JPH04246219A - Noise suppressor device - Google Patents

Abstract

PURPOSE:To obtain a noise eliminating device which can extend noise suppressing frequency area, simplify construction, miniaturize, and reduce cost. CONSTITUTION:A noise suppressing device of resonance type is provided with a resonant noise suppressing chamber 4 which is connected to an air hose 3 through a connecting hole 5. In the air hose 3, a noise suppressing frequency variable member 6 consisting of a pressure receiving part 7 which receives pressure of air flowing through the air hose 3 for displacement and a valve part 8 which displaces together with the pressure receiving part 7 to vary the opening area of the connecting hole 5. Also, a spring 9 for returning the displacement of the noise suppressing frequency variable member 6 is provided in the air hose.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a muffling device for muffling noise generated in an air flow pipe, and more particularly to a muffling device having a structure that widens the muffling frequency range.

0002

2. Description of the Related Art The frequency of noise generated in air flow pipes may change depending on various conditions. For example, the frequency of intake noise generated in an intake pipe or exhaust sound generated in an exhaust pipe of an internal combustion engine changes moment by moment approximately in proportion to the rotational speed of the internal combustion engine. In order to keep such changing noise constantly low, it is necessary to provide the air flow pipe with a muffling device having a wide muffling frequency range. There are various ways to widen the silencing frequency range of a silencing device depending on the silencing mechanism. For example, the following silencing devices are known.

[0003] Japanese Utility Model Publication No. 60-23245 discloses that the opening area of a through hole communicating with an intake pipe and a resonance silencing chamber is made variable by a slide cylinder, and the slide cylinder is used as an engine for detecting the rotational speed of an internal combustion engine. A resonance type muffler is shown in which the aperture area is changed according to the rotational speed by being driven by a /V converter and a potentiometer connected thereto (first conventional example).

Japanese Utility Model Application Publication No. 59-39760 discloses a bellows system in which the opening area of a resonance hole that communicates between a conduit and a resonance silencing chamber is made variable by a slide valve, and the slide valve is actuated by the negative pressure of the resonance silencing chamber. A resonance type muffling device is disclosed in which the opening area is changed in proportion to the negative pressure by driving with the above (second conventional example).

[0005] Japanese Utility Model Publication No. 61-202617 discloses that the cross-sectional area of a communication pipe that communicates the flow air pipe and the resonance muffling chamber is made variable by a bellows, and the bellows is expanded and contracted by back pressure in the communication pipe. A resonance type muffling device is shown in which the cross-sectional area is changed according to the back pressure (third conventional example).

[0006] Japanese Utility Model Application Publication No. 59-41664 discloses that the volume of a resonant silencing chamber communicating with the intake pipe is made variable by a bellows, and by expanding and contracting the bellows by the intake negative pressure, the volume is adjusted to the intake negative pressure. A resonance type muffling device is shown in which the noise is changed according to the noise level (fourth conventional example).

[0007]

[Problems to be Solved by the Invention] However, in the above-mentioned first conventional example, a control device such as an F/V converter,
Since an actuator such as a potentiometer is required, the structure becomes complicated and the cost increases significantly.

[0008] In addition, in the second to fourth conventional examples mentioned above, although not as much as the first conventional example, bellows with a large amount of expansion and contraction and a large spring for returning from the expansion and contraction are required, so the structure is complicated and large. However, there was a problem in that the cost also increased.

An object of the present invention is to solve the above-mentioned problems and provide a silencing device that not only can widen the silencing frequency range but also has a simple and compact structure and can suppress cost increases. be.

0010

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a muffling device of the resonance type in which a resonant muffling chamber is provided which communicates with the flow air pipe through a communication hole. A silencing frequency variable member is provided, which includes a pressure receiving part that is displaced in response to the wind pressure of the gas flowing in the airflow pipe, and a valve part that is displaced together with the pressure receiving part to change the opening area of the communication hole, and The present invention is characterized in that a spring is provided to restore the displacement of the silencing frequency variable member.

[0011] Here, the "flow air pipe" is not limited to any particular pipe as long as it is a pipe through which gas flows, and may include, for example, an intake pipe or an exhaust pipe of an internal combustion engine. In addition, a "resonant silencing chamber" is not limited to a specific shape or size as long as it has a volume necessary to resonate at a desired silencing frequency; room,
One example is a cylindrical muffling chamber provided coaxially around the outer periphery of the air flow pipe. In addition, "communicating hole" includes not only a simple hole with almost no length, but also a tubular hole with a clear length, and examples of the opening shape include circular, oval, oval, triangular, quadrilateral, etc. Can be done.

