Touch sensor, sanitary fitting with touch sensor and method for detecting the touching of an electrically conducting surface

Modern electronically controlled devices have so-called capacitive sensors, which make it possible to control the device via a close approach or touch of a sensor surface by hand. For example, touch-sensitive monitors are known whose contact controls the sequence of a computer program displayed on the monitor at a suitable position.

For example, modern electrically and electronically controlled sanitary fittings are also based on sophisticated, extensive electronic circuitry (microprocessors / microcontrollers) that are powered by either a battery or a mains voltage converter. Such a control of sanitary fittings usually has an electrical signal transmitter, in the simplest case a mechanical switch whose operation causes the electronic control to trigger the user desired function of the valve. For example, here the operation of a piezoelectric sensor in an electronic shower control called, with the actuation of the user control the flow of water, ie start or possibly also stop. In addition, infrared barriers are widespread in sanitary fittings as a signal generator for electronic circuitry, which transmits a corresponding electrical signal in the detection area of ​​a microprocessor control upon detection of an object, body, body part, etc. There are also electronically controlled fittings designs are known, which in addition to a first signal transmitter for the basic function of the valve have a further signal generator for activating and deactivating special functions or for changing operating parameters. For example, in DE-195 08 644 describes the operation of a controller with a built-in the valve and accessible from the outside push-button.

Mechanical signaling devices for controlling, in particular, electronic fittings, however, are easily destroyed from outside the fitting due to their low mechanical strength and therefore prone to vandalism. In addition, the mechanical signal transmitters are relatively easy to wear due to contact wear and therefore have an only limited life. When used in electronic sanitary fittings, it is also necessary to protect the mechanical switches from moisture, which requires complex insulation and sealing measures, which makes the production of such a fitting complicated and therefore expensive.

Due to the above disadvantages of the mechanically actuated signal transmitter (switch, button) for controlling in particular sanitary fittings was therefore trying to replace the mechanically actuated signal generator by capacitive sensors, which, as stated above, enable a function control via Nahannäherung or touch. Reference may be made, for example, to US Pat. No. 7,730,165, in which the water delivery of a valve is controlled by a capacitive sensor which detects the approach of a user to the valve.

However, such conventional capacitive sensors require a very complex signal processing electronics, which is associated with correspondingly high cost and large volume. In addition, such capacitive sensors are very susceptible to electrostatic discharge, electromagnetic radiation and extremely sensitive to changes in the dielectric constant in the surrounding media, eg. B. by moisture, wetting, steam, etc., which is why they can be used only to a limited extent, in particular in the sanitary fittings sector, even when a correspondingly complex control electronics are provided. In addition, the foregoing conventional capacitive touch sensors require a low-resistance, direct connection of the instrument base body to the protective conductor potential, which also complicates and increases the cost of installing such fittings.

It is therefore an object of the present invention to provide a simple as possible constructed reliable touch sensor, which is also problem-free and inexpensive to use in sanitary fittings.

The object of the present invention is achieved with the features of the independent claims. Advantageous embodiments of the invention are mentioned in the subclaims and / or the following description, which is accompanied by schematic drawings. This shows:<dl id="dl0001" compact="compact"><dt>Fig. 1 and 2</dt><dd>the functional principle of a capacitive touch sensor according to the invention;</dd><dt>Fig. 3</dt><dd>a first circuit diagram of a capacitive touch sensor according to the invention;</dd><dt>Fig. 4</dt><dd>a second circuit diagram of a capacitive touch sensor according to the invention;</dd><dt>Fig. 5</dt><dd>a touch sensor according to the invention, which is arranged in a sanitary fitting according to the invention.</dd></dl>

