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

Abstract

In a V-type internal combustion engine, the goal is to suppress the deterioration of fuel efficiency and the power imbalance associated with the regeneration process of the two exhaust particulate filters 7 and 8, and to regenerate them efficiently. [Solution] The amount of soot accumulated 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 accumulated in the exhaust particulate filter 7, which has a relatively larger amount of soot, exceeds the threshold SL, regeneration processing is started for both banks. The regeneration processing is performed by retarding the ignition timing of both banks and increasing the rotational speed by shifting gears in the automatic transmission. When the amount of soot accumulated in the exhaust particulate filter 8, which has a relatively smaller amount of soot, reaches the lower limit soot amount Min through regeneration, the regeneration processing is terminated.

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for regenerating an exhaust particulate filter of a V-type internal combustion engine for a vehicle, which includes a pair of banks and an exhaust particulate filter is provided in the exhaust passage of each bank, respectively, and consists of a spark ignition type internal combustion engine.

Background Art

[0002] With the increasing requirements for exhaust purification performance in recent automobiles, an exhaust particulate filter for removing soot in exhaust gas is also inclined to be provided in the exhaust system even in a spark ignition type internal combustion engine (so-called gasoline engine). 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.

[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 of forcibly raising the exhaust temperature to remove soot at an appropriate time.

[0004] Patent Document 1 relates to the regeneration process of an exhaust particulate filter of a diesel engine, not a spark ignition type internal combustion engine. However, when the amount of soot accumulation in the exhaust particulate filter of one bank of a V-type internal combustion engine exceeds a threshold value, the exhaust temperature is increased by retarding the fuel injection timing or post-injection of the cylinders included in the bank, and a technique for regenerating only one exhaust particulate filter is disclosed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In spark-ignition internal combustion engines, it is possible to increase exhaust temperature by retarding the ignition timing, but this alone may not necessarily complete the regeneration of the exhaust particulate filter quickly. Furthermore, retarding the ignition timing on only one bank may lead to an imbalance in output between the left and right banks. [Means for solving the problem]

[0007] This invention relates to a method for regenerating exhaust particulate filters for a V-type internal combustion engine for a vehicle, which comprises a pair of banks, each bank having an exhaust particulate filter in its exhaust passage, and is connected to an automatic transmission. 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. This 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 mentioned above.

[0008] By retarding the ignition timing in both banks and changing the gear ratio of the automatic transmission, the rotational speed of the internal combustion engine is increased, resulting in greater exhaust energy and faster regeneration of the exhaust particulate filter. By combining this method of raising the temperature by changing the gear ratio, the amount of ignition timing retardation required becomes relatively smaller, and no imbalance in output occurs between the left and right banks. Furthermore, since the temperature increase of the exhaust due to the change in gear ratio inevitably occurs in both banks, the resulting deterioration in fuel efficiency is less compared to when the exhaust particulate filters of the left and right banks are regenerated alternately. [Effects of the Invention]

[0009] According to this invention, in a V-type internal combustion engine, it is possible to suppress the deterioration of fuel efficiency and avoid power imbalance associated with the regeneration process of the exhaust particulate filter, and to regenerate the exhaust particulate filter efficiently. [Brief explanation of the drawing]

[0010] [Figure 1] A diagram illustrating the configuration of a V-type internal combustion engine for a vehicle, according to 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 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 process 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 for 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 for 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 retard 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 retard 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 speed stage. In the case of a continuously variable transmission, the transmission ratio is changed to an appropriate magnitude.

[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 associated with 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 amount of the exhaust particulate filters 7 and 8 that decreases 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. If 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 position is returned to the gear position 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 increase in exhaust temperature 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 for 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 increase in exhaust temperature due to the change in the gear ratio necessarily occurs in both banks 2 and 3, the fuel consumption deterioration is reduced as a result, compared with 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 process of both banks 2 and 3 even when only one of the exhaust particulate filters 7 and 8 is regenerated. Therefore, it is advantageous for fuel consumption to simultaneously regenerate both banks 2 and 3 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 larger one exceeds a predetermined threshold value SL. 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 smaller 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 7 accumulates more soot than exhaust particulate filter 8, and at time t1, the amount of soot accumulated on exhaust particulate filter 7 exceeds the threshold SL. As a result, regeneration processing begins at time t1. That is, the ignition timing of both banks 2 and 3 is retarded, and the automatic transmission 4 shifts 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. Note that the threshold SL is set to a level lower than 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 8, which has a relatively small 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 5, 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 5.

[0026] According to the first embodiment described above, regeneration is performed when the amount of soot accumulated in one of the exhaust particulate filters 7 or 8, which has a relatively larger amount of soot accumulation, exceeds the threshold SL. Therefore, neither of the two exhaust particulate filters 7 or 8 accumulates excessive soot. Furthermore, the regeneration process ends when the amount of soot accumulated in the exhaust particulate filter 7 or 8, which has a relatively smaller amount of soot accumulation, reaches the lower limit soot amount Min. Thus, both of the two exhaust particulate filters 7 or 8 are kept above the lower limit soot amount Min, and an excessive decrease in collection efficiency can be avoided.

[0027] Next, 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 with each other, and the start condition is met when the relatively smaller soot accumulation amount exceeds a predetermined threshold SL. Furthermore, the end condition for the regeneration process after it has started is the same as in the first embodiment: the soot accumulation amounts of the two exhaust particulate filters 7 and 8 are compared with each other, and the end condition is met when the relatively smaller soot accumulation amount drops to a predetermined lower limit soot amount Min.

[0028] In the example shown in Figure 4, 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 exhaust particulate filter 8 exceeds the threshold SL. 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 process, the amount of soot accumulated on the two exhaust particulate filters 7 and 8 gradually decreases.

[0029] Here, the threshold SL may be at the same level as the threshold SL in the first embodiment, or it may be set to a slightly lower level than the threshold SL in the first embodiment so that there is a larger margin for 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.

[0030] At time t2, the amount of soot accumulated in the exhaust particulate filter 8, which has a relatively small amount of soot accumulation, decreases to the lower limit soot amount Min, and thus the regeneration process is completed.

[0031] According to the second embodiment described above, regeneration processing is not performed until the amount of soot accumulated in the exhaust particulate filter 7, 8 with relatively less soot accumulation exceeds the threshold SL, thus suppressing regeneration processing at a stage where the amount of soot accumulation in the other exhaust particulate filter 7, 8 is low. In other words, although it depends on the setting of the threshold SL, the frequency of regeneration processing is basically reduced compared to the first embodiment, and the deterioration of fuel efficiency can be avoided accordingly.

[0032] 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, the regeneration process is terminated when the amount of soot accumulated in the exhaust particulate filter 7, 8 with the less accumulated soot reaches the lower limit soot amount Min. However, the regeneration process may be continued until the amount of soot accumulated in the exhaust particulate filter 7, 8 with the relatively larger amount of accumulated soot reaches the lower limit soot amount Min. Alternatively, in the case of an exhaust particulate filter in which collection efficiency can be ensured even with a small amount of accumulated soot, the regeneration process may be continued until the amount of accumulated soot becomes 0. Alternatively, the regeneration process termination condition may be the elapsed time.

[0033] Furthermore, the regeneration process initiation conditions are not limited to the above embodiment. For example, the regeneration process can be initiated when the difference in soot accumulation between the two exhaust particulate filters 7 and 8 exceeds a certain level. [Explanation of Symbols]

[0034] 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 for a vehicle, comprising a spark-ignition internal combustion engine having a pair of banks, each bank having an exhaust particulate filter in its exhaust passage, and connected to an automatic transmission, 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. This 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 exhaust particulate filters for V-type internal combustion engines used in vehicles.

2. 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 threshold. A method for regenerating an exhaust particulate filter for a V-type internal combustion engine for a vehicle, as described in claim 1.

3. 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 threshold. A method for regenerating an exhaust particulate filter for a V-type internal combustion engine for a vehicle, as described in claim 1.

4. The regeneration process is terminated when the amount of soot accumulated in the filter with the relatively smaller 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 an exhaust particulate filter for a V-type internal combustion engine for a vehicle, as described in claim 1.

5. When the amount of soot accumulated in the filter with the relatively larger amount of soot among the two exhaust particulate filters exceeds a predetermined threshold, the regeneration process described above is initiated. The regeneration process is terminated when the amount of soot accumulated in the relatively less abundant soot accumulation decreases through the regeneration process to a predetermined lower limit set to ensure collection efficiency. A method for regenerating an exhaust particulate filter for a V-type internal combustion engine for a vehicle, as described in claim 1.

6. A V-type internal combustion engine for vehicles, comprising a pair of banks, each bank having an exhaust particulate filter in its exhaust passage, and connected to an automatic transmission, A controller that performs regeneration processing on the exhaust particulate filter, An exhaust particulate filter regeneration device for a vehicle 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. This 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. Exhaust particulate filter regeneration device for V-type internal combustion engines used in vehicles.

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