GB2395147A - Controlling motor vehicle exhaust emissions - Google Patents

Controlling motor vehicle exhaust emissions Download PDF

Info

Publication number
GB2395147A
GB2395147A GB0225982A GB0225982A GB2395147A GB 2395147 A GB2395147 A GB 2395147A GB 0225982 A GB0225982 A GB 0225982A GB 0225982 A GB0225982 A GB 0225982A GB 2395147 A GB2395147 A GB 2395147A
Authority
GB
United Kingdom
Prior art keywords
engine
fuel
catalyst
air
temperature
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB0225982A
Other versions
GB0225982D0 (en
Inventor
Timothy James Bedford
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BEDFORD RACHEL ANNE
Original Assignee
BEDFORD RACHEL ANNE
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by BEDFORD RACHEL ANNE filed Critical BEDFORD RACHEL ANNE
Priority to GB0225982A priority Critical patent/GB2395147A/en
Publication of GB0225982D0 publication Critical patent/GB0225982D0/en
Publication of GB2395147A publication Critical patent/GB2395147A/en
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9445—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]
    • B01D53/9454—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC] characterised by a specific device
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9495—Controlling the catalytic process
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/021—Introducing corrections for particular conditions exterior to the engine
    • F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1473—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the regulation method
    • F02D41/1475—Regulating the air fuel ratio at a value other than stoichiometry
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/08—Exhaust gas treatment apparatus parameters
    • F02D2200/0802—Temperature of the exhaust gas treatment apparatus
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F02D41/3011—Controlling fuel injection according to or using specific or several modes of combustion
    • F02D41/3076—Controlling fuel injection according to or using specific or several modes of combustion with special conditions for selecting a mode of combustion, e.g. for starting, for diagnosing
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Abstract

An engine management system and method utilizes lean burn fuel control when the temperature of a catalyst in a catalytic converter is below a predetermined threshold (e.g. 250{C) at which the catalyst becomes active; and utilizes stoichiometric fuel control when the temperature of the catalyst is at or above the predetermined threshold.

