| 摘要 |
<p>PURPOSE:To purify sufficiently exhaust in diagnosing failure of a switch valve. CONSTITUTION:Three air supply paths 23, 24, 25 capable of supplying secondary air are connected to an exhaust path 14 and provided respectively with valves 31, 32, 33. When the air supply paths 24, 25 are provided on the downstream side of exhaust flow in the valves 31, 32 to be diagnosed with respect to failures, secondary air is supplied from the air supply paths 24, 25 along with the closing motion of the valves 31, 32, while, when the air supply path is absent on the downstream of exhaust flow in the valve 33 to be diagnosed with respect to the failure, secondary air is supplied from the upstream side air supply path 24 before the valve 33 is closed. Thus, even in the diagnosis of the failure of the valves 31, 32, 33, the secondary air can be supplied to the exhaust path 14 to sufficiently purify the exhaust.</p> |
