Intake and exhaust system

Abstract

To appropriately control a recirculation amount of EGR gas.SOLUTION: An intake / exhaust system includes: an engine; an intake flow passage; an exhaust flow passage; an EGR flow passage connecting the exhaust flow passage and the intake flow passage; an EGR valve provided in the EGR flow passage; and a control device executing EGR control for controlling a recirculation amount of EGR gas recirculating from the exhaust flow passage to the intake flow passage via the EGR flow passage by controlling an opening of the EGR valve. A shut-off valve is provided on the exhaust flow passage side of the EGR valve in the EGR flow passage, and an atmosphere introduction valve is provided on the exhaust flow passage side of the EGR valve and the intake flow passage side of the shut-off valve in the EGR flow passage. The control device executes learning processing for learning a relation between an actual flow rate that is a flow rate of air actually passing through the EGR valve in a state where the shut-off valve is closed and the atmosphere introduction valve is opened and a reference flow rate that is a reference value of a flow rate of air passing through the EGR valve in the state, and executes EGR control on the basis of a learning result obtained by the learning processing.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an intake and exhaust system. [Background technology]

[0002] Some intake and exhaust systems for engines are capable of performing exhaust gas recirculation (EGR), as disclosed in Patent Document 1, for example. Such intake and exhaust systems are provided with an EGR passage that connects the exhaust passage and the intake passage. In EGR, a portion of the exhaust gas flowing through the exhaust passage is recirculated to the intake passage via the EGR passage. This reduces the combustion temperature in the engine. Therefore, the generation of NOx is suppressed, and the amount of NOx emissions is reduced. Furthermore, improved fuel economy is also achieved. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5387914 Summary of the Invention [Problem to be solved by the invention]

[0004] An EGR valve is provided in the EGR flow path. By controlling the opening degree of the EGR valve, the amount of EGR gas returned from the exhaust flow path to the intake flow path via the EGR flow path is controlled. Here, if contaminants such as soot adhere to the EGR valve, the cross-sectional area of the EGR flow path at the location of the EGR valve may decrease, resulting in a decrease in the amount of EGR gas returned below the expected amount. In this case, the decrease in the amount of EGR gas returned may result in a decrease in fuel economy, an increase in NOx emissions, and a decrease in knocking suppression performance. Therefore, it is desirable to appropriately control the amount of EGR gas returned even when contaminants such as soot adhere to the EGR valve.

[0005] Therefore, an object of the present invention is to provide an intake and exhaust system that can appropriately control the amount of EGR gas recirculated. [Means for solving the problem]

[0006] In order to solve the above problem, an intake and exhaust system according to one embodiment of the present invention comprises: The engine and an intake passage connected to the engine; an exhaust passage connected to the engine; an EGR flow path connecting the exhaust flow path and the intake flow path; an EGR valve provided in the EGR flow path; a control device that executes EGR control to control the amount of EGR gas that is recirculated from the exhaust passage to the intake passage via the EGR passage by controlling an opening degree of the EGR valve; Equipped with At least one shutoff valve is provided in the EGR flow path closer to the exhaust flow path than the EGR valve, At least one atmosphere introduction valve is provided in the EGR passage closer to the exhaust passage than the EGR valve and closer to the intake passage than the shutoff valve, The control device executing a learning process to learn the relationship between an actual flow rate, which is the flow rate of air that actually passes through the EGR valve, with the shutoff valve closed and the atmosphere intake valve open, and a reference flow rate, which is a reference value of the flow rate of air that passes through the EGR valve in the above state; The EGR control is executed based on the learning result of the learning process. [Effects of the Invention]

[0007] According to the present invention, it is possible to appropriately control the amount of EGR gas recirculated. [Brief explanation of the drawings]

[0008] [Figure 1]FIG. 1 is a schematic diagram showing the general configuration of an intake and exhaust system according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing an example of a functional configuration of the control device according to the first embodiment of the present invention. [Figure 3] FIG. 3 is a flowchart showing an example of a flow of processing related to EGR control performed by the control device in the first embodiment of the present invention. [Figure 4] FIG. 4 is a flowchart showing an example of the flow of processing related to the learning processing performed by the control device in the first embodiment of the present invention. [Figure 5] FIG. 5 is a flowchart showing an example of the flow of the first learning process performed by the control device in the first embodiment of the present invention. [Figure 6] FIG. 6 is a schematic diagram showing the flow of gas during execution of the first learning process in the intake and exhaust system according to the first embodiment of the present invention. [Figure 7] FIG. 7 is a schematic diagram showing the general configuration of an intake and exhaust system according to a second embodiment of the present invention. [Figure 8] FIG. 8 is a flowchart showing an example of the flow of processing related to the learning processing performed by the control device in the second embodiment of the present invention. [Figure 9] FIG. 9 is a flowchart showing an example of the flow of the second learning process performed by the control device in the second embodiment of the present invention. [Figure 10] FIG. 10 is a schematic diagram showing the gas flow during execution of the second learning process in the intake and exhaust system according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Specific dimensions, materials, numerical values, etc. shown in the embodiments are merely examples for facilitating understanding of the invention and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present invention are not shown.

[0010] [First embodiment] An intake and exhaust system 1 according to a first embodiment of the present invention will be described with reference to FIGS.

[0011] <Configuration> The configuration of the intake and exhaust system 1 will be described with reference to FIGS.

[0012] 1 is a schematic diagram showing the general configuration of an intake and exhaust system 1. The intake and exhaust system 1 is mounted on a vehicle 100. As shown in FIG. 1, the intake and exhaust system 1 includes an engine 10, an intake passage 20, an exhaust passage 30, an EGR passage 40, and a control device 50.

[0013] The engine 10 is, for example, a spark-ignition internal combustion engine. The engine 10 has multiple cylinders. A piston is slidably provided inside each cylinder, and the pistons define a combustion chamber. Each cylinder is provided with a fuel injection valve that injects fuel into the combustion chamber. A mixture containing air and fuel is formed in the combustion chamber, and the mixture is burned by ignition of an ignition plug provided toward the combustion chamber. This causes the pistons to perform linear reciprocating motion, transmitting power to a crankshaft connected to the piston of each cylinder.

[0014] Each combustion chamber of the engine 10 is connected to an intake passage 20 via an intake port and to an exhaust passage 30 via an exhaust port. Each cylinder is provided with an intake valve that can open and close the intake port and an exhaust valve that can open and close the exhaust port. By driving the intake valve and exhaust valve, intake air is supplied to the combustion chamber and exhaust gas is discharged from the combustion chamber.

[0015] The intake passage 20 is connected to the engine 10. The intake passage 20 is a passage through which intake air, which is air supplied to the combustion chamber of the engine 10, flows. An intake port 21 is provided at the upstream end of the intake passage 20, through which outside air is taken in from outside the vehicle 100. A throttle valve 22 is provided in the intake passage 20 downstream of the intake port 21. The throttle valve 22 adjusts the flow rate of intake air taken into the intake passage 20 and sent to the engine 10. The flow rate of intake air sent to the engine 10 changes depending on the opening degree of the throttle valve 22. An intake manifold 23 is provided in the intake passage 20 downstream of the throttle valve 22. The intake manifold 23 branches toward each cylinder of the engine 10 and is connected to the intake port of each cylinder. As indicated by the white arrows, air taken into the intake passage 20 from the intake port 21 passes through the throttle valve 22 and the intake manifold 23 in this order before being sent to the engine 10.

[0016] An air flow meter 24 and an intake pressure sensor 25 are provided in the intake flow path 20. The air flow meter 24 is provided in the intake flow path 20 upstream of the throttle valve 22. The air flow meter 24 detects the flow rate of air taken into the intake flow path 20 from the intake port 21. The intake pressure sensor 25 is provided in the intake manifold 23. The intake pressure sensor 25 detects the intake pressure, which is the pressure of the intake air in the intake manifold 23.

[0017] The exhaust flow path 30 is connected to the engine 10. The exhaust flow path 30 is a flow path through which exhaust gas discharged from the combustion chamber of the engine 10 flows. An exhaust port 31 is provided at the downstream end of the exhaust flow path 30, through which the exhaust gas is discharged to the outside of the vehicle 100. An exhaust manifold 32 is provided in the exhaust flow path 30. The exhaust manifold 32 branches toward each cylinder of the engine 10 and is connected to the exhaust port of each cylinder. As shown by the white arrows, in the exhaust flow path 30, the exhaust gas discharged from the engine 10 passes through the exhaust manifold 32 and is then discharged from the exhaust port 31.

[0018] An air-fuel ratio sensor 33 is provided in the exhaust flow path 30. The air-fuel ratio sensor 33 is provided, for example, in the exhaust flow path 30 downstream of the exhaust manifold 32. The air-fuel ratio sensor 33 detects the air-fuel ratio of the exhaust gas flowing through the exhaust flow path 30.

[0019] The EGR flow path 40 connects the exhaust flow path 30 and the intake flow path 20. As indicated by the white arrow, a portion of the exhaust gas flowing through the exhaust flow path 30 flows into the EGR flow path 40. The exhaust gas that flows into the EGR flow path 40 passes through the EGR flow path 40 and is recirculated to the intake flow path 20. This technology of recirculating a portion of the exhaust gas to the intake flow path 20 is called EGR. By performing EGR, the combustion temperature in the engine 10 is lowered, the generation of NOx is suppressed, and NOx emissions are reduced. Furthermore, improved fuel economy is also achieved. Hereinafter, the gas flowing through the EGR flow path 40 is also referred to as EGR gas. The exhaust flow path 30 side of the EGR flow path 40 refers to the upstream side, and the intake flow path 20 side of the EGR flow path 40 refers to the downstream side.

[0020] 1, the upstream end of the EGR flow path 40 is connected to a portion of the exhaust flow path 30 downstream of the exhaust manifold 32. However, the upstream end of the EGR flow path 40 may be connected to the exhaust manifold 32. In the example of FIG. 1, the downstream end of the EGR flow path 40 is connected to the intake manifold 23. However, the downstream end of the EGR flow path 40 may be connected to a portion of the intake flow path 20 upstream of the intake manifold 23 and downstream of the throttle valve 22.

[0021] An EGR cooler 41 is provided in the EGR passage 40. The EGR gas flowing through the inside of the EGR cooler 41 is cooled by heat exchange with air outside the EGR cooler 41. An EGR valve 42 is provided in the EGR passage 40 on the intake passage 20 side of the EGR cooler 41. The EGR valve 42 adjusts the amount of EGR gas that is recirculated from the exhaust passage 30 to the intake passage 20 via the EGR passage 40. The amount of EGR gas recirculation is the flow rate of EGR gas flowing through the EGR passage 40. The amount of EGR gas recirculation is adjusted by adjusting the opening degree of the EGR valve 42.

[0022] In the intake / exhaust system 1, a shutoff valve 43 and an atmosphere introduction valve 44 are provided in the EGR passage 40. The shutoff valve 43 corresponds to an example of a first shutoff valve according to the present invention. The atmosphere introduction valve 44 corresponds to an example of a first atmosphere introduction valve according to the present invention.

[0023] The shutoff valve 43 is provided in the EGR flow path 40 closer to the exhaust flow path 30 than the EGR valve 42 and closer to the intake flow path 20 than the EGR cooler 41. The shutoff valve 43 is capable of opening and closing the exhaust flow path 30. When the shutoff valve 43 is open, the EGR gas flowing through the exhaust flow path 30 can pass through the shutoff valve 43. When the shutoff valve 43 is closed, the EGR gas flowing through the exhaust flow path 30 cannot pass through the shutoff valve 43.

[0024] The atmosphere introduction valve 44 is provided in the EGR flow path 40 closer to the exhaust flow path 30 than the EGR valve 42 and closer to the intake flow path 20 than the shutoff valve 43. The atmosphere introduction valve 44 is capable of introducing atmospheric air into the EGR flow path 40. For example, the atmosphere introduction valve 44 can open and close a branch flow path that branches off from the EGR flow path 40 closer to the intake flow path 20 than the EGR cooler 41 and opens to the atmosphere. When the atmosphere introduction valve 44 is open, atmospheric air outside the EGR flow path 40 can pass through the atmosphere introduction valve 44, and atmospheric air is introduced into the EGR flow path 40 from the atmosphere introduction valve 44. When the atmosphere introduction valve 44 is closed, atmospheric air outside the EGR flow path 40 cannot pass through the atmosphere introduction valve 44, and atmospheric air is not introduced into the EGR flow path 40 from the atmosphere introduction valve 44.

