JPH0755321Y2 - Variable resonance silencer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to a variable resonance silencer capable of reducing noise caused by engine noise of an automobile or the like in a wide driving range.

2. Description of the Related Art Generally, what is known as a silencer of a type that attenuates only a specific frequency due to engine-generated noise by resonance to reduce the noise, for example, a so-called having a branch portion in which a duct of an intake pipe is branched There are a side-branch silencer, a Helmholtz silencer in which a duct and a resonance box are connected by a neck, and a coaxial silencer in which a resonance body is provided coaxially through a duct through a communication hole. The resonance frequency fr in these three silencers can be expressed by the following equation.
That is, when the speed of sound is represented by C, in the case of a side-branch silencer: For Helmholtz silencers: For coaxial silencer: Is. In these equations, 1 is the neck length, and S is the inner diameter cross-sectional area of the neck portion or the communication hole.

However, it is already well known that these three types of silencers, which deal only with specific frequencies, cannot deal with a wide range of frequencies of intake noise that vary in a wide driving range from a low speed region to a high speed region, especially in a car engine. It is a fact.

Therefore, at present, it can be said that the variable resonance silencer having a structure capable of coping with the frequency due to the engine-generated noise which changes every moment is in the trend. As a technique found in this variable resonance type silencer, for example, there is a structure in which a part of a wall of a resonance box is made movable so as to change the internal volume so as to correspond to the resonance frequency. Further, a structure in which a bellows is provided inside the resonance box and the volume of the bellows is changed to correspond to the resonance frequency is also known.

As a specific example, a resonance box is attached to the intake duct of the engine, and a variable structure in which the internal volume of the resonance box changes is used to reduce the resonance at the frequency of engine-generated noise that changes according to the engine rotation speed. For example, connecting the intake duct and the resonance box with a communication pipe or a communication hole (neck),
In the case of a communication pipe, change the length and inner diameter. In the case of communication holes, the cross-sectional area is changed.

In this structure, when f ₀ is the resonance frequency, V is the internal volume of the resonance box, S is the cross-sectional area of the communication tube or communication hole, l is the length of the communication tube or communication hole, and a is a constant, the resonance frequency is generally It is expressed by the following equation.

As is clear from the above equation, the resonance frequency f ₀ is changed by changing each value of the internal volume V of the resonance box, the length l of the communication pipe (or the communication hole) and the cross-sectional area S.

Problems to be Solved by the Invention By the way, in the structure based on this general formula, in which the neck length is changed linearly, it is necessary to allow for a space when the neck length changes to the maximum. Yes, it is disadvantageous due to problems such as interference with other mechanisms. In addition, the provision of the drive mechanism for linear movement complicates the entire structure. With respect to this point, the same problem occurs when the neck length (opening) is changed by a switching valve such as a butterfly valve.

Further, based on the above equation, the cost becomes highest when the internal volume V of the resonance box is changed.

An object of the present invention is to provide a variable resonance silencer that solves these conventional problems.

Means for Solving the Problems A variable resonance silencer according to the present invention has a resonance part communicating with an intake or exhaust duct of an internal combustion engine via a cylindrical neck part, and the resonance part is connected to the neck part. A box body formed in the shape of a circular container, a cylindrical fixed tube that is concentrically fixed inside the box body, and has an annular passage formed between it and the box body connected to the neck, and the inner circumference of the box body. It includes a movable member that slides in contact with the surface and the outer peripheral surface of the fixed cylinder and moves in the annular passage, and a drive unit that drives the movable member.

By arranging a plurality of through holes in the circumferential direction or by providing a long hole extending in the circumferential direction in the fixed cylinder, the neck portion is communicated through the annular passage in the fixed cylinder, and the movable member slides to penetrate the fixed cylinder. It is a structure that opens and closes a hole or a long hole.

By the operation of the engine, the noise frequency due to the engine-generated sound changes in a wide range in the intake or exhaust duct in accordance with the engine rotation speed.

