Patent Publication Number: US-2011049966-A1

Title: Wheel hub

Description:
TECHNICAL FIELD 
     The present disclosure relates to a wheel hub and to a method of manufacturing a wheel hub. 
     BACKGROUND 
     Spoked wheels for vehicles such as trail motorcycles typically have a central hub and a rim for carrying a tire, with supporting spokes extending from the hub to the rim. Typically the hub is made from a lightweight material such as aluminium, and is machined from a billet of aluminium to form a unitary hub. This manufacturing method is very wasteful, as due to the shape of the hub a large amount of aluminium must be removed and disposed of as waste material. 
     Efforts have been made to overcome this problem. In one method, a wheel hub is manufactured in three parts: a hub center and two hub end parts having carriers for brake discs and drive chain sprockets respectively. The hub center is formed with a radially-extending terminal flange at each end, and the end parts are attached to the hub center by means of bolts, rivets or other fixing means which pass through apertures in the respective flanges and end parts to secure the respective end parts to the flanges. A disadvantage of this manufacturing method is that torque from a drive chain of the vehicle to which the wheel is attached is transferred through the bolts to drive the wheel. The bolts (or other fixing means) must therefore be extremely strong, which can lead to excessive weight. Any compromise on the weight of the bolts results in reduced reliability, as one or all of the bolts may shear due to the forces applied in use of the hub. 
     An alternative approach is to use a carbon fiber hub center with end parts attached to each end by means of an adhesive. This approach overcomes the problem of excessive weight, but requires the use of expensive carbon fiber. Moreover, the process of securing the end parts to the hub center using adhesive is extremely labor intensive and time consuming, requiring many hours of curing and baking in an oven before the wheel hub is complete. 
     SUMMARY 
     According to a first aspect there is provided a wheel hub comprising a hub center and an end part, the hub center having towards a first end thereof a first attachment formation comprising a bearing face, and the end part having an attachment formation which is configured to receive the first attachment formation of the hub center and which comprises a bearing face which is complementary to the bearing face of the hub center such that when the first attachment formation of the hub center is received in the attachment formation of the end part the bearing face of the hub center bears against the bearing face of the end part. 
     The wheel hub may offer reduced manufacturing costs over prior art systems, as it is not of a unitary construction thereby reducing the amount of material wasted in comparison to prior art methods. The mutual engagement of the bearing faces of the hub center and the complementary bearing faces of the end part assists in providing a close interference fit between the hub center and the end part whilst also providing for efficient transfer of torque from the hub center to the end part and thence to the wheel rim. 
     The hub center further may further comprise, towards a second end thereof, a second attachment formation comprising a bearing face, the second attachment formation being configured to be received in the attachment formation of the end part. 
     One or both of the first and second attachment formations of the hub center may comprise a peripheral flange which extends radially outwardly of the hub center, and the attachment formation of the end part may comprise a receiving formation for receiving the peripheral flange of the first or second attachment formation of the hub center. 
     The peripheral flange may comprise a plurality of bearing faces. 
     The peripheral flange and the receiving formation may be in the form of a nonagon. 
     One or both of the first and second attachment formations of the hub center may further comprise a generally cylindrical section which extends coaxially with the hub center, and the attachment formation of the end part may further comprise a bore for receiving the generally cylindrical section of the attachment formation of the hub center. 
     The generally cylindrical section may terminate in a generally open-ended tapering portion which defines an outer end of the hub center. 
     The bore and the receiving formation of the attachment formation of the end part may be concentric. 
     The end part may comprise a shoulder formed at an interface of the bore and the receiving formation of the attachment formation of the end part. 
     The second attachment formation may be angularly offset with respect to the first attachment formation. 
     According to a second aspect there is provided a hub center for a wheel hub according to the first aspect. 
     According to a third aspect there is provided an end part for a wheel hub according to the first aspect. 
