JP2602686B2 - Method of manufacturing piston for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston for an internal combustion engine, and more particularly, to a composite body reinforced with an annular cooling cavity in a head portion and at least a top ring groove portion made of reinforcing fibers. And a method for manufacturing a piston for an internal combustion engine.

2. Description of the Related Art One of the methods for manufacturing a piston for an internal combustion engine having an annular cooling cavity in a head portion is disclosed in, for example, JP-A-59-56966.
As described in JP-A-60-13955 and JP-A-61-67560, a soluble core for forming a cavity is positioned at a predetermined position by a fiber molding or the like partially engaging the core. Conventionally, there has been known a method of performing casting while holding the steel. However, in such a method, since the fiber molded article or the like is only partially engaged with the core, when the molten metal is poured into the mold, the core is moved to a predetermined position by the flow action or the like. There is a problem that the core is more likely to be moved or the core is easily cracked due to direct contact of the molten metal, and only a part of the wall surface of the formed cavity is composite reinforced with reinforcing fibers There is a problem that is not done.

Japanese Patent Application No. 61-26 filed by the same applicant as the present applicant.
No. 7762 describes a method of forming a molded body in which a soluble core for forming a cavity is wrapped with inorganic fibers, and performing casting using the molded body. According to the method according to the preceding proposal, it is possible to manufacture a piston in which the entire wall surface of the cooling cavity is compositely reinforced with inorganic fibers.

However, in this method, the core is wrapped in only one fiber molded body, and it is very difficult to form a fiber molded body wrapping the core. Further, in the above-mentioned prior application, it has been shown in the embodiment that the top ring groove is also compositely reinforced by the fiber molded body holding the core. When the part around the core and the top ring groove are compositely reinforced, the entire fiber molded body must be formed with high-performance reinforcing fibers suitable for compositely reinforcing the top ring groove. Due to the necessity of wrapping around the entire circumference, it is difficult to achieve the use and orientation of the fibers suitable for the composite reinforcement of the top ring groove, and furthermore, the cooling cavity to be formed and the top ring groove are difficult to achieve. There is a problem that the positional relationship is also restricted.

The present invention has been made in view of the above-described problems in the conventional method of manufacturing a piston for an internal combustion engine, and has an object to accurately form a cooling cavity at a predetermined position and appropriately compositely strengthen a top ring groove. It is an object of the present invention to provide a method capable of producing a piston for an internal combustion engine at a low cost and efficiently.

SUMMARY OF THE INVENTION According to the present invention, there is provided a piston for an internal combustion engine having an annular cooling cavity in a head portion and at least a top ring groove portion reinforced with a reinforcing fiber. In the method, a fiber molded body for compositely reinforcing the top ring groove, a soluble core for forming the cooling cavity, and at least one reinforcing material molded body for accommodating the core are provided. The core and the reinforcing material molded body are held by the fiber molded body such that the core is substantially wrapped around the entire periphery by the reinforcing material molded body or the reinforcing material molded body and the fiber molded body. This is achieved by a method for manufacturing a piston for an internal combustion engine, which comprises arranging these in a mold and pouring molten metal into the mold.

Effects and Effects of the Invention According to the present invention, the core and the reinforcing material molding are formed by the fiber molding such that the core is substantially wrapped around the whole circumference by the reinforcing material molding or the reinforcing material molding and the fiber molding. Since the metal is held and placed in the mold in that state, even when the molten metal is poured into the mold, it is possible to prevent the molten metal from directly contacting the core. It is possible to reliably prevent the core from being displaced by an action or the like and the core from being cracked due to a sudden thermal shock.

In addition, the core is not wrapped by one fiber molded body, but is wrapped by a plurality of reinforcing material molded bodies or fiber molded bodies, so that the core is reinforced as compared to the case where the core is wrapped by only one fiber molded body. It is possible to easily and efficiently produce the molded material and the fiber molded body, thereby reducing the cost of the piston, and appropriately setting the relative positional relationship between the reinforcing material molded body and the fiber molded body. By doing so, the relative positional relationship between the top ring groove and the cooling cavity can be set freely, as compared with the case where the core is wrapped by only one fiber molded body.

Further, the fiber molded body for compositely reinforcing the top ring groove and the reinforcing material molded body for accommodating the core are independent of each other. Since the orientation can be set to a suitable orientation, and the reinforcing material molded body can use a reinforcing material that is less expensive than the fiber used for the fiber molded body, the core is wrapped by only one fiber molded body. As compared with the case where the top ring groove is formed, the composite reinforcement of the top ring groove can be appropriately performed, and the cost of the piston can be reduced.

The reinforcing fiber constituting the fiber molded article in the present invention may be any reinforcing fiber which has been conventionally used in the production of a composite material and has excellent abrasion resistance improving effect, and the reinforcing fiber constituting the reinforcing material molded article The material may be any reinforcing fibers or particles conventionally used in the manufacture of composite materials.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings with reference to the accompanying drawings.

Embodiment FIG. 1 is an exploded perspective view showing a partially cutaway assembly in which a salt core is wrapped by one fiber molded body and two reinforcing material molded bodies, and FIG. 2 is shown in FIG. FIG. 3 is a cross-sectional view showing a casting process performed using the assembled assembly. FIG. 3 is a cross-sectional view showing a main part of one embodiment of a piston manufactured according to the present invention.

In these figures, reference numeral 10 denotes a substantially cylindrical fiber molded body for composite reinforcement of the top ring groove portion, the top land, and a part of the second land, and in the illustrated embodiment, , Suitable for composite reinforcement of the top ring groove,
It is made of two-dimensional randomly oriented reinforcing fibers 12 parallel to the cylindrical surface along the axis of the fiber molded body. Also, in FIG. 1, reference numerals 14 and 16 denote reinforcing material compacts having a substantially L-shaped cross section, each consisting of reinforcing fibers 18 and 20 which are substantially three-dimensionally randomly oriented. ing. The reinforcing material compacts 14 and 16 abut against each other at the end surfaces of their legs, and abut against the inner peripheral surface of the fiber compact 10 at their radially outer peripheral surfaces, and are pressed into the fiber compact 10. Is held by the fiber molded body. The fiber molded body 10 and the reinforcing material molded bodies 14 and 16 cooperate with each other to define an annular space 22, in which a salt core 24 is formed over the entire circumference of the fiber molded body and the reinforcing material molded body. It is arranged in a state of being wrapped by the body.

The assembly 26 composed of the fiber molded body 10, the reinforcing material molded bodies 14 and 16, and the salt core 24
May be formed by press-fitting, arranging the salt core 24 on the reinforcing material molded body 16, and further press-fitting the reinforcing material molded body 14 into the fiber molded body. 14 and 16
And may be formed by press-fitting or bonding them to the fiber molded body 10.

The assembly 26 is then placed in the mold cavity 32 of the mold 30 of the piston casting machine 28, as shown in FIG. In this case, the assembly 26 is fixed at a predetermined position by being pressed into the mold cavity up to a position where one end thereof abuts the shoulder 32a of the mold cavity. Next, the molten metal of the metal constituting the piston is placed in the mold cavity 32.
34 is poured, and the molten metal is pressurized to a predetermined pressure by the upper mold 36 fitted into the mold 30, and the pressurized state is maintained until the molten metal is completely solidified. In this case, the melt 34 penetrates between the reinforcing fibers of the fiber compact and the reinforcing material compact, thereby forming a fiber-reinforced metal composite material in the region of the original fiber compact and the reinforcing material compact.

When the molten metal is completely solidified, the formed piston coarse material is removed from the mold by the knockout pin 38. Next, as shown in FIG. 3, an oil introduction hole 40 is formed in the piston coarse material so as to reach the salt core, and the salt core is removed by injecting high-pressure water from the hole. Thereafter, a top ring groove 42, a second ring groove 44, and an oil ring groove 46 are formed. In FIG. 3, reference numeral 48 denotes a head portion, reference numeral 50 denotes a region of the composite material reinforced by the reinforcing fibers 12 of the original fiber molded body 10, 52 and 54.
Are the reinforcing fibers 18 and of the original reinforcing material moldings 14 and 16, respectively.
20 shows the area of the composite material reinforced composite by 20,
Reference numeral 56 denotes a cooling cavity.

4 to 9 are perspective views similar to FIG. 1 showing another embodiment of an assembly comprising a fiber molded body, a reinforcing material molded body, and a salt core in the method of the present invention. . In these figures, parts corresponding to the parts shown in FIG. 1 are denoted by the same reference numerals as those shown in FIG.
Also, in these figures, a part of the outer shape of the manufactured piston is indicated by a virtual line.

In the embodiment shown in FIG. 4, the fiber molded body 10 has an integral convex portion 10a, and the reinforcing material molded body 1 is formed at the tip of the convex portion.
4, and the salt core 24 is wrapped around the entire circumference by the fiber molded body 10 and the reinforcing material molded body 14.

In the embodiment shown in FIG. 5, the fiber molded body 10 has a convex portion 10a having an L-shaped cross section, and the tip of the convex portion 10a is brought into contact with a reinforcing material molded body 14 having an annular plate shape. The reinforcing material molded body 14 is pressed into the inner peripheral surface of the fiber molded body 10 at its radially outer peripheral surface, and the salt core 24 is formed around the entire circumference by the fiber molded body 10 and the reinforcing material molded body 14. It is in a state of being wrapped in.

In the embodiment shown in FIG. 6, the structure of the reinforcing material molded bodies 14 and 16 is the same as that of the embodiment shown in FIG. 1, but the axial length of the fiber molded body 10 is 1 is longer than that of the embodiment shown in FIG. 1, and the composite fiber is reinforced by the reinforcing fibers 12 up to the end face of the head portion of the piston.

In the embodiment shown in FIG. 7, the reinforcing material compacts 14 and 16 each have an L-shaped cross section composed of cylindrical portions 14a and 16a and legs 14b and 16b extending radially therefrom. The ends of the legs 14b and 16b abut against the cylindrical portions 16a and 14a, respectively, and the salt core 24 is wrapped around the entire circumference by these reinforcing material molded bodies. In the reinforcing material molded bodies 14, 16 and the salt core 24, the cylindrical portion 16a of the reinforcing material molded body 16 is
It is held by being press-fitted into the inner peripheral surface of the zero.

In the embodiment shown in FIG. 8, the reinforcing material molded body 14 is formed in an annular plate shape, the reinforcing material molded body 16 is formed in a J-shaped cross section, and the radially outer periphery of the reinforcing material molded body 14 is formed. Surface is reinforcement molding 16
Is fixed to the inner peripheral surface of the outer cylindrical portion 16c by press fitting,
The end face of the cylindrical portion 16a inside the reinforcing material molded body 16 abuts on the reinforcing material molded body 14, and the salt core 24 is wrapped around the entire circumference by the reinforcing material molded body. Also in this embodiment, the reinforcing material compacts 14, 16 and the salt core 24 are
The outer cylindrical portion is press-fitted into the fiber molded body 10 to be held thereby.

In the embodiment shown in FIG. 9, the reinforcement moldings 14 and 16 correspond to the reinforcement moldings 14 and 16 of the embodiment shown in FIG.
Has a configuration similar to that described above, and abuts against a substantially cylindrical reinforcing material molded body 58 made of reinforcing fibers 60 at their radially outer peripheral surfaces, and the salt core 24 is used as the reinforcing material molded bodies 14, 26, It is wrapped all around by 58. Further, in this embodiment, the reinforcing material molded product and the salt core are held by the reinforcing material molded product 58 being pressed into the inner peripheral surface of the fiber molded product 10. .

Although the present invention has been described in detail with reference to some embodiments, the present invention is not limited to these embodiments, and various other embodiments are possible within the scope of the present invention. Will be apparent to those skilled in the art.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a partially cutaway assembly in which salt suspension is wrapped by one fiber molded body and two reinforcing material molded bodies, and FIG. 2 is a set shown in FIG. FIG. 3 is a cross-sectional view showing a casting process performed by using a three-dimensional structure. FIG. 3 is a cross-sectional view showing a main part of one embodiment of a piston manufactured according to the present invention. FIGS. 4 to 9 are manufacturing methods according to the present invention. FIG. 10 is a perspective view showing another embodiment of the assembly including the fiber molded body, the reinforcing material molded body, and the salt core in the embodiment of the present invention, partially broken away. 10 …… fibre molding, 12 …… reinforced fiber, 14, 16 …… reinforced material molded article, 18, 20 …… reinforced fiber, 22 …… annular space, 24 …… salt core, 26 …… assembly, 28 …… Piston casting device, 30 …… Mold,
32 …… Mold cavity, 34… Metal melt, 36 …… Upper mold, 38 …… Knockout pin, 40 …… Oil introduction hole, 42…
... Top ring groove, 44 ... Second ring groove, 48 ... Head part, 50,52,54 ... Compound material area, 56 ... Cooling cavity, 58 ... Reinforcement molding, 60 ... Reinforcing fiber

Continued on the front page (72) Inventor Shoji Kanai 2-4-243, Jobanjo, Ueda-shi, Nagano Inside Art Metal Industry Co., Ltd. (72) Inventor Nao Nakashima 4--24, Motonohara, Toyokawa-shi, Aichi Prefecture (56) References JP-A-60-166158 (JP, A) JP-A-63-215363 (JP, A) JP-A-63-108549 (JP, U) JP-A-63-123746 (JP, U)

Claims (1)

(57) [Claims] 1. A method for manufacturing a piston for an internal combustion engine having an annular cooling cavity in a head portion and at least a top ring groove portion reinforced with a reinforcing fiber, the method comprising the steps of: A fiber molded body, a soluble core for forming the cooling cavity, and at least one reinforcing material molded body accommodating the core are prepared, and the reinforcing material molded body or the reinforcing material molded body and The core and the reinforcing material molded body are held by the fiber molded body so that the core is wrapped around the entire circumference by the fiber molded body, and these are arranged in a mold. A method for producing a piston for an internal combustion engine, comprising pouring molten metal.