JPS594220B2 - 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 little gas leakage from the sliding gap between the cylinder and the piston, which improves engine output and prevents 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 shown in the drawings will be described below.

In Figures 1 to 3, reference numeral 1 denotes an outer mold with a circular cross section and a space S open on the top and bottom, which is divided into left and right halves, and a semi-cylindrical shape that reaches from the outside to the mold inner surface 2 is located at a symmetrical position between the left and right mold parts. It has a through hole 3 of the shape.

The outer mold 1, in which the outer circumferential surface of the piston is formed by the inner surface 2 of the mold, 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 8 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, a head inner surface forming portion 8 continuous to the skirt inner surface forming portion 7, and a pair of pin boss portions starting from within the skirt inner surface forming portion and opening to the end surface of the head inner surface forming portion. It has a formation space S1.

In the illustrated example, the space S1 is formed by covering a recess 9 which has a substantially semicylindrical outline from the side surface of the core body with a plate 10 that is wrapped around and fixed to the core body.

Through-holes 11 are provided in portions of the plate material 10 facing the pair of spaces S1.

When positioning the main core 5, the space S1 is
through hole 3.

FIG. 4 shows the byproduct 12, which has a partition part 13 with a semicircular cross section, a pin hole forming protrusion 15 protruding from the arcuate end face 14, and a positioning pin provided on the end face of the protrusion. It has 16.

Two of the by-products 12 are inserted into the mold through the through-hole 3 of the outer mold 1, and their partition end faces are brought into contact with the through-hole mouth edge of the main core 5, and the protrusion 15 is inserted into the mold as the main core. The core 5 is assembled by passing through the through hole 11 and positioning it in the pin boss forming space S1, and fitting the positioning pin 16 into the hole 17 in the inner wall of the space S1.

When the outer mold 1, the main core 5, and the by-product 12 are combined as described above, the main core 5 and the by-product 12 form a skirt part forming space S2 and a head part forming space S3. space S2 and space S1 for forming the pin boss part
are insulated by the partition part 13 of the byproduct 12.

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 18 is connected to the head portion 19 as shown in FIG. Between the portion 18 and the inner circumferential surface of the skirt portion 20 opposing this, there is a thickness between the outer circumferential surface of the skirt inner surface forming portion 7 of the main core 5 and the inner surface of the pin boss forming space S1, i.e. Insulation gap S corresponding to the thickness of the plate material 10
A piston material 21 having a diameter of 4 is obtained.

22 indicates a pin hole.

The byproduct 12 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. A piston having a complicated shape 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 a 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 transverse 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 mold, 5... Main core, S...
... Space, 7 ... Skirt inner surface forming part, 8
...Head part inner surface forming part, Sl...Pin boss part forming space, 12...-By-product, 13
. . . Partition portion, 15 . . . Pin hole forming protrusion, 21 . . . Piston material.

Claims (1)

[Claims] 1. A two-split outer mold having a space with a circular cross section, a skirt inner surface forming portion, a head inner surface forming portion, and a pair of pin bosses starting from inside the skirt inner surface forming portion and opening at the end surface of the head portion inner forming portion. A main core having a space for forming a part and a pair of through holes provided in the inner surface forming part of the skirt part and facing the space for forming a pin boss part, an end surface protruding from the inner surface of the outer mold and having an end face at the rim of the through hole of the main core. A partition portion that is brought into contact to insulate the skirt portion forming space and the pin boss forming space, and a pin hole that protrudes from the end face of the partition portion and is inserted through the through hole of the main core and located within the pin boss forming space. A mold for a piston for an internal combustion engine, the mold having a pair of byproducts having a protrusion.