DE4339573C2 - Evaluation device for signals determined by an arrangement for measuring or recognizing the wetting of a surface - Google Patents

Description

The invention relates to an evaluation device according to the preamble of claim 1.

In such an evaluation device according to DE 33 14 770 A1 to control a wiper on an optoelectronic Measuring section the signals from the transmitter clocked to a receiver. To be able to evaluate the signals, each Wipe cycle the device by determining optimal viewing conditions corresponding maximum value are calibrated. This value corresponds to the maximum total reflection when the pane is clean. Kick one Wetting on, less light is totally reflected, so that The waveform gradually decreases until it drops below one of the maximum value a certain factor dependent minimum value that decreases to a Triggering the wiper leads. Through various aids tries to eliminate further interference so that only a small, for the evaluation usable signal range within the constantly pending signal level remains. Single, drop size or Signals corresponding to the amount of drops cannot be detected. Of the The wiping process is basically only ended when the calibrated Maximum value is reached again. Since it is due to pollution however, it is possible that the original maximum value will not return can be reached, it becomes available with a time constant of several minutes slowly reduced until a value is reached even if the window is dirty is achieved, which ensures adequate visibility. So here only the response thresholds shifted, but the signals themselves not affected because due to processing of the detected signals the large interference level is too little space.

From US 4,452,325 an evaluation device is known in which Intermittent control of a wiper only uses the signals are determined outside of the actual wiping cycle will. For this purpose, when a wiping process is triggered, all are first Memory deleted and only after the completion of the wiping process to Signal reception open. Because the time during wiping was not evaluated can, it is not possible for this device, directly from  Switch interval operation to continuous operation. To be in continuous operation To achieve an automatic wiping process, the must Windscreen wiper switch can be changed manually. Since only that Signals between individual wiping cycles are easily detected an uneven interval course, which is disruptive to the Vehicle users can impact.

From DE 40 18 903 C2 it is also known to influence subsequent interval cycles as a function of previous interval cycles. The soiling of the surface of the pane or a moisture deposit or a quantity of rain deposited on the pane should be detected by a sensor which emits a signal to a signal processing arrangement 13 , but how the signals are determined is not explained, so that it is not possible to understand how the individual signals are determined and can lead to a rain quantity and raindrop size analog signal.

A measuring arrangement is described in the unpublished DE 93 09 837 U1 described, which allows the wetting of a surface by measuring changes in reflection ascertain. For this purpose, this arrangement has several Measuring sections that are queried cyclically, with a difference value is formed between the values determined on individual test sections. These difference values are sent to an input signal on the one hand Transfer evaluation device, on the other hand at the same time the Occurrence of the signal started a regulation that is dependent a predetermined and if necessary switchable control time constant that received signal adjusted to zero again, so that a sensitivity for further changes in reflection. The scheme affects z. B. the setting of a current actuator for the radiation power of Radiation sources that emit the radiation to be reflected. The Control time constant is dimensioned so that it is a substantial multiple is greater than the slowest changes yet to be recorded Wetting process.

Such a device can be used for a wide variety of purposes be, e.g. B. to control a wiper motor on motor vehicles or basically for any purpose where wetting in particular due to splash water must be determined.  

The subject of this utility model is hereby also expressed Lich made the subject of the present application.

The object of the present invention is the sensitivity of a such measuring arrangement with regard to those occurring in practice Optimize problems.

This object is solved by the features of claim 1.  

Basically, the signals supplied by the measuring arrangement are in one Processing device that processes a control and / or measured value signal to control downstream consumers. In practice it has now shown that when the device depending on the Measuring arrangement determined control signal is operated, a Time constant switching is advantageous. Basically, the ge controlled device sweep the area of the sensor. Alone through however, the sweep leads to a change in the input signal, which must be taken into account accordingly. The time constant is therefore in a timely area while sweeping over the measuring arrangement set a shorter value, making the measuring arrangement less sensitive becomes. Occurring impulses appear shorter in time. The during this Time-determined values become complete or at least largely hidden so that they do not control the device initially can influence. In the example of the windshield wiper, the Clarify problems that occur. The windshield wiper usually pushes a gush of water in front of him would of course also lead to a signal from the measuring arrangement. This signal would report heavy wetting, which is in reality does not exist at all. For this reason, in the area of Do not sweep this signal for the control of the wiper used. Instead, the signals are exploited that before Overcoating or, if necessary, also after overcoating, that is are due solely to the external wetting.

