A system and method for reducing rate of increase of NOx feedgas emissions during an acceleration event in a vehicle having an engine with exhaust gas recirculation (EGR) and an electric machine, such as an integrated starter-generator (ISG) coupled to the engine include operating the electric machine to provide an assist torque and reducing engine torque accordingly in response to predicted NOx feedgas emissions exceeding a threshold. The NOx feedgas emissions may be predicted based on an exhaust gas sensor signal or a NOx model based on engine speed, engine torque, and intake EGR ratio. The engine torque may be reduced by reducing an engine torque set point. The electric machine torque may be reduced when a driver demand torque matches the reduced engine torque set point. The electric machine may be used to charge a battery in response to the driver demand torque matching the engine torque set point.

A control apparatus for a hybrid vehicle is provided with: an air-fuel ratio determinator configured to determine an air-fuel ratio of an internal combustion engine in a predetermined period until speed change by a transmission is actually performed; and a controller configured to control at least one of the internal combustion engine and an electric motor in such a manner that a possible amount of torque down of the internal combustion engine is increased if the air-fuel ratio of the internal combustion engine is lean in the predetermined period. By this, it is possible to avoid a detrimental effect, such as a torque shock, deterioration of durability of a friction material, and the like, which can occur in the speed change.

A control device for a hybrid vehicle, which can inhibit damage to an exhaust purification catalyst and also suppress deterioration of drivability, is provided. The control device exercises catalyst protective control, which inhibits operation of an engine and drives a traction motor, if a state where an exhaust air-fuel ratio detected by an exhaust air-fuel ratio detection unit is lean continues for a first predetermined time or longer.

A system and method for power management of hybrid electric vehicles is provided. In some implementations, a plug-in series hybrid electric vehicle may include an engine, a motor/generator (MG), a traction motor, an energy storage device, and a controller. The controller is coupled to the engine and the MG to control operation of the engine and the MG such that a state-of-charge (SOC) of the energy storage device tracks a dynamic reference SOC profile during a trip and an average engine power (AEP) is maintained above a threshold. In some instances, maintaining AEP above a threshold supports emission control of the vehicle.

A hybrid vehicle may include: an engine including a plurality of cylinders for generating power required for driving the hybrid vehicle by combustion of fuel; a first motor starting the engine and selectively operating as a generator to generate electrical energy; a second motor generating power required for driving the hybrid vehicle; a clutch provided between the engine and the second motor; and a controller configured for synchronizing a velocity of the second motor and an engine velocity and for coupling the clutch, in a transition section in which the engine moves from a stop state to an optimal operation point area as an operation area of the engine, and gradually decreasing a torque of the second motor and gradually adjusting the number of combusted cylinders among the plurality of combustion chambers to gradually increase the engine torque.

An electronic control unit includes processing circuitry. A hybrid electric vehicle has an electric traveling mode, in which the hybrid electric vehicle travels with a system clutch disengaged and an engine in a stopped state, and a hybrid traveling mode, in which the hybrid electric vehicle travels with the system clutch engaged and engine operating. The processing circuitry is configured to control, when the traveling mode is switched from the electric traveling mode to the hybrid traveling mode, a throttle opening degree of the engine at the time of completion of engagement of the system clutch in accordance with the atmospheric pressure such that a constant intake air amount is obtained regardless of the level of the atmospheric pressure.