JPH04117133U - Engine exhaust purification device - Google Patents

Abstract

(57) [Summary] [Purpose] With a configuration equipped with an exhaust particulate trap part and two oxidation catalyst parts, it is possible to reduce exhaust particulates containing SO ₂ components in the exhaust from an engine at a predetermined time when the exhaust gas is relatively high. To be able to effectively carry out the process under conditions where the increase in SO ₃ component content can be suppressed under the temperature range of . [Structure] An exhaust particulate trap part (10), an oxidation catalyst converter (15A) arranged downstream of the exhaust particulate trap part (10), and an oxidation catalyst part arranged in parallel with the oxidation catalyst converter (15A). Converter (15A)
Oxidation catalytic converter with lower oxidation capacity (1
5B), when the temperature of the exhaust gas is outside a relatively high predetermined range, the exhaust gas that has passed through the exhaust particulate trap section (10) is sent to the oxidation catalytic converter (15A), and when the temperature of the exhaust gas is outside the predetermined range, the temperature of the exhaust gas is within the predetermined range. At some point, the exhaust particulate trap section (1
0) to the oxidation catalytic converter (15B).

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention is installed in the exhaust system of an engine to remove atmospheric air contained in the exhaust from the engine. The present invention relates to an engine exhaust purification device that plays the role of purifying pollutant particles.

0002

[Conventional technology]

Engines installed in vehicles are usually equipped with an exhaust purification device for the purpose of preventing air pollution in the exhaust system. The exhaust gas discharged into the atmosphere from the exhaust system is purified. In particular, when the engine installed in a vehicle is a diesel engine, compared to a gasoline engine, hydrocarbon (HC) components and carbon monoxide (CO) generated by combustion of the air-fuel mixture and contained in the exhaust gas are ) components are said to be relatively small, but the amount of sulfur dioxide (SO ₂ ) components contained in exhaust gas tends to be large. In addition to the reduction treatment for HC components, CO components, etc. in the exhaust gas, it is required that the SO ₂ component in the exhaust gas be effectively reduced.

[0003] Regarding the HC components, CO components, etc. in the exhaust gas, for example, an oxidation catalyst is applied to the exhaust gas to promote the oxidation reaction of the HC components, CO components, etc. in the exhaust gas, and the HC components, CO components, etc. A method is adopted to reduce the amount of carbon dioxide by oxidizing it, and for this purpose, an oxidation catalyst section is provided in the exhaust system of the engine. On the other hand, when SO ₂ component in exhaust gas is oxidized, it produces sulfur trioxide (SO ₃ ) component, and when SO ₃ component is released into the atmosphere, it reacts with moisture to produce sulfuric acid. Oxidizing the SO ₂ component in the exhaust gas does not lead to exhaust gas purification, but instead results in the production of air polluting fine particles. Therefore, methods have been adopted to reduce the SO ₂ component in the exhaust gas by collecting it. An exhaust particulate trap section is provided which collects SO ₂ components contained in the exhaust gas as it passes through.

[0004] Therefore, in addition to the reduction treatment for HC components, CO components, etc. in the exhaust, the reduction treatment for the SO ₂ component in the exhaust is required to be effectively performed when attached to a diesel engine. The exhaust purification device is configured, for example, by a combination of an exhaust particulate trap section and an oxidation catalyst section, and exhaust gas passes through the oxidation catalyst section after passing through the exhaust particulate trap section.

[0005]

[Problem that the idea aims to solve]

However, an exhaust purification device attached to a diesel engine is constructed of a combination of an exhaust particulate trap part and an oxidation catalyst part as described above, and the exhaust gas passes through the oxidation catalyst part after passing through the exhaust particulate trap part. In this case, there is a problem in that when the temperature of the exhaust gas falls within a relatively high predetermined temperature range, the content of the SO ₃ component in the exhaust gas that has passed through the exhaust gas purification device temporarily increases.

[0006] When the temperature of the exhaust gas is within a relatively high predetermined temperature range, the SO ₂ component collected by the exhaust particulate trap part leaves the exhaust particulate trap part, and the SO 2 component is removed from the exhaust particulate trap part. A phenomenon occurs in which the separated SO ₂ component mixes with the exhaust gas passing through the exhaust particulate trap section, increasing the SO ₂ concentration in the exhaust gas passing through the oxidation catalyst section disposed after the exhaust particulate trap section. FIG. 3 shows the relationship between the temperature and SO ₂ concentration of the exhaust gas that has passed through the exhaust particulate trap section in the exhaust purification device attached to a diesel engine. When the temperature K of the catalyst falls within a relatively high temperature range, which is assumed to be within the range TK from about 350 degrees Celsius to about 550 degrees Celsius, the SO ₂ concentration SS will be lower than in other cases. has been shown to be significantly higher. When the temperature of such exhaust gas is within a relatively high predetermined temperature range, the SO ₂ component is oxidized and SO ₃ is generated in the oxidation catalyst section through which the exhaust gas with increased SO ₂ concentration passes. This may lead to a situation where the amount of ingredients increases.

[0007] In view of the above, the present invention is configured to include an exhaust particulate trap section and an oxidation catalyst section disposed in the exhaust system of an engine, and is configured to contain SO ₂ components contained in the exhaust gas from the engine. Exhaust particulate reduction processing can be effectively carried out without causing a situation where the content of SO ₃ components increases significantly when the exhaust gas reaches a temperature within a relatively high predetermined temperature range. The purpose of the present invention is to provide an exhaust purification device for an engine.

[0008]

[Means to solve the problem]

In order to achieve the above object, an engine exhaust purification device according to the present invention includes an exhaust particulate trap section disposed in the engine exhaust system to collect exhaust particulates containing SO ₂ components in exhaust from the engine; a first oxidation catalyst section disposed downstream of the exhaust particulate trap section in the exhaust system and oxidizing the exhaust particulates containing SO ₂ components; and a first oxidation catalyst section disposed in parallel with the first oxidation catalyst section in the exhaust system. , a second oxidation catalyst section whose ability to oxidize exhaust particulates containing SO ₂ components is lower than that of the first oxidation catalyst section, and detect the temperature of the exhaust gas from the engine or a temperature related thereto. The exhaust flow path switching section includes a temperature detection section and an exhaust flow path switching section disposed between the exhaust particulate trap section and the first and second oxidation catalyst sections, and the exhaust flow path switching section detects the temperature detected by the temperature detection section. is outside a relatively high predetermined range, the exhaust gas that has passed through the exhaust particulate trap part is guided to the first oxidation catalyst part, and when the temperature detected by the temperature detection part is within a predetermined range, the exhaust particulate matter is guided to the first oxidation catalyst part. The exhaust gas that has passed through the trap section is guided to the second oxidation catalyst section.

[0009]

[Effect]

In the engine exhaust purification device according to the present invention configured as described above, when the temperature of the exhaust gas is outside a relatively high predetermined range, the exhaust particulate trap section collects the exhaust particulates containing the SO ₂ component. The exhaust gas whose SO ₂ component has been reduced further passes through a first oxidation catalyst section that has a relatively high ability to oxidize exhaust particulates, and the exhaust particulates in the first oxidation catalyst part are In addition, when the temperature of the exhaust gas is within a relatively high predetermined range, the exhaust gas that has passed through the exhaust particulate trap section has the ability to oxidize the exhaust particulates by the first oxidation catalyst. The exhaust gas passes through a second oxidation catalyst section whose temperature is lower than that of the second oxidation catalyst section, and the exhaust particulates are reduced by oxidation in the second oxidation catalyst section. Therefore, when the temperature of the exhaust gas is outside a relatively high predetermined range, it is assumed that the exhaust particulates containing the SO ₂ component contained therein have been effectively reduced, and the temperature is also relatively high. When the temperature is within a high predetermined range, even if exhaust particulates containing SO ₂ components collected in the exhaust particulate trap part are detached and mixed into the exhaust gas, the second oxidation catalyst part The generation of the SO ₃ component due to the oxidation of _{the two} components is suppressed, and a reduction treatment of exhaust particulates other than the SO ₂ component due to the oxidation is achieved to some extent.

