Abstract:
The concept of the invention is based on a machine housing with a bearing housing, the bearing seat of which is connected to a housing wall of the machine housing by a bearing housing wall provided with ribs ( 42, 43 ) and is subjected to radially directed forces ( 11, 44 ). The proposal is made that the bearing housing wall possess at least one ring shaped annular rib ( 42 ) which at least partially encompasses the bearing seat in an area ( 21 ), the angle (α) of inclination of which, relative to its original unloaded condition, would change itself to the greatest extent under load ( 11 ). Further proposed is that a plurality of additional ribs ( 43 ) run transverse to the annular rib ( 42 ). Thereby, with a relatively small consumption of material, a good shape-retention is achieved. In addition, a tilting of the bearing seat and the bearing is held to a lesser extent than is the case of conventional bearing housing structures. By the use of shell shaped bearing housings, the bearing housing wall is characterized by a more intensive curvature in the more heavily stressed area ( 21 ) than is the case in the area ( 22 ) which lies diametrically (with respect to the bearing axis) opposite.

Description:
FIELD OF THE INVENTION 
     The invention concerns a machine housing. 
     BACKGROUND OF THE INVENTION 
     The majority of machine housings possess housing parts which are designed as bearing housings for rotating or sliding bearings. The bearing housing can be an integral component of the machine housing or it may be a separate entity, for example, a bearing cover affixed to the machine housing. The bearing housing, as a rule, possesses at least one bearing seat which is connected to the housing wall of the machine by means of a bearing housing wall. Under the stress of axial and radial forces, such a bearing housing wall is deformed and has a tendency to extend itself, more or less, overstepping its original positioning. In its unstressed original condition, the said bearing housing can be, to a great extent, quite flat. From the standpoint of construction as well as strength of material, the said bearing housing frequently is made in a shell form which may be enhanced with ribs in order to improve its shape-retention and to counter vibration or to cool the bearing. 
     Such machine housings are installed in a multiplicity of embodiments in the industry, including transmission housings, housings for drive engines, for metal working machines and to meet requirements of various applications. For example, reference is made to the book “Zahnradgetriebe”, wherein Johannes Loomann, in his design books, Volume 26, Springer-Verlag Berlin 1970, presents an axle drive, the housing of which exhibits a bearing housing for a tapered roller bearing in which the differential cage is located in the housing of the axle drive. In this case, a bearing housing is designed as a bearing cover, and covers a mounting opening for the axle drive, while the other bearing housing is an integral component of the drive housing. 
     The rear axle tapered drive serves a personal passenger car, wherein the differential cage is driven by a beveled pinion. The high drive moment at the said drive pinion generates a substantial radially directed bearing force, besides axial bearing forces, when motor is in a compression mode, which stresses the bevel roller bearing in a limited circumferential area. In power-input mode, the radial force is essentially less and runs about 30% of that of the compression mode. Moreover, the radial force in the power-input mode runs offset at an angle γ in the circumferential direction, in relation to the radial force of the compression mode, which angle is generally 90°. Because of the geometrical relationships of the tapered roller bearings, besides the axial forces which the bevel drive produces, the radial stresses also generate additional axial forces which act on a circumferential area wherein radial loading finds its abutment, producing, all together, an eccentrical bearing loading which results in an unsymmetrical deformation of the bearing housing wall. This is superimposed by deformations which arise because of irregular elasticities in the housing of the bearing wall and in the contiguous wall of the machine housing. 
     Structures pertaining to the bearing housings, which are not optimally designed in regard to their rigidity, exhibit a relatively large displacement and tipping of the bearing seat when under stress and as a result of the elastic deformation. The disadvantages which arise therefrom are multifaceted. In the building of drives and, in fact, anywhere that toothed gears are in question, such displacements of the bearing seats result in effects on the tooth contact. Deviations from the linear disposition of the tooth faces are a result of the said displacements and, in turn, lead to structural strength and to noisy operation. In order to obviate this problem, most of the toothing has a tooth-face correction. This, however, can be an optimal solution for no more than one operational condition. This said optimal condition, on the grounds of structural strength, is mostly at the maximum loading condition. Accordingly, correction is applied for that situation and correspondingly unwanted noise occurs in the preponderantly employed partially load areas. This set of problems largely comes about at the end of a drive trains in the case of bevel gear drives. At this location, high moments are in effect reacting on toothing which are sensitive in regard to their bearing support. This is the case in drives for front driven vehicles with longitudinally constructed front motors. 
     The same can be said for rear driven vehicles with, again, longitudinally set motors and in the case of 4-wheel drive, as well as for direct driven axles. Problems arise not only in the toothing, but also the bearing itself will fail earlier if the displacements become too great. The tilting of the inner ring and the outer ring of the bearing as well as the axial spread of the bearing seat in the case of bevel gear bearings, all lead to smaller load handling areas and therewith to higher pressures acting on the bearings. 
     As the loading areas become smaller, then the axial forces act with increasing eccentricity, whereby the effect of tilting is magnified and so, in turn, with increasing deformation of the bearing housing, the geometrical stress conditions become more and more unfavorable. 
     By means of an increased shape-retention of the bearing housing, the running wear and tilting deformation of the bearing seat can be maintained at a lower level, however, a greater stiffness of the housing leads, in general, to greater weight. This is due to the fact the most rigid state is reached when the entire available installation space is filled with supporting material. This indicates, in any case, the worst solution to the problem which, above all, is not acceptable in the vehicle world and in no way can be justified in the manufacturing design. 
     In the case of most of the known solutions, a larger portion of the installed material finds its place in the walls of the bearing housing. Furthermore, stiffening and reinforcing ribs are often placed in a traditional, radial disposition about the bearing axis and are circumferentially apportioned about the bearing seat. The ribs increase, in particular, the resistance moment of the bearing housing wall and, in common with the wall, are also subjected to bending. 
     Thus the invention has the purpose of optimizing the bearing housing of a generic machine housing in regard to the content of material and the rigidity of the same. 
     SUMMARY OF THE INVENTION 
     In accord with the invention, the bearing housing wall is to have at least one ring shaped annular rib which entirely or partially encompasses an area, which would alter its angle of inclination the most when stressed relative to its original condition ribbing, and further the said area is to possess a plurality of additional ribs running transversely to the said at least one annular ring. In the case of axial loading and a corresponding deformation of the bearing wall, the said annular rib tilts outward whereby the free segment of the annular ring displaces itself through the longest path. This acts to buildup corresponding tension in the direction of the circumference which acts counter to deformation. The course of the said tension just increases so much steeper the more the annular ring tilts beyond its original position. 
     On this account, it is of advantage to place the annular ring in that area of the bearing housing wall wherein the wall, without the said annular ring, would increase its angle of inclination the most under load. So that, first the angle, which encompasses the annular ring with the bearing housing wall, is held continually constant even under loading, and second so that the greatest possible elasticity can be attained, additional ribs are provided at appropriate intervals from one another which run transverse to and are integrated with the said annular rib. The annular rib, or a plurality thereof which are concentric to one another, obviously run, along their length, circumferentially to one another and/or are bound to a bearing block. This arrangement allows a satisfactory reception of the tension forces. 
     The said annular ribs encompass the highly stressed area of the bearing and/or bearing seat in the manner of a collar. Further the said ribs lie advantageously in an area which is diametrically opposite to the area where the maximal inclination changes of the bearing housing wall take place, and run proximal to the bearing block or are integral therewith. By means of the relatively shorter annular ribs, the material consumption is kept to a minimum, since the tension buildup is indeed positively influenced by the change in the inclination and the height of the ribs not, however, because of the length of the circumference of the annular ribs. The annular ribs act in this area very favorably for shape-retention since, because of geometric relationships, the tension stresses in the circumferential direction climb very rapidly with the deformation. 
     The annular ribs advantageously possess an essentially elliptic configuration. In principal, the elliptic incremental parts of the annular ribs, which are situated between the transversely running ribs, can be replaced by straight pieces whereby an even a more rigid structure is created. With a closely meshed connection by the transversely running ribs the effect is, in any case, very small. 
