JP2586564Y2 - Exhaust manifold with heat shielding structure - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust manifold having a heat shielding structure that collects exhaust gas discharged from each cylinder of a multi-cylinder engine into a collecting section and guides the exhaust gas to an exhaust pipe.

[0002]

2. Description of the Related Art At present, most of exhaust manifolds used for engines are manufactured by casting cast iron in order to improve heat resistance and reduce manufacturing costs. Although the heat resistance of cast iron is high, the heat conduction from the cast iron exhaust manifold is large because the heat conduction is relatively good. Today, many engines are equipped with a turbocharger, but an exhaust manifold made of cast iron has a large amount of heat radiation to the outside, and the thermal energy of the exhaust gas cannot be effectively transmitted to the turbocharger. In addition, the weight is very heavy, which hinders engine weight reduction. Therefore, the exhaust manifold was made of an aluminum alloy to reduce the weight, and a heat shield structure was configured to reduce the amount of heat released from the exhaust manifold. For example, the liner on the inner surface of the aluminum alloy was made of ceramics with low thermal conductivity. Things are disclosed.

[0003] Conventionally, Japanese Patent Application Laid-Open
There is one disclosed in Japanese Patent Publication No. -164094. The heat-insulating composite pipe is a composite pipe formed by integrally and coaxially superimposing a plurality of mutually different pipe members in an inner and outer coaxial manner. Among the pipe members, the inner pipe member has a lower thermal expansion coefficient than the outer pipe member. In addition to being formed by the heat insulating material of the above, the inner pipe is divided through an allowable gap for thermal expansion or thermal contraction of the outer pipe, with a size capable of following the thermal expansion of the inner pipe and the outer pipe. is there.

[0004]

By the way, the exhaust gas discharged from each cylinder of the multi-cylinder engine merges into the collecting portion through the branch portion and the bent portion of the exhaust manifold, and from the collecting portion to the exhaust pipe. However, the flow rate of the exhaust gas is increased in comparison with the branch part because of the merging at the collecting part, and the flow velocity is also increased. Also, in order to reduce the amount of heat released from the combustion chamber and effectively transfer the heat energy of the exhaust gas to the turbocharger installed in the engine, the exhaust made of ceramics with very low thermal conductivity and small specific gravity A manufacturing method in which the manifold liner is cast with a metal such as an aluminum alloy is considered.

[0005] Therefore, the engine is configured as a heat shield structure,
In order to efficiently recover the exhaust gas energy with a turbocharger or an energy recovery device, a ceramic liner is cast into metal when an exhaust manifold in an exhaust system is manufactured in a heat shielding structure. However,
Comparing the coefficient of thermal expansion of metal with the coefficient of thermal expansion of ceramics, the coefficient of thermal expansion of ceramics is very small. Therefore, when a manifold liner made of ceramics is directly cast into metal, the ceramic shrinks due to the thermal contraction of the metal. Since an excessive heat load acts to cause the ceramic liner to break, the problem has been to configure the exhaust manifold so that it can tolerate the heat load when casting.

The heat-insulating composite pipe disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 60-164094 is provided with a gap between the divided inner pipe members so as to cope with a difference in thermal expansion. Therefore, the processing accuracy of the inner pipe member itself is required, and extremely complicated work is required for the position setting, which has a problem.

An object of the present invention is to solve the above-mentioned problems. An exhaust manifold liner is made of ceramics such as aluminum titanate having a very low thermal conductivity and a small specific gravity, and the exhaust manifold liner is cast. When casting a metal such as an aluminum alloy by placing it in a recessed mold, a notch groove that can be broken by thermal stress is formed in the exhaust manifold liner to allow the metal to shrink, and the ceramic itself shrinks due to the heat shrinkage of the metal. Breaks along the cut grooves, absorbs the amount of heat shrinkage of the metal by the breaks, and since the exhaust manifold liner has an integral structure at the time of casting, it can be easily installed in the casting mold and casting can be facilitated. It is to provide an exhaust manifold having a thermal structure.

[0008]

The present invention is configured as follows to achieve the above object. That is, the present invention provides an exhaust manifold liner including a branch portion communicating with each cylinder of a multi-cylinder engine, and an assembly portion that gathers the branch portions into one through a bent portion, and a cast outside the exhaust manifold liner. In an exhaust manifold comprising a metal outer member disposed in a swirl, the exhaust manifold liner is made of ceramics having a low thermal conductivity, and in a circumferential direction of the exhaust manifold liner, the metal of the outer member when the outer member is cast is formed. A heat-shrinkable cut-off groove formed by a stress caused by thermal shrinkage, and further comprising a compressible covering member made of a low thermal conductive material wound along the cut-off groove formed in the exhaust manifold liner. An exhaust manifold having

[0009]

The exhaust manifold having the heat shielding structure according to the present invention is configured as described above, and operates as follows. In this exhaust manifold, the exhaust manifold liner is made of ceramics having a low thermal conductivity, and a notch groove which can be broken by a stress caused by a thermal contraction of the metal when the outer member is cast is formed in a circumferential direction of the exhaust manifold liner.
In particular, since a compressible covering member made of a low-thermal-conductivity material is wound around the cut groove formed in the exhaust manifold liner, heat shrinkage occurs when the exhaust manifold liner is cast into metal, and the cut groove is formed along the cut groove. The exhaust manifold liner is broken, and the heat breakage of the metal can be absorbed by the break, preventing the other parts of the exhaust manifold liner from being broken unexpectedly, ensuring the strength and durability. Even if it breaks, the covering member can absorb the thermal shrinkage of the metal, and it can cover the broken surface of the cut groove well, and the heat conduction in the area of the cut portion of the cut groove does not increase, A heat shield structure can be secured.

Further, since the heat flow to the outside can be cut off by the heat shielding by the exhaust manifold liner, for example, the exhaust gas discharged from the engine can be efficiently sent to a turbocharger or an energy recovery device arranged downstream. It is possible to efficiently recover the heat energy of the exhaust gas.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view of an exhaust manifold having a heat shielding structure according to the present invention. FIG. 1 is a plan view of an exhaust manifold liner showing one embodiment of an exhaust manifold having a heat shielding structure according to the present invention,
2 is a sectional view showing an embodiment of an exhaust manifold having a heat shielding structure according to the present invention.

FIG. 1 shows an exhaust manifold liner incorporated in the exhaust manifold having the heat shielding structure. FIG. 2 shows an exhaust manifold having a heat shielding structure used in a multi-cylinder engine (in the figure, a four-cylinder engine is shown). The exhaust manifold liner 1 includes branch portions 2A that communicate with cylinders of a multi-cylinder engine.
2B, 2C, 2D (general name is 2), bent portions 3A, 3B, 3C, 3D (general name is 3) leading to each branch portion 2, a straight portion 5 which collects the bent portions 3, and an outlet of the straight portion 5 It is composed of a constituent part 4 that constitutes.
The exhaust manifold liner 1 is made of ceramics such as aluminum titanate having a very low thermal conductivity.
The cut groove 7 which is broken by the stress due to the heat shrinkage of the metal at the time of casting is formed. The cut groove 7 formed in the exhaust manifold liner 1 may have a narrow groove shape for forming a narrow gap or a cut line shape.

With respect to the exhaust manifold having the heat shielding structure, the exhaust gas discharged from the multi-cylinder engine joins the branch portion 2 of the exhaust manifold liner 1 to the collecting portion 4 and then connects to the exhaust pipe ( (Not shown), the flow rate of the exhaust gas in the collecting part 4 is larger than that in the branch part 2, and the heat load of the collecting part 4 is increased. Therefore, if the outer member 8 made of metal is
Is formed in direct contact, the heat flow from the collecting portion 4 to the outer member 8 increases, the temperature of the outer member 8 rises, and the durability of the outer member 8 deteriorates. .

The exhaust manifold having a heat shield structure according to the present invention is particularly suitable for manufacturing an exhaust manifold by arranging the exhaust manifold liner 1 in a casting mold and casting a metal such as an aluminum alloy or cast iron. Prior to the casting step, a cut groove 7 is formed at an appropriate position of the exhaust manifold liner 1 having an integral structure, and then the exhaust manifold liner 1 is disposed in a casting mold and cast with metal to form a metal outer member 8. Is formed. Although the exhaust manifold liner 1 is formed with the cut groove 7, it is easy to set the exhaust manifold liner 1 into a casting mold because it has an integral structure, so that the manufacturing process can be simplified and the manufacturing cost can be reduced. Can be reduced.

In casting the exhaust manifold liner 1 having the cut grooves 7 into the metal, the outer member 8 is cooled. However, the heat contraction of the metal generated at that time causes a heat load on the exhaust manifold liner 1. ,
Due to the heat load, the cut groove 7 formed in the exhaust manifold liner 1 is lower in strength than other parts, so that the cut groove 7 breaks along the cut and a broken portion 6 is generated. The heat shrinkage of the metal is absorbed by the rupture along the cut of the cut groove 7, so that the heat load due to the heat shrinkage of the metal does not act on portions other than the cut portion of the exhaust manifold liner 1, No fractures such as cracks and cracks occur in the parts.

Since the exhaust manifold having the heat shielding structure according to the present invention is configured as described above, it is possible to limit the location where the exhaust manifold liner 1 is to be fractured in advance, and to specify the exhaust manifold liner 1. Therefore, it is possible to easily manufacture an exhaust manifold in which a ceramic liner is cast without deteriorating the heat shielding property and durability of the exhaust manifold.
Therefore, for example, high-temperature exhaust gas can be sent to a turbocharger or an energy recovery device arranged downstream, without dissipating the heat energy of the exhaust gas exhausted from the engine in the exhaust manifold. Can be collected, the collection efficiency can be improved, and the fuel consumption can be reduced. .