[0012] Also, as the "silencing frequency variable member",
(1) A pressure-receiving part is tiltably attached at one end near the communication hole, and a valve part that tilts together with the pressure-receiving part opens and closes the communication hole; An example is a valve that is slidably attached to a position of a communication hole, and the sliding valve part opens and closes the communication hole. Also,"
The "spring" may be any spring as long as it has the function of restoring the displacement of the silencing frequency variable member, and is not limited to a specific type of spring.

[0013]

[Operation] First, when the flow rate of gas flowing in the airflow pipe is low, the frequency of noise generated in the airflow pipe is generally low. At this time, since the wind pressure of the gas is small, the pressure receiving part of the silencing frequency variable member is hardly displaced, and the valve part closes a part of the communication hole to reduce its opening area. Then, the silencing frequency due to the resonance of the resonant silencing chamber becomes low and matches the frequency of the noise.

[0014] Next, when the flow rate of the gas flowing in the air flow pipe is high, the frequency of the noise generated in the air flow pipe generally becomes high. At this time, the wind pressure of the gas increases, so
The pressure receiving portion of the silencing frequency variable member is displaced against the elastic force of the spring, and the valve portion increases the opening area of the communication hole. Then, the silencing frequency due to resonance of the resonant silencing chamber becomes high, and can be synchronized with the frequency of the noise.

[0015] In this way, by changing the silencing frequency in synchronization with the noise frequency, the silencing frequency range can be efficiently expanded. Furthermore, the structure for expanding the silencing frequency range can be constructed using simple, small, and fewer parts such as the aforementioned silencing frequency variable member and spring.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. 1 to 4, in which the present invention is embodied in a resonance type muffling device provided in an intake pipe of an internal combustion engine. A resonance muffling chamber 4 formed in a box shape made of synthetic resin is provided adjacent to the outside of an air hose 3 serving as an intake pipe connecting an air cleaner 1 and a fuel injection device 2 of an internal combustion engine. A communication hole 5 is formed in the peripheral wall of the air hose 3 that separates the air hose 3 from the resonance muffling chamber 4, and the opening shape thereof is a square. The resonance frequency of the resonant silencing chamber 4, that is, the silencing frequency f0, is expressed by the following equation 1.

[0017]

[Equation 1] f0 = (C/2π)・√(C0 /V) Here, C0 = (n・Se)/(t+0.8√Se)C
=331.5+0.61t: Speed of sound (m/sec) V
: Volume of resonance silencing chamber 4 n : Number of communicating holes 5 Se : Opening area of communicating holes 5 t : Temperature (℃)

Since the volume V of the resonance silencing chamber 4 is constant, the larger the opening area Se of the communication hole 5, the larger C0 and the higher the silencing frequency f0. Now, since the frequency fi of the intake noise generated in the air hose 3 increases approximately in proportion to the rotational speed of the internal combustion engine, the opening area Se of the communication hole 5 should be adjusted appropriately as the rotational speed of the internal combustion engine increases. If the increase rate is increased, the silencing frequency f0 becomes the intake sound frequency f
It can be made higher in synchronization with i.

Therefore, in this embodiment, we focus on the fact that as the rotational speed of the internal combustion engine increases, the flow velocity of the intake air flowing through the air hose 3 increases and the wind pressure increases. A silencing frequency variable member 6 that changes the opening area Se of the communication hole 5 is provided. The silencing frequency variable member 6 includes a plate-shaped pressure receiving part 7 that is displaced in response to the wind pressure of the intake air flowing inside the air hose 3, and a plate-shaped pressure receiving part 7 that is displaced together with the pressure receiving part 7 to change the opening area Se of the communication hole 5. The valve part 8 is provided, and both parts 7 and 8 are connected to each other in a substantially L-shaped side surface. Then, on the peripheral wall of the air hose 3 immediately upstream of the communication hole 5 (on the air cleaner 1 side), an elastic metal wire is wound once to several times in a small manner, and both ends thereof are extended so as to form a substantially right angle to each other. An L-shaped spring 9 is fixed at one end, and the silencing frequency variable member 6 is fixed at the other end of the L-shaped spring 9 on the back surface of the pressure receiving part 7. Therefore, the silencing frequency variable member 6 is supported by the L-shaped spring 9 so as to be tiltable about its winding portion.

When the wind pressure of the intake air received by the pressure receiving portion 7 is small, the pressure receiving portion 7 protrudes toward the center of the air hose 3 without tilting, and the valve portion 8 partially extends downward from the communication hole 5. The opening area Se is reduced by closing the opening area Se. Further, when the wind pressure of intake air received by the pressure receiving part 7 is large, the pressure receiving part 7 tilts toward the downstream side (toward the fuel injection device 2 side) against the elastic force of the L-shaped spring 9, and the valve part 8 is arranged to move away from the communicating hole 5 and increase its opening area Se.

