A method and device for detecting the capability of a low-pressure EGR system

Abstract

The application discloses a low-pressure EGR system capacity detection method, comprising: low-pressure EGR system capacity detection under any working condition, determining low-pressure EGR system capacity detection conditions, reserving N target openings, comparing an actual EGR rate with an actual EGR rate maximum final value or an actual EGR rate minimum final value, and judging whether the EGR system capacity is faulty; low-pressure EGR system capacity detection under steady-state working condition, judging whether a steady-state working condition meets conditions, respectively accumulating a time t1 and an average value pct of a sum of positions of an electric control actuator which tend to be stable, and comparing t1 and pct with respective limit values to judge whether the EGR system capacity is faulty; and if one of the detection under any working condition and the detection under steady-state working condition is faulty, it is indicated that the low-pressure EGR system capacity is faulty. BoostAvg The application further discloses a low-pressure EGR system capacity detection device. BoostAvg The application can detect low-pressure EGR system capacity faults and can be widely applied in the field of engine control.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of engine control, in particular to a low-pressure EGR system capability detection method and device. BACKGROUND

[0002] Exhaust gas recirculation (EGR) takes exhaust gas from the exhaust system into the intake system. Studies have shown that the EGR system has certain advantages in improving emissions, reducing fuel consumption and improving anti-knock ability. Low-pressure EGR takes gas after the turbine, so there is no loss of turbine efficiency, and it can use EGR almost all the time, which is more significant for improving fuel efficiency. However, due to the low pressure difference, a large-diameter valve is needed to meet the flow requirements. In some operating conditions, the mixed valve opening degree needs to be controlled to adjust the pressure at the outlet of the EGR valve, thereby improving the pressure difference on both sides of the EGR valve and improving the EGR rate. If the response performance of the mixed valve deteriorates, the response performance of the EGR rate will also deteriorate, which will not improve the fuel consumption, emissions and other capabilities to the best extent, and even cause the engine intake control to oscillate and cause abnormal engine combustion jitter and other problems.

[0003] Therefore, some manufacturers have proposed a technical solution, for example, an application number CN202011247319.6, with the invention name of "a target EGR rate calculation method and system", which determines the basic target EGR rate according to the engine speed and load; obtains the corresponding correction rate according to the special working condition; determines the initial target EGR rate according to the basic target EGR rate and each correction rate; determines whether EGR is activated according to the EGR activation state condition; divides the EGR state according to the judgment result, and determines the final target EGR rate. However, this solution does not propose a detection method for EGR system capability failure in the EGR rate calculation process.

[0004] In another patent application number CN202110184826.8, with the invention name of "EGR system mixed valve target opening degree determination method", it is proposed that when the mixed valve control enters the low-pressure EGR, different mixed valve opening degree change rates are controlled according to different working conditions, and the detection method for EGR system capability is not proposed. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the above background art, and to provide a low-pressure EGR system capability detection method and device, which can detect the low-pressure EGR system capability failure according to the mixed valve response performance change.

[0006] The application provides a low-pressure EGR system capacity detection method, which comprises arbitrary working condition low-pressure EGR system capacity detection or / and steady working condition low-pressure EGR system capacity detection, wherein the arbitrary working condition low-pressure EGR system capacity detection comprises the following steps: determining a low-pressure EGR system capacity detection condition, reading and reserving N target EGR rates in the latest time, respectively determining an actual EGR rate initial value and a final value, comparing the actual EGR rate with the actual EGR rate maximum final value or the actual EGR rate minimum final value, and judging whether the EGR system capacity is faulty; the steady working condition low-pressure EGR system capacity detection comprises the following steps: judging whether a steady working condition meets a condition, performing low-pressure EGR system capacity detection on the basis of meeting the steady working condition condition, and respectively accumulating the sum of the electric control actuator positions from the target EGR rate being 0 to the time t1 when the supercharger turbine electric control actuator tends to be stable and the average value pct of the electric control actuator positions at the time t1 BoostAvg , and comparing t1 and pct BoostAvg with respective limits, so as to judge whether the EGR system capacity is faulty; as long as either the arbitrary working condition low-pressure EGR system capacity detection or the steady working condition low-pressure EGR system capacity detection is faulty, it is indicated that the low-pressure EGR system capacity is faulty, otherwise, the low-pressure EGR system capacity is not faulty.

[0007] In the technical scheme, the specific process of the arbitrary working condition low-pressure EGR system capacity detection step is as follows: the arbitrary working condition low-pressure EGR system capacity detection condition determining step comprises the following steps: determining a low-pressure EGR system capacity detection condition, and performing low-pressure EGR system capacity detection after the detection conditions are determined to meet the condition; the target EGR rate sampling step comprises the following steps: reading the target EGR rates sampled continuously for N times, and forming an array [r EGRDsr1 ,…,r EGRDsrdN ] therefrom; the actual EGR rate initial value determining step comprises the following steps: determining an actual EGR rate maximum initial value r EGRActMaxRaw and an actual EGR rate minimum initial value r EGRActMinRaw ; the actual EGR rate final value determining step comprises the following steps: determining an actual EGR rate maximum final value r EGRActMaxLim and an actual EGR rate minimum final value r EGRActMinLim ; and the arbitrary working condition low-pressure EGR system capacity judging step comprises the following steps: if the actual EGR rate is less than the actual EGR rate minimum final value or the actual EGR rate is greater than the actual EGR rate maximum final value, it is indicated that the mixed valve performance appears a response performance sampling fault once, and the fault occurrence time is taken as a sampling period time; if the fault occurrence time accumulation value in the T Total time in the current driving cycle is not less than the fault time T ErrLim , it is indicated that the low-pressure EGR system capacity is faulty.

[0008] In the above technical solution, the specific conditions for the arbitrary operating condition low-pressure EGR system capability detection and determination step are as follows: Voltage fault detection: no battery voltage fault; Sensor fault detection: no position sensor fault in the mixing valve; Motor circuit fault detection: no motor circuit fault in the mixing valve; First operating state detection: the engine is in the first operating state; Turbocharger fault detection: no turbocharger fault; Throttle valve fault detection: no throttle valve fault; EGR valve fault detection: no EGR valve fault; Intake system sensor fault detection: no sensor fault in the intake system; EGR closed-loop detection: EGR is in closed-loop state; The specific process of the target EGR rate sampling step is as follows: Read values ​​and form an array: read the target EGR rate sampled N times consecutively and form it into an array [r EGRDsr1 ,…,r EGRDsrdN ]; Element update: After each sampling period, update the elements in the array, and only retain the N target EGR rates in the most recent time.

[0009] In the above technical solution, the specific process of obtaining the number of samples N in the target EGR rate sampling step is as follows: First, the basic value of the number of samples is determined by the engine speed and the actual fresh air intake density; second, the first sampling number correction value 1 is determined by the engine speed and atmospheric pressure; third, the second sampling number correction value 2 is determined by the actual fresh air intake density and the actual fresh air intake density change rate; finally, the basic value of the number of samples is multiplied by the first sampling number correction value 1, then multiplied by the second sampling number correction value 2, and then rounded to obtain the final integer value N.

