Abstract:
A motorcycle lubrication oil cooling system that cools lubrication oil without increasing the number of parts, weight, or cost, and yet is simple in construction. The cooling system is applicable to motorcycles in which an engine is cooled by a coolant pump driven by a crankshaft. The coolant pump is provided on a side face of the engine, and an oil storage chamber capable of storing a specified amount of lubrication oil is provided adjacent to the coolant pump, while a covering member is provided to cover both the oil storage chamber and a coolant pump chamber that houses the coolant pump. This abstract is neither intended to define the invention discloses in this specification nor intended to limit the scope of the invention in any way.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to the field of motorcycle lubrication oil cooling systems. 
   2. Description of the Related Art 
   Since engines include many internal sliding parts and rotating parts, they are designed to function fully by decreasing friction between these parts by providing lubrication oil to lubricate these parts by a lubrication system. 
   Some lubrication systems have means to cool lubrication oil since lubrication oil loses its lubrication capability when its temperature rises. 
   When the temperature rise of lubrication oil is relatively small, such as in the case of low speed engines, there are means to prevent the lubrication oil temperature from rising by improving heat release characteristics by increasing the contact surface area between the lubrication oil and the outside air by providing an oil pan and oil tank. 
   On the other hand, for high speed engines, in which the lubrication oil temperature rise is relatively large requiring active cooling, it has been a general practice to provide an oil cooler to prevent the temperature of lubrication oil from rising. 
   For example, many oil coolers mounted on motorcycles are of a lightweight and simple construction of an air-cooled type. Yet, since the air cooled-type has limitations in terms of installation location (its full function cannot be utilized unless it is positioned to receive airflow caused by driving). In the case when the engine is water-cooled, some engines are equipped with a water-cooled oil cooler as indicated in Japanese Patent Application Laid-Open (Kokai) H5-131962. 
   If an oil cooler is provided to achieve a cooling performance beyond what is obtainable by providing an oil pan or an oil tank, the number of parts and the number of assembly process steps involved in piping, etc. will increase over and above what is required for the main oil cooler body. Even for the air-cooled type, a weight increase is unavoidable. 
   In addition, there are other difficulties resulting from the increase in potential oil leak locations, since the main body of the oil cooler and engine are connected by piping. 
   There is also a large difference in terms of engine cooling performance, cost, and weight between the systems with and without an oil cooler. There has been no technology to achieve a cooling performance, which is more than what is achieved by providing an oil pan or an oil tank, yet less than what can be achieved by an oil cooler. 
   SUMMARY OF THE INVENTION 
   With the foregoing in view, it is an object of the present invention to provide a motorcycle lubrication oil cooling system that will not increase the number of parts, weight, and cost, yet is simple in construction and is capable of cooling lubrication oil. 
   The motorcycle lubrication oil cooling system of the present invention for solving the problems mentioned above is applicable to motorcycles whose engines are cooled by a coolant pump driven by the crankshaft; the coolant pump is provided beside the engine; an oil storage chamber capable of holding a specified amount of lubrication oil is located adjacent to the coolant pump; and a covering member that covers both the oil storage chamber and the coolant pump chamber that holds the coolant pump. 
   In order to solve the problems mentioned above, the above mentioned oil storage chamber is provided as a lubrication filtering device housing space capable of housing lubrication oil filtering equipment. 
   In order to further solve the problems mentioned above, a plurality of cooling fins are formed unitarily and in one piece with the above mentioned covering member on its surface facing the above mentioned oil storage chamber; while at the same time, a plurality of cooling fins are formed on the inner wall of the above mentioned oil storage chamber on the inner wall side that contacts the coolant pump chamber. 
   In order to solve the problems mentioned above further, a piston cooling lubrication oil injector is provided at the downstream end of the oil passage that first extends from the above mentioned oil storage chamber, and this lubrication oil injector is placed in such a manner that it is directed to the rear side of the piston in the cylinder bore formed in the above mentioned engine. 
   In order also to solve the problems mentioned above, the above mentioned covering member that covers both the above mentioned oil storage chamber and the above mentioned coolant pump chamber is formed by a material having high thermal conductivity. 
