| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an exhaust gas turbocharger capable of ensuring overall, accurate boost pressure control.SOLUTION: A scroll chamber 7 in which exhaust gas flows and a bypass passage 13 through which the exhaust gas is released are formed in a turbine housing 4. The bypass passage 13 is opened or closed by a wastegate valve 14. The wastegate valve 14 includes a boss 23 entering into the scroll chamber 7, and a tip end surface 23a of the boss 23 constitutes an inner surface of the scroll chamber 7 in a state in which the wastegate valve 14 is closed. Just under the downstream side of the boss 23 is a concave portion 7d recessed toward a valve chamber 16, and a flow passage area increases in a starting end 7a of the scroll chamber 7 in a state in which the wastegate valve 14 is fully opened. This can reduce the kinetic energy of the exhaust gas acting on a turbine blade when the wastegate valve 14 is fully opened and prevent or considerably suppress a boost pressure from remaining. Since a change in the kinetic energy of the exhaust gas with respect to the opening of the wastegate valve 14 is slow in an initial state in which the wastegate valve 14 is opened, the fine adjustment of the boost pressure can be accurately made.</p> |
