Patent Publication Number: US-2010120345-A1

Title: Fresh air box

Description:
BACKGROUND 
     The present invention relates to a rooftop temperature control unit for a vehicle, in particular a bus. 
     Typical rooftop temperature control units for busses provide cooling to a conditioned space, or cabin, within the bus. A heat exchanger within the temperature control unit cools return air, which is directed back to the conditioned space. Some rooftop temperature control units include an opening through which fresh outdoor air enters the temperature control unit by natural flow to be cooled by the heat exchanger. The introduction of fresh air improves air quality in the conditioned space, but the natural flow of the fresh air is difficult to control. 
     SUMMARY 
     In one embodiment, the invention provides a rooftop temperature control unit for a vehicle having a conditioned space. The rooftop temperature control unit includes a housing defining a plenum and including an air inlet. The plenum is configured to receive an inflow of outdoor air from outside of the vehicle through the air inlet. The outdoor air defines an outdoor air temperature. A heat exchanger assembly is coupled to the housing and in fluid communication with the plenum. The heat exchanger assembly is configured to receive a first portion of the outdoor air from the plenum, to cool the first portion to a temperature below the outdoor air temperature, and to discharge the cooled first portion into the conditioned space. A blower is coupled to the housing and in fluid communication with the plenum, the blower configured to receive a second portion of the outdoor air from the plenum and to discharge the second portion into the conditioned space at a temperature equal to or greater than the outdoor air temperature. 
     In another embodiment, the invention provides a method of operating a rooftop temperature control unit for a vehicle having a conditioned space. The method includes receiving an inflow of outdoor air from outside of the vehicle through an air inlet of a housing and into a plenum defined by the housing, receiving with a heat exchanger assembly a first portion of the outdoor air from the plenum, cooling with the heat exchanger assembly the first portion to a temperature below an outdoor air temperature, discharging with the heat exchanger assembly the cooled first portion into the conditioned space, receiving with a blower a second portion of the outdoor air from the plenum, and discharging with the blower the second portion into the conditioned space at a temperature equal to or greater than the outdoor air temperature. 
     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a bus having a rooftop temperature control unit embodying the invention. 
         FIG. 2  is an exploded perspective view of the temperature control unit of  FIG. 1 . 
         FIG. 3  is an exploded perspective view of a second construction of the temperature control unit of  FIG. 1 . 
         FIG. 4  is a perspective view of a fresh air compartment of the temperature control unit of  FIG. 1 . 
         FIG. 5  is a cross section of the fresh air compartment taken along line  5 - 5  of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
     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. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
       FIG. 1  illustrates a temperature control unit  10  embodying the invention mounted to the rooftop  14  of a bus  18 . The temperature control unit  10  communicates with a conditioned space  20  inside the bus  18  by providing temperature-controlled air to the conditioned space  20 . It is to be understood that the temperature control unit  10  may be employed in any vehicle, but is preferably employed in a bus. Furthermore, the temperature control unit  10  may be mounted to any portion of the vehicle and is not limited to being mounted on the roof  14 . 
       FIG. 2  is an exploded view of a first construction of the temperature control unit  10 . The temperature control unit  10  includes a first compartment or fresh box  22 , a second compartment or fresh box  26 , an evaporator compartment  30  containing an evaporator  34  and an evaporator blower (not shown), and a condenser compartment  38  containing a condenser  42 . An evaporator assembly includes the evaporator compartment  30  housing the evaporator  34  and evaporator blower. The evaporator  34  and the condenser  42  belong to an air conditioning system (not shown in its entirety) including a compressor, expansion modules and fluid conduits forming a refrigeration circuit, as is commonly known in the art. Therefore, the air conditioning system will not be explained in further detail. 
     With reference to  FIG. 4 , the first compartment  22  contains first and second blowers  46 ,  50  and includes a first compartment inlet  54  and a first compartment damper  58  coupled to the first compartment inlet  54 . The first compartment damper  58  includes a moveable plate  56  to adjust the inflow of air to the first compartment  22  through the first compartment inlet  54 . A first dust filter  60  is coupled to the first compartment inlet  54  and is positioned substantially within the first compartment  22  to filter the inflow of air into the first compartment  22 . The first and second blowers  46 ,  50  are coupled to a first motor  52  for synchronized rotation with the first motor  52 . The motor  52  preferably runs at multiple speeds to operate the blowers  46 ,  50  at multiple speeds. For example, the motor  52  may run the blowers  46 ,  50  at a high speed, a low speed and off. Preferably, the motor  52  runs the blowers  46 ,  50  at a plurality of non-zero speeds. In other constructions, the first compartment  22  may contain fewer or more blowers and the blowers may be coupled to separate motors for separately controlled rotation. In the illustrated construction, the first and second blowers  46 ,  50  are centrifugal fans. In other constructions, other types of blowers, such as fans and other devices that move air, may be employed. Also in other constructions, the first dust filter  60  may be positioned substantially outside of the first compartment  22  or just partially within the first compartment  22 . 
       FIG. 5  is a cross-section of the first compartment  22  through the first compartment inlet  54  and the first blower  46 . The inflow and outflow of air through the first compartment  22  is indicated by arrows  61   a,    61   b.  Air enters the first compartment  22  through the first compartment damper  58  and passes through the first compartment inlet  54  and the first dust filter  60 . The first dust filter  60  substantially prevents dust and debris from entering the first compartment  22 . The air is then drawn by the first blower  46  and the second blower  50  ( FIG. 4 ) and directed through a first compartment outlet  62  into a bus duct (not shown) and into the conditioned space  20 . The air drawn into and expelled from the first compartment  22  and into the conditioned space  20  is at a temperature equal to or greater than the outdoor air temperature. In other words, outdoor air is drawn into the plenum  102 , drawn into the first compartment  22  and discharged to the conditioned space  20  without passing through a heat exchanger for cooling the outdoor air. The direction of the outflow  61   b  from the first compartment  22  is substantially perpendicular to the direction of the inflow  61   a  to the first compartment  22 . 
     It is to be understood that the second compartment  26  is substantially identical to the first compartment  22  in the illustrated construction. However, different reference numerals are used in  FIG. 2  to distinguish the first compartment  22  from the second compartment  26 . Although  FIGS. 4-5  are labeled with reference numerals corresponding to the first compartment  22 , the description of  FIGS. 4-5  above could be used to describe the second compartment  26  as well. Therefore, separate figures including reference numerals corresponding to the second compartment  26  will not be provided as it is to be understood that the description above of the first compartment  22  with respect to  FIGS. 4-5  can be applied to the second compartment  26 . However, the first and second compartments  22 ,  26  may be constructed differently and still fall within the scope of the invention. 
     With reference to  FIG. 2 , the second compartment  26  contains third and fourth blowers  66  and  70 , respectively, and includes a second compartment inlet  74  and a second compartment damper  78  coupled to the second compartment inlet  74 . The second compartment damper  78  includes a moveable plate  80  to adjust the inflow of air to the second compartment  26  through the second compartment inlet  74 . A second dust filter  82  is coupled to the second compartment inlet  74  and is positioned substantially within the second compartment  26  to filter the inflow of air into the second compartment  26 . The third and fourth blowers  66 ,  70  are coupled to a second motor  86  for synchronized rotation with the second motor  86 . The motor  86  preferably runs at multiple speeds to operate the blowers  66 ,  70  at multiple speeds. For example, the motor  86  may run the blowers  66 ,  70  at a high speed, a low speed and off. Preferably, the motor  86  runs the blowers  66 ,  70  at a plurality of non-zero speeds. In other constructions, the second compartment  26  may contain fewer or more blowers and the blowers may be coupled to separate motors for separately controlled rotation. In the illustrated construction, the third and fourth blowers  66 ,  70  are centrifugal fans. In other constructions other types of blowers, such as fans and other devices that move air, may be employed. Also in other constructions, the second dust filter  82  may be positioned substantially outside of the second compartment  26  or just partially within the second compartment  26 . 
     The inflow and outflow of air through the second compartment  26  is indicated by arrows  91   a,    91   b.  Air enters the second compartment  26  through the second compartment damper  78  and passes through the second compartment inlet  74  and the second dust filter  82 . The second dust filter  82  substantially prevents dust and debris from entering the second compartment  26 . The air is then drawn by the third blower  66  and the fourth blower  70  and directed through a second compartment outlet  90  into a bus duct (not shown) and into the conditioned space  20 . The air drawn into and expelled from the second compartment  26  and into the conditioned space is at a temperature equal to or greater than the outdoor air temperature. In other words, outdoor air is drawn into the plenum  102 , drawn into the second compartment  26  and discharged to the conditioned space  20  without passing through a heat exchanger for cooling the outdoor air. The direction of the outflow  91   b  from the second compartment  26  is substantially perpendicular to the direction of the inflow  91   a  to the second compartment  26 . 
     The first compartment  22  and the second compartment  26  are enclosed on the top by a fresh air cover  94  having a fresh air inlet  98 . The fresh air inlet  98  includes a plurality of elongated openings that allow fresh outdoor air from outside of the bus  18  to enter a plenum  102  inside the temperature control unit  10 . A housing, generally indicated with the numeral  100  and including the fresh air cover  94 , defines the plenum  102 . The plenum  102  is a space inside the housing  100  that serves as a holding chamber for air that is to be distributed to the conditioned space  20 . The fresh outdoor air enters the first and second compartments  22 ,  26  from the plenum  102  by way of the first and second compartment inlets  54 ,  74  and the first and second compartment dampers  58 ,  78  positioned inside the temperature control unit  10  adjacent the plenum  102 . In other constructions, the fresh air inlet  98  may include one or more openings of any shape and size. In yet other constructions, the first and second compartment inlets  54 ,  74  and the first and second compartment dampers  58 ,  78  may be positioned in the cover  94  in direct communication with fresh outdoor air for the direct passage of fresh outdoor air into the first and second compartments  22 ,  26 . 
     The inflow of fresh outdoor air into the plenum  102  and into the first compartment  22  and the second compartment  26  is controlled by the positions of the first and second compartment dampers  58 ,  78  and by the speed of the first and second blowers  46 ,  50 . When the dampers  58 ,  78  are closed, the inflow of air into the first and second compartments  22 ,  26  is minimal or non-existent. When the blowers  46 ,  50 ,  66 ,  70  are not operating, the inflow of air into the first and second compartments  22 ,  26  is minimal or non-existent. Preferably, the blowers  46 ,  50 ,  66 ,  70  do not operate when the dampers  58 ,  78  are closed. Furthermore, the outflow of air from the first and second compartments  22 ,  26  into the conditioned space  20  is also minimal or non-existent when the inflow is minimal or non-existent. When the blowers  46 ,  50 ,  66 ,  70  are operating, the inflows and outflows of air increase with increasing speed of the blowers  46 ,  50 ,  66 ,  70  and decrease with decreasing speed of the blowers  46 ,  50 ,  66 ,  70 . Preferably, the dampers  58 ,  78  are at least partially open when the blowers  46 ,  50 ,  66 ,  70  are operating. The inflow and outflow also increase as the dampers  58 ,  78  are moved to a more open position and decrease as the dampers  58 ,  78  are moved to a less open position. 
     Also positioned inside the temperature control unit  10  is an evaporator compartment inlet  106  and an evaporator compartment damper  110 . The evaporator compartment inlet  106  is positioned between the plenum  102  and the evaporator compartment  30 . The evaporator compartment  30  is positioned adjacent the first compartment  22 , the second compartment  26  and the plenum  102  and also adjacent the condenser compartment  38  at an opposite end. The evaporator compartment inlet  106  provides a passage for fresh outdoor air into the evaporator compartment  30  from the plenum  102 . The evaporator compartment damper  110  includes a moveable plate  112  to adjust the inflow of air to the evaporator compartment  30  through the evaporator compartment inlet  106 . A third dust filter  114  is positioned within or adjacent the evaporator compartment inlet  106  to filter the inflow of air into the evaporator compartment  30 . 