Preferably, according to claim 4, the switch is made to a shorter one Time constant before sweeping, and this toggle is only canceled again as soon as the motor limit switch again sends a signal. Depending on the signal, a timer can also be used later Determine when to switch.

Do you want to achieve that the device controlled by the control signals reacted quickly and flexibly to changes in the reflection according to claims 5-8, each signal is recorded on a memory unit, where an attenuator can be bridged with strong signals, so that it the device responds relatively quickly. It can do the same  especially in the example of the windshield wiper but also be required that the fastest possible return to the zero state is desired, if e.g. B. the vehicle stops at a traffic light or suddenly in a tunnel drives in. For this reason, they are used to control the device initially hidden signals are integrated and if there are any Integration results in a value that is below a certain limit, the storage unit can be discharged for the output signals the device is decisive. It is recommended for security reasons here, if necessary, a wipe, which is counted down as part of the Interval switching z. B. a wiper is possible.

In the following, the invention is explained in more detail using an exemplary embodiment explained. Show it:

Fig. 1 is a block diagram of an evaluation device,

Fig. 2 is a schematic representation of a windshield,

Fig. 3 diagrams a) to d) over the time course of the signals from the motor limit switch and motor; the measuring arrangement with little wetting; the measuring arrangement with star ker wetting; the changing time constant.

An evaluation device 10 is used to evaluate signals which are determined by a measuring arrangement 11 for measuring or detecting a wetting of a surface. The signals can be measured, for example, by at least one sensor on one or more measurement sections due to the internal reflection of a plate or wall which can be irradiated by radiation, the wetting leading to a change in the internal reflection. The changes can be intermittently queried in different sensors S or by applying different radiation sources, whereby different values result from the different arrangements, which enable a difference value formation. Based on these difference values, an input signal for the evaluation device 10 is determined in a control arrangement 12 . The detected signals are at the same time corrected in the control arrangement 12 in such a way that there is always sensitivity to further changes in the reflection path.

Although previously only from a measuring arrangement after the beginning mentioned utility model, it goes without saying that other measuring arrangements are suitable for these purposes, so far, on the one hand, based on the results of at least one measuring section Differential values are formed and on the other hand a regulation by means of a time constant. The adjustment takes place basically so that the difference value of the signal goes to zero, with a long time constant the difference value is slower approaches zero than with a short time constant. The So time constant is the link that determines the sensitivity of the Sensor significantly influenced. To change the time constant adjusting means are provided which during the occurrence of a Wetting change the time constant and preferably shorter set as at a time during which no wetting is available.  

This entire evaluation device and measuring arrangement can be shifted the most used purposes, such as B. to control Water removal or irrigation devices. Preferably fin it can be used wherever changes due to splash water occur. In the following, however, for the sake of simplicity, the ge Entire device based on a control or regulation of a Wiper motor explained.

In the case of a water removal device such as a windshield wiper motor M, the time constant is set to be shorter during the occurrence of wetting and thus during the wiping process than when the windshield wiper motor is at rest. This alone makes it possible to hide changes that occur due to self-drying streaks from the measurement signals. Rather, the measuring system registers the other states that change over time. The time constant is thus controlled by the evaluation device 10 , in which the control arrangement 12 may also be integrated, as a function of the input signal Es and the position of the drive device of the device, which is controlled as a function of the output or measured value signal Ms. Position detection means thus preferably detect the position of the windshield wiper or the signal from motor limit switch E is recognized as a signal for changing the time constant. After adjustment, if necessary with a very short time constant, at the beginning of the evaluation, adjusting means 13 set the time constant Tv to a value which is longer in time in order to detect even the slightest changes in the reflection signal. However, as soon as wetting occurs and in particular as soon as the wiping process of a windshield wiper 25 begins, the system is switched to another value, that is to say to a windshield wiper to a value which is shorter in time in order to also detect changes which occur more quickly.

