Abstract:
A demand-based air conditioning system for a passenger vehicle that may utilize one or both of a contaminate sensor and a door sensor. A controller operates a damper to send an estimated amount of fresh air into a passenger compartment, based on the sensed level of contaminate in the passenger compartment, to ensure the air quality in the passenger compartment is acceptable for passengers.

Description:
BACKGROUND 
       [0001]    A supply of fresh (outdoor) air is required for transport vehicle passenger compartments. It is the purpose of this invention to provide a system and method for providing an appropriate amount of fresh air to a vehicle passenger compartment. 
       SUMMARY 
       [0002]    In one embodiment, the invention provides a passenger vehicle air conditioning system that includes a fresh air duct fluidly connecting ambient air of the environment outside of the passenger vehicle and a passenger compartment inside of the passenger vehicle. The passenger vehicle air conditioning system also includes a damper disposed in the fresh air duct and movable within the duct to vary the amount of ambient air allowed to enter the passenger compartment, a sensor operable to monitor a level of contaminate indicative of the contaminate level within the passenger compartment of the passenger vehicle, and a controller in communication with the contaminate sensor and the damper. The controller moves the damper to vary the amount of fresh air that enters the passenger compartment based on the level of contaminate sensed by the contaminate sensor. 
         [0003]    In another embodiment, the invention provides a passenger vehicle having a passenger compartment and a fresh air duct fluidly connecting ambient air of the environment outside of the passenger vehicle and the passenger compartment inside of the passenger vehicle. The passenger vehicle also has a damper disposed in the fresh air duct and movable within the duct to vary the amount of ambient air allowed to enter the passenger compartment, a contaminate sensor operable to monitor a level of contaminate indicative of the contaminate level within the passenger compartment of the passenger vehicle, and a controller in communication with the contaminate sensor and the damper. The controller moves the damper to vary the amount of fresh air that enters the passenger compartment based on the level of contaminate sensed by the contaminate sensor. 
         [0004]    One embodiment of the invention provides a method of operating an air conditioning system of a passenger vehicle. The method includes fluidly connecting, with a fresh air duct of the air conditioning system, ambient air of the environment outside of the passenger vehicle and a passenger compartment inside of the passenger vehicle. The method also includes providing a damper disposed in the fresh air duct, monitoring a level of contaminate within a passenger compartment of the passenger vehicle, and moving the damper to vary the amount of fresh air that enters the passenger compartment based on the level of contaminate. 
         [0005]    Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a schematic view of one embodiment of the invention. 
           [0007]      FIG. 2  is a schematic view of the air conditioning system of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0008]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
         [0009]    Passengers in a passenger vehicle  10  produce various air contaminates which can be particulate or gaseous in nature. In order to provide a safe and comfortable environment for the driver and passengers riding in a passenger vehicle  10 , fresh (outdoor) air must be introduced to dilute the produced contaminates to a safe and acceptable level. The concentration level of the produced contaminants is proportional to the fresh (outdoor) air ventilation rate in a passenger vehicle where the air is mixed. The air in a passenger vehicle can be mixed by a fan, by the movement of people, or by the opening of doors or windows. At lower concentrations, carbon dioxide or other air contaminates can be used as a proxy for human produced odor. 
         [0010]      FIG. 1  is a schematic view of a passenger vehicle  10 . The passenger vehicle  10  has a passenger compartment  12 , a door  14 , a door sensor  16 , and an air conditioning system  18 . 
         [0011]      FIG. 2  is a schematic view of the air conditioning system  18  of  FIG. 1 . The air conditioning system  18  includes a fresh air duct  20  which fluidly connects ambient air of the environment outside of a passenger vehicle  10  and a passenger compartment  12  inside of the passenger vehicle  10 . A damper  22  is disposed in the fresh air duct  20  and is operable to vary the amount of fresh air that passes through the fresh air duct  20 . An evaporator  24  is disposed in the fresh air duct  20 , the evaporator  24  being connected to a compressor  26 . A return air duct  28  fluidly connects the passenger compartment  12  to the fresh air duct  20 . An evaporator fan  30  is coupled to the evaporator  24  and serves to move fresh air from the fresh air duct  20  into the passenger compartment  12 . In an alternative embodiment, the evaporator fan  30  is not coupled to the evaporator  24 . The evaporator fan  30  also serves to move air from the passenger compartment  12  into the return air duct  28  and then into the fresh air duct  20 . A damper sensor  32  monitors the position of the damper  22 . A carbon dioxide sensor  34  is disposed in the return air duct  28  and is operable to monitor a level of carbon dioxide indicative of the level of carbon dioxide within the passenger compartment  12  of the vehicle. A controller  36  communicates with the door sensor  16 , damper  22 , damper sensor  32 , evaporator  24 , compressor  26 , evaporator fan  30 , and carbon dioxide sensor  34 . 
