Patent Publication Number: US-2007108001-A1

Title: Hydraulic bearing and processes for manufacturing a hydraulic bearing

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      This application claims the benefit of priority under 35 U.S.C. § 119 of German Application DE 10 2005 054 851.2 filed Nov. 15, 2005, the entire contents of which are incorporated herein by reference.  
     FIELD OF THE INVENTION  
      The present invention pertains to a hydraulic bearing and to suitable processes for manufacturing a hydraulic bearing.  
     BACKGROUND OF THE INVENTION  
      Bearings designed as simple rubber bushings with an inner part, an outer sleeve or an outer tube and an elastomeric bearing body arranged between them are frequently used in the automobile industry and specifically above all in the area of the chassis. However, hydraulic damping methods are increasingly used to support the damping action of the elastomeric bearing body. These hydraulic bearings have at least two damping agent chambers, which are formed in the bearing body and which are filled with a viscous damping agent and are connected to one another in a flow-conducting manner through at least one channel. Concerning the design of the hydraulic bearings, it must be ensured in this connection that the viscous damping agent cannot escape, i.e., that the bearing is sealed and also remains sealed for the necessary service life. The hydraulic bearings have seals for this purpose.  
      One measure, which can frequently be encountered in practice in case of elastomeric bush bearings, is, for example, to design the elastomeric bearing body with an oversize compared to the outer sleeve accommodating the bearing in the area of its axial ends. A so-called calibration takes place in the course of the mounting of the hydraulic bearing and when the outer tube is being pushed on by the outside dimensions of the outer tube being reduced at least in the area of its axial ends by means of devices suitable for this purpose. A pretension, which leads to sealing action, is generated hereby in the elastomeric sealing areas formed at the axial ends of the bearing body. A bearing designed in this manner is disclosed, for example, in DE 28 41505 A1.  
      The latter solution has proved to be successful at least in respect to the sealing of the bearings against the escape of the viscous damping agent. However, it is also known for certain applications that hydraulic bearings can be designed such that vacuum is present against the ambient pressure in their damping agent chambers formed in the bearing body to accommodate the viscous damping agent. There is a risk in this case that even though the damping agent will not escape from the damping agent chambers, air will penetrate into the damping agent chambers and the function of the component will be compromised as a consequence of an increase in the pressure inside the chambers. This risk arises from the fact that the viscosity of the air is markedly lower than that of the damping agent present in the damping agent chambers, so that even though the sealing action achieved by means of a sealing lip formed at the bearing may be sufficient for the damping agent, it is not sufficient for sealing against the penetration of air. Air may thus penetrate into the damping agent chambers, especially as a consequence of temperature changes.  
      A similar problem also arises in case of the design according to EP 1 291 549 A1. This document describes a hydraulic bearing, which comprises a cylindrical inner part, an elastomeric bearing body surrounding the inner part and an outer sleeve accommodating the inner part with the bearing body, wherein two damping agent chambers, which are filled with a viscous damping agent and are connected to one another through a flow or throttle channel, are arranged in the bearing body. The damping agent chambers are sealed against the escape of the damping agent by sealing lips formed at the axial ends of the hydraulic bearing, and a volume, which is arranged separated from the damping agent chambers and the channel connecting same, is formed between the sealing lips, and this volume is filled with a viscous liquid.  
      It is necessary in this hydraulic bearing to use the same liquid in the volumes between the sealing lips and the damping agent chambers because a drawback of this prior-art embodiment is that air that has once penetrated into the sealing area can also enter the damping agent chambers via recesses at the axially inner sealing lip. However, this is to be avoided by all means, because the hydraulic bearing would thus become unfit for use.  
     SUMMARY OF THE INVENTION  
      The object of the present invention is to provide a hydraulic bearing that can be mounted in a simple manner, can be manufactured at a low cost and reliably guarantees the sealing action of the finished hydraulic bearing both against the escape of damping agent from the bearing and against the penetration of air into the bearing. Furthermore, corresponding processes for manufacturing such a hydraulic bearing are to be proposed.  
