JPH05240039A - Exhaust manifold for engine - Google Patents

Abstract

PURPOSE:To absorb distortion in a longitudinal direction and a bending direction due to a difference in thermal expansion between a cylinder block and an exhaust manifold for an engine and enable perfect sealing of exhaust gas. CONSTITUTION:An exhaust manifold for engine is provided with plural exhaust pipe bodies 11 disposed in the longitudinal direction and metallic bellows 12 interposed sealingly between the opposite ends 111 of adjoining exhaust pipe bodies 11. The metallic belows 12 are provided with metallic rings 122 integrally installed at both ends of a bellows core 121. The metallic ring 122 and the exhaust pipe body 11 are mutually fitted preferably in closed contact surfaces S in taper form. In this case, it is further preferable to have the relation of De>=D0 where De is the effective diameter of the bellows core 12 and D0 is the inner diameter of closed contact surfaces S in taper form of the metallic ring 122 and the exhaust pipe body 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an engine cylinder
The present invention relates to an exhaust manifold that is a collective exhaust pipe connected to a block.

[0002]

2. Description of the Related Art As shown in FIG. 2, an exhaust manifold 1 which is a collective exhaust pipe is connected to an exhaust port of a cylinder block 3 of an engine through a metal gasket 2. Usually about 800 ℃,
High-temperature, high-pressure combustion gas of 3-4 kgf / cm ² G is discharged through a muffler (not shown). However, in general, the cylinder block 3 is made of an aluminum alloy, whereas the exhaust manifold 1 is made of a cast iron material, and the thermal expansion coefficients of the two are different, so that the cylinder block 3 is repeatedly subjected to thermal strain at each operation, There is concern about cracking and damage due to fatigue. Further, due to the difference in thermal expansion, loose parts are generated in the close contact portion of the metal gasket 2, and exhaust gas may leak, which may lead to fire or environmental damage.

Therefore, in order to deal with the above problem, conventionally, as shown in FIG. 3, the exhaust manifold 1 is connected to a plurality of exhaust pipe main bodies 1a slidably fitted to each other at the pipe joint portions 1b at both ends. It is known that the exhaust pipe main body 1a is allowed to be displaced in the longitudinal direction due to a difference in thermal expansion by sealing a space between the opposed peripheral surfaces of the pipe joint portion 1b with a piston ring 1c. ing.

[0004]

However, according to the above conventional structure, in order to make the sealing surfaces of the pipe joint portion 1b and the piston ring 1c slidable with the displacement of each exhaust pipe body 1a in the longitudinal direction. Since it is necessary to provide a slight clearance on this sealing surface, it is impossible to completely seal the exhaust gas, and when the sealing surfaces of the pipe joint portion 1b and the piston ring 1c are worn over time due to sliding, the above-mentioned clearance is produced. As a result, the leakage of exhaust gas tends to become noticeable. Further, since the displacement of each exhaust pipe body 1a is allowed only in the longitudinal direction thereof, it is impossible to absorb the bending displacement in the direction perpendicular to the longitudinal direction which is considered to be actually necessary.

The present invention has been made under the circumstances as described above, and its technical problem is to prevent distortion in the longitudinal direction and bending direction due to the difference in thermal expansion between the cylinder block of the engine and the exhaust manifold. It is possible to absorb the gas and to completely seal the exhaust gas.

[0006]

The above-mentioned conventional technical problems can be solved by the present invention. That is, the exhaust manifold of the engine according to the present invention comprises a plurality of exhaust pipe main bodies arranged in the longitudinal direction, and a metal bellows which is hermetically interposed between opposed end portions of the exhaust pipe main bodies adjacent to each other. It is what Further, in the above-mentioned structure of the present invention, the metal bellows has a structure in which metal rings are integrally provided at both ends of a bellows core, and the metal ring and the exhaust pipe main body are tapered close contact surfaces corresponding to each other. It is preferable to have a configuration in which they are closely fitted together. Further, in this case, it is more preferable that the inner diameter D ₀ of the tapered close contact surfaces of the metal ring and the exhaust pipe main body is De ≧ D ₀ with respect to the effective diameter De of the bellows core. The material composition of the bellows core is, by weight%, Co ・ ・ ・ ≦ 1 Cr ・ ・ ・ 17-21 Mo ・ ・ ・ 2.8-3.3 Fe ・ ・ ・ 17-21 C ・ ・ ・ ≦ 0.08 Mn ・ ・ ・ ≦ 0.35 Si ・ ・ ・ ≦ 0.35 Al ・ ・ ・ 0.2 〜 0.8 Ti ・ ・ ・ 0.65 〜 1.15 Nb + Ta ・ ・ ・ 4.75 〜 5.5 Ni ・ ・ ・ Remainder or Co ・ ・ ・ 12〜16 Cr ・ ・ ・ 17〜 21 Mo ・ ・ ・ 3.8 〜 4.3 Fe ・ ・ ・ 0.8 〜 1.3 C ・ ・ ・ 0.05 〜 0.1 Mn ・ ・ ・ ≦ 0.08 Si ・ ・ ・ ≦ 0.7 Al ・ ・ ・ 1.0 〜 1.5 Ti ・ ・ ・ 2.8 〜 3.3 Is desirable.

