Abstract:
A method for producing a bearing assembly for mounting a control shaft, for example a camshaft, may include: providing a bearing; arranging at least two rings on respective axial front sides of the bearing; pushing the bearing together with the at least two rings onto an assembly mandrel; pre-tensioning the at least two rings against the respective axial front sides of the bearing; at least one of (i) pushing a shrink hose over the bearing and the at least two rings and heating the shrink hose, and (ii) winding a film strip over the bearing and the at least two rings; and withdrawing the assembly mandrel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to German Patent Application No. DE 10 2016 203 654.8, filed on Mar. 7, 2016, the contents of which are hereby incorporated by reference in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to a method for producing a bearing assembly for mounting a control shaft. The invention additionally relates to a bearing assembly produced by this method and a method for producing a control shaft using such a bearing assembly. 
       BACKGROUND 
       [0003]    The production of cam shafts or control shafts in general is usually made by joining individual components, for example, bearings and cams, on the camshaft, whereupon the camshaft is then ground, in particular in the area of the cams, and thereby finish-treated. Specifically during this finish treatment by grinding, grinding dust is produced which can penetrate into the bearing or in particular into the bearing surfaces, settle there and during subsequent operation of an internal combustion engine fitted with the camshaft, can result in increased wear and in the most unfavourable case, even in damage to the bearings. For this reason, it is known to protect the bearings, for example roller or needle bearings, from contamination during grinding of the cams by manually applied cages. However, these cages must be laboriously screwed on manually and unscrewed again after the actual grinding process, which is not only time-consuming but also cost-intensive. 
       SUMMARY 
       [0004]    The present invention is therefore concerned with the problem of providing a method for producing a control shaft which overcomes the disadvantages known from the prior art. 
         [0005]    This problem is solved according to the invention by the subject matter of the independent claim(s). Advantageous embodiments are the subject matter of the dependent claims. 
         [0006]    The present invention is based on the general idea of initially producing a pre-fabricated bearing assembly which is already protected by means of a shrunk-on shrink hose or wound-on film strip in such a manner that this can be used in the prefabricated state during the manufacture of control shafts without an additional (dirt) cage since the shrink hose or the film strip protects the bearing device from any grinding dust/grinding sludge/grinding particles which may occur. In the method according to the invention for producing a bearing assembly, firstly a bearing is prepared or produced by mounting, for example, roller bodies in a bearing ring. Then the bearing together with two rings arranged on the front side, in particular plastic or metal rings, is pushed onto an assembly mandrel. The two rings are thereby pre-tensioned against the front sides, that is the axial front sides, of the bearing. Now the shrink hose is pushed over the bearing and the two rings and shrunk onto these by heating. Alternatively to this, the film strip can also be wound over the bearing and the two rings. Then, the bearing assembly thus pre-fabricated and held together by the shrunk-on shrink hose or the wound-on film strip can be withdrawn from the assembly mandrel and supplied to further manufacture of the control shaft. The pre-fabricated bearing assembly can be reserved for the production of the control shaft, whereby a hitherto extremely complex production process can be at least slightly simplified. 
         [0007]    The present invention is further based on the general idea of now arranging the bearing assembly produced according to the previously described method on a corresponding control-shaft shaft/camshaft shaft together with at least one control element/cam, wherein the control elements/cams can, for example, be thermally joined whilst at least one pre-fabricated bearing assembly is merely pushed onto the control-shaft shaft and fixed by means of the two rings. In a following process step, the cams or control elements can now be ground, without the grinding dust or grinding sludge produced in this case penetrating into the bearings, that is into the bearing assembly (assemblies) and resulting in undesirable contamination there. Once the grinding process is completed, the shrink hose or the film strip over the at least one bearing assembly is removed by, for example, pulling a tear tab which tears the shrink hose along a material weakening, for example, a perforation seam and thereby makes it easily removable. A film strip can be simply unwound. In the method according to the invention for producing the control shaft, in particular the hitherto necessary, laborious and therefore costly mounting of the protective cage over the individual bearings can be dispensed with, with the result that the manufacturing process is not only considerably simplified but can also be significantly more cost-effective. When installing the camshaft according to the invention in a cylinder head cover or a cylinder head of an internal combustion engine, before reaching the final installation end position, this is displaced to and fro by a few tenths of a millimetre, for example, about 0.6 mm in the axial direction in order to achieve an at least slight spacing between the bearing and the two rings arranged on the front side thereto and thereby enable a clearance. Naturally not only cams per se but also eccentric disks, sensors, signal generators or other components with at least one bearing assembly can be slid onto the control shaft/camshaft according to the invention. 