   An aspect of the present invention includes a lubrication oil cooling system for a motorcycle in which the engine is cooled by a coolant pump driven by a crankshaft, wherein the coolant pump is positioned on a side face of the engine; an oil storage chamber that stores a specified amount of oil is provided adjacent to the coolant pump; and a covering member is provided that covers both of the oil storage chamber and a coolant pump chamber in which the coolant pump is housed. The oil storage chamber may form a space that houses a lubrication oil filtering device. 
   According to a further aspect of the present invention, the covering member may include a plurality of cooling fins formed on a surface of the covering member facing the oil storage chamber. Further, the covering member that covers both the oil storage chamber and the coolant pump chamber may be formed of a material having a high thermal conductivity. Further, the oil storage chamber may include a plurality of cooling fins formed on an inside wall thereof on a side of the oil storage chamber that adjoins the coolant pump chamber. The plurality of cooling fins formed on the surface of the covering member facing the oil storage chamber may be formed unitarily and in one piece with the covering member; and the plurality of cooling fins formed on the inside wall of the storage chamber may be formed unitarily and in one piece with a clutch housing on the inside wall of the oil storage chamber. 
   A further aspect of the present invention includes a motorcycle lubrication oil cooling system, wherein a piston cooling lubrication oil injector is provided at a downstream end of an oil passage that extends from the oil storage chamber, and the lubrication oil injector is positioned so that the injector is directed to a rear side of a piston in a cylinder bore formed in the engine. 
   A further aspect of the present invention includes, in combination, a motorcycle body; an engine; and a motorcycle lubrication oil cooling system. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is further described in the detailed description which follows, by reference to the noted plurality of drawings by way of non-limiting examples of preferred embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein: 
       FIG. 1  is a left side view of a motorcycle showing the lubrication oil cooling system for motorcycles, according to one embodiment of the present invention; 
       FIG. 2  is an enlarged left side view of the midsection of the body of the motorcycle of  FIG. 1 ; 
       FIG. 3  is an enlarged right side view of the midsection of the body of the motorcycle of  FIG. 1 ; 
       FIG. 4  is a cross-sectional view along line IV—IV in  FIG. 3 ; 
       FIG. 5  is a right side view of the crankcase of the motorcycle of the embodiment of  FIG. 1 ; 
       FIG. 6  is a cross-sectional view along line VI—VI in  FIG. 5 ; 
       FIG. 7  is a drawing showing the outer surface of a covering member; and 
       FIG. 8  is a drawing showing the inner surface of the covering member of  FIG. 7 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description is taken with the drawings making apparent to those skilled in the art how the forms of the present invention may be embodied in practice. 
   Preferred embodiments of the present invention are illustrated in  FIGS. 1–8 . 
     FIG. 1  is a left side view of one embodiment of a motorcycle of the present invention; and  FIG. 2  is an enlarged left side view of the midsection of the body of the motorcycle of  FIG. 1 .  FIG. 3  is an enlarged right side view of the midsection of the body of the motorcycle of  FIG. 1 . As indicated in  FIGS. 1 ,  2 , and  3 , this motorcycle  1  has, for example, a semi-double cradle frame type of body frame  2 . This body frame  2  includes a head pipe  3 , a tank rail  4 , vertical tubes  5 , lower tubes  6 , main tubes  7 , rear pipes  8 , and seat rails  9 . 
   The head pipe  3  is installed at the forward head section of the body frame  2 , and the tank rail  4  extends diagonally downward toward the rear of the frame  2  from the upper rear section of the head pipe  3 . In addition, the vertical tubes  5  extend substantially downwardly from the lower rear section of the head pipe  3 , so that lower tubes  6  can be connected to the lower end of the vertical tubes  5 . Lower tubes  6  are formed in a lateral pair, and extend downwardly initially, and midway bend toward the rear of the frame  2  before extending in a substantially horizontal direction. In addition, the upper end section of a lateral pair of main tubes  7  is laterally connected to the rear end of the tank rail  4 . These main tubes  7  extend substantially downwardly before they are connected to the rear end of lower tubes  6 . 
   Tips of a lateral pair of seat rails  9  are connected to the rear end of the tank rail  4 , and a pair of rear pipes  8  extends downwardly and forwardly in the direction of the lower portion of main tubes  7 . 
   An engine  10  is mounted at the middle lower section of the body frame  2 . As indicated in  FIGS. 2 and 3 , the engine  10  is anchored to the body frame  2  at three locations, the upper front side, the lower front side, and the rear side. Specifically, the upper front side of the engine  10  is anchored to the vertical tube  5  through a stay  11 , while the lower front side of the engine  10  is anchored in a sandwiched manner between the angled sections of the lateral pair of lower tubes  6 . 
   The rear end of the engine  10  is held in a sandwiched manner by a lateral pair of main tubes  7 , and each of the attachment sections, as viewed from the side, forms an approximate equilateral triangle. The engine  10  is installed in such a manner that its bottom surface is higher than the bottom surface of lower tubes  6 . If viewed from the side, the bottom of the engine  10  and the horizontal section of lower tubes  6  overlap. In addition, a fuel tank  12  is provided above the tank rail  4 , and a driver seat  13  and a rear fender  14  are anchored to the seat rail  9 . 
   A steering mechanism  15  is provided on the head pipe  3 . A front fork  17 , which supports a front wheel  16  in such a manner that it can rotate freely, and a handle bar  18  are provided to the steering mechanism  15 , and mounted so as to swivel freely in lateral directions. On the other hand, a swing arm  20  is attached to a pivot shaft  19  (in the same location where the rear part of the engine  10  is sandwiched), which is installed below main tubes  7 , in such a manner that a swing arm  20  is able to swivel freely around the pivot shaft  19 , the rear end section of which rotatably supports a rear wheel  21 , which is the drive wheel. 
     FIG. 4  is a cross-sectional view along line IV—IV of  FIG. 3 . 
   As can be seen from  FIGS. 1 through 4 , the engine  10  is, for example, a 4-cycle single cylinder engine, in which a cylinder assembly  25  including sequentially, from the top, a head cover  22 , a cylinder head  23 , and a cylinder block  24  is placed on an engine case  26  in a slightly forward inclined condition. 
   The engine case  26  includes mainly a crankcase  27 , which is split into left and right halves in the lateral direction of the vehicle; a clutch housing  28 , which is provided on the right side surface of the crankcase  27 ; and a generator cover  29 , which is provided on the left side surface of the crankcase  27 . The clutch housing  28  and the generator cover  29  are located above the horizontal section of the lower tube  6 , and project outwardly in the lateral direction of the vehicle. 
   Moreover, this engine  10  is a 4-cycle engine equipped, above the cylinder head  23 , with a gear mechanism  32  of a double overhead cam shaft (DOHC) type in which a couple of cam shafts  31  are provided, an intake valve  30   a  and an exhaust valve  30   b,  respectively, for opening and closing these valves  30   a  and  30   b.    
   An exhaust pipe  33  and a muffler  34  constituting the engine exhaust system are connected to the front section of the cylinder assembly  25 . In addition, a carburettor  35  constituting the engine intake system is connected to the rear section of the cylinder assembly  25 . Further, an air cleaner  36  located below the driving seat  13  is connected to the upstream side of the carburetor  35 . Moreover, a lateral pair of radiators  37  constituting the engine cooling system is provided to the upper front section of the engine  10  and to the lower rear section of the head pipe  3 . 
   As indicated in  FIGS. 2 through 4 , the interior of the crankcase  27  is divided by a partition wall  38  to form a crank chamber  39  in the front and a transmission chamber  40  in the rear, respectively. In addition, an oil pan  41  is formed below the crankcase  27  to temporarily store lubrication oil that lubricates all engine parts. The oil pan  41  is also divided into the front and rear  41 F,  41 R portions by the partition wall  38  as in the case of the crankcase  27 . 
   A crankshaft  42  is installed within the crank chamber  39  in the transverse direction of the vehicle, in other words, perpendicular to the travelling direction of the vehicle. A cylinder bore  44  is formed within the cylinder block  24  to house a piston  43 . A combustion chamber  45  that matches this cylinder bore  44  is formed within the cylinder head  23 , and an ignition plug  46  is inserted from outside toward this combustion chamber  45 . 
   The bottom end  48   a  of a connecting rod  48  is connected to a crankpin  47  located in an approximate center of the crankshaft  42 , while the top end  48   b  of the connecting rod  48  is connected to the piston  43 . This piston  43  makes reciprocating motions within the cylinder bore  44  in the axial direction thereof, and this reciprocating stroke is transmitted to the crankshaft  42  via connecting rod  48  to produce rotating motions of the crankshaft  42 . 
