CN106837496B - Engine Particulate Purification and Regeneration Control System - Google Patents

Abstract

The invention relates to an engine particulate purification and regeneration control system, which can accurately estimate and monitor the carbon black load of a particulate filter to determine an appropriate regeneration timing. The invention uses the average noise energy intensity to judge whether the signal of the differential pressure sensor is reliable. When the signal of the differential pressure sensor is reliable, the differential pressure signal of the particulate filter is used to calculate the load of carbon black; when the differential pressure signal is not reliable, the model is used to determine the carbon black load. The increased value of the black load is calculated cumulatively. The differential pressure noise energy is used to adjust the bandwidth of the differential pressure low-pass filter in real time to increase the accuracy of the differential pressure signal after filtering. The filtered differential pressure signal, exhaust temperature and exhaust volume are used to construct a carbon black model to obtain the total load of the particulate filter. The invention also considers the influence of ash content change on the carbon black load, converts the pressure difference caused by ash into the equivalent carbon black load when the same pressure difference changes, and removes the ash equivalent carbon black load to obtain accurate with reliable carbon black loading.

Description

Engine Particulate Purification and Regeneration Control System

technical field

The invention relates to an engine particle purification and regeneration control system, which belongs to the technical field of engine post-processing DPF system control.

Background technique

Tighter emission regulations introduced in my country, including restrictions on costs, fuel consumption and pollutants, are becoming the driving force for changes in the engine market. Considering the lower particulate emissions, the engine needs advanced aftertreatment technology to adapt to it (for example, the content of _NOx and PM has been greatly reduced due to the use of aftertreatment technology in recent years). Existing engines are equipped with exhaust particulate filters in the exhaust system to reduce the amount of particulate matter emitted into the atmosphere.

In order to improve the life of the exhaust particulate filter device, when the particulate trap device accumulates a certain amount of carbon black, exhaust gas combustion treatment is required to actively regenerate the trap device. The engine control module will control the engine and increase the temperature of the exhaust particulate filter to a predetermined value. level to complete its regeneration.

Regeneration of an overloaded particulate matter filter can generate high temperatures and degrade filter ceramics, resulting in reduced filter life, and excessively frequent regeneration can cause engine oil dilution, resulting in increased wear and failure of engine components. Therefore, a reliable particulate filter regeneration control system needs to be used to monitor the particulate filter carbon black load to determine the appropriate regeneration timing.

The patent CN1734067A published by Nissan provides a method for determining the carbon black of the particulate filter to control the regeneration timing. When the differential pressure sensor is reliable, the differential pressure signal of the particulate filter is used to calculate the load of carbon black; when the differential pressure signal is not When reliable, use the load and rotational speed to determine the increased value of the carbon black load, and carry out the cumulative calculation. The judgment of whether the pressure difference signal is reliable or not is realized by using a predetermined vehicle speed threshold (the vehicle speed greater than the threshold value is considered reliable; the vehicle speed less than the threshold value is considered unreliable).

The patent CN101598058 disclosed by Ford provides a method for determining the regeneration of carbon black. The basic idea is the same as that of Nissan, but the difference lies in the determination of the reliability of the differential pressure signal. The differential signal is true and reliable, but in transient conditions, due to the unstable fluid dynamics in the exhaust system and the effect of the sensor's high time constant (High Time Constants), it will lead to inaccurate measurement of the differential pressure signal. When the exhaust flow is small, the differential pressure sensor works at the limit of the detection range, which deteriorates the accuracy of the differential pressure signal. Therefore, when the engine is working in a steady state, the amount of carbon black obtained by the differential pressure estimation is used as the load output of the particulate filter; when the engine is working in a transient state or when the exhaust flow is small, the reliable carbon black determined by the differential pressure method is used. The calculated value is used as the initial cumulant, and the carbon black model is used to determine the smoke increment based on load and speed, and the final output result is subjected to operating/environmental corrections.

The patent application CN101936207B of the United States International Engine Intellectual Property Co., Ltd. also provides another method for determining the reliability of the differential pressure, which defines the concept of resistance sensitivity to evaluate the reliability of the differential pressure signal. The value of the pressure change of the exhaust gas flowing through the particulate filter at the current time. When the sensitivity drops below the predetermined threshold, it indicates that the reliability of the differential pressure signal is poor, and the method for determining carbon black will be converted from differential pressure-based detection to model-based carbon black accumulation estimation method detection.

The patent application CN101458108 of Hyundai Kia Company provides a method for measuring the effective volume of a particulate filter. There are two kinds of particles in the particulate filter, one is carbon black (soot) and the other is ash (ash). It cannot be actively regenerated, so during the operation of the vehicle, the effective volume of the particulate filter is constantly decreasing. Therefore, before determining the load of the diesel particulate filter, the effective volume must be determined and the effective volume caused by the removal of ash must be reduced. Effect of carbon black loading. The method of measuring the effective volume of the particulate filter disclosed in the patent is to calculate the change of the ash coefficient by monitoring the change of the pressure difference caused by the ash after regeneration and the exhaust gas flow, and to calculate the particle by using the accumulation of the change of the ash coefficient. The effective volume of the filter.

In the patents published by Nissan, Ford and IWC Intellectual Property Co., Ltd., the general process of the proposed method for detecting and determining the load of the particulate filter is the same, that is, when the differential pressure sensor is reliable, the differential pressure of the particulate filter is used. When the differential pressure signal is unreliable, the carbon black model based on load and rotational speed is used to determine the increased value of carbon black load, and the cumulative calculation is carried out, so this method is universal. The difference between the patents proposed by the three companies lies in the conditions for judging whether the differential pressure signal is reliable. The differential pressure signal is unreliable when it is small. The IWC IP even defines the concept of resistance sensitivity to evaluate the reliability of the differential pressure signal to solve the problem of judging the reliability of the differential pressure signal.

