JP2015206274A - 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 improve purification performance for a component to be purified in an exhaust gas discharged from an internal combustion engine, and also can prevent a component to be purified which temporarily has high concentration from being discharged to the atmosphere.SOLUTION: An exhaust gas purification system for internal combustion engine is provided with a first switching mechanism 21 which performs switching between a first state in which an exhaust gas G downstream from an exhaust gas purification device 12 flows to an exhaust passage 11 not through an adsorption device 20 and a second state in which the gas G flows to the exhaust passage 11 through the adsorption device 20, and also provided with a second switching mechanism 22 which performs switching between a third state in which an exhaust gas G upstream from the exhaust gas purification device 12 flows to the exhaust gas purification device 12 not through the adsorption device 20 and a fourth state in which the exhaust gas G flows to the exhaust gas purification device 12 through the adsorption device 20.

Description

  The present invention provides an exhaust gas for an internal combustion engine that can improve the purification capacity for the purification target component in the exhaust gas discharged from the internal combustion engine, and can temporarily prevent the high concentration concentration of the purification target component from being discharged into the atmosphere. The present invention relates to a purification system and an exhaust gas purification method for an internal combustion engine.

  In vehicles such as trucks equipped with diesel engines (internal combustion engines), oxidation catalyst devices (DOC), particulate collection devices (DPD), urea-based selective reduction catalyst devices (SCR), ammonia slip catalyst devices (ASC), etc. The exhaust gas purifying device combined with the above purifies the components to be purified such as nitrogen oxide (NOx), hydrocarbon (HC), carbon monoxide (CO) contained in the exhaust gas discharged from the engine.

However, during a period when engine warm-up is insufficient, such as when the vehicle is started (so-called low temperature start), there is sufficient catalyst in the exhaust gas purification device such as an oxidation catalyst device or a selective reduction catalyst device provided in the exhaust gas purification device. The hydrocarbons and carbon monoxide generated by soot combustion when the particulate collection device is not activated (first situation) or when the particulate collection device is regenerated are discharged at a high concentration and sufficiently purified by the ammonia slip catalyst device When it cannot be exhausted (second situation), or when ammonia (NH ₃ ) as a reducing agent is supplied and NOx is purified by the selective catalytic reduction catalytic converter, excess ammonia is also generated by the ammonia slip catalytic converter. When it is not sufficiently purified (third situation), there is a problem that there is a possibility that the purification target component may be temporarily discharged into the atmosphere at a high concentration. It is necessary to overcome this problem as exhaust gas regulations are strengthened in Japan, Europe and America.

  Several solutions have been proposed for these three situations. For example, for the first situation, as a promising thing in the future, an exhaust gas to which a device such as a lean NOx reduction catalyst (LNT) such as a NOx storage reduction catalyst (NSR) or an HC trap device is added is added. A gas purification system has been proposed, and it has been proposed to cope with the second situation and the third situation with an ammonia slip catalyst device carrying a noble metal.

  However, with this ammonia slip catalyst device, there is a concern that sufficient purification cannot be achieved if the component to be purified is temporarily discharged at a high concentration, and sufficient purification is possible even for high concentration discharge. In order to improve the purification performance, there is a problem that the ammonia slip catalyst device is required to carry a large amount of noble metal, which leads to a high price. No solution has been proposed for these three situations that would be comprehensive and cost-effective when using any of the above devices.

  In this connection, a DOC, an upstream NOx catalyst, a DPF, and a downstream NOx catalyst having a low activation temperature are arranged in series in the exhaust passage in order from the upstream side, and a bypass passage that bypasses the downstream NOx catalyst is provided. In the bypass structure, a flow path switching valve is provided at the junction on the downstream side of the bypass path, and the flow path is switched according to the temperature of the NOx catalyst. An exhaust passage bypass structure that achieves both performance improvement and prevention of SOx poisoning has been proposed (see, for example, Patent Document 1).

  However, in this configuration, during high load operation, exhaust gas is allowed to flow through the bypass passage to avoid inflow of high-temperature exhaust gas to the downstream NOx catalyst, preventing thermal deterioration of the downstream NOx catalyst, and upstream NOx. It is possible to prevent sulfur poisoning of the downstream NOx catalyst by flowing exhaust gas through the bypass passage and avoiding the inflow of exhaust gas containing sulfur to the downstream NOx catalyst even during the sulfur purge of the catalyst. However, there is a problem that the downstream NOx catalyst cannot be regenerated efficiently.

JP 2009-221904 A

  The present invention has been made in view of the above, and an object of the present invention is to improve the purification capacity for the purification target component in the exhaust gas discharged from the internal combustion engine, and temporarily increase the concentration of the purification target component. It is to provide an exhaust gas purification system for an internal combustion engine and an exhaust gas purification method for the internal combustion engine that can prevent exhaust gas from being discharged into the atmosphere.

  In order to achieve the above object, an exhaust gas purification system for an internal combustion engine of the present invention is an exhaust gas purification system for an internal combustion engine provided with an exhaust gas purification device for purifying exhaust gas exhausted from the internal combustion engine in an exhaust passage. An adsorption device having an adsorbent that adsorbs a purification target component contained in exhaust gas at a low temperature and desorbs the purified purification target component adsorbed at a high temperature is connected in parallel to an exhaust passage downstream of the exhaust gas purification device. A first state in which the exhaust gas on the downstream side of the exhaust gas purifying device is disposed in the provided bypass passage and flows into the exhaust passage without passing through the adsorption device; A first switching mechanism for switching between two states, and a branch passage branched from the first branch point of the exhaust passage on the upstream side of the exhaust gas purification device is in contact with the bypass passage on one side of the adsorption device. The bypass passage on the other side of the adsorption device is connected to the exhaust passage between the first branch point and the exhaust gas purification device, and the flow of exhaust gas upstream of the exhaust gas purification device is A second switching mechanism that switches between a third state that flows to the exhaust gas purification device without passing through the adsorption device and a fourth state that flows to the exhaust gas purification device via the adsorption device, the first switching mechanism, and the A control device for controlling the second switching mechanism is provided.

  According to this configuration, the adsorption device that adsorbs the purification target components such as NOx, HC, and CO purifies the adsorption device when the temperature of the exhaust gas flowing into the adsorption device is low (for example, 150 ° C. or less). When the target component is adsorbed and the temperature of the exhaust gas flowing into the adsorption device becomes high (for example, 250 ° C. or higher), the adsorbed target component is desorbed. Depending on the state, the exhaust gas can be discharged without passing through the adsorption device, or the exhaust gas can be passed through the adsorption device to temporarily adsorb the component to be purified to the adsorption device, and the desorption temperature. The above exhaust gas is allowed to flow into the adsorption device, the adsorbed device is desorbed by desorbing the adsorbed device, and the exhaust gas used for this regeneration is passed through the exhaust gas purifying device and desorbed. Exhaust gas purification It can be easily purified by the gasification device, and it is possible to temporarily prevent the high concentration component to be purified from being discharged into the atmosphere.

  In the exhaust gas purification system for an internal combustion engine, when the control device starts the internal combustion engine at a low temperature, the exhaust gas purification device includes a particulate collection device, and the particulate collection device is regenerated. In the case of any of the first conditions when the amount of NOx detected by the NOx concentration sensor arranged on the downstream side of the exhaust gas purification device exceeds a preset allowable NOx emission amount, In the second condition in which the first switching mechanism sets the second state, the second switching mechanism sets the third state, and the adsorbing device is regenerated, the first switching mechanism sets the first state. In addition, in the state under the third condition that is neither the first condition nor the second condition, the first switching mechanism is set to the first state in the fourth state by the second switching mechanism, and Front with the second switching mechanism Configured to perform control of the third state.

  According to this configuration, in the case of the first condition where sufficient purification of the component to be purified by the exhaust gas purification device cannot be expected, the exhaust gas after passing through the exhaust gas purification device in the second state and the third state. By passing the gas through the adsorption device, the purification target component that could not be purified by the exhaust gas purification device can be temporarily adsorbed to the adsorption device, so the amount of emission of the purification target component to the atmosphere can be ensured. Can be reduced.

  In addition, if the amount of the purification target component adsorbed on the adsorption device reaches the saturation amount, it will not be adsorbed any more, so the adsorption device must be regenerated before the amount of the purification target component temporarily adsorbed reaches the saturation amount. In the case of the second condition at the time of regeneration, it is necessary to carry out the high temperature exhaust gas through the adsorption device and then through the exhaust gas purification device in the first state and the fourth state. It is possible to desorb the purification target component adsorbed by the adsorption device using the exhaust heat of the high-temperature exhaust gas and purify the desorbed purification target component with the exhaust gas purification device. Therefore, the adsorption device can be reliably regenerated and the efficiency of energy utilization can be improved.

  In the exhaust gas purification system for an internal combustion engine, the exhaust gas temperature at the inlet of the selective catalytic reduction device provided in the exhaust gas purification device is preset when the control device starts the internal combustion engine at a low temperature. The temperature is lower than the set temperature. The set temperature is a temperature set in advance by experiment or the like, and is set to 150 ° C. or higher and 300 ° C. or lower, preferably 200 ° C.

  According to this configuration, it is determined by temperature whether or not the selective catalytic reduction device has been activated, and at a low temperature, the purification target component can be temporarily adsorbed by the adsorption device, and the purification target component air Emissions into the inside can be reduced.

  In the exhaust gas purification system for an internal combustion engine, the control device shifts from the second state to the first state by the first switching mechanism when the control device is under a second condition for regenerating the adsorption device. When the second switching mechanism is configured to control to gradually increase the amount of exhaust gas flowing into the adsorption device when shifting from the third state to the fourth state, the following is performed. Can produce various effects.

  That is, at the time of regeneration of the adsorption device, high-temperature exhaust gas flows into the adsorption device via the upstream branch passage, so that the temperature of the adsorbent of the adsorption device rises and the adsorbed purification target component is Detach. The adsorbent becomes high temperature by the exhaust gas, and the exhaust gas containing the decontaminated component to be purified passes through the downstream branch passage and flows into the exhaust gas purification device to be purified. At this time, if the exhaust gas flow is switched suddenly by completely switching from the second state to the first state and from the third state to the fourth state, the adsorbent is rapidly warmed and the high concentration purification target Since the components are temporarily released, in order to avoid this, the flow rate of the exhaust gas flowing into the adsorption device is gradually increased so that the adsorbent is gradually warmed.

  In the exhaust gas purification system for an internal combustion engine, the first switching mechanism includes a first three-way valve and a second three-way valve provided at each of a branch point and a junction point of the bypass passage, When the 2 switching mechanism is constituted by the third three-way valve and the fourth three-way valve provided at the branch point and the junction point of the exhaust passage on the upstream side of the exhaust gas purification device, the flow of exhaust gas is ensured. The path can be switched.

  Further, in the exhaust gas purification system for an internal combustion engine, the exhaust gas purification device includes any one of an upstream oxidation catalyst device, a selective reduction catalyst device, an ammonia slip catalyst device, or some combination thereof. Then, the following effects can be achieved.

