JPH0758048B2 - Intake device for multi-cylinder internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention (1) Field of Industrial Application The present invention is directed to improving the volumetric efficiency of a multi-cylinder internal combustion engine by controlling the intake pressure fluctuation in the intake system. The present invention relates to an improvement of an intake device, particularly a resonance chamber collecting part thereof.

(2) Prior Art In an intake system for a multi-cylinder internal combustion engine, each cylinder is divided into cylinder groups whose intake strokes are not continuous, and each cylinder group is connected to a separate resonance chamber by a manifold, and A resonance supercharging system is configured by merging the resonance passages connected to the upstream and opening it to the atmosphere, and the volume effect of the engine is enhanced by utilizing the resonance effect in which the intake pressure fluctuation between cylinders that does not cause intake interference resonates. Various proposals have already been made.

By the way, the resonance supercharging effect is high when the opening and closing timing of the intake valve of the engine is matched with a specific natural frequency determined by the length of the resonance passage and the volume of the resonance chamber. There is a problem that a sufficient supercharging effect cannot be obtained when the matching is deviated due to a change in rotation speed. For this reason, various proposals have been made in which the natural frequency of the intake system is made variable so as to obtain the resonance supercharging effect in a wide rotation range of the engine (for example, JP-A-62-62).
-210219 gazette).

In the intake system, two resonance passages, long and short, are connected upstream of the resonance chamber provided in the intake system, and the long resonance passage is connected to the resonance chamber in the low speed rotation region of the engine by a switching valve to provide high speed. By connecting the resonance passage on the shorter side to the resonance chamber in the rotational range, the natural frequency of the intake system is made variable to obtain the resonance supercharging effect in a wide rotational range of the engine.

(3) Problems to be Solved by the Invention However, the above-described conventional intake device requires two long and short resonance passages for each resonance chamber, so that the structure of the entire intake system becomes complicated and large. Have a point.

The present invention has been made in view of the above circumstances, and it is compact and easy to manufacture by rationally laying out a resonance chamber, a resonance passage, and an on-off valve that makes the length of the resonance passage variable. An object of the present invention is to provide an intake system for a cylinder internal combustion engine.

B. Configuration of the Invention (1) Means for Solving the Problems In order to achieve the above object, the present invention provides a pair of resonance passages connected to the downstream side of a throttle valve, and a pair of resonance passages at the downstream ends thereof, respectively. A pair of continuous resonance chambers, an intake manifold connecting each of the resonance chambers to a group of cylinders whose intake stroke is not continuous, and a pair of variable resonance passages for varying the length of the pair of resonance passages according to the operating conditions of the engine. In an intake system for a multi-cylinder internal combustion engine including an on-off valve, each resonance chamber is formed along a corresponding resonance passage, and the resonance chamber and the resonance passage are formed along their length direction. The resonance chambers are arranged adjacent to each other with an extending partition wall interposed therebetween, and the upstream ends of the resonance chambers and the downstream ends of the corresponding resonance passages are communicated with each other, and the communication is performed without passing through the communication parts. The first feature is that the partition wall is provided with an opening / closing valve capable of performing a valve opening operation so as to short-circuit between a resonance chamber and the corresponding resonance passage, and in addition to this feature, an upper surface opening overlapped with each other is opened. A lower collecting box, an upper collecting box with an open lower surface, and a plate-like valve unit that partitions the open surfaces of both collecting boxes to form a partition, and the one collecting box includes the pair of resonance chambers. A second feature is that the pair of resonance passages are formed in the other collecting box and the opening / closing valve is provided in the valve unit.

(2) Action If the on-off valve is controlled to be closed in the low speed operation range of the engine, the downstream end of each resonance passage and the corresponding upstream end of the resonance chamber communicate with each other to achieve matching in the low speed operation range of the engine. Relatively long resonant supercharging systems with low natural frequencies can be constructed. Further, if the on-off valve is controlled to open in the high-speed operating range of the engine, each resonance passage is short-circuited to the corresponding resonance chamber via the on-off valve, and a relatively high natural frequency that matches in the high-speed operating range of the engine is obtained. A short resonance supercharging system can be constructed.