The reliability detection methods of differential pressure signals disclosed in the solutions of the three companies all have shortcomings. First of all, in the method of detecting the reliability of differential pressure provided by Nissan, only the vehicle speed threshold is used to determine whether the differential pressure signal is reliable. The principle of this method is that when the vehicle speed is low, the exhaust flow is small, which leads to the The differential sensor operates at the limit of the detection range, degrading the accuracy of the differential pressure signal. The disadvantage of this method is that, firstly, it only avoids the problem of unreliable differential pressure signal caused when the sensor is at the measurement limit, but cannot avoid the unreliable differential pressure signal caused by the instability of the exhaust system; secondly, each engine has its own unique It is too simple to use only the vehicle speed threshold as the reliability parameter for determining the reliability of the differential pressure signal. Moreover, after the engine operation deteriorates, the vehicle speed threshold will be distorted, and the original calibration parameters may not be applicable. Therefore, using this method to judge the reliability of differential pressure is less accurate. The resistance sensitivity method defined by IWC Intellectual Property Co., Ltd. to detect the reliability of differential pressure is better than that of Nissan. Although this method can only detect the differential pressure signal caused by small exhaust flow, it is unreliable, but the resistance sensitivity is It is calculated in real time from the pressure change value of the exhaust gas flowing through the particulate filter at the previous time and the current time. Therefore, this method has high accuracy and can adapt synchronously even if the engine is degraded in long-term operation. However, the disadvantage of this method is that it cannot detect the unreliable pressure difference signal caused by the instability of the exhaust system. The patent proposed by Ford not only considers the unreliable differential pressure signal when the sensor is at the measurement limit, but also considers the unreliable differential pressure signal caused by the instability of the exhaust system, but this method also has shortcomings. The method of judging that the exhaust flow is small and the exhaust flow is unstable is to use the calibration values such as load and speed to perform threshold calibration. When the actual value is less than the calibration threshold, the engine is considered to be in transient or low speed, and the differential pressure method is prohibited. When calculating the carbon black load, this method does not consider the specificity of each engine and the deterioration of the engine after long-term operation, and the accuracy and synchronization adaptability of judging the unreliable pressure difference are insufficient.

The patent published by Hyundai-Kia believes that the effect of reducing the effective volume of the particulate filter caused by ash needs to be removed at the same time as the calculation of carbon black. true load. This is an important complement to the determination of particulate filter carbon black loading. However, the disadvantage of this method is that, first, the effective volume change caused by ash is a volume quantity, and when calculating the final carbon black estimate, the effective volume change caused by ash is converted into the pressure difference caused by ash conversion. is the amount of carbon black with the same load (kg); secondly, the change of effective volume caused by monitoring ash only occurs after active regeneration, so the calculated output of this method is not a continuous value, and the change of pressure difference caused by ash cannot be updated in real time .

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the deficiencies in the prior art, and to provide an engine particulate purification and regeneration control system, which mainly solves the problem of reliable detection and effective determination of the soot load of particulate filters, so as to obtain particulate filter The timing of automatic regeneration is suitable for the device.

According to the technical solution provided by the present invention, the engine particulate purification and regeneration control system is characterized by comprising: a differential pressure sensor capable of obtaining a differential pressure signal of the particulate filter and a temperature sensor disposed upstream and downstream of the particulate filter and the oxidation catalyst;

The output terminal of the differential pressure sensor is connected to the differential pressure signal acquisition module, the output terminal of the differential pressure signal acquisition module is respectively connected to the high-pass filter and the differential pressure low-pass filter module, and the output terminal of the high-pass filter is connected to the noise energy average calculation module, The average noise energy calculation module calculates the average noise energy intensity; the output end of the noise energy average calculation module is respectively connected to the low-pass filter bandwidth acquisition module and the pressure difference reliability determination module, and another input of the low-pass filter bandwidth acquisition module The end is connected to the carbon black model calculation module. The carbon black model calculation module includes a carbon black model load increment value acquisition module and a carbon black load to pressure difference conversion module. The carbon black model load increment value acquisition module is used to obtain the model estimated value. The output end of the carbon black model load increment value acquisition module is connected to the carbon black load to differential pressure conversion module, and the carbon black load to differential pressure conversion module is used to obtain the model to calculate the differential pressure change ; The low-pass filter bandwidth acquisition module uses the average noise energy intensity and the model to calculate the pressure difference variation to obtain the low-pass filter bandwidth; The low-pass filtering module uses the low-pass filtering bandwidth and the unfiltered differential pressure signal to perform low-pass filtering on the differential pressure to obtain the filtered differential pressure signal. The output terminal of the differential pressure low-pass filtering module connects the differential pressure to the carbon black load. The other input terminal of the conversion module from differential pressure to carbon black load is connected to the ash equivalent carbon black load signal, and the output terminal of the differential pressure to carbon black load conversion module outputs the carbon black calculated by the differential pressure method. load;

The output end of the differential pressure reliability determination module is connected to the conversion module from differential pressure to carbon black load and outputs the carbon black model calculation enable signal to the carbon black model load increment value acquisition module; After the pressure difference reliability judgment is passed, the pressure difference to carbon black load conversion module uses the filtered pressure difference signal and the ash equivalent carbon black load to obtain the carbon black load calculated according to the pressure difference method, as the active Judgment basis for regeneration; when the pressure difference reliability judgment module fails to pass the pressure difference reliability judgment, the carbon black model calculation module is used to determine the incremental value of the carbon black model load, and the cumulative carbon black model calculation load is obtained.

Further, the ash equivalent carbon black load signal is output from the output end of the ash equivalent carbon black load coordination output module, and the input end of the ash equivalent carbon black load coordination output module is connected to the differential pressure method to calculate the ash equivalent carbon black load. module.

