Method and apparatus for regenerating exhaust particulate filters of V-type internal combustion engines

Abstract

In a V-type internal combustion engine, this suppresses the pressure loss imbalance between banks caused by different amounts of soot accumulation on the two exhaust particulate filters 7 and 8. [Solution] The amount of soot accumulation in the exhaust particulate filters 7 and 8 of each bank in a V-type internal combustion engine is estimated, and when the amount of soot accumulation in the exhaust particulate filter 8 with relatively less soot accumulation exceeds the first threshold SL1, regeneration processing is started for both banks. Through regeneration, when the amount of soot accumulation in the exhaust particulate filter 7 with relatively more soot accumulation reaches the lower limit soot amount Min, the regeneration process is terminated. Since the amount of soot accumulation in the other exhaust particulate filter 8 will never fall below 0, the difference in the amount of soot accumulation between the two exhaust particulate filters 7 and 8 becomes small. By limiting the amount of soot accumulation in one exhaust particulate filter 7 to the lower limit soot amount Min, collection efficiency is ensured.

Description

Technical Field

[0001] This invention relates to a method and an apparatus for regenerating an exhaust particulate filter of a V-type internal combustion engine provided with a pair of banks and having an exhaust particulate filter provided in the exhaust passage of each bank respectively.

Background Art

[0002] With the recent requirements for exhaust purification performance in automobiles, not only diesel engines with a large amount of particulate emissions but also spark ignition internal combustion engines (so-called gasoline engines) tend to have an exhaust particulate filter provided in the exhaust system to remove soot in the exhaust. And in a V-type internal combustion engine having a pair of left and right banks, an exhaust particulate filter may be arranged in the exhaust passage of each independent bank respectively.

[0003] When soot accumulates excessively in the exhaust particulate filter, it becomes a so-called clogged state, resulting in a decrease in output. Therefore, it is necessary to perform a regeneration process to forcibly raise the exhaust temperature to remove soot at an appropriate time.

[0004] Patent Document 1 discloses a technique for a V-type diesel engine in which when the soot accumulation amount in the exhaust particulate filter of one bank exceeds a threshold value, the exhaust temperature is increased by retardation of the fuel injection timing or post-injection of the cylinders included in the bank, and only one exhaust particulate filter is regenerated.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In a V-type internal combustion engine with left and right banks, the increase in soot accumulation in the exhaust particulate filters of both banks is generally not perfectly equal. If the amount of soot accumulation in the exhaust particulate filters of each bank differs significantly, the pressure loss of each bank becomes unbalanced, resulting in an unbalanced combustion characteristic between the two banks, which is undesirable. In Patent Document 1, such an imbalance is actually exacerbated by the regeneration of one of the exhaust particulate filters. [Means for solving the problem]

[0007] This invention relates to a method for regenerating exhaust particulate filters in a V-type internal combustion engine having a pair of banks, each bank having an exhaust particulate filter in its exhaust passage, The amount of soot accumulation in the exhaust particulate filters of each bank was estimated. Based on the amount of soot accumulation in the exhaust particulate filter of at least one bank, the regeneration process of the exhaust particulate filters of both banks is started simultaneously. The regeneration process is terminated when the amount of soot accumulated in the filter with the relatively larger amount of soot among the two exhaust particulate filters decreases to a predetermined lower limit of soot set to ensure collection efficiency through the regeneration process.

[0008] In other words, the two exhaust particulate filters provided for each bank are always regenerated simultaneously. The regeneration process ends when the amount of soot accumulated in the filter with the relatively larger soot accumulation among the two filters decreases to a predetermined lower limit set to ensure collection efficiency. At the end of the regeneration process, the amount of soot accumulated in the other exhaust particulate filter will never fall below zero. Therefore, the difference in the amount of soot accumulated in the two filters decreases with each regeneration process. At the same time, the amount of soot accumulated in one of the exhaust particulate filters will never fall below the lower limit, ensuring collection efficiency. [Effects of the Invention]

[0009] According to this invention, it is possible to suppress the imbalance in soot accumulation between two exhaust particulate filters while ensuring collection efficiency, and to suppress the imbalance in combustion characteristics between banks due to pressure loss differences. [Brief explanation of the drawing]

[0010] [Figure 1] A diagram illustrating the configuration of a V-type internal combustion engine in one embodiment. [Figure 2] A flowchart showing the basic processing flow of the regeneration process in one embodiment. [Figure 3] A time chart showing the operation of the first embodiment. [Figure 4] A time chart showing the operation of the second embodiment. [Figure 5] A time chart showing the operation of the third embodiment. [Figure 6] A characteristic diagram showing the relationship between soot accumulation and collection efficiency in an exhaust particulate filter. [Modes for carrying out the invention]

[0011] Hereinafter, an embodiment of this invention will be described with reference to the drawings. Figure 1 shows a V-type internal combustion engine 1 of one embodiment mounted on a vehicle. The internal combustion engine 1 is a spark-ignition internal combustion engine, also known as a gasoline engine, and in this embodiment, it is configured as a V-type 6-cylinder engine having a first bank 2 and a second bank 3. This V-type internal combustion engine 1 is mounted on the vehicle in a so-called longitudinal configuration and drives the rear wheels 12 via an automatic transmission 4 connected to the rear end.

[0012] The automatic transmission 4 is, for example, a stepped automatic transmission that combines a torque converter and a stepped automatic transmission mechanism. In a stepped automatic transmission mechanism, as is well known, gear changes are basically performed along a gear change curve with vehicle speed and accelerator pedal opening as parameters. The automatic transmission 4 may also be, for example, a continuously variable transmission using a belt-type continuously variable transmission mechanism.

[0013] The first bank 2 and the second bank 3 each have exhaust passages 5 and 6, and exhaust particulate filters 7 and 8 (so-called GPFs) for removing soot from the exhaust are provided in each of the exhaust passages 5 and 6. The exhaust particulate filters 7 and 8 consist of wall-flow type filters using, for example, a sealed monolithic ceramic body made of cordierite. The inner wall surface of the fine passages (cells) may be coated with a catalytic metal to function as a three-way catalyst. The exhaust particulate filters 7 and 8 may be of any type, such as metal filters.

[0014] The exhaust passages 5 and 6 are equipped with differential pressure sensors 9 and 10 that detect the pressure difference across the exhaust particulate filters 7 and 8 in order to detect the pressure loss correlated with the amount of soot accumulated in the exhaust particulate filters 7 and 8. Alternatively, instead of the differential pressure sensors 9 and 10, pressure sensors may be placed on the inlet and outlet sides of the exhaust particulate filters 7 and 8, respectively.

[0015] The detection signals from the differential pressure sensors 9 and 10 are input to the engine controller 11, which performs various controls on the internal combustion engine 1. The engine controller 11 receives detection signals from various sensors, either directly or via other controllers, including a crank angle sensor for detecting engine rotational speed, an air flow meter for detecting intake air volume corresponding to the load, a water temperature sensor for detecting coolant temperature, an accelerator pedal position sensor for detecting the opening (pressure amount) of the accelerator pedal operated by the driver, an air-fuel ratio sensor for detecting the exhaust air-fuel ratio, and a vehicle speed sensor for detecting vehicle speed. Based on these detection signals, the engine controller 11 optimally controls the fuel injection amount and timing by the fuel injectors, the ignition timing by the spark plugs, the throttle valve opening, etc. Furthermore, the engine controller 11 can give shift instructions related to the regeneration process described later to the automatic transmission 4 via an AT controller (not shown).

[0016] Next, FIG. 2 is a flowchart showing the basic processing flow of the regeneration process of an embodiment. First, in step 1, the amount of soot accumulation in each of the exhaust particulate filters 7 and 8 is estimated. The amount of soot accumulation is estimated based on, for example, the pressure difference before and after the exhaust particulate filters 7 and 8 detected by the differential pressure sensors 9 and 10 described above, and the amount of gas passing through the exhaust particulate filters 7 and 8. The amount of gas is a known value for each operating point (combination of rotational speed and torque) of the internal combustion engine 1 at that time. In the present invention, the estimation of the amount of soot accumulation may be any other known method.

[0017] Next, in step 2, based on the amount of soot accumulation in each of the exhaust particulate filters 7 and 8, it is determined whether the start condition of the regeneration process is satisfied. If No, the process returns to step 1 and the estimation of the amount of soot accumulation is repeated.

[0018] If it is determined in step 2 that the start condition of the regeneration process is satisfied, then as the regeneration process, the processes of steps 3a, 3b, and 3c are performed in parallel. In step 3a, ignition timing retard is performed to delay the ignition timing of the first bank 2 from the basic ignition timing to the retard side. Similarly, in step 3b, ignition timing retard is performed to delay the ignition timing of the second bank 3 from the basic ignition timing to the retard side. The retard amounts of the ignition timings of the two banks 2 and 3 may basically be the same. In step 3c, the gear stage of the automatic transmission 4 is downshifted to a low gear stage. In the case of a continuously variable transmission, a change in the transmission ratio of an appropriate magnitude is made.

[0019] The exhaust temperature of each of the banks 2 and 3 increases due to the ignition timing retard. Also, the rotational speed of the internal combustion engine 1 increases due to the change in the transmission ratio accompanying the gear shift, and the exhaust energy applied to the exhaust particulate filters 7 and 8 of each of the banks 2 and 3 becomes large. As a result, the soot in the exhaust particulate filters 7 and 8 is oxidized or burned and removed. That is, the regeneration of the exhaust particulate filters 7 and 8 is performed.

[0020] In step 4, based on the soot accumulation amounts of the exhaust particulate filters 7 and 8 that decrease during the regeneration process, it is determined whether the end condition of the regeneration process is satisfied. If the answer is no, the regeneration process is continued. When it is determined in step 4 that the end condition of the regeneration process is satisfied, the process proceeds to step 5 and the regeneration process is terminated. That is, the forced ignition timing retard is terminated, and the gear stage is returned to the gear stage with normal characteristics.

[0021] As described above, in the above embodiment, the regeneration processes of the exhaust particulate filters 7 and 8 of both banks 2 and 3 are always performed simultaneously. In addition to the exhaust gas temperature increase due to the ignition timing retard of each bank 2 and 3, the exhaust energy is increased by changing the gear ratio. Therefore, the required retard amount of the ignition timing retard becomes relatively small, and the combustion instability due to the ignition timing retard is suppressed. Moreover, since the ignition timing retard is executed in both banks 2 and 3, an imbalance in the output between the left and right banks 2 and 3 does not occur.

[0022] In addition, since the exhaust gas temperature increase due to the change in the gear ratio inevitably occurs in both banks 2 and 3, the fuel consumption deterioration is less as a result compared to the case where the exhaust particulate filters 7 and 8 of the left and right banks 2 and 3 are regenerated alternately. That is, when the regeneration process is performed by combining the change in the gear ratio acting on both banks 2 and 3 with the ignition timing retard, the fuel consumption deterioration due to the increase in the rotational speed occurs equally during the regeneration of only one of the exhaust particulate filters 7 and 8 as during the regeneration processes of both banks 2 and 3. Therefore, it is advantageous for fuel consumption to regenerate both banks 2 and 3 simultaneously and reduce the total number of regeneration processes.

[0023] Next, FIG. 3 is a time chart showing the operation of a more specific first embodiment. In this first embodiment, as the start condition of the regeneration process, the soot accumulation amounts of the two exhaust particulate filters 7 and 8 are compared with each other, and it is assumed that the start condition is satisfied when the soot accumulation amount of the relatively smaller one exceeds a predetermined first threshold value SL1. Further, as the end condition of the regeneration process after starting the regeneration process, the soot accumulation amounts of the two exhaust particulate filters 7 and 8 are compared with each other, and it is assumed that the end condition is satisfied when the soot accumulation amount of the relatively larger one decreases to a predetermined lower limit soot amount Min.

[0024] In the example shown in Figure 3, the amount of soot accumulated on each exhaust particulate filter 7 and 8 increases from time t0. For example, exhaust particulate filter 8 accumulates less soot than exhaust particulate filter 7, and at time t1, the amount of soot accumulated on this less-accumulated exhaust particulate filter 8 exceeds the first threshold SL1. As a result, regeneration processing begins at time t1. That is, the ignition timing of both banks 2 and 3 is retarded, and the gear of the automatic transmission 4 is shifted to a lower gear, increasing the rotational speed. Through this regeneration processing, the amount of soot accumulated on the two exhaust particulate filters 7 and 8 gradually decreases. The first threshold SL1 is set to a level that has a certain margin over the maximum level of soot accumulation that can be considered as clogging of the exhaust particulate filters 7 and 8.

[0025] At time t2, the amount of soot accumulated in the exhaust particulate filter 7, which has a relatively large amount of soot accumulation, decreases to the lower limit soot amount Min, and the regeneration process ends. Here, the lower limit soot amount Min is the level of soot accumulation set to ensure the collection efficiency of the exhaust particulate filter. As shown in Figure 6, which illustrates the relationship between the amount of soot accumulated in the exhaust particulate filter and the collection efficiency, if the amount of soot accumulated in the exhaust particulate filter is extremely small, the collection efficiency decreases. In other words, although a large amount of soot accumulation results in a large pressure loss, from the viewpoint of collection efficiency that suppresses soot emission, it is desirable to have a certain amount of soot accumulated. Therefore, the lower limit soot amount Min is set to a level that does not cause the collection efficiency to become excessively low, as shown in Figure 6.

[0026] In the example shown in Figure 3, when the amount of soot accumulated in exhaust particulate filter 7, which has a relatively large amount of soot accumulation, drops to the lower limit of soot amount Min, the amount of soot accumulated in exhaust particulate filter 8, which has a relatively small amount of soot accumulation, reaches 0.

[0027] As described above, according to the first embodiment, when the regeneration process is completed at time t2, the amount of soot accumulated in one exhaust particulate filter 7 is at the lower limit of soot amount Min, and the amount of soot accumulated in the other exhaust particulate filter 8 does not fall below 0. Therefore, the difference between the two becomes smaller than the range from 0 to the lower limit of soot amount Min. Consequently, the imbalance in the amount of soot accumulated in the two exhaust particulate filters 7 and 8 is eliminated with each regeneration process. In other words, even when using a regeneration means in which both banks 2 and 3 are regenerated simultaneously, such as by increasing the rotational speed due to a change in the gear ratio, no imbalance in the amount of soot accumulated occurs.

[0028] At the same time, since the amount of soot accumulated in one of the exhaust particulate filters 7 is limited to the lower limit of soot amount Min at the end of the regeneration process, an excessive decrease in collection efficiency can be avoided. Therefore, compared to the case where the regeneration process is continued until the amount of soot accumulated in both exhaust particulate filters 7 and 8 becomes 0, the amount of soot emitted from the internal combustion engine 1 is reduced.

[0029] Figure 4 is a time chart showing the operation of the second embodiment. In the second embodiment, the start condition for the regeneration process is that the soot accumulation amounts of the two exhaust particulate filters 7 and 8 are compared, and the start condition is met when the relatively larger soot accumulation amount exceeds a predetermined second threshold SL2. As with the first embodiment, the end condition for the regeneration process after it has started is that the end condition is met when the relatively larger soot accumulation amount decreases to a predetermined lower limit soot amount Min.

[0030] In the example shown in Figure 4, the amount of soot accumulated in each exhaust particulate filter 7 and 8 increases from time t0. For example, exhaust particulate filter 7 accumulates more soot than exhaust particulate filter 8, and at time t1, the amount of soot accumulated in the larger exhaust particulate filter 7 exceeds the second threshold SL2. As a result, regeneration processing begins at time t1. Through this regeneration processing, the amount of soot accumulated in the two exhaust particulate filters 7 and 8 gradually decreases. Here, the second threshold SL2 is higher than the first threshold SL1 in the first embodiment and is set to a level relatively close to the clogging level Max, which is the amount of soot accumulation that can be considered as clogging of the exhaust particulate filters 7 and 8.

[0031] At time t2, the amount of soot accumulated in the exhaust particulate filter 7, which has a relatively large amount of soot accumulation, decreases to the lower limit soot amount Min, and the regeneration process is completed. This is the same as in the first embodiment.

[0032] According to this second embodiment, it is possible to reliably prevent the soot accumulation in the exhaust particulate filter 7, which has a relatively large amount of soot accumulation, from reaching the maximum clogging level. And, as with the first embodiment, it is possible to suppress the imbalance in soot accumulation between the two exhaust particulate filters 7 and 8 after each regeneration process.

[0033] The regeneration process initiation conditions of the first embodiment and the regeneration process initiation conditions of the second embodiment can also be applied in combination. That is, a first threshold SL1 is set to compare the amount of soot accumulation of the filter with the relatively smaller amount of soot accumulation among the two exhaust particulate filters 7 and 8, and a second threshold SL2 is set to compare the amount of soot accumulation of the filter with the relatively larger amount of soot accumulation. The regeneration process can then be configured to start when the amount of soot accumulation of the filter with the relatively smaller amount of soot accumulation exceeds the first threshold SL1, or when the amount of soot accumulation of the filter with the relatively larger amount of soot accumulation exceeds the second threshold SL2.

[0034] Next, Figure 5 is a time chart showing the operation of the third embodiment. In the third embodiment, the starting condition for the regeneration process is that the soot accumulation amounts of the two exhaust particulate filters 7 and 8 are compared with each other, and the starting condition is met when the difference in the soot accumulation amounts of the two exhaust particulate filters 7 and 8 exceeds a predetermined allowable soot amount difference ΔS. As for the ending condition for the regeneration process after it has started, the ending condition is met when the relatively larger soot accumulation amount decreases to a predetermined lower limit soot amount Min, as in the first embodiment.

[0035] In the example shown in Figure 5, the amount of soot accumulated on each exhaust particulate filter 7 and 8 increases from time t0. However, for example, exhaust particulate filter 7 accumulates more soot than exhaust particulate filter 8, and the rate of increase in soot accumulation on exhaust particulate filter 7 is higher than the rate of increase on exhaust particulate filter 8. As a result, the difference between the two gradually widens, and at time t1, it exceeds the allowable soot difference ΔS. Consequently, regeneration processing begins at time t1. Through this regeneration processing, the amount of soot accumulated on the two exhaust particulate filters 7 and 8 gradually decreases.

[0036] Then, at time t2, the amount of soot accumulated in the exhaust particulate filter 7, which has a relatively large amount of soot accumulation, decreases to the lower limit soot amount Min, and the regeneration process ends. This is the same as in the first embodiment.

[0037] Therefore, in the third embodiment, the difference in soot accumulation between the two exhaust particulate filters 7 and 8 does not exceed the allowable soot amount difference ΔS, and at the end of the regeneration process, the difference between the two is reduced to below the lower limit soot amount Min, thus ensuring that an excessive imbalance in pressure loss is avoided.

[0038] The regeneration process initiation conditions of the third embodiment described above can also be applied in combination with at least one of the regeneration process initiation conditions of the first embodiment and the regeneration process initiation conditions of the second embodiment. For example, when the three regeneration process initiation conditions are combined, the regeneration process can be configured to start when the soot accumulation amount of the relatively smaller amount exceeds the first threshold SL1, when the soot accumulation amount of the relatively larger amount exceeds the second threshold SL2, or when the difference between the two increases beyond the allowable soot amount difference ΔS.

[0039] Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, a combination of ignition timing retardation and rotational speed increase by shifting was exemplified as a regeneration process, but any regeneration process may be used. For example, a method of increasing the exhaust temperature by making the air-fuel ratio rich and lean different for each cylinder, or a method of increasing the torque of the internal combustion engine 1 by increasing the auxiliary load, can be appropriately used. Furthermore, the present invention can also be applied to an internal combustion engine for power generation in a series hybrid vehicle. [Explanation of Symbols]

[0040] 1…V-type internal combustion engine 2…Bank 1 3…Bank No. 2 4…Automatic transmission 7,8…Exhaust particulate filter 9,10…Differential pressure sensor 11…Engine controller

Claims

1. A method for regenerating exhaust particulate filters for a V-type internal combustion engine having a pair of banks, with each bank's exhaust passage equipped with an exhaust particulate filter, The amount of soot accumulation in the exhaust particulate filters of each bank was estimated. Based on the amount of soot accumulation in the exhaust particulate filter of at least one bank, the regeneration process of the exhaust particulate filters of both banks is started simultaneously. The regeneration process is terminated when the amount of soot accumulated in the filter with the relatively larger amount of soot accumulated in the filter is reduced by the regeneration process to a predetermined lower limit of soot set to ensure collection efficiency. A method for regenerating the exhaust particulate filter of a V-type internal combustion engine.

2. The regeneration process is initiated when the amount of soot accumulation in the filter with the relatively smaller amount of soot accumulation among the two exhaust particulate filters exceeds a predetermined first threshold. A method for regenerating an exhaust particulate filter for a V-type internal combustion engine according to claim 1.

3. The regeneration process is initiated when the amount of soot accumulation in the filter with the relatively larger amount of soot among the two exhaust particulate filters exceeds a predetermined second threshold. A method for regenerating an exhaust particulate filter for a V-type internal combustion engine according to claim 1.

4. When the amount of soot accumulated in the filter with the relatively smaller amount of soot among the two exhaust particulate filters exceeds a predetermined first threshold, or, When the amount of soot accumulation in the relatively larger portion exceeds a predetermined second threshold that is higher than the first threshold, Start the above playback process. A method for regenerating an exhaust particulate filter for a V-type internal combustion engine according to claim 1.

5. The regeneration process described above is initiated when the difference in the amount of soot accumulated in the two exhaust particulate filters exceeds a predetermined allowable difference in soot amount. A method for regenerating an exhaust particulate filter for a V-type internal combustion engine according to claim 1.

6. When the amount of soot accumulated in the filter with the relatively smaller amount of soot among the two exhaust particulate filters exceeds a predetermined first threshold, When the amount of soot accumulation in the relatively larger portion exceeds a predetermined second threshold that is higher than the first threshold, or, When the difference in soot accumulation between the two exhaust particulate filters exceeds a predetermined allowable difference in soot amount, Start the above playback process. A method for regenerating an exhaust particulate filter for a V-type internal combustion engine according to claim 1.

7. The above-mentioned V-type internal combustion engine is a spark-ignition internal combustion engine for vehicles connected to an automatic transmission. The above regeneration process is carried out by both retarding the ignition timing of both banks and increasing the rotational speed of the internal combustion engine by changing the gear ratio of the automatic transmission. A method for regenerating an exhaust particulate filter for a V-type internal combustion engine according to claim 1.

8. A V-type internal combustion engine having a pair of banks, with exhaust particulate filters provided in the exhaust passage of each bank, A controller that performs regeneration processing on the exhaust particulate filter, An exhaust particulate filter regeneration device for a V-type internal combustion engine, comprising: The above controller is The amount of soot accumulation in the exhaust particulate filters of each bank was estimated. Based on the amount of soot accumulation in the exhaust particulate filter of at least one bank, the regeneration process of the exhaust particulate filters of both banks is started simultaneously. The regeneration process is terminated when the amount of soot accumulated in the filter with the relatively larger amount of soot accumulated in the filter is reduced by the regeneration process to a predetermined lower limit of soot set to ensure collection efficiency. Exhaust particulate filter regeneration device for V-type internal combustion engines.

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