Patent Publication Number: US-10323818-B2

Title: Vehicle light assembly having moisture sensing and heating

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to vehicle lighting, and more particularly relates to vehicle lighting assemblies that sense and reduce moisture. 
     BACKGROUND OF THE INVENTION 
     Automotive vehicles are commonly equipped with various exterior lighting assemblies including vehicle headlights at the front of the vehicle and taillights at the rear of the vehicle. Vehicle exterior lighting assemblies typically include a light source disposed within a housing having an outer lens. Some assemblies experience moisture buildup on the inside of the lens. In addition, moisture in the form of snow and ice may accumulate on the outside of the lens in cold weather conditions. It is generally known to provide defogger elements on the lens to evaporate the moisture that may be present on the lens. It may be desirable to provide for an enhanced lighting assembly that effectively senses moisture and reduces the moistures buildup on the lens. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, a vehicle light assembly is provided. The vehicle light assembly includes a light source, a lens in front of the light source, and conductive circuitry provided on the lens and forming a capacitive sensor for sensing moisture on the lens and a heater for removing the moisture. 
     Embodiments of the first aspect of the invention can include any one or a combination of the following features:
         the conductive circuitry forming the capacitive sensor also serves as the heater;   the light assembly includes switching circuitry for selectively switching operation of the conductive circuitry between the capacitive sensor and the heater;   the light assembly includes a controller for controlling the switching circuitry to switch operation of the conductive circuitry between the capacitive sensor and the heater;   the light assembly forms a vehicle headlight;   the light assembly forms a vehicle rear taillight;   the conductive circuitry comprises an optically transparent conductive material;   the visually transparent conductive medium comprises indium tin oxide;   the capacitive sensor comprises a first electrode comprising a first plurality of electrode fingers and a second electrode comprising a second plurality of electrode fingers, and wherein the first plurality of conductive fingers are interdigitated with the second plurality of conductive fingers;   the heater operates as a resistive heater that generates heat based on electric current; and   the conductive circuitry comprises at least one electrode that generates a capacitive signal for the capacitive sensor and generates heat for the heater.       

     According to another aspect of the present invention, a vehicle light assembly is provided. The vehicle light assembly includes a light source, a lens in front of the light source, and conductive circuitry provided on the lens and forming a capacitive sensor having at least one electrode for sensing moisture on the lens and a heater for removing the moisture. The vehicle light assembly also includes switching circuitry for selectively energizing one of the capacitive sensor and the heater. 
     Embodiments of the second aspect of the invention can include any one or a combination of the following features:
         the light assembly includes a controller for controlling the switching to switch between the capacitive sensor and the heater;   the light assembly forms a vehicle headlight;   the light assembly forms a vehicle rear taillight;   the conductive circuitry comprises an optically transparent conductive material;   the capacitive sensor comprises a first electrode comprising a first plurality of electrode fingers and a second electrode comprising a second plurality of electrode fingers, wherein the first plurality of conductive fingers are interdigitated with the second plurality of conductive fingers;   the heater operates as a resistive heater that generates heat based on electric current; and   the at least one electrode forms the capacitive sensor and the heater.       

     According to yet another aspect of the present invention, a vehicle light assembly is provided. The vehicle light assembly includes a light source, a lens in front of the light source, and conductive circuitry provided on the lens and forming a capacitive sensor for sensing moisture on the lens and a heater for removing the moisture, wherein the conductive circuitry has at least one electrode that generates a capacitive signal in a sensing operation and generates heat in a heater operation. The vehicle light assembly also includes switching circuitry for selectively energizing one of the capacitive sensor and the heater. 
     These and other aspects, objects, and features of the present invention will be understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a front perspective view of a vehicle equipped with vehicle headlight assemblies having moisture sensing and removal, according to one embodiment; 
         FIG. 1A  is a rear perspective view of the vehicle having vehicle taillight assemblies that may include the moisture sensing and removal; 
         FIG. 2  is a cross-sectional view of one of the headlight assemblies taken through line II-II of  FIG. 1 ; 
         FIG. 3  is a schematic diagram of conductive circuitry formed on the lens for forming a capacitive sensor and heater and a control circuitry therefor; 
         FIG. 4  is an exploded view of the conductive circuitry shown in  FIG. 3 ; 
         FIG. 5  is a cross-sectional view taken through line V-V of  FIG. 3 ; 
         FIG. 5A  is a cross-sectional view taken through line VA-VA of  FIG. 3 ; 
         FIG. 6  is a block diagram illustrating controls for controlling the switching of the conductive circuitry; 
         FIG. 7  is a graph illustrating signals generated by the capacitive sensor indicative of moisture on the lens; and 
         FIG. 8  is a flow diagram illustrating a routine for controlling the switching between the capacitive sensor and heater, according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For purposes of description herein, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the invention as oriented in  FIG. 1 . However, it is to be understood that the invention may assume various alternative orientations, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. 
