JP2015206302A - Exhaust gas purification system for internal combustion engine and exhaust gas purification method for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas purification system for internal combustion engine and an exhaust gas purification method for internal combustion engine that can suppress local deterioration of a catalyst carried by a fine particle collection device in an exhaust gas purification device and improve fuel economy, and further can reduce troubles such as breakage of the catalyst.SOLUTION: An internal combustion engine 10 includes, in an exhaust passage 15 of the internal combustion engine 10, an exhaust gas purification device 20 having an oxidation catalyst device 22 and a fine particle collection device 23 in order from upstream, and reproduction processing of the fine particle collection device 23 is performed in a first state in which an exhaust gas Ga flows to both a center part 23a and an outer peripheral part 23b of the fine particle collection device 23 right after the start of reproduction, in a second state in which a flow to the center part 23a of the fine particle collection device 23 is stopped below a previously set amount in the middle of the reproduction, and in a third state in which the flow to the center part 23a of the fine particle collection device 23 is stopped at the set amount in the ending of the reproduction.

Description

  The present invention suppresses local deterioration of the catalyst carried by the particulate collection device that collects PM in the exhaust gas discharged from the internal combustion engine, improves fuel consumption, and further breaks down the catalyst. The present invention relates to an exhaust gas purification system for an internal combustion engine and an exhaust gas purification method for the internal combustion engine that can reduce problems.

  In an internal combustion engine such as a diesel engine mounted on a vehicle, particulate matter called PM (Particulate Matter) contained in the exhaust gas is collected in a particulate trap provided in an exhaust gas purification device disposed in an exhaust passage. The exhaust gas collected by the collector and exhausted into the atmosphere is purified. In this particulate collection device, PM is collected, and as the amount of accumulated PM increases, fuel consumption deteriorates due to an increase in pressure loss, or purification performance decreases due to an increase in the amount of PM that passes through. The particulate collection device is periodically heated to a temperature equal to or higher than the PM combustion temperature for a predetermined time, and a regeneration process for burning the collected PM is performed to recover the PM collection capability. By repeating this collection and regeneration, the PM collection capability of the particulate collection device is maintained, and the PM in the exhaust gas discharged into the atmosphere is reduced.

  The regeneration process of the particulate collection device is to estimate the amount of PM deposited and deposited by, for example, the differential pressure before and after the particulate collection device. If it has reached, the reproduction process is performed. Further, the temperature increase of the particulate collection device in the regeneration process is performed by, for example, providing an oxidation catalyst device (DOC) in the exhaust passage upstream of the particulate collection device and temporarily increasing the unburned fuel during the regeneration process. The hydrocarbon (HC) is oxidized with this oxidation catalyst, and with this oxidation heat, the exhaust gas that passes through the oxidation catalyst device is heated to a high temperature, and the heated exhaust gas is collected on the downstream particulate collection device The particulate collection device is heated by being caused to flow into.

  By the way, in general, there is a velocity distribution in the exhaust gas flowing in the exhaust passage, and the flow rate of the exhaust gas tends to decrease from the central portion of the exhaust passage toward the outer peripheral portion, and is incorporated into the exhaust gas purification device. Similarly, a flow velocity distribution exists for the exhaust gas passing through the particulate collection device.

  For example, referring to the exhaust gas purification device 21X including the oxidation catalyst device (DOC) 22X and the particulate collection device 23X shown in FIG. 12, in the particulate collection device 23X, PM has a high flow rate and a large amount. As the PM accumulates, the pressure loss at the center increases, so the flow of exhaust gas to the outer periphery gradually increases and PM accumulates on the outer periphery. To come.

  Even during the regeneration process of the particulate collection device 23X, the flow rate of the exhaust gas Ga decreases as it approaches the outer peripheral portion from the center of the particulate collection device 23X, and the exhaust gas has a large heat release to the external environment at the outer peripheral portion. Since the temperature tends to decrease, the energy of the exhaust gas decreases as the distance from the central portion approaches the outer peripheral portion. As a result, during regeneration, the catalyst at the center where the exhaust gas flow rate is high and a large amount of exhaust gas flows has a higher load such as heat and HC poisoning than the catalyst at the outer periphery, and the catalyst deteriorates. Get early. Therefore, local degradation of the catalyst occurs. This local deterioration of the catalyst becomes more prominent for vehicles used under conditions where the particulate collection device has a high frequency of regeneration. Therefore, a part of the catalyst is extremely deteriorated to lower the exhaust gas purification processing capacity. It becomes a problem of letting you.

  In addition, the reproduction at the outer peripheral portion tends to be insufficient during the reproduction process, and the reproduction at the center portion is completed earlier than the outer peripheral portion. Then, after the regeneration of the central portion is completed, the pressure loss in the central portion is improved and falls, so that the exhaust gas flows more easily to the central portion after the PM burns than the outer peripheral portion where the PM is accumulated. Since the difference between the gas flow rate in the central part and the gas flow rate in the outer peripheral part becomes larger, there is a difference in the progress of the regeneration between the central part and the outer peripheral part (hereinafter referred to as “unevenness of the regeneration state”).

  Since the regeneration processing of the outer peripheral portion remains insufficient, the differential pressure across the particulate collection device 23X does not drop quickly, so that fuel is used to advance the regeneration at the outer peripheral portion, and the fuel efficiency Gets worse. Further, the use of this fuel increases the heat load on the catalyst more than necessary, which promotes problems such as damage to the catalyst.

  In this connection, in order to minimize the fuel consumption required for the regeneration process, the activation rate necessary for PM combustion is calculated by calculating the combustion speed for each PM deposition amount at the time of PM combustion, and from that value There has been proposed a method of calculating the relationship between temperature and time required for PM to burn and executing regeneration under conditions that minimize fuel consumption (see, for example, Patent Document 1).

