| 摘要 |
<p>PURPOSE:To positively detect any failure of a valve timing switching mechanism by means of a relative simple constitution by comparing detection values of intake pressure on the upstream of an intake valve with a specified discriminant value. CONSTITUTION:In an engine 1, single pipe parts 2'' of an intake manifold 2' are con nected to respective cylinders, and throttle jets 24 are provided in single pipe parts 2'' close to an intake valve on the upstream of the intake valve. Surge tanks 26 are connected through pipes 5 to respective throttle jets 24, and further manifold absolute pressure sensor 16 are connected to the throttle jets. In the engine 1 where the valve timing V/T is switched to 'high speed' or 'low speed' depending on operating conditions, intake negative pressure in single pipe parts 2'' are smaller at the time of high speed V/T than that at the time of low speed V/T even when the opening of a throttle valve is the same. Thus, any abnormality with which a V/T switching mechanism remains fixed to high speed V/T is spite of low speed V/T indication, can be detected by comparing the intake negative pressures in respective cylinders detected during idle running of the engine by the manifold absolute pressure sensors 16 with a specified discriminant value.</p> |
