Abstract:
An apparatus ( 10 ) for detecting a window open condition comprises a first photoelectric cell ( 60 ) mountable to the window ( 20 ) for providing a reference output signal ( 61 ) independent of the window open condition. The apparatus ( 10 ) also comprises a second photoelectric cell ( 62 ) mountable to the window and providing a signal ( 63 ) having a first characteristic if the window ( 20 ) is open and a second characteristic if the window is not open. The apparatus ( 10 ) further comprises comparison means ( 82 ) for comparing the reference output signal ( 61 ) with the signal from the second photoelectric cell ( 63 ). The comparison is indicative of the open condition of the window. The apparatus ( 10 ) comprises means ( 88 ) responsive to the comparison means ( 82 ) for indicating if the vehicle window ( 20 ) is in the open condition.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a vehicle window position sensor. In particular, the present invention relates to an apparatus for detecting if a vehicle window is open and for providing an output signal indicative of the open or closed state of the window. 
     BACKGROUND OF THE INVENTION 
     It is sometimes desirable to know whether a window in a vehicle is open or closed. For example, if the vehicle is exited and locked, a signal can be provided to alert the driver if a window is inadvertently left open. 
     There are known ways of detecting if a vehicle window is open and of providing an output signal indicative of the open or closed state of the window. For example, U.S. Pat. No. 4,808,894 discloses the use of a switch at the top of a door frame to indicate when a window is fully closed. U.S. Pat. No. 4,931,74 discloses the use of a slide rheostat to determine the position of a window along a window track. U.S. Pat. No. 5,410,226 discloses the use of signals indicative of motor rotation and current draw to sense an obstacle to the movement of a window along a window track. In addition, U.S. Pat. No. 5,532,560 discloses the use of a photoresistive sensor for sensing the amount of light striking a window area and, in response, controlling a Venetian blind. 
     SUMMARY OF THE INVENTION 
     The present invention is an apparatus for detecting a window open condition. The apparatus comprises a first photoelectric cell mountable to the window for providing a reference output signal independent of the window open condition. The apparatus also comprises a second photoelectric cell mountable to the window and providing a signal having a first characteristic if the window is open and a second characteristic if the window is not open. The apparatus further comprises comparison means for comparing the reference output signal with the signal from the second photoelectric cell, the comparison being indicative of the open condition of the window, and means responsive to the comparison means for indicating if the vehicle window is in the open condition. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other features of the invention will become apparent to one skilled in the art to which the invention relates upon consideration of the following description of the invention with reference to the accompanying drawings, in which: 
     FIG. 1 is a sectional view of a portion of a vehicle including an apparatus in accordance with a first embodiment of the invention, the apparatus including a sensor assembly on a window shown in a closed condition; 
     FIG. 2 is a view similar to FIG. 1 showing the window in an open condition; 
     FIG. 3 is schematic illustration of the sensor assembly of FIG. 1; 
     FIG. 4 is a functional block diagram of the apparatus of FIG. 1; 
     FIG. 5 is a functional block diagram similar to FIG. 3 of an apparatus in accordance with a second embodiment of the invention; 
     FIG. 6 is a view similar to FIG. 1 of an apparatus in accordance with a third embodiment of the invention; 
     FIG. 7 is a view similar to FIG. 3 of a sensor assembly that forms part of an apparatus in accordance with a fourth embodiment of the invention; and 
     FIG. 8 is a functional block diagram of the apparatus assembly of FIG.  7 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention relates to a vehicle window position sensor. In particular, the present invention relates to an apparatus for detecting if a vehicle window is open and for providing an output signal indicative of the open or closed state of the window. As representative of the present invention, FIGS. 1-4 illustrate an apparatus  10  in accordance with a first embodiment of the present invention. 
     The apparatus  10  forms part of a vehicle  12  that includes a door  14  having a door frame  16 , only a portion of which is shown. The door frame  16  is made from an opaque material, such as steel. The door  14  also includes a seal  18  secured to the door frame  16 . The seal  18  also is made from an opaque material, such as rubber. 
     The door  14  includes a window  20  that is supported for vertical movement within the door frame  16  relative to the door frame. The window  20  has an upper portion  22  that is movable into and out of engagement with the seal  18 . The upper portion  22  of the window  20  has an inner side surface  24 , an outer side surface  26 , and a top edge surface  28 . The window  20  is made from a transparent material, i.e., glass. 
     FIG. 1 shows the window  20  in an “up” or “closed” state or condition. When the window  20  is in the closed condition, the upper portion  22  of the window is located adjacent the door frame  16  and in engagement with the seal  18 . The top edge surface  28  and the inner side surface  24  of the upper window portion  22  are covered by the seal  18  and are not exposed to ambient light. 
     FIG. 2 shows the window  20  in a “down” or “open” state or condition. When the window  20  is in the open condition, the upper portion  22  of the window  20  is spaced apart from the door frame portion  16  and from the seal  18 . As a result, the top edge surface  28  and the inner side surface  24  of the upper window portion  22  are exposed to ambient light. 
     The apparatus  10  is shown in FIGS. 1 and 2 as being mounted on the exterior of the window  20 . The apparatus  10  includes a sensor assembly  30  (FIGS. 1-3) having a first portion  31 , a second portion  32 , a third portion  33 , and a fourth portion  34 . 
     The sensor assembly  30  includes a flexible substrate  40  that extends along and forms a base for all four portions  31 - 34  of the sensor assembly. The substrate  40  is made from an opaque material. The substrate  40  is glued or otherwise adhered to the inner side surface  24 , the outer side surface  26 , and the top edge surface  28  of the window  20 , thereby to secure the sensor assembly  30  to the window. 
     The first portion  31  of the sensor assembly  30  includes a solar cell array  50  on a first portion  41  of the substrate  40 . The solar cell array  50  includes one or more solar cells  52 . The solar cells  52  are operative to produce an electric current for powering the sensor assembly  30  when light strikes the solar cells. Power produced by the solar cell array  50  is output through one or more leads  54 . 
     The second portion  32  of the sensor assembly  30  includes a second portion  42  of the substrate  40 . The leads  54  from the solar cells  52  extend across the second portion  42  of the substrate  40 . 
     The third portion  33  of the sensor assembly  30  includes a plurality of photoelectric cells  60  and  62  located on a third portion  43  of the substrate  40 . The photoelectric cells  60  and  62  are preferably photoconductive cells whose resistance is proportional to the intensity of light impinging on the cells. The photoelectric cells  60  and  62  may alternatively, as described below, be photovoltaic cells, which generate a voltage proportional to the intensity of light impinging on the cells. 
     The photoconductive cell  60  is a first photoconductive cell, or reference cell, of the sensor assembly  30 . The photoconductive cell  62  is a second photoconductive cell, or active cell, of the sensor assembly  30 . It should be understood that the reference cell  60  could comprise an array of more than one photoconductive cells, and that the active cell  62  could comprise an array of more than one photoconductive cells. 
     The reference cell  60  has a front surface  64  and an opposite back surface (not shown). The front surface  64  of the reference cell  60  is covered so that light can not impinge on the front surface  64  of the reference cell. The front surface  64  of the reference cell  60  may be covered by painting over or in any other manner. In addition, the third portion  33  of the substrate  30  is opaque, so that light can not impinge on the back surface of the reference cell  60 . As a result, the reference cell  60  sees a constant amount of light, and has a constant electrical resistance, regardless of lighting conditions. The reference cell  60  thus provides a reference output signal  61  (FIG.  4 ), over one or more lead wires  66  (FIG.  3 ), that is independent of the amount of ambient light at the window  20 . 
     The active cell  62  has a front surface  68  and an opposite back surface (not shown). The front surface  68  of the active cell  62  is not covered, and therefore light can impinge on the front surface. The third portion  33  of the substrate  30  prevents light from impinging on the back surface of the active cell  62 . The active cell  62  therefore has a resistance that varies depending on the amount of light impinging on the front surface  68  of the active cell. As a result, the active cell  62  provides an output signal  63  (FIG.  4 ), over one or more lead wires  72  (FIG.  3 ), having a first characteristic if the active cell is exposed to light and a second characteristic if the active cell is not exposed to light. 
     The fourth portion  34  of the sensor assembly  30  includes an electronics package  80 . The lead wires  66  from the reference cell  60  and the lead wires  72  from the active cell  62  extend into the electronics package  80  on the fourth portion  34  of the sensor assembly  30 . The lead wires  54  from the solar cell array  50  also extend into the electronics package  80 . 
     The electronics package  80  (FIG. 4) includes a microprocessor or similar electronic circuitry  82  operative to receive signals from the active cell  62  and the reference cell  60  and process them in a manner described below. The electronics package  80  includes a battery  84  that is charged by the output of the solar cells  52 . The battery  84  provides power for the other parts of the sensor assembly  30 . 
     The microprocessor  82  determines the difference  86  between the output  61  of the reference cell  60  and the output  63  of the active cell  62 . This difference  86  is output as an open (high) or closed (low) output to an RF transmitter  88 . The transmitter  88  is operative, in response, to transmit a signal  90  indicative of the open or closed state of the window  20 , to a receiver  92  elsewhere on the vehicle  12 . The transmitter  88  and an antenna  94  may be provided as part of the electronics package  80 . 
     The apparatus  10  can provide a warning signal if the window  20  is open and the vehicle ignition is turned off. For example, the vehicle operator may shut off the engine of the vehicle  12  and exit the vehicle, leaving the window  20  in the open condition as shown in FIG.  1 . If this occurs, ambient light  100  strikes the front surface  68  of the active cell  62 . As a result, the output of the active cell  62  has a first characteristic that is different from the output of the reference cell  60 , which is covered. The output of the active cell  62  is compared with the output of the reference cell  60  by the circuitry  82 . The difference  86 , which is not zero and is therefore indicative of an open condition of the window  20 , is directed to the transmitter  88  where an appropriate signal is transmitted to the receiver  92 . The receiver  92  can be connected with other vehicle electric circuitry in order to, for example, illuminate a warning light (not shown) on the vehicle instrument panel. 
     When the window  20  is in the closed condition as shown in FIG. 1, the door frame  16  and the seal  18  prevent light from striking the front surface  68  of the active cell  62 . The substrate  40  prevents light from striking the back surface  70  of the active cell  62 . As a result, the output of the active cell  62  has a second characteristic that is the same as the output of the reference cell  60 , which is covered. The output of the active cell  62  is compared with the output of the reference cell  60  by the circuitry  82 . The difference  86 , which is zero and is therefore indicative of a closed condition of the window  20 , is directed to the transmitter  88  where an appropriate signal is transmitted to the receiver  92 . 
     In a general low light condition, the sensor assembly  30  can sense vehicle interior lighting as opposed to ambient lighting. For example, when the vehicle ignition is first turned off and the vehicle door  14  is opened, the vehicle interior lighting comes on for a programmed time period to assist the occupant in getting out of the vehicle  12 . This interior lighting can be sensed by the sensor assembly  30  to provide an indication of a window open condition. 
     The apparatus  10  can provide a warning signal even in very low light conditions. For example, the window  20  may at times be rolled all the way down in the door frame  16 , so that the upper portion  22  of the window is inside the door cavity (not shown). In this case, the ambient light level should still be high enough to produce a difference between the output of the active cell  62  and the output of the reference cell  60 . If not, then the apparatus  10  could be designed so that at least a portion of the active cell  62  is on the upper edge surface  20  of the window  20 , to achieve a higher light sensitivity. 
     In a second embodiment of the invention, the photoelectric cells  60  and  62  are photovoltaic cells rather than photoconductive cells. The circuitry  82  is operative to look at the difference between the voltage output of the reference cell  60  and the voltage output of the active cell  62  to determine if the active cell is covered (indicating a closed window) or uncovered (indicating an open window). In this case, the photovoltaic cells  60  and  62  may be used as the power supply for the sensor assembly, obviating the solar cells. 
     During the lifetime of the apparatus  10 , the photoconductive cells  60  and  62  may age, so that their output changes. Both the reference cell  60  and the active cell  62 , however, age at the same rate. Thus, any aging of the active cell  62  will be counterbalanced by similar aging of the reference cell  60 , so that the active cell does not provide false readings. 
     FIG. 5 is a functional block diagram of an apparatus  10   a  in accordance with a second embodiment of the invention. The apparatus  10   a  is similar in construction to the apparatus  10  (FIGS.  1 - 4 ). Parts of the apparatus  10   a  that are the same as or similar to corresponding parts of the apparatus  10  are given the same reference numerals with the suffix “a” attached. 
     In the apparatus  10   a  (FIG.  5 ), the reference cell value is programmed into the microprocessor  82   a . Specifically, the microprocessor  82   a  includes a memory  100  in which is stored a value equivalent to the output of a reference cell  60 . This eliminates the need for the reference cell itself, and allows use of only the active cell  62   a  in the sensor assembly. This can make the apparatus  10   a  simpler and less expensive than the apparatus  10  (FIGS.  1 - 4 ). The apparatus  10   a  does not, however, obtain the above-mentioned benefit of the reference cell  60 , specifically, that its presence helps to alleviate concern about aging of the active cell  62   a.    
     FIG. 6 illustrates an apparatus  10   b  in accordance with a fourth embodiment of the invention. The apparatus  10   b  is similar in construction to the apparatus  10  (FIGS.  1 - 4 ). Parts of the apparatus  10   b  that are the same as or similar to corresponding parts of the apparatus  10  are given the same reference numerals with the suffix “b” attached. 
     The apparatus  10   b  includes a sensor assembly  30   b  that may be the same as the sensor assembly  30   a , but excluding the transmitter  88 . The sensor assembly  30   b  is molded into the window glass during the manufacture of the window  20 . The active cell  62   b  and the reference cell  60   b  are both exposed to ambient light when the window  20   b  is in the down or open condition. 
     One or more contacts  102  are provided on the glass  20   b . The contacts  102  are electrically connected with the sensor assembly  30   b . Wires  104  are soldered to the contacts  102 . Alternatively, a connector (not shown) may be glued on the window  20   b  and wire connections made with press down terminals. The output of the sensor assembly  30   b  is directed through the wires  104  to vehicle electric circuitry, to be processed and used as described above. 
     FIGS. 7 and 8 illustrate an apparatus  10   c  in accordance with a fifth embodiment of the invention. The apparatus  10   c  is similar in construction to the apparatus  10  (FIGS.  1 - 4 ). Parts of the apparatus  10   c  that are the same as or similar to corresponding parts of the apparatus  10  are given the same reference numerals with the suffix “c” attached. 
     The apparatus  10   c  includes a sensor assembly  30   c  that is similar to the sensor assembly  30  (FIG.  3 ). In the sensor assembly  30   c , however, a single array  110  (FIG. 7) of photovoltaic cells  112  extends across the first, second and third portions  31   c ,  32   c  and  33   c  of the sensor assembly. The output of the array  110  of photovoltaic cells  112  is connected with the electronics package  80   c . The electronics package  80   c  includes a memory  100   c.    
     The array  40  of photovoltaic cells  110  in the apparatus  10   c  serves two functions. First, the array  112  of photovoltaic cells  110  provides power for the sensor assembly  30   c . Second, the output of the array  110  of cells  112  varies depending on the amount of light impinging on the array. Thus, the array  110  of photovoltaic cells  112  provides an output value to the electronics package  80   c  that can be used to determine the open or closed state of the window. 
     From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications in the invention. For example, that the present invention is applicable to windows that are not located in doors of a vehicle. The invention is applicable also to a vehicle window whose upper portion is received in a channel in a door frame, covering both inner and outer side surfaces of the window upper portion. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.