WO2014148249A1 - 内燃機関の制御装置 - Google Patents
内燃機関の制御装置 Download PDFInfo
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- WO2014148249A1 WO2014148249A1 PCT/JP2014/055497 JP2014055497W WO2014148249A1 WO 2014148249 A1 WO2014148249 A1 WO 2014148249A1 JP 2014055497 W JP2014055497 W JP 2014055497W WO 2014148249 A1 WO2014148249 A1 WO 2014148249A1
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- temperature
- catalyst
- internal combustion
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- sulfur
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
- F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
- F01N3/023—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles
- F01N3/025—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters using means for regenerating the filters, e.g. by burning trapped particles using fuel burner or by adding fuel to exhaust
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
- F01N13/009—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00 having two or more separate purifying devices arranged in series
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
- F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
- F01N3/033—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices
- F01N3/035—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices with catalytic reactors, e.g. catalysed diesel particulate filters
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/105—General auxiliary catalysts, e.g. upstream or downstream of the main catalyst
- F01N3/106—Auxiliary oxidation catalysts
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N9/00—Electrical control of exhaust gas treating apparatus
- F01N9/002—Electrical control of exhaust gas treating apparatus of filter regeneration, e.g. detection of clogging
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/021—Introducing corrections for particular conditions exterior to the engine
- F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
- F02D41/027—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/021—Introducing corrections for particular conditions exterior to the engine
- F02D41/0235—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus
- F02D41/027—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus
- F02D41/029—Introducing corrections for particular conditions exterior to the engine in relation with the state of the exhaust gas treating apparatus to purge or regenerate the exhaust gas treating apparatus the exhaust gas treating apparatus being a particulate filter
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
- F01N2560/02—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor
- F01N2560/027—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being an exhaust gas sensor for measuring or detecting SOx
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
- F01N2900/06—Parameters used for exhaust control or diagnosing
- F01N2900/14—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust gas
- F01N2900/1402—Exhaust gas composition
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
- F01N2900/06—Parameters used for exhaust control or diagnosing
- F01N2900/14—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust gas
- F01N2900/1404—Exhaust gas temperature
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
Definitions
- the present invention relates to a control device for an internal combustion engine.
- Patent Document 1 Japanese Patent Document 1
- SO 2 sulfur dioxide
- SO 3 sulfur trioxide
- H 2 O water
- Patent Document 1 does not disclose such a chemical reaction.
- the oxidation catalyst also has a property of adsorbing SOx. For this reason, a large amount of white smoke may be generated when a filter (for example, DPF; Diesel Particulate Filter) that is installed in combination with the oxidation catalyst and supplements PM is regenerated. That is, the sulfur component (S component) contained in the fuel combusted by the internal combustion engine and the adsorbed SOx adsorbed by the oxidation catalyst and desorbed due to the exhaust gas temperature rise accompanying the PM regeneration request can become white smoke. There is sex.
- DPF Diesel Particulate Filter
- an object of the control device for an internal combustion engine disclosed in this specification is to suppress generation of white smoke due to sulfur desorption during PM regeneration.
- the control device for an internal combustion engine disclosed in this specification is a control device for an internal combustion engine including a filter downstream of a catalyst having an oxidation function, and the PM regeneration request for the filter is established.
- the exhaust temperature is lower than the PM oxidation start temperature and maintained for a certain period of time at a sulfur desorption temperature that is higher than the highest temperature of exhaust or the catalyst bed temperature from the time of completion of previous PM regeneration to the current PM regeneration request.
- a control unit for setting the PM oxidation start temperature or higher is provided.
- the control unit increases the sulfur desorption temperature to be higher than the maximum attainable temperature.
- the temperature can be set to any temperature that is equal to or lower than the allowable conversion temperature.
