JP3608255B2 - Clogging detection method for exhaust gas purification device of internal combustion engine - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a detection method for detecting clogging of an exhaust gas purification device of an internal combustion engine.
[0002]
[Prior art]
Conventionally, as a method for detecting clogging of an exhaust gas purification device, when the differential pressure between the upstream exhaust pressure and the downstream exhaust pressure of the purification device or the upstream pressure is measured, and this value exceeds a predetermined value Japanese Laid-Open Patent Publication No. 56-115806 discloses a method for determining that the exhaust gas purifying device is regenerated as clogging. In these pressure measurement methods, the detected pressure differs depending on the fluctuation of exhaust gas amount and the presence or absence of EGR. Therefore, the clogging of the purification device cannot be accurately determined, and the operability due to the abnormal increase in exhaust pressure due to the delay in regeneration. As a result of deterioration, or because the regeneration is too early, there is a problem that burner fuel is wasted in the burner type regenerator, and regenerative power is wasted in the electric heater type regenerator.
[0003]
In order to solve the above problems, Japanese Patent Application Laid-Open No. 59-12018 discloses a differential pressure (ΔP = P1) between the exhaust pressure (P1) on the upstream side of the purifier and the exhaust pressure (P2) on the downstream side. -P2) and the ratio of the pressure upstream of the purifier (ΔP / P1), or the ratio of the exhaust pressure upstream of the purifier and the exhaust pressure downstream (P2 / P1) is clogging the purifier. Focusing on the fact that it is proportional to the amount, a control device is disclosed that operates the burner when ΔP / P1 or P2 / P1 is greater than or equal to a predetermined value.
[0004]
[Problems to be solved by the invention]
The control device described in the above-mentioned Japanese Patent Application Laid-Open No. 59-12018 calculates the pressure ratio even if there is a difference in the detected pressure due to fluctuations in the exhaust gas amount or the presence or absence of EGR. Although it is a device that is not too early, the pressure detection position is about 1 m from the exhaust manifold of the engine and is very close to the downstream side, so it is easily affected by sudden engine fluctuations and load fluctuations. When the pressure change is large such as ON → OFF or OFF → ON, the pressure ratio fluctuates greatly, resulting in a spike-like noise-like output as shown in FIG. On the downstream side, it is necessary to measure a very low pressure when idling, and a pressure sensor with excellent accuracy is required.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, according to the present invention, the pressure between the exhaust pressure on the upstream side (hereinafter simply referred to as pressure) and the exhaust pressure on the downstream side (hereinafter simply referred to as pressure) of the exhaust gas purifying apparatus for an internal combustion engine. The pressure ratio is calculated by dividing the integrated value of the pressure ratio for the most recent specified period including the latest pressure ratio by the number of pressure ratio data used for the integration, and then averaging the pressure ratio to stabilize the pressure ratio. In addition, a detection method for stopping the clogging determination at the time of low rotation such as idling is provided.
[0006]
[Action]
According to the present invention, it is possible to stably determine clogging of the exhaust gas purification device even when there is a sudden rotation fluctuation or a sudden load fluctuation of the internal combustion engine.
[0007]
【Example】
Next, an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a configuration diagram of an embodiment of the present invention. In this figure, 1 is an internal combustion engine, and 2 is an exhaust gas bypass valve provided in an exhaust pipe 8 connected to an exhaust manifold 1 a of the internal combustion engine 1. Reference numeral 3 denotes an exhaust gas purification device, in which a catalyst or a particulate collection filter 3a is installed. Reference numeral 9 denotes a bypass.
Reference numeral 4 denotes a pressure sensor for detecting the upstream pressure Pf of the exhaust gas purification device 3 installed in the exhaust pipe 8, and reference numeral 5 denotes a pressure sensor for detecting the downstream pressure Pr. The pressure sensors 4 and 5 use conversion elements that convert pressure such as piezoelectric elements into electric signals. As the amount of clogging of the catalyst or the particulate collection filter 3a of the purification device 3 increases, the difference between the upstream pressure Pf and the downstream pressure Pr increases. By calculating the ratio of these pressures Pf and Pr, the influence of the exhaust gas flow rate can be removed, and the ratio of the pressures Pf and Pr is proportional to the clogging amount of the purification device 3. Therefore, the relationship between the clogging amount of the purification device 3 and the ratio of the pressures Pf and Pr is experimentally measured in advance, and the ratio of the pressures Pf and Pr to the clogging amount to be regenerated is set in advance. When the ratio of Pr exceeds the set value, the bypass valve 2 is switched to bypass the exhaust gas without flowing into the purifier 3.
[0008]
Reference numeral 6 denotes a control device for controlling the bypass valve 2 by inputting the signals of the pressure sensors 4 and 5 and the engine rotation sensor. . The control device can also use the fuel injection control device of the internal combustion engine 1. The control device 6 stores a processing program in the ROM, and performs processing such as taking in the pressure sensors 4 and 5 and the engine rotation signal, calculation processing, and exhaust gas bypass instruction according to the program. The ROM also stores a ratio (set value) between the upstream pressure Pf and the downstream pressure Pr with respect to the clogging amount to be reproduced.
[0009]
The control program stored in the ROM of the control device 6 will be described with reference to FIG. FIG. 2 is a diagram showing the flow of control, not the program itself.
First, when the control program is started, the signals of the pressure sensors 4 and 5 are acquired at S1 (upstream pressure Pf acquisition, downstream pressure Pr acquisition), and then at S2, the purification device upstream pressure (Pf) is obtained using these values. ) And the downstream pressure (Pr), the pressure ratio is calculated. Next, in S3, the pressure ratio data is sequentially averaged. That is, the following calculation process is performed.
Sequential average pressure ratio = (integrated value of pressure ratios in the past several minutes + latest pressure ratio) / pressure ratio data number S4 checks whether or not the engine speed is low. The sequential average pressure ratio is compared with the pressure ratio (set value) with respect to the clogging amount to be regenerated stored in the ROM. If the sequential average pressure ratio is large, the catalyst of the purifier is clogged. to decide. On the other hand, if it is determined in S4 that the engine speed is low, clogging is not determined, and the program is exited while the sequentially averaged data is retained. The sequential averaging time is preferably 10 minutes or less.
[0010]
FIG. 3 shows a comparison of signals with and without the successive averaging process. FIG. 3A shows the pressure ratio signal before the sequential averaging process, and it can be seen that the fluctuation is very large. On the other hand, FIG. 3B shows the pressure ratio signal of the present embodiment that has been subjected to the sequential averaging process, and it can be seen that the signal has a small fluctuation and the noise component is removed from the original signal.
As mentioned above, although this invention was demonstrated using the above-mentioned Example, various deformation | transformation are possible within the range of the main point of this invention, and these deformation | transformation are not excluded from the scope of the present invention.
[0011]
【The invention's effect】
According to the present invention, the pressure ratio between the pressure on the upstream side and the pressure on the downstream side of the exhaust gas purification apparatus is the pressure ratio obtained by using the integrated value of the pressure ratio for the most recent predetermined time including the latest pressure ratio for the integration. Since it is averaged by dividing by the number of data, clogging of the exhaust gas purification device can be determined stably even if there is a sudden rotation fluctuation or a sudden load fluctuation of the internal combustion engine. Further, since the determination of clogging is not performed at the time of engine low rotation, erroneous determination can be eliminated.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an embodiment of the present invention.
FIG. 2 is a diagram showing a control flow of an embodiment of the present invention.
FIG. 3 is a diagram showing a comparison of pressure ratio signals.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 2 ... Bypass valve, 3 ... Exhaust gas purification apparatus,
4 ... Pressure sensor, 5 ... Pressure sensor 6 ... Control device, 7 ... Battery

Claims (2)

First detection means for detecting the pressure on the upstream side of the exhaust gas purification device of the internal combustion engine, and second detection means for detecting the pressure on the downstream side of the exhaust gas purification device, the first detection means Calculating a pressure ratio between the upstream pressure and the downstream pressure from the respective pressures detected by the second detection means and the second detection means, and determining the clogging amount of the exhaust gas purifying device based on the pressure ratio The exhaust gas of an internal combustion engine, wherein the pressure ratio is sequentially averaged by dividing the integrated value of the pressure ratio of the most recent predetermined time including the latest pressure ratio by the number of pressure ratio data used for the integration Method for detecting clogging of purification device. 2. The method for detecting clogging in an exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein the determination of the clogging amount is stopped and the pressure ratio data is held when the engine speed such as idling is low.

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