Abstract:
An automobile steering wheel and method of manufacturing a steering wheel are disclosed. The steering wheel comprises a hub core connected with rods of a hub via t-shaped connectors. A cover layer includes a hard part and a soft part around the periphery of the hub core and connectors. A vinyl layer and a leather layer encompass the cover layer. A coupling protruder is formed at the front end of the hard part and extends toward the soft part. A plurality of coupling ribs are mounted on the surface of the coupling protruder.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application claims priority of Korean Application No. 2002-65876, filed on Oct. 28, 2002, the disclosure of which is incorporated fully herein by reference.  
         FIELD OF THE INVENTION  
         [0002]    The present invention relates to an automobile steering wheel and a manufacturing method thereof for preventing deterioration of the grained vinyl cover and leather cover of the steering wheel at the boundary thereof.  
         BACKGROUND OF THE INVENTION  
         [0003]    In a luxury steering wheel, some parts thereof are preferably covered with a grained material for a natural and elegant appearance while the residual parts are covered with leather for preventing slippage and improving the handling of the steering wheel.  
           [0004]    When the steering wheel is covered by two different kinds of materials such as a grained vinyl cover and leather, the connecting structure and connecting method of the two materials are important for maintaining a long lasting and fine external appearance.  
         SUMMARY OF THE INVENTION  
         [0005]    Embodiments of the present invention provide an automobile steering wheel and a manufacturing method thereof adapted to preliminarily prevent formation of a gap in the bordering area between the grained material and leather cover that may contract due to changes in temperature and moisture.  
           [0006]    In one embodiment of the present invention, a steering wheel comprises a hub core of a steering wheel rim integrally connected with rods of a hub via T-shaped connectors, a cover layer including a hard part and a soft part formed around the periphery of the hub core and the T-shaped connector, and a grained vinyl cover and a leather cover for encompassing the cover layer. The steering wheel further comprises a coupling protruder formed at the frontal end of the hard part toward the soft part where the frontal end of the hard part is positioned as a boundary of the grained vinyl cover and leather cover, and a plurality of coupling ribs mounted on the surface of the coupling protruder for being engaged with the soft part and the leather cover.  
           [0007]    In another embodiment of the present invention, a manufacturing method for a steering wheel comprises manufacturing a hub core constituting a steering wheel rim by either steel roll-molding or Magnesium (Mg) injection-molding; assembling a T-shaped connector formed by Aluminum (Al) die casting, with a hub core by welding; putting the hub core and T-shaped connector assembly into a mold for coating a cover layer thereon, where the cover layer includes a hard part and a soft part; and covering a grained vinyl cover and a leather cover on the cover layer. A preferred manufacturing method may further comprise injection-molding the hard part on a partial section of the hub core and T-shaped connector; foam-molding the soft part on the remaining part in order to overlap with the hard part; coating the grained vinyl cover on the surface of the hard part; and assembling the leather cover on the surface of the soft part for completion of the steering wheel cover. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    For fuller understanding of the nature and objects of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings in which:  
         [0009]    [0009]FIG. 1 illustrates a front view of a steering wheel according to an embodiment of the present invention;  
         [0010]    [0010]FIG. 2 is a partial sectional view taken along line II-II of FIG. 1 according to the embodiment of the present invention;  
         [0011]    [0011]FIG. 3 is a partial sectional view taken along line III-III of FIG. 2 according to the embodiment of the present invention; and  
         [0012]    [0012]FIG. 4 is a schematic flowchart describing a manufacturing method of a steering wheel according to the embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]    Hereinafter, the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.  
         [0014]    A steering wheel, as shown in FIGS.  1  to  3 , includes a steering wheel rim  1  taking a shape of a ring, a hub  2  into which the front end of a steering shaft is mounted in addition to a horn and an air-bag, and an upper spoke  3   a  and a lower spoke  3   b  for connecting the hub  2  and the steering wheel rim  1 .  
         [0015]    The upper and the lower spoke  3   a  and  3   b  include a T-shaped connector  4  manufactured in A 1  die casting. The three end openings of the T-shaped connector  4  are respectively inserted and welded into a hub core  5  and a hub rod  2   a  secured at the hub  2  for an integral form of the steering wheel rim  1  and the hub  2 .  