     Air enters the evaporator compartment  30  from the plenum  102  by way of the evaporator compartment inlet  106  and the evaporator compartment damper  110 , as indicated generally by arrows  115   a.  The air flows around the evaporator  34  and is cooled by the evaporator  34 . The cooled air exits the evaporator compartment  30  by way of an evaporator compartment outlet  118  and is directed into a bus duct (not shown) and into the conditioned space  20 . The outflow of air is indicated generally by arrows  115   b.  The cooled air is mixed with fresh outdoor air from the first compartment outlet  62  and the second compartment outlet  90  in the bus duct (not shown), if the outflow of fresh outdoor air is present. 
     The inflow and outflow of air in the evaporator compartment  30  depends on the evaporator blower and the evaporator compartment damper  110 . Air enters the evaporator compartment  30  from the plenum  102  by way of the evaporator compartment inlet  106  and the evaporator compartment damper  110 , as indicated generally by arrows  115   a.  When the evaporator blower is not operating, the inflow of air into the evaporator compartment  30  is minimal or non-existent. The evaporator compartment damper  110  is preferably closed when the evaporator blower is not operating. When the evaporator blower is operating and the evaporator compartment damper  110  is at least partially open, the inflow and outflow increases with increasing speed of the evaporator blower and decreases with decreasing speed of the evaporator blower. 
     A second construction of the temperature control unit  10  is illustrated in  FIG. 3  and is generally indicated with the numeral  10   a.  The same reference numerals are used for individual components that are unchanged from the construction of  FIG. 2 , and a successive letter, such as “a”, is appended to reference numerals referring to structure that exists in both the first and the second constructions but that is changed with respect to the first construction. The first compartment  22  and the second compartment  26  are enclosed on the top by the fresh air cover  94  having the fresh air inlet  98 . The fresh air inlet  98  includes a plurality of elongated openings that allow fresh outdoor air from outside of the bus  18  to enter a plenum  102   a  inside the temperature control unit  10   a.  The fresh outdoor air enters an intermediate plenum  122  from the plenum  102   a  by way of an intermediate plenum inlet  126  positioned on a partition  128  inside the temperature control unit  10   a  adjacent the plenum  102   a.  The intermediate plenum  122  is separated from the plenum  102   a  by the partition  128 . An intermediate plenum damper  130  is coupled to the intermediate plenum inlet  126  and includes a moveable plate  134  for adjusting the inflow of air into the intermediate plenum  122 . In other constructions, the intermediate plenum inlet  126  may be positioned in the cover  94  in direct communication with fresh outdoor air for the direct passage of fresh outdoor air into the intermediate plenum  122 . 
     In the construction of  FIG. 3 , the first and second compartment inlets  54 ,  74 , and dust filters  60 ,  82  are shifted slightly with respect to the blowers  46 ,  50 ,  66 ,  70 , toward the evaporator compartment  30 . Thus, the first and second compartment inlets and dust filters are referenced with the numerals  54   a,    74   a,    60   a,    82   a  in  FIG. 3 . Furthermore, the first and second compartments are referenced with the numerals  22   a,    26   a.  The shift is to accommodate the division of the plenum  102   a  and the intermediate plenum  122 . In this construction, there are no dampers coupled to the first and second compartment inlets  54   a,    74   a  or to the evaporator compartment inlet  106 . The first and second compartment inlets  54   a,    74   a  and the evaporator compartment inlet  106  are positioned downstream of the intermediate plenum inlet  126  and the intermediate plenum damper  130 . 
