JPH0610647A - Variable resonance type silencer - Google Patents

Abstract

PURPOSE:To easily vary the resonance frequency of a resonance type silencer over a wide range. CONSTITUTION:A duct, a resonance tube 3 and a resonance box 2 are communicated with each other to form the resonance tube 3 of a rectangular parallelopiped-shaped tube part and a square truncated pyramid-shaped tube part. Moreover, a wedge-shaped member 4 is slidably-provided inside the square truncated pyramid-shaped tube part of the resonance tube 3 to change the cross section of a clearance surrounded by the inner wall of the resonance tube 3 and the outer wall of the wedge-shaped member 4 by the movement of the wedge-shaped member 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a variable resonance type silencer, and more specifically, it significantly reduces intake and exhaust noises of an internal combustion engine and periodic noises in a duct generated from rotating equipment such as a blower and a ventilation fan. The present invention relates to a variable resonance type silencer for silencing.

[0002]

2. Description of the Related Art As a variable resonance silencer, Japanese Patent Laid-Open No. 59-
There is one disclosed in Japanese Patent No. 215913, which includes a plurality of tubular members whose one end is opened in a gas flow passage,
A resonance chamber formed of a closed space communicating with the other ends of the plurality of tubular members, an opening / closing plate that blocks or communicates with the tubular member, and an actuator that opens and closes the tubular member based on an electric signal to promote opening and closing of the tubular member. A Helmholtz silencer equipped with a control computer that controls an electric signal output to this actuator.

[0003]

The Helmholtz type silencer has a very large silencing effect at the resonance frequency expressed by the following equation, but has a problem that it is almost impossible to attenuate the sound of frequencies other than the resonance frequency.

[0004]

[Equation 1]

C: speed of sound, S: cross-sectional area of resonance tube, V: volume of resonance chamber, l: length of resonance tube

Therefore, when the Helmholtz type silencer is applied to an internal combustion engine or the like in which the number of revolutions constantly fluctuates, the silencing effect cannot be exhibited as it is, so the number of resonance tubes of the silencer is increased (Japanese Patent Laid-Open No. 59-59). No. 215913 Publication No. 1
2 to 14) and changing the shape of the resonance tube (the same publication, Nos. 2 to 3).
Although it is attenuated to some extent even at frequencies other than the resonance frequency as shown in the figure), there is a problem in that it is not possible to expect the silencing effect of a pure Helmholtz silencer because it sacrifices the extremely large damping effect at the resonance frequency. Therefore, the present invention has been made to solve the above problems,
The present invention provides a resonance type silencer that can easily change the resonance frequency over a wide range.

[0007]

A variable resonance silencer of the present invention is provided with a wedge-shaped member that is moved forward and backward by a driving means in a resonance tube having one end communicating with a duct and the other end communicating with a resonance chamber. The cross-sectional area of a gap surrounded by the inner wall of the resonance tube and the outer wall of the wedge-shaped member is variable,
The configuration is such that the substantial opening cross-sectional area and the substantial length of the gap are changed at the same time.

The wedge-shaped member is driven by appropriate means such as a combination of a shaft with a coil spring and a cable, a combination of a pinion with a motor connected thereto and a rack, a combination of an actuator and a shaft.

[0009]

When the wedge member is moved back and forth in the resonance tube to change the cross-sectional area of the gap surrounded by the inner wall of the resonance tube and the outer wall of the wedge member, the substantial opening cross-sectional area and the substantial length of the gap are changed. Simultaneously, the resonance frequency can be variably controlled over a wide range with a slight amount of movement of the wedge-shaped member.

[0010]

1 shows a first embodiment of the present invention in which a duct 1 and a resonance box 2 forming a resonance chamber 2a are connected via a resonance tube 3 and the resonance tube 3 side of the resonance box 2 is shown. Resonance chamber 2a
The duct 1, the resonance tube 3, and the resonance box 2 are inserted into each other and communicate with each other. The duct 1 side tube portion of the resonance tube 3 is formed into a rectangular parallelepiped shape, the resonance box 2 side tube portion of the resonance tube 3 is formed into a truncated pyramid shape, and the hollow wedge-shaped member 4 is formed into a square pyramid shape of the resonance tube 3. The wedge-shaped member 4 is slidably arranged along the inner wall of the trapezoidal tube portion, and is moved by a predetermined amount in the vertical direction of FIG. 1 by a driving means 5 including a shaft 5b with a coil spring 5a and a cable 5c. Along with this movement, a gap 6 surrounded by the inner wall of the resonance tube 3 and the outer wall of the wedge-shaped member 4 is formed.
Is variably controlled, and the substantial opening cross-sectional area of the gap 6 and its substantial length are simultaneously changed.

The wedge-shaped member 4 is moved forward and backward (upward and downward in FIG. 1) along the inner wall of the truncated pyramidal tube portion of the resonance tube 3 by the driving means 5 so that the inner wall of the resonance tube 3 and the wedge-shaped member 4 are separated from each other. When the cross-sectional area of the gap 6 surrounded by the outer wall is changed, the substantial opening cross-sectional area and the substantial length of the gap 6 are changed at the same time (when the substantial opening cross-sectional area is increased, the substantial length is shortened). The resonance frequency can be variably controlled over a wide range with a slight movement amount of 5b.

FIG. 2 shows a second embodiment of the present invention, in which the expansion chamber 11 of the exhaust silencer of the internal combustion engine and the resonance chamber 12 are connected by a communication pipe 13, and the pipe part of the communication pipe 13 on the expansion chamber 11 side. Is formed in a rectangular parallelepiped shape, the resonance chamber 12 side tube portion is formed in a quadrangular truncated pyramid shape, and the hollow wedge-shaped member 14 is slidable along the inner wall of the quadrangular pyramid trapezoidal tube portion of the communication pipe 13. 2, the wedge-shaped member 14 is moved in the left-right direction in FIG. 2 by a predetermined amount by the driving means 15 including the shaft 15b with the coil spring 15a and the cable 15c, and the inner wall of the communication pipe 13 is accompanied by this movement. The cross-sectional area of the gap 16 surrounded by the outer wall of the wedge-shaped member 14 is variably controlled, and the substantial opening cross-sectional area of the gap 16 and its substantial length change simultaneously.

The wedge-shaped member 14 is moved forward and backward (left and right in FIG. 2) along the inner wall of the quadrangular truncated pyramid-shaped pipe portion of the communication pipe 13 by the driving means 15 so that the inner wall of the communication pipe 13 and the wedge-shaped member 14 are separated from each other. When the cross-sectional area of the gap 16 surrounded by the outer wall is changed, the substantial opening cross-sectional area and the substantial length of the gap 16 are changed at the same time (when the substantial opening cross-sectional area is increased, the substantial length is shortened). The resonance frequency can be variably controlled over a wide range with a slight amount of movement of the shaft 15b.
The exhaust silencer of this embodiment can effectively reduce engine-generated noise from a low speed region to a high speed region.

FIG. 3 shows a third embodiment of the present invention, in which a variable control device 21 comprising a frame body 22, a wedge-shaped member 24 and a driving means 25 is provided with an exhaust silencer main body 23 via an end plate portion 22c. It is formed in the same manner as in the second embodiment except that it is provided so as to be replaceable, and has the same effect as the second embodiment. The frame body 22 is integrally formed of a square pyramid-shaped communication pipe portion 22a, a pair of opposing side plate portions 22b, and a rectangular end plate portion 22c, and the wedge-shaped member 24 and the driving means 25 are the second embodiment. It is formed in the same manner as the example, the communication pipe portion 22a is fitted to the communication pipe body 23a of the exhaust silencer body 23, and the end plate portion 2 is formed.
2c is locked to the end plate body 23b of the exhaust silencer body 23 by a bolt (not shown).

[0015]

According to the present invention, since the resonance frequency can be adaptively adjusted, a strong silencing power can be exerted even with respect to the noise whose frequency changes every moment. Further, since one resonator can be applied to a wide range of frequencies, it is not necessary to use many resonators having different resonance frequencies, and the silencer can be downsized.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the present invention.

FIG. 3 is a sectional view showing a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 duct 2a resonance chamber 3 resonance tube 4 wedge-shaped member 5 driving means 6 gap 13 communication pipe 14 wedge-shaped member 15 drive means 16 gap 22a communication pipe part 24 wedge-shaped member 25 drive means

Claims (3)

[Claims] 1. A wedge-shaped member that is moved forward and backward by a drive means is provided in a resonance tube having one end communicating with a duct and the other end communicating with a resonance chamber. The wedge-shaped member is formed by an inner wall of the resonance tube and an outer wall of the wedge-shaped member. A variable resonance silencer characterized by varying the cross-sectional area of the enclosed space. 2. A resonance type silencer in which an expansion chamber and a resonance chamber are connected by a communication pipe, comprising a wedge-shaped member for advancing and retracting in the communication pipe, and a drive means for advancing and retracting the wedge-shaped member. A variable resonance silencer, wherein a cross-sectional area of a gap surrounded by an inner wall of a pipe and an outer wall of the wedge-shaped member is variable. 3. The variable resonance silencer according to claim 2, wherein the communication tube, the wedge-shaped member, and the driving means are integrally replaceably provided.