Patent Abstract:
A vehicle interior cooling system ( 100 ) for a vehicle having a cabin ( 108 ) and an engine ( 107 ) for providing propulsion power is disclosed. The vehicle interior cooling system includes a cabin cooling system ( 102 ) driven by the engine of the vehicle and an electrically driven cooling system ( 103 ) having a cold storage device ( 110 ) coupled to the vehicle. The electrically driven cooling system selectively thermally charges the cold storage device when the engine is in an on and/or off position.

Full Description:
FIELD OF THE INVENTION 
   The present invention relates generally to vehicle interior cooling systems, and more particularly to vehicle interior cooling systems utilizing a cold storage device. 
   BACKGROUND OF THE INVENTION 
   Keeping the interior of a vehicle at a comfortable temperature is important in providing driver comfort. It is desirable to maintain the interior at a comfortable temperature while the vehicle is parked. This is most notably the case for long haul truckers who sleep in the cab of the truck for the required 10-hour rest period. One way of keeping the cab of the truck cool is to maintain the engine at an idle so that the truck&#39;s regular air conditioning system can be run to cool the cab; however, this results in increased fuel consumption, pollution, engine maintenance, and most often reduces battery life. Further, exasperating the problem is that the truck&#39;s engine must be run at a higher RPM than idle to produce enough current to support sleeper loads, especially if the air conditioning system is run. If the RPM of the engine is not increased above idle, the batteries will operate in deficit. 
   One option is to shutdown the engine. In fact, environmental considerations have lead to federal regulations that will soon require maintaining interior cab temperatures of a Class 8 vehicle in an engine off or no-idle condition. 
   Thus, there exists a need for a cooling system that can keep the cab cool not only when the engine of the truck is running but also when the truck is parked and the engine is shutdown. 
   Referring to  FIG. 1 , one previously developed solution for fulfilling this need is shown. The illustrated prior art cooling system  10  includes a cold storage device  12 . The cold storage device  12  is essentially a cold sink and is well known to those skilled in the art, and therefore will not be described in detail herein for the sake of brevity. While the truck engine is running, the air conditioning system  14  cools a cab  16  of the truck and turns a phase change material held within the cold storage device  12  from a liquid to a solid, i.e. freezes the phase change material. During hot days however, the conditioning system  14  does not have sufficient capacity to adequately both cool the cab  16  of the truck and cold charge the cold storage device  12 , leaving the driver in a dilemma, i.e. to be comfortable while driving but not charge the cold storage device  12 , making for an uncomfortable sleep, or forego cooling the cab, endure the high heat while driving, and charge the cold storage device  12  to make sleep more comfortable. 
   The air conditioning system  14  of  FIG. 1  includes a compressor  18 , a condenser  20 , a receiver  22 , a three-way valve  24 , two expansion valves  26  and  28 , and two evaporators  30  and  32 . During operation, the compressor  18  compresses a refrigerant, producing a hot pressurized gas which is converted into a cool, high pressure liquid by the condenser  20 . This is accomplished by passing cool ambient air by fan or other means over the condenser  20  to remove heat from the refrigerant. 
   The receiver  22  accumulates the liquid refrigerant produced in the condenser. The three-way valve  24  selectively directs the refrigerant to either pass through the first or the second evaporator  30  or  32  (or a selected combination thereof) via the appropriate expansion valves  26  and/or  28 . The expansion valves  26  and  28  transform the high pressure liquid refrigerant to a low temperature, low pressure gas and/or liquid mixture refrigerant. 
   The first evaporator  30  is located in heat exchange communication with the cab  16 . A fan  34  is used to pass air over the first evaporator  30 , which cools the air, which is then directed into the cab to cool the same. The second evaporator  32  is located in the cold storage device  12  and is used to cool the phase change material present therein, preferably converting the phase change material to a solid. 
   When the truck engine is shutdown, the engine driven compressor  18  cannot be run as it is driven by the engine. Further, even if one were to attempt to drive the compressor by using an electric motor utilizing power obtained from the truck&#39;s batteries, the current draw required to drive a compressor of the size required to draw down the entire cab would drain the batteries in such a short period that such an arrangement is unfeasible. For instance, a typical compressor of the size required to draw down the entire cab typically requires approximately 8 horsepower to run at full capacity, which, on a 12-volt system, would draw 200 amps. Such a large draw would drain a truck battery in a very short period. 