1 and 2 show a schematic representation of the basic structure of a touch sensor S according to the invention together with a simplified electro-technical analog of a human M. According to the invention, the touch sensor S consists of a conductive sensor surface Fs which is isolated from the earth potential and which is connected to an AC voltage generator Uo via a measuring resistor Rs, the phase shift of the voltage applied to the measuring resistor Rs being used as the measuring signal. The voltage applied to the measuring resistor Rs is evaluated by suitable signal processing electronics, consisting of differential amplifier AB, integrator (filter) TP and comparator C. Fig. 1 and 2 also show the simplified electrical equivalent circuit diagram ZM of a human body M, which in principle by means of a series-connected RC element, Rm, Cm whose capacitor Cm is at ground potential, can be represented. Likewise, the contact of the human M with the sensor surface Fs in the circuit diagram with the switch S1 can be shown, wherein the resistor Rm is electrically connected to the sensor surface Fs and the resistor Rs with the switch S1 closed, and with the switch S1 open electrically from the sensor surface Fs is interrupted. The functional principle of the touch sensor S according to the invention shown in FIGS. 1 and 2 can be described with the following equations.<tables id="tabl0001" num="0001"><img file="EP1134895A2_D0001.tif" /></tables><maths id="math0001" num=""><math display="block"><mrow><mtext>ZM = Rm + Cm</mtext></mrow></math><img file="EP1134895A2_D0002.tif" /></maths><maths id="math0002" num=""><math display="block"><mrow><munder accentunder="true"><mrow><mtext>M</mtext></mrow><mo>̲</mo></munder><mtext> = Rm + 1 / iω Cm;</mtext></mrow></math><img file="EP1134895A2_D0003.tif" /></maths><maths id="math0003" num=""><math display="block"><mrow><munder accentunder="true"><mrow><mtext>Us</mtext></mrow><mo>̲</mo></munder><mtext> = Uo - [Uo - Rs *</mtext><munder accentunder="true"><mrow><mtext>la</mtext></mrow><mo>̲</mo></munder><mtext>] ;</mtext></mrow></math><img file="EP1134895A2_D0004.tif" /></maths><maths id="math0004" num=""><math display="block"><mrow><munder accentunder="true"><mrow><mtext>Us</mtext></mrow><mo>̲</mo></munder><mtext> = Rs * </mtext><munder accentunder="true"><mrow><mtext>la</mtext></mrow><mo>̲</mo></munder><mtext> ;</mtext></mrow></math><img file="EP1134895A2_D0005.tif" /></maths><maths id="math0005" num=""><math display="block"><mrow><munder accentunder="true"><mrow><mtext>la</mtext></mrow><mo>̲</mo></munder><mtext> = </mtext><mfrac><mrow><mtext>uo </mtext></mrow><mrow><mtext>Rs + (Rm + 1 / iω Cm)</mtext></mrow></mfrac><mtext> ;</mtext></mrow></math><img file="EP1134895A2_D0006.tif" /></maths> ⇒<maths id="math0006" num=""><math display="block"><mrow><munder accentunder="true"><mrow><mtext>Us</mtext></mrow><mo>̲</mo></munder><mtext> = Uo - Uo (Rs + </mtext><munder accentunder="true"><mrow><mtext>M</mtext></mrow><mo>̲</mo></munder><mtext>) ;</mtext></mrow></math><img file="EP1134895A2_D0007.tif" /></maths><ul id="ul0001" list-style="none" compact="compact"><li>1.)<maths id="math0007" num=""><math display="block"><mrow><munder accentunder="true"><mrow><mtext>Us</mtext></mrow><mo>̲</mo></munder><mtext> = </mtext><mfrac><mrow><mtext>Rs * Uo </mtext></mrow><mrow><mtext>Rs + (Rm + 1 / i ω Cm)</mtext></mrow></mfrac><mtext>; for S1 = closed</mtext></mrow></math><img file="EP1134895A2_D0008.tif" /></maths></li><li>2.) <u>Us</u> = <i>φ</i> ; for S1 = open<maths id="math0008" num=""><math display="block"><mrow /></math><img file="EP1134895A2_D0009.tif" /></maths></li></ul>

According to the present invention, the contact sensor S detects the presence of the complex conductance of a human body and / or an optionally superimposed AC current impression (interference signal injection, for example, ripple voltage). The touch detection is done by the measurement and evaluation of the current flow<u>la</u> in the direction from the sensor to the user and / or in the direction of the user in the sensor. According to the invention, the touch sensor S is therefore based on a dual, bidirectional method whose advantages over the conventional methods are described below.

