Abstract:
The invention relates to a centrifugal force pendulum ( 100 ) for suppressing torsional oscillations in a drive train, comprising a first and a second flange ( 105, 110 ) that are non-rotatably connected to the drive train and a first and a second pendulum mass ( 125, 135 ) that are arranged axially offset between the flanges. The pendulum masses have different suppressing frequencies.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is the U.S. national stage application pursuant to 35 U.S.C. §371 of International Application No. PCT/DE2012/001050, filed Oct. 31, 2012, which application claims priority to German Application No. 10 2011 087 238.8, filed Nov. 28, 2011. 
     
    
     FIELD 
       [0002]    The invention relates generally to a centrifugal force pendulum. In particular, the invention relates to a centrifugal force pendulum for suppressing torsional oscillations in a drivetrain of a motor vehicle. 
       BACKGROUND 
       [0003]    During the transfer of a torque, in particular in a drivetrain between a drive engine and a transmission of a motor vehicle, different complex torsional oscillation dampers are used to isolate or suppress occurring torsional oscillations. A known measure for degrading such oscillations is the use of a centrifugal force pendulum. A centrifugal force pendulum comprises a flange that is coupled to a shaft in the drivetrain and with a number of pendulum masses that are shiftably arranged on a circumference of the flange. Tracks along which the pendulum masses can shift relative to the flange are selected in such a manner that that the pendulum masses act as short-time energy stores in order to suppress torsional oscillation in the drive train. 
         [0004]    A centrifugal force pendulum is an oscillatory system that has a predetermined resonance frequency. The suppression of torsional oscillations is great in the area of the resonance frequency and drops off in the direction of higher and lower frequencies of the torsional oscillations. 
         [0005]    A torque transfer device with a centrifugal force pendulum is known from German Patent No. 10 2009 042 825 A1. The pendulum masses are located in pairs on different sides of the flange and are coupled to each other by a bolt. 
         [0006]    A similar arrangement is shown in German Patent No. 10 2009 052 055 A1, whereby different pendulum masses with different resonance frequencies are arranged along a circumference of the flange in order to coordinate the suppression behavior of the centrifugal pendulum with different operating states of an internal combustion engine. 
         [0007]    A centrifugal force pendulum is shown in German Patent No. 10 2011 011 469 in which the pendulum masses are located between two flanges that are offset in the axial direction. 
         [0008]    In order to be able to effectively suppress oscillations, for example, in a reciprocating internal combustion engine with a small number of cylinders, it is desirable to be able to coordinate a centrifugal force pendulum with several different resonance frequencies. Here, the centrifugal force pendulum should be built up compactly and be as wear-resistant as possible. 
       BRIEF SUMMARY 
       [0009]    A centrifugal force pendulum for the suppression of torsional oscillations in a drivetrain, in particular of a motor vehicle, comprises a first and a second flange that are non-rotatably connected to the drivetrain, and comprises a first and the second pendulum mass that are arranged axially offset between the flanges. The pendulum masses have different suppression frequencies. 
         [0010]    The suppression frequencies concern primarily resonance frequencies of the pendulum masses and secondarily a damping course outside of the resonance frequencies. It is possible by using pendulum masses with different suppression frequencies to adapt the centrifugal force pendulum in an improved manner to an operating behavior of a drive engine, in particular of a reciprocating internal combustion engine. For example, an internal combustion engine with selective cylinder cutoff in which different numbers of cylinders are active in different operating states can be influenced in its torsional oscillation behavior in an improved manner by the centrifugal force pendulum. A compact centrifugal force pendulum with low axial and radial structural space requirements is produced by the axial arrangement of the pendulum masses. 
         [0011]    The different suppression frequencies are, for example, set by different pendulum paths of the pendulum masses. The suppression frequencies can be precisely coordinated with an internal combustion engine used and with its operating states by suitably designing the pendulum tracks, for example, as epicycloids or circular tracks. A mass manufacturing of such pendulum masses and of the resulting centrifugal force pendulum can also be facilitated in this manner. 
         [0012]    In another embodiment a pendulum shaft attached to the flanges runs in axial direction through apertures of both pendulum masses. In order to fix different pendulum tracks the apertures of the pendulum masses can be differently formed. As a result, a common support of the pendulum masses can be combined with a simple variation of the pendulum tracks and therefore of the suppression frequencies of the individual pendulum masses. 
         [0013]    Additionally or alternatively, in order to fix different pendulum tracks, active diameters of the pendulum shaft on the pendulum masses can be different. As a result, the apertures in the pendulum masses can be the same, if necessary, whereas different pendulum tracks and therefore different suppression frequencies are nevertheless achieved. The same pendulum masses can be multiply used, so that manufacturing costs can be lowered. 
         [0014]    In an embodiment roller bearings are arranged between the pendulum shaft and the pendulum masses, whereby the roller bearings have different outside diameters. The variation of the active diameters of the pendulum shaft can be realized in a simple manner as a consequence. In particular, the roller bearings can have the same inside diameter so that the pendulum shaft can be cylindrically formed in the area of the roller bearings. As a result, a manufacturing of the individual parts of the centrifugal force pendulum as well as a mounting can be simplified, whereby costs can be saved. 
         [0015]    In another embodiment the pendulum masses can have different masses in order to fix different suppression frequencies. In particular, the pendulum masses can be manufactured from a level, flat material, for example, a sheet, and can comprise different contours in a radial direction. As a consequence the suppression frequency of each pendulum mass can be readily influenced. 
         [0016]    In order to fix different suppression frequencies, centers of gravity of the pendulum masses can also have different positions. The positions of the centers of gravity, in particular in the radial direction, can be varied, for example, by the position of the apertures. 
         [0017]    In an embodiment the first pendulum mass comprises two separate pendulum weights that are arranged axially on different sides of the second pendulum mass. As a result, the mass of the first pendulum mass can be enlarged relative to the mass of the second pendulum mass while at the same time a symmetric distribution of forces can take place in the axial direction. The introduction of forces from the pendulum masses into the flanges by the pendulum shaft, in particular in the case of resonance, can be improved by this arrangement. 
         [0018]    In an embodiment three or more pendulum masses with different suppression frequencies are provided. As regards the number of pendulum masses there are theoretically no limitations and four or more axially offset pendulum masses can also be arranged between the flanges. In an embodiment pendulum masses can also be arranged axially outside of the flanges. Here, pendulum masses opposite each other, for example, act as a common pendulum mass in that they have the same suppression frequencies. Furthermore, the suppression frequency of the third pendulum masses, for example, differs from the suppression frequencies of the first and second pendulum masses. 
         [0019]    In an embodiment a fixing device is provided for the switchable coupling of the first pendulum mass to the second pendulum mass. As a result, the suppression behavior of the centrifugal force pendulum can be adapted, for example, in a purposeful manner to the number of cylinders of an internal combustion engine that are in operation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures, in which: 
           [0021]      FIG. 1  shows an axial view of a centrifugal force pendulum; 
           [0022]      FIG. 2  shows a sectional view of the centrifugal force pendulum of  FIG. 1 ; and 
           [0023]      FIG. 3  shows a perspective view of the section from  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    At the outset, it should be appreciated that like drawing numbers appearing in different drawing views identify identical, or functionally similar, structural elements. Furthermore, it is understood that this invention is not limited only to the particular embodiments, methodology, materials and modifications described herein, and as such may, of course, vary. It is also understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to limit the scope of the present invention, which is limited only by the appended claims. 
         [0025]    Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs. Although any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the invention, the following example methods, devices, and materials are now described. 
         [0026]    The following description is made with reference to  FIGS. 1-3 .  FIG. 1  shows an axial view of centrifugal force pendulum  100 . Centrifugal force pendulum  100  comprises first flange  105  and second flange  110  that are arranged in such a manner that they can rotate about axis of rotation  115 . Second flange  110  is not shown for the sake of a better understanding in  FIG. 1 . Flanges  105  and  110  are rigidly connected to each other by pendulum shafts  120 . Pendulum shafts  120 , for example, lie on a common circumference about axis of rotation  115 . 
         [0027]    First pendulum masses  125  including apertures  140  and second pendulum masses  135  including apertures  130  are attached in an axially offset manner so that pendulum shaft  120  runs through apertures  130  and  140 . This results in three stacks of pendulum masses  125 ,  135  uniformly distributed on the circumference of the pendulum shafts  120  about the axis of rotation  115 . In  FIG. 1  a section  125 . 1  of first pendulum mass  125  and facing the observer is not shown (cf.  FIG. 2 ). 
         [0028]    The shapes of apertures  130 ,  140  determine together with the effective diameters of pendulum shafts  120  a pendulum path for first pendulum mass  125  and second pendulum mass  135 . A first, circular pendulum track  145  and a second, epicyclical pendulum track  150  are sketched in by way of example. In different embodiments pendulum tracks  145 ,  150  can also be fixed in such a manner that pendulum masses  125 ,  135  rotate about their own axis during deflection along associated pendulum track  145 ,  150 , thus saving additional energy. Such an embodiment is known under the designation trapezoidal pendulum. In the embodiment shown in  FIG. 1  pendulum masses  125 ,  135  are suspended in a bifilar manner but a unifilar suspension is also possible. The number of pendulum shafts  120  and corresponding apertures  130 ,  140  is not limited to two. 
         [0029]    Centers of gravity of pendulum masses  125  and  135  can have different positions, in particular in the radial direction relative to pendulum masses  125 ,  135 . The positions of the centers of gravity can be influenced in particular by the placement of apertures  130  and  140 . 
         [0030]      FIG. 2  shows a sectional view of the centrifugal force pendulum  100  of  FIG. 1  in which the section takes place along section line A-A sketched into  FIG. 1 . 
         [0031]    Pendulum shaft  120  is cylindrical in a graduated manner between first flange  105  and second flange  110 . End sections of pendulum shaft  120  have smaller diameters than a middle section. End sections run through corresponding apertures in flanges  105  and  110  and can be caulked, riveted, welded or fastened in some other known manner on flanges  105 ,  110  for security. 
         [0032]    Needle bearings  155  are attached to pendulum shaft  120  in order to guide pendulum masses  125 ,  135  with low friction on pendulum tracks  145 ,  150 . Needle bearing  155  includes spacer  160  radially on the outside so that an effective diameter of pendulum shaft  120  is enlarged in this region. Alternatively or additionally, the effective diameter can also be formed, for example, by an enlarged cage of needle bearing  155 , roller bodies with larger diameters or in some other way. Pendulum track  145 ,  150  can be influenced by the variation of the effective diameter, as a result of which the suppression frequency of pendulum mass  125 ,  135  is influenced. 
         [0033]    In an example aspect, first pendulum mass  125  is divided into first pendulum weight  125 . 1  and second pendulum weight  125 . 2 . Pendulum weights  125 . 1  and  125 . 2  lie in the axial direction on different sides relative to second pendulum mass  135 . Individual pendulum weights  125 . 1  and  125 . 2 , for example, have identical suppression frequencies. This can be achieved in particular in that the material, the shape and the position of pendulum weights  125 . 1  and  125 . 2  as well as the shape, size and position of apertures  140  and the effective diameters of pendulum shaft  120  in the area of the pendulum weights  125 . 1  and  125 . 2  are identical. An additional mechanical coupling of pendulum weights  125 . 1  and  125 . 2  is then no longer required but can be made for the improved synchronization of the suppression frequencies, for example, by an axial rivet. 
         [0034]    The suppression frequencies of pendulum masses  125  and  135  are differently selected. Each suppression frequency is formed by a resonance frequency of the particular pendulum mass  125 ,  135  and by a damping course in the direction of higher and lower frequencies. In an example aspect, the suppression frequencies of pendulum masses  125 ,  135  overlap only slightly or not at all and cover torsional oscillations that, for example, occur in different operating states of a drive engine driving centrifugal force pendulum  100 . The drive engine can be in particular a reciprocating internal combustion engine with selective cylinder disengagement. In an example aspect, different numbers of pistons can be used to generate torque as a function of the internal combustion engine, as a result of which frequencies of torsional oscillations emanating from the drive engine are different in frequency and in amplitude. 
         [0035]      FIG. 3  shows a perspective view of the section of  FIG. 2 . 
         [0036]    Centrifugal force pendulum  100  also has different suppression frequencies by designing pendulum masses  125 ,  135  according to different suppression frequencies. One of pendulum masses  125 ,  135  can be fastened on flanges  105 ,  110  for an improved adaptation of the suppression frequencies of centrifugal force pendulum  100  to torsional oscillations of the drive engine to be expected while the drive engine is in a first operating state and released when the drive engine is in a second operating state. The different operating states can comprise different numbers of active cylinders. 
         [0037]    In another embodiment (not shown) more than two pendulum masses  125 ,  135  can also be used. A pendulum mass  165  (not shown) can be arranged between flanges  105 ,  110 . Third pendulum mass  165  is, for example, divided into two separate pendulum weights  165 . 1  and  165 . 2  that are arranged in mirror symmetry to the second pendulum mass  135  in a manner similar to the pendulum weights  125 . 1  and  125 . 2  of the first pendulum mass  125 . 
         [0038]    In another embodiment pendulum weights  165 . 1  and  165 . 2  are arranged axially outside of flanges  105  and  110 . The support of all pendulum masses  125 ,  135 ,  165 , for example, takes place by pendulum shafts  120 . 
         [0039]    Of course, changes and modifications to the above examples of the invention should be readily apparent to those having ordinary skill in the art, without departing from the spirit or scope of the invention as claimed. Although the invention is described by reference to specific preferred and/or example embodiments, it is clear that variations can be made without departing from the scope or spirit of the invention as claimed. 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
           100  centrifugal force pendulum 
           105  first flange 
           110  second flange 
           115  axis of rotation 
           120  pendulum shaft 
           125  first pendulum mass 
           125 . 1  first pendulum weight of the first pendulum mass  125   
           125 . 2  second pendulum weight of the first pendulum mass  125   
           130  aperture of the second pendulum mass  135   
           135  second pendulum mass 
           140  aperture of the first pendulum mass  125   
           145  first pendulum track (in the shape of a circular arc) 
           150  second pendulum track (epicyclical) 
           155  needle bearing 
           160  spacer 
           165  third pendulum mass 
           165 . 1  first pendulum weight of the third pendulum mass  165   
           165 . 2  second pendulum weight of the third pendulum mass  165