JPH0452374B2 - - 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 a device that uses intake pressure waves generated within the engine to obtain a supercharging effect when the engine is under high load and high rotation speed.

(Prior Art) Generally, a multi-cylinder engine has two systems of low-load intake passages that open independently to each cylinder, and a high-load intake passage that has a larger passage cross-sectional area than the low-load intake passage. an intake passage, the intake passage has at least 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;
When the engine is under low load, only the primary valve is opened to supply intake air to each cylinder only from the low-load intake passage, which has a narrow passage cross-sectional area, thereby increasing the intake flow rate and improving combustion stability. When the engine is under high load, the secondary valve is also opened to supply intake air from the high-load intake passage, thereby increasing filling efficiency and increasing output.This is a so-called dual induction system. The intake system of is well known.

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. Divided into two different passages, each with a separate intake port, the two intake passages are used when the engine is running at high speeds, and at low engine speeds, the intake passage that is at the later closing position is closed, allowing for early intake. By occluding the intake air, it is possible to obtain suitable charging efficiency over a wide range of engine speeds by utilizing the supercharging effect caused by the occlusion of the intake air at the maximum pressure of the intake air, which is a function of the intake pipe dimensions and engine speed. It has been proposed that

(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 cannot be put to 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 is generated 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 by the inertia of the engine, and a compression wave is generated in the intake port part of the intake passage.(iii) When the intake port starts to take air, an expansion wave is generated 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). If the supercharging effect is activated, a supercharging effect can be effectively obtained (hereinafter referred to as intake inertia effect), and the expansion wave in (iii) above in each cylinder is reversed into a compression wave to generate a supercharging effect at the end of the intake stroke of each cylinder. Focusing on the fact that a supercharging effect can be effectively obtained by applying the effects to It is intended to improve engine charging efficiency by utilizing the pulsation effect.

In that case, the inter-cylinder interference effect, especially the exhaust interference effect, has a stronger supercharging effect than the intake individual pulsation effect because the pressure waves are stronger, and the high-load intake passage has a larger passage area than the low-load intake passage. Because the pressure waves are large, the pressure waves can be propagated without attenuation as much as possible, so when the engine is under high load and rotation, which requires high output, the exhaust interference effect between cylinders with a large supercharging effect as mentioned above can be reduced to a high load. It is effective to obtain the unique pulsation effect of the intake air in the low-load intake system and to supplement it with the low-load intake system.

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.
When an engine that requires high output is loaded and rotates at high speeds, the high-load intake system effectively propagates the opening compression wave generated at the high-load intake port of one cylinder to the other cylinders at the end of the intake stroke, as described above. In addition, in the low-load intake system, an expansion chamber is installed to reverse expansion waves into compression waves, and the supercharging effect due to the above-mentioned intake-specific pulsation effect is achieved. By setting it so that it can also be used together, it is possible to increase the charging efficiency and increase the output at high engine load and high rotation speeds with a simple configuration by making slight design changes to the existing intake system without using a supercharger etc. This is not intended.

(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. The low-load intake passages communicate with each other, and an enlarged chamber is provided in the communication passage between the low-load intake passages. The minimum passage cross-sectional area of the high-load intake passage is set to be larger than the minimum passage cross-sectional area of the low-load intake passage. The opening timing of the high-load intake port is set to be earlier than the opening timing of the low-load intake port. Furthermore, the passage length of the high-load intake passage between each cylinder via the communication passage is determined by the compression wave that occurs when the high-load intake port of one cylinder opens at high engine speeds of 5000 to 7000 rpm. The supercharging is set to propagate to the high-load intake port of other cylinders at the end of the intake stroke to perform supercharging. In addition, the passage length _lP of the low-load intake passage from the expansion chamber to the low-load intake port of each cylinder is determined as follows:
The expansion wave generated by the start of intake at the low-load intake port of each cylinder is reversed in the expansion chamber, and the inverted secondary pulsating wave of the compression wave propagates to the intake port at the end of the intake stroke of each cylinder, causing supercharging. To do this, use the following formula l _P = (θ _P - θ ₂ ) x (60/360N) x (1/4) x a (where θ _P is the opening period of the low-load intake port, and θ ₂ is the low-load intake port opening period. The period from the opening of the load intake port until the expansion wave is substantially generated, and the low load intake port in which the secondary pulsating wave of the compression wave, which is the inversion of the expansion wave, is propagated in order to effectively perform supercharging. The invalid period, which is the sum of the period immediately before the closing of N
is the engine rotation speed, and a is the propagation speed of the pressure wave).

(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 At this time, when the high-load intake port of one cylinder opens, the compression wave generated near the high-load intake port passes through the communication path to the high-load intake port of the other cylinder at the end of the intake stroke. is propagated to. As a result, this opening compression wave forces intake air into the combustion chamber from the high-load intake ports of other cylinders at the end of the intake stroke, resulting in supercharging (exhaust interference effect).

At the same time, in each cylinder, the expansion wave generated in the low-load intake passage by the start of intake from the low-load intake port becomes a secondary pulsating wave of the compression wave that is reversed and reflected in the expansion chamber. Supercharging is carried out at the low-load intake port at the end of the intake stroke (intake-specific pulsation effect).

In that case, the high-load intake passage, which is the pressure wave propagation path for obtaining the above-mentioned exhaust interference effect, has a larger passage cross-sectional area than the low-load intake passage, so the resistance to pressure wave propagation is small; In particular, the exhaust interference effect between cylinders, which has a large supercharging effect, can be effectively exerted in a high-load intake system.

Further, the communication passage is located downstream of the secondary valve,
Moreover, since the passage cross-sectional area is greater than the minimum passage cross-sectional area of the high-load intake passage, pressure waves are not attenuated by the secondary valve, and pressure waves due to the expansion of the passage cross-sectional area of the communication passage itself. Although there is attenuation, the rate of attenuation is smaller than the pressure wave attenuation due to a reduction in the cross-sectional area of the passage (throttling), and the above-mentioned exhaust interference effect can be effectively exerted. In addition, the above expansion room is
Since it is located downstream of the primary valve, it can similarly effectively exhibit the unique pulsation effect of the intake air.

Furthermore, by opening the high-load intake port earlier than the low-load intake port, a particularly strong compression wave can be generated when the high-load intake port is opened, and the exhaust interference effect described above can generate excessive compression waves. It is effective by improving the supply effect.

In addition, since the minimum passage cross-sectional area of the low-load intake passage is smaller than that of the high-load intake passage,
The volume of the expansion chamber in the communication passage that communicates the low-load intake passages with each other is small, and the expansion chamber can be easily set, so that the above-mentioned exhaust interference effect in the high-load intake system and the low-load intake The second-order intake-specific pulsation effect in the system can be easily obtained in the same rotation range.

Here, 5000 ~
The limit of 7000 rpm is generally set in this range for maximum output and maximum speed, so it is a high load, high rotation area of the engine that requires high output, and is an effective area for improving charging efficiency and output. It depends.

Furthermore, the reason why the low-load intake passage and the high-load intake passage are 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 dispersed to the other side,
This is to prevent mutual interference and weakening, and in particular, the opening/closing timing and length of the intake ports are different between the low-load intake passage and the high-load intake passage due to the difference in requirements in the dual induction intake system. , since one pressure wave will be attenuated by the other.