[0007]

According to the structure of the present invention, the metal bellows interposed between the plurality of exhaust pipe main bodies is stretchable, and therefore the longitudinal and bending directions of the exhaust pipe main body due to the difference in thermal expansion from the cylinder block of the engine. Is allowed and the strain is absorbed. Further, since the metal rings at both ends of the metal bellows and the exhaust pipe main body, which are closely fitted to each other in the tapered close contact surfaces, do not slide with displacement of each exhaust pipe main body, wear is caused. Does not happen. Also, with respect to the effective diameter De of the metal bellows, the inner diameter D ₀ of the tapered close contact surfaces of the metal ring and the exhaust pipe main body is De ≧ D ₀
By this, the exhaust gas pressure on the inner circumference of the metal bellows imparts an extension force to the metal bellows, so that the close contact force of the tapered close contact surface increases and complete sealing is achieved. Further, by using the above-mentioned material component for the bellows core, heat resistance and corrosion resistance are enhanced, and sufficient elasticity and durability are provided under the condition of being exposed to high temperature exhaust gas.

[0008]

1 shows an embodiment of the present invention, in which an exhaust manifold 10 includes a plurality of exhaust pipe main bodies 11 arranged in a longitudinal direction and opposing end portions 111 of the exhaust pipe main bodies 11 adjacent to each other. The metal bellows 12 is hermetically interposed between 111, and the metal bellows 12 includes a bellows core 121 having elasticity and metal rings 122 integrally provided at both ends thereof by welding or brazing. .. Further, the metal ring 122 has a cylindrical outer peripheral surface 122a having a diameter gradually decreasing toward the front end side, which is formed on a cylindrical portion protruding outward in the axial direction, and both end portions 111 of the exhaust pipe main body 11 are formed. Is the tapered outer peripheral surface 122
A tapered inner peripheral surface 111a corresponding to a is formed, and the tapered surfaces 111a and 122a are closely fitted to each other to form a close contact surface S.

Here, let the inner diameter of the bellows core 121 be D
₁ , and the outer diameter is D ₂ , the effective diameter De of the bellows core 121 can be obtained by De ≈ (D ₁ + D ₂ ) / 2, but the diameter of the inner end S ₀ of the tapered close contact surface S, that is, the inner diameter. D ₀ is set so that De ≧ D ₀ . Reference numeral 112 denotes an inflow port provided in each exhaust pipe main body 11 and connected to an exhaust port of a cylinder block of an engine (not shown) through a metal gasket, 113 denotes a connection flange on the outer periphery of the inflow port 112, and 114 denotes this flange. A bolt for tightening and fixing 113 to the cylinder block.

Bellows core 121 of metal bellows 12
The heat resistance and corrosion resistance of the materials are improved by using the following material components.
The springiness and strength at (° C) can be sufficiently maintained. [Example 1] Co ・ ・ ・ ≦ 1 (wt%) Cr ・ ・ ・ 17-21 Mo ・ ・ ・ 2.8-3.3 Fe ・ ・ ・ 17-21 C ・ ・ ・ ≦ 0.08 Mn ・ ・ ・ ≦ 0.35 Si ・ ・・ ≦ 0.35 Al ・ ・ ・ 0.2 〜 0.8 Ti ・ ・ ・ 0.65 〜 1.15 Nb + Ta ・ ・ ・ 4.75 〜 5.5 Ni ・ ・ ・ Balance [Example 2] Co ・ ・ ・ 12〜16 (wt%) Cr ・ ・ ・ 17〜 21 Mo ・ ・ ・ 3.8 〜 4.3 Fe ・ ・ ・ 0.8 〜 1.3 C ・ ・ ・ 0.05 〜 0.1 Mn ・ ・ ・ ≦ 0.08 Si ・ ・ ・ ≦ 0.7 Al ・ ・ ・ 1.0 〜 1.5 Ti ・ ・ ・ 2.8 〜 3.3 Ni ・..Remainder

As the material of the metal ring 122,
It is selected from SUS (steel material) and FC (cast iron material) in consideration of weldability or brazing property with the bellows core 121.
Further, since the bellows core 121 is appropriately compressed in the illustrated assembled state, the spring load F in the thrust direction is
_{When 1} is generated, the spring constant is k, the free length is L ₁ , and the mounting length is L ₂ , the spring load F ₁ is obtained by the formula F ₁ = k (L ₁ −L ₂ ).

In addition to the shape shown in FIG. 1, the exhaust pipe main body 11 has, for example, a shape in which one end 111 is connected to both ends of the exhaust manifold 10 and is closed, and exhaust gas to a muffler (not shown). Including those with outflow ports.

