JPH11117724A - Muffler for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a noise absorbing effect by extending an upstream end part of an external pipe to an upstream side from an upstream end part of an internal pipe, and forming an exhaust gas leading part having porosity on the external pipe. SOLUTION: The inside of a casing 2 in a muffler 1A is partitioned into expansion chambers 6 to 9 by diaphragms 3 to 5, and an exhaust gas flow-in pipe 11 is hooked in an upstream wall 10 and the diaphragm 3. Contraction chambers 12, 13 are hooked in the diaphragms 3, 4, an upstream end part 12a of the contraction chamber 12 is opened to the expansion chamber 6, the downstream end part 13b of the contraction chamber 13 is opened to the expansion chamber 8, and noise absorbing double pipe body 19A is hooked in the diaphragm 5 and a downstream wall 18. The noise absorbing double pipe body 19A is formed by filling a noise absorbing member 23 between an internal pipe 21 and an external pipe 22. In this time, an upstream end part 22a of the external pipe 22 extends from the upstream end part 21a of the internal pipe 21 to an upstream side so as to form a contraction chamber 24. Many external pipe ventilation holes 25 are arranged on the contraction chamber 24 as an exhaust gas leading-in part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a silencer for an internal combustion engine.

[0002]

2. Description of the Related Art A muffler for reducing noise is connected to an outlet of an exhaust pipe of an internal combustion engine. The conventional silencer (1) includes a casing (2) having a larger diameter than the exhaust hole of the exhaust pipe, as shown in FIGS. 6 and 7, for example. In order from the left (in the drawing), first to third disk-shaped first to third partition plates (3) to (5), and first to fourth expansion chambers (6) to (9) partitioned thereby. Are provided.

[0003] An exhaust gas inflow pipe (11) connected to the end of the exhaust pipe of the internal combustion engine and having the same diameter is provided so as to bridge the upstream wall (10) of the casing (2) and the first partition plate (3). Have been. A vent hole through which the exhaust gas passes is provided between the exhaust gas inflow pipe (11) and the first and second contraction chambers (12) and (13) formed by bridging between the partition plates (3) to (5). Many (14), (15) and (16) are formed.

[0004] The third partition plate (5) has a through hole (17) for conducting the third expansion chamber (8) and the fourth expansion chamber (9) through a casing.
A plurality of holes are formed at equal intervals on a circle centered on the axis of (2). Third partition plate (5) and downstream wall (18) of casing (2)
A sound-absorbing double tube (19) is provided between and.

The noise in the silencer (1) is reduced by the exhaust gas passing through the expansion chamber and the contraction chamber and repeating the expansion and contraction. In these processes, the noise that could not be reduced and the secondary sound are absorbed by the sound-absorbing double pipe (19).

The conventional sound-absorbing double pipe (19) has a large number of ventilation holes (35) formed on the upstream outer periphery corresponding to the distance between the third partition plate (5) to be bridged and the downstream wall (18). The inner pipe (36) provided and the portion provided with the vent (35) are almost equally divided, and the outer pipe (37) provided on the outer periphery downstream of the inner pipe (36) and sealing the front and rear ends is provided. When,
A sound absorbing member (38) provided between the outer pipe (37) and the inner pipe (36)
have.

[0007] The noise and the secondary noise are generated when the exhaust gas flows into the inner pipe (36) from the vent hole (35) of the exhaust gas introduction section upstream of the inner pipe (36) where the sound absorbing member (38) is not provided. While flowing in and flowing through the inner tube (36), the air-absorbing member (38) absorbs the gas at the air hole (35) overlapping the outer tube (37).

[0008]

In such a sound-absorbing double pipe (19), in order to enhance the sound-absorbing effect of the sound-absorbing member (38), a portion of the ventilation hole (36) communicating with the sound-absorbing member (38) is required. Therefore, the sound absorption effect can be reduced without changing the length of the portion provided with the ventilation hole (36), that is, without changing the distance between the third partition plate (5) and the downstream wall (18). To increase the height, it is necessary to extend the outer pipe (37) upstream and extend the sound absorbing member (38) upstream of the flow of the exhaust gas. However, when the portion of the sound absorbing member (38) is lengthened, the length of the exhaust gas introduction portion of the inner pipe is shortened, so that the exhaust gas becomes difficult to flow and the pressure loss increases.

Therefore, a method of extending the sound absorbing member to the downstream side can be considered. However, this method uses a third partition plate (5).
And the downstream wall (18) to extend the space downstream,
Another problem arises that the overall length of 9) becomes longer and the silencer (1) becomes larger. A method of increasing the diameter of the inner pipe (36) is also conceivable, but this method also has a problem that the muffler (1) becomes large.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a silencer having an improved sound absorbing effect without increasing the shape and pressure loss.

[0011]

According to the present invention, the above-mentioned problem is solved as follows. (1) In a casing having an expansion chamber and a contraction chamber through which exhaust gas of an internal combustion engine passes, a number of ventilation holes are formed in the outer periphery, and an inner pipe through which the exhaust gas passes. In the muffler for an internal combustion engine including a provided outer pipe and a sound absorbing double pipe body including a sound absorbing member provided between the inner pipe and the outer pipe, an upstream end of the outer pipe is connected to the inner pipe. Extending upstream from the upstream end, a porous exhaust gas inlet is formed in the outer tube.

(2) In the above item (1), the cross section in the axial direction of the upstream end portion of the inner pipe is formed in an arc shape expanding toward the upstream side.

(3) In the above item (1) or (2),
The expansion chamber is formed in the outer tube by making the diameter of the exhaust gas introduction portion larger than the diameter of the other portion of the outer tube.

(4) In any one of the above items (1) to (3), the sound absorbing double pipe body has an axis crossing the casing.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the following description, portions having the same structure as those of the related art will be denoted by the same reference numerals, and the “upstream side” of the exhaust gas flow will be described.
Means the left side in FIG.

The casing (2) of the silencer (1A) has a cylindrical shape, and the interior thereof is formed by first to third disk-shaped partition plates (3) to (5) provided in order from the upstream side. , First to fourth
It is divided into four chambers of expansion chambers (6) to (9). casing
An exhaust gas inflow pipe (11) is provided to extend between the upstream wall (10) and the first partition plate (3) of (2). The exhaust gas inflow pipe (11) is coaxial with the axis of the casing (2), its upstream end (11a) is connected to the exhaust pipe of the internal combustion engine, and its downstream end (11b) is connected to the first partition plate (11). It is closed by 3).

The first and second partition plates (3) and (4) are provided with first and second cylindrical contraction chambers (12) and (13), respectively. The first and second contraction chambers (12) and (13) are alternately arranged at equal intervals on a circumference centered on the axis of the casing (2). The upstream end (12a) of the first contraction chamber (12) is the first expansion chamber (6).
And the downstream end (12b) is also closed.
The upstream end (13a) of the second contraction chamber (13) is closed, and the downstream end (13b) is also open to the third expansion chamber (8). The exhaust gas inlet pipe (11), the first and second contraction chambers (12), (1
In 3), a large number of ventilation holes (14), (15), (16) through which exhaust gas passes are formed.

The third partition plate (5) is provided with a through hole (17) for conducting the third expansion chamber (8) and the fourth expansion chamber (9) through the casing.
A plurality of holes are formed at equal intervals on a circumference centered on the axis of (2).

Between the third partition plate (5) and the downstream wall (18) of the casing (2), there is provided a sound-absorbing double tube according to the first embodiment.
(19A). FIG. 2 is an enlarged vertical sectional view showing details of the sound-absorbing double tube (19A). The sound-absorbing double tube (19A) has an inner pipe (19) having a large number of ventilation holes (20) formed on the outer periphery. The sound absorbing member (23) is filled between the inner tube (21) and the outer tube (22) provided on the outer periphery of the inner tube (21). Outer tube
The upstream end (22a) of (22) extends upstream from the upstream end (21a) of the inner tube (21) to form a third contraction chamber (24),
It has a large number of outer tube vents (25) and also serves as an exhaust gas inlet to the third shrinkage chamber (24).

The upstream end of the outer tube (22) is sealed by an end plate (26). At the upstream end of the inner pipe (21), a dish-shaped ring (27) whose upstream side is widened is provided to improve the flow of exhaust gas. The downstream end (21b) of the inner pipe (21) penetrates the downstream wall (28) of the casing (2) and projects outward.

FIG. 3 shows an example in which, instead of the dish-shaped ring (27) shown in FIG. 2, the upstream end (21a) of the inner pipe (21) is expanded outward to form an arc-shaped cross section in the axial direction. Another sound-absorbing double tube (19
14 shows an embodiment B).

Next, the operation will be described. The exhaust gas flowing into the casing (2) from the exhaust gas inflow pipe (11) is supplied to the first expansion chamber (6), the first contraction chamber (12), and the second expansion chamber.
(7), passing through the second contraction chamber (13), the third and fourth expansion chambers (8) and (9), and inside the outer pipe (22) of the sound-absorbing double pipe (19), 3
It flows into the contraction chamber (24). During this time, the exhaust gas repeats expansion and contraction. Thereby, the exhaust noise of the internal combustion engine is reduced.

Further, the exhaust gas passes through the inner pipe (21) and is released to the outside air. When exhaust gas passes through the inner pipe (21), noise that could not be reduced until then;
The next generated sound is absorbed by the sound absorbing member (23) exposed in the ventilation hole (20).

By the way, since the exhaust gas introduction part which is the upstream end (22a) of the outer pipe (22) is larger than the diameter of the inner pipe (21),
The outer pipe ventilation hole (25) has a larger total area than the conventional inner pipe ventilation hole. Therefore, even if the exhaust gas introduction part is shortened, the pressure loss of the exhaust gas is maintained substantially the same as in the related art, and the length of the sound absorbing member (23) can be increased by the shortened exhaust gas introduction part. Therefore, the silencer (1A) shown in FIG.
And a muffler (not shown) using the sound-absorbing double tube (19B) of FIG. 3 instead of the sound-muffling double tube (19A) of the muffler (1A).
The noise reduction effect can be enhanced without increasing the size and keeping the same dimensions.

The sound deadening double pipe shown in FIG. 2 and FIG.
(19) When (19A) is provided in the casing (2) with the distance between the third partition plate (5) and the downstream wall (18) and the length of the sound absorbing member (23) being the same as the conventional case, The number of outer pipe ventilation holes (25) drilled in the outer pipe (22) increases as much as the pipe diameter of the exhaust gas introduction section becomes larger than before, thereby reducing pressure loss and reducing exhaust gas flow. The flow can be improved to prevent the occurrence of secondary generation noise.

A silencer (1B) of another embodiment shown in FIG.
Is a sound-absorbing double tube (19
C), and the sound absorbing double pipe (19C) is provided with an exhaust gas introduction part (31a) of an outer pipe (31) outside the sound absorbing member (23).
The diameter of the sound-absorbing member (23) is enlarged to be larger than the diameter of the sound-absorbing member (23), and the peripheral area of the enlarged diameter portion is the same as that of the equivalent portion in FIGS.
The number of ventilation holes (25) formed there is made equal, thereby effectively shortening the length of the exhaust gas introduction part (31a) and making the sound absorbing member (23) longer by the shortened length. I have.

This silencer (19C) also has an enhanced silencing effect as much as the length of the sound absorbing member (23) is longer than the length of the sound absorbing member (23) in FIG. Also, the exhaust gas introduction section
If (31a) is not shortened so as to be equivalent to FIGS. 2 and 3 described above, the number of ventilation holes (25) in the exhaust gas introduction section (31a) increases,
The silencing effect is enhanced, and the pressure loss can be reduced.

A silencer (1C) of another embodiment shown in FIG.
Connects the exhaust gas inlet pipe (11A) and the sound-absorbing double pipe body (19D)
The axis crosses the casing (2A) at right angles. The sound-absorbing double pipe (19D) of this embodiment has the sound-absorbing double pipe shown in FIGS. 2 and 3 except that the exhaust gas output end (21C) of the inner pipe (21) is slightly bent. The pipes (19A) and (19B) have the same structure. In this example, the sound absorbing double pipe (19A) is used.
Part D of the outer tube (22) and the sound absorbing member (23) into the casing (2)
By protruding outside, the length of the casing (2A) in the longitudinal direction of the casing (2A) is shorter than that of the silencers (1A) (1B) shown in FIGS. 1 and 4.

[0029]

According to the first aspect of the present invention, since the vent hole is formed in the outer tube having a diameter larger than that of the inner tube, the sound absorbing member can be lengthened without increasing the shape and pressure loss of the muffler. The effect can be enhanced and noise can be reliably reduced.

When the upstream end of the inner pipe is formed in an arc shape as in the second aspect of the present invention, the flow of exhaust gas can be made smooth and the generation of secondary noise can be prevented.

According to the third aspect of the present invention, when the diameter of the exhaust gas introduction portion is made larger than the diameter of the other portion of the outer tube and the expansion chamber is formed in the outer tube, the total area of the ventilation holes is increased. Therefore, the pressure loss of the muffler can be reduced, the flow of the exhaust gas can be improved, and the generation of the secondary sound can be prevented. Further, since the length of the sound absorbing member can be increased by shortening the exhaust gas introduction section, the sound absorbing effect can be enhanced and the noise of the exhaust gas can be reduced.

When the sound-absorbing double tube crosses the casing as in the invention of claim 4, the downstream end of the outer tube and the sound-absorbing member can be projected outside the casing, and the casing can be made thin. Thus, the silencer can be made smaller.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view of a silencer for an internal combustion engine according to an embodiment of the present invention, which is broken along a longitudinal direction.

FIG. 2 is an enlarged vertical sectional front view of the sound-absorbing double pipe body of FIG.

FIG. 3 is an enlarged vertical sectional front view of a sound-absorbing double tube of another embodiment.

FIG. 4 is a schematic longitudinal sectional view of a silencer for an internal combustion engine according to another embodiment, which is cut along a longitudinal direction.

FIG. 5 is a schematic longitudinal sectional view of a silencer for an internal combustion engine according to another embodiment, which is cut along a longitudinal direction.

FIG. 6 is a schematic longitudinal sectional view of a conventional silencer for an internal combustion engine, which is cut along a longitudinal direction.

FIG. 7 is an enlarged vertical sectional front view of the sound-absorbing double pipe of FIG.

[Explanation of symbols]

 (1) (1A) (1B) (1C) silencer (2) (2A) casing (3) first partition plate (4) second partition plate (5) third partition plate (6) first expansion chamber ( 7) Second expansion chamber car (8) Third expansion chamber (9) Fourth expansion chamber (10) Upstream wall (11) Exhaust gas inflow pipe (11a) Upstream end (11b) Downstream end (12) First Shrinkage chamber (12a) Upstream end (12b) Downstream end (13) Second shrinkage chamber (13a) Upstream end (13b) Downstream end (14) Vent (15) Vent (16) Vent (17 ) Through hole (18) Downstream wall (19) (19A) (19B) (19C) (19D) Sound absorbing double pipe (20) Vent (21) Inner pipe (21a) Upstream end (exhaust gas introduction part) (21b) Downstream end (22) Outer pipe (22a) Upstream end (22b) Downstream end (22c) Exhaust gas introduction part (23) Sound absorbing member (24) Third shrinkage chamber (25) Outer pipe vent ( 26) End plate (27) Dish ring (28) Downstream wall (31) Outer pipe (31a) Exhaust gas inlet

Claims (4)

[Claims] An internal pipe through which a plurality of ventilation holes are formed in an outer periphery and an exhaust gas passes through the inside of a casing having an expansion chamber and a contraction chamber through which exhaust gas of an internal combustion engine passes; A muffler for an internal combustion engine including an outer pipe provided on the outer periphery and a sound absorbing double pipe body including a sound absorbing member provided between the inner pipe and the outer pipe, wherein an upstream end of the outer pipe is connected to the inner pipe. A muffler for an internal combustion engine, wherein a porous exhaust gas introduction portion is formed in the outer tube so as to extend upstream from an upstream end of the tube. 2. The axial cross section of the upstream end of the inner tube is
2. The muffler for an internal combustion engine according to claim 1, wherein the muffler has an arc shape spreading toward the upstream side. 3. The muffler for an internal combustion engine according to claim 1, wherein the diameter of the exhaust gas introduction portion is larger than the diameter of the other portion of the outer tube, and the expansion chamber is formed in the outer tube. 4. The muffler for an internal combustion engine according to claim 1, wherein an axis of the double sound-absorbing double pipe crosses the casing.