Abstract:
A heater system for clearing moisture (frozen and liquid) from a windshield ( 14 ) around a through-windshield vehicle sensor ( 18 ) provides a chamber between the sensor and the windshield containing air that may be heated by a chamber supported heating element ( 30, 51 ). The warm air within the chamber applies heat over the windshield in the critical viewing area ( 26 ) without obstructing the sensor ( 18 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional applications 62/095,388 filed Dec. 22, 2014 and 62/196,000 filed Jul. 23, 2015 both hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to vehicular systems and, in particular, to advanced vehicular sensor systems such as lane departure sensors. 
       BACKGROUND OF THE INVENTION 
       [0003]    Vehicular systems for determining whether a vehicle is being held within a road lane and, if not, providing a warning to the driver (lane departure warning) are being developed as part of current vehicle safety equipment. 
         [0004]    Sensors for use with lane departure warning (LDW) systems may include cameras mounted within the vehicle compartment, typically between the center rearview mirror and the windshield. From this location, the camera is positioned so that its field of view is directed toward the road in front of the vehicle. The space between the camera and the windshield may be protected by a glare shield to prevent light from outside of the field of view of the camera from interfering with the camera sensing. 
         [0005]    The image signals obtained from the camera for the LDW are critical to determining the location of the lane lines and thus the relative location of the vehicle. These image signals may be degraded by frost, ice, or fog on the windshield. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides a heater frame that can be inserted between the windshield and the camera to provide a pocket of heated air between the camera and the windshield for improved dissipation of frost, ice, and fog on the windshield without obstructing the camera view. Rearwardly extending flanges from the heater frame may fit into the lens pocket, or the frame may space the camera away from the windshield to provide a larger heated volume. The heater may employ a polymer positive temperature coefficient (PTC) material that provides automatic temperature regulation simplifying control of the heater. 
         [0007]    In one embodiment the invention may provide an adapter for a through-windshield sensor having a housing with a first face attachable to the inner surface of a windshield and a second face attachable to a front face of the through-windshield sensor to define an enclosed volume therebetween, the enclosed volume located with respect to the through-windshield sensor to permit sensing by the through-windshield sensor through an area of the windshield abutting the enclosed volume. An electrical resistance heater is supported by the housing and communicates with the enclosed volume to heat the air within the enclosed volume to improve transparency of the windshield against environmental moisture by heating the area of the windshield abutting the enclosed volume. 
         [0008]    It is thus a feature of at least one embodiment of the invention to provide a system for removing frost, fog, or ice from the windshield without interfering with the sensor function or requiring excessive power. By heating a contained volume of air, sensor obstruction is avoided while allowing a focused application of heat. 
         [0009]    The housing may provide sidewalls extending rearwardly from the windshield and supporting the electrical resistance heater. 
         [0010]    It is thus a feature of at least one embodiment of the invention to provide a mounting for the heater that minimizes obstruction with the sensor. 
         [0011]    The housing may be a thermoplastic polymer electrical resistance heater with a conductive polymer attached to the sidewalls. 
         [0012]    It is thus a feature of at least one embodiment of the invention to provide a thermally resistive housing material that helps contain the heat in the enclosed volume as well as a heater material compatible with that housing. 
         [0013]    The conductive polymer may be a positive temperature coefficient material. 
         [0014]    It is thus a feature of at least one embodiment of the invention to permit a spatially distributed heater that reduces the possibility of hotspots through an autoregulation feature of positive temperature coefficient. 
         [0015]    The conductive polymer may be attached to an inner surface of the sidewalls proximate to the enclosed volume. 
         [0016]    It is thus a feature of at least one embodiment of the invention to reduce thermal resistance between the heater material and the enclosed volume. 
         [0017]    The sidewalls may fit within a receiving pocket of the through-windshield sensor to extend along corresponding sidewalls of the receiving pocket of the through-windshield sensor. 
         [0018]    It is thus a feature of at least one embodiment of the invention to provide a heater system that may work with existing sensor systems having preconfigured glare shields. 
         [0019]    The first face of the housing may provide a first flange surface abutting an inner surface of the windshield and including an adhesive for attachment of the flange surface to the windshield. 
         [0020]    It is thus a feature of at least one embodiment of the invention to provide a simple mounting system that may seal and support the adapter on the windshield and may be usable with a variety of different windshield designs. 
         [0021]    The second face of the housing may provide a second flange surface abutting a front surface of the through-windshield sensor and include an attachment means for attaching the second plane surface to the through-windshield sensor. 
         [0022]    It is thus a feature of at least one embodiment of the invention to provide a heater adapter that may be placed between the sensor and the windshield to support the two and a predetermined orientation and separation. 
         [0023]    The first and second flange surfaces may be on opposite sides of a single flange extending radially outward around the enclosed volume. 
         [0024]    It is thus a feature of at least one embodiment of the invention to provide an extremely low profile heater system that may work with a variety of pre-existing sensor systems without unduly changing the spacing between the sensor and the windshield. 
         [0025]    The flange surface of the second face may include an adhesive for attaching the flange surface to the front surface of the through-windshield sensor. 
         [0026]    It is thus a feature of at least one embodiment of the invention to provide a low- profile attachment method for attaching the invention to both the windshield and the sensor system. 
         [0027]    Alternatively, the second flange surface may be on a flange extending inwardly from the sidewalls. 
         [0028]    It is thus a feature of at least one embodiment of the invention to allow movement of the sidewalls outward from the field of view of the sensor to prevent interference therewith. 
         [0029]    The electrical resistance heater may include a first portion extending inside the enclosed volume to attach to the windshield at a periphery of an area of the windshield abutting the enclosed volume. 
         [0030]    It is thus a feature of at least one embodiment of the invention to provide heat directly to the windshield for rapid response before the heated volume attains temperature. 
         [0031]    The electrical resistance heater may be a conductive polymer on a flexible substrate and may further include second portion deformable with respect to a plane of the first portion to attach to a wall of the housing. 
         [0032]    It is thus a feature of at least one embodiment of the invention to provide a simple fabrication method allowing two planes of heating zones, one on the windshield and one on the enclosure sidewalls. 
         [0033]    The second portion may attach to a lowermost sidewall of the housing. 
         [0034]    It is thus a feature of at least one embodiment of the invention to maximize heat transfer and take advantage of natural convection within the enclosed volume. 
         [0035]    The first and second portions may be formed from a single continuous sheet of flexible material with the second portion formed from the single continuous sheet from an area within the first portion. 
         [0036]    It is thus a feature of at least one embodiment of the invention to provide a manufacturing process that reduces waste by employing a nested heater portion layout. 
         [0037]    The first and second portions may be electrically joined by a flexible arm formed from the single continuous sheet within the first portion and outside of the second portion. 
         [0038]    It is thus a feature of at least one embodiment of the invention to permit displacement of the two heater portions when formed of a continuous material. 
         [0039]    The housing provides mechanical support for the through-windshield sensor. 
         [0040]    It is thus a feature of at least one embodiment of the invention to simplify manufacture and alignment of the sensor system when used with the heater of the present invention. 
         [0041]    Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0042]      FIG. 1  is a perspective view of an automobile windshield from outside of the automobile showing a typical placement of an LDW sensor and showing a detailed view of the camera and glare shield for the sensor; 
           [0043]      FIG. 2  is a top plan view of a heater assembly for heating the windshield and glare shield of  FIG. 1 ; 
           [0044]      FIG. 3  is a perspective view of the heater assembly of  FIG. 2  separated so that a portion of the heater assembly may attach to the windshield and a portion may fit beneath a bottom plate of the glare shield to heat the same; 
           [0045]      FIG. 4  is a simplified elevational cross-section of the assembled heater windshield and glare shield showing dual-mode of heating provided by the invention; 
           [0046]      FIG. 5  is an exploded perspective view of a second embodiment of the invention providing a heater frame that may be positioned between the camera and windshield and having rearwardly extending heater flanges extending into the camera lens pocket; 
           [0047]      FIG. 6  is a simplified elevational cross-section of the assembled heater frame and camera showing the extension of the flanges into the camera lens pocket; 
           [0048]      FIG. 7  is a fragmentary, front elevational view of the frame showing positioning of adhesive on a front surface of the frame attachable to the windshield and a heater element attached to the inner surface of the flange; 
           [0049]      FIG. 8  is a cross-sectional view along line  8 - 8  of  FIG. 7  showing adhesive on the rear surface of the frame for attachment of the frame to the camera assembly; 
           [0050]      FIG. 9  is a figure similar to  FIG. 5  of a third embodiment of the invention having a heater frame that spaces the camera assembly away from the windshield to provide an increased heated air volume; and 
           [0051]      FIG. 10  is a figure similar to  FIG. 6  showing an elevational cross-section of the heater frame of  FIG. 9  and camera assembled to the windshield. 
       
    
    
       [0052]    Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0053]    Referring now to  FIG. 1 , a vehicle  10  may provide for a lane departure warning (LDW) sensor system  12  positioned at a top center location on a windshield  14  of the vehicle  10 . Generally the LDW sensor system  12  may provide for a glare shield  16  positioned around a lens of a camera  18 , the latter of which may be directed along a view axis  20  toward a road in front of the vehicle  10  to monitor the position of lane lines on the road (not shown). The glare shield  16  may be constructed for example of an injection molded thermoplastic material of a dark color with a surface coated or textured to reduce reflection. 
         [0054]    Referring momentarily to  FIG. 4 , the glare shield  16  may include a lower triangular glare panel  22  extending from the windshield  14  to a lower edge of the camera  18  and an upper glare panel  24  extending from an upper edge of the camera  18  to the windshield  14 . The upper glare panel  24  and lower glare panel  22  angle away from each other as one moves from the camera  18  to the windshield  14  so as to follow but not obstruct a field of view  26  of the camera about axis  20 , the latter necessary for the camera to properly view the road. 
         [0055]    Referring now to  FIG. 2 , the present invention may employ a flexible heater sheet  30  providing a heater ring  32  having a trapezoidal shape whose inner periphery conforms to the field of view  26 . The heater ring  32  will be placed against the inner surface of the windshield  14  as will be described below. 
         [0056]    Nested within the trapezoidal heater ring is a smaller heater panel  34  having a trapezoidal periphery sized to fit against the lower surface of the lower glare panel  22  and heat a continuous area of that lower glare panel  22  as will be described below. 
         [0057]    The heater ring  32  communicates, via a tail conductor strip  36 , with an electrical connector  39  providing electrical power to the flexible heater sheet  30 . This electrical power is in turn communicated from the heater ring  32  through a flexible arm  38  passing from the heater ring  32  to the heater panel  34 . 
         [0058]    The heater ring  32 , flexible arm  38 , trapezoidal heater panel  34 , and tail conductor strip  36  may all be cut from a single planar sheet of flexible polymer through a die-cutting operation or the like. A suitable length of the flexible arm  38  is possible by displacing the smaller heater panel  34  rightward in the inner periphery of the heater ring  32  to provide a distance defining a length of the flexible arm  38  between a left surface of the smaller heater panel  34  and an inner wall of a right side of the heater ring  32 . 
         [0059]    The flexible heater sheet  30  may be constructed of a single, flexible, continuous thin sheet of polymer material  40  having the property of conducting electricity with a positive temperature coefficient of resistance. A positive temperature coefficient of resistance causes the amount of electrical flow to vary according to the temperature of the material, with increased electrical flow at lower temperatures and decreased electrical flow at higher temperatures. This property provides for a self-regulating temperature of the polymer material  40  when a substantially constant voltage source is applied across the polymer material  40 . 
         [0060]    The top surface of the polymer material  40  may support interdigitated electrodes  42   a  and  42   b  each connected to a different voltage polarity that apply voltage across the polymer material  40  promoting current flow through the polymer material  40  generally along the plane of its extent. 
         [0061]    Positive temperature coefficient (PTC) heaters, suitable for the present invention, are also disclosed in U.S. Pat. Nos. 4,857,711 and 4,931,627 to Leslie M. Watts hereby incorporated in their entirety by reference. 
         [0062]    Alternatively the flexible heater sheet  30  may be constructed of a flexible insulating sheet of polymer material with a resistive conductor applied to the upper surface to form a resistive or ohmic heating element. In this case, a constant voltage or current may be applied to the conductor to provide a given heat output. The current may be controlled according to a temperature sensor or operated in an “open loop” fashion. 
         [0063]    Referring now to  FIG. 3 , during manufacture, the heater ring  32  may be separated from the heater panel  34  by tipping a lower edge of a plane of the heater ring  32  upward with respect to a plane of the heater panel  34  allowing the lower glare panel  22  to be inserted therebetween. An upper surface  44  of the heater panel  34  may have a pressure sensitive adhesive  46  applied to that upper surface  44  to attach the heater panel  34  to the lower surface of the glare panel  22 . An upper surface  44  of the heater ring  32  may also have a pressure sensitive adhesive  46  applied to the upper surface  44  so that the heater ring  32  may be attached to the inside of the windshield  14 . 
         [0064]    Referring again to  FIG. 4 , the heater ring  32  may be attached to an inner surface of the windshield  14  to frame the field of view  26  and to provide heat to the glass of the windshield  14 , the heat passing by conductivity inward from the heater ring  32  as indicated by arrows  48 . In addition, heat from the heater panel  34  may pass upward into the space between the glare panels  22  and  24  through the glare panel  22  as indicated by arrows  50  to heat the volume defined between glare panels  22  and  24  and the windshield  14  for additional heating. 
         [0065]    It will be appreciated that in an alternative embodiment, the heater ring  32  may be attached directly to structure of the glare panels  22  and  24 , for example, onto flanges facing inward from the glare panels  22  and  24  at ends of the glare panels  22  and  24  proximate but not necessarily touching the windshield  14 . Alternatively, a clear window (not shown) may be provided spanning the edges of the glare panels  22  and  24  proximate to the windshield  14  and the heater ring  32  attached to that window. The adhesive  46  on these designs may be moved between a front and rear surface of the heater ring  32  as is necessary for the attachment required. In any one of these examples, the heater panel  34  may be placed either on the lower surface of the glare panel  22  or its upper surface or on other structure of the lens pocket  60  that will provide the desired heating effect. 
         [0066]    It will further be noted that a variety of different glare shield designs may be used and that the present heater system will accommodate a variety of different structures and surface attachments while providing dual plane heating. 
         [0067]    Referring now to  FIGS. 5 and 6 , in a second embodiment, the invention may provide for a heater assembly  51  having a generally planar heater frame  52  in the shape of a regular trapezoid with a planar front face  54 . The planar front face  54  may fit against and be attached to an underside of the windshield  14  in attachment area  56  by an adhesive or other means. 
         [0068]    Extending rearwardly from the inner edges of the heater frame  52  are heater support sidewalls  58  that are sized to be received in a lens pocket  60  of the sensor system  12 , the lens pocket  60  holding the camera  18  below the surface of a front housing face  61 , the latter which would otherwise attached directly to a planar rear surface of the windshield  14 . The trapezoidal shape of the heater frame  52  positions the heater support sidewalls  58  to conform closely to the walls of the lens pocket  60  out of the way of the field of view  26  of the camera  18  as the camera  18  is directed through the windshield  14 . 
         [0069]    Referring also to  FIG. 7 , inner surfaces of the rearwardly extending heater support sidewalls  58  hold a heater ring  32  similar to that discussed above. The heater ring  32  may have interdigitated electrodes  42  in electrical communication with a lower substrate of positive temperature coefficient polymer material  40 . Generally, the heater ring  32  may be fabricated separately as a strip and then applied by adhesive or other means to the inner surfaces of the heater support sidewalls  58 . Electricity is applied to the heater ring  32  by a tail conductor strip  36  which may connect through a connector in the sensor system  12  to share power provided to the sensor system  12  in order to heat the heater ring  32 . As shown by arrows  48 , heat from the heater ring  32  warms the air within the lens pocket  60  and consequently a portion of the windshield  14  within the attachment area  56  to reduce fogging, icing, and other similar obstructions on the windshield  14  within the attachment area  56 . 
         [0070]    Referring to  FIG. 8 , opposite faces of the frame  52  may have a pressure sensitive adhesive  63  so that the heater assembly  51  may serve to attach the sensor system  12  to the windshield  14  and thereby to fully support the sensor system  12 . This attachment first attaches heater assembly  51 , by lower adhesive  63  on the frame  52 , to the front housing face  61  of the sensor system  12  and then attaches the heater assembly  51  to the windshield  14  using an upper adhesive  63  attaching the front face  54  of the frame  52  to the windshield  14 . 
         [0071]    Referring now to  FIGS. 9 and 10 , in an alternative embodiment, the dimensions of the frame  52  may be increased so that the rearwardly extending sidewalls  58  do not fit within the lens pocket  60  but are larger than the lens pocket  60 . Rearward edges of the sidewalls  58  joined to an outer periphery of a secondary flanges  62  extending inward from the rearward edges of the sidewalls  58 . The secondary flanges  62  is generally parallel to the frame  52  although spaced rearwardly from the frame  52  and provides a central trapezoidal opening  64  generally conforming to the opening of the lens pocket  60  and sized to prevent interference with the field of view  26 . 
         [0072]    A rear face of the secondary flanges  62  may include rearwardly extending attachment elements  66 , for example, barbed studs, hooks or snaps that fit within and may be retained within corresponding sockets  68  in the front housing face  61  of the sensor system  12  to attach the secondary flanges  62  to the front housing face  61 . Alternatively, an adhesive may be used such as a pressure sensitive or two-part adhesive. As before, a front surface of the frame  52  may include adhesive  63  (for example, a pressure sensitive adhesive) to attach it to the inside of the windshield  14 . 
         [0073]    As shown in  FIG. 10 , heater ring  32  is attached to the inner walls of the rearwardly extending sidewalls  58  to provide heat as shown by arrows  48  both to the lens pocket  60  and an expanded volume between the sensor system  12  and the windshield  14 . This increased volume provides greater thermal mass thus helping regulate the temperature in the lens pocket  60  against abrupt changes in outdoor thermal conditions. 
         [0074]    It will be appreciated that the sensor system  12  of any of the above embodiments may be not only optical sensors such as cameras but also radar antennas for radar systems or ultrasonic acoustic transducers for ultrasound systems and in these latter cases, the windshield  14  may be replaced with a specialized window material. 
         [0075]    Variations and modifications of the foregoing are within the scope of the present invention. It is understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention. The claims are to be construed to include alternative embodiments to the extent permitted by the prior art. 
         [0076]    Various features of the invention are set forth in the following claim.