  However, in this regeneration method, the fuel consumption deterioration is optimized by optimizing the fuel consumption necessary for the regeneration process based on the PM accumulation amount in the particulate collection device. Therefore, the above-mentioned problems such as local deterioration of the catalyst, deterioration of fuel consumption, and promotion of problems such as damage to the catalyst cannot be solved.

JP 2013-44256 A

  The present invention has been made in view of the above, and an object of the present invention is to apply a local load to the catalyst during the regeneration processing of the particulate collection device, and to purify the exhaust gas with a part of the catalyst. Exhaust gas of an internal combustion engine that can suppress the drastic reduction of the gas, improve PM collection efficiency, improve fuel efficiency by saving fuel for regeneration treatment, and reduce catalyst malfunction A purification system and an exhaust gas purification method for an internal combustion engine are provided.

  In order to achieve the above object, an exhaust gas purification system for an internal combustion engine according to the present invention includes an exhaust gas purification system having an exhaust gas purification device having an oxidation catalyst device and a particulate collection device in order from the upstream side in an exhaust passage of the internal combustion engine. In the exhaust gas purification system, the state of the flow of the exhaust gas flowing into the particulate collection device into the exhaust passage upstream of the oxidation catalyst device is determined, and the exhaust gas is disposed between the central portion and the outer peripheral portion of the particulate collection device. A first state flowing into both, a second state in which a flow flowing into the central portion of the particulate collection device is hindered by less than a preset amount, and an inflow into the central portion of the particulate collection device A flow path changing mechanism for switching the flow to the third state where the flow is hindered by the set amount is provided, and at the time of regeneration processing of the particulate collection device, the regeneration is performed in the first state immediately after the regeneration is started, Reproduced by the second state, reproducing late it is configured to provide a controller configured to perform control of reproduction in the third state.

  This set amount is a limit value of a limit amount that restricts the flow to the central portion so that the differential pressure across the particulate collection device does not become excessively large, and is set in advance from experimental results and the like. Amount.

  According to this configuration, at the time of regeneration control, the state of the exhaust gas flow is changed from the first state to the third state through the second state according to the progress state of the regeneration process, so that the central portion of the oxidation catalyst device sequentially Since the exhaust gas containing the regeneration hydrocarbon can be spread from the outer periphery to the outer peripheral portion, the catalyst of the oxidation catalyst device can be used as a whole, so that local deterioration can be suppressed. It is possible to prevent the exhaust gas purification processing capacity from being extremely lowered at the portion.

  Further, by changing the portion through which the exhaust gas passes in the oxidation catalyst device from the central portion to the outer peripheral portion, the exhaust gas having a high temperature for regeneration is sequentially distributed from the central portion to the outer peripheral portion also in the particulate collection device. Therefore, it is possible to avoid that only the central portion of the particulate collection device is excessively heated. As a result, when the catalyst is supported on the particulate collection device, it is possible to prevent the exhaust gas purification processing capability from being extremely reduced by a part of the catalyst of the particulate collection device.

  Regarding the set amount, in the third state, if the set amount is not provided and the valve is fully closed, the flow rate of the exhaust gas flowing through the center of the particulate collection device becomes zero, and the flow of the exhaust gas burns PM. Since only the flow to the outer peripheral portion in a state where it is not performed, the pressure loss of the particulate collection device increases (increase in the differential pressure across the front and rear). Therefore, for example, the valve opening degree is provided with a set amount in which the projected flow passage area with respect to the flow passage direction of the valve body portion is the upper limit of the closing amount, and the minimum exhaust gas is supplied to the oxidation catalyst device and the fine particles. By flowing to the center of the collection device, the exhaust gas flowing through the center of the particle collection device is secured and the increase in pressure loss is suppressed, while PM is burned at the outer periphery of the particle collection device. Can be promoted.

  Therefore, by sequentially changing the portion to be regenerated in this particulate collection device from the center portion to the outer peripheral portion, the regeneration processing of the regeneration particulate collection device can be performed efficiently and without unevenness of regeneration. Therefore, the PM collection efficiency during normal PM collection can be improved, and the regeneration process of the particulate collection device can be efficiently performed in a short time, so that the fuel for the regeneration process can be saved. Fuel consumption can be improved.

  Furthermore, since the temperature rise in the central portion of the oxidation catalyst device and the particulate collection device can be suppressed, the heat load on the catalyst arranged in the central portion of the oxidation catalyst device can be reduced, and this catalyst can be damaged. Can be reduced. In addition, when the particulate collection device carries a catalyst, the thermal load on the catalyst disposed at the center of the particulate collection device can be reduced, and problems such as breakage of the catalyst are reduced. be able to.

  Contrary to this configuration, during the regeneration control of the particulate collection device, the exhaust gas is first flowed preferentially to the outer peripheral portion of the particulate collection device, and then the exhaust gas is preferentially flowed to the center portion. In this case, most of the exhaust gas whose temperature is increased by oxidation of hydrocarbons in the exhaust gas in the oxidation catalyst device first passes through the outer peripheral portion where the temperature is low, and from the outer peripheral surface of the particulate collection device to the outside. This increases the amount of heat released, which increases the time required for the temperature rise at the outer periphery, delays the start of the regeneration process at the outer periphery, and reduces the PM at the outer periphery where the deposition density is lower than at the center. Since it burns, the rate of temperature rise due to combustion of PM also becomes slow.

  Further, since the outer surface area of the outer peripheral portion is larger than the surface area at the boundary with the inner central portion, most of the combustion heat of PM is dissipated from the outer surface at this outer peripheral portion, so the combustion of PM by regeneration Since only a part of the heat can be used in the central portion, the time required for the temperature rise in the central portion is lengthened and the regeneration processing in the central portion is suppressed, so that the efficiency of the regeneration processing is reduced. Therefore, the combustion heat of PM cannot be efficiently used for the regeneration process.

  In the exhaust gas purification system for an internal combustion engine, the temperature detecting device for the center part that detects the center temperature that is the temperature of the exhaust gas flowing into the center part of the particle collecting device, and the outer periphery of the particle collecting device And an outer peripheral temperature detecting device that detects an outer peripheral temperature that is the temperature of the exhaust gas flowing into the portion, and in the second state, the control device is a temperature between the center temperature and the outer peripheral temperature. In order to keep the difference within a preset first determination temperature difference range, the flow path is more largely prevented from flowing exhaust gas flowing through the central portion continuously or stepwise according to the progress of regeneration. It is configured to control the change mechanism.

  According to this configuration, the ratio of the flow rate of the exhaust gas flowing into the central portion of the oxidation catalyst device and the particulate collection device and the flow rate of the exhaust gas flowing into the outer peripheral portion can be set according to the temperature difference between the central temperature and the peripheral temperature. The distribution of exhaust gas can be optimized according to the degree of progress of the regeneration of the central part of the particulate collection device and the regeneration of the outer peripheral part, so that the generation of uneven regeneration can be prevented more efficiently. Playback time can be shortened.

  In the exhaust gas purification system for an internal combustion engine, the oxidation catalyst device is provided upstream of the oxidation catalyst device, and the exhaust gas flows into the central portion of the oxidation catalyst device. If the flow path changing mechanism is configured to have an internal passage that divides into the second flow that flows into the outer peripheral portion and a flow rate adjustment valve that is provided in the internal passage, a relatively simple configuration In addition, the flow of the exhaust gas can be changed to the first state, the second state, or the third state only by controlling the valve opening degree of the flow rate adjusting valve.

  And the exhaust gas purification method of the internal combustion engine of the present invention for achieving the above object is an internal combustion engine provided with an exhaust gas purification device having an oxidation catalyst device and a particulate collection device in order from the upstream side in the exhaust passage of the internal combustion engine. In the exhaust gas purification method for an engine, at the time of regeneration processing of the particulate collection device, immediately after starting regeneration, regeneration is performed in a first state in which exhaust gas flows into both the central portion and the outer peripheral portion of the particulate collection device. The middle plate is regenerated in a second state where the flow flowing into the central portion of the particulate collection device is hindered by a preset amount less than the preset amount, and the final flow is a flow flowing into the central portion of the particulate collection device. The reproduction is performed in a third state that is hindered by the set amount.

  Further, in the exhaust gas purification method for an internal combustion engine, the exhaust gas flowing into the outer peripheral portion of the fine particle collecting device and the central temperature that is the temperature of the exhaust gas flowing into the central portion of the fine particle collecting device. An outer peripheral temperature that is a temperature is detected, and in the second state, according to the progress of regeneration, the temperature difference between the center temperature and the outer peripheral temperature falls within a preset first determination temperature difference range. The flow of the exhaust gas flowing through the central part continuously or stepwise is more hindered.

  According to these methods, the same effect as the exhaust gas purification system of the internal combustion engine can be obtained.

  According to the exhaust gas purification system for an internal combustion engine and the exhaust gas purification method thereof according to the present invention, the exhaust gas flow at the time of regeneration processing of the particulate collection device, both at the center and the outer periphery of the oxidation catalyst device immediately after the start of regeneration. In the middle of the regeneration, the flow in the central part of the oxidation catalyst device and the particulate collection device is reduced, and in the final stage of the regeneration, the flow is only in the outer peripheral portion of the oxidation catalyst device and the particulate collection device. The reproduction process can be sequentially advanced from the central portion to the outer peripheral portion while preventing the occurrence of uneven reproduction.

  Thereby, PM collection efficiency at the time of normal PM collection can be improved, and regeneration processing of the particulate collection device can be performed efficiently in a short time, so that fuel for regeneration processing can be saved. So fuel economy can be improved.

  In addition, it is possible to suppress a local load from being applied to the catalyst of the oxidation catalyst device, and the exhaust gas purification processing capacity from being extremely reduced by a part of the catalyst of the oxidation catalyst device. In addition, when the particulate collection device carries a catalyst, a local load is applied to the catalyst of the particulate collection device, and the exhaust gas purification processing capacity is extremely large in part of the catalyst of the particulate collection device. It can suppress that it falls.

  Therefore, it is possible to suppress a local load on the catalyst during the regeneration processing of the particulate collection device, and to suppress the exhaust gas purification processing capacity from being extremely reduced by a part of the catalyst, and to improve the PM collection efficiency. It is possible to improve the fuel efficiency by saving the fuel for the regeneration treatment and reduce the malfunction of the catalyst.

It is a figure showing typically an example of composition of an internal-combustion engine provided with an exhaust-gas purification system of an embodiment concerning the present invention. 1 is a side sectional view schematically showing a configuration of an exhaust gas purification system according to an embodiment of the present invention. It is the figure seen from the XX direction of FIG. 2 which shows typically the mode of the valve body of the butterfly type valve | bulb (flow-rate regulating valve) arrange | positioned in the upstream of the oxidation catalyst apparatus of FIG. It is a figure which shows an example of the control flow of the exhaust gas purification method of the internal combustion engine which concerns on this invention. It is a figure which shows the detail of step S400 of FIG. It is a sectional side view which shows typically the mode of the valve body of the butterfly valve in a 1st state. It is the figure seen from the XX direction of FIG. 6 which shows typically the mode of the valve body of the butterfly valve in a 1st state. It is a sectional side view which shows typically the mode of the valve element of the butterfly type valve in the 2nd state. It is the figure seen from the XX direction of FIG. 8 which shows typically the mode of the valve body of the butterfly valve in a 2nd state. It is a sectional side view which shows typically the mode of the valve body of the butterfly valve in a 3rd state. It is the figure seen from the XX direction of FIG. 10 which shows the mode of the valve body of the butterfly valve in a 3rd state typically. It is a figure which shows typically the mode of the flow velocity of the exhaust gas which passes an exhaust-gas purification apparatus of a prior art.

