Control panel with flexible piezoelectric sensor for a vehicle

A control panel for a vehicle includes a flexible trim element, a rigid supporting member, a piezoelectric sensor arranged between the trim element and the supporting member, and a flexible element arranged between the piezoelectric sensor and the rigid supporting member.

FIELD OF THE DISCLOSURE

The present invention relates to a control panel, for a vehicle.

BACKGROUND OF THE DISCLOSURE

The control panel comprises at least one control button suitable in particular for switching on or off vehicle equipment, such as the rear window defrosting system, seat heating, vehicle stability control system, warning lights, etc. The control button comprises a pressing detection element consisting of a piezoelectric sensor to change the equipment status.

The document FR2908681 A1 discloses a control panel of this type comprising:a trim element,a rigid supporting member, anda piezoelectric sensor arranged between the trim element and the supporting member.

An aim of the invention is that of proposing a robust control panel which can be industrialized easily and reliably, while making it possible to detect pressing ergonomically and reliably.

SUMMARY OF THE DISCLOSURE

For this purpose, according to the invention, the control panel further comprises a flexible element arranged between the piezoelectric sensor and the rigid supporting member.

By pressing on the trim element in the region of the control panel, the user induces localized deformation of the trim element which is transmitted to the piezoelectric sensor, whereas the flexible element does not need to deform the rigid supporting member to enable the deformation of the piezoelectric sensor. In other words, the flexible element makes it possible to reduce the stress applied by the user to induce a defined deformation of the piezoelectric sensor. The control panel is as such more satisfactory ergonomically and the robustness thereof is improved.

According to a further feature according to the invention, the flexible element is preferably elastically compressible.

As such, the flexible element actuates the piezoelectric sensor to a defined position.

According to a further feature according to the invention, preferably the supporting member comprises a cavity having an opening and the flexible element extends into said cavity.

As such, the deformation region is localized, which enables the user to have a better sense of the location where the user is to press.

According to an additional feature according to the invention, preferably the flexible element is restricted to the cavity.

As such, the deformation of the trim element will be restricted further and localized to the region of the piezoelectric sensor.

According to an additional feature according to the invention, preferably the flexible element is suitable for being compressed along a control direction without expanding along directions perpendicular to the control direction.

As such, the embodiment and the operation of the control panel are enhanced.

According to a further feature according to the invention, the piezoelectric sensor is preferably in the form of a layer printed on a supporting film.

As such, the positioning of the piezoelectric sensor with respect to the flexible trim element and to the rigid supporting member is easier, which simplifies the production of the control panel, particularly when it comprises multiple control buttons. The term printing denotes a deposition of material, particularly by serigraphy, material droplet jet printing or an equivalent technique.

According to an additional feature according to the invention, preferably the flexible element is in the form of a layer printed on the supporting film, the piezoelectric sensor and the flexible element being preferably arranged on either side of the supporting film.

As such, the positioning of the flexible element with respect to the piezoelectric sensor is enhanced and the production of the control panel is simplified.

According to a further additional feature according to the invention, the flexible element preferably has a thickness between 25 μm and 500 μm.

According to a further feature according to the invention, preferably the control panel comprises a plurality of piezoelectric sensors and a plurality of flexible elements, the flexible elements being separated from one another by the supporting member.

As such, the risk of pressure on the flexible trim element inducing deformation detected by two adjacent piezoelectric sensors is reduced.

In various embodiments of the control panel according to the invention, use may further be made of one and/or another of the following arrangements:the element is made of silicone, rubber, thermoplastic elastomer or the like;the supporting member is made of plastic;the supporting member is overmolded.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

FIG. 1illustrates a motor vehicle passenger compartment100with a dashboard7equipped with a central console6. The control console6comprises a control panel1.

The control panel1has an outward-facing surface10aforming a visible face. The control panel1comprises a plurality of control regions2,3,4, three control regions in the embodiment illustrated, in succession along a longitudinal direction X. Each of the control regions2,3,4comprises a control button8showing a pictogram and being suitable for detecting pressure applied along a control direction Z on the outward-facing surface10aof the control region2,3,4of the corresponding control button8. The control direction Z is perpendicular to the longitudinal direction X. The outward-facing surface10aextends along the longitudinal direction X and along a transverse direction Y, perpendicular to the longitudinal direction and to the control direction Z.

As illustrated inFIG. 3, the control panel1essentially comprises a trim element10, a control assembly20, flexible elements30and a supporting member40.

The trim element10forms a decorative layer and has the outward-facing surface10aand a rear surface10b, opposite the outward-facing surface10a, both extending substantially perpendicularly to the control direction Z. Alternatively the outward-facing surface10amay not be plane. In the embodiment illustrated, the trim element10comprises a plate, preferably metallic, particularly made of aluminum, of substantially constant thickness, less than 1 mm, preferably slightly less than 0.5 millimeters. Alternatively, the trim element10comprises a layer of carbon fiber, a layer of wood, a mineral layer for example a layer of stone, for example a layer of schist stone such as slate or mica or a layer of glass. In a further alternative embodiment, the trim element10comprises a layer of leather or a film of synthetic resin.

The control assembly20essentially comprises one piezoelectric sensor22per control region2,3,4and a supporting film24supporting the piezoelectric sensors22.

Each piezoelectric sensor22has a front surface22afacing the rear surface10bof the trim element10and a rear surface22bfacing the supporting film24. Each piezoelectric sensor22is mounted on the supporting film24, preferably by printing and has a thickness of the order of 0.1 millimeter. The piezoelectric elements22are connected to an electrical connector by conductive tracks (not shown) also supported by the supporting film24and preferably produced by printing.

The supporting film24comprises a front surface24afacing the piezoelectric elements and a rear surface24b, opposite the front surface24a. The supporting film24is electrically insulating, consisting of a thin layer of transparent plastic from the order of 0.1 millimeter to some tens of millimeters in thickness and is flexible.

The piezoelectric sensors22may also be produced according to alternative embodiments, instead of being printed on the supporting film. Alternatively, the piezoelectric sensors22may be produced independently from the supporting film24, the piezoelectric sensors22are then advantageously of the disk or membrane piezoelectric sensor type, and are mounted on the supporting film24, preferably by an adhesive. Furthermore, a spacer-film may be envisaged, the spacer-film comprising orifices inside which the piezoelectric sensors22are placed. For a more detailed description of these alternative embodiments, reference may be made to the application FR 3 031 940 A1. Furthermore, a plurality of piezoelectric sensors may be overlaid.

The thickness of the trim element10is adapted according to the type of material so that pressure by a user on the trim element10in a control region2,3,4is transmitted to the piezoelectric sensor22. The deformation of the trim element10during the application of the pressure is of the order of 15 μm to 500 μm. This deformation is reversible, to the extent that the trim element10returns to the initial shape thereof after the pressing by the user. As such, the outward-facing surface10aof the trim element10may advantageously have a smooth appearance, i.e. not having a hollow or raised region, which increases the esthetic appeal of the control panel.

The supporting member40comprises a front surface40aand a rear surface40b, opposite the front surface40aalong the control direction Z. The front surface40afaces the rear surface22bof the piezoelectric elements22. The supporting member40has a substantially constant thickness along the control direction Z, preferably between 1 and 2 millimeters.

In the embodiment illustrated inFIG. 3, the supporting member40comprises cavities42, facing each of the pressure sensors22. The cavities42present are not through, such that they each have a single opening44. The cavities42are preferably substantially plane and of substantially constant thickness.

The supporting member40is made of thermoplastic material. The supporting member40is produced by molding, by injection or by thermocompression. The supporting member40preferably consists of a mixture of polycarbonate and acrylonitrile butadiene styrene. The supporting member40is rigid. The term rigid denotes herein any element which cannot be deformed by merely pressing with a finger. The rigidity of the supporting member40is given either by the nature of the constituent material of the supporting member, or by the structural features thereof such as the thickness thereof, shape thereof, any reinforcing elements (ribs) thereof.

