JP4317702B2 - Silencer for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a silencer for an internal combustion engine in which a cylindrical portion of a shell has a double cylinder structure.
[0002]
[Prior art]
In general, a silencer for an internal combustion engine includes a cylindrical portion that is open at both ends, a shell including end plates that respectively close the open ends of the cylindrical portion, an inlet pipe that is disposed through one end plate, and the other. And an outlet pipe disposed through the end plate. And exhaust gas discharged from the engine is introduced into the shell from the inlet pipe to reduce the exhaust noise, and then discharged from the outlet pipe to the outside air.
[0003]
By the way, the exhaust sound of the exhaust gas introduced into the shell is considerably loud. Therefore, in order to avoid the exhaust sound from propagating from the shell to the outside, some conventional silencers have a double cylinder structure in which the cylindrical portion of the shell is composed of an inner cylinder and an outer cylinder (for example, patents). Reference 1).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-82125 (page 3, column 3, FIG. 1)
[0005]
[Problems to be solved by the invention]
However, when the cylindrical portion of the shell has a double cylinder structure, water may accumulate at the lowest point between the inner cylinder and the outer cylinder. That is, moisture contained in the exhaust gas is condensed and attached to the inner peripheral surface of the inner cylinder. Further, moisture contained in the outside air is condensed and attached to the outer peripheral surface of the outer cylinder. In the case of the water described in Patent Document 1, for example, these waters enter between the inner cylinder and the outer cylinder from the lock seam portion by capillary action. The inner cylinder and the outer cylinder are manufactured so as to be in press contact over substantially the entire circumference, but in reality, there are slight gaps in each part between them. Water that has entered the space between the inner cylinder and the outer cylinder from the lock seam portion accumulates in the gap that exists at the lowest position among these gaps. The accumulated water evaporates explosively when the shell is heated to high noise by exhaust gas after the engine is started. And there existed a possibility of deform | transforming so that the lower part of an outer cylinder may bulge below with the pressure of water vapor | steam. In particular, when the shell has a polygonal cross section, the inner cylinder and the outer cylinder are strongly adhered to each other at the corner, and the airtightness of the corner is increased. For this reason, the clearance gap which exists between the inner cylinder and outer cylinder located in the lower side part of a shell is sealed with high airtightness by two adjacent corner | angular parts. As a result, there is a problem that the pressure of the water vapor becomes higher and the outer cylinder is deformed more greatly.
[0006]
[Means for Solving the Problems]
The present invention has been made to solve the above-described problem. The cylindrical portion of the shell has an inner cylinder whose axis is oriented in a substantially horizontal direction, and an outer cylinder that is in contact with the outer periphery of the inner cylinder over almost the entire circumference. In the silencer for an internal combustion engine formed in a double cylinder structure, the relief extends upward along the circumferential direction from the lower part of the shell between the outer peripheral surface of the inner cylinder and the inner peripheral surface of the outer cylinder. A passage is formed, a through hole is formed at a position higher than a predetermined position of the inner cylinder, and an upper end portion of the escape passage is communicated with the through hole.
In this case, the shell has a polygonal cross-section, and the escape passage extends upward from the lower side of the shell through one corner adjacent to the lower side, with respect to the one corner. It is desirable that the through hole is formed in a side portion of the inner cylinder adjacent to the upper side.
The escape passage may be constituted by a recess formed along at least one of the outer peripheral surface of the inner cylinder and the inner peripheral surface of the outer cylinder along the circumferential direction, and the other facing the recess. Alternatively, at least one of the outer peripheral surface of the inner cylinder and the inner peripheral surface of the outer cylinder is formed along the circumferential direction, and a convex portion whose tip is pressed against the other, and one adjacent to the convex portion, and Further, it may be configured by a pressing contact portion with the tip of the convex portion and the other between the one portion and the portion in press contact with the portion away from the convex portion.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
1 to 5 show an embodiment of the present invention. As shown in FIG. 1, the silencer 1 for an internal combustion engine according to this embodiment includes a shell 2, an inlet pipe 3, and an outlet pipe 4 as main components.
[0008]
The shell 2 has a cylindrical portion 2A that is open at both ends, and end plates 2B and 2C that hermetically shield the both-end openings of the cylindrical portion 2A. As shown in FIG. 2, the cylindrical portion 2 </ b> A has a substantially right-angled cross section, and has a corner portion 2 a that is curved at a substantially right angle and two corner portions 2 b and 2 c that are curved at an acute angle. The cylindrical portion 2A is arranged such that the corner portions 2a and 2b are located at substantially the same height, and the remaining corner portion 2c is located at the uppermost side. The lower side 2d formed between the two corners 2a and 2b is curved so as to bulge downward with a large curvature radius, and the middle part of the corners 2a and 2b is positioned on the lowermost side. ing. The cylindrical portion 2A may be formed in other cross-sectional shapes. For example, it may be formed in an elliptical cross section or a rectangular cross section that is long in the horizontal direction.
[0009]
As shown in FIG. 1, a partition wall 2 </ b> D is provided at an intermediate portion in the axial direction (left-right direction in FIG. 1) of the inner peripheral surface of the cylindrical portion 2 </ b> A. The partition 2D divides the inside of the shell 2 into a first chamber 2E and a second chamber 2F. The first chamber 2E and the second chamber 2F are communicated with each other through a communication hole 2G formed in the partition wall 2D. In the case of this embodiment, only one communication hole 2G is formed, but a plurality of small holes smaller than the communication hole 2G are formed, and the first chamber 2E and the second chamber 2F are passed through the small holes. May be communicated with each other.
[0010]
The end plates 2B and 2C are airtightly fixed to the one end opening and the other end opening of the cylindrical portion 2A by winding or welding, respectively. As shown in FIG. 1, the inlet pipe 3 is airtightly fixed to the end plate 2 </ b> B in a penetrating state. The inlet pipe 3 extends through the second chamber 2F and the partition wall 2D to the first chamber 2E. Therefore, the exhaust gas discharged from the engine (not shown) is introduced into the first chamber 2E through the inlet pipe 3. An outlet pipe 4 is airtightly fixed to the end plate 2C in a penetrating state. The outlet pipe 4 extends through the first chamber 2E and the partition wall 2D to the second chamber 2F. Therefore, the exhaust gas flowing into the second chamber 2F from the first chamber 2E through the communication hole 2G is discharged to the outside air through the outlet pipe 4.
[0011]
As shown in FIG. 4, the cylinder portion 2 </ b> A is formed in a double cylinder structure by a metallic inner cylinder 21 and an outer cylinder 22. The inner cylinder 21 constitutes the inner peripheral surface of the cylinder portion 2A. The outer cylinder 22 constitutes the outer peripheral surface of the cylinder portion 2A. The inner peripheral surface of the outer cylinder 22 is brought into press contact with the outer peripheral surface of the inner cylinder 21 over substantially the whole. The outer cylinder 22 is pressed and contacted more strongly with the outer peripheral surface of the inner cylinder 21 at each corner 2a, 2b, 2c than the other parts.
[0012]
The cylinder portion 2A having a double cylinder structure can be manufactured, for example, by the method shown in FIG. The manufacturing method shown in FIG. 3 is such that a cylindrical portion 2A having a double cylindrical structure is manufactured by a single metal plate 5, and the metal plate 5 is a core metal (not shown) having a circular cross section. It is wound twice in a state where it is strongly pressed against the outer periphery of the. In this case, the winding is started until the winding start end 5a and the winding end 5b overlap each other. Therefore, a portion where the winding start end 5a and the winding end end 5b overlap has a triple structure. Thereafter, the winding start end 5a and the winding end end 5b are fixed by spot welding or the like. As a result, a double cylinder having a circular cross section is formed. After that, the double cylinder is formed into a predetermined cross-sectional shape shown in FIG. Here, when welding the winding start end 5a and the winding end 5b, if welding is performed over their entire length (the entire length of the cylindrical portion 2A), water such as condensed water enters between the inner cylinder 21 and the outer cylinder 22. Can be reliably prevented. However, such welding is very difficult and requires a lot of labor. As a result, the manufacturing cost of the cylinder portion 2A is significantly increased. Therefore, spot welding is usually employed.
The cylindrical portion 2A may be manufactured by a method other than the manufacturing method shown in FIG. 3, for example, the method described in Patent Document 1 above, or the ends of two superimposed metal plates are tightened together. (Lock seam).
[0013]
As shown in FIG. 4, a convex portion 22 a extending in the circumferential direction is formed on the outer peripheral surface of the outer cylinder 22 by bending the metal plate constituting the outer cylinder 22 so as to bulge outward. A recess 22 b is formed on the inner peripheral surface of 22. As shown in FIGS. 1 and 5, a plurality of convex portions 22 a and concave portions 22 b are formed apart from each other in the axial direction (longitudinal direction) of the silencer 1. The convex portions 22a and the concave portions 22b are formed in a trapezoidal cross section, but may be formed in other cross sectional shapes. For example, it may be formed in a semicircular cross section or a square cross section. Instead of the convex portions 22a and concave portions 22b, or the same time, by bending so as to bulge toward the metal plate constituting the inner cylinder 21 inward, a recess in the outer peripheral surface of the inner cylinder 21, the inner peripheral surface You may form a convex part , respectively. When the recess 22b is formed in the outer cylinder 22 and the recess is formed in the inner cylinder 21, the recess formed in the inner cylinder 21 may be opposed to the recess 22b formed in the outer cylinder 22. They may be separated from one another in the axial direction (longitudinal direction).
[0014]
The recess 22b formed on the inner peripheral surface of the outer cylinder 22 is closed by the outer peripheral surface of the inner cylinder 21 facing the recess 22b, whereby the inner peripheral surface of the outer cylinder 22 and the outer peripheral surface of the inner cylinder 21 are closed. An escape passage 6 extending in the circumferential direction is formed therebetween. The escape passage 6 is formed over a range indicated by Z in FIG. More specifically, as shown in FIG. 4, the escape passage 6 has a corner portion 2a as a substantially central portion and extends therefrom in the circumferential direction of the cylindrical portion 2A. One end portion 6a of the escape passage 6 extends from the corner portion 2a toward the other corner portion 2b (see Fig. 2) side of the lower side portion 2d, and is the most of the lower side portion 2d in a cross section orthogonal to the axis of the cylindrical portion 2A. It passes through the lower part. The one end portion 6a may be fastened to the lowermost portion of the lower side portion 2d. The other end portion (upper end portion) 6b of the escape passage 6 extends above a predetermined height indicated by the highest water level line L shown in FIGS. In particular, in this embodiment, it extends to a substantially central portion of a vertical side portion (side side portion) 2e extending substantially vertically upward from the corner portion 2a. If the other end 6b of the escape passage 6 is above the maximum water level line L, it may be stopped in the middle of the corner 2a. The highest water level line L indicates the water level when the most water has accumulated in the silencer 1, and when the water tries to accumulate above the water level line L, the water passes through the outlet pipe 4. Discharged outside. Therefore, water does not accumulate in the silencer 1 beyond the maximum water level line L.
[0015]
As shown in FIG. 4, a through hole 7 is formed at a location corresponding to the vertical side 2 e of the inner cylinder 21. The through hole 7 is disposed so as to face the other end portion 6 b of the escape passage 6. Therefore, the through hole 7 is in direct communication with the escape passage 6. The through-hole 7 may be disposed slightly apart from the escape passage 6 in the circumferential direction or the axial direction of the cylindrical portion 2 </ b> A without directly communicating with the escape passage 6. However, in that case, the through-hole 7 communicates with the escape passage 6 through a gap existing between the outer peripheral surface of the inner cylinder 21 and the outer peripheral surface of the outer cylinder 22 or the outer peripheral surface of the inner cylinder 21. When a gap is formed between the outer peripheral surface of the inner cylinder 21 and the inner peripheral surface of the outer cylinder 22 by the pressure of water vapor from which water between the outer cylinder 22 and the outer peripheral surface of the outer cylinder 22 evaporates, it escapes through the gap. It is necessary to configure to communicate with the passage 6. In any case, the through hole 7 is disposed above the highest water level line L. This is to prevent water accumulated in the silencer 1 from entering between the inner cylinder 21 and the outer cylinder 22 through the through hole 7. The through hole 7 may be formed at a location corresponding to the hypotenuse 2f (see FIG. 2) formed between the corners 2b, 2c of the inner cylinder 21. In that case, the other end portion 6b of the escape passage 6 extends through the corner portion 2b to the middle portion of the oblique side portion 2f and communicates with the through hole 7 formed in the oblique side portion 2f.
