JPH0246964A - Exhaust manihold for internal combustion engine and production thereof - Google Patents

Abstract

PURPOSE:To decrease the heat to be transferred from core bodies made of sintered ceramics bodies to a metal by internally chilling the core bodies in metal via many metallic projections and delineating spacings in the boundary part of the core bodies and the metallic body part except the projecting parts. CONSTITUTION:The core part 2 is mounted to a divided expendable pattern 1 on a lower side to delineate the spacings C between the expendable pattern and the core body. The divided expendable pattern 1 of the upper side is mated with and fixed to the expendable pattern 1 to constitute the mated expendable pattern A. Two pieces of the mated expendable patterns are mounted to a sprue pattern B made of polystyrene and the patterns A, B are charged together with dry sand S into a casting mold box 3 and is embedded therein. The casting mold box is oscillated to pack the dry sand S into the spacings C. A shielding film F is placed on the top end of the casting mold box and the pressure in a hollow chamber 4 is reduced by a vacuum pump to solidify the dry sand S. A molten metal is poured into the sprue pattern B and is solidified by cooling; thereafter, the suction effect is stopped and the internal chill body is taken out. The dry sand in the spacings C is removed to obtain the exhaust manihold. The spacings at the boundary between the core bodies and the metallic body are delineated in this way and the heat transfer from the core bodies to the metal is drastically decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust manifold for an internal combustion engine, which is made of a ceramic sintered body and is cast with a metal core, and a method for manufacturing the same.

(Prior art and problems) In recent years, attention has been paid to the fact that ceramic sintered bodies have excellent thermal shock resistance, and exhaust manifolds for internal combustion engines have been developed in which ceramic sintered bodies are cast with metal. , Conventional exhaust manifolds have a structure in which the entire outer surface of the ceramic sintered body is in direct contact with the metal, so heat from the ceramic sintered body is conducted directly to the metal, causing damage to the cast metal or the like. There is a problem that heat has an adverse effect on the connected parts, etc.
The current situation is that it has not been put into practical use.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide an exhaust manifold for an internal combustion engine using a casting method that can reduce the amount of heat transferred from a ceramic sintered body to a metal, and a method for manufacturing the same. It's about doing.

(Means for Solving the Inter-Mold Point) In order to achieve the above object, the exhaust manifold for an internal combustion engine according to the present invention has many protrusions formed on the surface of the metal that contacts the ceramic sintered body. A gap is defined at the boundary between the aggregate and the metal main body portion.

(Function) In the exhaust manifold of the present invention, heat is conducted from the ceramic sintered body to the metal using the metal protrusions and air as a medium, and the amount of heat conducted is significantly reduced.

(Example) An example will be described with reference to the drawings. In Fig. 1, (1) is a disappearing model for the full mold method for manufacturing the casting part of the exhaust manifold by the cast-in casting method.
Molded from polystyrene. The vanishing model (1) is a split vanishing model that is divided into two parts, which are molded together to form a hollow body shape, and have the same external shape as a predetermined exhaust manifold. A large number of protrusions (la) capable of supporting the solid core body (2) and defining a gap R (C) are formed at appropriate intervals. In addition, seven rungs (1b) and (IC) are formed at the upper and lower ends of the vanishing model (1), respectively, in consideration of machining allowance. (2) is the core of the exhaust manifold,
Constructed of aluminum titanate ceramic sintered body. (3) is a molding box for the full mold method in which a hollow chamber (4) is formed in the side wall and the bottom wall, and the hollow chamber (4) of the molding box (3) can be switched between three directions with a suction port (5). It is connected in communication to a vacuum pump (not shown) via a valve (not shown). The inner surface of the mold box (3) is configured to allow ventilation of the hollow chamber (4).

Next, the segmented vanishing model (1) (1
) and the core (2) to manufacture a desired exhaust manifold. First, as shown in Figure 2, the core body (2) is attached to the lower divided disappearing model (1) to define a gap C) between the disappearing model (1) and the core body (2). Then, the upper split-disappearance model (1) is fitted onto the split-disappearance model (1) on which the core body (2) is attached, and they are fixed together.
A mold-matching vanishing model (A) is constructed. Next, as shown in Fig. 3, the mold matching disappearing model (A) with built-in core body (2)
Then, these models (A), ■) are placed in the mold box (3) together with dry sand (S) to form the model (A), 03) with dry sand (
Bury the ink pad. Next, vibration is applied to the dry sand (S) in the mold box (3) to fill the space between the vanishing model (A) with dry sand (S), and then the dry sand (S) in the mold box (3) is filled. Cover the top opening and the dry sand (S) with a non-breathable shielding film such as a resin film, and then fill the hollow chamber (4) of the mold box (3) with a non-breathable shielding film such as a resin film.
is connected to a vacuum pump (not shown) to reduce the pressure in the #lJ type box (3) in which dry sand (S) etc. are charged, thereby solidifying the dry sand Q). Under this condition, a predetermined amount of molten metal is injected into the sprue model ) Take out the cast body from inside C), separate the sprue, and dry sand (S) inside C).
is removed to obtain an exhaust manifold for an internal combustion engine in which a gap is defined at the boundary between the core (2) and the metal body excluding the protruding portion.

In the above embodiment, aluminum titanate was used as the ceramic material, but tugerite or mullite may also be used. Further, in the above embodiment, the pressure inside the mold box is reduced prior to pouring the metal, but it is not necessarily necessary to reduce the pressure if conditions allow for good degassing.

(Effects of the Invention) As is clear from the above description, the present invention has a core made of a ceramic sintered body that is supported by a large number of protrusions so that the core body is cast, and the boundary between the core body and the metal body is Since the exhaust manifold for an internal combustion engine is designed to define a gap, it has the effect of significantly reducing heat conducted from the core to the metal. Further, according to the manufacturing method E of the present invention, it is possible to reliably and easily manufacture an exhaust manifold in which a gap is defined at the boundary between the core and the metal main body.

[Brief explanation of the drawing]

The drawings are reference drawings for explaining the present invention in detail, and FIG. 1 is a plan view of the split-disappearance model, and FIG. 2 shows a state in which the core body is attached to the split-disappearance model and the core body is cut on a horizontal plane. A plan view, FIG. 3 is a plan view showing a state in which a sprue model is fixed to a mold-fitting and disappearing model, and FIG. 4 is a longitudinal cross-sectional view showing a state in which the model is set in a molding box for the full mold method. (1): Matching disappearing model (la): Protrusion (2
): core body (C): gap grass diagram

Claims (1)

[Claims] 1. A core made of a ceramic sintered body is cast with metal through a large number of metal protrusions, thereby creating a gap at the boundary between the core and the metal body excluding the protrusions. An exhaust manifold for an internal combustion engine characterized by a defined structure. 2. Prepare two split disappearing models that are molded together to form a hollow body shape, have an outer shape that is almost the same as the outer shape of the exhaust manifold, and have a large number of protrusions formed at appropriate intervals on the inner surface, and one A core body made of ceramic sintered body having an inner shape that is almost the same as the inner shape of an exhaust manifold for an internal combustion engine is installed in the split-disappearance model of The model is placed in a mold box together with dry sand, the matching disappearing model is buried in the dry sand, and vibration is applied to the dry sand so that the matching disappearing model is buried in the gap between the matching disappearing model and the core body. 1. A method for manufacturing an exhaust manifold for an internal combustion engine, comprising filling dry sand and then pouring molten metal into the mold-fitting and disappearing model.