Control device for internal combustion engine system

Abstract

To provide a control device for an internal combustion engine system capable of suppressing the deterioration of an exhaust emission control device by appropriately suppressing the occurrence of caulking in the exhaust emission control device having a function to eliminate given components from exhaust gas using oxidation reaction, with less power consumption after stopping an internal combustion engine being in operation.SOLUTION: The control device controls a motor supercharger and an actuator including an EGR valve. The control device includes an exhaust emission control device temperature acquisition part, an operation stop detection part, and a deterioration suppression control part, the deterioration suppression control part including an anoxia timing estimation part for estimating an anoxia timing as a timing when oxygen around the exhaust emission control device is used for oxidation reaction until it runs out during stopping the internal combustion engine, on the basis of the temperature of the exhaust emission control device, and a fresh air replacement control part for setting the EGR valve into an opened state before the anoxia timing comes up, driving the motor supercharger to replace air around the exhaust emission control device with fresh air, and after completing the replacement, stopping the motor supercharger.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a control device for an internal combustion engine system, which suppresses deterioration of an exhaust gas purification device of the internal combustion engine. [Background technology]

[0002] 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 are equipped with various exhaust purification devices that purify the exhaust gas. Vehicles equipped with a diesel engine as the internal combustion engine are equipped with exhaust purification devices, such as a first oxidation catalyst, a particulate matter collection filter (DPF), urea SCR, and a second oxidation catalyst, from the upstream side to the downstream side of the exhaust. Other types of exhaust purification devices include a three-way catalyst and an NSR (NOx storage reduction catalyst).

[0003] Hydrocarbons (HC) are purified into water (H2O) and carbon dioxide (CO2) through oxidation reactions in the first oxidation catalyst, particulate filter, three-way catalyst, and NSR, which have an oxidation function. Carbon monoxide (CO) is also purified into carbon dioxide (CO2) through oxidation reactions in the first oxidation catalyst, particulate filter, three-way catalyst, and NSR, which have an oxidation function. Nitrogen oxides (NOx) are purified into nitrogen (N2) through reduction reactions in the urea SCR, which has a reduction function, and ammonia generated from the added urea water, and reduction reactions in the NSR, which also has a reduction function. If excess ammonia is generated, it is purified by an oxidation reaction in the second oxidation catalyst. Particulate matter (PM) is captured by the particulate filter and is not released into the atmosphere.

[0004] When an exhaust purification device purifies hydrocarbons (HC) through an oxidation reaction, the device adsorbs the hydrocarbons (HC) to itself and causes an oxidation reaction using the adsorbed hydrocarbons (HC) and the oxygen around the exhaust purification device. During operation of the internal combustion engine, new exhaust gas containing oxygen flows in one after another, so there is no shortage of oxygen. However, when the internal combustion engine stops while in operation, new exhaust gas does not flow in, so there is a possibility that the surrounding oxygen will disappear as the oxidation reaction progresses. If the temperature of the exhaust purification device is equal to or higher than the activation temperature and there is no oxygen in the surroundings, the oxidation reaction will not progress, hydrogen (H) will be desorbed from the adsorbed hydrocarbons (HC), and carbon (C) will accumulate as a deposit (so-called coking will occur (adhering due to polymerization reaction)), which may cause the deterioration of the exhaust purification device to progress. In order to suppress the occurrence of this coking, it is necessary to lower the temperature of the exhaust purification device after the internal combustion engine is stopped, or to prevent the oxygen around the exhaust purification device from disappearing.

[0005] For example, Patent Document 1 discloses an exhaust gas purification device for an internal combustion engine that, when the air-fuel ratio of the exhaust gas from an operating internal combustion engine transitions from a lean state to a stoichiometric or rich state, lowers the temperature of the exhaust gas by injecting air or water from the outside, thereby lowering the temperature of the exhaust purification device and suppressing a decrease in NOx purification performance.

[0006] Furthermore, Patent Document 2 discloses an engine exhaust gas purification device that opens an EGR path after the engine is stopped, drives an electric supercharger to supply fresh air to the SCR, and supplies urea after lowering the temperature of the SCR, in order to ensure NOx purification performance the next time the engine is started by making the amount of ammonia adsorbed to the SCR after the engine is stopped equal to or greater than a reference amount. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2006-104966 A [Patent Document 2] JP 2019-52579 A Summary of the Invention [Problem to be solved by the invention]

[0008] The exhaust gas purification device for an internal combustion engine described in Patent Document 1 does not suppress the occurrence of coking after the internal combustion engine is stopped. In addition, if water is used to lower the temperature in the exhaust pipe and the temperature of the exhaust purification device while the internal combustion engine is running, water droplets may come into direct contact with the exhaust purification device, which is not preferable. In addition, it is necessary to add a tank for storing water, a water injection device, etc., which complicates the system and requires installation space, which is not preferable.

[0009] Furthermore, the engine exhaust gas purification device described in Patent Document 2 is not intended to suppress the occurrence of coking in an exhaust gas purification device that causes an oxidation reaction of hydrocarbons after the internal combustion engine is stopped, but rather to lower the temperature of the SCR after the internal combustion engine is stopped to increase the amount of ammonia adsorption. After the internal combustion engine is stopped, fresh air is blown in using the electric supercharger and EGR piping, so oxygen is supplied to the exhaust gas purification device, but in order to lower the temperature of the SCR, the electric supercharger needs to be operated continuously for a relatively long period of time, which is not very preferable as it consumes a lot of power.

[0010] The present invention has been devised in consideration of the above points, and has an objective of providing a control device for an internal combustion engine system that can appropriately suppress the occurrence of coking and suppress deterioration of an exhaust purification device having a function of purifying specific components in exhaust gas through an oxidation reaction with less power consumption after an internal combustion engine that was in operation is stopped. [Means for solving the problem]

[0011] In order to solve the above problems, a first invention is a control device for an internal combustion engine system, the internal combustion engine system including an internal combustion engine, an electric supercharger provided in an intake pipe connected to the internal combustion engine and supercharging intake air to the internal combustion engine, an EGR pipe returning a part of the exhaust gas flowing through an exhaust pipe connected to the internal combustion engine to the intake pipe on the discharge side of the electric supercharger, an EGR valve for adjusting an opening degree of the EGR pipe, an exhaust gas purification device provided in the exhaust pipe downstream of a connection point between the EGR pipe and the exhaust pipe, the exhaust gas purification device including a function of adsorbing a predetermined component contained in the exhaust gas and purifying the adsorbed predetermined component by an oxidation reaction using ambient oxygen, and the control device detecting an operating state of the internal combustion engine and controlling an actuator including the electric supercharger and the EGR valve. The control device includes an exhaust gas purification device temperature acquisition unit for acquiring a temperature of the exhaust gas purification device, an operation stop detection unit for detecting that the internal combustion engine that was operating has been stopped, and a deterioration suppression control unit that is executed when the operation stop detection unit detects that the internal combustion engine that was operating has been stopped. The deterioration suppression control unit also includes an oxygen-free period estimation unit that estimates an oxygen-free period, which is a period when the oxygen around the exhaust purification device will be used for the oxidation reaction of the specified component and will be gone, based on the temperature of the exhaust purification device acquired by the exhaust purification device temperature acquisition unit while the internal combustion engine is stopped, after the operation stop detection unit detects that the internal combustion engine, which was operating, has been stopped, and a fresh air replacement control unit that opens the EGR valve and drives the electric supercharger before the estimated oxygen-free period occurs to replace the air around the exhaust purification device with fresh air, and stops driving the electric supercharger after the replacement is completed.This is a control device for an internal combustion engine system.

[0012] Next, a second invention is a control device for an internal combustion engine system related to the first invention above, wherein when estimating the oxygen-free period in the oxygen-free period estimation unit, the control device acquires an oxidation reaction rate of the exhaust purification device based on the temperature of the exhaust purification device acquired by the exhaust purification device temperature acquisition unit, and estimates the oxygen-free period based on the acquired oxidation reaction rate.

[0013] Next, a third invention is a control device for an internal combustion engine system according to the first or second invention, wherein, after the operation stop detection unit detects that the internal combustion engine, which was operating, has been stopped, the control device repeats the replacement of fresh air by the fresh air replacement control unit and the estimation of a new oxygen-free period by the oxygen-free period estimation unit based on the replaced fresh air while the oxidation reaction continues in the exhaust purification device while the internal combustion engine is stopped.

