Abstract:
A method for producing a lubricant feed in an axial bearing, wherein the lubricant feed is designed as a channel guiding lubricant from a lubricant pocket of the axial bearing, includes the following steps: preparing an initial axial bearing mold, stamping a groove in the area of the initial mold in which the channel is planned; embossing and putting through material on at least one or both sides of the groove along at least one segment of the groove; stamping the material on the side of the groove toward the groove so that the material and the groove form the channel.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a method for producing a lubricant feed line of a thrust bearing and a thrust bearing which can be used in particular for turbochargers, in motor vehicles for example. 
     Turbochargers generally serve to improve the efficiency of a combustion engine and consequently to increase its performance. For this purpose a shaft is rotatably mounted, for example by means of two radial bearings, around the longitudinal axis in the casing of the turbocharger. A turbine wheel and a compressor wheel are accordingly arranged on the shaft. Strong axial forces can occur due to fluid flows which impinge on the turbine wheel and the compressor wheel. Generally such axial forces cannot be suitably absorbed by the radial bearings. For this reason at least one or two additional thrust bearings are normally provided in order to absorb these axial forces. 
     Very high demands are normally placed on the mounting of the shaft of a turbocharger. Thus, the turbocharger is exposed to high temperatures, since hot exhaust gas, for example, is used to drive the turbine wheel. Furthermore the shaft of a turbocharger reaches very high rotational speeds of, for example, up to 300,000 rpm. As a result of this the rotating parts of the turbocharger must be very precisely balanced in order to minimize the occurrence of vibrations. 
     An axial or thrust bearing is known from the prior art, as disclosed in DE 693 09 860 T2. In this case the thrust bearing is a relatively thin and substantially cylindrical part having flat opposite faces and a cutout groove at its bottom edge. The thrust bearing is also equipped with an oil reservoir. The oil reservoir is in effect an oblong blind slot which is formed in the main body portion of the thrust bearing and does not extend completely through the thrust bearing. The oil reservoir communicates with a central bore by means of a drilled passageway. 
     However, thrust bearings as disclosed in DE 693 09 860 T2 in which an external oil pocket is connected via a drilled bore to a central bore located further inward toward the interior for the purpose of delivering oil have the disadvantage in production that chips (swarf) and burrs form. The drilled bore can therefore be very easily blocked by the metal chips if these are not removed cleanly. Furthermore, burrs which can form at the drilled bore can likewise lead to a constriction of the drilled bore if in this case the burrs protrude into the drilled bore. 
     Furthermore, EP 1 619 356 discloses a thrust bearing having an essentially disk-shaped bearing body with a central passageway opening for the shaft. The thrust bearing additionally has at least one bearing surface surrounding the passageway opening for a collar which is disposed on the shaft. In this arrangement an oil supply channel is provided which extends from a radially outer region of the bearing body to the passageway opening. The oil supply channel is in this case embodied in the form of a groove which can be produced by means of a drop forging, milling or punching method. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly it is the object of the present invention to provide an alternative method for embodying a lubricant feed line of a thrust bearing, wherein the lubricant feed line cannot be blocked by burrs or swarf. 
     This object is achieved by means of a method having the features recited in claim  1 . 
     Accordingly, a method for producing a lubricant feed line in a thrust bearing is inventively provided, wherein the lubricant feed line is embodied as a channel which guides lubricant from a lubricant pocket of the thrust bearing, said method comprising the steps of:
         providing an initial thrust bearing mold,   stamping a groove in the area of the initial mold in which provision is made for the channel,   stamping and punching through material on at least one side or on both sides of the groove along at least one section of the groove,   stamping the material on the side of the groove toward the groove such that the material together with the groove forms the channel.       

     In this case the method has the advantage that a channel can be embodied as a lubricant feed line, in particular also an at least partially or completely closed channel, in which no swarf or burrs which can constrict or block the channel are produced as a result of the production method. The lubricating function of the thrust bearing by means of the lubricant feed line or, as the case may be, the channel can thus be ensured. 
     Advantageous embodiments and developments of the invention will emerge from the dependent claims as well as from the description with reference to the drawings. 
     According to an embodiment of the invention, step d) entails stamping the material on one side or on both sides of the groove so far toward the groove that the material together with the groove forms an open, at least partially closed or completely closed channel. In this way a swarfless method involving no cutting can be used to form channels which replace the drilled channels known from the prior art in which chips and burrs can be produced during the drilling operation. 
     In a further embodiment variant according to the invention the method comprises the additional step of leveling the surface of the channel such that the thrust bearing has a plane channel. In this way, according to function and intended use, a thrust bearing can be provided which is embodied as essentially flat or planar, the thrust bearing being able to be embodied in this case as planar either over the entire surface area or in regions such as the lubricant feed line or the channel, for example. 
