Method for manufacturing a steering wheel

The invention relates to a method for manufacturing a steering wheel comprising a frame, a covering formed by a body, overmoulded onto the frame, and at least one insert, the method comprising steps aimed at: providing at least one recess in the covering, and producing the insert so that an assembly of the insert with the body of the covering allows the recess, to be at least partially covered, wherein the insert is obtained in a single piece with the body of the covering.

TECHNICAL FIELD

The present invention generally relates to the field of vehicles, particularly the field of steering wheels such as those for motor vehicles, for example.

A steering wheel typically consists of a frame comprising a hub from which spokes extend that connect the hub to a core or rim, which forms the circular or essentially circular part of the steering wheel. Forming the backbone or skeleton of the steering wheel, the frame may be obtained by injection under pressure of a light metal, such as aluminum or magnesium. This frame can then be overmoulded by a urethane foam obtained for example from a polyurethane elastomer (PU, PUR).

In language commonly used by those skilled in the art, the overmoulding of the frame constitutes the foaming operation of the steering wheel. This operation is carried out by placing the frame in a mould generally formed of two parts, one lower, the other upper. The mould comprises the steering wheel cavity that may be filled with a casting (one or several chemicals in liquid form) injected under pressure through feed channels under predefined temperature and pressure conditions. By chemical reaction, these conditions will allow the casting to change to foam, to solidify and harden after a certain time in order to form the rough covering of the frame.

This covering will essentially cover the circular or substantially circular part of the steering wheel, but may also extend to the spokes. Once out of the mould, this covering will be deburred especially in order to remove the excess foam cast around the steering wheel. Finally, the steering wheel may then be covered by a sheath, which may typically be made of natural or artificial leather, for example. This last operation is generally done manually by workers who apply glue to the covering, stretch the leather sheathing and sew it closed.

As is well known, steering wheels are currently equipped with control buttons, often even sensors, for the purpose of improving safety during driving, particularly by facilitating access to certain functionalities without releasing the steering wheel. These control buttons and other equipment need to be electrically supplied and connected by means of electric wires concealed in the steering wheel, particularly in the covering thereof and more specifically in channels left on the surface of the covering by the operation of overmoulding the frame (foaming).

The problem caused by these channels lies in the fact that when the sheathing is applied to the steering wheel, the electric wires arranged in these channels can be felt through the sheathing that has been deliberately stretched to conform to the shape of the steering wheel. If the electric wires or cables protrude from the channel, or conversely, if they are inset too far from the surface of the covering or do not completely fill the channel in which they are placed, ridges or deformations may be felt after application of the sheath.

Furthermore, the injection method and the movements of the two mould parts during injection operations restrict the positioning of the channels on the steering wheel so that they are not necessarily arranged where they will be the most unobtrusive. Their positions must allow the demoulding of the steering wheel, and minimum injection thicknesses must be respected.

From a functional point of view, it is important that the steering wheel be well-made in order not to compromise the safety of users. However, the steering wheel must also be pleasant to the touch and of flawless aesthetics and ergonomics for the pleasure and comfort of the driver. In any case, the steering wheel constitutes an important element in the interface between the steering mechanism of the vehicle and the driver.

PRIOR ART

Document US 2003/0075003 discloses a steering wheel capable of giving the impression that it is formed from a pattern and texture of natural wood, both from a visual aspect as well as tactile feel. In one embodiment, the covering of the steering wheel of this document is produced from two parts. The first part is a main portion that adopts a C-shaped cross-section in order to be inserted onto the core or the rim of the frame. This first part constitutes the front face of the covering. The second part is situated on the back face and involves an insert intended to close the open portion of the C-shape left by the first part

While seeking to improve the comfortable feel of the steering wheel so that it is pleasant for the driver to hold, the solutions of the prior art do not make it possible to efficiently resolve the problem of ridges or deformations resulting from a sheathing applied onto a covering in which recesses or channels have been made for arranging members therein such as electric wires.

Consequently, there is a benefit in finding a more appropriate and efficient solution that makes it possible, at least in part, to resolve the aforementioned disadvantages.

DISCLOSURE OF THE INVENTION

To that end, the present invention relates in a first aspect to a method for manufacturing a steering wheel comprising a frame, a covering formed by a body, overmoulded onto the frame, and at least one insert, said method comprising steps aimed at:providing at least one recess in the covering, andproducing said insert so that an assembly of the insert with the body of the covering allows the recess to be at least partially covered,
characterised in that said insert is obtained in a single piece with the body of the covering.

Advantageously, the recess provided in the covering constitutes a space that may be partially occupied by one or several non-structural members such as electric wires, for example. However, this space may also be fully occupied or left empty. Irrespective of the degree of occupancy or of filling of the space by such a member, the coverage of the space by the insert during assembly makes it possible to obtain a covering provided with a continuous or homogenous surface. Such a surface allows an optimal sheathing to be ensured, free of any ridges, folds, indentations or other deformations once the sheath is applied and stretched onto the covering.

More advantageously, the method of manufacturing this covering is particularly efficient because it makes it possible to obtain the expected result with a minimum of expense or effort. Indeed, because the insert and the body of the covering are obtained in a single piece, it is not necessary to use more than one moulding operation to obtain all the parts of the covering since it makes it possible to obtain simultaneously an overmoulding of the frame and at least one insert related to this overmoulding. More advantageously, it is no longer necessary to multiply the channels for feeding the material injected into the mould; since the body of the covering and the insert are of one piece, they are necessarily connected to one another, thus constituting one and the same cavity in the mould. Moreover, because the inserts are injected at the same time as the rest of the foaming, it becomes possible to guarantee that all the elements from the foaming will have the same pliability and will have similar injection characteristics. Also, during handling or transport of the steering wheel, it is advantageously no longer possible to misplace the insert without it being deliberately detached from the body of the covering. Finally, this makes it possible to manufacture only one part and therefore manage only one part reference.

In a preferred embodiment, the insert is obtained by being attached to the body of the covering by at least one attachment bridge.

In another embodiment, a depression is further provided in the periphery of the body of the covering and/or of the insert and is configured to be able to receive therein all or part of the attachment bridge.

According to one particular step of the method, the attachment bridge is detached from the insert and/or from the body of the covering.

Furthermore, according to a preferred embodiment the attachment bridge is inserted into said depression. For example and more particularly, the attachment bridge may be inserted into the depression in a movement consisting of folding the insert against the body of the covering. Preferably, the depression in this case is provided in front of the attachment bridge. This embodiment makes it possible to limit the operations of cutting the bridge, thereby saving time, material and avoiding having to manage scrap.

Preferably, said attachment bridge is arranged to form a hinge between the body and the insert, and said manufacturing method comprises an operation of inserting the insert into the recess by folding the attachment bridge forming a hinge. This embodiment eliminates the operation of cutting the attachment bridge, which simplifies the assembly operations.

Preferably, the recess is provided in the body of the covering. However, this recess could be provided in the insert, or even partly in the body of the covering and partly in the insert. Thus, in one embodiment, said recess is at least in part provided in said insert.

More preferably, the depression and/or the recess is obtained during the moulding of the covering.

In one embodiment, the insert has a shape at least partially matching that of the recess.

In one embodiment, the insert is inserted at least partially into the recess. This makes it possible to facilitate the positioning of the insert and ensure better joining of the different parts.

In one embodiment of the invention, the method further comprises the positioning of at least one member in said recess, prior to said assembly of the insert with the body of the covering. Preferably, said member is an electrical member. The method therefore makes it possible to integrate, simply and with great freedom of design, an electrical member such as a wire or set of wires in the foaming of the steering wheel.

In a preferred embodiment, said steering wheel comprises several inserts. The use of several inserts makes it possible to cover a larger surface area of the covering while limiting the size of the injection mould because of the general curvature of the rim.

In one embodiment, the insert or inserts are positioned at the periphery of the covering during their manufacture in a single piece with the body of the covering.

In one embodiment, the body of the covering has a joint plane and said attachment bridge is situated at said joint plane. This embodiment simplifies the design of the injection mould for the covering.

In other words, the insert and the body of the covering are manufactured in the same step of the method, thus forming a single piece. In other words, the insert and the body of the covering are made of the same material.

Consequently, upon completion of a single step of manufacturing the insert and the body of the covering, a part is obtained where the material is continuous between the insert and the body of the covering.

For example, if the manufacturing is carried out by moulding, then at the exit of the mould, the insert and the body of the covering are one and the same part, with a first portion intended to form the insert, and a second portion intended to form the body of the covering, both portions being able to be connected together by bridges, for example.

In a second aspect, the invention relates to a steering wheel obtained by the implementation of the method, relative to the first aspect of the invention, according to any one of the embodiments thereof. Preferably, this second aspect relates to a steering wheel comprising a frame and a covering formed by a body overmoulded onto said frame and at least one insert. This steering wheel is characterised in that the insert and the overmoulded body of the covering are obtained in a single piece.

In one embodiment, one end of an insert is adjacent to a sheathing groove of the covering. A sheathing groove is a hollow shape arranged to receive a seam of a sheath, for example made of natural or synthetic leather, glued and/or sewn at the periphery of the covering. When the end of the insert is adjacent to such a groove, it limits the risks of visibility of the juncture because the seam of the sheath is in this area.

In one embodiment, two ends of an insert are adjacent to two different sheathing grooves of the covering.

In a third aspect, the invention relates to a motor vehicle, comprising a steering wheel that is in accord with the second aspect of the invention.

In a fourth aspect, the invention relates to an injection mould for the implementation of the method, the object of the first aspect of the invention, according to any one of the embodiments of this method or according to any one of the possible combinations of these embodiments.

DETAILED DESCRIPTION

FIG.1represents a plan view of a steering wheel1comprising a frame10and a covering20. This steering wheel is typically obtained by overmoulding the frame10by the covering20. Produced from an alloy or a light metal such as magnesium or aluminum, the frame10typically constitutes the skeleton or backbone of the steering wheel. This frame comprises a hub11from which spokes13extend which connect the hub11to a core or rim15. Said rim constitutes the portion of the structure that gives the circular or substantially circular shape to the steering wheel.

The covering20essentially consists of a body21, overmoulded onto the frame, and at least one insert27. The at least partial overmoulding of the covering on the frame is obtained by moulding. To do this, the frame10is placed in a mould that comprises the cavity for the steering wheel1. This mould is generally formed from two parts, typically an upper half and a lower half, and comprises injection channels that enable a material to be injected, such as a urethane foam (PU, PUR) for example. The operation of moulding the steering wheel, namely the at least partial overmoulding of its frame, is also called foaming by those skilled in the art. After a certain time and under certain temperature and pressure conditions, the injected foam will solidify, then harden.

It can be seen inFIG.1that the covering20is formed not only of the body21but also of at least one insert27, preferably a plurality of inserts, of which there are four in this example. These inserts27constitute mating parts of the body of the covering and are related thereto in order to be able to complete it.

The method of manufacturing the steering wheel of the present invention especially comprises steps aimed at:providing at least one recess22in the covering20, andproducing said at least one insert27so that an assembly of the insert27with the body21of the covering allows the recess22to be at least partially covered.

According to the method of the invention, the insert27is obtained in a single piece with the body21of the covering. This feature is better shown inFIG.2, which represents a part of the steering wheel1and more specifically a perspective view of a portion of the steering wheel in front of one of the inserts27.

The recess22(more visible inFIG.2) will allow the arrangement of at least one member32in the body21of the covering of the steering wheel. In the example ofFIG.1, this member32consists of electric wires, in particular a strand of electric wires, that may be connected for example to a control button35of the steering wheel1(FIG.3). Such a control button35may typically be used to control a device of the vehicle in order to activate for example an audio function, a remote wireless connection, a speed regulator, an onboard computer or any other apparatus.

Advantageously, the recess22provided in the covering20offers a space that may either be left free or occupied, in other words partially or totally occupied, by at least one member32without producing an undesirable surface effect of the covering20. Consequently, any sheath41(FIG.4) applied stretched onto the covering20will not leave any deformation such as a ridge, crevice or fold to be felt.

More advantageously, as a result of the manufacturing method of the present invention, the aforementioned benefit may further be obtained particularly efficiently. This results especially from the fact that each insert27of the covering can be advantageously obtained in a single piece with the body of the frame during the overmoulding of the frame, i.e., in one and the same operation. Furthermore, obtaining the covering of the frame in one piece requires no additional injection of material. More advantageously, obtaining this covering in one piece, including inserts27capable of being detached from the body21facilitates the transport, handling, storage and tracing of the elements of the covering in the production line. Typically, obtaining the insert (or inserts) and the body in one piece is achieved by moulding.

In one embodiment, as shown by example inFIG.2, the insert27is obtained by being attached to the body21of the covering20by at least one attachment bridge25. This bridge can be considered as being a transition or a connection element that makes it possible to obtain, in a single piece, a covering formed of a body21and at least one insert27connected to this body. As shown in this figure, two attachment bridges25are preferably used to attach each complementary part or insert27to the body of the covering during production of this insert with this body. More preferably, the attachment bridge25comprises two ends, one adjoined to the body and the other adjoined to the insert. Alternatively, it would be possible to obtain a connection bridge with more than two ends, for example a Y-shaped attachment bridge comprising three ends, or H-shaped with four ends. According to another alternative, it would also be possible to consider an attachment bridge with one end if said bridge were in the shape of an I and would simply be a wire disposed longitudinally along the body and the insert connected thereto.

Furthermore, in one embodiment best viewed inFIG.2, a depression24is made in the periphery of the body21and is configured to be able to accommodate therein or to insert therein all or part of the attachment bridge25. It will be understood that there will preferably be as many depressions24as there are attachment bridges in the covering20. This depression can be an indentation having a shape complementary to that of the attachment bridge, or at least having a shape so that when the insert27is assembled onto the body21in order to cover the recess22, the attachment bridge25is matched and integrated (preferably freely) with the body21.

Alternatively, the depression24could, for the same purpose, be provided in the periphery of the insert27, even partially in the periphery of the body21and partially in the periphery of the insert27.

In one embodiment, the method of the invention further comprises a step in which the attachment bridge25is detached from the insert27and/or from the body21of the covering. Indeed, in order to be able to assemble the insert27and the body21, several scenarios may be considered.

In a first scenario, the body21may be detached from the attachment bridge25, for example by cutting the end(s) of this bridge that is(are) adjoined to the body21. In this first scenario, it is advantageously unnecessary to have to separate the attachment bridge25from the insert27since the body21includes a depression24specifically making it possible to receive the attachment bridge25that remains integral with the insert27. With reference toFIG.2, it will be noted that the cutting of a single end of each attachment bridge25, in this instance the end adjoined to the body21, enables the release of the insert27which, according to the illustration given by the arrows F, will be able to be placed against the body21in order to carry out the assembly of the insert with the body. To do this, the depressions24will then preferably be provided to match the attachment bridges25that remain integral with the insert27.

In a second scenario, the insert27may be detached from the attachment bridge25, for example by cutting the end(s) of this bridge that is(are) adjoined to the insert27. In this second scenario, it would be possible to make depressions24in the body21in positions adjoining the attachment bridges25. Thus, these bridges could be folded into these depressions24, particularly during the subsequent operation of sheathing the steering wheel. Furthermore, if necessary, each attachment bridge could be provided with a necking or line of weakness facilitating its folding in order to be folded against its depression, typically matching, at the periphery of the body of the covering.

In a third scenario, both the insert27and the body21could be detached from the attachment bridge25. This operation would typically require two cuts to obtain the complete separation of each attachment bridge25. These attachment bridges will preferably be discarded, but nevertheless could be inserted into the depressions24if said depressions are provided in the covering body for that purpose.

In a fourth scenario, it should be noted that the insert27and the body21may not be detached from the attachment bridge25. In this case, these bridges would be placed in such a way that, on the one hand the insert may be folded or turned down onto the body21during their assembly with the body, and on the other hand in this assembly position each attachment bridge25can be received at least in part in a matching depression24. Thus, there may be an embodiment in which the attachment bridge25is inserted into the depression24, for example by a movement consisting of folding or turning down the insert27against the body21of the covering.

In one embodiment of this scenario, the attachment bridge25could be arranged to form a hinge between the body21and the insert27, and the method would comprise an operation of inserting the insert27into the recess22by folding the attachment bridge forming a hinge.

Each of these scenarios makes it possible to obtain an assembly of the insert27with the body21such that the surface of the insert is located in the extension of the surface of the body. The same is true for the surface of the attachment bridge25with respect to the surface of the body21, since, in each of these scenarios, the attachment bridge may be inserted into the depression24provided for that purpose. Thus, the surfaces of the body, the insert and if applicable the attachment bridge, may advantageously be in line with one another, so that the covering20has, after such assembly, a unified or uniform surface that conceals the recess22without leaving deformations on the sheath once the subsequent operation of sheathing the steering wheel has been carried out.

In particular when the body21and the insert27are not detached from the attachment bridge25, it may be mentioned that the depression24will preferably be made in front of the attachment bridge so that it can easily be inserted thereinto during the assembly of the insert with the body of the covering.

Preferably, the recess22is provided in the body21of the covering. However, this recess22could be provided in the insert27, or partly in the body21and partly in the insert27. For this reason, it may be mentioned that the recess could be at least partly provided in the insert27.

In one embodiment, the insert27is inserted at least partially into the recess22. According to a preferred embodiment, the assembly of the insert and the body is carried out by interlocking and/or bonding. To do this, the body of the covering and the insert may further be configured to be assembled to one another. For example, the insert27may have a shape at least partially complementary to the recess22. Alternatively or additionally, the body21could comprise blind holes23(FIGS.1,2and4) configured to receive matching pins or other projections28(FIG.4) that are integral with the insert27. The blind holes23may be provided in a host surface of the body21intended to receive the insert, typically at the edges of the recess22as shown inFIG.4. However, these blind holes could also be made in the insert and the pins could then be made part of the body of the covering. Of course, other means of interlocking could be preferred in order to carry out the assembly of the insert with the body. These complementary shapes make it possible to facilitate the positioning of the insert and ensure better joining of the different parts.

Preferably, the recess22is obtained during the moulding of the covering, namely during the foaming operation. Advantageously, this recess can thus be obtained without requiring a subsequent operation, for example such as milling a portion of the covering20in order to create the recess therein. More preferably, and for the same reasons, this is also true for the depression24.

The method of the present invention may further comprise a step of placing at least one member32in the recess22prior to assembling the insert with the body of the covering. Preferably, this member32is an electrical member, typically one or several electrical conductors or wires.

It may also be mentioned that in one embodiment, the steering wheel1preferably comprises several inserts27.

The method of the invention may further comprise a step of sheathing the steering wheel1, in particular the covering20, after having arranged the member32in the recess22and having proceeded with the assembly of the insert27with the body21. More precisely, this sheathing step is for sheathing the covering, or a portion thereof, obtained by means of a sheath41(FIG.4). This sheath is typically stretched around the covering20, in other words around the assembly of the insert27with the body21or around a portion of this assembly. Such a sheath41will typically be produced from a flexible material such as leather, for example.

In another embodiment, the step of sheathing the sheath41may be preceded by sheathing another element such as a heating element or a presence sensor for example. The presence of such elements between the covering and the outer sheath makes it possible to hide any defect that may remain at the juncture between the insert and the covering.

In a second aspect, the invention also relates to a steering wheel1obtained by the implementation of the method of the first aspect, more specifically by any one of the embodiments of this method or any one of the possible combinations of these embodiments. Preferably, this second aspect relates to a steering wheel1comprising a frame10and a covering20which is formed by a body21, overmoulded onto this frame10, and at least one insert27. According to the invention, this steering wheel1is characterised in that the insert27and the overmoulded body21of the covering20are formed as a single piece.

In a third aspect, the invention relates to a vehicle, particularly a motor vehicle, comprising a steering wheel1that is in accord with the second aspect of the invention.

In a last aspect, the invention also relates to an injection mould for the implementation of the method according to any one of the embodiments of this method or according to any one of the possible combinations of these embodiments.