Furthermore, the installation of the low-load intake passage in the enlarged chamber is to obtain a unique intake pulsation effect in the low-load intake system as described above, and the combustion injection nozzle is usually provided in the low-load intake passage. For,
This is because it is advantageous in preventing deterioration of fuel responsiveness during transient operation (such as misfires due to breathing during acceleration or overheating during deceleration). In other words, 1 above
Downstream of the secondary valve, there is an expansion chamber where the low-load intake passages of each cylinder gather, so when the primary valve is at a low opening, intake negative pressure is generated and stored in the expansion chamber.
When the primary valve is at a high opening, intake pressure close to atmospheric pressure is generated and stored in the expansion chamber. Therefore, during acceleration operation, when the opening of the primary valve rapidly increases and the valve opens, the intake flow velocity in the intake passage upstream of the expansion chamber increases due to the negative intake pressure that had been stored in the expansion chamber until then. By speeding up the intake air flow rate and increasing the responsiveness of an intake air amount detector such as an air flow meter, a faster fuel increase (fuel responsiveness) can be ensured. In addition, during deceleration operation, when the opening of the primary valve suddenly decreases and closes, the intake air in the intake passage upstream of the expansion chamber is caused by the intake pressure close to atmospheric pressure that had been stored in the expansion chamber until then. By rapidly reducing the flow velocity and increasing the responsiveness of the intake air amount detector, a rapid fuel loss (fuel responsiveness) can be ensured.

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

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 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 has 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. A valve 11 is provided. In addition, in the main high-load intake passage 10,
A secondary valve is provided 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 when the engine is under high load.
Furthermore, the main low-load intake passage 9 has a primary valve 1
After branching into first and second low-load intake passages 9a and 9b having the same shape and dimensions at the downstream side, each cylinder 1A,
It communicates with the combustion chambers 2, 2 of 1B. Further, 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 to high-load intake ports 14 and 14, respectively. It communicates with the combustion chambers 2, 2 of the respective cylinders 1A, 1B via the cylinders 1A, 1B. Therefore, each cylinder 1
A, 1B, low load intake passages 9a, 9b
and the high-load intake passages 10a and 10b are the primary valve 1.
The valves are configured to open into the combustion chamber 2 independently on the downstream side of the primary and secondary valves 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 propagation of pressure waves through the high-load intake passages 10a and 10b can be effectively carried out with small 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 combustion 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 constituted by a communication passage 16 that communicates the first and second high-load intake passages 10a and 10b. has been done. The passage cross-sectional area A _CS of the communication passage 16 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 so as to effectively transmit pressure waves with less attenuation. (A _CS ≧ A _S ).

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 18 having a communication passage 17 that communicates the first and second low-load intake passages 9a and 9b. The passage cross-sectional area A _CP of the communication passage 17 is also the minimum passage cross-sectional area of each low-load intake passage 9a, 9b.
It is set larger than A _P (A _CP > A _P ).

Further, the volume of the expansion chamber 18 is set to 0.5 to 2.0 times the engine displacement; if it is less than 0.5 times, the reversal effect between expansion waves and compression waves cannot be obtained;
This is because the pressure waves exceeding 2.0 times are diffused and the inter-cylinder interference effect is significantly reduced.
Further, the enlarged chamber 18 functions as a surge tank for intake air during transient operation such as acceleration or deceleration of the engine, and ensures good fuel response.

Furthermore, each high-load intake port 14 is provided with a high-load intake valve 19 for opening and closing the high-load intake port 14, and although not shown, each low-load intake port 13 is provided with a high-load intake valve 19 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 addition, in each cylinder 1A, 1B, one end of 20 and 21 opens to the atmosphere, and the other end opens to the exhaust port 2.
2, 23 to open into the combustion chamber 2 of each cylinder 1A, 1B and discharge exhaust gas from the combustion chamber 2.
and a second exhaust passage, each of the exhaust ports 2
2 and 23 are provided with exhaust valves 24 and 24 that open and close the exhaust ports 22 and 23, respectively. Although not shown, a catalyst device for purifying exhaust gas is installed at the downstream collecting portion of each exhaust passage 20, 20, 21, 21 of each cylinder 1A, 1B, and the exhaust pressure is high. It's summery.

