Controller and control method for an internal combustion engine

Abstract

A controller is configured to perform a process for obtaining an exhaust pressure upstream of a filter inside an exhaust passage and an intake air amount detected by an air flow meter when the filter in which a deposition amount of particulate matter is a specified amount is referred to as a reference filter, a calculation process for calculating an exhaust pressure rate indicating a ratio of the obtained exhaust pressure to an exhaust pressure at the reference filter for the obtained intake air amount, and an adjustment process for adjusting the exhaust pressure rate maintained at a specific value during engine operation.

Description

BACKGROUND1. Area

[0001] The following description relates to a controller and a control method for an internal combustion engine. 2. Description of the state of the art

[0002] JP H11-280449 A describes an example of an internal combustion engine including a filter that collects particulate matter from exhaust gas and a pressure sensor that detects exhaust pressure upstream of the filter. In the internal combustion engine, the exhaust pressure detected by the pressure sensor increases as the amount of intake air drawn into the cylinders increases or the amount of particulate matter deposited in the filter increases, and the degree of clogging increases even if the intake air amount remains the same.

[0003] The internal combustion engine performs various types of engine controls based on the exhaust gas pressure, such as adjusting the opening degree of the EGR valve and calculating the intake air quantity using an air model.

[0004] During machine operation, the exhaust pressure fluctuates and exhibits unstable values. Thus, machine control based on exhaust pressure is unstable. It is desirable that values indicating the state of exhaust pressure during machine operation be as stable as possible while still indicating the actual state of exhaust pressure.

[0005] A controller according to the preamble of the independent claims is known from JP H08 - 109 818 A. Further prior art can be found in US 2007 / 0 180 818 A1 and JP 2008 - 157 187 A. SUMMARY

[0006] Based on the prior art, the object of the present invention is to provide a controller and a control method for an internal combustion engine that stabilize values indicating the state of an exhaust pressure during engine operation. This object is achieved from a device-related perspective by the controller having the features of claim 1 and from a process-related perspective by the control method according to claim 7; advantageous developments are the subject of the dependent claims.

[0007] This Summary is provided to introduce, in a simplified form, a selection of concepts further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0008] In a first general aspect, a first embodiment of the present invention provides a controller for an internal combustion engine. The internal combustion engine includes a filter disposed in an exhaust passage and collecting particulate matter from exhaust gas, and an intake flow rate sensor that detects an intake air amount drawn into a cylinder. The filter in which a deposition amount of particulate matter is a specified amount is referred to as a reference filter.The controller is configured to perform a process for obtaining an exhaust pressure upstream of the filter inside the exhaust passage and the intake air amount detected by the intake flow rate filter, a calculation process for calculating an exhaust pressure rate indicating a ratio of the obtained exhaust pressure to an exhaust pressure at the reference filter for the obtained intake air amount, a setting process for setting the exhaust pressure rate maintained at a specific value during engine operation, and a tracking process of a change in the exhaust pressure rate set during engine operation in accordance with a change in the obtained exhaust pressure when the exhaust pressure rate maintained at a specific value deviates from an actual state of the exhaust pressure.Here, a value of the exhaust pressure rate maintained at the concrete value is referred to as a fixed value, a value of the exhaust pressure rate changed in the tracking process is referred to as a tracking value, a condition in which a changed amount of the deposit amount is less than or equal to a preset value is defined as a first condition, and a condition in which a difference between the fixed value and the tracking value is less than or equal to a preset value is defined as a second condition.According to the invention, the controller is configured to: immediately perform switching from the fixed value to the tracking value when at least one of the first condition or the second condition is satisfied when a value of the exhaust pressure rate set during engine operation is switched from the fixed value to the tracking value, and perform switching from the fixed value to the tracking value while the engine operation is at idle when neither the first condition nor the second condition is satisfied.

[0009] In another general aspect, a second embodiment of the present invention provides a control method for an internal combustion engine. The internal combustion engine includes a filter disposed in an exhaust passage and collecting particulate matter from exhaust gas, and an intake flow rate sensor that detects an intake air amount drawn into a cylinder. The filter in which a deposition amount of particulate matter is a specified amount is referred to as a reference filter.The control method includes obtaining an exhaust pressure upstream of the filter inside the exhaust passage and the intake air amount detected by the intake flow rate sensor, calculating an exhaust pressure rate indicating a ratio of the obtained exhaust pressure to an exhaust pressure at the reference filter for the obtained intake air amount, setting the exhaust pressure rate maintained at a specific value during engine operation, and performing a tracking process of a change in the exhaust pressure rate set during engine operation in accordance with a change in the obtained exhaust pressure when the exhaust pressure rate maintained at a specific value deviates from an actual state of the exhaust pressure.Here, a value of the exhaust pressure rate maintained at the concrete value is referred to as a fixed value, a value of the exhaust pressure rate changed in the tracking process is referred to as a tracking value, a condition in which a changed amount of the deposit amount is less than or equal to a preset value is defined as a first condition, and a condition in which a difference between the fixed value and the tracking value is less than or equal to a preset value is defined as a second condition.The control method according to the invention further comprises: immediately switching from the fixed value to the tracking value when at least one of the first condition or the second condition is satisfied when a value of the exhaust pressure rate set during engine operation is switched from the fixed value to the tracking value, and switching from the fixed value to the tracking value while the engine operation is idling when neither the first condition nor the second condition is satisfied.

[0010] Further features and aspects will become apparent from the following detailed description, drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram of an internal combustion engine employing a controller according to a first embodiment of the present invention. Fig. Figure 2 is a flowchart showing the procedure of operations performed by the controller. Fig. 3 is a graph showing the relationship between a temperature difference and a correction coefficient. Fig. 4 is a graph showing the relationship between an exhaust pressure upstream of a filter and an intake air amount. Fig. Figure 5 is a flowchart showing the procedure of operations performed by the controller. Fig. Figure 6 is a flowchart showing the procedure of operations performed by the controller. Fig. 7 is a flowchart showing the procedure of operations performed by a controller according to a second embodiment of the present invention. Fig. 8 is a graph showing the relationship between an intake air amount and a set parameter. Fig. Figure 9 is a flowchart showing the procedure of operations performed by the controller. Fig. 10 is a flowchart showing the procedure of operations performed by a controller according to a third embodiment of the present invention.

