JP2015068266A - Exhaust emission control system and exhaust emission control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control system and an exhaust emission control method which can maintain the temperatures of catalyst units constituting an exhaust gas aftertreatment device provided in an exhaust passage of an internal combustion engine, within a catalyst activation temperature range for a long period.SOLUTION: An exhaust emission control system 1 includes an exhaust gas aftertreatment device 20 constituted of catalyst units 201a-201d supporting catalysts, and provided in an exhaust passage 13. In the exhaust gas aftertreatment device 20, a heat storage unit 202 in which a heat storage body 202a is provided at the upstream side of the catalyst units 201a-201d is provided at the upstream side of the catalyst units 201a-201d. The heat storage unit 202 is provided with a bypass passage 202b not passing through the heat storage body 202a and a bypass valve 23 for controlling the distribution of exhaust gas Go in the bypass passage 202b. Besides, a flow path control device 41 is provided for controlling the bypass valve 23 to be opened/closed.

Description

  The present invention relates to an exhaust gas purification system and an exhaust gas purification method capable of maintaining the temperature of a catalyst unit constituting an exhaust gas aftertreatment device provided in an exhaust passage of an internal combustion engine for a long time within a catalyst activation temperature range.

  In general, a vehicle that travels with an internal combustion engine travels with power generated by burning fuel in the internal combustion engine. The exhaust gas includes NOx (nitrogen oxide), PM (particulate matter), and the like. Therefore, an exhaust gas aftertreatment device is provided in the exhaust passage of the internal combustion engine to purify the exhaust gas and then release it into the atmosphere. The exhaust gas aftertreatment device includes a catalyst unit that carries an oxidation catalyst (DOC), a NOx reduction catalyst (deNOx catalyst), and the like, and purifies the exhaust gas by the catalyst unit. Each catalyst supported on this catalyst unit has the property that the catalytic action cannot be fully exerted unless the catalyst activation temperature (light-off temperature) or higher is maintained, and the catalyst unit temperature is maintained above this catalyst activation temperature. It is important to do.

  However, in a collection and delivery vehicle such as a delivery truck or a garbage truck, when the driving and stopping at an extremely low vehicle speed are frequently repeated, the operation of the internal combustion engine is not continuously performed, so the exhaust gas temperature and There is a problem that the temperature of the catalyst unit through which the exhaust gas passes does not rise above the catalyst activation temperature, making it difficult to sufficiently function the catalyst supported on the catalyst unit.

  In other words, in the prior art, when the exhaust gas temperature at the outlet of the internal combustion engine decreases due to the shutdown of the internal combustion engine, parts and devices that store the heat of the exhaust gas between the outlet of the internal combustion engine and the inlet of the catalyst unit Therefore, the temperature of the exhaust gas at the inlet of the catalyst unit also decreases immediately, heat is radiated from the catalyst unit, and the catalyst temperature decreases early.

  For example, when repeatedly running and stopping for a short time such that the vehicle travels for 5 minutes and then stops and then restarts after about 5 minutes, the state before the exhaust gas is heated, that is, the exhaust Since the internal combustion engine is stopped in a state where the gas temperature is low, the temperature of the exhaust gas and the temperature of the catalyst unit immediately fall below the catalyst activation temperature. Therefore, there is a possibility that the exhaust gas components such as HC and NOx released into the atmosphere are deteriorated because the oxidation catalyst does not function or the NOx reduction catalyst cannot reduce NOx.

  In connection with this problem, a plurality of catalysts are arranged in series in the exhaust passage through which the exhaust gas of the engine passes, and a heat storage body is arranged between the upstream catalyst and the downstream catalyst, and the exhaust gas. Configure the aftertreatment device, maintain the exhaust gas temperature flowing into the downstream catalyst in the catalytic activation temperature range as much as possible, activate the downstream catalyst and promote the chemical reaction, and clean the gas to be purified efficiently (For example, refer patent document 1).

  In the exhaust gas aftertreatment device having this heat accumulator, as a countermeasure against a decrease in the overall purification rate due to temporal temperature change and local temperature change in the catalyst, the upstream side of the catalyst is dispersed by disposing the catalyst. In the catalyst, the temperature change due to the chemical reaction of the catalyst on the upstream side is reduced, the time that is maintained in the catalyst activation temperature region is lengthened, and the exhaust gas temperature flowing into the downstream catalyst is kept in the catalyst activation temperature region as much as possible. By maintaining, the downstream catalyst is activated and the chemical reaction is promoted, so that the gas to be purified is efficiently purified. However, the upstream catalyst that is directly affected by the temperature of the exhaust gas cannot receive the effect of the heat accumulator.

JP 2000-274231 A

  The present invention has been made in view of the above, and an object of the present invention is to maintain the temperature of the catalyst unit constituting the exhaust gas aftertreatment device provided in the exhaust passage of the internal combustion engine long within the catalyst activation temperature range. An exhaust gas purification system and an exhaust gas purification method are provided.

  In order to achieve the above object, an exhaust gas purification system according to the present invention is an exhaust gas purification system in which an exhaust gas aftertreatment device comprising a catalyst unit carrying a catalyst is provided in an exhaust passage, upstream of the catalyst unit. A heat storage unit provided with a heat storage body on the upstream side of the catalyst unit in the exhaust gas aftertreatment device, a bypass passage that does not pass through the heat storage body, and a bypass valve that controls the flow of exhaust gas in the bypass passage Is provided in the heat storage unit, and further, a flow path control device for controlling opening and closing of the bypass valve is provided.

  According to this configuration, when the temperature of the exhaust gas is high, such as during medium-load / high-load operation of the internal combustion engine, the heat of the exhaust gas is stored in the heat storage body, and the exhaust gas is stored during low-load operation of the internal combustion engine. When the temperature is lowered, the temperature of the exhaust gas is raised by the heat of the heat storage body, and the exhaust gas having a relatively high temperature can flow into the catalyst unit downstream from the heat storage unit for a long time. Therefore, it is possible to prevent the temperature of the catalyst unit from lowering and to prevent deterioration in the purification performance of HC, NOx, etc. contained in the exhaust gas.

  Furthermore, since the exhaust gas flow path can be either the bypass passage or the heat storage body, the exhaust gas flow path is used as a bypass passage, and the temperature increase of the catalyst unit is given priority over the temperature increase of the heat storage body, Excessive temperature rise of the catalyst unit can be suppressed by increasing the temperature of the heat storage body through the exhaust gas flow path through the heat storage body, and the temperature of the catalyst unit can be kept long within the catalyst activation temperature range. .

  As used herein, “the exhaust gas flow path is either the bypass passage or the heat storage body” means that the entire flow rate of the exhaust gas does not have to flow completely to either the bypass passage or the heat storage body. It is only necessary that the flow rate of most (for example, 70% or more) of the exhaust gas can be passed through either the bypass passage or the heat storage body.

  When this heat storage unit is used, it is more suitable for the catalyst for oxidizing HC and CO than when increasing the temperature of exhaust gas by increasing HC and CO in the exhaust gas and oxidizing by the catalytic action of this HC and CO. As a result, it is possible to avoid the use of noble metal as a low cost.

  Also, in vehicles where the temperature of the catalyst unit tends to decrease due to frequent stopping and restarting, such as delivery trucks on a real road and collection and delivery of garbage vehicles, prevent the temperature of the catalyst unit from decreasing. This is particularly effective because the exhaust gas purification rate can be improved by maintaining the temperature of the catalyst unit long in the catalyst activation temperature range.

  Further, in the exhaust gas purification system, when the temperature of the exhaust gas flowing into the heat storage unit is equal to or higher than the temperature of the heat storage body and the temperature of the catalyst unit is lower than the catalyst activation temperature, The bypass valve is controlled so that the exhaust gas passes through the bypass passage, and when the temperature of the exhaust gas flowing into the heat storage unit is lower than the temperature of the heat storage body, or the temperature of the catalyst unit is activated. When the temperature is equal to or higher than the temperature, if the exhaust valve is controlled so that the exhaust gas does not pass through the bypass passage, the following effects can be obtained.

  When the temperature of the exhaust gas on the upstream side is equal to or higher than the temperature of the heat storage body and the temperature of the catalyst unit is lower than the catalyst activation temperature, the exhaust gas passes through the bypass passage and does not pass through the heat storage body. This heat is not stored in the heat accumulator and flows directly into the catalyst unit, so that the temperature of the catalyst unit can be raised quickly within the catalyst activation temperature range.