Furthermore, as shown in FIG. 3, the opening timing of the high-load intake valve 19 (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. In addition, the closing timing of the high-load intake valve 19 (the closing timing of the high-load intake port 14) is the closing timing of the low-load intake valve (the closing timing of the low-load intake port 14).
It is set at approximately the same time as the closing period of 3).
Due to the exhaust interference effect between cylinders, the opening compression wave propagated to the high-load intake port 14 at the end of the intake stroke is prevented from blowing through from the low-load intake port 13, thereby effectively obtaining a 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 ), which is 5000~ 7000rpm
In _{order to} obtain the exhaust interference effect between both cylinders 1A and _1B in the rotation range of is set to the value specified. In addition, in the above formula (), Z is the number of cylinders and Z=2,
720/Z indicates the phase difference between cylinders. θ _S is the opening period of the high-load intake valve 19. In addition, θ _O is the period from the opening of the high-load intake valve 19 (the opening of the high-load intake port 14) until the compression wave is substantially generated at the time of opening, and the period during which the opening is performed in order to effectively perform supercharging. This is an invalid period that is the sum of the period immediately before the closing of the high-load intake valve 19 of other cylinders (the opening of the high-load intake port 14) to which the compression wave is propagated until the valve closes, and is an invalid period that affects the valve opening characteristics, etc. It varies depending on the angle, but it is approximately 10 to 50 degrees. Therefore, {720/Z)+θ _S −θ _O } 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. Also, N is the engine speed and N=
5000 to 7000 rpm, and 60/360N represents the time (seconds) required to rotate 1°. Further, a is the propagation velocity (sound velocity) of the pressure wave, which is 343 m/s at 20°C.

Furthermore, the passage length l _P of each of the low-load intake passages 9a, 9b, that is, the low-load intake passages 9a, 9
Passage length _{l P} from the opening end face to the expansion chamber 18 of b to the opening to the combustion chamber 2 (low-load intake port 13)
In order to obtain the second-order intake unique pulsation effect in the rotation range of 5000 to 7000 rpm, l _P = (θ _P - θ ₂ ) × (60/360N) × (1/4) × a …(). Set to the value determined from the formula. In the above equation (), θ _P is the opening period of the low-load intake valve, and θ ₂ is the expansion wave that is substantially generated from the opening of the low-load intake port 13 due to the opening of the low-load intake valve. The period immediately before the closing of the low-load intake valve (low-load intake port 13 closing) during which the secondary pulsating wave of the compression wave, which is the inversion of the expansion wave, is propagated in order to effectively perform supercharging. The invalid period, which is _the sum of the period from
θ ₂ ) represents the rotation angle of the crankshaft required from the generation of the expansion wave to the propagation of the secondary pulsating wave of the compression wave. Moreover, 1/4 represents the reciprocal of the stroke in which the secondary pulsation makes two reciprocations. The rest is the same as in the case of formula () above.

The reason why we use secondary pulsation to obtain the intake-specific pulsation effect is that while primary pulsation has the above effect, the passage length l _P becomes too long. Since the length is twice that of the conventional one, it is difficult to mount it on a vehicle and tends to increase intake resistance.
On the other hand, in the case of tertiary pulsation, the passage length l _P is shortened to 2/3 of that of the secondary pulsation, but on the other hand, the above effect is reduced by about 15 to 25% with respect to the secondary pulsation, and the intake resistance is not much different. From this, the passage length l _P
This is to make the intake air pulsation effect as short as possible while effectively demonstrating the unique pulsation effect of the intake air.

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 is opened by opening the high-load intake valve 19 of one of the cylinders, for example, the second cylinder 1B, a problem occurs near the high-load intake port 14 of the second high-load intake passage 10b. The compression wave at the time of opening increases the passage length L _S of the high-load intake passages 10a and 10b between the two cylinders 1A and 1B from 5000 to 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
is propagated 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, resulting in supercharging (exhaust interference effect). .

At the same time, in the first cylinder 1A, after the low-load intake valve opens, an expansion wave generated in the first low-load intake passage 9a due to the start of intake from the low-load intake port 13 is transmitted to the first low-load intake passage 9a. By setting the passage length _lP of the intake passage 9a to a value determined by the above formula () with reference to high engine speeds of 5000 to 7000 rpm, the first low-load intake passage 9a→
Expansion chamber 18 (reflects as a compression wave) → first low-load intake passage 9a → combustion chamber 2 (reflects as an expansion wave) → first low-load intake passage 9a → expansion chamber 18
(Reflected as a compression wave) → Passes through the first low-load intake passage 9a and becomes the second pulsating wave of the compression wave.
Intake port 1 for low load at the end of intake stroke of cylinder 1A
3 and supercharging is performed (intake-specific pulsation effect).

