US20050055144A1 - Leak detection method for an evaporative emission system including a flexible fuel tank - Google Patents
Leak detection method for an evaporative emission system including a flexible fuel tank Download PDFInfo
- Publication number
- US20050055144A1 US20050055144A1 US10/971,791 US97179104A US2005055144A1 US 20050055144 A1 US20050055144 A1 US 20050055144A1 US 97179104 A US97179104 A US 97179104A US 2005055144 A1 US2005055144 A1 US 2005055144A1
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- Prior art keywords
- leak
- pressure
- calibrated
- time interval
- predetermined
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- 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.)
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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
- 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
- F02M25/0809—Judging failure of purge control system
-
- 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
- F02M2025/0845—Electromagnetic valves
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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)
- Examining Or Testing Airtightness (AREA)
Abstract
An improved method of testing for evaporative emission system leaks monitors vacuum decay in a closed system so that the effects of fuel tank expansion during the test interval are minimized. In a first embodiment pass/fail criteria are established in terms of the time required for the system pressure to decay by a calibrated amount for a predetermined leak size. A leak at least as large as the predetermined leak is detected if the measured time is shorter than a calibrated time. The effects of fuel tank expansion are minimized because the changes in fuel tank volume occur primarily due to the pressure differential across the tank, as opposed to the leak size, and the changes that occur during the test are essentially the same for any leak size under consideration. In a second embodiment, the pass/fail criteria are established in terms of the change in pressure that occurs in the calibrated time; a leak at least a large as the predetermined leak is detected if the measured change in pressure is larger than the calibrated pressure amount.
Description
- The present invention relates to leak detection in an automotive evaporative emission system, and more particularly to a detection method that accurately detects a leak in a system including a flexible fuel tank.
- In an automotive evaporative emission system, fuel vapor generated in the vehicle fuel tank is captured in a charcoal-filled canister and subsequently supplied to the engine air intake through a solenoid purge valve. Since the effectiveness of the system can be significantly impaired by faulty operation of a component or by a leak in one or more of the hoses or components, the engine controller is generally programmed to carry out a number of diagnostic algorithms for detecting such failures. If faulty operation is detected, the result is stored and a “check engine” lamp is activated to alert the driver so that corrective action can be taken.
- Experience has shown that small leaks in an evaporative system can be particularly difficult to reliably detect. Theoretically, leaks as small as 0.5 mm (0.02 in.) can be detected by closing the vapor purge valve, evacuating the system to a predetermined vacuum level, and then monitoring the vacuum decay rate over a predetermined interval of time. See for example, the U.S. Pat. No. 6,308,119, issued on Oct. 23, 2001, assigned to the assignee of the present invention, and incorporated by reference herein. However, it has been found that the test data can be misinterpreted, particularly in systems where the fuel tank is sufficiently flexible that its contained volume changes during the diagnostic test. Specifically, the volume of the tank tends to increase as the system pressure decays toward atmospheric pressure due to a leak or fuel vapor generation, and this has the effect of reducing the observed decay rate. As a result, a small leak in the evaporative system may go undetected. Accordingly, what is needed is a method of reliably detecting evaporative emission system leaks in a system including a flexible fuel tank.
- The present invention is directed to an improved method of testing for evaporative emission system leaks by monitoring vacuum decay in a closed system, wherein the effects of fuel tank expansion during the test interval are minimized. In a first embodiment, the pass/fail criterion is established in terms of the time required for the system pressure to decay by a calibrated amount corresponding to a predetermined leak size. A leak at least as large as the predetermined leak is detected if the measured time is shorter than a calibrated time. The effects of fuel tank expansion are minimized because the changes in fuel tank volume occur primarily due to the pressure differential across the tank, as opposed to the leak size, and the changes that occur during the test are essentially the same for any leak size under consideration. In a second embodiment, the pass/fail criterion is established in terms of the change in pressure that occurs in the calibrated time; a leak at least as large as the predetermined leak is detected if the measured change in pressure is larger than the calibrated pressure amount.
-
FIG. 1 is a diagram of an automotive evaporative emission system according to this invention, including a microprocessor-based engine control module (ECM). -
FIG. 2 graphically depicts the vacuum decay rate in the system ofFIG. 1 over a calibrated time interval vs. fuel tank level for a 0.01 inch diameter leak and a 0.02 inch diameter leak. -
FIG. 3 graphically depicts the time required for the pressure in the system ofFIG. 1 to decay by a calibrated amount vs. fuel tank level for a 0.01 inch diameter leak and a 0.02 inch diameter leak. -
FIG. 4 is a flow diagram representative of a software routine executed by the ECM ofFIG. 1 in carrying out the diagnostic method of this invention according to a first embodiment of this invention. -
FIG. 5 is a flow diagram representative of a software routine executed by the ECM ofFIG. 1 in carrying out the diagnostic method of this invention according to a second embodiment of this invention. - Referring to
FIG. 1 , thereference numeral 10 generally designates an evaporative emission system for anautomotive engine 12 andfuel system 14. Thefuel system 14 includes afuel tank 16, a fuel pump (P) 18, a pressure regulator (PR) 19, anengine fuel rail 20, and one ormore fuel injectors 22. Thefuel tank 16 has aninternal chamber 24, and thepump 18 draws fuel into thechamber 24 through afilter 26, as generally indicated by the arrows. Thefuel line 28 couples thepump 18 to thefuel rail 20, and thepressure regulator 19 returns excess fuel tochamber 24 viafuel line 30. Fuel is supplied to thetank 16 via aconventional filler pipe 32 sealed by theremovable fill cap 34. - The
evaporative emission system 10 includes acharcoal canister 40, asolenoid purge valve 42 and a solenoidair vent valve 44. Thecanister 40 is coupled tofuel tank 16 vialine 46, toair vent valve 44 vialine 48, and to purgevalve 42 vialine 50. Theair vent valve 44 is normally open so that thecanister 40 collects hydrocarbon vapor generated by the fuel intank 16, and in subsequent engine operation, the normally closedpurge valve 42 is modulated to draw the vapor out ofcanister 40 vialines engine 12. To this end, theline 52 couples thepurge valve 42 to theengine intake manifold 54 on the vacuum or downstream side ofthrottle 56. - The
air vent valve 44 andpurge valve 42 are both controlled by a microprocessor-based engine control module (ECM) 60, based on a number of input signals, including the fuel tank pressure (TP) online 62 and the fuel level (FL) online 64. The fuel tank pressure is detected with aconventional pressure sensor 66, and the fuel level is detected with a conventionalfuel level sender 68. Of course, the ECM 60 controls a host of engine related functions, such as fuel injector opening and closing, ignition timing, and so on. - In general, the
ECM 60 diagnoses leaks in theevaporative emission system 10 by suitably activating thesolenoid valves valve 44 to its closed state, modulating thevalve 42 to establish a predetermined vacuum level in thefuel tank 16, setting thevalve 42 to its closed state to establish a closed system, monitoring the TP signal to determine the pressure change over a predetermined interval, and computing the vacuum decay rate or pressure slope over the interval. If the slope exceeds a calibrated slope corresponding to a specified leak size (such as 0.02 inches), theECM 60 concludes that thesystem 14 has a leak at least as large as the specified leak. While this approach can be very effective with arigid fuel tank 16, it has been found that the test results are less reliable if the fuel tank is flexible, such as when the tank is made of plastic, for example. In that case, thetank 16 tends to expand somewhat in the course of the leak testing; this increases the tank volume, which has the effect of reducing the apparent vacuum decay rate, and lessening the difference in the observed decay rates for significant and insignificant leaks. This is illustrated in the graph ofFIG. 2 , where thetraces flexible tank 16. Thetrace 70 represents slope data taken with a 0.02 in. leak (which is considered to be significant), while thetrace 72 represents slope date taken with a 0.01 in. leak (which is considered to be insignificant). Although the slopes vary only slightly with fuel fill level, they are too closely spaced to reliable distinguish the 0.02 in. leak from the smaller 0.01 in. leak, as indicated by thedata envelopes 70′ and 72′. - The method of the present invention overcomes the above-described difficulty by carrying out the leak test so that the effects of fuel tank expansion during the test are minimized. In a first embodiment, this is achieved by establishing the pass/fail criteria in terms of the time required for the system pressure to decay by a calibrated amount for a predetermined leak size such as 0.02 in. A leak at least as large as 0.02 in. is detected if the measured time is shorter than a calibrated time. The effects of fuel tank expansion are minimized because the changes in fuel tank volume occur primarily due to the pressure differential across the
tank 16, as opposed to the leak size, and the tank volume changes that occur during the test are essentially the same for leaks of 0.02 in. and smaller. In a second embodiment, the pass/fail criteria is established in terms of the change in system pressure that occurs in the calibrated time; a leak at least a large as 0.02 in. is detected if the measured change in pressure is larger than the calibrated pressure amount. -
Traces FIG. 3 designate the time required for the system pressure to decay from an initial vacuum level of 10 inches of water to a lower value (8 inches of water), as a function of the level of fuel (% full) in aflexible tank 16. In this case, thelower trace 74 represents the required time with a system leak of 0.02 inches in diameter, while thetrace 76 represents the required time with a system leak of 0.01 inches in diameter. As with the example ofFIG. 2 , the required times vary only slightly with fuel fill level, and in this case, the times are separated sufficiently to reliably distinguish the 0.02 in. leak from the smaller 0.01 in. leak, as indicated by thedata envelopes 74′ and 76′. -
FIG. 4 is a flow diagram representing a software routine periodically executed by theECM 60 for carrying out the first embodiment of this invention. Following initialization, theblock 80 is executed to determine if the LEAK TEST COMPLETE flag is TRUE. Initially, block 80 is answered in the negative, and theblock 82 determines if specified leak detection enable conditions have been met. This may involve, for example, determining if the engine coolant temperature is within a predefined range, if the difference between the coolant temperature and the inlet air temperature is within a given range, if the measured fuel level is within a given range, and if the barometric pressure is within a given range. Additionally, it involves determining if the tank pressure TP has been drawn down to a predetermined vacuum level such as 10 in. of water. Once all of the conditions have been met, theblock 114 is executed to record the value of a system clock as TIME_START. When the tank pressure TP decays to a calibrated pressure such as 8 in. of water, as determined atblock 86, theblocks block 92, theblocks block 98 performs a vapor generation test, and corrects END_TIME for observed pressure changes due to fuel vapor generation, after which theblock 100 compares the corrected value of END_TIME to CAL_TIME. If the corrected value of END_TIME is greater than CAL_TIME, theblocks blocks -
FIG. 5 is a flow diagram representing a software routine periodically executed by theECM 60 for carrying out the second embodiment of this invention. Following initialization, theblock 110 is executed to determine if the LEAK TEST COMPLETE flag is TRUE. Initially, block 110 is answered in the negative, and theblock 112 determines if specified leak detection enable conditions have been met. This may involve, for example, determining if the engine coolant temperature is within a predefined range, if the difference between the coolant temperature and the inlet air temperature is within a given range, if the measured fuel level is within a given range, and if the barometric pressure is within a given range. Additionally, it involves determining if the tank pressure TP has been drawn down to a predetermined vacuum level such as 10 in. of water. Once all of the conditions have been met, theblock 114 is executed to enable a timer to determine elapsed time. When the timer reaches a calibrated time (CAL_TIME) such as 30 seconds, as determined atblock 116, theblock 118 records the tank pressure TP as END_VACUUM. If END_VACUUM is greater than a calibrated value (CAL_VACUUM) such as 8 in. of water, as determined atblock 120, theblocks block 126 performs a vapor generation test, and corrects END_VACUUM for observed pressure changes due to fuel vapor generation, after which theblock 128 compares the corrected value of END_VACUUM to CAL_VACUUM. If the corrected value of END_VACUUM is greater than CAL_VACUUM, theblocks blocks - In summary, the diagnostic method of the present invention provides an improved method of testing for evaporative emission system leaks, wherein the effects of fuel tank expansion during the test interval are minimized. While the present invention has been described in reference to the illustrated embodiment, it is expected that various modifications will occur to those skilled in the art. Accordingly, it will be understood that methods incorporating these and other modifications may fall within the scope of this invention, which is defined by the appended claims.
Claims (3)
1. A method of detecting a leak in a closed liquid storage system having a flexible storage tank subject to volume change in response to an internal vacuum, and in which the stored liquid is subject to fuel vapor generation, including the steps of:
reducing a pressure in the system to a predetermined vacuum level;
measuring a time interval required for the pressure in the system to decay from the predetermined vacuum level to a calibrated vacuum level;
correcting the measured time interval to compensate for fuel vapor generation in the system;
comparing the corrected measured time interval to a calibrated time interval corresponding to a specified leak in said system; and
detecting the existence of a system leak at least as large as said specified leak when the corrected measured time interval is less than the calibrated time interval.
2. The method of claim 1 , including the step of:
detecting the absence of a system leak at least as large as said specified leak when the measured time interval is greater than the calibrated time interval.
3. A method of detecting a leak in a closed liquid storage system having a flexible storage tank subject to volume change in response to an internal vacuum, and in which the stored liquid is subject to fuel vapor generation, including the steps of:
calibrating the system by establishing a pass/fail criteria by determining the time required for the system pressure to decay from a predetermined vacuum level to a calibrated vacuum level, for various predetermined leak sizes,
reducing a pressure in the system to a predetermined vacuum level;
measuring a time interval required for the pressure in the system to decay from the predetermined vacuum level to a calibrated vacuum level;
correcting the measured time interval to compensate for fuel vapor generation in the system;
comparing the corrected measured time interval to a calibrated time interval corresponding to one of the predetermined leak sizes in said system; and
determining the existence of a system leak at least as large as said one predetermined leak size when the corrected measured time interval is less than the calibrated time interval.
Priority Applications (1)
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US10/971,791 US20050055144A1 (en) | 2002-02-21 | 2004-10-22 | Leak detection method for an evaporative emission system including a flexible fuel tank |
Applications Claiming Priority (2)
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US10/080,244 US6807847B2 (en) | 2002-02-21 | 2002-02-21 | Leak detection method for an evaporative emission system including a flexible fuel tank |
US10/971,791 US20050055144A1 (en) | 2002-02-21 | 2004-10-22 | Leak detection method for an evaporative emission system including a flexible fuel tank |
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US10/080,244 Continuation US6807847B2 (en) | 2002-02-21 | 2002-02-21 | Leak detection method for an evaporative emission system including a flexible fuel tank |
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US10/080,244 Expired - Lifetime US6807847B2 (en) | 2002-02-21 | 2002-02-21 | Leak detection method for an evaporative emission system including a flexible fuel tank |
US10/971,791 Abandoned US20050055144A1 (en) | 2002-02-21 | 2004-10-22 | Leak detection method for an evaporative emission system including a flexible fuel tank |
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US10/080,244 Expired - Lifetime US6807847B2 (en) | 2002-02-21 | 2002-02-21 | Leak detection method for an evaporative emission system including a flexible fuel tank |
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Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
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US20050044941A1 (en) * | 2003-08-28 | 2005-03-03 | Yasushi Nakoji | Diagnostic device of evaporated fuel processing system and the method thereof |
US20050066717A1 (en) * | 2003-09-30 | 2005-03-31 | Toyo Roki Seizo Kabushiki Kaisha | Canister |
US20050241377A1 (en) * | 2004-03-26 | 2005-11-03 | Daisuke Takahashi | Diagnostic apparatus for evaporative emission control system |
US20070044550A1 (en) * | 2005-08-31 | 2007-03-01 | Audi Ag | Method for checking the gastightness of a motor vehicle tank ventilation system |
US20090007638A1 (en) * | 2007-07-05 | 2009-01-08 | Meskouri Mohamed S | Pump Assembly and Method for Leak Detection of Fluid System |
US20090211340A1 (en) * | 2008-02-21 | 2009-08-27 | Gm Global Technology Operations, Inc. | Purge valve leak diagnostic systems and methods |
US20120145133A1 (en) * | 2010-12-14 | 2012-06-14 | Toyota Jidosha Kabushiki Kaisha | Fuel vapor processing systems |
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JP2003090270A (en) * | 2001-09-17 | 2003-03-28 | Denso Corp | Pressurization device |
JP3930437B2 (en) * | 2002-04-11 | 2007-06-13 | 株式会社日本自動車部品総合研究所 | Failure diagnosis method and failure diagnosis apparatus for evaporated fuel processing apparatus |
US7168297B2 (en) * | 2003-10-28 | 2007-01-30 | Environmental Systems Products Holdings Inc. | System and method for testing fuel tank integrity |
DE10351893A1 (en) * | 2003-11-06 | 2005-06-09 | Robert Bosch Gmbh | Method for operating an internal combustion engine |
US7350512B1 (en) | 2007-04-30 | 2008-04-01 | Delphi Technologies, Inc. | Method of validating a diagnostic purge valve leak detection test |
US20090144959A1 (en) * | 2007-12-11 | 2009-06-11 | Colletti Michael J | Method for assembly of a direct injection fuel rail |
US8477040B2 (en) | 2011-01-26 | 2013-07-02 | Joseph D Jatcko | Method and apparatus for testing the integrity of a tank |
JP5704338B2 (en) * | 2011-07-07 | 2015-04-22 | 三菱自動車工業株式会社 | Fuel evaporative emission control device for internal combustion engine |
JP5672454B2 (en) * | 2011-07-07 | 2015-02-18 | 三菱自動車工業株式会社 | Fuel evaporative emission control device for internal combustion engine |
US9476792B2 (en) | 2012-05-10 | 2016-10-25 | Mahle Powertrain, Llc | Evaporative emissions leak tester and leak test method |
CN114215664B (en) * | 2021-12-24 | 2023-04-14 | 安徽江淮汽车集团股份有限公司 | Method and system for diagnosing leakage of evaporation system for fuel vehicle |
CN114837860B (en) * | 2022-03-17 | 2023-03-10 | 江铃汽车股份有限公司 | Leakage diagnosis device and method for fuel evaporation system |
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Cited By (14)
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US20050044941A1 (en) * | 2003-08-28 | 2005-03-03 | Yasushi Nakoji | Diagnostic device of evaporated fuel processing system and the method thereof |
US7080548B2 (en) * | 2003-08-28 | 2006-07-25 | Fuji Jukogyo Kabushiki Kaisha | Diagnostic device of evaporated fuel processing system and the method thereof |
US20050066717A1 (en) * | 2003-09-30 | 2005-03-31 | Toyo Roki Seizo Kabushiki Kaisha | Canister |
US7137293B2 (en) * | 2003-09-30 | 2006-11-21 | Toyo Roki Seizo Kabushiki Kaisha | Canister provided with a leak detection valve for treating evaporated fuel |
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US20070044550A1 (en) * | 2005-08-31 | 2007-03-01 | Audi Ag | Method for checking the gastightness of a motor vehicle tank ventilation system |
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US20090007638A1 (en) * | 2007-07-05 | 2009-01-08 | Meskouri Mohamed S | Pump Assembly and Method for Leak Detection of Fluid System |
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US20090211340A1 (en) * | 2008-02-21 | 2009-08-27 | Gm Global Technology Operations, Inc. | Purge valve leak diagnostic systems and methods |
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US20120145133A1 (en) * | 2010-12-14 | 2012-06-14 | Toyota Jidosha Kabushiki Kaisha | Fuel vapor processing systems |
US9181906B2 (en) * | 2010-12-14 | 2015-11-10 | Aisan Kogyo Kabushiki Kaisha | Fuel vapor processing systems |
Also Published As
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US20030154770A1 (en) | 2003-08-21 |
US6807847B2 (en) | 2004-10-26 |
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