JP4586629B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine that is provided in an exhaust passage of the internal combustion engine and purifies harmful substances in exhaust gas.

  Generally, a three-way catalyst is provided in an exhaust passage of an internal combustion engine as an exhaust purification device that purifies harmful substances in exhaust gas. This three-way catalyst purifies harmful substances such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) contained in the exhaust gas. When in the vicinity of the fuel ratio (stoichiometric), harmful substances in the exhaust gas can be efficiently purified.

  This three-way catalyst is based on alumina and carries a precious metal with platinum, palladium and rhodium added. Rhodium has a high ability to reduce nitrogen oxides, and platinum and palladium are hydrocarbons and carbon monoxide. High oxidation ability. In an internal combustion engine fueled with gasoline, the balance of hydrocarbons, carbon monoxide, and nitrogen oxides in the exhaust gas composition is good, so the oxidation reaction of hydrocarbons and carbon monoxide and the reduction reaction of nitrogen oxides Can be performed simultaneously.

  As a catalyst for purifying exhaust gas of an internal combustion engine burned under a combustion condition in which an air-fuel ratio is alternately repeated between a lean atmosphere and a stoichiometric or rich atmosphere, there is one described in Patent Document 1 below.

JP 2004-337773 A

  However, the above-described three-way catalyst has a problem that the exhaust gas purification performance is deteriorated due to deterioration of the catalyst due to a lean atmosphere, high temperature, phosphorus poisoning, and the like due to long-term use. That is, when the driver returns the accelerator pedal and the load on the internal combustion engine is reduced when the vehicle is traveling at high speed, the fuel injection is temporarily stopped by the fuel cut, and the exhaust gas becomes a lean atmosphere. Further, the electronic control unit controls the fuel injection amount so that the air-fuel ratio becomes stoichiometric. However, if a deviation occurs in the air-fuel ratio control for some reason, the exhaust gas becomes a lean atmosphere. When the exhaust gas is in a lean atmosphere as described above, the three-way catalyst is deteriorated by causing grain growth of the supported noble metal due to oxygen in the exhaust gas.

  Further, when the high-load operation of the internal combustion engine is continued, the exhaust gas becomes high temperature, and the exhaust gas that has become high temperature deteriorates by causing grain growth of the supported noble metal. For this reason, it is conceivable to suppress the increase in temperature by disposing the three-way catalyst downstream of the exhaust passage and away from the internal combustion engine. However, if the three-way catalyst is disposed downstream of the exhaust passage, The activation of the three-way catalyst is delayed at the time of warming up and the purification performance is deteriorated. Furthermore, the lubricating oil contains phosphorus, and when this phosphorus burns with the fuel, this phosphorus is mixed into the exhaust gas, and when the exhaust gas containing phosphorus is treated with a three-way catalyst, the phosphorus becomes the catalyst surface. And the purification performance deteriorates.

  In the exhaust gas purification catalyst described in Patent Document 1 described above, a composite oxide in which ceria and alumina having an oxygen storage function are dispersed upstream of the NOx storage reduction catalyst provided in the exhaust passage. However, since the exhaust gas always flows into the catalyst having ceria, for example, when the internal combustion engine is warmed up, the upstream catalyst is exhausted. Due to the gas flow resistance, the downstream catalyst cannot be warmed up early, and the activation of the catalyst is delayed, resulting in a reduction in purification performance.

  An object of the present invention is to provide an exhaust gas purification apparatus for an internal combustion engine that solves such a problem and that improves exhaust gas purification performance by suppressing deterioration of the catalyst.

In order to solve the above-described problems and achieve the object, an exhaust purification device for an internal combustion engine of the present invention is a first exhaust having an oxygen storage function provided in an exhaust gas passage and capable of storing oxygen components in the exhaust gas. A purification catalyst, and a second exhaust purification catalyst provided in the exhaust gas passage downstream of the first exhaust purification catalyst to purify harmful substances in the exhaust gas, wherein the first exhaust purification catalyst comprises an oxygen storage a first passage having no function, and a second passage having an oxygen storage function, the passage change-over means for guiding the first passage of the exhaust gas during warm-up of at least the internal combustion engine is provided, said passage switching means The exhaust gas is guided to the second passage when the air-fuel ratio of the exhaust gas of the internal combustion engine is a lean atmosphere, and when the air-fuel ratio of the exhaust gas is a lean atmosphere, the exhaust gas is sent to the second passage by the passage switching means. Led to the aisle , Is characterized in that the guides in the first passage of the exhaust gas for a predetermined period the exhaust gas from the rich atmosphere.

  In the exhaust gas purification apparatus for an internal combustion engine of the present invention, a first on-off valve that opens and closes the first passage and a second on-off valve that opens and closes the second passage are provided as the passage switching means, and the internal combustion engine is warmed up. In some cases, the first passage is opened by the first on-off valve, and the second passage is closed by the second on-off valve.

