US6085732A
Expired / Lapsed
US
⏱️ 0.0 years remaining
EGR fault diagnostic system
Assignee: Cummins Inc
•
Filing: 1999-01-25
•
Granted: 2000-07-11
•
Expires: 2019-01-25
Abstract
Abstract A system and method for diagnosing EGR system and EGR cooler faults evaluates a temperature signal generated by a sensor at the EGR cooler, such as a coolant or gas temperature sensor. An engine control module includes an on-board EGR diagnosis unit and DSP that reads the EGR cooler temperature signals over a predetermined time period or sample points, and generates a symmetric signal. A discrete fast Fourier transform is applied to the symmetric signal to develop values for the spectral magnitude and phase angle of a primary frequency component of the signal. These values can be compared to respective predetermined threshold values to determine whether a fault condition has occurred in the EGR system or EGR cooler. In an alternative embodiment, the DSP operates in the time domain to determine a signal power value for the change in cooler temperature signal over a predetermined time period. This signal power value can be compared against one or more threshold values to determine the health of the EGR system and cooler. In a further alternative embodiment, a temperature difference between the coolant temperature measured by the EGR cooler temperature sensor when the EGR valve is opened is compared to a baseline EGR cooler temperature value. Over successive cycles, this temperature difference is compared to various threshold values indicative of an EGR fault, an EGR cooler fault or a cooler failure.
Inventors
- 👤 Yue Yun Wang
- 👤 Steven W. Majors
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 21:27
CPC Classifications
F; F02; F02D; F02D41/00; F02D41/22; F02M; F02M26/00; F02M26/13; F02M26/22; F02M26/23; F02M26/28; F02M26/45; F02M26/46; F02M26/47; F02M26/49; F02D41/24; F02D41/26; F02D41/28; F02D2041/286; F02D2041/288; Y; Y02; Y02T; Y02T10/00; Y02T10/10; Y02T10/40
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
111 words
A method for determining a fault condition in an exhaust gas recirculation (EGR) system having an EGR valve operable to control the re-circulation of exhaust gas and an EGR cooler operable to reduce the temperature of the re-circulated gas, comprising: opening the EGR valve; sensing a temperature of the EGR cooler while the EGR valve is open to generate a temperature signal; generating a symmetric signal from the temperature signal; performing a frequency analysis on the symmetric signal to isolate the frequency components of the signal; evaluating the magnitude of the primary frequency component; and indicating a fault condition in the EGR system if the magnitude is outside a diagnostic threshold.
Claim 2
Independent Claim
111 words
A method for determining a fault condition in an exhaust gas recirculation (EGR) system having an EGR valve operable to control the re-circulation of exhaust gas and an EGR cooler operable to reduce the temperature of the re-circulated gas, comprising: opening the EGR valve; sensing a temperature of the EGR cooler while the EGR valve is open to generate a temperature signal; generating a symmetric signal from the temperature signal; performing a frequency analysis on the symmetric signal to isolate the frequency components of the signal; evaluating the magnitude of the primary frequency component; and indicating a fault condition in the EGR system if the magnitude is outside a diagnostic threshold.
Claim 3
Dependent Claim
38 words
The method for determining an EGR fault condition according to claim 1, wherein said step of generating a symmetric signal includes combining the temperature signal with a mirror image of the temperature signal to produce the symmetric signal.
Claim 4
Dependent Claim
29 words
The method for determining an EGR fault condition according to claim 1, wherein said step of performing a frequency analysis includes performing a discrete Fourier transform of the signal.
Claim 5
Dependent Claim
47 words
The method for determining an EGR fault condition according to claim 3, wherein the step of determining the magnitude of the primary frequency component includes: determining the power spectral density of the signal; and obtaining the magnitude of the power spectral density for the primary frequency component.
Claim 6
Dependent Claim
36 words
The method for determining an EGR fault condition according to claim 1, wherein the step of sensing the temperature includes sensing the temperature of the coolant or recirculated gas at an outlet of the EGR cooler.
Claim 7
Dependent Claim
40 words
The method for determining an EGR fault condition according to claim 1, wherein the step of sensing the temperature includes sampling the coolant temperature at discrete intervals such that the temperature signal is formed of a plurality of such samples.
Claim 8
Dependent Claim
30 words
The method for determining an EGR fault condition according to claim 6, further comprising the step of closing the EGR valve after a predetermined number of samples have been obtained.
Claim 9
Dependent Claim
27 words
The method for determining an EGR fault condition according to claim 1, further comprising the step of closing the EGR valve after a predetermined period of time.
Claim 10
Dependent Claim
55 words
The method for determining an EGR fault condition according to claim 1, wherein the step of performing a frequency analysis on the symmetric signal includes calculating the real and imaginary parts of the primary frequency component of the symmetric signal and calculating the magnitude of the primary frequency component from the real and imaginary parts.
Claim 11
Independent Claim
109 words
A method for determining a fault condition in an exhaust gas recirculation (EGR) system having an EGR valve operable to control the re-circulation of exhaust gas and an EGR cooler operable to reduce the temperature of the re-circulated gas, comprising the steps of: generating a temperature signal corresponding to a rise in EGR cooler temperature from an initial condition to a peak value; generating a symmetric signal from the temperature signal and its mirror image; isolating the primary frequency component of the symmetric signal; comparing a magnitude of the primary frequency component to a threshold value; and indicating a fault condition if the magnitude is outside the threshold value.
Claim 12
Independent Claim
109 words
A method for determining a fault condition in an exhaust gas recirculation (EGR) system having an EGR valve operable to control the re-circulation of exhaust gas and an EGR cooler operable to reduce the temperature of the re-circulated gas, comprising the steps of: generating a temperature signal corresponding to a rise in EGR cooler temperature from an initial condition to a peak value; generating a symmetric signal from the temperature signal and its mirror image; isolating the primary frequency component of the symmetric signal; comparing a magnitude of the primary frequency component to a threshold value; and indicating a fault condition if the magnitude is outside the threshold value.
Claim 13
Independent Claim
109 words
A system for determining a fault condition in an exhaust gas recirculation (EGR) system having an EGR valve operable to control the re-circulation of exhaust gas and an EGR cooler operable to reduce the temperature of the re-circulated gas, comprising: a temperature sensor for producing temperature signals indicative of a temperature of the EGR cooler of the EGR system; means for generating a symmetric signal from said temperature signals; a signal processor operable on said symmetric signal to isolate the magnitude of a primary frequency component of said signal; and means for indicating a fault condition in response to a comparison of said magnitude to a predetermined threshold value.
Claim 14
Independent Claim
109 words
A system for determining a fault condition in an exhaust gas recirculation (EGR) system having an EGR valve operable to control the re-circulation of exhaust gas and an EGR cooler operable to reduce the temperature of the re-circulated gas, comprising: a temperature sensor for producing temperature signals indicative of a temperature of the EGR cooler of the EGR system; means for generating a symmetric signal from said temperature signals; a signal processor operable on said symmetric signal to isolate the magnitude of a primary frequency component of said signal; and means for indicating a fault condition in response to a comparison of said magnitude to a predetermined threshold value.
Claim 15
Dependent Claim
46 words
The system for determining a fault condition in an EGR system according to claim 11, wherein said temperature sensor is a fluid temperature sensor disposed in the coolant outlet for the EGR cooler and operable to measure the temperature of coolant discharged from the EGR cooler.
Claim 16
Dependent Claim
30 words
The system for determining a fault condition in an EGR system according to claim 11, wherein said signal processor includes means for performing a Fourier transform on said symmetric signal.
Claim 17
Independent Claim
122 words
A method for determining a fault condition in an exhaust gas recirculation (EGR) system having an EGR valve operable to control the re-circulation of exhaust gas and an EGR cooler operable to reduce the temperature of the re-circulated gas, comprising the steps of: sensing an initial temperature T I of the EGR cooler; then opening the EGR valve; sensing a current temperature of the EGR cooler when the EGR valve is open at a plurality of sample times; determining a plurality of temperature difference values δT between the current temperature at each of the sample times and the initial temperature; summing the plurality of temperature difference values δT; and indicating a fault condition if the sum falls outside a predetermined threshold value.
Claim 18
Independent Claim
122 words
A method for determining a fault condition in an exhaust gas recirculation (EGR) system having an EGR valve operable to control the re-circulation of exhaust gas and an EGR cooler operable to reduce the temperature of the re-circulated gas, comprising the steps of: sensing an initial temperature T I of the EGR cooler; then opening the EGR valve; sensing a current temperature of the EGR cooler when the EGR valve is open at a plurality of sample times; determining a plurality of temperature difference values δT between the current temperature at each of the sample times and the initial temperature; summing the plurality of temperature difference values δT; and indicating a fault condition if the sum falls outside a predetermined threshold value.
Claim 19
Dependent Claim
34 words
The method for determining a fault condition in an EGR system according to claim 14, wherein the step of summing includes summing the squares of each of the plurality of temperature difference values δT.
Claim 20
Dependent Claim
82 words
The method for determining a fault condition in an EGR system according to claim 14, wherein the step of indicating a fault condition includes: comparing the sum to a first threshold value indicative of a functioning EGR system; indicating an EGR system fault if the sum is below the first threshold value; otherwise, comparing the sum to a second threshold value indicative of a functioning EGR cooler; and indicating an EGR cooler fault if the sum is above the second threshold value.
Claim 21
Independent Claim
158 words
A method for determining a fault condition in an exhaust gas recirculation (EGR) system having an EGR valve operable to control the re-circulation of exhaust gas and an EGR cooler operable to reduce the temperature of the re-circulated gas, comprising the steps of: sensing an initial temperature T I of the EGR cooler; then opening the EGR valve; sensing a current temperature of the EGR cooler when the EGR valve is open; determining a temperature difference value δT between the current temperature and the initial temperature T I ; comparing the temperature difference value δT to a first threshold value indicative of a functioning EGR system; indicating an EGR system fault if the value δT is less than the first threshold value; otherwise, comparing the temperature difference value δT to a second threshold value indicative of a properly functioning EGR cooler; and indicating an EGR cooler fault if the value δT is greater than the second threshold value.
Claim 22
Independent Claim
158 words
A method for determining a fault condition in an exhaust gas recirculation (EGR) system having an EGR valve operable to control the re-circulation of exhaust gas and an EGR cooler operable to reduce the temperature of the re-circulated gas, comprising the steps of: sensing an initial temperature T I of the EGR cooler; then opening the EGR valve; sensing a current temperature of the EGR cooler when the EGR valve is open; determining a temperature difference value δT between the current temperature and the initial temperature T I ; comparing the temperature difference value δT to a first threshold value indicative of a functioning EGR system; indicating an EGR system fault if the value δT is less than the first threshold value; otherwise, comparing the temperature difference value δT to a second threshold value indicative of a properly functioning EGR cooler; and indicating an EGR cooler fault if the value δT is greater than the second threshold value.
Claim 23
Dependent Claim
76 words
The method for determining a fault condition in an EGR system according to claim 17, further comprising the steps of: comparing the temperature difference value δT to a third threshold value if the value δT is greater than the second threshold value; indicating an EGR cooler fault condition if the value δT is less than the third threshold value; and indicating an EGR cooler failure if the value δT is greater than the third threshold value.
Claim 24
Dependent Claim
50 words
The method for determining a fault condition in an EGR system according to claim 17, further comprising: repeating at least the steps of sensing the current temperature and determining a temperature difference value for a predetermined time period; and closing the EGR valve after the predetermined time period has expired.
References Cited (Backward Citations)
US4149408A
Cited
US4164206A
Cited
US4267812A
Cited
US4394742A
Cited
US4462376A
Cited
US4424709A
Cited
US4715348A
Cited
US4870942A
Cited
US4793318A
Cited
US4834054A
Cited
US4870941A
Cited
US4967717A
Cited
US4974572A
Cited
US5014203A
Cited
US5301126C1
Cited
US5301126A
Cited
US5041976A
Cited
US5103655A
Cited
US5086745A
Cited
US5297047A
Cited
US5137004A
Cited
US5209212A
Cited
US5243949A
Cited
US5387253A
Cited
US5394744A
Cited
US5508926A
Cited
US5635633A
Cited
US5621167A
Cited
US5703285A
Cited
US5916130A
Cited
US5727533A
Cited
US5732688A
Cited
US6009709A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2003-07-11 | 2004-01-10 | 2004-07-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2007-07-11 | 2008-01-10 | 2008-07-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2011-07-11 | 2012-01-10 | 2012-07-11 | $7700.00 | Window Closed / Lapsed |