DE102004038872A1 - Capacitive touch switch for an operating device of an electrical appliance, operating device and method for evaluation - Google Patents

Abstract

A touch switch (20) for an operating device of an electrical appliance, such as a cooktop, has a sensor element (11, 111) with two sensor surfaces (13a, b; 113a, b) which have one or more triangular partial surfaces (15a, b; 115a, b ). The sensor surfaces are driven by drive signals (S1, S2) and, when touched with a finger (22), decouple part of the signal strength corresponding to the covered area. The remaining signal strength is compared in a microcontroller (25) to determine the location of the touch as a function of the ratio of residual signal strengths to overlapped areas.

Description

field of use and state of the art

The The invention relates to a capacitive proximity or touch switch according to the generic term of claim 1 for an operating device of an electrical appliance, such an operating device and a method for evaluating such a touch switch.

It is for example from the EP 1 158 838 A It is known that a larger control panel with control surfaces is monitored by a plurality of sensors and can detect a touch operation substantially at any point. In conjunction with various displays on this contact surface, it is possible to create freely configurable touch surfaces or control units. These are particularly advantageous with regard to menu navigation or menu-guided operation.

Task and solution

Of the Invention is based on the object, an aforementioned capacitive touch switch to create as well as a corresponding operating device and a method for the evaluation of the same, with which disadvantages of the prior art can be avoided in particular with as possible few different sensor elements and as simple as possible control and Evaluation of several control points on a control device in spatial Distribution can be detected.

Is solved this task through a touch switch with the features of claim 1, an operating device with the Features of claim 10 and a method with the features of claim 11. Advantageous and preferred embodiments The invention is the subject of the further claims and will be in the following explained in more detail. Of the Wording of the claims is by express Reference made to the content of the description. Characteristics of the proximity switch, the operating device and the method apply equally, are described in part only once, but meet independently of each other for all to. The approximation or touch switch will be brief in the following half as a touch switch but both should be included.

According to the invention, it is provided that the touch switch, essentially only by hanging up or putting on a finger or other triggering Object on a control surface without applied force works, having a sensor element. By activity at different points of the sensor element can from each other distinguishable electrical signals are generated or triggered. These allow a statement of the location of the operation and a triggering of the Function of the operating device connected to this point. The Sensor element is divided into at least two sensor surfaces. These begin at each in opposite ends or areas of the sensor element and walk from there to each other. If you look at this arrangement along a kind of connecting line between the opposite ends of the sensor element, so a sensor surface is always smaller or steadily smaller and the other sensor surface is at least not bigger, preferably she is getting smaller and smaller. The two sensor surfaces are located doing close to each other and are only by a narrow separation, For example, a ditch or a certain distance from each other separated. As a result, they are mainly electrically isolated from each other.

So is the basic principle of the structure so that at least along the Connecting line at each point the ratio of that by a normal sized finger or the like sensor surfaces different from each other. Advantageously, the sizes of the change sensor surfaces each exactly the same so that they always form the same total area and only their relationship is different to each other. Advantageously, it can be provided that the sensor element is subdivided into exactly two sensor surfaces. In order to can be particularly advantageous an easy evaluation done as well a cheap one Arrangement to be built.

In Advantageous embodiment of the invention, the sensor element Overall the shape of an elongated Strip. So can along this strip different functions are triggered. It is equally possible for example a performance setting from a variety of levels through, so to speak Roll Over a finger's height to change the power setting or to find a stage. Likewise along the strip several control surfaces as different functions be provided. The strip can be designed so that its Length a multiple its width is, for example, three to six times as long as it is wide.

From Advantage is when the total area of the sensor surfaces respectively is exactly the same size. In this way, it is particularly possible, a respective evaluation make.

