Internal combustion engine

Abstract

A vertical vortex, namely, a reverse tumble flow is formed inside a cylinder of an internal combustion engine to form an intake air flow for smooth intake and exhaust in the internal combustion engine and also to promote atomization of fuel and mixing of air and fuel in a combustion chamber. To form this reverse tumble flow, a downstream portion of an intake passage is formed extending toward a central axis of the cylinder. To promote the formation of the swirl and further to form the combustion chamber as an efficient compact combustion chamber, a recessed portion is formed in a top wall of a piston. The top wall of the piston is provided with a raised portion at a location adjacent to the recessed portion, whereby, in the vicinity of top dead center of the piston, a squish is produced in a direction flowing toward a side of a spark plug in the efficient combustion chamber. Under cooperation with the reverse tumble flow, the squish serves to have a rich air-fuel mixture centered around the spark plug upon lean burn.

We claim: 
     
       1. In an internal combustion engine having: a combustion chamber formed between a top wall of a piston fitted in a cylinder and a lower wall of a cylinder head,   an intake port formed through the cylinder head on one side of a reference plane in which a central axis of the cylinder is contained, said intake port communicating through an intake opening with the combustion chamber,   an exhaust port formed through the cylinder head on an opposite side of said reference plane, said exhaust port communicating through an exhaust opening with the combustion chamber, and   open/close valves disposed in the intake port and the exhaust port, respectively, the improvement comprising:   the intake port is formed extending upstream from the intake opening substantially along the cylinder axis; and   the piston is provided at the top wall thereof with a recessed portion and a raised portion, said recessed portion being formed at a location off-set toward said one side to guide an intake air flow, which has been inducted into the combustion chamber, as a swirl about an axis extending in parallel with a line which in turn extends at a right angle relative to the cylinder axis, and said raised portion being formed on the opposite side of said reference plane to extend in continuation with an .[.upwardly gently sloping.]. edge portion of the recessed portion, whereby the raised portion approaches the lower wall of the cylinder head at top dead center of the piston.   
     
     
       2. An internal combustion engine of claim 1, wherein fuel injection means is disposed on a side of the intake port through a side wall of the cylinder head, whereby said fuel injection means faces the combustion chamber. 
     
     
       3. An internal combustion engine of claim 2, wherein the intake port is wider on a side remote from the cylinder axis than on a side close to the cylinder axis. 
     
     
       4. An internal combustion engine of claim 3, wherein an intake pipe communicating with an upstream end of the intake port is formed extending from an upper wall of the cylinder head toward the opposite side of said reference plane so that an intake passage portion formed of the intake pipe and the intake port is smoothly curved. 
     
     
       5. An internal combustion engine of claim 4, wherein exhaust passage means communicating with the exhaust port is formed extending through the cylinder head toward the opposite side of said reference plane, an exhaust gas recirculation passage is arranged to connect the intake pipe to said exhaust passage means, and an exhaust gas recirculation valve is inserted in the exhaust gas recirculation passage. 
     
     
       6. An internal combustion engine of claim 2, wherein an upstream portion of the intake port in the cylinder head curves toward an upper portion of the exhaust port on the opposite side of said reference plane, an exhaust gas recirculation passage is arranged in the cylinder head to connect the intake port to the exhaust port, and an exhaust gas recirculation valve is inserted in the exhaust gas recirculation passage. 
     
     
       7. An internal combustion engine of claim 6, wherein the intake port is wider on a side remote from the cylinder axis than on a side close to the cylinder axis. 
     
     
       8. An internal combustion engine of claim 2, wherein an intake pipe communicating with the intake port is formed extending from an upper wall of the cylinder head toward the opposite side of said reference plane so that an intake passage portion formed of the intake pipe and an upstream side of the intake port is smoothly curved. 
     
     
       9. An internal combustion engine of claim 8, wherein exhaust passage constituting means communicating with the exhaust port is formed extending toward the opposite side of said reference plane through the cylinder head, an exhaust gas recirculation passage is arranged to connect the intake pipe to said exhaust passage constituting means, and an exhaust gas recirculation valve is inserted in the exhaust gas recirculation passage. 
     
     
       10. An internal combustion engine of claim 2, wherein an intake pipe communicating with the intake port is formed extending from an upper wall of the cylinder head toward the opposite side of said reference plane, exhaust passage means communicating with the exhaust port is formed extending toward the opposite side of said reference plane through the cylinder head, an exhaust gas recirculation passage is arranged to connect the intake pipe to said exhaust passage means, and an exhaust gas recirculation valve is inserted in the exhaust gas recirculation passage. 
     
     
       11. An internal combustion engine of claim 10, wherein said internal combustion engine is a multicylinder internal combustion engine and each cylinder is provided individually with the exhaust gas recirculation passage. 
     
     
       12. An internal combustion engine of claim 2, further comprising spark ignition means on the lower wall of the cylinder head, said spark ignition means being arranged centrally in an upper part of the combustion chamber so that said spark ignition means extends along the cylinder axis. 
     
     
       13. An internal combustion engine of claim 12, wherein said fuel injection means is arranged to inject fuel toward the recessed portion formed in the top wall of the piston. 
     
     
       14. An internal combustion engine of claim 13, wherein said fuel injection means is set to perform injection of fuel during a latter part of a compression stroke while the engine is operated under a low load and the engine is set to conduct combustion as lean burn. 
     
     
       15. An internal combustion engine of claim 13, wherein said fuel injection means is set in such a manner that fuel is injected during a latter part of a compression stroke of the engine to conduct combustion as lean burn while the engine is operated under a low load but fuel is injected during an intake stroke of the engine to conduct combustion at a air-fuel ratio higher than that for the lean burn while the engine is operated under a high load. 
     
     
       16. An internal combustion engine of claim 13, wherein the intake port is wider on a side remote from the cylinder axis than on a side close to the cylinder axis and the engine is set to conduct combustion as lean burn. 
     
     
       17. An internal combustion engine of claim 16, wherein an intake pipe communicating with the intake port is formed extending from an upper wall of the cylinder head toward the opposite side of said reference plane so that an intake passage portion formed of the intake pipe and an upstream side of the intake port is smoothly curved. 
     
     
       18. An internal combustion engine of claim 17, wherein exhaust passage constituting means communicating with the exhaust port is formed extending toward the opposite side of said reference plane through the cylinder head, an exhaust gas recirculation passage is arranged to connect the intake pipe to said exhaust passage means, and an exhaust gas recirculation valve is inserted in the exhaust gas recirculation passage. 
     
     
       19. An internal combustion engine of claim 12, wherein the engine is set to conduct combustion as lean burn, and an intake pipe communicating with the intake port is formed extending from an upper wall of the cylinder head toward the opposite side of said reference plane so that an intake passage portion formed of the intake pipe and an upstream side of the intake port is smoothly curved. 
     
     
       20. An internal combustion engine of claim 19, wherein exhaust passage constituting means communicating with the exhaust port is formed extending toward the opposite side of said reference plane through the cylinder head, an exhaust gas recirculation passage is arranged to connect the intake pipe to said exhaust passage means, and an exhaust gas recirculation valve is inserted in the exhaust gas recirculation passage. 
     
     
       21. An internal combustion engine of claim 12, wherein the engine is set to conduct combustion as lean burn, an intake pipe communicating with the intake port is formed extending from an upper wall of the cylinder head toward the opposite side of said reference plane, exhaust passage means communicating with the exhaust port is formed extending toward the opposite side of said reference plane through the cylinder head, an exhaust gas recirculation passage is arranged to connect the intake pipe to said exhaust passage means, and an exhaust gas recirculation valve is inserted in the exhaust gas recirculation passage. .Iadd. 
     
     
       22.  An internal combustion engine of claim 1, wherein the edge portion of the recessed portion extends as an upward gentle slope..Iaddend..Iadd. 
     
     
       23.  In an internal combustion engine having: a combustion chamber formed between a top wall of a piston fitted in a cylinder and a lower wall of a cylinder head,   an intake port formed through the cylinder head on one side of a reference plane in which a cylinder axis as a central axis of the cylinder is contained, said intake port communicating through an intake opening with the combustion chamber,   an exhaust port formed through the cylinder head on an opposite side of the reference plane, said exhaust port communicating through an exhaust opening with the combustion chamber, and   open/close valves disposed in the intake port and the exhaust port, respectively, the improvement comprising:   the intake port is formed extending upstream from the intake opening substantially along the cylinder axis and is connected at an upstream end thereof to an intake manifold in an upper part of said cylinder head, and   the internal combustion engine further comprises fuel injection means disposed in the cylinder head on the one side of the reference plane so that the fuel injection means faces the combustion chamber..Iaddend..Iadd.24. An internal combustion engine of claim 23, wherein the piston defines a recessed portion in the top wall thereof off-centered toward the one side of the reference plane so that the recessed portion is located opposite the intake port..Iaddend..Iadd.25. An internal combustion engine of claim 23, wherein the internal combustion engine further comprises an EGR passage for selective communication between the exhaust port and the intake port, and while the engine is operated under a low load, exhaust gas is introduced from the exhaust port into the intake port via the EGR passage in an intake stroke of the engine and said fuel injection means injects fuel into the combustion chamber in a subsequent compression stroke of the engine..Iaddend.