JPH0629559B2 - Multi-cylinder engine intake system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake device for supplying intake air to a combustion chamber of a multi-cylinder engine, and more particularly to a multi-cylinder that utilizes inertial supercharging. The present invention relates to an intake device for an engine.

(Prior Art) The output torque of an engine largely depends on the intake charge efficiency. Inertial supercharging is known as a method for increasing the intake charging efficiency.

Inertial supercharging utilizes the inertia of the intake flow generated by opening the intake valve so that the intake air is pushed into the combustion chamber in the latter half of the intake stroke. When the intake valve opens, the negative pressure in the combustion chamber that accompanies the downward movement of the piston accelerates the air column in the intake pipe toward the combustion chamber. Then, due to the inertia, the intake air continues to flow into the combustion chamber even when the lowering of the piston is completed. That is, it is supercharged.

By utilizing such inertial supercharging, the charging efficiency can be easily increased only by tuning the intake system. Therefore, this inertia supercharging is widely used.

By the way, when such inertia supercharging is used, the intake charging efficiency becomes maximum when the cycle of the intake pulsation generated in the intake pipe matches the opening time of the intake valve during the continuous operation of the engine. That is, the tuning point of inertia supercharging is determined by the length and diameter of the intake pipe. If the length and diameter of the intake pipe are constant, the supercharging effect can be obtained only when the engine speed is within a certain range.

Therefore, conventionally, for example, as disclosed in Japanese Utility Model Publication No. 58-56330, a long intake pipe and a short intake pipe are connected to one combustion chamber, and the intake pipe is changed by a switching valve according to the engine speed. The one that is switched is proposed. According to such an intake device, the intake air is supplied through the long intake pipe at the time of low engine speed rotation, and the intake air is supplied through the short intake pipe at the time of high engine speed rotation. In this way, a high intake inertia effect can be obtained and the output torque of the engine can be increased.

(Problems to be Solved by the Invention) However, in the case of an engine used in a wide rotation speed range such as an automobile engine, when an attempt is made to obtain an intake inertia effect in the low speed range, at that time, It is necessary to make the intake pipe of the extremely long. Moreover, since such a long intake pipe must be provided for each cylinder, the layout becomes extremely difficult in the case of a multi-cylinder engine. Especially when the space is limited, such as in an automobile, it becomes impossible to mount such an engine.

Therefore, even if the intake inertia effect is exhibited in both the low speed region and the high speed region of the engine as shown in the above publication, the low speed region is actually a region where the engine speed is considerably high, that is, It has to be in the medium speed range.

As described above, it is difficult to achieve high intake charge efficiency in the low speed range of the engine only by using inertial supercharging.

By the way, a method called resonance supercharging is also known as a method of increasing intake charging efficiency.

In resonance supercharging, multiple cylinders with different intake valve opening timings are connected to one chamber equipped with a resonance pipe by independent intake pipes, and the pressure oscillation generated in that chamber and the intake cycle of each cylinder are synchronized. By doing so, the intake charging efficiency is increased. A chamber equipped with a resonance tube has a natural frequency determined by the volume of the chamber and the length and diameter of the resonance tube. Therefore,
When the intake valve of each cylinder is opened and closed so as to match its natural frequency, maximum pressure is generated in the chamber when the intake valve is open, and a large supercharging effect can be obtained.

However, in the case of this resonance supercharging, the engine speed at which the resonance effect is obtained is determined by the natural frequency of the intake system, that is, the volume of the chamber acting as the resonance box and the length and diameter of the resonance tube. . Therefore, when they are constant, the resonance effect can be obtained only when the engine speed is within a certain range. Moreover, the engine speed range in which the resonance effect is obtained is narrow. And if it deviates from the area | region, filling efficiency will fall rather. Therefore, it is not possible to increase the output torque of the engine in a wide rotational speed range only by this resonance supercharging.

The present invention has been made in view of such circumstances, and an object thereof is to obtain a high output torque in a wide rotation range of an engine while using an intake system having a simple structure. .