[0014] Next, a fourth invention is a control device for an internal combustion engine system according to any one of the first to third inventions above, wherein one of the specified components is hydrocarbons, and the control device has an adsorbed hydrocarbon amount acquisition unit that estimates an adsorbed hydrocarbon amount, which is the amount of hydrocarbons adsorbed to the exhaust purification device while the internal combustion engine is operating and while it is stopped, and when estimating the oxygen-free period in the oxygen-free period estimation unit after detecting that the internal combustion engine, which was operating, has been stopped, the control device for an internal combustion engine system estimates the oxygen-free period based on the temperature of the exhaust purification device and the adsorbed hydrocarbon amount.

[0015] Next, a fifth invention is a control device for an internal combustion engine system according to the fourth invention, wherein the control device detects that the internal combustion engine, which was operating, has been stopped by the operation stop detection unit, and then performs fresh air replacement by the fresh air replacement control unit. When it is determined that the hydrocarbons in the adsorbed hydrocarbon amount have been eliminated by the oxidation reaction, the control device terminates execution of the deterioration suppression control unit.

[0016] Next, a sixth invention is a control device for an internal combustion engine system relating to any one of the first to fifth inventions above, wherein the control device is a control device for an internal combustion engine system, and when the operation stop detection unit detects that the internal combustion engine, which was operating, has been stopped, and then the fresh air replacement control unit replaces fresh air, and when the temperature of the exhaust purification device acquired by the exhaust purification device temperature acquisition unit becomes equal to or lower than an end judgment temperature, the control device terminates execution of the deterioration suppression control unit.

[0017] Next, a seventh invention is a control device for an internal combustion engine system according to any one of the first to sixth inventions above, the control device having a load adjustment unit capable of adjusting the load on the internal combustion engine, and when stopping the internal combustion engine that was operating, the load adjustment unit adjusts the load just before the internal combustion engine is stopped, and stops the internal combustion engine so that both the intake valve and the exhaust valve in any cylinder of the internal combustion engine are within a crank angle range that is open. Effect of the Invention

[0018] According to the first aspect of the present invention, after the internal combustion engine is stopped, the oxygen-free period is estimated based on the temperature of the exhaust gas purification device, and the air around the exhaust gas purification device is replaced with fresh air before the oxygen-free period (the period when there is no oxygen in the surroundings), so that the oxidation reaction can be continued and the occurrence of coking can be prevented. In addition, the driving of the electric supercharger is stopped after the replacement of the fresh air is completed, so that less power can be consumed.

[0019] According to the second aspect of the present invention, by estimating the oxygen-free period based on the oxidation reaction rate of the exhaust purification device, it is possible to estimate the oxygen-free period more accurately, and the power consumption of the electric supercharger can be appropriately reduced.

[0020] According to the third invention, even in cases where a single air exchange would eventually result in the surrounding oxygen being depleted, the surrounding oxygen can be prevented from being depleted by repeatedly exchanging fresh air and estimating the period of no oxygen.

[0021] According to the fourth aspect of the present invention, the oxygen-free period is estimated based on the temperature of the exhaust purification device and the amount of adsorbed hydrocarbons. This makes it possible to estimate the oxygen-free period more accurately, and therefore makes it possible to appropriately reduce the power consumption of the electric supercharger.

[0022] According to the fifth aspect of the present invention, the degradation suppression control unit can be terminated at an appropriate timing, so that unnecessary power consumption can be appropriately avoided.

[0023] According to the sixth aspect of the present invention, the degradation suppression control unit can be terminated at an appropriate timing, so that unnecessary power consumption can be appropriately avoided.

[0024] According to the seventh aspect of the present invention, when driving the electric supercharger to replace fresh air around the exhaust purification device, in addition to the EGR piping, the cylinder with both the intake valve and exhaust valve open is also used as the path for the fresh air, so that pressure loss when blowing fresh air is reduced and fresh air can be replaced more efficiently. [Brief description of the drawings]

[0025] [Figure 1] 1 is a diagram illustrating an example of the overall configuration of an internal combustion engine system. [Diagram 2] 1 is a flowchart illustrating an example of “overall processing of deterioration suppression control” for preventing (suppressing) the occurrence of coking after an internal combustion engine that was in operation is stopped. [Diagram 3] 3 is a flowchart illustrating details of the process of "adjusting the load on the internal combustion engine" in the flowchart shown in FIG. 2. [Figure 4] 3 is a flowchart illustrating details of the process of “detecting stop of an internal combustion engine that was in operation” in the flowchart shown in FIG. 2. [Diagram 5] 3 is a flowchart illustrating details of the process of “fresh air replacement control” in the flowchart shown in FIG. 2. [Figure 6] 4 is a flowchart illustrating the process of [EGR valve control]. [Figure 7] 11 is a flowchart illustrating the process of [control of electric supercharger]. [Figure 8] 3 is a flowchart illustrating details of a process of "determination of termination of deterioration suppression control" in the flowchart shown in FIG. 2. [Figure 9] 4 is an example of an operation waveform of degradation suppression control. [Figure 10] FIG. 2 is a diagram illustrating an example of temperature vs. oxidation reaction rate characteristics in an exhaust purification device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] [Overall configuration of internal combustion engine system 1 (Fig. 1)] Hereinafter, the control device 50 of the internal combustion engine system 1 of the present invention will be described with reference to the drawings. First, an example of the overall configuration of the internal combustion engine system 1 according to the present invention will be described with reference to Fig. 1. Note that the internal combustion engine 10 of the internal combustion engine system 1 in the example of Fig. 1 is a diesel engine. Below, the configuration of the internal combustion engine system 1 will be described in order from the intake side to the exhaust side.

[0027] An air flow rate detection device 31 is provided in the intake pipe 11A. The air flow rate detection device 31 is, for example, an intake air flow rate sensor, and outputs a detection signal corresponding to the flow rate of air taken in by the internal combustion engine 10 to the control device 50. The air flow rate detection device 31 is also provided with an intake air temperature detection device 32A and an atmospheric pressure detection device 33A. The intake air temperature detection device 32A is, for example, an intake air temperature sensor, and outputs a detection signal corresponding to the temperature of the intake air (outside air in this case) to the control device 50. The atmospheric pressure detection device 33A is, for example, a pressure sensor, and outputs a detection signal corresponding to the atmospheric pressure to the control device 50. The intake pipe 11A is also connected to a compressor 82 of a supercharger 80.

[0028] Further, a branch intake pipe 11B is connected to the intake pipe 11A, and an electric supercharger 83 is provided in the branch intake pipe 11B. A switching valve 83A is provided in the intake pipe 11A, and a switching valve 83B is provided in the branch intake pipe 11B. When the electric supercharger 83 is driven, the control device 50 controls the switching valve 83A to a closed state and the switching valve 83B to an open state, and when the electric supercharger 83 is stopped, the control device 50 controls the switching valve 83A to an open state and the switching valve 83B to a closed state. When the electric supercharger 83 is driven, the electric supercharger 83 pressure-feeds supercharged air toward the compressor 82 of the supercharger 80.

[0029] An intake pipe 11A is connected to the inlet side of a compressor 82 of the turbocharger 80, and an intake pipe 11C is connected to the discharge side of the compressor 82. The compressor 82 is driven to rotate by a turbine 81 that is driven to rotate by exhaust gas, and pressure-feeds the intake air that flows in from the intake pipe 11A to the intake pipe 11C. A pressure detection device 33B is provided in the intake pipe 11A, which is upstream of the compressor 82. The pressure detection device 33B outputs a detection signal corresponding to the pressure of the air before being compressed by the compressor 82 to the control device 50.

[0030] The downstream side of the intake pipe 11C is connected to the intake manifold 11D. The intake pipe 11C is provided with a pressure detection device 33C, an intercooler 84, a throttle device 64, and an intake air temperature detection device 32B. The pressure detection device 33C is, for example, a pressure sensor, and outputs a detection signal corresponding to the pressure of the intake air compressed by the compressor 82 to the control device 50. The intercooler 84 reduces the temperature of the intake air compressed by the compressor 82 to increase the oxygen density. The throttle device 64 adjusts the opening of the throttle valve to a target throttle opening based on a control signal from the control device 50. The intake air temperature detection device 32B is, for example, an intake air temperature sensor, and outputs a detection signal corresponding to the temperature of the intake air reduced by the intercooler 84 to the control device 50.

[0031] The downstream side of the intake manifold 11D is connected to an intake port that guides the intake air to each cylinder of the internal combustion engine 10. The intake air guided to the intake manifold 11D is drawn into each cylinder of the internal combustion engine 10 and used for combustion together with fuel injected from an injector.

[0032] The internal combustion engine 10 is provided with a rotation detection device 34A and a cylinder detection device 34B. The rotation detection device 34A is, for example, a rotation sensor of a crankshaft, and outputs a detection signal according to the rotation angle of the crankshaft of the internal combustion engine 10 to the control device 50. The cylinder detection device 34B is, for example, a rotation sensor of a camshaft, and outputs a detection signal to the control device 50 when the piston of the first cylinder reaches the compression top dead center. The internal combustion engine 10 is also provided with a load device 63 that can adjust the load of the internal combustion engine 10. The load device 63 is, for example, an alternator, and changes the load of the internal combustion engine 10 based on a load control signal (power generation control signal) from the control device 50.

[0033] Accelerator depression amount detection device 38 is, for example, an accelerator depression amount sensor, and outputs a detection signal corresponding to the depression amount of the accelerator pedal operated by the driver to control device 50. Furthermore, ignition switch 39 is an input device for the user to instruct starting or stopping the internal combustion engine, and the user operates ignition switch 39 when starting the internal combustion engine that is stopped or when stopping the internal combustion engine that is in operation.

[0034] The control device 50 calculates a required load based on the internal combustion engine speed based on a detection signal from the rotation detection device 34A and the accelerator pedal depression amount based on a detection signal from the accelerator depression amount detection device 38, and calculates a fuel amount according to the required load. Then, the control device 50 controls the injector at a predetermined timing based on the detection signals from the rotation detection device 34A and the cylinder detection device 34B to inject a fuel amount according to the required load.

[0035] An exhaust manifold 12A is connected to an exhaust port of the internal combustion engine 10. Exhaust from the internal combustion engine 10 is guided through the exhaust manifold 12A, an exhaust pipe 12B, and a turbine 81 of a turbocharger 80, where it drives the turbine 81 to rotate and is discharged into an exhaust pipe 12C. The exhaust from the internal combustion engine 10 (a diesel engine in this case) contains carbon monoxide (CO), hydrocarbons (HC), particulate matter (PM), and nitrogen oxides (NOx).

[0036] The inlet side of the EGR pipe 13 for returning a part of the exhaust gas to the intake is connected to the exhaust manifold 12A or the exhaust pipe 12B. The outlet side of the EGR pipe 13 is connected to the intake pipe 11C or the intake manifold 11D. The EGR pipe 13 is provided with an EGR valve 13A for adjusting the opening degree of the EGR pipe. The control device 50 can adjust the flow rate of the EGR gas by adjusting the opening degree of the EGR valve 13A while the internal combustion engine 10 is in operation. In addition, the control device 50 can lead the fresh air pressure-fed from the electric supercharger 83 to the exhaust purification device 40 via the intake pipe 11A, the branch intake pipe 11B, the intake pipe 11C, the EGR pipe 13, and the exhaust pipes 12B and 12C by opening the EGR valve 13A while the internal combustion engine 10 is stopped.

[0037] An exhaust pipe 12B is connected to the outlet side of the exhaust manifold 12A. The inlet side of a turbine 81 of a turbocharger 80 is connected to the downstream side of the exhaust pipe 12B. An exhaust pipe 12C is connected to the outlet side of the turbine 81, and the exhaust purification device 40 is connected to the downstream side of the exhaust pipe 12C.

[0038] The exhaust purification device 40 is provided in the exhaust pipe downstream of the connection point between the EGR pipe 13 and the exhaust pipe 12B (or the exhaust manifold 12A) (in this case, downstream of the exhaust pipe 12B). The exhaust purification device 40 is composed of an upstream exhaust purification device 41 and a downstream exhaust purification device 45 arranged downstream of the upstream exhaust purification device 41. Inside the upstream exhaust purification device 41, from the upstream side, a first oxidation catalyst 42 (DOC: Diesel Oxidation Catalyst) and a particulate matter collection filter 43 (DPF: Diesel Particulate Filter) are provided.

[0039] The first oxidation catalyst 42 purifies carbon monoxide (CO), hydrocarbons (HC), and other substances contained in the exhaust gas through an oxidation reaction. The particulate matter collection filter 43 (hereinafter referred to as "DPF") collects particulate matter (PM) contained in the exhaust gas and allows only the exhaust gas to flow downstream. The particulate matter collection filter 43 also has the function of purifying carbon monoxide and hydrocarbons through an oxidation reaction.

[0040] An additive valve 61 and an exhaust temperature detection device 36A (e.g., an exhaust temperature sensor) are provided in the exhaust pipe 12C upstream of the first oxidation catalyst 42 (upstream of the upstream exhaust purification device 41). When regenerating the DPF 43 on which the collected particulate matter has accumulated (when burning and incinerating the particulate matter), the additive valve 61 injects fuel (liquid additive) into the exhaust pipe 12C to cause an oxidation reaction in the first oxidation catalyst 42 and raise the temperature of the exhaust gas. The additive valve 61 is supplied with fuel from a fuel tank (not shown). An exhaust temperature detection device 36B (e.g., an exhaust temperature sensor) is provided downstream of the first oxidation catalyst 42 and upstream of the DPF 43.

[0041] An exhaust temperature detection device 36C (e.g., an exhaust temperature sensor) is provided downstream of the DPF 43. In addition, a differential pressure sensor 35 is provided downstream of the first oxidation catalyst 42 in the upstream exhaust purification device 41 to detect the differential pressure (pressure difference) between the exhaust pressure on the upstream side of the DPF 43 and the exhaust pressure on the downstream side of the DPF 43.

[0042] The control device 50 detects the pressure difference between the upstream and downstream sides of the DPF 43 based on the detection signal from the differential pressure sensor 35, and can estimate the amount of particulate matter trapped in the DPF 43 according to the detected pressure difference. When the estimated amount of deposition exceeds a threshold, the control device 50 injects fuel (liquid additive) from the addition valve 61 to increase the exhaust temperature and burn off the particulate matter deposited in the DPF 43 to regenerate the DPF 43. At that time, the control device 50 detects the exhaust temperature at each position based on the detection signals from the exhaust temperature detection devices 36A, 36B, and 36C, and injects fuel (liquid additive) from the addition valve 61 so as to maintain the desired temperature.

[0043] The downstream exhaust purification device 45 is provided with an addition valve 62, a selective catalytic reduction catalyst 46 (SCR), a second oxidation catalyst 47, and the like, from the upstream side. The selective catalytic 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 disposed in the exhaust pipe 12D downstream of the DPF 43 and upstream of the SCR 46, and injects urea water (liquid additive) into the exhaust at a predetermined timing. The injected urea water (liquid additive) is dispersed and atomized, and diffuses in the exhaust pipe 12D to reach the SCR 46. The addition valve 62 is supplied with urea water from a urea water tank (not shown). The SCR 46 reduces and purifies nitrogen oxides (NOx) contained in the exhaust using ammonia gas generated from the added urea water.

[0044] Furthermore, a NOx detection device 37A (e.g., a NOx sensor) is provided in the exhaust pipe 12D upstream of the SCR 46. Furthermore, a NOx detection device 37B (e.g., a NOx sensor) and an exhaust temperature detection device 36D (e.g., an exhaust temperature sensor) are provided in the exhaust pipe 12E downstream of the SCR 46. The NOx detection devices 37A and 37B output detection signals corresponding to the concentration of NOx in the exhaust to the control device 50, and the exhaust temperature detection device 36D outputs a detection signal corresponding to the temperature of the exhaust to the control device 50. The control device 50 calculates the NOx purification rate of the SCR 46 based on the detection signals from the NOx detection devices 37A and 37B and the exhaust temperature detection device 36D, and controls the addition valve 62 based on the calculated NOx purification rate.

[0045] The second oxidation catalyst 47 is connected downstream of the SCR 46 via the exhaust pipe 12E. The second oxidation catalyst 47 oxidizes and purifies the ammonia gas remaining in the exhaust gas. The second oxidation catalyst 47 also has a function of purifying carbon monoxide and hydrocarbons through an oxidation reaction.

[0046] The control device 50 is a known device including a CPU 51, a RAM 52, a ROM 53, a timer 54, an EEPROM 55, etc. The CPU 51 executes various calculation processes based on various programs and maps stored in the ROM 53. The RAM 52 temporarily stores the calculation results of the CPU and data input from each detection device, etc., and the EEPROM 55 is a non-volatile storage device, and stores, for example, data to be saved when the internal combustion engine 10 is stopped.

[0047] The control device 50 can detect the operating state of the internal combustion engine 10 based on the input detection signal. The control device 50 also outputs control signals to control various actuators such as the injector that injects fuel into the cylinder, the addition valves 61 and 62 that inject fuel and urea water, the electric supercharger 83, and the EGR valve 13A, in response to the detected operating state of the internal combustion engine 10 and a request from the driver based on the detection signal from the accelerator depression amount detection device 38. The control device 50 (CPU 51) has a deterioration suppression control unit 51A, an exhaust purification device 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 timing estimation unit 51F, and a fresh air replacement control unit 51G, the details of which will be described later.

