JP3336161B2 - Active silencer cooling structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the passage of noise-induced wind, such as the exhaust of an engine driving a ship, a pump or a generator, etc., through a main pipe, and the generation of an antiphase sound of the noise by a sound generator. In addition, the present invention relates to a cooling structure of a sound generating device in an active noise reduction device that causes an anti-phase sound to reach a wind passing through the main pipe and interferes with noise to reduce the noise.

[0002]

2. Description of the Related Art Conventionally, a wind accompanied by noise is passed through a main pipe to generate an anti-phase sound of noise by a sound generator, and a branch pipe is extended from the sound generator to be connected to the main pipe. An active silencer having a configuration in which an anti-phase sound from a branch pipe reaches the wind passing through the main pipe at the confluence of the main pipe and interferes with noise to muffle the noise is known. For example, the applicant has filed Japanese Patent Application
Application has been filed at −115518.

[0003]

The active silencer having such a structure has a main purpose of using an engine exhaust pipe as a main pipe, that is, passing exhaust with noise through the main pipe to muffle engine exhaust noise. There are many. The branch pipe is orthogonally connected to the main pipe so that the exhaust gas passing through the main pipe smoothly flows through the main pipe even at the junction of the two pipes and does not enter the branch pipe. However, when the engine is stopped or when a load is applied to the driving of the engine, the flow velocity of the exhaust gas is slowed down or stagnated. In this case, the two pipes are also provided in the branch pipe orthogonally connected to the main pipe. High-temperature exhaust gas flows from the upper part of the joint in the noise propagation direction, and the air in the branch pipe becomes high in temperature. As a result, the temperature of the sound generating device may be increased, and the performance of the sound generating device may be deteriorated. In order to prevent the exhaust air from flowing from the main pipe side to the branch pipe side, a cooling mechanism is sent to the sound generator, and a throttle mechanism with an appropriate opening area is provided in the noise interference section, and a guide for wind passing through the main pipe. It must be configured to have members.

[0004]

The present invention uses the following means to solve the above problems. In other words, an active silencer in which a main pipe through which noise propagates is connected to a branch pipe extending from a sound generating device that emits an anti-phase sound of the noise, and a noise interference part is formed in the pipe communicating with both pipes. , The side opposite to the branch pipe with respect to the sound generator
A fan is arranged in the
After cooling, the cooling air flows from the sound generator through the branch pipe to the main pipe.
It was configured to be winded .

Further, a duct communicating with the inside of the branch pipe is provided around the sound generating device, and the air blown by the fan is sent into the duct.

Further, an auxiliary fan for forcibly blowing air from the duct to the branch pipe is provided at a portion communicating with the branch pipe from the duct.

[0007] The auxiliary fan is covered with the duct.

[0008] In addition, the main pipe through which wind with noise passes
In an active silencer in which a branch pipe extending from a sound generating device that emits an anti-phase sound of the noise is connected to form a noise interference part in a pipe where the two pipes join, a pipe joint part in the noise interference part Member on the upper side of the noise propagation direction
And narrowing the opening of the branch pipe at the noise interference part,
The opening ratio of the main pipe at the noise interference section is configured from 80% to 85%.
Done .

The throttle member is formed in a wing shape facing the wind passing through the main pipe.

Further, the throttle member is a tapered cylindrical body facing the wind passing through the main pipe.

[0011]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a front view showing an embodiment of the active silencer, FIG. 2 is a bottom view thereof, FIG. 3 is a front sectional view showing a cooling structure of a speaker unit SU by a duct and a cooling fan, and FIG. FIG. 5 is a front cross-sectional view when an auxiliary fan is attached, FIG. 6 is a right side view, FIG. 7 is a front cross-sectional view when the auxiliary fan is covered with a duct, and FIG. 9 is a front cross-sectional view when a blower fan is installed inside the duct, FIG. 10 is a right side view thereof, and FIG. 11 is a front partial cross-sectional view showing the arrangement structure of the throttle plate 10 in the branch pipe 5. 12 is a right side view of the same.

FIG. 13 is a right side view of the branch pipe 5 when the throttle plate 10 'is provided in the branch pipe 5, FIG. 14 is a right side view of the same when the throttle plate 10 "is provided therein, and FIG. 16 is a front cross-sectional view showing the arrangement structure of the diaphragm blade members 11 and the blade members 12 in the branch pipe 5, FIG. 16 is a right side view thereof, and FIG. 17 is a front cross-section showing the arrangement structure of the throttle cylinder 13 in the branch pipe 5. FIG. 18 is a right side view, and FIG. 19 is a graph showing a change in temperature and a change in noise level with respect to an engine load in a negative pressure space formed by the throttle member, for each opening ratio, and FIG. A graph in which the sound pressure level of each frequency sound mixed with the exhaust sound reaching the noise interference unit 5a is measured when no
FIG. 21 is a schematic diagram showing the relationship between the tube length of the branch pipe 7 and the bent pipe section 5b and the wavelength of the speaker sound.

First, the overall configuration of the active silencer will be described with reference to FIGS. The purpose of the active silencer in this embodiment is to mute engine exhaust noise. As an exhaust passage system, an exhaust pipe, a main pipe 1, a resonance type silencer 2, a primary sound adjuster 3, a secondary sound adjuster 4, a branch pipe 5, and an outlet pipe 6 are connected in series by flanges in series. ing. Then, a branch pipe 6 is joined to a bent pipe 5b branched from the branch pipe 5 by a flange in a direction parallel to the main pipe 1 direction. Speaker units SU are joined by flanges.

The exhaust gas passing through the main pipe 1 generates a sound wave of noise, which mixes sounds of various frequencies and produces a specific tone, in a longitudinal wave form in the pipe. When the exhaust gas flows into the resonance type silencer 2, a sound of a specific frequency resonates in the Helmholtz resonator provided therein to attenuate the frequency sound in the exhaust gas. Regarding the frequency sound attenuated by the resonance type silencer 2, as will be described later, the exhaust gas passing therethrough then flows into the primary silencer 3, where the tubular sound absorber is formed. High frequency sound is absorbed by the material (glass wool, etc.). The sound absorbing material portion of the primary sound adjusting tube 3 has a certain thickness to enhance the sound absorbing effect, and the exhaust gas flowing into the sound absorbing material portion reaches the lower end thereof and flows again into the exhaust pipe. When doing so, the flow bends, generating new noise. Therefore, the primary sound control tube 3
In order to mitigate such newly generated noise, a secondary sound-absorbing tube 4 in which a sound-absorbing material is formed in a tubular shape is disposed on the lower side.

In the branch pipe 5 connected to the lower side of the secondary sound adjusting pipe 4, a noise interference part 5a (FIG. 5) in which the antiphase sound and the noise generated from the branch pipe 7 interfere with each other in the exhaust passage. 3) is formed. Exhaust gas that has reached the noise interference section 5a is attenuated in the high-frequency range by the two sound-tuning tubes 3 and 4, and is also attenuated by the resonance-type silencer 2 in the specific frequency range. (See FIG. 20). The speaker unit SU has a sound generator capable of adjusting the volume inside a box, and a speaker S facing the entrance of the branch pipe 7.
From P (illustrated in FIG. 21), an anti-phase sound of the low-frequency noise is generated toward the inside of the branch pipe 7. Note that a sensor microphone SM is attached to the main pipe 1 and a monitor microphone MM is attached to the outlet pipe 6 so that the volume of the exhaust sound passing through the main pipe 1 and the exhaust sound passing through the outlet pipe 6 after the silencing process are performed. And the volume of the
The volume of the speaker sound is also adjusted based on the detected value.

In the exhaust sound, some specific frequency sounds having high sound pressure levels are mixed. In the noise interference section 5a, high-frequency sounds are absorbed and attenuated by the sound-absorbing materials of the two sound-tuning tubes 3 and 4, but specific low-frequency sounds having high sound pressure levels remain in low-frequency sounds. . Here, when the resonance type silencer 2 is not provided, the sound pressure level of each frequency sound mixed in the noise reaching the noise interference section 5a is as shown in the graph of FIG. That is, in the low frequency range, a high sound pressure level of the sound of the frequency _{f 1 · f 2 · f 3} . Here, f ₂ = f ₁ × 2 and f ₃ = f ₁ × 3. If the sounds of these frequencies f ₁ , f ₂ , f ₃ are respectively a primary frequency sound, a secondary frequency sound, and a tertiary frequency sound,
Frequency f ₁ of the primary frequency is determined by the type and speed of the engine. Then, in the exhaust pipe system, the secondary frequency sounds and tertiary frequency sound having a frequency of an integral multiple of the frequency f ₁ of the primary frequency sound is also the sound pressure level is high.

On the other hand, since the sound pressure level of each frequency sound is averaged for the anti-phase sound of the speaker, the primary frequency sound, the secondary frequency sound, and the tertiary frequency sound are selected from among them in order to efficiently perform silencing. The sound must be amplified and sent to the branch pipe 5 with the sound pressure level raised. Therefore, the speaker SP in the speaker unit SU
The length of the pipe formed by the branch pipe 7 and the bent pipe 5b to the noise interference section 5a in the branch pipe 5 is set to a length that amplifies the primary frequency sound. Specifically, assuming that the wavelength of the primary frequency sound is λ, as shown in FIG. 21, this tube length is λ × (2n−1) /
4 (n is an integer). The branch pipe 7 and the bent pipe 5
The trachea formed by b has a fixed end on the speaker SP side,
This is because the noise interference portion 5a is an open end, and if this tube length is set, the antinode of the longitudinal wave formed by the sound wave of the primary frequency sound is located at the noise interference portion 5a (the thick line in FIG. 21). Solid waveform). Therefore, a sound wave having the antinode also located at the antinode of the sound wave of the primary frequency sound is generated. The frequency is f ₁ × 3,
That is, the tertiary frequency sound having the wavelength of λ / 3 is also amplified (see FIG. 2).
1 medium thin solid line waveform). However, since the sound wave of the secondary frequency sound has a node at the antinode of the sound wave of the primary frequency sound, the sound wave node is located at the noise interference unit 5a and is not amplified (the thin broken line in FIG. 21). Waveform). That is, when the branch pipe length is set to amplify the primary frequency sound and the tertiary frequency sound in the speaker sound, the secondary frequency sound cannot be amplified, and the secondary frequency sound in the noise cannot be completely eliminated. It is.

Therefore, as shown in FIGS. 1 and 2, a resonance type silencer 2 is provided to attenuate the secondary frequency sound having a high sound pressure level mixed in the noise before reaching the noise interference section 5a. It is. The resonance type silencer 2 includes a Helmholtz resonator 2a that resonates the secondary frequency sound. The secondary frequency sound in the noise is resonated by the Helmholtz resonator 2a and attenuated. Thus, in the exhaust noise reaching the noise interference unit 5a, the high sound pressure level is the primary frequency sound and the tertiary frequency sound, and the opposite phase sound of the speaker in which the primary frequency sound and the tertiary frequency sound are amplified. It is interfered and muted.

The overall structure of the active silencer and the silencing operation have been described above. Next, the cooling structure of the speaker unit SU, which is a sound producing device, will be described with reference to FIGS. First, the necessity is explained. In the case of engine exhaust, generally when the engine is driven,
The exhaust gas flows at a high speed, and the exhaust gas flows linearly from the main pipe 1 to the outlet pipe 6. However, when the engine is stopped or a load is applied to the driving of the engine, the exhaust gas slows down or stagnates. Exhaust gas flows into the bent pipe section 5b and the branch pipe 7 from the noise interference section 5a in the illustrated branch pipe 5. The exhaust gas is at a high temperature, and if the temperature of the air in the branch pipe 7 becomes high and the temperature of the speaker unit SU also becomes high, the functions of the internal parts of the speaker unit SU including the speaker may be deteriorated.

Therefore, it is necessary to adopt a configuration in which exhaust gas does not enter the branch pipe 7 from the main exhaust gas stream. As means therefor, in the branch pipe 7, the noise interference part 5
Blow toward a. In the embodiment shown in FIGS. 3 to 10, the air is forced to be blown by the blower fan F. In the embodiments shown in FIGS. This is to cause a wind toward the noise interference section 5a from the pipe 7. In both embodiments, the speed of the wind flowing through the branch pipe 7 and the bent pipe section 5b is very slow compared to the sound speed of the speaker sound, so that the sound quality of the speaker sound passing through the branch pipe is changed. Never.

