Abstract:
An oil cooling system of an air-cooled engine for cooling the oil reserved in a crankcase of the engine comprises a base plate assembled to the crankcase, an overlapping plate assembled to the base plate; an oil filter supported in the overlapping plate; and radiation fins formed on the base plate and the overlapping plate, wherein the base plate includes an inlet port for receiving the engine oil discharged from an oil pump of the engine, an outlet groove for outputting the engine oil and a first passage groove connecting the inlet port and the outlet groove, the overlapping plate includes an inlet groove opposed to the inlet port, an outlet port opposed to the outlet groove and a second passage groove opposed to the first passage groove to form an oil passage together with the first passage groove, and the base plate and the overlapping plate having through-holes where the filter outlet of the oil filter passes through for the connection with the crankcase.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   The disclosure of Japanese Application No. 2005-100519 filed on Mar. 31, 2005 including the specification, drawing and abstract is incorporated herein by reference in its entirety. 
   FIELD OF THE INVENTION 
   This invention is related to an oil cooling system for cooling the oil reserved in a crankcase of an engine, preferably the oil cooling system adapted to an air-cooled engine. 
   BACKGROUND OF THE INVENTION 
   Engine oil, which is supplied to the sliding portions that require lubrications, is stored in a crankcase of the engine. An air-cooled engine is used in an all-terrain vehicle (so-called as “ATV”). In the air-cooled engine, the engine is cooled by only the wind so that the temperature of the engine oil tends to rise. 
   To solve this problem, Japanese Patent Laid-Open No. 2002-225574 discloses an air-cooled engine having an oil cooler assembled to the engine body so as to cool the engine oil. 
   Furthermore, Japanese Patent Laid-Open No. 9-296991 discloses the air-cooled engine having an oil cooler to which an oil filter is directly assembled. 
   In order to improve the radiation performance of the oil cooler, it is desirable that enough winds blow the oil cooler. However, in the case that the oil filter is directly assembled to the oil cooler, the oil filter prevents the wind from blowing the oil cooler, as a result the cooling performance is not improved. 
   On the other hand, the oil cooler can be placed at a portion appropriate for cooling by connecting the oil filter and the oil cooler with a pipe. In this structure, however, pipes and connectors are required to assemble the oil cooler and the oil filter to the engine body. For this reason, the oil cooling system will be complicated. This causes not only increasing the assembling time of the engine but also increasing the production cost. 
   SUMMARY OF THE INVENTION 
   In view of the above circumstances, the first object of the present invention is to provide the simple structure of the oil cooling system of the air-cooled engine, and to obtain a desirable cooling performance. 
   According to the present invention, there is provided an oil cooling system of an air-cooled engine for cooling the oil reserved in a crankcase of the engine, the cooling system comprising a base plate assembled to the crankcase, an overlapping plate assembled to the base plate; an oil filter supported in the overlapping plate; and radiation fins formed on the base plate and the overlapping plate, wherein the base plate includes an inlet port for receiving the engine oil discharged from an oil pump of the engine, an outlet groove for outputting the engine oil and a first passage groove connecting the inlet port and the outlet groove, the overlapping plate includes an inlet groove opposed to the inlet port, an outlet port opposed to the outlet groove and a second passage groove opposed to the first passage groove to form an oil passage together with the first passage groove, and the base plate and the overlapping plate having through-holes where the filter outlet of the oil filter passes through for the connection with the crankcase. 
   It is preferable that the passage groove is formed as a meander shape in the base plate and the overlapping plate. 
   It is preferable that the base plate and the overlapping plate include a plurality of air holes in the thickness direction so that winds pass through the holes. 
   It is preferable that the base plate is assembled to the crankcase on its front side in a vehicle running direction. 
