Abstract:
A torsional vibration damper for operation in an oil bath comprising an input flange for connecting to a drive motor, an output flange for connecting to a transmission, and a bow spring for the torsionally elastic coupling of the input flange to the output flange, where the bow spring is in contact radially on the outside with an encircling holding device that is formed on one of the flanges. At the same time, the holding device has an opening in the area of the bow spring, in order to enable a flow of oil through an area of contact of the bow spring with the holding device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from German Patent Application No. 10 2011 087 865.3, filed on Dec. 7, 2011, which application is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The invention relates generally to torsional vibration dampers, more specifically to torsional vibration dampers operating in an oil bath, and, even more specifically, to torsional vibration dampers operating in an oil bath in a drivetrain of a motor vehicle. 
     BACKGROUND OF THE INVENTION 
     A known serial torsional vibration damper comprises an input flange, an intermediate flange and an output flange, wherein a bow spring positioned radially outside is provided for the elastic transmission of torque from the input flange to the intermediate flange, and a compression spring positioned radially inside is provided for the elastic transmission of torque from the intermediate flange to the output flange. The input flange is usually shaped so that it receives the bow spring in a cup-like manner and supports it in a radially outer area, so that the bow spring is in contact with the input flange under the influence of centrifugal force. Such a flange is known as a retainer. 
     In particular, when used on a multi-cylinder reciprocating internal combustion engine, the torsional vibrations initiated by the internal combustion engine can result in deflections of the intermediate flange relative to the input flange with small angles of attack at a high frequency. In the contact area between the flange and the bow spring there develops a rubbing of steel on steel, which causes an abrasion of at least one of the frictional partners. The abrasion particles can be very fine, and can collect between the spring coils of the bow spring. That causes the abrasion particles to be further tumbled during the continuing operation of the torsional vibration damper and to be ground between the retainer and the bow spring, which further accelerates the wearing of both frictional partners. 
     SUMMARY OF THE INVENTION 
     The present invention broadly comprises a torsional vibration damper for operation in an oil bath, where the torsional vibration damper comprises the following: an input flange for connecting to a drive motor; an output flange for connecting to a transmission; a bow spring for the rotationally elastic connection of the input flange to the output flange; wherein the bow spring can be in contact radially on the outside with an encircling holding device that is formed on one of the flanges, characterized in that the holding device includes an opening in the area of the bow spring, in order to enable a flow of oil through an area of contact of the bow spring with the holding device. 
     A torsional vibration damper according to the invention, for operation in an oil bath, comprises an input flange for connecting to a drive motor, an output flange for connecting to a transmission, and a bow spring for the torsionally elastic coupling of the input flange to the output flange, where the bow spring may be in contact radially on the outside with an encircling holding device that is formed on one of the flanges. In this case, the holding device has an opening in the area of the bow spring, in order to enable a flow of oil through an area of contact of the bow spring with the holding device. At the same time, in certain operating conditions the bow spring may be in contact with the holding device, for example when a defined speed of rotation is exceeded. 
     An abrasion which occurs due to wear caused by friction of the bow spring on the holding element can thus be flushed away by the oil, so that the abrasion particles are removed from the area of contact of the bow spring with the holding device, minimizing wear. The abrasion particles can be kept back from the oil, for example, by means of a conventional filter in an oil circuit. The service life of the torsional vibration damper, and in particular of the bow springs, can be prolonged by the oil flushing, without requiring expensive measures such as browning or nitrifying to increase the robustness of the bow springs and/or of the holding device. 
     In a preferred embodiment, the opening is situated in the area of a radial vertex of the holding device. Oil that is pressed out by centrifugal force in the area of the holding device, can thereby be removed in an improved manner from the holding device, so that the flow of oil can pass very close to the area of contact, or even through the area of contact. 
     The opening may also lie outside of the area of contact. Wear on the bow spring, which can be caused by a section of the spring sweeping over the opening, is thereby prevented. 
     Preferably, the opening is offset axially outward from the radial vertex of the holding device. The area of contact can thereby include the vertex, and thus provide for good radial bracing of the bow spring, while at the same time the opening is not swept over directly by sections of the bow spring. Additional wear due to sweeping over the boundaries of the cutout can thereby be prevented. 
     In one embodiment, the holding device is formed in a flat material of the flange, and the opening is formed by a lift flap in the flat material. The lift flap can be easy to produce, and in particular subsequent to a known fabrication of the flange with the holding device, for example from a piece of sheet metal. 
