JP5823842B2 - Exhaust gas recirculation device for multi-cylinder internal combustion engine with turbocharger - Google Patents

Description

  The present invention relates to an exhaust gas recirculation device for recirculating exhaust gas to an intake side in a multi-cylinder internal combustion engine with a turbocharger.

  Conventionally, as an exhaust gas recirculation device that recirculates a part of engine exhaust gas to the intake system, an exhaust pipe downstream of a turbocharger turbine and an exhaust purification device (DPF, oxidation catalyst, etc.) and an upstream side of a turbocharger compressor There is an apparatus that provides an exhaust gas recirculation pipe connected to the intake pipe and adjusts the amount of exhaust gas to be recirculated by an adjustment valve provided in the exhaust gas recirculation pipe (see, for example, Patent Document 1).

JP 2011-069305 A

By the way, in an internal combustion engine with a turbocharger, when exhaust gas is recirculated to the intake pipe downstream of the compressor, a high load region where the boost pressure is high, or a low load region where both the boost pressure and the back pressure are low. Then, the differential pressure between the exhaust side and the intake side becomes small, and it becomes difficult to recirculate exhaust gas in large quantities.
Here, if the intake side and / or exhaust side pipes are throttled to increase the differential pressure, the pumping loss increases and the fuel efficiency of the engine deteriorates.

  On the other hand, when the exhaust gas recirculation pipe connects the exhaust pipe downstream of the turbine and the exhaust gas purification device and the intake pipe upstream of the compressor as in Patent Document 1, the exhaust gas is recirculated even at a high load. Although it is possible, the piping of the exhaust gas recirculation pipe is long and the handling becomes complicated, and the responsiveness of the exhaust gas recirculation amount control deteriorates.

  Further, when the exhaust gas recirculation pipe connects the exhaust pipe upstream of the exhaust gas purification device and the upstream side of the compressor, the exhaust gas recirculation pipe becomes relatively short. However, when such an exhaust recirculation pipe is used, the recirculation exhaust includes not only soot (black smoke) but also fuel and lubricating oil discharged without being burned. For this reason, these exhaust components cause the compressor to become dirty or the corrosion of the compressor to proceed.

  Therefore, in view of the above-described problems of the prior art, the present invention provides a multi-cylinder internal combustion engine with a turbocharger that can perform a large amount of exhaust gas recirculation with high responsiveness while suppressing deterioration in fuel efficiency, compressor fouling, and corrosion. An object is to provide a reflux apparatus.

For this reason, the exhaust gas recirculation apparatus for a multi-cylinder internal combustion engine with a turbocharger according to the present invention separates the exhaust gas of some exhaust gas recirculation dedicated cylinders from the exhaust gases of cylinders other than the exhaust gas recirculation dedicated cylinder. An exhaust gas recirculation pipe that recirculates to an intake pipe upstream of the compressor of the turbocharger, an exhaust pipe downstream of a turbine of the turbocharger into which exhaust from a cylinder other than the exhaust recirculation dedicated cylinder flows, and the exhaust gas recirculation A communication pipe that connects the pipe and exhausts exhaust from the exhaust recirculation dedicated cylinder by bypassing the turbine of the turbocharger, a first valve provided in the exhaust recirculation pipe, and a second valve provided in the communication pipe And an exhaust component reducing means for reducing a predetermined component in the exhaust gas recirculated to the intake pipe through the exhaust gas recirculation pipe, as compared with exhaust of a cylinder other than the exhaust recirculation dedicated cylinder , It was to prepare for the.

According to the present invention, the exhaust gas of the exhaust gas recirculation dedicated cylinder is recirculated to the intake pipe upstream of the compressor, so that a large amount of exhaust gas recirculation is possible without being affected by the operating region (supercharging pressure) without providing a throttle. In addition, since the predetermined component in the recirculated exhaust gas is reduced, the compressor can be prevented from being contaminated and corroded by the predetermined component contained in the recirculated exhaust gas, and further, the exhaust purification device disposed downstream of the turbine or downstream of the turbine. Compared with the case where exhaust gas is taken out from the downstream side, the overall length of the exhaust gas recirculation pipe line can be shortened, the piping can be simplified, and the exhaust gas recirculation amount can be controlled with sufficient responsiveness.
Further, the pressure on the downstream side of the turbine is lower than that on the upstream side, and the communication pipe is connected to the downstream side of the turbine. Therefore, when the second valve is opened, exhaust is performed from the exhaust pipe side to the first valve side. Can be prevented from flowing back.