Further, the formula of the average noise energy intensity is: Among them, S _noise is the average noise energy intensity, and the noise energy intensity is obtained based on the accumulated value of a certain time T _fw and averaged.

Further, in the low-pass filtering bandwidth obtaining module, the average noise energy intensity and the model are used to calculate the pressure difference change value, and the low-pass filtering bandwidth is obtained by checking the two-dimensional table of low-pass filtering bandwidth.

Further, the unfiltered differential pressure signal obtained by the differential pressure signal acquisition module is converted from the differential pressure to the carbon black loading by the differential pressure to carbon black loading conversion module to obtain the unfiltered carbon black loading. , and then combined with the carbon black model load increment value acquisition module to use the carbon black load increment estimated by the model to check the two-dimensional table to obtain the low-pass filter bandwidth.

Further, the determination basis of the differential pressure reliability determination module includes: the noise energy intensity of the differential pressure signal is less than the threshold, the exhaust load is greater than the threshold, the vehicle speed is greater than the threshold, the engine speed is greater than the threshold and no fault flag is set.

Further, the carbon black load calculated by the differential pressure method is obtained by the following steps: first, the engine intake air flow and the filtered differential pressure signal are obtained; then the engine intake flow and the filtered differential pressure signal are jointly mapped to two. The basic amount of carbon black loading can be obtained from the basic amount table of carbon black loading; the temperature correction coefficient can be obtained by mapping the internal temperature of the particulate filter and the filtered differential pressure signal to the two-dimensional table; the temperature correction coefficient and the basic amount of carbon black loading are multiplied and combined After optimized low-pass filtering, the particulate filter load without removing the influence of ash was obtained, and after subtracting the equivalent carbon black load of ash, the carbon black load calculated according to the differential pressure method was obtained.

Further, in the calculation of the ash equivalent carbon black load, in the non-regeneration stage or the unreliable pressure difference stage, the ash model estimates the accumulated ash load increment, and the correction value estimated by the ash model is based on the pressure. The latest equivalent carbon black load obtained by the differential method; the ash load increment corrected by the correction value is multiplied by the equivalent conversion coefficient of the pressure difference between ash and carbon black, and the equivalent carbon black load required to generate the same pressure difference is obtained. The equivalent carbon black load estimated by the above ash model is corrected by the correction value, and the ash equivalent carbon black load is obtained.

Further, in the calculation of the ash equivalent carbon black load, when the regeneration is completed and the pressure difference is reliable, the carbon black load calculated by the differential pressure method is the ash equivalent carbon black load.

The engine particle purification and regeneration control system of the present invention can accurately monitor the carbon black load of the particle filter, effectively overcome the problem of insufficient reliability of the differential pressure sensor and the inaccurate calculation of the carbon black load caused by the influence of ash, and accurately provide a certain particle filter. The carbon black load at the time of regeneration of the filter can avoid high temperature during regeneration and prolong the life of the filter; avoid the dilution of engine lubricating oil caused by excessive and frequent regeneration, which will lead to increased wear and failure of engine components.

The present invention can accurately estimate and monitor the carbon black load of the particulate filter to determine the appropriate regeneration timing. In this method, when the signal of the differential pressure sensor is reliable, the differential pressure signal of the particulate filter is used to calculate the load of carbon black, that is, the differential pressure method; when the differential pressure signal is unreliable, the carbon black model based on load and rotation speed is used to determine the carbon black. The increased value of the black load, and the cumulative calculation is carried out, that is, the cumulative method. The method to determine whether the differential pressure is reliable is to obtain the noise energy intensity of the differential pressure signal through the high-pass filtering method and using the error integral (ISE) criterion. When the differential pressure noise energy intensity is too large, the differential pressure signal is considered unreliable. The estimated differential pressure noise energy can also be used to adjust the differential pressure low-pass filter bandwidth in real time, (when the noise energy is large, the filter bandwidth is reduced; when the noise energy is small, the filter bandwidth is relaxed) to increase the accuracy of the filtered differential pressure signal. . According to the requirements of the differential pressure method, the differential pressure signal obtained after filtering is combined with the exhaust gas temperature and exhaust gas volume to construct a carbon black model, and the total load of the particulate filter is calculated and obtained. Finally, the present invention also considers the influence of ash content change on the carbon black loading, and discloses a method of converting the pressure difference caused by ash to the equivalent carbon black loading when the same pressure difference is caused, and calculates When carbon black loading, the ash equivalent carbon black loading is removed from the total particulate filter loading to obtain accurate and reliable carbon black loading.

Description of drawings

Figure 1 is a diagram of a diesel engine aftertreatment arrangement equipped with a particle recovery system.

Figure 2 is a general diagram of the logic function module for obtaining carbon black loading.

FIG. 3 is a logic functional block diagram for the reliability determination of the differential pressure.

Figure 4 is a logical functional block diagram for the conversion of differential pressure to carbon black loading.

Figure 5 is a logical functional block diagram of the coordinated output of ash equivalent carbon black load.

Fig. 6 is a logic functional block diagram for calculating the ash equivalent carbon black load by using the differential pressure method when the regeneration is completed and the differential pressure signal is reliable.

Labels in the figure: diesel engine 1, combustion chamber 2, intake manifold 3, fuel injector 4, accelerator pedal 5, exhaust manifold 6, EGR valve 7, throttle valve 8, variable area supercharger 9, oxidation catalyst filter 10 , particulate filter 11 , first temperature sensor 12 , differential pressure sensor 13 , second temperature sensor 14 , third temperature sensor 15 , electronic controller 16 .

Detailed ways

The present invention will be further described below in conjunction with the specific drawings.

