Four stroke engine with secondary air introducing system

Abstract

A four stroke engine has an engine body that defines a cylinder bore. The cylinder bore has a longitudinal axis. A piston is reciprocally disposed within the cylinder bore. A crankshaft is rotatable with a movement of the piston. A valve actuating mechanism actuates intake and exhaust valves. The crankshaft drives the valve actuating mechanism. A first portion of the valve actuating mechanism is positioned at least adjacent to the exhaust valve. A second portion of the valve actuating mechanism is positioned adjacent to the crankshaft. The engine body defines an inner passage through which secondary air flows to the exhaust passage. The inner passage has an end at a surface of the engine body. The longitudinal axis intersects the surface.

1 . A four stroke engine comprising an engine body defining a cylinder bore, the cylinder bore having a longitudinal axis, a piston reciprocally disposed within the cylinder bore, the piston movable along the longitudinal axis, the piston defining a combustion chamber with the engine body in the cylinder bore, the engine body defining a first intake passage through which primary air is introduced into the combustion chamber and an exhaust passage through which exhaust gases are discharged from the combustion chamber, an intake valve arranged to connect or disconnect the first intake passage with the combustion chamber, an exhaust valve arranged to connect or disconnect the exhaust passage with the combustion chamber, a crankshaft rotatable with a movement of the piston, and a valve actuating mechanism arranged to actuate the intake and exhaust valves, the crankshaft driving the valve actuating mechanism, a first portion of the valve actuating mechanism being positioned at least adjacent to the exhaust valve, a second portion of the valve actuating mechanism being positioned adjacent to the crankshaft, the engine body further defining a second intake passage through which secondary air flows to the exhaust passage, the second intake passage having an end at a surface of the engine body, and the longitudinal axis intersecting the surface.  
   
   
       2 . The engine as set forth in  claim 1 , wherein the valve actuating mechanism additionally comprises a third portion that couples the first and second portions with each other, the third portion extends generally along the longitudinal axis.  
   
   
       3 . The engine as set forth in  claim 2 , wherein the third portion includes push rods.  
   
   
       4 . The engine as set forth in  claim 1 , wherein the first portion of the valve actuating mechanism comprises at least one rocker arm associated with the exhaust valve, the rocker arm and the second intake passage are positioned next to each other.  
   
   
       5 . The engine as set forth in  claim 4 , wherein the valve actuating mechanism additionally comprises at least one push rod that couples the rocker arm with the second portion.  
   
   
       6 . The engine as set forth in  claim 1 , wherein the first portion of the valve actuating mechanism comprises a pair of rocker arms associated with the intake and exhaust valves, the rocker arms generally interpose the second intake passage therebetween.  
   
   
       7 . The engine as set forth in  claim 1  additionally comprising a spark plug configured to make a spark in the combustion chamber, the spark plug and the second intake passage being positioned next to each other.  
   
   
       8 . The engine as set forth in  claim 1  additionally comprising a pair of spark plugs each of which is configured to make a spark in the combustion chamber, the spark plugs generally interpose the second intake passage therebetween.  
   
   
       9 . The engine as set forth in  claim 1 , wherein the longitudinal axis generally extends vertically, the surface of the engine body is generally located at a top of the engine body.  
   
   
       10 . The engine as set forth in  claim 1 , wherein the engine body has a plurality of cooling fins, the fins extend outward from another surface of the engine body.  
   
   
       11 . The engine as set forth in  claim 1 , wherein the second portion of the valve actuating mechanism includes a camshaft extending next to the crankshaft.  
   
   
       12 . A four stroke engine comprising a cylinder block defining a cylinder bore, a cylinder head closing one end of the cylinder bore, a piston reciprocally disposed within the cylinder bore the piston defining a combustion chamber with the cylinder block and the cylinder head in the cylinder bore, the cylinder head defining an exhaust passage through which exhaust gases are discharged from the combustion chamber, an exhaust valve arranged to connect or disconnect the exhaust passage with the combustion chamber, a crankshaft rotatable with a movement of the piston, and a valve actuating mechanism arranged to actuate the exhaust valve, the crankshaft driving the valve actuating mechanism, a first portion of the valve actuating mechanism being positioned adjacent to the exhaust valve, a second portion of the valve actuating mechanism being positioned adjacent to the crankshaft, the cylinder head further defining an intake passage through which air flows to the exhaust passage, the intake passage having an end at a surface of the cylinder head.  
   
   
       13 . The engine as set forth in  claim 11 , wherein the cylinder bore has a longitudinal axis, and the longitudinal axis intersects the surface.