Abstract:
The invention relates to a damper for vehicle components, particularly motor vehicle components such as steering tie rods and antiroll bar struts, with an elastic unit that is loaded in substantially axial direction of the component. To create a damper that will require little space but exhibit high reliability and a long service life and to permit a modular assembly from structurally simple and inexpensively producible parts for different applications, the elastic unit comprises at least two elastic elements  30  that are reciprocally, substantially pressure loaded and are disposed inside a housing ( 10 ) between the housing ( 10 ) and a coupling element ( 20 ) which transfers compression forces in substantially axial direction. The elastic elements ( 30 ) counteract an inclination and a coaxial offset of coupling element ( 20 ) with respect to the longitudinal axis of housing ( 10 ).

Description:
FIELD OF THE INVENTION 
     The invention relates to a damper for vehicle components, particularly motor vehicle components such as steering tie rods and antiroll bars, having an elastic unit that is loaded in substantially axial direction of the component. 
     BACKGROUND OF THE INVENTION 
     Particularly in the case of motor vehicle steering tie rods and antiroll bars, it is known to provide these chassis components with an elastic unit having a damper function. The elastic unit is loaded in substantially axial direction and thus permits limited axial travel, particularly to reduce or compensate any application of a sudden load. The damping of shocks introduced in the corresponding chassis component substantially reduces wear. Mounting the dampers on steering tie rods reduces steering susceptibility to shocks, reduces or compensates noise transmission, and provides a softer steering response. The market share of hydraulic and electrohydraulic assisted steering systems is increasing. Dampers will substantially reduce wear in the ball-and-socket joints of steering tie rods, racks, pinions, and the entire bearing, irrespective of whether the damper units are used in connection with axial or ball-and-socket joints. 
     In addition to their use for motor vehicle chassis components, these dampers may be used for general vehicle components such as the elastic suspension of motors and structural components, for example driver&#39;s cabs. 
     The prior art elastic units used as dampers have been formed by rubber-metal elements whose elastic parts are connected with the metal parts in such a way that the elastic parts are essentially subject to thrust loads. These known rubber-metal elements have the disadvantage that increased loads, particularly continuous loads, may cause the connection between metal and elastic parts to be loosened so that the dampers become ineffective. 
     To exclude these disadvantages as far as possible, the connecting surfaces between the metal and elastic components of the prior art rubber-metal elements must be made correspondingly large, which frequently causes space and installation-related problems. A further disadvantage of the prior art rubber-metal elements is that the application of a protective surface coating such as anode/cathode dip coating is limited because the related high temperatures would destroy the elastic elements and their bond with the metal elements. The coating of the metal parts is also limited because such coatings do not form a suitable bonding base for the elastic element. The bonding surface would therefore have to be reproduced after coating, which would entail additional costs. 
     The object of the invention is to create a damper of the above described type, which may be modularly assembled from simply designed and inexpensively producible separate parts for different applications and which requires little space and yet is distinguished by high reliability and a long component life. 
     SUMMARY OF THE INVENTION 
     The invention attains this object by providing a elastic unit comprising at least two elastic elements, which are reciprocally, substantially pressure loaded and arranged inside a housing between the housing and a coupling element that transfers pressure forces in substantially axial direction and which counteract any inclination or coaxial offset of the coupling element with respect to the longitudinal axis of the housing. 
     This embodiment of the elastic unit according to the invention creates a damper whose modular structure permits simple adaptation to the respective application. The stiffness of the elastic elements may be controlled not only by their dimensions but also by the Shore hardness of the respectively used materials, so that the respective elastic stiffness may be selected over a wide range without changing the geometry of the components. The protective surface coating of the metal parts may be freely selected to meet the respective requirements since there is no prior or subsequent rigid connection between the elastic elements on the one hand and the housing or coupling element on the other hand. The two elastic elements are reciprocally, substantially compressed and thus need not be rigidly connected to the metal parts but may instead be loosely arranged between the housing and the coupling element. Furthermore, the fact that the damper according to the invention lacks a rigid connection between the elastic elements and the housing or coupling element permits a space saving design. Consequently, the dampers are suitable even if space is limited, particularly for chassis components associated with motor vehicle steering systems taking into account the steering geometry. Finally, due to their compact structure, the dampers according to the invention are usable in connection with both axial and ball-and-socket joints. 
     According to an additional characteristic of the invention, the elastic elements are disposed in form-fitting manner as loose components between housing and coupling element. This permits a modular construction for the damper according to the invention so that it may be adapted to the respective application by selecting the corresponding module, particularly by selecting elastic elements that are made of a specific material. 
     According to a further characteristic of the invention, each elastic element includes a component that provides radial support of the coupling element in the housing and a component that permits an axial load transfer. In a preferred embodiment according to the invention, the elastic element component that provides radial support of the coupling element in the housing is made as a hollow cylinder whose surface fits against a cylindrical bore in the housing into which projects the shank of the coupling element. According to the invention, the component of the elastic element that effects the axial load transfer, via a surface tapered in cross-section fits against a corresponding, opposite housing surface, whereby the cross section may be circular, hyperbolic, parabolic or elliptical. As an alternative to this characteristic of the invention, it is proposed that a tapered surface of the elastic element component that effects the axial load transfer fit against a corresponding, opposite housing surface. 
     To permit greater manufacturing tolerances and to facilitate assembly, the hollow-cylinder elastic element component according to the invention may be provided with recesses that are preferably made as axially, annularly or helically extending grooves. This increases the compressibility of the elastic element both during assembly and in its mounted position. To prevent dirt from entering the recesses that are preferably formed as grooves, these grooves terminate at a distance from the end face of the elastic element to form an annular sealing lip. 
     According to an advantageous proposal of the invention, the elastic element comprises at least two parts. One part is preferably a supporting bush made, for example, of steel, aluminum or the like, in which is inserted a rubber element forming the second part. The bush is essentially a hollow cylinder and is provided at one end with an exterior circumferential collar. The rubber element fits tightly against the cylindrical area of the bush and completely overlaps the collar disposed at one end, whereby at least the area of the collar facing away from the rest of the bush in axial direction is overlapped and framed completely by the rubber element. Advantageously, the portion of the rubber-elastic element disposed on the collar in axial direction is formed in the manner of a compression spring, that is, as a thickened rubber area that absorbs compression forces. A distinguishing feature of the elastic element according to the invention is its simple and economical production and its simple application. Using a supporting bush with a cylindrical area and collar makes it possible to realize both the radial support and the axial mounting in a very simple manner so that the housing may also be designed very simply. 
     In a preferred embodiment of the invention, the coupling element is bolt-shaped with shanks effecting the radial support in the housing and a flange ring with an enlarged diameter to fit against the elastic element components effecting the axial load transfer. According to the invention, the flange ring of the coupling element is located between stop faces of the housing spaced at a distance from each other. This distance between the stop faces is greater than the axial thickness of the flange ring so that a short path results in axial direction of the damper. 
     To dampen the occurring motion, according to a further characteristic of the invention, each elastic element is provided with extensions that protrude into the clearance between the stop faces of the housing and are preferably formed as a closed ring. These extensions of the elastic element subject to compressive stress must be compressed before the flange ring of the coupling element will contact the corresponding stop face of the housing. 
     The invention finally proposes to make the housing in two parts with a base part to receive the coupling element and a sealing part to seal the base. This simplifies production and mounting of the damper. A further, inventory-related simplification is achieved if the two elastic elements are designed identically. 
     According to the invention, the housing and/or coupling element may form an integral part of a vehicle component or may be provided with a direct connection for a vehicle component. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawing depicts various exemplary embodiments of the damper according to the invention. 
     FIG. 1 shows a steering tie rod provided with a damper according to the invention. 
     FIG. 2 is an enlarged exploded view of the damper shown in FIG. 1 in cross-section. 
     FIG. 3 is an enlarged detail view of FIG.  1 . 
     FIG. 4 is a cross-section along line IV—IV in FIG.  2 . 
     FIG. 5 is an enlarged detail view of FIG.  2 . 
     FIG. 6 is a second embodiment of a steering tie rod provided with a damper according to the invention. 
     FIG. 7 is an exemplary embodiment of a chassis strut provided with a damper according to the invention. 
     FIG. 8 is a variant embodiment of a coupling element intended for a damper according to the invention. 
     FIG. 9 is half of a longitudinal section through a modified embodiment of a damper according to the invention. 
     FIG. 10 is an exploded view showing the two elastic elements and the coupling element of the damper according to FIG.  9 . 
     FIG. 11 shows an alternative embodiment of an elastic element. 
     FIG. 12 is an exploded view of a partial section of an assembly using the elastic element shown in FIG.  11 . 
     FIG. 13 shows the unit of FIG. 12 in its mounted state. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The steering tie rod shown in side view in FIG. 1 comprises a ball-and-socket joint K and an axial joint A, both known per se. The link pin A Z  of axial joint A is adjustably connected with joint housing K G  of ball-and-socket joint K by a rod unit S. 
     In the embodiment of the steering tie rod according to FIG. 1, a damper D is formed onto the joint housing K G  of ball-and-socket joint K, which is described below. According to the second embodiment of a steering tie rod, shown in FIG. 6, this damper D may also be formed onto link pin A Z  of the axial joint A. The structure and action of damper D in FIGS. 1 and 6 are otherwise identical. 
     As is evident particularly in the exploded view of FIG. 2, damper D comprises a housing  10 , a coupling element  20 , and two elastic elements  30 . These elastic elements  30  are designed identically in the first embodiment and are inserted as loose components between housing  10  and coupling element  20 . In the first embodiment, housing  10  of damper D forms a one-piece unit together with joint housing K G  of ball-and-socket joint K. A threaded rod integral with coupling element  20  connects coupling element  20  with rod unit S of the steering tie rod. 
     Each elastic element comprises a component  31  that effects radial support of coupling element  20  in housing  10  and a component  32  that permits an axial load transfer. In the exemplary embodiment shown in FIGS. 1 through 5, component  31  is made as a hollow cylinder whose surface fits against a cylindrical bore  11  of housing  10 , into which projects a cylindrical shank  21  of coupling element  20 . Coupling element  20  is provided with two such shanks  21  facing in opposite directions, between which a flange ring  22  with an enlarged diameter is formed. To accommodate this flange ring  22 , housing  10  has a bore  12  with a larger diameter. In the first embodiment, housing  10  comprises a base part with bores  11  and  12  and a sealing part  13 . Sealing part  13  is inserted into bore  12  and is secured against slipping out of the base part after mounting of damper D by a flanging of the housing edge as shown in the sectional view of FIG.  1 . 
     The two elastic elements  30  of the first exemplary embodiment are identical. They are mounted on shanks  21  of coupling element  20  such that the end faces of their components  32  permitting an axial load transfer fit against flange ring  22  of coupling element  20 , as shown in FIG. 1 and, in particular, in the enlarged detail view of FIG.  3 . The coupling element provided with the two elastic elements  30  is then inserted into housing  10  and sealed by sealing part  13 . In the exemplary embodiment, the elastic elements  30  are provided with a tapered surface  33  that fits against a corresponding tapered surface  14  of the base part of housing  10  and against a tapered surface  15  of the sealing part  13 , respectively, preferably in such a way as to achieve an initial stress obtained by selecting appropriate dimensions. 
     To obviate the necessity for tight manufacturing tolerances and permit both a certain inclination of the coupling element  20  with respect to the longitudinal axis of housing  10  and a small paraxial offset between coupling element  20  and housing  10 , the first embodiment provides for recesses in the cylindrical surface of component  31  of each elastic element  30  effecting the radial support of coupling element  20  in housing  10 . In the exemplary embodiment, these recesses are shaped as axial grooves  34 , as may be seen, in particular, in the cross section of FIG.  4 . To prevent dirt from entering these axial grooves  34  from the outside, axial grooves  34  terminate at a distance from the end face of component  31  of elastic element  30  so as to form an annular sealing lip  35 . This is most readily evident in the detail view of FIG.  5 . 