     In another embodiment variant according to the invention the channel is stamped in the thrust bearing to a depth that is sufficient to connect a lubricant pocket to a segment section on the same side and/or on the opposite side of the thrust bearing. In this way the segment sections can be provided with lubricant on two sides of the thrust bearing, with only one channel having to be provided. Additional manufacturing costs can be saved as a result. 
     According to a further inventive embodiment variant a thrust bearing is provided having at least one lubricant feed line that is produced in accordance with the inventive method. A thrust bearing of said kind has the advantage that the lubricant feed line has no burrs or swarf, in particular when the lubricant feed line is embodied as partially or completely closed. If the lubricant feed line is produced by drilling in the manner known from the prior art, this is only possible with additional overhead. 
     The invention is explained in more detail below with reference to the exemplary embodiments depicted in the schematic figures of the drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  shows a plan view onto a thrust bearing according to the prior art; 
         FIG. 2  shows a sectional view A-A of the thrust bearing according to  FIG. 1 , and 
         FIGS. 3   a - e  show schematic sectional views of the steps involved in the production of a lubricant feed line of a thrust bearing according to the invention. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     Unless expressly stated otherwise, identical or functionally identical elements and devices have been labeled by the same reference signs in all the figures. 
       FIG. 1  shows a perspective plan view of an example of a thrust bearing  10  according to the prior art. 
     In this case the thrust bearing  10  has a central passageway opening  12  in which e.g. the shaft (not shown) of a turbocharger is brought through. In addition a segment area  14  is arranged around the passageway opening  12  of the thrust bearing  10 . In this arrangement the segment area  14  has, for example, four segments  16  which form contact surfaces. The segments  16  are embodied herein as, for example, wedge-shaped and are arranged radially around the passageway opening  12 . In addition the segments  16  can also be provided with a bevel. 
     At least one lubricant pocket  18  is additionally provided on at least one first side  20  of the thrust bearing  10 . The lubricant pocket  18  is in this case arranged outside of the segment area  14 . From the lubricant pocket  18  a lubricant feed line  22  is formed to the segment area  14  by providing a bore  24  which connects the lubricant pocket  18  to the segment area  14  in order to supply the latter with lubricant or, as the case may be, lubricating oil. 
     However, drilled bores  24  of this type as a lubricant feed line have the disadvantage, as already described above, that chips and burrs form, in which case the swarf produced is difficult to remove and can also lead to a constriction or even to a blockage of the drilled bore  24 . A similar case also applies to the burrs. These, like the chips, have to be removed in an additional operating step in order to prevent them from protruding into the drilled bore  24 , for example, and unintentionally constricting the latter, thereby resulting in a considerable deterioration in the efficiency of operation of the thrust bearing. However, such additional operating steps and a corresponding re-inspection of the thrust bearing or, as the case may be, of its lubricant feed line lead to additional costs. 
     In  FIG. 2  the thrust bearing  10  according to  FIG. 1  is shown in a sectional view A-A. The segment area  14  is shown here in the form of a recess. Also shown are the segments  16  that are arranged in the segment area  14 . The drilled bore  24  which connects the lubricant pocket  18  to the segment area  14  is also shown. The segment area  14  and the segments  16  are in this case provided on the first and second side  20 ,  26  of the thrust bearing  10 . 
     According to the invention a thrust bearing  10  is provided which is comparable with that as depicted in  FIGS. 1 and 2 . In principle the thrust bearing  10  according to the invention can also have any other embodiment than that shown in  FIGS. 1 and 2 . The essential point is that the lubricant feed line  22  which connects a lubricant pocket  18  of the thrust bearing  10  to, for example, at least one segment area  14  is produced using a swarfless method, in contrast to the drilled channel  24  according to the prior art. 
     The steps of the method according to the invention are shown in  FIGS. 3   a  to  3   e.    
       FIG. 3   a  first shows, for example, an essentially flat base material or, as the case may be, an initial thrust bearing mold  28 , made of metal or a metal alloy, for example. The thickness of the base material or, as the case may be, of the initial mold  28  can in this case substantially correspond to the thickness of the finished thrust bearing  10  or be brought to the corresponding thickness subsequently. 
     In this connection it is possible for the initial thrust bearing mold  28  to have been already at least partially machined in order to form the subsequent finished thrust bearing  10 . Subsequently to the embodiment of a lubricant feed line  32 , further machining steps can optionally follow in this case in order to produce the finished thrust bearing. Alternatively the lubricant feed line  32  can also be realized as the final machining step or, for example, also as the first machining step at the start of the production of the thrust bearing  10 , or as one of the first machining steps. 
     In other words the production of the lubricant feed line  32  is beneficially or, as the case may be, suitably incorporated into a sequence of machining steps for producing the thrust bearing  10  such that the thrust bearing can be produced, for example, easily and cost-effectively. 