   On the other hand, a transmission system  49 , which is a speed reduction system, is installed in the transmission chamber  40 . Provided in this transmission system  49  are a counter shaft  51 , which is installed parallel to the crankshaft  42  and inputs the driving power from the crankshaft  42  through a clutch system  50 , and a drive shaft  52 , which outputs the driving power to the rear wheel  21 . 
   A primary drive gear  53  is provided at one end, or at the right end as shown in  FIG. 4  in this embodiment, of the crankshaft  42  so as to rotate together as an integral body, whereas a primary driven gear  54  that meshes with a primary drive gear  53  is provided on the counter shaft  51  in such a manner that they can freely rotate with respect to the counter shaft  51 ; and the primary driven gear  54  is anchored to a clutch body  55  in the clutch system  50  so as to rotate together as an integral body and to transmit rotational driving power of the crankshaft  42  to the clutch system  50 . 
   A plurality of transmission gears  56  having different numbers of teeth is provided on the counter shaft  51  and to the drive shaft  52 . The primary speed reduction is achieved by changing the combination of these transmission gears  56 . 
   One end of the drive shaft  52  protrudes to the outside of the transmission chamber  40 , and a drive sprocket  57  is provided at the protruding end of the drive shaft  52 . This drive sprocket  57  is connected to a driven sprocket  59 , which is provided at the rear wheel  21 , through a drive chain  58 . The engine driving power is transmitted to the rear wheel  21  after secondary speed reduction through this chain drive. 
   On the other hand, a generator chamber  60 , which is separated from the crankcase  27 , is formed on the left side surface of the crankcase  27 . In addition, the left end of the crankshaft  42  projects into the generator chamber  60 , and a generator  61  is provided at the projecting end. While this generator chamber  60  is covered by the generator cover  29  mentioned earlier, a cam drive gear  62  is provided inside the generator  61  of the crankshaft  42 . 
   In addition, a cam sprocket  63  is provided at one end of each of camshafts  31 . This cam sprocket  63  is operationally linked to the cam drive gear  62  through a cam chain  64  to operate the valve train system  32  by transmitting rotation of the crankshaft  42  to the camshaft  31  through a cam chain  64 . 
     FIG. 5  is the right side view of the crankcase, while  FIG. 6  is a cross-sectional drawing of the crankshaft along line VI—VI in  FIG. 5 . As can be seen from  FIGS. 3 to 6 , the clutch housing  28  mentioned above is located on the right side surface of the crankcase  27 , while the clutch body  55  described above is positioned within the rear portion of the frame, and an accessory chamber  65  is formed within the front portion of the frame so that coolant pump  66  and a pair of oil pumps  67  and  68  are housed in this accessory chamber  65 . Separately from the accessory chamber  65 , an oil storage chamber  69 , which is capable of storing a specified amount of lubrication oil, is formed in the clutch housing  28  located next to the coolant pump  66 . 
   In this embodiment, the oil storage chamber  69  is formed as a space for installing a lubrication oil filter, such as for example, an oil filter  90  housed therein. The section in the clutch housing  28 , in which the clutch body  55  is housed, is open to the side, and is closed by a detachable clutch cover  70 . 
   As shown in  FIG. 6 , a coolant pump shaft  71 , which is positioned parallel to the crankshaft  42 , is rotatably supported between the right side surface of the crankcase  27  and the inner surface of the clutch housing  28 . A coolant pump gear  72 , which meshes with the above mentioned primary drive gear  53 , is provided on the coolant pump shaft  71  so as to rotate together as an integral body. A coolant pump chamber  73 , in which the above mentioned coolant pump  66  is housed, is formed within the clutch housing  28  at the side of coolant gear pump  72 . This coolant pump chamber  73  is connected to a coolant passage  74 , which is formed in the crankcase  27 . 
   The right side end of the coolant pump shaft  71  projects toward the outside of the coolant pump chamber  73 , and an impeller  75  is provided at the projecting end on the coolant pump body  66 . The above mentioned oil storage chamber  69  is located adjacent to the coolant pump chamber  73 . This oil storage chamber  69  and the coolant pump chamber  73  are covered by a covering member  77  that is formed unitarily and in one piece from a material having a high thermal conductivity, such as aluminium or the like. A coolant union  78  is provided to this covering member  77 . And a coolant hose  79  extends from this coolant union  78  to the above mentioned radiator  37 . (see  FIG. 3 ) 
   As indicated in  FIGS. 3 ,  5  and  6 , a pair of oil pumps  67  and  68  is provided within the crankcase  27 , one of which is a scavenging pump for suction, while the other of which is a lubrication oil feed pump  68 . Both of these oil pumps  67  and  68  are operationally connected to an oil pump drive gear  81 , which is provided at the right end of the crankshaft  42  through an oil pump drive gear  80 . 
