JPH01170754A - Muffling device for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce air intake noise by communicating a resonance chamber with an intake passage, an air cleaner and a secondary air supply device through the first to third communicating portions and changing over the resonance chamber to the first or second communicating portion according to the operating condition of the secondary air supply device. CONSTITUTION:A resonance box 25 is communicated and connected with a cap 11 in an air cleaner 2 comprising a case 9, a filtration element 10, the cap 11 and an air duct 12 by the first and second communicating pipes 26, 27. The resonance box 25 is connected to an air introduction port of the secondary air supply device for supplying secondary air to an exhaust system by the third communicating pipe 28. A pipeline selector valve 29 for selectively opening and closing the first and second communicating pipes 26, 27 is disposed in the resonance box 25. The pipeline selector valve 29 is controlled to be switched in the direction of closing the first communicating pipe 29 when a switching valve is closed by a negative-pressure actuator 31 using a part of negative pressure supplied to open the switching valve of the secondary air supply device as a driving source.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a muffling device for reducing intake noise of an internal combustion engine.

``Prior art'' Noise caused by internal combustion intake mainly consists of intake noise generated by the engine's intake pulsating flow, and noise caused by exhaust gas purification.
Noise generated when the air supply device operates (hereinafter referred to as As noise)
(referred to as air suction sound).

Conventionally, as means for suppressing these noises, a resonator has been provided in the intake passage or an air cleaner chamber has been used as an expansion chamber. However, in general, intake noise and A
The frequency component is different from S sound, and in order to effectively reduce the noise, it is necessary to install a separate resonator etc. with a considerable volume for each, which makes it difficult to install it in the engine room. There was a point.

Additionally, a noise reduction device that selects or changes the cross-sectional area of the communication portion has been proposed as a device for changing the resonant frequency of the resonator (Utility Model Application Publication No. 59-2919), but AS sound has relatively flat frequency components. Therefore, there was a problem that it was not necessarily effective in reducing AS sound.

"Problems to be Solved by the Invention" The present invention was made to solve the above problems, and effectively reduces both intake noise and AS sound by using resonance boxes. The purpose of the present invention is to provide a noise reduction device that does not take up much space.

"Means for Solving the Problem" Therefore, in the present invention, a resonance chamber is communicated with a first communication section midway through an intake passage of an internal combustion engine, and a second communication chamber is provided that communicates the resonance chamber with an air cleaner chamber. and the resonance chamber.
a third communication section that communicates with the air inlet of the secondary air supply device; a switching valve that selectively opens and closes communication between the resonance chamber and the first communication section or the second communication section; There is provided a muffling device for an internal combustion engine, comprising a drive device that switches a switching valve depending on whether or not the secondary air supply device is in operation.

"Operation" According to the above configuration, when the secondary air supply device does not operate, the second communication section is closed and the first communication section is opened by the switching valve. Therefore, the resonance chamber is in communication with the middle of the intake passage by the first communication part, and the resonance chamber plays its original role as a resonance chamber.The resonance frequency at this time is equal to the length of the first communication part. The cross-sectional area can be appropriately set to match the frequency characteristics of intake noise.

On the other hand, when the secondary air supply device operates, the first communication section is closed and the second communication section is opened by the switching valve. Naturally, the air inlet of the secondary air supply device is also opened, and secondary air is supplied from the air cleaner chamber via the second communication section, the resonance chamber, and the third communication section. Therefore, the resonance chamber is provided in the middle of the flow path of the secondary air, and the resonance chamber acts as an expansion chamber to reduce noise. Since the air cleaner chamber also acts as an expansion chamber, its cutoff frequency can be appropriately set according to the frequency characteristics of the AS sound by the length of the second communication portion.

Generally, the secondary air supply device is operated during idling and deceleration operation of the engine, so when the secondary air supply device is operated, the resonance chamber is used as an expansion chamber,
During other normal operations, the resonance chamber is used as the original resonance chamber, and it is possible to effectively reduce noise according to the frequency characteristics of the intake sound and the AS sound.

"Embodiments" Examples of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of an embodiment. engine 1
From the air cleaner 2 to the intake pipe 3. Throttle body 4. Air is taken in via the surge tank 5 and intake manifold 6, and exhaust gas is passed through the exhaust manifold 7 and exhaust pipe 8.
Exhausted via. Air cleaner 2 is case 9.
Filtration element 10. A cap 11 and a cool air duct 12 for introducing outside air are provided. The intake pipe 3 is connected to an air cleaner cap 11.
The interior thereof constitutes an air cleaner chamber 13.