  In the exhaust gas purification apparatus for an internal combustion engine of the present invention, a first on-off valve that opens and closes the first passage is provided as the passage switching means, and the first passage is opened by the first on-off valve when the internal combustion engine is warmed up. It is characterized by opening.

  In the exhaust emission control device for an internal combustion engine according to the present invention, the first exhaust purification catalyst is provided with the first passage passing through a central portion of the second passage.

According to the exhaust purification device for an internal combustion engine of the present invention, the first exhaust purification catalyst having an oxygen storage function capable of storing oxygen components in the exhaust gas, and the exhaust gas provided in the downstream side of the first exhaust purification catalyst. A second exhaust purification catalyst for purifying the harmful substances, and the first exhaust purification catalyst is provided with a first passage that does not have an oxygen storage function and a second passage that has an oxygen storage function, and at least a warming of the internal combustion engine. A passage switching means for guiding the exhaust gas to the first passage during operation is provided . The passage switching means guides the exhaust gas to the second passage when the air-fuel ratio of the exhaust gas of the internal combustion engine is in a lean atmosphere, and When the air-fuel ratio is a lean atmosphere, the passage switching means guides the exhaust gas to the second passage, and then the exhaust gas is led to the first passage after the exhaust gas is rich for a predetermined period. Therefore, when the internal combustion engine is warmed up, the exhaust gas reaches the second exhaust purification catalyst through the first passage having no oxygen storage function, and the first exhaust purification catalyst does not become the flow resistance of the exhaust gas. Since the second exhaust purification catalyst flows smoothly into the second exhaust purification catalyst, the second exhaust purification catalyst can be appropriately heated by the exhaust gas to be activated early. On the other hand, after the internal combustion engine is warmed up, the exhaust gas is stored in oxygen. The second exhaust purification catalyst is reached through the second passage having the function, and even if the air-fuel ratio of the exhaust gas is lean, the second exhaust gas is stored in the second passage after the oxygen in the exhaust gas is occluded. Since it flows into the exhaust purification catalyst, the deterioration of the second exhaust purification catalyst due to the exhaust gas can be suppressed, and as a result, the exhaust purification performance can be improved.

  Embodiments of an exhaust emission control device for an internal combustion engine according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  FIG. 1 is a schematic configuration diagram illustrating an exhaust gas purification apparatus for an internal combustion engine according to a first embodiment of the present invention. FIG. 2 is a partially cutaway perspective view of a first catalyst device in the exhaust gas purification apparatus for the internal combustion engine according to the first embodiment. FIG. 3 is a cross-sectional view of the first catalyst device in the exhaust gas purification apparatus for the internal combustion engine of the first embodiment, and FIG. 4 is a flowchart showing the exhaust gas purification control in the exhaust gas purification apparatus for the internal combustion engine of the first embodiment.

  In the exhaust gas purification apparatus for an internal combustion engine of the first embodiment, as shown in FIG. 1, the engine 10 as the internal combustion engine is a cylinder injection type multi-cylinder type, and a cylinder head 12 is fastened on a cylinder block 11. A piston 14 is fitted in a plurality of cylinder bores 13 formed in the cylinder block 11 so as to be movable up and down. A crankcase 15 is fastened to the lower part of the cylinder block 11, and a crankshaft 16 is rotatably supported in the crankcase 15. Each piston 14 is connected to the crankshaft 16 via a connecting rod 17. Has been.

  The combustion chamber 18 includes a cylinder block 11, a cylinder head 12, and a piston 14, and the combustion chamber 18 has a pent roof shape that is inclined so that the central portion of the upper portion (the lower surface of the cylinder head 12) is raised. Yes. An intake port 19 and an exhaust port 20 are formed on the upper portion of the combustion chamber 18, that is, the lower surface of the cylinder head 12, and the intake valve 19 and the exhaust valve 20 are opposed to the intake port 19 and the exhaust port 20. The lower end portions of 22 are respectively positioned. The intake valve 21 and the exhaust valve 22 are supported by the cylinder head 12 so as to be movable in the axial direction, and are urged and supported in a direction to close the intake port 19 and the exhaust port 20. An intake camshaft 23 and an exhaust camshaft 24 are rotatably supported by the cylinder head 12, and the intake cam 25 and the exhaust cam 26 are connected to upper ends of the intake valve 21 and the exhaust valve 22 via a roller rocker arm (not shown). In contact with the part.

  Therefore, when the intake camshaft 23 and the exhaust camshaft 24 rotate in synchronization with the engine 10, the intake cam 25 and the exhaust cam 26 operate the roller rocker arm, and the intake valve 21 and the exhaust valve 22 move up and down at a predetermined timing. Thus, the intake port 19 and the exhaust port 20 can be opened and closed, and the intake port 19 and the combustion chamber 18 can be communicated with each other.

