Patent Document

CROSS-REFERENCE TO A RELATED APPLICATION 
       [0001]    This application is a division of earlier U.S. patent application Ser. No. 11/507,303 filed on Aug. 21, 2006. This earlier patent application, whose subject matter is incorporated herein by reference, provides the basis for a claim of priority of the invention disclosed in the present application. 
         [0002]    The invention described and claimed hereinbelow is also described in German Patent Application DE 10 2005 039 784.0 filed on Aug. 22, 2005. This German Patent Application, whose subject matter is also incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119(a)-(d). 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    The present invention relates to a device for non-rotatably connecting a hollow shaft with at least one component located on the hollow shaft. 
         [0004]    It is known from the related art, according to DE 196 25 555, to create “shaft-hub connections” by moving a mandrel inside a shaft body designed as a hollow shaft, the outer contours of which are designed such that they allow the hollow shaft to expand. In the exemplary embodiment shown, the mandrel is cylindrical in shape, and the outer diameter of the cylinder is greater than the inner diameter of the hollow shaft. To ensure that the mandrel can be placed in the hollow shaft, it includes a wedge-shaped or conical annular channel at one end that causes the hollow shaft to gradually expand to the outer diameter of the mandrel. 
         [0005]    The main disadvantage of designs of this type is the fact that the hollow shaft must be expanded along its entire length, although the components to be fixed on the hollow shaft using a press fit are positioned only at certain points. The unnecessary expansion of the hollow shaft along its entire length slows the assembly process, increases the amount of energy required for the assembly process, and results in much higher wear of the assembly tools. 
         [0006]    To reduce these disadvantages, and, in particular, to minimize tool wear, publication EP 0 650 550 discloses a method with which the hollow shaft includes a specially-shaped cross section that includes material accumulations in the region of the press fits to be formed. Given that the mandrel of the joining tool is now moved through the hollow shaft, material expands only in the areas where there are material accumulations, so that, with a method of this type, the press fits are realized only at the required points. 
         [0007]    The main disadvantage of a solution of this type is the complex manufacture of the hollow shaft, the special inner contour of which must be machined out either via mechanical machining or by using complicated forming tools during manufacture of the semi-finished product. 
       SUMMARY OF THE INVENTION 
       [0008]    The object of the present invention, therefore, is to provide a shaft-component connection that prevents the described disadvantages of the related art and, in particular, is an economical alternative to known devices while ensuring low wear of the joining tools. 
         [0009]    In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated in a device for non-rotatably connecting a hollow shaft with at least one component located on the hollow shaft and positioned with clearance on the hollow shaft so as to be fastened on the hollow shaft in a certain position by eliminating the clearance by means of expanding the hollow shaft, comprising a joining tool that is passable and expands the hollow shaft for eliminating the clearance, said adjoining tool including an expansion mandrel defined by at least one first shaping element and at least one further shaping element, said extension mandrel being movable inside the hollow shaft; guide means for guiding said expansion mandrel during its movement inside the hollow shaft, said shaping elements being movable relative to each other so that a motion of said shaping elements relative to each other causes at least partial expansion of the hollow shaft. 
         [0010]    Given that the joining tool includes at least one first shaping element and at least one further shaping element, and given that the shaping elements are movable relative to each other—the motion of the shaping elements relative to each other causing an at least partial expansion of the hollow shaft—it is ensured that the joining tools create press-fit connections only at the necessary points. This has the advantage, in particular, that an economical alternative to known methods is created that, in particular, ensures low wear of the joining tools. 
         [0011]    The motion of the shaping elements relative to each other and the motion of the joining tool inside the hollow shaft can be realized particularly easily when, in an advantageous embodiment of the present invention, the at least one first shaping element is designed as a conical mandrel, the largest conical diameter of which is smaller than the inner diameter of the hollow shaft. 
