JP4363395B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine including an exhaust gas recirculation device (EGR device).

A reducing agent addition valve is provided in one exhaust manifold connected to one cylinder group of the multi-cylinder internal combustion engine, and an EGR gas outlet of the EGR device is provided in the other exhaust manifold connected to the other cylinder group; A technique for suppressing the reducing agent added from the reducing agent addition valve from entering the EGR device is known (see Patent Document 1).
JP 2004-76595 A JP 2001-152842 A JP 2002-256854 A JP 2002-21539 A Japanese Patent Laid-Open No. 10-30446

  However, in the technique of Patent Document 1, the one exhaust manifold provided with the reducing agent addition valve and the other exhaust manifold provided with the EGR gas outlet are located in front of the turbine of the supercharger disposed downstream. Join at. For this reason, there is a possibility that the reducing agent added from the reducing agent addition valve will enter the other exhaust manifold at the junction before the turbine, and the reducing agent may enter the EGR device.

  This invention is made | formed in view of the said situation, The place made into the objective is providing the technique which can suppress more that the reducing agent added in exhaust_gas | exhaustion flows into an EGR apparatus.

In the present invention, the following configuration is adopted. That is,
A turbocharger having a turbine in which a turbine rotor is driven by exhaust from an internal combustion engine having a plurality of cylinders;
A first exhaust passage extending from one cylinder group of the internal combustion engine;
A second exhaust passage extending from the other cylinder group of the internal combustion engine;
A third exhaust passage extending downstream from the turbine;
An exhaust purification catalyst disposed in the third exhaust passage;
Reducing agent addition means for adding a reducing agent to the exhaust;
An EGR device that supplies a part of the exhaust gas as EGR gas to the intake system;
An exhaust purification device for an internal combustion engine comprising:
Providing the reducing agent adding means in the first exhaust passage;
An EGR gas outlet of the EGR device is provided in the second exhaust passage;
Each exhaust gas from the first exhaust passage and the second exhaust passage flows into the turbine rotor while being largely separated without being mixed with each other, and is an exhaust gas purification apparatus for an internal combustion engine.

According to the present invention, the respective exhausts from the first and second exhaust passages are separated without being largely mixed up to the turbine rotor of the turbine disposed downstream of the first and second exhaust passages. It remains. Therefore, the exhaust of the first exhaust passage is unlikely to enter the second exhaust passage and is prevented from reaching the EGR gas outlet of the second exhaust passage. Therefore, even if the reducing agent is added while the EGR gas is supplied to the intake system, the added reducing agent can be further suppressed from flowing into the EGR device from the EGR gas outlet.

  Exhaust gas that has flowed into the turbine from the first exhaust passage may pass through a portion of the turbine where the temperature is relatively high.

  The reducing agent added to the exhaust gas in the first exhaust passage and flowing into the turbine easily adheres to the turbine when the ambient temperature decreases. Further, when the reducing agent adheres to the turbine, the reducing agent becomes a bonding agent, and particulate matter in the exhaust gas easily accumulates in the turbine. According to the above, the exhaust gas containing the reducing agent flows through a portion having a relatively high temperature in the turbine. Therefore, it can suppress that a reducing agent adheres in a turbine. Moreover, it can suppress that a particulate matter accumulates in a turbine resulting from the adhering reducing agent.

  There may be provided intake air amount adjusting means for making the intake air amount in the cylinder in the one cylinder group smaller than the intake air amount in the cylinder in the other cylinder group.

  By reducing the amount of intake air in the cylinder, the temperature of the exhaust gas discharged from the cylinder can be raised. Therefore, according to the above, the temperature of the exhaust in the first exhaust passage can be made higher than that in the second exhaust passage. Thereby, it can suppress that a reducing agent adheres in a 1st exhaust passage and a turbine. Further, since the vaporization of the reducing agent can be promoted, it is possible to raise the temperature of the exhaust purification catalyst more efficiently and to purify the exhaust gas in the exhaust purification catalyst more efficiently.

  There may be provided swirl control means for making the intake air to the one cylinder group have a higher swirl than the intake air to the other cylinder group.

  When the intake air amount in the cylinder is reduced in one cylinder group, the air-fuel ratio is lowered in the one cylinder group, and smoke is likely to be generated. According to the above, the air-fuel ratio distribution in the cylinders can be made more uniform by increasing the intake air in one cylinder group. Thereby, generation | occurrence | production of smoke can be suppressed.

  According to the present invention, it is possible to further suppress the reducing agent added to the exhaust gas from entering the EGR gas outlet. Accordingly, it is possible to further suppress the reducing agent added to the exhaust from flowing into the EGR device.

  Specific examples of the present invention will be described below.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust gas purification apparatus according to Embodiment 1 of the present invention is applied and its intake / exhaust system.

  An internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine having four cylinders, a first cylinder # 1 to a fourth cylinder # 4.

  An intake manifold 2 is connected to the intake port of each cylinder on the upstream side of the internal combustion engine 1. An intake pipe 3 is connected to the intake manifold 2 on the upstream side. A compressor 4 a of a supercharger (turbocharger) 4 is arranged in the middle of the intake pipe 3.

  Further, an exhaust manifold is connected to the internal combustion engine 1 via an exhaust port of each cylinder on the downstream side. In this embodiment, the exhaust manifold is separated into two. A first exhaust manifold 5 is connected to the first cylinder # 1 and the fourth cylinder # 4, and a second exhaust manifold 6 is connected to the second cylinder # 2 and the third cylinder # 3. The 1st exhaust pipe 7 is connected to the downstream. A second exhaust pipe 8 is connected to the second exhaust manifold 6 on the downstream side. The first exhaust manifold 5 and the first exhaust pipe 7 correspond to the first exhaust passage according to the present invention. The second exhaust manifold 6 and the second exhaust pipe 8 correspond to the second exhaust passage according to the present invention.

  The downstream ends of the first and second exhaust pipes 7 and 8 are connected to a turbine 4 b of a supercharger (turbocharger) 4. The turbocharger 4 receives the exhaust from the first and second exhaust pipes 7 and 8, and the turbine rotor 46 of the turbine 4b rotates, whereby the compressor 4a connected to the turbine 4b rotates and supercharges the intake air. To do. The supercharger 4 is a variable capacity turbocharger (variable nozzle turbocharger) having a variable nozzle 41 in the turbine 4b.

  Here, as shown in FIG. 2, the inlet connecting the first and second exhaust pipes 7 and 8 of the turbine 4 b is divided into two parts, and the first and second exhaust pipes 7 and 8 are divided into two first parts. 1 and the second inlets 42 and 43, respectively.

  The supercharger 4 employs a twin scroll turbo in which the internal passages are divided into two from the first and second inlets 42 and 43 which are two inlets. A first scroll passage 44 extends from the first inlet 42, and a second scroll passage 45 extends from the second inlet 43. The first and second scroll passages 44 and 45 extend in a spiral shape, and exhaust gas flows out to the variable nozzle 41, and the turbine rotor 46 is rotated by the exhaust gas.

  The turbine 4 b is provided with a bearing housing 47 adjacent to the turbine rotor 46. Lubricating oil and cooling water are supplied to the bearing housing 47. For this reason, the temperature on the bearing housing 47 side in the turbine 4b is lower than that on the exhaust outlet side on the opposite side. In the turbine 4 b, the second inlet 43 is disposed on the bearing housing 47 side, and the first inlet 42 is disposed on the exhaust outlet side away from the bearing housing 47.

  A third exhaust pipe 9 is connected downstream of the turbine 4 b of the supercharger 4. In the middle of the third exhaust pipe 9, a filter 10 carrying an NOx storage reduction catalyst as an exhaust purification catalyst is disposed. A muffler (not shown) is disposed downstream of the filter 10, and the exhaust is discharged to the atmosphere via the muffler.

  On the other hand, an exhaust gas recirculation device (EGR device) 11 is mounted on the internal combustion engine 1. The EGR device 11 reduces the NOx contained in the exhaust gas by lowering the combustion temperature of the internal combustion engine 1 by recirculating part of the exhaust gas as EGR gas to the intake manifold 2 of the internal combustion engine 1.

  The EGR device 11 has an EGR pipe 12 having one end connected to the second exhaust pipe 8 and the other end connected to the intake manifold 2. An EGR gas outlet 13 for guiding EGR gas from the second exhaust pipe 8 to the EGR pipe 12 is provided in the middle of the second exhaust pipe 8.

  Further, a reducing agent addition nozzle 14 as a reducing agent addition means is attached to the first exhaust manifold 5 of the internal combustion engine 1. The reducing agent addition nozzle 14 adds fuel as a reducing agent into the exhaust gas. The reducing agent addition nozzle 14 is disposed immediately downstream of the cylinder # 1 of the first exhaust manifold 5.

  The internal combustion engine 1 having the above configuration is provided with an electronic control unit (ECU) 15 for controlling the internal combustion engine 1. The ECU 15 is a control computer including a CPU, a ROM, a RAM, a backup RAM, and the like.

  The ECU 15 operates in accordance with a program stored in the ROM, and executes an EGR operation using the EGR device 11 and a reducing agent addition using the reducing agent addition nozzle 14.

  Here, the EGR operation is when the operation state of the internal combustion engine 1 is in a predetermined operation region where the exhaust pressure is higher than the intake pressure in order to reduce the combustion temperature in the internal combustion engine 1 and suppress the generation of NOx. In addition, a part of the exhaust gas is introduced into the intake manifold 2 via the EGR pipe 12.

  The addition of reducing agent is to add fuel from the reducing agent addition nozzle 14. This is performed during processing on the filter 10 such as NOx reduction processing, SOx poisoning elimination processing, PM oxidation removal processing, and the like.

  In the NOx reduction process, the fuel as the reducing agent is added from the reducing agent addition nozzle 14 into the exhaust gas, so that the air-fuel ratio of the exhaust gas flowing into the NOx catalyst of the filter 10 is changed to the rich air-fuel ratio and stored in the NOx catalyst. This is a process for releasing / reducing NOx. In the SOx poisoning elimination process, when the catalyst temperature is 600 ° C. to 800 ° C., the fuel as the reducing agent is added from the reducing agent addition nozzle 14 into the exhaust gas, thereby reducing the air-fuel ratio of the exhaust gas flowing into the NOx catalyst of the filter 10. This is a process for releasing and reducing SOx stored in the NOx catalyst with a rich air-fuel ratio. In the PM oxidation removal process, fuel as a reducing agent is added into the exhaust gas from the reducing agent addition nozzle 14 to oxidize those unburned fuel components in the NOx catalyst of the filter 10 and filter the heat generated during the oxidation. 10 is a process for increasing the temperature of 10 and removing PM trapped in the filter 10.

  In the present embodiment, a reducing agent addition nozzle 14 is provided in the first exhaust manifold 5, and an EGR gas outlet 13 of the EGR device 11 is provided in the second exhaust pipe 8. The first and second exhaust pipes 7 and 8 are connected to the two divided first and second inlets 42 and 43 of the turbine 4b of the supercharger 4 which is a twin scroll turbo.

  That is, in the present embodiment, the respective exhausts from the first and second exhaust manifolds 5 and 6 and the first and second exhaust pipes 7 and 8 are arranged downstream of the first and second exhaust pipes 7 and 8. Even in the turbine 4b that has been separated, it flows into the turbine rotor 46 while being separated without being mostly mixed. Therefore, the exhaust from the first exhaust manifold 5 and the first exhaust pipe 7 is less likely to enter the second exhaust pipe 8 after passing through the turbine 4b, and is prevented from reaching the EGR gas outlet 13 of the second exhaust pipe 8. Is done. Therefore, even if fuel is added from the reducing agent addition nozzle 14 during the EGR operation, it is possible to further suppress the added fuel from entering the EGR gas outlet 13. Therefore, it can suppress more that the reducing agent added in exhaust_gas | exhaustion flows into the EGR apparatus 11. FIG.

  As a result, it is possible to reduce torque fluctuations and exhaust emission deterioration caused by the fuel as the reducing agent flowing into the intake system. Further, the reducing agent can be added more efficiently with as little added fuel as possible.

In addition, the supercharger 4 is a twin scroll turbo, and first and second scroll passages 44 and 45 are provided from the first and second inlets 42 and 43, respectively. The exhaust from the second exhaust pipes 7 and 8 is separated. For this reason, the exhaust gas from the first exhaust manifold 5 and the first exhaust pipe 7 reaches the EGR gas outlet 13 of the second exhaust pipe 8 without being easily routed to the second exhaust pipe 8 even through the turbine 4b. It is suppressed.

  Further, as shown in FIG. 2, the first inlet 42 is an exhaust outflow side where the exhaust discharged from the first exhaust pipe 7 is a portion where the temperature of the turbine 4 b of the turbocharger 4 is a twin scroll turbo is relatively high. The first scroll passage 44 is disposed at such a position.

  The fuel added to the exhaust gas in the first exhaust manifold 5 and flowing into the turbine 4b tends to adhere to the turbine 4b when the ambient temperature decreases. Further, when the fuel adheres to the turbine 4b, the fuel becomes a bonding agent, and particulate matter in the exhaust gas easily accumulates in the turbine. However, as shown in FIG. 2, when the first inlet 42 is arranged, the exhaust of the first exhaust manifold 5 to which fuel is added from the reducing agent addition nozzle 14 is a portion where the temperature of the turbine 4b is relatively high. It passes through the first scroll passage 44 on the exhaust outlet side. Therefore, it can suppress that the fuel which is a reducing agent adheres in the turbine 4b. Further, it is possible to suppress the particulate matter from being deposited, for example, between the variable nozzle 41 and the first scroll passage 44 in the turbine 4b due to the attached fuel.

  Furthermore, by providing the EGR gas outlet 13 in the middle of the second exhaust pipe 8 on the downstream side of the second exhaust manifold 6, the flow of the EGR gas can be made smooth, the pressure loss can be reduced, and the fuel efficiency can be maintained well. Can do.

  FIG. 3 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust purification system according to Embodiment 2 of the present invention is applied and its intake / exhaust system. In the present embodiment, only differences from the first embodiment will be described.

  In this embodiment, the internal combustion engine 1 includes a variable valve mechanism 16 that controls the valve timing of the intake valve in each cylinder. The variable valve mechanism 16 is electrically connected to the ECU 15.

  Then, using the variable valve mechanism 16, the intake air amount in the cylinders of the first and fourth cylinders # 1 and # 4 connected to the first exhaust manifold 5 is changed to the second exhaust manifold 6. The amount of intake air in the cylinders in the third cylinders # 2 and # 3 is made smaller.

  Specifically, the closing timing of the intake valves in the first and fourth cylinders # 1 and # 4 is retarded compared to the closing timing of the intake valves in the second and third cylinders # 2 and # 3. The variable valve mechanism 16 and the ECU 14 that perform this control correspond to intake air amount adjusting means.

  Thus, if the intake air amount in the cylinders of the first and fourth cylinders # 1 and # 4 is reduced, the temperature of the exhaust gas discharged from the first and fourth cylinders # 1 and # 4 having a small intake air amount is reduced. Can be raised. Accordingly, the exhaust temperature of the first exhaust manifold 5 and the first exhaust pipe 7 can be made higher than the exhaust temperature of the second exhaust manifold 6 and the second exhaust pipe 8. For this reason, even if fuel as a reducing agent is added from the reducing agent addition nozzle 14 to the exhaust of the first exhaust manifold 6, the fuel is in the first exhaust manifold 5 and the first exhaust pipe 7 or in the turbine 4b in the high-temperature exhaust. It is difficult to become a bonding agent for depositing particulate matter due to adhesion.

  Further, when the temperature of the exhaust of the first exhaust manifold 5 and the first exhaust pipe 7 is increased in this way, the vaporization of the fuel as the reducing agent can be promoted in the high-temperature exhaust, so that the temperature of the filter 10 can be increased more efficiently. Or purification of exhaust gas in the filter 10 can be performed more efficiently.

  FIG. 4 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust gas purification apparatus according to Embodiment 3 of the present invention is applied and its intake / exhaust system. In the present embodiment, only differences from the first embodiment will be described.

  In this embodiment, the internal combustion engine 1 is equipped with a swirl control valve (SCV) 17 at the intake port of each cylinder. The swirl control valve 17 is electrically connected to the ECU 15. The swirl control valve 17 can be controlled separately for each cylinder. The ECU 15 controls the opening and closing of each swirl control valve 17 corresponding to each cylinder to adjust the strength of the vortex generated in each cylinder.

  Then, the swirl control valve 17 is used to intake air to the first and fourth cylinders # 1 and # 4 connected to the first exhaust manifold 5 and to the second and third cylinders # connected to the second exhaust manifold 6. 2. Swirl higher than intake to # 3.

  Specifically, in the second and third cylinders # 2 and # 3, the swirl control valve 17 is opened and the intake amount is increased. On the other hand, in the first and fourth cylinders # 1 and # 4, the swirl control valve 17 is closed and the intake amount is reduced, and the swirl generated in the first and fourth cylinders # 1 and # 4 is increased ( High swirl).

  As described above, when the swirl in the first and fourth cylinders # 1 and # 4 is increased and the intake air amount in the first and fourth cylinders # 1 and # 4 is reduced, the intake air amount is reduced. 1. The temperature of exhaust discharged from the fourth cylinders # 1 and # 4 can be raised. Accordingly, the exhaust temperature of the first exhaust manifold 5 and the first exhaust pipe 7 can be made higher than the exhaust temperature of the second exhaust manifold 6 and the second exhaust pipe 8. For this reason, even if fuel as a reducing agent is added from the reducing agent addition nozzle 14 to the exhaust of the first exhaust manifold 6, the fuel is in the first exhaust manifold 5 and the first exhaust pipe 7 or in the turbine 4b in the high-temperature exhaust. It is difficult to become a bonding agent for depositing particulate matter due to adhesion.

  Further, when the temperature of the exhaust of the first exhaust manifold 5 and the first exhaust pipe 7 is increased in this way, the vaporization of the fuel as the reducing agent can be promoted in the high-temperature exhaust, so that the temperature of the filter 10 can be increased more efficiently. Or purification of exhaust gas in the filter 10 can be performed more efficiently.

  Here, when the intake air amount in the first and fourth cylinders # 1 and # 4 is decreased, smoke is generated in the first and fourth cylinders # 1 and # 4 because the air-fuel ratio decreases. It becomes easy. However, the swirl control valve 17 can make the air-fuel ratio distribution in the cylinders more uniform by increasing the intake air in the first and fourth cylinders # 1 and # 4. Thereby, generation | occurrence | production of smoke can be suppressed.

1 is a diagram illustrating a schematic configuration of an internal combustion engine to which an exhaust gas purification apparatus according to Embodiment 1 is applied and an intake / exhaust system thereof. 1 is a diagram illustrating a schematic configuration of a turbine according to Embodiment 1. FIG. It is a figure which shows schematic structure of the internal combustion engine to which the exhaust gas purification apparatus which concerns on Example 2 is applied, and its intake / exhaust system. It is a figure which shows schematic structure of the internal combustion engine to which the exhaust gas purification apparatus which concerns on Example 3 is applied, and its intake / exhaust system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Intake manifold 3 Intake pipe 4 Supercharger 4a Compressor 4b Turbine 5 1st exhaust manifold 6 2nd exhaust manifold 7 1st exhaust pipe 8 2nd exhaust pipe 9 3rd exhaust pipe 10 Filter 11 EGR apparatus 12 EGR pipe 13 EGR gas outlet 14 Reducing agent addition nozzle 15 ECU
16 Variable valve mechanism 17 Swirl control valve 46 Turbine rotor

Claims (3)

A turbocharger having a turbine in which a turbine rotor is driven by exhaust from an internal combustion engine having a plurality of cylinders;
A first exhaust passage extending from one cylinder group of the internal combustion engine;
A second exhaust passage extending from the other cylinder group of the internal combustion engine;
A third exhaust passage extending downstream from the turbine;
An exhaust purification catalyst disposed in the third exhaust passage;
Reducing agent addition means for adding a reducing agent to the exhaust;
An EGR device that supplies a part of the exhaust gas as EGR gas to the intake system;
An exhaust purification device for an internal combustion engine comprising:
Providing the reducing agent adding means in the first exhaust passage;
An EGR gas outlet of the EGR device is provided in the second exhaust passage;
Each of the exhaust from the first exhaust passage and the second exhaust passage flows into the turbine rotor while being largely separated without being mixed ,
An exhaust emission control device for an internal combustion engine, comprising: an intake air amount adjusting means for making an intake air amount in a cylinder in the one cylinder group smaller than an intake air amount in a cylinder in the other cylinder group .   2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the exhaust gas flowing into the turbine from the first exhaust passage passes through a portion of the turbine having a relatively high temperature. The exhaust gas purification apparatus for an internal combustion engine according to claim 1 or 2 , further comprising swirl control means for making the intake air to the one cylinder group have a higher swirl than the intake air to the other cylinder group.

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