JPS5852332Y2 - Intake system for multi-cylinder engines - Google Patents

Description

[Detailed description of the invention] This invention opens a low-load intake passage and a high-load intake passage that are independent of each other in the combustion chamber of each cylinder that constitutes a multi-cylinder engine, and when the engine is under low load, This relates to improvements to the so-called multiple intake system, which supplies air-fuel mixture only through the low-load intake passage, and when the engine is under high load, the air-fuel mixture is supplied from the high-load intake passage in addition to the low-load intake passage. It is.

Traditionally, this type of dual intake system has been well known.
In particular, when the engine is under low load, a small amount of air-fuel mixture can be squeezed through the low-load intake passage, so the air-fuel mixture flow speed can be increased compared to the case of a single intake passage, and the fuel flow rate can be increased. In addition to promoting vaporization and atomization, it is also possible to directively flow the air-fuel mixture at a high flow rate into the combustion chamber, creating a large swirl, which improves engine combustibility and fuel efficiency. This has the advantage of improving emission performance.

One form of the above-mentioned dual intake system is one in which the low-load intake passage and the high-load intake passage are completely independent from the carburetor as a fuel supply device to the combustion chamber. , in this form, in a dual intake system,
Since air-fuel mixture is not supplied to the high-load intake passage when the engine is under low load, when the engine is transitioned from low to high load, the throttle valve of the low-load carburetor is fully open. When the throttle valve of the high-load carburetor is opened from the fully closed state, the air that had accumulated in the high-load intake passage is suddenly supplied into the combustion chamber, causing the air-fuel mixture to become overlean, resulting in combustion. There is a problem in that the combustibility in the room is temporarily deteriorated, and especially when the engine is not completely warmed up, knocking occurs.

This is because, in the above-mentioned dual intake system, the high-load intake passage is independent over the entire length of the passage from just downstream of the high-load carburetor to the combustion chamber, and the volume of the high-load intake passage is This is due to the fact that it exists as a complete dead volume when the engine is under low load.

Furthermore, in the case of an engine in which the dead volume differs among the cylinders, when the auxiliary valve is opened, the combustibility among the cylinders varies, so there is a problem that a torque imbalance occurs between the cylinders.

In order to solve this problem, the intake passage downstream of the carburetor,
A common intake passage connected to the carburetor, and a first branch intake passage and a second branch intake passage connected to the common intake passage and each independently opened into the combustion chamber, and the second branch intake passage is connected to the engine. An auxiliary valve is provided that closes when the engine is under low load and opens when the engine has a high load. When the engine is under low load, the mixture is supplied only through the common intake passage and the first branch intake passage, and when the engine is under high load, the mixture is supplied through the common intake passage and the first branch intake passage. 1. By using a dual intake system that supplies air-fuel mixture through a second branch intake passage, and by minimizing the length of the intake passage where air-fuel mixture does not flow when the engine is under low load, One idea is to reduce the dead volume that exists when the load is low.

When applying the above-mentioned type of dual intake system to a multi-cylinder engine, the present invention particularly focuses on the arrangement structure of the first and second branch intake passages, and the opening/closing structure or operating mechanism of the auxiliary valve related to the arrangement structure. In order to be practically advantageous, the first branch intake passages and the second branch intake passages are arranged side by side along the crankshaft, and the second branch intake passages of adjacent cylinders are collected to form a gathering part of the second branch intake passages. The auxiliary valves are arranged so that the volumes of the second branch intake passages of the adjacent cylinders downstream of the gathering part of the second branch intake passages are equal, while the auxiliary valves are arranged in common parallel to the crankshaft. It is an object of the present invention to provide an intake device for a multi-cylinder engine, which is supported by a rotating shaft at a gathering portion of the second branch intake passage.

Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

In FIG. 1, -L- and E indicate the cylinder body (not specifically shown).

) and the cylinder head 1 form a total of four cylinders C1 to C4 arranged along the axis of the crankshaft. , from the side surface 1a to each cylinder C1~
It has internal intake passages 31 to 34 leading to intake ports 21 to 24 opening into the combustion chamber of C4, and an internal exhaust passage 51 leading from each exhaust port 41 to 44 opening to the combustion chamber on the other side to the side surface 1b on the other side. ~54.