Moreover, in the exhaust manifold having the heat shielding structure, since the exhaust manifold liner 1 is made of ceramics, when the metal to be cast is, for example, a metal such as an aluminum alloy having a smaller specific gravity than cast iron is used. Can reduce the weight of the exhaust manifold very much, which contributes to the weight reduction of the exhaust manifold.

Next, another embodiment of an exhaust manifold having a heat shielding structure according to the present invention will be described with reference to FIGS. FIG. 3 is a plan view of an exhaust manifold liner showing another embodiment of the exhaust manifold having the heat shield structure according to the present invention, and FIG. 4 is a cross-sectional view showing another embodiment of the exhaust manifold having the heat shield structure according to the present invention. It is. This embodiment has the same configuration as that of the above embodiment except that the covering member is wound along the cut grooves, so that the same portions are denoted by the same reference numerals, and redundant description will be omitted.

In the exhaust manifold having the heat shielding structure of this embodiment, a compressible covering member 9 made of a low heat conductive material such as asbestos or ceramic fiber is wound along cut grooves 7 formed in the exhaust manifold liner 1. ing. Therefore, even if the metal member is broken along the cut groove 7 of the exhaust manifold liner 1 due to the difference in thermal expansion with the metal outer member 8, the covering member 9 can cover the broken portion 6 of the cut groove 7 satisfactorily. In addition, since the covering member 9 is made of asbestos or ceramic fiber and is compressible, it can absorb the heat shrinkage of the metal, can cover the fractured surface of the cut groove 7 well, and The heat conduction in the region No. 6 does not increase, and the heat shielding structure can be secured.

[0020]

[Effect of the Invention] Since the exhaust manifold having the heat shielding structure according to the present invention is configured as described above, the cut grooves have lower strength than other parts, and the coefficient of thermal expansion of the ceramics is low. The coefficient of thermal expansion is much lower than the coefficient of thermal expansion of metal. A difference in thermal expansion occurs between the ceramic and the metal in accordance with the temperature difference. The cut groove of the exhaust manifold liner breaks due to thermal stress caused by heat shrinkage of the metal when the outer member is cast, so that the heat shrinkage of the metal can be absorbed without breaking other parts of the exhaust manifold liner. In particular, even if the cut member is broken along the cut groove during casting, the covering member can satisfactorily cover the cut part of the cut groove, and the heat transfer in the region of the cut part of the cut groove can be achieved. The can be maintained low, it can be secured heat insulating structure. Although the exhaust manifold liner is formed with the cut groove, it has an integral structure before casting, so that it is easy to set the position of the exhaust manifold liner in a casting mold, and the manufacturing process can be simplified. , The manufacturing cost can be reduced.

However, in the conventional divided manifold liner made of a plurality of divided ceramics, the processing accuracy of the gap size of each divided member is required, the cost of parts is high, and it is necessary to accurately position and set the mold. The work efficiency is inefficient and the manufacturing cost is high. On the other hand, the exhaust manifold liner in the exhaust manifold of the present invention has an integral structure during the manufacturing process, and thus does not require the above-mentioned processing accuracy and has extremely good workability.

Further, the location where the exhaust manifold liner is to be broken can be specified in advance, and it is possible to easily cope with the breakage of the exhaust manifold liner. Further, the heat flow to the outside can be cut off by the heat shielding by the exhaust manifold liner, and the heat energy of the exhaust gas can be efficiently transmitted to a turbocharger or an energy recovery device arranged downstream, and the exhaust gas energy is recovered.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of an exhaust manifold liner in an exhaust manifold having a heat shielding structure according to the present invention.

FIG. 2 is a cross-sectional view showing one embodiment of an exhaust manifold having a heat shielding structure according to the present invention.

FIG. 3 is a plan view showing another embodiment of the exhaust manifold liner in the exhaust manifold having the heat shielding structure according to the present invention.

FIG. 4 is a cross-sectional view showing another embodiment of an exhaust manifold having a heat shielding structure according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exhaust manifold liner 6 Break part 7 Cut groove 8 Outer member 9 Covering member

Continuation of the front page (56) References JP-A-60-164094 (JP, A) JP-A-60-187712 (JP, A) JP-A-60-81420 (JP, A) (U, U) 62-145921 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F01N 7/08-7/14

Claims (1)

(57) [Scope of request for utility model registration] 1. An exhaust manifold liner comprising: a branch portion communicating with each cylinder of a multi-cylinder engine; and a collecting portion which gathers the branch portions into one through a bent portion, and a cast-in outside the exhaust manifold liner. The exhaust manifold liner is made of ceramics having a low thermal conductivity, and the heat of the metal when the outer member is cast in the circumferential direction of the exhaust manifold liner. notches can be broken at a stress due to contraction is formed, further, the exhaust
Low along the notch formed in the manifold liner
An exhaust manifold having a heat shielding structure, wherein a compressible covering member made of a heat conductive material is wound .