Abstract:
A system ( 30 ) and method for removing heat from a confined space such as from engine compartment or service brake of a motor vehicle where heat is generated by operation of a heat engine ( 12 ) that propels the vehicle or application of a friction brake. The system and method do not use engine or electrical power because natural aspiration is used to remove heated air and Curie Temperature of a ferromagnetic material is used to selectively allow and disallow natural aspiration.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to removal of heat from confined spaces in a motor vehicle, such as from an engine compartment containing an engine that generates heat and from a wheel containing a friction brake that generates heat when operated to brake the wheel. 
       BACKGROUND OF THE INVENTION 
       [0002]    A motor vehicle typically houses a heat engine in an engine compartment, usually forward of a cab or body containing the occupant compartment. Engine compartment temperatures are a matter of concern to vehicle designers because excessively high temperatures can have adverse effects on the performance and durability of various devices and systems. 
         [0003]    Space within an engine compartment is often at a premium for vehicle designers. As an engine compartment becomes increasingly crowded, more components are exposed to engine compartment heat, and the more difficult it becomes to move air that can aid in limiting temperatures through the engine compartment. 
         [0004]    Control of engine operating temperature can to some extent control temperatures in various locations in the engine compartment, but engine operating temperature may itself be affected by various considerations that impose a lower limit on operating temperature. For example, higher operating temperature may be necessary in order to enable compliance with relevant emission control regulations, and while the cooling system of a liquid cooled engine can be sized to allow an engine to have a higher operating temperature, more engine heat will be transferred by convention, conduction, and/or radiation to devices in the engine compartment, to the structure bounding the engine compartment, and to air in the engine compartment because those forms of heat transfer do not occur through the liquid cooling system. 
         [0005]    Furthermore, radiator placement in certain vehicles causes at least some of the heat that is rejected to air flowing through the radiator to pass back through the engine compartment. Higher engine temperatures and reductions in air flow through an engine compartment can create hot spots, or hot zones, potentially affecting devices located in the immediate vicinity. 
         [0006]    Consequently, certain vehicles may benefit from a heat removal system and method devoted to improving heat removal from such hot spots, or hot zones. 
         [0007]    Another area where excessive heat may be generated involves service brakes at a vehicle&#39;s wheels for decelerating the vehicle when a brake pedal is depressed. The brakes are typically friction brakes that when operated, slow the vehicle by frictional force that converts kinetic energy into heat. A drum-type brake has brake shoes that are disposed within a confined space. Because significant heat can be generated in that space, it too may benefit from a heat removal system and method devoted to improving heat removal. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention relates to a system and method for aiding heat removal from confined spaces of a motor vehicle, such as an engine compartment and a drum-type wheel brake. The invention utilizes principles of natural aspiration and of the Curie Temperature (sometimes called Curie Point) of ferromagnetic materials to allow the system and method to function essentially without consumption of energy when the vehicle is operating, thereby rendering the system and method essentially passive in the sense that power does not have to be drawn from either the engine or the electrical system. 
         [0009]    An exemplary system embodying principles of the invention comprises a collection sub-system, a conveyance sub-system, an exit sub-system, and a sensor sub-system. The collection sub-system is organized and arranged to collect heat at a collection location within a generally confined space in a motor vehicle where a device whose operation generates heat is disposed. The conveyance sub-system provides a closed flow path having one end open to the collection sub-system and an opposite end open to the exit sub-system. The sensor sub-system allows and disallows flow from the collection sub-system through the conveyance sub-system to the exit sub-system based on temperature in the confined space. 
         [0010]    The collection sub-system can collect heat by convection, conduction, and or radiation. In general, the collection sub-system comprises a body that is shaped appropriately for the geometry of the confined space at the collection location and that has an entrance through which an interior void is made open to the confined space. The entrance is located at one end of the body. The conveyance sub-system extends from an opposite end, comprising a walled passageway through which flow from the collection sub-system can pass to the exit sub-system when the sensor sub-system allows flow. 
