Abstract:
A rotor for an electrical generator is disclosed, including a rotor body having a circular portion and a cylindrical portion coaxial with the circular portion. A generally cylindrical recess is defined by the cylindrical portion and the first side of the circular portion for receiving a stator. At least one first wall is at least partially spaced apart from the first side of the circular portion, defining at least one chamber therebetween. The chamber has an inlet. An aperture in the at least one first wall defines an outlet of the at least one chamber. At least one second wall extends outwardly from the first side of the circular portion. The at least one second wall has an end portion adjacent to the inlet of the at least one chamber. An internal combustion engine with an electrical generator and a method of cooling an electrical generator are also disclosed.

Description:
CROSS-REFERENCE 
       [0001]    The present application is a divisional of U.S. patent application Ser. No. 11/849,014, filed Aug. 31, 2007, the entirety of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a device and method for cooling for an electrical generator of an engine. 
       BACKGROUND 
       [0003]    Many internal combustion engines include an electrical generator driven by the engine to generate electrical power. The power generated by the generator can be used to power some engine systems (for example, the ignition and fuel injection systems), and some systems external to the engine (for example, lights and display gauges of a vehicle powered by the engine). 
         [0004]    A typical generator for an internal combustion engine has a rotor portion and a stator portion. The rotor includes a plurality of permanent magnets which generate a magnetic field and the stator includes one or more wire coils. The rotor is powered by the engine and is thereby caused to spin with respect to the stator. The relative motion of the magnets and the wire coils induces an electric current in the wire coils. The current can then be transmitted to the various electrical systems that are powered by the generator. 
         [0005]    The power output of the generator is typically determined by the internal structure of the generator, such as the arrangement of the magnets and coils, as well as by the rotational speed of the rotor. Thus, although the power consumption of the various electrical systems varies over time, the amount of power produced by the generator at a particular time cannot be conveniently adjusted to correspond to the varying levels of power consumption. Thus, the generator is typically designed to always produce sufficient electrical power to meet the needs of the electrical systems under all operating conditions, to ensure their continuous operation. When the actual power consumption of the electrical systems is less than the power produced by the generator, as is usually the case, the excess power is dissipated by the generator coils, in the form of heat. Thus, cooling must be provided for the generator coils. 
         [0006]    One method of cooling the generator coils is to spray them with a coolant, such as oil from the lubrication system of the engine. When the generator coils are in contact with the coolant, they will transfer a portion of their heat to the coolant. The coolant is subsequently transported to a heat exchanger to dissipate the heat into the environment. While this method is effective in cooling the generator coils, it suffers from a number of drawbacks. Because the rotor and stator are located in a confined space, and because the rotor is spinning, it is difficult to provide sufficient coolant to adequately cool the generator coils. In addition, particularly at low speeds, the rotation of the rotor does not adequately distribute the coolant within the generator to cool every part of the generator coils. 
         [0007]    Therefore, there is a need for a way of cooling an electrical generator. 
       SUMMARY 
       [0008]    It is an object of the present invention to ameliorate at least some of the inconveniences present in the prior art. 
         [0009]    It is also an object of the present invention to cool a stator of an electrical generator by using a flow of coolant fluid between the rotor and the stator of an electrical generator. 
         [0010]    In one aspect, the invention provides a rotor for an electrical generator, comprising a rotor body. The rotor body has a circular portion having a first side and a second side opposite the first side, and a cylindrical portion coaxial with the circular portion. The cylindrical portion extends from the first side of the circular portion. The circular portion and the cylindrical portion define a longitudinal axis of the rotor body. A plurality of permanent magnets are disposed on the cylindrical portion. A generally cylindrical recess is defined by the cylindrical portion and the first side of the circular portion for receiving a stator. At least one first wall is at least partially spaced apart from the first side of the circular portion. The at least one first wall and the first side of the cylindrical portion define at least in part at least one chamber therebetween. The at least one chamber has an inlet. An aperture in the at least one first wall defines an outlet of the at least one chamber. At least one second wall extends outwardly from the first side of the circular portion. The at least one second wall has an end portion adjacent to the inlet of the at least one chamber. 
         [0011]    In a further aspect, the at least one chamber is a plurality of chambers. The at least one second wall is a plurality of second walls. 
         [0012]    In a further aspect, the at least one chamber is three chambers. 
         [0013]    In a further aspect, the end portion of each of the plurality of second walls is a first end portion adjacent to a first chamber of the plurality of chambers. Each of the plurality of second walls has a second end portion adjacent to a second chamber of the plurality of chambers. 
         [0014]    In a further aspect, the inlet of the at least one chamber faces toward the longitudinal axis. 
         [0015]    In a further aspect, at least one third wall is adjacent to the at least one second wall. The at least one third wall has a portion extending generally parallel to, and spaced apart from, the first side of the circular portion. 
         [0016]    In an additional aspect, the invention provides an internal combustion engine having a crankcase. A crankshaft is disposed in the crankcase. At least one cylinder is connected to the crankcase. At least one piston is disposed in the at least one cylinder and operatively connected to the crankshaft. A generator is operatively coupled to the crankshaft. The generator comprises a stator fixedly mounted to the internal combustion engine. The stator comprises at least one wire coil. The generator comprises a rotor powered by the crankshaft. The rotor comprises a rotor body. The rotor body has a circular portion and a cylindrical portion. The circular portion has a first side and a second side opposite the first side. The cylindrical portion extends from the first side of the circular portion. The circular portion and the cylindrical portion define a longitudinal axis of the rotor body. A plurality of permanent magnets are disposed on the cylindrical portion. A generally cylindrical recess is defined by the cylindrical portion and the first side of the circular portion for receiving the stator. At least one first wall is at least partially spaced apart from the first side of the circular portion. The at least one first wall and the first side of the cylindrical portion define at least in part a chamber therebetween. The chamber having an inlet. An aperture in the at least one first wall defines an outlet of the chamber. At least one second wall extends outwardly from the first side of the circular portion. The at least one second wall has an end portion adjacent to the inlet of the at least one chamber. 
         [0017]    In a further aspect, the at least one chamber is a plurality of chambers, and wherein the at least one second wall is a plurality of second walls. 
         [0018]    In a further aspect, the at least one chamber is three chambers. 
         [0019]    In a further aspect, the end portion of each of the plurality of second walls is a first end portion adjacent to a first chamber of the plurality of chambers. Each of the plurality of second walls has a second end portion adjacent to a second chamber of the plurality of chambers. 
         [0020]    In a further aspect, the inlet of the at least one chamber faces toward the longitudinal axis. 
         [0021]    In a further aspect, at least one third wall is adjacent to the at least one second wall. The at least one third wall has a portion extending generally parallel to, and spaced apart from, the first side of the circular portion. 
         [0022]    In a further aspect, the stator further comprises a passage extending therethrough. The passage is generally parallel to, and spaced apart from, the longitudinal axis of the rotor body. 
         [0023]    For the purposes of this application, the terms “radial”, “axial” and “tangential” are defined with respect to the axis of rotation of the rotor. Thus, “radial” refers to a direction toward or away from the axis of rotation, “axial” refers to a direction along or parallel to the axis of rotation, and “tangential” refers to a direction perpendicular to the radial direction but not along the axial direction. 
         [0024]    Embodiments of the present invention each have at least one of the above-mentioned objects and/or aspects, but do not necessarily have all of them. It should be understood that some aspects of the present invention that have resulted from attempting to attain the above-mentioned objects may not satisfy these objects and/or may satisfy other objects not specifically recited herein. 
         [0025]    Additional and/or alternative features, aspects, and advantages of embodiments of the present invention will become apparent from the following description, the accompanying drawings, and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    For a better understanding of the present invention, as well as other aspects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where: 
           [0027]      FIG. 1  is a cross-section of an internal combustion engine taken vertically through a longitudinal centerline thereof; 
           [0028]      FIG. 2  is a cross-sectional view of an electrical generator and adjoining engine components according to an embodiment of the present invention; 
           [0029]      FIG. 3  is a perspective view of a catch plate according to a first embodiment of the present invention; 
           [0030]      FIG. 4  is an elevation view of one side of a catch plate according to a second embodiment of the present invention; 
           [0031]      FIG. 5  is a perspective view of the second side of the catch plate of  FIG. 4 ; 
           [0032]      FIG. 6  is a perspective view of a catch plate according to a third embodiment of the present invention; 
           [0033]      FIG. 7  is a perspective view of a catch plate according to a fourth embodiment of the present invention; 
           [0034]      FIG. 8  is an elevation view of a catch plate according to a fifth embodiment of the present invention; 
           [0035]      FIG. 9  is an elevation view of a catch plate according to a sixth embodiment of the present invention; 
           [0036]      FIG. 10  is a perspective view of the catch plate of  FIG. 3 , showing an exemplary flow path of coolant; and 
           [0037]      FIG. 11  is a schematic cross-sectional view of the electrical generator of  FIG. 2 , showing an exemplary flow path of coolant. 
       
    
    
     DETAILED DESCRIPTION 
       [0038]    An electrical generator in accordance with embodiments of the present invention will be described with respect to its use in an internal combustion engine. It should be understood that an internal combustion engine incorporating an electrical generator according to the present invention is suitable for use in many different types of vehicles, including snowmobiles, personal watercraft, ATVs, motorcycles and three-wheeled motorized vehicles. It is contemplated that the present invention could also be used in an alternator. 
         [0039]    Referring to  FIGS. 1 and 2 , a four-stroke internal combustion engine  10  has three cylinders  12  contained in a cylinder bank  14 . Each cylinder  12  has a piston  16  associated therewith. Each piston  16  can reciprocate within its respective cylinder  12  to change the volume of a combustion chamber  18  associated with the cylinder. Each piston  16  is coupled via a control rod  20  to a crankshaft  22  journaled in a crankcase  24 , such that combustion of fuel (not shown) in the combustion chambers  18  forces the pistons  16  downward to cause rotation of the crankshaft  22 . A number of valves  28  are provided for each cylinder  12 , some of which allow fuel to enter the combustion chambers  18  for combustion therein, and others of which allow exhaust gases (not shown) to exit the combustion chambers  18  after combustion has occurred. The opening and closing of the valves  28  is controlled by a camshaft  30 , which is driven by the crankshaft  22  via a chain  32 . Alternative valve control systems are also contemplated, such as electronically actuated valves. It should be understood that the present invention is not limited to the particular engine  10  described, and can be practiced with a variety of other engine types, including engines with more or fewer cylinders, V-type engines with cylinders arranged in two cylinder banks, two-stroke engines and other variations that will be apparent to a person skilled in the art. 
         [0040]    The crankshaft  22  is coupled to a rotor  36  of a generator  34 . The rotor  36  has a rotor body  37  having a number of permanent magnets  40  (best seen in FIG.  2 ) mounted thereon, such that rotation of the crankshaft  22  causes the rotor  36  to rotate about the axis  42 . Referring to  FIG. 2 , the rotor body  37  is composed of a circular portion  46  that is attached at its center to the crankshaft  22 , and a cylindrical portion  48  on which the permanent magnets  40  are mounted. The circular portion  46  and the cylindrical portion  48  together define a cylindrical recess  49  for receiving the stator  38 , and also define a longitudinal axis coaxial with the axis of rotation  42 . When the engine  10  is in operation, the rotation of the crankshaft  22  causes the rotor  36  to rotate about the axis  42  around the stator  38 . 
         [0041]    The stator  38 , comprising one or more coils of wire  44  (best seen in  FIG. 2 ), is fixed in position inside the cylindrical recess  49 , such that the rotation of the permanent magnets  40  induces an electrical current in the coils of wire  44 . The electrical current is conducted from the generator  34  to provide power to one or more systems or devices (not shown) that require electrical power, such as the electrical systems of the engine  10  and the electrical systems of the vehicle (not shown) in which the engine  10  is used. For example, the engine  10  may have one or more of an electrical ignition system, an electrical fuel injection system or an electronic valve actuation system. The engine  10  may be used in a vehicle (not shown) having lights, display gauges or a rechargeable battery. It is contemplated that not all of these systems will be present in a particular engine  10  or vehicle, or that not all of these systems will require electrical power in a particular engine  10  or vehicle. For example, the engine  10  may have a carburetor instead of an electronic fuel injection system, or a fuel injection system driven mechanically by the engine  10 . It is further contemplated that the generator  34  may power any other electrical system that forms part of the engine  10  or the vehicle in which the engine is used, as needed. It is further contemplated that the generator  34  could power any other system or device that requires electricity. 
         [0042]    While the engine  10  is in operation, excess power is generated by the generator  34 , and this excess power is dissipated as heat in the coils  44 . In order to reduce the heat build-up in the coils  44 , the rotor body  37  includes a catch plate  54  to assist in cooling the stator  38 , as will be described in further detail below. Referring to  FIG. 2 , the catch plate  54  is mounted to the circular portion  46  of the rotor body  37  within the cylindrical recess  49 . It is contemplated that the catch plate  54  can alternatively be mounted to the circular portion  46  by any other suitable means, such as welding. It is further contemplated that the catch plate  54  may be constructed integrally with the rotor body  37  in a one-piece construction. 
         [0043]    Referring to  FIG. 3 , the catch plate  54  will now be described according to a first embodiment of the present invention. The catch plate  54  is made of stamped sheet metal, and has a planar attachment flange  56  with a plurality of holes  58  formed therein, to allow the catch plate  54  to be mounted to the inside of the circular portion  46  of the rotor body  37  using bolts  57 , one of which can be seen in  FIG. 2 . As can be seen in  FIGS. 2 and 3 , the wall  60  extends away from the plane of the attachment flange  56 , and thus extends away from the circular portion  46  of the rotor body  37  when the catch plate  54  is mounted on the rotor body  37 . The wall  62  extends radially inwardly from the edge of the wall  60 , and generally parallel to the circular portion  46  of the rotor body  37  when the catch plate  54  is mounted to the rotor body  37 . Three walls  70  extend radially outwardly from the end portions  74  of the walls  60 , and cooperate with the walls  64  and the circular portion  46  of the rotor body  37  to define three chambers  66 . Each chamber has an inlet  67  adjacent to the end portions  74  and facing toward the axis  42 . It is contemplated that the catch plate  54  may have more or fewer than three chambers  66  and still be within the scope of the invention. An aperture  68  is provided in each wall  64  to serve as an outlet for the chamber  66 . It is contemplated that more than one aperture  68  may be provided in each wall  64 . The function of the catch plate  54  to deliver coolant to the stator  38  will be described in further detail below. 
         [0044]    Referring to  FIGS. 4 and 5 , the catch plate  154  will now be described according to a second embodiment of the present invention. The catch plate  154  is made of welded or cast metal, or moulded plastic, and has a plurality of planar attachment flanges  156 . Each attachment flange  156  has a hole  158  formed therein, to allow the catch plate  154  to be mounted to the inside of the circular portion  46  of the rotor body  37  using bolts  57 , one of which can be seen in  FIG. 2 . As can be seen in  FIGS. 4 and 5 , the wall  160  extends away from the plane of the attachment flanges  156 , and thus also extends away from the circular portion  46  of the rotor body  37  when the catch plate  154  is mounted on the rotor body  37 . The walls  162  and  170  extend radially inwardly from the edge of the wall  160  to define a channel  172 . Three walls  174  extend radially outwardly from the end portions  176  of the walls  160 , and cooperate with the walls  164 ,  170  to define three chambers  166 . Each chamber  166  has an inlet  167  adjacent to the end portions  176  and facing toward the axis  42 . It is contemplated that the catch plate  154  may have more or fewer than three chambers  166  and still be within the scope of the invention. An aperture  168  is provided in each wall  164  to serve as an outlet for the chamber  166 . It is contemplated that more than one aperture  168  may be provided in each wall  164 . The function of the catch plate  154  will be described in further detail below. 
         [0045]    Referring to  FIG. 6 , the catch plate  254  will now be described according to a third embodiment of the present invention. The catch plate  254  is made of stamped sheet metal, and has a planar attachment flange  256  with a plurality of holes  258  formed therein, to allow the catch plate  254  to be bolted to the inside of the circular portion  46  of the rotor body  37  as can be seen in  FIG. 2 . As can be seen in  FIG. 6 , the wall  260  extends away from the plane of the attachment flange  256 , and also extends away from the circular portion  46  of the rotor body  37  when the catch plate  254  is mounted on the rotor body  37 . Three walls  270  extend radially outwardly from the end portions  274  of the walls  260 , and cooperate with the walls  264  and the circular portion  46  of the rotor body  37  to define three chambers  266 . Each chamber  266  has an inlet  267  adjacent to the end portions  274  and facing toward the axis  42 . It is contemplated that the catch plate  254  may have more or fewer than three chambers  266  and still be within the scope of the invention. An aperture  268  is provided in each wall  264  to serve as an outlet for the chamber  266 . It is contemplated that more than one aperture  268  may be provided in each wall  264 . The function of the catch plate  254  will be described in further detail below. 
