Patent Publication Number: US-2020284231-A1

Title: Valve, in particular suction valve, in a high-pressure pump of a fuel injection system

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a valve, in particular a suction valve, particularly in a high-pressure pump of a fuel injection system, which comprises a valve element that can be moved between an open position and a closed position, having an armature which is in mechanical contact with the valve element via an armature pin, wherein the armature pin is connected to the armature by means of a press fit, wherein an actuating force can be transmitted to the valve element by the armature pin. The invention further relates to a pump, in particular a high-pressure pump of a fuel injection system, in which the suction valve is inserted. The invention furthermore relates to a method for producing a valve. 
     A solenoid-operated suction valve for a high-pressure pump of a fuel injection system, in particular a common-rail injection system, is disclosed by DE 10 2013 220 593 A1. This document furthermore discloses a high-pressure pump having such a suction valve. 
     The suction valve comprises a valve element that can be moved between an open position and a closed position and is at least indirectly in contact with an armature via an armature pin. An actuating force can therefore be transmitted to the valve element by the armature. The high-pressure pump comprises a pump housing having a housing part in which a reciprocating pump plunger is fitted in a cylinder bore and defines a pump working chamber in the cylinder bore. The pump working chamber can be connected via the suction valve to a fuel feed and via a non-return valve to a high-pressure fuel accumulator. 
     The armature is part of an electromagnetic actuator, which also comprises a solenoid. When the solenoid is energized, a magnetic field is formed, causing the armature to move relative to the solenoid against a spring force, in order to close the working air gap. 
     SUMMARY OF THE INVENTION 
     The valve according to the invention, the pump according to the invention and the method according to the invention have the advantage over the prior art that the armature pin is partially introduced into a depression in the armature, and the armature pin and the armature are non-positively connected together by means of a press fit in a contact area, and that the armature pin has a varying, in particularly continuously varying outside diameter along the contact area. This serves to prevent damaging of the armature due to an uneven voltage distribution and the overall surface in the area of the press fit is increased. The connection between the armature and the armature pin thereby has increased cohesion and therefore greater strength, which in turn has the advantage of increasing the mechanical load-bearing capacity and therefore prolonging the service life of the suction valve and hence of the high-pressure pump as a whole. 
     The armature advantageously has a varying inside diameter in the area of the depression along the contact area. In this way the overall surface in the area of the press fit is enlarged and the cohesion between the armature and the armature pin can therefore be increased, which leads to an increased mechanical load-bearing capacity. 
     A further advantage is that the outside diameter of the armature pin diminishes along the contact area in the direction of the depression in the armature. This serves on the one hand to increase the overall surface of the press fit and therefore the cohesion between the armature and the armature pin, which leads to an increase in the mechanical load-bearing capacity. On the other hand, this advantageous form of the armature pin makes it possible to improve and to simplify the assembly process, since this form improves the guidance during the assembly process and the risk of the armature pin component tilting is reduced. This reduces the risk of a mishap during assembly and any possible prior damaging of the armature pin and armature components due to tilting during the assembly process is reduced, which in turn leads to reduced costs. 
     The outside diameter of the armature pin advantageously increases along the contact area in the direction of the depression in the armature. This increases the surface of the press fit formed whilst at the same time reducing the surface stress per unit area on the armature pin component. This results in an improved distribution of stresses on the component and therefore a reduced risk of material fatigue and of the component failing. 
     In addition, a further advantage of the development according to the invention is that the inside diameter of the armature increases in the area of the depression along the contact area in the direction of the armature pin. This serves on the one hand to increase the overall surface of the press fit and therefore the cohesion between the armature and the armature pin, which leads to an increase in the mechanical load-bearing capacity and therefore to an increase in the service life of the valve and consequently of the pump. On the other hand, this advantageous form of the armature pin makes it possible to improve and to simplify the assembly process, since this form improves the guidance during the assembly process and reduces the risk of the armature pin component tilting. The risk of a mishap during assembly is thereby reduced and any possible incipient damaging of the armature pin and armature components due to tilting during assembly is reduced, which in turn leads to reduced costs. 
     It is moreover advantageous for the variation in the outside diameter of the armature pin and/or the variation in the inside diameter of the armature in the area of the depression to have a linear profile. This makes it possible to match the armature and armature pin components in the contact area of the press fit to one another in such a way that the press fit develops a maximum cohesion, whilst minimizing the fitting force required. In addition, the variation in the outside diameter of the armature pin and/or the variation in the inside diameter of the armature in the area of the depression advantageously has a curved profile. This allows a further increase in the surface in the area of the press fit formed. This further enlargement of the surface serves to increase the cohesion between the armature component and the armature pin yet further. 
     The armature pin with the outside diameter varying in the direction of the longitudinal axis [is advantageously introduced into the depression in the armature], which at least in respect of a portion of the part of the armature pin to be introduced into the depression, has a small inside diameter in proportion to the outside diameter of the armature pin, wherein the depression in the armature is expanded before, during or after the introduction of the armature pin, in order to form a non-positive connection through a press fit in the contact area with the armature pin. This advantageous form of the method makes it possible either to reduce the fitting force that is needed in order to introduce the armature pin into the depression in the armature to a very much smaller value than is needed without the use of this method, or to eliminate the fitting force altogether. 
     Furthermore, the inside diameter of the armature in the contact area is advantageously increased before pushing in the armature pin, wherein the process of enlarging the inside diameter is, in particular, reversible and done for a limited time and the inside diameter elastically returns again following insertion of the armature pin. 
     This advantageous form means that after inserting the armature pin into the depression in the armature with a greatly reduced fitting force—as described in the preceding paragraph—it is possible for the inside diameter to diminish again and to return to its original shape. Joining of the armature pin and the armature is therefore possible with a greatly reduced force, if any, and the compression occurs under the subsequent equalization of temperature, wherein the surface roughness is very largely retained, resulting in a firm seating of the press fit. 
     In a further advantageous form of the method for producing a valve the inside diameter of the armature is enlarged, in particular, by a thermal process. This makes it possible to reduce the fitting forces during assembly and to bring the assembly costs down. 
     A further advantage of the development of the method according to the invention is that the outside diameter of the armature pin is reduced by a thermal process, in particular by cooling, particularly in the area which forms the press fit, wherein the process of reducing the outside diameter is reversible and done for a limited time. This development of the method according to the invention makes it possible to reduce the fitting force required and therefore the energy needed during assembly, which in turn reduces the assembly costs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various exemplary embodiments of the invention are represented in the drawings and explained in more detail in the following descriptions. In the drawings: 
         FIG. 1  shows a pump in a longitudinal section, 
         FIG. 2  shows an enlarged representation of a detail of the pump, denoted by II in  FIG. 1 , having a suction valve, 
         FIG. 3  shows an enlarged representation of a detail of the suction valve, denoted by III in  FIG. 2 . 
         FIG. 4  shows a section of the armature according to a first exemplary embodiment. 
         FIG. 5  shows a section of the armature according to a second exemplary embodiment. 
         FIG. 6  shows a section of the armature according to a third exemplary embodiment. 
         FIG. 7  shows a section of the armature pin according to a first exemplary embodiment. 
         FIG. 8  shows a section of the armature pin according to a second exemplary embodiment. 
         FIG. 9  shows a section of the armature pin according to a third exemplary embodiment. 
         FIG. 10  shows a section of the armature pin according to a fourth exemplary embodiment. 
         FIG. 11  shows a section of the armature pin according to a fifth exemplary embodiment, which corresponds to the prior art. 
         FIG. 12  shows a method according to the invention for joining the armature and armature pin components. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a sectional representation of a schematically represented high-pressure pump  1 , which is embodied as a high-pressure fuel pump and is preferably fitted in a common-rail injection system. The high-pressure pump  1  delivers fuel provided from a low-pressure fuel system, which comprises at least a tank, a filter and a low-pressure pump, into a high-pressure accumulator, from where the stored fuel is drawn by fuel injectors for injection into assigned combustion chambers of an internal combustion engine. The fuel is fed to the pump working chamber via a solenoid-operated suction valve  2 , wherein the solenoid-operated suction valve is fitted to the high-pressure pump. 
