Abstract:
A torsional vibration damping apparatus, especially a web damper for mounting on a crankshaft of a piston engine, particularly an internal combustion engine for suppression of natural torsion frequencies from crankshafts can now be economically produced. The apparatus comprises a housing fastened to the engine crankshaft to which at least one rotary mass is coupled with spring elements disposed between the housing and the rotary mass allowing the apparatus to be pre-assembled. Advantageously, multiple parts of the torsional vibration damping apparatus, such as the housing can now be fabricated from more economic sheet metal in place of more costly cast parts.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to a torsional vibration damping apparatus, especially a web damper, for mounting on a crankshaft of a piston engine, especially an internal combustion engine. The invention also relates to a crankshaft and a piston engine having a torsional vibration damping apparatus. 
   Traditional torsional vibration damping apparatuses for crankshafts, especially web dampers, often comprise multiple cast parts, which must be expensively finish-machined. 
   OBJECTS OF THE INVENTION 
   The object of the present invention is therefore to provide a torsional vibration damping apparatus, especially a web damper of the type described at the outset, that can be inexpensively produced. 
   This objective is achieved for a torsional vibration damping apparatus, especially a web damper for mounting on a crankshaft of a piston engine, especially an internal combustion engine, in that the torsional vibration damping apparatus comprises multiple sheet metal parts. The sheet metal parts provide the advantage that they are easily and economically produced. The sheet metal parts can be produced, for example, from drawn sheet metal. Individual areas of the sheet metal parts, such as boreholes or openings can be punched out. It is also possible to machine individual areas of the sheet metal parts using metal cutting tools. 
   BRIEF SUMMARY OF THE INVENTION 
   A preferred exemplary embodiment of the torsional vibration damping apparatus is characterized in that the torsional vibration damping apparatus comprises a housing that is fastened to the crankshaft and to which at least one rotary mass is coupled, spring elements being disposed between said housing and said mass. This supplies the advantage that the torsional vibration damping apparatus can be pre-assembled. The pre-assembled torsional vibration damping apparatus can then be fastened to the crankshaft of a piston engine in one assembly step. 
   Another preferred exemplary embodiment of the torsional vibration damping apparatus is characterized in that the housing comprises an essentially pan-shaped sheet metal part with a base that has an essentially rectangular opening that is open on one side. The opening is used to join the torsional vibration damping apparatus in an interlocking manner to an area of the crankshaft of the piston engine that has a complementary configuration. 
   Another preferred exemplary embodiment of the torsional vibration damping apparatus is characterized in that an essentially circular-segment-shaped shoulder is formed on the housing in the area of the cutout. The circular-segment-shaped shoulder is used to fasten the torsional vibration damping apparatus to the crankshaft of a piston engine. 
   Another preferred exemplary embodiment of the torsional vibration damping apparatus is characterized in that at least one through hole is provided in the circular-segment-shaped shoulder. The through hole is used to receive fastening means, such as screws, with which the torsional vibration damping apparatus can be fastened to the crankshaft of a piston engine. 
   Another preferred exemplary embodiment of the torsional vibration damping apparatus is characterized in that the base of the housing has a round rim that is bent 90°. The bent or turned rim outwardly delimits the housing in the radial direction. 
   Another preferred exemplary embodiment of the torsional vibration damping apparatus is characterized in that the housing on the side that faces away from the base can be enclosed by a cover that is formed from a sheet metal part. The outer contour of the cover is preferably adapted to the inner contour of the bent rim of the housing base. 
   Another preferred exemplary embodiment of the torsional vibration damping apparatus is characterized in that the housing base and the housing cover are attached to each other using spacer bolts. The spacer bolts ensure a spaced arrangement of the two housing parts. The housing cover can, however, also be attached to the housing base using a welded joint at, for example, the bent rim of the base. 
   Another preferred exemplary embodiment of the torsional vibration damping apparatus is characterized in that arranged within the housing is at least one flywheel mass that is formed by at least one sheet metal part. The sheet metal part can be economically produced, for example, by punching. 
   Another preferred exemplary embodiment of the torsional vibration damping apparatus is characterized in that at least one sliding element is mounted on the flywheel mass on the radially outward side. The sliding element is used to minimize the friction between the flywheel mass and the housing, especially inside at the bent rim of the housing base. For this purpose, the sliding element is preferably made out of plastic. 
   Another preferred exemplary embodiment of the torsional vibration damping apparatus is characterized in that at least one oblong opening is made in each of the housing base, the flywheel mass and the housing cover, the openings in the housing base, the flywheel mass and the housing cover being tangentially arranged in such a manner that they are in alignment when the torsional vibration damping apparatus is in the assembled state. The openings are used to hold compression springs, by which the flywheel mass is coupled to the housing. 
   Another preferred exemplary embodiment of the torsional vibration damping apparatus is characterized in that through holes are provided on the housing base to hold weighting rivets. The weighting rivets are fastened as needed in different sizes and numbers on the housing bases. 
   Another preferred exemplary embodiment of the torsional vibration damping apparatus is characterized in that the torsional vibration damping apparatus is essentially configured in the shape of a horseshoe. This supplies the advantage that the torsional vibration damping apparatus can be integrated in a space-neutral manner in the crank web of a crankshaft. This means that both the housing base and the housing cover are configured in the shape of a horseshoe. 
   On a crankshaft for a piston engine, especially for an internal combustion engine, having several webs, the objective indicated above is achieved by a previously described torsional vibration damping apparatus being integrated into at least one web of the crankshaft. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional advantages, features and details of the invention emerge in the following description in which: 
       FIG. 1  is a perspective, partial cross-sectional view of a torsional vibration damper mounted on a crankshaft; 
       FIG. 2  is another perspective illustration of the mounted torsional vibration damper from  FIG. 1 ; 
       FIG. 3  is a perspective illustration of the housing base of the torsional vibration damping apparatus in isolation; 
       FIG. 4  is another perspective view of the housing base from  FIG. 3  in separated form; 
       FIG. 5  is an exploded view of the torsional vibration damping apparatus shown in  FIGS. 1 and 2 ; 
       FIG. 6  is an exploded view of the flywheel mass of the torsional vibration damping apparatus illustrated in  FIG. 5 ; 
       FIG. 7  is a perspective illustration as a line drawing of the torsional vibration damping apparatus; 
       FIG. 8  illustrates the torsional vibration damper from  FIG. 7  in horizontal projection; 
       FIG. 9  is a view taken generally along line IX—IX in  FIG. 8 ; 
       FIG. 10  is a view taken generally along line X—X in  FIG. 8 ; and, 
       FIG. 11  is a view taken generally along line XI—XI in FIG.  10 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Torsional vibration damping apparatuses, which can also be called vibration dampers, are used among other things to suppress natural torsion frequencies from crankshafts. In many cases, such a natural frequency is present in the range of approximately 300 to 450 Hz. It is stimulated in particular by the irregularity that results from the compression and expansion occurring in the pistons. A vibration in the torsional resonance can lead to breakage of the crankshaft, which is why torsional vibration dampers or torsional vibration cushions are used. The torsional vibration damping apparatus is also called a rotary vibration damping apparatus. 
   A torsional vibration damping apparatus having a spring coupling is comprised in principle of a rotary mass having a defined moment of inertia that is joined to the crankshaft via spring elements. The natural frequency of the damper, which must be harmonized with the natural frequency of the crankshaft, is produced by the torsion resistance of the spring elements and the moment of inertia of the rotary mass. The vibration properties of the crankshaft are altered by the torsional vibration damping apparatus. The system gains an additional degree of freedom; at damping to zero, the original point of resonance disappears completely, and therefore two new resonance levels occur. At a very high level of damping, no effect is produced, the damper is almost rigidly coupled, and approximately the base resonance of the crankshaft appears. When the damping is correctly designed, neither the new resonance levels nor the original ones emerge disruptively. 
   In  FIGS. 1 and 2 , a vibration damper  1 , is shown that is fastened with screws  2  and  3  to crankshaft  4 . Vibration damper  1 , located on the first crank web, is fastened to the crankshaft using two radial screws  2  and two axial screws  3  and then is installed together with it in the engine block. Vibration damper  1  simultaneously replaces one of the counterweights of crankshaft  4 . 
   Shown in isolation in  FIGS. 3 and 4  is a housing base  8  of the torsional vibration damping apparatus  1  that is described in  FIGS. 1 and 2 . Housing base  8  has essentially the form of a circular disk whose rim  9  is bent into an angle of approximately 90°. Two flat faces  10  and  11 , in which through holes  13  and  14  are placed, are formed on bent rim  9  of housing base  8 . Through holes  13  and  14  are used to pass through screws  2 , which are illustrated in  FIGS. 1 and 2  and used to fasten torsional vibration damping apparatus  1  to crankshaft  4 . 
   Between two flat faces  10  and  11 , an essentially rectangular opening  16  is arranged in housing base  8 . Opening  16  is open on one side and forms an interlocking area, which facilitates an interlocking joint between housing base  8  and the crankshaft (not shown in FIGS.  3  and  4 ). 
   In the central area of housing base  8 , rectangular opening  16  is delimited by a circular-segment-shaped shoulder  18  in which two through holes  19  and  20  are provided. Through holes  19  and  20  are used to pass through screws  3 , which are depicted in  FIGS. 1 and 2  and used in turn to fasten the torsional vibration damping apparatus to the crankshaft. 
   Moreover, through holes  22  and  23  for holding weighting rivets are provided in housing base  8  radially toward the outside close to bent rim  9 . Arranged radially further inward are mounting holes  24  and  25 . Mounting holes  24  and  25  are used, for example, to hold mounting tools or aids. 
   Radially toward the outside, also close to bent rim  9 , five through holes  27  that are used to hold or fasten spacer bolts (not shown) are provided in housing base  8 . Arranged between every two through holes  27  is an oblong window  30 , which is used to hold spring elements (not shown). 
   Housing base  8 , which is depicted in  FIGS. 3 and 4 , is formed out of drawn sheet metal. Through holes  13 ,  14 ,  19 ,  20 ,  22 ,  23 ,  24 ,  25  and  27 , as well as window  30  and opening  16 , were punched out of drawn sheet metal. Areas  34  and  35  of housing base  8  are machined out with metal cutting tools. 
   In  FIG. 5  one sees that housing base  8 , which can also be called a housing pan, can be enclosed by a housing cover  41  that is essentially configured in the shape of a horseshoe. Four windows  43  are provided in housing cover  41  that are configured to be congruent to windows  30  in housing base  8 . Windows  43  are each arranged between two through holes  45 - 46 ;  46 - 47 ;  47 - 48  and  48 - 49 . Through holes  45  to  49  are used, just like through holes  27  in housing base  8 , to hold or fasten spacer bolts  50  to  54 . Spacer bolts  50  to  54  are used to hold housing cover  41  at a defined distance from housing base  8 . 
   Weighting rivets  55 , which can be mounted in housing base  8  as needed in through holes  22  and  23 , are also depicted in FIG.  5 . 
   Spacer bolts  50  to  54  create a housing space between housing base  8  and housing cover  41  radially within bent rim  9  of housing base  8  for a flywheel mass  56 , which is also configured in the shape of a horseshoe. Flywheel mass  56 , like housing cover  41 , is a punched out sheet metal part. Provided at the open end of flywheel mass  56  are indentations  57  and  58  for spacer bolts  50  and  54 . Indentations  57  and  58  are sized so that in the assembled state it is possible to turn the torsional vibration damping apparatus within the housing, which is formed from housing base  8  and housing cover  41 , and specifically in spite of the presence of spacer bolts  50  and  54 . Moreover, oblong holes  59 ,  60  and  61 , through which spacer bolts  51 ,  52  and  53  project in the assembled state of the torsional vibration damping apparatus, are provided in flywheel mass  56 . Oblong holes  59  to  61  are sized so that, in spite of the presence of spacer bolts  51  to  53 , it is possible to turn flywheel mass  56  within the housing. Flywheel mass  56  can be formed in one part or in several parts. In the present case, flywheel mass  56  comprises multiple parts that are held together by rivets  63 . 
   Windows  30 ,  43  and  68  in housing base  8 , housing cover  41  and flywheel mass  56  are used to hold compression springs  65 , which are routed through cups  66 . Compression springs  65  are pre-tensioned in the installed state and couple flywheel mass  56  to the housing. Windows  68 , which are provided in flywheel mass  56 , have the same length but a greater width than windows  43  in housing cover  41  and windows  30  in housing base  8 . The lesser width of windows  43  and  30  prevents compression springs  65  from falling out of the housing through windows  30  and  43 . For this purpose, the width of windows  43  and  30  is smaller than the diameter of compression springs  65 . The width of window  68  in flywheel mass  56  is somewhat larger than the diameter of compression springs  65 . 
   In  FIG. 6  one sees that flywheel mass  56  from  FIG. 5  is formed from a first sheet metal part  71  and a second sheet metal part  72 . The two sheet metal parts  71  and  72  are held together by rivets  74 , which correspond to rivets  63  in FIG.  5 . Radially to the outside, a sliding element  75  made of plastic, which essentially has the shape of a circular ring section, is fastened between or on the two sheet metal parts  71  and  72 . Sliding element  75  in the installed state comes to rest against the inside of the bent rim  9  of housing base  8 . 
   In  FIGS. 7  to  11 , the torsional vibration damping apparatus in the assembled state is illustrated in different views. The frictional damping is produced by a combination of compression spring pre-tensioning and the centrifugal force on the flywheel mass or damper mass. To produce a pre-tensioning force and additional friction, an additional, axial spring element may be provided. 
   Thus it is seen that the objects of the invention are efficiently obtained, although modifications to the invention should be readily apparent to those having ordinary skill in the art, and these changes and modifications are intended to be within the scope of the claims.