JP2516687B2 - Internal combustion engine intake system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake system for an internal combustion engine, and more particularly to an intake system for reducing intake noise.

2. Description of the Related Art As a conventional intake system for an internal combustion engine of this type,
For example, the one shown in FIG. 4 is known (Shokaisho)
61-198562, etc.).

Briefly, 1 is an engine room on the front side of a vehicle body, 3 is an internal combustion engine vertically arranged in the engine room 1, and 4 is a front side of a left strut house 5 in the engine room 1. Air cleaner, 6
Is an intake pipe interposed between the air cleaner 4 and the intake collector 7, 8 is a bent intake duct connected to the air cleaner 4, and the intake duct 8 has a trumpet-like intake port 9 on the tip side. Is disposed near the front center of the engine room 1 so as to face the front of the vehicle body 2.

The air taken in through the intake port 9 as the engine 3 is driven is evenly distributed from the air cleaner 4 through the intake pipe 8 to the intake collector 7 in each cylinder of the engine 3.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention By the way, in the above-described intake device for an internal combustion engine, when air is sucked into each cylinder, a large discharge sound due to intake pulsation is generated from the intake port 9. It is generally known, and it is desired to take measures against intake noise due to the discharge noise. However, the reality is that sufficient measures have not yet been taken.

That is, the principle of intake noise in the conventional intake device will be described based on the noise level frequency characteristic diagrams shown in FIGS. 5A, 5B, and 5C. Here, FIG. A shows the sound pressure level of the intake air discharge sound from the intake port 9, FIG. B shows the acoustic amplification characteristics in the engine room 1, and FIG. C shows the resulting total intake noise level. Each one is represented. Also, 1 on each vertical axis
The scale is 10 dB.

In the frequency characteristic of the sound pressure level of the intake air discharge sound, there is the level of the level due to the resonance phenomenon of the duct system of the intake device, and in this conventional example, the low level frequency range centered at about 190 Hz and about 2
There is a high level frequency range around 80Hz.

Next, the amplification characteristics of the sound in the engine room 1 are
Since the engine room 1 is a semi-closed space, it is determined by the acoustic amplification effect, and it is significantly different depending on the mounting position of the intake port 9 in the engine room 1, and even the amplification amount for the same frequency. A large difference occurs depending on the mounting position. Further, even at the same position, the amount of amplification varies remarkably depending on the frequency. In this conventional example, as shown in FIG. 5B, the amount of amplification is low near about 70 Hz, around 170 Hz, and around 400 Hz, and is in the high frequency range other than that.

Since the resulting intake noise is determined by the sound pressure level of the intake discharge sound and the acoustic amplification amount, in this conventional example, the intake noise level is around 170 Hz as shown in FIG. While low noise can be achieved, it becomes extremely high near 290 Hz. Therefore, a muffled sound in the vehicle interior is generated due to a noise level higher than the high noise level, and the sound quality is deteriorated due to a significant change in the noise level frequency, and a large outside noise is also generated.

Therefore, it is conceivable to attach a silencer to the intake pipe or change the arrangement of the intake pipe, but there is a problem in that the silencer becomes large and the layout in the engine room is increased. It is also conceivable to attach a sound insulation member to the dash panel, but in this case, the weight and cost are inevitably increased.
Furthermore, various measures have been taken such as changing the mounting position of the intake port of the intake duct and changing the length of the intake duct, but in each case, restrictions on the layout in the engine room and sound amplification effects Are closely related to each other, and it is extremely difficult to design considering them.

Therefore, for example, Japanese Utility Model Publication No. 56-35551 and Japanese Utility Model Publication No. 59-1.
As in the invention described in Japanese Patent No. 24733, there is also provided a technology for canceling generated noise by branching the duct part of the intake duct into a plurality of parts and arranging the sound sources at positions where the phases of the sound sources are different from each other. Has been done. However, in these conventional examples, the inner diameters of the branched duct portions are all set to be the same, and therefore, although measures against intake noise are taken, the device for intake resistance is insufficient.

Means for Solving the Problems The present invention has been devised by comprehensively and fully considering the above-mentioned principle of intake noise and problems such as the layout in the engine room. It is formed by at least two independent duct elements having different sound pressure level characteristics of the sound discharged from the mouth, and the intake ports of the respective duct elements are respectively located at different acoustic amplification characteristics in the engine room. And the inner diameters of the one duct element and the other duct element are formed in different diameters, and the intake port of the small diameter duct element is arranged at a position where the amplification amount is large. The duct elements are individually connected to the air cleaner, and the intake port of the large-diameter duct element is arranged at a position where the amplification amount is small.

Action According to the present invention having the above-described configuration, for example, the sound pressure level of the intake discharge sound generated at each intake port of the two duct elements is
The peaks occur in almost the same frequency range, but the levels are significantly different. On the other hand, the amplification characteristic of the sound in the engine room has a significantly different frequency characteristic due to the difference in the mounting position of the intake port. Therefore, it is possible to match the peak frequency range of the sound pressure level with the frequency range in which the amplification amount is small, so that the noise levels of the both are canceled and the total noise level is smoothed as a whole, and the specific frequency This significantly suppresses a significant increase in noise level.

Further, since the intake port of the small-diameter duct element is arranged at the position where the amplification amount is large and the intake port of the large-diameter duct element is arranged at the position where the amplification amount is small, it is possible to reduce the intake noise in the small-diameter duct element. The large-diameter duct element makes it possible to reduce the flow resistance of intake air. In addition, since each duct element is formed separately and individually connected to the air cleaner, the effect of reducing the intake noise by the small diameter duct element and the reduction of the intake flow resistance by the large diameter duct element are surely achieved. can get.

Examples Hereinafter, each example of the present invention will be described in detail with reference to the drawings.
It should be noted that the same components as those of the above-described conventional device are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 1 shows a first embodiment of an intake device according to the present invention,
1 is an engine room on the front side of the vehicle body, 3 is an internal combustion engine, 4 is an air cleaner, 5 is a strut house, 6 is an intake pipe, 7 is an intake collector, and 11 is an intake duct connected to the air cleaner 4. The duct 11 is composed of a long first duct element 12 and a short second duct element 13.

Both duct elements 12 and 13 are respectively bent and formed in a substantially L shape, and one end portions 12a and 13a thereof are respectively connected to the inner side surface of the air cleaner 4 at right angles to communicate with each other inside the air cleaner 4 and to the other end. The first duct element 12 having the trumpet-shaped intake ports 14 and 15 and having a relatively large diameter as a whole has a relatively large diameter as a whole, and the intake port 14 is directed toward the front of the vehicle body 2. The engine room 1 is disposed near the front center of the engine room 1, that is, above the radiator 10. On the other hand, the second duct element 13 is formed so that the base end side is smaller in diameter than the inner diameter of the first duct element 12, and the intake port 15 on the tip side is directed toward the front of the vehicle body 2 in the engine room 1. It is arranged near the front end side.

The duct elements 12 and 13 have the same resonance frequency, but the resonance strength at those frequencies, that is, the sound pressure level of the discharge sound from each of the intake ports 14 and 15 is different. Further, the frequency characteristics of the acoustic amplification action at the positions of the first and second intake ports 14 and 15 are also different. That is, in this embodiment, the intake port 14 of the first duct element 12 having a relatively large diameter is located at a position where the discharge sound level is high and the acoustic amplification amount is low in the engine room 1.
In addition, the intake port 15 of the small-diameter second duct element 13 is arranged at a position where the discharge sound level is low and the acoustic amplification amount in the engine room 1 is high.

That is, as shown in FIGS. 3A and 3B, first, the intake ports 14 and 15
As for the sound pressure level of the intake / exhaust sound generated in each, the same peak frequency occurs at about 80Hz, 180Hz, 340Hz due to the difference in diameter and length, and the level is 2 The two intake ports 14 and 15 are significantly different (the first intake port 14 side is shown by a broken line, the second intake port 15 side is shown by a solid line.
One scale on each vertical axis of FIGS. 3A, 3B and 3C is 10 dB. ).

On the other hand, the sound amplification characteristic of the engine room 1 has remarkably different frequency characteristics due to the difference in the mounting positions of the intake ports 14 and 15 as shown in FIG.
The side is shown by a broken line, and the second intake port 15 side is shown by a solid line).

Then, as described above, the first intake port 14 whose discharge sound level becomes high at about 180 Hz is arranged at the position of the broken line in FIG. The second intake port 15 which becomes higher is arranged at the position indicated by the solid line in FIG. 9B in which the amplification amount also becomes larger in this vicinity. Therefore, as a result, the total intake noise level, which is determined as the sum of the two intake noises, has a frequency characteristic of the third level.
As shown by the one-dot chain line in FIG. C, the maximum sum of two intake noises is smoothed in a wide frequency range and at a frequency where the discharge sound levels of the first intake port 14 and the second intake port 15 are equal.
Compared with the conventional case shown in FIG. 5, it is significantly reduced. Therefore, the muffled sound in the vehicle compartment due to the extremely high peak of the intake noise can be sufficiently reduced, the sound quality is prevented from being deteriorated by the intake noise always being generated at a stable level, and the large body noise can be suppressed.

Also, since there are two sound sources that generate the intake and discharge sounds,
Due to the acoustic amplification effect in the engine room 1, the total intake noise can actually be suppressed to a level lower than the sum of the intake noise levels at the intake ports 14 and 15. This is because the phase of the three-dimensional standing wave in the space in the engine room 1 differs depending on the location, and the two intake ports 14,15
This is because it is possible to select the positions of two so that the standing waves have two opposite phases. In this case, 2
It becomes difficult for the two intake / exhaust sounds to be acoustically amplified by the standing wave. Therefore, the total intake noise level is 2
Since the intake noise level is lower than the higher one, the intake noise level is further reduced and the noise frequency characteristic can be smoothed.

Further, by arranging the small-diameter second duct element 13 at the position where the amplification amount is large, the intake noise generated at the intake port 15 can be suppressed to be small, and the relatively large-diameter first duct element is also provided.
By placing 12 in a position where the amplification amount is small, the intake port
Although the intake noise generated at 14 cannot be sufficiently suppressed, it has little effect on the total noise, and the intake flow resistance can be reduced by increasing the diameter.

 In the figure, 20 is a front side member.

FIG. 2 shows a second embodiment, in which the air cleaner 4 is arranged on the rear side of the left strut house 5, and the long first duct element 12 of the intake duct 11 is the strut house 5.
Is bent so as to detour around and extends to the front of the engine room 1, one end 12a is connected to the front end of the air cleaner 4, and the first intake port 14 is arranged in the left front part in the engine room 1. . Also, the short second duct element 13
Is connected to the outer side surface of the air cleaner 4 and extends leftward in the engine room 1, and the second intake port 15 is arranged in the left fender.

The second duct element 13 has a relatively large inner diameter, whereas the first duct element 12 has an inner diameter set sufficiently smaller than that of the second duct element 13. Further, the intake port 14 of the first duct element 12 is arranged at a position where the amplification amount is large, and the intake port 15 of the second duct element 13 is arranged at a position where the amplification amount is small. Therefore, the second embodiment also has the same effect as the first embodiment.

EFFECTS OF THE INVENTION As is apparent from the above description, according to the present invention, the intake noise level can be low and smoothed in a wide frequency range, so that the muffled sound in the vehicle interior can be sufficiently reduced and the intake air can be reduced. Since the noise is always generated at a stable level, the sound quality is prevented from being deteriorated and the noise emitted from the vehicle can be suppressed.

Moreover, since the structure is simple and small, the degree of freedom in layout in the engine room is improved, and the weight and cost can be reduced.

Further, since the intake port of the small-diameter duct element is arranged at the position where the amplification amount is large, and the intake port of the large-diameter duct element is arranged at the position where the amplification amount is small, it is possible to reduce the intake noise at the small-diameter duct element. The large-diameter duct element makes it possible to reduce the flow resistance of intake air. Further, since each of the duct elements is independently formed and individually connected to the air cleaner, the effect of reducing the intake noise by the small diameter duct element and the reduction of the intake flow resistance by the large diameter duct element are further enhanced. It is definitely obtained.

[Brief description of drawings]

FIG. 1 is a plan view of an essential part showing a first embodiment of the present invention, FIG. 2 is a plan view of an essential part showing a second embodiment, and FIGS. 3A, 3B, 3C are intake air noise characteristics in each embodiment. FIG. 4 is a plan view of a main part of a conventional intake device, and FIGS. 5A, 5B, and 5C are diagrams showing conventional intake noise characteristics. 1 ... Engine room, 3 ... Engine, 4 ... Air cleaner, 11 ... Intake duct, 12,13 ... First and second duct elements, 14,15 ... First and second intake ports.

Claims (1)

(57) [Claims] 1. An intake device provided in an engine room, comprising an intake duct for introducing air taken in from an intake port into an air cleaner, wherein the intake duct is provided with a sound pressure of a sound discharged from each intake port. It is formed by at least two independent duct elements having different level characteristics, and each intake port of each duct element is
The small-diameter duct elements are arranged at positions having different acoustic amplification characteristics in the engine room, and the inner diameters of the one duct element and the other duct element are formed to have different diameters. Of the internal combustion engine characterized in that the intake port of the large-diameter duct element is arranged at a position where the amplification amount is small, and the duct elements having different inner diameters are individually connected to the air cleaner. Inhaler.