JP2021161941A - Intake device for multi-cylinder engine - Google Patents

Abstract

To provide an intake device for multi-cylinder engine capable of suppressing air-fuel ratio variation between cylinders.SOLUTION: An intake device for multi-cylinder engine includes: a surge tank including an intake air introduction port connected to an intake passage for supplying combustion air to a multi-cylinder engine; and a plurality of branch passages connected respectively to combustion chambers of the plurality of cylinders from the surge tank via an intake valve. At the surge tank, the intake air introduction port is provided at a portion close to the branch passage of the center of the row of the plurality of branch passages arranged in one row so as to correspond to the cylinder row, and the passage volume of the branch passage closest to the intake air introduction port is set to be larger than the passage volume of the other branch passages.SELECTED DRAWING: Figure 4

Description

The present invention relates to an intake device for a multi-cylinder engine, and more particularly to an intake device for a multi-cylinder engine having a supercharger and an intercooler in the intake passage.

Conventionally, a multi-cylinder engine is equipped with a supercharger in order to improve engine output while improving fuel efficiency. The air that has been compressed by the supercharger and whose temperature has risen through the intake passage is cooled by the intercooler and supplied to the surge tank. Then, air is supplied to the engine from the surge tank through the branch passage connected to the intake port of each cylinder.

In an engine equipped with a supercharger, the volume of the surge tank is reduced in order to improve the responsiveness when increasing the intake air amount. However, it is known that when the volume of the surge tank is reduced, variations in the air-fuel ratio between cylinders are likely to occur.

Therefore, for example, in Patent Document 1, in a V-type 6-cylinder engine, a protrusion for suppressing the air flow rate of two air outlets near the intake inlet in a small-volume surge tank arranged between banks. Is provided. As a result, at the two air outlets near the intake inlet where the air flow rate is usually larger than that of the other air outlets, the air flow rate is suppressed to suppress the variation in the air flow rate between the cylinders, and the air-fuel ratio between the cylinders is suppressed. The variation is suppressed.

Japanese Unexamined Patent Publication No. 2017-20383

On the other hand, the passage length from the intercooler to the surge tank and the branch passage from the surge tank to the intake port of each cylinder so that the cooling effect of the air supplied to the engine through the supercharger by the intercooler does not decrease. The passage length is set short.

Here, in the engine operating region where the boost pressure by the supercharger is low or hardly acts, the timing of the intake valve that opens and closes the intake port is set in the exhaust stroke, intake stroke, and compression stroke of each cylinder in the engine cycle. Depending on the situation, burnt gas or a mixture of air and fuel may be blown back from the cylinder to the surge tank via the branch passage. At this time, the burnt gas blown back to the surge tank is taken into the same cylinder, but the air-fuel mixture blown back to the surge tank is taken into the next intake stroke together with the air supplied to the surge tank. Is inhaled to.

In particular, the air-fuel mixture blown back from the branch passage closest to the intake inlet on the upstream side of the intake air is blown back to the air flow path to the other cylinders, so that the air-fuel mixture is taken into the other cylinders that will be the next intake stroke. NS. On the other hand, the air-fuel mixture blown back from the other cylinders is hardly sucked into the cylinder to which the branch passage is connected closest to the intake inlet. Therefore, it is not preferable because the air-fuel ratio varies between cylinders.

An object of the present invention is to provide an intake device for a multi-cylinder engine capable of suppressing variations in air-fuel ratio between cylinders.

The intake device of the multi-cylinder engine according to the first aspect of the present invention includes a surge tank provided with an intake intake port connected to an intake passage for supplying combustion air to the multi-cylinder engine, and a combustion chamber of a plurality of cylinders from the surge tank. In the intake device of a multi-cylinder engine having a plurality of branch passages each connected via an intake valve, the surge tank is provided with one of the plurality of branch passages arranged in a row so as to correspond to the cylinder row. The intake intake port is provided at a portion near the branch passage in the center of the row, and the passage volume of the branch passage closest to the intake introduction port is set to be larger than the passage volume of the other branch passages.

According to the above configuration, a mixture of combustion air and fuel blown back to the intake side from the cylinder to which the branch passage having a large passage volume is connected until the intake valve is closed is introduced into the branch passage of this cylinder. Can be stopped. Therefore, when the cylinder to which the other branch passage is connected takes in the air, the amount of the air-fuel mixture that is taken in together with the air supplied from the intake inlet is reduced. Further, the air-fuel mixture retained in the branch passage is sucked into the cylinder to which the branch passage is connected in the next intake stroke. Therefore, it is possible to suppress variations in the air-fuel ratio between cylinders.

In the invention of claim 1, the intake device of the multi-cylinder engine according to the second aspect of the present invention has the passage length of the branch passage closest to the intake inlet set longer than the passage length of the other branch passages. It is a feature.
According to the above configuration, the passage volume can be increased by lengthening the branch passage closest to the intake inlet, and the variation in the air-fuel ratio between the cylinders can be suppressed.

In the intake device of the multi-cylinder engine according to the third aspect of the present invention, in the first aspect of the present invention, the passage cross-sectional area of the branch passage closest to the intake inlet is set to be larger than the passage cross-sectional area of the other branch passages. It is characterized by that.
According to the above configuration, the passage volume can be increased by increasing the passage cross-sectional area of the branch passage closest to the intake inlet, and the air-fuel ratio variation between cylinders can be suppressed.

The intake device of the multi-cylinder engine according to the fourth aspect of the present invention is characterized in that, in the invention of any one of the first to third aspects, the intake passage is provided with an intercooler and a supercharger.
According to the above configuration, in a multi-cylinder engine with a supercharger in which the passage length of the branch passage is set short to prevent knocking, it is possible to suppress variations in the air-fuel ratio between cylinders even if the branch passage is short.

In the invention of any one of claims 1 to 4, the intake device of the multi-cylinder engine of the invention of claim 5 is the in-line 6-cylinder engine, and the two branches closest to the intake inlet. The passages are connected to the combustion chambers of the two cylinders in the center of the corresponding cylinder row, respectively, and the passage volume up to the connection of these two branch passages to the intake port is up to the connection of the other branch passages to the intake port. It is characterized in that it is set to 1.08 to 1.2 times the passage volume.
According to the above configuration, it is possible to increase the passage volume of the two branch passages closest to the intake intake port and suppress the variation in the air-fuel ratio between the cylinders under various engine driving conditions.

In the invention of any one of claims 1 to 4, the intake device of the multi-cylinder engine of the invention of claim 6 is the in-line 6-cylinder engine, and the two branches closest to the intake inlet. The passages are connected to the combustion chambers of the two cylinders in the center of the corresponding cylinder row, respectively, and the passage volume to the connection part of these two branch passages to the intake port is up to the connection part to the intake port of the other branch passage. It is characterized in that it is set to 1.1 to 1.15 times the passage volume.
According to the above configuration, the passage volume of the two branch passages closest to the intake intake port can be increased to further suppress the variation in the air-fuel ratio between the cylinders under various engine driving conditions.

According to the intake device of the multi-cylinder engine of the present invention, it is possible to suppress variations in the air-fuel ratio between cylinders.

It is a figure which shows the intake system and the exhaust system of the engine which concerns on embodiment of this invention. It is external perspective view of the surge tank provided with the branch pipe which concerns on embodiment of this invention. It is a side view of the surge tank of FIG. It is explanatory drawing which shows an example inside the intake device of a multi-cylinder engine. It is explanatory drawing of the engine cycle in the adjacent cylinder. It is explanatory drawing of the flow of air and an air-fuel mixture in an adjacent cylinder. It is a figure which shows the relationship between the passage volume ratio of a branch pipe, and the air-fuel ratio variation under different engine driving conditions. It is explanatory drawing which shows the other example inside the intake device of a multi-cylinder engine.

Hereinafter, modes for carrying out the present invention will be described. The following description of preferred embodiments is merely exemplary and is not intended to limit the invention, its applications or its uses.

As shown in FIG. 1, the vehicle is supplied with a multi-cylinder engine 1 that generates driving force (here, an in-line 6-cylinder engine. Only one cylinder is shown in FIG. 1) and a multi-cylinder engine 1 is supplied with combustion air. The intake system 2 is equipped with an exhaust system 2 for discharging the exhaust gas discharged from the multi-cylinder engine 1 to the outside of the vehicle, a turbo supercharger 4 and the like. A mechanical turbocharger may be installed instead of the turbocharger 4.

The multi-cylinder engine 1 has a cylinder block 10 having a plurality of cylinders, a cylinder head 11 arranged on the upper side of the cylinder block 10, an oil pan 12 arranged on the lower side of the cylinder block 10, and the like. Pistons 14 are inserted into the plurality of cylinders so as to be reciprocating, and a combustion chamber 15 is formed for each cylinder by the top surface of the piston 14, the side wall of the cylinder (the side wall of the cylinder of the cylinder block 10), and the lower surface of the cylinder head 12. ing.

The piston 14 is connected to the crankshaft 17, which is the output shaft of the multi-cylinder engine 1, via a connecting rod 16. The crankshaft 17 is rotated by the reciprocating movement of the piston 14.

The cylinder head 11 is provided with an intake port 18 and an exhaust port 19 for each cylinder, and is equipped with an intake valve 20 for opening and closing the intake port 18 and an exhaust valve 21 for opening and closing the exhaust port 19, respectively. Further, the cylinder head 11 is equipped with a fuel injection valve 22 for supplying fuel of a fuel tank (not shown) into the combustion chamber 15 for each cylinder.

The intake system 2 includes an intake passage 5 for supplying combustion air, a surge tank 6 connected to the intake downstream end of the intake passage 5, and a plurality of surge tanks 6 connected to the intake ports 18 of a plurality of cylinders. It has a branch pipe 7 and the like. The surge tank 6 and the plurality of branch pipes 7 are formed so as to be integrated with each other by, for example, a synthetic resin material. The plurality of branch pipes 7 and the corresponding intake ports 18 form a plurality of branch passages connected to the plurality of combustion chambers 15 of the multi-cylinder engine 1 via the intake valve 20. The intake device 8 of the multi-cylinder engine has a surge tank 6 and a plurality of branch passages.

In the intake passage 5, an air cleaner 23, a compressor 4a of the turbocharger 4, a throttle valve 24, and an intercooler 25 are arranged in this order from the intake upstream side. The intercooler 25 cools the air compressed by the compressor 4a and whose temperature has risen, and supplies the air to the surge tank 6.

The exhaust system 3 has an exhaust passage 26 including an exhaust manifold connected to each of the exhaust ports 19 of a plurality of cylinders, a turbine 4b of a turbocharger 4 arranged in the exhaust passage 26, and the like. The turbocharger 4 is configured such that the turbine 4b is rotated by the exhaust gas (burned gas) flowing in the exhaust passage 26, and the compressor 4a is rotationally driven by the rotation of the turbine 4b. Then, the compressed air is supplied to the downstream side of the intake air by the rotation of the compressor 4a.

The high-pressure EGR passage 27 branches from the exhaust passage 26 on the exhaust upstream side of the turbine 4b and is connected to the intake passage 5 on the intake downstream side of the intercooler 25. The high-pressure EGR passage 27 has a high-pressure EGR valve 28 and the like for adjusting the amount of recirculation of the burnt gas. Hereinafter, the multi-cylinder engine 1 will be described assuming that the # 1 cylinder to the # 6 cylinder are arranged in order from the left side when viewed from the intake port 18 side.

