Abstract:
A pressure regulator for a fuel supply system of an internal combustion engine for regulating a fuel pressure, including a valve, having a valve ball forced against a valve seat into the closing position by the action of a valve leaf spring. With the valve open, at least some of the fuel flow that flows around the valve ball is deflected against an impact face coupled with the valve leaf spring for generating a flow force oriented counter to the closing force of the valve leaf spring. As a result, the pressure regulating performance of the pressure regulator is improved.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a 35 USC 371 application of PCT/DE 02/04478 filed on Dec. 6, 2002. 
   BACKGROUND OF THE INVENTION 
   1 . Field of the Invention 
   The invention is directed to an improved pressure regulator for a fuel supply system of an internal combustion engine for regulating a fuel pressure, including a valve which includes a valve ball that is forced against a valve seat into the closing position by the action of a valve leaf spring. 
   2 . Description of the Prior Art 
   One pressure regulator of the type with which this invention is concerned is described by German Patent Disclosure DE 101 07 223A1, in which the valve leaf spring is pivotably supported, and one arm of the valve leaf spring toward the valve seat with respect to the pivotable support is braced on the valve ball, while one arm of the valve leaf spring located on the side opposite the valve seat is braced on a support body, in such a way that torque equilibrium prevails at the valve leaf spring. The prestressing force generated by the support body is transmitted by the valve leaf spring to the valve ball in the form of closing force. If fuel pressure that is high enough to generate a greater pressure force than the closing force acting on the valve ball prevails at the pressure input, then the valve ball lifts from the valve seat and opens a defined flow cross section, so that fuel can flow to the pressure outlet. SUMMARY AND ADVANTAGES OF THE INVENTION 
   Without the impact face according to the present invention, the force exerted by the valve leaf spring on the valve ball of the known regulator increases steadily as the flow becomes greater and consequently the valve ball stroke lengthens. Since an equilibrium of force or moment ensues at the valve leaf spring, the result is that with an increasing flow, the fuel pressure likewise increases, in a way that is unwanted for a pressure regulator. 
   As a result of the definitive characteristics of the invention a comparatively lesser increase in the characteristic pressure and flow curve of the pressure regulator is obtained; therefore even if the flow quantity increases, the set pressure becomes only slightly greater. When the valve ball has lifted from the valve seat, the deflection according to the invention of the fuel flow to the impact face creates a flow force that acts on the valve leaf spring counter to the closing force of the valve leaf spring and that is greater, the greater the flow through the valve of the pressure regulator. Thus with a greater flow and a consequent longer stroke of the valve ball, on the one hand the force exerted by the elastic valve leaf spring on the valve ball in the closing direction increases, but on the other hand, the contrary flow force on the valve leaf spring also increases, so that these forces at least partly compensate for one another. As a result, the influence of the stroke of the valve leaf spring and thus the influence of the flow on the pressure are advantageously less. 
   In a preferred embodiment, the impact face is formed by a portion of a lower face of the valve leaf spring, which portion is adjacent to a contact point of the valve ball with the valve leaf spring. This is especially advantageous in terms of production costs, since because of the integration of the impact face with the valve leaf spring, no additional components are necessary. 
   In order to deflect the fuel flow, flowing around the valve ball, onto the impact face at the valve leaf spring, the valve seat preferably has a cone angle in a range between 40° and 110°, preferably 60°. 
   In a further embodiment, the impact face is formed by a face that is defined at the valve ball and extends radially outward into the fuel flow. As a result, the fuel flow flowing around the valve ball can strike the impact face nearly perpendicularly, and this is an ideal state in terms of the flow force generated as a result. 
   In an especially preferred embodiment, the valve leaf spring is provided with at least one opening, which increases in cross section in a direction pointing away from a leaf spring bearing point. As a result, if the valve leaf spring bends, a substantially constant tension ensues over the length, and the spring constant of the valve leaf spring becomes relatively low; changes in the stroke of the valve ball therefore have a lesser effect on the pressure. In the preferred embodiment, in which the impact face is located on the valve leaf spring, the opening is located outside the impact face, in order not to hinder the buildup of the flow force. 
