CN112539121B - Carbon deposition online detection method and detection device of EGR system and motor vehicle - Google Patents
Carbon deposition online detection method and detection device of EGR system and motor vehicle Download PDFInfo
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- CN112539121B CN112539121B CN202011364683.0A CN202011364683A CN112539121B CN 112539121 B CN112539121 B CN 112539121B CN 202011364683 A CN202011364683 A CN 202011364683A CN 112539121 B CN112539121 B CN 112539121B
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- 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
- F02M26/00—Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
- F02M26/49—Detecting, diagnosing or indicating an abnormal function of the EGR system
Abstract
The application provides a carbon deposition online detection method and device of an EGR system and a motor vehicle. When the EGR valve is determined to be in a diagnosis working condition, the opening degree of the EGR valve and a first primary NOx deviation value are obtained; and when the opening of the EGR valve and the first primary NOx deviation value meet a first preset condition, determining that carbon deposition exists in the EGR system. According to the method and the device, under the specific working condition of the diagnosis working condition, the carbon deposition of the EGR system can be detected on line according to the opening degree of the EGR valve and the first original NOx exhaust deviation value.
Description
Technical Field
The invention relates to the field of carbon deposition detection of an EGR (exhaust gas recirculation) system, in particular to a carbon deposition online detection method and device of the EGR system and a motor vehicle.
Background
In the process of engine Exhaust Gas Recirculation (EGR), the EGR system can reintroduce high-temperature Exhaust Gas discharged by an engine into an air inlet pipe to be mixed with fresh Gas and then enter a combustion chamber for combustion, so that the NOx emission of the engine can be effectively reduced; after long-term use, the EGR system can generate carbon deposition, and the normal work of the engine is influenced. And the carbon deposition of the EGR system can not be detected on line in the prior art.
Disclosure of Invention
In view of the above, the invention provides an online carbon deposition detection method and device for an EGR system, and a motor vehicle, which can effectively solve the technical problems in the prior art.
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
a carbon deposition online detection method of an EGR system comprises the following steps:
and determining to be in a diagnosis working condition, wherein the diagnosis working condition is a specific working condition for carbon deposition detection, and the EGR valve is in an opening state under the diagnosis working condition.
And acquiring the opening degree of the EGR valve and the first primary NOx deviation value.
And when the opening of the EGR valve and the first primary NOx deviation value meet a first preset condition, determining that carbon deposition exists in the EGR system.
Optionally, determining that the vehicle is in the diagnostic condition includes: it is determined that the current EGR rate is greater than the set EGR rate, and the driving pressure difference is not less than the first cooler pressure resistance and not greater than the second cooler pressure resistance. The second cooler pressure resistance is greater than the first cooler pressure resistance.
Optionally, the manner of obtaining the first NOx original deviation value includes:
and acquiring a current actual NOx value and a preset initial NOx value.
And taking the difference between the current actual NOx value and the preset initial NOx value as the first primary NOx deviation value.
Optionally, determining that the EGR valve opening and the first primary NOx deviation value meet a first preset condition includes: and determining that the opening degree of the EGR valve is not smaller than the preset opening degree of the EGR valve, and the first original NOx discharge deviation value is larger than the preset original NOx discharge deviation value.
Optionally, after determining that the EGR valve opening and the first primary NOx deviation value meet a first preset condition, the method further includes:
and controlling the EGR valve to close.
And acquiring a second primary NOx deviation value.
And determining the carbon deposition degree according to the second original NOx deviation value and the carbon deposition degree judgment value.
Optionally, determining the carbon deposition degree according to the second original NOx deviation value and the carbon deposition degree determination value, including:
and if the second original NOx deviation value is larger than the carbon deposition degree judgment value, determining that the carbon deposition degree is first-level carbon deposition.
And if the second original NOx deviation value is not larger than the carbon deposition degree judgment value, determining the carbon deposition degree to be secondary carbon deposition.
And the carbon deposition degree of the primary carbon deposition is smaller than that of the secondary carbon deposition.
Correspondingly, the invention also provides a carbon deposition on-line detection device of the EGR system, which comprises:
and the working condition determining module is used for determining a diagnosis working condition, wherein the diagnosis working condition is a specific working condition for carbon deposition detection, and the EGR valve is in an opening state under the diagnosis working condition.
The obtaining module is used for obtaining the opening of the EGR valve and the first primary NOx deviation value.
And the carbon deposit detection module is used for determining that carbon deposit exists in the EGR system when the opening of the EGR valve and the first original NOx deviation value meet a first preset condition.