[0011] Throughout the drawings and detailed description, the same reference numerals refer to the same elements. The drawings may not be to scale, and the relative size, proportions, and representation of elements in the drawings may be exaggerated for clarity, illustration, and simplification. DETAILED DESCRIPTION

[0012] This description provides a comprehensive understanding of the described methods, devices, and / or systems. Modifications and equivalents of the described methods, devices, and / or systems will be apparent to one skilled in the art. Procedures and operations are examples and may be changed as would be apparent to one skilled in the art, except for operations that necessarily occur in a certain order. Descriptions of functions and structures known to one skilled in the art may be omitted.

[0013] Embodiments may take various forms and are not limited to the examples described. However, the examples described are thorough and complete, and will fully convey the scope of the invention to those skilled in the art. First embodiment

[0014] A controller 100 for an internal combustion engine 10 according to a first embodiment will now be described with reference to Fig. 1 to Fig. 6 described.

[0015] As in Fig. As shown in Figure 1, the internal combustion engine 10 includes cylinders 10a. The intake port for the cylinders 10a is connected to an intake port 13. The intake port 13 includes a throttle valve 14 that adjusts an intake air quantity.

[0016] The combustion chambers of the cylinders 10a each contain a fuel injection valve 11. In the combustion chamber, air drawn in through the intake port 13 mixes with fuel injected through the fuel injection valve 11, forming an air-fuel mixture. The air-fuel mixture is ignited by a spark discharge and combusted in the combustion chamber. Exhaust gas generated when the air-fuel mixture is combusted is discharged from the exhaust port of the internal combustion engine 10 into an exhaust passage 15.

[0017] The exhaust passage 15 is connected to a three-way catalyst 17. The three-way catalyst 17 oxidizes hydrocarbons (HC) and carbon monoxide (CO) contained in the exhaust gas, producing water and carbon dioxide. The three-way catalyst 17 reduces nitrogen oxides (NOx) contained in the exhaust gas, producing nitrogen.

[0018] The exhaust passage 15, downstream of the three-way catalyst 17, contains a filter 18 that collects particulate matter (PM) in the exhaust gas. The internal combustion engine 10 includes an exhaust gas recirculation device that recirculates a portion of the exhaust gas into the intake passage 13. The exhaust gas recirculation device includes an EGR passage 20, an EGR cooler 21, and an EGR valve 22.

[0019] The EGR passage 20 connects the exhaust passage 15 to the intake passage 13. The EGR passage 20 connects the exhaust passage 15, which is arranged between the three-way catalyst 17 and the filter 18, to the intake passage 13, which is downstream of the throttle valve 14.

[0020] The EGR valve 22 is arranged in the EGR passage 20. When the EGR valve 22 is open, exhaust gas (EGR gas) flows into the EGR passage 20. The water-cooled EGR cooler 21 is arranged in the EGR passage 20 between the EGR valve 22 and the exhaust passage 15. Heat is exchanged between the EGR cooler 21 and an engine coolant.

[0021] The internal combustion engine 10 includes the controller 100, which includes a central processing unit (CPU), a memory, and the like. The controller 100 performs various types of controls and various types of operations for the internal combustion engine 10 by causing the CPU to execute programs stored in the memory.

[0022] Detection signals from various types of sensors are input to the controller 100. For example, a pressure sensor 50 is arranged in the exhaust passage 15 between the three-way catalyst 17 and the filter 18. The pressure sensor 50 detects an exhaust pressure EP (absolute pressure) upstream of the filter 18. The pressure sensor 50 also detects a differential pressure ΔP indicating the difference between the exhaust pressure EP and an atmospheric pressure. The differential pressure ΔP is used as a value indicating the pressure difference in the exhaust passage 15 between the exhaust pressure upstream of the filter 18 and the exhaust pressure downstream of the filter 18. The internal combustion engine 10 includes a crank angle sensor 53 near the crankshaft. The crank angle sensor 53 detects an engine speed NE of the internal combustion engine 10. An air flow meter 54 serving as an intake flow rate sensor is arranged upstream of the intake port 13.The air flow meter 54 detects an intake air quantity GA which is drawn into the cylinders 10a.

[0023] The controller 100 calculates an exhaust temperature THE, which is the temperature of the exhaust gas flowing into the filter 18, and a filter temperature TF, which is an estimated temperature of the filter 18, based on various engine operating conditions such as the intake air amount GA and the engine speed NE. The engine controller 100 also calculates a PM deposition amount Ps, which is a deposition amount of particulate matter of the filter 18, based on the engine speed NE, an engine load factor KL, the filter temperature TF, and the like.

[0024] When the PM deposition amount Ps is greater than or equal to a preset regeneration threshold α, the controller 100 performs regeneration control on the filter 18 to burn and remove the PM deposited in the filter 18 to regenerate the filter 18. The regeneration control includes a temperature increase control that heats the filter 18 and a PM combustion control that burns and removes the PM. PM is burned and removed when the atmosphere inside the filter 18, which is heated by the temperature increase control, becomes an oxidizing atmosphere.

[0025] In the first embodiment, the temperature increase control performs dither control so that some of the cylinders 10a of the internal combustion engine 10 serve as rich combustion cylinders and the other cylinders 10a serve as lean combustion cylinders. The rich combustion cylinders have an air-fuel ratio richer than the stoichiometric air-fuel ratio. The lean combustion cylinders have an air-fuel ratio leaner than the stoichiometric air-fuel ratio. When the dither control is performed, unburned fuel components and incompletely combustion components in exhaust gas discharged through the rich combustion cylinders react with oxygen in exhaust gas discharged through the lean combustion cylinders. The reaction is accelerated by the three-way catalyst 17, and the three-way catalyst 17 is heated.The heated three-way catalyst 17 raises the temperature of the exhaust gas passing through the three-way catalyst 17. When high-temperature exhaust gas flows into the filter 18 downstream of the three-way catalyst 17, the filter 18 has a high temperature. The PM combustion control, by which the atmosphere inside the high-temperature filter 18 becomes an oxidizing atmosphere, performs a fuel cut operation that stops fuel injection from the fuel injection valves 11 during engine operation and a lean combustion operation that sets a value leaner than the stoichiometric air-fuel ratio to a target air-fuel ratio for an air-fuel mixture. This provides oxygen to the exhaust passage 15, so that the PM collected in the filter 18 is burned (oxidized) and eliminated.

[0026] The controller 100 calculates a target EGR rate EGp as a command value for adjusting the exhaust gas amount (EGR amount) flowing into the intake passage 13 via the EGR passage 20, based on the engine speed NE and the engine load factor KL. The EGR rate is the ratio of the EGR amount to the total amount of in-cylinder charge gas. The controller 100 calculates a target opening degree of the EGR valve 22 by which an actual EGR rate becomes equal to the target EGR rate EGp, based on the target EGR rate EGp, the intake air amount GA, and the predicted exhaust pressure value EPc, which are described below. Then, the controller 100 adjusts the opening amount of the EGR valve 22 so that an actual opening degree of the EGR valve 22 becomes equal to the target opening degree.

[0027] The controller 100 calculates the subsequent exhaust pressure increase rate as a value indicating a state of exhaust pressure corresponding to the clogging degree in the current filter 18. The exhaust pressure below is the pressure of exhaust gas between the filter 18 and the three-way catalyst 17.

[0028] Fig. Figure 2 shows the sequence of operations performed by the controller 100 to calculate the exhaust pressure increase rate. This procedure is repeatedly performed when the filter 18 is not regenerated during engine operation. In the following description, the number of each step begins with the letter "S."

[0029] When the processing begins, the controller 100 determines whether the intake air amount GA and the exhaust pressure EP are stable (S100). If a state in which a fluctuation amount of the intake air amount GA and the exhaust pressure EP is within a specified range has continued for a specified period of time or longer, the controller 100 determines in S100 that the intake air amount GA and the exhaust pressure EP are stable. If the intake air amount GA and the exhaust pressure EP are not stable (S100: NO), the controller 100 ends the processing.

[0030] On the other hand, when the intake air amount GA and the exhaust pressure EP are stable (S 100: YES), the controller 100 obtains the currently detected intake air amount GA and exhaust pressure EP (S 110).

[0031] Then, the controller 100 calculates a temperature difference ΔT between a currently detected exhaust temperature THE and the reference temperature THbase (S 120). The temperature difference ΔT is a value obtained by subtracting the reference temperature THbase from the exhaust temperature THE. The reference temperature THbase is the exhaust temperature THE obtained by measuring the relationship between the intake air amount and the exhaust pressure at the subsequent first reference filter and the second reference filter.

[0032] Then, the controller 100 calculates a correction coefficient K (K > 0) based on the temperature difference ΔT (S130). The correction coefficient K is a value for correcting an obtained exhaust pressure EP based on the temperature difference ΔT.

[0033] As in Fig. 3, when the temperature difference ΔT is 0 (exhaust gas temperature THE = reference temperature THbase), 1 is set as the correction coefficient K. When the temperature difference ΔT is greater than 0 (exhaust gas temperature THE > reference temperature THbase), the value of the calculated correction coefficient K becomes smaller than 1 as the absolute value of the temperature difference ΔT increases. When the temperature difference ΔT is less than 0 (exhaust gas temperature THE < reference temperature THbase), the value of the calculated correction coefficient K becomes larger than 1 as the absolute value of the temperature difference ΔT increases.

[0034] Then, the controller 100 calculates the corrected exhaust pressure EPh by multiplying the obtained exhaust pressure EP by the correction coefficient K (S140). The corrected exhaust pressure EPh is a value obtained by converting the exhaust pressure EP at the current exhaust temperature THE into an exhaust pressure at the reference temperature THbase.

[0035] Then, the controller 100 calculates a first exhaust pressure EPn and a second exhaust pressure EPe to obtain the intake air amount GA (S150). The first exhaust pressure EPn and the second exhaust pressure EPe are the following values.

[0036] In the first embodiment, an unused filter 18 having 0 deposition amounts of particulate matter serves as the first reference filter. A filter 18 having the assumed maximum deposition amount of particulate matter serves as the second reference filter. The relationship between the intake air amount and the exhaust gas pressure in the first reference filter is measured in advance when the exhaust gas temperature THE is the reference temperature THbase. The relationship between the measured intake air amount and the exhaust gas pressure is stored as first reference exhaust gas pressure data in a memory.

[0037] As shown by line L1 with one long dash and double short dashes in Fig. As shown in Figure 4, the first reference exhaust pressure data shows a higher value of the exhaust pressure as the intake air amount increases. Similarly, the relationship between the intake air amount and the exhaust pressure is measured in advance in the second reference filter when the exhaust temperature THE is the reference temperature THbase. The relationship between the measured intake air amount and the exhaust pressure is stored in the memory as second reference exhaust pressure data.

[0038] As indicated by line L2 with one long dash and double short dashes in Fig. As shown in Figure 4, the second reference exhaust pressure data has a higher value of the exhaust pressure as the intake air amount increases. When the intake air amount is the same, the exhaust pressure in the second reference exhaust pressure data is higher than the exhaust pressure in the first reference exhaust pressure data.

[0039] The controller 100 refers to the first reference exhaust pressure data when calculating the first exhaust pressure EPn, which is the exhaust pressure at the first reference filter, for the intake air amount GA obtained in S110.

[0040] Similarly, the controller 100 refers to the second reference exhaust pressure data when calculating the second exhaust pressure EPe, which is an exhaust pressure at the second reference filter, for the intake air amount GA obtained in S110.

[0041] Then, the controller 100 calculates an instantaneous value EPrs of the exhaust pressure increase rate EPr based on the following equation (1) (S160). The exhaust pressure increase rate EPr is an exhaust pressure rate indicating the ratio of an obtained exhaust pressure to an exhaust pressure at a reference filter for an obtained intake air amount. The instantaneous value EPrs indicates an instantaneous value of the exhaust pressure increase rate EPr calculated from the intake air amount GA and the exhaust pressure EP obtained in this process. EPrs=(EPh−EPn) / (Epe−EPn)×100 EPrs: Instantaneous value of the exhaust pressure increase rate EPr EPh: corrected exhaust pressure EPn: first exhaust pressure EPe: second exhaust pressure

[0042] As understood from equation (1), the exhaust pressure increase rate EPr indicates the increase rate in an exhaust pressure of the current filter 18 when the exhaust pressure increase rate EPr at the first reference filter is 0% and the exhaust pressure increase rate EPr at the second reference filter is 100%.

[0043] Then, the controller 100 stores the calculated instantaneous value EPrs in the memory (S170) and terminates the process. The memory of the controller 100 stores calculated instantaneous values EPrs sequentially.