         [0011]    The exit sub-system serves to induce flow from the confined space into and through the collection sub-system and through the conveyance sub-system using the principle of natural aspiration, the same principle used in a naturally aspirated internal combustion engine to draw air into the engine. The exit sub-system communicates an end of the conveyance sub-system that is opposite the collection sub-system with a source of partial vacuum created by operation of the vehicle. When the sensor sub-system is allowing naturally aspirated flow and the vehicle is operating to create partial vacuum at the exit sub-system, a pressure differential is created between the collection sub-system entrance and the exit sub-system that creates naturally aspirated flow through the collection sub-system and the conveyance sub-system to the exit sub-system, drawing heated air out of the confined space to which the collection sub-system is open. 
         [0012]    By making the collection sub-system body approximate a “black body” as that term is understood in physics, the collection sub-system is endowed with the ability to absorb heat and to re-radiate the absorbed heat. Absorbed heat radiated to the interior void of the collection sub-system body will heat the naturally aspirated through-flow entering from the confined space. Heat transfer to the through-flow will also occur by contact of the through-flow with the wall surface of the interior void. The radiated and transferred heat are conveyed with heated air from the confined space through the conveyance sub-system to the exit system and from there to the ambient atmosphere. Hence, while air is the medium that is used to remove heat from the confined space, the collection system, by virtue of being disposed within the confined space and suitably constructed, can collect heat not only by collecting heated air from the confined space, but also by conductive and radiated heat transfer from the wall of the collection sub-system body. 
         [0013]    In allowing and disallowing flow from the collection sub-system through the conveyance sub-system to the exit sub-system, the sensor sub-system utilizes the Curie Temperature of a ferromagnetic material, enabling heat removal to be controlled without drawing energy from the engine or the electrical system. The use of natural aspiration for heat removal flow also avoids power draw from the engine or electrical system. 
         [0014]    One generic aspect of the invention relates to a self-propelled vehicle comprising wheels on which the vehicle travels, at least some of which wheels are driven to self-propel the vehicle when the vehicle is being operated and a heat removal system for removing heat from a confined space containing a device that generates heat when the vehicle is being operated. 
         [0015]    The heat removal system comprises a collection sub-system for collecting heat in the confined space, a conveyance sub-system for conveying heat from the collection sub-system to an exit sub-system, and a sensor sub-system for allowing and disallowing conveyance of heat collected by the collection sub-system through the conveyance sub-system to the exit sub-system based on temperature in the confined space. 
         [0016]    The exit sub-system is open to ambient atmosphere and is constructed and arranged to apply to the conveyance sub-system a partial vacuum that is created as a result of the vehicle being operated. 
         [0017]    When the sensor sub-system allows conveyance of heat, the partial vacuum creates natural aspiration of air carrying heat from the collection sub-system through the conveyance sub-system and the exit sub-system to ambient atmosphere thereby removing heat from the confined space to ambient atmosphere. 
         [0018]    According to another generic aspect, the invention relates to a method for removing heat from a confined space in a self-propelled vehicle, which space contains a device that generates heat when the vehicle is being operated. 
         [0019]    The method comprises: collecting heat in the confined space; on the basis of temperature in the confined space, selectively allowing and disallowing conveyance of collected heat to an exit that is open to ambient atmosphere; and operating the vehicle to create a partial vacuum at the exit that causes conveyance of heat by natural aspiration of air carrying heat from the confined space to the exit when conveyance of heat is allowed. 
         [0020]    The invention also relates to a system for selectively removing heat from an engine compartment of a self-propelled vehicle containing a heat engine that operates to propel the vehicle when the vehicle is being operated and in the process generates heat in the engine compartment. 
         [0021]    The system comprises a collection sub-system disposed in the engine compartment, an exit sub-system leading to ambient atmosphere, a conveyance sub-system from the collection sub-system to the exit sub-system, and a sensor sub-system for allowing and disallowing the system to remove heat. 
         [0022]    The exit sub-system is open to ambient atmosphere and is constructed and arranged to apply to the conveyance sub-system a partial vacuum that is created as a result of the vehicle being operated. 
