JPS6296762A - Piston for internal combustion engine - Google Patents

Abstract

PURPOSE:To achieve the enhancement in the primary compression ratio and the cooling efficiency of piston by constituting a piston made of A1 alloy and the like with a plural number of divided parts, and hermetically filling a high heat conductivity substance such as sodium in the internal space part thereof. CONSTITUTION:A piston 1 is formed by welding a lower half part 2 and an upper half part 3 being made of Al alloy, and the lower half part 2 forms a recess part 7 between the central part 4 having a piston-pin housing recess part 5a and a con'rod small end part housing recess part 5b, and the piston side wall part 6 on the outside thereof. Above the central part 4, a projection 9 having a through hole 10 in the transverse direction is integrally formed. While a space S is formed by the above recess part 7, through hole 10 and the inner surface of the upper half part 3, in this space S a substance which is excellent in the heat conductivity such as metallic sodium and the like is hermetically filled. Further, on the inner surface of the lower half part 2 and the upper half part 3 forming the space S, Ni-plated layers are formed to prevent the corrosion of the piston.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a piston suitable for a two-stroke engine.

(Prior Art) It has been known to improve the output of a two-stroke engine by increasing its primary compression ratio.

As a means of increasing the primary compression ratio of two-stroke engines, crank webs are made hollow.

(Problem to be solved by the invention) By the way, in order to increase the primary compression ratio of a two-stroke engine, it is conceivable to make the inside of the piston hollow.
If this is done, the heat at the top of the piston cannot be effectively dissipated, causing problems such as blowouts.On the other hand, if holes are formed to allow cooling air to pass through, the primary compression ratio will decrease.

(Means for Solving the Problems) In order to solve the above problems, the present invention improves the primary compression ratio by forming a hollow part inside the piston by welding a plurality of divided bodies, etc. Furthermore, the cooling effect is enhanced by filling the hollow portion with a substance having high thermal conductivity such as Na.

(Function) As the piston moves up and down while the engine is running, the molten metal Na and other substances in the piston's hollow section are shaken up and down, absorbing heat from the high-temperature top and transmitting it to the skirt.

(Example) Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a longitudinal cross-sectional view of a piston according to the present invention, and FIG. 2 is a cross-sectional view taken along the line A-A in FIG. 3) is electron beam welded, and the lower half body (2) has a central part (4) with a predetermined thickness and a piston pin storage recess (5a) and a small connecting rod, as shown in Figures 3 and 4. Storage recess at the end (5b)
, and a piston side wall portion (
6), and a recess (7) is formed between this piston side wall portion (6) and the central portion (4).

Also, a skirt portion (8) extends downward from the piston side wall portion (6).
The center part (from 0 there is a protrusion (9)
The upper surface of the protrusion (9) is the central part of the top of the piston, and the protrusion (9) is provided with a through hole (lO
) is installed.

- On the other hand, the lower half body (3) has an annular shape constituting the piston round part as shown in Fig. 5, and its inner diameter is approximately equal to the outer diameter of the protrusion (9) of the lower half body (2). A piston ring groove (11) is formed on the outer peripheral surface.

In the above, in a state where the lower half body (2) and the lower half body (3) are welded, the recess (7) and the through hole (10) of the lower half body (2)
A space (S) is formed by the inner surface of the lower half body (3), and the inner surfaces of the lower half body (2) and the upper half body (3) forming this space (S) are marked with the markings shown in FIG. As shown in FIG. 5, a Ni plating layer (12) is formed, and a substance with excellent thermal conductivity such as metallic sodium (13) is further sealed in the space (S).

Here, the metal sodium (13) is sealed through a small hole (14) formed in the lower half body (2), and after being sealed, the small hole (14) is sealed by welding.

Further, the amount of filling is approximately 40% of the volume of the space (S).

In the above, as the engine is driven, the piston (1)
When heated, metallic sodium (13) (melting point 98°
C) is melted, and by the downward movement of the piston (1), the molten sodium (13) is shaken up and down in the space (S), taking away the heat from the top of the piston, which is heated to about 280°C. This heat is transferred to the piston skirt, which has cooled to about 160°C, to efficiently cool the piston (1).

(Effects of the Invention) As explained above, according to the present invention, a space is formed inside the piston by joining a plurality of divided bodies, for example, a lower half and a lower half, and this space is filled with a space. Since it is filled with a substance with excellent thermal conductivity such as sodium, it is possible to efficiently cool the piston while increasing the primary compression ratio.

In addition, the inner walls of the space are plated with Ni, so
The piston made of A1 alloy will not corrode even if it is filled with sodium.Furthermore, the top of the piston is made up of a part of the lower half, so the part that is subject to the most pressure is supported by the lower half, which has excellent strength. There are also effects such as being able to.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a piston according to the present invention, FIG. 2 is a sectional view taken along the line A-A in FIG. Figure 5 is a single-piece view of the upper half of the piston. In one drawing, (1) is the piston, (2) is the lower half, (3)
is the lower half, (4) is the central part of the lower half, (7) is the concave part, (
9) is the protrusion of the lower half body, (10) is the through hole, (12) is the N
i plating layer, (13) is sodium, and (S) is space.

Claims (2)

[Claims] (1) In a piston for an internal combustion engine made of an Al alloy, etc., this piston is made up of a plurality of divided bodies joined together, and a space is formed inside the joined state, and this space has a thermal conductivity such as sodium. A piston for an internal combustion engine that is characterized by containing a substance with a high content. (2) The divided body consists of an upper half body and a lower half body, the upper half body constitutes a ring round part of the piston, and a part of the lower half body constitutes the top center part of the piston. A piston for an internal combustion engine according to claim 1.