[0048] Here, the hydrocarbons (HC) contained in the exhaust gas are adsorbed by the first oxidation catalyst 42 (and the DPF 43 and the second oxidation catalyst 47) that has reached an activation temperature or higher after the internal combustion engine 10 is warmed up, and undergo an oxidation reaction with the oxygen contained in the exhaust gas to be purified. During operation of the internal combustion engine 10, exhaust gas containing oxygen flows continuously, so there is no shortage of oxygen. However, when the internal combustion engine 10 is stopped in a state in which the hydrocarbons (HC) are adsorbed by the first oxidation catalyst 42 (and the DPF 43 and the second oxidation catalyst 47), if the activation temperature or higher is reached, the oxidation reaction proceeds using the surrounding oxygen, but the surrounding oxygen may eventually run out. When the surrounding oxygen runs out, the oxidation reaction of the adsorbed hydrocarbons (HC) does not proceed, hydrogen (H) is desorbed, and carbon (C) accumulates as a deposit (so-called coking occurs), and the deterioration of the first oxidation catalyst 42 (and the DPF 43 and the second oxidation catalyst 47) proceeds. The control device 50 described in this embodiment executes the processing described below to suppress the occurrence of the above-mentioned coking and suppress deterioration of the exhaust purification device (first oxidation catalyst 42, DPF 43, second oxidation catalyst 47).

[0049] [Processing procedure of the control device 50 (FIGS. 2 to 8) and an example of an operating waveform (FIG. 9)] The processing procedure of the control device 50 will be described below with reference to the flowcharts shown in FIGS. 2 to 8, while also describing an example of the operational waveforms shown in FIG.

[0050] ●[Overall processing of deterioration suppression control (Fig. 2)] The control device 50 (CPU 51) starts the "overall process of deterioration suppression control" shown in Fig. 2 at a predetermined time interval (several [ms] to several tens of [ms]), for example, and proceeds to step S010. In the following description, an example will be described in which the "exhaust gas purification device" is the "first oxidation catalyst".

[0051] In step S010, the control device 50 executes the process of "adjusting the load of the internal combustion engine" and proceeds to step S015. The process of "adjusting the load of the internal combustion engine" is a process of adjusting the load immediately before the internal combustion engine 10 is stopped, and stopping the internal combustion engine 10 so that both the intake valve and the exhaust valve of any cylinder are within a crank angle range in which they are open, and will be described in detail later.

[0052] In step S015, the control device 50 executes the process of "detecting the stop of the internal combustion engine that was in operation" and proceeds to step S020. The process of "detecting the stop of the internal combustion engine that was in operation" is a process of detecting that the internal combustion engine that was in operation has been stopped, and details will be described later. In the process of "detecting the stop of the internal combustion engine that was in operation", the operating flag is set to ON / OFF, and the deterioration suppression control flag is set to ON. The deterioration suppression control flag is a flag that is set to ON when the deterioration suppression control that suppresses the occurrence of the above-mentioned coking is started.

[0053] In step S020, controller 50 determines whether the deterioration suppression control flag is ON or not, and if the deterioration suppression control flag is ON (Yes), proceeds to step S025, and if not (No), proceeds to step S070.

[0054] When the process proceeds to step S025, the internal combustion engine 10, which had been in operation, is stopped, and the control device 50 updates the exhaust purification device temperature Ta while the internal combustion engine 10 is stopped, and proceeds to step S030. For example, the control device 50 obtains a temperature decrease ΔTb according to the passage of time, and updates the previous exhaust purification device temperature Ta - temperature decrease ΔTb to the current exhaust purification device temperature Ta. In the example of the operation waveform in FIG. 9, the "exhaust purification device temperature Ta" during the period from time T3 to time T7 when the "deterioration suppression control flag" is set to ON is obtained in this step S025. Note that the method of acquiring the exhaust purification device temperature Ta while the internal combustion engine 10 is stopped is not limited to this method.

[0055] In step S030, the control device 50 acquires the oxidation reaction rate Vx of the exhaust purification device based on the exhaust purification device temperature Ta, and proceeds to step S035. For example, the storage device of the control device 50 stores the [temperature vs. oxidation reaction rate characteristic] corresponding to the exhaust purification device shown in the example of FIG. 10. The [temperature vs. oxidation reaction rate characteristic] represents the oxidation reaction rate according to the temperature in the target exhaust purification device, and the example shown in FIG. 10 represents an example in which the oxidation reaction rate is almost zero below the activation temperature. The control device 50 acquires the oxidation reaction rate Vx for the exhaust purification device temperature Ta based on the temperature vs. oxidation reaction rate characteristic and the exhaust purification device temperature Ta. In the example of the operation waveform in FIG. 9, the "oxidation reaction rate Vx" for the period from time T3 to time T7 when the "deterioration suppression control flag" is set to ON is obtained in this step S030.

[0056] In step S035, the control device 50 updates the ambient oxygen amount Oa of the exhaust purification device based on the oxidation reaction rate Vx, and proceeds to step S040. For example, the control device 50 obtains the decreased oxygen amount ΔOb according to the passage of time, and updates the previous ambient oxygen amount Oa-decreased oxygen amount ΔOb to the current ambient oxygen amount Oa. In the example of the operation waveform of FIG. 9, the "ambient oxygen amount Oa" during the period from time T3 to time T4a, time T4c to time T5a, time T5c to time T6a, and time T6c to time T7 during which the "fresh air replacement flag" is set to OFF during the period from time T3 to time T7 during which the "deterioration suppression control flag" is set to ON is obtained in this step S035. Note that the method of obtaining the ambient oxygen amount Oa while the internal combustion engine 10 is stopped is not limited to this method.

[0057] In step S040, the control device 50 updates the adsorbed hydrocarbon amount Ma based on the oxidation reaction rate Vx, and proceeds to step S045. For example, the control device 50 obtains the decreased hydrocarbon amount ΔMb over time, and updates the previous adsorbed hydrocarbon amount Ma - decreased hydrocarbon amount ΔMb to the current adsorbed hydrocarbon amount Ma. In the example of the operational waveform in FIG. 9, the "adsorbed hydrocarbon amount Ma" during the period from time T3 to time T7 when the "deterioration suppression control flag" is set to ON is obtained in this step S040. Note that the method of obtaining the adsorbed hydrocarbon amount Ma while the internal combustion engine 10 is stopped is not limited to this method.

[0058] In step S045, the control device 50 estimates the oxygen-free time Tn, which is the time when the surrounding oxygen (ambient oxygen amount Oa) disappears, based on the oxidation reaction rate Vx, the ambient oxygen amount Oa, the adsorbed hydrocarbon amount Ma, etc., and proceeds to step S050. In the example of the operation waveform in Fig. 9, for example, if the current time is between time T3 and time T4a, the oxygen-free time T4b is estimated.

[0059] In step S050, the control device 50 determines whether the fresh air replacement flag is ON or not, and if the fresh air replacement flag is ON (Yes), the process proceeds to step S060, and if not (No), the process proceeds to step S055. The fresh air replacement flag is a flag that is set to ON while fresh air replacement is being performed in step S060, and is set to ON or OFF in step S060.

[0060] In step S055, the control device 50 judges whether the current time is within Tα before the anaerobic period Tn (times T4b, T5b, T6b), and if it is within Tα before the anaerobic period Tn (times T4b, T5b, T6b) (Yes), the process proceeds to step S060, and if it is not (No), the process proceeds to step S065. In the example of the operation waveform shown in FIG. 9, for example, if the current time is between time T4a and time T4b, the control device 50 judges that it is within Tα before the anaerobic period T4b, and if the current time is between time T3 and time T4a, the control device 50 judges that it is not within Tα before the anaerobic period T4b. The value of Tα is set to an appropriate value through various experiments, etc.

[0061] When the process proceeds to step S060, the control device 50 executes the process of [fresh air replacement control], and proceeds to step S065. The process of [fresh air replacement control] is a process for replacing the air around the exhaust purification device with fresh air by opening the EGR valve and driving the electric supercharger for a predetermined period while the internal combustion engine 10 is stopped, and will be described in detail later.

[0062] When the process proceeds to step S065, the control device 50 executes the process of [determination of end of deterioration suppression control] and ends the process shown in Fig. 2. The process of [determination of end of deterioration suppression control] is a process of setting the deterioration suppression control flag to OFF when a condition for turning OFF the deterioration suppression control flag that was set to ON in step S015 is met, and will be described in detail later.

