Patent Document

BACKGROUND 
       [0001]    The invention relates to a hydraulic directional valve with an electromagnetic actuating unit and a valve section, with an essentially cylindrical, blind hole-like receptacle being formed on one component of the actuating unit, with a flange section of a valve housing of the valve section engaging in the receptacle, with the flange section being provided with an annular groove extending in a circumferential direction, and with an essentially hollow, cylindrical wall of the receptacle in the region of the annular groove engaging in this annular groove, such that this wall contacts the groove base of this annular groove along the entire circumference of the annular groove. In addition, a method for producing such a control valve is provided. 
         [0002]    Such directional valves are used in internal combustion engines, for example, for controlling hydraulic camshaft adjusters or switchable cam followers. The directional valves are made from an electromagnetic actuating unit and a valve section. The valve section represents the hydraulic section of the directional valve, with at least one supply port, at least one working port, and a tank port also being formed on this valve section. Certain ports of the valve section can be selectively connected to each other hydraulically via the electromagnetic actuating unit and thus the pressure medium flows can be directed. 
         [0003]    For the use of a directional valve for controlling a camshaft adjuster, this is formed in the normal case as a 4/3 proportional directional valve. Such a proportional valve is disclosed, for example, in DE 199 56 160 A1. The electromagnetic actuating unit is comprised in this case from a first magnetic yoke, a coil, a second magnetic yoke, a housing, an armature, and a connection element, which holds an electrical plug connection that is used for supplying power to the coil. 
         [0004]    The valve section is made from a valve housing and a control piston arranged displaceable in the axial direction in this housing. The valve housing is arranged within a cylindrical, blind hole-like receptacle of the second magnetic yoke and is connected fixed in position with this magnetic yoke. Four annular grooves, which are used as pressure medium ports, are formed on the outer casing surface of the valve housing. Openings, through which pressure medium can be led into the interior of the valve housing, are formed in the groove bases. In the interior of the valve housing, a control piston is arranged axially displaceable, wherein the outer diameter of the control piston is adapted to the inner diameter of the valve housing. In addition, annular grooves, via which pressure medium ports can be connected to each other, are similarly formed on the control piston. 
         [0005]    The coil and the first and second magnetic yokes are arranged coaxial with respect to each other within the housing of the electromagnetic actuating unit. The first and the second magnetic yokes are here offset with respect to each other in the axial direction. In the region between the first and the second magnetic yokes there is the armature radially within the magnetic yokes, with this armature being surrounded by the coil in the radial direction. The armature, the housing and the first and second magnetic yokes form a flow path for the magnetic flux lines caused by the coils being energized. 
         [0006]    By energizing the coils, the armature is forced in the direction of the second magnetic yoke, with this motion being transmitted to the control piston by a tappet rod attached to the armature. This piston is now moved in the axial direction against a spring supported on the valve housing. 
         [0007]    Directional valves for controlling switchable cam followers are mostly constructed as switch valves. Such a switch valve is known from a setup as a 3/2 switch valve, for example, from DE 103 59 363 A1. The electromagnetic actuating unit is comprised, in turn, from a housing, an armature, a connection element and a first and a second magnetic yoke. The function and the construction of the electromagnetic actuating unit are in wide parts analogous to that of the proportional valve. 
         [0008]    In this case, a supply port, a working port, and a tank port are formed on the valve section. The working port communicates via each opening constructed as a valve seat both with the supply port and also with the tank port. Within the valve housing there is furthermore a control piston, on which two closing elements are formed. Each closing element can block or open the pressure medium flow through one of the valve seats as a function of the position of the control piston within the valve housing. The working port can be connected selectively to the supply port or to the tank port as a function of the axial position of the control piston. The axial position of the control piston is here fixed, in turn, by the axial position of the armature relative to the second magnetic yoke. 
         [0009]    A flange section of the valve housing of the directional valve disclosed in DE 199 56 160 A1 is arranged within a cylindrical, blind hole-like receptacle. The receptacle is a hollow cylindrical projection constructed in one piece with a magnetic yoke of the electromagnetic actuating unit. In this way, a thin-walled, end section of the projection engages radially in an annular groove formed on the valve housing along its entire periphery. Through this connection, the valve housing is fixed in the axial direction relative to the actuating unit. The connection opposes functionally secure high axial pull-off forces, which occur during the (dis-)assembly or during the operation of the internal combustion engine. 
         [0010]    The torsional rigidity of such a connection depends decisively on the joining forces during the production of the connection. To increase torsional rigidity, it is also provided to produce the connection through toothed crimping of the thin-walled section. For this purpose, a matrix provided with teeth is used to force the thin-walled section into the annular groove. Here, in the region of the teeth, the thin-walled section is forced into the valve housing, with a positive-fit connection being produced in the circumferential direction. 
         [0011]    For producing this connection, large forces acting radially are needed, increasing the expense for producing the connection. Forces that are too low lead to insufficient rigidity of the connection of the two components. During the service life of the component, a reduction in the torsional rigidity and thus rotation of the valve housing relative to the actuating unit can result due to axial forces, rocking moments or torques acting during the assembly or disassembly or due to vibrations during the operation of the internal combustion engine or thermal setting. This can lead to interruptions in function of the directional valve and thus the component to be controlled by the directional valve in applications, in which a fixed angular reference is needed between a valve bracket, by which the directional valve is fixed to a surrounding construction, and the valve section. 
         [0012]    Forces that are too high can lead to the valve housing being damaged and thus also to interruptions in function. 
       SUMMARY 
       [0013]    Therefore, the invention is based on the objective of avoiding these mentioned disadvantages and thus creating a hydraulic directional valve, whose valve section is locked in rotation with its actuating unit. Here, the assembly expense should be reduced or at least not increased. Furthermore, the production costs of the directional valve should not be negatively affected by these measures. 
         [0014]    According to the invention, the objective is met in that the groove base of the annular groove has external contours deviating from a circular form in cross section. 
         [0015]    The flange section of the valve housing is held in a cylindrical receptacle of a component of the actuating unit. The receptacle can be formed, for example, by an open end of a housing or a hollow cylindrical projection of a magnetic yoke. Here, the external diameter of the flange section is advantageously adapted to the inner diameter of the wall bounding the receptacle, through which the valve housing is centered radially with respect to the actuating unit. 
         [0016]    The flange section is provided with an annular groove extending in the circumferential direction, in which a thin-walled section of the wall of the receptacle engages in such a way that the flange section contacts the groove base of the annular groove. Here, the wall can engage in the annular groove axially at the end or with a middle section. 
         [0017]    During assembly, the flange section of the valve housing is positioned in the receptacle. Here, this contacts the base of the receptacle in the axial direction. In a next step, the wall is deformed, for example, by a fixing, rolling, or orbital forging method in the annular groove. Another possibility comprises producing the connection by an axial crimping method. In this case, the valve housing is positioned, in turn, in the receptacle. In a subsequent step, a hollow cylindrical plunger engages over the valve housing, with this being shifted in the axial direction up to the annular groove. The axial opening of the plunger has a conical or rounded construction, wherein its inner diameter has a smaller construction than the outer diameter of the wall. Through further axial shifting of the plunger, the wall of the receptacle is forced into the annular groove and thus the connection between the valve housing and the actuating unit is created. 
         [0018]    During the deformation of the wall, material is forced into the areas of the groove base which deviates from the circular form. Through the resulting positive fit in the peripheral direction, the torsional rigidity of the connection increases significantly in comparison to embodiments with a circular groove base. In the case of embodiments with bulges deviating from the circular form, the material of the wall nestles against these bulges, whereby, in turn, a positive-fit connection in the peripheral direction is created. 
         [0019]    Through this construction of a hydraulic directional valve, a connection with outstanding torsional rigidity between the valve housing and the actuating unit is produced. The connection withstands significantly higher moments, which result from forces or moments acting on the individual components. Likewise, the risk of the connection becoming loose due to thermal setting is eliminated. Furthermore, the connection of the components can be produced more easily and functionally more secure. 
         [0020]    The joining forces can be significantly reduced, because the torsional rigidity results not exclusively from the non-positive fit between the wall and the valve housing. Therefore, there is reduced risk that the valve housing or the housing or the magnetic yoke of the actuating unit will be damaged. 
         [0021]    Just as little material of the valve housing must be displaced by material of the wall during the joining process, whereby the exact positioning of the components and their dimensional accuracy are no longer taken into consideration. Consequently, the processing reliability of the assembly process increases. The reduction of the joining forces and the increase of the process reliability lead to lower production costs of the directional valves. 
         [0022]    In one embodiment, the groove base is formed with an essentially circular cross section, wherein at least one indentation is provided in the groove base. 
         [0023]    Alternatively it can be provided to form the groove base with an essentially circular cross section, wherein at least one bulge is provided in the groove base. 
         [0024]    Through these measures, a positive-fit connection can also be formed in addition to the non-positive fit in the circumferential direction. 
         [0025]    In one embodiment of the invention, it is proposed that the groove base has an essentially circular cross section, wherein at least one chord-like section is provided. During the production of the connection, the material of the wall is displaced against the outer circumferential surface of the groove base, with this also coming into contact with the chord-like section and in this way producing the positive-fit connection. Such chord-like sections can be produced easily and economically, for example, through milling or, in the case of valve housings produced by means of an injection molding process, through corresponding shapes of the injection mold. In addition to the formation of one chord-like section, also several such sections can be produced. 
         [0026]    Alternatively, it can be provided, for example, to form radial teeth on the groove base with an essentially circular cross section. During the production of the connection, material of the wall is displaced into the intermediate spaces of the teeth, wherein the formation of micro-teeth on the groove base already generates sufficient torsional rigidity. 
         [0027]    Furthermore, a method for producing a directional valve according to claim  1  is provided with the following method steps:
   positioning the valve housing within the cylindrical receptacle, and   displacing material of the wall into the annular groove.   
 
         [0030]    In this way, for producing the connection between the valve housing and the actuating unit, a section of the wall of the receptacle can be forced into the groove base by an axial crimping method, a fixing method, rolling, or a orbital forging method. 
         [0031]    Furthermore, it is possible to form the groove base with an essentially circular cross section, wherein at least one chord-like section is proposed on the groove base or radial teeth are formed. 
         [0032]    This type of production of the connection between the valve housing and the actuating unit represents a process-reliable and economic method. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0033]    Additional features of the invention emerge from the following description and from the drawings, in which embodiments of the invention are illustrated simplified. Shown are: 
           [0034]      FIG. 1   a  a longitudinal section view through an actuating unit, 
           [0035]      FIG. 1   b  a partial longitudinal section view through a hydraulic directional valve according to the invention, 
           [0036]      FIG. 1   c  a partial longitudinal section view through another hydraulic directional valve according to the invention, 
           [0037]      FIG. 2   a  a cross sectional view through the directional valve according to the invention from  FIG. 1   b  along the line IIA-IIA, 
           [0038]      FIG. 2   b  a cross sectional view through an alternative embodiment of the directional valve according to the invention from  FIG. 1   c  along the line IIB-IIB. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0039]      FIG. 1   b  shows a hydraulic directional valve  1  according to the invention in partial cross section using the example of a directional valve  1  constructed as a 4/3 directional proportional valve. The directional valve  1  comprises an actuating unit  2  and a valve section  3 . Such directional valves  1  are used, for example, for controlling hydraulic camshaft adjusters.  FIG. 1   a  shows a longitudinal section through an exemplary electromagnetic actuating unit  2 . 
         [0040]    The electromagnetic actuating unit  2  has a coil body  5  and a connection element  6  constructed in one piece with this coil body. The coil body  5  carries a coil  7  made from several windings of a suitable wire. The radially outer casing surface of the coil  7  is surrounded by a sleeve-shaped material layer  8 , which is made from a non-magnetizable material. The material layer  8  can be made, for example, from a suitable plastic and can be sprayed onto the wound coil  7 . Within the connection element  6 , an electrical plug connection  9  is held, by means of which the coil  7  can be connected to a current or voltage source. 
         [0041]    The coil body  5  is constructed with an essentially cylindrical, blind hole-like recess  10 , which is arranged concentric with respect to the coil  7 . In addition, the coil body  5  and the connection element  6  hold a sleeve-shaped first magnetic yoke  11  on the base-side end of the recess  10 . Within the recess  10 , a pot-shaped armature-guidance sleeve  12  is arranged, wherein its outer contours are adapted to the inner contours of the recess  10 . The thin-walled armature guidance sleeve  12  is made from a cylindrical section  12   b,  which is bounded by a sleeve base  12   c.  The sleeve base  12   c  is provided with axial stops  13  extending inwardly. The armature guidance sleeve  12  extends in the axial direction along the entire recess  10 , wherein the recess at least partially surrounds the coil body  5  at its opening in the radial direction. 
         [0042]    The coil body  5  is arranged within a pot-shaped housing  14 . The open end of the housing  14  projects past the connection element  6  in the axial direction, and this element and thus the coil body  5  are fixed within the housing  14  by a crimped connection  15 . 
         [0043]    Within the armature guidance sleeve  12  there is an armature  16  displaceable in the axial direction. The displacement path of the armature  16  is bounded in one direction by the stops  13  and in the other direction by a second magnetic yoke  17 . 
         [0044]    The second magnetic yoke  17  has a tubular section  18  and a cylindrical wall  19   a  connecting to this section in the axial direction. The tubular section  18  extends through an opening  21  constructed in the base  20  of the housing  14  in the armature guidance sleeve  12  arranged in the recess  10  of the coil body  5 . Here, the outer diameter of the tubular section  18  is adapted to the diameter of the opening  21 . The inner diameter of the axial end of the tubular section  18 , which faces the armature  16 , has a larger construction than the outer diameter of the armature  16 . Thus, the armature sinks into this section. In addition, the outer casing surface of the tubular section  18  tapers to a point in the direction of the armature  16 . 
         [0045]    The housing  14  is supported by a mounting flange  22  on the annular section  19 . The mounting flange  22  is used for attaching the directional valve  1  to a not-shown surrounding construction. 
         [0046]    In this embodiment, the second magnetic yoke  17  is made from two components, a pole core  23 , and a sleeve-shaped projection  24  constructed in one piece with the mounting flange  22 . 
         [0047]    A sealing ring  26  is arranged between the tubular section  18  of the second magnetic yoke  17 , the base  20  of the housing  14 , and the armature guidance sleeve  12 . In interaction with the armature guidance sleeve  12 , this prevents pressure medium from penetrating into the electromagnetic actuating unit  2 , as a rule motor oil, and reaching the coil body  5 , by which this coil body is protected from damage due to the pressure medium. 
         [0048]    A tappet rod  33  extends through the interior of the pole core  23  and is connected at one end to the armature  16 . 
         [0049]    In  FIG. 1   c,  an alternative embodiment of a hydraulic directional valve  1  according to the invention is shown, which is in wide parts identical to the embodiment shown in  FIG. 1   b.  In contrast, the receptacle  19   b  is constructed in this case by the wall  19   a  of an open end of the pot-shaped housing  14 . 
         [0050]    As can be seen in  FIGS. 1   b,    1   c,  the valve section  3  of the directional valve  1  constructed as a 4/3 directional proportional valve comprises a valve housing  27  and a control piston  28 . The valve housing  27  is constructed as a separate component and is connected to the actuating unit  2 . For this purpose, a flange section  27   a,  which is positioned in a receptacle  19   b  of the wall  19   a,  is formed on the valve housing  27 . Here, the inner diameter of the wall  19   a  is adapted to the outer diameter of the flange section  27   a.    
         [0051]    An annular groove  27   b,  in which a section of the wall  19   a  engages, is constructed on the flange section  27   a.  Therefore, the valve housing  27  is fixed axially with respect to the second magnetic yoke  17  and thus to the actuating unit  2 . 
         [0052]    On the outer casing surface of the valve housing  27  there are several annular grooves  29 , which communicate via recesses  30  formed in the groove bases of the annular grooves  29  with the interior of the essentially hollow, cylindrical valve housing  27 . The annular grooves  29  and the opening facing away from the electromagnetic actuating unit  2  in the valve housing  27  are used as pressure-medium ports A, B, P, T. The middle annular groove  29 , which is used as a feed port P, communicates via a not-shown pressure medium line with a similarly not shown pressure medium pump. The two outer annular grooves  29 , which are used as working ports A, B, communicate with users, for example, each with a pressure chamber or a group of counteracting pressure chambers of a similarly not shown camshaft adjuster. The axial port (tank port) T communicates with a similarly not shown pressure medium reservoir. 
         [0053]    Within the valve housing  27  there is the control piston  28  displaceable in the axial direction. Control sections  31  constructed as annular connecting pieces are formed on the outer casing surface of the control piston  28 . The outer diameter of the control sections  31  is adapted to the inner diameter of the valve housing  27 . Through suitable axial positioning of the control piston  28  relative to the valve housing  27 , adjacent pressure medium ports A, B, P can be connected to each other. Each working port A, B not connected to the feed port P is simultaneously connected to the tank port T. In this way, pressure medium can be selectively fed to or discharged from the individual pressure chambers of the camshaft adjuster. 
         [0054]    The control piston  28  is charged on one end with the force of a spring element  32  in the direction of the electromagnetic actuating unit  2 . At the other axial end of the control piston  28  there is a tappet rod  33 , which extends through a borehole of the second magnetic yoke  17  and is fixed in position with the armature  16 . 
         [0055]    In the non-energized state of the coil  7 , the control piston  28  is forced in the direction of the electromagnetic actuating unit  2  due to the force of the spring element  32 . 
         [0056]    The housing  14 , the first magnetic yoke  11 , the armature  16 , and the second magnetic yoke  17  are made from a magnetizable material, while the connection element  6 , the tappet rod  33 , the coil body  5 , and the armature guidance sleeve  12  are made from a non-magnetizable material. Thus, by energizing the coil  7  within the electromagnetic actuating unit  2 , a magnetic flux, which forces the armature  16  in the direction of the valve section  3 , is established via the armature  16 , the first magnetic yoke  11 , the housing  14 , the second magnetic yoke  17 , and an air gap  34  located between the armature  16  and the second magnetic yoke  17 . Therefore, the control piston  28  is shifted in the axial direction by the tappet rod  33  against the force of the spring element  32 . Through suitable regulation of the current flowing in the coil  7 , the control piston  28  can be adjusted into any position between two end stops relative to the valve housing  27 , and thus the pressure medium flows to or from the pressure chambers of the camshaft adjuster are regulated. 
         [0057]      FIG. 2   a  shows a cross section along the line IIA-IIA through a first embodiment of a hydraulic directional valve  1  according to the invention from  FIG. 1   b.  Essentially circular outer contours of a groove base  27   c  of the annular groove  27   b  have an indentation  35 . The indentation  35  can be, for example, as shown in  FIG. 2   a , a chord-like section  36 . 
         [0058]    The material of the wall  19   a  engages in the annular groove  27   b  in such a way that this contacts the groove base  27   c  along the entire periphery of the annular groove  27   b,  that is, also on the boundary surface of the indentation  35 . Thus, in the peripheral direction a positive-fit connection between the valve housing  27  and the actuating unit  2  is created. In addition to an indentation  35 , naturally any number of indentations  35  can be formed. 
         [0059]    Additionally or alternatively, a radially outward extending bulge  37  can be formed on the outer contours of the groove base  27   c.  During the production of the connection between the valve housing  27  and the wall  19   a,  the material of the wall  19   a  contacts the outer contours of the bulge  37 , whereby a positive fit is produced in the peripheral direction. 
         [0060]    The dimensions of the indentations or bulges  35 ,  37  shown in  FIG. 2   a  and deviating from a circular form are shown excessively large for simplification. To achieve sufficient torsional rigidity, these can be formed considerably smaller. 
         [0061]    Alternatively, it is also imaginable to form the groove base  27   c  of the annular groove  27   b  in cross section in a geometric shape, for example, elliptical, rectangular, or polygonal, deviating from the circular form. 
         [0062]      FIG. 2   b  shows a cross section along the line IIB-IIB through a second embodiment of a hydraulic directional valve  1  according to the invention from  FIG. 1   c.  The essentially circular outer contour of the groove base  27   c  of the annular groove  27   b  features teeth  38  extending in the radial direction. 
         [0063]    The material of the wall  19   a  engages in the annular groove  27   b  in such a way that this contacts the groove base  27   c  along the entire periphery of the annular groove  27   b.  Thus, the material of the wall  19   a  engages in the teeth  38 , via which a positive-fit connection between the valve housing  27  and the actuating unit  2  is created in the peripheral direction. 
         [0064]    The radial dimensions of the teeth  38  shown in  FIG. 2   a  is shown excessively large for clarification. To achieve sufficient torsional rigidity, micro-teeth can be formed on the groove base  27   c.    
         [0065]    The connection between the wall  19   a  and the valve housing  27  can be produced, for example, by a fixing, rolling, or orbital forging method. 
         [0066]    It is also conceivable to produce the connection by an axial crimping method. For this purpose, the valve housing  27  is positioned in the receptacle  19   b,  with the valve housing  27  being centered radially by the wall  19   a.  In a subsequent processing step, an essentially hollow, cylindrical plunger is guided by the valve housing  27  until its axial end contacts the wall  19   a.  The hollow cylindrical plunger is provided with a rounding or a conical counter surface at its end turned toward the wall  19   a.  The plunger is charged with a defined force in the axial direction, whereby material of the wall  19   a  is forced into the annular groove  27   b.  By forcing the wall  19   a  into the annular groove  27   b,  a connection between the valve housing  27  and the housing  14  is achieved with a high axial pull-off resistance, with the flange section  27   a  coming into contact with the second magnetic yoke  17 . Here, the force or the axial displacement is selected such that the material contacts the groove base  27   c  along the entire periphery of the annular groove  27   b.  Therefore, the positive-fit connection in the peripheral direction is produced with high torsional rigidity between the wall  19   a  and the valve housing  27 , without there being the risk of damaging the housing  14  or the second magnetic yoke  17  or the valve housing  27 . 
       REFERENCE SYMBOLS 
       [0000]    
       
           1  Directional valve 
           2  Actuating unit 
           3  Valve section 
           5  Coil body 
           6  Connection element 
           7  Coil 
           8  Material layer 
           9  Plug connection 
           10  Recess 
           11  First magnetic yoke 
           12  Armature guidance sleeve 
           12   b  Cylindrical section 
           12   c  Sleeve base 
           13  Stop 
           14  Housing 
           15  Crimped connection 
           16  Armature 
           17  Second magnetic yoke 
           18  Tubular section 
           19  Annular section 
           19   a  Wall 
           19   b  Receptacle 
           20  Base 
           21  Opening 
           22  Mounting flange 
           23  Pole core 
           24  Projection 
           26  Sealing ring 
           27  Valve housing 
           27   a  Flange section 
           27   b  Annular groove 
           27   c  Groove base 
           28  Control piston 
           29  Annular groove 
           20  Recesses 
           31  Control section 
           32  Spring element 
           33  Tappet rod 
           34  Air gap 
           35  Indentation 
           36  Chord-like section 
           37  Bulge 
           38  Teeth 
         P Feed port 
         T Tank port 
         A First working port 
         B Second working port

Technology Category: y