Patent Publication Number: US-2020300775-A1

Title: Automobile rain and temperature sensor module

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 62/820,980, filed Mar. 20, 2019, which is incorporated by reference herein in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     This disclosure relates generally to the field of automobile sensors, and more particularly to a rain and temperature sensor module configured to detect rainfall on, and to measure the temperature of, an automobile windshield. 
     BACKGROUND OF THE DISCLOSURE 
     Modern automobiles are commonly equipped with rain sensors that are configured to detect rainfall on an automobile&#39;s windshield. Information gathered from such sensors can be used to automatically activate and vary the speed of an automobile&#39;s windshield wipers and/or to control various other systems in an automobile (e.g., a traction control system). Modern automobiles are also commonly equipped with windshield temperature sensors that are configured to measure the temperature of an automobile&#39;s windshield. Information gathered from such sensors can be used to manage the operation of an automobile&#39;s automatic defogging system, for example. 
     In a typical implementation, an automobile rain sensor includes a light emitting element, a collimating lens adapted to collimate light emitted by the light emitting element and to direct the collimated light toward a sensing area on the windshield, a focusing lens adapted to receive the collimated light that is reflected off of the windshield and to focus the light, and a light receiving element (e.g., a photodiode) adapted to receive the focused light from the focusing lens and to convert the received light into an electrical output signal that is transmitted to a controller. If water (e.g., rain) is present at the sensing area on the exterior surface of the windshield, a portion of collimated light that strikes the sensing area will be refracted into the water instead of being reflected to the focusing lens. Thus, the amount of collimated light that is reflected off of the sensing area of the windshield and received by the light receiving element is generally attenuated relative to when the sensing area of the windshield is dry. 
     A shortcoming associated with conventional rain sensors of the type described above is that the collimating and focusing lenses of such sensors can be relatively expensive. Additionally, if it becomes necessary to change the configuration of the light emitting and light receiving elements in such sensors (e.g., in order suit various application environments in different vehicles), changes must generally also be made to the collimating and focusing lenses, the sensor housing, and the tooling used to manufacture the lenses and the housing. Such modifications are associated with significant time and expense. 
     An automobile windshield temperature sensor is commonly included as part of an integrated temperature and humidity sensing device that is implemented in a module alongside an automobile rain sensor of the type described above. A typical automobile windshield temperature sensor includes a temperature sensing element (e.g., a negative temperature coefficient element, a resistance temperature detector, a temperature and humidity sensing integrated circuit, a thermocouple, etc.) that is spring-biased against the windshield of an automobile. The various mechanical components of such sensors (e.g., springs, flexible circuit boards, etc.) are associated with significant cost and space requirements and are also subject to mechanical failure over time. 
     It is with respect to these and other considerations that the present improvements may be useful. 
     SUMMARY 
     This Summary is provided to introduce a selection of concepts in a simplified form further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is the summary intended as an aid in determining the scope of the claimed subject matter. 
     A rain sensing module in accordance with an exemplary embodiment of the present disclosure includes a housing having a cover plate formed of a transparent material, a printed circuit board disposed within the housing and having a light emitter and a light receiver disposed thereon, wherein the light receiver is configured to receive light emitted by the light emitter and reflected off of an automobile windshield, and a transparent compound disposed within the housing and filling a space between the printed circuit board and the cover plate. 
     A windshield temperature sensing module in accordance with an exemplary embodiment of the present disclosure includes a housing having a cover plate adapted to be mounted to a windshield of an automobile, a printed circuit board disposed within the housing and having a temperature sensing element disposed thereon, and a compound disposed within the housing and filling a space between the printed circuit board and the cover plate, wherein the compound provides a thermally conductive medium between the cover plate and the temperature sensing element. 
     A rain and temperature sensing module in accordance with an exemplary embodiment of the present disclosure may include a housing having a cover plate formed of a transparent material, a printed circuit board disposed within the housing and having a light emitter, a light receiver, and a temperature sensing element disposed thereon, and a transparent compound disposed within the housing and filling a space between the printed circuit board and the cover plate, wherein the transparent compound provides a thermally conductive medium between the cover plate and the temperature sensing element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is perspective view illustrating a rain and temperature sensing module in accordance with an embodiment of the present disclosure; 
         FIG. 1B  is cross-sectional side view illustrating the rain and temperature sensing module of  FIG. 1A ; 
         FIGS. 2A and 2B  are cross-sectional side views illustrating certain components of the rain and temperature sensing module of  FIGS. 1A and 1B  during operation. 
     
    
    
     DETAILED DESCRIPTION 
     An automobile rain and temperature sensor module in accordance with the present disclosure will now be described more fully with reference to the accompanying drawings, in which a preferred embodiment of the automobile rain and temperature sensor module is presented. The automobile rain and temperature sensor module may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will convey certain exemplary aspects of the automobile rain and temperature sensor module to those skilled in the art. 
     Referring to  FIGS. 1A and 1B , a perspective view and a cross-sectional view illustrating an automobile rain and temperature sensor module (hereinafter “the module  10 ”) in accordance with an exemplary embodiment of the present disclosure are shown. In the depicted, non-limiting embodiment, the module  10  may generally include a housing  12  that contains a printed circuit board (PCB)  14 , a light emitter  16 , a light receiver  18 , a temperature sensing element  20 , and a transparent compound  22 . While the module  10  is shown as including only a single light emitter  16  and a single light receiver  18 , it will be understood that the module  10  may include a greater number of light emitters and/or light receivers without departing from the scope of the present disclosure. 
     The housing  12  of the module  10  may generally be formed of an opaque plastic but may include a cover plate  26  formed of a transparent material that allows light to enter the interior of the housing  12 . In a non-limiting embodiment, the cover plate  26  may be formed of plastic that may be substantially transparent to infrared light but substantially opaque to visible light. The present disclosure is not limited in this regard. 
     The PCB  14  may be mounted to an interior of the housing  12  adjacent to, and in a substantially parallel relationship with, the cover plate  26 . The light emitter  16 , light receiver  18 , and temperature sensing element  20  may be disposed on a top surface of the PCB  14  (e.g., electrically connected to conductive traces on the top surface of the PCB  14 ) and may be operatively connected to a light sensor controller  30  and a temperature sensor controller  32 , respectively, that may be configured to manage the operation of, supply power to, and/or process output from the light emitter  16 , light receiver  18 , and temperature sensing element  20  as further described below. The light sensor controller  30  and temperature sensor controller  32  may be embodied by appropriately configured integrated circuits (ICs), for example. The PCB  14  may be connected to one or more electrical power sources and/or control elements (not shown) external to the housing  12  via conductors  28  that extend from the PCB  14  through a plug portion  34  of the housing  12 . 
     The transparent compound  22  may partially or entirely fill a space in the housing  12  between the PCB  14  and the cover plate  26  and may substantially surround and encase each of the light emitter  16 , the light receiver  18 , the temperature sensing element  20 , the light sensor controller  30 , and the temperature sensor controller  32 . The transparent compound  22  may be a fluid or semi-fluid material (e.g., a liquid or a gel) that is transparent to infrared and/or visible light and that has a refractive index that is substantially equal to that of glass. Particularly, the transparent compound  22  may have a refractive index that is substantially the same as that of the cover plate  26  and substantially the same as that of an automobile windshield (not shown) to which the cover plate  26  may be attached when the module  10  is operatively installed in an automobile. In various embodiments, the transparent compound  22  may have an index of refraction in the range of 1.45 to 1.55. More preferably, the transparent compound  22  may have an index of refraction in the range of 1.50 to 1.525. In various embodiments, the transparent compound  22  may be a silicone gel or liquid. The present disclosure is not limited in this regard. 
     Referring to  FIGS. 2A and 2B , cross-sectional side views illustrating the module  10  coupled to an interior surface of an automobile windshield  40  are shown. For clarity of description, only the PCB  14 , light emitter  16 , light receiver  18 , temperature sensing element  20 , transparent compound  22 , and cover plate  26  of the module  10  are shown in  FIGS. 2A and 2B . In various embodiments, the cover plate  26  may be fastened to the automobile windshield  40  by a thin layer of transparent adhesive (e.g., adhesive  42  shown in  FIGS. 1A and 1B ). 
     During operation of the module  10 , and as shown in  FIG. 2A , the light emitter  16 , which may be a light emitting diode (LED), may emit a beam of light (e.g., infrared light) through the transparent compound  22 , the cover plate  26 , and the windshield  40  to a detection area  44  on an exterior surface of the windshield  40 . If there is no water present at the detection area  44 , most or all of the light emitted by the light emitter  16  will be reflected back through the windshield  40 , the cover plate  26 , and the transparent compound  22  onto the light receiver  18 . The light receiver  18 , which may be a photodiode, may generate an electrical output signal corresponding to the amount of received light. If there is water present at the detection area  44 , most or all of the light emitted by the light emitter  16  will be refracted into and through the water as shown in  FIG. 2B , and little or none of the light will be reflected back through the windshield  40 , the cover plate  26 , and the transparent compound  22  onto the light receiver  18 . The light receiver  18  will therefore generate little or no corresponding electrical output signal. The output from the light receiver  18 , which may be communicated to the light sensor controller  30  ( FIG. 1B ), may therefore be used to determine whether moisture is present on the windshield  40  and to dictate the operation of various automobile systems (e.g., windshield wipers, traction control, etc.). 
     Advantageously, since the space between the light emitter  16 , light receiver  18 , and the cover plate  26  is filled with the transparent compound  22  having a refractive index that is substantially equal to that of the cover plate  26  and to that of the windshield  40 , the light emitted by the light emitter  16  may travel through the transparent compound  22 , the cover plate  26 , and the windshield  40  in a substantially straight line without being refracted at the boundaries therebetween. Thus, the module  10  of the present disclosure does not require any collimating or focusing lenses to accommodate the refraction of light at the juncture of the transparent compound  22  and the cover plate  26 . The module  10  of the present disclosure may therefore be manufactured at a significantly lower cost relative to conventional automobile rain sensor modules in which collimating and/or focusing lenses are necessary for accommodating refraction. Additionally, the configuration of the light emitter  16  and light receiver  18  of the module  10  can be easily changed (e.g., in order suit various application environments in different vehicles) without necessitating any modifications to the housing  12 , such as would be necessary in conventional automobile rain sensor modules for accommodating changes to the position and/or orientation of collimating and focusing lenses. 
     In addition to providing refraction-free optical coupling between the interior of the housing  12  and the cover plate  26  as described above, the transparent compound  22  may additionally provide a thermally conductive medium for communicating the temperature of the windshield  40  to the temperature sensing element  20 . In a non-limiting example, the transparent compound  22  may have a thermal conductivity that is greater than the thermal conductivity of air at room temperature (e.g., greater than about 0.028 watts per meter-kelvin). In another example, the transparent compound  22  may have a thermal conductivity that is greater than 0.20 watts per meter-kelvin. Thus, heat from the windshield  40  may be conducted through the cover plate  26  and through the transparent compound  22  to the temperature sensing element  20 . The temperature sensing element  20 , which may be a thermocouple, negative temperature coefficient (NTC) element, resistance temperature detector, or similar device, may communicate a measured temperature of the windshield  40  to the temperature sensor controller  32  ( FIG. 1B ). The measured temperature may then be used to dictate the operation of various automobile systems (e.g., automatic defogging system). 
     Advantageously, the temperature sensing element  20  is implemented in the same housing  12  as the rain sensing elements of the module  10  and does not require any of the mechanical components (e.g., springs, flexible circuit boards, etc.) of conventional windshield temperature sensors. The temperature sensing element  20  of the module  10  may therefore be implemented at a significantly reduced cost and in a smaller form factor relative to conventional windshield temperature sensors. Additionally, due to the lack of mechanical components associated with the temperature sensing element  20 , the temperature sensing element  20  is not susceptible to mechanical failure in the manner of conventional windshield temperature sensors. 
     While the module  10  has been described above as including both rain sensing elements and windshield temperature sensing elements, it is contemplated that, in various embodiments, the module  10  may be implemented as only a rain sensor module or only as a windshield temperature sensor module. That is, it is contemplated that only the rain sensing elements (i.e., the light emitter  16 , light receiver  18 , etc.) may be implemented while the windshield temperature sensing elements (i.e., the temperature sensing element  20  and the temperature sensor controller  32 ) are omitted, or that only the windshield temperature sensing elements may be implemented while the rain sensing elements are omitted. Notably, if only the windshield temperature sensing elements are implemented, then the transparent compound  22  may be replaced by another compound or other material having good thermal conductivity (e.g., a thermal conductivity that is superior to that of air) but that is not necessarily transparent. 
     As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
     While the present disclosure makes reference to certain embodiments, numerous modifications, alterations and changes to the described embodiments are possible without departing from the sphere and scope of the present disclosure, as defined in the appended claim(s). Accordingly, it is intended that the present disclosure not be limited to the described embodiments, but that it has the full scope defined by the language of the following claims, and equivalents thereof.