Abstract:
A self-contained electrical heat pump heating, ventilating and air conditioning unit (HVAC) adapted for mounting at the rear of a bus or other similarly large transport vehicle. The HVAC unit is unitary in construction, compactly arranged and provided with an integrated heat pump. The HVAC unit is specially constructed for use with electric buses or electric/hybrid buses, but can also be adapted for use on buses powered by internal combustion engines.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to a heating, ventilating and air conditioning unit (HVAC) adapted for mounting at the rear of a bus or similar type vehicle for transporting a large number of occupants. More specifically, the HVAC unit is self-contained, compactly arranged, and provided with an integrated heat pump. It is specially constructed for use with electric buses or electric/hybrid buses but can also be used with buses powered by internal combustion engines. 
     2. Description of the Prior Art 
     Heating and air conditioning units have been installed in various types of vehicles with the design and operating parameters of the HVAC units adapted for installation in specific types of vehicles. Passenger buses present particular problems due to the relatively large heating and cooling load produced by a plurality of passengers and extensive window areas. Also, it is difficult to obtain effective air circulation through a large volume of internal space to be heated or cooled. In prior art developments, passenger buses have been provided with HVAC units mounted on the roof or at other locations with the compressor assembly being driven from the engine which powers the bus. A condenser, condenser fan, evaporator and evaporator fan are associated with a compressor, expansion valve and other conventional components to provide a refrigeration system to supply conditioned air to the interior of the bus. Separate heating systems are usually provided for use when heated air is required to maintain the interior of the bus at a comfortable temperature level during periods of cold weather. 
     The following U.S. patents relate to the heating and cooling of a vehicle interior and the occupants therein: 
     
       
         
               
               
               
             
           
               
                   
               
             
             
               
                 4,201,064 
                 4,870,833 
                 5,428,967 
               
               
                 4,622,831 
                 4,926,655 
                 5,605,055 
               
               
                 4,727,728 
                 5,001,905 
                 5,609,037 
               
               
                 4,748,825 
                 5,184,474 
                 5,678,761 
               
               
                 4,787,210 
                 5,220,808 
               
               
                   
               
             
          
         
       
     