Similarly, in the second cylinder 1B, 5000
When the engine rotates at a high speed of ~7000 rpm, the opening compression wave from the first cylinder 1A is applied to the high-load intake port 14 at the end of the intake stroke, and the second cylinder 1B's own 2 compression wave is applied to the low-load intake port 13 at the end of the intake stroke. The next pulsating compression waves are propagated to perform supercharging.

Therefore, in this way, there is a strong main supercharging effect due to the exhaust interference effect between cylinders 1A and 1B in the high-load intake system, and a strong main supercharging effect due to the individual intake pulsation effect of each cylinder 1A and 1B in the low-load intake system. Due to the synergy with the complementary supercharging effect, the fourth
As shown in the figure, when the engine is under high load and at high revolutions (5000~
The charging efficiency in the 7000rpm rotation range increases significantly, making it possible to significantly and effectively improve output.

In addition, in FIG. 4, the high-load intake passages 10a and 10b of each cylinder 1A and 1B are made independent, respectively.
In contrast to the case where only the intake-specific pulsation effect was obtained based on 6000 rpm (indicated by the broken line), in addition to this,
The output torque characteristics of the engine are shown when the exhaust interference effect between the cylinders is obtained based on 6000 rpm (indicated by a solid line).

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 area than the low-load intake passages 9a and 9b, so the resistance to the propagation of pressure waves is small, and the exhaust interference effect between cylinders, which has a particularly large supercharging effect, is reduced in the high-load intake system. can be used effectively.

Furthermore, the communication passage 16 is located downstream of the secondary valve 12, and its passage cross-sectional area A _CS is greater than or equal to the minimum passage cross-sectional area A _S of the high-load intake passages 10a and 10b. 12 does not attenuate the pressure waves, and although there is pressure wave attenuation due to the expansion of the passage cross-sectional area of the communication passage 16 itself, the attenuation rate is Therefore, the above-mentioned exhaust interference effect can be effectively exhibited. Further, the expansion chamber 18 has 1
Since it is located downstream of the next valve, the intake-specific pulsation effect can be effectively exerted as well.

Furthermore, by making the opening timing of the high-load intake port 14 earlier than the opening timing of the low-load intake port 13, especially the high-load intake port 1
It is possible to generate a strong compression wave at the time of 4 openings, which is effective in improving the supercharging effect due to the exhaust interference effect. In addition, by making the closing timing of the high-load intake port 14 almost the same as that of the low-load intake port 13, the compression wave from the low-load intake port 13 at the time of opening due to the exhaust interference effect with a large supercharging effect is suppressed. This is advantageous because blow-through can be prevented.

Also, a fuel injection nozzle 1 as a fuel supply device
5 is a low-load intake passage 9a downstream of the communication passage 17;
9b is provided at the downstream end (near the opening to the combustion chamber 2), so the length of the intake passage becomes long, so that when the air flow meter 7 disposed upstream of the communication passage 17 accelerates or decelerates. It is possible to prevent deterioration of fuel responsiveness due to a delayed response (delayed response in fuel supply corresponding to a changed amount of air introduced into the combustion chamber 2) from occurring, and to ensure good fuel responsiveness. , a low-load intake passage 9 that can supply intake air and fuel in all operating ranges.
Only a and 9b need be installed, and the fuel supply device can be simplified.

Further, the supercharging effect due to the exhaust interference effect and the intake individual pulsation effect is achieved by the position of the communication passage 16 and the enlarged chamber 18, and by the position of the communication passage 16 and the expansion chamber 18.
Passage length of high-load intake passages 10a and 10b between
L _S and the passage length l _P of the low-load intake passages 9a, 9b between the enlarged chamber 18 and each cylinder 1A, 1B are set as described above, and the supercharger etc. Since this does not require a slight design change to the existing intake system, the structure is extremely simple and can be implemented easily and at low cost.

