Abstract:
An air conditioning module is constructed to include all the necessary components for an air conditioning system within a single housing, with the housing having a supply air opening and a return air opening. The various components within the housing are so situated that the return air opening is relatively large in its lateral extension across the roof of a bus such that a single module can accommodate various configurations and locations of the supply air and return air openings in the roof of a bus.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is related to the following pending applications being concurrently filed herewith and assigned to the assignee of the present invention: 
     
       
         
               
               
             
           
               
                   
               
               
                   
                 Our 
               
               
                   
                 Docket 
               
               
                 Title 
                 No.: 
               
               
                   
               
             
             
               
                 Modular Rooftop Air Conditioner for a Bus 
                 210_546 
               
               
                 Modular Bus Air Conditioning System 
                 210_545 
               
               
                 Supply Air Blower Design in Bus Air Conditioning Units 
                 210_549 
               
               
                 Bus Rooftop Condenser Fan 
                 210_550 
               
               
                 Method and Apparatus for Refreshing Air in a Bustop Air 
                 210_548 
               
               
                 Conditioner 
               
               
                 Coil Housing Design for a Bus Air Conditioning Unit 
                 210_547 
               
               
                 Integrated Air Conditioning Module for a Bus 
                 210_558 
               
               
                 Fresh Air Intake Filter and Multi Function Grill 
                 210_554 
               
               
                 Integrated Air Conditioning Module for a Bus 
                 210_557 
               
               
                 Modular Air Conditioner for a Bus 
                 210_561 
               
               
                 Modular Air Conditioner for a Bus Rooftop 
                 210_562 
               
               
                 Evaporator Section for a Modular Bus Air Conditioner 
                 210_564 
               
               
                 Wide Evaporator Section for a Modular Bus Air 
                 210_565 
               
               
                 Conditioner 
               
               
                 Condensate Pump for Rooftop Air Conditioning Unit 
                 210_568 
               
               
                 Condensate Removal System Rooftop Air Conditioning 
                 210_551 
               
               
                 Modular Rooftop Unit Supply Air Ducting Arrangement 
                 210_577 
               
               
                 Configuration for Modular Bus Rooftop Air Conditioning 
                 210_595 
               
               
                 System 
               
               
                 Unibody Modular Bus Air Conditioner 
                 210_596 
               
               
                   
               
             
          
         
       
     
