FR2789034A1 - Method for preventing ice formation on automobile windscreen includes first stage detecting ice presence on glass and actuating wiper motor - Google Patents

Abstract

Method has : first stage detecting ice presence on exterior surface of glass; and stage for actuating first cycle of wiper control of exterior surface as function of results of first detection stage. First stage compares external surface temperature (Ts) of glass with respect to dew point, followed by comparison of external surface temperature of glass with respect to first critical value. Dew point is calculated as function of ambient temperature (Ta) and exterior rate of relative humidity (HR). The first stage is actuated by wiper control (26) for first cycle when temperature of the external glass surface is less than or equal to the first critical value and greater than 0 degrees C. An Independent claim is also included for the description of the deicing installation.

Description

The present invention relates to a method of preventing icing of a

  motor vehicle window, or automatic defrost this window, including the windshield or the rear window, and an installation to prevent icing or automatically defrost the glass. The invention is more particularly applicable to a vehicle window provided with means for wiping its surface

  exterior, including a windshield wiper or windscreen wiper device.

  For proper operation of the vehicle and its equipment, including its wiper devices, and for safe use of the vehicle, including good visibility, it is desirable that the windows are free of frost, especially in this

  which concerns the windshield and the rear window.

  For this purpose, the invention proposes a method for preventing icing of a window of a motor vehicle, or of automatic deicing of this window, in particular of the windshield or the rear window, which is associated with at least one of the controlled means. wiper of its outer surface, characterized in that it comprises: - at least a first step of detecting the conditions of frost formation on the outer surface of the pane, or detecting the presence of frost on this outer surface ; and at least a first step of implementing the controlled wiping means of the outer surface according to at least a first wiping cycle according to the results of the first step

detection.

  According to other characteristics of the method - the first detection step is a step of detecting the conditions of frost formation on the outer surface of the pane by comparing the temperature of the external surface of the pane with respect to the dew point, followed by a comparison of the temperature of the outer surface of the window with respect to at least a first critical value, for example substantially close to 0 C; the dew point is calculated, prior to the comparison of the temperature of the external surface of the window with respect to the dew point, as a function of the ambient temperature and the external rate of relative humidity; the first step of implementing the controlled wiping means of the outer surface according to at least one first wiping cycle is triggered when the temperature of the outer surface of the window is less than or equal to said first critical value and greater than at 0 C; the method includes a second step of detecting frost formation conditions on the outer surface of the pane by comparing the temperature of the outer surface of the pane with respect to a second critical value, lower than said first critical value; and a second step of implementing the controlled wiping means of the outer surface in a second wiping cycle when the temperature of the outer surface of the window is less than or equal to said second critical value; - The second step of implementing the wiped control means is preceded by a step of implementation of heating means of the window to be wiped; the first detection step is a step of detecting the conditions of frost formation on the outer surface of the pane by detecting the presence of water, in particular rain, dew or mist, on the outer surface of the pane; the pane followed by a comparison of the temperature of the outer surface of the pane with respect to at least a first critical value; the first step of implementing the controlled wiping means of the outer surface according to at least one first wiping cycle is triggered when the temperature of the outer surface of the window is less than or equal to said first critical value and greater than at 0 C; the method includes a second step of detecting frost formation conditions on the outer surface of the pane by comparing the temperature of the outer surface of the pane with respect to a second critical value, lower than said first critical value; and a second step of implementing the controlled wiping means of the outer surface in a second wiping cycle when the temperature of the outer surface of the window is less than or equal to said second critical value; - The second step of implementing the wiped control means is preceded by a step of implementation of heating means of the window to be wiped; the first detection step is a step of detecting the presence of frost formed on the outer surface of the pane; the step of implementing the controlled wiping means of the outer surface according to at least one first wiping cycle, following the detection of the presence of frost, is preceded by a step of implementing means for heating the window to be wiped; The step of detecting the presence of ice is associated with a step of comparing the ambient outside temperature with respect to a low temperature reference value; - The detection step is preceded by at least one step of determining the state of stopping or use of the vehicle; The detection step is preceded by at least one step of evaluating the prior consumption of electrical energy of the wiped control means and / or the controlled means for heating the window used for the prevention of icing or for defrosting according to the process according to the invention; The step of evaluating the consumption is prior to the step of determining the state of stopping or use of the vehicle and subsequent to a step of implementing the controlled means for wiping the outer surface; ; The invention also proposes an installation, in particular for implementing the method according to the invention, for preventing icing of a window, or for automatically deicing said window, in particular the windshield or the rear window, of a motor vehicle comprising controlled means for wiping the window, characterized in that it comprises means for detecting the conditions of frost formation on the outer surface of the window, or for detecting the presence of frost on this outer surface , and a control unit of the implementation of the controlled means for wiping the outer surface according to at least a first wiping cycle, according to the data

  transmitted to it by the detection means.

  According to other features of the installation - the detection means are means for detecting the conditions of formation of frost on the outer surface comprising an ambient outside temperature sensor, a sensor of the temperature of the outer surface of the window and a sensor for measuring the external relative humidity rate for comparing the temperature of the outer surface of the window with respect to the dew point, and for comparing the temperature of the outer surface of the window with respect to the minus a first critical value of the temperature substantially close to 0 C, for example +1 to +3 C; the means for detecting the conditions of formation of ice on the outer surface of the window comprise a sensor for detecting the presence of water, in particular rain, rose or mist, on the outer surface of the window, and sensor of the temperature of the outer surface of the pane for comparison by the control unit of the temperature of the external surface of the pane with respect to at least a first critical value; the detection means are means for detecting the presence of frost formed on the outer surface of the pane; it comprises means for heating the window which are implemented by the control unit prior to implementation

  controlled means for wiping the window to be wiped.

  Other features and advantages of the invention will become apparent

  upon reading the detailed description that will follow for the

  FIG. 1 is a diagrammatic view of a first embodiment of an installation according to the teachings of the invention. FIG. 2 is a flowchart illustrating the main steps of FIG. a method according to the teachings of the invention using the device of Figure 1; FIGS. 3 to 10 are two-by-two views similar to those of FIGS. 1 and 2 which correspond to other exemplary embodiments

of the invention.

  In the following description, elements or steps

  identical, similar or similar will be designated by the same

numbers or reference signs.

  The icing of a window, for example the windshield of a vehicle, or the rear window, is the formation of ice on the outer surface of this window, that is to say the formation of a layer of ice that results from the sudden freezing of supercooled droplets that exist in fogs and clouds whose temperature is negative. The contact of a solid body, such as for example a window pane, ends this state of imbalance, and they form a layer of crystals of

ice very small and shiny.

  The dew point is the temperature Tr for which the water vapor contained in the air, in a given place and at a pressure

  constant atmospheric, becomes saturating.

  The relative humidity RH is the ratio, expressed in hundredths, of the absolute humidity, whatever its expression, to the value

  corresponding which characterizes the saturated air.

  For example, the relative humidity HR can be measured by means of

hygrostat or hygrometer.

  When a motor vehicle is in prolonged parking at a standstill, and particularly in extended parking outside, it is exposed to the formation of frost on its outer skin, and more particularly on the outer faces of its windows, and in particular on its front windshield and on its rear window. Frost formation occurs when climatic conditions (temperature and humidity),

  are conducive to the onset of icing.

  A driver who wishes to use his vehicle in good conditions of safety must take care to remove the frost of the windows, and more particularly of the windshield and the rear window, at least

  in the areas of visibility necessary for driving.

  To do this, he can scrape the glass, or the windows, in order to remove

mechanically frost.

  The aim of the invention is to propose various embodiments of an installation and a method making it possible to prevent the formation of frost, or to defrost, automatically the windows, by

  using vehicle equipment such as, in particular,

  ice cream and window heaters for defrosting.

  According to a first solution illustrated in FIGS. 1 and 2, use is made of an installation and a method in which frost formation is detected by means using measurements of

  temperatures and relative humidity.

  As can be seen in FIG. 1, the installation 10 comprises a central control unit 12 which receives information and

  data from different components and organs.

  Among these there is a sensor 14 for measuring the temperature Ts of the outer surface of the window (not shown), a sensor 16 for the ambient outside temperature Ta, and a sensor 18 for the relative humidity RH. These sensors 14, 16 and 18 transmit their temperature measurement data to the central computing unit and

order 12.

  The central unit 12 also receives a signal from a

  general switch 20 for commissioning the installation 10.

  For its power supply, the central computing and control unit 12 is connected by wires 22 and 24 respectively to the positive pole of the vehicle battery and to the electrical ground thereof. The central unit 12 also receives a + APC signal from the rotary switch for turning on the vehicle when it is actuated. The central unit 12 is able to control the start-up of a wiper device shown schematically in the form of its drive motor 26 via a feed line 28 and receives from motor 26, via a

  line 30 signals representative of the position of the motor 26, that is to say

  tell the wiper blade (s).

  For example, in the case of a motor vehicle in which a cabin calculator completely controls the operation of the wiper motor 26, in particular according to control commands sent to it by the driver by means of an organ manual control, such as a commodo (not shown) and possibly by a rain sensor of known design, the function of prevention of icing is achieved by associating with this calculator the sensors shown in Figure 11, the necessary interfaces (amplifiers and analog-to-digital converters) for these sensors, and an additional programming software module for processing the data and the information provided by the sensors and developing the control commands, in particular for operating the windscreen wipers, in application of the method according to the invention. The analog-digital conversion of the data provided by the sensors may be

  integrated into the central microcontroller of the computer.

  The control of the wiper motor 26 may be in a conventional all-or-nothing form, the motor 26 then having a high speed control terminal and a low speed control terminal. According to another embodiment, the control of the speed of rotation of the wiper motor 26 may be of the variable type continuously

  with a single motor control terminal.

  According to another possibility of electrical architecture, the wiping means can be controlled by an electronic module dedicated to this application comprising a data link with the electronic vehicle cockpit computer to receive the orders of

  classic manual wiper control provided by the commodo.

  In this case, the sensors illustrated in FIG. 1 are connected to this dedicated wiping module, which then comprises the additional means for processing the data and the information provided by the sensors, and for making decisions and developing order commands. dedicated to the function of prevention of icing or deicing, these means being

  realized in the form of structural and / or software means.

  Referring to the schematic representation of FIG. 1, it will be noted that the control or control unit 12 and the wiper motor 26 are powered directly by the positive pole of the vehicle battery without going through by the general contact of the vehicle. Means, not shown in detail, for controlling the electrical energy consumed are included in the installation, so as to avoid a complete inadvertent discharge of the battery resulting from the implementation of the invention. These control means comprise means of protection against blocking of the motor 26 as well as an energy consumption counter which can for example be estimated approximately by counting the number of wiping cycles carried out, in application of the of the invention, since the

last stop of the vehicle.

  If a maximum permissible energy consumption is exceeded, or if a number of wiping cycles are exceeded, such as for example one hundred cycles, the installation is inhibited until the next use of the vehicle which is identified. by the central control unit 12 thanks to the signal + APC which is transmitted to it when setting

  in operation again of the vehicle by establishment of the general contact.

  In order for the system to be active as long as possible, a wiping sequence for preventing icing or defrosting is only allowed after a given minimum time following a previous sequence, for example order of fifteen minutes. According to one variant, a shorter inhibition time interval can be used during the first fifteen hours of use of the installation, and then an inhibition time interval + long thereafter, which corresponds to an optimization of the use of the installation and the method according to the teachings of the invention for a vehicle used on a daily basis. Moreover, the installation and the method according to the invention are put into service only after a voluntary and positive command order from the user who

  this is done on switch 20.

  The installation shown for example in FIG. 1 can be used, with its control and control logic, to control

  simultaneously defrosting the windshield and the rear window.

  The same installation can be used, by adding an additional sensor (not shown) for measuring the temperature of the outer surface of the rear window, in order to differentiate the decisions and the wiping orders of the windshield and the rear window. respectively, thus increasing the overall efficiency of the installation

  and the method according to the teachings of the invention.

  We will now describe the first example of a process according to

  The invention with reference to the algorithm of FIG.

  After a first step E1 commissioning of the installation by means of the switch 20, and an initialization step E2, a first test step E3 is performed to determine, indirectly, whether the vehicle is stopped or in the process of driving thanks to the signal + APC. If the vehicle is not stopped, the procedure is

repeated in the test step E3.

  If the vehicle is stationary, a first measurement step E4 is then carried out, using the sensors 16 and 18, the

  ambient outside temperature Ta and the relative humidity RH.

  The central unit 12 then calculates the dew point

Tr in the next step E5.

  The central unit 12 also continuously receives, from the sensor 14, the measurement of the temperature Ts of the outer surface of the window, for example the windshield, which enables it, during the next step E6, to determine whether it there is misting or dew on the windshield,

that is, if Ts <Tr.

  If this is not the case, the central unit 12 proceeds to a

  new iteration of the steps E3 to E6.

  If Ts <Tr, the central unit 12 then proceeds to a new test step E7 in which it compares the value of the temperature Ts of the outer surface of the window to 0 C and a value

critical thresholdTcl.

  If the relation 0 C <Ts <Tcl is not verified, the central unit 12

  proceed to the E7 test step again.

  On the other hand, if the temperature Ts of the outer surface of the window has successively crossed, downwards, the two threshold values Tr then Tcl, the latter being close to 0 C and for example equal to

  1 C, there is an imminent risk of icing of the glass.

  During a step E8, control unit 12 acts on the wiper motor 26 to cause a first wiping sequence of the window, which may comprise several consecutive cycles of

  alternating scanning of the window or windows equipped with a wiper.

  Control unit 12 then proceeds to a step E9 of testing the consumption of electrical energy resulting from the implementation

of the invention.

  If an authorized and determined threshold of electric power consumption is reached, the control unit 12 terminates the process of

prevention of defrosting.

  On the contrary, at the end of step E9, if the authorized threshold has not been reached, the central control unit 12 repeats the process by proceeding to the test step E3 again, after a step of

time delay E10.

  By comparing the installation illustrated in FIG. 3 with that of FIG. 2, it can be seen that the second solution for preventing icing according to the invention comprises, in the installation 10, a relay 34 for controlling the electric power supply of the means for heating the window such as, for example, a network of heating wires incorporated in the window

  or means for blowing hot air on the window.

  The control of the start of these heating means, and therefore of the relay 34, is provided by the central control unit 12 at the

average of a line 32.

  As seen in FIG. 4, the process implemented by the control unit 12 is analogous, until step E8, to that described

  previously with reference to Figure 2.

  A hysteresis can be used which makes it possible to avoid repeating the first wiping step E8 when the temperature Ts oscillates around the first threshold critical value Tcl which is for example equal to

1 C.

  Step E8 is followed by a second test step E7bis during which the temperature Ts of the outer surface of the window pane is compared with a second critical value of threshold Tc2 which is lower

  at the first threshold critical value Tcl.

  As long as the second critical threshold value Tc2 is not crossed by the temperature Ts, the central unit 12 repeats

the test step E7bis.

  On the other hand, as soon as this second critical value Tc2 is crossed down by the external temperature Ts of the window, the central unit 12 triggers a step Ech heating the window which is immediately followed by a new step E8bis of wiping at

new window.

  The heating step Ech is delayed according to a determined duration, for example of the order of 10 minutes, depending on the heating power used, which is sufficient to guarantee that the

  Frost layer is melted for sure.

  The second step of scanning wiping E8bis may well

  heard have several cycles of alternating scanning.

  A hysteresis can be used which avoids repeating the second wiping step E8 when the temperature Ts oscillates around

  the second threshold critical value Tc2.

  The estimate of the electrical energy consumption carried out

  during step E9 can be carried out according to different modalities, that is

  for example, by counting the scanning cycles performed,

  as well as the cumulative heating time of the windshield.

  With regard to the third solution illustrated in FIGS. 5 and 6, the detection of the conditions of possible frost formation is carried out by means of a known sensor 34 for detecting the presence of water, on the outer surface of the pane, such as for example from the

rain, mist or dew.

  In the process implemented by the control unit 12, the test step E6 then aims to determine whether the sensor 36 has detected or not the presence of water on the windshield, this step being repeated both

  that the sensor has not detected such a presence of water.

  In case of presence of water, the central control unit 12 then proceeds to the step E7 for comparing the temperature Ts by

  relative to the first threshold critical value Tcl and relative to 0 C.

  The delay used in the first solution is no longer necessary because the wiping is triggered only when a

  a definite amount of water was deposited on the glass.

  If the temperature Ts of the outer surface of the window is maintained between OC and Tcl, the wipers are again actuated as the presence of a moisture deposit is detected by the sensor 36. The sensor 36 is either a external mist and dew sensor specially designed for this purpose, ie an existing rain sensor, for example for the automatic control of the windscreen wipers of the vehicle, the functions of which are extended to the detection of slow deposits or

  low humidity such as dew or mist.

  The fourth solution illustrated in FIGS. 7 and 8 is analogous to the preceding one by making use of means 34, similar to those described and shown in FIG. 3, for triggering a step Ech for heating the window sandwiched between the first wiping step E8 and the second wiping step E8bis after a second step E7bis for comparing the temperature Ts of the outer surface of the window with a second threshold critical value

Central section2.

  The joint use of heating and wiping of the

  breeze increases the effectiveness of the invention by ensuring the complete elimination of any trace of frost that could have formed despite

  the preventive wiping of step E8.

  Moreover, by using a comparison with a second threshold value Tc2, the quality of the result is independent of

  the homogeneity of the temperature Ts of the outer surface of the pane.

  The fifth solution illustrated in FIGS. 8 and 9 is structurally and functionally similar to the previous solution, but here it is resorted to a detection of the ice formed on the glass by means of

  a sensor 38 of the presence of frost on the glass.

  The sensor 38 may be a device that is also used for the detection of rain in order to automate the wiping of windows during normal use of the vehicle and which is also capable of detecting

and to distinguish the frost.

  The sensor 38 is preferably placed inside the passenger compartment

of the vehicle.

  As can be seen in FIG. 10, as soon as frost is detected in step E6, a glass heating step Ech is triggered for a duration of about ten minutes, which is followed by a step E8 of wiping to remove the water resulting from the melting of

  frost during the heating operation.

  A variant, not shown, of this fifth solution consists in associating with the control unit 12 with an additional sensor of the ambient outside temperature Ta which allows a dual detection, with the sensor 38, of the presence of frost and the existence of a low outside temperature, in order to overcome the

  risk of false detection of frost.

Claims (21)

