JPS5815649Y2 - Piston for 2-stroke engine - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to the structure of a piston used in a crank chamber compression type two-stroke engine having an exhaust port in the cylinder (such as a three-hole type).

Conventionally the first choice for high-speed, high-output 2-stroke engines.
An L-shaped hinge as shown in the figure is used.

In Fig. 1, 1 is a cylinder, 2 is a piston, 3Fi cylinder head, 4 is a gasket, 5 is a combustion chamber, and 6 is an L-shaped hinge.

The L-shaped tongue 6, when viewed in a vertical cross section including the centerline of the piston 2 (the plane in FIG. 1), has a vertical portion 6a and a horizontal portion 6b extending laterally inward from its lower end (towards the center of the piston 2). It is pressed against the inner surface of the cylinder 1 by the expanding tension.

The L-shaped groove in which the L-shaped hinge 6 is accommodated also corresponds to the L-shaped groove 6.
The vertical portion 7 and the horizontal portion 7b are provided to correspond to the shape of the vertical portion 7 and the horizontal portion 7b, respectively.

That is, the ring groove is directly connected to the combustion chamber 5 through the vertical portion 7a created by cutting out the outer peripheral portion of the top land of the piston 2 in an annular shape.

In FIG. 1, Bc1BC2 is the back clearance, and SC is the side clearance.

The reason for adopting such an L-shaped hinge is as follows.

(1) Since the tension can be controlled by gas pressure, the tension of the ring itself can be reduced, and friction loss between the ring 6 and the cylinder 1 can be reduced.

(2) Since the L-shaped ring 6 can be installed above the piston 2, the path through which the heat that enters the top surface of the piston passes through the ring 6 and is released into the cylinder 1 is shortened, and the piston 2 is closer to the cylinder than the piston 2. The heat dissipation characteristics to 1 can be improved.

However, on the other hand, it had the following drawbacks. (In order to take advantage of the features of isfI (1), the clearance BC1 shown in Figure 1 must be
, BC2 and SC need to be set to somewhat large values, but in that case, gas will enter the gap and this gas will come into direct contact with the combustion gas, inducing abnormal combustion in the gap.
Especially in the part facing the exhaust port, a melting phenomenon occurs on the ring structure surface.

(2) Due to the above phenomenon, a piston top land loss accident is induced on the exhaust side, which has a high heat load.

(3) The structure shown in Fig. 2 was considered to prevent top land breakage accidents, but because the clearance C was small, the advantage of tension control using gas pressure was lost.

8 in Figure 2 is the top land. In order to prevent the drawback of the L-shaped hinge (Fig. 1), namely the piston land loss accident on the exhaust side, which has a large heat load, the present invention has been developed to
The shape is shown in the figure.

□The heat dissipation characteristics of the configuration shown in Figure 2 are not much different from those of the configuration shown in Figure 1, but since the tension cannot be controlled by gas pressure, the output in the high-speed range is inferior to that of Figure 1. Since the configuration shown in FIG. 1 is adopted for the side, the above-mentioned drawbacks can be eliminated.

That is, in the present invention, an L-shaped swing is adopted, and while taking advantage of the features of the conventional L-shaped swing, the drawbacks of the conventional L-shaped swing are improved and overcome, and an example thereof is shown in Fig. 3 and below. .

Figure 3 is a vertical cross-sectional partial view, Figure 4 is a plan view, and 1 in Figure 4.
0 is the exhaust port, 1F is the scavenging port, and the left side in FIG. 4 is the intake side.

The cross-sectional shape of the exhaust port section (section B) including the section facing the exhaust port 10 is as shown in section B' in FIG. ) is as shown in section A' in FIG.

In FIG. 3, the L-shaped tongue groove 12 consists of a vertical portion 12a and a horizontal portion 12b extending laterally inward (toward the center of the piston) from the lower end of the vertical portion 12a, and a top land 8 is located above the portion B'.

Therefore, the L-shaped tongue groove 12 communicates with the combustion chamber through a small gap, and the thickness of the upper side of the horizontal portion 12b is increased, making it durable against thermal loads.

On the other hand, in the intake side section A, as shown in part A' in Fig. 3, the top of the piston including the crown and tongue lands on the upper side of the L-shaped groove 12 is cut out with a generally wedge-shaped cross section. The vertical portion 12a of the ring groove 12 is directly connected to the combustion chamber 5.

That is, it takes the form shown in FIG. 13 is a notch.

Both ends of the notch 13 in the circumferential direction are stepped portions 14 (see Fig. 4 and Fig. 5).
It is connected to the top surface of the piston in section B through the

This stepped portion 14 serves as the scavenging port 11. The direction of extension (blowout angle) of the side wall 15 on the exhaust port 10 side of Therefore, the stepped portion 14 allows the scavenging air to be directed in four directions away from the exhaust port 10.

As explained above, according to the present invention, the top land on the upper side of the L-shaped groove 12 excluding the portion facing the exhaust port 10 of the cylinder is cut out in the section A, and within the section A, the L-shaped groove 12 is cut out. The vertical part 12a- of the combustion chamber 5
Since the top land 8 is left in section B on the exhaust port 10 side, (1) it prevents the loss of the piston land on the exhaust side, which has a large heat load, which is a drawback of the L-shaped hinge (Fig. 1). can do.

(2) The heat dissipation characteristics of the configuration shown in Figure 2 are the same as those of the configuration shown in Figure 1, but because the tension cannot be controlled by gas pressure, it is inferior to the configuration shown in Figure 1 in terms of output at high speeds. According to the present invention, the form shown in FIG. 1 is adopted in the scavenging and intake side sections A, so that the above-mentioned drawbacks can be eliminated.

(3) That is, according to the present invention, by using an L-shaped swing, it is possible to improve the drawbacks of the conventional L-shaped swing while taking advantage of the features of the conventional L-shaped swing.

It is also easy to manufacture.

[Brief explanation of drawings]

Figures 1 and 2 are longitudinal cross-sectional partial views of a conventional L-shaped piston with resug fittings installed. Fig. 3 is a vertical cross-sectional □ partial view of the piston according to the present invention, Fig. 4 is a plan view, and Fig. 5 is a - of Fig. 4.
■It is a partial cross-sectional view. 1...Cylinder, 5...,...Combustion chamber,
8...Top land, 10...Exhaust port, 12...L-shaped tongue groove, 12a,...
...Vertical part, 12b...Horizontal part.

Claims (1)

[Scope of utility model registration request] An L-shaped groove is provided on the underside of the top land, which consists of a vertical section and a horizontal section extending laterally inward from its lower end when viewed in a vertical section including the piston center line, excluding the section facing the exhaust port of the cylinder. A piston for a two-stroke engine, characterized in that in the section, the top land on the upper side of the L-shaped groove is cut out so that the vertical part of the L-shaped groove is directly connected to the combustion chamber.