     Further, the more sharply curved ribs of the ellipse extend themselves farther radially outward than do the less curved ribs, so that the more intensively curved ribs are more greatly stressed, since the curvature of the bending line increases toward the outside. Finally, the annular ribs have the advantage that they enable the least stressed area, which lies diametrically opposite to the most stressed area, to carry more of the load. In accord with one embodiment of the invention, the bearing housing wall is subjected to a radially directed principal load and is designed in shell form wherein, in the shell area receiving the principal axial and radial loads, the shell is more acutely curved in its longitudinal cross-section than it is in that area which lies diametrically opposed, relative to the bearing axis. 
     With this in mind, the basic concept of the design is first that part of the bearing housing, which encompasses the loaded area, differs from that part of the bearing wall which lies diametrically opposite therefrom in relation to the bearing axis. The area of the loaded area carries the greatest apportionment of the stress. The reason for this is that the force from the shaft is introduced into the bearing wall exclusively from its contact points with the bearing and from the bearing seat. Thus, only compressive forces are exercised on the loaded area, while the diametrically opposite lying area must accept that loading which, emanating from the load area, is conducted around the bearing seat. The second reason to form the areas of the bearing housing differently is based on deformation characteristics and on the therewith connected fundamentals of technical mechanics. 
     By means of a more pronounced curvature of the bearing housing wall in the loaded area, the bearing seat, subjected to the combined axial and radial loading, is directed so that the bearing outer-ring inclines itself at a smaller angle. Further, the bearing housing wall is apportioned to a greater extent into one area parallel to the bearing plane and into another area which runs perpendicular thereto. While the first area is strongly stressed toward bending by the axial forces—thereby contributing to the mentioned tilting of the outer bearing rings—the second area is in its shape. On the first area and the transitional area to the second area, it is now possible to employ the inventive design features. 
     Reacting to the described construction, when the said shell is under stress, the bearing mid-point migrates in the direction of the load and toward the connection flange, that is, toward the flange of the bearing housing and locates itself at the same radial offset, in the case of the invented structure, but further inward than would be the case with a rotation-symmetrical structure of the bearing housing. With increasing radial loading, the force being transferred concentrates itself into a smaller load area so that, going to extremes, the loaded area shrinks to a point. In this condition, the complete axial force acts upon the load area entirely outside of the outer ring of the bearing, and thereby achieves the maximal eccentricity of its resultant line of action. In any case, the axial position of the shaft is fixed at this point. Although, in the case of a rotation-symmetric structure, the load area deviates toward the outside, in the case of the invented solution, the load area migrates inward so that this pretensioning effect works against the actual unfavorable axial displacement caused by elasticity. 
     In accord with the invention, on the convex side of the bearing house wall, especially in the outer area of the incremental part—which runs essentially parallel to the plane of the bearing, or in the neighboring incremental part, that is, toward which the area changes its inclination the most—at least one annular rib is placed, across which further ribs run essentially transversely thereto. In connection with the transversely running ribs, compressive forces are built up in the annular ribs in the circumferential direction which act in a mode providing rigidity to the structure. By means of the deformation, the annular ribs are drawn outward over their entire length, whereby they extend themselves and thereby build up tension stresses in the circumferential direction which, in a manner like a collar, enclose the highly stressed areas of the bearing and the bearing seat. 
     The most effective position for the annular rings is the outer area of the part parallel to the bearing plane, since at this location, because of elasticity, the start of the wall area inclination comes into play, as well as the angle-change of the said part parallel to the bearing plane. Both components are additive and effect an expansion of the annular ribs so that, even at small displacements, a stabilizing tension is brought into action in the circumferential direction. Where the optimization of the rigidity of the bearing housing is concerned, considerable importance must be laid on an ability to generate a substantial stabilizing tension, at an early point. Although the bearing housing wall, among other things, assures the housing function of the bearing housing, this being, namely, the protection of the internally situated components and to provide outward support, the ribs not only enhance the optimized properties of the wall but form substantial inherent wall components of the structure, which lend a high degree of rigidity to the bearing plane parallel area in the stressed area. 