A secondary air supply device 14 (AS system) is attached to this engine. That is, the air inlet 1 is provided in the exhaust pipe 8.
It is possible to introduce fresh air from 5 through a check valve 16 and a secondary air supply on-off valve 17 to purify the exhaust gas. The secondary air supply on-off valve 17 is a negative pressure driven valve equipped with a diaphragm and a spring, and the negative pressure switching valve 18
It is connected to a pipe 19 that communicates with the. Negative pressure switching valve 1
8 communicates with the downstream side of the throttle body 4, and is switched to the negative pressure side or the atmospheric side according to an electric signal from an electronic control unit (CPU) 20. The electronic control device 20 receives a signal from the throttle switch 21 and a signal from the engine rotation speed detector 22, and determines whether the engine is in an idle state or a deceleration state (throttle is closed) based on both signals. , and outputs a signal to the negative pressure switching valve 18 during idling or deceleration. Based on this signal, the negative pressure switching valve 18 is switched to the negative pressure side, and the intake negative pressure is introduced into the secondary air supply opening/closing valve 17 via the vibrator 19, and the secondary air supply opening/closing valve 17 is opened. Note that when both the signals of the throttle switch 214 and the rotation speed detector 22 indicate an operating state other than the idling state or deceleration state, the CPU 20 sends a signal to the negative pressure switching valve 18 to switch the negative pressure switching valve 18 to the atmospheric side. emanate. These negative pressure switching valve 18. Secondary air supply opening valve 17. The check valve 16, electronic control device 20, etc. are the secondary air supply device 14 (AS system)
It consists of

A resonance box 25 is connected to the air cleaner cap 11 through two communication pipes 26 and 27, so that the interior of the resonance box 25 and the air cleaner chamber 13 are communicated. First communication pipe 2
Reference numeral 6 denotes a communication pipe when the resonance box 25 is used as a Helmholtz resonator, and its pipe length and cross-sectional area are set so as to resonate at an intake pulsation frequency of several 100 H2. The second communication pipe 27 is connected to the secondary air supply device 14
This serves as a passageway for the air introduced into the pipe, and the length of the pipe is set to be somewhat long. Further, the resonance box 25 and the air inlet 15 of the secondary air supply device 14 are connected by a third communication pipe 28.

Inside the resonance box 25, there are a first communication pipe 26 and a second communication pipe 2.
A conduit switching valve 29 that selectively opens and closes 7 is provided. The pipe switching valve 29 has two valve bodies, which are rotatable around a swing shaft 30 and connected to a negative pressure actuator 31.
It is driven to open and close via the rod 32. The negative pressure actuator 31 is connected to a pipe 19 connecting the secondary air supply on-off valve 17 and the negative pressure switching valve 18 via a negative pressure hose 33.

The operation will be explained based on the above configuration.

During normal operation other than when idling or decelerating, the electronic control unit (CPU) 20 issues a signal to the negative pressure switching valve 18 to switch to the atmospheric side based on signals from the throttle switch 21 and the engine speed detector 22. This results in
Atmospheric pressure is introduced into the pipe 19 and the negative pressure hose 33 by the negative pressure switching valve 18 . As a result, the secondary air supply on-off valve 17 is closed, and the negative pressure actuator 31 closes the conduit switching valve 29 by the urging force of the internal spring 31A, and the second communication pipe 27 as shown in the figure. to press against. Therefore, as shown in FIG.
It is a closed resonance box that is connected to the air cleaner chamber 13 forming an intake passage only through the communication pipe 26, and the frequency is determined by the volume of the resonance box 25, the pipe length 11 of the first communication pipe 26, and the cross-sectional area S. It becomes a resonator that resonates with and attenuates the sound.

In this example, the pipe length 11 is set to about 50w+e, and 1
It was made to resonate around 50Hz.

