JP2008215135A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine capable of always maintaining the high NOx absorption capacity of a NOx absorbent by always maintaining the high SOx trap capacity of a sulfur trap device. <P>SOLUTION: This exhaust emission control device is so configured that a SOx adsorption device 20 is arranged upstream of a NOx adsorption device 30, SOx is adsorbed as manganese sulfate by manganese dioxide deposited on the SOx adsorption device 20, the manganese dioxide is dissolved and removed by heat of combustion of fuel injected from a fuel injection valve 40, and the fused manganese dioxide is collected and stored in a collecting container 50. Since the SOx contained in exhaust gas is always certainly eliminated on the side upstream of a NOx catalyst 30, SOx is certainly suppressed from being adsorbed on the NOx catalyst 30, and the high NOx absorption capacity of the NOx catalyst 30 is always maintained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine that purifies nitrogen oxide (hereinafter referred to as “NOx”) contained in the exhaust gas of the internal combustion engine with a catalyst.

Conventionally, as an exhaust gas purification apparatus for an internal combustion engine that purifies nitrogen oxides (hereinafter referred to as “NOx”) contained in the exhaust gas of an internal combustion engine with a catalyst, for example, when the air-fuel ratio of inflowing exhaust gas is lean, NOx is used. It is known that a NOx absorbent that absorbs and releases NOx when the oxygen concentration in the inflowing exhaust gas decreases is disposed in the exhaust passage, and a sulfur trap is provided in the exhaust passage upstream of the NOx absorbent. (See Patent Document 1). In such an exhaust purification device for an internal combustion engine, sulfur contained in exhaust gas (usually contained in the form of sulfur oxide, hereinafter referred to as “SOx”) is captured by a sulfur trapping device, It is suppressed that SOx is absorbed by the NOx absorbent and the NOx absorbent capacity of the NOx absorbent is reduced.
JP-A-6-58138

  By the way, in the exhaust gas purification apparatus for an internal combustion engine described in Patent Document 1, when the amount of SOx captured by the sulfur capture device increases as the operating time of the internal combustion engine increases, the SOx capture capability of the sulfur capture device decreases, There is a possibility that part of SOx contained in the exhaust gas flows into the NOx absorbent and is absorbed without being captured by the sulfur trap. As a result, the NOx absorption capacity of the NOx absorbent decreases, and the NOx absorption capacity of the NOx absorbent may decrease.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to maintain an SOx trapping capacity of a sulfur trapping device constantly high, and an NOx absorbent capable of constantly maintaining an NOx trapping capacity. It is providing the exhaust gas purification device.

  In order to achieve the above object, the present invention employs the following technical means.

  An exhaust purification device for an internal combustion engine according to claim 1 of the present invention is a NOx catalyst that is provided in an exhaust passage of the internal combustion engine and adsorbs NOx in the exhaust, and an SOx adsorption device that is provided upstream of the NOx catalyst in the exhaust passage. The SOx adsorbing device adsorbs SOx in the exhaust as a chemical reaction product of SOx and SOx adsorbing material, and reaches the temperature at which the chemical reaction product melts to melt. The separation means for separating the chemical reaction product from the SOx adsorption device by the above, and the capture means for capturing and storing the chemical reaction product separated from the SOx adsorption device provided in the exhaust passage downstream of the SOx adsorption device and upstream of the NOx catalyst. It is characterized by comprising.

  According to the above-described configuration, the SOx contained in the exhaust gas is adsorbed by the SOx adsorption device as a chemical reaction product of SOx and the SOx adsorption material, and this chemical reaction product is further removed from the SOx adsorption device by the detachment means. It is separated and captured and stored by the capturing means.

  First, SOx is adsorbed as a chemical reaction product on the surface of the SOx adsorbing substance provided in the SOx adsorption device. Here, when the operation time of the internal combustion engine elapses, the region covered with the chemical reaction product on the surface of the SOx adsorbing substance increases, and the SOx adsorption function of the SOx adsorption device may be lowered. Therefore, if the chemical reaction product of SOx and the SOx adsorbing material is released from the surface of the SOx adsorbing material by operating the disengaging means, the surface area of the SOx adsorbing material can be expanded as before. In other words, the SOx adsorption function of the SOx adsorption device can be recovered. Thus, according to the exhaust gas purification apparatus for an internal combustion engine according to claim 1 of the present invention, the SOx adsorption function of the SOx adsorption device can always be maintained in a good state. Therefore, the SOx contained in the exhaust gas can always be reliably removed by the SOx adsorption device upstream of the NOx catalyst, so that the NOx catalyst is reliably prevented from adsorbing SOx and the NOx of the NOx catalyst. Absorption capacity can always be kept high.

  The exhaust emission control device for an internal combustion engine according to claim 2 of the present invention is a fuel injection valve in which the detaching means is provided on the upstream side of the SOx adsorption device of the exhaust passage so that fuel can be supplied into the exhaust passage. It is characterized in that the chemical reaction product is melted by the heat generated by combustion of the fuel supplied from the valve to be separated from the SOx adsorption device.

  According to this configuration, since the amount of heat generated by combustion per unit weight of the fuel is usually large, by injecting fuel from the fuel injection valve, the exhaust gas temperature is quickly raised to melt the chemical reaction product and from the SOx adsorption device. Can be withdrawn. Further, by appropriately controlling the fuel injection amount from the fuel injection valve, the exhaust temperature flowing into the SOx adsorption device can be adjusted to a desired temperature. Chemical reaction products can be released.

  The exhaust emission control device for an internal combustion engine according to claim 3 of the present invention includes SOx concentration detection means for detecting the SOx concentration in the exhaust gas flowing out from the SOx adsorption device, and is based on the SOx concentration determined by the SOx concentration detection means. It is characterized by controlling the operation of the detaching means.

