DE102023113882A1 - HORN MODULE AND STEERING WHEEL WITH A HORN MODULE - Google Patents

Abstract

A horn module (10) in a steering wheel has a rigid base body (12), a sensor mat (16) and a flexible outer shell (14) which closes off the horn module (10) at the front, wherein the sensor mat (16) is arranged flatly between a front support surface (28) of the base body (12) and an inner side (34) of the outer shell (14) and forms a horn sensor (17). The sensor mat (16) is designed such that it converts an actuating force (FB) acting on the outer shell (14) into an analog actuating signal (S).

Description

The invention relates to a horn module for a steering wheel and a steering wheel with a horn module.

In a known horn module, a gas bag module inserted into a steering wheel hub is mounted so that it can move against the force of several springs. Electrical contacts are arranged on the gas bag module and on a skeleton of the steering wheel. In the non-actuated position, the springs keep the contacts spaced apart from one another. However, if the driver presses an actuating force on a gas bag module cover in the hub area of the steering wheel, the gas bag module is moved into the steering wheel hub against the spring force and the horn contacts come into contact with one another. This closes an electrical circuit, which leads to the activation of a horn unit and the output of an acoustic horn signal.

With this arrangement, it must be ensured that the gas bag module is guided without tilting and that the necessary actuation force remains low. In addition, it is complex to make the gap between the gas bag module and the surrounding area of the steering wheel hub visually appealing.

However, it is generally desirable to have as large an operating surface as possible for triggering the horn, which is not limited to individual small buttons on the steering wheel, but ideally covers the entire hub area.

The object of the invention is to provide a horn module with a large-area horn sensor that does not require mechanical bearings.

This object is achieved by a horn module for a steering wheel, which comprises a rigid base body, a sensor mat and a flexible outer shell which closes off the horn module at the front to the outside, wherein the sensor mat is arranged flatly between a front support surface of the base body and an inner side of the outer shell and forms a horn sensor, wherein the sensor mat is designed such that it converts an actuating force acting on the outer shell into an analog actuating signal.

This means that the base body can be mounted immovably on the steering wheel. External horn contacts, spring elements and movement of the base body are no longer required to trigger the horn.

The sensor mat makes it possible to provide a large-area horn sensor, which can in particular cover more than 50% of the surface of a steering wheel hub.

The flexible outer shell makes it possible to design the horn module in such a way that an actuation force is transmitted through the outer shell directly below the actuation point to the sensor mat, so that even with a low actuation force, accurate detection is easily possible and a homogeneous horn triggering force is achieved across the entire sensor mat.

The outer shell also simultaneously forms a decorative layer of the horn module and the steering wheel hub when the horn module is installed, with an outer side of the outer shell facing the vehicle interior, while the inner side faces the base body, i.e. the hub of the steering wheel.

The analogue actuation signal that the sensor mat emits is normally transmitted to a control unit and evaluated there. Only after this signal processing does the control unit decide whether or not to emit an acoustic signal. In contrast to conventional solutions, pressing the sensor mat does not directly close a horn circuit and cause a current to flow that produces an acoustic signal in a horn. The actual horn is usually in a different circuit to the sensor mat.

This arrangement also has the advantage that the value of the analog actuation signal provided by the sensor mat can be compared in the control unit with a preset threshold value that is adapted to the respective horn module. Only when this threshold value is exceeded does the control unit initiate the generation of an acoustic horn signal. By selecting the threshold value, the necessary level of actuation force can also be set at which a horn signal is triggered.

The sensor mat can be designed as a self-contained component and only needs to be positioned between the base body and the outer shell and connected to the control unit via an electrical cable. Return springs or horn contacts removed from the sensor mat can be omitted with this design.

Preferably, the base body is part of a gas bag module that accommodates a folded gas bag and in particular forms a cover for the gas bag module that covers the steering wheel hub when installed. The support surface The surface of the base body is then the side of the cover facing outwards towards the vehicle interior.

