JP2825162B2 - Non-rotating structure of piston ring - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detent structure for a piston ring mounted on a piston of an internal combustion engine, and more particularly to a method for preventing burrs from being formed at the abutment surface of the piston ring. The structure of the knock pin.

[Conventional technology]

The piston of the internal combustion engine reciprocates at a high speed in the cylinder to transmit high pressure due to combustion to a crankshaft via a connecting rod. FIG. 4 shows a piston for a two-stroke engine, which piston body 20
A piston pin hole 21 penetrating in the diameter direction is formed near the center in the height direction, ring grooves 22 are formed on the outer periphery of the head, and piston rings 23, 23 are formed in the ring groove 22.
Are mounted in a loosely fitted state. The piston ring 23 has a substantially C-shape having an abutment surface cut off at one location in the circumferential direction, and is for preventing combustion gas in the combustion chamber from leaking to the crank chamber side.

In the two-stroke engine, when the abutment surface of the piston ring 23 is located at the intake and exhaust ports of the cylinder, the portion may fly outward and be caught by the port. Are positioned so that they do not rotate. Conventionally, as such a detent structure of the piston ring 23,
Some are shown in FIGS. This configuration is such that a cylindrical knock pin 24 is driven in the radial direction into the ring groove 22 of the piston main body 20, and the abutment surface 23a of the piston ring 23 is brought into contact with the outer peripheral surface of the knock pin 24. When the knock pin 24 is driven, the intake and exhaust ports are avoided, and the knock pins are set so as not to overlap each other in the upward and downward directions. As the shape of the knock pin, in addition to the cylindrical shape, a shape in which a plurality of grooves are formed in the axial direction on the outer peripheral surface of the cylindrical body (see FIG. 6 (b)), or a strip-shaped plate is formed into a spiral shape. (Fig. 6 (c))
See).

Further, as shown in FIG. 7, the shape of the abutment surface of the piston ring is such that the inner portions of both ends of the piston ring 23 are cut out in a substantially U shape in plan view, and
The abutment surface 23a is brought into contact with the side peripheral surface of the knock pin 24. As shown in FIG. 8, the upper ends of both ends of the piston ring 25 are cut out in a substantially inverted trapezoidal shape when viewed from the front. To form an abutment surface 25a, or a piston ring 2
The upper part of both ends of 6 is cut out in an arc shape when viewed from the front and the abutment surface 26a
Are formed, and each of the abutting surfaces 25a, 26
The bottom peripheral surface of the knock pin 24 is made to abut on a.

By the way, in each of the piston rings 23, 25, and 26,
The width t of the ring groove 22 of the piston body 20 is, for example, 1.2 m
m or more, any of the above piston rings 23, 2
If the width t is as small as 1.0 mm or less, the abutment surfaces 25a and 26a (the structure shown in FIG. 8) which are brought into contact with the bottom peripheral surface of the knock pin 24 cannot be employed. Therefore, when the width t of the ring groove 22 is small, only the abutment surface 23a which is brought into contact with the side peripheral surface of the knock pin 24 can be adopted. Also, this abutment surface 23a is the other abutment surface 25a, 2
Compared with 6a, it is advantageous in that it does not require processing costs and is the cheapest.

[Problems to be solved by the invention]

However, in the conventional piston ring detent structure, as shown in FIG. 7, the piston ring 23 which is brought into contact with the side peripheral surface of the knock pin 24 has only the ridge line at the upper edge of the abutment surface 23a. This structure is in contact with the knock pin 24. As a result, as shown in FIG. 7 (d), there is a problem that a burr 30 is formed on the upper edge of the abutment surface 23a.

Here, as a method of preventing the burrs 30 on the abutment surface 23a, it is conceivable to reduce the diameter of the knock pin 24 to abut the central portion of the abutment surface 23a, but if this diameter is reduced, the knock pin is easily pulled out. No, it can't be too small. Further, it is conceivable to lower the driving position of the knock pin 24 so that the knock pin 24 is located at the center of the ring groove 22, but in this case, combustion gas pressure leaks (blow-by) occurs from the ring groove 22 portion. The position cannot be lowered.

In general, the piston ring presses the lower surface of the ring against the lower surface of the ring groove with the pressure of the combustion gas to prevent gas leakage, so that the combustion gas leaks only slightly from the small gap between the piston rings. However, when the pressure contact length (contact width) in the radial direction of the piston in the pressure contact portion is reduced, the combustion gas is easily bypassed in the radial direction. In order to prevent this bypass, the shape of the substantially U-shaped notch in a plan view of the inner portion of the abutment of the piston ring needs to be as small as possible. Therefore, the contact portion of the knock pin that abuts the abutment surface is thin. It will be vertically long.

