GB2150514A - Steering wheel - Google Patents

Abstract

An automotive steering wheel having a ring core metal, spoke core metals welded to the ring core metal, and a soft plastic layer covering the core metals. At least the portions of the ring core metal other than the portions to which the spoke core metals are welded are constituted by hollow pipes having a polygonal cross-section. <IMAGE>

Description

SPECIFICATION Steering wheel Background of the invention (1) Field of the invention The present invention relates to an automotive steering wheel and, more particularly, to a lightweight automotive steering wheel which facilitates the welding of core metal of the ring and the core metals of the spokes and which eliminates the necessity of bond for bonding a soft plastic covering material to the ring core metal, the bond being essential in the conventional steering wheel for the purpose of prevention of separation and slippage of the cover.

F2) Description of the prior art Old-fashioned automotive steering wheels have a ring portion constituted by a solid core metal having a cicular or an oval cross-section. In recent years, however, it is becoming popular to use a ring core metal made of a hollow pipe having a circular or an oval cross-section, in order to reduce the weight.

The fabrication of steering wheels, regardless of whether the ring core metal is solid or hollow, encounters a difficulty in the welding of the core metals of the spokes to the core metal of the ring due to the fact that the flat end surfaces of the spoke core metals can make only line contact with the curved surface of the ring core metal having circular or oval cross-section.

In consequence, as will be seen from Figure 5 showing a prior art, there is a tendency that the spoke core metals 16 are offset from the right positions on the ring core metal 12 so that quite a troublesome work is required for correctly arranging the spoke core metals correctly with respect to the cofre ring metal, unless a specific complicated jig is used.

In the conventional steering wheel having circular or oval cross-section of the ring core metal, another problem is encountered due to the provision of a covering layer of a soft plastic such as soft vinyl chloride, foamed polyurethane and so forth, formed on the core metals for improving the safety and for imparting a better feel of touch. Such a covering layer tends to be separated and slip on the core metals when twisted by the driver's hand gripping the handle. To avoid this problem, it has been necessary to apply a bond for fixing the covering layer onto the core metals.This in turn requires various works such as selection of the bond in relation to the kind of material of the covering layer, defatting and rinsing of the core metals, control of density and film thickness of the bond, as well as drying the same, resulting in an increased number of steps of the process and raised cost of production.

Summary of the invention Accordingly, an object of the invention is to provide a light-weight automotive steering wheel which permits an easy location of spoke core metals with respect to the ring core metal for welding and which eliminates the necessity for application of bond for fixing the soft plastic covering layer onto the ring core member.

To this end, according to the invention, there its provided a steering wheel having a ring core metal, spoke core metals welded to the ring core metal, and a covering layer of a plastic material formed on the ring core metaland the spoke core metal, wherein the improvement comprises that the ring core metal has a polygonal cross-sectional shape and that portions of the ring core metal other than the portions welded to the spoke core metals are constituted by hollow pipes having the polygonal cross-sectional shape.

According to the invention, the ring core metal has a polygonal cross-section such as triangular, rectangular or pentagonal cross-section, so that the flat ends of the spoke core metals can be placed in contact with substantially flat areas on the inner peripheral surface, upper surface or the lower surface. That is, the spoke core metals can be held in surface contact with the ring core metal, in contrast to the conventional steering wheel in which the spoke core metals make only line contact with the ring core metal. This in turn effectively prevent any offset of the spoke core metals from the right positions on the ring core metal. Such an offset, if any, can be detected and corrected easily so that the spoke core metals can be re-arranged at desired angles on the ring core metal.Therefore, the spoke core metals can be welded to the ring core metal highly precisely without using any complicated jig.

The polygonal cross-section of the ring core metal provides another advantage in that it can fix a soft plastic cover thereon without necessitating application of bond therebetween, so that the problem encountered by the conventional steering wheel such as the separation and slippage of the cover on the ring core metal is prevented advantageously.

Furthermore, the weight of the steering wheel can be decreased because the ring core metal, at at least portions thereof other than the weld to the spoke core metals, is formed of a hollow pipe having a polygonal cross-section.

Brief description of the drawings Figure lisa plan view of an embodiment of a steering wheel in accordance with the invention; Figure 2 is an end view taken along the line ll-ll of Figure 1; Figure 3 is a perspective view illustrating how a spoke core metal is welded to the ring core metal in the production of the steering wheel of the invention; Figure 5 is a sectional view showing how a spoke core metal is welded tote ring core metal in the production of a conventional steering wheel.

Description of the preferred embodiments Figure 1 schematically shows a steering wheel in accordance with the invention. This steering wheel 1 has a ring core metal 2 composed of two segments: namely, an upper core metal segment 3 and a lower core metal segment 4 which are connected to each other through connecting pieces 5 to which the core metals 6 of spokes are welded.

The ring core metal segments 3 and 4 are made of pipes having suitable lengths and a substantially rectangular cross-section, bent in arcuate forms with their one sides of the cross-sections directed radially inwardly. The connecting piece 5 is a member having a substantially rectangular cross-section sized to fit in both ring core metal segments 3 and 4 and bent in conformity with the curvature of these segments 3 and 4. The connecting pieces 5,5 are welded to respective ends of both ring core metal segments so as to form a rigid ring core metal 2 of the steering wheel.

Spoke core metals 6,6 are welded to the connecting pieces 5,5 so that the ring core metal 2 and the spoke core metals 6,6 are integrated with each other.

A covering layer 7 of a soft plastic material such as of soft vinyl chloride is formed to cover the ring core metal 2 and the spoke core metals 6,6. The radially inner ends of the spoke core metals 6,6 are welded to a boss plate 8. A horn pad 9 incorporating a horn mechanism is attached after mounting of the steering wheel 1 on the automobile.

The steering wheel 1 of the described embodiment is fabricated in a manner explained hereinunder.

As the first step, the boss plate 8, spoke core metals 6,6 and the ring core metal 2 are placed at predetermined positions on a jig. The spoke core metals 6,6 are welded first to the boss plate 8 and then to the ring core metal 2. According to the invention, since the connecting pieces 5,5 constituting a part of the ring core metal 2 have a rectangular cross-section, the end surfaces of the spoke core metals 6,6 to be welded are held stably in contact with the substantially flat surface of the ring core metal 2 although they do not make perfect surface contact with the ring core metal 2 because of curvature of the ring core metal 2, as compared with the conventional case shown in Figure 5 where the ring core metal 12 has a circular or an oval crosssection.In consequence, undesirable offset of the spoke core members 6,6 from right positions is suppressed and such an offset, if any, can be detected and corrected easily. It is thus possible to arrange the spoke core metals 6,6 at desired angles with respect to the ring core metal 2 and, therefore, the welding of the spoke core metals 6,6 to the ring core metal 2 can be accomplished at a high precision without using any special complicated jig.

After the welding, the integrated body core metals is placed in a mold and a molten plastic is poured into the mold to form the covering layer 7 on the ring core metal 2 and the spoke core metals 6. According to the invention, since the ring core metal 2 has a rectangular cross-section, the covering layer 7 is fixed securely to the ring core metal 2 and the spoke core metals 6,6 without any bond aplied therebetween. Therefore, the undesirable separation and slippage of the covering layer which is experienced with conventional steering wheel by a twisting force applied by the dirver's hand is avoided even though the covering layer 7 is made of a soft plastic material.

Needless to say, the steering wheel thus produced has a reduced weight because the upper and lower core ring metal segments 3 and 4 are made of hollow pipes having a rectangular cross-section.

In the described embodiment of the steering wheel of the invention, the spoke core metals 6,6 are welded to the connecting pieces 5,5 which are bars having a rectangular cross-section, taking into account the thermal fatigue caused on the material as a result of the welding and mechanical strength of the steering wheel after the welding. This, however, is not exclusive and the spoke core metals 6,6 may be welded directly to the ring core metal 2 provided that the ring core metal 2 has a sufficiently large thickness. In such a case, needless to say, the ring core metal 2 may be formed of an integral hollow pipe having a polygonal cross-section and, therefore, the connecting pieces 5,5 can be dispensed with.

It is to be noted also that the rectangular crosssection of the ring core metal 2 is not exclusive and the ring core metal can have any other polygonal cross-sectional shape such as chamfered rectangular shape, triagnular shape and pentagonal shape, provided that a substantially flat welding surface is presented for the welding to the spoke core metals.

It is to be noted also that the spoke core metals 6,6 may be welded to flat upper or lower surface of the ring core core metal 2, although in the described embodiment the spoke core metals 6,6 are welded to the inner peripheral surface of the ring core metal 2.

Claims (3)

1. A steering wheel having a ring core metal, spoke core metals welded to said ring core metal, and a covering layer of a plastic material formed on said ring core metaland said spoke core metal, wherein the improvement comprises that said ring core metal has a polygonal cross-sectional shape and that portions of said ring core metal other than the portions welded to said spoke core metals are constituted by hollow pipes having the polygonal cross-sectional shape.

2. A steering wheel according to claim 1,wherein said ring core metal is composed of ring core metal segments made of hollow pipes with polygonal cross-sectional shape and connected through connecting pieces constituted by solid bars having the polygonal cross-sectional shape, said spoke core metals being welded to said connecting pieces.

3. A steering wheel according to claim 1, wherein said ring core metal is wholly composed of a pipe having said polygonal cross-sectional shape, and the portions of said pipe to which said spoke core metals are to be welded have an increased wall thickness.