COLLECTING PART STRUCTURE OF EXHAUST MANIFOLD

Abstract

A collecting part structure of an exhaust manifold, in which connecting portions of branch pipes 2 to 5 to a head flange 1 are arranged on a straight line, has a reinforcement member that includes two flat plates 10 and 11 to collect and fix downstream side portions f the branch pipes 2 to 5. The flat plates have the same length as an inner diameter of a collecting part 6, and are formed at central positions thereof with slits S1 and S2 facing each other to be joined with each other like a cross shape. The flat plate 11 with the slit S2 at an exhaust-gas upstream side, of the two flat plates 10 and 11, is arranged on a line A2 parallel to a line on which the connecting portions of the branch pipes 2 to 5 to the head flange 1 are arranged.

Description

TECHNICAL FIELD

The present invention relates to a collecting part structure of an exhaust manifold that is connected with an engine of a motor vehicle or the likes.

BACKGROUND OF THE INVENTION

A conventional collecting part structure of an exhaust manifold is disclosed in Japanese Patent application Laid-Open Publication No. 2003-83062. The conventional collecting part structure of the exhaust manifold includes four branch pipes and a collecting part, where exhaust-gas upstream side end portions of the branch pipes are connected with a head flange in line thereon, exhaust-gas downstream side end portions thereof are formed to have a cross section shaped like a quadrant circle, and the collecting part collects and contains the exhaust-gas downstream side end portions assembled to form a circular cross section. A reinforcement member is provided among the exhaust-gas downstream side end portions, being fixed thereto. The reinforcement member is constructed by two flat plates that are coupled like a cross shape by engaging slits formed on the flat plates, and it is arranged so that the flat plates intersect in an oblique direction with a line on which collecting portion of the exhaust-gas upstream side end portions of the branch pipes are aligned.

DISCLOSURE OF THE INVENTION

Problem(s) to be Solved by the Invention

The conventional invention, however, needs to increase plate thicknesses of the flat plates of the collecting part or use expensive material for the flat plate for the following reason. Stress concentration could have generated at the exhaust-gas downstream end portions of the branch pipes and their peripheral portions, being generated by stress due to thermal expansion of the branch pipes and thermal stress due to thermal extension of the head flange in a longitudinal direction thereof. In this case, the flat plates are bent so that both upstream side end portions of the flat plates are not only bent in a width direction thereof so as to approach to each other, but also are twisted to depart from each other in a reverse direction with respect to a thickness direction of the plates, respectively. This requires the flat plates that have a larger plate thickness or are made of expensive material, in order to ensure sufficient strength thereof.

The present invention is made to solve the above-described problem, and its object is to provide a collecting part structure of an exhaust manifold that can easily increase the strength to resist stress concentration at exhaust-gas downstream side end portions and their circumferential portions of branch pipes.

Means for Solving the Problems

According to a first aspect of the present invention there is provided a collecting part structure of an exhaust manifold including four branch pipes, a collecting part and a reinforcement member. Exhaust-gas upstream side end portions of the four branch pipes are connected with a head flange on a straight line, while exhaust-gas downstream side end portions thereof are formed to have a cross section of a quadrant circle. The collecting part collects and contains the exhaust-gas downstream side end portions of the branch pipes to form a circular cross section. The reinforcement member is disposed among the exhaust-gas downstream side end portions of the branch pipes to fix the exhaust-gas downstream side end portions to the collecting part, and the reinforcement member has two flat plates with the same length as an inner diameter of the collecting part. The flat plates are provided at central positions with slits facing to each other to be joined like a cross shape. One flat plate, of the flat plates, that is formed with a slit at an exhaust-gas upstream side thereof is arranged parallel with the straight line on which connecting portions of the exhaust-gas upstream side end portions to the head flange.

EFFECT OF THE INVENTION

In the collecting part structure of the exhaust manifold of the present invention, the reinforcement member is composed of the two flat plates that have the same length as the inner diameter of the collecting part, the flat plates being provided at their central positions with slits facing to each other, the flat plates being coupled with each other by engaging the slits with each other. The one plate with the slit at the exhaust-gas upstream side is arranged parallel with the straight line on which the connecting portions of the exhaust-gas upstream side end portions to the head flange. Each of the flat plates is only bent by stress due to thermal expansion of the branch pipes and thermal stress of the head flange in a longitudinal direction thereof so that exhaust-gas upstream side end portions of the flat plates approach to each other. The flat plates can be prevented from being twisted so that exhaust-gas upstream side end portions thereof depart from each other in a reverse direction with respect to plate thickness directions of the plates. This is advantageous in strength. Further, the slit of the plate that is arranged parallel to the straight line is provided at the exhaust-gas upstream side of the plate, so that defects, such as stress concentration at the slit and cracks at its periphery, can be avoided. As a result, strength can be easily increased to resist against the stress concentration at the exhaust-gas downstream side end portions of the branch pipes and their peripheral portions.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, features and advantages of the present invention will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is an entire front view showing an exhaust manifold to which a collecting part structure of an exhaust manifold of an embodiment according to the present invention is applied;

FIG. 2 is an entire right side view showing the exhaust manifold to which the collecting part structure of the exhaust manifold of the embodiment according to the present invention is applied;

FIG. 3 is a cross sectional view taken along a line S3-S3 in FIG. 1;

FIG. 4A is an exploded view showing a reinforcement member that is used in the first embodiment, and FIG. 4B is a perspective view of the reinforcement member thereof;

FIG. 5A and FIG. 5B are views illustrating how to assemble the reinforcement member of the first embodiment;

FIG. 6A and FIG. 6B are views illustrating how to assemble branch pipes and the reinforcement member that are used in the first embodiment; and

FIG. 7 is a bottom view showing exhaust-gas downstream side end portions of the exhaust manifold of the embodiment where a collecting part is removed.

DESCRIPTION OF REFERENCE NUMBERS

• S1, S2 slit
• X1, X2 welded portion
• 1 head flange
• 1a connecting surface
• 2, 3, 4, 5 branch pipe
• 2a, 3a, 4a, 5a exhaust-gas downstream side end portion
• 2b, 3b, 4b, 5b wall portion (that contacts with a reinforcement member)
• 6 collecting part
• 6a exhaust-gas upstream side end portion
• 7 catalyst substrate
• 8 catalytic converter
• 9 reinforcement member
• 10, 11 flat plate
• 10a, 11a cut-off portion
• 20 assembly jig
• 20a cut-off portion

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment according to the present invention will be described with reference to the accompanying drawings.

First Embodiment

Hereinafter, a first embodiment will be described.

FIG. 1 is an entire front view showing an exhaust manifold to which a collecting part structure of an exhaust manifold of the first embodiment according to the present invention, FIG. 2 is a right side view of the same, FIG. 3 is a cross sectional view taken along a line S3-S3 in FIG. 1, FIG. 4A is an exploded view showing a reinforcement member of the first embodiment, and FIG. 4B is a perspective view showing the same.

FIG. 5A and FIG. 5B are views illustrating how to assemble the reinforcement member of the first embodiment, FIG. 6A and FIG. 6B are views illustrating how to assemble branch pipes and the reinforcement member, and FIG. 7 is a bottom view illustrating exhaust-gas downstream side end portions of the exhaust manifold of the first embodiment where a collecting part thereof is removed.

As shown in FIG. 1 and FIG. 2, the collecting part structure of the exhaust manifold of the first embodiment mainly includes a head flange 1 that is connected with a not-shown engine, four branch pipes 2 to 5 that are respectively connected with cylinders of the engine through the head flange 1, a collecting part 6 that is formed like a circular cylinder, and a catalytic converter 8 that is connected with the collecting part 6 and contains catalyst substrate 7.

As shown in FIG. 1 to FIG. 7, connecting portions, of the four branch pipes 2 to 5, to the head flange 1 are arranged in line on a straight line Al.

On the other hand, as shown in FIG. 3, exhaust-gas downstream side end portions of the branches 2 to 5 are formed to have a cross section of quadrant circle, and they are contained in an exhaust-gas upstream side end portion 6a of the collecting part 6 in a state where the exhaust-gas downstream side end portions of the branches 2 to 5 are collected to form a circular cross section.

In addition, the reinforcement member 9 is provided among the exhaust-gas downstream side end portions of the branches 2 to 5.

Specifically, as shown in FIG. 4A and FIG. 4B, the reinforcement member 9 is composed of two flat plates 10 and 11. Each of which has a length L1 that is approximately equal to an inner diameter of the collecting part 6, and they are provide at central positions on opposed sides thereof with slits S1 and S2, respectively. The flat plates 10 and 11 are joined by engaging the slits S1 and S2 with each other to form like a cross shape.

In addition, both end portions of the flat plate 10 is formed at an exhaust-gas upstream side thereof with cut-out portions 10a, while one end portion of the flat plate 11 is formed at an exhaust-gas upstream side thereof with a cut-off portion 11a.

In a case where the flat plates 10 and 11 are fixed with each other, the flat plate 10 is engaged with an assembly jig 20, and then the flat plate 11 is engaged with the assembly jig 20. In this assembly, the flat plates 10 and 11 are prevented from being assembled in a wrong state thereof, because three cut-off portions 20a that are formed on the assembly jig 20 correspond to the cut-off portions 10a and 11a of the flat plates 10 and 11. Incidentally, the flat plates 10 and 11 may be fixed with each other by welding.

In addition, as shown in FIG. 6, wall portions 2b to 5b of the branch pipes 2 to 5 and the reinforcement member 9 are fixed with each other at welded portions X1, as shown in FIG. 3, in a state where the reinforcement member 9 is disposed among the exhaust-gas downstream side end portions 2a to 5a and it slightly projects toward a collecting part 6 side.

In this state, the flat plate 11, which is formed with the slit S2 at the exhaust-gad upstream side thereof, is set parallel to a line A1, namely on a line A2 that is parallel to the line A1, on which connecting portions of the branch pipes 2 to 5 that are connected with the head flange 1 are aligned on a connecting surface 1 a of the head flange 1.

Further, as shown in FIG. 3, the branch pipes 2 to 5 are inserted into the exhaust-gas upstream side end portion 6a together with the reinforcement member 9, and then outer circumferential surfaces of the branches 2 to 5 are fixed to the collecting part 6 together with a part of the reinforcement member 9 at welded portions X2.

In the thus-constructed collecting part structure of the exhaust manifold, exhaust gas flows in the collecting part 6 from the cylinders of the engine through the branch pipes 2 to 5, and then it is discharged into the catalytic converter 8.

In this operation, the head flange 1 thermally expands mainly in a longitudinal direction thereof due to heat of the exhaust gas, since the connecting portions of the branch pipes 2 to 5 are arranged on the straight line L1. As a result, its thermal stress acts on the branch pipes 2 to 5 in a direction where the exhaust-gas downstream side end portions 2a to 5a of the branch pipes 2 to 5 are separated from each other outwardly in a longitudinal direction thereof.

Accordingly, since the flat plate 11, the slit S2 of which is provided at the exhaust-gas upstream side, is aligned on the line A2 that is parallel to the line A1 on which the connecting portions of the branch pipes 2 to 5 on the connecting surface 1a of the head flange 1 are arranged, the thermal stress acts on the flat plate 11 only in a direction where the flat plate 11 is bent in directions indicated by arrows B1 and B2, without stress acting thereon so that the upstream side both end portions of the flat plate 11 are twisted in reverse directions. Therefore, the plate 11 is advantageous in strength. In addition, when these bending forces acts, it becomes easy to avoid the stress that is concentrated at the slit S2 to tear the flat plate 11 at the slit S2, because the slit S2 is formed at the exhaust-gas upstream side of the flat plate 11 and there is no slit at the exhaust-gas downstream side thereof. Further, there is no twisting stress that twists the exhaust-gas upstream side end portions of the flat plate 10, which is arranged in perpendicular to the flat plate 11. Additionally, the bending stress acts in the directions indicated by B1 and B2, and accordingly it approximately does not act on the slit S1. This is advantageous in strength to the flat plate 10. Thus, there is no danger in compression buckling of the flat plate 10 due to the thermal stress, and strength can be improved at peripheral portions of the exhaust-gas downstream side end portions 2a to 5a of the branch pipes 2 to 5.

As described above, in the collecting part structure of the exhaust manifold of the first embodiment, the exhaust manifold includes the four branch pipes 2 to 5, the collecting part 6 and the reinforcement member 9. Exhaust-gas upstream side end portions of the four branch pipes 2 to 5 are connected with the head flange 1 on the straight line, while exhaust-gas downstream side end portions thereof are formed to have the cross section of the quadrant circle. The collecting part 6 collects and contains the exhaust-gas downstream side end portions 2a to 5a of the branch pipes to form the circular cross section. The reinforcement member 9 is disposed among the exhaust-gas downstream side end portions 2a to 5a of the branch pipes 2 to 5 to fix the exhaust-gas downstream side end portions to the collecting part 6, and the reinforcement member 9 has the two flat plates 10 and 11 with the same length L1 as an inner diameter of the collecting part 6. The flat plates 10 and 11 are provided at the central positions with slits S1 and S2 facing to each other to be joined like the cross shape. The one flat plate 11, of the flat plates 10 and 11, that is formed with the slit S2 at an exhaust-gas upstream side thereof is arranged parallel with the straight line A1 on which the connecting portions of the exhaust-gas upstream side end portions to the head flange 1. Therefore, the exhaust-gas upstream side both end portions of the flat plates 10 and 11 can be prevented from being twisted in the reverse direction, which is advantageous in strength. As a result, the strength can be easily increased to resist the stress concentration at the exhaust-gas downstream side end portions 2a to 5a and their peripheral portions.

While the embodiment has been explained above, the present invention is not limited to the above-described embodiment, and its design changes and modifications are contained in the present invention as long as they do not depart from the subject-matter of the present invention.

For example, as explained above, the flat plate 11 that is formed with the slit S2 at the exhaust-gas upstream side is arranged parallel to the connecting surface 1a of the head flange 1 in the first embodiment, while it is preferable that an exhaust-gas upstream side slit be formed on one of the flat plates 10 and 11 which is arranged in a state where the one is closer to parallel to the connecting surface la of the head flange 1. This case can also obtain the effects of the present invention.

Claims

1. A collecting part structure of an exhaust manifold including four branch pipes in which exhaust-gas upstream side end portions thereof are connected with a head flange on a straight line, exhaust-gas downstream side end portions thereof being formed to have a cross section of a quadrant circle; a collecting part that collects and contains the exhaust-gas downstream side end portions of the branch pipes to form a circular cross section; and a reinforcement member that is disposed among the exhaust-gas downstream side end portions of the branch pipes to fix the exhaust-gas downstream side end portions to the collecting part, the reinforcement member having two flat plates with the same length as an inner diameter of the collecting part, the flat plates being provided at central positions with slits facing to each other to be joined like a cross shape, the collecting part structure characterized in that

one flat plate, of the flat plates, that is formed with a slit at an exhaust-gas upstream side thereof is arranged parallel with the straight line on which connecting portions of the exhaust-gas upstream side end portions to the head flange.