JP3305884B2 - Exhaust manifold - 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 manifold of an engine, and more particularly, to an end branch pipe on both sides serving as an exhaust gas discharge path, and a plurality of central branch pipes also serving as an exhaust gas discharge path. A collecting section for collecting the end branch pipe and the central branch pipe, wherein a discharge path of the end branch pipe and the central branch pipe is separated, and the collecting section is formed at a center of the end branch pipe and the central branch pipe. The present invention relates to an exhaust manifold located at a distance from a line and provided with measures against thermal deformation.

[0002]

2. Description of the Related Art An exhaust manifold is a heat-resistant tubular member that collects exhaust gas from an engine and sends the exhaust gas to a muffler (muffler). As shown in FIG. 1, the exhaust manifold includes a mounting flange 3 attached to the cylinder head 7, and branch pipes 2a to 2d connected to the respective exhaust ports 7a of the cylinder head 7.
And a collecting part 6 for collecting the branch pipes 2a to 2d.
In the exhaust manifold 1 for the in-line four-cylinder engine, the branch pipes 2a to 2d are taken into consideration in order of exhaust from the engine so that the exhaust gases passing through the branch pipes 2a to 2d do not interfere with each other.
The combination of the end branch pipes 2a and 2d at both ends and the central branch pipe 2
b and 2c are designed so that they are separated and do not follow the same exhaust path to the collecting section 6 of the exhaust manifold 1.

Generally, the exhaust manifold 1 is provided without connecting the mounting flanges 3a to 3d for the purpose of preventing gas from leaking from warpage due to plastic deformation of the branch pipes 2a to 2d generated in the heating process of the engine. May have independent shape. The deformation behavior due to heat of the in-line four-cylinder engine exhaust manifold in which the mounting flanges 3a to 3d are independent and the collecting part 6 is largely deviated from the center of the exhaust manifold 1 will be described with reference to FIG. In FIG. 2, (a)
Shows a state in which the mounting flanges 3a to 3d attach the independent exhaust manifold 1 to the cylinder head 7 with bolts through bolt holes (not shown). (B) shows a state in which the engine starts to operate and the end branch pipe 2a of the exhaust manifold 1 is heated by the exhaust gas from the cylinder head 7 and thermally expanded. Only one end branch pipe 2a is isolated, and three branch pipes 2b to 2d other than the mounting flange 3 and the end branch pipe 2a.
It is restrained by being sandwiched between. (C) shows a state in which the end branch pipe 2a is restrained and cannot be thermally expanded freely, but undergoes plastic deformation by compression. Then, as shown in (d), the engine stops and enters a cooling process, and the mounting flange 3a is largely deformed due to the heat shrinkage of the end branch pipe 2a.

[0004] As described above, in the exhaust manifold having a structure in which the mounting flange is independent and the collecting portion is largely deviated from the center portion, the mounting flange on the collecting portion is easily deformed. In order to prevent damage to the exhaust manifold having an independent mounting flange, Japanese Utility Model Publication No. Hei 2-13699 discloses reinforcing ribs between adjacent branch pipes to increase rigidity.
There is a disclosure of preventing gas leakage due to thermal deformation and reducing the rigidity of the reinforcing rib at the portion where the thermal deformation is the largest to be less than the rigidity of the other ribs, thereby relaxing the portion where the thermal stress is maximized.

[0005] On the other hand, in order to suppress shrinkage due to plastic deformation due to compression generated in the heating process of the engine, a shape in which all the mounting flanges are connected may be adopted. In Japanese Utility Model Publication No. 2-24898, reinforcing ribs are provided at the intersections of the branch pipes and ribs are provided on the side faces of the end branch pipes. Two concave strips are formed on both sides of the exhaust pipe to form a large heat-dissipating surface to suppress temperature rise, reduce the temperature difference between the outer wall of the exhaust path and the partition near the central branch pipe, and reduce the difference in thermal expansion. There is a disclosure of reducing the size as much as possible to prevent the occurrence of cracks.

[0006]

However, according to Japanese Utility Model Publication No. 2-13699, a reinforcing rib is provided between adjacent branch pipes in a structure in which the mounting flange is independent.
The end branch pipe is easily deformed by heat shrinkage. On the other hand, according to Japanese Utility Model Publication No. 2-24898 in which all the mounting flanges are connected, the amount of plastic deformation of the collecting portion is increased due to the restraint by the connecting portion, and warpage is likely to occur. In addition, the weight increases and it is not economical. The present invention solves the above problems,
Reduce the amount of deformation of the end branch pipe on the side close to the gathering part, and
An object of the present invention is to provide a highly reliable exhaust manifold that reduces plastic deformation of an assembly.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention comprises an end branch pipe on both sides serving as an exhaust gas discharge path, and a plurality of central branch pipes also serving as an exhaust gas discharge path. A collecting part for collecting the end branch pipe and the central branch pipe, wherein discharge paths of the end branch pipe and the central branch pipe are separated,
In the exhaust manifold, in which the collecting portion is located away from the center line of the end branch pipe and the center branch pipe, between the mounting flange of the end branch pipe near the collecting section and the mounting flange adjacent thereto. And a connecting portion is provided to separate the other mounting flanges. A vertical wall is provided at the intersection of the end branch pipe and the branch pipe adjacent to the end branch pipe. Also, a rib is provided on the side surface of the end branch pipe on the side closer to the collecting portion.

[0008]

Operation The operation will be described with reference to FIG. The mounting flange 3a of the end branch pipe 2a close to the collecting portion 6 and the mounting flange 3
When the connecting portion 4 is provided between the end branch pipe 2a and the mounting flange 3a, the rigidity of the end branch pipe 2a and the mounting flange 3a is improved. Then, as shown in (b), in the subsequent cooling process, the end branch pipe 2a is not easily deformed against the tensile stress accompanying the heat shrinkage. And the warpage of the mounting flange 3a is also reduced. Also, the end branch pipe 2a and the adjacent central branch pipe 2
b, by selectively providing the ribs 9 on the side surfaces of the vertical wall 10 and the end branch pipe 2a, the rigidity of the end branch pipe 2a is further increased, and the plasticity of the compression generated in the end branch pipe 2a during heating is increased. The amount of deformation is reduced.

[0009]

【Example】

(Embodiment 1) FIG. 1 shows an exhaust manifold for a four-cylinder engine showing one embodiment of the present invention. In FIG. 1, an exhaust manifold 1 has end branch pipes 2a and 2d on both sides serving as exhaust gas discharge paths, and an exhaust gas discharge path 2 also serving as exhaust gas exhaust paths.
A central branch pipe 2b and 2c, an end branch pipe 2a and 2d, and a collecting part 6 that assembles the central branch pipes 2b and 2c. Are separated, and the collecting portion 6 is located away from the center lines of the end branch pipes 2a and 2d and the center branch pipes 2b and 2c. And
A connecting portion 4 is provided between the mounting flange 3a of the end branch pipe 2a near the collecting portion 6 and the mounting flange 3b adjacent thereto, and between the other mounting flanges 3b and 3c, 3c and 3
d is separated.

FIG. 4 is a diagram showing the transition of the shrinkage amount (d dimension) of the end branch pipe 3a after the exhaust manifold of the first embodiment of the present invention and the conventional exhaust manifold with the detached mounting flange subjected to a heating and cooling test. It is. As shown in FIG. 4, the d dimension of the conventional exhaust manifold contracts more rapidly than the initial stage. On the other hand, in the case of the present invention, the rigidity near the end branch pipe 3a is improved, and as a result, the shrinkage of the d dimension is almost suppressed.

(Embodiment 2) FIG. 2 shows an exhaust manifold for a four-cylinder engine showing another embodiment of the present invention. The exhaust manifold 1 is provided with a connecting portion 4 between a mounting flange 3a of an end branch pipe 2a near a collecting portion 6 and a mounting flange 3b adjacent thereto, and other mounting flanges 3b and 3c.
, 3c and 3d are separated and the end branch pipe 2a
A vertical wall 10 is provided at an intersection 8 of a branch pipe (central branch pipe) 2b adjacent to the end branch pipe 2a, and a rib 9 is provided on a side surface of the end branch pipe 2a closer to the collecting section 6. . By selectively adding the vertical wall 10 and the rib 9 described above, the end branch 3
The rigidity near a can be further improved.