  1. A method for preventing icing of a window of a motor vehicle, or automatic defrosting of the window, in particular the windshield or the rear window, which is associated with at least one controlled means (26) for wiping the vehicle window; its outer surface, characterized in that it comprises: at least a first step (E6, E7) for detecting the conditions of frost formation on the outer surface of the pane, or for detecting the presence of frost on this outer surface ; and at least a first step (E8) of implementation of the controlled means (26) for wiping the outer surface according to at least one first wiping cycle according to the results of the   first detection step (E6, E7).   2. Method according to the preceding claim, characterized in that the first detecting step is a step of detecting the conditions of frost formation on the outer surface of the pane by comparison (E6) of the temperature of the outer surface (Ts) of the window with respect to the dew point (Tr), followed by a comparison (E7) of the temperature of the external surface (Ts) of the window with respect to   minus a first critical value (Tcl).   3. Method according to the preceding claim, characterized in that the dew point (Tr) is calculated, (E5) prior to the comparison (E7) of the temperature of the outer surface (Ts) of the window relative to the point of dew (Tr), depending on the temperature   Ambient (Ta) and Outdoor Relative Humidity (RH).   4. Method according to one of claims 2 or 3, characterized in   in that the first step (E8) of operating the controlled means (26) for wiping the outer surface according to at least one first wiping cycle is triggered when the temperature of the outer surface (Ts) of the window is less than or equal to the first   critical value (Tcl) and greater than 0 C.   5. Method according to any one of claims 2 to 4,   characterized in that it comprises - a second step (E7bis) for detecting frost formation conditions on the outer surface of the pane by comparing the temperature of the external surface (Ts) of the pane with respect to a second value critical (Tc2), less than said first critical value (Tcl); and a second step (E8a) of implementing the controlled means (26) for wiping the outer surface according to a second wiping cycle when the temperature of the outer surface (Ts) of the   window is less than or equal to said second critical value (Tc2).   6. Method according to the preceding claim, characterized in that the second step (E8bis) of implementation of the controlled means (26) for wiping is preceded by a step (Ech) of setting   implementing means (32, 34) for heating the window to be wiped.   7. Method according to claim 1, characterized in that the first detection step is a step of detecting the conditions of frost formation on the outer surface of the pane by detecting (E6) the presence of water, in particular rain, dew or mist on the outer surface of the window followed by a comparison (E7) of the temperature of the external surface (Ts) of the window with respect to at least a first critical value (Tcl) of the outside temperature ambient (Ta).   8. Method according to the preceding claim, characterized in that the first step (E8) of implementation of the controlled means (26) for wiping the outer surface in at least a first wiping cycle is triggered when the temperature of the outer surface (Ts) of the window is less than or equal to said first value   critical (Tcl) and greater than 0 C.   9. Method according to one of claims 7 or 8, characterized in   it comprises: - a second step (E7bis) for detecting the conditions of frost formation on the outer surface of the pane by comparing the temperature of the external surface (Ts) of the pane with respect to a second critical value (Tc2), lower than said first critical value (Tcl), of the ambient outside temperature (Ta); and a second step (E8a) of implementing the controlled means for wiping the outer surface according to a second wiping cycle when the temperature of the outer surface (Ts) of the   window is less than or equal to said second critical value (Tc2).   10. Method according to the preceding claim, characterized in that the second step (E8bis) of implementation of the controlled wiping means is preceded by a step (Ech) of implementation.   use of heating means of the window to be wiped.   11. The method of claim 1, characterized in that the first detection step is a step (E6) for detecting the   presence of frost formed on the outer surface of the glass.   12. Method according to the preceding claim, characterized in that the step (E8) of implementation of the controlled means (26) for wiping the outer surface according to at least a first wiping cycle, subsequent to the detection of the presence of ice, is preceded by a step (Ech) of implementation of means of heating the glass to be wiped.   13. Method according to one of claims 11 or 12, characterized   in that the step (E6) for detecting the presence of ice is associated with a step of comparing the ambient outside temperature by   compared to a low temperature reference value.   14. Process according to any one of the claims   preceding, characterized in that the detecting step is preceded by at least one step (E3) of determining the stopping state or of use of the vehicle.   15. Process according to any one of the claims   preceding, characterized in that the detection step is preceded by at least one step (E9) for evaluating the prior consumption of electrical energy of the wiped control means (26) and / or the controlled means (32, 34 ) for heating the window used for the prevention of icing or for defrosting according to the method according to the invention. 16. The method of claim 15 taken in combination with claim 14, characterized in that the step (E9) of consumption evaluation is prior to the step (E3) of determining the state of stop or of use of the vehicle and after a step (E8, E8bis) of implementation of the controlled means (26) for wiping the vehicle. outer surface.   17. Installation for preventing icing of a window, or for automatically de-icing this window, in particular the windshield or the rear window, of a motor vehicle having controlled means for wiping the window, characterized in that it comprises means (14, 16, 18, 36, 38) for detecting the conditions of frost formation on the outer surface of the window, or for detecting the presence of frost on this outer surface, and a unit (12) controlling the implementation of the controlled means (26) for wiping the outer surface according to at least one first wiping cycle, according to the data transmitted to it by the   detection means (14, 16, 18, 36, 38).   18. Installation according to the preceding claim, characterized in that the detection means are means for detecting the conditions of formation of frost on the outer surface comprising a sensor (16) for measuring the ambient outside temperature (Ta), a sensor (14) for measuring the temperature of the outer surface (Ts) of the window and a sensor (18) for measuring the external relative humidity (RH) for comparing the temperature of the outer surface (Ts) of the window relative to the dew point (Tr), and for comparing the temperature of the external surface (Ts) of the window with respect to at least a first critical value (Tcl), by the unit of control (12).   19. Installation according to claim 17, characterized in that the means for detecting frost formation conditions on the outer surface of the window comprise a sensor (36) for detecting the presence of water, including rain, dew or misting, on the outer surface of the window, a sensor (14) of the temperature (Ts) of the outer surface of the window, and a sensor (16) for measuring the ambient outside temperature (Ta) for comparison of the the temperature of the outer surface (Ts) of the window with respect to at least   a first critical value (Tcl), by the control unit (12).   20. Installation according to claim 17, characterized in that the detection means are means (38) for detecting the presence of frost formed on the outer surface of the pane.   21. Installation according to any one of the claims of   Claims 17 to 20. characterized in that it comprises means   (32, 34) for heating the window which are implemented by the control unit (12) prior to implementation of the means   controlled (26) wiping the window to be wiped.