Schematic which shows the diesel engine provided with a double compressor in embodiment of this invention. Schematic showing a diesel engine with a single compressor in an embodiment of the invention

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a diesel engine for a vehicle (multi-cylinder internal combustion engine with a turbocharger) to which an exhaust gas recirculation apparatus according to the present invention is applied.
An exhaust gas recirculation device is a device that lowers the combustion temperature by mixing a part of exhaust gas into fresh air, thereby reducing NOx emission from the engine.

In the diesel engine 10 that is a multi-cylinder (four cylinders as an example), the exhaust manifold 11 includes a sub-exhaust manifold 11A that guides the exhaust of the first cylinder # 1, and cylinders other than the first cylinder # 1 (second cylinders # 2 to # 2). The main exhaust manifold 11B that collects the exhaust of the fourth cylinder # 4) is divided.
The sub exhaust manifold 11A and the main exhaust manifold 11B can be configured as separate parts or can be formed as an integral part.

Further, when the diesel engine 10 has, for example, six cylinders, the sub exhaust manifold 11A can collect the exhaust of two cylinders, and the main exhaust manifold 11B can collect the exhaust of other four cylinders.
That is, the number of cylinders of the diesel engine 10 and the number of cylinders in which the exhaust manifolds 11A and 11B collect exhaust are not limited to the settings shown in FIG.

An exhaust pipe 12 is connected to the collector of the main exhaust manifold 11B for discharging the exhaust into the atmosphere.
The exhaust pipe 12 is provided with a turbine 13A of the turbocharger 13 and an exhaust purification device 14 in order from the upstream side, and exhausts from cylinders other than the first cylinder # 1 (second cylinder # 2 to fourth cylinder # 4). Is discharged into the atmosphere after passing through the exhaust turbine 13A and the exhaust purification device 14.

The exhaust purification device 14 is a device that purifies particulate matter (solid component, liquid component) such as soot and gas components such as NOx contained in the exhaust gas, and includes a filter, various catalyst devices, and the like. .
As an example, the exhaust purification device 14 includes a continuous regeneration type DPF device, a reducing agent injection device, a NOx reduction catalyst, an oxidation catalyst, and the like.

The continuous regeneration type DPF device captures and removes particulate matter (Particulate Matter) in the exhaust gas. By placing an oxidation catalyst in front of the DPF (Diesel Particulate Filter), the continuous regeneration temperature of the DPF is increased. I try to lower it.
The reducing agent injection device is a device that injects a reducing agent (for example, ammonia) or a precursor thereof (for example, an aqueous urea solution) into the exhaust gas, and the NOx reduction catalyst uses the reducing agent to reduce NOx in the exhaust gas and oxidizes it. The catalyst oxidizes the reducing agent that has passed through the NOx reduction catalyst.

As an exhaust purification filter, a CSF (Catalyzed Soot Filter) having a catalyst (active component and additive component) supported on the filter surface can be used instead of the DPF.
On the other hand, one end of an EGR pipe (exhaust recirculation pipe) 15 is connected to the collector of the sub exhaust manifold 11A, and the exhaust of the first cylinder # 1 is recirculated to the intake side via the EGR pipe 15.
That is, the exhaust of the cylinders other than the first cylinder # 1 is not recirculated to the intake side, but the exhaust of the first cylinder # 1 is recirculated to the intake side via the EGR pipe 15 independently of the exhaust of other cylinders. The first cylinder # 1 is an exhaust recirculation dedicated cylinder.

In other words, the exhaust of the first cylinder # 1 is recirculated to the intake side as a part of the exhaust of all the cylinders.
When the sub exhaust manifold 11A and the main exhaust manifold 11B are integrally formed, the collector portion is introduced with the sub collector into which the exhaust of the first cylinder # 1 is introduced and the exhaust of other cylinders. The main collector is partitioned, the EGR pipe 15 is connected to the sub-collector, and the exhaust pipe 12 is connected to the main collector.

In addition, the intake manifold 16 of the diesel engine 10 includes a sub intake manifold 16A that guides air to the first cylinder # 1, which is a dedicated exhaust gas recirculation cylinder, and cylinders other than the first cylinder # 1 (second cylinder # 2 to fourth cylinder). It is divided into a main intake manifold 16B for distributing air to # 4).
The sub intake manifold 16A and the main intake manifold 16B can be configured as separate parts or can be formed as an integral part.

A sub intake pipe 17A is connected to the collector of the sub intake manifold 16A, and a main intake pipe 17B is connected to the collector of the main intake manifold 16B.
The sub-intake pipe 17A is provided with a sub-compressor 13B1 that is supported by the rotating shaft 13C of the turbine 13A and is driven to rotate by the turbine 13A. The main intake pipe 17B is supported by the rotating shaft 13C of the turbine 13A and is driven by the turbine 13A. A main compressor 13B2 that is driven to rotate is provided.
That is, the main compressor 13B2 and the sub compressor 13B1 are two series of compressors supported coaxially.

As a result, the air compressed by the sub-compressor 13B1 is sent to the first cylinder # 1, and the main compressor 13B2 supplies the other cylinders (second cylinder # 2 to fourth cylinder # 4). Compressed air is sent in.
An intercooler 18 for cooling the intake air compressed by the main compressor 13B2 is provided in the main intake pipe 17B on the downstream side of the main compressor 13B2.

The sub intake pipe 17A and the main intake pipe 17B are connected to the intake pipe 19 on the upstream side of the compressors 13B1 and 13B2, and the air introduced from the outside by the intake pipe 19 branches to the sub intake pipe 17A and the main intake pipe 17B. And then distributed to each cylinder via the intake manifolds 16A and 16B.
The other end of the EGR pipe 15 having one end connected to the sub exhaust manifold 11A is connected to the upstream side of the main compressor 13B2 of the main intake pipe 17B.

That is, the exhaust of the first cylinder # 1 that is the exhaust recirculation dedicated cylinder is separated and independent from the exhaust of the other cylinders, and is recirculated to the main intake pipe 17B upstream of the main compressor 13B2 of the turbocharger 13.
Thus, the exhaust of the first cylinder # 1 is recirculated to the intake side of the second cylinder # 2 to the fourth cylinder # 4 other than the first cylinder # 1, and the second cylinder # 2 to the fourth cylinder # 4 are The mixed gas of the recirculated exhaust gas and air is sucked, but the exhaust gas is not recirculated to the intake side of the first cylinder # 1, and the first cylinder # 1 sucks air not mixed with the exhaust gas.

In the EGR pipe 15, a DOC (Diesel Oxidation Catalyst) 20, an EGR cooler 21, and an EGR valve (first valve) 22 that are oxidation catalysts are provided in order from the upstream side.
The DOC 20 is a catalyst device that oxidizes and purifies components such as fuel that is discharged from the first cylinder # 1 as unburned, and an exhaust purification device that reduces unburned components in the recirculated exhaust gas by post-processing (exhaust component reduction). Means).

By providing the DOC 20, the unburned component contained in the exhaust gas recirculated to the intake side is reduced more than the unburned component discharged from the first cylinder # 1 and the other cylinders.
The EGR cooler 21 cools the exhaust gas recirculated to the intake side, thereby increasing the density of the recirculated exhaust gas so that a large amount of exhaust gas can be recirculated, and lowering the temperature of the air after the recirculated exhaust gas merges. A larger NOx reduction rate is obtained.

The EGR valve 22 is a valve that makes the opening area of the EGR pipe 15 variable, and the exhaust gas recirculation amount is adjusted by adjusting the opening degree of the EGR valve 22. As the EGR valve 22, for example, an electromagnetic valve is used.
Further, a communication pipe 23 for connecting the EGR pipe 15 between the EGR cooler 21 and the EGR valve 22 and the exhaust pipe 12 between the turbine 13A and the exhaust purification device 14 is provided. A relief valve (second valve) 24 is provided.

The relief valve 24 allows excess exhaust when the opening of the EGR valve 22 is throttled, that is, exhaust that is not recirculated to the intake side out of the exhaust of the first cylinder # 1 to the exhaust pipe 12 to be discharged outside. It is a valve. For example, an electromagnetic valve is used as the relief valve 24.
In addition, an injector 25 for injecting fuel into the combustion chamber of each cylinder is provided.

For example, the injector 25 constitutes a fuel injection device together with a supply pump, a pressure accumulating chamber, and the like (not shown), and injects high pressure fuel supplied from a pressure accumulating chamber (common rail) that stores high pressure fuel generated by the supply pump.
The injector 25 is composed of, for example, a solenoid coil, a needle valve, and the like, and the injection timing and the fuel injection amount are controlled by controlling on / off of the solenoid coil by an external electric signal. However, the fuel injection device is not limited to a so-called common rail type.

As described above, the exhaust gas recirculation device (EGR device) 30 in the diesel engine 10 includes the sub exhaust manifold 11A, the EGR pipe (exhaust gas recirculation pipe) 15, the DOC (oxidation catalyst) 20, the EGR cooler 21, the EGR valve 22, and the communication pipe. 23, a relief valve 24, and the like.
An engine control unit (ECU) 26 having a built-in computer inputs output signals of various sensors such as a rotational speed sensor 27 that detects the rotational speed NE of the diesel engine 10 and a load sensor 28 that detects the load Q of the diesel engine 10. .

Here, the load sensor 28 detects a state quantity closely related to the torque of the diesel engine 10 such as an intake air flow rate, an intake pressure, a supercharging pressure, and an accelerator opening degree as a state quantity indicating the load Q of the diesel engine 10. .
The engine control unit 25 controls the operation of the diesel engine 10 by executing a control program stored in a nonvolatile memory such as a built-in ROM (Read Only Memory).

Specifically, the engine control unit 25, based on signals from various sensors, injects fuel into the combustion chamber (injection timing, injection amount), injects reducing agent into the exhaust, and exhaust gas recirculation amount (exhaust gas recirculation rate). Then, an operation signal such as the opening of the variable nozzle in the turbocharger 13 is calculated and output.
Here, in the control of the exhaust gas recirculation amount, the engine control unit 26 sets a target of the exhaust gas recirculation amount (recirculation rate) from the engine operating conditions (for example, the engine speed NE, the engine load Q, etc.), and sets the target value. Based on this, the opening degree of the EGR valve 22 and the relief valve 24 is controlled.

For example, when stopping the exhaust gas recirculation, if the EGR valve 22 is closed while the relief valve 24 is opened, the exhaust of the first cylinder # 1 is not recirculated to the main intake pipe 17B, and the communication pipe 23 is recirculated. Through the exhaust pipe 12 and purified by the exhaust purification device (exhaust aftertreatment device) 14 together with the exhaust of the other cylinders and released into the atmosphere.
Here, since the pressure on the downstream side of the turbine 13A is lower than that on the upstream side and the communication pipe 23 is connected to the downstream side of the turbine 13A, when the relief valve 24 is opened, the EGR valve is opened from the exhaust pipe 12 side. Exhaust gas does not flow backward toward the 22 side.

On the other hand, when the EGR valve 22 is opened, the pressure in the main intake pipe 17B upstream of the main compressor 13B2 is atmospheric pressure or negative pressure, whereas the pressure in the sub exhaust manifold 11A is positive pressure. 1 exhaust passes through the EGR valve 22 and flows into the main intake pipe 17B, and fresh air mixed with the exhaust is distributed to the second cylinder # 2 to the fourth cylinder # 4.
Here, the engine control unit 26 adjusts the exhaust gas recirculation amount (exhaust gas recirculation rate) by increasing the opening degree of the relief valve 24 as the opening degree of the EGR valve 22 decreases, and the main intake pipe. Exhaust gas that is not recirculated into 17B is released to the exhaust pipe 12 via the communication pipe 23, and the back pressure of the first cylinder # 1 is prevented from becoming excessively high when the exhaust gas recirculation amount is reduced.

As described above, if the exhaust gas is recirculated into the main intake pipe 17B on the upstream side of the main compressor 13B2, it is not affected by the supercharging pressure change by the main compressor 13B2 (in other words, the engine operating condition). Large amount of exhaust gas recirculation can be performed.
That is, when the exhaust gas is recirculated downstream of the main compressor 13B2, the differential pressure between the exhaust side and the intake side is reduced by increasing the intake pressure due to supercharging, and particularly when high supercharging is performed. The pressure on the intake side may be higher than that on the exhaust side, and exhaust gas recirculation cannot be performed in a high load range.

On the other hand, when the exhaust gas is recirculated to the upstream side of the main compressor 13B2, even if high supercharging is performed, the pressure on the exhaust side can be maintained higher than that on the intake side. The exhaust gas recirculation in a high load range is possible without providing a throttle in the pipe, that is, without increasing the pumping loss by the throttle.
Further, since the first cylinder # 1 is a dedicated exhaust gas recirculation cylinder, the exhaust of the first cylinder # 1 is separated and independent from the exhaust of the other cylinders, and the entire amount of the exhaust of the first cylinder # 1 is introduced into the EGR pipe 15. During a low load when the pressure difference between the intake and exhaust sides becomes small, the exhaust of the first cylinder # 1 is forcibly guided to the EGR valve 22 to perform a large amount of exhaust gas recirculation.