         [0046]    Referring to  FIG. 7 , the catch plate  354  will now be described according to a fourth embodiment of the present invention. The catch plate  354  is made of stamped sheet metal, and has a planar attachment flange  356  with a plurality of holes  358  formed therein, to allow the catch plate  354  to be mounted to the inside of the circular portion  46  of the rotor body  37  using bolts  57 , one of which can be seen in  FIG. 2 . As can be seen in  FIG. 7 , the wall  360  extends away from the plane of the attachment flange  356 , and thus also extends away from the circular portion  46  of the rotor body  37  when the catch plate  354  is mounted on the rotor body  37 . In this embodiment, the wall  360  is composed of a number of straight portions, as opposed to the arcuate walls shown in the embodiments of  FIGS. 3-6 . Three walls  370  extend radially outwardly from the end portions  374  of the walls  360 , and cooperate with the walls  364  and the circular portion  46  of the rotor body  37  to define three chambers  366 . Each chamber  366  has an inlet  367  adjacent to the end portions  374  and facing toward the axis  42 . It is contemplated that the catch plate  354  may have more or fewer than three chambers  366  and still be within the scope of the invention. An aperture  368  is provided in each wall  364  to serve as an outlet for the chamber  366 . It is contemplated that more than one aperture  368  may be provided in each wall  364 . The function of the catch plate  354  will be described in further detail below. 
         [0047]    Referring to  FIG. 8 , the catch plate  454  will now be described according to a fifth embodiment of the present invention. The catch plate  454  is made of stamped sheet metal, and has a planar attachment flange  456  with a plurality of holes  458  formed therein, to allow the catch plate  454  to be mounted to the inside of the circular portion  46  of the rotor body  37  using bolts  57 , one of which can be seen in  FIG. 2 . The catch plate  454  is mounted on the rotor body  37  such that the geometric center  472  of the catch plate  454  lies on the axis  42 . As can be seen in  FIG. 8 , the wall  460  extends away from the plane of the attachment flange  456 , and thus also extends away from the circular portion  46  of the rotor body  37  when the catch plate  454  is mounted on the rotor body  37 . Three walls  476  extend radially outwardly from the end portions  470  and  474  of the walls  460 , and cooperate with the walls  464  and the circular portion  46  of the rotor body  37  to define three chambers  466 . In the present embodiment, the walls  460  between the chambers  466  each have a first end portion  470  at a first distance L 1  from the center  472  and a second end portion  474  at a second distance L 2  from the center  472 . The distance L 2  is greater than the distance L 1 . The walls  460  gradually increase in distance from the center  472  between the first end  470  and the second end  474 . This particular shape assists in guiding coolant along the portion of the wall  460  in the direction of the second end portion  474  and into the chambers  466  via the inlets  476  when the coolant is subjected to centrifugal force when the catch plate  454  spins in the clockwise direction, as will be described in further detail below. The inlets  478  are adjacent to the first ends  470  and second ends  474  of the walls  460  and face toward the axis  42 . An aperture  468  is provided in each wall  464  to serve as an outlet for the chamber  466 . It is contemplated that more than one aperture  468  may be provided in each wall  464 . The function of the catch plate  454  will be described in further detail below. 
         [0048]    Referring to  FIG. 9 , the catch plate  554  will now be described according to a sixth embodiment of the present invention. The catch plate  554  is made of stamped sheet metal, and has a planar attachment flange  556  with a plurality of holes  558  formed therein, to allow the catch plate  554  to be mounted to the inside of the circular portion  46  of the rotor body  37  using bolts  57 , one of which can be seen in  FIG. 2 . As can be seen in  FIG. 9 , the wall  560  extends away from the plane of the attachment flange  56 , and also extends away from the circular portion  46  of the rotor body  37  when the catch plate  554  is mounted on the rotor body  37 . Four walls  576  cooperate with the walls  564  and the circular portion  46  of the rotor body  37  to define four chambers  566 . In the present embodiment, the inlets  578  of the chambers  566  are oriented generally tangentially and not oriented toward the geometric center  572  of the catch plate  554 . An aperture  568  is provided in each wall  564 . In the present embodiment, the portions of the wall  560  between the chambers  566  have a first end  570  at a first distance L 3  from the center  572  and a second end  574  at a second distance L 4  from the center  572 . The distance L 4  is greater than the distance L 3 . The walls  560  gradually increase in distance from the center  572  between the first end portion  570  and the second end portion  574 . This particular shape assists in guiding coolant along the portion of the wall  560  from the first end  570  toward the second end  574  when the coolant is subjected to centrifugal force, as will be described in further detail below. This facilitates the collection of coolant in the chamber  566  adjacent the second end portion  574  when the catch plate  554  spins in the counterclockwise direction, as will be described in further detail below. An aperture  568  is provided in each wall  564  to serve as an outlet for the chamber  566 . It is contemplated that more than one aperture  568  may be provided in each wall  564 . The function of the catch plate  554  will be described in further detail below. 
