JPH0583319U - Exhaust manifold with heat shield structure - Google Patents

Abstract

(57) [Summary] [PROBLEMS] The present invention provides an exhaust manifold having a heat shield structure that alleviates thermal contraction stress caused by casting metal in an exhaust manifold liner made of ceramics. [Structure] An exhaust manifold liner 1 in an exhaust manifold having this heat shield structure is connected to each branch portion 2 that communicates with each cylinder of a multi-cylinder engine, and each branch portion 2 is a bent portion 3.
It is composed of a gathering unit 4 that gathers together through. The exhaust manifold 1 is made of ceramics having a low thermal conductivity, and is placed between a portion 6A on the side that receives compressive stress in the heat shrinkage stress of the metal due to the casting of the branch portion 2 and the bent portion 3 and the outer member 8 made of the metal. Since the molded body 7 made of alumina fiber or ceramic fiber made of potassium titanate is interposed, the molded body 7 can reduce the heat shrinkage stress in the lateral direction during casting.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an exhaust manifold having a heat shield 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]

[Prior Art]

 Currently, most exhaust manifolds used in engines are manufactured by casting cast iron in order to improve heat resistance and keep manufacturing costs low. Although cast iron has a high heat-resistant temperature, it also has a relatively good heat conduction, so it releases a large amount of heat from the combustion chamber. Many engines today are equipped with turbochargers, but engines with turbochargers use exhaust manifolds made of cast iron, which is very heavy and hinders engine weight reduction. There is.

[0003] Conventionally, as a composite refractory material for cast iron, there is one disclosed in Japanese Utility Model Publication No. 52-141023. The cast refractory composite refractory is placed on the inner wall surface of the casting that transports the heating fluid inside, and the refractory fibers and silicic acid are formed on the entire outer peripheral surface of the ceramic refractory formed in a desired pipe shape in advance. A composite coating layer composed of calcium hydrate is provided substantially uniformly, this refractory is installed in a mold, and molten metal is poured into the mold to form a composite refractory integrally formed with the casting. is there. 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 substantially uniformly provided on the refractory fiber layer. is there.

[0004]

[Problems to be solved by the device]

 Therefore, in order to reduce the amount of heat released from the combustion chamber and make the turbocharger installed in the engine effectively act on the thermal energy of the exhaust gas, an exhaust gas made of ceramics with extremely low thermal conductivity and low specific gravity is used. A manufacturing method in which the manifold liner is cast with a metal such as an aluminum alloy can be considered. However, since the coefficient of thermal expansion of ceramics is much smaller than that of metal, if the exhaust manifold liner made of ceramics is placed in the casting mold as it is and the metal is cast into it, the heat shrinkage stress of the metal causes the exhaust manifold to move. There is a risk of cracks, cracks, etc. occurring in the ceramics that make up the liner, and the exhaust manifold liner being 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, and this destruction phenomenon becomes remarkable.

Therefore, the object of the present invention is to solve the above-mentioned problems, and an exhaust manifold dryer is made of ceramics such as aluminum titanate having a very low thermal conductivity and a small specific gravity, and the exhaust gas is exhausted. Manifold liner is placed in a casting mold and cast by casting metal such as aluminum alloy, and the heat shrinkage amount of the metal during casting becomes large. The purpose is to provide an exhaust manifold with a heat shield structure that prevents the exhaust manifold from being damaged by arranging a ceramic fiber molded body only in it and casting metal.

[0006]

[Means for Solving the Problems]

 The present invention is configured as follows to achieve the above object. That is, the present invention provides an exhaust manifold including an branch manifold that communicates with each cylinder of a multi-cylinder engine and an aggregate that aggregates the branch parts into one through a bent part, and an exhaust manifold outside the exhaust manifold. In an exhaust manifold consisting of an outer member made of metal arranged by casting, the exhaust manifold liner is made of ceramics with low thermal conductivity, and the heat shrinkage stress of the metal due to casting at the branch portion and the bent portion. The exhaust manifold of the heat shield structure is characterized in that a molded body made of ceramic fiber is interposed between a portion on the side receiving the compressive stress and the outer member.

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

[0008]

[Action]

 Since the exhaust manifold of the heat shield structure according to the present invention is configured as described above, it operates as follows. In the exhaust manifold with this heat shield structure, the exhaust manifold is made of ceramics with low thermal conductivity, and of the heat shrinkage stress of the metal due to casting of the branch part and the bent part, the part on the side receiving the compressive stress and the outside made of metal. Since a molded body made of ceramic fiber is interposed between the member and the member, the molded body reduces the lateral heat shrinkage stress of the outer member during casting, and reduces the compressive stress applied to the exhaust manifold liner. Prevent damage to the exhaust manifold liner.

[0009]

【Example】

 An embodiment of an exhaust manifold having a heat shield structure according to the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing an exhaust manifold liner in an exhaust manifold having a heat shield structure according to the present invention, FIG. 2 is a cross-sectional view taken along the line XX in FIG. 1, and FIG. 3 is an illustration of a heat shrinkage stress distribution received by the exhaust manifold liner. FIG. 4 is a plan view showing an embodiment of an exhaust manifold of a heat shield structure according to the present invention, and FIG. 5 is a sectional view taken along line YY of FIG.

FIGS. 1, 2 and 3 show an exhaust manifold liner 1 used in a multi-cylinder engine (a four-cylinder engine is shown as an example in the drawings). This exhaust manifold liner 1 includes branch parts 2A, 2B, 2C, 2D (hereinafter, referred to as a general name of the branch parts indicated by reference numeral 2) communicating with each cylinder of a multi-cylinder engine, and a bent part 3A communicating with each branch part 2. , 3B, 3C, 3D (hereinafter, referred to as reference numeral 3 in the generic name of branch portions), a straight portion 5 that gathers the bent portions 3 and a gathering portion 4 that constitutes an outlet of the straight portion 5. This exhaust manifold liner 1 is made of ceramics such as aluminum titanate having a very low thermal conductivity and a small specific gravity.

When the exhaust manifold 1 having a heat shield structure is manufactured by placing the exhaust manifold liner 1 in a casting mold and casting a metal such as an aluminum (Al) alloy or cast iron (Fc), In the process, the exhaust manifold liner 1 is subjected to heat shrinkage stress due to heat shrinkage of the metal when the metal is cooled. The distribution of the heat shrinkage stress applied to the exhaust manifold liner 1 becomes higher in the bent portions 3 at the portions 6A 1 and 6B 2 shown by diagonal lines in FIG. That is, a phenomenon that the lateral heat shrinkage stress on the bent portion 3 of the exhaust manifold liner 1 becomes high appears. When the metal undergoes heat shrinkage, the heat shrinkage stress in the portion 6A becomes a compressive stress, and the heat shrinkage stress in the portion 6B acts as a tensile stress, so that the effect of the heat shrinkage stress on the exhaust manifold liner 1 is It gets smaller.

Therefore, the exhaust manifold of the heat shield structure according to the present invention has a molded body made of ceramic fiber as a stress relaxation member on the outside of the portion 6A where the compressive stress largely appears as the heat shrinkage stress when the metal thermally contracts. That is, a molded body 7A, 7B, 7C, 7D (hereinafter, referred to as a generic name of the blanch portion is denoted by reference numeral 7) of ceramic fiber molded but not fired is cast and a metal such as an aluminum alloy is cast. As shown in FIGS. 4 and 5, a metal member, that is, an outer member 8 is formed outside the exhaust manifold 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 having the heat shield structure according to the present invention has the above-described configuration, the portion of the heat contraction stress of the metal due to the casting of the branch portion 2 and the bent portion 3 which is on the side receiving the compressive stress and the metal 6A. Since the molded body 7 made of ceramic fiber is interposed between the molded body 7 and the outer member 8 made of, the molded body 7 functions as a stress relaxation member for relaxing the lateral heat shrinkage response at the time of casting, and the exhaust manifold. It is possible to reduce the compressive stress applied to the liner 1 and prevent the exhaust manifold liner 1 from being cracked or broken.

Moreover, in the exhaust manifold of this heat shield structure, the molded body 7 is a ceramic fiber, and since a large number of air layers are enclosed in the internal structure, the shield of the exhaust manifold liner 1 made of aluminum titanate is shielded. It does not deteriorate the heat resistance. Also, by using an aluminum alloy with a smaller specific gravity than cast iron for the metal into which the exhaust manifold 1 is cast, the weight of the exhaust manifold with a heat shield structure can be reduced, contributing to the weight reduction of the exhaust manifold. It will be. Furthermore, if the exhaust manifold with this heat shield 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 in the downstream of the exhaust system. Therefore, the energy recovery efficiency can be improved, and the fuel consumption can be reduced.

[0015]

[Effect of the device]

 Since the exhaust manifold of the heat shield structure according to the present invention is configured as described above, it has the following effects. That is, in the exhaust manifold of this heat shield structure, the exhaust manifold is made of ceramics having a low thermal conductivity, and receives the compressive stress of the heat shrinkage stress of the metal due to the casting of the branch portion and the bent portion of the exhaust manifold. Since the molded body made of ceramic fiber is interposed between the side part and the outer member made of metal, the heat shrinkage stress of the metal at the time of casting can be effectively relieved by the molded body, and it affects the exhaust manifold liner. It is possible to reduce the compressive stress and prevent the exhaust manifold from being broken.

Further, in this exhaust manifold having a heat shield structure, the molded body is potassium titanate or alumina fiber, and since many air layers are enclosed in the internal structure, it has sufficient heat shield properties. Therefore, it does not adversely affect the heat shielding property of the exhaust manifold liner made of aluminum titanate.

Further, by using an aluminum alloy having a low specific gravity as the metal for casting the exhaust manifold liner, the weight of the exhaust manifold situation can be reduced, which can contribute to the weight reduction of the engine. Also, if the exhaust manifold with this heat shield structure is used for the engine, the exhaust gas energy from the heat shield engine can be effectively maintained and the energy can be effectively recovered by the turbocharger placed downstream of the exhaust system. Therefore, it is possible to reduce fuel consumption.

[Brief description of drawings]

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

2 is a cross-sectional view taken along the line XX of FIG.

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

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

5 is a cross-sectional view taken along the line YY of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exhaust manifold liner 2 Branch part 3 Bending part 4 Assembly part 5 Straight part 6A, 6B part (part to which heat shrinkage stress is applied) 7 Molded body 8 Outer member

Claims (2)

[Scope of utility model registration request] 1. An exhaust manifold liner comprising a branch part communicating with each cylinder of a multi-cylinder engine and a collecting part collecting the branch parts into one through a bent part, and casting outside the exhaust manifold liner. In the exhaust manifold consisting of the outer member made of metal arranged by
The exhaust manifold liner is made of a ceramic having a low thermal conductivity, and a ceramic is provided between the outer member and a portion of the heat shrinkage stress of the metal due to casting in the branch portion and the bent portion, the portion receiving a compressive stress. An exhaust manifold with a heat shield structure, in which a molded body made of fibers is interposed. 2. The exhaust manifold with a heat shield structure according to claim 1, wherein the molded body is made of alumina fiber or potassium titanate, and the exhaust manifold is made of aluminum titanate.