JP2959307B2 - Exhaust pipe of internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust pipe used for an exhaust system of an internal combustion engine, and more particularly to an exhaust pipe having a heat insulating material disposed between an inner pipe and an outer pipe.

[0002]

2. Description of the Related Art Conventionally, as an exhaust pipe used in an exhaust system of an internal combustion engine, an exhaust pipe having a high heat retaining ability and a warm-up property has been used for the purpose of sending exhaust gas to a catalytic converter or the like while keeping the temperature of the exhaust gas. . An example of this type of exhaust pipe is a technique disclosed in Japanese Utility Model Laid-Open No. 50-96809. In this prior art, as shown in FIG. 11, an inner pipe 61 made of a flexible pipe having a relatively small thickness is used.
And a relatively thick outer tube 6 capable of maintaining mechanical strength.
2 is provided. Then, the inner pipe 61 and the outer pipe 62
An air as a heat insulating material is interposed in a space 63 between the two to form an exhaust pipe 64 having a three-layer structure. Here, the inner pipe 6
Since 1 is constituted by a flexible pipe, its inner tube 61 can be easily bent in accordance with the shape of the outer tube 62. As the heat insulating material interposed between the inner pipe 61 and the outer pipe 62, it is also considered to use a solid heat insulating material other than air.

[0003]

In the above-mentioned prior art, it is conceivable to use inorganic fibers such as ceramic fibers and glass fibers as a solid heat insulating material. In this case, in order to easily assemble the heat insulating material between the inner tube 61 and the outer tube 62, the heat insulating material of inorganic fibers is impregnated with a latix organic binder to form the heat insulating material into a required shape. It is also possible to do. Therefore, in the exhaust pipe configured as described above, the heat insulating material impregnated with the organic binder is heated by the high-temperature exhaust gas, so that the organic binder may burn and generate high-pressure combustion gas. Was. Therefore, when high-pressure combustion gas is generated, the pressure between the inner pipe 61 and the outer pipe 62 becomes excessive, and the inner pipe 62 having relatively low rigidity may be deformed.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide an exhaust pipe having a heat insulating material disposed between an inner pipe and an outer pipe. The present invention provides an exhaust pipe of an internal combustion engine capable of preventing the pressure between the inner pipe and the outer pipe from being excessively increased by the high-pressure gas when the high pressure gas is generated and improving the durability. .

[0005]

In order to achieve the above object, according to the present invention, there is provided an exhaust system which is used in an exhaust system of an internal combustion engine and has a heat insulating material provided between an inner pipe and an outer pipe. In the pipe, at least a part of the inner pipe has a double structure including an inner layer and an outer layer, and the inner layer and the outer layer are provided with openings at positions not overlapping with each other.

[0006]

According to the above construction, even if the heat insulating material is heated by the high-temperature exhaust gas passing through the inner pipe to generate a high-pressure gas, the high-pressure gas is generated in the double-structure portion of the inner pipe. It penetrates between the outer layer and the inner layer from the opening of the outer layer, and is further guided to the inside of the inner tube through the opening of the inner layer. For this reason, an increase in pressure between the inner pipe and the outer pipe is suppressed.

On the other hand, the pressure (back pressure) when the exhaust gas passes through the inner pipe is not so high, and the openings provided in the double structure portion of the inner pipe do not overlap between the inner layer and the outer layer. Therefore, the passage resistance between the opening in the inner layer and the opening in the outer layer is large. Therefore, the exhaust gas passing through the inner tube does not leak from the opening in the inner layer to the outside of the inner tube through the opening in the outer layer. Further, the heat insulating material does not leak from the opening in the outer layer to the inside of the inner tube through the opening in the inner layer.

[0008]

【Example】

(First Embodiment) A first embodiment of an exhaust pipe of an internal combustion engine according to the present invention will be described below in detail with reference to FIGS.

FIG. 3 is a perspective view showing an exhaust pipe assembly 1 used in an exhaust system for one bank of a V-type six-cylinder engine as an internal combustion engine. The exhaust pipe assembly 1 includes an exhaust manifold 2, a catalytic converter 4 connected to a collection portion 3 of the exhaust manifold 2, and an exhaust front pipe 5 connected to an outlet of the catalytic converter 4. The exhaust manifold 2 is formed with a flange 6 for attaching to an engine cylinder block. A plurality of exhaust outlets 7 corresponding to each cylinder are opened in the flange 6. A three-way catalyst for purifying exhaust gas is built in the catalytic converter 4. Further, the exhaust front pipe 5 is provided with a mounting flange 8.

Next, the structure of the exhaust manifold 2 will be described. FIG. 4 is a cutaway view of the exhaust manifold 2 at the portion indicated by arrow A in FIG. As is clear from this figure, the exhaust manifold 2 is connected to the outer pipe 9.
And an inner tube 10. The outer tube 9 is made of a different tube material 11,
It is formed by joining between 12 by welding 13. Further, the outer pipe 9 is formed to have a relatively large thickness in order to secure mechanical strength capable of supporting the weight of the exhaust manifold 2 itself and other catalytic converters 4 and the exhaust front pipe 5. In this embodiment, the thickness of the outer tube 9 is set to about "1.5 mm". On the other hand, inner tube 1
0 is formed by joining a bellows 16 by welding 17 between different pipes 14 and 15. Inner tube 10
Is formed with a relatively small thickness to reduce its own heat capacity. In this embodiment, the thickness of the inner tube 10 is set to about “0.6 mm”. The bellows 16 provided in the middle of the inner pipe 10 is provided between the outer pipe 9 and the inner pipe 10 to absorb a difference in thermal expansion caused by a temperature difference between the two. In this embodiment, the thickness of the bellows 16 is set to about 0.6 to 0.8 mm. The bellows 16 has three bulges 18 that protrude outward.

The outer tube 9 and the inner tube 10 constructed as described above
A solid heat insulating material 19 is interposed in the space between the exhaust manifold 2 and the exhaust manifold 2 to form a three-layer structure. In this embodiment, an inorganic fiber such as a ceramic fiber or a glass fiber is used for the heat insulating material 19. In addition, the heat insulating material 19
In order to make it easy to assemble between the outer pipe 9 and the inner pipe 10,
The inorganic fibers are impregnated with an organic binder of a lattice type, whereby the heat insulating material 19 is formed in a required shape.

The open end 9a of the outer tube 9 is reduced in diameter, and the open end 10a of the inner tube 10 is fitted to the open end 9a. Then, the opening end portions 9a, 10
a is fixed to the flange 6 by welding 20.
Although a part of the exhaust manifold 2 has been described here,
Regarding the overall configuration of the exhaust manifold 2, the
Basically, the outer pipe 9, the heat insulating material 19 and the inner pipe 10
To form a three-layer structure.

Next, the configuration of the bellows 16 will be described. FIG. 1 is an enlarged sectional view showing a portion of the bellows 16 in FIG. 4, and FIG. 2 is an enlarged sectional view showing one bulging mountain 18 of the bellows 16. The bellows 16 has a double structure with an inner layer 21 and an outer layer 22. In this embodiment, the thicknesses of the inner layer 21 and the outer layer 22 are each set to about 0.3 to 0.4 mm. or,
The inner layer 21 and the outer layer 22 are not completely in close contact with each other, and a certain gap G is formed between the inner layer 21 and the outer layer 22. Inner layer 21 at one bulge 18 of bellows 16
Is provided with a first opening 23. Further, in the outer layer 22 of the bulge 18, a position that does not overlap with the first opening 23, that is, the opposite side moved by “180 °” along the outer circumference of the bulge 18 from the first opening 23. position,
A second opening 24 is provided. That is, in this embodiment, the first and second openings 23 and 2 are formed in the bellows 16.
4 are provided only in pairs. In this embodiment, the diameter of the first and second openings 23 and 24 is "2.0 mm".
Set to about.

Next, the operation when the exhaust pipe assembly 1 constructed as described above is mounted on an engine and used will be described. Now, when the engine is operated and the exhaust gas flows into the exhaust manifold 2, the exhaust gas passes through the inside of the inner pipe 10, reaches the collecting portion 3 of the exhaust manifold 2, and flows to the catalytic converter 4 and the exhaust front pipe 5. . Here, in the exhaust manifold 2, the inner tube 10 has a small heat capacity, and the periphery of the inner tube 10 is surrounded by a heat insulating material 19. Therefore, the inner pipe 10 is quickly heated by the heat of the exhaust gas, and the heat retention of the exhaust gas flowing through the inner pipe 10 is ensured.

Therefore, according to the exhaust manifold 2,
When the engine is warmed up, relatively high temperature exhaust gas can be immediately sent to the catalytic converter 4, and the activation of the three-way catalyst in the converter 4 can be promoted.

Further, since a part of the inner pipe 10 is constituted by the bellows 16, when a difference in thermal expansion occurs between the inner pipe 10 and the outer pipe 9, the difference in thermal expansion is reduced by the bellows 1.
6 can be absorbed.

When the heat insulating material 19 is heated by the high temperature exhaust gas passing through the inner pipe 10 of the exhaust manifold 2, the organic binder impregnated in the heat insulating material 19 burns, and the high pressure combustion gas is discharged. May occur. However, in that case, the high-pressure combustion gas is
6 from the second opening 24 to the gap G between the inner layer 21 and the outer layer 22
And is led out of the first opening 23 to the inside of the bellows 16 through the gap G. That is, the high-pressure gas generated between the inner pipe 10 and the outer pipe 9 can be discharged into the inner pipe 10. Therefore, the inner pipe 10
The increase in pressure between the inner tube 10 and the outer tube 9 is suppressed, and the pressure between the inner tube 10 and the outer tube 9 can be prevented from becoming excessive. Further, since the pressure increase between the inner pipe 10 and the outer pipe 9 is suppressed, not only the heat insulating material 19 but also the bellows 16 and the inner pipe 10 having relatively low rigidity are prevented from being deformed or damaged. Therefore, the durability of the exhaust manifold 2 can be improved.

On the other hand, the pressure (back pressure) when the exhaust gas passes through the inner pipe 10 of the exhaust manifold 2 is not so high.
Further, since the first opening 23 and the second opening 24 are provided at positions not overlapping each other, the space between the first opening 23 and the second opening 24 is like a labyrinth. As a result, the passage resistance from the first opening 23 to the second opening 24 increases. Therefore, the exhaust gas passing through the inner pipe 10 does not leak from the first opening 23 through the gap G and the second opening 24 to the outside of the bellows 16, that is, to the heat insulating material 19 side. Conversely, the gap G between the inner layer 21 and the outer layer 22 and the first opening 23
Does not leak through the bellows 16.

In addition, in this embodiment, since the bellows 16 has a double structure, it is well known that the durability can be improved and the chatter can be prevented. (Second Embodiment) Next, a second embodiment of the exhaust pipe of the internal combustion engine according to the present invention will be described in detail with reference to FIGS.

FIG. 10 shows a front pipe 3 used in an exhaust system of a horizontal V-type engine as an internal combustion engine.
FIG. 1 is a perspective view showing the entirety of FIG. This front pipe 31
Is a pair of conduits 32, 33 on the upstream side and both conduits 32, 3
3 and a downstream conduit 35 connected to the outlet of the merge pipe 34.
At the inlet side of each of the upstream conduits 32 and 33, a flange 3 is provided.
6, 37 are provided respectively. These flanges 36 and 37 are connected to an exhaust manifold (not shown) corresponding to each bank of the V-type engine. Further, a thermal expansion absorbing portion 38 for absorbing thermal expansion of the conduit 32 itself is provided in the middle of the one conduit 32 on the upstream side. Further, the downstream conduit 35 is connected to a catalytic converter (not shown). Exhaust gas exhausted from each bank of the V-type engine flows from each exhaust manifold into each of the conduits 32 and 33, joins at a merging pipe 34, and then flows through a conduit 35 to a catalytic converter.

Next, the structure of the front pipe 31 will be described. FIG. 5 shows the conduit 3 centered on the thermal expansion absorbing portion 38.
2 is a cross-sectional view showing a part of FIG. As is apparent from this figure, the conduit 32 has an outer tube 39 and an inner tube 40.
The outer tube 39 includes the conduit 32 itself and the other conduits 33, 3
In order to secure a mechanical strength capable of supporting the weight of the joint pipe 5 and the joining pipe 34, it is formed to have a relatively large wall thickness. In this embodiment, the thickness of the outer tube 39 is set to about “1.2 mm”. On the other hand, the inner pipe 40 is configured such that a bellows 41 is joined by welding 42 in the middle thereof. Inner tube 40
Is formed with a relatively small wall thickness to reduce its own heat capacity. In this embodiment, the inner tube 4
0 has a double structure and its thickness is "0.8mm"
Set to about. The bellows 41 absorbs a difference in thermal expansion between the outer tube 39 and the inner tube 40 due to a temperature difference between the outer tube 39 and the inner tube 40. In this embodiment, the bellows 41 has a double structure,
The thickness is set to about 0.6 to 0.8 mm.
The bellows 41 have five bulging ridges 43 projecting outward.
It has.

The outer tube 39 and the inner tube 4 configured as described above
0 and the bellows 41, a solid heat insulating material 4
4, whereby the conduit 32 has a three-layer structure. In this embodiment, a ceramic fiber is used for the heat insulating material 44. Further, in order to facilitate assembling the heat insulating material 44 between the outer tube 39 and the inner tube 40, the ceramic fiber is impregnated with a latics type organic binder. Thereby, the heat insulating material 44 is formed in a required shape.

FIG. 7 is a sectional view showing the upstream end of the conduit 32, and FIG. 8 is a sectional view showing the downstream end of the same conduit 32. As is clear from these figures, the upstream and downstream opening ends 39a and 39b of the outer tube 39 are reduced in diameter, respectively, and the opening ends 39a and 39b of the inner tube 40 are Open ends 40a and 40b are fitted. The corresponding open ends 39a, 39b and open ends 40a, 40b are joined to each other by welding (not shown). A flange 36 is attached to the outer periphery of the upstream open end 39 a of the outer tube 39. A ring 45 is attached to the downstream end 39 b of the outer tube 39.

Here, the structure of the front pipe 31 has been described with respect to one conduit 32, but the other conduits 33, 35 and the junction pipe 34 constituting the front pipe 31 are also basically an outer pipe and a heat insulating pipe. It is assumed that the material and the inner tube are formed in a three-layer structure.

Next, the configuration of the bellows 41 will be described. FIG. 5 shows the entire bellows 41, and FIG. 6 shows one bulge 43 of the bellows 41 in an enlarged manner. The bellows 41 has a double structure with an inner layer 46 and an outer layer 47. In this embodiment, the thicknesses of the inner layer 46 and the outer layer 47 are each set to about “0.4 mm”. Further, the inner layer 46 and the outer layer 47 are not completely in close contact with each other, and a certain gap G is formed between the inner layer 46 and the outer layer 47. A first opening 48 is provided in the inner layer 46 of one bulge 43 of the bellows 41. Further, in the outer layer 47 of the bulge 43, a position that does not overlap with the first opening 48, that is, the opposite side moved by “180 °” along the outer circumference of the bulge 43 from the first opening 48. A second opening 49 is provided at the position. That is, in this embodiment, only one pair of the first and second openings 48 and 49 is provided in the bellows 41. In this embodiment, the diameters of the first and second openings 48 and 49 are
It is set to about “2.0 mm”.

In this embodiment, the inner tube 40 having a double structure has the same structure as described above.
FIG. 9 is an enlarged view of a part of the inner pipe 40 near the upstream end and the downstream end of the conduit 32. As is clear from FIGS. 7 to 9, the inner tube 40 includes an inner layer 50 and an outer layer 51. The inner layer 50 and the outer layer 51 are not completely in close contact with each other, and a certain gap G is formed between the inner layer 50 and the outer layer 51. The inner layer 50 has an opening 5
2 are provided. The outer layer 51 has the opening 5
Another opening 53 is provided at a position not overlapping with 2. That is, in this embodiment, a pair of openings 52 and 53 are provided at the upstream end and the downstream end of the inner tube 40, respectively.

Next, an operation when the front pipe 31 constructed as described above is mounted on an engine and used will be described. Now, when the engine is operated and its exhaust gas flows into the front pipe 31 through the exhaust manifold, the exhaust gas passes through the upstream conduits 32 and 33 to the merge pipe 34 and flows from the outlet to the conduit 35. . Here, for example, in the conduit 32, the inner tube 40 has a small heat capacity, and the periphery of the inner tube 40 is surrounded by a heat insulating material 44. Therefore, the inner pipe 40 is quickly heated by the heat of the exhaust gas, and the heat retention of the exhaust gas flowing through the inner pipe 40 is ensured. Other conduits 33 and 35 and merging pipe 34
The same effect can be obtained in

Therefore, according to the front pipe 31, when the engine is warmed up, relatively high-temperature exhaust gas can be sent to the catalytic converter, and the activation of the catalyst in the catalytic converter can be promoted.

In the conduit 32, a part of the inner tube 40 of the thermal expansion absorbing portion 38 is a bellows 41. Therefore, when a difference in thermal expansion occurs between the inner tube 40 and the outer tube 39, the difference in thermal expansion can be absorbed by deformation of the bellows 41.

When the heat insulating material 44 is heated by the high-temperature exhaust gas passing through the inner pipe 40 of the conduit 32, the organic binder impregnated in the heat insulating material 44 burns to generate high-pressure combustion gas. May be. However, in that case, the high-pressure combustion gas enters the gap G between the inner layer 46 and the outer layer 47 from the second opening 49 of the bellows 41, and passes through the gap G from the first opening 48. It will be led out inside the bellows 41. That is, the high-pressure gas generated between the inner pipe 40 and the outer pipe 39 can be discharged into the inner pipe 40. Therefore, the inner pipe 40 and the outer pipe 39
Between the inner pipe 40 and the outer pipe 39.
Can be prevented from becoming excessively high. In addition, since the pressure increase between the inner pipe 40 and the outer pipe 39 is suppressed, not only the heat insulating material 44 but also the bellows 41 and the inner pipe 40 having relatively low rigidity are prevented from being deformed or damaged. Therefore, the durability of the front pipe 31 can be improved.

On the other hand, the pressure (back pressure) when the exhaust gas passes through the inner pipe 40 of the conduit 32 is not so high. Also, the first
Since the first opening 48 and the second opening 49 are provided at positions where they do not overlap each other, the space between the first opening 48 and the second opening 49 functions as a labyrinth. Thus, the passage resistance from the first opening 48 to the second opening 49 also increases. Therefore, the exhaust gas passing through the inner pipe 40 does not leak from the first opening 48 to the outside of the bellows 41, that is, to the heat insulating material 44 side through the gap G and the second opening 49. Conversely, the heat insulating material 44 does not leak into the bellows 41 from the second opening 49 through the gap G between the inner layer 46 and the outer layer 47 and the first opening 48.

The same operation and effect as described above can be obtained also at the inner pipe 40 at the upstream end and the downstream end of the conduit 32.
That is, a pair of openings 52 and 53 formed in the inner pipe 40 are
It functions similarly to the first opening 48 and the second opening 49 described above. Therefore, an increase in the pressure between the inner pipe 40 and the outer pipe 39 is suppressed, and it is possible to prevent the pressure between the inner pipe 40 and the outer pipe 39 from becoming excessive. As a result, deformation and breakage of the heat insulating material 44 and the relatively low rigidity inner pipe 40 can be prevented beforehand, and in that sense, the durability of the front pipe 31 can be improved.
Exhaust gas passing through the inside of the inner pipe 40 is supplied to both the openings 5.
The heat insulating material 44 does not leak out to the inside of the inner tube 40 through the openings 53 and 52.

In addition, in this embodiment, since the inner tube 40 and the bellows 41 have a double structure, their durability can be improved and chattering can be prevented. still,
The present invention is not limited to the above-described embodiments, and may be implemented as follows by appropriately changing a part of the configuration without departing from the spirit of the invention.

(1) In the first embodiment, a part of the inner tube 10 is constituted by the bellows 16, but the entire inner tube may be constituted by the bellows. (2) In each of the above-described embodiments, in the bellows 16 and 41 forming a part of the inner tubes 10 and 40, the first openings 23 and 48 and the second The openings 24 and 49 are provided, but the first and second openings may be provided in the bulging ridge that protrudes inward of the bellows.

(3) In each of the above embodiments, the bellows 16,
The first opening 2 for one of the bulges 18 and 43
Although only one pair of holes 3, 48 and second holes 24, 49 are provided, the numbers of the first holes and the second holes may be changed as appropriate. The number and size of these first and second openings are determined by the amount of the organic binder impregnated in the heat insulating material,
What is necessary is just to change suitably according to the density etc. of a heat insulating material.

[0036]

As described above in detail, according to the present invention, in an exhaust pipe in which a heat insulating material is provided between an inner pipe and an outer pipe, the inner layer and the inner layer of the double structure of the inner pipe are provided. Openings are provided in the outer layer at positions that do not overlap each other. Therefore, when a high-pressure gas is generated from a heat insulating material or the like, the high-pressure gas penetrates between the outer layer and the inner layer from the opening in the outer layer, and is further guided to the inside of the inner tube through the opening in the inner layer. As a result, an increase in pressure between the inner pipe and the outer pipe is suppressed. As a result, it is possible to prevent the pressure between the inner pipe and the outer pipe from becoming excessive, prevent deformation or breakage of the inner pipe and the heat insulating material, and extend the exhaust pipe. It has an excellent effect that the durability can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a part of an exhaust manifold in a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an enlarged portion of one bulge of the bellows in the first embodiment.

FIG. 3 is a perspective view showing an exhaust pipe assembly mounted to one bank of a V-type six-cylinder engine in the first embodiment.

FIG. 4 is a diagram showing a part of the exhaust manifold in the first embodiment, with a part cut away.

FIG. 5 is a cross-sectional view showing a part of a conduit centered on a thermal expansion absorbing portion in a second embodiment embodying the present invention.

FIG. 6 is a cross-sectional view showing an enlarged portion of one bulge of a bellows in the second embodiment.

FIG. 7 is a sectional view showing an upstream end portion of a conduit in the second embodiment.

FIG. 8 is a sectional view showing a downstream end portion of a conduit in the second embodiment.

FIG. 9 is an enlarged sectional view showing a part of an inner pipe near an upstream end and a downstream end of a conduit in a second embodiment.

FIG. 10 is a perspective view showing an entire front pipe used in an exhaust system of a V-type engine in a second embodiment.

FIG. 11 is a view showing a part of an exhaust pipe according to the related art, which is cut away.

[Explanation of symbols]

2 ... exhaust manifold, 9 ... outer tube, 10 ... inner tube, 16 ... bellows, 19 ... heat insulating material, 21 ... inner layer, 22 ... outer layer, 23
... 1st opening, 24 ... 2nd opening, 31 ... front pipe, 39 ... outer pipe, 40 ... inner pipe, 41 ... bellows, 44 ...
Heat insulating material, 46 ... inner layer, 47 ... outer layer, 48 ... first opening,
49: second opening, 50: inner layer, 51: outer layer, 52, 5
3. Opening.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-55823 (JP, A) Japanese Utility Model Showa 49-60119 (JP, U) Japanese Utility Model Showa 51-33614 (JP, U) Japanese Utility Model Showa 50- 96809 (JP, U) Fully open sho 59-71918 (JP, U) Fully open sho 60-34517 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F01N 7/08 F01N 7 / 10 F01N 7/14

Claims (1)

(57) [Claims] 1. An exhaust pipe used in an exhaust system of an internal combustion engine, wherein a heat insulating material is disposed between an inner pipe and an outer pipe, wherein at least a part of the inner pipe is formed by an inner layer and an outer layer. An exhaust pipe for an internal combustion engine, wherein the exhaust pipe has a structure, and the inner layer and the outer layer are provided with openings at positions that do not overlap each other.