         [0049]    The operation of the catch plate  54  to distribute coolant  600  to the stator  38  will now be described, with reference to  FIGS. 10 and 11 . It should be understood that the catch plates  154 ,  254 ,  354 ,  454  and  554  all operate in a similar manner, and the operation of these embodiments will not be discussed in detail. 
         [0050]    Referring to  FIG. 11 , coolant  600  is delivered to the generator  34  via the passageway  50 . The coolant  600  may be supplied to the passageway  50  from the cooling or lubrication system of the engine  10 . After the coolant  600  exits the passageway  50 , it passes through the stator via the passageway  52 . Upon exiting the passageway  52 , the coolant  600  reaches the inside face of the circular portion  46  of the rotor body  37 , at a point  602  radially outward of the axis of rotation  42  and radially inward of the wall  60 . 
         [0051]    Referring now to  FIGS. 10 and 11 , due to the rotational motion of the rotor  36  about the axis  42 , the coolant  600  is subjected to a centrifugal force once it contacts the rotor  36  at the point  602 . The centrifugal force urges the coolant  600  generally radially outwardly from the geometric center  72  of the catch plate  54 , which is located on the axis  42 . Referring to  FIG. 10 , the coolant  600  flows from the point  602  to a point  604  situated along the walls  60  and  62 . Because the chamber  66  is disposed radially outwardly of the wall  60 , the centrifugal force, in combination with the rotational motion of the rotor  36 , cause the coolant  600  to flow along the walls  60  and  62 , and further radially outwardly to collect in the chamber  66 . In the case of a catch plate  54  having more than one chamber  66 , the coolant  600  will flow into all of the chambers  66  as the catch plate  54  rotates. Referring to  FIG. 11 , the coolant  600  may instead flow radially outwardly from the point  602  directly into the chamber  66 , without first flowing along the walls  60  and  62 , if the rotational position of the catch plate  54  is such that the axis  42 , the point  602  and the chamber  66  are aligned. 
         [0052]    Referring to  FIGS. 10 and 11 , the functioning of the chambers  66  will now be described. Each of the chambers  66  functions in the same way, and only one chamber  66  will be described in detail. As coolant  600  continues to be delivered to the rotor  36  via the passageways  50  and  52 , more coolant  600  enters the chamber  66  via the inlet  67 . Referring to  FIG. 11 , this causes the coolant  600  already inside the chamber  66  to be expelled from the chamber  66  via the aperture  68  in the wall  64 , in a spray  606  directed generally toward the stator  38 . As the rotor  36  continues to rotate about the axis  42 , the spray  606  distributes the coolant  600  evenly over the surface of the stator  38 . 
         [0053]    When the coolant  600  is in contact with the stator  38 , the coolant  600  absorbs heat from the stator  38 , thereby cooling the stator  38 . The coolant  600  may then flow by the force of gravity to the bottom of the chamber in which the generator  34  is located, where the coolant  600  can be collected and circulated through a heat exchanger (not shown) to dissipate heat into the environment. The coolant  600  may then be returned to the passageway  50  to further cool the stator  38 . 
         [0054]    In one embodiment, the coolant  600  is oil. In this embodiment, the passageway  50  is supplied with oil  600  by the oil pump (not shown) of the engine  10 . When the heated oil  600  is collected from the generator  34 , it may be circulated through a heat exchanger (not shown), and returned to the oil tank  608  of the engine  10 , or any suitable part of the oil circulation system of the engine  10 . It is contemplated that the oil  600  collected from the generator  34  may instead be returned directly to the oil tank  608 , without passing first through the heat exchanger. The oil  600  is then recirculated by the oil pump to the passageway  50 , as well as to other parts of the engine  10 . 
         [0055]    Modifications and improvements to the above-described embodiments of the present invention may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting. The scope of the present invention is therefore intended to be limited solely by the scope of the appended claims.