     The above listed patents disclose various roof and rear mounted air conditioning and heating units for buses and other vehicles. However, the above listed patents do not disclose a self-contained HVAC unit including a heat pump to provide a unitary climate control system utilizing a modular concept by which the heating and cooling capacity of the system may be varied depending upon the requirements of each installation without altering the size parameters of the supporting framework including a horizontally disposed support base and an upright support structure rigidly mounted on the base. 
     SUMMARY OF THE INVENTION 
     The self-contained electrical heat pump HVAC unit of this invention is mounted at the rear of a bus or other similar type vehicle in an area above the prime mover of the vehicle which is usually vacant and available. The mounting of the HVAC unit in this area of the bus enables installation without alteration of the roof or other external configuration of the bus. 
     The HVAC unit is preferably modular in design and includes a supporting framework on which is mounted and supported a condenser or condensers including a fan or fans, an evaporator or evaporators, an evaporator blower or blowers, a compressor or compressors, an air plenum assembly or air plenum assemblies and refrigeration and heat pump system components to provide a complete refrigeration and heat pump cycle. The supporting framework includes an upright support structure attached to a support base and panels are provided to enclose, protect the heat exchangers and isolate the condenser or condensers from the evaporator or evaporators to maintain proper air flow. The bus may be provided with a ducted or free blowing air circulation system or a combination of both depending upon the installation requirements for each individual bus. When in a cooling mode, the air circulation system in the bus is associated with the evaporator or evaporators and evaporator blowers. The condensers and condenser fans are associated with air inlet panels at the sides of the bus and an air outlet panel at the rear of the bus. When in a heating mode, the association of the components is switched with the condensers or condenser becoming evaporators and the evaporator or evaporators becoming condensers in a manner well known in the operation of a heat pump. 
     The rear mounted, multi-functional climate control system with integrated heat pump of this invention is especially designed for electric or electric/hybrid urban buses. However, it is also fully capable of being incorporated into a conventional bus utilizing an internal combustion engine as the prime mover. The construction of this system does not require the formation of holes or other alterations to the roof of the bus to accommodate the condenser and enables the integration of a heat pump system into the unit and eliminates the possibility of snow or ice clogging the condenser. The modular concept of the system simplifies the design and eases installation of the system by virtue of enabling different system capacities to be installed in the same available space by varying the number of compressors, condensers, evaporators and associated fans in the available space thereby minimizing energy consumption by adapting the capabilities of the HVAC unit with the requirements of the installation. 
     It is therefore an object of the present invention to provide a self-contained HVAC unit with integrated electric heat pump mounted at the rear of a bus or other similar vehicle with the components being mounted on a supporting framework capable of fitting into the normally available space above the bus internal combustion engine or power unit in an electric or electric/hybrid bus. The supporting framework or structure is capable of supporting different capacity HVAC components in the same available space thereby enabling the capacity of the HVAC unit to satisfy the heating and cooling requirement of each particular installation without altering the overall size of the unit. 
     Another object of this invention is to provide a self-contained unitary HVAC unit in which the supporting framework includes a supporting base and a centrally located upright support structure with a condenser or condensers mounted on the support base against one side of the upright support structure and an evaporator or evaporators mounted on the other side of the support structure with the evaporator assembly located forwardly of the condenser assembly. The evaporator assembly includes a blower or blowers and the condenser assembly includes a fan or fans for air circulation through the evaporator and condenser assemblies by circulating air through and over the coil and fin evaporator and condenser assemblies. The supporting framework also supports one or more electrically driven compressors and the other conventional components of a HVAC unit, such as an expansion valve, accumulator, dryer, fans, refrigerant circulating tubing and other components to form a closed refrigeration/heat pump system. 
     A further object of the invention is to provide a self contained modular HVAC unit in which the support structure includes panels to isolate the condenser and evaporator assemblies, an air plenum or plenums associated with the evaporator or evaporators for circulation of conditioned air into the passenger area of the bus by utilizing a blower or blowers and a ducted air circulation system, a free blowing air circulation system or a combination of both systems. 
     Yet another object of this invention is to provide a HVAC in accordance with the preceding objects and which will conform to conventional forms of manufacture, be of simple construction and easy to use so as to provide a device that will be economically feasible, long lasting and relatively trouble free in operation. 
    
