Control device for internal combustion engines

Abstract

Efficiently removes PM (particulate matter) from the filter. [Solution] A control device for an internal combustion engine equipped with a filter in the exhaust passage for collecting particulate matter in the exhaust gas, comprising a control unit that, when a fuel cut is performed to stop the supply of fuel to the internal combustion engine, predicts the duration of the fuel cut and, if the predicted duration of the fuel cut is short, increases the amount of air supplied to the filter while the fuel cut is in effect compared to when it is long.

Description

Technical Field

[0001] The present disclosure relates to a control device for an internal combustion engine.

Background Art

[0002] When a vehicle is traveling on a downhill road, the particulate matter (PM: Particulate Matter ) trapped in the filter has a PM accumulation amount equal to or greater than a predetermined amount, the vehicle speed is equal to or higher than a predetermined vehicle speed, and the accelerator opening is equal to or less than a predetermined opening, fuel cut is performed to burn the PM accumulated on the filter and regenerate the filter, which is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to efficiently remove PM from the filter.

Means for Solving the Problems

[0005] One aspect of the present disclosure is a control device for an internal combustion engine that controls an internal combustion engine equipped with a filter in the exhaust passage for collecting particulate matter in the exhaust gas, the control device for an internal combustion engine that, when a fuel cut is performed to stop the supply of fuel to the internal combustion engine, predicts the duration of the fuel cut and, if the predicted duration of the fuel cut is short, increases the amount of air supplied to the filter while the fuel cut is in effect compared to when it is long. [Effects of the Invention]

[0006] According to this disclosure, PM can be efficiently removed from the filter. [Brief explanation of the drawing]

[0007] [Figure 1] This figure shows a schematic configuration of an internal combustion engine according to an embodiment, and its intake and exhaust systems. [Figure 2] This is a time chart showing the increase in intake air volume during fuel cut-off. [Figure 3] This is a flowchart showing the flow of fuel cut control according to the embodiment. [Modes for carrying out the invention]

[0008] Internal combustion engines sometimes have filters in their exhaust passages to collect particulate matter (PM) in the exhaust. PM collected by the filter is oxidized and removed when the filter temperature exceeds a predetermined temperature and the oxygen concentration inside the filter exceeds a predetermined concentration. However, in spark-ignition gasoline engines, the engine is usually operated at a stoichiometric air-fuel ratio or a rich air-fuel ratio, resulting in a low oxygen concentration inside the filter. Furthermore, oxygen is supplied to the filter only when operating at a lean air-fuel ratio or when fuel cut is performed due to deceleration, etc. To oxidize more PM, it is known that the throttle opening can be adjusted during fuel cut to increase the intake air volume. However, if the intake air volume is increased for a long period, the filter temperature may become too high. To suppress such filter overheating, fuel cut is sometimes limited. As a result, there is a problem that the amount of PM oxidized is less than when the fuel is cut off and the intake air volume is not increased. To address this problem, the control device for the internal combustion engine in this disclosure increases the intake air volume under conditions that the filter does not overheat even when the intake air volume is increased during fuel cut-off.

[0009] Specifically, one aspect of the present disclosure is a control device for an internal combustion engine, which controls an internal combustion engine equipped with a filter in the exhaust passage for collecting particulate matter in the exhaust gas, and comprises a control unit. The control unit predicts the duration of the fuel cut when a fuel cut is performed to stop the supply of fuel to the internal combustion engine. The control unit may predict the duration of the fuel cut according to the inclination angle of the road on which the vehicle equipped with the internal combustion engine is traveling. The greater the inclination angle of the road, the greater the deceleration of the vehicle, and therefore the shorter the time until the driver presses the accelerator pedal again. In other words, the duration of the fuel cut may be shortened. The control unit may also predict the duration of the fuel cut according to the deceleration of the vehicle equipped with the internal combustion engine. The greater the deceleration, the shorter the time until the vehicle decreases to the speed desired by the driver, and therefore the shorter the time until the driver presses the accelerator pedal again. In other words, the duration of the fuel cut may be shortened.