     Referring to  FIGS. 1-1A , a wheeled motor vehicle  10  is generally illustrated having moisture sensing and removal circuitry provided in the vehicle exterior light assemblies. The vehicle  10  is shown having a pair of vehicle headlight assemblies  20  located at the front left and right corners of the vehicle  10  for providing headlight illumination forward of the vehicle  10 . The vehicle  10  is also shown having a pair of vehicle taillight assemblies  20 A located at the rear left and right corners of the vehicle  10  for providing taillight illumination generally rearward of the vehicle. Each of the headlamp assemblies  20  and taillight assemblies  20 A may be configured to include conductive circuitry that provides moisture sensing and removal of the moisture from the respective lighting assemblies. It should be appreciated that while each of the headlight assemblies  20  shown and described herein in detail has the conductive circuitry, the taillight assemblies  20 A may likewise be configured to include the conductive circuitry for sensing and removing moisture. 
     Referring to  FIG. 2 , the vehicle headlight assembly  20  is shown having a housing  22  and an outer lens  24  connected to housing  22 . Housing  22  is generally fixed to the vehicle body in a conventional manner. Disposed within the housing  22  and outer lens  24  is a light source  26 , a reflector  28 , and an inner lens  30 . The light source  26  may include one or more light emitting diodes (LEDs), incandescent bulbs, halogen bulbs, or other sources of light illumination. The reflector  28  is generally positioned to reflect light output from the light source forward of the vehicle through the inner lens  30  and outer lens  24  to illuminate the roadway generally forward of the vehicle  10 . The inner lens  30  and outer lens  24  may be made of a clear light transmissive polymeric material. The light assembly  20  may be configured as a low beam light assembly, a high beam light assembly, or a combination of low and high light beams assemblies. Additionally, the housing  22  and outer lens  24  may contain a plurality of light sources for multiple functions, such as headlight illumination, daylight running lamps, turn signals, flashers, and other lighting functions. 
     The vehicle light assembly  20  includes conductive circuitry  40  provided on the outer lens  24  for providing a capacitive sensor for moisture sensing and a heater for heating or defrost operations. The conductive circuitry  40  forms both a capacitive sensor for sensing moisture on the lens and a heater for removing the moisture. In the embodiment shown, the conductive circuitry  40  is formed on the inside surface of the outer lens  24 . However, it should be appreciated that the conductive circuitry  40  may otherwise be formed on the outside surface of the outer lens  24  or in an intermediate layer of the outer lens  24 , according to other embodiments. 
     The conductive circuitry  40  and control circuitry for controlling the conductive circuitry  40  is illustrated in  FIGS. 3-5A . The conductive circuitry  40  is made up of an electrically conductive material that allows electrical current and signals to be transmit thereon. The conductive circuitry  40  includes a first electrode  42  having a first plurality of electrode fingers  48  shown extending between the conductive lines  44  and  46 . The conductive circuitry  40  also includes a second electrode  50  having a second plurality of electrode fingers  52  that are electrically isolated or dielectrically isolated from the first plurality of electrode fingers  48 . The first and second plurality of electrode fingers  48  and  52  are interdigitated so as to form a capacitive coupling therebetween when configured as a capacitive sensor. A dielectric layer  54  is disposed between electrode fingers  52  and connecting line  46  to allow the signal lines to cross over without making electrical connections. As such, the second electrode  50  and corresponding electrode fingers  52  are dielectrically isolated from connecting line  46  and the first electrode  42  and corresponding electrode fingers  48 . 
     Switching circuitry including a plurality of switches, shown as first switch SW 1 , second switch SW 2 , third switch SW 3 , and fourth switch SW 4  are illustrated connected to the conductive circuitry  40  to control switching of the conductive circuitry  40  between the capacitive sensor and heater operations. Each of the switches SW 1 -SW 4  may be controlled by control circuitry including a microprocessor  62  as shown. The first switch SW 1  connects the first electrode  42  via connecting line  44  to a defrost voltage source shown as V D . The fourth switch SW 4  is shown connecting the first electrode  42  via the connecting line  46  to ground. As such, when the first switch SW 1  and fourth switch SW 4  are in the closed positions for the heater operation, the defroster voltage V O  is applied across the first electrode  42  from the first connecting line  44  across fingers  48  to the second connecting line  46  and to ground to cause electric current to flow therethrough and generate heat across the first electrode  42  to operate as a heater to defrost or defog the outer lens  24 . At the same time, switches SW 2  and SW 3  are in the open position during the heater/defogger or defrost operation. It should be appreciated that electrical current passing through the first electrode  42  generates heat due to the electrical resistance of the circuit which forms a resistive heater for removing moisture from the outer lens  24 . Moisture may be in the form of humidity which is water vapor in the air, or may be in the form of condensation which is water on a surface which can be in the form of liquid water or frozen water (e.g., ice or frost). 
     The conductive circuitry  40  may also be configured to operate in a sensing operation as a capacitive sensor to sense moisture on the outer lens  24  such as condensation on the inside or outside of the outer lens  24  or snow or ice on the outside of the outer lens  24 . When moisture is sensed on the outer lens  24 , the conductive circuitry  40  may be switched to the heater configuration to remove the sensed moisture. In order to operate as a capacitive sensor, the conductive circuitry  40  is controlled by opening the first switch SW 1  and the fourth switch SW 4  and closing the second switch SW 2  and the third switch SW 3 . With the first and fourth switches SW 1  and SW 4  open, electrical power from the defrost voltage is removed and with the second and third switches SW 2  and SW 3  closed, the microprocessor  60  is able to control drive and receive signals to and from the first and second electrodes  42  and  50  so as to generate a capacitive activation field for sensing moisture on the outer lens  24 . The capacitive sensor is configured to sense moisture, such as condensation on the interior surface of the outer lens  24  and humidity proximate to the interior surface of the lens  24  and water vapor on the outside of the lens  24  such as in the form of liquid or ice. The moisture is sensed by a change in the signal generated by the proximity sensor due to the moisture content in the air on the surface of the outer lens  24 . When moisture is detected, the conductive circuitry may be switched to the heater operation to remove the moisture. It should be appreciated that the housing  22  or lens  24  may have a moisture outlet such as a Gore-Tex® patch to allow heated moisture to exit the interior. 
     The capacitive sensor employs the first electrode  42  as a drive electrode and the second electrode  50  as a receive electrode, each having interdigitated fingers  48  and  52 , respectively, for generating a capacitive field. According to one embodiment, the first electrode  42  receives square wave drive signal pulses applied at a voltage. The second electrode  50  has an output for generating an output voltage. It should be appreciated that the first and second electrodes  42  and  50  and corresponding electrode fingers  48  and  52  may be arranged in various configurations for generating the capacitive fields as the sense activation fields, according to various embodiments. It should also be appreciated that the first and second electrodes  42  and  50  may otherwise be configured so that other types of single electrode sensors or other multiple electrode sensors may be used. The conductive circuitry  40  may be formed with conductive ink or may be alternatively be formed with rigid or flexible circuitry that may be adhered or otherwise attached to the outer lens  24 . 
     According to one embodiment, the first electrode  42  is supplied with an input voltage as square wave signal pulses having a charge pulse cycle sufficient to charge the second electrode  50  to a desired voltage. The second electrode  50  thereby serves as a measurement electrode. When moisture, such as humidity or condensation on the interior or exterior surface of the outer lens  24  is detected, the moisture causes a disturbance in the activation field which generates a signal that is processed to determine the moisture level. The disturbance of the activation field is detected by processing the charge pulse signals. 
     The conductive circuitry  40  may be formed with a film of indium tin oxide (ITO). The ITO forming the conductive circuitry  40  may be formed as an ink printed onto the interior surface of the outer lens  24 , according to one embodiment. The ITO may be deposited as a thin film onto the surface of the outer lens  24  and may have a thickness of about 1,000-3,000 angstroms to form a transparent electrical conductor. The ITO layer forming the conductive circuitry  40  is a substantially visually transparent medium that can be used to form the first and second electrodes  42  and  50  and other conductive signal lines for forming the proximity sensors and the heating elements. As such, the conductive circuitry  40  will remain substantially invisible to a user looking through the outer lens  24 . In other embodiments, other transparent and semi-transparent or visible conductive inks or films may be used to form the conductive circuitry  40 . 
     The first and second electrodes  42  and  50  and corresponding first and second plurality of conductive fingers  48  and  52 , respectively, may be formed on the inside surface of the outer lens  24  as shown in  FIGS. 4-5A . The first electrode  42  may be disposed on or adhered via an adhesive onto the inner surface of outer lens  24 , according to one example. The second electrode  50  is also disposed onto the inner surface of outer lens  24  such that the second plurality of fingers  52  is interdigitated with the first plurality of fingers  48 . In order to prevent short circuiting of the first and second electrodes  42  and  50 , a dielectric layer  54  is disposed between the first and second electrodes  42  and  50  on the inner surface of connecting line  46  such that the second electrode  50  and second plurality of conductive fingers  52  are separated from the first electrode  42  at that location as shown in  FIG. 5A . The remainder of the first and second electrodes  42  and  50  and conductive fingers  48  and  52  are substantially coplanar on the inner surface of the outer lens  24  as seen in  FIG. 5 . It should be appreciated that the dielectric layer  54  may be enlarged to cover substantially more or all of the surface area between the first and second electrodes, according to other embodiments. 
     Referring to  FIG. 6 , the conductive circuitry  40  is illustrated controlled by a controller  60 , according to one embodiment. The capacitive sensor generated signals are input to the controller  60 , such as a microcontroller. The controller  60  may include circuitry, such as a microprocessor  62  and memory  64 . The control circuitry may include sense control circuitry for processing the activation field of the capacitive sensor to sense moisture proximate to the outer lens  24 . It should be appreciated that other analog and/or digital control circuitry may be employed to process the capacitive field signals to determine the presence of moisture buildup on the outer lens  24  and initiate defogging or moisture removal with activation of the heater operation. 
     The controller  60  may include an analog-to-digital (A/D) comparator integrated within or coupled to the microprocessor  62  and may receive voltage output from the capacitive sensor, convert the analog signal to a digital signal, and provide a digital signal to the microprocessor  62 . The controller  60  may include a pulse counter integrated within or coupled to the microprocessor  62  that counts the charge signal pulses that are applied to the drive electrode, performs a count of the pulses needed to charge the capacitor until the voltage output reaches a predetermined voltage, and provides the count to the microprocessor  62 . The pulse count is indicative of the change in capacitance of the capacitive signal. The controller  60  may provide a pulse width modulated signal to a pulse width modulated drive buffer to generate the square wave pulse which is applied to the drive electrode. The controller  60  may determine the moisture present at or proximate to the outer lens  24  and control the heater by controlling the switches SW 1 -SW 4  as outputs. 
     Referring to  FIG. 7 , the change in signal charge pulse counts detected during various moisture conditions is shown as signals  70 A- 70 E, according to one example. The change in signal  70 A- 70 E is a count value difference between an initialized reference count value for different levels of moisture present on the outer lens  24 . As moisture in the form of condensation on the outer lens  24  or humidity proximate thereto increases, the moisture enters the activation field associated with the capacitive sensor and causes a disruption to the capacitance, thereby resulting in a raw signal increase as shown by signals  70 B- 70 E. Signal  70 A represents a clean lens having little or no moisture in which the signal  70 A is relatively low and steady. Signal  70 B shows the signal when sensing ice on the outside surface of the outer lens  24  which has a relatively high signal output. Signal  70 C shows the results of condensation formed on the outer lens  24 . Signal  70 D shows the effect of rain on the outer surface of the outer lens  24 . Signal  70 E shows a defogging signal pattern that shows the removal of moisture during the heater operation. By monitoring the signal generated by the capacitive sensor and comparing the signal to known moisture values, the condensation or humidity can be sensed and used to control the heater to remove the condensation from the outer lens  24 . 
     Referring to  FIG. 8 , routine  100  is illustrated for controlling the switches to switch operation of the conductive circuitry  40  between the capacitive sensing operation mode and the heater operation mode, according to one embodiment. Routine  100  begins at step  102  and proceeds to step  104  to open all switches SW 1 -SW 4 . Next, at step  106 , the second and third switches SW 2  and SW 3  are closed. This places the conductive circuitry  40  into the capacitive sensor mode of operation. The capacitance is then measured at step  108 . Proceeding to step  110 , routine  100  determines if de-icing is required based on the measured capacitance indicating that moisture has built up on the outer lens. De-icing may be required when there is sufficient condensation on the inside or outside of the lens or snow or ice on the outside of the lens. If de-icing is not required, routine  100  returns to step  102 . If de-icing is required, routine  100  proceeds to step  112  to open the second and third switches SW 2  and SW 3  and then to step  114  to close the first and fourth switches SW 1  and SW 4 . This places the conductive circuitry  40  into the heater mode of operation. At this point, the heater operates to heat the outer lens  24  to remove some or all of the moisture from the outer lens  24 . Routine  100  proceeds to step  116  to wait for a time period, such as two minutes to operate the heater before returning to step  102 . It should be appreciated that routine  100  may be repeated to cycle the conductive circuitry  40  between the capacitive sensing and heater modes of operation. 
     Accordingly, the vehicle light assembly  20  advantageously employs conductive circuitry  40  provided on the lens  24  for forming a capacitive sensor for sensing moisture on the lens and a heater for heating the lens to remove the moisture. It should be appreciated that the conductive circuitry  40  advantageously integrates both the capacitive sensing and the heater element into a common circuitry that allows for multiple functions with less components. 
     It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.