     The high-pressure pump  1  comprises a pump housing  3  having a camshaft chamber  5 . A camshaft  7  having a cam  9  in the form of a double cam, for example, extends into the cam chamber  5 . The camshaft  7  is supported in two radial bearings arranged on both sides of the cam  9 . The one bearing is a housing bearing  11  arranged in the pump housing  3  and the second bearing is a flange bearing  13 . The flange bearing  13  is arranged in a flange  15 , which is connected to the pump housing  3  and which tightly seals off the camshaft chamber  5  from the surroundings. The flange  15  has a through opening, through which a drive-side end portion  17  of the camshaft  7  extends. The drive-side end portion  17  has a taper, for example, onto which a drive wheel is mounted and secured. The drive wheel takes the form, for example, of a belt pulley or a gear wheel. The drive wheel is driven directly by the internal combustion engine or indirectly via a belt drive or a gear mechanism, for example. 
     A tappet guide  19 , into which a roller tappet  23  comprising a roller  21  is inserted, is furthermore let into the pump housing  3 . The roller  21  runs on the cam  9  of the camshaft  7  as the latter rotates and the roller tappet  23  is therefore moved translationally up and down in the tappet guide  19 . In so doing the roller tappet  23  interacts with a pump plunger  18 , which is arranged so that it can likewise perform a translational up and down movement in a cylinder bore  29  formed in a pump cylinder head  27 . A tappet spring  33 , which is supported on the one hand on the pump cylinder head  27  and on the other on the roller tappet  23 , and which ensures that the roller  21  continuously bears on the cam  9  in the direction of the camshaft  7 , is arranged in a tappet spring chamber  31  formed by the tappet guide  19  and the pump bore  29 . A pump working chamber  35 , into which fuel is introduced by the solenoid-operated suction valve  2 , is formed in the pump cylinder head  27  as an extension of the pump plunger  18 . The fuel is introduced during a downward movement of the pump plunger  18 , whereas during an upward movement of the pump plunger  18  fuel present in the pump working chamber  35  is delivered via a high-pressure outlet  39  with an outlet valve  16  inserted, via a further high-pressure line into the high-pressure accumulator. The high-pressure pump  1  as a whole is fuel-lubricated, wherein the fuel is delivered from the low-pressure system into the camshaft chamber  5 , which is flow-connected to the suction valve  2 . This solenoid-operated suction valve  2  and its working principle is described below. 
     The solenoid-operated suction valve  2  fitted to the high-pressure pump  1  as represented in  FIG. 2  comprises a plunger-shaped valve element  14 , which is acted upon in the closing direction by the spring force of a second compression spring  12 . The plunger-shaped valve element  14  comprises a stem  25 , in particular a cylindrically formed stem  25 , and an enlarged head  34 . The enlarged head  34  of the valve element  14  is arranged on the side facing the pump plunger  18 . The pump cylinder head  27  moreover comprises a valve seat  36  in the contact area with the closed valve element  14 . The plunger-shaped valve element  14  is guided by the stem  25  in a bore  38  in the pump cylinder head  27  and comprises the head  34  of enlarged diameter compared to the stem  25 . A sealing face  37 , which in the closed position of the valve element  14  bears on the valve seat  36  in the pump cylinder head  27 , is formed on this enlarged head  34  of the valve element  14 . The pump working chamber  35  is thereby separated from the fuel feed  26  and fuel cannot flow back. 