The flexible elements30are arranged facing the piezoelectric sensors22. More specifically, the flexible elements30are arranged in the cavities42and have a front surface30afacing the rear surface22aof a piezoelectric sensor22and a rear surface facing the front surface40aof the supporting member40. In the first embodiment illustrated inFIG. 3, the supporting film24is arranged between the piezoelectric sensors22and the flexible elements30. In the embodiment illustrated, the flexible elements30are advantageously printed on the supporting film24.

Alternatively, in the second embodiment illustrated inFIG. 4, the supporting film24is arranged between the trim element10and the piezoelectric sensors22, the flexible elements30being preferably printed on the piezoelectric sensors22.

According to a third embodiment illustrated inFIG. 5, the supporting film24is arranged between the trim element10and the piezoelectric sensors22, a second supporting film26is arranged between the piezoelectric sensors22and the flexible elements30. Preferably, on one hand, the piezoelectric sensors22are printed on the supporting film24, on the other, the flexible elements30are printed on the second supporting film26, and then the supporting film24with the piezoelectric sensors22is arranged between the trim element10and the second supporting film26with the printed flexible elements30.

The flexible elements30have a substantially constant thickness e and are substantially plane, in the embodiment illustrated. The front surface30aof the flexible elements is substantially flush with the opening44of the cavity, such that the flexible elements30are restricted to the cavities42and that, apart from the regions of the supporting film24where the flexible elements30are present, the supporting film24is substantially in contact with the supporting member40. As such, along the longitudinal direction X along which the control buttons8are arranged, the flexible elements are separated from one another by the supporting member40. The risk of the piezoelectric sensor22of a control region2,3,4detecting deformation in an adjacent region is consequently reduced.

The thickness e of the flexible elements is preferably between 25 μm and 500 μm.

The flexible elements30are preferably elastically deformable, so as to actuate the pressure sensors22to a defined position which consists, in the embodiment illustrated, of holding the front surface22aof the pressure sensors22bearing against the rear surface10bof the trim element10.

The flexible elements30are advantageously made of silicone, rubber, thermoplastic elastomer or equivalent. They are preferably suitable for being deformed by at least a quarter of the thickness thereof when subjected to a force of 10 N on the overall front surface30athereof.

Moreover, the flexible elements30are preferably suitable for being compressed along the control direction Z, without expanding perpendicularly to the control direction Z. For this purpose, the flexible elements30are preferably of the lacunose type, such as a foam or a sponge.

As illustrated inFIG. 3, when a user50presses with his/her finger onto the outward-facing surface10ain one of the control regions2,3,4, the trim element10is subject to the pressure applied by the user and is deformed slightly. The pressure is transmitted by deformation via the piezoelectric sensor22, the supporting film24and the flexible element30. The piezoelectric sensor22detects this deformation and transmits an electric signal to an electronic control unit (not shown), intended to control vehicle equipment, via conductive tracks. The flexible element30“absorbs” this deformation by being compressed along the deformation direction Z. The supporting member40is not substantially deformed.

The piezoelectric sensors22advantageously have a diameter of the order of 15 millimeters perpendicularly to the control direction Z. In the embodiment illustrated, the flexible elements30have substantially the same size as the piezoelectric sensors22perpendicularly to the control direction Z. Preferably, perpendicularly to the control direction Z, the flexible elements30present are at least equal in size to that of the piezoelectric sensors22. In one alternative embodiment, the flexible elements30may be greater in size to that of the piezoelectric sensors22, by between 25% and 100% along at least one of the longitudinal X and transverse Y directions, in order to enable the flexible elements to yield along these directions, when the flexible elements30are made of a material not suitable for mere compression.

The trim element10after having been optionally thermoformed is attached by the rear surface10bthereof to the front surface of the control assembly20, preferably by bonding.

As illustrated inFIG. 6, the trim element10and the control assembly20are subsequently preferably arranged in a cavity formed between a first part62and a second part64of a mold60. The supporting member40is then overmolded so as to adhere to the control assembly20and to the rear surface10bof the trim element10, the supporting member40then coming into contact with the flexible elements30such that the cavities42closely mold the shape of the flexible elements30with the exception of the side of the front surface30a.

Alternatively (not shown), the supporting member40may be produced independently from the trim element10and the control assembly20, preferably by thermoforming, and then be mounted by assembly or bonding to the trim element10.