  22 . 
     The component  38  is formed as an injection-molded part, a turned metal part or a cold-formed part. 
       FIG. 2  represents another variant of the piston pump  10  according to  FIG. 1 . 
     In this variant the second mount  44  is designed as a comparatively shallow, substantially disk-shaped seat for a valve spring  62  embodied as a leaf spring or spiral spring. 
       FIGS. 3 to 5  show the component  38  with its mount  40  in the form of a cup-shaped seat and its mount  44  in the shape of an annular disk angled at the outer edge. 
     A central opening  54  allowing the fluid coming from the valve body  39  to pass through to the rear side of the component  38  is provided on the cupped base of the mount  40 . Openings  52 , through which the fluid can flow back out from the rear side of the component  38  to the front side thereof, are arranged spaced at regular intervals in a circle on the annular disk of the mount  44 . Here the fluid must cause the outlet-restricting element in the form of a restrictor plate, situated in front of these openings, to pivot, so as to allow it to escape on the front side through the openings  52 . Six such openings  52  are provided here. 
     Outflow openings  56  in the form of depressions or recesses of the edge and likewise spaced at regular intervals are formed at the angled edge of the annular disk of the mount  44 . Through these outflow openings  56 , fluid can be discharged downstream of the outlet-restricting element  42  in the direction of flow into a substantially radial outlet opening  37 , which is formed in the pump housing  11 . 
       FIG. 6  represents the outlet-restricting element  42  in the form of a deflectable restrictor plate, enclosed  15  by the mount  44  on the component  38 , added to the component  38 . 
       FIGS. 7 and 8  show a variant of the component  38 , in which the openings  52  are designed as radially oriented slits. Here the slits as depressions also extend through the cup-shaped shoulder for the mount  40  and through the annular plate for the mount  44 . 
     Such a piston pump  10  functions as follows: 
     In a suction phase of the piston pump  10  the outlet valve  36  is closed and the inlet valve  24  is opened. Fluid is thereby carried through the fluid feed line  17 , towards and through a filter element  19 , the radial bores  16 , the axial bore  14  and the longitudinal bore  20  of the guide element  18  to the inlet valve  24 . The fluid is drawn into the delivery chamber  32  through the opened inlet valve  24 . At the bottom dead center of the piston  12  the direction of movement of the piston  12  changes, causing the inlet valve  24  to close. The piston  12  now moves in the direction of the outlet valve  36 . In the process pressure builds up in the delivery chamber  32 , until the pressure therein is greater than the return force of the valve spring  62  of the outlet valve  36 . 
     On the side of the outlet valve  36  remote from the delivery chamber  32  the outlet-restricting element  42  in the form of a restrictor plate is arranged on its mount  40  in the component  38 . Here, on the inside of the angled edge of the mount  40 , the component  38  comprises a step  64 , on which the restrictor plate bears with its outer edge area and is thereby pre-tensioned in an axial direction. Such pre-tensioning leads to a defined opening pressure for the restrictor plate in front of the openings  52 . 
     For this purpose the component  38  is secured in the pump housing  11  with the outlet-restricting element  42  between the cylinder element  22  and the closure element  46 . 
     With the outlet valve  36  opened, the fluid flows through the component  38  according to the disclosure, through its central opening  54 , then past the outlet-restricting element  42  back through the openings  52 , and then onwards into the outlet opening  37  acting as delivery line. In conducting the fluid past the outlet-restricting element  42 , the latter is deflected from its substantially radially oriented position or extent in an axial direction and thereby imposes a restricting and/or damping effect on the fluid. 
     All features represented in the description, the following claims and the drawings may be essential for the disclosure, both individually and in any combination with one another.