JPH0144741Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a two-stroke engine, and particularly to an improvement in the scavenging port formed on the inner peripheral surface of the cylinder.

FIG. 1 is a cross-sectional view of the main parts of a two-stroke engine 1 showing the conventional scavenging port shape of a two-stroke engine.

In this two-stroke engine 1, a cylinder liner 3 is arranged in the center of a cylinder block 2.
A pair of main scavenging ports 4, 4' are provided on the peripheral surface 3a of the
, second scavenging ports 5, 5', and third scavenging ports 6, 6' are formed symmetrically with respect to the drawing. Note that in FIG. 1, reference numeral 7 is an exhaust port.

Further, the piston (not shown) used in the two-stroke engine 1 is usually provided with two piston rings, and each piston ring has an abutment part formed in the cylinder liner 3. The abutments are positioned, for example, at positions facing A and B of the circumferential surface 3a of the cylinder liner 3 shown in FIG. The ring is stopped from rotating.

On the other hand, some conventional 2-stroke engines use only one piston ring to reduce the weight of the piston, thereby increasing the 2-stroke engine's high rotational speed and high output. Even in the case of two-stroke engines, no improvements have been made to the scavenging ports to improve scavenging efficiency, and as a result, two-stroke engines have had the disadvantage of being insufficiently high-speed and high-output.

In view of the above-mentioned circumstances, the object of this invention is to improve the scavenging efficiency of a two-stroke engine that uses one piston ring, and to provide a two-stroke engine that achieves high rotation and high output.

In order to achieve the above-mentioned purpose, this invention:
In a two-stroke engine that uses one piston ring, the cylinder liner is located in a position symmetrical to the cylinder liner part facing the abutment of the piston ring, among the cylinders in which scavenging ports are arranged symmetrically around the exhaust port. By narrowing the width of the portion, the opening area of the scavenging port adjacent to the cylinder portion is expanded, thereby improving the scavenging efficiency of the two-stroke engine.

An embodiment of the two-stroke engine according to the present invention will be described in detail below.

Figure 2 shows a two-stroke engine 10 according to the present invention.
FIG. 1 is a cross-sectional view of the main parts of the figure, in which the same parts as in FIG. 1 are designated by the same reference numerals.

In this two-stroke engine 10, a piston (not shown) using one piston ring is arranged in a cylinder liner 11. Furthermore, a ring knob that prevents the piston ring disposed on this piston from rotating is located on the circumferential surface of the cylinder liner 11 between the second scavenging port 5 and the third scavenging port 6, which are formed on the right side of the drawing in FIG. It is installed in a position opposite to section A'. Therefore, the abutment portion of the piston ring including the ring notch does not face the opening surface of each port formed on the circumferential surface 11a of the cylinder liner 11. On the other hand, among the scavenging ports formed on the circumferential surface 11a of the cylinder liner 11, the opening 5''a of one of the second scavenging ports 5'' extends in the circumferential direction (one of the second scavenging ports 5'' along the circumferential surface 11a of the cylinder liner 11). 3 scavenging port 6' side). Therefore, the second scavenging port 5'' in the circumferential direction of the cylinder liner 11 is
The length S' is the length S of the conventional second scavenging port 5'.
(FIG. 1), and the opening area of the second scavenging port 5'' increases by this amount.

In the above embodiment, the abutment portion including the ring notch that prevents the piston ring from rotating is installed at a position facing the circumferential surface of the cylinder liner 11 between the second scavenging port 5 and the third scavenging port 6. However, the present invention is of course not limited to the above-described embodiment, and the abutment portion including the ring notch may be attached at a position facing the circumferential surface of the cylinder liner 11 between other ports. Furthermore, in the present invention, the opening surface 5''a of one of the second scavenging ports 5'' is expanded toward the adjacent third scavenging port 6'.
Of course, the present invention is not limited to the above embodiments,
In short, except for the opening portion of the scavenging port adjacent to the abutment of the piston ring including the ring notch, the opening surface of the other scavenging port is opened along the circumferential direction of the cylinder liner 11 as appropriate (for example, to prevent the piston from wobbling). (to a certain degree).

As explained above, in the two-stroke engine of this invention, the opening surfaces of the other scavenging ports are expanded along the circumferential direction of the cylinder liner, except for the scavenging port adjacent to the abutment containing the ring notch of the piston ring. , the opening area of the scavenging port is increased and the scavenging efficiency is improved, which makes it possible to achieve high rotation and high output of a two-stroke engine using only one piston ring.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of main parts of a conventional two-stroke engine, and FIG. 2 is a cross-sectional view of main parts of a two-stroke engine according to the present invention. 4, 4', 5, 5', 6, 6'... scavenge port,
10... 2-cycle engine, 11... cylinder liner, 11a... circumferential surface.

Claims (1)

[Scope of utility model registration request] In a two-stroke engine that has a cylinder in which scavenging ports are arranged symmetrically around the exhaust port and a piston that uses one piston ring, the other cylinder liner part that is symmetrical to the cylinder liner part that faces the abutment part of the piston ring. A two-stroke engine characterized in that the width of a cylinder liner portion is narrowed, and at least one scavenging port adjacent to the cylinder liner portion is expanded along the circumferential direction of the cylinder liner.