  Under normal conditions, SOx in the exhaust discharged from the internal combustion engine is adsorbed by the SOx adsorbing device, so the SOx concentration in the exhaust flowing out from the SOx adsorbing device is stable at a very low value. When the amount of SOx adsorbed on the SOx adsorption device, that is, the amount of chemical reaction products increases and exceeds the adsorbed amount, the SOx adsorption function of the SOx adsorption device begins to deteriorate, and in the exhaust gas flowing out from the SOx adsorption device accordingly The SOx concentration begins to rise. That is, the adsorption amount of the chemical reaction product in the SOx adsorption device can be calculated based on the SOx concentration in the exhaust gas flowing out from the SOx adsorption device. Therefore, if the operation of the detachment means is controlled based on the SOx concentration determined by the SOx concentration detection means, the detachment means is operated immediately when the SOx adsorption function of the SOx adsorption device starts to decrease, thereby producing a chemical reaction product. Can be detached from the SOx adsorption device, and the SOx adsorption function of the SOx adsorption device can be immediately returned to a good state. Therefore, it is possible to provide an exhaust gas purification device for an internal combustion engine that can maintain the SOx adsorption function of the SOx adsorption device in a good state at all times and thereby maintain the NOx absorption capability of the NOx catalyst at a high level.

  Further, since the detaching means melts and releases the chemical reaction product, some energy is consumed during the operation. For this reason, if the operation of the separation means is controlled based on the SOx concentration determined by the SOx concentration detection means, the SOx contained in the exhaust gas is reliably detected by the SOx adsorption device while suppressing the operation frequency of the separation means to the minimum necessary level. Can be absorbed.

  In this case, as in the exhaust gas purifying apparatus for an internal combustion engine according to claim 4 of the present invention, if the configuration is such that the detaching means is operated when the SOx concentration determined by the SOx concentration detecting means is equal to or higher than a predetermined value, it is reliable. In addition, it is possible to provide an exhaust emission control device for an internal combustion engine that can maintain the SOx adsorption function of the SOx adsorption device in a good state at all times and thereby maintain the NOx absorption capability of the NOx catalyst at a high level.

  According to a fifth aspect of the present invention, there is provided an exhaust gas purification apparatus for an internal combustion engine, the SOx concentration calculating means for calculating the SOx concentration using information on the fuel injection amount per predetermined time, and the SOx concentration calculated by the SOx concentration calculating means. And a cumulative SOx amount calculating means for calculating the cumulative SOx amount discharged from the internal combustion engine based on the above, and controlling the operation of the detaching means based on the calculation result by the cumulative SOx amount calculating means.

  The SOx contained in the exhaust discharged from the internal combustion engine is caused by sulfur contained in the fuel. Therefore, the SOx concentration discharged from the internal combustion engine can be calculated based on the sulfur concentration contained in the fuel injected into the internal combustion engine and the information on the fuel injection amount per predetermined time of the internal combustion engine. Although this SOx concentration changes in the fuel injection amount per predetermined time, the cumulative value of the SOx amount discharged from the internal combustion engine using the cumulative value information of the fuel injection amount to the internal combustion engine and the SOx concentration described above. Can be calculated. Since SOx discharged from the internal combustion engine flows into the SOx adsorption device, the adsorption amount of the chemical reaction product by the SOx and the SOx adsorbent in the SOx adsorption device is calculated based on the calculated cumulative amount of SOx. Can be calculated. Therefore, by controlling the operation of the separation means based on the calculation result by the cumulative SOx amount calculation means, for example, by immediately operating the separation means immediately before the SOx adsorption capacity of the SOx adsorption device reaches the limit, a chemical reaction is generated. The object can be detached from the SOx adsorption device and the SOx adsorption function of the SOx adsorption device can be immediately returned to a good state. Therefore, it is possible to provide an exhaust gas purification device for an internal combustion engine that can maintain the SOx adsorption function of the SOx adsorption device in a good state at all times and thereby maintain the NOx absorption capability of the NOx catalyst at a high level.

  Further, since the detaching means is for detaching the chemical reaction product by reaching the temperature at which the chemical reaction product melts and melting it, it is necessary to increase the temperature of the SOx adsorption device during its operation. Consuming some energy for that. If the operation of the separation means is controlled based on the cumulative SOx amount calculated by the cumulative SOx amount calculation means, the operation frequency of the separation means is always operated by immediately operating the separation means immediately before the SOx adsorption capacity of the SOx adsorption device reaches the limit. Can be minimized. That is, the amount of energy consumed by the operation of the detaching means can be saved to the minimum necessary level.

  In this case, as in the exhaust gas purification apparatus for an internal combustion engine according to claim 6 of the present invention, the disengaging means is operated when the cumulative SOx amount of the internal combustion engine from the end of the operation of the disengaging means reaches a predetermined value. By doing so, it is possible to provide an exhaust purification device for an internal combustion engine that can reliably maintain the SOx adsorption function of the SOx adsorption device in a always good state, and thereby maintain the NOx absorption capacity of the NOx catalyst constantly high.

  In the exhaust emission control device for an internal combustion engine according to claim 7 of the present invention, the supplementary means communicates with a branch passage provided in a branch flow direction that branches from the main flow direction of the exhaust passage from the SOx adsorption device to the NOx catalyst. The exhaust flow direction when the exhaust gas flowing out from the SOx adsorbing device goes to the inlet of the collection chamber is a direction from the upper side to the lower side in the vertical direction. Thus, the exhaust passage and the branch passage are connected.

  The chemical reaction product which has melted and separated from the SOx adsorption device flows out of the SOx adsorption means under the fluid force of the exhaust gas. With the configuration of the exhaust gas purification apparatus for an internal combustion engine according to claim 7 of the present invention, the exhaust flow direction flowing out from the SOx adsorbing apparatus and heading toward the collection chamber is the direction from the upper side to the lower side in the vertical direction, that is, the action of gravity. It matches the direction. As a result, the molten chemical reaction product separated from the SOx adsorption device is reliably moved from the SOx adsorption device to the collection chamber by gravity acting on the chemical reaction product itself in addition to the fluid force of the exhaust gas. Can do. Thereby, the chemical reaction product detached from the SOx adsorption device can be reliably captured and stored in the collection chamber which is the capture means without staying in the exhaust passage.

  In the exhaust gas purification apparatus for an internal combustion engine according to claim 8 of the present invention, the collection container is a collection container body connected to the branch passage, and a plate protruding from the collection container body toward the internal space of the collection container The plate-like member is characterized in that the chemical reaction product that has reached the collection chamber is disposed so as to adhere thereto.

  According to such a configuration, when the chemical reaction product that has moved to the collection container in a molten state collides with the plate-like member, the plate-like member is deprived of heat and solidifies to adhere to the plate-like member. Thereby, it can suppress that the chemical reaction product which has moved to the repair container in the melted state is reliably captured in the repair container and flows out of the capturing means.

  Hereinafter, an embodiment of an exhaust gas purification apparatus for an internal combustion engine according to the present invention will be described with reference to FIGS. 1 to 5 by taking as an example a case where the present invention is applied to an exhaust gas purification apparatus 1 for a diesel engine that is an internal combustion engine mounted on an automobile. To do.

(First embodiment)
The exhaust purification device 1 is configured to adsorb and remove SOx and NOx contained in exhaust gas by an SOx adsorption device provided in an exhaust pipe that is an exhaust passage of the diesel engine 10 and a NOx adsorption device that is a NOx catalyst.

  First, the overall configuration of the exhaust emission control device 1 will be described with reference to FIG. FIG. 1 is a schematic diagram showing the overall configuration of the exhaust emission control device 1, and the upper side in FIG. 1 is the upper side when the diesel engine 10 is used, that is, when the diesel engine 10 is mounted on an automobile. Intake air sucked through the intake pipe 12 is sucked through the intake manifold 13 into each cylinder 11 of the diesel engine 10 which is an internal combustion engine. An electromagnetic valve type fuel injection valve 14 is attached to each cylinder 11. High-pressure fuel is supplied to the fuel injection valve 14 from a fuel supply means (not shown). By controlling the voltage application to the electromagnetic valve of the fuel injection valve 14, fuel is supplied from the fuel injection valve 14 into the cylinder 11. Supplied. Fuel burns in the cylinder 11 and the piston 15 reciprocates due to the pressure rise caused by the combustion. The reciprocating movement of the piston 15 is transmitted to rotate a crankshaft (not shown) and take out power. The fuel injection valve 14 performs post-injection for supplying HC (hydrocarbon) to a NOx adsorbing device 30 described later in the expansion process or exhaust process of the piston 15.

  The exhaust gas discharged from each cylinder 11 is discharged to one exhaust pipe 17 (exhaust passage) through the exhaust manifold 16. An SOx adsorption device 20 is connected to the downstream side of the exhaust pipe 17. A NOx adsorption device 30 that is a NOx catalyst is connected to the downstream side of the SOx adsorption device 20 via an exhaust pipe 18 (exhaust passage). As shown in FIG. 1, a fuel injection valve 40 as a detaching means is attached to the exhaust pipe 17 so that fuel can be injected into the exhaust pipe 17. Like the fuel injection valve 14 described above, the fuel injection valve 40 includes an electromagnetic valve and is supplied with high-pressure fuel from fuel supply means (not shown).

  As shown in FIG. 1, a branch passage 19 is connected downstream of the exhaust pipe 18 in a branch flow direction that branches from the exhaust main flow direction toward the NOx adsorption device 20. A collection container 50 is connected to the downstream end of the branch passage 19. These branch passages 19 and the collection container 50 constitute a capture means for collecting a chemical reaction product to be described later. The exhaust flow direction in the SOx adsorption device 20 and the exhaust flow direction from the SOx adsorption device 20 toward the collection container 50 are directions from the top to the bottom in the vertical direction, that is, directions from top to bottom in FIG. ing. On the other hand, the exhaust flow from the SOx adsorber 20 toward the NOx adsorber 30 is bent at a substantially right angle from the middle of the exhaust pipe 18 and flows into the NOx adsorber 30 as shown in FIG.

  In the middle of the exhaust pipe 18, as shown in FIG. 1, an SOx concentration sensor 60 as SOx concentration detecting means for detecting the SOx concentration in the exhaust is attached.

  In the diesel engine 10, the operation of the fuel injection valve 14 and a high-pressure pump (not shown) for supplying high-pressure fuel is controlled by a control device 80. The control device 10 is composed of a microcomputer or the like. The operation of the fuel injection valve 40 as the above-described detachment means is also controlled by the control device 80. The SOx concentration sensor 60 is also connected to the control device 80 so that a detection signal can be input.

  Next, the configuration of the NOx adsorption device 30 and the NOx removal operation in the exhaust gas by the NOx adsorption device 30 will be described.

  First, the configuration of the NOx adsorption device 30 will be described. The NOx adsorption device 30 is configured by storing and holding NOx adsorption means 31 in a casing 32 formed of, for example, a stainless steel plate or the like. The NOx adsorbing means 31 is formed by supporting a NOx absorbent on the surface of a honeycomb-like carrier made of, for example, alumina. That is, at least one selected from alkali metals such as potassium, sodium and lithium, alkaline earths such as barium and calcium, rare earths such as lanthanum and yttrium, and noble metals such as platinum are supported on the surface of the carrier. Yes.

  Next, the NOx removal operation in the exhaust gas by the NOx adsorption device 30 will be described. The NOx absorbent described above adsorbs NOx in an atmosphere having a high oxygen concentration and releases NOx in an atmosphere having a low oxygen concentration. Generally, since the diesel engine 10 is operated in a state where the excess air ratio is high, the oxygen concentration in the exhaust gas is high. Therefore, during normal operation of the diesel engine 10, NOx in the exhaust is adsorbed by the NOx absorbent of the NOx adsorption device 30. On the other hand, when post-injection is performed by the fuel injection valve 14 in the expansion process or exhaust process of the piston 15 in the diesel engine 10, a large amount of unburned HC (hydrocarbon) and CO (carbon monoxide) are discharged into the exhaust. At the same time, the oxygen concentration decreases. As a result, the adsorbed NOx is released from the NOx adsorbing device 30 and is immediately reduced by the HC and CO in the exhaust, thereby removing NOx.

  By the way, exhaust gas contains SOx caused by sulfur contained in the fuel. The NOx absorbent of the NOx adsorption device 30 adsorbs not only NOx but also this SOx. Moreover, since SOx is easier to combine with the NOx absorbent than NOx, if SOx is contained in the exhaust gas flowing into the NOx adsorption device 30, even the SOx is adsorbed by the NOx absorbent, and the NOx adsorption device 30 The NOx removal function will be reduced.

  Therefore, in the present invention, in order to prevent SOx from flowing into the NOx adsorption device 3, the SOx adsorption device 20 is disposed upstream of the NOx adsorption device 30 to adsorb SOx in the exhaust gas.

  The configuration of the SOx adsorption device 20 and the SOx removal operation in the exhaust gas by the SOx adsorption device 20 will be described below.

First, the configuration of the SOx adsorption device 20 will be described. The SOx adsorption device 20 is configured by accommodating and holding the SOx adsorption means 21 in a casing 22 formed of, for example, a stainless steel plate or the like. The SOx adsorbing means 21 is formed by supporting a SOx adsorbing material on the surface of a honeycomb-like carrier 23 made of, for example, alumina. For example, manganese dioxide (MnO ₂ ) 23 is used as the SOx adsorbing material. As shown in FIG. 1, a temperature sensor 70 that detects the exhaust gas temperature is attached to the outlet side of the SOx adsorption device 20.

  Here, the requirements that the SOx adsorbing material should have in the exhaust emission control device 1 according to the first embodiment of the present invention will be described. In the exhaust emission control device 1 according to the first embodiment of the present invention, SOx in the exhaust is adsorbed on the SOx adsorbent. Specifically, the SOx in the exhaust and the SOx adsorbent are generated by a chemical reaction. It is adsorbed as a chemical reaction product. Further, when the amount of the adsorbed chemical reaction product reaches a predetermined amount, that is, when the surface of the SOx adsorbing material of the SOx adsorbing device 20 is covered with the chemical reaction product and the SOx adsorbing function is about to decline, fuel injection as a desorption means The fuel is injected from the valve 40, and the chemical reaction product is melted by the heat generated from the combustion to be removed from the SOx adsorption means and removed, whereby the SOx adsorption function of the SOx adsorption device 20 is restored. As described above, the SOx adsorption function by the SOx adsorption device 20 is constantly maintained favorably by repeating each operation of SOx adsorption and chemical reaction product melting and removal, which is SOx.

  For this reason, the SOx adsorbing material is realized by the heat of combustion generated by the fuel injection from the fuel injection valve 40 which is the detachment means, that is, the melting temperature of the chemical reaction product by the SOx adsorbing substance, that is, the atmospheric temperature of the SOx adsorbing means 21. Must be within the possible range. On the other hand, the temperature is required to be equal to or lower than the allowable temperature related to the high temperature strength of the SOx adsorption device 20 component parts, particularly the carrier 23.

Therefore, in the exhaust emission control device 1 according to the first embodiment of the present invention, manganese dioxide (MnO ₂ ) is adopted as the SOx adsorbing material. Manganese dioxide reacts with SOx to produce manganese sulfate (MnSO ₄ ), which is a sulfate. The melting temperature of manganese sulfate (MnSO ₄ ) is 700 ° C. The exhaust temperature during operation of the diesel engine 10, that is, the exhaust temperature near the exhaust manifold 16 outlet is normally 300 ° C. to 500 ° C., and the ambient temperature of the SOx adsorbing means 21 is about 700 ° C. by fuel injection from the fuel injection valve 40. It is easy to increase to. Furthermore, depending on the operating conditions of the diesel engine 10, the exhaust temperature may reach around 700 ° C. (for example, at full load and high speed rotation). In such a case, the manganese sulfate is melted and removed by the exhaust heat. Therefore, the operating frequency of the detaching means can be reduced, and the amount of fuel consumed by the detaching means can be saved.

  Further, a noble metal catalyst 25 such as platinum is also supported on the surface of the carrier 23. By supporting the noble metal catalyst 25 on the SOx adsorption means 21, the fuel injected from the fuel injection valve 40 is reliably oxidized and burned in the SOx adsorption means 21 when the detachment means is operated, thereby reliably melting manganese sulfate. -Can be removed.

Next, the SOx removal operation in the exhaust gas by the SOx adsorption device 20 will be described. When the exhaust gas discharged from the diesel engine 10 flows into the SOx adsorption device 2, the exhaust gas passes through the cells 21a of the SOx adsorption means 21 as indicated by arrows in FIG. SOx contained in the exhaust gas reacts with manganese dioxide 24, which is the SOx adsorbing material supported on the wall surface of each cell 21a, to form manganese sulfate 26 (MnSO ₄ ), and is adsorbed as manganese sulfate 26. The That is, as shown in FIG. 2, the manganese sulfate 26 adheres to and is adsorbed on the surface of the manganese dioxide 24 supported by the SOx adsorption means 21. FIG. 2 is an enlarged cross-sectional view of one cell of the honeycomb-shaped carrier 23 constituting the SOx adsorption means 21. As the amount of SOx adsorbed on the SOx adsorption device 20 increases, that is, the amount of manganese sulfate 26 increases as the operation time of the diesel engine 10 elapses, the surface of the manganese dioxide 24 supported by the SOx adsorption means 21 is covered with manganese sulfate 26. The area expands, and the area where the manganese dioxide 24 itself is exposed, that is, the area of the SOx adsorbable portion decreases.

  By the way, when the SOx adsorption function by the SOx adsorption device 20 is sufficiently exerted, the SOx in the exhaust is adsorbed by the SOx adsorption device 20, and the amount of SOx in the exhaust flowing out of the SOx adsorption device 20 is very small. Therefore, the detection signal from the SOx concentration sensor 60 installed in the middle of the exhaust pipe 18 is also extremely small. However, when the area of the SOx adsorption device 20 in the SOx adsorption device 20 decreases as the operation time of the diesel engine 10 decreases, the amount of SOx passing through the SOx adsorption device 20 without being adsorbed by the SOx adsorption device 20 slightly increases. Correspondingly, the detection signal from the SOx concentration sensor 60 increases. Therefore, by detecting the SOx concentration in the exhaust gas flowing out from the SOx adsorption device 20, the SOx adsorption amount in the SOx adsorption device 20, in other words, the SOx adsorption function state can be determined based on the detected concentration.

  Therefore, in the exhaust emission control device 1 according to the embodiment of the present invention, based on the output signal from the SOx concentration sensor 60, the amount of SOx adsorbed from the SOx adsorption device 20, specifically, the amount of manganese sulfate 26, which is sulfate, is determined. However, when it exceeds a preset allowable value, SOx separation processing, in other words, processing for recovering the SOx adsorption function of the SOx adsorption device 20 is performed. That is, the fuel is injected into the exhaust pipe 17 from the fuel injection valve 40 which is the detachment means, burned in the exhaust pipe 17 and the SOx adsorption device 20, and the manganese sulfate adhering to the SOx adsorption device 20 by the combustion heat. 26 is melted and removed from the surface of the manganese dioxide 24 of the SOx adsorption device 20 and removed. The molten manganese sulfate 26 falls and moves downward in FIG. 1 due to the action of gravity and the action of the fluid force of exhaust, and reaches the collection container 50. The manganese sulfate 26 cools in the collection container 50 to become a solid, and is stored in the collection container 50 as it is.

  Here, the configuration of the collection container 50 will be described. As shown in FIG. 1, the collection container 50 includes a collection container main body 51 and fins 52 that are plate-like members protruding toward the internal space of the collection container main body 51. The collection container main body 51 and the fins 52 are made of a material that is stable and heat resistant to the manganese sulfate 26, such as stainless steel. The fins 52 are fixed to the collection container main body 51 by welding, brazing, or the like. The molten manganese sulfate 26 that has fallen from the SOx adsorption device 20 collides with the fins 52 in the collection container 50, cools and solidifies, and adheres to the fins 52 as it is. The fin 52 promotes the solidification of the molten manganese sulfate 26 and adheres to the finned manganese sulfate 26 so as to reliably hold the manganese sulfate 26 in the collection container 50. Further, by arranging the fins 52 as shown in FIG. 1, it is possible to suppress the manganese sulfate 26 accumulated at the bottom of the collection container 50 from jumping out of the collection container 50 due to engine vibration or the like. .

  Fuel injection by the fuel injection valve 40 is stopped when the exhaust temperature at the outlet of the SOx adsorption device 20 determined based on the detection signal from the temperature sensor 80 reaches the melting temperature of the manganese sulfate 26, that is, 700 ° C. Even after the fuel injection by the fuel injection valve 40 is stopped, the temperature in the SOx adsorption device 20 continues to rise due to the combustion of the fuel passing through the SOx adsorption device 20, and the melting and removal of the manganese sulfate 26 further proceeds. By the separation process described above, the surface area of the manganese dioxide 24 in the SOx adsorption device 20, that is, the area of the SOx adsorbable portion is expanded and restored to the initial state, and the SOx can be adsorbed again. Thereby, the SOx adsorption function of the SOx adsorption device 20 can always be maintained in a good state. Therefore, since SOx contained in the exhaust gas can always be reliably removed upstream of the NOx catalyst 30, the NOx absorption of the NOx catalyst 30 is suppressed by reliably suppressing the adsorption of SOx to the NOx catalyst 30. Capability can always be kept high.

  Next, the SOx removal processing from the SOx adsorption device 20 executed in the control device 80 of the exhaust gas purification device 1 for an internal combustion engine configured as described above will be described with reference to FIG. FIG. 3 is a flowchart showing a specific processing procedure of the SOx detachment processing executed by the control device 80.

  When the diesel engine 10 is started and activated through manual operation of an ignition switch (not shown) by the driver of the automobile, the SOx removal process shown in FIG. 3 is started. When the process is started, the control device 80 first executes the initialization process of step S1.

  Subsequently, the control device 80 performs a SOx concentration determination process as the process of the subsequent step S2. This SOx concentration determination process is executed based on a detection signal from the SOx concentration sensor 60. As a result of the SOx concentration determination process, when it is determined that the SOx concentration is equal to or greater than the allowable value K stored in advance in the control device 80, the control device 80 performs the fuel injection by the fuel injection valve 40 as the processing of the subsequent step S3. Let the jet run.

  Subsequently, in the subsequent step S4, the control device 80 determines that the exhaust temperature at the outlet of the SOx adsorption device 20 determined based on the detection signal of the temperature sensor 70 is a preset temperature stored in the control device 80, that is, sulfuric acid. It is determined whether or not the melting temperature of manganese 26 is 700 ° C. or higher. If the temperature is lower than 700 ° C., the process of step S3 is continued again. On the other hand, when the exhaust gas temperature at the outlet of the SOx adsorption device 20 is 700 ° C. or higher, the fuel injection by the fuel injection valve 40 is stopped as the processing of the subsequent step S5.

  On the other hand, when it is determined that the SOx concentration is equal to or less than the allowable value K stored in advance in the control device 80 as a result of the SOx concentration determination processing in step S2, the control device 80 performs fuel injection as the processing in step S5. The fuel injection by the valve 40 is stopped.

  Next, the operation of the SOx adsorption device 20 of the exhaust emission control device 1 according to the present embodiment will be summarized with reference to the timing charts shown in FIGS. 4A shows the time transition of the exhaust temperature at the outlet of the SOx adsorption device 20 determined based on the temperature sensor 70, and FIG. 4B shows the time transition of the fuel injection valve 40 drive signal in the control device 80. FIG. FIG. 4C is a timing chart showing the time transition of the output signal of the SOx concentration sensor 60, respectively.

  In the description of this figure, it is assumed that the diesel engine 10 is in operation and the operation of the SOx adsorption device 20 has already started.

  Under such a premise, as the operating time of the diesel engine 10 elapses, the amount of SOx adsorbed on the SOx adsorbing device 20, that is, the amount of manganese sulfate 26, which is a sulfate, increases, and at the same time a new amount in the SOx adsorbing device 20 The area of the portion capable of adsorbing SOx gradually decreases. For this reason, the amount of SOx that flows out of the SOx adsorption device 20 without being adsorbed by the SOx adsorption device 20 gradually increases, and the SOx concentration on the downstream side of the SOx adsorption device 20 also increases, so in the exhaust gas that flows out of the SOx adsorption device 20 As shown in FIG. 4C, the output signal of the SOx concentration sensor 60 that detects the SOx concentration of the SOx concentration gradually increases, and eventually, at the time t10, the SOx concentration allowable value K stored in advance in the control device 80. Over. The control device 80 detects this and immediately outputs a drive signal to the fuel injection valve 40 to cause the fuel injection valve 40 to perform fuel injection. The fuel injected from the fuel injection valve 40 into the exhaust pipe 17 is combusted in the SOx adsorption device 20 and the exhaust temperature passing through the SOx adsorption device 20 rises. Therefore, the exhaust temperature at the outlet of the SOx adsorption device 20 starts to rise from time t10 and reaches 700 ° C., that is, the melting temperature of manganese sulfate 26 at time t11. The control device 80 detects this and stops fuel injection by the fuel injection valve 40. However, even after the fuel injection by the fuel injection valve 40 is stopped, the temperature in the SOx adsorbing device 20 rises and decreases due to combustion of fuel passing through the SOx adsorbing device 20, and becomes 700 ° C. or lower after time t12. . At this time, since the exhaust temperature in the SOx adsorption device 20 is 700 ° C. or higher during the period from time t11 to time t12, the manganese sulfate 26 adsorbed in the SOx adsorption device 20 is melted and the manganese dioxide 24 is heated. It separates from the surface, falls downward in FIG. 1, adheres to the fins 52 of the collection container 50, and is captured there. As the manganese sulfate 26 melts and separates from the surface of the manganese dioxide 24, the SOx adsorption function of the SOx adsorption device 20 is restored, so that the detection signal of the SOx concentration sensor 60 decreases during the period from time t11 to time t12. That is, the period from time t10 to time t12 is a leaving process period.

  After time t12, the SOx concentration sensor 60 detection signal gradually increases as the amount of manganese sulfate 26 adsorbed on the SOx adsorption device 20 increases. Eventually, at time t13, the operating conditions of the diesel engine 10 change, for example, full load / high speed rotation state occurs, the exhaust gas temperature rises, and the exhaust gas temperature at the outlet of the SOx adsorption device 20 reaches 700 ° C. During the period up to t14, the exhaust temperature at the outlet of the SOx adsorption device 20 is 700 ° C. or higher. Therefore, during the period from time t13 to time t14, the manganese sulfate 26 adsorbed in the SOx adsorption device 20 is melted and separated from the surface of the manganese dioxide 24, and falls downward in FIG. It adheres to 50 fins 52 and is captured there. Therefore, the detection signal of the SOx concentration sensor 60 decreases during the period from time t13 to time t14.

  After time t14, the detection signal of the SOx concentration sensor 60 gradually increases as the amount of manganese sulfate 26 adsorbed on the SOx adsorption device 20 increases again. Eventually, at time t15, the SOx concentration sensor 60 detection signal exceeds the SOx concentration allowable value K stored in the controller 80 in advance. The control device 80 detects this and immediately starts the separation process, outputs a drive signal to the fuel injection valve 40, and causes the fuel injection valve 40 to perform fuel injection. As a result, the exhaust temperature at the outlet of the SOx adsorption device 20 starts to rise from time t15, reaches 700 ° C. at time t16, and the control device 80 detects this and stops fuel injection by the fuel injection valve 40. On the other hand, during the period from time t16 to time t17, the exhaust temperature in the SOx adsorption device 20 is 700 ° C. or higher, so that the manganese sulfate 26 adsorbed in the SOx adsorption device 20 is melted from the surface of the manganese dioxide 24. 1, falls down in FIG. 1, adheres to the fins 52 of the collection container 50, and is captured there. As the manganese sulfate 26 melts and separates from the surface of the manganese dioxide 24, the SOx adsorption function of the SOx adsorption device 20 is restored, so that the detection signal of the SOx concentration sensor 60 decreases during the period from time t15 to time t17.

  In the exhaust purification device 1 according to the first embodiment of the present invention described above, the exhaust temperature at the outlet of the SOx adsorption device 20 is 700 ° C. at the time when the fuel injection by the fuel injection valve 40 is stopped in the SOx separation process. It is time to reach. However, it is not necessary to limit to this time point, and it may be a time point determined based on other conditions. For example, the fuel injection valve 40 may be a point in time when a predetermined time has elapsed after the start of fuel injection. Or it is good also as the time of the magnitude | size of the detection signal of the SOx density | concentration sensor 60 reaching the predetermined value smaller than the above-mentioned permissible value K.

(Second Embodiment)
In the exhaust gas purification apparatus 1 for an internal combustion engine according to the second embodiment of the present invention, manganese dioxide, which is a SOx adsorbing material, is released from the fuel injection valve 40, and the manganese sulfate 26 is melted and removed by the combustion generated heat. The timing determination method for starting the separation process for recovering the 24 SOx adsorption function is changed. That is, in the exhaust gas purification apparatus 1 for an internal combustion engine according to the first embodiment of the present invention described above, the separation process is executed based on the detection result of the SOx concentration in the exhaust gas flowing out from the SOx adsorption device 20, In the exhaust gas purification apparatus 1 for an internal combustion engine according to the second embodiment of the present invention, the cumulative value of the amount of SOx discharged from the diesel engine 10 from the end of the disengagement process, that is, from the time when the fuel injection by the fuel injection valve 40 is stopped is calculated. Based on this accumulated SOx amount, the timing for performing the separation process is determined.

  Here, a method of calculating the cumulative amount of SOx discharged from the diesel engine 10 will be described.

  The SOx contained in the exhaust of the diesel engine 10 is caused by sulfur contained in the fuel. Therefore, the SOx concentration discharged from the diesel engine 10 can be calculated based on the sulfur concentration of the fuel injected into the diesel engine 10 and the information on the fuel injection amount per predetermined time of the diesel engine 10. The SOx concentration changes according to the change in the fuel injection amount per predetermined time. However, the SOx concentration is discharged from the diesel engine 10 using the accumulated value information of the fuel injection amount to the diesel engine 10 and the SOx concentration described above. The accumulated SOx accumulated amount can be calculated. The sulfur concentration contained in the fuel supplied to the diesel engine 10 is stipulated by a standard (for example, Japanese Industrial Standard, JIS in Japan) determined by related organizations. Pre-stored in the memory area. Further, it can be considered that the SOx adsorption amount in the SOx adsorption device 20 is almost zero immediately after the separation process.

  In the exhaust emission control device 1 according to the second embodiment of the present invention, the calculation of the cumulative fuel injection amount of the diesel engine 10 is started from the time when the detachment process is finished, and the exhaust from the diesel engine 10 is started from the time when the detachment process is finished based on the calculation. The calculated SOx cumulative amount Cs is calculated, and this SOx cumulative amount Cs is compared with the SOx adsorption amount Dk described above in the SOx adsorption device 20, and the separation process is performed when the SOx cumulative amount Cs reaches the SOx adsorption amount Dk. It is configured to start. Thereby, as in the case of the first embodiment, the SOx adsorption function of the SOx adsorption device 20 can be recovered while suppressing the amount of SOx that flows out without being adsorbed by the SOx adsorption device 20 to the minimum. Therefore, since SOx contained in the exhaust gas can always be reliably removed upstream of the NOx catalyst 30, the NOx absorption of the NOx catalyst 30 is suppressed by reliably suppressing the adsorption of SOx to the NOx catalyst 30. Capability can always be kept high.

  Next, the SOx detachment process from the SOx adsorption device 20 executed in the control device 80 of the exhaust gas purification device 1 according to the second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a flowchart showing a specific processing procedure of the SOx detachment processing executed by the control device 80.

  When the diesel engine 10 is started and activated through manual operation of an ignition switch (not shown) by the driver of the automobile, the SOx removal process shown in FIG. 3 is started. When the process is started, the control device 80 first executes the initialization process of step S1.

  Subsequently, in the subsequent step S2, the control device 80 uses the cumulative amount Cs of SOx discharged from the engine from the end of the previous SOx detachment processing and the SOx adsorption device 20 stored in advance in the control device 80. The allowable amount Dk of the SOx adsorption amount is compared. As a result, when it is determined that Cs> Dk, fuel injection by the fuel injection valve 40 is executed as the processing of the subsequent step S3.

  Subsequently, in the subsequent step S4, the control device 80 determines that the exhaust temperature at the outlet of the SOx adsorption device 20 determined based on the detection signal of the temperature sensor 70 is a preset temperature stored in the control device 80, that is, sulfuric acid. It is determined whether or not the melting temperature of manganese 26 is 700 ° C. or higher. If the temperature is lower than 700 ° C., the process of step S3 is continued again. On the other hand, when the exhaust temperature at the outlet of the SOx adsorption device 20 is 700 ° C. or higher, the fuel injection by the fuel injection valve 40 is stopped as the processing of the subsequent step S6.

  On the other hand, the cumulative amount Cs of SO discharged from the engine from the end of the processing of step S2, that is, the previous SOx separation processing, and the allowable value Dk of the SOx adsorption amount in the SOx adsorption device 20 stored in advance in the control device 80. As a result of comparing the above and the result, it is determined that Cs <Dk, as a process of subsequent step S5, from the diesel engine 10 based on the fuel consumption of the diesel engine 10, that is, the fuel amount injected from the fuel injection valve 14. The discharged SOx amount is calculated, and the SOx accumulated amount Cs is updated.

  Subsequently, the control device 80 stops the fuel injection by the fuel injection valve 40 as the processing of the subsequent step S6.

  In the exhaust purification device 1 according to the second embodiment of the present invention described above, the exhaust temperature at the SOx adsorbing device 20 outlet reaches 700 ° C. at the time when the fuel injection by the fuel injection valve 40 is stopped in the SOx removal processing. It is time. However, it is not necessary to limit to this time point, and it may be a time point determined based on other conditions. For example, the fuel injection valve 40 may be a point in time when a predetermined time has elapsed after the start of fuel injection.

In the above first invention described above, in the exhaust gas purification device 1 according to the second embodiment employs a manganese dioxide (MnO ₂₎ as the SOx adsorbent material, not necessarily limited to this, other Different types of SOx adsorbents may be used. For example, cobalt oxide (CoO) may be used. In this case, SOx is adsorbed as cobalt sulfate (CoSO ₄ ), and its melting temperature is 735 ° C. Alternatively, aluminum oxide (also referred to as alumina, Al ₂ O ₃ ) may be used. In this case, SOx is adsorbed as aluminum sulfate (Al ₂ (SO ₄ ) ₃ ), and its melting temperature is 770 ° C. Even if these are used, the same effect as the case where manganese dioxide is used is acquired.

  In addition, although each said embodiment has demonstrated the diesel engine for motor vehicles as an example as an internal combustion engine to which an exhaust gas purification apparatus is applied, the diesel engine of other uses, for example, for railway vehicles, for ships, a stationary generator May be used.

It is a mimetic diagram showing the whole exhaust gas purification device 1 composition by a 1st embodiment of the present invention. 2 is an enlarged cross-sectional view of a SOx adsorption device 20. FIG. It is the flowchart which showed the specific process sequence of the separation process performed in the exhaust gas purification apparatus 1 by 1st Embodiment of this invention. In the exhaust emission control device 1 according to the first embodiment of the present invention, (a) shows the time transition of the exhaust gas temperature at the outlet of the SOx adsorption device 20 determined based on the temperature sensor 70, and (b) shows the control device 80. FIG. 6C is a timing chart showing the time transition of the fuel injection valve 40 drive signal, and FIG. It is the flowchart which showed the specific process sequence of the separation | detachment process performed in the exhaust gas purification apparatus 1 by 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exhaust purification device 10 Diesel engine 11 Cylinder 12 Intake pipe 13 Intake manifold 14 Fuel injection valve 15 Piston 16 Exhaust manifold 17 Exhaust pipe (exhaust passage)
18 Exhaust pipe (exhaust passage)
19 Branch passage (capturing means)
20 SOx adsorption device 21 SOx adsorption means 22 Casing 23 Support 23a Cell 24 Manganese dioxide (SOx adsorption material)
25 Noble metal catalyst 26 Manganese sulfate (chemical reaction product)
30 NOx adsorption device (NOx catalyst)
31 NOx adsorption means 32 Casing 40 Fuel injection valve (detachment means)
50 Collection container (capture means)
51 Collection container body 52 Fin (plate-like member)
60 SOx concentration sensor (SOx concentration detection means)
70 Temperature sensor 80 Control device Cs SOx cumulative amount Dk SOx adsorption amount allowable value K Allowable value

Claims (8)

A NOx catalyst provided in the exhaust passage of the internal combustion engine and adsorbing NOx in the exhaust;
An exhaust purification device comprising an SOx adsorption device provided upstream of the NOx catalyst in the exhaust passage,
The SOx adsorption device adsorbs SOx in exhaust gas as a chemical reaction product between SOx and the SOx adsorbent,
Detaching means for detaching the chemical reaction product from the SOx adsorbing device by melting the chemical reaction product by reaching a melting temperature;
An exhaust gas purification apparatus comprising: a capture unit that captures and stores the chemical reaction product that is provided downstream of the SOx adsorption device and upstream of the NOx catalyst in the exhaust passage and separated from the SOx adsorption device. . The detaching means is a fuel injection valve provided on the upstream side of the exhaust passage so as to supply fuel into the exhaust passage.
2. The exhaust emission control device according to claim 1, wherein the chemical reaction product is melted by heat generated by combustion of the fuel supplied from the fuel injection valve to be separated from the SOx adsorption device. SOx concentration detection means for detecting the SOx concentration in the exhaust gas flowing out from the SOx adsorption device,
3. The exhaust emission control device according to claim 1, wherein the operation of the detachment unit is controlled based on the SOx concentration determined by the SOx concentration detection unit.   The exhaust emission control device according to claim 3, wherein the separation means is operated when the SOx concentration determined by the SOx concentration detection means is a predetermined value or more. SOx concentration calculation means for calculating the SOx concentration using information on the fuel injection amount per predetermined time;
Cumulative SOx amount calculating means for calculating a cumulative SOx amount discharged from the internal combustion engine based on the SOx concentration calculated by the SOx concentration calculating means;
3. The exhaust emission control device according to claim 1, wherein the operation of the detachment unit is controlled based on a calculation result by the cumulative SOx amount calculation unit.   6. The exhaust emission control device according to claim 5, wherein when the amount of accumulated SOx discharged from the internal combustion engine reaches a predetermined value from the time when the operation of the detachment means ends, the detachment means is operated. The supplementary means is communicated by a branch passage provided in a branch flow direction branched from the main flow direction of the exhaust passage from the SOx adsorption device to the NOx catalyst, and traps and stores the chemical reaction product. A collection container,
The exhaust passage and the branch passage are connected so that the exhaust flow direction when the exhaust gas flowing out from the SOx adsorbing device goes to the inlet of the collection container is a direction from the vertical direction upward to the downward direction. The exhaust emission control device according to any one of claims 1 to 6, wherein the exhaust emission control device is characterized in that The collection container is composed of a collection container main body connected to the branch passage and a plate-like member protruding from the collection container main body toward the internal space of the collection container,
The exhaust purification apparatus according to claim 7, wherein the plate-like member is disposed so that the chemical reaction product that has reached the collection chamber can be attached thereto.

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