  According to this configuration, when the exhaust gas purification device is provided with a catalyst device such as an oxidation catalyst device (DOC), a selective reduction catalyst device (SCR), an ammonia slip catalyst device (ASC), etc., this adsorption device is provided. Therefore, the purification capacity of these catalytic devices can be designed to be lower than that of conventional catalytic devices, so that the capacity of each catalytic device and the amount of noble metals can be reduced, thereby reducing costs. it can.

  Further, when the exhaust gas purifying device is provided with an ammonia slip catalyst device (ASC), it is not necessary to carry a large amount of noble metal on the ammonia slip catalyst device, so that the cost required for the noble metal can be reduced, and the adsorption device Can be made of a material (zeolite or the like) that does not contain a noble metal, so that the cost of the adsorption device itself can be reduced. As a result, the manufacturing cost of the entire exhaust gas purification system can be reduced.

  In addition, this adsorption device can use materials that are relatively difficult to deteriorate, and the exhaust gas that flows in is low temperature except during regeneration, and it deteriorates because it is exposed to a relatively low temperature environment. It is difficult to have excellent durability.

  An exhaust gas purification method for an internal combustion engine of the present invention for achieving the above object includes an exhaust gas purification device for purifying exhaust gas discharged from the internal combustion engine in the exhaust passage, and is included in the exhaust gas at a low temperature. An adsorption device having an adsorbent that adsorbs the component to be purified and adsorbs the component to be purified adsorbed at a high temperature is disposed in a bypass passage provided in parallel with the exhaust passage downstream of the exhaust gas purification device. A branch passage branched from the first branch point of the exhaust passage upstream of the exhaust gas purification device is connected to the bypass passage on one side of the adsorption device, and the bypass passage on the other side of the adsorption device In the exhaust gas purification method for an internal combustion engine connected to the exhaust passage between the first branch point and the exhaust gas purification device, when the internal combustion engine is cold started, the exhaust gas purification device When the particulate collection device is provided and the particulate collection device is regenerated, the amount of NOx detected by the NOx concentration sensor disposed downstream of the exhaust gas purification device exceeds a preset allowable NOx emission amount In the case of any of the first conditions, a first state in which exhaust gas downstream of the exhaust gas purification device flows into the exhaust passage without passing through the adsorption device, and an exhaust passage through the adsorption device When the second condition for regenerating the adsorption device is switched to the second state, the exhaust gas flow upstream of the exhaust gas purification device is not purified via the adsorption device. Switch to a third state flowing through the apparatus and a fourth state flowing through the adsorption device to the exhaust gas purification device, and further under a third condition that is neither the first condition nor the second condition, The first state and the third state A method characterized by switching to.

  According to this method, 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 of the present invention, the adsorption device that adsorbs the purification target component such as NOx, HC, CO, etc. has a low temperature of the exhaust gas flowing into the adsorption device. If so, it has the property of adsorbing the purification target component to the adsorption device and desorbing the adsorbed purification target component when the temperature of the exhaust gas flowing into the adsorption device becomes high. Depending on the state, the exhaust gas can be discharged without passing through the adsorption device, or the exhaust gas can be passed through the adsorption device to temporarily adsorb the component to be purified to the adsorption device, and the desorption temperature. The above exhaust gas is allowed to flow into the adsorption device, the adsorbed device is desorbed by desorbing the adsorbed device, and the exhaust gas used for this regeneration is passed through the exhaust gas purifying device and desorbed. Exhaust gas purifying device can be easily be or cleaned with, it is possible to prevent the cleaning target component temporarily high concentration is discharged to the atmosphere.

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. It is a figure which shows the flow path of the exhaust gas of 1st conditions in the schematic diagram of FIG. It is a figure which shows the flow path of the exhaust gas of 2nd conditions in the block diagram of FIG. It is a figure which shows the flow path of the exhaust gas of 3rd conditions in the block diagram of FIG. It is a figure which shows an example of the control flow in the exhaust gas purification method of the internal combustion engine which concerns on this invention.

  Hereinafter, an exhaust gas purification system for an internal combustion engine and 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 drawings. As shown in FIG. 1, an exhaust gas purification system 2 for an internal combustion engine according to this embodiment is configured as follows.

  In the exhaust passage 11 of the engine (internal combustion engine) 10, nitrogen oxides (NOx), hydrocarbons (HC), carbon monoxide (CO), particulate matter contained in the exhaust gas G exhausted from the engine 10 ( An exhaust gas purification device 12 that removes a purification target component such as (PM) is provided. In the configuration of FIG. 1, the exhaust gas purification device 12 includes an oxidation catalyst device (DOC) 12a, a particulate collection device (DPD) 12b, a selective reduction catalyst device (SCR) 12c, an ammonia slip catalyst in this order from the upstream side. A device (ASC) 12d is provided.

  Although the exhaust gas purification device 12 includes the four catalyst or filter devices 12a to 12d described above, the present invention is not limited to this configuration, and a lean NOx reduction catalyst such as a NOx storage reduction catalyst device (NSR). Equipment (LNT), oxidation catalyst equipment, particulate collection equipment, urea-based SCR catalyst equipment (Urea-SCR), SCR catalyst equipment using HC as a reducing agent (HC-SCR), ammonia slip catalyst equipment (ASC) and composites It is also possible to adopt a configuration in which any combination with a catalytic device having a specific function (for example, a selective catalytic combustion filter (SCRF) which is a combined device of a particulate collecting device and a selective catalytic reduction device) is possible.

  The oxidation catalyst device 12a includes, for example, an aluminum oxide in which an oxidation catalyst such as rhodium, cerium oxide, platinum, or palladium is dispersed in a porous ceramic honeycomb structure carrier such as a cordierite honeycomb or a metal catalyst carrier. It is formed by coating with zeolite. The oxidation catalyst device 12a oxidizes hydrocarbon (HC), carbon monoxide (CO), etc., which are unburned fuel, in the exhaust gas G, and raises the exhaust gas G by heat generated by this oxidation. The temperature of the exhaust gas G thus raised is raised, and the temperature of the particulate collection device 12b on the downstream side is raised.

  The particulate collection device 12b 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, and the filter portion In many cases, an oxidation catalyst such as platinum or cerium oxide or a PM oxidation catalyst is supported. By the particulate collection device 12b, PM in the exhaust gas G is collected by a porous ceramic wall.

The selective reduction catalyst device 12c is formed, for example, by coating a cordierite honeycomb structure with a vanadium catalyst, a zeolite catalyst, a noble metal catalyst such as platinum, a transition metal oxide, and a mixture thereof. In the selective catalytic reduction device 12c, nitrogen oxides (NOx) such as nitrogen monoxide (NO) and nitrogen dioxide (NO ₂ ) are reduced to nitrogen (N ₂ ) and water (H ₂ O) by a reduction reaction. To do. At this time, when NO: NO ₂ is 50:50, nitrogen oxides can be most efficiently reduced to nitrogen.

  The ammonia slip catalyst device 12d is the same as the above-described oxidation catalyst device 12a, or has a configuration in which the catalyst of the selective reduction catalyst device 12c is formed into a multilayer in the above-described oxidation catalyst device 12a, and is used in the selective reduction catalyst device 12c. It is a device that prevents the discharge of ammonia by oxidizing and decomposing ammonia that has not been used.

  In the present invention, the adsorption device 20 is further disposed in the bypass passage 13 provided in parallel with the exhaust passage 11 on the downstream side of the exhaust gas purification device 12. The adsorption device 20 is formed with an adsorbent 20a that has a property of adsorbing the purification target component contained in the exhaust gas G that flows in as the temperature becomes lower and desorbing the adsorbed purification target component at a higher temperature. .

  Moreover, as a raw material of the adsorbent 20a with which this adsorption | suction apparatus 20 is equipped, the zeolite which carried out the ion exchange of zeolite, transition metals, such as iron (Fe) and copper (Cu), clay mineral, porous silica, activated carbon, alumina, titania, Large surface area such as zirconia, adsorbs components to be purified such as NOx, HC, CO, etc., stable materials at high temperatures, alkali metals and alkaline earth metal oxides that increase NOx adsorption amount, etc. Mixtures and multilayers can be used. An adsorbent 20a produced by coating these materials on a cordierite or silicon carbide (SiC) -based monolith or kneading them into a carrier is used in the adsorbing device 20.

  The adsorption device 20 can use a material that is relatively difficult to deteriorate. In addition, the temperature of the exhaust gas G that flows in is low except when the adsorption device 20 is regenerated, and is exposed to a relatively low temperature environment. Since there are many cases, it is hard to deteriorate and it can have the outstanding durability.

  In addition, a first three-way valve 21a and a second three-way valve 21b are disposed at the bypass branch point 13A and the bypass junction 13B of the bypass passage 13 with the exhaust passage 11, respectively. The first switching mechanism 21 is constituted by the two three-way valve 21b. That is, the bypass passage 13 branched via the first three-way valve 21a is provided on the downstream side of the exhaust gas purification device 12, and the adsorption device 20 provided with the adsorbent 20a is disposed in the bypass passage 13. By providing the first three-way valve 21a, the second three-way valve 21b, the third three-way valve 22a, and the fourth three-way valve 22b, the flow path of the exhaust gas G can be switched reliably.

  The first switching mechanism 21 allows the exhaust gas G downstream of the exhaust gas purification device 12 to pass through the first three-way valve 21a and the second three-way valve 21b without passing through the adsorption device 20 as shown in FIG. And a mechanism for switching between a first state that flows through the exhaust passage 11 and a second state that flows through the exhaust passage 11 via the first three-way valve 21a, the adsorption device 20, and the second three-way valve 21b as shown in FIG. is there.

  In this configuration, in order to make the adsorption device 20 adsorb more purification target components, the temperature of the exhaust gas G flowing into the adsorption device 20 from the bypass passage 13 is preferably set to a low temperature of 150 ° C. or lower. Therefore, regarding the piping of the exhaust passage 11 between the exhaust gas purification device 12 and the first three-way valve 21a, a configuration in which the exhaust gas G is sufficiently cooled while the exhaust gas G is passing, for example, this piping The pipe length of the pipe is sufficiently long, the surface of the pipe is provided with an uneven shape to increase the surface area, the pipe is laid out so that the running air is well applied, and a cooling device such as a fan for cooling the pipe is provided. Preferably it is done.

  Further, the branch passage 14 branched from the branch point 14A of the exhaust passage 11 upstream of the exhaust gas purification device 12 is connected to the bypass passage 13 on one side of the adsorption device 20, and the bypass passage 13 on the other side of the adsorption device 20 is connected. Connected to the junction 14B of the exhaust passage 11 between the branch point 14A and the exhaust gas purification device 12. A third three-way valve 22a and a fourth three-way valve 22b are disposed at the branch point 14A and the junction point 14B, respectively, and the second switching mechanism 22 is configured by the third three-way valve 22a and the fourth three-way valve 22b. Is done.

  That is, the branch passage 14 branched via the third three-way valve 22a is provided on the upstream side of the exhaust gas purification device 12, and the adsorption device 20 including the adsorbent 20a is disposed in the branch passage 14. 1 to 4, the branch passage 14 and the bypass passage 13 are common to the upstream side and the downstream side of the adsorption device 20, but the branch passage 14 and the bypass passage 13 are individually upstream of the adsorption device 20. The exhaust gas may be connected to the side and the downstream side so that the exhaust gas merges inside the adsorption device 20.

  As shown in FIG. 2, the second switching mechanism 22 allows the flow of the exhaust gas G on the upstream side of the exhaust gas purification device 12 without passing through the adsorption device 20, and the third three-way valve 22a and the fourth three-way valve 22b. The third state of flowing to the exhaust gas purification device 12 via the first and the second state flowing to the exhaust gas purification device 12 via the third three-way valve 22a, the adsorption device 20 and the fourth three-way valve 22b as shown in FIG. It is a mechanism for switching to 4 states.

  In this configuration, in order to desorb more components to be purified from the adsorption device 20, it is preferable that the temperature of the exhaust gas G flowing into the adsorption device 20 from the branch passage 14 is a high temperature of 250 ° C. or higher. Therefore, with regard to the piping of the exhaust passage 11 between the branch point 14A and the adsorption device 20, a configuration for maintaining the temperature of the exhaust gas G while the exhaust gas G is passing, for example, the piping length of the piping is sufficiently short. It is preferable to make the pipe into a double pipe structure, or to make a layout in which the running wind does not easily hit the pipe.

  In this embodiment, the first three-way valve 21a and the second three-way valve 21b are provided as the first switching mechanism 21, but the first switching mechanism 21 is not limited to this configuration. The first switching mechanism 21 only needs to be able to switch between the first state and the second state, and the third three-way valve 22a and the fourth three-way valve 22b are provided as the second switching mechanism 22, but the present invention is limited to this configuration. Instead, it is only necessary that the second switching mechanism 22 can switch between the third state and the fourth state according to the state of the exhaust gas purification system 2.

  Further, the control device 41 is configured to control the flow path switching of the first switching mechanism 21 and the flow path switching of the second switching mechanism 22. The control device 41 may be incorporated into an overall system control device (ECU) 40 that performs overall control of the engine 10 based on information from various sensors such as an accelerator opening sensor (not shown), or provided independently. May be.

  Further, as shown in FIG. 1, a NOx concentration sensor 30 is provided in the exhaust passage 11 downstream from the second three-way valve 21b. The NOx concentration sensor 30 is a sensor that detects the amount N of NOx contained in the exhaust gas G.

  In FIG. 1, when the NOx concentration sensor 30 is provided downstream of the second three-way valve 21b, the detected value of the NOx concentration sensor 30 can also be used for determining the timing of NOx regeneration in the exhaust gas purification device 12. At the same time, since the accumulation state of the purification target component in the adsorbent 20a of the adsorption device 20 can be estimated, the arrangement at this position is preferable. Without being limited, the exhaust passage 11 may be provided at any position as long as it is on the downstream side of the exhaust gas purification device 12.

  In the present invention, the control device 41 controls the first switching mechanism 21 and the second switching mechanism 22, and the exhaust gas purification device 12 includes the particulate collection device 12 b when the engine 10 is started at a low temperature. Any one of the cases where the amount of NOx detected by the NOx concentration sensor 30 disposed on the downstream side of the exhaust gas purification device 12 exceeds a preset allowable NOx emission amount during the regeneration of the fine particle collecting device 12b. In the case of the first condition, as shown in FIG. 2, the first switching mechanism 21 controls the second state and the second switching mechanism 22 controls the third state. Here, this NOx discharge allowable amount is a value that is set in advance by experiments or the like and stored in the control device 41.

  The low temperature start of the engine 10 is assumed to be when the exhaust gas temperature at the inlet of the selective catalytic reduction device 12c is lower than a preset temperature. This set temperature is a temperature set in advance by experiments or the like, and is set to 150 ° C. or higher and 300 ° C. or lower, preferably 200 ° C. According to this configuration, whether or not the selective catalytic reduction catalyst device 12c has been activated is determined based on the temperature, and the purification target component can be temporarily adsorbed by the adsorption device 20 when the temperature is low. Emissions into the atmosphere can be reduced.

  In the second condition for regenerating the adsorption device 20, as shown in FIG. 3, the first switching mechanism 21 controls the first state and the second switching mechanism 22 controls the fourth state. Further, in a state under a third condition that is neither the first condition nor the second condition, as shown in FIG. 4, the first switching mechanism 21 sets the first state and the second switching mechanism 22 sets the first condition. It is configured to perform control to be in three states.

  When the control device 41 is in the second condition for regenerating the adsorption device 20, the first switching mechanism 21 shifts from the second state to the first state, and the second switching mechanism 22 shifts from the third state to the fourth state. When shifting to the state, it is preferable to perform control to gradually increase the amount of the exhaust gas G flowing into the adsorption device 20. That is, at the time of regeneration of the adsorption device 20, it is preferable to control the adsorption device 20 to gradually increase the temperature by gradually increasing the flow rate of the exhaust gas G flowing into the adsorption device 20 from the branch passage 14. Thus, it is possible to prevent a temporary large-scale desorption of a high concentration target component due to a rapid temperature increase of the adsorption device 20.

  That is, when the adsorber 20 is regenerated, the high-temperature exhaust gas G flows into the adsorber 20 via the upstream branch passage 14, so that the temperature of the adsorbent 20 a of the adsorber 20 rises and is adsorbed. The component to be purified that had been removed is desorbed. The adsorbent 20a is heated to a high temperature by the exhaust gas G, and the exhaust gas G including the desorbed component to be purified passes through the downstream branch passage 14 and flows into the exhaust gas purification device 12 to be purified. At this time, when the flow of the exhaust gas G is suddenly switched from the second state to the first state and from the third state to the fourth state, the adsorbent 20a is suddenly warmed, and the high concentration Since the component to be purified is temporarily released, in order to avoid this, the flow rate of the exhaust gas G flowing into the adsorption device 20 is gradually increased so that the adsorbent 20a is gradually warmed. .

  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 FIG. The control flow of FIG. 5 is called from the advanced control flow at regular control time intervals during the operation of the engine 10 and is started. After the control flow is controlled, the process returns to return to the advanced control flow. Is a control flow that is repeatedly performed while the engine 10 is in operation. When the operation of the engine 10 is stopped, an interruption occurs, the process returns to the advanced control flow, and the process is terminated together with the advanced control flow.

  When the control flow of FIG. 5 starts, in step S11, it is determined whether or not the first condition is satisfied. Whether or not the first condition is satisfied is whether or not the engine 10 is at a low temperature start, or the exhaust gas purification device 12 includes a particulate collection device 12b, and the particulate collection device 12b Whether or not it is a time of regeneration, or when the NOx amount E detected by the NOx concentration sensor 30 disposed downstream of the exhaust gas purification device 12 exceeds a preset allowable NOx emission amount E1. If any one of them is established, ie, “is” (YES), the process goes to step S12. If none of them is established, that is, “not” (NO), step Go to S21.

  Here, the determination at the time of starting the engine 10 at a low temperature is made when the temperature Ta of the exhaust gas G at the inlet of the selective catalytic reduction catalyst device 12c is lower than a preset set temperature Ta1 (for example, 200 ° C.), or For example, the temperature Tb of the exhaust gas G at the outlet of the selective catalytic reduction device 12c may be less than a preset temperature Ta2 (for example, 200 ° C.).

  Further, regarding the regeneration of the particulate collection device 12b, the regeneration start time may be a time when the differential pressure ΔPd before and after the particulate collection device 12b becomes equal to or higher than a preset regeneration start differential pressure threshold ΔP1. Alternatively, the deposition amount PMcm of particulates (PM) in the particulate collection device 12b may be estimated and calculated, and the estimated deposition amount PMcm may be equal to or greater than a preset regeneration start deposition amount threshold value PMcm1. The regeneration end time may be a time when the differential pressure ΔPd before and after the particulate collection device 12b becomes equal to or lower than a preset regeneration end differential pressure threshold ΔP2, or the estimated deposition amount PMcm is set to a preset regeneration end deposition. It may be when the quantity threshold value is equal to or less than PMcm2.

  The allowable NOx emission amount E1 is a threshold value set in advance through experiments or the like, and is a numerical value stored in the control device 41.

  In step S12, the first switching mechanism 21 switches the flow of the low-temperature exhaust gas G on the downstream side of the exhaust gas purification device 12 to the second state in which the flow passes through the adsorption device 20 to the exhaust passage 11, and the second state. “Adsorption control” in a state in which the switching mechanism 22 switches the flow of the high-temperature exhaust gas G upstream of the exhaust gas purification device 12 to the third state to flow to the exhaust gas purification device 12 without passing through the adsorption device 20. I do. Then, after a certain preset control time has elapsed, the process returns to step S11.

  In step S21, it is determined whether or not the second condition for regenerating the adsorption device 20 is satisfied. The regeneration of the adsorption device 20 is performed when the elapsed time t from the end of the previous regeneration has passed a regeneration start time t1 set in advance by experiment or the like, or when “adsorption control” is being performed. This is performed by determining whether or not the estimated accumulation amount of the purification target component estimated based on the detection value of the NOx concentration sensor 30 exceeds a preset regeneration start determination value.

  If the determination in step S21 is true (YES), the process proceeds to step S22, and the flow of the low-temperature exhaust gas G on the downstream side of the exhaust gas purification device 12 is passed through the adsorption device 20 by the first switching mechanism 21. Without switching to the first state that flows through the exhaust passage 11, and the second switching mechanism 22 causes the flow of the hot exhaust gas G upstream of the exhaust gas purification device 12 to pass through the adsorption device 20. The “reproduction control” in the state switched to the fourth state is performed. Then, after a certain preset control time has elapsed, the process returns to step S11.

  Here, when the second switching mechanism 22 switches the flow of the hot exhaust gas upstream of the exhaust gas purification device 12 from the third state to the fourth state, the flow rate of the exhaust gas G flowing into the adsorption device 20 is changed. It is preferable to increase the temperature gradually and switch the adsorption device 20 so that the temperature gradually increases. As a result, it is possible to prevent a temporary large-scale desorption of the high-concentration purification target component due to the rapid temperature rise of the adsorption device 20, and to achieve a reliable purification process in the exhaust gas purification device 12 on the downstream side. Can do.

  If the determination in step S21 is not satisfied (NO), the process proceeds to step S31, where the first switching mechanism 21 determines that the third condition that is neither the first condition nor the second condition is satisfied. The flow of the low-temperature exhaust gas G on the downstream side of the exhaust gas purification device 12 is switched to the first state in which the flow to the exhaust passage 11 without passing through the adsorption device 20, and the second switching mechanism 22 “Normal control” is performed in a state where the flow of the upstream high-temperature exhaust gas G is switched to the third state in which the flow of the high-temperature exhaust gas G flows to the exhaust gas purification device 12 without passing through the adsorption device 20. Then, after a certain preset control time has elapsed, the process returns to step S11.

  Then, the control from step S11 to any of steps S12, S22, and S31 is repeated, and when the engine 10 is stopped during this control flow, an interrupt is generated and the process returns to the advanced control flow. Then, this control flow is completed together with the advanced control flow.

  With this control, when the engine 10 is started at a low temperature, the exhaust gas purification device 12 includes the particulate collection device 12b. When the particulate collection device 12b is regenerated, the NOx disposed on the downstream side of the exhaust gas purification device 12 is used. In the case of any of the first conditions when the NOx amount E detected by the concentration sensor 30 exceeds a preset allowable NOx emission amount E1, the exhaust gas G on the downstream side of the exhaust gas purification device 12 is used. Can be switched between a first state in which the gas flows into the exhaust passage 11 without passing through the adsorption device 20 and a second state in which the gas flows into the exhaust passage 11 through the adsorption device 20.

  At the same time, in the case of the second condition for regenerating the adsorption device 20, the flow of the exhaust gas G upstream of the exhaust gas purification device 12 flows to the exhaust gas purification device 12 without passing through the adsorption device 20. It is possible to switch to the fourth state that flows to the exhaust gas purification device 12 via the state and the adsorption device 20.

  Furthermore, in a state under a third condition that is neither the first condition nor the second condition, the state can be switched between the first state and the third state.

  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 adsorption device 20 that adsorbs a purification target component such as NOx, HC, and CO is exhaust gas that flows into the adsorption device 20. When the temperature of the gas G is low, the purification target component is adsorbed to the adsorption device 20, and when the temperature of the exhaust gas G flowing into the adsorption device 20 becomes high, the adsorbed purification target component is desorbed. Therefore, depending on the state of the exhaust gas purification system 2, the exhaust gas G is discharged without passing through the adsorption device 20, or the exhaust gas G is passed through the adsorption device 20 to temporarily remove the components to be purified. It can be adsorbed to the adsorption device 20.

  At the same time, exhaust gas G having a temperature equal to or higher than the desorption temperature is caused to flow into the adsorption device 20 to desorb the components to be purified, and the adsorption device 20 is regenerated. The exhaust gas G used for this regeneration is regenerated. It is possible to easily purify the desorbed purification target component with the exhaust gas purification device 12 and to prevent the high concentration purification target component from being temporarily discharged into the atmosphere.

  Further, in the case of the first condition in which the exhaust gas purification device 12 is not expected to sufficiently purify the purification target component, the exhaust gas G after passing through the exhaust gas purification device 12 in the second state and the third state. By allowing the adsorption device 20 to pass through, the purification target component that could not be completely purified by the exhaust gas purification device 12 can be temporarily adsorbed to the adsorption device 20, so the amount of the purification target component discharged into the atmosphere can be reduced. It can be surely reduced.

  According to this configuration, after the exhaust gas purification device 12 passes through the exhaust gas purification device 12 in the second state and the third state in the first condition where sufficient purification of the component to be purified cannot be expected in the exhaust gas purification device 12. By passing the exhaust gas G of the exhaust gas G through the adsorption device 20, it is possible to temporarily adsorb the purification target component that could not be purified by the exhaust gas purification device 12 to the adsorption device 20. Can be reliably reduced.

  In addition, when the amount of the purification target component adsorbed on the adsorption device 20 reaches the saturation amount, no more adsorption is performed, so the amount of the purification target component temporarily adsorbed before the amount of the purification target component reaches the saturation amount. In the second condition at the time of this regeneration, it is necessary to perform regeneration. In the first state and the fourth state, the exhaust gas purification apparatus 12 is passed after passing the hot exhaust gas G through the adsorption device 20. Is exhausted to the atmosphere by using the exhaust heat of the high-temperature exhaust gas G to desorb the purification target component adsorbed by the adsorption device 20, and the desorbed purification target component is exhausted to the exhaust gas. Since it can purify | clean with the purification apparatus 12, while the reproduction | regeneration of the adsorption | suction apparatus 20 can be performed reliably, efficiency improvement of energy utilization can be achieved.

  In the exhaust gas purification system for an internal combustion engine, the exhaust gas purification device 12 includes an upstream oxidation catalyst device 12a, a particulate collection device 12b, a selective reduction catalyst device 12c, and an ammonia slip catalyst device 12d. However, if any one of the upstream oxidation catalyst device 12a, the selective reduction catalyst device 12c, the ammonia slip catalyst device 12d, or some combination thereof is provided, the following effects can be obtained.

  According to this configuration, by providing the adsorption device 20, it becomes possible to design the purification capacity of these catalyst devices 12a, 12c, and 12d to be lower than that of the conventional catalyst device, so that each of the catalyst devices 12a, 12c, The capacity can be reduced by 12d and the amount of noble metal can be reduced, and the cost can be reduced.

  Further, when the exhaust gas purification device 12 includes the ammonia slip catalyst device (ASC) 12d, it is not necessary to carry a large amount of noble metal on the ammonia slip catalyst device 12d, so that the cost required for the noble metal can be reduced. In addition, since the adsorption device 20 may be made of a material (zeolite or the like) that does not contain a noble metal, the cost of the adsorption device 20 itself can be reduced. As a result, the manufacturing cost of the exhaust gas purification system 2 as a whole is reduced. Can be reduced.

2 Exhaust gas purification system for internal combustion engine 10 Engine (internal combustion engine)
11 Exhaust passage 12 Exhaust gas purification device 12a Oxidation catalyst device (DOC)
12b Fine particle collecting device 12c Selective reduction type catalyst device (SCR)
12d Ammonia slip catalyst device (ASC)
13 bypass passage 13A bypass junction 13B bypass junction 14 branch passage 14A junction 14B junction 20 adsorber 20a adsorbent 21 first switching mechanism 21a first three-way valve 21b second three-way valve 22 second switching mechanism 22a third three-way Valve 22b Fourth three-way valve 30 NOx concentration sensor 40 Overall system controller (ECU)
41 Control device G Exhaust gas

Claims (7)

In an exhaust gas purification system of an internal combustion engine provided with an exhaust gas purification device in an exhaust passage for purifying exhaust gas discharged from the internal combustion engine,
An adsorption device having an adsorbent that adsorbs a purification target component contained in exhaust gas at a low temperature and desorbs the purified purification target component adsorbed at a high temperature is connected in parallel to an exhaust passage downstream of the exhaust gas purification device. A first state in which the exhaust gas on the downstream side of the exhaust gas purifying device is disposed in the provided bypass passage and flows into the exhaust passage without passing through the adsorption device; A first switching mechanism that switches between two states;
A branch passage branched from a first branch point of the exhaust passage upstream of the exhaust gas purification device is connected to the bypass passage on one side of the adsorption device, and the bypass passage on the other side of the adsorption device is connected to the first passage. A third point connected to the exhaust passage between the branch point and the exhaust gas purification device, and causing the flow of the exhaust gas upstream of the exhaust gas purification device to flow to the exhaust gas purification device without passing through the adsorption device; And a control device for controlling the first switching mechanism and the second switching mechanism, and a second switching mechanism for switching to a fourth state that flows to the exhaust gas purification device via the adsorption device. An exhaust gas purification system for an internal combustion engine. When the control device starts the internal combustion engine at a low temperature, the exhaust gas purification device is provided with a particulate collection device, and when the particulate collection device is regenerated, NOx disposed downstream of the exhaust gas purification device In the case of any of the first conditions when the amount of NOx detected by the concentration sensor exceeds a preset allowable NOx emission amount, the first switching mechanism sets the second state, and In the third state by the second switching mechanism,
In the case of the second condition for regenerating the adsorption device, the first switching mechanism is set to the first state, the second switching mechanism is set to the fourth state,
In a state under a third condition that is neither the first condition nor the second condition, the first switching mechanism controls the first state, and the second switching mechanism controls the third state. The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the exhaust gas purification system is configured as described above.   The control device is characterized in that the low temperature start of the internal combustion engine is when the exhaust gas temperature at the inlet of the selective catalytic reduction device provided in the exhaust gas purification device is lower than a preset set temperature. The exhaust gas purification system for an internal combustion engine according to claim 1 or 2.   When the control device is in a second condition for regenerating the adsorption device, the first switching mechanism shifts from the second state to the first state, and the second switching mechanism moves from the third state to the first state. The exhaust gas of the internal combustion engine according to any one of claims 1 to 3, wherein when shifting to the fourth state, control is performed to gradually increase the amount of exhaust gas flowing into the adsorption device. Purification system.   The first switching mechanism is composed of a first three-way valve and a second three-way valve provided at each of a branch point and a merging point of the bypass passage, and the second switching mechanism is located upstream of the exhaust gas purification device. The internal combustion engine according to any one of claims 1 to 4, comprising a third three-way valve and a fourth three-way valve provided at each of a branch point and a confluence of the exhaust passage. Exhaust gas purification system.   6. The exhaust gas purification device according to claim 1, wherein the exhaust gas purification device comprises any one of an upstream oxidation catalyst device, a selective reduction catalyst device, an ammonia slip catalyst device, or some combination thereof. An exhaust gas purification system for an internal combustion engine according to any one of the preceding claims. An exhaust gas purification device for purifying exhaust gas exhausted from an internal combustion engine is provided in the exhaust passage, and adsorbs a purification target component contained in the exhaust gas at a low temperature and desorbs the adsorbed purification target component at a high temperature. An adsorbing device having an agent is disposed in a bypass passage provided in parallel with an exhaust passage on the downstream side of the exhaust gas purification device, and branches from a first branch point of the exhaust passage on the upstream side of the exhaust gas purification device The branched passage is connected to the bypass passage on one side of the adsorption device, and the bypass passage on the other side of the adsorption device is connected to the exhaust passage between the first branch point and the exhaust gas purification device. In an exhaust gas purification method for an internal combustion engine,
When the internal combustion engine is started at a low temperature, the exhaust gas purification device is provided with a particulate collection device, and when the particulate collection device is regenerated, it is detected by a NOx concentration sensor arranged downstream of the exhaust gas purification device. In the case of any of the first conditions when the amount of NOx exceeds a preset allowable NOx emission amount, the exhaust gas on the downstream side of the exhaust gas purification device is not passed through the adsorption device. While switching between a first state flowing through the exhaust passage and a second state flowing through the adsorption device into the exhaust passage,
In the case of the second condition for regenerating the adsorption device, the third state in which the flow of the exhaust gas upstream of the exhaust gas purification device flows to the exhaust gas purification device without passing through the adsorption device and the adsorption Switch to the fourth state to flow to the exhaust gas purification device via the device,
Further, the exhaust gas purifying method for an internal combustion engine is characterized in that the state is switched between the first state and the third state under a third condition that is neither the first condition nor the second condition.

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