In one possible embodiment of the invention, a sensor surface may have one or more triangular partial surfaces, which at one end of the sensor element, so to speak a form wide area and are interconnected. The partial surfaces can, so to speak, point in the same direction from the broad region as a kind of base. Advantageously, they are each the same design. Particularly advantageously, both sensor surfaces have the same partial surfaces, for example three to seven. These in turn can be interlocked with each other, wherein in each case the tips of the partial surfaces of a sensor surface extend to the connected region or the base of the other sensor surface. This creates a toothing of the sensor surfaces. This makes it possible, even with deviations from an aforementioned connecting line, which runs from one end of the sensor element to the other, always to achieve approximately the same coverage ratio by the achieved coverage of the sensor surfaces or partial surfaces. For this purpose, the partial surfaces are advantageously so narrow that at normal coverage by a finger or the like. at least two faces are fully covered in width, advantageously even three or four.

The Sensor element can be formed both straight as a strip as well as a curvature exhibit. When curved Sensor elements, it is advantageous to give the sensor surfaces a course, in about the arc of curvature equivalent. Here, the area ratios should between the sensor surfaces each stay approximately the same.

The between the sensor surfaces existing separation should always be approximately the same especially the same width. Care should be taken that The separation, seen absolutely relatively narrow, is guaranteed electrical isolation against each other. So can be achieved by that the overlap preferably size Shares of the sensor surfaces covered become.

Of the Structure of such a proximity switch can be such that the sensor surfaces metallic surfaces or Metal layers or generally electrically conductive layers on an insulating support. Advantageously, they run in the same plane and are flat. there but are also curved user interfaces or the like conceivable.

From The advantage is not to provide the sensor element directly for the touch of a finger, but to arrange it under a cover. This can be done before damage as well as pollution protected become. Furthermore, in particular for the direct contact of a corresponding control device with a finger of this on the Cover to be set. For this purpose, the cover can be adjusted accordingly printed or with similar Be provided with markings for individual functions. The production of such a cover is possible on the one hand of plastic on the other hand, for example, vitreous or glass-containing material. In particular, this is a glass ceramic hob. Thus, an operating device for an electrical appliance, For example, a hob, as a unit under the hob be educated.

to Control or operation of the sensor element and the proximity switch can to both sensor surfaces Control signals are given. The respective attenuation of the drive signal is as a measure of the width the overlap one of the sensor surfaces determined because of the width of the overlap, the area of the overlap and thus the decoupling is determined from each sensor surface. The larger the coverage the one sensor surface and their partial surfaces the lower the coverage of the other sensor or the other partial surfaces. The quotient can be formed from both signal strengths which is then compared with given values that each associated with a particular location on the sensor element. Thus, it can be determined at which point of the sensor element a Operation has taken place. Several different places or Areas can be different triggered Functions are assigned.

alternative to form the quotient can advantageously a difference of the two Sensor signals are formed. This is especially hardware in one Microcontroller of a controller in a very simple way possible. Advantageously, then the difference between the two sensor signals in relation to the signal size of one the signals or both accumulated signals set. So a kind Standardization can be created, which under certain circumstances environmental influences or the like eliminated.

For the control the sensor surfaces can in principle Any sensor signals can be used. Advantageous are frequencies in the range of a few kHz to a few hundred kHz. Are the drive signals identical, so an evaluation can be made easier. Are they different, can in certain circumstances more information is gained. However, this depends significantly from the intended use.

These and other features will become apparent from the claims and from the description and drawings, wherein the individual features each alone or more in the form of sub-combinations in one embodiment of the invention and in other fields be realized and advantageous and protectable Represent embodiments for which protection is claimed here. The subdivision of the application into individual sections and intermediate headings do not restrict the general validity of the statements made thereunder.

Summary the drawings

embodiments The invention are shown schematically in the drawings and will be closer in the following explained. In the drawings show:

1 a sensor element of a touch switch according to the invention in a simple representation with two triangular sensor surfaces,

2 a modification of the sensor element 1 each with several triangular faces per sensor surface,

3 a plan view of a touch switch with an elongate sensor element and a plurality of control panels distributed thereon and

4 a lateral section through a possible installation of a sensor element according to the invention under a control surface.

detailed Description of the embodiments

In 1 is a sensor element 11 which is essentially an elongate strip. It consists of two sensor surfaces 13a and 13b , These are elongated triangular, each have identical shape and each form a triangular face 15a and 15b , These subareas 15a and 15b run from a broad base 16a and 16b on which connections 14a and 14b are attached as electrical connections, in each case in the direction of the other sensor surface. They end in tips 17a and 17b , which, so to speak, on the side to the base 16 the other sensor surface 13 pass. The sensor surfaces are separated by a distance or a separation 18 ,

In principle, it is important for the invention that in the ratio of the areas of the two sensor surfaces 13a and 13b to each other along the imaginary line 19 constantly making a change in one direction, so an increase or decrease. This does not necessarily have to be linear or even, which is advantageous for easier evaluation.

Along a dashed line connecting line 19 , which is the longitudinal extent of the sensor element 11 corresponds, are several contact points I to III shown. Thus, a coverage can be represented by a finger. At these points of contact is a respective different coverage of the two sensor surfaces 13 in front.

At the touch point I is the sensor surface 13a heavily covered, the sensor surface 13b only small. At the contact point II are both sensor surfaces 13 almost the same covered. At the contact point III is the sensor surface 13a only slightly covered, the sensor surface 13b strong against it. Below will be explained how from the respective covers the place of touch, so the touch point I to III , can be determined.

2 shows an alternative embodiment of a sensor element 111 , The two sensor surfaces 113a and 113b each have several triangular faces 115a and 115b on. These each run from a common broad base 116 out to the base 116 the other sensor surface 113 close to and shortly before each peak 117 , The sensor surface 113a has five whole faces 115a on. The sensor surface 113b has four whole and two half faces 115b on the outer edge, so that in total the areas of the sensor surfaces 113 each exactly the same size. These sensor surfaces are separated by a separation 118 ,

The advantage of this sensor element 111 lies in the fact that at a point of contact I to III which of the imaginary connecting line similar to the connecting lines 19 out 1 deviates up or down, the ratio of the overlap of the two sensor surfaces 113 does not change. Thus, such a system or one with this sensor element 111 provided contactor error-prone to be built.

function

In 3 and 4 is such a touch switch 20 shown. At the same time the function or the driving method is explained. The sensor element 11 or the sensor surfaces 13a and 13b are for example as copper coatings on the carrier 29 formed, which may be an insulating substrate such as plastic or ceramic. The connections 14 can be designed as conductor tracks.

A sensor element 11 is shown in dashed lines and, for example, under a control surface 26 arranged as in 4 you can see. It can, for example, after 1 or 2 be educated. On the control surface 26 are several panels 27a to 27e present, for example by imprinting corresponding fields. About the connections 14 becomes the first sensor surface 13a controlled with a drive signal S1 and the sensor surface 13b with a drive signal S2. At the same time are the connections 14 with inputs of a microcontroller 25 connected, which emits a signal after appropriate signal processing.

Becomes a finger 22 represented by a dashed circle in 3 according to the contact point II , on the control surface 26 or the control panel 27c As a result, it represents a capacitive short to ground. As a result, according to the overlap of the sensor surface 13a a certain portion of the signal S1 is coupled to ground or decoupled. Likewise, a certain portion of the drive signal S2 from the sensor surface 13b decoupled. The signal strength of the drive signals S1 and S2 is reduced as much as the sensor areas 13a and 13b through the finger 22 are covered and a decoupling takes place against mass. The signals S1 and S2 go with the residual signal strength to the microcontroller 25 for further processing.

This further processing, in a particularly simple version, can be such that the signals are subtracted from each other. This may, for example, be hardware-based in the microcontroller 25 be realized, which greatly reduces the susceptibility to interference and error and keeps the effort low. From the difference in signal strength can be an exact assignment to a point along the imaginary connecting line 19 or to one of the control panels 27a to 27e respectively.

In the case shown are at a touch of the finger 22 on the middle control panel 27c both sensor surfaces 13 Covered approximately equally, so that the decoupling is the same. With identical drive signals S1 and S2, the remaining signal strength is also the same, so that the subtraction results in zero. In the microcontroller 25 or a subsequent signal processing is deposited, that the result of subtraction of zero, the middle panel 27c is considered touched. Thus, when touching the control panel 27c an associated functionality can be effected. By the on the control surface 26 printed control panels 27 can be assumed that a touch with the finger 22 not at any point, but at discrete positions, so to speak. This allows a clearer distinction.

In a more elaborate form of evaluation can either be the previously formed difference still in a ratio to the total signal strength of the added residual signals are set. This can be confounding factors such as a bad capacitive coupling or the like balanced become. As an alternative to a difference, the quotient of the both residual signals S1 and S2 are formed, which is the calculation signal generation is more difficult, but also delivers a good result.

Claims (14)

Capacitive proximity or touch switch ( 20 ) for an operating device of an electrical appliance with a sensor element ( 11 . 111 ), whereby by actuation at different points ( I . II . III ) of the sensor element different electrical signals for different functions can be triggered, characterized in that the sensor element in at least two sensor surfaces ( 13 . 113 ), each extending from an opposite end or region of the sensor element to the other, wherein along the connecting line ( 19 ) between the two opposite ends of the sensor element, a first sensor surface ( 13a . 113a ) becomes steadily smaller and a second sensor surface ( 13b . 113b ) is continuously larger, with the two sensor surfaces are close to each other and by a separation ( 18 . 118 ) are separated. Touch switch according to claim 1, characterized in that the sensor element ( 11 . 111 ) exactly two sensor surfaces ( 13a , b; 113a , b) Touch switch according to claim 1 or 2, characterized in that the surface of the sensor surfaces ( 13 . 113 ) is exactly the same size. Touch switch according to one of the preceding claims, characterized in that the sensor element ( 11 . 111 ) has the overall shape of an elongate strip, preferably the length is a multiple of the width. Touch switch according to one of the preceding claims, characterized in that the sensor surfaces ( 13 . 113 ) one or more triangular faces ( 15 . 115 ) at one end of the sensor element ( 11 . 111 ) in its broad area ( 16 . 116 ) are connected to each other and point in the same direction at each sensor surface, wherein they are preferably interlocked with mating formed surface portions of the other sensor surface. Touch switch according to claim 5, characterized in that a sensor surface ( 113 ) at one end of the sensor element ( 111 ) extends over its entire width and into a plurality of elongated, triangular part surfaces ( 15 . 115 ), which are identical or similar, wherein preferably the partial surfaces of the other sensor surface are also formed identically or identically. Touch switch according to one of the preceding claims, characterized in that the separation ( 18 . 118 ) between the sensor surfaces ( 13 . 113 ) has a constant width. Touch switch according to one of the preceding claims, characterized in that the sensor surfaces ( 13 . 113 ) metallic surfaces or metal layers on a carrier ( 29 ), wherein they preferably extend in the same plane and are formed flat. Touch switch according to one of the preceding claims, characterized in that the sensor element ( 11 . 111 ) under a cover ( 26 ), in the vicinity of or on the surface of which a finger ( 22 ) or another triggering object of an operator is placed and moved along, wherein preferably the cover of plastic or glasarti gem or glass-containing material, in particular glass ceramic, consists. Control device for an electrical appliance, which has a proximity or touch switch ( 20 ) according to one of the preceding claims. Method for evaluating a touch switch ( 20 ) according to one of the preceding claims, characterized in that on both sensor surfaces ( 13 . 113 ) Ansteuersignale (S1, S2) are given and the respective attenuation of the drive signal is determined as a measure of the width of the coverage of one of the sensor surfaces and thus the point of operation ( I . II . III ) is determined by overlap. A method according to claim 11, characterized in that the drive signals (S1, S2) for both sensor surfaces ( 13 . 113 ) are identical. A method according to claim 11 or 12, characterized in that the quotient of both signal strengths is formed and from the spatial location of the operation ( I . II . III ) or the location is determined at which a finger ( 22 ) an operator or other triggering object above the sensor element ( 11 . 111 ) is placed. A method according to claim 11 or 12, characterized in that a difference of the two sensor signals is formed, preferably in hardware in a microcontroller ( 25 ) a control of the touch switch ( 20 Preferably, the difference is then subsequently set in proportion to the height of one signal or both signals.