JPH08200060A - Exhaust manifold - Google Patents

Abstract

PURPOSE: To provide an exhaust manifold whose cost can be reduced more than when the whole is manufactured by spheroidal graphite cast iron and by which generation of a crack by thermal strain can be prevented. CONSTITUTION: An exhaust manifold 1 of an internal combustion engine is divided into long and short two parts in the cylinder row direction, and the cylinder number large side 2 is formed of a material having high temperature fatigue strength higher than the cylinder number small side 3.

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 internal combustion engine which can prevent cracks caused by thermal strain and can be manufactured at low cost.

[0002]

2. Description of the Related Art In recent years, with the increase in engine output, there has been a problem that a heat spot where a heat load locally becomes high occurs at a specific portion of an exhaust manifold, and a crack easily occurs due to the thermal strain. . Therefore, for the purpose of eliminating this heat spot, there is a two-body structure in which the exhaust manifold is divided into two parts at a portion corresponding to the heat spot.

[0003]

By the way, the above-mentioned exhaust manifold has conventionally been made of flake graphite cast iron (gray cast iron).
However, the high temperature fatigue strength is low and it is not enough to prevent the occurrence of cracks caused by thermal strain.Therefore, it is necessary to use a material with higher high temperature fatigue strength. ing. Therefore, heat countermeasures such as manufacturing the entire exhaust manifold from spheroidal graphite cast iron (ductile cast iron) have been taken, but on the other hand, there is a problem that cost rises.

In view of the above problems, the present invention can reduce the cost as compared with the case where the whole is made of spheroidal graphite cast iron, and can prevent the generation of cracks due to thermal strain. It is intended to provide.

[0005]

In order to achieve the above object, an exhaust manifold of the present invention divides an exhaust manifold of an internal combustion engine into two cylinders, a long cylinder and a short cylinder, and a cylinder having a large number of cylinders has a cylinder having a large number of cylinders. It is formed of a material having higher high-temperature fatigue strength than the side with less fatigue. Incidentally, it is particularly preferable to form the side with a large number of cylinders with spheroidal graphite cast iron and the side with a small number of cylinders with vermicular graphite cast iron or CV graphite cast iron, but the point is that the side with a large heat load and the side with a small heat load are used. Since it is sufficient to form the side with a material having durability required for each heat load, the side with a large number of cylinders is formed of CV graphite cast iron, and the side with a small number of cylinders is formed with vermicular graphite. It can also be formed of cast iron.

[0006]

[Operation] Since the exhaust manifold of the present invention has the above-described structure, the one having the larger number of cylinders out of the two divided parts should use a material having high high temperature fatigue strength (for example, spheroidal graphite cast iron). This makes it possible to prevent the occurrence of cracks due to thermal strain even under operating conditions with a large heat load.In addition, the one with the smaller number of cylinders out of the two has the durability required. However, since it is possible to use a low cost material (for example, vermicular graphite cast iron), it is possible to reduce the cost compared to the case where the whole is made of an expensive material with high high temperature fatigue strength, and cracks due to thermal strain Can also be prevented.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An exhaust manifold according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the exhaust manifold 1 of the present embodiment is compatible with a 6-cylinder engine, and has branch portions 2a, 2b, 2c for four cylinders,
It is divided into a main structure 2 having 2d and a sub-structure 3 having branch portions 3a and 3b for two cylinders. In addition, the main structure 2
A collecting portion 2e connected to an exhaust pipe (not shown) is formed in the.

On the other hand, as shown in FIG. 2, a ring groove into which three seal rings 4a, 4b, 4c are fitted is formed in the joint portion 3c of the sub-structure 3, and each seal ring 4a is formed. ,Four
The gaps between the b and 4c are arranged so as to be offset by 120 °, and the seal lines are formed between the outer peripheral surfaces of the seal rings 4a, 4b and 4c and the inner peripheral surface of the joint 2f of the main structure 2. So that the main structure 2 is sealed with the seal rings 4a, 4b,
Fit from the outside of 4c so that they can be assembled together. When the exhaust manifold 1 is mounted on an internal combustion engine, the branch portions 2a,
A manifold gasket is interposed between the flanges 5 of 2b, 2c, 2d, 3a and 3b and a cylinder head (not shown) and bolted.

In the exhaust manifold 1 of this embodiment,
The main structure 2 is made of spheroidal graphite cast iron, and the sub-structure 3
Is made of vermicular graphite cast iron, and when the internal combustion engine equipped with the exhaust manifold 1 is operated, the main structure 2 on the side with a large number of cylinders has a large amount of exhaust gas, resulting in high temperature. Becomes On the contrary, the sub-structure 3, which has the smaller number of cylinders, tends to have a relatively low temperature because the amount of gas exhausted is small.

Under such an operating environment, as described above, the main structure 2 having a large number of cylinders uses spheroidal graphite cast iron having a high fatigue strength at high temperature, and therefore has a high durability against thermal strain. There is no risk of cracking under heavy heat load. On the other hand, since the substructure 3 having a small number of cylinders has a small heat load itself, even if inexpensive vermicular graphite cast iron is used, there is no problem such as cracking due to the influence of thermal strain.

The present invention is not limited to the above-described embodiment, but spheroidal graphite cast iron is used as the material of the main structure 2 and the sub-structure 3 of the main structure 2 is used depending on the conditions such as the output of the internal combustion engine. It is also possible to use CV graphite cast iron as the material. Other than that, for example, CV graphite cast iron can be used as the material of the main structure 2, and in that case, vermicular graphite cast iron can be used as the material of the sub structure 3.

[0012]

According to the exhaust manifold of the present invention, the exhaust manifold of the internal combustion engine is divided into two parts, that is, the long and short parts in the cylinder row direction, and the side having a large number of cylinders has a higher high temperature fatigue strength than the side having a small number of cylinders. Since it is formed by using, the one with the largest number of cylinders out of the two can be prevented from cracking due to thermal strain even under use conditions with a large heat load by using a material with high high temperature fatigue strength. In addition, the one with the smaller number of cylinders out of the two can be made of a material with low cost while maintaining the required durability, so the overall high temperature fatigue strength It is possible to reduce the cost and to prevent cracks due to thermal strain as compared with the case of manufacturing with a high-priced and expensive material.

[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 showing a substructure of the exhaust manifold shown in FIG.

[Explanation of symbols]

 1 Exhaust manifold 2 Main structure (side with many cylinders) 3 Sub-structure (side with few cylinders)

Claims (2)

[Claims] 1. An exhaust manifold in which an exhaust manifold of an internal combustion engine is divided into a long cylinder and a short cylinder in a cylinder row direction, and a side having a large number of cylinders is formed of a material having a high temperature fatigue strength higher than a side having a small number of cylinders. 2. The exhaust manifold according to claim 1, wherein the side having a large number of cylinders is formed of spheroidal graphite cast iron, and the side having a small number of cylinders is formed of vermicular graphite cast iron or CV graphite cast iron.