| 摘要 |
PURPOSE:To make it possible to remove sulfur oxides while preventing the thermal deterioration of a catalyst by supplying the secondary air to the upstream side of an exhaust gas purifying catalyst under the condition of rich fuel-air ratio, and stopping the secondary air supply before the catalyst exceeds a fixed temperature. CONSTITUTION:The secondary air supply section 3, where an air cleaner 3A, a reed valve 3B and the secondary air supply valve 4 are arranged in order, is connected to the upstream side of an oxidizing catalyst 2 in an exhaust pipe 1a. The secondary air supply valve 4 is formed as a vacuum actuating valve, and its negative pressure part 4b is connected with a vacuum generating part 5 which is formed of a three port-two position directional control valve 5 and a vacuum reservoir 5B connected to an intake manifold 1b. The directional control valve 5A is controlled so that it may be changed through a control part 7 to the side of the vacuum reservoir 5B to open the valve 4 under the condition of a mixture being richer in a fuel-air ratio than its theoretical value, and to the atmospheric side before the catalyst exceeds a fixed temperature when the valve 4 has been opened to close the valve 4. |
