Exhaust control device for internal combustion engine

Abstract

To provide an exhaust control device for an internal combustion engine that can enhance convenience while securing engine performance by automatically removing soot in an exhaust passage.SOLUTION: An exhaust control device 20 for an internal combustion engine 1 comprises a calculation unit 21 for calculating an amount of soot existing in an exhaust passage 3 of the internal combustion engine 1, as an estimated amount of the soot, and a first control unit 22 for performing soot removal control for removing the soot in the exhaust passage 3 by increasing an exhaust flow rate of the internal combustion engine 1 when the estimated amount of the soot calculated by the calculation unit 21 exceeds a predetermined amount.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an exhaust control device that performs control to remove soot present in an exhaust passage of an internal combustion engine (hereinafter also referred to as "engine"). [Background technology]

[0002] For example, exhaust gas from an engine mounted on a vehicle or ship is discharged outside the vehicle or ship through an exhaust passage, and since this exhaust gas contains soot, it is known that soot accumulates in the exhaust system, including the exhaust passage, depending on the operating time and operating mode of the engine. For example, Patent Document 1 discloses a technique for determining whether soot has accumulated on the inner wall of an EGR pipe that recirculates a portion of the exhaust gas back into the intake air. This technique estimates the soot accumulation state, and if it is determined that soot has accumulated, it notifies the driver by turning on a lamp or the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-89073 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the technology of Patent Document 1 only notifies the driver of the soot accumulation status, so the driver must take appropriate action after learning of the soot accumulation status, which places a heavy burden on the driver. Therefore, if the amount of soot present (accumulating) in the exhaust passage could be determined and the soot could be removed automatically (without bothering the driver), convenience could be improved while ensuring engine performance.

[0005] The present invention was invented in consideration of the above-mentioned problems, and one of its objectives is to automatically remove soot from the exhaust passage, thereby improving convenience while maintaining engine performance. However, this objective is not limited to this. Another objective of the present invention is to achieve operational effects that cannot be obtained by conventional techniques, which are derived from the configurations shown in the detailed description of the invention described below. [Means for solving the problem]

[0006] The disclosed exhaust control device for an internal combustion engine can be realized as the following disclosed embodiments (application examples), which solve at least part of the above-mentioned problems. Each of the embodiments from embodiment 2 onwards is an embodiment that can be selected additionally as appropriate, and each of the embodiments can be omitted. None of the embodiments from embodiment 2 onwards discloses an embodiment or configuration that is essential to the present invention.

[0007] Aspect 1. The disclosed exhaust control device for an internal combustion engine includes a calculation unit that calculates the amount of soot present in the exhaust passage of the internal combustion engine as an estimated soot amount, and a first control unit that, when the estimated soot amount exceeds a predetermined amount, performs soot removal control to remove the soot by increasing the exhaust flow rate of the internal combustion engine. The internal combustion engine is provided with a filter disposed in the exhaust passage for capturing particulate matter contained in the exhaust gas of the internal combustion engine. The exhaust control device further includes a second control unit that, when a predetermined first start condition is satisfied, performs regeneration control to increase the exhaust temperature of the internal combustion engine and incinerate the particulate matter captured on the filter, and when the soot removal control is performed by the first control unit, the second control unit starts the regeneration control when a second start condition that is a relaxed version of the first start condition is satisfied. Aspect 2 In the above aspect 1, it is preferable that the first control unit increases the exhaust flow rate by increasing the rotation speed of the internal combustion engine during the soot removal control.

[0008] Aspect 3. In the above aspect 2, the exhaust control device is preferably the exhaust control device applied to a vehicle including the internal combustion engine, a clutch interposed in a power transmission path connecting the internal combustion engine and drive wheels, and a supercharger interposed in an intake passage of the internal combustion engine and supercharging intake air. In this case, it is preferable that, during deceleration with the accelerator released, the first control unit, in the soot removal control, increases the rotation speed of the internal combustion engine with the clutch disengaged and increases the supercharging pressure of the supercharger to increase the exhaust flow rate.

[0009] Aspect 4. In the above-described aspect 2 or 3, the exhaust control device is preferably applied to a vehicle including the internal combustion engine and a clutch interposed in a power transmission path connecting the internal combustion engine and drive wheels. In this case, it is preferable that, during driving with an accelerator pedal stroke of substantially constant other than 0, the first control unit, in the soot removal control, shifts down and engages the clutch to increase the rotation speed of the internal combustion engine and increase the exhaust flow rate.

[0011] Aspects 5 The above aspects Any of 1 to 4 In the second regeneration control started in response to the second start condition being satisfied, it is preferable that the second control unit lowers the target value of the exhaust temperature compared to the normal regeneration control started in response to the first start condition being satisfied. Aspects 6 The above aspects 5 In the above, it is preferable that the second control unit extends the execution time of the second regeneration control compared to the normal regeneration control. [Effects of the Invention]

[0012] According to the disclosed exhaust control device for an internal combustion engine, soot can be blown away by increasing the exhaust flow rate, so that soot can be removed automatically (without bothering the driver), thereby improving convenience while maintaining engine performance. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing an internal combustion engine equipped with an exhaust control device according to an embodiment. [Figure 2] 2 is a flowchart example of soot removal control performed by the exhaust control device of FIG. 1. [Figure 3] 2 is a flowchart illustrating an example of regeneration control performed by the exhaust control device of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0014] An exhaust control device for an internal combustion engine (hereinafter also referred to as "engine") will be described as an embodiment with reference to the drawings. The embodiment described below is merely an example, and is not intended to exclude various modifications and applications of techniques not explicitly stated in the embodiment. Each configuration of this embodiment can be implemented with various modifications within the scope of the spirit thereof. Furthermore, it can be selected or combined as needed.

