An engine system is provided, which includes an engine, a swirl control valve, and a controller. The engine includes a cylinder, a piston, and a fuel injection valve provided incliningly with respect to an axial direction of the piston and configured to directly inject fuel into the cylinder. The swirl control valve is provided inside an intake passage and generates a swirl flow inside the cylinder at least when the valve closes. When an engine load is below a given threshold, the controller controls the swirl control valve to close, and controls the fuel injection valve to inject fuel during an intake stroke. While the engine load is below the threshold, at a fixed engine speed, the controller controls to advance a fuel injection timing when the engine load is at a first load, compared with at a second load higher than the first load.

An engine system is provided, which includes an engine, a swirl control valve, an EGR passage, an EGR gas adjusting mechanism, and a controller. The engine includes a cylinder, a piston, and a fuel injection valve. The swirl control valve is provided inside an intake passage and generates a swirl flow inside the cylinder when it closes. When an engine load is at or below a given threshold, the controller controls the swirl control valve to close. While the engine load is the threshold or below, the controller controls the EGR gas adjusting mechanism such that, at a fixed engine speed, an increase rate of an EGR gas amount with respect to an increase in the engine load is lower in a first load range than in a second load range, the first load range being on a higher load side of the second load range and including the threshold.

As a control method for internal combustion engine, a part of a low-medium revolution speed/low-medium load region of an internal combustion engine is set as a lean combustion region, homogeneous combustion is performed in an operating region within the lean combustion region where a load is relatively low, by injecting fuel at least once between an intake stroke and the first half of a compression stroke to form a homogeneous air-fuel mixture in a combustion chamber, and stratified combustion is performed in an operating region within the lean combustion region where the load is relatively high, by injecting the fuel at least once, respectively, between the intake stroke and the first half of the compression stroke as well as in the second half of the compression stroke to form a stratified air-fuel mixture in the combustion chamber. In this control method, ignition energy supplied to an ignition plug when the stratified combustion is performed is controlled to be smaller than ignition energy supplied to the ignition plug when the homogeneous combustion is performed.

A PCM (60) performs a catalyst early warming control (AWS control) for accelerating warm-up of a catalytic device. When the catalytic device (35) is not in an activated state and a vehicle is traveling, the PCM (60) is configured to perform: a fuel injection control to inject fuel such that a homogeneous fuel-air mixture can be formed in a combustion chamber (11) of an engine (10) so as to generate a homogeneous combustion; an intake air amount control to increase intake air amount; and an ignition control to retard ignition timing from a reference ignition timing. In addition, the PCM (60) is configured to vary ignition timing retard amount corresponding to a difference between the ignition timing retarded by the ignition timing control and the reference ignition timing, in accordance with engine speed and/or engine load.

A hybrid vehicle has an engine (E) that is capable of changing a combustion mode between a stoichiometric combustion mode and a lean combustion mode and a motor/generator (MG) that is capable of performing torque assist by a power running operation and torque absorption by a regenerative operation. As a boundary between a stoichiometric combustion operating region and a lean combustion operating region, a second boundary (L2) at a torque decrease has a hysteresis at a low torque side with respect to a first boundary (L1) at a torque increase. Upon shift from the stoichiometric combustion operating region to the lean combustion operating region, for delay in increase of an intake-air quantity, decrease in fuel and the torque assist by the motor/generator (MG) are carried out, and an exhaust air-fuel ratio is changed stepwise.

Methods and systems are provided for estimating a temperature of a direct injector. In one example, a method may include estimating the temperature of the direct injector based on a resistance of a solenoid coil of the direct injector. In one example, a pulse-width of the direct injector during an opening phase is adjusted in response to the temperature.

An acquisition unit acquires a required torque and an operating state of an internal combustion engine. A control unit is configured to: control operation of the internal combustion engine by using a required air amount, a required fuel amount, and a required ignition timing; acquire a required air amount by using the acquired required torque and a target air-fuel ratio of an air system determined according to the operating state; perform torque fluctuation correction on the target air-fuel ratio of the air system to determine a target air-fuel ratio of an injection system to reduce a difference between the required torque and an actual torque in a transition period between stoichiometric combustion and lean combustion; acquire a required fuel amount and a required ignition timing by using the determined target air-fuel ratio of the air system and the determined target air-fuel ratio of the injection system.

An internal combustion engine (1) is provided with a turbocharger (2), and is configured to be switchable between a stoichiometric combustion mode having a theoretical air-fuel ratio as a target air-fuel ratio and a lean combustion mode having a lean air-fuel ratio as a target air-fuel ratio. An air bypass valve (20) is provided in an air bypass passage (19) communicating a collector (11a) on the downstream of a throttle valve (12) with the upstream side of a compressor (2b) in an intake passage (11). At the time of the shifting from the lean combustion mode to the stoichiometric mode, the throttle valve (12) is closed and the air bypass valve (20) is temporarily opened to decrease the pressure inside the collector (11a) quickly.

A two-stroke engine (4) has a throttle motor (22) for driving a throttle valve (20), a fuel injection device (430) disposed in an intake system (18) including a crank chamber (420), and a control unit (24) controlling the throttle motor (22) and the fuel injection device. The two-stroke engine (4) is designed to achieve an engine rotation speed of 4,500 rpm to 7,000 rpm when the throttle valve (20) is fully open. The two-stroke engine (4) is operated with the throttle full open by the control unit (24), and a battery (8) is charged with electric power generated by a generator (6) using the two-stroke engine.

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 ΔP, 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.