Abstract:
Vehicle wheel comprising a rim part and a disc part formed from a one-piece sheet metal blank and including a central portion with bolt holes and a plurality of radially extending spoke arrangements merging into a disc edge delimiting together with the spoke arrangements ventilation apertures which extend over the region between the edge webs and the disc edge. In order to create steel wheels with four-hole fixing in which high strength and stiffness are achieved the number of spoke arrangements and of bolt holes is four and these are in each case arranged mirror-symmetrically with respect to a common radial line, with the width of each spoke arrangement narrowing radially towards the outside and each ventilation aperture extending in the circumferential direction over an arc length of more than ⅙ of the circumference of the disc part. Further, each ventilation aperture is having on a radial line a maximum radial clear width which is equal to or preferably greater than the radial width of the metal portion of the disc part on the same radial line.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a national stage of International Application No. PCT/IB2014/059136 filed Feb. 20, 2014, the disclosures of which are incorporated herein by reference in entirety, and which claimed priority to German Patent Application No. 20 2013 100 875.3, filed Feb. 28, 2013, the disclosures of which are incorporated herein by reference in entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to a vehicle wheel, in particular for passenger cars, comprising a rim part for receiving a tyre and a disc part which is connected to the rim part and is formed from a one-piece sheet metal blank by forming and cutting or punching, which disc part includes a central portion having bolt holes for wheel bolts and a central aperture for a vehicle hub and a plurality of radially extending spoke arrangements, formed by shaping the sheet metal, for transmitting force between vehicle hub and rim part, each spoke arrangement being provided with a radially extending central web which merges on each side into a radially extending lateral web, bent outwardly from the plane of the central web, and then into an edge web bent back again with respect to the lateral web, the radially outer ends of the central webs and of the lateral webs merging into a circumferential annular disc edge oriented precisely parallel or substantially parallel axially to the wheel axis and connecting all the spoke arrangements to one another, which disc edge is formed integrally from the sheet metal, forms the connecting part for the connection between rim part and disc part and in each case delimits, together with the edge webs of adjacent spoke arrangements, ventilation apertures which extend over the region between the edge webs and the disc edge. 
         [0003]    A generic vehicle wheel for passenger cars, on which the preamble of claim  1  is based, is known from EP 1 262 333 A2 of the applicant, is usually referred to commercially as a “structured wheel” and is marketed by the applicant under the trade name “Versastyle®”. Through its construction this vehicle wheel, which is produced from a steel blank by shaping and has comparatively large-area ventilation apertures, can compete with aluminium wheels not only economically in terms of weight but also in terms of style, on the one hand because the wheel has a striking appearance resulting from the interplay between the multiple shaping of the spoke arrangements and the large ventilation apertures and, on the other, because different hub caps can be used with this vehicle wheel without disadvantage to the total weight of the wheel fitted with hub cap, as compared to a comparable cast-aluminium vehicle wheel. 
         [0004]    The vehicle wheel known from EP 1 262 333 A1 forms a new type of embossed steel wheel for passenger cars which hitherto has been produced only with five bolt holes and five spoke arrangements distributed symmetrically with respect to the bolt holes. Other manufacturers have also proposed innovations to this type of vehicle wheel, as shown, for example, by U.S. Pat. No. 7,104,611 B2 or EP 1 790 499 A1, in which minimal modifications to the vehicle wheel according to EP 1 262 333 A1 are described and all of which start from this vehicle wheel as the nearest prior art. 
         [0005]    Passenger cars, especially in the small, compact and mid-sized classes, frequently require wheels with four-hole fixing. The wheel structure according to EP 1 262 333 A2 thus gives rise to a steel vehicle wheel with four spoke arrangements and four bolt holes. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    It is a feature of the invention to create steel wheels for vehicles with four-hole fixing in which high strength and stiffness are achieved in conjunction with ventilation apertures of especially large area. 
         [0007]    This feature is achieved according to the invention in that the number of spoke arrangements and the number of bolt holes is four and one spoke arrangement and one bolt hole are in each case arranged mirror-symmetrically with respect to a common radial line, the width of each spoke arrangement becoming constantly narrower from the central portion radially towards the outside, each ventilation aperture extending in the circumferential direction, at the narrowest point of the spoke arrangements, over an arc length of more than ⅙ of the circumference of the disc part, at least on this reference circle, and each ventilation aperture having a maximum radial clear width, on a radial line disposed midway between two adjacent spoke arrangements, which is greater than the radial width of the metal portion of the disc part on the same radial line. 
         [0008]    In the vehicle wheel according to the invention, having four bolt holes and four spoke arrangements, each of which spoke arrangements extends in prolongation of a bolt hole, each ventilation aperture has, according to the invention, at the narrowest point of the spoke arrangements, an arc length of more than ⅙ of the circumference of the disc part on the same reference circle on which the narrowest points of the spoke arrangements lie, and at the same time each ventilation aperture extends in the radial direction over a clear width which is equal to or preferably greater than the metal portion between the centre hole and the region of the disc part bordering the ventilation aperture radially on the inside, which region is formed at this location by the convergent edge webs of the adjacent spoke arrangements. The ratio of the radial width of the metal portion of the disc part to the clear width of a ventilation aperture on the same radial line is then either approximately equal to  1  or preferably less than 1. 
         [0009]    It is especially advantageous if the ratio of radial width to clear width, and therefore the quotient of radial width/clear width, is from 0.85 to 0.95 and preferably is 0.9±0.02. 
         [0010]    Further preferably, the central webs of all the spoke arrangements may each extend, in a radial partial section, in a plane disposed orthogonally to the wheel axis, each partial section in turn having a length which is equal to or preferably greater than half the clear width of the ventilation apertures. The quotient of partial section/clear width is preferably from 0.6 to 0.7. 
         [0011]    The edge webs may have a depth which, starting from a radial line bisecting a ventilation aperture midway between two adjacent spoke arrangements, at first increases continuously and then decreases continuously again. The edge webs therefore have their narrowest zones, firstly, on the radial line bisecting the ventilation apertures and, secondly, at the outer ends of the spokes. 
         [0012]    Further advantageously, the distance between the lateral webs of a spoke arrangement, starting from the central portion in the direction of the outer spoke ends, may first narrow continuously, and then widen again. This measure also contributes, like the aforementioned measures, to improving the stiffness and load-bearing capacity of the disc part despite the large-area ventilation apertures. 
         [0013]    It is additionally advantageous if the maximum relative deformation depth between the central web and the transition of the lateral web to the edge web, in the range of extent of the ventilation apertures, is from 10 mm to 30 mm, the minimum depth in the region of the radial partial section preferably being greater than 10 mm. 
         [0014]    The outside edges of the edge webs bordering the ventilation aperture may be disposed, in radially outer regions of the ventilation apertures, at an angle of 6° to 10°, preferably 8°±1°, to the common radial line of bolt hole and spoke arrangement. Alternatively or additionally, the outside edges of the edge webs and of the disc edge directly bordering the ventilation aperture may be disposed, or cut off, obliquely with respect to the wheel axis. 
         [0015]    Other advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  shows a plan view of a vehicle wheel according to the invention in a first exemplary embodiment; 
           [0017]      FIG. 2  shows the vehicle wheel of  FIG. 1  in a perspective view; 
           [0018]      FIG. 3  shows a sectional view along III-III in  FIG. 1 ; 
           [0019]      FIG. 4  shows schematically a section through one of the spoke arrangements; 
           [0020]      FIG. 5  shows a plan view of a vehicle wheel according to the invention in a second exemplary embodiment; and 
           [0021]      FIG. 6  shows the vehicle wheel of  FIG. 5  in a sectional view along VI-VI in  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    In  FIGS. 1 to 3 , a vehicle wheel according to the invention in a first exemplary embodiment, consisting essentially of a circular rim part  1  having multiple steps, to the inner side of which a disc part  10  is fastened, is denoted as a whole by reference  50 . The rim part  1 , which receives a tyre (not shown), is fastened via a central portion  11  of the disc part  10  to a hub (not shown) of a vehicle (also not shown), in particular a passenger car. The rim part  1  extends in a very largely rotationally symmetrical manner around the wheel axis R, which generally coincides with the axis of the vehicle hub in the installed state of the vehicle wheel  50 . In the exemplary embodiments shown, both the rim part  1  and the disc part  10  consist of respective sheet metal blanks which take on the ring shape in the case of the rim part  1  and the disc shape in that of the disc part  10  through shaping and cutting or punching, as is known in principle by the person skilled in the art. In order to fasten the vehicle wheel  1  to the vehicle hub, the central portion  11  of the disc part  10  is provided with a central aperture  12  and with four bolt holes  13  offset to one another by 90° and arranged in the central portion  11 . In the exemplary embodiment shown, the central aperture  12  has an edge  14  which is bent up towards the outside of the wheel. The transmission of force between the rim part  1  carrying the tyre and the central portion  11  connected to the vehicle hub is effected via four spoke arrangements  15  formed by shaping the sheet metal and having multiple steps, each spoke arrangement  15  extending radially outwards in prolongation of one of the bolt holes  13 . Each spoke arrangement  15  has a plane central web  16  which is disposed orthogonally to the wheel axis R and which, viewed in the circumferential direction, merges on each side into a lateral web  17  extending radially and bent from the plane of the central web  16  towards the outer side of the wheel, and then into an edge web  18  which is bent back again with respect to the lateral web, whereby each spoke arrangement  15  receives essentially an approximately U-shaped cross section, as is indicated schematically in  FIG. 4 . 
         [0023]    As can be seen especially clearly in  FIGS. 1 and 2 , the width of each spoke arrangement  15  decreases from the central portion  11  radially towards the outside up to the outer ends of the spoke arrangements  15 . The outer ends of the four spoke arrangements  15 , or the outer ends of the central webs  16  and of at least the lateral webs  17 , merge into an annular disc edge  19 . As can be seen especially clearly in  FIG. 3 , the disc edge  19 , especially in the region of the ventilation apertures  5 , is disposed, completely or almost completely, exactly parallel to the wheel axis R. The disc edge  19 , as a circumferential part of the disc formed integrally from the starting blank for the disc part  10 , connects all four spoke arrangements  15  to one another. The disc edge  19  forms the connecting part via which the disc part  10  is connected to the underside of a drop centre  2  of the rim part  1 , preferably via a welded joint, in order to form a vehicle wheel. The outer, exposed edges  18 ′ of two adjacent spoke arrangements  15 , and the disc edge  19  disposed parallel to the wheel axis, delimit between two spoke arrangements  15  large-area ventilation apertures  5 , which accordingly extend over the whole region between the edge webs  18  of two adjacent spoke arrangements  15  and the disc edge  19 . In the vehicle wheel  50  according to the invention, the number of bolt holes  13  and the number of spoke arrangements  15  is four, and a given bolt hole  13  and a given spoke arrangement  15  lie mirror-symmetrically with respect to a common radial line R 1 . Accordingly, the vehicle wheel  50  has four ventilation apertures  5 . 
         [0024]    It can also be seen clearly in  FIGS. 1 and 2  that the edge webs  18  oriented towards the same ventilation aperture  5  in each case merge with each other at the point of intersection with a radial line R 2  which is disposed symmetrically between two bolt holes  13  or two adjacent spoke arrangements  15 , and which therefore in each case bisects a ventilation aperture  5 , viewed in the circumferential direction. The lateral webs  17  of adjacent spoke arrangements  15  also merge with one another on this radial line R 2 , and the disc part  10  has its greatest depth deformation along this radial line R 2 . 
         [0025]    The individual spoke arrangements  15  narrow towards the outside radially in such a way that, at the narrowest point of each spoke arrangement  15 , which coincides substantially with the region of transition between the spoke arrangements  15  and the disc edge  19  and is denoted by reference B′ in  FIG. 1 , the width of each individual spoke arrangement  15  is equal to or preferably less than 1/12 of the circumference of the disc part  10 . By contrast, the varying width of each spoke arrangement  15 , viewed in the circumferential direction, is indicated generally by reference B in  FIG. 1 . On the same reference circle around the wheel axis on which the individual spoke arrangements  15  have their narrowest width B′, the ventilation apertures  5  correspondingly have their greatest arc length, which is indicated in  FIG. 1  by reference L′. According to the invention, this greatest arc length L′ is selected such that each ventilation aperture  15  extends over an arc length L′ which is equal to or preferably greater than ⅙ of the circumference of the disc part on the same reference circle on which L′ and B′ lie. All four ventilation apertures therefore together extend over ⅔ or preferably more than ⅔ of the circumference of the disc part  10 . The four spoke arrangements  15  therefore together cover, at their smallest width B′, less than ⅓ of the circumference of the wheel disc or of the disc edge. This has at the same time the result that the individual ventilation apertures  5  each extend over a maximum arc length L′ which is preferably more than twice as great as the narrowest width B′ of a spoke arrangement  15 . 
         [0026]    At the same time, each ventilation aperture  5  has its maximum radial clear width on the radial line R 2 , and therefore on the radial line which in each case bisects the ventilation apertures  5  and on which the edge webs  18  and the lateral webs  17  of adjacent spoke arrangements  15  merge into one another. The clear width W of each ventilation aperture  5  on the radial line R 2  is in this case dimensioned such that it is equal to or preferably slightly greater than the radial width S of the metal portion in the central region of the disc part  11  on the same radial line R 2 ; the radial width S of the metal portion of the disc  10  refers in this case to the width between the internal circumference of the central aperture  12  and the outside edge  18 ′ on the radial line R 2 , where the definitions of the clear width W and of the radial width S of the disc part  10  relates to the plan view or projection of the wheel disc shown in  FIG. 1  and to the sectional view in  FIG. 3 , respectively. In particular, it can be seen especially clearly from the sectional view in  FIG. 3  that the wheel disc  10 , as is apparent in the lower half of  FIG. 3 , has its greatest depth or depth deformation V between the underside of the central portion  11  and the upper side of the wheel disc on the radial line R 2 , while the central webs  16  of the individual spoke arrangements  15  are embossed approximately ⅓ less far outwards with respect to the underside of the hub connection face. 