[0044] Fig. Figure 5 shows the procedure of operations for setting the exhaust pressure increase rate EPr to be maintained at a specific value during engine operation. This procedure is performed by the CPU executing programs stored in the memory of the controller 100 at predetermined intervals.

[0045] When the procedure begins, the controller 100 first determines whether the engine has been stopped (S200). If a switch that stops the operation of the internal combustion engine 10 has been operated, the controller 100 determines in S200 that the engine has been stopped. The switch in this case may be an ignition switch disposed in the vehicle containing the internal combustion engine 10. If the engine has not been stopped (S200: NO), the controller 100 repeatedly performs the process in S200 until it is determined that the engine has been stopped.

[0046] When the engine is stopped (S200: YES), the controller 100 calculates an average value AV of the instantaneous values EPrs calculated in a single trip (S210). The controller 100 sets the exhaust pressure increase rate EPr, which is maintained at a specific value during engine operation, to the calculated average value AV (S220). Then, the controller 100 terminates the process.

[0047] The set exhaust pressure increase rate EPr is used as the exhaust pressure increase rate EPr that is maintained at a specific value during the next engine operation. The exhaust pressure increase rate EPr is a value indicating a state of exhaust pressure corresponding to a current clogging degree in the filter 18. The exhaust pressure increase rate EPr is used for various types of engine controls related to exhaust pressure. When an intake air amount is predicted using an air model, for example, an exhaust pressure increase rate EPr is used as a value indicating the pressure state inside the exhaust passage 15. A predicted exhaust pressure value EPc, which is used to calculate a target opening degree of the EGR valve 22, is calculated as described below.

[0048] The first embodiment predicts in advance the exhaust pressure EP obtained when the intake air amount GA reaches a target intake air amount GAp set in accordance with an engine operating condition. Thus, the controller 100 calculates the predicted exhaust pressure value EPc as a predicted value of the exhaust pressure EP and executes the Fig. 6 procedures shown.

[0049] Fig. 6 shows the procedure of operations for calculating the predicted exhaust pressure value EPc. The procedure is performed by the CPU executing programs stored in the memory of the controller 100. The operations are performed to calculate a target opening degree of the EGR valve 22.

[0050] When the procedure begins, the controller 100 first obtains the currently set target intake air amount GAp and exhaust pressure increase rate EPr (S300). Then, the controller 100 calculates a first exhaust pressure EPn and a second exhaust pressure EPe for the obtained target intake air amount GAp (S310). In S310, the controller 100 refers to the first reference exhaust pressure data when calculating the first exhaust pressure EPn, which is an exhaust pressure at the first reference filter, for the obtained target intake air amount GAp.

[0051] Similarly, the controller 100 refers to the second reference exhaust pressure data when calculating the second exhaust pressure EPe, which is an exhaust pressure at the second reference filter, for the obtained target intake air amount GAp.

[0052] Then, the controller 100 calculates the predicted exhaust pressure value EPc based on the following equation (2) (S320). EPc=Epn+(EPe−EPn)×EPr / 100 EPc: predicted exhaust pressure value EPn: first exhaust pressure EPe: second exhaust pressure EPr: Exhaust pressure increase rate

[0053] The predicted exhaust pressure value ePc is calculated from equation (2). As in Fig. 4, an exhaust pressure (predicted exhaust pressure value EPc) obtained when the intake air amount reaches the target intake air amount GAp is calculated in advance based on the exhaust pressure increase rate EPr at the current filter 18, which is indicated by line 3 with alternating long and short dashes.

[0054] The first embodiment achieves the following advantages. (1) The exhaust pressure state corresponding to the clogging degree in the current filter 18 influences the exhaust pressure increase rate EPr based on the first reference filter and the second reference filter. The exhaust pressure increase rate EPr is maintained at a specific value during engine operation, so the exhaust pressure increase rate EPr, which is a value indicative of an exhaust pressure state, is stable during engine operation. Thus, engine control based on the value indicative of the exhaust pressure state is stable. (2) Even if the intake air amount is the same, the exhaust pressure EP increases as the temperature of the exhaust gas increases, so the value of the exhaust pressure increase rate EPr increases. In this regard, the first embodiment corrects the calculated exhaust pressure increase rate EPr to decrease as the temperature of the exhaust gas flowing into the filter 18 increases. More specifically, when the value of the temperature difference ΔT increases and the exhaust temperature THE is higher than the reference temperature THbase, the correction coefficient K is reduced to correct the exhaust pressure EP to decrease it. When the corrected exhaust pressure EPh is lower, the value of (EPh - EPn) in equation (1) becomes smaller, so the value of the calculated instantaneous value EPrs is reduced. This reduces the exhaust pressure increase rate EPr, which is an average value AV of multiple instantaneous values EPrs.In this way, the exhaust pressure increase rate EPr is corrected to decrease as the exhaust temperature THE increases, thereby reducing an error in the exhaust pressure increase rate EPr caused by a difference in exhaust temperatures. With this structure, the exhaust pressure rate can be directly corrected based on the exhaust temperature. Alternatively, the exhaust pressure rate can be indirectly corrected by correcting an obtained exhaust pressure based on the exhaust temperature. (3) In Fig. 2, the instantaneous value EPrs of the exhaust pressure increase rate EPr is calculated each time the exhaust pressure EP and the intake air amount GA are obtained. During engine operation, the amount of particulate matter deposited in the filter 18 hardly increases rapidly. Thus, an average value of the plurality of instantaneous values EPrs calculated during engine operation will be a value approximating a true value indicative of the state of exhaust pressure of the current filter 18. Thus, in the first embodiment, a value of the exhaust pressure increase rate EPr maintained at a specific value during engine operation is set to the average value AV of the instantaneous values EPrs. This allows the exhaust pressure increase rate EPr maintained at a specific value during engine operation to be set to an appropriate value. (4) The Fig. The operations shown in FIG. 6 are performed to predict the exhaust pressure EP when the intake air amount GA reaches the target intake air amount GAp. Since an exhaust pressure can be predicted when the intake air amount reaches the target value, the predicted value can be used for engine control. For example, a target opening degree of the EGR valve 22 is set in consideration of a value of the predicted exhaust pressure EP (predicted exhaust pressure value EPc). This limits a deviation between an actual EGR rate and a target EGR rate EGp when the intake air amount GA reaches the target intake air amount GAp, thereby improving the accuracy of EGR rate control. Second embodiment

[0055] The controller 100 for the internal combustion engine 10 according to a second embodiment will now be described with reference to Fig. 7 to Fig. 9 described.

