JPH03290052A - Intake sound reducing device for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce the intake sound over the wide range of the number of engine revolution by forming the opened port edges of the first and second intake passages for introducing air into an air cleaner in proximity so that the sound pressure waves interfere each other and forming an expansion chamber on the downstream side from the opening/closing valve in the second intake passage. CONSTITUTION:The first intake passage 12 which is always in opened state and the second intake passage 18 which has an expansion chamber 14 and can be opened and closed by an opening/closing valve 16 installed on the upstream side from the expansion chamber 14 are formed as the intake passages for introducing air into an air cleaner 10. The second intake passage 18 is opened in the vicinity of the opened port of the first intake passage 12, and when both the intake passages 12 and 18 are opened, the sound pressure waves of the intake passages 12 and 18 are allowed to interfere each other. The opening/closing valve 16 is opening/closing-driven by a vacuum actuator 20, and when the number NE of engine revolution which is less than a prescribed value, the vacuum actuator 20 puts the opening/closing valve 16 into a closed state, while if the number NE of engine revolution is over the prescribed value, a control circuit 28 puts the opening/closing valve 16 into an opened state.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention has two intake passages for introducing air into an air cleaner, and opens and closes one of the intake passages according to the rotational speed of an internal combustion engine, thereby reducing intake noise. The present invention relates to an intake noise reduction device for an internal combustion engine that reduces noise.

[Prior Art] In order to increase the output of an internal combustion engine, it is sufficient to increase the opening cross-sectional area of the intake passage so that the amount of intake air can be increased.
There is a problem in that simply increasing the opening cross-sectional area increases the intake noise from the intake port. Therefore, conventionally,
Utility Model Publication No. 38-9002, Utility Model Publication No. 63-60072
As stated in the publication, there are two intake passages that introduce air into the air cleaner, and one passage is closed at low speeds to reduce noise, and at high rotations, both intake passages are opened to increase output. The idea is to ensure performance.

In other words, when the opening cross-sectional area is set to a small value at the cost of sacrificing some output performance of the internal combustion engine in order to reduce intake noise as shown in Fig. 9 (shown by the solid line in the figure), .Comparing the output performance with the case of increasing the engine speed by 8 times (shown by the broken line in the figure), there is almost no difference in output when the engine speed NE is low, and the difference in output increases as the engine speed NE increases. This results in a difference of 5 horsepower at maximum output. For this reason, in the past (as shown in FIG. 10), two intake passages 82 and 84 are formed as intake passages for introducing air into the air cleaner 80, and one of the intake passages 84 is provided with an on-off valve 86, and the engine rotational speed is The on-off valve 86 is closed when the engine speed NE is below a predetermined rotation speed (for example, 4000 [r, p, m, ]), and the on-off valve 86 is opened when the engine speed NE exceeds the predetermined rotation speed. The idea is to improve output performance at high engine speeds while reducing intake noise at low engine speeds.

[Problems to be Solved by the Invention] However, with these conventional measures, (as shown by the solid line in Fig. Peak noise (2 as shown in the figure)
000 [r, p, rn, ]) cannot be eliminated, and the cross-sectional area of the opening is large when the internal combustion engine rotates at high speeds, so there is a problem that the effect of reducing intake noise cannot be obtained. In addition, the engine speed NE increases and the on-off valve 8
6 is switched to the open state, the cross-sectional area of the opening increases and the intake noise rapidly worsens, which not only causes a problem in the noise level, but also causes problems such as a worsening of the sound feel during acceleration and deceleration. be. In FIG. 11, the solid line represents the sound pressure level when the on-off valve 86 is controlled to open and close according to the engine speed, the dotted line represents the sound pressure level when the on-off valve 86 is closed, and the dashed line represents the sound pressure level when the on-off valve 86 is closed. Each represents the sound pressure level when it is in the open state.

The present invention (1) was made in view of these problems, and an object of the present invention is to provide an intake noise reduction device for an internal combustion engine that can reduce intake noise over a wide range of engine speeds and also ensure sufficient output performance. .

[Means for Solving the Problems] In other words, the present invention has been made to achieve the above object (first and second intake passages for introducing an air chamber into an air cleaner, and a second intake passage provided in the second intake passage, An on-off valve that opens and closes, and an on-off control means that closes the on-off valve when the rotational speed of the internal combustion g & open is below a predetermined rotational speed, and opens the on-off valve when the rotational speed exceeds the predetermined rotational speed. In the intake noise reduction device for an internal combustion engine, the opening ends of both intake passages are formed close to each other so that the sound pressure waves of the intake passages interfere with each other, and the opening ends of the second intake passage are formed downstream of the opening/closing valve. The gist of this invention is an intake noise reduction device for an internal combustion engine, which is characterized by forming an expansion chamber.

[Function] As described above, in the intake noise reduction device of the present invention, the opening ends of the first and second intake passages are formed close to each other so that the sound pressure waves of the first and second intake passages interfere with each other. Since an expansion chamber is formed downstream of the opening/closing valve of the intake passage, when the engine speed is low and the opening/closing valve is closed, the expansion chamber acts as a resonator for the first intake passage. On the other hand, when the engine speed is high and the on-off valve is open, a phase difference occurs between the sound pressure waves generated from both intake passages due to the volume of the expansion chamber. The phase difference causes the intake noise to cancel each other out, reducing the intake noise.

In order to fully utilize the intake noise reduction effect of the expansion chamber when the on-off valve is in the open state, the equivalent pipe length of each intake passage should be
It is desirable to use the volume of the expansion chamber to shift the frequency of interest by half a wave. In other words, by doing this, the phase of the sound pressure waves exiting from the intake port of each intake passage can be shifted by 80 degrees, and intake noise can be reduced more efficiently.

[Example] Embodiments of the present invention will be described below with reference to drawings.

First, FIG. 1 shows the configuration of an intake noise reduction device according to a first embodiment.

As shown in the figure, the intake noise reduction device of this embodiment has a first intake passage 2 which is always open as an intake passage for introducing air into the air cleaner of an internal combustion engine, and an expansion chamber 4. A second intake passage 18 that can be opened and closed by an on-off valve] 6 provided upstream of the chamber 14 is provided.

The second intake passage 181 opens near the opening of the first intake passage 12, and when both intake passages 12.18 are open, the sound pressure waves of each intake passage 12.18 interfere with each other.

Next, a vacuum actuator 20 and a negative pressure source 22 that generates negative pressure to drive the vacuum actuator 20 are provided.
, a solenoid valve 24 that switches between connecting the vacuum actuator 20 to the negative pressure source 22 or opening it to the atmosphere, and a rotation speed sensor 26 that detects the rotation speed of the internal combustion engine.
and the engine speed NE detected by the rotation speed sensor 26.
The opening and closing of the solenoid valve 24 is controlled by a control device 30 as an opening/closing control means comprising a control circuit 28 that controls energization of the solenoid valve 24 based on the following.

The vacuum actuator 20 (1) is configured to close the on-off valve 16 when it is open to the atmosphere, and open the on-off valve 16 when negative pressure from a negative pressure source 22 is applied, and the control circuit 26 controls the engine speed NE. is a predetermined number of rotations (for example, 4000
[r, p, m, ]), the solenoid valve 24 is switched to the atmosphere side 1:, and conversely, when the engine rotation speed NE exceeds a predetermined rotation speed, the solenoid valve 24 is switched to the negative pressure source 22 side. Therefore, when the engine speed NE is below the predetermined speed, the vacuum actuator 20 is opened to the atmosphere and the on-off valve 16 is closed, and conversely, when the engine speed NE exceeds the predetermined speed, the vacuum actuator 20 is opened to the atmosphere and the on-off valve 16 is closed. Negative pressure is supplied to 20, and the on-off valve 16 becomes open.

When the expansion chamber is provided in the second intake passage 18 as described above,
When the engine speed NE is low and the opening/closing valve] 6 is closed, the expansion chamber 14 acts as a resonator, and the first intake passage 1
On the contrary, when the engine speed NE is high and the on-off valve 16 is open, the volume of the expansion chamber 14 is used to reduce the intake noise generated from each intake passage 12.・A phase difference occurs in the sound pressure waves from 18, and this phase difference reduces intake noise, but in this example (such an expansion chamber)
In order to maximize the intake noise reduction effect of 6,
The dimensions of each part of the second intake passage are set. The design procedure for this purpose will be explained below.

First, when the on-off valve [6] is closed, the expansion chamber [4] acts as a resonator to muffle the intake noise generated in the first intake passage [2], and the resonant frequency f1 of this resonator is
As shown in FIG. 2(a), if the length between the two is L2a and the volume of the expansion chamber 14 is V, then f is (C/2π)・f 7T possible 1 (however, C: speed of sound). Therefore, in this example (the second
The length L2a of the intake passage [r,
By making adjustments to greatly reduce the noise in the vicinity of p, m, ], intake noise at low rotational speeds of the internal combustion engine is reduced.

On the other hand, when the on-off valve is open, Sl,
Length between air cleaner 10 and expansion chamber 14 and expansion chamber]
4 is defined as L2b, and each intake passage 12. j
If the equivalent pipe lengths of 8 are LEI and LE2, respectively, LE
1=11, but LE2 is S 2cot(L 2b
/LE2) yr -S 1tan(L 2a/LE2
)yr-V・π/LE2=0. Therefore, since the intake passage 2 has an expansion chamber in the middle, the equivalent pipe length becomes longer by (LE2-LEI).

Here, if the frequency that becomes a problem at high rotation (the noise frequency around 4 500 [r, p, m,] shown in Figure 11) is 1,0002, then the wavelength is λ = C/f2, but the equivalent If the difference in pipe length ([ε2-LEI) is equal to the half wavelength of f2 (λ/2), then the sound pressure waves from the first and second intake passages 12.18 Phase is 180°
Because of the deviation, the sound pressure waves cancel each other out and the combined sound pressure wave becomes smaller.

Therefore, in this embodiment, the length L 2a of each part of the second intake passage is set so that λ/2=C/2·f 2=LE2−LEI.

By setting L2b and the volume V of the expansion chamber 14,
Reduces intake noise when the internal combustion engine rotates at high speeds.

In this case, even if the sound pressure waves are completely opposite in phase and their levels are the same (the L sound pressure wave becomes O, the respective levels will not be exactly the same due to attenuation by the expansion chamber 14). Therefore, the noise level never becomes completely O.

As shown by the solid line in FIG. 3, the intake noise reduction device of this embodiment configured as described above can reduce the peak noise caused by the resonance of the intake system when the internal combustion engine is running at low speeds. Intake noise can also be reduced when the valve 16 is opened to increase the opening cross-sectional area, and it is possible to reduce the intake noise without any level difference over a wide range of engine speeds. Further, since the opening cross-sectional area when the internal combustion engine is running at low speeds and the opening cross-sectional area when the engine is running at high speeds can be switched in the same way as in the conventional case, sufficient output performance of the combustion engine can be ensured. In FIG. 3, the solid line indicates the sound pressure level when the on-off valve 16 is controlled to open and close according to the engine speed NE by the control device 3O, the dotted line indicates the sound pressure level when the on-off valve 16 is in the closed state, and the - point The chain line represents the sound pressure level when the on-off valve 16 is open, and the two-dot chain line represents the sound pressure level when the on-off valve is opened in the conventional device shown in FIG. Figure 3 shows the measurement results of the intake sound pressure level of three engine rotation components in a six-cylinder engine.

Here, in the above embodiment, the first intake passage 12 and the second intake passage 8 were formed separately, but as shown in FIG. 38 may be integrally formed, and the expansion chamber 34 may be provided outside thereof. In this case, the ease with which both intake passages can be mounted on a vehicle is improved. In FIG. 4, 30 and 361i represent an air cleaner and an on-off valve, respectively.

Further, as shown in FIG. 5, not only the first intake passage 42 and the second intake passage 48 may be formed integrally, but also the expansion chamber 44 may be formed integrally with the air cleaner 40. In this case, the expansion chamber 44 may be formed integrally with the air cleaner 40. Compared to the intake system shown in FIG. 4, the ease of mounting on a vehicle can be improved. In addition, in Figure 5, 4
6 represents an on-off valve.

Next, in the above embodiment, the opening ends of the first intake passage 12 and the second intake passage 18 are provided close to each other so that the sound pressure waves interfere with each other, but as shown in FIG. Five interference chambers may be provided at the entrances of the first and second intake passages 52, 58 so that the pressure waves can cancel each other out better. In FIG. 6, 50, 54, and 56 represent an air cleaner, an expansion chamber, and an on-off valve, respectively.

Furthermore, in order to obtain an equivalent pipe length that can shift the phase of the sound pressure waves from each intake passage by 1800 in an expansion chamber with a smaller volume V, for example, as shown in FIG.
The pipe line between the expansion chamber 64 of No. 8 and the open end may be made to meander so that its length L2b becomes the length X. In FIG. 7, 60°62.66 represents an air cleaner, a first intake passage, and an on-off valve, respectively.

Further, as shown in FIG. 8, the expansion chamber 74 can also be formed by utilizing the space in the vehicle body 79.

In Fig. 8, 70, 72, 76.78 are respectively
Air cleaner, first intake passage, on-off valve.

It represents the second intake passage.

[Effects of the Invention] As detailed above, in the intake noise reduction device of the present invention, when the internal combustion engine is running at low speed, not only can the opening cross-sectional area be reduced to reduce intake noise, but also the expansion chamber can be used as the first intake air. Since it acts as a resonator for the passage, it can also reduce the peak noise caused by the resonance of the intake system, and when the internal combustion engine is running at high speeds, it can reduce the intake resistance and improve the output performance of the internal combustion engine. The volume of the chamber shifts the phase of the sound pressure waves generated from the first and second intake passages, thereby reducing intake noise. In other words, according to the present invention, ['L] without reducing the output performance of the internal combustion engine,
Intake noise can be reduced over a wide range of engine speeds. Further, in the present invention, it is only necessary to form an expansion chamber in the second intake passage,
Since the configuration is simple, it also has the effect of being easily realized.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the overall configuration of the intake noise reduction device according to the embodiment. Figure 2 is an explanatory diagram illustrating a method of designing an intake passage to maximize the intake noise reduction effect. Figure 3 is an illustration of the implementation. A diagram illustrating the intake noise reduction effect of the example intake noise reduction device,
4 to 8 are explanatory diagrams each explaining other configuration examples of the intake system, FIG. 9 is a diagram illustrating changes in the output performance of the internal combustion engine with respect to the opening cross-sectional area of the intake passage, and FIG. FIG. 11 is an explanatory diagram showing the configuration of a conventional intake system. FIG. 11 is a diagram illustrating intake noise generated from the conventional intake system.

Claims (1)

[Scope of Claims] First and second intake passages for introducing air into the air cleaner; an on-off valve provided in the second intake passage for opening and closing the passages; In the intake noise reduction device for an internal combustion engine, the sound pressure wave of each intake passage includes an opening/closing control means that closes the on-off valve when the rotation speed exceeds a predetermined rotation speed, and opens the on-off valve when the rotation speed exceeds a predetermined rotation speed. The intake noise of an internal combustion engine is characterized in that the opening ends of both intake passages are formed close to each other so that the two intake passages interfere with each other, and an expansion chamber is formed downstream of the opening/closing valve of the second intake passage. Reduction device.