Abstract:
A valve housing for a control valve of a camshaft adjuster, including a housing flange for fastening to a control unit as well as an essentially cylindrical housing component for accommodating a control piston. It is provided that the housing component is rotatably fixedly attached to the housing flange by a form-locked connection. A valve housing of this type is cost effective to manufacture and has a low weight, while ensuring operational reliability. The invention furthermore relates to a method for manufacturing an aforementioned valve housing.

Description:
The present invention relates to a valve housing for a control valve of a camshaft adjusting system, including a housing flange for fastening to a control unit as well as an essentially cylindrical housing component for accommodating a control piston. 
     The present invention furthermore relates to a method for manufacturing an aforementioned valve housing. 
     BACKGROUND 
     As part of a camshaft adjusting system, a camshaft adjuster is used to adjust the phase angle between a camshaft and a crankshaft in an internal combustion engine in a targeted manner and thus allows for the optimized setting of the valve control times. This makes it possible, for example, to increase the power of an internal combustion engine or reduce consumption. 
     A camshaft adjuster usually includes a stator, which is rotatably fixedly connected to the crankshaft, and a rotor held in this stator. The rotor, in turn, is rotatably fixedly connected to the camshaft and may be adjusted in relation to the stator. The adjustment of the rotor is induced by applying a hydraulic fluid to pressure chambers provided in the stator. 
     Control valves are used to ensure this pressure application. Control valves of this type usually include a valve housing and an electromagnetically activated control piston positioned in the valve housing. Activating this piston allows the supply and discharge of the hydraulic fluid to be adjusted and the valve control times to be influenced. Optimum valve control times in this case directly affect the driving performance as well as fuel consumption and the emissions associated therewith. 
     Common control valves are frequently manufactured with valve housings which are very heavy, due to their design as massive turned parts. With regard to the steadily increasing requirements of the automotive industry to reduce the weight of the components used and to minimize the cost of their manufacture, massive valve housings are thus not a permanent solution for a valve housing of a control valve. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a valve housing for a control valve which is cost-effective to manufacture, while ensuring its functionality and minimizing its weight. 
     Another object of the present invention is to provide a method for manufacturing an aforementioned valve housing. 
     The present invention provides a valve housing for a control valve of a camshaft adjusting system, including a housing flange for fastening to a control unit as well as an essentially cylindrical housing component for accommodating a control piston. It is provided that the housing component is rotatably fixedly attached to the housing flange by a form-locked connection. 
     The present invention takes into account the fact that the steadily increasing requirements with regard to weight and costs in the manufacture of a control valve may not be met by the use of massively produced valve housings. However, the manufacture of separate, individual parts which are connected to each other is one way to reduce the weight. As a result, lighter-weight and more cost-effective materials may be selected where less strict requirements are to be met. 
     However, difficulties occasionally arise in a mechanical connection of the individual parts, in particular with regard to an undesirable twisting of the components in relation to each other. Movements of this type may have a negative influence on the activation of the camshaft adjuster in the installed state, so that the operational reliability thereof may not be ensured. 
     Other options for connecting components, for example injection molding the created assembly, also do not provide reasonable alternatives, against the background of the increased logistics complexity and investment and manufacturing costs. 
     The present invention achieves a rotatably fixed attachment between the housing component and the housing flange with the aid of a form-lock between the two components. Due to the form-lock, a relative movement between the housing component and the housing flange may be prevented, so that the two components are rotatably fixedly attached to each other. In addition, the form-locked connection may transmit particularly high forces and offers the desired security against an undesirable detachment of the components from each other. 
     Thanks to the form-locked connection and the ability to prevent twisting associated therewith, it is possible to dispense with a one-piece and massive production of the valve housing or complex manufacturing steps for connecting the housing component to the housing flange. 
     As part of a control valve, the valve housing is used to position a control piston. The desired adjustment of the camshaft adjuster may be achieved by controlling the control piston within the valve housing and thus by metering the hydraulic medium. For this purpose, the control piston is usually electromagnetically activated, it being possible to implement the activation via a control unit fastened to the housing flange. This control unit usually includes a magnet which moves the control piston when it is supplied with electric current. In this way, the pressure is switched between the hydraulic chambers of the camshaft adjuster. The hydraulic chamber to which no pressure is applied is connected to a return line, so that hydraulic fluid may flow back into the circuit. 
     The control piston is usually axially movably mounted in the housing component of the valve housing. The housing component is preferably manufactured in a single piece made of plastic with the aid of an injection molding process. The use of a plastic allows a low weight of the valve housing to be ensured. Furthermore, the choice of the plastic makes it possible to influence the hardness and corrosion resistance of the housing component. 
     The housing component may be designed, for example, in the form of a lattice, it being possible to introduce a filter element into the lattice. A filter element is used to filter dirt particles out of the hydraulic medium which is needed to adjust the camshaft. This makes it possible to prevent particles from entering the hydraulic chambers of the camshaft adjuster. 
     In addition, a sleeve may be situated within the valve housing or within the housing component, which is used to guide the control piston and which is advantageously also provided with a lattice structure. In the installed state, the lattice openings in the sleeve may have different widths in relation to the lattice openings of the housing component. In all embodiments, it is ensured, in particular, that the lattice openings available for metering hydraulic fluid are dimensioned to be sufficiently large. Alternatively or additionally, a filter element may also be positioned in the openings in the sleeve. The sleeve is preferably made of a steel. 
     The housing flange is preferably made of a metallic material. The metallic material may be manufactured according to the environmental conditions and the forces acting upon it. A steel is preferably used. This makes it possible to ensure the necessary stability of the valve housing. 
     Overall, the weight of the valve housing may be reduced by selecting different materials for the housing component and the housing flange. In addition, the particular area of the resulting component may be specifically adapted to the intended use. A valve housing of this type may therefore be manufactured cost-effectively and in a customer-specific manner. 
     In one advantageous embodiment of the present invention, the housing component may be additionally axially fixed to the housing flange by the form-locked connection. This makes it possible to prevent the components from twisting in relation to each other and, at the same time, to ensure an axial fixing of the components to each other by establishing a form-locked connection. 
     In another advantageous embodiment of the present invention, the housing flange includes a collar, into which the housing component is inserted together with a shoulder. The collar may be provided in uninterrupted form or it may preferably entirely enclose the housing flange. The shoulder of the housing component is designed as an end ring of the housing component. The shoulder is inserted into the collar for assembly purposes. For this purpose, the collar advantageously has an inner diameter which is slightly larger than the outer diameter of the shoulder, thereby permitting easy assembly. 
     The shoulder of the housing component particularly preferably has a number of indentations along its outer circumference via which the housing flange is caulked to the housing component. This prevents the flange and the housing component from twisting in relation to each other and the components from being axially offset. 
     In principle, a caulking process permits all flexibly deformable materials to be connected to each other, which even makes it possible to join different materials. As a result, the material properties of the components may be combined according to the use requirements. The form-lock between the housing flange and the housing component created during caulking permits these parts to be securely fastened to each other. The plastic deformation of at least one of the components causes the component to be non-detachably interlocked. In a valve housing having a plastic housing component and a metallic housing flange, a secure connection of the two components may be implemented while minimizing the weight of the valve housing. 
     The indentations make it possible to accommodate material of the housing flange. Due to the caulking, the material enters the indentations in the housing component and thus forms the desired form-locked connection. The indentations may have, in principle, different designs for this purpose, for example they may be designed as pockets or grooves. They extend radially into the material of the shoulder and may be produced as a single piece therewith during manufacture of the housing component, for example in an injection molding process. Furthermore, the indentations are preferably distributed evenly over the outer circumference of the housing component to ensure a uniform attachment. 
     The indentation or every indentation is preferably designed as an edge recess on the edge of the shoulder facing axially away from the collar. Providing the edge recess in this location on the outer circumference offers the advantage that a sufficient wall thickness remains on the edge of the shoulder axially facing the collar. In this way, the forces acting upon the valve housing during operation of a camshaft adjuster, or the high load peaks arising during activation of a control piston, may be withstood without the material of the shoulder breaking off. 
     To axially secure the housing component on the housing flange, a nub extending radially toward the outside may be additionally produced in the indentation or in each indentation. In the caulked state, the nub is enclosed by the material of the housing flange and thus prevents an axial offset during operational loads, i.e., it prevents an axial shift of the components in relation to each other. The axial attachment may be achieved, in particular, by selectively crimping the nubs when the housing component is mounted on the housing flange. The size of the nub is adapted, in particular, to the design of the indentation. In principle, it is also conceivable to situate multiple nubs within one indentation, these numbers being used to axially attach the housing component to the housing flange. Alternatively or additionally, for example, elements having different shapes may also be provided for axial securing. 
     The housing component preferably includes a number of annular elements which are spaced an axial distance apart and are connected to each other by axial webs. Both the axial webs and the spaced-apart annular elements preferably run in parallel to each other, resulting in a stable lattice. The lattice openings may be used to introduce filter elements. The number of axial struts and rings may vary as a function of the requirements imposed on the housing component, for example with regard to the size of the valve housing. 
     In another advantageous embodiment of the present invention, at least one collar part of the housing flange is crimped around the shoulder of the housing component and rests against the axial webs for rotatably fixed attachment to the axial webs. The collar extends in the axial direction in such a way that it is able to accommodate the shoulder of the housing component. The collar parts provided on the collar are designed, for example, in the form of tabs which extend in the axial direction. They are advantageously provided on the collar in such a way that they are placed around the shoulder on the plastic part by crimping during assembly and make contact on both sides between the axial webs. By crimping the collar parts and the resulting lateral contact with the axial webs, the housing component and the housing flange may achieve a rotatably fixed attachment as well as an axial securing of the components. 
     To position the housing component uniformly on the housing flange, the collar is preferably provided with a plurality of axially extending collar parts which are provided over its circumference at a uniform distance from each other. The number of collar parts is preferably adapted to the number of axial webs, so that one collar part may be crimped between two axial webs converging on the shoulder of the housing component. 
     It is furthermore preferred to design the annular element on the axial end of the housing component as a shoulder, the axial webs converging on the shoulder, each forming an axial contact surface for the collar of the housing flange. In the assembled state, this embodiment permits an axial securing of the components to each other in both directions, in particular in combination with the edge recesses in the outer circumference of the shoulder of the housing component. 
     The second object of the present invention is achieved according to the present invention by a method for manufacturing a valve housing for a control valve, a housing flange being produced for attachment to a control unit, an essentially cylindrical housing component being produced for accommodating a control piston, and the housing component being rotatably fixedly attached to the housing flange by a form-locked connection. 
     This method provides a cost-effective and easily handled way to manufacture a valve housing which is suitable, in particular, for use in a control valve, due to its light weight. The rotatably fixed connection of the components to each other is achieved by a form-lock. 
     In another advantageous embodiment of the present invention, the valve housing is manufactured in such a way that the housing flange is produced with a collar, along whose outer circumference a number of indentations are provided, each having a nub which extends radially to the outside, and the shoulder of the housing component is inserted into the housing flange, a material of the collar being caulked into the indentations in the shoulder. 
     The shoulder of the housing component is caulked to the collar of the housing flange in such a way that the material of the collar enters the indentations in the housing component. Due to the form-locked connection thus provided, the housing component may be fixed axially to the housing flange in addition to being rotatably fixedly attached thereto. In other words, the form-lock simultaneously prevents the components from twisting in relation to each other and also permits an axial fixing of the housing flange to the housing component. 
     Due to the caulking, it is possible to produce the housing component and the housing flange from different materials. Accordingly, the particular area of the resulting valve housing may be specifically adapted to the intended use. A valve housing manufactured in this way may therefore be manufactured cost-effectively and in a customer-specific manner. The housing component is preferably made of a plastic in an injection molding process, together with the indentations and the nubs in a mold provided for this purpose, while the housing flange is designed, for example, as a turned part. 
     The use of an appropriate caulking tool is suitable for caulking. For this purpose, for example, the housing flange may be clamped into a holder, and the housing component may be inserted with its shoulder into the collar of the housing flange. The caulking tool is then positioned around the circumference of the components which have been inserted into each other in such a way that the caulking tool is placed on the circumference of the collar of the housing flange at the particular places to be caulked. This tool is preferably a tool which may be used to carry out a so-called segmented caulking process. The caulking tool or its caulking components are placed only at the points on the circumference where the indentations for accommodating material are provided in the shoulder of the housing flange. 
     By applying pressure to the collar of the housing flange, the material of the collar is pressed into the indentations in the housing component at the intended points. The material enters the indentations, where it encloses the nubs provided within the indentations. The form-lock established in this manner ensures the necessary axial and radial securing of the components to each other and thus increases the operational reliability of a camshaft adjuster. 
     Overall, the functional requirements to be met by the valve housing may be implemented cost-effectively by integrating indentations and nubs in combination with the segmented caulking process used to connect the components. 
     During manufacture of the valve housing, a sleeve may also be introduced, which is pressed with the housing flange before the shoulder of the housing component is inserted into the collar of the housing flange. The housing component is then pushed onto the sleeve after pressing and caulked to the housing flange. The sleeve is preferably made of a steel and has a lattice structure and may be provided with a filter element, for example alternatively or additionally to the housing component. 
     In another advantageous embodiment of the present invention, the valve housing is manufactured in such a way that the housing flange is produced with a collar, the housing component is produced with a shoulder and a number of axial webs converging on the shoulder, the shoulder of the housing component is inserted into the collar of the housing flange, at least one collar part being crimped around the shoulder in such a way that the shoulder rests against the axial webs for rotatably fixed attachment. 
     The components may be axially secured to each other by crimping one or multiple collar parts around the shoulder of the housing component. The collar parts are crimped between the axial webs after the shoulder is inserted, so that they make contact with the shoulder on both sides. In this way, the necessary axial attachment of the components to each other is achieved, and they are also rotatably fixedly attached to each other. 
     The advantages mentioned above for the valve housing may be transferred analogously to both methods. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention are explained in greater detail below with reference to one drawing. 
         FIG. 1  shows a housing component for a valve housing in a three-dimensional representation; 
         FIG. 2  shows a detailed view of the housing component according to  FIG. 1 ; 
         FIG. 3  shows a valve housing for a control valve, including a housing component according to  FIGS. 1 and 2 , in a three-dimensional representation; 
         FIG. 4  shows another valve housing for a control valve in a longitudinal section; 
         FIG. 5  shows a detailed view of the valve housing according to  FIG. 4 ; and 
         FIG. 6  shows the valve housing according to  FIGS. 4 and 5  in a three-dimensional representation. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a housing component  1  for a valve housing in a three-dimensional representation. Housing component  1  has an essentially cylindrical design and is made of a plastic in an injection molding process. Housing component  1  is used to accommodate an electrically controlled control piston in the installed state. Hydraulic fluid may be metered by this axially movable control piston for operating a camshaft adjuster. 
     Housing component  1  includes five annular elements  3 , which are spaced an axial distance apart and are connected to each other by four axial webs  5 . Axial webs  5  run in parallel to each other, thereby producing a lattice. Filter elements for filtering the hydraulic fluid may be introduced into lattice openings  7 . 
     On its axial ends, housing component  1  is provided with an annular element  3 , which has a cross section which tapers in the axial direction. This annular element  3  is used as a stop  9  for a control piston which is axially movably mounted in housing component  1  during operation of a camshaft adjuster. 
     On the other end, which terminates housing component  1 , annular element  3  is designed as a shoulder  11 . The outer diameter of shoulder  11  is smaller than the outer diameter of remaining annular element  3 , whereby an axial contact surface  13  for the collar of a housing flange is produced on each axial web  5  connected to shoulder  11  in the assembled state of a valve housing.  FIG. 3  shows a valve housing in an assembled representation. 
     Shoulder  11  has three indentations  17  along its outer circumference  15 , which are introduced an equal distance apart. Indentations  17  are designed as edge recesses on edge  19  of shoulder  11  facing away in the axial direction and are used for rotatably fixed attachment to a housing flange. A nub  21 , which extends radially to the outside, is additionally provided in each edge recess  17  to axially secure the housing component to a housing flange. 
     Due to indentations  17  and nubs  21 , the form-locked connection of housing component  1  to a housing flange may be established in the assembled state, which, in addition to preventing twisting, also permits the axial fixing of the components to each other. 
     For clarification,  FIG. 2  shows a detailed view of housing component  1  according to  FIG. 1 . This figure clearly shows indentations  17  and nubs  21 . During connection to a housing flange, material of the housing flange may be accommodated in indentations  17 , so that a form-locked connection is formed between the housing flange and housing component  1 . This form-locked connection may transmit particularly high forces and offers a great deal of security against an undesirable detachment of the components from each other. 
     Due to the design of indentations  17  as edge recesses, a sufficient wall thickness remains on the edge of shoulder  11  facing the collar in the axial direction, a wall thickness which withstands the high load peaks arising when a control piston is activated during operation. 
     In the caulked state, nub  21  is enclosed by the material of the housing flange and thus prevents an axial offset during operational loads, i.e., it prevents axial shifting of the components in relation to each other. The axial fastening may be achieved, in particular, by selectively crimping nubs  21  when housing component  1  is mounted on the housing flange. 
       FIG. 2  clearly shows axial contact surface  13  for the collar of a housing flange. The collar of a housing flange may be axially secured on axial contact surface  13 . In combination with edge recesses  17  in outer circumference  15  of shoulder  11 , an axial securing may be achieved in both directions in the assembled state. 
       FIG. 3  shows a valve housing  31  for a control valve in a three dimensional representation in the assembled state. The valve housing includes a housing component  1  according to  FIGS. 1 and 2 , a housing flange  33  as well as a sleeve  35 . Housing component  1  is described in detail in  FIGS. 1 and 2 , so that reference is hereby made to these figures at this point. 
     Housing flange  33 , which is produced from a metallic material, has a collar  37 , into which housing component  1 , along with its shoulder  11 , is inserted. The inner diameter of collar  37  is slightly enlarged in relation to the outer diameter of shoulder  11  of housing component  1 , so that shoulder  11  is easily insertable into collar  37 . During insertion of housing component  1 , collar  37  makes contact with axial contact surfaces  13 , which are not visible in  FIG. 3 , where it is secured against a shift in the axial direction. In combination with indentations  17  designed as edge recesses in outer circumference  15  of shoulder  11  an axial securing may be achieved in both directions in the assembled state. 
     Housing flange  33  is caulked to housing component  1 , forming a form-locked connection, via indentations  17 , which are provided along outer circumference  15  of shoulder  11  of housing component  1 . 
     This is achieved using a caulking tool. To assemble the two components, housing component  1 , together with its shoulder  11 , is inserted into collar  37  of housing flange  33 . The caulking tool then caulks shoulder  11  and collar  37  at each of the points at which indentations  17  are provided with nubs  21  on outer circumference  15  of shoulder  11 . Due to the pressure of the caulking tool, the material of collar  37  is pressed into indentations  17  in shoulder  11 . The material entering indentations  17  then also encloses nubs  21  provided therein. The axial attachment of the components to each other is achieved by selectively crimping nubs  21 . 
     The form-lock between collar  37  and shoulder  11  produced during this process permits an axial fixing of housing component  1  to housing flange  33 , in addition to the rotatably fixed attachment. 
     In the present case, sleeve  35  is pressed to housing flange  33  before housing component  1  and housing flange  33  are caulked. The housing component is pushed onto sleeve  35  only after pressing, and the caulking process described above is finally carried out. Like housing component  1 , sleeve  35  is also designed in the form of a lattice made of steel. Filter elements for filtering hydraulic fluid may be introduced into the lattice openings, which are not illustrated in the present case. In the assembled state, the lattice openings in sleeve  35  and lattice openings  7  in housing component  1  are located above each other, so that the openings needed for metering hydraulic fluid are sufficiently large. 
       FIG. 4  shows a valve housing  51  for a control valve having a housing component in a longitudinal section. Like valve housing  31  from  FIG. 3 , valve housing  51  includes a housing component  53  and a housing flange  55 , which are connected to each other in a form-locked manner. For this purpose, shoulder  57  of housing component  53  is inserted into collar  59  of housing flange  55 . 
     Valve housing  51  furthermore has a sleeve  61 , which is pressed into collar  59  of housing flange  55  before housing component  53  is mounted. Sleeve  61  is made of a steel and has lattice openings  63 , through which hydraulic fluid may be metered during operation for the purpose of adjusting a camshaft adjuster. 
     Housing component  53  includes five annular elements  65  and three axial webs  67  connected thereto. Final annular element  65  on one axial end of housing component  53  is designed as shoulder  57 , which is accommodated in collar  59  of housing flange  55 . In the present case, shoulder  57  has the same outer diameter as remaining annular elements  65 . 
     Annular element  65  provided on the other axial end of housing component  53  is provided with a cross section which tapers in the axial direction and which is used as a stop  69  for a control piston (not illustrated) guided axially within sleeve  61 . 
     The form-locked connection between housing component  53  and housing flange  55  in  FIG. 4  is established by the design of collar  59 . After shoulder  57  of housing component  53  is inserted into housing flange  55 , collar  59  of housing flange  55  encloses shoulder  57 . To attach shoulder  57 , collar  59  has three collar parts  71 , which are provided, spaced equidistantly apart, on its circumference. Of collar parts  71 , only one collar part  71  is shown according to the representation. 
     Collar parts  71  are designed as tabs and, in the uninstalled state, extend in the axial direction between axial webs  67  of housing component  53  converging on shoulder  57 . For attachment, collar parts  71  and their shoulder  57  are crimped so that they enclose shoulder  57  in the areas between axial webs  67 . Due to the crimping of collar parts  71  and the lateral contact on axial webs  67 , a rotatably fixed attachment as well as an axial securing of the components may be achieved. In this way, sufficient security may be ensured during operation of a camshaft adjuster, in particular under high loads. 
       FIG. 5  shows a detailed view of valve housing  51  according to  FIG. 4 . This figure clearly shows one of the three collar parts  71 , which is crimped around shoulder  57  of housing component  53 . An axial shift of the components in relation to each other is not possible, and housing component  53  and housing flange  55  are non-rotatably attached to each other, due to the lateral contact of crimped collar parts  71  on axial webs  67 . 
       FIG. 6  shows valve housing  51  according to  FIGS. 4 and 5  in a three-dimensional representation. Valve housing  51  is described in detail in  FIGS. 4 and 5 , so that reference is made to these figures at this point. 
     The form-lock between housing component  53  and housing flange  55  due to the design of collar  59  is clearly visible in  FIG. 6 . Collar  59  has three collar parts  71 , each of which is crimped between axial webs  67 . In the assembled state, collar parts  71  are placed around shoulder  57  of housing component  53  in such a way that axial webs  67  of housing component  53  come to a stop against surrounding collar parts  71  as soon as the components are twisted in relation to each other. 
     Overall, the form-lock between collar parts  71  of housing flange  55  and shoulder  57  of housing component  53  established during crimping prevents the components from twisting in relation to each other and additionally provides the axial securing thereof. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  Housing component 
           3  Annular element 
           5  Axial webs 
           7  Lattice openings 
           9  Stop 
           11  Shoulder 
           13  Axial contact surface 
           15  Outer circumference 
           17  Indentations 
           19  Edge 
           21  Nubs 
           31  Valve housing 
           33  Housing flange 
           35  Sleeve 
           37  Collar 
           51  Valve housing 
           53  Housing component 
           55  Housing flange 
           57  Shoulder 
           59  Collar 
           61  Sleeve 
           63  Lattice openings 
           65  Annular element 
           67  Axial webs 
           69  Stop 
           71  Collar parts