Patent Publication Number: US-2010129015-A1

Title: Method for producing a component made of metal, particularly for a head bearing housing of a spring strut, and such a component

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of pending International Patent Application PCT/EP2008/002729 filed on Apr. 5, 2008 designating the United States, which was published in German as WO 2008/141697, and claims priority of German Patent Application No. 10 2007 025 768.8 filed on May 23, 2007. The entire contents of these priority applications are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The invention generally relates to a method for producing a component made of metal. More specifically, the invention relates to a method for producing a head bearing housing of a spring strut. Still more specifically, the invention relates to a method for producing a component made of a metal, which comprises a base part and a flange that extends away from the base part, the flange comprising a substantially tubular portion that has a first diameter and comprising a collar-type rim portion that adjoins the tubular portion a free edge of which has a second diameter that is greater than the first diameter of the tubular portion. 
     The invention further relates to such a component made of metal, in particular to a head bearing housing of a spring strut. 
     A component of the aforementioned type is preferably used, in the sense of the present invention, for a head bearing housing of a spring strut in the chassis of a motor vehicle. In this case, the substantially tubular portion of the component serves to receive a damper bearing of a shock absorber, which is connected to the head bearing housing. For this purpose, the flange is additionally provided with a rubber-elastic damper element on the inside. In order that the damper element sits firmly in the flange, the free end of the flange, i.e. the end facing away from the base part, is provided with a collar-type rim portion, the free edge of which has a greater diameter than the smallest diameter of the tubular portion, such that the flange has a waisted shape. 
     In the case of the hitherto comparable components for a head bearing housing, the flange and the base part, constituted by two parts, had been connected to one another by joining, for example welding. In respect of the production costs, however, it is desirable for the supporting flange to be designed as a single piece with the base part. 
     Owing to the markedly waisted shape of the flange, however, single-piece production of the component mentioned at the outset proves to be problematic. It has been attempted to draw the flange, by a drawing method, in a plurality of drawings, until the tubular portion having the first diameter is obtained. However, in the subsequent folding-over of the free edge by means of a widening process, in order to form the collar-type rim portion whose free edge has a significantly greater diameter than the first diameter of the tubular portion, the collar-type rim portion has always become torn. 
     SUMMARY OF THE INVENTION 
     The invention is therefore based on the object of providing a method, of the type mentioned at the outset, by which the component mentioned at the outset can be produced as a single piece. 
     The invention is furthermore based on the object of providing a component produced in such a manner. 
     According to an aspect of the invention, a method for producing a component made of metal is provided, the component comprising a base part and a flange that extends away from the base part, the flange comprising a substantially tubular portion that has a first diameter and comprising a collar-type rim portion that adjoins the tubular portion and a free edge of which has a second diameter that is greater than the first diameter of the tubular portion, the method comprising the steps of: providing a raw component, the raw component comprising a base part and a cylindrically tubular portion having a third diameter that is at least greater than the first diameter, reducing the third diameter of the cylindrically tubular portion to the first diameter at a distance from an edge of the cylindrically tubular portion by forming by means of a forming tool that is applied to an outside of the cylindrically tubular portion and that acts approximately radially toward a longitudinal center axis of the cylindrically tubular portion, in such a way that the collar-type rim portion is constituted. 
     According to another aspect of the invention, a component made of metal is provided, comprising a base part and a flange that extends away from the base part, the flange comprising a substantially tubular portion that has a first diameter and comprising a collar-type rim portion that adjoins the tubular portion and a free edge of which has a second diameter that is greater than the first diameter of the tubular portion, the component being produced according to a method comprising the steps of: providing a raw component, the raw component comprising a base part and a cylindrically tubular portion having a third diameter that is at least greater than the first diameter, reducing the third diameter of the cylindrically tubular portion to the first diameter at a distance from an edge of the cylindrically tubular portion by forming by means of a forming tool that is applied to an outside of the cylindrically tubular portion and that acts approximately radially toward a longitudinal center axis of the cylindrically tubular portion, in such a way that the collar-type rim portion is constituted. 
