JP2011202511A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device of an internal combustion engine that includes an adsorbing part for adsorbing unburned hydrocarbon and has superior clean-up performance.SOLUTION: This exhaust emission control device of an internal combustion engine includes the adsorbing part, which adsorbs the unburned hydrocarbon contained in the exhaust gas when the temperature is less than a discharge temperature, and releases the adsorbed unburned hydrocarbon when the temperature exceeds a release temperature. The exhaust emission control device performs a second temperature raising control for raising the temperature of the adsorbing part to a second temperature higher than a first temperature while the air-fuel ratio of the exhaust gas flowing into the adsorbing part is lean after a first temperature raising control is performed several times for raising the temperature of adsorbing part to the first temperature while the air-fuel ratio of the exhaust gas flowing into the adsorbing part is lean.

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine.

Examples of exhaust gas from internal combustion engines such as diesel engines and gasoline engines include carbon monoxide (CO), unburned fuel (HC), nitrogen oxide (NO _X ), and particulate matter (PM). Contains ingredients. An exhaust gas purification device for an internal combustion engine includes an exhaust gas processing device for purifying these components.

  Of the components contained in the exhaust gas, nitrogen oxides are purified by an exhaust treatment device that reduces the nitrogen oxides. The particulate matter is removed by an exhaust treatment device that collects the particulate matter. Carbon monoxide and unburned fuel discharged from the engine body are purified by an exhaust treatment device for oxidizing these substances. For example, an oxidation catalyst or a three-way catalyst is disposed in the engine exhaust passage.

  In Japanese Patent Laid-Open No. 05-231134, in the adsorbent chamber, moisture absorbents are disposed at the upstream and downstream ends of the adsorbent that adsorbs unburned hydrocarbons, and in a steady state of the engine, caulking is performed. Thus, an engine exhaust purification system is disclosed in which air can be supplied into the adsorbent chamber from the air supply device at a high temperature sufficient to burn carbon adhering to the adsorbent. In this system, it is disclosed that the purification rate of hydrocarbons is improved and that it can be used repeatedly over a long period of time.

JP 05-231134 A

  The oxidation catalyst does not exhibit a sufficient oxidation reaction below a predetermined activation temperature, and has a characteristic of exhibiting a sufficient oxidation reaction above a predetermined activation temperature. That is, the oxidation catalyst has an activation temperature that can achieve a predetermined purification rate. When the oxidation catalyst at the time of cold start or the like is below the activation temperature, the inflowing carbon monoxide and unburned hydrocarbon pass through the oxidation catalyst without being sufficiently oxidized. For this reason, it has been proposed to dispose an adsorbent adsorbing unburned hydrocarbons below the predetermined temperature on the upstream side of the oxidation catalyst.

  In an exhaust purification system in which an adsorbent is arranged upstream of the oxidation catalyst, in the exhaust gas, the adsorbent adsorbs unburned hydrocarbons in the low temperature range until the temperature of the oxidation catalyst reaches the activation temperature. To remove unburned hydrocarbons. On the other hand, when the adsorbent and the oxidation catalyst reach a high temperature, the unburned hydrocarbon adsorbed by the adsorbent can be released and the unburned hydrocarbon released by the oxidation catalyst can be oxidized.

  In the above Japanese Patent Laid-Open No. 05-231134, when the engine is in a steady state and the exhaust temperature rises, air is supplied to the adsorbent by the air supply device and adsorbed by the soot or coking adhered to the adsorbent. An engine exhaust purification system that burns carbon is disclosed. However, the recovery of the adsorbent may be insufficient only by supplying air in the steady state of the engine.

  For example, during normal operation of an internal combustion engine, the temperature of the adsorbent does not rise sufficiently, and hydrocarbons adsorbed on the adsorbent may not be released sufficiently. Further, the hydrocarbon adsorbed on the adsorbent is coked and converted into carbon when a predetermined time elapses above a predetermined temperature. That is, the adsorbent may be held in the form of carbon. The release temperature of carbon in which hydrocarbons are reformed and held is higher than the release temperature of hydrocarbons, and in some cases, they could not be released sufficiently during normal operation of the internal combustion engine.

  As a result, if the use of the exhaust purification device is continued, there is a problem that hydrocarbons and carbon generated by coking accumulate in the adsorbent, and the adsorption ability of unburned hydrocarbons decreases. That is, when the adsorbent and the oxidation catalyst are cold at the time of cold start of the internal combustion engine or the like, there is a possibility that the unburned hydrocarbon cannot be sufficiently removed from the exhaust gas by the adsorbent.

  An object of the present invention is to provide an exhaust gas purification apparatus for an internal combustion engine that includes an adsorption portion that adsorbs unburned hydrocarbons and has excellent purification performance.

  The exhaust gas purification apparatus for an internal combustion engine of the present invention includes an adsorption unit that adsorbs unburned hydrocarbons contained in exhaust gas at a temperature lower than the release temperature and releases the adsorbed hydrocarbons at a temperature equal to or higher than the release temperature. The air-fuel ratio of the exhaust gas flowing into the adsorbing portion is changed after the first temperature increase control for raising the temperature of the adsorbing portion to the first temperature is performed a plurality of times while the air-fuel ratio of the exhaust gas flowing into the adsorbing portion is lean. In the lean state, second temperature rise control is performed to raise the temperature of the adsorption portion to a second temperature higher than the first temperature.

  In the above invention, the first adsorption capacity detecting means for detecting the adsorption capacity of the adsorption section during normal operation and the second adsorption capacity detection for detecting the adsorption capacity of the adsorption section after performing the first temperature rise control. Means for detecting the adsorption capacity by the first adsorption capacity detection means during normal operation, and if the detected adsorption capacity is less than the first determination value, the hydrocarbon adsorbed on the adsorption unit is removed. The adsorption capacity is recovered by performing the first temperature rise control for raising the temperature to a temperature higher than the first temperature to be released, and the adsorption ability is detected by the second adsorption ability detection means after the first temperature rise control, and the detection is performed. When the absorbed capacity is less than the second determination value larger than the first determination value, the second temperature increase control is performed to increase the temperature to a second temperature or higher at which carbon generated by coking is released. Is preferred.

  In the above invention, an oxidation part for oxidizing unburned hydrocarbons is provided, and the oxidation part is disposed downstream of the adsorption part in the engine exhaust passage, or is formed integrally with the adsorption part. Is preferred.

  In the above invention, at least one of the first adsorbing capacity detecting means and the second adsorbing capacity detecting means is such that the temperature of the oxidation part is lower than the temperature at which the hydrocarbon can be oxidized. When the temperature increase width of the oxidation catalyst due to the oxidation of carbon monoxide is detected and the temperature increase width is smaller than a predetermined increase width determination value, it may be determined that the adsorption capacity of the adsorption portion is less than the determination value. preferable.

  ADVANTAGE OF THE INVENTION According to this invention, the exhaust gas purification apparatus of the internal combustion engine provided with the adsorption | suction part which adsorb | sucks an unburned hydrocarbon and having the outstanding purification performance can be provided.

