Control device for an internal combustion engine

Abstract

An object of the present application is to efficiently remove PM from a filter. A control device of an internal combustion engine that controls an internal combustion engine that has a filter that traps particulate matter in exhaust gas in an exhaust passage, wherein the control device of the internal combustion engine has a control section that performs processing that, when fuel cut in which fuel supply to the internal combustion engine is stopped is implemented, predicts a duration of the fuel cut, and in a case where the predicted duration of the fuel cut is short, increases an amount of air supplied to the filter while the fuel cut is continued, as compared to a case where the duration is long.

Description

Technical Field

[0001] This invention relates to a control device for an internal combustion engine. Background Technology

[0002] It is known that when a vehicle is traveling downhill, the filter is regenerated by burning the PM accumulated on it when the PM accumulation in the filter is above a specified amount, the vehicle speed is above a specified speed, and the throttle opening is below a specified opening (for example, see Patent Document 1).

[0003] Patent Document 1: Japanese Patent Application Publication No. 2022-116895

[0004] Patent Document 2: Japanese Patent Application Publication No. 2022-128917

[0005] Patent Document 3: Japanese Patent Application Publication No. 2010-024844 Summary of the Invention

[0006] The purpose of this invention is to efficiently remove PM from a filter.

[0007] One aspect of the present invention is a control device for an internal combustion engine that controls an internal combustion engine having a filter in the exhaust passage for capturing particulate matter in the exhaust. The control device for the internal combustion engine includes a control unit that performs the following processing: when a fuel cut-off is implemented to stop the supply of fuel to the internal combustion engine, predicting the duration of the fuel cut-off; and if the predicted duration of the fuel cut-off is short, increasing the amount of air supplied to the filter during the duration of the fuel cut-off compared to a case where the duration is long.

[0008] Invention Effects

[0009] According to the present invention, PM can be efficiently removed from the filter. Attached Figure Description

[0010] Figure 1 It is a diagram showing the general structure of the internal combustion engine and its intake and exhaust systems involved in the implementation.

[0011] Figure 2 This is a timing diagram showing the increase in the amount of air drawn in when fuel is cut off.

[0012] Figure 3 It is a flowchart illustrating the process of fuel cut-off control involved in the implementation method. Detailed Implementation

[0013] Internal combustion engines sometimes include filters in their exhaust passages to capture particulate matter (PM) in the exhaust. The PM captured in the filter is oxidized and removed when the filter temperature is above a specified temperature and the oxygen concentration within the filter is above a specified concentration. Typically, in spark-ignition gasoline engines, the oxygen concentration within the filter is low because they usually operate at a stoichiometric or rich air-fuel ratio. Furthermore, oxygen supply to the filter is limited to situations such as operation with a lean air-fuel ratio or fuel cut-off due to deceleration. It is known that to increase the intake air volume by adjusting the throttle opening during fuel cut-off in order to oxidize more PM. However, if the increased intake air volume continues for a long time, the filter temperature may become excessively high. To suppress this overheating, when fuel cut-off is restricted, the amount of oxidized PM is less compared to when fuel cut-off is not increased. To address this problem, the control device for the internal combustion engine in this invention increases the intake air volume without causing filter overheating, even when increasing the intake air volume during fuel cut-off.

[0014] Specifically, as one aspect of the present invention, an internal combustion engine control device controls an internal combustion engine equipped with a filter in the exhaust passage for capturing particulate matter in the exhaust gas. The control device includes a control unit. When performing a fuel cut-off to stop fuel supply to the internal combustion engine, the control unit predicts the duration of the fuel cut-off. Furthermore, the control unit can predict the duration of the fuel cut-off based on the inclination angle of the road on which the vehicle carrying the internal combustion engine is traveling. A greater inclination angle results in greater vehicle deceleration, thus shortening the time until the driver next presses the accelerator pedal. That is, the duration of the fuel cut-off can be shortened. Also, the control unit can predict the duration of the fuel cut-off based on the deceleration of the vehicle carrying the internal combustion engine. A greater deceleration results in a shorter time until the speed reaches the driver's desired level, thus shortening the time until the driver next presses the accelerator pedal. That is, the duration of the fuel cut-off can be shortened.

[0015] Furthermore, the control unit of the internal combustion engine may also include a storage unit for storing map information, which can predict the duration of the fuel cut-off based on the map information stored in the storage unit. The map information may include, for example, information related to the length of the road or information related to the gradient of the road. The timing of the driver pressing the accelerator pedal can vary depending on the road conditions. For example, when the vehicle is traveling uphill, the driver presses the accelerator pedal for a longer period, thus the duration of the fuel cut-off can be relatively shorter. On the other hand, when the vehicle is traveling on a flat road or downhill, the driver presses the accelerator pedal more frequently. Therefore, the duration of the fuel cut-off can be relatively longer. Moreover, the control unit can predict the duration of the fuel cut-off based on the distance between the first vehicle equipped with the internal combustion engine and a second vehicle located further ahead of the first vehicle. The driver of the first vehicle intends to maintain an appropriate distance from the second vehicle. For example, the shorter the distance, the longer the driver releases the accelerator pedal to increase the distance. Therefore, the duration of the fuel cut-off can be relatively longer.

[0016] Furthermore, when the predicted fuel cut-off duration is short, the control unit increases the amount of air supplied to the filter during the fuel cut-off period compared to when the duration is long. The amount of air supplied to the filter can be the amount of air supplied per unit time. Since the intake air from the internal combustion engine is directly supplied to the filter during fuel cut-off, increasing the amount of air supplied to the filter includes increasing the intake air volume of the internal combustion engine. If the amount of air is increased when the predicted fuel cut-off duration is long, the filter may malfunction due to overheating. In contrast, when the fuel cut-off duration is long, the control unit suppresses filter overheating by reducing the amount of air supplied to the filter. Thus, even with a smaller amount of air, if the fuel cut-off duration is long, PM oxidation can be achieved. On the other hand, when the fuel cut-off duration is short, by supplying a larger amount of air to the filter, PM can be rapidly oxidized. In this case, the heat generated by the filter increases, but because the fuel cut-off duration is short, filter overheating is suppressed. This allows for efficient filter regeneration.

[0017] Hereinafter, with reference to the accompanying drawings, illustrative details will be provided regarding embodiments of the present invention. However, unless otherwise specified, the dimensions, materials, shapes, and relative arrangements of the constituent parts described in this embodiment are not intended to limit the scope of the present invention.

[0018] <First Embodiment>

[0019] Figure 1 It is a diagram showing the general structure of the internal combustion engine and its intake and exhaust systems involved in the implementation. Figure 1 The internal combustion engine 1 shown is a spark-ignition gasoline engine. Internal combustion engine 1 is mounted on vehicle 10. Alternatively, vehicle 10 can be a hybrid electric vehicle (HEV).

[0020] An exhaust passage 2 is connected to an internal combustion engine 1. Midway through the exhaust passage 2, from the upstream side, are a catalyst 3 and a GPF 4. The catalyst 3 is a catalyst with oxidation function that purifies the exhaust. The catalyst 3 can be, for example, a three-way catalyst, an oxidation catalyst, a NOx adsorption / reduction catalyst, or a selectively reduced NOx catalyst. The GPF 4 is a gasoline particulate filter that captures PM in the exhaust. The aforementioned catalyst can be coated onto the GPF 4.

[0021] Furthermore, a first temperature sensor 11 for detecting the exhaust temperature is installed in the exhaust passage 2, which is located upstream of the catalyst 3. A second temperature sensor 12 for detecting the exhaust temperature is installed in the exhaust passage 2, which is located downstream of the catalyst 3 and upstream of the GPF4. The temperature of the catalyst 3 can be detected based on the values ​​detected by the first temperature sensor 11 or the second temperature sensor 12. The temperature of the GPF4 can be detected based on the value detected by the second temperature sensor 12. Additionally, the temperatures of the catalyst 3 and the GPF4 can be estimated by the control unit 110 of the ECU 100 (described later) based on the operating state of the internal combustion engine 1.

[0022] Furthermore, an intake passage 5 is connected to the internal combustion engine 1. A throttle valve 6 is installed midway through the intake passage 5 to adjust the amount of air intake into the internal combustion engine 1. Additionally, an air flow meter 15 for detecting the amount of air intake into the internal combustion engine 1 is installed on the intake passage 5 upstream of the throttle valve 6.

[0023] Furthermore, a fuel injection valve 7 is installed on the internal combustion engine 1 to supply fuel to the internal combustion engine 1. Additionally, the fuel injection valve 7 can inject fuel into the cylinder of the internal combustion engine 1 or into the intake passage 5. Furthermore, a spark plug 8 is provided on the internal combustion engine 1 to generate an electric spark in the cylinder.

[0024] An ECU 100, serving as an electronic control unit, is connected to the internal combustion engine 1. The ECU 100 includes a control unit 110 and a storage unit 120. The control unit 110 can be implemented using a hardware processor such as a CPU. Furthermore, the control unit 110 can be configured to include RAM, ROM, cache memory, etc. The storage unit 120 is a mechanism for storing information and is composed of storage media such as RAM or flash memory. The storage unit 120 stores the program executed by the control unit 110, the data used by the program, etc. The ECU 100 controls the internal combustion engine 1 according to the operating conditions of the internal combustion engine 1 or the driver's requirements. Map information 121 is stored in the storage unit 120. The map information 121 includes information related to road length, road gradient, speed limits, etc.

[0025] Furthermore, in addition to the aforementioned sensors, the ECU 100 is also equipped with, via electrical wiring, a throttle opening sensor 17 that outputs an electrical signal corresponding to the amount of time the driver presses the accelerator pedal 16 and detects engine load, a crankshaft position sensor 18 that detects engine speed, a tilt sensor 91 that detects the tilt angle of the vehicle 10 in the pitch direction, a speed sensor 92 that detects the speed of the vehicle 10, and a radar 93 that detects the distance to the vehicle in front. The output signals of these various sensors are input to the ECU 100. However, the tilt sensor 91, speed sensor 92, and radar 93 are not all necessary and can be selected appropriately.

[0026] Furthermore, the throttle valve 6, fuel injection valve 7, and spark plug 8 are connected to the ECU 100 via electrical wiring, and these devices are controlled by the control unit 110 of the ECU 100. For example, the control unit 110 controls the amount of fuel injected from the fuel injection valve 7 so that the air-fuel ratio in the cylinder of the internal combustion engine 1 is normally at or near the stoichiometric air-fuel ratio.

[0027] Furthermore, the control unit 110 performs a process of stopping the fuel supply from the fuel injection valve 7, i.e., fuel cut-off, when the internal combustion engine 1 decelerates (or when the vehicle 10 decelerates). For example, fuel cut-off is performed when the throttle opening is below a specified opening and the internal combustion engine speed is above a specified speed. The specified opening is 0 or near the specified opening. The specified speed is set to a speed that is a certain degree higher than the idle speed so that idling operation can be performed.

[0028] Furthermore, the control unit 110 estimates the amount of PM accumulated on GPF4 (hereinafter referred to as PM accumulation). PM accumulation can be estimated based on past engine speeds and loads, or based on the pressure difference between exhaust gases upstream and downstream of GPF4. PM accumulated on GPF4 is oxidized and removed by supplying oxygen (or air) to GPF4 when the temperature of GPF4 is above its PM oxidation temperature. This regeneration of GPF4 occurs. Additionally, in gasoline engines, due to the high exhaust temperature, the temperature of GPF4 easily reaches above its oxidation temperature. Therefore, if air flows into GPF4 during fuel cut-off, GPF4 regeneration naturally occurs.

[0029] Furthermore, under specified conditions, the control unit 110 increases the amount of air supplied to the GPF4 by increasing the intake air volume of the internal combustion engine 1 at the time of fuel cutoff. The specified conditions are those under which the GPF4 will not overheat even when the intake air volume is increased at the time of fuel cutoff. Figure 2 This is a timing diagram showing the increase in intake air volume during fuel cutoff. Figure 2 In this context, "idle" indicates whether the internal combustion engine 1 is in an idling state; "yes" indicates it is in an idling state, and "no" indicates it is not in an idling state. The engine is in an idling "yes" state when the driver has not pressed the accelerator pedal 16, or when even if the driver presses the accelerator pedal 16, no additional fuel is needed to supply the internal combustion engine 1. Furthermore, in... Figure 2 In the code, "Uphill Determination" indicates whether the road is uphill; "Yes" indicates an uphill road, and "No" indicates a non-uphill road (flat road or downhill road). "Air Increment Fuel Cut-off Request" indicates whether an increase in intake air is required when fuel is cut off; "Yes" indicates an increase in intake air is required when fuel is cut off, and "No" indicates no increase in intake air is required when fuel is cut off.

[0030] When the air-increase fuel cut-off request is "yes", the control unit 110 increases the intake air volume while performing fuel cut-off. Increasing the intake air volume is achieved, for example, by increasing the opening of the throttle valve 6. During normal fuel cut-off, the throttle valve 6 is, for example, completely closed, but when the air-increase fuel cut-off request is "yes", the control unit 110 operates the throttle valve 6 in the opening direction. Furthermore, at this time, the deceleration sensation may be reduced; therefore, in the case of a HEV (Hybrid Electric Vehicle), the regenerative torque can be increased, for example. And, for example, the control unit 110 can increase the opening of the throttle valve 6 within a range where a deceleration sensation can be obtained. Furthermore, as another example, the speed of the internal combustion engine 1 can be increased by switching to a low-speed gear, thereby increasing the intake air volume of the internal combustion engine 1 while simultaneously obtaining a deceleration sensation.

[0031] exist Figure 2In this diagram, T1 represents the point in time when the internal combustion engine 1 enters an idling state. This idling state can be the point when the driver releases the accelerator pedal 16 or the point when the driver removes their foot from the accelerator pedal 16. Idling means that the internal combustion engine 1 is no longer under external load. T2 represents the point in time when a load begins to be applied to the internal combustion engine 1. This can be the point when the driver depresses the accelerator pedal 16. T3 represents the point in time when the road traveled by the vehicle 10 changes from an uphill road to a flat road. T4 represents the point in time when the internal combustion engine 1 enters an idling state. T5 represents the point in time when the road traveled by the vehicle 10 changes from a flat road to a downhill road. T6 represents the point in time when a load begins to be applied to the internal combustion engine 1 (the point when the driver depresses the accelerator pedal 16).

[0032] Here, during the time interval from T1 to T2, the internal combustion engine 1 is idling while the vehicle 10 is traveling uphill. In this situation, the air-increase fuel cutoff request becomes "yes," and the intake air volume increases during fuel cutoff. It is assumed that when the vehicle 10 is traveling uphill, its speed tends to decrease, therefore the time spent maintaining the idling "yes" state is relatively short. That is, it is assumed that the fuel cutoff duration is relatively short during the time interval from T1 to T2. In this case, even if the temperature of GPF4 rises due to the increased intake air volume, overheating of GPF4 is suppressed. Therefore, during the time interval from T1 to T2, the air-increase fuel cutoff request becomes "yes," promoting the regeneration of GPF4.

[0033] On the other hand, during the period from T4 to T6, the internal combustion engine 1 is idling, but the vehicle 10 is traveling on a flat road or downhill. In this situation, the likelihood of prolonged fuel cut-off is high. That is, it is assumed that the vehicle 10 can travel for a longer period even if the driver does not press the accelerator pedal 16, thus the duration of fuel cut-off is relatively long. In this case, the likelihood of natural GPF4 regeneration is high even if the intake air volume does not increase. Furthermore, in this situation, if the intake air volume is increased, the GPF4 may overheat. Therefore, during the period from T4 to T6, the air-increase fuel cut-off request becomes "No".

[0034] Figure 3 This is a flowchart illustrating the fuel cut-off control process involved in the implementation method. This process is executed by ECU100 at predetermined intervals.

[0035] In step S101, the control unit 110 acquires the operating status. Here, the control unit 110 acquires detection values ​​from various sensors. If the processing in step S101 is complete, the process proceeds to step S102. In step S102, the control unit 110 determines whether the idling speed is "yes". The control unit 110 determines whether the driver has not pressed the accelerator pedal 16 based on the detection value from the throttle opening sensor 17. In step S102, if the control unit 110 makes a positive determination, the process proceeds to step S103; if it makes a negative determination, the process proceeds to step S108.

[0036] In step S103, the control unit 110 determines whether a fuel cut-off request exists. The control unit 110 determines that a fuel cut-off request exists when the internal combustion engine speed detected by the crankshaft position sensor 18 is above a predetermined speed and the throttle opening detected by the throttle opening sensor 17 is below a predetermined opening. The predetermined speed and predetermined opening are determined optimally through experiments or simulations and stored in the storage unit 120. Additionally, in this step, it can be determined whether the conditions for implementing fuel cut-off are met. For example, if the internal combustion engine speed is above a predetermined speed and the throttle opening is below a predetermined opening, the control unit 110 determines that the conditions for implementing fuel cut-off are met. In step S103, if the control unit 110 makes an affirmative determination, the process proceeds to step S104; if it makes a negative determination, the process proceeds to step S108.

[0037] In step S104, the control unit 110 determines whether the temperature of the GPF4 is lower than the overheating temperature. The overheating temperature is the temperature at which an anomaly occurs in the GPF4 or the temperature at which an anomaly may occur. The overheating temperature is determined through experiments or simulations and stored in the storage unit 120. Furthermore, the temperature of the GPF4 is obtained, for example, based on the detection value of the second temperature sensor 12. In step S104, if the control unit 110 makes a positive determination, the process proceeds to step S105; if it makes a negative determination, the process proceeds to step S108.

[0038] In step S105, the control unit 110 determines whether the fuel cut-off prediction time is above a threshold. The fuel cut-off prediction time is a value indicating the predicted duration of fuel cut-off. The control unit 110 calculates the fuel cut-off prediction time, for example, based on the speed of the vehicle 10 and the acceleration of the vehicle 10's deceleration. The control unit 110 acquires the speed of the vehicle 10 via the speed sensor 92. Furthermore, the control unit 110 calculates the acceleration of the vehicle 10's deceleration by differentiating the acquired speed of the vehicle 10. Based on the current speed of the vehicle 10, the control unit calculates the time until the vehicle 10's speed reaches a predetermined speed when decelerating at the current acceleration, and uses this time as the fuel cut-off prediction time. The predetermined speed can be 0, or it can be a preset speed that is the speed at which the driver begins to accelerate when pressing the accelerator pedal 16. The threshold for the fuel cut-off prediction time is set to an upper limit of the time during which the vehicle will not overheat even if the intake air volume GPF4 is increased. This threshold is determined through experiments or simulations and stored in the storage unit 120. In step S105, if the control unit 110 makes an affirmative determination, the process proceeds to step S106; if it makes a negative determination, the process proceeds to step S107.

[0039] In another example, in step S105, the control unit 110 can calculate the fuel cut-off prediction time based on the road inclination detected by the tilt sensor 91. Here, it is assumed that the greater the inclination on an uphill road, the greater the deceleration acceleration of the vehicle 10, and therefore the shorter the fuel cut-off prediction time. The relationship between the vehicle 10's speed, tilt angle, and fuel cut-off prediction time at the current moment can be mapped and stored in the storage unit 120. The control unit 110 obtains the fuel cut-off prediction time by substituting the detection values ​​from the speed sensor 92 and the tilt sensor 91 into the graph.

[0040] Furthermore, as another example, in step S105, the control unit 110 can calculate the fuel cut-off prediction time based on the map information 121 stored in the storage unit 120. For example, it is assumed that the shorter the uphill distance, the shorter the fuel cut-off prediction time. Also, it is assumed that the steeper the uphill slope, the shorter the fuel cut-off prediction time. For example, the relationship between the vehicle 10's speed, the uphill distance, the uphill slope, and the fuel cut-off prediction time can be mapped and stored in the storage unit 120. The control unit 110 obtains the fuel cut-off prediction time by substituting the detection value from the speed sensor 92 and the uphill distance and slope obtained from the map information 121 into the map.

[0041] Furthermore, as another example, in step S105, the control unit 110 can calculate the fuel cutoff prediction time based on the distance (i.e., vehicle distance) to the vehicle ahead detected by the radar 93. If the driver releases the accelerator pedal 16 to allow for a safe distance, it can be assumed that the accelerator pedal 16 will not be pressed until an appropriate distance is achieved. Therefore, it is assumed that the longer the vehicle distance, the shorter the fuel cutoff prediction time. For example, the relationship between vehicle distance and fuel cutoff prediction time can be mapped and stored in the storage unit 120, and the control unit 110 obtains the fuel cutoff prediction time by substituting the vehicle distance detected by the radar 93 into the graph. Additionally, the appropriate vehicle distance can vary depending on the vehicle speed. The higher the vehicle speed, the longer the appropriate vehicle distance. For example, the relationship between the vehicle 10's speed, vehicle distance, and fuel cutoff prediction time can be mapped and stored in the storage unit 120, and the control unit 110 obtains the fuel cutoff prediction time by substituting the detection value from the speed sensor 92 and the vehicle distance detected by the radar 93 into the graph.

[0042] Furthermore, as another example, in step S105, in addition to the above-mentioned determination, the control unit 110 can also determine whether the road on which the vehicle 10 is traveling is an uphill road. That is, a positive determination can be made only when the vehicle 10 is traveling on an uphill road.

[0043] In step S106, the control unit 110 increases the intake air volume when fuel is cut off. The control unit 110 generates a control command and outputs it to the throttle valve 6, so that the opening of the throttle valve 6 becomes a predetermined opening when the intake air volume is increased. The predetermined opening can be changed according to the driving state of the vehicle 10. The predetermined opening is determined in advance through experiments or simulations and stored in the storage unit 120. Furthermore, the control unit 110 performs fuel cut-off while increasing the intake air volume. If the processing in step S106 is completed, the process ends.

[0044] On the other hand, in step S107, the control unit 110 sets the intake air volume at fuel cut-off to a normal volume. The normal volume is the intake air volume that prevents the GPF4 from overheating even if it regenerates naturally, and it is less than the intake air volume set in step S106. The control unit 110 generates a control command and outputs it to the throttle valve 6 to, for example, completely close the throttle valve 6. The control unit 110 sets the intake air volume to a normal volume and performs fuel cut-off. If the processing in step S107 is completed, the process ends.

[0045] In step S108, the control unit 110 releases the fuel cutoff. That is, the fuel cutoff is not performed. For example, in the idle "No" state, fuel that only provides driving force to the vehicle 10 needs to be injected, so the fuel cutoff is released. Furthermore, if there is no fuel cutoff request, the conditions for fuel cutoff are not met, so the control unit 110 does not perform the fuel cutoff. Also, if the temperature of GPF4 is above the superheat temperature, performing the fuel cutoff may further increase the temperature of GPF4, so the control unit 110 does not perform the fuel cutoff. If the processing of step S108 is completed, the process ends.

[0046] As explained above, according to this embodiment, when a prolonged fuel cutoff cannot be expected, increasing the intake air volume can suppress GPF4 overheating and enable more efficient GPF4 regeneration. Furthermore, when a prolonged fuel cutoff can be expected, by not increasing the intake air volume, premature temperature rise of GPF4 leading to fuel cutoff release can be prevented. Therefore, GPF4 regeneration can be continuous, and thus, appropriate GPF4 regeneration can be performed.

[0047] Symbol Explanation

[0048] 1-Internal combustion engine, 2-Exhaust passage, 4-GPF (filter), 6-Throttle body, 10-Vehicle, 16-Accelerator pedal, 17-Throttle opening sensor, 100-ECU, 110-Control unit, 120-Storage unit.

Claims

1. A control device for an internal combustion engine, comprising controlling an internal combustion engine having a filter in the exhaust passage for capturing particulate matter in the exhaust, characterized in that, The control device for the internal combustion engine includes a control unit, which performs the following processing: When implementing a fuel cutoff to stop fuel supply to the internal combustion engine, the duration of the fuel cutoff is predicted; and If the predicted duration of the fuel cut-off is short, the amount of air supplied to the filter during the duration of the fuel cut-off is increased compared to if the duration is long.

2. The control device for an internal combustion engine according to claim 1, characterized in that, The control unit predicts the duration of the fuel cut-off based on the inclination angle of the road while the vehicle equipped with the internal combustion engine is traveling.

3. The control device for an internal combustion engine according to claim 1, characterized in that, The control unit predicts the duration of the fuel cut-off based on the deceleration of the vehicle equipped with the internal combustion engine.

4. The control device for an internal combustion engine according to claim 1, characterized in that, It also has a storage unit for storing map information. The control unit predicts the duration of the fuel cut-off based on the map information stored in the storage unit.

5. The control device for an internal combustion engine according to claim 1, characterized in that, The control unit predicts the duration of the fuel cut-off based on the distance between the first vehicle equipped with the internal combustion engine and the second vehicle located further ahead of the first vehicle.

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