Method and system for particulate filter regeneration

Patent metadata

Field	Value
Publication number	US-2019345857-A1
Application number	US-201815975583-A
Country	US
Kind code	A1
Filing date	May 9, 2018
Priority date	May 9, 2018
Publication date	Nov 14, 2019
Grant date	—

Abstract

Methods and systems are provided for heating an exhaust particulate filter (PF) to enable filter generation. In one example, a method may include adjusting engine air fuel ratio and injecting secondary air flow upstream of the PF to increase PF temperature. The level of engine air fuel ratio adjustment and the amount of secondary air injection upstream of the PF may be adjusted to account for enrichment induced cooling at a three-way catalyst (TWC) positioned upstream of the PF.

First claim

1 . A method, comprising:
routing exhaust gases from an engine through a three-way catalyst (TWC) and then through a gasoline particulate filter (GPF); controlling enrichment of the engine exhaust gases to be overall richer than stoichiometry at the GPF; injecting air into the GPF to create an exotherm with the enriched exhaust gases entering the GPF; and controlling a degree of the enrichment to reduce any induced cooling of the TWC caused by the enrichment.

2 . The method of claim 1 , wherein the injecting air into the GPF is from an air pump via a first air passage and a first air injector, the first air passage including a first control valve.

3 . The method of claim 1 , wherein creation of the exotherm is in response to the GPF having each of a higher than threshold particulate matter load, a higher than first threshold temperature, and a lower than second threshold temperature.

4 . The method of claim 3 , wherein the first threshold temperature is an oxidation temperature of particulate matter deposited on the GPF and the second threshold temperature is an ignition temperature of air and fuel in an exhaust passage upstream of the GPF.

5 . The method of claim 3 , further comprising, in response to the GPF having each of the higher than threshold particulate matter load and the lower than second threshold temperature, one or more of retarding spark of engine ignition timing from maximum brake torque timing and operating engine cylinders with cylinder-to-cylinder air-fuel imbalance until GPF temperature reaches the first threshold temperature, the imbalance adjusted to maintain an overall stoichiometric exhaust air-fuel ratio.

6 . The method of claim 5 , wherein operating engine cylinders with cylinder-to-cylinder air-fuel imbalance includes operating a first set of cylinders at richer than stoichiometry while operating a second set of cylinders at leaner than stoichiometry, a number of cylinders in each of the first set and the second set based on each of a difference between a measured particulate filter temperature and the first threshold temperature, and a measured mass air flow.

7 . The method of claim 1 , wherein the degree of the enrichment is adjusted in response to a decrease in TWC temperature during the enrichment of the engine exhaust gases, the degree of enrichment decreased in response to a higher than threshold rate of decrease in TWC temperature.

8 . The method of claim 2 , further comprising adjusting an amount of air injected upstream of the GPF based on a difference between a requested air flow and a measured air flow, wherein the requested air flow is estimated as a function of each of a desired engine air fuel ratio, a desired GPF air fuel ratio, and an engine air mass, and wherein the measured air flow is a function of each of an estimated engine air fuel ratio, an estimated GPF air fuel ratio, and the engine air mass.

9 . The method of claim 8 , wherein the adjusting the amount of air injected upstream of the GPF includes adjusting a duty cycle of an exhaust air injection pump and/or adjusting an opening of the first control valve, the duty cycle of the exhaust air injection pump increased and/or the opening of the first control valve increased in response to an increase in a difference between the requested air flow and the measured air flow.

10 . The method of claim 8 , wherein each of the desired engine air fuel ratio and the desired GPF air fuel ratio is based on the second threshold temperature, the GPF air fuel ratio being the air fuel ratio of exhaust gas reaching the GPF.

11 . The method of claim 5 , further comprising, during cold-start conditions, operating the engine with richer than stoichiometry air fuel ratio and/or operating engine cylinders with cylinder-to-cylinder air-fuel imbalance while injecting air to an exhaust passage upstream of the TWC via a second air injector coupled to a second air passage, the second air passage including a second control valve.

12 . A method, comprising:
routing exhaust gases from an engine through an exhaust catalyst and then through a gasoline particulate filter (GPF); prior to exhaust catalyst light-off, adjusting engine air fuel ratio and injecting secondary air flow upstream of the exhaust catalyst; and after the exhaust catalyst light-off, in response to each of a higher than threshold particulate matter load on the GPF, and a lower than threshold GPF temperature, adjusting the engine air fuel ratio and injecting the secondary air flow upstream of the GPF to regenerate the GPF while maintaining the exhaust catalyst above a light-off temperature.

13 . The method of claim 12 , wherein the adjusting the engine air fuel ratio includes one or more of enriching engine air fuel ratio and operating engine cylinders with an air-fuel imbalance.

14 . The method of claim 12 , wherein the maintenance of the exhaust catalyst temperature above the light-off temperature includes one or more of reducing a level of the engine enrichment/air-fuel imbalance and reducing the secondary air flow upstream of the GPF in response to exhaust catalyst temperature reducing to below a threshold exhaust catalyst temperature, the threshold exhaust catalyst temperature higher than the light-off temperature.

15 . The method of claim 12 , wherein the injecting secondary air flow upstream of the exhaust catalyst includes adjusting an amount of the secondary air flow injected upstream of the exhaust catalyst based on a difference between a requested secondary air flow upstream of the exhaust catalyst and a measured air flow upstream of the exhaust catalyst, wherein the requested air flow is estimated as a function of each of a desired engine air fuel ratio, a desired catalyst air fuel ratio, and an engine air mass, and wherein the measured air flow is a function of each of an estimated engine air fuel ratio, an estimated exhaust catalyst air fuel ratio, and the engine air mass.

16 . The method of claim 15 , wherein the desired engine air fuel ratio is a function of the exhaust catalyst light-off temperature and the desired exhaust catalyst air fuel ratio is a function of a number of engine firing events, the exhaust catalyst air fuel ratio being the air fuel ratio of exhaust gas reaching the exhaust catalyst.

17 . An engine system, comprising:
a controller with computer readable instructions stored on non-transitory memory to: during a first condition, increasing exhaust temperature upstream of an exhaust catalyst coupled to an exhaust of an engine by enriching an air fuel ratio of an air and fuel mixture combusted by the engine, and/or spark timing of spark delivered to the engine for ignition of the air and fuel mixture, and injecting air upstream of the exhaust catalyst; and during a second condition, increasing exhaust temperature upstream of an exhaust gasoline particulate filter (GPF) by enriching the engine air fuel ratio and injecting air upstream of the exhaust catalyst, while maintaining exhaust catalyst temperature above a first threshold temperature.

18 . The system of claim 17 , wherein the first condition includes an estimated exhaust catalyst temperature being lower than an exhaust catalyst light-off temperature, and the second condition includes each of an estimated GPF particulate matter load being higher than a threshold load and an estimated GPF temperature being lower than a GPF regeneration temperature, the first threshold temperature higher than the exhaust catalyst light-off temperature.

19 . The system of claim 18 , wherein the maintaining exhaust cataly

Assignees

• Ford Global Tech Llc

Inventors

• Rollinger John
• Martin Douglas
• Martinez Vincent

Classifications

• F02D41/029

  the exhaust gas treating apparatus being a particulate filter · CPC title

• F02D41/024

  to increase temperature of the exhaust gas treating apparatus · CPC title

• F02P5/1502

  using one central computing unit · CPC title

• F02D41/0082

  per groups or banks (F02D41/0087 takes precedence) · CPC title

• F01N3/222

  using electric valves only · CPC title