As shown in Figure 1, it is a diagram of the aftertreatment layout of a diesel engine equipped with a particle collection system. The diesel engine 1 is equipped with a throttle valve 8, a variable area supercharger 9 and an exhaust gas recirculation system with cooling in the intake system. The EGR valve 7 is set in the exhaust gas recirculation system with cooling, and the oxidation catalyst 10 and the particulate filter 11 are arranged in the exhaust gas after-treatment system; after the electronic controller 16 collects the position information of the accelerator pedal 5, according to the driver's request Calculate the amount of air introduced into the combustion chamber 2 and the amount of oil injected per cylinder. The fresh air is supercharged by the variable area supercharger 9, mixed with part of the exhaust gas flowing through the EGR valve 7 after the throttle valve 8, and introduced into the combustion chamber through the intake manifold 3. Fuel injector 4 receives signals from electronic controller 16 to inject the desired amount of fuel into combustion chamber 2 at the appropriate timing. After the combustion is completed, the exhaust gas passes through the variable cross-section supercharger 9 through the exhaust gas manifold 6, and is purified by the oxidation catalyst 10 and the particulate filter 11, so that the harmful gas components in the exhaust gas meet the requirements of regulations, and the final exhaust gas is discharged. to the atmosphere.

The emission control system includes a catalyst system and a particulate filter 11, optionally using various types of catalysts (eg, urea-based selective catalytic reduction SCR catalyst, oxidation catalyst DOC and/or NO _x adsorbent, etc.) or These catalysts can be combined with particulate filters. The reductant (eg, hydrocarbon) is delivered to the exhaust aftertreatment device using any structure known to those skilled in the art, such as a hydrocarbon nozzle or post injection in a direct injection type engine. The catalyst system may include an oxidation catalyst (DOC) for rapidly converting hydrocarbons (HC), carbon monoxide (CO) and nitrogen monoxide (NO) in the engine, the oxidation catalyst comprising a precious metal catalyst, preferably containing Platinum precious metal catalyst. The oxidation catalyst may also be used to provide heat in the exhaust system, and as additional fuel (HC) is oxidized in the oxidation catalyst (DOC) exothermic, heat may be generated to meet the regeneration requirements of the particulate filter 11 . Additional fuel supply can be achieved by, for example, in-cylinder injection during the engine's power and exhaust strokes, or using methods such as retarding injection timing, increasing exhaust gas recirculation (EGR) and intake throttling, or increasing exhaust HC concentrations. Optional method to accomplish; or direct use of hydrocarbon (HC) nozzles to achieve reductant dosing.

The particulate filter 11, in this embodiment a diesel particulate filter DPF, may be coupled downstream of the catalyst system and used to capture particulate matter (eg soot) generated during the vehicle drive cycle. DPFs can be fabricated from a variety of materials, including cordierite, silicon carbide, and other high temperature oxide ceramics. Once the carbon black accumulation reaches a predetermined level, active regeneration can begin. Regeneration is achieved by heating the particulate filter to a certain temperature. At this temperature (400-600°C) carbon black particles can be burned at a faster rate than carbon black formation, in this embodiment the DPF can be a particulate filter containing a coating of precious metal (eg platinum), which can reduce The combustion temperature of carbon black and oxidation of hydrocarbons to carbon dioxide and water.

In addition, a first temperature sensor 12 is provided downstream of the particulate filter 11 , a second temperature sensor 14 is provided between the oxidation catalyst 10 and the particulate filter 11 , and a third temperature sensor 15 is provided upstream of the oxidation catalyst 10 , or an exhaust temperature model may be used to estimate particulate filter 11 temperature or exhaust temperature based on operating conditions. At the same time, the differential pressure signal of the particulate filter 11 can be obtained through the differential pressure sensor 13 . Alternatively, two pressure sensors may be installed upstream and downstream of the particulate filter 11 to detect the pressure difference. The pressure drop of the particulate filter 11 may be affected by exhaust volume flow and DPF soot loading, and if desired, may also include, but are not limited to, other factors such as temperature, fuel type, and the like.

The particulate purification and regeneration control system of the present invention can determine the appropriate active regeneration timing of the particulate filter, and completes the work of reliable monitoring of the carbon black load of the particulate filter. When the differential pressure sensor is reliable, the differential pressure method can be used to obtain the accurate carbon black load according to the input quantity such as the differential pressure signal. When the differential pressure sensor is unreliable, the carbon black model is used to determine the increased value of the carbon black load, and the cumulative calculation is carried out.

