JPH07127449A - Explosion preventing device for muffler for engine - Google Patents

Abstract

PURPOSE:To surely prevent the occurrence of explosion outside a cylinder at the muffler of an engine while suppressing the generation of a back pressure. CONSTITUTION:An explosion preventing means 3 for a muffler 1 comprises a butterfly valve 4, fronting on an exhaust gas outlet pipe 2, and a return spring 7. The butterfly valve 4 is supported to the exhaust gas outlet pipe 2 through a support shaft 5 in a manner to be switched to an opening posture and a closed posture. The return spring 7 is interlocked with the butterfly valve 4, which can be energized for opening. Thus, since, during stop operation of an engine, the butterfly valve 4 is closed through the energizing force of the return spring 7, entrance of outside air to the muffler 1 is blocked. Since, during operation of an engine, the butterfly valve 4 is opened as a result of an exhaust gas pressure being exerted thereon, a back pressure is not increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for preventing out-of-cylinder explosion of a muffler of an engine, while keeping back pressure low.
Provide a product that can reliably prevent external explosion.

[0002]

BACKGROUND OF THE INVENTION In general, when an engine is stopped, unburned air-fuel mixture is sent to a muffler due to inertial rotation of the engine. Since the air-fuel ratio of this air-fuel mixture is set to burn in a high-pressure combustion chamber, the air-fuel ratio in the muffler is too high and it will not explode as it is. However, due to the pulsation of the exhaust air, outside air (that is, fresh air) enters the muffler from the exhaust outlet
If is inhaled, the air-fuel mixture is diluted and enters the explosion range, and the heat of the muffler may cause an out-of-cylinder explosion. Therefore, the exhaust outlet pipe of the muffler is provided with an explosion-proof means for suppressing intake of outside air to prevent the out-of-cylinder explosion.

The present invention is directed to the muffler explosion-proof device of this engine, and its basic structure is, as shown in FIG. 1 or 6, in the exhaust outlet pipe 2 of the muffler 1 of a gasoline engine, in a cross-passage manner. 3 is provided.

[0004]

2. Description of the Related Art As a conventional technique of this type, as shown in FIG. 6, the explosion-proof means 3 is a net 50 made of stainless steel. A band of the net 50 is loosely wound with a ventilation gap, and the wound cross section 51 is formed. To the exhaust outlet pipe 2 and fill the exhaust outlet pipe 2 from the wall of the exhaust outlet pipe 2.
There is one in which the support nail 53 is pierced toward the side surface 52 of the above, and the net 50 made of stainless steel is fixed to the exhaust outlet pipe 2 by the support nail 53. In the related art, the entrained net 50 serves as suction resistance and prevents outside air from entering the muffler 1 through the exhaust outlet pipe 2.

[0005]

Generally, since the passage cross-sectional area of the exhaust outlet pipe 2 of the muffler 1 increases as the engine displacement increases, the larger exhaust outlet pipe 2 is used in the above-mentioned conventional technique. It is not easy to effectively fill the net 50, a gap is likely to be formed between the net 50 and the exhaust outlet pipe 2, and the side face of the net 50 is compressed and deformed in the driving direction by driving the support nail 53, so that the outside air is not exposed. Since it easily blows into the muffler 1, it is not sufficient to surely prevent the outside air from entering.

On the other hand, in the above-mentioned prior art, the net 50 housed in the exhaust outlet pipe 2 becomes an obstacle to the circulation of the exhaust gas and the back pressure is apt to increase, and this adverse effect increases as the packing density of the net 50 increases. An object of the present invention is to reliably prevent an out-of-cylinder explosion of an engine muffler while suppressing back pressure.

[0007]

Means for achieving the above object will be described below with reference to FIGS. 1 to 5 showing an embodiment. That is, according to the present invention, in the muffler explosion-proof device for an engine of the basic structure, the explosion-proof means 3 is a butterfly valve 4 and a return spring 7 facing the exhaust outlet pipe 2, and the butterfly valve 4 is connected to the exhaust outlet pipe 2. The butterfly valve 4 is supported via a support shaft 5 so that the posture can be switched between a valve opening posture P and a valve closing posture Q, and a return spring 7 is interlocked with the butterfly valve 4 so as to be able to urge the valve to be closed. When the exhaust pressure in the exhaust outlet pipe 2 becomes higher than the urging force of the return spring 7, the butterfly valve 4 becomes the valve opening posture P, and the exhaust pressure received by the valve surface 6 of the butterfly valve 4 becomes greater than the urging force of the return spring 7. When reduced, butterfly valve 4
Is configured to switch to a valve-closed posture Q. The exhaust outlet pipe 2 is a final exhaust pipe for exhausting the muffler body, a tail pipe attached to the muffler, or the like.

[0008]

Since the exhaust gas blows through the exhaust outlet pipe 2 of the muffler 1 while the engine is operating, the valve face 6 of the butterfly valve 4 is
Receives this exhaust pressure and resists the biasing force of the return spring 7 to maintain the valve-opening posture P. Therefore, the exhaust gas is smoothly discharged from the exhaust outlet pipe 2, and the back pressure does not rise.

On the other hand, when the engine is stopped, the amount of exhaust flowing through the exhaust outlet pipe 2 continues to decrease, so the exhaust pressure received by the valve face 6 of the butterfly valve 4 is reduced by the biasing force of the return spring, and the butterfly valve 4 Is from valve open position P to valve closed position Q
It is possible to effectively prevent the outside air from entering the muffler 1 from the exhaust outlet pipe 2 by switching the posture to.

[0010]

Since the butterfly valve is openably and closably supported by the exhaust outlet pipe via the return spring, the butterfly valve is automatically closed by the urging force of the return spring when the engine is stopped, and the outside air enters the muffler. Can be prevented, and the muffler can be reliably prevented from exploding outside the cylinder. For engines with large displacement,
The butterfly valve provided in the exhaust outlet pipe may be replaced with a large butterfly valve, and there is no problem as in the prior art.

Further, during operation of the engine, the butterfly valve is automatically opened by receiving the pressure of the exhaust gas, so that the back pressure does not increase and the output reduction of the engine can be effectively prevented.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a vertical side view of the engine muffler explosion-proof device.
FIG. 2 is a vertical sectional front view of a main part of the explosion-proof device, and FIG. 3 is a cross-sectional plan view of the main part of the explosion-proof device.

As shown in FIG. 1, an engine muffler 1
Divides the inner space surrounded by the sound absorbing material 11 into three expansion chambers by the partition wall 8, the inlet side expansion chamber 10a in the upper part, the outlet side expansion chamber 10c in the center, and the second expansion chamber 10b in the lower part. Formed, and the inlet side and the second expansion chambers 10a and 10b, and the second and outlet side expansion chambers 10b and 10c are communicated with each other by the communication pipe 12, and the exhaust inlet pipe 13 is projected into the inlet side expansion chamber 10a, The exhaust outlet pipe 2 is configured to project from the outlet side expansion chamber 10c.

As shown in FIGS. 1 to 3, an explosion-proof means 3 is provided in the exhaust outlet pipe 2 of the muffler 1 across the passage. The explosion-proof means 3 is a circular butterfly valve 4 and a return spring 7 facing the exhaust outlet pipe 2, and the butterfly valve 4 is supported on the exhaust outlet pipe 2 so that the posture can be switched between an open position P and a closed position Q. It is supported via a shaft 5, and a return spring 7 is interlocked with the butterfly valve 4 so that the return spring 7 can be closed and biased.

That is, as shown in FIGS. 2 and 3, the enlarged diameter portion 1 having the outer diameter enlarged toward the outlet 14 of the cylindrical exhaust outlet pipe 2.
5, the butterfly valve 4 is faced to the enlarged diameter portion 15, and the support shaft 5 of the butterfly valve 4 is arranged eccentrically to the outer diameter side by a distance A from the center C of the exhaust outlet pipe 2 (see FIG. 3). ), The left and right valve faces 6 sandwiching the support shaft 5 of the butterfly valve 4 are configured to have different surface areas.

As shown in FIGS. 2 and 3, a spring support portion 16 is provided on an upper portion of the support shaft 5 of the butterfly valve 4 so that the exhaust outlet pipe 2 is provided.
The locking arm 1 protrudes to the outside and is attached to the upper end of the spring support portion 16.
7 is provided sideways, and the return spring 7 formed of a torsion spring is locked to the spring support portion 16 and the locking arm 17 to allow the butterfly valve 4 to move.
Is urged to close in the direction of arrow B. Then, as shown in FIG. 3, the exhaust outlet pipe 2 received by the valve surface 6 of the butterfly valve 4 described above.
When the exhaust pressure inside increases more than the urging force of the torsion spring 7, the butterfly valve 4 becomes the opening posture P, and when the exhaust pressure received by the valve face 6 of the butterfly valve 4 is lower than the urging force of the torsion spring 7, the butterfly valve 4 is opened. The valve 4 is configured to switch to the closed valve posture Q. However, the biasing force of the torsion spring 7 is set to be smaller than the ventilation resistance of the net 50 filled in the exhaust outlet pipe 2 as shown in the above-mentioned prior art.

Therefore, the function of the muffler explosion-proof device of this embodiment will be described. Since the exhaust gas blows through the exhaust outlet pipe 2 of the muffler 1 during the operation of the engine, the valve face 6 of the butterfly valve 4 receives the pressure of the exhaust gas. Especially, since the support shaft 5 of the butterfly valve 4 is eccentrically arranged,
Exhaust pressure received by the valve surface 6 of No. 1 differs between the left and right surfaces sandwiching the support shaft 5. Therefore, as shown in FIG. 3A, the butterfly valve 4 smoothly swings in the direction of arrow R against the biasing force of the torsion spring 7 and is held in the valve-opening posture P. Therefore, the exhaust gas is smoothly discharged from the exhaust outlet pipe 2, the back pressure does not increase, and the engine output can be favorably prevented from decreasing.

On the other hand, when the engine is stopped, the amount of exhaust gas flowing through the exhaust outlet pipe 2 continues to decrease, so that the exhaust pressure applied to the valve face 6 of the butterfly valve 4 is less than the biasing force of the torsion spring 7. Therefore, as shown in FIG. 3B, the butterfly valve 4 swings in the direction of the arrow S by the returning action of the torsion spring 7, and switches the valve opening posture P to the valve closing posture Q. Therefore, it is possible to effectively prevent the outside air from invading the muffler 1 through the exhaust outlet pipe 2 and reliably prevent the muffler 1 from exploding outside the cylinder.

FIG. 4 shows a modification of the butterfly valve 4 in which the support shaft 5 is eccentrically arranged. In the above-described embodiment, since the circular butterfly valve 4 is eccentrically arranged, there is a risk that the portion of the maximum diameter of the butterfly valve 4 will hit the inner wall of the exhaust outlet pipe 2 due to the opening and closing swing. This is avoided by forming the enlarged diameter portion 15 in the. In this modified example, as shown in FIG. 4, flat portions 18 are arranged in parallel above and below the butterfly valve 4, and the exhaust outlet pipe 2 is formed in a flat elongated hole shape in accordance with the flat portion 18. The enlarged diameter portion 15 as in the example is unnecessary.

FIG. 5 shows an example in which the support shaft 5 of the butterfly valve 4 is aligned with the center C of the exhaust outlet pipe 2, which is different from the above embodiment in which the butterfly valve 4 is eccentrically arranged. Similar to this modification, when the support shaft 5 is arranged at the center of the exhaust outlet pipe 2,
Since it suffices to make the surface areas of the left and right valve surfaces 6 that sandwich the support shaft 5 different, for example, one valve surface 6 is formed into a flat surface,
The other valve surface 6 may be a curved surface.

In the present invention, the return spring 7 is not limited to the torsion spring as in the above embodiment, but may be a leaf spring or a spiral spring.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of an engine muffler explosion-proof device.

FIG. 2 is a vertical sectional front view of a main part of the explosion-proof device.

FIG. 3 is a cross-sectional plan view of main parts of the explosion-proof device.

FIG. 4 is a view corresponding to FIG. 2 showing a modified example in which a spindle of a butterfly valve is eccentrically arranged.

5 is a view corresponding to FIG. 2 showing an example in which a butterfly valve is arranged in the center.

FIG. 6 is a perspective view of an essential part of an explosion-proof device showing a conventional technique.

[Explanation of symbols]

1 ... Muffler, 2 ... Exhaust outlet pipe, 3 ... Explosion-proof means, 4 ... Butterfly valve, 5 ... Butterfly valve spindle, 6 ... Valve face, 7 ... Return spring, P ... Butterfly valve open posture, Q ... Butterfly Valve closed position.

Claims (1)

[Claims] 1. An exhaust outlet pipe (2) for a muffler (1) of an engine
In a muffler explosion-proof device for an engine in which an explosion-proof means (3) is installed inside the passage, a butterfly valve (4) and a return spring (7) which face the exhaust outlet pipe (2) by the explosion-proof means (3). ), The butterfly valve (4) is supported on the exhaust outlet pipe (2) through a support shaft (5) so that the butterfly valve (4) can be opened and closed (P) and closed (Q).
The return spring (7) is linked to (4) so that the return spring (7) can be biased so that the exhaust pressure in the exhaust outlet pipe (2) received by the valve surface (6) of the butterfly valve (4) is applied to the return spring (7). When the force exceeds the force, the butterfly valve (4) will be in the open position (P), and if the exhaust pressure received by the valve face (6) of the butterfly valve (4) is less than the biasing force of the return spring (7), the butterfly An explosion-proof device for an engine muffler, characterized in that the valve (4) is configured to switch to a closed position (Q).