Method and system for improved dilution purging
AssigneeFord Global Technologies, LLC
InventorsDaniel Joseph Styles, Stanley Larue Bower, James Alfred Hilditch, Robert Ralph Iorio, Gopichandra Surnilla
Life of this patent
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Abstract
Methods and systems are provided for expediting EGR purging in a hybrid vehicle during transient operations, such as tip-out to lower load conditions. In response to decreasing engine torque demand, engine fueling is disabled and a motor is used to spin the engine unfueled until a desired LP-EGR rate is achieved. Alternatively, engine operation is maintained with EGR disabled until the desired LP-EGR rate is achieved, and the excess engine torque generated is stored in a system battery.
Claims20
A method for a hybrid vehicle, comprising:
- in response to decreasing engine load while operating an engine with EGR, determining an EGR amount in an intake, and selecting from among a first method of engine operation and a second method of engine operation based on the determined amount of EGR in the intake,
- when the first method is selected, disabling fuel to the engine while using motor torque to propel the vehicle;
- and
- while propelling the vehicle,
- with each of an EGR valve and an intake throttle fully open, spinning the engine unfueled via a motor until the EGR amount is less than a threshold;
- and
- when the second method is selected, operating the engine fueled with the EGR valve closed while using additional torque to charge a battery until the determined EGR amount is less than another threshold.
A method for an engine in a hybrid vehicle, comprising:
- during a first engine shutdown from operating with EGR, disabling fuel injection, and with an EGR valve and an intake throttle fully open, spinning the engine unfueled via a motor until a determined EGR amount in an intake is below a threshold while propelling the vehicle using motor torque;
- and
- during a second engine shutdown from operating with EGR, closing the EGR valve, spinning the engine fueled to generate engine torque in excess of torque demanded for vehicle propulsion, and propelling the vehicle using engine torque until the determined EGR amount is below the threshold while charging a battery with excess engine torque, wherein the first engine shutdown is selected responsive to a state of charge of the battery being above a threshold charge and wherein the second engine shutdown is selected responsive to the state of the charge of the battery being below the threshold charge.
A hybrid vehicle system, comprising:
- an engine including an intake and an exhaust;
- an intake throttle;
- an electric motor/generator coupled to a battery;
- vehicle wheels propelled using torque from one or more of the engine and the electric motor/generator;
- a direct fuel injector coupled to an engine cylinder;
- a turbocharger including an intake compressor driven by an exhaust turbine;
- an EGR passage for flowing EGR from the exhaust, downstream of the turbine, to the intake, upstream of the compressor, via an EGR valve;
- a sensor for determining an amount of EGR in the intake;
- and
- a controller with computer readable instructions for:
- during a tip-out from operating the engine with EGR flowing,
- disabling the fuel injector;
- fully opening each of the EGR valve and the intake throttle;
- and
- using torque from the motor to meet an operator torque demand and spin the engine unfueled, the engine spinning continued for a duration while propelling a vehicle using motor torque until the determined amount of EGR in the engine is lower than a threshold, the threshold determined based on the operator torque demand.
Dependencies are inferred from the claim text.