Description

2395 1 47
TITLE Controlling Motor vehicle Exhaust Emissions DESCRIPTION
5 The field of the invention
The invention provides an internal combustion engine management method and apparatus designed to reduce the noxious exhaust emissions from the engine.
Background Art
10 Current practice to control the level of noxious exhaust emissions from an internal combustion engine centres mainly around the two mutually exclusive control systems of lean burn and the use of exhaust catalysts.
The "lean burn" philosophy is to reduce the proportion of fuel in the air/fuel mixture 15 to a value less than the stoichiometric ratio. This weakening of the fuel mixture assists complete combustion of the fuel particularly when the engine is under minimum load, and results in low levels of carbon dioxide and nitrous oxides (NOx) in the exhaust gases. When the engine power is increased, the temperature at the end of combustion rises, which has the consequence of causing the NOx content of the 20 exhaust gases to rise. The "lean burn" solution is therefore not a complete solution to exhaust emission control across the entire range of driving conditions. Also, careful control is needed of the degree to which the air/fuel ratio departs from the stoichiometric ratio. If the proportion of fuel in the air/fuel mixture is reduced too much, the engine ignition system may be inadequate properly to ignite the air/fuel 25 mixture, and misfiring or late firing may occur. That causes the exhaust emissions to pass unburned hydrocarbons, which clearly is undesirable.
The alternative "exhaust catalyst" solution involves using a stoichiometric air/fuel ratio, but placing a catalyst converter in the engine exhaust stream. Early catalytic 30 converters used the catalyst, heated by the exhaust gases to a working temperature, to oxidise the carbon monoxide and any unburned hydrocarbons in the exhaust gases.
NOX emissions were unaffected. Modern "three way" catalysts have been developed G] 02001.doc
- 2 which reduce the NOX content of the exhaust emissions as well. The catalyst is a mixture of heavy metals which reduces the NOx in the exhaust gases to nitrogen, and uses the resulting available oxygen to oxidise the carbon monoxide to carbon dioxide.
The catalyst operation is dependent on the presence of significant amounts of carbon 5 monoxide in the initial exhaust gas stream, which is why the catalytic converter is unsuitable for use with lean burn engines and why the two control methods of lean burn and exhaust catalyst are mutually exclusive.
Disadvantages of the exhaust catalyst solution to the control of vehicle emissions 10 include primarily the fact that the catalyst must be brought to a minimum operating temperature, typically 250 C, before it becomes active. The heat source is generally the exhaust gas stream itself. However when the catalyst does not reach its operating temperature, such as on initial start-up or in extreme cold wintry conditions or even in wet and rainy conditions when water spray thrown against the outer shell of the 15 catalytic converter cools the catalyst, the catalyst is ineffective and the exhaust emissions rise.
It is an object of the invention to provide an engine management apparatus and method which provides exhaust emission control over a wider range of engine 20 operating conditions.
The Invention The invention provides an engine management system having the features of claim herein. The invention is particularly well suited to the control of exhaust emissions in gaseous fuel engines. One fuel control system for controlling the air/fuel ratio in a gas power engine is disclosed in European Patent (UK) No. 525072, and is extremely suitable for use as the fuel control system used in accordance with the invention.
30 Alternatively other commercially available fuel control systems can be used, such as that sold under the Trade Mark IMPCO ECLIPSE. The sole limitation to the choice of fuel control system is that it must be capable of varying the air/fuel ratio within a G1 02001.doc
- 3 very wide range, from lean burn to substantially stoichiometric ratios, preferably with an ability closely to control the air/fuel ratio across the whole of that range.
Preferably the fuel control system used is able completely to shut off the fuel supply 5 to the engine as close to the gas-and-air mixing point as possible, and to achieve that injection systems are preferred. The fuel supply to the engine can then be stopped during over-run conditions, thus avoiding the passage of considerable quantities of unburned hydrocarbons into the exhaust stream in such conditions.
10 The temperature sensor may be in contact with the surface of the catalyst within the catalytic converter, or may be attached to the inlet to the catalytic converter and responsive to the temperature of the exhaust gases heating the catalyst surface. The predetermined threshold temperature is chosen to represent the temperature at which the catalyst in the catalytic converter becomes active. For example, a threshold 15 temperature of 250 C can be chosen, for a catalyst which at or above 250 C is at its active temperature.
The system of the invention prolongs the life of the catalyst in the catalytic converter, because when the air/fuel mixture supplied to the engine is a lean burn mixture with 20 an excess of oxygen, the excess oxygen (which normally would destroy the catalyst) is not detrimental to the catalyst because the lean burn mixture is supplied only when the catalyst temperature is below the predetermined threshold, and in those conditions catalyst oxidation is minimal.
25 If the engine is running in lean burn mode and the throttle is opened fully, a conventional lean burn engine management system would permit excess NOX emissions in the exhaust gases. The system of the invention, however, converts from lean burn fuel management to stoichiometric fuel management as soon as the opened throttle generates a rise in the temperature of the exhaust gases to raise the catalyst 30 temperature above the predetermined threshold.
G102001 doc
The invention also provides a method for the control of exhaust emissions in an internal combustion engine, as set forth in claim 6 herein.
5 DRAWINGS
Figure 1 is a block diagram illustrating an engine management system according to the invention; and Figure 2 is a graph of air/fuel ratio vs time using the system and method of the invention. Referring first to Figure 1, the system comprises a fuel control system 1 for supplying an air/fuel mixture to an i.c. engine 2. The exhaust gases from the engine 2 pass to a catalytic converter 3. A temperature sensor 4 on the input side of the catalytic converter 3 senses the temperature of the exhaust gases as they first contact the 15 catalyst surface. The temperature sensed by the sensor 4 is therefore an accurate indication of the surface temperature of the catalyst.
A wide band lambda sensor 5 is placed upstream of the catalytic converter 3 close to the engine to measure the oxygen content of the exhaust gases. Outputs from the 20 temperature sensor 4 and the lambda sensor 5 are supplied to a central processing unit 6 which controls the fuel control system 1.
Operation is as illustrated in Figure 2. When the engine is first started and the catalyst is cold (as sensed by the temperature sensor 4) the CPU 6 causes the fuel control 25 system to deliver an air/fuel mixture in a lean burn ratio of about 1.2:1. Feedback from the lambda sensor 5 effects a constantly varying fine control of the air/fuel ratio to maintain a desired oxygen content in the exhaust gases that is characteristic of the desired lean burn fuel mixture. This permits the maintenance of the carbon monoxide and NOX content of the exhaust gases at a minimum using lean burn engine 30 management technology. The air/fuel ratio during this lean burn operation is shown in Figure 2 as portion 7 of the fuel/time graph.
Gi02001.doc
- 5 A certain time after initial start-up (which time is variable according to ambient conditions) the hot exhaust gases heat up the catalyst. When the temperature sensed by the sensor 4 reaches a threshold, shown in Figure 2 as 250 C, the catalyst in the catalytic converter 3 becomes active. The CPU 6 immediately alters the operating 5 parameters of the fuel control system 1 so that it starts to deliver a substantially stoichiometric air/fuel mixture as illustrated by the line 8. The catalytic converter is a three-way catalytic converter which is at its most efficient in controlling NOX emissions when there is a small excess of oxygen in the exhaust gases (not as much as under lean burn conditions) . If the lambda sensor is a wide band sensor, then even 10 with that small amount of oxygen can be monitored and used as feedback to the fuel control system to maintain optimum control of the carbon monoxide and NOx in the exhaust gases.
The system and method of the invention enable the exhaust emissions to be closely 15 controlled over a wide range of operating conditions from idle to full throttle without the initial discharge of a high level of noxious exhaust gases when starting from cold, typical of current systems.
Advantageously a further level of control is provided by the CPU 6 by closing down 20 the fuel supply completely when the throttle is closed and the engine speed is above idle. Those conditions are typical of an engine over-run mode which normally gives excessive unburnt hydrocarbons in the exhaust. When the engine speed drops to idle speed, the fuel supply can be resumed.
G] 02001.doc

Claims (8)

- 6 CLAIMS:
1. An engine management system for controlling the exhaust conditions of an internal combustion engine, which comprises a fuel control system for delivery of air and fuel to the engine in ratios variable 5 from a "lean burn" ratio to a stoichiometric ratio; a three-way catalytic converter in the path of the exhaust gases from the engine; a temperature sensor associated with the catalytic converter, indicative of the surface temperature of a catalyst therein; and means for varying the air/fuel ratio from a "lean burn" ratio when the catalyst 10 surface temperature as sensed by the temperature sensor is below a predetermined threshold to a substantially stoichiometric ratio when the sensed catalyst surface temperature is at or above the predetermined threshold.
2. An engine management system according to claim 1, wherein the lean burn 15 ratio of air to fuel is about 1.2:1,
3. An engine management system according to claim I or claim 2, wherein the predetermined threshold temperature is about 250 C.
20
4. An engine management system according to any preceding claim, further comprising a lambda sensor in the exhaust gas stream upstream of the catalytic converter, wherein at or above the predetermined threshold temperature of the catalyst the fuel control system operates closed loop under the control of an output signal from the lambda sensor, to control the precise air/fuel ratio at about the stoichiometric ratio 25 within a range that produces an optimum output signal from the lambda sensor.
5. An engine management system according to claim 4, wherein the lambda sensor is a wide band lambda sensor capable of operating under lean burn engine conditions, and below the predetermined threshold temperature of the catalyst the fuel 30 control system operates closed loop under the control of an output signal from the lambda sensor to control the precise air/fuel ratio in a lean burn range to produce an optimum output signal from the lambda sensor.
Gl 02001.doc
- 7
6. A method for controlling the exhaust emissions of an internal combustion engine which has a catalytic converter in its exhaust gas stream, comprising delivering an air/fuel mixture to the engine in a lean burn air/fuel ratio when 5 the temperature of a catalyst in the catalytic converter is below a predetermined threshold, and delivering the air/fuel mixture to the engine in a substantially stoichiometric air/fuel ratio when the temperature of the catalyst is at or above the predetermined threshold.
7. A method according to claim 6, wherein the predetermined threshold temperature is about 250 C.
8. A method according to claim 6 or claim 7, wherein the fuel supply to the 15 engine is interrupted completely when the throttle is closed and the engine speed is above idle speed, and is resumed when the engine speed falls to idle speed.
G102001.doc
GB0225982A 2002-11-07 2002-11-07 Controlling motor vehicle exhaust emissions Withdrawn GB2395147A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB0225982A GB2395147A (en) 2002-11-07 2002-11-07 Controlling motor vehicle exhaust emissions