1 is a schematic diagram of an internal combustion engine in a first embodiment. 1 is a schematic cross-sectional view of a first exhaust treatment device in Embodiment 1. FIG. 3 is an enlarged schematic cross-sectional view of a first exhaust treatment device in Embodiment 1. FIG. It is an expanded schematic sectional drawing explaining the carbon which the hydrocarbon adsorb | sucked to the adsorbent, and coking produced. It is a graph explaining the relationship between the density | concentration of the unburned hydrocarbon which passes through an adsorption | suction part, and flows in into an oxidation part, and the purification rate of carbon monoxide. It is a graph explaining the relationship between the temperature of an adsorption | suction part and the density | concentration of the discharge | release component from an adsorption | suction part. 3 is a flowchart of operation control in the first embodiment. It is a graph explaining the temperature change of the oxidation part when detecting the adsorption capacity of an adsorbent. It is explanatory drawing of the injection pattern at the time of normal driving | operation. It is explanatory drawing of an injection pattern when increasing the unburned hydrocarbon supplied to an adsorption | suction part. It is explanatory drawing of the injection pattern when heating up an adsorption | suction part. 3 is a time chart of operation control in the first embodiment. 4 is a graph of the purification rate of carbon monoxide when traveling a long distance while performing operation control in the first embodiment. FIG. 3 is a schematic cross-sectional view of a second exhaust treatment device in the first embodiment. It is a map of the amount of unburned hydrocarbons discharged from the engine body per unit time. FIG. 4 is an enlarged schematic cross-sectional view of a third exhaust treatment device in the first embodiment. FIG. 6 is an enlarged schematic cross-sectional view of a fourth exhaust treatment device in the first embodiment. 6 is a flowchart of operation control in the second embodiment.

(Embodiment 1)
With reference to FIGS. 1 to 17, the exhaust gas purification apparatus for an internal combustion engine in the first embodiment will be described. The internal combustion engine in the present embodiment is arranged in a vehicle. In the present embodiment, a compression ignition type diesel engine will be described as an example.

  FIG. 1 shows an overall view of an internal combustion engine in the present embodiment. The internal combustion engine includes an engine body 1. The internal combustion engine also includes an exhaust purification device that purifies exhaust gas discharged from the engine body 1. The engine body 1 includes a combustion chamber 2 as each cylinder, an electronically controlled fuel injection valve 3 for injecting fuel into each combustion chamber 2, an intake manifold 4, and an exhaust manifold 5.

  The intake manifold 4 is connected to the outlet of the compressor 7 a of the exhaust turbocharger 7 via the intake duct 6. An inlet of the compressor 7 a is connected to an air cleaner 9 via an intake air amount detector 8. A throttle valve 10 driven by a step motor is disposed in the intake duct 6. Further, the intake duct 6 is provided with a cooling device 11 for cooling the intake air flowing through the intake duct 6. In the embodiment shown in FIG. 1, engine cooling water is guided to the cooling device 11. The intake air is cooled by the engine cooling water.

  The exhaust manifold 5 is connected to the inlet of the exhaust turbine 7 b of the exhaust turbocharger 7. The exhaust emission control device in the present embodiment includes an exhaust treatment device 13 for oxidizing unburned fuel (unburned hydrocarbon) discharged from the engine body 1 and substances to be oxidized such as carbon monoxide. The exhaust treatment device 13 is connected to the outlet of the exhaust turbine 7b via the exhaust pipe 12. A particulate filter 16 for collecting particulate matter in the exhaust gas is disposed in the engine exhaust passage downstream of the exhaust treatment device 13. The exhaust gas flows along the engine exhaust passage as indicated by an arrow 100.

  An EGR passage 18 is arranged between the exhaust manifold 5 and the intake manifold 4 for exhaust gas recirculation (EGR). An electronically controlled EGR control valve 19 is disposed in the EGR passage 18. The EGR passage 18 is provided with a cooling device 20 for cooling the EGR gas flowing through the EGR passage 18. In the embodiment shown in FIG. 1, engine cooling water is introduced into the cooling device 20. The EGR gas is cooled by the engine cooling water.

  Each fuel injection valve 3 is connected to a common rail 22 via a fuel supply pipe 21. The common rail 22 is connected to a fuel tank 24 via an electronically controlled variable discharge amount fuel pump 23. The fuel stored in the fuel tank 24 is supplied into the common rail 22 by the fuel pump 23. The fuel supplied into the common rail 22 is supplied to the fuel injection valve 3 through each fuel supply pipe 21.

  The electronic control unit 30 includes a digital computer. The electronic control unit 30 in the present embodiment functions as a control device for the exhaust purification device. The electronic control unit 30 includes a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, an input port 35 and an output port 36 that are connected to each other by a bidirectional bus 31.

  The ROM 32 is a read-only storage device. The ROM 32 stores in advance information such as a map necessary for control. The CPU 34 can perform arbitrary calculations and determinations. The RAM 33 is a readable / writable storage device. The RAM 33 can store information such as an operation history and can temporarily store calculation results.

  A temperature sensor 26 for detecting the temperature of the particulate filter 16 is disposed downstream of the particulate filter 16. A differential pressure sensor 28 for detecting the differential pressure across the particulate filter 16 is attached to the particulate filter 16. The output signals of the temperature sensor 26, the differential pressure sensor 28, and the intake air amount detector 8 are input to the input port 35 via the corresponding AD converters 37, respectively.

  A load sensor 41 that generates an output voltage proportional to the amount of depression of the accelerator pedal 40 is connected to the accelerator pedal 40. The output voltage of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37. Further, the input port 35 is connected to a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, 15 °. From the output of the crank angle sensor 42, the rotational speed of the engine body 1 can be detected.

  On the other hand, the output port 36 is connected to the fuel injection valve 3, the step motor for driving the throttle valve 10, the EGR control valve 19, and the fuel pump 23 through corresponding drive circuits 38. Thus, the fuel injection valve 3 and the throttle valve 10 are controlled by the electronic control unit 30.

  The particulate filter 16 is a filter that removes particulate matter (particulates) such as carbon particulates and ionic particulates such as sulfate contained in the exhaust gas. The particulate filter has, for example, a honeycomb structure and has a plurality of flow paths extending in the gas flow direction. In the plurality of channels, the channels whose downstream ends are sealed and the channels whose upstream ends are sealed are alternately formed. The partition walls of the flow path are formed of a porous material such as cordierite. Particulates are captured when the exhaust gas passes through the partition walls. Particulate matter that gradually accumulates on the particulate filter 16 is oxidized and removed by raising the temperature in an atmosphere of excess air.

Although the exhaust gas purification apparatus for an internal combustion engine in the present embodiment includes a particulate filter 16 in addition to the exhaust gas processing apparatus 13, the present invention is not limited thereto, and other exhaust gas processing apparatuses are arranged in addition to the exhaust gas processing apparatus 13. It does not matter. For example, the exhaust purification device may include a NO _X storage reduction catalyst (NSR) that purifies NO _X contained in the exhaust gas. The NO _X storage reduction catalyst can be disposed, for example, between the exhaust treatment device 13 and the particulate filter 16.

The NO _X storage reduction catalyst temporarily stores NO _X contained in the exhaust gas discharged from the engine body, and converts it to N ₂ when releasing the stored NO _X. In the NO _X storage reduction catalyst, a catalyst carrier containing, for example, aluminum oxide is supported on a substrate. Catalyst particles formed of a noble metal are dispersed and supported on the surface of the catalyst carrier. In addition, a layer of NO _X absorbent is formed on the surface of the catalyst carrier. For example, platinum Pt is used as the catalyst particles. As a component constituting the NO _X absorbent, an alkaline earth such as barium Ba is used.

In the present invention, the ratio of the air and fuel (hydrocarbon) of the exhaust gas supplied to the engine intake passage, the combustion chamber, or the engine exhaust passage is referred to as the air-fuel ratio (A / F) of the exhaust gas. By the time the air-fuel ratio of the exhaust gas is lean (greater time than the stoichiometric air-fuel ratio), NO contained in the exhaust gas is occluded in the oxidized _the NO _X absorbent. In contrast, the air-fuel ratio of the exhaust gas when the rich or becomes the stoichiometric air-fuel ratio, NO _X which is stored in _the NO _X absorbent is released. The released NO _X is reduced to N ₂ by unburned fuel, carbon monoxide or the like contained in the exhaust gas.

