JPH0578918U - Heat resistant material - Google Patents

Abstract

(57) [Abstract] [Purpose] A heat-resistant member with a tubular heat resistance that has sufficient durability even in high-temperature exhaust gas environments by reducing the amount of shrinkage deformation by suppressing plastic deformation associated with compressive stress. Provide a member. [Composition] According to the temperature distribution on the surface of the heat-resistant member, a positive gradient moment of inertia of area is formed from the low temperature side to the high temperature side. [Effect] Cross section 2 at high temperature where plastic deformation increases
The secondary moment is increased to improve rigidity and reduce shrinkage.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to the structure of heat-resistant members, particularly exhaust system components used in internal combustion engines of automobiles.

[0002]

[Prior Art]

 BACKGROUND ART Conventionally, a tubular heat-resistant member such as an exhaust manifold has been used as an exhaust system component that collects exhaust gas from an automobile engine or the like and sends it to a muffler pipe. The tubular heat-resistant member is heated by the high-temperature exhaust gas due to combustion of the engine and expands to generate compressive stress, which causes shrinkage plastic deformation, which is constrained by the mounting bolts and cracks or May leak gas. It is known that the degree of plastic deformation is remarkable as the temperature rises in the surface temperature distribution of the tubular heat resistant member.

As a technique for improving the durability of an exhaust manifold, the exhaust manifold of an internal combustion engine is disclosed in Japanese Utility Model Publication No. 61-142120, and the internal combustion engine with a turbocharger is disclosed in Japanese Utility Model Publication No. 62-130131. , And Japanese Utility Model Laid-Open No. 63-121 disclose an exhaust manifold and the like. These change the shape of the exhaust manifold to prevent deformation and cracks.

Further, in Japanese Utility Model Laid-Open No. 60-122523, the shape of the mounting bolt is changed to facilitate the deformation of the exhaust manifold, reduce the residual stress generated inside the exhaust manifold, and prevent the occurrence of cracks. There is disclosure to prevent.

[0005]

[Problems to be solved by the device]

 A tubular heat-resistant member under a high-temperature heating environment undergoes remarkable shrinkage plastic deformation due to compressive stress when the temperature rises. The flange of the exhaust manifold is attached to the cylinder head with mounting bolts, and the exhaust manifold is heated by the high-temperature exhaust gas generated during engine operation, causing thermal expansion. However, since the flange of the exhaust manifold is restricted by the mounting bolt, the amount of expansion due to thermal expansion acts as a plastic deformation of compression to the exhaust manifold. When the engine stops and reaches the cooling process, heat contraction starts anew from the state of contraction due to plastic deformation, and the exhaust manifold contracts more than the initial shape. As a result, problems such as gas leakage due to contraction, cracks due to interference with the mounting bolt, and warpage occur in the exhaust manifold.

Techniques for improving the shape of the exhaust manifold to prevent deformation and cracks, such as the above-mentioned Japanese Utility Model Publication No. 61-142120, Japanese Utility Model Publication No. 62-130131, and Japanese Utility Model Publication No. 63-121. Aims to improve durability by changing part of the shape of the exhaust manifold, but cannot improve the rigidity of the exhaust manifold.

In Japanese Utility Model Laid-Open No. 60-122523, the shape of the mounting bolt is changed to facilitate the deformation of the exhaust manifold, reduce the residual stress generated inside the exhaust manifold, and prevent the occurrence of cracks. However, the durability of exhaust manifolds and bolts in a hot exhaust gas environment cannot be guaranteed sufficiently.

The object of the present invention is to solve the above problems and to reduce the amount of shrinkage deformation by suppressing plastic deformation due to compressive stress, thereby having sufficient durability even in a high temperature exhaust gas environment. It is to provide a tubular heat-resistant member such as an exhaust manifold.

[0009]

[Means for Solving the Problems]

 In order to solve the above problems, the present inventor has clarified the following matters.

The exhaust manifold has rigidity in a direction parallel to the cylinder head mounting surface. The rigidity value (Gx) is such that when one end of the mounting flanges at both ends of the exhaust manifold is constrained and a load (W) is applied to the other end, the load (W) is applied between the two flanges at that time. It was found that it can be defined by the value divided by the displacement amount (dx) of. The definition formula is shown in Equation 1.

[0011]

## EQU1 ## Gx = W / dx Here, Gx: stiffness value W: load dx: displacement amount This equation 1 is the same equation as Hooke's law, and the stiffness value (Gx) is the spring constant in Hooke's law. Have the same physical meaning. Therefore, if the rigidity value (Gx) is large, the amount of displacement will be small if the loads acting are the same. Since the displacement amount is physically the same as the contraction amount of the exhaust manifold, the inventor can reduce the contraction amount of the exhaust manifold by increasing the rigidity value (Gx). I found a thing.

Next, the present inventor has clarified that the rigidity value Gx is based on the idea of the equation 1 and the following approximate equation by the equation 2 is established in the shape of the exhaust manifold.

