Abstract:
A wheel bearing for aircraft, that has a long service life and is reliable. The wheel bearing has a small number of individual parts and components that are simple to handle, to mount or to dismount. The wheel bearing of an aircraft landing gear has a wheel rim that is rotationally mounted about an axis over two roller bearings of a bearing arrangement. The external rings of the roller bearings are received together in a single-piece external ring bearing housing. The wheel rim can be detachably connected to the bearing arrangement in such a manner that it can be mounted or dismounted independently from the bearing arrangement.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 371 of PCT/DE2008/001430 filed Aug. 27, 2008, which in turn claims the priority of DE 10 2007 042 369.3 filed Sep. 6, 2007, the priority of both applications is hereby claimed and both applications are incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     The invention lies in the field of landing gear for aircraft, in particular freight aircraft and commercial aircraft. In this area of use, various, partially inverse, optimization criteria have to be met. For example, landing gear of this type and therefore wheel bearings are loaded only briefly in relation to the overall operating period of the aircraft but, in these phases, are extremely highly loaded. During these loading phases, the wheel bearings must operate with the maximum reliability, absorb extreme forces and torques—for example during the braking operation following the landing—and must nevertheless be as lightweight and as low-maintenance as possible. 
     With regard to the maintenance, in particular to the bearing and brake inspection/renewal, it is desirable to be able to use standard bearings but nevertheless to implement a high level of integration and to provide the simplest and most compact subassemblies. 
     Against this background, the object of the present invention consists in providing a wheel bearing for aircraft which has a long service life and reliability with the smallest possible number of individual parts and provides subassemblies which are simple to handle and to mount or dismount. 
     According to the invention, this object is achieved by a wheel bearing having the features of patent claim  1 . 
     BRIEF SUMMARY OF THE INVENTION 
     An important aspect of the invention consists in the outer rings being held jointly by a single component, namely the outer ring bearing housing. As a result, the bearing arrangement already experiences a considerable improvement with regard to its ability to be mounted or dismounted. The bearing arrangement can advantageously be fitted with the anti-friction bearings in advance and, in a mounting process, can simply be applied to the respective load-bearing hollow axle or the bearing journal, and the rotatable part of the bearing arrangement can then be fitted with the rim later. Within the context of the present invention, the rotatable part of the bearing arrangement is to be understood to be that region of the bearing arrangement which, during operation, rotates about the wheel axle relative to the stationary bearing (e.g. the hollow axle or the bearing journal of the wheel bearing). 
     A further aspect of the invention consists in the rim both being joined to the rotatable part of the bearing arrangement and being configured in such a way that it can be mounted or dismounted independently of the bearing arrangement. This represents a substantial advantage, primarily with regard to the maintenance of the aircraft landing gear, in particular to the inspection and maintenance of the brake arrangement. This is because, with the wheel bearing according to the invention, the rim (possibly with the tires located thereon) can be removed simply and therefore the brake arrangement can be made accessible. 
     According to an advantageous refinement of the invention, the outer ring bearing housing forms the rotatable part of the bearing arrangement, on which the rim is detachably mounted. Preferably, the rim can be joined by means of appropriate screw joints to a cast-on part or an extension of the outer ring bearing housing, extending radially. 
     According to a refinement of the invention that is preferred in terms of mounting technology, the rim is in two parts. The two rim parts can be joined to each other in advance—for example screwed together—so that the rim overall forms a one-piece simple-to-handle unit. 
     According to a further advantageous refinement of the invention, the outer rings are integral constituent parts of the outer ring bearing housing, specifically in that the anti-friction bearing outer rings are formed from the material of the bearing housing. This further reduces the number of individual parts to be mounted. 
     As is known, specific bearing types, for example tapered roller bearings or angular contact ball bearings, require a defined axial bearing prestress for optimum bearing properties and bearing service life. This is normally applied by appropriate axial prestress elements, such as axle nuts. In order to be able to set a particularly simply reproducible prestress during fabrication, a preferred development of the invention provides for the bearing rings to have extensions which run toward each other in order to set an axial spacing or prestress of the anti-friction bearings. 
     The mounting and dismounting are further facilitated, according to a preferred development of the invention, by the extensions being pre-joined to each other via a clip. 
     In order to implement a bearing arrangement that is closed with respect to the outside, according to a further preferred refinement of the invention, a peripheral seal is provided between the mutually facing end regions of the extensions. 
     A subassembly in aircraft landing gear which is particularly demanding and in need of maintenance is the brake arrangement. This usually comprises a plurality of brake disks rotatably fixedly coupled to the rim and brake blocks located alternatingly between the latter in the axial direction and rotatably fixedly arranged. During operational braking, the brake blocks are loaded with an axial force which, in order to ensure an adequate braking effect, must be absorbed by a counter-mounting or a counter-bearing. In this context a preferred refinement of the invention provides for a counter-bearing to be detachably fixed to the outer ring bearing housing and to absorb the axial force applied by a disk brake arrangement during braking. The detachable arrangement of the counter-bearing provides the advantage that, in order to replace the brake linings or the brake disks, it is not necessary for the entire brake caliper of the brake arrangement to be dismounted; instead, following the dismounting of the rim, the components to be replaced can be removed or refitted in the axial direction. 
     According to a further refinement of the invention, the outer anti-friction bearing of the wheel bearing has a greater diameter. As a result, on the one hand the load-bearing force of the bearing is increased and, on the other hand, any relatively high torques acting on the wheel bearing transversely with respect to the wheel axle—for example in the event of a crosswind landing—can be absorbed by the bearing. 
     In order to implement an arrangement with a high load-bearing capacity that is particularly compact in the radial direction, in a further advantageous refinement according to the invention, a provision is made for the bearing arrangement to be arranged beside the brake arrangement as seen in the axial direction. 
     In applications in which, although there is a comparatively large radial space, and at the same time a restricted axial space being available for the wheel bearing, a refinement of the invention is advantageous in which the bearing arrangement is surrounded by the brake arrangement. 
     These and other objects and advantages of the present invention will be readily appreciable from the following description of preferred embodiments of the invention and from the accompanying drawings and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawing: 
         FIG. 1  shows a first wheel bearing according to the invention for an aircraft landing gear; 
         FIG. 2  shows a second wheel bearing according to the invention; 
         FIG. 3  shows the detail A from  FIG. 2 ; 
         FIG. 4  shows a third wheel bearing according to the invention; 
         FIG. 5  shows a fourth wheel bearing according to the invention; 
         FIG. 6  shows a fifth wheel bearing according to the invention; 
         FIG. 7  shows a sixth wheel bearing according to the invention; 
         FIG. 8  shows a seventh wheel bearing according to the invention; and 
         FIG. 9  shows an eight wheel bearing according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the figures, identical or functionally identical elements are provided with the same designations. 
       FIG. 1  shows a wheel bearing  1  according to the invention of an aircraft landing gear. The wheel bearing comprises a two-part rim  2 , onto which a tire, not illustrated, is fitted and which is assembled from two rim parts  3 ,  4 . The rim parts  3 ,  4  are joined to each other by connecting screws provided on the circumference and thus form an independent structural unit. 
     By way of illustration, a brake arrangement  5  can be seen, which is formed from brake linings or brake blocks  7  and brake disks  8  arranged alternatingly along the longitudinal axis  6 . The brake arrangement  5  can be pressurized in the axial direction via a ram  10 , shown by way of illustration, by a corresponding axial braking force  12  being exerted on the arrangement. In order to absorb the opposing force, a counter-bearing  14  is provided on the other side of the brake arrangement  5 . 
     A stub axle or a hollow axle  20  of the aircraft landing gear, otherwise not specifically illustrated, bears inner rings  21 ,  22  of two anti-friction bearings  23 ,  24  arranged axially spaced apart. The anti-friction bearings  23 ,  24  are configured as tapered roller bearings in the exemplary embodiments. In principle, however, other bearings, for example angular contact ball bearings, can also be used. 
     The bearing outer rings  25 ,  26  of the anti-friction bearings  23 ,  24  are jointly accommodated in a one-piece outer ring bearing housing  28 . For example, the outer bearing rings  25 ,  26  can be pressed into the housing  28 . The inner ring  22  of the anti-friction bearing  24  is fixed on the axle  20  in a manner known per se with an axle nut. 
     In this configuration, the outer ring bearing housing  28  forms the part  30  which can be rotated—seen in relation to the stationary axle  20 —of the bearing arrangement  31 . The rim  2  is detachably joined to a flange-like peripheral extension  32  extending radially outward and belonging to the bearing housing  28 , by means of a plurality of screws  33  arranged on a pitch circle. 
     For the purpose of mounting and dismounting, for example within the context of maintenance and inspection work, the rim  2  can be removed axially to the right from the wheel bearing or the axle  20  in one piece as a structural unit by loosening the screws  33 . The brake arrangement  5  is therefore easily accessible. In addition, the outer ring bearing housing forms a structural unit which is simple to handle during the mounting and which, in order to fulfill the actual rotational mounting, comprises only a comparatively few individual parts to be mounted. 
       FIG. 2  shows a variant of a wheel bearing according to the invention. The outer ring bearing housing  40  shown in  FIG. 2  is modified in as much as it extends radially further outward than the bearing housing  28  in  FIG. 1 . By means of a plurality of screws  42  distributed on the outer pitch circle circumference, the two-part rim  2  with its rim parts  3  and  4  is detachably joined to the outer ring bearing housing  40 . The rim parts  3  and  4  are pre-joined by screw connections  44  that are merely indicated, forming a structural unit. 
     Here, too, the outer ring bearing housing forms the rotating part  45  of the bearing arrangement  46 . Here, a counter-bearing  50  is provided in a stationary base area  49 , joined by a screw fixing  48 , in order to absorb the axial force exerted by the brake arrangement  5  during operational braking. 
     The bearing arrangement  46  has a modification with regard to the bearing inner rings  21 ,  22 , in as much as the latter are each provided with an axial extension  53 ,  54 . The extensions  53 ,  54 , facing each other axially, form spacers for setting an axial distance between the anti-friction bearings  23 ,  24 . The extensions  53 ,  54  are pre-joined to each other via a clip  56 , as the detail view A illustrated enlarged in  FIG. 3  indicates. The clip holds the two extensions in position and clamps a peripheral seal  58  between them. Therefore, in an advantageous way, the bearing arrangement  46  is formed as a closed unit protected against contamination and against the penetration of media from outside. The bearing inner rings  21 ,  22 —and the running surfaces formed by the latter for the anti-friction elements—can advantageously be formed integrally from the material  60  of the outer ring bearing housing 
       FIG. 4  shows a modified wheel bearing according to the invention which, in the axial direction, is constructed more compactly and is particularly capable of bearing a load and absorbing torques as a result of the fact that the outer anti-friction bearing  70  of the bearing arrangement  71  has a greater diameter than the inner anti-friction bearing  72 . To this end, the outer ring bearing housing  74  is formed with a step, so to speak, the bearing part of the inner rings of the anti-friction bearings having a corresponding stepped portion  75 . The inner part is fixed on the hollow axle  78  of the wheel bearing via an axle nut  77 . 
     In the embodiment shown in  FIG. 5  of a wheel bearing according to the invention, the bearing arrangement  80  is arranged laterally beside the brake arrangement  5  in the axial direction. Here, too, the rim  2  with its two rim parts  3 ,  4  is joined to the outer ring bearing housing  82  via a plurality of axial screws  81  arranged on the pitch circle. The bearing inner rings  84 ,  85  are fixed on an axle  87  in a manner known per se by an axle nut  86 . For the purpose of dismounting, the screw connection  81  is released and the rim  2  can then be removed axially to the right. It therefore not only exposes the brake arrangement  5  but also, in this exemplary embodiment, a counter-bearing  89  detachably fixed to a support  88 . The counter-bearing, as already previously described, is used to absorb the braking forces applied by a brake ram  90  and transmitted via the brake linings/brake blocks  7  and brake disks  8 . 
     This configuration is particularly advantageous for the brake inspection and maintenance, since the counter-bearing  89  detachably fixed via a screw connection  92  can be removed simply by loosening the connection  92 , and, therefore, the brake disks and brake linings are accessible axially and can be removed from the brake arrangement  5 . For the purpose of torque-transmitting fixing of the brake blocks  7  on the one hand and the brake disks  8  on the other hand, these can have axial recesses or grooves distributed over the periphery, in which corresponding webs on the rims and the rotating elements, on the one hand, and corresponding webs or projections of a brake caliper or of the support  88 , on the other hand, engage. 
     The variants according to  FIGS. 6 to 9  show wheel bearings according to the invention in which the outer ring bearing housing  100  is in each case fixed to a hollow axle  101  or a stub axle rotatably fixed. In the manner described previously, in each case a counter-bearing  102  is detachably fixed to the outer ring bearing housing  100  via a screw connection  103  in the manner and with the advantages as previously already described ( FIGS. 6 and 7 ). Alternatively ( FIGS. 8 and 9 ), the counter-bearing  102  can also be fixed to the hollow axle  101 . 