[0010] Furthermore, the control unit for the internal combustion engine may further include a storage unit for storing map information, and the control unit may predict the duration of the fuel cut according to the map information stored in the storage unit. The map information may include, for example, information on the length of the road and information on the gradient of the road. The timing at which the driver presses the accelerator pedal may vary depending on the road. For example, when the vehicle is traveling on an uphill road, the driver will press the accelerator pedal for a longer period of time, so the duration of the fuel cut may be relatively shorter. On the other hand, when the vehicle is traveling on a flat road or a downhill road, the driver will release the accelerator pedal more frequently. Therefore, the duration of the fuel cut may be relatively longer. The control unit may also predict the duration of the fuel cut according to the distance between the first vehicle equipped with the internal combustion engine and a second vehicle located ahead of the first vehicle. The driver of the first vehicle will try to maintain an appropriate distance from the second vehicle. For example, the shorter the distance between vehicles, the longer the driver will release the accelerator pedal in order to increase the distance between vehicles. Therefore, the duration of fuel cut-off can be relatively longer.

[0011] The control unit then increases the amount of air supplied to the filter while the fuel cut is in effect, compared to when the fuel cut is in effect, if the predicted duration of the fuel cut is short. The amount of air supplied to the filter may be the amount of air supplied to the filter per unit time. Also, since the intake air from the internal combustion engine is supplied directly to the filter during a fuel cut, 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 a long duration of fuel cut is predicted, there is a risk that the filter may fail due to overheating. In response to this, the control unit suppresses filter overheating by relatively reducing the amount of air supplied to the filter when the duration of fuel cut is long. In this way, even with a relatively small amount of air, PM can be oxidized if the duration of fuel cut is relatively long. On the other hand, when the duration of fuel cut is short, PM can be oxidized quickly by relatively increasing the amount of air supplied to the filter. In this case, the amount of heat generated in the filter will be large, but because the duration of fuel cut is relatively short, filter overheating is suppressed. In this way, efficient filter regeneration becomes possible.

[0012] The following describes in detail, with reference to the drawings, embodiments for carrying out this disclosure. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, etc., of the components described in this embodiment are not intended to limit the scope of this disclosure to those.

[0013] <First Embodiment> Figure 1 is a diagram showing the schematic configuration of an internal combustion engine according to an embodiment, and its intake and exhaust systems. The internal combustion engine 1 shown in Figure 1 is a spark-ignition type gasoline engine. The internal combustion engine 1 is mounted on a vehicle 10. Note that the vehicle 10 may be a HEV (Hybrid Electric Vehicle). stomach.

[0014] An exhaust passage 2 is connected to the internal combustion engine 1. Along the exhaust passage 2, a catalyst 3 and a GPF 4 are provided, in order from the upstream side. Catalyst 3 is a catalyst that has an oxidation function and purifies the exhaust gas. Catalyst 3 may be, for example, a three-way catalyst, an oxidation catalyst, a storage-reduction type NOx catalyst, or a selective reduction type NOx catalyst. GPF 4 is a gasoline particulate filter that collects PM in the exhaust gas. The GPF 4 may be coated with the above-mentioned catalyst.

[0015] Furthermore, a first temperature sensor 11 for detecting the exhaust temperature is provided in the exhaust passage 2 upstream of the catalyst 3. A second temperature sensor 12 for detecting the exhaust temperature is provided in the exhaust passage 2 downstream of the catalyst 3 and upstream of the GPF 4. The temperature of the catalyst 3 can be detected based on the detection value of the first temperature sensor 11 or the second temperature sensor 12. The temperature of the GPF 4 can also be detected based on the detection value of the second temperature sensor 12. Additionally, the control unit 110 of the ECU 100, described later, can estimate the temperatures of the catalyst 3 and GPF 4 based on the operating state of the internal combustion engine 1.

[0016] Furthermore, an intake passage 5 is connected to the internal combustion engine 1. A throttle 6 is provided in the middle of the intake passage 5 to adjust the amount of intake air for the internal combustion engine 1. An airflow meter 15 for detecting the amount of intake air for the internal combustion engine 1 is also installed in the intake passage 5 upstream of the throttle 6.

