Abstract: A two-stroke engine comprising a spark plug arranged at the center of the inner wall of the cylinder head, and a fuel injector arranged on the periphery of the inner wall of the cylinder head. A depression extending from the point beneath the spark plug to the point beneath the tip portion of the fuel injector is formed on the top face of the piston. When the engine is operating under a light load, fuel is injected by the fuel injector only once toward the depression, and conversely, when the engine is operating under an intermediate load, fuel is injected twice. Namely, a first injection is carried out when the piston is at a lower position, and a second injection is carried out when the piston is at a higher position, to thus direct fuel toward the depression.

Abstract: An exhaust gas purification system for an internal combustion engine includes an engine capable of fuel combustion at lean air-fuel ratios, a catalyst constructed of zeolite carrying at least one kind of metal selected from transition metals and noble metals to reduce NOx under oxidizing conditions and in the presence of HC, engine operating condition detecting means for detecting the current engine operating condition, engine operating range determining means for determining whether or not the current engine operating condition is within an insufficient HC amount range, and an HC amount control means for controlling the amount of HC included in the exhaust gas when the engine operating range determining means determines that the engine operating condition is within the insufficient HC amount range.

Abstract: A fuel injector comprising a needle valve and a stop member cooperating with the needle valve. The stop member selectively controls the maximum amount of lift of the needle valve to provide a smaller maximum lift or a larger maximum lift thereof whereby, when the required amount of fuel to be injected by the fuel injector is small, the needle valve is lifted to the smaller maximum lift, and when the required amount of fuel is large, the needle valve is lifted to the larger maximum lift.

Abstract: An internal combustion engine comprising a piston having a top face with a depression formed therein, and a first fuel injector and a second fuel injector arranged on the inner wall of the cylinder head. Fuel is injected from the first fuel injector when the position of the piston is high, and fuel is injected from the second fuel injector when the position of the piston is low. The axes of fuel injection of both fuel injectors are determined such that fuel injected from the fuel injectors is directed to the central portion of the depression.

Abstract: A fuel supply device comprising a nozzle opening for injecting fuel and pressurized air. The opening operation of the nozzle opening is electromagnetically controlled by a needle. The nozzle of a fuel injector is arranged in a nozzle chamber. The nozzle chamber has an air inlet and an air outlet separately formed from and spaced from the air inlet. The air inlet is connected to a pressurized air source, and the air outlet is connected to the nozzle opening.

Abstract: A fuel supply device comprising an air compressor for supplying pressurized air to an air blast valve via a pressurized air passage, an oil supply device for supplying oil in an engine crankcase to the compressor, and an oil separator arranged in the pressurized air supply passage to separate oil from pressurized air discharged from the air compressor and return the thus-separated oil to the engine crankcase.

Abstract: An ignition device for an internal combustion engine comprising an ignition coil adapted to produce a secondary reversible voltage, two wires commonly branched from the one end of the ignition coil, and two spark plugs connected to the wires. In each of the two wires, there are provided a series gap forming device and a diode. The diodes are arranged in reverse directions relative to each other, so that the secondary high voltage generated in one direction can pass through one of the diodes and the secondary high voltage in the reverse direction can pass through the other diode, whereby a spark is realized at one end of the two spark plugs by a selective application of the primary current.