         [0027]    As can again be clearly seen in the sectional view of  FIG. 3 , each central web  16  extends parallel to the hub connection face and orthogonally to the wheel axis R over a relatively long radial partial section, the length of this partial section being denoted by reference T in  FIG. 1 . As a result, since all the spoke arrangements are identical, although offset circumferentially from one another, all the corresponding radial partial sections of the central webs  16  lie in a plane which runs perpendicularly to the wheel axis R. The length T, over which the central webs  16  of all the spoke arrangements  15  are disposed perpendicularly to the wheel axis R, is in each case longer than half the clear width W of a ventilation aperture and in this case is in the range 0.6 T/W 0.7, more precisely approximately 0.67. From the plan view in  FIG. 1  and the perspective view in  FIG. 2  it can also be clearly seen that the edge webs  18  have a depth X which changes continuously, viewed in the radial direction, at first increasing continuously, starting from the centre of the ventilation aperture, and then decreasing continuously again up to the spoke ends or the disc edge  19 . At the same time, the distance A between the lateral webs  17  of a spoke arrangement  15  (or the width of the central webs  16 ) also changes within each spoke arrangement  15 , which distance A, starting from the central portion  11  still encompassing the bolt holes  13 , first decreases continuously and then increases again. 
         [0028]    The maximum relative deformation depth between the upper side of the central web  16  and the upper side of the edge web  18  is designated in  FIG. 4  by reference Z and is preferably between 10 mm and 30 mm in the range of extent of the ventilation apertures, the minimum depth being greater than  10  mm in the region in which the central webs  16  are disposed plane-parallel to the hub connection face and perpendicularly to the wheel axis. 
         [0029]    As can again be clearly seen in the plan view in  FIG. 1 , the outside edges  18 ′ of the edge webs  18 , starting from the disc edge  19 , are disposed obliquely at an angle to the radial line R 1 , this oblique angle being from 6° to 10° and preferably being approximately 8°±1°.  FIGS. 3 and 4  show further that the outside edges  18 ′ of the edge webs  18  and the outside edges  19 ′ of the disc edge  19  are in each case disposed obliquely with respect to the wheel axis R. 
         [0030]    In the second exemplary embodiment of a wheel disc  150  as shown in  FIGS. 5 and 6 , the rim part  101  and the disc part  110  have almost the same structure as in the previous exemplary embodiment and the central portion  111  has, as in the previous exemplary embodiment, four bolt holes  113 , in prolongation of which in each case extends a spoke arrangement  115  with central web  116 , two lateral webs  117  which are bent towards the outside of the vehicle wheel  150  with respect to the central web  116 , and two edge webs  118  which are each bent back again, with respect to the bend from central web  116  to lateral web  117 , towards the rear side of a vehicle wheel  150 . The edge webs  118  of adjacent spoke arrangements  115  border large-area ventilation apertures  105 , and the disc edge  119  again runs exactly parallel to the wheel axis R in the region of the ventilation apertures  105 . The radial width S of the metal portion of the disc part  110  and the clear width W of each ventilation aperture  105 , and also the minimum width B′ and the greatest arc length L′ of the ventilation apertures  105  on the reference circle on which the minimum width B′ of the spoke arrangements  15  is located, have practically the same values as in the previous exemplary embodiment, and L′ is greater than ⅙ of the circumference of the disc part  110  on this wheel disc circumference. The radial partial length T, along which the central web  116  extends orthogonally with respect to the wheel axis R, is, however, considerably shorter than in the exemplary embodiment according to  FIGS. 1 to 4 , as can be seen especially clearly in  FIG. 6 , as a result of which a quotient T/W in the lower limit range of 0.6 is arrived at for the vehicle wheel  150 . 
         [0031]    For the person skilled in the art, the preceding description will yield numerous modifications which shall fall within the scope of protection of the appended claims. Although the arc length of the ventilation apertures is greater than ⅙ of the circumference of the disc part in all the preferred exemplary embodiments, the arc length may nevertheless also be equal to ⅙ of the circumference of the disc part or optionally even slightly less, without departing from the scope of protection of the appended claims. The central webs of the individual spoke arrangements might also be disposed slightly obliquely with respect to the wheel axis, even though the orthogonal orientation of the central webs is especially advantageous. The offset of the wheel disc in the rim part is in each case preferably selected such that the surfaces projecting furthest towards the outside of the wheel lie substantially flush with the outermost edge of the rim beads or further inwards, so that the disc part in no case projects beyond the rim part. Such and further modifications shall come within the scope of protection of the appended claims. 
         [0032]    In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiments. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.