Abstract:
An automatic defogging system of a vehicle according to an exemplary embodiment of the present invention includes: an input unit used for receiving a directly sensed window relative humidity value from a defogging sensor so as to directly sense a humidity generation degree in a window; a controller which controls operations of an air conditioning system programmed as a type of a logic that is selectively and phasedly controllable depending on the sensed relative humidity and; an output unit that is a selection mode of the air conditioning system that can be controlled by the controller. Accordingly, an automatic defogging system of a vehicle and a control method thereof automatically removes fog or frost on an inner surface of a window while maintaining comfortable conditions inside a vehicle.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims priority to of Korean Patent Application No. 10-2005-0122455 filed in the Korean Intellectual Property Office on Dec. 13, 2005, the disclosures of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   (a) Field of the Invention 
   The present invention relates to an automatic defogging system of a vehicle and a control method thereof. In particular, the present invention provides automatic defogging system of a vehicle and a control method thereof automatically removing fog or frost on an inner surface of a window while maintaining comfortable conditions inside the vehicle. 
   (b) Description of the Related Art 
   An air conditioning system makes comfortable conditions for occupants in a vehicle by removing fog or frost on the window. An air conditioning system includes an air ventilation device, an air conditioner, and a defrost switch included in the air conditioner. 
   The air ventilation device is divided into a spontaneous ventilation type which brings in air from the outside and sends the outer air into the vehicle by a pressure difference generated by vehicle driving and a compulsory ventilation type using a blower. The air conditioner adopts the compulsory ventilation type. 
   It is configured such that the hot air flows downward and the cold air flows upward or moves along a surface of a window from an outlet in order to removing fog on an inner surface of a window. The occupant can regulate air flow within the vehicle by controlling the opening and closing of a duct. 
   The duct controls operations of respective elements constituting an air conditioning system. The duct is controlled by switches located in an instrument panel such as a blower switch, a mode switch, and a heating/cooling switch. 
   By controlling the air conditioning system, the conditions in the vehicle are comfortable. In particular, the defrost switch is a device that removes humidity, fog or frost on a window. In particular, humidity, fog or frost can be removed thereby securing a view of an occupant. 
   An air conditioning system removes concentrated humidity or prevents the concentration of humidity, as shown in  FIG. 1 .  FIG. 1  includes an input unit  1  which sends out electrical signals from a window surface temperature sensor which detects the temperature of the surface of a window and an interior humidity sensor detects the humidity in a vehicle; a controller  2  which includes an air conditioning system that is programmed to a specific logic and selectively and phasedly is controlled based on a difference between a window surface temperature value detected by the window surface temperature sensor and a dew-point temperature calculated by the detected value of the interior humidity sensor, and an output unit  3  that is a selection mode of an air conditioning system that can be controlled by the controller  2 . In this application, “sensed” and “detected” are used interchangeably. Additionally, a control unit comprises a processor, a memory, and associated hardware and software as may be selected and programmed by persons of ordinary skill in the art based on the teachings of the present invention contained herein. 
   By operating an air cooling function or an air heating function according to the weather, the concentrated humidity on a window can be automatically removed or the concentration of humidity can be prevented. 
   However, since the humidity of the window is estimated by the temperature value detected by the window surface temperature and an interior humidity value detected by the interior humidity sensor, an accurate humidity value cannot be obtained. 
   In addition, since the defrost door cannot be independently controlled, a temperature change inside the vehicle may occur. 
   If a driver uses the control logic of the conventional air conditioning system, a driver may feel alienation according to a mode operation, and it is quite difficult to maintain a room temperature. 
   The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
   SUMMARY OF THE INVENTION 
   The present invention provides an automatic defogging system of a vehicle which includes a window humidity sensor installed on the inner surface of a window and phasedly operates an air conditioning system by a humidity removing logic depending on the detected signal thereby removing humidity and a control method. 
   An exemplary embodiment of the present invention provides an automatic defogging system of a vehicle which includes an input unit receiving a directly detected window relative humidity value from a defogging sensor so as to directly sense a humidity generation degree in a window; a controller which controls operations of an air conditioning system that is programmed in a specific logic that is selectively and phasedly controlled depending on the detected relative humidity and; an output unit that is a selection mode of the air conditioning system that can be controlled by the controller. 
   The controller may control an intake door allowing dry outer air to flow into a vehicle. A blower regulates an amount of the outer air which flows into the vehicle. An air conditioner supplies cool or hot air in which humidity is removed into the passenger room. A mode door sends out all air toward a window thereby maximally removing humidity. In case of excessive humidity within the vehicle, the defrost door sends out a portion of air toward the window while maintaining the temperature in the vehicle thereby removing humidity. 
   The defrost door may be independently controlled. 
   A control method of an automatic defogging system of a vehicle according to an embodiment of the present invention includes detecting a window relative humidity value, comparing the sensed window relative humidity value to a reference value, removing humidity by selectively operating a selection mode of an air conditioning system based on the comparison of the sensed window relative humidity to the reference value, and controlling a temperature in the vehicle. 
   When the window relative humidity in the vehicle increases, humidity is removed by: if the sensed value is greater or equal to value c and less than value d, the intake door and the defrost door is opened; if the sensed value greater than or equal to d and less than value g, the defrost door is fully opened, the air conditioner is operated, and the amount of air of a blower is increased; if the value is greater than or equal to g and less than value h, the defrost mode is converted and an amount of air is increased from the blower; if the sensed value is greater than or equal to value h, the amount of air of the blower is maximally increased, and; if the reference value is less than or equal to value a, the system goes to room temperature. The value a is about 55 to about 65%, the value c is about 65 to about 75%, the value d is about 70 to about 80%, the value g is about 85 to about 95%, and the value h is about 90 to about 100%. 
   When the window relative humidity in the vehicle decreases, the removing humidity may include: if the sensed value is greater than the value f, the intake door and defrost are opened, the air conditioner and defrost is operated and, amount of air of a blower is maximally increased; if the sensed value is less than or equal to the value f and greater than to the value e, the amount of blower is decreased; if the sensed value is less than or equal to the value e and greater than to a value b, the defrost mode is released and returns to a fully automatic temperature control (“FATC”) state and further decreases an amount of air of the blower; if the sensed value is less than or equal to the value b and greater than to a value a, the system turns to the FATC state by minimizing an amount of air of the blower and closing the defrost door and; if the sensed value is less than or equal to the value a, the system goes back to room temperature. The value a is about 55 to about 65%, the value b is about 60 to about 70%, the value e is about 75 to about 85%, and the value f is about 80 to about 90%. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing the conventional control process of an air conditioning system for automatically defogging windows in a vehicle. 
       FIG. 2  is a drawing showing an automatic defogging system of a vehicle according to an embodiment of the present invention. 
       FIG. 3  is a block diagram showing a control process of an automatic defogging system of a vehicle according to an embodiment of the present invention. 
       FIG. 4  is a logical diagram for controlling an air conditioning device of an automatic defogging system of a vehicle according to an embodiment of the present invention. 
       FIG. 5  is a flowchart of an air conditioning device when humidity near a window inside a vehicle increases in a control method of an automatic defogging system of a vehicle according to an embodiment of the present invention. 
       FIG. 6  is a flowchart of an air conditioning device when humidity near a window inside a vehicle decreases in a control method of an automatic defogging system of a vehicle according to an embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
   As shown in  FIG. 2 , a defogging sensor  12  installed on an inner surface of a window of a vehicle senses a relative humidity and outputs a corresponding signal in an automatic defogging system of a vehicle. A controller  20  receives the signal output from the defogging sensor  12  and outputs a control signal. An air conditioning system is selectively and phasedly operated by a defogging logic according to the output control signal of the controller  20 , thereby automatically removing humidity. 
   As shown in  FIG. 3 , an input unit  10  receives a window relative humidity value, which is directly detected, from the defogging sensor  12 . The controller  20  controls the operations of an air conditioning system which is programmed as a type of a logic that is selectively and phasedly controllable depending on the sensed relative humidity value. In an output unit  30 , a selection mode of an air conditioning system that can be operated by the controller  20  is operated thereby automatically removing humidity on the inner surface of a window. 
   The humidity removing logic of the controller  20  controls the operation of the air conditioning system which is configured to control an intake door  21 , a blower  22 , an air conditioner  23 , a mode door  24 , and a defrost door  25 . In addition, the humidity removing logic is added to logic of a FATC device that is currently used so as to remove frozen and concentrated humidity on the surface of a window. 
   Air conditioning devices controlled by the controller  20  will be briefly explained hereinafter. 
   If the intake door  21  is set to be open in an outer air intake mode, dry outer air flows into a vehicle, such that the dry air is mixed with inner moist air thereby removing humidity. 
   The blower  22  increases or decreases an amount of outer air flowing into the vehicle in order to remove humidity. 
   The air conditioner  23  regulates a temperature in a vehicle by supplying cool or hot air in which humidity is removed from the vehicle, thereby removing humidity within the passenger room. 
   The mode door  24  sends out air toward a window thereby maximally removing humidity in the vehicle. 
   The defrost door  25  continuously sends out air to a vent so as to maintain a temperature in the vehicle. When the defrost door is open, it sends out a portion of air toward the window thereby removing humidity. 
   In addition, the defrost door  25  is independently controlled by the controller  20 . 
   Operating states of the air conditioning system are automatically and phasedly controlled according to the amount of humidity inside the window by the controller  20 . This will be explained hereinafter with reference to  FIG. 4  to  FIG. 6 . 
   First, when the relative humidity inside the window in a vehicle increases, the operating states of the air conditioning system will be explained with reference to  FIG. 4  and  FIG. 5 . 
   A symbol a stated below indicates about 55 to about 65% of the relative humidity. A symbol b stated below indicates about 60 to about 70% of the relative humidity. A symbol c stated below indicates about 65 to about 75% of the relative humidity. A symbol d stated below indicates about 70 to about 80% of the relative humidity. A symbol e stated below indicates about 75 to about 85% of the relative humidity. A symbol f stated below indicates about 80 to about 90% of the relative humidity. A symbol g stated below indicates about 85 to about 95% of the relative humidity. A symbol h stated below indicates about 90 to about 100% of the relative humidity. 
