JP7435381B2 - engine system - Google Patents

Description

The present invention relates to an engine system that combines a multi-cylinder engine with a twin-scroll turbocharger and an exhaust gas recirculation device.

For example, as an engine with a turbocharger, a four-cylinder engine, a twin scroll turbocharger, two merging exhaust pipes that communicate independently from the exhaust port to the turbine, and a portion of the exhaust gas being taken in from each of the two merging exhaust pipes. An engine system is known that includes an exhaust gas recirculation device (hereinafter referred to as an EGR device) that recirculates the exhaust gas to the side (see Patent Document 1).

Furthermore, a structure is known in which an EGR passage of an EGR device is provided inside a cylinder head in which a water jacket is formed, and EGR gas is cooled in the cylinder head using engine cooling water (see Patent Document 2). ).

Japanese Patent Application Publication No. 2011-106361 Japanese Patent Application Publication No. 2015-140684

When a multi-cylinder engine equipped with two merging exhaust pipes and a twin-entry turbocharger as disclosed in Patent Document 1 has an EGR passage built into the cylinder head as disclosed in Patent Document 2, it is particularly difficult to use an automobile engine. When mounting such a multi-cylinder engine in a room, it is necessary to make the cylinder head as small as possible, so it is necessary to arrange the exhaust outlet and EGR inlet of the cylinder head next to each other.

In addition, in order to downsize the EGR device, it is best to provide an EGR intake port in the cylinder head, but when equipped with a twin scroll turbocharger, it is necessary to form two EGR passages in the cylinder head. This is not practical as it would lead to an increase in the size of the cylinder head. Therefore, two EGR intake ports are formed in the exhaust manifold attached to the exhaust outlet of the cylinder head or in the turbine housing formed downstream thereof, and each is communicated with one EGR inlet provided in the cylinder head. It is possible to make it as short as possible.

However, in this case, the EGR inlet of the cylinder head receives heat transmitted through the cylinder head itself from the exhaust gas passing through the adjacent exhaust outlet, and heat from the still-hot EGR gas that has passed through the short EGR passage. This causes an excessive temperature rise of the sealing surface of the gasket disposed between the cylinder head and the exhaust manifold in the EGR passage, leading to concerns about a decrease in sealing performance and, ultimately, leakage of EGR gas.

Therefore, there is still room for improvement regarding the arrangement of the EGR passage in a multi-cylinder engine equipped with a twin-scroll turbocharger.

The present inventors have discovered that in a multi-cylinder engine equipped with a twin scroll turbocharger and an EGR device, the exhaust gas is transmitted from each of two exhaust passages leading to two scrolls toward an EGR inlet of a cylinder head via the cylinder head. We carefully considered both the amount of heat and the amount of heat transmitted via the EGR passage.

As a result, by making the length of the EGR passage that communicates with cylinders close to the EGR inlet longer than the length of the EGR passage that communicates with cylinders located away from the EGR inlet, the surface area of the EGR passage is increased, and the amount of heat dissipated is increased. By increasing the amount of heat, it is possible to reduce the amount of heat transmitted to the EGR inlet via the EGR passage communicating with the cylinder adjacent to the EGR inlet. Even if the amount of heat transferred from the cylinder close to the EGR inlet via the cylinder head is large due to the proximity, the amount of heat transferred from the cylinder to the EGR inlet via the above two routes, that is, the EGR passage and the cylinder head. It was found that the amount of heat generated from the other cylinders can be suppressed to the same level.

The present invention, which embodies this knowledge, provides a twin scroll turbocharger having a first scroll part and a second scroll part, and a plurality of cylinders including a specific cylinder located at one end of a cylinder row among a plurality of cylinders arranged in series. An engine system having an internal combustion engine having a first cylinder group made up of cylinders and a second cylinder group made up of the remaining cylinders, the engine system having an exhaust port of each cylinder of the first cylinder group and the first cylinder group. A first exhaust passage that communicates with the scroll part, a second exhaust passage that communicates the exhaust port of each cylinder of the second cylinder group with the second scroll part, and a first EGR take-out part provided in the first exhaust passage. , a first EGR passage whose one end communicates with the first exhaust passage, a second EGR take-out portion provided in the second exhaust passage, a second EGR passage whose one end communicates with the second exhaust passage; The other end of the first EGR passage and the other end of the second EGR passage communicate with each other at one end thereof, and the other end is an entrance of an EGR passage provided in the cylinder head, and is adjacent to the exhaust port of the specific cylinder in the cylinder head. The third EGR passage further includes a third EGR passage whose other end communicates with the EGR inlet provided at the position. The passage length between the first EGR extraction part and the exhaust port of the specific cylinder is the longest passage length among the passage lengths between the second EGR extraction part and the exhaust port of each cylinder of the second cylinder group. It is longer than long.

