JP2008157200A - Abnormality detection device for exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abnormality detection device for a filter in an exhaust filtration device capable of constantly correctly detecting an abnormality in the filter. <P>SOLUTION: The exhaust emission control device is provided with a filter in an exhaust passage of an internal combustion engine to collect particulates in exhaust, and a differential pressure sensor to detect differential pressure between the upstream side and the downstream side of the filter. The abnormality detection device for the exhaust emission control device is provided with a differential pressure determination means to determine the value of differential pressure between the upstream side and the downstream side of the filter based on the operation state of the internal combustion engine, and a determination means to detect whether the filter has an abnormality by determining the value of a difference P between the actual measurement of a pressure difference between the upstream and the downstream of the filter detected by the differential pressure sensor and the value of differential pressure determined by the differential pressure determination means, and compare the difference P with a threshold. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an abnormality detection device for an exhaust purification device in an exhaust filtration device such as a DPF.

  An exhaust filtration device, for example, a DPF (Diesel Particulate Filter) device includes a filter therein, and traps particulates contained in the exhaust gas of the engine with the filter to purify the exhaust gas. Since the filter is clogged with trapped fine particles, the filter is appropriately combusted, replaced or cleaned. In addition, an increase in exhaust resistance in the DPF device may increase the back pressure and affect engine control.

  Therefore, the DPF device includes a differential pressure sensor that measures the pressure difference between the upstream side and the downstream side of the filter, and determines whether or not the filter is clogged with particulate components based on the value from the differential pressure sensor. In the case of clogging, the driver is prompted to perform manual combustion, or a signal is sent to the control device for use in engine control.

  As described above, the filter in the DPF device has a great influence on the running of the vehicle and the environment, and is greatly affected by the temperature change, pressure fluctuation, vibration and the like during use. The filter is usually formed of a ceramic having a large number of fine holes on its surface, and in some cases, the exhaust gas may leak due to cracks or melting due to the load.

  Therefore, when fine particles accumulate on the filter, the measured value of the differential pressure sensor increases due to the accumulated fine particles. However, if a crack or erosion occurs in the filter, the increase in the differential pressure due to fine particle accumulation is offset, It is possible that the differential pressure sensor shows a normal value despite the accumulation.

Therefore, for example, Japanese Patent Application Laid-Open No. 2003-155920 describes an invention of an abnormality detecting device for a particulate filter. In this method, the differential pressure before and after the particulate filter is obtained by a differential pressure sensor, the ash accumulation is compensated for by the differential pressure value, and clogging or melting damage of the particulate filter is determined.
JP 2003-155920 A

However, the conventional particulate filter abnormality detection device has the following problems.
The abnormality detection device for the particulate filter starts a failure diagnosis only when it is determined that the engine is in a steady state. Further, since the threshold value used for the determination is obtained from the average value of the engine speed and the fuel injection amount for a predetermined time, unless the steady state continues for a predetermined time, the threshold value is not determined and diagnosis is not performed.

  Further, since the threshold value is determined without involving the deposition amount of the fine particles, it is necessary to determine the threshold value in advance to increase the exhaust pressure due to the deposition of the fine particles. However, since the ash calculation accumulation value used for correcting the differential pressure is calculated by proportional calculation based on the travel distance, a difference in ash accumulation amount due to a difference in operation history is not reflected.

  An object of the present invention is to solve the above-mentioned problems and to provide an abnormality detection device for an exhaust filtration device that can accurately detect a filter failure.

In order to solve the above-mentioned problems, the present invention is configured as follows.
1. An exhaust emission control device provided in an exhaust passage of an internal combustion engine and comprising a filter for collecting particulates in exhaust gas and a differential pressure sensor for detecting a pressure difference generated between an upstream side and a downstream side of the filter A differential pressure value calculating means for calculating a pressure difference value between the upstream and downstream sides of the filter based on an operating state of the internal combustion engine; and a pressure difference between the upstream and downstream sides of the filter detected by the differential pressure sensor. Determining means for calculating a value of a difference P between the actually measured value and the calculated differential pressure value from the differential pressure value calculating means, comparing the difference P with a threshold value, and detecting that there is an abnormality in the filter; In this way, an abnormality detection device for the exhaust gas purification device was constructed.

  2. The determination means has a first threshold value used for determining clogging of the filter and a second threshold value used for determining leakage of the filter, and the value of the difference P exceeds the first threshold value In this case, or when the value of the difference P exceeds the second threshold value, it is determined that the filter is abnormal.

  3. The first threshold value is based on an exhaust flow rate and a clogging coefficient based on a soot calculation accumulation value and an ash calculation accumulation value accumulated on the filter, and the second threshold value is an exhaust flow rate on the filter. It was decided to calculate from the leak coefficient based on the deposited soot calculated deposition value and the ash calculated deposition value.

  4. The differential pressure value calculating means calculates the calculated differential pressure value based on the reference differential pressure value calculated from the temperature upstream of the filter and the exhaust gas flow rate.

  5. The determination means includes a determination means for determining that the filter is abnormal when the determination is continued for a predetermined time when it is determined that the filter is abnormal.

The abnormality detection device for an exhaust gas filtration device according to the present invention has the following effects.
Even when the vehicle is not in steady running, the calculated differential pressure value can be calculated to detect a filter abnormality. Since the threshold value is obtained from the running state one by one, the abnormality of the filter can be detected by comparison with the threshold value even if it is not steady running.

  The soot accumulation value is calculated in consideration of the disappearance due to NOx and heat, and the threshold value is corrected based on the soot accumulation value. Therefore, a value reflecting the actual operation history is always obtained. Anomaly detection can be performed using an appropriate threshold.

  Since the calculation of the ash accumulation value is performed using the fuel injection amount integrated value, a value reflecting the actual driving history can be obtained as compared with the case of calculation based on the travel distance.

  It is possible to detect both the clogging generated in the filter and the leak state due to the occurrence of cracks. Since the abnormality of the filter is determined after a predetermined time has elapsed, the reliability of the abnormality detection device can be improved.

An embodiment of a filter abnormality detection device according to the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration example of an engine 12 as an internal combustion engine that includes a filter abnormality detection device 10. The engine 12 is a diesel engine, and includes a supercharger (turbocharger) 14, a DPF device 16, a fuel supply device 18, an engine speed sensor 19, and the like. The supercharger 14 is connected to an exhaust pipe 20 as an exhaust passage and an intake pipe 22 as an intake passage, pressurizes the outside air sucked from the air cleaner 24 using exhaust pressure, and sends it to the engine 12.

  The intake pipe 22 is provided with an intake pressure sensor 26 for detecting the pressure in the intake pipe 22, that is, a boost pressure (boost pressure) by the supercharger 14, and an intake flow rate sensor 27 for detecting the flow rate in the intake pipe 22. It has been. The engine 12 is not limited to a diesel engine, and may be a naturally aspirated engine in which the supercharger 14 is not provided.

  The DPF device 16 has a cylindrical shape and includes a filter 28 inside. The DPF device 16 is connected to the exhaust side of the supercharger 14 on the upstream side, and communicates with the exhaust port 29 of the vehicle on the downstream side. The filter 28 is a ceramic filter and has fine holes formed on the surface for capturing fine particles contained in the exhaust gas. The DPF device 16 is provided with an upstream pressure sensor 30, a differential pressure sensor 32, an upstream temperature sensor 35, and a downstream temperature sensor 37, and catalyst devices 31 and 33 are connected to the front and rear.

  The upstream pressure sensor 30 is attached to the upstream side of the filter 28 and detects the pressure value on the upstream side of the filter 28. The differential pressure sensor 32 detects a pressure difference generated between the upstream side and the downstream side of the filter 28. The upstream temperature sensor 35 measures the temperature on the upstream side of the filter 28, that is, the temperature of the exhaust gas flowing into the filter 28. The downstream temperature sensor 37 measures the temperature on the downstream side of the filter 28.

  Each sensor is connected to a control device 36 (ECU (Electronic Control Unit)) as shown in FIG. Further, as shown in FIG. 2, various sensors such as an atmospheric pressure sensor 38 that detects the atmospheric pressure value and a water temperature sensor 40 that detects the coolant temperature are connected to the control device 36. The value detected by each sensor is sent to the control device 36.

  The fuel supply device 18 is a fuel injection device that injects fuel, and injects a predetermined amount of fuel into the engine 12 in accordance with an instruction from the control device 36.

  Further, as shown in FIG. 3, the control device 36 includes a determination unit 44, a soot accumulation value calculation unit 46, an ash accumulation value calculation unit 47, a threshold value calculation unit 48, a differential pressure value calculation unit 50, and a time measurement unit 60. And a determination means 62.

  As shown in FIG. 4, the soot accumulation value calculation means 46 includes a soot generation amount calculation means 52, a NOx amount calculation means 54, a soot loss amount (NOx) calculation means 56, and a soot loss amount (heat) calculation means 58. The integrating means 59 is formed.

  The soot generation amount calculation means 52 uses the map 1 shown in FIG. 7 to calculate the soot reference from the engine speed detected by the engine speed sensor 19 and the fuel supply amount injected from the fuel supply device 18 to the engine 12. Calculate the generated value. Further, using the correction graph of FIG. 8 and the correction graph of FIG. 9, the soot reference generation value is corrected to calculate the soot calculation discharge value.

  FIG. 7 is a three-dimensional map showing the soot reference generation amount (value) in the direction perpendicular to the paper surface with the horizontal axis along the paper surface as the engine speed Ne and the vertical axis as the fuel supply (injection) amount q. FIG. 8 is a correction value for correcting the soot reference generation amount (value) with respect to the fuel injection amount, and FIG. 9 is a correction value for correcting the soot reference generation amount (value) with respect to the coolant temperature.

  The NOx amount calculation means 54 is a map 2 (a three-dimensional map similar to FIG. 7) from the engine speed detected by the engine speed sensor 19 and the fuel supply amount to the engine 12 injected from the fuel supply device 18. (Not shown)), the NOx emission amount, that is, the reference generation value is calculated. Further, using the correction graph having a coefficient for the cooling water temperature shown in FIG. 10, the NOx calculated generation value is calculated by correcting the reference generation amount of NOx.

  The soot disappearance amount (NOx) calculation means 56 includes a ratio A between the soot calculation generation value obtained by the soot generation amount calculation means 52 and the NOx calculation generation value obtained by the NOx amount calculation means 54, and the upstream temperature sensor 35. From the obtained temperature on the upstream side of the filter 28, a soot calculation disappearance value (NOx) is obtained using a map 3 (a three-dimensional map similar to FIG. 7 (not shown)).

  The soot disappearance amount (heat) calculation means 58 calculates the air-fuel ratio R (the excess air ratio) from the flow rate in the intake pipe 22 detected by the intake flow rate sensor 27 and the fuel supply amount injected from the fuel supply device 18 to the engine 12. ) Is detected. From the air-fuel ratio R and the temperature upstream of the filter 28 detected by the upstream temperature sensor 35, the soot reference disappearance value is obtained using the map 4 (a three-dimensional map similar to FIG. 7 (not shown)). (Heat) is calculated. Further, the coefficient obtained using the correction graph shown in FIG. 11 is multiplied by the soot reference disappearance value (heat) to obtain the soot calculated disappearance value (heat). The soot deposition value on the horizontal axis of the correction graph shown in FIG. 11 is the soot deposition value up to the present time.

  When the soot calculation emission value, the soot calculation elimination value (NOx), and the soot calculation elimination value (heat) are obtained, the soot calculation elimination value (NOx) and the soot calculation elimination value (heat) are calculated from the soot calculation emission value. Subtract and calculate the soot calculation occurrence value. Then, the soot calculation generation value is integrated by the integration means 59 to calculate the soot accumulation value up to the present time, that is, the soot calculation accumulation value.

  The ash accumulation value calculating means 47 calculates the ash generation amount by multiplying the fuel supply amount injected from the fuel supply device 18 to the engine 12 by a coefficient, and integrates the ash calculation generation value (amount) to calculate the ash calculation accumulation. Calculate the value.

  As shown in FIG. 5, the threshold value calculation unit 48 includes a first threshold value calculation unit 64 and a second threshold value calculation unit 66.

  The first threshold value calculation means 64 obtains a coefficient (clogging) from the soot calculated deposition value and the ash calculated deposition value using the map 5 (a three-dimensional map similar to FIG. 7 (not shown)). . Next, a first threshold value is obtained from the coefficient (clogging) and the exhaust flow rate using a map 6 (a three-dimensional map similar to FIG. 7 (not shown)). The exhaust flow rate is obtained from the flow rate in the intake pipe 22 detected by the intake flow rate sensor 27, the fuel supply amount to the engine 12, the upstream pressure of the filter 28 detected by the upstream pressure sensor 30, and the gas constant.

  The second threshold value calculation means 66 obtains a coefficient (leakage) from the soot calculated deposition value and the ash calculated deposition value using a map 7 (a three-dimensional map similar to FIG. 7 (not shown)). Next, the second threshold value is obtained from the coefficient (leakage) and the exhaust flow rate by using a map 8 (a three-dimensional map similar to FIG. 7 (not shown)).

  The differential pressure value calculation means 50 multiplies the reference differential pressure value obtained from the exhaust gas flow rate and the temperature upstream of the filter 28 by the respective coefficients of the map 5 and the map 7, and calculates the calculated differential pressure value (clogging). Calculate the calculated differential pressure value (leakage).

  As shown in FIG. 6, the determination unit 44 includes a clogging determination unit 68 and a leak occurrence determination unit 70.

  The clogging determination means 68 calculates a difference P1 by subtracting the calculated differential pressure value (clogging) obtained by the differential pressure value calculation means 50 from the measured differential pressure value detected by the differential pressure sensor 32, and calculates the difference P1. The first threshold value obtained by the first threshold value calculation means 64 is compared, and if the difference P1 is larger than the first threshold value, it is determined that the blockage is clogged.

  The leak occurrence determination means 70 calculates the difference P2 by subtracting the measured differential pressure value detected by the differential pressure sensor 32 from the calculated differential pressure value (leak) obtained by the differential pressure value calculation means 50, and calculates the difference P2. The second threshold value obtained by the second threshold value calculation unit 66 is compared, and if the difference P2 is larger than the second threshold value, it is determined that a leak has occurred.

  The time measuring means 60 measures the duration of the determination by the determination means 44. The confirmation means 62 confirms that there is an abnormality when it is confirmed that the time measured by the time measuring means 60 has exceeded the confirmation time inputted in advance. The fixed time is, for example, 10 seconds. The confirmation time can be changed as appropriate.

Next, the operation of the filter abnormality detection device 10 will be described with reference to the flowchart of FIG.
First, a sampling time a and a fixed time T are determined (S1). The sampling time “a” is a repeated time interval when the comparison between the pressure difference and the threshold value is repeatedly performed. T is the time (determined time) required until it is determined that an abnormality has occurred. Next, the time t is set to 0 as an initial value (S2).

  Next, the control device 36 acquires detection values sent from the water temperature sensor 40, the atmospheric pressure sensor 38, the engine speed sensor 19, the intake air temperature sensor (not shown), etc. (S3). It is determined from the acquired value of each sensor whether or not it is a condition capable of detecting an abnormality of the filter 28 built in the DPF device 16. That is, it is confirmed that it is not immediately after the engine is started, is not operating abnormally, or is not abnormal in any of the sensors.

  If it is determined in S4 that the incidental condition is satisfied and the abnormality detection of the filter 28 is possible, the soot calculation generation amount is calculated as described above based on the value acquired from each sensor (S5). The generated values are sequentially integrated, and a soot calculation accumulation value is calculated (S6). Similarly, the ash calculation generation amount is calculated as described above (S7), and the calculated generation values are sequentially integrated to calculate the ash calculation accumulation value (S8).

  Further, the first threshold value, the second threshold value, and the calculated differential pressure value are calculated from the values of the sensors as described above (S9) (S10) (S11). When the calculated differential pressure value (both for clogging and leaking) and the first and second threshold values are calculated in this way, the difference P1 between the calculated differential pressure value and the measured value from the differential pressure sensor 32. Then, the difference 2 is obtained (S12), the difference P1 is compared with the first threshold value (S13), and if the determination is NO, the process proceeds to S14. On the other hand, if YES, the process proceeds to S15.

