A correction method and device for measuring flow rate using a venturi tube

Abstract

The present application discloses a method and device for correcting flow measurement by a venturi tube, wherein the method comprises: obtaining the current actual pressure difference measured by the venturi tube in real time; determining the corrected pressure difference range corresponding to the current working condition of the vehicle based on the pre-generated correspondence between the steady-state working condition and the pressure difference; the corrected pressure difference range corresponding to the steady-state working condition is calculated by the accurate pressure difference corresponding to the steady-state working condition by a preset correction amplitude; the accurate pressure difference corresponding to the steady-state working condition is the pressure difference measured by the unblocked venturi tube under the steady-state working condition; if it is determined that the current actual pressure difference is within the corrected pressure difference range corresponding to the current working condition, then based on the theoretical exhaust gas flow corresponding to the current working condition, the current actual exhaust gas flow measured by the venturi tube is corrected; wherein the theoretical exhaust gas flow corresponding to the current working condition is determined based on the oxygen concentration in the exhaust gas measured by the sensor under the current working condition; if it is determined that the current actual pressure difference is not within the corrected pressure difference range, then an alarm message is fed back.

Description

Technical Field

[0001] The present application relates to a flow correction method, and in particular to a method and device for correcting flow measured by a venturi tube. Background Art

[0002] In order to effectively reduce the emission of nitrogen oxides from the engine, current vehicles are equipped with an exhaust gas recirculation system. According to the current operating conditions of the vehicle, the exhaust gas discharged by the engine is reintroduced into the intake pipe at a certain flow rate, mixed with fresh intake air, and then enters the engine's combustion chamber for combustion.

[0003] In order to effectively reduce nitrogen oxides in exhaust gas, the recirculated exhaust gas flow rate needs to match the current working conditions of the vehicle, so the recirculated exhaust gas flow rate is measured through a venturi tube. The specific measurement process is calculated based on the static pressure difference between the gas flowing through the inlet and throat of the venturi tube. Since the throat of the venturi tube is relatively small, as the engine runs longer, the throat is easily clogged by dust, resulting in inaccurate measurement, which in turn causes excessive exhaust emissions.

[0004] Therefore, in order to ensure that exhaust emissions meet the standards, the exhaust gas flow measured by the venturi tube is monitored. However, when the exhaust gas flow measured by the venturi tube is not verified to meet the standards, a warning is issued to remind the venturi tube to remove carbon deposits. However, the blockage of the venturi tube is relatively serious at this time, and when the venturi tube is slightly blocked, it may also cause the exhaust gas to exceed the standard to a certain extent, so the existing method cannot effectively ensure that the exhaust emissions meet the standards. Summary of the invention

[0005] Based on the above-mentioned deficiencies of the prior art, the present application provides a method and device for correcting flow measurement by a venturi tube to solve the problem that the prior art cannot detect slight blockage of the venturi tube and cannot ensure that the exhaust gas meets the standards.

[0006] In order to achieve the above objectives, this application provides the following technical solutions:

[0007] The first aspect of the present application provides a method for correcting flow rate measured by a venturi tube, characterized by comprising:

[0008] When the vehicle is in steady-state operation, the current actual pressure difference measured by the venturi tube is obtained in real time;

[0009] Based on the pre-generated correspondence between the steady-state working condition and the pressure difference, a corrected pressure difference range corresponding to the current working condition of the vehicle is determined; wherein the corrected pressure difference range corresponding to a steady-state working condition is obtained by calculating the accurate pressure difference corresponding to the steady-state working condition by a preset correction amplitude; the accurate pressure difference corresponding to the steady-state working condition is the pressure difference measured by the unblocked venturi tube under the pre-simulated steady-state working condition;

[0010] Determining whether the current actual pressure difference is within the corrected pressure difference range corresponding to the current working condition;

[0011] If it is determined that the current actual pressure difference is within the corrected pressure difference range corresponding to the current operating condition, the current actual exhaust gas flow measured by the venturi tube is corrected based on the theoretical exhaust gas flow corresponding to the current operating condition; wherein the theoretical exhaust gas flow corresponding to the current operating condition is determined based on the oxygen concentration in the exhaust gas measured by the sensor under the current operating condition;

[0012] If it is determined that the current actual pressure difference is not within the corrected pressure difference range corresponding to the current operating condition, an alarm message is fed back.

[0013] Optionally, in the above method, it also includes:

[0014] Obtaining the current actual exhaust gas flow measured by the venturi tube;

[0015] Determine whether the current actual exhaust gas flow meets a preset restriction condition; wherein the preset restriction condition is that the current actual exhaust gas flow is not less than a preset minimum exhaust gas flow, and the difference between the current actual exhaust gas flow and the current filtered exhaust gas flow is not greater than a preset flow difference; the current filtered exhaust gas flow is obtained by filtering the current actual exhaust gas flow;

[0016] If it is determined that the current actual exhaust gas flow rate meets the preset restriction condition, determining whether the sensor has completed dew point release;

[0017] If it is determined that the sensor has completed dew point release, determining whether the oxygen concentration in the current exhaust gas measured by the sensor is greater than a preset minimum oxygen concentration;

[0018] If it is determined that the oxygen concentration in the current exhaust gas measured by the sensor is greater than the preset minimum oxygen concentration, it is determined that the vehicle is in steady-state operation.

[0019] Optionally, in the above method, the correcting the current actual exhaust gas flow measured by the venturi tube based on the theoretical exhaust gas flow under the current working condition includes:

[0020] Calculating the difference between the current actual pressure difference and the accurate pressure difference corresponding to the current working condition to obtain a current pressure difference error value;

[0021] Finding the correction coefficient corresponding to the current pressure difference error value from the correspondence between the pressure difference error value and the correction coefficient generated in advance; wherein the correspondence between the pressure difference error value and the correction coefficient is obtained in advance by testing different blockage degrees of the venturi tube under various steady-state conditions; the correction coefficient is obtained based on the ratio of the theoretical exhaust gas flow corresponding to each steady-state condition to the actual exhaust gas flow measured by the venturi tube;

[0022] The current actual exhaust gas flow is corrected using the correction coefficient corresponding to the current pressure difference error value.

[0023] Optionally, in the above method, the method for determining the theoretical exhaust flow rate corresponding to the current operating condition includes:

[0024] obtaining the oxygen concentration in the exhaust gas measured by the sensor under the current operating condition;

[0025] Calculating the excess air coefficient under the current working condition according to the measured oxygen concentration;

[0026] Calculate the fresh air intake of the engine under the current working condition by using the excess air coefficient and the fuel consumption under the current working condition;

[0027] The total air intake amount of the engine under the current working condition is subtracted from the fresh air intake amount of the engine under the current working condition to obtain the theoretical exhaust gas flow corresponding to the current working condition.

[0028] Optionally, in the above method, after the current actual exhaust gas flow measured by the venturi tube is corrected based on the theoretical exhaust gas flow corresponding to the current working condition, the method further includes:

[0029] Obtaining a target exhaust gas flow rate corresponding to the current operating condition;

[0030] Calculating the difference between the target exhaust gas flow rate and the corrected current actual exhaust gas flow rate to obtain an exhaust gas flow rate difference;

[0031] Based on the exhaust gas flow difference, the opening of the exhaust gas valve of the exhaust gas recirculation system is adjusted by a PID controller.

[0032] The second aspect of the present application provides a correction device for measuring flow through a venturi tube, comprising:

[0033] A first acquisition unit is used to acquire the current actual pressure difference measured by the venturi tube in real time when the vehicle is in steady-state operation;

[0034] A range determination unit, configured to determine a corrected pressure differential range corresponding to the current working condition of the vehicle based on a pre-generated correspondence between a steady-state working condition and a pressure differential; wherein the corrected pressure differential range corresponding to a steady-state working condition is obtained by calculating an accurate pressure differential corresponding to the steady-state working condition by a preset correction amplitude; the accurate pressure differential corresponding to the steady-state working condition is a pressure differential measured by the unblocked venturi tube under the pre-simulated steady-state working condition;

[0035] A first judgment unit, used to judge whether the current actual pressure difference is within the corrected pressure difference range corresponding to the current working condition;

[0036] a correction unit, configured to correct the current actual exhaust gas flow measured by the venturi tube based on a theoretical exhaust gas flow corresponding to the current operating condition if it is determined that the current actual pressure difference is within a correction pressure difference range corresponding to the current operating condition; wherein the theoretical exhaust gas flow corresponding to the current operating condition is determined based on an oxygen concentration in the exhaust gas measured by a sensor under the current operating condition;

[0037] The alarm unit is used to feedback alarm information if it is determined that the current actual pressure difference is not within the corrected pressure difference range corresponding to the current working condition.

[0038] Optionally, in the above device, it also includes:

[0039] A second acquisition unit, used to acquire the current actual exhaust gas flow measured by the venturi tube;

[0040] a second judgment unit, configured to judge whether the current actual exhaust gas flow rate satisfies a preset restriction condition; wherein the preset restriction condition is that the current actual exhaust gas flow rate is not less than a preset minimum exhaust gas flow rate, and the difference between the current actual exhaust gas flow rate and the current filtered exhaust gas flow rate is not greater than a preset flow difference; the current filtered exhaust gas flow rate is obtained by filtering the current actual exhaust gas flow rate;

[0041] a third judgment unit, configured to judge whether the sensor has completed dew point release if it is judged that the current actual exhaust gas flow meets a preset restriction condition;

[0042] a fourth determination unit, configured to determine whether the oxygen concentration in the current exhaust gas measured by the sensor is greater than a preset minimum oxygen concentration if it is determined that the sensor has completed dew point release;

[0043] The state determination unit is used to determine that the vehicle is in steady-state operation if it is determined that the oxygen concentration in the current exhaust gas measured by the sensor is greater than a preset minimum oxygen concentration.

