FR2764258A1 - DEVICE FOR HEATING A GLASS, PARTICULARLY A GLASS OF A MOTOR VEHICLE - Google Patents

Abstract

Device for optimizing the connection and cut-off of a window heater, in particular for a motor vehicle. The device comprises a heating installation (10) which is controlled as a function of the wetting of the window, the wetting being detected at least by a humidity sensor (18, 22).

Description

I State of the art: The present invention relates to a device for

  heat a window, in particular a window of a motor vehicle

  bile comprising a heating installation intended to heat the glass, in particular resistant heating wires

as well as a control device.

  Heating systems are already known

  for windshields or rear windows of a motor vehicle

  bile allowing, in the event of a layer being deposited on the glass, for example a layer of ice or condensate, to release

  the glass by heating it. The heating installation

  carries a resistance heating wire arranged according to the

  form a loop on the glass and this wire gives off heat.

  their when it is crossed by current. The installation of

  heater is manually connected by the vehicle conductor

  hicle. Cutting is also done manually or manually.

timed by a clock.

  The disadvantage of this solution is that the branch

  The heating installation is not paid on time, when the deposit is formed, because the driver

  only perceives the deposit when its visibility is already limited

which poses a risk.

  Another disadvantage is that the cut is made

  belatedly, because once visibility has been restored,

  tor forgets to turn off the heating system or the clock keeps the system connected regardless of

  the condition of the glass. This translates into low consumption

  useful current which charges the battery and wears the resistance wire

  both, heating Advantages of the invention: The present invention aims to remedy these drawbacks and for this purpose relates to a device of the type defined above characterized in that the device comprises at least one humidity sensor which detects the wetting of this window or of another window in an area to be heated and which, depending on the wetting, transmits a sensor signal to the control and the heating installation is controlled and in particular switched on and off, depending

  of the sensor signal, by the control device.

  The device according to the invention makes it possible to optimize

  ser the start and stop of the window heating since the heating installation is controlled as a function

wetting of the glass.

  It is particularly advantageous that the provision

  sitive includes at least one humidity sensor detecting the wetting of the outside and / or the inside

  of a window. The sensors for this can be used for this.

  already fitted to the vehicle at the windshield, to detect humidity and thus control the heating installation. In addition, another humidity sensor can be used to detect condensation on the inside of the glass. This humidity sensor can also be used alone. It is advantageous that this other sensor

  humidity cooperates with part of the resistant wire already pre-

  seen on or built into the glass.

  As a variant, it is advantageous to use a single humidity sensor which, by virtue of its construction and its operating principle, is able to detect a deposit

  on the outside and inside of the glass.

  According to other advantageous features of the invention:

  - the humidity sensor detects wetting on the outside

  laughing and / or on the inside of this window or / and of another window, - the humidity sensor is an optical humidity sensor for measuring the wetting on the outside, - the humidity sensor is a resistive or capacitive humidity to measure the wetting on the inside of the glass, - the humidity sensor is formed by part of the resistant heating wires of the heating installation, the heating installation includes a heating fan. Drawings: An exemplary embodiment of the invention is shown in the drawings and will be described below in more detail.5 Thus:

  - Figure 1 shows a simplified block diagram of a dis-

  positive according to the invention, - Figure 2 shows a heating installation according

  the invention equipped with a blowing machine.

  Description of the exemplary embodiments:

  FIG. 1 shows a device for heating a window not shown, using a heating installation 10 controlled by control signals 14 supplied by a control device 12. The control device 12 receives first signals 16 of a first humidity sensor 18, second signals 20 of a second humidity sensor 22 as well as switching signals 26 of a

control button 24.

  The first humidity sensor 18 is for example an optical humidity sensor placed on the inside of a window to detect a deposit (coating) corresponding to rain, fog, frost or fouling on the outside of the window in the wiping area of a wiper blade. Usually, as indicated by dashed lines, the signals 16 from the first humidity sensor 18 are applied to a control installation.

  wiper blades, known per se, for controlling auto-

  matically the wiper blades (see document DE-

19 485 Al).

  The emitter radiation, of known intensity, coupled into the glass by the optical humidity sensor 18 is

  totally reflected from the outside and the inside

  of the glass along a measuring field of the sensor 18

  to be decoupled at a certain point on the glass and back

  worm in a receiver. When the glass is wet, the local refractive index of the glass changes, so that the radiation is already partially decoupled along the path

  of measurement. The residual light intensity received by the

  sensor thus represents a measure of the degree of wetting of

the window.

  To correctly control, on request, the heating installation 10 of the rear window, it is necessary to detect the ice deposited on the outside of the rear window to be heated. In the case of an optical humidity sensor 18, a layer of frost on the measurement path of the glass corresponds to a decoupling practically

  total radiation and thus to the sending of a signal of cap-

  tor 16 practically nil. Due to the sensor signal 16 thus received, the control device 12 activates

  the heating installation 10 by the control signal 14.

  When the layer of frost has disappeared, the sensor signal 16 increases and the control device 12 switches off the installation

  heating 10. The connection and disconnection thresholds ne-

  for this purpose are registered and predetermined in

the control system 12.

  If rain or fog is detected on

  the outer face of the rear window by the first cap-

  humidity sensor 18, i.e. in the event of a sensor signal which does not cancel out, the heating installation 10 is not

  necessarily start up, because the only heating of the life

  tre only removes this coating very slowly

  of water. If however at the same time the wiper control

  glass starts the wipers preferably depending on the humidity, the heating installation 10 is also

getting started.

  The second humidity sensor 22 detects a deposit

  on the inner side of the rear window, frequently pro-

  evoked by the condensation of humidity on the rear window

  laugh. The condensate is then detected in a known manner by optical, capacitive or resistive humidity sensors,

  for example according to documents DE-37 22 510 Ai or DE-

  39 30 732 Al. The second humidity-dependent sensor signals 20 are used in the control device 12 and produce the heating of the rear window heater 10 as soon as a deposit on the side is detected.

  interior of the rear window; this device also cuts

  the heater 10 when the window is again dry. The second humidity sensor 22 is for example a resistance humidity sensor 22; it presents two conductive paths, facing each other, set to different potentials; these conductive paths are integrated into the glass

  to come to the surface from the inside of the glass. The life-

  be functioning as an isolator. When the glass is

  wet, the insulator is short-circuited and the resistance oh-

  humidity sensor 22 decreases. The second sensor signal 20 applied to the control 12 therefore provides

  humidity-dependent resistance measurement.

  A resistant humidity sensor 22 is preferably used, if the heating installation 10 comprises a resistant wire 28 and if the latter is arranged in the form of a loop on the surface of the glass. The earth side of the wire

  resistant heater 28 thus cooperates at the same time as a

  min of earthing of the resistive humidity sensor 22 (this is indicated in FIG. 1 by broken lines) as active connection 30. This is arranged in a loop form at a predetermined distance from the second path

  conductor 32 of the humidity sensor 22 for resistance

  tance to be measured, depending on the humidity between the path

  conductor 32 and the resistant heating wire 28.

  It is also possible to use a capacitive humidity sensor 22 in the active connection 30 with the resistive heating wires 28 of the heating device 10 making it possible, by measuring the capacity between the wires and the variation in capacity, to detect humidity of the glass and control, according to this, the installation of

heating 10.

  According to an alternative embodiment, the first humidity sensor 18 and / or the second humidity sensor 22 are placed on the windshield to control the installation for heating the windshield by depositing it on the outside.

  and / or the inner side of the windshield.

  According to another exemplary embodiment, the first

  humidity sensor 18 is placed on the windshield. At the

  detection of a layer of frost on the windshield, the heating installation 10 of the rear window is connected, because

  then also, for example due to a deposit of noxious frost

  windshield or freezing rain, there is a layer of ice on the rear window. The first humidity sensor 18 includes a heating means for heating a measuring range, so in this area of the front window, the ice has disappeared

  and thus indirectly allows by the first signal of cap-

  teur 16, to determine the clearance of the rear window

  by command 12. Command 12 provides a branch point

  switching on and off the heating installation 10 as a function of the first sensor signal 16, to take into account a different heating power from the heating installation 10 and the heating of the sensor 18 as a function of the different defrosting time thus resulting for the

  ice. The second humidity sensor 22 is suppressed or functions

  operates independently of the first humidity sensor 18 as described above for detecting the humidity of the windshield or of the rear window. According to another exemplary embodiment, only a humidity sensor 18 is used for detect humidity on the outside and inside of a window. An optical humidity sensor, according to document AZ-196 08 648,

  is particularly suitable for this; according to the cons-

  truction, it is possible to decouple both the radiation from the outside and the wetting of the inside of the glass and thus use the outside and the inside of the glass as measurement paths. When heating the glass, care must be taken that the heating device 10 or the heating resistant wire 28 does not interfere in a disturbing manner

  the optical properties of the measurement path.

  There is also a switch 24 for ac-

  manually operating the heating installation 10 and whose switching signals 26 are supplied to the control device 12. The switch 24 is provided for switching on and off the heating installation 10, to allow manual connection of the heating installation 10 in the event of partial icing of the glass and which would not be detected by the humidity sensors 18, 22. The inputs of the humidity sensors 18, 22 and of the switch 24 are combined in the control device 12 by an OR logic gate. As a variant, the control is performed so that the switch 24 is used to connect or cut the entire device.

  It is moreover possible that depending on the dimensions

  according to sensor signals 16, 20 supplied by humidity sensors 18, 22, the power of the installation is activated

  heating 10, in stages, by the control 12.

  In the embodiment of FIG. 2, a heating fan 10 is used as the heating device 10.

  heating 34 controlled by control 12 depending on the

  general of sensors 16, 20 of one or more humidity sensors 18, 22 and of an operating switch 24 such as

  those already described above using the example of realization

tion of Figure 1.

  The device according to the invention is also suitable for

  to clear other windows such as, for example,

  motor vehicles, side windows of coaches or buses or railways, windows of

  pond room, greenhouse glass or zoological gardens

ques.

Claims (4)

R E V E N D I C A T I ONS S   1) Device for heating a window, in particular a window   of a motor vehicle comprising a heating installation   fage (10) for heating the glass, in particular resistant heating wires (28) and a control device (12), characterized in that the device comprises at least one humidity sensor (18, 22) which detects the wetting of this window or of another window in an area to be heated which, depending on the   wetting, transmits a sensor signal (16, 20) to the   control (12) and the heating installation (12) is controlled and in particular switched on and off, depending on the signal   sensor (16, 20), by the control device (12).   2) Device according to claim 1, characterized in that the humidity sensor (18, 22) detects wetting on the outside and / or on the inside of this window or / and of a other window.   3) Device according to claim 2, characterized in that the humidity sensor (18) is an optical humidity sensor   to measure the wetting on the outside.   4) Device according to claim 2, characterized in that the humidity sensor (22) is a resistive or capacitive humidity sensor for measuring the wetting on the inside of the window.    ) Device according to claim 4, characterized in that the humidity sensor (22) is formed by a part of the resistant heating wires (28) of the heating installation (10). 6) Device according to claim 1, characterized in that the heating installation (10) comprises a heating fan (34) .5