| 摘要 |
PURPOSE:To improve the combustion in high loading, securing the combustion in low loading, by forming the valve head part of a poppet valve from the three-dimensional curved surface in barrel form or spherical form and varying the angle of spread of fuel spray according to the amount of lift of the poppet valve. CONSTITUTION:A contracted part 21 is formed in the vicinity of the lower edge of a poppet valve 20, and a valve head part 22 in barrel form or spherical form is formed contiguously to said contracted part 21. The upper part of the valve head part 22 constitutes a valve contact part 23. An injection port is constituted of a cylindrical part 25, spherical part 26, and a conical part 27, and said spherical part 27 cuts-off fuel, in cooperation with the valve contact part 23. Since the poppet valve lifts little in low loading, a throttle part 28 forms the smallest sectional area part in a fuel passage, and the flow speed of fuel becomes max. in this range, and the fuel is atomized. In high loading, the amount of lift of the poppet valve increases, and the gap between the conical part 27 of the injection port and the valve head part 22 increases, and the flow speed in the vicinity of the outer peripheral surface of the valve head part 22 reduces, and the degree of atomization of fuel is reduced. |