Optionally, the method further includes: and the carbon deposit degree determining module is used for controlling the EGR valve to be closed after determining that the opening of the EGR valve and the first original NOx deviation value meet a first preset condition. Acquiring a second primary NOx deviation value; and determining the carbon deposition degree according to the second original NOx deviation value and the carbon deposition degree judgment value.
Optionally, determining the carbon deposition degree according to the second original NOx deviation value and the carbon deposition degree determination value, including:
and if the second original NOx deviation value is larger than the carbon deposition degree judgment value, determining that the carbon deposition degree is first-level carbon deposition.
And if the second original NOx deviation value is not larger than the carbon deposition degree judgment value, determining the carbon deposition degree to be secondary carbon deposition.
And the carbon deposition degree of the primary carbon deposition is smaller than that of the secondary carbon deposition.
Correspondingly, the invention also provides a motor vehicle which comprises the carbon deposition detection device.
Compared with the prior art, the technical scheme provided by the invention at least has the following advantages:
the invention provides an online carbon deposition detection method and device of an EGR (exhaust gas recirculation) system and a motor vehicle. The detection method comprises the following steps: determining a diagnosis working condition, wherein the diagnosis working condition is a specific working condition for carbon deposition detection, and the EGR valve is in an open state under the diagnosis working condition; acquiring the opening of an EGR valve and a first primary NOx deviation value; and when the opening of the EGR valve and the first primary NOx deviation value meet a first preset condition, determining that carbon deposition exists in the EGR system.
According to the method, under the specific working condition of the diagnosis working condition, the carbon deposition of the EGR system can be detected on line according to the opening degree of the EGR valve and the first original-exhaust NOx deviation value.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a flowchart of an online carbon deposition detection method for an EGR system according to an embodiment of the present invention;
FIG. 2 is a flowchart illustrating a method for detecting soot in an EGR system in an online manner according to another embodiment of the present invention;
fig. 3 is a structural diagram of an online carbon deposition detection device of an EGR system according to an embodiment of the present invention;
fig. 4 is a structural diagram of an online carbon deposit detection device of an EGR system according to another embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As described in the background art, in the process of engine Exhaust Gas Recirculation (EGR), the EGR system reintroduces high-temperature Exhaust Gas discharged from the engine into the intake pipe to mix with fresh Gas and then enters the combustion chamber for combustion, which can effectively reduce the original NOx emission of the engine; however, after long-term use, the EGR system may generate carbon deposits, which may affect the normal operation of the engine. And the carbon deposition of the EGR system can not be detected on line in the prior art.
Based on the method, the device and the motor vehicle, the carbon deposition on-line detection method and device of the EGR system are provided. The detection method comprises the following steps: determining a diagnosis working condition, wherein the diagnosis working condition is a specific working condition for carbon deposition detection, and the EGR valve is in an open state under the diagnosis working condition; acquiring the opening of an EGR valve and a first primary NOx deviation value; and when the opening of the EGR valve and the first primary NOx deviation value meet a first preset condition, determining that carbon deposition exists in the EGR system.
According to the method, under the specific working condition of the diagnosis working condition, the carbon deposition of the EGR system can be accurately detected according to the opening degree of the EGR valve and the first original-exhaust NOx deviation value.
To achieve the above object, the technical solutions provided by the embodiments of the present invention are described in detail below, specifically with reference to fig. 1 to 4.
Referring to fig. 1, fig. 1 is a flowchart of an online soot detection method for an EGR system according to an embodiment of the present invention.
A carbon deposition online detection method of an EGR system comprises the following steps:
and determining to be in a diagnosis condition. The diagnosis working condition is a specific working condition for carbon deposition detection, and the EGR valve is in an open state under the diagnosis working condition.
And acquiring the opening degree of the EGR valve and the first primary NOx deviation value.
And when the opening of the EGR valve and the first primary NOx deviation value meet a first preset condition, determining that carbon deposition exists in the EGR system.
It should be noted that:
the carbon deposition detection method of the EGR system is applied to the EGR system adopting closed-loop control.
The opening degree of the EGR valve is obtained from an ECU (electronic control unit) of the engine.
And the first primary NOx deviation value is obtained from an ECU (electronic control unit) of the engine. The first raw NOx offset value represents an offset of a raw NOx value of the engine from a predetermined initial NOx value.
In this embodiment, after it is determined that carbon deposition exists in the EGR system, a prompt may be sent to the user through a sound, a text, or an image to remind the user that carbon deposition exists in the EGR system.
And when the opening degree of the EGR valve and the first primary NOx deviation value do not meet a first preset condition, the EGR system is free of carbon deposition.
It should be noted that: the EGR valve is an exhaust gas recirculation valve and is a valve for controlling the flow rate of EGR exhaust gas, and the control of the flow rate of exhaust gas can be realized by adjusting the opening degree of the EGR valve.
The inventor finds that: in the EGR system using the closed-loop control, a phenomenon that the opening degree of the EGR valve gradually increases occurs at the same exhaust gas flow rate during the closed-loop control with the long-term use of the EGR system. The inventor further researches and discovers that the reason is that after the EGR system is coked, the piezoresistance of the EGR system is increased, the passing exhaust gas is reduced, and in order to meet the closed-loop requirement of the EGR rate and achieve the purpose of reducing the piezoresistance, the control chip automatically increases the actual opening degree of the EGR valve so as to pass more exhaust gas to obtain the required exhaust gas quantity. And with the aggravation of carbon deposition, the actual opening degree of the EGR valve can reach the maximum finally, so that the EGR valve is in a full-open state, the minimum pressure resistance is realized, and the required exhaust gas quantity is obtained.
Based on this, the inventors have found that the opening degree of the EGR valve can be used as a detection condition for online determination of whether the EGR system is carbon-deposited. However, it is found later that if the opening degree of the EGR valve is simply used as a detection condition for online judging whether the EGR system deposits carbon, the stuck state (stuck at a certain opening degree) of the EGR valve is easily judged as the carbon deposit, so that the detection accuracy is low.
The inventors have further studied and found that, in an EGR system employing closed-loop control, a phenomenon in which the engine-out NOx, which is detected as NOx produced by combustion of the engine block, rises with long-term use of the EGR system. The reason for this phenomenon is that as the carbon deposition of the EGR system increases, the pipeline flow area decreases, the flow rate of the exhaust gas passing through the EGR decreases, and the pressure resistance of the EGR system increases, so that the capability of the EGR system to reduce the Nox emission of the engine deteriorates, and the Nox emission of the engine increases.
Based on this, the inventors have found that the raw NOx deviation value can be used as a detection condition for determining whether the EGR system is carbon-deposited. However, it was found later that if the raw NOx deviation value is simply used as a detection condition for determining whether the EGR system is carbon deposition, the engine combustion deterioration itself is easily erroneously determined as carbon deposition, so that the detection accuracy is low.
It can be understood that, in the above embodiment, under a specific condition of a diagnosis condition, carbon deposition of the EGR system is detected according to the opening degree of the EGR valve and the first NOx deviation value, and the opening degree of the EGR valve is used as a detection condition for judging whether the EGR system is carbon deposition, so as to eliminate erroneous judgment caused by combustion degradation of the engine itself; and the misjudgment caused by the clamping stagnation of the EGR valve is eliminated by taking the first primary NOx deviation value as a detection condition for judging whether the EGR system is carbon deposited or not. Therefore, the embodiment realizes the on-line detection of carbon deposition of the EGR system, ensures that misjudgment caused by the clamping stagnation of the EGR valve or the combustion degradation of the engine per se can not occur, and ensures the detection precision.
In one embodiment of the present application, determining that the vehicle is in the diagnostic operating condition includes: it is determined that the current EGR rate is greater than the set EGR rate, and the driving pressure difference is not less than the first cooler pressure resistance and not greater than the second cooler pressure resistance. The second cooler pressure resistance is greater than the first cooler pressure resistance.
It should be noted that: the current EGR rate, the set EGR rate, the driving pressure difference, the first cooler pressure resistance and the second cooler pressure resistance are all obtained from an ECU (electronic control unit) of the engine.
The specific value of the set EGR rate is not limited, and the specific value needs to be calculated and selected according to actual application. For example, the set EGR rate may be set to 10%.
The specific values of the first cooler pressure resistance and the second cooler pressure resistance are not limited, and the values need to be specifically calculated and selected according to actual application. The second cooler pressure resistance is greater than the first cooler pressure resistance, and in particular, the second cooler pressure resistance may be 2 times greater than the first cooler pressure resistance.
It should be noted that: because under different operating modes, EGR rate and driving pressure difference are different, and the detection precision to carbon deposit is different under different EGR rate and driving pressure difference, through confirming that the diagnosis operating mode is in this embodiment: "the current EGR rate is larger than the set EGR rate, and the driving pressure difference is not smaller than the first cooler pressure resistance and not larger than the second cooler pressure resistance. The second cooler pressure resistance is larger than the first cooler pressure resistance' so that the working condition is in a sensitive working condition for detecting the carbon deposition of the EGR system when the carbon deposition is detected, the carbon deposition of the EGR system can be detected more easily, and the detection precision is improved.
Alternatively, the diagnostic operating condition is determined to be "the current EGR rate is greater than 10%, the driving pressure differential is not less than the first cooler pressure resistance, and not greater than the second cooler pressure resistance, wherein the second cooler pressure resistance is 2 times greater than the first cooler pressure resistance. Under the condition, when carbon deposition is detected, the diagnosis working condition can be in the optimal working condition for detecting the carbon deposition of the EGR system, so that the carbon deposition of the EGR system can be optimally detected, and the detection precision is improved.
In an embodiment of the present application, the manner of obtaining the first NOx offset value includes:
acquiring a current actual NOx value and a preset initial NOx value;
and taking the difference between the current actual NOx value and the preset initial NOx value as the first primary NOx deviation value.
It should be noted that: the current actual NOx value and the preset initial NOx value both exist in the ECU electronic control unit, and the ECU electronic control unit may calculate and obtain the first primary NOx deviation value according to the current actual NOx value and the preset initial NOx value. Wherein the current actual value of NOx is indicative of a current on-board NOx value of the engine.
The specific value of the preset initial NOx value is not limited, and the specific value needs to be calculated and selected according to actual application. For example: the preset initial NOx value may be an actual NOx value detected when the new vehicle is off-line, or may be a value set in a unified manner according to a specific model of the engine.
In an embodiment of the present application, determining that the EGR valve opening and the first primary NOx offset value satisfy a first preset condition includes: and determining that the opening degree of the EGR valve is not smaller than the preset opening degree of the EGR valve, and the first original NOx discharge deviation value is larger than the preset original NOx discharge deviation value.
It should be noted that:
the preset EGR valve opening degree and the preset primary NOx deviation value can be obtained from an ECU (electronic control unit) of the engine.
The specific value of the preset EGR valve opening degree is not limited, and the specific value needs to be calculated and selected according to actual application. For example: the preset EGR valve opening degree may be 80% of the EGR valve limit opening degree. The EGR valve limit opening degree refers to a maximum opening degree of the EGR valve within a safe range.
The specific value of the preset primary NOx deviation value is not limited, and the specific value needs to be calculated and selected according to actual application. For example: the preset primary NOx bias value may be 2 g/kWh.
In this embodiment, after it is determined that the EGR valve opening is not smaller than the preset EGR valve opening and the first original NOx deviation value is larger than the preset original NOx deviation value, the duration that the EGR valve opening and the first original NOx deviation value meet the first preset condition is further determined, and when the duration is not smaller than the preset duration, it is determined that carbon deposition exists in the EGR system.
Referring to fig. 2, in an embodiment of the application, after determining that the EGR valve opening and the first NOx emission deviation value satisfy the first preset condition, the method further includes:
controlling the EGR valve to close;
acquiring a second primary NOx deviation value;
and determining the carbon deposition degree according to the second original NOx deviation value and the carbon deposition degree judgment value.
It should be noted that:
acquiring a second primary NOx deviation value, comprising: acquiring an actual NOx value after the EGR valve is closed and an actual NOx value when the EGR valve is opened; and taking the difference between the actual NOx value after the EGR valve is closed and the actual NOx value when the EGR valve is opened as the second original-exhaust NOx deviation value.
The actual NOx value after the EGR valve is closed may be an engine raw NOx value obtained at any time after the EGR valve is closed in the current detection. The actual value of NOx when the EGR valve is opened may be an engine original NOx value obtained at an arbitrary timing when the EGR valve is opened in this detection. Alternatively, the actual NOx value at which the EGR valve is opened may be an actual NOx value used to calculate the first NOx offset value.
The specific value of the carbon deposition degree judgment value is not limited, and the specific calculation and selection are carried out according to the actual application requirement and the second original NOx deviation value when a new vehicle is off-line.
And the second primary NOx deviation value is obtained from an ECU (electronic control unit) of the engine. The second raw NOx deviation value is indicative of a difference between the engine raw NOx value after the EGR valve is closed and the engine raw NOx value when the EGR valve is open.
The embodiment aims at the problem that the existing engine EGR rate has large influence on the original NOx value of the engine, so that the carbon deposition of an EGR system cannot be judged only through the original NOx value of the engine when the EGR valve is opened. And calculating a second original NOx deviation value by switching on and off the EGR valve to obtain an actual NOx value after the EGR valve is closed and an actual NOx value when the EGR valve is opened, determining the original NOx degradation condition of the engine according to the second original NOx deviation value and the carbon deposition degree determining value, and further judging the carbon deposition degree of the EGR system.
In principle, under the condition that the EGR system is determined to have carbon deposition, the carbon deposition of the EGR system is gradually increased along with the continuous use of the EGR system, and the capability of the EGR system for reducing the original NOx value of the engine is weakened, so that the original NOx value of the engine is gradually increased when the EGR valve is opened. And since the engine raw NOx value is substantially constant when the EGR valve is closed. Therefore, the difference between the actual NOx value after the EGR valve is closed and the actual NOx value when the EGR valve is opened becomes gradually smaller as the carbon deposition of the EGR system increases and the ability of the EGR system to reduce the original NOx value of the engine becomes weaker. That is, the second NOx emission deviation value may be indicative of the magnitude of the ability of the EGR system to reduce the NOx emission value of the engine, and may also be indicative of the severity of carbon deposition in the EGR system. The soot degree of the EGR system may be determined by the second NOx deviation value and a preset soot degree determination value.
In an embodiment of the present application, determining the degree of soot formation according to the second NOx deviation value and the degree of soot formation determination value includes:
and if the second original NOx deviation value is larger than the carbon deposition degree judgment value, determining that the carbon deposition degree is first-level carbon deposition.
And if the second original NOx deviation value is not larger than the carbon deposition degree judgment value, determining the carbon deposition degree to be secondary carbon deposition.
And the carbon deposition degree of the primary carbon deposition is smaller than that of the secondary carbon deposition.
The smaller the second primary NOx deviation value is, the weaker the EGR system is in its ability to reduce the engine primary NOx value is, and the higher the severity of the EGR system carbon deposit is. Conversely, the larger the second primary NOx deviation value is, the stronger the ability of the EGR system to reduce the primary NOx value of the engine is, and the lower the severity of carbon deposition of the EGR system is.
Based on this, in the present embodiment, the degree of soot can be determined by setting the second NOx bias value and the soot degree determination value for comparison. If the second original NOx deviation value is larger than the carbon deposition degree judgment value, determining that the carbon deposition degree is first-level carbon deposition; and if the second original NOx deviation value is not larger than the carbon deposition degree judgment value, determining the carbon deposition degree to be secondary carbon deposition. And the carbon deposition degree of the primary carbon deposition is smaller than that of the secondary carbon deposition.
When the carbon deposition degree is determined to be first-order carbon deposition, the carbon deposition degree is not serious, and the carbon deposition can not be processed.
When the carbon deposition degree is determined to be secondary carbon deposition, the serious carbon deposition degree or the air leakage of the outer surface of the EGR system needs to be treated, and the treatment comprises the following steps: and when the carbon deposition degree is determined to be secondary carbon deposition, prompting a user to check whether the outer surface of the EGR system leaks gas, and prompting the user to perform sealing treatment on the outer surface of the EGR system if the outer surface of the EGR system leaks gas. And if the air is not leaked, prompting a user to clean the carbon deposit of the EGR system, and avoiding the emission exceeding the standard or SCR crystallization.
In this embodiment, after determining that the carbon deposition degree is first-level carbon deposition, a first prompt may be sent to a user through a first sound and/or a first character and/or a first image to prompt the user that the carbon deposition degree of the EGR system is first-level carbon deposition. After the carbon deposition degree is determined to be secondary carbon deposition, a second prompt is sent to the user through a second sound and/or a second character and/or a second image so as to remind the user that the carbon deposition degree of the EGR system is the secondary carbon deposition. The first prompt and the second prompt have different prompt modes and/or prompt contents.
Referring to fig. 3, correspondingly, the present invention further provides an online carbon deposition detection apparatus for an EGR system, including:
and the working condition determining module is used for determining a diagnosis working condition, wherein the diagnosis working condition is a specific working condition for carbon deposition detection, and the EGR valve is in an opening state under the diagnosis working condition.
The obtaining module is used for obtaining the opening of the EGR valve and the first primary NOx deviation value.
And the carbon deposit detection module is used for determining that carbon deposit exists in the EGR system when the opening of the EGR valve and the first original NOx deviation value meet a first preset condition.
It should be noted that:
the carbon deposition detection device of the EGR system is applied to the EGR system adopting closed-loop control. The carbon deposition detection device may be a control chip.
The opening degree of the EGR valve is obtained from an ECU (electronic control unit) of the engine.
And the first primary NOx deviation value is obtained from an ECU (electronic control unit) of the engine. The first original-exhaust NOx deviation value represents a deviation value of a NOx value generated by current combustion of the engine body and a preset initial NOx value.
In this embodiment, after it is determined that carbon deposition exists in the EGR system, a prompt may be sent to the user through a sound, a text, or an image to remind the user that carbon deposition exists in the EGR system.
And when the opening degree of the EGR valve and the first primary NOx deviation value do not meet a first preset condition, the EGR system is free of carbon deposition.
It should be noted that: the EGR valve is an exhaust gas recirculation valve and is a valve for controlling the flow rate of EGR exhaust gas, and the control of the flow rate of exhaust gas can be realized by adjusting the opening degree of the EGR valve.
The inventor finds that: in the EGR system using the closed-loop control, a phenomenon that the opening degree of the EGR valve gradually increases occurs at the same exhaust gas flow rate during the closed-loop control with the long-term use of the EGR system. The inventor further researches and discovers that the reason is that after the EGR system is coked, the piezoresistance of the EGR system is increased, the passing exhaust gas is reduced, and in order to meet the closed-loop requirement of the EGR rate and achieve the purpose of reducing the piezoresistance, the control chip automatically increases the actual opening degree of the EGR valve so as to pass more exhaust gas to obtain the required exhaust gas quantity. And with the aggravation of carbon deposition, the actual opening degree of the EGR valve can reach the maximum finally, so that the EGR valve is in a full-open state, the minimum pressure resistance is realized, and the required exhaust gas quantity is obtained.
Based on this, the inventors have found that the opening degree of the EGR valve can be used as a detection condition for online determination of whether the EGR system is carbon-deposited. However, it is found later that if the opening degree of the EGR valve is simply used as a detection condition for online judging whether the EGR system deposits carbon, the stuck state (stuck at a certain opening degree) of the EGR valve is easily judged as the carbon deposit, so that the detection accuracy is low.
The inventors have further studied and found that, in an EGR system employing closed-loop control, a phenomenon in which the engine-out NOx, which is detected as NOx produced by combustion of the engine block, rises with long-term use of the EGR system. The reason for this phenomenon is that as the carbon deposition of the EGR system increases, the pipeline flow area decreases, the flow rate of the exhaust gas passing through the EGR decreases, and the pressure resistance of the EGR system increases, so that the capability of the EGR system to reduce the Nox emission of the engine deteriorates, and the Nox emission of the engine increases.
Based on this, the inventors have found that the raw NOx deviation value can be used as a detection condition for determining whether the EGR system is carbon-deposited. However, it was found later that if the raw NOx deviation value is simply used as a detection condition for determining whether the EGR system is carbon deposition, the engine combustion deterioration itself is easily erroneously determined as carbon deposition, so that the detection accuracy is low.
It can be understood that, in the above embodiment, the detection device detects the carbon deposition of the EGR system according to the opening of the EGR valve and the first NOx deviation value under the specific condition of the diagnosis condition, and can eliminate the erroneous determination caused by the combustion degradation of the engine by using the opening of the EGR valve as the detection condition for judging whether the EGR system is carbon deposition; and the misjudgment caused by the clamping stagnation of the EGR valve is eliminated by taking the first primary NOx deviation value as a detection condition for judging whether the EGR system is carbon deposited or not. Therefore, the detection device of the embodiment not only realizes online detection of carbon deposition of the EGR system, but also ensures that misjudgment caused by clamping stagnation of the EGR valve or combustion degradation of the engine per se can not occur, and ensures the detection accuracy.
Referring to fig. 4, in an embodiment of the present application, the carbon deposition online detection device further includes: the carbon deposition degree determining module is used for controlling the EGR valve to be closed after determining that the opening of the EGR valve and the first original NOx deviation value meet a first preset condition; acquiring a second primary NOx deviation value; and determining the carbon deposition degree according to the second original NOx deviation value and the carbon deposition degree judgment value.
It should be noted that:
the carbon deposition degree determining module obtains a second primary NOx deviation value, and the method comprises the following steps: acquiring an actual NOx value after the EGR valve is closed and an actual NOx value when the EGR valve is opened; and taking the difference between the actual NOx value after the EGR valve is closed and the actual NOx value when the EGR valve is opened as the second original-exhaust NOx deviation value.
The actual NOx value after the EGR valve is closed may be an engine raw NOx value obtained at any time after the EGR valve is closed in the current detection. The actual value of NOx when the EGR valve is opened can be the original value of NOx discharged by the engine obtained at any time when the EGR valve is opened in the detection; alternatively, the actual NOx value at the time when the EGR valve is opened may be an actual NOx value used for calculating the first-source NOx offset value.
The specific value of the carbon deposition degree judgment value is not limited, and the specific calculation and selection are carried out according to the actual application requirement and the second original NOx deviation value when a new vehicle is off-line.
And the second primary NOx deviation value is obtained from an ECU (electronic control unit) of the engine. The second raw NOx deviation value is indicative of a difference between the engine raw NOx value after the EGR valve is closed and the engine raw NOx value when the EGR valve is open.
The embodiment aims at the problem that the existing engine EGR rate has large influence on the original NOx value of the engine, so that the carbon deposition condition of an EGR system cannot be judged only through the original NOx value of the engine when the EGR valve is opened. Therefore, the actual NOx value after the EGR valve is closed and the actual NOx value when the EGR valve is opened are obtained by opening and closing the EGR valve, so that a second original NOx deviation value is calculated, the original NOx degradation condition of the engine is determined according to the second original NOx deviation value and the carbon deposition degree determining value, and the carbon deposition degree of the EGR system is further judged.
In principle, under the condition that the EGR system is determined to have carbon deposition, the carbon deposition of the EGR system is gradually increased along with the continuous use of the EGR system, and the capability of the EGR system for reducing the original NOx value of the engine is weakened, so that the original NOx value of the engine is gradually increased when the EGR valve is opened. And since the engine raw NOx value is substantially constant when the EGR valve is closed. Therefore, the difference between the actual NOx value after the EGR valve is closed and the actual NOx value when the EGR valve is opened becomes gradually smaller as the carbon deposition of the EGR system increases and the ability of the EGR system to reduce the original NOx value of the engine becomes weaker. That is, the second NOx emission deviation value may be indicative of the magnitude of the ability of the EGR system to reduce the NOx emission value of the engine, and may also be indicative of the severity of carbon deposition in the EGR system. The soot degree of the EGR system may be determined by the second NOx deviation value and a preset soot degree determination value.
In an embodiment of the present application, determining the carbon deposition degree according to the second NOx deviation value and the carbon deposition degree determination value includes:
and if the second original NOx deviation value is larger than the carbon deposition degree judgment value, determining that the carbon deposition degree is first-level carbon deposition.
And if the second original NOx deviation value is not larger than the carbon deposition degree judgment value, determining the carbon deposition degree to be secondary carbon deposition.
And the carbon deposition degree of the primary carbon deposition is smaller than that of the secondary carbon deposition.
The smaller the second primary NOx deviation value is, the weaker the EGR system is in its ability to reduce the engine primary NOx value is, and the higher the severity of the EGR system carbon deposit is. Conversely, the larger the second primary NOx deviation value is, the stronger the ability of the EGR system to reduce the primary NOx value of the engine is, and the lower the severity of carbon deposition of the EGR system is.
Based on this, in the present embodiment, the degree of soot can be determined by setting the second NOx bias value and the soot degree determination value for comparison. If the second original NOx deviation value is larger than the carbon deposition degree judgment value, determining that the carbon deposition degree is first-level carbon deposition; and if the second original NOx deviation value is not larger than the carbon deposition degree judgment value, determining the carbon deposition degree to be secondary carbon deposition. And the carbon deposition degree of the primary carbon deposition is smaller than that of the secondary carbon deposition.
When the carbon deposition degree is determined to be first-order carbon deposition, the carbon deposition degree is not serious, and the carbon deposition can not be processed.
When the carbon deposition degree is determined to be secondary carbon deposition, the serious carbon deposition degree or the air leakage of the outer surface of the EGR system needs to be treated, and the treatment comprises the following steps: and when the carbon deposition degree is determined to be secondary carbon deposition, prompting a user to check whether the outer surface of the EGR system leaks gas, and prompting the user to perform sealing treatment on the outer surface of the EGR system if the outer surface of the EGR system leaks gas. And if the air is not leaked, prompting a user to clean the carbon deposit of the EGR system, and avoiding the emission exceeding the standard or SCR crystallization.
In this embodiment, after determining that the carbon deposition degree is first-level carbon deposition, a first prompt may be sent to a user through a first sound and/or a first character and/or a first image to prompt the user that the carbon deposition degree of the EGR system is first-level carbon deposition. After the carbon deposition degree is determined to be secondary carbon deposition, a second prompt is sent to the user through a second sound and/or a second character and/or a second image so as to remind the user that the carbon deposition degree of the EGR system is the secondary carbon deposition. The first prompt and the second prompt have different prompt modes and/or prompt contents.
Correspondingly, the invention also provides a motor vehicle which comprises the carbon deposition detection device.
The invention provides an online carbon deposition detection method and device of an EGR (exhaust gas recirculation) system and a motor vehicle. Determining that the EGR valve is in a diagnosis working condition, wherein the diagnosis working condition is a specific working condition for carbon deposition detection, and the EGR valve is in an open state under the diagnosis working condition; acquiring the opening of an EGR valve and a first primary NOx deviation value; and when the opening of the EGR valve and the first primary NOx deviation value meet a first preset condition, determining that carbon deposition exists in the EGR system.
