JP2001193449A - Exhaust pipe for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust pipe for an internal combustion engine low which suppresses the heat capacity of an inner pipe and capable of suitably maintaining its strength though having a double structure of inner/outer pipes. SOLUTION: An exhaust pipe 20 for an engine 11 is constituted as a double- pipe structure of an inner/outer pipe 23, 22. For selectively enhancing strength in the end part on the side of the engine 11 in the inner pipe 23 of the exhaust pipe 20 thus constituted, this end part is formed into a large thickness, as compared with those at the other locations of the inner pipe 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust pipe of an internal combustion engine, and more particularly, to an exhaust pipe having a double pipe structure of an inner pipe and an outer pipe.

[0002]

2. Description of the Related Art Usually, a catalytic converter for purifying combustion gas discharged from an internal combustion engine is provided in an exhaust passage of the internal combustion engine. The purification characteristics of this catalytic converter largely depend on its own temperature, and when the temperature is higher than a predetermined value, the purification performance can be sufficiently exhibited. For this reason, when the temperature of the catalytic converter is low, such as when starting the engine, it is desirable to increase the temperature as early as possible in order to ensure its purification characteristics.

Therefore, conventionally, for example, Japanese Utility Model Laid-Open No. 63-130
As shown in Japanese Patent Application Laid-Open No. 616, the exhaust pipe has a double pipe structure, and the thickness of the inner exhaust pipe (inner pipe) which is a passage through which the combustion gas passes in the exhaust pipe is reduced to reduce the heat capacity. Some have been proposed to keep them small. In other words, in this exhaust pipe, by reducing the heat capacity of the inner pipe, the total amount of heat taken by the inner pipe by the combustion gas can be reduced. However, the temperature rise of the inner tube due to the heat deprived from the combustion gas thereafter becomes saturated early. As a result, the temperature of the fuel gas reaching the catalytic converter becomes high at an early stage, so that the temperature of the catalytic converter can be raised at an early stage.

[0004]

If the exhaust pipe is formed as a double pipe structure and the thickness of the inner pipe is reduced as in the above-mentioned conventional structure, the temperature of the catalytic converter can be raised at an early stage. Can do it.

However, in the exhaust pipe having the double pipe structure,
Since the inner pipe and the outer exhaust pipe (outer pipe) are only partially in contact with each other, a temperature difference is easily generated between the inner pipe and the outer pipe. For this reason, the temperature of the inner pipe is compared with the temperature of the outer pipe when starting the engine at a low temperature where the temperature of the inner pipe rises significantly due to the heat of the combustion gas, or when stopping the engine at a high temperature where the temperature of the outer pipe falls significantly. As a result, the amount of thermal expansion of the inner tube is larger than that of the outer tube. Therefore, at the joint between the inner tube and the outer tube, where the inner tube is restrained from deforming (thermal expansion of the inner tube) by the outer tube, the thermal stress caused by the difference in the amount of thermal expansion is generated inside the inner tube. Will occur.

Conventionally, for example, Japanese Utility Model Application Laid-Open No. 63-196
As shown in Japanese Patent No. 425, an exhaust pipe having a partition wall therein is also known. However, when such a partition wall is provided in the inner pipe, the partition wall is also thermally expanded by the heat of the combustion gas. And a difference in the amount of thermal expansion occurs between the partition wall and the inner tube. For this reason, in such an exhaust pipe, a thermal stress similar to the above occurs at a portion where the partition wall and the inner pipe are joined.

The present invention has been made in view of such circumstances, and has as its object to reduce the heat capacity of the inner tube while having a double structure of the inner tube and the outer tube. An object of the present invention is to provide an exhaust pipe of an internal combustion engine that can maintain strength suitably.

[0008]

The means for achieving the above object and the effects thereof will be described below. First, in the invention according to claim 1, in an exhaust pipe of an internal combustion engine having a double pipe structure of an inner pipe and an outer pipe, a reinforcing structure for selectively reinforcing an end of the inner pipe on the internal combustion engine side is provided. I will prepare it.

