JPH0367012A - Exhaust silencer of engine - Google Patents

Abstract

PURPOSE:To produce the device which effectively silence even though the frequency of exhaust sound has varied, by changing the resonance frequency with a mechanism which changes the length of a pipe to put the expansion chamber in the muffler in communication with the resonance chamber. CONSTITUTION:Synchronization is obtained with the revolving speed of an engine 1, and the resonance frequency of resonance chamber is slided, and the noise components of a certain order or orders due tyo explosion of the engine is damped effectively. The resonance frequency of a resonance chamber 10 depends upon the volume of resonance chamber. The pipe length in the resonance chamber, the section area of the pipe, and the sonic speed of the exhaust gas. The revolving speed of the engine l is sensed in the form of engine pulses etc., and in accordance with the value obtained, a motor 21 is rotated at the specified revolving speed. This causes movement of the external pipe 18 to change the effective length of the sum of the inner pipe 15 and external pipe 18, and it is made possible to allow the capacity of pipe and the resonance chamber 10 to be the order of engine 1 explosion or its integral multiple.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine exhaust silencing device that is attached to an automobile or motorcycle to attenuate exhaust noise.

(Conventional technology) Cars and motorcycles are equipped with mufflers (
Some mufflers are equipped with a plurality of resonance chambers (resonators) inside the muffler in order to increase the muffler's silencing effect. Figure 2 shows the engine l and exhaust manifold 2. A caterpillar (or subchamber) 3 and a muffler 4 are shown connected by an exhaust pipe 5. As shown in FIG. 3, the interior of the muffler 4 is divided into three resonance chambers 8, 9, and 8 by a partition wall 6.7. These resonance chambers 8, 9, and 10 are communicated with each other through pipes 11 and 12.

In the muffler 4 having a plurality of resonance chambers as described above, the phase of the noise frequency of the introduced air is converted into an opposite phase when passing through the plurality of resonance chambers 8.9.10, and the wave The sound will be muffled by cancellation.

(Problem to be solved by the invention) However, in automobiles and motorcycles, they are not used at a constant rotation speed like prime movers in general factory equipment, but at all rotation speeds between about 700 and 7000 rpm. and the frequency of the exhaust sound changes,
If the volume of the resonance chamber is constant and the resonance frequency does not change, there is a problem in that it is not possible to cover all frequencies.The present invention was made in view of this point. To provide a device that can effectively muffle sound even when the frequency of sound changes. Incidentally, there is a method disclosed in Japanese Utility Model Publication No. 62-37940 that was devised to eliminate intake system noise among engine noises, but it does not solve the problem of the present invention.

(Means for Solving the Problems) The present invention provides a plurality of resonance chambers 8.9. (1) In the exhaust silencer for the engine 1 provided with 0, a mechanism is provided to change the length of the pipes (inner pipe 15 and outer pipe 118) that communicate between the resonance chambers 8, 9, and 10 of the muffler 4, and the pipe The structure is such that the effective volume of the resonance chamber 8.9.10 is changed depending on the length (total of the inner pipe 15 and the outer pipe I8).

(Function) With this configuration, by changing the length of the pipe, it is possible to change the volume of the resonance chamber in synchronization with the engine speed, which reduces the noise order components caused by engine explosion. This means that it can be effectively attenuated.

(Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1, with the same members as in FIG. In the central resonance chamber 9 of my house,
A partition wall 13 that further divides this resonance chamber 9 into upper and lower parts.
A hole 14 is provided in the partition wall 13, and one end of an arc-shaped inner pipe 15 is connected thereto. Inner pipe 15
passes through holes 16 and 17 formed in the muffler 4, exits the muffler 4 at one end, and then enters the resonance chamber ■0. And on the outside of this inner pipe 15 is this inner pipe! The outer pipe 18, which has the same shape as 5 but has a slightly larger diameter, is inserted into the inner pipe 15, and slides against the inner pipe 15 as shown by the arrow. Outer pipe 18
has moved, and the combined effective length of the circular pipe 15 and the outer pipe I8 has become larger.

A rack gear 19 is provided on the outer periphery of the outer pipe 18 along its shape. This rack gear 19 has a gear 2 attached to the output shaft of a motor 21 via a gear 20.
2 are meshing. As the motor 21, a servo motor is used. The motor 21, gears 22.20, and rack gear 19 constitute a mechanism that changes the length of the pipes (inner pipe 15 and outer pipe 18) communicating between the resonance chambers 9.10. By changing the length of the pipe in this way,
The total effective volume of the entire resonance chamber 8.9.10 will be changed.

The engine exhaust silencing device configured in this manner is synchronized with the rotational speed of the engine 1, and is used to slide the resonance frequency of the resonance chamber to effectively attenuate noise order components resulting from engine explosion. The resonant frequency of the resonant chamber (the sum of resonant chambers 8, 9, and 10 in the muffler) is determined by (1) the volume of the resonant chamber, and (2) the length of the pipe within the resonant chamber. Therefore, in the present invention, the resonant frequency is changed by changing the effective length of the pipe.

The number of revolutions of the engine 1 is detected by an engine pulse or the like, and the motor 21 is rotated at a predetermined number of revolutions in accordance with the detected value. This moves the outer pipe 18, so the total effective length of the inner pipe 15 and outer pipe 18 changes, and the volume of the resonance chamber and the pipe can be adjusted to the explosion order of engine l or an integral multiple thereof. .

In the embodiment described above, a servo motor is used as the motor 21, but the present invention is not limited to this, and an actuator that utilizes the intake negative pressure of the engine 1 may also be used. Further, although the output is transmitted to the outer pipe 18 using gears and a rack, a mechanism using a cam instead of the gears may also be used.

(Effects of the Invention) Since the present invention is an engine exhaust silencing device configured as described above,
The resonant frequency can be changed within a range of about 30 to 200 Hz, which corresponds to 1. This makes it possible to attenuate the frequency in the sound head range inside the mold chamber. Note that, at present, it is often tuned to a frequency around 120 to 150 Hz.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the principle of an embodiment of the present invention, FIG. 2 is a side view showing an exhaust system of an engine, and FIG. 3 is a sectional view showing the internal structure of a conventional muffler. 1-・Engine 4-・Muffler 5...Exhaust manifold 6.7.13-Partition wall 15-Inner pipe I8-Outer pipe 9-・Rack gear 20.22-Gear 21-・Motor Fig. 1 Engine 4 Muffler 5 Exhaust pipe 6.7.13 ・Partition! 15 Inner pipe 18 Outer pipe 19/rack gear 2022 Gear 21 Motor Fig. 2 Fig. 3

Claims (1)

[Claims] (1) In an engine exhaust silencing device in which a plurality of resonance chambers are provided inside a muffler, a mechanism is provided to change the length of a pipe communicating between the resonance chambers of the muffler, and the length of the pipe changes the resonance chamber. An engine exhaust silencing device characterized by being configured to change the effective volume of a chamber.