Patent Publication Number: US-8985067-B2

Title: Heat pipe assembly in an engine lubrication system

Description:
BACKGROUND/SUMMARY 
     Engines utilize lubrication systems to lubricate moving parts, improve sealing, inhibit corrosion, and cool a number of components in the engine. However, the oil in the lubrication system may overheat causing the oil viscosity to decrease and engine temperature to increase. As a result, engine operation may be degraded. 
     Therefore, engine cooling systems have been developed to cool the lubrication system as well as the cylinder block and/or cylinder head in an engine. Specifically, liquid to liquid oil coolers are utilized in engines to decrease the temperature of the oil as well as the combustion chambers in the engine. In some engines, to remove heat from both the engine and the oil, engine coolant is routed in series through the engine and subsequently through a liquid to liquid heat exchanger in the lubrication system or vice-versa and then routed to a radiator where heat is transferred to the surrounding environment. Parallel arrangements may also be used where engine cooling is directed in parallel through the lubrication system, then to the engine, and then to a radiator. 
     However, the Inventors have recognized several drawbacks with the aforementioned types of cooling systems. When engine coolant is routed in series through the engine and the lubrication system, a desired amount of engine cooling and/or oil cooling may not be achieved. Furthermore, when engine coolant is routed in parallel through the engine and oil, the size of the radiator is increased, thereby increasing the size and cost of the engine. 
     As such, in one approach an engine lubrication system is provided, where the system includes an oil pan housing a lubricant, an oil pump having a pick-up tube including an inlet submerged in the lubricant, and a heat pipe assembly including a fluidly sealed heat pipe coupled to the oil pan adjacent to the inlet of the pick-up tube. 
     In this way, heat may be removed from the oil in the oil pan via a passive heat pipe, with the heat removal pin-pointed to a location where such heat removal is most needed. As a result, the temperature of the oil entering the pick-up tube may be decreased, thereby reducing the likelihood of oil degradation and engine overheating. 
     The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings. 
     It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows a schematic depiction of an engine; 
         FIG. 2  shows a schematic depiction of a vehicle including an engine lubrication system; 
         FIG. 3  shows an illustration drawn to scale of an oil pan and a heat pipe assembly in the engine lubrication system shown in  FIG. 1 ; 
         FIG. 4  shows another view, also to scale, of a portion of the engine lubrication system shown in  FIG. 2 ; and 
         FIG. 5  shows a method for operation of an engine lubrication system. 
     
    
    
     DETAILED DESCRIPTION 
     An engine lubrication system having a heat pipe assembly coupled to an oil pan is described herein. The heat pipe assembly includes a fluidly sealed heat pipe having a higher temperature end positioned in an oil pan enclosure adjacent to an inlet of an oil pump pick-up tube and a lower temperature end positioned vertically above the lower temperature end and external to the oil pan enclosure. In this way, the oil pan may be provided with a separate cooling system that is passive. 
     Referring to  FIG. 1 , internal combustion engine  10 , comprising a plurality of cylinders, one cylinder of which is shown in  FIG. 1 , is controlled by electronic engine controller  12 . Engine  10  includes combustion chamber  30  and cylinder walls  32  with piston  36  positioned therein and connected to a crankshaft  40 . Combustion chamber  30  is shown communicating with intake manifold  44  and exhaust manifold  48  via respective intake valve  52  and exhaust valve  54 . Each intake and exhaust valve may be operated by an intake cam  51  and an exhaust cam  53 . Alternatively or additionally, one or more of the intake and exhaust valves may be operated by an electromechanically controlled valve coil and armature assembly. The position of intake cam  51  may be determined by intake cam sensor  55 . The position of exhaust cam  53  may be determined by exhaust cam sensor  57 . 
     Fuel injector  66  is shown positioned to inject fuel directly into combustion chamber  30 , which is known to those skilled in the art as direct injection. Alternatively or additionally, fuel may be injected to an intake port, which is known to those skilled in the art as port injection. Fuel injector  66  delivers liquid fuel in proportion to the pulse width of signal FPW from controller  12 . Fuel is delivered to fuel injector  66  by a fuel system (not shown) including a fuel tank, fuel pump, and fuel rail (not shown). Fuel injector  66  is supplied operating current from driver  68  which responds to controller  12 . In addition, intake manifold  44  is shown communicating with optional electronic throttle  62  which adjusts a position of throttle plate  64  to control air flow from intake boost chamber  46 . In other examples, the engine  10  may include a turbocharger having a compressor positioned in the intake system and a turbine positioned in the exhaust system. The turbine may be coupled to the compressor via a shaft. A high pressure, dual stage, fuel system may be used to generate higher fuel pressures at injectors  66 . 
     Distributorless ignition system  88  provides an ignition spark to combustion chamber  30  via spark plug  92  in response to controller  12 . Universal Exhaust Gas Oxygen (UEGO) sensor  126  is shown coupled to exhaust manifold  48  upstream of catalytic converter  70 . Alternatively, a two-state exhaust gas oxygen sensor may be substituted for UEGO sensor  126 . 
     Converter  70  can include multiple catalyst bricks, in one example. In another example, multiple emission control devices, each with multiple bricks, can be used. Converter  70  can be a three-way type catalyst in one example. 
     Controller  12  is shown in  FIG. 1  as a conventional microcomputer including: microprocessor unit  102 , input/output ports  104 , read-only memory  106 , random access memory  108 , keep alive memory  110 , and a conventional data bus. Controller  12  is shown receiving various signals from sensors coupled to engine  10 , in addition to those signals previously discussed, including: engine coolant temperature (ECT) from temperature sensor  112  coupled to cooling sleeve  114 ; a position sensor  134  coupled to an accelerator pedal  130  for sensing accelerator position adjusted by foot  132 ; a knock sensor for determining ignition of end gases (not shown); a measurement of engine manifold pressure (MAP) from pressure sensor  122  coupled to intake manifold  44 ; an engine position sensor from a Hall effect sensor  118  sensing crankshaft  40  position; a measurement of air mass entering the engine from sensor  120  (e.g., a hot wire air flow meter); and a measurement of throttle position from sensor  58 . Barometric pressure may also be sensed (sensor not shown) for processing by controller  12 . In a preferred aspect of the present description, engine position sensor  118  produces a predetermined number of equally spaced pulses every revolution of the crankshaft from which engine speed (RPM) can be determined. 
     In some examples, the engine may be coupled to an electric motor/battery system in a hybrid vehicle. The hybrid vehicle may have a parallel configuration, series configuration, or variation or combinations thereof. Further, in some examples, other engine configurations may be employed, for example a diesel engine. 
     During operation, each cylinder within engine  10  typically undergoes a four stroke cycle: the cycle includes the intake stroke, compression stroke, expansion stroke, and exhaust stroke. During the intake stroke, generally, the exhaust valve  54  closes and intake valve  52  opens. Air is introduced into combustion chamber  30  via intake manifold  44 , and piston  36  moves to the bottom of the cylinder so as to increase the volume within combustion chamber  30 . The position at which piston  36  is near the bottom of the cylinder and at the end of its stroke (e.g. when combustion chamber  30  is at its largest volume) is typically referred to by those of skill in the art as bottom dead center (BDC). During the compression stroke, intake valve  52  and exhaust valve  54  are closed. Piston  36  moves toward the cylinder head so as to compress the air within combustion chamber  30 . The point at which piston  36  is at the end of its stroke and closest to the cylinder head (e.g. when combustion chamber  30  is at its smallest volume) is typically referred to by those of skill in the art as top dead center (TDC). In a process hereinafter referred to as injection, fuel is introduced into the combustion chamber. In a process hereinafter referred to as ignition, the injected fuel is ignited by known ignition means such as spark plug  92 , resulting in combustion. During the expansion stroke, the expanding gases push piston  36  back to BDC. Crankshaft  40  converts piston movement into a rotational torque of the rotary shaft. Finally, during the exhaust stroke, the exhaust valve  54  opens to release the combusted air-fuel mixture to exhaust manifold  48  and the piston returns to TDC. Note that the above is described merely as an example, and that intake and exhaust valve opening and/or closing timings may vary, such as to provide positive or negative valve overlap, late intake valve closing, or various other examples. 
       FIG. 2  shows a vehicle  200  including the engine  10 . An engine lubrication system  202  is provided in the vehicle  200 . The engine lubrication system  202  includes an oil pan  204  configured to receive oil or other suitable lubricant from the engine  10  during engine operation. Arrow  205  denotes the transfer of oil from the engine  10  to the oil pan  204 . The oil pan  204  is shown spaced away from the engine  10 , however it will be appreciated that the oil pan  204  may be directly coupled to an oil pan engaging surface on a bottom side of the engine  10 . An oil pump  206  is also included in the engine lubrication system  202 . The oil pump  206  is shown positioned in the oil pan  204 , however in other examples the oil pump  206  may be positioned outside of the oil pan  204 . The oil pump  206  includes a pick-up tube  208  having an inlet  210  positioned in the oil pan  204 . The inlet  210  is submerged in oil  212  or other suitable lubricant. At least one oil conduit, denoted via arrow  214 , may fluidly couple the oil pump  206  to the engine  10 . In this way, oil may be supplied to the engine  10  via the oil pump  206 . The oil conduit  214  is included in the engine lubrication system  202 . The oil conduit  214  is configured to provide oil to components in the engine  10  such as the piston  36  shown in  FIG. 1 , the crankshaft  40  shown in  FIG. 1 , etc. 
     A heat pipe assembly  250  may also be included in the engine lubrication system  202 . The heat pipe assembly  250  may be coupled to the oil pan  204  and is configured to provide passive cooling to the oil enclosed in the oil pan  204 . A more detailed illustration of the heat pipe assembly  250  is shown in  FIGS. 3 and 4  and described in greater detail herein. 
     The heat pipe assembly  250  includes at least one heat pipe  252 . It will be appreciated that heat pipe  252  may be included in a plurality of heat pipes. The heat pipe  252  is configured to transfer heat from the oil to the surrounding environment. In this way, the temperature of the oil in the oil pan  204  may be reduced. As a result, the likelihood of the oil increasing above an undesired temperature during engine operation may be reduced. 
     An expanded view of the heat pipe  252  is shown at  290 . The heat pipe  252  includes a housing  292  enclosing a wicking material  294 . Specifically, the wicking material  294  may be coupled to the housing  292 . The wicking material  294  may extend down the entire length of the heat pipe  252 . A working fluid may be enclosed within the housing  292 . The working fluid in the heat pipe  252  may comprise water, ammonia, ethanol, and/or other suitable fluids. The type of working fluid may be selected based on a desired working temperature range of the heat pipe  252 . Other characteristics of the heat pipe  252  may be altered to adjust the working temperature range such as the thickness of the size and/or geometry of the heat pipe and/or the types of materials used to construct the heat pipe (e.g., housing material and wicking material). The wicking material  294  is configured to draw the working fluid in liquid form from a first end  254  of the heat pipe  252  to a second end  256  of the heat pipe. The first end  254  may be referred to as a lower temperature end and the second end  256  may be referred to as a higher temperature end. The wicking material  294  may define a boundary of a vapor cavity  296 . The vapor cavity  296  may extend from the first end  254  to the second end  256 . Vapor may be generated in the second end  256  of the heat pipe  252  or in the section of the heat pipe  252  submerged in the oil  212  through the transfer of heat from the oil  212  to the working fluid of the heat pipe  252 . Subsequently, the vapor generated in the second end  256  may flow towards the first end  254  of the heat pipe  252  through the vapor cavity  296 . At the first end  254  or in the section of the heat pipe  252  external to the oil pan  204  vapor in the vapor cavity  296  may condense through the transfer of heat from the housing  292  to the external environment. The condensed vapor may then flow through the wicking material  294  back towards to the first end  254 . In this way, heat may be passively transferred from the oil  212  to the external environment via the heat pipe  252 . 
     The housing  292  may comprise copper, nickel-copper alloys, and/or titanium. The wicking material  294  may include mesh screens, axial grooves, sintered metal powders, sintered metal powder grooves, and/or sintered slabs. The heat pipe  252  is coupled to the oil pan  204  via a mounting component  253 . However, other suitable attachment techniques have been contemplated. 
     The heat pipe  252  extends through a wall  270  of the oil pan  204 . The wall  270  may be on a lateral side of the engine  10 . Specifically in some examples, the wall  270  may be on an exhaust side  271  of the engine  10 . The exhaust side of the engine  10  may include an exhaust manifold in fluidic communication with exhaust valves in the engine. In such an example, the other lateral side of the engine  10  may be referred to as an intake side  273  of the engine. It will be appreciated that in other examples, the cylinders in the engine  10  may have a different configuration and therefore the exhaust side  271  and the intake side  273  may be lateral sides. The first end  254  is positioned external to the oil pan  204  and the second end  256  is positioned in the oil pan  204  and submerged in the oil  212 . Specifically, the first end  254  may be submerged in oil when the engine is performing combustion as well as not performing combustion. The first end  254  is positioned vertically above the second end  256 . A vertical axis  280  is provided for reference. However, it will be appreciated that other oil pan orientations have been contemplated. 
     The heat pipe  252  is fluidly sealed. That is to say that the gas and/or liquid enclosed within the heat pipe  252  may not flow into the surrounding environment. A plurality of cooling plates  258  or fins may be coupled a section of the heat pipe external to the oil pan  204 . The cooling plates  258  may be spaced apart to enable air to flow between the plates, thereby increasing the amount of heat transferred from the plates to the surrounding air. In some examples, one or more fans  255 , such as electric fans, configured to direct airflow at the cooling plates  258  may be included in the vehicle  200 . The fans  255  may increase air circulation around and between the plates to increase heat transfer from the plates to the surrounding air. Arrow  257  denotes the flow of air from the fans  255  to the cooling plates  258  The cooling plates  258  are positioned adjacent to and at the first end  254  of the heat pipe  252 , where the plates are contiguous with an exterior wall of the heat pipe at first end  254 . The cooling plates  258  are configured to transfer heat from the heat pipe  252  to the surrounding environment. Additionally, the heat pipe  252  includes a section  259  substantially perpendicular to a section  266  of the heat pipe  252  positioned in the oil pan  204 . Section  259  extends in a vertical direction. However, other heat pipe geometries may be utilized in other examples. 
     The engine lubrication system  202  may also include a windage tray  260  positioned in the oil pan  204  adjacent to and slightly above inlet  210  of the pick-up tube  208 . The second end  256  of the heat pipe  252  is positioned vertically under the windage tray  260 . In one example, the windage tray  260  is contiguous with the pick-up tube  208 . The windage tray  260  is configured to keep the oil  212  near the inlet  210  during vehicle travel. The windage tray  260  is coupled to the oil pan  204  via attachment apparatuses  262  such as bolts, screws, etc. 
     The section  266  of the heat pipe  252  and specifically the second end  256  is positioned vertically below the windage tray  260 . Furthermore, the second end  256  is positioned vertically below the inlet  210  and adjacent to the pick-up tube  208  near the inlet  210 . Additionally, the second end  256  is adjacent to a bottom surface  261  of the oil pan  204 . Thus, no components are positioned between the second end  256  and the bottom surface  261 . Further, in one embodiment, there are no other component between an external wall of heat pipe  252  and the inlet  210 , other than potentially engine oil. The section  266  is shown laterally oriented. A lateral axis  275  has been provided for reference. However, other heat pipe arrangements have been contemplated. When heat pipe  252  is positioned below the windage tray  260 , the heat pipe  252  may be submerged in the oil for a greater amount of time during vehicle travel. As a result, a greater amount of heat may be transferred to the heat pipe  252  from the oil  212 . 
       FIG. 3  shows an illustration of an example engine  10 . The oil pan  204  may be coupled to a cylinder block included in the engine  10 . The cylinder block may be coupled to a cylinder head forming the combustion chamber  30 , shown in  FIG. 1 . The oil pan  204  is positioned vertically below the cylinder block. In this way, gravity may be used to collect oil in the oil pan  204 . The engine  10  includes a front side  300  including a front engine cover  302 . The engine  10  further includes a bottom side  306 , a first lateral side  308 , a second lateral side  310 , and a rear side  312 . The rear side  312  may be coupled to a transmission in the vehicle  200 . 
