JPS5877143A - Piston of 2-cycle internal-combustion engine - Google Patents

Abstract

PURPOSE:To smoothly operate a piston, by forming a lower skirt part to small thickness equivalent or less in an upper skirt part of the captioned piston and resiliently absorbing a deformation amount of a cyliner and the piston. CONSTITUTION:A piston 10 comprises a piston ring part 17, boss part 18 and skirt part 19, here a lower skirt part 19B is formed to a thin thickness equivalent or less in an upper skirt part 19A. In this way, under a condition of side pressure applied in operation, a resilient condition can be optained, in which the piston can not be destructed but easily deformed.

Description

[Detailed description of the invention] The present invention relates to a piston for a two-stroke internal combustion engine.

As shown in FIG. 1, a piston 1 of a two-stroke internal combustion engine
is formed from a piston head portion 2, a piston ring portion 3, a boss portion 4 that supports the piston/bin, and a skirt portion 5. Here, the lower skirt portion 5 below the boss portion 4
A has the function of closing the exhaust port of the cylinder, and the function of receiving side pressure from the piston head to enable quiet operation while maintaining an appropriate clearance with the cylinder.

By the way, in order to support the side pressure acting on the piston 1, the lower skirt portion 5A of the conventional piston 1 has a relatively thick wall thickness as a whole, and has a lateral lip 6 and a lateral lip 6 on the inner surface of the opening edge. It is provided with a vertical lip 1 and has a highly rigid structure.

However, when the lower skirt portion 5A has high rigidity as in the past, the piston 1 expands during operation, the clearance between the cylinder and the lower skirt portion 5A becomes small, and the piston 1 cannot fully deform. 1 causes tension in the cylinder. %, in the piston 1 of a two-stroke internal combustion engine, there is an explosion stroke for each reciprocation of the piston 1, so the heat load is greater than in a four-stroke internal combustion engine, and lubricating oil is mixed into the fuel. Histone lF1
The piston 1 tends to expand to a large extent and tends to cause the above-mentioned tension condition against the cylinder, which may hinder the smooth operation of the piston 1.

The present invention has been made in view of the above facts, and an object of the present invention is to provide a piston for a two-stroke internal combustion engine with good operability.

In order to achieve the above object, the present invention provides a piston for a two-stroke internal combustion engine in which the lower skirt portion below the boss is provided with a contour that allows the exhaust port of the cylinder to be closed. The thickness of the upper skirt around the upper skirt is equal to or smaller than that of the upper skirt.

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

FIG. 2 is a sectional view showing a two-stroke internal combustion engine to which a piston according to an embodiment of the present invention is applied, and FIG. 3 is a sectional view showing an embodiment of the piston according to the present invention. It is a sectional view showing a piston according to an example,
FIG. 4 is a sectional view taken along line -W in FIG. 3.

That is, the piston 10 reciprocates within the cylinder 11 in response to combustion gas pressure, and transmits rotational force to the crankshaft 14 via the piston pin 12 and the connecting rod 13. Piston 10u, piston head portion 15,
Piston ring part 17 having ring groove 16, boss part 1
8 and a skirt portion 19.

Here, the piston head part 15 of the piston 10 forms the bottom part of the combustion chamber and has a large wall thickness because high combustion gas pressure acts thereon.
Since it is the part that supports 2, the wall thickness is large.

These piston head portion 15 and boss portion 18 are connected via a lip 20, so that they can be mutually reinforced.

The 1*1 skirt 1618 is formed from an upper skirt 111 SA around the boss 18 and a lower skirt 1811 below the boss 18. Upper skirt part 19A
The wall thickness of the connection part with the boss l118 is made large, and the wall thickness of other parts is made small in the KLI downward from the piston head part 15 and piston ring part 17 side, and weight reduction is achieved. A lateral lip 21 connected to the boss portion 18 is provided at the lower edge to maintain rigidity. The lower skirt portion 19B is made of 21IIFM that is approximately symmetrical with respect to the axis of the boss portion 180 through the notch 22 immediately below the boss portion 18, and the contour of one measurement is similar to that of the cylinder 1.
1 exhaust port 23 can be closed at top dead center. Further, the lower skirt portion 11B is formed only with a thinner wall thickness equal to or less than that of the upper skirt portion 19A, and therefore does not have a reinforcing lip.

The inner thickness of the lower skirt part ISB is set to be thin within the allowable range for strength, and is in a resilient state where it is easily deformed but not damaged under lateral pressure applied during operation. .

Therefore, according to the above embodiment, the piston 1
0 expands or the cylinder deforms and the clearance between the lower skirt part 19B and the cylinder becomes small, the lower skirt part 19B deforms elastically and the piston 1 (1
) It absorbs the amount of expansion of 1 m and the amount of deformation of the cylinder, and the lower skirt portion 19B does not cause tension on the cylinder. Therefore, it is possible to ensure smooth and quiet operation under conditions where the clearances between the piston IQfl, the lower skirt portion ISB, and the cylinder are set smaller.

Since the t+, the piston 10Fi, and the lower skirt portion have a lightweight structure, the inertia is small, making it suitable for high-speed operation.

As described above, the present invention has focused solely on increasing the rigidity of a two-stroke internal combustion engine piston in which the lower skirt portion below the boss is provided with a contour that allows the exhaust port of the cylinder to be closed. 180% of conventional thinking
Taking a completely opposite approach, we decided to make the lower skirt part as thin as or less than the thickness of the upper skirt part around the boss part. This makes it possible to elastically absorb the amount of deformation of the cylinder and piston during operation, and has the effect of ensuring good operability.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a piston according to a conventional example, FIG. 2 is a cross-sectional view showing a two-stroke internal combustion engine to which a piston according to an embodiment of the present invention is applied, and FIG. 3 is a cross-sectional view showing an embodiment of the present invention. A sectional view showing a piston according to an example, FIG.
It is a sectional view along WIIK. 10...Piston, 11...Cylinder, 18°
...Boss part, 19...Skirt part, 19A...
Upper skirt portion, 19B--lower skirt Fig. 3, Fig. 1, Fig. 2'. 1! Figure 4/l: 18] 235-/10)) 6 7

Claims (1)

[Claims] (1) In a piston of a two-stroke internal combustion engine, in which the lower skirt section below the boss has a contour that allows the exhaust port of one cylinder to be closed, the lower skirt section is equivalent to the upper skirt section around the boss section. A piston for a two-stroke internal combustion engine, characterized in that it is formed only with the following thin wall thickness: