JPH0452376B2 - - 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 charging efficiency and increasing output. Intake systems are 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 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 especially 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 It was discovered that the intake air is compressed due to the inertia of the engine, and a compression wave is generated in the intake port part of the intake passage, and (iii) that an expansion wave is generated in the intake passage when the intake port starts to intake air.

Therefore, in a multi-cylinder engine equipped with two independent intake passages as described above, the present invention is capable of converting the opening compression wave of (i) in one cylinder to other cylinders, especially the blowback of intake air. A supercharging effect can be effectively obtained by applying it to the end of the intake stroke that occurs (hereinafter referred to as the exhaust interference effect). (hereinafter referred to as the intake inertia effect), and by reversing the expansion wave in (iii) above into a compression wave in each cylinder, the same intake stroke of each cylinder can be obtained. Focusing on the fact that a supercharging effect can be effectively obtained if it is applied at the final stage (hereinafter referred to as the intake-specific pulsation effect), we have focused on the fact that the above-mentioned inter-cylinder interference effect (exhaust interference effect and intake inertia effect) and the intake individual It is intended to improve engine charging efficiency by utilizing the pulsating 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 speed, the opening compression wave generated at the high-load intake port of one cylinder in the high-load intake system as described above is effectively propagated to other cylinders at the end of the intake stroke. While preventing the compression wave from blowing back from the low-load intake port, the settings are made to effectively obtain a supercharging effect through the exhaust interference effect between the cylinders, and the expansion wave is replaced with the compression wave in the low-load intake system. By providing an enlarged chamber that can be reversed to obtain the supercharging effect due to the intake pulsation effect described above, a simple configuration can be achieved by making slight design changes to the existing intake system without using a supercharger etc. This is intended to effectively improve output by increasing charging efficiency when the engine is under high load and rotating at high speeds.

(Means for Solving the Problems) In order to achieve this object, the present invention has a low-load intake passage and a high-load intake passage independent of each other for each cylinder, and also provides a low-load intake passage for each cylinder. The combustion chamber of each cylinder is provided with an intake passage that opens through a low-load intake port and a high-load intake port that are independent of each other. A primary valve that changes the amount of intake air flowing through the intake passage, and 2 that changes the amount of intake air that flows through the high-load intake passage.
This assumes an engine intake system having a following valve.

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 earlier than the opening timing of the low-load intake port, while the closing timing of the high-load intake port is set later than the closing timing of the low-load intake port. .

Furthermore, the passage length of the high-load intake passage between each cylinder is controlled via the above-mentioned communication passage, so that the compression wave generated when the high-load intake port of one cylinder is opened at high engine speeds of 5,000 to 7,000 rpm is applied to the intake air. The supercharging is set to propagate to the high-load intake ports of other cylinders at the end of the stroke.

In addition, the passage length of the above-mentioned low-load intake passage from the above-mentioned expansion chamber to the low-load intake port of each cylinder, l _P
When the engine rotates at a high speed of 5000 to 7000 rpm, the expansion wave generated by the start of intake at the low-load intake port of each cylinder is reversed and reflected in the expansion chamber, and the secondary pulsating wave of the compression wave is the intake air of each cylinder. In order to carry out supercharging by propagating to the intake port at the end of the stroke, the following formula l _P ] (θ _P - _{θ 1} ) x (60/360N) x (1/4) x a (where θ _P is a low The opening period of the load intake port, θ ₁ is the period from the opening of the low load intake port until the expansion wave is substantially generated, and the compression wave which is the inversion of the expansion wave in order to effectively perform supercharging. The invalid period, 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 low-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, by closing the high-load intake port later than the low-load intake port,
The above-mentioned intake individual pulsation effect from the low-load intake port (compression caused by the expansion wave generated in the low-load intake passage by the start of intake at the low-load intake port of each cylinder being reversed and reflected in the low-load expansion chamber) The pressure in the combustion chamber within the cylinder is increased by the supercharging effect that causes the wave to act at the end of the intake stroke of each cylinder, and after the low-load intake port closes, a strong compression wave is applied at the time of opening due to the exhaust interference effect. It is possible to feed the combustion chamber through the open high-load intake port to further increase its pressure and obtain a sufficient intake air charge. In addition, when the compression wave from other cylinders propagates to the combustion chamber due to the exhaust interference effect, the low-load intake port is already closed, so the opening compression wave propagates to the high-load intake port at the end of the intake stroke. It is possible to prevent the exhaust gas from blowing directly through the low-load intake port after passing through the combustion chamber, thereby effectively exhibiting the exhaust interference 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 ~ 5000 at high engine speed to obtain the above-mentioned exhaust interference effect and intake unique pulsation effect.
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 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 a dual induction intake system, the intake port This is because the opening/closing timing and length are different, and one pressure wave is 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 fuel injection nozzle is usually installed 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, it is possible to ensure a rapid fuel increase (fuel responsiveness). 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.