     In a further common feature in the exemplary embodiments according to  FIGS. 6 to 9 , the bearing arrangement  105  is, so to speak, arranged completely inside the brake arrangement  5 . Therefore, despite a comparatively wider spacing of the anti-friction bearings  107 ,  108 , a design of the wheel bearing that is very compact in the axial direction can be implemented. 
     As illustrated by  FIG. 7 , for example, in the event of loosening the screw connection  110 , indicated only schematically, between the rim  2  and an inner hollow axle  112 , which is mounted via the anti-friction bearings  107  and  108  such that it can rotate with respect to the outer ring bearing housing  100 , particularly good access to the brake arrangement  5  is possible. The embodiment shown in  FIG. 7  also has the additional advantage that, following the dismounting of the rim  2  and of the counter-bearing  102  and removal of the brake arrangement  5 , a connecting screw  114 , via which the outer ring bearing housing  100  is screwed to the hollow axle  101 , also becomes accessible from the right-hand side. 
       FIG. 8  shows a further form of configuration in which, in the outer ring bearing housing  100 , running surfaces  116 ,  117  for the anti-friction elements  118 ,  119  of the anti-friction bearings  107 ,  108  are integrally formed at the same time. The outer ring bearing housing  100  is fixed, for example via a screw fixing or a circlip  120 , in the hollow axle  101  serving as a support. With this form of configuration according to  FIGS. 8 and 9 . the brake arrangement  5  can be implemented as what is known as a “floating” brake caliper even without a specific brake caliper base. 
       FIG. 9  shows a further special feature with regard to the fixing of the rim in the rotatable region of the bearing arrangement, which, in this example, is formed by the inner hollow axle  121 . To be specific, the rim  2  here is screwed to the hollow axle  121  in a particularly simple way via an axle nut  122 . 
     Thus, it is seen that the objects of the present invention are efficiently obtained, although modifications and changes to the invention should be readily apparent to those having ordinary skill in the art, which modifications are intended to be within the spirit and scope of the invention as claimed. It also is understood that the foregoing description is illustrative of the present invention and should not be considered as limiting. Therefore, other embodiments of the present invention are possible without departing from the spirit and scope of the present invention. 
     LIST OF DESIGNATIONS 
     
         
         
           
             A Detail view from  FIG. 2   
               1  Wheel bearing 
               2  Rim 
               3 ,  4  Rim parts 
               5  Brake arrangement 
               6  Longitudinal axis 
               7  Brake linings/brake blocks 
               8  Brake disks 
               10  Ram 
               12  Braking force 
               14  Counter-bearing 
               20  Stub axle/hollow axle 
               21 ,  22  Inner rings 
               23 ,  24  Anti-friction bearings 
               25 ,  26  Bearing outer rings 
               28  Outer ring bearing housing 
               30  Axle nut 
               31  Rotatable part 
               32  Extension 
               33  Screws 
               40  Outer ring bearing housing 
               42  Screw joints 
               44  Screw connections 
               45  Rotating part 
               46  Bearing arrangement 
               48  Screw joint 
               49  Base area 
               50  Counter-bearing 
               53 ,  54  Extensions 
               56  Clip 
               58  Seal 
               60  Material of the outer ring bearing housing 
               70  Outer anti-friction bearing 
               71  Bearing arrangement 
               72  Inner anti-friction bearing 
               74  Outer ring bearing housing 
               75  Stepped portion 
               77  Axle nut 
               78  Hollow axle 
               80  Bearing arrangement 
               81  Screw joint 
               82  Outer ring bearing housing 
               84 ,  85  Bearing inner rings 
               86  Axle nut 
               87  Axle 
               88  Support 
               89  Counter-bearing 
               90  Brake ram 
               92  Screw connection 
               100  Outer ring bearing housing 
               101  Hollow axle 
               102  Counter-bearing 
               103  Screw connection 
               105  Bearing arrangement 
               107 ,  108  Anti-friction bearings 
               110  Screw connection 
               112  Hollow axle 
               114  Connecting screw 
               116 ,  117  Running surfaces 
               118 ,  119  Anti-friction elements 
               120  Circlip 
               121  Inner hollow axle 
               122  Axle nut