   As indicated in  FIG. 5 , the scavenging pump  67  withdraws lubrication oil from an oil strainer  82 F located within the oil pan  41 F portion on the side of the crank chamber  39 , and supplies the lubrication oil by dripping for example, to all parts in the transmission system  49  including the counter shaft  51  and the drive shaft  52  from a transmission lubrication oil passage  83 , which is provided at an upper portion within the transmission chamber  40 . The lubrication oil that lubricates all parts in the transmission system  49  accumulates within an oil pan  41 R located on the side of the transmission chamber  40 . 
   On the other hand, the feed pump  68  withdraws lubrication oil from an oil strainer  82 R located within an oil pan  41 R on the side of the transmission chamber  40 , and guides the lubrication oil to all parts of the crankshaft  42 , the piston  43  and the valve train system  32  through the oil storage chamber  69 . 
   Specifically, for example, as indicated in  FIG. 4 , a first oil passage  91  extends from the oil storage chamber  69  first toward the lower interior of the cylinder block  24 . An oil nozzle  92 , which is a piston cooling lubrication oil injector, is positioned at the downstream end of the first oil passage in such a manner that it is directed to the rear side of the piston  43  in the cylinder bore  44 . Lubrication oil injected from this nozzle  92  lubricates the sliding contact surface between the cylinder bore and the piston  43  while cooling them at the same time. 
   A second oil passage  93  branches off midway in the first oil passage  92  and extends toward the right end of the crankshaft  42 , as viewed in  FIG. 4 . Lubrication oil that is guided to the right side of the crankshaft  42 , for example, passes through a third oil passage  94 , which is formed within the crankshaft  42 , and through a fourth oil passage  95  before it is guided to the sliding contact surface between the piston pin  47  and the large end  48   a  of the connecting rod  48  to lubricate this sliding surface. 
   Part of the lubrication oil that has lubricated all the parts mentioned above falls into the above mentioned generator chamber  60  through the side of the cylinder assembly  25 , or through a cam chain tunnel  85  which is a space for arranging the cam chain  64  that is on the left side in this embodiment, as viewed in  FIG. 4 . In addition, in order to prevent the generator  61  from becoming immersed in lubrication oil, most of the lubrication oil falls naturally into the crank chamber  39  through a connecting hole  87  that is bored into the left side surface of the crankcase  27  before it accumulates in the oil pan  41 F next to the crank chamber  39 . 
   When lubrication oil that has accumulated in the oil pan  41 F next to the crank chamber  39  becomes greater than a specified amount, the rotational resistance of the crankshaft  42  increases, necessitating the withdrawal of lubrication oil that exceeds the amount of lubrication oil that can be pushed out by the above mentioned feed pump  68  to the side of the transmission chamber  40 . For this reason, the scavenging pump  67  has a greater capacity than the feed pump. 
     FIG. 7  shows the outer surface of above mentioned covering member  77 , while  FIG. 8  shows the inner surface or rear side of the covering member  77 . As shown in  FIG. 7 , the covering member  77  is formed as an integral body made of a material having high thermal conductivity in such a manner that it covers both the oil storage chamber  69  and the coolant pump chamber  73 , which are located adjacent each other. As indicated in  FIGS. 6 and 8 , a plurality of cooling fins  96  are formed unitarily and in one piece with the covering member  77  on the inner surface facing the oil storage chamber  69 . A plurality of cooling fins  97  are also formed unitarily and in one piece with the clutch housing  28  on the inside wall of the oil storage chamber  69  in the side touching the coolant pump chamber  73 . 
   Described hereinafter are the operations of an embodiment of this invention. 
   The coolant pump  66 , which is rotationally driven by the crankshaft  42  through the primary drive gear  53  and the coolant pump gear  72 , and the oil storage chamber capable of holding a specified amount of lubrication oil are provided adjacent to the coolant pump  66  in the clutch housing  28 , which is located at the right side surface of the crankcase  27 . With this arrangement, it is possible to cover both the oil storage chamber  69  and the coolant pump chamber  73 , in which the coolant pump  66  is housed, under one covering member  77 , which results in the reduction in the number of parts, the number of assembly line process steps, and weight. 