[0013]

[Formula 2] Gx = (3 · E · I) / {(L2 (2 · L + 3 · l)} where Gx: rigidity value (N / m) E: Young's modulus (N / m2) I: cross section 2 Next moment (m4) t: Thickness of tubular heat-resistant member (m) L: Length of branch pipe of tubular heat-resistant member (m) l: Total length of tubular heat-resistant member (m) Therefore, from equation 2, cross section 2 The rigidity value (G x) can be increased by increasing the secondary moment (I), and the amount of shrinkage can be effectively suppressed. From the above results, the heat-resistant member is formed so that the second moment of area (I) of the tubular heat-resistant member at the high temperature portion becomes larger than that at the low temperature portion in accordance with the surface temperature distribution. ..

[0014]

[Action]

 In the temperature distribution formed on the surface of the heat-resistant member, the second moment of area at the high temperature part where plastic deformation becomes large is made larger than the second moment of area at the low temperature part to reduce the amount of shrinkage that increases at the high temperature part. , Improve high temperature durability.

[0015]

【Example】

 FIG. 1 is a diagram showing the relationship between the contraction rate (%) obtained by dividing the contraction amount of the exhaust manifold by the total length of the exhaust manifold and the rigidity value (Gx) in the direction parallel to the cylinder head mounting surface of the exhaust manifold. In FIG. 1, it is clear that the shrinkage ratio (%) and the rigidity value (Gx) have a negative correlation.

FIG. 2 is a plan view showing a temperature gradient generated on the surface of the exhaust manifold 1 according to one embodiment of the present invention, and a cross-sectional view showing a moment of inertia of area provided on the exhaust manifold 1 by an AA cross section. It is a figure. As shown in the AA cross section of FIG. 2, the inner diameter r1 of the portion where the surface temperature of the exhaust manifold 1 becomes high is made larger than the inner diameter r2 of the portion where the surface temperature becomes low. For this reason, the second moment of area (I1) of the high temperature portion is larger than the second moment of area (I2) of the low temperature portion, the rigidity is improved as a whole, and the amount of shrinkage is reduced.

FIG. 3 is a diagram showing another embodiment of the present invention. By changing the shape of the cross section according to the temperature gradient formed on the surface of the exhaust manifold 1, the gradient of the second moment of area is changed, the rigidity of the exhaust manifold is improved, and the amount of contraction is reduced.

FIG. 3 is a view showing still another embodiment of the present invention. By providing ribs 2 on the surface of the exhaust manifold 1 where the surface temperature becomes high, the moment of inertia of area of the high temperature part is made larger than the moment of inertia of area of the low temperature part to improve rigidity and reduce the amount of shrinkage. It

FIG. 5 is an exhaust manifold having a gradient of the second moment of inertia of the embodiment shown in FIG. 3 of the present invention and an exhaust manifold having an average wall thickness of 4.0 mm regardless of the conventional temperature gradient. The exhaust manifold for an in-line 6-cylinder engine with a total length of about 600 mm was subjected to a heating / cooling durability test, and the sum of the movement amounts of the flanges at both ends of the exhaust manifold was shown as the amount of shrinkage. As shown in FIG. 5, the amount of contraction of the exhaust manifold having a gradient in the second moment of area of the embodiment is much smaller than that of the exhaust manifold of the conventional example in which the second moment of sectional has no slope. Has been reduced to.

[0020]

[Effect of the device]

 As described above, according to the temperature distribution formed on the surface of the heat resistant member of the present invention, the second moment of area of the high temperature part is increased to increase the rigidity of the member and suppress the plastic deformation, and as a result, the shrinkage amount is significantly increased. And a tubular heat resistant member having sufficient durability even in a high temperature exhaust gas environment can be obtained.

[Brief description of drawings]

FIG. 1 shows the contraction rate (%) obtained by dividing the contraction amount of the exhaust manifold by the total length of the exhaust manifold and the rigidity value (G in the direction parallel to the cylinder head mounting surface of the exhaust manifold).
It is a figure which shows the relationship with x).

FIG. 2 is a plan view of an exhaust manifold according to an embodiment of the present invention and a partial cross-sectional view in a direction parallel to a cylinder head mounting surface.

FIG. 3 is a plan view of an exhaust manifold according to another embodiment of the present invention and a partial cross-sectional view in a direction parallel to a cylinder head mounting surface.

FIG. 4 is a plan view of an exhaust manifold of still another embodiment of the present invention and a partial cross-sectional view in a direction parallel to a cylinder head mounting surface.

FIG. 5 is a diagram showing the relationship between the number of heating / cooling endurance cycles and the amount of movement of both end flanges of the exhaust manifold of the embodiment of the present invention and the conventional manifold in comparison with the amount of contraction.

[Explanation of symbols]

 1 Heat resistant member 2 Rib

Claims (1)

[Scope of utility model registration request] 1. A cross-section 2 of a heat-resistant member facing a high temperature side from a low temperature side of the heat resistant member having a temperature distribution on the surface during use.
A heat-resistant member, wherein the second moment has a substantially positive gradient.