     In a preferred embodiment, the lift flap is formed in a radial connecting section of the flange and is opened radially toward the inside, in order to let oil pass through that is flowing radially outward at the surface of the connecting section. This enables the flow of oil to be initiated in the area of contact without requiring an active supply of fresh oil, for example by means of a device for spraying the flange with oil. 
     The object of the invention is to specify a torsional vibration damper that has an extended service life. 
     The object is fulfilled by a torsional vibration damper having the features of the independent claim. Subordinate claims describe preferred embodiments. 
     These and other objects and advantages of the present invention will be readily appreciable from the following description of preferred embodiments of the invention and from the accompanying drawings and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described in greater detail by reference to the accompanying figures, in which: 
         FIG. 1  shows a torsional vibration damper with a bow spring; 
         FIG. 2  shows another embodiment of the torsional vibration damper of  FIG. 1 ; 
         FIG. 3  shows a sectional view of the torsional vibration damper of  FIG. 2 ; 
         FIG. 4  shows a sectional view of a torsional vibration damper according to  FIGS. 1 through 3  in yet another embodiment; 
         FIG. 5  shows another view of the torsional vibration damper from  FIG. 4 ; and, 
         FIG. 6  shows the input flange from  FIG. 5  in a different perspective. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical, or functionally similar, structural elements of the invention. While the present invention is described with respect to what is presently considered to be the preferred aspects, it is to be understood that the invention as claimed is not limited to the disclosed aspect. The present invention is intended to include various modifications and equivalent arrangements within the spirit and scope of the appended claims. 
     Furthermore, it is understood that this invention is not limited to the particular methodology, materials and modifications described 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. 
     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 preferred methods, devices, and materials are now described. 
     Adverting now to the Figures,  FIG. 1  shows torsional vibration damper  100  for operating in an oil bath (“wet-running”), preferably in a drivetrain of a motor vehicle. 
     Torsional vibration damper  100  comprises input flange  105 , output flange  110  positioned coaxially thereto (shown only schematically), and a number of bow springs  115  that are situated on a circumference around the axis of rotation of flanges  105  and  110 . Here, each bow spring  115  is realized as a coaxial system of two bow springs. 
     Each bow spring  115  is in contact in an axial direction with two first contact elements  120 , which are rigidly connected to input flange  105 . In a corresponding manner, the ends of each bow spring  115  are also in contact with second contact elements  125 , which are rigidly connected to output flange  110 . Here, contact elements  120  and  125  are shaped so that a collision-free rotation of input flange  105  relative to output flange  110  is possible. During the rotation, no matter which direction, all of bow springs  115  are compressed. 
     Output flange  119  may also be an intermediate flange, which acts on an actual output flange through an arrangement of compression springs or some other vibration-damping transmission device. In this case, the depicted torsional vibration damper  100  is part of a serial torsional vibration damper. Other embodiments based on the depicted torsional vibration damper are likewise possible, for example having springs connected in parallel and/or using a centrifugal force pendulum or a dual mass flywheel. 
     In the depiction in  FIG. 1 , input flange  105  is connected to internal clutch basket  130 . Through internal clutch basket  130 , a torque can be introduced into torsional vibration damper  100 , which is conveyed elastically to output flange  110  while absorbing torsional vibrations. In other embodiments, torque can also be introduced into input flange  105  in a different way, for example by means of a hub, a sprocket or gearing. Output flange  110  is usually set up for passing the conveyed torque to a transmission, for example by means of a hub having gear teeth. 
     Input flange  105  is designed as a so-called retainer; that is, it is formed essentially like a flat pot or a bowl, in order to surround bow springs  115  on one radial outer side. The section of input flange  105  which leads past bow springs  115  radially on the outside is therefore designated hereinafter as holding device  135 . In an embodiment, holding device  135  can also be formed on output flange  110 . 
     On one radial outer side of holding device  135 , where input flange  105  extends farthest from the axis of rotation, a number of openings  140  are made in holding device  135 . Openings  140  are distributed evenly around a circumference and have an elongated shape which extends in the circumferential direction, with rounded edges. Oil that is present in area of contact  145  of bow spring  115  with holding device  135  can absorb abrasion particles that occur due to rubbing of bow spring  115  on holding device  135 . The abrasion particles may be present in the form of a fine metallic dust. As a result of centrifugal forces, the oil is pressed farther radially outward, and leaves torsional vibration damper  100  through one of openings  140 . The oil in the area of torsional vibration damper  100  can be circulated by means of an external circulating pump, the oil being pressed through a filter that removes the abrasion particles from the oil. 