         [0012]    The controller  36  is operable to move the damper  22  and vary the speed of the compressor  26  and evaporator fan  30 . The damper sensor  32  senses the status of the damper  22 , including the percentage of full open, the occurrence of a damper opening event and the duration of the damper opening event. The door sensor  16  senses the occurrence of a door opening event, and also measures the duration of the door opening event. The controller  36  is operable to control the damper  22  and the evaporator fan  30  to vary the amount of fresh air that enters the passenger compartment  12  based on the level of carbon dioxide sensed by the carbon dioxide sensor  34 . In an alternative embodiment the controller  36  varies the damper  22  and the evaporator fan speed based on the occupancy of the passenger compartment  12 , which is predicted by at least one of the level of carbon dioxide sensed by the carbon dioxide sensor  34 , the rate of change of the level of carbon dioxide sensed by the carbon dioxide sensor  34 , and the amount of fresh (outdoor) air that is introduced into the passenger vehicle  10 . Fresh air is introduced into the passenger vehicle  10  through the door  14  and/or the vehicle air conditioning system  18 . 
         [0013]    The controller  36  can be programmed with at least one of a preset carbon dioxide level that is based on the amount of carbon dioxide exhaled by a person (i.e. grams of carbon dioxide per minute per person), a required amount of fresh air per person, the interior volume of the passenger compartment  12 , and how quickly fresh air can mix with the air in the passenger compartment  12 . In another embodiment, the controller  36  can be programmed with a preset carbon dioxide level, where the preset carbon dioxide level is determined by an expressed comfort level of persons in the passenger compartment  12  of a passenger vehicle  10  in a test situation. That is, various levels of carbon dioxide are tested to determine passenger comfort for the tested level of carbon dioxide. The level of carbon dioxide in ambient air outside of the vehicle  10  is well known and substantially stable. 
         [0014]    The embodiment illustrated in  FIG. 1  functions as follows. The carbon dioxide sensor  34  monitors the level of carbon dioxide in the passenger compartment  12  and communicates the level of carbon dioxide to the controller  36 . The controller  36  receives the monitored carbon dioxide level and compares it to the preset carbon dioxide level. In some embodiments the preset carbon dioxide level is a range of carbon dioxide levels. If the monitored level of carbon dioxide is above the preset level of carbon dioxide, then the controller  36  directs the damper  22  to open. If the monitored level of carbon dioxide is equal to the preset level of carbon dioxide, then the controller  36  does not change the position of the damper  22 . If the monitored level of carbon dioxide is less than the preset level of carbon dioxide, then the controller  36  directs the damper  22  to close. In some embodiments multiple carbon dioxide level ranges are programmed into the controller  36 . Depending on the carbon dioxide level range which is monitored, the controller  36  can direct the damper  22  to fully open or close, partially open or close, or maintain the current position. 
         [0015]    An alternative embodiment of the illustrated invention functions as follows. The carbon dioxide sensor  34  monitors the level of carbon dioxide in the passenger compartment  12  and communicates the level of carbon dioxide to the controller  36 . The door sensor  16  senses the occurrence and duration of a door opening event of a door  14  of the passenger vehicle  10  and communicates the occurrence and duration of the door opening event to the controller  36 . The damper sensor  32  senses the status of damper opening event (for example percentage of opening if operated continuously, or the occurrence of the damper opening event and the duration of the damper opening event, if operated on/off) and communicates the occurrence, percentage open, and duration of the damper opening event to the controller  36 . The controller  36  estimates the amount of fresh air that is introduced into the passenger compartment  12  by comparing the information received from the door sensor  16  and damper sensor  32  with a programmed table which gives the amount of fresh air that is introduced into the passenger compartment  12  by the door opening event and/or damper opening event. If the amount of fresh air that is introduced into the passenger vehicle  10  by the door opening events and/or damper opening events is sufficient to lower the level of carbon dioxide in the passenger compartment  12  to the preset level, then the controller  36  directs the damper  22  to close. If the amount of fresh air that is introduced into the passenger vehicle  10  by one or more door opening events and/or damper opening events is not sufficient to lower the level of carbon dioxide in the passenger compartment  12  to the preset level, then the controller  36  directs the damper  22  to open. In some embodiments the preset level of carbon dioxide is a range of carbon dioxide levels. In some embodiments, multiple carbon dioxide level ranges are programmed into the controller  36 . Depending on the monitored carbon dioxide level, the controller  36  can direct the damper  22  to fully open or close, partially open or close, or maintain the current position. 