  A surge tank 28 is connected to the intake port 19 via an intake manifold 27, and an intake pipe 29 is connected to the surge tank 28, and an air cleaner 30 is attached to an air intake port of the intake pipe 29. . An electronic throttle device 32 having a throttle valve 31 is provided on the downstream side of the air cleaner 30. The cylinder head 12 is provided with an injector 33 that injects fuel directly into the combustion chamber 18. The injector 33 is located on the intake port 19 side and is inclined at a predetermined angle in the vertical direction. Further, the cylinder head 12 is equipped with a spark plug 34 that is positioned above the combustion chamber 18 and ignites the air-fuel mixture.

  On the other hand, an exhaust pipe 36 is connected to the exhaust port 20 via an exhaust manifold 35. The exhaust pipe 36 is a first catalyst for adsorbing harmful substances such as oxygen and phosphorus contained in the exhaust gas. A device (first exhaust purification catalyst) 37 and a second catalyst device (second exhaust purification catalyst) 38 for purifying harmful substances such as HC, CO, NOx contained in the exhaust gas are mounted.

  The first catalyst device 37 has an oxygen storage function capable of storing oxygen components in the exhaust gas. That is, in the first catalyst device 37, as shown in detail in FIGS. 2 and 3, a small-diameter pipe 52 having a cylindrical shape is disposed in the center of a large-diameter housing 51 having a cylindrical shape. Thus, the first passage 53 is formed in the pipe 52 and the second passage 54 is formed between the housing 51 and the pipe 52. A catalyst portion 55 having a honeycomb shape is formed in the second passage 54, and ceria having an oxygen storage function is supported on the catalyst portion 55. Accordingly, a first passage 53 having no oxygen storage function and a second passage 54 having an oxygen storage function are formed in the first catalyst device 37.

  On the downstream side of the first passage 53, a butterfly-type first on-off valve 56 that opens and closes the first passage 53 is provided at the rear end of the pipe 52, while on the downstream side of the second passage 54. The second opening / closing valve 57 is provided at the rear end of the housing 51 and the pipe 52 to form a ring shape that opens and closes the second passage 54 and is biased and supported by a spring 58. Therefore, exhaust gas can be introduced into the first passage 53 by opening the first passage 53 by the first opening / closing valve 56 and closing the second passage 54 by the second opening / closing valve 57, so that the first opening / closing valve The exhaust gas can be introduced into the second passage 54 by closing the first passage 53 with the valve 56 and opening the second passage 54 with the second on-off valve 57. In this case, the first on-off valve 56 and the second on-off valve 57 constitute a passage switching means.

  On the other hand, the second catalyst device 38 purifies harmful substances in the exhaust gas, and specifically, hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides contained in the exhaust gas. This is a three-way catalyst that purifies harmful substances such as (NOx), and can effectively purify harmful substances in exhaust gas particularly when the air-fuel ratio is in the vicinity of the stoichiometric air-fuel ratio (stoichiometric). . This three-way catalyst is based on alumina and carries a noble metal to which platinum, palladium, and rhodium are added. The oxidation reaction of hydrocarbon and carbon monoxide and the reduction reaction of nitrogen oxide are performed simultaneously. be able to.

As shown in FIG. 1, an electronic control unit (ECU) 40 is mounted on the vehicle, and the ECU 40 can control the injector 33, the spark plug 34, and the like based on the engine operating state. That is, an air flow sensor 41 and an intake air temperature sensor 42 are mounted on the upstream side of the intake pipe 29, and the measured intake air amount and intake air temperature are output to the ECU 40. The electronic throttle device 32 is equipped with a throttle position sensor 43 and outputs the current throttle opening to the ECU 40. Further, the crank angle sensor 44 outputs the detected crank angle of each cylinder to the ECU 40, and the ECU 40 determines each stroke of intake, compression, expansion (explosion), and exhaust in each cylinder based on the detected crank angle. At the same time, the engine speed is calculated. The cylinder block 11 is provided with a water temperature sensor 45 that detects the engine cooling water temperature, and outputs the detected engine cooling water temperature to the ECU 40. Further, an upstream side of the second catalyst device 38 in the exhaust pipe 36 is provided with an O ₂ sensor 46 that detects the oxygen concentration of the exhaust gas, and outputs the current oxygen concentration of the exhaust gas to the ECU 40. Accordingly, the ECU 40 determines the engine such as the detected intake air amount, intake temperature, throttle opening (or accelerator opening detected by an accelerator position sensor not shown), engine speed, engine cooling water temperature, oxygen concentration in the exhaust gas, and the like. Based on the operating state, the fuel injection amount, injection timing, ignition timing, and the like are determined.

  The ECU 40 can control the first on-off valve 56 and the second on-off valve 57 described above based on the engine operating state. That is, the engine cooling water temperature detected by the water temperature sensor 45 is input to the ECU 40, and the ECU 40 determines whether the engine 10 is in the start warm-up state based on the engine cooling water temperature, that is, in the fast idle state. Determine if. When the engine 10 is in the fast idle state, the first passage 53 is opened by the first opening / closing valve 56, and the second passage 54 is closed by the second opening / closing valve 57, so that the exhaust gas is passed to the first passage 53. When it is introduced and in a state other than the fast idle state, the first passage 53 is closed by the first opening / closing valve 56, and the second passage 54 is opened by the second opening / closing valve 57, so that the exhaust gas is passed through the catalyst portion of the second passage 54. 55 is introduced.

