A method of protecting a diesel particulate filter from overheating

摘要

Disclosed is a method of operating a Diesel internal combustion engine which prevents overheating of a diesel particulate trap, DPF 15, when an engine 10 from which the diesel particulate trap 15 receives a flow of exhaust gas is idling and regeneration of the DPF 15 is occurring. The method comprises using an electric machine such as an electric motor/generator 16 to apply a load to the engine 10 and compensating for the increase in applied load by increasing an engine torque set point. The load provides a drag on the engine and allows the engine to operate with a richer air to fuel ratio than would normally be the case when idling. This causes the quantity of oxygen reaching the DPF 15 to drop, slowing the rate of soot combustion at the DPF 15 and thus lowering the temperature of the DPF 15. The embodiment uses a rechargeable battery-operated starter-generator as the electric motor. The electric motor may also be used to provide a limited torque boost to the engine when accelerated. An associated vehicle using the method is also disclosed.