Control unit for internal combustion engine systems

Abstract

A control unit for an internal combustion engine system is disclosed. The control unit is configured to control an electric turbocharger and an EGR valve. When the internal combustion engine is stopped, an oxygen-free period is estimated based on the temperature of the exhaust gas purifier. The oxygen-free period is a period during which oxygen available for oxidation reactions around the exhaust gas purifier is depleted. Before the oxygen-free period begins, the EGR valve is opened and the electric turbocharger is driven. The air around the exhaust gas purifier is replaced with fresh air. After the replacement with fresh air is completed, the electric turbocharger is stopped.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Japanese Patent Application No. 2021-190079, filed on November 24, 2021, which is hereby incorporated by reference herein in its entirety for all purposes. Technical Field

[0003] The present disclosure relates to a control unit for an internal combustion engine system. For example, the present disclosure relates to a control unit for preventing degradation of an exhaust gas purifier of an internal combustion engine. Background Art

[0004] The exhaust gas from an internal combustion engine contains hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), particulate matter (PM), etc. Vehicles equipped with an internal combustion engine can be equipped with various exhaust gas purifiers for purifying the exhaust gas. Some vehicles are equipped with a diesel engine as an internal combustion engine. Such vehicles can be equipped with, for example, a first oxidation catalyst, a particulate filter (DPF), a urea selective catalytic reducer (SCR), a second oxidation catalyst, etc. from the upstream side to the downstream side of the exhaust gas. In addition, a three-way catalyst, an NSR (NOx storage-reduction catalyst), etc. can be used as an exhaust gas purifier.

[0005] Hydrocarbons (HC) are generally converted into water (H2O) and carbon dioxide (CO2). For example, a first oxidation catalyst, a particulate filter, a three-way catalyst and an NSR having an oxidation function can be used to purify hydrocarbons from exhaust gas by utilizing an oxidation reaction. Carbon monoxide (CO) is generally converted into carbon dioxide (CO2). For example, a first oxidation catalyst, a particulate filter, a three-way catalyst and an NSR having an oxidation function are used to purify carbon monoxide from exhaust gas by utilizing an oxidation reaction. Nitrogen oxides (NOx) are generally converted into nitrogen (N2). For example, nitrogen oxides are purified from exhaust gas by utilizing a reduction function through a reduction reaction between ammonia generated by the added urea water and a urea SCR, or by utilizing a reduction function through a reduction reaction of an NSR. If excess ammonia is generated, the second oxidation catalyst utilizes an oxidation reaction to purify nitrogen oxides. Particulate matter (PM) is captured by the particulate filter and is not released into the atmosphere.

[0006] The exhaust gas purifier purifies hydrocarbons (HC) through an oxidation reaction. In this case, the exhaust gas purifier adsorbs hydrocarbons (HC). The adsorbed hydrocarbons (HC) undergo an oxidation reaction with the oxygen around the exhaust gas purifier. Since fresh exhaust gas containing oxygen continuously flows through the exhaust gas purifier when the internal combustion engine is running, oxygen shortage usually does not occur. On the other hand, if the operation of the internal combustion engine stops, the fresh exhaust gas will no longer flow through the exhaust gas purifier. In this case, the surrounding oxygen supply may be exhausted. If the surrounding oxygen is exhausted when the temperature of the exhaust gas purifier is higher than or equal to the activation temperature, the oxidation reaction will stop. As a result, hydrogen (H) is desorbed from the adsorbed hydrocarbons (HC). Carbon (C) therefore accumulates as deposits (so-called coking (adhesion through polymerization reaction) occurs), which may lead to deterioration of the exhaust gas purifier. In order to prevent coking from occurring after the internal combustion engine stops operating, it is necessary to lower the temperature of the exhaust gas purifier or ensure that the oxygen around the exhaust gas purifier is not exhausted.

[0007] A conventional exhaust gas purifier system for an internal combustion engine can convert the air / fuel ratio of exhaust gas from a running internal combustion engine from a lean state to a stoichiometric state or a rich state. In this case, the exhaust gas temperature is lowered using external air or water. This lowers the temperature of the exhaust gas purifier and prevents degradation of NOx purification performance.

[0008] A second conventional system for an engine's exhaust gas purifier increases the amount of ammonia adsorbed by the SCR after the engine stops. This ammonia absorption is increased to a level greater than or equal to the standard amount to ensure adequate NOx purification performance upon subsequent engine startup. More specifically, after the engine stops, the EGR (Exhaust Gas Recirculation) passage is opened while the electric turbocharger is driven to supply fresh air to the SCR. Urea is then supplied after the SCR temperature decreases.

[0009] Conventional exhaust gas purifiers for internal combustion engines are not designed to prevent coking after the engine stops. While the engine is running, water is used to reduce the temperature in the exhaust pipe and the exhaust gas purifier. In this case, water droplets directly contact the exhaust gas purifier, potentially damaging it. Furthermore, additional water tanks or water injection equipment are required, for example, to store water. This complicates the system and requires more space for installation.

[0010] A second conventional exhaust gas purifier is designed to lower the SCR temperature after the internal combustion engine stops to increase the amount of adsorbed ammonia. In other words, this device is not intended to enable hydrocarbon oxidation reactions—which would prevent coking after the internal combustion engine stops. With this exhaust gas purifier, fresh air is blown in via the electric turbocharger and EGR duct after the internal combustion engine stops. Therefore, to lower the SCR temperature, the electric turbocharger must continue to operate for a relatively long time. As a result, power consumption increases.

[0011] Therefore, an exhaust gas purifier having the function of purifying specific components in exhaust gas through oxidation reaction is generally required. For example, a structure for appropriately preventing the occurrence of coking is generally required to prevent degradation of the exhaust gas purifier while minimizing power consumption. Summary of the Invention

[0012] One aspect of the present disclosure relates to a control unit for an internal combustion engine system. The internal combustion engine system includes an internal combustion engine. An intake pipe is connected to the internal combustion engine. An electric turbocharger is provided at the intake pipe for supercharging intake air of the internal combustion engine. An exhaust pipe is connected to the internal combustion engine. An exhaust gas purifier (EGR) pipe is configured to return a portion of exhaust gas flowing through the exhaust pipe to the intake pipe at the outlet of the electric turbocharger. An EGR valve adjusts the opening of the EGR pipe. An exhaust gas purifier is provided at the exhaust pipe downstream of the connection between the EGR pipe and the exhaust pipe. The exhaust gas purifier adsorbs specific components contained in the exhaust gas. The adsorbed specific components undergo an oxidation reaction using ambient oxygen to remove these specific components from the exhaust gas. A control unit detects the operating state of the internal combustion engine to control actuators including the electric turbocharger and the EGR valve. An exhaust gas purifier temperature acquisition unit of the control unit is configured to acquire the temperature of the exhaust gas purifier. An operation stop detection unit detects that the operating internal combustion engine has stopped. When the operation stop detection unit detects that the operating internal combustion engine has stopped, a degradation prevention control unit is executed. The exhaust gas purifier temperature acquisition unit acquires the exhaust gas purifier temperature while the internal combustion engine is stopped. The deterioration prevention control unit's oxygen-free period estimation unit estimates the oxygen-free period based on the exhaust gas purifier temperature. The oxygen-free period is the period during which oxygen surrounding the exhaust gas purifier, which is used for oxidation reactions of specific components, is estimated to be depleted. The deterioration prevention control unit's fresh air replacement control unit allows the EGR valve to open before the estimated oxygen-free period begins and drives the electric turbocharger to replace the air surrounding the exhaust gas purifier with fresh air. After the replacement is completed, the electric turbocharger is deactivated.

[0013] Therefore, the oxidation reaction continues to prevent the occurrence of coking. In addition, since the electric turbocharger is stopped after the replacement with fresh air is completed, power consumption can be reduced.

[0014] According to another aspect of the present disclosure, when estimating the oxygen-free period by the oxygen-free period estimation unit, the control unit acquires the oxidation reaction rate of the exhaust gas purifier based on the exhaust gas purifier temperature acquired by the exhaust gas purifier temperature acquisition unit. The control unit estimates the oxygen-free period based on the acquired oxidation reaction rate. Consequently, a more accurate estimate of the oxygen-free period can be made. This enables more appropriate reduction in the power consumption of the electric turbocharger.

[0015] According to another aspect of the present disclosure, an operation stop detection unit is configured to detect whether a running internal combustion engine has stopped. The fresh air replacement control unit replaces fresh air while the oxidation reaction in the exhaust gas purifier continues while the internal combustion engine is stopped. The oxygen-free period estimation unit estimates a new oxygen-free period after the fresh air is replaced. The replacement of fresh air and the estimation of the oxygen-free period may be repeated.

[0016] The ambient oxygen may eventually be depleted after only a single fresh air exchange. Even in this case, the fresh air exchange and the estimation of the oxygen-free period can be repeated. This prevents the ambient oxygen from being depleted.

[0017] According to another aspect of the present disclosure, one of the specific components may be a hydrocarbon. An adsorbed hydrocarbon amount acquisition unit of the control unit estimates the adsorbed hydrocarbon amount. The adsorbed hydrocarbon amount is the amount of hydrocarbon adsorbed to the exhaust gas purifier while the internal combustion engine is operating and / or once the internal combustion engine is stopped. The operation stop detection unit detects that the operating internal combustion engine has stopped. The oxygen-free period estimation unit estimates the oxygen-free period. At this time, the control unit estimates the oxygen-free period based on the temperature of the exhaust gas purifier and the adsorbed hydrocarbon amount.

[0018] This enables a more accurate estimation of the oxygen-free period, thereby enabling a more appropriate reduction in the electric turbocharger's power consumption.

[0019] According to one aspect of the present disclosure, an operation stop detection unit detects that a running internal combustion engine has stopped. A fresh air replacement control unit replaces the engine with fresh air. In this case, if the control unit determines, based on the amount of adsorbed hydrocarbons, that the hydrocarbons have been sufficiently removed by the oxidation reaction, the control unit terminates execution of the degradation prevention control unit. Consequently, the degradation prevention control unit can be terminated at an appropriate timing. As a result, unnecessary power consumption can be appropriately avoided.

[0020] According to another aspect of the present disclosure, an operation stop detection unit detects that a running internal combustion engine has stopped. The fresh air replacement control unit replaces the engine with fresh air. In this case, if the exhaust gas purifier temperature acquired by the exhaust gas purifier temperature acquisition unit falls below or equals a termination determination temperature, the control unit terminates execution of the degradation prevention control unit. Consequently, the degradation prevention control unit can be terminated at an appropriate timing. As a result, unnecessary power consumption can be more appropriately avoided.

[0021] According to another aspect of the present disclosure, a load adjustment unit of a control unit can adjust the load of an internal combustion engine. Before the running internal combustion engine stops, the load adjustment unit adjusts the load existing immediately before the internal combustion engine stops so that the internal combustion engine stops at a crank angle within a range in which both an inlet valve and an outlet valve of at least one cylinder of the internal combustion engine are open.

[0022] Therefore, in addition to the EGR duct, any cylinder with both its inlet and outlet valves open can also be used as a fresh air passage when the electric turbocharger is driven to replace fresh air around the exhaust gas purifier. This reduces pressure loss when fresh air is blown in, resulting in more efficient fresh air exchange. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a diagram showing an example of the overall structure of an internal combustion engine.

[0024] Figure 2 1 is a flowchart showing an example of “the entire process for degradation prevention control” for preventing (reducing) the occurrence of coking after the operating internal combustion engine is stopped.

[0025] Figure 3 It shows Figure 2 Flowchart of details of the process of “adjusting the load of the internal combustion engine” shown in the flowchart of FIG.

[0026] Figure 4 It shows Figure 2 Flowchart showing details of the process of “detecting stop of the running internal combustion engine” shown in the flowchart of FIG.

[0027] Figure 5 It shows Figure 2 Flowchart of details of the process of “controlling replacement of fresh air” shown in the flowchart of FIG.

[0028] Figure 6 This is a flowchart showing the process for “controlling the EGR valve”.

[0029] Figure 7 1 is a flowchart showing the process for “controlling the electric turbocharger”.

[0030] Figure 8 It shows Figure 2 A flowchart showing details of the process of “determining the end of the degradation prevention control” shown in the flowchart of FIG.

[0031] Figure 9 This is an example of an operation waveform of the degradation prevention control.

[0032] Figure 10 is a diagram showing an example of temperature / oxidation reaction rate characteristics of an exhaust gas purifier. DETAILED DESCRIPTION

[0033] [Overall structure of internal combustion engine system 1 ( Figure 1 )]

[0034] Hereinafter, the control unit 50 for the internal combustion engine system 1 of the present embodiment will be described with reference to the accompanying drawings. Figure 1 An example of the overall structure of the internal combustion engine system 1 according to the present embodiment will be described. Figure 1 The internal combustion engine 10 in the internal combustion engine system 1 of the illustrated example is a diesel engine. Hereinafter, the structure and the like of the internal combustion engine system 1 will be described in order from the intake side to the exhaust side.

[0035] The intake duct 11A is provided with an air flow detector 31. The air flow detector 31 may be, for example, an intake air flow sensor, which is configured to output a detected signal to the control unit 50 based on the flow rate of intake air entering the internal combustion engine 10. Furthermore, the air flow detector 31 is provided with an intake air temperature detector 32A and an atmospheric pressure detector 33A. The intake air temperature detector 32A may be, for example, an intake air temperature sensor, which is configured to output a detected signal to the control unit 50 based on the temperature of the intake air (in this case, ambient air). The atmospheric pressure detector 33A may be, for example, a pressure sensor, which is configured to output a detected signal to the control unit 50 based on the atmospheric pressure. Furthermore, the intake duct 11A is connected to the compressor 82 of the turbocharger 80.

[0036] Furthermore, a branch intake duct 11B is connected to the intake duct 11A. The branch intake duct 11B is provided with an electric turbocharger 83. The intake duct 11A is provided with a switching valve 83A, while the branch intake duct 11B is provided with a different switching valve 83B. When the electric turbocharger 83 is driven, the control unit 50 closes the switching valve 83A of the intake duct 11A and opens the switching valve 83B of the branch intake duct 11B. When the electric turbocharger 83 is stopped, the switching valve 83A of the intake duct 11A is opened and the switching valve 83B of the branch intake duct 11B is closed. When the electric turbocharger 83 is driven, the electric turbocharger 83 supplies pressurized air to the compressor 82 of the turbocharger 80.

[0037] An intake duct 11A is connected to the inlet side of a compressor 82 of a turbocharger 80. Another intake duct 11C is connected to the outlet side of the compressor 82. A turbine 81 driven by exhaust gas rotates the compressor 82. The compressor 82 supplies intake air under pressure, which enters through the inlet-side intake duct 11A, to the outlet-side intake duct 11C. A pressure detector 33B is provided for the intake duct 11A upstream of the compressor 82. The pressure detector 33B outputs a detected signal to the control unit 50 based on the pressure of the air before being compressed by the compressor 82.

[0038] The downstream side of the intake duct 11C is connected to the intake manifold 11D. A pressure detector 33C, an intercooler 84, a throttle device 64, and an intake air temperature detector 32B are provided in the intake duct 11C. The pressure detector 33C may be, for example, a pressure sensor, configured to output a detected signal to the control unit 50 based on the pressure of the intake air supplied under pressure by the compressor 82. Furthermore, the intercooler 84 reduces the temperature of the intake air supplied under pressure from the compressor 82 to increase its oxygen density. The throttle device 64 adjusts the throttle valve opening to a target throttle opening based on a control signal from the control unit 50. The intake air temperature detector 32B may be, for example, an intake air temperature sensor, which outputs a detected signal to the control unit 50 based on the intake air temperature reduced by the intercooler 84.

[0039] The downstream side of the intake manifold 11D is connected to an intake port to guide intake air to each cylinder of the internal combustion engine 10. The intake air guided to the intake manifold 11D is sucked into each cylinder of the internal combustion engine 10 and used for combustion together with fuel injected from an injector.

[0040] The internal combustion engine 10 is provided with a rotation detector 34A and a cylinder detector 34B. The rotation detector 34 may be, for example, a rotation sensor of a crankshaft, which is configured to output a detected signal to the control unit 50 according to the rotation angle of the crankshaft of the internal combustion engine 10. The cylinder detector 34B may be, for example, a rotation sensor of a camshaft, which is configured to output a detected signal to the control unit 50 when the piston of the first cylinder reaches compression top dead center. In addition, the internal combustion engine 10 is provided with a loading device (a load apparatus) 63 capable of adjusting the load of the internal combustion engine 10. The loading device 63 may be, for example, an AC generator, which is configured to change the load of the internal combustion engine 10 based on a load control signal (power generation control signal) from the control unit 50.

[0041] The accelerator pedal depression amount detector 38 may be, for example, an accelerator pedal depression amount sensor, which is configured to output a detected signal to the control unit 50 based on the amount of depression of the accelerator pedal by the driver. The ignition switch 39 is an input device for the user to instruct the start or stop of the internal combustion engine. The user operates the ignition switch 39 to start a stopped internal combustion engine or to stop a running internal combustion engine.

[0042] The control unit 50 calculates the required load based on the engine speed according to the detection signal from the rotation detector 34A and the amount of accelerator pedal depression according to the detection signal from the accelerator pedal depression amount detector 38. These signals are used to calculate the amount of fuel corresponding to the required load. The control unit 50 then controls the injector at predetermined timing based on the detection signals from the rotation detector 34A and the cylinder detector 34B, and injects the amount of fuel corresponding to the required load.

[0043] The exhaust manifold 12A is connected to the exhaust port of the internal combustion engine 10. The exhaust gas from the internal combustion engine 10 is guided to the exhaust manifold 12A, the exhaust pipe 12B, and the turbine 81 of the turbocharger 80. When the exhaust gas is discharged to the exhaust pipe 12C, the exhaust gas drives the turbine 81 to rotate. The exhaust gas from the internal combustion engine 10 (in this case, a diesel engine) contains carbon monoxide (CO), hydrocarbons (HC), particulate matter (PM), and nitrogen oxides (NOx).

[0044] The inflow side of the EGR pipe 13, which is used to return a portion of the exhaust gas to the intake air, is connected to the exhaust manifold 12A or the exhaust pipe 12B. The outflow side of the EGR pipe 13 is connected to the intake pipe 11C or the intake manifold 11D. An EGR valve 13A for adjusting the opening of the EGR pipe 13 is provided at the EGR pipe 13. When the internal combustion engine is running, the control unit 50 can adjust the flow rate of the EGR gas by adjusting the opening of the EGR valve 13A. In addition, the control unit 50 opens the EGR valve 13A when the internal combustion engine 10 stops. This allows the fresh air supplied under pressure from the electric turbocharger 83 to flow through the intake pipe 11A, the branch pipe 11B, the intake pipe 11C, the EGR pipe 13 and the exhaust pipes 12B and 12C, and reach the exhaust purifier 40.

[0045] The exhaust pipe 12B is connected to the outflow side of the exhaust manifold 12A. The inflow side of the turbine 81 of the turbocharger 80 is connected to the downstream side of the exhaust pipe 12B. Another exhaust pipe 12C is connected to the outflow side of the turbine 81, and the exhaust gas purifier 40 is connected to the downstream side of this exhaust pipe 12C.

[0046] The exhaust gas purifier 40 is provided in the exhaust pipe on the downstream side of the connection between the EGR pipe 13 and the exhaust pipe 12B (or the exhaust manifold 12A) (in this case, on the downstream side of the exhaust pipe 12B). The exhaust gas purifier 40 includes an upstream exhaust gas purifier 41 and a downstream exhaust gas purifier 45 provided downstream of the upstream exhaust gas purifier 41. Inside the upstream exhaust gas purifier 41, from the upstream side, a first oxidation catalyst 42 (DOC: Diesel Oxidation Catalyst) and a particulate filter 43 (DPF: Diesel Particulate Filter) are provided.

[0047] First oxidation catalyst 42 is used to remove carbon monoxide (CO), hydrocarbons (HC), and the like contained in the exhaust gas through an oxidation reaction. Particulate filter 43 (hereinafter referred to as "DPF") is used to trap particulate matter (PM) contained in the exhaust gas. Exhaust gas flows downstream through particulate filter 43. Particulate filter 43 also functions to remove carbon monoxide (CO) and hydrocarbons (HC) through an oxidation reaction.

[0048] The exhaust pipe 12C located on the upstream side of the first oxidation catalyst 42 (upstream side of the upstream exhaust purifier 41) is provided with an addition valve 61, an exhaust temperature detector 36A (for example, an exhaust temperature sensor), etc. The addition valve 61 injects fuel (liquid additive) into the exhaust pipe 12C. The fuel undergoes an oxidation reaction in the first oxidation catalyst 42 to increase the temperature of the exhaust gas. The hotter exhaust gas burns and incinerates the particulate matter captured by the DPF 43 and deposited in the DPF 43, thereby making the DPF 43 reusable (regenerate). The fuel is supplied to the addition valve 61 from a fuel tank (not shown). In addition, an exhaust temperature detector 36B (for example, an exhaust temperature sensor) is provided on the downstream side of the first oxidation catalyst 42 and upstream side of the DPF 43.

[0049] An exhaust temperature detector 36C (e.g., an exhaust temperature sensor) is provided on the downstream side of the DPF 43. Furthermore, a differential pressure sensor 35 is provided within the upstream exhaust purifier 41 for detecting a pressure difference (e.g., a pressure difference) between the exhaust pressure on the downstream side of the first oxidation catalyst 42 and the upstream side of the DPF 43 and the exhaust pressure on the downstream side of the DPF 43.

[0050] The control unit 50 is configured to detect the pressure difference between the upstream side of the DPF 43 and the downstream side of the DPF 43 based on the detection signal from the differential pressure sensor 35. The amount of particulate matter trapped in the DPF 43 can be estimated based on the detected pressure difference. If the estimated amount of deposits exceeds a threshold value, the control unit 50 injects fuel (liquid additive) from the addition valve 61. The injected fuel increases the exhaust temperature, which in turn burns and incinerates the particulate matter deposited in the DPF 43, making the DPF 43 reusable. At this time, the control unit 50 detects the exhaust temperature at each location based on the detection signals from the exhaust temperature detectors 36A, 36B, and 36C, and allows the fuel (liquid additive) to be injected from the addition valve 61 to maintain the desired temperature.

[0051] Furthermore, the downstream exhaust purifier 45 is equipped with an addition valve 62, a selective reduction catalyst 46 (SCR), a second oxidation catalyst 47, and the like, from the upstream side. The selective reduction catalyst 46 (hereinafter referred to as "SCR") is connected to the downstream side of the DPF 43 via the exhaust pipe 12D. The addition valve 62 is provided in the exhaust pipe 12D, which is located downstream of the DPF 43 and upstream of the SCR 46. The addition valve 62 injects urea water (a liquid additive) into the exhaust gas at a predetermined timing. The injected urea water (a liquid additive) is dispersed, atomized, and diffused within the exhaust pipe 12D and reaches the SCR 46. Furthermore, the urea water is supplied to the addition valve 62 from a urea water tank (not shown). The SCR 46 uses ammonia generated from the added urea water to reduce and purify nitrogen oxides (NOx) contained in the exhaust gas.

[0052] Furthermore, a NOx detector 37A (e.g., a NOx sensor) is provided in the exhaust pipe 12D upstream of the SCR 46. Another NOx detector 37B (e.g., a NOx sensor) and an exhaust temperature detector 36D (e.g., an exhaust temperature sensor) are provided in the exhaust pipe 12E downstream of the SCR 46. The NOx detectors 37A and 37B output detected signals to the control unit 50 based on the NOx concentration in the exhaust gas. The exhaust temperature detector 36D outputs detected signals to the control unit 50 based on the temperature of the exhaust gas. The control unit 50 calculates the NOx purification rate of the SCR 46 based on the detection signals from the NOx detectors 37A and 37B and the exhaust temperature detector 36D. The control unit 50 controls the addition valve 62 based on the calculated NOx purification rate.

[0053] The second oxidation catalyst 47 is connected to the downstream side of the SCR 46 via the exhaust pipe 12E. The second oxidation catalyst 47 oxidizes and purifies residual ammonia from the exhaust gas. The second oxidation catalyst 47 also has the function of removing carbon monoxide (CO) and hydrocarbons (HC) through oxidation reaction.

[0054] The control unit 50 may be a known control unit and may include a CPU 51, a RAM 52, a ROM 53, a timer 54, an EEPROM 55, and the like. The CPU 51 may be configured to implement various computational processes based on various programs or maps stored in the ROM 53. In addition, the RAM 52 may be configured to temporarily store computational results computed by the CPU and to store data input from each detector. The EEPROM 55 may be a nonvolatile storage device configured to store data regarding the internal combustion engine 10, for example, when the internal combustion engine 10 is stopped.

[0055] Furthermore, the control unit 50 can detect the operating state of the internal combustion engine 10 based on the input detection signal. The control unit 50 also receives a request from the operator based on the detected operating state of the internal combustion engine 10, the detected signal from the accelerator pedal depression amount detector 38, and the like. The control unit 50 outputs control signals for controlling various actuators, such as the injectors for injecting fuel into the cylinders, the addition valves 61 and 62 for injecting fuel or urea water, the electric turbocharger 83, the EGR valve 13A, and the like. The control unit 50 (CPU 51) may include a degradation prevention control unit 51A, an exhaust gas purifier temperature acquisition unit 51B, a load adjustment unit 51C, an operation stop detection unit 51D, an adsorbed hydrocarbon amount acquisition unit 51E, an oxygen-free period estimation unit 51F, and a fresh air replacement control unit 51G, details of which will be described later. These units may be implemented using a circuit system or any other suitable structure.

[0056] Here, hydrocarbons (HC) contained in the exhaust gas are adsorbed to the first oxidation catalyst 42 (as well as the DPF 43, the second oxidation catalyst 47). As the internal combustion engine 10 heats up, the temperature of the first oxidation catalyst 42 (as well as the DPF 43, the second oxidation catalyst 47, etc.) can rise to a temperature higher than or equal to the activation temperature. Hydrocarbons can undergo an oxidation reaction with the oxygen contained in the exhaust gas. Since the exhaust gas contains oxygen and flows continuously when the internal combustion engine 10 is running, there is generally no shortage of oxygen for the oxidation reaction. However, the internal combustion engine 10 may stop when hydrocarbons (HC) are still adsorbed to the first oxidation catalyst 42 (as well as the DPF 43, the second oxidation catalyst 47, etc.). In this case, if the temperature is higher than or equal to the activation temperature, the oxidation reaction of the hydrocarbons will be carried out using the surrounding oxygen. However, the surrounding oxygen may eventually be exhausted. If the surrounding oxygen is exhausted, the oxidation reaction of the adsorbed hydrocarbons (HC) will not proceed, so that instead hydrogen (H) will be desorbed and carbon will accumulate as deposits. This accumulation of carbon may lead to the occurrence of so-called coking. As a result, the first oxidation catalyst 42 (as well as the DPF 43, the second oxidation catalyst 47, etc.) will further deteriorate. The control unit 50 described in this embodiment is used to prevent the occurrence of coking by performing the following processing. The control unit 50 is also used to prevent the exhaust gas purifier 40 (which may include the first oxidation catalyst 42, the DPF 43, the second oxidation catalyst 47, etc.) from deteriorating.

[0057] [Processing process of control unit 50 ( Figures 2 to 8 ) and operation waveform examples ( Figure 9 )]

[0058] In the following, reference will be made to Figures 2 to 8 The flowchart shown describes the processing of the control unit 50. Figure 9 Describes an example of an operating waveform.

[0059] [Overall Processing for Deterioration Prevention Control ( Figure 2 )]

[0060] The control unit 50 (CPU 51) initiates the operation at predetermined time intervals (several milliseconds to several tens of milliseconds). Figure 2 The “entire process for degradation prevention control” is shown. After initiation, the control unit 50 causes the process to proceed to step S010. In the following description, an example will be described in which the “first oxidation catalyst” is regarded as the “exhaust gas purifier”.

[0061] In step S010, control unit 50 executes the "Engine Load Adjustment" process and proceeds to step S015. In the "Engine Load Adjustment" process, the load existing immediately before stopping internal combustion engine 10 is adjusted. More specifically, internal combustion engine 10 is stopped so that the crankshaft angle is within a range where both the intake and exhaust valves of at least one cylinder are open. Details of the implementation of this process will be described later.

[0062] In step S015, the control unit 50 performs the process of "detecting the stop of the running internal combustion engine" and advances the process to step S020. The process of "detecting the stop of the running internal combustion engine" is a process of detecting that the previously running internal combustion engine 10 has stopped. The details of this embodiment will be described later. In the process of "detecting the stop of the running internal combustion engine", the operating flag is set to ON (enabled) or OFF (disabled), and the degradation prevention control flag is set to ON or OFF. The degradation prevention control flag is a flag that is set to ON when the degradation prevention control for preventing the occurrence of the above-mentioned coking is started.

[0063] In step S020, the control unit 50 determines whether the degradation prevention control flag is ON. If the degradation prevention control flag is ON (Yes), the process proceeds to step S025. If the degradation prevention control flag is not ON (No), the process proceeds to step S070.

[0064] When the process proceeds to step S025, the running internal combustion engine 10 is completely stopped. Once the internal combustion engine 10 is stopped, the control unit 50 updates the exhaust gas purifier temperature Ta and causes the process to proceed to step S030. For example, the control unit 50 determines the reduced temperature ΔTb after a certain time has passed. The previous exhaust gas purifier temperature Ta is updated to the current exhaust gas purifier temperature Ta. The current exhaust gas purifier temperature Ta is obtained by subtracting the reduced temperature ΔTb from the previous exhaust gas purifier temperature Ta. Figure 9 In the example of the operating waveform of FIG, the "deterioration prevention control flag" is set to ON during the period from time T3 to time T7. The "exhaust gas purifier temperature Ta" during the period from time T3 to time T7 is determined using the process described in step S025. The method for obtaining the exhaust gas purifier temperature Ta when the internal combustion engine 10 is stopped is not limited to this method.

[0065] In step S030, the control unit 50 obtains the oxidation reaction rate Vx of the exhaust gas purifier based on, for example, the exhaust gas purifier temperature Ta. Then, the control unit 50 proceeds to step S035. For example, the "temperature / oxidation reaction rate characteristics" corresponding to the exhaust gas purifier are stored in the storage device of the control unit 50, and its embodiment is described in detail in the following. Figure 10The "temperature / oxidation reaction rate characteristic" represents the oxidation reaction rate according to the target exhaust gas purifier temperature. Figure 10 The example shown in indicates that the oxidation reaction rate is almost zero below the activation temperature. The control unit 50 obtains the current oxidation reaction rate Vx of the exhaust gas purifier temperature Ta based on the temperature / oxidation reaction rate characteristic and the exhaust gas purifier temperature Ta. Figure 9 In the example of the operation waveform of , during the period from time T3 to time T7 (ie, the “deterioration prevention control flag” is set to ON), the “oxidation reaction rate Vx” is continuously determined using this step S030.

[0066] In step S035, the control unit 50 updates the ambient oxygen amount Oa corresponding to the oxygen amount around the exhaust gas purifier based on the oxidation reaction rate Vx. The control unit 50 advances the process to step S040. For example, the control unit 50 determines the reduced oxygen amount ΔOb according to the passage of time. The reduced oxygen amount ΔOb is subtracted from the previous ambient oxygen amount Oa and the resulting value is used as the current ambient oxygen amount Oa. Figure 9 In the example of the operating waveform, the "deterioration prevention control flag" is set to ON during the period from time T3 to time T7. During this period, the "fresh air replacement flag" is set to OFF during certain periods from time T3 to time T4a, from time T4c to time T5a, from time T5c to time T6a, and from time T6c to time T7. Step S035 is used to determine the "ambient oxygen amount Oa" during each of these periods. However, the method for obtaining the ambient oxygen amount Oa when the internal combustion engine 10 is stopped is not limited to this method.

[0067] In step S040, the control unit 50 updates the adsorbed hydrocarbon amount Ma based on the oxidation reaction rate Vx and proceeds to step S045. For example, the control unit 50 determines the reduced hydrocarbon amount ΔMb according to the passage of time. The reduced hydrocarbon amount ΔMb is subtracted from the previous adsorbed hydrocarbon amount Ma and the resulting value is used as the current adsorbed hydrocarbon amount Ma. Figure 9 In the example of the operating waveform, the "degradation prevention control flag" is set to ON during the period from time T3 to time T7. The "adsorbed hydrocarbon amount Ma" during this period is determined using step S040. However, the method for obtaining the adsorbed hydrocarbon amount Ma when the internal combustion engine 10 is stopped is not limited to this method.

[0068] In step S045, the control unit 50 estimates when the oxygen-free period Tn will occur. In this embodiment, the oxygen-free period Tn is a period of time during which the ambient oxygen (ambient oxygen amount Oa) will be depleted. The control unit 50 can estimate when the oxygen-free period Tn will occur based on the current oxidation reaction rate Vx, the current ambient oxygen amount Oa, the current adsorbed hydrocarbon amount Ma, etc. Then, the control unit 50 causes the process to proceed to step S050. Figure 9 In the example of the operation waveform of , it is estimated that the anaerobic period T4b will occur, for example, after the current time has passed the time T3 and before the time T4a.

[0069] In step S050, the control unit 50 determines whether the fresh air replacement flag is on. If the fresh air replacement flag is on (yes), the process proceeds to step S060. If the fresh air replacement flag is not on (no), the process proceeds to step S055. The fresh air replacement flag is a flag that is set to on or off during step S060. When fresh air replacement is performed in step S060, the fresh air replacement flag is set to on.

[0070] In step S055, the control unit 50 determines whether the current time is within Tα (time T4b, T5b, T6b) before the start of the anaerobic period Tn. If the current time is within Tα (time T4b, T5b, T6b) before the anaerobic period Tn (yes), the process proceeds to step S060, and if the current time is not within Tα (time T4b, T5b, T6b) before the anaerobic period Tn (no), the process proceeds to step S065. Figure 9 In the example of the operating waveform shown, for example, if the current time is between time T4a and time T4b, the control unit 50 determines that the current time is within Tα before the anaerobic period T4b. If the current time is between time T3 and time T4a, the system is determined not to be within Tα before the anaerobic period T4b. The value of Tα can be set to an appropriate value based on various experiments, etc.

[0071] When the process proceeds to step S060, the control unit 50 executes a process for "controlling the replacement of fresh air" and proceeds to step S065. The process for "controlling the replacement of fresh air" allows the EGR valve to be opened for a certain period of time while the internal combustion engine 10 is stopped. During this period of time, the electric turbocharger is driven to replace the air surrounding the exhaust gas purifier with fresh air. This process will be described in detail later.

[0072] When the process proceeds to step S065, the control unit 50 executes the process of "determining the end of the degradation prevention control" and ends the process. Figure 2The process of "determining the end of degradation prevention control" is a process that can be used to set the degradation prevention control flag to OFF. More specifically, the process of "determining the end of degradation prevention control" is executed when the conditions are met in which the degradation prevention control flag set to ON in step S015 is set to OFF. If these conditions are met, the control unit 50 sets the flag to OFF. This process will be described in detail later.

[0073] If the process proceeds to step S070 (see Figure 2 ), the control unit 50 determines whether the operating flag is ON. If the operating flag is ON (yes), the process proceeds to step S075. If the operating flag is not ON (no), the process proceeds to step S090. In step S015, if the internal combustion engine is in operation, the operating flag is set to ON, and if the internal combustion engine has stopped, the operating flag is set to OFF (see Figure 9 The details of ON / OFF of the in-operation flag will be described later.

[0074] When the processing proceeds to step S075, it has been determined that the internal combustion engine 10 is not stopped, but is instead still running. When the internal combustion engine 10 is running, the control unit 50 obtains the exhaust gas purifier temperature Ta based on the operating state of the internal combustion engine 10. Then, the processing proceeds to step S077. For example, the control unit 50 can obtain (estimate) the exhaust gas purifier temperature Ta based on the temperature of the exhaust gas detected by the exhaust gas temperature detector 36A, the exhaust gas flow rate estimated according to the intake air amount, the rotation speed, etc. Figure 9 In the example of the operating waveform of , the "in-operation flag" is set to ON during the period from time T2 to time T3. The "exhaust gas purifier temperature Ta" during this period is determined using step S075, although other methods may be used instead.

[0075] In step S077, the control unit 50 obtains the oxidation reaction rate Vx based on the exhaust gas purifier temperature Ta. Then, the process proceeds to step S080. For example, similar to the process of step S030, the control unit 50 may obtain the oxidation reaction rate Vx based on the exhaust gas purifier temperature Ta and Figure 10 The oxidation reaction rate Vx is obtained by using the "temperature / oxidation reaction rate characteristics" shown in FIG. Figure 9 In the example of the operating waveform of , the "in-operation flag" is set to ON during the period from time T2 to time T3. Step S077 is used to determine the "oxidation reaction rate Vx" during this period, although other methods may be used instead.

[0076] In step S080, the control unit 50 estimates the ambient oxygen amount Oa based on the operating state of the internal combustion engine. The ambient oxygen amount Oa is the amount of oxygen around the exhaust gas purifier during operation. Then, the process proceeds to step S085. For example, the control unit 50 may estimate the ambient oxygen amount Oa based on the intake air amount, the rotation speed, the fuel injection amount, etc. Figure 9 In the example of the operation waveform of , during the period from time T2 to time T3, the "in-operation flag" is set to ON. Step S080 is used to determine the "ambient oxygen amount Oa" during this period, although other methods may be used instead.

[0077] In step S085, the control unit 50 estimates the adsorbed hydrocarbon amount Ma, which is the amount of hydrocarbons adsorbed to the exhaust gas purifier during operation, based on the operating state of the internal combustion engine. Then, the control unit 50 ends the operation. Figure 2 For example, the control unit 50 estimates the amount of adsorbed hydrocarbons Ma based on the intake air amount, the fuel injection amount, the rotation speed, the exhaust gas purifier temperature Ta, etc. Figure 9 In the example of the operation waveform of , the "in-operation flag" is set to ON during the period from time T2 to time T3. The "adsorbed hydrocarbon amount Ma" during this period is determined using step S085, although other methods may be used instead.

[0078] If the process proceeds to step S090 (see Figure 2 ), the control unit 50 acquires (estimates) the exhaust gas purifier temperature Ta based on the operating state of the internal combustion engine (in this case, when the engine is stopped). Then, the control unit 50 ends Figure 2 For example, the control unit 50 determines the ambient air temperature (the intake air temperature detected by the intake air temperature detector 32A) and uses the temperature as the exhaust purifier temperature Ta.

[0079] [Regulating the load of the internal combustion engine ( Figure 3 )]

[0080] Will refer to Figure 3 Detailed description Figure 2 When executing step S010 "adjusting the load of the internal combustion engine", Figure 2 When the process of step S010 in the flowchart shown in FIG. 1 is completed, the control unit 50 advances the process to step S110. Figure 3 An embodiment of this process is shown in FIG.

[0081] In step S110, the control unit 50 determines whether the internal combustion engine has stopped. This can be achieved by determining whether the user has issued a stop request for the internal combustion engine (operation of the ignition switch). If it is determined that the engine has stopped due to the stop request (Yes), the process proceeds to step S115. If it is determined that the engine has not stopped due to the stop request (No), the process proceeds to step S150.

[0082] If the process proceeds to step S115, the control unit 50 determines whether the rotation speed of the internal combustion engine is lower than or equal to an adjusted rotation speed (e.g., a speed lower than or equal to the rotation speed immediately before the internal combustion engine is completely stopped). If the rotation speed is lower than the adjusted rotation speed (yes), the process proceeds to step S120. If the rotation speed is not lower than the adjusted rotation speed (no), the process proceeds to step S150.

[0083] If the process proceeds to step S120, the control unit 50 determines whether the crankshaft angle is greater than or equal to the first rotation angle θ1 and less than or equal to the second rotation angle θ2. If the crankshaft angle is greater than or equal to the first rotation angle θ1 and less than or equal to the second rotation angle θ2 (yes), the process proceeds to step S125. If the crankshaft angle is not greater than or equal to the first rotation angle θ1 and less than or equal to the second rotation angle θ2 (no), the process proceeds to step S150. For example, a crankshaft angle greater than or equal to the first rotation angle θ1 and less than or equal to the second rotation angle θ2 is a crankshaft angle when both the inlet valve and the outlet valve of at least one cylinder (e.g., the first cylinder) are open. This allows, when replacing oxygen-deficient air with fresh air using an electric turbocharger, to provide a passage from the inlet valve through at least one cylinder to the outlet valve in addition to the passage of the EGR duct. As a result, pressure loss during the replacement of fresh air can be reduced, which in turn improves efficiency during the replacement of fresh air.

[0084] If the process proceeds to step S125, the control unit 50 increases the load of the internal combustion engine to stop the internal combustion engine immediately. Figure 9 In the example of the operating waveform in FIG, the “load adjustment amount” increases immediately before time T3. More specifically, the control unit 50 outputs a control signal for increasing the load amount (a signal for increasing the power generation amount) to the loading device 63 (AC generator) so as to immediately stop the internal combustion engine. Then, the control unit 50 ends Figure 3 The process shown in Figure 2 Step S015 shown.

[0085] If the process proceeds to step S150, the control unit 50 performs the existing control of the loading device 63. Since this control is the existing control, the details will be omitted. Then, the control unit 50 ends Figure 3 The process shown in Figure 2 Step S015 shown.

[0086] [Detection of stopping of a running internal combustion engine ( Figure 4 )]

[0087] Will refer to Figure 4 Detailed description Figure 2 The process of "detecting the stop of the running internal combustion engine" in step S015 is executed. Figure 2 When processing step S015 in the flowchart shown in FIG. 1 , the control unit 50 performs the processing until Figure 4 Step S210 is shown.

[0088] In step S210, the control unit 50 determines whether the internal combustion engine has stopped. If the internal combustion engine has stopped (Yes), the control unit 50 advances the process to step S215. If the internal combustion engine has not stopped (No), the process advances to step S220B.

[0089] If the process proceeds to step S215, the control unit 50 determines whether the in-operation flag was previously set to ON. If the in-operation flag is set to ON (yes), the process proceeds to step S220A. If the in-operation flag is not set to ON (no), the control unit 50 ends the process. Figure 4 The process shown and returns the process to Figure 2 Step S020 shown.

[0090] If the process proceeds to step S220A, the control unit 50 sets the degradation prevention control flag to ON and the operating flag to OFF. Then, the control unit 50 ends Figure 4 The process shown and returns the process to Figure 2 Step S020 shown.

[0091] If the process proceeds to step S220B, the control unit 50 sets the degradation prevention control flag to OFF and the operating flag to ON. Then, the control unit 50 ends Figure 4 The process shown and returns the process to Figure 2 Step S020 shown.

[0092] Through these treatments, such as Figure 9As shown in the example of the operating waveform in FIG, when the internal combustion engine 10 is in operation, the "operating flag" is set to ON. When the operating internal combustion engine stops, the "operating flag" switches from ON to OFF. In this case, the "deterioration prevention control flag" is set to ON.

[0093] [Control fresh air replacement ( Figure 5 )]

[0094] Next, we will refer to Figure 5 Detailed description Figure 2 The process of "controlling the replacement of fresh air" in step S060 is executed. Figure 2 When processing step S060 in the flowchart shown in FIG. 1 , the control unit 50 performs the processing until Figure 5 Step S310 is shown. Figure 9 In the example of the operation waveform in FIG, the “control of fresh air replacement” process is executed during the period from time T4a (or time T5a, or time T6a) until the “fresh air replacement flag” is set to OFF. The fresh air replacement flag is Figure 5 The flag shown is set to ON or OFF during the "control of fresh air replacement" process. As will be described below, the fresh air replacement flag is set to ON when the air around the exhaust gas purifier is replaced with fresh air due to the electric turbocharger being driven (this can be done after the running internal combustion engine has stopped).

[0095] In step S310, the control unit 50 determines whether the fresh air replacement flag has been set to ON. If the fresh air replacement flag has been set to ON (Yes), the control unit 50 advances the process to step S325. If the fresh air replacement flag has not been set to ON (No), the control unit 50 advances the process to step S315.

[0096] If the process proceeds to step S315 , the control unit 50 initializes and starts a fresh air replacement timer, and then proceeds to step S320 .

[0097] In step S320 , the control unit 50 sets the fresh air replacement flag to ON, and proceeds with the process to step S325 .

[0098] like Figure 9 As shown in the example of the operation waveform in FIG, the "fresh air replacement flag" is set from OFF to ON in the processing of steps S310 to S320. In this case, the "fresh air replacement timer" is initialized and started to start counting the operating time of the electric turbocharger.

[0099] When the process proceeds to step S325, the control unit 50 determines whether the time counted by the fresh air replacement timer is longer than or equal to the target replacement time. If the time counted by the fresh air replacement timer is longer than or equal to the target replacement time (Yes), the control unit 50 causes the process to proceed to step S360. If the time counted by the fresh air replacement timer is not longer than or equal to the target replacement time (No), the control unit 50 causes the process to proceed to step S340. As will be described later, the "target replacement time" is the time to replace the air around the exhaust purifier with fresh air when the speed of the electric turbocharger is driven at the "target speed". The "target replacement time" can be set to an appropriate value based on various experiments, etc.

[0100] If the process proceeds to step S340, the control unit 50 controls the EGR valve to be fully open. Furthermore, the control unit 50 drives the electric turbocharger so that its rotational speed approaches the target rotational speed. The control unit 50 then proceeds to step S345. The "target rotational speed" may be set to the rotational speed of the electric turbocharger that achieves the highest power efficiency.

[0101] In step S345, the control unit 50 determines the volume of the replaced fresh air based on the rotation speed and the operating time of the electric turbocharger (for example, based on the time counted by the fresh air replacement timer). In addition, the control unit 50 calculates the increased ambient oxygen amount ΔOd based on the volume of the replaced fresh air. Then, the control unit 50 adds the increased oxygen amount ΔOd to ​​the previously determined ambient oxygen amount Oa, and then sets the amount as the current ambient oxygen amount Oa. Then, the control unit 50 ends Figure 5 The process shown and returns the process to Figure 2 As shown in step S065. Figure 9 As shown in the example of the operating waveform in FIG, the "fresh air replacement flag" is on during the time periods from time T4a to time T4c, from time T5a to time T5c, and from time T6a to time T6c. During these time periods (corresponding to when the electric turbocharger is operating), the "ambient oxygen amount Oa" gradually increases due to the increased oxygen amount ΔOd.

[0102] If the process proceeds to step S360 , the control unit 50 stops and initializes the fresh air replacement timer, and proceeds to step S365 .

[0103] In step S365, the control unit 50 stops the operation of the electric turbocharger and proceeds to step S370. At this time, the EGR valve does not need to be fully closed or fully opened. Therefore, the EGR valve can be uncontrolled to reduce power consumption.

[0104] In step S370, the control unit 50 sets the fresh air replacement flag to OFF. Then, the control unit 50 ends Figure 5 The process shown in Figure 2 Step S065 is shown. Figure 9 In the example of the operation waveform of , the "adsorbed hydrocarbon amount Ma" becomes 0 (zero) at time T7. Therefore, the "deterioration prevention control flag" is set to OFF at time T7.

[0105] As mentioned above, and as Figure 9 As shown in the example of the operating waveform in Figure 5 During the "Controlling Fresh Air Replacement" process, the electric turbocharger is driven from time T4a (or time T5a, time T6a), thereby increasing the "ambient oxygen amount Oa." Time T4a is before the oxygen-free period T4b (or time T5b, time T6b) occurs. As a result, oxygen can be added to the system before oxygen deficiency is determined, thereby preventing the occurrence of coking.

[0106] exist Figure 9 In the example of the operating waveform in , time T4a to time T4c (or time T5a to time T5c, or time T6a to time T6c) is the operating time period of the electric turbocharger, which can be, for example, about a few seconds (for example, about 1 second or 2 seconds). Time T4c to time T5a (or from time T5c to time T6a) is the time period when the electric turbocharger is not driven, which can be, for example, about tens of seconds (for example, 20 seconds or 30 seconds). Therefore, compared with the case of continuously driving the electric turbocharger, power consumption can be significantly reduced. Since power consumption can be reduced, there is no need to install a large battery. A small battery may be sufficient, which can help reduce the weight of the vehicle. The amount of power required to drive the internal combustion engine to generate electricity using the AC generator can also be reduced. This helps improve fuel consumption.

[0107] As mentioned above and as Figure 9 As shown in the example of the operation waveform in FIG, the control unit 50 replaces the fresh air through the fresh air replacement unit (through the process of "controlling the replacement of fresh air"). This is done while the oxidation reaction continues in the exhaust gas purifier. In addition, the oxygen-free period estimation unit (see Figure 2 In step S045) a new oxygen-free period is estimated based on the replaced fresh air. These operations can be repeated.

[0108] [Control EGR valve ( Figure 6 )]

[0109] In the following, reference will be made to Figure 6 Describe in detail the process of "Control (existing) EGR valve". If the "Fresh air replacement flag" passes Figure 5 If the "Control of Fresh Air Replacement" shown is set to ON, this will cause the EGR valve to operate. In this case, the EGR valve is prohibited from operating due to another process, that is, the process for "Control (Existing) EGR Valve". The control unit 50 starts at the time when the "Control (Existing) EGR Valve" is usually executed. Figure 6 The process shown, and proceed to Figure 6 Step SA010 is shown.

[0110] In step SA010, the control unit 50 determines whether the fresh air replacement flag has been set to ON. If the fresh air replacement flag has been set to ON (yes), the control unit 50 does not control (drive) the EGR valve and ends the process. Figure 6 If the fresh air replacement flag is not set to ON (No), the process proceeds to step SA020.

[0111] When the process proceeds to step SA020, the control unit 50 controls (drives) the EGR valve based on the previously existing EGR valve control process, and ends the process. Figure 6 The processing shown.

[0112] [Control of electric turbocharger ( Figure 7 )]

[0113] In the following, reference will be made to Figure 7 Describe in detail the process of "Control (existing) electric turbocharger". If the "Fresh air replacement flag" passes Figure 5 If the "Control fresh air replacement" shown is set to ON, the electric turbocharger will be instructed to operate. In this case, the electric turbocharger is prohibited from operating by other processing such as the processing for "Control (existing) electric turbocharger". The control unit 50 starts at the time when the "Control (existing) electric turbocharger" is usually executed. Figure 7 The process shown, and the process is carried out to Figure 7 Step SB010 shown.

[0114] In step SB010, the control unit 50 determines whether the fresh air replacement flag has been set to ON. If the fresh air replacement flag has been set to ON (yes), the control unit 50 ends the process. Figure 7 The electric turbocharger is controlled (driven) based on the processing shown in the figure instead of other processing. If the fresh air replacement flag is not set to ON (No), the process proceeds to step SB020.

[0115] When the process proceeds to step SB020, the control unit 50 controls (drives) the electric turbocharger based on other (existing) processes, and ends Figure 7 The processing shown.

[0116] [Confirmation of the end of degradation prevention control ( Figure 8 )]

[0117] In the following, reference will be made to Figure 8 Detailed description Figure 2 When the process of step S065 is executed, the control unit 50 causes the process to proceed to Figure 8 Step S410 is shown. “Determine the end of the degradation prevention control” can be Figure 2 The degradation prevention control flag set to ON in step S015 shown is turned OFF.

[0118] In step S410, the control unit 50 determines whether the amount of adsorbed hydrocarbons Ma is 0 (zero). If the amount of adsorbed hydrocarbons Ma is 0 (zero) (Yes), the process proceeds to step S420 (because coking generally does not occur). If the amount of adsorbed hydrocarbons Ma is not 0 (zero) (No), the process proceeds to step S415. Instead of determining whether the amount of adsorbed hydrocarbons Ma is 0 (zero), the control unit 50 may alternatively determine whether the amount of adsorbed hydrocarbons is less than or equal to an acceptably small amount.

[0119] If the process proceeds to step S415, the control unit 50 determines whether the exhaust gas purifier temperature Ta is lower than or equal to the end determination temperature. If the exhaust gas purifier temperature Ta is lower than or equal to the end determination temperature (yes), the process proceeds to step S420 (because the oxidation reaction of the exhaust gas purifier will not proceed). If the exhaust gas purifier temperature Ta is not lower than or equal to the end determination temperature (no), the control unit 50 ends. Figure 8 The processing shown and returns Figure 2 The process under step S065 is shown. The "end determination temperature" may be a temperature based on the activation temperature of the exhaust gas purifier, for example, and an appropriate temperature is set.

[0120] If the process proceeds to step S420, the control unit 50 sets the degradation prevention control flag to OFF. The process "degradation prevention control" for preventing coking after the internal combustion engine stops ends, and the process proceeds to step S425.

[0121] In step S425, the process for controlling the prevention of degradation after the running internal combustion engine stops is completed. Therefore, the control unit 50 can stop supplying power to itself. The power supply stop command to the control unit 50 can be executed by other processing, which can be executed after the internal combustion engine stops.

[0122] exist Figure 9In the example of the operation waveform of , the control unit 50 determines that the amount of adsorbed hydrocarbons = 0 (zero) at time T7, and sets the degradation prevention control flag to OFF.

[0123] The control unit 50 (CPU 51) executes Figure 2 The processes of steps S025, S075 and S090 shown correspond to the exhaust gas purifier temperature acquisition section 51B (see FIG. 5 ) configured to acquire the temperature of the exhaust gas purifier. Figure 1 ) implementation method.

[0124] The control unit 50 (CPU 51) executes Figure 3 The process of "adjusting the load of the internal combustion engine" shown corresponds to the load adjustment unit 51C (see Figure 1 The load adjustment unit 51C is configured to adjust the load existing immediately before the internal combustion engine stops. The internal combustion engine can be stopped so that the crankshaft angle is within a range where both the inlet valve and the outlet valve of at least one cylinder are open.

[0125] The control unit 50 (CPU 51) is configured to execute Figure 4 The process of "detecting the stop of the running internal combustion engine" shown corresponds to the operation stop detection unit 51D (see Figure 1 The operation stop detection unit 51D is used to detect whether the running internal combustion engine has stopped.

[0126] The control unit 50 (CPU 51) executes Figure 2 The processing of steps S040 and S085 shown corresponds to the adsorbed hydrocarbon amount acquiring section 51E (see Figure 1 The adsorbed hydrocarbon amount acquiring portion 51E estimates the adsorbed hydrocarbon amount Ma, which is the amount of hydrocarbons adsorbed in the exhaust gas purifier when the internal combustion engine is operating or stopped.

[0127] The control unit 50 (CPU 51) executes Figure 2 The process of step S045 shown corresponds to the anaerobic period estimating section 51F (see Figure 1 ) embodiment. Operation stop detection unit 51D (see Figure 1 ) detects that the running internal combustion engine has stopped. Then, once the internal combustion engine stops, the exhaust gas purifier temperature acquisition unit 51B (see Figure 1 ) acquires the exhaust gas purifier temperature Ta. The oxygen-free period estimating portion 51F estimates the oxygen-free period, which is a period during which oxygen around the exhaust gas purifier for oxidation reaction with specific components (in this case, hydrocarbons) is depleted, based on the exhaust gas purifier temperature Ta.

[0128] The control unit 50 (CPU 51) executes the process of "controlling the replacement of fresh air" corresponding to the fresh air replacement control unit 51G (see Figure 1 ) embodiment. The fresh air replacement control unit 51G enables the EGR valve to open before the estimated oxygen-free period occurs, and drives the electric turbocharger to replace the air around the exhaust gas purifier with fresh air. After the replacement with fresh air is completed, the electric turbocharger is instructed to stop operation.

[0129] like Figure 1 As shown, the degradation prevention control portion 51A (see Figure 1 ) includes an exhaust gas purifier temperature acquiring portion 51B, a load adjusting portion 51C, an operation stop detecting portion 51D, an adsorbed hydrocarbon amount acquiring portion 51E, an oxygen-free period estimating portion 51F, and a fresh air replacement control portion 51G.

[0130] The control unit 50 of the internal combustion engine system 1 should not be limited to the structure, shape, configuration, and processing steps described in the present embodiment, and various modifications, additions, and deletions may be made without departing from the subject matter of the present invention.

[0131] The present embodiment includes a (first) oxidation catalyst as an exhaust purifier. The oxidation catalyst adsorbs specific components (e.g., hydrocarbons) in the exhaust gas. The adsorbed specific components undergo an oxidation reaction using the surrounding oxygen, which in turn can purify these specific components. The exhaust purifier should not be limited to the above-mentioned oxidation catalyst. For example, the exhaust purifier can be a DPF (particulate filter), an NSR (NOx storage-reduction catalyst), a three-way catalyst, a (second) oxidation catalyst, etc. The exhaust purifier can have the function of purifying predetermined adsorbed components (e.g., hydrocarbons) by performing an oxidation reaction using the surrounding oxygen. In addition, the present embodiment should not be limited to diesel engines, but can be applied to various other internal combustion engines having an exhaust purifier. For example, the present embodiment can be applied to gasoline engines or natural gas engines. The exhaust purifier can also have the function of purifying adsorbed specific components (e.g., hydrocarbons) by performing an oxidation reaction using the surrounding oxygen.

[0132] In the above embodiment, regarding the "adjusting the load of the internal combustion engine" process, the process of stopping the internal combustion engine at a crank angle where both the intake valve and the exhaust valve of at least one cylinder are open is executed. This process may be omitted.

[0133] In the above-described embodiment, regarding the "determination of termination of degradation prevention control" process, termination of degradation prevention control is determined based on the amount of adsorbed hydrocarbons Ma and the exhaust gas purifier temperature Ta. Alternatively, termination of degradation prevention control may be determined based on the elapse of a certain period of time since the degradation prevention control flag was set to ON, or based on the number of times the electric turbocharger was driven while the degradation prevention control flag was set to ON.

[0134] In the above embodiment, Figure 2In step S085 shown, the adsorbed hydrocarbon amount Ma is estimated while the internal combustion engine is in operation. Alternatively, it may be assumed that the maximum amount of hydrocarbons is adsorbed in the exhaust gas purifier when the internal combustion engine is in operation.

[0135] In the above embodiment, in addition to opening the EGR valve when the electric turbocharger is driven to replace fresh air, both the inlet and outlet valves of at least one cylinder are also open. Alternatively, the process of "adjusting the load of the internal combustion engine" can be omitted, allowing only the EGR valve to open regardless of the cylinder's open / closed state. Furthermore, if the internal combustion engine uses hydraulic pressure to actuate the inlet and outlet valves rather than a cam, the hydraulic pressure can be used to keep both the inlet and outlet valves open when the electric turbocharger is driven to replace fresh air.

[0136] When referring to greater than or equal to (≥), less than or equal to (≤), greater than (>), less than (<), etc., they may or may not include an equal sign. The numerical values ​​used to describe the above embodiments are just some examples, and the range should not be limited to these numerical values.

[0137] The control unit 50 may include at least one programmed electronic processor. The control unit 50 may include at least one memory configured to store instructions or software to be executed by the electronic processor to implement at least one of the functions of the control unit 50 described herein. For example, in some embodiments, the control unit 50 may be implemented as a microprocessor with a separate memory.

[0138] The data storage device of the control unit 50 may include volatile and / or non-volatile memory. Examples of suitable data storage devices include RAM (random access memory), flash memory, ROM (read only memory), PROM (programmable read only memory), EPROM (erasable programmable read only memory), EEPROM (electrically erasable programmable read only memory), registers, magnetic disks, optical disks, hard drives, or any other suitable storage medium, or any combination thereof.

[0139] Where the terms "processor" or "central processing unit" or "CPU" are used to identify a unit that performs specific functions, it is understood that, unless expressly stated otherwise, these functions may be performed by a single processor or multiple processors arranged in any manner, including parallel processors, serial processors, tandem processors, or cloud processing / cloud computing configurations. Software may include, for example, firmware, one or more applications, program data, filters, rules, one or more program modules, and / or other executable instructions. Software includes, for example, firmware, one or more applications, program data, filters, rules, one or more program modules, and / or other executable instructions.

Claims

1. An internal combustion engine system, comprising: internal combustion engine; an electric turbocharger provided at an intake duct connected to the internal combustion engine, the electric turbocharger being configured to flow intake air in the intake duct; an EGR conduit configured to return a portion of exhaust gas flowing through an exhaust conduit connected to the internal combustion engine to the intake conduit; an EGR valve configured to adjust an opening of the EGR conduit; an exhaust gas purifier provided at the exhaust pipe on a downstream side of a connection between the EGR pipe and the exhaust pipe, the exhaust gas purifier being configured to adsorb a specific component contained in the exhaust gas and to enable the adsorbed specific component to undergo an oxidation reaction using ambient oxygen; as well as a control unit configured to detect an operating state of the internal combustion engine and control the electric turbocharger and the EGR valve; The control unit is implemented by at least one programmed processor, and the programmed processor is further configured to: obtaining a temperature of the exhaust gas purifier; Detecting whether a running internal combustion engine has stopped; and A degradation prevention step is performed after detecting that the operating internal combustion engine has stopped; wherein: In the degradation prevention step: After detecting that the internal combustion engine has stopped, the control unit estimates an oxygen-free period based on an acquired temperature of the exhaust gas purifier, the acquired temperature of the exhaust gas purifier being acquired by the control unit, the oxygen-free period being a period of time during which oxygen around the exhaust gas purifier is insufficient for an oxidation reaction of the specific component; the control unit instructing the EGR valve to open before the estimated oxygen-free period and instructing driving the electric turbocharger to replace air around the exhaust gas purifier with fresh air for a predetermined period of time; and After replacement with fresh air is completed, the control unit stops instructing driving of the electric turbocharger; Here, when the control unit estimates the oxygen-free period, the control unit acquires an oxidation reaction rate of the exhaust gas purifier based on the acquired temperature of the exhaust gas purifier, and estimates the oxygen-free period based on the acquired oxidation reaction rate.

2. An internal combustion engine system comprising: internal combustion engine; an electric turbocharger provided at an intake duct connected to the internal combustion engine, the electric turbocharger being configured to flow intake air in the intake duct; an EGR conduit configured to return a portion of exhaust gas flowing through an exhaust conduit connected to the internal combustion engine to the intake conduit; an EGR valve configured to adjust an opening of the EGR conduit; an exhaust gas purifier provided at the exhaust pipe on a downstream side of a connection between the EGR pipe and the exhaust pipe, the exhaust gas purifier being configured to adsorb a specific component contained in the exhaust gas and to enable the adsorbed specific component to undergo an oxidation reaction using ambient oxygen; as well as a control unit configured to detect an operating state of the internal combustion engine and control the electric turbocharger and the EGR valve; The control unit is implemented by at least one programmed processor, and the programmed processor is further configured to: obtaining a temperature of the exhaust gas purifier; Detecting whether a running internal combustion engine has stopped; and A degradation prevention step is performed after detecting that the operating internal combustion engine has stopped; wherein: In the degradation prevention step: After detecting that the internal combustion engine has stopped, the control unit estimates an oxygen-free period based on an acquired temperature of the exhaust gas purifier, the acquired temperature of the exhaust gas purifier being acquired by the control unit, the oxygen-free period being a period of time during which oxygen around the exhaust gas purifier is insufficient for an oxidation reaction of the specific component; the control unit instructing the EGR valve to open before the estimated oxygen-free period and instructing driving the electric turbocharger to replace air around the exhaust gas purifier with fresh air for a predetermined period of time; and After replacement with fresh air is completed, the control unit stops instructing driving of the electric turbocharger; After the control unit stops instructing the electric turbocharger to drive, the control unit estimates a second oxygen-free period based on the replaced fresh air and again instructs the electric turbocharger to drive to replace the air around the exhaust purifier with fresh air.

3. The internal combustion engine system according to claim 2, wherein: When the control unit estimates the oxygen-free period, the control unit acquires an oxidation reaction rate of the exhaust gas purifier based on the acquired temperature of the exhaust gas purifier and estimates the oxygen-free period based on the acquired oxidation reaction rate.

4. An internal combustion engine system comprising: internal combustion engine; an electric turbocharger provided at an intake duct connected to the internal combustion engine, the electric turbocharger being configured to flow intake air in the intake duct; an EGR conduit configured to return a portion of exhaust gas flowing through an exhaust conduit connected to the internal combustion engine to the intake conduit; an EGR valve configured to adjust an opening of the EGR conduit; an exhaust gas purifier provided at the exhaust pipe on a downstream side of a connection between the EGR pipe and the exhaust pipe, the exhaust gas purifier being configured to adsorb a specific component contained in the exhaust gas and to enable the adsorbed specific component to undergo an oxidation reaction using ambient oxygen; as well as a control unit configured to detect an operating state of the internal combustion engine and control the electric turbocharger and the EGR valve; The control unit is implemented by at least one programmed processor, and the programmed processor is further configured to: obtaining a temperature of the exhaust gas purifier; Detecting whether a running internal combustion engine has stopped; and A degradation prevention step is performed after detecting that the operating internal combustion engine has stopped; wherein: In the degradation prevention step: After detecting that the internal combustion engine has stopped, the control unit estimates an oxygen-free period based on an acquired temperature of the exhaust gas purifier, the acquired temperature of the exhaust gas purifier being acquired by the control unit, the oxygen-free period being a period of time during which oxygen around the exhaust gas purifier is insufficient for an oxidation reaction of the specific component; the control unit instructing the EGR valve to open before the estimated oxygen-free period and instructing driving the electric turbocharger to replace air around the exhaust gas purifier with fresh air for a predetermined period of time; and After replacement with fresh air is completed, the control unit stops instructing driving of the electric turbocharger; wherein some of the specific components are hydrocarbons, and wherein the control unit estimates an adsorbed hydrocarbon amount, the adsorbed hydrocarbon amount being an amount of hydrocarbons adsorbed to the exhaust purifier while the internal combustion engine is operating and / or after the internal combustion engine is detected to have stopped, and The oxygen-free period is estimated based on the acquired temperature of the exhaust purifier and the amount of adsorbed hydrocarbons after it is detected that the internal combustion engine has stopped.

5. The internal combustion engine system according to claim 4, wherein: When the control unit estimates the oxygen-free period, the control unit acquires an oxidation reaction rate of the exhaust gas purifier based on the acquired temperature of the exhaust gas purifier and estimates the oxygen-free period based on the acquired oxidation reaction rate.

6. The internal combustion engine system according to claim 4 or 5, wherein: When the control unit determines that the amount of adsorbed hydrocarbons is lower than a threshold value during fresh air replacement after detection of stop of the internal combustion engine, the control unit ends execution of the degradation preventing step.

7. An internal combustion engine system comprising: internal combustion engine; an electric turbocharger provided at an intake duct connected to the internal combustion engine, the electric turbocharger being configured to flow intake air in the intake duct; an EGR conduit configured to return a portion of exhaust gas flowing through an exhaust conduit connected to the internal combustion engine to the intake conduit; an EGR valve configured to adjust an opening of the EGR conduit; an exhaust gas purifier provided at the exhaust pipe on a downstream side of a connection between the EGR pipe and the exhaust pipe, the exhaust gas purifier being configured to adsorb a specific component contained in the exhaust gas and to enable the adsorbed specific component to undergo an oxidation reaction using ambient oxygen; as well as a control unit configured to detect an operating state of the internal combustion engine and control the electric turbocharger and the EGR valve; The control unit is implemented by at least one programmed processor, and the programmed processor is further configured to: obtaining a temperature of the exhaust gas purifier; Detecting whether a running internal combustion engine has stopped; and A degradation prevention step is performed after detecting that the operating internal combustion engine has stopped; wherein: In the degradation prevention step: After detecting that the internal combustion engine has stopped, the control unit estimates an oxygen-free period based on an acquired temperature of the exhaust gas purifier, the acquired temperature of the exhaust gas purifier being acquired by the control unit, the oxygen-free period being a period of time during which oxygen around the exhaust gas purifier is insufficient for an oxidation reaction of the specific component; the control unit instructing the EGR valve to open before the estimated oxygen-free period and instructing driving the electric turbocharger to replace air around the exhaust gas purifier with fresh air for a predetermined period of time; and After replacement with fresh air is completed, the control unit stops instructing driving of the electric turbocharger; Here, during fresh air replacement after detection of the internal combustion engine stop, when the control unit determines that the acquired temperature of the exhaust gas purifier is lower than or equal to a termination determination temperature, the control unit terminates execution of the degradation prevention step.

8. The internal combustion engine system according to claim 7, wherein: When the control unit estimates the oxygen-free period, the control unit acquires an oxidation reaction rate of the exhaust gas purifier based on the acquired temperature of the exhaust gas purifier and estimates the oxygen-free period based on the acquired oxidation reaction rate.

9. An internal combustion engine system comprising: internal combustion engine; an electric turbocharger provided at an intake duct connected to the internal combustion engine, the electric turbocharger being configured to flow intake air in the intake duct; an EGR conduit configured to return a portion of exhaust gas flowing through an exhaust conduit connected to the internal combustion engine to the intake conduit; an EGR valve configured to adjust an opening of the EGR conduit; an exhaust gas purifier provided at the exhaust pipe on a downstream side of a connection between the EGR pipe and the exhaust pipe, the exhaust gas purifier being configured to adsorb a specific component contained in the exhaust gas and to enable the adsorbed specific component to undergo an oxidation reaction using ambient oxygen; as well as a control unit configured to detect an operating state of the internal combustion engine and control the electric turbocharger and the EGR valve; The control unit is implemented by at least one programmed processor, and the programmed processor is further configured to: obtaining a temperature of the exhaust gas purifier; Detecting whether a running internal combustion engine has stopped; and A degradation prevention step is performed after detecting that the operating internal combustion engine has stopped; wherein: In the degradation prevention step: After detecting that the internal combustion engine has stopped, the control unit estimates an oxygen-free period based on an acquired temperature of the exhaust gas purifier, the acquired temperature of the exhaust gas purifier being acquired by the control unit, the oxygen-free period being a period of time during which oxygen around the exhaust gas purifier is insufficient for an oxidation reaction of the specific component; the control unit instructing the EGR valve to open before the estimated oxygen-free period and instructing driving the electric turbocharger to replace air around the exhaust gas purifier with fresh air for a predetermined period of time; and After replacement with fresh air is completed, the control unit stops instructing driving of the electric turbocharger; When the running internal combustion engine is to be stopped, the control unit sends a signal to stop the internal combustion engine so that the crankshaft angle of the internal combustion engine is within a range in which both the inlet valve and the outlet valve of at least one cylinder of the internal combustion engine are open.

10. The internal combustion engine system according to claim 9, wherein: When the control unit estimates the oxygen-free period, the control unit acquires an oxidation reaction rate of the exhaust gas purifier based on the acquired temperature of the exhaust gas purifier and estimates the oxygen-free period based on the acquired oxidation reaction rate.

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