  Here, the exhaust purification control by the exhaust purification device of the internal combustion engine of the first embodiment will be described in detail based on the flowchart of FIG.

  In the exhaust purification control of the engine 10, as shown in FIG. 4, in step S11, the ECU 40 reads the engine cooling water temperature detected by the water temperature sensor 45, and in step S12, the engine cooling water temperature is read based on the engine cooling water temperature read by the ECU 40. Determine whether 10 is in the fast idle state. If it is determined that the engine 10 is in the fast idle state, the first passage 53 is opened by the first opening / closing valve 56 and the second passage 54 is closed by the second opening / closing valve 57 in step S13. The exhaust gas is introduced into the first passage 53.

  Therefore, when the engine 10 is in a warm-up state, the exhaust gas discharged from the combustion chamber 18 reaches the first catalyst device 37 through the exhaust pipe 36, and here, the first passage 53 that does not have an oxygen storage function. The first catalyst device 37 (catalyst portion 55 of the second passage 54) does not become the flow resistance of the exhaust gas, and the heat of the exhaust gas is released. However, the exhaust gas smoothly flows into the second catalyst device 38 without a large temperature drop. Therefore, the second catalytic device 38 can be appropriately heated by the high-temperature exhaust gas and activated early.

  On the other hand, when the warm-up is completed after a predetermined time has elapsed since the engine 10 was started, the ECU 40 determines in step S12 that the engine 10 is not in the fast idle state. Then, in step S 14, the first passage 53 is closed by the first opening / closing valve 56, and the second passage 54 is opened by the second opening / closing valve 57, thereby introducing the exhaust gas into the catalyst portion 55 of the second passage 54. To do.

  Therefore, after the engine 10 is warmed up, the exhaust gas discharged from the combustion chamber 18 reaches the first catalyst device 37 through the exhaust pipe 36, and then passes through the second passage 54 having an oxygen storage function. Even when the air-fuel ratio of the exhaust gas reaches a lean atmosphere, the oxygen in the exhaust gas is occluded by the catalyst portion 55 of the second passage 54 in the first catalyst device 37 even if the air-fuel ratio of the exhaust gas reaches a lean atmosphere. 2 flows into the catalyst device 38. Therefore, the air-fuel ratio of the exhaust gas becomes near the stoichiometric range, and the deterioration of the second catalyst device 38 due to this exhaust gas can be suppressed.

  Further, since the exhaust gas reaches the second catalyst device 38 after passing through the second passage 54 on the outer peripheral side of the first catalyst device 37, the heat of the high-temperature exhaust gas is exposed to the outside through the housing 51 of the first catalyst device 37. It will be discharged | emitted, and the thermal deterioration of the 2nd catalyst apparatus 38 by this exhaust gas can be suppressed. Further, since the exhaust gas passes through the catalyst portion 55 of the second passage 54 in the first catalyst device 37 and reaches the second catalyst device 38, even if lubricating oil containing phosphorus is mixed into the fuel and burned, the exhaust gas is exhausted. The phosphorus contained in the gas is adsorbed by the catalyst unit 55, and phosphorus poisoning of the second catalyst device 38 by the exhaust gas can be suppressed.

  As described above, in the exhaust gas purification apparatus for the internal combustion engine according to the first embodiment, the exhaust pipe 36 of the engine 10 has the first catalyst device 37 for adsorbing oxygen, phosphorus, etc. contained in the exhaust gas and the exhaust gas. A second catalytic device 38 for purifying the contained HC, CO, NOx, etc. is mounted, a first passage 53 is formed in the first catalytic device 37 and a second passage 54 is formed outside thereof, and a second passage 54 is formed. The first and second on-off valves 56 and 57 are provided in the first and second passages 53 and 54. At least when the engine 10 is warmed up, the first on-off valve 56 While the first passage 53 is opened, the second passage 54 is closed by the second on-off valve 57 so that the exhaust gas reaches the second catalytic device 38 through the first passage 53.

  Therefore, when the engine 10 is warmed up, the exhaust gas discharged from the combustion chamber 18 reaches the second catalytic device 38 after passing through the first passage 53 having no oxygen storage function in the first catalytic device 37. The catalyst portion 55 of the second passage 54 does not cause the flow resistance or temperature decrease factor of the exhaust gas, and the exhaust gas smoothly flows into the second catalyst device 38 without a large temperature decrease. The two-catalyst device 38 can be appropriately heated and activated early.

  On the other hand, after the engine 10 is warmed up, the exhaust gas discharged from the combustion chamber 18 reaches the second catalyst device 38 after passing through the second passage 54 having the oxygen storage function in the first catalyst device 37. Even when the air-fuel ratio of the exhaust gas becomes a lean atmosphere, oxygen in the exhaust gas is occluded by the catalyst portion 55 of the second passage 54 in the first catalyst device 37 and then flows into the second catalyst device 38. The air-fuel ratio becomes near the stoichiometric range, and the deterioration of the second catalytic device 38 due to the exhaust gas can be suppressed.