(Means for Solving the Problems) In order to achieve this object, in the present invention, a pair of distribution chambers are provided in correspondence with a pair of cylinder groups formed by a plurality of cylinders having different intake valve opening timings. The distribution chamber and each cylinder of the corresponding cylinder group are connected by a long main intake pipe, and the distribution chamber and each cylinder belonging to the corresponding cylinder group or the other cylinder group are short bypass intake pipes. I am trying to connect to each other. The bypass intake pipe is provided with a pipe length switching valve capable of opening and closing the bypass intake pipe. In addition, each of the distribution chambers is configured to communicate with each other or to be blocked by a large-diameter communication passage provided with an opening / closing valve. Each distribution chamber is connected to a small-volume collecting chamber by an independent intake passage.

The length and diameter of the main intake pipe and the bypass intake pipe are dimensioned so that the intake inertia effect is maximized in the medium speed range and the high speed range of the engine, respectively. Further, the volume of each distribution chamber and the length and diameter of the intake passage connected to it are set to such a size that the maximum resonance effect is exhibited when the distribution chambers are cut off in the low speed region of the engine. The pipe length switching valve that opens and closes the bypass intake pipe operates between the medium speed region and the high speed region of the engine, and the opening and closing valve that opens and closes the communication passage between the distribution chambers operates between the medium speed region and the low speed region of the engine. It is designed to work with.

(Operation) With this configuration, if the bypass intake pipe is opened / closed by the pipe length switching valve, each cylinder is connected to the distribution chamber via the bypass intake pipe or the main intake pipe, and accordingly In the engine speed range, that is, in the high-speed range of the engine when the bypass intake pipe is open, and in the medium-speed range of the engine set in the main intake pipe when the bypass intake pipe is closed, the intake inertia effect is You will get it. On the other hand, if the distribution chambers are shut off by an on-off valve, the intake system of each cylinder group becomes independent, and the resonance effect occurs in the engine speed region corresponding to the natural frequency of the intake system, that is, in the low speed region of the engine. Will be obtained.

Therefore, if the open / close valve is opened / closed between the low speed region and the medium speed region of the engine and the pipe length switching valve is opened / closed between the medium speed region and the high speed region, the resonance effect is generated in the low speed region of the engine. The intake charge efficiency is increased, and the intake charge efficiency is increased by the intake inertia effect in the medium speed range and the high speed range. That is, the intake charging efficiency is increased in the entire engine rotation range, and a high and flat torque characteristic curve can be obtained.

Further, the intake inertia effect only has to be exhibited in the middle and high speed regions of the engine, so that the length of the intake pipe for that purpose can be made relatively short. Further, in order to exert the resonance effect in the low speed region of the engine, the intake passage serving as the resonance pipe may be set long. Since it is sufficient to provide one intake passage for each cylinder group, the layout is easy even if the intake passage is long. Since the volume of the intake passage is increased by increasing the length of the intake passage, the volume of each distribution chamber that determines the natural frequency of the intake system together with the intake passage can be made relatively small. Therefore, the entire engine can be made compact.

(Examples) Examples of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of an intake system for a multi-cylinder engine according to the present invention. FIG. 1 is a cutaway front view of a main part of the engine, and FIG. 2 is a schematic plan view thereof.

As is clear from these figures, this engine is a V-6
A cylinder engine, the engine body 1 a pair of cylinder groups, that is, the first cylinder bank 2 ₁ and a second cylinder bank 2 _2, are disposed to open to the left and right V-shape. Each cylinder row 2 ₁ , 2 ₂
In each of the three cylinders 3 ₁ , 3 ₁ , 3 ₁ ; 3 ₂ , 3
_2, 3 ₂ are arranged in the axial direction of the crankshaft (not shown).

Cylinder block 4 cylinders _{3 1} or _{3 2} are formed
A cylinder head 5 is attached to the upper surface of the.
The combustion chamber 6 is provided on the bottom surface of the cylinder head 5 at a position facing the cylinders 3 ₁ and 3 ₂ . An intake port 7 and an exhaust port 8 that open to the combustion chamber 6 are provided inside the cylinder head 5, and the openings of the ports 7 and 8 on the combustion chamber 6 side are an intake valve 9 and an exhaust gas, respectively. It is designed to be opened and closed by the valve 10. Cylinder ₃ 1 of each present 3 belonging to each cylinder row _{2 1} or _{2 2,} 3 1, _{3 1} or ₃ 2,
3 _2, 3 ₂ of the intake valve 9,9,9, the opening timing has a 120 ° phase difference, are adapted not to overlap each other. The inlet of the intake port 7 is a cylinder row 2 ₁ ,
The upper surface of the cylinder head 5 located on the valley side between the _two 22 is opened, and the outlet of the exhaust port 8 is opened on the other side surface of the cylinder head 5.

A first distribution chamber 11 ₁ and a second distribution chamber 11 ₂ are arranged in parallel between the cylinder rows 2 ₁ and 2 ₂ . These first and second distribution chambers 11 ₁ , 11
₂ is located on the side far from the first and second cylinder rows 2 ₁ and 2 ₂ , respectively. Then, the intake ports 7, 7, 7 of the first distribution chamber 11 ₁ and the first cylinder row 2 ₁
Are independent of each other and have a relatively long main intake pipe 12 of relatively small diameter.
They are connected by ₁ , 12 ₁ and 12 ₁ . Further, the second distribution chamber 11 ₂ and the intake ports 7, 7, 7 of the second cylinder row 2 ₂ have the same main intake pipes 12, ₂ , 12 ₂ , 12 respectively.
Connected by _two . Furthermore, the second distribution chamber 1
1 ₂ and the first cylinder row _{2 1} of the intake ports 7, 7, 7 is,
Independent, relatively large bypass intake pipes 13 with a relatively large diameter
They are connected by ₁ , 13, ₁ and 13 ₁ . Similarly,
The first distribution chamber 11 ₁ and the intake ports 7, 7, 7 of the second cylinder row 2 ₂ are connected to the bypass intake pipes 13 ₂ , 1 respectively.
_They are connected by 3 ₂ and 13 ₂ . Main intake pipe 1
One end of each of 2 ₁ and 12 ₂ is a distribution chamber 11 ₁ ,
11 ₂ has an opening on the lower surface and the other end has a bypass intake pipe 13 ₁ ,
It is adapted to open the end of the 13 ₂ of the cylinder head 5 side. Then, the bypass intake pipes 13 ₁ and 13 ₂
Are attached to the end portions of the fuel injection nozzles 14 for injecting fuel into the intake ports 7, 7 ,. Further, at the ends of the bypass intake pipes 13 ₁ , 13 _{2 on} the distribution chamber 11 ₂ , 11 ₁ side, pipe length switching valves 15, 15, which can open and close the bypass intake pipes 13 ₁ , 13 ₂ , respectively.
... is provided. The pipe length changeover valves 15, 15, ... Are of the butterfly type and each have three bypass intake pipes 1.
Each of the three valves 15 provided on 3 ₁ , 13 ₂ interlock,
The actuators 16 and 16 are adapted to be opened and closed at the same time.

When the engine speed reaches a predetermined high speed, the actuator 16 is actuated relatively slowly according to the change in the speed, and in the high speed range of the engine, the pipe length switching valve 15 is opened and rotations below that are performed. In the area, the valve 15 is closed. Therefore, the pipe length switching valve 15
In the engine speed range from fully closed to fully open, the engine has an intermediate opening degree according to the engine speed at that time. The length and diameter of the main intake pipe 12 _1, 12 _2, an intake inertia effect when the predetermined rotational speed Nm is set to maximize the speed range in the engine, a bypass intake pipe 13 _1, 13 ₂ The length and diameter are set so that the intake inertia effect is maximized at a predetermined engine speed Nh in the high speed range of the engine.

The first and second distribution chambers 11 ₁ and 11 ₂ are connected to each other by a large-diameter communication passage 17. The communication passage 17 is opened and closed by a butterfly-type on-off valve 18. The on-off valve 18 is opened and closed relatively slowly in response to changes in the engine speed by an actuator 19 which operates when the engine speed becomes equal to or higher than a predetermined low speed. The communication path 17 is cut off, and the communication path 17 is made conductive in the rotation range beyond that. For the sake of convenience, in the figure, the communication passage 17 is shown to be relatively long with the same diameter as the bypass intake pipes 13 ₁ and 13 ₂ , but in reality, the diameter is as large as possible and the length is Be as short as possible. However, if the diameter is increased, the on-off valve 18 also needs to be large, and the actuator 19 becomes large. Therefore, when it is not desirable to make the diameter of the communication passage 17 too large, a plurality of the communication passages 17 are provided, and the communication passages 17 are simultaneously opened and closed by the multiple open / close valve 18.

Further, the first and second distribution chambers 11 ₁ and 11 ₂ are connected to the small-volume collecting chamber 21 by long independent intake passages 20 ₁ and 20 ₂ extending from one end thereof and extending to the other end side. ing. This intake passage 20 ₁ , 2
The length and diameter of 0 ₂ are the same as the volumes of the distribution chambers 11 ₁ and 11 _{2 and} the predetermined rotation speed N in the low speed region of the engine
When 1, the maximum resonance effect is obtained. A throttle body 22 is attached to the collecting chamber 21, and intake air taken in from an air cleaner (not shown) is metered by a throttle valve 23 and then introduced into the collecting chamber 21.

Next, the operation of the intake device thus configured will be described.

When the engine is running at low speed, the pipe length switching valve 15 and the on-off valve 1
8 is closed, bypass intake pipes 13 ₁ , 13
₂ and the communication paths 17 between the distribution chambers 11 ₁ and 11 ₂ are both blocked. Therefore, the intake air introduced from the air cleaner into the collecting chamber 21 through the throttle body 22 is distributed to the pair of intake passages 20 ₁ and 20 ₂ , and the first and second distribution chambers 11 ₁ and 11 ₂ are respectively distributed.
Be led to. Then, each of the distribution chambers 11 ₁ and 11
₂ are distributed to the three main intake pipes 12 ₁ and 12 ₂ respectively, and are introduced into the combustion chamber 6 of each cylinder 3 ₁ and 3 ₂ through the intake port 7 of the corresponding cylinder row 2 ₁ and 2 ₂ . During this time, fuel is injected from the fuel injection nozzle 14 and the fuel is supplied to the combustion chamber 6 together with the intake air.

By the way, such a flow of intake air flows in each cylinder 3 ₁ , 3 ₂
Caused by the intake stroke of. At this time, the intake system on the downstream side of the collecting chamber 21 is independent for each of the cylinder rows 2 ₁ and 2 ₂ . Moreover, the three cylinders 3 belonging to each of the cylinder rows 2 ₁ and 2 _2
1 , 3, ₁ 3, 3 ₁ ; 3 ₂ , 3 ₂ , 3 ₂ are designed so that the opening timing of the intake valve 9 thereof has a phase difference of 120 °. Therefore, when a certain cylinder 3 ₁ , 3 ₂ enters the intake stroke, the pressure wave generated in the cylinder 3 ₁ , 3 ₂ is distributed from the main intake pipes 12 ₁ , 12 ₂ to the distribution chambers 11 ₁ , 11 ₂ and the intake passage 20. Propagation to the collecting chamber 21 through ₁ and 20 ₂ . As a result, pressure oscillations occur in the distribution chambers 11 ₁ and 11 ₂ .