   The oil storage chamber  69  is established as a space for housing lubrication oil filtering equipment, inside of which the oil filter  90 , which is a lubrication oil filtering device, is housed. With this design, lubrication oil in the oil storage chamber  69  can be cooled by coolant in the coolant pump chamber  73  through the covering member  77 . Since the oil filter  90  does not require driving power, it is fully possible to install an oil storage chamber  69  adjacent to the coolant pump  66 , which is located next to the crankshaft  42 . 
   A plurality of cooling fins  96  are formed unitarily and in one piece with the covering member  77  on the inner surface of the covering member  77  facing the oil storage chamber  69 , while a plurality of cooling fins are also formed unitarily and in one piece with the clutch housing  28  on the inside wall of the oil storage chamber on the side touching the coolant pump chamber  73 . With this design, the contact area between lubrication oil and the covering member  77  increases resulting in an improvement in the lubrication oil cooling efficiency. 
   In addition, the oil nozzle  92 , which is a lubrication oil injecting device for piston cooling, is provided in the downstream end of the first oil passage  91 , which first extends from the oil storage chamber  69 , in such a manner that the nozzle points to the rear side of the piston  43  in the cylinder bore. The system is so configured so that lubrication oil injected from this oil nozzle  92  can lubricate the sliding surface between the cylinder bore  44  and the piston  43 . With this design, it is possible to inject lubrication oil, which is cooled in the oil storage chamber  69 , into the cylinder bore  44  before its temperature is elevated by other parts of the engine  10 , resulting in an improvement in the cooling performance of the piston  43 . 
   In addition, the covering member  77 , which covers the oil storage chamber  69  and the coolant pump chamber that houses the coolant pump  66 , is formed unitarily and in one piece of any suitable material having a high thermal conductivity such as, for example, aluminium. With this design, the heat conduction from the oil storage chamber  69  to the coolant pump chamber  73  increases, resulting in the decrease in the lubrication oil temperature and a further increase in the cooling efficiency and further improvement in the cooling performance of all parts of the engine  10 . 
   Finally, according to the configuration of the present embodiment described above, it is possible to obtain a cooling performance, e.g., active cooling of the piston  43 , without providing an oil cooler and without using a large size oil pan  41 , better than what is achievable by providing a large oil pan  41  or a large oil tank. 
   In addition, since there are no complicated piping systems, there should be no large scale increase in the number of parts, number of processing steps, weight, and cost. Since the number of locations having potential oil leakage will not increase, the number of sealing members can be decreased, leading to improved engine reliability. 
   Since the exterior undulation of the engine  10  decreases compared with the case in which an oil cooler is mounted, the amount of mud adhesion to the exterior of the engine  10  when driving over muddy ground decreases, leading to improved serviceability. 
   Although the embodiment of this invention described above showed an example in which the oil storage chamber  69  is provided next to the coolant pump  66  so that one covering member  77  covers both the oil storage chamber  69  and the coolant pump chamber, which houses the coolant pump, this design may be replaced by the following, although the details of which are not shown here by drawings. For example, oil pumps  67  and  69  may be provided next to the coolant pump  66  in lieu of the oil storage chamber  69 , so that one covering member (not shown in the drawing) can cover both the oil pump chamber (not shown in the drawing), which houses oil pumps  67  and  68 , and the coolant pump chamber, which houses the coolant pump  66 , 
   As explained above, according to the present invention related to the motorcycle lubrication oil cooling system, it is possible to improve cooling efficiency by lowering the lubrication oil temperature. 
   In addition, the number of parts, the number of assembly process steps, and the weight can be decreased. 
   Furthermore, the cooling performance of engine parts can be improved. 
   Although the invention has been described with reference to an exemplary embodiment, it is understood that the words that have been used are words of description and illustration, rather than words of limitation. Changes may be made within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the invention in its aspects. Although the invention has been described with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed. Rather, the invention extends to all functionally equivalent structures, methods, and uses such as are within the scope of the appended claims. 
   The present disclosure relates to the subject matter contained in priority Japanese Application No. 2001-362558, filed on Nov. 28, 2001, which is herein expressly incorporated by reference in its entirety.