Sensor unit for detecting moisture on a glass pane

The invention relates to a sensor unit for detecting wetting of a window, in particular an automotive windshield.

Hardware sensors are known for detecting internal and rain sensors for detecting an outer wetting of the window surface. Here are the condensation sensor signals used to drive an air conditioning, heating and / or ventilation system. The signals of the rain sensor, however, are for controlling a windscreen wiper. or washing system for motor vehicles used. Such sensors work amongst other things by the optoelectronic, the resistive or the capacitive principle. rain sensors are applied externally to the vehicle window, fitting sensors the inside. Both operate independently.

A working according to the principle of optoelectronic sensor device for detecting the external wetting is disclosed in DE 198 15 748 C2.

In DE 43 34 381 A1, a device for the automatic control of a Wiper motor shown that a humidity sensor and an evaluation includes. In the apparatus for operating a windscreen wiper motor from the DE 197 13 835 A1 also uses a rain sensor.

A method of adjusting the sensitivity of a precipitation sensor system at ambient conditions and a sensor system with a precipitation sensor disclosed in DE 41 34 432 A1.

DE 6 9115647 T2 discloses an apparatus for heating and ventilation of the passenger compartment a motor vehicle, in which a fitting sensor provided at the inside of a vehicle window is mounted, with an electronic module to control the closing flaps connected is.

From DE 44 27 627 C2 is a process for preparing a resistive measurement principle according to the operating rain sensor is known, the at least two electrically conductive, mutually having adjacent sensor elements which, in cooperation with the sensor array wetting electrically conductive substances, preferably water, an its impedance form changing resistance. The sensor consists essentially of two fan-like engaging surfaces which are applied on a glass plate and the resistive element form.

Another humidity sensor windshield is described in DE 40 41 160 C2. This is applied to the outer pane of the windshield and comprises two electrically conductive members, which have a distance from each other and from each other by a gap of predetermined width from each other are electrically insulated. The gap is preferably not greater than the width of a raindrop or mist droplet.

The DE 44 24 985 A1 discloses a rain sensor on the windshield in the area a wiper arranged having resistance structures which, in dependence the raindrops, changing the resistance linearly.

In WO 94/08247, the structure and the operation of a capacitive humidity sensor disclosed.

The principle of capacitively operating the humidity sensor is also described in EP 0 753 438 A1 described.

The object of the invention now is to show a sensor unit with the at the same time an outer, for example, rain, as well as an internal wetting is detected and the also is inexpensive.

The object is achieved by the features of claim 1.

The invention is based on the idea to provide the sensor unit with at least two sensors, both of which are applied to the inner side of a disc. In training the invention, both sensors with a common switchable evaluation coupled so that by mutually evaluating the two sensors both incipient Fitting or incipient wetting of the inside of a vehicle window as well incipient wetting of the outside of the disk, for example, is detected by rain.

In a preferred embodiment of the invention, both sensors are in addition integrated small construction executed sensor module. Each not desired detection has no influence on the analysis of the desired detection. In addition, can also Measures are provided, for example, a capacitive screen, whereby the adverse influence is also prevented.

However, the sensor unit forming or incorporated in the module sensors can also separate evaluation units are operated.

The condensation sensor has a responsive polymer moisture on gold foil, can Alternatively, however, also have an interdigital structure with a cover glass layer.

The rain sensor is a capacitive electrode structure in non-differential arrangement the sensor surfaces formed.

In a further design of the invention, together with further integration of the two sensors with the common switchable evaluation a compact built Sensor Module offered. In this module, other sensors such as light sensor, Sun sensor etc. are easily integrated.

Reference to an embodiment with drawing the invention is explained in detail.

It shows<dl tsize="6"><dt>Fig. 1</dt><dd>a windscreen of a motor vehicle with an applied sensor unit,</dd><dt>FIG. 2</dt><dd>a block diagram representation of the sensor unit of FIG. 1,</dd><dt>Fig. 3</dt><dd>a general configuration of a sensor module,</dd><dt>Fig. 4</dt><dd>the internal structure of the sensor module.</dd></dl>

In Fig. 1 is a general sensor unit 10 is shown, the two separate sensors, one Condensation sensor 1 and a rain sensor 2 comprises. Both sensors 1, 2 are each an evaluation unit 3a and 3b electrically connected. but it can also have a common switchable evaluation be provided 3. The respective supply or signal lines are preferably integrated into a structure. The condensation sensor 1 operates on a capacitive basis, the capacitance of the capacitor by moisture absorption of a polymer structure (not shown in detail) of the condensation sensor 1 is changed. The sensor surface of the rain sensor 2 consists of two electrically separated conductive paths 21, 22 (see Figure 4). The capacity of the rain sensor 2 is represented by the Influencing the stray fields of these two operating as capacitor electrodes interconnects 21, 22 as modified by the rain. By switching the input of the evaluation unit 3 or by the individual evaluation 3a and 3b, the respective one of the two signal sensors 1, 2 is used to evaluate brought, which is to be evaluated according to programming. Since both sensors 1, 2 operate on the same measuring principle, is also the evaluation as such equal. Switching between the two sensors 1, 2 is not time critical, since the response to the sensor signals compared with the Shift and evaluation time can be long.

The rain sensor 2 as well as the fitting sensor 1 are shown from the inside on a in Fig. 2 Vehicle window 100, preferably applied in the area of ​​a mirror base one hundred and first

In Fig. 3 is as advantageous further design of a sensor module 30 is shown, both the a condensation sensor 31 and a rain sensor 32 comprises the signals of a common switchable evaluation unit 33 is brought to the evaluation, which in the preferred variant, the entire evaluation unit 33 component of the sensor module 30 is. The condensation sensor 31 measures the internal fittings, the rain sensor 32, the outer Moisture. The sensor module 30 is composed of a common carrier member 35 on which the sensor fitting 31 and the rain sensor 32 are applied together in combination. The Support member 35 is so constructed that it is the function of the rain sensor 32 behind a vehicle windshield unaffected. The structure of the both sensors 31, 32 is, for example, as shown in Fig. 1 described. At least on the sensor surface 20 of the rain sensor 32 is a shield 36 applied, the influence of moisture occurring in the passenger compartment on the Rain sensor 32 prevented. It is advantageous, the shield 36 also over the evaluation unit bring 33rd

An internal construction of the sensors 31 and 32 is shown in Fig. 4, wherein the sensor fitting 10 is an interdigital structure 10. Here is at least part of the 34 Evaluation unit 33, for example, a switch-over of the evaluation unit 33 with at the support member 35, wherein here too the entire evaluation unit 33 on the support member 35 can be integrated (Figure 3). Via electrical terminals 30.1 to 30.4 is the sensor module 30 interconnected with other electrical components.