METHOD OF REDUCING NOX EMISSIONS FROM AN ENGINE

摘要

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.

主权项

1. A vehicle comprising:
an engine having an exhaust gas recirculation (EGR) valve controllable to supply exhaust gas to an engine intake; an emissions control device disposed in an exhaust flow downstream of the engine; a lambda sensor disposed in the engine intake to measure an EGR ratio in the engine intake; an electric machine connected to the engine and a battery; and a controller communicating with the EGR valve, the sensor, and the electric machine, the controller programmed to, in response to an increased rate of requested engine torque during an acceleration event resulting in predicted NOx feedgas emissions exceeding a threshold, the NOx feedgas emissions determined by a NOx model based on engine speed, engine torque, and the EGR ratio measured by the lambda sensor, control the electric machine to provide an assist torque and correspondingly reduce the rate of increase of requested engine torque to meet a driver demand torque.