Abstract:
A dual use of a heater core that enables heating the cabin, cooling the engine or both on demand regardless of the passenger&#39;s cabin heating and cooling requirements. This use of the heater core is enabled by an HVAC airbox system with a cooling door that can be selectively positioned such that at least some of the air moving through the heater core is directed to the underhood area of a vehicle thereby providing supplemental engine cooling on demand regardless of the passenger&#39;s cabin heating and cooling requirements. The cooling door can be positioned automatically by the Engine Control Unit (“ECU”) dependent on any parameter, or combination of parameters, of the engine such as the engine coolant temperature or the engine oil temperature. The blower speed and the position of the cooling door are adjusted by the ECU depending on the whether and how much supplemental engine cooling is required.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to heating, ventilation and air conditioning (“HVAC”) airbox systems and methods of cooling an engine. Particularly, the present invention relates to HVAC airbox systems and cooling methods for an engine, which is part of a vehicle having a passenger cabin and an underhood area in which the HVAC airbox system is located. Even more particularly, preferred HVAC airbox systems have a dual use of a heater core that enables heating the passenger cabin, cooling the engine or both on demand regardless of the passenger&#39;s cabin heating and cooling requirements. 
         [0003]    2. Description of the Related Art 
         [0004]    Combustion engines must be cooled to prevent overheating, which can cause damage to the engine. In a typical engine cooling system, a radiator is primarily used for cooling the engine, whereas a heater core draws heat from the engine and is used to heat the cabin. When the cabin is being heated, the heater core draws heat from the engine and contributes to engine cooling. However, when the cabin heat is not turned on, there is no airflow across the heater core and, therefore, the heater core does not draw heat from the engine. 
         [0005]    The present invention addresses problems and limitations associated with the related art. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention uses a heater core of a vehicle in not only heating the passenger cabin but also for engine cooling. In preferred heating, ventilation and air conditioning (“HVAC”) airbox systems, the airbox is configured to enable airflow across the heater core by implementing a cooling door such that at least some of the air from exiting the heater core is directed to the underhood area of the vehicle. This contributes to engine cooling on demand, even when passenger cabin heating is turned off. Such a configuration enables the heater core to supplement the radiator in engine cooling, which means that the radiator can be smaller and/or require less airflow through the front grill, which can directly improve the fuel economy of the vehicle. 
         [0007]    Preferred HVAC airbox systems are configured for a combustion engine, which is part of a vehicle having a radiator having a coolant capable of absorbing heat from the engine, a passenger cabin and an underhood area in which the HVAC airbox system is located. The HVAC airbox system includes a heater core connected to the engine using coolant passages such that heat absorbed by the coolant can be transferred to the heater core. The HVAC airbox system further includes at least one blower capable of directing air through the heater core and a cooling door that can selectively be positioned such that at least some of the air moving through the heater core is directed to the underhood area of the vehicle. 
         [0008]    The invention also includes methods of cooling an engine. Preferred methods of the invention generally include at least partially opening or closing the cooling door such that at least some of the air from exiting the heater core is directed to the underhood area of the vehicle. Whether the cooling door is opened or closed can depend on a variety of factors including coolant temperature or whether the passenger cabin heat is on, for example. In preferred methods, the HVAC airbox system is configured to have high and low threshold temperatures for the engine coolant. Preferably, the cooling door opens such that air is directed to the underhood area when the coolant temperature reaches the high threshold temperature and the cooling door closes when the coolant temperature reaches the low threshold temperature such that air is no longer directed to the underhood area. During such operation, the heater core provides supplemental cooling of the engine. 
         [0009]    These and various other advantages and features of novelty which characterize the present invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages and objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described preferred embodiments of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    In the drawings, in which corresponding reference numerals and letters indicate corresponding parts of the various embodiments throughout the several views, and in which the various embodiments generally differ only in the manner described and/or shown, but otherwise include corresponding parts; 
           [0011]      FIG. 1  is a partial, perspective view of a vehicle V having a hood H, a radiator  112 , an engine  124  and a HVAC airbox system  110  having an AC evaporator  120 , a heater core  140  and a blower (blower  116  not shown in this Figure for clarity); 
           [0012]      FIG. 2  is a schematic illustration of a known HVAC airbox system  10 ; 
           [0013]      FIG. 3  is a schematic illustration of a preferred HVAC airbox  110  of  FIG. 1 , the HVAC airbox  110  including heater core  140  and a cooling door  134 ; wherein the cooling door  134  is positioned to direct air A 4  exiting the heater core  140  to an underhood area U of the vehicle V; 
           [0014]      FIG. 4  is a schematic illustration of the preferred HVAC airbox system  110  of  FIGS. 1 and 3 , wherein the cooling door  134  is positioned to direct air A 4  exiting the heater core  140  into the passenger cabin C of the vehicle V; 
           [0015]      FIG. 5  is a schematic illustration of the preferred HVAC airbox system  110  of FIGS.  1  and  3 - 4 , wherein the cooling door  134  is positioned to direct air exiting the heater core  140  into both the underhood area U and the passenger cabin C of the vehicle V; 
           [0016]      FIG. 6  is a schematic illustration of the preferred HVAC airbox system  110  of FIGS.  1  and  3 - 5 , wherein an air conditioning evaporator  120  of the HVAC airbox system  110  is on and is directing cool, dehumidified air into the passenger cabin C, bypassing the heater core  140  to cool the passenger cabin C; 
           [0017]      FIG. 7  is a schematic illustration of a second preferred HVAC airbox system  110 ′ including first and second blowers  116 ′,  116 ″, one blower  116 ′ for directing air to through the AC evaporator  120  to the passenger cabin C and the second blower  116 ″ dedicated to directing air to a heater core  140 ″; 
           [0018]      FIG. 8  is a schematic illustration of an alternative known HVAC airbox system  10 ′; 
           [0019]      FIG. 9  is a schematic illustration of a preferred HVAC airbox system  210  including a cooling door  234  that can direct air from a heater core  240  to the underhood area U of the vehicle V, wherein air A 4  directed to the underhood U is further transferred down a duct  260  to the bottom of the vehicle V; 
           [0020]      FIG. 10  is a flow chart illustrating one preferred method of operating the HVAC airbox systems  110 ,  110 ′,  210 ; 
           [0021]      FIG. 11A  is a first part of a flow chart illustrating another preferred method of operating the HVAC airbox systems of  110 ,  110 ′,  210 ; and 
           [0022]      FIG. 11B  is a second part of the flow chart of  FIG. 11A  illustrating one preferred method of operating the HVAC airbox systems  110 ,  110 ′,  210 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    Known HVAC airbox systems  10 ,  10 ′ are illustrated in  FIGS. 2 and 8 . In these systems, air is directed through an airbox or passageway  52 ,  52 ′ to an AC evaporator  20 ,  20 ′ with a blower  16 ,  16 ′. A blend door  30 ,  30 ′ can then selectively direct the air from the AC evaporator  20 ,  20 ′ to either the passenger cabin (via cabin vent doors  32   a,    32   b,    32   a ′,  32   b ′) or to the heater core  40 ,  40 ′ or both areas. If air is directed to the heater core  40 ,  40 ′, the air passing through the heater core will be heated and can only escape the system via passenger cabin vent doors  32   a,    32   b,    32   a ′,  32   b ′ (see air A 1 -A 3 ). If heated airflow is not desired in the passenger cabin C, there is no airflow across the heater core  40 ,  40 ′, and therefore it cannot remove heat from the engine. The HVAC airflow system preferably further includes a blower door  36 ,  36 ′ which can selectively direct fresh air  42   a  or re-circulated air  42   b  into the system and toward blower  16 ,  16 ′. 