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 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 when the engine load is low. 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 has first and second high-load intake passages 1 of the same size downstream of the secondary valve 12.
After being branched into 0a and 10b, they communicate with the combustion chambers 2 and 2 of the respective cylinders 1A and 1B via high-load intake ports 14 and 14, respectively. 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 combustion chamber 2 is configured to open into the combustion chamber 2 downstream of the primary and secondary valves 12 through an intake port 13 for low load and an intake port 14 for high load, respectively.

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 ), and each high-load intake passage 10a, 10b
The passage length l _S is set shorter than the passage length l _P of each low-load intake passage 9a, 9b (l _S < l _P ),
In particular, the propagation of pressure waves through the high-load intake passages 10a and 10b is made more effective by reducing its 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 has a high-load communication passage 16 that communicates the first and second high-load intake passages 10a and 10b with each other. It is made up of an expansion chamber 17. Passage cross-sectional area of the communication passage 16
A _CS is arranged in each high-load intake passage 10a, 10b so as to reduce the attenuation of the pressure wave and effectively transmit it.
The minimum passage cross-sectional area is set to be equal to or greater than the minimum passage cross-sectional area A _S (A _CS ≧ A _S ).

Further, the branch part of the main low-load intake passage 9 is
It is constituted by a low-load expansion chamber 19 located downstream of the primary valve 11 and having a communication passage 18 that communicates the first and second low-load intake passages 9a and 9b with each other. The passage cross-sectional area _ACP of the low-load intake passage 18 is the same as that of each low-load intake passage 9a, 9b.
( _{A CP}
≧ _AP ).

Further, the low load expansion chamber 19 is provided for each cylinder 1.
The expansion wave generated in the low-load intake passages 9a, 9b by the start of intake from the low-load intake ports 13 of A and 1B is reversed into a compression wave and reflected, and its volume is 0.5 to 0.5 of the engine displacement. This is because the pressure wave is set to 2.0 times, and if it is less than 0.5 times, the reversal effect between expansion waves and compression waves cannot be obtained, while on the other hand, pressure waves exceeding 2.0 times will be diffused, and the inter-cylinder interference effect will be significantly reduced. be. In addition, each of the above expansion rooms 1
7 and 19 function as a surge tank for intake air during transient operations such as acceleration or deceleration of the engine to ensure good fuel response.