[0010] In the above technical solution, the specific process of determining the initial value of the actual EGR rate is as follows: Based on the target EGR rates in the N arrays from the previous step, determine the maximum target EGR rate r. EGRDsrdMax and the minimum target EGR rate r EGRDsrdMin r EGRActMaxRaw =r EGRDsrdMax +Δ, r EGRActMinRaw =r EGRDsrdMin -Δ, where Δ is the allowable deviation of EGR rate accuracy; the specific process for determining the final value of the actual EGR rate is as follows:

[0011] Increase the opening degree of the mixing valve: the target opening degree of the mixing valve in the current sampling period (pct). Dsrd Not less than the target opening of the mixing valve in the previous sampling period (pct) Dsrd (z) is when pct Dsrd ≥pct Dsrd (z) indicates that as the opening of the mixing valve increases, the normal response performance of the mixing valve will deteriorate. Therefore:

[0012] r EGRActMaxLim =rEGRActMaxRaw + Δrate x Δt,

[0013] r EGRActMinLim = r EGRActMinRaw - Δrate x Δt

[0014] mixed valve opening is reduced: the mixed valve target opening pct Dsrd in the current sampling period is less than the mixed valve target opening pct Dsrd (z) in the last sampling period, i.e. pct Dsrd < pct Dsrd (z), which indicates that the mixed valve opening is reduced, the normal response performance of the mixed valve will be improved, so there is:

[0015] r EGRActMaxLim = r EGRActMaxRaw + Δrate x Δt,

[0016] r EGRActMinLim = r EGRActMinRaw - Δrate x Δt,

[0017] where Δt is the sampling period; Δrate is the sampling period allowable change rate, which is determined by the engine speed n, the atmospheric temperature T Amb , and the battery voltage V Battery ; sampling period basic change rate calculation and judgment: at different engine speeds, the lower the atmospheric temperature, the weaker the EGR system execution motor response ability will be affected; the mixed valve motor control relies on the battery power supply, and the lower the battery voltage, the larger Δrate will be at this time, so there is: Δrate = Δrate Base x f(n, T Abm ) x f(V Battery ), where Δrate Base is determined by the engine speed n, the atmospheric temperature T Amb , and the battery voltage V Battery , and the sampling period basic change rate obtained by the sampling period basic change rate of the mixed valve with normal response performance fault and the mixed valve with normal response performance, i.e. the sampling period basic change rate can accurately distinguish whether the mixed valve has a response performance fault, f(n, T Abm ) is the first correction factor determined by the engine speed and the atmospheric temperature, and f(V Battery ) is the second correction factor determined based on the battery voltage V Battery ; the larger the battery voltage is, the larger the motor working current is, and the better the response ability is, so the second correction factor is smaller.

[0018] In the above technical solution, the specific process of the steady state working condition low pressure EGR system capability detection step is as follows: steady state working condition condition judgment: judging whether the steady state working condition meets the condition, when the steady state working condition conditions are all met, fault detection is performed again; steady state working condition low pressure EGR system capability fault detection: on the basis of meeting the steady state working condition condition, low pressure EGR system capability detection is performed, and the sum of the electric control actuator positions at the time t1 and t1 from the target EGR rate 0 to the time when the supercharger turbine electric control actuator tends to be stable is accumulated respectively BoostAvg t1 and pct BoostAvg are compared with respective limits respectively, to judge whether the EGR system capability has a fault.

[0019] In the above technical solution, the specific conditions of the steady state condition meeting condition judgment step are: second running state detection: the engine is in the second running state; engine speed fluctuation detection: the engine speed is within a certain range, and the engine speed fluctuation when entering the low pressure EGR system capacity detection is small; target fresh air intake density detection: the target fresh air intake density is greater than a preset value, and the actual fresh air intake density fluctuation when entering the EGR system capacity detection is small; target fresh air intake density and actual fresh air intake density difference detection: the difference between the target fresh air intake density and the actual fresh air intake density is within a certain range; actual fresh air intake density parameter detection: the actual fresh air intake density is greater than a preset value, and the actual fresh air intake density fluctuation when entering the EGR system capacity detection is small; target EGR rate parameter detection: the target EGR rate is greater than a preset value, and the target EGR rate is stable when entering the EGR system capacity detection; actual EGR rate fluctuation detection: the actual EGR rate is within a certain range, and the actual EGR rate fluctuation when entering the EGR system capacity detection is small; hybrid valve actual opening parameter detection: the hybrid valve actual opening is not greater than a preset value, and the hybrid valve actual opening is stable when entering the EGR system capacity detection; target EGR rate and actual EGR rate difference detection: the difference between the target EGR rate and the actual EGR rate is within a certain range; engine water temperature detection: the engine water temperature is within a certain range; EGR valve fault detection: the EGR valve has no fault; misfire fault and knock detection: no misfire fault and knock occurs; throttle state detection: the throttle is in the full open state; supercharger working capacity maximum limit detection: the supercharger working capacity has not reached its maximum limit; first preset time T0 detection: the above 14 conditions are all met for more than the first preset time T0; second preset time T1 detection: the low pressure EGR system capacity detection method has not been executed for more than the second preset time T1; after the above conditions are met, low pressure EGR system capacity fault detection is performed; the specific process of the steady state condition low pressure EGR system capacity fault detection step is as follows: cumulative time T2: the engine speed sum, the actual fresh air intake density sum, and the target EGR rate sum within the cumulative time T2; average value calculation: calculating the average value of the engine speed, the actual fresh air intake density, and the target EGR rate within the T2 time Avg , the actual fresh air intake density average value rho Avg , and the target EGR rate average value r DsrdEGRAvg ; target EGR rate setting: setting the target EGR rate to 0, i.e. forcibly closing the EGR system; parameter accumulation: accumulating the sum of the time t1 from the target EGR rate being 0 to the supercharger turbine electric control actuator tending to be stable and the average value of the electric control actuator position at the t1 time pct BoostAvg, the stable determination method tends to be that the position change range of the supercharger turbine electric control actuator is not more than the position preset value, and the position change time is more than the time preset value; the parameters are compared with respective limit values: t1 is compared with the limit values t1_limHi and t1_limLo under the same working condition, and pct BoostAvg is compared with the limit values pct BoostAvgHi and pct BoostAvgLo under the same working condition, if the following conditions are met simultaneously: 1) t1 > t1_limHi; 2) pct BoostAvg > pct BoostAvgHi , it is indicated that the EGR system capacity fault occurs, if the above conditions are not met, the following conditions are judged again, if the following conditions are met simultaneously: 1) t1 < t1_limLo; 2) pct BoostAvg < pct BoostAvgLo , it is indicated that the EGR system capacity fault occurs, otherwise, the response performance fault does not occur; wherein, the time limit values t1_limHi, t1_limLo, pct BoostAvgHi and pct BoostAvgLo are obtained by using a mixed valve with response too fast and response too slow under the conditions of fixed engine speed, actual fresh air intake density and target EGR rate, and the average value is obtained by sampling multiple times.

[0020] In the above technical solution, the fault judgment and self-learning updating step further comprises the following brief content: when no low-pressure EGR system capacity fault is detected, the average value pct BoostAvg of the sum of t1 and the electric control actuator position under the same working condition is accumulated in time sequence, if the sequence number is greater than a preset value, and both arrays show a non-decreasing or non-increasing trend, when both arrays show a non-decreasing trend, the last number divided by the first number of the array is greater than a preset value, or when both arrays show a non-increasing trend, the last number divided by the first number of the array is less than a preset value, the fault time of the low-pressure EGR system capacity detection under any working condition is updated, and the t1 and pct BoostAvg arrays under the same working condition meeting the steady state working condition are cleared, and the combination is performed again when the conditions are met again.

[0021] In the above technical solution, the detailed specific process of the fault judgment and self-learning updating step is as follows: the parameter array change trend: if no mixed valve response performance fault is detected, the average value pct BoostAvgAccording to the cumulative time sequence, the parameter arrays [t1_1, t1_2, …t1_M] and [t2_1, t2_2, …t2_M] are composed from early to late, if M is greater than a preset value, and any two conditions are met as follows: the arrays [t1_1, t1_2, …t1_M] and [pct BoostAvg1 ,pct BoostAvg2 ,…pct BoostAvgM ] all show a non-decreasing trend; t1_M divided by t1_1 is greater than a preset value; pct BoostAvgM divided by pct BoostAvg1 is greater than a preset value; or, the arrays [t1_1, t1_2, …t1_M] and [pct BoostAvg1 ,pct BoostAvg2 ,…pct BoostAvgM ] all show a non-increasing trend; t1_M divided by t1_1 is less than a preset value; pct BoostAvgM divided by pct BoostAvg1 is less than a preset value; after any of the above conditions is met, the following actions are performed: arbitrary condition fault time update: the fault time T ErrLim of the arbitrary condition low-pressure EGR system capability detection is updated, and the updating method is as follows:

[0022]

[0023] ,T ErrLimOld is the fault time after the last update; steady state condition parameter array clearing: the t1 and pct BoostAvg arrays corresponding to the same condition under the steady state condition are cleared, and are combined again after being satisfied again.

[0024] The application also provides a low-pressure EGR system capability detection device with a computer program capable of executing the low-pressure EGR system capability detection method.

[0025] The low-pressure EGR system capability detection method and device have the following beneficial effects: the EGR system performance is determined according to the EGR rate response speed or the supercharging response performance, so that the EGR system performance is determined as early as possible, the detection rate is improved by effectively updating the diagnosis fault time, and the engine shaking and other problems caused by the system response failure are effectively avoided. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a schematic diagram of the low-pressure EGR system architecture of the application;

[0027] Figure 2 is a whole flow chart of the low-pressure EGR system capability detection method of the application;

[0028] Figure 3A flowchart of the process of the low-pressure EGR system capability detection method for detecting the low-pressure EGR system capability under any working condition;

[0029] Figure 4 A flowchart of the method of obtaining the sampling number N for the sampling step of determining the target EGR rate in the low-pressure EGR system capability detection method for detecting the low-pressure EGR system capability under any working condition;

[0030] Figure 5 A flowchart of the step of determining the final value of the actual EGR rate in the low-pressure EGR system capability detection method for detecting the low-pressure EGR system capability under any working condition;

[0031] Figure 6 A flowchart of the process of the low-pressure EGR system capability detection method for detecting the low-pressure EGR system capability under steady-state working condition;

[0032] Figure 7 A flowchart of the step of determining whether the steady-state working condition meets the condition in the low-pressure EGR system capability detection method for detecting the low-pressure EGR system capability under steady-state working condition;

[0033] Figure 8 A flowchart of the step of detecting the low-pressure EGR system capability fault under steady-state working condition in the low-pressure EGR system capability detection method for detecting the low-pressure EGR system capability under steady-state working condition;

[0034] Figure 9 A flowchart of the steps of fault judgment and self-learning update in the low-pressure EGR system capability detection method;

[0035] Figure 10 A structural diagram of the low-pressure EGR system capability detection device. DETAILED DESCRIPTION

[0036] The application will be further described in conjunction with the accompanying drawings and embodiments, but the embodiments should not be understood as limiting the application.

[0037] The low-pressure EGR system architecture is shown in Figure 1 The low-pressure EGR system includes an air filter, a supercharger compressor, a throttle valve, an engine, a supercharger turbine, a catalyst, a particulate trap, an EGR cooler, an EGR valve, an EGR temperature sensor, an EGR differential pressure sensor, a flowmeter, a linear oxygen sensor, a mixing valve, etc.

[0038] The supercharger compressor compresses fresh air to increase the pressure; the supercharger turbine controls the working efficiency of the turbine by controlling the opening degree of the waste gas bypass valve of the supercharger, so as to realize different supercharging capacities; wherein the low-pressure EGR system has the following additional components compared with the non-low-pressure EGR system: an EGR cooler, an EGR temperature sensor, an EGR valve, an EGR differential pressure sensor, a mixing valve, a flow meter and an oxygen sensor; wherein the flow meter is installed between the air filter and the mixing valve, and is used to detect the fresh air flow entering the engine; the mixing valve is used to adjust the pressure at the outlet of the EGR valve, increase the pressure difference across the EGR valve, and increase the EGR rate. The mixing valve comprises a position sensor, an actuator and a valve plate, the position sensor reads the position of the valve plate, i.e. the opening degree of the mixing valve, the actuator controls the action of the valve plate, so that the actual opening degree of the mixing valve follows the control target opening degree; the oxygen sensor is installed between the compressor and the throttle valve, close to the throttle valve, and is used to detect the mixture flow entering the cylinder; the EGR cooler is used to cool the exhaust gas, so as to increase the exhaust gas flow and reduce the exhaust gas temperature; the EGR valve throttles the exhaust gas flow entering the cylinder; the EGR temperature sensor is used to detect the temperature of the exhaust gas entering the EGR valve; and the EGR differential pressure sensor is used to detect the pressure difference between the exhaust gas on both sides of the EGR.

[0039] The low-pressure EGR system capacity detection is the detection of the influence of the mixing valve on the system capacity, and is the fault detection of the inaccurate EGR rate control caused by the failure of the mixing valve.

[0040] The default state of the mixing valve is fully open, i.e. the opening degree of the mixing valve is maximum. When it is required to reduce the pressure at the outlet of the EGR valve, the opening degree of the mixing valve is controlled to reduce the pressure. The specific calculation method of the target opening degree of the mixing valve is shown in the patent application CN202110184826.8 "EGR system mixing valve target opening degree determination method". After the target opening degree of the mixing valve is determined, if the mixing valve fails to accurately control the EGR rate, the fault can be reported in time to quickly respond and protect the engine.

[0041] Referring to Figure 2 The low-pressure EGR system capacity detection method comprises arbitrary working condition low-pressure EGR system capacity detection or / and steady state working condition low-pressure EGR system capacity detection, and fault judgment and self-learning update steps, wherein,

[0042] The arbitrary working condition low-pressure EGR system capacity detection comprises the following steps: determining the low-pressure EGR system capacity detection condition, reading and retaining N target EGR rates in the recent time, respectively determining the initial value and the final value of the actual EGR rate, comparing the actual EGR rate with the maximum final value of the actual EGR rate or the minimum final value of the actual EGR rate, and judging whether the EGR system capacity is faulty.