On the other hand, in order to ensure the press-fitting of the above-mentioned knock pin, it is necessary to make the press-fitting hole circular and to have a predetermined diameter because the press-fitting hole is difficult to machine if the press-fitting hole is rectangular and precision cannot be obtained. Therefore, the conventional dowel pin has a thin, vertically long contact portion formed at the head of a thick cylindrical press-fit portion, and as a result, the change in the cross-sectional area between the press-fit portion and the contact portion becomes extremely large. However, stress concentrates on the base of the contact portion, and the contact portion may be broken by a slight shock.

The present invention has been made in order to solve the above-mentioned conventional problems, and can prevent the burring of the abutment surface of the piston ring without causing the knock pin to come off or leak, and further, the abutment with the abutment surface of the piston ring. An object of the present invention is to provide a piston ring detent structure that can improve the strength of a contact portion of a piston pin.

[Means for solving the problem]

Therefore, the present invention provides a piston ring mounted in a ring groove formed on the outer periphery of a piston for an internal combustion engine, a dowel pin is radially pressed into a ring groove portion of the piston, and a flat portion inside a joint of the piston ring is formed. In the detent structure of a piston ring formed by notching in a substantially U-shape to form an abutment surface and bringing the knock pin into contact with the abutment surface, the knock pin has a cylindrical shape press-fit into a ring groove portion of the piston. And a head protruding into the ring groove, the head extending axially outward from an upper half portion of the press-fitting portion, and an arc-shaped portion having a cross-section arch shape; A vertical rectangular piece hanging down in the axial direction of the piston from the center of the chord of the portion, flat contact surfaces formed on both sides thereof, and a contact portion extending axially from the press-fit portion integrally with the bow portion And the above The Kupin is press-fitted into the piston with its axis deviated upward from the center of the vertical width of the ring groove.A contact portion is inserted from above into the joint of the piston ring, and the contact surface is brought into surface contact with the joint surface. It is characterized by having.

[Action]

According to the structure for preventing the rotation of the piston ring according to the present invention, since the flat contact surface is formed at the portion of the knock pin where the abutment surface of the piston ring abuts, the contact state between the abutment surface and the knock pin can be reduced by a conventional line. Surface contact can be made from contact, and occurrence of burrs can be prevented. Also, since the present invention can be realized only by making the contact surface of the knock pin flat,
There is no need to reduce the diameter of the knock pin or lower the driving position, and the above-described problems of the detachment and pressure leakage of the knock pin do not occur.

In addition, the head of the knock pin has an arcuate section having a cross-section bow shape in which the upper half portion of the cylindrical press-fitting part extends in the axial direction, and a vertically long part hanging down from the center of the chord of the arcuate section in the piston axis direction. Since the rectangular piece is constituted by the abutting portion formed integrally with the bow portion and extending from the press-fit portion, the contact portion can be supported by both the bow portion and the press-fit portion, and the strength of the contact portion can be reduced. Can be improved.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 and FIG. 2 are views for explaining a rotation preventing structure of a piston ring according to an embodiment of the present invention. In this embodiment, a case where the present invention is applied to a piston for a two-cycle engine will be described as an example. In the drawings, the same reference numerals as those in FIGS. 4 and 7 indicate the same or corresponding parts.

The piston of the present embodiment is configured by forming ring grooves 22, 22 on the outer periphery of the head of the piston main body 20 and mounting piston rings 23, 23 in the ring grooves 22, and has a basic structure. It is the same as the conventional one.

The knock pin 13 of this embodiment is press-fitted into the ring groove 22 of the piston body 20. This knock pin 13
Is a cylindrical press-fit portion 13 press-fit into the ring groove 22 portion.
c and a head 13d protruding into the ring groove 22.

The head 13d is formed by extending an upper half portion of the press-fitting portion 13c outward in the axial direction, and has a bow-shaped portion 13 having a bow-shaped cross section.
b, a vertically long rectangular piece hanging down from the center of the chord of the bow 13b in the axial direction of the piston extends from the press-fitting portion 13c integrally with the bow 13b, and flat contact surfaces 13a on both sides thereof. The contact portion 13e is formed.

The above-mentioned knock pin 13 biases the axis of the knock pin 13 upward from the center of the vertical width of the ring groove 22 to move the piston.
The abutment portion 13e is inserted into the abutment of the piston ring 23 from above from above, and the abutment surface 13a is in surface contact with the abutment surface 23a.