Further, 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 addition, 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 and discharge exhaust gas from the combustion chamber 2.
and a second exhaust passage, each of the exhaust ports 2
3 and 24 are provided with exhaust valves 25 and 25 for opening and closing 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 timing is set to be earlier than the opening timing of the intake port 13 for high-load use, and a strong compression wave is generated at the time of opening in the high-load intake passages 10a and 10b. Further, the closing timing of the high-load intake valve 20 (the closing timing of the high-load intake port 14) is set later than the closing timing of the low-load intake valve (the closing timing of the low-load intake port 13). The opening compression wave propagated to the high-load intake port 14 at the end of the intake stroke is transmitted to the low-load intake port 1.
3 to prevent the air from blowing through, thereby effectively demonstrating the exhaust interference 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 length of the communication path 16.
It is the sum of l _CS and the 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 ~
In order to obtain the exhaust interference effect between both cylinders 1A and 1B in the rotation range of 7000 rpm, L _S = {(720/Z) + θ _S - θ _O } × (60/360 N) × a ...() is calculated from the formula. set to the value specified. In addition, 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. In addition, θ _O is the period from the opening of the high-load intake valve 20 (opening of the high-load intake port 14) until the compression wave is substantially generated at the time of opening, and the time at which the opening is performed in order to effectively perform supercharging. Closing of high-load intake valves 20 of other cylinders to which compression waves are propagated (closing of high-load intake ports 14)
The invalid period is the sum of the period from the previous period until the valve closes, and varies depending on the valve opening characteristics, etc., but 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 rotation speed, N = 5000 to 7000 rpm, and 60/360N
represents the time (seconds) required to rotate 1°. Also, a is the propagation velocity (sound velocity) of the pressure wave, and at 20℃
=343m/s.

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 19 of b to the opening to the combustion chamber 2 (low-load intake port 13)
is the low-load intake port 13 of each cylinder 1A, 1B.
If the expansion wave generated in the low-load intake passages 9a, 9b at the start of intake is inverted in the low-load expansion chamber 19 and the reflected compression wave is applied to the end of the intake stroke of each cylinder 1A, 1B, the Since the intake effect (intake individual pulsation effect) can be obtained, l _P = (θ _P − θ ₁ ) × (60/360N )×(1/4)×a...() The length is set equal to the value obtained from the formula. still,
In the above equation (), θ _P is the opening period of the low-load intake valve, and θ ₁ is the period from the opening of the low-load intake port 13 due to the opening of the low-load intake valve until the expansion wave is substantially generated. Closing of the low-load intake valve (low-load intake port 1
3) The invalid period, which is the sum of the period from the previous period to the valve closing, is about 60 to 100 degrees, and therefore (θ _P - _{θ 1} ) is the second pulsating wave propagation from the expansion wave generation to the compression wave. Represents the rotation angle of the crankshaft required to reach Moreover, 1/4 represents the reciprocal of the stroke of the secondary pulsating wave twice. 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 ensure that the unique pulsation effect of the intake air is effectively exhibited unless it is made as short as possible.

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 this 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 intake air is compressed by the pressure of the residual exhaust gas in the combustion chamber 2, and the intake air is compressed by the pressure of the residual exhaust gas in the combustion chamber 2. A compression wave is generated near the high-load intake port 14 of the high-load intake passage 10b when opening. This compression wave at the time of opening is caused by setting the opening timing of the high-load intake port 14 earlier than that of the low-load intake port 13, so that the residual exhaust gas from the combustion chamber 2 is blown back to the high-load intake port 14 side. It is concentrated in the air, and occurs very strongly in conjunction with the fact that engine exhaust pressure is increasing due to exhaust gas purification as mentioned above. This opening compression wave increases the passage length L _S of the high-load intake passages 10a and 10b between both cylinders 1A and 1B.
By setting the value determined by the above formula () based on the high engine speed of 5000 to 7000 rpm, the second high-load intake passage 10b → communication passage 1
6→The air is propagated through the first high-load intake passage 10a to the high-load intake port 14 of the first cylinder 1A at the end of the intake stroke. As a result, this strong 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 19 (reflects as a compression wave and reflects it) → first low-load intake passage 9a → combustion chamber 2 (reflects as an expansion wave and reflects it) → first low-load intake passage 9a → expansion chamber 19
(Reflected as a compression wave) → Passes through the first low-load intake passage 9a and becomes the second pulsating wave of the compression wave.
Cylinder 1A and low load intake port 1 at the end of the intake stroke
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 waves are propagated and supercharging is performed.

