JPS58158308A - Muffler - Google Patents

Abstract

PURPOSE:To enable to prevent more efficiently a whistle from occurring, by a method wherein a partition wall dividing a resonance chamber into a plurality of small chambers is provided so as to make its natural number of oscillations sufficiently higher than fluctuating frequency of a vortex generating within a gas duct. CONSTITUTION:Supporting brackets 21 and 22 are welded to an inner wall of an external cylinder 1, an insertion pipe 23, a connecting pipe 17 and an inlet pipe 11 respectively. A partition plate 24 is welded between the brackets 21 and 23. A gap is provided among both ends of the partition plate 24 and partition plates 4 and 5. In consequence of the above, a resonance chamber 25 is divided into small chambers 26, 27 and 28 and their natural number of oscillations are raised. The natural number of oscillations of cavity resonance of the resonance chamber 25 is made high so that it becomes sufficienthy higher than fluctuating frequency of a governable vortex generating within a gas duct.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a muffling device, and a V-sweet, to a muffling device for muffling the exhaust gas noise of an internal combustion engine for an automobile.

As a conventional sound muffling device, for example, the one shown in "1 Noise Countermeasures and Silencing Design" published by Kyoritsu Shuppan Co., Ltd. is known. To explain this silencer as shown in Figure 1,
fi+ is an outer cylinder.This outer cylinder fi+1 defines a space with flanone +21 (31) that closes both ends.This space is divided by partition plates +41 +51 t6+: Two U-turn chambers (July 8) and two resonance chambers +9
1 (IQI), and the outlet end of the inlet pipe is open to the U-turn chamber (7). This inlet pipe (11
) is connected to the exhaust manifold of the internal combustion engine, not shown. U-turn chamber (7) and resonance chamber (9)
) is communicated with the cervical canal (12), and the resonance chamber (9
) and the cervical canal (12) constitute a resonance type muffling element (13) that muffles noise in the low frequency range. The U-turn chamber (7) communicates with the U-turn chamber (8) via the insertion tube (141), and the insertion tube (141) has many resonance holes (15). The exhaust gas flowing through u4I passes through the resonance hole (15) to the resonance chamber IJ with a predetermined volume.
The insertion tube (14) and the resonance chamber (IO
l constitutes a porous resonance type silencing element (161) that muffles noise in the medium and high frequency range.The U-turn chamber (8) and the outside air are communicated through a connecting pipe 07) and an outlet pipe (18), Exhaust gas emitted from internal combustion engines is
flows into the U-turn chamber (7), and on the way, a resonant sound deadening element (
After being muffled by the forward and porous resonance type muffling element Oe, it is discharged to the outside air through the U-turn chamber (8), the connecting pipe α71 and the outlet pipe 0&.

However, in the conventional muffler, the porous resonance muffler element t161 muffles the noise in the medium and high frequency range, so the cavity resonance generation frequency of the resonance chamber (10) is low to high when the flow velocity of the exhaust gas is low. There was a problem in that a so-called whistling sound was generated over a wide area and increased exhaust noise. That is, as shown in FIG. 2, the whistling sound is caused by the fluctuation of the vortex generated in the exhaust gas when it passes through the resonance hole (151) inputs acoustic energy (El) into the resonance chamber 00, and this is caused by Resonance chamber (10
) is caused by cavity resonance in the exhaust gas, which again excites the vortex fluctuations in the exhaust gas. Therefore, the generation of the whistling sound constitutes a self-excited vibration system, and the whistling sound is radiated through the outlet pipe Q81.

This invention has been made to address the above problems,
The resonance chamber and the insertion tube include an outer cylinder having a resonance chamber defined therein, and an insertion tube inserted into the resonance chamber and having a gas flow path and a resonance hole that communicates the flow path and the resonance chamber. In a silencing device in which a porous resonant silencing element is constructed, a partition wall extending in the axial direction of the insertion tube and dividing the resonant chamber into a plurality of small chambers is installed so that the natural frequency of the cavity resonance of the resonant chamber is adjusted to the gas flow. It is an object of the present invention to solve the above-mentioned problems by providing a silencing device characterized in that the frequency is sufficiently higher than the fluctuation frequency of the dominant vortices generated in the road.

Hereinafter, this invention will be explained based on the drawings.

FIG. 3.4 is a diagram showing a first embodiment of the present invention, and the configuration will be explained first. Incidentally, only the same reference numerals are given to the parts having the same configuration as the conventional one, and the explanation thereof will be omitted. (21) ■ is a support bracket that is in contact with the inner wall of the outer tube il+, the insertion tube Q1, the connecting tube αB, and the inlet tube αυ, respectively. Between these brackets CIIJIl'lr is a partition plate (the two slopes are welded). The inner edge of the partition plate s → and the partition plate t
41 (a gap is provided between 51. As a result,
Resonance chamber (2 heating is 3 small chambers Cl61 CJ7) 128)
The natural frequency increases by one degree. That is,
The fluctuation frequency (fp) of the dominant vortex that occurs when exhaust gas flows through the insertion tube (231) is determined by the flow velocity (υ) of the exhaust gas inside the insertion tube (231) and the resonance hole (231) in the streamline direction of the exhaust gas. 291
When the aperture length of the Since the aim is to induce cavity resonance within the resonant chamber (5), the insertion tube (23) is
Find the fluctuation range of the exhaust gas flow velocity (υ) in j, and calculate the fluctuation frequency (1p) of the dominant vortex calculated from this flow velocity (υ).
It is sufficient to determine the volume of the small chamber (26) so that the natural frequency of the resonance chamber is always high (11 t28) from the region ).

