WO2006024475A1

WO2006024475A1 - Sensor mechanism and method for operating such a sensor mechanism

Info

Publication number: WO2006024475A1
Application number: PCT/EP2005/009281
Authority: WO
Inventors: Walter Gänsler; Ewald Bayer; Rolf Streifler
Original assignee: E.G.O. Control Systems Gmbh
Priority date: 2004-09-01
Filing date: 2005-08-29
Publication date: 2006-03-09
Also published as: DE102004043415A1

Abstract

According to the invention, a sensor key of a contact switch is provided with a switching area (23) on the front face of a cover (12) of a household appliance or similar. Said switching area is composed of an electrically conductive layer (22) that is covered by a coating (24) which optionally supports a decoration. A sensor element (15) which is made of conductive foam and whose contact surface (16) on the cover has a shape that is different from that of the switching area (13) is disposed on the rear face (14) of the cover (12). Said sensor element bridges a gap between the cover and a circuit board (20) on which a contact area (19) is provided that is part of the electronic evaluation circuit for the sensor mechanism.

Description

description

Sensor device and method for operating such a Sensorvor¬ direction

Field of application and state of the art

The invention relates to a sensor device for generating a switching signal or triggering signal when approaching and / or touching a finger or the like, and to a method for operating or evaluating such a sensor device.

EP 859 467 B describes a sensor device with a capacitive sensor element consisting of conductive foam, which is pressed against the rear side of a panel.

DE 201 197 00 U describes a sensor device in which an electrically conductive layer is provided on the back of a transparent panel, which is contacted by means of a contact part.

Task and solution

The invention is based on the object of providing a sensor device and a corresponding operating or evaluation method which enable a large freedom of movement in the design of the button activated by the approach or contact, the sensor device preferably being cost-effective also in large quantities manufacture and assemble is.

This object is achieved by a sensor device with the features of claim 1 and by a method having the features of claim 12. Advantageous and preferred embodiments of

Invention are the subject matter of the further claims and are described below. described in greater detail. The wording of the claims is made explicit reference to the content of the description. Some features concerning the sensor device and the method will be described in part only once in the following. However, they apply independently and generally both for the sensor device and for the operating or evaluation method.

Due to the fact that the sensor element, which is pressed against the rear side of a diaphragm with a pressure surface, cooperates with a conductive layer applied to the front side of the diaphragm in the area of this pressure surface, according to an advantageous feature of the invention, the resulting button can have a different shape and / or or size have to be printed as the pressure surface and preferably on. This makes it possible to adapt the buttons to the respective requirements, for example to make them long rectangular or even to form themself in the manner of a pictogram, without having to configure the sensor element located behind the panel accordingly. Here, therefore, the shape and size of the button, which is advantageously substantially larger than the pressure surface, is decoupled from the shape of the sensor element itself. Nevertheless, the button is usable as such up to the very edge. This training thus concentrates the capacitive effect that triggers the switching function on a core that is formed by the sensor element. This can be advantageously cylindrical and form the contact surface with its one end face and with the other end face a contact surface with the electronics. The sensor element can have a transverse hole, by the size of which the pressure force can be determined without the size of the sensor element itself or its material having to be changed. In this application, the term "cover" also refers to another operating surface or cover, for example also a front side of an electrical appliance or a cooktop plate of a hob, for example made of glass ceramics. It has also been found that the switching function is not impaired thereby, but even improved, that the diaphragm is interposed between the conductive layer and the sensor element.

According to a further advantageous feature of the invention, the switching surface applied as a conductive layer on the front side of the panel can be covered by a cover layer. This cover layer may optically cover the conductive layer and possibly a decor, lettering or the like. contain. It is to be applied as a coating, or preferably by printing.

Since the conductive layer is often printed with a silver-containing ink, it is possible that, especially in household machines, such as washing machines, dishwashers or the like, by cleaning agents or by exposure to light, the conductive layer darkens or otherwise discolored or worn. The cover layer does not affect the effect of the button as a touch switch, but the adverse effects can be eliminated altogether. In this case, the cover layer may be formed by a high-straightenable lacquer or a similar layer, wherein it should be as thin as possible.

In the method according to the invention for operating or evaluating the sensor device, the sensor device has just the aforementioned control. The latter can detect capacitive leakage currents or their changes, which flow via the sensor element to the pressure surface, whereby they are capacitively coupled through the diaphragm into the conductive layer. They flow via direct or almost direct ohmic contact by an applied finger of an operator. The leakage currents between the sensor element and the contact surface can therefore be transmitted capacitively into the conductive layer, while they are transmitted from the conductive layer to the finger essentially by ohmic contact.

The controller can provide a medium to high frequency alternating signal as a signal to the sensor element, in particular with a frequency between 10 kHz and 500 kHz, preferably with about 50 kHz to 100 kHz. This improves a capacitive coupling or signal transmission.