On the other hand, the IM is an intake manifold, which is a casting, that distributes the air-fuel mixture supplied by the two-carrier 6, which has a low-load carburetor and a high-load carburetor connected to each other, to each cylinder C1 to C4. , the intake manifold IM is constructed by aligning the mounting flange 7 formed on the end surface on the downstream side with respect to the flow of the air-fuel mixture with the side surface 1a of the cylinder head 1, and attaching the mounting flange 7 with a bolt (not shown).

) is supported in a fixed state on the cylinder head 1.

This intake manifold IM supports the dual carburetor 6 at the top, and has a gathering part 9 that communicates with the low-load intake passage 8p and the high-load intake passage 8S of the carburetor 6 in common directly below the carburetor. Thick central support part 10 formed inside
A pair of left-right symmetrical pipe wall portions 13.14 protrude from the center support portion 10 to the left and right in the figure, extend around the cylinder head 1 side, and form a common intake passage 11.12 that communicates with the collecting portion 9 inside. Then, the passage width gradually increases continuously from the tip of each tube wall portion 13, 14, and a pair of separation walls 16a are formed inside.
, 16b, 17a, 17b, a pair of symmetrical branch walls 1B, 19, and a pair of branch walls 18, 19.
and the above-mentioned mounting flange 7 which commonly supports the.

The pair of branch wall parts 1B and 19 are respectively connected to the pipe wall part 1.
3 and 14, and is substantially continuous with the side surface 1a of the cylinder head 1.
A pair of left and right separation walls 16 are formed to be perpendicular to each other.
a, 16b, 17a, and 17b.
Branch intake passage 20.21 and each separation wall 16a, 16b,
The common intake passages 11 and 12 are connected to each other through openings 22a, 22b, 23a and 23b opened at the connecting portions of the pipe walls 13 and 14 of the partition walls 17a and 17b, respectively.
6a, 16b, 17a, 17b, each pair of first branch intake passages 24a, 24b.

25a and 25b are formed inside.

On the other hand, internal intake passages 31 to 31 formed in the cylinder head 1
34 is adapted to the intake passage structure of the intake manifold IM, and the two internal intake passages 31 and 32 on the left side of the figure and the two internal intake passages 33 and 34 on the right side in the figure are paired, respectively.
Each branch wall portion 18, 1 of the symmetrical intake manifold IM
They are formed to be left-right symmetrical with respect to each symmetry center line Pl, P2 of 9.

Therefore, the volumes of the internal intake passages 31 and 32, 33 and 34 are equal, and the volumes of the second branch internal intake passages 31a and 34 are equal.
The volumes of 1b, 32a and 32b are equal.

That is, each internal intake passage 31 to 34 is connected to each separation wall L6.
Each partition wall 27a continuous to a, 16b, 17a, 17b
, 27b, 28a, 28b each intake port 21
24, the first branch internal intake passages 29a, 29b have a small passage cross-sectional area.

30a, 30b, and second branch internal intake passages 31a, 31b, 32a, 32b having a large passage cross-sectional area, each first branch internal intake passage 29a, 29b.

30a and 30b are connected to the first branch intake passages 24a, 24b, 25a and 25b of the intake manifold IM, respectively.

O, each second branch internal intake passage 31a, 31b, 32a
, 32b are the two second branch internal intake passages 31a on the left side.
, 31b commonly open to the common second branch intake passage 20 of the left branch wall 18, and the two right second branch internal intake passages 32a, 32b open to the common second branch intake passage 20 of the right branch wall 19.
The branch intake passage 21 has a common opening.

In addition, each passage 20° 24a of the branch wall portions 1B and 19,
The intermediate cross-sectional shapes of 24b, 21.25a, and 25b and the opening shape in the mounting flange 7 are as shown in FIG. 5 and FIG. 3, respectively.

As a result of the intake manifold IM and the intake passage configuration of the cylinder head 1, the intake passages from the downstream gathering portion 9 of the dual carburetor 6 to the intake ports 22 to 24 of each cylinder C1 to C4 are connected to the common intake passage 11. .12 and each common intake passage 11
．． A first branch intake passage 33a having a small passage cross-sectional area is branched by the 12 downstream VCs.

33b, 34a, and 34b, and the first branch intake passage 33a is continuous with the common intake passages 11 and 12, respectively.

Second branch intake passages 35a, 35b, 36a having a large passage cross-sectional area are independent from those of 33b, 34a, 34b.

36b.

Note that the second branch intake passages 35a, 35b, 36a, 3
The upstream side of 6b is constituted by a common second branch intake passage 20.21 as a gathering part of the second branch intake passages.