In the exhaust pipe having the double pipe structure, as described above, a temperature difference is easily generated between the inner pipe and the outer pipe, and when the temperature of the inner pipe is greatly increased by the heat of the combustion gas, at the time of a low temperature start of the engine,
The temperature of the inner tube becomes higher than the temperature of the outer tube, and this temperature difference causes thermal stress inside the inner tube. Also,
In such an inner tube, especially in a portion close to the internal combustion engine, the influence of heat and pressure of the combustion gas discharged from the internal combustion engine is further increased, and there is a concern that the strength is insufficient.

In this respect, according to the above configuration, by selectively reinforcing the end of the inner pipe on the side of the internal combustion engine, it is possible to suitably reinforce only the portion having insufficient strength. Further, according to the configuration, the heat capacity of the other portion, which does not require much strength as compared with the end portion of the inner pipe on the side of the internal combustion engine, can be suppressed by providing no reinforcing structure. Therefore, the strength of the inner tube can be suitably maintained while keeping the heat capacity of the inner tube low.

Further, according to the second aspect of the present invention, the first aspect of the present invention is provided.
In the exhaust pipe of the internal combustion engine according to the above, the reinforcing structure,
Only the end of the inner pipe on the internal combustion engine side has a thicker structure than the other parts of the inner pipe.

According to the above configuration, the heat capacity of the inner pipe can be reduced and the strength can be maintained through a simple structure in which only the end of the inner pipe on the engine side is selectively made thick. become able to.

According to a third aspect of the present invention, in the exhaust pipe of the internal combustion engine according to the first or second aspect, the reinforcing structure is selectively applied to a joint portion with the outer pipe. It shall be.

As described above, the thermal stress generated inside the inner tube due to the temperature difference between the outer tube and the inner tube mainly occurs in a portion restricted by the outer tube. In this regard, according to the above configuration, the influence of the thermal stress can be reduced by selectively reinforcing the strength of the portion where the inner tube and the outer tube are joined, that is, the portion where the deformation of the inner tube is restricted. Avoidance can be efficiently performed.

Further, according to the invention described in claim 4, according to claim 1,
4. An exhaust pipe of an internal combustion engine according to any one of
The inner pipe is partitioned into a plurality of passages by a partition provided therein, and the reinforcing structure is provided over the entire circumference of an end of the inner pipe on the internal combustion engine side. It shall be.

As described above, in the exhaust pipe having the partition in the inner pipe, the partition also thermally expands due to the heat of the combustion gas, and a difference in the amount of thermal expansion occurs between the partition and the inner pipe. . For this reason, in such an exhaust pipe, a thermal stress also occurs in a portion where the partition wall and the inner pipe are joined.

In this respect, according to the above configuration, by reinforcing the entire periphery of the end portion of the inner tube on the side of the internal combustion engine, the portion where stress is generated due to the difference in the amount of thermal expansion between the partition wall and the inner tube is also reduced. Reinforcement can be suitably performed.

According to the fifth aspect of the present invention, the exhaust gas has a double-pipe structure of an inner pipe and an outer pipe, and the combustion gas discharged from an exhaust manifold provided on the exhaust side of the internal combustion engine is supplied to the catalytic converter. In the exhaust pipe of the internal combustion engine to be guided, the entire circumference of the end of the inner pipe on the exhaust manifold side is thicker than other parts of the inner pipe.

Usually, on the exhaust side of the internal combustion engine, an exhaust manifold for guiding the combustion gas discharged from each cylinder to an exhaust pipe is provided. In such an exhaust pipe, the above-mentioned end portion on the exhaust manifold side is used. The influence of the heat and pressure of the combustion gas is greatest.