In addition, the minimum passage cross-sectional area of the low-load intake passages 9a, 9b is the same as that of the high-load intake passages 10a, 10b.
By being smaller than the above, the low load intake passage 9
Expansion chamber 1 in communication path 16 that communicates between a and 9b
8 requires a small volume and the expansion chamber 18 can be easily set, so that the above-mentioned exhaust interference effect in the high-load intake system and the secondary intake individual pulsation effect in the low-load intake system are the same. Easily obtained in the rotation range.

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 types of dual-induction type cylinder engines. 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' downstream of the secondary valve 12, and each cylinder 1A to
~1D low load intake passages 9a~9d are primary valves 1
They are communicated with each other by a communication passage 17' formed by an enlarged chamber 18' downstream of the two, and a fuel injection nozzle 15 is provided in each of the low-load intake passages 9a to 9d downstream of the communication passage 17'. There is. In addition, in order to obtain the exhaust interference effect, the passage length L _S of the high-load intake passages 10a to 10d between the cylinders 1A to 1D via the communication passage 16' is determined by the first term on the right side of the above equation (). Rotation angle required from generation of compression wave to propagation when opening)
are different (see Figure 8), and are set by L _S = (θ _S −180 − θ _O )×(60/360N)×a...('). In addition, the low-load intake passage 9a,
The passage length _lP of 9b is set according to the above equation () so as to obtain a second-order intake-specific pulsation effect. still,
Although not shown in the figure, the same applies to a 3-cylinder 4-cycle engine as in the case of a 2-cylinder engine, and the length of each passage is
L _S and l _P may be set using the above equations () and (). In addition, in the second embodiment (four-cylinder four-cycle engine), the passage lengths l _S1 and l _S4 of the corresponding high-load intake passages 10a and 10d of the first and fourth cylinders 1A and 1D are the same. _S1 = l _S4 , and each high-load intake passage 1 of the second and third cylinders 1B and 1C
Similarly, the passage lengths l _S2 and l _S3 of 0b and 10c are l _S2 = l _S3
becomes. Therefore, 1st cylinder 1A→3rd cylinder 1C→
In the ignition order from the fourth cylinder 1D to the second cylinder 1B, the passage lengths L _S between consecutive combustion cylinders are all the same. Further, the passage lengths l P1 , l _P2 of the low-load intake passages 9a, 9b, 9c, 9d of each cylinder 1A to _1D ,
l _P3 and l _P4 are all the same. That is, l _P = l _P1 = l _P2 = l _P3 = l _P4 L _S = l _S1 (l _S4 ) + l _S2 (l _S3 ).

Furthermore, the action process of inter-cylinder interference is shown in Figures 6 to 8.
(In the same figure, the high-load intake system obtains the exhaust interference effect, while the low-load intake system allows the compression wave generated when the low-load intake port of one cylinder is closed to be suppressed from the other cylinders.) (This figure shows the case where the intake inertia effect is propagated to the low-load intake port at the end of the intake stroke to perform supercharging.) In the case of a general two-cylinder engine, as shown in Figure 6, the exhaust interference effect (indicated by the solid line arrow) and the intake inertia effect (indicated by the dashed line arrow) are transferred from the first cylinder to the second cylinder. , act sequentially and alternately from the second cylinder to the first cylinder. In addition, in the case of a three-cylinder engine, as shown in Fig. 7, the above two effects are the same as in the case of two cylinders: 1st cylinder → 2nd cylinder, 2nd cylinder → 3rd cylinder, 3rd cylinder → It acts sequentially on the first cylinder. Furthermore, in the case of a four-cylinder engine, as shown in Figure 8, the intake inertia effect is caused by the firing order: 1st cylinder → 3rd cylinder, 3rd cylinder → 4th cylinder,
It acts sequentially from the 4th cylinder to the 2nd cylinder, and from the 2nd cylinder to the 1st cylinder, and the exhaust interference effect is reversed in phase.
The action is received from the cylinder that is delayed by 180°, and the 3rd cylinder → 1st cylinder
It acts on the cylinders, 4th cylinder → 3rd cylinder, 2nd cylinder → 4th cylinder, 1st cylinder → 2nd cylinder, 3rd cylinder → 1st cylinder. Therefore, the passage length L _S between the cylinders that performs the inter-cylinder interference in this way may be set so as to obtain the exhaust interference 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, Effectively achieves a strong supercharging effect due to the exhaust interference effect between cylinders in the high-load intake system, and a complementary supercharging effect due to the secondary intake individual pulsation effect of each cylinder itself in the low-load intake system. As a result, even with a simple configuration that requires only slight design changes to the existing intake system without the need for a supercharger, the charging efficiency at high engine load and high rotation speeds can be significantly increased, resulting in a significant increase in output. Therefore, it is useful for easily implementing measures to improve engine output and reducing costs.