       FIG. 2  shows an embodiment of torsional vibration damper  200 . Openings  240  are again arranged along a circumference around the axis of rotation of torsional vibration damper  200 ; in contrast to the embodiment depicted in  FIG. 1 , however, openings  240  are not made in input flange  105  at the outermost circumference, but radially farther inward, which simultaneously means an axial shift on the surface of the bulging holding device  135 . The shift occurs in the direction of the closed surface of input flange  105 , toward the left in the depiction in  FIG. 2 . A shift in the other direction is likewise possible. 
     The embodiment depicted in  FIG. 2  arranges openings  240  outside of area of contact  145  of bow spring  215  with input flange  105 . As a result, coils of bow spring  215  do not have to run past boundaries of openings  240  during compression or decompression. 
       FIG. 3  shows a sectional view of torsional vibration damper  200  of  FIG. 2 . The sectional plane runs through the axis of rotation of torsional vibration damper  200   
     Vertex  160  of input flange  105  is a point on the input flange at the greatest distance from the axis of rotation of torsional vibration damper  100 . It is possible to recognize the manner in which opening  240  is displaced both radially and axially from vertex  160  of input flange  105 . Opening  240  is outside of contact area  145 . Line L 1 , parallel to axis of rotation AR, passes through opening  240  and bow spring  215 . 
       FIG. 4  shows a sectional view of torsional vibration damper  300 . The sectional plane encloses an acute angle with the axis of rotation. 
     In the depicted embodiment, opening  340  is realized by lift flap  150  in input flange  105 . Input flange  105  is made from sheet metal, for example by deep drawing or pressing. 
     Lift flap  150  can be produced by making a U-shaped cut or a punching in the sheet metal of input flange  105 , followed by bending out the resulting tongue. The cut or punching may also be made before a metal sheet is formed into input flange  105 . When the sheet metal is later shaped into input flange  105 , the tongue is deformed less than a surrounding area, resulting in the depicted lift flap  150 . Line L 2 , orthogonal to axis AR, passes through opening  340  and flap  150 . 
     The open side of lift flap  150  points in the direction of connecting section  155  of input flange  105  that runs radially inward. Oil that collects, for example, due to splashing on the surface of connecting section  155  migrates outward on the surface of connecting section  155  as torsional vibration damper  300  rotates, due to centrifugal force. Oil flowing along on the left side of input flange  105  can pass through an opening  340  in the lift flap and flow to the area of contact  145 . Due to the constant inflow of oil into contact area  145 , its storage capacity is exhausted at some time, so that part of the stored oil is removed again from contact area  145  through one of openings  340  or in the area of the upper right boundary of input flange  105  in  FIG. 4 . The abrasion particles from bow spring  315  or from input flange  105  can be removed in this way from contact area  145  by means of the oil, so that the formation of a polishing layer or grinding paste based on the abrasion particles is prevented. 
       FIG. 5  shows another view of torsional vibration damper  300  from  FIG. 4 . For better understanding, only input flange  105  is shown, without bow springs  315  and output flange  110 . At lift flaps  150  which form the openings  340 , the U-shaped separating lines, cuts or stampings in the material of input flange  105  are clearly recognizable. 
       FIG. 6  shows input flange  105  from  FIG. 5  in a different perspective. In addition to openings  340  formed by lift flaps  150 , an additional opening  340  is made in holding device  135  of input flange  105 . The additional opening  340  is located opposite lift flaps  150  relative to the vertex, so that it is not made in the area of connecting section  155 , but rather in the area of the edge of input flange  105  shown at the upper right in  FIG. 4 . 
     The additional opening  340  enables an improved flow of oil out of holding device  135 , while lift flaps  150  transport oil in an improved manner into holding device  135  or contact area  145 . 
     LIST OF REFERENCE NUMBERS 
       100  torsional vibration damper 
       200  torsional vibration damper 
       300  torsional vibration damper 
       105  input flange 
       110  output flange 
       115  bow spring 
       215  bow spring 
       315  bow spring 
       120  first contact element 
       125  second contact element 
       130  internal clutch basket 
       135  holding device 
       140  opening 
       240  opening 
       340  opening 
       145  contact area 
       150  lift flap 
       155  connecting section 
       160  vertex 
     AR axis of rotation 
     Ll line parallel to axis of rotation 
     L 2  line orthogonal to axis of rotation