     The annular ribs react to the deformation of the bearing housing with a constant increase of the tension force and act, in this way, to counter the said deformation. The invented bearing housings, for example, can be used especially advantageously in connection with highly stressed axle drives, which transmit high torques at the end of a drive chain and, as a rule, include a beveled gear differential drive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described, by way of example, with reference to the accompanying drawings in which: 
         FIG. 1  is a longitudinal cross-section through an invented bearing housing with a flat bearing housing wall, 
         FIG. 2  is a plan view on a bearing housing in accord with  FIG. 1 , 
         FIG. 3  is a schematic longitudinal cross-section through an invented, shell type designed bearing housing, serving as a bearing cover without ribs, 
         FIG. 4  is a schematic sketch of deformation of a bearing seat of a taper roller bearing in a bearing housing in accord with  FIG. 3 , being subjected to radial loading, 
         FIG. 5  is a schematic sketch of deformation in accord with  FIG. 4 , in comparison to deformation of a rotation-symmetrically designed bearing housing, 
         FIG. 6  is a perspective presentation of a bearing housing in accord with  FIG. 3  showing ribs. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The bearing housing  1 , presented by dotted lines in  FIG. 1 , is shown as it appears in a load free state. The presentation with the full lines represents deformation of the bearing housing  1 —in an exaggerated scale—when subjected to loading by axial forces  10  and resolving into a radial principal load  11 . The bearing housing  1  has a bearing housing wall  3 , which extends on into the wall of a machine housing, the latter is not shown. The transition surface is indicated by  6 . The bearing housing wall  3  which, in its load-free original state, is essentially flat, carries a bearing block  5  concentric to a bearing axis  4 , which has a bearing seat  2  for reception of a shaft bearing (not shown), namely, a tapered roller bearing. 
     When subjected to loading, as indicated by  10 ,  11 , and because of the connection of the bearing housing wall  3  with the wall of the machine housing, the bearing housing wall  3  deforms itself in various ways so that it has areas which, under stress, show a varying angle of inclination a to the original load-free position. At the same time, the bearing seat  2  tilts, whereby the bearing axis  4  moves a corresponding angle β and a piece is displaced in the direction of the principal load  11 . In an area  9 , in which the angle of inclination a normal changes itself to the greatest degree, an annular rib  7  is placed. By means of the deformation of the bearing housing wall  3 , the annular rib  7  is forced from a clearance  12  with the bearing axis  4  to a greater clearance  13 . When this occurs, compressive stresses in the circumferential direction of the annular rib  7  are generated. These act contrary to the deformation of the bearing housing wall and lead to a higher degree of shape-retention, especially if the upward curve of the compressive stress is steep, in other words, when the compressive stress gradient is large because of the deformation. 
     This situation is achieved in the case of the invented arrangement, in that the annular rib  7 , due to the large change of the angle of inclination α, tilts strongly outward and produces large tension stresses, especially in the area of its free end. The magnitude of said stresses, besides being dependent upon the change of the angle of inclination α, also dependent upon the height of the annular rib  7 . Additional ribs  8  are provided, which run transverse to the annular rib  7 , which obstruct an inward deviation of the annular rib  7  so that the annular rib  7 , subjected to the influence of the tension stress, does not change its angle δ to the bearing housing wall  3 . 
     The annular rib  7  is, preponderantly, effective in the area, which is most greatly subjected to stress and which area would suffer the greatest deformation. In that area, which lies diametric to the bearing axis  4 , which is less stressed and is essentially in tension, the annular rib  7  can well be omitted. In this case, it is principally advantageous that the annular rib  7  possess a closed annular structure, which is intended to bring the said less stressed area into a load sharing condition. To this end, the annular ribs  7  run in this area near to the bearing block  5  or joins therewith, so that the said block assumes a part of the annular rib structure. By means of the shortness of the annular rib  7 , the material consumption can be reduced, even as the shape-stability characteristics are increased. 
     In  FIGS. 3 ,  6 , a bearing housing  14  in the shape of a bearing cover can be seen which, by means of a centering connection  20 , is accordingly centered in a machine housing (not shown), for example in the housing of a vehicle transmission with a bevel gear differential drive. The said bearing cover  20  is bolted to a flange  18  by means of bolt eyes  19  so that the bearing cover, with its flange  18 , lies on a corresponding receiving surface of the machine housing. Generally, it is also possible that the bearing housing  14 , similar to the bearing housing  1 , forms an integral part of the machine housing in which the bearing housing wall  16  in the area of the flange  18  has a transition into the machine housing. 
     The bearing housing  14  possesses a bearing seat  15  for the reception of a bearing, for example a tapered roller bearing, for the placement of a differential cage. A mean bearing plane is designated as  23  in which radial forces form the principal load  11 , during power input mode, and form a smaller load  44 , during the compression mode (FIG.  6 ). These said forces act through the outer bearing ring  33  on the bearing seat  15  and on the bearing housing wall  16 . The bearing axis carries the reference number  4 . 
     The bearing housing  14 , with reference to the bearing axis  4 , has a rotational symmetric bearing block  17  which encompasses the bearing seat  15  and a boring  32  therein for a shaft. Basing considerations on the rotation-symmetrical bearing block  17 , the bearing housing wall  16  runs in shell shape to the flange  18 , whereby the said wall  16 , in an area  21  on the side of the principal load  11 , exhibits a tighter curve  24  than does the curve in an area  22  which, relative to the bearing axis, lies diametrically opposite to said area  21  and has a less intense curvature  25 . The curvatures  24 ,  25  of the bearing housing wall  16  can be assembled out of a plurality of incremental pieces  26 ,  28 ,  30  and  27 ,  29 ,  31 , whereby the pieces  26 ,  27  run essentially parallel to the bearing plane  23 . However, the incremental piece  30  in the stressed area  21 , which abuts the flange  18 , forms such a large angle with the bearing plane  23  that, giving consideration to necessary slopes in casting technology, it approaches a right angle. The corresponding piece  31 , in the less stressed area  22 , shows an angle less inclined to the bearing plane  23  so that the incremental parts  27 ,  29 ,  31  bind the flange  18  with the bearing block  17  practically in a straight line. The incremental parts  28 ,  29 , between the incremental parts  26 ,  30  or  27 ,  31 , form a transition with the contiguous incremental parts  26 ,  30  and  27 ,  31 . 
     In the schematic sketches as set forth in  FIGS. 4 and 5 , the complex, three-dimensional structural problem is simplified by a two-dimensional presentation. Further, the assumption is made that the structural elements are rigid and bound to one another by linkages. These oversimplified, theoretical viewpoints can, however, illustrate without elasticity the principal differences very well. If the outer bearing ring  33  of a tapered roller bearing, which is set into the bearing seat  15  (FIG.  3 ), is stressed by a principal radial load  11 , the bearing housing  14  deforms, and its bearing housing wall  16  yields back toward the direction of the said radial principal load  11 . As this occurs, the bearing seat  15  tilts, taking with it the outer bearing ring  33 , and the bearing centerpoint  34  positions itself deeper in the bearing housing  14  toward the flange plane  35 , wherein the said centerpoint displaces itself through a radial offset  41  in the direction of the said principal load  11  (FIG.  5 ). In  FIG. 4 , the new position of the deformed bearing housing wall  16  and of the bearing ring  33  with the accompanying centerpoint  34  is sketched in dotted lines. 
     In comparison to the deformed bearing housing  14  of the invention, which in  FIG. 5  is depicted with full lines, is a deformed rotation-symmetrically designed bearing housing  40  with the bearing housing shown in dotted lines.  FIG. 5  makes clear that, in the case of an equal radial offset  41  of the bearing centerpoint  34 ,  36 , the bearing ring  39 , in the rotation-symmetrically designed bearing housing  40 , is more intensely tilted than in the case of the bearing ring  33  when the bearing housing  14  is in the form as dictated by the invention. The bearing centerpoint  36  positions itself somewhat less toward the interior of the bearing housing  40  than did the centerpoint  34  in the case of the invented bearing housing  14 . Most significantly, however, the load area  38  of the bearing ring  39  migrates outward, while the load area  37  of the invented design of the bearing ring  37  positions itself inward and thus the original position of the carried shaft (not shown) is stabilized. 
     These consideration are based on rigid structure elements, that is, on structure elements which possess a high capability of holding their shape. This is the case where flatter structures are concerned, which are only slightly stressed by tension, if at all, for example, in the area  22  and in the area  21  of the incremental part  30 . The shape-stability would be generally, advantageously increased by means of at least one annular rib  42  accompanied by ribs  43  running transversely thereto. The annular rib  42 , which is located in an area of the bearing housing wall  16 , the angle of inclination α of which would change the most, at least partially encloses the load area  37  on the bearing seat  15 , through which the principal load  11  is directed. This said seat is connected, in the load area  22 , onto the bearing block  17 , so that a closed ring structure is achieved. 
