| 摘要 |
PURPOSE:To enhance response to accelerating an engine which is supplied with lean mixture at the time of low-speed operation and to increase the engine output, by making the volume of an intake passage from the position thereof located on the downstream side of a throttle valve to the position of an intake valve equal to or smaller than 1/3 of the total stroke volume of the engine, and delaying the valve closing time of the intake valve at the time of high-speed operation of the engine. CONSTITUTION:In an engine which is supplied with lean mixture at the time of steady, low-speed operation and supplied with rich mixutre at the tine of high-output operation, the volume of an intake passage 28 from the position thereof located on the downstream side of a throttle valve 31 to the position of an intake valve 26 is selected to be equal to or smaller than 1/3 of the total stroke volume of the engine. Further, the valve closing timing of the intake valve 26 is varied according to the engine speed. That is, the valve closing timing of the intake valve 26 at the low-speed operation of the engine is set at the position near the bottom dead point while it is delayed at the time of high-speed operation of the engine. Thus, since the volume of the intake passage on the downstream side of the intake valve is small, it is enabled to enhance response for accelerating an engine and to raise the charging efficiency by the pulsation effect of intake-air flow. |