   A relative humidity of an inner surface of a window is sensed by the defogging sensor  12  at step S 10 . The sensed value is compared to a reference interior humidity value (a˜h) at step S 20 . 
   Subsequently, at step S 30 , it is determined that the sensed relative humidity value is less than the value c. 
   If the sensed value is not less than the value of value c at step S 30 , then it is determined whether the sensed value is greater than or equal to the value c and less than the value d at step S 31 . If the sensed relative humidity value is greater than or equal to the value c and less than the value d, the control process enters into a defogging control mode. In other words, the intake door  21  is converted to an outer air intake mode, and the defrost door  25  begins to be open, at step S 32 . 
   If the sensed relative humidity value is not greater than or equal to the value c and less than the value d at step S 31 , then it is determined whether the sensed relative humidity value is greater than or equal to the value d and less than the value g at step S 33 . If the sensed relative humidity value is greater than or equal to the value d and less than the value g at step S 33 , the defrost door  25  is fully opened, the air conditioner  23  is operated, and an amount of air of the blower  22  is increased, at step S 34 . As the relative humidity at the window increases, an amount of air of the blower  22  is further increased. 
   If the sensed relative humidity value is not greater than or equal to the value d and less than the value g at step S 33 , it is determined whether the sensed relative value humidity value is greater than or equal to the value g and less than the value h at step S 35 . If the sensed relative value humidity value is greater than or equal to the value g and less than the value h at step S 35 , the control mode is converted to a defrost mode, and an amount of air of the blower  22  is further increased, at step S 36 . 
   If the sensed relative value humidity value is not greater than or equal to the value g and less than the value h at step S 35 , it is determined whether the sensed relative humidity value is greater than or equal to the value h at step S 37 . If the sensed relative humidity value is greater than or equal to the value h at step S 37 , an amount of air of the blower  22  is controlled to be a maximum value (e.g., 10V) at step S 38 . If the sensed relative humidity value is not greater than or equal to the value h at step S 37 , the control proceeds back to step S 31 . 
   By selectively and phasedly controlling the air conditioning system, the air conditioning system is controlled along a descent line (referring to a logic shown in  FIG. 4 ). If the relative humidity becomes less than or equal to the value a at step S 39 , the defogging mode is released and the control mode returns to a room temperature control mode at step S 40 . 
   Meanwhile, if the sensed relative humidity value is less than value c, the control procedure proceeds to step S 40 . 
   On the other hand, when the relative humidity inside the window in a passenger room decreases, the operating states of the air conditioning system are explained with reference to  FIG. 4  and  FIG. 6 . 
   A relative humidity of an inner surface of a window is sensed by the defogging sensor  12  at step S 10 , and then the sensed value is compared to a reference interior humidity value (a˜h) at step S 20 . 
   Subsequently, at step S 30 , it is determined whether the sensed relative humidity value is less than the value a. If the sensed relative humidity value is less than the value a, then the system proceeds to step S 40 . 
   If the sensed relative humidity value is not less than the value a, it is determined whether the sensed relative humidity value is greater than the value f at step S 331 . If the sensed relative humidity value is greater than the value f at step S 331 , then the system proceeds to step S 332  in which all devices are maximally operated. In other words, the intake door  21  is opened, the defrost door  25  is fully opened, the air conditioner  23  is operated, the control mode is converted to a defrost mode, and an amount of air of the blower  22  is controlled to be a maximum value. 
   If the sensed relative humidity value is not greater than the value f at step S 331 , it is determined whether the sensed relative humidity value is greater than the value e and less than or equal to the value f at step S 333 . If the sensed relative humidity value is greater than the value e and less than or equal to the value f and at step S 333 , the amount of air of the blower  22  is decreased at step S 334 . 
   If the sensed relative humidity value is not greater than the value e and less than or equal to the value f and at step S 333 , it is determined whether the sensed relative humidity value is greater than the value b and less than or equal to the value e at step S 335 . If the sensed relative humidity value is greater than the value b and less than or equal to the value e at step S 335 , the defrost mode is released so that the mode door  24  returns to the FATC state, and an amount of air of the blower  22  is further decreased at step S 336 . 
   If the sensed relative humidity value is not greater than the value b and less than or equal to the value e at step S 335 , it is determined whether the sensed relative humidity value is greater than the value a and less than or equal to the value b at step S 337 . If the sensed relative humidity value is greater than the value a and less than or equal to the value b at step S 337 , the amount of air of the blower  22  is decreased to a minimum value so as to return to the FATC state, and the defrost door  25  is closed, at step S 338 . 
   If the sensed relative humidity value is not greater than the value a and less than or equal to the value b at step S 337 , it is determined whether the sensed relative humidity value is less than or equal to the value a at step S 339 . If the sensed relative humidity value is less than or equal to the value a at step S 339 , the air conditioner  23 , the defrost door  25 , and the intake door  21  are returned to the FATC state, and the controller  20  returns to the room temperature control mode, at step S 40 . 
   While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.