According to this invention, the passage length between the first EGR extraction part and the exhaust port of a specific cylinder is the maximum of the passage lengths between the second EGR extraction part and the exhaust port of each cylinder of the second cylinder group. By being longer than the passage length, the amount of heat dissipated from the exhaust port of the first cylinder group including the specific cylinder to the EGR inlet via the first EGR extraction part increases.

As a result, the exhaust gas discharged from the second cylinder group radiates heat while passing through a part of the second exhaust passage, the second EGR passage, and the third EGR passage from the exhaust port provided in the cylinder head, and then enters the EGR inlet. Compared to the amount of heat transferred, the exhaust gas discharged from the first cylinder group including the specific cylinder adjacent to the EGR inlet is transferred from the exhaust port provided in the cylinder head to a part of the first exhaust passage, the first EGR After the heat is radiated while passing through the passage and the third EGR passage, the amount of heat transmitted to the EGR inlet is suppressed to the same extent. At the same time, the length of the second EGR path can be minimized.

This makes it possible to both reduce the heat load on the EGR inlet and downsize the EGR passage, which requires two passages due to the twin scroll turbocharger.

In the engine system of the present invention, the first cylinder group is configured by cylinders whose exhaust strokes are not adjacent to each other among the plurality of cylinders, and the second cylinder group is constituted by cylinders whose exhaust strokes are not adjacent to each other among the plurality of cylinders. It may also be configured with cylinders without any cylinders.

With this configuration, exhaust from cylinders whose exhaust strokes are adjacent to each other joins the turbine blades of the twin scroll turbocharger in parallel, and exhaust interference does not occur, so that the first exhaust passage and the second exhaust passage are The length can be shortened. Therefore, it is possible to further downsize the engine system.

Furthermore, in the engine system of the present invention, the first exhaust passage includes a plurality of independent exhaust passages communicating with the exhaust ports of each cylinder of the first cylinder group, and a collective exhaust passage connected downstream of each of the plurality of independent exhaust passages. The first EGR extraction section may be provided at a downstream end of an independent exhaust passage that communicates with an exhaust port of a specific cylinder among the plurality of independent exhaust passages.

For example, the closer the first EGR extraction section is provided on the downstream side of the first exhaust passage to the turbocharger, the more heat is radiated from the first exhaust passage, and the temperature of the first EGR extraction part can be lowered. However, the further downstream the first EGR passage is provided, the farther it is from the cylinder head, which increases the size of the entire system. The heat dissipation efficiency of the exhaust passage decreases as the ratio of the cross-sectional circumference to the cross-sectional area of the exhaust passage decreases. Therefore, it is preferable to provide the first EGR extraction part in an independent exhaust passage rather than providing the first EGR extraction part in the collective exhaust passage where this ratio is low. By providing this, it is possible to obtain an improvement in the amount of heat dissipation commensurate with the increase in the size of the system. Furthermore, by providing it at the downstream end of the independent exhaust passage, the effect can be maximized. By providing the first EGR extraction section at the downstream end of the independent exhaust passage, the first EGR passage can be brought closer to the cylinder head, which is advantageous for downsizing the entire system.

Furthermore, in the engine system of the present invention, the cylinder head is provided with a collective exhaust outlet that communicates with all the cylinders of the second cylinder group, the upstream end of the second exhaust passage is connected to the collective exhaust outlet, and the second EGR take-out portion is preferably provided at the upstream end of the second exhaust passage.

With this configuration, since the second EGR passage is provided outside the cylinder head, it is possible to suppress the cylinder head from increasing in size.

Furthermore, in the engine system of the present invention, the first EGR passage has a first constriction part with a reduced passage cross-sectional area in its middle, and the second EGR passage has a second constricted part with a reduced passage cross-sectional area in its middle. It may have a constriction part.

With this configuration, the surface area of the passage is expanded from the first constriction part of the first EGR passage to the third EGR passage, thereby increasing the efficiency of heat radiation. Similarly, by increasing the surface area of the passage from the second throttle part of the second EGR passage to the third EGR passage, the efficiency of heat dissipation can be increased, which has the effect of further lowering the temperature of EGR gas at the EGR inlet. can get.

According to the present invention, by arranging the EGR passage of a multi-cylinder engine equipped with a twin-scroll turbocharger, the multi-cylinder engine can be made compact by suppressing the enlargement of the EGR device, and at the same time, excessive EGR gas can be returned to the intake passage while suppressing a temperature rise.

FIG. 1 is a configuration diagram showing the configuration of a turbocharged engine according to the present invention. FIG. 3 is a front view showing the appearance of the turbocharger as seen from the rear of the engine. FIG. 2 is a plan view showing the appearance of the turbocharger and exhaust manifold as seen from below the engine. FIG. 4 is an end view showing the mounting surface of the exhaust manifold with the cylinder head, taken along the line DD in FIG. 3; FIG. 4 is a schematic diagram showing an exhaust manifold internal passage and a turbocharger internal passage in FIG. 3; 3 is a cross-sectional view showing a first exhaust passage and a second exhaust passage taken along the line AA in FIG. 2. FIG. FIG. 3 is a cross-sectional view showing the cross-sectional shape of the first EGR extraction portion taken along the line BB in FIG. 2; 3 is a cross-sectional view showing the cross-sectional shape of the first EGR passage taken along the line CC in FIG. 2. FIG. FIG. 4 is a cross-sectional view showing the cross-sectional shape of the second EGR passage taken along the line EE in FIG. 3;

Embodiments of the present invention will be specifically described below.

The turbocharged engine of this embodiment is a multi-cylinder engine in which a twin scroll turbocharger and an EGR device are combined via two exhaust passages. Such a turbocharged engine 1 will be explained using FIGS. 1 to 9.

1 shows a configuration diagram of a turbocharged engine 1 according to the present invention, FIG. 2 shows a front view of a turbocharger 5 seen from the rear of the multi-cylinder engine 2, and FIG. 3 shows a bottom view of the multi-cylinder engine 2. FIG. 4 shows a plan view of the turbocharger 5 and the exhaust manifold 8 as seen from above, and FIG. 4 shows an end view of the attachment surface of the exhaust manifold 8 to the cylinder head 2a.

Furthermore, FIG. 5 shows a schematic diagram of the exhaust passage inside the exhaust manifold 8 and the exhaust passage inside the turbine housing 5a, FIG. 6 shows a cross-sectional view of the first exhaust passage and the second exhaust passage, and FIG. A cross-sectional view of the cross-sectional shape of the take-out part is shown. FIG. 8 shows a cross-sectional view of the cross-sectional shape of the first EGR passage, and FIG. 9 shows a cross-sectional view of the cross-sectional shape of the second EGR passage.

Further, in the figure, an arrow X indicates a direction in which the cylinders are arranged in parallel (hereinafter referred to as "cylinder row direction X"). 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 and lower sides are defined based on the state in which the multi-cylinder engine 2 is mounted on the vehicle.

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 an 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, the multi-cylinder engine 2 includes four cylinders 21 that accommodate pistons (not shown) slidably in the cylinder axis direction, the cylinders 21, the pistons, and the cylinder head 2a. 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 each cylinder 21 with the outside of the multi-cylinder engine 2, are formed for each cylinder 21. ing.

In addition, as shown in FIG. 1, inside the multi-cylinder engine 2, a fourth EGR passage 63b through which exhaust gas flows is provided as part of an EGR device to be described later, which is substantially orthogonal to the cylinder row direction X in plan view. It is formed along the orthogonal direction. Note that, as shown in FIG. 1, the fourth EGR passage 63b 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. Specifically, as shown in FIG. 1, the multi-cylinder engine 2 includes a first exhaust port 26 that communicates with the first cylinder 21a, and a second exhaust port 27 that communicates with the second cylinder 21b and the third cylinder 21c. and a third exhaust port 28 communicating with the fourth cylinder 21d.

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. One merging exhaust port 27b communicates with each of the exhaust ports. 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.

An outlet of the first exhaust port 26 (first opening 85a) and an outlet of the third exhaust port 28 (third opening 85b) are formed on the side surface of the cylinder head, and an outlet of the second exhaust port 27 is formed. An outlet (second opening 84, that is, a collective exhaust outlet) of the combined exhaust port 27b is formed. That is, a total of three exhaust port outlets are lined up on the side surface of the cylinder head. The exhaust manifold 8 is provided with three exhaust passage inlets 81, 82, and 83 arranged in line in the cylinder row direction X to correspond to the three exhaust port outlets (see FIG. 4). The inlet 81 is connected to a first opening 85a, the inlet 82 is connected to a second opening 84, and the inlet 83 is connected to a third opening 85b.

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 a pair of branched exhaust ports for the cylinder 21. Assume that the exhaust ports are in communication.

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, this intake passage 3 is connected to 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 the air cleaner 32. A second intake passage 33 connected to the charger 5 is provided in this order from the upstream side.

Furthermore, as shown in FIG. 1, the intake passage 3 includes a third intake passage 34 connected to a second intake passage 33 via a turbocharger 5, and an intercooler that cools fresh air pressure-fed by the turbocharger 5. 35 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 each cylinder 21 of the multi-cylinder engine 2 toward the turbocharger 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. Note that the exhaust stroke order of the second cylinder 21b and the third cylinder 21c is not consecutive.

More specifically, as shown in FIG. The multi-cylinder engine 2 and the turbocharger 5 are connected to each other by a fourth independent exhaust passage 41b communicating with the fourth cylinder 21d and a collective exhaust passage 41c where the first independent exhaust passage 41a and the fourth independent exhaust passage 41b merge. are doing. The first independent exhaust passage 41a is connected to the first opening 85a, and the fourth independent exhaust passage 41b is connected to the third opening 85b.

As shown in FIG. 1, the second exhaust passage 42 is connected to the outlet of the combined exhaust port 27b, that is, the second opening 84, and communicates with the second cylinder 21b and the third cylinder 21c. The second exhaust passage 42 communicates the multi-cylinder engine 2 and the turbocharger 5.

Moreover, the turbocharger 5 is a twin scroll turbocharger, as shown in FIG. As shown in FIG. 1, this turbocharger 5 includes a turbine housing 5a that communicates independently with a first exhaust passage 41 and a second exhaust passage 42, and a second intake passage 33 and a third intake passage 34 connected to each other. and a compressor housing 5b. The turbine housing 5a has a first scroll portion 5a1 and a second scroll portion 5a2 that are independent from each other. The first exhaust passage 41 is connected to the first scroll part 5a1, and the second exhaust passage 42 is connected to the second scroll part 5a2.

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 the other end of the turbine shaft 52. The compressor wheel 53 is connected to the compressor wheel 53. A turbine wheel 51 is housed inside the turbine housing 5a, and a compressor wheel 53 is housed inside the compressor housing 5b. The exhaust gas flowing through the first exhaust passage 41 and the exhaust gas flowing through the second exhaust passage 42 are supplied to the turbine wheel 51 independently of each other. As mentioned above, the first exhaust passage 41 is connected to two cylinders that are not adjacent in the exhaust order, and the second exhaust passage 42 is also connected to two cylinders that are not adjacent in the exhaust order, so that this engine No exhaust interference occurs in the system. As a result, the lengths of the first exhaust passage and the second exhaust passage can be shortened. Therefore, it is possible to further downsize the engine system.

Note that the turbine housing 5a is not only composed of a portion that accommodates the turbine wheel 51, but also includes the first exhaust passage 41, the second exhaust passage 42, and a portion of the first EGR passage 61, which will be described later. It is formed in the turbine housing 5a (see the two-dot chain line in FIG. 1).

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, this EGR device 6 has a first EGR passage 61 and a second EGR passage 62 that take in exhaust gas as EGR gas, and a first EGR passage 61 and a second EGR passage 62 that merge into a multi-cylinder engine 2. A third EGR passage 63a and a fourth EGR passage 63b provided inside the multi-cylinder engine 2 are provided.

Further, the EGR device 6 includes a first EGR merging pipe 64 that connects the fourth EGR passage 63b and the fifth intake passage 38, an EGR valve 65, a second EGR merging pipe 66, an EGR cooler 67, and a third EGR merging pipe 68. There is.

The first EGR passage 61 connects the first exhaust passage 41 and the third EGR passage 63a. The second EGR passage 62 connects the second exhaust passage 42 and the third EGR passage 63a. The first EGR passage 61 is formed inside the exhaust manifold 8 and the turbine housing 5a, and the second EGR passage 62 is formed inside the exhaust manifold 8. Note that the first EGR passage 61 and the second EGR passage 62 will be described in detail later.

The third EGR passage 63a is formed inside the exhaust manifold 8 as a passage where EGR gas from the first EGR passage 61 and the second EGR passage 62 join together.

The fourth EGR passage 63b is formed inside the cylinder head 2a of the multi-cylinder engine 2 as a passage from the third EGR passage 63a. The fourth EGR passage 63b opens on the exhaust side side of the cylinder head 2a, and also opens on the intake side side. The opening on the exhaust side is an EGR inlet 63c, and the opening on the intake side is an EGR outlet 63d. The EGR inlet 63c is formed near the third opening 85b on the side surface of the cylinder head 2a. As illustrated in FIG. 4, an outlet 63e of a third EGR passage 63a is formed adjacent to the inlet 83 in the exhaust manifold 8 and is connected to the EGR inlet 63c. Here, the fourth cylinder 21d constitutes a specific cylinder that is located at one end of the cylinder row among the plurality of cylinders arranged in series, and whose third exhaust port 28 is adjacent to the EGR inlet 63c.

Furthermore, the fourth EGR passage 63b 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 fourth EGR passage 63b 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.

2 and 3 illustrate the external appearance of the exhaust manifold 8 and the turbine housing 5a attached to the side surface of the cylinder head 2a. The lower surface of the exhaust manifold 8 shown in FIG. 3 is an engine mounting surface that is attached to the side surface of the cylinder head 2a (not shown). The turbine housing 5a is fixed to an end surface of the exhaust manifold 8 on the opposite side to the engine mounting surface. The exhaust manifold 8 is interposed between the cylinder head 2a and the turbine housing 5a.

Next, an exhaust passage 4 connecting the multi-cylinder engine 2 and the turbocharger 5 described above, which is formed in the exhaust manifold 8 and the turbine housing 5a, and an exhaust passage 4 connected in the middle of the exhaust passage 4. The EGR passage will be described in further detail using FIGS. 5 to 9.

FIG. 5 is a diagram showing an exhaust passage and an EGR passage inside the exhaust manifold 8, and an exhaust passage and an EGR passage inside the turbine housing 5a. FIG. 5 shows a core used to form the exhaust passage and the EGR passage when casting the exhaust manifold 8, and a core used to form the exhaust passage and the EGR passage when casting the turbine housing 5a. It corresponds to a combination of children. Note that FIG. 5 is a diagram of the exhaust passage and the EGR passage when viewed from below in a state in which the exhaust manifold 8 and the turbine housing 5a are attached to the multi-cylinder engine 2, as shown in FIG. FIG. 6 is a cross section taken along line AA in FIG.

As described above, the exhaust passage 4 includes a first exhaust passage 41 that communicates with the first cylinder 21a and the fourth cylinder 21d, and a second exhaust passage 42 that communicates with the second cylinder 21b and the third cylinder 21c. It is configured.

Specifically, the first exhaust passage 41 includes a first independent exhaust passage 41a communicating with the first exhaust port 26, a fourth independent exhaust passage 41b communicating with the third exhaust port 28, and a first independent exhaust passage 41a. The multi-cylinder engine 2 and the turbocharger 5 are communicated through a collective exhaust passage 41c where the fourth independent exhaust passage 41b and the fourth independent exhaust passage 41b merge. The first independent exhaust passage 41a and the fourth independent exhaust passage 41b are each formed across the exhaust manifold 8 and the turbine housing 5a, and the collective exhaust passage 41c is formed in the turbine housing 5a. The collective exhaust passage 41c extends toward the turbine wheel 51 located on the back side in the direction perpendicular to the plane of the drawing in FIG. 5 or 6.

The second exhaust passage 42 is formed across the exhaust manifold 8 and the turbine housing 5a, and communicates between the multi-cylinder engine 2 and the turbocharger 5. Further, the second exhaust passage 42 is formed to be sandwiched between the first independent exhaust passage 41a and the fourth independent exhaust passage 41b. The second exhaust passage 42 extends independently of the collective exhaust passage 41c toward the turbine wheel 51 arranged on the back side in the direction perpendicular to the plane of the drawing in FIG. 5 or 6.

Next, the EGR passage formed in the exhaust manifold 8 and the turbine housing 5a will be described in detail using FIGS. 5 to 9.

First, the first EGR take-out part 61a of the first EGR passage 61, that is, the connection part between the first EGR passage 61 and the first exhaust passage 41, communicates with the exhaust port of each cylinder of the first cylinder group of the first exhaust passage 41. In particular, the fourth independent exhaust passage 41b is provided at the downstream end of the fourth independent exhaust passage 41b, which is connected to the third opening 85b adjacent to the EGR inlet 63c of the cylinder head 2a. In addition, in FIG. 6, the position of the first EGR extraction part 61a is shown virtually. That is, the first EGR take-out part 61a is located near the collective exhaust passage 41c, and the first EGR take-out part 61a is located away from the side surface of the cylinder head 2a. The first EGR extraction portion 61a is provided in the turbine housing 5a. The first EGR take-out portion 61a and the side surface of the cylinder head 2a are separated from each other in the vertical direction in the paper of FIG. 5 or 6.

Here, FIG. 7 shows a cross section taken along line B-B in FIG. 2, and by providing the first EGR take-out part 61a at the downstream end of the fourth independent exhaust passage 41b, it is possible to place the first EGR take-out part 61a at the downstream end of the fourth independent exhaust passage 41b. The EGR gas can be taken out from the area where the cross-sectional area of the exhaust passage is large and the amount of heat dissipated is high. It is possible to improve the amount of heat dissipated from the EGR gas sent from the first exhaust passage 41 to the EGR inlet 63c through the first EGR take-out portion 61a.

The second EGR take-out portion 62a of the second EGR passage 62, that is, the connection portion between the second EGR passage 62 and the second exhaust passage 42 is provided within the exhaust manifold 8. In addition, in FIG. 6, the second EGR extraction section 62a is shown virtually. The second EGR take-out portion 62a is located relatively close to the side surface of the cylinder head 2a.

The first EGR passage 61 extends within the turbine housing 5a from a position away from the side surface of the cylinder head 2a in a direction toward the side surface of the cylinder head 2a. A downstream end of the first EGR passage 61 extends into the exhaust manifold 8.

The second EGR passage 62 extends in the cylinder row direction X in the exhaust manifold 8 from a position away from the EGR inlet 63c so as to approach the EGR inlet 63c.

Further, as shown in FIG. 5, the first EGR passage 61 and the second EGR passage 62 merge into a third EGR passage 63a provided in the exhaust manifold 8, and flow into an EGR inlet 63c that opens on the side surface of the cylinder head 2a. It's communicating.

Here, in the middle of the first EGR passage 61, a first throttle part 70 is formed which has a smaller passage cross-sectional area than the parts before and after it. The first aperture portion 70 will be explained using FIG. 8, which is a cross section taken along the line CC in FIG.

The first throttle portion 70 is formed in the turbine housing 5a. More specifically, the first throttle portion 70 is provided near the attachment surface of the turbine housing 5a to the exhaust manifold 8. The surface area of the first EGR passage 61 expands between the first throttle part 70 and the third EGR passage 63a.

By providing the first constricted part 70 in the first EGR passage 61 in this way, the surface area of the passage is expanded from the first constricted part 70 of the first EGR passage 61 to the third EGR passage 63a, thereby increasing the efficiency of heat dissipation. It can be raised.

Similarly, a second constricted portion 71 having a smaller passage cross-sectional area than the portions before and after the second EGR passage 62 is also formed in the middle of the second EGR passage 62. The second aperture portion 71 will be explained using FIG. 9, which is a cross section taken along the line EE in FIG. The second constriction portion 71 is formed in the exhaust manifold 8. More specifically, the second throttle part 71 is provided in the middle part of the second EGR passage 62 that extends diagonally downward from the second exhaust passage 42 toward the third EGR passage 63a.

By providing the second constricted part 71 in the second EGR passage 62 in this way, the surface area of the passage is expanded from the second constricted part 71 of the second EGR passage 62 to the third EGR passage 63a, thereby increasing the efficiency of heat dissipation. It can be raised.

Further, the second EGR passage 62 will be described in detail using FIGS. 1 and 9.

Exhaust gas discharged from the second opening 84 of the second exhaust port 27 branches within the exhaust manifold 8, passes through the second EGR passage 62, and returns to the cylinder head 2a. The passage length of the second EGR passage 62 is shorter than that of the first EGR passage 61 connected to the first exhaust passage 41, and the second opening 84 is located at a position apart from the third opening 85b from the EGR inlet 63c. In addition, by arranging the second EGR passage 62 outside the cylinder head 2a, the thermal load on the cylinder head 2a can be reduced, and at the same time, the length of the second EGR passage 62 can be minimized.

Next, the flow of EGR gas and the flow of heat transmitted to the EGR inlet 63c of the cylinder head 2a will be described in detail using FIG.

With respect to the flow direction of exhaust gas discharged from the first exhaust port 26 and the third exhaust port 28 and directed toward the turbocharger 5 through the first exhaust passage 41, the EGR introduced into the first EGR passage 61 from the first EGR extraction part 61a is , is introduced into a third EGR passage 63a forming a passage that joins EGR gas from a second EGR passage 62 formed in the exhaust manifold 8, and communicates with a fourth EGR passage 63b in the cylinder head 2a.

The EGR inlet 63c is most susceptible to heat conduction from the exhaust manifold heated by exhaust heat from the third opening 85b adjacent to the cylinder row direction X, and is connected to the second opening 84, the first opening 85a, and the cylinder row. As the distance increases in the direction X, the heat conduction to the EGR inlet 63c becomes weaker.

For example, if the third opening 85b is directly connected to the EGR inlet 63c through the shortest route, the high temperature EGR gas and the heat of the exhaust manifold 8 will cause an excessive temperature rise at the EGR inlet 63c.

Therefore, as shown by the black arrow in FIG. 5, the EGR gas passing through the first EGR passage 61 communicating with the first exhaust passage 41 is discharged from the third opening 85b and flows into the downstream end of the fourth independent exhaust passage 41b. After flowing to the first EGR passage 61 from the first EGR take-out portion 61a, the EGR passage 61 returns to the cylinder head 2a. This increases the passage length and increases the surface area of the passage, making it possible to return the EGR gas whose temperature has dropped to the cylinder head 2a side. Furthermore, since the downstream end of the first EGR passage 61 where the outlet is provided is located near the collective exhaust passage 41c with the first independent exhaust passage 41a, the exhaust from the first independent exhaust passage 41a is also treated as EGR gas and the temperature is lowered. It can be returned to the cylinder head 2a while being lowered.

Further, although the second EGR passage 62 communicating with the second exhaust passage 42 is connected to the second exhaust passage 42 at a position close to the cylinder head 2a, the second exhaust passage 42 is connected from the EGR inlet 63c to the cylinder row. It is far away in direction X. Therefore, the EGR gas passing through the second EGR passage 62 flows over a relatively long distance from the second EGR passage 62 along the third EGR passage 63a, as shown by the white arrow in FIG. As a result, the EGR gas whose temperature has decreased can be allowed to flow into the EGR inlet 63c.

According to such a configuration, the turbocharged engine 1 can increase the amount of heat dissipated by increasing the total length of the first EGR passage 61, and at the same time, by minimizing the length of the second EGR passage 62, the amount of heat dissipated can be increased. It is possible to suppress the increase in size. This makes it possible to both reduce the size of the EGR passage, which requires two passages because of the twin-scroll turbocharger, and to reduce the heat load on the EGR inlet.

Note that in the engine system, the second exhaust port 27 has two independent exhaust ports 27a that communicate independently with the second cylinder 21b and the third cylinder 21c, and two independent exhaust ports 27a with the outside. The second exhaust passage 42 is constituted by one passage connected to the second opening 84 of the combined exhaust port 27b. Differently from this, the exhaust port of the second cylinder 21b and the exhaust port of the third cylinder 21c may be provided independently. In this configuration, the second exhaust passage, like the first exhaust passage 41, includes two independent exhaust passages connected to the respective exits of the two exhaust ports, and a collective exhaust passage where the two independent exhaust passages merge. and will have. Note that the second EGR extraction portion may be provided in the collective exhaust passage, or may be provided in either one of the two independent exhaust passages.

In this case, the passage length between the first EGR extraction part and the exhaust port of the specific cylinder (that is, the fourth cylinder 21d) is equal to the passage length between the second EGR extraction part and the exhaust port of the second cylinder 21b, and , the passage length may be longer than the maximum passage length among the passage lengths between the second EGR extraction part and the exhaust port of the third cylinder 21c.

1...Turbocharged engine 2...Multi-cylinder engine 5...Turbocharger 21...Cylinder 21a...First cylinder 21b...Second cylinder 21c...Third cylinder 21d...Fourth cylinder 27a...Independent exhaust port 27b...Combined exhaust port 41... First exhaust passage 41a...First independent exhaust passage 41b...Fourth independent exhaust passage 41c...Combined exhaust passage 42...Second exhaust passage 42a...Second independent passage section 42b...Third independent passage section 42c...Second merging passage section 61...First EGR passage 62...Second EGR passage 63a...Third EGR passage 63b...Fourth EGR passage 70...First throttle part 71...Second throttle part 84...Second opening (collective exhaust outlet)

Claims (5)

A twin scroll turbocharger having a first scroll part and a second scroll part, and a first cylinder group including a plurality of cylinders including a specific cylinder located at one end of the cylinder row among the plurality of cylinders arranged in series. , and a second cylinder group constituted by the remaining cylinders, the engine system includes:
a first exhaust passage that communicates the exhaust port of each cylinder of the first cylinder group with the first scroll portion;
a second exhaust passage that communicates the exhaust port of each cylinder of the second cylinder group with the second scroll portion;
a first EGR passage provided in the first exhaust passage, one end of which communicates with the first exhaust passage;
a second EGR take-out portion provided in the second exhaust passage, a second EGR passage whose one end communicates with the second exhaust passage;
The other end of the first EGR passage and the other end of the second EGR passage communicate with each other at one end thereof, and are connected to an exhaust port of the specific cylinder in the cylinder head, the inlet of the EGR passage provided in the cylinder head. further comprising a third EGR passage whose other end communicates with the EGR inlet provided at a position adjacent to the
The passage length between the first EGR extraction part and the exhaust port of the specific cylinder is the maximum passage length among the passage lengths between the second EGR extraction part and the exhaust port of each cylinder of the second cylinder group. An engine system that is characterized by a longer length. The first cylinder group is composed of cylinders whose exhaust strokes are not adjacent to each other among the plurality of cylinders,
The engine system according to claim 1, wherein the second cylinder group is comprised of a group of cylinders whose exhaust strokes are not adjacent to each other among the plurality of cylinders. The first exhaust passage includes a plurality of independent exhaust passages communicating with exhaust ports of each cylinder of the first cylinder group, and a collective exhaust passage connected downstream of each of the plurality of independent exhaust passages, and the first exhaust passage 3. The engine system according to claim 1, wherein the take-out part is provided at a downstream end of an independent exhaust passage that communicates with an exhaust port of the specific cylinder among the plurality of independent exhaust passages. A collective exhaust outlet communicating with all cylinders of the second cylinder group is provided in the cylinder head, an upstream end of the second exhaust passage is connected to the collective exhaust outlet, and the second EGR take-out portion is connected to the second exhaust passage. The engine system according to claim 1, wherein the engine system is provided at an upstream end of the exhaust passage. The first EGR passage has a first constriction part in the middle thereof, the passage cross-sectional area being reduced;
The engine system according to any one of claims 1 to 4, wherein the second EGR passage has a second constriction portion having a reduced passage cross-sectional area in the middle thereof.

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