JP2008050964A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device capable of accelerating depolymerization of fuel injected from a fuel adding valve irrespective of operation conditions of an engine. <P>SOLUTION: A distal end portion 30a of the fuel adding valve 30 projects into an exhaust port 4a. A first oxidation catalyst 33 oxidizing and depolymerizing fuel injected from the fuel adding valve 30 is provided in a downstream of the distal end portion 30a of the fuel adding valve 30 in the exhaust port 4a. Non-permeable member 32 through which exhaust gas can not permeate is provided in the exhaust port 4a. The non-permeable member 32 comprises a vertical portion 32a extending vertically to an axial direction of the exhaust port 4a, and a horizontal portion 32b extending in a horizontal direction to the axial direction of the exhaust port 4a. The vertical portion 32a is provided in an upstream of the distal end portion 30a of the fuel adding valve 30, and the horizontal portion 32b is connected to the first oxidation catalyst 33 and is positioned below the distal end portion 30a of the fuel adding valve 30. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification device for an internal combustion engine, and more particularly to an exhaust gas purification device for purifying exhaust gas from a diesel engine.

Since a diesel engine is normally operated at a lean air-fuel ratio, a three-way catalyst cannot be used as exhaust purification means. For this reason, various exhaust gas purification means specific to diesel engines have been proposed. Among them, exhaust gas such as a fuel addition device and a nitrogen oxide reduction catalyst, a fuel addition device and a DPF, or a fuel addition device and a DPNR catalyst are included. Several systems have been proposed in which a fuel addition device is arranged in the passage.
The fuel addition device is disposed on the exhaust passage on the upstream side of the catalyst or the DPF, and adds fuel to the exhaust gas. This fuel acts to raise the temperature of exhaust gas and DPF by an oxidation reaction, or to reduce nitrogen oxide by a catalyst. By the way, in order to promote atomization of the fuel (light oil), prevent adhesion to the wall of the passage, and facilitate the reaction, it is preferable to lower the polymer component in the fuel. For this reason, a technique has been proposed in which an oxidation catalyst is arranged between the fuel addition device and the DPF or the catalyst for the purpose of reducing the molecular weight of the fuel.
Patent Document 1 describes an example of such an exhaust gas purification device. A diesel engine equipped with this exhaust gas purification device is shown in FIG. An exhaust pipe 67 is connected to the diesel engine 61 via an exhaust manifold 62. A nitrogen oxide reduction catalyst device 66 is provided in the exhaust pipe 67, and a fuel addition device 65 is provided upstream of the nitrogen oxide reduction catalyst device 66 in the exhaust pipe 67. The fuel addition device 65 includes a fuel addition valve 63 that injects fuel, and an oxidation catalyst 64 that oxidizes the fuel injected from the fuel addition valve 63 to reduce the molecular weight. The fuel injected from the fuel addition valve 63 is oxidized and reduced in molecular weight by the oxidation catalyst 64 and then merges with the exhaust gas flowing through the exhaust pipe 67 and flows into the nitrogen oxide reduction catalyst device 66 together with the exhaust gas. In the nitrogen oxide reduction catalyst device 66, exhaust gas is purified by reducing nitrogen oxide in the exhaust gas using fuel as a reducing agent.

Japanese Patent Laid-Open No. 9-38467

  In the technique of Patent Document 1, an oxidation catalyst 64 that forms part of the fuel addition device 65 is provided in the exhaust pipe 67. The temperature of the exhaust gas discharged from the diesel engine 61 decreases by the heat radiation from the exhaust manifold 62 or the exhaust pipe 67 before reaching the fuel addition device 65. For this reason, when the diesel engine 61 is in a low load and low rotation state or the like, in an operation state where the exhaust gas temperature itself discharged from the diesel engine 61 is low, there is also a heat dissipation action until it reaches the fuel addition device 65, and the oxidation catalyst The temperature of 64 does not rise sufficiently, and the oxidation catalyst 64 may not exhibit sufficient activity. In this case, the oxidation of the fuel by the oxidation catalyst 64 becomes insufficient, that is, the fuel has a low molecular weight. In particular, in an engine in which the turbine of the supercharger is arranged upstream of the fuel addition device 65, the exhaust temperature greatly decreases before and after the turbine, and this problem becomes significant.

  The present invention has been made to solve such problems, and it is an object of the present invention to provide an exhaust gas purifying apparatus that can promote low molecular weight of fuel injected from a fuel addition valve regardless of the operating state of the engine. Objective.

In an exhaust gas purification apparatus in which fuel is supplied by a fuel addition valve to exhaust gas discharged from a combustion chamber of a diesel engine and a purification catalyst or a DPF is disposed in an exhaust passage downstream of the fuel addition valve, An exhaust port that communicates with the combustion chamber, a fuel addition valve that supplies fuel into the exhaust port, a first oxidation catalyst that is disposed on the downstream side of the fuel addition valve, and the exhaust port via the first oxidation catalyst A front end portion of the fuel addition valve is disposed in the compartment chamber, and at least a part of the compartment chamber in which the first oxidation catalyst is disposed protrudes into the exhaust port. . By providing the first oxidation catalyst downstream of the fuel addition valve in the exhaust port, the high-temperature exhaust gas immediately after being discharged from the diesel engine comes into contact with the first oxidation catalyst, and the temperature of the first oxidation catalyst is increased. Since the first oxidation catalyst is sufficiently activated by raising, the fuel injected from the fuel addition valve is sufficiently reduced in molecular weight.
The exhaust port further includes a second oxidation catalyst that is provided upstream of the fuel addition valve and oxidizes the fuel, and a non-permeating member that is provided in the exhaust port and does not transmit exhaust gas. And a second catalyst and a non-permeable member.
Around the exhaust port, a heat insulating member may be provided in the vicinity of the compartment and at least in the same range as the compartment.

  According to this invention, since the first oxidation catalyst is provided downstream of the fuel addition valve in the exhaust port, the high-temperature exhaust gas immediately after being discharged from the diesel engine comes into contact with the first oxidation catalyst. Since the temperature of the first oxidation catalyst rises and the first oxidation catalyst is sufficiently activated, the fuel injected from the fuel addition valve is sufficiently reduced in molecular weight. Thereby, atomization of the fuel injected from the fuel addition valve can be promoted.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Embodiment 1 FIG.
FIG. 1 shows the configuration of a diesel engine provided with the exhaust gas purifying apparatus according to the first embodiment. In a cylinder block of a diesel engine, combustion chambers 1a, 1b, 1c, and 1d are provided in four cylinders, and an intake manifold 2 and an exhaust manifold 3 are provided so as to communicate with these. An intake passage 4 through which air flows is connected to the other end and upstream side of the intake manifold 2, and an exhaust passage 5 through which exhaust gas flows is connected to the other end and downstream side of the exhaust manifold 3. The intake passage 4 is provided with an air flow meter 6 for measuring the air flow rate, a compressor 7a of the supercharger 7, an intercooler 8 for cooling the air, and a throttle valve 9 for adjusting the air flow rate. In the exhaust passage 5, a turbine 7 b of the supercharger 7, a first oxidation catalytic converter 10, a diesel particulate filter (DPF) catalytic converter 11, an air-fuel ratio sensor 12, and a second oxidation catalytic converter 13 are provided. It has been. Further, an EGR passage 14 having one end connected to the exhaust manifold 3 and the other end connected to the intake passage 4 between the intake manifold 2 and the throttle valve 9 is provided. The EGR passage 14 is provided with an EGR cooler 15 and an EGR valve 16.

  Each of the four combustion chambers 1a to 1d is provided with injection nozzles 20a, 20b, 20c and 20d for injecting fuel. Each of the injection nozzles 20a to 20d is an electromagnetic valve that injects high-pressure fuel into the combustion chambers 1a to 1d in a fine spray state. Each of the injection nozzles 20 a to 20 d is connected to a common rail 21. One end of a fuel passage 22 is connected to the common rail 21. The other end of the fuel passage 22 is connected to the fuel supply pump 23. The common rail 21 receives supply of high-pressure fuel from a fuel supply pump 23, discharges a part of the fuel by a relief valve 24, and returns it to a fuel supply system such as a fuel tank (not shown) via a discharge passage 25. A high pressure fuel of a predetermined pressure is always maintained inside. A desired amount of fuel is injected into each of the combustion chambers 1a to 1d by controlling the opening and closing time of the injection nozzles 20a to 20d using the pressure of the high pressure fuel in the common rail 21.

The cylinder head 1 is formed with four exhaust ports 4a, 4b, 4c, and 4d passing therethrough so as to communicate with the four combustion chambers 1a to 1d. The exhaust manifold 3 has four branch pipes 3a, 3b, 3c, and 3d, and each of the branch pipes 3a to 3d is connected to the exhaust ports 4a to 4d.
The exhaust port 4a is provided with a fuel addition valve 30 for injecting fuel into the exhaust port 4a. The fuel addition valve 30 communicates with the fuel supply pump 23 via the fuel passage 26 so that fuel having a lower pressure than that in the common rail 21 is supplied.

  As shown in FIG. 2, the fuel addition valve 30 is attached so that the tip portion 30 a of the fuel addition valve 30 protrudes from the upper portion of the cylinder head 1 to the exhaust port 4 a. A water jacket through which cooling water flows is formed inside the cylinder head 1, and a water jacket 31 is also formed around the fuel addition valve 30. In the exhaust port 4a, a first oxidation catalyst 33 that oxidizes the fuel injected from the fuel addition valve 30 to lower the molecular weight is provided downstream of the tip portion 30a of the fuel addition valve 30. The exhaust port 4a is provided with a non-permeable member 32 through which exhaust gas does not permeate. The non-permeable member 32 includes a vertical portion 32a extending perpendicular to the axial direction of the exhaust port 4a and a horizontal portion 32b extending horizontally to the axial direction of the exhaust port 4a, and has a L-shaped cross section. Have. The vertical portion 32 a is provided upstream of the tip portion 30 a of the fuel addition valve 30, and the horizontal portion 32 b is connected to the first oxidation catalyst 33 and is positioned below the tip portion 30 a of the fuel addition valve 30. Thereby, the first oxidation catalyst 33 and the non-permeating member 32 form a compartment 34, and the tip portion 30 a of the fuel addition valve 30 is located in the compartment 34. That is, the tip portion 30 a of the fuel addition valve 30 is covered with the first oxidation catalyst 33 and the non-permeable member 32.

  FIG. 3 shows the exhaust port 4a viewed from the direction of arrow A in FIG. The horizontal portion 32b of the non-permeable member 32 located below the tip portion 30a of the fuel addition valve 30 is curved in a convex shape toward the tip portion 30a. For this reason, in the circular cross section of the exhaust port 4a, the area occupied by the first oxidation catalyst is made as small as possible. Thereby, when exhaust gas flows through the exhaust port 4a, pressure loss due to the first oxidation catalyst 33 and the non-permeating member 32 is minimized.

Next, the operation of the diesel engine provided with the exhaust gas purifying apparatus according to the first embodiment will be described.
As shown in FIG. 1, when the diesel engine starts, air is taken into the intake passage 4 and flows through the intake passage 4. While flowing through the intake passage 4, the air is measured for flow rate by the air flow meter 6, compressed by the compressor 7 a of the supercharger 7, and cooled by the intercooler 8. The flow rate of air flowing through the intake passage 4 is controlled by adjusting the opening of the throttle valve 9 based on the flow rate of air measured by the air flow meter 6. The air flowing through the intake passage 4 flows into the intake manifold 2 and is then sucked into the combustion chambers 1a to 1d.

  The air sucked into the combustion chambers 1a to 1d is compressed by a piston (not shown), and then fuel is injected from the injection nozzles 20a to 20d into the combustion chambers 1a to 1d to burn and become exhaust gases. The air is discharged from the chambers 1a to 1d to the exhaust ports 4a to 4d. The exhaust gas discharged to each of the discharge ports 4 a to 4 d is collected in the exhaust manifold 3, and a part of the exhaust gas flows through the EGR passage 14. The flow rate of the exhaust gas flowing through the EGR passage 14 is controlled by the EGR valve 16. The exhaust gas flowing through the EGR passage 14 is cooled by the EGR cooler 15, then returned to the intake passage 4 as EGR gas, merged with air, and sucked into the combustion chambers 1 a to 1 d.

  On the other hand, the remainder of the exhaust gas collected in the exhaust manifold 3 flows through the exhaust passage 5. The exhaust gas flowing through the exhaust passage 5 drives the turbine 7 b of the supercharger 7. Thereby, the compressor 7a mentioned above is driven. After the exhaust gas drives the turbine 7b, fine particles are captured by the DPF catalytic converter 11, and are discharged outside the vehicle. When the amount of exhaust particulate trapped by the DPF catalytic converter 11 increases, the differential pressure of the DPF catalytic converter 11 increases. When this differential pressure exceeds a predetermined value, regeneration of the DPF catalytic converter 11 is started.

  When regeneration of the DPF catalytic converter 11 is started, fuel is injected from the fuel addition valve 30 to the exhaust port 4a as shown in FIG. Since the exhaust gas flowing through the exhaust port 4a is an exhaust gas immediately after being discharged from the combustion chamber 1a (see FIG. 1), the temperature is high. Since the first oxidation catalyst 33 is exposed to the exhaust gas having a high temperature, the first oxidation catalyst 33 is in a sufficiently activated state. Under this condition, when fuel is injected from the fuel addition valve 30, the fuel is oxidized by the first oxidation catalyst 33 to reduce the molecular weight. This oxidation reaction heat further increases the exhaust gas temperature. When the molecular weight of the fuel is reduced, the fuel is easily atomized in the exhaust gas, and easily flows through the exhaust port 4a together with the exhaust gas. This prevents a part of the fuel from adhering to the tip end portion 30a of the fuel addition valve 30 so as to easily attach particulates or the like in the exhaust gas. Further, since the exhaust gas cannot flow into the compartment 34 by the non-permeable member 32, the particulates contained in the exhaust gas do not contact the tip portion 30 a of the fuel addition valve 30. This prevents particulates contained in the exhaust gas from adhering to the tip portion 30a of the fuel addition valve 30 and causing clogging.

  As shown in FIG. 1, the exhaust gas containing fuel in the exhaust port 4 a is mixed with the exhaust gas flowing out from the other exhaust ports 4 b to 4 d in the exhaust manifold 3 and flows through the exhaust passage 5. Due to the reaction heat of the oxidation reaction of the fuel in the exhaust port 4a, the temperature of the exhaust gas flowing through the exhaust passage 5 is sufficient to activate the first oxidation catalytic converter 10. In this state, when exhaust gas containing fuel flows into the first oxidation catalytic converter 10, the fuel is oxidized by activating the first oxidation catalytic converter 10. The exhaust gas temperature rises due to this oxidation reaction heat. When the exhaust gas whose temperature has risen flows into the DPF catalytic converter 11, the trapped particulates are oxidized and removed, and the DPF catalytic converter 11 is regenerated. The air-fuel ratio of the exhaust gas flowing out from the DPF catalytic converter 11 is measured by the air-fuel ratio sensor 12, and the amount of fuel injected from the fuel addition valve 30 is optimized based on this measured value. Here, since the sensitivity of the air-fuel ratio sensor 12 becomes low when the molecular weight of the fuel is high, the fuel amount is not sufficiently optimized. However, since the fuel injected from the fuel addition valve 30 is sufficiently reduced in molecular weight by the first oxidation catalyst 33 (see FIG. 2), the sensitivity of the air-fuel ratio sensor 12 is improved and the fuel amount is sufficiently optimized. To be done. Thereafter, the exhaust gas flows into the second oxidation catalytic converter 13 and the remaining fuel is oxidized and discharged outside the vehicle. When the differential pressure of the DPF catalytic converter 11 becomes equal to or less than a predetermined value, the fuel injection from the fuel addition valve 30 is stopped and the regeneration of the DPF catalytic converter 11 is ended.

  As described above, since the fuel addition valve 30 and the first oxidation catalyst 33 are provided in the exhaust port 4a, the first oxidation catalyst 33 provided downstream of the fuel addition valve 30 in the exhaust port 4a is supplied from the diesel engine. Since it is activated by the high-temperature exhaust gas immediately after being discharged, the fuel injected from the fuel addition valve 30 is sufficiently reduced in molecular weight even in a low rotation low load state where the exhaust gas temperature is relatively low. Thereby, the atomization of the fuel injected from the fuel addition valve 30 can be promoted. Further, since the tip portion 30 a of the fuel addition valve 30 is covered by the first oxidation catalyst 33 and the non-permeating member 32, the exhaust gas containing particulates or the like flows around the tip portion 30 a of the fuel addition valve 30. Therefore, there is no possibility that fine particles or the like adhere to the tip portion 30a of the fuel addition valve 30 and clogging occurs.

Embodiment 2. FIG.
Next, an exhaust gas purification apparatus according to Embodiment 2 of the present invention will be described with reference to FIG. In the following embodiments, the same reference numerals as those in FIGS. 1 to 3 are the same or similar components, and thus detailed description thereof is omitted.
The exhaust gas purification apparatus according to Embodiment 2 of the present invention is different from that of Embodiment 1 in that another oxidation catalyst is provided upstream of the fuel addition valve 30 in the exhaust port 4a.
As shown in FIG. 4, in the exhaust port 4a, a first oxidation catalyst 33 is provided downstream of the fuel addition valve 30, and a second oxidation catalyst 43 is provided upstream. Further, a non-permeable member 42 that is connected to both the first oxidation catalyst 33 and the second oxidation catalyst 43 and does not transmit exhaust gas is provided. The non-permeable member 42 extends in the horizontal direction with respect to the axial direction of the exhaust port 4 a so as to be positioned below the tip portion 30 a of the fuel addition valve 30. The compartment chamber 34 is formed by the first oxidation catalyst 33, the second oxidation catalyst 43, and the non-permeable member 42, and the tip portion 30 a of the fuel addition valve 30 is located in the compartment chamber 34. That is, the tip portion 30 a of the fuel addition valve 30 is covered with the first oxidation catalyst 33, the second oxidation catalyst 43, and the non-permeable member 42. Other configurations are the same as those of the first embodiment.

  As in the first embodiment, when regeneration of the DPF catalytic converter 11 (see FIG. 1) is started, fuel is injected from the fuel addition valve 30 into the exhaust port 4a. Since the exhaust gas flowing through the exhaust port 4a is an exhaust gas immediately after being discharged from the combustion chamber 1a (see FIG. 1), the temperature is high. Since the first oxidation catalyst 33 and the second oxidation catalyst 43 are exposed to the exhaust gas having a high temperature, the first oxidation catalyst 33 and the second oxidation catalyst 43 are sufficiently activated. Under this condition, when fuel is injected from the fuel addition valve 30, the fuel is oxidized by the first oxidation catalyst 33 and the second oxidation catalyst 43 to reduce the molecular weight. The exhaust gas temperature rises due to this oxidation reaction heat. When the molecular weight of the fuel is reduced, the fuel is easily atomized in the exhaust gas, and easily flows through the exhaust port 4a together with the exhaust gas. Further, since the exhaust gas flowing through the exhaust port 4a passes through the first oxidation catalyst 33 and the second oxidation catalyst 43, the flow of the exhaust gas inside the compartment 34, that is, around the tip portion 30a of the fuel addition valve 30. It comes to exist. For this reason, the fuel injected from the fuel addition valve 30 is further easily atomized. In addition, since the exhaust gas flowing through the exhaust port 4 a is blocked by the non-permeable member 42, only the gas that has permeated the second oxidation catalyst 43 flows around the tip portion 30 a of the fuel addition valve 30. Since the exhaust gas is purified by the second oxidation catalyst 43, it is possible to prevent the fine particles contained in the exhaust gas from adhering to the tip portion 30a of the fuel addition valve 30 and causing clogging.

  Thus, in the exhaust port 4a, the first oxidation catalyst 33 is provided downstream of the fuel addition valve 30, the second oxidation catalyst 43 is provided upstream, and further connected to both the first oxidation catalyst 33 and the second oxidation catalyst 43. Thus, by providing the non-permeable member 42 extending horizontally with respect to the axial direction of the exhaust port 4a, the tip portion 30a of the fuel addition valve 30 is provided with the first oxidation catalyst 33, the second oxidation catalyst 43, and the non-permeable member. 42. As a result, the first oxidation catalyst 33 and the second oxidation catalyst 43 are sufficiently activated by being exposed to the high-temperature exhaust gas, so that the fuel injected from the fuel addition valve 30 can be sufficiently reduced in molecular weight. . That is, fuel atomization can be promoted. Further, only the exhaust gas that has passed through the second oxidation catalyst 43 and has been purified flows around the tip portion 30a of the fuel addition valve 30 to promote fuel atomization, and the fine particles contained in the exhaust gas, etc. Can be prevented from adhering to the tip portion 30a of the fuel addition valve 30 and causing clogging.

Embodiment 3 FIG.
Next, an exhaust gas purification apparatus according to Embodiment 3 of the present invention will be described with reference to FIGS. The exhaust gas purifying apparatus according to Embodiment 3 of the present invention is such that a heat insulating member is provided on the cylinder head 1 as compared with Embodiment 1.
As shown in FIG. 5, in the cylinder head 1, a ceramic heat insulating member 50 is provided around the fuel addition valve 30 and between the water jacket 31 and the exhaust port 4a. The heat insulating member 50 is provided in a range between the first oxidation catalyst 33 and the vertical portion 32a of the non-permeable member 32 with respect to the axial direction of the exhaust port 4a. Further, as shown in FIG. 6, the heat insulating member 50 is provided in the same range as the circumferential direction of the first oxidation catalyst 33 with respect to the circumferential direction of the exhaust port 4 a. Thereby, the heat insulation member 50 comprises a part of inner peripheral surface of the exhaust port 4a. That is, the compartment 34 is formed by the heat insulating member 50, the first oxidation catalyst 33, and the non-permeable member 32. Other configurations are the same as those in the first embodiment.

Cooling water flows through the water jacket 31 to cool the fuel addition valve 30, but the cooling water cools a part of the cylinder head 1 around the water jacket 31 in order to cool the fuel addition valve 30. For this reason, a low temperature part may arise in a part of inner peripheral surface of the exhaust port 4a, and there exists a possibility that the exhaust gas which distribute | circulates the exhaust port 4a may be cooled. However, since the inner peripheral surface of the exhaust port 4 a in the compartment 34 is constituted by the heat insulating member 50, the influence of the cooling water does not reach the inside of the compartment 34 and the first oxidation catalyst 33. Thereby, a decrease in the temperature of the exhaust gas around the first oxidation catalyst 33 is prevented, and sufficient activation of the first oxidation catalyst 33 is maintained.
Thus, in the cylinder head 1, the heat insulating member 50 is provided between the water jacket 31 and the exhaust port 4 a, and the inner peripheral surface of the exhaust port 4 a in the compartment 34 is configured by the heat insulating member 50. Since the influence of the cooling water flowing through the chamber does not reach the inside of the compartment 34 and the first oxidation catalyst 33, the activation of the first oxidation catalyst 33 is maintained, and the fuel injected from the fuel addition valve 30 is sufficiently reduced in molecular weight. can do. That is, fuel atomization can be further promoted.

In the third embodiment, the inner peripheral surface of the exhaust port 4a in the compartment 34 is configured by the heat insulating member 50. However, the present invention is not limited to this configuration. The heat insulating member 50 may be provided so as to be embedded in the cylinder head 1 so that the heat insulating member 50 is not exposed in the compartment 34. Further, the range in which the heat insulating member 50 is provided is not limited to the range of the compartment 34, and the heat insulating member 50 may be provided in a range larger than the range of the compartment 34. That is, the heat insulating member 50 can be provided in the vicinity of the compartment 34 and at least in the same range as the compartment 34 around the exhaust port 4a.
Furthermore, in Embodiment 3, although the heat insulation member 50 was provided with respect to Embodiment 1, it is not limited to Embodiment 1, The heat insulation member 50 can also be provided with respect to Embodiment 2. FIG.

Embodiment 4 FIG.
Next, an exhaust gas purification apparatus according to Embodiment 4 of the present invention will be described with reference to FIG. The exhaust gas purifying apparatus according to Embodiment 4 of the present invention is such that the compartment is integrally formed with the cylinder head as compared with Embodiment 1.
As shown in FIG. 7, the compartment chamber 34 is formed of the first oxidation catalyst 33 and the non-permeable member 52, and is formed integrally with the cylinder head so that a part of the compartment chamber 34 is recessed with respect to the exhaust port 4a. . The first oxidation catalyst 33 and the non-permeable member 52 protrude to the exhaust port 4a. The tip portion 30a of the fuel addition valve 30 is disposed in the compartment 34, but does not protrude into the exhaust port 4a. Other configurations are the same as those in the first embodiment.

  Thus, even if the part of the compartment 34 is formed integrally with the cylinder head so as to be recessed with respect to the exhaust port 4a, the first oxidation catalyst 33 protrudes into the exhaust port 4a. Is activated by the hot exhaust gas immediately after being discharged from the diesel engine. In addition, since the tip portion 30 a of the fuel addition valve 30 is covered by the first oxidation catalyst 33 and the non-permeating member 52, exhaust gas containing particulates or the like flows around the tip portion 30 a of the fuel addition valve 30. Disappear. As a result, the same effects as in the first embodiment can be obtained.

  In the first to fourth embodiments, the first oxidation catalytic converter 10 is provided immediately upstream of the DPF catalytic converter 11, but the first oxidation catalytic converter 10 is not necessarily an essential component. The exhaust gas flowing through the exhaust passage 5 is particularly cooled before and after the supercharger 7. Therefore, when the temperature of the exhaust gas flowing into the DPF catalytic converter 11 can be maintained at a predetermined temperature or more like a diesel engine without a supercharger, the first oxidation catalytic converter 10 may not be provided. Further, the second oxidation catalytic converter 13 is not an essential constituent element. If the exhaust gas flowing out from the DPF catalytic converter 11 is sufficiently purified, the second oxidation catalytic converter 13 may not be provided.

It is a block diagram of the diesel engine provided with the exhaust-gas purification apparatus which concerns on Embodiment 1 of this invention. FIG. 3 is a cross-sectional view of the vicinity of a fuel addition valve of the exhaust gas purification apparatus according to the first embodiment. In FIG. 2, it is the top view seen from the direction of arrow A. FIG. 6 is a cross-sectional view of the vicinity of a fuel addition valve of an exhaust gas purification apparatus according to Embodiment 2. FIG. 6 is a cross-sectional view of the vicinity of a fuel addition valve of an exhaust gas purification apparatus according to Embodiment 3. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5. FIG. 6 is a cross-sectional view around a fuel addition valve of an exhaust gas purification apparatus according to Embodiment 4; It is a block diagram of the conventional diesel engine provided with the exhaust gas purification apparatus.

Explanation of symbols

  1a, 1b, 1c, 1d Combustion chamber, 4a, 4b, 4c, 4d Exhaust port, 11 Diesel particulate filter catalytic converter, 30 Fuel addition valve, 30a Tip part of fuel addition valve, 32, 42, 52 Non-permeating Member, 33 1st oxidation catalyst, 34 compartment, 43 2nd oxidation catalyst, 50 heat insulation member.

Claims (3)

In the exhaust gas purification apparatus in which fuel is supplied to the exhaust gas discharged from the combustion chamber of the diesel engine by a fuel addition valve, and a purification catalyst or a DPF is disposed in the exhaust passage downstream of the fuel addition valve,
An exhaust port communicating with the combustion chamber of the diesel engine;
A fuel addition valve for supplying fuel into the exhaust port;
A first oxidation catalyst disposed downstream of the fuel addition valve;
A compartment that communicates with the exhaust port via the first oxidation catalyst;
The tip of the fuel addition valve is disposed in the compartment, and at least a part of the compartment in which the first oxidation catalyst is disposed protrudes into the exhaust port. apparatus. A second oxidation catalyst that is provided upstream of the fuel addition valve in the exhaust port and oxidizes the fuel;
A non-permeable member that is provided in the exhaust port and does not transmit the exhaust gas;
2. The exhaust gas purification device according to claim 1, wherein the compartment is formed of the first oxidation catalyst, the second catalyst, and the non-permeable member.   The exhaust gas purification device according to claim 1, wherein a heat insulating member is provided in the vicinity of the compartment and at least in the same range as the compartment around the exhaust port.

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