JPS595764B2 - Silencer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to the so-called low-frequency pulsation noise having the engine explosion frequency and secondary and tertiary frequencies based on this frequency (generally 9011z, 9011z,
The invention relates to a device that reduces noise (of about 180 Hz).

In the past, there was a silencer of this type as shown in FIG.

In the silencer shown in FIG. 1, an exhaust pipe a directly connected to an engine (not shown) opens into a first expansion chamber, and a resonance chamber C disposed adjacent to the extension side of the exhaust pipe a. The first expansion chamber S is located on the extension line of the exhaust pipe a and is communicated with an exhaust resonance pipe d having a certain length l, and a common pipe f is connected to the second expansion chamber e on the opposite side of the resonance chamber C. The first expansion chamber e is communicated with the atmosphere through the exhaust outlet pipe g.

V Resonant frequency fFi of the conventional Helmholtz resonator silencer constructed in this way, where V: Effective volume S of resonance chamber C; Cross-sectional area C of resonance tube d; Sound velocity 18; Acoustic frequency of resonance tube d Effective length = 4! -) -0,8d) d: The inner diameter of the resonance tube d is such that this resonance frequency fnO sound is attenuated.

However, such a silencer can only attenuate the sound at a fixed resonance frequency fnO, and cannot broadly attenuate sounds at other frequencies.

Moreover, when trying to reduce low-frequency sounds using the fixed effective volume of the resonance chamber (2), the diameter of the resonance tube (d) becomes narrower (that is, the cross-sectional area S becomes narrower), making it difficult to introduce sufficient engine exhaust gas into the resonance chamber (C). ? was not possible, and the sound reduction effect was inferior.

Furthermore, in order to widen the resonant frequency band, a number of resonance tubes d of different lengths may be provided in parallel, but the inflow fluctuating pressure from the exhaust pipe a can be distributed approximately equally to the many resonance tubes d. Therefore, the resonance chamber C cannot be introduced into the resonance chamber cK, and the resonance tube dt-, which is placed away from the extension of the exhaust pipe a, becomes a communication tube without functioning as a resonance tube. Therefore, the resonance chamber C is simply expanded. This made it impossible to achieve the desired effect, making it impossible to obtain a sufficient silencing effect.

The present invention relates to an improvement of a muffling device that eliminates such drawbacks, and includes an expansion chamber provided so that the pipe end of an exhaust pipe connected to an engine type opens inside the muffler, and an expansion chamber provided on the extension side of the exhaust pipe. a resonance chamber arranged therein; and a resonance pipe that is located approximately on an extension line of the exhaust pipe, opens into the expansion chamber with a predetermined gap from the end of the exhaust pipe, and communicates with the resonance chamber. The edge of the resonant tube on the side of the resonant chamber is formed obliquely, and the object is to provide a simple muffling device with a structure that can effectively attenuate noise in a wide range of frequencies. .

As described above, the present invention provides an expansion chamber so that the pipe end of the exhaust pipe connected to the engine opens into the interior thereof, and a resonance chamber is arranged on the extension side of the exhaust pipe, and the resonance chamber is provided on the extension line of the exhaust pipe. A resonance tube located approximately at The same effect can be obtained by arranging a large number of resonance tubes with different lengths in parallel from the edge on the expansion chamber side to the edge on the resonance chamber side. The sound can be muted.

The present invention will be described below with reference to the embodiment shown in FIG. 2. Reference numeral 1 denotes a silencer main body, which is partitioned from the left into a second expansion chamber, a first expansion chamber 3, 2, and a resonance chamber 4 in its longitudinal direction. An exhaust pipe 5 having a pipe diameter of 42.7ig is provided so as to penetrate through the second expansion chamber 3 and open into the first expansion chamber 2, and the exhaust pipe 5 is directly connected to an engine (not shown).

Further, the length of the pipe communicating with the resonance chamber 4 is 245 mm.

A resonance tube 6Iri having a diameter of 42.7 mm is located on an extension of the exhaust pipe 5 and opens into the first expansion chamber 2 at a predetermined distance from the end of the exhaust pipe 5.

Further, the first and second expansion chambers 2 and 3 communicate with the resonance tube 6 through an exhaust introduction tube 7 having a small diameter, and the second expansion chamber 3 communicates with the resonance tube 6 through an exhaust introduction tube 7 having a small diameter. An exhaust outlet pipe 8 having a diameter of 45.6 mm passes through the chamber 4 and communicates with the atmosphere.

The resonance chamber side end of the resonance tube 6 is cut obliquely so as to pass through a point 45 degrees closer to the expansion chamber 2.
Further, the volume of the resonance chamber 4 is approximately 4. θ is set to little.

Since the embodiment shown in FIG. 2 is configured as described above, exhaust gas discharged from the engine (not shown) enters the first expansion chamber 2 from the exhaust pipe 5 as shown by the arrow, but at that time, the exhaust gas is discharged from the exhaust pipe 5. The sound pressure energy entering the muffler from 5 is weakened in the resonance chamber 4.

In this case, the resonance tube 6 has a length of 200 mm to 245 mm.
The presence of a large number of lengths of tubes over
The frequency in the range of ±5 Hz centered on 0 Z, that is, f
-5 to in+5H2 (95 to 105 Hz) sounds can be effectively reduced.

The sound reduction level of a resonance tube with a length of 222.5 mm and both ends at right angles is theoretically determined as shown by the solid line in Figure 3, and is large when it is close to fn, but when other On the contrary, the sound reduction level according to the embodiment described above is large over a wide range, changing gently around fn, as shown by the dotted line in FIG.

Using a 2000 cc engine, the exhaust gas temperature is 45
Exhaust sound when exhaust gas at 0°C is introduced into a conventional muffler having a resonance chamber with the same volume (4 liters) as in the above example and a rectangular and thin resonance pipe with both edges at right angles. When the level was determined by experiment, a result as shown by the curve ■ in FIG. 4 was obtained.

Further, in the conventional muffler having a longer and thicker resonant tube, a curve (2) shown in FIG. 4 was obtained.

Furthermore, when the exhaust gas is introduced into the embodiment described above, a curve (2) shown in FIG. With this device, the curve (■) shown in FIG. 4 was obtained.

As is clear from the characteristic curves ■, ■, ■, and ■ in FIG. 4, if the edge of the resonance tube 6 on the side of the resonance chamber is formed obliquely, the discharge sound level will be widened over a wide range of engine speeds. The sound reduction effect is noticeable.

In the above embodiment, the setting frequency that is desired to be attenuated the most is 1001'lz, and the frequency is ±5Hz around this.
That is, the length of the resonance tube 6 and the axial length of the inclined portion were determined so as to reduce the sound of 95 to 105 Hz.
If the set frequency that you want to attenuate the most is fn, then if the dimensions of the resonance tube 6 are defined as shown in Figure 5, then the following formula is obtained, and if you set 11 and 12, f n -5Hz
It is possible to effectively reduce the sound from f n + 5 Hz.

The present invention has been described above with reference to embodiments, but of course the present invention is not limited to such embodiments, and various design modifications may be made without departing from the spirit of the present invention. It is.

[Brief explanation of the drawing]

FIG. 1 is a vertical side view of a conventional muffling device, FIG. 2 is a vertical side view of an embodiment of the muffling device according to the present invention, and FIG.
The figure shows the characteristics of the theoretical sound reduction level between the conventional model and the above embodiment, and Figure 4 shows the experimental results of the exhaust sound level when the conventional model and the present invention are applied to an actual engine. FIG. 5 is a side view showing the dimensional relationship of the resonance tube of the present invention. 1... Silencer main body, 2... First expansion chamber, 30. . ...Second expansion chamber, 4...Resonance chamber, 5...
... Exhaust pipe, 6 ... Resonance pipe, 7 ... Exhaust introduction pipe, 8 ... Exhaust outlet pipe.

Claims (1)

[Claims] 1: an expansion chamber provided so that the pipe end of an exhaust pipe connected to the engine opens therein; a resonance chamber provided on the extension side of the exhaust pipe; and a resonance chamber located approximately on the extension line of the exhaust pipe. and a resonance tube that opens into the expansion chamber with a predetermined gap from the end of the exhaust pipe and communicates with the resonance chamber, and the resonance chamber side edge of the resonance tube is formed obliquely. A silencer characterized by: