Abstract:
In order to provide a steering wheel that can prevent chattering of a wooden member with respect to a metal core, a steering wheel comprising: an annular metal core, the metal core connecting to a vehicle; and a wooden member, the wooden member curving in a substantial arc corresponding to the metal core and having a passing hole formed therein, with the metal core passing through the passing hole; wherein a space is formed at, at least a portion of boundary between the metal core and an inner wall, forming the passing hole, of the wooden member, the space being for absorbing relative movement of the metal core and the wooden member, is provided.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a steering wheel in which a wooden member is mounted on a metal core.  
           [0003]    2. Description of the Related Art  
           [0004]    Vehicular steering wheels are disposed with, for example, an annular core made of metal, and the core connects with the vehicle. Part of the core is disposed with a wooden member for decoration and such. The wooden member is formed in an arc with respect to the metal core and has a passing hole formed in an interior thereof. The wooden member is mounted to the metal core by the metal core being substantially fitted into the passing hole. A rigid adhesive having no elasticity is disposed between the metal core and an inner wall of the passing hole formed in the wooden member. The metal core and the inner wall of the wooden member are thus adhered together by the rigid adhesive, whereby the wooden member is fixed to the metal core.  
           [0005]    However, in such a steering wheel, the metal core and the wooden member expand and contract in response to changes in external temperature and external humidity. More precisely, the coefficients of expansion and contraction of the metal core due to changes in temperature are large, while the coefficients of expansion and contraction of the metal core due changes in humidity are quite small. In comparison, the coefficients of expansion and contraction of the wooden member due to humidity is large, while the coefficients of expansion and contraction of the wooden member due to changes in temperature are quite small. For this reason, when there are changes in external temperature and humidity, the metal core and the wooden member move relative to one another as a result of differences in respective coefficients of expansion and contraction. Moreover, because the rigid adhesive is inelastic, it becomes easy for the adhesive to the metal core and to the wooden member to exfoliate and for the gap between the metal core and the wooden member to become non-uniform, whereby the metal core and the wooden member separate from one another and chattering of the wooden member with respect to the metal core is generated.  
           [0006]    In particular, because the amount of relative movement with respect to the metal core is large at inner sides and outer sides of the inner wall (i.e., inner and outer sides of the inner wall with respect to the boss) of the wooden member (in relation to these portions of the inner wall of the wooden member, for example, the amount of deformation of the metal core is large when the metal core expands or contracts due to changes in external temperature), there is a large amount of chattering.  
         SUMMARY OF THE INVENTION  
         [0007]    In consideration of the aforementioned facts, it is an object of the present invention to obtain a steering wheel that can prevent chattering of a wooden member with respect to a metal core.  
           [0008]    In order to achieve this object, a first aspect of the present invention is a steering wheel comprising: an annular metal core, the metal core connecting to a vehicle; and a wooden member, the wooden member curving in a substantial arc with respect to the metal core and having a passing hole formed therein, with the metal core passing through the passing hole; wherein radial direction spaces in the radial direction of the metal core are disposed between the metal core and an inner wall of the wooden member including the passing hole.  
           [0009]    In the steering wheel of the first aspect, the metal core is passed through a passing hole in the interior of the wooden member, whereby the wooden member is mounted to the metal core.  
           [0010]    Radial direction spaces in the radial direction of the metal core are disposed between the metal core and the inner wall of the wooden member including the passing hole. Therefore, the radial direction spaces absorb relative movement of the metal core and the wooden member when the metal core and the wooden member relatively move as a result of changes in external temperature or humidity. Accordingly, it is possible to prevent the wooden member from chattering with respect to the metal core. (It is possible to prevent backlash between the wooden member  20  and the metal core  16 .)  
           [0011]    A steering wheel according to a second aspect of the present invention comprises the steering wheel of the first aspect, wherein axial direction spaces in a steering shaft longitudinal direction are disposed between the metal core and the inner wall of the wooden member, and elastic members are disposed at areas where the radial direction spaces and the axial direction spaces border.  
           [0012]    In the steering wheel according to the second aspect, not only are radial direction spaces disposed between the metal core and the inner wall of the wooden member, but axial direction spaces in the steering shaft longitudinal direction are also disposed between the metal core and the inner wall of the wooden member, and elastic members are disposed at areas where the radial direction spaces and the axial direction spaces border. For this reason, the radial direction spaces and the axial direction spaces absorb relative movement of the metal core and the wooden member when there are changes in external temperature or humidity. Moreover, because the elastic member expands and contracts in response to relative movement of the metal core and the wooden member, absorption of the relative movement of the metal core and the wooden member by the radial direction spaces and the axial direction spaces is not hindered. Accordingly, it is further possible to prevent the wooden member from chattering with respect to the metal core.  
           [0013]    A steering wheel according to a third aspect of the present invention comprises the steering wheel of the second aspect, wherein the elastic member adheres the inner wall of the wooden member and the metal core.  
           [0014]    In the steering wheel of the third aspect, because the elastic member adheres the inner wall of the wooden member and the metal core, the wooden member can be reliably adhered to the metal core.  
           [0015]    Further, because the elastic member has elasticity, exfoliation of the elastic member to the inner wall of the wooden member and to the metal core when the metal core and the wooden member relatively move can be prevented. Accordingly, it is possible to reliably prevent the wooden member from chattering with respect to the metal core without the metal core and the wooden member separating from one another.  
           [0016]    A steering wheel of a fourth aspect of the present invention comprises an annular metal core, the metal core connecting to a vehicle (body); and a wooden member, the wooden member curving in a substantial arc corresponding to the metal core and having a passing hole formed therein, with the metal core passing through the passing hole; wherein a space is formed at, at least a portion of boundary between the metal core and an inner wall, forming the passing hole, of the wooden member, the space being for absorbing relative movement of the metal core and the wooden member.  
           [0017]    A steering wheel according to a fifth aspect of the present invention comprises the steering wheel of the fourth aspect, wherein an elastic member having elasticity is disposed in at least a portion of the space.  
           [0018]    A steering wheel according to a sixth aspect of the present invention comprises the steering wheel of the fourth aspect, wherein the elastic members are disposed in positions which face each other with respect to the metal core.  
           [0019]    A steering wheel according to a seventh aspect of the present invention comprises the steering wheel of the fourth aspect, wherein the passing hole has a substantially rectangular cross sectional configuration, and the elastic members are disposed in corner portions of the passing hole.  
           [0020]    A steering wheel according to an eighth aspect of the present invention comprises the steering wheel of the fourth aspect, wherein the elastic member is disposed around the entire periphery of the metal core.  
           [0021]    In the steering wheel of the fourth aspect, the metal core is passed through a passing hole in the interior of the wooden member, whereby the wooden member is mounted to the metal core.  
           [0022]    The space is disposed at, at least the portion of boundary between the metal core and an inner wall, forming the passing hole, of the wooden member, the space being for absorbing relative movement of the metal core and the wooden member when the metal core and the wooden member relatively move as a result of changes in external temperature or humidity. Therefore, the space can absorb the relative movement of the metal core and the wooden member when the metal core and the wooden member relatively move as a result of changes in external temperature or humidity. Accordingly, it is possible to prevent the wooden member from chattering with respect to the metal core.  
           [0023]    In the steering wheel of the fifth aspect, the elastic member having elasticity is disposed in at least the portion of the space. Therefore, the space absorbs the relative movement of the metal core and the wooden member when the metal core and the wooden member relatively move as a result of changes in external temperature or humidity. Accordingly, it is possible to prevent the wooden member from chattering with respect to the metal core. Moreover, because the elastic member expands and contracts in response to relative movement of the metal core and the wooden member, absorption of the relative movement of the metal core and the wooden member is not hindered. Accordingly, it is further possible to prevent the wooden member from chattering with respect to the metal core.  
           [0024]    In the steering wheel of the sixth, seventh and eighth aspects, as same as the fourth and fifth aspects, the space absorbs the relative movement of the metal core and the wooden member when the metal core and the wooden member relatively move as a result of changes in external temperature or humidity. Accordingly, it is possible to prevent the wooden member from chattering with respect to the metal core. Moreover, because the elastic member expands and contracts in response to relative movement of the metal core and the wooden member, absorption of the relative movement of the metal core and the wooden member is not hindered. Accordingly, it is further possible to prevent the wooden member from chattering with respect to the metal core. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]    [0025]FIG. 1 is a cross-sectional view (taken along line  1 - 1  of FIG. 2) of main portions (metal core, wooden member and elastic adhesive) of a steering wheel pertaining to an embodiment of the present invention.  
         [0026]    [0026]FIG. 2 is a front view of the steering wheel.  
         [0027]    [0027]FIG. 3 is a cross-sectional view of the metal core and the wooden member at the time the metal core has expanded due to a rise in external temperature.  
         [0028]    [0028]FIG. 4 is a cross-sectional view of another example of main portions (metal core, wooden member and elastic adhesive) of the steering wheel pertaining to the embodiment of the present invention.  
         [0029]    [0029]FIG. 5 is a cross-sectional view of another example of main portions (metal core, wooden member and elastic adhesive) of the steering wheel pertaining to the embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0030]    In FIG. 1, main portions of a steering wheel  10  pertaining to an embodiment of the present invention are illustrated in cross-sectional view (taken along line  1 - 1  of FIG. 2). In FIG. 2, the steering wheel  10  is shown in front view.  
         [0031]    The steering wheel  10  pertaining to the embodiment of the present invention is disposed with a boss  12  that is fixed to a steering shaft (not shown in the drawings) of a vehicle. Proximal ends (with respect to the boss) of spokes  14  (three in the present embodiment) join with the boss  12 . The spokes  14  extend respectively beneath, to the right of and to the left of the boss  12 .  
         [0032]    A metal core  16  (e.g., comprising magnesium) is disposed at respective distal ends of the spokes  14 . Accordingly, the metal core  16  is connected to the vehicle via the spokes  14  and the boss  12 . Further, the metal core  16  is formed in an annular manner when seen in front view and in a substantially U-shape when seen in cross section, and is disposed in opposition to the driver&#39;s seat.  
         [0033]    A leather portion (leather coated portion)  18  is disposed at an area of the steering wheel  10  other than an upper area of the steering wheel  10 . The leather portion  18  comprises leather which has been coated on a resin surface. The leather portion  18  encircles the metal core  16  and distal areas (i.e., distal with respect to the boss  12 ) of the spokes  14 , whereby the leather portion  18  is mounted on the metal core  16  and the respective spokes  14 . It should be noted that the leather portion  18  may also comprise a structure in which leather is not coated on a resin surface (i.e., the leather portion  18  may alternatively comprise only resin).  
         [0034]    A wooden member  20  is disposed for decoration or such at an upper area of the steering wheel  10 . The wooden member  20  curves in an arc-like manner with respect to the metal core  16 . The wooden member  20  is cylindrical and has a passing hole (substantially square (rectangle) when seen in cross-section) that passes through an interior of the wooden member  20  (the peripheral wall of the passing hole will hereinafter be referred to as “inner wall  22  of the wooden member  20 ”). The wooden member  20  comprises a pair of pieces (piece  20 A and piece  20 B). Piece  20 A is disposed at an upper side (vehicle occupant side) of the metal core  16  in a steering shaft direction and piece  20 B is disposed at a lower side (anti-vehicle occupant side) of the metal core  16  in the steering shaft direction. By joining (adhering) piece  20 A with piece  20 B, a state is achieved wherein the metal core  16  is passed through the passing hole formed by the interior wall  22  of the wooden member  20  (i.e., a state in which the wooden member  20  surrounds the metal core  16 ), whereby the metal core  16  is mounted with the wooden member  20 .  
         [0035]    Between the metal core  16  and the inner wall  22  of the wooden member  20 , a pair of radial direction spaces  24  are formed in the radial direction of the metal core  16 . The radial direction spaces  24  are disposed at outer and inner sides of the metal core  16  (i.e., outer and inner sides of the metal core  16  with respect to the boss  12 ). Further, between the metal core  16  and the inner wall  22  of the wooden member  20 , a pair of axial direction spaces  26  are formed in a longitudinal direction of the steering shaft. The axial direction spaces  26  are disposed at upper and lower sides of the metal core  16  in the longitudinal direction of the steering shaft (i.e., vehicle occupant side anti-vehicle occupant side). In this manner, the periphery of the metal core  16  is enclosed by the pair of radial direction spaces  24  and the pair of axial direction spaces  26 . The pair of radial direction spaces  24  and the pair of axial direction spaces  26  have predetermined widths (roughly  0 . 5  mm in the present embodiment). Thus, when the metal core  16  and the wooden member  20  relatively move as a result of changes in external temperature or humidity (e.g., see FIG. 3 which illustrates a state in which the metal core  16  has expanded due to a rise in external temperature), the radial direction spaces  24  and the axial direction spaces  26  can absorb the relative movement.  
         [0036]    At all areas at which the radial direction spaces  24  and the axial direction spaces  26  border, an elastic adhesive  28  (e.g., an elastomer resin) is disposed as an elastic member. The elastic adhesive  28  has an effect of adhering wood to metal, and by adhering the inner wall  22  of the wooden member  20  to the metal core  16  at four corners thereof with the elastic adhesive  28 , the wooden member  20  is fixed to the metal core  16 . The elastic adhesive  28  has a predetermined elasticity. Thus, when the metal core  16  and the wooden member  20  move relatively due to changes in external temperature or humidity, the elastic adhesive  28  expands or contracts in correspondence with the relative movement of the metal core  16  and the wooden member  20 . Hence, relative movement of the metal core  16  and the wooden member  20  is not only allowed, but exfoliation of the adhesive to the inner wall  22  of the wooden member  20  and to the metal core  16  is prevented.  
         [0037]    Next, operation of the present embodiment will be described.  
         [0038]    In the steering wheel  10  comprising the structure described above, the metal core  16  is passed through the passing hole formed by the inner wall  22  of the wooden member  20 , whereby the wooden member  20  is mounted on the metal core  16 .  
         [0039]    Between the inner wall  22  of the wooden member  20  and the metal core  16 , radial direction spaces  24  (radial direction spaces  24  at the outer and inner sides of the metal core  16 ) are provided in the radial direction of the metal core  16 . For this reason, when the metal core  16  and the wooden member  20  move relatively as a result of changes in external temperature or humidity, the radial direction spaces  24  absorb the relative movement of the metal core  16  and the wooden member  20  (as described later, absorption of relative movement of the metal core  16  and the wooden member  20  by the radial direction spaces  24  is not prevented by the elastic adhesive  28 ). Accordingly, it is possible to prevent the wooden member  20  from chattering with respect to the metal core  16 . (It is possible to prevent backlash between the wooden member  20  and the metal core  16 .)  
         [0040]    Moreover, between the metal core  16  and the inner wall  22  of the wooden member  20 , not only, the radial direction spaces  24  (radial direction spaces  24  at the outer and inner sides of the metal core  16 ) are disposed in the radial direction of the metal core  16 , but also, the axial direction spaces  26  (axial direction spaces  26  at the upper side and the lower side on the metal core  16  in the longitudinal direction of the steering shaft) are disposed in the longitudinal direction of the steering shaft, and the elastic adhesive  28  is disposed at regions at which the radial direction spaces  24  and the axial direction spaces  26  border (at regions between the radial direction spaces  24  and the axial direction spaces  26 ). For this reason, when there are changes in external temperature and humidity, the radial direction spaces  24  and the axial direction spaces  26  absorb relative movement of the metal core  16  and the wooden member  20 . In addition, because the elastic adhesive  28  expands and contracts in response to relative movement of the metal core  16  and the wooden member  20 , absorption of relative movement of the metal core  16  and wooden member  20  by the radial direction spaces  24  and axial direction spaces  26  is not prevented by the elastic adhesive  28 . Accordingly, it is possible to prevent the wooden member  20  from chattering with respect to the metal core  16 . (It is possible to prevent backlash between the wooden member  20  and the metal core  16 .)  
         [0041]    Further still, because the elastic adhesive  28  adheres the inner wall  22  of the wooden member  20  and the metal core  16 , the wooden member  20  can be reliably fixed to the metal core  20 .  
         [0042]    Since the elastic adhesive  28  has elasticity, the elastic adhesive  28  adhering to the inner wall  22  of the wooden member  20  and to the metal core  16  can be prevented from exfoliating (detaching). Accordingly, it is further possible to prevent the wooden member  20  from chattering with respect to the metal core  16  without the metal core  16  and the wooden member  20  separating from one another.  
         [0043]    It should be noted that, although an embodiment has been described in which the elastic adhesive  28  is disposed at four corners of the metal core  16 , an elastic adhesive (elastic member) may also be disposed only at a pair of corners of the metal core that oppose each other. As in steering wheel  50  shown in FIG. 4, an elastic adhesive  52  may be disposed at vehicular front (the upper side in the longitudinal direction of the steering shaft (vehicle occupant side)) and vehicular rear (the lower side in the longitudinal direction of the steering shaft (anti-vehicle occupant side)) areas of the metal core  16  (including corners or not including corners). Furthermore, the elastic adhesive (elastic member) may alternatively be disposed at the inner and outer sides of the metal core (including corners or not including corners). Further still, as shown in FIG. 5, the elastic adhesive may be disposed around the entire periphery of the metal core.  
         [0044]    Finally, although the wooden member  20  is disposed at an upper area (in FIG. 2) of the steering wheel  10  in the present embodiment, the wooden member may alternatively be disposed at any area(s) of the steering wheel, including disposing a wooden member at a plurality of areas of the steering wheel, or even around the entire periphery of the steering wheel.  
         [0045]    In the steering wheel of the first aspect, because radial direction spaces in the radial direction of the metal core are disposed between the metal core and the inner wall of the wooden member including the passing hole. Therefore, the radial direction spaces absorb relative movement of the metal core and the wooden member when the metal core and the wooden member relatively move as a result of changes in external temperature or humidity. Accordingly, it is possible to prevent the wooden member from chattering with respect to the metal core.  
         [0046]    In the steering wheel of the second aspect of the present invention, because axial direction spaces in a steering shaft longitudinal direction are disposed between the metal core and the inner wall of the wooden member, and elastic members are disposed at boundaries between the radial direction spaces and the axial direction spaces, the radial direction spaces and the axial direction spaces absorb relative movement of the metal core and the wooden member when there are changes in external temperature or humidity. Accordingly, it is further possible to prevent the wooden member from chattering with respect to the metal core.  
         [0047]    In the steering wheel of the third aspect of the present invention, because the elastic member adheres the inner wall of the wooden member and the metal core.  
         [0048]    In the steering wheel of the third aspect, because the elastic member adheres the inner wall of the wooden member and the metal core, the wooden member can be reliably adhered to the metal core. Further, exfoliation of the elastic member to the inner wall of the wooden member and to the metal core when the metal core and the wooden member relatively move can be prevented. Accordingly, it is possible to reliably prevent the wooden member from chattering with respect to the metal core.