[0044] Optionally, in the above device, the correction unit includes:

[0045] A first calculation unit, used for calculating the difference between the current actual pressure difference and the accurate pressure difference corresponding to the current working condition, to obtain a current pressure difference error value;

[0046] A search unit, used to search for the correction coefficient corresponding to the current pressure difference error value from the correspondence between the pressure difference error value and the correction coefficient generated in advance; wherein the correspondence between the pressure difference error value and the correction coefficient is obtained in advance by testing different blockage degrees of the venturi tube under various steady-state conditions; the correction coefficient is obtained based on the ratio of the theoretical exhaust gas flow corresponding to each steady-state condition to the actual exhaust gas flow measured by the venturi tube;

[0047] The correction subunit is used to correct the current actual exhaust gas flow rate using the correction coefficient corresponding to the current pressure difference error value.

[0048] Optionally, in the above device, it also includes:

[0049] a third acquisition unit, configured to acquire the oxygen concentration in the exhaust gas measured by the sensor under the current working condition;

[0050] A second calculation unit is used to calculate the excess air coefficient under the current working condition according to the measured oxygen concentration;

[0051] a fourth calculation unit, configured to calculate the fresh air intake amount of the engine under the current working condition by using the excess air coefficient and the fuel consumption under the current working condition;

[0052] The fifth calculation unit is used to subtract the fresh air intake amount of the engine under the current working condition from the total air intake amount of the engine under the current working condition to obtain a theoretical exhaust gas flow rate corresponding to the current working condition.

[0053] Optionally, in the above device, it also includes:

[0054] a fourth calculation unit, configured to obtain a target exhaust gas flow rate corresponding to the current operating condition;

[0055] a sixth calculation unit, configured to calculate a difference between the target exhaust gas flow rate and the corrected current actual exhaust gas flow rate to obtain an exhaust gas flow rate difference;

[0056] The regulating unit is used to regulate the opening of the exhaust valve of the exhaust gas recirculation system through a PID controller based on the exhaust gas flow difference.

[0057] The present application provides a method for correcting the flow rate measured by a venturi tube. When the vehicle is in steady-state operation, the current actual pressure difference measured by the venturi tube is obtained in real time, and then based on the correspondence between the pre-generated steady-state working condition and the pressure difference, the corrected pressure difference range corresponding to the current working condition of the vehicle is determined, and it is judged whether the current actual pressure difference is within the corrected pressure difference range corresponding to the current working condition. Since the corrected pressure difference range corresponding to a steady-state working condition is calculated by the preset correction amplitude to the accurate pressure difference corresponding to the steady-state working condition, and the accurate pressure difference corresponding to the steady-state working condition is the pressure difference measured by the unblocked venturi tube under the pre-simulated steady-state working condition, if it is judged that the current actual pressure difference is within the corrected pressure difference range corresponding to the current working condition, it means that the venturi tube may be slightly blocked and can be corrected. Therefore, at this time, the theoretical exhaust gas flow corresponding to the current working condition is determined based on the oxygen concentration in the exhaust gas measured by the sensor under the current working condition, and the current actual exhaust gas flow measured by the venturi tube is corrected, so that when the venturi tube is slightly blocked, its measurement process can be corrected to ensure that the exhaust gas emissions do not exceed the standard. If it is determined that the current actual pressure difference is not within the corrected pressure difference range corresponding to the current operating conditions, it means that the Venturi tube is seriously blocked or damaged, so the feedback warning information has enabled the driver to remove carbon deposits or repair them in time. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0059] Figure 1 A flow chart of a method for correcting flow rate measured by a venturi tube provided in an embodiment of the present application;

[0060] Figure 2 A flowchart of a method for determining that a vehicle is in steady-state operation provided in an embodiment of the present application;

[0061] Figure 3 A flow chart of a method for determining a theoretical exhaust gas flow rate corresponding to a current operating condition provided in an embodiment of the present application;

[0062] Figure 4 A flowchart of a method for correcting the current actual exhaust gas flow provided in an embodiment of the present application;

[0063] Figure 5 A flow chart of a method for controlling the flow rate of recirculated exhaust gas provided in an embodiment of the present application;

[0064] Figure 6A schematic diagram of the structure of a correction device for measuring flow through a venturi tube provided in an embodiment of the present application;

[0065] Figure 7 A structural schematic diagram of a correction unit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0066] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0067] In this application, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0068] The present application embodiment provides a method for correcting the flow rate measured by a venturi tube, such as Figure 1 As shown, the following steps are included:

[0069] S101. When the vehicle is in steady-state operation, obtain in real time the current actual pressure difference measured by the venturi tube.

[0070] The current actual pressure difference measured by the venturi tube refers to the difference between the static pressure at the inlet of the venturi tube and the static pressure at the throat thereof.

[0071] Since the exhaust flow measured by the venturi tube cannot be accurately corrected when the vehicle is not in steady-state operation, in the embodiment of the present application, it is necessary to set corresponding release conditions to determine that the vehicle is in steady-state operation and to perform correction on the exhaust flow measured by the venturi tube.

[0072] Optionally, in another embodiment of the present application, a method for determining that the vehicle is in steady-state operation is improved, such as Figure 2 As shown, including:

[0073] S201. Obtain the current actual exhaust gas flow measured by the venturi tube.

[0074] S202: Determine whether the current actual exhaust gas flow rate meets the preset restriction condition.