The foregoing and other features will become apparent from the description and the drawings as well as the claims, the individual features of which are themselves or several, in the form of sub-combinations, realized and advantageous in one embodiment of the invention and in other fields represent protections for which protection is claimed here. The subdivision of the application into individual sections and between headings does not limit the general validity of the statements made thereunder.

Brief description of the drawings

Embodiments of the invention are shown schematically in the drawings and will be explained in more detail below. The drawings show:

1 shows a section through a sensor device,

2 is a plan view, seen in the direction of arrow II in Fig. 1,

FIG. 3 shows a section corresponding to FIG. 1 through a sensor device with a differently shaped diaphragm, FIG.

Fig. 4 shows a modification of the arrangement of FIG. 1 with differently formed conductive layer and 5 is a plan view of the arrangement of FIG .. 4

Detailed description of the embodiments

The sensor device 11 shown in FIGS. 1 and 2 belongs to a capacitive touch switch, which changes the capacitance by approaching a body, such as a finger, to the switching surface or touching it by means of an electronic circuit (not shown) Evaluates switching process. The functional principle and the circuit can be as contained in the publications mentioned at the beginning, to which reference is made here. A slightly modified functional principle will be explained in more detail later.

An aperture 12 made of non-metallic material, for example plastic, usually opaque thermoplastic material, which is not electrically conductive, is an inserted panel of an electrical appliance or even part of the housing of such a device, such as a washing machine, a dishwasher, a tumble dryer or similar household appliances. But it can also be about blades on a machine tool or other devices. This panel has a front side 13 and a rear side 14, to which a sensor element 15 is pressed. The sensor element is a cylinder made of an electrically conductive elastic material, preferably a foam. He has an upper end face in the drawing, which forms a pressure surface (16), with which the sensor element rests under pressure bias on the back 14 of the diaphragm. The opposite end face 17 of the cylindrical sensor element is fastened by means of a commercially available fixing adhesive 18 for SMD components (Surface Mounted Devices) on a contact surface 19 of a circuit board 20. This should be electrically conductive. The contact surface is normally part of a printed circuit and the board is at the same time a carrier of the evaluation electronics for the contact switch and possibly further control elements of the associated device. It is mounted at a distance approximately parallel to the diaphragm. However, it is also possible that the circuit board 20 with the contact surface 19 is merely a support for the sensor element (s) and the associated circuit is installed separately therefrom.

The sensor element has a transverse hole 21, through the size and / or position of which the pressure force exerted on the two end faces 16 and 17 can be adjusted. As a result, different distances of the printed circuit board from the diaphragm can also be taken into account, without the need for other sensor elements.

On the front side 13 of the diaphragm 12, a conductive layer 22 is auf¬ brought forming a button 23 and defined. The application is carried out by printing with an electrically conductive paint or ei¬ ner other coating technology. It is not necessary that the surfaces are electrically contacted, but it is sufficient for a conductivity within the layer. Here silver-based colors are best suited.

The button 23 is, as can be seen from the figures, much larger than the pressure surface 16 of the sensor element 15 and also has a different shape. It is shown in FIG. 2 that this shape may be formed as a "+", for example, or numbers, letters or pictograms, arrows or the like could also form the basic form, but also rectangles or circles of different sizes make sense Size relationships between the button and the contact surface may be different, in particular in the case of different designs of the switching surface, this may also be smaller than the contact surface for individual or all buttons. The button 23 is preferably applied to the panel in such a way that the associated sensor element 15 is arranged substantially in the center of the area on the other side of the panel. Again, however, a different arrangement is possible. This gives a great creative freedom in the arrangement of the sensor element on the board, eben¬ as well as in the design of the front panel.

The button 23 is covered by a cover layer 24, e.g. may consist of a resistant lacquer, preferably an opaque lacquer, which covers the underlying conductive layer 22 and may preferably be colored and / or decorated or decorated. The cover layer 24 covers the button 23 at the edges with only a slight protrusion 25, so as to represent the button 23 in both shape and size.

FIG. 3 shows that an even better and also tactile limitation of the button is given if the diaphragm forms a demarcated region which is plastically formed or applied in the diaphragm, such as, for example, an elevation 26. Here, too, a corresponding depression would be present. Outlining, rounding, curvature or the like. Possible. The limitation of the button 23 becomes particularly obvious as its boundaries are both visible and palpable. Together with a Pikto¬ gram design is thus the sensor device also blind.

The top layer should meet the wear resistance of its surface to the requirements that are placed on the appropriate equipment, as there are water vapor, heat or climatic resistance, smudge resistance, resistance to commercial cleaning agents, abrasion resistance, tear-off with tape, gloss, light and UV resistance etc .. Significant advantages are achieved by the invention compared to previous sensor devices: So far, the buttons on the back of the panel were occupied by contact surfaces, which corresponded in shape and size of the button. This required the most varied designs of the sensor elements, which thus had to be manufactured, stored, sorted or prepared differently and usually had to be assembled manually. The pressure and contact surfaces and the entire sensor elements were usually very large and took up a lot of space on the associated boards.

The invention makes it possible to use identically identical sensor elements for a wide variety of sizes and shapes of buttons. Since such buttons are usually provided with numerous buttons, these can now be used in their specific form, e.g. applied by printing on the front and provided with the cover layer. On the other hand, the board can already be equipped with a corresponding placement machine when the electronic circuit is equipped, wherein only a single type of sensor element has to be provided. However, it is also possible to insert the sensor elements later. Thereafter, the board is mounted by appropriate spacers with distance to the back of the panel and the Berührungs¬ switch is functional.

This results in considerable savings both in costs for the sensor elements and, above all, in the ease of assembly. Also, the board surface can be exploited much better, so that even here a saving is possible. Nevertheless, the Schalt¬ surfaces are usable as such to the edge and the transmission of the capacitive signal to the circuit ensured. In Fig. 4 a sensor device 111 is shown in a modification of the arrangement of FIG. 1 with a curved aperture 112, which in turn may consist of the aforementioned material. At its rear side 114 it has an integrally formed receptacle 129. In this, the sensor element 115, which in turn is a cylinder made of electrically conductive elastic material such as electrically conductive foam, are used. Advantageously, it is held therein with a certain clamping effect. This is particularly advantageous for the assembly until the board 120 is applied with the contact surface 119 to the sensor element 115 for the final fixation of the same. In this case, the conductive adhesive 18 according to FIG. 1 can also be dispensed with.

Furthermore, this diaphragm 112 has an increase 126. As can be clearly seen in FIG. 4, a conductive layer 122, which in turn may be an aforementioned color, covers precisely and precisely this elevation 126. In contrast to FIG. 2, the conductive layer 122 is substantially smaller than the pressure surface 116.

On the conductive layer 122, in turn, a cover layer 124 is shown. This has, as mentioned, above all the task of preventing wear of the conductive layer 122 by frequent touching or applying a finger 130 and thus a removal or destruction of the layer 122. The said conductive layers or colors are often not wear-resistant enough. Thus, therefore, the cover layer 124 may be a wear-resistant paint or coating, in particular a clearcoat. Furthermore, the cover layer 124 should be relatively thin while ensuring wear resistance, which will be explained in more detail below.

It is also shown that a schematically illustrated control 132 is arranged on the circuit board 120, which controls or evaluates the sensor device 111, as well as, for example, other sensors. Sorelemente 115. Of course, it is also possible that the control 132 tion on another than the board 120 is arranged. In this case, it is to be electrically connected to this or contact surface 119 or the sensor element 115.

It can be seen from the plan view of FIG. 5 that the conductive layer 122, which corresponds to the innermost rectangle shown by dashed lines, is long and narrow. The cover layer 124 overlaps it a little. At the same time, the course of the conductive layer 122 defines the formation of the elevation 126.

The sensor element 115, which is considerably larger than the conductive layer 122 here by its dimensions or also by the contact surface 116, is also shown in phantom below the diaphragm 112. This will also make it clearer, which will be discussed in greater detail below There are certainly possibilities for variation for the size ratio between conductive layer 122 and contact surface 116 or sensor element 115.

function

The function of the described sensor device or the control and evaluation method can, deviating from the one described in the above-mentioned publications, also be as follows, this being explained with reference to FIG. 4:

Drive signals from the controller 132 are applied to the sensor element 115 via the contact surface 119. This, in turn, transmits these signals capacitively to this layer via the capacitive coupling of the sensor element between the contact surface 116 and the conductive layer 122. Since the drive signal, as mentioned above, is hochfre¬ quent, this signal coupling is relatively good or relatively strong. The application of a finger 130 to the conductive layer 122 directly without the overlying cladding layer 124 undoubtedly produces direct ohmic contact between the two. Thus, in this case, the capacitive leakage current of the drive or of the drive signals can flow away from the conductive layer 122 via the finger 130. In the event that a cover layer 124 is applied to the conductive layer 122, which layer is usually not electrically conductive, it should be noted that this cover layer 124, as stated above, is very thin. This results in such a good contact between the finger 130 and conductive layer 122 through the cover layer 124 that this contact acts almost like a direct ohmic contact. In this case, the aforementioned capacitive leakage current can also flow into the finger 130 here.

Thus, as soon as the finger 130 is placed on the conductive layer 122 directly or on the cover layer 124 and thus overall on the button 123, said capacitive leakage currents can flow and the controller 122 can easily recognize this. This can then be evaluated by the controller 132 as a corresponding operation of the sensor device 111 and can be converted into a function or the like. be implemented on an associated Elektroge¬.

