Apparatus for determining an abnormality of a control valve of an internal combustion engine

An apparatus for determining an abnormality of a control valve, the apparatus being applied to an internal combustion engine having:

• a first supercharger comprising a first turbine disposed in an exhaust gas passage of the engine and a first compressor disposed in an intake air passage of the engine and driven by the first turbine which is driven by an exhaust gas flowing in the exhaust gas passage;
• a second supercharger comprising a second turbine disposed in the exhaust gas passage at a downstream side of the first turbine and a second compressor disposed in the intake air passage at an upstream side of the first compressor and driven by the second turbine which is driven by the exhaust gas;
• a first passage section whose one end is connected to the exhaust gas passage at an upstream side of the first turbine and whose the other end is connected to the exhaust gas passage between the first turbine and the second turbine;
• a first control valve, disposed in the first passage section, for varying a flow passage area of the first passage section depending on an opening degree of the first control valve;
• a second passage section whose one end is connected to the intake air passage between the first compressor and the second compressor and whose the other end is connected to the intake air passage at a downstream side of the first compressor, and
• a second control valve, disposed in the second passage section, for varying a flow passage area of the second passage section depending on an opening degree of the second control valve,
• the engine is configured in such a manner that the first control valve and the second control valve are operated in such a manner that the first supercharger superchargers the engine more efficiently than the second supercharger when the engine is operated in a predetermined operating area,
• the apparatus for determining an abnormality of a control valve comprising an electronic control unit having control logic configured to cause the electronic control unit to perform the following:
• first operation to obtain a supercharging-pressure-corresponding-value which becomes larger as a pressure of air in the intake air passage at the downstream side of the first compressor becomes larger;
• second operation to obtain, as a first value, the obtained supercharging-pressure-corresponding-value;
• operate the first control valve, at a first timing after the timing at which the first value is obtained, in such a manner that the opening degree of the first control valve coincides with a second opening degree different from a first opening degree which is an opening degree of the first control valve at a timing when the first value is obtained;
• and
• obtain, as a second value, the obtained supercharging-pressure-corresponding-value at a second timing at which a predetermined time has elapsed from the first timing,
• during a period in which an abnormality determining condition including at least a condition that the engine is operated in the predetermined area is satisfied,
• and
• third operation to determine that the second control valve is abnormal, if the second opening degree is larger than the first opening degree and the second value is larger than the first value, or if the second opening degree is smaller than the first opening degree and the second value is smaller than the first value.