DE20119700U1 - sensor device - Google Patents

Description

Description Sensor device

Area of application and state of the art

The invention relates to a sensor device according to the preamble of claim 1. The sensor device has a sensor element that works capacitively and is a so-called touch sensor. This means that the sensor element generates a signal when approached or touched with a finger, which can be used as a switching signal to trigger a switching process. The sensor element is arranged behind a touch surface or panel, such as an operating panel. It defines or occupies an area. There is also a control that processes the sensor signal or switching signal of the sensor element and triggers a switching process or something similar.

It is known to design sensor elements, for example as flat metal plates, and to press them elastically onto the underside of a panel or user interface by means of a spring or the like. Elastic bodies made of a conductive plastic are also known, which are connected to a surface lying on the underside of the panel

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function in a similar way. However, the problem here is that, on the one hand, it is difficult to adjust the spring force. On the other hand, with a number of sensor elements, the total pressure force must be applied and, above all, care must be taken to ensure that all sensor elements have a desired contact with a defined pressure force on the underside of the panel.

Task and solution

The invention is based on the object of creating a sensor device mentioned at the outset in which, on the one hand, the sensor element is arranged in a protected manner beneath a cover and, on the other hand, the attachment of the sensor element to the underside of the cover is possible in a defined manner.

This object is achieved by a sensor device having the features of claim 1. Advantageous and preferred embodiments of the invention are the subject of the subclaims and are described in more detail below. The content of the claims is made part of the content of the application by express reference.

According to the invention, the sensor element consists of a layer of conductive material, in particular with metal inclusions. This layer is firmly attached to the back or underside of the panel. In this context, firmly means that the layer cannot come off by itself or due to mechanical influences that normally occur during operation. Sensor signals can be sent to the control system by means of an electrically conductive connection to the control system.

The application of the sensor element as a layer directly onto the aperture according to the invention has the great advantage that the mechanical assignment between the sensor element and the aperture is carried out in such a way that

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has been ensured that it is unchangeable. Problems with pressure or the like are reduced. This improves the function of the capacitive sensor element. Since the control itself is not applied to the panel, but is advantageously separate, for example on its own circuit board or the like, the sensor element is connected to the control via the conductive connection. Here, too, a certain mechanical connection between the panel or the sensor element on the panel and a separate component is necessary. However, here it is sufficient to establish a connection using various existing contact pressures or similar, since this only has to be electrically conductive. Such an electrical connection is much easier to establish than a defined mechanical one. Especially with capacitive sensor elements, even air gaps on partial surfaces have a negative effect on a sensor signal, which is not the case with electrical contacts.

The sensor element is preferably glued, for example from thin film material, or permanently attached to the panel. This makes it possible to specify the assignment very precisely and in a defined manner. According to one possibility, it can be designed as a layer or coating and, for example, printed on as a coating material using a screen printing process. The printing principle can advantageously correspond to that used for decorative or colored layers. This means that only a single printing principle is required to produce the entire panel.

A type of enamel paint consisting of glass particles and silver particles can be used as a coating material. This paint is baked after application, similar to other paints for decorations that are applied to glass, at a temperature of approx. 600 700 ⁰ C, preferably per coat of paint. Another possible coating material is a type of paint made of graphite powder with binding agents.

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medium. This can harden by air drying. Instead of graphite, other conductive material could be used.

Additional layers or coatings can be provided on the panel, for example covers or decorations or even electrically functional coatings. In particular, it is possible to provide these coatings between the rear of the panel and the sensor element. For the function of the sensor element, it is essentially important that there is a consistent and unchangeable assignment to the surface or front of the panel and the contact surface formed thereby. It does not play a significant role whether one or more layers or layers of another material are present in between. Different thicknesses or numbers of layers can also be applied underneath in different areas of the sensor element. However, these layers must not interfere with the function of the capacitive sensor.

A panel is preferably made of a translucent material. The material is particularly preferably transparent. This makes it possible to arrange decorations or lamps or displays underneath the panel. For example, a lamp or display can be arranged behind the panel in the area of the sensor element. These can then be seen through the panel when it is put into operation. They can be designed to display either information, for example related to the specific sensor element, or local assignments. Glass, for example glass ceramic, is the best material for a panel. This has the great advantage that glass is very mechanically resistant and at the same time can be easily cleaned. With glass ceramic, the problem of the usually dimpled underside can be solved, but this is possible with printing processes.

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Particularly preferably, the cover is designed as a closed surface without openings. This protects the sensor element underneath and a control system, particularly in applications that involve moisture.
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It is also possible to process or structure the surface of the front of the panel, at least in the area of the sensor element. One possibility is to create a raised area on the surface that is visually appealing and can provide a correct contact point for the sensor element. In the case of materials such as glass or similar, which are usually manufactured as flat material, this can also advantageously be a recess.

A conductive connection between the sensor element and the control can advantageously be offset laterally from the sensor element surface. It is particularly advantageous if the conductive connection is connected to the edge of the sensor element surface, for example by means of an attached contact surface. It is possible to establish the conductive connection to the sensor element via a touch contact. For this purpose, the conductive connection can have a conductive projection or contact pin or the like. This can establish the contact and rest on the sensor element on the one hand and be conductively connected to the control on the other. In one embodiment of the invention, the control can be arranged as a control circuit on a circuit board and attached at a distance from the rear of the panel. The conductive connection or a conductive pin or the like can extend from the sensor element to the circuit board. The electrical contact here can also be made by means of a conductive contact, in particular a touch contact. A contact pin can thus be clamped between two contact fields and establish the electrical connection.

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The sensor element surface is advantageously essentially a simple, geometric basic shape, for example rounded, circular or rectangular. The sensor element surface can have at least one opening or recess, in particular approximately in the middle. Such a sensor element can therefore form a kind of circumferential frame that is closed and in this way defines the surface according to the invention. In such a design, the cover should be translucent or transparent and lighting or display means can be provided behind the sensor element. These can be seen essentially in the middle of the sensor element through the cover.

Electronic switches and/or relays for electrical switching functions can be provided in the control system. These are controlled by control signals which the control system obtains from signals from the sensor element.

In a further embodiment of the invention, a carrier device or carrier means can be provided, which can be arranged between the rear of the panel and a circuit board carrying the control.

Such a support device can be a guide or a spacer element for the connection between the cover and the circuit board. It can also be an assembly aid. A support device can also form the conductive connection between the sensor element and the control system.

In one embodiment of a sensor device according to the invention, a plurality of sensor elements can be provided. These are advantageously arranged in spatial proximity to one another in order to form a so-called control panel. These sensor elements are preferably connected to the same control or a single control. In this way, it is possible to use a sensor device according to the invention to control an electrical device with a plurality of functional units, for example

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for example, a hob with four cooking zones. Another preferred application is an oven, in particular with a fully electronic control system. For this purpose, a large number of sensor elements are to be provided for the various operating options, as well as displays. The sensor elements can be designed to be the same, at least in groups, and in particular all the same.

These and other features emerge not only from the claims but also from the description and the drawings, whereby the individual features can be implemented individually or in combination in the form of sub-combinations in an embodiment of the invention and in other fields and can represent advantageous and protectable embodiments for which protection is claimed here. The division of the application into individual sections and subheadings does not limit the general validity of the statements made under these.

Short description of the drawings

Embodiments of the invention are shown in the drawings and are explained in more detail below. In the drawings:

Fig. 1 is a schematic section through a simple embodiment of a sensor device with a sensor element,

Fig. 2 a view of the sensor element from Fig. 1 from below and

Fig. 3 a section similar to Fig. 1 through a more complex

sensor device with spacers.

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Detailed description of the implementation examples

In Fig. 1, a sensor device 11 is shown in a schematic sectional view. It has a panel 12, a sensor element 14 attached to the back of the panel, and a control 16 on a circuit board 17. The control 16 is symbolically represented by an indicated, box-shaped component. The structure and function of such a control for a capacitive sensor element 14 are known and are shown by way of example in EP 859 468, the content of which is hereby made part of the content of the present application by express reference. The size of such a sensor element 14 is in the range of the size of a fingertip. For example, a side edge length can be approximately 10 to 25 mm.

An elongated and pin-like contact part 19 extends from the circuit board 17 with the controller 16, with which it is electrically connected via a flat contact, to a contact field 20 of the sensor element 14. In this way, the sensor element 14 is electrically connected to the controller 16 or the circuit board 17. The contact part can be designed to be elastic, for example as a metallic coil spring or made of conductive, elastic plastic.

As shown, the sensor element 14 is not applied directly to the back of the panel 12. A decorative print 21 is first applied to this back using a process that is customary for such prints. For example, screen printing processes are suitable for this. The decorative print 21 can extend essentially over the entire back of the panel 12. It has a cutout 22, the shape of which can be seen in Fig. 2.

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The sensor element 14 is then applied or printed onto the decorative print 21 as a conductive layer. On the one hand, this can be a screen printing process with an electrically conductive mass. Other possibilities are gluing or otherwise attaching a metal foil-like part or plate. The sensor element 14 can also be designed as a metallized or metallic adhesive film and applied to the back of the panel 12 or the decorative print 21.