         [0012]    In an advantageous embodiment of the present invention, the translatory motion of the first shaping element can be realized using a simple design by the fact that a guide means designed as a connecting rod is integrally formed on the first shaping element, and by the fact that the connecting rod makes a translatory motion inside the hollow shaft via its coupling with a drive. 
         [0013]    In an advantageous refinement of the present invention, the expansion of the hollow shaft—which is carried out to create the inventive press fit—can be ensured in a manner that is economical yet still ensures proper function by the fact that the at least one further shaping element is designed as an annular bushing formed by annular segments, and by the fact that the annular segments are movable to and fro in the radial direction of the annular bushing between a non-working position and at least one working position. In this context, it is advantageous when, in the non-working position, the outer diameter of the annular bushing is smaller than the inner diameter of the hollow shaft and, in the at least one working position, the outer diameter of the annular bushing is greater than the inner diameter of the hollow shaft. 
         [0014]    In an advantageous embodiment of the present invention, the translatory motion of the further shaping element can be realized in a manner similar to that of the first shaping element using a simple design by the fact that a guide means designed as a support tube is integrally formed on the further shaping element, and by the fact that the support tube makes a translatory motion inside the hollow shaft via its coupling with a drive. 
         [0015]    Given that the drive of the support tube is frame-mounted at one end and, at the other end, is coupled with a bracket fixed to the support tube, and given that the bracket simultaneously accommodates the drive of the first shaping element, it is ensured that the motion of the shaping elements relative to each other is enabled using a simple, space-saving design. 
         [0016]    In an advantageous refinement of the present invention, to realize a precise motion of the shaping elements relative to each other and to ensure that strong shaping forces are transferred, the further shaping element is shaped such that the inner surfaces of the annular segments of the further shaping element define a truncated cone surface, the edge inclination angle of which corresponds to the edge inclination angle of the first shaping element designed as a conical mandrel. 
         [0017]    To ensure that the inventive joining tool can be flexibly adapted to different inner diameters of hollow shafts, it can be provided in an advantageous embodiment of the present invention that the shaping elements and the guide means associated therewith are detachably interconnected and/or are located such that they touch each other. The particular advantage of this is that, when the joining tool is used in hollow shafts with a different inner diameter, it is only necessary to replace the mandrel and, optionally, the annular bushing. The need to replace the annular bushing could even be eliminated if the radial motion of the annular segments of the annular bushing takes place such that the required quality of the inventive press fit is attained even when different inner diameters of the hollow shaft are involved. 
         [0018]    A particularly efficient implementation of the inventive method and the associated device is attained when the present invention is used—in the field of camshaft manufacture—to fix the cams to the camshaft. 
         [0019]    Due to the very high requirements placed on the quality of press-fit connections, it is advantageous when the drives of the guide means are coupled to a control and evaluation unit, the control and evaluation unit controlling the motion of the shaping elements relative to each other as a function of characteristic curves stored in the control and regulating unit. This has the advantage, in particular, that the press-fit connections can always be manufactured with the same high level of quality, since electronic systems are better suited to reacting quickly and precisely to highly diverse basic conditions, so that, ultimately, the same high-quality working results can always be attained, even when the basic conditions fluctuate. 
         [0020]    In this context, it is advantageous when the characteristic curves take the following into account: the position of the shaping elements, and the edge inclination angle and material characteristics of the hollow shaft and the components, it being possible for the material characteristics to include the elasticity module, density, temperature and/or material composition of the hollow shaft and/or the components. 