         [0023]    When the sensor sub-system allows removal of heat, the partial vacuum creates natural aspiration of air carrying heat from the engine compartment through the collection, conveyance, and exit sub-systems to ambient atmosphere, and when the sensor sub-system disallows removal of heat, natural aspiration through the collection, conveyance, and exit sub-systems to ambient atmosphere is stopped. 
         [0024]    The foregoing, along with further features and advantages of the invention, will be seen in the following disclosure of a presently preferred embodiment of the invention depicting the best mode contemplated at this time for carrying out the invention. This specification includes drawings, now briefly described as follows. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  shows a representative motor vehicle to which principles of the invention are applied. 
           [0026]      FIG. 2  is schematic diagram of a first embodiment illustrating principles of the invention. 
           [0027]      FIG. 2A  is a longitudinal cross section view through an example of a device that incorporates certain functions performed in accordance with principles of the invention. 
           [0028]      FIG. 3  is schematic diagram of a second embodiment. 
           [0029]      FIG. 4  is a diagram showing application of certain inventive principles to a portion of the vehicle shown in  FIG. 1 . 
           [0030]      FIG. 5  is a diagram similar to  FIG. 4  showing a different application. 
           [0031]      FIG. 6  is a diagram showing application of certain inventive principles to another portion of the vehicle shown in  FIG. 1 . 
           [0032]      FIG. 7  is a diagram similar to  FIG. 6  showing a different application. 
           [0033]      FIG. 8  is a generic representation of a preferred form for one sub-system of the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0034]      FIG. 1  shows a truck  10  having an internal combustion engine  12 , a diesel engine for example, and a drivetrain  14  that couples engine  12  to driven rear wheels  16 R for propelling the truck. Engine  12  is housed within an engine compartment  18  that is forward of a cab  20 . 
         [0035]    Engine  12  is liquid-cooled, with the engine cooling system comprising a radiator  22  disposed generally vertical at the front of engine compartment  18  behind a grille opening. A fan  24  behind radiator  22  can draw air through radiator  22  to aid in cooling engine coolant flowing through radiator  22  when needed. 
         [0036]    Engine  12  also has an exhaust system  26  for conveying exhaust gases generated by combustion of fuel in cylinders of engine  12  from the engine to the ambient atmosphere surrounding truck  10 . 
         [0037]    For reasons that were mentioned earlier, engine heat may create temperatures within engine compartment  18  that are higher than desired. Consequently, a heat removal system that can remove some engine compartment heat may be helpful in avoiding undesirably high engine compartment temperatures. 
         [0038]    A first embodiment of inventive heat removal system  30  is shown in  FIG. 2  to comprise a collection sub-system  32  for collecting heat in engine compartment  18 , a conveyance sub-system  34  for conveying heat from collection sub-system  32  to an exhaust manifold of exhaust system  26 , and a sensor sub-system  36  for allowing and disallowing conveyance of heat collected by collection sub-system  32  through conveyance sub-system  34  to exhaust system  26  based on temperature in engine compartment  18 . 
         [0039]    Exhaust system  26  serves as an exit sub-system that is open to ambient atmosphere. When engine  12  is running, the exhaust flow applies a partial vacuum to the outlet of conveyance sub-system  34  by an effect similar to that performed by an ejector or eductor. When sensor sub-system  36  allows conveyance of engine compartment heat by opening collection sub-system  32  to conveyance sub-system  34 , the partial vacuum creates natural aspiration of air carrying engine compartment heat from collection sub-system  32  through conveyance sub-system  34  and the exit sub-system to ambient atmosphere thereby removing heat from the engine compartment to ambient atmosphere. The use of natural aspiration for heat removal avoids power draw from engine  12  or the electrical system of truck  10 . 
         [0040]    For opening and closing collection sub-system  32  to conveyance sub-system  34 , sensor sub-system  36  utilizes the Curie Temperature of a ferromagnetic material, enabling heat removal to be controlled without drawing energy from the engine or the electrical system. 