[0017] Furthermore, the internal combustion engine 1 is equipped with a fuel injection valve 7 that supplies fuel to the internal combustion engine 1. The fuel injection valve 7 may inject fuel into the cylinders of the internal combustion engine 1, or it may inject fuel into the intake passage 5. The internal combustion engine 1 is also provided with a spark plug 8 that generates an electric spark in the cylinder.

[0018] An internal combustion engine 1 is connected to an ECU 100 which is an electronic control unit. The ECU 100 includes a control unit 110 and a storage unit 120. The control unit 110 can be implemented by, for example, a hardware processor such as a CPU. The control unit 110 may also be configured to include RAM, ROM, cache memory and the like. The storage unit 120 is a means for storing information, and is configured by a storage medium such as RAM or flash memory. The storage unit 120 stores programs executed by the control unit 110, data used by the programs, and the like. The ECU 100 controls the internal combustion engine 1 in accordance with the operating conditions of the internal combustion engine 1 and the driver's requests. The storage unit 120 stores map information 121. The map information 121 includes information related to road length, road gradient, road speed limit, and the like.

[0019] In addition to the above sensors, the ECU 100 is connected via electrical wiring to an accelerator opening sensor 17 that outputs an electric signal corresponding to the amount by which the driver depresses the accelerator pedal 16 to detect the engine load, a crank position sensor 18 that detects the engine rotation speed, an inclination sensor 91 that detects the inclination 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 inter-vehicle distance to the preceding vehicle, and output signals from these various sensors are input to the ECU 100. Note that the inclination sensor 91, the speed sensor 92, and the radar 93 are not all necessarily required, and may be appropriately selected and provided.

[0020] Further, the ECU 100 is connected to a throttle 6, a fuel injection valve 7, and a spark plug 8 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 fuel injection amount from the fuel injection valve 7 so that the air-fuel ratio in the cylinders of the internal combustion engine 1 normally becomes the stoichiometric air-fuel ratio or in the vicinity thereof.

[0021] The control unit 110 then performs a fuel cut, which is a process that stops the supply of fuel from the fuel injector 7 when the internal combustion engine 1 is decelerating (or when the vehicle 10 is decelerating). The fuel cut is performed, for example, when the accelerator opening is below a predetermined opening and the engine rotation speed is above a predetermined rotation speed. The predetermined opening is 0 or close to it. The predetermined rotation speed is set to a rotation speed that is somewhat higher than the idle speed so that idle operation is possible.

[0022] Furthermore, the control unit 110 estimates the amount of PM (hereinafter referred to as PM accumulation) deposited in the GPF4. The PM accumulation may be estimated based on past engine rotational speed and engine load, or it may be estimated based on the exhaust pressure difference between the upstream and downstream sides of the GPF4. PM accumulated in the GPF4 is oxidized and removed when the temperature of the GPF4 is above the oxidation temperature of PM and oxygen (which may be air) is supplied to the GPF4. This regenerates the GPF4. In gasoline engines, the temperature of the GPF4 tends to exceed the oxidation temperature due to the high exhaust temperature. Therefore, when air flows into the GPF4 during fuel cut-off, regeneration of the GPF4 occurs automatically.

[0023] Furthermore, the control unit 110 increases the amount of air supplied to the GPF4 by increasing the intake air amount of the internal combustion engine 1 when fuel is cut off, if predetermined conditions are met. The predetermined condition is that the GPF4 does not overheat even if the intake air amount is increased when fuel is cut off. Here, Figure 2 is a time chart when the intake air amount is increased when fuel is cut off. In Figure 2, "Idle" indicates whether the internal combustion engine 1 is in an idle state, "ON" indicates that it is in an idle state, and "OFF" indicates that it is not in an idle state. The Idle ON state occurs when the driver is not pressing the accelerator pedal 16, or when the driver is pressing the accelerator pedal 16 but there is no need to increase the fuel supplied to the internal combustion engine 1. Also, in Figure 2, "Uphill Judgment" indicates whether the road is an uphill road, "ON" indicates that it is an uphill road, and "OFF" indicates that it is not an uphill road (flat road or downhill road). The "Increased Air Volume Fuel Cut Request" setting indicates whether an increase in intake air volume is required during fuel cut-off. "ON" indicates that an increase in intake air volume is required during fuel cut-off, while "OFF" indicates that an increase in intake air volume is not required during fuel cut-off.

