| 摘要 |
PURPOSE:To improve the scavenging efficiency and prevent knocking by constituting a timing changing means changing the valve timing of an exhaust valve so as to accelerate the valve opening timing of the exhaust valve when the detected supercharged air pressure exceeds a predetermined value. CONSTITUTION:An intake valve 15 and an exhaust valve 17b are opened or closed by cams 23a, 25a on cam shafts 23, 25 rotated synchronously with a crank shaft via tappets 43, 35a. The opening/closing timing of the exhaust valve 17 is made variable by displacing an operating shaft 39 in its axial direction with a motor 41 and rotating a rotary member 33a around the cam shaft 25. In this case, a supercharged air pressure detecting means detecting the supercharged air pressure generated by a supercharger is provided, and if the supercharged air pressure detected by it exceeds a predetermined value, control is performed so as to accelerate the valve opening timing of the exhaust valve 17 in response to an increase of the engine speed. Accordingly, the scavenging efficiency is improved as the engine speed is increased. |