Fig. 3 shows a circuit diagram of a touch sensor according to the invention S. A grounded AC voltage generator with low voltage amplitude Uo is connected via a measuring resistor Rs with a sensor surface Fs, which also has no low-resistance galvanic connection to the ground potential. The AC generator Uo is suitably provided by means of a first gate GATTER 1, which is constructed such that a square-wave AC voltage with a frequency in the range of 100 kHz is generated. According to the voltage applied to the measuring resistor Rs voltage at points A and B is tapped as follows. A first entrance<maths id="math0009" num=""><math display="inline"><mrow><mover accent="true"><mrow><mtext>A</mtext></mrow><mo>¯</mo></mover></mrow></math><img file="EP1134895A2_D0010.tif" /></maths>, an AND circuit is connected via an emergency circuit to the point A of the measuring resistor Rs, and a second input B, the AND circuit is sensor surface side (point B) connected to the measuring resistor Rs. The AND circuit is followed by an integrator TP, and the integrator TP, for example, a comparator C and / or a microcontroller C, to filter out drift, downstream. In this case, the NOT circuit is provided by a second gate, GATE 2, and the AND circuit by a third gate, GATE 3 and a fourth gate, GATE 4. The AND circuit and the NOT circuit act together as the differential element D schematically illustrated in FIG. The NOT circuit reverses the sign of the voltage CLK_A and outputs the voltage CLK_A, and the AND circuit sums the voltage of its two inputs CLK_A and CLK_B, and the result is sent to the integrator TP and to the comparator C and / or or downstream microcontroller C passed. When the switch S1 is open, the phase shift of the voltage CLK_B and CLK_A is equal to 0 when viewed ideally. In reality, however, a small phase shift fH0 of CLK_A and CLK_B also occurs when switch S1 is open. fH0 in FIG. 3 represents the zero signal of the sensor S according to the invention. When the switch S1 is closed, ie when a human M with the surface Fs is touched, a current flows<u>la</u> from the measuring resistor Rs towards the human resistor Rm and / or from the human resistor Rm to the measuring resistor Rs, and produces a phase shift fHM increased in relation to the zero phase shift. fHM represents the output signal of the sensor according to the invention when the surface Fs is touched by a human M.

4 shows a detailed embodiment of the touch sensor S according to the invention, which has an integrator TP constructed by means of diode D1 and capacitor C3 and resistor R3. Thus, the zero and measurement signals fH0 and fHM from FIG. 3 are converted into corresponding DC voltage amplitudes. The output voltage<u>Us</u> can now be evaluated for example in a subsequent comparator C and / or a downstream microcontroller C. In addition, the contact sensor S shown in the circuit diagram of FIG. 4 has a compensation element KS for zero adjustment consisting of the resistor R2 and the capacitor C2, which is connected between the second gate GATE 2 of the NOT element and the third gate GATTER3 of the AND element is.

The touch sensor S according to the invention described above with reference to FIGS. 1 to 4 has the following advantages over known capacitive touch sensors. The contact sensor S according to the invention has the simplest structure, wherein the actual sensor element consists only of an ohmic resistor Rs. In addition, the Signalauswerteelektronik with minimal component cost can be realized only using low-cost components and therefore easy, space and time saving and inexpensive to produce. The electrical connection of the sensor surface Fs to the control electronics also takes place unlike conventional capacitive touch sensors via a single conductor that does not need to be shielded. It is therefore possible to dispense with the touch sensor S according to the invention on shielded coax lines for connecting the sensor surface to the evaluation, which are required in previously known capacitive sensors. Since the sensor surface is also coupled to the signal processing electronics with low resistance (typically 10 to 20 kΩ), the contact sensor S is very immune to interference and insensitive to external parasitic complex conductances, which are e.g. B. due to contamination of the sensor surface Fs occur in conventional capacitive sensors. Due to the relatively low-impedance signal connection, the contact sensor S can be made insensitive to electromagnetic interference fields. The functionality is almost independent of the shape and shape and the size of the sensor surface Fs, since the touch sensor S is almost independent of the surface capacitance of the contact surface Fs to the environment, as well as the functionality of the touch sensor S is insensitive to changes in the dielectric constant of the environment. The sensor surface Fs to be touched can therefore be of almost any desired design and must actually be touched by the user to trigger a sensor signal. Separately isolated partial surfaces of the contact surface Fs for selectable, different functions are likewise possible without problems. The sensor is also absolutely wear-free, with its lifetime determined only by the reliability of the signal electronics, eliminating the need for a minimum number of cycles, as required by contact switches.