In such a resonance supercharging system, each resonance chamber is formed along a corresponding resonance passage, and the resonance chamber and the resonance passage are arranged adjacent to each other with a partition wall extending along their length direction interposed therebetween. Since the partition wall is provided with an on-off valve that short-circuits the resonance chamber and the resonance passage, only one resonance passage needs to be provided corresponding to one resonance chamber, and the resonance passage and the resonance chamber are connected to each other. Since the spaces are partitioned by a common partition and the partition also serves as the housing of the on-off valve, a large structural simplification of the device as a whole is achieved. Further, in particular, since the resonance chamber is arranged adjacent to the corresponding resonance passage so as to be along the corresponding resonance passage, even if each of the resonance chamber and the resonance passage is formed long, the spatial expansion of the entire resonance chamber can be suppressed as much as possible. it can.

According to the second feature of the present invention, a lower collecting box with an open upper surface, an upper collecting box with an open lower surface, and plate-like valve units for partitioning open surfaces of both collecting boxes are overlapped with each other, and one collecting box is provided with a pair. The resonance chamber of
Since the pair of resonance passages is formed in the other collecting box and the opening / closing valve is provided in the valve unit, not only the resonance chamber, the resonance passage and the opening / closing valve are compactly integrated, but also the assembling of the opening / closing valve is performed. This makes it possible to further simplify the structure of the intake system and reduce the manufacturing cost.

(3) Embodiments Embodiments in which the present invention is applied to a V-type 6-cylinder internal combustion engine will be described below with reference to the drawings.

1 to 5 show a first embodiment of the present invention. FIG. 1 is a longitudinal sectional view of a main part of a V-type 6 cylinder internal combustion engine equipped with the device of the present invention, and FIG. 2 is a plan view of the cylinder block. 3 and 4 are enlarged partial plan views taken along line III-III in FIG. 1, FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3, and FIG.
It is sectional drawing which follows the -V line.

In FIGS. 1 and 2, the engine body E of the 6-cylinder internal combustion engine is shown.
Includes a pair of left and right engine blocks Bl, Br which are arranged in a V shape with each other. The left and right engine blocks Bl, Br are joined to the cylinder blocks 1l, 1r and their deck surfaces, respectively. The left cylinder block 1l is formed with three left cylinders 3l in series, and the right cylinder block 1r is also formed with three cylinders 3r in series. The three cylinders 3l on the left side constitute a left cylinder group Cl in which the intake stroke is not continuous, that is, the intake valve 10 described later does not overlap, and the three cylinders 3r on the right side
Also constitutes the right cylinder group Cr in which the intake stroke is not continuous, that is, the intake valves 10 described later do not overlap.

Pistons 4 are slidably fitted in the left and right cylinders 3l and 3r as usual, and these pistons 4 are interlocked with a crankshaft 6 via a connecting rod 5. Further, the left and right cylinder heads 2l, 2r are respectively provided with a combustion chamber 7 facing the piston 4 and a suction chamber communicating with the combustion chamber 7.
Exhaust ports 8 and 9 are formed, each intake port 8 is provided with an intake valve 10 that opens and closes the port 8, and each exhaust port 9 is provided with an exhaust valve 11 that opens and closes the port 9. To be The intake / exhaust valves 10, 11 are opened / closed by a conventionally known shaft valve mechanism 12 at a predetermined timing.

An intake system In, which will be described in detail later, is connected to the intake ports 8 of the left and right cylinder heads 2l and 2r0, and a conventionally known exhaust system is connected to the exhaust ports 9 of the left and right cylinder heads 2l and 2r. (Not shown) is connected.