[0056] In the first embodiment, the exhaust pressure increase rate EPr is maintained at a specific value during engine operation. The second embodiment, on the other hand, performs a tracking process of a change in the exhaust pressure increase rate EPr set during engine operation in accordance with a change in the obtained exhaust pressure EP when the exhaust pressure increase rate EPr maintained at a specific value during engine operation deviates from an actual exhaust pressure state.

[0057] Fig. Fig. 7 is a flowchart showing the procedure of operations performed by the controller 100. This procedure is repeatedly performed when the Fig. 2 is calculated. When the procedure begins, the controller 100 sets a parameter PR based on the intake air amount GA (S400). The parameter PR is used to calculate a moving average MAV of the instantaneous values EPrs.

[0058] As in Fig. As shown in Figure 8, the parameter PR is variably set to decrease as the intake air amount GA increases. Then, the controller 100 calculates the moving average MAV of the instantaneous values EPrs based on the parameter PR set in S400 (S410).

[0059] Then, the controller 100 sets a tracking value EPrt of the exhaust pressure increase rate EPr to calculate the moving average MAV (S420), and ends the process. In this way, the controller 100 also calculates the tracking value EPrt when calculating the average value EPrs during engine operation.

[0060] The procedure of operations for setting a fixed value or a tracking value to the exhaust pressure increase rate EPr set during engine operation will now be described with reference to Fig. 9. This procedure is repeatedly performed by the controller 100 during machine operation.

[0061] The fixed value is a value of the exhaust pressure increase rate maintained at a specific value during engine operation. The fixed value corresponds to the average value AV. The tracking value is a value of the exhaust pressure increase rate adjusted in accordance with a change in the exhaust pressure EP obtained during engine operation. The tracking value corresponds to the tracking value EPrt. In the Fig. In the series of operations shown in Figure 2, the value of the calculated instantaneous value EPrs is also changed when the value of the obtained exhaust pressure EP is changed. Thus, the tracking value EPrt is also changed when the value of the obtained exhaust pressure EP is changed. A mode by which the exhaust pressure increase rate EPr set during engine operation is a fixed value is referred to as a fixed mode. A mode by which the exhaust pressure increase rate EPr set during engine operation is a tracking value is referred to as a tracking mode.

[0062] When the procedure begins, the controller 100 first determines whether the current mode is a fixed mode (S500). As described in the first embodiment, the exhaust pressure increase rate EPr is fixed to the average value AV when the engine starts. Thus, the controller 100 determines that the current mode is the fixed mode when the procedure is first performed after the engine is started.

[0063] In the case of the fixed mode (S500: YES), the controller 100 determines whether a tracking mode switching condition is satisfied (S510). The tracking mode switching condition is satisfied when the exhaust pressure increase rate EPr maintained at a specific value, that is, the exhaust pressure increase rate that is a fixed value, deviates from an actual exhaust pressure state. If at least one of the following conditions (A) to (D), for example, is satisfied, the controller 100 in the second embodiment determines that the tracking mode switching condition is satisfied.

[0064] Condition (A): A forced regeneration process was performed on filter 18 at a maintenance factory. This condition is set for the following reasons. When a forced regeneration process is performed on filter 18, the PM deposition amount of filter 18 is significantly reduced, and the exhaust pressure decreases. Thus, the exhaust pressure increase rate EPr, which is currently a fixed value, deviates from the actual exhaust pressure state.

[0065] Condition (B): A changed amount Psha of the PM deposition amount Ps is greater than or equal to a preset determination value A. The changed amount Psha is the difference between the PM deposition amount Ps at the time when the exhaust pressure increase rate EPr was previously updated, for example, and the current PM deposition amount Ps. This condition is set for the following reasons. When the changed amount Psha is greater than or equal to the preset determination value A, the clogging degree in the filter 18 is changed, and the exhaust pressure increase rate EPr, which is currently a fixed value, deviates from an actual state of the exhaust pressure. A value suitable for the determination is set to the determination value A.

[0066] Condition (C): An absolute value AB of a difference (AB=|EPr-EPrt|) between the exhaust pressure increase rate EPr, for which a fixed value is currently set, and the currently calculated tracking value EPrt is greater than or equal to a preset determination value B. This condition is set for the following reasons. For example, when the filter 18 is replaced, an operation to reset the value of the exhaust pressure increase rate EPr is performed. If the resetting operation is not performed, the absolute value AB increases. Furthermore, an erroneous value of the tracking value EPrt or the exhaust pressure increase rate EPr caused by an unexpected error also increases the absolute value AB. That is, when the absolute value AB increases, the exhaust pressure increase rate EPr, which is currently a fixed value, deviates from an actual state of the exhaust pressure.A value suitable for determination is set to the determination value B.

[0067] Condition (D): Regeneration control has been performed on the filter 18 for a specified period or longer. This condition is set for the following reasons. When regeneration control has been performed on the filter 18 for a long period, the PM deposition amount of the filter 18 is significantly reduced and the exhaust pressure decreases. Thus, the exhaust pressure increase rate EPr, which is currently a fixed value, deviates from an actual exhaust pressure state. A value suitable for determination is set to the specified period.

[0068] If the tracking mode switching condition is met (S510: YES), the controller 100 enters the tracking mode (S520). The tracking mode performs a tracking operation to adjust the exhaust pressure increase rate EPr during engine operation to the currently calculated tracking value EPrt. Then, the controller 100 terminates the operation.

[0069] When the switching condition for the tracking mode is not satisfied (S510: NO), the controller 100 performs a process in S530 that continues the fixed mode, so that the controller 100 ends the process while maintaining the exhaust pressure increase rate EPr at the average value AV during the engine operation.

[0070] If the current mode is not the fixed mode (S500: NO), specifically, if the current mode is the tracking mode, the controller 100 determines whether the switching conditions for the fixed mode are met (S540). For example, if both condition (E) and condition (F) below are met, the controller 100 determines that the switching conditions for the fixed mode are met.

[0071] Condition (E): A changed amount Pshb of the PM deposition amount Ps is less than or equal to a preset determination value C. The changed amount Pshb is the difference between the PM deposition amount Ps immediately after a regeneration operation of the filter 18 is stopped and the current PM deposition amount Ps. A value that appropriately allows the determination that a changed amount of the PM deposition amount Ps is small is set to the determination value C. More specifically, when the changed amount Pshb is less than or equal to the preset determination value C, the change in the currently calculated instantaneous value EPrs is small. Thus, an actual state of the exhaust pressure is applied to the exhaust pressure increasing rate EPr even if the exhaust pressure increasing rate EPr is set to the average value ΔV of the instantaneous values EPrs as a fixed value.