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB0225982A GB2395147A (en) 2002-11-07 2002-11-07 Controlling motor vehicle exhaust emissions

Publications (2)

Publication Number Publication Date
GB0225982D0 GB0225982D0 (en) 2002-12-11
GB2395147A true GB2395147A (en) 2004-05-19

Family

ID=9947387

Family Applications (1)

Application Number Title Priority Date Filing Date
GB0225982A Withdrawn GB2395147A (en) 2002-11-07 2002-11-07 Controlling motor vehicle exhaust emissions

Country Status (1)

Country Link
GB (1) GB2395147A (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5564404A (en) * 1994-09-20 1996-10-15 Nissan Motor Co., Ltd. Air/fuel ratio control system of internal combustion engine
EP1149623A1 (en) * 2000-04-25 2001-10-31 Nissan Motor Company, Limited Catalyst and process for purifying exhaust gas

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5564404A (en) * 1994-09-20 1996-10-15 Nissan Motor Co., Ltd. Air/fuel ratio control system of internal combustion engine
EP1149623A1 (en) * 2000-04-25 2001-10-31 Nissan Motor Company, Limited Catalyst and process for purifying exhaust gas

Also Published As

Publication number Publication date
GB0225982D0 (en) 2002-12-11

Similar Documents

Publication Publication Date Title
US6340014B1 (en) Control for direct fuel injection spark ignition internal combustion engine
US6463734B1 (en) Exhaust emission control device of internal combustion engine
US6637192B2 (en) Cylinder injection type internal combustion engine
US20040194450A1 (en) Exhaust emission control device
CN111734517B (en) Device and method for exhaust gas aftertreatment of an internal combustion engine
KR101991260B1 (en) Ultra low emission gas engine and its fuel quantity control method
CN111322140B (en) Method and device for exhaust gas aftertreatment of an internal combustion engine
US8607545B2 (en) Air-fuel ratio control device
US11268421B2 (en) Regeneration air system for an exhaust aftertreatment system of an internal combustion engine, and method for exhaust aftertreatment
JPH0518234A (en) Secondary air control device for internal combustion engine
US5822976A (en) Method and system for controlling the amount of secondary air introduced into an internal combustion engine
US6880329B2 (en) Exhaust gas purifying system for internal combustion engines
JPH1193729A (en) Operating method of internal combustion engine
US6490860B1 (en) Open-loop method and system for controlling the storage and release cycles of an emission control device
US5893039A (en) Catalytic method
US6233924B1 (en) Temperature control method for a direct injection engine
GB2395147A (en) Controlling motor vehicle exhaust emissions
US6453666B1 (en) Method and system for reducing vehicle tailpipe emissions when operating lean
CN115929447A (en) Method, calculation unit and computer program for determining the air quantity provided by an air pump
US5974785A (en) Closed loop bias air/fuel ratio offset to enhance catalytic converter efficiency
US6360529B1 (en) Method and apparatus for enabling lean engine operation upon engine start-up
JP2003193885A (en) Internal combustion engine
JP2002161733A (en) Exhaust gas cleaning device for internal combustion engine
JPH11247684A (en) Fuel injection control device of internal combustion engine
JP2874480B2 (en) Catalyst warm-up device for internal combustion engine

Legal Events

Date Code Title Description
WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)