Therefore, the second branch intake passages 35a, 35b are downstream of the common second branch intake passage 20.21.

The volumes of 36a and 36b become equal.

and each first branch intake passage 33a, 33b.

34a, 34b, and each second branch intake passage 35a.

35b, 36a, and 36b are each partition wall 27a.

27b, 28a, 28b are connected to the intake ports 21~
A partition member (described later) provided to partition the intake valve 24 into a chord shape almost completely partitions off the intake valve immediately upstream of the fully closed intake valve.

Therefore, when the engine is under low load, when the air-fuel mixture is supplied only from each of the first branch intake passages 33a, 33b, 34a, and 34b, there is no intake interference, and when the intake valve is opened, the combustion It flows into the outer circumference of the chamber at a high velocity and with good directionality, generates a large swirl, and is ignited and burns well by ignition by each of the spark plugs q1 to q4 facing on the circumference of the swirl.

On the other hand, as shown in FIGS. 1, 2, and 5, there are a pair of left and right separation walls 16a, 16b, and 17a.

17bK, the common second branch intake passage 20
．． On the upstream side of 21, each common second branch intake passage 20.2
An auxiliary valve 41 consisting of a butterfly valve that opens and closes the valves 1 and 1, respectively.
42 are provided.

In this embodiment, since the auxiliary valves 41, 42 are provided in the common second branch intake passage 20.21, there is an advantage that the number of required valves can be reduced to half the number of cylinders.

These auxiliary valves 41 and 42 are connected to the intake manifold IM.
The pair of left and right branch walls 1B and 19 are rotatably penetrated parallel to the axis of the crankshaft, and fixed using screws 45 to the through shafts 43 and 44 supported at four points, respectively. The through shafts 43 and 44 of the pair of branch walls 18 and 1
A pair of coupling fittings 46 and 47 are placed in the space between the two to form a common rotating shaft 48.

The pair of coupling fittings 46, 47 are for absorbing misalignment between the pair of through shafts 43, 44 caused by machining errors, etc., and are attached to opposite shaft ends of the pair of through shafts 43, 44, respectively. A spring 51 is inserted between a pair of coupling fittings 46 and 47 that are fixed so that they will not come off by the fixed oak) 49 and 50.
A pair of joining pieces 46a are joined together by a pair of joining pieces 46a and bent from each joining fitting 46, 47 so as to face each other.

47a are coupled by bolts 53 so as to rotate together.

In addition, in the figure, 54 is the coupling fitting 47 of the long side penetrating shaft 44.
This is a coil spring compressed between the inner outer wall surface of the branch wall portion 19 and the inner outer wall surface of the branch wall portion 19 to restrict misalignment in the axial direction.

This common rotating shaft 48 may be formed by a single shaft.

In any case, since the common rotating shaft 48 can be supported at eight points in total, four points on each side, the support structure can be made strong.

Further, the rotation shaft 48 is connected to each of the first branch intake passages 24a, 24b, and 25a in the intake manifold IM.

As shown in FIG. 4, the passage cross-sectional area caused by penetrating through the shaft 25b is reduced by curving the earthen wall in advance in an upwardly convex manner through which the rotating shaft 48 passes. It is preferable to make it large to some extent so that it is substantially equal to the passage cross-sectional area of the portion through which the rotating shaft 48 does not penetrate.

A nut 56 is fixed to one end of the common rotating shaft 48 via a washer 55, while a pair of auxiliary valves 41, 42 are connected to the other end by rotating the rotating shaft 48 during high engine loads.
is coupled to an operating mechanism that operates to open.

As shown in FIGS. 1 and 2, this operating mechanism consists of a free end of a lever 58 fixed to the shaft end of a common rotating shaft 48 with a nut 57, and a low-load Throttle valve 59
A link rod 62 connects the free end of a bending lever 61 whose one end is rotatably fitted to the shaft end of the operating shaft 60 of the low-load throttle valve 59. It is fastened and fixed to the collar 63 with a nut 64, and is bent by an operating lever 65 provided with an engaging piece 6'5a that engages with the bending lever 61 when the low-load throttle valve 59 is opened beyond the set opening degree. When the low-load throttle valve 59 is opened beyond the set opening degree, the lever 61 is rotated counterclockwise in FIG. When operated, the auxiliary valves 41 and 42 supported on the rotating shaft 48 are opened.

Note that the other end of the operating shaft 60 of the low-load throttle valve 59 is connected to an accelerator pedal (not shown).

) (not shown).

), and is rotated according to the depression of the accelerator pedal.

Further, the operating lever 58, link rod 62 button, and bending lever 61 of the rotating shaft 48 are normally kept in the state shown in FIG. is held in position.

Next, the internal intake passages 31 to 34 of the cylinder head 1
and each first branch internal intake passage 29a.

29b, 30a, 30b and each second branch internal intake passage 3
1 a, 31b, 32a, 32b and the above partition wall 27a.
, 27b, 28a, and 28b, a partition structure that partitions directly above the intake valve 70 in the fully closed state will be described.

That is, as shown in FIG. 6, the partition plate γ2 that continuously partitions the internal space above the intake valve 70 from the partition wall 27a has a center portion in the plate width direction that is connected to the intake valve, as shown in FIG. A curved arc portion 72 surrounding the valve stem portion 73 of 70
a, with arcuate portions 72 on both sides in the vertical direction.
It has wing portions 72b and 72c that extend on both sides with an opening angle of about 120° to 150° continuously from a, and the wing portion 72b
, 72c has a flange 7 with a constant width plate surface protruding from the side edge.
2b.

72e is provided, and a ninth
The slit groove 74a provided in the axial direction of the cylindrical pin 74 shown in Figures a and b is shown in Figure 10a.

It is formed by being inserted as shown in b.

In this way, a cylindrical insertion portion 75 is formed using the cylindrical pin 74.

On the other hand, a fitting groove 76 provided in the cylinder wall corresponding to this insertion portion 75 is formed by drilling it into a cylindrical shape with a drill, as shown in FIGS. 1 and 6. The insertion part 75.75 of the partition plate 72 assembled as shown in FIG.
7 to fit it, and then insert it into the combustion chamber side opening 77.
By press-fitting the valve seat 80 into the ring-shaped fitting part 79 provided on the cylinder inner peripheral wall 7BK, the fitting groove 76
．． The insertion part 75 inserted into the partition plate 76 is pressed and held from below, thereby fixing the entire partition plate 72 without wobbling.

Regarding the formation of the cylindrical insertion portion 75 of the partition plate 720, the flange 72d is a flat plate as described above.

Although a cylindrical pin T4 inserted in 72e may be used,
The cylindrical insertion portion may be formed integrally with the flat plate, and although not specifically shown, the flanges 72d, 7 of the flat plate may be formed integrally with the flat plate.
A cylindrical insertion portion may be formed by forming 2e wide and bending it into a cylindrical shape.

The method in which the cylindrical pin 74 is inserted into the flat plate requires more parts than the one in which the flat plate and the insertion portion are integrally formed, but the former is formed by cutting the flat plate and a round bar with a slit. The partition plate can be manufactured using pins, and is easier to manufacture than the latter method, which is a partition plate in which a flat plate and an insertion portion are formed as a pair by drawing bending.

In addition, the insertion portion 15 and the fitting groove 76 have a tapered shape that tapers in the axial direction, so that when the insertion portion 75 is pushed in the axial direction, the pushing force ensures a secure fitting state between the two. It may be possible to do so.

In addition, as a partition member, Fig. 11 a m b * C
A truncated cone-shaped partition member as shown in can be used,
When this truncated conical partition member is used, the connection with the partition wall and the guidance of the air-fuel mixture can be made even better.

The truncated cone-shaped partition member 81 is shown in FIGS. 11a to 11c.

That is, although this partition member 81 is not shown, since it is cast with the downstream end surface of the separation wall in contact with a truncated conical outer mold, the partition member 81 has a contact end surface 81d that comes into contact with the downstream end surface of the separation wall. has almost the same shape as the downstream end surface of the separation wall, that is, it consists of a part of the cut upper surface of a truncated cone and a part of the conical surfaces on both sides thereof, and is also similar to the partition member 72 of the above embodiment. It has a central part 81a that is curved in the center so as to surround the valve stem part 73 of the intake valve TO, and side parts 81b and 81c that extend like strings on both sides of the central part 81a. Two-branch intake passage side side surfaces 81e, 81f
is a surface that smoothly continues from the abutting end surface 81d to the lower end surface 81g facing the combustion chamber side opening 77.

Additionally, the lower end surface 81g is formed in a shape that follows the valve head of the umbrella-shaped intake valve 70.

81h and 81i are the outer peripheral surfaces of the side portions 81b and 81c;
1j is a keyway into which a locking pin is inserted.

The partition member 81 having the shape described above can be molded by various molding methods, but molding by casting, particularly precision casting, has the advantage that it can be molded easily and accurately.

Furthermore, as shown in FIGS. 12 to 14, the partition member may be integrated with the intake valve guide, and the partition member and the intake valve guide may be assembled by being inserted from the combustion chamber side opening. .

The detailed structure of the partition member 91 and the intake valve guide 92 is
2 to 14 a * b t C.

First, the intake valve guide 92 is provided in the shape of a pipe, with a through hole 92a formed in the center thereof through which the valve stem 13 of the intake valve TO is slidably inserted. The outer peripheral surface of the one end 92b on the Oa side is set to have a small diameter.

On the other hand, the partition member 91 has a cylindrical engagement portion 91a at the center base.
The engaging portion 91a has an inner peripheral surface that is connected to the intake valve guide 9.
2, and the intake valve γ
It has a through hole 91b through which the valve stem portion 73 of No. 0 is inserted.

A plate-shaped partition 91c is provided protruding from the retaining portion 91a, and this partition 91c has a central portion curved in a semicircular shape so as to surround the valve shaft portion 73 of the intake valve 10, and a central portion formed in the central portion. The end edge 91d is formed in a chevron shape along the valve head 70a of the umbrella-shaped intake valve 70, and the side edges 91e, 91e are formed in the internal intake passage 31. It is formed to follow the shape of the wall surface and the shape of the downstream end surface of the separation wall 27a.

Further, the partition body 91c is provided so that the engaging portion 91a side is thicker and becomes thinner toward the end edge 91d side.

A pin 93 is fixed to a press-fitting portion between the partition member 91 and the intake valve guide 92.

Note that in FIG. 12, the same parts as in FIG. 6 are given the same numbers and their explanations are omitted for the sake of brevity.

Regarding the passage configuration of the above-mentioned intake device, as shown in FIG.
The first branch internal intake passages 29a, 29b, 30a, 30b branch from the side opposite to the internal exhaust passages 51 to 54.
along parallel to the intake manifold I with a slight thickness.
Exhaust gas recirculation passage 9 with a vertically elongated cross section that opens on the M side side surface 1aK
5t to 954 are provided, and each first branch internal intake passage 29a, 29b is heated by the heat possessed by the recirculated exhaust gas.

The wall surfaces of the passages 30a and 30b may be heated.

In this way, if the air-fuel mixture flowing down each of the first branch internal air passages 29a, 29b, 30a, and 30b is preheated by exhaust gas heat, the vaporization and dewization of the fuel will be improved accordingly. I can do it.

In this case, each second branch internal intake passage 31a. 31b, 3
2a and 32b are far away from each exhaust gas recirculation passage 951 to 954, so the second branch internal intake passage 31a
, 31b, 32a, and 32b are not preheated, and the air-fuel mixture filling efficiency is not reduced during high engine load.

That is, the recirculated exhaust gas from each of the exhaust gas recirculation passages 951 to 954 is collected in a common exhaust gas recirculation passage 96, and then
What is necessary is to make it flow back to the gathering part 9 of the intake manifold IM.

In FIG. 15, the same parts as in FIG. 1 are given the same numbers as in FIG. 1, and the description thereof will be omitted.

In the embodiment detailed above, the common second branch intake passage 20.21 is formed in the intake manifold IM.
Each second branch intake passage 35a, 35b.

In order to reduce the volumes of 36a and 36b as much as possible, the common second branch intake passage may be provided within the cylinder head 1.

In short, each second branch intake passage 35a, 35b is longer than the passage length 11 of the common intake passage 11.12.

The purpose is to create a passage structure in which the passage length t2 of the passages 36a and 36b is as short as possible (for example, t1≧tz).

In the above embodiment, a double carburetor 6 is used as the carburetor, but in this case, the upstream side of the intake passage is used as a common intake passage, so the carburetor is not limited to the double carburetor 6. However, it is also possible to use a variable venturi type vaporizer that utilizes venturi negative pressure.

Additionally, in the above embodiment, the first branch intake passage and the second branch intake passage were opened and closed by a single intake valve, but each branch passage may be opened and closed by a separate intake valve. .

As is clear from the above detailed explanation, the present invention provides an intake passage downstream of the fuel supply device, a common intake passage continuous to the fuel painting, and a common intake passage continuous to the common intake passage, each of which is independently connected to the combustion chamber. The intake system for a multi-cylinder engine is constructed of first and second branch intake passages that are open to each other, and each of the second branch intake passages is provided with an auxiliary valve that closes at a low load and opens at a high load. and a second branch downstream of the gathering part of the second branch intake passages formed by arranging the second branch intake passages in parallel along the axial direction of the crankshaft and collecting the second branch intake passages of adjacent cylinders. An intake of a multi-cylinder engine, characterized in that the volumes of the intake passages are configured to be equal, and each of the auxiliary valves is supported at a gathering part of the second branch intake passage by a common rotating shaft parallel to the crankshaft. It provides equipment.

According to the present invention, by arranging the first and second branch intake passages in parallel along the crankshaft, it is possible to support each auxiliary valve on a common rotation shaft, and this common rotation Since each auxiliary valve can be opened and closed by operating the shaft, the operation mechanism of the auxiliary valve can be made extremely simple. Since it can be supported by the separation wall of the intake passage, the support structure can be made strong, and it can be made suitable for the practical use of the above-mentioned type of intake device.

Additionally, in this invention, since the first branch intake passage and the second branch intake passage are arranged parallel to each other around the crankshaft KffEJ, when the engine is under low load, the mixture flow is directed to a higher flow velocity than the first branch intake passage. It can flow in the circumferential direction of the combustion chamber with good flexibility, making it possible to advantageously generate swirl, and when the engine is under high load, the first
The second valve is located opposite the direction of the air-fuel mixture flowing in from the branch intake vent.
By allowing the air-fuel mixture to flow in through the branched intake passage, it is possible to reduce swirl and reduce combustion noise.

Furthermore, since the auxiliary valve is arranged at the convergence part of the second branch intake passage where the second branch intake passages of adjacent cylinders are assembled, the number of auxiliary valves can be halved. The volume of the second branch intake ventilation can be made equal between the cylinders.

[Brief explanation of the drawing]

FIG. 1 is a horizontal cross-sectional view showing an intake system for a multi-cylinder engine according to an embodiment of the present invention, FIG. 2 is a side view of the intake manifold including a cross-section along the line ■-■ in FIG. 1, and FIG. is a front view of the intake manifold (with the rotating shaft and auxiliary valve removed), FIG. 4 is a sectional view taken along the line IV-IV in FIG. 1, and FIG. 5 is a sectional view taken along the line V-V shown in FIG. 1. , Figure 6 is the first
7 is a sectional view showing the internal intake passage of the cylinder head, FIGS. 8a and 8b are a plan view and a front view of the partition member in FIG. 6, and FIG. a. 10b is a plan view and a front view of the pins forming the insertion portion of the partition member, FIG.
ebse is a perspective explanatory view, a top view, and a bottom view of each partition member, FIG. 12 is a sectional view similar to FIG. 6 showing another partition structure, and FIG. Partial cross-sectional front view of intake valve guide, Figure 14 a * b g
15 is a left side view, a right side view, and a bottom view, and FIG. 15 is a horizontal sectional view similar to FIG. 1, showing a modification of FIG. 1. 1...Cylinder head, 21-24...
・Intake port, 6... Carburetor, 1M...
- Intake manifold, 11, 12... - common intake passage, 16a, 16b. 17a, 17b... Separation wall, 20, 21...
...Gathering part of the second branch intake passage, 33a, 33b, 3
4a. 34b...First branch intake passage, 35a, 35b
. 36a, 36b''...First branch intake passage, 41.42...Auxiliary valve, 48...Common rotating shaft.

Claims (1)

[Claims for Utility Model Registration] A common intake passage that connects the intake passage downstream of the fuel supply device to the fuel supply device, and first and second branches that are connected to the common intake passage and each independently open into the combustion chamber. In the intake system for a multi-cylinder engine, the intake system for a multi-cylinder engine is provided with an auxiliary valve arranged in the intake passage, and in the second branch intake passage, the auxiliary valve closes when the engine is under low load and opens when the engine is under high load. The two-branch intake passages are arranged in parallel along the axial direction of the crankshaft, and the second branch intake passages of adjacent cylinders are collected to form a collection part of the second branch intake passages, and the second branch intake passages of adjacent cylinders are arranged in parallel. The second branch intake passages of the two-branch intake passage are constructed so that the downstream volumes of the two-branch intake passages are equal to each other, and the auxiliary valves are connected to the second branch intake passage by a common rotation axis parallel to the crankshaft. An intake system for a multi-cylinder engine, characterized in that it is supported at a gathering part of.