Next, the operation and effect of the silencer of the first embodiment constructed as above will be explained. First, when the rotational speed of the internal combustion engine is low, the intake sound frequency fi is also low. At this time, the flow velocity of the intake air flowing inside the air hose 3 is low and its wind pressure is also small, so as shown by the solid line in FIG.
The pressure receiving part 7 of the silencing frequency variable member 6 hardly tilts,
The valve portion 8 closes a portion of the communication hole 5 from below to reduce its opening area Se. Then, as is clear from Equation 1 above, the silencing frequency f0 due to the resonance of the resonant silencing chamber 4 becomes low and matches the intake sound frequency fi. Of course,
This coincidence is based on the premise that the volume V of the resonant silencing chamber 4 and the opening area Se of the communication hole 5 when reduced are appropriately set. It can be done easily.

Next, as the rotational speed of the internal combustion engine increases, the intake sound frequency fi also increases. At this time, air hose 3
As the flow velocity of the intake air flowing inside increases and the wind pressure increases, as shown by the chain line in Figure 1 or the solid line in Figure 2,
The pressure receiving portion 7 of the silencing frequency variable member 6 tilts downstream against the elastic force of the L-shaped spring 9, and the valve portion 8 moves away from the communication hole 5 to increase its opening area Se. Then, the number 1 mentioned above
As is clear from the above, the silencing frequency f0 due to the resonance of the resonant silencing chamber 4 becomes high and can be synchronized with the intake sound frequency fi. Of course, this synchronization is based on the premise that the increase rate of the opening area Se is appropriately set, but this setting can be easily performed by adjusting the elastic force of the L-shaped spring 9, etc.

As described above, according to the silencing device of this embodiment, the silencing frequency range can be efficiently expanded by changing the silencing frequency f0 in synchronization with the intake sound frequency fi. In addition, the structure for expanding the silencing frequency range is the silencing frequency variable member 6 and the L-shaped spring 9.
Since it is simple, small, and can be constructed with fewer parts, the structure is simpler and smaller than conventional silencers of this type, and an increase in cost can also be suppressed.

Next, a description will be given of the second embodiment of the silencer shown in FIGS. 5 to 7. This second embodiment includes: The valve portion 8 of the silencing frequency variable member 6 is slidably fitted on both sides of the shaped guide member 10, and the sliding valve portion 8 opens and closes the communication hole 5; The only difference from the first embodiment is that a coil spring 12 is attached between the back surface of the pressure receiving part 7 of the variable noise damping frequency member 6 and the fixed piece 11 attached to the peripheral wall of the air hose 3 near the downstream side thereof. are doing.

According to this second embodiment, when the rotational speed of the internal combustion engine is low, as shown in FIG. The opening area Se is reduced by closing the opening area Se. Therefore, the silencing frequency f0 becomes low and matches the intake sound frequency fi. Furthermore, as the rotational speed of the internal combustion engine increases, as shown in FIG. Increase area Se. Therefore, the silencing frequency f0
becomes high and can be synchronized to the intake sound frequency fi.

[0026] Therefore, like the first embodiment, this second embodiment can also efficiently widen the silencing frequency range. Further, the structure for that purpose is also the same as the above-mentioned silencing frequency variable member 6.
Since it can be constructed with simple, small, and fewer parts such as the coil spring 12 and the coil spring 12, the structure is simpler and smaller than conventional silencers of this type, and an increase in cost can also be suppressed.

It should be noted that the present invention is not limited to the configuration of the above-mentioned embodiments, but can be modified and embodied as desired without departing from the spirit of the invention.

[0028]

[Effects of the Invention] Since the silencing device of the present invention is constructed as described above, it is possible not only to widen the silencing frequency range, but also to have a simple and compact structure, thereby suppressing an increase in cost. It has excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the first embodiment in which the opening area of the communication hole is reduced.

FIG. 2 is a cross-sectional view of the first embodiment in which the opening area of the communication hole is increased.

FIG. 3 is an enlarged view of the main part of FIG. 1 viewed from below.

FIG. 4 is a front view showing the installed state of the first embodiment.

FIG. 5 is a cross-sectional view of the second embodiment in which the opening area of the communication hole is reduced.

FIG. 6 is a cross-sectional view of the second embodiment in which the opening area of the communication hole is increased.

FIG. 7 is an enlarged view of the main part of FIG. 5 viewed from below.

[Explanation of symbols]

3 Air hose as a flow air conduit 4 Resonance muffling chamber 5 Communication hole
6 Silent frequency variable member

Claims (1)

[Claims] 1. A resonance type muffling device provided with a resonant silencing chamber communicating with an air flow pipe through a communication hole, comprising: a pressure receiving part that is displaced in response to wind pressure of gas flowing in the air flow pipe; A silencing frequency variable member including a valve portion that is displaced together with a pressure receiving portion to change the opening area of the communication hole, and a spring that returns the displacement of the silencing frequency variable member. Device.