JPS594222B2 - 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 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 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.

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 is divided into three parts, a center part 7 and left and right side parts 8, and has a skirt inner surface forming part 9 and a head inner surface forming part 10 connected thereto.

The left and right sides 8 have a pair of pin boss forming recesses 11 which drop down from a part of the skirt inner surface forming part 9 with a semicylindrical outline and open at the end face of the head inner surface forming part.

Six U-shaped edges 12 are formed on the outer periphery of the depressed portion of the recess 11, respectively.

When positioning the main core 5, the depressed portion of the recess 11 is made to face the through hole 3 of the outer mold 1.

FIG. 4 shows the byproduct 13, which includes a partition portion 14 having a semicircular cross section, a pin hole forming protrusion 16 protruding from the arcuate end surface 15 of the partition portion 14, and a positioning pin provided on the end surface of the protrusion portion. It has a section 17.

Two of the by-products 13 are inserted into the mold through the through holes 3 of the outer mold 1, and their partition end faces are brought into contact with the six edges 12 of the main core 5, and the protrusions 16 are inserted into the recess. The positioning pin portion 17 is then fitted into the hole 18 of the recess 11 to be assembled.

When the outer mold 1, the main core 5, and the by-product 13 are combined as described above, the main core 5 and the by-product 13 create a skirt part forming space S1, a head part forming space S2, and a pin boss part forming space. S3 is formed, and the skirt forming space S1 is insulated by the white edge 12 of the main core 5 and the partition part 14 of the byproduct 13.

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 19 is connected to the head part 20, and there is still a U-shaped slit between the pin boss part 19 and the skirt part 21 with a slight width corresponding to the thickness of the white edge 12 of the main core 5. A piston material 22 having S4 is obtained.

23 indicates a pin hole.

The above-mentioned by-product 13 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 complicated shape having an insulating slit between the pin boss part and the skirt part can be manufactured all at once. Therefore, the troublesome grooving process required to form 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 one embodiment of the present invention, Fig. 2 is a cross-sectional 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, and FIG. 6 is a side view thereof. 1... Outer shape, S... Space, 5...
...Main core, 9...Skirt inner surface forming part, 1
0...Head part inner surface forming part, 11...
Concave portion for forming pin boss portion, 12...White edge, 13.
... By-product, 14 ... Partition part, 16.
...Protrusion for forming pin holes, 22...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 pin boss forming recesses and six edges protruding from the outer periphery of the depressed portion of the recess, which protrudes from the inner surface of the outer mold and has an end surface abutted against the end surface of the curved edge of the main core to form a skirt portion. An internal/combustion device comprising: a partition portion for insulating a space for forming a pin boss portion from a space for forming a pin boss portion; and a pair of by-products having a pin hole forming protrusion protruding from an end face of the partition portion and located within the main core recess. Engine piston mold.