  In addition, when the temperature of the exhaust gas on the upstream side is lower than the temperature of the heat storage body, the temperature can be raised by passing the exhaust gas through the heat storage body, so that the exhaust gas whose temperature has been increased can flow into the catalyst unit. The temperature of the catalyst unit can be quickly raised within the catalyst activation temperature range, and can be kept long within the catalyst activation temperature range.

  Furthermore, when the temperature of the catalyst unit is equal to or higher than the catalyst activation temperature, the exhaust gas can be stored in the heat storage body by passing the exhaust gas through the heat storage body, so that the temperature of the catalyst unit is increased unnecessarily. The heat used when the temperature of the exhaust gas is low can be stored.

  Further, in the exhaust gas purification system, when the flow path control device performs PM regeneration control of the DPF device of the catalyst unit or NOx regeneration control of the NOx reduction catalyst device, the exhaust gas passes through the bypass passage. When the control of the bypass valve is performed, the PM regeneration control of the DPF device or the NOx regeneration control of the NOx reduction catalyst device avoids the heat of the exhaust gas being taken away by the heat storage body, Since the high-temperature exhaust gas can be directly flowed into the DPF device or the NOx reduction catalyst device, each regeneration control can be completed in a short time.

  Further, in the above exhaust gas purification system, the bypass passage is provided inside the heat storage unit, the heat storage body is arranged on the outer periphery of the bypass passage to constitute the heat storage unit, and an open / close valve is provided in the bypass passage. When the bypass valve configured as described above is arranged, the exhaust gas passing through the bypass passage is difficult to be cooled, which is advantageous for early temperature rise of the catalyst unit, and the heat storage body and the bypass passage are compact and the exhaust gas is exhausted. Since it becomes easy to fit in the case of the processing apparatus, the exhaust gas purification system does not increase in size and can be easily mounted on a vehicle.

  The exhaust gas purifying method of the present invention for achieving the above object provides an exhaust gas after-treatment device comprising a catalyst unit carrying a catalyst in an exhaust passage, and a heat accumulator upstream of the catalyst unit. A heat storage unit provided with an upstream side of the catalyst unit in the exhaust gas aftertreatment device, a bypass passage that does not pass through the heat storage body is provided in the heat storage unit, and a bypass that controls the flow of exhaust gas in the bypass passage In the exhaust gas purification method provided with a valve and further provided with a flow path control device for controlling the valve opening degree of the bypass valve, the temperature of the exhaust gas flowing into the heat storage unit is equal to or higher than the temperature of the heat storage body. When the temperature of the unit is lower than the catalyst activation temperature, the exhaust gas passes through the bypass passage, and the exhaust gas flowing into the heat storage unit Degree is, when lower than the temperature of the heat storage body, or the when the temperature of the catalyst unit is not less than the catalyst activation temperature, a method of exhaust gas, characterized in that to avoid passing through the bypass passage.

  According to this method, an effect similar to that of the exhaust gas purification system having the same configuration as described above can be obtained.

  According to the exhaust gas purification system and the exhaust gas purification method of the present invention, when the temperature of the exhaust gas is high, the heat of the exhaust gas is stored in the heat storage body, and when the temperature of the exhaust gas is lowered, The exhaust gas post-treatment device provided in the exhaust passage of the internal combustion engine can raise the temperature of the exhaust gas by heat and allow the exhaust gas having a relatively high temperature to flow into the catalyst unit downstream from the heat storage unit for a long time. Can be maintained for a long time within the catalyst activation temperature range, and the deterioration of the purification capacity of HC, NOx, etc. contained in the exhaust gas can be prevented.

  Further, the exhaust gas flow path is used as a bypass passage, and the temperature rise of the catalyst unit is prioritized over the temperature rise of the heat storage body, or the exhaust gas flow path is routed through the heat storage body so that the excess temperature of the catalyst unit is increased. Temperature rise can be suppressed.

It is a figure which shows an example of a structure of the exhaust gas purification system of embodiment which concerns on this invention, and is a figure which shows the case where the thermal storage unit is provided upstream from LNT (lean NOx catalyst). It is a figure which shows another example of a structure of the exhaust gas purification system of embodiment which concerns on this invention, and is a figure which shows the case where the thermal storage unit is provided upstream from SCR (selective reduction type | mold catalyst). It is a figure which shows another example of a structure of the exhaust gas purification system of embodiment which concerns on this invention, and is a figure which shows the case where the thermal storage unit is provided upstream from DPF (diesel particulate filter). It is an example of the flow which shows control of the exhaust gas purification method of embodiment which concerns on this invention. It is a figure which shows the time series of the exhaust gas temperature (Tg) at the time of providing the heat storage unit in the exhaust gas purification system of embodiment which concerns on this invention, the temperature (Th) of a thermal storage body, and the temperature (Tc) of a catalyst unit. . It is a figure which shows the time series of the exhaust gas temperature (Tg) when not providing a thermal storage unit in the exhaust gas purification system of a prior art, and the temperature (Tc) of a catalyst unit.

  Hereinafter, an exhaust gas purification system and an exhaust gas purification method according to embodiments of the present invention will be described with reference to the drawings. As shown in FIGS. 1, 2, and 3, an exhaust gas purification system 1 according to an embodiment of the present invention is configured as follows.

  The engine 10 is provided with an intake passage 12 and an exhaust passage 13. The intake passage 12 is connected to an intake manifold 11a, and in order from the upstream side, a compressor 15b of a turbocharger (turbo supercharger) 15, an intake throttle valve. 16 is provided. The exhaust passage 13 is connected to the exhaust manifold 11b, and a turbine 15a of the turbocharger 15 is provided.

  Further, an EGR passage 14 is provided by connecting the intake passage 12 upstream of the compressor 15b and the exhaust passage 13 downstream of the turbine 15a. The EGR passage 14 includes an EGR cooler 17 and an EGR valve 18 in order from the upstream side. Is provided.

  Then, fresh air A introduced from the atmosphere is accompanied by exhaust gas (EGR gas) Ge flowing into the intake passage 12 from the EGR passage 14 via the compressor 15b and the intake throttle valve 16 as necessary. It is sent to the intake manifold 11a. This intake gas (A + Ge) is mixed and compressed with the fuel injected into the cylinder (cylinder), and the fuel burns, thereby generating power in the engine 10.

  Exhaust gas G generated by combustion in the engine 10 flows out into the exhaust passage 13 and partly flows as EGR gas Ge into the EGR passage 14 via the turbine 15a, and the remaining exhaust gas Go (G− Ge) is purified by the catalyst units 201a to 201d arranged in the exhaust gas aftertreatment device 20, and then discharged to the atmosphere as exhaust gas Gc via a muffler.

  The catalyst units 201a to 201d include, for example, an LNT (Lean NOx Trap) unit 201a, an SCR (Selective Catalytic Reduction) unit 201b, and a DPF (Diesel Particulate Filter) with catalyst. A collection filter) unit 201c, an oxidation catalyst (DOC) unit 201d, and the like are used.

  On the other hand, in the turbocharger 15, when the turbine 15a is rotationally driven using the energy of the exhaust gas G, the compressor 15b directly connected to the turbine 15a is driven to compress the intake gas (A + Ge), and the intake air Since the pressure can be increased and the intake air amount can be increased, the power generated in the engine 10 can be increased.

  In the present invention, the heat storage unit 202 including the heat storage body 202a is provided in the exhaust gas aftertreatment device 20 and upstream of the catalyst units 201a to 201d. That is, the heat storage unit 202 is housed and provided in the case of the exhaust gas aftertreatment device 20 housing the catalyst units 201a to 201d.

  At the same time, the heat storage unit 202 is provided with a bypass passage 202b that does not pass through the heat storage body 202a, and a bypass valve 23 that controls the flow of exhaust gas Go (G-Ge) in the bypass passage 202b. A flow path control device 41 is provided for controlling the opening and closing.

  As the heat storage body 202a, a material having a large heat capacity and a small heat transfer coefficient is used. Actually, it is also effective to use a ceramic carrier such as cordierite or silicon carbide (SiC) which is used for a usual catalyst carrier. In addition, the carrier used as the heat storage body 202a does not need to be coated with a catalyst. However, the material used for the catalyst coating is low-cost, and the heat capacity of the heat storage body 202a is further increased by performing the catalyst coating. If possible, it is desirable to perform catalyst coating. For example, general alumina or zeolite can be used as the catalyst coat. In this case, an expensive noble metal is unnecessary, so that the cost can be kept low.

  Further, although there is no particular restriction on the capacity of the heat storage body 202a, the heat capacity that enables the catalyst units 201a to 201d to be kept warm for about 5 minutes at the time of idling of the engine 10 is tested or examined on the assumption of actual use conditions. It is desirable to obtain and set by the above. In addition, as a result of confirmation on a trial basis, it was confirmed that there is a battery that has a capacity corresponding to the engine displacement and that can satisfy the heat capacity that enables the above-mentioned heat insulation.

  According to this configuration, the heat of the exhaust gas Go is stored in the heat storage body 202a when the temperature Tg of the exhaust gas Go is high when the engine 10 is at a medium load / high load operation, and the engine 10 is operated at a low load operation. When the temperature Tg of the exhaust gas Go is decreasing, the heat stored in the heat storage body 202a moves to the exhaust gas Go, so that the heat transfer increases the temperature Tg of the exhaust gas Go for a long time. Since the exhaust gas Go having a relatively high temperature can flow into the catalyst units 201a to 201d downstream of the heat storage unit 202, the temperature Tc of the catalyst units 201a to 201d is maintained within the catalyst activation temperature range for a while. Thus, the decrease in the temperature Tc of the catalyst units 201a to 201d can be delayed. As a result, the temperature Tc of the downstream catalyst units 201a to 201d is maintained when the temperature of the exhaust gas Go decreases, and the purification process of HC, NOx, etc. contained in the exhaust gas Go when the engine 10 is restarted or restarted. The deterioration of ability can be prevented.

  Furthermore, since the flow path of the exhaust gas Go can be either the bypass passage 202b or the heat storage body 202a, the bypass valve 23 is opened and the flow path of the exhaust gas Go is changed to the bypass passage 202b. Priority is given to the temperature rise of 201a-201d over the temperature rise of the thermal storage body 202a, or the catalyst unit 201a-201d is heated quickly, or the exhaust gas Go passage (if the bypass valve 23 is fully closed, the exhaust gas Go All the flow paths) can be used as the heat storage body 202b to suppress an excessive temperature rise of the catalyst units 201a to 201d due to the temperature rise of the heat storage body 202b, and the temperature Tc of the catalyst units 201a to 201d can be controlled within the catalyst activation temperature range. It will be able to be maintained for a long time.

  In the case where the bypass valve 23 is opened and the flow path of the exhaust gas Go is used as the bypass passage 202b, the configuration of FIGS. 1 to 3 does not close the inlet of the heat storage body 202a. The entire amount of the exhaust gas Go does not pass through the bypass passage 202b, and there is a possibility that a part of the exhaust gas Go passes through the inside of the heat storage body 202a. When a part of the exhaust gas Go passes through the inside of the heat storage body 202a, a temperature decrease due to heat radiation of the heat storage body 202a can be somewhat prevented.

  Also, in this heat storage system, compared with the increase in HC and CO in the exhaust gas Go and the exhaust gas temperature increase due to oxidation by the catalytic action of this HC and CO, noble metal as a catalyst for oxidizing HC and CO is used. Since use can be avoided, the cost is low.

  In addition, in a vehicle where the temperature of the catalyst units 201a to 201d tends to decrease due to frequent stop and restart, such as a delivery truck on a real road or a collection and delivery vehicle of a garbage truck, the catalyst units 201a to 201d This is particularly effective because the temperature reduction can be prevented, the temperature Tc of the catalyst units 201a to 201d can be maintained long in the catalyst activation temperature range, and the purification rate of the exhaust gas Go can be improved.

  The bypass passage 202b is provided inside the heat storage unit 202, the heat storage body 202a is arranged on the outer periphery of the bypass passage 202b to constitute the heat storage unit 202, and the bypass valve 23 constituted by an on-off valve is arranged in the bypass passage 202b. If configured, the exhaust gas Go passing through the bypass passage 202b is not easily cooled, which is advantageous for early temperature rise of the catalyst units 201a to 201d on the downstream side of the heat storage unit 202, and the heat storage body 202a and the bypass passage 202b are compact. Thus, the exhaust gas aftertreatment device 20 can easily be accommodated in the case, so that the exhaust gas purification system 1 is not increased in size and can be easily mounted on the vehicle.

  And in the exhaust gas purification system 1 of this invention, the flow-path control apparatus 41 which controls the valve opening degree of the bypass valve 23 is provided and comprised. The flow path control device 41 is usually configured to be incorporated in an overall system control device 40 that performs overall control of the engine 10 and overall control of a vehicle on which the engine 10 is mounted.

  The flow path control device 41 is used when the temperature Tg of the exhaust gas Go flowing into the heat storage unit 202 is equal to or higher than the temperature Th of the heat storage body 202a and the temperature Tc of the catalyst units 201a to 201d is lower than the catalyst activation temperature Tca, or In the PM regeneration control of the attached DPF unit (DPF device) 201c or the NOx regeneration control of the LNT unit (NOx reduction catalyst device) 201a, the bypass valve 23 is controlled so that the exhaust gas Go passes through the bypass passage 202b.

  When the temperature Tg of the exhaust gas Go flowing into the heat storage unit 202 is lower than the temperature Th of the heat storage body 202a, or when the temperature Tc of the catalyst units 201a to 201d is equal to or higher than the catalyst activation temperature Tca, the exhaust gas Go is The bypass valve 23 is configured not to pass through the bypass passage 202b.

  Next, an exhaust gas purification method in the exhaust gas purification system 1 will be described with reference to an example of a control flow shown in FIG. The control flow shown in FIG. 4 is called from the advanced control flow when the engine 10 is started. The control of the bypass valve 23 in steps S11 to S15 is repeated, and the engine 10 is stopped and returned by an interrupt. The control flow returns to the advanced control flow, and is shown as a control flow that ends when the advanced control flow ends.

  When the control flow of FIG. 4 is called from the advanced control flow and started, it is determined in step S11 whether or not the temperature Tg of the exhaust gas Go flowing into the heat storage unit 202 is equal to or higher than the temperature Th of the heat storage body 202a. I do.

  If it is determined in step S11 that the temperature Tg of the exhaust gas Go is equal to or higher than the temperature Th of the heat storage body 202a (YES), the process goes to step S12. In step S12, the temperature Tc of the catalyst units 201a to 201d is activated. It is determined whether or not the temperature is lower than Tca. If the temperature Tg of the exhaust gas Go is not equal to or higher than the temperature Th of the heat storage body 202a (NO), the process goes to step S13.

  When the temperature Tc of the catalyst units 201a to 201d is lower than the catalyst activation temperature Tca (YES) in step S12, the process goes to step S14 to open the bypass valve 23 so that the exhaust gas Go passes through the bypass passage 202b. Control. When the temperature Tc of the catalyst units 201a to 201d is not lower than the catalyst activation temperature Tca (NO), the process goes to step S13.

  In this step S13, it is determined whether or not the PM regeneration control of the DPF unit with catalyst (DPF device) 201c or the NOx regeneration control of the LNT unit (NOx reduction catalyst device) 201a. If it is determined in step S13 that the PM regeneration control of the DPF unit with catalyst (DPF device) 201c or the NOx regeneration control of the LNT unit (NOx reduction catalyst device) 201a is performed, the process goes to step S14, and the exhaust gas Go is bypassed. The opening of the bypass valve 23 is controlled so as to pass through 202b.

  If the determination in step S13 is not PM regeneration control of the DPF unit with catalyst (DPF device) 201c or NOx regeneration control of the LNT unit (NOx reduction catalyst device) 201a, the process goes to step S15.

  If neither the DPF unit with catalyst 201c nor the LNT unit 201a is provided in the exhaust gas aftertreatment device 20, the determination in step S13 is skipped, the process goes to step S15, and the exhaust gas Go does not pass through the bypass passage 202b. Thus, the valve closing control of the bypass valve 23 is performed.

  And when it goes to step S15, it is already a case where it is NO by determination of step S11, and it is a case where the temperature Tg of the exhaust gas Go flowing into the heat storage unit 202 is lower than the temperature Th of the heat storage body 202a, or This is a case where the determination in step S12 is NO, and any of the cases where the temperature Tc of the catalyst units 201a to 201d is equal to or higher than the catalyst activation temperature Tca.

  In step S14 and step S15, when a preset control time has elapsed, the process returns to step S11. In steps S11 to S15, the control of opening or closing the bypass valve 23 is repeated, and when the engine 10 is stopped, the process returns by an interrupt to return to the advanced control flow, and ends when the advanced control flow ends.

  By this control, when the temperature Tg of the exhaust gas Go upstream from the heat storage unit 202 is equal to or higher than the temperature Th of the heat storage body 202a and the temperature Tc of the catalyst units 201a to 201d is lower than the catalyst activation temperature Tca, or the DPF unit with catalyst (DPF device) When performing PM regeneration control of the 201c or NOx regeneration control of the LNT unit (NOx reduction catalyst device) 201a, the valve opening control of the bypass valve 23 is performed so that the exhaust gas Go passes through the bypass passage 202b. Can do.

  Further, when the temperature Tg of the exhaust gas Go upstream from the heat storage unit 202 is lower than the temperature Th of the heat storage body 202a, or when the temperature Tc of the catalyst units 201a to 201d is equal to or higher than the catalyst activation temperature Tca, the exhaust gas Go. The valve closing control of the bypass valve 23 can be performed so that the valve does not pass through the bypass passage 202b.

  Therefore, when the temperature Tg of the exhaust gas Go passing through the exhaust passage 13 upstream from the heat storage unit 202 is equal to or higher than the temperature Th of the heat storage body 202a, the exhaust gas Go is allowed to pass through the bypass passage 202b. When the temperature Tg of the exhaust gas Go passing through the exhaust passage 13 upstream of 202 is lower than the temperature Th of the heat storage body 202a, the exhaust gas Go can be prevented from passing through the bypass passage 202b.

  As a result, when the temperature Th of the heat storage body 202a is lower than the temperature Tg of the exhaust gas Go, the exhaust gas Go passes through the bypass passage 202b and does not pass through the heat storage body 202a. Since the exhaust gas Go can be flowed into the catalyst units 201a to 201d as it is without being deprived of the heat stored in the body 202a, the catalyst units 201a to 201d can be quickly heated.

  Further, when the temperature Th of the heat storage body 202a is equal to or higher than the temperature Tg of the exhaust gas Go, the exhaust gas Go passes through the heat storage body 202a and does not pass through the bypass passage 202b, thereby storing the heat storage of the heat storage body 202a. Since it can be transmitted to the exhaust gas Go, the temperature of the exhaust gas Go can be raised and the temperature of the catalyst device 201 can be prevented from decreasing.

  Here, the effects of the heat storage unit 202 according to the present invention will be described in comparison with the prior art with reference to FIGS. 5 and 6. FIG. 5 is a diagram showing the effect of the heat storage unit 202 according to the present invention. In the configuration in which the heat storage unit 202 is provided on the upstream side of the catalyst units 201a to 201d in the exhaust passage 13, the traveling is restarted from the stopped state of the engine 10. In this case, the temperature Tg of the exhaust gas Go (detected value of the first temperature sensor 24), the temperature Th of the heat storage body 202a (detected value of the second temperature sensor 25), the temperature Tc of the catalyst device 201 (of the third temperature sensor 26). (Detection value). According to FIG. 5, since the temperature Th of the heat accumulator 202a is higher than the temperature Tg of the exhaust gas Go during the period from the resumption of travel (0 sec) to 400 sec (indicated as “warming period” in FIG. 5), the exhaust gas By controlling Go so that it passes through the heat storage body 202a and not through the bypass passage 202b, the heat stored in the heat storage body 202a is transmitted to the exhaust gas Go, the temperature of the exhaust gas Go is raised, and the catalyst unit The temperature drop of 201a-201d is prevented.

  When the transition of the temperature Tc of the catalyst units 201a to 201d in the heat retention period of FIG. 5 is compared with the transition of the temperature Tc of the catalyst units 201a to 201d in the prior art of FIG. 6, the period from the resumption of travel (0 sec) to 400 sec. 6, the temperature Tc of the catalyst units 201a to 201d in FIG. 6 changes from 150 ° C. to 200 ° C., whereas the temperature Tc of the catalyst units 201a to 201d according to the present invention in FIG. In the present invention, it can be seen that the temperature Tc of the catalyst units 201a to 201d is maintained in the catalyst activation temperature range.

  According to the exhaust gas purification system 1 and the exhaust gas purification method described above, when the temperature Tg of the exhaust gas Go is high, the heat of the exhaust gas Go is stored in the heat storage body 202a, and the temperature Tg of the exhaust gas Go is lowered. In some cases, the temperature Tg of the exhaust gas Go is increased by the heat of the heat storage body 202a, and the exhaust gas Go having a relatively high temperature can flow into the catalyst units 201a to 201d downstream from the heat storage unit 202 for a long time. The temperature Tc of the catalyst units 201a to 201d constituting the exhaust gas aftertreatment device 20 provided in the exhaust passage 13 of the engine 10 can be kept long within the catalyst activation temperature range, and HC, NOx, etc. contained in the exhaust gas Go can be maintained. It is possible to prevent deterioration of the purification treatment capacity.

  Further, the flow path of the exhaust gas Go is used as the bypass passage 202b, and the temperature rise of the catalyst units 201a to 201d is prioritized over the temperature rise of the heat storage body 202a, or the heat storage body 202a is connected via the heat storage body 202a. The excessive temperature rise of the catalyst units 201a to 201d can be suppressed by the temperature rise.

1 exhaust gas purification system 10 engine (internal combustion engine)
12 Intake passage 13 Exhaust passage 14 EGR passage 15 Turbocharger (turbo supercharger)
20 Exhaust gas aftertreatment device 201a LNT unit (catalyst unit)
201b SCR unit (catalyst unit)
201c DPF unit with catalyst (catalyst unit)
201d DOC unit (catalyst unit)
202 Heat storage unit 202a Heat storage body 202b Bypass passage 23 Bypass valve 24 First temperature sensor 25 Second temperature sensor 26 Third temperature sensor 40 Overall system control device 41 Flow path control device A Fresh air G Exhaust gas Gc Purified exhaust gas Ge EGR gas Go Exhaust gas Tc flowing into the catalyst unit Temperature of catalyst unit Tca Catalyst activation temperature Tg Temperature of exhaust gas Th Temperature of heat storage body

Claims (5)

In an exhaust gas purification system in which an exhaust gas aftertreatment device comprising a catalyst unit carrying a catalyst is provided in an exhaust passage,
A heat storage unit provided with a heat storage body on the upstream side of the catalyst unit is provided on the upstream side of the catalyst unit in the exhaust gas aftertreatment device, a bypass passage that does not pass through the heat storage body, and an exhaust gas in the bypass passage An exhaust gas purification system, wherein a bypass valve for controlling circulation is provided in the heat storage unit, and a flow path control device for controlling opening and closing of the bypass valve is further provided. The flow path control device is
When the temperature of the exhaust gas flowing into the heat storage unit is equal to or higher than the temperature of the heat storage body and the temperature of the catalyst unit is lower than the catalyst activation temperature, the bypass valve is controlled so that the exhaust gas passes through the bypass passage. Done
When the temperature of the exhaust gas flowing into the heat storage unit is lower than the temperature of the heat storage body, or when the temperature of the catalyst unit is equal to or higher than the catalyst activation temperature, the bypass gas is prevented from passing through the bypass passage. The exhaust gas purification system according to claim 1, wherein the exhaust gas purification system is configured to control a valve. The flow path control device is
In the PM regeneration control of the DPF device of the catalyst unit or the NOx regeneration control of the NOx reduction catalyst device, the bypass valve is controlled so that the exhaust gas passes through the bypass passage. The exhaust gas purification system according to claim 1 or 2.   The bypass passage is provided inside the heat storage unit, the heat storage body is arranged on the outer periphery of the bypass passage to constitute the heat storage unit, and the bypass valve constituted by an on-off valve is arranged in the bypass passage. The exhaust gas purification system according to any one of claims 1 to 3. An exhaust gas aftertreatment device comprising a catalyst unit carrying a catalyst is provided in the exhaust passage, and a heat storage unit having a heat storage body upstream of the catalyst unit is provided upstream of the catalyst unit in the exhaust gas aftertreatment device. Provided on the side, a bypass passage that does not pass through the heat storage body is provided in the heat storage unit, a bypass valve that controls the flow of exhaust gas in the bypass passage is provided, and further, a flow path control that controls the valve opening degree of the bypass valve In the exhaust gas purification method provided with the device,
When the temperature of the exhaust gas flowing into the heat storage unit is equal to or higher than the temperature of the heat storage body and the temperature of the catalyst unit is lower than the catalyst activation temperature, the exhaust gas passes through the bypass passage, and the heat storage unit When the temperature of the exhaust gas flowing in is lower than the temperature of the heat storage body, or when the temperature of the catalyst unit is equal to or higher than the catalyst activation temperature, the exhaust gas is prevented from passing through the bypass passage. Exhaust gas purification method.

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