         [0024]    HVAC airbox systems  110 ,  110 ′,  210  of the present invention, such as the ones disclosed herein, can be used for cooling an engine  124 , located in the underhood area U, under the hood H of a vehicle V, which has a passenger cabin C that may be heated or cooled, as desired. Illustrative embodiments are shown in FIGS.  1  and  3 - 7  and  9 - 11 B. Collectively, FIGS.  1  and  3 - 6  illustrate one preferred HVAC airbox  110 , a radiator  112  having hoses  118   a  filled with coolant fluid  119  and a fan (not shown) that can direct air across the radiator  112  and a blower  116  to direct air toward an AC evaporator  120  and heater core  140 . As with known systems, the engine  124  is fluidly connected with hoses  118   b  to the heater core  140 . Hoses  118   a  are interconnected to hoses  118   b.  Air A 1 -A 3  can be directed, via a blend door  130 , to a passenger cabin of the vehicle via cabin vent doors  132   a,    132   b,  to the heater core  140  or to both the heater core  140  and the passenger cabin C. A passageway  152  for air movement is located between the blower door  136 , blower  116 , AC evaporator  120 , heater core  140  cabin vent doors  132   a,    132   b  and passenger cabin C. Blower door  136  is configured to selectively allow blower  116  to intake either fresh air  42   a  from the outside of the vehicle V or re-circulated air  42   b  from inside the passenger cabin C. The HVAC airflow system  110  further includes a cooling door  134  which can be selectively positioned to direct air via a first passageway  150  either to the underhood area U of the vehicle V or to the passenger cabin C or both. The cooling door  134  preferably is pivotal and has at least three positions, wherein, in the first position, air A 4  exiting the heater core  140  is directed to the passenger cabin C; in the second position, air A 4  exiting the heater core  140  is directed to the underhood area U; and, in the third position, air A 4  exiting the heater core  140  is directed to both the passenger cabin C and the underhood area U. Preferably, the cooling door  134  will have many positions in between fully open and fully closed to enable a precise control of air temperature entering the passenger cabin C. Therefore, preferred embodiments are capable of supplementing the cooling of the engine  124  by using the heater core  140  on demand at all operating conditions regardless of whether the cabin heating is turned on or off. A blower  16  for the heater core  140  is provided to direct airflow across the heater core  140 , and this heated air A 4  is vented to the underhood area U if the passenger does not desire cabin C heating. Such a configuration enables the heater core  140  to have airflow across it on demand and draw heat from the engine  124  even when the passenger cabin C heating is turned off. In preferred embodiments, the cooling door  134  is activated automatically by an engine control unit (“ECU” or powertrain control module “PCM”) depending on any parameter in the engine such as coolant fluid  119  temperature or engine oil temperature, for example. The invention is not intended to be limited to any specific metric for evaluating engine temperature. It will be understood that different car OEMs might want to set different trigger or threshold points to activate the cooling door depending on what other fuel economy strategies may be employed by the particular vehicle design. 
         [0025]    Referring now also to  FIG. 7 , which illustrates another preferred HVAC airbox  110 ′. In this embodiment, two blowers  116 ′,  116 ″ are employed. HVAC airbox system  110 ′ can be used with a vehicle V having an engine  124  capable of producing heat, a radiator  112  and fan capable of directing air past the radiator  112  (see engine  124  and radiator  112  disclosed herein). HVAC airbox system  110 ′ includes a heater core  40 ′ fluidly connected to the engine  124  other and at least one of the two blowers  116 ′  116 ″ (see also,  FIG. 1  and the discussion thereof). One blower  116 ″ directs air to the heater core  140 ′ via a first passageway  150 ′ and the second blower  116 ′ directs air to the AC evaporator  120 ′ via a second passageway  152 ′. Blower door  136 ′ is configured to selectively allow blowers  116 ′,  116 ″ to intake either fresh air  42   a  from outside of the vehicle V or re-circulated air  42   b  from inside the passenger cabin C. Cabin vent doors  132   a ′,  132   b ′ are employed to direct air A 4  into the passenger cabin C and cooling door  134 ′ is configured to direct air toward the passenger cabin C, the underhood area U of the vehicle V or both areas as also disclosed with respect to FIGS.  1  and  3 - 6 . As before, the cooling door  134 ′ preferably is pivotal and has at least three positions, wherein, in the first position, air A 4  exiting the heater core  140 ′ is directed to the passenger cabin C; in the second position, air A 4  exiting the heater core  140 ′ is directed to the underhood area U; and, in the third position, air A 4  exiting the heater core  140 ′ is directed to both the passenger cabin C and the underhood area U. Preferably, the cooling door  134 ′ will have many positions in between fully open and fully closed to enable a more precise control of air temperature entering the passenger cabin C. Such an embodiment may be preferred over the single blower embodiment if a single blower cannot sufficiently deliver enough air to the AC evaporator  120 ′ for cooling the passenger cabin C and enough air to the heater core  140 ′ for cooling the engine  124  at the same time. Advantages of the HVAC airbox system  110 ′ of  FIG. 7  potentially include less noise, more control of airflow and more airflow at a higher efficiency as compared to a single blower system such as that illustrated in  FIGS. 3-6 . Disadvantages of the HVAC airbox system  110 ′ of  FIG. 7  as compared to the HVAC airbox system  110  of  FIGS. 3-6  include additional cost, additional space required for the second blower and more power is consumed by two blowers, which may offset some of the fuel economy gains. 
