Abstract:
A vibration damper includes an input side and output side, one or more elastic elements for transmitting force between the input side and the output side, and a centrifugal force pendulum having a pendulum flange and one or more pendulum masses which are attached movably to the pendulum flange in the plane of rotation of the pendulum flange. It is proposed that certain ratios of masses and volumes of the elastic elements and of the pendulum masses be formed. If one or more of the ratios lie in specified ranges, then good damping or elimination of torsional vibrations by the vibration damper can be assumed.

Description:
[0001]    The invention relates to a vibration damper for transmitting a torque between an input side and an output side. In particular, the invention relates to a vibration damper having an elastic element and a centrifugal force pendulum. 
         [0002]    A vibration damper may be used to transmit torque in a drivetrain, for example in a motor vehicle. The vibration damper may be placed, for example, between a drive motor and a gear unit. In particular, when the drive motor comprises a reciprocating internal combustion engine, fluctuations are superimposed on the torque provided, which are to be reduced by the vibration damper and kept away from the gear unit. The vibration damper is usually constructed so that torque fluctuations which may be impressed on a flow of torque in the reverse direction are also reduced or isolated. 
       BACKGROUND 
       [0003]    A known vibration damper comprises an elastic element and a centrifugal force pendulum. The elastic element is usually formed by a cylindrical or arciform coil spring, which transmits forces between the input side and the output side of the vibration damper on a circumference around an axis of rotation. The centrifugal force pendulum comprises one or more pendulum masses, which are situated movably on a pendulum flange in the plane of rotation of the pendulum flange. The pendulum flange is connected, rigidly or by means of an elastic element, to the input side or the output side. 
       SUMMARY OF THE INVENTION 
       [0004]    It has been found that not every combination of elastic elements and pendulum masses results in adequate isolation or elimination of vibrations. An object of the invention is to specify criteria which simplify the dimensioning of an elastic element and of a centrifugal force pendulum in a vibration damper. 
         [0005]    The present invention provides a vibration damper having an input side and output side, one or more elastic elements for transmitting force between the input side and the output side, and a centrifugal force pendulum having a pendulum flange and one or more pendulum masses which are attached movably to the pendulum flange in the plane of rotation of the pendulum flange. 
         [0006]    Experiments have shown that good isolation of vibrations can succeed when the ratio of the sum of the masses of the pendulum masses and the sum of the masses of the elastic elements lies in a range between 0.5 and 4. 
         [0007]    By adjusting the masses of the pendulum masses relative to the masses of the elastic elements, an especially efficient combination of isolating the torsional vibrations by means of the elastic elements and eliminating the torsional vibrations by means of the centrifugal force pendulum can be achieved. In an especially preferred embodiment, the forenamed ratio lies in the range between 0.95 and 1.60. 
         [0008]    Starting from the vibration damper described above, other parameters than the masses of the elastic elements and the pendulum masses can also be considered. If one of the elastic elements includes a cylindrical spring, for example, then a solid cylinder may be specified within which the cylindrical spring extends. If one of the elastic elements includes a bow spring, for example, then in an analogous manner a solid torus sector may be specified within which the bow spring extends. It has been found that especially good vibration damping or eliminating properties of the vibration damper can be achieved when the ratio of the sum of the volumes of the pendulum masses and the sum of the volumes of the solid cylinders and solid torus sectors lies in a range between 0.3 and 1.3. The forenamed ratio preferably lies in a range between 0.44 and 0.63. 
         [0009]    By considering the volumes of geometric bodies that envelop the elastic elements or enclose them as tightly as possible, constructions in particular may be taken into account in which the space of the geometric body is essentially completely filled by the elastic element. This point of view suggests itself in particular in embodiments in which another straight or bent coil spring is situated inside the straight or bent coil spring. 
         [0010]    If it can be assumed that the elastic elements are formed by coil springs on whose radially inner side no additional elastic element is constructed, then hollow cylinders can be considered instead of the solid cylinders described above, and hollow torus sectors instead of the described solid torus sectors. In this case, it is preferred that the ratio of the sum of the volumes of the pendulum masses and the sum of the volumes of the hollow cylinders and hollow torus sectors are in the range between 0.5 and 4. In an especially preferred embodiment, the forenamed ratio is in a range between 0.97 and 1.94. 
         [0011]    Another approach to characterizing a high-quality vibration damper of the described type consists in setting the ratio of masses named at the beginning and the last-named ratio of the volumes of the pendulum masses and the hollow cylinders and hollow torus sectors in another ratio. This ratio falls in a range between 0.35 and 2. In an especially preferred embodiment, the ratio lies in a range between 0.72 and 1.05. 
         [0012]    The ranges according to the invention for predetermined ratios make it possible to estimate the quality of the vibration damping of an existing vibration damper mathematically. Alternatively, it is also possible when designing a vibration damper to proceed in such a way that at least one of the forenamed ratios lies within the respective assigned range in order to provide a high-quality vibration damper. In both cases, one or more of the stated criteria may be used in order to identify the high-quality vibration damper according to the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The invention will now be described in greater detail by reference to the accompanying figures, in which the figures represent the following: 
           [0014]      FIG. 1  schematic depictions of a vibration damper; 
           [0015]      FIG. 2  a bow spring for use on the vibration damper of  FIG. 1 ; 
           [0016]      FIG. 3  a cylindrical spring for use on the vibration damper of  FIG. 1 ; 
           [0017]      FIG. 4  a cylindrical force pendulum for use on the vibration damper of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0018]      FIG. 1  shows schematic depictions of two embodiments of a vibration damper  100 . The vibration damper is set up, for example, to be used in a drivetrain of a motor vehicle. In particular, the vibration damper  100  is set up to be used on a wet or dry clutch, for example a starting clutch, on a hydrodynamic converter, a torque converter, a dual clutch or an automatic transmission. 
         [0019]    The vibration damper  100  in the top depiction comprises an input side  105  which is connected as an example to an input flange  110 , an output side  115  which is connected as an example to an output flange  120 , a centrifugal force pendulum  125 , and a first elastic element  130  and a second elastic element  135 . The centrifugal force pendulum  125  includes a pendulum flange  140 , on which a pendulum mass  145  is movably situated. The pendulum flange  140  is rotatably mounted, preferably around the same axis of rotation around which the input side  105  with the input flange  110  and the output side  115  with the output flange  120  are also rotatably mounted. The first elastic element  130  couples the input flange  110  with the pendulum flange  140 , and the second elastic element  135  couples the pendulum flange  140  with the output flange  120 . 
         [0020]    In the depicted embodiment, the first elastic element  130  comprises a bow spring and the second elastic element  135  comprises a cylindrical spring. In other embodiments, the first elastic element  130  may also comprise a cylindrical spring and the second elastic element  135  a bow spring. Both elastic elements  130 ,  135  are situated on a circumference around the axis of rotation of the pendulum flange. Compression springs are preferably used for the elastic elements  130 ,  135 , which compression springs are situated on the flanges  110  and  140  or  120  and  140  in such a way that both a positive and a negative rotation of the flanges  110 ,  120 ,  140  meshing with the respective elastic element  130 ,  135  result in compression of the elastic element  130 ,  135 . The flanges  110 ,  120 ,  140  usually have congruent cut-outs for this purpose, in which the elastic elements  130 ,  135  are situated. 
         [0021]    The elastic elements  130  and  135  can overlap each other axially, in which case one of the elastic elements  130 ,  135  is situated further inside radially than the other radial element  130 ,  135 . Especially preferred is an embodiment in which a bow spring is used radially outside and a cylindrical spring radially inside. 
         [0022]    The lower area of Figurel depicts a variant in which the pendulum flange  140  takes the place of the output flange  120  depicted above. In this case, the pendulum flange  140  used in the upper embodiment is replaced by an intermediate flange  150 . In other respects, the statements made above about the other embodiment are valid. In an analogous embodiment, the pendulum flange  140  can also take the place of the input flange  110 , in which case the first elastic element  130  couples the pendulum flange  140  with the intermediate flange  150  and the second elastic element  135  couples the intermediate flange  150  with the output flange  120 . 
         [0023]      FIG. 2  shows the first elastic element  130 , which is designed as a bow spring. At the top, only the elastic element  130  is shown, in the middle the elastic element  130  together with an enveloping geometric figure, and at the bottom only the geometric figure. 
         [0024]    The first elastic element  130  is formed by a steel wire which is wound helically around a circular line  205 . The first elastic element  130  extends inside a solid torus sector VTA. The volume VT of a solid torus is stated as follows: 
         [0000]        VT= 2π 2   Rr   a   2   (Equation 1)
 
         [0025]    where: 
         [0026]    VT volume of the solid torus 
         [0027]    R radius of the centerline 
         [0028]    r a  radius of the cross section of the solid torus. 
         [0029]    The volume of the solid torus sector is determined as a fraction of the volume of the solid torus. 
         [0000]    
       
         
           
             
               
                 
                   VTA 
                   = 
                   
                     
                       ϕ 
                       
                         360 
                         ∘ 
                       
                     
                     · 
                     VT 
                   
                 
               
               
                 
                   ( 
                   
                     Equation 
                      
                     
                         
                     
                      
                     2 
                   
                   ) 
                 
               
             
           
         
       
     
         [0030]    where: 
         [0031]    VTA volume of the solid torus sector 
         [0032]    VT volume of the solid torus. 
         [0033]    In particular, when the first elastic element  130  comprises a plurality of concentric coil springs, the volume of the first elastic element  130  can be approximated as the volume of the described solid torus sector. If the wire of the first elastic element  130  encircles a considerable volume that is not filled by another section of the first elastic element  130 , then the volume of the first elastic element can also be approximated as the volume of a hollow torus sector. The volume of a hollow torus is determined as follows: 
         [0000]      VHT=2π 2   R ( r   a   2   −r   i   2 )  (Equation 3)
 
         [0034]    where: 
         [0035]    VHT volume of the hollow torus 
         [0036]    R radius of the centerline 
         [0037]    r a  outer radius of the cross section of the solid torus 
         [0038]    r i  inside radius of the cross section of the solid torus. 
         [0039]    In turn, the volume of a hollow torus sector is determined as a fraction of the volume of the entire hollow torus. 
         [0000]    
       
         
           
             
               
                 
                   VHTA 
                   = 
                   
                     
                       ϕ 
                       
                         360 
                         ∘ 
                       
                     
                     · 
                     VHT 
                   
                 
               
               
                 
                   ( 
                   
                     Equation 
                      
                     
                         
                     
                      
                     4 
                   
                   ) 
                 
               
             
           
         
       
     
         [0040]    where: 
         [0041]    VHTA volume of the hollow torus sector 
         [0042]    VHT volume of the hollow torus 
         [0043]    φopening angle of the torus sector. 
         [0044]      FIG. 3  shows the second elastic element  135  from  FIG. 1  as a straight cylindrical spring Similarly to the description above referring to the first elastic element  130 , the volume of the second elastic element  135  can be approximated by an enveloping geometric body. In the case of the second elastic element  135 , this geometric body is a straight circular cylinder. This approach suggests itself in particular when the second elastic element  135  comprises two mutually coaxial coil springs, so that no appreciable space remains on a radial inner side of the second elastic element  135 . The volume of the solid cylinder is determined as follows: 
         [0000]        VZ=π·l·r   a   2   (Equation 5)
 
         [0045]    where: 
         [0046]    VZ volume of the solid cylinder 
         [0047]    l length of the solid cylinder 
         [0048]    r a  radius of the solid cylinder. 
         [0049]    If a coaxial cylindrical cavity is to be considered which is not filled by an element or by a section of the second elastic element  135 , then the volume of the second elastic element  135  can also be approximated by a hollow cylinder. The volume of the hollow cylinder is determined as follows: 
         [0000]      VHZ=π·l·( r   a   2   −r   i   2 )  (Equation 6)
 
         [0050]    where: 
         [0051]    VHZ volume of the hollow cylinder 
         [0052]    r a  outside diameter of the hollow cylinder 
         [0053]    r i  inside diameter of the hollow cylinder. 
         [0054]      FIG. 4  shows an embodiment of the centrifugal force pendulum  125  from  FIG. 1 . For reasons of illustration, only one pendulum mass  145  is depicted on the pendulum flange  140 . Contrary to the depiction, each pendulum mass  145  usually comprises two individual masses, which are attached to opposing axial sides of the pendulum flange  140  and are rigidly connected to each other. Furthermore, usually two, three, four or more pendulum masses  145  are distributed on a circumference around the axis of rotation of the pendulum flange  140 . The volumes of the pendulum masses  145  can be determined on the basis of their total mass and their specific weight. The total mass can be specified by a manufacturer of the centrifugal force pendulum  125 . Alternative possibilities are a geometric approximation of a hydraulic displacement measurement of the pendulum masses  145  separate from the pendulum flange  140 . When the displacement is measured, the volume of the pendulum masses  145  is determined as the volume that they displace when completely immersed in a hydraulic fluid. 
         [0055]    On the basis of the volumes described above and the masses of the pendulum masses  145  and the spring elements  130 ,  135 , certain mathematical ratios can now be derived which are useful for assessing the vibration damper  100  from  FIG. 1 . In extensive series of tests with elastic elements  130 ,  135  of different sizes and weights and pendulum masses  145  of different sizes and weights it has been found that the properties of the vibration damping or vibration suppression of the vibration damper  100  are especially good when at least one of the ratios that are indicated in columns in the following table lies within a range that is specified in the respective lines below as minimum and maximum. 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Q1 = 
                 Q2 = 
                 Q3 = 
                 Q4 = 
               
               
                   
                 MPM/MEL 
                 VPM/VZT 
                 VPM/VHZT 
                 Q1/Q3 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Maximum 
                 4 
                 1.3 
                 4 
                 2 
               
               
                 Minimum 
                 0.5 
                 0.3 
                 0.5 
                 0.35 
               
               
                   
               
             
          
         
       
     
         [0056]    The following second table specifies even stricter minimum and maximum values for the ratios Q1 through Q4. In these ranges even greater improvement of the quality of the vibration damper  100  can be expected. 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Q1 = 
                 Q2 = 
                 Q3 = 
                 Q4 = 
               
               
                   
                 MPM/MEL 
                 VPM/VZT 
                 VPM/VHZT 
                 Q1/Q3 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Maximum 
                 1.60 
                 0.63 
                 1.94 
                 1.05 
               
               
                 Minimum 
                 0.95 
                 0.44 
                 0.97 
                 0.72 
               
               
                   
               
             
          
         
       
     
         [0057]    The quality of the vibration damper  100  can exist when one of the ratios Q1 through Q4 lies in a range assigned to it by one of the tables, or when a plurality of the ratios Q1 through Q4 lie in the ranges assigned to them. A simple and rapid determination of the quality of an existing or planned vibration damper  100  can be carried out on the basis of these specifications. 
       REFERENCE LABELS 
       [0000]    
       
           100  vibration damper 
           105  input side 
           110  input flange 
           115  output side 
           120  output flange 
           125  centrifugal force pendulum 
           130  first elastic element 
           135  second elastic element 
           140  pendulum flange 
           145  pendulum mass 
           150  intermediate flange 
           205  circular line