GB2329217A - Purging a fuel vapour canister of an i.c. engine and supplying heat to vapour canister to maintain a steady flow rate - Google Patents

Purging a fuel vapour canister of an i.c. engine and supplying heat to vapour canister to maintain a steady flow rate Download PDF

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Publication number
GB2329217A
GB2329217A GB9719443A GB9719443A GB2329217A GB 2329217 A GB2329217 A GB 2329217A GB 9719443 A GB9719443 A GB 9719443A GB 9719443 A GB9719443 A GB 9719443A GB 2329217 A GB2329217 A GB 2329217A
Authority
GB
United Kingdom
Prior art keywords
canister
vapour
engine
fuel
fuel vapour
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Withdrawn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
GB9719443A
Other versions
GB9719443D0 (en
Inventor
Thomas Tsoi Hei Ma
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.)
Ford Global Technologies LLC
Original Assignee
Ford Global Technologies LLC
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 Ford Global Technologies LLC filed Critical Ford Global Technologies LLC
Priority to GB9719443A priority Critical patent/GB2329217A/en
Publication of GB9719443D0 publication Critical patent/GB9719443D0/en
Priority to PCT/GB1998/002755 priority patent/WO1999014481A1/en
Publication of GB2329217A publication Critical patent/GB2329217A/en
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M25/00—Engine-pertinent apparatus for adding non-fuel substances or small quantities of secondary fuel to combustion-air, main fuel or fuel-air mixture
    • F02M25/08—Engine-pertinent apparatus for adding non-fuel substances or small quantities of secondary fuel to combustion-air, main fuel or fuel-air mixture adding fuel vapours drawn from engine fuel reservoir
    • F02M25/089—Layout of the fuel vapour installation
    • 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
    • F02D41/0025—Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
    • F02D41/003—Adding fuel vapours, e.g. drawn from engine fuel reservoir
    • F02D41/0042—Controlling the combustible mixture as a function of the canister purging, e.g. control of injected fuel to compensate for deviation of air fuel ratio when purging
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M25/00—Engine-pertinent apparatus for adding non-fuel substances or small quantities of secondary fuel to combustion-air, main fuel or fuel-air mixture
    • F02M25/08—Engine-pertinent apparatus for adding non-fuel substances or small quantities of secondary fuel to combustion-air, main fuel or fuel-air mixture adding fuel vapours drawn from engine fuel reservoir
    • F02M2025/0881—Engine-pertinent apparatus for adding non-fuel substances or small quantities of secondary fuel to combustion-air, main fuel or fuel-air mixture adding fuel vapours drawn from engine fuel reservoir with means to heat or cool the canister

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Supplying Secondary Fuel Or The Like To Fuel, Air Or Fuel-Air Mixtures (AREA)

Abstract

Apparatus for and method of purging a fuel vapour canister comprising a canister 20 for collecting fuel vapour from a tank 30, means to temporarily isolate the canister 20, preferably a shut-off valve 56, means to apply a suction to the canister 20 to draw only fuel vapour to the air intake, suction created preferably by a vacuum in the air intake, means 28 to supply heat to the vapour canister to maintain a steady temperature and hence a steady discharge flow rate and means 48 to measure the mass flow rate of the fuel vapour so an engine management system 100 may compensate the normal fuel supply by the amount of the fuel vapour. The heat may be provided by an electric heater 28 or by a heat exchanger. The fuel vapour may be introduced to the air intake at a venturi 12 upstream of a throttle valve 14 or directly downstream of the throttle valve 14.

Description

Purging of a vapour canister Field of the invention The present invention relates to the purging of a vapour canister that stores fuel vapour evaporated from the fuel storage tank of an engine.
Background of the invention Hitherto, vapour produced while purging of a vapour canister could not be used in a controlled manner. When such vapour is dumped into the intake system of an engine without the engine fuel system compensating for its presence, it disturbs the fuel calibration of the engine and is not burnt efficiently.
It is difficult to determine the quantity of fuel vapour purged from the vapour canister for several reasons.
First, the amount of vapour stored in the canister may vary.
Second, as the canister is being purged, it is cooled and the rate of evaporation varies with the local temperature occurring inside the canister. Third, the vacuum pressure applied to purge the canister may be variable and this, in turn, will affect the rate of evaporation of the vapour and the flow rate of purge air drawn through the canister, the two effects resulting in variable concentrations of the vapour in the air.
As a result of all the above variables, the content of the purge flow from the canister may range from neat fuel vapour, through mixtures of varying concentrations of vapour in air, to air containing little or no fuel vapour.
Object of the invention The present invention seeks to enable the quantity of fuel contained in the gas flow drawn from a vapour canister and delivered to an engine intake system to be more accurately determined.
Summary of the invention According to a first aspect of the present invention, there is provided a method of purging a vapour canister which stores fuel vapour evaporated from a fuel storage tank of an engine, and delivering the resultant purge flow to the air intake system of the engine, the method comprising the steps of temporarily isolating the vapour canister from the ambient atmosphere, applying a suction to the canister while the canister is isolated from the ambient air to draw neat fuel vapour from the canister into the engine intake system, supplying heat to the vapour canister to maintain a steady discharge rate of fuel vapour, and measuring the mass flow rate of the fuel vapour supplied to the engine from the canister, thereby enabling compensation by an engine management system for the remaining fuel to be metered to the engine while purging the vapour canister.
The measured flow rate at which the fuel vapour is drawn from the vapour canister and supplied to the engine can be regulated to a predetermined value while purging the vapour canister so as to enable direct metering of this fuel flow to be made by the engine management system.
The invention allows an accurate determination of the fuel vapour flow because ambient air is eliminated from the purge flow. The elimination of air from the purge flow also means that the purging does not interfere with the regulation of the engine speed, thereby enabling the canister to be purged unobtrusively even while the engine is idling.
According to a second aspect of the present invention, there is provided an engine comprising means for temporarily isolating from the ambient atmosphere a vapour canister which stores fuel vapour evaporated from a fuel storage tank of the engine, means for applying a suction to the vapour canister while the canister is isolated from the ambient air to draw neat fuel vapour from the canister into the engine intake system, means for supplying heat to the vapour canister to maintain a steady discharge rate of fuel vapour, means for measuring the mass flow rate of the fuel vapour supplied to the engine from the canister, and means for reducing the remainder of the fuel metered to the engine to compensate for the fuel supplied to the engine by the purging of the vapour canister.
Preferably, means are provided for regulating the rate at which fuel vapour is drawn from the vapour canister into the engine intake system, as a function of the estimated density of the fuel vapour in the vapour canister, such that a predetermined mass flow rate of the fuel is supplied to the engine during the purging of the canister regardless of the vapour content of the canister at the time of purging.
The means for temporarily isolating the vapour canister from the ambient atmosphere may be a shut-off valve which is closed as soon as purging commences, and which is opened to connect the vapour canister to the ambient atmosphere as soon as purging is terminated.
The means for applying a suction to the vapour canister may be a pipe connecting the vapour canister to a venturi in the intake passage leading to the intake system of the engine or directly to the intake manifold of the engine downstream of the main throttle.
The means for supplying heat to the canister to maintain a steady discharge rate of fuel vapour may be a heat sink, a heat exchanger or an electric heater for supplying heat to the canister to compensate for the evaporative cooling within the canister. As the fuel storage material (such as activated carbon) of the canister has poor thermal conductivity, the heating means may comprise heating fins or rods penetrating into the vapour storage material to transfer heat directly into the vapour storage material.
The means for measuring the mass flow rate of the fuel vapour supplied to the engine from the canister may be a flow metering orifice or a venturi located in the pipe connecting the vapour canister to the engine intake system in combination with a pressure sensor measuring the pressure drop across the flow metering orifice or venturi, and a temperature sensor for estimating the density of the fuel vapour discharged from the vapour.
