Abstract:
A steering wheel that enables heat to be efficiently conducted to a steering wheel outer covering. The steering wheel includes: a core; a spacer member arranged around an outer periphery of a rim portion of the core; a temperature adjusting element provided on the spacer member; and a resin layer formed to cover an outside portion of the spacer member. The spacer member keeps at least a part of the temperature adjusting element away from the core.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to Japanese Patent Application No. 2013-052290, filed on Mar. 14, 2013 and PCT International Patent Application No. PCT/JP2014/056213, filed on Mar. 10, 2014. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a structure of a motor vehicle steering wheel with a temperature adjusting function (heater and/or cooler function). 
       DESCRIPTION OF THE RELATED ART 
       [0003]    In recent years, steering wheels with a temperature adjusting function (heater and/or cooler function) have been adopted for automobiles and the like. In common steering wheels, a foamed urethane layer is formed outside a rim portion of a metallic core. In some steering wheels, the urethane layer is externally covered with leather. For example, a structure has been proposed in which a heater element is arranged outside the core in order to apply a heater function to the steering wheel. A conventional steering wheel with a heater function is disclosed, for example, in Japanese Patent Application Laid-open No. 2007-153026. 
         [0004]    In the steering wheel with the heater function, it is important to efficiently transfer heat to a steering outer covering. There is also a demand to minimize an increase in costs resulting from the addition of the heater function. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention has been developed in view of the above-described problems. An object of the present invention is to provide a steering wheel that enables heat (warmth or cold) to be efficiently transferred to a steering outer covering. 
         [0006]    Another object of the present invention is to provide a steering wheel that enables minimization of an increase in costs resulting from addition of a temperature adjusting function. 
         [0007]    To accomplish the object, a steering wheel according to the present invention includes: a core; a spacer member arranged around an outer periphery of a rim portion of the core; a temperature adjusting element provided on the spacer member; and a resin layer formed to cover an outside portion of the spacer member. The spacer member keeps at least a part of the temperature adjusting element away from the core. For example, the temperature adjusting element may be a heating unit provided outside the frame structure. 
         [0008]    In the present invention configured as described above, the spacer member keeps at least a part of the temperature adjusting element away from the core, allowing avoidance of a situation where most of heat generated by the temperature adjusting element is conducted toward the core, which has a high heat conductivity. Thus, the heat can be efficiently conducted to the steering outer covering. Furthermore, molding of the resin layer can be completed during one step, enabling minimization of an increase in costs resulting from addition of the temperature adjusting function. 
         [0009]    The spacer member may have a framework-like frame structure. The resin layer may be formed to lie between the core and the frame structure and to cover an outside portion of the frame. In this case, when a foamed resin layer is molded, the resin easily reaches the core through a gap in the frame structure, leading to simplification of manufacturing steps. 
         [0010]    An electric current may be passed through the frame structure to generate heat. The frame structure itself may be used as a heater element. In this case, the heater element may be omitted, allowing simplification of the structure and the manufacturing steps. 
         [0011]    The spacer member may be a flexible cushion layer. A heating unit may be provided outside the cushion layer as the temperature adjusting element. In this case, the resin layer may be formed to cover an outside portion of the cushion layer. In such an aspect, the core is covered with the resin layer and the cushion layer, both of which are flexible. Thus, the steering wheel can be made to feel soft. Furthermore, simplified manufacturing steps and reduced material costs are expected. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a plan view depicting a steering wheel according to the present invention; 
           [0013]      FIG. 2  is a sectional view taken along line A-A in  FIG. 1 ; 
           [0014]      FIG. 3  is a perspective view illustrating a manufacturing step for a steering wheel according to an embodiment of the present invention depicted in  FIG. 1  and  FIG. 2 ; 
           [0015]      FIG. 4  is a perspective view illustrating a manufacturing step for the steering wheel according to the embodiment of the present invention depicted in  FIG. 1  and  FIG. 2 ; 
           [0016]      FIG. 5  is a perspective view illustrating a manufacturing step for the steering wheel according to the embodiment of the present invention depicted in  FIG. 1  and  FIG. 2 ; 
           [0017]      FIG. 6  is a sectional view of a steering wheel according to another embodiment of the present invention, corresponding to a cross section taken along a direction A-A in  FIG. 1 ; and 
           [0018]      FIG. 7  is a sectional view of a steering wheel according to another embodiment of the present invention, corresponding to a cross section taken along the direction A-A in  FIG. 1 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0019]    Embodiments of the present invention will be described below with reference to the drawings.  FIG. 1  is a plan view depicting a steering wheel  10  according to the present invention.  FIG. 2  is a sectional view taken along a direction A-A in  FIG. 1 .  FIGS. 3 to 5  are perspective views illustrating manufacturing steps for the steering wheel according to the embodiment of the present invention, as shown in  FIG. 1  and  FIG. 2 . The steering wheel according to the present invention has a heater function and includes a core  12  formed by die-casting aluminum or magnesium, frame structures  14  and  16  arranged around an outer periphery of a rim portion of the core  12  and serving as spacer members, a heater element  20  provided on the frame structures  14  and  16 , a resin layer (foamed urethane)  22   a  formed to cover outside portions of the frame structures  14  and  16 , and a resin layer (foamed urethane)  22   b  enclosed in a gap between the core  12  and each of the frame structures  14  and  16 . 