         [0041]    A ferromagnetic part senses engine compartment temperature. A magnet and the ferromagnetic part are organized and arranged such that when the temperature of the ferromagnetic part does not exceed the Curie Temperature, the magnetic force exerted by the magnet on the ferromagnetic part relatively positions them to close collection sub-system  32  to conveyance system  34 , disallowing the natural aspiration of heated air out of the engine compartment. When the temperature of the ferromagnetic part equals or exceeds the Curie Temperature, the loss of ferromagnetism in the part allows the part and magnet to assume relative positions that open collection sub-system  32  to conveyance system  34 , disallowing natural aspiration. 
         [0042]    The operating position of an obturator for allowing and disallowing natural aspiration is established by the relative positions of the ferromagnetic part and the magnet. When the part and magnet assume relative positions that allow natural aspiration, the obturator opens collection sub-system  32  to conveyance system  34 . When the part and magnet assume relative positions that disallow natural aspiration, the obturator closes collection sub-system  32  to conveyance system  34 . 
         [0043]      FIG. 2A  shows an example where the obturator, a sphere  31 , is unseated from a magnet  33  above a certain temperature to allow flow indicated by arrow  35 . Attribution for this example is given to Invention Machine Corporation. 
         [0044]    Collection sub-system  32  is embodied by way of example as a walled body having an interior void and an entrance to that void through which the void is open to air in engine compartment  18 . By making the walled body approximate a “black body” as that term is understood in physics, it becomes an approximate ideal absorber of radiant heat. This allows the body wall to collect heat radiated from engine  12  and to re-radiate the heat to the interior void. Heat is also transferred by conduction to air that is in contact with the interior wall surface of the void. 
         [0045]      FIG. 5  shows a “control valve” (understood to comprise the magnet, the ferromagnetic part, and the obturator), as sensor sub-system  36 . The collection sub-system  32  comprises a walled black body having an entrance at an end opposite the end where the “control valve” is associated. The conveyance sub-system tees into exhaust system  26  to provide the exit to ambient atmosphere for both engine exhaust and removed engine compartment heat. 
         [0046]      FIG. 3  shows principles of the invention being applied to removal of heat from the service brakes of truck  10 . Both rear wheels  16 R and front wheels  16 F have friction brake mechanisms that when operated by a brake pedal inside cab  20  to brake the truck generate heat. In the case of a drum-type brake the heat is generated within a confined space. Placement of a sensor sub-system  36  and a collection sub-system  32  in association with a friction brake can remove some of the brake heat, with the removed heat being removed to atmosphere as in  FIG. 2 . 
         [0047]      FIGS. 6 and 7  show a sensor sub-system  36  and a collection sub-system  32  in association with a friction brake. The sensor sub-system is understood to comprise the magnet, the ferromagnetic part, and the obturator, collectively named “control valve” in both Figures. The collection sub-system comprises a walled black body having an entrance at an end opposite the end where the sensor sub-system is associated. 
         [0048]    Although not specifically shown by  FIGS. 6 and 7 , a preferred geometry for the body of collection sub-system has a narrowing taper in the direction of natural aspiration flow, as shown generically by  FIG. 8 . 
         [0049]    The exit sub-system of  FIG. 7  is the same as in  FIGS. 2 and 3 . The exit sub-system of  FIG. 6  is somewhat different. The outlet of the exit system is open to ambient atmosphere and is arranged in relation the direction of air flow along the truck when the truck is moving such that partial vacuum is created at the outlet. 
         [0050]      FIG. 4  shows an embodiment like  FIG. 5  insofar as sub-systems  32 ,  34 , and  36  are concerned. The exit system of  FIG. 5  is like the one in  FIG. 7 . 
         [0051]    With the ability of the inventive system to selectively allow and disallow removal of heat from an engine compartment, it may be possible to incorporate the system into the design of an engine compartment in a way that makes obstruction of the radiator in winter, such as by covering, unnecessary. 
         [0052]    While a presently preferred embodiment of the invention has been illustrated and described, it should be appreciated that principles of the invention apply to all embodiments falling within the scope of the following claims.