JPH0586869A - Multi-cylinder engine intake system - Google Patents

Abstract

PURPOSE:To provide an intake device for a multiple cylinder engine by which resonance supercharging can be carried out over a wide range of rotating speed, and also inertia supercharging can be carried out. CONSTITUTION:A collecting chamber 16a to which independent intake passages 19 to 21 of first to third cylinders are collected, and a collecting chamber 16b to which independent intake passages 22 to 24 of fourth to sixth cylinders are collected are formed by partitioning a surge tank 16 with a gate valve 41 which is opened only at the time of high rotating speed. The first collecting chamber 16a is connected to first to third upstream intake passages 9 to 11, and the second collecting chamber 16b is connected to fourth to sixth upstream intake passages 12 to 14, and then the first to sixth upstream intake passages 9 to 14 are collected by an upstream collecting part 8. In the second to fifth upstream intake passages 10 to 13, open/close valves 26, 35, 36, 27 which are opened or closed in accordance with the rotating speed of an engine are provided. The upstream intake passages 9 to 14 and independent intake passages 19 to 24 corresponding thereto are coaxially arranged in the vicinity of the surge tank 16, and also intake systems from the upstream intake passages to the independent intake passages are formed in an approximately U-shape, and the surge tank 16 is arranged in the curved part thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake system for a multi-cylinder engine.

[0002]

2. Description of the Related Art An intake system for a multi-cylinder engine has been conventionally known in which resonance supercharging, which is one of dynamic supercharging, is performed to enhance intake charging efficiency (volume efficiency). Here, the resonance supercharging is the following supercharging method. That is, for example, as shown in FIG. 7, in a 6-cylinder engine in which resonance supercharging is performed, first to third cylinders # 1 whose intake strokes are not adjacent to each other.
First collection chamber 1 that collects the upstream ends of the independent intake passages # 3 to # 3
01 and the fourth to sixth cylinders # 4 to # whose intake strokes are not adjacent to each other
Second collecting chamber 102 for collecting the upstream ends of the independent intake passages 6
And are provided. A first upstream intake passage 103 having a downstream end connected to the first collecting chamber 101 and a second upstream intake passage having a downstream end connected to the second collecting chamber 102 are provided, and the first upstream intake passage 103 is provided. And an upstream end of the second upstream intake passage 104 are collected by the upstream collecting portion 105, and the upstream collecting portion 105 is opened to the atmosphere via the duct 106.

Here, for example, on the side of the first cylinder group,
The first to third cylinders # 1 to # 3 allow the first intake collecting chamber 10
1, the intake pressure vibration of a frequency corresponding to the engine speed (hereinafter referred to as a vibration frequency) is induced. And
When the vibration frequency matches the resonance frequency determined by the volume of the first collection chamber 101 (resonance chamber) and the pipe length and diameter of the first upstream intake passage 103 (resonance pipe), the inside of the first collection chamber 101 In addition, a large intake pressure oscillation occurs such that a pressure peak occurs immediately before the intake valves of the first to third cylinders # 1 to # 3 are closed. Resonant supercharging enhances intake charging efficiency by pushing (supercharging) intake air into the first to third cylinders # 1 to # 3 by the high intake pressure at the time of this pressure peak.

Therefore, in such resonance supercharging,
The supercharging effect is enhanced only in a predetermined narrow rotation region that is determined by the volume of the first collecting chamber 101 and the pipe length and pipe diameter of the first upstream intake passage 103, and substantially in other rotation regions. There is a difficulty that you can not get.

Therefore, as shown in FIG.
The second upstream intake passages 103, 104 are arranged substantially parallel to each other, and a communication passage for communicating the both upstream intake passages 103, 104 with each other at a predetermined position is provided, and an on-off valve 107-109 is provided in each of the communication passages. Device A'is proposed
(See Japanese Utility Model Laid-Open No. 59-88221). In the intake system A ′, for example, when the open / close valve 109 is opened, the communication passage in which the open / close valve 109 is interposed causes the constant pressure portion, that is, the constant pressure portion, due to mutual interference between the first cylinder group side and the second cylinder group side. It becomes a pressure wave reflection part, and only the upstream intake passages 103 and 104 on the downstream side from this position function as a resonance tube. Therefore, the resonance tube length is shortened and the resonance frequency is increased. For this reason, the engine speed at which the vibration frequency that matches the resonance frequency is obtained becomes high, and the rotation region where a high supercharging effect is obtained shifts to the high rotation side. Therefore, it is possible to perform resonance supercharging over a wide rotation range by preferably opening and closing the on-off valves 107 to 109 according to the engine speed.

As shown in FIG. 8, in a 6-cylinder V-type engine, the first, third, and fifth cylinders # 1, # 3, and # 5, which do not have adjacent intake strokes, communicate with the independent intake passages. 1st branch intake passage 111 and 2nd, 4th, 6th which intake stroke does not adjoin
A second branch intake passage 112 communicating with the independent intake passages of the cylinders # 2, # 4, # 6 is provided, and both branch intake passages 111, 11 are provided.
While connecting the upstream end of 2 to the common intake passage 113, the first communication passage 114 having a small diameter and a long pipe length that connects the downstream ends of both branch intake passages 111 and 112 with the large diameter pipe that connects the intermediate points And a second communication passage 116 having a short length
The first and second on-off valves 11 are provided in the second communication passages 114 and 116, respectively.
An intake device A "having 5,117 interposed is proposed (see Japanese Patent Laid-Open No. 63-263218).

In this intake device A ", the first opening / closing valve 1
When 15 is opened, the first and second branch intake passages 11
A series of intake passages composed of 1, 112 and the first communication passage 114 serves as a resonance pipe. However, since the pipe length of the first communication passage 114 is long and the pipe diameter is small, the intake passage is high when the engine speed is relatively low. The salary effect will be obtained. When the second on-off valve 117 is opened, a series of intake passages including the first and second branch intake passages 111 and 112 and the second communication passage 116 become resonance passages. Since the pipe length is short and the pipe diameter is large, a high supercharging effect can be obtained when the engine speed is relatively high.

[0008]

However, in the conventional intake system A'as shown in FIG. 7, since the resonance frequency is switched by changing only the tube length of the resonance tube, the degree of freedom in setting the resonance frequency is high. Is relatively low. Further, in the conventional intake device A "as shown in FIG. 8, although the resonance frequency is changed by changing the pipe length and pipe diameter of the resonance pipe, the number of switching stages is small, so that the supercharging effect over a wide rotation range is achieved. It is difficult to increase the intake air pressure and it is not possible to effectively use another dynamic supercharging method, that is, inertia supercharging, because a volume portion communicating with the independent intake passage is not provided. The present invention has been made in order to solve the above-mentioned conventional problems, and it is a compact multi-purpose type capable of performing resonance supercharging over a wide rotation range and effectively performing inertia supercharging. An object is to provide an intake system for a cylinder engine.

[0009]

In order to achieve the above object, a first aspect of the present invention is to provide a plurality of collecting chambers for collecting independent intake passages of cylinders whose intake strokes are not adjacent to each other on an upstream side, and the collecting chambers. In an intake system for a multi-cylinder engine, which is provided with an upstream intake passage that is connected to the upstream intake passage and an upstream collecting portion that collects the upstream intake passages on the upstream side, the upstream intake passages are substantially parallel to each collecting chamber. A plurality of opening / closing valves are provided in the upstream intake passage, and opening / closing valve control means for controlling opening / closing of the opening / closing valves according to the engine speed is provided. Provided is a characteristic multi-cylinder engine intake device.

According to a second aspect of the present invention, in the intake system for a multi-cylinder engine according to the first aspect, a surge tank and a sluice valve that divides the surge tank into a plurality of compartments when the valve is closed are provided. Is formed so as to form a collecting chamber, and a sluice valve control means for closing the sluice valve is provided up to a predetermined high rotation region where all the on-off valves are opened. An intake system for a cylinder engine is provided.

In a third aspect of the present invention, in the intake system for a multi-cylinder engine according to the first or second aspect, the same number of upstream intake passages are provided corresponding to the independent intake passages, and the upstream intake passages corresponding to each other are provided. An intake device for a multi-cylinder engine, characterized in that the independent intake passage and the independent intake passage are arranged in the vicinity of the collecting chamber so as to share their respective axes.

According to a fourth aspect of the present invention, in the intake system for a multi-cylinder engine according to the second or third aspect, the upstream intake passages are arranged in a line in the cylinder arrangement direction, and the cylinder arrangement is performed on each collecting chamber side. The upstream and downstream intake passages other than the one upstream intake passage disposed on the end side in the direction are provided with respective on-off valves, and the on-off valve control means controls each on-off valve from the end side as the engine speed increases. Provided is an intake system for a multi-cylinder engine, which is characterized in that the valves are opened sequentially.