      The hydraulic bearing according to the present invention may be, for example, a hydraulic elastomeric bush bearing (the basic concepts of the design being known). It comprises an inner part, an elastomeric bearing body, which surrounds the inner part and is connected to same by vulcanization, as well as an outer sleeve accommodating the aforementioned components, i.e., the inner part with the bearing body. To embody hydraulic damping, at least two damping agent chambers, which are filled with a viscous damping agent and are connected to one another through a throttle or flow channel, are arranged in the elastomeric bearing body. The damping agent chambers are sealed against the escape of the damping agent by sealing lips, which may be present, for example, at the axial front sides of the hydraulic bearing in a hydraulic bearing designed as an elastomeric bush bearing. These sealing lips are preferably embodied by areas of the elastomeric bearing body that have an enlarged external diameter compared to the internal diameter of the outer sleeve. When the outer sleeve is mounted or pushed on the bearing body, a pretension is generated hereby in the elastomer in the areas with an oversize. Reliable sealing is formed as a result. It shall be emphasized that the volume formed between the sealing lips is not connected to the damping agent chambers in a flow-conducting manner and it is thus a volume arranged separated from the damping agent chambers and the channel connecting these.  
      It is proposed according to the present invention that a rheological liquid each be filled into the at least one volume between the sealing lips. Magneto-rheological and electro-rheological substances are generally known. These substances are liquids, gel-like suspensions or similar substances, whose viscosity undergoes considerable changes and which may even pass over from the liquid into the solid state of aggregation due to the application of a magnetic or electric field.  
      Consequently, the viscosity of the Theological liquid introduced into the at least one volume between the sealing lips can be set as desired with the solution according to the present invention. The bearing properties as a whole can thus be affected without there arising a considerable extra effort in manufacture. The hydraulic bearing has a simple design and is therefore very inexpensive. Substantially improved sealing action is achieved compared to prior-art solutions.  
      Various possibilities, which also depend, last but not least, on the particular application, can be considered for the geometric design of the seals and that of the Theological liquid. Thus, it is conceivable to form corresponding seals by channel grooves extending completely circularly at the two axial ends of the bearing. However, it is also possible to interrupt such a groove at points at which sealing action is not necessary, for example, in the area of a load-bearing support. The seals have a segmented design in this case.  
      At least one correspondingly designed volume is preferably present at each of the axial ends of the bearing in case of hydraulic bearings that are designed as elastomeric bush bearings.  
      Magneto-rheological or electro-rheological substances may be used as the Theological liquid for a hydraulic bearing according to the present invention. Thus, the energy supplied originates from a magnetic or electric field. Accordingly, the hydraulic bearing may have at least one permanent magnet, an electromagnet, a coil system or means for generating an electric field for setting the properties of the Theological liquid in the volume. The decision in favor of a principle of action and hence of a particular rheological liquid having the above-mentioned properties depends on the design conditions of the hydraulic bearing and the site of installation intended for it in the vehicle.  
      It is advantageous to use an injection method to fill the at least one volume between the sealing lips with the rheological liquid. Corresponding to one embodiment of the present invention, at least one filling opening is provided for this purpose either in the elastomeric bearing body or in the outer sleeve. This filling opening can be closed after the volume has been filled.  
      A hydraulic bearing according to the present invention may have the peculiarity that there is a flow-conducting connection between at least two of its volumes. Corresponding to one embodiment of this idea, it is possible, moreover, for all volumes of the hydraulic bearing to have flow-conducting connections with one another.  
      Corresponding to a practical embodiment, ethylene glycol may be used as the viscous liquid in the damping agent chambers to achieve the damping action.  
      The manufacture of the hydraulic bearing according to the present invention is relatively simple. After the inner part with the elastomeric bearing body vulcanized to it as well as the outer sleeve have been prefabricated, the outer sleeve is first pushed onto the elastomeric bearing body up to the inner sealing lip facing the damping agent chamber, and the damping agent chambers are filled with the damping agent at the same time. Corresponding to a process according to the present invention for manufacturing a hydraulic bearing, which is presented here, the outer sleeve is then pushed completely over the elastomeric bearing body of the hydraulic bearing for the subsequent filling of the at least one volume in order to make it subsequently possible to fill the volume or the volumes with the rheological liquid through the respective filling opening.  
      Another process for manufacturing a hydraulic bearing is characterized in that the damping agent chambers are first filled with the damping agent and the outer sleeve is first pushed onto the hydraulic bearing only up to the axially inner sealing lip, i.e., the sealing lip facing the damping agent chamber, for the subsequent filling of the volume with a rheological liquid, to push the outer sleeve completely over the elastomeric bearing body after the volume has been filled with the rheological liquid. Unlike in the process described above, the at least one volume between the sealing lips can be filled here, for example, in a liquid bath in a very simple manner.  
      Cleaning of the volumes after the filling of the damping agent chambers, which becomes necessary, do not need to be mentioned here separately.  
      Furthermore, it is advantageous if the filling of the damping agent chamber for manufacturing a hydraulic bearing according to the present invention is carried out directly in a damping agent bath. The outer sleeve is logically also pushed over the elastomeric bearing body in the damping agent liquid. The filling of the damping agent chambers can thus be carried out without inclusions of air under the liquid surface, which guarantees an end product of high quality.  
      The processes according to the present invention are also applicable to a hydraulic bearing provided with volumes on both sides. The filling of the volumes can now be carried out alternatingly or simultaneously.  
      Calibration taking place after the mounting of the hydraulic bearing, i.e., the reduction of the outer circumference of the outer sleeve at least in some sections, has considerable advantages, especially in the process according to the present invention. The increase in pressure brought about by the calibration in the sealing areas guarantees reliable sealing of the volumes and of the damping agent chambers against each other and against the environment.  
      An injection nozzle, which is guided by the filling opening and is removed after the filling, may be used, e.g., to fill the at least one volume.  
      The present invention shall be explained in greater detail below on the basis of an exemplary embodiment. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      In the drawings:  
       FIG. 1  is an axial sectional detail cut away view of a hydraulic bearing according to a first process step of a first process according to the present invention;  
       FIG. 2  is an axial sectional detail cut away view of a hydraulic bearing according to a second process step according to the present invention;  
       FIG. 3  is an axial sectional detail cut away view of a hydraulic bearing according to a third process step according to the present invention;  
       FIG. 4  is an axial sectional detail cut away view of a completely mounted hydraulic bearing according to the present invention;  
       FIG. 5  is an axial sectional detail cut away view of a hydraulic bearing corresponding to a second process according to the present invention;  
       FIG. 6  is a schematic side view showing the connection between damping agent chambers as well as the interconnection of end volumes of a hydraulic bearing according to the present invention; and  
       FIG. 7  is a schematic sectional view taken at line  7 - 7  of  FIG. 6 .  
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Referring to the drawings in particular, the hydraulic bearing shown in the figures comprises an inner part  1  made of metal or plastic, an elastomeric bearing body  2  connected to the inner part  1  by vulcanization and an outer sleeve  3 , which accommodates the inner part  1  with the bearing body  2  and is tubular in this example. The outer sleeve  3  may likewise be made of metal or plastic. Two damping agent chambers  4 ,  4 ′, which are filled with a viscous damping agent and which are connected to one another through an overflow channel or throttle channel  44 , which is shown in  FIGS. 6 and 7 , are formed in the bearing body  2  ( FIGS. 1-5  showing only one half of the body), which is essentially rotationally symmetrical with the axis X.  FIGS. 6 and 7  shows that the hydraulic bearing has the same design on both ends, i.e., it is mirror symmetrical to a plane extending at right angles to the central longitudinal axis X of the bearing.  
      In the area of the front-side end of the bearing, the elastomeric bearing body  2 , which is designed as a rubber spring here, has a section with an enlarged outside diameter. The outside diameter of the bearing body  2  is made with an oversize compared to the inside diameter of the outer sleeve  3 . By pushing the outer sleeve  3  onto the bearing body  2  and an optional calibration performed subsequent thereto, i.e., a reduction of the diameter of the outer sleeve  3 , pretension is generated in the sections of the bearing body  2  whose diameter is increased, especially at the axial ends of the bearing body, so that these areas act as a respective sealing lip  5  or  5 ′. The bearing is reliably sealed thereby against the escape of the viscous liquid present in the damping agent chambers  4 ,  4 ′. The volume  6  present between the sealing lips  5 ,  5 ′ has no flow-conducting connection with the damping agent chambers  4 ,  4 ′. This volume  6  is either a circular channel, which is not to be confused with the throttle channel, or a channel groove or chambers formed in some sections along the circumference of the hydraulic bearing, whose volume is usually, but not necessarily, smaller than that of the damping agent chambers  4 ,  4 ′ provided for generating the damping action of the bearing.  
      The inner part  1  and the outer sleeve  3  are manufactured separately in both processes according to the present invention for manufacturing a hydraulic bearing. The elastomeric bearing body  2  is subsequently connected to the inner part  1 , which is possible by means of a vulcanization process in a manner known per se.  