  Further, after the engine 10 is warmed up, the exhaust gas passes through the second passage 54 on the outer peripheral side of the first catalyst device 37, so that the heat of the exhaust gas is released to the outside through the housing 51, and the high-temperature exhaust gas. The thermal deterioration of the second catalyst device 38 due to the above can be suppressed. Further, since the exhaust gas passes through the catalyst portion 55 of the second passage 54 in the first catalyst device 37, phosphorus contained in the exhaust gas is adsorbed by the catalyst portion 55, and the second catalyst device 38 by this exhaust gas is used. Can suppress phosphorus poisoning.

  FIG. 5 is a sectional view of the first catalyst device in the exhaust gas purification apparatus for an internal combustion engine according to the second embodiment of the present invention, and FIG. 6 is a flowchart showing the exhaust gas purification control in the exhaust gas purification apparatus for the internal combustion engine according to the second embodiment. . The internal combustion engine to which the exhaust gas purifying apparatus for the internal combustion engine of the second embodiment is applied is substantially the same as that described in the first embodiment, so that it will be described with reference to FIG. 1 and the one described in the first embodiment. The members having the same functions as those in FIG.

  In the exhaust gas purification apparatus for an internal combustion engine according to the second embodiment, as shown in FIGS. 1 and 5, a first catalyst device that adsorbs harmful substances such as oxygen and phosphorus contained in the exhaust gas is disposed in the exhaust pipe 36 ( A first exhaust purification catalyst) 61 (see FIG. 5) and a second catalytic device 38 for purifying harmful substances such as HC, CO, NOx contained in the exhaust gas are mounted.

  In the first catalyst device 61, as shown in detail in FIG. 5, the pipe 52 is disposed in the center of the housing 51, thereby forming the first passage 53 in the pipe 52 and the housing 51. A second passage 54 is formed between the pipe 52 and the pipe 52. A catalyst portion 55 having a honeycomb shape is formed in the second passage 54, and ceria having an oxygen storage function is supported on the catalyst portion 55. A first on-off valve 56 that opens and closes the first passage 53 is provided on the downstream side of the first passage 53. Therefore, exhaust gas can be introduced into the first passage 53 by opening the first passage 53 by the first on-off valve 56, and exhaust gas can be introduced by closing the first passage 53 by the first on-off valve 56. Can be introduced into the second passage 54. In this case, the first opening / closing valve 56 constitutes a passage switching means.

  As shown in FIGS. 1 and 5, the ECU 40 introduces exhaust gas into the first passage 53 by opening the first passage 53 by the first on-off valve 56 when the engine 10 is in the fast idle state. When the vehicle is not in the fast idle state, the first passage 53 is closed by the first on-off valve 56 so that the exhaust gas is introduced into the catalyst portion 55 of the second passage 54.

  Here, the exhaust gas purification control by the exhaust gas purification apparatus of the internal combustion engine of the second embodiment will be described in detail based on the flowchart of FIG.

  In the exhaust gas purification control of the engine 10, as shown in FIG. 6, in step S21, the ECU 40 reads the engine cooling water temperature detected by the water temperature sensor 45, and in step S22, the engine 10 is fast based on this engine cooling water temperature. It is determined whether the engine is in an idle state (engine warm-up state). If it is determined that the engine 10 is in the fast idle state, exhaust gas is introduced into the first passage 53 by opening the first passage 53 with the first on-off valve 56 in step S23. Therefore, when the engine 10 is in the warm-up state, the exhaust gas reaches the second catalyst device 38 after passing through the first passage 53 having no oxygen storage function in the first catalyst device 37, and the second passage. The catalyst portion 55 of the exhaust gas 54 does not become the flow resistance of the exhaust gas, the heat of the exhaust gas is not released, and the exhaust gas flows smoothly into the second catalyst device 38 without a large temperature drop. Therefore, the second catalytic device 38 can be appropriately heated by the high-temperature exhaust gas and activated early.

  On the other hand, when the warm-up is completed after a predetermined time has elapsed since the engine 10 was started, the ECU 40 determines in step S22 that the engine 10 is not in the fast idle state. Then, the exhaust gas is introduced into the catalyst portion 55 of the second passage 54 by closing the first passage 53 by the first opening / closing valve 56 in step S24. Therefore, after the engine 10 is warmed up, the exhaust gas passes through the second passage 54 having the oxygen storage function in the first catalyst device 37 and then reaches the second catalyst device 38, and the catalyst in the second passage 54. The oxygen in the exhaust gas is occluded in the part 55 and then flows into the second catalytic device 38. Therefore, the air-fuel ratio of the exhaust gas becomes near the stoichiometric range, and the deterioration of the second catalyst device 38 due to this exhaust gas can be suppressed.