According to a fifth aspect of the present invention, in the intake system for a multi-cylinder engine according to the fourth aspect, a series of intake systems extending from the upstream intake passage to the independent intake passage are bulged to the side of the engine as seen in the intake flow direction. Provided is an intake device for a multi-cylinder engine, which is formed so as to be curved downward in a substantially U shape, and a collecting chamber is arranged in the curved portion.

[0014]

EXAMPLES Examples of the present invention will be specifically described below.
As shown in FIG. 1 and FIG. 2, first to sixth cylinders # 1 to # 6
In each cylinder of the in-line 6-cylinder engine E, the air-fuel mixture is sucked into the combustion chamber 3 from the intake port 2 when the intake valve 1 is opened, and the air-fuel mixture is compressed by a piston (not shown). After being ignited and burned by a spark plug (not shown), combustion gas is emitted when the exhaust valve 4 is opened.
It is supposed to be discharged from. Where each cylinder # 1
~ # 6 are ignited in the order of # 1 → # 5 → # 3 → # 4 → # 2 → # 6. Therefore, the first to third
The intake strokes of the cylinders # 1 to # 3 are not adjacent to each other, and
The intake strokes of the sixth cylinders # 4 to # 6 are not adjacent to each other.

An intake device A is provided to supply air to the engine E. 1 and 2, the left side is simply referred to as “left” and the right side is simply referred to as “right.” The upstream end (not shown) of this intake device A communicates with the atmosphere. A common intake passage 7 is provided,
The downstream end of the common intake passage 7 is connected to the left side surface of the upstream collecting portion 8. The upstream collecting portion 8 is formed in an elongated shape, and is arranged to extend in the cylinder arrangement direction over substantially the entire length of the engine. The upstream ends of the first to sixth upstream intake passages 9 to 14 are connected to the right side surface of the upstream collecting portion 8 at positions corresponding to the first to sixth cylinders # 1 to # 6 when viewed in the cylinder arrangement direction. ing. These first to sixth upstream intake passages 9
Nos. 14 to 14 are formed and arranged so as to be parallel to each other in a plan view and extend in a direction (left-right direction) orthogonal to the cylinder arrangement direction. Further, when viewed in an elevational view, they are formed and arranged so as to bulge rightward and curve downward.

The downstream ends of the first to sixth upstream intake passages 9 to 14 are connected to the right side surface of the surge tank 16 arranged at a position slightly lower than the upstream collecting portion 8. Surge tank 1
Reference numeral 6 is formed in an elongated shape, and is arranged in a cylinder arrangement over the entire length of the engine so as to be long. Then, on the left side surface of the surge tank 16, when viewed in the cylinder arrangement direction,
At positions corresponding to the sixth upstream intake passages 9 to 14, the upstream ends of the first to sixth independent intake passages 19 to 24 (see FIG. 3) are connected, and the first to sixth independent intake passages 19 to 24 are connected.
The downstream ends of 24 are connected to the intake ports 2 of the first to sixth cylinders # 1 to # 6, respectively. Here, the surge tank 16
In the vicinity, the corresponding upstream intake passages 9 to 14 and the corresponding independent intake passages 19 to 24 are formed and arranged so as to share their axes. That is, each upstream intake passage 9-14
Are formed and arranged so as to be smoothly connected to the corresponding independent intake passages 19 to 24 without being offset. Therefore, the flow of intake air from the upstream intake passages 9-14 to the corresponding independent intake passages 19-24 is made smooth, and the intake resistance is reduced.

Further, the intake system A is provided with various valve mechanisms for switching the intake supply path or the pressure wave propagation path in accordance with the operating state of the engine E. A second upstream intake passage opening / closing valve 26 is provided in the second upstream intake passage 10, and a fifth upstream intake passage opening / closing valve 27 is provided in the fifth upstream intake passage 13. Here, both on-off valves 26, 27
Are linked by a link mechanism 28, and are opened and closed in conjunction with each other by a first actuator 29. The first actuator 29 includes a first negative pressure supply passage 30.
When the negative pressure in the vacuum chamber 31 is supplied, both the on-off valves 26 and 27 are closed, and when the atmospheric pressure is supplied, both the on-off valves 26 and 27 are opened. A first solenoid valve 32 is provided in the first negative pressure supply passage 30.
Supplies negative pressure to the first actuator 29 when turned off by the control unit 45, and supplies atmospheric pressure when turned on. In addition,
A negative pressure in the upstream collecting portion 8 is introduced into the vacuum chamber 31 through a negative pressure introducing passage 33 in which a check valve 34 is provided.

