Intake and exhaust system

Abstract

To perform warming-up of a catalyst at appropriate timing.SOLUTION: An intake and exhaust system comprises an engine, an exhaust flow passage connected to the engine, a catalyst that is provided in the exhaust flow passage for controlling emissions of exhaust gas, and a control device. The control device has one or more processors, and one or more memories connected to the one or more processors. The processor executes processing including: before the engine is started, execution of scavenging control that causes the exhaust gas remaining in the engine and the exhaust flow passage to pass through the catalyst and be discharged; and before the engine is started, execution of warming-up control that warms up the catalyst on the basis of a degree of emission-control of the exhaust gas by the catalyst during execution of the scavenging control.SELECTED DRAWING: Figure 6

Description

Technical Field

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

Background Art

[0002] A catalyst for purifying exhaust gas is provided in an exhaust passage connected to an engine. For example, as disclosed in Patent Document 1, examples of the catalyst provided in the exhaust passage include a nitrogen oxide storage catalyst.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to effectively exert the purification effect of the exhaust gas by the catalyst provided in the exhaust passage, it is necessary to warm up the catalyst to increase the temperature of the catalyst. Here, unnecessary warm-up of the catalyst in a situation where the temperature of the catalyst has not decreased is a factor that deteriorates environmental performance or fuel consumption. Therefore, it is desirable to perform the warm-up of the catalyst at an appropriate timing.

[0005] Therefore, an object of the present invention is to provide an intake and exhaust system capable of performing the warm-up of the catalyst at an appropriate timing.

Means for Solving the Problems

[0006] In order to solve the above problems, an intake and exhaust system according to an embodiment of the present invention includes an engine, an exhaust passage connected to the engine, a catalyst provided in the exhaust passage for purifying exhaust gas, a control device, and The control device is configured to: include one or more processors; one or more memories connected to the processors; and is configured to: Before starting the engine, the processor is configured to execute scavenging control to pass and discharge the exhaust gas remaining in the engine and the exhaust passage through the catalyst; Before starting the engine, based on the degree of purification of the exhaust gas by the catalyst during the execution of the scavenging control, the processor is configured to execute warm-up control to warm up the catalyst. The processor is configured to execute the processes including the above.

Advantages of the Invention

[0007] According to the present invention, it is possible to warm up the catalyst at an appropriate timing.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The specific dimensions, materials, numerical values, etc. shown in such embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals to omit redundant description, and elements not directly related to the present invention are not shown.

[0010] <Configuration of intake and exhaust system> With reference to FIGS. 1 and 2, the configuration of the intake and exhaust system 1 according to an embodiment of the present invention will be described.

[0011] FIG. 1 is a schematic diagram showing a schematic configuration of the 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, a starter motor 40, and a control device 50. The vehicle 100 may be an engine vehicle equipped only with the engine 10 as a drive source, or may be a hybrid vehicle equipped with a traveling motor in addition to the engine 10 as a drive source.

[0012] The engine 10 is, for example, a spark ignition internal combustion engine. The engine 10 has one or more cylinders 11. In FIG. 1, only one cylinder 11 out of the plurality of cylinders 11 provided in the engine 10 is shown for ease of understanding. A piston 12 is slidably provided in the cylinder 11. A combustion chamber 13 is formed inside the cylinder 11. The combustion chamber 13 is defined by the inner surface of the cylinder 11 and the crown surface of the piston 12. The cylinder 11 is provided with a spark plug 14 facing the combustion chamber 13. Further, the cylinder 11 is provided with a fuel injection valve 15 that injects fuel toward the combustion chamber 13. An air-fuel mixture containing air and fuel is formed in the combustion chamber 13. The air-fuel mixture is ignited by the spark plug 14 and burns. Thereby, the piston 12 in each cylinder 11 performs a linear reciprocating motion, and power is transmitted to a crankshaft connected to each piston 12.

[0013] Note that the fuel injection valve 15 is not limited to a type that directly injects fuel into the combustion chamber 13. For example, the fuel injection valve 15 may be provided in the intake passage 20 and inject fuel into the intake passage 20. In this case, the fuel is inhaled into the combustion chamber 13 together with the intake air. Also, the fuel supplied to the fuel injection valve 15 is, for example, gasoline. However, the fuel supplied to the fuel injection valve 15 may be a fuel other than gasoline.