         [0021]    The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  shows the inventive joining tool in a non-working position, in a side view in accordance with the present invention; 
           [0023]      FIG. 2  shows the joining tool in  FIG. 1 , in a front view in accordance with the present invention; 
           [0024]      FIG. 3  shows the inventive joining tool in a working position, in a side view in accordance with the present invention; 
           [0025]      FIG. 4  shows the inventive joining tool in a further non-working position, in a side view in accordance with the present invention; 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]      FIG. 1  shows a section of a camshaft  1 , the shaft body  2  of which is designed as a hollow shaft  3 . At any position, hollow shaft  3  passes through a component  5  designed as a cam  4 ; component  5  is fixed to hollow shaft  3  using a press fit in a manner according to the present invention and to be described in greater detail below. To ensure that component  5  and hollow shaft  3  can be easily positioned initially in the correct position relative to each other in a manner that is known per se and will therefore not be described in greater detail, a bore  6  is formed in component  5 , the diameter of bore  6  being greater than outer diameter  7  of hollow shaft  3 , so that clearance  8  results between hollow shaft  3  and component  5 . 
         [0027]    Inventive joining tool  10  passes through at least part of inner space  9  of tubular hollow shaft  3 , it being possible for joining tool  10  to make a translatory motion—in a manner to be described in greater detail—toward either end of hollow shaft  3 , as indicated by direction arrow  11 . Joining tool  10  is composed of at least one first shaping element  12  and at least one further shaping element  13 . In the exemplary embodiment shown, first shaping element  12  is defined by a conical mandrel  14 , on one end of which a guide means  16  designed as a connecting rod  15  is integrally formed. It is within the framework of the present invention for guide means  16  and mandrel  14  to be designed as a single component or, e.g., to be detachably interconnected via a not-shown thread. 
         [0028]    The conical shape of mandrel  14  is selected such that the largest conical diameter  17  of mandrel  14  is smaller than inner diameter  18  of hollow shaft  3 . At the end opposite from the mandrel, connecting rod  15  is coupled via interface elements  19  known per se with a drive  20  designed, e.g., as an electrically or hydraulically driven linear motor that can move the at least one first shaping element  12  inside hollow shaft  3  as indicated by arrow direction  11 . 
         [0029]    The at least one further shaping element  13  is defined by an annular bushing  21 , which is composed of a large number of annular segments  22 , as shown in  FIG. 2 . Annular segments  22  are fixed in position in the circumferential direction using suitable fixing means  35 , e.g., snap rings or O rings, such that they ensure a nearly annular shape of annular bushing  21  and also allow annular segments  22  to move in the radial direction as indicated by arrow direction  23 . 
         [0030]    Furthermore, a guide means  16  designed as a support tube  24  is assigned to annular segments  22  on an end face. A U-bent bracket  36  is assigned to support tube  24  at one end that, in a manner similar to connecting rod  15 , couples support tube  24  via interface elements  25  known per se with a drive  26  designed, e.g., as an electrically or hydraulically driven linear motor. In this manner, annular bushing  21  can be fixed in position inside hollow shaft  3 . 
         [0031]    It is within the framework of the present invention for annular segments  22  of annular bushing  21  to be lockable with support tube  24  in a not-shown manner such that the at least one further shaping element  13  moves inside hollow shaft  3  as indicated by arrow direction  11  and can be brought into a new position. A simpler design results when drive  26  of support tube  24  is fixed to the frame and drive  20  of first shaping element  12  is hinge-mounted on bracket  36  connected with support tube  24 . Displacement of shaping elements  12 ,  13  inside hollow shaft  3  can thereby be realized without any additional arrestment. 
         [0032]    It is within the framework of the present invention for mandrel  14  and annular bushing  21  to each include described guide means  16  on each of their end faces, so that, instead of a drive and support on only one side, it is possible to realize a drive on both sides and support of shaping elements  12 ,  13  on both sides in order to ensure that joining tool  10  functions in a precise manner. 
         [0033]    Furthermore, inner surfaces  27  of annular segments  22  of annular bushing  21  as a whole form the shape of a truncated cone  28 . The orientation of truncated cone  28  is selected such that mandrel  14 —which also has the shape of a truncated cone—of first shaping element  12  can move into and out of this truncated cone  28 . A very effective relative motion between the two shaping elements  12 ,  13  can be attained when edge inclination angles  29 ,  30  of truncated cone  28  and mandrel  14  are nearly identical, so that mandrel  14  can penetrate annular bushing  21  entirely. 