On the other hand, when idling or decelerating, throttle switch 2
Based on the signals from 1 and the engine rotation speed detector 22, the electronic control unit (CPU) 20 issues a signal to the negative pressure switching valve 18 to switch to the negative pressure side. As a result, intake negative pressure is introduced into the pipe 19 and the negative pressure hose 33. As a result,
When the secondary air supply on-off valve 17 is opened, negative pressure is also introduced into the negative pressure actuator 31, and the line switching valve 29 closes the first communication pipe 26 as shown by the imaginary line in the figure. be done. Therefore, as shown in FIG. 3, the secondary air flows into the air cleaner chamber 13. Second communication pipe 27° resonance box 25. Third
The air is supplied into the exhaust pipe 8 via the communication pipe 28 and check valve 16, and the resonance box 25 and air cleaner chamber 13 act as an expansion chamber to reduce the AS sound. The frequency characteristics are determined by the pipe length 12 of the second communication pipe 27, and the longer the pipe length 12, the more low frequencies can be muffled. In this embodiment, the pipe length 12 was set to 200 mm.

FIGS. 4 and 5 show the measurement results of sound pressure levels. All measurements were taken at the outlet of the cool air duct 12. FIG. 4 shows the change in intake noise when the pipe switching valve 29 is switched with the secondary air supply device 14 not operating.
Compared to the sound pressure characteristic A when the communication pipe 26 of
It can be seen that the sound pressure characteristic B when the communication pipe is opened shows that the sound pressure level is greatly reduced at 1 at a frequency specific to intake sound. FIG. 5 shows the change in AS sound when the pipe switching valve 29 is switched while the secondary air supply device 14 remains in operation, and the sound pressure characteristic C when the second communication pipe 27 is closed. Compared to this, the sound pressure characteristics when the second communication pipe 27 is open show that the AS sound is greatly reduced down to low frequencies.

In the embodiment described above, the pipe switching valve 29 and the negative pressure actuator 31 are installed in the resonance box 25, but in short, the effective pipe length of the first communication pipe 26 and the second communication pipe 27 is Since it is only necessary to switch, various modifications can be considered.

FIG. 6 shows a structure in which the second communication pipe 27 is branched from the middle of the first communication pipe 26, and a line switching valve 41 consisting of one valve body and a negative pressure An example in which actuators 31 are arranged is shown.

FIG. 7 shows an embodiment in which a conduit switching valve 42 consisting of two valve bodies and a negative pressure actuator 31 are arranged in the air cleaner cap 11, and the conduit is switched on the air cleaner 2 side.

Further, the first communication pipe 26 and the second communication pipe 27 do not necessarily need to be connected to the air cleaner cap 11, and they may be connected to the intake pipe 3.

In addition to the negative pressure actuator 31, an electromagnetic solenoid may be used as a drive device for driving the pipe switching valves 29, 41, 42.

Furthermore, the first. Second. Although the third communication pipe 26, 27° 28 is tubular, it may be configured as a band-shaped communication part using the RIA wall of the air cleaner 2, and its shape is not limited. Not limited to.

"Effects of the Invention" As explained above, the present invention has the above configuration and uses the resonance chamber as an original resonance chamber for attenuating intake sound and as an expansion chamber for attenuating AS sound. This has the excellent effect that both intake noise and As noise can be effectively reduced without taking up space, and installation in the engine room is extremely advantageous.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a block diagram showing the general structure of the silencer, FIGS. 2 and 3 are schematic diagrams explaining the operation, and FIGS. 4 and 5 are diagrams showing the sound pressure level. FIG. 6 is a sectional view showing the second embodiment, and FIG. 7 is a sectional view showing the third embodiment. 160. Engine, 20. , air cleaner, 11°1. Air cleaner cap, 13. ,,air cleaner room, 14,. Secondary air supply device, 15, air inlet, 18. ,,Negative pressure switching valve, 25,,Resonance box, 26. ,,first communication pipe, 27. ,, second communication pipe, 28. ,,Third communication pipe, 29,41゜4
2. Pipe switching valve 31. Negative pressure actuator.

Claims (1)

[Scope of Claims] A resonance chamber that communicates with a first communication section in the middle of an intake passage of an internal combustion engine, a second communication section that communicates the resonance chamber with an air cleaner chamber, and the resonance chamber and secondary air. a third communication section that communicates with an air inlet of a supply device; a switching valve that selectively opens and closes communication between the resonance chamber and the first communication section or the second communication section; and the switching valve. A silencing device for an internal combustion engine, comprising: a drive device that switches the noise reduction depending on whether or not the secondary air supply device is in operation.