Next, the structure of the intake system In will be described in detail with reference to FIGS. 2 to 5. The intake system In is arranged in the V space C between the left and right cylinder blocks 11 and 1r, and the air cleaner Ac
And the intake passage Pi connected to the outlet of this air cleaner Ac.
And a resonance chamber assembly box Bg having a pair of left and right resonance chambers Cr-l, Cr-r connected to the downstream end of the intake passage Pi, and intake ports of the left and right cylinder blocks 1l, 1r. The left and right resonance chambers Cr-l, Cr-r are connected to the open end face of the cylinder 8 and communicate with the right and left cylinder groups Cr, Cl respectively, which will be described later.

The intake passage Pi is provided with an air cleaner Ac as shown in FIG.
A throttle body 15 is integrally connected to the downstream end of the intake passage 14 connected to the. Intake passage 14 is air cleaner Ac
The throttle body 15 is formed in an intermediate cylindrical shape so as to suck in the intake air from, and the throttle body 15 is divided into two or branched into left and right branch passages 18l, 18r downstream of the connection portion with the intake passage 14. Throttle valves 20l, 20r controlled to be opened / closed by a common operation unit 19 are provided inside the both branch passages 18l, 18r. A resonance chamber collecting box Bg is integrally connected to the downstream end of the throttle body 15 with a bolt 16.

The resonance chamber set box Bg is, as is clear from 4,5 drawing, wherein substantially a rectangular parallelepiped open top lower collection box 21 ₁ that connects to the throttle body 15, is formed integrally with an intake manifold Mi, which will be described later that substantially a rectangular lower surface opening of the upper set box 21 _2, both the set box 2
1 ₁ and 21 ₂ are composed of a plate-like valve unit 22 that forms a partition wall by airtightly adhering the upper and lower surfaces thereof to the open surface.
The two members are assembled with bolts 23 in a state where they are stacked one above the other.

Third to fifth lower collection box 21 ₁ of the resonance chamber set box Bg As apparent from the figure engine crankshaft 6
Direction, that is, the left and right resonance passages 25l and 25r that are parallel to each other and extend along the flow direction of intake air flowing in the box Bg
The left and right branch passages 18l, 18 of the throttle body 15 are provided at the upstream ends of the left and right resonance passages 25l, 25r.
The downstream ends of r communicate with each other. The left upper set box 21 ₂ in parallel with each other by the partition wall 24, the right resonance chamber Cr-l, is partitioned into a Cr-r, one of the resonance chambers Cr-l in an upper portion of the one resonance passage 25l, other The resonance chamber Cr-r is disposed above the other resonance passage 25r so as to extend along the length direction of the corresponding passages 25l and 25r.

The valve unit 22 includes left and right resonance chambers Cr-l,
The left and right inflow ports 26l, which serve as communicating portions that connect the upstream end of Cr-r to the downstream ends of the corresponding resonance passages 25l, 25r,
26r, left and right resonance chambers Cr-l, Cr-r, and resonance passages 25l, 25r are short-circuited before the inflow ports 26l, 26r, and left and right valve ports 27l, 27r are opened. Further valve unit 2
The left and right valve openings 27l and 27r are opened at 2 to provide open / close valves 28l and 28r capable of short-circuiting the left and right resonance chambers Cr-l and Cr-r and the resonance passages 25l and 25r. Ie valve unit 2
Two valve shafts 30l and 30r on the left and right, which are rotationally driven by a resonance actuator 29, are axially supported at 2 so as to penetrate through the central portions of the inflow ports 26l and 26r and the valve ports 27l and 27r. Rectangular plate-shaped valve bodies 31a and 31b provided at the valve openings 27l and 27r are fixed to the valve shafts 30l and 30r with screws 32.
The actuator 29 is operated and controlled according to the operating state of the engine, and controls the opening / closing valves 28l, 28r to be opened / closed.For example, the opening / closing valves 28l, 28r are closed during low-speed operation of the engine, and its high speed The open / close valves 28l and 28r are controlled to open during operation.

On the upper walls of the left and right resonance chambers Cr-l and Cr-r, left and right discharge ports 34l and 34r, which form three ellipses along the longitudinal direction, are opened. The three exhaust ports 34l of the left resonance chamber Cr-1 are connected to the three cylinders 3r of the right cylinder block 1r located on the opposite side of the left resonance chamber Cr-1 via an intake manifold Mi described later.
The three exhaust ports 34r of the right resonance chamber Cr-r are also connected to each other (intake order is not continuous), and the three exhaust ports 34r of the right resonance chamber Cr-r are also connected to the right resonance chamber Cr via an intake manifold Mi described later.
3 of left cylinder block 1l located on the opposite side of -r
It is connected to each of the three cylinders 3l (the intake order is not continuous).

The intake manifold Mi is longitudinal of the 1,5 first to sixth of the pipe 35 _{1-35 6} six to curved convexly upward as shown in FIG left, right resonance chamber Cr-l, Cr-r Are arranged in parallel in a direction substantially orthogonal to the direction and alternately intersect in opposite directions and extend to the left and right. Every other three of these, the second, fourth and sixth distribution pipes 35 ₂ , 35 ₅ and 35 ₆ upstream end left resonance chamber Cr-l three three cylinders the downstream end thereof extends on the opposite side of the resonance chamber Cr-l after each communicated with the discharge port 34l is right cylinder block 1r of It is connected to each 3r, and the rest of every other three first, third
And a 5-minute pipe 35 _1, 35 ₃ and 35 the upstream end of the ₅ extends on the opposite side of the resonance chamber Cr-r after being communicated respectively to the three discharge ports 34r of the right resonance chamber Cr-r, their downstream 3 cylinders 3l with left cylinder block 1l
Will be connected to each.

Each fuel injection nozzle 36 in the upper wall of the downstream end of the first to sixth of the pipe 35 _{1-35 6} is provided as shown in Figure 1.

Next, the operation of the first embodiment will be described.

The actuator 29 is actuated and controlled in accordance with the operating state of the engine. For example, in the low speed operating state, the on-off valves 28l, 28r are closed and controlled as shown by the solid lines in FIGS.
When 27r is closed, left and right resonance chambers Cr-l, Cr-r
The communication between the resonance passages 25l and 25r corresponding to and is cut off. In this state, branch passages 18l and 18r for each cylinder group, resonance passages 25l and 25r for each cylinder group, and left and right resonance chambers Cr for each cylinder group
-L, Cr-r and left and right distribution pipes for each cylinder group 35 ₁ , 35 ₂ , 35 ₃ , 35
_4, 35 _5, 35 ₆ which two systems of the intake system consisting of, that is, each three cylinders 3l, 3r resonance supercharge intake system of two systems does not cause intake interference leading to the outlet of the throttle body 15 is composed of.
The length of the intake system is relatively long, and the volume of the resonance chambers Cr-l, Cr-r is determined by the opening / closing cycle of each intake valve 10 when the natural frequency of the resonance supercharging system is in the low speed rotation range of the engine. The resonance supercharging effect is effectively exhibited and the volume efficiency in the low speed rotation range of the engine is enhanced.

When the engine is in a high-speed operation state, the actuator 29 operates and the left and right on-off valves 28l, 28r are controlled to open, and the left and right resonance chambers Cr-, which have been communicated with each other through the inflow ports 26l, 26r, until now. l, Cr-r and the resonance passages 25l, 25r are short-circuited via the valve ports 27l, 27r. As a result, the substantial length of the resonance passages 25l, 25r is reduced, and the resonance passages 25l, 25r are reduced.
Becomes a part of the resonance chambers Cr-l, Cr-r, and the substantial volume of the resonance chambers Cr-l, Cr-r increases, and the natural frequency of the resonance supercharging system increases in the high-speed rotation range of the engine. In order to substantially match the opening / closing cycle of each intake valve 10, the resonance supercharging effect is effectively exerted, and the volume efficiency in the high speed rotation range of the engine is enhanced.

