JP4779926B2 - Exhaust system for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust system for an internal combustion engine, and more particularly to an exhaust system for an internal combustion engine including a plurality of exhaust passages, an exhaust purification device, and an exhaust gas recirculation device.

As a technique for reducing the amount of nitrogen oxide (hereinafter also referred to as “NOx”) contained in the exhaust gas of an internal combustion engine, exhaust gas recirculation (hereinafter also referred to as “EGR”) in which a part of the exhaust gas is recirculated to the intake system. .) The device is known. On the other hand, in order to purify NOx and particulate matter in the exhaust gas of an internal combustion engine, an NOx storage reduction catalyst or a particulate filter (hereinafter referred to as “
This is called “filter”. A technique for providing an exhaust purification device such as) is known. And NOx
An exhaust gas recirculation device that reduces the amount of NOx and an exhaust gas purification device that purifies NOx and particulate matter in exhaust gas are used in combination.

On the other hand, it is provided with a plurality of exhaust passages, each exhaust passage is provided with an exhaust purification device and an exhaust gas recirculation device, and the amount of exhaust gas passing through the exhaust gas purification device or the exhaust gas recirculation device provided in each exhaust passage. Is controlled to efficiently suppress the amount of NOx generated or to improve the purification efficiency in the exhaust purification device.

  As a related technology, for an internal combustion engine having a plurality of exhaust passages and an exhaust purification device, the exhaust gas upstream of the turbine of the turbocharger is recirculated to the intake passage downstream of the compressor for each of the plurality of exhaust passages. A high-pressure EGR passage is provided, and the high-pressure EGR passage is communicated with each other in the EGR-on region, the high-load high-speed region, and the EGR-off operation state. In the EGR-on region, the EGR valve is further opened. A technique is disclosed in which the communication between the high-pressure EGR passages is cut off in a region where the rotation is low and medium speed and the EGR is off (see Patent Document 1).

By the way, in order to enable EGR in a wider operating range, a low pressure EGR passage for recirculating exhaust gas downstream of the turbine of the turbocharger to an intake passage upstream of the compressor is provided. A technique is known in which exhaust gas is recirculated using an EGR passage (see, for example, Patent Document 2). Such low-pressure EGR technology is applied to an exhaust system including a plurality of exhaust passages and an exhaust purification device, and development of a technology capable of more efficiently suppressing NOx generation and purifying exhaust is required.
JP 2006-22808 A JP-A-2005-76456 JP 2005-163752 A

  The present invention has been made in view of the above circumstances, and in an exhaust system of an internal combustion engine including a plurality of exhaust passages, an exhaust purification device, and an exhaust recirculation device, exhaust recirculation by the exhaust recirculation device, and an exhaust purification device It is an object of the present invention to provide a technique that makes it possible to more suitably execute the purification processing of the purification ability.

In order to achieve the above object, the present invention comprises a plurality of passages through which exhaust passes, and an exhaust purification device provided in each of the plurality of passages. A low pressure EGR passage is provided downstream of the exhaust purification device. An EGR gas intake port is provided, and an exhaust throttle valve is further provided downstream thereof. By controlling the exhaust throttle valve, the amount of EGR gas recirculated through the low pressure EGR passage and the exhaust gas flow rate passing through the exhaust purification device The best feature is to optimize both.

More specifically, an exhaust passage through which exhaust from a cylinder of the internal combustion engine passes,
A turbocharger in which a turbine is disposed in the exhaust passage and a compressor is disposed in an intake passage of the internal combustion engine;
A plurality of downstream exhaust passages through which the exhaust discharged from the turbine of the supercharger passes;
A communication passage communicating the plurality of downstream exhaust passages;
A communication path flow rate control valve provided in the communication path and capable of changing a flow rate of exhaust gas in the communication path;
An exhaust purification device that is provided in each of the downstream exhaust passages, purifies the exhaust gas passing through the downstream exhaust passages, and regenerates the purification ability by supplying a reducing agent;
When the exhaust purification device is disposed in the exhaust passage or the downstream exhaust passage upstream of the exhaust purification device and regenerates the purification capability of the exhaust purification device, it is reduced to the exhaust purification device by adding a reducing agent to the exhaust gas. Reducing agent addition means for supplying the agent;
An exhaust throttle valve that is provided on the downstream side of the exhaust purification device in the downstream side exhaust passage and controls the flow rate of exhaust gas in the downstream side exhaust passage;
The same number as the plurality of downstream exhaust passages is provided corresponding to each of the downstream exhaust passages, one end connected to the downstream exhaust passage and the other end connected to the upstream side of the compressor in the intake passage. Low pressure EGR passage,
A low pressure EGR valve provided in the low pressure EGR passage and controlling an amount of exhaust gas passing through the low pressure EGR passage,
One end of the low-pressure EGR passage is connected to a portion of the downstream exhaust passage between the exhaust purification device and the exhaust throttle valve.

  That is, in the present invention, a plurality of downstream exhaust passages are provided, and the plurality of downstream exhaust passages are communicated with each other by a communication passage. Further, the amount of exhaust gas exchanged between the downstream exhaust passages or distributed to the downstream exhaust passages can be changed by the communication passage flow control valve. In addition, each downstream exhaust passage is provided with an exhaust purification device, an exhaust intake port of the low pressure EGR passage, and an exhaust throttle valve in this order from the upstream side.

  According to the configuration of the present invention, by appropriately changing the opening degree of the exhaust throttle valve, the low pressure EGR valve, and the communication passage flow control valve, the exhaust purification device provided in each downstream exhaust passage, and the low pressure EGR passage are passed. The amount of exhaust can be controlled arbitrarily. That is, by adjusting the opening of the exhaust throttle valve, the amount of exhaust flowing into the exhaust purification device and the amount of exhaust flowing into the low pressure EGR passage can be controlled. Further, the amount of exhaust gas passing through the low pressure EGR valve can be controlled by adjusting the opening degree of the low pressure EGR valve. Also, by adjusting the opening of the communication passage flow control valve, the amount of exhaust passing through the downstream exhaust passage can be controlled by allowing the exhaust passing through the downstream exhaust passage to flow to another downstream exhaust passage. It is.

  Changes in the amount of exhaust gas passing through the downstream exhaust passage and the low pressure EGR passage by changing the opening of each of the exhaust throttle valve, the low pressure EGR valve, and the communication passage flow control valve are related to each other. And is determined in relation to the opening of other valves.

  According to this, it is possible to suitably maintain both the efficiency of NOx reduction processing, SOx poisoning recovery processing, PM regeneration processing and the like for the exhaust purification device and the exhaust amount recirculated by the low pressure EGR passage.

In the present invention, the internal combustion engine has a plurality of cylinders, and the cylinders are aggregated to form two or more cylinder groups.
The exhaust passage, the supercharger, and the downstream exhaust passage are provided in the same number as the cylinder group, corresponding to each of the cylinder groups,
The exhaust from each cylinder group passes through the exhaust passage corresponding to the cylinder group, rotates the turbine of the corresponding turbocharger, and then passes through the corresponding downstream exhaust passage. May be.

  That is, when controlling the cylinders of an internal combustion engine into a plurality of cylinder groups, an exhaust passage, a supercharger, a downstream exhaust passage, an exhaust purification device attached to the downstream exhaust passage, a low pressure EGR passage, a low pressure EGR valve An exhaust throttle valve is provided for each cylinder group. Then, for example, the exhaust gas purification efficiency and the exhaust gas recirculation amount can be independently controlled for the exhaust gas from each bank of the V-type multi-cylinder internal combustion engine.

