GB2208434A

GB2208434A - Detecting water droplets on a vehicle window and controlling windscreen wiper in response thereto

Info

Publication number: GB2208434A
Application number: GB8818112A
Authority: GB
Inventors: Sergio Stibelli
Original assignee: Veglia Borletti SRL
Current assignee: Veglia Borletti SRL
Priority date: 1987-07-31
Filing date: 1988-07-29
Publication date: 1989-03-30
Also published as: IT212441Z2; DE3825663A1; ES1008715U; ES1008715Y; BE1000827A6; IT8753569V0; GB8818112D0; FR2618896B3; FR2618896A1

Description

1 1.

1 220 8 43) 4 A SENSOR DEVICE FOR DETECTING THE PRESENCE OF WATER DROPLETS ON A VEHICLE WINDOW AND WINDSCREEN WIPER CONTROL APPARATUS PROVIDED WITH SAID DEVICE The present invention relates to a sensor device for detecting the presence of water droplets on a window. The present invention further relates to windscreen wiper control apparatus provided with said device.

An object of the present invention is that of providing a sensor device for detecting the presence of water droplets on a vehicle window which can be simple to manufacture and assemble, and of low production cost.

A further object of the present invention is that of providing windscreen wiper control apparatus incorporating the said device, which can be simple to produce and of low production cost.

According to the-present invention there is provided a sensor device for detecting the presence of water droplets on a vehicle window, characterised by the fact that it comprises a light source operable to emit light rays towards the face of the window outside the vehicle, and a diffractive optical element mounted on the inner face of the said window and operable to convey the light f 1 1 2 rays refracted from the said window towards a photodetector operable to emit an electrical signal corresponding to the intensity of light incident thereon.

According to the present invention there is further provided windscreen wiper control apparatus, characterised by the fact that it comprises: at least one sensor device for detecting the presence of water droplets on a vehicle window, of the type provided with a light source operable to emit light rays towards the said window and a diffractive optical element carried by the said window and operable to convey the light rays refracted from the said window towards a photodetector which generates an electrical signal correspondingto the intensity of light incident thereon; electrical processing means for the said electrical signal generated by the said photodetector; and electrical control means for actuating the said windscreen wiper.

For a better understanding of the present invention a preferred embodiment is now described purely by way of non-limitative example and with reference to the attached drawings, in-which:

- Figures 1 and 2 illustrate the operation of a sensor device formed according to the principles of the 1. ' 1 k v CI 1 1 3 present invention in two different working conditions; and - Figure 3 is an electrical block diagram of control apparatus for a window wiper provided with the 5 device of Figure As illustrated in Figures 1 and.2, a sensor device for detecting the presence of water droplets 2 on a window wiper 3 of a vehicle is generally indicated with the reference numeral 1. The window 3 illustrated in Figures 1 and 2 is constituted by the windscreen of the vehicle, but this does not constitute a limitation of the present invention in that the device 1 can be applied also to detect the presence of water droplets on the rear window of the vehicle. This latter is illustrated partially and in particular a portion 4 of the front part of the body and a portion 5 of the dashboard corresponding to the driver's position are also shown.

The device 1 comprises a light source 6 installed on the portion 4 of the front part of the vehicle body, a diffractive optical element 7 fixed to the face of the window 3 within the vehicle, and a photodetector 8 installed on the portion 5 of the dashboard.

Conveniently, the source 6 generates a collimated, almost 1 1 4 monochromatic beam of light and is formed by a light emitting diode (LED), whilst the photodetector 8 could be constituted by a common phototransistor.

The optical element 7 is constituted by a holographic lens the principal charateristic of which'consists in diffracting light rays incident thereon with a predetermined angle of incidence towards a precise point which is called the focus of the lens.

In use, by fixing the position of the light source 6 and of the optical element 7 it is possible to determine the position of the focus of this latter to which the light rays coming from the light source 6 are conveyed. The photodetector-8 is installed at this focus position which, naturally, is sought to be made on the portion 5 of the dashboard.

In the absence of water droplets on the face of the window 3 (see Figure 1) the light rays emitted from the source 6 incident on the outer surface of the window 3 are subjected to refraction by the window 3 itself and subsequently diffraction by the optical element 7 which causes them to be focussed on the photodetector 8. In these conditions the electrical signal generated by the photodetector 8 is at a maximum.

1 1 When a droplet of water is interposed in the optical path of the light rays emitted by the source 6 (see Figure 2) deviation of the rays intercepted by the droplet is caused in that it acts as a spherical dioptric surface. This causes a reduction in the intensity of the light incident on the photodetector 8 and, obviously, a reduction in the electrical signal generated by this latter.

Electrical apparatus, generally indicated with the reference numeral 11, is shown in Figure 3; this, on the basis of the light intensity which is conveyed to the photodetector 8 operates to control the actuation of a windscreen wiper, not illustrated for simplicity, but obviously operable to wipe the outer face of the window 3.

The apparatus 11 comprises a sensor device 1 which commonly in this embodiment, has a light emitting diode (LED) 12 as a light source and a phototransistor 13 as photodetector. The apparatus 11 further includes an electric current source 14 operable to supply the diode 12, and a processing and control circuit which comprises, downstream from the phototransistor 13, a capacitor 15, a signal amplifier block 16, a detector block 17 a 1 1 6 comparator block 18, a power amplifier block 21, and a block 22 for controlling an electric motor 23 operable to actuate the windscreen wiper.

As is known, a phototransistor is a junction transistor in which illumination of the base results in an injection of electrical charges from the emitter. Therefore the value of the light intensity conveyed to the phototransistor 13 corresponds to a proportional electrical signal which is processed by the blocks 16, 17, 18 and 21. In particular, the block 16 amplifies this electrical signal, the block 17 detects its presence and transmits it to the block 18 which effects a comparison of the amplitude of the signal with a predetermined reference signal.

If the signal coming from the block 17 is less than the reference value (which signifies that there are water droplets 2 on the window 3) the apparatus 11, via the blocks 21 and 22, controls the supply of electricity to the motor 23 which in turn puts the windscreen wiper in motion.

As specified above, the apparatus 11 automatically controls operation of the windscreen wiper (at least one blade) whenever it detects the presence of water droplets 1 7 on the surface of the window itself. Naturally it is possible to modify the apparatus 11 in such a way that it controls the actuation of the windscreen wiper for example for two or more passes upon each detection of 5 water droplets.

From what has been described above the dvantages achieved by the present invention are apparent.

In particular, the driver does not have to perform any manipulations and can therefore concentrate solely on driving the vehicle. This advantage is more evident in particular conditions such as, for example, in the case of intermittent rain and in the case of a wet road such is that the window becomes sprayed with water thrown up by other vehicles, and in which the driver, in the absence of the apparatus 11, must operate the windscreen wiper often but with an irregular frequency. Further, the constructional simplicity and ease of assembly of the device 1 and the apparatus 11 is to-be emphasised, which allows its production at low cost.

Finally, it is clear that the device 1 and the apparatus 11 described and illustrated here can have modifications and variations introduced thereto without by this departing from the protective ambit of the present g 8 k invention.

In particular the apparatus 1 could include a plurality of devices 1 connected in parallel and disposed along the windscreen 3 at a predetermined separation. This arrangement would allow the windscreen 3 to be cleaned even when, for example in the second of the particular conditions described above, the water droplets on the window 3 may be spaced from the driving position but no less important for correct visibility (thinking, for example, of the wide window of industrial vehicles or goods or passenger transports).

4w 4 1 1 4.

9

Claims

1. A sensor device for detecting the presence of wazer droplets on the window of a vehicle,charcterised by the fact that it comprises a light source operable to emit light rays towards one f ace of the said window, and an optical diffractive element mounted on the said window and operable, in combination with the refraction of the said window. to direct the light rays from the source towards a photodetector which in ope ration emits an electrical signal in dependence on the intensity of light incident thereon.

2. A sensor device according to Claim 1, characterised by the fact that the said light source is installed on a portion of the front part of the body of the vehicle and in that the said photodetector is installed on a portion of the dashboard of the vehicle.

3. A sensor device according to Claim 1 and/or Claim 2, characterised by the fact that the said optical element comprises a holographic lens A sensor device according to at least one of the preceding Claims, characterised by the fact that the said 1 i light source comprises a light emitting diode (12).

1 1.

5. A sensor device according to at least one of the preceding Claims, characterised by the fact that the said photodetector comprises a phototransistor, 6. Windscreen wiper control apparatus, characterised by the fact that it comprises:

at least one sensor device for detecting the presence of water droplets on a window of a vehicle and of the type provided with a light source operable to emit light rays towards the said window and a diffractive optical element carried by the said window and operable to convey the light rays refracted by the said window - towards a photodetector (8) which generates an electrical signal corresponding to the intensity of light incident thereon; electrical means. for processing the said electrical signal generated"by the said photodetector and electrical means actuation of the said windscreen wiper.

for controlling the 7. Apparatus according to Claim 6, characterised by the fact that the said processing means comprise a comparator block operable"to compare the value of 1 1 J v 11 the said electrical signal with a predetermined reference value.

8. Apparatus according to Claim 7, characterised by the fact that the said processor means comprise, in succession from the said photodetector. a signal amplification block. a signal detection block the said comparator block and a power amplification block Published 1988 at The Patent Office State House. 6E -, 1 High HclborrLondon WC1R 4TP 9. Apparatus according to at least one of Claims from 6 to 8, characterised by the fact that the said control means include a block for controlling an electric motor operable to actuate the said windscreen wiper 10. A sensor device for detecting the presence of water droplets on a vehicle window, according to any of Claims from 1 to 5, as described and illustrated with reference to Figures 1, 2 and 3 of the-drawings.

11. Windscreen wiper control apparatus according to any of Claims from 6 to 9, as described and illustrated with reference to Figure 3 of the drawings.

Firtner copies mkv be obtaineJ fro:T- 7rie Patent Office Sales Branch- St Mary Cray. OrDington. Kent BRZ- 3IRD Primed by Multiplex techmques 1W. St Mar,, Cray. Ke-, Cc-. a-