Abstract:
Vehicle apparatus includes a glass windshield and a wiper system. A wiper blade has a parking region on the windshield. A deicer selectably provides heat to the parking region. A windshield temperature sensor detects a temperature of the windshield at the parking region. A head-up display is mounted proximate the windshield to display a temperature indicator responsive to the detected temperature. An automatic control circuit is configured to automatically deactivate the deicer when detecting a deiced condition in response to the detected temperature. A manual control element is configured to manually activate and deactivate the deicer. Thus, excessive heating can be avoided based on feedback of the windshield temperature. In addition, the driver is reminded that the deicer is active in a way that simultaneously provides information enabling the driver to independently evaluate the vehicle conditions and to make informed decisions about when to intervene in the automatic operation.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not Applicable. 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
       [0002]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
       [0003]    The present invention relates in general to deicing of windshields of road vehicles, and, more specifically, to reduction of energy use in connection with heating the windshield at the park position of a wiper blade. 
         [0004]    To improve the performance of windshield wiper blades in cold or freezing weather, a wiper deicer has become a desirable feature. In particular, such a deicer may provide heating to the windshield and to the wiper blades (which may be parked at a wiper park position at a lower edge of the windshield). The applied heat can reduce or eliminate ice and snow buildup on a wiper blade that impairs performance or that necessitates manual cleaning of a wiper blade by a driver. 
         [0005]    While a wiper deicer can be activated manually, it may be particularly beneficial in connection with the remote starting of a vehicle so that the vehicle is in a ready state when the driver enters the vehicle. A typical deicer system will automatically turn off after a predetermined time. Although a manual switch is provided for deactivating the deicer, a user may inadvertently forget to turn the system off after sufficient warming has occurred. Automatic turn-on times are typically chosen to keep the deicer activated long enough to complete deicing under the majority of freezing conditions to be expected. 
         [0006]    A commonly used source of heat is an electrical resistance heating layer incorporated into or applied onto the windshield and driven by the vehicle electrical system. Heat can also be obtained via a hot air (i.e., defrost) outlet from a cabin HVAC system. Depending on the type of vehicle, the HVAC heat can be derived from an electrical resistance (positive temperature coefficient) heater or as waste heat from an internal combustion engine. In any case, the deicer can consume significant amounts of battery charge. 
         [0007]    Automatic deactivation of the deicer after a predetermined amount of time fails to adapt the deicing function to the actual conditions. Thus, known systems may result in excessive battery discharge if left on too long or may result in insufficient deicing if turned off too soon. In electric or hybrid-electric vehicles, any excess battery drain becomes especially problematic since the electric driving range of the vehicle may be reduced. 
       SUMMARY OF THE INVENTION 
       [0008]    In one aspect of the invention, a vehicle apparatus comprises a glass windshield and a wiper system including a wiper blade having a parking region on the windshield. A deicer selectably provides heat to the parking region. A windshield temperature sensor detects a temperature of the windshield at the parking region. A head-up display is mounted proximate the windshield to display a temperature indicator responsive to the detected windshield temperature. An automatic control circuit is configured to automatically deactivate the deicer when detecting a deiced condition in response to the detected windshield temperature. A manual control element is configured to manually activate and deactivate the deicer. Thus, excessive heating can be avoided based on feedback of the windshield temperature. In addition, the driver is reminded that the deicer is active in a way that simultaneously provides information enabling the driver to independently evaluate the vehicle conditions and to make informed decisions about when to intervene in the automatic operation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  shows a windshield with a wiper system and windshield heating by a glass-mounted heater and by a warm air flow from an HVAC system. 
           [0010]      FIG. 2  is an interior view within a vehicle passenger cabin including a windshield and a remote temperature sensor mounted in a rearview mirror. 
           [0011]      FIG. 3  is a side view showing the placement of one type of head-up display in proximity to the windshield. 
           [0012]      FIG. 4  is a block diagram of an electric vehicle with a deicer system according to one embodiment of the invention. 
           [0013]      FIG. 5  is a state diagram for a deicer control according to a preferred embodiment of the invention. 
           [0014]      FIG. 6  shows one embodiment with a head-up display providing a visible indicator that overlaps with a wiper parking region. 
           [0015]      FIG. 7  shows additional display options including a text display and a display indicator installed along a vertical side of the windshield. 
           [0016]      FIG. 8  shows one preferred embodiment with head-up indicators for windshield temperature and battery charge. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0017]    Referring now to  FIG. 1 , a glass windshield  10  has an associated wiper system  11  which includes wiper blades  12  and  13  on wiper arms  14  and  15  linked to a wiper motor  16  by a linkage  17 . Wiper motor  16  may respond to a user interface  20  for activating the wiper system (e.g., in intermittent or continuous modes). 
         [0018]    Windshield  10  can be heated in one or more ways. For example, a resistive heating layer  21  is incorporated in windshield  10  as known in the art. Layer  21  is transparent and can extend over the entire windshield surface as shown or can alternatively cover only a lower portion of windshield  10  to provide heating at a wiper parking region. One end of layer  21  is connected to an electrical ground  22  and an opposite end is connected to a battery  23  via a controllable switch  24 . Battery  23  is likewise connected to a ground  25 . Switch  24  has a control input which is coupled to user interface  24  so that battery power can be selectably coupled from battery  23  to resistive heating layer  21 . User interface  20  may include stalk mounted switches and/or dash panel switches as known in the art. 
         [0019]    As shown in  FIG. 2 , user interface  20  may be located on a front face of an instrument panel  26  in the vicinity of a steering wheel  27 . A wiper parking region  30  at a lower edge of windshield  10  is monitored by a remote temperature sensor  31 . Sensor  31  can be mounted on a rearview mirror  32 , for example. Sensor  31  is preferably comprised of an infrared sensor arranged to have a field of view coincident with parking region  30 . One example of an infrared remote sensing device is the MLX90614 infra red thermometer available from Melexis Microelectronic Integrated Systems in Novi, Mich. 
         [0020]    Temperature sensor  31  may be connected by a wiring harness to a control circuit (not shown) via rearview mirror  32 . The control circuit may comprise a microcontroller or other processor which may be integrated with user interface  20  or may be located in another electronic module within the vehicle. A head-up display  33  is located proximate windshield  10  to display a temperature indicator for easy viewing by the driver at a position close to wiper parking region  30  to establish an intuitive relationship between the display and the controlled function. The indicator is generated in response to the detected windshield temperature from sensor  31 , and the magnitude of the temperature can be represented using text, a color mapping, light intensity or brightness, a flashing icon with a variable blinking rate, a partially-illuminated bar (similar to a progress bar), or other visual features. As shown in  FIG. 2 , head-up display  33  may be incorporated into a vehicle&#39;s A-pillar along an edge of windshield  10 . Display  33  may preferably be comprised of a multicolor LED, an array of LEDs, an LCD panel or other display technologies. 
         [0021]    As shown in  FIG. 3 , a head-up display based on reflection by the windshield of an indicator generated by a light projector can be used. Thus, a light projector  36  mounted to instrument panel cover  33  projects a temperature indicator (and/or indicators for other parameters) onto windshield  10  which may be reflected toward the driver as shown at  37 . Preferably, light projector  36  and windshield  10  are oriented such that the apparent location for the temperature indicator as seen by the driver overlaps or adjoins with the wiper parking region. Light projector  36  may be comprised of a multicolor LED for representing hotter temperatures with shades of red and colder temperatures with shades of blue, as commanded by a controller  38 . 
         [0022]      FIG. 4  shows a vehicle  40  having a windshield  41  with a wiper park deicer  42  to selectively provide heat to a wiper parking region under control of a controller  43 . Controller  43  may include a discrete control circuit, a programmable gate array, or a general-purpose microcontroller, for example. Vehicle  40  is shown as an electric vehicle including a battery pack  44  and an electric drive  45 . A battery control module (BCM)  46  is used in conjunction with battery pack  44  as known in the art. BCM  46  is coupled with controller  43  for providing data relating to a charge level of the battery pack to allow the battery charge to be displayed to the driver. Thus, the driver can consider the impact on battery charge when choosing to activate or deactivate the deicer. 
         [0023]    A remote keyless entry (RKE) module  47  communicates with a remote transmitter  48  permitting a driver to initiate a remote start of vehicle  40  as known in the art. In the case of an electric vehicle, a “remote start” may include an initiation of heating or cooling of the passenger cabin and activation of the windshield wiper deicer before the driver enters the vehicle. Thus, RKE module  47  is coupled with controller  43  to initiate deicer operation when a remote start event occurs. 
         [0024]    Controller  43  is coupled to a plurality of sensors for determining an iced-up or a deiced (i.e., ice-free) condition of the windshield wiper parking region. The sensors include windshield temperature sensor  50 , an outside ambient air temperature sensor  51 , an inside ambient air temperature sensor  52 , and a sunload sensor  53 . Windshield temperature sensor  50  is preferably comprised of an infrared temperature sensor for monitoring the wiper parking region as described above. In response to the various sensor inputs, controller  43  uses a pre-programmed model to determine the most likely iced/deiced state of the windshield glass. Using the determined condition, controller  43  may be further configured to provide automatic control of deicer activation and deactivation. 
         [0025]    The present invention additionally provides for manual intervention via a user interface  55  and head-up display  56 . User interface  55  includes one or more manual control elements configured to manually activate and/or deactivate the deicer heating function. Head-up display  56  is located proximate (i.e., directly upon, next to, or visible by reflection from) windshield  41  in order to display a temperature indicator responsive to detected windshield temperature as described above. Head-up display  56  may include a light projector/generator installed to the side of windshield  41  or may alternatively include light generating elements applied directly to windshield  41  such as a printed LED film  57  which would likewise be controlled by controller  43 . 
         [0026]    Controller  43  may preferably implement an empirically-based model for determining whether freezing conditions exists at windshield  41  which can be inferred using the various sensed temperatures, sunload, and other factors. A model which estimates heat flow within the air, glass, and surrounding materials to predict whether a deiced condition would be present can be easily derived using known methods. 
         [0027]    In addition to or instead of the temperature based model, the presence of ice on the wiper blade or windshield (or even a blade that is frozen in place at the parking region) can be determined based on an electrical response of the wiper system. For example, a current drawn by the wiper motor under normal, deiced conditions (e.g., a current waveform) could be characterized in advance. By energizing the wiper motor and then monitoring an actual current, the normal deiced condition could be detected based on how well the actual current matches the predetermined current. 
         [0028]    In a simplified alternative embodiment, the additional temperature/sunload sensing and the processing for predicting the deiced condition could be avoided. Controller  43  could provide automatic deactivation based only upon a predetermined “on-time” or delay for energizing the deicer. In such an embodiment, the driver can still obtain increased efficiency based on the head-up display showing the windshield temperature 1) as a reminder that the deicer is active, and  20  as a source of data that is helpful in determining when the deicer can be deactivated. 
         [0029]      FIG. 5  shows one preferred embodiment of a state diagram for a deicer system of the invention. In an initial state  60 , the deicer is deactivated. In response to a start signal (e.g., starting of the vehicle via a remote fob or an in-vehicle start switch), the system control circuit transitions to a state  61  wherein measured inputs (e.g., temperatures and sunload) are gathered, and the controller performs a check for detecting a deiced condition. If a deiced (i.e., ice-free) condition is detected, then a transition is made back to state  60  and the deicer remains deactivated. If a deiced condition does not exist (i.e., a certain probability of freezing exists), then a transition is made to On state  62 , whereupon the deicer is activated. While in On state  62 , periodic re-checks for the deiced condition may be performed by transitioning back to state  61 . Thus, the deicer will turn off (i.e., deactivate) once the deiced condition is reached. While in state  62 , the head-up display(s) are continuously updated in order to inform the driver of the windshield temperature and/or other parameters such as battery charge level and an amount of time remaining until an automatic deactivation of the deicer is scheduled to occur. While in On state  62 , a manual off event can be initiated by the driver using a manual control element, which causes a transition back to Off state  60 . 
         [0030]    When entering On state  62 , a predetermined on-time may be loaded into a countdown timer that deactivates the deicer upon expiration of the on-time. Decrementing of the timer occurs in response to periodically-timed transitions made from On state  62  to a Compute Time state  63  which adjusts the remaining time (e.g., by decrementing the contents of the timer). If the timer has not yet expired (i.e., not yet decremented to zero), then a return is made to On state  62 . A different adjustment of the remaining time would occur in response to a corresponding manual activation of a manual control element by the driver while in On state  62 . In other words, a transition is made from On state  62  to Compute Time state  63  where the contents of the countdown timer are increased by a predetermined amount in order to extend the time remaining before an automatic deactivation. Thus, the driver may have been informed by the head-up display of an imminent automatic deactivation, and the driver responds by pressing the control element for extending activation of the deicer based on visible icing-up of the wiper blade, for example. If decrementing the timer in state  63  results in a zero (i.e., the timer expires), a transition is made to Off state  60  and the deicer is deactivated. 
         [0031]      FIGS. 6-8  provide specific examples for a head-up display. In  FIG. 6 , a light projector  70  (such as an array of colored LED elements with projection lenses if needed) is arranged at a periphery of a windshield  71 . The wiper parking region  72  on windshield  71  is heated by a deicer (not shown). Light projected from projector  70  onto windshield  71  is reflected toward the driver with an apparent position  73  overlapping or adjoining wiper park region  72 . A driver circuit  74  coupled to LED array  70  receives corresponding control signals for varying a color, brightness (intensity), and/or flashing at a commanded pulse repetition rate. The control signals implement a chosen schema that communicates to the driver the windshield temperature data. For example, a temperature below freezing may be represented by blue (e.g., with different shades of blue for different temperature ranges) and a temperature above freezing represented by a red light (e.g., with different shades of red for different temperature ranges). As a timed activation of the deicer approaches expiration, a pulse repetition rate for the temperature data can be increased to signal the driver of the impending deactivation. 
         [0032]    As shown in  FIG. 7 , and on-window head-up display  75  on a windshield  76  may include a text display for indicating the deicer status. A text display can be implemented using a printed LED film, for example. A driver circuit  77  responds to a controller (not shown) for configuring the display. The head-up display may further include an LED array  78  which is located proximate to windshield  76  by installing it along an edge of windshield  76 . An array of LEDs may be arranged in a lineal pattern with a variable number of LEDs being illuminated beginning at one end in order to indicate the desired information. Thus, the length of an illuminated bar and/or the color(s) shown along the bar can be used to convey temperature and or time information. Poor battery charge information. 
         [0033]    In yet another embodiment as shown in  FIG. 8 , a windshield  80  may include a plurality of individual head-up displays  81  and  82  projected on windshield  80  to provide a coordinated representation to the driver for windshield temperature, battery charge, or other relevant information. 
         [0034]    As shown by the foregoing description, a head-up display can be constructed with various different display technologies such as printed LED films, LED projectors, and discrete LEDs or text displays. Display indicators can use text, color, flashing, and other changes of intensity to convey temperature and other data. The invention provides an improved deicer performance and a reduced energy consumption by employing an infrared sensor to monitor glass temperature at the windshield wiper park area before, during, and after heating by the deicer. The measured glass temperature is used to generate a driver information display and/or to use in an algorithm for inferring a deiced condition and automatically controlling deicer turn on/turn off. The preferred embodiment provides a coordination of automatic and manual methods that ensures deicer power consumption occurs only when needed. The use of an intuitive indicator in a convenient viewing location reduces the amount of the driver&#39;s attention required. The invention provides an effective reminder of system status, remaining activation time, and temperature of the windshield. The head-up display indicators can be configured to provide light over a large area while allowing the driver to see through the indicator, thereby maintaining attention of the road while obtaining the head-up display information. The small size of the display elements and the unobtrusive locations allow the vehicle manufacturer more styling freedom to create an attractive product. In a preferred embodiment, the automatic control of the deicer is adapted to accept manual overrides and to provide useful information to the driver for making effective activation decisions based on important considerations including wiper performance and electric vehicle driving range.