0010

【Example】

Figure 1 shows an example of an engine exhaust purification device according to the present invention, and a device to which it is applied. Shown with diesel engine.

[0011] In FIG. 1, an engine body 1 is provided with a plurality of cylinders. Fuel is pumped from the fuel pump to the top of the piston inserted into each cylinder. A combustion chamber 5 having a swirl chamber 4 in which a fuel injection valve 3 is provided is formed, and each combustion An intake passage 7 and an exhaust passage 8 are connected to the chamber 5, respectively. And each fuel injection Fuel is injected from the injection valve 3 into the swirl chamber 4 and supplied into the combustion chamber 5 through the intake passage 7. A mixture is formed with the supplied intake air, and the exhaust gas generated by its combustion is It is discharged from the combustion chamber 5 into the exhaust passage 8.

0012 The exhaust passages 8 include a plurality of exhaust passages connected to the plurality of combustion chambers 5 in the engine body 1, respectively. The upstream part is formed by the exhaust manifold 9 having a branch exhaust passage section. Both include a first common exhaust passage section 12 in which an exhaust particulate trap section 10 is disposed, and an acid a first catalyst passage section 16A in which an oxidation catalyst converter 15A is disposed, and an oxidation catalyst An intermediate portion is formed by the second catalyst passage portion 16B in which the converter 15B is disposed. Further, the second common exhaust passage section 19 in which the silencer 18 is disposed allows the downstream It is said that the side parts were formed. In the exhaust particulate trap section 10, , detects the temperature of the exhaust gas from the engine body 1, and represents the detected temperature of the exhaust gas. An exhaust temperature sensor 20 that sends a detection output signal ST to the control unit 30 is arranged. Ru.

[0013] The first common exhaust passage section 12 in the exhaust passage 8 has an upstream end connected to an exhaust manifold. The downstream end is connected to the three-way solenoid valve 22, The first and second catalyst passage sections 16A and 16B each have an upstream end that is a three-way solenoid valve. 22 to the first common exhaust passage section 12, and the downstream end is connected to the first common exhaust passage section 12 through the is connected to the upstream end of the second common exhaust passage section 19, and is connected to the upstream end of the second common exhaust passage section 19; The oxidation catalytic converter 15A and the second catalyst passage section disposed in the catalyst passage section 16A of The oxidation catalytic converter 15B is arranged in parallel with the oxidation catalytic converter 15B. Also, A downstream portion of the second common exhaust passage section 19 is configured to protrude to the outside. difference Furthermore, at the downstream end of each of the first and second catalyst passage sections 16A and 16B, A butterfly valve 25 is provided at the merging portion thus formed.

The exhaust particulate trap part 10 disposed in the first common exhaust passage part 12 traps exhaust particulates containing SO ₂ components in the exhaust discharged from the engine body 1 into the exhaust passage 8 by converting them into activated carbon. The exhaust gas is purified by collecting it and performing a reduction process. The exhaust particulate trap section 10 also controls the temperature of the oxidation catalytic converter 15A disposed in the first catalytic passage section 16A through which the exhaust gas passes or the oxidation catalytic converter 15B disposed in the second catalytic passage section 16B. That is, when the catalyst temperature K' is within a relatively high temperature range, for example taken to be within the range TK' from about 350 degrees Celsius to about 550 degrees Celsius, the captured SO ₂ It is assumed that component separation occurs.

[0015] Further, the oxidation catalytic converter 15A disposed in the first catalytic passage portion 16A and the second Each of the oxidation catalyst converters 16B disposed in the catalyst passage portion 16B of type, by impregnating the alumina layer coated on the surface of the cordierite carrier. A platinum-rhodium catalyst is provided, and the catalyst reduces the amount of exhaust gas from the engine body 1. Promotes the oxidation of HC components, CO components, etc. in the air, and removes HC components, CO components, etc. It purifies exhaust gas by oxidizing it. oxidation catalytic converter Each of 15A and 15B exhibits better oxidation catalytic performance as the catalyst temperature increases. However, the oxidation catalytic converter disposed in the first catalyst passage section 16A 15A, the amount of platinum impregnated per liter of monolithic carrier is, for example, about 1.3 to 1.6 g, and the oxidation catalyst controller disposed in the second catalyst passage section 16B For Verta 15B, the amount of platinum impregnated per liter of monolithic carrier is, for example, For example, it is said to be about 1.04 to 1.28 g, and the oxidation catalytic converter 15B is , the oxidizing ability is lower than that of the oxidizing catalytic converter 15A.

[0016] Furthermore, the first common exhaust passage section 12, the first catalyst passage section 16A, and the second catalyst The operation of the three-way solenoid valve 22 connected to the passage section 16B is controlled by the control unit 30. When the control drive signal Cd is supplied from the control unit 30, the first common exhaust The air passage section 12 and the first catalyst passage section 16A are cut off, and the first common The ventilation and exhaust passage section 12 and the second catalyst passage section 16B are brought into communication, and the control drive When the dynamic signal Cd is not supplied, the first common exhaust passage section 12 and the first catalyst passage section 16A, and the first common exhaust passage section 12 and the second catalyst passage section 12 are brought into communication with each other. The line 16B is cut off. Furthermore, the butterfly valve 25 is connected to the first catalyst passage section. Operation control according to the exhaust pressure difference between the catalyst passage section 16A and the second catalyst passage section 16B The first common exhaust passage section 12 and the first catalyst passage section 16A are brought into communication. When this happens, the first catalyst passage section 16A and the second common exhaust passage section 19 are brought into communication. At the same time, the second catalyst passage section 16B and the second common exhaust passage section 19 are cut off. None, and the first common exhaust passage section 12 and the second catalyst passage section 16B are in communication state. when the second catalyst passage section 16B and the second common exhaust passage section 19 are in communication with each other. while blocking the first catalyst passage section 16A and the second common exhaust passage section 19. It is assumed that the state of

The control unit 30 that controls the operation of the three-way solenoid valve 22 selectively supplies the control drive signal Cd to the three-way solenoid valve 22 based on the detection output signal ST obtained from the exhaust temperature sensor 20, and controls the exhaust particulate matter. The exhaust gas that has been purified by trapping exhaust particulates containing SO ₂ components by the trap section 10 is transferred to a first catalyst passage section 16A in which an oxidation catalytic converter 15A is disposed or an oxidation catalytic converter 15B disposed therein. The catalyst is guided to the second catalyst passage section 16B for further purification.

Then, the control unit 30 determines that the temperature of the exhaust gas indicated by the detection output signal ST is within the range TK' where the catalyst temperature K' is from about 350 degrees Celsius to about 550 degrees Celsius. , when the temperature is not within a relatively high temperature range, the control drive signal Cd is not supplied to the three-way solenoid valve 22, and the first common exhaust passage section 12 and the first catalyst passage section 16A are brought into communication. As a result, exhaust particles containing SO ₂ components are collected by the exhaust particulate trap section 10 and purified exhaust gas is introduced into the oxidation catalytic converter 15A disposed in the first catalyst passage section 16A. . In the oxidation catalytic converter 15A, the oxidation of exhaust particulates such as HC components and CO components in the exhaust whose SO ₂ concentration is sufficiently low is promoted on the catalyst surface of the oxidation catalytic converter 15A. Accordingly, the reduction process is performed. At this time, the SO ₂ concentration of the exhaust gas passing through the oxidation catalytic converter 15A is considered to be sufficiently low, so the amount of the SO ₃ component produced by oxidizing the SO ₂ component in the oxidation catalytic converter 15A is extremely small. It is said that In this way, exhaust particulates containing SO ₂ components are collected by the exhaust particulate trap section 10, and exhaust particulates such as HC components and CO components are reduced by the oxidation catalytic converter 15A, and the exhaust particulates are sufficiently purified. Exhaust gas is exhausted to the outside through the second common exhaust passage section 19.

[0019] The control unit 30 also controls whether the temperature of the exhaust gas represented by the detection output signal ST is The temperature K' is within the range TK' from about 350 degrees Celsius to about 550 degrees Celsius. When the temperature is within a relatively high temperature range, the control for the three-way solenoid valve 22 is The control drive signal Cd is supplied to the first common exhaust passage section 12 and the second catalyst passage section. 16B is brought into communication. As a result, the exhaust gas passing through the exhaust particulate trap section 10 is introduced into the oxidation catalytic converter 15B disposed in the second catalytic passage section 16B. Ru. The exhaust gas introduced into the oxidation catalytic converter 15B is transferred to the exhaust particulate trap section. SO in 10₂Desorption of components occurs and SO₂Although the concentration is said to be relatively high, , the oxidation catalytic converter 15B has a lower oxidation ability than the oxidation catalytic converter 15A. In the oxidation catalytic converter 15B, SO₂ SO due to oxidation of components₃In addition to suppressing the generation of components, HC components and CO components A certain degree of reduction treatment through oxidation of exhaust particulates will be attempted. and, Even under such conditions where the temperature of the exhaust gas is within a relatively high predetermined temperature range, the SO ₂ SO produced when components are oxidized₃The situation where the amount of ingredients increases is imitated. There is no reduction treatment by oxidation of exhaust particulates such as HC components and CO components. The purified exhaust gas is discharged to the outside through the second common exhaust passage section 19. .

In an example of the exhaust purification device according to the present invention that purifies exhaust gas as described above, the conversion rate of SO ₂ components to SO ₃ in the exhaust gas discharged from the engine body 1 to the exhaust passage 8 is reduced. SB is relatively constant, as shown by curve a in FIG. This results in a relatively small degree of increase when the temperature is within a high temperature range. On the other hand, suppose that the exhaust particulate trap section 10 is not disposed in the first common exhaust passage section 12 of the exhaust passage 8, and the exhaust passage 8 is located in a second catalyst passage section in which the oxidation catalytic converter 15B is disposed. 16B is not provided and the exhaust gas is purified only by the oxidation catalyst converter 15A disposed in the first catalyst passage section 16A, the engine The conversion rate SB of the SO ₂ component to the SO ₃ component in the exhaust gas discharged from the main body 1 to the exhaust passage 8 is determined when the exhaust temperature is within the range TK of the catalyst temperature K' from about 350 degrees Celsius to about 550 degrees Celsius. It is assumed that the degree of increase is relatively large when the temperature is within a relatively high temperature range. Furthermore, if the second catalyst passage section 16B in which the oxidation catalytic converter 15B is disposed in the exhaust passage 8 is not provided, and the exhaust gas is disposed in the first common exhaust passage section 12, the exhaust particulate trap section 10, If the exhaust gas is purified by the oxidation catalytic converter 15A disposed in the first catalytic passage section 16A, the exhaust gas discharged from the engine body 1 into the exhaust passage 8 as shown by curve c in FIG. The conversion rate SB of the SO ₂ component to the SO ₃ component in the exhaust gas is assumed to be such that the temperature of the exhaust gas is within the range TK' where the catalyst temperature K' is from about 350 degrees Celsius to about 550 degrees Celsius. , the degree of increase when the temperature is within a relatively high temperature range is such that SO ₂ trapped in the exhaust particulate trap section 10 is separated and mixed into the exhaust gas, and is oxidized in the oxidation catalytic converter 15A. By doing so, it is made to be even larger than the case shown by curve b. As is clear from FIG. 2, in the example of the exhaust purification device according to the present invention, exhaust particulates such as SO ₂ components, HC components, and CO components in the exhaust from the engine body 1 are removed from the exhaust gas. SO even when the temperature is within a relatively high temperature range, the catalyst temperature K' is to be within a relatively high range TK', for example from about 350 degrees Celsius to about 550 degrees Celsius. Exhaust gas will be purified by effectively reducing the increase in the _three components while suppressing them.

[0021]

[Effect of the idea]

As is clear from the above description, the engine exhaust purification device according to the present invention includes an exhaust particulate trap section disposed in the engine exhaust system, and first and second oxidation catalyst sections. When performing a process to reduce exhaust particulates containing SO ₂ components contained in exhaust from an engine, when the temperature of the exhaust gas is outside a relatively high predetermined range, the exhaust particulate trap section removes exhaust particulates containing SO ₂ components. The exhaust gas whose SO ₂ component has been reduced by collecting the Furthermore, when the temperature of the exhaust gas is within a relatively high predetermined range, the exhaust gas that has passed through the exhaust particulate trap has the ability to oxidize the exhaust particulates. The exhaust gas passes through a second oxidation catalyst section whose temperature is lower than that of the first oxidation catalyst section, and the exhaust particulates are reduced by oxidation in the second oxidation catalyst section. Therefore, when the temperature of the exhaust gas is outside a relatively high predetermined range, it is assumed that the exhaust particulates containing the SO ₂ component contained therein have been effectively reduced, and the temperature is also relatively high. When the temperature is within a high predetermined range, even if exhaust particulates containing SO ₂ components collected in the exhaust particulate trap part are detached and mixed into the exhaust gas, the second oxidation catalyst part The generation of the SO ₃ component due to the oxidation of the ₂ components is suppressed, and exhaust particulates other than the SO ₂ component are reduced to some extent by oxidation, and as a result, the exhaust gas containing the SO ₂ component contained in the exhaust from the engine is reduced. Particulate reduction processing can be effectively carried out without causing a situation where the content of the SO ₃ component increases significantly when the temperature of the exhaust gas is within a relatively high predetermined temperature range.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an example of an engine exhaust purification device according to the present invention together with a diesel engine to which the device is applied.

FIG. 2 is a characteristic diagram used to explain the operation of the example shown in FIG. 2;

FIG. 3 is a characteristic diagram illustrating the SO ₂ concentration in exhaust gas purified by the exhaust gas purification device of a diesel engine.

[Explanation of symbols]

1 Engine body 8 Exhaust passage 10 Exhaust particulate trap section 15A oxidation catalytic converter 15B Oxidation catalytic converter 16A First catalyst passage section 16B Second catalyst passage section 20 Exhaust temperature sensor 22 Three-way solenoid valve 30 Control unit

Continuation of front page (72) Creator Kazuya Komatsu Mazda, 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside the corporation

Claims (1)

[Scope of utility model registration request] 1. An exhaust particulate trap part disposed in an exhaust system of an engine to collect particulates containing sulfur dioxide components in exhaust gas from the engine; and an exhaust particulate trap part disposed downstream of the exhaust particulate trap part in the exhaust system. a first oxidation catalyst section which is arranged in parallel to the first oxidation catalyst section in the exhaust system and has the ability to oxidize the particulates containing sulfur dioxide components; a second oxidation catalyst section whose temperature is lower than that of the first oxidation catalyst section; a temperature detection section that detects the temperature of the exhaust gas from the engine or a temperature related thereto; When the detected temperature is outside a relatively high predetermined range, guiding the exhaust gas that has passed through the exhaust particulate trap section to the first oxidation catalyst section;
an exhaust flow path switching section that guides the exhaust gas that has passed through the exhaust particulate trap section to the second oxidation catalyst section when the temperature detected by the temperature detection section is within the predetermined range. Exhaust purification device for engines.