appropriate level.
In general, the WGV is driven by using a positive-pressure actuator. The mechanism of driving the WGV is as follows. Specifically, the intake passage of the engine (particularly, an upstream portion of a throttle valve, in which the pressure increases) and a wastegate actuator (hereinafter referred to as “WGA”) are connected to each other. When the pressure in the intake passage of the engine becomes higher than an atmospheric pressure, an operation of the WGA is enabled. In general, the WGV, which is a bypass valve, is maintained in a fully-closed position until the operation of the WGA is enabled.
The turbine provided in the exhaust passage blocks the passage of the exhaust gas from a combustion chamber, and therefore becomes a factor for an increase in exhaustpressure. As the exhaust pressure increases, an exhaust loss becomes larger to lower the efficiency of the engine.
With a conventional configuration, an opening degree of the WGV cannot be operated unless the pressure in the intake passage of the engine increases. Therefore, when the pressure in the intake passage such as that during the operation of the engine in the non-supercharging operation range is equal to or lower than a predetermined value, the WGV is not operated even when an opening-degree changing request for the WGV is issued. Therefore, the efficiency of the engine is lowered.
In view of the above-mentioned situation, in recent years, there has been proposed a system including a motorized WGA, which is capable of operating the WGV when needed regardless of the pressure in