Patent ID: 8099954

Claim:
An exhaust manifold comprising: a plurality of branch pipes that guide exhaust gas discharged from cylinders; and a junction pipe that converges downstream-side end portions of the plurality of branch pipes in a flow direction of exhaust gas, and that has a drawn portion that is formed by drawing so as to be constricted in a radial direction of the drawn portion, wherein the junction pipe is provided with a sensor that detects oxygen concentration in exhaust gas, and the sensor is provided at a downstream side of a deepest draw inside diameter in the flow direction of exhaust gas, and the deepest draw inside diameter is the smallest inside diameter of the drawn portion, the junction pipe includes a lead-in portion that is provided at an upstream side of the drawn portion in the flow direction of exhaust gas and that guides the exhaust gas discharged from the branch pipes, into the drawn portion, and a lead-out portion that is provided at the downstream side of the drawn portion in the flow direction of exhaust gas and that guides the exhaust gas out toward a purification catalyst device, and the drawn portion is formed so that an inner peripheral surface of the drawn portion is curved and protruded radially inwards, in a section of the drawn portion taken along an axial direction of the junction pipe.