JP2006348850A - Exhaust pipe structure of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress vibration of an inner pipe provided inside of an outer pipe and reduce noise caused by the vibration, in an exhaust pipe of multiple pipe structure of an internal combustion engine. <P>SOLUTION: In the exhaust pipe structure of the internal combustion engine structured by the inner pipe 1 for making exhaustion gas flow through inside and an outer pipe 2 covering the inner pipe 1, contact parts 1a, 1b, 1c, 1d protruding toward an inside surface 2u of the outer pipe 2 and contacting the inside surface 2u of the outer pipe 2 are provided in the inner pipe 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust pipe structure of an internal combustion engine such as an automobile, and more particularly to a technique for reducing noise caused by vibration of an inner pipe in an exhaust pipe having a multiple pipe structure.

Conventionally, in an exhaust pipe structure of an internal combustion engine such as an automobile, a technique of making the exhaust manifold and the exhaust pipe into a double structure is well known, and there is a document disclosing this double structure (for example, Patent Document 1). reference.).
In this double structure, by reducing the heat capacity of the inner pipe by reducing the thickness of the inner pipe and preventing the temperature of the exhaust gas from decreasing, the catalyst is activated early, and the emission performance at the start of the engine (exhaust gas purification) (Performance) can be improved.
Patent Document 1 discloses a technique for reducing thermal stress generated in an inner tube by providing a bead portion protruding radially outward in the inner tube in a double structure.
JP-A-7-317540

In recent years, further improvement of the emission performance has been demanded from the viewpoint of environmental measures, and further thinning of the inner pipe is required.
However, when the inner tube is made thinner, the rigidity of the material itself decreases, so the vibration of the inner tube becomes larger than that of a thicker inner tube, resulting in a greater noise due to the vibration. There was a problem of becoming.
This noise problem is an important problem particularly in automobiles and the like that require high quietness.
In addition, in patent document 1, although the structure which provided the bead part is disclosed, it is neither disclosed nor suggested about the relationship of the vibration and noise of this bead part and an inner pipe.

  Therefore, the present invention proposes a technique for suppressing the vibration of the inner pipe and reducing the noise caused by the vibration in the exhaust pipe having the multi-pipe structure of the internal combustion engine.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

  That is, an exhaust pipe structure of an internal combustion engine comprising an inner pipe that allows exhaust to pass inside and an outer pipe that covers the inner pipe as defined in claim 1, wherein the inner pipe includes the outer pipe A configuration is provided in which an abutting portion that protrudes toward the inner surface of the tube and contacts the inner surface of the outer tube is provided.

  Further, as described in claim 2, the portion constituting the bent portion of the inner tube is configured to protrude toward the outer side or the inner side of the inner tube.

  Further, as described in claim 3, the inner tube and the contact portion are formed by press molding.

  Further, as described in claim 4, the press molding is performed by a hydraulic molding method.

  In the first aspect of the present invention, by providing the contact portion on the inner tube, the inner tube is restrained with respect to the outer tube via the contact portion, so that the vibration of the inner tube is suppressed. The noise generated due to the vibration can be reduced.

  In the invention according to claim 2, it is possible to improve the surface rigidity at the protruded portion, and the noise due to the vibration of the inner tube can be reduced by improving the surface rigidity.

  In the invention according to claim 3, the number of press forming steps for forming the conventional inner pipe can be maintained, and the operating cost and labor cost of the press can be maintained at substantially the same values as before. .

  Further, in the invention according to claim 4, since it is possible to perform plastic deformation by uniformly applying a liquid pressure to the surface of the molding object, it is possible to mold a complicated shape, and it is possible to mold wrinkles and cracks. Such defects can be reduced.

  As shown in FIGS. 1 and 2, the present invention is an exhaust pipe structure of an internal combustion engine including an inner pipe 1 that allows exhaust to pass through and an outer pipe 2 that covers the inner pipe 1. The tube 1 is provided with contact portions 1 a, 1 b, 1 c, and 1 d that protrude toward the inner surface 2 u of the outer tube 2 and abut against the inner surface 2 u of the outer tube 2.

Thus, by providing the abutting portions 1a, 1b, 1c, and 1d on the inner tube 1, the inner tube 1 is restrained with respect to the outer tube 2 via the abutting portions 1a, 1b, 1c, and 1d. Therefore (being supported (see FIG. 6)), the vibration of the inner tube 1 can be suppressed, and the noise generated due to the vibration can be reduced.
The abutting portions 1a, 1b, 1c, and 1d are formed at appropriate locations on the inner tube 1. In particular, the abutment portions 1a, 1b, 1c, and 1d are strengthened on the outer tube 2 by being formed at portions where vibrations are generated. Is preferred.