As shown in FIG. 2 , in order to obtain the general diagram of the logical function modules of the carbon black loading, it includes a differential pressure signal acquisition module 203, and the differential pressure signal acquisition module 203 obtains an unfiltered differential pressure signal from the differential pressure sensor; the differential pressure signal The output terminal of the signal acquisition module 203 is respectively connected to the high-pass filter 204 and the differential pressure low-pass filtering module 210, and the high-pass filter 204 performs high-pass filtering on the differential pressure signal to obtain high-frequency noise; the output terminal of the high-pass filter 204 is connected to the noise Energy average calculation module 214, the noise energy average calculation module 214 is used to calculate the average noise energy intensity; the output end of the noise energy average calculation module 214 is respectively connected to the low-pass filter bandwidth acquisition module 208 and the pressure difference reliability determination Module 209, the other input end of the low-pass filter bandwidth acquisition module 208 is connected to the carbon black model calculation module 215. The carbon black model calculation module 215 includes the carbon black model load increment value acquisition module 201 and the conversion of the carbon black load to pressure difference Module 202, the carbon black model load increment value acquisition module 201 is used to obtain the carbon black load increment estimated by the model, and the output end of the carbon black model load increment value acquisition module 201 is connected to a conversion module from carbon black load to differential pressure 202, the conversion module 202 of carbon black load to differential pressure is used to obtain the model to calculate the differential pressure variation; the low-pass filter bandwidth acquisition module 208 uses the average noise energy intensity and the model to calculate the differential pressure variation, and looks up the two-dimensional table to obtain Low-pass filter bandwidth; the output end of the low-pass filter bandwidth acquisition module 208 is connected to the differential pressure low-pass filtering module 210, and the differential pressure low-pass filtering module 210 uses the low-pass filtering bandwidth and the unfiltered differential pressure signal to pair the differential pressure Low-pass filtering is performed to obtain the filtered differential pressure signal. The output end of the differential pressure low-pass filtering module 210 is connected to the differential pressure to carbon black load conversion module 213, and the other side of the differential pressure to carbon black load conversion module 213. The input terminal is connected to the ash equivalent carbon black load signal, and the output terminal of the conversion module 213 from differential pressure to carbon black load outputs the differential pressure method to obtain the carbon black load; the ash equivalent carbon black load signal is obtained from the ash equivalent carbon black load signal. The output terminal of the black load coordination output module 212 outputs the output, and the input terminal of the ash equivalent carbon black load coordination output module 212 is connected to the ash equivalent carbon black load calculation module 211 by the differential pressure method. The output end of the differential pressure reliability determination module 209 is connected to the differential pressure to carbon black load conversion module 213 and outputs a carbon black model calculation enable signal to the carbon black model load increment value acquisition module 201 . After the pressure difference reliability judgment by the pressure difference reliability judgment module 209 is passed, the pressure difference to carbon black load conversion module 213 uses the filtered pressure difference signal and the ash equivalent carbon black load to calculate and obtain according to the pressure difference method The amount of carbon black loading is used as the judgment basis for active regeneration; when the pressure difference reliability judgment module 209 fails to pass the pressure difference reliability judgment, it means that the pressure difference signal is unreliable, and only the carbon black model can be used to calculate the carbon black load. Use the carbon black model calculation module 215 to estimate and obtain the carbon black model load increment value, and accumulate the carbon black model calculation load (dotted line output in FIG. 2 ).

In the regeneration control process, the unfiltered differential pressure signal is first obtained from the differential pressure sensor, and the high-frequency noise is obtained by high-pass filtering in the high-pass filter 204. Because the frequency band of the real differential pressure signal of the engine and the noise signal is relatively different. The frequency band range of its real signal can be obtained in a laboratory environment to confirm the high-pass filter bandwidth. The noise energy average calculation module 214 includes the |u ² | operator 205, the accumulator 206 and the unit time average noise energy calculator 207, and the |u ² | operator 205, the accumulator 206 and the unit time average noise energy calculator 207 , using the improved ISE criterion to calculate the average high-frequency noise energy value per unit time of the differential pressure signal. The calculation formula is as follows:

Among them, S _noise represents the average noise intensity, and the noise intensity is obtained based on the accumulated value of a certain time T _fw (can be calibrated) and obtained by averaging, and represents the noise energy intensity per unit time. The average noise energy intensity calculated by the noise energy average calculation module 214 has two functions. The first is to input it to the differential pressure reliability determination module 209 to judge whether the noise energy of the differential pressure signal is too large, so that the differential pressure method can calculate Unreliable; secondly, as one of the inputs, an adaptive low-pass filter bandwidth is obtained in the low-pass filter bandwidth acquisition module 208, so as to obtain a differential pressure signal with no distortion and less noise interference. Another input in the low-pass filter bandwidth acquisition module 208 is the model calculated differential pressure change calculated by the carbon black model calculation module 215, which can be obtained from the carbon black model load increment value acquisition module 201 and the carbon black load to pressure differential. The conversion module 202 obtains, wherein the carbon black load increment estimated by using the model is obtained in the carbon black model load increment value acquisition module 201, and the carbon black load to pressure difference is completed through the carbon black load to pressure difference conversion module 202. The conversion of the difference (this step is the inverse function of the conversion module 213 of the pressure difference to the carbon black loading), finally obtains the model to calculate the pressure difference change. In the low-pass filter bandwidth acquisition module 208, the average noise energy intensity and the model are used to calculate the pressure difference change value, and the two-dimensional table is searched to obtain the low-pass filter bandwidth, so that under the premise of not destroying the change trend of the pressure difference signal (calculated by the model) The pressure difference value is used as the reference of the real pressure difference signal), and high-frequency noise is filtered out as much as possible (the high average sound energy intensity is used as the reference of the noise intensity). The two-dimensional table of low-pass filter bandwidth can be calibrated in the laboratory. The calibration criterion is: when the noise energy is large or the increase in carbon black load is small, the filter bandwidth is reduced; when the noise energy is small or the increase in carbon black load is large, the filter Bandwidth is relaxed. It is also possible to first convert the unfiltered differential pressure signal from the differential pressure to carbon black loading conversion module 213 to the carbon black loading to obtain the unfiltered carbon black loading, and then combine the carbon black model. The load increment value acquisition module 201 uses the carbon black load increment estimated by the model to look up a two-dimensional table to obtain the low-pass filter bandwidth. Both methods can achieve the same goal. In the carbon black model load increment value acquisition module 210, low-pass filtering is performed on the differential pressure using the low-pass filtering bandwidth and the unfiltered differential pressure signal, and the filtered differential pressure signal can be obtained. When the differential pressure reliability determination module 209 After the pressure difference reliability judgment is passed, the filtered pressure difference signal and the ash equivalent carbon black load can be used to obtain the carbon black load calculated according to the differential pressure method using the pressure difference to carbon black load conversion module 213, This is used as the basis for the judgment of active regeneration. When the pressure difference reliability judgment module 209 fails to pass the pressure difference reliability judgment, it means that the pressure difference signal is unreliable, and only the carbon black model can be used to calculate the carbon black load. The model estimates the carbon black loading increments and accumulates the carbon black model-calculated loadings (dashed output).

As shown in FIG. 3 , it is a logical functional block diagram of the pressure difference reliability determination module 209 . It is determined according to the following steps: S304 the noise energy intensity of the differential pressure signal is less than the threshold, S303 the exhaust load is greater than the threshold, S302 the vehicle speed is greater than the threshold, S301 the engine speed is greater than the threshold and S305 no fault flag is set, then step S306 adopts AND logic , to activate the differential pressure method to calculate the carbon black load enable flag.

As shown in FIG. 4 , it is a logical functional block diagram of the conversion module 213 from differential pressure to carbon black loading. First, the engine intake air flow is obtained through step S401, and the filtered differential pressure signal obtained through step S404; then through step S402, the two-dimensional carbon black load basic quantity table is jointly mapped by the engine intake air flow and the filtered differential pressure signal. Obtain the basic amount of carbon black load; step S405 obtains the internal temperature of the DPF, and through step S407, the temperature correction coefficient can be obtained by mapping the two-dimensional table of the internal temperature of the DPF and the filtered differential pressure signal, and the temperature correction coefficient is multiplied by the basic amount of carbon black load After performing optimized low-pass filtering in step S403, the particulate filter load without removing the influence of ash can be obtained. After subtracting the ash equivalent carbon black load obtained in step S406, the carbon black load calculated according to the differential pressure method can be obtained.

As shown in FIG. 5 , a logical functional block diagram of the ash equivalent carbon black load coordination output module 212 is shown. In the non-regenerating state, the ash model can be used to estimate the cumulative ash load increment, and multiply it by the equivalent conversion factor of the pressure difference between ash and carbon black to obtain the final equivalent carbon black load. Specifically include the following steps:

S501: Obtain the fuel consumption;

S502: Obtain the fuel consumption threshold C _Ash ; the confirmation formula of this threshold is as follows:

Among them, C _Ash is the amount of fuel consumed in the laboratory to increase a certain amount of ash accumulation according to the principle of ash generation; Z _Oil/Fuel is the efficiency of oil consumption caused by the consumption of fuel, and this consumption efficiency is based on the working conditions. Small changes; Z _Ash/Oil is the efficiency of ash generation caused by the amount of burning oil, which varies according to the brand of oil; η _st is the efficiency of particulate filter capturing ash, which is based on the aging of particulate filter. The parameters such as degree and EGR rate are slightly changed. It can be seen from the formula that ash is mainly produced in the combustion of oil, and the fuel consumption consumed by producing a certain amount of ash can be determined by the above three efficiencies. When the engine configuration is determined, C _Ash is determined accordingly;

S503: Use the fuel consumption accumulator to accumulate the fuel consumption. When the accumulated value of the fuel consumption is greater than the C _Ash fuel consumption threshold, it means that a certain amount of ash is generated. Therefore, in S504, the ash accumulator is used to accumulate the ash to obtain the basic ash content. value (when replacing or cleaning the DPF, the basic value of ash needs to be removed);

Then through step S505: according to parameters such as rotational speed, load, exhaust temperature, particle filter aging degree, engine oil brand and EGR rate, the ash content estimation correction coefficient is obtained to correct the ash content basic value, and the final ash content accumulation value is obtained;

The final accumulated ash value is converted by the equivalent conversion coefficient of the differential pressure from ash to carbon black to obtain the equivalent carbon black load required to generate the same differential pressure;

Finally, in step S506: the equivalent carbon black load estimated by the above ash model is corrected by the correction value to obtain the ash equivalent carbon black load; the correction value is obtained in step S507 when the regeneration is completed and the pressure difference When the signal is reliable, the latest equivalent carbon black load calculated by the differential pressure method is used to ensure the accuracy of the model calculation correction value.

The equivalent conversion coefficient of differential pressure from ash to carbon black is derived from the following principles: According to Darcy's Law, the differential pressure of the particulate filter can be expressed as the following formula:

where μ is the viscosity coefficient, Q _exh is the exhaust gas volume, k is the wall transmittance, w is the wall thickness, D _h is the flow diameter, x is the effective length of the DPF channel, and A is the effective cross-sectional area of the particulate filter; The formula A=4D _h x represents; a represents the filter coefficient, which can be represented by the formula get.

When there are ash and carbon black in the particulate filter, these two substances will affect the filter pressure difference, so the pressure drop in the filter can be composed of three parts: ΔP = ΔP _{carbon black} + ΔP _ash + ΔP ₀ , where ΔP ₀ is the fixed pressure drop that occurs when the particulate filter is clean, ΔP _carbon black is the DPF pressure drop caused by carbon black, and ΔP _ash is the DPF pressure drop caused by ash. Due to the difference in the properties of ash and carbon black, the parameters such as wall transmittance are different, and finally the filter coefficient is different. Therefore, the pressure drop in the filter can finally be expressed as ΔP=(a _{carbon black} + a _ash )*μ *Q _exh +ΔP ₀ , from this formula, the equivalent conversion coefficient of differential pressure from ash to carbon black can be deduced as a _{carbon black} /a _ash , the equivalent conversion coefficient of differential pressure from ash to carbon black is a constant, when the engine configuration is determined After that, it can be obtained by laboratory calibration. Using the ash to carbon black differential pressure equivalent conversion factor, the ash load can be easily converted to the equivalent carbon black load; finally, when calculating the carbon black load, this equivalent value can be used to remove the ash-to-particulate filter differential pressure Impact.

As shown in Figure 6, it is a logical functional block diagram for obtaining the ash equivalent carbon black load by using the differential pressure method when the regeneration is completed and the differential pressure signal is reliable. When the noise energy intensity of the differential pressure signal in S604 is less than the threshold value, the exhaust gas flow rate in S603 is greater than the threshold value, the vehicle speed in S602 is greater than the threshold value, and the no-fault flag in S605 is set, it means that the differential pressure sensor works reliably. Then, only ash exists in the particulate filter, and the carbon black load calculated by the ECU through step S606 using the differential pressure method according to the differential pressure signal is the equivalent carbon black load of ash. Compared with the ash equivalent carbon black load calculated by the model, the carbon black load measured by the differential pressure sensor is more accurate. Therefore, in step S607, the accumulator is used to obtain the average ash equivalent carbon black within a period of time after the regeneration is completed. The load amount is used as the input of step S506 (the ash content accumulator correction module after regeneration is completed), and the model calculated ash equivalent carbon black load is corrected to ensure the accuracy of the model calculation.

The particulate purification and regeneration control system of the present invention uses the differential pressure signal of the particulate filter to calculate the load of carbon black when the signal of the differential pressure sensor is reliable, that is, the differential pressure method; The carbon black model of the rotational speed is used to determine the increase value of the carbon black load, and the cumulative calculation is carried out, that is, the cumulative method.

The method to determine whether the pressure difference is reliable is to calculate the noise energy intensity of the obtained pressure difference signal through high-pass filtering and using the error integral (ISE) criterion. When the pressure difference noise energy intensity is too large, the pressure difference signal is considered unreliable. The working principle of this method is that when the fluid mechanics characteristics in the exhaust system are unstable or the exhaust flow rate is small, the intensity of the noise interference signal in the differential pressure signal relative to the real differential pressure signal will inevitably increase. By detecting the differential pressure signal Compared with the traditional method, the use of this method can meet the accuracy and adaptability requirements of the pressure difference reliability detection.

Even when the differential pressure is reliable, the calculated noise energy can also be used in the low-pass filtering of the differential pressure signal. Map the two-dimensional table and obtain the low-pass filtering bandwidth of the differential pressure signal. The general principle of the mapping is that when the noise energy is large, the filtering bandwidth is reduced, and when the noise energy is small, the filtering bandwidth is widened; The bandwidth is widened, and the filter bandwidth is reduced when the cumulative value of the carbon black model increases.

According to the requirements of the differential pressure method, the differential pressure signal obtained after filtering will build a carbon black model together with the exhaust gas temperature and exhaust gas volume, and calculate and obtain the total load of the particulate filter. Finally, the present invention also considers the influence of ash content change on the carbon black loading, and discloses a method of converting the pressure difference caused by ash to the equivalent carbon black loading when the same pressure difference is caused, and calculates When carbon black loading, the ash equivalent carbon black loading is removed from the total particulate filter loading to obtain accurate and reliable carbon black loading.

The ash equivalent carbon black loading method is implemented as follows: 1) When the regeneration is completed and the conditions for reliable measurement by the differential pressure sensor are met (the reliable measurement conditions include but are not limited to vehicle speed higher than a certain threshold or exhaust flow greater than a certain threshold or the noise energy intensity of the differential pressure sensor is less than a certain threshold), record the average value of the differential pressure within a period of time, as the change in the differential pressure of the particulate filter caused by ash; record the output of the carbon black load calculated from the differential pressure caused by the ash The average value is converted into the equivalent carbon black loading amount when the same pressure difference is caused as the ash-induced pressure difference. 2) Under other working conditions, use the ash model to estimate the cumulative ash load increment, and multiply it by the equivalent conversion factor of the pressure difference between ash and carbon black to obtain the final equivalent carbon black load. The correction value estimated by the ash model adopts the equivalent carbon black load obtained after the regeneration is completed and the pressure difference signal is reliable, so as to ensure the accuracy of the correction value calculated by the model. The cumulative basic value of ash estimated by the ash model can be obtained by using the cumulative amount of fuel consumption, and the basic value can be calculated by calculating the correction coefficient according to parameters such as speed, load, exhaust temperature, particle filter aging degree, engine oil brand and EGR rate. Correction, and finally obtain the final value of ash increase.

The present invention is based on the real-time monitoring of the noise intensity, and its working principle is that when the fluid mechanics characteristics in the exhaust system are unstable or the exhaust flow rate is small, the intensity of the noise interference signal in the differential pressure signal relative to the real differential pressure signal is inevitable. Enhancement, by detecting and calculating the energy intensity of the noise signal in the differential pressure signal, it is possible to determine whether the differential pressure signal is reliable or not in real time and accurately. The use of this method meets the accuracy requirements and adaptability of the differential pressure reliability detection. Require. Even when the differential pressure is reliable, the calculated noise energy can also be used in the low-pass filtering of the differential pressure signal. Map the two-dimensional table and obtain the low-pass filtering bandwidth of the differential pressure signal. The general principle of the mapping is that when the noise energy is large, the filtering bandwidth is reduced, and when the noise energy is small, the filtering bandwidth is widened; The bandwidth is widened, and the filter bandwidth is reduced when the cumulative value of the carbon black model increases.

