Internal combustion engine

Abstract

An in-line four-cylinder internal combustion engine wherein exhaust ports ( 8, 9 ) of a pair of cylinders positioned at the center are connected to a single merged exhaust port ( 11 ) and this merged exhaust port ( 11 ) is connected through a first exhaust pipe ( 19 ) to a catalytic converter ( 18 ). On the other hand, exhaust ports ( 7, 10 ) of pairs of cylinders positioned at the two ends are connected through a second exhaust pipe ( 21 ) to a catalytic converter ( 18 ). A length of the first exhaust pipe ( 19 ) from the merged exhaust port ( 11 ) to the catalytic converter ( 18 ) is made shorter than the length of the second exhaust pipe ( 21 ) from the exhaust ports ( 7, 10 ) to the catalytic converter ( 18 ).

1 . An in-line four-cylinder internal combustion engine wherein central exhaust ports of a pair of cylinders positioned at the center open on a side wall surface of the cylinder head, exhaust ports of a pair of cylinders positioned at the two ends open on the side wall surface of the cylinder head at the two sides of the opening part of the central exhaust ports as independent exhaust ports, and the opening part of said central exhaust ports is connected through a first exhaust pipe to an exhaust inflow part of a catalytic converter, the opening parts of said pair of independent exhaust ports being connected through a second exhaust pipe merged midway to the same exhaust inflow part, and a length of the first exhaust pipe from the corresponding opening part to said exhaust inflow part being made shorter than the length of the second exhaust pipe from the corresponding opening parts to said exhaust inflow part, characterized in that the central exhaust ports ( 8 ,  9 ) of a pair of the cylinders (# 2 , # 3 ) positioned at the center merge inside the cylinder head ( 1 ) into a single merged exhaust port ( 11 ) which has the single opening part ( 14 ) connected to the first exhaust pipe ( 19 ), and the exhaust ports ( 7 ,  10 ) of a pair of the cylinders (# 1 , # 4 ) at the two ends extend along the merged exhaust port ( 11 ) separated from the merged exhaust port ( 11 ) by corresponding thin walls ( 12 ,  13 ) at the sides of the merged exhaust port ( 11 ) until the side wall surface ( 5 ) of the cylinder head ( 1 ). 
   
   
       2 . An internal combustion engine as set forth in  claim 1 , wherein the catalytic converter ( 18 ) is provided with a pair of exhaust inflow openings ( 22 ,  23 ), and said first exhaust pipe ( 19 ) and second exhaust pipe ( 21 ) are connected to the corresponding exhaust inflow openings ( 22 ,  23 ). 
   
   
       3 . An internal combustion engine as set forth in  claim 1 , wherein an exhaust turbocharger ( 24 ) is provided in place of a catalytic converter and is provided with a pair of exhaust inflow openings ( 26 ,  27 ), and said first exhaust pipe ( 19 ) and second exhaust pipe ( 21 ) are connected to the corresponding exhaust inflow openings ( 26 ,  27 ). 
   
   
       4 . An internal combustion engine as set forth in  claim 1 , wherein said first exhaust pipe ( 19 ) and second exhaust pipe ( 21 ) are bent in the middle of the distance from the corresponding opening parts ( 14 ,  15 ,  16 ) toward said exhaust inflow part toward the same direction, and said second exhaust pipe ( 21 ) extends along the outside of the first exhaust pipe ( 19 ) after branches of said second exhaust pipe ( 21 ) merge at the outside of the first exhaust pipe ( 19 ). 
   
   
       5 . An internal combustion engine as set forth in  claim 1 , wherein the opening area of the opening part ( 14 ) of said merged exhaust port ( 11 ) is larger than the opening area of the opening part ( 15 ,  16 ) of each independent exhaust port ( 7 ,  10 ).