   Thus, in previously developed cooling systems, if cab cooling is desired with the engine shutdown, a heat transfer system  35  is used. The heat transfer system  35  uses an electric pump  36 . The electric pump  36  pumps antifreeze infused water through heat exchange coils  38  embedded in the cold storage device  12 , thereby reducing the temperature of the antifreeze infused water and partially melting the phase change material contained in the cold storage device  12 . The cooled antifreeze infused water then passes through a heat exchanger  40 . An electric fan  42  blows air over the coils of the heat exchanger  40 , thereby blowing cold air into the cab  16  to cool the cab  16 . 
   Although effective, this previously developed cooling system  10  is not without its problems. First, the standard truck air conditioning system  14  is required to produce 38–42° F. air at a cabin diffuser while the thermal storage unit is required to support temperatures in the 26° F. range. Therefore, the truck air conditioning system must cycle off for a short time while the storage system switches the compressor to a higher pressure mode to produce 26° F. temperatures for use in the thermal storage unit. Typically, when the ambient temperatures are in excess of 100° F., the standard engine air conditioning system is not adequate and often becomes overloaded attempting to cool the cab  16  and convert the phase change material of the cold storage device  12  to a solid. Further, with the engine shutdown, the cold storage device  12  cannot be recharged; thus the ability to cool the cab  16  is limited to the cooling capacity of the cold storage device  12  at time of engine shut-down. Thus, there exists a need for a vehicle cooling system that reduces the load on the truck&#39;s regular air conditioning system so it does not become overloaded attempting to cool both the cab of the truck and the cold storage device. Further, there exists a need for a vehicle cooling system that is operable to recharge the cold storage device even when the engine of the vehicle is shutdown and plugged into shore power, i.e. plugged into an alternating current power source provided to mobile users at places such as truck stops, parking lots, warehouses, loading docks, driver&#39;s home, etc. 
   SUMMARY OF THE INVENTION 
   One embodiment of a vehicle interior cooling system formed in accordance with the present invention for a vehicle having a cabin and an engine for providing propulsion power is disclosed. The vehicle interior cooling system includes a cabin cooling system driven by the engine of the vehicle and an electrically driven cooling system having a cold storage device coupled to the vehicle. The electrically driven cooling system selectively thermally charges the cold storage device when the engine is in an on position. 
   Another embodiment of a vehicle interior cooling system formed in accordance with the present invention for a vehicle having a cabin and an engine for providing propulsion power is disclosed. The vehicle interior cooling system includes a first cooling system disposed within the vehicle and driven by the engine. The vehicle interior cooling system further includes a second cooling system having a cold storage device coupled to the vehicle. The second cooling system is selectable to thermally charge the cold storage device when the engine is in an off position. 
   An alternate embodiment of a vehicle mounted cooling system for cooling an interior space of a vehicle, the vehicle having an engine for providing propulsion power to the vehicle, is disclosed. The vehicle mounted cooling system includes a cabin cooling system powered by the engine for cooling the interior space of the vehicle. The vehicle mounted cooling system also includes a cold storage system operable independently of the standard cabin cooling system normally found on a truck. The cold storage system has a cold storage device thermally chargeable and dischargeable by the cold storage system for cooling the interior space of the vehicle. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a piping schematic of a previously developed vehicle cooling system having a regular vehicle cooling system, a cold storage device, and a heat transfer system; and 
       FIG. 2  is a piping schematic of one embodiment of a vehicle cooling system formed in accordance with the present invention having a regular vehicle cooling system, a cold storage device, a heat transfer system, and a cold storage charging system. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 2  illustrates a vehicle cooling system  100  formed in accordance with one embodiment of the present invention. Although the embodiments of the present invention will be described as implemented with regard to a cab of a Class 8 truck, one skilled in the relevant art will appreciate that the disclosed vehicle cooling system  100  is illustrative in nature and should not be construed as limited to application for cooling a cab of a Class 8 truck. It should therefore be apparent that the vehicle cooling system  100  has wide application, and may be used in any situation wherein cooling any space of any structure is desirable both when a drive source for a space&#39;s regular air conditioning system is running and when the drive source is shutdown. 
   For purposes of this detailed description, the vehicle cooling system  100  may be divided into two main subassemblies: a main cooling system  102  and a cold storage system  103 . Both subassemblies are adapted to cool a cab  108  of the truck. Generally stated, the main cooling system  102  is the air conditioning system and is used to cool the cab  108  of the truck (not shown) while an engine  107  of the truck is running. 
