Method and apparatus for controlling vacuum pressure in internal combustion engine

An apparatus for controlling vacuum in a vehicle, wherein the vehicle comprises:

• a) an engine, wherein the engine performs stratified combustion, the engine including:
• a combustion chamber;
• an air intake passage for introducing air to the combustion chamber;
• a throttle valve located in the intake passage for controlling airflow in the intake passage, the throttle valve being movable between a fully open position and a closed position, wherein the throttle valve is in an open position when the engine performs stratified charge combustion, and wherein the throttle valve decreases the pressure in the intake passage when the throttle valve is moved toward the closed position;
• and
• an exhaust passage for discharging exhaust gas from the combustion chamber;
• an exhaust gas recirculation passage connecting the exhaust passage with the intake passage to recirculate some of the exhaust gas to the intake passage;
• and
• an exhaust gas flow control valve for regulating the flow of exhaust gas passing through the recirculation passage;
• b) a brake booster for increasing the braking force of the vehicle, wherein the brake booster has a vacuum pressure chamber connected to the intake passage;
• c) sensor for detecting the pressure of the vacuum chamber;
• d) determining means for determining whether the pressure in the vacuum chamber is higher than a reference level based on the detected pressure and for determining whether the pressure in the vacuum chamber is deficient;
• and
• e) a controller for controlling the exhaust gas regulator to positively restrict the recirculation of exhaust gas when the controller determines that the detected pressure is higher than the reference level, wherein the controller moves the throttle valve toward the closed position to decrease the pressure in the vacuum chamber when the determining means determines that the pressure of the vacuum chamber is deficient and after the recirculation of exhaust gas has been restricted.

A method for controlling vacuum in a vehicle comprising:

• controlling air flow to an engine through an intake passage with a throttle valve;
• producing, at selected times, a vacuum in the engine with the throttle valve;
• recirculating exhaust from the engine to the intake passage at certain times;
• employing the vacuum produced in the engine to maintain a vacuum in a vacuum chamber, which is used to increase a vehicle braking force;
• detecting the pressure of the vacuum chamber;
• determining whether the pressure of the vacuum chamber is higher than a reference level;
• determining whether the pressure in the vacuum chamber is at a deficiency level;
• restricting the recirculation of exhaust gas when the detected pressure is higher than the reference level;
• and
• controlling the throttle valve to reduce the pressure in the intake passage and consequently to reduce the pressure in the vacuum chamber when it is determined that the pressure in the vacuum chamber is at the deficiency level.