JPH0452375B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an intake system for an engine, and particularly to an intake passage in a multi-cylinder engine equipped with two independent intake passages, one for low load and one for high load. This relates to an engine that uses intake pressure waves generated within the engine to obtain a supercharging effect over the medium to high rotation range of the engine.

(Prior Art) Generally, a multi-cylinder engine is provided with an intake passage having two systems, a low-load intake passage and a high-load intake passage, which open independently to each cylinder, and the intake passage has at least a low-load intake passage. It has a primary valve that changes the amount of intake air flowing through the intake passage for normal use, and a secondary valve that changes the amount of intake air that flows through the intake passage for high loads.When the engine is under low load, only the primary valve is opened. By supplying intake air to each cylinder only from the low-load intake passage, which has a narrow passage area, it increases the intake flow rate and improves combustion stability.At the same time, when the engine is under high load, the secondary valve is also opened. A so-called dual-induction type intake system is well known, in which intake air is supplied from a high-load intake passage as well, thereby increasing filling efficiency and increasing output.

By the way, the technology of supercharging the intake air by installing a supercharger in the intake passage in order to improve the filling efficiency and output of the engine is well known, but since it is equipped with a supercharger, the structure is large-scale. At the same time, there was a dislike of increasing costs.

In addition, as disclosed in Japanese Utility Model Publication No. 45-2321, a technique for obtaining a supercharging effect using intake pressure waves generated in the intake passage of an engine has conventionally been used in a single-cylinder engine to reduce the size of the intake pipe. It is divided into two different passages, each with a separate intake port, and when the engine is running at high speeds, the two intake passages are used.
At low engine speeds, by closing the intake passage with the slower closing position and occluding the intake air earlier, the supercharging effect is achieved by occluding the intake air at the point of maximum intake pressure, which is a function of the intake pipe dimensions and engine speed. It has been proposed to obtain suitable charging efficiency over a wide range of engine rotations by utilizing this.

(Problem to be solved by the invention) However, this device is for a single-cylinder engine, and its structure and operation are unclear, such as how to utilize the intake pressure waves generated in the intake passage. Therefore, it could not be put into practical use immediately.

Therefore, when examining the intake characteristics of the engine, the present inventors found that (i) When the intake port is opened, the intake air is compressed by the pressure of the residual exhaust gas in the combustion chamber, and a compression wave is generated at the intake port part in the intake passage. This compression wave occurs particularly strongly when the intake port is closed because the engine exhaust pressure has been increased in recent commercial vehicles to reduce noise and purify exhaust gas. (ii) When the intake port is closed, the compression wave It was discovered that the intake air is compressed due to the inertia of the engine, and a compression wave is generated at the intake port in the intake passage.

Therefore, in a multi-cylinder engine equipped with two independent intake passages as described above, the present invention is capable of converting the compression wave (i) in one cylinder upon opening into other cylinders, in particular, causing intake air to blow back. If the supercharging effect is applied at the end of the intake stroke, the supercharging effect can be effectively obtained (hereinafter referred to as the exhaust interference effect). Focusing on the fact that a supercharging effect can be effectively obtained by making it work on the engine (hereinafter referred to as the intake inertia effect), the engine This is intended to improve filling efficiency.

That is, an object of the present invention is to provide an intake system for a multi-cylinder engine having two intake passages as described above.
By setting one of the low-load and high-load intake systems to obtain an exhaust interference effect with a strong supercharging effect in the high engine speed range, and the other to obtain an intake inertia effect in a lower engine speed range, This system aims to effectively improve output by increasing filling efficiency from the mid- to high-speed range of the engine with a simple configuration by making slight design changes to the existing intake system without using a feeder or the like. It is.

(Means for Solving the Problem) In order to achieve this object, the solving means of the present invention has a low-load intake passage and a high-load intake passage independent of each other for each cylinder, and a low-load intake passage for each cylinder. A load intake passage and a high load intake passage are opened into the combustion chamber of each cylinder through independent low load intake ports and high load intake ports, and the intake passage has at least the above-mentioned The present invention is based on an engine intake system having a primary valve that changes the amount of intake air flowing through the low-load intake passage and a secondary valve that changes the amount of intake air that flows through the high-load intake passage. Further, downstream of the primary valve and the secondary valve, the low-load intake passages of each cylinder and the high-load intake passages of each cylinder are connected by communication passages having a passage cross-sectional area larger than the minimum passage cross-sectional area of each intake passage. communicate with each other. The minimum passage cross-sectional area and the opening cross-sectional area to the combustion chamber of either the high-load intake passage or the low-load intake passage are set larger than the other. The opening timing of the intake port having a larger opening cross-sectional area to the combustion chamber among the high-load intake port and the low-load intake port is set to be earlier than the opening timing of the other intake port. Furthermore, in the intake system of the high-load intake passage and the low-load intake passage, whichever has a larger minimum passage cross-sectional area, the passage length of the intake passage between each cylinder via the communication passage is set to 5000 to 5000.
When the engine rotates at a high speed of 7,000 rpm, the compression wave generated when the intake port of one cylinder opens will propagate to the intake ports of other cylinders at the end of the intake stroke to perform supercharging. In addition, in the other intake system, the passage length of the intake passage between each cylinder via the communication passage is set at a rotation speed 1000 to 2000 rpm lower than the reference rotation speed set between 5000 and 7000 rpm, It is assumed that the compression wave generated when the intake port of one cylinder is closed propagates to the intake port of another cylinder at the end of the intake stroke to perform supercharging.

(Function) As a result, in the present invention, the 5000
When the engine is running at high speeds of ~7000rpm, the secondary valve opens to open both the low-load intake passage and the high-load intake passage. Intake air is supplied independently of the In this case, in the intake system where the minimum passage cross-sectional area is large and opens quickly, when the intake port of one cylinder opens, the opening cross-sectional area generated near the intake port passes through the communication passage to the other cylinder at the end of the intake stroke. Propagates to the intake port of the cylinder. As a result, this opening compression wave forces the intake air into the combustion chamber from the intake ports of other cylinders at the end of the intake stroke, resulting in supercharging (exhaust interference effect in the high rotation range).

On the other hand, compared to the reference rotation speed of 5000 to 7000 rpm above,
On the low speed side of 1000 to 2000 rpm, in the other intake system, when the intake port of one cylinder is closed, the compression wave generated near the intake port passes through the communication path to the other cylinder, which is also at the end of the intake stroke. It is propagated to the intake port of the cylinder and supercharging is performed (intake inertia effect in the middle rotation range).

In that case, the intake passage, which is the pressure wave propagation path in the intake system on which the exhaust interference effect occurs, must have a larger passage cross-sectional area and opening cross-sectional area to the combustion chamber than the intake passage in the other intake system. Therefore, the resistance to the propagation of pressure waves is small, and the exhaust interference effect described above is effectively exerted, which is advantageous because it meets the output requirements particularly at high engine speeds (5000 to 7000 rpm), which require high output.

Further, the communication passages are located downstream of the primary valve and the secondary valve, respectively, and the passage cross-sectional area of each communication passage is set to be greater than or equal to the minimum passage cross-sectional area of each intake passage, so that each of the above-mentioned valves The pressure waves are not attenuated, and although the pressure waves are attenuated due to the expansion of the passage cross-sectional area of each communication passage, the attenuation rate is small compared to the pressure wave attenuation due to the reduction of the passage cross-sectional area (throttling). Therefore, the exhaust interference effect and the intake inertia effect described above can be effectively exhibited.

Furthermore, by opening the intake port of the intake system on the side that obtains the above-mentioned exhaust interference effect earlier than the intake port of the other intake system, a strong compression wave can be generated at the time of opening. It is effective by improving the supply effect.

Here, the limitation of 5000 to 7000 rpm as the engine high speed to obtain the above exhaust interference effect is because the maximum output and maximum speed are generally set within this range. This is because it requires a lot of power and is an effective area for improving filling efficiency and power.

Furthermore, the reason why the low-load intake passage and the high-load intake passage are made independent downstream of the primary and secondary valves is that the pressure waves generated in the low-load and high-load intake passages of each cylinder are This is to prevent the intake passage from dispersing to the other or from weakening due to interference with each other.In particular, due to the difference in requirements between the low-load intake passage and the high-load intake passage in the dual induction system, the intake port This is because the opening and closing timings and lengths of the two are different, and one pressure wave is attenuated by the other.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIGS. 1 and 2 show a first embodiment as a basic structural example in which the present invention is applied to a dual induction type four-valve two-cylinder four-cycle engine. In the figure, 1A and 1B are a first cylinder and a second cylinder, and 2 is a combustion chamber formed by a cylinder 3 and a piston 4 in each cylinder 1A, 1B.