The aforementioned insertion officer 1. ! ! 31 and the resonance chamber (c) together constitute a porous resonance type silencing element circle.

Explain the effect arbitrarily. Exhaust gas discharged from the internal combustion engine flows from the exhaust manifold into the U-turn chamber (7) via the inlet pipe 0υ. Here, noise in the low frequency range in the exhaust gas is muffled by the resonant muffling element u1. next,
Exhaust gas is inserted into CL! 3), many vortices are generated in the exhaust gas. Here, when the opening length (1) of the resonance hole 4 is kept constant and the flow velocity (υ) of the exhaust gas inside the insertion tube (23j) is varied, the whistling sound becomes as shown in FIG.
The natural frequency of the resonance chamber (C) is likely to occur within the range of Bl. However, the natural frequency of the resonance chamber (C) is the dominant In other words, the flow velocity (υ
)/Naganobu Kai) is sufficiently lower than point (5), so no whistling sound is generated. In addition, medium and high frequency noise in the exhaust gas is muffled by the porous resonance type muffling element (7). After this, the exhaust gas is discharged to the outside air from the U-turn chamber (8) through the connecting pipe α and the outlet port.

FIG. 7.8 is a diagram showing a second embodiment of the invention,
Components having the same configuration as those of the first embodiment are given the same reference numerals, and their explanations will be omitted. (3υ is U-turn room (7)
This is an insertion tube that connects (8) and (8), and this insertion tube 011 has a large number of resonance holes (321) bored therein.

These resonance holes (three are the opening lengths in the streamline direction of the exhaust gas flowing inside the insertion tube 6υ) are formed in an elliptical shape so as to be large. As a result, the dominant fluctuating frequency of the vortex can be further reduced, and the occurrence of whistling noise can be further prevented.

As described above, according to the present invention, a silencing device includes an outer cylinder in which a resonance chamber is defined, a gas flow path inserted into the resonance chamber, and a resonance tube that communicates the flow path with the resonance chamber. an insertion tube in which a hole is formed, the resonance chamber and the insertion tube constitute a multi-hole resonance type muffling element, and a partition wall is provided that extends in the axial direction of the insertion tube and divides the resonance chamber into a plurality of small chambers. Since the 44 frequency of the cavity resonance of the resonance chamber is made to be sufficiently higher than the fluctuating frequency of the dominant vortex generated in the gas flow path, it is possible to prevent whistling noise from occurring.

Furthermore, in the second embodiment, since the resonance hole of the insertion tube is made into an elliptical shape, the fluctuation frequency of the dominant vortex can be lowered.
This provides the effect of further sufficiently preventing the occurrence of whistling noise.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view showing a conventional silencing device, FIG. 2 is an enlarged sectional view of the insertion tube shown in FIG. 1, FIG. 3 is a front sectional view showing a first embodiment of the present invention, and FIG. A cross-sectional view taken along the line IV-IV in Figure 3, Figure 5 is a graph showing the fluctuation frequency of the vortex and the fluctuation of the vortex, and Figure 6 is a graph showing the relationship between the flow velocity/opening length and the fluctuation frequency of the dominant vortex. , FIG. 7 is a front cross-sectional view showing a second embodiment of the present invention, and FIG. 8 is a cross-sectional view taken along the line Vl-Vl in FIG. 7. (II...outer tube, &31C3υ...insertion tube, (to)...partition wall (partition plate), ω...resonance chamber, (to) to (g)...small chamber, (29) +321
... Resonance hole, (to) ... Porous resonance type silencing element. Patent Applicant Nissan Motor Co., Ltd. Agent Patent Attorney - Part 4, Figure 5, Filtration') ¥1vJ Same as iFi, -

Claims (1)

[Claims] An outer cylinder having a resonance chamber defined therein, and an insertion tube inserted into the resonance chamber and having a gas flow path and a resonance hole communicating between the flow path and the resonance chamber. In a sound damping device in which the insertion tube constitutes a porous resonance type sound damping element, a partition wall extending in the axial direction of the insertion tube and dividing the resonance chamber into a plurality of small chambers is provided, and the natural frequency of the cavity resonance of the resonance chamber is A noise reduction device whose characteristic is that the mJ frequency is sufficiently higher than the variable mJ frequency of the dominant vortex generated in the flow path.