JP3250201B2 - Piston ring for two-cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston ring structure of a two-stroke engine in which a piston ring housed in a ring groove is stopped by a stopper pin so as not to rotate with respect to the piston.

[0002]

2. Description of the Related Art In a two-stroke engine, a piston ring, which is a compression ring, is usually fitted in two ring grooves formed on the outer periphery of a piston. A stopper pin is pressed into a press-fitting hole formed in the piston so that the piston ring is in an offset state and is not located in the scavenging hole or the exhaust hole of the cylinder. Stopped against rotation with respect to piston.

[0005] Therefore, as shown in FIGS. 5 to 7, in the piston ring, as shown in FIGS. 5 to 7, a recess 5 for pin engagement is formed on the inner peripheral surface 2 b of the ring at the joint 3 with respect to the stopper pin press-fitted into the piston. Alternatively, in such a structure, the lower surface 2c of the ring at the joint portion and the bottom wall 10c of the ring groove
As shown in FIGS. 8 to 10, the sealing surface formed by the lower surface 2c of the ring and the bottom wall 10c of the ring groove becomes larger, so that the pin engaging recess 5 is formed. The ring upper surface 2a at the joint 3
Has been conventionally performed.

[0004]

In the conventional piston ring for a two-stroke engine as described above, the seal surface formed by the lower surface of the ring and the bottom wall of the ring groove is increased in order to prevent gas from flowing through. As shown in FIG. 9, near the stopper pin 4 the ring 2
Has a structure in which the inner peripheral surface 2b is close to the inner wall of the ring groove 10.

Therefore, when the stopper pin 4 is pressed into the press-fit hole of the piston and the flesh of the piston around the press-fit hole protrudes and rises, the rise 11 causes the piston to move up and down in the cylinder. The movement of the piston ring 2 in the ring groove 10 due to the deflection is hindered.

Therefore, as shown in FIG. 11, with respect to the piston ring 2 having the pin engaging recess 5 formed on the upper surface 2a, the corner of the pin engaging recess 5 on the ring upper surface 2a side becomes an inclined surface 9. As shown in FIG. 12, a structure has been conventionally considered in which the scraping is performed so as to avoid interference with the raised portion 11 of the piston.

However, in the case where such an inclined surface 9 is formed, depending on the relationship between the height of the piston ring and the vertical width of the ring groove, when the piston ring moves relative to the piston in the circumferential direction, the inclination is increased. Surface 9 is stopper pin 4
And the piston ring may be stuck between the lower surface of the stopper pin and the bottom wall of the ring groove and may not move.

An object of the present invention is to eliminate the disadvantages of the conventional piston ring for a two-stroke engine as described above. More specifically, it is possible to prevent gas from flowing through at a joint portion, The movement of the piston ring in the groove is not hindered by the protruding part of the piston meat protruding by the press fit of the stopper pin,
It is an object of the present invention to provide a piston ring for a two-cycle engine in which the piston ring does not become stuck due to the lower surface of the stopper pin becoming stuck.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and to achieve the object, the present invention provides a stopper pin which is press-fitted into a piston, and which is formed on both sides of the upper surface of the ring toward the joint. In a piston ring for a two-cycle engine in which a pin engagement recess is formed, at least at a position corresponding to the stopper pin, a corner portion of the pin engagement recess on the inner peripheral surface side of the ring is cut off. .

[0010]

According to the above construction, since the engagement recess of the stopper pin is formed on the upper surface of the piston ring, the sealing surface formed by the lower surface of the ring and the bottom wall of the ring groove may be reduced. It is possible to prevent gas from flowing through at the joint.

Further, even if the flesh of the piston rises and protrudes around the stopper pin press-fitting hole due to the press-fitting of the stopper pin, the raised portion does not interfere with the corner of the engagement concave portion of the ring. The movement of the ring in the ring groove is not hindered.

Further, the corner of the upper surface of the ring is shaved off to avoid interference with the raised portion due to press-fitting of the stopper pin (an inclined surface having a small inclination angle is formed at the corner of the engagement concave portion on the ring upper surface side). Is not performed, so that the inclined surface of the pin engaging recess does not fit into the lower surface of the stopper pin, and the piston ring does not get stuck and become stuck.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a piston ring for a two-cycle engine according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a piston of a two-cycle engine to which the piston ring of the present invention is applied.
The piston 1 has piston rings 2 and 2 as compression rings in a ring-shaped groove formed on the outer periphery of the piston 1 as compression rings for preventing mixture, explosive gas, exhaust gas and the like in the cylinder. It is fitted so as to have a small gap in the radial direction and the vertical direction between the piston and the ring groove while being in close contact with the cylinder wall surface due to elasticity.

Each of the piston rings 2 is provided with an abutment (cut) 3 at one position.
Is attached to the piston 1 with a slight gap left for releasing the thermal expansion of the ring 2 itself by the joint 3, and the joints 3, 3 of the upper and lower piston rings 2, bypass the gas flow. In order to reduce the leakage of gas, these are offset from each other, and their joints 3 and 3 are located so as not to pass through the scavenging holes and exhaust holes of the cylinder.

The piston 1 has a stopper pin 4 for stopping rotation of the piston ring 2 with respect to the piston.
Is press-fitted into a press-fitting hole formed in the piston 1 so as to be inserted into the ring groove at a position corresponding to the abutment 3 so that its lower part protrudes. The upper surface of the piston ring 2 is formed with a recess 5 for pin engagement which is inclined downward from both sides toward the abutment 3.

FIGS. 2 and 3 show the vicinity of the abutment 3 in one embodiment of the piston ring 2 of the present invention. The upper surface 2a of the piston ring 2 has an inclined surface 6 inclined downward toward the abutment 3. FIG. And a step 7 following the lower end of the inclined surface 6 is formed on both sides thereof, so that the pin engaging recess 5 engages with the stopper pin 4 in the circumferential direction of the ring.
Are formed.

The inner circumferential surface 2b of the piston ring 2 has a ring 2 at a portion corresponding to the pin engaging recess 5 and the abutment 3.
A notch 8 extending from the upper surface to the lower surface of the piston ring 2 is provided, and the notch 8 allows the pin engagement concave portion 5 (that is, the inclined surface 6 and the step portion 7) on the inner peripheral surface 2b side of the piston ring 2 and the joint 3 to be formed. The corners are shaved off.

In the embodiment shown in FIGS. 2 and 3, the notch 8 provided on the inner peripheral surface 2b of the piston ring 2 is viewed from the upper surface of the ring 2 as shown in FIG. It is formed over the lower surface, and this has the advantage that the corner portion can be easily cut off. However, it is not necessary to cut off the entire joint 3 and the piston ring In order to make the sealing surface formed by the lower surface 2c and the bottom wall 10c of the groove 10 as large as possible, and to effectively prevent gas blow-through at the portion, FIG.
As shown in (B), the notch 8 may be formed at least to a position corresponding to the stopper pin 4.

Further, the piston ring 2 itself is not limited to the shape shown in the figure, but as shown in FIG. 4C, the top wall 10a of the ring groove 10 is inclined and the upper surface 2a of the piston ring 2 is formed. It goes without saying that the same applies to a keystone type compression ring in which is inclined.

In the above-described embodiments in which the corners of the pin engaging recesses 5 on the inner peripheral surface 2b side of the piston ring 2 are cut off by providing the cutouts 8 as described above,
Since the engagement recess 5 with the stopper pin 4 is formed on the upper surface 2a of the piston ring 2, the piston ring 2 near the abutment 3 is different from the conventional example as shown in FIGS.
The sealing surface formed by the lower surface 2c of the ring groove 10 and the bottom wall 10c of the ring groove 10 does not become small, and gas can be prevented from being blown through in the vicinity of the joint 3.

When the stopper pin is pressed into the piston, the flesh of the piston protrudes in a raised state, particularly around the stopper pin press-fitting hole at the upper corner of the ring groove, as shown in FIGS. In the conventional example shown in FIG. 1, when the raised portion 11 of the meat is formed by the press-fitting of the stopper pin 4, the piston ring 2 moves the ring groove 1 in response to the movement of the piston in the cylinder.
When trying to move within zero, the part 11 hits a corner of the piston ring 2 and hinders the movement of the piston ring 2.

On the other hand, in the present embodiment, as shown in FIG.
Is formed, since the corner of the piston ring 2 that interferes with the portion 11 is shaved off, the movement of the piston ring 2 in the ring groove 10 is not hindered by the portion 11.

Further, in this embodiment, in order to avoid interference by the raised portion 11 around the stopper pin 4 as in the conventional improved example shown in FIG. Since the surface is not formed on the upper surface of the ring 2, the inclined surface of the concave portion 5 for pin engagement fits into the lower surface of the stopper pin 4, so that the piston ring 2
There is no such thing as getting stuck.

[0025]

According to the piston ring for a two-stroke engine of the present invention as described above, it is possible to prevent gas from flowing through at the abutment portion, and to use the raised portion of the piston meat that protrudes by press-fitting the stopper pin. The movement of the piston ring in the ring groove is not hindered, and the piston ring does not get stuck on the lower surface of the stopper pin.

[Brief description of the drawings]

FIG. 1 is a front view showing a piston to which an embodiment of a piston ring for a two-cycle engine according to the present invention is applied.

FIG. 2 is a perspective view of a main part showing one embodiment of the present invention.

FIG. 3 is a top view of a main part of the embodiment shown in FIG. 2;

4A is a sectional view of the embodiment shown in FIG. 2 along the line AA in FIG. 3, FIG. 4B is a sectional view corresponding to FIG. 3A in another embodiment, and FIG. Sectional drawing corresponding to figure (A) in another example by different piston rings.

FIG. 5 is a perspective view of a main part showing a conventional example of a piston ring for a two-cycle engine.

FIG. 6 is a top view of a main part of the conventional example shown in FIG.

FIG. 7 is a sectional view taken along the line BB of FIG. 6;

FIG. 8 is a perspective view of a main part showing another conventional example of a piston ring for a two-cycle engine.

FIG. 9 is a top view of a main part of the conventional example shown in FIG.

FIG. 10 is a sectional view taken along the line CC of FIG. 9;

FIG. 11 is a perspective view of a main part showing a conventional improved example of a piston ring for a two-cycle engine.

FIG. 12 is a front view of a main part of the improved example shown in FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piston 2 Piston ring 3 Abutment 4 Stopper pin 5 Pin engaging recess

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Claims (1)

(57) [Claims] At least at a position corresponding to a stopper pin in a piston ring having a pin engaging recess formed from both sides toward an abutment on an upper surface of the ring corresponding to the stopper pin press-fitted into the piston, A piston ring for a two-stroke engine, wherein a corner of the pin engaging recess on the inner peripheral surface side of the ring is cut off.