   Generally, the cold storage system  103  is used to cool the cab  108  of the truck while the engine  107  of the truck is shutdown, however it may also be used to cool the cab  108  while the engine  107  is running. The cold storage system  103  includes a cold storage charging system  104 , a heat transfer system  106 , and a cold storage device  110 . The cold storage charging system  104  is used to cold charge the cold storage device  110  while the engine  107  is running, and may also be used to recharge the cold storage device  110  while the engine  107  is shutdown (with or without shore power being provided). 
   The heat transfer system  106  is used to transfer low thermal energy stored in the cold storage device  110  to the cab  108  of the truck while the engine  107  is shutdown. Thus, the cold storage charging system  104  of the present invention provides a cooling system separate from the main cooling system  102  for cold charging the cold storage device  110 . This aids in preventing the main cooling system  102  from becoming overloaded, while also permitting the cold storage device  110  to be recharged while the engine  107  is shutdown. 
   The main cooling system  102  contains well known components arranged in accordance with standard practices in the art of cooling system design and manufacture. These components include a compressor  112 , a condenser  114 , a receiver  116 , an expansion valve  118 , and an evaporator  120 . 
   The compressor  112  is driven by the engine  107  of the truck by any number of suitable methods, such as by a belt and pulley system. In operation, the compressor  112  compresses a refrigerant, producing a hot, high pressure refrigerant at the outlet of the compressor  112 . The refrigerant then moves through the condenser  114 , wherein relatively cold air, typically ambient air, is driven, such as by a fan  122 , over a set of heat exchange coils  124  of the condenser  114 . As the cool air passes over the coils  124 , heat is removed from the refrigerant, causing the refrigerant to condense into a liquid, where it is accumulated in the receiver  116 . 
   The expansion valve  118  flashes the liquid refrigerant into a low pressure, low temperature gas and/or liquid mixture. The low pressure, low temperature refrigerant is passed through the evaporator  120  via a set of heat exchange coils  126  disposed in heat exchange communication with the interior air of the cab  108 . A fan  128  directs air to pass over the heat exchange coils  126 , thereby causing heat to be transferred from the air to the refrigerant, thereby cooling the air and heating the refrigerant, converting the refrigerant into a low pressure, hot gas. The cooled air is directed into the cab  108  of the vehicle thereby cooling the cab  108 . The refrigerant, as a low pressure, hot gas, is directed to the inlet of the compressor  112  and the cycle is started anew. 
   Although a particular main cooling system  102  is depicted and described, it should be apparent to those skilled in the art that many other cooling system designs and types are suitable for use with and are within the spirit and scope of the present invention, the described main cooling system being only illustrative in nature. 
   Still referring to  FIG. 2 , the cold storage charging system  104  includes an electrically driven compressor  130 , a condenser  132 , a receiver  134 , an expansion valve  136 , and a set of evaporator coils  139 . The electrically driven compressor  130  is preferably connected to the vehicle&#39;s electrical system  152  and driven by an electric motor  131 . In one embodiment, the compressor  130  is driven by electricity provided by an engine driven alternator (not shown) while the engine  107  is running and from the batteries  154  (or shore power) when the engine  107  is shutdown. 
   In operation, the compressor  130  compresses a gaseous refrigerant, forming a hot, high pressure refrigerant at the outlet of the compressor  130 . The refrigerant is moved through the condenser  132 , wherein relatively cold air, typically ambient air, is driven, such as by a fan  136 , over a set of heat exchange coils  138  of the condenser  132 . As the cool air passes over the coils  138 , heat is removed from the refrigerant, causing the refrigerant to condense into a liquid, where it is accumulated in the receiver  134 . 
   An expansion valve  136  flashes the liquid refrigerant into a low pressure, low temperature gas and/or liquid mixture. The low pressure, low temperature refrigerant is passed through the set of evaporator coils  139  set within a cold storage device  110 . As the gas is passed through the evaporator coils  139 , heat is transferred from a phase change material present in the cold storage device  110  into the low pressure, low temperature refrigerant, thereby cooling the phase change material and converting the refrigerant into a superheated gas. The low pressure, superheated gas is compressed by the compressor  130  as the cycle begins anew. 
