Abstract: During a transient period, the opening degree of a throttle valve (throttle opening degree) is varied from a steady-period target throttle opening degree in a region A1 toward a valve closing side by a predetermined amount ?P, and is thereafter controlled so as to become a steady-period target throttle opening degree in the region A1. The transient period is a transient period in which the operation state is shifted from a region B2 in which an air-fuel ratio in a supercharged state becomes a predetermined lean air-fuel ratio to a region A1 in which the air-fuel ratio in a non-supercharged state becomes a predetermined rich air-fuel ratio richer than the lean air-fuel ratio. In this transient period, by reducing the air amount in a cylinder, the combustion torque of an internal combustion engine is suppressed, and consequently; a torque overshoot can be suppressed.

Abstract: A negative pressure control valve (44) is disposed in a part of an intake passage (12) upstream of a confluence (30) of an EGR passage (27) and the intake passage (12). When in an EGR region (Regr) where an EGR gas is recirculated to the intake passage (12) through the EGR passage (27), the negative pressure control valve (44) is controlled in a manner to ensure a differential pressure between an exhaust passage (13) and the intake passage (12). When in an operation region (R2) lower in load than the EGR region (Regr), the negative pressure control valve (44) is controlled in a closing direction so as to suppress occurrence of noise.

Abstract: During a transient period, the opening degree of a throttle valve (throttle opening degree) is varied from a steady-period target throttle opening degree in a region A1 toward a valve closing side by a predetermined amount ?P, and is thereafter controlled so as to become a steady-period target throttle opening degree in the region A1. The transient period is a transient period in which the operation state is shifted from a region B2 in which an air-fuel ratio in a supercharged state becomes a predetermined lean air-fuel ratio to a region A1 in which the air-fuel ratio in a non-supercharged state becomes a predetermined rich air-fuel ratio richer than the lean air-fuel ratio. In this transient period, by reducing the air amount in a cylinder, the combustion torque of an internal combustion engine is suppressed, and consequently; a torque overshoot can be suppressed.

Abstract: An intake control method for an internal combustion engine equipped with a low-pressure EGR system includes setting a target intake pressure, which is a target value of an intake pressure in an intake passage between a negative pressure generating valve and an intake throttle valve, necessary for performing EGR control in a state of an exhaust pressure determined for each operating point, setting a target total opening area, which is a sum of a target opening area of an EGR valve and a target opening area of the negative pressure generating valve, on the basis of the target intake pressure, a target fresh air amount, and a target EGR gas amount, setting a target EGR valve opening area, which is an opening area of the EGR valve for achieving the target EGR gas amount, assuming that the negative pressure generating valve is fully open, and setting a value obtained by subtracting the target EGR valve opening area from the target total opening area to be a target negative pressure generating valve opening area, w

Abstract: A basic opening (A0) of an EGR control valve (22) is set, based on a current engine operation state. A differential pressure (?P1) across the EGR control valve (22) is calculated, based on an actual exhaust system temperature (T1) sensed by an exhaust temperature sensor (33). A reference differential pressure (?P0) is calculated, which is a differential pressure across the EGR control valve (22) in a steady state corresponding to the current engine operation state. A reference pulsation amplitude (D) is calculated, which is an amplitude of pulsation of the reference differential pressure (?P0). The basic opening (A0) is corrected, based on the differential pressure (?P1), the reference differential pressure (?P0), and the reference pulsation amplitude (D).

Abstract: An intake control method for an internal combustion engine equipped with a low-pressure EGR system includes setting a target intake pressure, which is a target value of an intake pressure in an intake passage between a negative pressure generating valve and an intake throttle valve, necessary for performing EGR control in a state of an exhaust pressure determined for each operating point, setting a target total opening area, which is a sum of a target opening area of an EGR valve and a target opening area of the negative pressure generating valve, on the basis of the target intake pressure, a target fresh air amount, and a target EGR gas amount, setting a target EGR valve opening area, which is an opening area of the EGR valve for achieving the target EGR gas amount, assuming that the negative pressure generating valve is fully open, and setting a value obtained by subtracting the target EGR valve opening area from the target total opening area to be a target negative pressure generating valve opening area, w

Abstract: A basic opening (A0) of an EGR control valve (22) is set, based on a current engine operation state. A differential pressure (?P1) across the EGR control valve (22) is calculated, based on an actual exhaust system temperature (T1) sensed by an exhaust temperature sensor (33). A reference differential pressure (?P0) is calculated, which is a differential pressure across the EGR control valve (22) in a steady state corresponding to the current engine operation state. A reference pulsation amplitude (D) is calculated, which is an amplitude of pulsation of the reference differential pressure (?P0). The basic opening (A0) is corrected, based on the differential pressure (?P1), the reference differential pressure (?P0), and the reference pulsation amplitude (D).

Abstract: A negative pressure control valve (44) is disposed in a part of an intake passage (12) upstream of a confluence (30) of an EGR passage (27) and the intake passage (12). When in an EGR region (Regr) where an EGR gas is recirculated to the intake passage (12) through the EGR passage (27), the negative pressure control valve (44) is controlled in a manner to ensure a differential pressure between an exhaust passage (13) and the intake passage (12). When in an operation region (R2) lower in load than the EGR region (Regr), the negative pressure control valve (44) is controlled in a closing direction so as to suppress occurrence of noise.