     According to a fourth aspect there is provided a method of manufacturing a wheel hub according to the first aspect, the method comprising the steps of producing a hub center having towards a first end thereof a first attachment formation comprising a plurality of bearing faces, producing an end part having an attachment formation comprising a plurality of bearing faces, the attachment formation of the end part being configured to receive the attachment formation of the hub center, and attaching the hub center to the end part such that the bearing faces of the hub center bear against the bearing faces of the end part. 
     The attachment formation of the end part may comprise a through bore and a receiving formation which is concentric with the through bore, and the method may comprise forming the through bore and the receiving section simultaneously. 
     The method may further comprise the step of inserting into a central bore of the hub center a bearing assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the wheel hub and method of manufacturing will now be described, strictly by way of example only, with reference to the accompanying drawings, of which: 
         FIG. 1  is an exploded cross-sectional view showing elements of a wheel hub according to an embodiment; 
         FIG. 2  is a view from one end of a hub center; and 
         FIG. 3  is a schematic representation of part of a hub end part. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Referring first to the exploded cross-sectional view of  FIG. 1 , a wheel hub according to an embodiment is shown generally at  10 , and comprises a hub center  12  and first and second hub end parts  14 ,  16 . In this example the wheel hub  10  is for a spoked front wheel of a motorcycle, but it will be appreciated that the principles of the disclosed wheel hub and method of manufacturing are also applicable to other wheels. The hub center  12  comprises a hollow, generally cylindrical tube  18  defining a central bore in which a bearing assembly can be received such that the hub  10  can be rotatably mounted on an axle or the like. Towards each end of the hub center  12  there are provided first and second attachment formations  20 ,  22 , each of which is configured to engage with a complementary attachment formation  24 ,  26  of the respective hub end part  14 ,  16 . 
     The first attachment formation  20  has a peripheral flange  28  which extends radially outwardly of the cylindrical tube  20  of the hub center  12 . The peripheral flange  28  is provided with a plurality of outwardly-facing engagement faces  30  which are configured to engage with complementary engagement faces of the attachment formation  24  of the first hub end part  14 , as is described in more detail below. 
     Similarly, the second attachment formation  22  has a peripheral flange  32  which extends radially outwardly of the cylindrical tube  20  of the hub center  12 . The peripheral flange  32  is provided with a plurality of outwardly-facing engagement faces  34  which are configured to engage with complementary engagement faces of the attachment formation  26  of the second hub end part  16 , as is described in more detail below. 
     The first attachment formation  20  includes a hollow cylindrical section  36  which extends coaxially with the cylindrical tube  20  of the hub center. The hollow cylindrical section  36  terminates in a generally open-ended frusto-conical tapering portion  38  which defines an open, generally circular, first outer end of the hub center  12 . Thus, the first attachment formation  20  of the hub center  12  has three sections of decreasing diameter: the peripheral flange  28 , which has the greatest diameter; the cylindrical section  36 , which has a smaller diameter than the peripheral flange  28 ; and the open outer end of the tapering portion  38 , which has a smaller diameter than the cylindrical section  36 . 
     The second attachment formation  22  has a similar configuration to the first attachment formation  20 , including a hollow cylindrical section  40  which extends coaxially with the cylindrical tube  20  of the hub center. The hollow cylindrical section  40  terminates in a generally open-ended frusto-conical tapering portion  42  which defines an open, generally circular, second outer end of the hub center  12 . Thus, the second attachment formation  22  of the hub center  12  also has three sections of decreasing diameter: the peripheral flange  32 , which has the greatest diameter; the cylindrical section  40 , which has a smaller diameter than the peripheral flange  32 ; and the open outer end of the tapering portion  42 , which has a smaller diameter than the cylindrical section  40 . 
     The first attachment formation  20  of the hub center  12  will now be described in more detail by reference to  FIG. 2 , which is a view from one end of the hub center  12 . 
     As will be seen from  FIG. 2 , the peripheral flange  28  is in the form of a nonagon, and thus there are nine generally flat engagement faces  30 . In the example the hub  10  is intended for use in a wheel having thirty-six spokes (i.e. eighteen spokes on each of the first and second end parts  14 ,  16 ), so a nonagon-shaped peripheral flange  28  is particularly appropriate as it provides for an even distribution of spokes (two per engagement face  30 ) around the diameter of the hub  10 . It will be appreciated however that the peripheral flange  28  can take any shape, provided that it has at least one generally flat engagement face  30  which can engage with a corresponding engagement face of a hub end part  14 ,  16 . 
     The second engagement formation  22  has a similar configuration of a nonagonal peripheral flange  32  having nine generally flat engagement faces  34 , although again the peripheral flange  32  can take any shape, provided that it has at least one generally flat engagement face  34  can engage with a corresponding engagement face of a hub end part  14 ,  16 . It will be apparent from  FIG. 2  that the peripheral flange  32  of the second attachment formation  22  is angularly offset with respect to the peripheral flange  28  of the first attachment formation  20  to permit correct timing of spokes attached to the hub  10 . 
     The engagement formation  24  of the first hub end part  14  will now be described with reference to  FIG. 3 , which is a schematic representation of a hub end part. The hub end part  14  has a main body  44  with a plurality of equispaced holes or bores for accommodating spokes disposed towards its outer edge. As these are not relevant, they are not shown in  FIG. 3  for reasons of clarity, but the position, size and orientation of these holes or bores will be readily apparent to those skilled in the art of wheel hub manufacture. The hub end part  14  also includes attachment formations such as threaded bores for the attachment of a brake disc or the like, although again these are not shown in  FIG. 3  since they do not form part of the disclosed wheel hub and method of manufacturing. 
     The attachment formation  24  of the first hub end part  14  is positioned in the center of the main body  44  and has a generally cylindrical through bore  46  whose diameter is equal to or very slightly larger than the diameter of the cylindrical portion  36  of the first attachment formation  20  of the hub center. The bore  46  opens out into a receiving formation  48 , which is concentric with the through bore, and is in the shape of a nonagon having nine internal, inwardly-facing engagement faces  50 . The diameter of the receiving formation  48  is equal to or very slightly greater than that of the peripheral flange  28  of the first attachment formation  20  of the hub center  12 . Thus, an inner face  52  of the first hub end part  14  presents a nonagonal receiving formation  48  which is complementary to the shape of the peripheral flange  28  of the first attachment formation  20  of the hub center  12  in which the peripheral flange  28  can be received, such that the engagement faces  30  of the peripheral flange  28  bear against the engagement faces  50  of the attachment formation  24  of the first hub end part  14 . A shoulder  54  is formed at the interface of the through bore  46  and the receiving formation  48 , which shoulder  54  acts as a stop for the peripheral flange  28  of the first attachment formation  20  of the hub center  12  when it is received in the attachment formation  24  of the first end part  14 . 
     The attachment formation  26  of the second hub end part  16  has the same structure as the attachment formation  24  of the first hub end part  14 , having a central cylindrical through bore  58  opening out into a concentric nonagonal receiving formation  58  of a diameter equal to or slightly greater than that of the peripheral flange  32  of the second attachment formation  2  of the hub center  12 . The receiving formation  58  has nine inwardly facing engagement faces  60  which bear against the engagement faces  34  of the peripheral flange  32  of the second attachment formation  22  when the peripheral flange  32  is received in the receiving formation  58 . A shoulder  62  is formed at the interface of the through bore  56  and the receiving formation  58 , which acts as a stop for the peripheral flange  32  of the second attachment formation  22  when the peripheral flange  32  is received in the receiving formation  58 . In this example the diameter of a body  64  of the second hub end part  16  is smaller than that of the first end part  14 , as the second end part does not have to carry a brake disc or other components. It will be appreciated however that the diameter of the second end part  16  could be equal to or greater than that of the first end part  14 , depending upon the construction of the wheel in which the hub  10  is incorporated. 
     To manufacture the hub  10  described above, the hub center  12  and the first and second end parts  14 ,  16  are formed separately, for example by milling from billets of aluminium. Forming the hub center  12  and the first and second end parts  14 ,  16  separately in this way reduces the amount of waste material, since it not necessary to use a single large billet of aluminium to form the whole hub  10 , but rather smaller billets can be used to form the individual parts  12 ,  14 ,  16 . In forming the first end part  14  it is advantageous to mill the nonagonal receiving formation  48  and the through bore  46  simultaneously to ensure that they are concentric. Similarly, it is advantageous to mill the nonagonal receiving formation  58  and the through bore  56  of the second end part  16  simultaneously. 