As shown in FIGS. 2 and 3, in the surge tank 6 provided with the plurality of branch pipes 7, the branch pipes 7a to 7f corresponding to the # 1 cylinder to the # 6 cylinder are provided from the surge tank 6 extending in the direction of the cylinder row. It is extending. The connection portions 8a of the plurality of branch pipes 7a to 7f to the intake port 18 of the plurality of cylinders are integrated so as to be easily and surely fixed to the cylinder head 11. Although not shown, the connecting portion 8a is formed so that a plurality of branch pipes 7a to 7f are branched to correspond to a plurality of (for example, two) intake ports 18 possessed by one cylinder.

The intake downstream end of the intake passage 5 is connected to the lower part of the surge tank 6 on the side opposite to the side where the plurality of branch pipes 7a to 7f are lined up. A connection portion of the high-pressure EGR passage 27 is provided in the vicinity of the connection portion of the intake passage 5. An intercooler 25 is arranged near the lower side of the surge tank 6 to shorten the passage length from the intercooler 25 to the surge tank 6.

FIG. 4 schematically shows an internal passage of an intake device 8 of a multi-cylinder engine having a surge tank 6 and a plurality of branch passages 9a to 9f. The inside of the surge tank 6 communicates with the intake passage 5 via the intake inlet 6a, and the intake valve is connected to the combustion chamber 15 of the cylinder corresponding to the plurality of branch passages 9a to 9f (branch pipes 7a to 7f and the intake port 18). Communicate with each other via 20 (see FIG. 1). The intake inlet 6a is provided at a portion corresponding to the center of the row of the branch pipes 7a to 7f arranged in a row so that the distance from the intake inlet 6a to the plurality of branch pipes 7a to 7f is shortened.

As shown in FIG. 5, the # 1 to # 6 cylinders of the multi-cylinder engine 1 are in a predetermined order (for example, # 1 cylinder → # 5 cylinder → # 3 cylinder → # 6 cylinder → # 2 cylinder → # 4 cylinder). Burn the fuel with. In the engine cycle, after combustion is an expansion stroke, and after the expansion stroke, the exhaust stroke, the intake stroke, and the compression stroke are passed in order, and then the next combustion is performed.

For example, when the # 4 cylinder is in the intake stroke, the # 5 cylinder shifts from the expansion stroke to the exhaust stroke. Then, when the # 4 cylinder is in the compression stroke, the # 5 cylinder shifts from the exhaust stroke to the intake stroke. When the # 4 cylinder shifts from the exhaust stroke to the intake stroke, the valve timing is such that the open state of the exhaust valve 21 shown by the curve EV and the open state of the intake valve 20 shown by the curve IV overlap for a short time. Is set. As a result, a part of the burnt gas is once blown back to the surge tank 6 side due to the high in-cylinder pressure, and is again sucked into the combustion chamber 15 in the intake stroke.

As shown in FIGS. 5 and 6, in the intake stroke, the # 4 cylinder takes in air from the surge tank 6 through the branch passage 9d, fuel is injected from the fuel injection valve 22, and the air-fuel mixture is injected into the combustion chamber 15. M is generated. Then, when shifting to the compression stroke, a part of the air-fuel mixture M is blown back to the surge tank 6 side by the rise of the piston 14 before the intake valve 20 is closed. The air-fuel mixture M that has been blown back remains in the branch passage 9d after the intake valve 20 is closed, and is taken in at the next intake stroke of the # 4 cylinder. However, a part of the air-fuel mixture M that has been blown back returns to the surge tank 6 and is sucked into the # 5 cylinder that shifts to the intake stroke together with the air supplied from the intake inlet 6a.

In this way, part of the fuel injected in the # 4 cylinder will move to the # 5 cylinder, and the air-fuel ratio of the # 4 cylinder will increase and the air-fuel ratio of the # 5 cylinder will decrease, resulting in variations in the air-fuel ratio between the cylinders. Becomes larger. Since the branch pipe 7d of the branch passage 9d of the # 4 cylinder is closest to the intake inlet 6a on the upstream side of the intake air, the air-fuel mixture of the other cylinders is hardly taken into the # 4 cylinder. Similarly, in the # 3 and # 2 cylinders, part of the fuel injected in the # 3 cylinder will move to the # 2 cylinder, and the air-fuel ratio of the # 3 cylinder will increase and the air-fuel ratio of the # 2 cylinder will increase. Becomes smaller and the air-fuel ratio variation between cylinders becomes larger.

Therefore, the passage volume of the branch passages 9c and 9d having the branch pipes 7c and 7d of the # 3 cylinder and the # 4 cylinder provided closer to the intake inlet 6a than the branch pipes 7a, 7b, 7e and 7f is set to the branch pipe 7a. , 7b, 7e, 7f are set to be larger than the passage volume of the branch passages 9a, 9b, 9e, 9f. As a result, the air-fuel mixture blown back from the # 3 and # 4 cylinders is kept in the branch passages 9c and 9d more than the cylinders other than these, and the air-fuel mixture returning to the surge tank 6 is reduced.

As shown in FIG. 4, the branch passages 9c and 9d of the # 3 and # 4 cylinders can have a larger passage volume by making the passage length longer than the other branch passages 9a, 9b, 9e and 9f. In this case, the passage volume can be easily increased by lengthening the branch pipes 7c and 7d, but the intake port 18 of the # 3 and # 4 cylinders may be lengthened. Further, as shown in FIG. 8, the branch passages 9c and 9d of the # 3 and # 4 cylinders have a larger passage cross-sectional area as they approach the surge tank 6 than the other branch passages 9a, 9b, 9e and 9f. The passage volume can be increased by setting the width and height. In this case, the passage volume can be easily increased by increasing the passage cross-sectional area of the branch pipes 7c and 7d, but even if the passage cross-sectional area of the intake ports 18 of the # 3 and # 4 cylinders is also increased. good.

FIG. 7 shows the passage volume ratio and the air-fuel ratio variation ΔA / obtained by dividing the passage volumes of the branch pipes 7c and 7d of the # 3 and # 4 cylinders by the average value of the passage volumes of the other branch pipes 7a, 7b, 7e and 7f. The result of evaluating the relationship of F in a plurality of engine driving states in which the engine speed and the boost pressure are different is shown. The air-fuel ratio variation ΔA / F is the difference between the maximum value and the minimum value of the air-fuel ratios of the # 1 to # 6 cylinders. The straight line UL indicates the upper limit of the allowable air-fuel ratio variation, and the upper limit of the air-fuel ratio variation is set smaller for a multi-cylinder engine that requires precise combustion control.

Depending on the engine driving state, the air-fuel ratio variation is sensitively affected by the passage volume ratio, but at least the passage volume ratio is in the range of 1.08 to 1.2, that is, the branch pipes 7c and 7d of # 3 and # 4 cylinders. By setting the passage volume to 1.08 to 1.2 times the average value of the passage volumes of the other branch pipes 7a, 7b, 7e, 7f, the air-fuel ratio variation was set regardless of the engine driving state. It can be suppressed below the upper limit. By setting the passage volume ratio of the branch pipe in the range of 1.1 to 1.15, the variation in the air-fuel ratio can be further suppressed.

When increasing the passage volume by increasing the passage length, as shown in FIG. 4, the branch passages 9c and 9d of the # 3 and # 4 cylinders from the surge tank 6 are branched into other branch passages 9a and 9b. , 9e, 9f are separated from the combustion chamber 15 and the passage lengths of the branch passages 9c and 9d (branch pipes 7c and 7d) are set to be longer by, for example, about 5 to 6 mm.

When the passage volume is increased by increasing the passage cross-sectional area, as shown in FIG. 8, the branch passages 9c and 9d at the branch portion ( The passage width and passage height of the branch pipes 7c and 7d) are set larger than those of the other branch passages 9a, 9b, 9e and 9f, and the branch pipes 7c and 7d are connected smoothly from the branch to the intake port 18 side. Form.

The operation and effect of the intake device 8 of the multi-cylinder engine of the above embodiment will be described.
The intake device 8 of the multi-cylinder engine has a surge tank 6 provided with an intake inlet 6a connected to an intake passage 5 for supplying combustion air, and an intake valve 20 from the surge tank 6 to a combustion chamber 15 of a plurality of cylinders. It has a plurality of branch passages 9a to 9f connected via each. In the surge tank 6, among a plurality of branch pipes 7a to 7f arranged in a row so as to correspond to the cylinder row, the portion closest to the branch pipes 7c and 7d of the # 3 and # 4 cylinders on the center side of the row. Is provided with an intake inlet 6a. The passage volume of the branch passages 9c and 9d having the branch pipes 7c and 7d closest to the intake inlet 6a is set to be larger than the passage volumes of the other branch passages 9a, 9b, 9e and 9f.

Since the branch passages 9c and 9d connected to the # 3 and # 4 cylinders have a large passage volume, the air-fuel mixture blown back from the # 3 and # 4 cylinders to the surge tank 6 side by the time the intake valve 20 is closed is supplied. It can be kept in each of the branch passages 9c and 9d. Therefore, when the # 1, # 2, # 5, and # 6 cylinders to which the other branch passages 9a, 9b, 9e, and 9f are connected take in the air, they are taken in together with the air supplied from the intake inlet 6a. The amount of air-fuel mixture blown back from the 3rd and # 4 cylinders is reduced. Further, the air-fuel mixture retained in the branch passages 9c and 9d is sucked into the # 3 and # 4 cylinders to which the branch passages 9c and 9d are connected, respectively, in the next intake stroke of the # 3 and # 4 cylinders. Therefore, the condition where the fuel in the # 3 and # 4 cylinders is low is improved, and the air-fuel ratio variation between the cylinders can be suppressed because the air-fuel mixture of the # 3 and # 4 cylinders taken in by the other cylinders is reduced. can.

In order to increase the passage volume of the branch passages 9c and 9d connected to the # 3 and # 4 cylinders, the passage length of the branch passages 9c and 9d closest to the intake inlet 6a is changed to the other branch passages 9a, 9b and 9e. , 9f is set longer than the passage length. Alternatively, the passage cross-sectional area of the branch passages 9c and 9d closest to the intake inlet 6a is set to be larger than the passage cross-sectional area of the other branch passages 9a, 9b, 9e and 9f. Therefore, the passage volume of the branch passages 9c and 9d closest to the intake intake port 6a can be increased to suppress the variation in the air-fuel ratio between the cylinders.

The intake passage 5 is equipped with an intercooler 25 and a turbocharger 4. In the multi-cylinder engine 1 with a supercharger, the passage lengths of the branch passages 9a to 9f are set short so that the intake air temperature does not rise in order to prevent knocking. Therefore, the air-fuel ratio variation between the cylinders is likely to occur due to the intake of the air-fuel mixture of the other cylinders, but the passage volumes of the branch passages 9c and 9d closest to the intake introduction port 6a are set to the other branch passages 9a and 9b. By making it larger than the passage volume of 9e and 9f, it is possible to suppress the variation in the air-fuel ratio between cylinders even in a short branch passage.

The multi-cylinder engine 1 is an in-line 6-cylinder engine, and is located in the combustion chambers 15 of the two cylinders (# 3, # 4 cylinders) in the center of the cylinder row corresponding to the two branch passages 9c and 9d closest to the intake inlet 6a, respectively. It is connected. The passage volume of these branch passages 9c and 9d to the connection portion 8a to the intake port 18 (passage volume of the branch pipes 7c and 7d) is the connection portion to the intake port 18 of the other branch passages 9a, 9b, 9e and 9f. It is set to 1.08 to 1.2 times the average value of the passage volume up to 8a (passage volume of branch pipes 7a, 7b, 7e, 7f). As a result, the passage volumes of the two branch passages 9c and 9d closest to the intake intake port 6a can be increased, and the air-fuel ratio variation between the cylinders can be suppressed to a certain level or less under various engine driving conditions. In particular, the passage volume of the branch passages 9c and 9d to the connection portion 8a to the intake port 18 is relative to the average value of the passage volume of the other branch passages 9a, 9b, 9e and 9f to the connection portion 8a to the intake port 18. When the value is set to 1.1 to 1.15 times, the variation in the air-fuel ratio between cylinders can be suppressed more effectively.

The multi-cylinder engine 1 may be a 5-cylinder or more in-line engine or a V-type engine. In addition, a person skilled in the art can carry out the embodiment in a form in which various modifications are added to the above embodiment without deviating from the gist of the present invention, and the present invention also includes such modified forms.

1: Multi-cylinder engine 2: Intake system 3: Exhaust system 4: Turbo turbocharger 4a: Compressor 4b: Turbine 5: Intake passage 6: Surge tank 6a: Intake inlet 7 (7a to 7f): Branch pipe 8: Many Cylinder engine intake devices 9a to 9f: Branch passage 10: Cylinder block 11: Cylinder head 12: Oil pan 14: Piston 15: Combustion chamber 16: Connecting rod 17: Crank shaft 18: Intake port 19: Exhaust port 20: Intake valve 21: Exhaust valve 22: Fuel injection valve 23: Air cleaner 24: Throttle valve 25: Intercooler 26: Exhaust passage 27: High pressure EGR passage 28: High pressure EGR valve

Claims (6)

A surge tank equipped with an intake intake port connected to an intake passage that supplies combustion air to a multi-cylinder engine, and a plurality of branch passages that are connected to the combustion chambers of the multiple cylinders from the surge tank via an intake valve. In the intake system of a multi-cylinder engine with
The surge tank is provided with the intake inlet at a portion of the plurality of branch passages arranged in a row so as to correspond to the cylinder row, near the branch passage in the center of the row.
An intake device for a multi-cylinder engine, characterized in that the passage volume of the branch passage closest to the intake inlet is set to be larger than the passage volume of the other branch passage. The intake device for a multi-cylinder engine according to claim 1, wherein the passage length of the branch passage closest to the intake intake port is set longer than the passage length of the other branch passage. The intake device for a multi-cylinder engine according to claim 1, wherein the passage cross-sectional area of the branch passage closest to the intake intake port is set to be larger than the passage cross-sectional area of the other branch passage. The intake device for a multi-cylinder engine according to any one of claims 1 to 3, wherein the intake passage is provided with an intercooler and a supercharger. The multi-cylinder engine is an in-line 6-cylinder engine.
The two branch passages closest to the intake inlet are connected to the combustion chambers of the two cylinders in the center of the corresponding cylinder row, respectively, and the passage volume of these two branch passages to the connection to the intake port is the other branch. The intake of the multi-cylinder engine according to any one of claims 1 to 4, wherein the intake is set to 1.08 to 1.2 times the volume of the passage to the connection portion of the passage to the intake port. Device. The multi-cylinder engine is an in-line 6-cylinder engine.
The two branch passages closest to the intake inlet are connected to the combustion chambers of the two cylinders in the center of the corresponding cylinder row, respectively, and the passage volume of these two branch passages to the connection to the intake port is the other branch. The intake of the multi-cylinder engine according to any one of claims 1 to 4, wherein the intake is set to 1.1 to 1.15 times the volume of the passage to the connection portion of the passage to the intake port. Device.

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