    
     These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout. 
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic perspective view of a self-contained unitary HVAC unit employing a free blowing air circulation system in accordance with the present invention installed at the rear of a bus in a space below the roof. 
     FIG. 2 is a schematic top plan view illustrating the orientation of the components of the HVAC unit in FIG.  1 . 
     FIG. 3 is a rear elevational view of the HVAC unit of FIG.  1 . 
     FIG. 4 is a side elevational view of the HVAC unit of FIG.  1 . 
     FIG. 5 is a schematic perspective view of a HVAC unit employing a ducted air circulation system from the rear with one condenser fan shown removed. 
     FIG. 6 is a group perspective view of the HVAC unit in accordance with this invention with the components from the front with components of the evaporator assembly in exploded relation. 
     FIG. 7 is an exploded perspective view of the supporting framework components and components of the condenser assembly and evaporator assembly of the HVAC unit in accordance with this invention illustrating the supporting framework with supporting base and upright supporting structure. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Although only two preferred embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. Also, in describing the preferred embodiments, specific terminology will be resorted to for the sake of clarity. It is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. 
     The HVAC units of the present invention as illustrated in FIGS. 1-4 and FIGS. 5-7 are basically the same and utilize a compression/expansion refrigeration system. As illustrated in FIGS. 1-4, the HVAC unit  10  which is a free blowing unit is mounted in the rear of a bus  12  below the roof  14  and in a space  16  located above a compartment area  18  occupied by the electrical components of an electric vehicle or electric/hybrid bus or an internal combustion engine if fuel powered. The rearward side of the HVAC unit  10  includes a condenser assembly generally designated by the numeral  20  and the forward side of the HVAC unit  10  includes an evaporator assembly generally designated by the numeral  22 . These assemblies are mounted on a supporting framework generally designated by the numeral  23 , see FIG. 7, to form a self-contained HVAC unit. The framework  23  includes a horizontally disposed supporting base generally designed by the numeral  24  and an upright support structure generally designed by the numeral  26  rigid with the base  24 . Also supported on the base  24  is a compressor assembly  28 , preferably a hermetically sealed compressor. The HVAC unit shown in the drawings, may also include an optional second compressor assembly  28  at the opposite side of the base  24 . 
     As illustrated in FIGS. 5-7 which show a ducted air flow embodiment, the base  24  includes a rectangular supporting frame  30  in the form of a plurality of rigidly interconnected longitudinal and transverse structural members oriented in spaced relation. The upright support structure  26  includes upwardly extending rigid side members  32  connected with the base  24  with the upper ends of the members  32  being rigidly interconnected by a top member  34 . 
     The condenser assembly  20  includes a lower condenser  36  and an upper condenser  38  each of which is provided with a pair of air circulating axial flow fans  40  for circulating air through the condenser assembly from the periphery thereof and out the rear of the condenser assembly and out through a grill (not shown) in the rear opening of the space  16 . Each of the upper and lower condensers  36  and  38  is a conventional coiled tube and fin heat exchanger and includes side walls  42  and a central wall  44  which are rigidly affixed to the supporting base  24  and abutted against upright frame member  32 . As illustrated in FIG. 7, there is an air space  33 , about 4 inches wide which permits air flow into the condensers  36  and  38 . A top panel  46  is connected with the walls  42  and central wall  44  to form a closure for the upper end of the condenser assembly  20  and protect the coil fins. Also, a rear wall  48  is provided for each of the upper and lower condensers  36  and  38  with the rear wall including large openings  50  of a size substantially equal to the diameter of the axial flow fans  40 . The fans  40  each have a circular grill type cover to prevent injury to personnel who may come into contact with-the HVAC unit. The fans  40  are driven in a conventional manner by a centrally supported electric motor  49  with the rear wall  48  supporting the fans in the openings  50  for circulating air through the condensers  36  and  38  in a well known manner. 
     The evaporator assembly  22  includes a lower evaporator  54  and an upper evaporator  56  each of which is a conventional rectangular coiled tube and fin heat exchanger and each of which includes end walls  58 . The evaporators  54  and  56  are supported from the supporting base  24  and side members  32  above a drain pan  60  and in front of a blower housing  62 . The upper evaporator  56  includes a top panel  64  to protect the coil fins and is attached to housing  62  supported by support structure  26 . A pair or more of evaporator blowers  66  are located in an air manifold  63  to move air through the evaporators  54  and  56  into an air plenum  70  mounted above each end of manifold  63 . Each air plenum  70  includes an air duct connection  72  which may be cylindrical in configuration for connection with a ducted air circulating system for the bus. The air plenum  70  includes a generally horizontal frame work including side panels  74  which have angulated upper edges  76  for supportingly engaging and connection with top panels  78  and  80 . Top panel  80  is angulated and provided with the outwardly inclined air duct connector  72 . 
     Depending upon the capacity requirements for each installation, a single condenser, a single evaporator and a single compressor may be employed or dual condensers, evaporators and compressors may be utilized on the same supporting framework and occupying the same available space. For example, if the bus length ranges between 22 and 36 feet, a single condenser, evaporator and compressor are preferably used. When the bus length is over 36 feet up to approximately 50 feet, dual condensers, evaporators and compressors are preferably utilized. 
     As illustrated in FIG. 1, the bus  12  is preferably provided with side openings  90  with grill covers (not shown) to permit inlet of ambient air to the space forwardly of the condensers  36  and  38 . This inlet of ambient air enables the fans  40  to circulate air through the condensers and out through a grilled opening  51  in the rear of the bus. 
     FIGS. 1-4 illustrate a free blowing embodiment of the invention including a housing  91  and air manifold  92  in which blowers are mounted. The air manifold  92  includes a forwardly facing open area or areas  94  to provide a free blow type air circulation. The structure of the condensers, fans, evaporators, and supporting framework in FIGS. 1-4 is the same as that illustrated in FIGS. 5-7. The schematic illustration in FIGS. 5-7 illustrate the length of the condenser assembly  22  to provide space for one or two compressors  28  depending upon whether dual condensers and evaporators are used. Below the drain pan, a compartment  96  may be provided in the form of the invention in FIGS. 1-4 for all control electronics as shown in FIG.  4 . The evaporators  54  and  56  and condensers  36  and  38  are conventional tube and fin heat exchangers and they may be provided with the capability of adding a supplemental heater for use in extreme cold conditions. The drain pan is preferably provided with a pair of drain tubes  61  on each end thereof to drain excess water that may have condensed on the evaporators. When condensers  36  and  38  function as evaporators when the systems is operating in a heat pump mode, no drip pan is required as the vehicle will have a discharge for any condensate. 
     The overall dimensions of the HVAC unit may vary but in order to fit the space normally available at the rear of the bus, the HVAC unit preferably has an overall height of approximately 37-38 inches, an overall side-to-side dimension of approximately 68-69 inches, and an overall front-to-rear dimension of approximately 21-22 inches. By using a standard supporting framework with a standard supporting base and supporting upright structure, a single evaporator, condenser and compressor may be used or dual evaporators, condensers and compressors may be used with it being understood that an appropriate expansion valve or valves may be employed along with a reversing valve for use when switching between air conditioning mode and heat pump mode and other conventional components and controls used in refrigeration and air conditioning systems may be employed. 
     Installation of the HVAC unit does not require holes being formed in the roof  14  of the bus  12  which reduces the possibility of the condenser unit becoming clogged by snow or ice. The modular structure of the HVAC unit of this invention enables a single system unit or a dual system unit to be installed in the same available space thereby providing simplified design and easier installation. The air distribution system to circulate air from the passenger compartment, through the evaporator assembly when in a cooling mode and back to the interior of the bus may utilize two, three or more small blowers depending on the cooling requirements of the bus and provides flexibility and choice of ducted, free blow or combined air circulating systems. 
     When in a heating mode the air from the passenger compartment of the bus circulates through the evaporator assembly  22  which now functions as a condenser assembly and ambient air circulates through the condenser assembly  20  which now functions as an evaporator assembly in order to extract heat from ambient air and transfer heat to the air being returned to the passenger compartment. When in a heating mode, the thermal energy contained in the warm air being exhausted from the passenger compartment can be recovered by the evaporator coil (condenser coil when cooling) and recycled through the heat pump system to provide heat as well as conserve electricity. Similarly, the cool air exhausted from the passenger compartment during the cooling mode can be utilized to reduce the heat load on the condenser and in turn to save energy and improve performance. To recover waste energy, the HVAC unit may have built-in provisions for accommodating one or two additional heat exchangers by attaching one exchanger to the condenser and the other to the evaporator. Electric buses all require cooling for its drive motor(s) and the electronics, therefore most electric bus have two separate liquid-to-air heat exchangers. So when the electric bus is in operation, the heat collected from the cooling system, instead of being dumped into the ambient air can be recovered either for heating the bus interior and/or heating the evaporator coil (condensing coil when cooling) so that the reclaimed energy can recycle back to the heat pump system to heat and also prevent ice from forming on the coil. 
     The fresh air makeup of the air circulated in the passenger compartment of the bus may be varied from 0 to 100% of outside air to be brought in and the same amount of inside air purged out by utilizing a motorized proportional damper. Fresh air intake and exhaust air outlet can occur at  98  and  100  in FIG. 1. A humidity sensor may also be provided for the interior of the bus to insure that both adequate passenger comfort and energy efficiency can be accomplished. 
     To utilize this system with a conventional bus, an engine driven electric generator is required together with a voltage regulator and controls to supply power to a climate control system utilizing one or two DC electric motor driven compressors. This enables the HVAC to be easily transformed into either a DC drive system or a conventional engine driven system by changing compressors. 
     The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and, accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.