In that case, from the collecting chamber 21 to the distribution chamber 11 ₁ ,
The intake passages 20 ₁ and 20 ₂ reaching 11 ₂ are set to a sufficiently long predetermined dimension. In addition, the distribution chamber 11 ₁ ,
11 ₂ volume is also set to a predetermined size. Therefore, from the intake passages 20 ₁ and 20 ₂ to the distribution chamber 1
The intake air flowing through 1 ₁ , 11 ₂ will have a relatively low predetermined natural frequency. As a result, in the low speed range of the engine, the main intake pipes 12 ₁ and 12 ₂ and the distribution chamber 1 are
Resonance occurs between 1 ₁ and 11 _2, and intake air is pushed into the combustion chamber 6 due to the pressure oscillation. In this way, the resonance effect works and the intake charging efficiency is enhanced.

At this time, the pressure wave in _one intake passage 20 _{1 and} the pressure wave in the other intake passage 20 ₂ have opposite directions. Since the collecting chamber 21 has a small volume, the damping of the pressure vibration by the collecting chamber 21 is small. Therefore, one of the intake passage, for example, 20 pressure wave toward the collection chamber 21 at ₁ is transmitted to the other intake passage 20 _2, the pressure wave toward the distribution chamber 11 ₂ at its intake passage 20 ₂ is intensified.
As a result, a large supercharging effect can be obtained even in the low speed rotation range of the engine, and the intake charging efficiency is further improved.

Thus, the engine torque characteristic curve at this time is, as shown by I in FIG. 3, a low engine speed N
The curve has a peak at 1. That is, the output torque of the engine becomes high in the low speed range.

When the engine speed increases and exceeds a predetermined medium speed, the actuator 19 operates and the on-off valve 18 gradually opens. Thereby, the first and second distribution chambers 1
1 ₁ and 11 ₂ are in communication with each other through the communication passage 17 and work like one distribution chamber. Therefore,
Each cylinder ₃ 1, _{3 2} pressure wave generated from is canceled by the distribution chamber ₁₁ 1, 11 _2, the resonance effect will not occur. However, also at this time, the pipe length switching valve 1
5 is closed and the intake air is distributed to the distribution chambers 11 ₁ , 11
₂ is led to each cylinder 3 ₁ , 3 ₂ through a relatively long main intake pipe 12 ₁ , 12 ₂ . And the main intake pipe 1
2 ₁ and 12 ₂ are set to dimensions such that the intake inertia effect can be obtained in the medium speed range of the engine. Therefore, at this time, the intake charging efficiency is enhanced by the inertial effect.

Thus, the torque characteristic curve of the engine at this time becomes a curve having a peak at the engine speed Nm at medium speed, as indicated by II in FIG. That is, the output torque of the engine becomes high in the medium speed range.

When the engine speed further increases and exceeds a predetermined high speed engine speed, the actuator 16 operates to cause the pipe length switching valve 15 to operate.
Gradually opens. As a result, the bypass intake pipe 13 ₁ ,
13 ₂ are turned on. Therefore, the distribution chamber 11 ₁ ,
Air drawn into the 11 _2, not only is distributed to the main intake pipe ₁₂ 1, 12 _2, the bypass intake pipe ₁₃ 2, 13
It will be distributed to ₁ . Then, the intake air that has flowed into the bypass intake pipes 13 ₁ and 13 ₂ is transferred to the corresponding main intake pipe 1
It merges with the intake air guided through 2 ₁ and 12 ₂ and is supplied to the combustion chamber 6 of each cylinder 3 ₁ and 3 ₂ . At this time, the bypass intake pipes 13 ₁ and 13 ₂ are connected to the main intake pipes 12 ₁ and 12 _2.
Since the pipe length is shorter and the cross-sectional area is larger than that of the above, the flow of intake air guided to each cylinder 3 ₁ , 3 ₂ is dominated by the flow through the bypass intake pipes 13 ₁ , 13 ₂ . That is, as the pipe length, the bypass intake pipe 13
₁ and 13 ₂ come to influence. Then, since the bypass intake pipes 13 ₁ and 13 ₂ are set to a size that can obtain the intake inertia effect in the high speed region of the engine, at this time, the intake charging efficiency is increased by the inertia effect.

The torque curve of the engine at this time has a peak at a high engine speed Nh, as indicated by III in FIG. That is, the output torque of the engine becomes high in the high speed range.

When the opening / closing valve 18 is opened in the medium speed range or the high speed range of the engine as described above, the distribution chambers 11 ₁ , 1
Since 1 ₂ between is adapted to communicate with the communication passage 17, also so that the pressure vibration occurs in the communication passage 17. However, since the diameter of the communication passage 17 is sufficiently large and short, the frequency of the pressure vibration is extremely high. Therefore, due to the pressure oscillation, the main intake pipes 12 ₁ and 12 ₂ or the bypass intake pipe 1
The intake air flowing through 3 ₁ , 13 ₂ is not affected.

In this way, according to this intake device, a high output torque can be obtained in any of the low speed region, the medium speed region, and the high speed region of the engine. And that low speed range,
Between the medium speed range and the high speed range, the butterfly type on-off valve 18 or the pipe length switching valve 15 passes through the half open state, so that the resonance effect or the intake inertia effect gradually appears. Therefore, the torque characteristic curve of the engine becomes a flat curve with shallow valleys as shown by the thick line in FIG. 3, and shock does not occur at the time of switching.

Moreover, since the intake effect is increased by the resonance effect in the low speed region of the engine, the intake pipe for performing inertial supercharging has a long main intake pipe 12 ₁ , 12 ₂ even in the medium speed region of the engine. The length may be set to a relatively short length so that the maximum intake inertia effect can be obtained. In addition, the intake passages 20 ₁ and 20 for performing resonance supercharging
_{Since 2} is sufficient for two, even if the length is long, handling is easy. Further, distribution chamber ₁₁ 1, 11 ₂ of the volume may also be relatively small. Therefore, in the case of the V-type multi-cylinder engine as in the above embodiment, the cylinder row 2 ₁ ,
Using spatial like between 2 _2, it will be able to accommodate all of the intake system in that space can be a compact engine.

In the above embodiment, the first cylinder bank 2 ₁ and a second
The main intake pipes 12 ₁ and 12 ₂ connected to the respective cylinders 3 ₁ and 3 ₂ belonging to the cylinder row 2 ₂ are connected to the first distribution chamber 11 ₁ and the second distribution chamber 11 ₂ arranged on the far side, respectively. , The bypass intake pipes 13 ₁ and 13 ₂ are respectively connected to the second distribution chamber 11 ₂ and the first distribution chamber 11 ₁ arranged on the near side, but the first and second distribution chambers 11 ₁ , 11 _2, respectively first and second
The intake pipes 12 ₁ and 13 ₁ arranged on the side closer to the cylinder rows 2 ₁ and 2 ₂ and connected to the first cylinder row 2 ₁ are connected to the second distribution chamber 11 ₁ and the second cylinder row 2 ₂ It is also possible to connect each of the intake pipes 12 ₂ and 13 ₂ connected to the second distribution chamber 11 ₂ . In that case, the main intake pipes 12 ₁ and 12 ₂ are connected to the respective distribution chambers 11 ₁ and 11 _2.
It may be formed to be sufficiently longer than the bypass intake pipes 13 ₁ and 13 ₂ by surrounding the outer circumference thereof.

Further, the present invention is not limited to the V-type 6-cylinder engine as in the above embodiment, but can be applied to an in-line multi-cylinder engine or the like. In that case, all the cylinders are divided into two cylinder groups, that is, a first cylinder group and a second cylinder group according to different intake valve opening timings, and each cylinder group and the first and second distribution chambers 11 ₁ , 11 and ₂ main intake pipe ₁₂ 1, 1
Be connected by 2 ₂ and the bypass intake pipe ₁₃ 1, 13 ₂ may be configured similarly to the above embodiment.