     In a first step, as shown schematically in  FIG. 3   b , initially a groove  30  is now stamped on a first side  20  of the base material  28  on which the channel  32  is to be provided. In this case the groove  30  is stamped in such a way that it connects the lubricant pocket  18  to, for example, a segment area similar to that shown in  FIG. 1 , for example. As already stated hereintofore, the thrust bearing  10  in  FIG. 1  is merely one example out of many of the embodiment of a thrust bearing  10 . 
     In a further step, as shown in  FIG. 3   c , material  34  is punched from the second side  26  of the base material  28  to the right and left of the groove  30  likewise by means of stamping. That is to say that material  34  is not simply displaced exclusively to the side, but essentially is pressed through or, as the case may be, pressed out or punched toward the first side  20  of the base material  28 . This stamping of the base material from the second side  26  is performed over the entire length or at least over at least a part of the length of the groove  30  in order subsequently to form a channel  32  out of it. In this case the length can be chosen as a function of whether the channel  32  is to be embodied over its entire length, for example, as at least partially or completely closed or is to have, for example, at least one additional open section. The amount or, as the case may be, the height of the punched material on the right and left of the groove  30  can in this case be the same or different, according to function or intended use. 
     According to the next step, as shown in  FIG. 3   d , the material  34  previously pressed through to the first side  20  of the base material  28  is stamped together inwards, for example, toward the center of the groove  30  in order to embody the channel or, as the case may be, the lubricant feed line  32 . In this case the material  34  projecting on the right- and left-hand side of the groove  30  is stamped together to such an extent that the material  34  comes together, for example, in the center in order to embody a channel or, as the case may be, lubricant feed line  32  that is essentially closed at the top. 
     Depending on function and intended use, the channel  32  can also be embodied as open at the top (not shown) or, as the case may be, as partially closed. In this case the material  34  that stands proud on the right and left of the groove  30  is stamped together only to the point where the channel  32  still remains at least partially open at the top or, as the case may be, is not completely closed. 
     In both cases, however, the material  34  initially protrudes from the first side  20  of the base material  28 , as shown in the case of the variant having the closed channel  32  in  FIG. 3   d.    
     In an additional, next step, as shown schematically in  FIG. 3   e , the surface of the first side  20  is therefore leveled if necessary at least over the formed channel  32  or, as the case may be, the lubricant feed line such that an essentially flat surface is achieved. This means that the material  34  projecting upward in  FIG. 3   d  is planed level over the groove  30 . In the process the thickness can be adjusted to the thickness of the finished thrust bearing  10 . The method and the thus obtained thrust bearing  10  have the advantage that in a small number of process steps a channel or, as the case may be, a lubricant feed line  32  can be produced which connects the lubricant pocket  18 , for example, to the segment area, wherein no swarf or sharp burrs can be produced which have to be carefully removed in separate operating steps. 
     Although the present invention has been described hereintofore with reference to the preferred exemplary embodiments, it is not limited thereto, but can be modified in a multiplicity of ways. 
     In this case the present invention is in particular not restricted to an embodiment of a thrust bearing  10  according to  FIGS. 1 and 2 , but can be applied to all possible embodiment variants of thrust bearings in which at least one channel is provided as a lubricant feed line. The thrust bearing  10  shown in  FIGS. 1 and 2  is merely an example presented for the purpose of explaining the inventive principle in greater detail. In this connection the groove  30  as the lubricant feed line of the thrust bearing also does not necessarily have to have an angular cross-section as shown, for example, in  FIG. 3   e , but can have any shape of cross-section, for example round, oval etc. 
     Furthermore it is also conceivable, instead of punching through material  34  on both sides of the groove  30  as shown in  FIG. 3   c , to punch through material  34  on one side of the groove  30  only. In this case the material  34  on one side of the groove  30 , as shown in  FIG. 3   d , can be punched toward the groove such that it together with the groove  30  forms a channel  32 . If necessary the surface of the channel  30  can be leveled accordingly, as shown in  FIG. 3   e , if the material  34 , after being punched through toward the groove  30 , still stands proud of the surface of the thrust bearing  10  in an undesired manner as shown in  FIG. 3   d . Furthermore it is also conceivable to stamp the groove  30  or, as the case may be, the channel  32  to such a depth that the channel  32  connects a lubricant pocket to a segment area on the first and/or second side  20 ,  26  of the thrust bearing  10 . 
     Furthermore the individual machining steps, as described hereintofore with reference to  FIGS. 3   b  to  3   e , can be performed not just sequentially. Instead, individual steps can also be combined or, as the case may be, performed in one operating step. Thus, for example, stamping the groove ( FIG. 3B ) and punching through the material ( FIG. 3   c ), or, for example, stamping together the material ( FIG. 3   d ) and leveling the surface ( FIG. 3   e )—to name two examples—can be implemented in one operating step. 
     Moreover, the thrust bearing  10  according to the invention can be used not only for turbochargers, but also in any other field in which thrust bearings are required to absorb axial forces.