JPH07247836A - Exhaust manifold - Google Patents

Abstract

PURPOSE:To improve reliability by forming a slit on a part connecting installation flanges to each other, specifying difference between a bolt hole across the slit and an outer diameter of a bolt, and thereby preventing occurrence of deformation and cracks of parts of a manifold. CONSTITUTION:A slit 4 formed between a first installation flange 2a and a second installation flange 2b of an exhaust manifold has width b1. Sum of a gap a1 or a3 and a gap a6 or a8, for instance a+1+a8, is greater than b1; where a1 or a8 is the gap between an inner diameter of a bolt hole 9 of the flange 2a and an outer diameter of a bolt 10, a6 or a8 is the gap between the inner diameter of the bolt hole 9 of the flange 2 and the outer diameter of the bolt 10. In such a manner, the mainfold having the slit 4 is mounted on a cylinder head and an engine is started. Collected pipes of the manifold are thus expanded, while the installation flanges 2a to 2d are independently and freely moved in a follow-up manner since the slit 4 is formed. During a cooling process, the collected pipes are contracted and the slit is closed. The installation flanges 2a to 2d are integrally moved and thermal contraction is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust manifold as an exhaust system component used in an internal combustion engine, which has improved durability and reliability.

[0002]

2. Description of the Related Art Conventionally, an exhaust manifold has been used as a tubular heat-resistant member for collecting exhaust gas from an engine and sending it to a muffler. As shown in FIG. 3, the exhaust manifold includes a mounting flange 2 attached to a cylinder head (not shown), a branch pipe 5 connected to each exhaust port of the cylinder head, and a collecting pipe 6 for collecting the branch pipes 5. Become. Generally, the exhaust manifold has the purpose of suppressing thermal contraction due to plastic deformation of compression that occurs during heating and cooling processes by the engine.
As shown in FIG. 3, the mounting flanges 2 may be connected by the connecting portion 3 in some cases. Further, in order to suppress shrinkage deformation due to plastic deformation of compression that occurs in the heating process of the engine, the mounting flanges 2 may be formed as independent shapes without being connected as shown in FIG.

[0003]

In the exhaust manifold having the connecting portion 3 on the mounting flange portion shown in FIG. 3, although the contraction is prevented by the connecting portion 3, since the connecting portion 3 restrains, the collecting pipe 6 part is provided. The amount of plastic deformation of is large, and warpage and cracks are likely to occur. Further, when the flange portion 2 is independent like the exhaust manifold shown in FIG. 4, the restraint of the flange portion 2 becomes small and the plastic deformation amount of compression generated at the time of heating becomes small, but since the contraction of the exhaust manifold cannot be stopped, After contracting by the difference between the inner diameter of the bolt hole 7 and the outer diameter of the bolt to be inserted into the bolt hole 7, there is a problem that the bolt is restrained and warps or cracks easily occur, and it becomes difficult to remove the exhaust manifold. Will happen.

With respect to the exhaust manifold having a shape in which the mounting flanges 2 shown in FIG. 3 are connected, the influence of heat will be described with reference to FIG. In FIG. 8, (1) shows a basic shape in which the exhaust manifold 1 to which the mounting flange 2 is connected is attached to the cylinder head with bolts through bolt holes. When the engine starts to operate, the exhaust gas from the cylinder head heats the collecting pipe 6 of the exhaust manifold 1 (2).
Thermally expands like. However, since the mounting flange 2 is connected, the deformation of the mounting flange 2 part is suppressed, and a large dimensional difference occurs between the mounting flange 2 part and the collecting pipe 6 part. Eventually, a compressive stress acts on the collecting pipe 6 as in (3), and plastic deformation occurs when the yield strength of the material is exceeded. This amount of plastic deformation substantially matches the dimensional difference. When the engine is stopped and the cooling process is started, heat contraction of the collecting pipe 6 portion is newly started. However, since the mounting flanges 2 are connected to each other, they cannot move following the contraction of the collecting pipe 6, and both ends of the mounting flange 2 are deformed so as to warp as shown in (4). This causes problems such as cracks in the exhaust manifold and leakage of exhaust gas.

Next, the influence of heat of the exhaust manifold having the independent mounting flange 2 will be described with reference to FIG. Figure 9
Here, (1) is a basic shape in which the exhaust manifold 1 having an independent mounting flange 2 is attached to the cylinder head with bolts through bolt holes. When the engine starts running,
Exhaust manifold 1 by exhaust gas from the cylinder head
The collecting pipe 6 is heated and thermally expanded as shown in (2).
Further, since the mounting flange 2 is independent, the mounting flange 2 part can move following the deformation of the collecting pipe 6 part. Therefore, the dimensional difference between the mounting flange 2 part and the collecting pipe 6 part becomes small. As a result, compressive stress acts on the collecting pipe 6 as in (3), and the amount of plastic deformation that occurs when the yield strength of the material is exceeded is also small. When the engine is stopped and the cooling process is started, the heat contraction of the collecting pipe 6 starts anew, but since the mounting flange 2 is independent, the collecting pipe 6
The part moves freely following the contraction of the part, and the mounting flange 2 part continues to largely contract until it is restrained by the bolt as shown in (4).

In order to prevent deformation and cracks in the exhaust manifold, in Japanese Utility Model Laid-Open No. Sho 60-66822, a slit is provided in a reinforcing rib for connecting a collecting pipe of the exhaust manifold, and an inner end portion of the slit is provided with a reinforcing rib. There is a disclosure to prevent cracks in the reinforcing ribs due to thermal deformation by connecting to the circular holes provided in.

However, according to the technique disclosed in Japanese Utility Model Laid-Open No. 60-66822, since the reinforcing rib has slits but does not penetrate therethrough, thermal contraction due to plastic deformation of the exhaust manifold is completely prevented. It is not possible.

The present invention solves the above problems and provides the advantages of both the exhaust manifold in which the mounting flanges are connected to each other and the exhaust manifold in which the mounting flanges are independent, and the exhaust manifolds in which the mounting flanges are independent during heating are provided. As described above, the mounting flange is moved in accordance with the thermal expansion of the collecting pipe to suppress the plastic deformation of the collecting pipe due to the compressive stress, and at the time of cooling, it is assembled by the connecting part like the exhaust manifold connecting the mounting flanges. An object of the present invention is to provide a highly reliable exhaust manifold that resists thermal contraction of the pipe portion to suppress the amount of shrinkage, has no deformation of the mounting flange portion, and has no cracks in each portion of the exhaust manifold.

[0009]

In order to solve the above-mentioned problems, an exhaust manifold (1) of the present invention has a mounting flange (2) mounted on a cylinder head and a connecting portion () connecting the mounting flange (2). 3) and an exhaust manifold (1) having a bolt hole (7) for attachment, at least one connecting portion (3) is provided with a slit (4), and the bolt hole (7) sandwiching the slit (4) is provided. ) And the outer diameter of the bolt inserted into the bolt hole (7) are larger than the total size of the voids of the slit (4).

[0010]

The operation will be described with reference to FIG. FIG. 7 is a two-cylinder model showing a conceptual diagram of the heat effect of the exhaust manifold 1 having a slit penetrating the connecting portion.
(1) is a basic shape in which an exhaust manifold 1 having a slit 4 penetrating a connecting portion 3 of a mounting flange 2 is attached to a cylinder head. When the engine starts to operate, the exhaust gas from the cylinder head causes the collecting pipe 6 of the exhaust manifold 1 to thermally expand as shown in (2), but the mounting flange 2 is independent because of the slit 4 and can be freely followed. And can move. In the cooling process, the collecting pipe 6
When the contraction occurs as in (3), the mounting flange 2 follows the width of the slit 4 and contracts, but after that, the slit 4 is closed and the connecting portion 3 of the mounting flange 2 is integrated. The amount of heat shrinkage is almost the same as the width of the slit 4 and stops.

[0011]

EXAMPLES The present invention will be described in detail below with reference to examples. (Embodiment 1) FIG. 1 shows an embodiment of the present invention. The exhaust manifold 1 is for a 4-cylinder engine, and is provided with a mounting flange 2 that is mounted on the cylinder head and a connecting portion 3 that connects the mounting flanges 2 to each other. Then, the connecting portion 3 is provided with a through slit 4 having a width of 1.5 mm. The slit 4 serves to reduce the dimensional difference between the mounting flange 2 and the collecting pipe 6 during thermal expansion due to high-temperature exhaust gas, and at the time of thermal contraction, the connecting portion 3 functions to suppress contraction of the mounting flange 2 portion.

FIG. 2 shows the width (b1, b2, b3) of the slit 4 of the connecting portion 3 connecting between the mounting flanges 2 and the inner diameter of the bolt hole 7 and the outer diameter of the bolt 10 in the exhaust manifold for a four-cylinder engine. The method of forming the voids (a1, a2, ... A16) is shown. Exhaust manifold 1 from left to right
No. 2, No. 3, No. 4, and No. 4 mounting flange 2. The width of the slit 4 provided between the first mounting flange 2a and the second mounting flange 2b is b1. At this time,
Inner diameter of the bolt hole 7 of the No. 1 mounting flange 2a and the bolt 10
A1 or a3 with the outer diameter of the 2nd mounting flange 2
The total (a1 + a8) of the gaps a6 or a8 between the inner diameter of the bolt hole 7 of b and the outer diameter of the bolt 10 is set to be larger than b1. Similarly, the widths of the three slits 4 provided between the No. 1 mounting flange 2a and the No. 4 mounting flange 2d are respectively b1, b2 and b3, the inner diameter of the bolt hole 9 of the No. 1 mounting flange 2a and the bolt 10 respectively. The total size (a1 + a16) of the space a1 or a3 with the outer diameter of the space and the space a14 or a16 with the inner diameter of the bolt hole 9 of the third mounting flange 2b and the outer diameter of the bolt 10 is set to be larger than (b1 + b2 + b3). In this way, the gap size between the inner diameter of the bolt hole 7 and the outer diameter of the bolt 10 between all the mounting flanges 2 is determined according to the width of the slit 4 provided between the mounting flanges 2.

