JP2581900Y2 - Exhaust manifold with heat shield - 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 from a branch portion to a collecting portion 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 combustion chamber is large because the heat conduction is relatively good. Today, many engines are equipped with turbochargers, but engines with such turbochargers use an exhaust manifold made of cast iron, which is extremely heavy and hinders engine weight reduction. .

Conventionally, as a composite refractory for cast-in, there is one disclosed in Japanese Utility Model Laid-Open Publication No. 52-141023.
The composite refractory for as-cast is to be disposed on the inner wall surface of a cast product for transporting a heating fluid therein, and refractory fibers and calcium silicate are formed on the entire outer peripheral surface of a ceramic refractory formed in a desired pipe shape in advance. A composite coating layer made of a hydrate is provided substantially uniformly, the refractory is placed in a mold, and a molten metal is poured into the mold to form the composite refractory into a cast-in piece. . The composite coating layer is a coating layer in which a refractory fiber layer is first formed on the outer peripheral surface of a ceramic refractory, and a calcium silicate hydrate coating layer is provided substantially uniformly on the refractory fiber layer.

[0004]

Therefore, in order to reduce the amount of heat radiation from the combustion chamber and make the heat energy of the exhaust gas work effectively on the turbocharger provided in the engine,
A method of casting an exhaust manifold liner made of ceramics having a very low thermal conductivity and a small specific gravity with a metal such as an aluminum alloy is conceivable. However,
Ceramics have a very low coefficient of thermal expansion compared to metal, so if the ceramic exhaust manifold liner is placed in a casting mold as it is and the metal is cast, the exhaust manifold liner is caused by the heat shrinkage stress of the metal. Cracks, cracks, etc. may occur in the constituent ceramics, and the exhaust manifold liner may be destroyed. In particular, in the case of casting the exhaust manifold, the amount of heat shrinkage in the lateral direction of the exhaust manifold becomes large, so that this destruction phenomenon becomes remarkable.

An object of the present invention is to solve the above-mentioned problems. An exhaust manifold liner is made of a ceramic such as aluminum titanate having a very low thermal conductivity and a small specific gravity, and the exhaust manifold liner is cast. It is made by casting metal such as aluminum alloy
In order to reduce the lateral heat shrinkage stress of the exhaust manifold liner, which increases the amount of heat shrinkage of the metal during casting, in particular, the outer region of the bent portion of the exhaust manifold liner, which receives the compressive stress among the heat shrinkage stress of the metal, It is an object of the present invention to provide an exhaust manifold having a heat shield structure in which a molded body of ceramic fiber is disposed only in a region between the outer member and a metal, and metal is cast to prevent breakage of an exhaust manifold liner.

[0006]

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. The exhaust manifold liner is made of ceramics having a low thermal conductivity, and heat shrinkage of the metal by casting the branch portion and the bent portion of the exhaust manifold liner is provided. The present invention relates to an exhaust manifold of a heat shielding structure, wherein a molded body made of ceramic fiber is interposed only in a region between the outer region of the bent portion and the outer member, which receives a compressive stress among stresses.

In the exhaust manifold having the heat shield structure, the molded body is made of alumina fiber or potassium titanate. Further, the ceramic having low thermal conductivity constituting the exhaust manifold liner is made of aluminum titanate.

[0008]

[Function] The exhaust manifold of the heat shield structure according to the present invention is:
The configuration described above operates as follows. In the exhaust manifold of this heat shield structure, the exhaust manifold liner is made of ceramics with low thermal conductivity. Since the molded body made of ceramic fiber is interposed only between the outer member and the outer member, that is, only between the outer region of the bent portion and the outer member, the lateral direction of the outer member when the outer member is cast by the molded body. Of the heat shrinkage stress of the exhaust manifold liner, the compressive stress applied to the region outside the bent portion of the exhaust manifold liner is reduced, and breakage occurring from the bent portion of the exhaust manifold liner can be prevented. .

[0009]

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 showing an exhaust manifold liner in an exhaust manifold having a heat shielding structure according to the present invention, and FIG. 2 is a line X in FIG.
3 is a cross-sectional view, FIG. 3 is a plan view illustrating a heat shrinkage stress distribution applied to the exhaust manifold liner, FIG. 4 is a plan view showing one embodiment of the exhaust manifold of the heat shield structure according to the present invention, and FIG. 4 is a sectional view taken along line YY in FIG.

FIGS. 1, 2 and 3 show an exhaust manifold liner 1 used in a multi-cylinder engine (in the figures, a four-cylinder engine is shown as an example). The exhaust manifold liner 1 includes branch portions 2A, 2B, 2C, 2D (hereinafter, referred to as "branches") communicating with respective cylinders of a multi-cylinder engine.
The branch part is generically indicated by reference numeral 2), and each branch part 2
3A, 3B, 3C, and 3D (hereinafter, collectively referred to by reference numeral 3), a straight portion 5 that collects the bent portions 3, and a collecting portion 4 that forms an outlet of the straight portion 5. I have. The exhaust manifold liner 1
It is made of ceramics such as aluminum titanate having very low thermal conductivity and low specific gravity.

When the exhaust manifold liner 1 is arranged in a casting mold and a metal such as an aluminum (Al) alloy or a cast iron (Fc) is cast to manufacture an exhaust manifold having a heat shielding structure, a metal casting process is performed. When the metal is cooled, the exhaust manifold liner 1 receives heat shrinkage stress due to heat shrinkage of the metal. The distribution of the heat shrinkage stress applied to the exhaust manifold liner 1 is higher at the bent portion 3 as indicated by the oblique lines in FIG. 3, that is, the outer region 6A and the inner region 6B. That is, a phenomenon occurs in which the heat shrinkage stress in the lateral direction with respect to the bent portion 3 of the exhaust manifold liner 1 increases. When the metal thermally contracts, the heat shrinkage stress in the outer region 6A becomes a compressive stress, and the heat shrinkage stress in the inner region 6B acts as a tensile stress, and the effect of the heat shrinkage stress on the exhaust manifold liner 1. Becomes smaller.

The exhaust manifold of the heat shielding structure according to the present invention is formed of a ceramic fiber as a stress relaxation member in a portion where a compressive stress largely appears as a thermal contraction stress when the metal is thermally contracted, that is, outside the outer region 6A. A body, that is, a molded body 7A, 7B, 7C, 7D (hereinafter, generally denoted by reference numeral 7 in the branch portion) formed of ceramic fibers but not fired, is cast with a metal such as an aluminum alloy. As shown in FIGS. 4 and 5, a metal member, that is, an outer member 8 is formed outside the exhaust manifold liner 1 and the molded body 7. As the ceramic fiber, for example, alumina fiber (Al ₂ O ₃ fiber), potassium titanate fiber (K ₂ Ti ₆ O ₃ fiber) or asbestos fiber can be used.

Since the exhaust manifold of the heat shield structure according to the present invention has the above-described structure, a portion on the side receiving the compressive stress, that is, the outer region, of the heat shrinkage stress of the metal due to the casting of the branch portion 2 and the bent portion 3. Since the molded body 7 made of ceramic fiber is interposed between the outer member 8 made of metal and the outer body 6A, the molded body 7 functions as a stress relieving member for relieving the heat shrinkage stress in the horizontal direction during casting. It is possible to reduce the compressive stress applied to the manifold liner 1 and prevent the exhaust manifold liner 1 from being broken or cracked from the bent portion 3.

Moreover, in the exhaust manifold of this heat shielding structure, the molded body 7 is a ceramic fiber, and since a large number of air layers are sealed in the internal structure, the heat shielding property of the exhaust manifold liner 1 made of aluminum titanate is reduced. It does not lower. Exhaust manifold liner 1
By using an aluminum alloy having a lower specific gravity than cast iron as a metal for casting, the weight of the exhaust manifold of the heat shield structure can be reduced, which contributes to the weight reduction of the exhaust manifold. Furthermore, if the exhaust manifold having this heat shielding structure is used in an engine, the exhaust gas energy from the engine can be maintained in the exhaust manifold and effectively recovered by a turbocharger and an energy recovery device arranged downstream of the exhaust system. Thus, energy recovery efficiency can be improved and fuel consumption can be reduced.

[0015]

The exhaust manifold of the heat shield structure according to the present invention has the following effects because it is configured as described above. That is, the exhaust manifold of this heat shield structure
The exhaust manifold liner is made of ceramics having a low thermal conductivity, and among the heat shrinkage stress of the metal caused by casting the branch portion and the bent portion of the exhaust manifold liner, in particular, the portion on the side subjected to the compressive stress, that is, the bent portion of Since the molded body made of ceramic fiber is interposed only in the region between the outer region and the outer member made of metal, the compression stress of the heat shrinkage stress of the metal during casting can be effectively reduced by the molded body. The compressive stress applied to the region outside the bent portion of the exhaust manifold liner can be reduced, and breakage of the exhaust manifold liner from the bent portion can be prevented.

Further, in the exhaust manifold having the heat shielding structure, the molded body is made of potassium titanate or alumina fiber, and has a sufficient heat shielding property because a large number of air layers are sealed in the internal structure. There is no adverse effect on the heat shielding properties of the exhaust manifold liner made of aluminum titanate.

Further, by using an aluminum alloy having a small specific gravity as the metal into which the exhaust manifold liner is cast, the weight of the exhaust manifold itself can be reduced.
This can contribute to the weight reduction of the engine. Also, if the exhaust manifold of this heat shield structure is used for the engine, the exhaust gas energy from the heat shield engine can be maintained effectively, and the energy can be effectively recovered by the turbocharger arranged downstream of the exhaust system. Fuel economy can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a sectional view taken along line XX of FIG. 1;

FIG. 3 is a plan view illustrating a heat shrinkage stress distribution applied to an exhaust manifold liner.

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

FIG. 5 is a sectional view taken along line YY in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exhaust manifold liner 2 Branch part 3 Bending part 4 Assembly part 5 Straight part 6A Outer area (part to which compressive stress of thermal contraction stress is applied) 6B Inner area (part to which tensile stress of thermal contraction stress is applied) 7 Molded body 8 Outer member

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F01N 7/10 F01N 7/14

Claims (2)

(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 an assembly portion which collects the branch portions into one through a bent portion, and is cast outside the exhaust manifold liner. An exhaust manifold comprising: a metal outer member disposed according to:
The exhaust manifold liner is made of ceramics with low thermal conductivity, the outer region of the bent portion for receiving the compressive stress of the exhaust manifold liner of the branch portion between the bent portion and the casting of a metal of the heat shrinkage stress against the And said
An exhaust manifold having a heat shield structure, wherein a molded body made of ceramic fiber is interposed only in a region between the outer member and the outer member . 2. The exhaust manifold according to claim 1, wherein the molded body is made of alumina fiber or potassium titanate, and the exhaust manifold liner is made of aluminum titanate.