Due to the above-described advantages over conventional capacitive touch sensors, in particular due to the insensitivity to changes in the dielectric constant of the environment and the immunity to interference and insensitivity to external parasitic complex conductances, the electromagnetic compatibility, and the connection of the sensor surface Fs to the control electronics via a single unshielded conductor, the contact sensor S according to the invention is particularly suitable for the control of modern electrically or electronically controlled sanitary fittings used and integrated into such sanitary fittings.

Fig. 5 shows a sanitary fitting according to the invention EHM, in which the touch sensor S is integrated, the example of a single-lever mixer EHM with a cold water inlet KW, a hot water inlet, HW, each with a solenoid valve MV, a valve body AK, which is connected to an outlet AL, and with a mechanical valve, not shown in the drawing, which is formed for example as an intervention mixing valve cartridge which is actuated via a handle AH. The control lever AH of the armature EHM is according to the invention via an electrical insulator GT galvanically isolated from the other parts of the fitting and sensor surface Fs of the touch sensor S and connected via a single isolated, but not shielded conductor AFs with the control electronics SE of the touch sensor S, the is arranged within the body AK of the valve. The control electronics of the touch sensor is connected in a known manner via a connecting line AMV with the solenoid valves MV and connected via a second connecting line ASV for the power supply with a battery SV, which is suitably also disposed within the main body AK of the valve. However, the battery SV can also be arranged separately from the fitting, in which case advantageously a in FIG. 4 shown coupling member KP, which consists of the capacitor Ce1 and the resistor Re1, is connected between the negative terminal of the battery and the valve body AK. It is clear that the touch sensor S can also be supplied with a mains voltage source, which is not desirable in the sanitary fittings sector for safety reasons.

In this embodiment of the present invention, the entire handle AH of the fitting is formed as a sensor surface Fs of the touch sensor S, wherein the control electronics SE of the touch sensor S is set such that when a touch of the handle at any point with the hand or a finger, the two Solenoid valves MV, be opened and at the same time the cold water and hot water supply KW, HW, release. Advantageously, in the armature EHM also an infrared sensor IRS integrated, which is also connected via an electronic control unit with the solenoid valves MV and is arranged such that the infrared sensor detects the status of presence detection, for example a hand in the water outlet, the valve is and the infrared sensors are also controlled in a known manner, the solenoid valves MV. The following operating states are possible with the above-described valve EHM according to the invention.<ul id="ul0002" list-style="none"><li>1. The mechanical valve which can be actuated mechanically via the handle AH is closed, the handle is not touched and the infrared sensor IRS detects no presence of a body part or an object near the outlet area of ​​the fitting. In this operating state, the two solenoid valves MV are also closed, with the result that no water leaks from the valve.</li><li>Second The handle AH of the mechanical valve is touched at any point by hand and / or the infrared sensor detects an object in the vicinity of the vicinity of the water outlet AL of the valve, and the mechanical valve is closed. In this operating state, the control electronics of the touch sensor S detects a touch of the sensor surface Fs and / or the control electronics of the infrared sensor detects the presence of an object or body part in the vicinity of the vicinity of the water outlet and the two solenoid valves MV are opened, with the result that from the No water leaks, as the mechanical valve is closed.</li><li>Third The valve which can be actuated mechanically via the handle AH is opened, the sensor surface Fs is not touched and the infrared sensor system does not detect any object or body part in the vicinity of or near the water outlet of the fitting. In this operating state, the mechanical valve is open and the two solenoid valves MV are closed, with the result that no water leaks from the valve.</li><li>4th The valve which can be actuated mechanically via the handle AH is opened and the handle is touched by hand and / or the infrared sensor system detects an object or a body part in the vicinity of or near the water outlet AL of the fitting. In this operating state, the two solenoid valves MV are open, and the mechanical valve is also open, with the result that water exits the valve.</li></ul>