[0072] Condition (F): The number of calculated instantaneous values EPrs is greater than or equal to a determination value D. When the exhaust pressure increase rate EPr is set to the average value AV of the instantaneous values EPrs as a fixed value, a sufficient number of instantaneous values EPrs should be calculated so that an exhaust pressure condition corresponding to a clogging degree in the filter 18 is applied to the average value AV. A value suitable for determining such a number is set to the determination value D.

[0073] If the switching conditions for the fixed mode are met (S540: YES), the controller 100 starts the fixed mode (S550). The fixed mode performs a process of calculating the average value AV of the instantaneous values EPrs, the number of which is determined to be greater than or equal to the determination value D, and setting a fixed value of the exhaust pressure increase rate EPr, which is maintained at a specific value during engine operation, to the average value AV. Then, the controller 100 terminates the process.

[0074] When the switching conditions for the fixed mode are not satisfied (S540: NO), the controller 100 performs a process in S560 that continues the tracking mode, so that the controller 100 sets the exhaust pressure increase rate EPr during the engine operation to the tracking value EPrt and ends the process.

[0075] The second embodiment has the following advantages in addition to the advantages of the first embodiment. (5) When the amount of particulate matter deposited in the filter 18 is rapidly reduced when the filter 18 is regenerated, for example, the exhaust pressure increase rate EPr, which is fixed at a specific value, deviates from an actual exhaust pressure state corresponding to a clogging degree in the filter 18. Thus, when such a deviation occurs, the controller 100 in the second embodiment enters the tracking mode to perform the tracking process that changes the exhaust pressure increase rate EPr in accordance with a change in the obtained exhaust pressure EP. This prevents the exhaust pressure increase rate EPr, which is set during engine operation, from deviating from an actual exhaust pressure state. (6) In the tracking process, the exhaust pressure increase rate EPr set during engine operation is set to the moving average MAV of the instantaneous values EPrs calculated each time the exhaust pressure EP and the intake air amount GA are obtained. This changes the exhaust pressure increase rate EPr set during engine operation in accordance with a change in the exhaust pressure EP, while reducing variations in the obtained exhaust pressure EP. (7) When the intake air amount increases, the exhaust pressure EP is higher than when the intake air amount decreases. Thus, variations in the exhaust pressure EP do not significantly affect the instantaneous value EPrs of the exhaust pressure increase rate. Thus, in the second embodiment, the parameter PR of the moving average MAV decreases as the intake air amount increases. In this way, when the intake air amount GA increases and variations in the exhaust pressure EP do not significantly affect the instantaneous value EPrs of the exhaust pressure increase rate, the parameter PR of the moving average MAV is reduced to improve tracking of the moving average MAV relative to a change in the exhaust pressure EP. Third embodiment

[0076] The controller 100 for the internal combustion engine 10 according to a third embodiment will now be described with reference to Fig. 10 described.

[0077] The controller 100 according to the third embodiment executes the Fig. 10, which is carried out by partially modifying the process described in the second embodiment in Fig. 9. The description of the third embodiment focuses on the difference from the Fig. The process shown in Figure 9.

[0078] Fig. 10 shows the procedure of operations performed by the controller 100 according to the third embodiment. The procedure is repeatedly performed during engine operation. When the procedure starts, the controller 100 first determines whether the switching conditions to a non-fixed mode are met (S600). The non-fixed mode performs an operation that sets a value of the exhaust pressure increase rate EPr to a value indicating that the exhaust pressure increase rate EPr is not set when the value of the exhaust pressure increase rate EPr is unclear due to a failure of the pressure sensor 50 or the like. The switching conditions for the non-fixed mode include various conditions such as when an abnormality of the pressure sensor 50 is detected and when the value of the exhaust pressure increase rate EPr is an abnormal value outside a preset range.

[0079] If the switching conditions for the non-fixed mode are met (S600: YES), the controller 100 determines the presence or absence of urgency for switching to the non-fixed mode (S700). An abnormality that affects machine operation, such as a failure of the pressure sensor 50, and requires immediate fail-safe action is determined as urgent. An abnormality that does not significantly affect machine operation is determined as less urgent.

[0080] In an emergency (S700: YES), the controller 100 immediately enters the non-fixed mode (S710) and terminates the procedure. When the non-fixed mode starts, a value indicating that the exhaust pressure increase rate EPr is not set is set to the exhaust pressure increase rate EPr. When the non-fixed mode value is set to the exhaust pressure increase rate EPr, fail-safe operations are performed in various types of machine controls that use the exhaust pressure increase rate EPr.

[0081] In the less urgent case (S700: NO), the controller 100 sets a flag or the like to start the non-fixed mode in the next trip (S720) and terminates the procedure.

[0082] If the switching conditions for the non-fixed mode are not met (S600: NO), the controller 100 determines whether the current mode is the fixed mode (S610). The operation in S610 is the same as the operation in S500.

[0083] If the current mode is the fixed mode (S610: YES), the controller 100 determines whether the tracking mode switching condition is met (S620). The process in S620 is the same as the process in S510.

[0084] When the tracking mode switching condition is satisfied (S620: YES), the controller 100 determines whether at least one of condition (G) or condition (H) below is satisfied (S630).

[0085] Condition (G): The changed amount Psha of the PM deposition amount Ps is less than or equal to a preset value E. The changed amount Psha is the difference between the PM deposition amount Ps at the time when the exhaust pressure increase rate EPr was previously updated, for example, and the current PM deposition amount Ps in the same manner as Condition (B). The determination value E is greater than or equal to the determination value A and is set in accordance with the description below. More specifically, when the changed amount Psha is small, a clogging degree in the filter 18 is not significantly changed. Thus, the exhaust pressure increase rate EPr is not significantly changed even if the exhaust pressure increase rate EPr, for which a fixed value is currently set, is changed to the tracking value EPrt.Thus, even if the exhaust pressure increase rate EPr is switched from a fixed value to a tracking value during engine operation, switching the exhaust pressure increase rate EPr does not adversely affect engine control. The magnitude of the determination value E is set to appropriately allow the determination of the changed amount Psha, so that when the changed amount Psha is less than or equal to the determination value E, switching the exhaust pressure increase rate EPr does not adversely affect engine control, even if the exhaust pressure increase rate EPr is switched from a fixed value to a tracking value during engine operation.

[0086] Condition (H): The absolute value AB of the difference (AB = |EPr-EPrt|) between the exhaust pressure increase rate EPr, for which a fixed value is currently set, and the currently calculated tracking value EPrt is less than or equal to a preset determination value F. The determination value F is greater than or equal to the determination value B and is set in accordance with the description below. When the absolute value AB is small, the exhaust pressure increase rate EPr is not significantly changed even if the exhaust pressure increase rate EPr, for which a fixed value is currently set, is changed to the tracking value EPrt. Thus, even if the exhaust pressure increase rate EPr is switched from the fixed value to a tracking value during engine operation, the switching of the exhaust pressure increase rate EPr does not adversely affect engine control.The magnitude of the determination value F is set to suitably allow the determination of the absolute value AB, so that when the absolute value AB is less than or equal to the determination value F, switching of the exhaust pressure increase rate EPr does not adversely affect the engine control even if the exhaust pressure increase rate EPr is switched from a fixed value to a tracking value during engine operation.

[0087] If at least one of condition (G) or condition (H) is satisfied (S630: YES), the controller 100 performs the operation in S640 and enters the tracking mode. The operation in S640 is the same as the operation in S520. Then, the controller 100 terminates the procedure.

[0088] If neither condition (G) nor condition (H) is satisfied (S630: NO), the controller 100 sets a flag or the like to start the tracking mode during the next idle (S650) and terminates the procedure.

[0089] If the tracking mode switching condition is not met (S620: NO), the controller 100 performs an operation in S660 and continues the fixed mode. The operation in S660 is the same as the operation in S530. Then, the controller 100 terminates the procedure.

[0090] If the current mode is not the fixed mode (S610: NO), namely, if the current mode is the tracking mode, the controller 100 determines whether the switching conditions for the fixed mode are met (S670). The process in S670 is the same as the process in S540.

[0091] If the switching conditions for the fixed mode are met (S670: YES), the controller 100 starts the fixed mode (S680). The operation in S680 is the same as the operation in S550. Then, the controller 100 ends the procedure.

[0092] If the fixed mode switching conditions are not met (S670: NO), the controller 100 performs an operation in S690 and continues the tracking mode. The operation in S690 is the same as the operation in S560. Then, the controller 100 terminates the procedure.

[0093] The third embodiment has the following advantages in addition to the advantages of the second embodiment. (8) When the exhaust pressure increase rate EPr is used for engine control, if the average AV, which is set to a fixed value, is switched to the tracking value EPrt during engine operation, so that the exhaust pressure increase rate EPr set during engine operation is significantly changed, this will adversely affect engine control. In other words, even if the average AV, which is set to a fixed value, is switched to the tracking value EPrt, a small change in the exhaust pressure increase rate EPr will not have a significant impact on engine control.

[0094] Thus, in the third embodiment, the controller 100 performs a process in S630 that determines whether at least Condition (G) or Condition (H) is satisfied when the tracking mode switching condition in S620 is satisfied, to switch the exhaust pressure increase rate EPr, which is set during engine operation, from the average value AV for which a fixed value is set to the tracking value EPrt. When at least one of Condition (G) or Condition (H) is satisfied (S630: YES), specifically, when the exhaust pressure increase rate EPr is not significantly changed even when the value of the exhaust pressure increase rate EPr is switched from a fixed value to a tracking value, the controller 100 performs the process in S640 to immediately switch from the fixed value to the tracking value. This limits an influence on engine control caused by switching from the fixed value to the tracking value.

[0095] If neither condition (G) nor condition (H) is satisfied when switching from the fixed value to the tracking value (S630: NO), specifically, if the exhaust pressure increase rate EPr is predicted to change significantly when the exhaust pressure increase rate EPr is switched from the fixed value to the tracking value, the controller 100 switches from the fixed value to the tracking value while the engine is idling. During idling, the engine operation is stable and does not significantly affect the engine control even if the exhaust pressure increase rate EPr is changed significantly. This limits an influence on the engine control caused by switching from the fixed value to the tracking value when the exhaust pressure increase rate EPr is changed significantly by switching from the fixed value to the tracking value.

[0096] The above-described embodiments may be modified as follows. The above-described embodiments and the following modifications may be combined as long as the combined modifications remain technically consistent with each other.

[0097] For a filter in which a deposition amount of particulate matter is a specified amount, the unused filter 18 having 0 deposition amounts of particulate matter serves as the first reference filter. The filter 18 having the assumed maximum deposition amount of particulate matter serves as the second reference filter. Further, a value indicating an increase rate of an exhaust pressure of the current filter 18 is the exhaust pressure increase rate EPr when the exhaust pressure increase rate EPr in the first reference filter is 0% and the exhaust pressure increase rate EPr in the second reference filter is 100%. Instead, the setting of the reference filters may be changed.

[0098] For example, for a filter in which the deposition amount of particulate matter is a specified amount, the unused filter 18 having 0 deposition amounts of particulate matter serves as the best reference filter. The ratio of an exhaust pressure in the current filter 18 to an exhaust pressure in the best reference filter for the same intake air amount GA can be calculated as an exhaust pressure rate corresponding to the exhaust pressure increase rate EPr.

[0099] A filter 18 that has the assumed maximum deposition amount of particulate matter can serve as the worst-case reference filter. The ratio of an exhaust pressure in the current filter 18 to an exhaust pressure in the worst-case reference filter for the same intake air amount GA can be calculated as an exhaust pressure rate corresponding to the exhaust pressure increase rate EPr.

[0100] The exhaust pressure EP is corrected with the correction coefficient K. Instead, the instantaneous value EPrs and the exhaust pressure increase rate EPr can be corrected with coefficients similar to the correction coefficient K. This corrects the calculated exhaust pressure increase rate EPr so that it decreases as the temperature of the exhaust gas flowing into the filter 18 increases.

[0101] The correction coefficient K is calculated to decrease the calculated exhaust pressure increase rate EPr as the temperature of the exhaust gas flowing into the filter 18 increases. Instead, the calculated exhaust pressure increase rate EPr may be corrected in other ways, such as by referring to a map that presets the relationship between the temperature difference ΔT and the corrected exhaust pressure EPh.

[0102] The process of correcting the calculated exhaust pressure increase rate EPr in accordance with the temperature of the exhaust gas flowing into the filter 18 may be omitted. Specifically, the process of calculating the correction coefficient K or the process of calculating the corrected exhaust pressure EPh may be omitted. In this case, the advantages other than those of (2) above can still be obtained.

[0103] The parameter PR of the moving average MAV is varied based on the intake air quantity GA. Instead, the parameter PR can be a fixed value. In this case, the advantages other than those of (7) above can still be obtained.

[0104] The procedure can be simplified by omitting the Fig. 10 operations shown in S600, S700, S710 and S720 start at S610.

[0105] The exhaust pressure EP is detected by the pressure sensor 50. Instead, the exhaust pressure EP can be estimated based on an engine operating condition.

[0106] The controller 100 is not limited to a device that includes a CPU and a memory and executes software processing. For example, a dedicated hardware circuit (such as an ASIC) may be provided that executes at least part of the software processing performed in each of the above-mentioned embodiments. That is, the controller 100 may be modified to have any of the following configurations (a) to (c). (a) A configuration that includes a processor that executes all of the above-described operations according to programs, and a program storage device, such as a memory, that stores the programs. (b) A configuration that includes a processor and a program storage device that executes part of the above-described operations according to the programs, and a dedicated hardware circuit that executes the remaining operations.(c) A configuration including a dedicated hardware circuit that performs all of the above-described operations. A plurality of software processing circuits, each including a processor and a program storage device, and a plurality of dedicated hardware circuits may be provided. That is, the above-mentioned operations can be performed in any manner as long as the operations are performed by a processing circuit including at least one of a set of one or more software processing circuits or a set of one or more dedicated hardware circuits.

Claims

[1] Controller (100) for an internal combustion engine (10), wherein the internal combustion engine (10) contains: a filter (18) arranged in an exhaust duct (15) and collecting fine dust from exhaust gas, and an intake flow rate sensor (54) that detects an amount of intake air drawn into a cylinder, the filter (18) in which a deposition amount of the fine dust is a specified amount is referred to as a reference filter, and the controller (100) is designed to perform the following: a process for obtaining an exhaust pressure upstream of the filter (18) inside the exhaust passage (15) and the intake air amount detected by the intake flow rate sensor (54); a calculation process for calculating an exhaust pressure rate indicating a ratio of the obtained exhaust pressure to an exhaust pressure at the reference filter (18) for the obtained intake air amount; an adjustment process for setting the exhaust pressure rate maintained at a specific value during engine operation; and to perform a tracking operation of a change in the exhaust pressure rate set during engine operation in accordance with a change in the obtained exhaust pressure when the exhaust pressure rate maintained at a specific value deviates from an actual state of the exhaust pressure; characterized by , that a value of the exhaust pressure rate maintained at the specific value is called a fixed value, a value of the exhaust pressure rate that is changed in the tracking process is called a tracking value, a condition in which a changed amount of the deposit amount is less than or equal to a preset value is defined as a first condition, a condition in which a difference between the fixed value and the tracking value is less than or equal to a preset value is defined as a second condition, and that the controller (100) is designed to: immediately perform a switch from the fixed value to the tracking value if at least one of the first condition or the second condition is satisfied when a value of the exhaust pressure rate set during engine operation is switched from the fixed value to the tracking value, and to perform the switching from the fixed value to the tracking value while the machine is idle when neither the first condition nor the second condition is met. [2] The controller (100) for an internal combustion engine (10) according to claim 1, wherein the controller (100) is configured to correct the calculated exhaust pressure rate in the calculation process so that it decreases as a temperature of the exhaust gas flowing into the filter (18) increases. [3] A controller (100) for an internal combustion engine (10) according to claim 1 or 2, wherein the controller (100) is configured to set the exhaust pressure rate maintained at a specific value in the setting process to an average value of the exhaust pressure rate calculated in the calculation process each time the exhaust pressure and the intake air amount are obtained. [4] The controller (100) for an internal combustion engine (10) according to claim 1, wherein the controller (100) is configured to set the exhaust pressure rate, which is set during engine operation, in the tracking process to a moving average of the exhaust pressure rate, which is calculated in the calculation process each time the exhaust pressure and the intake air amount are obtained. [5] A controller (100) for an internal combustion engine (10) according to claim 4, wherein the controller (100) is configured to variably set a parameter of the moving average value such that the parameter decreases as the intake air quantity increases. [6] Controller (100) for an internal combustion engine (10) according to one of claims 1 to 5, wherein the controller (100) is designed to perform the following: a process for obtaining a target intake air quantity; and a process of calculating an exhaust pressure when the intake air amount reaches the target value based on an exhaust pressure at the reference filter (18) for the obtained target value and the exhaust pressure rate. [7] Control method for an internal combustion engine (10), wherein the internal combustion engine (10) contains: a filter (18) arranged in an exhaust duct (15) and collecting fine dust from exhaust gas, and an intake flow rate sensor (54) that detects an amount of intake air drawn into a cylinder, the filter (18) in which a deposition amount of the fine dust is a specified amount is referred to as a reference filter, and the tax procedure has: Obtaining an exhaust pressure upstream of the filter (18) inside the exhaust passage (15) and the intake air quantity detected by the intake flow rate sensor (54); Calculating an exhaust pressure rate indicating a ratio of the obtained exhaust pressure to an exhaust pressure at the reference filter (18) for the obtained intake air quantity; Setting the exhaust pressure rate to be maintained at a specific value during engine operation; and Performing a tracking operation of a change in the exhaust pressure rate set during engine operation in accordance with a change in the obtained exhaust pressure when the exhaust pressure rate maintained at a specific value deviates from an actual state of the exhaust pressure; characterized by , that a value of the exhaust pressure rate maintained at the specific value is called a fixed value, a value of the exhaust pressure rate that is changed in the tracking process is called a tracking value, a condition in which a changed amount of the deposit amount is less than or equal to a preset value is defined as a first condition, a condition in which a difference between the fixed value and the tracking value is less than or equal to a preset value is defined as a second condition, and that the tax procedure also includes: immediately switching from the fixed value to the tracking value when at least one of the first condition or the second condition is met when a value of the exhaust pressure rate set during engine operation is switched from the fixed value to the tracking value, and Switching from the fixed value to the tracking value while the machine is idle when neither the first condition nor the second condition is met.

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