JP2009287424A - Variable exhaust device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To switch an exhaust flow passage in accordance with an exhaust pressure while suppressing deterioration of engine output caused by pressure loss. <P>SOLUTION: In an exhaust system wherein an exhaust pipe 10 of the internal combustion engine (engine) and a muffler 20 are arranged in parallel, the variable exhaust device of the internal combustion engine is provided with an opening 11 disposed in a halfway of the exhaust pipe 10 and communicating the exhaust pipe 10 and the muffler 20, a switching part 12 opening and closing the opening 11, a branch pipe 30 branched from the exhaust pipe 10, and a switch operation part for operating the switching part 12 by a back pressure of the branch pipe 30. The switch operation part comprises a movable part 40 energized to a direction moving the switching part 12 to a fully closed position by receiving the back pressure of the branch pipe 30, a spring 43 for energizing the movable part 40 to a direction moving the switching part 12 to a fully opened position, and a connecting part 41 connecting the movable part 40 and the switching part 12 and moving the switching part 12 interlockingly with the movable part 40. Switching of the flow passage of the exhaust gas is performed by the movable part 40 to which the back pressure of the branch pipe 30 branched from the exhaust pipe 10 is applied. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a variable exhaust device for an internal combustion engine.

In an exhaust system of an internal combustion engine (engine), exhaust noise is silenced by a silencer provided in an exhaust passage. In the exhaust system of the engine, when the engine is rotating at a low speed, the flow of the exhaust gas is obstructed to improve the noise reduction efficiency, and when the engine is rotating at a medium or high speed, the exhaust gas is easily flowed to reduce the back pressure. To increase the output.
Therefore, the exhaust flow path used during low / medium / high speed rotation and the exhaust flow path used only during medium / high speed rotation are provided in the silencer, and the exhaust gas exhaust flow path is variable. A device that is switched by a mechanism has been proposed (for example, Patent Document 1).
Japanese Utility Model Publication No. 06-073309

FIG. 3 is a diagram schematically illustrating a flow path variable mechanism of a silencer according to a conventional example as disclosed in Patent Document 1.
The flow path variable mechanism 50 of the silencer according to the conventional example includes a switching valve 53 that opens and closes an opening 52 on the outlet side of a pipe 51 that constitutes an exhaust flow path, and a spring that biases the switching valve 53 in a direction to close the opening 52. 54.
In this variable flow path mechanism 50, when the back pressure acting on the switching valve 53 is low speed rotation smaller than the biasing force of the spring 54, the opening 52 is closed (see FIG. 3A), and the back pressure is applied to the spring 54. The opening 52 is opened during medium / high speed rotation that is greater than the urging force (see FIG. 3B), so that the opening 52 is opened and closed according to the rotation of the engine, and the exhaust passage is switched. ing.

  When a silencer having this flow path variable mechanism 50 is employed, the switching valve 53 is provided on the exhaust flow path, so that it can be rotated at medium and high speeds compared to a silencer without the flow path variable mechanism 50. There was a problem that the pressure loss of the engine increased and the engine output decreased accordingly.

  An object of the present invention is to enable appropriate switching of an exhaust flow path while suppressing a decrease in engine output due to pressure loss.

  The present invention relates to an exhaust system in which an exhaust pipe of an internal combustion engine and a silencer are provided in parallel, an opening provided in the middle of the exhaust pipe, and an opening / closing for opening and closing the opening. A switching unit, a branch pipe branched from the exhaust pipe, and a switching operation part for operating the open / close switching part by back pressure of the branch pipe are provided.

  According to the present invention, the open / close switching unit that opens and closes the opening that communicates the exhaust pipe and the silencer is operated by the switching operation unit that receives the back pressure of the branch pipe that branches from the exhaust pipe. When opening and closing the opening, the switching operation unit does not receive the back pressure of the exhaust pipe and does not directly impede the flow of exhaust gas flowing in the exhaust pipe. The flow path can be switched.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view for explaining an exhaust gas exhaust passage provided with a variable exhaust device according to an embodiment. FIG. 1 (a) shows a fully open position where a switching unit 12 for switching the exhaust passage is fully opened. The case of the position is shown, (b) is a cross-sectional view taken along the line AA in (a), and (c) is a cross-sectional view taken along the line BB in (a). FIG. 2 is a diagram illustrating a case where the position of the switching unit 12 that switches the exhaust flow path is a fully closed position where the opening 11 is fully closed.

An exhaust pipe 10 for releasing exhaust gas from an engine (not shown) into the atmosphere is provided through the silencer 20.
The exhaust pipe 10 is a cylindrical body having a substantially circular cross section, and the exhaust flow path inside the exhaust pipe 10 and the silencer 20 are located upstream of the portion of the exhaust pipe 10 inserted into the silencer 20. An opening 11 that communicates with the inside is provided.
A plurality of openings 11 are provided in a predetermined range in the axial direction (longitudinal direction) of the exhaust pipe 10 at predetermined intervals along the circumferential direction. Of the exhaust gas introduced into the exhaust pipe 10 from the left side in the drawing, The exhaust gas discharged into the silencer 20 through the opening 11 passes through a silencer passage (not shown) in the silencer 20 and is then released into the atmosphere.

Inside the silencer 20, a switching unit 12 for opening and closing the opening 11 and switching the exhaust gas exhaust flow path is extrapolated to the exhaust pipe 10.
The switching unit 12 has a cylindrical shape, and the axial length L1 is set longer than the axial length L2 of the opening 11 so that the switching unit 12 can close the opening 11.
The switching unit 12 is provided so as to be slidable along the longitudinal direction of the exhaust pipe 10, and is fully opened (see FIG. 1A) for fully opening the opening 11, and fully closed (see FIG. 2). (See below).

A branch pipe 30 having a smaller channel cross-sectional area than the exhaust pipe 10 is branched from the exhaust pipe 10 at a position upstream of the silencer 20 of the exhaust pipe 10.
The branch pipe 30 is bent toward the downstream side of the exhaust pipe 10 at a position away from the exhaust pipe 10, and the branch pipe 30 a ahead of the bent portion is arranged in parallel with the exhaust pipe 10. .
The branch pipe 30a is inserted into the silencer 20, and the distal end of the branch pipe 30a is expanded in the silencer 20 to form an enlarged diameter portion 30b.

At the tip of the enlarged diameter portion 30b, a bottomed cylindrical movable portion 40 is externally fitted so as to be slidable in the longitudinal direction of the enlarged diameter portion 30b, and the distal end portion of the branch pipe 30a. In addition, a pressure chamber P composed of the enlarged diameter portion 30b and the movable portion 40 is formed.
Here, the tip of the enlarged diameter portion 30b is closed by the movable portion 40, and the pressure in the pressure chamber P increases as the engine speed increases and the back pressure of the branch pipe 30a increases. Therefore, the movable portion 40 that is slidably fitted to the enlarged-diameter portion 30b is directed toward the downstream side of the exhaust pipe 10 (the right side in the figure) with a larger urging force as the engine speed increases. Is energized.

  The movable portion 40 is connected to the switching portion 12 by a connection portion 41 provided on the peripheral wall portion 40a that is fitted around the enlarged diameter portion 30b. Here, since the exhaust pipe 10 and the branch pipe 30a are arranged in parallel to each other, when the movable part 40 slides along the axial direction (axis X direction) of the enlarged diameter part 30b, the switching part 12 is movable. In conjunction with the sliding of the portion 40, it slides along the axial direction of the exhaust pipe 10 (the axis Y direction passing through the center of the exhaust pipe 10). That is, the switching unit 12 is arranged at a predetermined position between the fully closed position and the fully open position by the movable unit 40.

A spring engaging portion 42 to which the spring 43 is fitted is provided on the bottom portion 40 b of the movable portion 40.
One end of the spring 43 is externally fitted and fixed to the spring engaging portion 42 of the movable portion 40 and the other end is fixed to the spring engaging portion 22 provided on the inner wall 21 of the silencer 20. The spring 43 is disposed on the axis X passing through the center of the branch pipe 30a, and always urges the movable portion 40 in the upstream direction (left direction in the figure) of the exhaust pipe 10.

For this reason, when the engine is stopped, the movable portion 40 receives only the urging force of the spring 43, places the switching portion 12 in the fully open position, and fully opens the opening 11 (see FIG. 1A).
When the engine is started, the movable portion 40 moves to a position where the urging force due to the back pressure of the branch pipe 30 and the urging force due to the spring 43 are balanced, and is determined according to the balance of these urging forces. The switching part 12 is arrange | positioned in a position, and the opening 11 is made into a predetermined opening degree.
When the urging force due to the back pressure of the branch pipe 30 becomes larger than the urging force due to the spring 43, the movable portion 40 places the switching portion 12 in the fully closed position and fully closes the opening 11 (see FIG. 2).

Here, the characteristics of the opening / closing operation of the opening 11 by the switching unit 12 are determined by the biasing force acting on the movable unit 40 by the back pressure of the branch pipe 30 and the biasing force by the spring 43.
In the embodiment, as shown in FIG. 1B, the flow passage cross-sectional area B of the enlarged diameter portion 30b is made larger than the flow passage cross-sectional area A of the branch pipe 30a to widen the pressure receiving surface of the movable portion 40. Thus, a desired urging force determined according to the back pressure determined according to the engine speed and the flow rate cross-sectional area of the enlarged diameter portion 30b is applied to the movable portion 40.
Further, the spring constant of the spring 43 and the channel cross-sectional areas A and B are set so that the exhaust channel can be switched appropriately based on the experimental results.

In the exhaust gas exhaust passage provided with the variable exhaust device having such a configuration, the movable portion 40 is moved in the downstream direction of the exhaust pipe 10 while the back pressure of the branch pipe 30 acting on the pressure chamber P is low because the engine speed is low. Since the urging force to be urged is smaller than the urging force by which the spring 43 urges the movable portion 40 in the upstream direction of the exhaust pipe 10, the switching portion 12 is held in the fully open position (see FIG. 1).
Therefore, a part of the exhaust gas is released into the atmosphere after passing through the silencing channel in the silencer 20, so that the exhaust noise is reduced.

As the engine speed increases, the back pressure of the branch pipe 30 increases, and the urging force that urges the movable portion 40 in the right direction in the figure is applied by the spring 43 that urges the movable wall in the left direction in the figure. When the force is greater than the force, the movable unit 40 slides the switching unit 12 toward the fully closed position.
When the engine speed continues to increase, the opening 11 is narrowed by the switching unit 12, and at the point where the engine speed reaches the high rotation region, the switching unit 12 is disposed at the fully closed position. The opening 11 is closed.
Accordingly, the exhaust gas does not pass through the silencing channel in the silencer 20, but is released as it is into the atmosphere from the exhaust pipe 10, and the back pressure is reduced accordingly. Increase.

  Here, the enlarged diameter part 30b, the movable part 40, the connection part 41, and the spring 43 of the embodiment constitute a switching operation part in the invention.

As described above, in the embodiment, in the exhaust system in which the exhaust pipe 10 of the internal combustion engine (engine) and the silencer 20 are provided in parallel, the exhaust pipe 10 and the silencer 20 are provided in the middle of the exhaust pipe 10. An opening 11 communicating with the opening 11, a switching part 12 that opens and closes the opening 11, a branch pipe 30 that branches from the exhaust pipe 10, and a switching operation part that operates the switching part 12 by the back pressure of the branch pipe 30, The switching of the exhaust gas flow path is performed by the switching operation unit that receives the back pressure of the branch pipe 30 branched from the exhaust pipe 10.
Thus, when the opening is opened and closed, the switching operation unit does not receive the back pressure of the exhaust pipe and does not directly disturb the flow of the exhaust gas flowing in the exhaust pipe, so that the switching for switching the exhaust flow path on the extension of the exhaust pipe is performed. Compared to a conventional device provided with a valve, it is possible to suppress pressure loss when switching the flow path of the exhaust gas. Therefore, the exhaust flow path can be switched in accordance with the exhaust pressure while suppressing a decrease in engine output due to pressure loss.
Further, since the back pressure of the internal combustion engine is used for the operation of the switching unit 12, it is not necessary to separately provide a mechanism for operating the switching unit, such as a servo motor. Further, it is not necessary to provide a switching valve as in the conventional example in order to enable switching of the exhaust flow path. Therefore, the number of parts of the variable exhaust device of the internal combustion engine can be reduced, and the device can be provided at a lower cost.

The switching unit 12 is movable between a fully closed position (FIG. 2) for fully closing the opening 11 and a fully open position ((a) of FIG. 1) for fully opening the opening 11. The unit receives the back pressure of the branch pipe 30 and attaches the movable unit 40 biased in the direction to move the switching unit 12 to the fully closed position and the movable unit 40 in the direction to move the switching unit 12 to the fully opened position. The spring 43 to be urged, the movable portion 40 and the switching portion 12 are connected, and the connection portion 41 that moves the switching portion 12 in conjunction with the movable portion 40 is provided.
Thus, when the engine speed is low and the urging force by the spring 43 is larger than the urging force by the back pressure of the branch pipe 30, the opening 11 is fully opened and the exhaust gas is guided to the silencer 20. It is written. Therefore, the silencing efficiency during low-speed rotation can be improved.
When the engine speed increases, the urging force due to the back pressure of the branch pipe 30 increases, the switching unit 12 is moved toward the fully closed position, and the opening 11 is fully closed. Therefore, the amount of exhaust gas guided to the silencer 20 is reduced, and eventually the exhaust gas does not flow to the silencer 20 side, so that exhaust gas can be easily removed and the output of the engine is improved.
Therefore, both low noise required when the engine is rotating at a low speed and low back pressure required when the engine is rotating at a medium / high speed can be achieved.
As a result, even if the back pressure of the internal combustion engine is high to ensure the required performance of the silencer and catalytic device due to the recent tightening of exhaust noise regulations and the demand for reduction of exhaust harmful substances, A decrease in engine output can be suitably prevented.

  The spring 43 is provided on an extension of the axis X passing through the center of the branch pipe 30, and the movable portion 40 is a position where the biasing force due to the back pressure of the branch pipe 30 and the biasing force due to the spring 43 are balanced. And the opening degree of the opening 11 by the switching unit 12 is determined. As a result, the opening / closing characteristics of the opening 11 can be adjusted by the urging force of the spring 43, so that it is possible to provide a variable exhaust device for an internal combustion engine that can switch the exhaust flow path at a desired timing. Also, by preparing a plurality of springs having different urging forces, it is possible to provide a variable exhaust device for an internal combustion engine in which the switching timing of the exhaust flow path is set to a desired timing by simply replacing the springs.

Furthermore, the distal end portion of the branch pipe 30a is expanded into a diameter-expanded portion 30b, and the movable portion 40 has an urging force determined by the back pressure of the branch tube 30a and the channel cross-sectional area of the diameter-expanded portion 30b, The position of the opening 11 by the switching unit 12 is determined by moving to a position where the urging force by the urging means (spring 43) is balanced.
Accordingly, by appropriately adjusting the flow path cross-sectional area of the enlarged diameter portion 30b and the urging force by the spring 43, a variable exhaust device for an internal combustion engine capable of switching the exhaust flow path at a desired timing is provided. Can do.

In the above-described embodiment, the case where the branch pipe 30 branches from the position upstream of the silencer 20 of the exhaust pipe 10 is illustrated. However, the branch pipe 30 may be provided to branch from the exhaust pipe 10 in the silencer 20. good.
In addition, as long as the sealing performance of the silencer 20 is not impaired, the branch pipe 30, the movable portion 40 at the tip thereof, and the spring 43 are provided outside the silencer 20, and are switched at a connection portion inserted into the silencer 20. The unit 12 may be operated.

  Furthermore, in the above-described embodiment, the case where a plurality of openings 11 are provided at predetermined intervals along the circumferential direction of the exhaust pipe 10 is illustrated. However, the shape of the openings is the silence flow of the exhaust flow path and the silencer 20. Any shape that can communicate with the road can be selected as appropriate, such as a circle, an ellipse, and a slit shape.

It is sectional drawing of the exhaust flow path of exhaust gas provided with the variable exhaust apparatus which concerns on embodiment. It is a figure which shows the action | operation of the variable exhaust apparatus which concerns on embodiment. It is a figure explaining the action | operation of the flow-path variable mechanism which concerns on a prior art example.

Explanation of symbols

10 Exhaust pipe 11 Opening 12 Switching part (open / close switching part)
20 silencer 21 inner wall 22 spring engaging portion 30 branch pipe 30a branch pipe 30b expanded diameter portion 40 movable portion 41 connecting portion 42 spring engaging portion 43 spring (biasing means)
50 Flow path variable mechanism 51 Piping 52 Opening 53 Switching valve 54 Spring P Pressure chamber

Claims (4)

In an exhaust system in which an exhaust pipe of an internal combustion engine and a silencer are provided in parallel,
An opening provided in the middle of the exhaust pipe to communicate the exhaust pipe and the silencer;
An open / close switching unit for opening and closing the opening;
A branch pipe branched from the exhaust pipe;
A variable exhaust device for an internal combustion engine, comprising: a switching operation unit that operates the open / close switching unit by a back pressure of the branch pipe. The switching operation unit is
A movable part that receives a back pressure of the branch pipe and is biased in a direction to move the opening / closing switching part to a position where the opening is fully closed;
Biasing means for biasing the movable part in a direction to move the opening / closing switching part to a position where the opening is fully opened;
2. The internal combustion engine according to claim 1, further comprising: a connecting portion that connects the movable portion and the opening / closing switching portion and moves the opening / closing switching portion in conjunction with movement of the movable portion. Variable exhaust system. The biasing means is a spring provided on an extension of the branch pipe,
The said movable part moves to the position where the urging | biasing force by the back pressure of the said branch pipe and the urging | biasing force by the said spring balance, and determines the opening degree of the said opening. A variable exhaust system for an internal combustion engine. The tip of the branch pipe is expanded in diameter to be an expanded diameter part,
The movable portion moves to a position where the urging force determined by the back pressure of the branch pipe and the flow passage cross-sectional area of the enlarged diameter portion and the urging force by the urging means are balanced, and the opening degree of the opening is increased. The variable exhaust device for an internal combustion engine according to claim 2 or 3, wherein the variable exhaust device is determined.

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