JPS594221B2 - Mold for internal combustion engine pistons - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold for casting a piston for an internal combustion engine, particularly a piston in which a pin boss portion and a skirt portion are insulated by a narrow slit formed in the skirt portion.

In this type of piston, the effect of thermal expansion of the pin boss on the skirt is cut off by the insulating slit, so the skirt expands uniformly when the engine is at high temperature.
Good sliding condition with the inner surface of the cylinder is maintained.

As a result, there is less gas leakage from the sliding gap between the cylinder and the piston, and this has the effect of improving engine output and preventing air pollution.

An object of the present invention is to provide a mold that can manufacture a piston having the above structure all at once by casting.

An illustrated embodiment will be described below.

In Figures 1 to 3, reference numeral 1 denotes an outer mold with a circular cross section and a left and right half space S with an open top and bottom. It has a semicylindrical through hole 3.

The mold inner surface 2 forms the outer peripheral surface of the piston.

The outer mold 1 is placed on a bottom plate 4, and the top surface of the bottom plate 4 forms the top surface of the head portion.

The main core 5 is inserted from above into the space S of the outer mold 1 as shown in FIG.
The main core 5 is positioned by placing it on the upper surface of the main core 5.

The main core 5 has a skirt inner surface forming part 7 connected to the cover 6, a head part inner surface forming part 8 connected thereto, and a part of the side surface of the skirt inner surface forming part drops down with a hollow-shaped outline, and the head part It has a pair of pin boss forming recesses 9 that open at the end face of the inner surface forming part.

When positioning the main core 5, the depressed portion of the recess 9 is made to face the through hole 3 of the outer mold 1.

FIG. 4 shows a byproduct 10, which has a semi-circular cross section and a partition 1 having a U-shaped curved edge 1 at the end surface.
2, a pin hole forming protrusion 14 protruding from the arcuate end face recess 13, and a positioning pin part 15 provided on the end face of the protrusion.

Two of the by-products 10 are inserted into the mold through the through holes 3 of the outer mold 1, and the curved end surfaces of the partition portions 12 are brought into contact with the outer peripheral edge of the depressed portion of the main core recess 9. , protrusion 14
is positioned in the recess, and the positioning pin part 15 is positioned in the recess 9.
It is assembled by fitting into the hole 16 of.

When the outer mold 1, the main core 5, and the by-product 10 are combined as described above, the main core 5 and the by-product 10 form a skirt part forming space S1, a head part forming space S2, and a pin boss part forming space S3. Moreover, the skirt part forming space S1 and the pin boss forming space S3 are insulated by the partition part curved edge 11 of the byproduct 10.

For example, molten aluminum alloy is injected into the outer mold inner spaces 81 to S3 and cast, and the product is removed from the mold.
As shown in the figure, the base of the pin boss part 17 is connected to the head part 18, and between the pin boss part 17 and the skirt part 19 there is a U-shaped slit S4 with a slight width corresponding to the thickness of the byproduct partition part curved edge 11. A piston material 20 having the following properties is obtained.

21 indicates a pin hole.

The byproduct 10 does not need to be separate from the outer mold 1, and may be provided integrally with the outer mold 1.

As described above, according to the present invention, by using a mold with an extremely simple structure consisting of an outer mold, a main core, and a by-product, a piston with a complex shape having an insulating slit between the pin boss and the removing skirt can be manufactured. It can be cast all at once, so the troublesome grooving process for forming the insulating slits is of course unnecessary, and the product can be supplied at low cost.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional front view of an embodiment of the present invention, Fig. 2 is a cross-sectional plan view thereof, Fig. 3 is a side view illustrating the insertion direction of the main core into the outer mold, and Fig. 4 is a side view of the by-product. A perspective view, FIG. 5 is a longitudinal sectional front view of a piston material cast using the mold of the present invention,
FIG. 6 is a side view thereof. 1... Outer shape, S... Space, 5...
... Main core, 7 ... Skirt inner surface forming part, 8
...Head part inner surface forming part, 9... Pin boss part forming recess, 10... By-product, 11...
... White border, 12 ... Partition part, 14 ...
... Protrusion for forming pin holes, 20 ... Piston material.

Claims (1)

[Claims] 1 A two-part outer mold having a space with a circular cross section, a skirt inner surface forming portion, a head inner surface forming portion, and a part of the side surface of the skirt inner surface forming portion falling down and opening to the end surface of the head inner surface forming portion. A main core having a pair of four parts for forming pin boss parts, protruding from the inner surface of the outer mold, and having a curved edge abutting the outer peripheral edge of the depressed part of the main core recess, insulating the space for forming the skirt part and the space for forming the pin boss. A mold for a piston for an internal combustion engine, comprising a partition part and a pair of by-products having a pin hole forming protrusion protruding from a recessed part in the end face of the partition part and located in the main core recessed part.