In a preferred variant, the outer shell is shell-shaped and consists in particular of an elastic material. In this way, the outer shell can be designed to be so flexible that the actuating force only acts on the area directly below the point that is pressed down. The actuating force therefore acts directly on a flexible, flexible component and not on a rigid element. The actuating force is thus concentrated on a small area, which reduces the necessary level of actuating force.

A shell shape is understood here to mean that at least one edge region is provided which adjoins a central section in the middle of the outer shell at an angle other than zero. The angle is in particular between 15° and 90°. The central section can of course also be convexly curved.

For example, the outer shell is a molded part, i.e. a three-dimensionally prefabricated component. The molded part can be made of silicone, leather, synthetic leather or plastic, e.g. polyurethane or thermoplastic polyurethane. This can optionally be designed as a thin, but already preformed skin that can be pulled over the base body with the sensor mat already mounted on it.

For this purpose, the outer shell can comprise a radially inwardly bent edge which, when mounted, can encompass a radially protruding edge region of the support surface so that the sensor mat is completely enclosed between the base body and the outer shell.

In general, the outer shell is preferably manufactured in its final three-dimensional shape and is no longer significantly deformed during assembly on the horn module.

If necessary, all components, i.e. base body, sensor mat and outer shell, are connected to each other by thin layers of adhesive.

The support surface of the base body, for example, has a recess in which the sensor mat is accommodated. The sensor mat is thus secured at its edges against displacement. This also results in a good visual appearance even with a very thin outer shell.

The sensor mat can have suitable fastening elements on its underside or its peripheral edge, such as pins or openings, which engage positively with corresponding structures on the base body in order to correctly position the sensor mat and hold it in its position.

In one possible variant, the sensor mat is flexible in itself, so that its three-dimensional shape adapts to the bottom of the recess and/or the inside of the outer shell.

In another possible variant, the sensor mat is shaped so that its underside corresponds to the shape of a base of the recess and/or an inner side of the outer shell. In this case, the sensor mat can also be designed as a self-supporting component, the three-dimensional shape of which is already specified during production.

In both variants, the sensor mat preferably fits snugly and without play over its entire surface on both the base body and the outer shell. The actuation force can therefore be recorded with high accuracy at any point on the sensor mat.

Away from the sensor mat, an inner side of the outer shell is preferably directly connected to the support surface.

However, it is also possible to choose a sensor mat that is large enough to completely or practically completely cover the contact surface of the base body.

The outer shell and the sensor mat are preferably point-elastic.

The sensor mat is preferably pressure-sensitive, and the actuation force exerted on the outer shell acts on an upper side of the sensor mat and causes the actuation signal. The sensor mat is therefore designed in such a way that a force measurement is possible based on a defined deformation of the sensor mat, i.e. a defined change in distance within the sensor mat.

The sensor mat is preferably designed in such a way that when the actuating force is applied, a characteristic of the sensor mat changes, which can be detected by the control unit, wherein the characteristic is in particular a capacitive, resistive, piezoelectric, magnetic and/or inductive variable.

The change in the parameter correlates particularly with the level of the actuation force.

Preferably, the control unit is connected to the sensor mat and designed to transmit a signal correlating with the level of the changed parameter to a vehicle-side control unit.

For example, the sensor mat has two parallel sensitive layers, the change in the distance between which results in a change in one or more parameters, in particular a change in a flowing electrical current or an applied electrical voltage. This can be done, for example, by changing the electrical resistance, capacitance or inductance of the sensor mat.

The sensitive layers can, for example, be two electrically conductive layers of a resistive or capacitive sensor.

The sensor mat has, for example, at least two sensitive layers that are spaced apart from each other by a neutral distance when not actuated, with the neutral distance being the same across the entire surface of the sensor mat. If an actuating force acts on the sensor mat, the sensor mat deforms and the distance between the sensitive layers decreases.

The signal strength is preferably dependent on the distance between the sensitive layers, whereby the signal strength is set to zero by the control unit, for example, when the layers are at a neutral distance from each other and increases the closer the layers approach.

