Excess air rate detecting apparatus and an excess air rate control apparatus for an engine

In an excess air rate control apparatus for an engine which is mounted in a vehicle and which includes a suction passage, an exhaust passage, a turbo charger for supercharging the engine with intake by driving a turbine by means of exhaust gas of the engine, and an exhaust gas recirculation system for recirculating part of the exhaust gas, taken out of the exhaust passage on an upstream side of the turbo charger, into the suction passage, the excess air rate control apparatus controlling, in accordance with operating conditions of the engine, an excess air rate of that air-fuel mixture which is supplied to the engine while the exhaust gas recirculation system is operating, the excess air rate control apparatus comprising:

• intake pressure detecting means for detecting an intake pressure of the engine;
• exhaust pressure detecting means for detecting an exhaust pressure of the engine;
• exhaust gas recirculation quantity estimating means for estimating a quantity of recirculation of the exhaust gas by the exhaust gas recirculation system in accordance with the intake pressure detected by said intake pressure detecting means and the exhaust pressure detected by said exhaust pressure detecting means;
• total intake quantity detecting means for detecting a total intake quantity of the engine, including the quantity of the exhaust gas recirculated by the exhaust gas recirculation system;
• equivalent intake air quantity estimating means for estimating an equivalent intake air quantity of the engine;
• fuel supply quantity setting means for setting a quantity of fuel supply to the engine in accordance with a depression amount of an accelerator pedal of the vehicle;
• fuel supply means for supplying a fuel to the engine in accordance with the fuel supply quantity set by said fuel supply quantity setting means;
• excess air rate estimating means for estimating the excess air rate for the engine in accordance with the fuel supply quantity set by said fuel supply quantity setting means and the equivalent intake air quantity estimated by said equivalent intake air quantity estimating means;
• storage means for storing the excess air rate estimated by said excess air rate estimating means;
• target excess air rate setting means for setting a target excess air rate of the air-fuel mixture supplied to the engine;
• valve opening degree setting means for setting a target valve opening degree of the exhaust gas recirculation system in accordance with the excess air rate estimated by said excess air rate estimating means and the target excess air rate set by said target excess air rate setting means;
• and
• operation control means for controlling operation of the exhaust gas recirculation system in accordance with the target valve opening degree set by said valve opening degree setting means,
• said equivalent intake air quantity estimating means for estimating the equivalent intake air quantity in accordance with the total intake quantity detected by said total intake quantity detecting means, the excess air rate stored in said storage means and estimated for a last cycle but a predetermined number of cycles, and the exhaust gas recirculation quantity estimated by said exhaust gas recirculation quantity estimating means.

In an excess air rate detecting apparatus for an engine which is mounted in a vehicle and which includes a suction passage and an exhaust gas recirculation system for recirculating part of exhaust gas into the suction passage, the excess air rate detecting apparatus repeatedly detecting, in accordance with operating conditions of the engine, an excess air rate of that air-fuel mixture which is supplied to the engine while the exhaust gas recirculation system is operating, the excess air rate detecting apparatus comprising:

• intake pressure detecting means for detecting an intake pressure of the engine;
• exhaust gas recirculation quantity estimating means for estimating a quantity of recirculation of the exhaust gas by the exhaust gas recirculation system in accordance with at least the intake pressure detected by said intake pressure detecting means;
• equivalent intake air quantity estimating means for estimating an equivalent intake air quantity of the engine;
• fuel supply quantity setting means for setting a quantity of fuel supply to the engine;
• excess air rate estimating means for estimating the excess air rate for the engine in accordance with the fuel supply quantity set by said fuel supply quantity setting means and the equivalent intake air quantity estimated by said equivalent intake air quantity estimating means;
• and
• storage means for storing the excess air rate estimated by said excess air rate estimating means,
• said equivalent intake air quantity estimating means estimating the quantity of recirculation of the exhaust gas in accordance with at least the exhaust gas recirculation quantity estimated by said exhaust gas recirculation quantity estimating means and the excess air rate stored in said storage means and estimated for a last cycle but a predetermined number of cycles.