The advantage of the invention lies in the fact that in otherwise known similar Berührschalteranordnungen the Sensorele¬ ment or its pressure surface opposite surface, which is formed by the applied finger on the panel, may vary. Above all, it varies depending on the size of the finger and the pressing pressure. This in turn means that the capacitive coupling between the sensor element and the finger, which depends on the respectively involved and opposite surfaces, is different in size. This makes evaluation of a touch more difficult, in particular visibly distinguishing unwanted touches or other disturbances.

In the invention, the opposing surfaces, which cause the capacitive coupling, by the pressure surface 16 and 116 of the sensor element 15 or 115 and the conductive layer 22 and 122 are precisely defined. Nothing changes to them, not even in the case of actuation or contact. So here is the capacitive coupling always the same. Since the contact between finger 130 and conductive layer 22 is either completely or substantially ohmic, which in particular does not depend on the size of the contact surface, conditions are always defined when a finger is created. This is, as I said, especially advantageous for a reliable evaluation.

Claims

claims

First sensor device (11, 111) for generating a switching signal when approaching and / or touching a finger or the like., With a capacitive sensor element (15, 115), preferably of conductive foam, a diaphragm (12, 112) or cover non-metallic material having a front side (13, 113) and a rear side (14, 114), wherein the sensor element is arranged on the rear side of the panel facing away from a user and has a contact surface (16, 116) thereon Rücksei¬ te (14, 114) is pressed with a connected to the sensor element (15, 115) controller (132), wherein on the front side (13, 113) of the diaphragm (12, 112) in the region of the pressure surface (16, 116) a conductive layer (22, 122) is applied, which defines a button (23, 123).

2. Sensor device according to claim 1, characterized in that the button (23, 123) or conductive layer (22, 122) has a different shape and / or size than the pressure surface (16, 116), in particular smaller than that Expression surface and / or narrow and elongated.

3. Sensor device according to claim 1 or 2, characterized gekenn¬ characterized in that the button (24) is substantially larger than the pressure surface (16).

4. Sensor device according to one of the preceding claims, characterized in that the conductive layer (22, 122) of a cover layer (24, 124) is covered.

5. Sensor device according to claim 4, characterized in that the cover layer (24, 124) is a conductive layer (22, 122) optically covering, optionally a decor-containing coating or preferably a printing, wherein the cover layer in particular a considerable has higher abrasion resistance than the conductive layer and is preferably thinner than the diaphragm (12, 112) by at least an order of magnitude.

6. Sensor device according to one of the preceding claims, characterized in that the pressure surface (16, 116) in Be¬ rich the surface center of the button (23, 123).

7. Sensor device according to one of the preceding claims, characterized in that the button (23, 123) or in a in the aperture (12, 112) plastically demarcated area (26, 126), such as an increase, depression, border , Bowing, etc., preferably exactly on an increase.

8. Sensor device according to one of the preceding claims, characterized in that the conductive layer (22, 122) is a printing with a metal, preferably silver, the color ist¬, wherein it is preferably prepared by a Heißversiege¬ ment.

9. Sensor device according to one of the preceding claims, characterized in that the sensor element (15, 115) is zy¬ lindrisch, with its one end face the pressure surface (16, 116) and with the other end face (17, 117) on a contact surface (19, 119) of an electronic board (20, 120) rests.

10. Sensor device according to one of the preceding claims, characterized in that the sensor element (15) has a Quer¬ hole (21).

11. Sensor device according to claim 1, characterized in that a plurality of identical sensor elements (15, 115) are provided for generating a plurality of different switching signals, the buttons having possibly differently sized and / or differently configured buttons (23 , 123) or conductive layers (22, 122) cooperate.

12. Method for operating or evaluating a sensor device (11, 111) according to one of the preceding claims, characterized in that the sensor device has a control (132) which is designed to generate capacitive discharge currents or to detect their changes, which flow via the sensor element (15, 115) with the pressure surface (16, 116), are capacitively coupled through the diaphragm into the conductive layer (22, 122) and are transmitted via direct or nearly di ¬ ohmic direct contact flow through an open finger (130) of an operator.

13. The method according to claim 12, characterized in that the leakage currents in a sensor device according to claim 4 zwi¬'s sensor element (15, 115) and pressure surface (16, 116) ka¬ pazitive in the conductive layer (22, 122) are transmitted while being transmitted from the conductive layer to the finger (130) substantially by ohmic contact.

14. The method according to claim 12 or 13, characterized in that the controller (132) is a medium to high-frequency Wechsel¬ signal as a signal to the sensor element (15, 115), in particular with a frequency between 10 kHz and 500 kHz Preferably, about 50 kHz to 100 kHz.