     In the construction of  FIG. 3 , the inflow of air into the temperature control unit  10   a  is controlled by the intermediate plenum damper  130 . The inflow of air into the first and second compartments  22   a,    26   a  depends on the blowers  46 ,  50 ,  66 ,  70 , as the first and second compartment inlets  54 ,  74  are without dampers. When the blowers  46 ,  50 ,  66 ,  70  are not operating, the inflow of air into the first and second compartments  22   a,    26   a  is minimal or non-existent. Furthermore, the outflow of air from the first and second compartments  22   a,    26   a  into the conditioned space  20  is also minimal or non-existent. When the blowers  46 ,  50 ,  66 ,  70  are operating, the respective inflows and outflows of air increase with increasing speed of the blowers  46 ,  50 ,  66 ,  70  and decrease with decreasing speed of the blowers  46 ,  50 ,  66 ,  70 . Similarly, the inflow and outflow of air in the evaporator compartment  30  depends on the evaporator blower as the evaporator compartment inlet  106  is without a damper. Air enters the evaporator compartment  30  from the intermediate plenum  122  by way of the evaporator compartment inlet  106 , as indicated generally by arrows  115   a.  When the evaporator blower is not operating, the inflow of air into the evaporator compartment  30  is minimal or non-existent. When the evaporator blower is operating, the inflow and outflow increases with increasing speed of the evaporator blower and decreases with decreasing speed of the evaporator blower. 
     The evaporator compartment inlet  106  is positioned between the intermediate plenum  122  and the evaporator compartment  30 . The evaporator compartment  30  is positioned adjacent the first compartment  22 , the second compartment  26  and the intermediate plenum  122  and also adjacent the condenser compartment  38 . 
     It is to be understood that in other constructions, the first and second compartments  22 ,  26  may be separate from the temperature control unit  10  and effectively define a second temperature control unit. That is, the first temperature control unit would include the evaporator and condenser compartments  30 ,  38 , and the second temperature control unit would include the first and second compartments  22 ,  26  or  22   a,    26   a,  the plenum  102  or  102   a  and the intermediate plenum  122 , if applicable. The first and second temperature control units could be mounted to the vehicle  18  at different locations. Furthermore, each of the first and second compartments  22 ,  26  could be separate. Each of the first and second compartments  22 ,  26  could have separate plenums and be mounted to the vehicle  18  at different locations. 
     A control module  138  is positioned in the evaporator compartment  38  to control the positions of the dampers  58 ,  78 ,  110  (in the construction illustrated in  FIG. 2) and 130  (in the construction illustrated in  FIG. 3 ) and to control the speed of the first and second compartment blower motors  52 ,  86  and the evaporator blower. An operator control module (not shown) is positioned in the driver&#39;s cab of the bus  18  and allows the operator to control the temperature control unit  10 . For example, the operator may enter a setpoint temperature that is a desired temperature within the conditioned space  20 . The operator control module is coupled to the control module  138 , which adjusts the positions of the dampers  58 ,  78 ,  110  and  130 , the speed of the first and second compartment blower motors  52 ,  86  and the evaporator blower, and the operation of the air conditioning system including whether the compressor (not shown) is on or off, in order to reach or maintain the setpoint temperature. 
     A first temperature sensor (not shown) is positioned outside the bus  18  to measure an outdoor ambient temperature of fresh air outside of the bus  18 . A second temperature (not shown) is positioned inside the conditioned space  20  to measure a cabin temperature of the conditioned space  20 . The control module  138  compares the outdoor ambient temperature to the cabin temperature and the setpoint temperature to determine whether the outdoor ambient temperature is cooler than the cabin temperature and the setpoint temperature. 
     If the outdoor ambient temperature is lower than the cabin temperature or the setpoint temperature, then the control module  138  operates blowers  46 ,  50 ,  66 ,  70  by operating the blower motors  52 ,  86  to blow outdoor air through the first and second compartments  22 ,  26  and into the conditioned space  20 . All or a part of the cooling capacity comes from fresh air. Preferably, the blowers  46 ,  50 ,  66 ,  70  are operated at a high speed. Furthermore, the control module  138  opens the dampers  58 ,  78  to allow a first portion of outdoor air to pass through the respective compartment  22 ,  26  into the conditioned space  20 . A second portion of outdoor air may simultaneously enter the evaporator compartment  20  by way of the evaporator compartment inlet  106  and the evaporator compartment damper  110  to be cooled by the evaporator  34  and directed to the conditioned space  20  by the evaporator blower. 
