FR2723448A1 - DEVICE FOR DETECTING WATER OR THE LIKE ON ICE OF A MOTOR VEHICLE - Google Patents

Abstract

A device for detecting water or the like on a motor vehicle window, and in particular rain on a windshield with a view to automatically controlling a windshield wiper, comprises an optoelectronic sensor which comprises at least two control members. emission of radiation (D1-D3) and reception means (19) of the radiation coming from the emission members and refracted by the windshield. According to the invention, means are provided for sequential control of the switching on and off of the emission members defining a plurality of phases during which one of the emission members is on, respectively, and at least one phase during which all the emission members are switched off, and means for sequential measurement of the intensity of the refracted radiation for each emission member and in the absence of radiation coming from the emission members.

Description

The present invention relates generally to

  detection of water or the like on a motor vehicle ice, and in particular rain on a

  windscreen for the automatic control of a paper towel

  ice cream. A rain sensor using an optoelectronic solution and based on the measurement of the variation of light intensity refracted and backscattered through the glass of the windshield is widely known in the

technical.

  Such a sensor uses one or more emitting diodes (LEDs) and one or more elements for measuring the refracted light power such as a photodiode or

a phototransistor.

  Figure 1 schematically represents the principle

of such a known rain sensor.

  An emission diode 1 emits an incident beam 3

  at an angle of incidence 2 with the windshield 4.

  Part of the transmitted power is lost by direct reflection on the first side of the windshield, indicated by a path of radius 5, while the rest of the transmitted power passes through the windshield (radiation 6) with a refraction angle 7 different from the angle

incidence 2.

  When the radiation 6 reaches the second face of the windshield, a small part of the received power is reflected (radiation 8), whereas the majority of the

  transmitted power is lost (radiation 9).

  When the radiation 8 reaches the inner face of the windshield, part of it is again reflected (radiation 10), while the other part emerges from the ice (radiation 11) and reaches a

  measuring device 12 with photodiode or phototransistor.

  It is understood that any disturbance occurring on the outer face of the ice and modifying the medium 13 located outside the windshield 4 modifies the ratio between the transmitted power of the radiation 9 and the

  reflected power of the radiation 8.

  As a result, the variations in the luminous flux recorded on the receiver 12 reflect the modifications of the medium 13 and make it possible to interpret the

  raindrops on the windshield.

  It is also understood that, in order to optimize the received power, it is necessary to tilt the transmission diode as well as the receiver, and that the distance 14 between the point of incidence of the beam 3 and the point must be taken into account. of emergence of the reflected ray 8, which depends on the thickness of the windshield 15, to position

components 1 and 12.

  It is certainly possible to position the components perpendicular to the windshield, but in this case, the power emitted will not be maximum. This is related to the fact that most often the emission diodes have an emission diagram giving generally the maximum transmitted power in the axis. It is therefore necessary to use emission diodes with a large opening angle to position them orthogonally to the windshield, whereas diodes with a small opening angle must be inclined and positioned more

precisely.

  Document US-A-4 355 271 discloses a rain sensor which comprises three transmission diodes arranged in a triangle and associated with two photosensitive reception elements whose output signals are the subject of an individual treatment. followed by a comparison. The three diodes are connected in series, and are all on or off simultaneously, following a pulse command. This results in an output signal having a DC component representative of the value of ambient illumination. The elimination of this continuous component makes it possible to obtain a value of differential illumination, and thus to get rid of

effects of ambient lighting.

  Such a known sensor however comprises a complex electronics and requiring a number of adjustments. In addition, it is sensitive to soiling, scratches, etc ... present on the windshield, as well as aging and failure of the emitting diodes, to the extent that all these phenomena will affect the

differential measurement mentioned above.

  The present invention aims at overcoming the drawbacks of the prior art and at proposing a sensor which, while avoiding the effects of ambient lighting (solar radiation, street lighting, lighting of vehicles traveling in the opposite direction,), makes it possible to to cope with the aging of the emitting diodes, the presence of dirt, scratches or points of impact on the windshield, without requiring adjustment. The present invention also aims at providing a sensor having a sensitivity allowing an extended detection ranging from fine droplets to water floes, for detecting the wear of the brushes

the windscreen wiper.

  The invention aims to achieve all of these

  objectives in a simple and economical way.

  It proposes for this purpose a water detection device or the like on a motor vehicle ice, and in particular rain on a windshield for the automatic control of a windshield wiper, comprising an optoelectronic sensor which comprises at least one minus two radiation emitting members and means for receiving the radiation emitted from the transmission members and refracted by the windshield, characterized in that it comprises means for sequentially controlling the ignition and extinguishing transmitters defining a plurality of phases during which one of the transmitting members is turned on, respectively, and at least one phase during which all the transmitting members are extinguished, and means for sequentially measuring the intensity of the refracted radiation for each transmitting organ and in the absence of radiation from the

transmission organs.

  Some preferred, but not limiting, aspects of the device according to the invention are the following: a single phase is provided during which

  all transmitters are off.

  the device comprises means for subtracting from each measurement of the refracted radiation coming from a transmitting member a measurement of the radiation received in

  the absence of radiation from the transmitting organs.

  the device comprises means for performing a sliding average of a succession of measurements of

  refracted radiation received for each transmitting organ.

  the device comprises means for comparing the sliding averages obtained for the different

transmission organs.

  the device comprises means for triggering the start-up of a wiper device when the speed of evolution of at least one average

  slippery exceeds a predetermined threshold.

  the device comprises a detection unit housing the transmission members, the reception means and a sequential control circuit of the transmission members operating in response to logic selection signals supplied by a processing unit located at

  distance from said detection unit.

  this sequential control circuit comprises a decoder. - The device comprises three transmission members arranged at the three vertices of an equilateral triangle extending in a plane substantially parallel to the ice. Other aspects, objects and advantages of the present invention will become more apparent upon reading the

  following detailed description of an embodiment

  preferred of this, given by way of non-limiting example and with reference to the accompanying drawings, in which, in addition to Figure 1 already described: Figure 2 is a front view showing a sensor unit of a sensor to three emission diodes according to the present invention, FIG. 3 represents an electronic detection circuit belonging to the detection unit of FIG. 2, FIG. 4 represents in the form of a chronogram various control combinations of the electronic circuit of FIG. and the corresponding measurement

obtained on the detector.

  FIG. 5 represents an electronic processing circuit associated with the detection unit of FIGS. 2 and 3, FIG. 6 represents the diagram of a power circuit associated with the control of a windscreen wiper motor of the vehicle, and FIG. 7 is another illustrative chronogram

  operation of the device according to the invention.

  Referring firstly to Figure 2, there is shown an optical detection unit which comprises three light-emitting diodes D1, D2 and D3 regularly distributed at the three vertices of an equilateral triangle, around and equidistant from a photodiode central reception 19. The three diodes D1 to D3 are oriented at the same angle of incidence relative to the windshield. Alternatively, they may be placed at different distances from the receiving photodiode 19, being oriented such that the backscattered flux

  is maximal on said phtodiode 19.

  The orientation and placement of each of the emission diodes are chosen so that the emission beam of each diode covers a certain surface 20 of the windshield, indicated by hatching, and that after reflection this spot is reflected on the sensitive surface 21 of the receiving photodiode 19. The area covered by the radiation from the three diodes after reflection on the outer face of the windshield is

  indicated by a circle in rows.

  It will be observed here that a rain sensor according to the invention comprising only two emission diodes, could be suitable. Nevertheless, explanations on the operation of the proposed device will be given for a sensor using three emission diodes. These explanations can easily be transposed to

  devices with four, five or more diodes.

  Referring now to FIG. 3, there are the three emission diodes D1-D3 each controlled by a transistor, respectively 25, 26 and 27, as well as the

receiving photodiode 19.

  The signal received by this photodiode 19 is amplified by an operational amplifier 29, and is available on a measurement terminal 30 to be processed by an electronic processing circuit, located in an electronic box placed inside the passenger compartment and

which will be described later.

  In the present example, the electronic circuit of Figure 3 is integrated in the housing housing the elements of Figure 2, and is connected to the electronic processing circuit described below by five conductors, namely: a supply conductor 31; a ground conductor 32; two conductors 33, 34 of selection signals A and B; and an amplified output lead of the measured signal. The supply of the detection device of FIG. 2 and the electronic sensor circuit of FIG. 3 is carried out by a regulated voltage delivered by a regulator circuit 35 associated with capacitors of FIG.

  filtering 36 and 37 from an input voltage + V.

  Depending on the number of transmission diodes chosen, the number of conductors for selection logic signals may vary; thus to control three diodes, two conductors are sufficient. For four to seven diodes, three logical signals of

  selection, and therefore three drivers.

  Each transistor making it possible to obtain the control of a transmission diode is controlled by an output of a decoder circuit 38, the outputs of which are actuated by decoding the signals A and B present on the drivers.

Selection 33 and 34.

  The operation of the sensor will be better understood by means of FIG. 4, in which the various combinations of the commands on the input signals A and B are represented in chronogram form. The processing of these signals is carried out, for example, in FIG. ugly

  a wired logic circuit or a microcontroller.

  It is observed that when the two signals A and B are at a logic zero level, during a phase indicated at 39, no transistor control is activated, and the three diodes D1, D2 and D3 are off; the output signal 40 is at a level corresponding to the measurement of the residual illumination due to solar or ambient radiation. When the signal A is at a logic level "1" while the signal B is at a logic zero level, during the phase indicated at 41, only the control of the transistor T1 (reference 42) is activated, and the output signal 43 is at a level corresponding to the measurement of the residual illumination plus the illumination corresponding to the value of the measurement of the radiation

refracted from the diode D1.

  When the signal A is at a logic zero level, while the signal B is at a logic level "1" as indicated during the phase 44, only the control of the transistor T2, indicated at 45, is activated, and the output signal 46 is at a level corresponding to the measurement of the residual illumination plus the illumination corresponding to the value of the measurement of the radiation

refracted from the diode D2.

  When the signals A and B are both at the logic level "1" as indicated during the phase 47, only the control of the transistor T3, indicated at 48, is activated, and the output signal 49 is at a level corresponding to the measurement residual illumination plus illumination corresponding to the value of the

  measuring the refracted radiation from the diode D3.

  The process is then repeated to give a new measure corresponding to the measurement of the illuminance

  residual due to solar or ambient radiation 50.

  It can be seen that there is thus a series of signal measurements from the different paths defined by the optical paths between each transmission diode and the receiving diode, as well as a measurement

  representative of ambient lighting.

  FIG. 5 represents the electronic processing circuit associated with the detection unit and in which there is found, grouped around a microcontroller 51: an interface circuit with the sensor, including the five connecting conductors 31, 33, 34 , 30 and 32; a control circuit built around two transistors 52 and 53, connected to two logic outputs of the microcontroller and for generating the selection signals A and B used as described above; 5. an analog / digital converter 54 for acquiring the various measurements successively supplied by the receiving photodiode and the associated amplifier; a voltage supply and regulation device 55; optionally, a watchdog device 56 associated with the microcontroller, which can be quite conventional in itself and which will not be described; two relays 57 and 58 controlled by two respective outputs of the microcontroller via two transistors 59 and; a plurality of control input terminals 61, 62 and 63 readable by three inputs 64, 65 and

66 of the microcontroller.

  FIG. 6 represents the diagram of the power circuit associated with the control of the windscreen wiper motor 67, supplied through the contacts of the two relays 57 and 58.

  Relay contacts are shown at rest.

  Relay 57 allows the motor to operate on the low speed. The simultaneous control of the relay 58 makes it possible to operate the motor on the high speed. In a conventional manner, the return of the inverters in the rest position allows the automatic return of the brushes in the low position as the cam C called "fixed stop cam" did not switch the contact

  stationary stop, designated by CA, to ground.

  Thus the circuits of FIGS. 5 and 6 make it possible to take into account a command via

  reading one of the contacts 61, 62 and 63.

  By way of non-limiting example, the first command can be assigned to a low speed operation, the second command to high speed operation, and the third command to operate in automatic mode. The microcontroller 51, which reads the activated command, brings the device, through the two relays 57 and 58, into the desired operating mode. FIG. 7 again shows the appearance of the output signal consisting of the different successive voltages V1, V2, V3, V4, V1 ', V2', V3 ', etc., also indicated in FIG.

, 43, 46, 49 and 50 in FIG.

  The microcontroller, after having set its two outputs connected to the transistors 52 and 53 to the appropriate logic value, acquires the read value Vl, V2, V3, v4, etc., by controlling an analog / digital conversion during the duration of the the

  provision of this value on the driver 30.

  For this purpose, the duration of the provision of the value to be read is chosen greater than the time required for the analog / digital conversion of the acquired value. Typically, this value can be 100 microseconds for a conversion time of the order of 50

microseconds.

  It is thus understood that the device is capable of

  to make about 10,000 acquisitions per second.

  Of course, this value is only indicative to help better understand

  possibilities of the proposed device.

  These possibilities make it possible in particular to smooth each measurement by performing a sliding average on several consecutive values corresponding to the same emission diode, to evaluate the quantity of rain by measuring the rate of change of each of the values, to remove the doubt. on sudden variations in values by exploiting the combined evolution of the three measurements made, and correcting the errors due to

parasitic lighting.

  We will now describe below the means that can be implemented within the microcontroller to meet the constraints outlined in the preamble of

this application.

  The insensitivity of the sensor to outside parasitic radiation, solar radiation, public illumination, etc ..., can be obtained by subtracting from the values found V2 to V4 the measurement Vl corresponding to the level of the parasitic illumination. In this way, the value found remains an absolute value of rain level that can be used to trigger an automatic operation. As already mentioned, the processed values can be smoothed by setting a sliding average in the microcontroller to avoid any

nuisance tripping.

  The device makes it possible to cope with differences in the emission power of the diodes, their aging over time and the resulting misalignments. Specifically, the device avoids resorting to fixed thresholds to trigger different wiping strategies. On the contrary, the device measures the evolution of the wetting of the windshield and triggering occurs automatically when the slope of this change, as measured on at least two of the three voltages V2 to V4, exceeds a certain threshold. In addition, if the powers of the emission diodes are different, the signal measured for each diode will be different at equal wetting. A command is triggered only when it is confirmed that a parallel evolution, in the same direction, takes place on more

of a sensor.

  Immunity against dirt, scratches or points of impact on the windshield, which may affect the operation of the sensor, is achieved by using the three consecutive emissions from the three diodes, and monitoring the evolution of the level of illumination on three different courses. This confirms a trend by detecting a dominant behavior and not taking into account the evolution of a point information before and after scanning. This principle thus makes it possible to overcome the problems of soiling, scratches or points of impact which could otherwise disturb the

sensor operation.

  The device according to the invention does not require any adjustment because the principle of the detection is based on the measurement of the variations and not on absolute values, which

  would require a setting at the origin.

  The device has a sensitivity allowing an extended detection ranging from fine droplets

to the torrents of water.

  The extent of the measurement can be divided into as many jumps as necessary, depending on the value of the

  measurement delivered by the analog / digital converter.

  If need be, it is easy to define a non-linear progressivity

slight variations.

  The device according to the invention can integrate a diagnostic function and offer the possibility of detecting the efficiency, and therefore the degree of wear of the brushes

the windscreen wiper.

  More specifically, the device is able to detect the non-operation of a transmission diode, a fixed dirt, the quality of the wiping by measuring the transmission through the windshield just after the passage of the brushes, etc. The device proposed by the present invention is simple and inexpensive in that it requires only

  ordinary components, low cost.

  The processing electronics require a small microcontroller and few peripheral components. In addition, the flexibility given by the software controlling the microcontroller makes it possible to adapt quickly to

  different command strategies requested.

  Of course, the present invention is not

  in no way limited to the embodiment described below.

  above and shown in the drawings, but those skilled in the art will be able to make any variant or modification

in keeping with his spirit.

Claims (9)

  1. Device for detecting water or the like on a motor vehicle ice, and particularly rain on a windshield for the automatic control of a windscreen wiper, comprising an optoelectronic sensor which comprises at least two d radiation emission (D1-D3) and means (19) for receiving radiation emitted by the transmission members and refracted by the windshield, characterized in that it comprises sequential control means (51, 52, 53, 38, 25, 26, 27) of the switching on and off of the transmitting members defining a plurality of phases (41, 44, 47) during which one of the transmitting members is turned on, respectively , and at least one phase (39) during which all transmitting members are extinguished, and means (29, 54, 51) for sequentially measuring the intensity of the refracted radiation for each transmitting member and in Absence of   radiation from the transmitting organs.   2. Device according to claim 1, characterized in that the sequential control means (51, 52, 53, 38, 25, 26, 27) of the ignition and extinguishing of the transmission members control a single phase (39) during which all the transmitting (D1-D3) are off.   3. Device according to claim 2, characterized in that it comprises means (51) for subtracting from each measurement (V2-V4) refracted radiation from a transmitting member a measurement (Vl) of the radiation received in the absence of radiation from transmission organs.   4. Device according to one of claims 1 to   3, characterized in that it comprises means (51) for performing a sliding average of a succession of measurements (V2-V4) of the refracted radiation received for each transmission organ.   5. Device according to claim 4, characterized in that it comprises means (51) for comparing the sliding averages obtained for the different transmission members.   6. Device according to one of claims 4   and 5, characterized in that it comprises means (57, 58) for triggering the start of a wiper device when the speed of evolution of at least one   sliding average exceeds a predetermined threshold.   7. Device according to one of claims 1 to   , characterized in that it comprises a detection unit housing the transmission members (D1-D3), the reception means (19) and a sequential control circuit (FIG. 3) for the transmission elements operating in response to logic selection signals (A, B) provided by a processing unit (FIG. 5) located at a distance from said detection unit.   8. Device according to claim 7, characterized in that the sequential control circuit includes a decoder (38).   9. Device according to one of claims 1 to   8, characterized in that it comprises three transmission members (D1-D3) arranged at the three vertices of an equilateral triangle extending in a plane   essentially parallel to the ice.