A third upstream intake passage opening / closing valve 35 is provided in the third upstream intake passage 11, and a fourth upstream intake passage opening / closing valve 36 is provided in the fourth upstream intake passage 12. here,
Both the on-off valves 35 and 36 are connected by a link mechanism 37 and are opened and closed in conjunction with each other by a second actuator 38. Similarly to the first actuator 29, the second actuator 38 is also supplied with negative pressure through the second negative pressure supply passage 39 to close both the on-off valves 35 and 36 when the second solenoid valve 40 is turned off. When the valve 40 is turned on, atmospheric pressure is supplied to open both open / close valves 35 and 36.

A sluice valve 41 is provided in the surge tank 16 at an intermediate position between the third cylinder # 3 and the fourth cylinder # 4 when viewed in the cylinder arrangement direction. When the sluice valve 41 is closed, the surge tank 16 includes the first to third upstream intake passages 9 to 11 and the first to third independent intake passages 19 to 11.
21 and the 4th-6th upstream intake passages 12-14 and the 4th-6th independent intake passages 22-24.
It is configured to be divided into a second branch chamber 16b that communicates with. The sluice valve 41 is adapted to be opened and closed by the third actuator 42. First actuator 29
Similarly, the third actuator 42 also has a third negative pressure supply passage 43 when the third solenoid valve 44 is turned off.
A negative pressure is supplied through the gate valve 41 to close the gate valve 41, and when the third solenoid valve 44 is turned on, atmospheric pressure is supplied to open the gate valve 41. Note that FIG.
In addition, the intake system of the intake device A is schematically shown.

Then, the control unit 45 determines whether the control unit 45 has the first to third values based on the engine speed and the engine load.
ON / OFF control the solenoid valves 32, 40, 44,
As a result, the opening / closing valves 26, 27, 35, 36 and the sluice valve 41 are opened / closed to switch the intake air supply path or the pressure wave propagation path to perform resonance supercharging or inertia supercharging over a wide rotation range of the engine E. This is done to improve the intake filling efficiency. Hereinafter, the control method of the first to third solenoid valves 32, 40, 44 by the control unit 45, that is, the on-off valves 26, 27, 35, 36 and the sluice valve 4
The control method 1 will be described. Control unit 45
Is, for example, according to the map as shown in FIG. 5, the first to third solenoid valves 32, 40,
Turn 44 on and off. In addition, in FIG. 5, S _{1 to} S ₃
Represent the first to third solenoid valves 32, 40 and 44, respectively.

(1) Region where engine speed is N ₁ or less (region 1) All the first to third solenoid valves 32, 40, 44 are turned off, and all the on-off valves 26, 27, 35, 36 and sluice valves. 41 and 41 are closed. Therefore, the effective intake path or pressure wave propagation path is as shown in FIG. Here, the first and sixth upstream intake passages 9 and 14 and the upstream collecting portion 8 serve as a resonance passage. In this case, as shown by the arrow X ₁ , the resonance passage length is long and only the first and sixth upstream intake passages 9 and 14 are used, so that the passage cross-sectional area of the upstream intake passage portion becomes small.
Resonant frequency becomes low. Therefore, the tuning rotational speed of the engine E with respect to the resonance frequency becomes low, and the curve G _{1 in} FIG.
Resonance supercharging having a characteristic such that a peak is obtained in a region where the engine speed is N ₁ or less, as shown in FIG. In addition,
The process of resonance supercharging and its characteristics are described in the above "Prior Art".
As described in.

(2) Region where engine speed is higher than N _{1 and} lower than N ₂ (region 2) The first solenoid valve 32 is turned on, and the second and third solenoid valves 40, 44 are turned off. The fifth upstream intake passage opening / closing valves 26, 27 are opened, and the third and fourth upstream intake passage opening / closing valves 35, 36 and the sluice valve 41 are closed. Therefore, the effective intake path or pressure wave propagation path is as shown in FIG. 4 (b). Where 1st, 2nd, 5th, 6th
The upstream intake passages 9, 1013, 14 and the upstream collecting portion 8 form a resonance passage. In this case, since the pressure wave has a characteristic that it easily propagates through the shortest path, the substantial resonance path length becomes short as shown by an arrow X ₂ . Moreover, the first, second, fifth, and sixth upstream intake passages 9, 10, 13, 14 are opened, and the passage cross-sectional area of the upstream intake passage portion is increased, so that the resonance frequency is increased accordingly. Therefore, the tuning rotational speed of the engine E with respect to the resonance frequency becomes high, and the resonance having the characteristic that a peak is obtained in the region where the engine rotational speed is N _{1 to} N ₂ as shown by the curve G ₂ in FIG. Supercharged.