In this respect, according to the above configuration, by making the entire circumference of the end portion of the inner pipe on the exhaust manifold side thicker than other portions, the portion where the thermal stress becomes the largest is suitably reinforced. You. In addition, since the thickness of the other portions where the thermal stress is not so large as compared with the end portion on the exhaust manifold side can be reduced, also in this case, the heat capacity of the inner tube is suppressed while the strength is reduced. Can be suitably maintained.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an exhaust pipe of an internal combustion engine according to the present invention will be described below.

First, an arrangement of an exhaust pipe in an exhaust system of an internal combustion engine will be described with reference to FIG. Here, an example in which the exhaust pipe is applied to an in-vehicle four-cylinder in-line engine is shown.

An exhaust manifold 12 is attached to the exhaust side of each of the combustion chambers # 1 to # 4 of the engine 11 via an exhaust valve (not shown). # 4 and the exhaust manifold 12 are connected or cut off, respectively.
An exhaust pipe 20 is attached to the downstream side of the manifold 12 via a connection portion 13, and a three-way catalytic converter 14 is attached to the downstream side of the exhaust pipe 20. The exhaust manifold 12, the connecting portion 13, the exhaust pipe 20, and the three-way catalytic converter 14 are connected to each other to form an exhaust passage.

The connection portion 13 is provided with a cushioning material such as a ball joint inside the connection portion 13 so as to secure the strength of the entire exhaust passage against vibration and the like caused by running of the vehicle by the connection portion 13. The connection portion 13 has such a structure that the hermeticity between the inside and the outside of the exhaust passage can be ensured.

Here, the combustion gas after the explosion combustion of the engine 11 is discharged into the exhaust passage by opening the exhaust valve after passing through the explosion stroke in the combustion chamber # 1, and the exhaust gas passes through the exhaust manifold 12 and the exhaust pipe 20. After that, it is led to the three-way catalytic converter 14. Then, after being purified by the converter 14, it is discharged out of the exhaust passage. Further, in the other combustion chambers # 2 to # 4, the combustion gas is discharged to the exhaust passage, purified, and then discharged to the outside of the exhaust passage in the same manner as the combustion chamber # 1.

Here, as described above, the purification performance of the three-way catalytic converter 14 largely depends on its own temperature. Can be. For this reason, when the temperature of the three-way catalytic converter 14 is low, such as when starting the engine, it is desirable to increase the temperature as early as possible in order to ensure its purification characteristics.

Therefore, in the present embodiment, the exhaust pipe 20 has a double pipe structure to secure the strength of the entire exhaust pipe, and the thickness of the exhaust pipe (inner pipe) inside the exhaust pipe 20 is reduced as a whole. The heat capacity of the inner pipe, which is the passage through which the combustion gas passes in the exhaust pipe 20, is reduced.

Next, the structure of the exhaust pipe 20 will be described with reference to FIGS. As shown in FIG. 2, at the end of the exhaust pipe 20 on the engine 11 side, a part of the connection portion 13 is opened to the engine 11 side and the cushioning material is disposed therein. A case 21 having a shape having a space is provided. On the three-way catalytic converter 14 side of this case 21, an outer exhaust pipe (outer pipe) 22 joined at the end on the engine 11 side to form a double pipe structure is formed to be thin as a whole. The inner tube 23 is attached, and the inside of the inner tube 23 and the space in the case 21 are communicated. The inner tube 23 is provided with a partition wall 24 that partitions the inside of the inner tube 23 into two passages (see FIG. 3).

As described above, since the exhaust pipe 20 has a double-pipe structure to reduce the heat capacity of the inner pipe 23, the total amount of heat taken by the inner pipe 23 from the combustion gas can be suppressed. Therefore, when the engine 11 is started at a low temperature, the exhaust pipe 2
0 and even when the temperature of the three-way catalytic converter 14 is low, the inner pipe 2
The temperature rise of 3 saturates early. That is, the temperature of the combustion gas reaching the three-way catalytic converter 14 becomes high at an early stage, and the temperature of the three-way catalytic converter 14 becomes early.

By the way, in the exhaust pipe 20 having such a double pipe structure, since the inner pipe 23 and the outer pipe 22 are partially in contact with each other, a temperature difference is easily generated between the inner pipe 23 and the outer pipe 22. . For this reason, when the temperature of the inner pipe 23 is significantly increased by the heat of the combustion gas, the engine 11 is started at a low temperature,
For example, when the engine 11 is stopped at a high temperature when the temperature of the engine 11 drops significantly, the temperature of the inner pipe 23 becomes higher than the temperature of the outer pipe 22, and the amount of thermal expansion of the inner pipe 23 becomes larger than that of the outer pipe 22. .

Therefore, at those joints where the deformation of the inner tube 23 (thermal expansion of the inner tube) is restrained by the outer tube 22, the thermal stress resulting from the difference in the amount of thermal expansion is reduced by the inner tube 23.
Easily occur in the inside of

In the exhaust pipe 20 of the present embodiment, since the partition 24 is provided inside the inner pipe 23, the partition 24 also thermally expands similarly to the inner pipe 23, and A difference in the amount of thermal expansion also occurs between 24 and the inner tube 23. For this reason, thermal stress is also likely to occur in a portion where the partition wall 24 and the inner tube 23 are joined.

In the inner pipe 23, particularly at the end on the exhaust manifold 12 side (the portion close to the engine 11), the combustion gas discharged from the engine 11 is short because the distance from the engine 11 is short. And the amount of thermal expansion also increases. Furthermore,
In such a portion, since the flow of the combustion gas discharged from the engine 11 is fast, the pressure of the combustion gas is not negligible.

Therefore, in the exhaust pipe 20 of the present embodiment,
In order to ensure the strength against the heat and pressure of the combustion gas, a reinforcing portion 23a having a thick wall is formed over the entire circumference of the end of the inner pipe 23 on the engine 11 side. That is, in the inner pipe 23, only the end portion on the engine 11 side where the influence of the heat and pressure of the combustion gas is large is thickened and the strength is increased. In addition, other portions that do not require much strength as compared with the end of the inner tube 23 on the engine 11 side are formed to be thin as a whole as described above, and the heat capacity of the inner tube 23 is suppressed to be small. Like that.

Further, of the portions where thermal stress is generated inside the inner tube 23 due to the difference in the amount of thermal expansion between the inner tube 23 and the partition 24, the portion where the largest thermal stress is applied, that is, the inner tube 23 and the partition Similarly, the end on the engine 11 side at the portion where the joint 24 is joined is also reinforced.

The reinforcing portion 23a of the inner tube 23
The outer tube 22 is joined to the inner tube 23 in such a manner that the outer peripheral surface of the outer tube 22 abuts on the inner peripheral surface of the end of the outer tube 22 on the engine 11 side, and the outer tube 22 and the inner tube 23 form a double tube structure. ing. Therefore, the reinforcing portion 23a of the inner tube 23 is located at a portion where the outer tube 22 and the inner tube 23 are joined, and the temperature difference between the inner tube 23 and the outer tube 22 causes With respect to the thermal stress generated inside, a strength sufficient to withstand this can be obtained.

According to the exhaust pipe of the present embodiment having the above-described structure, the following excellent functions and effects can be obtained. (1) Only the end of the inner pipe 23 on the engine 11 side is reinforced so that its strength is greater than other parts of the inner pipe 23, so that the heat of the combustion gas discharged from the engine 11 and It is possible to suitably reinforce only the portion where the influence of the pressure is large and the strength is required. In addition, other portions that do not require much strength as compared with the end of the inner tube 23 on the engine 11 side are formed to be thinner as a whole, thereby reducing the heat capacity of the entire inner tube 23. be able to. Therefore, the strength can be maintained while keeping the heat capacity of the inner tube 23 low.

(2) In addition, since the above-mentioned reinforcement is applied with a simple structure in which only the end portion of the inner tube 23 on the engine 11 side is thickened, the realization is easy.

(3) Further, the strength of the inner tube 23 is reinforced at the portion where the inner tube 23 and the outer tube 22 are joined, so that the inner tube 23 transfers its deformation to the outer tube 22. The strength of the constrained portion can be appropriately reinforced. Therefore, a strength capable of withstanding the thermal stress generated inside the inner tube 23 due to the temperature difference between the inner tube 23 and the outer tube 22 can be obtained.

(4) The thickness of the inner pipe 23 is increased over the entire circumference of the end of the inner pipe 23 on the engine 11 side to reinforce the inner pipe 23, so that the amount of thermal expansion between the inner pipe 23 and the partition wall 24 is increased. The strength of the portion where the largest thermal stress is applied among the portions where thermal stress occurs inside the inner tube 23 due to the difference, that is, the portion where the inner tube 23 and the partition wall 24 are joined can be reinforced.

The above embodiment can be implemented by changing its configuration as follows. In the above-described embodiment, the thickness of the end of the inner tube 23 on the engine 11 side is increased to reinforce the strength of the same portion. May be achieved.

Further, a reinforcing member may be provided at the end of the inner pipe 23 on the engine 11 side to reinforce the inner pipe 23. In the above embodiment, the partition wall 24 is provided in such a manner as to partition the inside of the inner tube 23 into two passages. However, the partition wall 24 may be provided in any manner as long as it partitions into a plurality of passages. Good. Even with such a configuration, the portion where the largest thermal stress is applied to the inside of the inner tube 23 due to the difference in the amount of thermal expansion between the inner tube 23 and the partition wall 24, that is, the inner tube 23 It is possible to reinforce the end on the engine 11 side at the portion where the and the partition are joined.

The present invention can be similarly applied to an exhaust pipe which does not necessarily have the above-mentioned partition wall.

[Brief description of the drawings]

FIG. 1 is a plan view showing an arrangement of an exhaust pipe according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a side sectional structure of the exhaust pipe of the embodiment.

FIG. 3 is a sectional view showing a sectional structure along the line AA in FIG. 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Engine, 12 ... Exhaust manifold, 13 ... Connection part, 14 ... Three-way catalytic converter, 20 ... Exhaust pipe, 21 ...
Case, 22: outer tube, 23: inner tube, 23a: reinforcing portion, 2
4: Partition wall.

Claims (5)

[Claims] An exhaust pipe of an internal combustion engine having a double pipe structure of an inner pipe and an outer pipe, characterized by comprising a reinforcing structure for selectively reinforcing an end of the inner pipe on the internal combustion engine side. Exhaust pipe of internal combustion engine. 2. The exhaust pipe of an internal combustion engine according to claim 1, wherein the reinforcing structure has a thickness only at an end of the internal pipe on the internal combustion engine side as compared with other portions of the internal pipe. An exhaust pipe for an internal combustion engine having a thick structure. 3. The exhaust pipe of an internal combustion engine according to claim 1, wherein the reinforcing structure is selectively provided at a joint portion with the outer pipe. . 4. The exhaust pipe of an internal combustion engine according to claim 1, wherein said inner pipe is partitioned into a plurality of passages by a partition provided therein. An exhaust pipe for an internal combustion engine, wherein the reinforcing structure is provided over the entire circumference of an end of the internal pipe on the internal combustion engine side. 5. An exhaust pipe of an internal combustion engine having a double pipe structure of an inner pipe and an outer pipe and guiding combustion gas discharged from an exhaust manifold provided on the exhaust side of the internal combustion engine to a catalytic converter. An exhaust pipe for an internal combustion engine, wherein the entire circumference of an end portion of the inner pipe on the exhaust manifold side is thicker than other portions of the inner pipe.