  FIG. 2 shows an enlarged schematic cross-sectional view of the first exhaust treatment apparatus in the present embodiment. The first exhaust treatment device 13 in the present embodiment has a plurality of passages along the flow direction of the exhaust gas. The first exhaust treatment device 13 is divided in the middle of the exhaust gas flow direction. The first exhaust treatment device 13 includes an adsorbent 13a for adsorbing unburned hydrocarbons and an oxidation catalyst 13b for oxidizing unburned hydrocarbons and carbon monoxide. A temperature sensor 29 for detecting the temperature of the adsorbent 13a is disposed between the adsorbent 13a and the oxidation catalyst 13b. Further, a temperature sensor 27 for detecting the temperature of the oxidation catalyst 13b is disposed downstream of the oxidation catalyst 13b. The output signals of these temperature sensors 27 and 29 are each input to the input port 35 via the AD converter 37 of the electronic control unit 30.

  FIG. 3 shows an enlarged schematic cross-sectional view of the first exhaust treatment apparatus in the present embodiment. FIG. 3 is an enlarged schematic cross-sectional view of a boundary portion between the adsorbent 13a and the oxidation catalyst 13b. Each of the adsorbent 13 a and the oxidation catalyst 13 b includes a base material 55. The substrate 55 in the present embodiment has a plurality of flow paths and is formed in a honeycomb structure. The substrate 55 is formed of a monolith substrate such as cordierite or SiC, for example.

An adsorption part 51 is formed on the surface of the base material 55 of the adsorbent 13a. The adsorption part 51 is formed in a plurality of flow paths of the base material 55. The adsorbing part 51 is formed in layers along the engine exhaust passage. The adsorption part 51 has a function of adsorbing unburned hydrocarbons. The adsorption part 51 in the present embodiment includes a support 60 and beta (β) zeolite particles 61. The carrier 60 includes a porous oxide powder such as aluminum oxide (alumina: Al ₂ O ₃ ). The carrier 60 and the beta zeolite particles 61 are supported on the base material 55 by, for example, a binder. The adsorption part 51 preferably contains zeolite. As the zeolite, in addition to beta zeolite, any zeolite such as ZSM5 and mordenite (MOR) can be used. In addition, as an adsorption | suction part, it is not restricted to this form, What is necessary is just to be formed so that unburned hydrocarbon can be adsorbed.

  An oxidation part 52 is formed on the surface of the base 55 of the oxidation catalyst 13b. The oxidation unit 52 is formed in a plurality of flow paths of the base material 55. The oxidation part 52 is formed in layers along the engine exhaust passage. The oxidation unit 52 has a function of oxidizing unburned hydrocarbons, carbon monoxide, and the like. The oxidation unit 52 of the first exhaust treatment device 13 includes a support 60 and catalyst particles 62. The carrier 60 is fixed to the base material 55 with a binder. The catalyst particles 62 are supported on the support 60. The catalyst particles 62 are metal particles for oxidizing a substance to be oxidized contained in the exhaust gas.

  The catalyst particles 62 in the present embodiment are formed from a noble metal. As the catalyst particles 62, platinum group metals (PGM) can be used. For the catalyst particles 62, for example, at least one noble metal of platinum Pt, palladium Pd, and rhodium Rh can be used. Alternatively, the catalyst particles can include any metal having an oxidizing ability.

  In the first exhaust treatment apparatus according to the present embodiment, the adsorbent 13a is disposed on the upstream side in the engine exhaust passage, and the oxidation catalyst 13b is disposed on the downstream side. The adsorbent 13a and the oxidation catalyst 13b are arranged so as to contact the oxidation unit 52 after the exhaust gas contacts the adsorption unit 51. In the present embodiment, the base material 55 is divided to form the adsorbent and the oxidation catalyst. However, the present invention is not limited to this form, and the base material may be integrally formed. That is, on the surface of one base material, an adsorption part may be formed on the upstream side along the flow direction of the exhaust gas, and an oxidation part may be formed on the downstream side.

  In the present embodiment, the exhaust treatment device 13 that oxidizes a substance to be oxidized adsorbs unburned hydrocarbons in the adsorption unit 51 when the exhaust gas is at a low temperature. For example, when the temperature of the exhaust treatment device 13 is lower than the hydrocarbon release temperature, unburned hydrocarbon is adsorbed. When the temperature of the exhaust gas rises, the adsorption unit 51 releases the adsorbed hydrocarbon. For example, when the temperature of the exhaust treatment device 13 becomes equal to or higher than the hydrocarbon release temperature, the hydrocarbon is released. On the other hand, the oxidation part 52 exhibits a sufficient oxidation function when the temperature rises and becomes, for example, the activation temperature or higher. The released hydrocarbon is purified by being oxidized in the oxidation unit 52. Further, the carbon monoxide flowing into the exhaust treatment device is oxidized in the oxidation unit 52. Thus, carbon monoxide and unburned hydrocarbons contained in the exhaust gas are converted into water and carbon dioxide by being oxidized.

  FIG. 4 shows an enlarged schematic cross-sectional view for explaining the form when unburned hydrocarbon is held in the adsorbent. In the low temperature region where the adsorbing part adsorbs the unburned hydrocarbon, when the unburned hydrocarbon flows into the adsorbing part, the adsorbing part holds the hydrocarbon in the form of hydrocarbons. The hydrocarbon is adsorbed on the acid sites 63 of the zeolite 64, for example. However, after elapse of a predetermined time at a predetermined temperature, a dehydrogenation reaction occurs in the adsorbed hydrocarbon. That is, coking occurs and changes to carbon. As a result, the unburned hydrocarbons that have flowed into the adsorption section are held at the acid sites 63 of the zeolite 64 in the form of carbon. As described above, the carbon component retained in the form of hydrocarbon gradually cokes with time. Carbon produced by coking is released at a temperature higher than the temperature at which hydrocarbons are released.

  By the way, in a conventional exhaust gas purification apparatus for an internal combustion engine, there is a case where hydrocarbons held in the adsorption section are not sufficiently released during normal operation. For example, the temperature of the exhaust gas may not reach the temperature at which hydrocarbons are sufficiently released during the driving period of the internal combustion engine. When the internal combustion engine is arranged in an automobile and traveling in a traffic jam lasts for a long time, the internal combustion engine is kept driven at a low load. For this reason, the state where the exhaust gas is at a low temperature continues, and the temperature of the adsorbing portion may not sufficiently rise to a temperature at which hydrocarbons can be released. Or, in an internal combustion engine in which the amount of fuel supplied is suppressed in order to improve fuel consumption, the temperature of the exhaust gas may be lowered and the temperature of the adsorbing portion may not be sufficiently increased.

  When the state where the temperature of the adsorption part does not reach the temperature at which the hydrocarbons are sufficiently released continues, the hydrocarbon gradually accumulates in the adsorption part. Furthermore, since carbon generated by coking is not released unless the temperature is higher than the temperature range where hydrocarbons are released, it has a characteristic that it is likely to accumulate in the adsorption part. For this reason, hydrocarbons and carbon produced by coking accumulate in the adsorption section, and the amount of unburned hydrocarbons that can be adsorbed, the adsorption rate, and the like decrease. That is, the adsorption capacity of the adsorption unit is reduced.

