JP2003003820A - Muffler for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To gain a muffler for an internal combustion engine improved in the output of the internal combustion engine. SOLUTION: An on-off valve 36 for opening and closing of an opening 34 is provided in a valve body 48 swingably supported around a fulcrum shaft 46, being subjected to the pressure of the exhaust gas exhausted from the internal combustion engine, and an energizing member 52 for energizing the valve body 48 in the valve closing direction by the energizing force of expansion direction between an action point at the valve body side and an action point at the fixed side. The action point at the fixed side is provided at the reverse side of the valve body 48 for the opening 34, and the action point at the fixed side is provided at the position where the moment around the fulcrum shaft 46 of the valve body 48 by the energizing member 52 decreases according to the opening increase of the valve body 48. The backpressure rise is suppressed by changing the exhaust passage according to the rotational number of the internal combustion engine with opening and closing of the on-off valve 36.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a muffler for an internal combustion engine, which is designed to be quiet in a low speed range and to improve output in a medium / high speed range.

[0002]

2. Description of the Related Art Conventionally, as disclosed in Japanese Patent Laid-Open No. 9-195749, a plurality of partition walls for partitioning a muffler body into a plurality of chambers have been provided. It is known that an on-off valve is provided that urges a valve element that is swingably supported by a spring in a direction to close the opening by a spring. The on-off valve is configured to be closed when the rotation speed of the internal combustion engine is low, so that the exhaust passage focuses on reduction of exhaust noise.

When the rotational speed of the internal combustion engine increases and the pressure of the exhaust gas discharged increases, the valve body is opened by the action of this pressure to prevent the back pressure from rising. The exhaust passage is configured to improve the output of the internal combustion engine.

[0004]

However, in such a conventional device, as shown in FIG. 4, when the valve body opens under the pressure of exhaust gas against the biasing force of the spring, as shown in FIG.
When the opening degree of the valve body increases, the moment around the fulcrum shaft also increases in proportion to it. If the rotational speed of the internal combustion engine increases and the pressure of the exhaust gas does not increase sufficiently, the opening degree of the valve element does not increase and there is a problem that the output of the internal combustion engine cannot be sufficiently improved.

An object of the present invention is to provide a muffler for an internal combustion engine, which has improved output of the internal combustion engine.

[0006]

In order to achieve the above object, the present invention takes the following means in order to solve the object. That is, a valve body that is swingably supported around a fulcrum shaft is provided with an on-off valve that opens and closes an opening in response to the pressure of exhaust gas discharged from an internal combustion engine. In an internal combustion engine muffler that changes the exhaust passage according to the engine speed, an urging force in the extension direction between the valve body side action point and the fixed side action point urges the valve body in the valve closing direction. A biasing member is provided, the fixed-side action point is provided on the side opposite to the valve body with respect to the opening, and the moment about the fulcrum axis of the valve body due to the biasing member increases the opening degree of the valve body. The muffler for an internal combustion engine is characterized in that the fixed-side action point is provided at a position where

The valve body of the on-off valve may be a conical valve body that opens and closes the opening formed in the partition wall. At this time, the biasing member may be a coil spring. Also,
The valve body of the on-off valve may be an arc-shaped valve body that closes an opening formed on the outer circumference of the pipe. At this time, the biasing member may be a coil spring. Further, the valve body may have the maximum opening degree before the valve body side action point, the fixed side action point, and the fulcrum axis are aligned.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. As shown in FIG. 1, 1 is a cylindrical muffler body, and both ends of the muffler body 1 are closed by lid members 2 and 4, respectively. Further, the inside of the muffler body 1 is partitioned by a plurality of first to third partition walls 6, 8 and 10 to form a plurality of first to fourth expansion chambers 11 to 14.

An inlet pipe 16 into which exhaust gas discharged from an internal combustion engine (not shown) is introduced is one of the lid members 2,
The third partition wall 6, 8 and 10 is penetrated and the tip thereof is opened to the fourth expansion chamber 14. Inlet pipe 1 in the first expansion chamber 10
6, a plurality of through holes 18 are formed, and a plurality of through holes 20 are also formed in the inlet pipe 16 in the third expansion chamber 13.

The outlet pipe 22 penetrates the other lid member 4,
The third, second, and first partition walls 10, 8, and 6 are sequentially penetrated, and the tip thereof is opened to the first expansion chamber 11. The outlet pipe 22 in the second expansion chamber 12 is formed with a plurality of through holes 24, and the outlet pipe 22 in the third expansion chamber 13 is also formed with a plurality of through holes 26.

A large diameter hole 28 is formed in the third partition 10 to connect the third expansion chamber 13 and the fourth expansion chamber 14 to each other. Further, in the second partition wall 8, a plurality of small diameter holes 30 are formed, a cylindrical portion 32 is formed coaxially with the large diameter hole 28, and an opening 34 is formed.

As shown in FIG. 2, an opening / closing valve 36 is attached to the cylindrical portion 32. The on-off valve 36 is the cylindrical portion 3
2 has a supporting member 40 provided with a cylindrical portion 38, and the supporting member 40 has a tapered portion 42 connected to the cylindrical portion 38.
Is equipped with. A ring-shaped wire mesh 44 is attached to the inner peripheral surface of the tapered portion 42.

The on-off valve 36 is provided with a valve body 48 which is swingably supported around a fulcrum shaft 46 provided on the support member 40. The valve body 48 is provided with a conical portion 50 protruding toward the tapered portion 42. The valve body 48 is formed so as to swing around the fulcrum shaft 46, and the conical portion 50 contacts the inner peripheral surface of the wire mesh 44 to close the opening 34.

The valve element 48 is opened by the biasing member 52.
4 is urged to close. In the present embodiment, a helical spring is used for the biasing member 52, one end of the biasing member 52 is engaged with the valve body side action point a at the tip of the valve body 48, and the biasing member 52 is used. The other end of is engaged with the fixed side action point b of the support portion 41 provided to project from the support member 40.

The valve element 48 is arranged so as to reach the maximum opening (35 degrees in this embodiment) before the fulcrum shaft 46, the valve element side action point a and the fixed side action point b are aligned on a straight line. Has been done. Further, when the exhaust gas flows from the third expansion chamber 13 side to the second expansion chamber 12 side through the opening 34, the biasing member 52 is provided.
Is arranged on the back side of the valve body 48 with respect to the opening 34 so as not to be directly exposed to the exhaust gas.

As shown in FIG. 3A, when the valve body 48 closes the opening 34, a triangle is formed by the fulcrum shaft 46, the valve body side action point a, and the fixed side action point b.
The urging force F0 of the urging member 52 acts in the extension direction on a straight line passing through the valve body side action point a and the fixed side action point b. A vertical component force a0 perpendicular to the line segment connecting the fulcrum shaft 46 and the valve body side action point a due to this urging force F0 acts on the valve body 48 as a moment around the fulcrum shaft 46 of the valve body 48.

FIG. 3B when the opening is 15 degrees, the opening 30
As shown in FIG. 3C in the case of degrees, as the opening degree of the valve body 48 increases, the line segment connecting the fulcrum shaft 46 and the valve body side action point a, and the fixed side action point b and the valve body side action point The angle θ formed by the line segment connecting the point a becomes small. The biasing forces F15 and F30 of the biasing member 52 increase as the opening degree of the valve body 48 increases (F0 <F15 <F30), but the vertical component forces a15 and a30.
Becomes smaller (a0>a15> a30).

Then, as shown in FIG. 3D, before the fulcrum shaft 46, the valve body side action point a, and the fixed side action point b are on a straight line, the valve body 48 reaches the maximum opening and the vertical component force. Is the smallest. At this time, it is preferable that the valve body 48 hits a stopper (not shown) and is regulated so that the opening degree does not exceed the limit. As shown in FIG. 4, as the opening degree of the valve body 48 increases, the moment around the fulcrum shaft 46 decreases. still,
The strength of the urging force of the urging member 52 may be appropriately determined by experiments or the like according to the pressure of the exhaust gas.

Next, the operation of the above-described muffler for an internal combustion engine of the first embodiment will be described. First, when the rotation speed of the internal combustion engine is low, the exhaust gas discharged from the internal combustion engine is introduced into the inlet pipe 16, and the exhaust gas is supplied to the inlet pipe 1
It flows into the fourth expansion chamber 14 from 6, and flows into the third expansion chamber 13 from the large diameter hole 28. In addition, some of the small holes 30 to the second
Each of the through holes 1 of the inlet pipe 16 flows into the expansion chamber 12.
Also from 8 and 20, it flows into the first expansion chamber 11 and the third expansion chamber 13. At that time, exhaust noise is reduced due to the expansion effect and the interference effect. The exhaust gas that has flowed into the first expansion chamber 11 to the third expansion chamber 13 is discharged through the through holes 24, 26 and the like to the outlet pipe 22.
And is discharged to the outside through the outlet pipe 22.

When the engine is rotating at a low speed, the pressure of the exhaust gas is low, and the pressure of the exhaust gas flowing into the third expansion chamber 13 acts on the valve element 48 through the opening 34, but the pressure is low and the urging force is increased. The valve body 48 cannot be swung against the biasing force of the member 52, and the open / close valve 36 does not open. Therefore, the exhaust gas passes through the small diameter hole 30 from the third expansion chamber 13
The exhaust gas is guided to the expansion chamber 12 and exhaust noise is sufficiently reduced.

On the other hand, when the rotation speed of the internal combustion engine is medium or high speed, it flows from the inlet pipe 16 into the fourth expansion chamber 14,
The large-diameter hole 28 flows into the third expansion chamber 13. The pressure of the exhaust gas guided to the third expansion chamber 13 is high, and the valve body 48 receives the pressure of this exhaust gas on the conical portion 50 via the opening 34. Therefore, the valve body 48 is swung around the fulcrum shaft 46 against the moment around the fulcrum shaft 46 due to the urging force F0 of the urging member 52, and the on-off valve 36 opens. Fulcrum shaft 46
Since the rotating moment is proportional to the vertical component force a0 of the urging force F0 of the urging member 52, the moment decreases as the opening degree increases.

As a result, when the pressure of the exhaust gas becomes high, the valve body 48 is opened to the maximum opening in response to this pressure, and the exhaust gas guided to the third expansion chamber 13 passes through the opening 34 to the second opening. It flows into the expansion chamber 12, and is further discharged from the through hole 24 to the outlet pipe 22. Therefore, a part of the exhaust passage is changed to pass through the opening 34 as well, so that the pressure increase of the exhaust gas is suppressed and the back pressure increase of the exhaust gas discharged from the internal combustion engine at the medium / high speed rotation is suppressed. Therefore, the output of the internal combustion engine is improved.

Next, a muffler for an internal combustion engine of a second embodiment different from the above-mentioned first embodiment will be described with reference to FIGS. As shown in FIG. 5, 101 is a muffler body,
Both ends of the muffler body 101 are provided with lid members 102, 1 respectively.
It is blocked by 04. Also, inside the muffler body 1,
Partitioned by the plurality of first and second partition walls 106 and 108, a plurality of first to third expansion chambers 111 to 113 are formed.

An inlet pipe 114 into which exhaust gas is introduced passes through one lid member 102 and the first and second partition walls 106 and 108, and its tip is open to the third expansion chamber 113. The outlet pipe 116 penetrates the other lid member 104,
The second and first pipe walls 108 and 106 are sequentially penetrated, and the tip end thereof is opened to the first expansion chamber 111.

At the outlet pipe 116 in the first expansion chamber 111,
A plurality of through holes 118 are formed, and the third expansion chamber 11
An outer pipe 120 is covered on the outlet pipe 116 in the inner casing 3, and both ends thereof are closed. A sound absorbing material 122 made of glass wool is provided between the outlet pipe 116 and the outer pipe 120.
Is filled. Corresponding to this, a plurality of through holes 124 are formed on the outer circumference of the outlet pipe 116.

The first partition 106 has a plurality of small holes 126.
Is formed, and the first expansion chamber 111 and the second expansion chamber 112 are communicated with each other. Further, a plurality of small diameter holes 128 are also formed in the second partition wall 108 to connect the second expansion chamber 112 and the third expansion chamber 113.

In the inlet pipe 114 in the first expansion chamber 111,
The opening 130 is formed, and the opening / closing valve 132 is attached to correspond to the opening 130. As shown in FIG. 6, the on-off valve 132 is provided with a valve body 134 which is formed in an arc shape and can close the opening 130.

A valve element 134 is swingably attached via a fulcrum shaft 140 supported by a pair of support members 136 and 138 attached to the outer circumference of the inlet pipe 114. In addition, the fulcrum shaft 140 is provided on the pair of support members 136 and 138.
A working shaft 142 is supported in parallel with.

A spring bearing 144 is swingably mounted on the action shaft 142, and a compression coil spring is used between the spring bearing 144 and the spring bearing portion 146 provided upright on the valve body 134. A biasing member 148 is arranged. The biasing member 148 is arranged so that the biasing force F0 in the extension direction acts on the line segment connecting the valve body side action point a of the spring receiving member 146 and the fixed side action point b at the center of the action shaft 142. There is.

As in the case of the first embodiment described above, as shown in FIG. 7, the valve element 134 swings so that the fulcrum shaft 140, the valve element side action point a, and the fixed side action point b are on the same straight line. It is arranged so as to reach the maximum opening (25 degrees in the second embodiment) before it becomes. In addition, the first expansion chamber 11 is opened through the opening 130.
1, so that the biasing member 148 is not directly exposed to the exhaust gas when the exhaust gas flows into the valve body 1.
It is arranged on the back side of 34.

As shown in FIG. 7A, when the valve body 134 is blocking the opening 130, the fulcrum shaft 14
0, the valve body side action point a, and the fixed side action point b form a triangle, and the urging force F0 of the urging member 148 acts on a straight line passing through the valve body side action point a and the fixed side action point b. A vertical component force a0 perpendicular to the line segment connecting the fulcrum shaft 140 and the valve body side action point a by the urging force F0 is the fulcrum shaft 14 of the valve body 134.
It acts as a moment around 0.

As shown in FIG. 7C, the line segment connecting the fulcrum shaft 140 and the valve body side action point a, and the fixed side action point b and the valve body side action point as the opening degree of the valve body 134 increases. The angle θ formed by the line segment connecting a and a becomes small. The biasing force F10 of the biasing member 148 increases as the opening degree of the valve element 134 increases.
Becomes larger (F0 <F10), the vertical component force a10 becomes smaller (a0> a10).

Then, as shown in FIG. 7C, before the fulcrum shaft 140, the valve body side action point a and the fixed side action point b are on the same straight line, the valve body 134 reaches the maximum opening and the vertical portion. The force is minimal. At this time, it is preferable to regulate the valve body 134 so that it does not hit the stopper (not shown) and the opening is larger than that.

Next, the operation of the internal combustion engine muffler of the second embodiment will be described. First, when the rotation speed of the internal combustion engine is low, the exhaust gas discharged from the internal combustion engine is introduced into the inlet pipe 114, and the exhaust gas is discharged from the inlet pipe 1.
From 14 flows into the third expansion chamber 113. It flows into the second expansion chamber 112 through the small diameter hole 128, and further, the small diameter hole 126.
Through the first expansion chamber 111. Then, from the opening or the through hole 118 at one end of the outlet pipe 116, the outlet pipe 116
It is discharged to the outside via. At that time, exhaust noise is reduced due to the expansion effect and the interference effect.

When the engine is rotating at a low speed, the pressure of the exhaust gas is low, and the pressure of the exhaust gas introduced into the inlet pipe 114 acts on the valve element 134 through the opening 130.
The valve element 134 cannot be swung against the biasing force of the valve 48, and the opening / closing valve 132 does not open. Therefore, the exhaust gas is generated in the third expansion chamber 113, the second expansion chamber 112, and the first expansion chamber 11
The exhaust noise is sufficiently reduced.

On the other hand, when the number of revolutions of the internal combustion engine is medium to high, the pressure of the exhaust gas introduced into the inlet pipe 114 is high, and the valve element 134 receives the pressure of this exhaust gas through the opening 130. Therefore, the valve body 134 is urged by the biasing member 148.
The on-off valve 132 is opened by being swung around the fulcrum shaft 140 against the urging force of. Since the moment around the fulcrum shaft 140 is proportional to the vertical component force a0 of the urging force F0 of the urging member 148, the moment decreases as the opening degree increases.

As a result, when the pressure of the exhaust gas becomes high, the valve body 134 is opened to almost the maximum opening under the pressure, and the exhaust gas introduced into the inlet pipe 114 is opened.
And flows into the first expansion chamber 111. Then, it is discharged from the outlet pipe 116 to the outside, and at that time, the through hole 12
4. Due to the sound absorbing effect of the sound absorbing material 122, high frequency noise is reduced.

Therefore, a part of the exhaust passage is changed and the opening 1
Since it also passes through 30, the rise in the pressure of the exhaust gas is suppressed, the rise in the back pressure of the exhaust gas discharged from the internal combustion engine at medium to high speed rotation is suppressed, and the output of the internal combustion engine is improved. The present invention is not limited to such an embodiment as described above, and can be implemented in various modes without departing from the scope of the present invention.

[0039]

As described in detail above, in the muffler for an internal combustion engine of the present invention, when the pressure of the exhaust gas becomes high, the valve body opens to the maximum opening due to this pressure, and the exhaust passage changes,
Since it passes through the opening, the rise in exhaust gas pressure is suppressed, the rise in back pressure of exhaust gas discharged from the internal combustion engine at medium and high speed rotation is suppressed, and the output of the internal combustion engine is improved. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an internal combustion engine muffler as an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is an explanatory diagram showing the relationship between the opening degree of the valve body of the on-off valve and the biasing force of the biasing member of the present embodiment.

FIG. 4 is a graph showing the relationship between the opening degree of the valve body and the moment around the fulcrum axis.

FIG. 5 is a sectional view of a muffler for an internal combustion engine of a second embodiment.

6 is a cross-sectional view taken along the line BB of FIG.

FIG. 7 is an explanatory diagram showing the relationship between the opening degree of the valve body of the on-off valve and the biasing force of the biasing member of the second embodiment.

[Explanation of symbols]

1,101 ... Muffler body 2, 4, 102, 104 ... Lid member 6, 106 ... 1st partition 8, 108 ... 2nd partition 10 ... Third partition wall 11, 111 ... First expansion chamber 12, 112 ... Second expansion chamber 13,113 ... Third expansion chamber 14 ... 4th expansion chamber 16, 114 ... Inlet pipe 18, 20, 24, 26, 118, 124 ... Through hole 22, 116 ... Outlet pipe 28 ... Large diameter hole 30, 126, 128 ... Small diameter holes 34,130 ... Opening 36,132 ... Open / close valve 40, 136 ... Support member 44 ... wire mesh 46, 140 ... fulcrum shaft 48,134 ... Valve body 50 ... Cone part 52 ... Biasing member 120 ... Outer tube 122 ... Sound absorbing material 142 ... Working shaft 148 ... Energizing member

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Claims (6)

[Claims] 1. A valve body, which is swingably supported around a fulcrum shaft, is provided with an on-off valve that opens and closes an opening in response to a pressure of exhaust gas discharged from an internal combustion engine. In an internal combustion engine muffler that changes an exhaust passage according to the number of revolutions of the internal combustion engine, the valve body is biased in the valve closing direction by an urging force in an extension direction between a valve body side action point and a fixed side action point. A biasing member for biasing is provided, the fixed-side action point is provided on a side opposite to the valve body with respect to the opening, and a moment about a fulcrum axis of the valve body by the biasing member is applied to the valve body. A muffler for an internal combustion engine, wherein the fixed-side action point is provided at a position that decreases as the opening degree increases. 2. The muffler for an internal combustion engine according to claim 1, wherein the valve element of the on-off valve is a conical valve element that opens and closes the opening formed in the partition wall. 3. The muffler for an internal combustion engine according to claim 2, wherein the urging member is a coil spring. 4. The muffler for an internal combustion engine according to claim 1, wherein the valve body of the on-off valve is an arcuate valve body that closes an opening formed on the outer circumference of the pipe. 5. The muffler for an internal combustion engine according to claim 4, wherein the biasing member is a coil spring. 6. The valve-side action point, the fixed-side action point,
The muffler for an internal combustion engine according to any one of claims 1 to 5, wherein the valve body has a maximum opening degree before the fulcrum shaft is aligned.