  In S14, the difference P2 is compared with the second threshold value, and when the determination is NO, the process proceeds to S2. On the other hand, if YES, the process proceeds to S15. In S15, sampling time a is added to time t, and this is newly set as time t. Then, it is determined whether or not the time t exceeds the fixed time T (S16). If not, the process returns to S3. When the process returns to S3, the above-described operation from S3 is performed again. If the difference from the threshold value is YES in either (S13) or (S14), the process proceeds to S15, and sampling time a is added to time t. , Until the time t exceeds the fixed time T.

  If the determination with the threshold value is NO in S13 or S14 during circulation, the process exits the circulation and returns to S2. Then, the time t is set to 0 again, and the work is resumed.

  On the other hand, when the time t exceeds the determination time T in S16, the process proceeds to S17, and the determination means 62 determines that the filter 28 is clogged or leaked and is abnormal.

  As described above, according to the abnormality detection device 10, an abnormality occurring in the filter 28, that is, occurrence of clogging or leakage can be determined by comparison with the threshold value, and the threshold value can be determined at any time while the vehicle is traveling. Since the calculated value is obtained, it is possible to reliably determine whether the filter 28 has malfunctioned even if the engine 12 is not driven in a steady state.

The figure which shows the structure of the engine provided with one Example of the abnormality detection apparatus concerning this invention. The block diagram which shows an abnormality detection apparatus. The block diagram which shows a control apparatus. The block diagram which shows a soot accumulation value calculation means. The block diagram which shows a threshold value calculation means. The block diagram which shows a determination means. The figure which shows the map for calculating | requiring a soot reference | standard generation value. The graph showing the coefficient of fuel injection quantity. The graph showing the coefficient of cooling water temperature. The graph showing the coefficient of cooling water temperature. The graph showing the coefficient of a soot deposition value. The flowchart for showing an action | operation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Abnormality detection device 12 ... Engine 16 ... DPF device 18 ... Fuel supply device 28 ... Filter 30 ... Upstream pressure sensor 32 ... Differential pressure sensor 35 ... Upstream temperature sensor 36 ... Control device 37 ... Downstream temperature sensor 38 ... Large Atmospheric pressure sensor 44 ... determination means 46 ... soot accumulation value calculation means 47 ... ash accumulation value calculation means 48 ... threshold value calculation means 50 ... differential pressure value calculation means

Claims (5)

An exhaust purification device comprising a filter that is provided in an exhaust passage of an internal combustion engine and collects particulates in exhaust gas, and a differential pressure sensor that detects a pressure difference generated between an upstream side and a downstream side of the filter,
Differential pressure value calculating means for calculating the value of the pressure difference between the upstream and downstream of the filter based on the operating state of the internal combustion engine;
The difference P between the measured value of the pressure difference between the upstream and downstream of the filter detected by the differential pressure sensor and the calculated differential pressure value from the differential pressure value calculating means is calculated, and the difference P and the threshold value are calculated. An abnormality detection device for an exhaust emission control device, comprising: a determination unit that detects that the filter is abnormal in comparison.   The determination means has a first threshold value used for determining clogging of the filter and a second threshold value used for leak determination of the filter, and when the value of the difference P exceeds the first threshold value, The abnormality detection device for an exhaust gas purification device according to claim 1, wherein when the value of the difference P exceeds the second threshold value, it is determined that the filter is abnormal.   The first threshold value is based on the exhaust gas flow rate and the clogging coefficient based on the soot calculation deposition value and the ash calculation deposition value accumulated on the filter, and the second threshold value is on the exhaust flow rate and the filter accumulated on the filter. The abnormality detection device for an exhaust emission control device according to claim 1 or 2, wherein the abnormality detection device is calculated from a leak coefficient based on a soot calculation accumulation value and an ash calculation accumulation value.   The differential pressure value calculation means calculates a calculated differential pressure value based on a reference differential pressure value calculated from a temperature upstream of the filter and an exhaust flow rate. An abnormality detection device for an exhaust purification device as described.   The determination means includes a determination means for determining that the filter is abnormal when the determination is continued for a predetermined time when it is determined that the filter is abnormal. 5. The abnormality detection device for an exhaust gas purification device according to any one of 4 above.

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