[0024] When the increased air-fuel-cut request is ON, the control unit 110 increases the intake air volume while performing a fuel cut. The increase in intake air volume is achieved, for example, by increasing the opening of the throttle 6. During a normal fuel cut, the throttle 6 is, for example, fully closed, but when the increased air-fuel-cut request is ON, the control unit 110 operates the throttle 6 in the direction of opening. Note that this may reduce the feeling of deceleration, so if the vehicle 10 is an HEV, the regenerative torque may be increased, for example. Alternatively, the control unit 110 may increase the opening of the throttle 6 within a range in which a feeling of deceleration is obtained. Another example is to increase the intake air volume of the internal combustion engine 1 while obtaining a feeling of deceleration by switching to a low gear and increasing the rotational speed of the internal combustion engine 1.

[0025] In Figure 2, T1 indicates the point in time when the internal combustion engine 1 becomes idle. The point in time when the internal combustion engine 1 becomes idle may also be the point in time when the driver releases pressure on the accelerator pedal 16, or the point in time when the driver takes their foot off the accelerator pedal 16. When the internal combustion engine 1 becomes idle, it means that there is no external load on the internal combustion engine 1. T2 indicates the point in time when a load begins to be applied to the internal combustion engine 1. The time of this change may be the time when the driver presses down on the accelerator pedal 16. T3 indicates the time when the road on which the vehicle 10 is traveling changes from an uphill road to a flat road. T4 indicates the time when the internal combustion engine 1 becomes idle. T5 indicates the time when the road on which the vehicle 10 is traveling changes from a flat road to a downhill road. T6 indicates the time when the internal combustion engine 1 begins to be loaded (the time when the driver presses down on the accelerator pedal 16).

[0026] Here, during the time from T1 to T2, the internal combustion engine 1 is idle and the vehicle 10 is traveling uphill. In such cases, the increased air-fuel cut request is turned ON, and the intake air volume is increased during the fuel cut. When the vehicle 10 is traveling uphill, its speed tends to decrease, so the time during which the idle state is maintained is considered to be relatively short. In other words, the duration of the fuel cut is considered to be relatively short during the time from T1 to T2. In this case, even if the temperature of the GPF4 rises due to the increased intake air volume, overheating of the GPF4 is suppressed. Therefore, during the time from T1 to T2, the increased air-fuel cut request is turned ON, and the regeneration of the GPF4 is promoted.

[0027] On the other hand, from T4 to T6, the internal combustion engine 1 is idle, but the vehicle 10 is traveling on a flat road or a downhill road. In such cases, there is a high probability that fuel cut will be performed for a long time. That is, since the vehicle 10 can travel for a longer period of time even without the driver pressing the accelerator pedal 16, it is thought that the duration of fuel cut will be relatively long. In this case, even if the intake air volume is not increased, there is a high probability that GPF4 regeneration will occur automatically. Also, if the intake air volume is increased in such cases, there is a risk that GPF4 will overheat. For this reason, the request for increased air and fuel cut is turned OFF from T4 to T6.

[0028] Figure 3 is a flowchart showing the flow of fuel cut control according to the embodiment. This routine is executed by the ECU 100 at predetermined intervals.

[0029] In step S101, the control unit 110 acquires the driving state. Here, the control unit 110 acquires detection values ​​from various sensors. Once the processing in step S101 is complete, the process proceeds to step S102. In step S102, the control unit 110 determines whether or not the idle state is ON. The control unit 110 determines whether or not the driver is not pressing the accelerator pedal 16, based on the detection value of the accelerator pedal position sensor 17. If the control unit 110 makes a positive determination in step S102, the process proceeds to step S103; if it makes a negative determination, the process proceeds to step S108.

[0030] In step S103, the control unit 110 determines whether or not there is a fuel cut request. The control unit 110 determines that there is a fuel cut request if the engine rotation speed detected by the crank position sensor 18 is above a predetermined rotation speed and the accelerator opening detected by the accelerator opening sensor 17 is below a predetermined opening. The predetermined rotation speed and predetermined opening are determined to be optimal values ​​through experimentation or simulation and stored in the storage unit 120. In this step, the control unit 110 may also determine whether or not the conditions for performing a fuel cut are met. For example, if the engine rotation speed is above a predetermined rotation speed and the accelerator opening is below a predetermined opening, the control unit 110 determines that the conditions for performing a fuel cut are met. If the control unit 110 makes an affirmative determination in step S103, the process proceeds to step S104; if it makes a negative determination, the process proceeds to step S108.

[0031] In step S104, the control unit 110 determines whether the temperature of the GPF4 is below the overheating temperature. The overheating temperature is the temperature at which an abnormality occurs in the GPF4 or a temperature at which an abnormality is likely to occur. The overheating temperature is determined by experiment or simulation and stored in the storage unit 120. The temperature of the GPF4 is obtained, for example, based on the detection value of the second temperature sensor 12. If the control unit 110 makes a positive determination in step S104, the process proceeds to step S Proceed to step 105, and if a negative result is obtained, the process proceeds to step S108.

[0032] In step S105, the control unit 110 determines whether the predicted fuel cut time is above a threshold. The predicted fuel cut time is a value that predicts the duration of fuel cut. The control unit 110 calculates the predicted fuel cut time, for example, according to the speed of the vehicle 10 and the deceleration acceleration of the vehicle 10. The control unit 110 obtains the speed of the vehicle 10 using the speed sensor 92. The control unit 110 also calculates the deceleration acceleration of the vehicle 10 by differentiating the obtained speed of the vehicle 10. The time it takes for the vehicle 10 to reach a predetermined speed when decelerating from the current speed of the vehicle 10 at the current deceleration acceleration is calculated as the predicted fuel cut time. The predetermined speed may be 0, or it may be a speed that is pre-set as the speed at which the driver starts accelerating by pressing the accelerator pedal 16. The threshold for the predicted fuel cut time is set as the upper limit of the time during which the GPF4 does not overheat even when the intake air amount is increased. This threshold is determined by experimentation or simulation and stored in the storage unit 120. If the control unit 110 determines in step S105 to be positive, the process proceeds to step S106; if it determines to be negative, the process proceeds to step S107.

[0033] As another example, in step S105, the control unit 110 may calculate the predicted fuel cut time according to the road inclination detected by the inclination sensor 91. Here, it is thought that the greater the inclination on an uphill road, the greater the deceleration acceleration of the vehicle 10, and therefore the shorter the predicted fuel cut time. The relationship between the current speed of the vehicle 10, the inclination angle, and the predicted fuel cut time may be mapped and stored in the storage unit 120, and the control unit 110 may obtain the predicted fuel cut time by substituting the detected values ​​of the speed sensor 92 and the inclination sensor 91 into the map.

[0034] As another example, in step S105, the control unit 110 may calculate the fuel cut prediction time according to the map information 121 stored in the memory unit 120. For example, it is thought that the shorter the distance of the uphill road, the shorter the fuel cut prediction time will be. Also, for example, it is thought that the higher the gradient of the uphill road, the shorter the fuel cut prediction time will be. For example, the relationship between the vehicle speed 10, the distance of the uphill road, the gradient of the uphill road, and the fuel cut prediction time may be mapped and stored in the memory unit 120, and the control unit 110 may obtain the fuel cut prediction time by substituting the detected value of the speed sensor 92 and the distance and gradient of the uphill road obtained from the map information 121 into the map.

[0035] As another example, in step S105, the control unit 110 may calculate the fuel cut prediction time according to the distance to the vehicle ahead (i.e., the following distance) detected by the radar 93. If the driver eases off the accelerator pedal 16 to increase the following distance, it is assumed that the accelerator pedal 16 will not be pressed until the appropriate following distance is reached. Therefore, it is assumed that the longer the following distance, the shorter the fuel cut prediction time will be. For example, the relationship between the following distance and the fuel cut prediction time may be mapped and stored in the storage unit 120, and the control unit 110 may obtain the fuel cut prediction time by substituting the following distance detected by the radar 93 into the map. Note that the appropriate following distance may vary depending on the vehicle speed. The higher the vehicle speed, the longer the appropriate following distance. For example, the relationship between the vehicle speed 10, the distance between vehicles, and the predicted fuel cut time may be mapped and stored in the storage unit 120, and the control unit 110 may obtain the predicted fuel cut time by substituting the detected value from the speed sensor 92 and the distance between vehicles detected by the radar 93 into the map.

[0036] As another example, in step S105, the control unit 110 may, in addition to the above determination, determine whether the road on which the vehicle 10 is traveling is an uphill road. That is, a positive determination may be made in step S105 only when the vehicle 10 is traveling on an uphill road.

[0037] In step S106, the control unit 110 increases the amount of intake air during fuel cut-off. The control unit 110 generates a control command and outputs it to the throttle 6 so that the opening of the throttle 6 becomes a predetermined opening when the amount of intake air is increased. The predetermined opening may be changed according to the driving state of the vehicle 10. The predetermined opening is determined in advance by experiment or simulation and stored in the memory unit 120. Then, the control unit 110 performs fuel cut-off while increasing the amount of intake air. When the processing in step S106 is completed, this routine ends.

[0038] Meanwhile, in step S107, the control unit 110 sets the intake air amount at the time of fuel cut to the normal amount. The normal amount is the amount of intake air that does not cause the GPF4 to overheat even if the GPF4 is regenerated as a result, and is less than the intake air amount set in step S106. The control unit 110 generates a control command and outputs it to the throttle 6 so that the opening of the throttle 6 becomes, for example, fully closed. The control unit 110 performs fuel cut while setting the intake air amount to the normal amount. Once the processing in step S107 is completed, this routine ends.

[0039] In step S108, the control unit 110 cancels the fuel cut-off, that is, it prevents the fuel cut-off from being performed. For example, when the idle is OFF, it is necessary to inject enough fuel to provide driving force to the vehicle 10, so the fuel cut-off is canceled. Also, if there is no fuel cut-off request, the conditions for fuel cut-off are not met, so the control unit 110 does not perform a fuel cut-off. Furthermore, if the temperature of the GPF4 is above the superheating temperature, the control unit 110 does not perform a fuel cut-off because performing a fuel cut-off may cause the temperature of the GPF4 to rise even further. Once the processing in step S108 is completed, this routine terminates.

[0040] As described above, according to this embodiment, when a long-term fuel cut-off is not expected, the intake air volume is increased, thereby suppressing overheating of the GPF4 and enabling more efficient regeneration of the GPF4. Furthermore, when a long-term fuel cut-off is expected, the intake air volume is not increased, thus preventing the temperature of the GPF4 from rising prematurely and releasing the fuel cut-off. Therefore, since the regeneration of the GPF4 can be carried out continuously, the regeneration of the GPF4 can be performed effectively. [Explanation of Symbols]

[0041] 1. Internal combustion engine 2 Exhaust passage 4. GPF (Filter) 6 Throttles 10 vehicles 16. Accelerator pedal 17. Accelerator position sensor 100 ECU 110 Control Unit 120 Storage section

Claims

1. A control device for an internal combustion engine that controls an internal combustion engine equipped with a filter in the exhaust passage for collecting particulate matter in the exhaust gas, When a fuel cut is implemented to stop the supply of fuel to the internal combustion engine, predict the duration of the fuel cut. If the predicted duration of the fuel cut is short, the amount of air supplied to the filter during the fuel cut is increased compared to when it is longer. A control device for an internal combustion engine, comprising a control unit that performs the following actions.

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

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

4. It further includes a memory unit for storing map information, The control unit predicts the duration of the fuel cut-off according to the map information stored in the memory unit. A control device for an internal combustion engine according to claim 1.

5. 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 ahead of the first vehicle. A control device for an internal combustion engine according to claim 1.

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