JPH0821236A - Exhaust manifold - Google Patents

Abstract

PURPOSE:To provide an exhaust manifold excellent in reliability, wherein exhaust gas is not leaked if the exhaust manifold is repeatedly heated and cooled, by decreasing the warping deformation amount of attaching flanges. CONSTITUTION:In an exhaust manifold 1 having the shape wherein the collection part is largely deviated from the center, connection parts 4 are provided on an attaching flange near the collection part, and between attaching flanges 3a to 3d adjacent to it and a vertical wall is selectively added onto the intersecting part of end branched pipes 2a, 2d and the branched pipe adjacent to the end branched pipes 2a, 2d, and ribs are selectively added onto the side surface of the end branched pipes near the collection part 6, thereby stiffness of the vicinities of the end branched pipes 2a to 2d and the collection part 6 is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust manifold for an engine, and more specifically, to end branch pipes on both sides serving as exhaust gas exhaust passages, and a plurality of central branch pipes also serving as exhaust gas exhaust passages. A discharge path of the end branch pipe and the central branch pipe is separated, and the gathering part is the center of the end branch pipe and the central branch pipe. The present invention relates to an exhaust manifold located away from the line with measures against thermal deformation.

[0002]

2. Description of the Related Art An exhaust manifold is a tubular heat-resistant member that collects exhaust gas from an engine and sends it to a muffler. As shown in FIG. 1, the exhaust manifold includes a mounting flange 3 attached to the cylinder head 7 and branch pipes 2 a to 2 d connected to the exhaust ports 7 a of the cylinder head 7.
And a collecting unit 6 that collects the branch pipes 2a to 2d,
In the exhaust manifold 1 for an in-line 4-cylinder engine, the branch pipes 2a to 2d are considered in consideration of the exhaust order from the engine so that the exhaust gases passing through the branch pipes 2a to 2d do not interfere with each other.
Is a combination of the end branch pipes 2a and 2d at both ends and the central branch pipe 2
b and 2c are separated from each other, and are designed so as not to pass through the same exhaust path to the collecting portion 6 of the exhaust manifold 1.

In general, the exhaust manifold 1 does not connect between the mounting flanges 3a to 3d for the purpose of preventing gas from leaking from a warp due to plastic deformation of compression generated in the branch pipes 2a to 2d during the engine heating process. 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 portion 6 is largely deviated from the central portion of the exhaust manifold 1 will be described with reference to FIG. In FIG. 2, (a)
Shows a state in which the exhaust manifold 1 having independent mounting flanges 3a to 3d is attached to the cylinder head 7 with bolts through bolt holes (not shown). (B) shows a state in which the engine starts operation 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 sandwiched between and and is restrained. (C) shows a state in which the end branch pipe 2a is constrained to be unable to freely perform thermal expansion and to cause plastic deformation due to compression. Then, as shown in (d), the engine is stopped and starts the cooling process, and the mounting flange 3a is largely deformed due to the thermal contraction of the end branch pipe 2a.

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 central portion, the mounting flange on the collecting portion side is easily deformed. As a means for preventing damage to an exhaust manifold having a structure in which a mounting flange is independent, in Japanese Utility Model Publication No. 2-13699, reinforcing ribs are provided between adjacent branch pipes to enhance rigidity,
It is disclosed that gas leakage due to thermal deformation is prevented, and the reinforcing ribs of the portion where the thermal deformation is maximized are made smaller than the rigidity of other ribs to relax the portion where the thermal stress is maximum.

On the other hand, in order to suppress shrinkage caused by plastic deformation of compression that occurs during the heating process of the engine, all the mounting flanges may be connected in a shape. In Japanese Utility Model Publication 2-24898, reinforcing ribs are provided at the intersections of the branch pipes, ribs are provided on the side surfaces of the end branch pipes, and a ridge is formed outside the central branch pipe portion. 2 concave lines are formed on both sides of the to reduce the temperature rise by forming a large heat dissipation surface and reduce the temperature difference between the outer wall of the exhaust path and the partition of the central branch pipe to reduce the thermal expansion difference. There is a disclosure to prevent the occurrence of cracks by reducing the size as much as possible.

[0006]

However, according to Japanese Utility Model Publication No. 2-13699, a reinforcing rib is provided between adjacent branch pipes with a structure in which the mounting flanges are independent of each other.
The end branch pipe is easily deformed by heat contraction. On the other hand, according to Japanese Utility Model Publication No. 2-24898, in which all the mounting flanges are connected to each other, due to the restraint by the connecting portion, the plastic deformation amount of the collecting portion becomes large and the warp is likely to occur. In addition, the weight increases and it becomes uneconomical. The present invention solves the above problems,
Reduce the amount of deformation of the end branch pipe near the gathering part, and
An object of the present invention is to provide an exhaust manifold with excellent reliability that reduces plastic deformation of the collecting portion.

[0007]

In order to achieve the above object, the present invention provides end pipes on both sides which are exhaust gas discharge paths, and a plurality of central branch pipes which are also exhaust gas discharge paths. A discharge part of the end branch pipe and the center branch pipe is separated from each other,
In the exhaust manifold in which the collecting portion is located away from the center lines of the end branch pipe and the central branch pipe, between the mounting flange of the end branch pipe on the side closer to the collecting portion and the mounting flange adjacent thereto. It is characterized in that a connecting portion is provided on the and the other mounting flanges are separated from each other. A vertical wall is provided at the intersection of the end branch pipe and the branch pipe adjacent to the end branch pipe. Further, a rib is provided on the side surface of the end branch pipe near the gathering portion.

[0008]

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 this mounting flange 3
Providing the connecting portion 4 between the mounting flange 3b adjacent to a improves the rigidity of the end branch pipe 2a and the mounting flange 3a. Then, as shown in (b), in the subsequent cooling process, the end branch pipe 2a is not easily deformed against the tensile stress due to the thermal contraction. Also, the warp of the mounting flange 3a is reduced. Further, the central branch pipe 2 adjacent to the end branch pipe 2a
By selectively providing the ribs 9 on the vertical wall 10 or the side surface of the end branch pipe 2a between b, the rigidity of the end branch pipe 2a is further increased, and the plasticity of compression generated in the end branch pipe 2a during heating is increased. The amount of deformation is reduced.

[0009]

【Example】

(Embodiment 1) FIG. 1 is an exhaust manifold for a four-cylinder engine showing an embodiment of the present invention. In FIG. 1, an exhaust manifold 1 serves as end exhaust pipes 2a and 2d on both sides which are exhaust gas exhaust paths, and also serves as exhaust gas exhaust path 2
The central branch pipes 2b and 2c, the end branch pipes 2a and 2d, and the collecting portion 6 that collects the central branch pipes 2b and 2c, and the discharge path of the end branch pipes 2a and 2d and the central branch pipes 2b and 2c. Are separated from each other, and the collecting portion 6 is located away from the center lines of the end branch pipes 2a and 2d and the central branch pipes 2b and 2c. And
The 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 3c.
It is separated between d.

FIG. 4 is a diagram showing the transition of the shrinkage amount (dimension d) of the end branch pipe 3a after the heating and cooling test of the exhaust manifold of the first embodiment of the present invention and the exhaust manifold in which the conventional mounting flange is separated. Is. From FIG. 4, in the conventional exhaust manifold, the d dimension is contracted more rapidly from the initial stage. On the other hand, in the case of the present invention, it is understood that the rigidity in the vicinity of the end branch pipe 3a is improved, and as a result, the shrinkage of the d dimension is almost suppressed.

(Embodiment 2) FIG. 2 is 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 the mounting flange 3a of the end branch pipe 2a near the collecting portion 6 and the mounting flange 3b adjacent thereto, and the other mounting flanges 3b and 3c.
And 3c and 3d are separated from each other, and the end branch pipe 2a is provided.
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 near the collecting portion 6. . By selectively adding the vertical wall 10 and the rib 9 described above, the end branch pipe 3
The rigidity near a can be further improved.

