JPH08218861A - Exhaust pipe joint structure of internal combustion engine - Google Patents

Abstract

PURPOSE: To provide a joint structure of an exhaust pipe of an internal combus tion engine having improved leakage resistance for exhaust gas. CONSTITUTION: The first overlapping cylinder part 10 of a first inner pipe body 1 through which exhaust gas flows and the expanding second overlapping cylinder part 20 of a second inner pipe 2 are coaxially fitted in each other with a fit-in gap 7. The annular seal protrusion part 12 of the first overlapping cylinder part 10 is radially externally protruded (in a direction R1) and brought into contact with the inner peripheral surface of the second overlapping cylinder part 20 at a given contact pressure for sealing. An ring like regulation protrusion pipe 23 at the tip of the second overlapping cylinder part 20 is radially internally bent (in a direction R2), and the gap width of the fit-in gap 7 is decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust pipe joint structure provided with a thermal expansion absorbing mechanism for absorbing thermal expansion generated when high temperature exhaust gas from an internal combustion engine is discharged.

[0002]

2. Description of the Related Art As an exhaust pipe joint structure for discharging exhaust gas of an internal combustion engine, as shown in FIG. 6, an inlet pipe 100 having a ring-shaped seal projection 101 protruding in the radial direction and extending in the circumferential direction, and an expansion pipe. Exhaust pipe 2 having a diameter of the overlapping cylinder portion 201
00, and fit the ring-shaped seal projection 101 of the introduction pipe 100 into the overlapping cylinder portion 201 of the exhaust pipe 200,
Further, a structure in which the fitting region is surrounded by the bellows 300 is known (Japanese Utility Model Laid-Open No. 61-126026).

The high temperature and high pressure exhaust gas discharged from the internal combustion engine is exhausted from the exhaust passage 100a of the introduction pipe 100 through the exhaust passage 200a of the exhaust pipe 200. Exhaust gas leakage is restricted by the shielding function of the ring-shaped seal projection 101. According to this, the introduction pipe 100 and the exhaust pipe 200 thermally expand when the internal combustion engine is driven because the high-temperature exhaust gas flows, and when the internal combustion engine is stopped, the intake pipe 100 and the exhaust pipe 200 cool because they cool from the heated state. Such thermal expansion or thermal contraction is absorbed by relative movement of the ring-shaped seal protrusion 101 in the axial direction in the overlapping cylinder portion 201.

[0004]

However, the above technique alone is not always sufficient as a measure for preventing high-temperature and high-pressure exhaust gas from leaking from the ring-shaped seal projection 101. Therefore, the introduction pipe 100 and the exhaust pipe 20
The outer tube surrounding 0 is exposed to the leaked high-temperature exhaust gas, and there is a problem that the temperature tends to increase.

The present invention has been made in view of the above situation, and is advantageous for ensuring the sealing performance of the ring-shaped seal projection and for improving the exhaust gas leakage reduction effect. An object is to provide an exhaust pipe joint structure.

[0006]

An exhaust pipe joint structure for an internal combustion engine according to the present invention has at least two inner pipes arranged in series and having an exhaust passage through which exhaust gas passes, and an inner pipe arranged in series. Of the outer tubular body that surrounds the outer peripheral surface of the tubular body, the first superposed cylindrical portion that is provided substantially coaxially at one tip of the inner tubular bodies that are adjacent to each other, and the inner tubular body that is adjacent to each other A second overlapping cylinder portion that is provided substantially coaxially on the other end of the first overlapping cylinder portion and surrounds the outer peripheral surface of the first overlapping cylinder portion via a ring-shaped fitting gap;
A ring-shaped seal that is formed on one of the overlapping cylinder portion and the second overlapping cylinder portion, projects in the radial direction, approaches or contacts the other of the first overlapping cylinder portion and the second overlapping cylinder portion, and extends in the circumferential direction. In an exhaust pipe joint structure including a protrusion,
The other tip of the first overlapping cylinder portion and the second overlapping cylinder portion is
It is bent in the radial direction so as to narrow the gap width of the fitting gap,
It is characterized in that the bent tip is provided with a ring-shaped restricting projection that faces one of the first overlapping cylinder portion and the second overlapping cylinder portion.

[0007]

According to the structure of the present invention, the high temperature exhaust gas discharged from the internal combustion engine is discharged through the exhaust passage of the inner pipe body. Thus, according to the structure of the present invention, in the exhaust passage of the inner pipe, high temperature exhaust gas flows when the internal combustion engine is driven, so that the inner pipe thermally expands, and when the internal combustion engine is stopped Heat shrinks to cool. Such thermal expansion and thermal contraction are absorbed by the relative movement of the ring-shaped protrusions.

The ring-shaped seal projection improves the sealing performance in the fitting gap. Further, since the ring-shaped restriction protrusion is formed so as to be bent in the radial direction to narrow the gap width of the fitting gap, the sealing property in the fitting gap is also improved by the ring-shaped restriction protrusion.

[0009]

Embodiments of the present invention will be described below. The overall structure is shown in FIGS. (Structure of Embodiment) As shown in FIG. 1, the exhaust pipe joint structure according to the present embodiment has first inner pipes 1, which are arranged in series with each other.
The second inner tube body 2 and the third inner tube body 3 are provided, and the outer tube body 8 that fits and surrounds the outer peripheral surfaces of these with the outer clearance 80 therebetween.

As shown in FIG. 1, the first inner pipe body 1 has a first port opening 1a connected to an exhaust port of the internal combustion engine and a first exhaust passage 1b connected to the port opening 1a. The second inner pipe body 2 is a second port port 2 connected to the exhaust port of the internal combustion engine.
a and a second exhaust passage 2b connected to the second port port 2a. The third inner pipe body 3 has a third port opening 3a connected to the exhaust port of the internal combustion engine and a third exhaust passage 3b connected to the third port opening 3a.

Here, the first inner tube body 1 and the holding frame 4 are fixed by welding. The second inner tube body 2 and the holding frame 4 are fixed by welding. The third inner tube body 3 and the holding frame 4 are fixed by welding. The attachment portion 8k of the outer tube body 8 and the holding frame 4 are fixed by welding. In addition, 4 m is an attachment hole for attaching the holding frame 4 to the internal combustion engine. FIG. 3 shows an enlarged cross section taken along line W3-W3 of FIG. As shown in FIG. 3, a first overlapped cylindrical portion 10 is provided substantially coaxially at the left end of the first inner tubular body 1 in the figure. A ring-shaped seal protrusion 12 is formed on the first overlapping cylinder portion 10 so as to protrude radially outward, that is, in the direction of arrow R1. The ring-shaped seal projection 12 extends in the circumferential direction and substantially coaxially.

The ring-shaped seal projection 12 is formed by partially bulging the peripheral wall constituting the first overlapping cylinder portion 10 radially outward by a processing means such as spinning or bulging. . The outer diameter end 13 which is the top of the ring-shaped seal projection 12 is an arc surface 1 curved with a predetermined curvature.
3 i, and the arcuate surface 13 i is in contact with or close to the inner peripheral surface of the second overlapping cylinder portion 20 with a predetermined surface pressure. The outer diameter end 13 of the ring-shaped seal protrusion 12 is formed at a position separated from the tip 10f of the first overlapping cylinder portion 10 by the dimension S in the axial direction.

As shown in FIG. 3, a second overlapped cylindrical portion 20 is extended substantially coaxially at the right end of the second inner tubular body 2 in the figure. The second overlapped tubular portion 20 is bent on the peripheral wall of the second inner tubular body 2 by a processing means such as spinning or bulging.
It is formed by expanding the peripheral wall while forming r and 2t. The inner peripheral surface of the second overlapping cylinder portion 20 substantially coaxially surrounds the outer peripheral surface of the first overlapping cylinder portion 10 via a ring-shaped fitting gap 7. The fitting gap 7 and the outer gap 80 are expected to serve as a heat insulating layer and a sound insulating layer by air.

As can be understood from FIG. 3, in the normal temperature range,
The inner diameter D2 of the second inner tubular body 2 and the inner diameter D1 of the first inner tubular body 1 are basically the same, and the inner diameter D3 of the second overlapping tubular portion 20 and the outside of the ring-shaped seal projection 12 are the same. The diameter D4 is basically the same. Now, in the present embodiment, the ring-shaped regulating projection 23 is bent at the tip of the second overlapping cylindrical portion 20 of the second inner tubular body 2 via the bent portion 23k inward in the radial direction, that is, in the arrow R2 direction. ing. Therefore, the bent front end 23a closely faces and faces the outer peripheral surface of the first overlapping cylinder portion 10. The angle of inclination of the ring-shaped regulating projection 23 with respect to the axis is indicated by θ1. θ1 can be set to, for example, about 60 to 90 degrees, but is not limited to this.

As can be seen from the drawing, the ring-shaped regulating projection 2
The vicinity of 3 is shaped like a dogleg cross section. When there is a springback in the vicinity of this, an action of pressing the outer diameter end 13 against pressure can be expected. As can be understood from FIG. 3, the ring-shaped restriction protrusion 23 narrows the gap width of the fitting gap 7. The minute gap width between the curved tip 23a and the outer peripheral surface of the first overlapping cylinder portion 10 is shown as La. Since the minute gap width La is provided in this manner, the ring-shaped restricting protrusion 23
Does not hinder the relative movement of the ring-shaped seal projection 12 in the directions of the arrows C1 and C2. Note that La can be set to 0.5 to 1 mm, for example.

A tip 10f in the axial direction of the first overlapping cylinder portion 10
It is preferable that the gap Lc between the bent portion 2r and the bent portion 2r of the second inner tubular body 2 is set to be zero or close to zero in a high temperature region where the high temperature exhaust gas passes. Therefore, the gap Lc is set to about 1 to 2 mm in the normal temperature region such as when the internal combustion engine is stopped. As can be understood from FIG. 1, the fitting form between the illustrated right end of the third inner pipe body 3 and the illustrated left end of the second inner pipe body 2 is also similar to the form shown in FIG. 3. That is, at the right end of the third inner tubular body 3 in the figure, the second overlapping tubular portion 20 having the ring-shaped restricting projection 23 is formed, and the second inner tubular body 2 is also formed.
At the left end of the figure, a first ring-shaped seal projection 12 is provided.
The overlapping cylinder portion 10 is formed.

The inner tube bodies 1 to 3 and the outer tube body 8 are each constructed by welding and joining the half bodies obtained by press-forming the plate body. The inner tube bodies 1 to 3 and the outer tube body 8 can be formed of a metal such as ferritic stainless steel, austenitic stainless steel, heat resistant steel, or cast iron in some cases in consideration of high temperature strength and high temperature corrosion resistance. The thickness of the inner tube bodies 1 to 3 can be 0.5 to 1 mm, especially 0.8 mm. Outer tube 8
Can have a thickness of 1.0 to 2 mm, especially 1.5 mm.

(Operation and Effect of Embodiment) According to the structure of this embodiment, the high-temperature and high-pressure exhaust gas released from the exhaust port of the internal combustion engine when the internal combustion engine is driven is the first inner pipe body. The first exhaust passage 1b, the second exhaust passage 2b of the second inner pipe body 2, and the third exhaust passage 3b of the third inner pipe body 3 are exhausted toward the downstream side, that is, in the arrow X1 direction. It

The exhaust gas discharged from the internal combustion engine is
Generally, the temperature is about 700 to 900 ° C. and the pressure (gauge pressure) is 0.2 although it varies depending on the type of internal combustion engine.
It is estimated to be about 1.0 kgf / cm ² . Since the hot exhaust gas flows in this manner, the inner tube bodies 1 to 3 thermally expand. Thermal expansion occurs not only in the axial direction but also in the radial direction and the circumferential direction. On the other hand, when the internal combustion engine is stopped, since the exhaust gas does not flow, the inner tubes 1 to 3 cool from the heated state and thermally contract.

The thermal expansion and the thermal contraction in the axial direction are absorbed by the ring-shaped seal projection 12 relatively moving in the axial direction of the second overlapped cylindrical portion 20, that is, in the directions of arrows C1 and C2 shown in FIG. It At this time, even when the outer diameter end 13 of the ring-shaped seal projection 12 is in pressure contact with the second overlapping cylinder portion 20, the outer diameter end 13 of the ring-shaped seal projection 12 has the arc surface 13i. Therefore, the ring-shaped seal projection 12 can relatively move with a small resistance.

As can be understood from FIG. 3, the high temperature exhaust gas touches the inner peripheral surface of the first superimposing cylinder portion 10 when passing through it, so that the first superimposing cylinder portion 10 is heated and radially outward, that is, the arrow R.
Thermally expands in one direction. Since the exhaust gas has a high pressure, it tends to leak into the outer gap 80 on the outer tube body 8 side through the fitting gap 7, but the leakage is restricted by the sealing effect of the ring-shaped seal projection 12. Further, according to this embodiment,
The ring-shaped regulating projection 23 is bent to form a bent tip 23a.
Since it is formed so as to narrow the gap width of the fitting gap 7, a sealing effect by the ring-shaped regulating projection 23 can be expected. Therefore, the exhaust gas leakage is also restricted by the ring-shaped restriction projection 23.

As described above, according to this embodiment, both the ring-shaped seal projection 12 and the ring-shaped restriction projection 23 can be expected to have the effect of reducing the leakage of exhaust gas into the fitting gap 7 and the outer gap 80. This is advantageous for reducing or avoiding heat conduction to the outer pipe body 8 due to leakage of high-temperature exhaust gas, and for preventing overheat of the outer pipe body 8. According to the present embodiment, as described above, the amount of exhaust gas leaking into the fitting gap 7 and the outer gap 80 is reduced, and thus the degree to which the outer peripheral surface of the ring-shaped seal projection 12 comes into contact with high-temperature exhaust gas is reduced. To be done. Therefore, overheating of the ring-shaped seal projection 12 can be reduced or avoided, and abnormal deformation due to overheating of the ring-shaped seal projection 12 can be reduced or avoided. Therefore, there is an advantage that the sealing effect of the ring-shaped seal projection 12 is easily maintained normally.

Here, if the ring-shaped seal projection 12 is strongly pressed against the inner peripheral surface of the second overlapping cylinder portion 20, the sealing effect of the ring-shaped seal projection 12 is likely to be improved. In this respect, according to the present embodiment, the high-temperature exhaust gas is less likely to leak into the fitting gap 7 and the outer gap 80, so that the degree of contact of the inner peripheral surface of the second overlapping cylindrical portion 20 with the high-temperature exhaust gas can be reduced. . Therefore, the second overlapped cylinder portion 2 caused by the contact with the hot exhaust gas
It is advantageous to alleviate the increase in temperature to 0, and it can be expected that the amount of thermal expansion of the second superposed tubular portion 20 in the radial direction is reduced. Therefore, it is advantageous to increase the degree to which the arcuate surface 13i of the outer diameter end 13 of the ring-shaped seal projection 12 comes into pressure contact with the inner peripheral surface of the second overlapping cylinder portion 20. Therefore, it is advantageous for improving the sealing effect by the ring-shaped seal projection 12.

(Other Example) FIG. 4 shows another example. This example has basically the same configuration as the above-described embodiment, and basically the same action and effect can be obtained. The same parts will be described with the same reference numerals. Also in this example, the sealability in the fitting gap 7 is improved by the ring-shaped seal projection 12 and the ring-shaped restriction projection 23. Therefore, as in the case of the above-described embodiment, the hot exhaust gas is less likely to leak into the fitting gap 7, and the degree of contact of the hot exhaust gas with the ring-shaped seal projection 12 can be reduced. Therefore, the ring-shaped seal projection 12
Of the ring-shaped seal projection 12 can be reduced, and abnormal deformation of the ring-shaped seal projection 12 due to overheating can be reduced.
It is possible to obtain the advantage that the sealing effect of 2 can be easily secured.

According to this example, the first stacking cylinder 10 has two
Since the individual ring-shaped seal projections 12 are arranged side by side, it is advantageous in improving the sealing effect. Further, the first overlapping cylinder portion 10
Bent piece 1 bent outward in the radial direction at the tip of the
0p is formed in a ring shape and substantially coaxially. The bent piece 10p is also expected to improve the sealing effect. FIG. 5 shows another different example. This example also has basically the same configuration as the above-described embodiment, and basically the same action and effect can be obtained. The same parts will be described with the same reference numerals. In this example, the inclination angle of the wall surface 12h forming the ring-shaped seal protrusion 12 and the inclination angle of the ring-shaped restriction protrusion 23 are made to correspond to each other, and basically both are set to be along each other. . Therefore, when the ring-shaped seal projection 12 relatively moves in the direction of arrow C2 and absorbs thermal expansion, the wall surface 12h of the ring-shaped seal projection 12 and the ring-shaped restriction projection 2 are absorbed.
Even if 3 and 3 collide with each other, they come into contact with each other, which is advantageous in preventing local stress concentration at the time of collision.

Further, in the example shown in FIGS. 1 to 3, the ring-shaped seal projection 12 is provided in the first overlapped tubular portion 1 of the first inner tubular body 1.
The ring-shaped restricting projection 23
Is formed in the second superposed tubular portion 20 of the second inner tubular body 2,
Not limited to this, and in some cases, the ring-shaped seal protrusion 1
2 is formed on the inner peripheral side of the second overlapping cylinder portion 20 of the second inner pipe body 2, and the ring-shaped regulating projection 23 is formed on the first overlapping cylinder portion 10 of the first inner pipe body 1. You can also

The materials of the inner tube bodies 1 to 3 and the outer tube body 8 are not limited to those described above. The dimensional relationship is not limited to the above-mentioned values, and may be appropriately changed within the range where the effect is obtained. (Supplementary Note) The following technical idea can be understood from the above-described embodiment. The structure according to claim 1, wherein the second superposed cylindrical portion 20 is formed by expanding the diameter of the tip of the inner tubular body. According to this, the peripheral wall of the second overlapping cylinder portion 20 is likely to be urged in the diameter reducing direction due to the springback. Therefore, it is possible to expect further improvement in the degree of contact between the inner peripheral surface of the second overlapping cylinder portion 20 and the ring-shaped seal protrusion 12.

[0028]

According to the structure of the present invention, the sealing effect in the fitting gap is improved by both the ring-shaped seal projection and the ring-shaped restriction projection. Therefore, the leakage of the high-temperature and high-pressure exhaust gas discharged from the internal combustion engine into the fitting gap is restricted as compared with the related art.

Therefore, overheating of the ring-shaped protrusion due to the high-temperature exhaust gas leaking into the fitting gap can be reduced and avoided, which is advantageous for avoiding abnormal deformation of the ring-shaped seal protrusion due to overheating. Therefore, it is advantageous to normally secure the sealing effect of the ring-shaped protrusion. According to the structure of the present invention, the sealing effect in the fitting gap is improved, which is advantageous in reducing the degree of contact between the second overlapping cylinder portion and the hot exhaust gas. Therefore, at the time of exhausting the exhaust gas, it is advantageous to reduce the temperature rise of the second polymerization cylinder portion, and further, it can be expected that the amount of thermal expansion of the second polymerization cylinder portion in the radial direction is reduced.

Therefore, according to the structure of the present invention, the degree to which the ring-shaped seal protrusion approaches or contacts the inner peripheral surface of the second overlapping cylinder portion can be increased. Therefore, further improvement of the sealing effect by the ring-shaped seal projection can be expected.

[Brief description of drawings]

FIG. 1 is an overall sectional view.

FIG. 2 is an overall plan view.

3 is a cross-sectional view taken along the line W3-W3 of FIG.

FIG. 4 is a cross-sectional view of a main part according to another example.

FIG. 5 is a cross-sectional view of a main part according to still another example.

FIG. 6 is a cross-sectional view according to a conventional technique.

[Explanation of symbols]

In the figure, 1 is a first inner pipe, 1b is a first exhaust passage, 10 is a first overlapping cylinder, 12 is a ring-shaped seal projection, 2 is a second inner pipe, 2b is a second exhaust passage, 20 Is a second overlapping cylinder portion, 23 is a ring-shaped restricting protrusion, 7 is a fitting gap, 8 is an outer tubular body, and 80 is an outer gap.

Claims (1)

[Claims] 1. An inner pipe body having at least two exhaust pipes arranged in series and having an exhaust passage through which exhaust gas passes, an outer pipe body surrounding an outer peripheral surface of the inner pipe bodies arranged in series, and adjacent to each other. And a first superimposing cylinder portion provided substantially coaxially on one end of the inner tubular body, and a first superposed tubular portion provided substantially coaxially on the other tip of the inner tubular bodies adjacent to each other. A second overlapping cylinder part that surrounds the outer peripheral surface of the overlapping cylinder part with a ring-shaped fitting gap, and one of the first overlapping cylinder part and the second overlapping cylinder part, which protrudes in the radial direction. In the exhaust pipe joint structure, which comprises a ring-shaped seal projection that approaches or contacts the other of the first overlapping cylinder portion and the second overlapping cylinder portion and extends in the circumferential direction. The other tip of the second overlapping cylinder portion is bent in the radial direction so as to narrow the gap width of the fitting gap. The exhaust pipe joint structure for an internal combustion engine, characterized in that the bent tip is provided with a ring-shaped restricting protrusion facing one of the first polymerization tube portion and the second polymerization tube portion.