[0015] [1. Equipment configuration] The internal combustion engine (hereinafter also referred to as "engine") of this embodiment is mounted on a vehicle (not shown). This vehicle is an engine vehicle equipped with an engine as a drive source, or a hybrid vehicle (HEV, Hybrid Electric Vehicle) or plug-in hybrid vehicle (PHEV, Plug-in Hybrid Electric Vehicle) equipped with an engine and a motor as drive sources, a generator as a power generation device, and a battery (battery pack) as a power storage device. A plug-in hybrid vehicle is a hybrid vehicle in which the battery can be externally charged or externally supplied with power from the battery. Plug-in hybrid vehicles and electric vehicles are provided with a charging port (inlet) for inserting a charging cable that supplies power from external charging equipment, and a receptacle (outlet) for external power supply.

[0016] The type of engine may be a diesel engine or a gasoline engine. There are no particular limitations on the number of cylinders, the arrangement of cylinders, the fuel injection type (direct injection, port injection), the presence or absence of a mechanism for changing the valve lift and valve timing of the intake and exhaust valves, or the presence or absence of an EGR system (high-pressure EGR system, low-pressure EGR system) that returns part of the exhaust gas to the intake passage. The following explanation will be given as an example of a multi-cylinder direct-injection diesel engine equipped with a high-pressure EGR system.

[0017] As shown in Fig. 1, engine 1 has an intake passage 2 and an exhaust passage 3, and various devices and sensors installed in these passages 2, 3. Engine 1 of this embodiment has a turbocharger 4 installed across intake passage 2 and exhaust passage 3. In intake passage 2 of engine 1, an air cleaner 5 (air filter), a compressor (not shown) of turbocharger 4, an intercooler 6, a throttle valve 7, and a surge tank 8 are installed, in this order from the upstream side. In exhaust passage 3 of engine 1, a turbine (not shown), a catalyst 9, and a filter 10 of turbocharger 4 are installed, in this order from the upstream side. The catalyst 9 and filter 10 are examples of an exhaust purification device, and are housed in a casing.

[0018] The turbocharger 4 of this embodiment is a device that supercharges intake air by utilizing exhaust pressure, rotates a turbine using the exhaust pressure (exhaust energy), compresses intake air (air) using a compressor provided coaxially with the turbine, and sends the high-pressure intake air to the cylinders of the engine 1. The turbocharger 4 of this embodiment is also a variable geometry turbocharger that can control the supercharging pressure (intake pressure). That is, a plurality of variable vanes are attached to the turbine blades of the turbine of the turbocharger 4, and the supercharging pressure can be controlled by adjusting and changing the opening of the variable vanes using an actuator 4A. The operating state of the actuator 4A is controlled by a control device 20, which will be described later.

[0019] The intake air introduced into the intake passage 2 is filtered by an air cleaner 5, compressed by the compressor of the turbocharger 4, and then cooled by an intercooler 6. After that, the flow rate of the intake air is adjusted by a throttle valve 7, and the intake air is temporarily stored in a surge tank 8 before flowing toward the intake port.

[0020] On the other hand, exhaust gas discharged from an exhaust port of the engine 1 turns the turbine of the turbocharger 4, and then passes through a catalyst 9 where hydrocarbon (HC) components, carbon monoxide (CO), nitrogen oxides (NOx), and other components contained in the exhaust gas are purified. After that, particulate matter (PM), such as soot, contained in the exhaust gas is collected by a filter 10, and the exhaust gas is then discharged outside the vehicle. Note that the exhaust purification device disposed in the exhaust passage 3 is not limited to the catalyst 9 and the filter 10, and either one of them may be used alone, or other catalysts (oxidation catalyst, three-way catalyst, NOx trap catalyst) may also be provided.

[0021] The engine 1 of this embodiment has an EGR system 11 that recirculates a portion of the exhaust gas to the intake side. The EGR system 11 has an EGR passage 12 that connects the upstream side (exhaust port side) of the turbocharger 4 in the exhaust passage 3 with the downstream side (intake port side) of the turbocharger 4 in the intake passage 2. In other words, this EGR system 11 is a high-pressure EGR system. An EGR valve 13 that adjusts the amount of EGR gas (the flow rate of exhaust gas to be recirculated) and an EGR cooler 14 that cools the EGR gas are installed in the EGR passage 12. By closing the EGR valve 13, the amount of EGR gas becomes zero, and all exhaust gas discharged from the exhaust port flows downstream. On the other hand, the amount of EGR gas increases as the opening of the EGR valve 13 increases, and the flow rate of exhaust gas flowing downstream decreases accordingly.

[0022] Various sensors for acquiring information about the operating state of the engine 1 are provided in the engine 1. The engine 1 of this embodiment has an engine speed sensor 30 that detects the speed of the engine 1, an intake air flow rate sensor 31, an intake air temperature sensor 32, an intake pressure sensor 33, and an EGR temperature sensor 34 provided in the intake system, and exhaust gas temperature sensors 35A, 35B, and 35C and a differential pressure sensor 36 provided in the exhaust system.

[0023] The intake air flow rate sensor 31 and the intake air temperature sensor 32 are provided on the upstream side of the supercharger 4, and the intake air pressure sensor 33 is provided on the downstream side of the throttle valve 7 and the EGR passage 1. 2These sensors 31, 32, and 33 detect the flow rate, temperature, and pressure of the intake air at their respective installation locations. The EGR temperature sensor 34 is provided in the surge tank 8 and detects the temperature of the intake air (intake air containing EGR gas if EGR gas is introduced into the intake passage 2) at this location.

[0024] The exhaust gas temperature sensors 35A, 35B, and 35C are provided downstream of the turbocharger 4 and detect the temperature of the exhaust gas at their respective installation positions. Here, a configuration is shown in which the exhaust gas temperature sensors 35A, 35B, and 35C are provided immediately upstream of the catalyst 9 and immediately upstream and downstream of the filter 10. The differential pressure sensor 36 detects the differential pressure between the upstream pressure and the downstream pressure of the filter 10. Information detected by these sensors 31 to 36 is sent to the control device 20.

[0025] In this embodiment, further, Both A vehicle speed sensor 37 that detects the vehicle speed and an accelerator position sensor 38 that detects the amount of depression of the accelerator pedal (accelerator position) are provided. Information detected by these sensors 37, 38 is also transmitted to the control device 20. Note that these sensors, including their locations, are merely examples. In addition to these sensors, sensors that detect the operating state of the engine 1 and the state of the vehicle (exhaust flow rate sensor, engine water temperature sensor, torque sensor, brake sensor, etc.) may also be provided.

[0026] The control device 20 (exhaust control device) is an electronic control device (computer) that controls the operating state of the engine 1, and is an electronic device that integrates processor devices such as a CPU and an MPU, and memory devices such as a ROM and a RAM. The control device 20 of this embodiment is connected to an in-vehicle network and can acquire the vehicle state (information).

[0027] When the amount of soot present in the exhaust passage 3 exceeds a predetermined amount, the control device 20 performs control to remove the soot (hereinafter referred to as "soot removal control"). That is, in the engine 1 of this embodiment and a vehicle equipped with this engine 1, the control device 20 automatically removes soot without bothering the driver, thereby ensuring the performance of the engine 1. Furthermore, the control device 20 of this embodiment performs regeneration control of the filter 10 when it is necessary to remove PM accumulated on the filter 10.

[0028] [2. Control configuration] The control device 20 has a calculation unit 21 and a soot removal control unit 22 (first control unit) as functional elements for carrying out the soot removal control, and a regeneration control unit 23 (second control unit) as a functional element for carrying out the regeneration control. These elements 21 to 23 may be realized by electronic circuits (hardware), or may be programmed as software, or some of these functions may be provided as hardware and the other parts may be software.

[0029] [2-1. Soot removal control] First, the soot removal control will be described. The calculation unit 21 calculates the amount of soot present in the exhaust passage 3 as an estimated soot amount. The exhaust gas discharged from the exhaust port contains soot, and as the exhaust gas flows, some of this soot may remain and accumulate in the exhaust passage 3. Note that the inside of the exhaust passage 3 here includes not only the inner wall of the exhaust passage 3, but also the surface of a variable vane attached to the turbine of the turbocharger 4 and the inner wall of the casing of the exhaust purification device.

[0030] As a result of experiments conducted by the inventors, it was found that the amount of soot that accumulates in the exhaust passage 3 depends mainly on the exhaust flow rate. Specifically, it was found that, from 0 to a predetermined flow rate, the amount of soot that accumulates increases as the exhaust flow rate increases, and that after the predetermined flow rate, the amount of soot that accumulates decreases as the exhaust flow rate increases. This is because the flow velocity increases as the exhaust flow rate increases, and so, once the predetermined flow rate is exceeded, the soot contained in the exhaust no longer remains in the exhaust passage 3, and further, the force of the exhaust blows away the soot that has begun to accumulate in the exhaust passage 3.

[0031] Therefore, it is preferable that calculation unit 21 calculates the estimated soot amount based on the exhaust flow rate. One method of this calculation is to store a two-dimensional map of exhaust flow rate and estimated soot amount in control device 20 in advance, apply the actual exhaust flow rate to the two-dimensional map to obtain the current estimated soot amount at that time, and integrate this over the operating time of engine 1 (the time during which exhaust gas flows). The actual exhaust flow rate can be calculated from the intake flow rate detected by intake flow rate sensor 31, the engine speed detected by engine speed sensor 30, information on the opening degree of EGR valve 13, etc. Alternatively, an exhaust flow rate sensor may be provided in the exhaust passage to obtain the sensor value.

[0032] The amount of soot that accumulates in the exhaust passage 3 can also vary depending on the amount of soot contained in the exhaust (the proportion of soot in the exhaust, hereinafter referred to as "smoke concentration"). Note that the smoke concentration can vary depending on the operating conditions of the engine 1 (for example, the amount of fuel injection (air-fuel ratio), engine water temperature, etc.).

[0033] Therefore, it is more preferable that the calculation unit 21 calculates the estimated soot amount based on the exhaust flow rate and smoke concentration. One method of this calculation is to store in advance in the control device 20 a three-dimensional map of the exhaust flow rate, smoke concentration, and estimated soot amount, apply the actual exhaust flow rate and smoke concentration to the three-dimensional map to obtain the estimated soot amount at that time, and integrate this over the operating time of the engine 1 (the time during which the exhaust flows). The actual smoke concentration may be calculated using a formula, a map, etc. based on the operating state of the engine 1.

[0034] Alternatively, the amount of soot and the smoke concentration emitted during operation of the engine 1 may be regarded as fixed values, and the estimated soot amount may be calculated based only on the operation time of the engine 1. That is, the calculation unit 21 may calculate the estimated soot amount based only on the operation time (timer count value) of the engine 1. Although this method has lower calculation accuracy than the above two methods, it can be simplified because it does not require information such as calculation or detection of the exhaust flow rate, calculation of the smoke concentration, or two-dimensional or three-dimensional maps.

[0035] When the calculation unit 21 calculates or detects an exhaust flow rate that is large enough to blow away soot in the exhaust passage 3 due to the force of the exhaust, for example when the engine 1 is operating at high speed and high load, it is preferable that the calculation unit 21 resets the integrated value and the timer count value to 0. As a result, when soot is removed from the exhaust passage 3 during normal engine 1 operation, soot removal control is not performed, and unnecessary control is prevented from being performed.

[0036] The soot removal control unit 22 performs soot removal control when the estimated soot amount calculated by the calculation unit 21 exceeds a predetermined amount. In soot removal control, the soot accumulated in the exhaust passage 3 is blown off and removed (discharged) by increasing the exhaust flow rate of the engine 1. In other words, soot removal control is a physical method that utilizes the flow (momentum) of the exhaust. With this method, it is only necessary to temporarily increase the exhaust flow rate, so removal is completed in about a few seconds. The blown off soot can be collected by the filter 10 located downstream. If the filter 10 is not present, the blown off soot would be discharged directly from the tailpipe.

[0037] The condition for starting soot removal control is that the estimated amount of soot exceeds a predetermined amount. This predetermined amount may be a fixed value set in advance, or may be a variable value that can be changed depending on the operating state of the engine 1 and the state of the vehicle. For example, if the filter 10 is provided, the predetermined amount is set to a value that does not exceed the amount of PM that can be captured by the filter 10 (the capacity of the filter 10), and if the filter 10 is not provided, the predetermined amount is set to a value that can reliably prevent black smoke from being emitted from the tailpipe.

[0038] There are three methods for increasing the exhaust flow rate in soot removal control: Method 1: Increase engine speed Method 2: Increase the boost pressure Method 3: Close the EGR valve 13 (EGR opening = 0) These methods will be described below.

[0039] Method 1 is a method that can be implemented regardless of the devices (supercharger 4 and EGR system 11) equipped in the engine 1. Method 2 is a method that can be implemented when the engine 1 is equipped with a supercharger 4. Method 3 is a method that can be implemented when the engine 1 is equipped with a high-pressure EGR system 11. The soot removal control unit 22 can use these methods 1 to 3 alone or in combination, and preferably uses method 1, and also uses one or both of methods 2 and 3 depending on the devices equipped in the engine 1.

[0040] The soot removal control unit 22 of this embodiment uses Method 1 and, depending on the situation, also uses Method 2. That is, the soot removal control unit 22 first attempts to increase the exhaust flow rate by increasing the engine speed. There are two methods for increasing the engine speed: Method 1-1. Increase fuel injection amount with the clutch disengaged Method 1-2: Shift down and engage the clutch

[0041] The clutch here refers to a power connection / disconnection mechanism interposed on a power transmission path connecting the engine 1 and the drive wheels of the vehicle, and when the clutch is engaged, the power of the engine 1 is transmitted to the drive wheels, and when the clutch is disengaged, the power of the engine 1 is not transmitted to the drive wheels. The connection / disconnection state of the clutch may be controlled by the control device 20 (for example, the soot removal control unit 22), or may be controlled by an electronic control device separate from the control device 20, with the connection / disconnection state being transmitted to the control device 20. It is sufficient for the control device 20 to be able to at least grasp the connection / disconnection state of the clutch.

[0042] The soot removal control unit 22 selectively selects either method 1-1 or method 1-2 according to the vehicle's running state (more specifically, the accelerator opening) to perform soot removal control. This is because in method 1-1, the clutch is disengaged, and therefore the situation must be one in which there is no problem (no effect on running) even if the power of the engine 1 is no longer transmitted to the drive wheels, i.e., the accelerator must be released and the vehicle must be decelerating.