  At this time, since the heat of the high-temperature exhaust gas is released to the outside through the housing 51 of the first catalyst device 37, thermal degradation of the second catalyst device 38 due to the high-temperature exhaust gas can be suppressed. Furthermore, since phosphorus contained in the exhaust gas is adsorbed by the catalyst unit 55, phosphorus poisoning of the second catalyst device 38 by the exhaust gas can be suppressed.

  When the engine 10 is in the fast idle state and the first passage 53 is opened by the first on-off valve 56, the second passage 54 is opened, but the second passage 54 has a catalyst portion 55 having a honeycomb shape. Since the flow resistance is larger than that of the first hollow passage 53 having nothing, the exhaust gas flows into the first passage 53 without substantially flowing into the second passage 54.

  As described above, in the exhaust gas purification apparatus for an internal combustion engine according to the second embodiment, the exhaust gas in the exhaust pipe 36 of the engine 10 is adsorbed with the first catalyst device 37 for adsorbing oxygen, phosphorus, and the like contained in the exhaust gas. A second catalytic device 38 for purifying the contained HC, CO, NOx, etc. is mounted, a first passage 53 is formed in the first catalytic device 37 and a second passage 54 is formed outside thereof, and a second passage 54 is formed. Is provided with a catalyst portion 55 carrying ceria, a first opening / closing valve 56 is provided in the first passage 53, and at least when the engine 10 is warmed up, the first passage 53 is opened by the first opening / closing valve 56, thereby The gas reaches the second catalytic device 38 through the first passage 53.

  Accordingly, when the engine 10 is warmed up, the exhaust gas passes through the first passage 53 of the first catalytic device 37 and then reaches the second catalytic device 38, so that the high-temperature exhaust gas smoothly flows into the second catalytic device 38. The second catalyst device 38 can be appropriately heated and activated early. On the other hand, after the engine 10 is warmed up, the exhaust gas passes through the first catalyst device 37 and the second passage 54 and then reaches the second catalyst device 38, so that the oxygen contained in the catalyst portion 55 is stored in the exhaust gas in the lean atmosphere. Thus, deterioration of the second catalyst device 38 due to the exhaust gas can be suppressed.

  Further, in the exhaust gas purification apparatus for an internal combustion engine according to the second embodiment, the first catalyst device 37 forms the second passage 54 having the first passage 53 and the catalyst portion 55, and the first passage 53 has only the first passage 53. A first opening / closing valve 56 is provided, and at least when the engine 10 is warmed up, the first opening / closing valve 56 opens the first passage 53 so that the exhaust gas passes through the first passage 53. Therefore, the exhaust gas passage in the first catalyst device 37 can be switched according to the operating state of the engine 10 with a simple configuration, and the device can be simplified.

  FIG. 7 is a flowchart showing the exhaust purification control in the exhaust purification device of the internal combustion engine according to the third embodiment of the present invention. The exhaust gas purification apparatus for an internal combustion engine according to the third embodiment is substantially the same as that described in the first embodiment, so that it will be described with reference to FIGS. 1 to 3 and the same as that described in the first embodiment. The members having a function are denoted by the same reference numerals, and redundant description is omitted.

  In the exhaust gas purification apparatus for an internal combustion engine according to the third embodiment, as shown in FIGS. 1 to 3, the exhaust pipe 36 has a first catalyst device 37 for adsorbing harmful substances such as oxygen and phosphorus contained in the exhaust gas. And a second catalytic device 38 for purifying harmful substances such as HC, CO and NOx contained in the exhaust gas. In the first catalyst device 37, a second passage 54 is formed outside the first passage 53, and a catalyst portion 55 having a honeycomb shape is formed in the second passage 54. The catalyst portion 55 has an oxygen storage function. The ceria which has is carried. A first on-off valve 56 that opens and closes the first passage 53 is provided on the downstream side of the first passage 53, while a second that opens and closes the second passage 54 on the downstream side of the second passage 54. An on-off valve 57 is provided.

  In this embodiment, the ECU 40 closes the first passage 53 by the first on-off valve 56 when the exhaust gas is in a lean air-fuel ratio or a high temperature state higher than a predetermined temperature, while the second on-off valve The second passage 54 is opened by 57 so that the exhaust gas is introduced into the catalyst portion 55 of the second passage 54 and the oxygen in the exhaust gas is occluded before flowing into the second catalyst device 38. In addition, after the exhaust gas has become a lean air-fuel ratio or high temperature and the catalyst portion 55 of the second passage 54 performs the occlusion processing of oxygen in the exhaust gas, the catalyst portion 55 is reduced. In this case, when the driver returns the accelerator pedal and the engine load is reduced when the vehicle is traveling at high speed, the ECU 40 temporarily stops fuel injection by fuel cut, so the air-fuel ratio of the exhaust gas becomes a lean atmosphere. Further, when the high load state of the engine 10 continues, the temperature of the exhaust gas rises abnormally and becomes a high temperature state. The high temperature state of the exhaust gas is a temperature range in which the temperature of the exhaust gas is too high and the second catalytic device 38 is deteriorated.

  Here, the exhaust gas purification control by the exhaust gas purification apparatus of the internal combustion engine of the third embodiment will be described in detail based on the flowchart of FIG.

In the exhaust purification control of the engine 10, as shown in FIG. 7, in step S31, the ECU 40 determines whether the air-fuel ratio of the exhaust gas is in a lean atmosphere or is in a high temperature state equal to or higher than a predetermined temperature. . In this case, whether or not the air-fuel ratio of the exhaust gas is a lean atmosphere is determined based on the oxygen concentration in the exhaust gas detected by the O ₂ sensor. Further, the temperature of the exhaust gas is estimated based on the combustion state of the engine 10 (intake air amount, fuel injection amount, engine load, etc.), or detected by attaching a temperature sensor to the exhaust pipe. What is necessary is just to determine high temperature.

  If it is determined in step S31 that the air-fuel ratio of the exhaust gas is a lean atmosphere or is in a high temperature state, the first passage 53 is closed by the first on-off valve 56 in step S32, and the second Exhaust gas is introduced into the catalyst portion 55 of the second passage 54 by opening the second passage 54 with the on-off valve 57. Therefore, when the air-fuel ratio of the exhaust gas is a lean atmosphere, the exhaust gas reaches the second catalyst device 38 after passing through the second passage 54 having the oxygen storage function in the first catalyst device 37, and the second passage. After the oxygen in the exhaust gas is occluded by the catalyst unit 55 of 54, it flows into the second catalyst device 38. Therefore, the air-fuel ratio of the exhaust gas becomes near the stoichiometric range, and the deterioration of the second catalyst device 38 due to this exhaust gas can be suppressed. Further, when the exhaust gas is in a high temperature state, the exhaust gas passes through the second passage 54 located outside the first catalyst device 37 and then reaches the second catalyst device 38, and the exhaust gas passes through the second passage 54. Is released to the outside and then flows into the second catalytic device 38. Therefore, the temperature of the exhaust gas is reduced, and the thermal deterioration of the second catalyst device 38 due to the high temperature exhaust gas can be suppressed.

  On the other hand, if it is determined that the air-fuel ratio of the exhaust gas is not a lean atmosphere and is not in a high temperature state, in step S33, the air-fuel ratio of the exhaust gas was in a lean atmosphere or a high temperature state last time and the second passage It is determined whether or not the oxygen storage process in the exhaust gas has been performed by the catalyst unit 55 of 54. Here, if it is determined last time that the oxygen storage process in the exhaust gas was performed, the process proceeds to step S35. If it is determined that the oxygen storage process in the exhaust gas has not been performed last time, it is determined in step S34 whether the reduction process for the catalyst unit 55 in the second passage 54 has been completed. If it is determined that the reduction process has not ended, the process proceeds to step S35. In step S35, the engine 10 is richly operated for a predetermined time, whereby exhaust gas in a rich atmosphere is caused to flow to the catalyst portion 55 of the second passage 54, and reduction processing of the catalyst portion 55 (ceria) of the second passage 54 is executed. To do. In step S36, when the reduction processing time of the catalyst unit 55 reaches a predetermined time, the process proceeds to step S32.

  Thereafter, in step S31, it is determined that the air-fuel ratio of the exhaust gas is neither a lean atmosphere nor a high temperature state. In step S33, it is determined that the oxygen storage process in the exhaust gas has not been performed last time. In step S34, the catalyst is If it is determined that the reduction process of the unit 55 has been completed, the first passage 53 is opened by the first opening / closing valve 56 and the second passage 54 is closed by the second opening / closing valve 57 in step S37, thereby exhaust gas. Is introduced into the first passage 53. Accordingly, the exhaust gas reaches the second catalyst device 38 after passing through the first passage 53 having no oxygen storage function in the first catalyst device 37, and the catalyst portion 55 of the second passage 54 flows into the exhaust gas. There is no resistance, oxygen in the exhaust gas is not occluded, and heat of the exhaust gas is not released, and the exhaust gas in an appropriate state smoothly flows into the second catalyst device 38. Therefore, the exhaust gas purification process can be efficiently performed by the second catalyst device 38.

  Thus, in the exhaust gas purification apparatus for an internal combustion engine according to the third embodiment, the first catalyst device 37 and the second catalyst device 38 are mounted on the exhaust pipe 36 of the engine 10, and the first passage 53 is connected to the first catalyst device 37. And a second passage 54 is formed on the outside of the second passage 54. A catalyst portion 55 carrying ceria is provided in the second passage 54. The first and second on-off valves 56, 57 is provided, and when the air-fuel ratio of the exhaust gas is in a lean atmosphere or when the exhaust gas is in a high temperature state, the first passage 53 is closed by the first on-off valve 56 and the second on-off valve 57 By opening the passage 54, the exhaust gas reaches the second catalytic device 38 through the second passage 54.

  Therefore, when the air-fuel ratio of the exhaust gas discharged from the engine 10 is a lean atmosphere, the exhaust gas reaches the second catalyst device 38 after passing through the catalyst portion 55 of the second passage 54 in the first catalyst device 37. Thus, since oxygen in the exhaust gas is occluded in the catalyst unit 55 and the air-fuel ratio becomes close to the stoichiometric vicinity, it flows into the second catalyst device 38, so that the air-fuel ratio of the second catalyst device 38 by the exhaust gas in the lean atmosphere is reduced. Deterioration can be suppressed.

  Further, when the exhaust gas discharged from the engine 10 is in a high temperature state, the exhaust gas reaches the second catalyst device 38 after passing through the second passage 54 located outside the first catalyst device 37. Since the heat of the exhaust gas is released to the outside through the second passage 54 and flows into the second catalyst device 38 after the temperature is lowered, thermal deterioration of the second catalyst device 38 due to the high-temperature exhaust gas can be suppressed.

  In each of the above-described embodiments, in the first catalyst device 37, the second passage 54 is formed outside the first passage 53 located at the center, and the catalyst portion in which ceria is supported in the second passage 54. However, the present invention is not limited to this configuration, and the first passage and the second passage may be arranged side by side in the left-right or up-down direction. The first and second passages 53 and 54 are provided with the first and second on-off valves 56 and 57. However, the configuration of the on-off valves 56 and 57 is not limited to each embodiment. An on-off valve may be used.

  In addition, the exhaust gas purification apparatus for an internal combustion engine according to the present invention has been described as applied to an in-cylinder injection type multi-cylinder engine.

  As described above, the exhaust gas purification apparatus for an internal combustion engine according to the present invention improves the exhaust gas purification performance by suppressing the deterioration of the catalyst, and is suitable for use in any type of internal combustion engine.

1 is a schematic configuration diagram illustrating an exhaust gas purification apparatus for an internal combustion engine according to a first embodiment of the present invention. 1 is a partially cutaway perspective view of a first catalyst device in an exhaust gas purification apparatus for an internal combustion engine according to Embodiment 1. FIG. 1 is a cross-sectional view of a first catalyst device in an exhaust gas purification apparatus for an internal combustion engine according to a first embodiment. 3 is a flowchart showing an exhaust purification control in the exhaust purification device of the internal combustion engine of the first embodiment. It is sectional drawing of the 1st catalyst apparatus in the exhaust gas purification apparatus of the internal combustion engine which concerns on Example 2 of this invention. 6 is a flowchart showing an exhaust purification control in an exhaust purification device for an internal combustion engine according to a second embodiment. It is a flowchart showing the exhaust gas purification control in the exhaust gas purification apparatus of the internal combustion engine which concerns on Example 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Engine 18 Combustion chamber 19 Intake port 20 Exhaust port 21 Intake valve 22 Exhaust valve 33 Injector 34 Spark plug 36 Exhaust pipe (exhaust passage)
37, 61 First catalyst device (first exhaust purification catalyst)
38 Second catalyst device (second exhaust purification catalyst)
40 Electronic control unit, ECU
51 Housing 52 Piping 53 First Passage 54 Second Passage 55 Catalyst Part 56 First On-off Valve (Passage Switching Means)
57 Second on-off valve (passage switching means)

Claims (4)

A first exhaust purification catalyst provided in the exhaust gas passage and having an oxygen storage function capable of storing an oxygen component in the exhaust gas; and provided in the exhaust gas passage downstream of the first exhaust purification catalyst in the exhaust gas. A second exhaust purification catalyst that purifies the harmful substances of
The first exhaust purification catalyst has a first passage that does not have an oxygen storage function and a second passage that has an oxygen storage function, and at least a passage switch that guides exhaust gas to the first passage when the internal combustion engine is warmed up. Means are provided ,
The passage switching means guides the exhaust gas to the second passage when the air-fuel ratio of the exhaust gas of the internal combustion engine is a lean atmosphere,
When the air-fuel ratio of the exhaust gas is a lean atmosphere, the exhaust gas is guided to the second passage by the passage switching means, and then the exhaust gas is led to the first passage after the exhaust gas is made rich for a predetermined period. An exhaust purification device for an internal combustion engine.   2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the passage switching means includes a first on-off valve that opens and closes the first passage, and a second on-off valve that opens and closes the second passage. An exhaust purification device for an internal combustion engine, wherein the first passage is opened by the first opening / closing valve and the second passage is closed by the second opening / closing valve when the engine is warmed up.   2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein a first on-off valve that opens and closes the first passage is provided as the passage switching means, and the first on-off valve causes the first on-off valve when the internal combustion engine is warmed up. An exhaust emission control device for an internal combustion engine, wherein one passage is opened. 4. The exhaust gas purification apparatus for an internal combustion engine according to claim 1 , wherein the first exhaust gas purification catalyst is provided with the first passage passing through a central portion of the second passage. 5. An exhaust gas purification apparatus for an internal combustion engine characterized by the above.

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