     An oil filter  314  is also shown. The oil filter  314  is adjacent to the heat pipe assembly  250 , in that an external wall of the filter is positioned adjacent to edges of the cooling plates  258 . However, other locations have been contemplated. The figure also illustrates heat pipe  252 . As previously discussed, the heat pipe assembly  250  may include additional heat pipes  316 . In the depicted example, the heat pipe  252  and the heat pipes  316  are substantially identical in shape, material and size. Thus the heat pipes  316  and heat pipe  252  are substantially parallel to one another. However, in other examples the shape, material, and/or size of the heat pipe may vary between heat pipes. 
     The mounting component  253  is also shown in  FIG. 3 . The mounting component  253  is coupled to an external surface of the oil pan  204 . The mounting component  253  is configured to receive the heat pipe  252  and the heat pipes  316  and fix the relative position of the heat pipes with regard to the oil pan  204 . 
     The cooling plates  258  are also shown in  FIG. 3 . As shown, the cooling plates  258  are locate near the first end  254  of the heat pipe  252  shown in  FIG. 2 . As shown the cooling plates  258  are positioned adjacent to a belt driver component  317 , such as an air conditioning compressor, power steering pump, alternator, etc. The cooling plates  258  transfer heat from the heat pipes to the ambient air surrounding the engine  10 . In this way, heat may be dissipated into the surrounding environment. The cooling plates  258  enable a greater amount of heat to be transferred from the oil to the external environment by increasing surface area. In this way, engine operation may be improved. The cooling plates  258  are horizontally aligned in the depicted example. However, in other examples the cooling plates  258  may have an alternate orientation. A lateral axis and a vertical axis are provided for reference. The cooling plates  258  may comprise a metal such as aluminum, steel, etc. 
       FIG. 4  shows an illustration of the oil pan  204  and the heat pipe assembly  250  shown in  FIG. 3 . The oil pan  204  includes a cylinder block engaging surface  400  configured to attach to the cylinder block shown in  FIG. 2 . The cylinder block engaging surface  400  includes openings  402  configured to receive attachment apparatuses for attaching the oil pan  204  to a cylinder block included in the engine  10  shown in  FIG. 3 . The oil pan includes a bottom side  404 , a front side  406 , a rear side  408 , and two lateral sides  410  defining the boundary of an oil pan enclosure  412 . The front side  406  includes a front engine cover engaging surface  411  configured to attach to the front engine cover  302 , shown in  FIG. 3 . It will be appreciated that the oil pan enclosure  412  may receive oil during operation of the engine  10  shown in  FIGS. 1 and 2 . The windage tray  260  is also shown in  FIG. 4 . Heat pipe  252  and heat pipes  316  are also shown in  FIG. 4 . The heat pipes ( 252  and  316 ) extend through a lateral side wall  414  of the oil pan  204 . 
       FIG. 5  shows a method  500  for operation of an engine lubrication system. Method  500  may be implemented via the engine lubrication system described above with regard to  FIGS. 2-4  or may be implemented via another suitable engine lubrication system. 
     At  502  the method includes transferring heat from oil in an oil pan enclosure to a first end of a heat pipe, the first end of the heat pipe submerged in the oil. The first end of the heat pipe may be positioned vertically below a windage tray in the oil pan enclosure and/or adjacent to an inlet of a pick-up tube of an oil pump. 
     At  504  the method includes flowing vapor through a vapor cavity extending down the length of the heat pipe from the first end to a second end, the second end position vertically above the second end and external to the oil pan enclosure. 
     At  506  the method includes transferring heat from the second end to the surrounding environment and at  508  the method includes flowing liquid through a wicking material traversing the heat pipe from the second end to the first end. 
     This concludes the description. The reading of it by those skilled in the art would bring to mind many alterations and modifications without departing from the spirit and the scope of the description. For example, single cylinder, I2, I3, I4, I5, V6, V8, V10, V12 and V16 engines operating in natural gas, gasoline, diesel, or alternative fuel configurations could use the present description to advantage.