- the sulfur S adsorbed on the catalyst is desorbed and maintained at the minimum temperature at which it can be released, that is, the sulfur desorption temperature for a certain period of time, and after the sulfur is desorbed and released, the exhaust temperature is increased to the temperature of starting PM oxidation Raise.
- regeneration can be suppressed.
- the control unit sets the sulfur desorption temperature to the conversion allowable temperature when the maximum temperature reached is the conversion allowable temperature or less at which the conversion rate from SO 2 to SO 3 in the catalyst is equal to or less than an allowable value. be able to.
- the sulfur desorption temperature can be set within the range of the conversion allowable temperature or lower.
- SO 3 that contributes to the generation of white smoke is caused by oxidation of SO 2 .
- the conversion rate from SO 2 to SO 3 is affected by the exhaust temperature.
- the sulfur desorption temperature needs to be higher than the maximum temperature reached, and the higher the temperature, the higher the sulfur desorption efficiency.
- the sulfur desorption temperature is set as the conversion allowable temperature, so that efficient sulfur desorption can be performed while suppressing white smoke within the allowable range. it can. By setting the sulfur desorption temperature to the conversion allowable temperature, sulfur desorption can be accelerated while effectively suppressing white smoke generation.
- the control unit can raise the exhaust gas or the catalyst bed temperature stepwise until the sulfur desorption temperature is reached. Thereby, sulfur with different deposition temperatures can be desorbed while suppressing the generation of white smoke.
- the control unit burns the oxygen concentration in the exhaust gas flowing into the catalyst in the internal combustion engine when a PM regeneration request for the filter is established and an exhaust temperature increase request is made downstream of the catalyst.
- the oxygen concentration can be lowered below the upper limit threshold according to the S concentration value in the fuel.
- Oxygen is required when regenerating the filter provided in the exhaust path and disposed downstream of the catalyst having an oxidizing function.
- SO 2 produced due to the combustion of the fuel containing the S component is oxidized to produce SO 3 .
- sulfur S component deposited on the catalyst and the filter is also desorbed and oxidized to become SO 3 .
- the SO 3 produced in this way is combined with H 2 O to become H 2 SO 4 to become mist, that is, white smoke. Therefore, in order to regenerate substances accumulated on the filter, mainly PM (Particulate Matter), control is performed to reduce the oxygen concentration when an exhaust temperature increase request is recognized. Thereby, generation
- control device for an internal combustion engine disclosed in this specification, it is possible to suppress generation of white smoke due to sulfur desorption during PM regeneration.
- FIG. 1 is an explanatory diagram showing a schematic configuration of the internal combustion engine of the embodiment.
- FIG. 2 is a flowchart illustrating an example of control performed by the control device for an internal combustion engine according to the embodiment.
- FIG. 3 is a graph showing the relationship between the exhaust temperature and the SO 3 conversion rate.
- FIG. 4 is a graph showing the relationship between the S deposition temperature and the S desorption temperature.
- FIG. 5 is a flowchart illustrating an example of control performed by the control device for an internal combustion engine according to the embodiment.
- FIG. 6 is an example of a time chart of PM regeneration performed by the control device for an internal combustion engine of the embodiment.
- FIG. 7 is an explanatory diagram showing the relationship between the amount of accumulated S and the fuel S concentration.
- FIG. 8 is a graph showing the relationship between the fuel S concentration value and the white smoke suppression target A / Ftrg.
- FIG. 9 is a graph showing the occurrence of white smoke.
- FIG. 10 is a graph showing the relationship between the fuel S concentration value and the white smoke suppression control execution period ⁇ trg.
- FIG. 11 is a graph showing the effect of A / F on white smoke during PM regeneration.
- FIG. 12A is an explanatory diagram schematically showing a state in which candidates for fixed values provided in advance for each destination are stored, and FIG. 12B shows how fixed values are set according to the destination. It is explanatory drawing which shows this typically.
- FIG. 13 is a graph showing an example of the exhaust temperature change during the PM regeneration interval.
