JP2006057593A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine for minimizing the turn-around of reducer through an EGR passage into an intake system with exhausting pulsation when additionally supplied during great-amount EGR operation. <P>SOLUTION: In the internal combustion engine with a separate type exhaust manifold, when EGR valves 7a, 7b are opened during additionally supplying fuel from injectors 5a, 5b, if a difference in the amount of air detected by air flow meters 15a, 15b is greater than a specified value set in a control device 18, the control device 18 forcibly closes the EGR valves 7a, 7b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, and more particularly to an exhaust gas purification apparatus for an internal combustion engine having a split exhaust manifold.

In the V-type engine, there is a high demand for attaching two turbochargers, one for each of the left and right banks, for reasons such as startability improvement and output improvement. In this case, the left and right air flow meters attached to the respective turbo inlet portions are used to correct the left and right air amount variations caused by the individual variations of the two turbos. In particular, in an engine equipped with an EGR device, not only the amount of fresh air but also the amount of EGR gas affects the amount of air. Therefore, two EGR valves and two throttle valves are installed to eliminate the variation in the amount of air on the left and right. The amount of air is made the same on the left and right sides by correcting the opening degree with the output of.
As a V-type engine layout, it is necessary to quickly scavenge EGR gas remaining in the intake system when the EGR valve is closed in order to improve acceleration performance. For this purpose, there is a countermeasure to either return the EGR gas to the intake side (hereinafter referred to as the return position) near the intake manifold or install the throttle valve near the intake manifold. is necessary. If the return position and the throttle valve are mounted so as to be close to each other, the pressure pulsation causes the EGR gas to spray on the throttle valve, causing sticking. As a countermeasure, before returning the EGR gas taken out from the exhaust manifolds of both banks to the intake air, it is advisable to join them together to eliminate the pressure pulsation and then return to the intake system. On the other hand, when the EGR gas is not returned to the intake system, it is necessary to improve the turbo responsiveness by closing the EGR valve and reducing the exhaust volume. .
In addition, regarding the addition of exhaust fuel, usually, fuel is added in the cylinder head, and is directly passed through a turbo and used as a catalyst reducing agent. However, if the mounting position of the EGR pipe for returning the exhaust gas to the intake system is mounted at a position close to the turbo, the added fuel flows back to the intake system due to the exhaust pulsation, and the EGR valve and the EGR cooler are fixed. Furthermore, torque fluctuation is induced. For this reason, Patent Document 1 describes that the mounting position of the EGR pipe is separated from the turbo.

JP 2004-76595 A

However, in an internal combustion engine that has two turbos and each has an exhaust system divided into two and an EGR device is attached to each exhaust system, the pressure in each exhaust system is caused by variations in each turbo. When the difference occurs, when the EGR valve is opened, each exhaust system communicates, so that there is a problem that the added reducing agent flows back to the intake system together with the air flow across each exhaust system. .
In addition, the internal combustion engine that employs the DPF device also has a problem that the air-fuel ratio and flow rate of the gas entering the DPF device are unclear.

  The present invention has been made to solve such problems. Even when a reducing agent is added during a large amount of EGR operation, the reducing agent passes through the EGR passage due to exhaust pulsation and pressure difference between the left and right banks. An object of the present invention is to provide an exhaust emission control device for an internal combustion engine that can suppress the sneaking into the intake system as much as possible.

An exhaust gas purification apparatus for an internal combustion engine according to the present invention is an internal combustion engine having a split exhaust manifold connected to one cylinder group and the other cylinder group, wherein a reducing agent is added to the exhaust gas discharged from the internal combustion engine. Reducing agent addition means to be supplied, EGR device provided with an EGR valve, a supercharger provided downstream of each of the split exhaust manifolds, and operating state detecting means for detecting the respective operating states of the supercharger The difference between the detected value indicating the operating state of the corresponding supercharger detected by one operating state detecting means and the detected value indicating the operating state of the corresponding supercharger detected by the other operating state detecting means Includes control means for closing each of the EGR valves when the specified value is larger than a preset specified value.
When the difference between the detected values detected by the respective operating state detecting means is larger than a predetermined value preset in the control device, it is determined that the operating states of the respective superchargers vary, and the control is performed. Since the apparatus closes each EGR valve, it is possible to suppress the added reducing agent from entering the intake system of the internal combustion engine through the EGR passage by the exhaust pulsation as much as possible.
In addition, after the EGR valve is closed, the control device compares the elapsed time measured from the end of the addition of the reducing agent with the release time required to release the reducing agent remaining in the split exhaust manifold. When the elapsed time exceeds the discharge time, the control device may open each EGR valve. Since the reducing agent remaining between the installation position of the reducing agent supply means and the EGR valve is released, when the EGR valve is opened, the remaining reducing agent passes through the EGR passage to the intake system of the internal combustion engine. It is possible to suppress wraparound as much as possible.
Further, the release time may be a time required for a predetermined number of rotation cycles of the internal combustion engine.