   A refinement provides that the valve leaf spring is embodied as rectangular and the opening is embodied as essentially triangular. The valve leaf spring is preferably supported tiltably at a pivot shaft, and one arm of the valve leaf spring is tensed against a prestressing spring for generating a force by which the other arm of the valve leaf spring holds the valve ball down in the valve seat. Then, both arms of the valve leaf spring are provided with at least one triangular opening, since they both contribute to the overall bending strength of the valve leaf spring. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the invention are shown in the drawing and described in further detail, herein below, with reference to the drawings. in which: 
       FIG. 1  shows a cross-sectional view of a preferred embodiment of a pressure regulator in accordance with the invention; 
       FIG. 2  shows a cross-sectional view of a further embodiment of a pressure regulator in accordance with the invention; 
       FIG. 3  shows a perspective view of a valve leaf spring of the pressure regulator of  FIG. 1  or  FIG. 2 ; and 
       FIG. 4  shows a characteristic pressure and flow curve of a pressure regulator of  FIG. 1  or  FIG. 2 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The pressure regulator of the invention is designated generally by reference numeral  1  and is shown there in  FIG. 1  in a closing position. In use, the regulator is secured to a tank fitting unit or filter unit, not shown for reasons of scale, that is disposed in a fuel tank of a motor vehicle, and serves to regulate the fuel pressure in the fuel system of a self-igniting internal combustion engine. The pressure regulator  1  has a housing  2 , and in each of two upward-drawn housing necks there is a respective lateral opening which connects an interior  6  of the housing  2  to the fuel tank. Protruding into the housing  2  at the bottom is a connection piece  10  that forms a pressure inlet  8 ; it is connected to a pressure line, not shown, of the fuel system, and fuel flowing back from a fuel distributor flows through it. 
   On the end of the connection piece  10 , there is a valve seat  12  with a conical face  14  for centering a valve ball  18 . Instead of being embodied directly on the connection piece  10 , the valve seat  12  can also be embodied on the housing  2 ; in this case, the housing  2  and the valve seat  12  are embodied for instance as a one-piece cast part machined in metal-cutting fashion. The cone angle of the conical face  14  is in a range between 40° and 110° and is preferably 60°. The conical face  14  has a length of essentially 0.5 mm. Because of the action of a valve leaf spring  16 , the valve ball  18  is urged against the valve seat  12 , and the valve ball  18  touches the conical face  14  along a line. The valve leaf spring  16 , valve ball  18  and valve seat  12  together form an overflow valve  20  of the pressure regulator  1 . The valve ball  18  may be of steel, ceramic, or plastic; its diameter is in a range between 3 mm and 12 mm and is preferably 7 mm. mm. 
   The valve leaf spring  16  preferably has an angular form, comprising two arms  22 ,  24  extending essentially at right angles to one another, and is pivotable about an a pivot shaft  26 , which is supported in the housing  2  and preferably formed by a pin extending transverse to the length of the valve leaf spring  16  and perpendicular to a plane that contains the center axis  28  of the valve seat  12 . The shaft  26  furthermore extends in the region of an imaginary abutting line of the two arms  22 ,  24  of the valve leaf spring  16 . The total length of the coiled valve leaf spring is from 10 to 40 mm, for instance, and its width is approximately 5 mm to 20 mm. The spacing of the center axis  28  of the valve seat  12  from the articulated shaft  26  is preferably 8 mm to 35 mm. 
   Between the arm  22  of the valve leaf spring  16  toward the valve seat, which preferably extends perpendicular to the center axis  28  of the valve seat, and the valve ball  18  that with its apex contacts the valve leaf spring  16 , there is a damping ring  29 , which for instance has a circular cross section and comprises an elastomer. More precisely, the valve ball  18 , with one spherical segment of its hemisphere pointing toward the valve leaf spring  16 , protrudes into an annular opening in the damping ring  29  and thereby retains this ring on the valve leaf spring  16 . The diameter of the annular opening and the valve ball  18  are preferably selected such that a slight freedom of motion, in the form of a narrow gap, is still present between the valve leaf spring  16  and the damping ring  29 . In operation, frictional forces develop between the damping ring  29 , valve leaf spring  16  and valve ball  18 , and these forces are on the one hand great enough to damp vibrational motions of the valve ball  18 , but on the other are not so great that centering of the valve ball  18  in the valve seat  12  when the overflow valve  20  closes is hindered. 
   A prestressing force engages the arm  24  of the valve leaf spring located on the side opposite the valve seat  12  with respect to the shaft  26 , and at the arm  22  toward the valve seat this force generates a force that urges the valve ball  18  against the valve seat  12 . This prestressing force is preferably formed by a tensing leaf spring  30 , which extends essentially parallel to the arm  24  of the valve leaf spring  16  located on the side opposite the valve seat  12 . The tensing leaf spring  30  is preferably embodied in one piece with a cap  32  that closes the housing  2  of the pressure regulator  1  at the bottom and that is engaged from behind, in the assembled state, by a radially outer annular shoulder  34  of the connection piece  10  and protrudes away from the connection piece at a right angle. The free end  36  of the tensing leaf spring  30  is bent toward the arm  24  of the valve leaf spring  16  located on the end portion opposite the valve seat  12  and engages a rounded recess  37 , embodied on this arm, in such a way that a prestressing force generated by the tensing leaf spring  30  is introduced essentially perpendicularly into the arm  24  of the valve leaf spring  16 . The tensing leaf spring  30 , with its curved end  36 , exerts a torque on the pivotably supported valve leaf spring  16 , by which torque the valve ball  18  is urged against the valve seat  12 . The magnitude of the closing force that is operative on the head end in reaction to the prestressing force of the tensing leaf spring  30  on the valve ball  18  is the result of the selected lever ratios of the two arms  22 ,  24 . In that case, a torque equilibrium then prevails at the valve leaf spring  16 . 
   As seen from  FIG. 3 , in which the valve leaf spring  16  is shown by itself, its two arms  22 ,  24  are each provided with a respective opening  38 , which increases in cross section in a direction pointing away from the shaft  26 . Preferably, both openings  38  are embodied essentially triangularly and are stamped out from the valve leaf spring  16 . 
   In the context of the above description, the mode of operation of the pressure regulator  1  is as follows: When fuel pressure that is high enough to generate a greater pressure force than the closing force acting on the valve ball  18  prevails at the pressure inlet  8 , the valve ball  18  lifts from the valve seat  12  and opens a defined flow cross section, so that fuel can flow into the interior  6  of the housing  2  and from there to the pressure outlets  4 . Because of the elastic properties of the valve leaf spring  16 , the flow cross section increases as the fuel volume increases. 
   In this process, the fuel flows around the valve ball  18 , approximately as indicated by the arrows P in  FIG. 1 , and because of the above-described embodiment of the conical face  14  of the valve seat  12 , the streamlines are deflected onto an impact face  40 , which is disposed approximately annularly around the valve leaf spring adjacent to a contact point  42  of the valve ball  18  and the valve leaf spring  16  and is formed by part of the lower face of the arm  22  toward the valve seat of the valve leaf spring  16 . The impact face  40  is an annular face, with the contact point  42  as its center point, and the internal diameter of the annular face, as is usual for a ring, has some spacing from the center point. The oncoming flow of the fuel against the impact face  40  generates a flow force, acting counter to the closing force of the valve leaf spring  16 , that is greater, the greater the flow through the overflow valve  20  of the pressure regulator  1 , and its effect on the pressure difference between the pressure inlet  8  and the pressure outlets  4  has been described above. In order not to hinder the buildup of the flow force, the opening  38  in the arm  22  toward the valve ball  18  is located in a region between the impact face  40  and the articulated shaft  26 . 
   In the further exemplary embodiment of the invention shown in  FIG. 2 , those elements that remain the same and function the same as in the previous example are identified by the same reference numerals. In a distinction from the previous example, the impact face  44  is embodied not on the valve leaf spring  16  itself but rather on the valve ball  18 . The impact face  44  for the fuel flowing around the valve ball  18  is embodied here by a face  44  that is defined on the valve ball  18  and extends radially outward into the fuel flow and forms the lower annular face of a ring  46  surrounding the valve ball  18 , preferably along its equator line. The flow force acting on the ring  46  is then transmitted to the valve leaf spring  16  via the valve ball  18 . 
   The effect of the invention is shown in the pressure-flow graph in  FIG. 4 , in which the pressure course  48  of a pressure regulator without the impact face  40 ,  44  of the invention is represented by rectangular marking points, and the pressure course  50  of the pressure regulator  1  of the invention with the impact face  40 ,  44  is represented by diamond-shaped marking points. As the graph shows, the slope of the characteristic curve  50  of the pressure regulator  1  with the impact face  40 ,  44  is less than that of the characteristic curve  48  of a pressure regulator without an impact face. In addition, the pressure level for the characteristic curve  50  of the pressure regulator  1  with the impact face  40 ,  44  is already relatively high at low flow rates and is thus closer to the corresponding pressure values at higher flow rates than is the case for the characteristic curve  48  of the pressure regulator without the impact face, in which the slope at low flow rate values is relatively great. Consequently, the pressure changes in the pressure regulator  1  of the invention, especially at low flow quantities, are substantially less than in a pressure regulator without an impact face. 
   The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.