         [0016]    Following the completion of the frame of a steering wheel, a cover layer  6  having a hard part  6   a  and a soft part  6   b  is formed thereon for a fine external look and easy operation. The hard part  6   a  is preferably formed by an injection molding using a glass fiber, while the soft part  6   b  is preferably formed by a foam molding using a Polyurethane (PU). Moreover, a grained vinyl cover  7  and a leather cover  8  are used to shroud the external surface of the cover layer  6  for a good external look and non-slippage of the steering wheel. In other words, as shown in FIG. 1, the grained vinyl cover  7  is wrapped around the upper part of the steering wheel  1  above the upper spoke  3   a  and around the lower part of the steering wheel  1  below the lower spoke  3   b . The leather  8  is covered at the remaining portions of the steering wheel rim  1 .  
         [0017]    On the other hand, because the grained vinyl cover  7  and the leather cover  8  respectively have different contraction and expansion coefficients in response to temperature and moisture, the boundary part (M) therebetween may generate a gap when a hard contraction occurs. This drawback, however, can be overcome by extensively protruding the frontal end of the hard part  6   a  toward the soft part  6   b  and by coupling the hard part  6   a  protruded toward the soft part  6   b  with the soft part  6   b  and the leather cover  8 .  
         [0018]    As a result, the frontal end of the hard part  6   a  is formed with a coupling protruder  6   a - 1  projected to the soft part  6   b , wherein a plurality of coupling ribs  6   a - 2  are formed at the surface of the coupling protruder  6   a - 1 . The soft part  6   b  is coupled with the plurality of coupling ribs  6   a - 2  by foam molding so as to be overlapped with the hard part  6   a . In addition, when the leather cover  8  embraces the soft part  6   b , the plurality of coupling ribs  6   a - 2  are closely attached to the inner side of the leather cover  8 , thereby preventing the boundary part (M) of the grained vinyl cover  7  and leather cover  8  from being widened even if contraction or expansion occurs due to the temperature and moisture.  
         [0019]    The coupling protruder  6   a - 1  and the plurality of coupling ribs  6   a - 2  are preferably integrally formed with the hard part  6   a , the hard part  6   a  made via injection molding. Further, coupling rib grooves  8   b  into which the plurality of coupling ribs  6   a    2  are inserted are formed inside the leather cover  8  for increasing the connecting force of the grained vinyl cover  7  and leather cover  8 .  
         [0020]    The steering wheel is preferably configured through a process as illustrated in the flowchart in FIG. 4. A hub core  5  of the steering wheel rim  1  is manufactured by either steel roll-molding or Mg injection-molding (S1). A T-shaped connector  4  manufactured by Al die casting is assembled with a hub core  5  by welding (S2). The hub core  5  and T-shaped connector  4  assembly is put into a mold for integrally forming with a hard part  6   a , a coupling protruder  6   a - 1 , and a plurality of coupling ribs  6   a - 2  at a predetermined section thereon by glass fiber injection molding (S3). A soft part  6   b  embraces the leftover section unformed with the hard part  6   a , by PU foam-molding (S4), thereby completing the exterior of the steering wheel.  
         [0021]    A film sheet of a grained vinyl cover  7  is attached onto the surface of the hard part  6   a  manufactured by the glass fiber (S5). A leather cover  8  is wound by stitches around the surface of the soft part  6   b  manufactured by PU (S6), allowing to complete the manufacturing process of a steering wheel having the grained vinyl cover  7  and the leather cover  8 .  
         [0022]    Thus, there is an advantage in embodiments of the present invention in that a soft part  6   b  shrouds a coupling protruder  6   a - 1  and a plurality of coupling ribs  6   a - 2  embedded into coupling rib grooves  8   b  of a leather cover  8 . As a result, the end of the leather cover  8  may be held by the plurality of coupling ribs  6   a - 2 , preventing contraction between the grained vinyl cover  7  and the leather cover  8  even in varying temperature and moisture conditions.  
         [0023]    There is another advantage in that the structure thus described prevents the boundary part (M) of the grained vinyl cover  7  and the leather cover  8  from being widened, thereby maintaining a fine look of the steering wheel.  
         [0024]    As apparent from the foregoing, there is still another advantage in that the automobile steering wheel is integrally formed with a coupling protruder and a plurality of coupling ribs at a frontal end of a hard part as a cover layer wherein a soft part is overlapped with the coupling protruder and the plurality of coupling ribs by foam molding, enabling to prevent a gap at a boundary caused by changes in temperature and moisture between the grained vinyl cover and leather cover which respectively encompass the hard part and soft part.