As described above, the left and right resonance chambers Cr-l, Cr-r and the resonance passages 25l, 25r provided in the resonance chamber assembly box Bg are short-circuited / isolated via the opening / closing valves 28l, 28r to reduce the engine speed. It is possible to obtain high volumetric efficiency in a wide range of operating conditions from high speed to high speed. The upper set box 21 ₂ formed by laminating a resonance chamber set box Bg vertically, the lower collection box 21 _1, and consist of a valve unit 22, the left to the upper set box 21 _2, right resonance chamber Cr
-L, and Cr-r, the resonance passage 25l in the lower collection box 21 _1, 25r
The valve unit 22 and the inflow port 26
Since the l, 26r and the opening / closing valves 28l, 28r are provided, the resonance chamber collecting box Bg can be formed extremely compact and the manufacturing cost thereof can be reduced.

Next, a second embodiment of the present invention will be described with reference to FIG.

FIG. 6 is a sectional view of the same intake system as in FIG. 3, in which the same reference numerals as in the first embodiment indicate the same members.

In the second embodiment, the left and right open / close valves 28l, 28r for short-circuiting the left and right resonance chambers Cr-l, Cr-r and the resonance passages 25l, 25r in the previous embodiment are respectively two open / close valves 28l _1. , 28
r _1; as well as divided into 28l _2, 28r _2, the valve shaft 30l _1, 30r ₁ which is rotationally driven on-off valve 28l _1, 28r ₁ in the actuator 29 _1,
Off valve 28l _2, 28r ₂ the actuator 29 ₂ valve shaft 30l ₂ which is rotationally driven at, 30r ₂ each is installed.

According to this embodiment, in the low speed rotation range of the engine, all the on-off valves 28l ₁ , 28r ₁ ; 28l ₂ , 28r ₂ are closed as in the previous embodiment, and the volume efficiency in the low speed rotation range is increased. . Then, in the medium speed rotation range of the engine, one of the actuators 29 ₁ is driven to control the opening / closing valves 28l ₁ and 28r ₁ on the side closer to the inflow ports 26l and 26r. As a result, the substantial length of the resonance passages 25l, 25r is slightly reduced, and the resonance passages 25l, 25r are reduced.
Part of r becomes a part of the resonance chambers Cr-l, Cr-r, and the substantial volume of the resonance chambers Cr-l, Cr-r is slightly increased, and the natural frequency of the resonance supercharging system is increased. It is increased so as to substantially coincide with the opening / closing cycle of each intake valve 10 in the medium speed rotation range of the engine. Further, in the high-speed operation range of the engine, both actuators 29 ₁ and 29 ₂ are driven, and all the on-off valves 28l ₁ and 28r ₁ ; 28 are driven as in the previous embodiment.
The l ₂ , 28r ₂ are opened, and the volume efficiency in the high speed rotation range is enhanced.

In this way, according to the second embodiment, the natural frequency of the resonance supercharging system is switched in three stages, so that the resonance supercharging effect is effectively exhibited in a wide range from the low speed operating range to the high speed operating range. The volumetric efficiency of the engine is improved.

Next, a third embodiment of the present invention will be described with reference to FIGS.

Figures 7 and 8 are sectional views of the same intake system as in Figures 3 and 4,
In the figure, the same reference numerals as those used in the first embodiment denote the same members.

The third embodiment is resonance chamber set box Bg is connected downstream of the 'throttle body 15 having a' throttle valve 20 therein, is composed of the cover member 21 ₂ covering a collection box body 21 ₁ 'and the upper surface , The inside is crankshaft 6
It is partitioned into left and right by a partition wall 24 'extending along the longitudinal direction of the. A pair of bubbling units 22l ', 22r' forming partition walls are provided on the left and right sides of the partition wall 24 '.
It is mounted in a state of being sandwiched from above and below by 1 ₁ ′ and a lid pair 21 ₂ ′, and a pair of resonance passages 25 l ′, 25 r is provided between the left and right valve units 22 l ′, 22 r ′ and the partition wall 24 ′. Has been formed. Outside the left and right valve units 22l ', 22r', left,
The right resonance chambers Cr-l, Cr-r are formed, and both resonance chambers Cr-l, Cr-r and the downstream ends of the resonance passages 25l ', 25r' are shaped into valve units 22l ', 22r' inflow port 26l '. , 26r '.

The valve units 22l 'and 22r' have valve openings 27l 'and 27, respectively.
r ′ is open, and on-off valves 28l ′, 28r ′ connected to an actuator 29 ′ are mounted on the valve openings 27l ′, 27r ′ so as to open and close. The on-off valves 28r ', 28l' have the same structure as the on-off valves 28l, 28r in the previous embodiment, and the valves penetrating the valve openings 27l ', 27r' formed in the valve units 22l ', 22r'. It has a structure in which rectangular valve bodies 31l 'and 31r' are fixed to the shafts 30l 'and 30r' with screws 32 '.

According to this embodiment, the opening / closing valve 28l ',
28r 'is closed and the left and right resonance passages 25l', 25r 'communicate with the left and right resonance chambers Cr-l, Cr-r through their entire length.
As a result, a resonant supercharging intake system having a long passage length and a small natural frequency is configured, and the volume efficiency in the low speed rotation range of the engine is enhanced.

When the engine is in a high-speed operation state, the actuator 29 operates and the left and right on-off valves 28l ', 28r' are controlled to open, and the left, which has been in communication via the inflow ports 26l ', 26r' until now,
The right resonance chambers r-l, Cr-r and the resonance passages 25l ', 25r' are short-circuited via the valve ports 27l ', 27r', and the resonance passages 25l ', 2
As the substantial length of 5r ′ is reduced, this resonance path
25l 'and 25r' become a part of the resonance chambers Cr-l and Cr-r, and the substantial volume of the resonance chambers Cr-l and Cr-r increases, so that the volume efficiency in the high speed rotation range of the engine is improved. To be enhanced.

Also in this third embodiment, the resonance passages 25l ', 25
r ', resonance chamber Cr-l, Cr-r, valve unit 22
The rational layout of l ', 22r' and the on-off valves 28l ', 28r' enables simplification and downsizing of the intake system structure.

C. Effects of the Invention As described above, according to the first feature of the present invention, the resonance supercharging system in which the length of the resonance passage can be changed according to the operating region of the engine is provided for each cylinder group in which the intake stroke is not continuous. In the intake system for a multi-cylinder internal combustion engine, the resonance chambers of each resonance supercharging system are formed along the corresponding resonance passages, and the resonance chambers and the resonance passages extend in the length direction thereof. Since the partition walls are arranged adjacent to each other with the partition wall interposed, and the partition wall is provided with an on-off valve for short-circuiting between the resonance chamber and the resonance passage, only one resonance passage needs to be provided for each resonance chamber. The resonance passage and the resonance chamber are partitioned by a common partition, and the partition also serves as the housing of the on-off valve. As a result,
As a whole, it can greatly contribute to the simplification of the structure of the device and further cost reduction. And especially the resonance chamber,
Since the resonance chamber and the resonance passage are formed so as to be along the corresponding resonance passage and are adjacent to the resonance passage, the spatial expansion of the entire resonance chamber and the resonance passage can be suppressed as much as possible. It can also contribute to the compactness of.

According to the second feature of the present invention, a lower collecting box with an open upper surface, an upper collecting box with an open lower surface, and plate-like valve units for partitioning open surfaces of both collecting boxes are overlapped with each other, and one collecting box is provided with a pair. The resonance chamber of
Since the pair of resonance passages is formed in the other collecting box and the opening / closing valve is provided in the valve unit, not only the resonance chamber, the resonance passage and the opening / closing valve are compactly integrated, but also the assembling of the opening / closing valve is performed. This makes it possible to further simplify the structure of the intake system and reduce the manufacturing cost.

[Brief description of drawings]

1 to 5 show a first embodiment of the present invention. FIG. 1 is a longitudinal sectional view of a main part of a V-type 6 cylinder internal combustion engine equipped with the device of the present invention, and FIG. 2 is a plan view of the cylinder block. Fig. 3 is an enlarged partial plan view taken along line III-III in Fig. 1, Fig. 4 is a sectional view taken along line IV-IV in Fig. 3, and Fig. 5 is taken along line VV in Fig. 4. FIG. 6 is a sectional view taken along line 6, FIG. 6 shows a second embodiment of the present invention, and FIG. 7 is a sectional view of the same intake system as that of FIG. 3, and FIGS. 7 and 8 show a third embodiment of the present invention. 7 is a sectional view of the same intake system as in FIG. 3, and FIG. 8 is a sectional view of the same intake system as in FIG. Cl, Cr ... Cylinder group, Cr-l, Cr-r ... Left and right resonance chambers, Mi ... Intake manifold, 20l, 20r; 20 '... Throttle valve, 21 ₁ ...... Lower assembly box, 21 ₂ ...... Upper assembly box, 22; 22l ′, 22r ′ …… Valve unit (bulk),
25l, 25r; 25l ′, 25r ′ …… Resonance passage, 26l, 26r; 26l ′, 26
r ′ …… Inflow port as a communication part, 28l, 28r; 25l ′, 25
r ′ …… Open / close valve

Claims (2)

[Claims] 1. A pair of resonance passages (25l, 25r; 25l ', 25r) connected to the downstream side of a throttle valve (20l, 20r; 20') and a pair of resonance passages (25l, 25r; 25l ', 25r). ′) And a pair of resonance chambers (Cr-l, Cr-r) connected to each other, and an intake air connecting each resonance chamber (Cr-l, Cr-r) to a cylinder group (Cl, Cr) whose intake stroke is not continuous. A manifold (Mi),
The pair of resonance passages (25l, 25r;
In the intake system of a multi-cylinder internal combustion engine equipped with a pair of on-off valves (28l, 28r; 28l ', 28r') for varying the lengths of 25l ', 25r'), each resonance chamber (Cr -L, Cr-r) is formed along the corresponding resonance passage (25l, 25r; 25l ', 25r'), and the resonance chambers (Cr-l, Cr-r) and the resonance passage (25l) are formed. , 25r; 25l ', 25r') are arranged adjacent to each other with a partition wall (22; 22l ', 22r') extending along their length direction interposed therebetween, and each of the resonance chambers (Cr-l, Cr-r) ) And the corresponding resonance passage (25l, 25r; 25l ′, 25
r ′) is connected to the downstream end, and the communication part (26l, 2
6r; 26l ′, 25r ′) without passing through each resonance chamber (Cr-l,
Cr-r) and the corresponding resonance passage (25l, 25r; 25l ', 25
r ') is provided with an opening / closing valve (28l, 28r; 28l', 28r ') which can be opened so as to short-circuit with the partition wall (22; 22l', 22
r ′) is provided, the intake device for a multi-cylinder internal combustion engine. 2. A lower collecting box (21 ₁ ) having an open upper surface and an upper collecting box (2) having a lower open surface, which are stacked on each other.
1 ₂ ) and a plate-shaped valve unit (22) that partitions the open surfaces of both collection boxes (21 ₁ , 21 ₂ ) to form the partition wall, and the one collection box includes the pair of resonance chambers ( Cr-l, Cr-r), the pair of resonance passages (25l, 25r) are formed in the other collecting box, and the opening / closing valve (28l, 28r) is provided in the valve unit (22). An intake system for a multi-cylinder internal combustion engine according to claim 1.