     BACKGROUND OF THE INVENTION 
     This invention relates generally to air conditioning systems and, more particularly, to an air conditioning system for the rooftop of a bus. 
     The most common approach for air conditioning a bus is to locate the air conditioning components on the rooftop thereof. Inasmuch as power is available from the engine that drives the bus, it has become common practice to locate the air conditioning compressor near the drive engine such that the drive engine is drivingly connected to the compressor, with the compressor then being fluidly interconnected to the air conditioning system on a rooftop of a bus. This, of course, requires rather extensive piping between the engine compartment and the air conditioning unit, thereby increasing installation and maintenance costs. 
     Another problem with such existing systems is that the speed that the compressor is driven is dependent on the speed in which the drive engine is running. Thus, when the drive engine is idling in a parking lot, for example, the compressor is running at a relatively slow speed which may not be sufficient to provide the desired degree of air conditioning. It is therefore generally necessary to oversize the compressor in order to obtain the performance needed under these conditions. 
     Others problems associated with such a motor driven compressor system is that the open drive compressor needs a shaft seal and a mechanical clutch, both of which are subject to maintenance problems. Further, since DC power is available on a bus, DC motors have been used for the air conditioning system. In general, DC motors are not as reliable as AC motors since they have brushes that wear out, and brushless motors are relatively expensive. 
     In addition to the problems discussed hereinabove, it is recognized, that because the wide variety of bus types and application requirements, it has been necessary to provide many different types and variations of air conditioning systems in order to meet these different requirements and vehicle interfaces. As a result, the manufacturing and installation costs, and sustaining engineering resources that are necessary in order to properly maintain and service these units, are relatively high. 
     Traditionally, the condenser coils and fans have been located near the centerline of the bus rooftop, whereas the evaporator coils and fans are closer to the lateral sides of the rooftop. Further, the evaporator fans are of the draw-through type wherein the evaporator fans are placed downstream of the coils and act to draw the conditioned air from the coils. This provides a uniform velocity distribution at the coil but leads to undesirable high jet flow leaving the fan and subsequently pushing into the bus ducting system. Also, because of the need to have the fan outboard of the coil, it has been necessary to place the coil more toward the center of the bus than might be otherwise desired. 
     It is therefore an object of the present invention to provide an improved bus rooftop air conditioning system. 
     Another object of the present invention is the provision for a bus air conditioning system which is effective at all engine operating speeds of the bus, while at the same time does not require an oversized compressor. 
     Yet another object of the present invention is the provision for reducing the manufacturing, installation, and maintenance costs of a bus air conditioning system. 
     Still another object of the present invention is the provision in an evaporator section of a bus rooftop air conditioning system for locating the evaporator coil more toward the lateral edges of the bus. 
     Yet another object of the present invention is the provision for a bus rooftop air conditioning system which is economical to manufacture and effective in use. 
     These objects and other features and advantages become more readily apparent upon reference to the following descriptions when taken in conjunction with the appended drawings. 
     SUMMARY OF THE INVENTION 
     Briefly, in accordance with one aspect of the invention, an air conditioning module is assembled with its condenser coil, evaporator coil and respective blowers located within the module and so situated that a standard module can accommodate various installation interfaces with different types and locations of return air and supply air ducts on a bus. 
     In accordance with another aspect of the invention, each of a plurality of modules are installed in a centered relationship with respect to a longitudinal centerline of the bus and extend transversely across the width of the bus. The number and length of modules is dependent of the total air conditioning capacity requirement of the bus. 
     By yet another aspect of the invention, each of the modules include all the necessary components with electrical power being provided to the electrical components by an inverter/controller that is powered by an engine driven generator. 
     By another aspect of the invention, the evaporator blower is placed inboard of the evaporator coils and acts to blow air from the return air duct through the coils to be cooled. 
     By still another aspect of the invention the evaporator section of the module has a return air plenum that spans a substantial width of the bus to thereby accommodate various sizes and types of return air interface requirements. 
     By yet another aspect of the invention the evaporator section of each module has two different vertical levels to accommodate the respective incoming flows of return air and replenishing fresh air, and includes a mixer for selectively varying the amount of each which passes to the fan and then to the evaporator coil. 
     In the drawings as hereinafter described, a preferred embodiment is depicted; however various other modifications and alternate constructions can be made thereto without departing from the true sprit and scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a module as installed on the rooftop of a bus in accordance with a preferred embodiment of the invention. 
     FIG. 2 is a perspective view of a module with the top cover removed. 
     FIG. 3 is a schematic illustration of the electrical and refrigerant circuits within the module in accordance with the preferred embodiment of the invention. 
     FIG. 4 is a front elevational view of the condenser section of the module. 
     FIG. 5 is a front elevational view one embodiment of the evaporator section of the module. 
     FIGS. 6-8 are front elevational views of the evaporator section as applied to different types of bus rooftops. 
     FIG. 9 is a top view of an alternate evaporator section. 
     FIG. 10 is a sectional view thereof as seen along lines  10 — 10  of FIG.  9 . 
     FIG. 11 is a sectional view thereof as seen along lines  11 — 11  of FIG.  9 . 
     FIG. 12 is a top view of yet another embodiment of an evaporator section. 
     FIG. 13 is a sectional view thereof as seen along lines  13 — 13  of FIG.  12 . 
     FIG. 14 is a sectional view as seen along lines  14 — 14  of FIG.  12 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The inventive module is shown generally at  10  in FIG. 1 as applied to the rooftop  11  of a bus in accordance with the present invention. Electrical power is provided to the module  10  by way of line  12 , which in turn receives its power from a generator  13  driven by the bus engine  14  as shown. 
     The module  10  interfaces with openings in the bus top so that fans within the module  10  cause the return air from the passenger compartment to flow upward into the module  10  where it is conditioned, and the conditioned air to then flow downwardly into supply air ducts that carry the conditioned air to the passenger compartment. The various structures and the manner in which they interface with the bus rooftop  11  will more fully described hereinafter. 
     In FIG. 2, the module  10  is shown with its cover removed to include a frame  16  with an evaporator section  17  attached to one end thereof and a condenser section  18  attached to the other end thereof. Adjacent the condenser section  18  is a power section  19  which includes a compressor  21  and an inverter/controller  22 . The manner in which they provided motive power to the refrigerant circuit and electrical power to the electrical components of the module  10  will be more fully described hereinafter. 
     The evaporator section  17  comprises a pair of identical units in abutting end-to-end relationship with each unit including an evaporator blower  23  with is evaporator blower motor  24 , and an evaporator coil  26 . Briefly, the evaporator blower  23  draws in return air from the passenger compartment of the bus, and fresh air from outside and passes a mixture of the two through the evaporator coil  26  to be conditioned, after which it flows back to the passenger compartment by way of the supply air ducts. This will be more fully described hereinafter. 
     Within the condenser section  18 , there is provided a condenser fan  27  driven by an electric motor, and a pair of condenser coils  28  and  29 . Briefly, the condenser fan draws air upwardly to create a vacuum below, which in turn causes fresh air to be drawn through the condenser coils  28  and  29  to condense the refrigerant flowing through the coils  28  and  29 . The resulting warm air is then discharged upwardly to the atmosphere by the fan  27 . 
     Referring now to FIG. 3, the module  10  is shown with its electrical connection by way of line  12  to the generator  13  and driving motor  14 . The inverter/controller  22  receives AC power from the generator, or alternator, and, in turn provides discretely controlled AC power to the evaporator blower motor  24 , the drive motor  31  of the condenser fan  27  and the drive motor  32  of the compressor  21 . A plurality of control sensors, shown generally at  33  provide feedback to the inverter/controller  22  as necessary for it to control the AC power being delivered to the various drive motors. 
     As will be seen, the refrigeration circuit is a closed circuit through which the refrigerant flows from the compressor  21  to the condenser  29 , an expansion valve  34 , the evaporator  26  and finally back to the compressor  21 . This is accomplished in a conventional manner. 
     It will be seen that the module  10  is self-contained with all of the necessary components, with the only input thereto being the electrical power by way of the electrical line  12 . Other modules, indicated as numbers  2 - 6  are identically configured and are powered and controlled in the same manner. 
     Returning now to the condenser section  18  as shown in FIG. 4, the flow of air as caused by the condenser fan  27  is shown by the arrows. Fresh air is drawn in through the fresh air intake openings  36  and  37 , passes through the respective condenser coils  28  and  29  and then flow upwardly through the condenser fan  27  and the condenser outlet air opening  38  as shown. 
     Within the evaporator section  17  as shown in FIG. 5, the relatively warm return air flows upwardly from a return air opening (not shown) communicating with the passenger compartment and enters a return air plenum  39  of the evaporator section  17  as shown by the arrows. The evaporator blower  23  causes the return air to flow upwardly to its inlet at the top, and at the same time, fresh air may be brought in by way of a fresh air flap in a manner to be described hereinafter. A mixture of the two airflow streams is thus admitted at the intake of the evaporator blower  23  and caused to flow downwardly and outwardly as indicated by the arrows to the evaporator coils  26 . After passing through the evaporator coil  26  it is then caused by a curved cowling  41  to flow downwardly to a supply air duct leading to the passenger compartment. Thus, while the module is operating, there is a constant circuitous flow of return air out of the passenger compartment and of conditioned air back into the passenger compartment. The amount of return air that is discharged to the outside, and also the amount of fresh air that is brought into the circuit from the outside is controlled by the selective movement of the fresh air flaps as will be described hereinafter. 
     There are shown in FIGS. 6-8, installations of the module  10  with various types of buses and associated return air and supply air openings. In FIG. 6, for example, a wide bus installation is shown wherein the existing ductwork within the bus includes supply air ducts  43  and  44  near the lateral sides of the bus, and return air openings  46  and  47  that are closer to the centerline of the bus, but are substantially spaced apart. Here it will be seen that the return air openings  46  and  47  communicate directly with the return air plenum  39  of the module  10 , but at a position at near the outer end thereof. 
     In FIG. 7, which shows a narrow bus installation, again the supply air ducts  48  and  49  are near the transverse sides of the bus. But the return air openings  51  and  52  are abutting each other at the centerline of the bus. Again, the return air openings  51  and  52  fluidly communicate with the return air plenum  39 , but at the other end thereof. 
     Finally, in FIG. 8 there is shown a curved top bus wherein the supply air ducts  53  and  54  are again near the transverse sides of the bus, but the return air openings  56  and  57  are in intermediate positions, relatively close to the centerline but substantially spaced apart. Again, the return air openings  56  and  57  fluidly communicate with the return air plenum  39 , but at a position intermediate the two ends thereof. 
     It will thus be seen that the same identical module is so constructed and designed that it can accommodate any of these various installation requirements without modification of the module itself. That is, the conditioned air discharge opening  40  is sufficiently large and the transverse direction to accommodate the various supply air duct orientations, and, more importantly, the return air plenum  39  is relatively large in the transverse direction so as to accommodate each of the various types of return air opening configuration as shown. 
     Referring now to FIGS. 9-11, an alternate evaporator section is shown at  61  to include a pair of identical units  62  and  63  in back-to-back relationship with respect to the centerline of the bus. Centrifugal fans  64  and  66  driven by respective motors  67  and  68  are located near the centerline of the bus, and with their axis oriented vertically. 
     As will be seen, the fans  64  and  66  are surrounded by respective scrolls  69  and  71  having relatively short diffusers  72  and  73  leading to the evaporator coils  74  and  76 , respectively. 
     As will be seen in FIG. 10, the fans  64  and  66  are raised so as to provide for the return air plenums  77  and  78 , respectively, therebelow. It should be noted that the longitudinal length L 1  (i.e., the distance the plenum  39  extends laterally across the half-width of the bus) of the plenum  39  is substantial as compared with the width of the return air duct (see FIGS. 6-8) and also as compared with the total lateral length of the unit L 2 . The present design has a dimension of L 1  =595 mm. The dimension L 2  will vary depending on the particular installation. In this regard, the dimension x represents the lateral length of the unit structure between the return air plenum and the supply air discharge opening. This dimension will vary from a minimum of 130 mm to a maximum of 230 mm. The lateral dimension of the supply air discharge opening will also vary from a minimum of 60 mm to a maximum of about 120 mm. Accordingly, the lateral length L 2  will vary from 785 mm to 945 mm. The ration of L 1 /L 2  will therefore be in the range of 0.629 to 0.758 mm. The feature of this relatively large ratio is important in allowing the use of the identical units for various rooftop installation requirements as discussed hereinabove. 
     In comparing the lateral length of the return air plenum with the lateral width of the return air opening it will be seen that the lateral length L, is substantially greater than the width w. Typically the width w of the return air opening is around 120-450 mm. Considering then the ration of the two, the length of 595 mm is on the order of 1.322 to 1.983 times that of the width w of the return air opening. 
     Finally, comparing the length L 1  to the half-width of a bus, a typical bus is about 2150 mm wide, such that the ration of the unit length L 1  to a half-width of a typical bus is about 0.553. Thus, it can be said that the length L 1  is about half of the half width of a bus. 
     With the two level approach, i.e., with the return air plenums  77  and  78  being at one level, and with the fans  64  and  66  being at a higher level, the return air is drawn into the return air plenums  77  and  78  and then enters the fans  64  and  66  by way of inlets  79  and  81 , respectively. The air then remains at the second level and is blown radially outwardly toward the coils  74  and  76 , respectively. 
     The centrifugal fans  64  and  66  are relatively shallow in the vertical direction but relatively large in diameter. The drive motors  67  and  68  are shown in positions above the fans but may be positioned below the fans. The fan rotors may have backward curved, radial or forward curved blades. Located outboard the evaporator coils  74  and  76 , are the pressure plenums  82  and  83  as partially defined by curved cowlings  84  and  86 , respectively. Downstream of the pressure plenums  82  and  83  are the supply air discharge openings  87  and  88 , respectively. 
     Referring now to FIG. 11, the return air is shown by the arrows at the right. On each side of the fan, a fresh air opening with an associated flap is provided to introduce fresh ambient air into the return air plenum  78  to be mixed with the return air prior to its entering into the fan  66 . The fresh air openings are shown by numerals  89  and  91 , whereas the flaps are indicated at  92  and  93 , respectively. It will be recognized that the openings  89  and  91  are relatively small compared with the return air opening into the plenum  78 . Accordingly, this design is intended to allow for a fractional quantity of fresh air to be drawn in and mixed with the return air passing through the fan. There is thus a blockage of a small quantity of return air flow when the flaps  92  and  93  are open, but even when fully opened, the flaps  92  and  93  do not provide for a large blockage of return air flow. 
     In operation, the return air flows into the plenum  78  with a fraction of fresh air being introduced into the openings  89  and  91  as desired. The mixture of air then passes through the fan  66  and is caused to flow outwardly through the scrolls  69  and  71  and the diffusers  72  and  73 , respectively. After passing through the evaporator coils  74  and  76 , the conditioned air flows into the pressure plenums  82  and  83 , respectively and then through the supply air discharge openings  87  and  88  to be discharged to the passenger compartment. 
     Unlike a draw-through fan system of the prior art, wherein the cooled air comes off the fans as a high velocity jet flow blasting into the bus supply air ducts, the present design provides for low velocity, but high pressure flow in the pressure plenums  82  and  83 . The openings,  87  and  88  can be, and preferably are, larger than the conventional openings for a draw-through fan in order to take advantage of the low velocity flow and lower losses. This may preferably take the form of rather narrow but relatively long slots through which the air is discharged. 
     Referring now to FIGS. 12-14, an alterative embodiment of the evaporator section is shown to include a similar blow through arrangement, but with the fans having their axes disposed in the horizontal plane as shown. The respective scrolls are shown at  99  and  101 , and the diffusers at  102  and  103 . The placement of the evaporator coils  74  and  76  are identical as in the previous embodiment, and the structure and function of the pressure plenums  82  and  83  are identical as previously described. 
     Because of the height limitations of the evaporator units, the diameter of the fans  94  and  96  are necessarily smaller than those for the fans with a vertical axes orientation. Thus, a forward curved blower wheel is desirable, and, as will be seen, they are of the double inlet type wherein air can enter from both ends of the fan. The diffusers  102  and  103  are relatively long as compared with their described diffusers for use with the vertical axes fans. 
     Again, return air plenums  104  and  106  are provided at a lower level of the units, and the fans  94  and  96  are provided at a second level for receiving the air and then blowing it outwardly to the coils  74  and  76 . Like the earlier described design, the return air plenums  104  and  106  are longitudinally extensive and have substantially the same relative dimensions as described hereinabove with respect to the vertical axes fans. 
     Referring now to FIG. 14, the flow of return air is shown by the arrows at the right as flowing in to enter each end of the fan  96  as driven by the motor  98 . In order to facilitate the introduction of fresh air to be mixed with the flow of return air, a fresh air opening  107  and associated flap  108  is provided in the one side as shown. The position of the flap  108  is selectively adjustable so as to bring fresh air into the system as desired. In a manner similar as described hereinabove, as the flap  108  is moved toward the fully opened position, it both uncovers the fresh air opening  107  and increasingly tends to decrease the flow of return air coming into the system. However, even when it is in the fully opened position, there is a relatively small percentage of the return air flow that is blocked. 
     In operation, the return air and fresh air come into the lower return air plenum  106 , after which a mixture of the two flows upwardly into the two inlet openings on either side of the fan  96 . The fan  96  then blows the air out from the scroll  101  and the diffuser  103  to the evaporator coil  76  where it is cooled, after which the air enters the pressure plenum  83  and is discharged, at a relatively high pressure and low velocity, to the supply air duct which carries it to the passenger compartment. 
     While the present invention has been particularly shown and described with reference to the preferred mode as illustrated in the drawings, it will be understood by one skilled in the art that various changes in detail may be effected therein without departing from the sprit and scope of the invention as defined by the claims.