JP2009024619A - Exhaust control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate early warm-up and the like of a catalyst without generating pressure loss, in an exhaust control device of an internal combustion engine provided with two superchargers serially arranged in an air intake passage and an exhaust passage. <P>SOLUTION: The exhaust control device of the internal combustion engine is provided with the first and second superchargers serially arranged in the air intake passage and the exhaust passage, a first bypass passage for bypassing a first turbine of the first supercharger, a first bypass valve arranged in the first bypass passage, a first bypass valve control means, a second bypass passage for bypassing a second turbine of the second supercharger, a second bypass valve and the first catalyst arranged in the second bypass passage and a second bypass valve control means. Exhaust gas can flow to a route including the first catalyst or another route via the second bypass valve by appropriately controlling the first and the second bypass valves according to a loading state of the internal combustion engine. Thus, early warm-up of the first catalyst can be facilitated without generating pressure loss. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust control device for an internal combustion engine including two superchargers arranged in series in an intake passage and an exhaust passage.

  Conventionally, exhaust gas from an internal combustion engine that purifies nitrogen oxides (NOx) contained in exhaust gas using an exhaust gas recirculation device (EGR device), a NOx catalyst, a reducing agent addition device that supplies a reducing agent to the NOx catalyst, and the like. An example of the purification device is disclosed in Patent Documents 1 and 2.

  In the exhaust gas purification apparatus for an internal combustion engine described in Patent Document 1, a catalytic converter including a NOx catalyst is disposed downstream of a turbine of one supercharger. In this exhaust gas purification apparatus for an internal combustion engine, the reducing agent addition device and the exhaust gas recirculation device are arranged at positions separated from each other in the exhaust manifold. Thus, the reducing agent discharged from the reducing agent addition device can be prevented from flowing into the intake system via the exhaust gas recirculation device, and the occurrence of torque fluctuation or the like of the internal combustion engine can be prevented.

  On the other hand, in the exhaust gas purification apparatus for an internal combustion engine described in Patent Document 2, a catalytic converter including a NOx catalyst is arranged downstream of two turbocharger turbines. Further, in this exhaust gas purification apparatus for an internal combustion engine, a split type exhaust manifold, a NOx catalyst arranged downstream of the exhaust collecting part of each split exhaust type manifold, and an FGR device are provided, and the reducing agent adding means is one exhaust gas. It is provided on the manifold side, and the EGR outlet is provided on the other exhaust manifold side. As a result, even if a reducing agent is added during mass EGR operation, it is possible to minimize the added reducing agent from flowing into the intake system through the EGR pipe due to exhaust pulsation, such as torque fluctuations of the internal combustion engine, etc. It is said that the occurrence of

  Patent Documents 3 to 5 describe an example of a two-stage turbo system configured by arranging two turbos in series in an intake system and an exhaust system. In such a two-stage turbo system, two low-pressure turbos and high-pressure turbos are selectively used according to the engine speed or the like. Thereby, there exists an effect that suitable supercharging can be obtained over the full load area | region of an internal combustion engine. In particular, in the two-stage turbo system described in Patent Documents 3 to 5, in order to properly use two low-pressure turbo and high-pressure turbo, the low-pressure turbo and high-pressure turbo are bypassed with respect to the intake passage and the exhaust passage. A bypass path and an on-off valve that controls opening and closing of the bypass path are provided.

JP 2002-21539 A JP 2004-76595 A JP 2005-98250 A JP-A-2005-146906 Utility Model Registration No. 2522802

  In the exhaust gas purification apparatus for an internal combustion engine described in Patent Documents 1 and 2, a catalytic converter including a NOx catalyst is disposed downstream of one or two turbocharger turbines. The capacity is not described. Here, in a vehicle equipped with an engine with a supercharger as in Patent Documents 1 and 2 above, since the heat capacity of the supercharger is large, the supercharger absorbs the temperature of the exhaust gas, and the NOx catalyst is exhausted by the exhaust gas. It is difficult to warm up enough. From this point of view, under such a configuration, when the capacity of the NOx catalyst is reduced in order to quickly warm up the NOx catalyst in a low temperature state immediately after engine startup, the pressure in the NOx catalyst is thereby reduced. There is a problem that loss increases. In addition, the increase in pressure loss in the NOx catalyst causes a problem that supercharging by the turbine of the supercharger decreases and fuel consumption deteriorates.

  Further, in the exhaust gas purification apparatus for an internal combustion engine described in Patent Documents 1 and 2, since the reducing agent addition valve is provided in the exhaust port of a predetermined cylinder, the reducing agent may circulate to the exhaust gas recirculation device to some extent. Although it can be prevented, the prevention effect is not sufficient. That is, in these exhaust gas purification apparatuses for internal combustion engines, the reducing agent addition valve is positioned upstream of the EGR pipe due to the above-described configuration, so that the reducing agent is mixed into the EGR gas, thereby reducing the reducing agent. There is a problem that a part of the agent easily goes around to the exhaust gas recirculation device.

  Further, according to this configuration, since the reducing agent addition valve is provided in the exhaust port of the predetermined cylinder (or in the vicinity of the exhaust valve), the reducing agent addition valve is constantly exposed to the exhaust gas, and the temperature rises. There is also a problem that the reducing agent remaining in the tip or the injection hole of the reducing agent addition valve is carbonized due to heat and the reducing agent addition valve is clogged.

  The present invention has been made in view of the above points, and in an exhaust control device for an internal combustion engine including two superchargers arranged in series in an intake passage and an exhaust passage, a catalyst without causing pressure loss is provided. The purpose of this is to prevent the reductant from flowing into the exhaust gas recirculation device, prevent the reductant from clogging with the reductant, and the like.

  In one aspect of the present invention, an exhaust control device for an internal combustion engine includes a first supercharger disposed in an intake passage and an exhaust passage, and disposed in the intake passage and the exhaust passage. A second turbocharger arranged in series with the supercharger, and an upstream side of the first turbine of the first supercharger and a downstream side of the first turbine are connected in the exhaust passage. A first bypass passage, a first bypass valve provided in the first bypass passage, first bypass valve control means for controlling an open / closed state of the first bypass valve, and the exhaust A second bypass passage connecting the upstream side of the second turbine of the second turbocharger and the downstream side of the second turbine, and the second bypass passage. The second bypass valve and the open / closed state of the second bypass valve. Comprising a second bypass valve control means for, and a first catalyst provided in the second bypass passage.

  The exhaust control device for an internal combustion engine described above is arranged in a first supercharger arranged in the intake passage and the exhaust passage, and arranged in series with the first supercharger while being arranged in the intake passage and the exhaust passage. A second supercharger. In a preferred example, the first supercharger is configured as a low-capacity low-speed supercharger having a large supercharging capability in the low and medium speed range, and the second supercharger is configured to have a supercharging capability in the medium and high speed range. A so-called two-stage supercharging system configured as a large-capacity, high-speed supercharger is preferable. In this case, supercharging is performed mainly by the first supercharger in the low / medium speed region, and supercharging is performed mainly by the second supercharger in the medium / high speed region. The exhaust control device for an internal combustion engine includes: a first bypass passage connecting an upstream side of the first turbine of the first supercharger and a downstream side of the first turbine in the exhaust passage; The first bypass valve provided in the first bypass passage, the first bypass valve control means for controlling the open / closed state of the first bypass valve, and the second supercharger second in the exhaust passage. A second bypass passage connecting the upstream side of the turbine and the downstream side of the second turbine, a second bypass valve provided in the second bypass passage, and opening and closing of the second bypass valve 2nd bypass valve control means which controls a state, and the 1st catalyst provided in the 2nd bypass passage. The first catalyst is preferably a small catalyst having a small volume, and is preferably a NOx occlusion reduction catalyst that occludes and purifies nitrogen oxides (NOx).