The sensor mat preferably has at least one elastically deformable layer that is in contact with an electrically conductive layer. The actuation signal is advantageously generated when the elastically compressible layer is compressed and the associated change in distance between the sensitive layers occurs.

The elastically compressible layer also preferably provides the restoring force to push the sensitive layers of the sensor mat apart again to their neutral distance after the actuation force has ended.

In this case, the rigid support surface of the base body generates the required counterpressure to achieve a reproducible deformation of the sensor mat due to the actuation force and thus a precise triggering of the horn sensor.

At least one electrically conductive layer and/or the elastically compressible layer can be structured, i.e. have different shapes in their layer surface or comprise different materials.

The layers all extend in parallel layer surfaces, but do not have to be continuous or flat in the respective layer surface.

For example, an electrically conductive layer can be formed by a meander or grid structure of conductor paths.

An elastically deformable layer is, for example, structured and has spaced-apart structures that extend perpendicular to the layer surface, or is formed from these. The structures are designed in particular as webs or knobs.

Such structures can also serve as spacers for two sensitive layers of the sensor mat and specify the neutral distance between the layers of the sensor mat.

For example, an electrically conductive layer is formed by one or more conductor tracks running in a meandering or grid-like manner in the layer surface.

The elastically compressible layer may be present in addition to two or more sensitive layers, but may also form one of the sensitive layers.

The elastically compressible layer does not have to be continuous across the entire surface. It can, for example, consist of a network of webs running parallel to the surface of the electrically conductive layer. Alternatively, the elastically compressible layer can have discrete structures, such as webs or knobs, that protrude perpendicularly from a layer surface.

In one possible variant, the elastically deformable layer is arranged as an independent layer between two adjacent sensitive layers. In another possible variant, the elastically deformable layer is molded onto one or both of the sensitive layers. In this case, the elastically deformable layer can only consist of spatially separated structures that are made of a different material than the sensitive layer that serves as the carrier. The sensitive layer can be a conductive film, for example, while the elastically deformable layer consists of knobs made of an electrically insulating elastomer molded onto it.

Structures can also be provided on sensitive layers. For example, the electrically conductive layer can be formed by one or more meandering or grid-shaped conductor tracks. Electrically conductive nubs are also possible, which can be molded onto an electrically insulating carrier, for example. The carrier is then an elastically deformable layer, for example.

When an actuating force is applied to the outside of the outer shell, the elastically compressible layer is compressed at certain points, whereby individual structures are compressed and the distance between the two layers is thus locally reduced.

The sensor mat therefore provides a change in the measured quantity through deformation of the elastically compressible layer and the resulting change in the distance between the layers of the sensor mat, whereby specific electrical parameters change under the influence of the actuating force.

The sensor mat can be designed according to any suitable physical principle. For example, it is designed as a resistive, capacitive or inductive sensor or a combination of these. It would also be conceivable to integrate strain gauges or piezoelectric elements into the sensor mat.

In a purely capacitive sensor, for example, the elastically compressible layer is electrically insulating and continuous over its entire surface and also ensures that two electrically conductive sensitive layers always remain spatially separated from one another.

If, for example, the elastically compressible layer is interrupted at certain points, a capacitive-resistive sensor can also be realized.

In a resistive sensor, however, the elastically compressible layer can be a grid of bars or knobs, for example, so that two electrically conductive sensitive layers can come into increased contact with each other when force is applied. Here, the elastically compressible layer could also be electrically conductive and at the same time form one of the sensitive layers.

The elastically compressible layer can therefore be electrically conductive or electrically insulating, depending on requirements.

The structuring of the individual layers can vary across the surface of the sensor mat, for example to create zones that are more sensitive to an actuation force or have a higher or lower resolution for detecting the actuation force.

In general, it is possible to use the layers of the sensor mat or individual areas of a layer made of different materials and with different electrical and mechanical properties. In particular, individual layers can be electrically conductive, electrically insulating, rigid, elastic, filled with magnetic or electrically conductive particles, structured, smooth or adhesive. It is also possible, for example, to apply one or more electrically conductive tracks or a large number of spatially separated electrically conductive knobs to a layer made of an electrically insulating material. On the other hand, it is possible to form elastically deformable, electrically insulating structures on an electrically conductive layer. In general, all layers of the sensor mat can form separate components or individual or all layers can be manufactured together. In this way, a sensor mat can be created whose properties can be adapted very flexibly to the respective requirements.

If necessary, a combination of such layers with a proximity sensor or touch sensor as an additional sensor layer in the sensor mat would also be conceivable. For example, an electrically conductive material is applied to an insulating layer of the sensor mat and connected to the control unit. It would also be possible to structure such a material in the form of discrete conductor tracks. The approach of an electrically conductive object, such as the driver's hand, or a touch of the outer shell leads to a change in the capacitance, which can be recorded and evaluated by the control unit. This could, for example, be used to integrate additional control functions in the vehicle into the horn module.

The sensor mat is advantageously located between the base body and the outer shell without any tension. This ensures that a neutral distance between two parallel sensitive layers of the sensor mat is identical for all practical purposes across the entire surface of the sensor mat, even with a curved contact surface. This means that the actuation force required to trigger a horn signal is the same across the entire surface of the sensor mat.

A stress-free arrangement is understood here in particular to mean that the components adjacent to the sensor mat do not cause any significant permanent deformation of the sensor mat during its assembly.

If the support surface is curved, this goal can be achieved in particular with a curved, particularly shell-shaped prefabricated sensor mat, the curvature of which corresponds as closely as possible to the curvature of the support surface.

In order to avoid unwanted deformation of the sensor mat by the outer shell, in this case the inner side of the outer shell should of course be shaped three-dimensionally so that it corresponds to the curvature of the sensor mat.

For example, the sensor mat, the outer shell and the support surface are coordinated in their three-dimensional shape and size in such a way that the support surface and the sensor mat as well as the sensor mat and the outer shell each adjoin one another flatly and without tension.

It is possible to manufacture the sensor mat, the base body and the outer shell as separate components and to assemble the horn module from them. It is also conceivable to manufacture the sensor mat based on the support surface of the base body or the inside of the outer shell, e.g. in a multi-component injection molding process and/or a painting process. In this case, any curvature of the support surface or the outer shell can easily be transferred to the sensor mat.

Preferably, the base body, the sensor mat and the outer shell each have a predetermined weakening zone at which the horn module is opened in a controlled manner in order to allow the gas bag accommodated in the gas bag module to escape.

The above-mentioned task is also solved with a steering wheel with a horn module, as described above, in which the base body comprises a cover of a gas bag module and the horn module is immovably accommodated in the steering wheel. Separate spring elements and the movable arrangement of the gas bag module are omitted in this arrangement.

It is also possible to arrange several sensor mats next to each other, which may differ in their properties.

• - 1 eine schematische geschnittene Ansicht eines erfindungsgemäßen Hupenmoduls;
• - 2 eine schematische Darstellung eines erfindungsgemäßen Lenkrads mit einem erfindungsgemäßen Hupenmodul;
• - 3 eine schematische Darstellung der Komponenten des Hupenmoduls aus 1 mit einer Sensormatte nach einer ersten Variante;
• - 4 und 5 schematische Darstellungen von einzelnen Schichten der Sensormatte des Hupenmoduls aus 3;
• - 6 eine schematische Darstellung der Komponenten des Hupenmoduls aus 1 mit einer Sensormatte nach einer zweiten Variante;
• - 7 bis 9 die einzelnen Schichten der Sensormatte des Hupenmoduls aus 6; und
• - 10 bis 13 schematische Schnittansichten des Hupenmoduls aus 1 mit Sensormatten nach verschiedenen Varianten.

The invention is described in more detail below using several embodiments with reference to the attached figures. In the figures:

• - 1 a schematic sectional view of a horn module according to the invention;
• - 2 a schematic representation of a steering wheel according to the invention with a horn module according to the invention;
• - 3 a schematic representation of the components of the horn module from 1 with a sensor mat according to a first variant;
• - 4 and 5 schematic representations of individual layers of the sensor mat of the horn module from 3 ;
• - 6 a schematic representation of the components of the horn module from 1 with a sensor mat according to a second variant;
• - 7 to 9 the individual layers of the sensor mat of the horn module 6 ; and
• - 10 to 13 schematic sectional views of the horn module from 1 with sensor mats in different variants.

1 shows a horn module 10 for fixed and immovable installation in the hub area 110 of a steering wheel 112 (shown schematically in 2 ).

The horn module 10 comprises a base body 12, an outer shell 14 and a sensor mat 16 which is arranged between the base body 12 and the outer shell 14.

The base body 12 is here connected in one piece to a holder of a gas bag module 18 (not shown in detail), in which a folded gas bag is accommodated. The base body 12 forms a cover of the holder towards the vehicle interior.

The outer shell 14 closes off the horn module 10 at the front towards the outside of the vehicle interior.

The sensor mat 16 is a flat pressure or force sensor and forms a horn sensor 17 of the horn module 10 and generates an analog actuation signal S when an actuation force F _B acts on a front side 20 of the outer shell 14. In this example, the strength of the actuation signal S correlates with the level of the actuation force F _B .

As in the 3 and 6 As indicated, the sensor mat 16 is connected to a control unit 24 via an electrical line 22. The analog signal S is transmitted from the sensor mat 16 to the control unit 24 and evaluated there.

If the control unit 24 determines that the actuation signal S exceeds a predetermined threshold value that is specified for triggering an acoustic horn signal, it generates a further signal H that causes a vehicle-side control unit 26, e.g. a horn unit of the vehicle, to emit an acoustic horn signal. The signal H optionally consists of the control unit 24 causing a horn circuit to close. In any case, the line 22 is not connected directly to the horn unit, but only to the control unit 24 and is therefore not part of a horn circuit.

The base body 12 has a front support surface 28 which is convexly curved and which has a central section 30 and a peripheral edge section 32 which here projects downwards from the center section 30 at an angle of approximately 15" to 90°.

The base body 12 consists of a suitable rigid plastic. The support surface 28 is designed in such a way that it does not give way when the actuating force F _B is applied to the front side 20 of the outer shell 14.

A recess 33 is formed in the support surface 28, which is adapted to the dimensions of the sensor mat 16 in such a way that the sensor mat 16 inserted into the recess 33 is flush at its peripheral edge with the rest of the support surface 28 surrounding it (see 1 ). In this example, the recess extends over the entire center section 30 of the base module 12 up to the transition into the more angled edge section 32. The bottom 35 of the recess 33 may be convexly curved.

A bottom side 36 of the sensor mat 16 has exactly the shape of the bottom 35 of the recess 33 (or possibly larger dimensions by the dimensions of an adhesive layer 37 between the bottom 35 and the bottom side 36 of the sensor mat 16, as in 10 and 13 is indicated), while the geometric shape of the inner side 34 of the outer shell 14 corresponds exactly to the shape of the support surface 28 and an upper side 38 of the sensor mat 16 (and optionally adhesive layers 37 between the support surface 28, the upper side 38 of the sensor mat 16 and the inner side 34 of the outer shell 14).

The sensor mat 16 is, for example, so flexible that it adapts its shape to a curvature of the base 35 and the inner side 34 of the outer shell 14. In another variant, the sensor mat 16 is prefabricated in such a three-dimensional shape that it can be inserted precisely into the recess 33 and the outer shell 14 rests against the upper side 38 of the sensor mat 16 without play.

In this example, the outer shell 14 is a flexible and elastic silicone molded part that is optionally manufactured as a thin skin.

An edge region 39 of the outer shell 14 is curved or folded radially inwards so that it encompasses a contact region 40 on an underside of the base body 12 so that the outer shell 14 completely covers the sensor mat 16 and the support surface 28 of the base body 12 (see 1 ).

Each of these components, i.e. the base body 12 as well as the sensor mat 16 and outer shell 14, each have a weakening zone 41 at which the respective component opens when the gas bag exits the gas bag module 18 arranged below the support surface 28 of the base body 12.

The sensor mat 16 can be designed according to any suitable physical principle. For example, resistive, capacitive or inductive sensors are possible, which can also be combined with one another.

The 3 to 5 show a horn module 10 with a sensor mat 16 in the form of a resistive force sensor.

The sensor mat 16 comprises a sensitive, electrically conductive layer 42 and a sensitive, elastically compressible layer 44, which is also electrically conductive at least in sections. Both layers 42, 44 are arranged with their layer surfaces E parallel to one another and extend over the entire surface of the sensor mat 16.

The layer 42 here has two comb-shaped, interlocking, electrically separated conductor tracks 46, wherein in combination with the layer 44 a current flow between the two conductor tracks 46 is detected and evaluated by the control unit 24 as a measure of the electrical resistance between the conductor tracks 46.

The elastically compressible layer 44 has a plurality of electrically conductive nubs 48 which protrude from the layer surface E in the direction of the layer 42 (see 5 ). The studs 48 have two different heights and are arranged in alternating rows. The arrangement of the studs 48 harmonizes with the comb structures of the layer 42. Studs 48 with one height touch one side of the comb structure and studs 48 with the other height touch the other side. When force is applied, the studs 48 are deformed and a current flows. The measured electrical resistance depends on the material and correlates with the actuation force F _B .

10 shows a similar sensor mat 16. The only difference is that an additional elastically compressible layer 50 is arranged between the layers 42, 44. This is grid-shaped here and has recesses in the area of the knobs 48. The layer 50 is electrically insulating here. Optionally, the layer 50 is formed by webs or individual longer knobs made of an electrically insulating elastomer, which are molded onto the layer 42 or the layer 44.

The elastically deformable layer 50 (or the layer 44 in 3 ) ensures that a neutral distance d in the unloaded state of the sensor mat 16, in which no actuating force F _B is applied to the outer cover 14 is the same at every point over the surface of the sensor mat 16 for practical purposes.

In addition, the elastically deformable layer 50 (or the layer 44 in 3 ) a restoring force to move the layers 42, 44 back to their unloaded position after the action of the actuating force F _B has ended.

If the layer 44 is now pressed down by a point-based force with the actuation force F _B in the direction of the support surface 28 of the base body 12, the distance between the two layers 42, 44 is reduced at this point and some of the knobs 48 come into contact with the layer 42. This forms electrical contact points between the conductor tracks 46 and increases the conductivity between the two conductor tracks 46. If a higher actuation force F _B is applied, more knobs 48 are brought into contact with the layer 42, which further increases the conductivity. The electrical resistance of the sensor mat 16 thus changes as a parameter depending on the actuation force F _B . This is reflected in the actuation signal S and is evaluated by the control unit 24.

Of course, a resistive sensor with at least one electrically conductive layer 42 and at least one elastically compressible layer 44 could also be designed in any other suitable manner.

Between the support surface 28 and the underside 36 of the sensor mat 16 as well as between the upper side 38 of the sensor mat 16 and the inner side 34 of the outer shell 14, an adhesive layer 37 is indicated here (see 10 ).

The layer surfaces E of the individual layers 42, 44 extend approximately perpendicular to the actuating force F _B (the direction of the layer surface E is in 10 indicated).

6 shows a horn module 10 with a sensor mat 16 in the form of a capacitive-resistive sensor. The sensor mat 16 is also shown in the 7 to 9 and 11 shown.

The sensor mat 16 has three layers 42, 44, 52, which are arranged directly on top of one another. The layer 44 lies between the layers 42, 52 and is designed as a structured, elastically compressible, electrically insulating layer.

As in the previous example, the layer 42 has electrically separated, interlocked conductor tracks 46. Here, for example, two pairs of conductor tracks 46 are arranged next to each other (see also 9 ).

As in the previous example, a plurality of individual studs 48 (or webs or a grid with suitable openings) are arranged on the surface of the layer 44, which protrude from the layer surface E and keep the layers 42, 44 at a defined neutral distance d when no actuating force F _B acts on the outer shell 14.

Here, the surface of layer 44 is electrically insulating and consists of an elastomer. The nubs 48 lie directly on layer 42.

In addition, a further layer 52 is arranged on the side of the layer 44 opposite the layer 42. The layer 52 is electrically conductive throughout, for example a thin film or a coating on the layer 44 (possibly also on the inner side 34 of the outer shell 14).

The layer 44 electrically insulates the layers 42, 52 from one another and at the same time allows the layer 52 to approach the layer 42 when an actuating force F _B is applied by being compressed. This change in distance between the sensitive layers 42, 52 leads to a charge shift in the layers 42, 52, which is detected and evaluated as a capacitive signal by the control unit 24.

In addition, when the outer shell 14 is pressed down, one or more of the nubs 48 are deformed and come into contact with two adjacent conductor tracks 46 of the layer 42, thus increasing the conductivity of the layer 42, which results in a change in resistance. This is also detected and evaluated by the control unit 24.

It is also conceivable to arrange several such or different layer structures on top of each other, for example to increase the sensitivity of the sensor mat 16. This is shown in the 12 and 13 indicated.

The 12 and 13 show sensor mats 16 in the form of capacitive sensors.

In the example of 12 two thin, electrically conductive, sensitive layers 42, 52 are separated by a smooth, insulating, elastically compressible, continuous layer 44. The layer 44 holds the two layers 42, 52 at their neutral distance d without the action of an actuating force F _B.

In the structure shown, the elastically compressible layer 44 and the outer electrically conductive layer 52 surround the electrically conductive high layer 42 on both sides of the layer 42, resulting in a double layer structure.

If an actuating force F _B acts on the outer shell 14, the layer 44 is compressed and the distance between the layers 42, 52, which are at different electrical potentials, is reduced, which in turn results in a change in the capacitance, which can be detected and evaluated as voltage changes by the control unit 24. The layer 44 prevents the two sensitive layers 42, 52 from touching.

If, for example, openings are built into the elastically compressible layer 44, there is a possibility that the electrically conductive layers 42, 52 will touch when force is applied. In addition to the capacitive change, a change in the electrical resistance can then also be measured. This effect can be further enhanced by coating one of the two electrically conductive layers 42, 52 with an electrically resistive material such as carbon.

In the example of 13 the inner electrically conductive layer 42 is designed with structures in the form of nubs 48 protruding on both sides of the layer surface E, while the outer electrically conductive layer 52 is smooth. The two layers 42, 52 are at different potentials. The nubs 48 form the elastically compressible layer 44. As in the previous example, the outer layer 52 surrounds the inner layer 42 on both sides of the layer 42 in a double layer structure.

When an actuating force F _B is applied, the knobs 54 are deformed and the two layers 42, 52 approach each other, which causes a change in the actuating signal S.

The layers 42, 52 are insulated from each other by thin, electrically insulating layers 56 arranged therebetween.

In general, the sensor mat 16 can be constructed from any number of suitable layers, each of which has suitable electrical and mechanical properties. Flat, structured, electrically conductive, electrically insulating, elastic or rigid layers are conceivable, whereby only parts of a layer, for example suitable structures, can have a corresponding property. The properties of a layer can also vary across its surface, so that the sensor mat 16, for example, has differently sensitive zones in its surface.

The structure of the sensor mat 16 is optionally similar for the different measuring principles: at least one electrically conductive layer and at least one elastically deformable layer lie one above the other perpendicular to the direction of the actuating force F _B , wherein the elastically deformable layer defines the neutral distance d in the unloaded position and generates a restoring force in the unloaded position.

When manufacturing the horn module 10, it is possible to manufacture all components separately from one another, i.e. the base body 12, the outer shell 14 and the sensor mat 16. The sensor mat 16 is inserted into the recess 33 and the outer shell 14 is pulled over the contact surface 28 and the sensor mat 16 so that the edge area 39 encompasses the contact area 40 on the base body 12 (see 1 ).

However, it is also possible to mold all or some of these components on top of each other, for example on the base plate 12 or on the inside 34 of the outer shell 14. This can be done, for example, in a multi-component injection molding process, or also in suitable painting processes. In particular, structures such as webs or knobs are optionally manufactured in a multi-component injection molding process, whereby the structures, which can consist of a different material than the layer, are also molded onto it. Conductor tracks 46 are, for example, applied directly to the support surface 28 of the base body or the inside 34 of the outer shell 14 by masking in a painting process.

The selection of which components are manufactured separately and which are molded onto existing components is at the discretion of the specialist.

All features of the individual embodiments and variants can be freely exchanged or combined with one another at the discretion of the person skilled in the art. This applies in particular to the details of the different sensor mats 16, e.g. with regard to the structuring, the material, the number and/or the design of the individual layers.

For reasons of clarity, not all identical components are always provided with reference symbols.

The same reference symbols designate identical or essentially identical or equivalent components and parts in different embodiments.

Claims (15)

Horn module (10) for a steering wheel, with a rigid base body (12), a sensor mat (16) and a flexible outer shell (14) which closes off the horn module (10) at the front to the outside, wherein the sensor mat (16) is arranged flat between a front support surface (28) of the base body (12) and an inner side (34) of the outer shell (14) and forms a horn sensor (17), wherein the sensor mat (16) is designed such that it converts an actuating force (F _B ) acting on the outer shell (14) into an analog actuating signal (S). Horn module (10) after claim 1 , wherein the outer shell (14) is shell-shaped. Horn module (10) after claim 2 , wherein the outer shell (14) is a molded part. Horn module (10) according to one of the preceding claims, wherein the support surface (28) of the base body (12) has a recess (33) in which the sensor mat (16) is received. Horn module (10) after claim 4 , wherein the sensor mat (16) is inherently flexible so that it adapts in its three-dimensional shape to a bottom (35) of the recess (33) and/or an inner side (34) of the outer shell (14). Horn module (10) after claim 4 , wherein the sensor mat (16) is shaped such that its underside (36) corresponds in the shape of a bottom (35) of the recess (33) and/or an inner side (34) of the outer shell (14). Horn module (10) according to one of the preceding claims, wherein the sensor mat (16) is pressure-sensitive and the actuating force (F _B ) exerted on the outer shell (14) acts on an upper side (38) of the sensor mat (16) and causes the actuating signal (S). Horn module (10) according to one of the preceding claims, wherein the sensor mat (16) is designed such that when the actuating force (F _B ) is applied, a characteristic of the sensor mat (16) changes, which can be detected by a control unit (24), wherein the characteristic is in particular a capacitive, resistive, piezoelectric, magnetic and/or inductive variable. Horn module (10) after claim 8 , whereby the change in the parameter correlates with the magnitude of the actuating force (F _B ). Horn module (10) according to one of the Claims 8 and 9 , wherein the control unit (24) is connected to the sensor mat (16) and is designed such that it transmits a signal correlating with the level of the changed parameter to a vehicle-side control unit (26). Horn module (10) according to one of the preceding claims, wherein the sensor mat (16) has at least one elastically deformable layer (44) which is in contact with an electrically conductive layer (42, 46). Horn module (10) after claim 11 , wherein at least one electrically conductive layer (42, 46) and/or the elastically compressible layer (44) is structured. Horn module (10) according to one of the preceding claims, wherein the sensor mat (16) lies stress-free between the base body (12) and the outer shell (14). Horn module (10) according to one of the preceding claims, wherein the base body (12), the sensor mat (16) and the outer shell (14) each have a predetermined weakening zone (41). Steering wheel (112) with a horn module (10) arranged in a hub (110) of the steering wheel (112) according to one of the preceding claims, wherein the base body (12) comprises a cover of a gas bag module (18) and the horn module (10) is immovably received in the steering wheel (112).

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