- FIG. 1 is an explanatory diagram showing a schematic configuration of an internal combustion engine 1 according to an embodiment.
- the internal combustion engine 1 includes an engine body 2 and a control device (hereinafter referred to as a control device) 3 for the internal combustion engine.
- An intake passage 4 and an exhaust passage 5 are connected to the engine body 2.
- One end of an EGR (Exhaust Gas Recirculation) passage 6 is connected to the engine body 2.
- the other end of the EGR passage 6 is connected to the intake passage.
- An EGR cooler 7 and an EGR valve 8 are disposed in the EGR passage 6.
- a throttle 9 is disposed in the intake passage 4.
- a DOC (Diesel Oxidation Catalyst) 10 is disposed in the exhaust passage 5.
- the DOC 10 is a catalyst having an oxidation function and is included in the internal combustion engine 1.
- a DPF (Diesel Particulate Filter) 11 is disposed on the downstream side of the DOC 10 in the exhaust passage.
- the DPF 11 is a filter that supplements PM and is included in the internal combustion engine 1.
- an SOx sensor 12, an exhaust addition fuel valve 13, and a first temperature sensor 14 are arranged in order from the upstream side.
- the SOx sensor 12, together with an A / F sensor 17 described later, is included in a means for acquiring an S concentration value (hereinafter referred to as fuel S concentration) in the fuel combusted in the internal combustion engine 1, more specifically, the engine body 2.
- the exhaust addition fuel valve 13 adds fuel to the exhaust gas by injecting fuel into the exhaust passage 5.
- the exhaust gas to which fuel is added is combusted in the DOC 10 and becomes high-temperature exhaust gas.
- the first temperature sensor 14 measures the temperature of the exhaust gas introduced into the DOC 10 (DOC temperature, catalyst-containing gas temperature).
- a second temperature sensor 15 is disposed in the exhaust passage 5 between the DOC 10 and the DPF 11.
- the second temperature sensor 15 measures the temperature (DPF temperature) Tex of the exhaust gas introduced into the DPF 11.
- the temperature of the exhaust gas will be described as the exhaust temperature Tex.
- a third temperature sensor 16 and an A / F sensor 17 are arranged in order from the upstream side.
- the third temperature sensor 16 measures the temperature of the exhaust gas discharged from the DPF 11. From the measured value of the third temperature sensor 16 and the measured value of the second temperature sensor 15, the DPF temperature, that is, the catalyst bed temperature Tm is grasped.
- the catalyst temperature Tm may be set as the DOC temperature, or the catalyst bed temperature Tm may be acquired using a value correlated with these.
- the sulfur desorption temperature is higher than the highest reached temperature of the exhaust or the catalyst bed temperature from the completion of the previous PM regeneration to the current PM regeneration request. Control for maintaining the period is performed.
- the maximum temperature reached is defined, either the exhaust temperature Tex or the catalyst bed temperature Tm may be taken into consideration. Since the sulfur S component to be desorbed is deposited and adsorbed on the catalyst, the catalyst bed temperature is directly involved. However, since the exhaust gas temperature and the catalyst bed temperature are correlated, The temperature should be taken into consideration. In the following description, the exhaust temperature Tex will be unified.
- the A / F sensor 17 measures the exhaust A / F. As described above, the A / F sensor 17 is included in the means for obtaining the fuel S concentration value together with the SOx sensor 12. The fuel S concentration value and the SOx concentration in the exhaust gas have a correlation. Therefore, the fuel S concentration can be calculated from the SOx concentration value in the exhaust detected by the SOx sensor 12 and the exhaust A / F. Incidentally, SOx discharged from the engine body 2, since it is almost SO 2, SOx sensors may be used SO 2 sensor.
- the internal combustion engine 1 includes an ECU (Electronic Control Unit) 18.
- the ECU 18 performs various controls in the internal combustion engine 1.