     The enlarged view in FIG. 3 finally shows that the base part of housing  10  and the sealing part  13  form stop faces  16 , which are spaced apart from each other by a distance exceeding the axial thickness of flange ring  22  of coupling element  20 . This permits coupling element  20  to move within housing  10  in substantially axial direction. To achieve a predetermined damping action when such movements occur, both elastic elements  30 , in the area of their component  32 , are provided with extensions projecting into the clearance between stop faces  16 , which in the exemplary embodiment form a closed ring  36 . A relative motion of flange ring  22  in substantially axial direction toward one of stop faces  16  thus initially causes a compression of component  32  of the prestressed component  32  [sic] of the respective elastic element  30 , which is approximately linear in its progression. Only when ring  36  of the respective compressed elastic element  30  sits between stop face  16  and flange ring  22 , there is a progressive increase in the elastic stiffness until flange ring  22  immediately contacts the respective stop face  16 . This prevents shocks in axial direction. Mounting the elastic element  30  under pretension furthermore has the effect of returning the coupling element  20  to its center position after the pressure is relieved. 
     Since the elastic elements  30  are loose components inserted between housing  10  and coupling element  20 , any type of surface protection may be applied to housing  10  and coupling element  20  without taking into consideration a rigid connection between elastic elements  30  on the one hand and housing  10  or coupling element  20  on the other hand. By appropriate selection of the dimensions and the material of elastic element  30 , damper D can thus be readily adapted to the respective application. 
     In the first exemplary embodiment illustrated by FIGS. 1 through 5, damper D forms an integral component of a ball-and-socket joint K associated with the steering tie rod. FIG. 6, on the other hand, shows a steering tie rod where damper D forms an integral component with link pin A Z  of axial joint A. FIG. 7 shows an embodiment with a chassis strut F provided at its two ends with a ball-and-socket joint K, respectively. In this embodiment, damper D with housing  10  is formed onto the housing of one ball-and-socket joint K and a coupling element  20  is formed onto chassis strut F. The other components of damper D correspond to the previously discussed components of the embodiment shown in FIGS. 1 through 5. 
     In the exemplary embodiment shown in FIG. 8, a damper coupling element  20  is provided with a threaded through-hole  23  to receive a threaded stem S Z  of a rod unit S. In this embodiment, the two elastic elements  30  are identical. Their design corresponds to that described with reference to the first exemplary embodiment. 
     Finally, FIGS. 9 and 10 show an additional embodiment of a damper D wherein the two elastic elements  30  differ from each other. Elastic element  30  shown on the left in the exploded view of FIG. 10 is a full-walled element with smaller dimensions than the other elastic element  30 , which is provided with a through-hole as described above. In this embodiment each elastic element is again provided with a component  31  effecting a radial support of coupling element  20  in housing  10  and a component  32  for the axial load transfer. In this embodiment, tapered surfaces are again provided for the respective elastic element  30  to fit against housing  10  and against sealing part  13 , respectively. Instead of two shanks  21 , however, the coupling element  20  of this embodiment has only one shank  21 . The other shank is replaced by a blind hole  24  on the other side of flange ring  22 , into which projects cylindrical component  31  of the smaller elastic element  30  for radial support of coupling element  20  in housing  10 . 
     FIG. 11 shows an alternative embodiment of an elastic element. This element is made in two parts and comprises a supporting bush  41  made of steel, aluminum or the like and a rubber element  42 . Bush  41  has a cylindrical area  43  that is provided with a collar  44  on one side. Rubber element  42  is inserted in form-fitting manner in supporting bush  41  and is provided with a cylindrical area extending over the axial length of the supporting bush, which in the area of the collar has a collar projection  46  that completely overlaps the collar. A part  47  of rubber element  42  absorbing axial forces in the manner of a compression spring is attached to the collar in axial direction. FIGS. 12 and 13 show the mounting area for the elastic element according to FIG. 11, whereby a damper housing  50  is disposed directly adjacent to an axial joint A. This housing has a first hollow cylinder area  54  in which an elastic element  40  may be inserted. Coupling element  51  is then inserted as described above and an elastic element is mounted from the other side. The use of supporting bush  41 , which provides the elastic element with a substantially perpendicular collar projection, greatly simplifies the assembly for the absorption of axial forces. After mounting, the second elastic element  40  is overlapped by a mounting bush  52 , which has a collar projection and is inserted into a third hollow-cylinder area  56 . Thus elastic elements  40  in hollow-cylinder areas  54 ,  55 , together with mounting bush  52 , are optimally positioned in axial direction with respect to each other and, at the same time, are optimally radially supported. The projection of damper housing  50  forming the hollow-cylinder area  56  is provided with a projecting flanged edge that is subsequently pressed in. The assembled state is shown in FIG.  13 .