JPH063182Y2 - Muffler structure of vehicle intake pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a sound deadening structure for a vehicle intake pipe.

[Prior Art] The air flow in the intake pipe of a vehicle pulsates as the engine rotates and emits noise. As a silencing structure that reduces such noise,
It is known that a bypass pipe is attached to the intake pipe, and the phase of the sound wave is shifted by a half wavelength in the bypass pipe to offset and reduce noise in the intake pipe.

[Problems to be Solved by the Invention] Although the above-mentioned sound deadening structure is effective in significantly reducing noise at a specific frequency, it is necessary to set the bypass pipe relatively long in order to reduce low frequency noise. However, it is difficult to use because it requires an installation space and there is a concern that the strength of the bypass pipe may decrease.

Further, as described above, the bypass pipe produces a large silencing effect in a relatively narrow region near a specific frequency determined by its length, but there is a problem that a sufficient silencing effect cannot be expected outside this region.

In view of such a problem, the present invention aims to provide a bypass type vehicle intake pipe sound deadening structure that is capable of effectively reducing a wide range of low frequency noise, is compact, and has sufficient strength. To do.

[Means for Solving the Problems] The sound deadening structure of the present invention will be described with reference to FIGS. 1 and 2. In the hermetically sealed housing 11, partition walls 13A and 13B partition the interior of the long flow path 14 to meander. Form the above long channel 1
4 are connected to the side walls of the vehicle intake pipe 12 to form bypass passages, and the long passages 14
A semi-transmissive partition wall 15 that passes half of the sound wave reaching the opening and reflects the remaining half of the sound wave is provided across the long flow path 14 in the vicinity of either of the openings 141 and 142 from the center.

[Operation and Effect] According to the above structure, since half of the sound wave passes through the semi-transmissive partition wall 15, the long flow path 14 functions as a bypass flow path, and is determined by the length of the long flow path 14 between the openings 141 and 142. Silence is exerted in a predetermined frequency range.

Further, since the remaining half of the sound wave is reflected by the semi-transmissive partition wall 15, a pair of side branches whose ends are closed with the partition wall 15 as a boundary are formed in the long flow path 14, and the openings 141 and 142 are formed. The silencing effect is also exhibited in a predetermined frequency range determined by the length of each side branch from the partition wall 15. As a result, the noise reduction effect can be obtained in a wide range.

In the present invention, since the inside of the closed housing is divided by the partition wall to form the meandering long flow path, a relatively long flow path can be formed compactly, low frequency sound can be reduced, and the installation space is small. Good.

In addition, since it does not use a long bypass pipe, it has excellent strength.

[Embodiment] In the following embodiment, the present invention is realized as a silencer provided in the intake pipe.

FIG. 1 shows a perspective view of the muffler 1. The muffler 1 is a resin integrally molded product, and includes a main tube portion 12 in the shape of a rectangular tube and a housing portion 11 projecting from the side surface thereof. The main pipe portion 12 is connected and provided in an intake pipe (not shown).

The housing portion 11 is a flat rectangular closed box body,
A long flow path 14 (FIG. 2) which meanders at a right angle is formed inside thereof by double partition walls 13A and 13B which are bent along the inner circumference of the box. The adjacent both-end openings 141 and 142 of the long flow path 14 face the main portion 12.

As shown in FIG. 2, a partition wall 15 of urethane foam, which is a porous elastic body, is provided in the long flow path 14 across the flow path, and the partition wall 15 allows half of the sound waves reaching this to pass through. Has a semi-transparent material that reflects the other half,
It is provided closer to one of the openings 141 and 142 from the center of the long flow path 14.

In the silencer 1 having the above structure, a part of the sound wave traveling in the main pipe 12 branches into the long flow path 14 through the openings 141 and 142, and half of the sound wave bypasses the partition wall 15.
Then, the half-wave phase is delayed while passing through the long flow path 14, and merges with the sound wave in the main pipe 12 again to cancel and reduce it.

The noise frequency fn (Hz) to be reduced is expressed by the following formula.

fn = c / 2 where c is the speed of sound and is the total length of the long flow path 14.

The remaining half of the sound waves branched and invaded into the long flow path 14 are reflected by the partition wall 15, and as a result, a pair of side branches whose ends are closed by the partition wall 15 are formed in the long flow path 14.

That is, when the entire length of the long flow path 14 is divided into 1 and 2 by the partition wall 15, by the side branch function,
The noise reduction effect can be obtained also at the frequencies fa and fb before and after the frequency fn. Each of these frequencies is represented by the following formula.

fa = c / 41 fb = c / 42 An example of this effect is shown in FIG. According to the figure, 60Hz
It is possible to reduce the sound pressure level in a wide range up to 160 Hz.

As the semipermeable partition wall, a plate material provided with a large number of through holes may be used in addition to the porous elastic body wall.

[Brief description of drawings]

FIG. 1 is an overall perspective view of a silencer showing an embodiment of the present invention,
FIG. 2 is a horizontal sectional view of the silencer, and FIG. 3 is a frequency characteristic diagram showing a noise reduction effect. DESCRIPTION OF SYMBOLS 1 ... Silencer 11 ... Housing part (sealed housing) 12 ... Main part (vehicle intake pipe) 13A, 13B ... Partition wall 14 ... Long flow path 141, 142 ... Opening 15 ... Semi-permeable partition wall

Claims (2)

[Scope of utility model registration request] 1. A hermetically-sealed housing is partitioned by a partition wall to form a meandering long passage having a predetermined length, and both end openings of the long passage are connected to side walls of a vehicle intake pipe to form a bypass passage. From the center of the long flow path to one of the openings,
A sound-deadening structure for a vehicle intake pipe, characterized in that a semi-transmissive partition wall is provided across the long flow path to pass half of the sound waves reaching this and to reflect the remaining half. 2. A sound deadening structure for a vehicle intake pipe according to claim 1, wherein the semi-permeable partition wall is a porous elastic wall or a porous partition plate.