     Also represented in  FIG. 2  are the elements of an electromagnetic actuator, which serves to actuate the suction valve  2  of the high-pressure pump  1 . This comprises an armature  10  having a cylindrical external contour and a central bore  32 . A first compression spring  4 , which exerts an axial force on the armature  10  towards the valve element  14 , moreover extends into this central bore  32  of the armature  10 . The armature  10  is moreover axially guided in its reciprocating motion in a carrier element  40 . The armature  10  is surrounded in a radial direction by a solenoid coil  6 , which when energized forms a magnetic field and is therefore able to exert a magnetic force on the armature  10 . The valve element  14  is in contact with the armature  10  via an armature pin  8 , wherein the two elements are not connected to one another in an axial direction but are held in contact with one another only by magnetic forces and spring forces. On the side remote from the valve element  14  the armature pin  8  is connected to the armature  10  in that the armature pin  8  is partially inserted into the armature  10  and is non-positively connected to the armature  10  by means of a press fit  20 . The armature  10  and armature pin  8  elements in particular form a contact area  48 . 
     The first compression spring  4  presses on the armature pin  8  and the armature  10  in an axial direction. In an unenergized state the first compression spring  4  ensures that the armature pin  8  acts on the valve element  14  and holds it in an open position. Although the second compression spring  12  acts in opposition to this, since the first compression spring  4  has a greater spring force than the second compression spring  12  the valve element  14  is kept in an open state. Energizing the armature  10  by means of the solenoid coil  6  causes the armature  10  to move away from the valve element  14  against the force of the first compression spring  4 , in order to close the working air gap  28 . Its moving away causes the armature pin  8  to lose the non-positive contact with the valve element  14 , so that the valve element  14  moves towards the closed state under the force of the second compression spring  12 . In a fully closed state the valve element  14  bears on the sealing face  37  on the valve seat  36  and seals the pump working chamber  35  off from the fuel feed  26 . 
     With the high-pressure pump  1  in suction mode, the solenoid-operated suction valve  2  is opened and the pump working chamber  35  is connected to the fuel feed  26 , so that fuel is delivered to the pump working chamber  35  via the suction valve  2 . With the high-pressure pump  1  in delivery mode the fuel delivered to the pump working chamber  35  is compressed and delivered to a high-pressure accumulator (not shown) via the outlet valve  16  arranged in the high-pressure outlet  39 . With the high-pressure pump  1  in compression mode, in which the pump plunger  18  moves upward, the suction valve  2  is closed when fuel delivery is to ensue, and seals off the pump working chamber  35  from the fuel feed  26 . 
     The detail III represented in  FIG. 3  shows precisely how the armature pin  8  is pressed into the armature  10  in order to form a positively interlocking connection in the form of a press fit  20 . In order to allow the formation of the press fit  20  in the contact area  48  between the armature  10  and the armature pin  8 , the outside diameter  47  of the armature pin  8  in the contact area  48 , at least at one point over its length in the insertion direction (V), must have a larger diameter than the smallest inside diameter  45  of the armature  10  in the contact area. 
     Also shown is the carrier element  40 , which serves as guide and receiving element for the armature  10  and the armature pin  8 . 
     The optional annular shoulder  30 , which is in bearing contact with the armature  10  and prevents the armature pin  8  being pressed too far into the armature, is also shown. The annular shoulder  30  ensures that the armature pin  8  cannot be pressed further into the depression  24  in the armature  10 . It therefore serves as an assembly aid in order to prevent the armature pin  8  being pressed too far into the armature  10 . 
     The figure also shows that the armature pin  8  has an internal recess  22 , which is open on the side facing the armature  10 . The armature pin  8 , moreover, is in bearing contact with the valve element  14  on the one side, and the armature pin  8  is in bearing contact with the first compression spring  4  on the other side. In particular, the inside diameter  45  of the armature  10  may be expanded prior to fitting of the armature pin  8 , in order to ensure an improved and simplified assembly process. This can be ensured, in particular, by a thermal process. 
     The sectional representations of the armature  10  represented in  FIGS. 4, 5 and 6  show different exemplary embodiments of the depression  24  in the armature  10 , into which the armature pin  8  is introduced.  FIGS. 7 to 10  show sectional representations of the armature pin  8 , in which various embodiments of the outside diameter  47  of the armature pin  8  in the area of the press fit  20  are represented. 
     A center line  41 , which at the same time forms the axis of rotation of the sectional representation, is represented in each of the  FIGS. 4 to 11 . Running parallel to the center line  41  in  FIG. 5  are two reference lines  43  and in  FIGS. 7, 8 and 9  the two reference lines  49 . The reference lines  43  in  FIG. 5  run parallel to the center line  41  and as an extension of the line which forms the constant profile of the inside diameter  42  of the armature  10  in the sectional representation. In each of the  FIGS. 7, 8 and 9  the reference lines  49  run parallel to the center line  41  and as an extension of the line which forms or would form the constant profile of the outside diameter  47  of the armature pin  8 . The center line  41  and the reference lines  43  and the reference lines  49  moreover run parallel to the insertion direction (V) of the armature pin  8 . 
       FIG. 4 , as first exemplary embodiment, in a sectional representation of the armature  10  shows that the area of the depression  24  in the armature  10  has a constant profile  42  of the inside diameter  45  over the entire axial length in the insertion direction (V) of the armature pin  8 . This shaping of the armature  10  in the contact area  48  of the press fit  20  means that armature  10  does not need to undergo additional finishing work in a further production operation in order to modify the contour of the inside diameter  45  of the armature  10 . The geometric shape that serves to improve the formation of the press fit  20  can therefore be shifted into the armature pin  8 . 
       FIG. 5  shows a section of the armature  10  according to a second exemplary embodiment, wherein the armature  10 , in the insertion direction (V) of the armature pin  8 , has an inside diameter  45  varying over a part of the length, which reveals a linear profile  44 . The part of the length of the armature  10  that has a varying inside diameter  45  is the area facing the armature pin  8 . The linear profile  44  of the varying inside diameter  45  runs at an angle α to the reference line  43 . This exemplary embodiment serves to provide a guide for the armature pin when introducing the armature pin  8  into the recess  22  in the armature  10 . This reduces the risk of the armature pin tilting and reduces the fitting force at the beginning of the introduction process. 
       FIG. 6  represents a section of the armature  10  according to a third exemplary embodiment, wherein the armature  10 , in the insertion direction (V) of the armature pin  8 , has an inside diameter  45  varying over a part of the length. The part of the length of the armature  10  which has a varying inside diameter  45  is the area facing the armature pin  8 . This varying inside diameter  45  has any optional profile, but has a diminishing inside diameter  45  over the entire length in the insertion direction. In particular, this may take the form of a curved profile  46 . This design shape of the armature  10  serves decisively to increase the strength of the connection between the armature pin  8  and the armature  10 . This applies particularly to the form of the press fit  20  in the contact area  48 , so that the effect of the surface roughness of the two elements is exploited to form the press fit  20 . This form of the inside diameter  45  of the armature  10  means that the cohesion between the armature  10  and the armature pin  8  can be increased, since the strength of the press fit  20  is increased in the contact area  48 . 
       FIG. 7  shows a section of the armature pin  8  according to a first exemplary embodiment, wherein the armature pin  8 , in the insertion direction (V), has an outside diameter  47  which diminishes over the entire length of the contact area  48  of the press fit  20  but which has a linear profile  44 . The linear profile  44  of the varying outside diameter  47  runs at an angle θ to the reference line  49 . The recess  22  in the armature pin  8  affords further functions described below: 
     For one thing the recess  22  in the armature pin  8  serves to reduce the weight, which is advantageous, since the armature  10 /armature pin  8  assembly performs a high-frequency movement during the operation of the pump  1  and the weight saving afforded by the recess  22  is capable of reducing the inertia of the assembly and in addition can reduce the input energy needed for electromagnetic actuation. The recess  22  in the armature pin  8  moreover affords further advantages during assembly in that it lends the armature pin  8  component a certain elasticity in the area of the press fit  20 . This firstly ensures that the fitting force when introducing the armature pin  8  into the depression  24  in the armature  10  is reduced, but secondly after introduction the elasticity ensures that the outside diameter  47  of the armature pin  8  is pressed more heavily against the inside diameter  45  of the armature  10 , thereby forming a better non-positive connection in the area of the press fit  20 . 
       FIG. 8  represents a section of the armature pin  8  according to a second exemplary embodiment, wherein the armature pin  8 , in the insertion direction (V), has an outside diameter  47  which diminishes over only a part of the length of the contact area  48 , but which has a linear profile  44 . In  FIG. 8  the part that has a diminishing outside diameter  47  extends over less than half of the length of the contact area  48  and is situated on the side of the armature pin  8  facing the armature  10 . Over the remaining part of the length of the contact area  48  with the armature  10  the armature pin  8  has a constant outside diameter  47 . This small part of the length which has a diminishing outside diameter  47  is situated on the side of the armature pin  8  facing the armature  10 . The varying inside diameter  45  runs at an angle γ to the reference line  49 . This shaping of the armature pin  8  in the area of the press fit  20  serves to center the armature pin  8  at the beginning of the operation to fit it into the armature  10  and to reduce the risk of tilting or tipping. The second embodiment of the armature pin  8  represented in  FIG. 8  furthermore affords the advantage over the embodiment represented in  FIG. 7  that a smaller outlay is needed for machining of the component. 
       FIG. 9  shows a third exemplary embodiment, showing the section of the armature pin  8 . The armature pin  8 , in the insertion direction (V), has an outside diameter  47  which increases over the entire length of the contact area  48  and which has a linear profile  44 . The varying outside diameter  47  runs at an angle δ to the reference line  43 . This exemplary embodiment serves, particularly in combination with the temporary expansion of the inside diameter  45  of the armature  10  undertaken prior to the assembly process, to produce an improvement in the formation of the press fit  20 , resulting in a firmer seat. 
       FIG. 10  shows a section of the armature pin  8  according to a fourth exemplary embodiment, wherein the armature pin  8 , in the insertion direction (V), has an outside diameter which varies over the entire length of the contact area  48 , but which has a curved, non-linear profile  46 . The function of this exemplary embodiment is to enlarge the surface in the area of the press fit  20  and therefore to further increase the cohesion between the armature  10  component and the armature pin  8 . 
       FIG. 11  shows a section of the armature pin according to the prior art. The section of the armature pin  8  shown in  FIG. 11  serves as reference and in the prior art is combined with the embodiment of the armature  10  in  FIG. 4 . This explicit combination of the armature pin  8  in  FIG. 11  and the armature  10  in  FIG. 4  is therefore not an integral part of the form according to this invention. 
       FIG. 12  shows the method according to the invention for joining the armature  10  and armature pin  8  components. The aim of the method is to introduce the armature pin, at least partially, into a depression in the armature and to connect the armature pin and the armature together non-positively in a contact area by means of a press fit. The method  1201  commences by choosing an armature  10  component and an armature pin  8  component, each of any embodiment, as represented in  FIGS. 4 to 10 . In preparation for the next step  1204 , the actual assembly of the two components, particularly by means of an assembly fixture, this may optionally be preceded by the additional steps  1202  and  1203  of the method: 
     In step  1202  of the method the depression in the armature is expanded before and/or during the introduction of the armature pin  8  into the depression  24  in the armature  10 , particularly by a thermal or mechanical process. In particular, the mechanical process is performed through the use of a tool. 
     In step  1203  of the method the armature pin  8 , which is introduced into the depression  24  in the armature  10 , is heat-treated. For this purpose, the outside diameter  47  of the armature pin  8  is reduced by a thermal process, in particular by cooling. 
     This is followed in step  1204  of the method by the actual process of joining the armature  10  and armature pin  8  components. It should be noted with regard to this that the steps  1202  and  1203  of the method can each be employed separately or in combination. Using the steps  1202  and  1203  of the method reduces the fitting force required. 
     Step  1205  of the method describes the formation of the press fit in the contact area of the armature  10  and the armature pin  8  following assembly in step  1204  of the method. After employing steps  1202  and  1203  of the method, in particular, these are followed, owing to the possible reversibility of the two steps of the method and their temporary nature, by a return movement of either the armature  10  and/or the armature pin  8 . This means, in particular, that the press fit  20  between the armature  10  and the armature pin  8  is not formed until step  1205  of the method. Compression therefore occurs, wherein the surface roughness is very largely retained, resulting in a firm seating of the press fit.