JPS622360Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of an engine exhaust system connection structure.

Conventionally, in the exhaust system of an engine, a gasket is interposed at the connection between the engine and the exhaust manifold, or between the exhaust manifold and the exhaust pipe, etc., to prevent gas leakage from the connection, and to tighten the connecting members together using fastening bolts. A connection structure designed to prevent loosening of the gasket is well known, and steel veneer or laminated plates are commonly used as the material for the gasket (see Utility Model Publication No. 46-4567). reference).

However, when the above-mentioned steel gasket undergoes a high-temperature thermal cycle due to exhaust gas heat and repeatedly expands and contracts over a long period of time,
The high temperature creep phenomenon causes a sagging phenomenon, and as a result, it has the disadvantage that it cannot sufficiently perform its original functions such as preventing gas leakage and preventing loosening of fastening bolts.

Therefore, in view of this, the present invention uses an austenite structure layer as a material for the gasket, and a material on both the front and back surfaces of the austenite structure layer to suppress thermal expansion in a direction perpendicular to the thickness direction of the austenite structure layer. By using a stainless steel material with a sandwich structure consisting of a pair of ferrite structure layers formed to a thickness that causes expansion deformation in the longitudinal direction, the austenite structure layer and ferrite structure can withstand long-term high-temperature thermal cycles. The difference in thermal expansion coefficient between the two layers causes creep deformation in the austenite structure layer in the layer thickness direction, increasing the overall thickness during cooling, thereby preventing gas leakage from connections for a long time. It is an object of the present invention to provide an engine exhaust system connection structure that can be maintained for a long period of time.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

In FIG. 1, 1 is a cylinder block having a cylinder 1a, 2 is a piston that slides inside the cylinder 1a, and 3 is a cylinder head tightly fastened to the upper part of the cylinder block 1 via a cylinder head gasket 4. A combustion chamber 5 is formed in the cylinder head 3 between the cylinder head 3 and the head surface of the piston 2, and an exhaust port 7 is formed to communicate the combustion chamber 5 with the outside via an exhaust hole 6. , and the exhaust hole 6 has a
An exhaust valve 8 is provided to open and close the exhaust valve. still,
8a is a valve guide that guides the exhaust valve 8.

Further, one end flange portion 10a of the exhaust manifold 10 is connected to the downstream end of the exhaust port 7 of the cylinder head 3 via the gasket 9 with bolts 11,1.
1...Connected by fastening, and a gasket 12 is attached to the other end flange portion 10b of the exhaust manifold 10.
The flange portion 13a of the exhaust pipe 13 is connected by fastening bolts 14, 14, . . . and nuts 15, 15, . .

The connecting portion between the cylinder head 3 and the exhaust manifold 10 and the exhaust manifold 1
As shown in FIG. 2, the gaskets 9 and 12 respectively interposed at the connection between the exhaust pipe 13 and the exhaust pipe 13 are made of an austenite structure layer 17 and a pair of ferrite structure layers 18 formed on the front and back surfaces of the austenite structure layer 17. The layer thickness tf of each ferrite structure layer 18 is such that tf>1/3ta with respect to the layer thickness ta of the austenite structure layer 17.
The relationship is set as follows.

That is, the layer thickness of each of the above-mentioned ferrite structure layers 18
The relationship between tf and the layer thickness ta of the austenite structure layer 17 is that if tf≦1/3ta, the gaskets 9 and 12 will expand in the radial direction during long-term high-temperature thermal cycles, and the thickness will increase. On the other hand, if tf > 1/3ta, the radial expansion of gaskets 9 and 12 will be suppressed and the wall thickness will increase, preventing the sagging phenomenon and ensuring sealing performance. Therefore, the relationship is set as tf>1/3ta.

Incidentally, such a stainless steel plate having a side German structure can be obtained by a structure modification method in which aluminum or the like is thermally diffused from the surface of an austenitic stainless steel plate to change only the surface layer from an austenite structure to a ferrite structure, or by a structure modification method in which only the surface layer is changed from an austenite structure to a ferrite structure, or an austenitic stainless steel plate. It can be manufactured by a bonding method in which a thin ferritic stainless steel plate is bonded under heat and pressure to the surface of the plate, and the two are diffusion bonded.

Therefore, in the above embodiment, when the high temperature thermal cycle caused by the exhaust gas flowing through the exhaust passage 16 acts on the gaskets 9 and 12 of each connection part, the ferrite structure layer 1 of each gasket 9 and 12
The layer thickness tf of layer 8 is the layer thickness ta of austenite structure layer 17.
By setting the value to be larger than one-third of Since the gaskets 9 and 12 undergo creep deformation in the thickness direction, the thickness of the gaskets 9 and 12 becomes larger than their initial dimensions during cooling. As a result, the connection surface between the cylinder head 3 and the exhaust manifold 10 and the exhaust manifold 1
0 and the exhaust pipe 13 are pressed into tight contact with each other, thereby reliably preventing leakage of exhaust gas from each connection, loosening of the bolts 11 and 14, etc.

In the above embodiment, an example was described in which the present invention was applied to the connection between the cylinder head 3 and the exhaust manifold 10 and the connection between the exhaust manifold 10 and the exhaust pipe 13. Needless to say, the present invention can be applied to various exhaust system connection parts such as a connection part with a converter or a muffler.

As explained above, according to the engine exhaust system connection structure of the present invention, the gasket interposed at the exhaust system connection part is installed on both the front and back surfaces of the austenite structure layer in a direction perpendicular to the thickness direction of the austenite structure layer. The stainless steel material has a ferrite structure layer that is thick enough to suppress thermal expansion and cause expansion deformation in the thickness direction, so when a high temperature thermal cycle is applied by exhaust gas. Furthermore, the austenite structure layer is creep-deformed in the layer thickness direction by the restraining force of the ferrite structure layer, making it possible to increase the thickness of the entire gasket from its initial dimension, thereby preventing the gasket from sagging. This makes it possible to reliably prevent gas leakage from connections, bolt loosening, etc. over a long period of time.

[Brief explanation of the drawing]

The drawings illustrate an embodiment of the present invention; FIG. 1 is a longitudinal sectional view, and FIG. 2 is a partially cutaway perspective view of a gasket. 3...Cylinder head, 7...Exhaust port,
9, 12... Gasket, 10... Exhaust manifold, 13... Exhaust pipe, 17... Austenite structure layer, 18... Ferrite structure layer.

Claims (1)

[Scope of utility model registration request] An austenite structure layer is provided at the connection part of the exhaust passage that guides engine exhaust gas, and an austenite structure layer is provided on both the front and back surfaces of the austenite structure layer to suppress thermal expansion in a direction perpendicular to the thickness direction of the austenite structure layer. An exhaust system connection structure for an engine, characterized by interposing a gasket made of stainless steel and comprising a pair of ferrite structure layers formed to a thickness sufficient to cause expansion deformation.