Such a sanitary fitting EHM provided with a touch sensor S according to the invention can therefore be operated particularly comfortably. An operator is able to open by touching the handle AH of the mechanical valve, the two solenoid valves MV, which occurs only when opening and the mechanical valve water from the outlet of the valve. In this operating state, the person is allowed to reach with the second hand in the water outlet area, for example, to check the temperature of the water, while the first hand adjusts the water temperature by pivoting the handle as needed. Upon reaching the desired water temperature and the desired outflow, which is also adjustable over the handle of the fitting, the person lets go of the handle, whereby the sensor surface Fs is no longer touched. However, as long as the operator keeps a body part or an object near or around the water outflow and thus uses the outflowing water, this is detected by the infrared sensor IRS, and the two solenoid valves MV therefore remain open. However, when the operator removes their hands or object from the detection range of the infrared sensor IRS, this is detected by the infrared sensor IRS, and the two solenoid valves MV are closed with the mechanical valve open, so that no water enters the fitting and accordingly no water leaves the fitting. This results in the particular advantage that a set once with the handle of the mechanical valve Wasserausflußmenge and temperature is maintained and does not need to be adjusted again, but by simply touching the handle AH and / or by introducing objects or body parts in the vicinity of the water outlet and thus the magnetic valves MV opens in the detection range of the infrared sensor IRS, and water comes out of the valve with preset stored temperature and discharge amount.

The arrangement of the touch sensor S according to the invention in a sanitary fitting is particularly advantageous because for the provision of a sanitary fitting with the above-described operating conditions and resulting benefits to activate control functions additional mechanical switching elements such as piezo pushbuttons or switches and required outbreaks, seals, etc. not necessary are, since the fitting body or Parts of the fitting body itself signal generator or sensor element. A further advantage of the arrangement of a touch sensor S according to the invention in a sanitary fitting is that, unlike conventional touch sensors, no additional low-impedance direct connection of the instrument base body to the protective conductor potential (PE) is required.

The advantageous arrangement of a contact sensor S according to the invention in a sanitary fitting in the embodiment of the fitting or a part of the fitting as a touch-sensitive surface connected to the sensor electronics is in no way limited to the above-described embodiment of a single-lever mixer EHM, and can be modified in many ways. Thus, for example, valves with a plurality of touch-sensitive, galvanically isolated areas can be formed, each for a touch-sensitive surface Fs of a touch sensor S for activating and deactivating different functions, such as only cold water, warm water only, test mode, sleep mode, pause function , Endurance, caster, etc. can be. With the contact sensor S according to the invention, valves with more than one to a plurality of such touch-sensitive surfaces whose contact triggers different functions, can be realized in a simple manner, it being possible because portions of the valve itself act as a sensor signal generator To make these visually appealing without the design of the valve is affected by the sensors on the valve. In this case, the surface of the sensor surface may be formed electrically conductive, but also electrically insulated, for example: be painted, which does not affect the functionality of the contact sensor S according to the invention with sufficiently thin trained insulating layer. In fact, in the case of sensor surface Fs formed with an electrically insulated surface (eg, painted surface), the capacitance change caused by its contact is detected by sensor S. It is also clear that the touch sensor S described above on the example of a human being can also be activated by an animal which touches the sensor surface.

The contact sensor S according to the invention is in its use according to the invention in sanitary fittings in a suitable manner, as stated above, supplied with a battery with electricity. For the operation of the touch sensor S, although only very little power is consumed in relation to the likewise supplied by the battery with power solenoid valves. However, since it is necessary for the operation of the valve that the sensor electronics SE queries a touch of the sensor surface FS in continuous operation, while the solenoid valves need to be powered only at their opening / closing with energy, it is desirable for a long life of the battery, To keep the power consumption of the control electronics of the touch sensor S according to the invention as low as possible. For this purpose, according to the invention provided with the AC voltage generator of the control electronics switching device for alternating activation and deactivation of the AC voltage generator whose pulse-pause ratio (timing) is adapted to the desired tolerable response time, for example, by the maximum frequency of successive contact of the sensor surface Fs with the finger of a human being can be predetermined. The timing is appropriate, given also by the particular use of the valve (eg: in household, public areas, etc.), optimized accordingly to fail-safe operation (eg: the detection of double touch) with minimal energy consumption. For a smooth functioning of the touch sensor S, for example, the control electronics over a period of up to 1/10 second be deactivated, followed by an activation time of the control electronics of only 1/100 second. As a result, it is advantageously possible to reduce the energy requirement of the control electronics of the touch sensor S according to the invention by a multiple, thereby correspondingly prolonging the life of a battery.