The sensor element 14 has a cutout 15. This is essentially concentric with the cutout 22 of the decorative print 21. Likewise, a contact field 20 extends to the left of the sensor element 14, against which the contact part 19 rests. The sensor element 14 thus forms a frame.

A light source 24 is arranged on the circuit board 17 below the cutouts 15 and 22. This can be an LED or the like exclusively for lighting. It is also possible to use a luminous seven-segment display or the like. This can be used to illuminate the sensor element 14 and thus provide a localization aid. Values and other information can also be displayed. For such light sources or displays arranged under the panel 12, it is necessary to make the panel 12 at least translucent or transparent.

From the view of the underside of the arrangement from Fig. 1 in Fig. 2, it can be seen how the sensor element 14 essentially forms a rectangular or square frame. The sensor element 14 is applied to the decorative print 21.

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The decorative print 21 and the sensor element 14 have central cutouts 22 and 15 that are congruent with the shape of the sensor element 14. The cutout 22 in the decorative print 21 is somewhat smaller. This is because it is applied directly to the back of the panel 12 and therefore the sensor element 14 should recede slightly on the decorative print.

Furthermore, the contact field 20 can be seen, which extends as an approximately semicircular bulge to the left of the sensor element 14. A light source 24 or a similar display can be present in the same perspective as the arrangement in Fig. 2 appears to the viewer.

Fig. 3 shows a further sensor device 111 which is more complex than the one in Fig. 1. Here, a decorative print 121 with a cutout 122 is also applied to the back of a panel 112. The sensor element 114 is applied to this decorative print 122 as a surface with a central cutout 115. The sensor element 114 also has a contact field 120 which is arranged on the left in front of the cutout 115 in Fig. 3.

A controller 116 is carried by a circuit board 117 and is arranged below the cover 112. An electrically conductive connection between the controller 116 and the sensor element 114 is made through the contact part 119. The contact part 119 is designed similarly to the contact part 19 in Fig. 1 and rests against the contact field 120 of the sensor element 114. A conductive connection between the sensor element or associated contact field and the controller or circuit board can also be made flexibly via a soldered or plug-in cable.

As can be seen in Fig. 3, the decorative print 121 extends over the entire back of the panel 112 except for the cutout 122.

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Only further cutouts corresponding to the cutout 122 can be provided for further sensor elements similar to the sensor element 114 and cutout 115.

The cover 112 has an opening 133 through which an upper screw 130 extends. A lower screw 131 also extends through the circuit board 117. A spacer 128 with a support function is arranged between the cover 112 and the circuit board 117. The spacer 128 has an elongated thread into which the two screws 130 and 131 engage from both sides. The circuit board 117 is screwed or fastened to the cover 112 by this screw connection. The assignment between the two is fixed via the spacer 128.

Another carrier part 126 with a shielding function is arranged below the sensor element 114, centrally to the cutout 115. It extends, similar to the spacer 128, from the circuit board 117 to the back of the cover 112 or, in this case, to the sensor element 114. On the one hand, the carrier part 126 leaves the cutouts 115 and 122 free. On the other hand, it frames a light source 124 in its lower area in such a way that it simultaneously forms a shield for the light source 124 from the outside. Light from the light source 124 can therefore only escape to the outside through the cutouts 115 and 122 and the transparent cover 112. In this way, the previously mentioned lighting, localization or provision of information to the sensor element 114 is possible.

Of course, a sensor device 11 or 111 can have further sensor elements similar to the sensor elements 14 and 114. It is thus possible to provide a given panel 12 or 112 with a decorative print that essentially covers the entire back. This decorative print merely has several of the given

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The number of sensor elements provided is then applied to the decorative print in one of the ways described above. A circuit board corresponding to circuit board 17 or 117 has a contacting option with an associated contacting part 19 or 119 for each sensor element. It is mounted on the panel with a corresponding assignment to the sensor elements or with a fixed assignment to the panel. A control system can be provided for a large number of sensor elements. It can control and/or evaluate these, for example, with a multiplexer or a similar circuit.

A great advantage of the invention is that, as can be seen in the figures, the panel can generally be designed without any openings. Furthermore, the front of the panel can be free of sensor elements or parts of the sensor elements. On the other hand, the type of application of both the decorative print and the sensor elements to the back of the panel provides a defined and no longer changeable assignment.

It is also conceivable to create an electrically conductive connection between the sensor element and the control via a spacer similar to the spacer 128 or a shield similar to the shield 126, which can be made of conductive material. For example, conductive plastics can be used for this, which are sufficiently well known in the prior art. In principle, it is also possible to mechanically attach the control to the back of the panel. For example, a circuit board carrying the control can be glued to the panel.

Claims (17)

1. Sensor device for generating a switching signal upon approach and/or contact of a sensor element ( 14 , 114 ) by approaching a finger or the like, comprising: - a capacitive sensor element ( 14 , 114 ) and a flat panel ( 12 , 112 ), wherein the sensor element is arranged on a rear side of the panel facing away from a user and defines a surface and - a control ( 16 , 116 ) connected to the sensor element, characterized in that the sensor element ( 14 , 114 ) consists of a layer of conductive material which is firmly applied to the back of the panel and that the sensor element has a conductive connection ( 19 , 119 ) for control. 2. Sensor device according to claim 1, characterized in that the sensor element ( 14 , 114 ) is permanently applied to the aperture ( 12 , 112 ), wherein it is preferably printed as a thin conductive layer. 3. Sensor device according to claim 1 or 2, characterized in that further layers, for example decorations ( 21 , 121 ) or the like, are arranged between the sensor element ( 14 , 114 ) and the cover ( 12 , 112 ). 4. Sensor device according to one of the preceding claims, characterized in that the aperture ( 12 , 112 ) consists of translucent material, in particular transparent material. 5. Sensor device according to one of the preceding claims, characterized in that the aperture ( 12 , 112 ) consists of glass. 6. Sensor device according to one of the preceding claims, characterized in that the aperture ( 12 , 112 ) is closed. 7. Sensor device according to one of the preceding claims, characterized by a surface treatment of the front side of the panel ( 12 , 112 ) in the region of the sensor element ( 14 , 114 ), in particular a structuring of the surface, preferably a surface depression. 8. Sensor device according to one of the preceding claims, characterized in that the conductive connection ( 19 , 119 ) between the sensor element ( 14 , 114 ) and the controller ( 16 , 116 ) is arranged laterally offset to the surface of the sensor element, preferably adjacent to the edge of the surface of the sensor element ( 14 , 114 ). 9. Sensor device according to one of the preceding claims, characterized in that the conductive connection ( 19 , 119 ) has a touch contact with the sensor element ( 14 , 114 ), wherein preferably the conductive connection has a conductive projection which contacts the sensor element and is conductively connected to the controller ( 16 , 116 ). 10. Sensor device according to claim 9, characterized in that the control is arranged as a control circuit ( 16 , 116 ) on a printed circuit board ( 17 , 117 ) behind the panel ( 12 , 112 ) at a distance from the rear side, wherein in particular the conductive connection ( 19 , 119 ) extends to the printed circuit board and preferably has a conductive contact with the printed circuit board. 11. Sensor device according to one of the preceding claims, characterized in that lighting means ( 24 , 124 ) and/or display means are arranged behind the aperture ( 12 , 112 ) in the region of the sensor element ( 14 , 114 ), wherein they preferably remain laterally within the surface of the sensor element, in particular protrude a little within this surface. 12. Sensor device according to one of the preceding claims, characterized in that the sensor element ( 14 , 114 ) essentially covers a surface and this surface has at least one opening ( 15 , 115 ), in particular in a central region. 13. Sensor device according to claim 12, characterized in that the sensor element ( 14 , 114 ) consists essentially of a surrounding frame, wherein preferably the cover ( 12 , 112 ) is at least translucent and in particular lighting means ( 24 , 124 ) are provided on the rear side of the cover below the sensor element. 14. Sensor device according to one of the preceding claims, characterized in that the controller ( 16 , 116 ) has electronic switches and/or relays for the switching function, wherein the electronic switches or relays are controlled by control signals which are generated by the controller from signals of the sensor elements ( 14 , 114 ). 15. Sensor device according to one of the preceding claims, characterized in that a carrier device ( 126 , 128 ) is provided between the rear side of the cover ( 12 , 112 ) and a circuit board ( 17 , 117 ) carrying the control ( 16 , 116 ), wherein the carrier device is preferably a guide and/or assembly aid for the connection between the cover and the circuit board. 16. Sensor device according to one of the preceding claims, characterized in that the carrier device ( 126 , 128 ) with the conductive connection ( 19 , 119 ) between the sensor element ( 14 , 114 ) and the circuit board ( 17 , 117 ) with the controller ( 16 , 116 ) is arranged. 17. Sensor device according to one of the preceding claims, characterized in that it has a plurality of sensor elements ( 14 , 114 ), in particular in spatial proximity to one another, wherein preferably the sensor elements are connected to the same controller ( 16 , 116 ).