   The heat transfer system  106  includes an electrically driven pump  142 , a first set of heat exchange coils  144  located in the cold storage device  110 , and a second set of heat exchange coils  146  disposed in heat exchange communication with the interior air of the cab  108 . 
   In operation, the electrically driven pump  142  drives a heat transfer fluid, such as antifreeze infused water, through the first set of heat exchange coils  144  disposed in the cold storage device  110 . As the heat transfer fluid passes through the coils  144 , heat is transferred from the heat transfer fluid to the phase change material present in the cold storage device  110 , thereby cooling the heat transfer fluid and heating the phase change material. The cooled heat transfer fluid is then passed through the second set of heat exchange coils  146 . A fan  148  drives air over the second set of heat exchange coils  146  and into the cab  108  thereby cooling the cab  108 . Preferably, the cool air exiting the heat exchange coils  146  is directed toward the headboard end of a driver bunk and air to be cooled is drawn from the foot of the driver bunk. As the air passes over the coils  146 , heat is transferred from the air into the heat transfer fluid, thereby heating the heat transfer fluid and cooling the air. The heat transfer system  106  continues in a cyclic pattern, thereby transferring the low thermal energy stored in the cold storage device  110  to the interior air of the cab  108 . 
   In light of the above description of the components and individual operation of the main cooling system  102 , the cold storage charging system  104 , and the heat transfer system  106 , the operation of these system relative to one another will now be described. 
   Operation of the vehicle cooling system  100  may be divided into two distinct modes: a first mode when the engine  107  of the truck is running, and a second mode when the engine  107  of the truck is shutdown. When the engine  107  is running, the main cooling system  102  is selectively run to maintain the interior air of the cab at a predetermined comfortable temperature or within a selected range of temperatures. The cold storage charging system  104  is run while the engine is running and is powered by electricity generated by the engine&#39;s  107  alternator (not shown) to cold charge the phase change material present in the cold storage device  110  via an electrically driven compressor, preferably converting the phase change material from a liquid to a solid. Inasmuch as the cooling load of the cold storage device  110  is borne by a separate system, i.e. the cold storage charging system  104 , the cooling load of the main cooling system  102  is reduced as it is only required to cool the cab  108 , and not the cab  108  and the cold storage device  110 . Thus, because the cooling load of the main cooling system  102  has been reduced, less expensive, lighter, and lower capacity components may be used in the main cooling system  102 . 
   Further, inasmuch as the cooling load of the cold storage device  110  is borne by a separate system, there is no lag time when initiating cold charging of the cold storage device  110  as was the case with previously developed vehicle cooling systems. More specifically, in previously developed cooling systems, a single compressor was used to provide both low temperature coolant (such as 26° Fahrenheit) to cold charge the cold storage device and higher temperature coolant (such as 42° F.) to provide cabin cooling. To provide both a low and high temperature coolant, the compressor of the main cooling system was reconfigured between a high pressure mode and a low pressure mode to provide a reduced temperature coolant for cold charging the cold storage device  110  and an elevated temperature coolant for cabin cooling. As the system was reconfigured, a lag time existed as the system was toggled between high and low pressure modes of operation. 
   Of note, when the engine  107  is running at an idle, the engine  107 , or more specifically an alternator (not shown) coupled to the engine  107 , may not produce enough electricity to power the cold storage charging system  104  necessitating the drawing of current from the batteries of the vehicle. Thus, in one embodiment of the present invention, a control system  150  is used which automatically shuts down the electrical compressor  130  of the cold storage charging system  104  to impede the batteries of the vehicle from being overly depleted when a select condition is present, such as the RPM of the vehicle falling below a predetermined RPM (for instance when the engine is idling), or when the voltage of the batteries of the vehicle fall below a predetermined voltage, such as 12.5 volts. 
   The heat transfer system  106  is normally not run while the engine  107  is running, since the main cooling system  102  preferably provides sufficient cooling capacity to handle the cooling load of the cab  108 . However, the heat transfer system  106 , and preferably the cold storage charging system  104 , may be run simultaneously with the main cooling system  102  in some instances. For example, running the heat transfer system  102  and the cold storage charging system  104  simultaneously with the main cooling system  102  is especially beneficial in handling peak loads such as during the initial drawing down of the cab temperature. In this mode of operation, the heat transfer system  106  supplements the main cooling system  102  to provide increased capacity during peak loads. Preferably, in this mode, the heat transfer system  106  would be run at a reduced capacity such that the cold storage charging system  104  would still be able to cold charge the cold storage device  110 . In other words, the heat transfer system  106  would be run at a reduced capacity such that more heat would be removed from the cold storage device  110  than transferred into the cold storage device  110  such that the phase change material in the cold storage device  110  will still be able to undergo phase change to a solid in a reasonable amount of time. 
   The operation of the vehicle cooling system  100  when the engine  107  is shutdown, such as when a driver is sleeping in the cab  108 , will now be described. Because the engine  107  is shutdown, the engine driven compressor  112  of the main cooling system  102  cannot be run, and therefore the main cooling system  102  is shutdown and non-operational. As discussed above in the Background Section of this detailed discussion, even if one were to attempt to drive the compressor from a separate electrically driven drive motor, the current required to run the compressor of the main cooling system  102 , which is sized sufficiently large to handle a maximum cooling load of the cab, would drain the truck&#39;s batteries  154  in short order, making such a configuration impractical. For instance, as discussed above, a typical compressor of the size required to draw down the entire cab typically requires approximately 7 horsepower to run at full capacity, which, on a 12-volt system, would draw 435 amps. Such a large draw would drain a truck battery in a very short period. 
   Thus, cooling of the cab  108  is provided by the cold storage system  103  during engine  107  shutdown. Moreover, the heat transfer system  106  is energized and run off of electricity obtained from the truck&#39;s electrical system  152 . In one working embodiment, operation of the components of the heat transfer system  106  draws a light load, such as approximately 4 to 5 amps, thus the heat transfer system  106  may be continuously operated over extended periods without significantly draining the truck&#39;s batteries  154  during the required driver rest period. 
   Operation of the heat transfer system  106  results in the low thermal energy stored in the cold storage device  110  to be transferred to the interior air of the cab  108  as described above while drawing only a small amount of electricity from the truck&#39;s storage batteries  154 . The cold storage charging system  104  normally is not run when the engine  107  is shutdown. However, the compressor  130  and fan  136 , since they are electrically driven, may be run for a limited period to recharge the cold storage device  110  while the engine  107  is shutdown, using electrical energy stored in the truck&#39;s electrical system  152 , such as energy stored in the batteries  154  of the truck&#39;s electrical system  152 . 
   In one working embodiment, operation of the components of the heat transfer system  106  in combination with the cold storage charging system  104  draws a mid-sized load, such as approximately 25 to 30 amps. Thus, from comparisons of the amperage draws, it should be apparent to those skilled in the art that the compressor  130  of the cold charging system  104  is sized at least half of the capacity of the compressor  112  of the main cooling system  102 , and preferably at about one quarter or less of the capacity of the main cooling system  102  compressor  112 . In one working embodiment, the capacity of the compressor  130  of the cold charging system  104  is sized at ½ of the capacity of the compressor  112  of the main cooling system  102  since the main cooling system is required to pull the cabin down while the cold charging system is used just to maintain the temperature in an already cooled cabin. Thus, the heat transfer system  106  and/or the cold storage charging system  104  may be simultaneously run for short periods without completely draining the truck&#39;s batteries  154 . By running the cold storage charging system  104  while the engine  107  is shutdown, the max cooling capacity of the cold storage device  110  may be in effect expanded. 
   In a further mode of operation, with the engine  107  shutdown and the vehicle coupled to shore power, an inverter/charger (not shown) may be used to charge the vehicle batteries, drive the electrically driven compressor  130  to charge the cold storage device  110 , and/or run the heat transfer system  106  to cool the cab  108  of the truck. Thus, the illustrated vehicle cooling system  100  permits the cooling of the cab  108  and/or the thermal charging of the cold storage device  110  while the engine  107  shutdown, a departure from previously developed vehicle cooling systems, which require the engine to be run during cooling of the cab and thermal charging of the cold storage device. 
   Although the above described and illustrated embodiment shows the main cooling system  102  disassociated from the cold storage device  110 , it should be apparent to those skilled in the art that other configurations are within and suitable for use with the present invention. For instance, the main cooling system  102  may be coupled in heat exchange communication with the cold storage device  110  as shown in  FIG. 1 . In this configuration, the main cooling system  102  may be operated to aid in cold charging the cold storage device  110  while the truck engine  107  is running, thereby decreasing the amount of time required to fully charge the cold storage device  110 . 
   While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.

Technology Classification (CPC): 1