  Hereinafter, an exhaust gas purification system for an internal combustion engine and an exhaust gas purification method for an internal combustion engine according to embodiments of the present invention will be described with reference to the drawings.

  First, an engine (internal combustion engine) 10 in which the exhaust gas purification system 2 for an internal combustion engine of this embodiment is arranged will be described with reference to FIG. The engine 10 is provided with a fuel injection device 11, an intake valve 12 and an exhaust valve 13 facing a cylinder (cylinder) 10 a, and further, an intake passage 14 communicating with the intake valve 12 and an exhaust valve 13. An exhaust passage 15 and an EGR passage 16 are provided.

  The intake passage 14 is provided with an air cleaner 17, a turbocharger (turbo supercharger) 18 compressor 18 b, an intercooler 19 a, and an intake throttle valve 19 b in order from the upstream side. The turbine 18a of the turbocharger 18 and the exhaust gas purification device 20 are provided in this order from the side. The EGR passage 16 is provided by connecting an intake passage 14 downstream of the compressor 18b and an exhaust passage 15 upstream of the turbine 18a. The EGR passage 16 is provided with an EGR cooler 16a and an EGR valve 16b in this order from the upstream side. Is provided.

  The fresh air A introduced from the atmosphere is sent to the cylinder (cylinder) 10a via the intake valve 12 with the exhaust gas (EGR gas) Ge flowing into the intake passage 14 from the EGR passage 16 as necessary. It is done. Further, the exhaust gas G generated in the cylinder 10a flows into the exhaust passage 15 via the exhaust valve 13, a part of which flows as the EGR gas Ge in the EGR passage 16, and the remaining exhaust gas Ga (= G-Ge) is Then, after flowing into the exhaust gas purification device 20 via the turbine 18a and being purified, it is discharged into the atmosphere as a purified exhaust gas Gc via a muffler (not shown).

  Further, in the configuration of FIG. 1, the exhaust gas purification device 20 includes an oxidation catalyst device (DOC) 22, a particulate collection device 23, a selective catalytic reduction device (SCR) 24, an oxidation catalyst device (DOC) 25, and the like. Is done.

  The oxidation catalyst device 22 is formed, for example, by supporting rhodium, cerium oxide, platinum, aluminum oxide, or the like on a support of a porous ceramic honeycomb structure such as a cordierite honeycomb. The oxidation catalyst device 22 oxidizes hydrocarbons (HC) and carbon monoxide (CO) such as unburned fuel present in the exhaust gas Ga, and raises the temperature of the exhaust gas Ga passing through the oxidation heat. .

  The particulate collection device 23 is generally formed of a monolith honeycomb wall flow type filter or the like in which the inlet and outlet of a porous ceramic honeycomb channel are alternately sealed. In many cases, an oxidation catalyst such as platinum or cerium oxide or a PM oxidation catalyst is supported. By the particulate collection device 23, PM in the exhaust gas Ga is collected by a porous ceramic wall.

  The fuel injection device 26 is a device arranged on the upstream side of the oxidation catalyst device 22 and injects unburned fuel into the exhaust passage 15. When the particulate collection device 23 is regenerated, the fuel injection device 26 is disposed in the exhaust passage 15. The unburned fuel is injected into the gas, and the exhaust gas Ga is heated by the oxidation heat of the unburned fuel oxidized by the oxidation catalyst device 22 to raise the temperature of the particulate collection device 23 to a temperature range where PM combustion is possible. ing.

  The urea injection device 27 is a device that is disposed upstream of the selective catalytic reduction device 24 and injects urea water for NOx reduction into the exhaust passage 15. The injected urea water is decomposed. Ammonia is generated, and NOx in the exhaust gas Ga is reduced to water and nitrogen by the selective reduction catalyst device 24 by this ammonia to make it harmless.

  Furthermore, a differential pressure sensor 41 for detecting the differential pressure across the particulate collection device 23 is provided, and a temperature sensor 42 for measuring the temperature of the exhaust gas Ga flowing into the exhaust gas purification device 20 is provided, and A temperature sensor for the center portion that detects the temperature Ti (hereinafter referred to as the center temperature) Ti of the exhaust gas Gi flowing through the center portion 23a of the particulate collection device 23 in the exhaust passage 15 between the oxidation catalyst device 22 and the particulate collection device 23. (Temperature detection device for central portion) 43 and a temperature sensor for outer periphery (hereinafter referred to as an outer periphery temperature) To detect the temperature of exhaust gas Go flowing through the outer periphery 23b of the particulate collection device 23 (hereinafter referred to as the outer periphery temperature). 44).

  2, 6, 8, and 10, only the first half of the exhaust gas purification device 20 is illustrated. In these drawings, the center temperature sensor 43 and the outer periphery temperature sensor 44 are both arranged on the upper part of the exhaust gas purification device 20, but are not necessarily inserted from one direction. In other words, the arrangement of the two is not limited to this arrangement, and it is only necessary that the arrangement is such that the center temperature Ti and the outer peripheral temperature To can be detected.

  In the present invention, the exhaust gas purification system 2 is further provided with an internal passage 31 upstream of the oxidation catalyst device 22 as shown in FIGS. The first flow that flows into 22 a and the second flow that flows into the outer peripheral portion 22 b of the oxidation catalyst device 22 are divided. This internal passage 31 is provided up to immediately before the upstream side of the oxidation catalyst device 22, but in the interior of the oxidation catalyst device 22 and the inside of the particulate collection device 23, in particular, center portions 22 a and 23 a and outer peripheral portions 22 b and 23 b are provided. A partition wall for partitioning is not provided, and a state in which heat transfer is possible between the center portions 22a and 23a and the outer peripheral portions 22b and 23b is made.

  Most of the exhaust gas Ga flowing inside the internal passage 31 flows through the central portion 23a of the particulate collection device 23, and most of the exhaust gas Ga flowing outside the internal passage 31 is the outer peripheral portion of the particulate collection device 23. 23b will flow.

  Further, a butterfly valve (flow rate adjusting valve) 32 in which a valve body 32 a is disposed is provided in the internal passage 31. As a drive source of the butterfly valve 32, for example, an actuator (not shown) such as a stepping motor is used. The internal passage 31 and the butterfly valve 32 constitute a flow path changing mechanism 30. According to this configuration, since there are few movable parts and a simple configuration, the flow path changing mechanism 30 has a low failure frequency and high durability.

  When the butterfly valve 32 is fully opened as shown in FIG. 7, the state of the flow of the exhaust gas Ga flowing into the oxidation catalyst device 22 and the particulate collection device 23 is changed to the exhaust gas Gi + Go as shown in FIG. The first state that flows into both the central portion 23a and the outer peripheral portion 23b of the collection device 23, and the butterfly valve 32 is closed from the fully opened state as shown in FIG. As shown in FIG. 11, the second state where the flow Gi flowing into the central portion 23a of the particulate collection device 23 is partially blocked and the butterfly valve 32 are shown in FIG. By closing at a preset amount, the flow Gi flowing into the central portion 23a of the particulate collection device 23 is blocked by the set amount as shown in FIG. Cut off It can be replaced. In the second state, the valve opening of the butterfly valve 32 is decreased (in the closing direction) continuously or stepwise.

  Further, the control unit 51 is configured to control the regeneration process of the particulate collection device 23 and the flow path changing mechanism 30. The control device 51 operates the actuator in accordance with the progress of the regeneration process of the particulate collection device 23 to shift the butterfly valve 32 from the open state to the closed state. The control device 51 is normally configured to be incorporated in an overall system control device (ECU) 50 that performs overall control of the engine 10 based on information from various sensors such as an accelerator opening sensor (not shown). However, it may be provided independently.

  In the present invention, the control device 51 controls the butterfly valve 32 during the regeneration process of the particulate collection device 23 so that the regeneration is performed in the first state immediately after the regeneration is started, and the middle of the regeneration is performed in the second state. In the final stage of playback, playback is controlled in the third state.

  Regarding the timing of starting the transition to each state, one or several combinations of the regeneration duration t, the differential pressure ΔP before and after the particulate collection device 23, and the temperature difference ΔT between the center temperature Ti and the outer peripheral temperature To When each value exceeds a preset threshold value, the next state is entered. These threshold values are set in advance based on experimental results and stored in the control device 51 as map data or the like. These threshold values are preferably configured to be corrected according to the operating state (engine speed and load) of the engine 10 during the regeneration process.

  According to this configuration, immediately after the start of regeneration, the exhaust gas Ga flowing into the oxidation catalyst device 22 is in a first state in which the flow of the exhaust gas Ga tends to be biased toward the central portion 22a, thereby exhausting into the central portion 23a of the particulate collection device 23. By preferentially raising the center temperature Ti of the gas Gi and causing the exhaust gas Ga to flow into the particulate collection device 23, the regeneration of the central portion 23a can be performed with priority. As a result, the temperature of the central portion 23a can be quickly raised to the temperature at which PM combustion starts, so that PM combustion can be started quickly. In this embodiment, the first state is a state in which the valve body 32a is inclined in a direction parallel to the inner tube 31 (fully opened state) as shown in FIGS.

  In the middle of the regeneration, regeneration of the central portion 23a of the particulate collection device 23 progresses to some extent due to the concentrated passage of the high-temperature exhaust gas Ga to the central portion 23a and the combustion of PM immediately after the start of regeneration. Since the temperature of the central portion 23a of the device 23 has risen, the heat generation at the central portion 22a of the oxidation catalyst device 22 is set to the second state in which the flow to the central portion 22a of the oxidation catalyst device 22 is limited to less than the set amount. By suppressing the heat generation and promoting the heat generation at the outer peripheral portion 22b of the oxidation catalyst device 22, an excessive increase in the temperature of the central portion of the oxidation catalyst device 22 can be avoided. At the same time, regeneration at the central portion 23a of the particulate collection device 23 can be suppressed, and an excessive increase in the temperature of the central portion 23a can be avoided. At the same time, it is possible to increase the temperature of the outer peripheral portion 23b of the particle collecting device 23 and to promote the regeneration in the outer peripheral portion 23b of the particle collecting device 23. In this embodiment, the second state is a state in which the valve body 32a is slightly inclined (half-opened state) with respect to the inner tube 31, as shown in FIGS.

  The second state corresponds to a transition stage from the first state to the third state, and the opening degree of the butterfly valve 32 is continuously or stepwise from fully opened to a set amount as the regeneration proceeds. Is preferred. Thereby, the ratio of the flow rate Qi of the exhaust gas Gi flowing into the central portion 23a of the particulate collection device 23 and the flow rate Qo of the exhaust gas Go flowing into the outer peripheral portion 23b can be changed more finely. The distribution of the exhaust gas Ga can be optimized in accordance with the progress of regeneration and regeneration of the outer peripheral portion 23b.

  Further, at the end of regeneration, regeneration in the central portion 23a of the particulate collection device 23 is almost completed and PM combustion becomes a lower flame, while in the particulate collection device 23, heat from the central portion 23a is outside. Since the temperature of the outer peripheral portion 23b has also risen since it has moved to the portion 23b, the exhaust gas is allowed to flow positively through the outer peripheral portion 23b of the particulate collection device 23 that has risen in temperature in the third state, Furthermore, by suppressing the heat generation at the central portion of the oxidation catalyst device 22 and promoting the heat generation at the outer peripheral portion of the oxidation catalyst device 22, the temperature has risen from the central portion 23a where PM has almost burned. By burning the PM in the outer peripheral portion 23b intensively, the combustion of the PM in the outer peripheral portion 23b can be completed and the regeneration process can be completed. In this embodiment, as shown in FIGS. 10 and 11, the third state is a state in which the valve body 32 a is inclined to the set amount to the inner pipe 31 (maximum closed state: not completely closed). It is in a state. In this state, the flow rate of the exhaust gas Gi passing through the central portion 23a is secured at a minimum.

  That is, during the regeneration control, the exhaust gas Ga passes through the particulate collection device 23 by changing the flow state of the exhaust gas Ga from the first state to the third state according to the progress state of the regeneration. The exhaust gas Ga at the high temperature during regeneration control can be spread over the entire particulate collection device 23 in sequence, by changing the portion to be changed from the central portion 23a to the outer peripheral portion 23b, and only the central portion 23a rises excessively. You can avoid warming. As a result, when the particulate collection device 23 carries a catalyst, local degradation of the catalyst can be suppressed, so that the exhaust gas Ga purification processing capability is extremely high in a part of the catalyst of the particulate collection device 23. Can be prevented.

  In the valve closing control of the butterfly valve 32, if the valve is fully closed without setting a set amount, the flow rate of the exhaust gas Ga flowing through the central portion 23a of the particulate collection device 23 becomes zero, and the flow of the exhaust gas Ga is reduced. Since only the flow to the outer peripheral portion 23b of the particulate collection device 23 in a state where PM is not combusted, an increase in pressure loss is caused. Therefore, by providing a set amount for the amount of closing of the butterfly valve 32 and avoiding the full closing, the flow of the exhaust gas Gi flowing through the central portion 23a is ensured, and the increase in pressure loss is suppressed, and the particulate collection is performed. The combustion of PM at the outer peripheral portion 23b of the device 23 can be promoted.

  Further, in the second state, the control device 51 detects the temperature difference ΔT (= Ti−To) between the center temperature Ti detected by the center temperature sensor 43 and the outer temperature To detected by the outer temperature sensor 44. ) Flows through the central portion of the oxidation catalyst device 22 and the central portion 23a of the particulate collection device 23 in a continuous or stepwise manner in accordance with the progress of the regeneration so as to fall within the preset first determination temperature difference ΔT1. The flow path changing mechanism 30 is configured to control the flow of the exhaust gas Ga so that the flow of the exhaust gas Ga is less than the set amount. The first determination temperature difference ΔT1 is set in advance based on experimental results and stored in the control device 51.

  With this configuration, the ratio of the flow rate of the exhaust gas Ga flowing into the central portion 22a and the outer peripheral portion 22b of the oxidation catalyst device 22 is changed more finely, and the exhaust gas Ga flowing into the central portion 23a of the particulate collection device 23 is changed. The flow rate Qi, the central temperature Ti, the flow rate Qo of the exhaust gas Ga flowing into the outer peripheral portion 23b, and the outer peripheral temperature To are changed more finely to regenerate the central portion 23a and the outer peripheral portion 23b of the particulate collection device 23, respectively. The distribution of the exhaust gas Ga can be optimized in accordance with the degree of progress, and the regeneration time can be shortened while preventing the occurrence of uneven regeneration. By shortening the regeneration time, fuel for regeneration processing can be saved and fuel consumption can be improved. In addition, since the heat load on the catalyst can be reduced, problems such as damage to the catalyst can be reduced.

  Next, an exhaust gas purification method for an internal combustion engine according to an embodiment of the present invention will be described with reference to the control flow of FIGS. The control flow of FIG. 4 is called from the high-level control flow when it is determined that regeneration of the particulate collection device 23 is necessary in the high-level control flow, and the control flow is controlled to return. Then, returning to the advanced control flow, and when it is determined that the particulate collection device 23 needs to be regenerated, it is called from the advanced control flow and is shown to be repeatedly executed during the operation of the engine 10. It is. Note that when the engine 10 stops in the middle of the control, an interrupt is generated and a return is made to return to the advanced control flow, and when the operation of the engine 10 is stopped, the operation ends with the end of the advanced control flow.

  In the advanced control flow, whether the measured value of the differential pressure across the particle collection device 23 measured by the differential pressure sensor 41 exceeds a preset differential pressure for determining regeneration start, or the amount of PM deposited It is determined whether or not the regeneration process of the particulate collection device 23 is started based on whether or not the PM accumulation amount obtained by accumulating the calculated PM accumulation amount exceeds a preset regeneration start determination PM accumulation amount. Then, the control flow of FIG. 4 is called from the advanced control flow and starts.

  When the control flow in FIG. 4 starts, “start of regeneration processing of the particulate collection device” in step S100 is performed, “regeneration processing” in the next step S200, “end determination of regeneration processing” in step S300, “Channel control” in step S400 is performed in parallel.

  In the “regeneration process” in step S200, the exhaust gas temperature raising control for raising the temperature of the exhaust gas Ga, which is a well-known technique, and the exhaust gas temperature maintenance for keeping the temperature of the exhaust gas Ga after the subsequent temperature rise are performed. Take control. The exhaust gas temperature maintenance control ends when receiving a signal for determining completion from step S300 being performed in parallel.

  In “reproduction process end determination” in step S300, the end of the reproduction process is determined based on whether or not the reproduction continuation time from the start of reproduction has continued for a preset end determination time t1. When the reproduction continuation time exceeds the end determination time t1, “reproduction process end determination” is performed to end the reproduction process control, and this “end determination signal” is transmitted to the steps S200 and S400. This step S300 is completed. Note that the end determination based on the differential pressure across the particulate collection device 23 may be used, or both determinations may be combined.

  The “flow path control” in step S400 is a feature of the present invention. The flow path changing device 30 is controlled, and immediately after the start of the control, the first state “center part priority flow path control” is set, and the regeneration middle stage is the second state. The state is “parallel flow path control”, and the final stage of the regeneration is the third state “peripheral section priority flow path control”.

  The timing of the transition from the first state to the second state and the transition from the second state to the third state in step S400 is the first transition determination time related to the reproduction duration set in advance by an experimental result or the like. And detection using the second transition determination time, or detection using the first transition determination differential pressure value and the second transition determination differential pressure time related to the differential pressure across the particulate collection device 23. it can.

  For example, the control flow shown in FIG. 5 is based on the PM accumulation amount obtained for each control time. In this control flow, the regeneration start PM accumulation amount PMcm is input in step S401, and in the next step S402, a first determination threshold value PM1 for determining the timing of transition from the first state to the second state, A second determination threshold value PM2 for determining the timing of transition from the second state to the third state is set. The first determination threshold value PM1 and the second determination threshold value PM2 are set in advance based on experimental results and stored in the control device 51.

  In the next step S403, the PM accumulation amount PMc at the time of control is calculated by subtracting the PM removal amount ΔPMem for each control time, which occurs during the regeneration process, from the regeneration start PM deposition amount PMcm. This PM removal amount ΔPMem is calculated by referring to map data or the like set beforehand by experiments or the like with respect to the engine operating state (engine speed and load), the temperature of the exhaust gas Ga, and the like.

  In step S404, whether or not the regeneration of the central portion 23a of the particulate collection device 23 has been completed to a preset level is determined based on whether or not the PM deposition amount PMc is greater than or equal to the first determination threshold value PM1. . If YES in this determination, the process goes to step S405, and after performing “center-priority channel control” in the first state for a preset control time, the process goes to step S409. In the case of NO, it is determined that the reproduction of the central portion 23a has been completed to a preset level, and the process goes to step S406.

  In this step S406, whether or not the regeneration of the central portion 23a of the particulate collection device 23 has been completed to a preset level but has not been sufficiently completed is determined based on whether or not the PM deposition amount PMc is the second. Judgment is made based on whether or not it is equal to or greater than the threshold value PM2. If YES in this determination, the process goes to step S407, and after performing the “parallel flow path control” in the second state for the control time, the process goes to step S409. If the determination in step S406 is NO, the regeneration of the central part 23a of the particulate collection device 23 has been sufficiently completed, and the process goes to step S408, where the “peripheral part priority flow path control” in the third state is performed. Is performed for the control time, and then the process proceeds to step S409.

  In step S409, it is determined whether or not the “end determination signal” from step S300 has been received. If NO, the process returns to step S403. In the case of YES, the process goes to step S410, and in the flow path control end process, the butterfly valve 32 is fully opened, and the “flow path control” in step S400 is ended.

  Then, in the control flow of FIG. 4, when “reproduction process end determination” is made in step S300, “reproduction process end process” is performed in step S200, and control of “reproduction process” is terminated. In step S400, the “flow path control end process” is performed, and the “flow path control” control is ended. When these three parallel controls are all finished, the process goes to return and returns to the advanced control flow. When it is determined that the particulate collection device 23 needs to be regenerated, the control flow of FIG. 4 is called from the advanced control flow and is repeatedly performed.

  In the exhaust gas purification method for an internal combustion engine provided with the exhaust gas purification device 20 having the oxidation catalyst device 22 and the particulate collection device 23 in order from the upstream side in the exhaust passage 15 of the engine 10 by the above control, the particulate collection device 22 During the regeneration process, immediately after the regeneration is started, the exhaust gas Ga is regenerated in a first state where the exhaust gas Ga flows into both the central portion 23a and the outer peripheral portion 23b of the particulate collection device 23, and the regeneration middle is the central portion of the particulate collection device 23. Regeneration is performed in the second state where the flow flowing into 23a is hindered by a preset amount less than the preset amount, and the end of the regeneration is performed in a third state where the flow flowing into the central portion 23a of the particulate collection device 23 is hindered by the set amount. Can be made.

  Further, the center temperature Ti, which is the temperature of the exhaust gas Gi flowing into the central portion 23a of the particulate collection device 23, and the outer peripheral temperature To, which is the temperature of the exhaust gas Go, which flows into the outer peripheral portion 23b of the particulate collection device 23 are detected. In the second state, the temperature difference ΔT between the center temperature Ti and the outer peripheral temperature To is continuously or stepwise according to the progress of regeneration so that the temperature difference ΔT falls within the preset first determination temperature difference ΔT1. The flow of the exhaust gas Gi flowing through the central portion 23a can be largely prevented.

  According to the exhaust gas purification system 2 for an internal combustion engine and the exhaust gas purification method for an internal combustion engine configured as described above, the flow of the exhaust gas Ga during the regeneration process of the particulate collection device 23, and the oxidation catalyst device 22 and the It flows to both the central portions 22a, 23a and the outer peripheral portions 22b, 23b of the particulate collection device 23, the middle of the regeneration reduces the flow of the central portions 22a, 23a of the oxidation catalyst device 22 and the particulate collection device 23, By using only the outer peripheral portions 22b and 23b of the oxidation catalyst device 22 and the particulate collection device 23, the regeneration processing of the particulate collection device 23 is performed from the central portion 23a to the outer peripheral portion 23b while preventing the occurrence of uneven regeneration. You can proceed sequentially.

  As a result, PM collection efficiency during normal PM collection can be improved, and regeneration processing of the particulate collection device 23 can be efficiently performed in a short time, thus saving fuel for regeneration processing. This can improve fuel economy.

  Further, it is possible to suppress a local load from being applied to the catalyst of the oxidation catalyst device 22 and the exhaust gas Ga purification processing capability to be extremely reduced by a part of the catalyst of the oxidation catalyst device 22. Further, when the particulate collection device 23 carries a catalyst, a local load is applied to the catalyst of the particulate collection device 23, and the exhaust gas Ga is purified by a part of the catalyst of the particulate collection device 23. It is possible to suppress the ability from being extremely lowered.

  Therefore, it is possible to prevent the exhaust gas Ga purification processing capability from being extremely reduced due to a local load applied to the catalyst during the regeneration process of the particulate collection device 23, and the PM trapping. It is possible to improve the collection efficiency, improve the fuel consumption by saving the fuel for the regeneration process, and reduce the malfunction of the catalyst.

2 Exhaust gas purification system for internal combustion engine 10 Engine (internal combustion engine)
11 Fuel injection device 14 Intake passage 15 Exhaust passage 20 Exhaust gas purification device 22 Oxidation catalyst device (DOC)
22a Central part 22b of oxidation catalyst device Peripheral part 23 of oxidation catalyst device Particulate collection device 23a Central part 23b of particulate collection device Peripheral part 24 of particulate collection device Selective reduction type catalytic device (SCR)
25 Oxidation catalyst equipment (DOC)
26 Fuel Injector 27 Urea Injector 30 Channel Change Mechanism 31 Internal Passage 32 Butterfly Valve (Flow Control Valve)
32a Valve body 41 Differential pressure sensor 42 Temperature sensor 43 Temperature sensor for center (temperature detection device for center)
44. Temperature sensor for outer periphery (temperature detection device for outer periphery)
50 Overall system control unit (ECU)
51 Control Device A Fresh Air A + Ge Intake Gas G Generated Exhaust Gas Ga Exhaust Gas (G-Ge) Flowing into Exhaust Gas Purification Device
Gc Purified exhaust gas Ge EGR gas Gi Exhaust gas Go flowing to the center of the particulate collection device Go Exhaust gas flowing to the outer periphery of the particulate collection device

Claims (5)

In an exhaust gas purification system for an internal combustion engine comprising an exhaust gas purification device having an oxidation catalyst device and a particulate collection device in order from the upstream side in the exhaust passage of the internal combustion engine,
The state of the flow of the exhaust gas flowing into the particulate collection device into the exhaust passage upstream of the oxidation catalyst device is the first state where the exhaust gas flows into both the central portion and the outer peripheral portion of the particulate collection device. A state, a second state where the flow flowing into the central portion of the particulate collection device is hindered by less than a preset amount, and a flow flowing into the central portion of the particulate collection device at the set amount. While providing a flow path changing mechanism for switching to the blocked third state,
At the time of regeneration processing of the particulate collection device, control is performed to perform regeneration in the first state immediately after the start of regeneration, regeneration in the middle of regeneration in the second state, and regeneration in the third state of the regeneration end. An exhaust gas purification system for an internal combustion engine, characterized in that a control device is provided. A temperature detecting device for the center that detects the center temperature that is the temperature of the exhaust gas flowing into the center of the particulate collection device, and an outer periphery that is the temperature of the exhaust gas that flows into the outer periphery of the particulate collection device While comprising a temperature detection device for the outer periphery to detect the temperature,
In the second state, the control device continuously adjusts according to the progress of regeneration so that the temperature difference between the center temperature and the outer peripheral temperature falls within a preset first determination temperature difference. 2. The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the flow path changing mechanism is controlled so as to largely prevent the flow of exhaust gas flowing through the central portion in a stepwise manner.   Provided upstream of the oxidation catalyst device, the flow of exhaust gas is divided into a first flow that flows into the central portion of the oxidation catalyst device and a second flow that flows into the outer peripheral portion of the oxidation catalyst device. 3. The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the flow path changing mechanism is configured to include an internal passage for diversion and a flow rate adjustment valve provided in the internal passage. . In an exhaust gas purification method for an internal combustion engine comprising an exhaust gas purification device having an oxidation catalyst device and a particulate collection device in order from the upstream side in the exhaust passage of the internal combustion engine,
At the time of regeneration processing of the particulate collection device, immediately after the start of regeneration, the exhaust gas is regenerated in a first state where it flows into both the central portion and the outer periphery of the particulate collection device. Regeneration is performed in a second state where the flow flowing into the central portion is hindered by a preset amount less than a preset amount, and at the end of the regeneration, the flow flowing into the central portion of the particulate collection device is hindered by the set amount. An exhaust gas purification method for an internal combustion engine, characterized by regenerating in a state. Detecting a central temperature that is a temperature of exhaust gas flowing into the central portion of the particulate collection device and an outer peripheral temperature that is a temperature of exhaust gas flowing into the outer peripheral portion of the particulate collection device;
In the second state, the center is continuously or stepwise according to the progress of regeneration so that the temperature difference between the center temperature and the outer peripheral temperature falls within a preset first determination temperature difference range. 5. The exhaust gas purification method for an internal combustion engine according to claim 4, wherein the flow of the exhaust gas flowing through the section is largely hindered.

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