     The method according to the invention is based on a different approach to the production of the waisted shape of the flange for the purpose of realizing the collar-type rim portion, in which there is first provided a raw component having a cylindrically tubular portion, the diameter of which is yet greater than the first diameter that the tubular portion of the finished flange is to have. Instead of the free edge of the tubular portion being subsequently folded over outward in a widening process, in order to form the collar-type rim portion, provision is additionally made, according to the invention, in that the originally cylindrically tubular portion is formed, by means of a radially inwardly acting forming tool that is applied to the outside of the tubular portion and at a distance from the edge of the tubular portion, in such a way that the third diameter is reduced to the lesser, first diameter. 
     The invention is based on the knowledge that, in the case of the other procedure, namely, producing the originally cylindrically tubular portion already having the first diameter, for example by drawing, a very great hardening of material occurs in the cylindrically tubular portion, with the consequence that the remaining residual formability that is necessary for folding over the edge outward is insufficient, such that tearing of the collar-type rim portion occurs. If, on the other hand, the originally cylindrically tubular portion is produced to have a diameter that is greater than the diameter of the tubular portion of the flange, for example likewise by a drawing method, the hardening of material in the cylindrically tubular portion is substantially less, and the residual formability is entirely sufficient to shape the collar-type rim portion, by the aforementioned forming process by which the waist of the flange is produced by diameter reduction, without there being a risk of the rim portion becoming torn. 
     The method according to the invention therefore enables the component mentioned at the outset, particularly for a head bearing housing of a spring strut, to be produced as a single piece, and therefore cost-effectively, and nevertheless without a significant spoilage proportion. 
     In a preferred refinement of the method, the third diameter of the cylindrically tubular portion is greater than the second diameter. 
     In the reducing of the third diameter of the cylindrically tubular portion to the first diameter, it can be the case, particularly if the first diameter is substantially smaller than the third diameter, that, in the forming for the purpose of shaping the collar-type rim portion, the second diameter of the free edge of the collar type rim portion that is to be achieved is gone below. By means of the aforementioned measure, going below the second diameter can be prevented, advantageously, through provision of a sufficiently large initial diameter. 
     In a further preferred refinement of the method, the forming comprises rolling or pressing with radially inwardly directed direction of action. 
     In the context of tests, rolling or pressing have proved to be particularly suitable forming methods in the context of the method according to the invention and, moreover, these methods are controllable. 
     In a further preferred refinement, the forming comprises a preliminary forming step, by means of a first forming tool, and at least one further forming operation, by means of at least one second forming tool. 
     In the case of rolling for the purpose of realizing the waist of the flange, or of the collar-type rim portion on the flange, in this case a first diameter reduction of the cylindrically tubular portion can first be performed by means of a preliminary roller, and the further diameter reduction to the first diameter can then be performed by means of a contour roller. The advantage of a two-stage or multi-stage procedure in the case of the forming operation for the purpose of realizing the collar-type rim portion consists in that the method according to the invention can be adapted flexibly to differing final geometries of the component, in which case, for example, the preliminary forming operation can be the same for the differing geometries. 
     In a further preferred refinement, an axial pressure is exerted, at least for a time, upon the edge of the tubular portion during forming. 
     This measure is advantageous particularly if the free edge of the collar-type rim portion is to extend as transversely as possible relative to the longitudinal axis of the flange, because the axial pressure in conjunction with the radially inwardly acting forming force helps to turn the free edge of the collar-type rim portion outward. 
     In a further preferred refinement, the raw component is prefabricated from a metal blank, from which the cylindrical, tubular portion having the third diameter is drawn. 
     In this refinement, the method comprises a combination of a drawing method, particularly deep-drawing, with a subsequent forming for the purpose of diameter reduction, particularly rolling or pressing, as mentioned above. In this development, the component according to the invention can therefore be produced very cost-effectively overall. Since the cylindrically tubular portion of the raw component is drawn to have a greater diameter than the first diameter that is to be achieved subsequently, the number of drawings in the case of the drawing operation is advantageously reduced, further reducing the costs of the method according to the invention. 
     A component, according to the invention, made of metal, particularly for a head bearing housing of a spring strut, comprising a base part and a flange that extends away therefrom, the flange comprising a substantially tubular portion that has a first diameter and comprising a collar-type rim portion that adjoins the tubular portion and the free edge of which has a second diameter that is greater than the first diameter of the tubular portion, is produced according to a method according to one or more of the aforementioned configurations. 
     Preferably, the base part and the flange are realized to constitute a single piece with one another, this being rendered possible by the method according to the invention. 
     In a preferred embodiment, the component produced by the method according to the invention is a head bearing housing of a spring strut. 
     Further advantages and features are disclosed by the following description and the appended drawing. 
     It is understood that the above-mentioned features and those to be explained in the following can be applied, not only in the respectively specified combination, but also in other combinations or singly, without departure from the scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the invention is represented in the drawing and described more fully in the following with reference to this drawing, wherein: 
         FIG. 1  shows, in cross-section along a plane that includes the longitudinal center axis of the component, a component made of metal for a head bearing housing of a spring strut; 
         FIG. 2  shows, in cross-section, a raw component according to an example not according to the invention; 
         FIG. 3  shows a raw component in an embodiment according to the invention, for the production of a component made of metal for a head bearing housing of a spring strut, similar to the component in  FIG. 1 ; 
         FIG. 4  shows a schematic representation of a tool arrangement for forming the raw component in  FIG. 3 , in a first forming stage; 
         FIG. 5  shows, in cross-section, the raw component in  FIG. 3  after the forming according to  FIG. 4 ; 
         FIG. 6  shows, partially in a sectional representation, a tool arrangement for the further forming of the raw component in  FIG. 5 ; and 
         FIG. 7  shows, in cross-section, the raw component obtained after the further forming according to  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EXEMPLARY EMBODIMENT 
     Represented in  FIG. 1  and having the general reference  10  is a component made of metal, particularly of steel, which can be used for a head bearing housing of a spring strut. 
     The component  10  has a base part  12 , which is realized in the form of a plate  14 . In the context of the present invention, the base part  12  may be of any shape and is adapted, expediently, to the respective spring strut, according to the intended application of the component  10 . 
     Extending away from the base part  12  is a flange  16 , which serves as a supporting flange for a damper bearing. 
     The flange  16  has a substantially tubular portion  18 , which has a first diameter D 1 , the first diameter D 1  to be understood, in the present description, as the smallest diameter D 1  of the flange  16 . It is immaterial in this case whether the diameter D 1  as shown in  FIG. 1  is the outer diameter of the tubular portion  18  or the corresponding inner diameter of the tubular portion  18 , the latter resulting from the difference of the outer diameter and double the material thickness of the tubular portion  18 . 
     At its free end, i.e. the end facing away from the base part  12 , the flange  16  has a collar-type rim portion  20  that adjoins the tubular portion and the free edge of which has a second diameter D 2  that is substantially greater than the first diameter D 1  of the tubular portion  18 . 
     The flange  16  is realized overall to be rotationally symmetrical about a longitudinal axis  24  of the component  10 . 
     Following completion of the component  10 , there is inserted in the flange  16 , for example, an elastic damper element, not represented, in the form of a rubber element, the damper element being able to be well fixed in place, owing to the waisted shape of the inside of the flange  16 . 
     As evident from  FIG. 1 , the flange  16  is realized to constitute a single piece or single part with the base part  12 . 
     It is described in the following, with reference to the schematic  FIGS. 2 to 7 , how the component  10  can be produced from a raw component through cold-forming or hot-forming (preferably cold-forming). 
     The raw components represented in  FIGS. 2 to 7  are not true to scale in relation to  FIG. 1  and each other, but references to the first diameter D 1  and to the second diameter D 2  are to be understood in the sense of  FIG. 1 . 
       FIG. 2  shows a single-piece raw component  26 , which is not suitable for producing the component according to  FIG. 1 . 
     The raw component  26  has a base part  28  and a cylindrically tubular portion  30 . The cylindrically tubular portion  30  has already been drawn, through a plurality of drawings in a deep-drawing process, to the first, small diameter D 1 . 
