Patent ID: 8028515

Claim:
An engine exhaust controlling device for a four stroke engine including at least one cylinder and a piston disposed in the cylinder and connected to a crankshaft, the device comprising: a catalyst for removing pollutants from exhaust emitted by the engine; a fuel injection device for injecting fuel at a fuel pressure into the cylinder; an intake valve for supplying an intake air quantity of air to the cylinder; an ignition device for igniting a mixture of the fuel and the air in the cylinder at an ignition timing; an intake valve adjustment mechanism for adjusting the intake air quantity by changing one or both of the lift amount and the operating angle of the intake valve; and a controller for controlling the fuel injection device, the ignition device, and the intake valve adjustment mechanism, the controller being configured to detect whether or not a request is present for activating the catalyst when the engine is started, the controller being further configured to determine whether or not the fuel pressure is greater than or equal to a predetermined pressure; wherein when the controller detects that a request is not present for activating the catalyst when the engine is started, the engine is operated in a homogeneous combustion mode in which the fuel is injected during the intake stroke and in which ignition timing is set to ignite the fuel-air mixture before compression top dead center; and wherein when the controller detects that a request is present for activating the catalyst when the engine is started, the intake valve adjustment mechanism is controlled so that one or both of the lift amount and the operating angle of the intake valve are larger than one or both of the lift amount and the operating angle of the intake valve when the request for activating the catalyst is not present, wherein when the controller determines that the fuel pressure is not greater than or equal to the predetermined fuel pressure, the engine is operated in the homogeneous combustion mode; and wherein when the controller determines that the fuel pressure is greater than or equal to the predetermined fuel pressure, the engine is operated in a retarded combustion mode in which the ignition timing is retarded to ignite the fuel-air mixture after compression top dead center and after the fuel has been injected.