  When the adsorption capacity in the adsorption unit is reduced, more unburned hydrocarbons pass through the adsorption unit when the adsorption unit and the oxidation unit are at a low temperature. Further, when the amount of unburned hydrocarbon that passes through the adsorbing portion increases, the amount of unburned hydrocarbon that passes through the oxidized portion increases. Thus, the purification rate of unburned hydrocarbons discharged from the engine body deteriorates. Moreover, if the adsorption capacity of the adsorption part is reduced, the purification rate of carbon monoxide in the oxidation catalyst may be adversely affected.

  FIG. 5 shows a graph for explaining the relationship between the concentration of unburned hydrocarbons flowing into the oxidation catalyst and the purification rate of carbon monoxide. The horizontal axis represents the concentration of unburned hydrocarbons flowing into the oxidation catalyst, and corresponds to the concentration of unburned hydrocarbons that pass through the adsorption portion in the present embodiment. The vertical axis represents the purification rate of carbon monoxide in the oxidation catalyst. The graph of FIG. 5 shows the results of a test conducted at a temperature at which carbon monoxide can be oxidized although hydrocarbons cannot be oxidized sufficiently. It can be seen that the purification rate of carbon monoxide decreases as the concentration of hydrocarbons flowing into the oxidation catalyst increases, that is, as the concentration of unburned hydrocarbons passing through the adsorption section increases.

  Among the unburned hydrocarbons contained in the exhaust gas, the lower olefin has a characteristic that strongly affects the oxidation reaction of carbon monoxide in the oxidation catalyst. For example, propylene or the like has a strong effect of inhibiting the oxidation reaction of carbon monoxide in the oxidation catalyst. The lower olefin is preferably adsorbed on the acid sites of the zeolite in the adsorption section. However, if the unburned hydrocarbon is already held at the acid point, or the carbon produced by coking is held at the acid point, the ability to adsorb the lower olefin at the adsorption portion is reduced. Thus, when there are many carbon components which remain | survive in an adsorption | suction part, the lower olefin which slips through an adsorption | suction part will increase, and the purification rate of the carbon monoxide in an oxidation catalyst will fall.

FIG. 6 shows a graph for explaining the relationship between the temperature of the adsorption unit and the concentration of the released component from the adsorption unit. The hydrocarbon adsorbed on the adsorption part is released in the form of hydrocarbon when the temperature exceeds the hydrocarbon release temperature. On the other hand, when the carbon produced by coking reaches or exceeds the carbon release temperature, it is oxidized by oxygen contained in the exhaust gas and released in the form of carbon monoxide (CO) or carbon dioxide (CO ₂ ).

  In the graph of FIG. 6, the solid line indicates the concentration of the hydrocarbon when the carbon component held in the form of hydrocarbon is released, and the one-dot chain line indicates the carbon concentration held in the form of carbon. The combined concentration of carbon oxide and carbon dioxide is shown. In this test, after the use of the exhaust purification device is continued under the condition that coking sufficiently proceeds in the adsorption portion, the adsorption portion is taken out from the exhaust purification device. Next, the density | concentration of the discharge | release component when the temperature of an adsorption | suction part is raised gradually is measured in nitrogen atmosphere which contains oxygen enough.

  As can be seen from the test results, when the temperature of the adsorbing portion is increased, hydrocarbons are first released. That is, the carbon component adsorbed on the adsorption portion in the form of hydrocarbon is released. The amount of released hydrocarbons increases within a range of 300 ° C. or more and 500 ° C. or less, for example. Alternatively, the amount of released hydrocarbon increases at approximately 400 ° C.

  As the temperature is further increased, the amount of carbon monoxide and carbon dioxide released increases. That is, carbon generated by coking is released from the adsorption section, and the amount of carbon monoxide or carbon dioxide released increases. The release amount of carbon generated by coking increases within a range of 500 ° C. or more and 700 ° C. or less, for example. Alternatively, the amount of carbon generated by coking increases at about 600 ° C.

  FIG. 7 shows a flowchart of operation control in the present embodiment. The exhaust emission control device in the present embodiment recovers the adsorption capability of the adsorption unit by raising the temperature of the adsorption unit in at least two stages during the driving period of the internal combustion engine. In the operation control of the present embodiment, after releasing the carbon component adsorbed to the adsorption part in the form of hydrocarbon, if the adsorption capacity of the adsorption part is still low, it is retained in the form of carbon. Control to release carbon components.

  First, in step 81, the adsorption capacity of the adsorption unit is detected. The adsorption capacity includes, for example, the amount of unburned hydrocarbon that can be adsorbed, the unburned hydrocarbon adsorption rate, or the unburned hydrocarbon removal rate. The exhaust emission control device in the present embodiment includes a first adsorption capacity detection means for detecting the adsorption capacity of the adsorption unit during normal operation. The first adsorption capacity detecting means in the present embodiment detects the adsorption capacity of the adsorption section by detecting the temperature rise width of the oxidation catalyst when the unburned hydrocarbon supplied to the adsorption section is increased. Referring to FIG. 1, the first adsorption capacity detecting means includes a temperature sensor 27, an electronic control unit 30, and a fuel injection valve 3. The temperature sensor 27 can detect the temperature of the oxidized portion.

  In the oxidation section, when the temperature is gradually raised from a low temperature state such as cold start, oxidation of carbon monoxide occurs first, and when the temperature is further increased, oxidation of hydrocarbons occurs. In the present embodiment, the temperature of the oxidation catalyst is increased in a temperature range in which carbon monoxide is oxidized and hydrocarbons are not sufficiently oxidized.

  FIG. 8 is a graph for explaining the temperature change of the oxidation unit when the adsorption capability of the adsorption unit is detected by the first adsorption capability detection means. In the first adsorption capacity detecting means in the present embodiment, the adsorption capacity of the adsorption section is detected by selecting a time when the temperature of the oxidation section is lower than the temperature at which the hydrocarbon is sufficiently oxidized. For example, it is possible to select a time immediately after the internal combustion engine is cold started or a time when the exhaust gas is at a low temperature in the normal operation state. In the present embodiment, the process starts from a temperature lower than the temperature at which carbon monoxide is sufficiently oxidized. The start time of the detection of the adsorption capacity is not limited to this form. For example, the temperature of the oxidation part may be equal to or higher than the temperature at which the oxidation of carbon monoxide is sufficiently generated.

  In the present embodiment, the time when the temperature TS of the adsorption unit 51 and the oxidation unit 52 is approximately 100 ° C. is selected, and detection of the adsorption capability of the adsorption unit is started. At time t1, control is performed to increase unburned hydrocarbons supplied to the adsorption unit 51. In the present embodiment, control is performed to increase unburned hydrocarbons discharged from the engine body 1 and flowing into the adsorbent 13a. In the present embodiment, control is performed to increase the fuel injected in the combustion chamber by a predetermined amount.

  FIG. 9 shows an explanatory diagram of an injection pattern during normal operation of the internal combustion engine in the present embodiment. The injection pattern A is a fuel injection pattern during normal operation. During normal operation, the main injection FM is performed at a compression top dead center TDC. Main injection FM is performed at a crank angle of approximately 0 °. Further, in order to stabilize the combustion of the main injection FM, the pilot injection FP is performed before the main injection FM. During normal operation, pilot injection FP may not be performed. When operating with the injection pattern A in normal operation, the air-fuel ratio of the exhaust gas is lean.

  In FIG. 10, explanatory drawing of the injection pattern when increasing the unburned hydrocarbon which flows into the adsorption | suction part in this Embodiment is shown. In the injection pattern B, the first auxiliary injection FPO is performed after the main injection FM. The first auxiliary injection is auxiliary injection performed when fuel does not burn in the combustion chamber. The first auxiliary injection is also referred to as post injection. The first auxiliary injection has a feature that does not contribute to the engine output. The first auxiliary injection is performed, for example, when the crank angle after compression top dead center is in the range of approximately 90 ° to approximately 120 °. By performing the first auxiliary injection FPO, the amount of unburned hydrocarbons flowing into the adsorption section can be increased. In this embodiment, the air-fuel ratio of the exhaust gas discharged from the engine body at this time is controlled to be lean.

  Further, in the injection pattern B, the injection timing of the main injection FM is delayed from the compression top dead center TDC. That is, the injection timing of the main injection FM is retarded. As the injection timing of the main injection FM is retarded, the injection timing of the pilot injection FP is also retarded. By delaying the injection timing of the main injection FM, the temperature of the exhaust gas can be raised. In the present embodiment, the control for retarding the main injection is performed. However, the present invention is not limited to this, and the control for retarding the main injection may not be performed.

  In the present embodiment, post-injection increases the unburned hydrocarbons supplied to the adsorption unit. However, the present invention is not limited to this mode. For example, by performing after-injection described later, the adsorbent You may increase the unburned hydrocarbon supplied to. Or as a supply means which supplies unburned hydrocarbon to an adsorption part, it is not restricted to change of a fuel injection pattern, and unburned hydrocarbon can be supplied to an adsorption part by arbitrary means. For example, a fuel addition valve may be disposed in the engine exhaust passage upstream of the adsorption portion, and unburned hydrocarbons supplied to the adsorption portion may be increased by releasing unburned hydrocarbons into the engine exhaust passage. Absent.

  Referring to FIG. 8, when the adsorption capacity of the adsorption unit is high, the unburned hydrocarbon is sufficiently adsorbed in the adsorption unit even if the supplied unburned hydrocarbon increases. As a result, less unburned hydrocarbons flow into the oxidation part. In particular, the inflow of lower olefin that greatly inhibits the oxidation of carbon monoxide is reduced. In this way, HC (hydrocarbon) poisoning in the oxidation part is reduced. On the other hand, carbon monoxide discharged from the engine body passes through the adsorption part and flows into the oxidation part. In the oxidation catalyst, carbon monoxide contained in the exhaust gas is oxidized. Due to the heat of oxidation reaction of carbon monoxide, the temperature of the oxidized portion increases. In the present embodiment, the temperature increase in the oxidation part includes a temperature increase due to the retardation of the main injection in addition to the temperature increase due to the reaction heat of carbon monoxide. In the example shown in FIG. 8, when the adsorption capacity of the adsorption part is maximum, the temperature of the oxidation part rises from the temperature TS to the temperature TH. In the present embodiment, the temperature TH of the oxidation part is in the range of 220 ° C. or higher and 230 ° C. or lower, for example.

  On the other hand, when the adsorption capacity of the adsorption part is low, when the unburned hydrocarbon flowing into the adsorption part increases, a part of the unburned hydrocarbon is removed by the adsorption part. Hydrogen passes through the adsorption section. The amount of unburned hydrocarbons flowing into the oxidation catalyst increases. In particular, the inflow of lower olefins contained in the exhaust gas increases and HC poisoning increases. The oxidation reaction of carbon monoxide in the oxidation part is suppressed. For this reason, the temperature rise of an oxidation part becomes small. In the example shown in FIG. 8, when the adsorption capacity of the adsorption part is low, the temperature of the oxidation part rises from the temperature TS to the temperature TL. In the present embodiment, the temperature TL of the oxidation part is, for example, in the range of 150 ° C. or higher and 160 ° C. or lower.

  In the detection of the adsorption capacity of the adsorption unit in the present embodiment, the temperature rise width when the unburned hydrocarbon supplied to the adsorption unit is increased is detected. In the present embodiment, the temperature TX reached by the oxidation part is detected. A temperature rise width DTX (= TX−TS) is calculated from the temperature TX and the initial temperature TS. The temperature rise width DTX when the unburned hydrocarbon is increased corresponds to the adsorption capacity of the adsorption unit. It can be determined that the adsorption capacity is high if the temperature rise is large, and the adsorption capacity is low if the temperature rise is small.

  With reference to FIG. 7, in step 82, it is determined whether or not the suction capability of the suction portion is less than a first determination value. In the first adsorption capacity detecting means in the present embodiment, the first increase range determination value DTX1 is provided as the first determination value. Referring to FIG. 8, first increase width determination value DTX1 is larger than the temperature range when the oxidation part rises from temperature TS to temperature TL, and the temperature when the oxidation part rises from temperature TS to temperature TH. It is set within a range smaller than the width. When the unburned hydrocarbon is supplied to the adsorption unit, if the temperature increase width DTX of the oxidation unit is less than the first increase range determination value DTX1, the adsorption capability of the adsorption unit is less than the first determination value. It can be judged.

  Referring to FIG. 7, if the suction capability of the detected suction portion is greater than or equal to the first determination value in step 82, this control is terminated. That is, the adsorbing part has an adsorbing capacity that exceeds the desired capacity. In step 82, when the detected adsorption capacity is less than the first determination value, the process proceeds to step 83.

  In step 83, first temperature increase control for increasing the temperature of the adsorption unit is performed. In the first temperature rise control of the present embodiment, the temperature is raised while the air-fuel ratio of the exhaust gas flowing into the adsorption portion is lean. That is, the oxygen contained in the exhaust gas raises the temperature in a state sufficient for the oxidation of the carbon component. In the first temperature rise control in the present embodiment, the temperature of the exhaust gas is raised by changing the fuel injection pattern in the combustion chamber. By increasing the temperature of the exhaust gas, the temperature of the adsorption part is increased. In the present embodiment, the temperature is raised to a predetermined first temperature or higher.

  FIG. 11 shows an explanatory diagram of an injection pattern when the temperature of the exhaust gas is raised in the temperature raising control. In the temperature rise control of the present embodiment, the temperature of the exhaust gas is raised by changing the injection pattern in the combustion chamber. In the injection pattern C, the temperature of the exhaust gas is raised by retarding the injection timing of the main injection FM. Further, in the injection pattern C, the second auxiliary injection is performed at the combustible time after the main injection FM. The second auxiliary injection is referred to as after injection FA. The second auxiliary injection FA is performed, for example, in a range where the crank angle after compression top dead center is approximately 40 °. By performing the second auxiliary injection FA, the afterburning period becomes longer and the temperature of the exhaust gas can be raised.

  Referring to FIG. 6, the first temperature as the target temperature in the first temperature increase control is selected as a temperature at which the carbon component held in the adsorption section in the form of hydrocarbon can be released. For example, the first temperature may be a temperature of 300 ° C. or higher and 500 ° C. or lower. In the present embodiment, approximately 400 ° C. is adopted as the first temperature. In the first temperature increase control in the present embodiment, the temperature is increased until the temperature of the adsorption portion becomes approximately 400 ° C. or higher. In the first temperature rise control in the present embodiment, control is performed so that the temperature of the adsorption portion becomes equal to or higher than the first temperature in a predetermined length of time. By performing the first temperature increase control, the hydrocarbons adsorbed by the adsorption unit can be released. At least a part of the adsorption capacity of the adsorption part can be recovered.

  Referring to FIG. 7, when the first temperature increase control is completed in step 83, the process proceeds to step 84. In step 84, the adsorption capacity of the adsorption unit is detected again. The exhaust emission control device of the present embodiment includes a second adsorption capacity detection unit that detects the adsorption capacity of the adsorption unit after performing the first temperature rise control.

  The second adsorption capability detection means in the present embodiment is the same as the first detection capability detection means. That is, in the state where the adsorbing portion is at a low temperature, unburned hydrocarbons supplied to the adsorbing portion are increased to cause an oxidation reaction of carbon monoxide. The adsorption capacity of the adsorption unit is detected by detecting the temperature rise width DTX of the oxidation unit at that time (see FIG. 8).

  Next, in step 85, it is detected whether the suction capability of the suction part detected in step 84 is less than a second determination value. In the present embodiment, the same control as the evaluation of the adsorption capacity in step 82 is performed. Referring to FIG. 8, the second increase width determination value DTX2 is adopted as the determination value of the second adsorption capacity determination means. As the second increase width determination value DTX2, a value larger than the first increase width determination value DTX1, which is the determination value of the first adsorption capacity determination means, is employed. If the detected temperature increase width DTX of the oxidized portion is smaller than the second increase width determination value DTX2, it can be determined that the detected adsorption capacity is less than the second determination value.

  Referring to FIG. 7, in step 85, when the suction capability of the suction portion is equal to or greater than the second determination value, this control is terminated. That is, the adsorbing part has an adsorbing capacity that exceeds the desired capacity. If the suction capacity of the suction part is less than the second determination value, the process proceeds to step 86.

  In step 86, second temperature rise control is performed. In the second temperature rise control, control is performed to raise the temperature of the adsorption portion to a second temperature higher than the first temperature reached in the first temperature rise control. As the second temperature that is the target temperature of the second temperature increase control, a temperature that sufficiently releases the carbon component held in the form of carbon by coking can be selected. For example, referring to FIG. 6, a temperature of 500 ° C. or higher and 700 ° C. or lower can be adopted as the second temperature. The second temperature in the present embodiment employs approximately 600 ° C.

  In the second temperature increase control of the present embodiment, the air-fuel ratio of the exhaust gas flowing into the adsorption unit is set to a lean state. Further, the temperature of the adsorption portion can be raised by the same method as in the first temperature rise control. In the present embodiment, as shown in FIG. 11, the temperature of the exhaust gas is raised by retarding the main injection FM and further performing the after injection FA. As the temperature of the exhaust gas rises, the temperature of the adsorption section is raised. In the second temperature rise control in the present embodiment, the adsorption unit is maintained at the second temperature or higher for a predetermined length of time. By performing the second temperature rise control, carbon generated by coking can be released from the adsorption portion. The adsorption capacity of the adsorption part can be recovered.

  Referring to FIG. 7, the normal operation is resumed when the second temperature raising control is completed. In the present embodiment, the second temperature raising control is completed once, but the present invention is not limited to this mode, and the adsorption capability of the adsorption unit is detected after the second temperature raising control is completed, and the adsorption capability is If it is less than the predetermined determination value, the second temperature rise control may be repeated.

  FIG. 12 shows a time chart of operation control in the present embodiment. Normal operation is performed until time t1. The adsorption capacity decreases as the hydrocarbons and carbon retained in the adsorption section increase. At time t1, the suction capacity of the suction part has reached the first determination value. In the present embodiment, the temperature increase width DTX in the oxidation catalyst is less than the first increase width determination value DTX1.

  From time t1 to time t2, first temperature increase control is performed. The temperature of the adsorption part is raised so as to be equal to or higher than the first temperature. By performing the first temperature rise control, the carbon component adsorbed in the form of hydrocarbon is released from the adsorption portion. At time t2, the adsorption capacity is recovered. The adsorption capacity at this time exceeds the second determination value. For this reason, normal operation is performed from time t2 to time t3.

  At time t3, the suction capacity has reached the first determination value. From time t3 to time t4, the first temperature rise control is performed again. Normal operation is performed from time t4 to time t5. Further, the first temperature increase control is performed from time t5 to time t6. As described above, the first temperature increase control is repeatedly performed a plurality of times during the normal operation period.

  At time t6, the adsorption capacity when the first temperature raising control is finished is smaller than the second determination value. For this reason, the second temperature rise control is performed from time t7 to time t8. In the second temperature rise control, control is performed so that the temperature of the adsorption portion becomes equal to or higher than the second temperature. By performing the second temperature rise control, the carbon component held in the form of carbon is released. As a result, the suckable amount is recovered at time t8, and the suction capacity becomes larger than the second determination value. After the time t8, these operation controls are repeated.

  FIG. 13 shows a graph for explaining the purification rate of carbon monoxide when the operation control in the present embodiment is performed. The horizontal axis is the evaluation travel distance in the test apparatus, and corresponds to the travel distance of the vehicle when the internal combustion engine is arranged in the vehicle. The travel distance on the horizontal axis increases in the order of travel distance D1, travel distance D2, travel distance D3, and travel distance D4. The vertical axis represents the purification rate of carbon monoxide.

  Each bar graph shows a state immediately after the first temperature increase control or the second temperature increase control is performed. The state of the travel distance D1 is a state at the start of use, and has an excellent carbon monoxide purification rate.

  At the mileage D2, a reduction in the purification rate due to hydrocarbons remaining without being released and carbon produced by coking is manifested. In the travel distance D2, the carbon monoxide purification rate is less than the first determination value. By performing the first temperature increase control at this time, the remaining hydrocarbon is released, and a part of the purification rate of carbon monoxide is recovered.

  However, in the first temperature rise control, most of the carbon generated by coking remains without being released. For this reason, as shown in the travel distance D2 and the travel distance D3, the purification rate of carbon monoxide decreases as the travel distance increases. Thus, when the first temperature increase control is performed while continuing normal operation, the purification rate of carbon monoxide gradually decreases.

  In the example shown in FIG. 13, the carbon monoxide purification rate is less than the second determination value even when the first temperature increase control is performed at the travel distance D4. That is, the suction capacity of the suction part is less than the second determination value. At this time, by performing the second temperature increase control, carbon generated by coking can be released, and the purification rate of carbon monoxide can be recovered. In FIG. 13, the carbon monoxide purification rate has been described as an example, but the same effect is achieved with respect to the unburned hydrocarbon purification rate.

  As described above, in the operation control of the present embodiment, the second temperature higher than the first temperature is performed after the first temperature rise control for raising the temperature of the adsorption unit to the first temperature is performed a plurality of times. The second temperature rise control is performed to raise the temperature of the adsorption part. By performing this control, it is possible to release hydrocarbons adsorbed on the adsorption part and carbon produced by coking, and maintain excellent purification performance of the adsorption part.

  By the way, as operation control of the comparative example, in each temperature increase control, control for increasing the temperature to a temperature at which carbon generated by coking can be released from the adsorption portion can be taken up. However, in this control, in order to release the carbon generated by coking, it is necessary to make the adsorption part very high in each temperature increase control.

  On the other hand, in the operation control according to the present embodiment, a target temperature for performing temperature increase control is selected according to the amount of carbon retained by coking. That is, the first temperature or the second temperature is selected as the target temperature. For this reason, the frequency | count of heating up to the temperature for releasing the carbon produced | generated by coking can be decreased, and fuel consumption can be suppressed. Alternatively, when the exhaust treatment device disposed in the engine exhaust passage causes thermal degradation, the thermal degradation can be suppressed.