  According to this invention, the operating state detecting means for detecting the operating state of the supercharger provided downstream of each divided exhaust manifold is provided, and the difference between the detected values detected by the respective operating state detecting means is provided. However, if the value is larger than the specified value, it is determined that the respective superchargers are dispersed, and the control device is configured to close the respective EGR valves. The pressure difference between the left and right banks can be prevented from entering the intake system of the internal combustion engine through the EGR passage as much as possible.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Embodiment 1 FIG.
As shown in FIG. 1, the exhaust gas purification apparatus for an internal combustion engine according to this embodiment is provided with separate exhaust manifolds (split manifolds) in each of the left and right banks of a V-type engine.
The internal combustion engine 1 is a V-type 6-cylinder diesel engine, and intake manifolds 2a and 2b and exhaust manifolds 3a and 3b that share three cylinders are connected to left and right banks each having three cylinders. . The exhaust manifold 3a includes three branch pipes 3a1, 3a2, 3a3 and an exhaust collecting portion 3a4 in which these are gathered into one. The three branch pipes 3a1, 3a2, 3a3 are provided in three left banks, respectively. The three cylinders 4a1, 4a2, 4a3 are connected to exhaust ports (not shown). On the other hand, the exhaust manifold 3b includes three branch pipes 3b1, 3b2, 3b3, and an exhaust collecting portion 3b4 in which these are gathered into one, and each of the three branch pipes 3b1, 3b2, 3b3 has three left banks. Are connected to exhaust ports (not shown) of the three cylinders 4b1, 4b2 and 4b3.

Of the three cylinders provided in the left and right banks, injectors 5a and 5b as reducing agent addition means are provided in cylinder heads (not shown) of the cylinders 4a1 and 4b1, respectively. Here, a fuel for operating the internal combustion engine 1 is used as the reducing agent.
Of the three branch pipes provided in each of the exhaust manifolds 3a and 3b, EGR passages 6a and 6b extending toward the intake manifolds 2a and 2b of the internal combustion engine 1 are connected to the branch pipes 3a3 and 3b3, respectively. The EGR passages 6a and 6b are respectively provided with EGR valves 7a and 7b for opening and closing the respective passages. Here, the EGR passage 6a and the EGR valve 7a, and the EGR passage 6b and the EGR valve 7b constitute EGR devices 8a and 8b, respectively. Downstream of the EGR valves 7a and 7b, the EGR passages 6a and 6b merge to form one EGR passage 6c, which is connected to an intake pipe (described later) connected to the two intake manifolds 2a and 2b. Here, the connection position between the EGR passage 6 c and the intake pipe constitutes a return position 10. The EGR passage 6c is provided with an EGR cooler 9 for cooling the gas flowing through the EGR passage 6c.
Furthermore, superchargers 11a and 11b are provided in the exhaust collecting portions 3a4 and 3b4 provided in the exhaust manifolds 3a and 3b, respectively, and the DPF device 12a is connected via the turbine wheels 11a1 and 11b1 constituting the superchargers 11a and 11b. , 12b.

The intake pipes 14a and 14b divided into two through the air cleaner 13 extend toward the intake manifolds 2a and 2b via the compressor wheels 11a2 and 11b2 of the superchargers 11a and 11b. Air flow meters 15a and 15b for measuring the amount of air flowing into the compressor wheels 11a2 and 11b2 are provided upstream of the superchargers 11a and 11b of the intake pipes 14a and 14b. Here, since the operating state of the superchargers 11a and 11b changes in accordance with the amount of air flowing into the compressor wheels 11a2 and 11b2, the air flow meters 15a and 15b constitute an operating state detection unit for the superchargers 11a and 11b. To do.
Intercoolers 16a and 16b are provided downstream of the superchargers 11a and 11b of the intake pipes 14a and 14b. The intake pipes 14a and 14b join together downstream of the intercoolers 16a and 16b to form one intake pipe, and are further divided into two and connected to the intake manifolds 2a and 2b. Throttle valves 17a and 17b are provided on the downstream side of the intercoolers 16a and 16b of the intake pipes 14a and 14b.
Further, the air flow meters 15 a and 15 b and the EGR valves 7 a and 7 b are electrically connected to the control device 18.

Next, the operation of the exhaust gas purification apparatus for an internal combustion engine according to this embodiment will be described.
As shown in FIG. 1, when the internal combustion engine 1 is operated, air taken in from an intake duct (not shown) passes through the two intake pipes 14 a and 14 b after foreign matters are removed by the air cleaner 13. The flow rate is measured by the air flow meters 15a and 15b and sent to the superchargers 11a and 11b. The air sent to the superchargers 11a and 11b is compressed by the compressor wheels 11a2 and 11b2 and cooled in the intercoolers 16a and 16b. The flow rate of the cooled air is adjusted by the throttle valves 17a and 17b and sent to the intake manifolds 2a and 2b. The air sent to the intake manifolds 2a and 2b is sucked into combustion chambers (not shown) of the six cylinders 4a1 to 4a3 and 4b1 to 4b3, and is exploded and burned together with fuel to become exhaust gas. The exhaust gas discharged from each cylinder is collected in the exhaust manifolds 3a and 3b and then sent to the superchargers 11a and 11b. The exhaust gas sent to the superchargers 11a and 11b rotates the turbine wheels 11a1 and 11b1. The turbine wheels 11a1 and 11b1 and the compressor wheels 11a2 and 11b2 are interlocked, and the compressor wheels 11a2 and 11b2 are rotated by the rotation of the turbines 11a1 and 11b1 by the exhaust gas. The compressed air is compressed and sent to the intercoolers 16a and 16b. The exhaust gas that has passed through the superchargers 11a and 11b is discharged into the atmosphere through a catalyst device, a silencer, etc. (not shown) after particulates mainly composed of carbon are removed in the DPF devices 12a and 12b. Is done.

In order to reduce the generation of harmful nitrogen oxides due to explosion / combustion in the combustion chamber, not all exhaust gas is discharged into the atmosphere through such a path, the EGR devices 8a and 8b A part of the exhaust gas is circulated to the intake manifolds 2a and 2b. The amount of exhaust gas (EGR gas) to be circulated is adjusted by the opening degree of the EGR valves 7a and 7b.
Further, when particulates in the exhaust gas are captured by the DPF devices 12a and 12b, the differential pressure between the DPF devices 12a and 12b eventually increases. When this differential pressure is detected, fuel as a reducing agent is added from the injectors 5a and 5b, and the captured particulates are burned by applying heat to the DPF devices 12a and 12b.

  Here, if fuel is injected from the injectors 5a and 5b while a part of the exhaust gas is circulated through the intake manifolds 2a and 2b by the EGR devices 8a and 8b, the fuel flows along with the flow of EGR gas. May wrap around the intake manifolds 2a and 2b. This is because when the two EGR valves 7a and 7b are opened, the two intake manifolds 2a and 2b communicate with each other through the EGR passages 6a and 6b. In particular, when a large amount of EGR gas is circulated through the intake manifolds 2a and 2b, there is a variation in the operating state of the two superchargers 11a and 11b, for example, a variation in the amount of air flowing through the superchargers 11a and 11b. Exhaust pulsation occurs, and thus fuel passes through the EGR passages 6a and 6b and flows into the intake manifolds 2a and 2b.

Therefore, the following control can suppress the added fuel from entering the intake manifolds 2a and 2b as much as possible. This control will be described based on the flowchart of FIG.
When the internal combustion engine 1 is started, the control device 18 determines whether or not fuel is being added from the injectors 5a and 5b (step S1). When the fuel is not added, the fuel does not flow into the intake manifolds 2a and 2b, so this control is not performed. On the other hand, when the fuel is added, the control device 18 determines the open / closed state of the EGR valves 7a and 7b (step S2). When the EGR valves 7a and 7b are closed, the added fuel does not flow into the intake manifolds 2a and 2b through the EGR passages 6a and 6b, so the process returns to step S1. On the other hand, when the EGR valves 7a and 7b are open, the control device 18 calculates the difference in the air amount detected by each of the air flow meters 15a and 15b (hereinafter referred to as a calculated value), and the control device 18 Is compared with a predetermined value for the difference in the amount of air flowing into the superchargers 11a and 11b set in advance (step S3). If the calculated value is smaller than the specified value, it is determined that the variation in the operating state of the superchargers 11a and 11b is small, and the process returns to step S1. On the other hand, when the calculated value is equal to or greater than the specified value, it is determined that the variation in the operating state of the superchargers 11a and 11b is large, so that the fuel does not flow into the intake manifolds 2a and 2b due to exhaust pulsation. The control device 18 forcibly closes the EGR valves 7a and 7b (step S4). As a result, the exhaust manifold 3a and the EGR valve 7a and the exhaust manifold 3b and the EGR valve 7b are independent from each other.

  In subsequent step S5, the control device 18 determines whether or not fuel is being added from the injectors 5a and 5b. If fuel is being added, the EGR valves 7a and 7b are kept closed (step S4). On the other hand, when the addition of fuel is not performed, the control device 18 measures the elapsed time from the end of the fuel addition (step S6). In subsequent step S7, the control device 18 calculates the discharge time of the fuel remaining in the exhaust manifolds 3a and 3b. The fuel release time is the time required for the rotation cycle based on the number of rotation cycles preset in the internal combustion engine 1. However, the number of rotation cycles may always be constant, or the discharge time may be determined by calculation immediately before the control of this embodiment is performed each time or until step S6. Moreover, you may fix in the fixed time between 0.1-0.5 second irrespective of the rotation cycle number. Next, the control device 18 compares the elapsed time from the end of fuel addition with the fuel release time (step S8), and returns to step S6 if the fuel release time is longer. On the other hand, when the elapsed time from the end of fuel addition is longer, the control device 18 opens the EGR valves 7a and 7b (step S9), and the EGR valve opening degree is adjusted by the EGR devices 8a and 8b. become.

As described above, when the air flow meters 15a and 15b for measuring the amount of air flowing into the superchargers 11a and 11b are provided, and the difference between the air amounts detected by the air flow meters 15a and 15b is larger than a specified value, the control device 18 forcibly closes the EGR valves 7a and 7b, so that the added fuel can be prevented from flowing into the intake manifolds 2a and 2b through the EGR passages 6a and 6b due to exhaust pulsation as much as possible. Therefore, sticking of the EGR valves 7a and 7b, clogging in the EGR cooler 9, and torque fluctuation of the internal combustion engine 1 caused by the added fuel passing through the EGR passages 6a and 6b and entering the intake manifolds 2a and 2b. Can be prevented.
Further, by closing the EGR valves 7a and 7b, no back flow occurs between the two banks, so that it is possible to prevent the air-fuel ratio of the exhaust gas entering the DPF devices 12a and 12b from becoming unknown.

Embodiment 2. FIG.
Next, an exhaust gas purification apparatus for an internal combustion engine according to Embodiment 2 of the present invention will be described with reference to FIG. In the following embodiments, the same reference numerals as those in FIG. 1 are the same or similar components, and detailed description thereof will be omitted.
The exhaust gas purification apparatus for an internal combustion engine according to the second embodiment is different from the first embodiment in that the internal combustion engine 1 that is a V-type 6-cylinder diesel engine is changed to an internal combustion engine 20 that is an in-line 6-cylinder diesel engine. is there.
As shown in FIG. 3, among the six cylinders, an intake manifold 2a and an exhaust manifold 3a are connected to the left three cylinders 4a1 to 4a3 to an intake port and an exhaust port (not shown) of each cylinder, and the right three The configuration is the same as that of the first embodiment except that the intake manifold 2b and the exhaust manifold 3b are connected to the cylinders 4b1 to 4b3 to an intake port and an exhaust port (not shown) of each cylinder.
As described above, even in an in-line cylinder engine having a split manifold, when the difference in air amount detected by the air flow meters 15a and 15b is larger than a specified value, the control device 18 sets the EGR valves 7a and 7b. By forcibly closing, the same effect as in the first embodiment can be obtained.

Embodiment 3 FIG.
The exhaust gas purification apparatus for an internal combustion engine according to the third embodiment is different from the first embodiment in that the internal combustion engine 1 that is a V-type six-cylinder diesel engine is changed to an internal combustion engine 30 that is an in-line four-cylinder diesel engine. is there.
As shown in FIG. 4, one intake manifold 31 is connected to an intake port (not shown) of each of the four cylinders 30a, 30b, 30c, 30d. Of the four cylinders, an exhaust manifold 32a is connected to an exhaust port (not shown) of each of the two cylinders 30a and 30d, and an exhaust manifold 32b is connected to an exhaust port (not shown) of each of the other two cylinders 30b and 30c. Is connected. The exhaust manifold 32a includes branch pipes 32a1 and 32a2 that are connected to exhaust ports (not shown) of the cylinders 30a and 30d. The exhaust manifold 32b is a branch pipe 32b1 that is connected to exhaust ports (not shown) of the cylinders 30b and 30c. 32b2.
In addition, injectors 33a and 33b for adding fuel as a reducing agent are provided in cylinder heads (not shown) of the cylinders 30c and 30d. The two EGR passages 6a and 6b are connected to the branch pipes 32a1 and 32b1, respectively.
Other parts are the same as those in the first embodiment.
Thus, in the case of an internal combustion engine having a split exhaust manifold, when the difference in the air amount detected by the air flow meters 15a and 15b is larger than a specified value, the control device 18 switches the EGR valves 7a and 7b. By forcibly closing, the same effect as in the first embodiment can be obtained.

In the first to third embodiments, the present invention has been described by taking a diesel engine as an example. However, the present invention is not limited to a diesel engine, and may be a gasoline engine.
Moreover, although the air flow meters 15a and 15b which measure the air quantity which flows into a supercharger were used as an operation state detection means of the superchargers 11a and 11b, it is not limited to this. A pressure gauge may be provided downstream of the superchargers 11a and 11b, and the operating state of the superchargers 11a and 11b may be determined from the pressure of the air discharged from the superchargers 11a and 11b. Alternatively, a pressure gauge that measures the pressure or differential pressure at the inlet and / or outlet of the DPF devices 12a and 12b may be provided, and the operating state of the superchargers 11a and 11b may be determined from these detected values.

1 is a configuration diagram of an exhaust gas purification apparatus for an internal combustion engine according to Embodiment 1 of the present invention. 3 is a flowchart showing control of the exhaust gas purification apparatus for an internal combustion engine according to the first embodiment. FIG. 3 is a configuration diagram of an exhaust gas purification apparatus for an internal combustion engine according to a second embodiment. FIG. 6 is a configuration diagram of an exhaust emission control device for an internal combustion engine according to a third embodiment.

Explanation of symbols

  1, 20, 30 Internal combustion engine, 3a, 3b, 32a, 32b Exhaust manifold, 4a1, 4a2, 4a3, 4b1, 4b2, 4b3, 30a, 30b, 30c, 30d Cylinder, 5a, 5b, 33a, 33b Injector (reducing agent Addition means), 7a, 7b EGR valve, 8a, 8b EGR device, 11a, 11b supercharger, 15a, 15b air flow meter (operating state detection means), 18 control device.

Claims (3)

In an internal combustion engine having a split exhaust manifold connected to one cylinder group and the other cylinder group,
Reducing agent addition means for supplying a reducing agent to the exhaust gas discharged from the internal combustion engine;
An EGR device equipped with an EGR valve;
A supercharger provided downstream of each of the split exhaust manifolds;
An operating state detecting means for detecting each operating state of the supercharger;
A detection value representing the operating state of the corresponding supercharger detected by one of the operating state detecting means, and a detection value representing the operating state of the corresponding supercharger detected by the other operating state detecting means And an exhaust gas purifying apparatus for an internal combustion engine comprising a control means for closing each of the EGR valves when the difference between the two is greater than a preset specified value. After the EGR valve is closed,
The controller is
Elapsed time measured from the end of addition of the reducing agent,
Compare the release time required to release the reducing agent remaining in the split exhaust manifold,
2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein when the elapsed time exceeds the release time, the control device opens each of the EGR valves.   The exhaust emission control device for an internal combustion engine according to claim 2, wherein the release time is a time required for a predetermined number of rotation cycles of the internal combustion engine.

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