Patent ID: 6499292
Filing Date: 2002-12-31
Classification: F01N,F02B,F02D,Y02T

Abstract:
A four stroke internal combustion engine comprising a cylinder block that defines a cylinder bore, a cylinder head fixed at one end of the cylinder block enclosing one end of the cylinder bore, a crankcase member fixed at the other end of the cylinder block and enclosing the other end of the cylinder bore, the crankcase member defining a crankcase chamber, a piston positioned in the cylinder bore, a crankshaft rotably journaled in the crankcase and driven by the piston, the piston, the cylinder bore and the cylinder head together defining a combustion chamber, at least one intake port and intake passage for transferring an air charge to the combustion chamber, at least one exhaust port and exhaust passage for discharging exhaust gases from the combustion chamber, a spark plug having one end exposed to the combustion chamber and operatively connected to a control system, a fuel injector disposed to inject fuel directly into the combustion chamber, the fuel injector including an actuator that is operatively connected to the control system, an exhaust system connected to the exhaust passage, the exhaust system including a catalytic treatment device, the control system being configured, at least during low engine speeds, to begin injecting fuel into the combustion chamber before the intake port closes, the control system also being configured to increase a temperature of the exhaust gases if the temperature of the exhaust gases is insufficient to activate the catalytic treatment device, wherein the exhaust system comprises an exhaust manifold defining a plurality of exhaust runners communicating with the combustion chambers, a merging portion in which the exhaust runners merge, and a common exhaust passage which receives exhaust gases from the merging portion, the common exhaust passage communicating with an expansion chamber configured to quiet exhaust noises traveling through the common exhaust passage, a valve disposed in the common exhaust passage and controlling a flow of exhaust gases therethrough, a catalytic treatment passage branched from the common exhaust passage at a position upstream from the valve, the catalytic treatment passage extending from the common exhaust passage to the catalytic treatment device so as to guide exhaust gases from the common exhaust passage upstream from the valve into the catalytic device, a throttle device configured to control the flow of air into the combustion chambers, a linkage arrangement connecting the throttle device to the valve so as to control movement of the valve proportionally to a movement of the throttle device, the linkage arrangement being configured to bias the valve to a closed position when the throttle device is in a position corresponding to an idle speed of the engine.