Relevant signals for the change are, according to FIG. 3a, the on-off signal of the motor limit switch indicated in the upper part and the signal of the windshield wiper motor. The control signal of the motor limit switch gives a signal to the control means 13 , which change the time constant Tv in the control arrangement. As soon as the limit switch emits a signal when it starts to rain, the signal for changing the time constant Tv is given, possibly limited by a timer T1 or extended beyond a single wiping process.

If the measuring arrangement is not arranged outside the wiping area or the area covered by the device, which is controlled depending on the wetting, it is not sufficient to change the time constant alone during the wiping process, since even during the wiping process itself, especially with wipers, but also when the measuring arrangement is swept over, for example by a sprinkling device, changes take place which may need to be hidden or evaluated differently. When sweeping over a windshield as shown in FIG. 2, the windshield wiper 25 usually sweeps the measuring arrangement 11 at least once, provided that the measuring arrangement is located in the edge region of the wiping zone. Normally, however, it is swept twice, and since exactly the change in the wiping behavior is to be registered, it is necessary that the measuring arrangement actually lies in the wiping area. In Fig. 3a below the time course of a wiping process is shown, the wiper motor is still switched off and then on, and at each of the two positions x sweeps the measuring arrangement. Usually the windshield wiper pushes a surge of water in front of it, so that strong impulses and signals occur at this point. B. is shown in Fig. 3b for a quantity of water Q₁. Even with a small amount of water, as shown in Fig. 3b, there is a pronounced input signal Es (Q₁) This signal now falsifies the measured values, so that it must be hidden. This can either be done by making the measuring arrangement so insensitive that these changes are no longer registered or only leading to short pulses that are masked out. With a short time constant, there is no input signal Es due to the amount of water.

This switchover can now either take place in the evaluation device in that a switchover via switching means 21 to preset high and low values takes place or that a time constant element is switched to the control arrangement via the adjusting means 14 in a manner not shown in the drawing. The switching means 21 can during a long time constant, for. B. at the preset time constant Tv, which is predetermined by the control arrangement, the signals are passed to a memory unit 15 . The signals, on the other hand, which are emitted in the time in which the time constant is switched to the value Tv₂, can be passed on via another line for other purposes. Here it is possible to either completely or at least partially hide the last-mentioned input signals Es. To control the windshield wiper motor, particular attention is paid to the signals collected during the time constant Tv. To simplify, there is the possibility, depending on a timer T2 to make a certain time T 1 after motor end signal 30 a switch to Tv 2 and maintain this time constant until the next motor end signal of the motor limit switch E occurs. Of course, other switching times depending on position detection means are also possible here. The memory unit 15 itself initially comprises a first memory 16 , which outputs its signals to a further memory 18 via a threshold-dependent attenuator 17 . By means of a bypass circuit 22 , however, this attenuator can be bypassed, so that the further memory 18 is loaded more quickly in the case of extremely strong signals. Depending on the memory content, the measured value signal Ms is sent to the wiper motor via an oscillator 23, which in turn gives signals for the actuating means 13 and 14 via its limit switch. Possibly. the memory content can also be used directly as control parameters for the actuating means. Depending on the signals determined, the wiper motor can also be set to a higher speed in heavy rain. Here, the timer T2 of the actuating means 14 can also react accordingly, if necessary.

However, the values transmitted during the sweep of the measuring arrangement can also be used. When controlling a windshield wiper, it makes sense to record these values as dry running control. Such dry running can e.g. B. occur when a vehicle has to brake at a traffic light or suddenly a tunnel is entered. Basically pushes a certain amount of water in front of you when sweeping over the measuring arrangement of the wipers. During the existence of the time constant Tv₂, the occurring signals can now be determined in terms of their intensity, for example, by integration using integrator 19 . As soon as a certain preset limit value G _{ref is} undershot and continued operation of the windshield wiper is reported via the flip-flop switch 24 , the switching means 20 discharges the memory 18 on the white line of a control arrangement 29 , so that no new measured value signals Ms are formed by the oscillator can be. If the comparison in the integrator 19 reveals that the limit value has still been exceeded, the flip-flop element is reset each time and set again by the actuation of the limit switch. This makes it possible to ensure that the wipers are set to zero in the event of a sudden tunnel travel. For safety reasons it may be necessary that this downshift does not take place immediately. Here, the time constant is first set to a longer value via the adjusting means 14 and there is also the possibility of gradually switching the interval control, for example of the windshield wiper, back to zero. This can be done by simply counting down the other wiping processes.

Depending on the time constants Tv and Tv₂, which are switched according to FIG. 3d, there is an input signal Es (Q₂) in the amount of water Q₂, which in the short time constant shown in dashed lines only leads to two short signals when the sensor is swept , otherwise with a long time constant only leads to a signal if the threshold value As (Tv) is exceeded in the shaded area. The time constant Tv₂ is assigned the threshold As (Tv₂) ( Fig. 3c).

Claims (8)

1. Evaluation device ( 10 ) for signals which have been determined by an arrangement for measuring or detecting a wetting of a surface ( 11 ), for generating a control and / or measured value signal (Ms), for a device which is dependent on the wetting is controlled and which sweeps over the measuring arrangement ( 11 ) at least once per actuation interval, the signals being determined by intermittent interrogation of at least one measuring section (S), and with adjusting means ( 14 ) for a time constant that can also be changed during the wetting process by a control arrangement ( 12 ) which influences the generation of the control and / or measured value signal (Ms), characterized in that the signals are determined by intermittently querying a plurality of measuring sections and forming the difference values of the values recorded on the individual measuring sections, and in that the signals determined by the measuring arrangement ( 11 ) are also included Help of the variable time constant (Rv, Tv₂) in the control arrangement ( 12 ) can be regulated so that the difference value of the signals themselves goes to zero with time, and that the adjusting means ( 14 ) adjust the time constant (Tv₂) at least during the sweep so that the control signal is largely suppressed by the device itself and / or is generated by the wetting displaced by the device. 2. Evaluation device according to claim 1, characterized in that a memory unit ( 15 ) stores the signals that occur as long as the time constant (Tv) is set long, and at least partially hides the signals that during the sweep with a short time constant (Tv₂ ) attack. 3. Evaluation device according to claim 2, characterized in that the memory unit ( 15 ) comprises a first memory ( 16 ) which is connected via an attenuator ( 17 ) to a further memory ( 18 ), the attenuator ( 17 ) for strong signals can be bridged with a bridging circuit ( 22 ) and that the time constant (Tv) is changed as a function of the memory content. 4. Evaluation device according to one of the preceding claims, characterized in that the device, which is controlled in dependence on the wetting, is a windshield wiper ( 25 ), the motor limit switch (E) gives a signal for switching to another time constant, wherein switching can be delayed by a timer (T1, T2). 5. Evaluation device according to one of claims 1 to 4, characterized in that the signals determined at a short time constant (Tv₂) during the sweep of the measuring arrangement ( 11 ) are evaluated with regard to their intensity and discharge the storage unit when the value falls below an adjustable limit. 6. Evaluation device according to claim 5, characterized in that the signals are inte grated with respect to their intensity by means of an integrator ( 19 ) and that when the value falls below a predetermined limit (Gref) the further memory ( 18 ) is discharged. 7. Evaluation device according to claim 5 or 6, characterized in that when falling below the limit (Gref) switching means ( 20 ) switch back a device for eliminating the wetting and the adjusting means ( 14 ) set the time constant to a long time value. 8. Evaluation device according to claim 7, characterized in that the switching means ( 20 ) gradually switch back the interval control of the windshield wiper ( 25 ) designed as a removal device to zero.