Control unit for internal combustion engine system

Abstract

Internal combustion engine system (1) with: an internal combustion engine (10); an electric turbocharger (83) provided on an intake pipe (11A) connected to the internal combustion engine (10), wherein the electric turbocharger (83) is configured to cause intake air to flow in the intake pipe (11A); an exhaust gas recirculation (EGR) pipe (13) which is designed to return a portion of exhaust gas flowing through an exhaust pipe (12B) connected to the internal combustion engine (10) to the intake pipe (11A); an exhaust gas recirculation (EGR) valve (13A) which is configured to adjust the opening degree of the EGR pipe (13); an exhaust gas purifier (40) provided on the exhaust pipe (12B) on a downstream side of a connection between the EGR pipe (13) and the exhaust pipe (12B), wherein the exhaust gas purifier (40) is configured to adsorb specific components contained in the exhaust gas and to allow the adsorbed specific components to undergo an oxidation reaction using ambient oxygen; and a control unit (50) which is set up to detect operating states of the internal combustion engine (10) and to control the electric turbocharger (83) and the EGR valve (13A); wherein the control unit (50) is implemented by at least one programmed processor, further configured to: to measure the temperature of the exhaust gas cleaner (40); to detect whether the running internal combustion engine (10) has stopped; and to implement a deterioration prevention step after it has been detected that the running internal combustion engine (10) has stopped; wherein: in the deterioration prevention step: the control unit (50) estimates an oxygen-free period based on a detected temperature of the exhaust gas purifier (40), which is detected by the control unit (50) after it has been detected that the internal combustion engine (10) has stopped, wherein the oxygen-free period is a period of time during which the oxygen surrounding the exhaust gas purifier (40) is insufficient for the oxidation reaction of the specific components; the control unit (50) instructs the EGR valve (13A) to open before the estimated oxygen-free period and instructs the electric turbocharger (83) to be driven to exchange the air surrounding the exhaust gas purifier (40) with fresh air; and the control unit (50) finishes instructing the electric turbocharger (83) to be driven after the exchange with fresh air is complete.

Description

Background of the invention: Technical field

[0001] This application claims priority over Japanese patent application JP 2021-190079, filed on November 24, 2021, the contents of which are incorporated herein by reference in full for all purposes.

[0002] The present disclosure relates to control units for internal combustion engine systems. For example, the present disclosure relates to a control unit for preventing deterioration of an exhaust gas purifier of an internal combustion engine.

[0003] Exhaust gases from internal combustion engines contain hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), particulate matter (PM), and other pollutants. Vehicles equipped with an internal combustion engine may be fitted with various exhaust gas purifiers. Some vehicles are equipped with a diesel engine. Such vehicles may be equipped with, for example, a first oxidation catalyst, a diesel particulate filter (DPF), a selective catalytic reduction (SCR), a second oxidation catalyst, and / or similar devices from one side of the exhaust system to the other. Additionally, a three-way catalytic converter, a NOx storage-reduction catalyst, and / or similar devices may be used as exhaust gas purifiers.

[0004] Hydrocarbons (HC) are frequently converted into water (H2O) and carbon dioxide (CO2). For example, a first oxidation catalyst with an oxidation function, a particulate filter, a three-way catalytic converter, and an NSR (for this purpose) can be used to clean hydrocarbons from the exhaust gas via an oxidation reaction. Carbon monoxide (CO) is frequently converted into carbon dioxide (CO2). For example, the first oxidation catalyst with an oxidation function, the particulate filter, the three-way catalytic converter, and the NSR are used to clean carbon monoxide from the exhaust gas via an oxidation reaction. Nitrogen oxides (NOx) are frequently converted into nitrogen (N2). For example, nitrogen oxides are reduced by a reduction reaction between ammonia, which is produced from added urea water (or...The exhaust gas is cleaned by a urea-based SCR (a mixture of added aqueous urea solution) and by a urea-based SCR (selective catalytic reduction) system using a reduction function or by a reduction reaction using an NSR (nitrogen oxide reduction) system. If excess ammonia is produced, a second oxidation catalyst cleans nitrogen oxides via an oxidation reaction. Fine particulate matter (PM) is captured by the particulate filter and is not released into the atmosphere.

[0005] The exhaust gas purifier cleans hydrocarbons (HC) through an oxidation reaction. In this process, the purifier adsorbs the hydrocarbons (HC). The adsorbed hydrocarbons (HC) then undergo an oxidation reaction with the oxygen surrounding the purifier. An oxygen deficiency does not normally occur because, during the operation of an internal combustion engine, fresh, oxygen-rich exhaust gas constantly flows through the purifier. However, if the engine stops running, the fresh exhaust gas no longer flows through the purifier. In this case, the surrounding oxygen supply can become depleted. If the ambient oxygen runs out while the purifier's temperature is higher than or equal to an activation temperature, the oxidation reaction is terminated. As a result, hydrogen (H) is desorbed from the adsorbed hydrocarbons (HC).Thus, carbon (C) accumulates as a deposit (so-called coking occurs (adhered by a polymerization reaction)), which can lead to a deterioration of the exhaust gas purifier. To prevent coking from occurring after the combustion engine has stopped running, it is necessary to lower the temperature of the exhaust gas purifier or to ensure that the oxygen surrounding the purifier does not run out. State of the art

[0006] A first conventional exhaust gas purification system for an internal combustion engine can shift the air / fuel ratio of the exhaust gas from a lean to a stoichiometric or rich state. In this case, air or water is used from outside to lower the temperature of the exhaust gas. This lowers the temperature of the exhaust gas purifier and prevents a deterioration in NOx removal performance.

[0007] A second conventional exhaust aftertreatment system for an engine increases the amount of ammonia adsorption by the SCR after the engine has stopped. This ammonia adsorption amount is increased to a level greater than or equal to a standard amount to ensure sufficient NOx removal performance when the engine is subsequently restarted. Specifically, an exhaust gas recirculation (EGR) channel is opened while an electric turbocharger is driven after the engine has stopped to supply fresh air to the SCR. Urea is then added after the SCR temperature has dropped.

[0008] The first conventional exhaust gas purifier for an internal combustion engine is not designed to prevent carbon buildup after the engine has stopped. The temperature within the exhaust pipe and the purifier itself are lowered using water while the engine is running. In this case, water droplets come into direct contact with the purifier, which can damage it. Furthermore, it is necessary to add components such as a water storage tank or a water injection system. This makes the system more complex and requires more installation space.

[0009] The second conventional exhaust gas purifier serves to lower the temperature of the SCR after the combustion engine has stopped, thereby increasing the amount of ammonia adsorbed. In other words, this device is not designed to allow the hydrocarbons to undergo an oxidation reaction, which would prevent coking after the combustion engine has stopped. This exhaust gas purifier uses an electric turbocharger and an EGR pipe to inject fresh air after the combustion engine has stopped. Therefore, to lower the SCR temperature, an electric turbocharger must operate continuously for a relatively long period. As a result, energy consumption increases.

[0010] DE 10 2018 105 633 A1 discloses an exhaust gas purification system for an internal combustion engine comprising a heat and hydrogen generation device (50) and an exhaust gas purification catalyst including a three-way catalyst. Heat and hydrogen generated in the heat and hydrogen generation device are supplied to the exhaust gas purification catalyst. When the air-fuel ratio of the air and fuel combusted in the heat and hydrogen generation device is adjusted to a predetermined, set target air-fuel ratio, the air-fuel ratio of the exhaust gas emitted by the engine is adjusted to the adapted target air-fuel ratio, which is necessary to adjust the air-fuel ratio of the gas flowing into the exhaust gas purification catalyst to the stoichiometric air-fuel ratio.

[0011] DE 10 2018 111 879 A1 discloses a vehicle with an internal combustion engine, a catalytic converter integrated into an exhaust system, and an electronic control unit. When the engine stop condition is met, the electronic control unit stops the fuel injection and increases the amount of oxygen flowing into the catalytic converter by a specific oxygen increase amount. The engine stop condition is a condition for stopping the operation of the internal combustion engine. This specific oxygen increase amount is greater than the increased proportion of oxygen flowing into the catalytic converter resulting from the cessation of fuel injection.

[0012] DE 10 2013 202 693 A1 discloses methods and systems for controlling a power engine that can be automatically stopped and started to reduce engine emissions. In one example, a method sets the amount of current to an electrical device that exerts torque on a power engine in order to regulate the amount of air pumped through the power engine to a catalyst.

[0013] EP 3 557 016 A1 discloses a method for managing an active SCR (selective catalytic reduction) of an ATS (aftertreatment system), wherein the ATS is connected to an exhaust manifold of an internal combustion engine. The method includes the step of increasing an NH3 storage level when a command to shut down the engine is detected, so that the increased NH3 storage level is ready for a subsequent cold start of the engine.

[0014] Accordingly, there is a conventional need for an exhaust gas purifier that cleans specific components in the exhaust gas through oxidation. For example, there is a conventional need for a structure to adequately prevent the formation of coking, thus preventing deterioration of the exhaust gas purifier and simultaneously minimizing energy consumption. Summary of the invention

[0015] The present technical problem is solved by an internal combustion engine system according to claim 1.

[0016] One aspect of the present disclosure relates to a control unit for an internal combustion engine system. The internal combustion engine system comprises an internal combustion engine. An intake manifold is connected to the internal combustion engine. An electric turbocharger, used to supercharge intake air to the internal combustion engine, is provided on the intake manifold. An exhaust manifold is connected to the internal combustion engine. An exhaust gas recirculation (EGR) pipe is provided to return a portion of the exhaust gas flowing through the exhaust manifold to the intake manifold at an outlet side of the electric turbocharger. An exhaust gas recirculation (EGR) valve adjusts the opening degree of the EGR pipe. An exhaust gas purifier is provided on the exhaust manifold on one side downstream of a connection between the EGR pipe and the exhaust manifold. The exhaust gas purifier adsorbs specific components contained in the exhaust gas.The adsorbed specific components undergo an oxidation reaction with surrounding oxygen to remove them from the exhaust gas. The control unit detects the operating states of the combustion engine to control an actuator, including the electric turbocharger and the EGR valve. An exhaust gas purifier temperature sensing section of the control unit monitors the temperature of the purifier. An engine stop detection section detects when the running combustion engine has stopped. When the engine stop detection section detects that the running combustion engine has stopped, a deterioration prevention control section is implemented. The exhaust gas purifier temperature sensing section monitors the temperature of the purifier while the combustion engine is stopped.An oxygen-free period estimation section of the deterioration prevention control unit estimates an oxygen-free period based on the temperature of the exhaust gas purifier. The oxygen-free period is a period during which the oxygen surrounding the exhaust gas purifier, required for the oxidation reaction of its specific components, is expected to become depleted. A fresh air exchange control section of the deterioration prevention control unit allows the EGR valve to open before the estimated oxygen-free period begins and drives the electric turbocharger to exchange the air surrounding the exhaust gas purifier with fresh air. Once the exchange is complete, the electric turbocharger is switched off / stopped.

[0017] Therefore, the oxidation reaction continues to prevent coking. Furthermore, since the electric turbocharger has stopped after the exchange with / against fresh air, energy consumption can be reduced.

[0018] According to another aspect of the present disclosure, the control unit determines the oxidation rate of the exhaust gas purifier based on the measured temperature of the exhaust gas purifier, which was measured in an exhaust gas purifier temperature measurement section, when the oxygen-free period is estimated in the oxygen-free period estimation section. The control unit estimates the oxygen-free period based on the measured oxidation rate. Therefore, a more accurate oxygen-free period can be estimated. This allows for a more appropriate reduction of the power consumption of the electric turbocharger.

[0019] According to another aspect of the present disclosure, an engine stop detection section serves to detect whether the internal combustion engine has stopped running. While the oxidation reaction in the exhaust gas purifier continues when the internal combustion engine is stopped, the fresh air exchange control section replaces the air with fresh air. The oxygen-free period estimation section estimates a new oxygen-free period after the fresh air has been exchanged. The fresh air exchange and the oxygen-free period estimation can be repeated.

[0020] The surrounding oxygen can eventually run out after just a single fresh air exchange. Even in such a case, the fresh air exchange and the oxygen-free period can be repeated. This prevents the ambient oxygen from becoming depleted.

[0021] According to another aspect of the present disclosure, one of the specific components may be hydrocarbon(s). An adsorbed hydrocarbon quantity detection section of the control unit estimates an adsorbed hydrocarbon quantity. The adsorbed hydrocarbon quantity is the amount of hydrocarbons adsorbed in the exhaust gas purifier while the internal combustion engine was running and / or after it stopped. An engine stop detection section detects that the running internal combustion engine has stopped. The oxygen-free period estimation section estimates an 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 quantity.

[0022] This allows for a more accurate estimation of the oxygen-free period. The power consumption of the electric turbocharger can then be reduced more appropriately.

[0023] According to one aspect of the present disclosure, the engine stop detection section recognizes that the running internal combustion engine has stopped. A fresh air exchange control section exchanges the fresh air. In this case, the control unit terminates the implementation of the deterioration prevention control section when it has determined that the hydrocarbons, based on the amount of hydrocarbons adsorbed, have been sufficiently eliminated due to the oxidation reaction. Therefore, the deterioration prevention control section can be terminated at an appropriate time. As a result, unnecessary energy consumption can be avoided.

[0024] According to another aspect of the present disclosure, the engine stop detection section recognizes that the running internal combustion engine has stopped. The fresh air exchange control section then exchanges the fresh air. In this case, the control unit terminates the implementation of the deterioration prevention control section when the temperature of the exhaust gas cleaner, as detected in the exhaust gas cleaner temperature detection section, becomes lower than or equal to a final target temperature. Therefore, the deterioration prevention control section can be terminated at an appropriate time. As a result, unnecessary energy consumption can be more effectively avoided.

[0025] According to another aspect of the present disclosure, a load-adapting section of the control unit can adjust / set the load for the internal combustion engine. Before the running internal combustion engine has stopped, the load-adapting section adjusts the load present immediately before the engine stops in order to stop the engine such that the crankshaft angle is in the range in which both the intake and exhaust valves of at least one of the cylinders of the internal combustion engine are open.

[0026] Therefore, in addition to the EGR pipe, any cylinder where both the intake and exhaust valves are open can be used as a fresh air channel when the electric turbocharger is driven to exchange the fresh air surrounding the exhaust gas purifier. This reduces pressure loss during fresh air injection, resulting in more efficient fresh air exchange. Brief description of the characters

[0027] Further features, characteristics and advantages of the present invention will be easily understood after reading the following detailed description together with the claims and the accompanying drawings: Fig. Figure 1 is a view illustrating an example of the overall structure of an internal combustion engine. Fig. Figure 2 is a flowchart illustrating an example of an “overall deterioration prevention control procedure” to prevent (reduce) the occurrence of coking after a running internal combustion engine has stopped. Fig. 3 is a flowchart that details the flowchart of Fig. The procedure (sequence) of “load adjustment of internal combustion engine” is illustrated in section 2. Fig. 4 is a flowchart that details the flowchart of Fig. The procedure shown in section 2 illustrates "detecting the stop / cessation of a running internal combustion engine". Fig. 5 is a flowchart that details the flowchart of Fig. The process (sequence) of "fresh air exchange control" is illustrated in Figure 2. Fig. Figure 6 is a flowchart illustrating the procedure for "EGR valve control". Fig. Figure 7 is a flowchart illustrating the procedure for "electric turbocharger control". Fig. 8 is a flowchart that details the flowchart of Fig. The procedure (sequence) for "determining the end of the deterioration prevention tax" is illustrated in section 2. Fig. 9 is an example of operational waves of deterioration prevention control. Fig. Figure 10 is a view illustrating an example of the temperature / oxidation reaction rate characteristics of the exhaust gas purifier. Detailed description of the embodiments [Overall structure of the internal combustion engine system 1 (Fig. 1)]

[0028] A control unit 50 for an internal combustion engine system 1 of the present embodiment is described below with reference to the drawings. First, the following is described based on: Fig. 1 An example of an overall structure of the internal combustion engine system 1 according to the present embodiment is described. An internal combustion engine 10 of the internal combustion engine system 1 of a Fig. The example shown is a diesel engine. The structure, etc., of the internal combustion engine system 1 is described below, proceeding from the intake side to the exhaust side.

[0029] An intake pipe 11A is provided with an air flow detector 31. The air flow detector 31 can, for example, be an intake air flow sensor configured to output detected signals to the control unit 50 corresponding to the intake air flow rate into the 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 can, for example, be an intake air temperature sensor configured to output detected signals to the control unit 50 corresponding to the temperature of the intake air (in this case, the ambient air). The atmospheric pressure detector 33A can, for example, be a pressure sensor configured to output detected signals to the control unit 50 corresponding to the atmospheric pressure. Furthermore, the intake pipe A is connected to a compressor 82 of a turbocharger 80.

[0030] Furthermore, a branch intake pipe 11B is connected to the intake pipe 11A. The branch intake pipe 11B is equipped with an electric turbocharger 83. The intake pipe 11A is equipped with a switching valve 83A, while the branch intake pipe 11B is equipped with a different switching valve 83B. The control unit 50 closes the switching valve 83A of the intake pipe 11A and opens the switching valve 83B of the branch intake pipe 11B when it actuates the electric turbocharger 83. The switching valve 83A of the intake pipe 11A is open and the switching valve 83B of the branch intake pipe 11B is closed when the electric turbocharger 83 is stopped. When the electric turbocharger 83 is driven, the electric turbocharger 83 pumps pressurized air towards the compressor 82 of the turbocharger 80.

[0031] The intake pipe 11A is connected to an inlet side of the compressor 82 of the turbocharger 80. Another intake pipe 11C is connected to an outlet side of the compressor 82. The compressor 82 is rotated by a turbine 81, which is driven by the exhaust gas. The compressor 82 directs the intake air arriving from the inlet-side intake pipe 11A under pressure to the outlet-side intake pipe 11C. A pressure detector 33B is provided on the intake pipe 11A located upstream of the compressor 82. The pressure detector 33B outputs signals to the control unit 50, based on the pressure of the air before it is compressed by the compressor 82.

[0032] A downstream side of the intake pipe 11C is connected to an intake manifold 11D. A pressure detector 33C, an intercooler / charge air cooler 84, a throttle device 64, and an intake air temperature detector 32B are provided on the intake pipe 11C. The pressure detector 33C can, for example, be a pressure sensor configured to output detected signals to the control unit 50 corresponding to 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 by the compressor 82 in order to increase its oxygen density. The throttle device 64 adjusts the opening degree of a throttle valve to a set throttle opening degree based on control signals from / to the control unit 50.The intake air temperature detector 32B can, for example, be an intake air temperature sensor that outputs detected signals to the control unit 50 according to the temperature of the intake air lowered by the intercooler 84.

[0033] A downstream side of the intake manifold 11D is connected to an intake port to direct the intake air to the respective cylinders of the internal combustion engine 10. The intake air directed to the intake manifold 11D is drawn into the respective cylinders of the internal combustion engine 10 and is used for combustion with the fuel injected by an injector.

[0034] The internal combustion engine 10 is equipped with a rotation detector 34A and a cylinder detector 34B. The rotation detector 34 can, for example, be a rotation sensor of a crankshaft configured to output detected signals to the control unit 50 corresponding to a rotation angle of the crankshaft of the internal combustion engine 10. The cylinder detector 34B can, for example, be a rotation sensor of the camshaft configured to output detected signals to the control unit 50 at the time when a piston for a first cylinder reaches top dead center. Furthermore, the internal combustion engine 10 is equipped with a load device 63 capable of adjusting the load of the internal combustion engine 10. The load device 63 can, for example, be a generator configured to change the load of the internal combustion engine 10 based on load control signals (power generation control signals) from / to the control unit 50.

[0035] An accelerator pedal actuation amount detector 38 can, for example, be an accelerator pedal actuation amount sensor configured to output detected signals to the control unit 50 corresponding to the actuation amount (or depression amount) of the accelerator pedal actuated by a driver. An ignition switch 39 is an input device for a user instruction to start or stop the internal combustion engine. A user actuates the ignition switch 39 when starting a stopped internal combustion engine or when stopping a running internal combustion engine.

[0036] The control unit 50 calculates a required load based on the rotational speed of the internal combustion engine according to the signals detected by the rotation detector 34A and based on the accelerator pedal actuation amount according to signals detected by the accelerator pedal actuation amount detector 38. These signals are used to calculate a fuel quantity corresponding to the required load. The control unit 50 then controls an injector at a predetermined time according to the signals detected by the rotation detector 34A and the cylinder detector 34B and injects a fuel quantity corresponding to the required load.

[0037] An exhaust manifold 12A is connected to an exhaust port of the internal combustion engine 10. The exhaust gas from the internal combustion engine 10 is directed to the exhaust manifold 12A, an exhaust pipe 12B, and a turbine 81 of the turbocharger 80. The exhaust gas drives the turbine 81 to rotate as it is discharged into the exhaust pipe 12C. 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).

[0038] An inlet side of an EGR pipe 13, which serves to recirculate (partial) portions of the exhaust gas into the intake air, is connected to the exhaust manifold 12A or to the exhaust pipe 12B. An outlet side of the EGR pipe 13 is connected to the intake pipe 11C or to the intake distributor 11D. An EGR valve 13A for adjusting the opening degree of the EGR pipe 13 is provided on the EGR pipe 13. The control unit 50 can adjust the flow rate of the EGR gas by adjusting the opening degree of the EGR valve 13A while the combustion engine is running / in operation. Furthermore, the control unit 50 opens the EGR valve 13A while the combustion engine 10 is stopped / being stopped. This allows fresh air, supplied under pressure by the electric turbocharger 83, to flow through the intake pipe 11A, the branching intake pipe 11B, the intake pipe 11C, the EGR pipe 13 and the exhaust pipes 12B, 12C and to an exhaust gas purifier 40.

[0039] Exhaust pipe 12B is connected to an outlet side of exhaust manifold 12A. An inlet / flow side of turbine 81 of turbocharger 80 is connected to a downstream side of exhaust pipe 12B. Another exhaust pipe 12C is connected to an outlet side of turbine 81, and the exhaust gas cleaner 40 is connected to a downstream side of this exhaust pipe 12C.

[0040] The exhaust gas cleaner 40 is provided on the exhaust pipe on a downstream side (in this case, the downstream side of exhaust pipe 12B) of a connection between the EGR pipe 13 and the exhaust pipe 12B (or the exhaust manifold 12A). The exhaust gas cleaner 40 comprises an upstream exhaust gas cleaner 41 and a downstream exhaust gas cleaner 45, which is arranged on a downstream side of the upstream exhaust gas cleaner 41. On the upstream side, a first oxidation catalyst 42 (DOC: Diesel Oxidation Catalyst) and a particulate filter 43 (DPF: Diesel Particulate Filter) are provided inside the upstream exhaust gas cleaner 41.

[0041] The first oxidation catalyst 42 serves to remove carbon monoxide (CO), hydrocarbons (HC), etc., contained in the exhaust gas by means of oxidation reactions. The particulate filter 43 (hereinafter referred to as "DPF") serves to capture the particulate matter (PM) contained in the exhaust gas. The exhaust gas flows downstream through the particulate filter 43. Additionally, the particulate filter 43 has the function of removing carbon monoxide (CO) and hydrocarbons (HC) by means of oxidation reactions.

[0042] The exhaust pipe 12C on the upstream side of the first oxidation catalyst 42 (upstream side of the upstream exhaust gas purifier 41) is equipped with an additive / additive valve 61, an exhaust gas temperature detector 36A (e.g., an exhaust gas temperature sensor), and the like. The additive 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 exhaust gas temperature. The hotter exhaust gas combusts and burns off the particles captured and deposited in the DPF 43, thereby regenerating the DPF 43. Fuel is supplied to the additive valve 61 from a fuel tank (not shown). Furthermore, the exhaust gas temperature detector 36B (e.g. an exhaust gas temperature sensor) is provided on a downstream side of the first oxidation catalyst 42 and on a top side of the DPF 43.

[0043] The exhaust gas temperature detector 36C (e.g., an exhaust gas temperature sensor) is provided on a downstream side of the DPF 43. Furthermore, a differential pressure sensor 35, which is used to detect the differential pressure (e.g., a pressure difference) of the exhaust gas pressure between the downstream side of the first oxidation catalyst 42 and the upstream side of the DPF 43, as well as the exhaust gas pressure on the downstream side of the DPF 43, is provided within the upstream exhaust gas purifier 41.

[0044] The control unit 50 is configured to determine the differential pressure between the upstream and downstream sides of the DPF 43 based on signals received from the differential pressure sensor 35. The amount of particles trapped in the DPF 43 can be estimated according to the detected pressure difference. The control unit 50 then injects fuel (liquid additive) from the additive injection valve 61 when the estimated amount of deposit(s) exceeds a threshold. The injected fuel increases the exhaust gas temperature, which in turn burns and incinerates the particles deposited in the DPF 43, thus regenerating the DPF 43.At this point, the control unit 50 detects the exhaust gas temperature at each position based on the detected signals from / to the exhaust gas temperature detectors 36A, 36B, 36C and enables the fuel (liquid additive) to be injected from / to the additive valve 61 in order to maintain the desired temperature.

[0045] Furthermore, the downstream exhaust gas purifier 45 is equipped on the upstream side with an additive injection valve 62, a selective reduction catalyst 46 (SCR: Selective Catalytic Reduction), a second oxidation catalyst 47, etc. The selective reduction catalyst 46 (hereinafter referred to as "SCR") is connected to the downstream side of the DPF 43 via an exhaust pipe 12D. The additive injection valve 62 is located in the exhaust pipe 12D, which is on the downstream side of the DPF 43 and on the upstream side of the SCR 46. The additive injection valve 62 injects urea solution (liquid additive) at predetermined times during exhaust gas recirculation. The injected urea water (liquid additive) is distributed, atomized / atomized, and diffused within the exhaust pipe 12D and reaches the SCR 46. Furthermore, the urea water (or...The aqueous urea solution is fed from a urea water tank (not shown) to the auxiliary valve 62. The SCR 46 serves to reduce and purify the nitrogen oxides (NOx) contained in the exhaust gas using ammonia gas produced from the added urea water.

[0046] Furthermore, a NOx detector 37A (e.g., a NOx sensor) is provided on the upstream exhaust pipe 12D of the SCR 46. Another NOx detector 37B (e.g., a NOx sensor) and an exhaust gas temperature detector 36D (e.g., an exhaust gas temperature sensor) are provided on an exhaust pipe 12E downstream of the SCR 46. The NOx detectors 37A and 37B serve to output detected signals to the control unit 50 corresponding to the NOx concentration in the exhaust gas. The exhaust gas temperature detector 36D serves to output detected signals to the control unit 50 corresponding to the exhaust gas temperature. The control unit 50 calculates a NOx cleaning rate for the SCR 46 based on the detected signals from the NOx detectors 37A and 37B and the exhaust gas temperature detector 36D. The control unit 50 controls the additive valve 62 based on the calculated NOx cleaning rate.

[0047] 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 removes residual ammonia gas from the exhaust gas. The second oxidation catalyst 47 also removes carbon monoxide (CO) and hydrocarbons (HC) through oxidation reactions.

[0048] The control unit 50 can be a known unit and can include a CPU 51, a RAM 52, a ROM 53, a timer 54, an EEPROM 55, and the like. The CPU 51 can be configured to implement various calculation procedures based on different programs or maps stored in the ROM 53. Furthermore, the RAM 52 can be configured to temporarily store the calculation results performed by the CPU and to store the data input from each of the detectors. The EEPROM 55 can be a non-volatile memory device, configured, for example, to store data concerning the internal combustion engine 10 while the internal combustion engine 10 is stopped.

[0049] Furthermore, the control unit 50 is capable of recognizing operating states of the internal combustion engine 10 based on the input signals. The control unit 50 also receives requests from an operator based on the recognized operating states of the internal combustion engine 10, signals from the accelerator pedal actuation detector 38, etc. The control unit 50 outputs control signals to control various actuators, such as an injector for injecting fuel into the cylinder, the additive valves 61, 62 for injecting fuel or urea solution (or aqueous urea solution), the electric turbocharger 83, the EGR valve 13A, etc.The control unit 50 (CPU 51) can include a deterioration prevention control section 51A, an exhaust gas purifier temperature detection section 51B, a load matching section 51C, an operating stop detection section 51D, an adsorbed hydrocarbon quantity detection section 51E, an oxygen-free period estimation section 51F, a fresh air exchange control section 51G, etc., the details of which are described later. These sections can be implemented by circuits or any other suitable structure.

[0050] Here, the hydrocarbons (HC) contained in the exhaust gas are adsorbed onto the first oxidation catalyst 42 (and the DPF 43, the second oxidation catalyst 47). The temperature of the first oxidation catalyst 42 (and the DPF 43, the second oxidation catalyst 47, etc.) can be raised to a temperature higher than or equal to an activation temperature when the combustion engine 10 warms up. The hydrocarbons could then undergo an oxidation reaction with oxygen contained in the exhaust gas. Since the exhaust gas contains oxygen and flows continuously while the combustion engine 10 is in operation, oxygen is not normally in short supply to allow the oxidation reaction to occur. However, the combustion engine 10 can be stopped while hydrocarbons (HC) are still adsorbed onto the first oxidation catalyst 42 (and 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 continues using ambient oxygen. However, the ambient oxygen may eventually become depleted. When the ambient oxygen is depleted, the oxidation reaction of the adsorbed hydrocarbons (HC) will cease, so the hydrogen (H) will instead be desorbed, and carbon will accumulate as a deposit. This accumulation of carbon can lead to the occurrence of so-called coking. As a result, the deterioration of the first oxidation catalyst 42 (and the DPF 43, the second oxidation catalyst 47, etc.) will progress. The control unit 50 described in the present embodiments serves to prevent the occurrence of coking by executing procedures as described below.The control unit 50 also serves to prevent deterioration of the exhaust gas purifier 40 (which may include the first oxidation catalyst 42, the DPF 43, the second oxidation catalyst 47, etc.). [Procedure sequences of the control unit 50 (Fig. 2 to Fig. 8) and example of operating shafts (Fig. 9)]

[0051] The following describes the procedures of control unit 50 with reference to the one in Fig. 2 to Fig. The flowcharts shown in section 8 describe this. An example of operating waves is also given with reference to... Fig. 9 described. [Overall procedure for deterioration prevention management (Fig. 2)]

[0052] The control unit 50 (CPU 51) directs to Fig. The two shown “overall process(s) of deterioration prevention control” are executed, for example, at predetermined time intervals (several milliseconds to several tens of milliseconds). After triggering, the control unit 50 continues with step S010. The following description presents an example in which the “first oxidation catalyst” is considered the “exhaust gas purifier”.

[0053] In step S010, the control unit 50 implements the "load adjustment of internal combustion engine" procedure and proceeds to step S015. In the "load adjustment of internal combustion engine" procedure, the load immediately before the internal combustion engine 10 is stopped is adjusted. Specifically, the internal combustion engine 10 is stopped such that the crankshaft angle is within a range in which both the intake and exhaust valves of at least one of the cylinders are open. Details of an embodiment of this procedure are described later.

[0054] In step S015, the control unit 50 implements a procedure (sequence) "Detect Stop / Halt of Running Internal Combustion Engine" and continues the procedure to step S020. The procedure "Detect Stop / Halt of Running Internal Combustion Engine" is a procedure (sequence) to detect that a previously running internal combustion engine 10 has stopped. The details of an embodiment of this procedure are described later. In the procedure "Detect Stop / Halt of Running Internal Combustion Engine," an in-operation flag is set to ON or OFF, and a deterioration prevention control flag is set to ON or OFF. The deterioration prevention control flag is the flag that is set to ON when the deterioration prevention control is started to prevent the coking described above.

[0055] In step S020, control unit 50 determines whether the deterioration prevention tax flag is ON or OFF. If the deterioration prevention tax flag is ON (Yes), the procedure continues with step S025. If not (No), the procedure continues with step S070.

[0056] As the procedure progresses to step S025, the running combustion engine 10 comes to a complete standstill. The control unit 50 then updates an exhaust gas purifier temperature Ta as soon as the combustion engine 10 has stopped and continues the procedure to step S030. For example, after a certain time interval, the control unit 50 determines a reduced temperature ΔTb. 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. In an example of the operating shafts in Fig. 9. The “Deterioration Prevention Tax Flag” is set to ON for a period from time T3 to time T7. The “Exhaust Cleaner Temperature Ta” during the period from time T3 to time T7 is determined using the procedure described in step S025. A method for sensing the exhaust cleaner temperature Ta while the internal combustion engine 10 is stopped is not limited to this procedure.

[0057] In step S030, the control unit 50 detects an oxidation reaction rate Vx of the exhaust gas purifier based, for example, on the exhaust gas purifier temperature Ta. The control unit 50 then continues the process in step S035. For example, “temperature / oxidation reaction rate characteristics” are determined for the exhaust gas purifier, of which one embodiment in an example is described. Fig. The values ​​shown in Figure 10 correspond to those stored in a storage device of the control unit 50. The "temperature / oxidation rate characteristics" represent the oxidation rate corresponding to the temperature of the target exhaust gas cleaner. The values ​​shown in Figure 10 correspond to the values ​​stored in a storage device of the control unit 50. Fig. The example shown in Figure 10 indicates that the oxidation reaction rate is almost zero below the activation temperature. The control unit 50 detects the current oxidation reaction rate Vx of the exhaust gas cleaner temperature Ta based on the "temperature / oxidation reaction rate characteristics" and the exhaust gas cleaner temperature Ta. In the example of the operating waves in Fig. 9 The “oxidation reaction rate Vx” is continuously determined by this step S030 during the time span from time T3 to time T7, which is when the “deterioration prevention control flag” is set to ON.

[0058] In step S035, the control unit 50 updates an ambient oxygen quantity Oa (or amount of ambient oxygen Oa) that corresponds to the amount of oxygen surrounding the exhaust gas cleaner, based on the oxygen reaction rate Vx. The control unit 50 then proceeds to step S040. For example, the control unit 50 determines a reduced oxygen quantity ΔOb according to a time interval. The reduced oxygen quantity ΔOb is subtracted from the previous ambient oxygen quantity Oa, and the resulting value is used as the current ambient oxygen quantity Oa. In the operating wave example in Fig. 9. The "Deterioration Prevention Control Flag" is set to ON during the period from time T3 to time T7. During this period, a "Fresh Air Exchange Flag" is set to OFF during specific 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. The "Ambient Oxygen Quantity Oa" during each of these periods is / are determined in step S035. However, the procedure for determining the ambient oxygen quantity Oa while the combustion engine 10 is stopped should not be limited to this procedure.

[0059] In step S040, the control unit 50 updates an adsorbed hydrocarbon quantity Ma based on the oxidation reaction rate Vx and continues the process with step S045. For example, the control unit 50 determines a reduced hydrocarbon quantity ΔMb according to a time interval. The reduced hydrocarbon quantity ΔMb is subtracted from the previous adsorbed hydrocarbon quantity Ma, and the resulting value(s) is / are used as a current adsorbed hydrocarbon quantity Ma. In the example of the operating waves in Fig. 9. The “deterioration prevention tax flag” is set to ON for a period from time T3 to time T7. The “adsorbed hydrocarbon quantity Ma” during this period is determined by step S040. However, the procedure for determining the adsorbed hydrocarbon quantity Ma while the combustion engine 10 is stopped should not be limited to this procedure.

[0060] In step S045, the control unit 50 estimates when an oxygen-free period Tn will occur. In this embodiment, the oxygen-free period Tn is a time interval during which the ambient oxygen (the amount of ambient oxygen Oa) will be depleted. The control unit 50 can estimate when the oxygen-free period Tn will occur based on the current oxidation rate Vx, the current amount of ambient oxygen Oa, the current amount of adsorbed hydrocarbon Ma, etc. The control unit 50 then proceeds with the process to step S050. In the example of the operating shafts in Fig. 9 will be estimated to occur over an oxygen-free period T4b, for example, if the current time has exceeded time T3 before time T4a.

[0061] In step S050, control unit 50 determines whether the fresh air exchange flag is enabled or disabled. If the fresh air exchange flag is enabled (Yes), the procedure continues with step S060; if not (No), the procedure continues with step S055. The fresh air exchange flag is a flag that is set to ON or OFF during step S060. If fresh air exchange is implemented in step S060, the fresh air exchange flag is a flag that is set to ON.

[0062] In step S055, the control unit 50 determines whether the current time is within Tα and before the start of the oxygen-free period Tn (time T4b, T5b, T6b). If the current time is within Tα and before the oxygen-free period Tn (time T4b, T5b, T6b) (Yes), the procedure continues with step S060; if not (No), the procedure continues with step S065. In the Fig. In the example of operating waves shown in Figure 9, the control unit 50 determines that the current time is within Tα before the oxygen-free period T4b if, for example, the current time lies between time T4a and time T4b. If the current time lies between time T3 and time T4a, it will be determined that the system is not within Tα before the oxygen-free period T4b. Values ​​for Tα are set to suitable values, e.g., based on various experiments, etc.

[0063] As the process progresses to step S060, the control unit 50 implements a "fresh air exchange control" procedure and continues the process to step S065. The "fresh air exchange control" procedure allows the EGR valve to remain open for a specific period of time while the combustion engine 10 is stopped. During this period, the electric turbocharger is driven to exchange the air surrounding the exhaust cleaner with fresh air. This procedure is described in detail later.

[0064] When the procedure progresses to step S065, the control unit 50 implements a procedure (sequence) of "Determination of Deterioration Prevention Tax End" and terminates the in Fig. Two procedures are described. The "Determination of Deterioration Prevention Tax End" procedure is a method that can be used to set the deterioration prevention tax flag to OFF. Specifically, it is a procedure to be implemented / executed when conditions are met in which the deterioration prevention tax flag, which was set to ON in step S015, is fulfilled. When the conditions are met, control unit 50 will set the flag to OFF. This procedure will be described in detail later.

[0065] If the procedure proceeds to step S070 (see Fig. 2) As the process progresses, control unit 50 determines whether an "In Operation" flag is ON or not. If the "In Operation" flag is ON (Yes), the procedure continues with step S075. If not (No), the procedure continues with step S090. The "In Operation" flag is set to ON in step S015 if the internal combustion engine is running / in operation, and set to OFF if the internal combustion engine has stopped (see "In Operation Flag" in [reference]). Fig. 9) Details regarding the ON / OFF setting of the operational flag will be described later.

[0066] When the procedure proceeds to step S075, it has been determined that the internal combustion engine 10 is not stopped, but is still running / in operation. While the internal combustion engine 10 is running, the control unit 50 detects the exhaust gas purifier temperature Ta based on the operating conditions of the internal combustion engine 10. The procedure then continues with step S077. For example, the control unit 50 can detect (estimate) the exhaust gas purifier temperature Ta based on the exhaust gas temperature detected by the exhaust gas temperature detector 36A, the exhaust gas flow rate estimated from an intake air volume, the engine speed, etc. In the example of the operating shafts in Fig. 9. The "In Operation" flag is set to ON during the period from time T2 to time T3. The "Exhaust Cleaner Temperature Ta" during this period is determined using step S075, although other methods can also be used.

[0067] In step S077, the control unit 50 records the oxidation reaction rate Vx based on the exhaust gas purifier temperature Ta. The process then continues with step S080. For example, the control unit 50 can determine the oxidation reaction rate Vx based on the exhaust gas purifier temperature Ta and the temperature in Fig. Record the 10 “temperature / oxidation rate characteristics” shown, similar to the procedure in step S030. In the example of the operating waves in Fig. 9. The "In Operation" flag is set to ON during the time period from time T2 to time T3. The "Oxidation Reaction Rate Vx" during this time period is determined using step S077, although other methods can also be used.

[0068] In step S080, the control unit 50 estimates an ambient oxygen quantity Oa, which is the amount of oxygen surrounding the exhaust gas purifier during operation, based on the operating conditions of the combustion engine. The procedure then continues with step S085. For example, the control unit 50 can estimate the ambient oxygen quantity Oa based on the intake air quantity, the engine speed, a fuel injection quantity, etc. In the example of the operating shafts in Fig. 9. The "In Operation" flag is set to ON during the period from time T2 to time T3. The "Ambient Oxygen Quantity Oa" during this period is determined using step S080, although other methods can also be used.

[0069] In step S085, the control unit 50 estimates the amount of hydrocarbons adsorbed Ma, which is the quantity of hydrocarbons adsorbed onto the exhaust gas purifier during operation, based on the operating conditions of the combustion engine. The control unit 50 then terminates the process in Fig. Two methods are shown. For example, the control unit 50 estimates the adsorbed hydrocarbon quantity Ma based on the intake air quantity, the fuel injection quantity, the rotational speed, the exhaust gas purifier temperature Ta, etc. In the example of the operating shafts in Fig. 9. The "In Operation" flag is set to ON during the period from time T2 to time T3. The "amount of hydrocarbon adsorbed Ma" during this period is determined using step S085, although other methods can also be used.

[0070] If the procedure starts with step S090 (see Fig. 2) continues, the control unit 50 detects (estimates) the exhaust gas purifier temperature Ta based on the operating conditions of the combustion engine (in this case, while the engine is stopped). The control unit 50 then terminates the process described in Fig. 2 methods are shown. For example, the control unit 50 determines an ambient air temperature (intake air temperature detected by the intake air temperature detector 32A) and uses this temperature as the exhaust gas cleaner temperature Ta. [Load matching of internal combustion engine (Fig. 3)]

[0071] A procedure (sequence) of “Load matching of internal combustion engine” from step S010 of Fig. 2 is referred to Fig. 3 described in detail. When implementing the procedure (sequence) of step S010 of the in Fig. In the flowchart shown in section 2, the control unit 50 continues with the procedure (sequence) to step S110, one embodiment of which is shown in Fig. 3 is shown.

[0072] In step S110, control unit 50 determines whether the internal combustion engine has stopped or not. This can be done by determining whether a user has issued a stop request (activation of an ignition switch) for the internal combustion engine. If it has been determined that the engine has stopped due to the stop request (Yes), the procedure continues with step S115. If not (No), the procedure continues with step S150.

[0073] If the procedure continues with step S115, control unit 50 determines whether the internal combustion engine speed is less than or equal to a set / adjusted speed (e.g., less than or equal to the speed immediately before the internal combustion engine comes to a complete stop). If the speed is less than or equal to the set / adjusted speed (Yes), the procedure continues with step S120. If not (No), the procedure continues with step S150.

[0074] If the procedure proceeds to step S120, the control unit 50 determines whether the crank angle is greater than or equal to a first rotation angle θ1 and less than or equal to a second rotation angle θ2. If the crank 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 procedure proceeds to step S125. If not (No), the procedure proceeds to step S150. For example, a crank angle greater than or equal to the first rotation angle θ1 and less than or equal to the second rotation angle θ2 is a crank angle at which both the intake and exhaust valves of at least one of the cylinders (e.g., the first cylinder) are open.This allows air to flow from an intake port to an exhaust port through at least one of the cylinders, in addition to the passage through the EGR pipe, when fresh air exchanges / replaces the oxygen-depleted air using the electric turbocharger (in this case). As a result, pressure loss during the fresh air exchange can be reduced, which in turn improves efficiency during this process.

[0075] As the procedure progresses to step S125, the control unit 50 increases the load quantity to / for the internal combustion engine in order to stop the internal combustion engine immediately. For example, a "load adjustment quantity" is applied immediately before time T3 in the operating shaft example. Fig. 9 increased. In particular, the control unit 50 outputs control signals (signals for increasing the amount of electricity generated) to the load device 63 (generator) to increase the load quantity, in order to stop the combustion engine immediately. The control unit 50 then terminates the operation in Fig. The three procedures shown are described, and the procedure (sequence) returns to the one described in the text. Fig. Step S015 shown in step 2 goes back.

[0076] If the procedure continues with step S150, the control unit 50 implements the existing control of the load device 63. Since this control is an existing control, details are omitted. The control unit 50 then terminates the process in Fig. The three procedures shown are described, and the procedure (sequence) returns to the one described in the text. Fig. Step S015 shown in step 2 goes back. [“Detection of stop / cessation of running internal combustion engine” (Fig. 4)]

[0077] A procedure (sequence) of “detecting stop / halt of running combustion engine” in step S015 of Fig. 2 is referred to Fig. 4 described in detail. During the implementation of the procedure (sequence) of step S015 of the in Fig. In the flowchart shown in section 2, the control unit 50 operates with the [unclear text]. Fig. Continue with step S210 as shown in step 4.

[0078] In step S210, control unit 50 determines whether the internal combustion engine has stopped or not. If the internal combustion engine has stopped (Yes), control unit 50 proceeds to step S215. If not (No), the procedure continues with step S220B.

[0079] If the procedure continues with step S215, the control unit 50 determines whether the Operation flag was previously set to ON or not. If the Operation flag was set to ON (Yes), the procedure continues with step S220A. If not (No), the control unit 50 terminates the process. Fig. The 4 procedures shown and returns with the procedure (sequence) to the one in Fig. Step 2 shown, S020, back.

[0080] As the procedure progresses to step S220A, control unit 50 sets the deterioration prevention tax flag to ON and the in-operation flag to OFF. Control unit 50 then terminates the in Fig. 4 methods shown and returns with the method to the one in Fig. Step 2 shown S020 back.

[0081] When the procedure progresses to step S220B, control unit 50 sets the deterioration prevention tax flag to OFF and the in-operation flag to ON. Control unit 50 then terminates the in Fig. The 4 methods shown and returns with the procedure (sequence) to the one in Fig. Step 2 shown S020 back.

[0082] These procedures (sequences) are used, as in the example of the operating waves in Fig. Figure 9 shows the "In-Operation Flag" set to ON while the internal combustion engine 10 is running / in operation. When the running internal combustion engine has stopped, the "In-Operation Flag" is switched from ON to OFF. In this case, the "Deterioration Prevention Control Flag" is set to ON. [Fresh air exchange control (Fig. 5)]

[0083] Next, a procedure (sequence) of "fresh air exchange control" from step S060 of Fig. 2 with reference to Fig. 5 described in detail. When implementing the procedure (sequence) of step S060 of the in Fig. In the flowchart shown in section 2, the control unit 50 implements the procedure with the one shown in Fig. Step S310, as shown in section 5, continues. In the example of the operating shafts in Fig. 9. The "Fresh Air Exchange Control" procedure is implemented for a period of time starting from time T4a (or time T5a or time T6a) until the "Fresh Air Exchange Flag" is set to OFF. The fresh air exchange flag is a flag that is set during the Fig. In the procedure described in section 4, the "fresh air exchange control" is set to ON or OFF. As described below, the fresh air exchange flag is set to ON while the air surrounding the exhaust gas purifier is being exchanged with / against fresh air because the electric turbocharger is (currently) being driven (which can be done after the running combustion engine has stopped).

[0084] In step S310, the control unit 50 determines whether the fresh air exchange flag has been set to ON or not. If the fresh air exchange flag has been set to ON (Yes), the control unit 50 continues the procedure with step S325, and if not (No), the control unit 50 continues the procedure with step S315.

[0085] As the procedure progresses to step S315, the control unit 50 initializes and starts a fresh air exchange timer and then continues the procedure with step S320.

[0086] In step S320, the control unit 50 sets the fresh air exchange flag to ON and continues the process with step S325.

[0087] The "fresh air exchange flag" is set from OFF to ON in the procedures of steps S310 to S320 above, as in the example of the operating waves in Fig. Figure 9 is shown. In this case, the "fresh air exchange timer" is initialized and started, so that the running time of the electric turbocharger begins to be counted / stopped.

[0088] As the procedure progresses to step S325, the control unit 50 determines whether the time counted / timed by the fresh air exchange timer is longer than or equal to a target exchange time. If the time counted / timed by the fresh air exchange timer is longer than or equal to the target exchange time (Yes), the control unit 50 continues the procedure to step S360. If not (No), the control unit 50 continues the procedure to step S340. The "target exchange time" is the time during which the air surrounding the exhaust gas purifier is to be exchanged with fresh air while the speed of the electric turbocharger is maintained at a "target speed," as described later. The "target exchange time" is set to a suitable value, which may be based on various experiments, etc.

[0089] As the process progresses to step S340, the control unit 50 controls the EGR valve to be in a fully open state. Furthermore, the control unit 50 drives the electric turbocharger so that its speed approaches the target speed. The control unit 50 then proceeds to step S345. The target speed can be set to the speed of the electric turbocharger with the highest efficiency.

[0090] In step S345, the control unit 50 determines the volume of exchanged fresh air based on the rotational speed and runtime of the electric turbocharger (e.g., the time based on the time counted by the fresh air exchange timer). Furthermore, the control unit 50 calculates the amount by which the ambient oxygen ΔOd has increased, based on the volume of exchanged fresh air. The control unit 50 then adds this increased amount of oxygen ΔOd to ​​the previously determined amount of ambient oxygen Oa and sets this amount as the current amount of ambient oxygen Oa. The control unit 50 then terminates the process. Fig. The 5 procedures shown and returns to the procedure (sequence) described in Fig. Step S065 shown in step 2 is returned. As in the example of the operating shafts in Fig. As shown in Figure 9, the "fresh air exchange flag" is ON for a period from time T4a to time T4c, from time T5a to time T5c, and from time T6a to time T6c. During these periods (which correspond to when the electric turbocharger is running), the "ambient oxygen quantity Oa" is gradually increased due to the increased oxygen quantity ΔOd.

[0091] As the procedure progresses to step S360, the control unit 50 stops and initializes the fresh air exchange timer and continues the procedure with step S365.

[0092] In step S365, control unit 50 stops the operation / running of the electric turbocharger and continues the process with step S370. At this point, the EGR valve does not need to be fully closed, nor does it need to be fully open. Therefore, the EGR valve cannot be controlled to reduce energy consumption.

[0093] In step S370, control unit 50 sets the fresh air exchange flag to OFF. Control unit 50 then terminates the process in Fig. The 5 procedures shown and returns with the procedure (sequence) to the one in Fig. Step S065 shown in step 2 is shown. In the example of the operating shafts in Fig. 9. The "adsorbed hydrocarbon quantity Ma" is set to 0 (zero) at time T7. Therefore, the "deterioration prevention tax flag" is set to OFF at time T7.

[0094] As described above and as in the example of the operating waves in Fig. As shown in Figure 9, the "ambient oxygen quantity Oa" increases in the process (sequence) "fresh air exchange control" of Fig. 5, because the electric turbocharger is driven from time T4a (or time T5a, time T6a). Time T4a is a time before the occurrence of the oxygen-free period T4b (or oxygen-free periods T5b, T6b). As a result, oxygen can be supplied to the system before it is determined that there was an insufficient amount of oxygen, thus preventing the occurrence of coking.

[0095] In the example of the operating waves in Fig. 9. The time T4a to time T4c (or time T5a to time T5c; or time T6a to time T6c), which is the operating time of the electric turbocharger, can be, for example, a few seconds (e.g., about 1 or 2 seconds). Time T4c to T5a (or from time T5c to time T6a), which is the period during which the electric turbocharger is not driven, can be, for example, several tens of seconds (e.g., 20 or 30 seconds). Therefore, energy consumption can be significantly reduced compared to the case where the electric turbocharger is continuously driven. Since energy consumption can be reduced, it is not necessary to install a large battery. A small battery can suffice, which can help to reduce the vehicle weight. It is also possible to reduce the amount of energy required to drive the internal combustion engine in order to use it for electricity generation via a generator.This helps to contribute to an improvement in fuel consumption.

[0096] As described above and in the example of the operating waves in Fig. As shown in Figure 9, the control unit 50 replaces the fresh air with the fresh air exchange section (through the process sequence of "Fresh Air Exchange Control"). This occurs while the oxidation reaction continues in the exhaust gas cleaner. Additionally, the oxygen-free period estimation section (see step S045 in Figure 9) estimates the oxygen-free period. Fig. 2) A new oxygen-free period based on the exchanged fresh air. These processes can be repeated. [Control of EGR valve (Fig. 6)]

[0097] The following describes a procedure for "controlling (existing) EGR valve" with reference to Fig. 6 described in detail. If the “fresh air exchange flag” is triggered by the in Fig. Setting the "Fresh Air Exchange Control" shown in section 5 to ON causes the EGR valve to operate. In this case, the EGR valve is not permitted to be in operation due to another procedure (sequence), namely the procedure (sequence) for "controlling the (existing) EGR valve". The control unit 50 starts the process described in Fig. The procedure described in section 6 is implemented at a point in time that would typically implement the "control of (existing) EGR valve", and the procedure is combined with the one described in section 6. Fig. Continue with step SA010 as shown in step 6.

[0098] In step SA010, control unit 50 determines whether the fresh air exchange flag has been set to ON or not. If the fresh air exchange flag has been set to ON (Yes), control unit 50 does not actuate (drive) the EGR valve and terminates the process. Fig. 6 procedures are shown. If the fresh air exchange flag has not been set to ON (No), the procedure continues with step SA020.

[0099] When the procedure moves to step SA020, the control unit 50 actuates (drives) the EGR valve based on the previously existing EGR valve control procedure and terminates the process. Fig. 6 procedures are shown. [Control of electric turbocharger (Fig. 7)]

[0100] The following describes a procedure for the "control of (existing) electric turbocharger" with reference to Fig. 7 described in detail. If the “fresh air exchange flag” is set using in Fig. When the "fresh air exchange control" shown in section 5 is set to ON, the electric turbocharger is instructed to operate. In this case, it is not permitted for the electric turbocharger to be operated using other methods, e.g., the method for "controlling (existing) electric turbocharger". The control unit 50 starts the Fig. The process shown in Figure 7 is implemented at a point in time that would typically implement the "control of (existing) electric turbocharger" and carries out the procedure with the one shown in Figure 7. Fig. Continue with step SB010 as shown in step 7.

[0101] In step SB010, control unit 50 determines whether the fresh air exchange flag has been set to ON or not. If the fresh air exchange flag has been set to ON (Yes), control unit 50 terminates the process described in Fig. The seven methods shown do not control (drive) the electric turbocharger based on the other method (sequence). If the fresh air exchange flag has not been set to ON (No), the method continues with step SB020.

[0102] When the process moves to step SB020, the control unit 50 controls (drives) the electric turbocharger based on the other (existing) process and terminates the in Fig. 7 procedures are shown. [Determination of the end of the deterioration prevention tax (Fig. 8)]

[0103] The following describes a procedure (sequence) for the "determination of the end of the deterioration prevention tax" from step S065 of Fig. 2 with reference to Fig. 8 described in detail. During the implementation of the procedure (sequence) of step S065, the control unit 50 executes the procedure with the in Fig. The process continues as shown in step S410. The "Determination of Deterioration Prevention Tax End" is a procedure that can set the Deterioration Prevention Tax flag to OFF, as described in step S015. Fig. 2 was set to ON.

[0104] In step S410, the control unit 50 determines whether the amount of hydrocarbons adsorbed is Ma 0 (zero) or not. If the amount of hydrocarbons adsorbed is Ma 0 (zero) (yes), the process proceeds to step S420 (because coking cannot normally occur). If not (no), the process proceeds to step S415. Instead of determining whether the amount of hydrocarbons adsorbed is Ma 0 (zero) or not, the control unit 50 may instead determine whether the amount of hydrocarbons adsorbed is less than or equal to an acceptable low amount or not.

[0105] When the procedure progresses to step S415, the control unit 50 determines whether the exhaust gas purifier temperature Ta is less than or equal to a final target temperature. If the exhaust gas purifier temperature Ta is less than or equal to the final target temperature (Yes), the procedure proceeds to step S420 (since the exhaust gas purifier oxidation reaction will not proceed). If not (No), the control unit 50 terminates the process described in step S415. Fig. 8 procedures shown and returns with the procedure (sequence) to that in Fig. Return to step S065 as shown in step 2. The "final determination temperature" can, for example, be a temperature based on the activation temperature of the exhaust gas purifier, and a suitable temperature is set.

[0106] When the procedure progresses to step S420, control unit 50 sets the deterioration prevention control flag to OFF. The "deterioration prevention control" procedure for preventing coking after the combustion engine is stopped ends, and the procedure continues to step S425.

[0107] In step S425, the procedure for controlling deterioration prevention ends after the running combustion engine has stopped. Therefore, the control unit 50 can stop supplying itself with energy. The energy supply stop command to the control unit 50 can be implemented by other procedures (sequences) that can be implemented after the combustion engine stops (or has stopped).

[0108] In the example of the operating waves in Fig. 9 determines the control unit 50 that the amount of hydrocarbons adsorbed at time T7 = 0 (zero), and sets the deterioration prevention control flag to OFF.

[0109] The control unit 50 (CPU 51), which is in Fig. The implementation of the procedures shown in steps S025, S075 and S090 corresponds to an embodiment of an exhaust gas purifier temperature detection section 51B (see 2). Fig. 1), which is set up to detect the temperature of the exhaust gas cleaner.

[0110] The control unit 50 (CPU 51), which is in Fig. The 3 methods shown for “load matching of the internal combustion engine” implemented corresponds to an embodiment of a load matching section 51c (see Fig. 1) The load-adapting section 51C is designed to adapt the load present immediately before the internal combustion engine is stopped. The internal combustion engine can be stopped / switched off such that the crankshaft angle is within a range in which both the intake and exhaust valves of at least one of the cylinders are open.

[0111] The control unit 50 (CPU 51), which is configured to handle the in Fig. Implementing the methods shown in Figure 4 for “detecting the stop / cessation of a running internal combustion engine” corresponds to an embodiment of an operating stop detection section 51D (see Figure 4). Fig. 1) The operating stop detection section 51D serves to detect whether the running internal combustion engine has stopped.

[0112] The control unit 50 (CPU 51), which is in Fig. The implementation of the procedures (sequences) of steps S040 and S085 shown in section 2 corresponds to an embodiment of an adsorbed hydrocarbon quantity detection section 51E (see Fig. 1) The Adsorbed Hydrocarbon Amount Detection Section 51E estimates the Adsorbed Hydrocarbon Amount Ma, i.e., the amount of hydrocarbons adsorbed in the exhaust gas purifier while the internal combustion engine is running or stopped.

[0113] The control unit 50 (CPU 51), which is in Fig. The procedure (sequence) shown in step S045 is implemented, corresponding to an embodiment of an oxygen-free period estimation section 51F (see Fig. 1) The operational stop detection section 51D (see Fig. 1) detects that the running combustion engine has stopped. The exhaust gas purifier temperature detection section 51B (see Fig. 1) The system then records the exhaust gas purifier temperature Ta once the combustion engine has stopped. The oxygen-free period estimation section 51F estimates an oxygen-free period, which is a period during which the oxygen surrounding the exhaust gas purifier is depleted for use in the oxidation reaction of the specific components (in this case, hydrocarbons), based on the exhaust gas purifier temperature Ta.

[0114] The control unit 50 (CPU 51), which implements the method for "fresh air exchange control", corresponds to an embodiment of a fresh air exchange control section 51G (see Fig. 1) The fresh air exchange control section 51G allows the EGR valve to open before the estimated oxygen-free period begins and drives the electric turbocharger to exchange the air surrounding the exhaust gas purifier with fresh air. Once the fresh air exchange is complete, the electric turbochargers are instructed to stop operating.

[0115] As in Fig. As shown in Figure 1, the deterioration prevention control unit 51A (see Figure 1) has the following features: Fig. 1) the exhaust gas purifier temperature detection section 51B, the load adjustment section 51C, the operating stop detection section 51D, the adsorbed hydrocarbon quantity detection section 51E, the oxygen-free period estimation section 51F and the fresh air exchange control section 51G.

[0116] The control unit 50 of the internal combustion engine system 1 is not to be limited to the structures, shapes, configurations and process steps described in the present embodiments, and various modifications, additions and deletions are possible without deviating from the subject matter of the present invention.

[0117] The present embodiments feature a (first) oxidation catalyst as an exhaust gas purifier. The oxidation catalyst adsorbs specific components (e.g., hydrocarbons) in the exhaust gas. The adsorbed components undergo oxidation reactions with the surrounding oxygen, which in turn purifies these components. The exhaust gas purifier is not limited to the oxidation catalyst described above. For example, the exhaust gas purifier can be a DPF (diesel particulate filter), an NSR (NOx storage and reduction catalyst), a three-way catalyst, a (second) oxidation catalyst, or the like. The exhaust gas purifier can have the function of purifying predetermined adsorbed components (e.g., hydrocarbons) through oxidation reactions using ambient oxygen.Furthermore, the present embodiments are not limited to diesel engines, but can be applied to various other internal combustion engines equipped with an exhaust gas purifier. For example, they can be applied to gasoline or natural gas engines. The exhaust gas purifier can also have the function of cleaning adsorbed specific components (e.g., hydrocarbons) by means of oxidation reactions using ambient oxygen.

[0118] In the embodiments described above, with regard to the "load adjustment of internal combustion engine" procedure, a process (sequence) is carried out to stop the internal combustion engine at a crankshaft angle in which both the intake and exhaust valves of at least one of the cylinders are open. This process sequence can be omitted.

[0119] In the embodiments described above, with regard to the "Determination of Deterioration Prevention Control End" procedure, a deterioration prevention control end was determined based on the amount of hydrocarbons adsorbed (Ma) and the exhaust gas purifier temperature (Ta). Alternatively, a deterioration prevention control end can be determined based on the elapsed time since the deterioration prevention control flag was set to ON, or based on the number of times the electric turbocharger was driven while the deterioration prevention control flag was set to ON.

[0120] In the embodiments described above, in which Fig.In step S085, shown in Figure 2, the amount of hydrocarbons adsorbed, Ma, was estimated while the combustion engine was running / in operation. Alternatively, it can be assumed that the maximum amount of hydrocarbons adsorbed in the exhaust gas purifier was / were adsorbed while the combustion engine was running / in operation.

[0121] In the embodiments described above, in addition to the EGR valve opening when the electric turbocharger is driven to exchange fresh air, both the intake and exhaust valves of at least one of the cylinders are open. Alternatively, the procedure for "load matching of internal combustion engine" can be omitted to allow only the EGR valve to open, regardless of the open / closed state of the cylinders. Furthermore, in a case where the internal combustion engine uses hydraulic pressure to actuate the intake and exhaust valves, instead of using a cam, both the intake and exhaust valves can be open / open using hydraulic pressure when the electric turbocharger is driven to exchange fresh air.

[0122] When greater than or equal to (≥), less than or equal to (≤), greater than (>), less than (<), etc., are mentioned, they may or may not include an equals sign. The numerical values ​​used to describe the above embodiments are only a few examples, and the scope is not intended to be limited to these numerical values.

[0123] The control unit 50 can comprise at least one programmed electronic processor. The control unit 50 can also comprise at least one memory configured to store instructions or software to be executed by the electronic processor in order to perform at least one of the functions of the control unit 50 described herein. For example, in some embodiments, the control unit 50 can be implemented as a microprocessor with separate memory.

[0124] The data storage of the control unit 50 can be volatile and / or non-volatile. Examples of suitable data storage 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 disks, or any other suitable storage medium or a combination thereof.

[0125] Where the term "processor," "central processing unit," or "CPU" is used to identify a unit performing a particular function, it should be understood that, unless explicitly stated otherwise, these functions may be performed by a single processor or by multiple processors arranged in any configuration, including parallel processors, serial processors, tandem processors, or cloud processing / cloud computing configurations. The software may include, for example, firmware, one or more applications, program data, filters, rules, one or more program modules, and / or other executable instructions.

Claims

[1] Internal combustion engine system (1) with: an internal combustion engine (10); an electric turbocharger (83) provided on an intake pipe (11A) connected to the internal combustion engine (10), wherein the electric turbocharger (83) is configured to cause intake air to flow in the intake pipe (11A); an exhaust gas recirculation (EGR) pipe (13) which is designed to return a portion of exhaust gas flowing through an exhaust pipe (12B) connected to the internal combustion engine (10) to the intake pipe (11A); an exhaust gas recirculation (EGR) valve (13A) which is configured to adjust the opening degree of the EGR pipe (13); an exhaust gas purifier (40) provided on the exhaust pipe (12B) on a downstream side of a connection between the EGR pipe (13) and the exhaust pipe (12B), wherein the exhaust gas purifier (40) is configured to adsorb specific components contained in the exhaust gas and to allow the adsorbed specific components to undergo an oxidation reaction using ambient oxygen; and a control unit (50) which is set up to detect operating states of the internal combustion engine (10) and to control the electric turbocharger (83) and the EGR valve (13A); wherein the control unit (50) is implemented by at least one programmed processor, further configured to: to measure the temperature of the exhaust gas cleaner (40); to detect whether the running internal combustion engine (10) has stopped; and to implement a deterioration prevention step after it has been detected that the running internal combustion engine (10) has stopped; wherein: in the deterioration prevention step: the control unit (50) estimates an oxygen-free period based on a detected temperature of the exhaust gas purifier (40), which is detected by the control unit (50) after it has been detected that the internal combustion engine (10) has stopped, wherein the oxygen-free period is a period of time during which the oxygen surrounding the exhaust gas purifier (40) is insufficient for the oxidation reaction of the specific components; the control unit (50) instructs the EGR valve (13A) to open before the estimated oxygen-free period and instructs the electric turbocharger (83) to be driven to exchange the air surrounding the exhaust gas purifier (40) with fresh air; and the control unit (50) finishes instructing the electric turbocharger (83) to be driven after the exchange with fresh air is complete. [2] Internal combustion engine system (1) according to claim 1, wherein, when the control unit (50) estimates the oxygen-free period, the control unit (50) detects an oxidation reaction rate of the exhaust gas purifier (40) based on the detected temperature of the exhaust gas purifier (40) and estimates the oxygen-free period based on the detected oxidation reaction rate. [3] Internal combustion engine system (1) according to claim 1 or 2, wherein the control unit (50), after it has finished instructing the electric turbocharger (83) to be driven, estimates a second oxygen-free period based on the exchanged fresh air and again instructs the electric turbocharger (83) to be driven in order to again exchange the air surrounding the exhaust gas purifier (40) with fresh air. [4] Internal combustion engine system (1) according to one of claims 1 to 3, wherein some of the specific components are hydrocarbons, and wherein the control unit (50) estimates an adsorbed hydrocarbon quantity, which is an amount of the hydrocarbons that have been adsorbed on the exhaust gas purifier (40) while the internal combustion engine (10) was in operation and / or after it has been detected that the internal combustion engine (10) has stopped, and after detecting that the internal combustion engine (10) has stopped, estimates the oxygen-free period based on the detected temperature of the exhaust gas purifier (40) and the adsorbed hydrocarbon quantity. [5] Internal combustion engine system (1) according to claim 4, wherein the control unit (50), while the fresh air is being exchanged after detecting that the internal combustion engine (10) has stopped, stops performing the deterioration prevention step when the control unit (50) has determined that the amount of hydrocarbons adsorbed is below a threshold value. [6] Internal combustion engine system (1) according to any one of claims 1 to 5, wherein the control unit (50), while the fresh air is being exchanged after detecting that the internal combustion engine (10) has stopped, stops performing the deterioration prevention step when the control unit (50) has determined that the detected temperature of the exhaust gas purifier (40) is lower than or equal to a final target temperature. [7] Internal combustion engine system (1) according to one of claims 1 to 6, wherein the control unit (50), while the running internal combustion engine (10) is to be stopped, sends a signal to stop the internal combustion engine (10) such that a crank angle of the internal combustion engine (10) is within a range in which both an inlet valve and an exhaust valve of at least one cylinder of the internal combustion engine (10) are open.

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