Further, in the present invention, when performing NOx reduction treatment of any exhaust purification device among the exhaust purification devices provided in the plurality of downstream exhaust passages,
The reducing agent is added from the reducing agent addition means upstream of the exhaust purification device that is the target of the NOx reduction process, and the communication passage flow control valve and the exhaust throttle valve on the downstream side of the exhaust purification device that is the target of the NOx reduction process Is closed, and the low pressure EGR valve in the low pressure EGR passage connected to the downstream side of the exhaust purification device that is the target of the NOx reduction treatment is opened,
The flow rate of the exhaust gas that passes through the exhaust gas purification device that is the subject of the NOx reduction treatment is reduced, and the exhaust gas is recirculated through the low-pressure EGR passage connected to the downstream side of the exhaust gas purification device that is the subject of the NOx reduction treatment. You may make it make it.

If it does so, about the exhaust gas purification apparatus which is the object of NOx reduction process, it can suppress that the fuel added from the reducing agent addition means slips through, and can complete a sufficient oxidation-reduction reaction in the exhaust gas purification apparatus. Further, it is possible to increase the amount of exhaust gas (hereinafter also referred to as “low pressure EGR gas amount”) that is recirculated through the low pressure EGR passage by increasing the back pressure downstream of the exhaust gas purification device. Therefore, the control for increasing the NOx reduction efficiency of the exhaust purification device and the low pressure EG
Control for increasing the amount of R gas can be performed efficiently at the same time.

Further, in the present invention, when performing NOx reduction treatment of any exhaust purification device among the exhaust purification devices provided in the plurality of downstream exhaust passages,
The reducing agent is added from the reducing agent addition means upstream of the exhaust purification device that is the target of the NOx reduction treatment, and the exhaust throttle valve on the downstream side of the exhaust purification device that is the target of the NOx reduction processing is closed, and By opening the passage flow control valve on the open side,
The flow rate of the exhaust gas that passes through the exhaust purification device that is the subject of the NOx reduction treatment is reduced, and the exhaust gas is recirculated through the low-pressure EGR passage connected to the downstream side of the exhaust purification device that is not the subject of the NOx reduction treatment. You may do it.

Here, when the NOx reduction treatment of any exhaust purification device is performed, the reducing agent is added from the reducing agent addition means upstream of the exhaust purification device that is the subject of the NOx reduction treatment and the NOx reduction treatment subject. The point that the control for increasing the NOx reduction efficiency of the exhaust purification device is carried out by restricting the exhaust throttle valve on the downstream side of a certain exhaust purification device is equivalent to the above-described control.

In this control, unlike the above-described control, the communication passage flow rate control valve in the communication passage is opened. That is, depending on the operating state of the internal combustion engine, the exhaust throttle valve downstream of the exhaust purification device that is subject to NOx reduction processing is throttled, and the flow rate of the exhaust gas passing through the downstream exhaust passage is reduced by the NOx reduction of the exhaust purification device. When the value is optimal for processing, it may be difficult to control the amount of low-pressure EGR gas recirculated through the low-pressure EGR passage to the required amount.

In the present invention, in such a case, by setting the communication passage flow control valve to the open side, the exhaust gas is exchanged with other downstream exhaust passages, and the exhaust gas purification that is the target of the NOx reduction process For the downstream exhaust passage provided with the device, priority is given to the efficiency of the NOx reduction treatment, and the exhaust gas is recirculated through the low pressure EGR passage in the downstream exhaust passage provided with the exhaust purification device that is not subject to the NOx reduction treatment. I decided to do it.

The amount of low-pressure EGR gas at that time is satisfied by appropriately controlling the exhaust throttle valve and the low-pressure EGR valve in the downstream exhaust passage provided with the exhaust purification device that is not subject to NOx reduction treatment. As a result, the degree of freedom in controlling the amount of low-pressure EGR gas can be secured, and the control for increasing the NOx reduction efficiency of the exhaust purification device and the control for recirculating the exhaust gas through the low-pressure EGR passage can be performed more accurately. Both can be achieved.

Further, in the present invention, when performing NOx reduction treatment of any exhaust purification device among the exhaust purification devices provided in the plurality of downstream exhaust passages,
While adding the reducing agent from the reducing agent addition means upstream of the exhaust gas purification device that is the subject of the NOx reduction treatment,
When the operating state of the internal combustion engine belongs to a predetermined low load / low rotation speed region, the communication passage flow control valve and the exhaust throttle valve on the downstream side of the exhaust purification device to be subjected to the NOx reduction process are closed. By opening the low-pressure EGR valve in the low-pressure EGR passage connected to the downstream side of the exhaust purification device that is the target of the NOx reduction treatment,
The flow rate of the exhaust gas that passes through the exhaust gas purification device that is the subject of the NOx reduction treatment is reduced, and the exhaust gas is recirculated through the low-pressure EGR passage connected to the downstream side of the exhaust gas purification device that is the subject of the NOx reduction treatment. Let
When the operating state of the internal combustion engine belongs to a predetermined high load / high rotation speed region, the exhaust throttle valve on the downstream side of the exhaust purification device that is the target of the NOx reduction process is closed, and the communication passage flow control is performed. By opening the valve to the open side,
The flow rate of the exhaust gas that passes through the exhaust purification device that is the subject of the NOx reduction treatment is reduced, and the exhaust gas is recirculated through the low-pressure EGR passage connected to the downstream side of the exhaust purification device that is not the subject of the NOx reduction treatment. You may do it.

That is, when the operating state of the internal combustion engine is a high load and high rotation speed, the flow rate of the exhaust gas in the downstream exhaust passage provided with the exhaust gas purification device that is the target of the NOx reduction process increases. Then, when the exhaust throttle valve is controlled so that the amount of exhaust gas that passes through the exhaust gas purification device that is the target of the NOx reduction treatment is optimized, the exhaust gas is recirculated through the low-pressure EGR passage in the downstream exhaust passage. The amount of low pressure EGR gas is often excessive.

Therefore, in this case, a part of the exhaust gas passing through the downstream exhaust passage provided with the exhaust purification device that is the target of the NOx reduction treatment is opened via the communication passage with the communication passage flow control valve opened. The exhaust gas is caused to flow into a downstream exhaust passage provided with an exhaust purification device that is not subject to NOx reduction treatment. As a result, it is possible to reduce the amount of low-pressure EGR gas that is recirculated through the low-pressure EGR passage in the downstream exhaust passage provided with the exhaust purification device that is the target of the NOx reduction treatment.

On the other hand, when the operating state of the internal combustion engine is a low load and a low rotational speed, the downstream side exhaust equipped with the exhaust gas purification device that is the target of the NOx reduction process without opening the communication path flow control valve. Since an appropriate amount of low-pressure EGR gas can be secured from the low-pressure EGR passage in the passage, in this case, the communication passage flow control valve is closed.

Thus, according to the present invention, the low pressure EGR passage for recirculating the low pressure EGR gas in accordance with the operating state of the internal combustion engine is provided with the low pressure E related to the exhaust purification device that is the target of the NOx reduction treatment.
It changes suitably between the GR passage and the low-pressure EGR passage relating to the exhaust gas purification apparatus that is not subject to NOx reduction treatment. Thereby, irrespective of the operating state of the internal combustion engine, it is possible to appropriately maintain the amount of exhaust gas flowing into the exhaust gas purification device that is the target of the NOx reduction process and the low-pressure EGR gas amount.

Here, the predetermined low load / low rotation speed region is a target of NOx reduction processing even when the operation state of the internal combustion engine belongs to this region, without opening the communication passage flow rate control valve. When the exhaust throttle valve is controlled so that the amount of exhaust gas that passes through the exhaust purification device is optimized, the amount of low-pressure EGR gas that is recirculated through the low-pressure EGR passage in the downstream exhaust passage is adjusted to the required amount This is a range of the operating state of the internal combustion engine that can be obtained, and may be obtained experimentally in advance.

In addition, the predetermined high load / high rotation speed region is defined as the exhaust purification that is the target of NOx reduction processing when the operation state of the internal combustion engine belongs to this region and the communication flow rate control valve is closed. When the exhaust throttle valve is controlled so that the amount of exhaust gas passing through the device is optimized, the amount of low-pressure EGR gas recirculated through the low-pressure EGR passage in the downstream exhaust passage is larger than the required amount. It is the range of the operating state of the internal combustion engine that is too low, and may be obtained experimentally in advance.

Further, in the present invention, during the NOx reduction process of any exhaust purification device among the exhaust purification devices provided in the plurality of downstream exhaust passages,
When a predetermined required EGR amount suddenly decreasing in which the required amount of EGR gas rapidly decreases, the exhaust throttle valve on the downstream side of the exhaust purification device during the NOx reduction process is opened at a predetermined speed or more, The flow rate of the exhaust gas recirculated from the low pressure EGR passage connected to the downstream side of the exhaust gas purification apparatus during the NOx reduction process may be rapidly reduced.

Here, let us consider a case where the operating state of the internal combustion engine suddenly changes during the execution of the NOx reduction process and the amount of EGR gas required for the internal combustion engine suddenly decreases. In such a case, if the responsiveness of the actual decrease in the amount of low-pressure EGR gas is poor, the amount of EGR gas temporarily increases excessively, and the amount of PM may increase.

Therefore, in the present invention, when the required amount of EGR gas suddenly decreases, such as when sudden acceleration occurs during NOx reduction processing, the exhaust throttle valve on the downstream side of the exhaust purification device during NOx reduction processing Is opened at high speed, and the low pressure EGR downstream of the exhaust purification system during NOx reduction treatment
The amount of low-pressure EGR gas recirculated from the passage was suddenly reduced.

  By doing so, the responsiveness of the low-pressure EGR gas amount to the case where the required amount of EGR gas is rapidly reduced can be improved, and inconveniences such as an increase in PM in the exhaust due to an excessive amount of EGR gas can be suppressed.

  Here, the predetermined required EGR amount suddenly decreasing state is a range of acceleration of the internal combustion engine that has been experimentally determined in advance, and the valve opening speed of the exhaust throttle valve that is equal to or higher than the predetermined speed is required by the acceleration of the internal combustion engine. In the case of the EGR amount suddenly decreasing state, this is the opening speed of the exhaust throttle valve necessary for satisfying the required amount of the EGR gas amount, and may be experimentally obtained in advance according to the acceleration of the internal combustion engine.

In the present invention, when performing PM regeneration processing of any exhaust purification device among the exhaust purification devices provided in the plurality of downstream exhaust passages,
The reducing agent is added from the reducing agent addition means upstream of the exhaust purification device that is the target of the PM regeneration process, and the communication passage flow rate control valve and the exhaust throttle valve on the downstream side of the exhaust purification device that is the target of the PM regeneration process Are closed, and the low pressure EGR valve in the low pressure EGR passage connected to the downstream side of the exhaust gas purification device that is the target of the PM regeneration process is opened,
The flow rate of the exhaust gas that passes through the exhaust gas purification device that is the target of the PM regeneration process is reduced, and the exhaust gas is recirculated through the low-pressure EGR passage that is connected to the downstream side of the exhaust gas purification device that is the target of the PM regeneration process. You may make it make it.

  That is, when performing the PM regeneration processing of the exhaust purification device provided in the downstream exhaust passage, the reducing agent is added from the reducing agent addition means upstream of the exhaust purification device that is the target of the PM regeneration processing. Some of the reducing agent added from the agent adding means slips through the exhaust gas purification device, and there is a possibility that the reducing agent slipped through may be diffused into the atmosphere.

  Therefore, in the present invention, when performing PM regeneration processing of any exhaust purification device among the exhaust purification devices provided in the plurality of downstream exhaust passages, the exhaust purification device that is the target of the PM regeneration processing The reducing agent is added from the reducing agent addition means upstream of the exhaust gas, and the exhaust throttle valve on the downstream side of the exhaust gas purification apparatus that is the target of the PM regeneration process is throttled.

  Then, the reducing agent added to the exhaust can be recirculated through the low pressure EGR passage and recombusted in the internal combustion engine without being diffused into the atmosphere as it is. Thereby, the emission during PM regeneration can be improved.

Further, in the present invention, similarly, when performing the SOx poisoning recovery process of any of the exhaust purification devices provided in the plurality of downstream exhaust passages,
A reducing agent is added from a reducing agent addition means upstream of the exhaust gas purification device that is the object of the SOx poisoning recovery process, and the downstream side of the communication flow rate control valve and the exhaust gas purification device that is the object of the SOx poisoning recovery process By closing the exhaust throttle valve and the low-pressure EGR valve in the low-pressure EGR passage connected to the downstream side of the exhaust purification device that is the object of the SOx poisoning recovery process,
The low-pressure E connected to the downstream side of the exhaust purification device that is the target of the SOx poisoning recovery process while reducing the flow rate of the exhaust gas that passes through the exhaust purification device that is the target of the SOx poisoning recovery process.
The exhaust gas may be recirculated through the GR passage.

By doing so, the reducing agent added to the exhaust gas during the SOx poisoning recovery process can be recirculated through the low-pressure EGR passage and recombusted in the internal combustion engine without being directly diffused into the atmosphere. Thereby, the emission during the SOx poisoning recovery process can be improved.

Further, in the present invention, when performing PM regeneration processing or SOx poisoning recovery processing of any exhaust purification device among the exhaust purification devices provided in each of the plurality of downstream exhaust passages,
By closing the exhaust throttle valve on the downstream side of the exhaust purification device that is the target of the PM regeneration process or the SOx poisoning recovery process, and opening the communication passage flow control valve,
The flow rate of the exhaust gas that passes through the exhaust purification device that is the target of the PM regeneration process or SOx poisoning recovery process is reduced and connected to the downstream side of the exhaust purification device that is not the target of the PM regeneration process or SOx poisoning recovery process The exhaust gas may be recirculated through the low pressure EGR passage.

Here, when performing PM regeneration processing or SOx poisoning recovery processing of the exhaust purification device provided in the downstream side exhaust passage, the temperature of the exhaust discharged from the exhaust purification device often increases. If the temperature of the exhaust gas rises excessively, the temperature of the low-pressure EGR gas recirculated through the low-pressure EGR passage on the downstream side of the exhaust gas purification device that is the target of the PM regeneration process or the SOx poisoning recovery process becomes excessive. There was a risk of rising.

If it does so, there exists a possibility that the malfunction that the combustion temperature in an internal combustion engine may rise and the generation amount of NOx increases may arise.

Therefore, in the present invention, when performing PM regeneration processing or SOx poisoning recovery processing of the exhaust purification device, an exhaust throttle valve on the downstream side of the exhaust purification device that is the target of PM regeneration processing or SOx poisoning recovery processing is used. The exhaust gas is recirculated through the low-pressure EGR passage connected to the downstream side of the exhaust purification device that is closed and the communication passage flow control valve is opened and is not subject to PM regeneration processing or SOx poisoning recovery processing. did.

By doing so, the amount of exhaust gas flowing into the exhaust purification device that is the target of the PM regeneration process or the SOx poisoning recovery process is optimally controlled in terms of efficiency, and the temperature of the low-pressure EGR gas is prevented from excessively rising. it can. As a result, inconveniences such as an increase in the amount of NOx generated due to the high temperature of the low pressure EGR gas can be suppressed.

  The means for solving the problems in the present invention can be used in combination as much as possible.