- the ECU 18 is also included in the control device 3 and functions as a control unit of the control device 3.
- the ECU 18 is electrically connected to the EGR valve 8, the throttle 9, the SOx sensor 12, the exhaust addition fuel valve 13, the first temperature sensor 14, the second temperature sensor 15, the third temperature sensor 16, and the A / F sensor 17.
- the control device 3 is formed.
- the ECU 18 acquires the PM accumulation amount. Specifically, the ECU 18 calculates the PM accumulation amount in the DPF 11 from the operation pattern (vehicle travel pattern) of the internal combustion engine 1. Then, it is determined whether a PM regeneration request is established. Further, the ECU 18 continuously records the exhaust gas temperature Tex, and obtains the maximum exhaust gas temperature TexMAX from the time when the previous PM regeneration is completed until the current PM regeneration request.
- the ECU 18 functioning as a control unit performs PM regeneration based on an exhaust temperature increase request on the downstream side of the DOC 10, more specifically, a PM regeneration request in the DPF 11.
- the ECU 18 first sets the exhaust gas temperature Tex to a sulfur desorption temperature lower than the PM oxidation start temperature and higher than the highest attained temperature TexMAX from the previous PM regeneration completion to the current PM regeneration request. Maintain for a certain period of time. Then, the ECU 18 thereafter sets the exhaust temperature Tex to be equal to or higher than the PM oxidation start temperature. At this time, oxygen concentration lowering control is performed to reduce the oxygen concentration flowing into the DOC 10.
- the flowchart shown in FIG. 2 shows the overall control for the PM regeneration of the filter, that is, the DPF 11.
- step S1 the exhaust temperature Tex during travel is continuously acquired and stored in the ECU 18.
- step S2 every time the exhaust temperature Tex is acquired, it is determined whether or not it is higher than the exhaust temperature Tex stored at that time (previous acquisition Tex).
- step S3 the process proceeds to step S3, and the currently acquired Tex is stored as the highest temperature TexMAX at that time. Note that when the exhaust gas temperature Tex is acquired for the first time, there is no value to be compared, so that the exhaust gas temperature Tex is stored as it is as the maximum temperature TexMAX.
- step S4 which is performed subsequent to step S3, it is determined whether there is a PM regeneration request.
- the process of step S4 is also performed when it is determined No in step S2. When it is determined No in step S4, the processing from step S1 is repeated. If it is determined Yes in step S4, it is determined that the PM regeneration request is made this time, and the process proceeds to step S5.
- step S5 it is determined whether higher conversion allowable temperature TSO 3 to maximum temperature TexMAX the exhaust temperature at that time conversion from SO 2 to SO 3 in DOC10 or DPF11 is equal to or less than the allowable value. That is, in step S5, the maximum temperature TexMAX determines whether higher conversion allowable temperature TSO 3 in up to this PM regeneration request from the previous PM regeneration completion.
- the conversion allowable temperature TSO 3 will be described with reference to FIG. Referring to FIG. 3, the allowable conversion temperature TSO 3 is related to the rate at which SO 2 is oxidized and converted from SO 2 to SO 3 . Therefore, for example, when the SO 3 conversion rate is allowed to 40%, the highest temperature in the “allowable range” in FIG. 3 is the conversion allowable temperature TSO 3 . For example, when the SO 3 conversion rate is 0%, the lowest temperature in the “allowable range” in FIG. 3 is the conversion allowable temperature TSO 3 .
- the permissible conversion temperature TSO 3 varies depending on the catalyst specifications and is set by adaptation.
- step S6 TexMAX is directly adopted as the value of TexMAX.
- step S7 convertible permissible temperature TSO 3 is adopted as the value of TexMAX.
- values that can be adopted as TexMAX are as follows. That is, the value that can be employed as TexMAX is higher than the maximum temperature TexMAX set in step S3, is any temperature set within the range of convertible allowable temperature TSO 3 below.
- the requirement that the temperature is higher than the maximum temperature TexMAX is required to desorb sulfur.
- the requirement that the conversion is within the allowable temperature TSO 3 range or less is required to keep the conversion rate of SO 3 within the allowable range.
- the arbitrary temperature it can be employed satisfies the above conditions temperature, efficient sulfur to desorption, it is desirable to employ the conversion allowable temperature TSO 3.
- the efficiency There is room for improvement. That is, if the conversion allowable temperature is TSO 3 or less, the conversion from SO 2 to SO 3 is allowed, and therefore, the purpose is to perform the most efficient desorption of sulfur within the range.
- step S8-1 which is performed subsequent to step S6, TexMAX + ⁇ is set as the sulfur desorption temperature.
- + ⁇ means that the temperature is set higher than TexMAX.
- the temperature at which sulfur is desorbed is equal to or higher than the temperature at which the sulfur is deposited.
- SO 2 deposited on the catalyst when the exhaust temperature is A ° C. is desorbed when the catalyst temperature becomes A + ⁇ ° C.
- SO 2 deposited on the catalyst when the exhaust temperature is B ° C. is desorbed when the catalyst temperature becomes B + ⁇ ° C.
- TexMAX + ⁇ is set as the sulfur desorption temperature. Note that the specific value of + ⁇ can be determined as appropriate according to the fit. At this time, if the temperature is excessively higher than TexMAX, the release rate of sulfur S increases and white smoke tends to be formed. That is, the sulfur desorption temperature is set to the effect of adopting the lowest temperature at which sulfur can be desorbed and released.
- step S8-2 performed subsequent to step S7, TexMAX is set as the sulfur desorption temperature. That is, the measure of + ⁇ is not necessary. This is because the conversion allowable temperature TSO 3 is replaced with TexMAX in Step S7, and the replaced TexMAX is at a higher temperature than the actual TexMAX, so that the sulfur S is desorbed.
- step S9 which is performed subsequent to step S8-1 or step S8-2, sulfur desorption processing is performed.
- step S9 is a subroutine, the contents of which will be described in detail later.
- step S10 performed subsequent to step S9, the value of TexMAX is cleared.
- step S11 PM regeneration control is performed. Specifically, the exhaust temperature Tex is set to be equal to or higher than the PM oxidation start temperature. Thereby, PM regeneration is performed.
- the PM oxidation start temperature is higher than the sulfur desorption temperature, but prior to PM regeneration control, the exhaust temperature Tex is maintained at the sulfur desorption temperature for a certain period, and sulfur S is desorbed. . For this reason, generation
- step S11 When the process of step S11 is completed, a series of processes regarding the current PM regeneration is completed, and the processes from step S1 are repeated again for the next PM regeneration request.
- step S9 In the flow chart shown in FIG. 2 will be described with reference to the flowchart shown in FIG.
- step S8-1 TexMAX + ⁇
- step S8-2 TexMAX is maintained for a predetermined time, so that sulfur is desorbed and then normal PM regeneration control (step S11) is performed. Move on.
- step S91 it is determined whether or not the exhaust gas addition fuel condition is satisfied. Specifically, it is determined whether or not the catalyst input gas temperature measured by the first temperature sensor 14 exceeds the threshold value T1. This threshold value T1 is set in view of whether or not the added fuel can be combusted. When it is determined Yes in step S91, the process proceeds to step S92. When it is determined No in step S91, the process of step S91 is repeated until it is determined Yes in step S91.
- step S92 a fuel S concentration value is acquired. That is, as described above, the fuel S concentration value is acquired based on the measured values of the SOx sensor 12 and the A / F sensor 17.
- a fuel property sensor may be installed in place of the SOx sensor 12, and the fuel S concentration value may be obtained from the measured value of the fuel property sensor.
- step S93 the white smoke suppression target A / F and the oxygen concentration reduction control execution period are read.
- the oxygen concentration reduction control execution period is a period in which the sulfur desorption process is executed.
- the A / F is controlled toward the rich state in the sulfur desorption process performed prior to PM regeneration. That is, the oxygen concentration is controlled to decrease in the sulfur desorption process.
- the control in the direction of lowering the oxygen concentration only needs to be controlled to lower the oxygen concentration. That is, the oxygen concentration reduction control includes not only the case where the rich state is exceeded beyond the stoichiometric but also the case where the stoichiometric state is approached.
- the white smoke suppression A / F is set with reference to the range before and after the stoichiometry.
- the oxygen concentration reduction control includes the following measures. The intention of each measure is as follows.
- the ECU 18 sets the oxygen concentration based on the fuel S concentration value. This is because the S concentration in the exhaust gas becomes higher corresponding to the fuel S concentration value. Further, the ECU 18 sets an upper limit threshold value of the oxygen concentration according to the fuel S concentration value. In other words, the upper limit value of the oxygen concentration is the upper limit value of lean. Leaning means that the amount of air is relatively increased, and thus setting the upper limit value of the oxygen concentration is intended not to increase the amount of air too much. Or SO 2 discharged from the engine body 2, SO 3 is generated when DOC10 or SO 2 deposited on the DPF11 is oxidized. Since the S concentration in the exhaust gas becomes higher according to the fuel S concentration value, if the upper limit value of the oxygen concentration is set according to the fuel S concentration value, the production of SO 3 can be effectively suppressed.
- FIG. 7 shows the relationship between the travel distance of the vehicle and the amount of accumulated S for three types of fuel.
- fuel S concentration values 2000 ppm, 500 ppm, and 50 ppm.
- the amount of accumulated S increases as the fuel S concentration value increases. If the amount of accumulated S is large, the amount of S released increases during PM regeneration. Therefore, the higher the fuel S concentration value, the more likely SO 3 is generated. Thus, if the fuel S concentration value is high, a large amount of SO 3 may be generated. Therefore, as shown in FIG. 8, the upper limit threshold value of the white smoke suppression target A / Ftrg is set.
- the range of ⁇ ⁇ of the reference A / F corresponding to the fuel S concentration value is set as the allowable range of the white smoke suppression target A / Ftrg.
- the range of ⁇ ⁇ is taken into consideration that it is difficult to accurately control the A / F to a target value.
- step S94 it is determined whether or not the A / Fm measured by the A / F sensor 17 is equal to or less than the white smoke suppression target A / Ftrg + ⁇ .
- the process proceeds to step S95.
- step S95 the EGR additional increase by ⁇ EGR is performed.
- the allowable range of the white smoke suppression target A / Ftrg that is, the upper limit value of the oxygen concentration is exceeded, so the EGR amount is increased, the air amount is decreased, and the oxygen concentration is decreased. The purpose is to take measures.
- step S96 it is determined whether A / Fm measured by the A / F sensor 17 is equal to or greater than the white smoke suppression target A / Ftrg- ⁇ .
- step S97 EGR reduction by ⁇ EGR is performed.
- the allowable range of the white smoke suppression target A / Ftrg is exceeded, so that the EGR amount is reduced and the air concentration is maintained.
- the EGR amount is adjusted in order to control A / Fm to an appropriate range, but other means that can control A / Fm can also be used.
- a / Fm may be controlled within an appropriate range by adjusting the amount of exhaust added fuel.
- the white smoke suppression target A / Ftrg is controlled within an allowable range by performing the processing from step S94 to step S97.
- the exhaust temperature and the catalyst temperature are set to be substantially the sulfur desorption temperature.
- the sulfur desorption temperature is the temperature set in step S8-1 or step S8-2. Since the sulfur desorption temperature is set so that rapid desorption is not performed in consideration of the sulfur deposition temperature, generation of white smoke can be suppressed.
- step S98 it is determined whether or not the measured bed temperature Tm of the catalyst is equal to or higher than the sulfur desorption temperature.
- the sulfur desorption temperature differs depending on whether it passes through step S8-1 or step S8-2 in the flowchart shown in FIG. That is, in the case of going through step S8-1, the value of TexMAX + ⁇ set in step S8-1 is adopted as the sulfur desorption temperature. On the other hand, in the case of going through step S8-2, TexMAX set in step S8-2 is adopted as the sulfur desorption temperature.
- step S98 the process proceeds to step S99.
- step S99 the amount of exhaust added fuel is increased. Thereby, the bed temperature Tm is raised.
- step S99 the process of step S98 is repeated again.
- step S100 it is determined whether a control execution period ⁇ trg for desorbing sulfur has elapsed.
- step S94 empty processing is repeated.
- step S11 the subroutine ends. Thereafter, the process proceeds to step S10 shown in FIG. 2, and then the process proceeds to PM regeneration control in step S11.
- Step S11 is a subroutine, but when the subroutine ends, the process ends (END).
- FIG. 11 is a graph showing the effect of A / F on white smoke during PM regeneration.
- the white smoke is suppressed as the A / F is controlled to the rich side during PM regeneration, specifically, the closer to the b point direction from the point a.
- the SO 3 peak value decreases as A / F is controlled to the rich side.
- the oxygen concentration corresponding to the S concentration value and the execution period of the oxygen concentration lowering control may be set in advance according to the adaptation. it can. In this case, the steps S92 and S93 are omitted.
- the S concentration value of fuel used in an internal combustion engine is roughly grasped depending on the destination. Therefore, adaptation considering the S concentration value assumed in advance for each destination can be performed, and the oxygen concentration in the exhaust gas, that is, the white smoke suppression target A / Ftrg can be set to a fixed value. This fixed value may be a value set corresponding to the S concentration value of the fuel combusted in the internal combustion engine 1.
- the execution period of the oxygen concentration reduction control may be set to a period set corresponding to the S concentration value of the fuel combusted in the internal combustion engine 1.
- the oxygen concentration is set lower as the assumed S concentration value is higher.
- the period is set to be longer as the assumed S concentration value is higher.
- This implementation period may be a period set corresponding to the S concentration value of the fuel combusted in the internal combustion engine 1.
- the ECU 18 stores the oxygen concentration for each destination, specifically, the white smoke suppression target A / Ftrg-n. Similarly, the execution period ⁇ trg-n of the oxygen concentration reduction control is stored. That is, when the ECU 18 is prepared in a state having general versatility and the destination is determined, the white smoke suppression target A / Ftrg-n and the implementation period ⁇ trg-n corresponding to the destination are selected. In this manner, the oxygen concentration reduction control is performed based on the fixed value corresponding to the destination. As a fixed value setting method, as shown in FIG. 12B, the white smoke suppression target A / Ftrg-n and the implementation period ⁇ trg-n in the ECU are initially blank.
- the white smoke suppression target A / Ftrg-n and the execution period ⁇ trg-n in the ECU corresponding to the destination are written. In this way, the oxygen concentration reduction control can be performed based on the fixed value corresponding to the destination.
- TexMAX1, TexMAX2 may be recorded as an example of the history of the exhaust gas temperature Tex between PM regeneration intervals.
- the sulfur desorption process is performed at a temperature higher than TexMAX1, which is the highest temperature reached.
- sulfur deposited by TexMAX1 is desorbed at a moderate rate, so that generation of white smoke can be suppressed.
- sulfur deposited by TexMAX2 is desorbed at a temperature considerably higher than the temperature at the time of deposition and is released at a high speed. As a result, white smoke is likely to be generated.
- an appropriate period is set such that the maximum reached temperature until the start of PM regeneration after the 80% accumulation amount at which PM regeneration starts is recognized and the maximum reached temperature before that.
- the maximum temperature reached may be extracted by dividing.
Abstract
Description
図1は実施形態の内燃機関1の概略構成を示す説明図である。内燃機関1は、エンジン本体2と内燃機関の制御装置(以下、制御装置という)3を備える。エンジン本体2には、吸気通路4と排気通路5が接続されている。エンジン本体2には、EGR(Exhaust Gas Recirculation)通路6の一端が接続されている。EGR通路6の他端は、吸気通路に接続されている。EGR通路6には、EGRクーラ7とEGR弁8が配置されている。吸気通路4には、スロットル9が配置されている。排気通路5には、DOC(Diesel Oxidation Catalyst)10が配置されている。DOC10は、酸化機能を有する触媒であり、内燃機関1に含まれる。排気通路のDOC10の下流側には、DPF(Diesel Particulate Filter)11が配置されている。DPF11は、PMを補足するフィルタであり、内燃機関1に含まれる。
内燃機関に使用される燃料のS濃度値が既知である場合や想定されている場合は、予め適合により、そのS濃度値に対応させた酸素濃度、酸素濃度低下制御の実施期間とすることができる。この場合、ステップS92及びステップS93の措置は省略される。内燃機関に用いられる燃料のS濃度値は、仕向地によっておおよそ把握される場合が多い。そこで、仕向地毎に予め想定されるS濃度値を考慮した適合を行い、排気ガス中の酸素濃度、すなわち、白煙抑制目標A/Ftrgを、固定値としておくことができる。この固定値は、内燃機関1で燃焼する燃料のS濃度値に対応させて設定された値としてもよい。また、同様に、酸素濃度低下制御の実施期間を、内燃機関1で燃焼する燃料のS濃度値に対応させて設定された期間に設定してもよい。このように、適合により、酸素濃度を設定するときは、想定するS濃度値が高いほど、酸素濃度を低く設定することとなる。また、適合により、酸素濃度低下制御の実施期間を設定するときは、想定するS濃度値が高いほど、その期間を長期に設定することとなる。この実施期間は、内燃機関1で燃焼する燃料のS濃度値に対応させて設定された期間としてもよい。
2 エンジン本体
3 制御装置
4 吸気通路
5 排気通路
10 DOC
11 DPF
12 SOxセンサ
13 排気添加燃料弁
17 A/Fセンサ
Claims (4)
- 酸化機能を有する触媒の下流にフィルタを備える内燃機関の制御装置であって、
前記フィルタのPM再生要求が成立した場合に、
排気温度を、PM酸化開始温度よりも低く、前回PM再生完了時から今回PM再生要求迄における排気又は前記触媒の床温の最高到達温度よりも高い硫黄脱離温度に一定期間維持した後、前記PM酸化開始温度以上とする制御部を備え、
前記制御部は、前記最高到達温度が、前記触媒におけるSO2からSO3への転換率が許容値以下となる転換許容温度以下の場合は、前記硫黄脱離温度を前記最高到達温度よりも高く、前記転換許容温度以下となる任意の温度に設定する内燃機関の制御装置。 - 前記制御部は、前記最高到達温度が、前記触媒におけるSO2からSO3への転換率が許容値以下となる転換許容温度以下の場合は、前記硫黄脱離温度を前記転換許容温度に設定する請求項1に記載の内燃機関の制御装置。
- 前記制御部は、前記硫黄脱離温度に到達するまでに段階的に排気又は前記触媒の床温を上昇させる請求項1又は2に記載の内燃機関の制御装置。
- 前記制御部は、前記フィルタのPM再生要求が成立し、前記触媒の下流側における排気温度上昇要求があった場合に、前記触媒へ流入する排気ガス中の酸素濃度を、前記内燃機関で燃焼する燃料中のS濃度値に応じた酸素濃度の上限閾値以下に低下させる請求項1乃至3のいずれか一項に記載の内燃機関の制御装置。
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