  According to this configuration, the first bypass valve control means and the second bypass valve control means control the open / close state of the first bypass valve and the second bypass valve in accordance with the load state of the internal combustion engine. Thus, the exhaust gas discharged from the internal combustion engine to the exhaust passage can be flowed to a desired passage among the exhaust passage, the first bypass passage, and the second bypass passage. Therefore, the first supercharger and the second supercharger are flowed through the desired passage by flowing the exhaust gas to the first turbine of the first supercharger or the second turbine of the second supercharger. It is possible to properly use the feeder. Further, by flowing the exhaust gas to the second bypass passage through a desired passage, the exhaust gas can be introduced into the first catalyst, and early warm-up of the first catalyst can be promoted. .

  In one aspect of the exhaust control device for an internal combustion engine, in the exhaust passage, downstream of the joining portion of the second bypass passage that joins the exhaust passage on the downstream side of the second turbine, When a second catalyst having a larger capacity than the first catalyst is provided, and immediately after starting the internal combustion engine, when the exhaust temperature of the internal combustion engine is low and / or when the temperature of the second catalyst is low The first bypass valve control means keeps the first bypass valve in a closed state, and the second bypass valve control means opens the second bypass valve. Here, the second catalyst is preferably a NOx occlusion reduction catalyst that occludes and purifies nitrogen oxides (NOx).

  In this aspect, the exhaust gas discharged from the internal combustion engine to the exhaust passage mainly includes the first turbine of the first supercharger, the branch portion of the second bypass valve, the first catalyst, and the second bypass. It flows with the junction of the valve, the second catalyst. As a result, part of the exhaust gas flows to the first catalyst via the second bypass valve, so that the temperature of the first catalyst can be raised quickly. As a result, nitrogen oxide (NOx) contained in the exhaust gas can be purified by the first catalyst and the second catalyst. Further, even when the internal combustion engine becomes a heavy load from such a state, a large amount of exhaust gas flows to the first catalyst because the second bypass valve is open, so that the first catalyst Warm-up is further promoted.

  In a preferred example, the second bypass valve control means closes the second bypass valve after the internal combustion engine is warmed up. As a result, the exhaust gas does not pass through the first catalyst having a small volume. Therefore, it is possible to avoid an increase in the exhaust pressure generated by passing through the first catalyst and a pressure loss in the first catalyst. Furthermore, since it is possible to avoid the occurrence of pressure loss in the first catalyst, the supercharging by the first turbine of the first supercharger is reduced accordingly, and the fuel consumption is deteriorated. Can be prevented. Further, according to the exhaust control after warming up the internal combustion engine, the first catalyst is not exposed to the high-temperature exhaust gas, so that the deterioration of the first catalyst due to the heat of the high-temperature exhaust gas can be prevented. .

  In another aspect of the exhaust control device for an internal combustion engine, when the internal combustion engine is at a low load after the warm-up of the internal combustion engine, the first bypass valve control means is configured to control the first bypass valve control means. While maintaining the bypass valve in the closed state, the second bypass valve control means maintains the second bypass valve in the closed state.

  In this aspect, the exhaust gas discharged from the internal combustion engine to the exhaust passage flows through the first turbine of the first supercharger, the second turbine of the second supercharger, the second catalyst, and the like. As a result, the first turbine and the second turbine rotate, and the torque generated by the rotation is transmitted to the first compressor of the first supercharger and the second compressor of the second supercharger, respectively. Pay is done. In this operating state, the amount of exhaust gas is small, so that supercharging is mainly obtained by the first turbine. In this case, nitrogen oxide (NOx) contained in the exhaust gas is purified by the second catalyst.

  In another aspect of the exhaust control apparatus for an internal combustion engine, the first bypass valve control means opens the first bypass valve when the internal combustion engine becomes a high load. This is after the warm-up of the internal combustion engine, and when the internal combustion engine is changed from a low load to a high load, the amount of the exhaust gas increases, so the first turbine with a small capacity for the low and medium speed range. This is because resistance becomes difficult and the exhaust gas hardly passes through the first turbine. As a result, a large amount of exhaust gas discharged from the internal combustion engine to the exhaust passage flows mainly through the first bypass passage, the second turbine of the second supercharger, and the second catalyst. Therefore, the second turbine is rotated by a large amount of exhaust gas, and the torque generated by the rotation is transmitted to the second compressor of the second supercharger to perform supercharging. As a result, the required supercharging amount and supercharging pressure can be obtained in the medium to high speed range. In this case, nitrogen oxide (NOx) contained in the exhaust gas is purified by the second catalyst.

  In another aspect of the exhaust gas control apparatus for an internal combustion engine, the internal combustion engine further includes a reducing agent addition valve that supplies a reducing agent to the exhaust passage, and the reducing agent addition valve is connected to the first turbine in the exhaust passage. It is provided between the second turbines.

  As a result, the reducing agent addition valve is disposed in the exhaust passage downstream of the first turbine of the first supercharger, and is injected (added) from the reducing agent addition valve toward the exhaust passage. It is possible to prevent the reducing agent from entering the EGR passage located upstream of the first supercharger. Further, since the reducing agent addition valve is disposed in the exhaust passage upstream of the second turbine of the second supercharger, the reducing agent injected from the reducing agent addition valve toward the exhaust passage is the first. By passing through the second turbine, mixing / stirring of the exhaust gas and the reducing agent is promoted by the second turbine. Furthermore, according to this aspect, the reducing agent addition valve is not disposed near the exhaust manifold where the temperature is higher than that of the exhaust passage between the first turbine and the second turbine. The heating temperature can be lowered, and the reducing agent remaining in the tip of the reducing agent addition valve or the injection hole may be carbonized due to the heat of the exhaust gas, resulting in clogging of the reducing agent addition valve, or the heat of the exhaust gas. This can prevent the reducing agent addition valve from being damaged.

  In another aspect of the exhaust control device for an internal combustion engine, the first catalyst is disposed in a branch portion of the second bypass passage that branches from the exhaust passage on the upstream side of the second turbine, The reducing agent addition valve is arranged coaxially with respect to the branch portion of the second bypass passage and the first catalyst in the exhaust passage. According to this aspect, the distance until the reducing agent injected from the reducing agent addition valve collides with the inner wall of the exhaust passage can be increased. In other words, the reducing agent is sprayed in the second bypass passage or the like. Can take a large space. As a result, it is possible to reduce the adhesion of the injected reducing agent to the inner wall of the exhaust passage, and it is possible to promote the vaporization of the reducing agent and promote the mixing of the exhaust gas and the reducing agent.

  In another aspect of the exhaust gas control apparatus for an internal combustion engine, the second bypass valve control means may be configured such that the reducing agent addition valve adds the reducing agent toward the branch portion of the second bypass passage. Then, the second bypass valve in the closed state is controlled to the open side. Here, controlling the second bypass valve to the open side includes controlling the second bypass valve in a partially opened state, or controlling the second bypass valve in a half opened state, and the like. Moreover, it is preferable that the ratio of the opening degree of the second bypass valve is adjusted based on vehicle specifications such as engine speed and torque and various conditions.

  According to this aspect, the reducing agent introduced into the second bypass passage through the reducing agent addition valve is cracked (chemical decomposition reaction) by the first catalyst or partially oxidized. This makes it possible to supply an appropriate amount of cracked reducing agent to the second catalyst during the reduction in the low load or medium load state of the internal combustion engine, and the unburned fuel component in the exhaust gas by the second catalyst. It is possible to improve the reduction efficiency of nitrogen oxide (NOx) with respect to (CO, HC) and to introduce a part of the injected reducing agent into the second turbine side of the second supercharger. The effect of mixing / stirring the exhaust gas and the reducing agent by the second turbine can be promoted.

  In another aspect of the present invention, an exhaust control device for an internal combustion engine includes a first supercharger disposed in the intake passage and the exhaust passage, the first supercharger disposed in the intake passage and the exhaust passage, and the first supercharger. A second turbocharger arranged in series with the supercharger, and an upstream side of the first turbine of the first supercharger and a downstream side of the first turbine are connected in the exhaust passage. A first bypass passage, a first bypass valve provided in the first bypass passage, a first bypass valve control means for controlling an open / closed state of the first bypass valve, The first catalyst is located between the branch portion of the first bypass passage that branches from the exhaust passage on the upstream side of the first turbine and the first turbine. To the exhaust passage, or to the exhaust passage downstream of the first turbine. A merging portion of the first bypass passage merging with, is provided in the exhaust passage located between the first turbine.

  The exhaust control device for an internal combustion engine described above is arranged in a first supercharger arranged in the intake passage and the exhaust passage, and arranged in series with the first supercharger while being arranged in the intake passage and the exhaust passage. A second supercharger. In a preferred example, the first supercharger is configured as a low-capacity low-speed supercharger having a large supercharging capability in the low and medium speed range, and the second supercharger is configured to have a supercharging capability in the medium and high speed range. A so-called two-stage supercharging system configured as a large-capacity, high-speed supercharger is preferable. In this case, supercharging is performed mainly by the first supercharger in the low / medium speed region, and supercharging is performed mainly by the second supercharger in the medium / high speed region. The exhaust control device for an internal combustion engine includes: a first bypass passage connecting an upstream side of the first turbine of the first supercharger and a downstream side of the first turbine in the exhaust passage; And a first bypass valve provided in the first bypass passage, a first bypass valve control means for controlling an open / closed state of the first bypass valve, and a first catalyst. Here, the first catalyst is preferably a small catalyst having a small volume, and is preferably a NOx occlusion reduction catalyst that occludes and purifies nitrogen oxides (NOx).

  In particular, the first catalyst is an exhaust passage located between the branch portion of the first bypass passage branched from the exhaust passage on the upstream side of the first turbine and the first turbine, or of the first turbine. It is provided in the exhaust passage located between the joining portion of the first bypass passage that joins the downstream exhaust passage and the first turbine.

According to this configuration, the exhaust gas discharged from the internal combustion engine to the exhaust passage by the first bypass valve control means controlling the open / close state of the first bypass valve in accordance with the load state of the internal combustion engine or the like. Can flow into a desired passage of the exhaust passage and the first bypass passage.
Therefore, the first supercharger and the second supercharger are flowed through the desired passage by flowing the exhaust gas to the first turbine of the first supercharger or the second turbine of the second supercharger. It is possible to properly use the feeder. In addition, by introducing the exhaust gas into the first catalyst through a desired passage, early warm-up of the first catalyst can be promoted.

  In one aspect of the exhaust control device for an internal combustion engine described above, when the internal combustion engine is at a low load after the warm-up of the internal combustion engine, the first bypass valve control means includes the first bypass valve. Keep closed.

  According to this aspect, the exhaust gas discharged from the internal combustion engine to the exhaust passage flows through the first turbine of the first supercharger, the first catalyst, and the first turbine of the second supercharger. As a result, the first turbine and the second turbine rotate, and the torque generated by the rotation is transmitted to the first compressor of the first supercharger and the second compressor of the second supercharger, respectively. Pay is done. In this operating state, the amount of exhaust gas is small, so that supercharging is mainly obtained by the first turbine. Further, since the temperature of the exhaust gas is low when the internal combustion engine is at a low load, the temperature of the first catalyst can be quickly raised by passing most of the exhaust gas through the first catalyst. As a result, the nitrogen oxide (NOx) contained in the exhaust gas can be purified by the first catalyst.

  In another aspect of the exhaust control device for the internal combustion engine, the first bypass valve control means opens the first bypass valve when the internal combustion engine becomes a high load. This is because when the internal combustion engine is changed from a low load to a high load, the amount of the exhaust gas increases. Therefore, the first turbine with a small capacity for the low and medium speed range becomes a resistance and the exhaust gas This is because it becomes difficult to pass through the first turbine. As a result, a large amount of exhaust gas discharged from the internal combustion engine to the exhaust passage flows mainly through the first bypass passage and the second turbine of the second supercharger. Therefore, the second turbine is rotated by a large amount of exhaust gas, and the torque generated by the rotation is transmitted to the second compressor of the second supercharger to perform supercharging. As a result, the required supercharging amount and supercharging pressure can be obtained in the medium to high speed range. Further, in this case, the exhaust gas flows to the first bypass passage side without passing through the first catalyst, so that an increase in exhaust pressure generated by passing through the first catalyst, And it is possible to avoid the occurrence of pressure loss in the first catalyst. Furthermore, since it is possible to avoid the occurrence of pressure loss in the first catalyst, the supercharging by the first turbine of the first supercharger is reduced accordingly, and the fuel consumption is deteriorated. Can be prevented. Further, according to the exhaust control after warming up the internal combustion engine, the first catalyst is not exposed to the high-temperature exhaust gas, so that the deterioration of the first catalyst due to the heat of the high-temperature exhaust gas can be prevented. .

  In another aspect of the exhaust gas control apparatus for an internal combustion engine, the exhaust gas control apparatus further includes a reducing agent addition valve that supplies a reducing agent to the exhaust passage, and the reducing agent addition valve includes the first bypass passage in the exhaust passage. Between the branch portion and the junction portion of the first bypass passage. As a result, the reducing agent addition valve is disposed in the exhaust passage downstream of the first turbine of the first supercharger, so that the reducing agent injected toward the exhaust passage from the reducing agent addition valve is reduced. Therefore, it is possible to prevent the EGR passage located upstream of the first supercharger. Further, according to this aspect, the reducing agent addition valve is not disposed near the exhaust manifold where the temperature is higher than that of the exhaust passage between the first turbine and the second turbine. The heating temperature can be lowered, and the reducing agent remaining in the tip of the reducing agent addition valve or the injection hole may be carbonized due to the heat of the exhaust gas, resulting in clogging of the reducing agent addition valve, or the heat of the exhaust gas. This can prevent the reducing agent addition valve from being damaged.

