Patent ID: 6647962
Filing Date: 2003-11-18
Classification: F01L,F02B,F02D,F02F,Y02T

Abstract:
An outboard motor provided with an internal combustion engine comprising:a vertical crankshaft; a cylinder head provided, for one combustion chamber, with an intake port terminating in a pair of intake openings, and an exhaust port terminating in exhaust openings; a pair of intake valves for opening and closing the pair of intake openings; a pair of exhaust valves for opening and closing the exhaust openings; a valve train for operating the pair of intake valves and the pair of exhaust valves for opening and closing operation; and a fuel supply device for supplying a liquid fuel into an air intake passage connected to the pair of intake openings; wherein the intake port has a main section, an upper branch section branching from a downstream end of the main section, and a lower branch section branching from the downstream end of the main section and extending below the upper branch section; the pair of intake openings are an upper intake opening of the upper branch section, and a lower intake opening of the lower branch section, respectively; the pair of intake valves are a first intake valve for opening and closing the upper intake opening, and a second intake valve for opening and closing the lower intake opening, respectively; the valve train includes a valve-operation mode changing mechanism capable of changing the respective operating modes of the first and the second intake valve according to engine speed; and the valve-operation mode changing mechanism has a mode selecting system for making the valve-operation mode changing mechanism pause the opening and closing operation of the first intake valve, hold the first intake valve at its closed position and operate the second intake valve for opening and closing operation while the internal combustion engine is operating at engine speeds in a low-speed range.