[0016]
In the silencer 1 having the above-described configuration, it is assumed that water accumulated between the inner cylinder 21 and the outer cylinder 22 in the lower side portion 2d has evaporated explosively. In this case, when water has accumulated in the escape passage 6, the water vapor expands in the escape passage 6 and flows from the one end portion 6 a to the other end portion 6 b side. Further, when water is accumulated between two escape passages 6 adjacent to each other in the axial direction of the cylinder portion 2A, the evaporated water vapor slightly deforms toward the inner cylinder 21 toward the inside and the outer cylinder 22 toward the outside. By doing so, a gap is formed between the outer peripheral surface of the inner cylinder 21 and the outer peripheral surface of the outer cylinder 22 and reaches the one end portion 6 a of the passage 6 through the gap. And it flows in the escape passage 6 from one end 6a to the other end 6b. In any case, the water vapor that reaches the other end 6 b of the escape passage 6 enters the silencer 1 from the through hole 7. Then, it is discharged from the outlet pipe 4 together with the exhaust gas to the outside air. Therefore, the part located in the lower side 2d of the outer cylinder 22 is not bulged and deformed downward by high-pressure steam.
[0017]
If the water vapor generated by evaporation of water accumulated between the inner cylinder 21 and the outer cylinder 22 corresponding to the lower side portion 2d is only allowed to flow into the silencer 1, the inner cylinder located at the lower side portion 2d. The through-hole 7 should just be formed in the location located in the lowest side in 21. However, in this case, the water accumulated in the silencer 1 not only enters the space between the inner cylinder 21 and the outer cylinder 22 through the through hole 7, but also a portion facing the through hole 7 of the outer cylinder 22. Always exposed to water, especially exhaust gas condensate. As a result, there arises a problem that the outer cylinder 22 corrodes early and the life of the silencer 1 is shortened. Of course, even when the through hole 7 is not formed in the lower part of the inner cylinder 21, if the part corresponding to the lower side 2d of the inner cylinder 21 is corroded by condensed water and the hole is opened, the outer cylinder 22 is corroded. The part facing the hole is corroded by the condensed water, and the hole becomes clear. However, in this case, the outer cylinder 22 is not corroded unless the inner cylinder 21 is corroded by the condensed water to form a hole. Therefore, the service life of the silencer 1 can be significantly improved as compared with the case where a through hole is formed in the lower portion of the inner cylinder 21.
[0018]
FIG. 6 shows a second embodiment of the present invention. In this embodiment, a pair of convex portions 21 a and 21 a extending in the circumferential direction are formed on the outer peripheral surface of the inner cylinder 21 by bending the metal plate constituting the inner cylinder 21 so as to protrude outward. The pair of convex portions 21a and 21a are disposed away from each other in the axial direction of the cylindrical portion 2A. Moreover, the pair of convex portions 21a and 21a are located at the lowermost side in the center of the convex portions 21a and 21a with respect to the axial direction of the cylindrical portion 2A, and are identical to the convex portions 22a of the above-described embodiment in the circumferential direction. It is arranged to be located. The inner peripheral surface of the outer cylinder 22 is in press contact with the lower surface (tip surface) of each convex portion 21a, and the inner peripheral surface of the outer cylinder 22 located between the pair of convex portions 21a, 21a is the inner peripheral surface of the inner cylinder 21. It is separated downward from the outer peripheral surface by the height of the convex portion 21a. As a result, a relief passage 8 extending in the circumferential direction is formed by the pair of convex portions 21a, 21a and the outer peripheral surface of the inner cylinder 21 and the inner peripheral surface of the outer cylinder 22 positioned therebetween. The relief passage 8 is arranged at the same position as the escape passage 6 in the circumferential direction, as is apparent from the arrangement relationship of the pair of convex portions 21a, 21a, and the lower side portion 2d of the silencer 1 in the axial direction. Arranged at the lowest position. The upper end portion (other end portion) of the escape passage 8 is also communicated with the through hole 7 formed in the inner cylinder 21 corresponding to the intermediate portion in the vertical direction of the vertical side portion 2e. Therefore, also in this embodiment, it is possible to prevent the lower portion of the outer cylinder 22 from being deformed so as to bulge downward by water vapor.
[0019]
Moreover, in this embodiment, two escape passages 9 other than the escape passage 8 are formed by forming the pair of convex portions 21a and 21a. That is, the inner peripheral surface of the outer cylinder 22 that runs along the axis line from the tip of each convex portion 21a to the cylindrical portion 2A and goes to the opposite side of the passage 8 approaches the outer peripheral surface of the inner cylinder 21 as the distance from the convex portion 21a increases. Then, it is in press contact with the inner peripheral surface of the inner cylinder 21 at a position separated by a predetermined distance. As a result, the convex portion 21 a, the outer peripheral surface of the inner cylinder 21, and the inner peripheral surface of the outer cylinder 22 form a space whose width decreases as the distance from the convex portion 21 a increases, and this space becomes the escape passage 9. Yes. Of course, the escape passage 9 is disposed at the same position as the escape passage 8 in the circumferential direction of the cylinder portion 2A, and communicates with a through hole formed in the inner cylinder 21 at the upper end portion (the other end portion). . In this case, the through hole through which the escape passage 9 communicates may be the through hole 7 or another through hole formed separately.
[0020]
In this embodiment, only one pair of convex portions 21a is formed, but a plurality of pairs may be formed, and thereby the escape passages 8 may be formed in the same number as the number of pairs of convex portions 21a. Alternatively, three or more convex portions 21a are not formed as a pair, and the inner peripheral surface of the outer cylinder 22 between the two convex portions 21a and 21a adjacent to each other in the axial direction of the cylindrical portion 2A is the inner cylinder 21. (N-1) relief passages 8 may be formed when the number of convex portions 21a is n.
[0021]
【The invention's effect】
As described above, according to the present invention, the water that has entered between the inner cylinder and the outer cylinder evaporates explosively, so that the lower portion of the outer cylinder bulges downward. The effect that it can prevent is acquired.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a front view showing a part of an embodiment of the present invention with a part cut away.
FIG. 2 is a cross-sectional view taken along line XX in FIG.
3 is a cross-sectional view similar to FIG. 2, showing a method for manufacturing the cylindrical portion used in the embodiment. FIG.
4 is an enlarged view of a range indicated by a symbol Z in FIG.
5 is a cross-sectional view taken along line XX of FIG.
FIG. 6 is a cross-sectional view similar to FIG. 5 showing a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Silencer for internal combustion engines 2 Shell 2A Tube portion 2a Corner portion (one corner portion)
2d Lower side 2e Vertical side (side)
6 Escape passage 6b The other end (upper end)
21 Inner cylinder 21a Convex part 22 Outer cylinder 22b Concave part 7 Through hole 8 Relief passage 9 Relief passage

Claims (2)

In the silencer for an internal combustion engine in which the cylindrical portion of the shell is formed in a double cylinder structure by an inner cylinder whose axis is oriented in a substantially horizontal direction and an outer cylinder that is in contact with the outer periphery of the inner cylinder almost entirely .
An escape passage extending upward in the circumferential direction from the lower portion of the shell is formed between the outer peripheral surface of the inner cylinder and the inner peripheral surface of the outer cylinder, and penetrates to a location higher than a predetermined position of the inner cylinder Forming a hole, communicating the upper end of the escape passage with the through hole ,
The escape passage is constituted by a recess formed along at least one of the outer peripheral surface of the inner cylinder and the inner peripheral surface of the outer cylinder along the circumferential direction, and the other facing the recess. Silencer for internal combustion engine.   The shell has a polygonal cross section, and the escape passage extends upward from the lower side of the shell through one corner adjacent to the lower side, and is adjacent to the upper side with respect to the one corner. 2. The silencer for an internal combustion engine according to claim 1, wherein the through hole is formed in a side portion of the inner cylinder.

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