First, an embodiment in which the former blower fan F is mounted will be described. In this example,
Instead of simply blowing air from the blower fan F into the branch pipe 7, the periphery of the speaker unit SU is covered with a duct 8 communicating with the branch pipe 7, and air is blown into the duct 8 from the blower fan F to directly make a speaker. Cooling air is applied to the unit SU, and after flowing through the duct 8, the cooling air enters the branch pipe 7. That is, the exhaust air is not flown into the speaker unit SU, and at the same time, the cooling is directly applied to the speaker unit SU for cooling. Note that a sound absorbing material 8 a is attached to the inner surface of the duct 8 to absorb the sound of cooling air circulating in the duct 8.

The operation will be described with reference to FIGS. 3 and 4. A speaker unit SU and a part of an inlet portion of the branch pipe 7 are fitted into the duct 8, and a communication port that communicates with the inside of the duct 8 at a portion where the branch pipe 7 fits into the duct 8. 7a is open. A blower pipe 9 extending from the outlet of the blower fan F is connected to a lower portion of the side of the duct 8 opposite to the side where the branch pipe 7 is inserted. The blower fan F sucks air from the suction port Fa and blows out cooling air from the outlet into the blower tube 9, and the cooling air enters the duct 8 via the blower tube 9.

In the duct 8, a communication port 8b between the blower pipe 9 and the duct 8 is located below the speaker unit SU, and the cooling air W flowing from the communication port 8b is provided.
Flows straight under the speaker unit SU. In this state, cooling air does not flow above the speaker unit SU, and cooling air does not circulate throughout the speaker unit SU.
A shielding plate 8c is provided vertically from the flange joint between U and the branch pipe 7 to the lower end of the duct 8. The cooling air W linearly flowing from the communication port 8b is
Therefore, the cooling air flows upward along the branch pipe 7 joint of the speaker unit SU and the side surface on the opposite side, and flows into the speaker unit SU. Further, it goes around the branch pipe joining side of the speaker unit SU, descends, and enters the branch pipe 7 through the communication port 7a. Thus, in the branch pipe 7, a wind flow W 'directed toward the noise interference unit 5a occurs.

Next, the embodiment shown in FIGS. 5 and 6 will be described. Basically, similar to the embodiment of FIGS. 3 and 4, after circulating the cooling air in the duct 8, the cooling air W is sent from the communication port 7a into the branch pipe 7. In the present embodiment, an auxiliary fan SF is disposed above the speaker unit SU near the junction with the branch pipe. The auxiliary fan SF connects the suction port SFa to the speaker unit SU.
, And the cooling air W circulating in the duct 8 is forcibly forced to flow through the communication port 7a, that is, the branch pipe 7 with the outlet SFb facing downward, that is, the communication port 7a. It blows inside.

In the embodiment of FIGS. 7 and 8, similarly to the embodiment of FIGS. 5 and 6, an auxiliary fan SF is provided to forcibly send cooling air circulating in the duct 8 to the communication port 7a. 5 and 6, the size of the duct 8 is limited, and a part of the auxiliary fan SF protrudes outside the duct 8. On the other hand, in the embodiment of FIGS. 7 and 8, the auxiliary fan SF is completely covered in the duct 8, and the size of the entire duct 8 is correspondingly increased. This has the effect of being cooled by the cooling air W inside.

The above-mentioned blower fan F and auxiliary fan SF
May be automatically controlled to operate only when the engine load is particularly high and the main exhaust gas flow is delayed. Also,
A configuration may be adopted in which the temperature inside the branch pipe extension pipe 5b of the branch pipe 5 is measured, and if the temperature exceeds the allowable temperature, the fan is operated.

Next, in the embodiment shown in FIGS. 9 and 10, a blower fan F is provided in a duct 8 'covering the speaker SU, and the duct 8' is constructed so as to take in outside air into the blower fan F. A suction duct 14 is provided.
A filter 15 is provided inside the suction duct 14 via a packing 16 so as to purify the wind W taken in through the suction ports 14a of the suction duct 14.
The portion where the suction port 14a is provided is on the opposite side to the side where the main pipe 1 is provided, and the portion close to the main pipe 1 is the outside air heated by the high temperature of the exhaust gas flowing through the main pipe 1. The suction port 14a is not drilled so as not to be taken in.

The blower fan F draws outside air from the suction duct 14 with the suction port Fa facing the suction duct 14, and blows air into the duct 8 'from the outlet Fb. The wind W cools the periphery of the speaker unit SU, and is further sent into the branch pipe 7 through the communication port 8'a. In addition,
The speaker unit SU is provided with a small hole SUa communicating with the inside of the duct 8 '.
It has the function of adjusting the internal pressure. Further, in order to mute the sound from the fan, a sound absorbing material K 'may be attached to the inner surface of the duct 8' as shown by a dashed line.

The above is a description of the speaker unit S using a fan.
In this configuration, the U is directly cooled, and the air is sent into the branch pipe 7 toward the branch pipe 5. Next, the embodiment shown in FIGS. 11 to 18 has a configuration in which the internal structure of the branch pipe 5 is devised so as to generate air in the branch pipe 7 from the speaker side to the noise interference section 5a side. This configuration is similar to that of the blower fan F shown in FIGS.
May be used in combination, or one without the blower fan F may be used. When used together with the blower fan F, it can be expected that the wind force (wind speed) of the blown air generated in the branch pipe 7 is increased.

The configuration shown in FIGS. 11 and 12 will be described. At the boundary between the noise interference part 5a and the bent pipe part 5b in the branch pipe 5, the upper part 5 of the joint part of the extension pipe part 5b
c, the diaphragm plate 10 is slightly inclined toward the noise interference portion 5a.
Is protruding. The throttle plate 10 pushes the bottom flow of the main exhaust gas flowing through the noise interference unit 5a slightly upward. Therefore, the space between the throttle plate 10 and the lower side portion 5d of the joint portion becomes the negative pressure space S, and the bent pipe portion 5b
Inhale the air inside. That is, the branch pipe 7 and the bent pipe portion 5b
Inside, a wind flow W ″ directed toward the noise interfering portion 5a occurs. The wind flow pushes back the exhaust gas flowing into the branch pipe 7 from the noise interfering portion 5a. This avoids raising the temperature of the speaker SP and the speaker unit SU at the seven ends.

The aperture plate 10 shown in FIGS. 11 and 12 is
Although it has a flat plate shape, the aperture plate 10 ′ shown in FIG.
Although the lower end is horizontal, the portion of the upper joint portion that is fixed to the upper portion 5c is curved in an arc along the joint portion. In addition, the lower end of the diaphragm plate material 10 ″ shown in FIG. 14 is also curved in an arc shape so that the overall shape is a gutter shape. In this manner, the volume of the negative pressure space S increases, and the bending is performed. It is possible to increase the suction amount of air in the pipe portion 5b and the branch pipe 7.

The aperture area of the aperture opening O, which is formed between the tip of the aperture plate 10, 10 ′, 10 ″ and the upper part of the noise interference section 5 a in the branch pipe 5, Plate 10
It is determined by the length and the inclination angle of 10 ′ · 10 ″.
If the cross-sectional area of the inlet of the noise interference part 4a of the branch pipe 4, that is, the ratio of the opening area of the throttle opening O to the cross-sectional area of the main pipe 1, is defined as the opening ratio, the large opening ratio is caused by the exhaust gas. This means that the aperture amount is small. If the aperture is small,
Since the increase in the flow velocity of the exhaust gas is small and the negative pressure in the negative pressure space S is small, the air in the bent pipe portion 5b and the branch pipe 7 cannot be taken in much, so that the temperature on the branch pipe 7 side is not sufficiently reduced. Conversely, a small aperture ratio means that the amount of throttle of the exhaust is large, the flow velocity of the exhaust increases, the negative pressure in the negative pressure space S also increases, and a large amount of air is taken in the branch pipe 7 side. Thus, it is possible to avoid the high temperature on the branch pipe 7 side.

Therefore, first, the aperture ratio is set based on the temperature change in the negative pressure space S in the bent tube portion 5b. The graphs X, Y, and Z shown in FIG.
%, 85%, and 95% when the air temperature in the negative pressure space S1 is measured. T indicates an allowable temperature in the negative pressure space S. The negative pressure space S has an allowable temperature T.
When the temperature becomes higher, the amount of high-temperature exhaust gas flowing from the main exhaust stream into the negative pressure space increases, and the branch pipe 7 and the speaker unit SU
This high temperature may propagate to the side. When the load of the engine is low and the flow of the main exhaust stream is fast, the main exhaust stream flows smoothly to the outlet pipe 6 through the noise interference part 5a.
The temperature in the negative pressure space S is lower than the allowable temperature T, without much difference between X, Y and Z. However, as the engine load increases, the flow of the main exhaust gas is delayed, so that the main exhaust gas flows into the negative pressure space S and the temperature increases. Graph X
As can be seen from FIGS. And Y, when the opening ratio is 75% or 85%, the negative pressure in the negative pressure space S is high, so that the wind W ″ flows from the branch pipe 7 side. The temperature does not rise above the temperature T, and there is no possibility that the temperature of the speaker unit SU will increase.
As shown by the graph Z, when the engine load increases, the high temperature from the exhaust main stream propagates to the negative pressure space S, and the temperature exceeds the allowable temperature T, and the temperature of the speaker unit SU may be increased. Therefore, the aperture ratio must be less than 95%,
If it is 85%, there is no possibility of high temperature irrespective of the increase of the engine load, so the aperture ratio is desirably 85% or less.

In view of the above, the smaller the aperture ratio, the better, but on the other hand, on the other hand, the aperture opening O
As the opening ratio of the exhaust gas becomes smaller, the increase in the flow velocity of the exhaust main flow increases, the airflow noise of the exhaust main flow flowing through the throttle opening O increases, and this sound becomes louder than the original muffled sound. There is a defect. The graph X 'in FIG.
Y ′ and Z ′ respectively have an aperture ratio of 75%, 85%, and 95%.
%, The noise level in the load space S is measured. In each case, the higher the engine load, the higher the noise level caused by the airflow noise, but the lower the aperture ratio, the higher the noise level. That is, as the aperture ratio increases, the noise level increases.

As described above, in order to keep the noise level low and to avoid the high temperature inside the branch pipe 7, the opening ratio is 75%
Among 85% and 95%, an aperture ratio of 85% is most desirable. To obtain these desirable effects, the aperture ratio should be set to 80% to 85%.

Next, the configuration of FIGS. 15 and 16 will be described. Similar to the embodiment shown in FIGS.
1 is protruded from the upper side portion 5c of the joint portion, and a diaphragm opening O 'formed between the tip of the diaphragm blade material 11 and the upper part of the noise interference part 5a (the aperture ratio is also 80%) ~ 8
5%. ), The wing material 12 is disposed from the lower side portion 5d to the bottom in the outlet pipe 6. In this way, a blade is formed by the throttle blade material 11 and the blade material 12, and the flow of the underflow of the main exhaust gas flowing on the upper surface is made smooth. From the inside of the bent tube portion 5b generated by the negative pressure space S 'generated below the throttle opening O' by the throttle blade material 11, a noise interference portion 5a is formed.
The flow of the main exhaust stream becomes a resistance f 'with respect to the suction force f. When the underflow flow of the main exhaust stream is formed in the airfoil shape in this way, the resistance f' becomes small, and the branch pipe is extended. Only the suction force f is applied to the air in the portion 5b and the branch pipe 7, and the air is strongly sucked into the noise interference section 5a. The effect of preventing the inflow into the speaker unit SU can be enhanced.

Next, the configuration of FIGS. 17 and 18 will be described. A tapered throttle cylinder 13 is provided at the inlet of the noise interference portion 5a in the branch pipe 5 so as to be joined to the inner surface of the branch pipe 5 so as to face the main exhaust stream, and a flow path of the entire main exhaust stream is provided. The cross-sectional area is reduced to the opening area of the throttle opening O ″ on the lower side of the throttle cylinder 13. In this way, the periphery of the exhaust main flow narrowed toward the center of the cross section has a negative pressure state.
In the noise interference section 5a, a negative pressure space S "is formed in a cylindrical shape surrounding the main exhaust flow. The air in the bent pipe portion 5b and the branch pipe 7 is sucked into the negative pressure space S". Further, since there is no corner in the throttle cylinder 13, the airflow noise of the exhaust flowing therethrough can be suppressed low. Accordingly, the throttle amount of the throttle opening O ″ can be increased by that much, that is, the opening area can be reduced, and the flow of wind that prevents the inflow of exhaust gas from the main exhaust stream into the branch pipe 7 can be generated more strongly. it can.
Also in this case, the aperture ratio of the aperture opening O ″ is set to 80.
% To 85%.

[0038]

As described above, the present invention has the following advantages. With the configuration as described in claim 1, air with high temperature noise, for example, when an active silencer is installed with an engine exhaust pipe as a main pipe, an engine load is increased or the engine is stopped, so that the main exhaust stream is retained. In this case, it is possible to prevent the high temperature of the exhaust gas from propagating from the main pipe to the air in the branch pipe by blowing air toward the noise interfering section in the branch pipe by the fan, thereby avoiding a decrease in the performance of the sound generator.
At the same time, the sound generator can be directly cooled, preventing the sound generator from becoming too hot.
Can be further assured .

Further, since a duct communicating with the inside of the branch pipe is provided around the sound generating device and the air blown by the fan is sent into the duct, high temperature of the exhaust gas is avoided. The fan that generates air flow in the branch pipe to cool the sound generator directly at the same time can prevent the temperature of the sound generator from becoming higher.

According to a third aspect of the present invention, an auxiliary fan for forcibly blowing air from the duct to the branch pipe is provided at a portion where the duct communicates with the branch pipe, so that air from the duct to the branch pipe is blown. As a result, the wind directed toward the noise interference portion in the branch pipe can be reliably and more strongly generated, and the effect of preventing the sound generator from being heated to a high temperature can be enhanced.

Further, by covering the auxiliary fan with the duct, the auxiliary fan itself can be cooled by circulation of cooling air in the duct, and the durability of the auxiliary fan is improved. This contributes to the prevention of high temperature of the sound generator.

Further, with the construction as claimed in claim 5, when the active silencer is installed with air accompanied by high-temperature noise, for example, with the engine exhaust pipe as the main pipe, the underflow of the main exhaust stream is pushed up by the throttle member. The air inside the branch pipe is sucked into the negative pressure space created by the push-up, which naturally causes the air flow to the noise interference part in the branch pipe, and the engine load rises or the engine stops, so the main exhaust stream stays. In this case, the high temperature of the exhaust gas is prevented from propagating to the air in the branch pipe by the flow of the wind toward the noise interference portion in the branch pipe, so that the performance of the sound generator can be prevented from deteriorating.

In the noise interference part, the opening area of the throttle part in the noise interference part narrowed at the tip of the throttle member is set to 80% to 85% of the cross-sectional area of the main pipe, and the opening area is set to be more than 80%. By not increasing the area, it is possible to prevent the high-temperature exhaust from flowing into the branch pipe side when the engine load rises or when the main exhaust stream stays when the engine is stopped, and it is possible to reliably prevent the sound generator from becoming hot. In this case, by keeping the opening area smaller than that, it is possible to suppress newly generated noise due to the airflow from the main pipe passing through the throttle portion.

[0044] Also, as in claim 6, wherein the restrictor member, by forming the wing facing the wind to pass through the main pipe, the flow of the stream of the exhaust main stream becomes smooth, an air branch pipe Since the resistance of the force sucked into the noise interference part is suppressed to a low level, the suction force effectively acts on the air in the branch pipe, and the flow of air to the noise interference part in the branch pipe can be more reliably caused. This contributes to preventing the temperature of the sounding device from rising.

Further, as described in claim 7 , the throttle member is extended to be a tapered cylindrical body facing the wind passing through the main pipe, so that the cylindrical body has no corners, The airflow noise generated when the wind from the pipe passes therethrough can be reduced. Therefore, the amount of throttle of the wind can be increased, and the flow of air to the noise interference portion in the branch pipe can be more reliably generated, which contributes to preventing the sound generator from becoming hot.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of an active silencer.

FIG. 2 is a bottom view of the same.

FIG. 3 is a front sectional view showing a cooling structure of the speaker unit SU by a duct and a cooling fan.

FIG. 4 is a right side view of the same.

FIG. 5 is a front sectional view when an auxiliary fan is additionally provided.

FIG. 6 is a right side view of the same.

FIG. 7 is a front sectional view when the auxiliary fan is covered with a duct.

FIG. 8 is a right side view of the same.

FIG. 9 is a front sectional view when a blower fan is provided inside the duct.

FIG. 10 is a right side view of the same.

FIG. 11 is a partial front sectional view showing the arrangement structure of the diaphragm plate member 10 in the branch pipe 5.

FIG. 12 is a right side view of the same.

FIG. 13 is a right side view of the branch pipe 5 in a case where a throttle plate member 10 ′ is disposed in the branch pipe 5.

FIG. 14 is a right side view when the aperture plate member 10 ″ is provided.

15 is a drawing blade material 11 and a blade material 1 in a branch pipe 5. FIG.
2 is a front sectional view showing an arrangement structure of No. 2; FIG.

FIG. 16 is a right side view of the same.

FIG. 17 is a front sectional view showing the arrangement structure of the throttle cylinder 13 in the branch pipe 5.

FIG. 18 is a right side view.

FIG. 19 is a graph showing, for each opening ratio, a change in temperature and a change in noise level with respect to an engine load in a negative pressure space formed by a throttle member.

FIG. 20 is a graph illustrating the sound pressure level of each frequency sound mixed with the exhaust sound reaching the noise interference unit 5a when the resonance type silencer 2 is not provided.

FIG. 21 is a schematic diagram showing the relationship between the tube length of the branch pipe 7 and the bent pipe section 5b and the wavelength of the speaker sound.

[Explanation of symbols]

 SU speaker unit SP speaker F blower fan SF auxiliary fan KK 'Sound absorbing material 5 Branch pipe 5a Noise interference part 5b Bend tube part 7 Branch pipe 7a Communication port 8.8' Duct 8a Sound absorbing material 8b Communication port 8c Blocking plate 10・ 10 '・ 10 "diaphragm plate material 11 diaphragm blade material 12 blade material 13 diaphragm cylinder

Continued on the front page (51) Int.Cl. ⁷ Identification code FI H05K 7/20 G10K 11/16 B (72) Inventor Norihisa Tomita 1-32 Chayacho, Kita-ku, Osaka-shi, Osaka Inside Yanmar Diesel Co., Ltd. (72) Inventor Kazuo Migita 1-32 Chaya-cho, Kita-ku, Osaka City, Osaka Prefecture Inside Yanmar Diesel Co., Ltd. (56) References JP-A-8-95574 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F01N 1/00 F01P 1/06 F01P 5/06 504 G10K 11/16 G10K 11/178 H05K 7/20

Claims (7)

(57) [Claims] 1. A main pipe through which noise is transmitted and propagated is connected to a branch pipe extending from a sound-generating device that emits an anti-phase sound of the noise, and a noise interference part is formed in the pipe communicating with both pipes. In an active silencer, the branch pipe and the sound producing device are opposed to each other.
A fan is arranged on the opposite side, and the sound
The cooling air is passed from the sound generator to the main pipe through the branch pipe.
A cooling structure for an active silencer, characterized in that the structure is directed to the air. 2. A branch pipe communicating in the middle of a main pipe through which noise passes through is provided with a sound generating device that emits an anti-phase sound of the noise to form a noise interference portion in the pipe communicating with both pipes. A fan is provided for sending wind toward the noise interference unit into the branch pipe by the sound generator, and a duct is provided around the sound generator so as to communicate with the inside of the branch pipe, and the air blown by the fan is sent into the duct. A cooling structure for an active silencer characterized by having the above-described configuration. 3. A branch pipe provided with a sound generating device that emits an anti-phase sound of the noise is connected in the middle of the main pipe through which the noise passes and propagates,
A noise interference part is formed in a pipe communicating with both pipes, a duct communicating with the inside of the branch pipe is provided around the sound generator, and a blower fan is provided in the duct, while communication from the duct to the branch pipe is provided. A cooling structure for an active silencer, wherein an auxiliary fan for forcibly blowing air from the duct to the branch pipe is provided in a portion. 4. The cooling structure for an active silencer according to claim 3, wherein said auxiliary fan is covered by said duct. 5. A main pipe through which a wind accompanied by noise passes, and a branch pipe extending from a sound generating device which emits an anti-phase sound of the noise is connected to the main pipe to form a noise interference part in the pipe where the two pipes join. In the formed active silencer, a throttle member is provided on the upper side of the noise interference part in the noise propagation direction at both joints.
In addition, while narrowing the opening of the branch pipe at the noise interference section,
The opening ratio of the main pipe at the sound interference section is configured from 80% to 85%.
A cooling structure for an active silencer. 6. A cooling structure for an active silencer according to claim 5 , wherein said throttle member is formed in a wing shape facing a wind passing through said main pipe. 7. A cooling structure for an active silencer according to claim 5, wherein said throttle member is a tapered cylindrical body facing the wind passing through the main pipe. .