GB2243204A

GB2243204A - Steering wheel manufacture

Info

Publication number: GB2243204A
Application number: GB9105439A
Authority: GB
Inventors: Suzuaki Hongou; Katsunobu Sakane; Takanori Tsubouchi; Tetsuya Takamori; Yoshiyuki Fujita; Atsushi Nagata
Original assignee: Toyoda Gosei Co Ltd
Current assignee: Toyoda Gosei Co Ltd
Priority date: 1990-03-29
Filing date: 1991-03-14
Publication date: 1991-10-23
Also published as: DE4110171A1; GB9105439D0; DE4110171C2

Abstract

The region 13 of each spoke 12 at which it is joined by resistance welding to the rim 11 has a concavity to facilitate positioning before welding and to increase the weld area and therefore, the weld strength. The region (13) may have welding projections 13a, 13b and the concavities may be formed by holes (Fig. 7) or depressions (Fig. 10) in these projections. <IMAGE>

Description

STEERING WHEEL AND MANUFACTURING METHOD THEREFOR

BACKGROUND OF THE INVENTION

1. field of the Invention

The present invention relates to a steering wheel and a manufacturing method -therefor, and more particularly, to a steering wheel in which spoke portion mandrels and a ring portion mandrel are joined with each other by means of resistance welding and a manufacturing method therefor.

2. Description of the Prior Art

It has been conventionally known that the resistance welding may be used to join together mandrels of the steering wheel as disclosed in, for example, Japanese Patent Unexamined Publication No. 59-89265.

The spoke portion mandrels and the ring portion mandrel have been joined with each other by making use of the resistance welding in the manner shown in Figures 15 and 16.

More specifically, the forward end portion of each spoke portion mandrel 2 extends horizontally to form a welding seat 3 with welding projections 4 being formed in the welding seat 3.

A ring portion mandrel 1 is disposed so as to come into pressure contact with the upper surface side of the welding seat 3, and then, an electric current is sent therethrough to perform the resistance welding.

According to the conventional welding technique, however, the outer peripheral surface of the ring portion mandrel 1 is only permitted to be partially brought into point contact with welding projections 4, with the result that it is - 2 impossible to obtain a sufficient weld strength. Further, in case of setting the ring portion mandrel 1 on the welding seat 3, the ring portion mandrel 1 is liable to slip on the welding seat 3, with the result that it takes a great deal of time to perform the positioning operation.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a steering wheel and a manufacturing method therefor that are capable of overcoming the above deficiencies and improving the weld strength when spoke portion mandrels and a ring portion mandrel are joined with each other by means of resistance welding as well as efficiently performing the positioning without difficulty at the time of welding.

To this end, a steering wheel is provided comprising a boss portion connectable with a steering shaft, a ring portion having a ring portion mandrel embedded in a coating layer, and spoke portions each having a spoke portion mandrel and serving to connect the boss portion and ring portion with each other. The spoke portion mandrel is formed at the forward end of the base portion with a joining portion to which the ring portion mandrel is joined. The joining portion has a concave area to receive the ring portion mandrel so that the ring portion mandrel is joined thereto by means of resistance welding over the entire contact surface of the concave area with the ring portion mandrel.

There is further provided according to the present invention a method for manufacturing a" steering wheel comprising the steps of preparing spoke portion mandrels each having a concavity formed in a joining portion thereof and preparing a ring portion mandrel, setting the ring portion mandrel in the concavity, sending an electric current to the joining portion and the ring portion mandrel while applying pressure thereto so as to weld the two mandrels together over the entire contact surface thereof, and forming a coating layer around the welded ring portion mandrel.

In accordance with the steering wheel of the present invention, the welding.portion formed in the spoke portion mandrel to be welded to the ring portion mandrel is-formed to have a design that conforms to the sectional outer peripheral surface of the ring portion mandrel. A welding projection is formed in the welding portion to be brought into contact with the ring portion mandrel along the sectional outer peripheral surface thereof. The welding projection is formed with a concavity when it is formed in a welding seat of the spoke portion mandrel. the concavity serves to assist the positioning of the ring portion mandrel at the time of resistance welding.

For this reason, by performing the resistance welding while maintaining the ring portion mandrel in pressure contact with the welding portion of the spoke portion mandrel, the welding projection in the welding portion can be brought into linear contact or into contact at a plurality of points with the sectional outer peripheral surface of the ring portion mandrel, and therefore, the welding area can be increased and hence the weld strength can be improved. In this case, by setting the ring portion mandrel in the concavity of the welding projection, the ring portion mandrel can be fitted roughly in the concavity so that the positioning can be performed without difficulty.

As a consequence, according to the steering wheel of the present invention, by joining the spoke portion mandrel a nd the ring portion mandrel with each other by means of resistance welding, it is possible to increase the welding area so that the welding can be performed with improved weld strength.

BRIEF DESCRIPTION OF THE DRAWING other objects, features and characteristics of the present invention, as well as the methods of operation of the related elements of the structure will become apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification. In the drawings, like reference numerals designate corresponding parts and wherein:

FIGURE 1 is a sectional view of a first embodiment of a steering wheel according to the present invention, showing the section of a part taken along the line I-I of FIGURE 3; FIGURE 2 is a partial perspective view of the first embodiment showing a welding portion of a spoke portion mandrel and a ring portion mandrel; FIGURE 3 is a plan view of the first embodiment; FIGURE 4 is a partial perspective view of a modification of the first embodiment; FIGURE 5 is a partial perspective view of another modification of the first embodiment; FIGURE 6 is a sectional view of a second embodiment of the steering wheel according to the present invention, showing the section of the part taken along the line I- I of FIGURE 3; is FIGURE 7 is a partial perspective view of the second embodiment showing a welding seat of the spoke portion mandrel and the ring portion mandrel; FIGURES 8A and 8B are views of the second embodiment explaining of the manner of welding the ring portion mandrel to the welding seat of the spoke portion mandrel; FIGURE 9 is a partial sectional view of a modification of the second embodiment; FIGURE 10 is a partial perspective view of the modification shown in FIGURE 9 showing the welding seat of the spoke portion mandrel and the ring portion mandrel; FIGURE 11 is a partial sectional view of another modification of the second embodiment; FIGURE 12 is a partial perspective view of the modification shown in FIGURE 11 showing the welding seat of the spoke portion mandrel and the ring portion mandrel; FIGURE 13 is a partial sectional view of still another modification of the second embodiment; FIGURE 14 is a partial perspective view of the modification shown in FIGURE 13 showing the welding seat of the spoke portion mandrel and the ring portion mandrel; FIGURE 15 is a partial sectional view of a conventional steering wheel; and FIGURE 16 is a partial perspective view of the conventional steering wheel showing the welding seat of the spoke portion mandrel and the ring portion mandrel.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY EMBODIMENTS

Description will be given below of a preferred. embodiment of the present invention with reference to the drawings.

A steering wheel W according to this embodiment is constituted, as shown in FIGURE 3, by a ring portion R, a boss portion B arranged at the center of the ring portion R, and two spoke portions S each extending radially from the boss portion B so as to join the boss portion B and the ring portion R with each other.

The ring portion R has a ring portion mandrel 11 made of a steel pipe arranged therein.

The boss portion B comprises a steel boss 14 serving to be connected with a steering shaft of a vehicle (not shown) and a boss plate 15 made of a steel plate and serving to be welded to the boss 14.

Each spoke portion S has a spoke portion mandrel 12 made of a sCeel plate and arranged therein. It is noted that the left and right spoke portion mandrels 12, 12 and the boss plate 15 are formed unitarily as one piece in this embodiment.

A coating layer 16 made of synthetic resin such as soft urethane is formed around the outer periphery of the ring portion mandrel 11 and the outer periphery of a portion of each spoke portion mandrel 12 near the ring portion mandrel 11.

Reference numeral 17 denotes a pad for covering the top of the boss portion B. In the steering wheel W of the embodiment, the welding portion 13 formed at the forward end of each spoke portion mandrel 12 so as to be welded to the ring portion mandrel 11 has such an external form so as to conform to the 7 bottom side of the sectional outer peripheral surface of the ring portion mandrel 11 as shown in FIGURES 1 and 2.

Each of the welding portions 13 is further formed with welding projections 13a and 13b that are brought into contact with the outer peripheral surface of the ring portion mandrel 11. Of the welding projections 13a and 13b, the welding projection 13b is designed to come into point contact with the peripheral surface of the ring portion mandrel 11 like the prior art. On the other hand, the welding projection 13a is formed to extend along the sectional outer peripheral surface of the ring portion mandrel 11 so as to come into linear contact with the outer peripheral surface of the ring portion mandrel 11.

Therefore, to weld the ring portion mandrel 11 to the welding portion 13 of each of the spoke portion mandrels 12 of the steering wheel W according to the present embodiment by making use of the resistance welding, the ring portion mandrel 11 is put on the upper surface of each welding portion 13 and both are held under pressure between the predetermined electrodes, and then, a fixed electric current is sent therethrough, thereby making it possible to weld the ring portion mandrel 11 to the spoke portion mandrels 12.

Further, the boss 14 is welded separately to the boss plate 15 which is united with the spoke portion mandrels 12 by resistance welding.

A steering wheel core assembly C formed by joining together the mandrels 11 and 12, boss 14 and plate 15 is set in a fixed mold. After.the- coating layer 16 is formed, the pad 17 is onto the top of the boss portion B with an appointed home switch mechanism disposed therebetween. A lower cover (not shown) is fit to the bottom of the boss portion B. In this way, the steering wheel W of the embodimnt can be manufactured.

In the steering wheel W thus formed, the welding projection 13a in the welding portion 13 of each spoke portion mandrel 12 can be brought into linear contact with the outer peripheral surface of the ring portion mandrel 11. In consequence, the welding area can be increased so that the welding can be performed with improved weld strength.

Particularly in the case of the steering wheel W wherein the span between the spoke portions S is longer on the side of a front ring portion Rf, when an impact force is applied to the front ring portion Rf, the stress is liable to concentrate in the vicinity of the welding projection 13a formed at the front of the welding portion 13 of the spoke portion mandrel 12. In this case, however, no problem is caused because the stress concentration portion is improved in weld strength as described in the above embodiment. In this respect, according to the present invention, it is possible to locally improve the weld strength in an easy and effective manner without requiring a greatly deal of trouble or steps. Moreover, by making only the welding projection 13a on the stress concentration portion side longer so that it can be brought into linear contact as described above, the remaining welding projection 13b can have the same length as a conventional one, with the result being that there is no need to make every welding projection serve as in the manner of the longer welding projection 13a. In such cases, the welding current may not be increased so much as compared with the prior art.

Although a single welding projection 13a is formed continuously in the illustrated embodiment, it is also possible to form welding projections 23a which stand in a row leaving a space therebetween so as to extend along the sectional outer peripheral surface of the ring portion mandrel 11 as shown in FIGURE 4.

Further, although the spoke portion mandrel 12 Of the plate shape is used in the illustrated embodiment,a round bar may be used to form a welding portion 33 by press work and welding projections 33a may be formed in the thus formed welding portion 33 so as to extend along the outer peripheral surface of a ring portion mandrel 31 as shown in FIGURE 5.

In addition, although the ring portion mandrel 11 is made of the steel pipe in the illustrated embodiment, a solid ring portion mandrel 31 may be used as shown in FIGURE 5.

Moreover, although the ring portion mandrel 11 has the circular external form in cross section in the illustrated embodiment, the ring portion mandrel may have an elliptic of polygonal external form in cross section and the prescribed welding projections may be formed in the welding portion of the spoke portion mandrel so as-to extend along the outer peripheral surface of such a ring portion mandrel.

In a steering wheel W according to another embodiment illustrated in FIGURES 6 and 7, a plurality of welding projections 18 are formed in a welding seat 13 formed horizontally at the forward end of each spoke portion mandrel 12 so as to extend in the longitudinal direction of the spoke portion mandrel 12 and in the sectional direction of the ring portion mandrel 11 like above embodiment. Each of these welding projections 18 is formed with a concavity 19 of the shape that is roughly conformed to the bottom side of the sectional outer peripheral surface of the ring portion mandrel 11. In this case, each concavity 19 is formed by boring the welding projection 18 to make a through hole which vertically penetrates the welding seat 13.

Therefore, in the described steering wheel W according to the second embodiment, when it is intended to weld the ring portion mandrel 11 to the welding seat 13 of each of the spoke portion mandrels 12 by making use of resistance welding, by.setting the ring portion mandrel 11 in the concavities 19 of the welding projections 18 formed in each of the welding seats 13 as shown in FIGURE 8A, the ring portion mandrel 11 can be roughly fit in the concavities 19, thereby making it possible to perform positioning without difficulty.

Subsequently, the welding seat 13 of the spoke portion mandrel 12 and the ring portion mandrel 11 are maintained under pressure between the predetermined electrodes D1 and D2 as shown in FIGURE 8B, and then, a fixed electric current is sent for mandrels 11 and 12. In this way, the spoke portion mandrels 12 and the ring portion mandrel 11 are welded to each other.

In the steering wheel W thus formed, the peripheral edge of the concavity 19 of each of the welding projections 18 formed in the wplding seat 13 of each spoke portion mandrel 12 can be brought into contact at a plurality of points thereof or into linear contact with the outer peripheral surface of the ring portion mandrel 11. In consequence, the welding area is increased so that the welding is performed with improved weld strength. In the second embodiment, the concavity 1 - 1 1 - 19 is formed by boring the welding projection 18 to make the through hole. However, the through hole may be replaced by a concavity 25 formed by partially depressing a welding projection 24, as shown in FIGURES 9 and 10, so that the ring portion mandrel 11 can be roughly fitted therein.

Further, in the above embodiment, each of the welding projections 18 is formed continuously so as to extend roughly along the sectional outer peripheral surface of the ring portion mandrel 11. However, it can be replaced by a welding projection 34 formed by two spaced convexes 34a as shown in Figures 11 and 12. In this case, a space between the convexes 34a is made to Serve as a concavity 35 wherein the ring portion mandrel 11 is roughly fit.

In addition, in the above embodiment, the ring portion mandrel 11 is set on the upper surface of the welding seat 13 of the spoke portion mandrel 12. However, the ring portion mandrel 11 can be welded to the lower surface side of the welding seat as shown in FIGURES 13 and 14. a welding seat 43 is formed on the lower surface side with welding projections 44 each comprising two downward cover projections 44a and a concavity 45 defined therebetween where the ring portion mandrel 11 is welded to the lower surface side of the welding seat 43, the set portion of the ring portion mandrel 11 is put out of sight by the welding seat 43 itself. In this respect, the positioning of the ring portion mandrel 11 can be performed remarkably smoothly at the time of welding as compared with the case in which no concavity 45 is formed.

Further, although the spoke portion mandrel 12 is plate-shaped in the above embodiment as well, a round bar may be used to form a welding seat by press work and welding projections each formed with a concavity may be formed in the welding seat thus formed.

In addition, although the ring portion mandrel 11 is made of steel pipe in the above embodiment as well, a solid ring portion mandrel can be used. .

Moreover, although the ring portion mandrel 11 has the circular external form in cross section in the above embodiment as well, the ring portion mandrel may have an elliptic or polygonal external form in cross section and the concavity of the welding projection in the welding seat of the spoke portion mandrel may be formed to have the shape that is roughly conformed to the outer peripheral surface of such a ring portion mandrel.

Furthermore, although the spoke portion mandrels 12 and the boss plate 15 are formed united with each other in the embodiments described above, it is of course possible that they are formed separately from each other.

While the invention has been described in connection with what are presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment, but is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1 C L A I M S

1. A steering wheel comprising: a boss portion connected to a steering shaf t; a ring portion having a ring portion mandrel embedded in a coating layer; spoke portions each having a spoke portion mandrel which serve to connect said boss portion and said ring portion with each other; and said spoke portion ntandrel formed at the end thereof with a joining portion to which said ring portion mandrel is joined; wherein said joining portion has a concavity serving to receive said ring portion mandrel so that the ring portion mandrel is joined thereto by means of resistance welding over the entire contact surface of said concavity with the ring portion mandrel.

2. A steering wheel according to Claim 1, wherein said joining portion has an elongated projection serving to provide said contact surface and extending in such a direction as to intersect perpendicularly to the ring portion mandrel.

3. A steering wheel according to Claim 2, wherein said concavity includes a bent portion of said elongated projection.

4. A steering wheel according to Claim 2, wherein said concavity includes divisions formed on said elongated projection.

5. A method for manufacturing a steering wheel which comprises a boss portion connected to a steering shaft, a ring portion having a ring portion mandrel embedded in a coating layer and spoke portions each having a spoke portion mandrel and serving to connect said boss portion and ring portion with each other, said spoke portion mandrel having formed at the end thereof a joining portion to which said ring portion mandrel is joined, said method comprising the steps of: preparing the spoke portion mandrels to each have a concavity formed in said joining portion thereof; preparing said ring portion mandrel; setting the ring portion mandrel in said concavity; sending an electric current to said joining portion and ring portion mandrel while applying pressure thereto so as to weld the joining portion to the ring portion mendrel over an entire contact surface therebetween; and forming the coating layer around the welded ring portion mandrel.

6. A method according to Claim 5, wherein said joining portion includes an elongated projection serving to provide said contact surface and extending in such a direction as to intersect perpendicularly to the ring portion mandrel.

7. A method according to Claim 6, further comprising the step of by bending said elongated projection to form said concavity.

A method according to Claim 6, further comprising the step of dividing said elongated projection to form said concavity.

i I 1 9. A steering wheel constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

10. A method of manufacturing a steering wheel substantially as hereinbefore described with reference to the accompanying drawings.

1 Published 1991 at The Patent office. Concept House. Cardiff Road. Newport. Gwent NP9 I RH. Further copies may be obtained from Sales Branch. Unit 6. Nine Mile Point. Cwmfelinfach. Cross Keys. Newport. NP1 7HZ. Printed bv Multiplex techniques lid. St Marv Cray. Kent.