Reference numeral 5 denotes a main intake passage whose one end opens to the atmosphere via an air cleaner 6 to supply intake air to each cylinder 1A, 1B, and the main intake passage 5 is equipped with an air flow meter 7 for detecting the amount of intake air. It is arranged. The main intake passage 5 is partitioned downstream of the air flow meter 7 by a partition 8 into a main low-load intake passage 9 and a main high-load intake passage 10. The main low-load intake passage 9 includes a primary valve that opens as the engine load increases, and when the load exceeds a predetermined load, opens fully to change the amount of intake air flowing through the main low-load intake passage 9. 11 are arranged. Further, the main high-load intake passage 10 is provided with a secondary valve 12 that opens when the engine load exceeds a predetermined load and changes the amount of intake air flowing through the main high-load intake passage 10 during high engine load. has been done. Further, the main low-load intake passage 9 is branched downstream of the primary valve 11 into first and second low-load intake passages 9a and 9b having the same shape and dimensions, and then connected to low-load intake ports 13 and 13, respectively. Through each cylinder 1
It communicates with the combustion chambers 2, 2 of A and 1B. Also,
The main high-load intake passage 10 is branched into first and second high-load intake passages 10a and 10b having the same shape and dimensions downstream of the secondary valve 12, and then connected through high-load intake ports 14 and 14, respectively. Each cylinder 1A, 1
It communicates with the combustion chambers 2, 2 of B. Therefore, for each cylinder 1A, 1B, low load intake passage 9a,
9b and the high-load intake passages 10a and 10b are configured to open into the combustion chamber 2 independently at the downstream of the primary valve 11 and the secondary valve 12.

The minimum passage cross-sectional area A _S of each of the above-mentioned high-load intake passages 10a, 10b is the respective low-load intake passage 9a, 9b.
The minimum passage cross-sectional area of A _P is set larger than (A _S
> A _P ), the opening cross-sectional area of each high-load intake port 14 to the combustion chamber 2 is the same as the low-load intake port 13 above.
The cross-sectional area of the opening is set larger than the cross-sectional area of the opening, so that pressure waves can be effectively propagated through the high-load intake passages 10a and 10b by reducing their attenuation.

In addition, the downstream ends (near the opening to the combustion chamber 2) of each of the low-load intake passages 9a and 9b (naturally located downstream of the communication passage 18, which will be described later) are equipped with air flow meters based on the output of the air flow meter 7, respectively. Electromagnetic valve type fuel injection nozzles 15, 15 whose fuel injection amount is controlled according to the intake air amount are provided to ensure good fuel response.

The branch part of the main high-load intake passage 10 is located downstream of the secondary valve 12, and is an enlarged chamber having a communication passage 16 that communicates the first and second high-load intake passages 10a and 10b. 17. The passage cross-sectional area A _CS of the communication passage 16 is:
It is set to be equal to or greater than the minimum passage cross-sectional area A _S of each high-load intake passage 10a, 10b (A _CS ≧A _S ) so that pressure waves are effectively transmitted with less attenuation.

Further, the branch part of the main low-load intake passage 9 is
It is located downstream of the primary valve 11 and is constituted by an enlarged chamber 19 having a communication passage 18 that communicates the first and second low-load intake passages 9a and 9b. The passage cross-sectional area A _CP of the communication passage 18 is set to be equal to or larger than the minimum passage cross-sectional area A _P of each low-load intake passage 9a, 9b so as to transmit pressure waves effectively (A _CP ≧A _P ).

Each of the expansion chambers 17 and 19 functions as a surge tank for intake air during transient operations such as acceleration or deceleration of the engine, and prevents breathing during acceleration and fuel overflow during deceleration. This prevents misfires and other misfires caused by the engine and ensures good response of the fuel.

