Patent Publication Number: US-2019186586-A1

Title: Bushing

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the national stage of PCT/EP2017/064230, filed Jun. 12, 2017, designating the United States and claiming priority from German patent application no. 10 2016 215 735.3, filed Aug. 23, 2016, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a bushing, preferably a hydraulic bushing, including an inner part and an outer part with a supporting spring radially connecting the inner part and the outer part to each other. A stop element is arranged between the inner part and the outer part. The stop element is connected to the inner part or to the outer part and is configured so as to cause the stop element to limit the radial spring travel between the inner part and the outer part in a predetermined manner. 
     BACKGROUND OF THE INVENTION 
     In the field of vibration-damping devices, inter alia, elastomer bushings which can be used, inter alia, as chassis bearings are known. The devices are usually embodied either as conventional rubber/metal bushings or as hydraulic bushings. In any case, an inner part of the bushing is connected in a radial direction to an outer part via an elastic supporting spring or a pair of elastic supporting springs which are spaced apart in the longitudinal direction, with the result that both radial movements and movements in the longitudinal direction as well as torsion can be absorbed in an elastically damping fashion. 
     Such bushings and, in particular, hydraulic bushings, can be equipped with stops in order to limit the maximum travel of the spring compression in the radial direction, that is, the spring travel. In this context, a differentiation is made between internal and external stops, wherein the internal stops are arranged in the longitudinal direction between the supporting springs and/or within the fluid chambers, and the external stops are arranged outside. 
     The stops are usually composed of a strength member which is connected in a fixed fashion to the inner part or to the outer part, and a rubber layer which covers the strength member with respect to the surroundings, such as for example, the fluid chamber. The stop and/or the rubber layer thereof, can come into contact in the radial direction with the inner part or outer part lying opposite and as a result limit the maximum radial spring compression. 
     It is disadvantageous here that in the case of the maximum radial spring compression, for example, as a result of braking, high torsional forces can also occur simultaneously as result of the spring compression of the wheels. Owing to the resulting torsional stresses with simultaneous high radial stress, the stop and/or the rubber coating thereof can be made to rub against the inner part or outer part lying opposite, or even be sheared off. This can give rise to wear in itself and/or to accelerated wear and can even lead to the destruction of the stop. 
     In addition, it is disadvantageous with external stops generally that they require a relatively large amount of space, which can adversely affect the size of the working chamber, particularly in the longitudinal direction. This can give rise to a worse performance with respect to the damping properties. 
     With internal stops it is disadvantageous generally that the available installation space as a rule is limited in the longitudinal direction between elastic supporting springs. This can result in a very high surface pressure for the rubber coating of the stop. 
     Furthermore, internal stops are as a rule embodied in such way that they are connected to the inner part, which is usually composed of metal. The inner metal part can have, for improving the connection, elevated portions which require either manufacture as a pressure die cast part or as a small tube with an integrally injection molded-on stop contour. It can be disadvantageous in the case of manufacture as a pressure die cast part that as a result the weight of the inner part can be increased, which can have disadvantageous effects on the damping properties of the bushing. It can be disadvantageous in the case of manufacture as a small tube with an integrally injection molded-on stop contour that this can make the manufacture more complex. 
     If the inner part is configured to absorb high torsional forces in steel, this can lead to the contour of the stop being formed separately and then being fixedly connected to the stop, in order to reduce the weight and/or the costs. However, this can require a complex process for the integral injection molding of a plastic or pressure die cast contour and additionally damage the protection against corrosion. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to make available a bushing of the type described beginning with an improved service life of the stop. In particular, it is sought to reduce the wear of the stop. This is to be achieved, in particular, as simply and/or cost-effectively as possible. In particular, a large stop face is to be made possible. In particular, such a bushing is to be provided with additional possibilities for adjusting the stop characteristic curve and/or with additional cardanic flexibility of the stop. The intention is to obtain at least one alternative to known bushings. 
     Bushings are known from the prior art and have the disadvantages described above. 
     In order to overcome these disadvantages, according to the invention the stop element is elastically connected to the inner part or to the outer part in such a way that the stop element can be elastically twisted relative to the inner part or relative to the outer part. In this context, the dimension of this possible torsion is configured in such a way that when there is contact of the stop element with the inner part and/or the outer part, the relative torsion between the inner part and the outer part can be at least largely, preferably as far as possible completely, absorbed by the elastic connection of the stop element. 
     In other words, the stop element can make contact with the inner part and/or the outer part, and in the case of torsion which then occurs between the inner part and the outer part these torsional forces can be largely to completely absorbed by means of the elastic connection thereof, with the result that only a small relative movement, extending as far as possible to no relative movement, comes about between the stop element and the inner part with which contact has been made or the outer part with which contact has been made at the contact point. As result, the torsional loading for the stop element can be reduced to completely avoided, with the result that the service life of the stop element can be made longer. 
     It is also advantageous here that the elastic connection between the stop element and the inner part or outer part can also absorb cardanic stresses, since the stop element can also adapt better to these movements and/or loads. This can also increase the service life of the stop element. 
     According to one aspect of the present invention, the stop element is connected at least in certain sections, preferably over the entire surface, to the inner part or to the outer part via an elastic connecting layer. The thickness of the connecting layer, that is, the radial extent of the connecting layer, is to be dimensioned here in such a way that the previously described advantageous effect of the absorption of torsion by the connecting layer can be achieved. The connecting layer can for this purpose be provided in certain sections between the stop element and the inner part or the outer part insofar as this is sufficient to achieve the desired effect. 
     The connecting layer is preferably to be provided over the entire surface between the stop element and the inner part or the outer part, to permit the torsional forces to be absorbed to be distributed as uniformly as possible over the connecting layer. This can also increase the service life of the connecting layer. 
     It is also advantageous here that the connecting layer can bring about acoustic decoupling. As a result, penetration or passing on an acoustic signal into the vehicle structure can be prevented or at least reduced. 
     According to a further aspect of the present invention, the stop element has, at least in certain sections and preferably over the entire surface, an elastic outer layer which is oriented radially in the direction of the spring travel. As result, elastic damping and therefore also elastic absorption of torsional forces can therefore additionally also take place on that side of the stop element which radially faces the contact with the inner part or the outer part. This can distribute the torsional loading onto both elastic layers and reduce the elastic connection between the stop element and inner part or outer part, with the result that the elastic connection can hold for longer. 
     According to a further aspect of the present invention, the elastic outer layer has structuring, which is preferably in the form of radial projections and is configured to deform elastically on contact. As result, the absorption of contact—and in particular of torsional forces—can be improved. 
     According to a further aspect of the present invention, the stop element is formed substantially in the direction of the spring travel, from two stop regions which lie diametrically opposite one another. In this way, the effect of the stop element can be applied to an amplified degree in this spatial direction. 
     According to a further aspect of the present invention, the stop element is made narrower substantially perpendicularly with respect to the direction of the spring travel. As result, the effect of the stop element in this spatial direction can be avoided. In addition, as result, a space can be formed within the bushing, in order for example, to arrange the fluid-filled chambers of a hydraulic bushing. 
     According to a further aspect of the present invention, the inner part and the stop element are composed of different materials. In this way, the damping behaviour of the bushing can be influenced. In particular, the inner part and the stop element can be configured and optimized differently by means of the respective materials. As result, it is also possible, where appropriate, to reduce material costs and/or manufacturing costs. 
     The article weight can also be influenced positively by this flexibility in the selection of material and in the configuration of the inner part and stop element components. 
     According to a further aspect of the present invention, the inner part is composed of steel or of aluminum, and the stop element is composed of plastic. As result, the inner part can absorb high loads and the stop element can be embodied in a comparatively lightweight fashion. 
     According to a further aspect of the present invention, the stop element has at least one passage, preferably a multiplicity of passages, which extends/extend preferably substantially, and particularly preferably entirely, in the longitudinal direction. In this way, the weight of the stop element can be reduced without substantially reducing its stability. In addition, a better connection can be brought about between the stop element and its elastic connection by virtue of the fact that the elastic connecting material can penetrate the passage. If the passage is embodied linearly in the longitudinal direction, this can simplify the manufacture, for example, as an injection molded part or else by means of drilling. 
     According to further aspect of the present invention, at least one passage is arranged in a first stop region, and at least one passage is arranged in a second stop region. In this way, it is possible to bring about a connection between the stop element and its elastic connection which is as uniform as possible. 
     According to a further aspect of the present invention, at least one first chamber and one second chamber are embodied between the inner part and the outer part, wherein the two chambers are connected to one another in a media-conducting fashion. As result, additional damping of the bushing can be achieved. 
     According to a further aspect of the present invention, the two chambers are filled with a fluid. As result, the present invention can be applied to a hydraulic bushing. 
     The present invention also relates to a chassis or to an assembly having at least one bushing as described above. In this way, the previously described properties and advantages of a bushing according to the invention can be applied to a chassis and/or to an assembly. 
     The present invention also relates to a vehicle having a chassis and/or having an assembly as described above. In this way, the previously described properties and advantages of a chassis according to the invention and/or of an assembly according to the invention can be applied to a vehicle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described with reference to the drawings wherein: 
         FIG. 1  shows a schematic illustration of a longitudinal section through a bushing according to the invention from the side; and, 
         FIG. 2  shows a schematic illustration of a cross section A through a bushing according to the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
     A bushing  1  according to the invention is illustrated in  FIGS. 1 and 2  in the Cartesian coordinates of a longitudinal direction X, which can also be referred to as an axial direction X, a transverse direction Y, and a vertical direction Z. The transverse direction Y can also be referred to as a width Y, and the vertical direction Z can also be referred to as a height Z. The bushing  1  has a longitudinal axis L, with respect to which a radial direction R is oriented perpendicularly. A circumferential direction U runs around the longitudinal axis L. 
     The bushing  1  has an inner part  10  in the form of an inner sleeve  10 . The bushing  1  also has an outer part  11  in the form of an outer sleeve  11 . Arranged in the height Z between the inner sleeve  10  and the outer sleeve  11  is an elastomer supporting spring  12  which connects the inner sleeve  10  and the outer sleeve  11  elastically to one another in the radial direction R, cf. for example,  FIG. 1 . The elastomer supporting spring  12  has here in the longitudinal direction X a left-hand supporting spring wall  12   a  and a right-hand supporting spring wall  12   b.    
     Two fluid-full chambers  13 ,  14 , which are connected in a fluid-conducting fashion to one another (not illustrated) and serve to perform fluidic damping of the bushing  1 , are formed in the longitudinal direction X by the two supporting spring walls  12   a ,  12   b  and by the inner sleeve  10  and the outer sleeve  11  in the radial direction R. In this context, the first upper fluid chamber  13  is arranged in the height Z above the second lower fluid chamber  14 , see for example,  FIG. 2 . The two fluid chambers  13 ,  14  are separated from one another by two horizontally running chamber walls  15 . 
     Arranged at the inner sleeve  10 , within the two fluid chambers  13 ,  14 , is a stop element  16  which extends radially away from the inner sleeve  10  and as result limits the spring travel D in the radial direction R, by virtue of the fact that the radially outer edge of the stop element  16  can enter into contact with the inner side of the outer sleeve  11 . In order to reduce the weight of the bushing  1 , the stop element  16  is fabricated from plastic. The inner sleeve  10  is fabricated from steel, in order to be able to absorb relatively high loads. The inner sleeve  10  has at the end side knurl-like toothing arrangements, in order to prevent rotation in the installed state (not illustrated). 
     The stop element  16  is embedded in the elastic material of the supporting spring  12 , in the longitudinal direction X between the two supporting spring walls  12   a  and  12   b , and is completely surrounded by them. In this way, the stop element  16  is elastically connected to the inner sleeve  10  via the elastic material of the supporting spring  12  as an elastic connecting layer  17   a . In this context, the elastic connecting layer  17   a  is dimensioned in respect of its thickness, that is, in the radial direction R, in such a way that when there is contact between the stop element  16  and the inner side of the outer sleeve  11 , possible torsional loading relatively between the inner sleeve  10  and the outer sleeve  11  can be as far as possible completely absorbed by the elastic connecting layer  17   a . This can relieve the torsional loading acting on the stop element  16  and as a result increase the service life of the stop element  16 . In addition, the connecting layer  17   a  brings about acoustic decoupling, that is, the penetration or passing on of an acoustic signal into the vehicle structure can as a result be prevented or at least reduced. 
     The elastic material of the supporting spring  12  also surrounds the stop element  16  in such a way that an elastic outer layer  17   b  of the stop element  16  is also formed, which elastic outer layer  17   b  performs the contact with the inner side of the outer sleeve  11 . As result, torsional loading can also be accommodated elastically. In order to improve this, the elastic outer layer  17   b  of the stop element  16  has structuring  19  in the form of radial projections  19  which can deform elastically and as a result effectively absorb loading. 
     This stop element  16  has a first stop region  16   a , which is the upper one in terms of the height Z, and a second stop region  16   b , which is the lower one in terms of the height Z, with the result that the bushing  1  has an effect of the stop element  16  substantially in terms of the height Z. No stop effect occurs transversely with respect thereto, that is, in the transverse direction Y. The two fluid chambers  13 ,  14  are substantially arranged in this region. 
     The two stop regions  16   a ,  16   b  each have a multiplicity of passages  18  which run in the longitudinal direction X and are penetrated by the elastic material of the supporting spring  12 . As a result, a more durable connection can be produced between the elastic material of the supporting spring  12  and the stop element  16 . 
     In this way, according to the invention a bushing  1  can be formed with an improved service life of the stop element  16 . In particular, the wear of the stop element  16  can be reduced. This is done simply and cost-effectively. At the same time, a comparatively large stop surface can be formed. Such a bushing  1  also offers additional possibilities for the adjustment of the stop characteristic curve and additional Cardanic flexibility of the stop element  16 . 
     It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims. 
     LIST OF REFERENCE NUMERALS: 
     
         
         A Cross section 
         D Spring travel in the radial direction R 
         L Longitudinal axis 
         R Radial direction 
         U Circumferential direction 
         X Axial direction; longitudinal direction 
         Y Transverse direction; width 
         Z Vertical direction; height 
           1  (Hydraulically damping) bushing 
           10  Inner part; inner sleeve 
           11  Outer part; outer sleeve 
           12  Elastomer supporting spring 
           12   a  Left-hand supporting spring wall 
           12   b  Right-hand supporting spring wall 
           13  First (upper) (fluid) chamber 
           14  Second (lower) (fluid) chamber 
           15  Chamber wall between first chamber  13  and second chamber  14   
           16  Stop element 
           16   a  First (upper) stop region of the stop element  16   
           16   b  Second (lower) stop region of the stop element  16   
           17   a  Elastic connecting layer 
           17   b  Elastic outer layer 
           18  (Longitudinal) passages of the stop element  16   
           19  Structuring or radial projections of the first stop region  16   a  or of the second stop region  16   b