      The components of the hydraulic bearing, thus prefabricated, are subsequently introduced into a bath containing damping liquid, in which the outer sleeve  3  is pushed on in the direction of arrow A shown in  FIG. 1  under the liquid surface.  
      The outer sleeve  3  is now pushed on only up to the inner sealing lip  5 ′, i.e., the sealing lip facing the damping agent chamber, as this appears from  FIG. 2 . The assembly unit thus assembled is removed from the damping agent bath and at least the area of the volume  6  formed between the sealing lips  5  and  5 ′ is cleaned, which is possible with a rinsing agent that is suitable for this.  
      The processes being present here differ from each other after this cleaning. Thus, to manufacture a hydraulic bearing, the entire hydraulic bearing may be immersed into a bath of the rheological liquid  7 , which is enclosed in volume  6  after the hydraulic bearing has been finished. A simplified view of the volume  6  filled with the Theological liquid  7  is also shown in  FIG. 2 .  
      As is shown in  FIG. 3 , the outer sleeve  3  is pushed beyond the axial end of the hydraulic bearing in the next process step to the extent that a projection  11  of the outer sleeve  3  will be formed, whose length corresponds to the distance between the sealing lips  5  and  5 ′ on the axially opposite side of the left-hand part of the hydraulic bearing as shown in  FIG. 3 . Thus, the other end of the outer sleeve  3 , which is not shown in  FIG. 3 , is sealingly in contact with the inner sealing lip  5 ′ present there, as this was already explained in the reverse direction in connection with the view in  FIG. 2 . The second volume  6 ′ can thus likewise be filled with the rheological liquid  7 .  
      The hydraulic bearing is finally finished by displacing the outer sleeve  3  in the direction opposite the direction of arrow A relative to the central longitudinal axis X of the bearing, whereby flush closure of the front sides of the elastomeric bearing element  2  and of the outer sleeve  3  is achieved. The completely mounted hydraulic bearing is shown in a sectional view in  FIG. 4 .  
      A permanent magnet, which is embedded in the elastomeric bearing body  2 , is designated by  10  in the figures in a highly simplified form. However, it is also possible to use an electromagnet or a coil system here. Feed lines that may be necessary can be led to the outside through the elastomeric bearing body  2  and/or the outer sleeve  3 .  
      Regardless of the pressure in the damping agent chambers  4 ,  4 ′, a quantity of Theological liquid  7 , by which a pressure, preferably an overpressure, is generated in relation to the ambient pressure in the course of the pushing on and the subsequent calibration of the outer sleeve  3 , is introduced into the damping agent chambers  4 ,  4 ′. Since the sealing action of the sealing lips  5 ,  5 ′ against the viscous damping agent is sufficient in any case, the damping agent does not escape from the volumes  6 ,  6 ′ either to the outside or into the damping agent chambers  4 ,  4 ′. At the same time, the pressure prevailing in the volumes  6 ,  6 ′ reliably prevents air from penetrating from the environment into the bearing and into the damping agent chambers  4 ,  4 ′ of the bearing, which may be under a vacuum.  
      The hydraulic bearing illustrated in  FIG. 5  has a design that is basically identical to the design described above. The same process steps as those described before are also observed in this hydraulic bearing until the filling of the damping agent chambers.  
      After the filling of the damping agent chambers, the volumes  6  are cleaned and the outer sleeve  3  is subsequently pushed onto the elastomeric bearing body  2 . The rheological liquid  7  can now be introduced into the volume  6  by means of an injection nozzle  9 . A filling opening  8 , through which the injection nozzle  9  is passed into the volume  6 , is provided in the outer sleeve  3  for this. After filling the volume  6  with the liquid in the direction of arrow B in  FIG. 5 , the injection nozzle  9  is removed from the filling opening against the direction of arrow B. This operation is concluded by a subsequent sealing of the volume  6  against the environment.  
      The schematic showing of  FIG. 6  illustrates the basically symmetrical design of the sealing (additional) volumes  6  and  6 ′ at each end and the damping agent chambers  4 ,  4 ′, that are on each side.  FIGS. 6 and 7  also illustrate the flow-conducting connection  66  between the two volumes  6  and  6 ′. The flow-conducting connection  66  may be provided between an outer part of the elastomeric bearing body  2  (provided in a groove or recess of the elastomeric bearing body  2 ) and the inner surface adjacent to the outer sleeve  3  and between the damping agent chambers  4 ,  4 ′, but opposite the throttle channel  44 .  
      While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.