Abstract:
A climate control system for the interior cabin of an automotive vehicle. The climate control system includes a mode selection device configured for selecting a defrost mode. When the system is in the defrost mode, a controller receives a signal from a humidity sensor indicative of the measured humidity level in the vicinity of the window. The controller compares this measured humidity level with a threshold humidity level and, if the humidity is below the threshold humidity level, the controller stops operation of a compressor being used to dehumidify the air being provided to defrost the window, thereby minimizing possible fogging of the window and increasing the efficiency of the vehicle.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The present invention generally relates to the climate control system of an automotive vehicle. More specifically, the invention relates to a climate control system for preventing the fogging of a window of an automotive vehicle while improving fuel efficiency. 
         [0003]    2. Description of Related Art 
         [0004]    Generally, the climate control system in an automotive vehicle performs several functions. In addition to generally maintaining the interior cabin temperature of the vehicle, the climate control system can also be used to defrost or defog certain windows of the vehicle. 
         [0005]    The exterior of the front windshield of the vehicle is subject to becoming covered with ice. In addition to this, if humidity and temperature conditions are right, frost or fog may either alternatively or simultaneously form on the interior surface of the windshield. Similarly, this fogging on the interior surface may occur on side windows of the vehicle as well. One factor contributing to fogging of the windows of the vehicle is that the climate control system may direct warm humid air onto a cool window surface if the climate control system is in its defrost setting. 
         [0006]    To combat the fogging problem, climate control systems have been configured to automatically dehumidify air when the system is in the defrost mode. To dehumidify air being directed toward window surfaces of the vehicle, when the HVAC system is placed into the defrost mode, the compressor of the HVAC system is automatically turned on. Air is then passed over the condenser or heat exchanger coupled to the compressor. The temperature of the condenser causes moisture in the air to condense on the exterior surfaces of the condenser, thus drying the air. The dry air is then heated and directed at the targeted window surface. 
         [0007]    The operation of a compressor, however, is a significant source of power consumption in the vehicle, and vehicles can see decreases of 10-20 hp. As a result, operation of the compressor decreases the fuel economy in gasoline, diesel and hybrid vehicles by up to 10% and decreases the mileage range in an electric vehicle. 
       SUMMARY 
       [0008]    In overcoming the enumerated drawbacks and other limitations of the related art, the present invention provides a climate control system for the interior cabin of an automotive vehicle, the climate control system comprising: a mode selection device configured for selecting between a defrost mode and at least one non-defrost mode; a compressor and condenser configured to dehumidify air being provided to an interior cabin of the automotive vehicle; a humidity sensor located adjacent to a window of the automotive vehicle; a controller coupled to the mode input device, the compressor and condenser, and to the humidity sensor; a blower configured to move air over the condenser in providing air to the cabin of the automotive vehicle; and wherein, when the mode selection device is in the defrost mode, the controller being configured to receive a humidity signal from the humidity sensor indicative of the humidity in the vicinity of the window and being configured to operate a compressor if the humidity is above a threshold value and to not operate the compressor if the humidity is below the threshold value. 
         [0009]    In another aspect of the invention, the window is a windshield of the automotive vehicle. 
         [0010]    In a further aspect of the invention, the window is a side window of the automotive vehicle. 
         [0011]    In still another aspect of the invention, two humidity sensors are provided and the controller is configured to operate the compressor if the humidity signal from at least one of the two humidity sensors is greater than the threshold value and is configured to not operate the compressor if the humidity signals from all of the humidity sensors are below the threshold value. 
         [0012]    In an additional aspect of the invention, an air vent is located adjacent to the window and coupled to direct air from the blower onto the window. 
         [0013]    In a still further aspect of the invention, the humidity sensor is spaced apart from the vent. 
         [0014]    In yet another aspect of the invention, the humidity sensor is located adjacent to a lower portion of the window. 
         [0015]    In another aspect of the invention, a method of operating a climate control system of an automotive vehicle is provided comprising the steps of: measuring the humidity of air in a vicinity of a window of the automotive vehicle; determining if the climate control system is in a defrost mode; providing a flow of air specifically directed toward the window when the climate control system is in the defrost mode; measuring the humidity of air in the vicinity of the window; comparing the measured humidity with a threshold humidity value; determining if a compressor coupled to a condenser provided as part of an air conditioning subsystem is operating; and if the compressor is operating, turning OFF the compressor when the measured humidity is less than the threshold humidity value. 
         [0016]    In a further aspect of the invention, the step of measuring the humidity of air is performed at two locations within the vicinity of the window. 
         [0017]    In another aspect of the invention, if the measured humidity at one of the two locations is above the threshold humidity value, the compressor is not turned OFF. 
         [0018]    In still another aspect of the invention, if the measured humidity at both of the two locations is below the threshold humidity value, the compressor is turned OFF. 
         [0019]    In yet another aspect, the invention further comprises the step of heating the flow of air. 
         [0020]    In a further aspect, the invention provides a climate control system for the interior cabin of an automotive vehicle, the climate control system comprising: a defrost mode selection device provided as part of a user interface and being selectable to enter a defrost operational mode of the climate control system; a compressor and a condenser configured to dehumidify a flow of air being provided to an interior cabin of the automotive vehicle, the condenser being located within the flow of air; at least one humidity sensor located adjacent to a window of the automotive vehicle and configured to provide a measured humidity signal indicative of a measured humidity level; a controller coupled to the defrost mode input device, the at least one humidity sensor, and the compressor and condenser; a blower configured to move air over the condenser in providing the flow of air to the cabin of the automotive vehicle; and wherein, when the defrost mode selection device is selected, the controller being configured to receive the measured humidity signal from the at least one humidity sensor and being configured to compare the measured humidity level to a threshold humidity level, wherein the controller is configured to stop operation of the compressor if the measured humidity level is less than the threshold humidity level. 
         [0021]    In an additional aspect of the invention, the window is one of a windshield and a side window of the automotive vehicle. 
         [0022]    In yet another aspect of the invention, the controller is configured to continue operation of the compressor if the measured humidity level is greater than the threshold humidity level. 
         [0023]    In a still further aspect, the invention further comprises a plurality of humidity sensors, the controller being configured to stop operation of the compressor if the measured humidity levels from all of the humidity sensors are less than the threshold humidity level. 
         [0024]    In another aspect, the invention further comprises a plurality of humidity sensors, the controller being configured to not stop operation of the compressor if the measured humidity levels from all of the humidity sensors are not less than the threshold humidity level. 
         [0025]    In yet another aspect of the invention, the plurality of humidity sensors are spaced along a windshield of the automotive vehicle. 
         [0026]    Further objects, features and advantages of this invention will become readily apparent to persons skilled in the art after a review of the following description, with reference to the drawings and claims that are appended to and form a part of this specification. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1  is a schematic illustration of a climate control system embodying the principles of the present invention; and 
           [0028]      FIG. 2  is a flowchart illustrating a method of operating the climate control system illustrated in  FIG. 1  in accordance with the principles of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    Referring now to the drawings, an HVAC or climate control system embodying the principles of the present invention is illustrated therein and designated at  10 . The climate control system  10  generally resides behind an instrument panel (not shown) that is located in the interior cabin of the automotive vehicle, generally immediately below the front windshield  12 . In at least one mode of operation, the climate control system  10  directs air towards the interior surface of the windshield  12  and may, additionally, direct air towards an interior surface of a side window  14 , such as the driver&#39;s side window shown in  FIG. 1 . When used herein, the term “window” is intended to be generic for either the windshield  12  or the side window  14 . As such, the latter terms are interchangeable or alternative considerations. If the context of the text is meant to connote a specific interpretation, the terms windshield  12  and side window  14  are employed. 
         [0030]    In order to direct air towards the window, the climate control system  10  includes one or more vents  16  located near the window. The vents  16  are positioned such that when air is provided by a blower  18 , the air is directed by the vent  16  out and onto the interior surface of the window. Air being discharged by the vent  16  is generally designated at  20 . 
         [0031]    The blower  18  is controlled by an electronic control unit (ECU)  22  of the climate control system  10 . The ECU  22  is additionally coupled to a user interface  24 , provided on part of the instrument panel, and which includes various inputs for operating the climate control system  10 . Some of these inputs, but by no means an exhaustive illustration thereof, are seen in  FIG. 1 . At least one of these inputs allows for the selection of a mode within which the climate control system  10  will operate. 
         [0032]    The mode for operation of the climate control system  10  may be made by way of a general mode selection button  26  that allows for the switching between or sequencing through a number of different modes. Alternatively or additionally, the user interface  24  may include one or more designated mode buttons  28 . As seen in  FIG. 1 , user interface  24  includes a designated mode button  28  for selection of the defrost mode of the climate control system  10 , as well as a general mode selection button  26 . 
         [0033]    The ECU  22  is also coupled to one or more humidity sensors  30 . If a single humidity sensor  30  is employed, the sensor  30  is preferably positioned in a location adjacent to the interior surface of the windshield  12 . If multiple humidity sensors  30  are employed, more than one humidity sensor  30  may be located adjacent to the windshield  12  and/or an additional humidity sensor  30  may be located adjacent to the side window  14 . In locating the humidity sensors  30  adjacent to the windshield  12  and side window  14 , the humidity sensors  30  may be mounted directly to the interior surface of these windows or may be mounted to a trim component located adjacent to these windows. With either configuration, the humidity sensors  30  are mounted such that they are not directly positioned in front of the vents  16 . In other words, the air  20  being discharged from the vents  16  should not be directed directly at or over the humidity sensors  30 . In this way, the humidity sensors  30  are capable of providing to the ECU  22  a measured value (H m ) for the humidity of the ambient air in the region adjacent to the windows without undue influence from the air being discharged from the vents  16 . 
         [0034]    Air from the blower  18  is routed by a conduit  32  such that the air passes over the chilled or cooler surfaces of a condenser (a heat exchanger) coupled to a compressor, which are collectively designated at  34  in  FIG. 1 , of the air conditioning subsystem of the climate control system  10 . From the condenser  34 , the air is directed by the conduit  32  to a heater core  36  (also a heat exchanger) of the heating subsystem of the climate control system  10 . Typically, the heater core  36  is coupled to the coolant system of the vehicle&#39;s engine and uses heat derived from the engine to warm the air as it passes over the surfaces of the heater core  36 . From the heater core  36 , the warmed air is directed to the vents  16  and discharged at  20  toward the interior surface of the windshield  12 . 
         [0035]    When it is desired that air being provided to the cabin be dehumidified, the air conditioning subsystem of the climate control system  10  is operated, resulting in operation of the compressor  34  and cooling of fluid passing through the condenser  34 , and thereby cooling of the surfaces of the condenser  34  itself. If the relative humidity in the air is sufficiently high as it passes over the condenser  34 , the water vapor in the air will condense on the surfaces of the condenser  34 , thereby resulting in less humid air being passed from the condenser  34  to the heater core  36  and discharged into the cabin of the vehicle. With drier air  20  being directed at the interior surface of the window during the defrost mode of operation, the likelihood that the window will become fogged is decreased. 
         [0036]    In theory, the compressor  34  can be continuously run to remove excess water vapor from the air in the cabin compartment of the vehicle. As previously noted, however, when operating the compressor  34 , the vehicle&#39;s power consumption is increased while fuel economy and mileage range are decreased. For this reason, most climate control systems do not operate the compressor in all modes of operation. Typically, the compressor  34  will be run by the climate control system in the air-conditioning mode and, surprisingly to many people, in the defrost mode. The compressor  34  is operated during the defrost mode in order to dry the air being provided to the window and thereby prevent or minimize fogging of the window. 
         [0037]    In the present climate control system  10 , if the defrost mode has been selected, either by using the general mode selection button  26  or the designated defrost mode button  28 , the system makes a determination as to whether the compressor  34  is running and, if so, if it should be kept running The method of operating the climate control system  10  is set out in  FIG. 2 . If operation of the compressor  34  is not needed because the relative humidity of the air adjacent to the window is not likely to cause fogging, the compressor  34  is turned OFF. This directly results in increased available power to the vehicle, better fuel economy and mileage range. 
         [0038]    Referring now to  FIG. 2 , generally the climate control system  10  operates to determine if the humidity of the air near the window is high enough to promote fogging. In doing this, a measured humidity level is compared against a threshold humidity level. The threshold humidity level is the humidity level at which water vapor in the air will condense if warmed and brought into contact with the cooler window. This threshold may be dynamically determined based on ambient conditions or it may be static and based on average conditions as to when the defrost mode might be employed. If the measured humidity is less than the threshold, the system  10  then determines if the compressor  34  is running If it is running, the system  10  turns OFF the compressor  34 , increasing the efficiency of the operation of the vehicle. 
         [0039]    Operation of the system  10  begins in step  50 . After beginning, the ECU  22  determines in step  52  whether the climate control system  10  is being operated in the defrost mode. As noted above, the system  10  enters the defrost mode by a person in the vehicle manually selecting the mode via the designated defrost mode button  28  or general mode selection button  26 . Alternatively, the system  10  may enter the defrost mode automatically because of various sensed parameters. 
         [0040]    If the system  10  is not in the defrost mode, then the procedure proceeds to box  60 , returns to box  50  and starts over. If the system  10  determines in step  52  that it is in the defrost mode, the method proceeds to step  54 . 
         [0041]    In step  54 , the ECU  22  determines if the humidity level in the vicinity of the windshield  12  is less than a threshold humidity level (H t ). The measured humidity level (H m ) is determined by the humidity sensors  30 , which are in communication with the ECU  22 . If only a single humidity sensor  30  is used in the system  10 , the ECU  22  compares that measured value with the threshold humidity level (H t ). If more than one humidity sensor  30  is used, the ECU  22  determines if all of the measured humidity levels (H m ) are below the threshold humidity level (H t ). If it is determined that the measured humidity level (H m ) is not less than the threshold humidity level (H t ), the method proceeds to box  62 . 
         [0042]    In box  62 , the ECU  22  determines if the compressor  34  is ON. If the compressor  34  is ON, the process proceeds to box  60  and restarts. If the compressor  34  is not ON, in other words, the compressor  34  is OFF, the process proceeds to box  64 . In box  64 , the ECU  22  turns the compressor  34  ON then proceeds to box  60  and restarts the process. 
         [0043]    If, in box  54 , the ECU  22  determines that the measured humidity level (H m ) is less than the threshold humidity level (H t ), the process then proceeds to box  56 . It should be noted that, if more than one humidity sensor  30  is being employed in the system  10 , then all of the measured humidity levels (H m ) should be less than the threshold humidity level (H t ). 
         [0044]    In box  56 , the ECU  22  determines if the compressor  34  is ON. If the ECU  22  determines that the compressor  34  is OFF (not ON), the method proceeds to box  60  and returns to start. If the compressor  34  is determined by the ECU  22  to be ON, then the method proceeds to box  58 , wherein the compressor  34  is turned OFF because the need for drier air to prevent fogging either does not exist or has been abated. 
         [0045]    As a person skilled in the art will readily appreciate, the above description is meant as an illustration of implementation of the principles this invention. This description is not intended to limit the scope or application of this invention in that the invention is susceptible to modification, variation and change, without departing from the spirit of this invention, as defined in the following claims.