[0063] When the process proceeds to step S070, the control device 50 determines whether the in-operation flag is ON or not, and if the in-operation flag is ON (Yes), the process proceeds to step S075, and if not (No), the process proceeds to step S090. The in-operation flag is a flag that is set to ON while the internal combustion engine is operating in step S015 and is set to OFF while the internal combustion engine is stopped (see "in-operation flag" in FIG. 9), and the details of the ON / OFF of the in-operation flag will be described later.

[0064] If the process proceeds to step S075, the internal combustion engine 10 is not stopped but is in operation, and the control device 50 acquires the exhaust purification device temperature Ta during operation based on the operating state of the internal combustion engine, and proceeds to step S077. For example, the control device 50 acquires (estimates) the exhaust purification device temperature Ta based on the exhaust gas temperature detected by the exhaust temperature detection device 36A, the exhaust flow rate estimated from the intake amount, the rotation speed, etc. In the example of the operational waveform in FIG. 9, the "exhaust purification device temperature Ta" during the period from time T2 to time T3 when the "operating flag" is set to ON is obtained in this step S075.

[0065] In step S077, the control device 50 obtains the oxidation reaction rate Vx based on the exhaust purification device temperature Ta, and proceeds to step S080. For example, similar to the process of step S030, the control device 50 obtains the oxidation reaction rate Vx based on the exhaust purification device temperature Ta and the [temperature vs. oxidation reaction rate characteristics] shown in Fig. 10. In the example of the operational waveform in Fig. 9, the "oxidation reaction rate Vx" for the period from time T2 to time T3 when the "operating flag" is set to ON is obtained in this step S077.

[0066] In step S080, the control device 50 estimates the ambient oxygen amount Oa, which is the amount of oxygen around the exhaust purification device during operation, based on the operating state of the internal combustion engine, and proceeds to step S085. For example, the control device 50 estimates the ambient oxygen amount Oa based on the intake amount, rotation speed, fuel injection amount, etc. In the example of the operational waveform in FIG. 9, the "ambient oxygen amount Oa" during the period from time T2 to time T3 when the "operating flag" is set to ON is calculated in this step S080.

[0067] In step S085, the control device 50 estimates the amount of adsorbed hydrocarbons Ma, which is the amount of hydrocarbons adsorbed in the exhaust purification device during operation, based on the operating state of the internal combustion engine, and ends the processing shown in Fig. 2. For example, the control device 50 estimates the amount of adsorbed hydrocarbons Ma based on the intake air amount, fuel injection amount, rotation speed, exhaust purification device temperature Ta, etc. In the example of the operational waveforms in Fig. 9, the "amount of adsorbed hydrocarbons Ma" during the period from time T2 to time T3 when the "operating flag" is set to ON is found in this step S085.

[0068] When the process proceeds to step S090, the control device 50 acquires (estimates) the exhaust purification device temperature Ta based on the operating state of the internal combustion engine (in this case, a stopped state), and ends the process shown in Fig. 2. For example, the control device 50 sets the outside air temperature (the intake air temperature detected by the intake air temperature detection device 32A) as the exhaust purification device temperature Ta.

[0069] ●[Adjusting the load on the internal combustion engine (Figure 3)] Next, the details of the process of "adjusting the load on the internal combustion engine" in step S010 shown in Fig. 2 will be described with reference to Fig. 3. When executing the process of step S010 in the flowchart shown in Fig. 2, the control device 50 advances the process to step S110 shown in Fig. 3.

[0070] In step S110, the control device 50 determines whether or not the internal combustion engine is stopped due to a user request to stop the internal combustion engine (operation of the ignition switch), and if the internal combustion engine is stopped due to a stop request (Yes), the control device 50 proceeds to step S115, and if not (No), the control device 50 proceeds to step S150.

[0071] If the processing proceeds to step S115, the control device 50 determines whether the internal combustion engine's rotation speed is below the adjustment rotation speed (below the rotation speed just before the internal combustion engine is stopped), and if the rotation speed is below the adjustment rotation speed (Yes), the processing proceeds to step S120, and if not (No), the processing proceeds to step S150.

[0072] When the process proceeds to step S120, the control device 50 judges whether the crank angle is equal to or greater than the first rotation angle θ1 and equal to or less than the second rotation angle θ2. If the crank angle is equal to or greater than the first rotation angle θ1 and equal to or less than the second rotation angle θ2 (Yes), the process proceeds to step S125. If not (No), the process proceeds to step S150. For example, a crank angle equal to or greater than the first rotation angle θ1 and equal to or less than the second rotation angle θ2 is a crank angle at which both the intake valve and the exhaust valve of any cylinder (for example, the first cylinder) are open. This allows an additional path from the intake port to the exhaust port of any cylinder to be added to the path of the EGR piping when replacing fresh air with the electric supercharger, thereby reducing pressure loss during replacement of fresh air and improving efficiency during replacement of fresh air.

[0073] When the process proceeds to step S125, the control device 50 increases the load on the internal combustion engine to quickly stop the internal combustion engine. For example, the control device 50 outputs a control signal (power generation increase signal) to increase the load to the load device 63 (alternator), quickly stops the internal combustion engine (see "load adjustment amount" immediately before time T3 in the example of the operation waveform in FIG. 9), ends the process shown in FIG. 3, and returns the process to step S015 shown in FIG. 2.

[0074] If the process proceeds to step S150, the control device 50 executes control of the existing load device 63 (details of the existing control are omitted), ends the process shown in FIG. 3, and returns the process to step S015 shown in FIG.

[0075] ● [Detection of the stop of an internal combustion engine that was in operation (Fig. 4)] Next, details of the process of "detecting stop of the internal combustion engine that was in operation" in step S015 shown in Fig. 2 will be described with reference to Fig. 4. When executing the process of step S015 in the flowchart shown in Fig. 2, the control device 50 advances the process to step S210 shown in Fig. 4.

[0076] In step S210, the control device 50 determines whether the internal combustion engine is stopped. If the internal combustion engine is stopped (Yes), the control device 50 advances the process to step S215, and if not (No), the control device 50 advances the process to step S220B.

[0077] If the process proceeds to step S215, the control device 50 determines whether the previous driving flag is ON or not, and if it is ON (Yes), the process proceeds to step S220A, and if not (No), the process proceeds to step S220B.

[0078] If the process proceeds to step S220A, the controller 50 sets the deterioration suppression control flag to ON, sets the in-operation flag to OFF, ends the process shown in FIG. 4, and returns the process to step S020 shown in FIG.

[0079] If the process proceeds to step S220B, the controller 50 sets the deterioration suppression control flag to OFF, sets the in-operation flag to ON, ends the process shown in FIG. 4, and returns the process to step S020 shown in FIG.

[0080] Through the above processing, while the internal combustion engine is operating, the "operating flag" is set to ON, as shown in the example of the operational waveforms in Fig. 9. Also, as shown in the example of the operational waveforms in Fig. 9, when the "operating flag" changes from ON to OFF (when the internal combustion engine that was operating is stopped), the "deterioration suppression control flag" is set to ON.

[0081] ● [Fresh air replacement control (Fig. 5)] Next, the details of the process of [fresh air replacement control] in step S060 shown in Fig. 2 will be described with reference to Fig. 5. When executing the process of step S060 in the flowchart shown in Fig. 2, the control device 50 advances the process to step S310 shown in Fig. 5. In the example of the operation waveform in Fig. 9, the [fresh air replacement control] is executed for a period from time T4a (or time T5a, or time T6a) until the "fresh air replacement in progress flag" is set to OFF. Note that the fresh air replacement in progress flag is a flag that is set to ON or OFF in the [fresh air replacement control] shown in Fig. 4, and is set to ON while the air around the exhaust purification device is replaced with fresh air by driving the electric supercharger (after the internal combustion engine that was in operation is stopped) as described below.

[0082] In step S310, the control device 50 determines whether the fresh air replacement flag is ON. If the fresh air replacement flag is ON (Yes), the control device 50 proceeds to step S325, and if not (No), the control device 50 proceeds to step S315.

[0083] If the process proceeds to step S315, the control device 50 initializes and starts the fresh air replacement timer, and proceeds to step S320.

[0084] In step S320, the control device 50 sets the fresh air replacement in progress flag to ON, and proceeds to step S325.

[0085] In the processing of steps S310 to S320 described above, when the "fresh air replacement flag" is set from OFF to ON, as shown in the example of the operational waveform in FIG. 9, the "fresh air replacement timer" is initialized and started, and starts measuring the drive time of the electric supercharger.

[0086] When the process proceeds to step S325, the control device 50 judges whether or not the time measured by the fresh air replacement timer is equal to or longer than the target replacement time. If the time measured by the fresh air replacement timer is equal to or longer than the target replacement time (Yes), the control device 50 proceeds to step S360, and if not (No), the control device 50 proceeds to step S340. Note that the "target replacement time" is the time during which the air around the exhaust purification device can be replaced with fresh air when the electric supercharger is driven at a "target rotation speed" described later, and is set to an appropriate value through various experiments, etc.

[0087] When the process proceeds to step S340, the control device 50 controls the EGR valve to be fully open, drives the electric supercharger so that the rotation speed approaches the target rotation speed, and proceeds to step S345. Note that the "target rotation speed" is set to, for example, the rotation speed at which the electric supercharger has the highest power efficiency.

[0088] In step S345, the control device 50 obtains the amount of fresh air replacement corresponding to the driving time of the electric supercharger (the time based on the measurement time of the fresh air replacement timer), and calculates ΔOd, which is the increase in the amount of ambient oxygen corresponding to the amount of fresh air replacement. Then, the control device 50 adds the oxygen increase amount ΔOd to ​​the previous ambient oxygen amount Oa, updates the current ambient oxygen amount Oa, ends the process shown in Fig. 5, and returns the process to step S065 shown in Fig. 2. As shown in the example of the operation waveform in Fig. 9, during the period when the "fresh air replacement in progress flag" is ON (during the driving of the electric supercharger), from time T4a to time T4c, from time T5a to time T5c, and from time T6a to time T6c, the "ambient oxygen amount Oa" gradually increases due to this oxygen increase amount ΔOd.

[0089] If the process proceeds to step S360, the control device 50 stops and initializes the fresh air replacement timer, and proceeds to step S365.

[0090] In step S365, the control device 50 stops driving the electric supercharger, and proceeds to step S370. Note that since the EGR valve does not particularly need to be fully closed or fully open, it is sufficient to control the EGR valve so as to reduce the amount of power consumption.

[0091] In step S370, the control device 50 sets the fresh air replacement in progress flag to OFF, ends the process shown in Fig. 5, and returns the process to step S065 shown in Fig. 2. In the example of the operation waveforms in Fig. 9, since the "amount of adsorbed hydrocarbons Ma" became 0 (zero) at time T7, the "deterioration suppression control flag" is set to OFF.

[0092] As described above, in the [fresh air replacement control] of Fig. 5, as shown in the example of the operating waveform of Fig. 9, the "ambient oxygen amount Oa" is increased by driving the electric supercharger from time T4a (or time T5a, T6a) before the oxygen-free period T4b (or oxygen-free period T5b, T6b). This suppresses the occurrence of coking.

[0093] In the example of the operation waveform in FIG. 9, the driving period of the electric supercharger, time T4a to time T4c (or time T5a to time T5c, or time T6a to time T6c), is, for example, about several seconds (for example, about 1 to 2 seconds), and the stop period of the electric supercharger, time T4c to time T5a (or time T5c to time T6a), is, for example, several tens of seconds (for example, about 20 to 30 seconds). Therefore, the amount of power consumption can be greatly reduced compared to the case where the electric supercharger is continuously driven. Since the amount of power consumption can be reduced, there is no need to mount a large battery, and a small battery is sufficient, so the vehicle weight is reduced, and the power of the internal combustion engine used for generating electricity by the alternator is also reduced, which contributes to improving fuel efficiency.

[0094] As explained above and shown in the example of the operating waveforms in Figure 9, while the oxidation reaction continues in the exhaust purification device, the control device 50 repeats the replacement of fresh air by the fresh air replacement control unit (through the processing of [Fresh air replacement control]) and the estimation of a new oxygen-free period by the oxygen-free period estimation unit (see step S045 in Figure 2) based on the replaced fresh air.

[0095] ●[EGR valve control (Fig. 6)] Next, the details of the [(existing) EGR valve control] process will be described with reference to Fig. 6. When the "fresh air replacement flag" is set to ON in the [fresh air replacement control] shown in Fig. 5 to forcibly operate the EGR valve, the [(existing) EGR valve control] process prohibits the EGR valve from operating. The control device 50 starts the process shown in Fig. 6 at the execution timing of the [(existing) EGR valve control], and proceeds to step SA010 shown in Fig. 6.

[0096] In step SA010, the control device 50 determines whether the fresh air replacement flag is ON. If the fresh air replacement flag is ON (Yes), the control device 50 ends the process shown in Fig. 6 without controlling (driving) the EGR valve, and if the fresh air replacement flag is not ON (No), the control device 50 proceeds to step SA020.

[0097] If the process proceeds to step SA020, controller 50 controls (drives) the existing EGR valve, and ends the process shown in FIG.

[0098] ●[Control of electric supercharger (Fig. 7)] Next, the details of the process of [control of (existing) electric supercharger] will be described with reference to Fig. 7. When the "fresh air replacement flag" is set to ON in the [fresh air replacement control] shown in Fig. 5 to forcibly operate the electric supercharger, the process of [control of (existing) electric supercharger] prohibits the electric supercharger from operating. The control device 50 starts the process shown in Fig. 7 at the execution timing of the [control of (existing) electric supercharger], and proceeds to step SB010 shown in Fig. 7.

[0099] In step SB010, the control device 50 determines whether the fresh air replacement flag is ON. If the fresh air replacement flag is ON (Yes), the control device 50 ends the process shown in Fig. 7 without controlling (driving) the electric supercharger, and if the fresh air replacement flag is not ON (No), the control device 50 proceeds to step SB020.

[0100] When the process proceeds to step SB020, the control device 50 controls (drives) the existing electric supercharger, and ends the process shown in FIG.

[0101] ● [Determination of the end of deterioration suppression control (Fig. 8)] Next, the details of the process of [Determination of End of Deterioration Suppression Control] in step S065 shown in Fig. 2 will be described with reference to Fig. 8. When executing the process of step S065 in the flowchart shown in Fig. 2, the control device 50 advances the process to step S410 shown in Fig. 8. [Determination of End of Deterioration Suppression Control] is a process of setting the deterioration suppression control flag, which was set to ON in step S015 shown in Fig. 2, to OFF.

[0102] In step S410, the control device 50 judges whether the amount of adsorbed hydrocarbons Ma is 0 (zero). If the amount of adsorbed hydrocarbons Ma is 0 (zero) (Yes) (because coking does not occur), the control device 50 advances the process to step S420, and if not (No), the control device 50 advances the process to step S415. Note that it is also possible to judge whether the amount of adsorbed hydrocarbons Ma is equal to or less than an allowable minute amount, rather than whether it is 0 (zero).

[0103] When the process proceeds to step S415, the control device 50 judges whether the exhaust purification device temperature Ta is equal to or lower than the end judgment temperature. If the exhaust purification device temperature Ta is equal to or lower than the end judgment temperature (Yes) (because the oxidation reaction of the exhaust purification device is not progressing), the control device 50 proceeds to step S420, and if not (No), the control device 50 ends the process shown in Fig. 8 and returns to the process below step S065 shown in Fig. 2. Note that the "end judgment temperature" is a temperature based on, for example, the activation temperature of the exhaust purification device, and an appropriate temperature is set.

[0104] If the process proceeds to step S420, the control device 50 sets the deterioration suppression control flag to OFF, ends the process of "deterioration suppression control" that suppresses the occurrence of coking after the internal combustion engine is stopped, and proceeds to step S425.

[0105] In step S425, the control device 50 stops the power supply to the control device 50 (itself) since the process of the deterioration suppression control after the internal combustion engine that was in operation is stopped has ended. Note that the power supply to the control device 50 may be stopped by another process that is executed after the internal combustion engine is stopped.

[0106] In the example of the operational waveforms in FIG. 9, the control device 50 determines that the amount of adsorbed hydrocarbons=0 (zero) at time T7, and sets the deterioration suppression control flag to OFF.

[0107] The control device 50 (CPU 51) executing the processes of steps S025, S075, and S090 shown in FIG. 2 corresponds to an exhaust purification device temperature acquisition unit 51B (see FIG. 1) that acquires the temperature of the exhaust purification device.

[0108] In addition, the control device 50 (CPU 51) executing the process of "adjusting the load of the internal combustion engine" shown in Figure 3 corresponds to a load adjustment unit 51C (see Figure 1) that, when stopping an internal combustion engine that was in operation, adjusts the load just before the internal combustion engine is stopped, and stops the internal combustion engine so that both the intake valve and the exhaust valve in any one of the cylinders of the internal combustion engine are within the crank angle range open.

[0109] In addition, the control device 50 (CPU 51) executing the process of “detecting the stop of an internal combustion engine that was in operation” shown in FIG. 4 corresponds to an operation stop detection unit 51D (see FIG. 1) that detects that an internal combustion engine that was in operation has been stopped.

[0110] Moreover, the control device 50 (CPU 51) which executes the processing of steps S040 and S085 shown in FIG. 2 corresponds to an adsorbed hydrocarbon amount acquisition unit 51E (see FIG. 1) which estimates the adsorbed hydrocarbon amount Ma, which is the amount of hydrocarbons adsorbed in the exhaust purification device while the internal combustion engine is operating and while it is stopped.

[0111] In addition, the control device 50 (CPU 51) executing the processing of step S045 shown in Figure 2 corresponds to an oxygen-free period estimation unit 51F (see Figure 1) that estimates the oxygen-free period, which is the period when the oxygen around the exhaust purification device is used for the oxidation reaction of a specified component (in this case, hydrocarbons) and is no longer present, based on the exhaust purification device temperature Ta acquired by the exhaust purification device temperature acquisition unit 51B (see Figure 1) while the internal combustion engine is stopped after detecting that the internal combustion engine, which was operating, has been stopped by the operation stop detection unit 51D (see Figure 1).

[0112] In addition, the control device 50 (CPU 51) that executes the processing of the [fresh air replacement control unit] shown in Figure 5 corresponds to a fresh air replacement control unit 51G (see Figure 1) that opens the EGR valve before the estimated oxygen-free period and drives the electric supercharger to replace the air around the exhaust purification device with fresh air, and stops driving the electric supercharger after the replacement is completed.

[0113] In addition, the deterioration suppression control unit 51A (see Figure 1) includes, as shown in Figure 1, an exhaust purification device 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 timing estimation unit 51F, and a fresh air replacement control unit 51G.

[0114] The control device 50 of the internal combustion engine system 1 of the present invention is not limited to the configuration, shape, structure, processing procedures, etc. described in this embodiment, and various modifications, additions, and deletions are possible without changing the gist of the present invention.

[0115] In the description of the present embodiment, the (first) oxidation catalyst has been described as an example of an exhaust purification device that includes a function of adsorbing a specific component (such as hydrocarbons) in exhaust gas and purifying the adsorbed specific component by oxidizing the adsorbed specific component using surrounding oxygen. However, the present invention is not limited to the (first) oxidation catalyst, and can also be applied to exhaust purification devices that include a function of purifying the adsorbed specific component (such as hydrocarbons) by oxidizing the adsorbed specific component using surrounding oxygen, such as a DPF (particulate matter collection filter), an NSR (NOx storage reduction catalyst), a three-way catalyst, and a (second) oxidation catalyst. In addition, the present invention is not limited to diesel engines, and can be applied to various internal combustion engines, such as gasoline engines and natural gas engines, that have an exhaust purification device that includes a function of purifying the adsorbed specific component (such as hydrocarbons) by oxidizing the adsorbed specific component using surrounding oxygen.

[0116] Also, in [Adjusting the Load on the Internal Combustion Engine], the process of stopping the internal combustion engine at a crank angle where both the intake valve and exhaust valve of any cylinder are open has been described, but this process may be omitted.

[0117] Furthermore, in [Determination of End of Deterioration Suppression Control], the end of deterioration suppression control is determined based on the amount of adsorbed hydrocarbons Ma and the exhaust purification device temperature Ta, but the end of deterioration suppression control may also be determined based on the elapsed time since the deterioration suppression control flag was set to ON, the number of times the electric supercharger is driven when the deterioration suppression control flag is set to ON, etc.

[0118] Also, an example has been described in which the amount of adsorbed hydrocarbons Ma during operation of the internal combustion engine is estimated in step S085 shown in FIG. 2, but it is also possible to assume that the maximum amount of adsorption is adsorbed in the exhaust purification device during operation of the internal combustion engine without estimating the amount of adsorbed hydrocarbons Ma during operation of the internal combustion engine.

[0119] In the description of this embodiment, when the electric supercharger is driven to exchange fresh air, in addition to opening the EGR valve, both the intake valve and the exhaust valve of one of the cylinders are opened, but the process of "adjusting the load on the internal combustion engine" may be omitted and the EGR valve may be opened. Also, in the case of an internal combustion engine in which the intake valve and the exhaust valve are driven by hydraulic pressure rather than by a cam, when the electric supercharger is driven to exchange fresh air, both the intake valve and the exhaust valve may be opened by using the hydraulic pressure.

[0120] When greater than or equal to (≧), less than or equal to (≦), greater than (>), less than (<), etc. are written, the equal sign may or may not be included. Furthermore, the numerical values ​​used in the explanation of this embodiment are merely examples, and the present invention is not limited to these numerical values. [Explanation of symbols]

[0121] 1 Internal Combustion Engine System 10 Internal combustion engine 11A, 11C intake pipe 11B Branched intake pipe 11D Intake manifold 12A Exhaust manifold 12B, 12C, 12D, 12E Exhaust pipe 13 EGR piping 13A EGR valve 31 Air flow detector 32A, 32B Intake air temperature detector 33A Atmospheric pressure detector 33B, 33C, 33D Pressure detection device 34A Rotation detector 34B Cylinder detection device 35 Differential Pressure Sensor 36A~36D Exhaust temperature detector 37A, 37B NOx detector 38 Accelerator pedal depression amount detection device 39 Ignition Switch 40 Exhaust purification device 41 Upstream exhaust purification device 42 First oxidation catalyst 43 DPF (Particulate matter collection filter) 45 Downstream exhaust purification device 46 SCR (Selective Catalytic Reduction) 47 Second Oxidation Catalyst 50 Control device 51 CPU 51A Deterioration suppression control unit 51B Exhaust purification device temperature acquisition unit 51C Load adjustment section 51D Operation stop detection unit 51E Adsorbed hydrocarbon amount acquisition unit 51F Anoxic Time Estimation Section 51G New air replacement control unit 61, 62 Additive valve 63 Load device (alternator) 80 Turbocharger 81 Turbine 82 Compressor 83 Electric Supercharger 83A, 83B Switching valve 84 Intercooler

Claims

1. A control device for an internal combustion engine system, The internal combustion engine system includes: An internal combustion engine; an electric supercharger provided in an intake pipe connected to the internal combustion engine to supercharge intake air to the internal combustion engine; an EGR pipe that returns a portion of exhaust gas flowing through an exhaust pipe connected to the internal combustion engine to an intake pipe on a discharge side of the electric turbocharger; an EGR valve that adjusts the opening degree of the EGR pipe; an exhaust gas purification device provided in the exhaust pipe downstream of a connection point between the EGR pipe and the exhaust pipe, the exhaust gas purification device having a function of absorbing a predetermined component contained in the exhaust gas and purifying the absorbed predetermined component by an oxidation reaction using ambient oxygen; a control device that detects an operating state of the internal combustion engine and controls an actuator including the electric supercharger and the EGR valve; having The control device includes: an exhaust purification device temperature acquisition unit that acquires a temperature of the exhaust purification device; an operation stop detection unit that detects that the internal combustion engine that was in operation has been stopped; a deterioration suppression control unit that is executed when the operation stop detection unit detects that the internal combustion engine that was in operation has been stopped; having The deterioration suppression control unit includes: an oxygen-free time estimation unit that estimates an oxygen-free time, which is a time when oxygen around the exhaust purification device is used for the oxidation reaction of the predetermined component and is no longer present, based on the temperature of the exhaust purification device acquired by the exhaust purification device temperature acquisition unit while the internal combustion engine is stopped after the operation stop detection unit detects that the internal combustion engine that was in operation has been stopped; a fresh air replacement control unit that opens the EGR valve and drives the electric supercharger before the estimated oxygen-free period to replace the air around the exhaust gas purification device with fresh air, and stops driving the electric supercharger after the replacement is completed; Contains The control device includes: When the anoxic period estimation unit estimates the anoxic period, an oxidation reaction rate of the exhaust purification device based on the temperature of the exhaust purification device acquired by the exhaust purification device temperature acquisition unit, and estimating the oxygen-free period based on the acquired oxidation reaction rate; A control device for an internal combustion engine system.

2. A control device for an internal combustion engine system, comprising: The internal combustion engine system includes: An internal combustion engine; an electric supercharger provided in an intake pipe connected to the internal combustion engine to supercharge intake air to the internal combustion engine; an EGR pipe that returns a portion of exhaust gas flowing through an exhaust pipe connected to the internal combustion engine to an intake pipe on a discharge side of the electric turbocharger; an EGR valve that adjusts the opening degree of the EGR pipe; an exhaust gas purification device provided in the exhaust pipe downstream of a connection point between the EGR pipe and the exhaust pipe, the exhaust gas purification device having a function of absorbing a predetermined component contained in the exhaust gas and purifying the absorbed predetermined component by an oxidation reaction using ambient oxygen; a control device that detects an operating state of the internal combustion engine and controls an actuator including the electric supercharger and the EGR valve; having The control device includes: an exhaust purification device temperature acquisition unit that acquires a temperature of the exhaust purification device; an operation stop detection unit that detects that the internal combustion engine that was in operation has been stopped; a deterioration suppression control unit that is executed when the operation stop detection unit detects that the internal combustion engine that was in operation has been stopped; having The deterioration suppression control unit includes: an oxygen-free time estimation unit that estimates an oxygen-free time, which is a time when oxygen around the exhaust purification device is used for the oxidation reaction of the predetermined component and is no longer present, based on the temperature of the exhaust purification device acquired by the exhaust purification device temperature acquisition unit while the internal combustion engine is stopped after the operation stop detection unit detects that the internal combustion engine that was in operation has been stopped; a fresh air replacement control unit that opens the EGR valve and drives the electric supercharger before the estimated oxygen-free period to replace the air around the exhaust gas purification device with fresh air, and stops driving the electric supercharger after the replacement is completed; Contains The control device includes: After the operation stop detection unit detects that the internal combustion engine that was in operation has been stopped, while the oxidation reaction continues in the exhaust gas purification device while the internal combustion engine is stopped, the fresh air replacement control unit repeats replacing fresh air and the oxygen-free period estimation unit repeats estimating a new oxygen-free period based on the replaced fresh air. A control device for an internal combustion engine system.

3. A control device for an internal combustion engine system, comprising: The internal combustion engine system includes: An internal combustion engine; an electric supercharger provided in an intake pipe connected to the internal combustion engine to supercharge intake air to the internal combustion engine; an EGR pipe that returns a portion of exhaust gas flowing through an exhaust pipe connected to the internal combustion engine to an intake pipe on a discharge side of the electric turbocharger; an EGR valve that adjusts the opening degree of the EGR pipe; an exhaust gas purification device provided in the exhaust pipe downstream of a connection point between the EGR pipe and the exhaust pipe, the exhaust gas purification device having a function of absorbing a predetermined component contained in the exhaust gas and purifying the absorbed predetermined component by an oxidation reaction using ambient oxygen; a control device that detects an operating state of the internal combustion engine and controls an actuator including the electric supercharger and the EGR valve; having The control device includes: an exhaust purification device temperature acquisition unit that acquires a temperature of the exhaust purification device; an operation stop detection unit that detects that the internal combustion engine that was in operation has been stopped; a deterioration suppression control unit that is executed when the operation stop detection unit detects that the internal combustion engine that was in operation has been stopped; having The deterioration suppression control unit includes: an oxygen-free time estimation unit that estimates an oxygen-free time, which is a time when oxygen around the exhaust purification device is used for the oxidation reaction of the predetermined component and is no longer present, based on the temperature of the exhaust purification device acquired by the exhaust purification device temperature acquisition unit while the internal combustion engine is stopped after the operation stop detection unit detects that the internal combustion engine that was in operation has been stopped; a fresh air replacement control unit that opens the EGR valve and drives the electric supercharger before the estimated oxygen-free period to replace the air around the exhaust gas purification device with fresh air, and stops driving the electric supercharger after the replacement is completed; Contains one of the predetermined components is a hydrocarbon; The control device includes: an adsorbed hydrocarbon amount acquisition unit that estimates an adsorbed hydrocarbon amount, which is the amount of hydrocarbons adsorbed in the exhaust purification device while the internal combustion engine is operating and while the engine is stopped; when estimating the oxygen-free time period in the oxygen-free time period estimation unit after the operation stop detection unit detects that the internal combustion engine that was in operation has been stopped, the oxygen-free time period is estimated based on the temperature of the exhaust purification device and the amount of adsorbed hydrocarbons. A control device for an internal combustion engine system.

4. A control device for an internal combustion engine system according to claim 3, The control device includes: When the operation stop detection unit detects that the internal combustion engine that was in operation has been stopped, and then the fresh air replacement control unit replaces fresh air, When it is determined that the hydrocarbons in the adsorbed hydrocarbon amount have been consumed by the oxidation reaction, the execution of the deterioration suppression control unit is terminated. A control device for an internal combustion engine system.

5. A control device for an internal combustion engine system, comprising: The internal combustion engine system includes: An internal combustion engine; an electric supercharger provided in an intake pipe connected to the internal combustion engine to supercharge intake air to the internal combustion engine; an EGR pipe that returns a portion of exhaust gas flowing through an exhaust pipe connected to the internal combustion engine to an intake pipe on a discharge side of the electric turbocharger; an EGR valve that adjusts the opening degree of the EGR pipe; an exhaust gas purification device provided in the exhaust pipe downstream of a connection point between the EGR pipe and the exhaust pipe, the exhaust gas purification device having a function of absorbing a predetermined component contained in the exhaust gas and purifying the absorbed predetermined component by an oxidation reaction using ambient oxygen; a control device that detects an operating state of the internal combustion engine and controls an actuator including the electric supercharger and the EGR valve; having The control device includes: an exhaust purification device temperature acquisition unit that acquires a temperature of the exhaust purification device; an operation stop detection unit that detects that the internal combustion engine that was in operation has been stopped; a deterioration suppression control unit that is executed when the operation stop detection unit detects that the internal combustion engine that was in operation has been stopped; having The deterioration suppression control unit includes: an oxygen-free time estimation unit that estimates an oxygen-free time, which is a time when oxygen around the exhaust purification device is used for the oxidation reaction of the predetermined component and is no longer present, based on the temperature of the exhaust purification device acquired by the exhaust purification device temperature acquisition unit while the internal combustion engine is stopped after the operation stop detection unit detects that the internal combustion engine that was in operation has been stopped; a fresh air replacement control unit that opens the EGR valve and drives the electric supercharger before the estimated oxygen-free period to replace the air around the exhaust gas purification device with fresh air, and stops driving the electric supercharger after the replacement is completed; Contains The control device includes: When the operation stop detection unit detects that the internal combustion engine that was in operation has been stopped, and then the fresh air replacement control unit replaces fresh air, When the temperature of the exhaust purification device acquired by the exhaust purification device temperature acquisition unit becomes equal to or lower than a termination determination temperature, the execution of the deterioration suppression control unit is terminated. A control device for an internal combustion engine system.

6. A control device for an internal combustion engine system, comprising: The internal combustion engine system includes: An internal combustion engine; an electric supercharger provided in an intake pipe connected to the internal combustion engine to supercharge intake air to the internal combustion engine; an EGR pipe that returns a portion of exhaust gas flowing through an exhaust pipe connected to the internal combustion engine to an intake pipe on a discharge side of the electric turbocharger; an EGR valve that adjusts the opening degree of the EGR pipe; an exhaust gas purification device provided in the exhaust pipe downstream of a connection point between the EGR pipe and the exhaust pipe, the exhaust gas purification device having a function of absorbing a predetermined component contained in the exhaust gas and purifying the absorbed predetermined component by an oxidation reaction using ambient oxygen; a control device that detects an operating state of the internal combustion engine and controls an actuator including the electric supercharger and the EGR valve; having The control device includes: an exhaust purification device temperature acquisition unit that acquires a temperature of the exhaust purification device; an operation stop detection unit that detects that the internal combustion engine that was in operation has been stopped; a deterioration suppression control unit that is executed when the operation stop detection unit detects that the internal combustion engine that was in operation has been stopped; having The deterioration suppression control unit includes: an oxygen-free time estimation unit that estimates an oxygen-free time, which is a time when oxygen around the exhaust purification device is used for the oxidation reaction of the predetermined component and is no longer present, based on the temperature of the exhaust purification device acquired by the exhaust purification device temperature acquisition unit while the internal combustion engine is stopped after the operation stop detection unit detects that the internal combustion engine that was in operation has been stopped; a fresh air replacement control unit that opens the EGR valve and drives the electric supercharger before the estimated oxygen-free period to replace the air around the exhaust gas purification device with fresh air, and stops driving the electric supercharger after the replacement is completed; Contains The control device includes: a load adjusting unit capable of adjusting a load on the internal combustion engine, When stopping the internal combustion engine that was in operation, the load adjusting unit adjusts the load immediately before the internal combustion engine is stopped, and stops the internal combustion engine so that both an intake valve and an exhaust valve in any one of the cylinders of the internal combustion engine are within a crank angle range in which they are open. A control device for an internal combustion engine system.

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