  Further, the function of the abutting portions 1a, 1b, 1c, and 1d eliminates the need for a restraining member such as a wire mesh for restraining the inner tube 1, thereby making it possible to keep component manufacturing costs low.

Further, since the inner tube 1 is provided with the contact portions 1a, 1b, 1c, and 1d, the plate member constituting the inner tube 1 is formed with uneven portions, and thus the contact portions 1a, 1b, and 1c are formed. The surface rigidity of the inner tube 1 (the rigidity of the plate material against bending and twisting) can be increased compared to the case where the plate material is configured with a flat surface without providing 1d.
By improving the surface rigidity, it is possible to reduce noise caused by the vibration of the inner tube 1.

Further, from the viewpoint of improving the surface rigidity, as shown in FIG. 1, the portions 1r, 1s, 1t, and 1u constituting the bent portion of the inner tube 1 protrude toward the outside or the inside of the inner tube 1. It is set as the structure which improves the surface rigidity of the said site | part 1r * 1s * 1t * 1u.
In the example of FIG. 1, the branch pipes 1A, 1A... Connected to the cylinder block 5 constitute the inner pipe 1 of the exhaust manifold 6 that is joined to the main pipe 1B, and the exhaust gas is the branch pipe. The parts 1r, 1s, 1t, and 1u joined from 1A, 1A,... To the main pipe 1B are configured to protrude toward the outside or the inside of the inner pipe 1, and the parts 1r, 1s, 1t, and 1u. The surface rigidity is improved.

In such portions 1r, 1s, 1t, and 1u where the exhaust gas discharged from the cylinder block 5 joins the main pipe 1B from the branch pipes 1A, 1A,. Therefore, there is a concern that vibration is generated particularly in a pulsating flow when receiving a large pressure from the exhaust gas.
Therefore, the surface rigidity of the parts 1r, 1s, 1t, and 1u is improved, and according to this, the vibration of the inner tube 1 in the parts 1r, 1s, 1t, and 1u can be suppressed.
In addition, about the site | part 1r, it shall be comprised by the said contact part 1b, and it shall contribute to the vibration prevention mentioned above by contact | abutting to the inner surface 2u of the outer tube | pipe 2. FIG. About other site | part 1s * 1t * 1u, it is supposed that surface rigidity will be improved by projecting toward the inner side of the inner tube | pipe 1. FIG.

  Further, as shown in FIGS. 1 and 2, the exhaust flowing through the inner pipe 1 reaches about 300 degrees to about 550 degrees with respect to the abutting portions 1a, 1b, 1c, and 1d. The inner tube 1 thermally expands due to the temperature rise of the inner tube 1, and the contact portions 1 a, 1 b, 1 c, and 1 d are pressed against the inner surface 2 u of the outer tube 2 by this thermal expansion. Therefore, the inner tube 1 can be reliably supported by the outer tube 2.

  The above configuration can be applied to, for example, an exhaust manifold 6 attached to an engine cylinder block 5 as shown in FIG. Further, the portions 16a, 16b, and 16c constituting the bent portions in the exhaust manifold 16 having the shape shown in FIG. 3 and the bent portions of the pipes 17 arranged on the downstream side of these exhaust manifolds as shown in FIG. It is also possible to apply to the parts 17a and 17b. Further, as shown in FIG. 4, with respect to the linear portion in the pipe 17, contact portions 17 c to 17 f that are in contact with the inner surface 2 u of the outer tube 2 are provided, thereby reducing vibration in the linear portion. Can be achieved.

Further, as shown in FIG. 5, for example, the inner tube 1 is formed by arranging two halved shapes while bulging the contact portions 1a, 1a,... From a flat plate material 1M by press molding. The intermediate molded body 1N is formed, and the inner tube 1 having a circular cross-sectional view is formed by bending the half-shaped joint 1n.
Then, after the inner tube 1 is formed, the half-shaped outer tube members 2a and 2b are covered from both sides of the inner tube 1, and as shown in FIG. 6, welding 4 and 4 of the joint portions of the outer tube members 2a and 2b is performed. Thus, the pipe 3 is configured.

  Incidentally, the intermediate molded body 1N in FIG. 5 has a half-shaped shape, but is not limited to this form, and constitutes an arc member having a larger number of arc shapes in cross-section such as three or four, The inner tube 1 having a circular cross-sectional view may be formed by bending the joint portion of each arc member. Moreover, it is good also as comprising the circular-section view circular inner tube 1 by mutually joining the circular arc member which makes the cross-section-view circular arc shape, for example.

  As described above, by molding the inner tube 1 and the contact portions 1a, 1b, 1c, and 1d (see FIG. 1) by press molding, the inner tube 1 and the contact portions 1a, 1b, and 1d are formed. 1c and 1d can be formed at the same time, the number of press forming steps for forming the conventional inner tube 1 can be maintained, and the operating cost and labor cost of the press can be maintained at substantially the same values as before. be able to.

The press molding is performed by a hydraulic molding method.
This hydraulic forming method is a method of forming a plate-shaped object by using the pressure of the liquid. As a general method, a liquid such as water or oil is applied to one surface of the plate-shaped object. The pressure is applied to the other surface of the molding to be plastically deformed along a mold having a predetermined shape, or the pressure is applied to the inner peripheral surface of the cylindrical molding by a liquid. There is known one that plastically deforms an outer peripheral surface of an object along a mold or the like having a predetermined shape.

According to this hydraulic forming method, it is possible to perform plastic deformation by uniformly applying liquid pressure to the surface of the object to be molded, so that it is possible to form a complicated shape, and it is possible to form wrinkles and cracks. Such defects can be reduced.
For example, as shown in FIG. 1, the contact portions 1a, 1b, 1c, and 1d can have different shapes.
Further, as shown in the inner tube 1F of FIG. 7, the contact portion 1f having a long shape in the flow direction of the exhaust gas is formed, and as shown in the inner tube 1G, the protruding contact portion 1g is formed. In addition, as shown in the inner tube 1H, it is possible to configure the contact portion 1h having a shape that is long in the circumferential direction.
Further, as shown in an inner tube 1I of FIG. 7, a configuration in which an abutting portion 1i protruding outward and recesses 1j and 1j protruding inward are alternately provided so that the inner tube 1 has a corrugated cross section. Also good.

Further, the contact portions 1a, 1b, 1c, and 1d described above are configured to be in point contact or line contact with the inner surface 2u of the outer tube 2, and are transmitted from the inner tube 1 to the outer tube 2. The amount of heat generated is minimized.
Thereby, the temperature fall of the exhaust gas which passes through the inside of the inner pipe 1 can be minimized, and deterioration of the emission performance due to the adoption of the configuration of the present invention can be prevented.

Further, as shown in FIG. 8, the inner tube 1 may have a multiple structure in which a plurality of plate materials are stacked so that a double structure is formed from the plate materials 1P and 1Q, for example.
When the inner tube 1 has a multiple structure as described above, the plate members 1P and 1Q constituting the inner tube 1 mutually dampen vibrations, and the entire inner tube 1 is a single plate member. Compared with the case where it comprises, vibration will be damped and the noise which originates in this vibration can be reduced.
Further, since the inner tube 1 has a multiple structure, the rigidity of the inner tube 1 is improved, so that the inner tube 1 is not vibrated with the outer tube 2, and the improvement in the rigidity Noise can be reduced.

Sectional drawing shown about the structure of the exhaust manifold to which the exhaust pipe structure concerning this invention is applied. Sectional drawing of piping shown about the state which made the contact part contact the inner surface of an outer pipe | tube. Sectional drawing shown about the other structural example of the exhaust manifold to which the exhaust pipe structure concerning this invention is applied. Sectional drawing shown about the structure at the time of applying the exhaust pipe structure concerning this invention about piping provided in the downstream of an exhaust manifold. The figure shown in steps about the manufacturing process of an inner pipe. Sectional drawing of piping which applied the exhaust pipe structure concerning this invention. The figure shown about the variation of the shape of a projection part. Sectional drawing of piping shown about the example which made the inner pipe the double structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner pipe 1a, 1b Contact part 2 Outer pipe 2u Inner surface 3 Piping 4 Welding 5 Cylinder block 6 Exhaust manifold

Claims (4)

An exhaust pipe structure of an internal combustion engine comprising an inner pipe that allows exhaust to pass inside and an outer pipe that covers the inner pipe,
An exhaust pipe structure for an internal combustion engine, wherein the inner pipe is provided with a contact portion that protrudes toward the inner surface of the outer pipe and contacts the inner surface of the outer pipe.   2. The exhaust pipe structure for an internal combustion engine according to claim 1, wherein a portion constituting the bent portion of the inner pipe protrudes outward or inward of the inner pipe. The inner tube and the contact portion are formed by press molding,
An exhaust pipe structure for an internal combustion engine according to claim 1 or 2. The press molding is performed by a hydraulic molding method,
The exhaust pipe structure for an internal combustion engine according to claim 3.

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