   According to the present invention, there is further provided an oil cooling apparatus of an air-cooled engine for cooling the engine oil stored in a crankcase of the engine, the apparatus comprising a cooling unit assembled to the crankcase and having a pair of half bodies forming therebetween inlet and outlet ports for the engine oil and an oil passage connecting the inlet and outlet ports; an oil filter supported by the cooling unit and connected to the crankcase through the cooling unit, the oil filter being communicated with the outlet port of the cooling unit and having an outlet portion for discharging the engine oil after filtering to the crankcase; and an radiation fins integrated to the cooling unit for cooling the engine oil flowing through the oil passage of the cooling unit. 
   According to the oil cooling system of this invention, since the oil filter is directly assembled to the oil cooler, and cooled engine oil in the oil cooler can be directly guided to the oil filter. 
   Furthermore, since the winds can directly blow the oil cooler without being disturbed by the oil filter, the cooling performance can be improved. Therefore, the oil cooling system with compact size and high performance can be achieved in a low cost. 
   Moreover, since the oil cooler comprises a pair of half bodies such as the base plate and the overlapping plate and the air-holes and the radiation fins are provided on the oil cooler to pass through the wind flows, the cooling performance of the oil cooler can be improved. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic drawing to show an engine. 
       FIG. 2  is a schematic drawing to show cross-sectional view of the engine along the line  2 - 2  in  FIG. 1 . 
       FIG. 3  is a schematic drawing to show cross-sectional view of the engine along the line  3 - 3  in  FIG. 1 . 
       FIG. 4  is front view of the engine represented in  FIGS. 1-3 . 
       FIG. 5  is enlarged perspective view of an oil cooling unit shown in  FIG. 4 . 
       FIG. 6  is schematic drawing to show hydraulic circuit of engine oil flowing through the oil cooling unit. 
       FIG. 7  is exploded perspective view to show a base plate and an overlapping plate as the components of the cooling unit. 
       FIG. 8  is front view of the base plate viewed from the direction of an arrow  8  in  FIG. 7 . 
       FIG. 9  is front view of the overlapping plate viewed from the direction of an arrow  9  in  FIG. 7 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A preferred embodiment of the present invention is explained with figures, however, the scope of the invention is not limited by the illustrated embodiments of the figures. 
   An engine  10  is used in a vehicle such as an all terrain vehicle (so-called as “ATV”). As shown in  FIG. 1 , the engine  10  comprises a crankcase  12 , a cylinder  16 , a cylinder head  30  assembled to the cylinder  16  and other component parts. The crankcase  12  rotatably incorporates a crankshaft  11  inside thereof. The crankcase  12  comprises a first half body  12   a  and a second half body  12   b  which is fixed to the first half body  12   a . A crank room is formed inside the crankcase  12 . The bottom of the crankcase  12  forms an oil pan  15  for reserving the engine oil. The cylinder  16  is assembled to the crankcase  12 . A piston  17  is reciprocally incorporated in the cylinder  16 . The piston  17  is connected to the crankshaft  11  through a connecting rod  18 . Thus, the reciprocal motion of the piston  17  is converted to the rotational motion of the crankshaft  11  through the connection rod  18 . 
   As shown in  FIG. 1 , an output shaft  27  is rotatably supported by a cover  26  which is fixed to the crankcase  12 , coaxially with the crankshaft  11 . A centrifugal clutch  28  is incorporated between the crankshaft  11  and the output shaft  27 . When the rotational speed of the crankshaft  11  is higher than a predetermined speed, the centrifugal clutch  28  engages the output shaft  27  and the crankshaft  11  by the centrifugal force, thereby to transmit the torque of the crankshaft  11  to the output shaft  27 . The output torque of the output shaft  27  is transmitted to drive wheels through a power transmission device (not shown). 