         [0026]    Yet another alternate HVAC airbox system  210  is illustrated in  FIG. 9 . In previously disclosed embodiments, there are no aspects of the HVAC airbox system that assist to dissipate the heated air once it is vented to the underhood area U. Air in the underhood area U will eventually escape the system through the bottom of the vehicle V. In alternative embodiments as illustrated in  FIG. 9 , the HVAC airbox system  210  can include a duct  260  proximate an exit area  262  near the heater core  240  such that hot air A 4  exiting the heater core  240  is directed through the duct  260  and to the bottom of the vehicle V, or alternate location, as desired. Such embodiments will help reduce the temperature of the underhood area U, which could lower the temperature of the engine  124 . Such embodiments are also beneficial in that they are believed to increase the airflow through the front-end radiator (see, for example, radiator  112  of  FIG. 1 ) by lowering the airflow resistance. Whether this increase in airflow and other benefits of releasing the heated air to the bottom of the vehicle is worth the additional costs is up to the preference of the vehicle manufacturer. 
         [0027]    The HVAC airbox system  210  of  FIG. 9  includes a blower  216  that directs air past an AC evaporator  220 . From there, a blend door  230  directs the air either through a heater core  240  if heating of the passenger cabin C is desired or directly to the passenger cabin C if no heating is desired. Passenger cabin vent doors  232   a,    232   b  can selectively direct air A 1 -A 3  to various areas of the passenger cabin C, as with previous embodiments. An airbox or passageway  252  for air movement is located between the blower door  236 , blower  216 , AC evaporator  220 , heater core  240  cabin vent doors  232   a,    232   b  and passenger cabin C. Blower door  236  is configured to selectively allow blower  216  to intake either fresh air  42   a  from outside of the vehicle V or re-circulated air  42   a  from inside the passenger cabin C. This invention differs from the prior art embodiment illustrated in  FIG. 8  in that a cooling door  234  can direct the airflow from the heater core to the underhood when the cabin heating is not required but the supplemental engine cooling is required. This air flow through the heater core  240  can then, if required, be directed via duct  260  toward the bottom of the vehicle V when blend door  230  and cooling door  234  are selectively positioned as illustrated in  FIG. 9 . It will be understood that duct  260  is not required. The cooling door  234  preferably is pivotal and has at least three positions, wherein, in the first position, air A 4  exiting the heater core  240  is directed to the passenger cabin C; in the second position, air A 4  exiting the heater core  240  is directed to the underhood area U; and, in the third position, air A 4  exiting the heater core  240  is directed to both the passenger cabin C and the underhood area U. 
         [0028]    The cooling doors and blend/vent doors  130 ,  132   a,    132   b,    134 ,  132   a ′,  132   b ′,  134 ′,  230 ,  232   a,    232   b,    234  of the present invention may be of the type used for other vent doors used in known vehicle HVAC airflow systems. For example, the cooling and cabin blend/vent doors  30 ,  32   a,    32   b,    34 ,  32   a ′,  32   b ′,  34 ′ can be of the type commonly used to regulate airflow to the passenger cabin, to regulate passenger cabin/outside air intake and various blend doors to regulate a mix of air from the AC evaporator  120 ,  120 ′,  220  and heater core  140 ,  140 ′,  240 . It will be understood that there are many ways in which air can be effectively directed and the present invention is not intended to be limited to any specific method, apparatus for directing air. 
         [0029]    The recent trend in engine design is toward more powerful engines desired by consumers and better fuel economy driven by oil prices and federal Corporate Average Fuel Economy (“CAFE”) requirements. This means that increasingly engines are turbocharged and use many technologies such as EGR coolers, transmission oil coolers and the like to meet the power and fuel economy goals. Many of these fuel economy improvement technologies generate more heat under the hood and, therefore, require more air flow under the hood to adequately cool the engine. The under hood engineer typically desires to design the vehicle with as open of a front-end as possible to allow lots of airflow to come into the underhood to help meet the engine cooling requirements. The external body designer of the vehicle, on the other hand, typically desires for the vehicle design to be a sleek, aerodynamic shape with very little front-end opening to reduce the drag of the vehicle and make it look visually appealing to potential buyers. Reducing the drag also improves the fuel economy significantly. One of the most significant impacts of the present invention is that less airflow is needed from the front end of the vehicle, which will, in turn, reduce the drag of the vehicle and the fuel consumed by the vehicle. For example, at highway speeds, about 60% of the power required to cruise is used to overcome aerodynamic effects. By minimizing this drag, by reducing airflow requirements underhood, embodiments of the present invention translated directly into improved fuel economy. 
         [0030]    For example, a typical front end radiator needs to remove about 50 kW from a typical passenger carengine when running in normal city driving. The heat that needs to be removed jumps up to about 60 kW when the engine is working hard and towing a trailer. The front end radiator and grill opening are designed for the higher strain scenario. A typical heater core can remove about 10 kW of heat. This means that if the heater core is employed to remove heat to its full potential, then the radiator can be deigned to remove 50 kW (enough heat under most circumstances) and the heater core can remove the remaining 10 kW of heat from the engine. The airflow required through the front-end radiator to remove 50 kW of heat rather than 60 kW of heat is almost linearly related to the amount of heat that needs removing. Therefore, about 20% less airflow through the radiator is required in this example, which will lead to fuel economy gains presuming that the vehicle manufacturer designs the front end of the vehicle accordingly to take advantage of the lower airflow requirement. 
         [0031]    Preferred methods are disclosed herein and further illustrated in the flow charts of  FIGS. 10-11  B. Turning now also to  FIG. 10 , it is preferably determined if supplemental engine cooling is required  180  by monitoring the desired parameter of the engine  124  such as coolant fluid  119  temperature or engine  124  oil temperature, for example. If supplemental engine cooling is required and the cabin heat is on  181 , the cooling door  134 ,  134 ′,  234  will preferably be partially open  183  so that heated air A 4  from the cooling system is vented to both the underhood area U and the passenger cabin C (see also,  FIG. 5 , for example). If supplemental engine cooling is required but the cabin heat is not on  181 , the cooling door  134 ,  134 ′,  234  will be completely open  184  so that heat from the HVAC airbox system  110 ,  110 ′,  210  is vented only to the underhood area U (see also,  FIG. 3 , for example). If supplemental engine cooling is not required  180  and the cabin heat is on  182 , the cooling door  134 ,  134 ′,  234  will be closed  185  so that heated air A 4  from the cooling system  110 ,  110 ′,  210  is directed into the passenger cabin C. If supplemental engine cooling is not required  180  and the cabin heat is off  182 , the cooling door  134 ,  134 ′,  234  and the blend door  230  are closed  186 . 
         [0032]    Turning also now to  FIGS. 11A-11B , which illustrates a further preferred method of operating the HVAC airbox systems  110 ,  110 ′,  210  disclosed herein. As illustrated, initially the engine cooling door  134 ,  134 ′,  234  is closed and engine coolant temperature is measured  119 . When supplementary engine cooling is required  190  (e.g. when the radiator  112  cannot sufficiently cool the engine  124 ), as determined by when the coolant  119  temperature is greater than the predetermined high threshold temperature  192 , the cooling door  134 ,  134 ′,  234  is opened  193  and the blower  116 ,  116 ″,  216  speed is increased to achieve adequate engine cooling and cabin C heating and/or requirements  194 . This mode of operation continues as long as supplemental cooling is required. The cooling door and the blower speed might be adjusted by the ECU to increase the supplemental cooling provided. When the coolant temperature becomes less than a predetermined lower threshold temperature, the engine cooling door  196  is closed and the blower  116 ,  116 ′,  216  speed is adjusted according to cabin C heating requirements  197 . This cycle is repeated  198  as the coolant  119  temperature fluctuates. As will be appreciated, the methods disclosed in  FIGS. 10-11B  can be performed with any metric desired, such as a specific engine oil temperature, and are not limited only to evaluating coolant temperature. 
         [0033]    In one example, if the coolant  119  temperature is greater than 220 degrees F., the engine cooling door  134 ,  134 ′,  234  is opened, and the cooling door  134 ,  134 ′,  234  is closed when the coolant temperature falls below 220 degrees F. Then the cooling door  134 ,  134 ′,  234  will reopen when the coolant  119  temperature reaches 221 degrees F. and will close as soon as temperature drops to 219 degrees F. This will make the door open and close every few seconds, which is less preferred as it will increase wear and tear on the cooling door  134 ,  134 ′,  234 . 
         [0034]    What is more preferred is that the cooling door  134 ,  134 ′,  234  should be closed when coolant  119  temperature drops below 210 degrees F. (i.e., the cooling door  134 ,  134 ′,  234  is open when coolant temperature goes above 220 degrees F. (higher threshold coolant temperature”, but the door only closes when coolant temperature drops to a lower threshold coolant temperature (e.g. 210 degrees F.). It is believed that this method will result in an engine cooling system that is more stable. In preferred embodiments, the difference between the high threshold temperature and the low threshold temperature is about 2 to about 15 degrees Fahrenheit and the exact temperature gap between low and high threshold can vary depending the size of the engine and the design of the vehicle. 
         [0035]    Preferred methods of cooling a combustion engine  124  that is part of a vehicle V having a passenger cabin C and an underhood area in which the combustion engine  124 ,  124 ′ is located include the steps of providing a combustion engine  124 ,  124 ′ capable of generating heat; a radiator  112  fluidly connected to the engine  124 ,  124 ′, the radiator having a coolant  119 . The coolant  119  capable of absorbing heat from the engine  124 . The vehicle V further including a HVAC airbox system  110 ,  110 ′,  210  having a heater core  140 ,  140 ′,  240  fluidly connected to the engine  124 ,  124 ′ such that heat absorbed by the coolant  119  can be transferred to the heater core  140 ,  140 ′,  240 . The HVAC airbox system  110 ,  110 ′,  210  further including at least one blower  116 ,  116 ″,  216  capable of directing air through the heater core  140 ,  140 ′,  240 . The HVAC airbox system  110 ,  110 ′,  210  further comprises an AC evaporator  120 ,  220 , wherein air is directed from the blower  116 ,  216 , through the AC evaporator  120 ,  220  and then to the heater core  140 ,  240 . The method further includes the step of actuating a cooling door  134 ,  134 ′,  234  such that at least some of the air from exiting the heater core A 4  is directed to the underhood area U of the vehicle V. In various methods, at least some of the air A 4  exiting the heater core  140 ,  140 ′,  240  is directed to the passenger cabin C. In further preferred methods, the cooling door  134 ,  134 ′,  234  is adjustable such that the cooling door  134 ,  134 ′,  234  can direct the air exiting to the heater core  140 ,  140 ′,  240  to only the underhood area U, only the passenger cabin C or both the underhood area U and the passenger cabin C. In alternate preferred methods, substantially all of the air A 4  exiting the heater core  140 ,  140 ′,  240  is directed to the underhood area U of the vehicle V. In further preferred methods, the engine cooling system  210  further includes a duct  260  proximate the heater core  240  such that the air A 4  passing through the heater core  240  can be directed to the underhood area U and then to the bottom of the vehicle V via the duct  260 . 
         [0036]    Although the preferred embodiments of the present invention have been described herein, the above description is merely illustrative. Further modification of the invention herein disclosed will occur to those skilled in the respective arts and all such modifications are deemed to be within the scope of the invention as defined by the appended claims.