[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... Fuel injection nozzle,
16, 16'...Communication path, 17,17'...Communication path, 1
8,18'...Enlargement room.

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 a communication passage having a passage cross-sectional area larger than the minimum passage cross-sectional area of each intake passage, and an enlarged chamber is provided in the communication passage between the low-load intake passages, and the high-load The minimum passage cross-sectional area of the intake passage for low-load use is set to be larger than the minimum passage cross-sectional area of the intake passage for low-load use, and the opening timing of the intake port for high-load use is set to be earlier than the opening time of the intake port for low-load use. Then, the passage length of the high-load intake passage between each cylinder via the above-mentioned communication passage is determined by the compression wave that occurs when the high-load intake port of one cylinder opens at high engine speed of 5000 to 7000 rpm. The setting is such that supercharging is carried out to the high-load intake ports of other cylinders at the end of the intake stroke, and the passage length of the low-load intake passage from the enlarged chamber to the low-load intake ports of each cylinder. sl _p , 5000
When the engine rotates at a high speed of ~7000 rpm, the expansion wave generated by the start of intake at the low-load intake port of each cylinder is reversed and reflected by the expansion chamber, and the secondary pulsating wave of the compression wave is generated at the end of the intake stroke of each cylinder. The following formula l _P = (θ _P - θ ₂ ) × (60/360N) (1/4) × a (here, θ _P is the intake port for low load) The opening period of θ ₂ is the period from the opening of the low-load intake port until the expansion wave is substantially generated, and the secondary pulsating wave of the compression wave that is the inversion of the expansion wave in order to effectively perform supercharging. Invalid period, N
is the engine rotational speed, and a is the propagation speed of pressure waves. 2 In a 2-cylinder or 3-cylinder 4-cycle engine, the passage length L _S of the high-load intake passage between each cylinder via the communication passage is calculated using the following formula L _S = {(720/Z) + θ _S −θ _O } × (60/360N) × a (Here, Z is the number of cylinders, θ _S is the opening period of the high-load intake port, and θ _O is the time when the compression wave from the opening of the high-load intake port is substantially an ineffective period that is the sum of the period until the generation occurs and the period from the period immediately before the closing of the high-load intake ports of other cylinders through which the opening compression waves are propagated in order to effectively perform supercharging;
(N is the engine rotational speed, and a is the propagation velocity of the pressure wave.) The engine intake device according to claim 1, wherein N is the engine rotation speed, and a is the propagation speed of the pressure wave. 3 In a 4-cylinder 4-stroke engine, the passage length L _S of the high-load intake passage between each cylinder via the communication passage is calculated using the following formula L _S = (θ _S −180 − θ _O ) × (60/ 360N) × a (Here, θ _S is the opening period of the high-load intake port, θ _O is the period from the opening of the high-load intake port until the compression wave is substantially generated at the time of opening, and the effective supercharging period. N is the engine rotation speed, and a is the propagation of pressure waves. An intake system for an engine according to claim 1, wherein the engine intake system is set according to the following: