JP7347210B2 - turbocharged engine - Google Patents

Description

The present invention relates to a turbocharged engine, such as a multi-cylinder engine equipped with a twin-scroll turbocharger connected via two exhaust passages.

For example, as an engine with a turbo supercharger, a four-cylinder multi-cylinder engine and a twin-scroll turbo supercharger are connected to a first exhaust passage (first confluence A structure is known in which the two exhaust gases are connected via a second exhaust pipe (exhaust pipe) and a second exhaust passage (second merging exhaust pipe) (see Patent Document 1).
Further, Patent Document 1 includes an exhaust gas recirculation device (hereinafter referred to as an EGR device) that recirculates exhaust gas to an intake passage in order to reduce nitrogen oxides in exhaust gas and improve fuel efficiency.

In a multi-cylinder engine equipped with such a turbo supercharger and an EGR device, the flow rate of EGR gas recirculated to the intake passage is ensured even in a high load range, and the flow rate of exhaust gas supplied to the turbo supercharger is ensured. There is a need to secure this from a low load range.

Therefore, in Patent Document 1, a first EGR passage branched from an independent passage part of a first exhaust passage that communicates with the first cylinder, and a merging passage part of a second exhaust passage that communicates with both the second cylinder and the third cylinder. Exhaust gas is returned to the intake passage via the branched second EGR passage.

As a result, in Patent Document 1, compared to an EGR device configured with only one EGR passage, the flow rate of EGR gas returned to the intake passage is ensured even in a high load range.
However, in the case of the configuration of Patent Document 1, the applicant notes that as the exhaust gas is recirculated into the intake passage, the flow rate of the exhaust gas supplied to the turbocharger decreases, and the supercharging pressure decreases. confirmed by.

For this reason, Patent Document 1 addresses the need to ensure the flow rate of EGR gas recirculated to the intake passage even in the high load range, and to ensure the flow rate of exhaust gas supplied to the turbocharger from the low load range. There was a possibility that this could not be done, and there was room for improvement.

Japanese Patent Application Publication No. 2011-106361

In view of the above-mentioned problems, the present invention provides a turbocharged engine that can ensure the flow rate of EGR gas recirculated to the intake passage even in a high load range, and can suppress a drop in supercharging pressure in a low load range. The purpose is to

The present invention provides a multi-cylinder engine having at least four cylinders, a first exhaust passage communicating with a set of cylinders whose exhaust stroke order is not consecutive, and a cylinder whose exhaust stroke order is adjacent to the set of cylinders. A turbocharged engine comprising: a second exhaust passage communicating with the multi-cylinder engine; and a turbocharger connected to the multi-cylinder engine via the first exhaust passage and the second exhaust passage. , the first exhaust passage includes an independent passage portion that independently communicates with one of the cylinders in the set, and the second exhaust passage communicates with all the cylinders adjacent to the cylinder in the set in exhaust stroke order. a first EGR passage branching from the independent passage part of the first exhaust passage; and a second EGR passage branching from the merging passage part of the second exhaust passage; Either the passage or the second EGR passage is characterized in that it is formed in a shape having a minimum passage cross-sectional area smaller than the minimum passage cross-sectional area of the other EGR passage.

According to the present invention, the flow rate of EGR gas returned to the intake passage through one EGR passage is higher than in the case where the minimum flow cross-sectional area of the first EGR passage and the minimum flow cross-sectional area of the second EGR passage are substantially the same. It is possible to suppress this and increase the flow rate of exhaust gas supplied to the turbocharger.

Furthermore, since exhaust gas can be recirculated to the intake passage through the first EGR passage and the second EGR passage, the turbocharged engine has the problem that the flow rate of EGR gas recirculated to the intake passage becomes insufficient in high load ranges. can be suppressed.

Therefore, in a turbocharged engine, the flow rate of EGR gas recirculated to the intake passage is set to a higher load than when the minimum flow cross-sectional area of the first EGR passage and the minimum flow cross-sectional area of the second EGR passage are approximately the same. This can be ensured even in the low load range, and it is possible to suppress a drop in supercharging pressure in the low load range.

As an aspect of the invention, the multi-cylinder engine is a four-cylinder engine having four cylinders, and the first exhaust passage includes a first independent passage portion communicating with the first cylinder and a first independent passage portion communicating with the fourth cylinder. and a first merging passage section where the first independent passage section and the fourth independent passage section merge, and the second exhaust passage includes a second independent passage section communicating with the second cylinder. a third independent passage communicating with a third cylinder; and a second merging passage where the second independent passage and the third independent passage merge, and the second EGR passage is connected to the second EGR passage. The first EGR passage branches from the merging passage part, and the first EGR passage branches from the first independent passage part or the fourth independent passage part, and has a minimum passage cross-sectional area smaller than the minimum passage cross-sectional area of the second EGR passage. It may be formed into a shape having.

According to this configuration, the turbocharged engine has a longer path length from the first cylinder or the fourth cylinder to the entrance of the first EGR passage than in the case where the first EGR passage is branched from the first merging passage. can be shortened.
In other words, in the turbocharged engine, the inflow pressure of the exhaust gas flowing into the first EGR passage can be made higher than when the first EGR passage is branched from the first merging passage.

Therefore, even when the minimum flow cross-sectional area of the first EGR passage is made smaller than that of the second EGR passage, the turbocharged engine has a flow rate of exhaust gas that is returned to the intake passage through the first EGR passage. It is possible to ensure this, and at the same time, it is possible to suppress a drop in the pressure of the exhaust gas supplied to the turbocharger.

As a result, the turbocharged engine can suppress the difference in flow rate between the exhaust gas supplied to the turbocharger from the first exhaust passage and the exhaust gas supplied to the turbocharger from the second exhaust passage. I can do it.
Therefore, in a four-cylinder multi-cylinder engine, the turbocharged engine can ensure the flow rate of EGR gas recirculated to the intake passage even in a high load range, and can suppress fluctuations in supercharging pressure.

Moreover, as an aspect of the present invention, a ratio of the minimum passage cross-sectional area of the first EGR passage to the minimum passage cross-sectional area of the second EGR passage may be in a range of 90% or more and 95% or less.
According to this configuration, the turbocharged engine can more reliably suppress variations in the flow rate of EGR gas recirculated to the intake passage. Therefore, the turbocharged engine facilitates stable control of a multi-cylinder engine, and can suppress deterioration in fuel efficiency and increase in vibration.

Further, as an aspect of the present invention, the multi-cylinder engine includes a plurality of independent exhaust ports each independently communicating with a plurality of cylinders whose exhaust stroke order is adjacent to the one set of cylinders, and a plurality of independent exhaust ports. an upstream portion of the merging passage section of the second exhaust passage is configured with the merging exhaust port, and the second EGR passage has a merging exhaust port that is higher than the merging exhaust port in the second exhaust passage. It may be branched from downstream.

According to this configuration, in the turbocharged engine, the second EGR passage is located closer to the multi-cylinder engine than in a case where all the merging passages of the second exhaust passage are located outside the multi-cylinder engine. Can be branched.

Furthermore, since the first EGR passage branches off at a position close to the multi-cylinder engine, the turbocharged engine can reduce the total length of the first EGR passage and the total length of the second EGR passage. Therefore, the turbocharged engine can suppress the increase in size of a multi-cylinder engine equipped with a turbocharger.
Therefore, the turbocharged engine can efficiently recirculate exhaust gas to the intake passage without increasing its size.

According to the present invention, it is possible to provide a turbocharged engine that can ensure the flow rate of EGR gas recirculated to the intake passage even in a high load range, and can suppress a decrease in supercharging pressure in a low load range.

FIG. 1 is a configuration diagram showing the configuration of a turbocharged engine. FIG. 3 is a front view showing the external appearance of the exhaust manifold seen from the first flange. FIG. 3 is an external perspective view showing the external appearance of the exhaust manifold seen from the second flange portion. FIG. 3 is a cross-sectional perspective view showing the external appearance taken along the line AA in FIG. 2; FIG. 3 is an external perspective view showing the appearance of an upper internal passage and a lower internal passage when viewed from above. FIG. 3 is an external perspective view showing the appearance of an upper internal passage and a lower internal passage when viewed from below. FIG. 3 is a cross-sectional view showing the cross-sectional shapes of the first EGR passage and the second EGR passage at the position of the minimum flow passage cross-sectional area. FIG. 4 is an explanatory diagram illustrating a variation value of the EGR gas ratio with respect to the throttling rate of the first EGR passage. FIG. 3 is an explanatory diagram illustrating boost pressure and EGR gas flow rate in this embodiment. FIG. 7 is an explanatory diagram illustrating supercharging pressure in another embodiment.

An embodiment of this invention will be described below with reference to the drawings.
The turbocharged engine of this embodiment includes a multi-cylinder engine and a twin-scroll turbocharger connected through two exhaust passages. Such a turbocharged engine 1 will be explained using FIGS. 1 to 8.

1 shows a configuration diagram of the turbocharged engine 1, FIG. 2 shows a front view of the exhaust manifold 8 seen from the first flange part 81, and FIG. 3 shows a front view of the exhaust manifold 8 seen from the second flange part 82. An external perspective view of the manifold 8 is shown, and FIG. 4 is a cross-sectional perspective view taken along the line AA in FIG.

Further, FIG. 5 shows an external perspective view of the upper internal passage 84 and the lower internal passage 85 when viewed from above, and FIG. 6 shows an external perspective view of the upper internal passage 84 and the lower internal passage 85 when viewed from below. There is.
In addition, FIG. 7 shows a cross-sectional view of the first EGR passage 61 and the second EGR passage 62 at the position of the minimum flow passage cross-sectional area, and FIG. 8 explains the fluctuation value of the EGR gas proportion with respect to the throttling ratio of the first EGR passage 61. An explanatory diagram is shown.

In addition, in the figure, arrow X indicates the direction in which the cylinders are arranged in parallel (hereinafter referred to as "cylinder row direction X"), and arrow Y indicates the direction in which exhaust gas is discharged from the multi-cylinder engine 2. (Hereinafter referred to as exhaust direction Y).
Further, in the cylinder row direction X, the first cylinder 21a side (right direction in FIG. 1) is one side Xa in the cylinder row direction Let the other side be Xb.
In addition, the upper side of the figure is defined as the upper side, and the lower side of the figure is defined as the lower side.

As shown in FIG. 1, the turbocharged engine 1 includes a multi-cylinder engine 2, an intake passage 3, an exhaust passage 4, a turbocharger 5, and an EGR device 6.
As shown in FIG. 1, the multi-cylinder engine 2 is a so-called in-line four-cylinder engine in which four cylinders 21 are arranged in series along the axial center of a crankshaft (not shown).

As shown in FIG. 1, inside this multi-cylinder engine 2, there are four cylinders 21 that accommodate pistons (not shown) in a vertically slidable manner, the cylinders 21, the pistons, and a cylinder head (not shown). Four combustion chambers (not shown) are formed along the cylinder row direction X.

Note that, as shown in FIG. 1, the four cylinders 21 are, in order from one side Xa in the cylinder row direction X, a first cylinder 21a, a second cylinder 21b, a third cylinder 21c, and a fourth cylinder 21d.
Furthermore, the ignition order of the multi-cylinder engine 2 described above is the first cylinder 21a, the third cylinder 21c, the fourth cylinder 21d, and the second cylinder 21b.

Inside such a multi-cylinder engine 2, as shown in FIG. 1, an intake port and an exhaust port, which are passages that communicate the combustion chamber with the outside of the multi-cylinder engine 2, are formed for each cylinder 21. There is.
In addition, as shown in FIG. 1, inside the multi-cylinder engine 2, as part of an EGR device to be described later, there is an internal engine passage 63 through which exhaust gas flows, which is substantially perpendicular to the cylinder row direction X in plan view. It is formed along the orthogonal direction. Note that, as shown in FIG. 1, the engine internal passage 63 is formed adjacent to the fourth cylinder 21d.

The four intake ports are arranged in parallel along the cylinder row direction X, as shown in FIG. This intake port extends from each cylinder 21 toward one side in the orthogonal direction.

Specifically, as shown in FIG. 1, the multi-cylinder engine 2 includes a first intake port 22 communicating with the first cylinder 21a, a second intake port 23 communicating with the second cylinder 21b, and a third cylinder 21c. The third intake port 24 communicates with the fourth cylinder 21d, and the fourth intake port 25 communicates with the fourth cylinder 21d. Although detailed illustrations are omitted, the first intake port 22, the second intake port 23, the third intake port 24, and the fourth intake port 25 each consist of a pair of intake ports that communicate with the cylinder 21. It is assumed that there is

The exhaust ports are arranged in parallel along the cylinder row direction X, as shown in FIG. This exhaust port extends from each cylinder 21 toward the other side in the orthogonal direction.
Specifically, as shown in FIG. 1, the multi-cylinder engine 2 has a first exhaust port 26 that communicates between the first cylinder 21a and the outside, a second cylinder 21b, and a third cylinder 21c that communicate with the outside. The fourth cylinder 21d is provided with a second exhaust port 27, and a third exhaust port 28, which communicates the fourth cylinder 21d with the outside.

Of these, the second exhaust port 27 includes two independent exhaust ports 27a that independently communicate with the second cylinder 21b and the third cylinder 21c, and two independent exhaust ports 27a, as shown in FIG. It is integrally formed with one merging exhaust port 27b that communicates with the outside. In other words, the combined exhaust port 27b is formed as an exhaust port that communicates with both the second cylinder 21b and the third cylinder 21c.
Although detailed illustrations are omitted, the two independent exhaust ports 27a, the first exhaust port 26 and the second exhaust port 27, and the third exhaust port 28 are each composed of a pair of exhaust ports communicating with the cylinder 21. It is assumed that

Further, the intake passage 3 is a passage that takes in fresh air from the outside and introduces the taken in fresh air into each cylinder 21 of the multi-cylinder engine 2. As shown in FIG. 1, the intake passage 3 includes a first intake passage 31 that takes in outside air as fresh air, an air cleaner 32 that removes dust contained in the fresh air, and a second intake passage connected to the air cleaner 32. passages 33 in this order from the upstream side.

Furthermore, as shown in FIG. 1, the intake passage 3 is connected to a third intake passage 34 connected to a second intake passage 33 via a turbocharger 5, and fresh air compressed by the turbocharger 5. An intercooler 35 is provided in this order from the upstream side.

In addition, as shown in FIG. 1, the intake passage 3 includes a fourth intake passage 36 connected to an intercooler 35, a throttle body 37 that adjusts the flow rate of fresh air, and a fifth intake passage connected to the throttle body 37. passages 38 in this order from the upstream side.

As shown in FIG. 1, the intake passage 3 includes four independent intake passages 39 branched from the fifth intake passage 38, and a first intake port 22 of the multi-cylinder engine 2 that communicates with each of the four independent intake passages 39. , a second intake port 23, a third intake port 24, and a fourth intake port 25.
Note that the downstream portion of the fifth intake passage 38 and the four independent intake passages 39 are integrally formed as a so-called intake manifold 7.

Further, the exhaust passage 4 is a passage that guides exhaust gas generated in the combustion chamber of the multi-cylinder engine 2 toward the turbo supercharger 5, as shown in FIG.
As shown in FIG. 1, this exhaust passage 4 includes a first exhaust passage 41 communicating with a first cylinder 21a and a fourth cylinder 21d whose exhaust stroke order is not continuous with each other, and a first cylinder 21a whose exhaust stroke order is not continuous with each other. and a second cylinder 21b adjacent to the fourth cylinder 21d, and a second exhaust passage 42 communicating with the third cylinder 21c.

Specifically, as shown in FIG. 1, the first exhaust passage 41 includes a first independent passage part 41a communicating with the first cylinder 21a, a fourth independent passage part 41b communicating with the fourth cylinder 21d, and a fourth independent passage part 41b communicating with the fourth cylinder 21d. The multi-cylinder engine 2 and the turbo supercharger 5 are communicated with each other through a first merging passage portion 41c where the first independent passage portion 41a and the fourth independent passage portion 41b merge.

As shown in FIG. 1, the second exhaust passage 42 includes a second independent passage part 42a communicating with the second cylinder 21b, a third independent passage part 42b communicating with the third cylinder 21c, a second independent passage part 42a, The multi-cylinder engine 2 and the turbo supercharger 5 are communicated with each other through a second merging passage section 42c where the third independent passage section 42b and the third independent passage section 42b merge.

In the first exhaust passage 41 and the second exhaust passage 42, a portion connecting the multi-cylinder engine 2 and the turbo supercharger 5 is formed as a so-called exhaust manifold 8.
Note that the first exhaust passage 41 and the second exhaust passage 42 will be described in detail later.

Moreover, the turbo supercharger 5 is a twin scroll type turbo supercharger, as shown in FIG. As shown in FIG. 1, this turbocharger 5 includes a turbine housing 5a that independently communicates with a first exhaust passage 41 and a second exhaust passage 42, a second intake passage 33, and a third intake passage 34. The compressor housing 5b is connected to the compressor housing 5b.

Furthermore, as shown in FIG. 1, the turbocharger 5 includes a turbine wheel 51 that rotates by exhaust gas from the exhaust passage 4, a turbine shaft 52 whose one end is connected to the turbine wheel 51, and a turbine shaft 52 that is connected to the turbine wheel 51 at one end. A compressor wheel 53 is connected to the other end.

In the turbocharger 5, as shown in FIG. 1, a turbine wheel 51 is housed inside a turbine housing 5a, and a compressor wheel 53 is housed inside a compressor housing 5b.

Further, the EGR device 6 is a device that recirculates exhaust gas discharged into the exhaust passage 4 to the intake passage 3. As shown in FIG. 1, the EGR device 6 includes a first EGR passage 61 and a second EGR passage 62 that take in exhaust gas as EGR gas, and an internal engine passage 63 provided inside the multi-cylinder engine 2. .
Further, the EGR device 6 includes a first EGR merging pipe 64, an EGR valve 65, a second EGR merging pipe 66, an EGR cooler 67, and a third EGR merging pipe 68, which connect the engine internal passage 63 and the fifth intake passage 38. There is.

The first EGR passage 61 connects the first exhaust passage 41 and the engine internal passage 63.
The second EGR passage 62 connects the second exhaust passage 42 and the internal engine passage 63.
The first EGR passage 61 and the second EGR passage 62 are integrally formed in the exhaust manifold 8, as shown in FIG. Note that the first EGR passage 61 and the second EGR passage 62 will be described in detail later.

The internal engine passage 63 is formed inside the multi-cylinder engine 2 as a passage where EGR gas from the first EGR passage 61 and the second EGR passage 62 join together. Further, the internal engine passage 63 has a function of cooling the EGR gas flowing down with the cooling water flowing down inside the multi-cylinder engine 2.

The first EGR confluence pipe 64 connects the engine internal passage 63 and an EGR valve 65 that adjusts the flow rate of EGR gas.
The second EGR confluence pipe 66 connects the EGR valve 65 and an EGR cooler 67 that cools EGR gas.
The third EGR confluence pipe 68 connects the EGR cooler 67 and the fifth intake passage 38.

Here, the exhaust manifold 8 that connects the multi-cylinder engine 2 and the turbocharger 5 and forms a part of the exhaust passage 4 will be described in more detail.
As shown in FIGS. 2 to 4, the exhaust manifold 8 includes a first flange portion 81 connected to the multi-cylinder engine 2, a second flange portion 82 connected to the turbo supercharger 5, and a first flange portion 81 connected to the multi-cylinder engine 2. 81 and a body portion 83 that connects the second flange portion 82 in the exhaust direction Y.

Furthermore, as shown in FIG. 2, the first flange portion 81 has a first opening 81a communicating with the first exhaust port 26, a second opening 81b communicating with the second exhaust port 27, and a third opening 81b communicating with the third exhaust port 28. The communicating third openings 81c are formed in this order from one side Xa to the other side Xb in the cylinder row direction X.

Note that the first opening 81a, the second opening 81b, and the third opening 81c are formed into substantially rectangular shapes that are vertically long, as shown in FIG.
On the other hand, as shown in FIG. 3, the second flange portion 82 is formed with a generally rectangular upper opening 82a and a lower opening 82b extending in the cylinder row direction X in this order from the top to the bottom.

Inside the exhaust manifold 8, as shown in FIGS. 4 to 6, there is an upper internal passage which is an internal space passing through the first flange part 81 and the second flange part 82 along the exhaust direction Y. 84 and a lower internal passage 85 are formed.

As shown in FIG. 2, FIG. 3, and FIG. This is an internal space that communicates with the turbo supercharger 5.

The upper internal passage 84 is formed in the exhaust manifold 8 in a shape that is bent upward from the second opening 81b of the first flange portion 81 toward the exhaust direction Y.
Further, as shown in FIGS. 2, 4, and 6, the lower internal passage 85 passes through the first opening 81a, the third opening 81c, and the lower opening 82b of the second flange part 81. This is an internal space that allows the first exhaust port 26 and the third exhaust port 28 to communicate with the turbo supercharger 5.

More specifically, as shown in FIGS. 2, 4, and 6, the lower internal passage 85 includes a first lower passage part 85a that communicates with the first exhaust port 26 via the first opening 81a, and a third opening. The second lower passage section 85b communicates with the third exhaust port 28 through an opening 81c, and the third lower passage section 85c communicates with the turbocharger 5 through a lower opening 82b.

As shown in FIGS. 2, 4, and 6, the first lower passage portion 85a is formed in a shape extending from the first opening 81a in the exhaust direction Y and toward the bottom of the upper internal passage 84.
The second lower passage portion 85b is formed in a shape extending from the third opening 81c toward the exhaust direction Y and below the upper internal passage 84, as shown in FIGS. 2, 4, and 6.
As shown in FIGS. 2, 4, and 6, the third lower passage section 85c extends in the exhaust direction Y from the first lower passage section 85a and the second lower passage section 85b, which merge below the upper internal passage 84. It is formed in a shape that extends toward the

As shown in FIGS. 1 to 6, the first exhaust passage 41 of the exhaust passage 4 described above is connected to the first exhaust port 26 and the third exhaust port 28 of the multi-cylinder engine 2, and the inside of the lower stage of the exhaust manifold 8. It is composed of a passage 85.

Further, the second exhaust passage 42 of the exhaust passage 4 is constituted by the second exhaust port 27 of the multi-cylinder engine 2 and the upper internal passage 84 of the exhaust manifold 8.
More specifically, as described above, the first exhaust passage 41 has a first independent passage part 41a that independently communicates with the first cylinder 21a, and an independent passage part 41a that communicates with the fourth cylinder 21d, as shown in FIGS. 1 to 6. The fourth independent passage section 41b communicates with the fourth independent passage section 41b, and the first merging passage section 41c integrally communicates both of them with the turbo supercharger 5.

The first independent passage section 41a is composed of the first exhaust port 26 of the multi-cylinder engine 2 and the first lower passage section 85a of the exhaust manifold 8, as shown in FIGS. 1 to 6.
The fourth independent passage section 41b is composed of the third exhaust port 28 of the multi-cylinder engine 2 and the second lower passage section 85b of the exhaust manifold 8, as shown in FIGS. 1 to 6.
As shown in FIGS. 1 to 6, the first merging passage section 41c is constituted by a third lower passage section 85c of the exhaust manifold 8.

Further, as described above, the second exhaust passage 42 has a second independent passage section 42a that independently communicates with the second cylinder 21b and an independent passage section 42a that communicates with the third cylinder 21c, as shown in FIGS. 1 to 5. It is composed of a third independent passage section 42b that communicates with the third independent passage section 42b, and a second merging passage section 42c that integrally communicates both of them with the turbo supercharger 5.

As shown in FIG. 1, the second independent passage portion 42a includes an independent exhaust port 27a communicating with the second cylinder 21b.
As shown in FIG. 1, the third independent passage portion 42b includes an independent exhaust port 27a communicating with the third cylinder 21c.
The second merging passage section 42c includes the merging exhaust port 27b of the multi-cylinder engine 2 and the upper internal passage 84 of the exhaust manifold 8, as shown in FIGS. 1 to 5.

Subsequently, the above-mentioned exhaust manifold 8 will be explained in detail. As shown in FIG. 2, the first flange portion 81 of the exhaust manifold 8 described above has a first EGR opening 81d adjacent to the third opening 81c on the other side Xb in the cylinder row direction X. .
Furthermore, as shown in FIG. 2, the first flange portion 81 has a second EGR opening 81e adjacent to the first EGR opening 81d on the other side Xb in the cylinder row direction X.

Inside the exhaust manifold 8, as shown in FIGS. 4 to 6, the above-described first EGR passage 61 and second EGR passage 62 are formed.
As shown in FIGS. 2 and 4 to 6, the first EGR passage 61 branches from the second lower passage part 85b of the lower internal passage 85 and communicates with the engine internal passage 63 via the first EGR opening 81d. It is formed as an internal space.

In other words, the first EGR passage 61 branches from the fourth independent passage portion 41b that communicates with the fourth cylinder 21d, as shown in FIG.
Therefore, the branch point of the first EGR passage 61 is provided at a position relatively close to the fourth cylinder 21d with respect to the distance from the first cylinder 21a.

Specifically, the first EGR passage 61 is formed in a shape that extends from the second lower passage portion 85b of the lower internal passage 85 toward the other side Xb in the cylinder row direction X, and then bends toward the first EGR opening 81d. has been done.
As shown in FIGS. 4 and 7, the first EGR passage 61 is formed so that the cross-sectional area of the passage in the longitudinal section along the cylinder row direction X is minimized in the vicinity of the first EGR opening 81d.

Further, as shown in FIGS. 2, 5, and 6, the second EGR passage 62 is formed as an internal space that branches from the upper internal passage 84 and communicates with the internal engine passage 63 via the second EGR opening 81e. ing.
In other words, as shown in FIG. 1, the second EGR passage 62 branches from the second merging passage portion 42c that communicates with both the second cylinder 21b and the third cylinder 21c.

Specifically, the second EGR passage 62 extends from the upper internal passage 84 to the other side Xb in the cylinder row direction It is formed in a shape that extends toward the second EGR opening 81e and then bends toward the second EGR opening 81e.

Therefore, the second EGR passage 62 is formed with a longer overall length than the entire length of the first EGR passage 61.
Furthermore, as shown in FIG. 7, the second EGR passage 62 is formed so that the passage cross-sectional area in the longitudinal section along the cylinder row direction X is minimized in the vicinity of the second EGR opening 81e.

As shown in FIG. 7, the minimum passage cross-sectional area of the first EGR passage 61 described above is set to a size suitable for stably securing the flow rate of EGR gas returned to the intake passage 3 and the boost pressure. Therefore, the cross-sectional area of the second EGR passage 62 is made smaller than the minimum passage cross-sectional area of the second EGR passage 62.

Specifically, as shown in FIG. 7, the first EGR passage 61 is formed such that the ratio of the minimum passage cross-sectional area to the minimum passage cross-sectional area of the second EGR passage 62 is 90% or more and 95% or less. There is.

Here, the relationship between the proportion of EGR gas in the total intake amount of the multi-cylinder engine 2 and the minimum flow passage cross-sectional area of the first EGR passage 61 is expressed as follows: This will be explained with reference to FIG. 8, which shows a relationship diagram in which the vertical axis represents the fluctuation value of the EGR gas ratio.
Note that the throttle ratio of the first EGR passage 61 to the second EGR passage 62 is the ratio of the minimum passage cross-sectional area of the first EGR passage 61 to the minimum passage cross-sectional area of the second EGR passage 62. Furthermore, the fluctuation value of the EGR gas proportion is the difference between the maximum value of the proportion occupied by EGR gas and the minimum value of the proportion occupied by EGR gas among the total intake amount of the multi-cylinder engine 2.

First, when the minimum passage cross-sectional area of the first EGR passage 61 is the same as the minimum passage cross-sectional area of the second EGR passage 62, that is, when the throttling ratio of the first EGR passage 61 with respect to the second EGR passage 62 is 100%, the fourth cylinder Exhaust gas discharged from 21d easily flows into the intake passage 3 via the first EGR passage 61. Therefore, the maximum value of the proportion occupied by EGR gas becomes large, and the fluctuation value of the EGR gas proportion also becomes large.

As shown in FIG. 8, the fluctuation value of the EGR gas ratio decreases as the minimum flow passage cross-sectional area of the first EGR passage 61 becomes smaller, that is, as the throttling ratio of the first EGR passage 61 with respect to the second EGR passage 62 becomes smaller. Become.
This is because the exhaust gas discharged from the fourth cylinder 21d becomes less likely to flow into the intake passage 3 via the first EGR passage 61 as the throttling ratio of the first EGR passage 61 with respect to the second EGR passage 62 becomes smaller. be.

However, as the throttling ratio of the first EGR passage 61 with respect to the second EGR passage 62 becomes smaller than 95%, the fluctuation value of the EGR gas ratio gradually decreases as shown in FIG. The aperture ratio of 61 is the minimum at 93%.

Then, as the throttling ratio of the first EGR passage 61 with respect to the second EGR passage 62 becomes smaller than 93%, the fluctuation value of the EGR gas ratio increases, as shown in FIG. 8. At this time, in a range where the throttling ratio of the first EGR passage 61 with respect to the second EGR passage 62 is in the range of 90% or more and 93% or less, the fluctuation value of the EGR gas ratio gradually increases as shown in FIG.

On the other hand, in a range where the throttling ratio of the first EGR passage 61 with respect to the second EGR passage 62 is smaller than 90%, the fluctuation value of the EGR gas ratio is within the range where the throttling ratio is 90% or more and 93% or less, as shown in FIG. becomes larger rapidly.

This is because if the minimum flow cross-sectional area of the first EGR passage 61 is reduced beyond a certain range, the exhaust gas discharged from the first cylinder 21a will flow into the intake passage 3 via the first intake passage 31. This is because it becomes difficult. For this reason, the minimum value of the proportion occupied by EGR gas is further reduced, and the fluctuation value of the EGR gas proportion is also increased.

In this way, the fluctuation value of the EGR gas proportion becomes the smallest when the throttling ratio of the first EGR passage 61 is 93%, and increases as the throttling ratio of the first EGR passage 61 becomes larger than or smaller than 93%.
Therefore, in the present embodiment, the minimum passage cross-sectional area of the first EGR passage 61 is set to such a size that the ratio of the minimum passage cross-sectional area of the second EGR passage 62 to the minimum passage cross-sectional area of the second EGR passage 62 is in the range of 90% to 95%.

Next, the supercharging pressure due to the exhaust gas flowing through the first exhaust passage 41, the supercharging pressure due to the exhaust gas flowing through the second exhaust passage 42, and the flow rate of EGR gas recirculated to the intake passage 3 (hereinafter referred to as "EGR gas flow rate") are determined. ") will be explained using FIG. 9.
Note that FIG. 9 shows an explanatory diagram illustrating the boost pressure and EGR gas flow rate in this embodiment.

Specifically, FIGS. 9(a) and 9(b) show the supercharging pressure when the minimum passage cross-sectional area of the first EGR passage 61 and the minimum passage cross-sectional area of the second EGR passage 62 are approximately equal, and A relationship diagram comparing the minimum flow cross-sectional area of the second EGR passage 62 with the supercharging pressure when the minimum flow cross-sectional area of the first EGR passage 61 is throttled at a throttling rate of 90% is shown.

Note that FIG. 9(a) shows the supercharging pressure due to the exhaust gas flowing through the first exhaust passage 41 in a relational diagram in which the horizontal axis is the advancement of the crank angle and the vertical axis is the supercharging pressure.
On the other hand, FIG. 9(b) shows the supercharging pressure due to the exhaust gas flowing through the second exhaust passage 42 in a relationship diagram in which the horizontal axis is the progress of the crank angle and the vertical axis is the supercharging pressure.

Further, FIG. 9(c) shows the EGR gas flow rate when the minimum passage cross-sectional area of the first EGR passage 61 and the minimum passage cross-sectional area of the second EGR passage 62 are approximately the same, and the minimum passage cross-section of the second EGR passage 62. With respect to the area, the EGR gas flow rate when the minimum passage cross-sectional area of the first EGR passage 61 is throttled at a throttling rate of 90%, and the minimum passage cross-sectional area of the first EGR passage 61 when the throttling rate is 100%. , is a relational diagram comparing the EGR gas flow rate when the minimum flow passage cross-sectional area of the second EGR passage 62 is throttled at a throttling rate of 90%.
Note that FIG. 9(c) shows the EGR gas flow rate recirculated to the intake passage 3 in a relationship diagram in which the horizontal axis represents the progress of the crank angle and the vertical axis represents the boost pressure.

Furthermore, in the relationship diagram in FIG. 9, the thick solid line indicates the case where the minimum flow passage cross-sectional area of the first EGR passage 61 is throttled at a throttling rate of 90%, and the broken line represents the minimum flow passage cross-sectional area of the first EGR passage 61. This shows a case where the minimum flow passage cross-sectional area of the second EGR passage 62 and the second EGR passage 62 are approximately the same, that is, a case without a restriction.
Furthermore, in the relationship diagram in FIG. 9(c), the thin solid line indicates the case where the minimum flow passage cross-sectional area of the second EGR passage 62 is throttled at a throttling rate of 90%.

First, the supercharging pressure due to the exhaust gas flowing through the first exhaust passage 41 is increased by narrowing down the minimum passage cross-sectional area of the first EGR passage 61 at the exhaust timing T1 of the first cylinder 21a, as shown in FIG. 9(a). It can be seen that the supercharging pressure B2 when the minimum flow passage cross-sectional area of the first EGR passage 61 is throttled at a throttling rate of 90% is higher than the supercharging pressure B1 when there is no supercharging pressure.

Similarly, the supercharging pressure due to the exhaust gas flowing through the first exhaust passage 41 narrows down the minimum passage cross-sectional area of the first EGR passage 61 at the exhaust timing T2 of the fourth cylinder 21d, as shown in FIG. 9(a). It can be seen that the supercharging pressure B2 when the minimum flow passage cross-sectional area of the first EGR passage 61 is throttled at a throttling rate of 90% is higher than the supercharging pressure B1 when the first EGR passage 61 is not closed.

On the other hand, as shown in FIG. 9(b), the supercharging pressure due to the exhaust gas flowing through the second exhaust passage 42 narrows the minimum flow passage cross-sectional area of the first EGR passage 61 at the exhaust timing T3 of the second cylinder 21b. It can be seen that the supercharging pressure B3 when the first EGR passage 61 is not closed is approximately the same as the supercharging pressure B4 when the minimum flow passage cross-sectional area of the first EGR passage 61 is throttled at a throttling rate of 90%.

Similarly, the supercharging pressure due to the exhaust gas flowing through the second exhaust passage 42 narrows down the minimum passage cross-sectional area of the first EGR passage 61 at the exhaust timing T4 of the third cylinder 21c, as shown in FIG. 9(b). It can be seen that the supercharging pressure B3 when the first EGR passage 61 is not closed is approximately the same as the supercharging pressure B4 when the minimum flow passage cross-sectional area of the first EGR passage 61 is throttled at a throttling rate of 90%.

This is possible when the minimum flow cross-sectional area of the second EGR passage 62 is not narrowed down to the minimum flow cross-sectional area of the first EGR passage 61, and when the minimum flow cross-sectional area of the first EGR passage 61 is narrowed at a throttling rate of 90%. This is because it is the same as when Therefore, the boost pressure is higher when the minimum flow cross-sectional area of the first EGR passage 61 is throttled at a throttling rate of 90% than when the minimum flow cross-sectional area of the first EGR passage 61 is not throttled. It can be seen that it is in good condition.

Furthermore, as shown in FIG. 9(c), the flow rate of the EGR gas returned to the intake passage 3 is lower than that when the minimum flow passage cross-sectional area of the second EGR passage 62 is throttled at a throttling rate of 90%. It can be seen that the minimum flow passage cross-sectional area of the 1EGR passage 61 can be more stably secured when the narrowing ratio is 90%.

Specifically, first, as a comparative example, the EGR gas flow rate D1 when the minimum flow passage cross-sectional area of the second EGR passage 62 is throttled at a throttling rate of 90% is as shown in FIG. 9(c). When the minimum passage cross-sectional area of the passage 61 and the minimum passage cross-sectional area of the second EGR passage 62 are approximately equal, that is, when the minimum passage cross-sectional area of the first EGR passage 61 and the second EGR passage 62 are not narrowed down. The amount of variation is larger than that of the EGR gas flow rate D2.

On the other hand, the EGR gas flow rate D3 when the minimum flow passage cross-sectional area of the first EGR passage 61 is throttled at a throttling rate of 90% is as shown in FIG. 9(c). The amount of variation in the EGR gas flow rate D2 is larger than that in the case where the minimum flow path cross-sectional area is not reduced.

However, when the minimum flow passage cross-sectional area of the first EGR passage 61 is throttled at a throttling rate of 90%, the EGR gas flow rate D3 varies with respect to the EGR gas flow rate D2 as shown in FIG. 9(c). The amount of variation with respect to the EGR gas flow rate D2 is small compared to the amount.

Therefore, the EGR gas flow rate returned to the intake passage 3 is smaller than the minimum passage cross-sectional area of the first EGR passage 61 compared to the case where the minimum passage cross-sectional area of the second EGR passage 62 is throttled at a throttling ratio of 90%. It can be seen that it is possible to more stably secure the aperture when the aperture ratio is 90%.

As described above, the turbocharged engine 1 includes a multi-cylinder engine 2 having at least three cylinders 21 and a set of cylinders 21 whose exhaust stroke order is not consecutive (the first cylinder 21a, the fourth cylinder 21d). ), a second exhaust passage 42 that communicates with the cylinders 21 (second cylinder 21b, third cylinder 21c) adjacent to one set of cylinders 21 in the exhaust stroke order, and a first exhaust passage 41 and a turbo supercharger 5 connected to the multi-cylinder engine 2 via a second exhaust passage 42.

The first exhaust passage 41 includes an independent passage portion (fourth independent passage portion 41b) that independently communicates with one of the cylinders 21 (fourth cylinder 21d). On the other hand, the second exhaust passage 42 is a merging passage part (second merging passage part 42c) that communicates with all of the cylinders 21 (second cylinder 21b, third cylinder 21c) that are adjacent to one set of cylinders 21 in the order of exhaust strokes. It is equipped with

Furthermore, the turbocharged engine 1 has a first EGR passage 61 branched from an independent passage part (fourth independent passage part 41b) of the first exhaust passage 41 and a confluence passage part (second confluence passage part) of the second exhaust passage 42. A second EGR passage 62 branched from the passage part 42c).
The first EGR passage 61 is formed in a shape having a minimum passage cross-sectional area smaller than the minimum passage cross-sectional area of the second EGR passage 62.

According to this invention, the turbocharged engine 1 has a higher flow rate through the first EGR passage 61 than when the minimum flow cross-sectional area of the first EGR passage 61 and the minimum flow cross-sectional area of the second EGR passage 62 are substantially the same. This makes it possible to suppress the flow rate of EGR gas recirculated to the intake passage 3 and increase the flow rate of exhaust gas supplied to the turbocharger 5.

Furthermore, since the exhaust gas can be recirculated to the intake passage 3 via the first EGR passage 61 and the second EGR passage 62, the turbocharged engine 1 can control the flow rate of the EGR gas recirculated to the intake passage 3 under high load. This can prevent shortages in the area.

Therefore, in the turbocharged engine 1, the amount of EGR gas recirculated to the intake passage 3 is smaller than when the minimum flow cross-sectional area of the first EGR passage 61 and the minimum flow cross-sectional area of the second EGR passage 62 are substantially the same. A flow rate can be ensured even in a high load range, and a decrease in supercharging pressure can be suppressed in a low load range.

Further, the multi-cylinder engine 2 is a four-cylinder engine having four cylinders.
Further, the first exhaust passage 41 includes a first independent passage part 41a communicating with the first cylinder 21a, a fourth independent passage part 41b communicating with the fourth cylinder 21d, a first independent passage part 41a, and a fourth independent passage part 41a. It includes a first merging passage part 41c where the passage part 41b merges.

Furthermore, the second exhaust passage 42 includes a second independent passage part 42a communicating with the second cylinder 21b, a third independent passage part 42b communicating with the third cylinder 21c, a second independent passage part 42a, and a third independent passage part 42a. It includes a second merging passage part 42c where the independent passage part 42b merges.

In addition, the second EGR passage 62 branches from the second merging passage section 42c.
The first EGR passage 61 branches from the fourth independent passage portion 41b and is formed in a shape having a minimum passage cross-sectional area smaller than the minimum passage cross-sectional area of the second EGR passage 62.

According to this configuration, the turbocharged engine 1 has a longer path length from the fourth cylinder 21d to the inlet of the first EGR passage 61 than in the case where the first EGR passage 61 is branched from the first merging passage part 41c. You can shorten the length.
In other words, the turbocharged engine 1 can increase the inflow pressure of the exhaust gas flowing into the first EGR passage 61 compared to the case where the first EGR passage 61 is branched from the first merging passage portion 41c.

Therefore, in the turbocharged engine 1, even when the minimum flow passage cross-sectional area of the first EGR passage 61 is made smaller than that of the second EGR passage 62, the air is returned to the intake passage 3 through the first EGR passage 61. It is possible to ensure the flow rate of the exhaust gas, and to suppress the pressure drop of the exhaust gas supplied to the turbocharger 5.

As a result, the turbocharged engine 1 can separate the exhaust gas supplied to the turbocharger 5 from the first exhaust passage 41 and the exhaust gas supplied to the turbocharger 5 from the second exhaust passage 42. Flow rate difference can be suppressed.
Therefore, in the four-cylinder multi-cylinder engine 2, the turbocharged engine 1 can ensure the flow rate of EGR gas recirculated to the intake passage 3 even in a high load range, and can suppress fluctuations in supercharging pressure. .

Further, the ratio of the minimum passage cross-sectional area of the first EGR passage 61 to the minimum passage cross-sectional area of the second EGR passage 62 is in a range of 90% or more and 95% or less.
According to this configuration, the turbocharged engine 1 can more reliably suppress variations in the flow rate of the EGR gas recirculated to the intake passage 3. Therefore, the turbocharged engine 1 can facilitate stable control of the multi-cylinder engine 2, and can suppress deterioration in fuel efficiency and increase in vibration.

In addition, the multi-cylinder engine 2 includes a plurality of cylinders each independently communicating with a second cylinder 21b and a third cylinder 21c, which are adjacent to a set of cylinders 21 (first cylinder 21a, fourth cylinder 21d) in the exhaust stroke order. It includes an independent exhaust port 27a and a combined exhaust port 27b where a plurality of independent exhaust ports 27a merge.

The upstream portion of the second merging passage section 42c of the second exhaust passage 42 is configured with a merging exhaust port 27b.
Furthermore, the second EGR passage 62 is branched from the second exhaust passage 42 downstream of the combined exhaust port 27b.

According to this configuration, the turbocharged engine 1 has a larger number of second EGR passages 62 than when the second merging passage portion 42c of the second exhaust passage 42 is located outside the multi-cylinder engine 2. It can be branched at a position close to the cylinder engine 2.

Furthermore, since the first EGR passage 61 branches off at a position close to the multi-cylinder engine 2, the turbocharged engine 1 can suppress the total length of the first EGR passage 61 and the total length of the second EGR passage 62. can. Therefore, the turbocharged engine 1 can suppress the multi-cylinder engine 2 including the turbocharger 5 from increasing in size.
Therefore, the turbocharged engine 1 can efficiently recirculate exhaust gas to the intake passage 3 without increasing its size.

In the correspondence between the configuration of this invention and the above-described embodiments,
A set of cylinders of the present invention corresponds to the first cylinder 21a and the fourth cylinder 21d of the embodiment,
Similarly below,
The cylinders adjacent to the set of cylinders correspond to the second cylinder 21b and the third cylinder 21c,
The independent passage portion corresponds to the fourth independent passage portion 41b,
The merging passage portion corresponds to the second merging passage portion 42c,
This invention is not limited to the configuration of the above-described embodiments, and can be implemented in many other embodiments.

For example, in the embodiment described above, the in-line 4-cylinder multi-cylinder engine 2 is used, but the invention is not limited to this, and any multi-cylinder engine having at least three cylinders may be used, such as an in-line 3-cylinder multi-cylinder engine or an in-line 6-cylinder multi-cylinder engine. It may be a multi-cylinder engine.

Further, although the first EGR passage 61 is provided inside the exhaust manifold 8, the first EGR passage 61 is provided inside the multi-cylinder engine 2 so as to communicate the third exhaust port 28 and the internal engine passage 63. A passage may be provided.

Similarly, although the second EGR passage 62 is provided inside the exhaust manifold 8, the second EGR passage 62 is provided inside the multi-cylinder engine 2, but is not limited to this. A passage may be provided.

Further, although the first EGR passage 61 was configured to branch from the fourth independent passage part 41b of the first exhaust passage 41, and the second EGR passage 62 was branched from the second merging passage part 42c of the second exhaust passage 42, However, the present invention is not limited to this, and the first EGR passage is branched from the second independent passage part or the third independent passage part of the second exhaust passage, and the second EGR passage is branched from the first merging passage part of the first exhaust passage. You can also use it as

Further, although the minimum flow cross-sectional area of the first EGR passage 61 is smaller than the minimum flow cross-sectional area of the second EGR passage 62, the minimum flow cross-sectional area of the second EGR passage 62 is made smaller than the minimum flow cross-sectional area of the second EGR passage 62. It may be smaller than the minimum cross-sectional area of the passage 61.
In this case, for example, the second EGR passage may be formed such that the ratio of the minimum passage cross-sectional area to the minimum passage cross-sectional area of the first EGR passage is 90% or more and 95% or less.

Even in this case, the same effects as in the embodiment described above can be obtained.

Specifically, the supercharging pressure due to the exhaust gas flowing through the first exhaust passage 41 is the same as that of the first cylinder 21a, as shown in FIG. At exhaust timing T5, supercharging pressure B5 when the minimum passage cross-sectional area of the second EGR passage 62 is not throttled and supercharging when the minimum passage cross-sectional area of the second EGR passage 62 is throttled at a throttling rate of 90%. The pressure B6 is approximately the same.

Similarly, the supercharging pressure due to the exhaust gas flowing through the first exhaust passage 41 narrows the minimum passage cross-sectional area of the second EGR passage 62 at the exhaust timing T6 of the fourth cylinder 21d, as shown in FIG. 10(a). The supercharging pressure B5 when the EGR passage 62 is not closed is approximately equal to the supercharging pressure B6 when the minimum flow passage cross-sectional area of the second EGR passage 62 is throttled at a throttling rate of 90%.

This is possible when the minimum flow cross-sectional area of the first EGR passage 61 is not narrowed down to the minimum flow cross-sectional area of the second EGR passage 62, and when the minimum flow cross-sectional area of the second EGR passage 62 is narrowed at a throttling rate of 90%. This is because it is the same as when

On the other hand, the supercharging pressure due to the exhaust gas flowing through the second exhaust passage 42 is increased by narrowing the minimum flow passage cross-sectional area of the second EGR passage 62 at the exhaust timing T7 of the second cylinder 21b, as shown in FIG. 10(b). It can be seen that the supercharging pressure B8 when the minimum flow passage cross-sectional area of the second EGR passage 62 is throttled at a throttling rate of 90% is higher than the supercharging pressure B7 when there is no supercharging pressure.

Similarly, the supercharging pressure due to the exhaust gas flowing through the second exhaust passage 42 narrows the minimum flow passage cross-sectional area of the second EGR passage 62 at the exhaust timing T8 of the third cylinder 21c, as shown in FIG. 10(b). It can be seen that the supercharging pressure B8 when the minimum passage cross-sectional area of the second EGR passage 62 is throttled at a throttling rate of 90% is higher than the supercharging pressure B7 when the EGR passage 62 is not closed.

Therefore, the boost pressure is higher when the minimum flow cross-sectional area of the second EGR passage 62 is throttled at a throttling rate of 90% than when the minimum flow cross-sectional area of the second EGR passage 62 is not throttled. It can be seen that it is in good condition.
Thereby, the turbocharged engine 1 can suppress a decrease in supercharging pressure in a low load region.

Although the first EGR passage 61 is branched from the fourth independent passage portion 41b of the first exhaust passage 41, the present invention is not limited to this, and for example, when the internal engine passage 63 is provided adjacent to the first cylinder 21a. , the first EGR passage may be branched from the first independent passage portion 41a of the first exhaust passage 41.

1...Engine with turbo supercharger 2...Multi-cylinder engine 5...Turbo supercharger 21...Cylinder 21a...First cylinder 21b...Second cylinder 21c...Third cylinder 21d...Fourth cylinder 27a...Independent exhaust port 27b...Merge Exhaust port 41...First exhaust passage 41a...First independent passage part 41b...Fourth independent passage part 41c...First merging passage part 42...Second exhaust passage 42a...Second independent passage part 42b...Third independent passage part 42c ...Second merging passage section 61...First EGR passage 62...Second EGR passage

Claims (4)

a multi-cylinder engine having at least four cylinders;
a first exhaust passage communicating with a set of cylinders whose exhaust strokes are not consecutive;
a second exhaust passage communicating with a cylinder adjacent to the set of cylinders in exhaust stroke order;
A turbocharged engine comprising a turbocharger connected to the multi-cylinder engine via the first exhaust passage and the second exhaust passage,
The first exhaust passage is
comprising an independent passage portion that independently communicates with one of the set of cylinders,
The second exhaust passage is
a merging passage portion communicating with all cylinders adjacent to the set of cylinders in the order of exhaust strokes;
a first EGR passage branching from the independent passage portion of the first exhaust passage;
a second EGR passage branching from the merging passage portion of the second exhaust passage;
Either the first EGR passage or the second EGR passage,
A turbocharged engine formed in a shape having a minimum passage cross-sectional area smaller than the minimum passage cross-sectional area of the other EGR passage. The multi-cylinder engine is a four-cylinder engine having four cylinders,
The first exhaust passage is
a first independent passage portion communicating with the first cylinder;
a fourth independent passage portion communicating with the fourth cylinder;
comprising a first merging passage portion where the first independent passage portion and the fourth independent passage portion merge;
The second exhaust passage is
a second independent passage portion communicating with the second cylinder;
a third independent passage portion communicating with the third cylinder;
comprising a second merging passage portion where the second independent passage portion and the third independent passage portion merge;
The second EGR passage is
branching from the second merging passage section;
The first EGR passage is
The first independent passage section or the fourth independent passage section is branched from the first independent passage section and is formed in a shape having a minimum passage cross-sectional area smaller than a minimum passage cross-sectional area of the second EGR passage. Engine with turbocharger. The minimum passage cross-sectional area of the first EGR passage is:
The turbocharged engine according to claim 2, wherein the ratio of the size of the second EGR passage to the minimum flow passage cross-sectional area is in the range of 90% or more and 95% or less. The multi-cylinder engine is
a plurality of independent exhaust ports each independently communicating with a plurality of cylinders whose exhaust stroke order is adjacent to the set of cylinders;
and a combined exhaust port where the plurality of independent exhaust ports merge,
The upstream portion of the merging passage portion of the second exhaust passage is
consisting of said combined exhaust port;
The second EGR passage is
The turbocharged engine according to any one of claims 1 to 3, wherein the second exhaust passage is branched downstream from the merging exhaust port.

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