Claims (9)

1. An engine particulate purification and regeneration control system, characterized in that it comprises a differential pressure sensor (13) capable of obtaining a differential pressure signal of a particulate filter (11), and a differential pressure sensor (13) arranged on the particulate filter (11) and an oxidation catalyst (10) upstream and downstream temperature sensors; The output end of the differential pressure sensor (13) is connected to a differential pressure signal acquisition module (203), and the output ends of the differential pressure signal acquisition module (203) are respectively connected to a high-pass filter (204) and a differential pressure low-pass filter module (210) , the output end of the high-pass filter (204) is connected to the noise energy average calculation module (214), and the noise energy average calculation module (214) calculates the average noise energy intensity; the output of the noise energy average calculation module (214) The terminals are respectively connected to the low-pass filter bandwidth acquisition module (208) and the pressure difference reliability determination module (209), and the other input terminal of the low-pass filter bandwidth acquisition module (208) is connected to the carbon black model calculation module (215), and the carbon black model The calculation module (215) includes a carbon black model load increment value acquisition module (201) and a carbon black load-to-pressure difference conversion module (202), and the carbon black model load increment value acquisition module (201) is used to obtain a model estimate The obtained carbon black load increment, the output end of the carbon black model load increment value acquisition module (201) is connected to the carbon black load to differential pressure conversion module (202), the carbon black load to differential pressure conversion module (202) ) is used to obtain the model to calculate the differential pressure variation; the low-pass filtering bandwidth acquisition module (208) uses the average noise energy intensity and the model to calculate the differential pressure variation to obtain the low-pass filtering bandwidth; the low-pass filtering bandwidth acquiring module The output end of (208) is connected to the differential pressure low-pass filtering module (210), and the differential pressure low-pass filtering module (210) performs low-pass filtering on the differential pressure using the low-pass filtering bandwidth and the unfiltered differential pressure signal, and obtains the filtered The output terminal of the differential pressure low-pass filter module (210) is connected to the differential pressure to carbon black loading conversion module (213), and the other input terminal of the differential pressure to carbon black loading conversion module (213) Connect the ash equivalent carbon black load signal, and output the carbon black load calculated by the differential pressure method at the output end of the conversion module (213) from the differential pressure to the carbon black load; The output end of the differential pressure reliability determination module (209) is connected to the differential pressure to carbon black load conversion module (213) and outputs the carbon black model calculation enable signal to the carbon black model load increment value acquisition module (201) After the pressure difference reliability judgment of the pressure difference reliability judgment module (209) is passed, the pressure difference to carbon black load conversion module (213) uses the filtered pressure difference signal and the ash equivalent carbon black load to obtain the basis The carbon black load calculated by the differential pressure method is used as the judgment basis for active regeneration; when the differential pressure reliability judgment of the differential pressure reliability judgment module (209) fails, the carbon black model calculation module (215) is used to determine The incremental value of the carbon black model load is accumulated, and the calculated load of the carbon black model is obtained. 2. The engine particulate purification and regeneration control system according to claim 1, wherein the ash equivalent carbon black load signal is output from the output end of the ash equivalent carbon black load coordination output module (212), and the ash equivalent The input end of the carbon black load coordination output module (212) is connected to the pressure difference method to calculate the ash equivalent carbon black load module (211). 3. The engine particle purification and regeneration control system according to claim 1, wherein the formula of the average noise energy intensity is: Among them, S _noise is the average noise energy intensity, the noise energy intensity is obtained based on the accumulated value of a certain time T _fw and averaged, and e(τ) represents the high-frequency noise signal obtained by the high-pass filter of the differential pressure signal. 4. The engine particle purification and regeneration control system according to claim 1, characterized in that: in the low-pass filter bandwidth acquisition module (208), the average noise energy intensity and the model are used to calculate the pressure difference change value, and the low-pass filter is used to calculate the pressure difference value. Bandwidth two-dimensional table to find the low-pass filter bandwidth. 5. The engine particulate purification and regeneration control system according to claim 1, wherein the unfiltered differential pressure signal acquired by the differential pressure signal acquisition module (203) is converted from the differential pressure to the carbon black load conversion module (213) Convert the pressure difference to the carbon black loading to obtain the unfiltered carbon black loading, and then use the carbon black loading increment estimated by the model in combination with the carbon black model load increment value acquisition module (201), Look up a two-dimensional table to find the low-pass filter bandwidth. 6. The engine particulate purification and regeneration control system according to claim 1, wherein the determination basis of the differential pressure reliability determination module (209) comprises: the noise energy intensity of the differential pressure signal is less than a threshold, the exhaust load Greater than threshold, vehicle speed greater than threshold, engine speed greater than threshold and no fault flag set. 7. The engine particulate purification and regeneration control system according to claim 1, wherein the carbon black load calculated by the differential pressure method is obtained by the following steps: first, the engine intake air flow and the filtered differential pressure signal are obtained. ; Then, the basic amount of carbon black load is obtained by mapping the two-dimensional carbon black load basic amount table by the engine intake air flow and the filtered differential pressure signal; the two-dimensional table can be mapped by the internal temperature of the particulate filter and the filtered differential pressure signal. The temperature correction coefficient is obtained; the temperature correction coefficient is multiplied by the basic amount of carbon black load and after optimized low-pass filtering, the particle filter load without removing the effect of ash is obtained, and after subtracting the equivalent carbon black load of ash, the pressure difference is obtained. Calculated carbon black loading. 8 . The engine particulate purification and regeneration control system according to claim 2 , wherein in the calculation of the ash equivalent carbon black load, in the non-regeneration stage or the pressure difference unreliable stage, the ash model estimates the accumulated ash content. 9 . The ash load increment, the correction value estimated by the ash model, adopts the latest equivalent carbon black load calculated by the differential pressure method; the ash load increment corrected by the correction value is multiplied by the pressure difference from ash to carbon black, etc. The equivalent carbon black load required to generate the same pressure difference is obtained by the conversion coefficient of the efficiency; the equivalent carbon black load estimated by the above ash model is corrected by the correction value, and the ash equivalent carbon black load is obtained. 9 . The engine particulate purification and regeneration control system according to claim 1 , wherein: in the calculation of the ash equivalent carbon black load, when the regeneration is completed and the pressure difference is reliable, the carbon black calculated by the pressure difference method is obtained. 10 . The black load is the particulate filter load without removing the effect of ash.