In the above structure, the bellows core 121
When the internal pressure P due to the high-temperature and high-pressure exhaust gas flowing in through the inflow port 112 from the exhaust port of the cylinder block of the engine is received, De of the bellows core 121 is tapered close surface S of the exhaust pipe body 11 and the metal ring 122. Since there is a relation of De ≧ D ₀ with respect to the inner diameter D _{0 of} , the thrust force (extension force) F _{2 in the} thrust direction due to the internal pressure P is generated in addition to the spring load F ₁ , and this thrust force F ₂ is , F ₂ = {π (De ² −D ₀ ² ) × P} / 4. Therefore, the metal rings 122 on both ends of the metal bellows 12 self-seal the contact surface S with the exhaust pipe body 11 by the combined force F of the spring load F ₁ and the thrust F ₂ . Moreover, since the close contact surface S has a tapered shape,
The surface pressure of the close contact surface S due to the load F can be sufficiently increased.

Further, when a displacement occurs between the exhaust pipe main bodies 11 due to a difference in thermal expansion from the cylinder block of the engine, the strain due to this displacement is absorbed by the expandability of the bellows core 121, and the tapered close contact surface S becomes Does not slide. As a result, the tapered close contact surface S is abraded and the metal rings 1 at both ends 111 of the exhaust pipe body 11 and both ends of the metal bellows 12 are worn.
During 22, no clearance that allows the exhaust gas to leak is generated.

[0015]

As is apparent from the above description, the present invention has the following effects. (1) Due to the elasticity of the metal bellows, both displacement in the longitudinal direction and bending direction of the exhaust pipe main body due to the difference in thermal expansion from the engine cylinder block can be allowed, and thermal strain can be absorbed well. it can. (2) Wear of the seal part as in the case of the conventional structure that absorbs thermal strain by sliding at the joint part of each exhaust pipe body,
Also, leakage of exhaust gas due to this does not occur. (3) Since the metal rings at both ends of the metal bellows and the close contact surface of the exhaust pipe body do not slide, it is not necessary to provide a clearance between these close contact surfaces to allow sliding, and therefore the sealing performance at the close contact surface Can be improved. (4) The metal rings on both ends of the metal bellows and the exhaust pipe body
Since the tapered ends are closely fitted to each other, connection by fitting is easy. (5) The exhaust gas pressure imparts an extension force to the bellows core by setting the inner diameter D ₀ of the tapered contact surface of the metal ring and the exhaust pipe body to De ≧ D ₀ with respect to the effective diameter De of the bellows core. Therefore, the contact force of the tapered contact surface increases,
The exhaust gas can be completely sealed. (6) Since the heat resistance and corrosion resistance of the bellows core are improved, the spring property and strength under high temperature conditions (about 800 ° C) due to exhaust gas can be sufficiently maintained.

[Brief description of drawings]

FIG. 1 is a partial sectional view showing an embodiment of an exhaust manifold of the present invention.

FIG. 2 is a diagram schematically showing a connection relationship between an engine cylinder block and an exhaust manifold.

FIG. 3 is a partial cross-sectional view showing an example of an exhaust manifold having a conventional structure.

[Explanation of symbols]

 10 Exhaust Manifold 11 Exhaust Pipe Main Body 12 Metal Bellows 121 Bellows Core 122 Metal Ring S Tapered Close Contact Surface

Claims (5)

[Claims] 1. An engine comprising: a plurality of exhaust pipe main bodies arranged in a longitudinal direction; and a metal bellows hermetically interposed between opposed end portions of the exhaust pipe main bodies adjacent to each other. Exhaust manifold. 2. The metal bellows according to claim 1, wherein a metal ring is integrally provided at both ends of a bellows core, and the metal ring and the exhaust pipe body are tapered closely corresponding to each other. An engine exhaust manifold characterized in that the surfaces are closely fitted together. 3. The inner diameter D ₀ of the tapered close contact surfaces of the metal ring and the exhaust pipe main body is set to De ≧ D ₀ with respect to the effective diameter De of the bellows core according to claim 2. Engine exhaust manifold. 4. The material component of the bellows core according to claim 2 or 3, in terms of weight%, Co ... ≤ 1 Cr ... 17-21 Mo ... 2.8-3.3 Fe ... 17 to 21 C ・ ・ ・ ≦ 0.08 Mn ・ ・ ・ ≦ 0.35 Si ・ ・ ・ ≦ 0.35 Al ・ ・ ・ 0.2 〜 0.8 Ti ・ ・ ・ 0.65 〜 1.15 Nb + Ta ・ ・ ・ 4.75 〜 5.5 Ni ・ ・ ・ The balance An exhaust manifold for the engine. 5. The material component of the bellows core according to claim 2 or 3, in terms of weight%, Co ... 12-16 Cr ... 17-21 Mo ... 3.8-4.3 Fe.・ 0.8-1.3 C ・ ・ ・ 0.05-0.1 Mn ・ ・ ・ ≦ 0.08 Si ・ ・ ・ ≦ 0.7 Al ・ ・ ・ 1.0-1.5 Ti ・ ・ ・ 2.8-3.3 Ni ・ ・ ・ The engine characterized by the balance Exhaust manifold.