(3) Region where engine speed is higher than N _{2 and} lower than N ₃ (region 3) The first and second solenoid valves 32 and 40 are turned on, and
The solenoid valve 44 is turned off, so that all the upstream intake passage opening / closing valves 26, 27, 35, 36 are opened and the sluice valve 41 is closed. Therefore, the effective intake path or pressure wave propagation path is as shown in FIG. 4 (c). here,
The first to sixth upstream intake passages 9 to 14 and the upstream collecting portion 8 form a resonance passage. In this case, the substantial resonance path length is the arrow X
_As indicated by ₃ , the resonance frequency is further increased because the upstream intake passages 9 to 14 are opened and the passage cross-sectional area of the upstream intake passage portion is increased as shown by ₃ . Therefore, the tuning rotational speed of the engine E with respect to the resonance frequency becomes higher, and as shown by the curve G ₃ in FIG.
Resonant supercharging having a characteristic that a peak is obtained in the engine speed range of N _{2 to} N ₃ is performed.

(4) Region where engine speed is higher than N ₃ (region 4) All the first to third solenoid valves 32, 40, 44 are turned on, and all the on-off valves 26, 27, 35, 36 and the sluice valves. 41 and are opened, and the effective intake path is as shown in FIG. 4 (d). In this case, since the surge tank 16 is a single chamber, intake pressure vibrations such as during resonance supercharging occur in the surge tank 16 due to intake interference between the first to sixth cylinders # 1 to # 6. Does not happen. Note that some vibration, that is, intake pulsation occurs. In this case, inertia supercharging is performed using the surge tank 16 as a volume portion. Here, the inertia supercharging means that in each of the cylinders # 1 to # 6, the negative pressure wave generated in the intake port 2 when the intake valve 1 is opened is the independent intake passage 19
(To 24), is transmitted to the surge tank 16, is inverted to a positive pressure wave in this surge tank 16 (volume part), and is then transmitted to the downstream side again via the independent intake passage 19 (to 24), and the intake valve This is a supercharging method in which the air reaches the intake port 2 immediately before 1 is closed, and the positive pressure wave pushes air into the combustion chamber 3 to improve the intake charging efficiency. And
Such inertial supercharging has a supercharging characteristic in which a peak occurs in a predetermined high rotation region that is determined by the passage length and the passage diameter of the independent intake passage 19 (to 24). Therefore, inertial supercharging having a characteristic that a peak is obtained in a region where the engine speed is higher than N ₃ as shown by a curve G ₄ in FIG. 6 is performed. In general, in order to enhance the effect of inertial supercharging, it is effective to increase the volume of the volume section (pressure reversal section) to reduce the intake pulsation in the volume section. Since the first to sixth upstream intake passages 9 to 14 that communicate with the above function together with the surge tank 16 as a volume portion, intake pulsation is reduced and the inertia supercharging effect is further enhanced.

Therefore, as is apparent from FIG. 6, the intake charge efficiency is effectively increased by the resonance supercharging or the inertia supercharging in almost the entire rotation region of the engine E, so that the output of the engine E is increased. As described above, according to the present invention,
By changing the resonance passage length and the resonance passage cross-sectional area according to the operating state of the engine E, effective resonance supercharging can be performed in a wide rotation range, and effective inertia supercharging can be performed. ..

[0026]

According to the first invention, the engine E is
Since the resonance passage length and the resonance passage cross-sectional area are switched according to the operating state of (3), effective resonance supercharging can be performed in a wide rotation range, and intake charging efficiency can be improved. Also,
Since the plurality of upstream intake passages are arranged in parallel for each collecting chamber, a sufficient intake passage cross-sectional area is secured, the intake resistance is reduced, and the intake system is made compact. Further, the upstream intake passage has the same effect as that of substantially increasing the volume of the collecting chamber, so that the intake pulsation is reduced.

According to the second invention, basically, the same operation and effect as those of the first invention can be obtained. Further, at the time of high rotation, by opening the sluice valve, inertia supercharging can be performed, and the supercharging effect can be enhanced over a wider rotation region. Further, at the time of inertia supercharging, the upstream intake passage functions as a volume portion (pressure reversal portion) together with the surge tank, so that the inertia effect is further enhanced. Further, since each collecting chamber is formed by partitioning one surge tank, the intake system can be made more compact.

According to the third invention, basically, the same operation and effect as those of the first or second invention can be obtained. further,
The inflow of intake air from the upstream intake passage to the independent intake passage is made smooth, so the intake resistance is reduced.

According to the fourth invention, basically, the same operation and effect as those of the second or third invention can be obtained. Further, the resonance passage length (upstream intake passage) is shortened and the resonance passage cross-sectional area is increased as the engine speed increases, so that effective resonance supercharging can be performed according to the engine speed. ..

According to the fifth invention, basically the same action and effect as the fourth invention can be obtained. Further, the upstream intake passage, the collecting chamber (surge tank), and the independent intake passage are made compact.

[Brief description of drawings]

FIG. 1 is an explanatory plan view of an engine and an intake device thereof showing an embodiment of the present invention.

FIG. 2 is an elevational cross-sectional explanatory view of the engine and the intake system shown in FIG. 1 at a second cylinder position.

FIG. 3 is a schematic diagram showing an intake flow system of the intake device shown in FIG.

4 (a), (b), (c), and (d) are views showing only an opening portion in a predetermined rotation region of the intake device shown in FIG. 3, respectively.

FIG. 5 is a diagram showing ON / OFF characteristics of first to third solenoid valves.

FIG. 6 is a diagram showing characteristics of engine output with respect to engine speed.

FIG. 7 is a schematic view of a conventional intake device that performs resonance supercharging.

FIG. 8 is a schematic diagram of another conventional intake device configured to perform resonance supercharging.

[Explanation of symbols]

A ... Intake device E ... Engine # 1- # 6 ... 1st-6th cylinder 8 ... Upstream collecting part 9-14 ... 1st-6th upstream intake passage 16 ... Surge tank 16a, 16b ... 1st, 2nd branch chamber 19-24 ... 1st-6th independent intake passages 26, 27, 35, 36 ... 2nd, 5th, 3rd, 4th upstream intake passage opening / closing valve 41 ... Gate valve 45 ... Control unit

Claims (5)

[Claims] 1. A plurality of collecting chambers for collecting independent intake passages of cylinders whose intake strokes are not adjacent to each other on the upstream side, an upstream intake passage connected to the collecting chambers, and each upstream intake passage for collecting on the upstream side. In an intake device for a multi-cylinder engine provided with an upstream collecting portion, a plurality of upstream intake passages are provided so as to be substantially parallel to each collecting chamber, and the upstream intake passages are respectively provided. An intake system for a multi-cylinder engine, wherein an on-off valve is provided, and on-off valve control means for controlling the on-off valve to open and close according to the engine speed is provided. 2. The intake system for a multi-cylinder engine according to claim 1, wherein a surge tank and a sluice valve that divides the surge tank into a plurality of compartments when the valve is closed are provided, and each of the compartments is a collection chamber. Of the multi-cylinder engine, which is formed so as to form a valve and is provided with a sluice valve control means for closing the sluice valve up to a predetermined high rotation region where all the on-off valves are opened. Inhaler. 3. The intake system for a multi-cylinder engine according to claim 1 or 2, wherein the same number of upstream intake passages are provided corresponding to the independent intake passages, and the upstream intake passages independent of each other are provided. An intake device for a multi-cylinder engine, characterized in that the intake passage and the intake passage are arranged so as to share an axis in the vicinity of the collecting chamber. 4. The intake system for a multi-cylinder engine according to claim 2 or 3, wherein the upstream intake passages are arranged in a line in the cylinder arrangement direction, and the ends in the cylinder arrangement direction are arranged on the side of each collecting chamber. On-off valves are provided in the upstream intake passages other than the one upstream intake passage, and the on-off valve control means sequentially opens each on-off valve from the end side as the engine speed increases. Intake device for a multi-cylinder engine, which is characterized in that 5. The intake system for a multi-cylinder engine according to claim 4, wherein a series of intake systems extending from the upstream intake passage to the independent intake passage extend downward toward the engine while bulging toward the side of the engine. An intake device for a multi-cylinder engine, wherein the intake chamber is formed so as to be curved in a substantially U shape, and the collecting chamber is arranged in the curved portion.