According to the method, under the specific working condition of the diagnosis working condition, the carbon deposition of the EGR system can be detected on line according to the opening degree of the EGR valve and the first original-exhaust NOx deviation value.
All parts in the specification are described in a mode of combining parallel and progressive, each part is mainly described to be different from other parts, and the same and similar parts among all parts can be referred to each other.
In the above description of the disclosed embodiments, features described in various embodiments in this specification can be substituted for or combined with each other to enable those skilled in the art to make or use the present application. The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
It is further noted that, in the present application, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
Claims (8)
1. An online carbon deposition detection method for an EGR system is characterized by comprising the following steps:
determining a diagnosis working condition, wherein the diagnosis working condition is a specific working condition for carbon deposition detection, and the EGR valve is in an open state under the diagnosis working condition;
acquiring the opening of an EGR valve and a first primary NOx deviation value;
determining that carbon deposition exists in the EGR system when the opening of the EGR valve and the first primary NOx deviation value meet a first preset condition;
wherein the determining is in a diagnostic condition comprising: determining that the current EGR rate is greater than the set EGR rate, and that the driving pressure differential is not less than a first cooler pressure resistance and not greater than a second cooler pressure resistance, the second cooler pressure resistance being greater than the first cooler pressure resistance;
the manner of obtaining the first primary NOx offset value includes:
acquiring a current actual NOx value and a preset initial NOx value;
and taking the difference between the current actual NOx value and the preset initial NOx value as the first primary NOx deviation value.
2. The method of claim 1, wherein determining that the EGR valve opening and the first NOx emissions offset value meet a first predetermined condition comprises: and determining that the opening degree of the EGR valve is not smaller than the preset opening degree of the EGR valve, and the first original NOx discharge deviation value is larger than the preset original NOx discharge deviation value.
3. The method of claim 1, wherein determining that the EGR valve opening and the first NOx emissions offset value meet a first predetermined condition further comprises:
controlling the EGR valve to close;
acquiring a second primary NOx deviation value;
and determining the carbon deposition degree according to the second original NOx deviation value and the carbon deposition degree judgment value.
4. The method according to claim 3, wherein determining the degree of soot based on the second NOx bias value and the degree of soot determination value includes:
if the second original NOx deviation value is larger than the carbon deposition degree judgment value, determining that the carbon deposition degree is first-level carbon deposition;
if the second original NOx deviation value is not larger than the carbon deposition degree judgment value, determining the carbon deposition degree to be secondary carbon deposition;
and the carbon deposition degree of the primary carbon deposition is smaller than that of the secondary carbon deposition.
5. The utility model provides a carbon deposit on-line measuring device of EGR system which characterized in that includes:
the working condition determining module is used for determining a diagnosis working condition, wherein the diagnosis working condition is a specific working condition for carbon deposition detection, and the EGR valve is in an opening state under the diagnosis working condition;
the acquiring module is used for acquiring the opening of the EGR valve and the first primary NOx deviation value;
the carbon deposition detection module is used for determining that carbon deposition exists in the EGR system when the opening of the EGR valve and the first original-exhaust NOx deviation value meet a first preset condition;
the working condition determining module is specifically used for determining that the current EGR rate is greater than the set EGR rate, and the driving pressure difference is not less than a first cooler pressure resistance and not greater than a second cooler pressure resistance, wherein the second cooler pressure resistance is greater than the first cooler pressure resistance;
the obtaining module is specifically configured to obtain a current actual NOx value and a preset initial NOx value, and use a difference between the current actual NOx value and the preset initial NOx value as the first primary NOx deviation value.
6. The apparatus of claim 5, further comprising: the carbon deposition degree determining module is used for controlling the EGR valve to be closed after determining that the opening of the EGR valve and the first original NOx deviation value meet a first preset condition; acquiring a second primary NOx deviation value; and determining the carbon deposition degree according to the second original NOx deviation value and the carbon deposition degree judgment value.
7. The apparatus according to claim 6, wherein determining the degree of soot based on the second NOx bias value and the degree of soot determination value includes:
if the second original NOx deviation value is larger than the carbon deposition degree judgment value, determining that the carbon deposition degree is first-level carbon deposition;
if the second original NOx deviation value is not larger than the carbon deposition degree judgment value, determining the carbon deposition degree to be secondary carbon deposition;
and the carbon deposition degree of the primary carbon deposition is smaller than that of the secondary carbon deposition.
8. A motor vehicle, comprising: the carbon deposition online detection device according to any one of claims 5 to 7.
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| CN114753947A (en) * | 2022-03-28 | 2022-07-15 | 江铃汽车股份有限公司 | EGR valve carbon deposition real-time judgment method |
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