[0014] Each combustion chamber 13 of the engine 10 communicates with the intake passage 20 via an intake port and with the exhaust passage 30 via an exhaust port. Each cylinder 11 is provided with an intake valve 16 that can open and close the intake port and an exhaust valve 17 that can open and close the exhaust port. By driving the intake valve 16 and the exhaust valve 17, the supply of intake air to the combustion chamber 13 and the discharge of exhaust gas from the combustion chamber 13 are performed.

[0015] The intake passage 20 is connected to the engine 10 and is a passage through which the air supplied to the combustion chamber 13 of the engine 10 flows. An intake port (not shown) through which outside air is taken in from outside the vehicle 100 is provided at the upstream end of the intake passage 20.

[0016] An air filter 21 is provided on the downstream side of the intake port in the intake passage 20. The air filter 21 removes foreign substances contained in the air flowing through the intake passage 20.

[0017] An electric compressor 22 is provided on the downstream side of the air filter 21 in the intake passage 20. The electric compressor 22 is driven by electric power, compresses the air, and discharges it to the downstream side.

[0018] Downstream of the electric compressor 22 in the intake air passage 20, a throttle valve 23 is provided. The throttle valve 23 adjusts the flow rate of the intake air sent to the engine 10 through the intake air passage 20. The flow rate of the intake air sent to the engine 10 varies according to the opening degree of the throttle valve 23. Further, the throttle valve 23 can open and close the intake air passage 20. When the throttle valve 23 is open, gas can pass through the installation position of the throttle valve 23 in the intake air passage 20. On the other hand, when the throttle valve 23 is closed, gas cannot pass through the installation position of the throttle valve 23 in the intake air passage 20. The throttle valve 23 is, for example, a butterfly valve.

[0019] Downstream of the throttle valve 23 in the intake air passage 20, a surge tank 24 is provided. In the surge tank 24, the intake air sent to the engine 10 is temporarily stored.

[0020] Downstream of the surge tank 24 in the intake air passage 20, an intake manifold (not shown) is provided. The intake manifold branches toward each cylinder 11 of the engine 10 and is connected to the intake port of each cylinder 11.

[0021] In the intake air passage 20, outside air is taken in from the intake port. The taken-in air passes through the air filter 21 and then sequentially passes through the electric compressor 22, the throttle valve 23, and the surge tank 24 and is sent to the engine 10.

[0022] The exhaust passage 30 is connected to the engine 10 and is a passage through which the exhaust gas discharged from the combustion chamber 13 of the engine 10 flows. At the downstream end of the exhaust passage 30, an exhaust port (not shown) for discharging the exhaust to the outside of the vehicle 100 is provided.

[0023] An exhaust manifold (not shown) is provided in the exhaust passage 30. The exhaust manifold branches toward each cylinder 11 of the engine 10 and is connected to the exhaust port of each cylinder 11.

[0024] A catalyst 31 is provided downstream of the exhaust manifold in the exhaust passage 30. The catalyst 31 is, for example, a nitrogen oxide storage catalyst capable of storing NOx in the exhaust gas. Hereinafter, an example in which the catalyst 31 is a nitrogen oxide storage catalyst will be described. However, as will be described later, the catalyst 31 is not limited to a nitrogen oxide storage catalyst.

[0025] An on-off valve 32 is provided downstream of the catalyst 31 in the exhaust passage 30. The on-off valve 32 can open and close the exhaust passage 30. When the on-off valve 32 is open, gas can pass through the installation position of the on-off valve 32 in the exhaust passage 30. On the other hand, when the on-off valve 32 is closed, gas cannot pass through the installation position of the on-off valve 32 in the exhaust passage 30. In the example of FIG. 1, the on-off valve 32 is a butterfly valve. However, the on-off valve 32 may be a valve of a type other than a butterfly valve.

[0026] In the exhaust passage 30, the exhaust gas discharged from the engine 10 passes through the catalyst 31, is purified by the catalyst 31, then passes through the on-off valve 32, and is discharged from the exhaust port.

[0027] A first exhaust gas sensor 33 and a second exhaust gas sensor 34 are provided in the exhaust passage 30. The first exhaust gas sensor 33 is provided upstream of the catalyst 31 in the exhaust passage 30 and detects the concentrations of various components of the exhaust gas flowing into the catalyst 31. The second exhaust gas sensor 34 is provided downstream of the catalyst 31 in the exhaust passage 30 and detects the concentrations of various components of the exhaust gas flowing out of the catalyst 31. In the example of FIG. 1, the second exhaust gas sensor 34 is provided upstream of the on-off valve 32 in the exhaust passage 30. However, the second exhaust gas sensor 34 may be provided downstream of the on-off valve 32 in the exhaust passage 30.

[0028] For example, the first exhaust gas sensor 33 and the second exhaust gas sensor 34 detect the concentration of NOx in the exhaust gas. However, as will be described later, the first exhaust gas sensor 33 and the second exhaust gas sensor 34 may detect the concentrations of components other than NOx in the exhaust gas.

[0029] The starter motor 40 is connected to the engine 10. The starter motor 40 is used to start the engine 10. Specifically, the output shaft of the starter motor 40 is connected to the crankshaft of the engine 10 via a gear, and the power output from the starter motor 40 is transmitted to the crankshaft of the engine 10. The starter motor 40 is driven by electric power.

[0030] The control device 50 includes one or more processors 50a and one or more memories 50b connected to the processor 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 the processes executed by the CPU.

[0031] The control device 50 communicates with each device provided in the intake and exhaust system 1. The communication between the control device 50 and each device is realized, for example, using CAN (Controller Area Network) communication.

[0032] 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 includes an acquisition unit 51 and a control unit 52.

[0033] Note that various processes including the processes described below performed by the acquisition unit 51 and the control unit 52 can be executed by the processor 50a. Specifically, by the processor 50a executing the program stored in the memory 50b, various processes are executed.

[0034] Note that the functions of the control device 50 according to this embodiment may be divided among a plurality of devices, or a plurality of functions may be realized by one device. When the functions of the control device 50 are divided among a plurality of devices, the plurality of devices may be connected to each other via a communication bus such as CAN.

[0035] The acquisition unit 51 acquires various information used in the processes performed by the control unit 52 and outputs it to the control unit 52. For example, the acquisition unit 51 acquires information from the first exhaust gas sensor 33 and the second exhaust gas sensor 34.

[0036] The control unit 52 controls the operations of the devices in the intake and exhaust system 1. For example, the control unit 52 controls the ignition timing by the ignition plug 14. Also, for example, the control unit 52 controls the fuel injection timing and the fuel injection amount in the fuel injection by the fuel injection valve 15. The fuel injection amount is the injection amount of the fuel supplied to the engine 10. Also, for example, the control unit 52 controls the operation of the electric compressor 22. Also, for example, the control unit 52 controls the opening degree of the throttle valve 23. Also, for example, the control unit 52 controls the opening degree of the on-off valve 32. Also, for example, the control unit 52 controls the operation of the starter motor 40.

[0037] <Operation of the intake and exhaust system> With reference to FIGS. 3 to 6, the operation of the intake and exhaust system 1 according to the embodiment of the present invention will be described.

[0038] As described above, in the intake and exhaust system 1, the exhaust gas is purified by the catalyst 31. Here, in order to effectively exhibit the exhaust gas purification effect of the catalyst 31, it is necessary to warm the catalyst 31 and raise the temperature of the catalyst 31. Therefore, the control device 50 executes warm-up control for warming the catalyst 31. The details of the warm-up control will be described later.

[0039] In the intake and exhaust system 1, before the engine 10 is started, the control device 50 executes scavenging control to pass the exhaust gas remaining in the engine 10 and the exhaust passage 30 through the catalyst 31 and discharge it, and executes warm-up control based on the degree of purification of the exhaust gas by the catalyst 31 during the execution of the scavenging control. Thereby, as will be described later, warm-up of the catalyst 31 is realized at an appropriate timing.

[0040] The scavenging control is performed to specify the degree of purification of the exhaust gas by the catalyst 31. Therefore, in the scavenging control, it is preferable to pass a large amount of exhaust gas through the catalyst 31. Here, after the engine 10 stops, the control device 50 performs a process for increasing the exhaust gas passing through the catalyst 31 in the scavenging control. Hereinafter, an example of the process after the engine 10 stops performed by the control device 50 will be described with reference to FIGS. 3 and 4.

[0041] FIG. 3 is a flowchart showing an example of the flow of the process after the engine 10 stops performed by the control device 50. The process flow shown in FIG. 3 starts, for example, when the ignition of the engine 10 is switched from on to off.

[0042] When the process flow shown in FIG. 3 is started, first, in step S101, the control unit 52 closes the throttle valve 23. Next, in step S102, the control unit 52 closes the on-off valve 32, and the process flow shown in FIG. 3 ends.

[0043] FIG. 4 is a diagram showing a state in which the throttle valve 23 and the on-off valve 32 are closed in the intake and exhaust system 1. As shown in FIG. 4, after the engine 10 stops, the throttle valve 23 and the on-off valve 32 are closed. Thereby, the exhaust gas remaining in the engine 10 and the exhaust passage 30 is not discharged to the outside of the vehicle 100 and remains in the space partitioned by the throttle valve 23 and the on-off valve 32. In this way, after the engine 10 stops, by retaining the exhaust gas in the engine 10 and the exhaust passage 30, it is possible to increase the exhaust gas passing through the catalyst 31 in the scavenging control described later.

[0044] Next, an example of the processing before starting the engine 10 performed by the control device 50 will be described with reference to FIGS. 5 and 6.

[0045] FIG. 5 is a flowchart showing an example of the flow of processing before starting the engine 10 performed by the control device 50. The processing flow shown in FIG. 5 starts, for example, when the ignition of the engine 10 is switched from off to on.

[0046] When the processing flow shown in FIG. 5 starts, first, in step S201, the control unit 52 opens the throttle valve 23. Next, in step S202, the control unit 52 opens the on-off valve 32.

[0047] FIG. 6 is a diagram showing a state in which the throttle valve 23 and the on-off valve 32 are open in the intake and exhaust system. As shown in FIG. 6, before starting the engine 10, the throttle valve 23 and the on-off valve 32 are open. Thereby, in the intake passage 20, the engine 10, and the exhaust passage 30, the gas can flow from the upstream side to the downstream side.

[0048] Next to step S202 in FIG. 5, in step S203, the control unit 52 executes scavenging control. As described above, the scavenging control is control for passing the exhaust gas remaining in the engine 10 and the exhaust passage 30 through the catalyst 31 and discharging it.

[0049] For example, in scavenging control, the control unit 52 may drive the starter motor 40 to cause the exhaust gas remaining in the engine 10 and the exhaust passage 30 to pass through the catalyst 31 and be discharged. In this case, when the starter motor 40 is driven, in each cylinder 11 of the engine 10, the piston 12 slides, the intake valve 16 and the exhaust valve 17 are driven, and the flow of gas from the intake passage 20 into each cylinder 11 and the flow of gas from each cylinder 11 into the exhaust passage 30 occur. Therefore, as indicated by the arrows in FIG. 6, the exhaust gas remaining in the engine 10 and the exhaust passage 30 is sent to the catalyst 31. Then, the exhaust gas passes through the catalyst 31 and is discharged from the exhaust port.

[0050] Also, for example, in scavenging control, the control unit 52 may drive the electric compressor 22 to cause the exhaust gas remaining in the engine 10 and the exhaust passage 30 to pass through the catalyst 31 and be discharged. In this case, the gas in the intake passage 20 is forcibly sent downstream by the electric compressor 22. Thereby, the flow of gas from the intake passage 20 to the exhaust passage 30 occurs through the cylinder 11 in which both the intake valve 16 and the exhaust valve 17 are open. Therefore, as indicated by the arrows in FIG. 6, the exhaust gas remaining in the engine 10 and the exhaust passage 30 is sent to the catalyst 31. Then, the exhaust gas passes through the catalyst 31 and is discharged from the exhaust port.

[0051] The control unit 52 may drive both the starter motor 40 and the electric compressor 22 in scavenging control. Thereby, it is more appropriately realized that the exhaust gas remaining in the engine 10 and the exhaust passage 30 passes through the catalyst 31 and is discharged. However, the control unit 52 may drive only one of the starter motor 40 and the electric compressor 22 in scavenging control.

[0052] Note that in scavenging control, the control unit 52 may use devices other than the starter motor 40 and the electric compressor 22. For example, in scavenging control, the control unit 52 may drive a blower device or the like provided at a location communicating with the intake passage 20 or the exhaust passage 30 and other than the intake passage 20. Further, when the electric compressor 22 is not used in scavenging control, the electric compressor 22 may be omitted from the intake and exhaust system 1.

[0053] Next to step S203 in FIG. 5, in step S204, the control unit 52 specifies the degree of purification of the exhaust gas by the catalyst 31 during the execution of the scavenging control. The above-mentioned degree of purification means, for example, the degree of the height of the exhaust gas purification action by the catalyst 31.

[0054] In step S204, the control unit 52 specifies the above-mentioned degree of purification based on the detection results of the first exhaust gas sensor 33 and the second exhaust gas sensor 34 during the execution of the scavenging control, for example.

[0055] For example, the acquisition unit 51 acquires the concentration of NOx in the exhaust gas flowing into the catalyst 31 during the execution of the scavenging control based on the detection result of the first exhaust gas sensor 33 during the execution of the scavenging control. Further, the acquisition unit 51 acquires the concentration of NOx in the exhaust gas flowing out of the catalyst 31 during the execution of the scavenging control based on the detection result of the second exhaust gas sensor 34 during the execution of the scavenging control. Then, the control unit 52 specifies the above-mentioned degree of purification based on the comparison result between the concentration of NOx in the exhaust gas flowing into the catalyst 31 during the execution of the scavenging control and the concentration of NOx in the exhaust gas flowing out of the catalyst 31 during the execution of the scavenging control. For example, the control unit 52 can determine that the lower the difference or ratio between the concentration of NOx in the exhaust gas flowing into the catalyst 31 during the execution of the scavenging control and the concentration of NOx in the exhaust gas flowing out of the catalyst 31 during the execution of the scavenging control, the lower the above-mentioned degree of purification.

[0056] Next to step S204, in step S205, the control unit 52 estimates the temperature of the catalyst 31 based on the specified result of the degree of purification of the exhaust gas by the catalyst 31 in step S204.

[0057] For example, information indicating the relationship between the degree of purification of the exhaust gas by the catalyst 31 specified in step S204 and the temperature of the catalyst 31 is stored in the control device 50 in advance. In step S205, the control unit 52 estimates, for example, the temperature corresponding to the degree of purification of the exhaust gas by the catalyst 31 specified in step S204 as the temperature of the catalyst 31 using the above information stored in the control device 50. For example, the lower the degree of purification of the exhaust gas by the catalyst 31 specified in step S204, the lower the temperature of the catalyst 31. Therefore, the control unit 52 can determine that the lower the degree of purification of the exhaust gas by the catalyst 31 specified in step S204, the lower the temperature of the catalyst 31.

[0058] Here, from the viewpoint of more accurately estimating the temperature of the catalyst 31, in addition to the result of specifying the degree of purification of the exhaust gas by the catalyst 31 in step S204, the control unit 52 preferably estimates the temperature of the catalyst 31 based on the degree of deterioration of the catalyst 31. For example, the control unit 52 can determine that the longer the usage period of the catalyst 31, the higher the degree of deterioration of the catalyst 31. When the temperature of the catalyst 31 is constant, the higher the degree of deterioration of the catalyst 31, the lower the degree of purification of the exhaust gas by the catalyst 31. Therefore, even if the degree of purification of the exhaust gas by the catalyst 31 is the same, the control unit 52 can determine that the higher the degree of deterioration of the catalyst 31, the higher the temperature of the catalyst 31.

[0059] Next to step S205, in step S206, the control unit 52 determines whether the temperature of the catalyst 31 is lower than a threshold value.

[0060] The threshold value in step S206 is set to a value that can determine, for example, whether the temperature of the catalyst 31 is high enough for the purification action of the exhaust gas by the catalyst 31 to be effectively exerted. For example, the threshold value in step S206 is set to a value corresponding to the lower limit value of the temperature range in which the purification action of the exhaust gas by the catalyst 31 reaches a desired level.

[0061] When it is determined that the temperature of the catalyst 31 is lower than the threshold value (YES in step S206), the process proceeds to step S207. On the other hand, when it is determined that the temperature of the catalyst 31 is equal to or higher than the threshold value (NO in step S206), the processing flow shown in FIG. 5 ends.

[0062] When it is determined as YES in step S206, in step S207, the control unit 52 executes warm-up control, and the processing flow shown in FIG. 5 ends. As described above, the warm-up control is control for warming the catalyst 31.

[0063] For example, in the warm-up control, the control unit 52 changes the ignition timing by the ignition plug 14 to the retarded side compared to when the warm-up control is not executed. Thereby, the temperature in the combustion chamber 13 at the timing when the exhaust valve 17 opens can be increased, and the high-temperature exhaust gas can be discharged from the combustion chamber 13 to the exhaust passage 30. Therefore, the catalyst 31 can be warmed by supplying the high-temperature exhaust gas to the catalyst 31.

[0064] Also, for example, in the warm-up control, the control unit 52 increases the fuel injection amount in the fuel injection by the fuel injection valve 15 compared to when the warm-up control is not executed. Thereby, the combustion temperature in the combustion chamber 13 can be increased, and the high-temperature exhaust gas can be discharged from the combustion chamber 13 to the exhaust passage 30. Therefore, the catalyst 31 can be warmed by supplying the high-temperature exhaust gas to the catalyst 31.

[0065] In the warm-up control, the control unit 52 may change both the ignition timing and the fuel injection amount compared to when the warm-up control is not executed. Thereby, warming of the catalyst 31 can be more appropriately realized. However, in the warm-up control, the control unit 52 may change only one of the ignition timing and the fuel injection amount compared to when the warm-up control is not executed.

[0066] As described above, in the present embodiment, before starting the engine 10, the control unit 52 executes scavenging control to pass the exhaust gas remaining in the engine 10 and the exhaust passage 30 through the catalyst 31 and discharge it, and based on the purification degree of the exhaust gas by the catalyst 31 during the execution of the scavenging control, executes warm-up control to warm the catalyst 31. Thereby, after appropriately specifying the purification degree of the exhaust gas by the catalyst 31, considering the temperature of the catalyst 31 estimated based on the purification degree of the exhaust gas by the catalyst 31, the warm-up of the catalyst 31 can be performed. Therefore, it is possible to suppress the unnecessary warm-up of the catalyst 31 in a situation where the temperature of the catalyst 31 has not decreased. Thus, the warm-up of the catalyst 31 can be performed at an appropriate timing. Thereby, the deterioration of environmental performance or fuel consumption is suppressed.

[0067] Here, as a method for estimating the temperature of the catalyst 31, for example, there is a method of estimating the temperature of the catalyst 31 based on the temperature of the cooling water of the engine 10. However, the relationship between the temperature of the cooling water of the engine 10 and the temperature of the catalyst 31 can vary due to various factors. Therefore, when estimating the temperature of the catalyst 31 based on the temperature of the cooling water of the engine 10, the temperature of the catalyst 31 may be underestimated compared to the actual temperature, and the warm-up of the catalyst 31 may be performed unnecessarily. On the other hand, in the present embodiment, the warm-up of the catalyst 31 is performed considering the temperature of the catalyst 31 estimated based on the purification degree of the exhaust gas by the catalyst 31. Therefore, the warm-up of the catalyst 31 is appropriately realized at an appropriate timing.

[0068] As described above, with reference to FIGS. 3 to 6, the processing performed by the control device 50 has been described. However, the processing performed by the control device 50 may be processing in which changes are made to the processing described above.

[0069] For example, in the processing flow of FIG. 3 above, after the engine 10 stops, the control unit 52 closes both the on-off valve 32 and the throttle valve 23. However, the control unit 52 may close only one of the on-off valve 32 and the throttle valve 23 after the engine 10 stops. However, from the viewpoint of effectively retaining the exhaust gas in the engine 10 and the exhaust passage 30, it is preferable that the control unit 52 closes both the on-off valve 32 and the throttle valve 23 after the engine 10 stops. When only the throttle valve 23 is closed after the engine 10 stops, the on-off valve 32 may be omitted from the intake and exhaust system 1.

[0070] Also, for example, the processing flow of FIG. 3 above may not be performed after the engine 10 stops. That is, the control unit 52 does not have to perform both the process of closing the on-off valve 32 and the process of closing the throttle valve 23 after the engine 10 stops. In this case, although the effect of retaining the exhaust gas in the engine 10 and the exhaust passage 30 decreases, some exhaust gas remains in the engine 10 and the exhaust passage 30 before the engine 10 starts. Therefore, by executing scavenging control before starting the engine 10, the degree of purification of the exhaust gas by the catalyst 31 can be specified. When neither the process of closing the on-off valve 32 nor the process of closing the throttle valve 23 is performed after the engine 10 stops, the on-off valve 32 may be omitted from the intake and exhaust system 1.

[0071] Further, for example, in the above, an example in which the catalyst 31 is a nitrogen oxide storage catalyst has been described. However, the catalyst 31 is not limited to a nitrogen oxide storage catalyst. For example, the catalyst 31 may be a three-way catalyst. The three-way catalyst oxidizes hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas and reduces NOx in the exhaust gas, thereby purifying these harmful components into harmless water vapor (H2O), carbon dioxide (CO2), and nitrogen (N2). Also in this case, in step S204 of FIG. 5, the control unit 52 can specify the degree of purification of the exhaust gas by the catalyst 31 during the execution of the scavenging control based on the detection results of the first exhaust gas sensor 33 and the second exhaust gas sensor 34 during the execution of the scavenging control. In this case, the first exhaust gas sensor 33 and the second exhaust gas sensor 34 may detect the concentration of NOx in the exhaust gas, or may detect the concentration of components other than NOx such as oxygen in the exhaust gas.

[0072] Further, for example, in the above processing flow of FIG. 5, the control unit 52 estimates the temperature of the catalyst 31 based on the specified result of the degree of purification of the exhaust gas by the catalyst 31, and executes warm-up control based on the estimated result of the temperature of the catalyst 31. However, the control unit 52 does not necessarily have to perform the process of estimating the temperature of the catalyst 31. For example, the control unit 52 may directly use the specified result of the degree of purification of the exhaust gas by the catalyst 31 without estimating the temperature of the catalyst 31 to determine whether to execute warm-up control.

[0073] <Effect of the intake and exhaust system> The effect of the intake and exhaust system 1 according to the embodiment of the present invention will be described.

[0074] In the intake and exhaust system 1 according to the present embodiment, before starting the engine 10, the processor 50a executes scavenging control to pass the exhaust gas remaining in the engine 10 and the exhaust passage 30 through the catalyst 31 and discharge it, and before starting the engine 10, based on the degree of purification of the exhaust gas by the catalyst 31 during the execution of the scavenging control, executes warm-up control to warm up the catalyst 31. Thereby, after appropriately specifying the degree of purification of the exhaust gas by the catalyst 31, considering the temperature of the catalyst 31 estimated based on the degree of purification of the exhaust gas by the catalyst 31, the catalyst 31 can be warmed up. Therefore, it is possible to suppress the unnecessary warm-up of the catalyst 31 in a situation where the temperature of the catalyst 31 has not decreased. Thus, the warm-up of the catalyst 31 can be performed at an appropriate timing. Thereby, the deterioration of environmental performance or fuel consumption is suppressed.

[0075] Further, the intake and exhaust system 1 according to the present embodiment includes an on-off valve 32 provided in the exhaust passage 30, and it is preferable that the processor 50a executes a process including closing the on-off valve 32 after the engine 10 stops and executing scavenging control after opening the on-off valve 32 before starting the engine 10. Thereby, after the engine 10 stops, it is appropriately realized to retain the exhaust gas in the engine 10 and the exhaust passage 30. Therefore, since the exhaust gas passing through the catalyst 31 can be increased by the scavenging control, the specification accuracy of the degree of purification of the exhaust gas by the catalyst 31 can be improved.

[0076] Further, in the intake and exhaust system 1 according to the present embodiment, it is preferable that the processor 50a executes a process including closing the throttle valve 23 after the engine 10 stops and executing scavenging control after opening the throttle valve 23 before starting the engine 10. Thereby, after the engine 10 stops, it is appropriately realized to retain the exhaust gas in the engine 10 and the exhaust passage 30. Therefore, since the exhaust gas passing through the catalyst 31 can be increased by the scavenging control, the specification accuracy of the degree of purification of the exhaust gas by the catalyst 31 can be improved.

[0077] In addition, in the intake and exhaust system 1 according to the present embodiment, it is preferable that the processor 50a executes a process including passing the exhaust gas remaining in the engine 10 and the exhaust passage 30 through the catalyst 31 and discharging it by driving the starter motor 40 in scavenging control. Thereby, in scavenging control, passing the exhaust gas remaining in the engine 10 and the exhaust passage 30 through the catalyst 31 and discharging it is appropriately realized.

[0078] In addition, the intake and exhaust system 1 according to the present embodiment includes an electric compressor 22 provided in the intake passage 20, and it is preferable that the processor 50a executes a process including passing the exhaust gas remaining in the engine 10 and the exhaust passage 30 through the catalyst 31 and discharging it by driving the electric compressor 22 in scavenging control. Thereby, in scavenging control, passing the exhaust gas remaining in the engine 10 and the exhaust passage 30 through the catalyst 31 and discharging it is appropriately realized.

[0079] As described above, the preferred embodiments of the present invention have been described with reference to the accompanying drawings. However, it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications or corrections within the scope described in the claims also belong to the technical scope of the present invention.

[0080] For example, the processes described using flowcharts in this specification do not necessarily have to be executed in the order shown in the flowcharts. Also, additional processing steps may be adopted, and some processing steps may be omitted.

Explanation of Reference Numerals

[0081] 1 Intake and exhaust system 10 Engine 11 Cylinder 12 Piston 13 Combustion chamber 14 Spark plug 15 Fuel injection valve 16 Intake valve 17 Exhaust valve 20 Intake air passage 21 Air filter 22 Electric compressor 23 Throttle valve 24 Surge tank 30 Exhaust gas passage 31 Catalyst 32 On-off valve 33 First exhaust gas sensor 34 Second exhaust gas sensor 40 Starter motor 50 Control device 50a Processor 50b Memory 51 Acquisition unit 52 Control unit 100 Vehicle

Claims

1. The engine, an exhaust passage connected to the engine; A catalyst provided in the exhaust passage for purifying exhaust gas; A control device; Equipped with The control device includes: one or more processors; one or more memories coupled to the processor; having The processor, executing a scavenging control for causing the exhaust gas remaining in the engine and the exhaust passage to pass through the catalyst before starting the engine; before starting the engine, executing a warm-up control for warming up the catalyst based on a degree of purification of the exhaust gas by the catalyst during execution of the scavenging control; Perform a process that includes Intake and exhaust system.

2. An opening and closing valve is provided in the exhaust passage, The processor, closing the on-off valve after the engine is stopped; Before starting the engine, the opening / closing valve is opened and then the scavenging control is executed; Perform a process that includes The intake and exhaust system according to claim 1 .

3. an intake passage connected to the engine; a throttle valve provided in the intake passage; Equipped with The processor, closing the throttle valve after the engine is stopped; before starting the engine, executing the scavenging control after opening the throttle valve; Perform a process that includes The intake and exhaust system according to claim 1 .

4. a starter motor connected to the engine; The processor executes a process including, in the scavenging control, driving the starter motor to pass the exhaust gas remaining in the engine and the exhaust passage through the catalyst and discharge the exhaust gas. The intake and exhaust system according to any one of claims 1 to 3.

5. an intake passage connected to the engine; an electric compressor provided in the intake passage; The processor executes a process including, in the scavenging control, driving the electric compressor to pass the exhaust gas remaining in the engine and the exhaust passage through the catalyst and discharge the exhaust gas. The intake and exhaust system according to any one of claims 1 to 3.

Images