         [0008]    The present invention is further based on the general idea of pre-fabricating a bearing assembly produced according to the method described initially in a separate fabrication step and thus being able to make the mounting of a control shaft fitted therewith simpler and in particular more flexible. As already mentioned initially, the shrink hose can in this case comprise a tear tab by means of which by applying a corresponding pulling force, it is possible to tear off the shrink hose and thereby easily remove the same. In order to simplify the tearing off and also the removal of the shrink hose, this can have a material weakening, for example a perforation, with the result that a comparatively simple and cost-effective desired tearing point is created. The material weakening can naturally also be produced by scoring, cutting or by means of a laser, with the result that not only a high-quality but in addition, also a cost-effective manufacture of such a material weakening is possible. In a further advantageous embodiment of the solution according to the invention, the ring have a smaller outside diameter that the bearing, whereby it can be ensured that the rings are used exclusively for axial securing of the bearing on the control-shaft shaft but do not come in contact, for example with a bearing seat of a cylinder head or a cylinder head cover. 
         [0009]    In a further advantageous embodiment of the bearing assembly according to the invention, it is provided that the shrink hose has a larger axial length than the bearing assembly and as a result, at the longitudinal end side in the shrunk-on state, embraces the two rings on the front side and thereby holds together the entire bearing assembly. As a result, a not only compact by also extremely stable bearing assembly can be created without individual components thereof such as, for example, the two rings and the bearing needing to be additionally fixed on one another. 
         [0010]    In a further advantageous embodiment of the solution according to the invention, the rings have front-side oil conveying structures, in particular grooves, slots, webs or hemispherical elevations. After mounting of the bearing assembly on the control-shaft shaft, the control-shaft shaft is displaced to and/or fro slightly in the axial direction, with the result that an at least small axial gap is formed between the bearing and the two rings arranged on the front side which allows clearance. At least on the front side facing the bearing, the rings have the previously described oil conveying structures which during operation of the internal combustion engine allow a continuous oil supply, for example, generally a continuous lubricant supply into the bearing and thereby ensure a reliable lubrication of the roller bearings and in addition enable a smooth-running mounting of the camshaft in the long term. 
         [0011]    Further important features and advantages of the invention are obtained from the subclaims, from the drawings and from the relevant description of the figures with reference to the drawings. 
         [0012]    It is understood that the features mentioned previously and to be explained hereinafter can be used not only in the respectively given combination but also in other combinations or alone without departing from the framework of the present invention. 
         [0013]    Preferred exemplary embodiments of the invention are shown in the drawings and are explained in detail in the following description where the same reference numbers refer to the same or similar or functionally the same components. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    In the figures, schematically in each case 
           [0015]      FIG. 1  shows a sectional view through a bearing assembly according to the invention during assembly on an assembly mandrel, 
           [0016]      FIG. 2  shows a sectional view through a camshaft produced according to the invention before grinding the cams with shrink hose still applied to the bearing assemblies, 
           [0017]      FIG. 3  shows a detailed view from  FIG. 2 , 
           [0018]      FIG. 4  shows a sectional view through a cylinder head or a cylinder head over with installed camshaft with shrink hoses removed from the bearing assemblies at the same time, 
           [0019]      FIG. 5  shows a sectional view through the control shaft during axial displacement of the control-shaft shaft to create a clearance. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    According to  FIG. 1 , in a method according to the invention for producing a bearing assembly  1  by means of which subsequently, for example a control shaft/camshaft  2  is mounted in a cylinder head  3  or a cylinder head cover  4  (cf.  FIG. 4 ), a bearing  5  is firstly prepared or produced by mounting or arranging roller bodies  6  in a bearing ring  7 . The term “control shaft” can hereinafter frequently be equated to the term “camshaft”. The roller bodies  6  can in this case, for example, be configured as rolls or as needles but also as spheres. This bearing  5  together with two rings  8  arranged on the front side thereto, in particular with plastic or metal rings, is then pushed onto an assembly mandrel  9  (cf.  FIG. 1 ), where the two rings  9  are pre-tensioned towards the front sides of the bearing  5  by means of a corresponding sleeve  10 . This is brought about by the sleeve  10  pressing onto the upper ring  8  and the lower ring  8  resting on a bracket or a stop  11  of the assembly mandrel  9 . A shrink hose  12  is then pushed over the bearing  5  and the two rings  8  and shrunk onto these by heating. Alternatively to this, a film strip  12 ′ can also be wound over the bearing  5  and the two rings  8 . The film strip  12  is thereby wound under tension and partially overlapping over the bearing  5  and the two rings  8  in order to ensure tightness. 
         [0021]      FIG. 1  shows the state of the shrink hose  12  before heating, whereas  FIGS. 2 and 3  show the state after shrinking the shrink hose  12  onto the rings  8  and the bearing  5  or the film strip  12 ′ wound under tension over the bearing  5  and the two rings  8 . This is wound in a partially overlapping manner so that gaps can be avoided and a tight packing for the bearing  5  and the ring  8  can be ensured. The bearing assembly  1  now thus pre-fabricated can now be removed from the assembly mandrel  9 . As can be deduced from  FIG. 1 , the bracket  11  or the stop  11  has the effect that the shrink hose  12  can be pushed further downwards on the front side so that for example, it is also possible for the rings  8  to be embraced by the shrink hose  12  on the front side. The rings  8  can in this case have a structuring radially on the outer side at least in the overlap region of the shrink hose  12 . According to  FIGS. 2 and 3 , the shrink hose  12  thereby however does not embrace the front sides of the two rings but merely holds these firmly on its outer lateral surface. 
         [0022]    The bearing assembly  1  according to the invention thus consists of the actual bearing  5 , the bearing ring  7  and the roller bodies  6  mounted therein, the two rings  8  arranged on the front side thereto and the shrink hose  12  shrunk thereon, which fixes the two rings  8  on the bearing  5 . 
         [0023]    The shrunk-on shrink hose  12  or the wound-on film strip  12 ′ protects the bearing  5  during grinding of cams  13  from penetrating grinding particles and therefore from any accompanying damage. A tear tab  14 , for example, can be provided on the shrink hose  12 , which makes it easier to tear off and therefore remove the shrink hose  12  from the bearing assembly  1  after grinding. A film strip  12 ′ can be simply unwound. The shrink hose  12  can furthermore have a material weakening, for example, in the manner of a perforation which additionally simplifies the removal of the shrink hose  12  after grinding of the cams  13 . The shrink hose  12  or the film strip  12 ′ can also have a layer which increases the sealing effect at least partially from inside, in particular an adhesive layer. 
         [0024]    The bearing assembly  1  generally fabricated separately according to the invention is now slid onto a control-shaft shaft  15  during assembly of the control shaft/camshaft  2  with at least one control element, in particular a cam  13 , where it is naturally clear that not only one bearing assembly  1  and one control element/cam  13  are slid onto the control-shaft shaft  15  but in each case a plurality thereof. When the bearing assemblies  1  are pushed onto the control-shaft shaft  15  and the control elements, in particular the cams  13  are joined to the control-shaft shaft  15 , for example, by a thermal shrink fit, an after-treatment or finishing of the control element/cams  13  can be accomplished, in particular by grinding. The bearing assemblies  8  are held on the control-shaft shaft  15 . When the finishing, for example, by grinding the cams  13  is completed, the camshaft  2  can be cleaned and the shrink hose  12  or the film strip  12 ′ can be opened and removed from the individual bearing assemblies  1 , for example, by tearing on the tear tab  14  and the pre-fabricated camshaft  2  can be inserted into the cylinder head  3  or the cylinder head cover  4 . 
         [0025]    Before reaching the end position of the camshaft  2  in the cylinder head  3  or in the cylinder head cover  4 , the control-shaft shaft  15  is moved to and fro slightly in the axial direction relative to the bearing  5  and a minimal distance  17  in the axial direction  16  between the two rings  8  and the bearing  5  is thereby created, enabling a clearance of the bearing  5 . 
         [0026]    Usually after removal of the shrink hose  12  or the film strip  12 ′, the bearings  5  of the control shaft  2  can be fixed axially to create the clearance before insertion in the cylinder head  3  and the control shaft  2  is displaced in the axial direction preferably by at least 1/10 mm as shown in  FIG. 5 . For this purpose an axial force is exerted on the control shaft  2  and at the same time the bearings  5  are held by means of retaining contours  23 . 
         [0027]    In order to be able to reliably ensure sufficient lubrication of the bearing  5  during operation of the control shaft  2  installed in an internal combustion engine  8 , oil-conveying structures or oil conveying structures  20  (see detailed view from  FIG. 3 ), in particular grooves, slots, webs or hemispherical elevations  22  can be provided on one of the front sides  19  of the two rings  8  facing the bearing ring  7 , which enable a reliable transport of oil into the area between the roller bodies  6  and the control-shaft shaft  15  and thereby on the one hand enable reliable lubrication of the bearing  5  and on the other hand a smooth-running mounting of the control shaft  2 . 
         [0028]    If  FIGS. 1 to 4  are viewed again, it can be see that the rings  8  have a smaller outside diameter than the bearing ring  7  with the result that a simplified insertion of the control shaft  2  into the relevant bearing opening  21  of the cylinder head  3  or cylinder head cover  4  is made possible. 
         [0029]    Using the method according to the invention for producing the bearing assembly  1  according to the invention and the resulting method according to the invention for producing the control shaft  2 , the latter can be produced significantly more simply and cost-effectively since in particular a laborious covering of the bearings  5  during grinding of the control elements, in particular the cams  13  is omitted. On the contrary the bearings  5  are protected from any unwanted ingress of grinding dust by means of the two rings  8  arranged on the front side thereto and the shrink hose  12  shrunk thereover or the film strip  12 ′ wound thereover. This can be removed significantly more simply compared to the protective cages known hitherto from the prior art, for example by simply tearing off or away or unwinding.