[0025] The control device 50 has one or more processors 50a and one or more memories 50b connected to the processors 50a. The processor 50a includes, for example, a CPU (Central Processing Unit). The memory 50b includes, for example, a ROM (Read Only Memory) and a RAM (Random Access Memory). The ROM is a storage element that stores programs and calculation parameters used by the CPU. The RAM is a storage element that temporarily stores data such as variables and parameters used in processing executed by the CPU.

[0026] The control device 50 communicates with each device provided in the intake and exhaust system 1. For example, the control device 50 communicates with the throttle valve 22, the air flow meter 24, the intake pressure sensor 25, the air-fuel ratio sensor 33, the EGR valve 42, the shutoff valve 43, and the air intake valve 44. The communication between the control device 50 and each device is realized, for example, using CAN (Controller Area Network) communication.

[0027] Fig. 2 is a block diagram showing an example of the functional configuration of the control device 50. For example, as shown in Fig. 2, the control device 50 has an acquisition unit 51 and a control unit 52. Note that various processes, including the processes described below, performed by the acquisition unit 51 or the control unit 52 may be executed by the processor 50a. In detail, the various processes are executed by the processor 50a executing a program stored in the memory 50b.

[0028] The acquisition unit 51 acquires various information used in the processing performed by the control unit 52, and outputs the information to the control unit 52. For example, the acquisition unit 51 acquires information from the air flow meter 24, the intake pressure sensor 25, and the air-fuel ratio sensor 33.

[0029] The control unit 52 controls the operation of each device in the intake and exhaust system 1. In particular, the control unit 52 controls the operation of the throttle valve 22, the EGR valve 42, the shutoff valve 43, and the atmosphere introduction valve 44, thereby controlling the flow of gas in the intake and exhaust system 1.

[0030] The functions of the control device 50 according to this embodiment may be divided among multiple devices, or multiple functions may be realized by one device. When the functions of the control device 50 are divided among multiple devices, the multiple devices may be connected to each other via a communication bus such as a CAN.

[0031] <Operation> The operation of the intake and exhaust system 1 will be described with reference to FIGS.

[0032] In this embodiment, the control device 50 performs EGR control to control the amount of EGR gas recirculated from the exhaust passage 30 to the intake passage 20 via the EGR passage 40 by controlling the opening degree of the EGR valve 42. Here, if contaminants such as soot adhere to the EGR valve 42, the cross-sectional area of the portion of the EGR passage 40 where the EGR valve 42 is provided may decrease, resulting in a decrease in the amount of EGR gas recirculated. In this case, the decrease in the amount of EGR gas recirculated may result in a decrease in fuel economy, an increase in NOx emissions, a decrease in knocking suppression performance, and the like.

[0033] Therefore, in this embodiment, in order to appropriately control the amount of recirculation of EGR gas, the control device 50 executes a learning process, which will be described later, and executes EGR control based on the learning results of the learning process. Below, the process flow for EGR control will be described, and then the process flow related to the learning process will be described.

[0034] Fig. 3 is a flowchart showing an example of the flow of processing related to EGR control performed by the control device 50 in this embodiment. The control flow shown in Fig. 3 is repeatedly executed, for example, in parallel with the control flow related to the learning processing shown in Fig. 4, which will be described later, or sequentially.

[0035] 3 starts, first, in step S101, the acquisition unit 51 acquires various parameters used to determine the target opening degree of the EGR valve 42. Examples of the various parameters include the load on the engine 10, the rotation speed of the engine 10, the temperature of the intake air, and the flow rate of the intake air taken in through the intake port 21. For example, the vehicle 100 is provided with sensors that detect these various parameters, and the acquisition unit 51 can acquire the various parameters from the sensors.

[0036] Next, in step S102, the acquisition unit 51 acquires a learning result from a learning process described below. As described below, in the learning process, the relationship between an actual flow rate, which is the flow rate of air that actually passes through the EGR valve 42, and a reference flow rate, which is a reference value of the flow rate of air that passes through the EGR valve 42, is learned. The reference flow rate is an estimated value of the flow rate of air that passes through the EGR valve 42 in a state where the EGR valve 42 is not contaminated with soot or other contaminants. Hereinafter, the flow rate of air that actually passes through the EGR valve 42 will also be simply referred to as the actual flow rate, and the reference value of the flow rate of air that passes through the EGR valve 42 will also be simply referred to as the reference flow rate. The learning result from the learning process is stored in, for example, the memory 50b of the control device 50.

[0037] Next, in step S103, the control unit 52 determines the target opening degree of the EGR valve 42 based on the various parameters acquired in step S101 and the learning result acquired in step S102.

[0038] In step S103, the control unit 52 determines the target opening so that the combustion temperature in the engine 10 is appropriately lowered by EGR control, and an amount of EGR gas recirculated that appropriately achieves a reduction in NOx emissions and an improvement in fuel economy is obtained. For example, the control unit 52 determines a reference value of the target opening based on the various parameters acquired in step S101, and adjusts the determined reference value of the target opening based on the learning result acquired in step S102, thereby determining the final target opening. Details of the adjustment of the target opening using the learning result in the learning process will be described later.

[0039] Next, in step S104, the control unit 52 controls the opening degree of the EGR valve 42 to the target opening degree, and the control flow shown in FIG. 3 ends.

[0040] Fig. 4 is a flowchart showing an example of the flow of processing related to the learning processing performed by the control device 50 in this embodiment. The control flow shown in Fig. 4 is repeatedly executed, for example, in parallel with the control flow of the EGR control shown in Fig. 3 described above, or sequentially.

[0041] When the control flow shown in FIG. 4 starts, first, in step S201, the control unit 52 determines whether or not the execution conditions for the learning process are satisfied.

[0042] In the learning process, the controller 52 learns the extent to which the flow rate of air passing through the EGR valve 42 has changed due to the adhesion of soot and other contaminants to the EGR valve 42. Therefore, the execution condition for the learning process may be, for example, that it is determined that the amount of soot and other contaminants adhering to the EGR valve 42 has increased to a certain extent. By executing the learning process when such an execution condition is satisfied, the timing of the learning process can be optimized. For example, when the mileage of the vehicle 100 exceeds a predetermined distance, the controller 52 can determine that the amount of soot and other contaminants adhering to the EGR valve 42 has increased to a certain extent. Furthermore, for example, when the cumulative total time that the EGR valve 42 is open exceeds a predetermined time, the controller 52 can determine that the amount of soot and other contaminants adhering to the EGR valve 42 has increased to a certain extent.

[0043] Furthermore, during the learning process, the amount of air supplied to the engine 10 fluctuates, as will be described later. Furthermore, fluctuations in the amount of air supplied to the engine 10 may also cause fluctuations in the fuel injection amount. Therefore, the output of the engine 10 is more likely to fluctuate. Therefore, it is preferable to execute the learning process when the vehicle 100 is in steady operation and the operating state of the engine 10 is stable. This improves the accuracy of the learning process. Therefore, the execution condition for the learning process may be, for example, that the vehicle 100 is determined to be in steady operation. Steady operation means that the vehicle 100 is traveling under stable operating conditions. By executing the learning process when such an execution condition is satisfied, the learning process can be executed at a timing when the behavior of the vehicle 100 is less likely to become unstable even if the output of the engine 10 fluctuates. For example, the control unit 52 can determine that the vehicle 100 is in steady operation when the engine speed, etc. of the engine 10 remains stable without significant changes over a predetermined period of time.

[0044] When the vehicle 100 is equipped with a traction motor as a drive source in addition to the engine 10, the vehicle 100 can operate in an HEV mode in which it runs using both the output of the engine 10 and the output of the traction motor. In this case, the condition for executing the learning process may be, for example, that the HEV mode is being executed. For example, when the learning process is executed while the HEV mode is being executed, the control unit 52 can suppress fluctuations in the driving force applied to the vehicle 100 by controlling the output of the traction motor in accordance with fluctuations in the output of the engine 10 due to the learning process. This suppresses the behavior of the vehicle 100 from becoming unstable due to the execution of the learning process.

[0045] Although examples of execution conditions for the learning process have been described above, the execution conditions may be conditions other than the examples described above. Furthermore, the execution condition may be that multiple conditions are satisfied. For example, the execution condition may be that two or more of the three conditions described above as examples of the execution conditions are satisfied.

[0046] If it is determined that the execution conditions for the learning process are not satisfied (NO in step S201), the learning process is not performed, and the control flow shown in Fig. 4 ends. On the other hand, if it is determined that the execution conditions for the learning process are satisfied (YES in step S201), the process proceeds to step S202. In step S202, the control unit 52 executes the first learning process, and the control flow shown in Fig. 4 ends.

[0047] As described above, in this embodiment, the control device 50 executes the first learning process in the learning process. An example of the flow of the first learning process will be described below with reference to FIG.

[0048] 5 is a flowchart showing an example of the flow of the first learning process performed by the control device 50 in this embodiment. The control flow shown in FIG. 5 is performed in step S202 in the control flow shown in FIG.

[0049] 5 starts, first, in step S301, the control unit 52 closes the shutoff valve 43. This makes it impossible for the EGR gas flowing through the exhaust passage 30 to pass through the shutoff valve 43.

[0050] Next, in step S302, the control unit 52 opens the atmosphere intake valve 44. This allows the atmosphere outside the EGR passage 40 to pass through the atmosphere intake valve 44, and the atmosphere is introduced into the EGR passage 40 from the atmosphere intake valve 44.

[0051] FIG. 6 is a schematic diagram showing the gas flow during execution of the first learning process in the intake / exhaust system 1. As described above, the first learning process results in a first state in which the shutoff valve 43 is closed and the atmosphere intake valve 44 is open. In the first state, as indicated by the white arrow in FIG. 6, atmosphere is introduced into the EGR flow path 40 from the atmosphere intake valve 44. Here, a negative pressure is created inside the intake manifold 23. Therefore, the air introduced into the EGR flow path 40 passes through the EGR valve 42 and is sent into the intake manifold 23. Returning to FIG. 5, the following description will be continued.

[0052] After step S302, in step S303, the control unit 52 controls the opening degree of the EGR valve 42 to an initial value.

[0053] As will be described later, in a first learning process, the control device 50 learns the relationship between an actual flow rate, which is the flow rate of air that actually passes through the EGR valve 42, and a reference flow rate, which is a reference value for the flow rate of air that passes through the EGR valve 42, for each of a plurality of different opening degrees of the EGR valve 42. First, the control device 50 learns the relationship between the actual flow rate and the reference flow rate while controlling the opening degree of the EGR valve 42 to an initial value. Thereafter, the control device 50 changes the opening degree of the EGR valve 42 to learn the relationship between the actual flow rate and the reference flow rate. In this way, learning for each opening degree is performed by repeatedly changing the opening degree of the EGR valve 42 and learning the relationship between the actual flow rate and the reference flow rate.

[0054] Next, in step S304, the control unit 52 calculates an actual flow rate, which is the flow rate of air that actually passes through the EGR valve .

[0055] For example, the control unit 52 can calculate the actual flow rate based on the detection result of the air flow meter 24, the detection result of the air-fuel ratio sensor 33, and the fuel injection amount in the engine 10. Specifically, the control unit 52 can calculate the total flow rate of air supplied to the engine 10 based on the detection result of the air-fuel ratio sensor 33 and the fuel injection amount in the engine 10. The control unit 52 can then calculate the difference between the total flow rate of air supplied to the engine 10 and the flow rate of air taken into the intake flow path 20 from the intake port 21 as the actual flow rate. The flow rate of air taken into the intake flow path 20 from the intake port 21 can be obtained based on the detection result of the air flow meter 24.

[0056] When control is being executed to maintain the air-fuel ratio at a target value, the fuel injection amount increases as air is supplied to the engine 10 from the EGR valve 42 by the first learning process. The control unit 52 may calculate the actual flow rate based on this increase in the fuel injection amount, the detection result of the air flow meter 24, and the detection result of the air-fuel ratio sensor 33. Furthermore, when a sensor that detects the actual flow rate or a physical quantity that can be substantially converted into the actual flow rate is provided in the intake and exhaust system 1, the control unit 52 may obtain the actual flow rate from the sensor.

[0057] Next, in step S305, the control unit 52 calculates a reference flow rate, which is a reference value of the flow rate of air passing through the EGR valve 42, based on the opening degree of the EGR valve 42 and the intake pressure. The intake pressure is the pressure of the intake air in the intake manifold 23, and can be obtained based on the detection result of the intake pressure sensor 25.

[0058] As described above, the reference flow rate is an estimated value of the flow rate of air passing through the EGR valve 42 when the EGR valve 42 is free of contaminants such as soot. The greater the opening of the EGR valve 42, the larger the flow path cross-sectional area of the portion of the EGR flow path 40 where the EGR valve 42 is provided, and therefore the flow rate of air passing through the EGR valve 42. Therefore, for example, the greater the opening of the EGR valve 42, the larger the value calculated by the control unit 52 as the reference flow rate. Furthermore, the lower the intake pressure, the larger the pressure difference between the upstream and downstream sides of the EGR valve 42, and therefore the larger the flow rate of air passing through the EGR valve 42. Therefore, for example, the lower the intake pressure, the larger the value calculated by the control unit 52 as the reference flow rate.

[0059] Next, in step S306, the control unit 52 learns the relationship between the actual flow rate calculated in step S304 and the reference flow rate calculated in step S305. For example, the control unit 52 extracts the relationship between the actual flow rate and the reference flow rate, and stores it in the memory 50b of the control device 50.

[0060] The relationship between the actual flow rate and the reference flow rate may be, for example, the ratio of the actual flow rate to the reference flow rate. Note that the relationship between the actual flow rate and the reference flow rate may be learned as something other than the ratio. For example, the control unit 52 may learn the difference between the actual flow rate and the reference flow rate as the relationship between the actual flow rate and the reference flow rate.

[0061] Next, in step S307, the control unit 52 determines whether or not learning has been completed for all opening degrees of the EGR valve 42. The multiple opening degrees to be learned in the first learning process may be set at equal intervals or at unequal intervals.

[0062] If it is determined that learning has been completed for all openings (YES in step S307), the control flow shown in Fig. 5 ends, and the first learning process ends. On the other hand, if it is determined that learning has not been completed for all openings (NO in step S307), the process proceeds to step S308.

[0063] In step S308, the control unit 52 changes the opening of the EGR valve 42 to an unlearned opening, and the process returns to step S304. As a result, the relationship between the actual flow rate and the reference flow rate is learned for the changed opening.

[0064] As described above, in the learning process, the control device 50 learns the relationship between the actual flow rate, which is the flow rate of air that actually passes through the EGR valve 42, and the reference flow rate, which is a reference value for the flow rate of air that passes through the EGR valve 42. This allows the control device 50 to learn the extent to which the flow rate of air that passes through the EGR valve 42 has changed due to the adhesion of soot or other contaminants to the EGR valve 42. Then, as described above, the control device 50 executes EGR control based on the learning results of the learning process. This allows the EGR control to control the opening degree of the EGR valve 42, taking into account the extent to which the recirculation amount of EGR gas is reduced due to the adhesion of soot or other contaminants to the EGR valve 42.

[0065] Here, in EGR control, if the opening degree of the EGR valve 42 is controlled without taking into account the degree to which the recirculation amount of EGR gas is reduced due to the adhesion of soot or other contaminants to the EGR valve 42, it is expected that the recirculation amount of EGR gas will be smaller than the desired recirculation amount. For example, in the control flow of FIG. 3 described above, if the control unit 52 determines the target opening degree of the EGR valve 42 based only on the various parameters acquired in step S101, the recirculation amount of EGR gas will be smaller than the desired recirculation amount, which may result in a deterioration in fuel economy, an increase in NOx emissions, a decrease in knocking suppression performance, and the like.

[0066] 3 , the control unit 52 determines the target opening of the EGR valve 42 based on the various parameters acquired in step S101 and the learning result acquired in step S102. For example, the control unit 52 divides the reference value of the target opening determined based on the various parameters acquired in step S101 by the ratio of the actual flow rate to the reference flow rate, and determines the resulting opening as the final target opening. This makes it possible to increase the opening of the EGR valve 42 in accordance with the degree to which the recirculation amount of EGR gas is reduced due to the adhesion of contaminants such as soot to the EGR valve 42, thereby obtaining an EGR gas recirculation amount that appropriately reduces NOx emissions and improves fuel economy.

[0067] As described above, according to this embodiment, in EGR control, the opening degree of the EGR valve 42 can be controlled taking into account the degree to which the recirculation amount of EGR gas is reduced due to the adhesion of soot or other contaminants to the EGR valve 42. Therefore, even when soot or other contaminants are attached to the EGR valve 42, the recirculation amount of EGR gas can be appropriately controlled. This makes it possible to suppress deterioration in fuel economy, an increase in NOx emissions, a decrease in knocking suppression performance, and the like.

[0068] <Effects> The effects of the intake and exhaust system 1 will be described.

[0069] In the intake / exhaust system 1 according to this embodiment, at least one shutoff valve 43 is provided in the EGR flow path 40 closer to the exhaust flow path 30 than the EGR valve 42. At least one atmosphere intake valve 44 is provided in the EGR flow path 40 closer to the exhaust flow path 30 than the EGR valve 42 and closer to the intake flow path 20 than the shutoff valve 43. The control device 50 executes a learning process to learn the relationship between an actual flow rate, which is the flow rate of air actually passing through the EGR valve 42 when the shutoff valve 43 is closed and the atmosphere intake valve 44 is open, and a reference flow rate, which is a reference value for the flow rate of air passing through the EGR valve 42 under these conditions. The control device 50 then executes EGR control based on the learning results. This allows the EGR control to control the opening degree of the EGR valve 42, taking into account the degree to which the recirculation flow rate of EGR gas is reduced due to the adhesion of contaminants such as soot to the EGR valve 42. Therefore, the recirculation flow rate of EGR gas can be appropriately controlled even when contaminants such as soot are attached to the EGR valve 42. Therefore, it is possible to suppress deterioration in fuel economy, an increase in NOx emissions, and a decrease in knocking suppression performance.

[0070] Here, the positions of the shutoff valve 43 and the atmosphere introduction valve 44 are not limited to the above example. For example, the shutoff valve 43 may be provided in the EGR flow path 40 closer to the exhaust flow path 30 than the EGR cooler 41, like a shutoff valve 45 in Fig. 7 described later. Furthermore, for example, the atmosphere introduction valve 44 may be provided in the EGR flow path 40 closer to the exhaust flow path 30 than the EGR cooler 41 and closer to the intake flow path 20 than the shutoff valve 45, like an atmosphere introduction valve 46 in Fig. 7 described later.

[0071] However, it is preferable that the shutoff valve 43 be provided in the EGR flow path 40 closer to the exhaust flow path 30 than the EGR valve 42 and closer to the intake flow path 20 than the EGR cooler 41, and that the air intake valve 44 be provided in the EGR flow path 40 closer to the exhaust flow path 30 than the EGR valve 42 and closer to the intake flow path 20 than the shutoff valve 43. This allows the learning process to accurately learn the relationship between the actual flow rate, which is the flow rate of air actually passing through the EGR valve 42, and the reference flow rate, which is a reference value for the flow rate of air passing through the EGR valve 42. For example, the relationship between the actual flow rate and the reference flow rate can be learned after eliminating the influence of the state of the EGR cooler 41 on the relationship between the actual flow rate and the reference flow rate. Therefore, it is possible to accurately learn the extent to which the flow rate of air passing through the EGR valve 42 has changed due to the adhesion of contaminants such as soot to the EGR valve 42.

[0072] Furthermore, in the intake and exhaust system 1 according to this embodiment, the control device 50 preferably learns the relationship between the actual flow rate and the reference flow rate for each of a plurality of different opening degrees of the EGR valve 42 during the learning process. Here, the relationship between the actual flow rate and the reference flow rate may differ depending on the opening degree of the EGR valve 42. Therefore, by learning the relationship between the actual flow rate and the reference flow rate for each opening degree of the EGR valve 42, it is possible to appropriately learn the relationship between the actual flow rate and the reference flow rate for each opening degree of the EGR valve 42. Therefore, it is possible to more appropriately control the opening degree of the EGR valve 42, taking into account the degree to which the recirculation amount of EGR gas is reduced due to the adhesion of contaminants such as soot to the EGR valve 42.

[0073] Furthermore, in the intake and exhaust system 1 according to this embodiment, it is preferable that the control device 50 varies the reference flow rate in accordance with the opening degree of the EGR valve 42. In other words, varying the reference flow rate is equivalent to changing the set value of the reference flow rate. This allows the reference flow rate to be appropriately set to a value close to the estimated value of the flow rate of air passing through the EGR valve 42 in a state where the EGR valve 42 is free of contaminants such as soot. This makes it possible to appropriately learn the relationship between the actual flow rate and the reference flow rate. In particular, by varying the reference flow rate in accordance with the opening degree of the EGR valve 42 in the learning process, it is possible to appropriately learn the relationship between the actual flow rate and the reference flow rate for each opening degree of the EGR valve 42.

[0074] [Second embodiment] An intake and exhaust system 1A according to a second embodiment of the present invention will be described with reference to FIGS.

[0075] <Configuration> The configuration of the intake and exhaust system 1A will be described with reference to FIG.

[0076] 7 is a schematic diagram showing the overall configuration of an intake and exhaust system 1A. Similar to the above-described intake and exhaust system 1, the intake and exhaust system 1A is mounted on a vehicle 100. The intake and exhaust system 1A differs from the above-described intake and exhaust system 1 in that a shutoff valve 45 and an atmosphere introduction valve 46 are further provided in the EGR flow path 40.

[0077] The shutoff valve 45 corresponds to an example of a second shutoff valve according to the present invention. The atmosphere introduction valve 46 corresponds to an example of a second atmosphere introduction valve according to the present invention.

[0078] The shutoff valve 45 is provided in the EGR flow path 40 closer to the exhaust flow path 30 than the EGR cooler 41. Similar to the shutoff valve 43 described above, the shutoff valve 45 is capable of opening and closing the exhaust flow path 30. When the shutoff valve 45 is open, the EGR gas flowing through the exhaust flow path 30 can pass through the shutoff valve 45. When the shutoff valve 45 is closed, the EGR gas flowing through the exhaust flow path 30 cannot pass through the shutoff valve 45.

[0079] The atmosphere introduction valve 46 is provided in the EGR flow path 40 closer to the exhaust flow path 30 than the EGR cooler 41 and closer to the intake flow path 20 than the shutoff valve 45. The atmosphere introduction valve 46 is capable of introducing atmospheric air into the EGR flow path 40, similar to the above-described atmosphere introduction valve 44. For example, the atmosphere introduction valve 46 can open and close a branch flow path that branches off from the exhaust flow path 30 side of the EGR flow path 40 closer to the EGR cooler 41 and opens to the atmosphere. When the atmosphere introduction valve 46 is open, atmospheric air outside the EGR flow path 40 can pass through the atmosphere introduction valve 46, and atmospheric air is introduced into the EGR flow path 40 from the atmosphere introduction valve 46. When the atmosphere introduction valve 46 is closed, atmospheric air outside the EGR flow path 40 cannot pass through the atmosphere introduction valve 46, and atmospheric air is not introduced into the EGR flow path 40 from the atmosphere introduction valve 46.

[0080] In the intake and exhaust system 1A, the control unit 52 of the control device 50 controls the operations of the throttle valve 22, the EGR valve 42, the shutoff valve 43, and the air intake valve 44, as well as the shutoff valve 45 and the air intake valve 46.

[0081] <Operation> The operation of the intake and exhaust system 1A will be described with reference to FIGS.

[0082] In this embodiment, the control device 50 executes EGR control in the same manner as in the first embodiment described above. The processing flow related to the EGR control is the same as the control flow shown in Fig. 3 described above. Here, unlike the first embodiment described above, in this embodiment, the control device 50 executes a second learning process in addition to the first learning process described above in the learning process.

[0083] Fig. 8 is a flowchart showing an example of the flow of processing related to the learning processing performed by the control device 50 in this embodiment. The control flow shown in Fig. 8 is repeatedly executed, for example, in parallel with the control flow of the EGR control shown in Fig. 3 described above, or sequentially.

[0084] The control flow shown in Fig. 8 differs from the control flow shown in Fig. 4 described above in that step S203 is added after step S202. Specifically, in step S202 of the control flow shown in Fig. 8, control unit 52 executes a first learning process, similar to the control flow shown in Fig. 4 described above. The flow of the first learning process is similar to the control flow shown in Fig. 5 described above. After step S202, in step S203, control unit 52 executes a second learning process, and the control flow shown in Fig. 8 ends.

[0085] 9 is a flowchart showing an example of the flow of the second learning process performed by the control device 50 in this embodiment. The control flow shown in FIG. 9 is performed in step S203 in the control flow shown in FIG.

[0086] 9 starts, first, in step S401, the control unit 52 opens the shutoff valve 43. This allows the EGR gas flowing through the exhaust passage 30 to pass through the shutoff valve 43.

[0087] Next, in step S402, the control unit 52 closes the atmosphere intake valve 44. As a result, the atmosphere outside the EGR passage 40 cannot pass through the atmosphere intake valve 44, and the atmosphere is not introduced into the EGR passage 40 from the atmosphere intake valve 44.

[0088] Next, in step S403, the control unit 52 closes the shutoff valve 45. This makes it impossible for the EGR gas flowing through the exhaust passage 30 to pass through the shutoff valve 45.

[0089] Next, in step S404, the control unit 52 opens the atmosphere intake valve 46. This allows the atmosphere outside the EGR passage 40 to pass through the atmosphere intake valve 46, and the atmosphere is introduced into the EGR passage 40 from the atmosphere intake valve 46.

[0090] FIG. 10 is a schematic diagram showing the gas flow during execution of the second learning process in the intake / exhaust system 1A. As described above, the second learning process results in a second state in which the shutoff valve 43 is open, the shutoff valve 45 is closed, the air intake valve 44 is closed, and the air intake valve 46 is open. In the second state, as indicated by the white arrow in FIG. 10, air is introduced into the EGR flow path 40 from the air intake valve 46. Here, negative pressure is created inside the intake manifold 23. Therefore, the air introduced into the EGR flow path 40 passes through the EGR cooler 41 and the EGR valve 42 and is sent into the intake manifold 23. Returning to FIG. 9, the following description will be continued.

[0091] After step S404, in step S405, the control unit 52 fully opens the EGR valve 42. That is, the control unit 52 controls the opening degree of the EGR valve 42 to the maximum opening degree.

[0092] Next, in step S406, control unit 52 calculates the actual flow rate, which is the flow rate of air that actually passes through EGR valve 42. The calculation of the actual flow rate in step S406 is similar to the calculation of the actual flow rate in step S304 in FIG. 5 described above.

[0093] Next, in step S407, control unit 52 calculates a reference flow rate, which is a reference value of the flow rate of air passing through EGR valve 42, based on the opening degree of EGR valve 42 and the intake pressure. The calculation of the reference flow rate in step S407 is similar to the calculation of the reference flow rate in step S305 in FIG. 5 described above.

[0094] Next, in step S408, the control unit 52 learns the relationship between the actual flow rate calculated in step S406 and the reference flow rate calculated in step S407, and the control flow shown in FIG. 9 ends, and the second learning process ends. For example, the control unit 52 extracts the relationship between the actual flow rate and the reference flow rate and stores it in the memory 50b of the control device 50. The learning of the relationship between the actual flow rate and the reference flow rate in step S408 is similar to the learning of the relationship between the actual flow rate and the reference flow rate in step S306 of FIG. 5 described above. As described above, in the first learning process, the relationship between the actual flow rate and the reference flow rate is learned for each of a plurality of different opening degrees of the EGR valve 42, while in the second learning process, the relationship between the actual flow rate and the reference flow rate is learned only for a state in which the EGR valve 42 is fully open, for example.

[0095] As described above, in the learning process, the control device 50 executes the second learning process in addition to the first learning process. In the first learning process, the air passing through the EGR valve 42 does not pass through the EGR cooler 41. Therefore, in the first learning process, the relationship between the actual flow rate and the reference flow rate is learned after eliminating the influence of the state of the EGR cooler 41 on the relationship between the actual flow rate and the reference flow rate. On the other hand, in the second learning process, the air passing through the EGR valve 42 also passes through the EGR cooler 41. Therefore, in the second learning process, the relationship between the actual flow rate and the reference flow rate is learned, thereby making it possible to learn the influence of the state of the EGR cooler 41 on the flow rate of air passing through the EGR valve 42.

[0096] For example, when contaminants such as soot adhere to the EGR cooler 41, the cross-sectional area of the flow path in the EGR cooler 41 decreases, and the amount of EGR gas recirculated is reduced. In the second learning process, it is possible to learn how much the flow rate of air passing through the EGR valve 42 has changed due to the adhesion of contaminants such as soot to the EGR cooler 41. In particular, in the processing example of FIG. 9, the second learning process is performed with the EGR valve 42 fully open. When the EGR valve 42 is fully open, the flow rate of air passing through the EGR valve 42 is less affected by the adhesion of contaminants such as soot to the EGR valve 42. Therefore, in the second learning process, it is possible to accurately learn how much the flow rate of air passing through the EGR valve 42 has changed due to the adhesion of contaminants such as soot to the EGR cooler 41.

[0097] Then, as described above, the control device 50 executes EGR control based on the learning results of the learning process. That is, the control device 50 executes EGR control based on the learning results of the second learning process in addition to the learning results of the first learning process. As a result, in the EGR control, the opening degree of the EGR valve 42 can be controlled taking into account the degree to which the recirculation amount of EGR gas is reduced due to the adhesion of contaminants such as soot to the EGR cooler 41.

[0098] For example, in this embodiment, in step S103 of the control flow shown in FIG. 3 , the control unit 52 first determines a reference value for the target opening based on the various parameters acquired in step S101. The control unit 52 then divides the determined reference value for the target opening by the ratio of the actual flow rate to the reference flow rate learned in the first learning process, and then further divides the ratio by the ratio of the actual flow rate to the reference flow rate learned in the second learning process. The control unit 52 determines the opening obtained in this manner as the final target opening. This allows the control unit 52 to increase the opening of the EGR valve 42 in accordance with the degree to which the recirculation amount of EGR gas is reduced due to the adhesion of contaminants such as soot to the EGR valve 42, as well as the degree to which the recirculation amount of EGR gas is reduced due to the adhesion of contaminants such as soot to the EGR cooler 41. This makes it possible to obtain an EGR gas recirculation amount that more appropriately achieves reduced NOx emissions and improved fuel economy.

[0099] As described above, according to this embodiment, in EGR control, the opening degree of the EGR valve 42 can be controlled by taking into account the degree to which the recirculation amount of EGR gas is reduced due to the adhesion of soot or other contaminants to the EGR valve 42, as well as the degree to which the recirculation amount of EGR gas is reduced due to the adhesion of soot or other contaminants to the EGR cooler 41. Therefore, even when soot or other contaminants are attached to the EGR valve 42, the recirculation amount of EGR gas can be more appropriately controlled. This makes it possible to more appropriately suppress deterioration in fuel economy, an increase in NOx emissions, a decrease in knocking suppression performance, and the like.

[0100] <Effects> The effects of the intake and exhaust system 1A will be described.

[0101] In the intake / exhaust system 1A according to this embodiment, a shutoff valve 45 is further provided in the EGR flow path 40 closer to the exhaust flow path 30 than the EGR cooler 41, and an atmosphere introduction valve 46 is further provided in the EGR flow path 40 closer to the exhaust flow path 30 than the EGR cooler 41 and closer to the intake flow path 20 than the shutoff valve 45. In addition to the first learning process, the control device 50 also executes a second learning process in the learning process to learn the relationship between the actual flow rate and the reference flow rate in a second state in which the shutoff valve 43 is opened, the shutoff valve 45 is closed, the atmosphere introduction valve 44 is closed, and the atmosphere introduction valve 46 is open. As a result, in the EGR control, the opening degree of the EGR valve 42 can be controlled taking into account the degree to which the recirculation flow rate of EGR gas is reduced due to the adhesion of contaminants such as soot to the EGR valve 42, as well as the degree to which the recirculation flow rate of EGR gas is reduced due to the adhesion of contaminants such as soot to the EGR cooler 41. Therefore, the amount of EGR gas recirculated can be more appropriately controlled even when soot or other contaminants are attached to the EGR valve 42. This makes it possible to more appropriately suppress deterioration in fuel economy, an increase in NOx emissions, and a decrease in knocking suppression performance.

[0102] The above describes a preferred embodiment of the present invention with reference to the accompanying drawings. However, it goes without saying that the present invention is not limited to the above-described embodiment, and various modified or altered examples within the scope of the claims also fall within the technical scope of the present invention.

[0103] For example, the processes described herein using flowcharts do not necessarily have to be performed in the order shown in the flowcharts, and additional process steps may be employed or some process steps may be omitted. [Explanation of symbols]

[0104] 1. Intake and exhaust system 1A Intake and Exhaust System 10 Engine 20 intake passage 21 Air intake 22 Throttle valve 23 Intake manifold 24 Air flow meter 25 Intake pressure sensor 30 Exhaust flow path 31 Exhaust port 32 Exhaust manifold 33 Air-fuel ratio sensor 40 EGR passage 41 EGR cooler 42 EGR valve 43 Shut-off valve (first shut-off valve) 44 Atmospheric intake valve (first atmospheric intake valve) 45 Shut-off valve (second shut-off valve) 46 Atmospheric intake valve (second atmospheric intake valve) 50 Control device 50a processor 50b memory 51 Acquisition Department 52 Control section 100 vehicles

Claims

1. The engine and an intake passage connected to the engine; an exhaust passage connected to the engine; an EGR flow path connecting the exhaust flow path and the intake flow path; an EGR valve provided in the EGR flow path; a control device that performs EGR control to control a recirculation amount of EGR gas that recirculates from the exhaust flow path to the intake flow path via the EGR flow path by controlling an opening degree of the EGR valve; Equipped with At least one shutoff valve is provided in the EGR flow path closer to the exhaust flow path than the EGR valve, At least one atmosphere introduction valve is provided in the EGR passage closer to the exhaust passage than the EGR valve and closer to the intake passage than the shutoff valve, The control device executing a learning process to learn the relationship between an actual flow rate, which is the flow rate of air that actually passes through the EGR valve, with the shutoff valve closed and the atmosphere intake valve open, and a reference flow rate, which is a reference value of the flow rate of air that passes through the EGR valve in the above state; The EGR control is executed based on a learning result of the learning process. Intake and exhaust system.

2. In the learning process, the control device learns a relationship between the actual flow rate and the reference flow rate for each of a plurality of different opening degrees of the EGR valve. The intake and exhaust system according to claim 1 .

3. The control device changes the reference flow rate in accordance with the opening degree of the EGR valve. The intake and exhaust system according to claim 1 or 2.

4. an EGR cooler is provided in the EGR passage on the exhaust passage side of the EGR valve; a first shutoff valve is provided as the shutoff valve in the EGR passage closer to the exhaust passage than the EGR valve and closer to the intake passage than the EGR cooler; a first atmosphere introduction valve is provided as the atmosphere introduction valve in the EGR passage closer to the exhaust passage than the EGR valve and closer to the intake passage than the first shutoff valve; In the learning process, the control device executes a first learning process to learn a relationship between the actual flow rate and the reference flow rate in a first state in which the first shutoff valve is closed and the first atmosphere introduction valve is opened. The intake and exhaust system according to any one of claims 1 to 3.

5. a second shutoff valve is further provided as the shutoff valve in the EGR passage on the exhaust passage side of the EGR cooler; a second atmosphere introduction valve is further provided as the atmosphere introduction valve in the EGR passage closer to the exhaust passage than the EGR cooler and closer to the intake passage than the second shutoff valve; In the learning process, the control device executes, in addition to the first learning process, a second learning process for learning a relationship between the actual flow rate and the reference flow rate in a second state in which the first shutoff valve is opened, the second shutoff valve is closed, the first atmosphere introduction valve is closed, and the second atmosphere introduction valve is opened. The intake and exhaust system according to claim 4.

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