     If the outdoor ambient temperature is lower than the cabin temperature or the setpoint temperature by a predetermined amount, the control module  138  prevents the air conditioner from cooling the conditioned space  20 . The predetermined amount is an amount such that the capacity of the fresh outdoor air is enough to keep the cabin temperature close to the setpoint temperature without using the air conditioner. In this case, all of the cooling capacity comes from fresh outdoor air. Preferably, the control module  138  shuts off the compressor (not shown), effectively shutting off the air conditioner to prevent the air conditioner from cooling the conditioned space  20 . The control module  138  may also or alternatively close the evaporator compartment damper  110  and/or shut off the evaporator blower to effectively shut off the air conditioner to prevent the air conditioner from cooling the conditioned space  20 . Other means may also be employed. 
     The control module  138  may also vary the speed of the blower motors  52 ,  86  (and thus the blowers  46 ,  50 ,  66 ,  70 ) depending on the difference between the outdoor ambient temperature and the cabin temperature or the setpoint temperature. If the outdoor ambient temperature is higher than the cabin temperature and the setpoint temperature, the control module  138  runs the blower motors  52 ,  86  (and thus the blowers  46 ,  50 ,  66 ,  70 ) at a low speed to direct a first portion of outdoor air to the conditioned space  20  to maintain air quality, or shuts them off. Furthermore, the air conditioning system runs when the outdoor ambient temperature is higher than the cabin temperature and the setpoint temperature. A second portion of outdoor air enters the evaporator compartment  20  by way of the evaporator compartment inlet  106  and the evaporator compartment damper  110  to be cooled by the evaporator  34  and directed to the conditioned space  20  by the evaporator blower. 
     Furthermore, when the outdoor ambient temperature is higher than the cabin temperature and the setpoint temperature, and with respect to the first construction of the temperature control system  10 , the first and second compartment dampers  58 ,  78  are open when the blowers  46 ,  50 ,  66 ,  70  are running Conversely, the first and second compartment dampers  58 ,  78  are closed when the blowers  46 ,  50 ,  66 ,  70  are not running The blowers  46 ,  50 ,  66 ,  70  are shut off when the outdoor ambient temperature is higher than the cabin and setpoint temperatures by a predetermined amount to prevent a large loss in cooling capacity. Similarly, the evaporator compartment damper  110  is closed when the outdoor ambient temperature is higher than the cabin and setpoint temperatures by a predetermined amount to prevent a large loss in cooling capacity. In this case, the evaporator compartment  30  receives and cools only return air from the conditioned space  20 . 
     With respect to the second construction of the temperature control system  10   a,  when the outdoor ambient temperature is higher than the cabin temperature and the setpoint temperature the intermediate plenum damper  130  is open when the blowers  46 ,  50 ,  66 ,  70  are running. When the blowers  46 ,  50 ,  66 ,  70  are not running, however, the intermediate plenum damper  130  may be open or completely closed depending on whether fresh air is desired in the conditioned space  20  to improve air quality. In some instances, the outdoor ambient temperature may be too high and may affect the cooling capacity of the system  10  too greatly. In such instances, the intermediate plenum damper  130  is completely closed to prevent warmer outdoor air from entering the conditioned space. In such instances, only return air is received and cooled by the evaporator  34 . 
     In other constructions, the flow of fresh outdoor air into the conditioned space  20  can be controlled manually. 
     Thus, the invention provides, among other things, a temperature control system  10 ,  10   a  that effectively utilizes the cooling capacity of fresh outdoor air. Various features and advantages of the invention are set forth in the following claims.