In this way, the piston ring 23 is
The abutment surface 23a is positioned by contact with the contact surface 13a.

The head 13d of the knock pin 13 may be formed by cutting out the lower part of the tip of the cylinder so that the rectangular piece-shaped contact part 13e remains.

 Next, the operation and effect of this embodiment will be described.

According to the present embodiment, the knock pin 13 is formed of a cylindrical body,
Since the contact surface 13a that comes into contact with the abutment surface 23a of the piston ring 23 is formed as a flat surface, the contact surface 13a and the abutment surface 23a are in surface contact with each other, thereby preventing burrs from occurring on the abutment surface 23a. Can be. Further, in this case, it is not necessary to reduce the diameter of the knock pin or to lower the position of the knock pin so as to close the ring groove.

Also, the head 13d of the knock pin 13 is formed into an arcuate section having an arcuate cross section formed by extending the upper half portion of the cylindrical press-fitting portion 13c in the axial direction.
13b and a contact portion 13e formed by extending a vertically elongated rectangular piece hanging from the center of the chord of the bow 13b in the piston axis direction from the press-fit portion 13c integrally with the bow 13b. The contact portion 13e can be supported by both the bow 13b and the press-fit portion 13c, and the strength of the contact portion 13e can be improved. Therefore, while ensuring the reliability of the press-fitting portion 13c as a thick cylindrical shape, the notch of the piston ring abutment, which is substantially U-shaped in plan view, can be reduced to prevent gas leakage from this portion.

Further, in the above embodiment, the case where the present invention is applied to a piston of a two-cycle engine has been described as an example. However, the present invention can also be applied to a case where a piston ring needs to be prevented from rotating in a four-cycle engine piston.

〔The invention's effect〕

As described above, according to the piston ring detent structure according to the present invention, since the flat contact surface is formed at the portion of the knock pin that comes into contact with the abutment surface of the piston ring, the knock pin comes off or the combustion gas leaks. Without causing
This has the effect of preventing burrs at the abutment surface of the piston ring. In addition, the head having the contact surface is provided with an arcuate portion having a cross-sectional arc shape in which an upper half portion of a cylindrical press-fit portion extends in the axial direction, and a piston axial direction from a center of a chord of the arcuate portion. Since the vertically elongated rectangular piece that hangs is constituted by the arcuate portion and the abutting portion integrally extended from the press-fit portion, the contact portion can be supported by both the arcuate portion and the press-fit portion. The strength of the part can be improved.

[Brief description of the drawings]

1 and 2 are views for explaining a structure for preventing rotation of a piston ring according to an embodiment of the present invention. FIG. 1 (a) is a front view thereof, and FIG. 1 (b) is a view thereof. FIG. 2 is a perspective view showing the shape of the knock pin, FIG.
The figures are perspective views of the knock pin, FIGS. 4 and 5 are front views showing a piston for a two-stroke engine, respectively, and a partial cross-sectional view of the knock pin portion, and FIGS.
7 (c) is a view showing a conventional knock pin, FIGS. 7 (a) to 7 (d) are views showing a conventional detent structure, and FIGS. 8 (a) and 8 (b). [FIG. 2] is a perspective view showing an abutment surface of a conventional piston ring. In the figure, 13 is a knock pin, 13a is a contact surface, 13b is an arcuate portion, 13c is a press-fit portion, 13d is a head, 13e is a contact portion, 20 is a piston body, 22 is a ring groove, 23 is a piston ring, 23a Is the joint face.

Claims (1)

(57) [Claims] 1. A piston ring is mounted in a ring groove formed on an outer periphery of a piston for an internal combustion engine, a knock pin is radially pressed into a ring groove portion of the piston, and an inner portion of a joint portion of the piston ring is flat. In a substantially U-shaped cutout to form an abutment surface, and in the detent structure of a piston ring formed by bringing the knock pin into contact with the abutment surface,
The knock pin includes a cylindrical press-fit portion press-fitted into a ring groove portion of a piston and a head projecting into the ring groove, and the head extends an upper half portion of the press-fit portion outward in the axial direction. An arcuate section having an arcuate cross section and a vertically elongated rectangular piece hanging in the axial direction of the piston from the center of the chord of the arcuate section have flat contact surfaces formed on both sides thereof, and are integral with the arcuate section. And a contact portion extending in the axial direction from the press-fitting portion.The knock pin is press-fitted into the piston with its axis deviated upward from the center of the vertical width of the ring groove. A contact portion is inserted from above into the piston ring so that the contact surface is in surface contact with the abutment surface.