Method and device for controlling an internal combustion engine

Abstract

When the maximum output operation is requested to the internal combustion engine having the exhaust particulate filter, if the exhaust particulates are deposited in the exhaust particulate filter, the maximum output cannot be secured.SOLUTION: An internal combustion engine for driving a motor generator for power generation in a series hybrid vehicle includes an exhaust particulate filter in an exhaust system. During operation, an accumulated amount (PM) of exhaust particulates in the exhaust particulate filter is estimated (step 1), and it is determined whether or not a maximum output operation is required (step 2). If the maximum output operation is required, the regeneration process of the exhaust particulate filter is executed (step 3). Preferably, it is predicted that the maximum output operation is required based on map information of a car navigation system. By executing the regeneration process, the ventilation resistance of the exhaust particulate filter is reduced, and the maximum output can be secured.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to the control of an internal combustion engine equipped with an exhaust particulate filter in its exhaust system. [Background technology]

[0002] It is known that an exhaust particulate filter is provided in an exhaust system to suppress the release of exhaust particulates contained in the exhaust of an internal combustion engine into the atmosphere. Patent Document 1 describes a method of estimating the amount of particulates accumulated in the exhaust particulate filter, and when this amount reaches a predetermined limit, performing a so-called regeneration process to oxidize and remove the exhaust particulates accumulated in the exhaust particulate filter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-113870 Summary of the Invention [Problem to be solved by the invention]

[0004] Excessively frequent regeneration of the particulate filter is undesirable because it leads to a deterioration in fuel efficiency, etc. However, if a large amount of exhaust particulates has accumulated on the particulate filter when the internal combustion engine is required to operate at maximum power, the power of the internal combustion engine will decrease due to the airflow resistance of the particulate filter, making it impossible to achieve maximum power.

[0005] Patent Document 1 does not mention anything about the treatment of the exhaust particulate filter during such maximum power operation. [Means for solving the problem]

[0006] The present invention relates to an internal combustion engine that is provided with an exhaust particulate filter in an exhaust system and is capable of forced regeneration of the exhaust particulate filter, When maximum output operation of the internal combustion engine is required, the regeneration process is executed. [Effects of the Invention]

[0007] By executing the regeneration process when maximum power operation is required in this manner, the airflow resistance of the exhaust particulate filter is reduced, making it possible to ensure maximum power output. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is an explanatory diagram of the configuration of a series hybrid vehicle. [Figure 2] 4 is a flowchart showing the flow of processing in the first embodiment. [Figure 3] 10 is a flowchart showing the flow of processing in a second embodiment. [Figure 4] 10 is a flowchart showing the flow of processing according to a third embodiment. [Figure 5] 10 is a flowchart showing the flow of processing according to a fourth embodiment. [Figure 6] 10 is a flowchart for setting a density threshold. [Figure 7] FIG. 4 is a characteristic diagram showing the relationship between the ignition timing retard amount and the density threshold value. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a schematic configuration of a series hybrid vehicle as an example of a vehicle to which the present invention can be applied. The series hybrid vehicle includes a power-generating motor-generator 1 that operates primarily as a generator, an internal combustion engine 2 used as a power-generating internal combustion engine that drives the power-generating motor-generator 1 in response to a power demand, a traction motor-generator 4 that operates primarily as a motor to drive drive wheels 3, and a battery 5 that stores the generated power. The power obtained by the internal combustion engine 2 driving the power-generating motor-generator 1 is stored in the battery 5 via an inverter device (not shown). The traction motor-generator 4 is driven and controlled using the power from the battery 5. The power generated by the traction motor-generator 4 during regeneration is stored in the battery 5 via an inverter device (not shown).

[0010] The operation of the motor generators 1 and 4, the charging and discharging of the battery 5, and the operation of the internal combustion engine 2 are controlled by a controller 6. The controller 6 is composed of multiple controllers connected to each other so that they can communicate with each other, such as a motor controller 7 that controls the motor generators 1 and 4, an engine controller 8 that controls the internal combustion engine 2, and a battery controller 9 that manages the battery 5. Information such as the accelerator pedal position and vehicle speed (not shown) is input to the controller 6. The battery controller 9 also calculates the SOC of the battery 5 based on the voltage and current of the battery 5. When the SOC drops to a predetermined lower limit, the internal combustion engine 2 is started via the engine controller 8 to generate electricity. Such a series hybrid vehicle has two driving modes: an EV mode in which the vehicle runs on power from the battery 5 without combustion operation of the internal combustion engine 2, and an HEV mode in which the vehicle runs while generating electricity through combustion operation of the internal combustion engine 2. Even if the SOC is above the lower limit, the internal combustion engine 2 is driven and the vehicle runs in the HEV mode when the required driving force of the vehicle is relatively large. Therefore, the internal combustion engine 2 repeatedly performs combustion operation and stops of combustion operation while the main switch of the vehicle is on.

[0011] In one embodiment, the internal combustion engine 2 is a four-stroke spark-ignition gasoline engine equipped with a turbocharger, such as a so-called direct injection internal combustion engine in which a fuel injection valve injects fuel directly into the cylinder. An exhaust passage of the internal combustion engine 2 is provided with an exhaust particulate filter (so-called GPF) for collecting exhaust particulates. While any type of exhaust particulate filter may be used in the present invention, in one embodiment, a so-called wall-flow particulate filter is used, in which a large number of cells are provided in a substantially cylindrical monolithic carrier made of a porous ceramic material and alternately sealed. The wall surfaces of the cells are coated with a three-way catalyst, so that the filter also functions as an exhaust purification catalyst.

[0012] Such an exhaust particulate filter increases its airflow resistance as exhaust particulates accumulate. Therefore, the amount of accumulated exhaust particulates is estimated during operation of the internal combustion engine 2, and when the amount exceeds a certain reference amount, the engine controller 8 executes a forced regeneration process for the exhaust particulate filter. In the present invention, any specific method for the regeneration process may be used. For example, the temperature of the exhaust particulate filter is increased by retarding the ignition timing, and oxygen is supplied to the exhaust particulate filter by motoring the internal combustion engine 2 by powering the power-generating motor / generator 1, introducing secondary air, or making the air-fuel ratio lean, thereby oxidizing and removing the accumulated exhaust particulates. The monolithic support of the exhaust particulate filter may be made of a conductive ceramic material such as SiC, and the monolithic support itself may be heated by passing current through it.

[0013] Furthermore, in the present invention, regeneration processing is actively executed when maximum output operation is required of the internal combustion engine 2. In a series hybrid vehicle, when the required driving force of the vehicle becomes extremely large, for example, when climbing a slope, the electric power supplied from the battery 5 to the traction motor / generator 4 cannot satisfy the required driving force, so electric power is supplied from the power generation motor / generator 1 in parallel. In such cases, the internal combustion engine 2 may be required to operate at maximum output.

[0014] 2 is a flowchart showing the processing flow of the first embodiment. In step 1, the amount of exhaust particulate matter (PM) deposited on the exhaust particulate filter is estimated. This can be estimated based on the pressure difference between the front and rear of the exhaust particulate filter, or by integrating the amount of deposition per unit time or per unit cycle based on the engine operating conditions.

[0015] In the next step 2, it is determined whether or not the conditions require maximum power operation. If the conditions require maximum power operation, the process proceeds to step 3, where the regeneration process of the exhaust particulate filter is performed. If possible, it is desirable to determine in step 2 whether or not the conditions require maximum power operation before maximum power operation is actually required. For example, it is possible to predict, based on map information from a car navigation system, whether a long uphill road is ahead. Furthermore, in a series hybrid vehicle, for example, in the initial stage of acceleration when the accelerator pedal is fully depressed, acceleration is performed using power from the battery 5, and then power generation by the internal combustion engine 2 is required. Therefore, it is possible to predict that maximum power operation will be required from changes in the accelerator pedal depression.

[0016] By executing the regeneration process when maximum power operation is required in this manner, the airflow resistance of the exhaust particulate filter is reduced, making it possible to ensure maximum power output.

[0017] 3 is a flowchart showing the processing flow of the second embodiment. In this second embodiment, when it is determined in step 2 that maximum output operation is required, the process proceeds to step 11, where the reference deposition amount PM# for performing regeneration processing is set to a maximum output reference deposition amount PMpower, which is lower than the normal amount. Then, in step 12, the exhaust particulate deposition amount PM at that time is compared with the maximum output reference deposition amount PMpower, and if the deposition amount PM exceeds the maximum output reference deposition amount PMpower, the process proceeds to step 3, where regeneration processing is performed.

[0018] Therefore, if the actual amount of PM deposited is equal to or less than the reference amount of PM for maximum power output, regeneration processing is not performed. This prevents the deterioration of fuel economy and the decrease in SOC caused by excessively frequent regeneration processing.

[0019] FIG. 4 is a flowchart showing the processing flow of a third embodiment. In this third embodiment, when it is determined in step 2 that maximum output operation is required, the process proceeds to step 21, where the SOC of battery 5 is compared with a reference value SOC#. If the SOC of battery 5 is greater than the reference value SOC#, the process proceeds to step 3, where regeneration processing is executed. If the SOC is equal to or less than the reference value SOC#, the regeneration processing is not executed. Regardless of the method of regeneration processing, it will in some way involve a reduction in the power generated by the power generation motor / generator 1 or a consumption of power from battery 5. Therefore, it is desirable to execute the regeneration processing on the condition that the SOC is greater than the reference value SOC#.

[0020] FIG. 5 is a flowchart showing the processing flow of the fourth embodiment. In this fourth embodiment, when it is determined in step 2 that maximum power operation is required, the process proceeds to step 31, where intake air information related to the intake air density is acquired. For example, atmospheric pressure information detected by an atmospheric pressure sensor is read. Note that altitude information obtained by a car navigation system or temperature information obtained by an outside air temperature sensor may be used instead of the atmospheric pressure sensor. Then, in step 32, the intake air density ρ is calculated from this information.

[0021] Next, in step 33, the density ρ of the intake air is compared with a density threshold ρ#. Specifically, it is determined whether the density ρ is less than the density threshold ρ#. If the density ρ is less than the density threshold ρ#, the process proceeds to step 3, where regeneration processing is performed.

[0022] For example, if the atmosphere is in a normal state, maximum output can be ensured even if exhaust particulates accumulate, but if the intake air density decreases at high altitudes, etc., it may not be possible to ensure the required maximum output. Therefore, in the fourth embodiment, regeneration processing is actively performed when the density ρ is low.

[0023] Furthermore, it is desirable to correct the density threshold ρ# according to the likelihood of knocking. Because output power decreases significantly under conditions where knocking is likely to occur, it is desirable to execute the regeneration process when the intake air density is relatively high to ensure output power. In other words, an index indicating the degree of knocking that is occurring or the likelihood of knocking occurring is obtained, and based on this index, the density threshold ρ# is set to a higher density as the conditions become more likely to cause knocking.

[0024] Indicators that indicate the degree of knocking or the likelihood of knocking occurring include outside air temperature, as well as the octane number of the fuel, intake air temperature, coolant temperature, etc., and the density threshold ρ# can be set based on one or more of these indicators, including the outside air temperature.

[0025] Furthermore, the amount of ignition timing retard in ignition timing retard control based on the output of a knocking sensor (not shown) can also be used as an index indicating the actual degree or likelihood of knocking, regardless of factors such as outside air temperature. Figures 6 and 7 show an example of setting the density threshold ρ# based on the amount of ignition timing retard. The flowchart in Figure 6 shows the process for setting the density threshold ρ#, in which the amount of ignition timing retard due to knocking is read in step 41, and the density threshold ρ# is set using a predetermined table in step 42. Figure 7 shows an example of the characteristics of the table used in step 42, in which the density threshold ρ# is set higher as the amount of ignition timing retard increases.

[0026] Although one embodiment of the present invention has been described above in detail, the present invention is not limited to the above embodiment and various modifications are possible. While the above embodiment has been described using a series hybrid vehicle as an example, other types of hybrid vehicles may also be used. Furthermore, the present invention may also be applied to an internal combustion engine that serves as a power source for a non-hybrid vehicle. [Explanation of symbols]

[0027] 1...Power generating motor generator 2...Internal combustion engine 4...Traction motor generator 5. Battery 6...Controller

Claims

1. An internal combustion engine having an exhaust particulate filter in an exhaust system and capable of forced regeneration of the exhaust particulate filter, When maximum output operation of the internal combustion engine is required, the regeneration process is executed. A method for controlling an internal combustion engine.

2. an amount of particulate matter accumulated in the exhaust particulate filter is estimated, and when the amount of particulate matter accumulated exceeds a reference amount of particulate matter, the regeneration process is executed; When the maximum output operation is required, the reference deposition amount is set to a value lower than that during normal operation.

2. The method for controlling an internal combustion engine according to claim 1.

3. The internal combustion engine is an internal combustion engine for generating electricity that drives a generator in a series hybrid vehicle.

2. The method for controlling an internal combustion engine according to claim 1.

4. When the maximum output operation is required, the regeneration process is executed on the condition that the SOC of the battery is greater than a reference value.

4. The method for controlling an internal combustion engine according to claim 3.

5. Obtain information on the density of the intake air taken in as fresh air, When the maximum output operation is requested, if the density of the intake air is lower than a density threshold, the regeneration process is executed.

2. The method for controlling an internal combustion engine according to claim 1.

6. An index indicating the degree of knocking that is occurring or the likelihood of knocking occurring is obtained, and based on this index, the density threshold is set to a higher density side as the condition becomes more likely to cause knocking.

6. The method for controlling an internal combustion engine according to claim 5.

7. The indicator includes at least one of the octane number of the fuel, the outside air temperature, the intake air temperature, and the coolant temperature.

7. The method for controlling an internal combustion engine according to claim 6.

8. The above indicators are A retard amount in knocking control that retards ignition timing based on a detection signal from a knocking sensor.

7. The method for controlling an internal combustion engine according to claim 6.

9. Predict the power output required from the internal combustion engine, When it is predicted that maximum output operation will be required, the regeneration process is executed.

2. The method for controlling an internal combustion engine according to claim 1.

10. An internal combustion engine having an exhaust particulate filter in an exhaust system and capable of forced regeneration of the exhaust particulate filter, When maximum output operation of the internal combustion engine is required, the regeneration process is executed. Control device for internal combustion engines.

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