The invention relies upon the fact that by drawing neat fuel vapour from the vapour canister without purging it with air, the mass flow rate of the fuel vapour may be accurately measured. However, without a flow of purge air which would have carried with it heat for sustaining the evaporation rate within the vapour canister, the discharge rate of fuel vapour will rapidly diminish as the temperature inside the canister drops. To compensate for this cooling of the vapour canister, means are provided for supplying it with heat.
In addition to the above mentioned shut-off valve, which is normally open and is temporarily shut to isolate the vapour canister from the ambient atmosphere during purging, a second shut-off valve may be provided in the connection between the vapour canister and the fuel storage tank of the engine to temporarily isolate the fuel storage tank from the vacuum pressure applied to the canister when the canister is being purged. This valve is opened at the same time as the first shut-off valve as soon as purging is terminated so as to equalise the pressure in the fuel storage tank to atmosphere pressure and the vapour canister will resume its function as a buffer between the fuel storage tank and the ambient atmosphere.
Brief description of the drawing The invention will now be described further, by way of example, with reference to the accompanying drawing which is a schematic diagram of an engine and its management system.
Detailed description of the preferred embodiment The drawing shows an engine 10 having an intake manifold 16 to which air is supplied by way of a venturi 12 disposed upstream of a main butterfly throttle 14. Fuel injectors 18 inject fuel into the intake charge from a pressurised fuel rail 34, the pressure in the rail 34 being maintained by a fuel pump 32 that draws fuel from the main fuel storage tank 30 and a pressure relief valve 36 that returns surplus fuel to the storage tank 30 by way of a return line 38.
The storage tank 30 is vented to atmosphere through a pipe 40 that includes a vapour canister 20 that stores fuel vapour from the ullage space of the storage tank 30 to prevent it from being discharged into the atmosphere. The canister 20 needs to be purged from time to time to prevent it from being saturated, this being effected by drawing air through the canister 20 and returning the vapour laden air to the engine intake system.
As so far described the engine and the fuelling system are conventional and the problem that arises is that it is not readily possible for the engine management system to take into account the fuel vapours derived from the vapour canister 20. This is because the amount of fuel returned to the intake system varies with several parameters of which some, such as the extent of saturation of the vapour canister, are not quantifiable.
The vent pipe for the vapour canister 20 contains a shut-off valve 56 controlled by the engine management system 100 by way of a line 106. In this manner, during purging of the canister 20, the engine management system 100 can isolate the vapour canister 20 from the ambient atmosphere so that only neat fuel vapour can be drawn out of the canister 20 by the vacuum in the engine intake system. The canister 20 is connected to the intake system by a pipe 46 that contains a flow meter 48. The pipe 46 after the flow meter 48 branches into two pipes 42 and 44, the first leading to the venturi 12 and including a flow regulating valve 52 and the second leading to the intake manifold downstream of the main throttle 14 and including a second flow regulating valve 54.
The engine management system 100 receives input signals from the flow meter 48 by way of line 103 and receives a signal over the line 105 from a temperature and pressure sensor exposed to the fuel vapour drawn from the vapour canister 20. Output lines 102 and 104 of the engine management system 100 serve to control the regulating valves 52 and 54.
When the canister 20 is to be purged, the engine management system 100 closes the shut-off valve 56 to isolate the canister 20 from ambient air and may also close an optional second shut-off valve 58 to which is connected by a line 108 to isolate the canister 20 from the fuel storage tank 30. At the same time, one or more of the flow regulating valves 52, 54 is opened by the management system 100 to create a suction in the vapour canister. It will be appreciated that the venturi 12 will produce a vacuum at high engine speed and load because of the high air flow rate while the line 44 will see a high vacuum at low engine speed and load when the main throttle 14 obstructs the air flow.
This vacuum will draw neat vapour from the canister 20 to purge it and the rate of fuel flow can be determined by the engine management system 100 based on the known fuel density and the known vapour flow rate. Based on this estimation of the quantity of fuel reaching the engine cylinders from the vapour canister 20, the engine management system 100 can appropriately control the fuel injectors 18 to compensate for this additional fuel.
Drawing of fuel vapour from the vapour canister 20 by the application of a vacuum without a purge air flow will result in a drop in the temperature of the canister thereby making it more and more difficult for the fuel to evaporate.
To compensate for this effect, a heater 28 is provided having fins 26 penetrating into the canister 20. The heater may be electrically powered but it is more convenient for it to be an element having a large thermal capacity and acting as a heat sink. In between purge cycles, the element will reach ambient temperature and this should suffice to release sufficient vapour from the canister during each purge cycle to maintain the canister active at all times.

Claims (10)

1. A method of purging a vapour canister which stores fuel vapour evaporated from a fuel storage tank of an engine, and delivering the resultant purge flow to the air intake system of the engine, the method comprising the steps of temporarily isolating the vapour canister from the ambient atmosphere, applying a suction to the canister while the canister is isolated from the ambient air to draw neat fuel vapour from the canister into the engine intake system, supplying heat to the vapour canister to maintain a steady discharge rate of fuel vapour, and measuring the mass flow rate of the fuel vapour supplied to the engine from the canister, thereby enabling compensation by an engine management system for the remaining fuel to be metered to the engine while purging the vapour canister.
2. An engine comprising means for temporarily isolating from the ambient atmosphere a vapour canister which stores fuel vapour evaporated from a fuel storage tank of the engine, means for applying a suction to the vapour canister while the canister is isolated from the ambient air to draw neat fuel vapour from the canister into the engine intake system, means for supplying heat to the vapour canister to maintain a steady discharge rate of fuel vapour, means for measuring the mass flow rate of the fuel vapour supplied to the engine from the canister, and means for reducing the remainder of the fuel metered to the engine to compensate for the fuel supplied to the engine by the purging of the vapour canister.
3. An engine as claimed in claim 2, wherein means are provided for regulating the rate at which fuel vapour is drawn from the vapour canister into the engine intake system as a function of the estimated density of the fuel vapour in the vapour canister.
4. An engine as claimed in claim 2 or claim 3, wherein the means for isolating the vapour canister from the ambient atmosphere is a shut-off valve that is closed at the commencement of a purge cycle and opened to connect the vapour canister to the ambient atmosphere at the end of each purge cycle.
5. An engine as claimed in any one of claims 2 to 4, wherein the means for applying a suction to the vapour canister includes at least one of a pipe connecting the vapour canister to a venturi in the intake passage leading to the intake system of the engine and a pipe connected directly to an intake manifold of the engine downstream of a main throttle.
6. An engine as claimed in any one of claims 2 to 5, wherein the means for supplying heat to the canister to maintain a steady discharge rate of fuel vapour comprises an element having a large thermal capacity and acting as a heat sink.
7. An engine as claimed in any one of claims 2 to 5, wherein the means for supplying heat to the canister to maintain a steady discharge rate of fuel vapour comprises a heat exchanger.
8. An engine as claimed in any one of claims 2 to 5, wherein the means for supplying heat to the canister to maintain a steady discharge rate of fuel vapour comprises an electric heater.
9. An engine as claimed in any of claims 2 to 8, wherein a shut-off valve is provided to isolate the vapour canister from the engine fuel storage tank during purge cycles.
10. An engine and engine management system substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.
GB9719443A 1997-09-13 1997-09-13 Purging a fuel vapour canister of an i.c. engine and supplying heat to vapour canister to maintain a steady flow rate Withdrawn GB2329217A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB9719443A GB2329217A (en) 1997-09-13 1997-09-13 Purging a fuel vapour canister of an i.c. engine and supplying heat to vapour canister to maintain a steady flow rate
PCT/GB1998/002755 WO1999014481A1 (en) 1997-09-13 1998-09-11 Purging of a vapour canister

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9719443A GB2329217A (en) 1997-09-13 1997-09-13 Purging a fuel vapour canister of an i.c. engine and supplying heat to vapour canister to maintain a steady flow rate

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GB9719443D0 GB9719443D0 (en) 1997-11-12
GB2329217A true GB2329217A (en) 1999-03-17

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GB9719443A Withdrawn GB2329217A (en) 1997-09-13 1997-09-13 Purging a fuel vapour canister of an i.c. engine and supplying heat to vapour canister to maintain a steady flow rate

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GB (1) GB2329217A (en)
WO (1) WO1999014481A1 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7444996B2 (en) 2004-07-22 2008-11-04 Inergy Automotive Systems Research (Societe Anonyme) Fuel vapour storage and recovery apparatus with heat exchanger
EP2199587A2 (en) * 2008-12-18 2010-06-23 MAHLE Filter Systems Japan Corporation Vaporized fuel processing device and method
US20120260893A1 (en) * 2011-04-15 2012-10-18 Aisan Kogyo Kabushiki Kaisha Fuel vapor processing devices

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GB2044848A (en) * 1979-03-08 1980-10-22 Nissan Motor Regulating vapour flow from an ic engine fuel vapour absorbing canister
US5080078A (en) * 1989-12-07 1992-01-14 Ford Motor Company Fuel vapor recovery control system
US5400759A (en) * 1992-08-21 1995-03-28 Mitsubishi Denki Kabushiki Kaisha Fuel vapor purge system for internal combustion engine and method of diagnosis thereof

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US5373822A (en) * 1991-09-16 1994-12-20 Ford Motor Company Hydrocarbon vapor control system for an internal combustion engine
DE4316728A1 (en) * 1992-05-23 1994-03-03 Atlas Fahrzeugtechnik Gmbh Controlled feeding and recycling set=up for fuel fraction from vehicle tank - collects vented components in storage unit for re-emission into inlet manifold when richer mixture is required
US5349934A (en) * 1992-06-19 1994-09-27 Honda Giken Kogyo K.K. Evaporative emission control system for internal combustion engines
JPH06146948A (en) * 1992-10-16 1994-05-27 Unisia Jecs Corp Air/fuel ratio control device of internal combustion engine provided with evaporated fuel processing device
FR2709790B1 (en) * 1993-09-09 1995-11-17 Renault Method for supplying fuel to an internal combustion engine and engine for implementing it.
US5482023A (en) * 1994-12-27 1996-01-09 Hitachi America, Ltd., Research And Development Division Cold start fuel control system
US5596972A (en) * 1995-10-30 1997-01-28 General Motors Corporation Integrated fueling control

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2044848A (en) * 1979-03-08 1980-10-22 Nissan Motor Regulating vapour flow from an ic engine fuel vapour absorbing canister
US5080078A (en) * 1989-12-07 1992-01-14 Ford Motor Company Fuel vapor recovery control system
US5400759A (en) * 1992-08-21 1995-03-28 Mitsubishi Denki Kabushiki Kaisha Fuel vapor purge system for internal combustion engine and method of diagnosis thereof

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7444996B2 (en) 2004-07-22 2008-11-04 Inergy Automotive Systems Research (Societe Anonyme) Fuel vapour storage and recovery apparatus with heat exchanger
DE112005001728B4 (en) * 2004-07-22 2017-04-06 Inergy Automotive Systems Research (Sa) Fuel vapor storage and recovery device
EP2199587A2 (en) * 2008-12-18 2010-06-23 MAHLE Filter Systems Japan Corporation Vaporized fuel processing device and method
EP2199587A3 (en) * 2008-12-18 2014-08-13 MAHLE Filter Systems Japan Corporation Vaporized fuel processing device and method
US20120260893A1 (en) * 2011-04-15 2012-10-18 Aisan Kogyo Kabushiki Kaisha Fuel vapor processing devices
US9074561B2 (en) * 2011-04-15 2015-07-07 Aisan Kogyo Kabushiki Kaisha Fuel vapor processing devices

Also Published As

Publication number Publication date
GB9719443D0 (en) 1997-11-12
WO1999014481A1 (en) 1999-03-25

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