Air Conditioning System and Method For Avoiding Condensation of Humidity on Vehicle Windows

Abstract

An air-conditioning system in a vehicle comprises an air-temperature sensor for measuring the interior temperature, an air-conditioning unit and a regulating and control unit for regulating the air-conditioning unit. Moreover, a moisture sensor for measuring the air humidity and a window-temperature sensing device for determining the window temperature of a vehicle window are provided. The air-conditioning unit is actuated in the case where the difference between the window temperature and the dew-point temperature undershoots a limiting value.

1 . An air conditioning system in a motor vehicle, having an air temperature sensor ( 3 ) for measuring the interior temperature (T air ) in the vehicle, an air conditioner ( 8 ), and a regulation and control unit ( 7 ) for regulating the air conditioner ( 8 ) as a function of the measured interior temperature (T air ), wherein
 a moisture sensor ( 4 ) for measuring the humidity (up) inside the vehicle and a window temperature determining device ( 5 ) for determining the window temperature (T window ) of the vehicle window ( 2 ) are provided,   based on the measured interior temperature (T air ) and humidity (φ), it is possible for the associated dew point temperature (T dew ) to be determined in the regulation and control unit ( 7 ), and   the air conditioner ( 8 ) is activated if the difference between the window temperature (T window ) and dew point temperature (T dew ) falls below a threshold value (T threshold ).   
   
   
       2 . The air conditioning system as recited in  claim 1 , wherein in the regulation and control unit ( 7 ),
 the associated saturation pressure (p sat (T air )) lying on the saturated vapor curve is determined based on the interior temperature (T air ) and   the dew point temperature (T dew ) is determined as a function of the humidity (φ) and the saturation pressure (p sat (T air )).   
   
   
       3 . The air conditioning system as recited in  claim 2 , wherein the dew point temperature (T dew ) is determined as a function of the humidity (φ) and the saturation pressure (P sat (T air )), based on the following relation: 
     
       
         
           
             
               
                 T 
                 dew 
               
               = 
               
                 
                   
                     C 
                     1 
                   
                   * 
                   
                     ( 
                     
                       
                         ln 
                          
                         
                           ( 
                           
                             ϕ 
                             * 
                             
                               
                                 p 
                                 sat 
                               
                                
                               
                                 ( 
                                 
                                   T 
                                   air 
                                 
                                 ) 
                               
                             
                           
                           ) 
                         
                       
                       - 
                       
                         C 
                         2 
                       
                     
                     ) 
                   
                 
                 
                   
                     C 
                     3 
                   
                   - 
                   
                     ln 
                      
                     
                       ( 
                       
                         ϕ 
                         * 
                         
                           
                             p 
                             sat 
                           
                            
                           
                             ( 
                             
                               T 
                               air 
                             
                             ) 
                           
                         
                       
                       ) 
                     
                   
                 
               
             
             , 
           
         
       
     
     where
 C 1  is a constant with the value 243.12 
 C 2  is a constant with the value 1.81 
 C 3  is a constant with the value 19.43. 
 
   
   
       4 . The air conditioning system as recited in  claim 1 ,
 wherein the window temperature determining device is embodied in the form of an infrared temperature sensor ( 5 ).   
   
   
       5 . The air conditioning system as recited in  claim 1 ,
 wherein the air conditioner ( 8 ) is activated if the condensation tendency (κ),   which is determined as a function of the window temperature (T window ) and the dew point temperature (T dew ) based on the relation   
     
       
         
           
             
               κ 
               = 
               
                 1 
                 
                   
                     T 
                     window 
                   
                   - 
                   
                     T 
                     dew 
                   
                 
               
             
             , 
           
         
       
     
     exceeds a threshold value (κ threshold ). 
   
   
       6 . The air conditioning system as recited in  claim 1 ,
 wherein the air conditioner ( 8 ) includes an air conditioning unit.   
   
   
       7 . The air conditioning system as recited in  claim 1 ,
 wherein the air conditioner ( 8 ) includes a blower.   
   
   
       8 . The air conditioning system as recited in  claim 1 ,
 wherein the air conditioner ( 8 ) includes a heater.   
   
   
       9 . A rain sensor module equipped with an air conditioning system as recited in  claim 1 . 
   
   
       10 . A method for avoiding condensation of moisture on vehicle windows, in particular a method for operating the air conditioning system ( 1 ) as recited in  claim 1 , in which the interior temperature (T air ), the humidity (φ) in the vehicle, and the window temperature (T window ) of a vehicle window ( 2 ) are measured or determined and the interior is air conditioned if the difference between the window temperature (T window ) and the dew point temperature (T dew ) falls below a threshold value (T threshold ), with the dew point temperature (T dew ) being determined as a function of the humidity (φ) and the interior temperature (T air ).