(Effect of the invention) As is apparent from the above description, according to the present invention, the intake air flows through the long main intake pipe in the medium speed range and the short bypass intake pipe flows in the high speed range. The intake charge efficiency can be increased by inertia supercharging in both the medium speed range and the high speed range. Further, since the resonance supercharging is performed in the low speed range of the engine, the intake charge efficiency can be increased even in the low speed range where the inertia supercharging is difficult. Therefore, the output torque of the engine can be increased in each rotation speed range, and the engine with high output over the entire operation range can be obtained.

The structure of the intake system does not become significantly complicated because it is sufficient to add a resonance system to the conventional inertial supercharged intake system equipped with, for example, a pipe length switching system. Moreover, since a pair of distribution chambers are used,
It is also easy to provide the main intake pipe and the bypass intake pipe having different lengths. In particular, the dimension of the longer main intake pipe may be set so as to obtain the maximum intake inertia effect in the medium speed range of the engine, and its length may be relatively short. As described above, it is possible to use the space between the cylinder rows of the V-type multi-cylinder engine or the like to accommodate all the intake pipes in the space. Therefore, the engine can be made compact.

Further, by allowing the pipe length switching valve to take an intermediate opening degree during the opening and closing of the valve, it is possible to prevent a shock due to the switching and perform a smooth switching.

[Brief description of drawings]

FIG. 1 shows an embodiment of an intake device according to the present invention. A front view of a cutout of a main part of a multi-cylinder engine equipped with the intake device is shown in FIG. A plan view and FIG. 3 are graphs showing torque characteristic curves of the engine. 1 ... Engine main body 2 ₁ , 2 ₂ ...... First and second cylinder rows (cylinder group) 3 ₁ , 3 ₂ ...... Cylinder 9 ...... Intake valves 11 ₁ , 11 ₂ ...... First and second distribution chambers 12 ₁ , 12 ₂ ...... Main intake pipe 13 ₁ , 13 ₂ ...... Bypass intake pipe 15 ...... Pipe length switching valve 17 ...... Communication passage, 18 ...... Open / close valve 20 ₁ , 20 ₂ ...... Intake passage 21 ...... Assembly Chamber

Claims (2)

[Claims] 1. A first cylinder group 2 ₁ and a second cylinder group 2 ₂ each composed of a plurality of cylinders 3 ₁ , 3 ₁ , ...; 3 ₂ , 3 ₂ , ... With different intake valve opening timings. An intake system for a multi-cylinder engine; a first distribution chamber 11 ₁ and a second distribution chamber 11
_2, their first and second distribution chamber ₁₁ 1, 11 ₂ and the cylinder of the first cylinder group _{2 1 3} 1, _{3 1,} ... and the cylinders ₃ of the second cylinder group _{2 2, 3} 2, The relatively long main intake pipes 12 ₁ and 12 ₂ and the relatively short bypass intake pipes 13 ₁ and 13 _2, which connect to and, respectively, and the bypass intake pipes 13 ₁ and 13 ₂ A pipe length switching valve 15 that opens and closes between the _first and second distribution chambers 11 ₁ and 11
A large-diameter communication passage 17 for communicating ₂ from each other, and the on-off valve 18 and the communication passage 17 that opens and closes between the speed range and the low speed range in the engine, the first and second distribution chamber 11 _1, 11 ₂ And a small-volume collecting chamber 21 that supplies intake air through independent intake passages 20 ₁ and 20 ₂ , respectively, and the main intake pipes 12 ₁ and 12 ₂ and the bypass intake pipe 1
The lengths and diameters of 3 ₁ and 13 ₂ are set such that the intake inertia effect is maximized in the medium speed region and the high speed region of the engine, and the first and second distribution chambers 1 are
The volumes of 1 ₁ and 11 ₂ and the lengths and diameters of the intake passages 20 ₁ and 20 ₂ are set such that the maximum resonance effect is exhibited in the low speed range of the engine when the communication passage 17 is closed. Intake device for multi-cylinder engine. 2. The intake system for a multi-cylinder engine according to claim 1, wherein the pipe length switching valve 15 is adapted to take an intermediate opening degree with a change in engine speed.