  In the present invention, in an exhaust system of an internal combustion engine including a plurality of exhaust passages, an exhaust purification device, and an exhaust recirculation device, exhaust recirculation by the exhaust recirculation device and regeneration processing of the purification capability of the exhaust purification device are performed. , And more preferably.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine, an intake / exhaust system, and a control system to which the present invention is applied. The internal combustion engine shown in FIG. 1 is a V-type internal combustion engine that has a right bank 1 and a left bank 51, and each bank 1, 51 has four cylinders 2, 52. Here, the four cylinders 2 and 52 formed in each bank 1 and 51 correspond to a cylinder group in the present embodiment.

  A common intake manifold 3 is connected to the left and right banks 1 and 51 of the internal combustion engine, and each branch pipe of the intake manifold 3 is connected to the combustion chambers of the cylinders 2 and 52 of the left and right banks 1 and 51 via an intake port. It is communicated. The intake manifold 3 is connected to a common intake pipe 5 upstream. A surge tank 6 is provided in the common intake pipe 5. An intercooler 7 for cooling the intake air before flowing into the common intake pipe 5 is provided further upstream of the common intake pipe 5.

  The common intake pipe 5 branches into a right intake pipe 8 and a left intake pipe 58 upstream of the intercooler 7. The right intake pipe 8 is provided with a compressor 10a of the right supercharger 10 that operates using exhaust energy as a drive source. The right intake pipe 8 further upstream of the compressor 10a is provided with an air flow meter and an air cleaner (not shown).

  On the other hand, the left intake pipe 58 is provided with a compressor 60a of the left supercharger 60 that operates using exhaust energy as a drive source. An air flow meter and an air cleaner (not shown) are provided on the left intake pipe 58 further upstream of the compressor 60a.

Next, the exhaust system of the internal combustion engine will be described. A right exhaust manifold 4 is connected to the right bank 1 of the internal combustion engine, and each branch pipe of the right exhaust manifold 4 communicates with a combustion chamber of each cylinder 2 of the right bank 1 through an exhaust port. The right supercharger 1 is located at the collecting portion of the right exhaust manifold 4.
Zero turbine 10b is connected. A right exhaust pipe 12 is connected to an opening through which the exhaust of the turbine 10b flows.

  A left exhaust manifold 54 is connected to the left bank 51 of the internal combustion engine, and each branch pipe of the left exhaust manifold 54 communicates with the combustion chamber of each cylinder 2 of the left bank 51 through an exhaust port. A turbine 60 b of the left supercharger 60 is connected to a collecting portion of the left exhaust manifold 54. A left exhaust pipe 62 is connected to an opening through which the exhaust of the turbine 60b flows out. In the present embodiment, the right exhaust manifold 4 and the left exhaust manifold 54 correspond to exhaust passages. The right exhaust pipe 12 and the left exhaust pipe 62 correspond to downstream exhaust pipes.

Downstream of the right exhaust pipe 12 and the left exhaust pipe 62 are provided a right DPNR 20 and a left DPNR 70 for purifying exhaust NOx and particulate matter passing therethrough, respectively. The right exhaust pipe 12 on the downstream side of the right DPNR 20 and the left exhaust pipe 62 on the downstream side of the left DPNR 70 are provided with a right exhaust throttle valve 31 and a left exhaust gas for controlling the flow rate of the exhaust gas passing through the right exhaust pipe 12 and the left exhaust pipe 62. A throttle valve 81 is provided. On the downstream side of the right exhaust throttle valve 31 and the left exhaust throttle valve 81, the right exhaust pipe 12 and the left exhaust pipe 62 are open to the atmosphere.

  Here, the right exhaust manifold 4 and the right intake pipe 8 are communicated with each other by a right high pressure EGR passage 22. Further, the left exhaust manifold 54 and the left intake pipe 58 are communicated with each other through a left high pressure EGR passage 72. The right high-pressure EGR passage 22 and the left high-pressure EGR passage 72 are provided with a right high-pressure EGR valve 23 and a left high-pressure EGR valve 73 that control the flow rate of exhaust gas that passes through each high-pressure EGR passage. The right high pressure EGR valve 23 and the left high pressure EGR valve 73 are connected to an ECU 35, which will be described later, through electrical wiring, and the right high pressure EGR passage 22 is controlled by controlling the valve opening degree based on a control signal from the ECU 35. In addition, the amount of exhaust gas flowing through the left high pressure EGR passage 72 can be adjusted. The right high pressure EGR passage 22 and the right high pressure EGR valve 23 constitute a right high pressure EGR device 30. Similarly, the left high pressure EGR passage 72 and the left high pressure EGR valve 73 constitute a left high pressure EGR device 80 (hereinafter, exhaust gas flowing through the right high pressure EGR passage 22 or the left high pressure EGR passage 72 is referred to as “high pressure EGR gas”. The amount is referred to as “high pressure EGR gas amount”).

  On the other hand, a portion between the right DPNR 20 and the right exhaust throttle valve 31 in the right exhaust pipe 12 and a portion on the upstream side of the compressor 10 a in the right intake pipe 8 are communicated with each other by a right low pressure EGR passage 28. Similarly, a portion between the left DPNR 70 and the left exhaust throttle valve 81 in the left exhaust pipe 62 and a portion on the upstream side of the compressor 60 a in the left intake pipe 58 are communicated with each other through a left low pressure EGR passage 78.

  The right low pressure EGR passage 28 and the left low pressure EGR passage 78 are provided with a right low pressure EGR valve 29 and a left low pressure EGR valve 79 for controlling the flow rate of exhaust gas passing through the respective low pressure EGR passages. The right low pressure EGR valve 29 and the left low pressure EGR valve 79 are also connected to the ECU 35 through electric wiring, and the valve opening degree is controlled based on a control signal from the ECU 35, so that the right low pressure EGR passage 28 and the left low pressure EGR valve 28 are The amount of exhaust flowing through the low pressure EGR passage 78 can be adjusted. The right low pressure EGR passage 28 and the right low pressure EGR valve 29 constitute a right low pressure EGR device 40. The left low pressure EGR passage 78 and the left low pressure EGR valve 79 constitute a left low pressure EGR device 90. (Hereinafter, the exhaust gas flowing through the right low pressure EGR passage 28 or the left low pressure EGR passage 78 is referred to as “low pressure EGR gas”, and the amount thereof is referred to as “low pressure EGR gas amount”).

  Further, the upstream side of the right DPNR 20 of the right exhaust pipe 12 and the upstream side of the left DPNR 70 of the left exhaust pipe 62 are communicated by a communication pipe 15, and the flow rate of the exhaust gas passing through the communication pipe 15 is set in the communication pipe 15. A communication pipe valve 16 to be changed is provided. The communication pipe 15 and the communication pipe valve 16 correspond to a communication path and a communication path flow rate control valve, respectively, in this embodiment.

  Further, the right exhaust manifold 4 is provided with a right pre-turbo fuel addition valve 25 that adds a reducing agent to the exhaust when the purification ability of the right DPNR 20 is regenerated. On the other hand, on the upstream side of the right DPNR 20 in the right exhaust pipe 12, there is also provided a right post-turbo fuel addition valve 26 that adds a reducing agent to the exhaust when the purification ability of the right DPNR 20 is regenerated. Similarly, the left exhaust manifold 54 is provided with a left turbo pre-fuel addition valve 75 that adds a reducing agent to the exhaust when the purification ability of the left DPNR 70 is regenerated. On the other hand, on the upstream side of the left DPNR 70 in the left exhaust pipe 62, a left turbo post-fuel addition valve 76 for adding a reducing agent to the exhaust when the purification capability of the left DPNR 70 is regenerated is provided. Here, the right turbo pre-fuel addition valve 25, the right turbo post-fuel addition valve 26, the left turbo pre-fuel addition valve 75, and the left turbo post-fuel addition valve 76 correspond to reducing agent addition means in this embodiment.

  The internal combustion engine is also provided with an ECU 35 that is an electronic control computer. The ECU 35 includes a ROM, a RAM, a CPU, an input port, an output port, and the like (not shown), and performs known control such as fuel injection according to the operation state of the internal combustion engine 1 detected by the various sensors and the request from the driver. At the same time, an opening degree command signal is output to the left and right high pressure EGR valves 23 and 73, the left and right low pressure EGR valves 29 and 79, and the communication pipe valve 16. Further, a fuel addition command signal is output to the left and right pre-turbo fuel addition valves 25 and 75 and the left and right post-turbo fuel addition valves 26 and 76.

  In the above configuration, the air introduced into the right intake pipe 8 and the left intake pipe 58 is supercharged by the compressor 10a of the right supercharger 10 and the compressor 60a of the left supercharger 60, and is also intercooler 7, surge The refrigerant is introduced into the cylinders 2 and 52 of the right bank 1 and the left bank 51 of the internal combustion engine via the tank 6 and the intake manifold 3.

Exhaust gas discharged from the cylinders 2 and 52 passes through the right exhaust manifold 4 and the left exhaust manifold 54 and flows into the turbine 10b of the right supercharger 10 and the turbine 60b of the left supercharger 60 to drive each turbine. . After that, it passes through the right exhaust pipe 12 and the left exhaust pipe 62, and the particulate matter and NOx in the exhaust are collected in the right DPNR 20 and the left DPNR 70, and finally discharged into the atmosphere.

  Here, when the right high pressure EGR valve 23 is opened, the right high pressure EGR passage 22 becomes conductive, and a part of the exhaust gas flowing through the right exhaust manifold 4 passes to the right intake pipe 8 via the right high pressure EGR passage 22. The refrigerant flows into the cylinders 2 and 52 of the banks 1 and 51 of the internal combustion engine via the intercooler 7, the surge tank 6 and the intake manifold 3. When the left high pressure EGR valve 73 is opened, the left high pressure EGR passage 72 becomes conductive, and a part of the exhaust flowing through the left exhaust manifold 54 flows into the left intake pipe 58 via the left high pressure EGR passage 72, The refrigerant is recirculated to the cylinders 2 and 52 of the banks 1 and 51 of the internal combustion engine via the intercooler 7, the surge tank 6 and the intake manifold 3.

  When the right low pressure EGR valve 29 is opened, the right low pressure EGR passage 28 becomes conductive, and a part of the exhaust gas passing through the right exhaust pipe 12 passes through the right low pressure EGR passage 28 in the right intake pipe 8. It flows into the upstream side of the compressor 10a. The low-pressure EGR gas that has flowed into the right intake pipe 8 is supercharged by the compressor 10 a and is introduced into the cylinders 2 and 52 of the banks 1 and 51 of the internal combustion engine via the intercooler 7, the surge tank 6, and the intake manifold 3. .

Further, when the left low pressure EGR valve 79 is opened, the left low pressure EGR passage 78 becomes conductive, and a part of the exhaust gas passing through the left exhaust pipe 62 passes through the left low pressure EGR passage 78 in the left intake pipe 58. It flows into the upstream side of the compressor 60a. The low-pressure EGR gas flowing into the left intake pipe 58 is supercharged by the left compressor 60a, and is introduced into the cylinders 2 and 52 of the banks 1 and 51 of the internal combustion engine via the intercooler 7, the surge tank 6, and the intake manifold 3. The

  A part of the exhaust gas is recirculated to the cylinders 2 and 52 of the internal combustion engine through the left and right high-pressure EGR passages 22 and 72 and / or the left and right low-pressure EGR passages 28 and 78, thereby reducing the combustion temperature in the combustion chamber and generating it in the combustion process. The amount of NOx to be reduced can be reduced. Further, by opening the communication pipe valve 16, the exhaust gas can be circulated between the right exhaust pipe 12 and the left exhaust pipe 62.

  As described above, in this embodiment, a part of the exhaust discharged from the left and right banks 1 and 51 of the internal combustion engine is recirculated by the left and right high pressure EGR devices 30 and 80 depending on the operating state, or the left and right low pressure EGR devices 40. , 90, so that the generation of NOx in the internal combustion engine is suppressed by a wider operating range.

  Specifically, the exhaust gas is recirculated using the left and right low-pressure EGR devices 40 and 90 in the high-load operation state, and the left and right low-pressure EGR devices 40 and 90 and the left and right high-pressure EGR device in the medium-load operation state. 30 and 80 may be used in combination. In the low-load operation state, the left and right high-pressure EGR devices 30 and 80 may be used to recirculate the exhaust gas.

  Further, as described above, in this embodiment, the left and right DPNRs 20 and 70, the left and right low pressure EGR passages 28 and 78, the right and left exhaust throttle valves 31 and the left and right exhaust pipes 12 and 62, respectively. , 81 are provided in this order, the left and right DPNRs 20, 70 and the left and right low pressure EGR passages 28 are appropriately controlled by controlling the communication pipe valve 16, the left and right low pressure EGR valves 29, 79, and the left and right exhaust throttle valves 31, 81. , 78 can be controlled arbitrarily.

<NOx reduction treatment>
Next, as an example of the NOx reduction process in the present embodiment, for example, control when performing the NOx reduction process of the right DPNR 20 will be described. In particular, let us consider a case where the NOx reduction process of the right DPNR 20 is performed in an intermediate load operation state in which the left and right low pressure EGR devices 40 and 90 are used. In this case, as described above, the left and right low pressure EGR devices 40 and 90 and the left and right high pressure EGR devices 30 and 80 are used in combination to perform exhaust gas recirculation.

In the above operating state, when the NOx reduction process of the right DPNR 20 is executed, fuel as a reducing agent is added from the right turbo front fuel injection valve 25. The communication pipe valve 16 is closed and the right exhaust throttle valve 31 is throttled. Then, the right low pressure EGR valve 29 is fully opened.

  Then, fuel is added from the right turbo pre-fuel addition valve 25 to the exhaust gas that passes through the right exhaust manifold 4. Then, the exhaust gas with the fuel added is agitated by the turbine 10 b of the right supercharger 10, passes through the right exhaust pipe 12, and is introduced into the right DPNR 20.

At this time, since the right exhaust throttle valve 31 is throttled, the flow rate of the exhaust gas introduced into the right DPNR 20 is reduced, and the reduction reaction of NOx is more reliably completed in the right DPNR 20 by the introduced fuel. Can do. In addition, since the right exhaust throttle valve 31 is throttled, the back pressure on the downstream side of the right DPNR 20 is increased, and the right low pressure EGR valve 29 is fully opened. It passes through the low pressure EGR passage 28 and is recirculated to the right intake pipe 8.

Next, a case where the operating state of the internal combustion engine when performing the NOx reduction process is a high load and a high rotation speed will be described. In this operating state, EGR is performed only by the left and right low pressure EGR devices 40 and 90, and the left and right high pressure EGR devices 30 and 80 are not used. In this case, since the flow rate of the exhaust gas from the right bank 1 is large, in the NOx reduction process of the right DPNR 20, the right exhaust throttle valve 31 is fully closed in order to complete a sufficient reduction reaction in the right DPNR 20. Keep close.

Then, since the back pressure on the downstream side of the right DPNR 20 becomes very high, the amount of EGR gas that is recirculated through the right low pressure EGR passage 28 may be excessively larger than the required amount. In such a case, in this embodiment, the communication pipe valve 16 is opened, and a part of the exhaust gas passing through the right exhaust pipe 12 is caused to flow into the left exhaust pipe 62. Since the left DPNR 70 provided in the left exhaust pipe 62 is not subjected to NOx reduction processing, the left exhaust throttle valve 81 is fully open. Therefore, after the exhaust gas that has passed through the communication pipe 15 is purified by the left DPNR 70, a part of the exhaust is discharged outside the vehicle, and a part passes through the left low pressure EGR passage 78 and is recirculated to the left intake pipe 58.

As described above, in this embodiment, when the operating state of the internal combustion engine is high load and high rotation speed, the communication pipe valve 16 is opened, and the right low pressure EGR device 40 on which NOx reduction processing is performed is performed. This reduces the amount of low-pressure EGR gas recirculated. Then, a small amount of low-pressure EGR gas is recirculated using the left low-pressure EGR device 90 on which NOx reduction processing has not been performed. Accordingly, the overall low-pressure EGR gas amount can be suppressed, and inconveniences such as an increase in the amount of PM generated due to the amount of low-pressure EGR gas being too large relative to the required amount can be suppressed.

Next, consider the case where the operating state of the right DPNR 20 during the NOx reduction process becomes a rapid acceleration state and the required amount of EGR gas rapidly decreases. Even in such a case, when the responsiveness of the amount of EGR gas that passes through the right low pressure EGR passage 28 and is recirculated to the right intake pipe 8 is low, the amount of EGR gas is excessive with respect to the required amount. In some cases, inconveniences such as an increase in PM generated in an internal combustion engine may occur.

On the other hand, in the present embodiment, when the operating state of the right DPNR 20 during the NOx reduction process becomes a rapid acceleration state and the required amount of EGR gas rapidly decreases, the right exhaust throttle valve 31 is rapidly opened. The amount of low-pressure EGR gas that passes through the right low-pressure EGR passage 28 and is recirculated to the right intake pipe 8 is rapidly reduced.

  By doing so, the amount of low-pressure EGR gas that passes through the right-low pressure EGR passage 28 and is recirculated to the right intake pipe 8 can be reduced sufficiently quickly as the required amount of EGR gas decreases. Inconveniences such as an increase in PM in the exhausted gas can be suppressed.

<PM regeneration process>
Next, control when performing PM regeneration processing on the right DPNR 20 will be described. Here, when performing the PM regeneration processing, the temperature of the right DPNR 20 is increased by adding fuel to the exhaust from the right turbo pre-fuel addition valve 25 or the right turbo post-fuel addition valve 26. In this case, the communication pipe valve 16 is fully closed, the right exhaust throttle valve 31 is throttled, the right low pressure EGR valve 29 is opened, and the amount of low pressure EGR gas by the right low pressure EGR device 40 is positively increased.

  As a result, the fuel that has passed through the right DPNR 20 can be reburned in the right bank 1 of the internal combustion engine, and the fuel that has passed through the right DPNR 20 can be prevented from being diffused out of the vehicle as it is and the emission can be prevented from deteriorating.

  In addition, when the temperature of the exhaust gas from the right DPNR 20 increases excessively during PM regeneration of the right DPNR 20, the control for opening the right exhaust throttle valve 31 to a larger opening degree and opening the communication pipe valve 16 is performed. May be performed. Then, the amount of low-pressure EGR gas recirculated by the right low-pressure EGR device 40 decreases, and the amount of low-pressure EGR gas recirculated by the left low-pressure EGR device 90 relatively increases.

  As a result, the amount of exhaust gas recirculated after passing through the right DPNR 20 during PM regeneration processing can be relatively reduced, and the temperature of the entire low-pressure EGR gas recirculated to the internal combustion engine can be reduced. Can do. As a result, inconveniences such as an increase in the amount of NOx generated due to the high temperature of the low pressure EGR gas can be suppressed.

<SOx poisoning recovery process>
Next, control when performing SOx poisoning recovery processing on the right DPNR 20 will be described. Here, when the SOx poisoning recovery process is performed, the temperature of the right DPNR 20 is increased by adding fuel to the exhaust from the right turbo pre-fuel addition valve 25 or the right turbo post-fuel addition valve 26 as in the case of performing the PM regeneration process. To raise. In this case, the communication pipe valve 16 is fully closed, the right exhaust throttle valve 31 is throttled, the right low pressure EGR valve 29 is opened, and the EGR gas amount by the right low pressure EGR device 40 is positively increased.

As a result, even when performing SOx poisoning recovery processing for the right DPNR 20,
The fuel that has passed through the NR 20 can be reburned in the right bank 1 of the internal combustion engine, and the fuel that has passed through the right DPNR 20 can be prevented from being diffused to the outside as it is and the emission being deteriorated.

Further, particularly in the SOx poisoning recovery process of the right DPNR 20, the right turbo front fuel addition valve 25
Alternatively, when adding fuel to the exhaust from the right turbo post-fuel addition valve 26, rich spike processing is often performed. At this time, the communication pipe valve 16 is fully closed during the rich period and the right exhaust throttle is closed. The valve 31 is throttled and the right low pressure EGR valve 29 is opened to actively increase the amount of EGR gas by the right low pressure EGR device 40. During the lean period, the communication pipe valve 16 is fully opened and the right exhaust throttle is opened. The valve 31 may be opened to a larger opening degree so that the amount of EGR gas recirculated by the left low pressure EGR device 40 is increased than the amount of EGR gas recirculated by the right low pressure EGR device 40.

  Then, the fuel that has passed through the right DPNR 20 can be more reliably prevented from being diffused to the outside of the vehicle and the emission can be prevented from worsening, and the low-pressure EGR device 90 can also recirculate relatively low-temperature EGR gas. The temperature of the low-pressure EGR gas as a whole can be lowered.

Further, during the SOx poisoning recovery process of the right DPNR 20, if the temperature of the exhaust gas from the right DPNR 20 increases excessively, control is performed to open the right exhaust throttle valve 31 and open the communication pipe valve 16. May be. Then, the amount of low-pressure EGR gas recirculated by the right low-pressure EGR device 40 decreases, and the amount of low-pressure EGR gas recirculated by the left low-pressure EGR device 90 relatively increases.

As a result, the temperature of the entire low-pressure EGR gas recirculated to the internal combustion engine can be reduced, and inconveniences such as an increase in the amount of NOx generated due to the high temperature of the low-pressure EGR gas can be suppressed. Can do.

  In the first embodiment, the internal combustion engine is a V-type internal combustion engine, and the four cylinders 2 and 52 provided in the banks 1 and 51 correspond to the cylinder group, respectively, but the present invention is applied. This is not limited to the V-type internal combustion engine. For example, three cylinders of an in-line 6-cylinder internal combustion engine are divided into two cylinder groups, and the left and right superchargers 10, 60, left and right exhaust pipes 12, 62, You may assign components, such as DPNR20 and 70, right-and-left low voltage EGR apparatuses 40 and 90, and the like.

Further, in the above embodiment, the fuel addition control in the NOx reduction process of the DPNR 20 has been described, but it is needless to say that the same idea may be applied to the SOx poisoning recovery process and the PM regeneration process of the DPNR 20.

In the first embodiment, the case where the NOx reduction process, the PM regeneration process, and the SOx poisoning recovery process are performed on the right DPNR 20 has been described. However, the NOx reduction process, the PM regeneration process, and the SOx poisoning recovery process of the left DPNR 70 are described. In the case of performing the control, the control may be performed by switching the left and right of the components related to the control.

  Next, a second embodiment of the present invention will be described. In the first embodiment, an example of a V-type internal combustion engine having eight cylinders has been described. In this embodiment, an example in which the present invention is applied to an in-line four-cylinder internal combustion engine will be described.

  FIG. 2 is a diagram showing a schematic configuration of an internal combustion engine, an intake / exhaust system, and a control system to which the present invention is applied. The internal combustion engine shown in FIG. 2 is an in-line four-cylinder internal combustion engine having a bank 11 and four banks 42 in the bank 11.

  An intake manifold 13 is connected to the bank 11 of the internal combustion engine, and each branch pipe of the intake manifold 13 communicates with a combustion chamber of each cylinder 42 of the bank 11 through an intake port. The intake manifold 13 is connected to an intake pipe 18. An intercooler 27 is provided in the intake pipe 18, and a compressor 50 a of the supercharger 50 is provided further upstream of the intercooler 27. The intake pipe 18 further upstream of the compressor 50a is provided with an air flow meter and an air cleaner (not shown).

  Next, the exhaust system of the internal combustion engine will be described. An exhaust manifold 14 is connected to the bank 11 of the internal combustion engine, and each branch pipe of the exhaust manifold 14 communicates with a combustion chamber of each cylinder 42 of the bank 11 via an exhaust port. A turbine 50 b of the supercharger 50 is connected to the collecting portion of the exhaust manifold 14. An exhaust pipe 19 is connected to an opening through which the exhaust of the turbine 50b flows out.

  The exhaust pipe 19 is connected to a substantially central portion of the communication pipe 15, and the communication pipe 15 is connected to the right exhaust pipe 12 and the left exhaust pipe 62 at both ends as described in the first embodiment. A connecting portion between the communication pipe 15 and the exhaust pipe 19 is provided with a three-way valve 17 that determines the amount of exhaust gas passing through the exhaust pipe 19 to the right exhaust pipe 12 side and the left exhaust pipe 62 side in the communication pipe 15. It has been. Note that the components disposed in the right exhaust pipe 12 and the left exhaust pipe 62 are the same as those described in the first embodiment, and thus the description thereof is omitted here.

  However, the right low pressure EGR passage 38 and the left low pressure EGR passage 88 in this embodiment are different from the first embodiment in that both are connected to the upstream side of the compressor 50a in the intake pipe 18. Here, the right low pressure EGR passage 38 and the right low pressure EGR valve 29 constitute a right low pressure EGR device 110. Similarly, the left low pressure EGR passage 88 and the left low pressure EGR valve 79 constitute a left low pressure EGR device 120.

  The exhaust manifold 14 and the intake pipe 18 are communicated with each other through a high pressure EGR passage 32. The high-pressure EGR passage 32 is provided with a high-pressure EGR valve 33 that controls the flow rate of exhaust gas that passes through the high-pressure EGR passage 32. The high pressure EGR passage 32 and the high pressure EGR valve 33 constitute a high pressure EGR device 100.

Even in the configuration as described above, part of the exhaust discharged from the bank 11 of the internal combustion engine is recirculated by the high pressure EGR device 100 or recirculated by the left and right low pressure EGR devices 110 and 120 depending on the operating state. Therefore, the generation of NOx in the internal combustion engine is suppressed by a wider operating range.

  Further, as described above, in this embodiment, the left and right DPNRs 20 and 70, the left and right low pressure EGR passages 38 and 88, the exhaust intake ports, the left and right exhaust throttle valves, respectively, for the two exhaust pipes of the left and right exhaust pipes 12 and 62. Since 31 and 81 are provided in this order, the left and right DPNRs 20 and 70 and the left and right low pressure EGR passage 38 are controlled by appropriately controlling the three-way valve 17, the left and right low pressure EGR valves 29 and 79, and the left and right exhaust throttle valves 31 and 81. , 88 can be controlled arbitrarily.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows schematic structure of the internal combustion engine in Example 1 of this invention, its intake-exhaust system, and a control system. It is a figure which shows schematic structure of the internal combustion engine in Example 2 of this invention, its intake-exhaust system, and a control system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Right bank 2 ... Cylinder 3 ... Intake manifold 4 ... Right exhaust manifold 8 ... Right intake pipe 10 ... Right supercharger 11 ... Bank 12 ... Right exhaust Pipe 15 ... Communication pipe 16 ... Communication pipe valve 17 ... Three-way valve 18 ... Intake pipe 19 ... Exhaust pipe 20 ... Right DPNR
22 ... Right high pressure EGR passage 23 ... Right high pressure EGR valve 28, 38 ... Right low pressure EGR passage 29 ... Right low pressure EGR valve 31 ... Right exhaust throttle valve 32 ... High pressure EGR passage 33 ... High pressure EGR valve 35 ... ECU
50 ... supercharger 51 ... left bank 52 ... cylinder 58 ... left intake pipe 60 ... left supercharger 62 ... left exhaust pipe 70 ... left DPNR
72 ... Left high pressure EGR passage 73 ... Left high pressure EGR valve 78, 88 ... Left low pressure EGR passage 79 ... Left low pressure EGR valve

Claims (8)

An exhaust passage through which exhaust from a cylinder of the internal combustion engine passes;
A turbocharger in which a turbine is disposed in the exhaust passage and a compressor is disposed in an intake passage of the internal combustion engine;
A plurality of downstream exhaust passages through which the exhaust discharged from the turbine of the supercharger passes;
A communication passage communicating the plurality of downstream exhaust passages;
A communication path flow rate control valve provided in the communication path and capable of changing a flow rate of exhaust gas in the communication path;
An exhaust purification device that is provided in each of the downstream exhaust passages, purifies the exhaust gas passing through the downstream exhaust passages, and regenerates the purification ability by supplying a reducing agent;
When the exhaust purification device is disposed in the exhaust passage or the downstream exhaust passage upstream of the exhaust purification device and regenerates the purification capability of the exhaust purification device, it is reduced to the exhaust purification device by adding a reducing agent to the exhaust gas. Reducing agent addition means for supplying the agent;
An exhaust throttle valve that is provided on the downstream side of the exhaust purification device in the downstream side exhaust passage and controls the flow rate of exhaust gas in the downstream side exhaust passage;
The same number as the plurality of downstream exhaust passages is provided corresponding to each of the downstream exhaust passages, one end connected to the downstream exhaust passage and the other end connected to the upstream side of the compressor in the intake passage. Low pressure EGR passage,
A low pressure EGR valve provided in the low pressure EGR passage and controlling an amount of exhaust gas passing through the low pressure EGR passage,
One end of the low pressure EGR passage is connected to a portion between the exhaust purification device and the exhaust throttle valve in the downstream exhaust passage,
When performing NOx reduction treatment of any exhaust purification device among the exhaust purification devices provided in the plurality of downstream exhaust passages,
The reducing agent is added from the reducing agent addition means upstream of the exhaust purification device that is the target of the NOx reduction process, and the communication passage flow control valve and the exhaust throttle valve on the downstream side of the exhaust purification device that is the target of the NOx reduction process Is closed, and the low pressure EGR valve in the low pressure EGR passage connected to the downstream side of the exhaust purification device that is the target of the NOx reduction treatment is opened,
The flow rate of the exhaust gas that passes through the exhaust gas purification device that is the subject of the NOx reduction treatment is reduced, and the exhaust gas is recirculated through the low-pressure EGR passage connected to the downstream side of the exhaust gas purification device that is the subject of the NOx reduction treatment. An exhaust system for an internal combustion engine. An exhaust passage through which exhaust from a cylinder of the internal combustion engine passes;
A turbocharger in which a turbine is disposed in the exhaust passage and a compressor is disposed in an intake passage of the internal combustion engine;
A plurality of downstream exhaust passages through which the exhaust discharged from the turbine of the supercharger passes;
A communication passage communicating the plurality of downstream exhaust passages;
A communication path flow rate control valve provided in the communication path and capable of changing a flow rate of exhaust gas in the communication path;
An exhaust purification device that is provided in each of the downstream exhaust passages, purifies the exhaust gas passing through the downstream exhaust passages, and regenerates the purification ability by supplying a reducing agent;
When the exhaust purification device is disposed in the exhaust passage or the downstream exhaust passage upstream of the exhaust purification device and regenerates the purification capability of the exhaust purification device, it is reduced to the exhaust purification device by adding a reducing agent to the exhaust gas. Reducing agent addition means for supplying the agent;
An exhaust throttle valve that is provided on the downstream side of the exhaust purification device in the downstream side exhaust passage and controls the flow rate of exhaust gas in the downstream side exhaust passage;
The same number as the plurality of downstream exhaust passages is provided corresponding to each of the downstream exhaust passages, one end connected to the downstream exhaust passage and the other end connected to the upstream side of the compressor in the intake passage. Low pressure EGR passage,
A low pressure EGR valve provided in the low pressure EGR passage and controlling an amount of exhaust gas passing through the low pressure EGR passage,
One end of the low pressure EGR passage is connected to a portion between the exhaust purification device and the exhaust throttle valve in the downstream exhaust passage,
When performing NOx reduction treatment of any exhaust purification device among the exhaust purification devices provided in the plurality of downstream exhaust passages,
The reducing agent is added from the reducing agent addition means upstream of the exhaust purification device that is the target of the NOx reduction treatment, and the exhaust throttle valve on the downstream side of the exhaust purification device that is the target of the NOx reduction processing is closed, and By opening the passage flow control valve on the open side,
The flow rate of the exhaust gas that passes through the exhaust purification device that is the subject of the NOx reduction treatment is reduced, and the exhaust gas is recirculated through the low-pressure EGR passage connected to the downstream side of the exhaust purification device that is not the subject of the NOx reduction treatment. An exhaust system for an internal combustion engine. An exhaust passage through which exhaust from a cylinder of the internal combustion engine passes;
A turbocharger in which a turbine is disposed in the exhaust passage and a compressor is disposed in an intake passage of the internal combustion engine;
A plurality of downstream exhaust passages through which the exhaust discharged from the turbine of the supercharger passes;
A communication passage communicating the plurality of downstream exhaust passages;
A communication path flow rate control valve provided in the communication path and capable of changing a flow rate of exhaust gas in the communication path;
An exhaust purification device that is provided in each of the downstream exhaust passages, purifies the exhaust gas passing through the downstream exhaust passages, and regenerates the purification ability by supplying a reducing agent;
When the exhaust purification device is disposed in the exhaust passage or the downstream exhaust passage upstream of the exhaust purification device and regenerates the purification capability of the exhaust purification device, it is reduced to the exhaust purification device by adding a reducing agent to the exhaust gas. Reducing agent addition means for supplying the agent;
An exhaust throttle valve that is provided on the downstream side of the exhaust purification device in the downstream side exhaust passage and controls the flow rate of exhaust gas in the downstream side exhaust passage;
The same number as the plurality of downstream exhaust passages is provided corresponding to each of the downstream exhaust passages, one end connected to the downstream exhaust passage and the other end connected to the upstream side of the compressor in the intake passage. Low pressure EGR passage,
A low pressure EGR valve provided in the low pressure EGR passage and controlling an amount of exhaust gas passing through the low pressure EGR passage,
One end of the low pressure EGR passage is connected to a portion between the exhaust purification device and the exhaust throttle valve in the downstream exhaust passage,
When performing NOx reduction treatment of any exhaust purification device among the exhaust purification devices provided in the plurality of downstream exhaust passages,
While adding the reducing agent from the reducing agent addition means upstream of the exhaust gas purification device that is the subject of the NOx reduction treatment,
When the operating state of the internal combustion engine belongs to a predetermined low load / low rotation speed region, the communication passage flow control valve and the exhaust throttle valve on the downstream side of the exhaust purification device to be subjected to the NOx reduction process are closed. By opening the low-pressure EGR valve in the low-pressure EGR passage connected to the downstream side of the exhaust purification device that is the target of the NOx reduction treatment,
The flow rate of the exhaust gas that passes through the exhaust gas purification device that is the subject of the NOx reduction treatment is reduced, and the exhaust gas is recirculated through the low-pressure EGR passage connected to the downstream side of the exhaust gas purification device that is the subject of the NOx reduction treatment. Let
When the operating state of the internal combustion engine belongs to a predetermined high load / high rotation speed region, the exhaust throttle valve on the downstream side of the exhaust purification device that is the target of the NOx reduction process is closed, and the communication passage flow control is performed. By opening the valve to the open side,
The flow rate of the exhaust gas that passes through the exhaust purification device that is the subject of the NOx reduction treatment is reduced, and the exhaust gas is recirculated through the low-pressure EGR passage connected to the downstream side of the exhaust purification device that is not the subject of the NOx reduction treatment. An exhaust system for an internal combustion engine. The internal combustion engine has a plurality of cylinders, and the cylinders are aggregated to form two or more cylinder groups,
The exhaust passage, the supercharger, and the downstream exhaust passage are provided in the same number as the cylinder group, corresponding to each of the cylinder groups,
Exhaust gas from each cylinder group passes through the exhaust passage corresponding to the cylinder group, rotates the turbine of the corresponding turbocharger, and then passes through the corresponding downstream exhaust passage. The exhaust system for an internal combustion engine according to any one of claims 1 to 3, wherein the exhaust system is an internal combustion engine. During the NOx reduction process of any one of the exhaust purification devices provided in the plurality of downstream exhaust passages,
When a predetermined required EGR amount suddenly decreasing in which the required amount of EGR gas rapidly decreases, the exhaust throttle valve on the downstream side of the exhaust purification device during the NOx reduction process is opened at a predetermined speed or more, The exhaust gas of an internal combustion engine according to any one of claims 1 to 4, wherein the flow rate of exhaust gas recirculated from the low pressure EGR passage connected to the downstream side of the exhaust gas purification device during NOx reduction treatment is rapidly reduced. system. When performing PM regeneration processing of any exhaust purification device among the exhaust purification devices provided in the plurality of downstream exhaust passages,
The reducing agent is added from the reducing agent addition means upstream of the exhaust purification device that is the target of the PM regeneration process, and the communication passage flow rate control valve and the exhaust throttle valve on the downstream side of the exhaust purification device that is the target of the PM regeneration process Are closed, and the low pressure EGR valve in the low pressure EGR passage connected to the downstream side of the exhaust gas purification device that is the target of the PM regeneration process is opened,
The flow rate of the exhaust gas that passes through the exhaust gas purification device that is the target of the PM regeneration process is reduced, and the exhaust gas is recirculated through the low-pressure EGR passage that is connected to the downstream side of the exhaust gas purification device that is the target of the PM regeneration process. An exhaust system for an internal combustion engine according to any one of claims 1 to 5, wherein: When performing SOx poisoning recovery processing of any of the exhaust purification devices provided in the plurality of downstream exhaust passages,
A reducing agent is added from a reducing agent addition means upstream of the exhaust gas purification device that is the object of the SOx poisoning recovery process, and the downstream side of the communication flow rate control valve and the exhaust gas purification device that is the object of the SOx poisoning recovery process By closing the exhaust throttle valve and the low-pressure EGR valve in the low-pressure EGR passage connected to the downstream side of the exhaust purification device that is the object of the SOx poisoning recovery process,
Through the low-pressure EGR passage connected to the downstream side of the exhaust purification device that is the target of the SOx poisoning recovery process, while reducing the flow rate of the exhaust gas that passes through the exhaust purification device that is the target of the SOx poisoning recovery process. The exhaust system for an internal combustion engine according to any one of claims 1 to 6, wherein the exhaust gas is recirculated. When performing PM regeneration processing or SOx poisoning recovery processing of any exhaust purification device of the exhaust purification devices provided in each of the plurality of downstream exhaust passages,
By closing the exhaust throttle valve on the downstream side of the exhaust purification device that is the target of the PM regeneration process or the SOx poisoning recovery process, and opening the communication passage flow control valve,
The flow rate of the exhaust gas that passes through the exhaust purification device that is the target of the PM regeneration process or SOx poisoning recovery process is reduced and connected to the downstream side of the exhaust purification device that is not the target of the PM regeneration process or SOx poisoning recovery process The exhaust system for an internal combustion engine according to any one of claims 1 to 5, wherein the exhaust gas is recirculated through the low-pressure EGR passage.

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