阅读说明：本技术 一种用于柴油机dpf捕集效率故障诊断方法 (Fault diagnosis method for diesel engine DPF trapping efficiency ) 是由 李金� 张正兴 佀庆涛 吴峰胜 张正扬 肖孙波 李军 于 2021-08-20 设计创作，主要内容包括：本发明属于发动机排放技术领域,公开了一种用于柴油机DPF捕集效率故障诊断方法,包括：S1、采集不同工况的DPF压差测量值,获取对应的发动机废气体积流量、DPF载体平均温度和DPF碳载量；S2、建立DPF实时压差值计算模型,计算DPF实时压差值；S3、根据工况信息,标定故障诊断使能区域；S4、计算DPF压差测量值和DPF实时压差值的压差偏差值,并与压差偏差阈值比较,当压差偏差值不大于压差偏差阈值内时,判定捕集效率正常；否则,判定存在故障。本发明的用于柴油机DPF捕集效率故障诊断方法,通过DPF实时压差值的数学计算模型对DPF捕集效率故障进行诊断,方法简单、精确,不使用PM传感器,成本大大降低。(The invention belongs to the technical field of engine emission, and discloses a fault diagnosis method for diesel engine DPF trapping efficiency, which comprises the following steps: s1, collecting DPF pressure difference measurement values under different working conditions, and acquiring corresponding engine exhaust gas volume flow, DPF carrier average temperature and DPF carbon loading capacity; s2, establishing a DPF real-time differential pressure value calculation model, and calculating a DPF real-time differential pressure value; s3, calibrating a fault diagnosis enabling area according to the working condition information; s4, calculating a pressure difference measured value of the DPF and a pressure difference deviation value of a real-time pressure difference value of the DPF, comparing the pressure difference deviation measured value with a pressure difference deviation threshold value, and judging that the trapping efficiency is normal when the pressure difference deviation value is not greater than the pressure difference deviation threshold value; otherwise, it is determined that there is a failure. According to the fault diagnosis method for the DPF trapping efficiency of the diesel engine, the fault of the DPF trapping efficiency is diagnosed through the mathematical calculation model of the real-time differential pressure value of the DPF, the method is simple and accurate, a PM sensor is not used, and the cost is greatly reduced.)

1. A fault diagnosis method for DPF trapping efficiency of a diesel engine is characterized by comprising the following steps:

step S1, collecting a plurality of DPF differential pressure measurement values of a DPF system in different working states by using a DPF differential pressure sensor, and acquiring engine exhaust gas volume flow, DPF carrier average temperature and DPF carbon loading capacity corresponding to the DPF differential pressure measurement values through a calculation module of the DPF system;

step S2, establishing a DPF real-time pressure difference value mathematical calculation model according to the engine exhaust gas volume flow, the DPF carrier average temperature and the DPF carbon loading amount, and calculating a DPF real-time pressure difference value;

step S3, calibrating an enabling area of DPF trapping efficiency fault diagnosis according to the working condition information of the DPF system;

step S4, setting a differential pressure deviation threshold value, calculating a differential pressure deviation value between the DPF differential pressure measured value and the DPF real-time differential pressure value, comparing the differential pressure deviation threshold value with the differential pressure deviation value, and judging that the DPF trapping efficiency is normal when the differential pressure deviation value is less than or equal to the differential pressure deviation threshold value; and when the differential pressure deviation value is larger than the differential pressure deviation threshold value, judging that the DPF trapping efficiency is in fault.

2. The method for diagnosing a DPF trapping efficiency failure in a diesel engine according to claim 1, wherein the step S2 specifically includes:

step S21, selecting a plurality of different DPF carbon loading amounts, forming a plurality of numerical intervals, and determining the numerical intervals of the DPF carbon loading amounts corresponding to a plurality of DPF pressure difference measurement values;

step S22, fitting a DPF real-time differential pressure value MAP curve of the DPF carbon loading capacity according to the selected DPF carbon loading capacity and the corresponding DPF differential pressure measurement value by combining the volume flow of the engine exhaust gas and the average temperature of the DPF carrier;

step S23, inquiring the DPF real-time pressure difference value MAP curve according to the numerical interval of the carbon loading amount of the DPF to obtain a first DPF real-time pressure difference value and a second DPF real-time pressure difference value;

and step S24, calculating to obtain the DPF real-time differential pressure value according to the first DPF real-time differential pressure value and the second DPF real-time differential pressure value.

3. The method for diagnosing a DPF trapping efficiency failure for a diesel engine as set forth in claim 2, wherein the step S21 further includes: and determining the position of the DPF carbon loading corresponding to the DPF pressure difference measured value in the numerical interval through linear interpolation calculation.

4. The method for diagnosing a DPF trapping efficiency failure for a diesel engine as set forth in claim 3, wherein the step S24 further includes: and calculating to obtain the DPF real-time differential pressure value through linear interpolation according to the first DPF real-time differential pressure value and the second DPF real-time differential pressure value and by combining the carbon loading amount of the DPF at the linear interpolation position of the numerical interval.

5. The method as claimed in claim 2, wherein in step S21, eight different DPF carbon loadings are selected and seven of the numerical intervals are formed.

6. The method for diagnosing failure of DPF trapping efficiency for diesel engine according to claim 1, wherein in the step S3, the operating condition information of the DPF system includes environmental condition and/or engine state condition and/or actuator state condition and/or sensor operating state condition.

7. The DPF trapping efficiency failure diagnosis method for a diesel engine according to claim 1, further comprising, before the step S4:

step S40, determining whether the DPF system enters the enabled region, and executing step S4 when the DPF system enters the enabled region.

8. The method for diagnosing a DPF trapping efficiency failure for a diesel engine as set forth in claim 1, further comprising, after the step S4:

in step S5, when it is determined that there is a failure in the DPF trapping efficiency, time delay is performed for entry and exit of the failure by the debounce calculation.

9. The method for diagnosing a DPF trapping efficiency failure for a diesel engine as set forth in claim 8, further comprising, after the step S5:

and step S6, confirming the fault, and sending out a prompt signal by the fault lamp.

10. The method for diagnosing the DPF trapping efficiency failure for the diesel engine according to claim 1, wherein the step S4 further includes correcting the differential pressure deviation threshold value by the DPF carbon loading.

Technical Field

The invention relates to the technical field of engine emission, in particular to a fault diagnosis method for diesel engine DPF trapping efficiency.

Background

The diesel engine has high thermal efficiency, dynamic property, economy and durability, and is widely applied to the fields of transportation, engineering machinery, agricultural machinery and the like, but the exhaust emission of the diesel engine also has great influence on the atmospheric environment. The main emissions of diesel engines include nitrogen oxides (NOx), Hydrocarbons (HC), carbon monoxide (CO), Particulate Matter (PM), and the like. A Diesel Particulate Filter (DPF) is an effective device for solving the problem of diesel particulate emission, and is a necessary device for reducing the requirements on the quality and quantity of particulate matters in emissions in national standards and industrial specifications. At present, a PM sensor (particulate matter sensor) is mainly adopted in the automobile industry to monitor the trapping efficiency of the DPF. Due to the fact that the working principle of the PM sensor is complex, fault monitoring items of the PM sensor reach more than thirty items, the PM sensor is high in fault rate and low in reliability in the market application process, and meanwhile, the cost is high because a single PM sensor is sold for more than four hundred yuan.

Disclosure of Invention

The invention aims to provide a fault diagnosis method for DPF trapping efficiency of a diesel engine, which is used for diagnosing whether the DPF trapping efficiency has faults or not by comparing a real-time pressure difference value of the DPF with a pressure difference measured value of the DPF.

In order to achieve the purpose, the invention adopts the following technical scheme:

a fault diagnosis method for DPF trapping efficiency of a diesel engine comprises the following steps:

step S1, collecting a plurality of DPF differential pressure measurement values of a DPF system in different working states by using a DPF differential pressure sensor, and acquiring engine exhaust gas volume flow, DPF carrier average temperature and DPF carbon loading capacity corresponding to the DPF differential pressure measurement values through a calculation module of the DPF system;

step S2, establishing a DPF real-time pressure difference value mathematical calculation model according to the engine exhaust gas volume flow, the DPF carrier average temperature and the DPF carbon loading amount, and calculating a DPF real-time pressure difference value;

step S3, calibrating an enabling area of DPF trapping efficiency fault diagnosis according to the working condition information of the DPF system;

step S4, setting a differential pressure deviation threshold value, calculating a differential pressure deviation value between the DPF differential pressure measured value and the DPF real-time differential pressure value, comparing the differential pressure deviation threshold value with the differential pressure deviation value, and judging that the DPF trapping efficiency is normal when the differential pressure deviation value is less than or equal to the differential pressure deviation threshold value; and when the differential pressure deviation value is larger than the differential pressure deviation threshold value, judging that the DPF trapping efficiency is in fault.

As a preferred embodiment of the present invention, the step S2 specifically includes:

step S21, selecting a plurality of different DPF carbon loading amounts, forming a plurality of numerical intervals, and determining the numerical intervals of the DPF carbon loading amounts corresponding to a plurality of DPF pressure difference measurement values;

step S22, fitting a DPF real-time differential pressure value MAP curve of the DPF carbon loading capacity according to the selected DPF carbon loading capacity and the corresponding DPF differential pressure measurement value by combining the volume flow of the engine exhaust gas and the average temperature of the DPF carrier;

step S23, inquiring the DPF real-time pressure difference value MAP curve according to the numerical interval of the carbon loading amount of the DPF to obtain a first DPF real-time pressure difference value and a second DPF real-time pressure difference value;

and step S24, calculating to obtain the DPF real-time differential pressure value according to the first DPF real-time differential pressure value and the second DPF real-time differential pressure value.

As a preferred embodiment of the present invention, the step S21 further includes: and determining the position of the DPF carbon loading corresponding to the DPF pressure difference measured value in the numerical interval through linear interpolation calculation.

As a preferred embodiment of the present invention, the step S24 further includes: and calculating to obtain the DPF real-time differential pressure value through linear interpolation according to the first DPF real-time differential pressure value and the second DPF real-time differential pressure value and by combining the carbon loading amount of the DPF at the linear interpolation position of the numerical interval.

In a preferred embodiment of the present invention, in step S21, eight different DPF carbon loadings are selected and seven numerical intervals are formed.

In a preferred embodiment of the present invention, in step S3, the operating condition information of the DPF system includes an environmental condition and/or an engine state condition and/or an actuator state condition and/or a sensor operating state condition.

As a preferred embodiment of the present invention, before the step S4, the method further includes:

step S40, determining whether the DPF system enters the enabled region, and executing step S4 when the DPF system enters the enabled region.

As a preferred embodiment of the present invention, after the step S4, the method further comprises:

in step S5, when it is determined that there is a failure in the DPF trapping efficiency, time delay is performed for entry and exit of the failure by the debounce calculation.

As a preferred embodiment of the present invention, after the step S5, the method further comprises:

and step S6, confirming the fault, and sending out a prompt signal by the fault lamp.

In a preferred embodiment of the present invention, the step S4 further includes correcting the differential pressure deviation threshold value according to the DPF carbon loading.

The invention has the beneficial effects that: the fault diagnosis method for the diesel engine DPF trapping efficiency comprises the steps that firstly, a plurality of DPF differential pressure measurement values of a DPF system in different working states are collected through a DPF differential pressure sensor, a mathematical calculation model can be established by utilizing the corresponding relation among numerical values based on the physical characteristics and the working principle of a DPF carrier according to the engine exhaust gas volume flow, the DPF carrier average temperature and the DPF carbon loading capacity corresponding to each DPF differential pressure measurement value, and therefore the DPF real-time differential pressure value corresponding to each DPF differential pressure measurement value is calculated; and comparing a differential pressure deviation value between the DPF differential pressure measured value and the DPF real-time differential pressure value with a set differential pressure deviation threshold value so as to judge whether the DPF trapping efficiency is in failure. In the determination process, the real-time pressure difference value of the DPF is calculated through a mathematical calculation model, and the DPF trapping efficiency diagnosis is carried out by combining a pressure difference sensor, so that a PM sensor is not needed, the diagnosis method is simple, the diagnosis result is accurate, and the cost is greatly reduced.

Drawings

FIG. 1 is a schematic flow chart diagram of a fault diagnosis method for DPF trapping efficiency of a diesel engine according to an embodiment of the invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

In the description of the present invention, unless expressly stated or limited otherwise, the terms "connected," "connected," and "fixed" are to be construed broadly, e.g., as meaning permanently connected, removably connected, or integral to one another; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.

In the description of the present embodiment, the terms "upper", "lower", "left", "right", and the like are used based on the orientations and positional relationships shown in the drawings only for convenience of description and simplification of operation, and do not indicate or imply that the referred device or element must have a specific orientation, be configured and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used only for descriptive purposes and are not intended to have a special meaning.

As shown in fig. 1, an embodiment of the present invention provides a failure diagnosis method for DPF trapping efficiency of a diesel engine, wherein the diesel engine DPF system is a part of an engine aftertreatment system, is communicated with an exhaust system of an engine, and comprises a DPF carrier, a DPF differential pressure sensor connected to two ends of the DPF carrier, and a plurality of calculation modules, and the like, and the calculation modules can calculate real-time values such as engine exhaust gas volume flow, DPF carrier average temperature, and DPF carbon loading. The method for diagnosing the DPF trapping efficiency fault of the diesel engine comprises the following steps:

step S1, collecting a plurality of DPF differential pressure measurement values of the DPF under different working states by using a DPF differential pressure sensor, and acquiring engine exhaust gas volume flow, DPF carrier average temperature and DPF carbon loading capacity corresponding to each DPF differential pressure measurement value;

in this step S1, a plurality of DPF differential pressure measurement values of the DPF are collected by the DPF differential pressure sensors connected to the two ends of the DPF carrier under different working conditions, wherein each DPF differential pressure measurement value corresponds to the corresponding engine exhaust gas volume flow, the DPF carrier average temperature, and the DPF carbon loading amount, and these values can be obtained by the calculation module of the DPF system, which is not repeated herein.

Step S2, establishing a DPF real-time differential pressure value calculation model according to the volume flow of the exhaust gas of the engine, the average temperature of the DPF carrier and the carbon loading amount of the DPF, and calculating the DPF real-time differential pressure value;

in step S2, according to the engine exhaust gas volume flow, the average temperature of the DPF carrier, the DPF carbon loading amount, and the DPF differential pressure measurement value which have been calculated and obtained in step S1, the values are in a one-to-one correspondence relationship, and based on the physical characteristics and the operating principle of the DPF carrier, a mathematical calculation model can be established according to the correspondence relationship between the values, and the DPF real-time differential pressure value can be calculated using the engine exhaust gas volume flow, the average temperature of the DPF carrier, and the DPF carbon loading amount.

Step S3, calibrating an enabling area of DPF trapping efficiency fault diagnosis according to the working condition information of the DPF system;

in step S3, an enable region for performing DPF trapping efficiency failure diagnosis is first set based on factors that mainly affect the DPF system operation process. The operating condition information of the DPF system comprises environmental conditions and/or engine state conditions and/or actuator state conditions and/or sensor operating state conditions. The environment conditions comprise atmospheric temperature, pressure and the like, and the engine state conditions comprise engine running time, static working conditions, dynamic working conditions, combustion modes, coolant temperature and the like; the actuator state conditions comprise a supercharging pressure condition, an EGR valve condition, a throttle valve state and the like, and the sensor working state conditions comprise a DPF pressure difference sensor, a temperature sensor working state and the like. The above-mentioned operating condition information is specifically set according to the vehicle parameters, and this embodiment is not limited herein. By setting the enabling area, the fault diagnosis of the DPF trapping efficiency of the DPF system under the normal working condition is ensured, and the influence of the bad working condition on the diagnosis result is avoided. Preferably, when the working condition information of the DPF system meets the requirements of the set conditions, the diagnosis of the DPF trapping efficiency enters an enabling area; that is, it is determined whether the DPF system enters the enabled region, and when entering the enabled region, the process proceeds to step S4.

Step S4, setting a differential pressure deviation threshold, calculating a differential pressure deviation value of a DPF differential pressure measured value and a DPF real-time differential pressure value, comparing the differential pressure deviation threshold with the differential pressure deviation value, and judging that the DPF trapping efficiency is normal when the differential pressure deviation value is within the differential pressure deviation threshold; and if the differential pressure deviation value exceeds the differential pressure deviation threshold value, judging that the DPF trapping efficiency is in fault.

In step S4, the DPF real-time differential pressure value calculated in step S2 is compared with the DPF differential pressure measurement value measured in step S1 to determine a differential pressure deviation value. Under ideal conditions, the differential pressure offset value should be zero. By setting a differential pressure deviation threshold value, the differential pressure deviation value is compared with the differential pressure deviation threshold value, the DPF trapping efficiency is diagnosed within a certain precision range, and misdiagnosis is avoided. When the differential pressure deviation value is within the differential pressure deviation threshold value, judging that the DPF trapping efficiency is normal; if the differential pressure deviation value exceeds the differential pressure deviation threshold value, the trapping efficiency of the DPF is judged to be in fault, and system inspection or correction is needed.

According to the fault diagnosis method for the DPF trapping efficiency of the diesel engine, firstly, a plurality of DPF differential pressure measurement values of a DPF system in different working states are collected through a DPF differential pressure sensor, a mathematical calculation model can be established according to the corresponding relation among values according to the engine exhaust gas volume flow, the average temperature and the carbon loading capacity of a DPF carrier corresponding to each DPF differential pressure measurement value, and based on the physical characteristics and the working principle of the DPF carrier, so that the real-time pressure difference value of the DPF corresponding to each DPF differential pressure measurement value is calculated, and the pressure difference deviation value between the DPF differential pressure measurement value and the DPF real-time pressure difference value is compared with a set pressure difference deviation threshold value, so that whether the DPF trapping efficiency has faults or not is judged. In the determination process, the real-time pressure difference value of the DPF is calculated through a mathematical calculation model, and the DPF trapping efficiency diagnosis is carried out by combining a pressure difference sensor, so that a PM sensor is not needed, the diagnosis method is simple and accurate, and the cost is greatly reduced.

Further, step S2 specifically includes:

step S21, selecting a plurality of different DPF carbon loading amounts, forming a plurality of numerical intervals, and determining the numerical intervals of the DPF carbon loading amounts corresponding to the DPF pressure difference measurement values; preferably, the position of the DPF carbon loading in the numerical interval corresponding to the DPF pressure difference measured value is determined through linear interpolation calculation.

In this embodiment, eight different DPF carbon loadings are selected and seven numerical intervals are formed; a mathematical calculation model is established by taking eight different DPF carbon loading amounts as standards, and the analysis and calculation processes can be simplified under the condition of meeting the requirement of precision conditions. Preferably, the eight different DPF carbon loadings comprise values from empty to full. For the DPF differential pressure measurement value corresponding to the DPF carbon loading in seven numerical intervals, the specific position of the corresponding DPF carbon loading in the corresponding numerical interval needs to be calculated through linear interpolation.

In other embodiments, other amounts of DPF carbon loading may be selected for analysis to complete the construction of the mathematical calculation model, as long as the selected DPF carbon loading includes a value from no load to full load, which is not limited herein.

Step S22, fitting a DPF real-time differential pressure value MAP curve of the DPF carbon loading capacity according to the selected DPF carbon loading capacity and the corresponding DPF differential pressure measurement value by combining the volume flow of the engine exhaust gas and the average temperature of the DPF carrier;

in this step S22, in the eight DPF carbon loadings selected, each DPF carbon loading has a plurality of different DPF differential pressure measurement values, and each DPF differential pressure measurement value has a corresponding engine exhaust gas volume flow and a corresponding DPF carrier average temperature, so that a DPF real-time differential pressure value MAP curve of the DPF carbon loadings can be fitted, and the eight DPF carbon loadings have eight different DPF real-time differential pressure value MAP curves. By selecting the specific DPF carbon loading capacity and combining an MAP curve, the relation among the DPF pressure difference measured value, the engine exhaust gas volume flow, the DPF carrier average temperature and the DPF carbon loading capacity can be subjected to dimension reduction analysis, a mathematical calculation model can be conveniently established, and the DPF real-time pressure difference value can be calculated more accurately.

Step S23, inquiring a DPF real-time pressure difference value MAP curve according to a numerical interval of the carbon loading amount of the DPF to obtain a first DPF real-time pressure difference value and a second DPF real-time pressure difference value;

in step S23, the DPF carbon loadings at the two end points of the numerical interval can be determined according to the numerical interval in which the DPF carbon loadings are located, and the first DPF real-time differential pressure value and the second DPF real-time differential pressure value corresponding to the two DPF carbon loadings can be obtained by searching the MAP curves of the DPF real-time differential pressure values of the two DPF carbon loadings.

And step S24, calculating the real-time pressure difference value of the DPF according to the real-time pressure difference value of the first DPF and the real-time pressure difference value of the second DPF by combining the linear interpolation result of the carbon loading amount of the DPF in the numerical interval.

In step S24, a final DPF real-time differential pressure value is obtained by performing re-interpolation calculation based on the first DPF real-time differential pressure value and the second DPF real-time differential pressure value obtained in step S23 in combination with the DPF carbon loading amount corresponding to the DPF differential pressure measurement value determined by the linear interpolation in step S21 at the position of the numerical range.

Further, after step S4, the method further includes:

step S5, when the DPF trapping efficiency is judged to have faults, time delay is carried out on the entering and exiting of the faults through rebound calculation;

and step S6, confirming the fault, and sending out a prompt signal by the fault lamp.

Through the step S5, the calculation module in the DPF system can record the calculation result of judging the fault in one driving period, and the industry requirement of the national six standards is met; preferably, a fault lamp is set for the DPF system, and when the DPF trapping efficiency is judged to have a fault, the fault lamp sends out a prompt signal; and the operator can observe the diagnosis result visually.

Further, step S4 includes correcting the differential pressure deviation threshold by the DPF carbon loading. Because the carbon loading of the DPF has a large influence on the DPF pressure difference measured value and the DPF real-time pressure difference value, after the fault diagnosis method for the DPF collection efficiency of the diesel engine of the embodiment is used for diagnosing a plurality of cycles, verification of the enabling area and the pressure difference deviation threshold value can be carried out according to the diagnosis result, and the pressure difference deviation threshold value is corrected through the carbon loading of the DPF, so that the diagnosis precision is higher.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Numerous obvious variations, adaptations and substitutions will occur to those skilled in the art without departing from the scope of the invention. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.