GB2309192A

GB2309192A - Moulding onto steering wheels using multi-injection technique

Info

Publication number: GB2309192A
Application number: GB9700965A
Authority: GB
Inventors: Tous Luis Gras
Original assignee: Dalphi Metal Espana SA
Current assignee: Dalphi Metal Espana SA
Priority date: 1996-01-17
Filing date: 1997-01-17
Publication date: 1997-07-23
Also published as: GB9700965D0; FR2743538A1; ES2147047A1; ES2147047B1; DE19703039A1

Description

IMPROVEMENTS MADE IN THE MANUFACTURE OF STEERING WHEELS FOR MOTOR VEHICLES DESCRIPTION SUBJECT OF THE INVENTION The present invention relates to improvements made in the manufacture of steering wheels for motor vehicles, which provide essential characteristics of novelty, and also considerable advantages and improvements with regard to the methods for the manufacture of such articles which are known and are used in the current state of the art.

In more detail, the basic object of the invention is that of providing a steering wheel which can be obtained by multiple injection, with all the advantages derived from this type of method, for the manufacture of which only materials of the thermoplastic type are used which can be moulded by means of the said injection method, in one operation and without the need for other subsequent additional operations. To this end, the invention starts from a conventional metallic rim of the type used in the manufacture of steering wheels, provided with one or more spokes according to the model of steering wheel which it is desired to produce, on which one or more thermoplastic materials are moulded in order to be able to provide the said steering wheel with the desired characteristics of rigidity and surface finish. The invention provides for the resulting steering wheel to be of the integral type, that is to say, already including with the actual injected part the means for the arrangement of the airbag components or other functions of the motor vehicle, or optionally to include the housing for such components, which can be protected and retained by means of a cover fixed in a conventional manner.

The field of application of the present invention is comprised, as will be obvious, within the industry which is dedicated to the manufacture of steering wheels for motor vehicles.

ANTECEDENTS OF THE INVENTION It is known to all persons skilled in that art that in the manufacture of steering wheels for motor vehicles certain materials are used, as is the case with polyurethane.

This material is injected by means of suitable systems available commercially, so that it is arranged round those metallic parts of the steering wheel which it is desired to protect. The use of polyurethane brings with it a series of drawbacks inherent in the characteristics of the material itself, and which basically consist in the fact that during its injection a quantity of excess material is produced on the injected part, which requires a series of subsequent operations to eliminate such excess material and therefore to provide the characteristics of finish which are required, all of which entails a considerable expenditure of time and labour, with a consequent increase in the production costs. The steering wheel thus obtained is completed by a cover which is mounted on the centre front part of the steering wheel, closing a housing in which are located the components of the airbag for the driver, with all the consequent operations, and the said cover needing to possess a finish which is acceptable both to the touch and to the sight of the user.

There exist, then, certain drawbacks inherent in the manufacture and assembly of the present steering wheels, which entail excessive expenditure of time and labour, for which reason it would be desirable to be able to develop a process by means of which the operations of manufacture and assembly are simplified, and consequently the problem posed at present is eliminated.

SUMMARY OF THE INVENTION By means of the present invention an improved process is provided for the manufacture of steering wheels for motor vehicles, which process combines the characteristics previously indicated as being desirable, assuming in addition a considerable simplification of the current processes of manufacture of this type of article. To this end, the invention provides for the use of suitable thermoplastic materials which, by means of multiple injection, can be moulded in order to form the different parts which are associated with the inner metallic rim with which the above-mentioned steering wheel must obviously be provided.

According to the different options and alternatives offered by the invention, two or more thermoplastic materials will be used, both for the formation of the filling material which covers the metallic rim and the different spokes with which the latter can be provided, and also for the formation of the outer piece which covers all of the former and which also forms the cover for the closure of the central part of the steering wheel above the hub. The said outer cover will be provided with the characteristics of finish which are desired for its visible face. Moreover, this type of manufacture makes it possible, as indicated previously, to produce steering wheels of the integrated type, with the consequent elimination of a series of stages related to the mounting of the steering wheel assembly.

As can be clearly seen, the use of thermoplastic materials capable of being moulded by means of multiple injection processes offers the additional advantage of providing a rapid and clean process, which can be carried out on a single injection moulding machine and without the need for subsequent operations of cleaning and finishing the part obtained, thereby also achieving a considerable saving of waste.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and different characteristics of the subject of the present invention will be revealed by the description which follows with reference to the accompanying drawings, in which, by way of example and without implying any limitation, a preferred embodiment is shown.

In the drawings: Figure 1 is a diagrammatic view in transverse section of a first embodiment of an integrated steering wheel constructed in accordance with the present invention, and also a section taken at another position on the steering wheel.

Figure 2 is a diagrammatic view in transverse section of a second embodiment of a steering wheel according to the invention, likewise integrated, and also including a transverse section taken at any other position on the steering wheel.

Figure 3 shows, also diagrammatically, a transverse section with respect to a third embodiment of an integrated steering wheel according to the invention, in which there also appears a transverse section of the steering wheel.

Figure 4 shows a diagrammatic transverse section of a fourth embodiment of an integrated steering wheel which includes the improvements of the invention, together with a transverse section taken at another position on the steering wheel.

Figure 5 shows a view in transverse section of a steering wheel according to the invention, together with a further transverse section taken at another position, in which the adaptation of the airbag module is effected separately.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to provide the detailed description of the different alternatives or preferred embodiments of the invention, reference will at all times be made to the Figures of the drawings, of which Figure 1 shows a diagrammatic view of a transverse section through a steering wheel manufactured in accordance with a first option which includes the improvements of the invention, such that this section has been taken so that it also shows all of the central part of the steering wheel corresponding to the hub region. In addition, in this Figure there also appears another transverse section which can correspond to any position on the steering wheel at which there is no spoke joining the metallic rim and the central hub.

As duly shown, the steering wheel is constituted in a conventional manner by a metallic rim (1) from which extend(s) one or more radial spokes (2), likewise metallic, which are joined to the hub (3) of the steering wheel provided with a region (4) by means of which it will fit onto the upper end of a steering column (not shown). The rigid connection of the different spokes (2) to the said hub (3) can be effected by means of screws (5) or by means any other known method which provides the said connection with the desired characteristics of reliability.

The improvements provided by the invention are applicable to a conventional steering wheel structure thus formed. In fact, in accordance with this first option, two thermoplastic materials are used which have different characteristics according to the qualities which it is desired to obtain, so that with one of the said materials the said metallic parts are covered by means of injection in order to provide an injected filling region (6) round the rim (1) and the spokes (2). This thermoplastic material will have suitable characteristics so as to form an injected region (6) which is soft and which therefore provides a certain degree of internal flexibility. With this it is possible to provide the steering wheel with a resilient region transmitting a spongy feel which improves the grip of the user's hands in the handling regions of the steering wheel.

Once the region (6) which covers the metallic parts has been injected, there follows the injection of the outer region (7) by means of which the whole front assembly is enclosed and at the same time the housing (8) is provided for the airbag components and/or other functions. This region (7) is likewise of thermoplastic material, but, unlike the region (6) described previously, its mechanical characteristics are more rigid and are dependent on the requirements for the perfect functioning of the airbag module and whatever standard is to be applied. In its turn, the lower region can be covered by means of a separate part (9) of conventional type and having suitable characteristics.

In the lower view there appears a section taken at any other point on the steering wheel, for example, in a position diametrically opposed to the first section, in which it can be seen that the metallic rim (1) is covered by the soft thermoplastic material (6) and, covering the whole of it, the material (7) having more rigid characteristics and the outer surface of which will be provided with the degree of finish and presentation which is desired for the steering wheel.

Referring now to the view shown in Figure 2, it will be observed that there appears therein a transverse section of a steering wheel constructed in accordance with a second embodiment of the invention. In this case, three thermoplastic materials are used, and in order to obtain the said steering wheel the starting point is the same basic steering wheel structure as in Figure 1, so that round the metallic rim (1) there is injected a first thermoplastic material (6), having very soft characteristics in order to provide a certain degree of internal flexibility, while in the regions of the spokes (2) and in the central part an intermediate region (10) is formed from a second thermoplastic material having rigid mechanical characteristics, depending on the requirements of the airbag module. This region (10) is that intended to form the housing (12) in which the said airbag module and/or other components will be mounted. Covering the whole assembly there is injected a further outer region (11), arranged in close surface contact with the aforesaid intermediate injected region (10), and such that the outer region (11) will likewise be injected in thermoplastic material, but having characteristics such as to provide the quality of finish which is desired both with regard both to the user's sight and touch. In the view of the lower transverse section, which can be taken at any position on the steering wheel where there is no spoke, it will be observed that round the rim (1) there is the region (6) of soft material and, covering the assembly, the finish region (11) of the steering wheel.

As in the previous case, the lower part will be provided with a closure member (9).

Referring now to the embodiment shown in Figure 3, a transverse section through an integrated wheel constructed in accordance with the improvements of the invention is observed, in which two thermoplastic materials are used.

This alternative embodiment is similar to that which is shown in Figure 2, but with the difference that the metallic rim (1) is covered directly by the region (20) obtained by injection of a thermoplastic material having rigid characteristics according to the requirements of the airbag module, and such that the said region (20) is that intended to cover the spokes and to form the housing (22) for the airbag components and/or other functions. Covering the whole assembly there is injected a region (21) which is positioned in close surface contact with the inner region (20) and constructed by means of the injection of a suitable thermoplastic material which provides the characteristics of surface finish, with regard to appearance and feel, which are desired for the said outer region (21). In the second transverse section, which can be taken at any position on the steering wheel where there is no spoke, it will be observed that the rim (1) is completely covered by the region (20) and the latter, in turn, by the outer region (21).

An important characteristic of the embodiment in Figure 3 consists in the fact that the outer region (21) has been provided, during the injection process, with a greater thickness in the region (23) corresponding to the position of the metallic rim, such that it is possible to improve the prehensile function and adaptability of the hands of the user on the steering wheel.

As in the case of the previous options, the embodiment in Figure 3 is provided with a lower cover (9) which makes it possible to close, underneath, the steering wheel constructed in accordance with what has been stated previously.

Figure 4 shows a further version of an integrated wheel, in transverse section, in the construction of which two thermoplastic materials having different characteristics are used. Starting from a steering wheel structure identical to that of the preceding embodiments, a first thermoplastic material is injected in order to form a region (30) which covers the metallic spokes (2) and which shapes the housing (32) for the airbag module. This first thermoplastic material will provide characteristics of rigidity appropriate to the requirements of the aforesaid airbag module. Following this, an outer region (31) is injected such that the latter is intended to cover both the metallic rim (1), giving the shape and size to the said rim , and also the aforesaid inner region (30) to which it adapts in close surface contact. The thermoplastic material in which the said outer region (31) is injected will have characteristics such that it provides the assembly with the desired finish, from the point of view of feel and appearance. The steering wheel is completed by a lower closure cover (9).

In the lower transverse section, which corresponds to any point on the steering wheel where there is no spoke, it will be observed that the metallic rim (1) is completely covered by the region (31) intended to provide the steering wheel with its surface finish.

Finally, in the exemplary embodiment which is shown in transverse section in Figure 5 of the drawings, there is shown an alternative form of a multiple injection steering wheel in which the airbag module is not totally integrated as in the previous alternative forms. In this case two thermoplastic materials are used which are injected in the same way as in the embodiment in Figure 4, in order to constitute an inner region (40) which adapts to the spokes and an outer region (41) which adapts to the rim (1) and which covers the front, such that also in this embodiment the outer region (41) is injected in a material which is suitable for providing the characteristics of surface finish which it is desired to obtain. However, differing from the embodiment in Figure 4, the aforesaid regions (40, 41) injected in thermoplastic material extend only to a certain distance from the position of the metallic rim (1), leaving a central space (42) over the hub (3) of the steering wheel intended to receive the components of the airbag module or other functions, which will be closed above by means of a cover (43) of conventional type, which can be constructed of thermoplastic material or also of polyurethane. The lower part of the steering wheel is likewise closed by means of a suitable cover (9).

In the lower section taken on the steering wheel at any point thereon at which there is no spoke, it will be seen that the metallic rim (1) is completely covered by the region (41) of injected thermoplastic material by means of which the characteristics of finish of the steering wheel are provided.

It is not considered necessary to extend the content of this description further in order that a person skilled in the art may understand its scope and the advantages derived from the invention, and also develop and put into practice the subject thereof.

However, it should be understood that the invention has been described according to preferred embodiments of the latter, so that it is capable of modifications without assuming any change in the basis of the said invention, it being possible to make such modifications to the shape, the size and/or the manufacturing materials.

Claims

1. Improvements made in the manufacture of steering wheels for motor vehicles, the steering wheel being formed from a metallic rim provided with a variable number of radial spokes, also metallic, and having sections and shapes likewise variable depending on the type of steering wheel which it is desired to obtain, which are characterized in that provision has been made to mould a first region which adapts to the part of the said metallic rim and of the spokes and at least a second region which covers the former and which extends to the part of the central hub of the steering wheel where various functions are incorporated such as the airbag module or the like, such aforesaid regions being produced by the use of multi-injection moulding techniques and using for this purpose at least two thermoplastic materials having different physical characteristics.

2. Improvements according to Claim 1, which are characterized in that the first covering round the rim and the spokes is preferably produced with a soft thermoplastic material in order to provide a resilient part to allow the hands to fit comfortably on the steering wheel and hold it easily.

3. Improvements according to Claim 1 or 2, which are characterized in that the second covering is produced on the basis of a thermoplastic material having a certain mechanical rigidity which allows it to provide suitable protection for the components which it covers, and the characteristics of which at the same time make it possible to provide it with a suitable surface finish with regard to appearance and feel.

4. Improvements according to any one of the preceding claims, which are characterized in that, optionally, a third thermoplastic material having rigid mechanical characteristics is used which is moulded so as to constitute an inner region which extends round the spokes, round the region of the steering wheel which includes the central hub and round the inner region of the metallic rim, whilst, covering the whole of this assembly, the outer region is moulded using a thermoplastic material which makes it possible to give the steering wheel the surface appearance and feel which its finish requires.

5. Improvements according to Claim 1, which is characterized in that, optionally, the cover which adapts to the central region of the steering wheel in which are housed the members relating to the functions mentioned, may consist of an element which is separate from the moulded region which covers the remainder of the steering wheel, the said cover thus being able to be constructed alternatively in a different material.