[0075] Among them, the preset restriction condition is that the current actual exhaust gas flow rate is not less than the preset minimum exhaust gas flow rate, and the difference between the current actual exhaust gas flow rate and the current filtered exhaust gas flow rate is not greater than the preset flow rate difference. The current filtered exhaust gas flow rate is obtained by filtering the current actual exhaust gas flow rate, thereby ensuring that there is a certain exhaust gas recirculation flow rate at present, and the flow rate is relatively stable, which also reflects that the current operating condition of the vehicle is relatively stable.

[0076] If it is determined that the current actual exhaust gas flow rate meets the preset restriction condition, the next condition is determined, that is, step S203 is executed.

[0077] It should be noted that the execution order of each step in the embodiment of the present application is only one of the optional relationships, because the judgment of each condition is independent of each other, and only when each condition is met can it be determined that the release condition is met and the exhaust flow measured by the Venturi tube is corrected. Therefore, the execution order in the embodiment of the present application is only one of the optional methods.

[0078] S203: Determine whether the sensor has completed dew point release.

[0079] Optionally, the sensor in the embodiment of the present application may refer to a nitrogen oxide sensor installed in an existing vehicle after-treatment system, which can be used to measure the oxygen concentration in the exhaust gas, thereby eliminating the need to install an additional sensor.

[0080] The sensor in the embodiment of the present application is mainly used to measure the oxygen concentration in the exhaust gas so that the theoretical exhaust gas flow rate can be calculated later using the oxygen concentration. The sensor cannot accurately measure the oxygen concentration in the initial stage, so it is necessary to ensure that the dew point release has been completed, thereby ensuring that the accurate theoretical exhaust gas flow rate can be obtained. Therefore, if it is determined that the sensor has completed the dew point release, step S204 is executed.

[0081] S204: Determine whether the oxygen concentration in the current exhaust gas measured by the sensor is greater than a preset minimum oxygen concentration.

[0082] In order to ensure that the vehicle's engine is not allowed to operate in harsh conditions, it is necessary to determine whether the oxygen concentration in the current exhaust gas measured by the sensor is greater than the preset minimum oxygen concentration. If it is determined that the oxygen concentration in the current exhaust gas measured by the sensor is greater than the preset minimum oxygen concentration, step S205 is executed to start correcting the exhaust gas flow measured by the venturi tube.

[0083] S205: Determine that the vehicle is in steady-state operation.

[0084] S102: Based on the pre-generated correspondence between the steady-state operating condition and the pressure difference, determine a corrected pressure difference range corresponding to the current operating condition of the vehicle.

[0085] Among them, the current operating condition of the vehicle mainly refers to the operating condition of the vehicle's engine.

[0086] The corrected pressure difference range corresponding to a steady-state condition is calculated by presetting the correction amplitude to obtain the accurate pressure difference corresponding to the steady-state condition. The accurate pressure difference corresponding to a steady-state condition is the pressure difference measured by the unblocked venturi tube under the pre-simulated steady-state condition.

[0087] Specifically, in the embodiment of the present application, the vehicle is simulated in advance under various steady-state operating conditions, and then the exhaust gas pressure difference is measured through an unblocked Venturi tube to obtain the accurate pressure difference corresponding to each steady-state operating condition.

[0088] Since the correction effect is not good when the Venturi tube is seriously blocked or fails, the Venturi tube is cleaned of carbon deposits or repaired at this time. Therefore, in the embodiment of the present application, only a certain measurement deviation of the Venturi tube is corrected, that is, only the measurement value of the Venturi tube when it is slightly blocked is corrected, so the corresponding preset correction amplitude is set according to the test situation, that is, the preset correction amplitude can be set to a corresponding value according to the situation and needs. Then, the accurate pressure difference is adjusted by the preset correction amplitude to obtain the corresponding corrected pressure difference range. For example, if the preset correction amplitude is 10%, 90% of the accurate pressure difference measured by the Venturi tube in a steady-state condition is used as the lower limit of the corrected pressure difference range corresponding to the steady-state condition, and 110% of the accurate pressure difference is used as the steady-state condition.

[0089] Optionally, the correspondence between the steady-state condition and the pressure difference can be stored in MAP. Furthermore, the steady-state condition and the pressure difference can specifically be the parameters of the steady-state condition and the corrected pressure difference range, or the correspondence between the parameters of the steady-state condition, the accurate pressure difference, and the upper and lower limits of the corrected pressure difference range, so that the corrected pressure difference range corresponding to the current condition can be directly found from the correspondence. Of course, it can also be the correspondence between the parameters of the steady-state condition and the accurate pressure difference, first query the corresponding accurate pressure difference, and then calculate the accurate pressure difference according to the preset correction amplitude to obtain the corresponding corrected pressure difference range.

[0090] S103: Determine whether the current actual pressure difference is within the corrected pressure difference range corresponding to the current working condition.

[0091] When it is determined that the current actual pressure difference is within the corrected pressure difference range corresponding to the current working condition, it means that the current venturi tube is within the correctable range, so step S104 is executed at this time. If it is determined that the current actual pressure difference is not within the corrected pressure difference range corresponding to the current working condition, it means that the current venturi tube is seriously blocked or damaged, so step S105 is executed at this time.

[0092] S104: Based on the theoretical exhaust gas flow corresponding to the current working condition, correct the current actual exhaust gas flow measured by the venturi tube.

[0093] It should be noted that since the accurate pressure difference corresponding to the current operating conditions is also within the corrected pressure difference range, when the current actual pressure difference is equal to the accurate pressure difference corresponding to the current operating conditions, that is, when the Venturi tube is not blocked, a correction process will also be performed. However, at this time, the corrected current actual exhaust gas flow rate, because the theoretical exhaust gas flow rate is equal to the current actual exhaust gas flow rate, or the correction coefficient corresponding to this situation is set to 1, etc., there is no need to compile the corresponding processing logic for the situation where the current actual pressure difference is equal to the accurate pressure difference corresponding to the current operating conditions.

[0094] Of course, this is only one of the optional methods. Before executing step S102, it is also possible to first determine whether the current actual pressure difference is equal to the accurate pressure difference corresponding to the current working condition. When it is determined that the current actual pressure difference is not equal to the accurate pressure difference corresponding to the current working condition, step S102 is then executed.

[0095] It should be noted that the theoretical exhaust gas flow corresponding to the current operating condition is determined based on the oxygen concentration in the exhaust gas measured by the sensor under the current operating condition.

[0096] Optionally, a method for determining the theoretical exhaust flow rate corresponding to the current operating condition is as follows: Figure 3 As shown, the following steps are included:

[0097] S301. Obtaining the oxygen concentration in the exhaust gas measured by the sensor under the current working condition.

[0098] S302, calculating the excess oxygen air coefficient under the current working condition according to the measured oxygen concentration.

[0099] S303, using the excess air coefficient and fuel consumption under the current working condition, calculate the fresh air intake amount of the engine under the current working condition.

[0100] S304, subtracting the fresh air intake amount of the engine under the current working condition from the total air intake amount of the engine under the current working condition to obtain a theoretical exhaust gas flow rate corresponding to the current working condition.

[0101] Optionally, the current actual exhaust gas flow measured by the venturi tube is corrected, and the theoretical exhaust gas flow corresponding to the current operating condition can directly replace the current actual exhaust gas flow measured by the venturi tube and be directly used as the current exhaust gas flow to control the intake volume of the exhaust gas recirculation system.

[0102] Considering the existence of error factors such as the calculation error of the theoretical exhaust gas flow rate, it is also possible to predetermine the relationship between the theoretical exhaust gas flow rate under each steady state and the actual exhaust gas flow rate measured by the venturi tube, and use this relationship to calculate the actual exhaust gas flow rate measured by the venturi tube. Based on this principle, another embodiment of the present application provides a specific implementation of step S104, such as Figure 4 As shown, the following steps are included:

[0103] S401. Calculate the difference between the current actual pressure difference and the accurate pressure difference corresponding to the current working condition to obtain a current pressure difference error value.

[0104] S402: Find out the correction coefficient corresponding to the current pressure difference error value from the correspondence between the pressure difference error value and the correction coefficient generated in advance.

[0105] The corresponding relationship between the pressure difference error value and the correction coefficient is obtained in advance by testing different blockage degrees of the venturi tube under various steady-state conditions. The correction coefficient is obtained based on the ratio of the theoretical exhaust gas flow corresponding to each steady-state condition to the actual exhaust gas flow measured by the venturi tube.

[0106] Specifically, in the embodiment of the present application, for each steady-state condition, the theoretical exhaust gas flow rate under the steady-state condition and the actual exhaust gas flow rate measured by the venturi tube with a certain degree of blockage under the steady-state condition are calculated. The calculation method of the theoretical exhaust gas flow rate can be found in Figure 3 The method shown. Then, the ratio of the theoretical exhaust gas flow rate to the actual exhaust gas flow rate under the steady-state condition is calculated to obtain the initial correction coefficient. Then, according to the conditions of the exhaust valve of the exhaust gas recirculation system under different simulated blockage conditions, the initial correction coefficient is adjusted to obtain the final correction coefficient. In addition, considering that when the measurement error is small, it will not affect the exhaust emissions, the initial correction coefficient can also be adjusted appropriately. Finally, the difference between the pressure difference measured by the Venturi tube in the simulation scenario and the corresponding accurate pressure difference is obtained, and the corresponding relationship between the difference and the correction coefficient is constructed.

[0107] S403: Correct the current actual exhaust gas flow rate using a correction coefficient corresponding to the current pressure difference error value.

[0108] Specifically, the correction coefficient corresponding to the current pressure difference error value is multiplied by the current actual exhaust gas flow rate to obtain the corrected current actual exhaust gas flow rate.

[0109] It should be noted that, after obtaining the corrected current actual exhaust gas flow rate, the corrected current actual exhaust gas flow rate can be used to control the recirculation exhaust gas flow rate.

[0110] Optionally, the present application embodiment provides a method for controlling the flow rate of recirculated exhaust gas, such as Figure 5 As shown, including:

[0111] S501. Obtain a target exhaust gas flow rate corresponding to the current operating condition.

[0112] The target exhaust gas flow rate corresponding to the current operating condition is the optimal target exhaust gas flow rate under the current operating condition, which is determined in advance through experiments.

[0113] S502: Calculate the difference between the target exhaust gas flow rate and the corrected current actual exhaust gas flow rate to obtain the exhaust gas flow rate difference.