Furthermore, each of the high-load intake ports 14 is provided with a high-load intake valve 20 that opens and closes the high-load intake port 14, and although not shown, each of the low-load intake ports 13 is provided with a high-load intake valve 20 for opening and closing the high-load intake port 14. Intake port 1
A low-load intake valve that opens and closes 3 is provided.
In each cylinder 1A, 1B, one end of 21 and 22 opens to the atmosphere, and the other end opens to the exhaust port 2.
3, 24 to open into the combustion chamber 2 of each cylinder 1A, 1B to discharge exhaust gas from the combustion chamber 2.
and a second exhaust passage, each of the above exhaust ports 2
3 and 24 are provided with exhaust valves 25 and 25 that open and close the exhaust ports 23 and 24, respectively. Although not shown, a catalyst device for purifying exhaust gas is installed at the downstream collecting portion of each exhaust passage 21, 21, 22, 22 of each cylinder 1A, 1B, and the exhaust pressure is high. It's summery.

Further, as shown in FIG. 3, the opening timing of the high-load intake valve 20 (the opening timing of the high-load intake port 14) is the same as the opening timing of the low-load intake valve (not shown) (the opening timing of the high-load intake port 14). The opening timing of the intake port 13 for high-load use is set earlier than the opening timing of the intake port 13 for
At 10b, a strong compression wave is generated when opening. Also, the closing timing of the high-load intake valve 20 (the closing timing of the high-load intake port 14) and the closing timing of the low-load intake valve (the closing timing of the low-load intake port 14)
This is set at almost the same time as the closing timing of No. 3), and the opening compression wave propagated to the high-load intake port 14 at the end of the intake stroke due to inter-cylinder interference and the low-load intake port 13 at the end of the intake stroke. The propagated compression wave at the time of closing is transmitted to the other intake port 13 or 1.
This prevents the air from blowing through from 4 to effectively obtain the supercharging effect.

In addition, both cylinders 1 via the communication passage 16
Passage length L _S of high load intake passages 10a and 10b between A and 1B (that is, high load intake ports 14 and 1
4) is the passage length of the communication passage 16 l _CS
and the respective passage lengths l _{S and} l _{S of the first and second high-load intake passages 10a and 10b downstream of the communication passage 16 (L S =} l _CS +2l _S , and at 5000 to 7000 rpm In order to obtain an exhaust interference effect as an inter-cylinder interference effect between both cylinders 1A and 1B in the rotation range, L _S = {(720/Z) + θ _S − θ _C } × (60/360 N) × a …(). It is set to the value obtained from the formula.In the above formula (), Z is the number of cylinders, and in the case of two cylinders, Z
=2, and 720/Z indicates the phase difference between the cylinders.
θ _S is the opening period of the high-load intake valve 20, and θ _C is the period from the opening of the high-load intake valve 20 (opening of the high-load intake port 14) until the opening compression wave is substantially generated. The high-load intake valve 2 of the other cylinder through which the compression wave is propagated at the time of opening in order to effectively perform supercharging during this period.
The invalid period is the sum of the period from the time just before the valve closes (the high-load intake port 14 closes) until the valve closes, and is about 10 to 50 degrees, although it varies depending on the valve opening characteristics. Therefore, {(720/Z)+θ _S −θ _C } represents the rotation angle of the crankshaft required from generation of the opening compression wave in one cylinder to propagation to the other cylinder at the end of the intake stroke. Further, N is the engine rotation speed, N = 5000 to 7000 rpm, and 60/360N represents the time (seconds) required to rotate 1 degree. Also, a
is the propagation velocity (sound velocity) of the pressure wave, and at 20℃ a=
It is 343m/s.

Furthermore, both cylinders 1 via the communication passage 18
Similarly, the passage length L _P of the low-load intake passages 9a and 9b between A and 1B (that is, the communication length between the low-load intake ports 13 and 13) is the passage length of the communication passage 18.
It is the sum of l _CP and the respective passage lengths l _P and l P of the first and second low-load intake passages 9a and 9b downstream of the communication passage 18 ( _{L P =} l _CP +2l _P ), and the above 5000～
1000 than the reference rotation speed set between 7000rpm
~2000rpm In order to obtain the intake inertia effect as an inter-cylinder interference effect between both cylinders 1A and 1B on the low rotation side (for example 4000~5000rpm), L _P = {(720/Z) - θ ₁ } × (60/360N) )×a...() is set to the value determined by the formula. In the above equation (), θ ₁ is the period from when the low-load intake valve closes (low-load intake port 13 closes) until the compression wave is substantially generated when the valve closes, and in order to effectively perform supercharging. The invalid period, which is the sum of the period from just before the closing of the low-load intake valves of other cylinders to which the compression wave is propagated during closing, is also about 10 to 50 degrees, and {(720/ Z)-θ ₁ } represents the rotation angle of the crankshaft required from generation of the compression wave at closing in one cylinder to propagation to the other cylinder at the end of the intake stroke. The rest is the same as in the case of formula () above.

Note that in the above equations () and (), the influence of the flow of intake air on the propagation of pressure waves is ignored. This is because the flow velocity is smaller than the speed of sound and causes almost no change in the length of the intake passage.

Next, the operation of the first embodiment will be explained with reference to FIG. 3.
When the engine is running at high speed, the secondary valve 12 is opened to open the main high-load intake passage 10 as well as the main low-load intake passage 9, and the main high-load intake passage 10 is opened for each cylinder 1A, 1B.
Intake air is supplied from each high-load intake passage 10a, 10b independently from each low-load intake passage 9a, 9b. At that time, when the high-load intake port 14 of one cylinder, for example, the high-load intake valve 20 of the second cylinder 1B is opened, the second high-load intake passage 1 is opened.
The opening compression wave generated near the high-load intake port 14 of 0b increases the passage length L _S of the high-load intake passages 10a and 10b between both cylinders 1A and 1B by 5000~
By setting the value determined by the above formula () based on the engine high speed of 7000 rpm, the second high-load intake passage 10b → communication passage 16 →
After passing through the first high-load intake passage 10a, the high-load intake port 14 of the first cylinder 1A at the end of the intake stroke
propagate to. As a result, this opening compression wave forces the intake air into the combustion chamber 2 from the high-load intake port 14 of the first cylinder 1A at the end of the intake stroke, and supercharging is performed (high-load intake exhaust interference effects in the system).

On the other hand, when the engine rotates at a lower speed of 1000 to 2000 rpm than 5000 to 7000 rpm, when the low load intake port 13 of the second cylinder 1B is closed, the second low load intake passage 9b is closed. The compression wave generated near the low-load intake port 13 is caused by the low-load intake passage 9 between both cylinders 1A and 1B.
By setting the passage length L _P of a and 9b to a value determined by the above formula () at a rotation speed 1000 to 2000 rpm lower than the reference rotation speed of 5000 to 7000 rpm, the second low-load intake passage 9b→ Supercharging is carried out via the communication passage 18 → the first low-load intake passage 9a to the low-load intake port 13 of the first cylinder 1A, which is also at the end of the intake stroke (in the low-load intake system). Inspiratory inertia effect).

Similarly, in the second cylinder 1B, the opening compression wave or the closing compression wave from each intake port 13, 14 of the first cylinder 1A is applied to each intake port 13, 14 at the end of the intake stroke. Supercharging is carried out through propagation.

Therefore, in this way, there is a supercharging effect due to exhaust interference effect in the high engine speed range of 5000 to 7000 rpm in the high-load intake system, and an intake effect in the low-speed range of 5000 to 7000 rpm in the low-load intake system. Due to the supercharging effect due to the inertia effect, as shown in FIG. 4, the charging efficiency increases from the middle speed range to the high speed range of the engine, and the output can be effectively improved. In addition, in FIG. 4, each cylinder 1A,
In contrast to the conventional example (indicated by broken lines) in which the intake passages 9a, 9b, 10a, and 10b of 1B are made independent, the exhaust interference effect (indicated by solid lines) in the high-load intake system is adjusted to 6000 rpm in the low-load intake system. In the intake system for
The output torque characteristics of the engine are shown when the intake inertia effect (indicated by the dashed line) is obtained based on 4000 rpm.

In addition, in that case, the high-load intake passages 10a and 1, which are pressure wave propagation paths for obtaining the exhaust interference effect.
0b has a larger passage cross-sectional area and opening cross-sectional area to the combustion chamber 2 than the low-load intake passages 9a and 9b, so the resistance to pressure wave propagation is small and there is no exhaust interference in the high-load intake system. By effectively demonstrating the effect,
Especially at high engine speeds that require high output (5000~
It is advantageous because it meets the output requirement at 7000rpm).

Further, the communication passages 16 and 18 are located downstream of the primary valve 11 and the secondary valve 12, respectively, and the passage cross-sectional areas A _CP and A _CS of the communication passages 16 and 18 are equal to each intake passage 9a and 9b. , 10a, 10b is set to be greater than or equal to the minimum passage cross-sectional area A _P , A _S , each of the above-mentioned valves 11,
12, and although there is pressure wave attenuation due to the expansion of the passage cross-sectional area of each communication passage 16, 18 itself, compared to the pressure wave attenuation due to passage cross-sectional area reduction (throttle). The attenuation rate is small, so the exhaust interference effect and intake inertia effect described above can be effectively exerted.

Furthermore, by opening the high-load intake port 14 earlier than the low-load intake port 13, a strong compression wave can be generated especially when the high-load intake port 14 opens, resulting in an exhaust interference effect. This is more effective due to improved supercharging effect. In addition, by making the closing timing of the high-load intake port 14 and the closing timing of the low-load intake port 13 almost the same, compression waves are generated at the intake port 1 due to inter-cylinder interference effects.
This is advantageous because it can prevent blow-through from 3 or 14.

Also, a fuel injection nozzle 1 as a fuel supply device
5 is a low-load intake passage 9a downstream of the communication passage 18;
9b is provided at the downstream end (near the opening to the combustion chamber 2), the length of the intake passage becomes longer in order to obtain the inter-cylinder interference effect, and the communication passage 1
8 Deterioration of fuel response (delay in response of fuel supply corresponding to the changed amount of air introduced into the combustion chamber 2) occurs due to a delay in response during continuous acceleration/deceleration of the air flow meter 7 located upstream. It is possible to prevent this and ensure good fuel response, and to simplify the fuel supply system by installing only the low-load intake passages 9a and 9b, which can supply intake air and fuel in all operating ranges. It is possible to aim for

Further, the supercharging effect due to the exhaust interference effect and intake inertia effect is determined by the position of the communicating passages 16, 18, the cross-sectional area of the passage, and the high load effect between the two cylinders 1A, 1B via the communicating passages 16, 18. Intake passage 10
A, 10b and the low-load intake passages 9a, 9b are obtained by setting the respective passage lengths L _S , L _P etc. as described above, and since a supercharger etc. is not required, the existing intake system can be used. It requires only a slight design change, has an extremely simple structure, and can therefore be implemented easily and at low cost.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but also includes various other modifications. For example, although the first embodiment described above shows an example in which the present invention is applied to a two-cylinder four-stroke engine, it goes without saying that the present invention can also be applied to various other multi-cylinder engines of the dual induction type. For example, as an example, FIG. 5 shows a second embodiment applied to a four-valve, four-cylinder, four-stroke engine (the same parts as in the first embodiment are denoted by the same reference numerals, and detailed explanations thereof are given below). (Explanation omitted).

In the case of this example, the high-load intake passages 10a to 10d of each cylinder 1A to 1D are communicated with each other by a communication passage 16' formed by an enlarged chamber 17' downstream of the secondary valve 12, and each cylinder 1A to The 1D low-load intake passages 9a to 9d are connected to the expansion chamber 1 downstream of the primary valve 11.
A fuel injection nozzle 15 is provided in each of the low-load intake passages 9a to 9d downstream of the communication passage 18'. Also, the high-load intake passages 10a to 1 between the cylinders 1A to 1D are connected via the communication passages 16' and 18'.
Passage length of 0d and low load intake passages 9a to 9d
When obtaining the exhaust interference effect, L _S and L _P differ in the first term on the right side of the above equation () (rotation angle required from generation of compression wave to propagation during opening) (see Figure 8), and L _S = It is set by (θ _S −180−θ _O )×(60/360N)×a (′), and when obtaining the intake inertia effect, it is set as Z=4 according to the above equation ().
Although not shown, the same applies to a three-cylinder, four-stroke engine as in the case of a two-cylinder engine, and the passage lengths L _S and L _P may be set using the above () and ().

Further, in the second embodiment (four-cylinder four-cycle engine), the passage lengths l _P1 , l P4, l _S1 of the corresponding intake passages 9a and 9d, 10a and 10d of the first and fourth cylinders 1A and _{1D are} and l _S4 are the same, and l _P1
=l _P4 >l _S1 =l _S4 , and the second and third cylinders 1
B, 1C intake passages 9b and 9c, 10b and 10
The path lengths l _P2 and l _P3 and l _S2 and l _S3 of c are the same, respectively.
And l _P2 = l _P3 > l _S2 ] l _S3 . Therefore, 1st cylinder 1A → 3rd cylinder 1C → 4th cylinder 1D → 2nd cylinder 1
In the ignition order B, the passage lengths L _P and L _S between consecutive combustion cylinders are all the same. That is, L _P = l _P1 (l _P4 ) + l _P2 (l _P3 ) L _S = l _S1 (l _S4 ) + l _S2 (l _S3 ), so each intake passage 9a of each cylinder 1A to 1D
9d and 10a to 10d are preferably branched from near the enlarged chambers 17' and 19'.

Furthermore, in the case of a general two-cylinder engine, the inter-cylinder interference of the exhaust interference effect and the intake inertia effect has the same effect as the exhaust interference effect (indicated by the solid line arrow) and the intake inertia effect, as shown in Figure 6. The inertial effect (indicated by the dashed arrow) acts alternately from the first cylinder to the second cylinder, and from the second cylinder to the first cylinder. In addition, in the case of a three-cylinder engine, as shown in FIG. 7, both of the above effects can be achieved from the first cylinder to the second cylinder, from the second cylinder to the third cylinder, as in the case of a two-cylinder engine.
It acts sequentially from the 3rd cylinder to the 1st cylinder. Furthermore, in the case of a 4-cylinder engine, as shown in Figure 8, the intake inertia effect is caused by the following firing order: 1st cylinder → 3rd cylinder, 3rd cylinder → 4th cylinder, 4th cylinder → 2nd cylinder. , the exhaust interference effect acts sequentially from the 2nd cylinder to the 1st cylinder, and conversely, the exhaust interference effect acts from the cylinder whose phase is delayed by 180 degrees, from the 3rd cylinder to the 1st cylinder, and from the 4th cylinder to the 3rd cylinder. , from the second cylinder to the fourth cylinder, from the first cylinder to the second cylinder, and from the third cylinder to the first cylinder. Therefore, the lengths L _S and L _P of the passages between the cylinders that perform the inter-cylinder interference in this way may be set so as to obtain the exhaust interference effect or the intake inertia effect.

Further, in the above embodiment, the primary valve 11 is provided in the main low-load intake passage 9, but the primary valve 11 is provided in the main low-load intake passage 9 and the main high-load intake passage 9. A type provided in the main intake passage 5 upstream of the branching part with the intake passage 10 can also be adopted.

(Effects of the Invention) As explained above, according to the present invention, in a multi-cylinder engine equipped with two independent intake passages for low load and high load, when the engine rotates at a high speed of 5000 to 7000 rpm, In the rotation range where the exhaust pressure is high, the opening area to the combustion chamber suddenly increases and the exhaust interference effect in the intake system on the side that opens earlier allows a strong supercharging effect to be sufficiently and effectively obtained.
Since the supercharging effect is obtained by the intake inertia effect in the other intake system at 1000 to 2000 rpm lower than the standard rotation speed of 7000 rpm, a slight reduction in the existing intake system can be achieved without the need for a supercharger etc. Even with a simple configuration based on design changes, it is possible to increase charging efficiency and effectively improve output from the mid- to high-speed range of the engine, thus making it easier to implement measures to improve engine output and reducing costs. This is something that can greatly contribute to the development of society.

[Brief explanation of the drawing]

The drawings show embodiments of the invention, FIGS. 1 and 2.
The figure is an explanatory diagram of the overall configuration and a schematic diagram of the main parts of the first embodiment, FIG. 3 is an explanatory diagram showing the intake stroke of the first embodiment, FIG. 4 is a diagram showing the output torque characteristics, and FIG. A diagram corresponding to FIG. 1 showing the second embodiment, FIGS. 6 to 8
The figures are explanatory diagrams showing inter-cylinder interference in two-cylinder, three-cylinder, and four-cylinder engines, respectively. 1A to 1D...1st to 4th cylinders, 2...Combustion chamber, 5
... Main intake passage, 7... Air flow meter, 9... Main low load intake passage, 9a to 9d... 1st to 4th low load intake passage, 10... Main high load intake passage, 10a
~10d...first to fourth high-load intake passages, 11...
Primary valve, 12... Secondary valve, 15... Combustion injection nozzle,
16, 16'...Communication path, 18, 18'...Communication path.

Claims (1)

[Scope of Claims] 1. Each cylinder has an independent low-load intake passage and a high-load intake passage, and the low-load intake passage and high-load intake passage of each cylinder are connected to the combustion chamber of each cylinder. The chamber is provided with an intake passage opened through a low-load intake port and a high-load intake port that are independent of each other, and the intake passage includes at least a primary valve that changes the amount of intake air flowing through the low-load intake passage. , an intake system for an engine having a secondary valve that changes the amount of intake air flowing through the high-load intake passage, wherein downstream of the primary valve and the secondary valve, the low-load intake passages of each cylinder are connected to each other and The high-load intake passages are communicated with each other through communication passages having a passage cross-sectional area larger than the minimum passage cross-sectional area of each intake passage, and the minimum passage cross-section of either the high-load intake passage or the low-load intake passage is The area and opening cross-sectional area to the combustion chamber are set larger than the other, and the opening timing of the intake port with a larger opening cross-sectional area to the combustion chamber among the high-load intake port and low-load intake port is set to be larger than the other. Set earlier than the opening timing of the intake port, the intake passage between each cylinder via the communication passage in the intake system with the larger minimum passage cross-sectional area among the above-mentioned high-load intake passage and low-load intake passage. The passage length is set so that when the engine rotates at high speeds of 5,000 to 7,000 rpm, the compression wave that occurs when the intake port of one cylinder opens propagates to the intake ports of other cylinders at the end of the intake stroke to perform supercharging. Set the passage length of the intake passage between each cylinder via the communication passage in the other intake system to the above 5000.
- than the standard rotation speed set between 7000rpm
An engine characterized in that, at low rotation speeds of 1000 to 2000 rpm, compression waves generated when the intake port of one cylinder is closed propagate to the intake ports of other cylinders at the end of the intake stroke to perform supercharging. intake device. 2 In a 2-cylinder or 3-cylinder 4-cycle engine, the passage length L _S of the intake passage between each cylinder via the communication passage when supercharging is performed by the compression wave when the intake port is opened, and the intake port closing The passage length L _P of the intake passage between each cylinder via the communication passage when _{supercharging} is performed by the compression _{wave of} 60/360N)×a L _P = {(720/Z)−θ ₁ }×(60/360N)×a (Here, Z is the number of cylinders, and θ _S is the opening of the intake port with the larger opening cross-sectional area. The period θ _O is the period from the opening of the intake port until the opening compression wave is substantially generated, and the period just before the intake port of another cylinder closes, where the opening compression wave is propagated in order to effectively perform supercharging. The invalid period, which is the sum of the period from the time to the closing, θ ₁
is the period from when the intake port closes until the compression wave at closing actually occurs, and the period from just before the intake ports of other cylinders close when the compression wave at closing is propagated in order to effectively perform supercharging. The engine intake system according to claim 1, wherein N is the engine rotational speed and a is the propagation speed of the pressure wave. 3 In a 4-cylinder 4-cycle engine, the length of the intake passage between each cylinder via the communication passage when supercharging is performed by the compression wave when the intake port is opened.
L _S and the passage length L _P of the intake passage between each cylinder via the communication passage when supercharging is performed by the compression wave when the intake port is closed, are calculated using the following formula L _S = (θ _S −180− θ _O ) × (60/360N) × a L _P = {(720/Z) − θ ₁ } × (60/360N) × a (Here, Z is the number of cylinders, and θ _S is the number of cylinders with larger opening area. The opening period of the intake port, θ _O is the period from the opening of the intake port until the opening compression wave is substantially generated, and the intake air of other cylinders to which the opening compression wave is propagated in order to effectively perform supercharging. The ineffective period, which is the sum of the period from just before the port closes to the time when the port closes, θ ₁ is the period from when the intake port closes to when the compression wave is substantially generated at the time of closing, and corresponds to the period for effective supercharging. A patent set by the invalid period, which is the sum of the period from just before closing to the closing of the intake ports of other cylinders through which compression waves are propagated during closing, where N is the engine rotation speed and a is the propagation speed of pressure waves. An intake system for an engine according to claim 1.