     Once the hub center  12  and the first and second end parts  14 ,  16  have been formed the hub  10  can be assembled. The first attachment formation  20  of the hub center  12  is inserted into the attachment formation  24  of the first end part  14 . The peripheral flange  28  of the first attachment formation  20  is aligned with the complementary receiving formation  48  of the first end part  14  and the hub center  12  and the first end part  14  are urged together. The inwardly tapering portion  38  of the first attachment formation  20  of the hub center  12  reduces the risk of misalignment of the first attachment formation  20  of the hub center  12  and the attachment formation  24  of the first end part  14 . 
     As the hub center  12  and the first end part are urged together the engagement faces  30  of the peripheral flange engage with the complementary engagement faces  50  of the first end part  14 , whilst the outer surface of the cylindrical portion  36  of the first engagement formation of the hub center  12  engages with the outer surface of the through bore  46  of the first end part  14 . When the first attachment formation  20  of the hub center  12  is fully engaged with the attachment formation  24  of the first end part  14  the peripheral flange  28  bears against the shoulder  54  of the first end part  12 , whilst the engagement faces  30  of the peripheral flange  28  bear against the complementary engagement faces  50  of the first end part  14 . In attaching the first end part  14  to the hub center  12  the cylindrical portion  36  and the peripheral flange  28  may undergo some minor deformation due to the very similar (or identical) diameters of the cylindrical portion  36  and the through bore  46  and of the peripheral flange  28  and the receiving formation  48 . These diameters ensure a very close interference fit between the cylindrical portion  36  and the through bore  46  and between the peripheral flange  28  and the receiving formation  48 . 
     Once the first end part  14  has been attached to the first attachment formation  20  of the hub center  12  the second end part  16  is attached to the second attachment formation  22  of the hub center in a similar manner. 
     A bearing assembly is then inserted into the central bore defined by the cylindrical tube  18  of the hub center. Insertion of the bearing unit may cause the inwardly tapering portions  38 ,  42  of the first and second attachment formations  20 ,  22  of the hub center  12  to deform by flaring outwardly, thereby enhancing the interference fit engagement of the first and second attachment formations  20 ,  22  of the hub center with the attachment formations  24 ,  26  of the first and second end parts  14 ,  16 . 
     This method of construction offers a number of advantages over prior art methods. A major advantage is the reduce waste of material in comparison to prior art methods. This method is quicker and more straightforward than the prior art method involving carbon fiber hub centers, whilst producing hubs with improved performance than the prior art method which uses a flanged hub to which hub end parts are bolted. The mutual engagement of the bearing faces  30 ,  34  of the first and second end parts  14 ,  16  and the complementary bearing faces  50 ,  60  of the receiving formations  24 ,  26  of the first and second end parts  14 ,  16  assists in providing a close interference fit between the respective attachment formations  20 ,  24  and  22 ,  26  whilst also providing for efficient transfer of torque from the hub center  12  to the end parts  14 ,  16  and thence to the wheel rim. 
     In the exemplary embodiment described above the wheel hub  10  is formed from three separate parts, the hub center  12  and the two hub end parts  14 ,  16 . It will be appreciated, however, that the disclosed principles are equally applicable to other constructions, For example, the hub center  12  could be formed with an integral end part, with the other end part being attachable using attachment formations as described above. Alternatively, one end part  14 ,  16  could be attached to the hub center  12  using bolts or adhesive, as is known from the prior art, with the other end part  16 ,  14  being attachable using attachment formations as described above. 
     While the present invention has been described with reference to specific examples, which are intended to be illustrative only and not to be limiting of the invention, it will be apparent to those of ordinary skill in the art that changes, additions or deletions may be made to the disclosed embodiments without departing from the spirit and scope of the invention.