FIG. 5 shows (a) an exhaust manifold according to a second embodiment of the present invention, (b) an exhaust manifold having a structure in which a conventional mounting flange is separated, and (c) another structure in which a conventional mounting flange is connected. FIG. 3 is a diagram illustrating a warp state of an exhaust manifold after a durability test. In the exhaust manifold of the present invention shown in FIG. 5A, the mounting flanges 3a to 3d have less warpage. On the other hand, in the conventional case (b), the mounting flange 3a is largely warped, and there is a risk that the exhaust gas leaks. (C) of a conventional product having another structure is a connecting portion 4 between the mounting flanges 3a to 3d.
Due to the restraints a to 4c, the amount of plastic deformation in the compression of the collecting portion 6 increases, and the entire exhaust manifold 1 warps, and there is a risk that the exhaust gas leaks.

EXAMPLE 3 An exhaust manifold for a high-performance gasoline engine having a displacement of 2 liters in the in-line four-cylinder engine shown in FIG. 2 was integrally manufactured by casting from 4% Si spheroidal graphite cast iron. Then, an endurance test was performed using a single-unit thermal fatigue test apparatus that emits exhaust gas. As a test condition, a cooling (GO-STOP) cycle in which heating (10 minutes) -cooling (10 minutes) corresponding to a full load operation at an engine speed of 6000 rpm as one cycle was performed up to 500 cycles. The exhaust gas temperature at full load was about 860 ° C. Under these conditions, the temperature of the assembly 6 was about 780 ° C. As a result of the evaluation test, the exhaust manifold 1 showed a small amount of warpage deformation of the mounting flange 3a alone, and did not cause gas leakage and cracks due to the deformation.

On the other hand, a similar test was conducted by assembling an exhaust manifold having a conventional structure made of 4% Si spheroidal graphite cast iron and having independent mounting flanges 3a to 3d. As a result, in the conventional exhaust manifold, the mounting flange 3a is warped and deformed, and the mounting flange 3a generated from the initial stage of the endurance test.
Gas suddenly spread at the 153th cycle, making it impossible to continue the durability test. In addition, a similar test was conducted by assembling a conventional exhaust manifold made of 4% Si spheroidal graphite cast iron and connecting the mounting flanges 3a to 3d. As a result, the durability evaluation up to 500 cycles was completed.
Gas leakage from the mounting flange 3a was observed continuously from the beginning of the durability test.

[0015]

As described above, the exhaust manifold according to the present invention, in which the collecting portion is greatly deviated from the central portion, is as follows.
A connecting portion is provided between the mounting flange on the side closer to the collecting portion and the mounting flange adjacent thereto, and furthermore, a vertical wall or a collecting portion is provided at the intersection of the end branch pipe and the branch pipe adjacent to the end branch pipe. By selectively adding ribs to the side of the end branch pipe closer to the part, the rigidity of the vicinity of the end branch pipe and the gathering part is improved, and the warpage of the mounting flange can be prevented even when repeated heating and cooling is performed. There is little leakage of exhaust gas and reliability is remarkably improved.

[Brief description of the drawings]

FIG. 1 is a front view of an exhaust manifold according to one embodiment of the present invention.

FIG. 2 is a front view of an exhaust manifold according to another embodiment of the present invention.

FIG. 3 is a diagram for explaining the deformation behavior of the exhaust manifold due to heat.

FIG. 4 is a diagram showing the transition of the end branch pipe (d dimension) of the exhaust manifold of the present invention and the conventional exhaust manifold.

FIG. 5 is a view showing a warp state of a mounting flange after a durability test of the present invention and a conventional exhaust manifold.

[Explanation of symbols]

1: exhaust manifold, 2a, 2d: end branch pipe,
2b, 2c: central branch pipe, 3a to 3d: mounting flange,
4: connecting part, 5: collecting flange, 6: collecting part, 7: cylinder head, 8: crossing part, 9: rib, 10: vertical wall.

Claims (3)

(57) [Claims] 1. An end branch pipe on both sides serving as an exhaust gas discharge path, a plurality of central branch pipes also serving as an exhaust gas discharge path, and an assembling part which collects the end branch pipe and the central branch pipe. The outlet branch of the end branch and the center branch are separated,
In the exhaust manifold in which the collecting portion is located apart from the center line of the end branch pipe and the center branch pipe, between the mounting flange of the end branch pipe close to the collecting section and the mounting flange adjacent thereto. An exhaust manifold provided with a connecting portion and separated from other mounting flanges. 2. The exhaust manifold according to claim 1, further comprising a vertical wall at an intersection of the end branch pipe and a branch pipe adjacent to the end branch pipe. 3. The exhaust manifold according to claim 1, wherein a rib is provided on a side surface of an end branch pipe closer to the collecting portion.