     The annular rib  42  exhibits an elliptical shape. In this way, incremental parts  45  can be placed between the transverse ribs  43  and run either as curved or straight pieces. Further, it is possible that one or more annular ribs  42  are provided wherein, at least one of the annular ribs  42  can reach up to the outer area of the incremental parts  26  of the bearing housing wall  16  where, in the area  21  of the principal load  11 , the said incremental part  26  extends itself essentially parallel to the plane  23  of the bearing. This incremental part  26  as well as the contiguous incremental part  28  and on the incremental part  30  are very much subjected to bending stresses and require, on this account, especially high shape retaining characteristic. The areas  21  and  22  are marked out with crosshatching. These areas are not clearly delineated as to borders, but rather can merge into one another. The ribs  43 , where a combination bearing cover and bearing housing  14  is concerned, are advantageously united with the bolt eyes  19  so that the forces can be well introduced into the machine housing. 
     Below the principal load  11  and the outer and the induced axial forces, in the annular ribs  42 , tension stresses in the circumferential direction are generated which, to an extreme measure, act to increase the rigidity of the structure of the bearing housing  14 . The annular ribs  42 , in this case, are drawn outward throughout their entire length. This means that the annular ribs  42  are stretched and thus, by means of the tensional forces in the said circumferential direction, act to hold together, i.e., put in compression, the entire encompassed area. Even by motions of small displacement, stabilizing tension stresses build in the circumferential direction which work to counter further deformation. 
     The depicted principal load in  FIG. 6  presents radial loading of the bearing cover  14  in the power input mode, although in the compression mode with no power input a smaller radial load  44  is active. This smaller radial load  44  forms with the principal load  11  an angle γ which, as a rule, runs about 90°. The area of the loading at the bearing seat  15  brought about by the smaller load  44  is designated as area  46 . In order to be able to withstand loading of the bearing cover  14  in the compression mode, it is advantageous to design the annular ribs  42  and the transversely running ribs  43  so that they react to the inclinational changing of the bearing housing wall  16  also when subjected to the load  44 . 
     The features of the invention are not only of value for the design of a bearing housing  16  in the case of an axle drive, but the said concepts can be employed advantageously in an equivalent manner for the bearing housing  16  with similar loading relationships. 
     REFERENCE NUMBERS AND CORRESPONDING COMPONENTS 
     
         
           1  Bearing Housing 
           2  Bearing Seat 
           3  Bearing Housing wall 
           4  Bearing axis 
           5  Bearing block 
           6  Connection surface 
           7  Annular rib 
           8  Transverse rib 
           9  Area 
           10  Axial loading 
           11  Radial loading 
           12  Original distance 
           13  Distance after deformation 
           14  Bearing housing 
           15  Bearing seat 
           16  Bearing housing wall 
           17  Bearing block 
           18  Flange 
           19  Bolt eye(s) 
           20  Centering connection 
           21  Area of the principal load 
           22  Diametrically opposite area 
           23  Plane of bearing ( FIG. 3 ) 
           24  Intensive curvature (short radius) 
           25  Less intensive curvature (long radius) 
           26  Incremental part ( FIG. 3 ) 
           27  Incremental part ( FIG. 3 ) 
           28  Incremental part ( FIG. 3 ) 
           29  Incremental part ( FIG. 3 ) 
           30  Incremental part ( FIG. 3 ) 
           31  Incremental part ( FIG. 3 ) 
           32  Boring 
           33  Outside bearing ring 
           34  Bearing centerpoint 
           35  Flange surface 
           36  Bearing centerpoint 
           37  Area of load 
           38  Area of load 
           39  Outside bearing ring 
           40  Bearing housing 
           41  Offset 
           42  Annular rib 
           43  transverse rib 
           44  Radial load in compression mode 
           45  Area 
           46  Area 
         α Angle of inclination 
         β Angle of tilt 
         δ Angle (annular rib)