Steering wheel

Abstract: A steering wheel having a covering layer (C) integrally formed by connecting covering layers of the spoke members (S1, S2) above the boss member (B) and having an energy absorbing member (2) embedded in the covering layer. One end (3) of the energy absorbing member (2) is fixed to the spoke core of the spoke members (S1) which extends to the left from the boss plate (4) of the boss member (B) to a ring core of the ring member (R). The other end (6) of the energy absorbing member (2) is fixed to the spoke core of the spoke member (S2) which extends to the right from the boss plate (4) of the boss member (B) to the ring core of the ring member (R). The center portion of the energy absorbing member (2) is disposed in a position generally above the boss plate (4).

Description: BACKGROUND OF THE INVENTION The present invention relates to steering wheels. More particularly, the present invention relates to a steering wheel including a boss member, a ring member surrounding said boss member, at least a pair of spoke members connecting said boss member to said ring member, a cover layer formed over at least a portion of said spoke members and said ring member, an energy absorbing means embedded within said cover layer for absorbing energy impact of a force against said cover layer, said energy absorbing means being fixed to a pair of said spoke members and having a center portion being generally disposed above the boss member. An example of a conventional steering wheel WO, which is disclosed in Japanese Unexamined Utility Model Publication No. 61-75372, is illustrated in Figs. 3 and 4. The steering wheel WO comprises a boss member (B), a ring member (R) provided around the outer periphery of the boss member, spoke members (S1, S2, S3) connecting the boss member to the ring member, and a pad member (P) mounted on the boss member. Each of the spoke members includes a spoke core member (SC). A covering layer (C), made from a urethane resin, covers the outer periphery of parts of the spoke core members and the outer periphery of the entire ring member. In addition, an energy absorbing apparatus (EAA) made of a metal is disposed within a pad compartment of the pad member. In the conventional steering wheel WO, the pad cover of the pad member is not formed integrally with the covering layer of the spoke members. Therefore, boundary lines are visible between the pad cover and the covering layer. The boundary line is a deficiency in that design. In order to avoid that design deficiency, it would be desirable to provide a steering wheel in which a cover layer which covers the right spoke member is integrally connected to a covering layer which covers the left spoke member. In order to achieve that object, the inventors proposed providing a covering layer for the right spoke member which is integrally formed with the covering layer for the left spoke member by connecting these layers at a point above the boss member. However, they found that it is very difficult to maintain a predetermined configuration of the connected portion of the covering layers at the point above the boss member. Further, the connected portion of the covering layers makes the space for the pad member smaller as compared to the conventional steering wheel, so that the pad member must be smaller. Consequently, the energy absorption of the energy absorbing member is reduced. This presents a significant problem. DE-A-2 251 791 discloses a steering wheel with the features as mentioned in the introductory portion of this specification. The energy absorbing means of this prior art steering wheel is formed by a U-shaped sheet metal which is welded at its lengthwise edges to the edges of the spoke members. This welding step necessitates an additional effort in manufacturing. Furthermore, the U-shaped sheet metal is a bulky part. SUMMARY OF THE INVENTION It is an object of the invention to provide a steering wheel having a good, desirable design and a good energy absorption capability which can be simply manufactured. A steering wheel provided in accordance with the present invention-includes a boss member a ring member surrounding said boss member, at least a pair of spoke members connecting said boss member to said ring member, a cover layer formed over at least a portion of said spoke members and said ring member, an energy absorbing means embedded within said cover layer for absorbing energy impact of a force against said cover layer, said energy absorbing means being fixed to a pair of said spoke members and having a center portion being generally disposed above the boss member and is characterized in that a first end of the energy absorbing means being fixed to one of said pair of spoke members and a second end of said energy absorbing means being fixed to the other one of said pair of spoke members whereby the energy absorbing means defines a bridge between said pair of spoke members. The steering wheel according to the invention can be simply manufactured, for the ends of the energy absorbing means are fixed to the respective spoke members. By this the energy absorbing means which can be a simple part defines a bridge with a good energy absorption capability. The cover layer giving a desirable design to the whole steering wheel can be integrally formed by connecting covering layers of spoke members above the boss member and incorporating the energy absorbing member as will be described below. An advantageous embodiment of a steering wheel according to the invention is characterized in that the fixation between the ends of the energy absorbing means and said pair of spoke members being removable. By this removability a sub-standard cover layer can be removed together with the energy absorbing means from a steering wheel core, so that the steering wheel core can further be used for manufacturing a satisfactory steering wheel. The removability of the energy absorbing means is attained advantageously by the fixation between the ends of the energy absorbing means and said pair of spoke members being made by caulking. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view showing a main portion of one embodiment of a steering wheel according to the present invention; FIG. 2 is a perspective view of an energy absorbing member of the steering wheel of Fig. 1; FIG. 3 is a perspective view of a conventional steering wheel; and FIG. 4 is a cross-sectional view taken along lines III-III of the Fig. 3. A steering wheel provided in accordance with the present invention has an energy absorbing member 2 which is provided at a center portion between the right spoke core S1 and the left spoke core S2 of the steering wheel core 1. The energy absorbing member 2 is made from a metal plate which has been bent into a U-shape. As shown in Figs. 1 and 2, the energy absorbing member 2 extends between the left spoke core S1 and the right spoke core S2, so that the configuration of the entire energy absorbing member 2 is that of a bridge. As shown in the left hand portion of Fig. 1, a mounting portion 5 adapted to be fixed to the left spoke core S1 by caulking is formed at a left end portion 3 of the energy absorbing member 2. The left spoke core S1 extends to the left from a boss plate 4 of the boss member B to a ring core of the ring member R. In addition, as shown in the right hand portion of Fig. 1, a mounting portion 7 adapted to be fixed to the right spoke core S2 by caulking is formed at a right end portion 6 of the energy absorbing member 2. The right spoke core S2 extends to the right from the boss plate 4 of the boss member B to the ring core of the ring member R. As clearly shown in Figs. 1 and 2, a center portion 8 of the energy absorbing member 2 is located substantially at a position above the boss plate 4. When the center portion 8 of the energy absorbing member 2 is subjected to an impact force, the energy absorbing member 2 is deformed so that the U-shaped cross-section of the energy absorbing member 2 is opened and the energy absorbing member 2 is bent in a downward direction. Thus, the energy of impact can be absorbed by deformation of the energy absorbing member 2. Coupling members 13 and 14 interconnect the left end portion 3 and the right end portion 6 of the energy absorbing member 2 respectively to the left spoke core S1 and the right spoke core S2. In the illustrated embodiment, coupling member 13 includes a recessed portion 11 in the left end portion 3 for receiving a projecting portion 9 formed on the left spoke core S1. However, the projecting portion 9 could be provided on the left end portion 3 and the recessed portion 11 in the left spoke core S1. Further, in the illustrated embodiment, coupling member 14 includes a recessed portion 12 in the right end portion 6 for receiving a projecting portion 10 formed on the right spoke core S2. However, the recessed portion 12 could be provided in the right spoke core S2 and the projecting portion 10 on the right end portion 6. Coupling members 13 and 14 position the energy absorbing member 2 with respect to the spoke cores S1 and S2 when they are assembled, and prevent the energy absorbing member 2 from shifting in the longitudinal direction with respect to the spoke cores S1 and S2 after assembly. The left and right spoke cores S1 and S2 are respectively fixed to a ring core of the ring member R and a boss of the boss member B by welding or the like. Reference numeral 17 designates a covering layer 17, made from an urethane resin, for covering a part of the spoke member S and the entire ring member R. A method of manufacturing the above-described embodiment of the present invention will now be described with reference to the drawings. The energy absorbing member 2 is mounted on the steering wheel core 1. The energy absorbing member 2 and the steering wheel core 1 thus assembled are set on a predetermined molding die. In order to form the covering layer 17, circumferences of the steering core 1 and the energy absorbing member 2 are injecting-molded. A sub-standard covering layer is occasionally formed because a blow hole (foam) is sometimes generated in a part of the covering layer 17 during injection. If so, the sub-standard covering layer 17 is removed from the steering wheel core 1 and the steering wheel core 1 is reset on the predetermined molding die so that the injection molding can be repeated. Recycling the steering wheel core 1 advantageously saves the material of the steering wheel core 1. Contrary to the present invention, when the energy absorbing member 2 is fixed to the steering wheel core 1 by a fixing process such as a welding, it is very difficult to completely remove the covering layer 17 from the steering wheel member 1 because small clearances are respectively formed between the spoke cores S1, S2 and the both ends of the energy absorbing member 2. Accordingly, it is difficult to remove a sub-standard covering layer. The removal of a sub-standard covering layer 17 from the structure of the present invention will now be described. Both ends 3 and 5 of energy absorbing member 2 are respectively coupled to the spoke cores S1 and S2 by caulking, so that the caulking therebetween can be easily removed by forcefully pulling the covering layer 17 together with the energy absorbing member 2 upwardly. In this manner, the energy absorbing member 2 can be easily removed from the spoke cores S1 and S2 of the steering wheel 1. Removal of the sub-standard covering layer 17 which is formed on each of the energy absorbing member 2 and the steering wheel core 1 can be conducted once the energy absorbing member 2 and the steering wheel core 1 have been disassembled, so that the removing operation can be easily carried out. After the cover removing operation, another energy absorbing member 2 is mounted on the steering wheel core 1 and the assembly is repositioned in the molding die so that the covering layer can be formed by inject molding. Accordingly, a satisfactory steering wheel can be obtained by reusing the steering wheel core 1. In accordance with the present invention, the configuration of the connecting portion of the covering layer 17 is maintained by the energy absorbing member 2 so that the covering layers are integrally formed at a point above the boss member. No boundary line appeared between those covering layers, so that a steering wheel having an advantageous design is obtained with the structure of the invention. In addition, an energy absorbing function above the boss member is provided with the energy absorbing member 2. Accordingly, even if the pad member is reduced in size, the steering wheel as a whole can absorb at least the same energy as can be absorbed with a conventional steering wheel. Further, the energy absorbing member 2 is coupled with the spoke member S1 and S2 of steering wheel member 1 by caulking, so that the energy absorbing member can be easily removed from the steering wheel core 1. Therefore, if a sub-standard covering layer 17 is molded, it can be easily removed from the steering wheel core 1 and the energy absorbing member 2. Furthermore, as shown in Fig. 2, the energy absorbing member 2 can be formed with a predetermined hole(s) or a predetermined slit(s) (shown in phantom), so that the energy absorption of the energy absorbing member 2 is adjustable. While a preferred embodiment of the invention has been described, it is to be understood that various changes and modifications may be made to the structure thereof without departing from the invention, and all such changes and modifications are limited only by the appended claims.

Claims: A steering wheel including a boss member (B), a ring member (R) surrounding said boss member, at least a pair of spoke members (S1, S2) connecting said boss member to said ring member, a cover layer (C) formed over at least a portion of said spoke members and said ring member, an energy absorbing means (2) embedded within said cover layer for absorbing energy impact of a force against said cover layer, said energy absorbing means (2) being fixed to a pair of said spoke members (S1, S2) and having a center portion (8) being generally disposed above the boss member (B), characterized in that a first end (3) of the energy absorbing means (2) being fixed to one of said pair of spoke members (S1, S2) and a second end (6) of said energy absorbing means (2) being fixed to the other one of said pair of spoke members (S1, S2), whereby the energy absorbing means (2) defines a bridge between said pair of spoke members (S1, S2). A steering wheel according to claim 1, characterized in that the fixation between the ends (3, 6) of the energy absorbing means (2) and said pair of spoke members (S1, S2) being removable. A steering wheel according to claim 1 or 2, characterized in that the fixation between the ends (3, 6) of the energy absorbing means (2) and said pair of spoke members (S1, S2) is made by caulking.

Inventors: FUJITA YOSHIYUKI C O TOYODA GO, SAKANE KATSUNOBU C O TOYODA GO, FUJITA, YOSHIYUKI, C/O TOYODA GOSEI TECH. CENTER, SAKANE, KATSUNOBU, C/O TOYODA GOSEI TECH. CENTER
Applicants: TOYODA GOSEI KK, TOYODA GOSEI CO., LTD.
Application year: 1991
Main classification: B62D1
IPC codes: B60R21, B62D1