     Consideration could now be given to producing the collar-type rim portion on the cylindrically tubular portion  30  by folding over a free end  32  of the cylindrically tubular portion  30  outward, i.e. bending the free end  32  outward, as represented by the broken lines in  FIG. 2 . This procedure in the shaping of the collar-type rim portion  20  in  FIG. 1  has the disadvantage, however, that the material in the region of the free edge  32  becomes torn in the case of this forming operation. Tearing of the material is all the more probable since the diameter D 2  is substantially greater than the diameter D 1 . The reason for the tearing of the edge  32  is that, in the shaping of the cylindrically tubular portion  30  already having the small, first diameter D 1 , many drawings are required in the deep-drawing process, this causing great hardening of material in the cylindrically tubular portion  30 , as a result of which the residual formability of the cylindrically tubular portion  30  is no longer sufficient, when the edge  32  is being bent outward, to obtain a collar-type rim portion having a large diameter D 2 . 
     Shown in  FIG. 3 , by contrast, is a raw component  34  that is used in the method according to the invention for producing a component such as that according to  FIG. 1 . 
     The raw component  34  again has a base part  36  and a cylindrically tubular portion  38 . The base part  36  differs from the base part  12  of the component  10 , but it is understood that the base part  36  may be identical to the base part  12 , and that only a schematic drawing is presented here. The cylindrically tubular portion  38  has again been drawn out of the base part  36  in a deep-drawing process, but having, unlike the raw component  26  in  FIG. 2 , a third diameter D 3  that is greater than the first diameter D 1  of the tubular portion  18  of the finished component  10 . 
     The diameter D 3  in this case can be equal to the second diameter D 2  of the finished collar-type rim portion  20  or, also, yet greater than this second diameter D 2 . 
     Unlike the procedure according to  FIG. 2 , in which the collar-type rim portion  20  is shaped by folding over the free end or edge  32  outward, the third diameter D 3  of the cylindrically tubular portion  38  is reduced, starting from the raw component  34  in  FIG. 3 , by a forming tool  44  that is applied to the outside of the tubular portion  38 , at a distance from an edge  40  of the tubular portion  38 , and that acts approximately radially toward the longitudinal center axis  42 , in order to constitute the collar-type rim portion  20  in  FIG. 1 . This procedure is represented in  FIGS. 4 to 7 . 
       FIG. 4  shows the raw component  34  in a tool arrangement  46 , which comprises the forming tool  44 . The forming tool  44  is a roller that exerts a radially inwardly directed pressure upon the outside of the cylindrically tubular portion  38  of the raw component  34 , as indicated by an arrow  48  in  FIG. 4 . 
     The tool arrangement  46  has a tool holder  50  for holding the raw component  34 , and has a pressing-on means  52 , which, for example by means of the force of springs  54 , exerts, at least for a time, an axial pressure, according to an arrow  56 , upon the end  40  of the tubular portion  38 . 
     The forming tool  44  is a preliminary roller, by means of which, in a first stage, a preliminary forming operation is performed for the purpose of initially reducing the third diameter D 3  by pressing-in or rolling. 
     A raw component  34  after the forming operation shown in  FIG. 4  is represented in  FIG. 5 . After the preliminary rolling or preliminary pressing, the tubular portion  38  has been reduced, at a distance from the free edge  40 , to an intermediate diameter D 2 , the collar-type rim portion  20 ′ having been constituted in an initial state. 
     Proceeding from the forming stage according to  FIG. 5 , the raw component  34  in the tool arrangement  46  is now pressed-in further by radially inwardly directed force, according to an arrow  60 , by means of a further forming tool  58 , which is likewise realized as a roller, for example as a contour roller, the pressing-on means  52  continuing to exert an axial pressure, at least for a time, upon the free edge  40 . 
     The raw component  34  after the further forming according to  FIG. 6  is represented by itself in  FIG. 7 . 
     In principle, the further forming according to  FIG. 6  can be so performed that the tubular portion  38  has now been reduced to the final first diameter D 1  by the rolling or pressing-in and the collar-type rim portion  20  has already been shaped with the finished second diameter D 2 . 
     In order to achieve the exact design of the component  10  according to  FIG. 1 , however, further rolling or pressing-in operations can also be performed, depending on the predefined shape of the finished component  10 . 
     In the case of the method according to the invention, which is based on shaping the tubular portion  18  of the finished component  10  having the first diameter D 1  by inwardly directed forming of the tubular portion  38  of the raw component  34 , and on thereby constituting the collar-type rim portion  20 , it has been found that the collar-type rim portion  20  does not tend to become torn.