FIG. 5 shows a four-cylinder exhaust manifold,
It is a comparison of the warp deformation amount of the mounting flange after the exhaust manifold durability evaluation test depending on the presence or absence of a slit penetrating the connecting portion. The horizontal axes # 1 to # 4 represent four cylinders, and the vertical axis represents the warp deformation amount of the mounting flange. The warp deformation amount of the mounting flange with the slit is reduced to about 1/8 in # 2 and # 3 as compared with the one without the slit. 6 is 4
FIG. 6 is a comparison of shrinkage deformation amounts of the mounting flanges of the cylinder exhaust manifold after the exhaust manifold durability evaluation test depending on the size of the slit width of the slit penetrating the connecting portion. The horizontal axis represents the size of the slit width, and the vertical axis represents the shrinkage deformation amount of the mounting flange. It can be seen that the amount of shrinkage of the mounting flange portion is almost proportional to the slit width. Therefore, by controlling the slit width, it is possible to control the amount of contraction that occurs in the exhaust manifold.

(Example 2) Made of high Si cast iron and having a displacement of 200
An exhaust manifold equivalent to a 0 cc high performance gasoline engine was cast, and the width of the connecting portion that connects the mounting flanges was 1.
An exhaust manifold of the present invention was manufactured by providing a 5 mm through slit. The exhaust manifold of the present invention was subjected to a durability test using an exhaust simulator. As a test condition, a cooling / heating (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 900 ° C. The temperature of the collecting manifold section of the exhaust manifold under these conditions was about 800 ° C. As a result of the evaluation test, the exhaust manifold of the present invention has a small amount of warpage deformation of the mounting flange, the amount of contraction deformation is slightly larger than the slit width, does not cause gas leakage or thermal cracking due to thermal deformation, and is excellent. It was confirmed to have durability and reliability.

On the other hand, the same test was carried out by assembling a conventional exhaust manifold which is also made of high Si cast iron and has no through slit in the connecting portion. As a result, the conventional exhaust manifold was unusable because the exhaust gas leaked due to the warp deformation of the mounting flange in 268 cycles, and the excellent durability of the exhaust manifold of the present invention was confirmed.

[0016]

As described above, in the exhaust manifold of the present invention, the connecting portion is provided with the slit, and the difference between the inner diameter of the bolt hole sandwiching the slit and the outer diameter of the bolt inserted into the bolt hole is determined by the gap of the slit. Since it is larger than the total size, the mounting flange moves independently following thermal expansion during operation, so the dimensional difference due to the thermal expansion difference between the mounting flange and the collecting pipe part is reduced, and the occurrence of plastic deformation is suppressed. . Also, when the collecting pipe shrinks during the cooling process when stopped, the mounting flange follows the width of the slit and shrinks, but after that, since the slit is closed, the connecting part of the mounting flange is assumed to be integrated. It works, and the amount of heat shrinkage is generated almost by the width of the slit and stops. Therefore, in the exhaust manifold of the present invention, the mounting flange portion is less deformed and the thermal stress is less, so the durability is greatly improved.

[Brief description of drawings]

FIG. 1 is a plan view showing an exhaust manifold in which a slit is provided in a connecting portion between mounting flanges according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a slit width provided in a connecting portion between mounting flanges of the present invention and a gap between an inner diameter of a bolt hole sandwiching the slit and an outer diameter of the bolt.

FIG. 3 is a plan view showing an exhaust manifold having a connecting portion between conventional mounting flanges.

FIG. 4 is a plan view showing a conventional exhaust manifold having an independent mounting flange for each collecting pipe.

FIG. 5 is a diagram comparing the amount of warp deformation of a mounting flange after a durability evaluation test with and without a slit penetrating a connecting portion in a 4-cylinder exhaust manifold.

FIG. 6 is a diagram showing a size of a slit width penetrating a connecting portion and a shrinkage deformation amount of a mounting flange after an exhaust manifold durability evaluation test in a four-cylinder exhaust manifold.

FIG. 7 is a diagram showing a two-cylinder model as a conceptual diagram of a heat effect in an exhaust manifold having a through slit in a connecting portion.

FIG. 8 is a conceptual diagram showing an influence of heat of an exhaust manifold connected to a mounting flange.

FIG. 9 is a conceptual diagram showing an influence of heat of an exhaust manifold having an independent mounting flange for each collecting pipe.

[Explanation of symbols]

1: Exhaust manifold, 2: Mounting flange,
3: connection part, 4: slit, 5: branch pipe, 6: collecting pipe, 7: bolt hole,
8: Slit width, 9: Bolt hole 10: Bolt

Claims (1)

[Claims] 1. An exhaust manifold (1) having a mounting flange (2) mounted on a cylinder head, a connecting portion (3) connecting the mounting flange (2) and a bolt hole (7) for mounting, at least 1. A slit (4) is provided in the connecting portion (3) at more than one place, and the difference between the inner diameter of the bolt hole (7) sandwiching the slit (4) and the outer diameter of the bolt inserted into the bolt hole (7) is defined as above. An exhaust manifold characterized in that it is larger than the total size of the air gaps of the slits (4).