         [0034]    According to the inventive method for realizing a press fit between component  5  and a hollow shaft  3 , the first step is to position component  5  on hollow shaft  3 . In a manner known per se, this is accomplished by sliding component  5  onto hollow shaft  3  and fixing it in the desired joining position. Depending on the configuration, one or more components  5 —which are designed, e.g., as cams  4  on a camshaft  1 —can be positioned simultaneously or in succession on hollow shaft  3 . 
         [0035]    When components  5  are fixed in the correct position, further shaping element  13  is moved in a translatory manner into the region of component  5  by starting up drive  26  associated with further shaping element  13 , the translatory motion being brought about, in the exemplary embodiment shown, by displacing bracket  36  associated with support tube  24  in arrow direction  37 . Depending on the press fit geometry desired, the width of annular bushing  21  associated with further shaping element  13  can be equal to, greater than or less than the width of component  5 . 
         [0036]    In the next step, first shaping element  12  is also moved in a translatory manner inside hollow shaft  3  in the direction of annular bushing  21  of further shaping element  13  by starting up linear motor  20 . As shown in  FIG. 3 , during this motion, mandrel  14  of first shaping element  12  enters annular bushing  21  of further shaping element  13 . Given that edge angles  29 ,  30  of truncated conical mandrel  14  are matched to those of truncated conical recess  28  in annular bushing  21 , annular segments  22 —which are held together in an annular formation—of annular bushing  21  are moved outwardly in radial direction  23  from an inner non-working position  31  ( FIG. 1 ) into a working position  32 . 
         [0037]    This results in deformation  33  of hollow shaft  3  in the areas where annular bushing of further shaping element  13  is in contact with the inside of hollow shaft  3 . Deformation  33  spreads inside shaft body  2  of hollow shaft  3  in the radial direction such that outer diameter  7  of hollow shaft  3  is also expanded. Clearance  8  between component  5  and hollow shaft  3  is thereby eliminated and, depending on how far mandrel  14  penetrates annular bushing  21 , a press fit that is more or less pronounced is formed between component  5  and hollow shaft  3 . 
         [0038]    In a subsequent method step, as shown in  FIG. 4 , after the press fit connection is created, mandrel  14  is removed from annular bushing  21 , so that annular segments  22  of annular bushing  21  return to their original, non-working position  31 . In non-working position  31  of further shaping element  13 , shaping elements  12 ,  13  of joining tool  10  can be moved inside the hollow shaft again, since the various outer diameters of shaping elements  12 ,  13  are now smaller than inner diameter  18  of the hollow shaft again. According to the method steps described above, shaping element  12 ,  13  can then be moved to the position of further component  5 , where the inventive method for creating a press fit is repeated. 
         [0039]    To create highly precise press fits, an electronic control and regulating unit  34  can be provided in a further embodiment of the present invention as shown in  FIG. 4 , in which characteristic curves are stored that define—as a function of translatory motion  11  of shaping elements  12 ,  13 —edge inclination angles  29 ,  30  and material characteristics of hollow shaft body  2  and components  5 , e.g., elasticity module, density, temperature, and material composition. 
         [0040]    Using the characteristic curves, a position of shaping elements  12 ,  13  relative to each other that corresponds to the desired quality of the press fit is then determined, and the control of drives  20 ,  26  is actuated and monitored to attain these positions. In a preferred exemplary embodiment, the characteristic curves form a load displacement characteristic curve. 
         [0041]    It is within the ability of one skilled in the art to modify the described formation of a press fit between a component  5  and a hollow shaft  3  in a manner not shown, or to use it in applications other than those shown here, in order to obtain the effects described, without leaving the scope of the present invention. 
         [0042]    It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above. 
         [0043]    While the invention has been illustrated and described as embodied in a device for non-rotatably connecting a hollow shaft with a component, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
         [0044]    Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.

Technology Category: 7