FIG. 5 shows (a) an exhaust manifold of Embodiment 2 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. It is a figure which shows the warp situation after an endurance test about an exhaust manifold. The exhaust manifold of the present invention shown in FIG. 5 (a) has little warp with the mounting flanges 3a to 3d. On the other hand, in the conventional case (b), the mounting flange 3a is largely warped, and there is a risk of exhaust gas leaking. Further, (c) of the conventional product having a different structure is the connecting portion 4 between the mounting flanges 3a to 3d.
Due to the restraint by a to 4c, the amount of plastic deformation of the compression of the collecting portion 6 becomes large, the warp of the entire exhaust manifold 1 is large, and there is a risk of exhaust gas leakage.

(Embodiment 3) An exhaust manifold for a high-performance gasoline engine having a displacement of 2 liters in the in-line 4-cylinder engine shown in FIG. 2 was integrally manufactured by casting of 4% Si spheroidal graphite cast iron. Then, an endurance test was carried out with a single-unit thermal fatigue test device that emits exhaust gas. As a test condition, a heating / cooling (GO-STOP) cycle having one cycle of heating (10 minutes) -cooling (10 minutes) corresponding to full load operation at an engine speed of 6000 rpm was performed up to 500 cycles. The exhaust gas temperature at full load was about 860 ° C. Under this condition, the temperature of the collecting portion 6 was about 780 ° C. As a result of the evaluation test, the exhaust manifold 1 had a small amount of warp deformation of the mounting flange 3a alone, and gas leakage and cracks due to the deformation did not occur.

On the other hand, an exhaust manifold having a conventional structure made of 4% Si spheroidal graphite cast iron and having independent mounting flanges 3a to 3d was assembled and the same test was conducted. As a result, in the conventional exhaust manifold, the mounting flange 3a is warped and deformed, and the mounting flange 3a has been generated since the initial stage of the durability test.
The gas leak from the tank spread all at once at the 153rd cycle, making it impossible to continue the durability test. Further, a similar test was carried out by assembling a conventional exhaust manifold having a different structure with 4% Si spheroidal graphite cast iron, and the mounting flanges 3a to 3d were connected. As a result, the durability evaluation up to 500 cycles was completed,
Gas leakage from the mounting flange 3a was continuously observed from the beginning of the durability test.

[0015]

As described above, regarding the exhaust manifold in which the collecting portion of the present invention has a shape largely deviated from the central portion,
A connecting portion is provided between the mounting flange on the side close to the collecting portion and the mounting flange adjacent to the mounting flange, and a vertical wall is formed at the intersection of the end branch pipe and the branch pipe adjacent to this end branch pipe, or By selectively adding ribs to the side surface of the end branch pipe on the side closer to the end part, the rigidity of the vicinity of the end branch pipe and the gathering part is improved, and the mounting flange warps even after repeated heating and cooling. There is little exhaust gas leakage and reliability is greatly improved.

[Brief description of drawings]

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

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

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

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

FIG. 5 is a diagram showing a warp state of a mounting flange after an endurance test on the exhaust manifold of the present invention and the conventional exhaust manifold.

[Explanation of symbols]

1: Exhaust manifold, 2a, 2d: End branch pipe,
2b and 2c: central branch pipe, 3a to 3d: mounting flange,
4: Connection part, 5: Assembly flange, 6: Assembly part, 7: Cylinder head, 8: Intersection part, 9: Rib, 10: Vertical wall.

Claims (3)

[Claims] 1. An end branch pipe on both sides, which is an exhaust gas discharge path, a plurality of central branch pipes, which are also exhaust gas discharge paths, and a collecting portion that collects the end branch pipe and the central branch pipe. And the 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 lines of the end branch pipe and the central branch pipe, between the mounting flange of the end branch pipe on the side closer to the collecting portion and the mounting flange adjacent thereto. An exhaust manifold having a connecting portion and other mounting flanges separated from each other. 2. The exhaust manifold according to claim 1, wherein a vertical wall is provided at an intersection of the end branch pipe and the branch pipe adjacent to the end branch pipe. 3. The exhaust manifold according to claim 1 or 2, wherein a rib is provided on a side surface of the end branch pipe near the collecting portion.