The drive unit is activated by the activation signal corresponding to this change,
The movable member slides in the annular passage to move to a desired position inside the box by the operation of the drive unit. Multiple through-holes (or long holes) that were previously blocked by movable members
However, due to the movement of the movable member, several or partially opened,
The fixed cylinder is communicated with the annular passage and the neck. That is, according to the internal volume of the fixed cylinder and the number of open through holes,
The natural frequency due to the volume at this time is made to resonate with the frequency of the engine generated noise at that time.

It can be said that this is a coaxial type resonator in which the number of through-holes is changed while the volume is invariable, and corresponds to the frequency due to engine-generated noise in each operating region of the engine rotation speed that changes over a wide range.

Since the plurality of through holes are concentrically opened without being opened and closed linearly, it is not necessary to design the maximum installation space when all the through holes are opened, unlike the conventional case.

Embodiment Hereinafter, an embodiment of a variable resonance silencer according to the present invention will be described with reference to the drawings. Here, in particular, it is assumed that the noise generated by the engine generated sound in the intake duct of the automobile engine is reduced.

As shown in FIG. 1 and FIG. 2, the main structure of the muffler 10 of the present invention has a resonance part 13 communicating with the intake duct 11 via a cylindrical neck part 12, and the resonance part 13 is A box body 14 that is connected to the neck portion 12 and is formed into a circular container shape, and an annular passage 15 that is fixed inside the box body 14 by concentric circles and is formed between the box body 14 and the box body 14.
A cylindrical fixed cylinder 16 connected to the neck 12, a movable member 17 that slides in contact with the inner peripheral surface of the box body 14 and the outer peripheral surface of the fixed cylinder 16 to move the annular passage 15, and a drive that drives the movable member. It includes part 20 and.

By arranging a plurality of through holes 16a ~ in the circumferential direction or by providing an elongated hole extending in the circumferential direction in the fixed cylinder 16, the neck 12 is communicated through the annular passage 15 in the fixed cylinder 16, and the movable member 17 is provided. Is a structure for opening and closing the through holes 16a to (or the long holes) of the fixed cylinder 16 by sliding.

Specifically, a tubular neck portion 12 is branched in the middle of the intake duct 11, and a resonance portion 13 is provided so as to be connected to the neck portion 12. As is clear from the figure, the entire resonance part 13 is formed of plastic (the material is not particularly limited) into a circular container shape. That is, it has a circular container-shaped box body 14 that constitutes the main body, and this box body 14 is joined to the neck portion 12. Inside the box body 14, a cylindrical fixed tube 16 having a concentric circle and an internal volume V is fixed. The fixed cylinder 16 is provided with a plurality of through holes 16a to 16d along its peripheral wall. The number of installations is not limited to the illustrated example. Alternatively, a plurality of through holes may be formed as a long hole in a row.

Further, the space between the outer peripheral surface of the box body 14 which is a concentric circle and the fixed cylinder 16 is formed as an annular passage 15. As is apparent from the figure, the annular passage 15 is directly connected to the neck portion 12 described above.

In the annular passage 15, a movable member 17 formed in an arc shape can slide. The movable member 17 has an opening / closing arc portion 17a curved to have a curvature capable of slidingly contacting the outer peripheral surface of the fixed barrel 16, and the opening / closing arc portion 17a simultaneously closes several through holes 16a to 16a on the fixed barrel 16 side. Has a size and a shape. Further, blocking walls 17b, 17b capable of blocking the annular passage 15 are provided at both ends of the opening / closing arc portion 17a and are bent with a length substantially equal to the width dimension of the annular passage 15. Therefore, when the movable member 17 moves in the annular passage 15 and moves in the counterclockwise direction in the figure, for example, the annular passage 15 at the portion connected to the neck portion 15 becomes long.
Hereinafter, the total length of the variable length annular passage 15 and the neck portion 12 is referred to as a neck length L.

The movable member 17 having such a shape is connected to a rotating shaft 18 at the center of the box body 14 (this connecting means is not shown), and the rotation of the rotating shaft 18 rotates the annular passage 15 by sliding contact. It can be moved. The rotary shaft 18 is connected to a drive unit 20 as shown in FIG. 2 and rotates by the drive output of the drive shaft 20. The form of the drive unit 20 shown in FIG. 2 is an example, and the form is not limited to this. Drive unit 20
For example, the control device performs control based on a signal that detects the engine speed R (rpm), and the motor 21 of the drive unit 20 is operated by the operation signal sent from the control device. Reduction gears 22, 23 and the like are arranged as necessary, and the output gear 23 is connected to the rotary shaft of the rotary cylinder 16 described above. A servo motor or the like is suitable as the motor 21 used in such control.

Next, the operation mode and operation of this embodiment will be described.

When the engine is operating at a low rotation speed, the noise frequency generated by the engine generated sound is low and the amount of intake air that passes through the intake duct 11 is small. For example, the engine speed R at this time is detected, this detection signal is sent to the control device, and the controlled actuation signal is sent to the drive unit 20. The operation of the drive unit 20 is transmitted, and the drive member 17 slides and moves in the annular passage 15 to a desired position.

The movement of the movable member 17 changes the neck length L which is the total distance between the neck 12 and the annular passage 15. Also, the through hole of the fixed barrel 16
Several 16a are released by control. The internal volume V of the fixed cylinder 16 does not change. Due to the natural frequency of the neck length L and the opened several through holes 16a, the natural frequency held by these is set to the frequency f that resonates corresponding to the noise frequency due to the engine generated sound in the duct 11. The correlation between the resonance frequency f and the engine speed R (rpm) can be expressed by the following equation. That is, Is. The resonance frequency f can be replaced with the resonance frequency fr in the case of the coaxial silencer described above. That is, Here, r is the radius of the neck portion 12 (circulation passage 15), N is the number of cylinders of the engine, m is the number of through holes 16a to 16a when opened, n is an arbitrary integer corresponding to the design conditions, and V is fixed. Tube 16
In this case, the internal volume of is invariable in this case, and C is the speed of sound. As is apparent, as the engine speed increases, the movable member 17 moves counterclockwise in FIG.
It will be understood that more are opened at a and the neck length L, which is the total distance of the neck 12 and the annular passage 15, is increased.

Advantageous Effects of Invention The variable resonance silencer according to the present invention operates a drive unit by a signal based on a noise frequency generated by an engine-generated sound in an intake or exhaust duct that changes according to an engine rotation speed, and a movable member in the resonance unit. By moving the, it is possible to freely control the number of open through holes and the neck length as a silencer called a coaxial type. Accordingly, the rotational speed of the automobile engine is changed over a wide range, and the rotational speed is suitable for causing resonance at a noise frequency generated by the engine sound at that time, and the noise can be effectively reduced.

Moreover, in the case of the present invention, the open through hole and the neck length are not changed linearly as in the conventional structure, but are changed on a concentric circle, so there is no need to allow for a space for the maximum change of both elements in the layout. There is an advantage that the entire device is made compact.

[Brief description of drawings]

1 and 2 show an embodiment of a variable resonance silencer according to the present invention, FIG. 1 is a sectional view, and FIG. 2 is a perspective view. 11 ... Intake or exhaust duct, 12 ... Neck, 13 ... Resonator, 14 ... Box, 15 ... Annular passage, 16 ... Fixed tube, 16a
~ ... through hole, 17 ... movable member, 17a ... open / close arc part, 1
7b ... shield wall, 20 ... driving section.

Claims (1)

[Scope of utility model registration request] 1. A box body having a resonance part communicating with an intake or exhaust duct of an internal combustion engine via a cylindrical neck part, the resonance part being connected to the neck part to form a circular container shape, and a box. A cylindrical fixed cylinder that is concentrically fixed inside the body and has an annular passage formed between it and the box that is connected to the neck, and an annular ring that slidably contacts the inner peripheral surface of the box and the outer peripheral surface of the fixed cylinder. Including a movable member that moves in the passage and a drive unit that drives the movable member, a plurality of through-holes are arranged in the circumferential direction in the fixed cylinder or an elongated hole extending in the circumferential direction is provided to form an annular shape in the fixed cylinder. A variable resonance silencer characterized in that a neck portion is made to communicate with each other through a passage and a through hole or a long hole of a fixed cylinder is opened and closed by sliding of a movable member.