Further, since the EGR pipe 15 of the exhaust gas recirculation device 30 is provided with a DOC (oxidation catalyst) 20, unburned components such as fuel discharged from the first cylinder # 1 without being burned are oxidized by the DOC 20. Thus, the unburned component contained in the exhaust gas recirculated to the main intake pipe 17B is reduced as compared with the exhaust amount from the first cylinder # 1.
Therefore, it is possible to suppress the main compressor 13B2 from being contaminated and corroded by unburned components contained in the recirculated exhaust gas.

However, the soot contained in the exhaust of the first cylinder # 1 passes through the DOC (oxidation catalyst) 20 and is returned to the main intake pipe 17B on the upstream side of the main compressor 13B2. The compressor 13B2 will be soiled.
Therefore, the concentration of soot (particulate component) discharged from the first cylinder # 1 is made lower than the concentration of soot discharged from the other cylinders, and soot (particulate component) contained in the recirculated exhaust gas is reduced. Combustion control is performed to reduce the main compressor 13B2 from being contaminated with soot contained in the recirculated exhaust gas.

That is, the unburned components contained in the exhaust gas recirculated to the main intake pipe 17B and the exhaust gas recirculated to the main intake pipe 17B as compared with the case where the exhaust gas of the second cylinder # 2 to the fourth cylinder # 4 is recirculated as it is by post-processing by the DOC 20 and combustion control The soot component is reduced, and the main compressor 13B2 is prevented from being damaged and corroded.
As the combustion control, by setting the air-fuel ratio of the first cylinder # 1 to be leaner than the air-fuel ratio of the other cylinders, the concentration of soot (particulate component) discharged from the first cylinder # 1 is changed from the other cylinders. Lower than the concentration of soot discharged.

In general, soot is known to be produced at a high equivalent ratio and in a specific temperature range, so that the generation of soot can be suppressed by making the air-fuel ratio lean (low equivalent ratio). it can.
In the diesel engine 10 described above, the exhaust gas is not recirculated with respect to the intake air of the first cylinder # 1, whereas the exhaust gas is recirculated with respect to the intake air of the other cylinders. Even if the total amount of fresh air and recirculated exhaust gas is the same, the amount of fresh air sucked into the first cylinder # 1 is larger than that of the other cylinders.

For this reason, even if the same amount of fuel is injected into each cylinder, the air-fuel ratio of the first cylinder # 1 becomes lean (low equivalence ratio) compared to the other cylinders, and thereby the first cylinder # 1 discharges. The amount of soot can be reduced compared to other cylinders.
That is, in the diesel engine 10 described above, the air-fuel ratio of the first cylinder # 1 and the air-fuel ratio of the other cylinders are made different depending on the presence or absence of exhaust gas recirculation. Is not recirculated, the air-fuel ratio of the first cylinder # 1 is made leaner than that of the other cylinders, and the soot discharged from the first cylinder # 1 is reduced as compared with the other cylinders, so that the soot contained in the recirculated exhaust gas is reduced. Is reduced.

Accordingly, the intake manifold 16 is divided into the sub intake manifold 16A and the main intake manifold 16B, and the exhaust structure is recirculated to the main intake pipe 17B connected to the main intake manifold 16B. However, as means for reducing soot that is exhaust gas recirculated to the intake side (exhaust component reducing means, combustion control means), the amount of soot discharged from the first cylinder # 1 is reduced as compared to other cylinders. Will work.
In other words, while the exhaust gas is recirculated to the upstream side of the compressor, the first cylinder # 1 does not suck the fresh air mixed with the recirculated exhaust gas, so that the fresh air mixed with the recirculated exhaust gas is sucked. In order to make the air-fuel ratio of the first cylinder # 1 lean, an intake system including a compressor, an intake pipe, and an intake manifold is divided into two for the first cylinder # 1 and for the second cylinder # 2 to the fourth cylinder # 4. A system is provided, and exhaust gas is recirculated to the upstream side of the main compressor 13B2 constituting the intake system for the second cylinder # 2 to the fourth cylinder # 4.

As described above, the air-fuel ratio of the first cylinder # 1 is set to be leaner than that of the other cylinders depending on the presence or absence of exhaust gas recirculation, and the fuel injection amount of the first cylinder # 1 is further set to the fuel injection amount of the other cylinders. As a result, the air-fuel ratio (lean level) in the first cylinder # 1 can be controlled.
Further, in the exhaust gas recirculation device 30 shown in FIG. 1, the pipe length of the EGR pipe 15 is made shorter than in the case where the exhaust gas recirculated to the intake side is taken out from the exhaust pipe 12 downstream of the exhaust gas purification device 14. The piping can be simplified.

Therefore, the exhaust gas recirculation amount can be changed with good response to changes in the opening degree of the EGR valve 22, and the actual EGR rate can be followed with good response to changes in the target EGR rate accompanying changes in engine operating conditions. It is possible to suppress a transient excess or deficiency in the exhaust gas recirculation amount.
The EGR pipe 15 is provided with a DPF as an exhaust purification device, and soot contained in the exhaust of the first cylinder # 1 is collected by the DPF, so that soot as a component contained in the exhaust gas recirculated to the intake side is obtained. Can be reduced.

However, since soot gradually accumulates in the DPF, regeneration processing is necessary, and high-temperature exhaust gas is recirculated to the intake side along with the regeneration processing, and by providing the DGR of the EGR pipe 15, The EGR pipe 15 becomes long or the handling of the EGR pipe 15 becomes complicated.
Therefore, as a means (exhaust component reducing means) for reducing soot (particulate component) contained in the recirculated exhaust gas, it is discharged from the first cylinder # 1, which is an exhaust recirculation dedicated cylinder, instead of post-processing means such as DPF. It is preferable to use means for reducing soot (combustion control means).

FIG. 2 shows an example in which the exhaust of the first cylinder # 1 is recirculated to all of the first cylinder # 1 to the fourth cylinder # 4. In FIG. 2, the same elements as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.
In the diesel engine 31 shown in FIG. 2, as in the diesel engine 10 shown in FIG. 1, the exhaust manifold 11 has a sub exhaust manifold 11A that guides the exhaust of the first cylinder # 1, and cylinders other than the first cylinder # 1. The main exhaust manifold 11B that collects the exhaust of (second cylinder # 2 to fourth cylinder # 4) is divided.

An exhaust pipe 12 is connected to the collector of the main exhaust manifold 11B, and one end of an EGR pipe (exhaust gas recirculation pipe) 15 is connected to the collector of the sub exhaust manifold 11A.
On the other hand, in the diesel engine 31 shown in FIG. 2, the intake manifold 32 is formed so as to distribute air to all the cylinders, and an intake pipe 33 provided with the intercooler 18 and the compressor 13B is connected to the collector of the intake manifold 32. The

An EGR pipe (exhaust gas recirculation pipe) 15 is connected to the intake pipe 33 upstream of the compressor 13B. Then, the air mixed with the recirculated exhaust gas is compressed by the compressor 13B, then cooled by the intercooler 18, and distributed to all the cylinders.
In the diesel engine 31, air in which recirculated exhaust gas is mixed is sucked into all cylinders, and the amount of fresh air sucked by each cylinder is substantially the same. When substantially the same amount of fuel is injected into each cylinder, the air-fuel ratio of each cylinder Are substantially the same, and soot contained in the exhaust of the first cylinder # 1 is not reduced more than soot contained in the exhaust of the cylinders other than the first cylinder # 1.

  Therefore, the engine control unit 25 controls the fuel injection amount for the first cylinder # 1, which is a dedicated exhaust gas recirculation cylinder, in the other cylinders (second cylinder # 2 to fourth cylinder # 4) in the control of the fuel injection amount by the injector 25. The air-fuel ratio of the first cylinder # 1 is made leaner than that of the other cylinders by reducing the fuel injection amount relative to the fuel injection amount, thereby reducing the amount of soot discharged from the first cylinder # 1 as compared to the other cylinders. be able to.

In addition, soot discharge exhibits a maximum value at a certain air-fuel ratio, and soot discharge may decrease on both the rich side and the lean side from the air-fuel ratio at which soot discharge becomes maximum. By making the fuel injection amount for cylinder # 1 larger than for the other cylinders and making the air-fuel ratio of the first cylinder # 1 richer than for the other cylinders, soot discharged from the first cylinder # 1 can be larger than that for the other cylinders In some cases, it can be reduced.
Note that, by setting the fuel injection amount to the first cylinder # 1 to be leaner or richer than that of the multi-cylinder, a difference between the generated torque of the first cylinder # 1 and the generated torque of the other cylinders occurs. Therefore, the air-fuel ratio of the first cylinder # 1 is controlled so that the deterioration of the operation stability due to the difference in generated torque between the cylinders can be suppressed and the fouling of the compressor 13B due to soot can be suppressed.

As another means for reducing the amount of soot discharged from the first cylinder # 1 as compared with other cylinders, for example, in the first cylinder # 1 which is a dedicated exhaust gas recirculation cylinder, a small amount of fuel is injected immediately after the end of the main injection. (After-injection), by burning, the inside of the cylinder is disturbed, so that the known combustion control capable of reducing soot such as reducing the amount of soot discharged from the first cylinder # 1 can be adopted as appropriate. A plurality of controls can be implemented in combination.
By the fuel injection control as described above, the soot discharged from the first cylinder # 1 is reduced from the soot discharged from the other cylinders, and the amount of soot contained in the exhaust gas recirculated upstream of the compressor 13B is reduced. It is possible to prevent the compressor 13B from being soiled with the soot.

Accordingly, in this case, the fuel injection control function for the first cylinder # 1 by the engine control unit 25 corresponds to means for reducing soot that is an exhaust component recirculated to the intake side (exhaust component reducing means, combustion control means). It will be.
Further, unburned fuel or the like discharged from the first cylinder # 1 is oxidized by a DOC (oxidation catalyst) 20 as an exhaust purification device provided in the EGR pipe 15 as in the diesel engine 10 shown in FIG. Therefore, the amount of unburned fuel contained in the exhaust gas recirculated to the upstream side of the compressor 13B is reduced, and the compressor 13B is prevented from corroding with unburned fuel or lubricating oil.

In addition, if the diesel engine 31 is an engine that performs combustion with a sufficiently small amount of soot discharged by, for example, premixed compression ignition or the like, in order to reduce soot discharge from the first cylinder # 1 as compared with other cylinders. Combustion control (fuel injection control) is not performed, and the unburned components discharged from the first cylinder # 1 are post-processed by the DOC (oxidation catalyst) 20 of the EGR pipe 15 so that the compressor 13B is sufficiently fouled and corroded. Can be suppressed.
Further, in the diesel engine 31, the exhaust of the first cylinder # 1, which is a dedicated exhaust gas recirculation cylinder, is recirculated into the intake pipe 33 upstream of the compressor 13B, so that it is affected by a change in the supercharging pressure by the compressor 13B. There is no (in other words, not greatly influenced by engine operating conditions), and a large amount of exhaust gas recirculation can be performed.

  Further, since the diesel engine 31 shown in FIG. 2 includes one compressor 13B and one intake pipe 33 that guides the air compressed by the compressor 13B to each cylinder, the diesel engine 31 is compared with the diesel engine 10 shown in FIG. The structure of the intake system is simplified, and the engine can be reduced in size and cost.

Although the contents of the present invention have been specifically described with reference to the preferred embodiments, it is obvious that those skilled in the art can take various modifications based on the basic technical idea and teachings of the present invention. It is.
For example, as means for reducing the amount of soot discharged from the exhaust recirculation dedicated cylinder (exhaust component reducing means, combustion control means), a fuel dedicated to the exhaust recirculation dedicated cylinder instead of or together with the air fuel ratio control Or a device for reducing soot in the combustion chamber of the exhaust recirculation dedicated cylinder.

  Specifically, while supplying light oil to the other cylinders, for the exhaust gas recirculation dedicated cylinder, emulsion fuel mixed with light oil and water, biodiesel fuel 100%, biodiesel fuel and light oil mixed By supplying fuel or the like, soot discharged from the first cylinder # 1 can be reduced more than soot discharged from other cylinders.

  Further, for example, as disclosed in Japanese Patent Application Laid-Open No. 2011-196331, an ultrasonic generator that generates vibration is provided in the combustion chamber of the exhaust recirculation dedicated cylinder, and the soot is applied by applying ultrasonic vibration to the soot. The amount of soot discharged from the cylinder dedicated to exhaust gas recirculation can be reduced as compared with other cylinders not equipped with an ultrasonic generator.

Further, in the diesel engines 10 and 31 shown in FIG. 1 or FIG. 2, the EGR pipe 15 is switched between a state connected to the upstream side of the compressors 13B2 and 13B and a state connected to the downstream side of the compressors 13B2 and 13B. To be able to.
Then, whether or not the exhaust gas can be recirculated downstream of the compressors 13B2 and 13B is determined based on engine operating conditions (engine load, engine speed, supercharging pressure, etc.), and the compressor 13B2 , 13B, the exhaust gas recirculation path is switched so that the exhaust gas is recirculated downstream of the compressors 13B2, 13B.

Here, when the exhaust gas is recirculated to the downstream side of the compressors 13B2 and 13B, the injection control for reducing soot discharged from the exhaust gas recirculation cylinder can be stopped.
On the other hand, if the conditions are such that a sufficient amount of exhaust gas cannot be recirculated downstream of the compressors 13B2 and 13B, the exhaust gas recirculation path is switched so that the exhaust gas is recirculated upstream of the compressors 13B2 and 13B, and the exhaust gas is exhausted. The injection control for reducing soot discharged from the reflux cylinder is resumed.

  In addition, a communication passage is provided to connect the collector portion of the sub exhaust manifold 11A and the collector portion of the main exhaust manifold 11B, and a valve provided in the communication passage is opened at a low load when the exhaust pressure (back pressure) is low. Thus, the exhaust gas recirculation amount can be increased by applying the exhaust pressure of all cylinders to the EGR pipe 15.

DESCRIPTION OF SYMBOLS 10 Diesel engine 11 Exhaust manifold 11A Sub exhaust manifold 11B Main exhaust manifold 12 Exhaust pipe 13 Turbocharger 13A Turbine 13B1 Subcompressor 13B2 Main compressor 14 Exhaust purification device 15 EGR pipe (exhaust recirculation pipe)
16 Intake manifold 16A Sub intake manifold 16B Main intake manifold 17A Sub intake pipe 17B Main intake pipe 18 Intercooler 19 Intake pipe 20 DOC (oxidation catalyst)
21 EGR cooler 22 EGR valve (first valve)
23 Communication pipe 24 Relief valve (second valve)
25 Injector 26 Engine control unit 30 Exhaust gas recirculation device (EGR device)
31 Diesel engine 32 Intake manifold 33 Intake pipe

Claims (6)

In a multi-cylinder internal combustion engine equipped with a turbocharger,
An exhaust gas recirculation pipe that separates and separates the exhaust gas of a part of the multi-cylinder dedicated exhaust gas recirculation cylinder from the exhaust gas of cylinders other than the exhaust gas recirculation cylinder and returns the exhaust gas to the intake pipe upstream of the compressor of the turbocharger. When,
The exhaust pipe on the downstream side of the turbine of the turbocharger into which the exhaust of the cylinder other than the exhaust recirculation dedicated cylinder flows is connected to the exhaust recirculation pipe, and the exhaust of the exhaust recirculation dedicated cylinder is bypassed to the turbine of the turbocharger. A communication pipe to be discharged
A first valve provided in the exhaust gas recirculation pipe;
A second valve provided in the communication pipe;
Exhaust component reducing means for reducing a predetermined component in the exhaust gas recirculated to the intake pipe through the exhaust gas recirculation pipe, as compared with exhaust of a cylinder other than the exhaust recirculation dedicated cylinder;
An exhaust gas recirculation device for a turbocharged multi-cylinder internal combustion engine. The exhaust gas recirculation apparatus for a multi-cylinder internal combustion engine with a turbocharger according to claim 1, wherein an exhaust gas purification device is provided in the exhaust gas recirculation pipe as the exhaust component reducing means . The exhaust gas recirculation device for a turbocharged multi-cylinder internal combustion engine according to claim 2, wherein the exhaust gas purification device is an oxidation catalyst . 4. The combustion control means for reducing a predetermined component in the exhaust discharged from the exhaust recirculation dedicated cylinder as compared with exhaust of a cylinder other than the exhaust recirculation dedicated cylinder as the exhaust component reducing means. An exhaust gas recirculation device for a turbocharged multi-cylinder internal combustion engine according to any one of the above. The exhaust gas recirculation of a multi-cylinder internal combustion engine with a turbocharger according to claim 4, wherein the combustion control means sets the air-fuel ratio of the exhaust recirculation dedicated cylinder to be leaner than the air-fuel ratio of cylinders other than the exhaust recirculation dedicated cylinder. apparatus. While independently including a sub intake pipe that guides air to the exhaust recirculation dedicated cylinder and a main intake pipe that guides air to cylinders other than the exhaust recirculation cylinder,
The turbocharger includes a sub compressor and a main compressor that are coaxially supported, the sub compressor is interposed in the sub intake pipe, and the main compressor is interposed in the main intake pipe.
The exhaust gas recirculation apparatus for a multi-cylinder internal combustion engine with a turbocharger according to any one of claims 1 to 5, wherein the exhaust gas recirculation pipe is connected upstream of the main compressor of the main intake pipe .

Images