         [0020]    As depicted in  FIG. 3 , the frame structures  14  and  16  are rib-like members with the same sectional shape and may be formed of metal, resin, or the like. A protruding portion  14   a  extending toward the center of the rim is formed in the center of the upper frame structure  14  and contacts an upper end of the core  12 . On the other hand, a protruding portion  16   a  extending toward the center of the rim is formed in the center of the lower frame structure  16  and extends into a recess portion of the core  12 . The frame structures  14  and  16  form spaces around the core  12  to locate the heater element  20  away from the core  12 . The heights of the protrusions  14   a  and  16   a  of the frame structures  14  and  16  may be set as needed in accordance with the sizes of the gaps (spaces) formed around the core  12 . The frame structures  14  and  16  are not limited to rib-like structures but may have other shapes as long as spaces are formed around the core  12 . To allow resin to be subsequently enclosed around the core  12 , it is important to mold the frame structures  14  and  16  such that the frame structures  14  and  16  have sufficiently large voids. 
         [0021]    Metal wiring that generates heat when an electrical current is passed through the metal wiring may be adopted as the heater element  20 . The heater element  20  may be arranged outside a mesh  18  serving as a base. The mesh  18  may be configured to cover the entire rim portion, including the frame structures  14  and  16  shown in  FIG. 4 . The mesh  18  may be molded using, for example, metal or resin. As is the case with the frame structures  14  and  16 , to allow resin to be subsequently enclosed around the core  12 , it is important to mold the mesh  18  such that the mesh  18  has sufficiently large voids (mesh). 
         [0022]    To manufacture the steering wheel  10  according to the present embodiment, the frame structures  14  and  16  are arranged outside the core  12  as depicted in  FIG. 3 . Subsequently, as depicted in  FIG. 4 , the mesh  18  is placed so as to cover the outside of the frame structures  14  and  16 . Then, as depicted in  FIG. 5 , the heater element  20  is laid over the mesh  18 . Then, the foamed resins  22   a  and  22   b  are simultaneously formed between the core and each of the frame structures  14  and  16  ( 22   b ) and outside the frame structures  14  and  16  ( 22   a ). 
         [0023]    In the present embodiment configured as described above, the frame structures  14  and  16  keep the heater element  20  away from the core  12  to allow avoidance of a situation where most of heat generated by the heater element  20  is conducted toward the core  12 , which has a high heat conductivity. Thus, the heat can be efficiently conducted to a steering outer covering ( 22   a ). That is, the steering wheel  10  can be efficiently warmed (cooled) with reduced electric power. Furthermore, molding of the resin layers  22   a  and  22   b  can be completed during one step, allowing minimization of an increase in costs resulting from addition of the heater function. 
         [0024]      FIG. 6  is a sectional view of a steering wheel according to another embodiment of the present invention, and corresponds to a cross section in the direction A-A in  FIG. 1 . In a structure in the present embodiment, frame structures  24  and  26  themselves are used as heater elements, and a current is passed directly through the structures  24  and  26  to generate heat. The remaining part of the structure is similar to the corresponding part of the embodiment depicted in  FIG. 2 , and thus, duplicate descriptions are omitted. In the present embodiment, the frame structures  24  and  26  may be molded using metal or the like. Compared to the embodiment depicted in  FIGS. 2 to 5 , the present embodiment enables the heater element ( 20 ) and the base member ( 18 ) to be omitted, allowing simplification of the structure and the manufacturing steps. 
         [0025]      FIG. 7  is a sectional view of a steering wheel according to yet another embodiment of the present invention, and corresponds to a cross section in the direction A-A in  FIG. 1 . In a structure in the present embodiment, instead of the frame structures, a flexible cushion member  34  is wound around the core  12 . The remaining part of the structure is similar to the corresponding part of the embodiment depicted in  FIG. 2 , and thus, duplicate descriptions are omitted. In the present embodiment, the cushion layer  34  may be molded using a foamed resin, urethane, or the like, and needs sufficient flexibility. In the present embodiment, the core  12  is covered with the resin layer  36  and the cushion layer  34 , both of which are flexible, allowing the steering wheel  10  to be made to feel soft to grip. Furthermore, simplified manufacturing steps and reduced material costs can be expected. In the present embodiment, the thickness of the cushion layer  34  enables a sufficient gap to be secured between the core  12  and the heater element  20 . Thus, no resin layer is enclosed between the cushion layer  34  and the core  12 . Adjustment of the thickness of the cushion layer  34  also enables heat conduction efficiency to be controlled. 
         [0026]    The embodiments of the present invention have been described, but the present invention is not limited to the above-described embodiments. Various design changes and the like may be made to the embodiments without departing from the technical scope described in the claims. For example, the present invention is applicable to a steering wheel with a cooler function instead of the heater function. 
         [0027]    While the above description constitutes the preferred embodiment of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.