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 (only showing the exhaust interference effect), the charging efficiency increases significantly when the engine is under high load and high rotation (in the rotation range of 5000 to 7000 rpm), and the output can be significantly and effectively improved. .

In addition, in FIG. 4, compared to the conventional example (indicated by broken lines) in which the high-load intake passages 10a and 10b of each cylinder 1A and 1B are made independent, the engine speed is 5000~
Engine output in the case of Inventive Example 1 (indicated by the dashed-dotted line) in which the exhaust interference effect was obtained with 7000 rpm as a reference, and in the case of Inventive Example 2 (indicated by the solid line) in which the exhaust interference effect was obtained in accordance with 7000 rpm. Indicates torque characteristics.

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 and shorter passage length than the low-load intake passages 9a and 9b, and the passage area A _CS of the high-load communication passage 16 is the smallest of the high-load intake passages 10a and 10b. By having a passage cross-sectional area of A _S or more, the resistance to the propagation of pressure waves 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.

Furthermore, since the communication passages 16 and 18 are located downstream of the primary valve 11 and the secondary valve 12, respectively,
The pressure waves are not attenuated by the secondary valve 11 or the secondary valve 12, and the exhaust interference effect and intake unique pulsation effect described above can be effectively exhibited.

Furthermore, by setting the opening timing of the high-load intake port 14 earlier than the opening timing of the low-load intake port 13, a strong compression wave can be generated especially when the high-load intake port 14 opens, and the exhaust This is effective because the supercharging effect is improved by the interference effect, and the blowback of residual exhaust gas from the combustion chamber 2 is concentrated on the high-load intake port 14 side, so the intake air from the low-load intake port 13 is It is possible to strengthen the generation of expansion waves due to the start, and it is also possible to enhance the unique pulsation effect of the intake air. In addition, by setting the closing timing of the high-load intake port 14 later than that of the low-load intake port 13, the compression wave at the time of opening is reduced due to the exhaust interference effect that acts on the high-load intake port 14 at the end of the intake stroke. This is advantageous in that blow-by from the load intake port 13 is reliably prevented in combination with the enhancement of the intake-specific pulsation effect, and the exhaust interference effect can be effectively utilized.

Additionally, a fuel injection nozzle 15 is used as a fuel supply device.
are the low-load intake passages 9a, 9 downstream of the communication passage 18.
Since it is provided at the downstream end of b (near the opening to the combustion chamber 2), in order to obtain the intake-specific pulsation effect, the intake length l _P becomes longer and the response of the fuel deteriorates (the combustion chamber It is possible to ensure good fuel response by preventing the delay in response of fuel supply corresponding to the changed air amount introduced in 2), and to ensure a low load that allows intake air to be supplied and fuel to be supplied in the entire operating range. Only the intake passages 9a and 9b need to be installed, and the fuel supply system can be simplified.

In addition, the supercharging effect due to the above exhaust interference effect and intake individual pulsation effect depends on the position of each communication passage 16, 18 and its passage area, the opening/closing timing of each intake port 13, 14, the high load between both cylinders 1A, 1B. intake passage 1
This can be obtained by setting the passage length L _S of 0a and 10b as described above, and since a supercharger etc. is not required, a slight design change to the existing intake system is required, and the structure is extremely simple. Therefore, it can be implemented easily and inexpensively.

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 multi-cylinder engines of the dual induction type. For example, as an example, Fig. 5 shows a 4-valve type 4-cylinder 4-stroke engine with
An example will be shown (the same parts as in the first example are given the same reference numerals, and detailed explanation thereof will be 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'. Further, the cylinder 1A is connected to the cylinder 1A via the communication passage 16'.
The passage length L _S of the high-load intake passages 10a to 10d between ~1D and 1D is determined by the rotation angle required from the first term 4 on the right side of the above equation (4) from generation to propagation of the compression wave at the time of opening in order to obtain the exhaust interference effect. ) 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 l _P of 9b is set according to the above equation ( ) so as to obtain a second-order intake-specific pulsation effect.
Although not shown, the same applies to a 3-cylinder 4-cycle engine as in the case of a 2-cylinder engine, and the passage lengths L _S and l _P can be calculated as Z= by the above equations () and ().
It can be set as 3. In addition, in the second embodiment (four-cylinder four-cycle engine), the first and fourth
High-load intake passages 1 corresponding to cylinders 1A and 1D
The path lengths l _S1 and l _S4 of 0a and 10d are the same, l _S1 = l _S4
Also, the passage length l _S2 of each high-load intake passage 10b, 10c of the second and third cylinders 1B, 1C,
Similarly for l _S3 , l _S2 = l _S3 . Therefore, the first cylinder 1
A → 3rd cylinder 1C → 4th cylinder 1D → 2nd cylinder 1B
The ignition order is the passage length between successive cylinders of combustion.
All L _S 's will be the same. Furthermore, each cylinder 1A to 1D
The passage lengths l _P1 , l _P2 , l _P3 , and l _P4 of the low-load intake passages 9a, 9b, 9c, and 9d 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 addition, in the same figure, the exhaust interference effect is obtained in the high-load intake system, while the compression wave at the time of closing of the low-load intake port of one cylinder is calculated in the low-load intake system. (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.) Generally, in the case of a two-cylinder engine, as shown in Figure 6, the exhaust interference effect acts alternately from the first cylinder to the second cylinder and from the second cylinder to the first cylinder, as described above. be. 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 4-cylinder engine, as shown in Figure 8, the exhaust interference effect acts from the cylinders that are 180 degrees behind in phase, and the 3rd cylinder → 1st cylinder, the 4th cylinder → 3rd cylinder, etc. , 2nd cylinder → 4th cylinder, 1st cylinder →
It acts on the second cylinder, the third cylinder, and then the first 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, , 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 in the low-load intake system. This system is designed to achieve a high efficiency, and even with a simple configuration that requires only a slight design change to the existing intake system, without the need for a supercharger, it significantly increases the charging efficiency and output at high engine load and high rotation speeds. This method can be widely and effectively implemented, and is therefore useful for easily implementing measures to improve engine output and reducing costs. In addition, since the closing timing of the high-load intake port is set later than the closing timing of the low-load intake port, the unique pulsation effect of the intake air from the low-load intake port increases the pressure in the combustion chamber in the cylinder, and lowers the pressure. After the load intake port closes, a strong opening compression wave due to the exhaust interference effect is supplied to the combustion chamber from the open high load intake port, making it possible to obtain a sufficient amount of intake air and It is possible to prevent the opening compression wave propagated to the high-load intake port at the end of the stroke from passing through the combustion chamber and directly through the low-load intake port, thereby effectively exerting the exhaust interference effect.

[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, 18,18'...Communication path, 1
9,19'...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. On the other hand, the closing timing of the high-load intake port is set later than the closing timing of the low-load intake port, and the passage length of the high-load intake passage between each cylinder via the above-mentioned communication passage is set to 5000~ When the engine rotates at a high speed of 7,000 rpm, the compression wave generated when the high-load intake port of one cylinder opens will propagate to the high-load intake ports of other cylinders at the end of the intake stroke, resulting in supercharging. , The passage length l _P of the above low load intake passage from the above expansion chamber to the low load intake port of each cylinder is 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 ₁ ) × (60/360N) × (1/4) × a (here, θ _P is the intake port for low load) The opening period of the port, θ ₁ is the period from the opening of the low-load intake port until the expansion wave is substantially generated, and the secondary pulsation wave of the compression wave that is the inversion of the expansion wave to effectively perform supercharging. The ineffective 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: