JP3450296B2 - Stress relief structure for two-pass exhaust pipe - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-passage type exhaust pipe in a multi-cylinder engine, which is capable of performing exhaust while avoiding interference of exhaust generated between cylinders.

[0002]

2. Description of the Related Art Although the pipe shown in FIG. 5 is a conventionally known double pipe, a θ pipe P having a θ shape and having two exhaust passages is used as an inner pipe (as an example). JP-A-9
-192727). The θ pipe P forms peripheral wall parts b and b from both edges of the partition wall part a by bending a predetermined part of the peripheral wall part at a substantially right angle and then forming a peripheral wall parts b and b from the end parts of the peripheral wall parts b and b. The short connecting piece c is bent at a substantially right angle, and the connecting piece c is welded to the partition wall a at the welded portion e to make the outer surface substantially circular, thereby forming two semicircular passages d and d.

In this type of θ pipe P, it is common to weld the connecting portion between the partition wall portion a and the peripheral wall portion b at a substantially right angle as described above so that the cross-sectional areas of the passages d and d do not become small. ,
The outer surface of the welded portion e is located outside the virtual inner diameter surface of the peripheral wall portion b and is substantially continuous with the outer peripheral surface of the peripheral wall portion b.

[0004]

When the above-mentioned θ pipe P is used as an exhaust pipe of a multi-cylinder engine, when exhaust gas passes through a passage d on the right side in the figure, the partition wall a is moved to the left side by the exhaust pressure.
When the exhaust passes through the passage d on the left side as shown by 1 and bends to the right side as shown by a2, the two passages d,
Due to the pulsation of the exhaust gas that alternately passes through d, the partition wall a alternately bends and vibrates in the opposite direction as indicated by a1 and a2. This bending uses the welded portion e of the connection piece c and the partition wall a or the inside thereof as a bending point, and bending stress concentrates at this bending point, and fatigue occurs here when vibration continues. An object of the present invention is to reduce the concentration of bending stress and fatigue.

[0005]

Means for solving the above-mentioned problems are as described in each claim, and in claim 1, two passages are formed by a partition wall portion and peripheral wall portions on both sides thereof. The two-passage exhaust pipe was bent at both ends
A single bent metal plate member is used to divide the partition wall and the circumference of both sides.
A wall portion is formed, and the partition wall portion and the peripheral wall portion define a valley portion.
Form, the contacts of the partition wall portion and the peripheral wall portion causes located inside from the inner virtual line of the peripheral wall, the peripheral wall portion defining a valley portion
The valley wall of is formed by the curved surface on the side of the peripheral wall and the flat surface following it.
However, the vicinity of the contact points of the valley walls is welded . According to the means of this, since the dimension of the partition wall between the two contacts of the partition wall and the peripheral wall portion is smaller than that without the valley, the total pressure is reduced which acts on the partition wall from the exhaust, As a result, the deflection of the partition wall due to the exhaust pressure is reduced, so that the stress concentration at the contact point between the partition wall and the peripheral wall portion is alleviated, and the durability is increased.

As a method of manufacturing a two-passage exhaust pipe having a partition wall and a peripheral wall, a plurality of plate members having a desired shape are formed rather than extrusion molding, draw molding, casting, etc. for forming the partition wall and the peripheral wall. It is cheap and common to position and weld the outer longitudinal sides to each other, but not easy to position. However, according to this means, since one plate is bent and the troughs are welded, positioning and holding of the plates are easier than the manufacturing method in which a plurality of plates extending in the longitudinal direction are positioned and welded in the longitudinal direction. The equipment is simple and the welding is easy and the productivity is improved. Further, the mutual contact between the valley walls is at the bottom of the valley formed inside from the inner virtual line of the peripheral wall, and the vicinity thereof is welded, so that the weld bead does not project to the outside of the peripheral wall. Further, since the valley wall is formed by the curved surface portion on the peripheral wall side and the flat surface portion following the curved surface, the flow passage cross-sectional area can be increased and weldability can be improved compared to the case where the valley portion is composed of only curved surfaces. improves.

[0007] According to claim 2, in claim 1, the maximum width of the valley and is W, the maximum depth of the valley as d, the dimensional ratio of the valley, characterized in that the d / W <2 . According to the measure of this, inexpensive TIG, it is possible to the welding operation MIG like from valley side. If this range is exceeded, TIG,
Since the welding torch such as MIG does not enter, it is difficult to weld from the valley side.

According to claim 3 , in claim 1 or 2 ,
Let L be the depth of the valley and D be the virtual inner diameter inside the peripheral wall, and L
/D≧0.05. According to this means, the stress concentration at the contact point between the partition wall portion and the peripheral wall portion can be reliably alleviated.

A fourth aspect of the present invention is characterized in that, in the first, second, and third aspects, the bending rigidity of the central portion of the partition wall portion is larger than that of both end portions of the partition wall portion. According to this means
The bending of the partition wall is reduced, and the stress can be reduced.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1 , 1 is a two-passage exhaust pipe of the present invention, 2 is a planar partition wall portion, 3 and 4 are peripheral wall portions having a substantially semicircular cross section. Between the peripheral wall portions 3, 4 and the partition wall portion 2, the valley wall 5, 6, 7, 8 inclined with respect to the partition wall portion 2 is formed.
Is formed as a part of the peripheral wall portions 3, 4, and the valley wall 5,
Reference numerals 6, 7, and 8 denote curved surface portions 5 provided on the main portion side of the peripheral wall portions 3 and 4.
a, 6a, 7a, 8a and the flat surface portions 5b, 6 on the partition wall 2 side
b, 7b, 8b, and independent passages 1 welded at joints 9 and 10 along the contact points of a pair of valley walls and partition walls
1 and 12 are formed, and a valley 13 is formed between the opposing valley walls. The two-passage exhaust pipe 1 of FIG. 1 is formed by bending one plate material.

A passage 11 formed of a partition wall and a peripheral wall,
If 12 is a substantially semicircular section as shown in the drawing, the cross section of the two-passage exhaust pipe will be substantially circular, and there is no restriction on the direction of bending and the flexibility of bending is high, which is desirable. Other shapes such as a substantially square shape may be used. In the embodiment shown in FIG. 1 , since the peripheral wall portions 3 and 4 have a substantially semicircular shape, the inner virtual line of the peripheral wall portions 3 and 4 has a substantially semicircular shape indicated by the virtual inner diameter D.

When the exhaust pipe 1 is attached to a multi-cylinder engine and the engine is operated, the pressure of both passages fluctuates oppositely due to the pulsation of the exhaust gas that alternately passes through the two passages 11 and 12, and the partition wall portion 2 Due to the pressure difference between the two passages, as shown by 2a and 2b in FIG. 1 , the operation of bending in an arc shape from the high pressure side to the low pressure side is alternately repeated with the vicinity of the welded portions 9 and 10 as a bending point. The radial width of the partition wall portion 2 is narrower than the conventional width by twice the distance L from the contact point between the partition wall portion and the peripheral wall portion to the maximum inner position in the partition wall direction in the peripheral wall portion. Since the pressure receiving area of 2 is narrowed and the total pressure acting from the exhaust is reduced, the bending near the contact is reduced and the valley walls 5, 6, 7, 8 are also slightly curved, so that bending stress and stress near the contact are reduced. Concentration is eased,
Increases durability.

In the above embodiment, the virtual inner diameter of the two-passage exhaust pipe 1 is D, the depth from the virtual inner diameter surface to the joints 9 and 10 is L, and the outer ends of the curved surface portions 5a and 8a of the trough walls facing each other. The distance between the outer ends of the spaces 6a and 7a is W, and the depth from the outer end to the joints 9 and 10 is d. Upon verification, the data shown in FIG. 4 was obtained. In FIG. 4 , increasing the valley depth L can reduce the stress as compared with the case of L = 0 in which no valley is provided, and the stress can be remarkably increased as compared with the conventional example shown in FIG. Can be reduced.

The depth L of the valley portion is 5% or more of the virtual inner diameter D,
That is, when L / D ≧ 0.05, the stress in the vicinity of the joint can be reliably reduced. As a result, the material plate can be made thinner and the exhaust pipe can be made lighter,
When the engine is started, the temperature of the exhaust pipe rises in a short time, and the high temperature exhaust gas can be sent to the catalyst at an early stage.

A general stainless steel material JI as a plate material
When L / D ≧ 0.05 using SSUS430J1L, the stress could be reduced by 10% or more as compared with the case where L / D was close to 0. Also, assuming that the time for the catalyst activation temperature to reach the catalyst activation temperature is x seconds for a plate thickness t, it is 0.9x seconds when the plate thickness is 0.8t, and 0.77x when the plate thickness is 0.6t. Seconds, which is activated early to improve purification performance.

If this L or d is too large, the passages 11, 1
If the cross-sectional area of 2 is reduced and W is too small, MIG, TIG
Since it is impossible to perform inexpensive welding work such as the above from the valley side, it is desirable that d / W <2. Further, it is more preferable that 0.5 <d / W <2, which is a substantially acute angle in which the spread of the welded portion to the outside can be easily regulated and positioning can be easily performed.

Further, it is desirable that the valley wall is formed by a curved surface portion on the side of the peripheral wall portion and a flat surface portion following the curved surface portion. As compared with curved surface portions 5c and 8c shown by phantom lines in FIG. 1 , which are formed by only curved surface portions without providing flat portions, the cross-sectional area of the flow path can be increased, and from the valley side in the vicinity of the joint portion 9. Has good weldability.

The second passage exhaust pipe 15 shown as another embodiment in FIG. 2 is obtained by the inner or central portion and the thick partition wall portion 16 than the contact in the second passage exhaust pipe of FIG. 1, thereby partition wall The bending rigidity of the central portion of the partition wall is increased, the bending of the partition wall portion is reduced, and the stress can be reduced.

In the two-passage exhaust pipe 18 shown in FIG. 3 , ribs 19a in the width direction, that is, the diametrical direction of the pipe are provided at intervals in the partition wall to form the ribbed partition wall portion 19. According to this, The bending rigidity of the partition wall in the width direction is improved, the deflection of the partition wall is reduced, and the stress can be reduced. The portions to be the thick wall partition 16 and the ribbed partition 19 are formed in advance on the plate material before bending the peripheral walls 3, 4.

[0020]

According to the first aspect of the present invention, since the trough wall is provided in the peripheral wall portion to narrow the width of the partition wall portion, the total pressure acting on the partition wall portion from the exhaust gas is reduced, and the peripheral wall portion and the trough portion are reduced. Stress concentration near the contact points on the wall is relieved and durability is increased,
It is possible to use a thin plate material, which allows the weight of the exhaust pipe to be reduced, which reduces heat transfer at engine start, increases the temperature early and accelerates catalyst activation, improving purification performance. Has the effect of

Further , since the exhaust pipe is formed by bending a single plate, the positioning and holding of the plate is easy, the device is simple and the welding is easy, and the productivity is improved. Also, the contact points between the valley walls are at the bottom of the valley formed inside from the inner virtual line of the peripheral wall, and the vicinity is welded, so the weld bead does not project to the outside of the peripheral wall and impairs the appearance. There is no. Further, since the weld bead does not come into contact with the jig of the bending apparatus for the two-pass exhaust pipe, the jig can be held uniformly and a two-pass exhaust pipe with high bending accuracy can be obtained. It
In addition, the volume of the valley can be reduced while maintaining a space where welding can be performed, and the cross-sectional area of the flow path can be increased compared to the case where the valley is composed of only curved surfaces, which improves weldability. is there.

According to the means of the second aspect , the width of the valley portion is effective in ensuring that the welding work of MIG, TIG or the like, which is an inexpensive welding means, is possible from the valley portion side.

According to the third aspect of the invention, there is an effect that the stress concentration near the contact point between the peripheral wall portion and the partition wall portion is surely relieved.

According to the means of the fourth aspect , the bending rigidity of the central portion of the partition wall portion is made larger than that of the both end portions, so that the bending of the partition wall portion can be reduced and the stress can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a perspective view showing another embodiment.

FIG. 3 is a perspective view showing still another embodiment.

FIG. 4 is a diagram showing changes in stress value.

FIG. 5 is a sectional view of a conventional example.

[Explanation of symbols]

1 2 Passage Exhaust Pipe 2 Partition 3, 4 Peripheral Wall 5, 6, 7, 8 Valley Wall 9, 10 Joint 13 Valley

Front page continued (72) Inventor Hiroto Yanagibayashi Yutaka Giken, one share company at 508 Toyocho, Hamamatsu City, Shizuoka Prefecture (72) Inventor Akihiro Suzuki 1 508 Toyomachi, Hamamatsu, Shizuoka Prefecture Yutaka Giken (72) Inventor Kazuo Ishii 1-4-1 Chuo, Wako-shi, Saitama Prefectural Research Institute of Honda (72) Inventor Takeshi Somura 4-1-1 Chuo, Wako-shi, Saitama Incorporated of Honda Technical Research Institute (72) Inventor Masayuki Uekane, 1-4-1, Chuo, Wako-shi, Saitama, Ltd., Honda R & D Co., Ltd. (72) Inventor, Yoshihiko Eguchi, 1-4-1, Chuo, Wako, Saitama, Ltd. 56) References JP-A-11-294154 (JP, A) JP-A-9-209747 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F01N 7/08 F01N 7/18 F16L 9/19

Claims (4)

(57) [Claims] 1. A two-passage exhaust pipe in which two passages are formed by a partition wall and peripheral wall portions on both sides of the partition wall, and the partition wall is formed by a bent metal plate member having both ends bent.
Parts and forming a peripheral wall portion on both sides, define a valley portion by the partition wall portion and the peripheral wall portion, it is located inside the contact of the partition wall portion and the peripheral wall portion from the inner virtual line of the peripheral wall
Causes, and the curved surface portion of the valley wall peripheral portion of the peripheral wall portion defining a valley portion
A stress relief structure for a two-pass exhaust pipe, characterized in that it is formed by a flat surface portion following this, and the vicinity of the contact points of the valley walls are welded . 2. The maximum width of the valley portion according to claim 1,
The maximum depth of the valley is d, and the dimension ratio of the valley is d / W
<2 . A stress relief structure for a two-pass exhaust pipe, characterized in that 3. The depth of the valley portion according to claim 1 or 2,
L, L / D ≧ 0.0, where D is the virtual inner diameter of the peripheral wall
The structure for reducing stress of a two-pass exhaust pipe is characterized in that 4. The partition wall part according to claim 1, 2, or 3.
A stress relief structure for a two-pass exhaust pipe, characterized in that the bending rigidity of the central portion is made larger than that of both end portions of the partition wall portion .