         [0016]    In some embodiments the controller  36  estimates the occupancy of the passenger compartment  12  based on the level of carbon dioxide sensed by the carbon dioxide sensor  34  and a fresh airflow rate. The fresh airflow rate is calculated by estimating the amount of fresh air that is introduced into the passenger compartment  12  by the damper  22 . The controller  36  is programmed with an approximate airflow rate for a range of positions of the damper  22  and the speed of the evaporator fan  30 . In an alternate embodiment the fresh airflow rate is calculated by estimating the amount of fresh air that is introduced into the passenger compartment  12  by the damper  12 , the evaporator fan  30 , and the door  14 . The controller is also programmed with an approximate airflow rate that occurs when the door  14  is in the open position. The occupancy is calculated by multiplying the fresh airflow rate (volume/time) by the difference between the concentration of carbon dioxide in the passenger compartment  12  and the outdoor concentration of carbon dioxide (mass/volume), and dividing the result by the average carbon dioxide production rate per person (mass/time*person). Symbolically, the formula is: 
         [0000]      (fresh airflow rate*(CO2 concentration of passenger compartment−CO2 concentration of outdoor air))/CO2 production rate per person=passenger compartment occupancy
 
         [0017]    After the controller  36  calculates the occupancy of the passenger compartment  12 , the controller  36  operates at least one of the compressor  26  and the evaporator fan  30  at a level corresponding to a preset level for the occupancy of the passenger compartment  12 . In this embodiment, the damper  22  is not opened or closed based on the occupancy of the passenger compartment  12 ; instead, the damper  22  is opened or closed based on the level of carbon dioxide sensed by the carbon dioxide sensor  34  as described in the preceding paragraph. In an alternative embodiment, the controller  36  estimates the occupancy of the passenger compartment  12  based on level of carbon dioxide sensed by the carbon dioxide sensor  34 , the rate of change of the level of the carbon dioxide sensed by the carbon dioxide sensor  34 , and a fresh airflow rate. 
         [0018]    In an alternative embodiment, the controller determines the occupancy of the passenger compartment  12  as described above. At the same time, the controller can apply a control algorithm to reduce the energy consumption of the air conditioning system  18 . The controller  36  is able to move the damper  22  to vary the amount of fresh air that enters the passenger compartment  12  based on the occupancy of the passenger compartment  12 . The controller  36  is also able to vary the speed of the evaporator fan  30  based on the occupancy of the passenger compartment  12 . In addition, the controller  36  can vary the speed of the compressor  26  based on the occupancy of the passenger compartment  12 . By varying how often the damper  22  opens, the speed of the evaporator fan  30 , and the speed of the compressor  26 , the passenger vehicle  10  air conditioning system  18  is able to operate more efficiently because the air conditioning system  18  only operates at a level needed for the occupancy of the passenger compartment  12 . In an alternative embodiment a variable displacement compressor (not shown) is used in place of the compressor  26 , and the controller  36  varies the displacement of the variable displacement compressor based on the occupancy of the passenger compartment  12 . 
         [0019]    The illustrated embodiments described above have employed a carbon dioxide sensor  34  to monitor the level of carbon dioxide in the passenger compartment  12 . However, any of the embodiments illustrated above can use a volatile organic compound (VOC) sensor (not shown), a dust sensor (not shown), or some other sensor which measures contaminates produced by humans, in place of the carbon dioxide sensor  34 . In addition, the carbon dioxide sensor  34  can be used in conjunction with at least one of a VOC sensor, a dust sensor, and some other sensor which measures contaminates produced by humans. One or more alternate or additional sensors communicate with the controller  36  and the controller  36  compares the level of sensed contaminate to a preset level of sensed contaminate. The controller  36  then operates as described in one of the embodiments above. 
         [0020]    In one embodiment at least one of the carbon dioxide sensor  34 , VOC sensor, dust sensor, and some other sensor which measures contaminates produced by humans, can be placed in the return air duct  28  of the passenger vehicle  10  air conditioning system  18 . In another embodiment, at least one of the carbon dioxide sensor  34 , VOC sensor, dust sensor, and some other sensor which measures contaminates produced by humans, can be placed in the passenger compartment  12  of the passenger vehicle  10 . 
         [0021]    Thus, the invention provides, among other things, a passenger vehicle air conditioning system. Various features and advantages of the invention are set forth in the following claims.