JPH0144728Y2 - - Google Patents

Description

[Detailed explanation of the idea] B Industrial application field The present invention relates to a silencer for internal combustion engines.

B. Prior Art Exhaust noise generated from internal combustion engines includes low-frequency noise based on the internal combustion engine's explosion pressure and high-frequency noise associated with high-temperature, high-pressure exhaust gas.

Conventionally, in a muffler for an internal combustion engine, as shown in FIG. 1, a low-frequency resonance pipe 3 communicating with a low-frequency resonance chamber 2 provided in a muffler 1 is fixedly installed to suppress low-frequency noise. In the case where the low frequency is muted, the low frequency to be muted is determined by the flow cross-sectional area and flow length of the low frequency resonance pipe 3. Therefore, as shown in FIG. 1, in the case where only one low frequency resonance pipe 3 is fixed, only a single low frequency exhaust sound can be muffled. However, the low frequencies generated by internal combustion engines are
Since the internal combustion engine has a wide range of rotational fluctuations ranging from 30 Hz to 200 Hz (in the case of a four-cylinder engine), it has been inconvenient to use a muffler that only mutes a single low frequency as described above.

C. Purpose of the invention In view of the above, the present invention provides a plurality of low-frequency resonant pipes with different low frequencies that can be silenced, and selects and uses them to match the rotational conditions of the internal combustion engine, thereby suppressing a wide range of low-frequency noise. The purpose is to make it possible to mute the sound.

D. Structure of the invention In order to achieve the above-mentioned object, the present invention is provided with a fixed resonance pipe communicating with a low-frequency resonance chamber, in which a plurality of variable resonance pipes with different flow lengths are installed in the low-frequency resonance chamber. A plurality of variable resonance pipes are disposed such that the pipes are displaceable so that the inflow ports of the variable resonance pipes are close to and opposite to the rear openings of the fixed resonance pipes, and the variable resonance pipes include a plurality of variable resonance pipes. The present invention is characterized in that a displacement means is provided for selectively positioning the fixed resonance pipe to face the fixed resonance pipe depending on the rotational speed of the internal combustion engine.

E. Embodiment An embodiment of the present invention shown in FIGS. 2 and 3 will be described.

Reference numeral 1 denotes a muffler body, in which exhaust gas from the internal combustion engine flows through an inlet pipe 4, an inner pipe 5, and an outlet pipe 6, and is discharged to the outside air. Reference numeral 3 denotes a fixed resonance pipe fixed to the fixed partition wall 7, the rear part of which is opened to the low frequency resonance chamber 2. Reference numeral 8 denotes a rotating shaft installed in the low frequency resonance chamber 2 in a direction parallel to the axial direction of the fixed resonance pipe 3, and the bearing 9 fixed to the fixed partition wall 7 and the rear wall 1a of the muffler main body 1. It is rotatably supported by. Reference numerals 10, 11, and 12 designate three variable resonance pipes, which are arranged in parallel on a circumferential line that passes through the center of the fixed resonance pipe 3 with the axis of the rotating shaft 8 as its center, and their respective flow It is fixed to the rotating shaft 8 such that the inlet is close to the rear opening of the fixed resonance pipe 3. The variable resonance pipe 1
Pipe lengths l1, l2, l of 0, 11, and 12, respectively
3 is set so that l2 is longer than l1, and l3 is longer than l2, so that different low frequency noises can be muffled by the variable resonance pipes 10, 11, and 12, respectively. Note that the number and length of the variable resonance pipes are set as desired depending on the low frequency to be muted. The rotating shaft 8 is rotatably driven by a step motor or the like that detects the rotational speed of the internal combustion engine and changes its rotational position in accordance with the detected rotational speed. That is, when the rotation speed of the internal combustion engine is high, the short variable resonance pipe is placed opposite to the fixed resonance pipe 3, and when the rotation speed of the internal combustion engine is low, the long variable resonance pipe is placed opposite to the fixed resonance pipe 3. The rotating shaft 8 is rotated as shown in FIG.

F. Effect of the invention As described above, according to the invention, when the low frequency that generates low-frequency noise based on the explosive force fluctuates due to fluctuations in the rotational speed of the internal combustion engine, the fluctuated low frequency Since the fixed resonance pipe can be made to correspond to a variable resonant pipe having a length capable of muffling low-frequency noise caused by noise, it has the advantage of being able to muffle low-frequency noise over a wide range.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a conventional muffler, FIG. 2 is a sectional view showing a muffler according to the present invention, and FIG. 3 is a perspective view showing a fixed resonant pipe and a variable resonant pipe. 1... Silencer main body, 2... Low frequency resonance chamber, 3
... Fixed resonance pipe, 8 ... Rotating shaft, 9 ... Bearing, 10, 11, 12 ... Variable resonance pipe.

Claims (1)

[Scope of utility model registration request] In a device provided with a fixed resonance pipe communicating with a low frequency resonance chamber, in the low frequency resonance chamber,
A plurality of variable resonance pipes having different flow lengths are provided so as to be displaceable so that the inlets of these variable resonance pipes are close to and opposite to the rear opening of the fixed resonance pipe, and the variable resonance pipes include: A muffler for an internal combustion engine, comprising a displacement means for selectively positioning the plurality of variable resonance pipes to face the fixed resonance pipe according to the rotational speed of the internal combustion engine.