  In a preferred example, the reducing agent addition valve is preferably provided between the branch portion of the first bypass passage and the first turbine of the first supercharger. As a result, the reducing agent addition valve is disposed in the exhaust passage upstream of the second turbine of the second supercharger, so that the reducing agent injected toward the exhaust passage from the reducing agent addition valve is reduced. By passing through the second turbine, mixing / stirring of the exhaust gas and the reducing agent is promoted by the second turbine.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

[overall structure]
First, the overall configuration of a system to which an exhaust control device for an internal combustion engine according to an embodiment of the present invention is applied will be described.

  FIG. 1 is a schematic diagram showing a configuration of a vehicle to which an exhaust control device for an internal combustion engine according to the present embodiment is applied. In FIG. 1, solid arrows indicate the flow of air or gas, and broken arrows indicate input / output of signals.

  The vehicle mainly includes an air cleaner 1, an intake passage 2, a first turbocharger 3, a second turbocharger 4, an intercooler 5, an intake manifold 6, an internal combustion engine 7, An exhaust manifold 8, an exhaust passage 9, an EGR passage 10, an EGR valve 11, a first bypass passage 12, a first bypass valve 13, a first catalyst 14, and a second bypass passage 15 , A second bypass valve 16, a second catalyst 17, and an ECU (Engine Control Unit) 50.

  The air cleaner 1 is connected to the most upstream side of the intake passage 2, purifies air (intake air) introduced from the outside, and supplies the air to the intake passage 2. In the middle of the intake passage 2, a second compressor 4a of the second turbocharger 4, a first compressor 3a of the first turbocharger 3, and an intercooler 5 are connected.

  In the supercharging system of the present embodiment, the first turbocharger 3 is configured as a low-capacity low-speed supercharger with a large supercharging capability in a low and medium speed range, and the second turbocharger 4 is A so-called two-stage supercharging system configured as a large-capacity high-speed supercharger having a large supercharging capability in a medium to high speed range is preferable. In this case, supercharging is performed mainly by the first turbocharger 3 in the low and medium speed ranges, and supercharging is performed mainly by the second turbocharger 4 in the medium and high speed ranges.

  The first turbocharger 3 includes a compressor 3 a that compresses intake air that passes through the intake passage 2, and the second turbocharger 4 includes a compressor 4 a that compresses intake air that passes through the intake passage 2. . The compressor 3a (hereinafter referred to as “first compressor 3a”) of the first turbocharger 3 is referred to as a compressor 4a (hereinafter referred to as “second compressor”) of the second turbocharger 4 on the intake passage 2. It is arranged downstream of the compressor 4a ". As a result, the intake air compressed by the second compressor 4a is further compressed by the first compressor 3a. The intercooler 5 is arranged on the intake passage 2 downstream of the first compressor 3a, and cools the intake air compressed by the first compressor 3a. The most downstream side of the intake passage 2 is connected to the intake manifold 6. The intake manifold 6 is connected to an intake port (not shown) provided for each cylinder of the internal combustion engine 7.

  The internal combustion engine 7 is a device that generates power by burning an air-fuel mixture of intake air and fuel supplied from the intake passage 2 via the intake manifold 6. The internal combustion engine 7 is configured by, for example, a gasoline engine or a diesel engine.

  The most upstream side of the exhaust passage 9 is connected to the exhaust manifold 8. The exhaust manifold 8 is connected to an exhaust port (not shown) provided for each cylinder of the internal combustion engine 7. For this reason, the exhaust gas generated by the combustion in the internal combustion engine 7 is discharged to the exhaust passage 9 through the exhaust manifold 8.

  The EGR passage 10 has one end connected to the exhaust manifold 8 and the other end connected to the intake manifold 6. The EGR passage 10 is a passage for returning exhaust gas (EGR gas) to the intake system. The EGR passage 10 is provided with an EGR valve 11 for opening and closing the EGR passage 10. The EGR valve 11 is a valve that adjusts the flow rate of EGR gas that passes through the EGR passage 10, in other words, a valve that adjusts the amount of EGR gas that is recirculated to the intake system. The opening degree of the EGR valve 11 is controlled by a control signal S1 supplied from the ECU 50.

  In the middle of the exhaust passage 9, the turbine 3 b of the first turbocharger 3 (hereinafter referred to as “first turbine 3 b”) and the turbine 4 b of the second turbocharger 4 (hereinafter referred to as “first turbocharger 4”). 2 ”, a second catalyst 17, a first bypass passage 12, and a second bypass passage 15. The first turbine 3b is disposed on the exhaust passage 9 upstream of the second turbine 4b. The first turbine 3b and the second turbine 4b are rotated by the exhaust gas passing through the exhaust passage 9, respectively. Such torque due to the rotation of the first turbine 3b and the second turbine 4b is caused by the first compressor 3a in the first turbocharger 3 and the second torque in the second turbocharger 4, respectively. The intake air is compressed (ie, supercharged) by being transmitted to the second compressor 4a and rotating.

  The first bypass passage 12 connects the upstream side of the first turbine 3 b of the first turbocharger 3 and the downstream side of the first turbine 3 b in the exhaust passage 9. The first bypass passage 12 bypasses the exhaust gas discharged from the exhaust manifold 8 side to the exhaust passage 9, bypassing the first turbine 3b of the first turbocharger 3, and downstream of the first turbine 3b. This is a passage for flowing to the exhaust passage 9 on the side. A first bypass valve 13 is provided in the first bypass passage 12. The first bypass valve 13 is a valve that adjusts the flow rate of exhaust gas that passes through the first bypass passage 12. The opening degree of the first bypass valve 13 is adjusted by a control signal S2 supplied from first bypass valve control means (not shown) of the ECU 50 that controls the open / close state of the first bypass valve 13.

  The second bypass passage 15 connects the upstream side of the second turbine 4 b of the second turbocharger 4 and the downstream side of the second turbine 4 b in the exhaust passage 9. The second bypass passage 15 converts the exhaust gas discharged to the exhaust passage 9 downstream of the first turbine 3 b of the first turbocharger 3 into the second turbine of the second turbocharger 4. This is a passage for bypassing 4b and flowing to the exhaust passage 9 on the downstream side of the second turbine 4b. The second bypass passage 15 is provided with a second bypass valve 16 and a first catalyst 14. The second bypass valve 16 is a valve that adjusts the flow rate of the exhaust gas that passes through the second bypass passage 15. The opening degree of the second bypass valve 16 is adjusted by a control signal S3 supplied from second bypass valve control means (not shown) of the ECU 50 that controls the open / closed state of the second bypass valve 16.

  The first catalyst 14 is a small catalyst having a small volume, and is disposed on the second bypass passage 15 upstream of the second bypass valve 16. More specifically, the first catalyst 14 is disposed in the branch portion 15a of the second bypass passage 15 that branches from the exhaust passage 9 on the upstream side of the second turbine 4b. However, in the present invention, the first catalyst 14 may be provided on the downstream side of the second bypass valve 16 on the second bypass passage 15. In a preferred example, the first catalyst 14 is preferably a NOx storage reduction catalyst that stores and purifies NOx.

  The second catalyst 17 is a large-sized catalyst having a larger volume than the first catalyst 14, and is provided in the exhaust passage 9 downstream of the junction 15 b between the exhaust passage 9 and the second bypass passage 15. . In a preferred example, the second catalyst 17 is preferably a NOx occlusion reduction catalyst that occludes and purifies NOx, similarly to the first catalyst 14.

  The ECU 50 includes a CPU, a ROM, a RAM, an A / D converter, and the like (not shown). The ECU 50 controls the inside of the vehicle based on outputs supplied from various sensors in the vehicle, and also controls the first bypass valve control means, the second bypass valve control means, and the reducing agent addition valve control in the present invention. Functions as a means.

[Exhaust control device for internal combustion engine]
The exhaust control device for an internal combustion engine according to the present embodiment includes a first turbocharger 3 disposed in the intake passage 2 and the exhaust passage 9, and a first turbocharger disposed in the intake passage 2 and the exhaust passage 9. In the second turbocharger 4 arranged in series with the supercharger 3 and the exhaust passage 9, the upstream side of the first turbine 3 b of the first turbocharger 3, and the first turbine 3 b The first bypass passage 12 connected to the downstream side, the first bypass valve 13 provided in the first bypass passage 12, and the first bypass that controls the open / closed state of the first bypass valve 13 In the exhaust passage 9, the valve control means (not shown) and the second turbocharger 4 are connected to the upstream side of the second turbine 4 b and the downstream side of the second turbine 4 b. Bypass passage 15 and second bypass provided in second bypass passage 15 In the exhaust passage 9, the valve 16, second bypass valve control means (not shown) for controlling the open / close state of the second bypass valve 16, the first catalyst 14 provided in the second bypass valve 16, and the exhaust passage 9 A second catalyst 17 that is provided downstream of the joining portion 15b of the second bypass passage 15 that joins the exhaust passage 9 on the downstream side of the second turbine 4b and has a larger capacity than the first catalyst 14; It is configured with.

  According to this configuration, the first bypass valve control means and the second bypass valve control means are configured to open and close the first bypass valve 13 and the second bypass valve 16 according to the load state of the internal combustion engine 7 and the like. By controlling the exhaust gas, the exhaust gas discharged from the internal combustion engine 7 through the exhaust manifold 8 to the exhaust passage 9 is changed to a desired passage among the exhaust passage 9, the first bypass passage 12, and the second bypass passage 15. Can be made to flow. Thus, the first turbocharger is caused to flow through the desired passage to the first turbine 3b of the first turbocharger 3 or the second turbine 4b of the second turbocharger 4. It is possible to selectively use the machine 3 and the second turbocharger 4. Further, by flowing the exhaust gas to the second bypass passage 15 through a desired passage, the exhaust gas can be introduced into the first catalyst 14, and early warm-up of the first catalyst 14 can be promoted. it can.

[Example of exhaust control by exhaust control system of internal combustion engine]
(For example, immediately after starting the internal combustion engine)
Immediately after starting the internal combustion engine 7, when the exhaust temperature of the internal combustion engine 7 is low and / or when the temperature of the second catalyst 17 is low, the first bypass valve control means connects the first bypass valve 13. The control signal S2 is output to maintain the first bypass valve 13 in the closed state, and the second bypass valve control means outputs the control signal S3 to the second bypass valve 16 to thereby output the second bypass valve. The valve 16 is opened (that is, from the closed state to the open state).

  According to this example of exhaust control, the exhaust gas discharged from the internal combustion engine 7 through the exhaust manifold 8 to the exhaust passage 9 mainly includes the first turbine 3b of the first turbocharger 3, the first exhaust gas. The second bypass valve 16 flows through the branch portion 15 a, the first catalyst 14, the merging portion 15 b of the second bypass valve 16, and the second catalyst 17. As a result, a part of the exhaust gas flows to the first catalyst 14 via the branch portion 15a of the second bypass valve 16, so that the temperature of the first catalyst 14 can be quickly raised. As a result, the first catalyst 14 and the second catalyst 17 can purify nitrogen oxide (NOx) contained in the exhaust gas.

  Even when the internal combustion engine 7 is at a high load, since the second bypass valve 16 is open, a large amount of exhaust gas flows to the first catalyst 14. 14 warm-up is further promoted. Since the amount of exhaust gas increases after the internal combustion engine 7 is warmed up, the second bypass valve control means outputs the control signal S3 to the second bypass valve 16 to open the second second valve in the open state. The bypass valve 16 is closed (that is, closed). As a result, the exhaust gas does not pass through the first catalyst 14 having a small capacity. Therefore, it is possible to avoid an increase in exhaust pressure generated by passing through the first catalyst 14 and a pressure loss in the first catalyst 14. Further, since it is possible to avoid the occurrence of pressure loss in the first catalyst 14, the supercharging by the first turbine 3 b of the first turbocharger 3 is reduced accordingly, and the fuel consumption is deteriorated. Can be prevented. Further, according to the exhaust control after the internal combustion engine 7 is warmed up, the first catalyst 14 is not exposed to the high temperature exhaust gas, so that the deterioration of the first catalyst 14 due to the heat of the high temperature exhaust gas is prevented. Can do.

(When the internal combustion engine has a low load after the internal combustion engine is warmed up)
When the internal combustion engine 7 has been warmed up and the internal combustion engine 7 has a low load, the first bypass valve control means outputs a control signal S2 to the first bypass valve 13 and While maintaining the bypass valve 13 in the closed state, the second bypass valve control means outputs a control signal S3 to the second bypass valve 16 to maintain the second bypass valve 16 in the closed state.

  According to this example of exhaust control, the exhaust gas discharged from the internal combustion engine 7 through the exhaust manifold 8 to the exhaust passage 9 is used for the first turbine 3b and the second turbocharger 3 of the first turbocharger 3. It flows with the second turbine 4b and the second catalyst 17 of the supercharger 4. Thereby, the 1st turbine 3b and the 2nd turbine 4b rotate, the torque by the rotation is each transmitted to the 1st compressor 3a and the 2nd compressor 4a, and supercharging is performed. In this case, since the amount of exhaust gas is small, supercharging is obtained mainly by the first turbine 3b. In this case, nitrogen oxide (NOx) contained in the exhaust gas is purified by the second catalyst 17.

(When the internal combustion engine is heavily loaded after the internal combustion engine is warmed up)
When the internal combustion engine 7 is warmed up and the internal combustion engine 7 changes from a low load to a high load, the amount of exhaust gas increases, so the first turbine 3b having a small capacity for the low and medium speed range is provided. It becomes resistance and it becomes difficult for exhaust gas to pass the 1st turbine 3b. Therefore, in such a case, the first bypass valve control means outputs a control signal S2 to the first bypass valve 13 to open the first bypass valve 13 (that is, from the closed state to the open state). .

  As a result, a large amount of exhaust gas discharged from the internal combustion engine 7 via the exhaust manifold 8 to the exhaust passage 9 is mainly used for the first bypass passage 12 and the second turbine of the second turbocharger 4. 4b flows with the second catalyst 17. Therefore, the second turbine 4b is rotated by a large amount of exhaust gas, and the torque due to the rotation is transmitted to the second compressor 4a to perform supercharging. As a result, the required supercharging amount and supercharging pressure can be obtained in the medium to high speed range. In this case, nitrogen oxide (NOx) contained in the exhaust gas is purified by the second catalyst 17.

[Modification 1]
In Modification 1 of the present invention, in the exhaust control device for the internal combustion engine 7 described above, a reducing agent addition valve (exhaust fuel addition valve) for supplying a reducing agent to the exhaust passage 9 may be further provided. Hereinafter, this configuration will be described with reference to FIG. In the following, the same elements as those in the above embodiment are denoted by the same reference numerals, and the description thereof is omitted as appropriate. FIG. 2 is a schematic diagram showing the configuration of a vehicle to which the exhaust control device for the internal combustion engine 7 according to the first modification of the present invention is applied.

  Here, assuming a configuration in which the reducing agent addition valve is disposed in the vicinity of the exhaust manifold located upstream of the supercharger, the reducing agent addition valve is positioned upstream of the EGR passage under this configuration. Therefore, when the reducing agent is injected (added) from the reducing agent addition valve toward the exhaust passage, there is a disadvantage that the reducing agent is mixed into the intake passage side via the EGR passage, but the addition of the reducing agent. Since the reducing agent injected from the valve also passes to the turbine side of the supercharger, there is an advantage that mixing / stirring of the exhaust gas and the reducing agent is promoted by the turbine. On the other hand, under the configuration in which the reducing agent addition valve is disposed downstream of the supercharger, the reducing agent addition valve is located downstream of the EGR passage, and therefore the reducing agent is directed from the reducing agent addition valve toward the exhaust passage. However, since the reducing agent does not pass through the turbine, the mixing / stirring effect of the exhaust gas and the reducing agent by the turbine is lost. There are drawbacks.

  Therefore, in the first modification of the present invention, in order to solve such a contradictory problem all at once, the reducing agent addition valve (exhaust fuel addition valve) 18 is connected to the first turbocharger 3 in the exhaust passage 9. Between the first turbine 3 b and the second turbine 4 b of the second turbocharger 4. Note that the reducing agent injection amount, the injection time, the injection interval, and the like of the reducing agent addition valve 18 are adjusted based on a control signal S4 supplied from the ECU 50 functioning as a reducing agent addition valve control means.

  As a result, the reducing agent addition valve 18 is disposed in the exhaust passage 9 downstream of the first turbine 3 b of the first turbocharger 3, so that the reducing agent addition valve 18 is directed toward the exhaust passage 9. Therefore, the reducing agent injected in this way can be prevented from entering the EGR passage 10. Further, since the reducing agent addition valve 18 is disposed on the exhaust passage 9 upstream of the second turbine 4 b of the second turbocharger 4, the reducing agent addition valve 18 is directed toward the exhaust passage 9. When the reducing agent injected in this manner passes through the second turbine 4b, the mixing / stirring of the exhaust gas and the reducing agent is promoted by the second turbine 4b. Further, according to this configuration, the reducing agent addition valve 18 is not disposed near the exhaust manifold where the temperature is higher than that of the exhaust passage 9 between the first turbine 3b and the second turbine 4b. The heating temperature of the reducing agent addition valve 18 can be lowered, and the reducing agent remaining in the tip of the reducing agent addition valve 18 or in the injection hole is carbonized by the heat of the exhaust gas, and the reducing agent addition valve 18 is clogged. It is possible to prevent the reducing agent addition valve 18 from being damaged by the heat of the exhaust gas.

  In a preferred example of the first modification, the first catalyst 14 is connected to the exhaust passage 9 upstream of the second turbine 4b of the second turbocharger 4 as shown in FIGS. 2 and 3 (b). The reducing agent addition valve 18 is arranged coaxially with respect to the branch portion 15a of the second bypass passage 15 and the first catalyst 14 in the exhaust passage 9. It is preferable to arrange | position. The reason for this will be described with reference to FIG.

  FIG. 3A shows a main part in a state in which the reducing agent addition valve 18 is attached to a part of the exhaust passage 9 between the first turbine 3b and the second turbine 4b at a predetermined angle. A cross-sectional view is shown. FIG. 3B is an enlarged cross-sectional view of the main part of the broken line region E1 of FIG. 2, and the reducing agent addition valve 18 is connected to the branch portion 15a of the second bypass passage 15 and the first catalyst 14 in the exhaust passage 9. And attached on the same axis. 3A and 3B, the thin solid line extending radially from the reducing agent addition valve 18 indicates the injected reducing agent.

  Here, if the second bypass valve 16 is opened when the second catalyst 17 is warmed up or when the internal combustion engine 7 is under a low load, the exhaust is discharged from the internal combustion engine 7 under the conditions. Since the temperature of the exhaust gas is still low, even if the reducing agent is injected from the reducing agent addition valve 18 toward the exhaust passage 9 at this time, the reducing agent is not easily vaporized. It tends to adhere to the inner wall. In particular, when the configuration shown in FIG. 3A is employed under such conditions, the distance between the injection port (not shown) of the reducing agent addition valve 18 and the inner surface of the exhaust passage 9 facing it is short. Therefore, the distance d1 until the reducing agent injected from the reducing agent addition valve 18 collides with the inner wall of the exhaust passage 9 is reduced, and thereby the reducing agent is more likely to adhere to the inner wall of the exhaust passage 9.

  On the other hand, as in the preferred example of Modification 1 shown in FIG. 3B, the reducing agent addition valve 18 is connected to the branch portion 15a of the second bypass passage 15 and the first catalyst in the exhaust passage 9. 14, the distance d2 (> d1) until the reducing agent injected from the reducing agent addition valve 18 collides with the inner wall of the exhaust passage 9 can be increased. The space for spraying the reducing agent in the second bypass passage 15 or the like can be made large. Thereby, it can reduce that the injected reducing agent adheres to the inner wall of the exhaust passage 9, and can promote the vaporization of the reducing agent and the mixing of the exhaust gas and the reducing agent, respectively. .

  Further, in the first modification of the present invention and its preferred example, when the internal combustion engine 7 is in a low load or medium load state, the reduction is performed from the reducing agent addition valve 18 toward the branch portion 15a of the second bypass passage 15. When the agent is added, it is conceivable to adjust the ratio of the opening degree of the second bypass valve 16 for the purpose of early warming up of the first catalyst 14 or the like.

  If the second bypass valve 16 that is in the closed state is fully opened for such a purpose, most of the reducing agent flows to the second bypass valve 16 side, and the second turbo valve 16 The turbocharger 4 no longer flows to the second turbine 4b side, and the effect of mixing / stirring the exhaust gas and the reducing agent by the second turbine 4b cannot be obtained.

  Therefore, in the first modification of the present invention and its preferred example, the second bypass valve control means is configured so that the reducing agent addition valve 18 adds the reducing agent toward the branch portion 15a of the second bypass passage 15. The second bypass valve 16 in the closed state is preferably controlled to open. Note that controlling the second bypass valve 16 to the open side includes controlling the second bypass valve 16 to be in a partially opened state, or controlling the second bypass valve 16 to be in a half-open state. . In addition, the ratio of the opening degree of the second bypass valve 16 is preferably adjusted based on vehicle specifications such as engine speed and torque and various conditions.

  According to this configuration, the reducing agent introduced into the second bypass passage 15 through the reducing agent addition valve 18 is cracked (chemical decomposition reaction) by the first catalyst 14 or partially oxidized. As a result, when the internal combustion engine 7 is in a low load or medium load state, an appropriate amount of cracked reducing agent can be supplied to the second catalyst 17 at the time of reduction. The reduction efficiency of nitrogen oxides (NOx) with respect to the fuel components (CO, HC) can be improved, and a part of the injected reducing agent can be used for the second turbine 4b side of the second turbocharger 4. The effect of mixing / stirring the exhaust gas and the reducing agent by the second turbine 4b can be promoted.

[Another configuration example of an exhaust control device for an internal combustion engine]
Next, another configuration example of the exhaust control device for an internal combustion engine according to the present invention will be described with reference to FIG. In the following, the same elements as those in the above embodiment are denoted by the same reference numerals, and the description thereof is omitted as appropriate. FIG. 4 is a schematic diagram showing the configuration of a vehicle to which another configuration example of the exhaust control device for an internal combustion engine of the present invention is applied.

  Another configuration example of the exhaust control device for the internal combustion engine 7 of the present invention is arranged in the first turbocharger 3 disposed in the intake passage 3 and the exhaust passage 9, and in the intake passage 3 and the exhaust passage 9. A second turbocharger 4 arranged in series downstream of the first turbocharger 3, and an upstream side of the first turbine 3 b of the first turbocharger 3 in the exhaust passage 9. The first bypass passage 12 connecting the downstream side of the first turbine 3b, the first bypass valve 13 provided in the first bypass passage 12, and the open / close state of the first bypass valve 13 The first bypass valve control means (not shown) for controlling the first catalyst 14 and the first catalyst 14 are provided, and the second bypass passage 15 and the second bypass valve 16 are not provided. In particular, the first catalyst 14 is an exhaust gas positioned between the joining portion 12b of the first bypass passage 12 that joins the exhaust passage 9 on the downstream side of the first turbine 3b and the first turbine 3b. It is provided in the passage 9. However, in the present invention, the first catalyst 14 is positioned between the first turbine 3b and the branch portion 12a of the first bypass passage 12 that branches from the exhaust passage 9 on the upstream side of the first turbine 3b. The exhaust passage 9 may be provided.

  According to this configuration, the first bypass valve control means controls the open / close state of the first bypass valve 13 according to the load state of the internal combustion engine 7 and the like, thereby passing the exhaust manifold 8 from the internal combustion engine 7. Thus, the exhaust gas discharged to the exhaust passage 9 can flow to a desired passage among the exhaust passage 9 and the first bypass passage 12. Thus, the first turbocharger is caused to flow through the desired passage to the first turbine 3b of the first turbocharger 3 or the second turbine 4b of the second turbocharger 4. It is possible to selectively use the machine 3 and the second turbocharger 4. In addition, by introducing the exhaust gas into the first catalyst 14 through a desired passage, it is possible to promote early warm-up of the first catalyst 14.

[Example of exhaust control by another configuration example of an exhaust control device of an internal combustion engine]
(When the internal combustion engine has a low load after the internal combustion engine is warmed up)
When the internal combustion engine 7 has been warmed up and the internal combustion engine 7 has a low load, the first bypass valve control means outputs a control signal S2 to the first bypass valve 13 and The bypass valve 13 is kept closed.

  According to the example of the exhaust control, the exhaust gas discharged from the internal combustion engine 7 through the exhaust manifold 8 to the exhaust passage 9 is converted into the first turbine 3b of the first turbocharger 3, the first catalyst. 14, flows with the first turbine 4 b and the second catalyst 17 of the second turbocharger 4. Thereby, the 1st turbine 3b and the 2nd turbine 4b rotate, the torque by the rotation is each transmitted to the 1st compressor 3a and the 2nd compressor 4a, and supercharging is performed. In this state, since the amount of exhaust gas is small, supercharging is mainly obtained by the first turbine 3b. Further, since the temperature of the exhaust gas is low when the internal combustion engine has a low load, the temperature of the first catalyst 14 can be increased quickly by allowing most of the exhaust gas to pass through the first catalyst 14. it can. As a result, the first catalyst 14 and the second catalyst 17 can purify nitrogen oxide (NOx) contained in the exhaust gas.

(When the internal combustion engine is heavily loaded after the internal combustion engine is warmed up)
When the internal combustion engine 7 is warmed up and the internal combustion engine 7 changes from a low load to a high load, the amount of exhaust gas increases, so the first turbine with a small capacity for the low and medium speed range. 3b becomes resistance and it becomes difficult for the exhaust gas to pass through the first turbine 3b. Therefore, in such a case, the first bypass valve control means outputs a control signal S2 to the first bypass valve 13 to open the first bypass valve 13 (that is, from the closed state to the open state). .

  As a result, a large amount of exhaust gas discharged from the internal combustion engine 7 via the exhaust manifold 8 to the exhaust passage 9 is mainly used for the first bypass passage 12 and the second turbine of the second turbocharger 4. 4b flows with the second catalyst 17. Therefore, the second turbine 4b is rotated by a large amount of exhaust gas, and the torque due to the rotation is transmitted to the second compressor 4a to perform supercharging. As a result, the required supercharging amount and supercharging pressure can be obtained in the medium to high speed range. Further, in this case, the exhaust gas flows to the first bypass passage 12 side without passing through the first catalyst 14, so that the exhaust pressure generated by passing through the first catalyst 14 is reduced. It is possible to avoid the increase and the pressure loss in the first catalyst 14. Further, since it is possible to avoid the occurrence of pressure loss in the first catalyst 14, the supercharging by the first turbine 3 b of the first turbocharger 3 is reduced accordingly, and the fuel consumption is deteriorated. Can be prevented. Further, according to the exhaust control after the internal combustion engine 7 is warmed up, the first catalyst 14 is not exposed to the high temperature exhaust gas, so that the deterioration of the first catalyst 14 due to the heat of the high temperature exhaust gas is prevented. be able to.

[Modification 2]
In the second modification of the present invention, in the other configuration example of the exhaust control device for the internal combustion engine 7 described above, a reduction agent addition valve (exhaust fuel addition valve) for supplying a reduction agent to the exhaust passage 9 is further provided. It may be. Hereinafter, this configuration will be described with reference to FIG. In the following, the same elements as those in the above embodiment are denoted by the same reference numerals, and the description thereof is omitted as appropriate. FIG. 5 is a schematic diagram showing the configuration of a vehicle to which another configuration example of the exhaust control device for the internal combustion engine 7 according to the second modification of the present invention is applied.

  In the second modification of the present invention, based on the problem described in the first modification, the reducing agent addition valve (exhaust fuel addition valve) 18 is connected to the branch portion 12a of the first bypass passage 12 and the first branch passage 12a in the exhaust passage 9. It is provided between the merging portion 12 b of the one bypass passage 12. In an example of the second modification, the reducing agent addition valve 18 is provided between the branch portion 12 a of the first bypass passage 12 and the first turbine 3 b of the first turbocharger 3. As a result, the reducing agent addition valve 18 is disposed in the exhaust passage 9 downstream of the first turbine 3 b of the first turbocharger 3, so that the reducing agent addition valve 18 is directed toward the exhaust passage 9. Therefore, the reducing agent injected in this way can be prevented from entering the EGR passage 10. Further, since the reducing agent addition valve 18 is disposed in the exhaust passage 9 upstream of the second turbine 4 b of the second turbocharger 4, the reducing agent addition valve 18 is directed toward the exhaust passage 9. As the injected reducing agent passes through the second turbine 4b, the mixing / stirring of the exhaust gas and the reducing agent is promoted by the second turbine 4b. Further, according to this configuration, the reducing agent addition valve 18 is not disposed near the exhaust manifold where the temperature is higher than that of the exhaust passage 9 between the first turbine 3b and the second turbine 4b. The heating temperature of the reducing agent addition valve 18 can be lowered, and the reducing agent remaining in the tip of the reducing agent addition valve 18 or in the injection hole is carbonized by the heat of the exhaust gas, and the reducing agent addition valve 18 is clogged. It is possible to prevent the reducing agent addition valve 18 from being damaged by the heat of the exhaust gas.

  In the present invention, the reducing agent addition valve 18 may be provided between the first turbine 3 b of the first turbocharger 3 and the first catalyst 14. In the present invention, when the first catalyst 14 is provided in the exhaust passage 9 positioned between the branch portion 12a of the first bypass passage 12 and the first turbine 3b, the reducing agent addition valve 18 is provided. Is preferably provided in the exhaust passage 9 located between the branch portion 12 a of the first bypass passage 12 and the first catalyst 14. Thereby, the effect which concerns on the above-mentioned modification 2 can be acquired.

1 is a diagram illustrating a schematic configuration of a vehicle to which an exhaust control device for an internal combustion engine according to the present embodiment is applied. FIG. It is a figure which shows schematic structure of the vehicle to which the exhaust-gas control apparatus of the internal combustion engine which concerns on the modification 1 was applied. FIG. 9 is a cross-sectional view of a main part showing a positional relationship between a reducing agent addition valve, a second bypass passage, and a first catalyst according to a preferred example of Modification 1; It is a figure which shows schematic structure of the vehicle to which the other structural example of the exhaust-gas control apparatus of the internal combustion engine of this invention was applied. FIG. 10 is a diagram illustrating a schematic configuration of a vehicle to which another configuration example of an exhaust control device for an internal combustion engine according to a second modification is applied.

Explanation of symbols

2 intake passage 3 first turbocharger 3b first turbine 4 second turbocharger 4b second turbine 7 internal combustion engine 8 exhaust manifold 9 exhaust passage 10 EGR passage 11 EGR valve 12 first bypass passage 13 First bypass valve 14 First catalyst 15 Second bypass passage 16 Second bypass valve 17 Second catalyst 18 Reductant addition valve 50 ECU

Claims (12)

A first supercharger disposed in the intake passage and the exhaust passage;
A second supercharger disposed in the intake passage and the exhaust passage and disposed in series with the first supercharger;
A first bypass passage connecting the upstream side of the first turbine of the first supercharger and the downstream side of the first turbine in the exhaust passage;
A first bypass valve provided in the first bypass passage;
First bypass valve control means for controlling the open / closed state of the first bypass valve;
A second bypass passage connecting the upstream side of the second turbine of the second supercharger and the downstream side of the second turbine in the exhaust passage;
A second bypass valve provided in the second bypass passage;
Second bypass valve control means for controlling the open / closed state of the second bypass valve;
An exhaust control device for an internal combustion engine, comprising: a first catalyst provided in the second bypass passage. In the exhaust passage, a second catalyst having a capacity larger than that of the first catalyst is downstream of the joining portion of the second bypass passage that joins the exhaust passage on the downstream side of the second turbine. Provided,
Immediately after starting the internal combustion engine, when the exhaust temperature of the internal combustion engine is low and / or when the temperature of the second catalyst is low, the first bypass valve control means includes the first bypass valve. 2. The exhaust control device for an internal combustion engine according to claim 1, wherein the second bypass valve control means opens the second bypass valve while maintaining the valve in a closed state.   The exhaust control device for an internal combustion engine according to claim 2, wherein the second bypass valve control means closes the second bypass valve after the internal combustion engine is warmed up.   When the internal combustion engine is warmed up and the internal combustion engine has a low load, the first bypass valve control means maintains the first bypass valve in a closed state and the second bypass valve. The exhaust control device for an internal combustion engine according to claim 1, wherein the bypass valve control means maintains the second bypass valve in a closed state.   The exhaust control device for an internal combustion engine according to claim 4, wherein the first bypass valve control means opens the first bypass valve when the internal combustion engine becomes a high load. A reductant addition valve for supplying a reductant to the exhaust passage;
The internal combustion engine according to any one of claims 1 to 5, wherein the reducing agent addition valve is provided between the first turbine and the second turbine in the exhaust passage. Exhaust control device. The first catalyst is disposed in a branch portion of the second bypass passage that branches from the exhaust passage on the upstream side of the second turbine,
The internal combustion engine according to claim 6, wherein the reducing agent addition valve is arranged coaxially with respect to the branch portion of the second bypass passage and the first catalyst in the exhaust passage. Engine exhaust control device.   The second bypass valve control means opens the second bypass valve in a closed state when the reducing agent addition valve adds the reducing agent toward the branch portion of the second bypass passage. The exhaust control device for an internal combustion engine according to claim 7, wherein the exhaust control device is controlled to the side. A first supercharger disposed in the intake passage and the exhaust passage;
A second supercharger disposed in the intake passage and the exhaust passage and disposed in series with the first supercharger;
A first bypass passage connecting the upstream side of the first turbine of the first supercharger and the downstream side of the first turbine in the exhaust passage;
A first bypass valve provided in the first bypass passage;
First bypass valve control means for controlling the open / closed state of the first bypass valve;
A first catalyst,
The first catalyst includes the exhaust passage located between the branch portion of the first bypass passage branched from the exhaust passage on the upstream side of the first turbine and the first turbine, or the It is provided in the exhaust passage located between the joining portion of the first bypass passage that joins the exhaust passage on the downstream side of the first turbine and the first turbine. An exhaust control device for an internal combustion engine.   When the internal combustion engine is warmed up and the internal combustion engine has a low load, the first bypass valve control means maintains the first bypass valve in a closed state. The exhaust control device for an internal combustion engine according to claim 9.   The exhaust control device for an internal combustion engine according to claim 10, wherein the first bypass valve control means opens the first bypass valve when the internal combustion engine becomes a high load. A reductant addition valve for supplying a reductant to the exhaust passage;
The reductant addition valve is provided in the exhaust passage between the branch portion of the first bypass passage and the junction portion of the first bypass passage. The exhaust control device for an internal combustion engine according to claim 11.

Images