[0114] S503 , based on the exhaust gas flow difference, adjusting the opening of the exhaust gas valve of the exhaust gas recirculation system through a PID controller.

[0115] S105: Feedback warning information.

[0116] Among them, the warning information is used to remind the driver to remove carbon deposits or repair the Venturi tube.

[0117] The embodiment of the present application provides a method for correcting the flow rate measured by a venturi tube. When the vehicle is in steady-state operation, the current actual pressure difference measured by the venturi tube is obtained in real time, and then based on the correspondence between the steady-state working condition and the pressure difference generated in advance, the corrected pressure difference range corresponding to the current working condition of the vehicle is determined, and it is judged whether the current actual pressure difference is within the corrected pressure difference range corresponding to the current working condition. Since the corrected pressure difference range corresponding to a steady-state working condition is calculated by the preset correction amplitude to the accurate pressure difference corresponding to the steady-state working condition, and the accurate pressure difference corresponding to the steady-state working condition is the pressure difference measured by the unblocked venturi tube under the pre-simulated steady-state working condition, if it is judged that the current actual pressure difference is within the corrected pressure difference range corresponding to the current working condition, it means that the venturi tube may be slightly blocked and can be corrected. Therefore, at this time, the theoretical exhaust gas flow corresponding to the current working condition is determined based on the oxygen concentration in the exhaust gas measured by the sensor under the current working condition, and the current actual exhaust gas flow measured by the venturi tube is corrected, so that when the venturi tube is slightly blocked, its measurement process can be corrected to ensure that the exhaust gas emissions do not exceed the standard. If it is determined that the current actual pressure difference is not within the corrected pressure difference range corresponding to the current operating conditions, it means that the Venturi tube is seriously blocked or damaged, so the feedback warning information has enabled the driver to remove carbon deposits or repair them in time.

[0118] The second aspect of the present application provides a correction device for measuring flow rate through a venturi tube, such as Figure 6As shown, including:

[0119] The first acquisition unit 601 is used to acquire the current actual pressure difference measured by the venturi tube in real time when the vehicle is in steady-state operation.

[0120] The range determination unit 602 is used to determine a corrected pressure difference range corresponding to the current working condition of the vehicle based on a pre-generated correspondence between the steady-state working condition and the pressure difference.

[0121] The corrected differential pressure range corresponding to a steady-state condition is calculated by presetting the correction amplitude to the accurate differential pressure corresponding to the steady-state condition. The accurate differential pressure corresponding to the steady-state condition is the differential pressure measured by the unblocked venturi tube under the pre-simulated steady-state condition.

[0122] The first judgment unit 603 is used to judge whether the current actual pressure difference is within the corrected pressure difference range corresponding to the current working condition.

[0123] The correction unit 604 is used to correct the current actual exhaust gas flow measured by the venturi tube based on the theoretical exhaust gas flow corresponding to the current operating condition if it is determined that the current actual pressure difference is within the corrected pressure difference range corresponding to the current operating condition.

[0124] The theoretical exhaust gas flow corresponding to the current operating condition is determined based on the oxygen concentration in the exhaust gas measured by the sensor under the current operating condition.

[0125] The alarm unit 605 is used to feedback alarm information if it is determined that the current actual pressure difference is not within the corrected pressure difference range corresponding to the current working condition.

[0126] Optionally, in the correction device for measuring flow through a venturi tube provided in another embodiment of the present application, the device further includes:

[0127] The second acquisition unit is used to acquire the current actual exhaust gas flow measured by the venturi tube.

[0128] The second judgment unit is used to judge whether the current actual exhaust gas flow meets the preset restriction condition.

[0129] The preset restriction condition is that the current actual exhaust gas flow is not less than the preset minimum exhaust gas flow, and the difference between the current actual exhaust gas flow and the current filtered exhaust gas flow is not greater than the preset flow difference. The current filtered exhaust gas flow is obtained by filtering the current actual exhaust gas flow.

[0130] The third judgment unit is used to judge whether the sensor has completed the dew point release if it is judged that the current actual exhaust gas flow meets the preset restriction condition.

[0131] The fourth judgment unit is used to judge whether the oxygen concentration in the current exhaust gas measured by the sensor is greater than a preset minimum oxygen concentration if it is judged that the sensor has completed the dew point release.

[0132] The state determination unit is used to determine that the vehicle is in steady-state operation if the oxygen concentration in the current exhaust gas measured by the sensor is greater than a preset minimum oxygen concentration.

[0133] Optionally, in a correction device for measuring flow through a venturi tube provided in another embodiment of the present application, the correction unit, such as Figure 7 As shown, including:

[0134] The first calculation unit 701 is used to calculate the difference between the current actual pressure difference and the accurate pressure difference corresponding to the current working condition to obtain the current pressure difference error value.

[0135] The searching unit 702 is used to search for the correction coefficient corresponding to the current pressure difference error value from the pre-generated correspondence between the pressure difference error value and the correction coefficient.

[0136] The corresponding relationship between the pressure difference error value and the correction coefficient is obtained in advance by testing different blockage degrees of the venturi tube under various steady-state conditions. The correction coefficient is obtained based on the ratio of the theoretical exhaust gas flow corresponding to each steady-state condition to the actual exhaust gas flow measured by the venturi tube.

