Internal combustion engine

An internal combustion engine comprising:

• an engine body having an array of cylinders defined therein;
• a bearing member fixed to said engine body, said engine body and said bearing member upper and lower mating surfaces, respectively, joined to each other;
• a crankshaft rotatably and at least one balancer shaft rotatably supported between said engine body and said bearing member parallel to each other;
• said engine body and said bearing member defining substantially semicylindrical recesses therein which jointly constitute bearings in which said crankshaft and said balancer shaft are rotatably supported;
• and
• at least one of said upper and lower mating surfaces having an oil groove communicating with said recesses for being supplied with lubricating oil, said oil groove and said recesses being formed upon casting of said engine body or said bearing member case having said at least one of said upper and lower mating surfaces.

An internal combustion engine comprising:

• a cylinder block having an array of cylinders defined therein;
• a crankcase coupled to a lower end of said cylinder block, said crankcase including an upper case integrally formed with said cylinder block and a lower case fixed to said upper case, said upper and lower cases having upper and lower mating surfaces, respectively, joined to each other;
• a crankshaft rotatably supported in said crankcase;
• at least one balancer shaft rotatably supported parallel to said crankshaft;
• said upper and lower cases defining substantially semicylindrical recesses therein which jointly constitute bearings in which said crankshaft and said balancer shaft are rotatably supported;
• and
• at least one of said upper and lower mating surfaces having an oil groove communicating with said recesses for being supplied with lubricating oil, said oil groove and said recesses being formed upon casting of said upper or lower case having said at least one of said upper and lower mating surfaces.

An internal combustion engine comprising:

• a cylinder block having an array of cylinders defined therein;
• a crankcase coupled to a lower end of said cylinder block, said crankcase including an upper case integrally formed with said cylinder block and a lower case fixed to said upper case, said upper and lower cases jointly defining a crank chamber therebetween, said upper and lower cases having a plurality of journal support walls projecting from inner wall surfaces thereof, said lower case having an open lower end;
• a crankshaft rotatably sandwiched by said journal support walls in said crankcase;
• a balancer chamber mounted on one side of said crankcase separately from said crank chamber and defined by recesses on confronting surfaces of said upper and lower cases;
• and
• a balancer shaft rotatably supported in said balancer chamber.