JPH0124327Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a muffling device for an exhaust pipe system of an internal combustion engine.

BACKGROUND ART In order to meet the demand for lower noise from internal combustion engines, various exhaust silencing devices have been proposed. Among these, so-called branch-type silencers are often used because of their simple configuration. However, although branch-type silencers are an effective means of reducing sound at specific frequencies depending on the length of the branch pipe, they conversely increase the sound pressure level in other frequency regions, making it difficult to tune. There is a problem in that the sound becomes high at engine speeds other than the above.

Purpose of the invention In view of the above points, the purpose of this invention is to add the function of a phase difference type silencer to a branch type silencer and improve it so that it can muffle sounds of different frequency components depending on the engine operating conditions. shall be.

Structure of the invention The exhaust silencer according to the invention includes a muffler, an exhaust pipe connected to the muffler to guide exhaust gas from the engine into the muffler, and a branch pipe that branches from the exhaust pipe and is closed at the end. a connecting pipe that connects the middle of the branch pipe to the exhaust pipe; a control valve that opens and closes the connecting pipe; and a control mechanism that drives the control valve. The length of the exhaust pipe is substantially longer than the length of the exhaust pipe.

Example The present invention will be explained below with reference to the illustrated embodiments.

FIG. 1 shows an embodiment of the present invention, in which exhaust gas exhausted from an engine (not shown) passes through an exhaust pipe 1, is muffled by a branch pipe 2, is further muffled by a muffler 3, and is discharged into the atmosphere from an exhaust pipe 4. It is starting to be released.

The branch pipe 2 branches at a branch part 15 of the exhaust pipe 1, and an end part 16 extends toward the muffler 3 and is closed. The branch pipe 2 includes a first vertical part 2a extending from the branch part 15 in a direction perpendicular to the exhaust pipe 1.
a first parallel part 2b extending parallel to the exhaust pipe 1 from the end of the vertical part 2a; and a second vertical part 2b extending straight from the parallel part 2b toward the exhaust pipe 1 and terminating in front of the exhaust pipe 1. part 2c and this second vertical part 2c
A second parallel portion 2d extends parallel to the exhaust pipe 1 from the end thereof and closes near the muffler 3. The second parallel portion 2d is connected to the exhaust pipe 1 by a connecting pipe 6 provided with a control valve 5. However, branch pipe 2
The length from the branch 15 to the connecting pipe 6 is several times longer than the similar length of the exhaust pipe 1.

The control valve 5 is a poppet valve, and is driven to open and close via a negative pressure actuator 11, as will be described later. Of course, a butterfly valve may be used as the control valve 5.

The muffler 3 is connected to the first
to fourth expansion chambers 21, 22, 23, and 24. First and second expansion chambers 21, 22
communicate with each other via a plurality of holes 25 formed in the partition wall 18. second and third expansion chambers 22,
23 communicates with each other via a communication tube 26, and the third and fourth expansion chambers 23, 24 communicate with each other via communication tubes 27, 28 having different lengths. The outlet end 1 a of the exhaust pipe 1 opens into the third expansion chamber 23 , and the inlet end 4 a of the exhaust outlet pipe 4 opens into the first expansion chamber 21 .

FIG. 2 shows the opening/closing drive mechanism of the control valve 5. As shown in FIG. In this figure, an electromagnetic switching valve 10 is configured to selectively connect a negative pressure source 12 or an atmospheric pressure source 13 to a negative pressure actuator 11 of a control valve 5. The electromagnetic switching valve 10 is controlled by an electronic control device 14, and the electromagnetic control device 14 controls the electromagnetic switching valve 10 to supply negative pressure to the actuator 11 in the low rotation range of the engine, closes the control valve 5, and closes the control valve 5. The electromagnetic switching valve 1 is configured to supply atmospheric pressure to the actuator 11 in the high rotation range of
0 to open the control valve 5.

Since the device of this embodiment has the above-mentioned configuration, it operates as follows to achieve the silencing effect.

When the engine is running at low speed, the control valve 5 closes the connecting pipe 6. Therefore, this muffler functions as a branch-type muffler, and muffles frequency components corresponding to the length from the branch portion 15 to the end portion 16 of the branch pipe 2, that is, low-frequency sounds. On the other hand, when the engine is running at high speed, the control valve 5 opens the connecting pipe 6. Therefore, the first vertical part 2 of the branch pipe 2
a, a frequency component according to the difference between the total length of the first parallel part 2b and the second vertical part 2c and the length from the branch part 15 of the exhaust pipe 1 to the part where the control valve 5 is provided; The sound of the frequency component corresponding to the length of the portion 2d is muted. That is, among these frequency components, the former is muted by acting as a phase difference type muffler, and the latter is muffled by acting as a branch type muffler.

As described above, according to this embodiment, it is possible to reduce sounds in different frequency ranges and improve silencing performance. However, if this improvement in silencing performance is replaced by a reduction in exhaust resistance, the output of the engine can be reduced. You can improve your performance.

It goes without saying that the engine load may be used instead of or in addition to opening and closing the control valve 5 based on the engine speed.

Effects of the invention As described above, according to the invention, it is possible to obtain an exhaust muffling device that has both the functions of a branch type muffler and a phase difference type muffler, which can muffle sounds of different frequency components depending on the operating state of the engine. can.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing one embodiment of the present invention;
The figure is a block diagram showing the drive mechanism of the control valve. 1... Exhaust pipe, 2... Branch pipe, 3... Muffler, 5... Control valve, 6... Connection pipe, 14... Electronic control device (control mechanism).

Claims (1)

[Scope of utility model registration request] A muffler, an exhaust pipe connected to this muffler and guiding exhaust gas from the engine into this muffler, a branch pipe that branches from this exhaust pipe and is closed at the end, and a part of this branch pipe connected to the above exhaust pipe. A connecting pipe for communication, a control valve for opening and closing this connecting pipe, and a control mechanism for driving this control valve,
An exhaust silencer characterized in that a length from a branching portion of the branch pipe to the connecting pipe is substantially longer than the length of the exhaust pipe.