  The exhaust gas purification apparatus for an internal combustion engine in the present embodiment includes a particulate filter that removes particulate matter contained in the exhaust gas. In order to regenerate the particulate filter, the exhaust gas may be heated to a high temperature while the air-fuel ratio of the exhaust gas discharged from the engine body is lean. In this case, hydrocarbons held in the adsorption unit and carbon generated by coking can be released from the adsorption unit. However, regeneration of the particulate filter is performed every very long time. For this reason, when waiting for regeneration of a particulate filter, the adsorption capacity of an adsorption part will fall greatly. In the present embodiment, by performing the first temperature rise control and the second temperature rise control separately from the regeneration of the particulate filter, it is possible to maintain the excellent adsorption capability of the adsorption unit.

  The first adsorption capacity detecting means in the present embodiment increases the amount of unburned hydrocarbons flowing into the adsorption unit in a state where the temperature of the exhaust gas is lower than a predetermined temperature. At this time, the temperature rise of the oxidation catalyst due to the oxidation of carbon monoxide is detected. When the temperature rise width is smaller than a predetermined first rise width determination value, it is determined that the suction capacity of the suction portion is less than the first determination value. Similarly, in the second adsorption capacity detecting means, when the temperature increase width is smaller than a predetermined second increase width determination value, it is determined that the adsorption capacity of the adsorption portion is less than the second determination value. ing. With this configuration, the adsorption capability of the adsorption unit can be easily detected.

  In the present embodiment, the first adsorbing capacity detecting means and the second adsorbing capacity detecting means use the same means. However, the present invention is not limited to this mode, and different means may be adopted. . Alternatively, any means capable of detecting the adsorption capability of the adsorption unit can be adopted as each adsorption capability detection unit.

  FIG. 14 is a schematic cross-sectional view of the second exhaust treatment apparatus in the present embodiment. The second exhaust treatment device includes another adsorption capacity detection unit different from the above adsorption capacity detection unit in order to detect the adsorption capacity of the adsorption unit. The other adsorption capacity detecting means includes an air-fuel ratio sensor 71a that is arranged upstream of the adsorbent 13a including the adsorbing portion 51 and detects the air-fuel ratio of the exhaust gas. Further, the other adsorption capacity detecting means includes an air-fuel ratio sensor 71b that is disposed on the downstream side of the adsorbent 13a and detects the air-fuel ratio of the exhaust gas flowing out from the adsorbent 13a. Each air-fuel ratio sensor 71a, 71b is connected to the input port 35 of the electronic control unit 30 (see FIG. 1).

  The air-fuel ratio sensors 71a and 71b in the present embodiment show output values corresponding to the respective points of the air-fuel ratio of the exhaust gas. For example, as the air-fuel ratio of the exhaust gas becomes smaller (the air-fuel ratio of the exhaust gas becomes richer) ) The output current of the air-fuel ratio sensor becomes small. The air-fuel ratio sensors 71a and 71b in the present embodiment are linear air-fuel ratio sensors in which the air-fuel ratio of the exhaust gas and the output value have a substantially proportional relationship, and can detect the air-fuel ratio in each state of the exhaust gas. it can.

  Other adsorption capacity detecting means in the present embodiment can detect the concentration of unburned hydrocarbons at the respective positions from the air-fuel ratio of the exhaust gas detected by the air-fuel ratio sensors 71a and 71b. The hydrocarbon purification rate can be detected from the concentration of unburned hydrocarbons flowing into the adsorbent 13a and the concentration of unburned hydrocarbons flowing out from the adsorbent 13a. For example, the purification rate of hydrocarbons in the adsorbent is (purification rate) = (concentration of hydrocarbons flowing into the adsorbent-concentration of hydrocarbons flowing out from the adsorbent) / (concentration of hydrocarbons flowing into the adsorbent) Can be detected.

  The other adsorption capacity detecting means can detect the hydrocarbon purification rate as the adsorption capacity of the adsorption section in a predetermined temperature range where hydrocarbons should be adsorbed. When the detected hydrocarbon purification rate is smaller than the first purification rate determination value, it can be determined that the adsorption capacity of the adsorption unit is less than the first determination value. Alternatively, when the detected hydrocarbon purification rate is smaller than the second purification rate determination value, it can be determined that the adsorption capacity in the adsorption unit is less than the second determination value.

  Although the other adsorption capacity detecting means in the present embodiment includes an air-fuel ratio sensor, a sensor such as a carbon monoxide sensor can be arranged instead of the air-fuel ratio sensor. By disposing a sensor capable of detecting the concentration of carbon monoxide, the purification rate of carbon monoxide can be detected as the adsorption capacity of the adsorption unit. Alternatively, the concentration of unburned hydrocarbons and the concentration of carbon monoxide flowing into the adsorbent may be estimated using a map.

  Further, the first suction capacity detection means of the suction capacity detection means can be implemented even if the estimation accuracy is not high. The first adsorption capacity detecting means can estimate the adsorption capacity of the adsorption section using a map prepared in advance without using a sensor such as a temperature sensor or an air-fuel ratio sensor.

  FIG. 15 shows a map of unburned hydrocarbons contained in the exhaust gas discharged from the engine body per unit time. The unburned hydrocarbon amount HCA discharged from the engine body per unit time can be estimated from the engine speed N and the fuel injection amount TAQ. This map is stored in the ROM 32 of the electronic control unit 30, for example. In the internal combustion engine in the present embodiment, the amount of unburned hydrocarbons discharged from the engine body is equal to the amount of unburned hydrocarbons flowing into the adsorption section.

  By using the map shown in FIG. 15, it is possible to estimate the amount of unburned hydrocarbons flowing into the adsorption unit per unit time according to the operating state. The temperature of the adsorption part at that time can be detected, and the amount of unburned hydrocarbons adsorbed on the adsorption part can be estimated according to the temperature of the adsorption part. By accumulating the amount of unburned hydrocarbons adsorbed per unit time, the amount of unburned hydrocarbons held in the adsorbing portion at an arbitrary time can be estimated.

  When the integrated value of the amount of unburned hydrocarbons held in the adsorbing part becomes larger than the predetermined unburned hydrocarbon integrated value judgment value, it is judged that the adsorption capacity of the adsorbing part is less than the judgment value. can do. For example, when the integrated value of the amount of unburned hydrocarbons held in the adsorption unit becomes larger than a predetermined integrated value determination value of the first unburned hydrocarbon, the adsorption capability of the adsorption unit is the first. It can be determined that it is less than the determination value.

  In this first adsorption capacity detection means, the estimation accuracy of the amount of carbon component remaining in the adsorption section is lowered, but in the second adsorption capacity determination means, the carbon component adsorbed in the form of hydrocarbon is released. By detecting the adsorption capacity after the adsorption, it is possible to detect a decrease in the adsorption capacity due to the carbon component produced by the remaining coking.

  In the exhaust purification apparatus of the present embodiment, the adsorbing portion is disposed upstream and the oxidizing portion is disposed downstream of the adsorbing portion. However, the present invention is not limited to this, and the adsorbing portion and the oxidizing portion are exhaust gas. As long as it passes through the adsorption part, it may be formed so as to flow into the oxidation part. Alternatively, the adsorption part and the oxidation part may be integrally formed.

  FIG. 16 shows an enlarged schematic cross-sectional view of a third exhaust treatment apparatus in the present embodiment. In the third exhaust treatment apparatus, the adsorption part 51 and the oxidation part 52 are formed in layers on the surface of the base material 55 formed of cordierite or the like. The oxidation part 52 is arranged on the surface of the base material 55, and the adsorption part 51 is arranged on the surface of the oxidation part 52. In the third exhaust treatment apparatus, exhaust gas flows into the oxidation unit 52 after passing through the adsorption unit 51. In this exhaust treatment apparatus, the temperature of the adsorption unit 51 and the temperature of the oxidation unit 52 are substantially the same. Thus, the adsorption part and the oxidation part may be laminated.

  FIG. 17 shows an enlarged schematic cross-sectional view of a fourth exhaust treatment apparatus in the present embodiment. In the fourth exhaust treatment apparatus, a coat layer including a carrier 60 and beta zeolite particles 61 formed of aluminum oxide is formed on the surface of a base material 55 formed of cordierite or the like. In the layer of the support 60 and the beta zeolite particles 61, catalyst particles 62 are arranged. In this exhaust treatment apparatus, the temperature of the adsorption part and the temperature of the oxidation part are substantially the same. Thus, the adsorption part and the oxidation part may be integrally formed.

  In the present embodiment, the exhaust treatment device in which the adsorption unit and the oxidation unit are adjacent to each other is illustrated, but the present invention is not limited to this configuration, and the adsorption unit and the oxidation unit may be separated from each other. Further, another member may be disposed between the adsorption part and the oxidation part.

  In the first temperature rise control and the second temperature rise control described above, the temperature of the exhaust gas is raised by changing the fuel injection pattern to raise the temperature of the adsorption unit. Any temperature raising means for raising the temperature can be employed. For example, even if the temperature of the exhaust gas is increased by disposing a small oxidation catalyst upstream of the adsorption unit and supplying unburned hydrocarbons to the small oxidation catalyst to cause an oxidation reaction. I do not care.

  Further, the second temperature rise control for raising the temperature of the adsorption portion to a second temperature higher than the first temperature after performing the first temperature rise control for raising the temperature of the adsorption portion to the first temperature a plurality of times. Control for performing is not limited to the above-described form, and arbitrary control can be performed. For example, the number of times that the first temperature increase control is continuously performed may be determined in advance, and the second temperature increase control may be performed after the predetermined number of times of the first temperature increase control.

  In the present embodiment, the diesel engine is taken as an example of the internal combustion engine. However, the present invention is not limited to this embodiment, and the present invention can be applied to an exhaust gas purification apparatus for any internal combustion engine that discharges unburned hydrocarbons.

(Embodiment 2)
With reference to FIG. 18, the exhaust gas purification apparatus for an internal combustion engine in the second embodiment will be described. The exhaust gas purification apparatus for an internal combustion engine according to the present embodiment includes an adsorption unit and an oxidation unit, as in the first embodiment (see FIGS. 1 and 2).

  FIG. 18 shows a flowchart of the operation control in the present embodiment. In step 91, the suction capacity of the suction part is detected by the first suction capacity detection means. In step 92, it is determined whether or not the detected adsorption capacity is less than a first determination value. Steps 91 and 92 are the same as steps 81 and 82 in the operation control of the first embodiment (see FIG. 7).

  In step 92, when the suction capacity of the suction part is less than the first determination value, the process proceeds to step 93. In step 93, temperature rise control is performed. In the temperature rise control of the present embodiment, the same control as the second temperature rise control in the first embodiment can be performed. That is, in the temperature rise control, the temperature is raised to a temperature at which carbon generated by coking can be released. For example, in the temperature increase control, the temperature of the adsorption unit is increased so as to be approximately 600 ° C. or higher.

  By performing the temperature rise control in step 93, the hydrocarbons adsorbed in the adsorbing portion and the carbon generated by coking can be released. In the present embodiment, the temperature increase control in step 93 is continued for a predetermined time.

  Next, in step 94, the suction capacity of the suction part is detected by the second suction capacity detection means. Step 94 is the same as step 84 in the operation control of the first embodiment (see FIG. 7).

  Next, in step 95, it is determined whether or not the detected adsorption capacity is less than a second determination value. The second determination value is set so that it is possible to determine whether a sufficient amount of hydrocarbons and carbon are released by the temperature rise control and the adsorption capacity is recovered. The second determination value can be determined in advance. Step 95 is the same as step 85 in the operation control of the first embodiment (see FIG. 7).

  In step 95, when the adsorption | suction capability of an adsorption | suction part is less than a 2nd determination value, it returns to step 93 and temperature rising control is performed again. In step 95, when the suction capability of the suction part is equal to or greater than the second determination value, this control is terminated.

  Also in the exhaust gas purification apparatus for an internal combustion engine of the present embodiment, it is possible to release hydrocarbons remaining in the adsorption section and carbon generated by coking, and to provide an exhaust gas purification apparatus having excellent purification performance. it can. In addition, for example, by setting the time for temperature increase control in step 93 to be short, it is possible to avoid the temperature of the exhaust gas from being excessively long. For example, the integration time for raising the temperature to 600 ° C. or higher can be shortened, and the fuel consumption can be suppressed or the thermal deterioration can be suppressed.

  Other configurations, operations, and effects are the same as those in the first embodiment, and thus description thereof will not be repeated here.

  The above embodiments can be combined as appropriate. In the respective drawings described above, the same or corresponding parts are denoted by the same reference numerals. In addition, said embodiment is an illustration and does not limit invention. Further, in the embodiment, changes included in the scope of claims are intended.

DESCRIPTION OF SYMBOLS 1 Engine main body 2 Combustion chamber 13 Exhaust treatment device 13a Adsorbent 13b Oxidation catalyst 27, 29 Temperature sensor 30 Electronic control unit 51 Adsorption part 52 Oxidation part 55 Base material 60 Carrier 61 Beta zeolite particle 62 Catalyst particle 63 Acid point 64 Zeolite

Claims (4)

It has an adsorption part that adsorbs unburned hydrocarbons contained in exhaust gas below the release temperature and releases the adsorbed hydrocarbons above the release temperature,
The air-fuel ratio of the exhaust gas flowing into the adsorbing portion is changed after the first temperature increase control for raising the temperature of the adsorbing portion to the first temperature is performed a plurality of times while the air-fuel ratio of the exhaust gas flowing into the adsorbing portion is lean. An exhaust emission control device for an internal combustion engine, wherein a second temperature rise control is performed to raise the temperature of the adsorption portion to a second temperature higher than the first temperature in a lean state. First adsorption capacity detection means for detecting the adsorption capacity of the adsorption unit during normal operation;
A second adsorbing capacity detecting means for detecting the adsorbing capacity of the adsorbing portion after performing the first temperature rise control,
During normal operation, the first adsorption capacity detecting means detects the adsorption capacity, and if the detected adsorption capacity is less than the first determination value, the first adsorbing unit releases hydrocarbon adsorbed. By performing the first temperature rise control to raise the temperature above the temperature, the adsorption capacity is recovered,
After the first temperature rise control, the adsorption capability is detected by the second adsorption capability detection means, and if the detected adsorption capability is less than the second determination value larger than the first determination value, it is generated by coking. 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein a second temperature rise control is performed to raise the temperature to a temperature equal to or higher than a second temperature at which the carbon is released. It has an oxidation part for oxidizing unburned hydrocarbons,
The exhaust gas purification apparatus for an internal combustion engine according to claim 1 or 2, wherein the oxidation part is disposed downstream of the adsorption part in the engine exhaust passage, or is formed integrally with the adsorption part. .   At least one of the first adsorption capacity detection means and the second adsorption capacity detection means is capable of oxidizing carbon monoxide when the temperature of the oxidation part is lower than the temperature at which the hydrocarbon can be oxidized. The temperature increase width of the oxidation catalyst due to is detected, and when the temperature increase width is smaller than a predetermined increase width determination value, it is determined that the adsorption capacity of the adsorption portion is less than the determination value. Item 6. An exhaust emission control device for an internal combustion engine according to Item 3.

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