JPH0210248Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an exhaust silencing device for an engine, and particularly to an exhaust silencing device that reduces engine back pressure during acceleration without reducing silencing performance.

(Prior art) Silencers that reduce engine exhaust noise generally have silencers that allow the exhaust to pass through multiple resonance chambers partitioned by partition walls, or silencers that allow the exhaust to pass through multiple resonance chambers partitioned by partition walls, or silencers that have open holes in the exhaust passage covered with sound-absorbing material. There are various types of resonance chambers, and even a combination of these.
As shown in the figure, it is effective in reducing low-frequency exhaust noise that peaks at a certain engine speed and causes so-called interior muffled noise. It is effective in reducing medium to high frequency exhaust noise such as sound. However, since the resonance chamber acts as a resistance to the flow of exhaust gas, when it is provided in the exhaust passage, there is a drawback that the back pressure of the engine increases and the output is reduced.

On the other hand, according to Japanese Utility Model Application Publication No. 57-44925, a bypass passage without a silencer is provided between an exhaust inlet pipe that connects the engine and the silencer and an exhaust outlet pipe that is connected downstream of the silencer. A device has been disclosed in which exhaust gas is discharged through the bypass passage when high output is required. However, when exhaust is exhausted through the bypass passage in this way, a problem arises in that exhaust noise is not reduced.

(Purpose of the invention) This invention addresses the above-mentioned problems in engine exhaust silencing devices.The low-frequency noise that causes indoor muffled noise is suppressed at a specific engine speed as shown in Figure 1. Since it has a peak value, we focused on the fact that this low-frequency noise does not pose a problem during acceleration, which instantly passes through this rotation speed, so we decided to exhaust the exhaust through a bypass passage that bypasses the resonance chamber during acceleration. Make it. As a result, during steady operation, the resonance chamber allows the first
As shown in the figure, low-frequency noise is suppressed to reduce indoor noise, and at the time of acceleration, when a large engine output is required, the back pressure of the engine is reduced so that the required output can be obtained. The bypass passage is equipped with a sound-absorbing material that effectively reduces high-frequency exhaust noise, such as airflow noise that becomes noticeable during acceleration, and does not increase engine back pressure, thereby reducing exhaust noise during acceleration. It also prevents In this way, the purpose is to realize an exhaust silencing device that can effectively reduce both low-frequency, medium-, and high-frequency exhaust noise, reduce back pressure of the engine during acceleration, and obtain the required engine output. .

(Structure of the invention) The present invention is characterized by the following structure in order to achieve the above object.

That is, in an engine exhaust silencing device that connects an inlet pipe that introduces exhaust gas into a silencer having a resonance chamber and an outlet pipe that discharges the exhaust gas into the atmosphere, the tip of the inlet pipe is opened to the atmosphere to reduce back pressure. Opening and closing of opening and closing the back pressure reduction passage while branching the passage, passing the reduction passage through the inside of the silencer, forming a plurality of open holes in the penetrating portion, and surrounding the passage with a sound absorbing material. The engine includes a valve and a control means for operating the valve in the opening direction when the engine accelerates.

According to such a configuration, in a steady state of operation, exhaust gas is introduced into the silencer having a resonance chamber through the introduction pipe, so that low-frequency noise such as indoor muffled noise is reduced, During acceleration, when low frequency noise is not much of a problem, the on-off valve is operated in the direction of opening the back pressure reduction passage, so the exhaust gas is released into the atmosphere through the back pressure reduction passage with less passage resistance. This reduces engine back pressure and improves output performance.

In particular, since the back pressure reduction passage passes through the silencer and the plurality of open holes provided in the passage are surrounded by a sound absorbing material, high-frequency noise such as airflow noise generated during acceleration can be The exhaust noise is effectively reduced by being absorbed by the sound absorbing material. Furthermore, since the sound absorbing material is provided so as to surround the open hole provided in the penetrating portion of the silencer in the back pressure reduction passage, the exhaust noise leaking from the sound absorbing material is blocked by the case portion of the silencer. This not only improves the silencing performance, but also makes this type of exhaust silencing device more compact compared to a case where the silencing section, which consists of these sound-absorbing materials and open holes, is installed at a separate location from the silencer. It also happens.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

As shown in FIG. 2, the exhaust silencer 1 includes an exhaust introduction pipe 4 connected to an exhaust manifold 3 of an engine 2, a silencer 5 provided at the downstream end of the exhaust introduction pipe 4, and a silencer 5 provided at the downstream end of the exhaust introduction pipe 4. It has an exhaust outlet pipe 6 connected to the air and whose tip is open to the atmosphere, and a bypass passage 7 from the exhaust introduction pipe 4.
is branched, and this bypass passage 7 is connected to the silencer 5.
It penetrates inside and the tip is open to the atmosphere. An on-off valve 8 for opening and closing the entrance to the bypass passage 7 is provided at a branch point from the exhaust gas introduction pipe 4 in the bypass passage 7, and a control device 9 for controlling the opening and closing of the on-off valve 8 is provided. ing. This control device 9 includes an actuator 10 that operates the on-off valve 8, an acceleration determination means 11 that determines the acceleration state of the engine 2, and a drive means 12 that drives the actuator 10 in response to a signal from the acceleration determination means 11. When the acceleration determining means 11 determines the acceleration state of the engine 2, the on-off valve 8 operates to open the bypass passage 7. Here, a pre-silencer 13 is provided on the upstream side of the exhaust gas introduction pipe 4, but this pre-silencer 13 is for performing a first stage of silencing action before introducing the exhaust gas into the silencer 5. be.

3, the inside of the silencer 5 is divided into a plurality of chambers (in this embodiment, three expansion chambers 15, 15', 15'' and
The downstream end of the exhaust introduction pipe 4 communicates with one of the expansion chambers 15', and the upstream end of the exhaust outlet pipe 6 communicates with the other expansion chamber 15'. ”, and each chamber 15,
15', 15'', and 15 are provided with communication passages 16...16 that communicate with each other.On the other hand, a bus pass passage 7 that is branched from the exhaust introduction pipe 4 and passes through the inside of the silencer 5 is provided with A large number of open holes 17 . . . 17 are provided in the peripheral wall of the portion that penetrates the silencer 5 , and the open holes 17 . . . 17 are surrounded by a sound absorbing material 18 .

According to such a configuration, when the engine 2 is in a steady operating state, a control signal for opening the on-off valve 8 is not outputted from the acceleration determining means 11 in the control device 9 to the drive device 12 or the actuator 10. The valve 8 is in a state in which the inlet of the bypass passage 7 is closed, as shown by the solid line in FIG. Therefore, exhaust gas discharged from the engine 2 flows into one expansion chamber 15' of the silencer 5 through the exhaust introduction pipe 4. And communication path 16...1
6 into the expansion chamber 15'', which communicates with the expansion chamber 15 and the resonance chamber 15, and then the exhaust outlet pipe 6.
released into the atmosphere. In this manner, in the steady operating state, exhaust gas is released into the atmosphere via the expansion chamber 15'' communicating with the resonance chamber 15, so that the resonance chamber 15 and each of the expansion chambers 15, 1
By the action of 5' and 15'', low frequency noise such as indoor muffled noise is reduced.

When the engine 2 is accelerated, a control signal is output from the acceleration determining means 11 of the control device 9 to the actuator 10 via the driving means 12,
The on-off valve 8 is operated as shown by the chain line in FIG. 3 to open the inlet of the bypass passage 7. Therefore, the exhaust gas flows into the bypass passage 7 from the branch point of the exhaust introduction pipe 4 and is discharged into the atmosphere through the passage 7. In other words, during acceleration, the exhaust gas is released into the atmosphere without passing through the expansion chambers 15, 15', 15'' and the resonance chamber 15, so the exhaust gas flows smoothly and the back pressure of the engine 2 is reduced. This means that the output necessary for acceleration can be obtained.
In that case, the bypass passage 7 has open holes 17...17.
In addition, since the open holes 17...17 are surrounded by the sound absorbing material 18, high frequency exhaust noise among the air flow noise generated during acceleration is absorbed by the sound absorbing material 18, Exhaust noise will also be reduced.

In this embodiment, when the on-off valve 8 opens the bypass passage 7, the valve 8 closes the exhaust introduction pipe 4, but the exhaust passage of the exhaust introduction pipe 4 is always open and the bypass passage 7 is closed. Only the passage 7 may be opened and closed.

(Effects of the invention) As described above, according to the exhaust silencing device of the present invention, in the steady state of operation, the exhaust gas is introduced into the silencer having the resonance chamber through the introduction pipe, so that no indoor noise is caused. While low-frequency noise such as sound is reduced, during acceleration, when low-frequency noise is not so much of a problem, the on-off valve is operated in the direction of opening the back pressure reduction passage, so the exhaust gas flows through the back pressure passage with less resistance. It is released into the atmosphere through a pressure reduction passage, which reduces engine back pressure and improves power performance.

In particular, since the back pressure reduction passage passes through the silencer and the plurality of open holes provided in the passage are surrounded by a sound absorbing material, high-frequency noise such as airflow noise generated during acceleration can be The exhaust noise is effectively reduced by being absorbed by the sound absorbing material. Furthermore, since the sound absorbing material is provided so as to surround the open hole provided in the penetrating portion of the silencer in the back pressure reduction passage, the exhaust noise leaking from the sound absorbing material is blocked by the case portion of the silencer. This not only improves the silencing performance, but also makes this type of exhaust silencing device more compact compared to a case where the silencing section, which consists of these sound-absorbing materials and open holes, is installed at a separate location from the silencer. It also happens.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram of low-frequency exhaust noise, Figs. 2 and 3 show examples of the present invention, Fig. 2 is a schematic diagram of an exhaust silencing device, and Fig. 3 is an enlarged cross-section of a silencer in the device. It is a diagram. 1... Exhaust silencer, 4... Inlet pipe (exhaust introduction pipe), 5... Silencer, 6... Outlet pipe (exhaust outlet pipe), 7... Back pressure reduction passage (bypass passage), 8
...Opening/closing valve, 9...Control means (control device), 15,
15', 15''...expansion chamber, 15...resonance chamber, 1
7...Open hole, 18...Sound absorbing material.

Claims (1)

[Scope of utility model registration request] In an engine exhaust silencing device that connects an inlet pipe that introduces exhaust gas into a silencer having a resonance chamber and an outlet pipe that discharges the exhaust gas into the atmosphere, a back pressure reduction passage whose tip is opened toward the atmosphere from the inlet pipe is provided. branching and passing the passage through the inside of the silencer to form a plurality of open holes in the penetrating portion;
An engine exhaust noise muffling device comprising: an on-off valve that opens and closes the back pressure reducing passage, and a control means that operates the valve in the opening direction when the engine accelerates, the periphery of which is surrounded by a sound-absorbing material. Device.