[0043] Therefore, the soot removal control unit 22 of this embodiment selects method 1-1 during deceleration with the accelerator off (accelerator opening degree is 0). Hereinafter, the soot removal control performed during deceleration with the accelerator off will also be referred to as "first soot removal control." When the accelerator is off, the engine speed will decrease if control is simply performed based on the driver's requested torque (mainly accelerator opening degree), but the first soot removal control increases the fuel injection amount with the clutch disengaged, so the engine speed is forcibly increased (regardless of the accelerator opening degree, which is the driver's intention).

[0044] In this case (i.e., when Method 1-1 is selected), the soot removal control unit 22 of this embodiment also uses the above-mentioned Method 2. That is, in the first soot removal control, the soot removal control unit 22 increases the engine speed with the clutch disengaged and increases the boost pressure of the turbocharger 4 to increase the exhaust flow rate. This temporarily increases the exhaust flow rate without affecting driving, and efficiently removes soot from the exhaust passage 3. Note that the soot removal control unit 22 may also use Method 3 at this timing. By closing the EGR valve 13, all of the increased amount of exhaust is used for soot removal.

[0045] There are three ways to increase the boost pressure: Method 2-1: Retard the fuel injection timing and supply exhaust energy to the turbocharger Method 2-2. For variable geometry turbochargers, reduce the opening of the variable vanes. Method 2-3. Electric turbochargers use electricity to turn the turbine. Both methods increase the intake flow rate, which results in an increase in the exhaust flow rate.

[0046] Method 2-1 is a method that can be implemented regardless of the type of turbocharger 4. By retarding the fuel injection timing, energy not used as engine output (energy not used to push the piston down) is discharged from the exhaust port. This exhaust energy is used by the turbocharger 4 to increase the boost pressure and increase the intake flow rate. Method 2-2 is a method that can be implemented when the turbocharger 4 is a variable geometry turbocharger, and by reducing the opening of the variable vanes, the rotation speed of the turbine blades increases, thereby increasing the intake flow rate. Method 2-3 is a method that can be implemented when the turbocharger 4 is an electric turbocharger (electric turbocharger), and increases the rotation speed of the turbine blades by using electricity to increase the intake flow rate. Note that in the case of an electric turbocharger, it is installed in the intake passage of the engine 1 and uses electricity instead of exhaust pressure to rotate the turbine. Methods 2-1 to 2-3 can be used independently, and Method 2-1 alone or in combination with Method 2-2 or 2-3.

[0047] The soot removal control unit 22 selects the above-described method 1-2 when the vehicle is traveling with an accelerator pedal stroke other than 0 and substantially constant. Hereinafter, the soot removal control performed when the vehicle is traveling with an accelerator pedal stroke other than 0 and substantially constant is also referred to as the "second soot removal control." During steady-state traveling without the accelerator pedal being released or accelerating, the clutch cannot be kept disengaged. Therefore, the soot removal control unit 22 increases the engine speed by downshifting and engaging the clutch. The second soot removal control can remove soot with the clutch engaged and increase the engine speed without increasing the fuel injection amount. However, there is a limit to the increase in engine speed associated with downshifting in method 1-2. This is because method 1-2 requires maintaining the traveling state, i.e., preventing a sudden change in vehicle speed before and after downshifting. Therefore, the increase in engine speed associated with downshifting is smaller than the increase in engine speed associated with disengaging the clutch and injecting more fuel. Therefore, method 1-1 has a higher soot removal capability than method 1-2.

[0048] During acceleration, such as when the accelerator pedal is depressed, the engine speed increases and the exhaust flow rate increases. In other words, during acceleration, there is a high possibility that the soot in the exhaust passage 3 will be blown away, so neither of the above methods 1-1 nor 1-2 is selected, and soot removal control is not performed.

[0049] [2-2. Playback Control] Next, regeneration control will be described. Regeneration control is a control that increases the exhaust gas temperature to burn off the PM trapped in the filter 10 and regenerate the function (capability) of the filter 10. In other words, regeneration control is a chemical method that uses oxygen in the exhaust gas to cause an oxidation reaction. This method requires increasing the exhaust gas temperature, so it takes longer than soot removal control, and removal is completed in, for example, several minutes to several tens of minutes.

[0050] The regeneration control is initiated when the operating state of the engine 1 is suitable for regenerating the filter 10 and a predetermined first initiation condition is met. The former condition (enablement condition) can be confirmed based on, for example, any of the following conditions A to C. Similarly, the latter condition (first initiation condition) can be confirmed based on, for example, any of the following conditions D to F.

[0051] Condition A: The engine speed is below the specified value. Condition B: Throttle opening is below the specified opening. Condition C: The engine water temperature is above the specified temperature. Condition D: The amount of PM accumulation is greater than the specified amount. Condition E: The differential pressure between the upstream pressure and the downstream pressure of the filter 10 is equal to or greater than a specified value. Condition F: A predetermined time has passed since the end of the previous playback control

[0052] The regeneration control unit 23 determines that it is possible to implement regeneration control (the implementation condition is met) when, for example, at least one of conditions A to C (preferably all three conditions) is met. Also, the regeneration control unit 23 determines that a first start condition for regeneration control is met when, for example, at least one of conditions D to F is met. The regeneration control unit 23 starts regeneration control when it determines that both the implementation condition and the first start condition are met, and does not implement regeneration control when it determines that at least one of the conditions is not met.

[0053] The engine speed, engine water temperature, and pressure difference of the filter 10 can be obtained from various sensors, and the throttle opening can be obtained from a control device (control device 20 or another control device) that controls the throttle valve 7. The amount of PM accumulation can be calculated (estimated) from the operating state of the engine 1, etc.

[0054] In this embodiment, when soot removal control is performed by the soot removal control unit 22, the regeneration control unit 23 starts regeneration control when a second start condition, which is a more relaxed version of the first start condition, is met. That is, the second start condition is set as a condition that makes it easier to start regeneration control than the first start condition. This is because when soot removal control is performed and soot is blown away, a large amount of soot (PM) adheres to the filter 10, increasing the possibility of clogging. In other words, by making it easier to perform regeneration control after soot removal control is performed, deterioration in the function of the filter 10 is suppressed.

[0055] The second start condition is, for example, that at least one of conditions d to f, which are obtained by relaxing the above conditions D to F, is satisfied. Condition d: The amount of PM accumulation is equal to or greater than the second specified amount (< specified amount). Condition e. The differential pressure is greater than the second specified value (< specified value). Condition f: A second predetermined time (< predetermined time) has elapsed since the end of the previous playback control

[0056] Alternatively, the regeneration control unit 23 may relax the first start condition by increasing the estimated PM accumulation amount or increasing the differential pressure, and then determining whether the above conditions D to F are met. In this way, instead of changing the specified amounts, specified values, etc. of conditions D to F, the second start condition may be set by correcting the values ​​to be compared with the specified amounts, specified values, etc. Hereinafter, when it is necessary to particularly distinguish between them, the regeneration control that is started when the first start condition (the start condition that is not relaxed) is met will be referred to as "normal regeneration control," and the regeneration control that is started when the second start condition is met will be referred to as "second regeneration control."

[0057] In the second regeneration control, the regeneration control unit 23 lowers the target value of the exhaust temperature (target exhaust temperature) compared to normal regeneration control. As described above, in the regeneration control, the exhaust temperature is increased to burn the PM trapped in the filter 10, but in the second regeneration control, a larger amount of PM is expected to be burned compared to normal regeneration control, so there is a possibility that the temperature of the filter 10 will become too high. Therefore, the regeneration control unit 23 lowers the target exhaust temperature in the second regeneration control than the target exhaust temperature in normal regeneration control. This prevents the temperature of the filter 10 from rising excessively.

[0058] Furthermore, the regeneration control unit 23 extends the execution time of the second regeneration control compared to the normal regeneration control. This is to eliminate the possibility that the second regeneration control will not completely incinerate the PM trapped in the filter 10, leaving some PM unburned, because the target exhaust gas temperature is set low. In other words, by extending the execution time of the control to compensate for the lowered target exhaust gas temperature, the unburned PM is eliminated and the filter 10 is reliably regenerated. The execution time of the regeneration control may be a preset fixed value, or may be a variable value determined from the differential pressure or the PM accumulation amount detected or estimated during the regeneration control. In either case, the execution time is corrected to be longer in the second regeneration control.

[0059] [3. Flowchart] Fig. 2 is an example of a flowchart for explaining the above-mentioned soot removal control, and Fig. 3 is an example of a flowchart for explaining the above-mentioned regeneration control. These two flowcharts are both executed by the control device 20, but are executed independently at a predetermined calculation cycle. However, the value of flag F, which will be described later, is shared between the two flowcharts.

[0060] First, the soot removal control will be described. As shown in FIG. 2, in step S1, various sensor information is acquired, and in step S2, the calculation unit 21 calculates the estimated soot amount based on the acquired information. In step S3, it is determined whether the estimated soot amount exceeds a first predetermined amount (a predetermined amount in the claims), and if it is equal to or less than the first predetermined amount, the flow returns. In this case, steps S1 to S3 are repeated from the next calculation cycle onwards. By constantly calculating the estimated soot amount in this way, it is possible to determine whether soot removal control is necessary using the latest estimated soot amount. For example, even if the estimated soot amount is approaching the first predetermined amount, if soot in the exhaust passage 3 is naturally blown away due to acceleration, the value of the estimated soot amount in step S2 will be small, and soot removal control will be suspended.

[0061] If the estimated soot amount exceeds the first predetermined amount in step S3, it is determined in step S4 whether the accelerator is off. If the accelerator is off, the first soot removal control can be performed, so the clutch is disengaged in step S5 and the first soot removal control is performed (step S6). Specifically, the engine speed is increased by increasing the fuel injection amount (method 1-1), and the boost pressure is increased using at least one of methods 2-1 to 2-3. At this time, the EGR valve 13 may be closed.

[0062] When the first soot removal control is completed, the clutch is brought into an engaged state in step S7. Then, in step S10, flag F is set to F=1, and this flow returns. Flag F is used to determine whether or not second regeneration control should be performed. Flag F is set to F=1 immediately after soot removal control is performed, and is reset to F=0 once regeneration control is performed. It is preferable that the estimated soot amount and the value of flag F are not reset even when the main power supply of the vehicle is turned off, but are carried over the next time the main power supply is turned on. This suppresses performance degradation of filter 10.

[0063] On the other hand, if it is determined in step S4 that the accelerator is not released, the process proceeds to step S8, where it is determined whether the estimated soot amount calculated in step S2 is equal to or greater than a second predetermined amount. If the estimated soot amount is less than the second predetermined amount, the process returns and starts again from step S1. In other words, even if the estimated soot amount exceeds the first predetermined amount, the first soot removal control is not started unless the accelerator is released. For this reason, for example, when steady driving continues for a long period of time on a highway, the soot in the exhaust passage 3 cannot be removed. The determination in step S8 is a process for performing the second soot removal control when a situation in which the first soot removal control cannot be performed continues for a long period of time. The second predetermined amount in step S8 is preset to a value greater than the first predetermined amount in step S3.

[0064] If the estimated soot amount is equal to or greater than the second predetermined amount in step S8, the process proceeds to step S9, where second soot removal control is performed. Specifically, the clutch is disengaged, then the transmission is quickly downshifted, and the clutch is re-engaged, thereby increasing the engine speed and transmitting engine output to the drive shaft (method 1-2). Note that in the second soot removal control, the boost pressure cannot be increased, but the EGR valve 13 may be closed. When the second soot removal control is completed, the process proceeds to step S10, where flag F is set to F=1, and the flow returns.

[0065] Next, the regeneration control will be described. As shown in Fig. 3, in step R1, various sensor information is acquired, and in step R2, it is determined whether or not flag F is F = 0. If flag F is F = 0, that is, if soot removal control has not yet been performed, the process proceeds to step R3, where it is determined whether or not a first start condition for regeneration control is satisfied. If the first start condition is not satisfied, the process returns, and if the first start condition is satisfied, normal regeneration control is performed in step R4. When normal regeneration control is completed, the process proceeds to step R7, where flag F remains at F = 0, and the process returns.

[0066] On the other hand, if flag F is F=1 in step R2, that is, if soot removal control has been performed, the process proceeds to step R5, where it is determined whether a second start condition for regeneration control is met. If the second start condition is not met, the process returns. If the second start condition is met, the second regeneration control is performed in step R6. After the second regeneration control is completed, the process proceeds to step R7, where flag F is reset to F=0, and the process returns.

[0067] [4. Actions and Effects] (1) In the control device 20 described above, the calculation unit 21 calculates the amount of soot present in the exhaust passage 3 as an estimated soot amount, and the soot removal control unit 22 performs soot removal control to remove soot by increasing the exhaust flow rate of the engine 1 when the calculated estimated soot amount exceeds a predetermined amount. In this way, the soot can be blown away by increasing the exhaust flow rate, soot can be removed automatically (in other words, without bothering the driver), improving convenience while ensuring engine performance. Furthermore, by removing soot before it exceeds the predetermined amount and accumulates in the exhaust passage 3, it is possible to prevent a large amount of soot from being released all at once. This makes it possible to prevent soot accumulated in the exhaust passage 3 from being emitted as black smoke.

[0068] (2) In the soot removal control, the soot removal control unit 22 increases the exhaust flow rate by increasing the engine speed. Therefore, the exhaust flow rate can be increased in a simple manner, regardless of the equipment provided in the engine 1, and soot can be blown away.

[0069] (3) Furthermore, the above-described control device 20 is applied to a vehicle equipped with an engine 1 equipped with a turbocharger 4 and a clutch, and the above-described soot removal control unit 22 performs the first soot removal control during deceleration with the accelerator released. Specifically, the exhaust flow rate is increased by increasing the engine speed and increasing the boost pressure of the turbocharger 4 while the clutch is disengaged. In other words, when the clutch is disengaged during deceleration, the output of the engine 1 is no longer transmitted to the drive wheels, so increasing the engine speed and increasing the boost pressure does not affect the running state of the vehicle. Therefore, by performing the first soot removal control during deceleration with the accelerator released, the exhaust flow rate can be increased efficiently and soot can be effectively removed.

[0070] (4) The soot removal control unit 22 also performs the second soot removal control when the vehicle is traveling at a substantially constant accelerator pedal stroke other than 0 (steady driving). Specifically, the engine speed is increased by engaging the clutch immediately after downshifting, thereby increasing the exhaust flow rate. In other words, when the vehicle is traveling with the accelerator pedal depressed at a substantially constant stroke, the clutch is not disengaged, so the engine speed is increased by downshifting. This allows soot to be removed without affecting driving.

[0071] Furthermore, as in the above embodiment, if the second soot removal control is performed when a situation in which the first soot removal control cannot be performed continues for a long period of time, it is possible to reliably prevent the soot in the exhaust passage 3 from being discharged as black smoke, thereby ensuring engine performance.

[0072] (5) The above-described control device 20 is applied to an engine 1 having a filter 10 installed in the exhaust passage 3, and when a predetermined first start condition is met, the regeneration control unit 23 performs regeneration control, separate from the soot removal control, to increase the exhaust temperature of the engine 1 and burn off PM trapped on the filter 10. When the soot removal control unit 22 performs soot removal control, the regeneration control unit 23 starts regeneration control when a second start condition, which is a more relaxed version of the first start condition, is met. This is because it is expected that a large amount of soot blown away by the soot removal control will adhere to the filter 10 located downstream. For this reason, by relaxing the condition for starting regeneration control when soot removal control is performed, clogging of the filter 10 can be prevented, and degradation of the function of the filter 10 can be prevented.

[0073] (6) In the second regeneration control started in response to the second start condition being satisfied, the regeneration control unit 23 lowers the target value of the exhaust gas temperature compared to the normal regeneration control. In the second regeneration control, there is a possibility that the temperature of the filter 10 may rise excessively due to the burning of a large amount of soot. However, by setting the target exhaust gas temperature for the second regeneration control lower than the target exhaust gas temperature for the normal regeneration control, it is possible to prevent the temperature of the filter 10 from rising excessively, and to protect the filter 10.

[0074] (7) Furthermore, the regeneration control unit 23 performs the second regeneration control for a longer period of time than the normal regeneration control. As a result, even if the target value of the exhaust gas temperature is lowered in the second regeneration control, the longer regeneration time ensures that the PM trapped on the filter 10 can be regenerated by burning it.

[0075] [5. Other] The configurations of the engine 1 and the control device 20 described above are both examples. For example, the engine may not be equipped with the filter 10, or the engine may not be equipped with the turbocharger 4. If the engine 1 is not equipped with the filter 10, the regeneration control unit 23 may be omitted. Alternatively, if the engine 1 is equipped with another catalyst in addition to the catalyst 9 and the filter 10, the control device 20 may perform control related to the other catalyst.

[0076] The soot removal control unit 22 described above performs the first soot removal control and the second soot removal control, but may perform only one of them. Furthermore, in the soot removal control, it is not necessary to use Method 1 for increasing the engine speed. To increase the exhaust flow rate, the various methods described above may be used alone or in combination.

[0077] In the above-described embodiment, the engine 1 is mounted on a vehicle, but the present invention is not intended to be limited to vehicles. For example, the control device 20 (exhaust control device) may be applied to an engine mounted on a ship or an aircraft, or may be applied to an engine built into a generator or industrial machine. [Explanation of symbols]

[0078] 1. Engine (internal combustion engine) 2 Intake passage 3 Exhaust passage 4. Turbocharger 10 Filters 20 Control device (exhaust control device) 21 Calculation section 22 soot removal control unit (first control unit) 23 Playback control unit (second control unit)

Claims

1. a calculation unit that calculates an amount of soot present in an exhaust passage of the internal combustion engine as an estimated soot amount; a first control unit that performs soot removal control to remove the soot by increasing an exhaust flow rate of the internal combustion engine when the estimated soot amount exceeds a predetermined amount, the internal combustion engine is provided with a filter interposed in the exhaust passage to capture particulate matter contained in the exhaust gas of the internal combustion engine, The exhaust control device further includes a second control unit that, when a predetermined first start condition is satisfied, performs regeneration control to increase an exhaust temperature of the internal combustion engine to incinerate the particulate matter trapped in the filter, When the soot removal control is performed by the first control unit, the second control unit starts the regeneration control when a second start condition that is a relaxed version of the first start condition is met. An exhaust control device for an internal combustion engine.

2. The first control unit increases the exhaust flow rate by increasing the rotation speed of the internal combustion engine in the soot removal control.

2. An exhaust control device for an internal combustion engine according to claim 1.

3. the internal combustion engine; a clutch interposed on a power transmission path connecting the internal combustion engine and drive wheels; a supercharger that is installed in an intake passage of the internal combustion engine and supercharges intake air, When decelerating with the accelerator released, the first control unit increases the rotation speed of the internal combustion engine and increases the supercharging pressure of the supercharger in the soot removal control while the clutch is in a disengaged state, thereby increasing the exhaust flow rate.

3. An exhaust control device for an internal combustion engine according to claim 2.

4. the internal combustion engine; a clutch interposed in a power transmission path connecting the internal combustion engine and drive wheels, The first control unit, during the soot removal control, when the vehicle is traveling with an accelerator opening degree other than 0 and substantially constant, shifts down and engages the clutch to increase the rotation speed of the internal combustion engine and increase the exhaust flow rate.

4. An exhaust control device for an internal combustion engine according to claim 2 or 3.

5. The second control unit, in the second regeneration control started in response to the second start condition being satisfied, lowers the target value of the exhaust gas temperature compared to the normal regeneration control started in response to the first start condition being satisfied.

4. An exhaust control device for an internal combustion engine according to claim 1.

6. The second control unit extends the execution time of the second regeneration control compared to the normal regeneration control.

6. An exhaust control device for an internal combustion engine according to claim 5.

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