Negative pressure control apparatus for engine mounted in vehicle

摘要

A brake booster (50) is actuated based on negative pressure in an intake passage (32). When an engine is operating in the stratified charge combustion, an ECU (92) decreases the throttle opening size to lower the pressure in the intake passage (32) if the pressure in the brake booster (50), or a booster working pressure, is higher than a demanded value. When the booster working pressure is lower than the demanded value, the ECU (92) increases the throttle opening size as the difference between the booster working pressure and the demanded value increases. Therefore, when the difference between the booster working pressure and the demanded value is small, the booster working pressure is rapidly lowered if the booster working pressure increases above the demanded value. When the difference between the booster working pressure and the demanded value is great, the pumping loss of the engine is decreased.