[0043] Steady state condition low pressure EGR system capability detection: judge whether the steady state condition is met, and perform low pressure EGR system capability detection on the basis of meeting the steady state condition, and respectively accumulate the sum of the electric control actuator positions from the target EGR rate of 0 to the time t1 when the supercharger turbine electric control actuator tends to be stable and the average value pct of the electric control actuator positions at the time t1 BoostAvg Compare t1 and pct BoostAvg with the respective limit values respectively, and judge whether the EGR system capability has a fault;

[0044] Fault judgment and self-learning update: when no low pressure EGR system capability fault is detected, update t1 and the average value pct of the sum of the electric control actuator positions under the same condition BoostAvg According to the accumulation time sequence, respectively form an array, if the sequence number is greater than a preset value, and both arrays show a non-decreasing or non-increasing trend, when both arrays show a non-decreasing trend, the last number divided by the first number of the array is greater than a preset value, or when both arrays show a non-increasing trend, the last number divided by the first number of the array is less than a preset value, then update the fault time of the low pressure EGR system capability detection under the arbitrary condition, and update t1 and the average value pct of the sum of the electric control actuator positions under the same condition meeting the steady state condition BoostAvg The array is cleared, and is combined again when the conditions are met again.

[0045] Referring to Figure 3 , the specific process of the arbitrary condition low pressure EGR system capability detection step is as follows:

[0046] First step, arbitrary condition low pressure EGR system capability detection determination condition: after all the following conditions are met, low pressure EGR system capability detection can be performed, otherwise, when the conditions are not met, the response performance detection will appear a false judgment. The conditions for low pressure EGR system capability detection are:

[0047] 1) Voltage fault detection: no battery voltage fault;

[0048] 2) Sensor fault detection: no position sensor fault of the hybrid valve;

[0049] 3) Motor circuit fault detection: no motor circuit fault (such as open circuit, short circuit fault, etc.) of the hybrid valve;

[0050] 4) First running state detection: the engine is in the first running state.

[0051] 5) Supercharger fault detection: no fault of the supercharger;

[0052] 6) Throttle fault detection: no fault of the throttle;

[0053] 7) EGR valve fault detection: no fault of the EGR valve;

[0054] 8) Intake system sensor fault detection: no sensor fault in the intake system;

[0055] 9) EGR closed loop detection: EGR is in a closed loop state;

[0056] Second step, target EGR rate sampling: after the above conditions are met, read the target EGR rate sampled continuously N times (the sampling period in this example is 10 ms, i.e. the target EGR rate is read once every 10 ms. The method for obtaining the target EGR rate can be found in patent CN202011247319.6 "Method and system for calculating target EGR rate"), which is composed of an array [r EGRDsr1 ,…,r EGRDsrdN ]. The elements in the array are updated at the end of each sampling period, and only the N target EGR rates in the recent time are retained. The method for obtaining N depends on the engine speed, actual fresh air intake density (real-time fresh air intake density into the cylinder), atmospheric pressure, and actual fresh air intake density rate. Among them, the engine speed and the actual fresh air intake density, atmospheric pressure represent the basic information of the engine working condition, and under different engine speeds, actual fresh air intake densities, the smaller the atmospheric pressure, the thinner the air. Based on the demand of supercharging control, the compressor inlet pressure needs to be further improved, and the compressor inlet pressure affects the mixed valve outlet pressure, while the mixed valve inlet pressure decreases with the decrease of atmospheric pressure. In this way, the ratio of the mixed valve outlet pressure to the inlet pressure is smaller, and the EGR rate response accuracy is poor. Similarly, the greater the actual fresh air intake density rate, the greater the target EGR rate (EGR rate equal to exhaust gas flow divided by the total flow of exhaust gas and fresh air flow) may change, and more target EGR rates need to be collected for accurate detection of EGR system capacity. Based on this, the method for obtaining the number of samples N is designed.

[0057] Referring to Figure 4 , first, the basic value of the number of samples is determined by the engine speed and the actual fresh air intake density. The greater the engine speed or the smaller the actual fresh air intake density, the more samples are needed to accurately obtain whether a system capacity failure occurs. For details, see Table 1 below:

[0058] Table 1

[0059]

[0060] Second, the first sampling number correction value 1 is determined by the engine speed and the atmospheric pressure. The smaller the engine speed or the smaller the atmospheric pressure, the greater the EGR rate jitter probability, and the more samples are needed to accurately obtain whether a system capacity failure occurs. For details, see Table 2 below:

[0061] Table 2

[0062]

[0063] Again, the second sampling frequency correction value 2 is determined by the actual fresh air intake density and the actual fresh air intake density change rate. The greater the change rate, the more accurate the sampling frequency is required to accurately determine whether a system capacity failure occurs. See Table 3 below:

[0064] Table 3

[0065]

[0066]

[0067] The basic value of the sampling frequency is first multiplied by the first sampling frequency correction value 1, then multiplied by the second sampling frequency correction value 2, and then rounded to an integer to obtain the final N value. The above N value calibration idea is to minimize the N value as much as possible under the premise of ensuring the accuracy of EGR system capacity detection failure, so as to report whether the EGR system capacity detection failure occurs as soon as possible.

[0068] Third step, determine the actual EGR rate initial value: determine the actual EGR rate maximum initial value r EGRActMaxRaw and the actual EGR rate minimum initial value r EGRActMinRaw . The determination method is as follows: according to the target EGR rate in the N array in the above step, determine the target EGR rate maximum value r EGRDsrdMax and the target EGR rate minimum value r EGRDsrdMin . r EGRActMaxRaw = r EGRDsrdMax + Δ, r EGRActMinRaw = r EGRDsrdMin - Δ, where Δ is the EGR rate accuracy allowable deviation (i.e. the maximum allowable deviation of the EGR rate is 1% in this example, in order to avoid the occurrence of incorrect detection of the EGR system capacity, Δ is 2% in this example).

[0069] See Figure 5 , fourth step, determine the actual EGR rate final value: determine the actual EGR rate maximum final value r EGRActMaxLim and the actual EGR rate minimum final value r EGRActMinLim . The determination method is as follows:

[0070] 1) Increase the mixture valve opening: when the mixture valve target opening pct Dsrd in the current sampling period is not less than the mixture valve target opening pct Dsrd (z) in the last sampling period, i.e. pct Dsrd ≥ pct Dsrd(z), which indicates that the mixed valve opening degree is increasing, and because the direction of the airflow is opposite to the direction of the mixed valve action, the normal response performance of the mixed valve will be poor, and therefore there is:

[0071] r EGRActMaxLim = r EGRActMaxRaw + Δrate x Δt,

[0072] r EGRActMinLim = r EGRActMinRaw - Δrate x Δt,

[0073] 2) Mixed valve opening degree decreases: when the mixed valve target opening degree pct Dsrd in the current sampling period is less than the mixed valve target opening degree pct Dsrd in the last sampling period, that is, pct Dsrd < pct Dsrd (z), which indicates that the mixed valve opening degree is decreasing, and because the direction of the airflow is the same as the direction of the mixed valve action, the normal response performance of the mixed valve will be good, and therefore there is:

[0074] r EGRActMaxLim = r EGRActMaxRaw - Δrate x Δt

[0075] r EGRActMinLim = r EGRActMinRaw + Δrate x Δt

[0076] Where Δt is the sampling period, which is 10 ms in the present example; and Δrate is the allowable change rate thereof, which is determined by the engine speed n, the atmospheric temperature T Amb , and the battery voltage V Battery .

[0077] 3) Sampling period basic change rate calculation and judgment: at different engine speeds, the lower the atmospheric temperature, the weaker the EGR system execution motor response ability will be affected; the mixed valve motor control relies on the battery power supply, and the lower the battery voltage, the greater Δrate will be at this time, and therefore there is:

[0078] Δrate = Δrate Base x f(n, T Abm ) x f(V Battery ),

[0079] Where Δrate Base is the engine speed n is 850 rpm, the atmospheric temperature T Amb is 20°C, and the battery voltage V Batteryis 12V, the sampling period basic change rate obtained by responding to the performance fault of the mixed valve and the normal mixed valve, that is, the sampling period basic change rate can accurately identify whether the mixed valve has a response performance fault, and the present example Δrate Base is 5 / s. f(n, T Abm is a first correction factor determined by the engine speed and the atmospheric temperature (see Table 4 below for details), f(V Battery is a second correction factor determined based on the battery voltage V Battery , see Tables 4-5 below for details.

[0080] Table 4

[0081]

[0082]

[0083] The battery voltage is also large, the motor operating current is larger, the response ability is better, and therefore the correction factor is smaller, see Table 5 below for details:

[0084] Table 5

[0085]

[0086] Fifth step, low pressure EGR system capacity judgment under any working condition: Perform low pressure EGR system capacity detection, if the actual EGR rate r EGRAct < r EGRActMinLim or the actual EGR rate r EGRAct > r EGRActMaxLim , it indicates that the low pressure EGR system capacity sampling fault occurs once, and the fault occurrence time is the sampling period time 10ms, if the fault occurrence time cumulative value within the present driving cycle T Total time (the present example takes 150ms) is not less than the fault time T ErrLim , it indicates that the low pressure EGR system capacity fault occurs. Generally speaking, the sampling fault occurrence does not represent the final fault occurrence, only one of them occurs. It is necessary to have a larger fault time within a certain time to consider that the final fault occurs. That is, if the sampling fault occurs within the T Total time (the opening degree is calculated once every 10ms), the sampling fault times *10ms are taken as the fault time T ErrLim .

[0087] It needs to be specially pointed out that the actual EGR rate maximum final value r EGRActMaxLim and the actual EGR rate minimum final value r EGRActMinLim will be continuously updated and learned, and will be saved after power-off.

[0088] The foregoing scenario can be detected in any working condition with low pressure EGR system capability, compared with another low pressure EGR system capability detection method, which is to judge according to the reaction of the mixture valve in the process of EGR rate change in steady state working condition, and to update the detection method failure time T in any working condition according to the change and parameters ErrLim .

[0089] Compared with the detection in any working condition, the second type of detection is in steady state working condition, and the detection in any working condition can be carried out at any time. The steady state working condition needs to be diagnosed after the conditions are met.

[0090] Referring to Figure 6 , the specific process of the steady state working condition low pressure EGR system capability detection step is as follows:

[0091] Referring to Figure 7 , the steady state working condition meets the condition, which is to judge whether it is in steady state working condition, and when the following conditions are met, the fault detection can be carried out:

[0092] 1. Second running state detection: the engine is in the second running state;

[0093] 2. Engine speed fluctuation detection: the engine speed is in a certain range, and the engine speed fluctuation is small when entering the low pressure EGR system capability detection, and the engine speed fluctuation is ± 15 rpm in the embodiment;

[0094] 3. Target fresh air intake density detection: the target fresh air intake density is greater than the preset value, and the preset value is 1000 mgpl in the embodiment (to ensure that the engine load is large, to ensure that the throttle is fully open, and to avoid error learning caused by the interference of throttle action on learning update value), and the actual fresh air intake density fluctuation is small when entering the EGR system capability detection, and the actual fresh air intake density fluctuation is ± 12 mgpl in the embodiment;

[0095] 4. Target fresh air intake density and actual fresh air intake density difference detection: the difference between the target fresh air intake density and the actual fresh air intake density is within a certain range, and the difference is ± 12 mgpl in the embodiment;

[0096] 5. Actual fresh air intake density parameter detection: the actual fresh air intake density is greater than the preset value, and the preset value is 1000 mgpl in the embodiment (to ensure that the engine load is large, to ensure that the throttle is fully open, and to avoid error learning caused by the interference of throttle action on learning update value), and the actual fresh air intake density fluctuation is small when entering the EGR system capability detection, and the actual fresh air intake density fluctuation is ± 12 mgpl in the embodiment;

[0097] 6. Target EGR rate parameter detection: the target EGR rate is greater than a preset value (the preset value is 0.05 in this example, and the target EGR rate is too small, the EGR system control is unstable, and the mixed valve opening degree fluctuates greatly, so that the mixed valve response performance detection cannot be accurately performed), and the target EGR rate is stable when entering the EGR system capacity detection, that is, the target EGR rate fluctuation range in this example does not exceed ±1%.

[0098] 7. Actual EGR rate fluctuation detection: the actual EGR rate is within a certain range, and the actual EGR rate fluctuation is small when entering the EGR system capacity detection, and the actual EGR rate in this example is ±1%.

[0099] 8. Mixed valve actual opening degree parameter detection: the mixed valve actual opening degree is not greater than a preset value (the preset value is 65% in this example, and the mixed valve opening degree is not in the full open state), and the mixed valve actual opening degree is stable when entering the EGR system capacity detection, that is, the mixed valve actual opening degree fluctuation range in this example does not exceed ±1%.

[0100] 9. Target EGR rate and actual EGR rate difference detection: the difference between the target EGR rate and the actual EGR rate is within a certain range, and the difference in this example is ±1%.

[0101] 10. Engine water temperature detection: the engine water temperature is within a certain range (0°C to 100°C in this example), and the engine water temperature fluctuation is small when entering the EGR system capacity detection, and the engine water temperature in this example is ±2°C.

[0102] 11. EGR valve fault detection: the EGR valve has no fault;

[0103] 12. Misfire fault and knock detection: no misfire fault and knock occurs;

[0104] 13. Throttle state detection: the throttle is in the full open state, and the larger the effective area of the throttle, the same the inlet and outlet pressures of the throttle.

[0105] 14. Supercharger working capacity maximum limit detection: the supercharger working capacity has not reached its maximum limit. According to the fact that the supercharger electric control actuator has not reached its maximum working capacity, the exhaust gas has not achieved the maximum efficiency of the supercharger turbine.

[0106] If any of the above conditions is not met, the low-pressure EGR system capacity detection is not performed. When all the above conditions are met, the following conditions are judged again:

[0107] 15. First preset time T0 detection: the above 14 conditions are met for more than the first preset time T0, and the first preset time T0 in this example is 3s.

[0108] 16. Second preset time T1 detection: the EGR system capacity detection is not performed for more than the second preset time T1 (500 h in this embodiment, since the EGR system capacity detection is performed, the EGR is prohibited, which causes the deterioration of emission and fuel consumption, and the change of the EGR system capacity is not great, so the performance should not be too frequent);

[0109] After the above two conditions are met, the low-pressure EGR system capacity fault detection is performed.

[0110] Referring to Figure 8 , the specific process of the steady-state working condition low-pressure EGR system capacity fault detection step is as follows:

[0111] 1. Accumulation time T2: the total sum of the engine speed, the actual fresh air intake density, and the target EGR rate in a certain time T2 (3 s in this embodiment) is accumulated. After the time T2 is met, the next stage is entered.

[0112] 2. Average value of each parameter in T2 time: the average value of the engine speed n Avg , the average value of the actual fresh air intake density rho Avg , and the average value of the target EGR rate r DsrdEGRAvg in T2 time are obtained.

[0113] 3. Target EGR rate setting: the target EGR rate is set to 0, that is, the EGR system is forcibly closed. From this step to the following steps, the conditions of the 6th, 7th, and 8th conditions in the steady-state working condition for updating the allowable EGR rate limit value are no longer judged, and the other conditions will still be judged. If it is not met, the EGR system capacity detection is terminated.

[0114] 4. Parameter accumulation: the sum of the time t1 from the target EGR rate being 0 to the turbocharger turbine electric control actuator tending to be stable and the average value pct of the electric control actuator position in the t1 time is accumulated. BoostAvg , wherein the determination method of tending to be stable is that the position change range of the turbocharger turbine electric control actuator does not exceed the position preset value (±0.5% in this embodiment), and the position change time exceeds the time preset value (0.2 s in this embodiment).

[0115] 5. Parameter comparison with respective limit values: t1 is compared with the limit values t1_limHi and t1_limLo in the same working condition (the average value of the engine speed n Avg , the average value of the actual fresh air intake density rho Avg , and the average value of the target EGR rate r DsrdEGRAvg are the same), and pct BoostAvg is compared with the same working condition (the average value of the engine speed n Avg, actual fresh air intake density average value rho Avg , target EGR rate average value r DsrdEGRAvg , limit value pct BoostAvgHi and pct BoostAvgLo are compared.

[0116] After the EGR exhaust gas is introduced, the exhaust gas temperature is reduced, which leads to a reduction in turbine energy. In order to maintain the engine torque stable, the opening of the supercharging turbine electric control actuator needs to be increased (the opening is increased, and the supercharging capacity is stronger), so after the EGR rate suddenly changes to 0, the opening of the supercharging turbine electric control actuator is reduced. Similarly, after the EGR rate suddenly changes to 0, the opening of the mixture valve is increased. If the mixture valve responds too quickly, the actual pressure at the inlet of the compressor will increase quickly, and the opening of the supercharging turbine electric control actuator will be relatively further reduced; if the mixture valve responds too slowly, the actual pressure at the inlet of the compressor will increase slowly, and the opening of the supercharging turbine electric control actuator will not be relatively reduced too small. Based on this idea, the detection method is designed, and if the following conditions are met at the same time:

[0117] 1) t1> t1_limHi;

[0118] 2) pct BoostAvg > pct BoostAvgHi ;

[0119] , it is indicated that the mixture valve responds too slowly, and an EGR system capacity failure occurs. If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time:

[0120] 1) t1< t1_limLo;

[0121] 2) pct BoostAvg < pct BoostAvgLo ;

[0122] , it is indicated that the mixture valve responds too quickly, and an EGR system capacity failure occurs. Otherwise, no response performance failure occurs.

[0123] In the embodiment, the acquisition method of the time limit t1_limHi, t1_limLo, pct BoostAvgHi and pct BoostAvgLo is that, under the conditions of fixed engine speed, actual fresh air intake density, and target EGR rate (the performance of the mixture valve after the target EGR is suddenly changed to 0 is used to detect the response performance), two kinds of response performance degradation (response too quickly and response too slowly) of the mixture valve are used for testing, and the average value is obtained by sampling and reading multiple times (the number of times in the example is greater than 5000). In the example, when the engine speed is 1000 rpm, the actual fresh air intake density is 300 mgpl, and the target EGR rate is 0.1, t1_limHi is 0.3 s, t1_limLo is 0.1 s, pctBoostAvgHi Take 60%, pct BoostAvgLo Take 10%.

[0124] Referring to Figure 9 , the detailed specific process of the fault judgment and self-learning updating step is as follows:

[0125] 1. Parameter array change trend: if no low-pressure EGR system capacity fault is detected (the following actions are no longer performed after a low-pressure EGR system capacity fault is detected), the time t1 and the sum of the electric control actuator positions average value pct Avg , the actual fresh air intake density average value rho Avg , and the target EGR rate average value r DsrdEGRAvg are all the same under the same working condition (the average value of the engine speed n BoostAvg is the same), the array [t1_1, t1_2, … t1_M] and [pct BoostAvg1 , pct BoostAvg2 , … pct BoostAvgM ] are composed in the order of the cumulative time from early to late, if M is greater than a preset value, the present instance takes 500, and any two of the following conditions are met:

[0126] 1) the array [t1_1, t1_2, … t1_M] and [pct BoostAvg1 , pct BoostAvg2 , … pct BoostAvgM ] all show a non-decreasing trend; t1_M divided by t1_1 is greater than a preset value, the present instance takes 1.24; pct BoostAvgM divided by pct BoostAvg1 is greater than a preset value, the present instance takes 1.3;

[0127] Or,

[0128] 2) the array [t1_1, t1_2, … t1_M] and [pct BoostAvg1 , pct BoostAvg2 , … pct BoostAvgM ] all show a non-increasing trend; t1_M divided by t1_1 is less than a preset value, the present instance takes 0.8; pct BoostAvgM divided by pct BoostAvg1 is less than a preset value, the present instance takes 0.95;

[0129] After any of the above conditions is met, the following actions are performed:

[0130] 2. Fault time update under any working condition: the fault time T ErrLim under any working condition of the low-pressure EGR system capacity detection is updated, and the updating method is:

[0131]

[0132] ,T ErrLimOld This is the downtime since the last update;

[0133] 3. Clear the steady-state operating condition parameter array: Clear the same operating conditions that satisfy the steady-state operating condition (average engine speed n). Avg The average actual fresh air intake density rho Avg Target EGR rate average r DsrdEGRAvg The t1 and pct values ​​for the corresponding working conditions under the same (meaning the working conditions are the same) BoostAvg The array is cleared, and the array is recombined once the conditions are met again.

[0134] It should be noted that if either the arbitrary operating condition low-pressure EGR system capability testing method or the steady-state operating condition low-pressure EGR system capability testing method detects a fault, it indicates a fault in the mixing valve's response performance; otherwise, no fault has occurred. Once a fault is detected, testing will cease until the fault is cleared by the diagnostic instrument.

[0135] The above completes the description of the low-pressure EGR system capability testing method.

[0136] See Figure 10 The present invention provides a low-voltage EGR system capability testing device, comprising an arbitrary operating condition low-voltage EGR system capability testing module and / or a steady-state operating condition low-voltage EGR system capability testing module, and a fault judgment and self-learning update module, wherein...

[0137] Arbitrary operating condition low-pressure EGR system capacity detection module: Determine the low-pressure EGR system capacity detection conditions, read and retain N target EGR rates in the most recent time, determine the initial and final values ​​of the actual EGR rate respectively, compare the actual EGR rate with the final value of the maximum or minimum value of the actual EGR rate, and determine whether the EGR system capacity is faulty.

[0138] Steady-state low-pressure EGR system capability detection module: Determines if steady-state conditions are met. Based on meeting these conditions, performs low-pressure EGR system capability detection and accumulates the average value (pct) of the time t1 from the target EGR rate of 0 until the turbocharger turbine electronic actuator stabilizes, and the sum of the actuator positions at time t1. BoostAvg , t1 and pct BoostAvg Compare each value with its respective limit to determine if the EGR system has malfunctioned.

[0139] Fault diagnosis and self-learning update module: When no low-voltage EGR system capability fault is detected, the average value of t1 and the sum of the positions of the electronic actuators under the same operating conditions, pct, is calculated. BoostAvgThe fault time of the low-pressure EGR system capability detection under any working condition is updated, and t1 and pct of the same working condition meeting the steady state working condition are updated BoostAvg The array is cleared, and the combination is performed again when the conditions are met again.

[0140] The technical key points and technical principles of the present application are as follows:

[0141] 1. A method for judging the fast and slow response of EGR rate;

[0142] 2. A method for judging the response performance of the electric control actuator of the supercharging turbine under steady state working condition.

[0143] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application belong to the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and variations.

[0144] The contents not described in detail in the specification belong to the prior art known to those skilled in the art.

Claims

1. A method of detecting the capability of a low pressure EGR system, characterized by: The low-pressure EGR system capability detection includes arbitrary condition low-pressure EGR system capability detection and / or steady condition low-pressure EGR system capability detection, wherein, The arbitrary condition low-pressure EGR system capability detection determines a low-pressure EGR system capability detection condition, reads and retains N target EGR rates in the recent time, respectively determines an actual EGR rate initial value and a final value, compares the actual EGR rate with the actual EGR rate maximum final value or the actual EGR rate minimum final value, and judges whether the EGR system capability is faulty or not; Steady state condition low pressure EGR system capability detection: judging whether the steady state condition is met, detecting the low pressure EGR system capability on the basis of meeting the steady state condition, and respectively accumulating the sum of the electric control actuator positions from the target EGR rate of 0 to the time t1 when the electric control actuator of the supercharger turbine tends to be stable and the average value of the electric control actuator positions at the time t1 BoostAvg , t1 and pct BoostAvg are compared with respective limit values respectively, and whether the EGR system capability is faulty is judged. If any one of the arbitrary condition low-pressure EGR system capability detection and the steady condition low-pressure EGR system capability detection is faulty, it is indicated that the low-pressure EGR system capability is faulty, otherwise, it is not faulty.

2. The method of claim 1, wherein: The specific process of the arbitrary condition low-pressure EGR system capability detection step is as follows: The arbitrary condition low-pressure EGR system capability detection determines a low-pressure EGR system capability detection condition, and the detection is performed after the detection conditions are all met; Target EGR rate sampling: read the target EGR rate of continuous N times of sampling, compose an array [r EGRDsr1 ,…,r EGRDsrdN ] of it, update the element in the array after each sampling period, only keep the N target EGR rates in the recent time; Determination of actual EGR rate initial value: determination of actual EGR rate maximum initial value r EGRActMaxRaw and actual EGR rate minimum initial value r EGRActMinRaw ; determining the final value of the actual EGR rate maximum value r EGRActMaxLim and the final value of the actual EGR rate minimum value r EGRActMinLim ; Arbitrary working condition low pressure EGR system capacity judgment: if the actual EGR rate is less than the actual EGR rate minimum final value or the actual EGR rate is greater than the actual EGR rate maximum final value, it indicates that the mixed valve performance appears a response performance sampling fault once, and the fault occurrence time is taken as the sampling period time, if within the current driving cycle, T Total The fault occurrence time accumulation value within the time is not less than the fault time T ErrLim , it indicates that the low pressure EGR system capacity has a fault.

3. The method of claim 2, wherein: The specific conditions of the arbitrary condition low-pressure EGR system capability detection condition step are as follows: The voltage fault detection is that there is no battery voltage fault; The sensor fault detection is that there is no hybrid valve position sensor fault; The motor circuit fault detection is that there is no hybrid valve motor circuit fault; The first running state detection is that the engine is in the first running state; The supercharger fault detection is that there is no supercharger fault; The throttle fault detection is that there is no throttle fault; The EGR valve fault detection is that there is no EGR valve fault; The intake system sensor fault detection is that there is no intake system sensor fault; The EGR closed loop detection is that the EGR is in the closed loop state; The specific process of the target EGR rate sampling step is as follows: Read and compose array: read the target EGR rate of continuous N times of sampling, compose array [r EGRDsr1 ,…,r EGRDsrdN ] Element updating: the elements in the array are updated after each sampling period, and only N target EGR rates in the recent time are retained.

4. The method of claim 3, wherein: The specific process of the sampling number N acquisition method in the target EGR rate sampling step is as follows: Firstly, the sampling number basic value is determined according to the engine speed and the actual fresh air intake density; Secondly, the first sampling number correction value 1 is determined according to the engine speed and the atmospheric pressure; Thirdly, the second sampling number correction value 2 is determined according to the actual fresh air intake density and the actual fresh air intake density change rate; Finally, the sampling number basic value is multiplied by the first sampling number correction value 1, then multiplied by the second sampling number correction value 2, and then rounded to obtain the final integer N value.

5. The method of claim 4, wherein: The specific process of the actual EGR rate initial value determination step is as follows: According to the target EGR rate in the N arrays in the previous step, the maximum target EGR rate r is determined EGRDsrdMax and the minimum target EGR rate r EGRDsrdMin , r EGRActMaxRaw = r EGRDsrdMax + Δ, r EGRActMinRaw = r EGRDsrdMin - Δ, where Δ is the EGR rate accuracy allowed deviation The specific process of the actual EGR rate final value determination step is as follows: Mixed valve opening increase: the mixed valve target opening pct at the current sampling cycle Dsrd No less than the mixed valve target opening pct at the last sampling cycle Dsrd (z), that is, pct Dsrd ≥ pct Dsrd (z), which indicates that the mixed valve opening is increasing, and the normal response performance of the mixed valve will be poor, so there is: r EGRActMaxLim = r EGRActMaxRaw + Δrate x Δt, r EGRActMinLim = r EGRActMinRaw - Δrate x Δt, Hybrid valve opening reduction: the hybrid valve target opening pct at the current sampling period Dsrd Less than the hybrid valve target opening pct at the previous sampling period Dsrd (z) at the current sampling period, i.e. pct Dsrd < pct Dsrd (z) indicates that the hybrid valve opening is being reduced, the normal response performance of the hybrid valve will be better, so there is: r EGRActMaxLim = r EGRActMaxRaw - Δrate x Δt, r EGRActMinLim = r EGRActMinRaw + Δrate x Δt, Where Δt is a sampling period; Δrate is a sampling period allowable variation, which is determined by engine speed n, atmospheric temperature T Amb , battery voltage V Battery in common. Sampling period basic change rate calculation and judgment: At different engine speeds, the lower the atmospheric temperature, the weaker the EGR system execution motor response capability; the hybrid valve motor control depends on the battery power supply, and the lower the battery voltage, the greater the Δrate, that is, Δrate = Δrate Base × f(n, T Abm ) × f(V Battery ), where Δrate Base is the engine speed n, the atmospheric temperature T Amb , the battery voltage V Battery collectively determine a sampling period fundamental change rate obtained by comparing the response performance of the faulty mixture valve with that of the normal mixture valve, i.e., the sampling period fundamental change rate can accurately identify whether the mixture valve has a response performance fault, f(n, T Abm ) is a first correction factor determined by the engine speed and the atmospheric temperature, and f(V Battery ) is a second correction factor determined based on the battery voltage V Battery . The higher the battery voltage, the greater the motor working current, and the better the response capability, so the second correction factor is smaller.

6. The method of claim 5, wherein: The specific process of the steady condition low-pressure EGR system capability detection step is as follows: Steady condition satisfaction condition judgment: the steady condition satisfaction condition is judged, and the fault detection is performed when the steady condition conditions are all met; Steady state condition low pressure EGR system capacity fault detection: on the basis of meeting the steady state condition, the low pressure EGR system capacity is detected, and the sum of the electric control actuator positions at the time t1 from the target EGR rate 0 to the time t1 when the electric control actuator of the supercharger turbine tends to be stable and the average value pct are accumulated respectively BoostAvg t1 and pct BoostAvg are compared with the respective limit values respectively, to determine whether the EGR system capacity has a fault.

7. The method of claim 1, wherein: The specific conditions of the steady state working condition meeting condition judging step are: Second running state detection: the engine is in the second running state; Engine speed fluctuation detection: the engine speed is within a certain range, and the engine speed fluctuation when entering the low pressure EGR system capability detection is small; Target fresh air intake density detection: the target fresh air intake density is greater than a preset value, and the actual fresh air intake density fluctuation when entering the EGR system capability detection is small; Target fresh air intake density and actual fresh air intake density difference detection: the difference between the target fresh air intake density and the actual fresh air intake density is within a certain range; Actual fresh air intake density parameter detection: the actual fresh air intake density is greater than a preset value, and the actual fresh air intake density fluctuation when entering the EGR system capability detection is small; Target EGR rate parameter detection: the target EGR rate is greater than a preset value, and the target EGR rate is stable when entering the EGR system capability detection; Actual EGR rate fluctuation detection: the actual EGR rate is within a certain range, and the actual EGR rate fluctuation when entering the EGR system capability detection is small; Actual hybrid valve opening degree parameter detection: the actual hybrid valve opening degree is not greater than a preset value, and the actual hybrid valve opening degree is stable when entering the EGR system capability detection; Target EGR rate and actual EGR rate difference detection: the difference between the target EGR rate and the actual EGR rate is within a certain range; Engine water temperature detection: the engine water temperature is within a certain range; EGR valve fault detection: the EGR valve has no fault; Misfire fault and knock detection: no misfire fault and knock occurs; Throttle state detection: the throttle is in the full open state; Supercharger working capability maximum limit detection: the supercharger working capability has not reached its maximum limit; First preset time T0 detection: the above 14 conditions are all met for more than the first preset time T0; Second preset time T1 detection: the low pressure EGR system capability detection method has not been executed for more than the second preset time T1; After the above conditions are met, low pressure EGR system capability fault detection is performed; The specific process of the steady state working condition low pressure EGR system capability fault detection step is as follows: Cumulative time T2: the total engine speed, the total actual fresh air intake density, and the total target EGR rate within the cumulative time T2; Obtaining the average value of each parameter in T2 time: obtaining the average value of engine speed in T2 time n Avg , the average value of actual fresh air intake density rho Avg , the average value of target EGR rate r DsrdEGRAvg ; Target EGR rate setting: the target EGR rate is set to 0, i.e. the EGR system is forcibly closed; Parameter accumulation: accumulate the sum of the electric control actuator position at time t1 and t1 time from the target EGR rate of 0 to the time when the electric control actuator of the supercharger turbine tends to be stable, and the average value pct of the sum BoostAvg Wherein the determination method of tending to be stable is that the position change range of the electric control actuator of the supercharger turbine does not exceed the preset position value, and the position change time exceeds the preset time value; Parameters compared with their respective limits: t1 is compared with the limits t1_limHi and t1_limLo under the same operating conditions, and pct is also compared. BoostAvg The limit value pct under the same working conditions BoostAvgHi and pct BoostAvgLo Compare if the following conditions are met simultaneously: 1) t1 > t1_limHi; 2) pct BoostAvg > pct BoostAvgHi ; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; 2) pct BoostAvg <pct BoostAvgLo ; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: wherein the time limit values t1_limHi, t1_limLo, pct BoostAvgHi and pct BoostAvgLo The acquisition method of the above-mentioned values is as follows: under the condition of fixed engine speed, actual fresh air intake density and target EGR rate, a test is performed using a mixed valve with both too fast and too slow response performance deterioration, and the average value is obtained by multiple sampling.

8. The method of claim 7, wherein: 1) t1 < t1_limLo; When no low-pressure EGR system capacity fault is detected, the average value pct of the sum of t1 and the electric control actuator position under the same working condition is obtained BoostAvg The arrays are formed in the order of accumulation time sequence, if the sequence number is greater than a preset value, and both arrays show a non-decreasing or non-increasing trend, when both arrays show a non-decreasing trend, the last number divided by the first number of the array is greater than a preset value, or when both arrays show a non-increasing trend, the last number divided by the first number of the array is less than a preset value, then the fault time of low-pressure EGR system capacity detection under any working condition is updated, and the t1 and pct under the same working condition meeting the steady-state working condition are obtained BoostAvg The arrays are cleared, and then combined again when the conditions are met again.

9. The method of claim 8, wherein: If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: Parameter array variation trend: if the sum of the average values of the time t1 and the electric control actuator position under the same working condition tends to be stable when no mixed valve response performance fault is detected BoostAvg The parameter arrays [t1_1, t1_2, …t1_M] and [t2_1, t2_2, …t2_M] are composed of the former to the latter in the order of the accumulation time sequence, if M is greater than the preset value, and any two of the following conditions are met: The array [t1_1, t1_2,... t1_M] and [pct BoostAvg1 , pct BoostAvg2 ,... pct BoostAvgM ] both exhibit a non-decreasing trend; t1_M divided by t1_1 is greater than a preset value; pct BoostAvgM divided by pct BoostAvg1 is greater than a preset value; 1) t1 < t1_limLo; The arrays [t1_1, t1_2,... t1_M] and [pct BoostAvg1 , pct BoostAvg2 ,... pct BoostAvgM ] both exhibit a trend of not increasing; t1_M divided by t1_1 is less than a preset value; pct BoostAvgM divided by pct BoostAvg1 less than a preset value; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: Arbitrary working condition fault time update: the fault time T of the arbitrary working condition low pressure EGR system capability detection is updated ErrLim Update is performed, and the update method is: T ErrLimOld is the last updated failure time; Steady state working condition parameter array clearing: the corresponding t1 and pct under the same working condition meeting the steady state working condition are cleared, and are combined again after meeting again BoostAvg arrays are cleared, and are combined again after meeting again.

10. A low pressure EGR system capability detection apparatus having a computer program, characterized by: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_limLo; If the above conditions are not met, the following conditions are judged again, and if the following conditions are met at the same time: 1) t1 < t1_lim

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