   As shown in  FIG. 2 , a pump drive shaft  47  is rotatably assembled to the crankcase  12 . A driven gear  47   a  is secured to the pump drive shaft  47  to mesh with a drive gear  11   a  fixed to the crankshaft  11 . As shown in  FIG. 3 , this pump drive shaft  47  is connected to the oil pump  48  incorporated in the crankcase  12 . The engine oil  14  suctioned from the oil pan  15  by the oil pump  48  is supplied to the sliding surfaces between a crankpin of the crankshaft  11  and a connecting rod  18  through an oil passage formed in the crankcase  12 . On the other hand, the engine oil  14  is supplied through a oil passage formed in the crankcase  12  and then sprayed to the sliding surfaces of the piston  17  and a cylinder bore. The engine oil  14  is also supplied to a clutch shoe of the centrifugal clutch  28  and any other oil requiring portions, such as a camshaft  39  of a valve operating mechanism  46 , through oil passages formed in the crankcase  12 . 
   As shown in  FIG. 4 , a cooling unit  51  is assembled to the crankcase  12  of the engine  31 . More specifically, as shown in  FIG. 2  and  FIG. 3 , the cooling unit  51  is assembled to the front side of the crankcase  12  in the vehicle running direction F. The cooling unit  51  forms an oil cooler  52  on which an oil filter  53  is removably mounted. As shown in  FIG. 6  the engine oil flowing into the oil pump  48  through a strainer  54  is supplied to the cooling unit  51 . After the engine oil  14  is cooled in the oil cooler  52 , the engine oil  14  is filtered by a filter element  53   a  in the oil filter  53  so as to be supplied to oil requiring portions. 
   The cooling unit  51  comprises a pair of half bodies such as a base plate  55  and an overlapping plate  56 . The base plate  55  is formed approximately rectangular shape. An inner surface of the base plate  55  is defined as a flat matching surface  55   a  as shown in  FIG. 7 . On the other hand, the flat portion is formed in the half area of the outside surface of the base plate  55  to define a mounting surface  55   b  to the crankcase  12  as shown in  FIG. 8 . 
   The shape of overlapping plate  56  is corresponding to the base plate  55 , as shown in  FIG. 9  a flat matching surface  56   a  is formed on an inner surface of the overlapping plate  56 , and a filter mounting hole  57  is formed on an outer surface of the overlapping plate  56 . The matching surface  56   a  of the overlapping plate  56  and the matching surface  55   a  of the base plate  55  are coupled across a sheet material therebetween to form the cooling unit  51 . Both the base plate  55  and the overlapping plate  56  are cast from light-alloy material such as aluminum alloy. 
   To assemble the overlapping plate  56  to the base plate  55 , the base plate  55  has a plurality of tapped holes  58   a , and the overlapping plate  58  has a plurality of through-holes  58   b  corresponding to the respective tapped holes  58   a . As shown in  FIG. 4  and  FIG. 5 , the overlapping plate  56  is assembled to the base plate  55  by tightening screws passing through the respective through-holes  58   b  into the respective tapped holes  58   a . Some of the screws extend through the tapped holes  58   a  so as to be engaged with the crankcase  12  so that the cooling unit  51  is assembled to the crankcase  12 . 
   In the middle part of the base plate in the width direction, as shown in  FIG. 7  and  FIG. 8 , a circular through-hole  59   a  to which the outlet of the oil filter  53  is fit, is formed through the base plate  55  in its thickness direction. Furthermore, an inlet port  61   a  shaped in circular arc is formed through the base plate  55  in its thickness direction, surrounding the circular through-hole  59   a.    
   The engine oil discharged from the oil pump  48  flows into the inlet port  61   a  as shown in the arrow A. An outlet groove  62   a  is formed in the matching surface  55   a  of the base plate  55  to be opposed to the inlet port  61   a  with respect to the through-hole  59   a . The outlet groove  62   a  has the bottom surface without penetrating the base plate  55 . A passage groove  63   a  (as a first passage groove) is formed in a meander shape between the inlet port  61   a  and the outlet groove  62   a , as shown in  FIG. 7 . The passage groove  63   a  has two turning portions near the side edge of the base plate  55 , one turning portion at the center of the base plate  55  and four straight portions connecting these turning portions. The straight portions are provided in parallel so as to extend in the longitudinal direction of the base plate  55 . 