[0137] The correction subunit 703 is used to correct the current actual exhaust gas flow rate using the correction coefficient corresponding to the current pressure difference error value.

[0138] Optionally, in the correction device for measuring flow through a venturi tube provided in another embodiment of the present application, the device further includes:

[0139] The third acquisition unit is used to acquire the oxygen concentration in the exhaust gas measured by the sensor under the current working condition.

[0140] The second calculation unit is used to calculate the excess oxygen air coefficient under the current working conditions according to the measured oxygen concentration.

[0141] The fourth calculation unit is used to calculate the fresh air intake volume of the engine under the current working condition by using the excess air coefficient and the fuel consumption under the current working condition.

[0142] The fifth calculation unit is used to subtract the fresh air intake volume of the engine under the current working condition from the total air intake volume of the engine under the current working condition to obtain a theoretical exhaust gas flow rate corresponding to the current working condition.

[0143] Optionally, in the above device, it also includes:

[0144] The fourth calculation unit is used to obtain the target exhaust gas flow corresponding to the current working condition.

[0145] The sixth calculation unit is used to calculate the difference between the target exhaust gas flow rate and the corrected current actual exhaust gas flow rate to obtain the exhaust gas flow rate difference.

[0146] The regulating unit is used to regulate the opening of the exhaust valve of the exhaust gas recirculation system through a PID controller based on the exhaust gas flow difference.

[0147] It should be noted that the specific working process of each unit provided in the above embodiments of the present application can refer to the corresponding steps in the above method embodiments, which will not be repeated here.

[0148] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0149] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for correcting flow rate measured by a venturi tube, characterized in that: include: When the vehicle is in steady-state operation, the current actual pressure difference measured by the venturi tube is obtained in real time; Based on the pre-generated correspondence between the steady-state working condition and the pressure difference, a corrected pressure difference range corresponding to the current working condition of the vehicle is determined; wherein the corrected pressure difference range corresponding to a steady-state working condition is obtained by calculating the accurate pressure difference corresponding to the steady-state working condition by a preset correction amplitude; the accurate pressure difference corresponding to the steady-state working condition is the pressure difference measured by the unblocked venturi tube under the pre-simulated steady-state working condition; Determining whether the current actual pressure difference is within the corrected pressure difference range corresponding to the current working condition; If it is determined that the current actual pressure difference is within the corrected pressure difference range corresponding to the current operating condition, it is determined that the venturi tube is slightly blocked, and based on the theoretical exhaust gas flow corresponding to the current operating condition, the current actual exhaust gas flow measured by the venturi tube is corrected; wherein the theoretical exhaust gas flow corresponding to the current operating condition is determined based on the oxygen concentration in the exhaust gas measured by the sensor under the current operating condition; If it is determined that the current actual pressure difference is not within the corrected pressure difference range corresponding to the current working condition, it is determined that the current Venturi tube is seriously blocked or damaged, and an alarm message is fed back.

2. The method according to claim 1, characterized in that Also includes: Obtaining the current actual exhaust gas flow measured by the venturi tube; Determine whether the current actual exhaust gas flow meets a preset restriction condition; wherein the preset restriction condition is that the current actual exhaust gas flow is not less than a preset minimum exhaust gas flow, and the difference between the current actual exhaust gas flow and the current filtered exhaust gas flow is not greater than a preset flow difference; the current filtered exhaust gas flow is obtained by filtering the current actual exhaust gas flow; If it is determined that the current actual exhaust gas flow rate meets the preset restriction condition, determining whether the sensor has completed dew point release; If it is determined that the sensor has completed dew point release, determining whether the oxygen concentration in the current exhaust gas measured by the sensor is greater than a preset minimum oxygen concentration; If it is determined that the oxygen concentration in the current exhaust gas measured by the sensor is greater than the preset minimum oxygen concentration, it is determined that the vehicle is in steady-state operation.

3. The method according to claim 1, characterized in that The correcting the current actual exhaust gas flow measured by the venturi tube based on the theoretical exhaust gas flow under the current working condition includes: Calculating the difference between the current actual pressure difference and the accurate pressure difference corresponding to the current working condition to obtain a current pressure difference error value; Finding the correction coefficient corresponding to the current pressure difference error value from the correspondence between the pressure difference error value and the correction coefficient generated in advance; wherein the correspondence between the pressure difference error value and the correction coefficient is obtained in advance by testing different blockage degrees of the venturi tube under various steady-state conditions; the correction coefficient is obtained based on the ratio of the theoretical exhaust gas flow corresponding to each steady-state condition to the actual exhaust gas flow measured by the venturi tube; The current actual exhaust gas flow is corrected using the correction coefficient corresponding to the current pressure difference error value.

4. The method according to claim 1, characterized in that: The method for determining the theoretical exhaust gas flow rate corresponding to the current operating condition includes: obtaining the oxygen concentration in the exhaust gas measured by the sensor under the current operating condition; Calculating the excess air coefficient under the current working condition according to the measured oxygen concentration; Calculate the fresh air intake of the engine under the current working condition by using the excess air coefficient and the fuel consumption under the current working condition; The total air intake amount of the engine under the current working condition is subtracted from the fresh air intake amount of the engine under the current working condition to obtain the theoretical exhaust gas flow corresponding to the current working condition.

5. The method according to claim 1, characterized in that After the current actual exhaust gas flow measured by the venturi tube is corrected based on the theoretical exhaust gas flow corresponding to the current working condition, the method further includes: Obtaining a target exhaust gas flow rate corresponding to the current operating condition; Calculating the difference between the target exhaust gas flow rate and the corrected current actual exhaust gas flow rate to obtain an exhaust gas flow rate difference; Based on the exhaust gas flow difference, the opening of the exhaust gas valve of the exhaust gas recirculation system is adjusted by a PID controller.

6. A correction device for measuring flow rate through a venturi tube, characterized in that: include: A first acquisition unit is used to acquire the current actual pressure difference measured by the venturi tube in real time when the vehicle is in steady-state operation; A range determination unit, configured to determine a corrected pressure differential range corresponding to the current working condition of the vehicle based on a pre-generated correspondence between a steady-state working condition and a pressure differential; wherein the corrected pressure differential range corresponding to a steady-state working condition is obtained by calculating an accurate pressure differential corresponding to the steady-state working condition by a preset correction amplitude; the accurate pressure differential corresponding to the steady-state working condition is a pressure differential measured by the unblocked venturi tube under the pre-simulated steady-state working condition; A first judgment unit, used to judge whether the current actual pressure difference is within the corrected pressure difference range corresponding to the current working condition; a correction unit, configured to determine that the venturi tube is slightly blocked if it is determined that the current actual pressure difference is within a corrected pressure difference range corresponding to the current operating condition, and to correct the current actual exhaust gas flow measured by the venturi tube based on a theoretical exhaust gas flow corresponding to the current operating condition; wherein the theoretical exhaust gas flow corresponding to the current operating condition is determined based on an oxygen concentration in the exhaust gas measured by a sensor under the current operating condition; The alarm unit is used to determine that the current Venturi tube is seriously blocked or damaged, and to feedback alarm information if it is determined that the current actual pressure difference is not within the corrected pressure difference range corresponding to the current working condition.

7. The device according to claim 6, characterized in that Also includes: A second acquisition unit, used to acquire the current actual exhaust gas flow measured by the venturi tube; a second judgment unit, configured to judge whether the current actual exhaust gas flow rate satisfies a preset restriction condition; wherein the preset restriction condition is that the current actual exhaust gas flow rate is not less than a preset minimum exhaust gas flow rate, and the difference between the current actual exhaust gas flow rate and the current filtered exhaust gas flow rate is not greater than a preset flow difference; the current filtered exhaust gas flow rate is obtained by filtering the current actual exhaust gas flow rate; a third judgment unit, configured to judge whether the sensor has completed dew point release if it is judged that the current actual exhaust gas flow meets a preset restriction condition; a fourth determination unit, configured to determine whether the oxygen concentration in the current exhaust gas measured by the sensor is greater than a preset minimum oxygen concentration if it is determined that the sensor has completed dew point release; The state determination unit is used to determine that the vehicle is in steady-state operation if it is determined that the oxygen concentration in the current exhaust gas measured by the sensor is greater than a preset minimum oxygen concentration.

8. The device according to claim 6, characterized in that The correction unit comprises: A first calculation unit, used for calculating the difference between the current actual pressure difference and the accurate pressure difference corresponding to the current working condition, to obtain a current pressure difference error value; A search unit, used to search for the correction coefficient corresponding to the current pressure difference error value from the correspondence between the pressure difference error value and the correction coefficient generated in advance; wherein the correspondence between the pressure difference error value and the correction coefficient is obtained in advance by testing different blockage degrees of the venturi tube under various steady-state conditions; the correction coefficient is obtained based on the ratio of the theoretical exhaust gas flow corresponding to each steady-state condition to the actual exhaust gas flow measured by the venturi tube; The correction subunit is used to correct the current actual exhaust gas flow rate using the correction coefficient corresponding to the current pressure difference error value.

9. The device according to claim 6, characterized in that Also includes: a third acquisition unit, configured to acquire the oxygen concentration in the exhaust gas measured by the sensor under the current working condition; A second calculation unit is used to calculate the excess air coefficient under the current working condition according to the measured oxygen concentration; a fourth calculation unit, configured to calculate the fresh air intake amount of the engine under the current working condition by using the excess air coefficient and the fuel consumption under the current working condition; The fifth calculation unit is used to subtract the fresh air intake amount of the engine under the current working condition from the total air intake amount of the engine under the current working condition to obtain a theoretical exhaust gas flow rate corresponding to the current working condition.

10. The device according to claim 6, characterized in that Also includes: a fourth calculation unit, configured to obtain a target exhaust gas flow rate corresponding to the current operating condition; a sixth calculation unit, configured to calculate a difference between the target exhaust gas flow rate and the corrected current actual exhaust gas flow rate to obtain an exhaust gas flow rate difference; The regulating unit is used to regulate the opening of the exhaust valve of the exhaust gas recirculation system through a PID controller based on the exhaust gas flow difference.

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