JPS594219B2 - 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 small insulating gap is formed between a pin boss part and the inner circumferential surface of a skirt part facing the pin boss part. .

In this type of piston, the effect of thermal expansion of the pin boss part on the skirt part is cut off by the above insulation gap.
When the engine is at high temperature, the skirt portion thermally expands uniformly and maintains a good sliding condition with the inner surface of the cylinder.

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 embodiment of the present invention will be described below with reference to the drawings.

In Figures 1 to 3, G is an outer mold with a circular cross section and a left and right half with a space S open at the top and bottom, and a semicircular mold that reaches from the outside to the mold inner surface 2 at a symmetrical position between the left and right mold parts. It has a through hole 3 of the shape.

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.

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 includes a skirt inner surface forming portion 7 connected to the cover 6, an inner surface forming portion 8 connected to the skirt portion 8 that is attached to the head, and a substantially semicylindrical outline that falls from a part of the side surface of the skirt inner surface forming portion, and the head It has a pair of pin boss forming portions 9 that are open to the end surface of the inner surface forming portion.

When positioning the main core 5, the depressed portions of its four parts 9 are made to face the through holes 3 of the outer mold 1.

FIG. 4 shows the sub-core 10, which has a partition part 11 with a semicircular cross section, a pin hole forming protrusion 13 protruding from the arc-shaped end face 12, and a positioning part provided on the end face of the protrusion. It has a pin 14.

Two of the secondary cores 10 are inserted into the mold through the through holes 3 of the outer mold 1, and the outer periphery of the partition portion 11 is fitted into the inner periphery of the depressed portion of the main core recess 9. , the protrusion 13 is positioned within the recess, and the positioning pin 14 is fitted into the hole 15 of the recess 9 to be assembled.

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

For example, when a molten aluminum alloy is injected into the outer mold inner space 81 to S3 and the product is removed from the mold, the base of the pin boss portion 16 is connected to the head portion 17 as shown in FIG. A piston material 19 is obtained which has an insulating gap S4 corresponding to the depth of the byproduct partition part 11 fitted into the main core recess 9 between the part 16 and the inner circumferential surface of the skirt part 18 facing thereto. .

20 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, an insulating gap is created between the pin boss part and the inner circumferential surface of the skirt part facing the pin boss part. Stones with complicated shapes can be cast all at once, so the troublesome cutting process required to form the insulation gap 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 essential parts of one embodiment of the mold of the present invention, Fig. 2
The figure is a cross-sectional plan view, Figure 3 is a side view illustrating the insertion direction of the main core into the outer mold, Figure 4 is a perspective view of a by-product, and Figure 5 is a piston material cast using the mold of the present invention. Fig. 6 is a side view thereof. 1... Outer mold, 5... Main core, 7...
...Skirt part inner surface forming part, 8...Head part inner surface forming part, 9...Pin boss part forming recess, 1
0... by-product, 11... partition, 1
3... Protrusion for forming pin holes, 19...
Piston material, S...space.

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 recesses for forming pin boss portions, protruding from the inner surface of the outer mold, the outer periphery of the edge fitting into the inner periphery of the depressed portion of the main core recess, and forming a space for forming a skirt portion and a space for forming a pin boss portion. A mold for a piston for an internal combustion engine, comprising a partition portion for insulating the partition portion, and a pair of sub-cores having a protrusion portion for forming a pin hole protruding from the end face of the partition portion and located within the recess portion.