   As shown in  FIG. 7  and  FIG. 9 , in the matching surface  56   a  of the overlapping plate  56 , a through-hole  59   b  is formed at a position corresponding to the through-hole  59   a  and a inlet groove  61   b  is formed at a position corresponding to the inlet port  61   a . The inlet groove  61   b  has the bottom surface without penetrating the overlapping plate  56  in the thickness direction. Furthermore, the overlapping plate  56  has an outlet port  62   b  at a position corresponding to the outlet groove  62   a  of the base plate  55 , which is formed through the overlapping plate  56  in its thickness direction. As shown in  FIG. 9  a passage groove  63   b  (as a second passage groove) is formed in the matching surface  56   a  between the inlet groove  61   b  and the outlet port  62   b , and also at a position corresponding to the passage groove  63   a . By engaging the base plate  55  and overlapping plate  56  with a seal material, the oil passage  63  is formed by the passage grooves  63   a  and  63   b  in the cooling unit  51  so as to guide the engine oil  14  discharged from the oil pump  48  to the oil filter  53 . 
   As shown in  FIG. 8 , the base plate  55  has a plurality of air holes  64   a  in its thickness direction. Those air holes  64   a  are located at respective areas nestled between the adjacent straight portions of the passage groove  63   a  at a predetermined interval along such straight portions. In the overlapping plate  56 , an air holes  64   b  is formed at a position corresponding to the respective air holes  64   a  as shown in  FIG. 9 . By engaging the base plate  55  and the overlapping plate  56 , a plurality of air passages  64  as through-holes are formed by the air holes  64   a  and  64   b  in the thickness direction of the cooling unit  51  as shown  FIG. 6 . 
   As shown in  FIG. 8 , at the outer surface of the base plate  55 , a plurality of heat radiation fins  65   a  outwardly projecting and extending in the width direction of the base plate  55  are provided. Similarly, as shown in  FIG. 7 , a plurality of heat radiation fins  65   b  are also provided on the overlapping plate  56 . 
   As described above, the cooling unit  51  is formed by engaging the base plate  55  and the overlapping plate  56  with seal material therebetween and tightened by the screw members  58 . When the oil filter  53  is assembled to the cooling unit  51 , a case of the oil filter  53  is fit into the filter mounting hole  57  of the cooling unit  51  and an outlet portion of the oil filter  53  passing though the through-holes  59   a  and  59   b  is screwed firmly into the crankcase  12 . Therefore, the oil filter  53  can be removably assembled to the cooling unit  51  and the crankcase  12 . 
   As described above, the cooling unit  51  acts as a support member to assemble the oil filter  53  to the crankcase  12 . Since the cooling unit  51  is assembled to the front face of the crankcase  12  in the vehicle running direction, the winds directly blow the outside surface and the heat radiation fins  56   b  of the overlapping plate  55  while the vehicle is running. Therefore, the air flows into the air holes  64   a  and  64   b , and then flows into a clearance between the cooling unit  51  and the crankcase  12 . Accordingly, the engine oil  14  is cooled by the winds while flowing through the oil passage  63  formed by the passage grooves  63   a  and  63   b  of the cooling unit  51  Thus, the cooled engine oil flows into the oil filter  53  to be filtered. 
   As described above, since the cooling unit  51  is formed by coupling two half plates, the radiating efficiency ratio can be improved. Furthermore, since the oil filter  53  is supported by the cooling unit  51 , additional pipes and connectors are not required for the connection of the oil filter  53  and the oil cooler  52 , thereby to reduce the production cost of the cooling unit  51 . 
   The present invention is not limited by detailed description of the preferred embodiment. It can be changed in the range which does not deviate from the gist in various ways. For example, the described preferred embodiment show the air-cooled engine for the boggy car that is ATV (All Terrain Vehicle), however, the present invention can be applied to another type of vehicles such as two-wheeled vehicle.