JP2860156B2 - Piston for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston for an internal combustion engine that uses a tapered piston ring and uses a detent pin to stop the circumferential rotation of the tapered piston ring.

(Prior Art) In a piston for an internal combustion engine, carbon or the like contained in gas entering from a gap between the upper surface of a piston ring and a ring groove adheres to a surface that defines the gap, and a gap between the piston ring and the ring groove is formed. In order to increase the frictional force acting on the ring, a so-called keystone ring having a tapered upper surface may be used (see JP-A-56-85545).

On the other hand, particularly in a two-stroke engine, the notch formed in the joint portion of the piston ring is provided with a piston so that the joint portion of the piston ring does not interfere with the scavenging port or the exhaust port opened in the cylinder wall. The rotation of the piston ring is prevented in the circumferential direction by engaging a locking pin substantially vertically implanted on the side wall of the main body (see JP-A-61-187563).

(Problems to be Solved by the Invention) However, in the case where the keystone ring is used as a piston ring and its circumferential rotation is stopped by a detent pin, the radial cross section of the keystone ring tapers inward in the radial direction. Since the detent pin is implanted substantially vertically on the side wall of the piston body, the amount of engagement (lap margin) between the detent pin and the notch formed at the abutment portion of the keystone ring is reduced, and the keystone ring is It may not be possible to reliably prevent rotation in the circumferential direction.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a piston for an internal combustion engine that can reliably prevent a circumferential rotation of a piston ring.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, at least one of upper and lower surfaces forms a tapered surface in a ring groove formed on an outer periphery of a side wall of a piston body, A tapered piston ring having a radial cross section that tapers toward the other side is mounted, and a notch formed at an abutment portion on the tapered surface side of the tapered piston ring is formed around the side wall of the piston body. In a piston for an internal combustion engine which performs detent in the circumferential direction of a tapered piston ring by engaging a detent pin, the detent pin is disposed substantially parallel to a tapered surface of the tapered piston ring. Features.

(Operation) According to the present invention, since the detent pin is arranged along the tapered surface of the tapered piston ring, even if the radial cross section of the tapered piston ring tapers inward in the radial direction. In addition, it is possible to sufficiently secure an allowance (lap allowance) between the notch formed in the abutment portion of the piston ring and the detent pin, and to reliably prevent the piston ring from rotating in the circumferential direction.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

1 is a front view of a detent portion of a piston according to the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, FIG. 3 is a front view of a piston, and FIG. FIG. 5 is a plan view, and FIG. 5 is an enlarged sectional view taken along line VV of FIG.

As shown in FIG. 3, a piston 1 according to the present invention is vertically slidably fitted in a cylinder 2 of an internal combustion engine.
It is connected to the small end of the connecting rod 4 by a piston pin 3. The large end of the control rod 4 is connected to a crankshaft (not shown).

By the way, the main body 1a of the piston 1 is integrally cast with a lightweight aluminum alloy or the like, and upper and lower two-stage ring grooves 5, 6 are formed on the entire upper periphery thereof. , 6 are fitted with a tapered piston ring (keystone ring) 7 for preventing gas leakage and a rectangular ring 8, respectively. The tapered piston ring 7 is provided with a detent pin 9 implanted on the side wall of the piston body 1a.
The other rectangular ring 8 is similarly stopped in the circumferential direction by a not-shown detent pin implanted on the opposite side of the detent pin 9.

Here, the configuration of the tapered piston ring 7 and the rotation preventing structure will be described.
As shown in FIG. 4, is formed into a ring shape with iron, and an abutment portion 10 is formed in a part thereof. The upper surface of the tapered piston ring 7 forms a tapered surface 7a that is inclined obliquely downward toward the radially inward (left in FIG. 5) as shown in FIG. The piston ring 7
Has a radial cross section that tapers inward in the radial direction, and the width of the inner peripheral surface is smaller than the width of the outer peripheral surface.

As shown in FIG. 1, the tapered piston ring 7 is fitted in the ring groove 5 formed on the outer periphery of the piston main body 1a. The tapered surface 7a is formed along a tapered surface 7a, and both tapered surfaces 5a, 7a can be brought into uniform surface contact.

Also, the tapered surface of the joint 10 of the tapered piston ring 7
In the 7a side portion, as shown in FIG. 1 and FIG.
1,11 are formed, and the depth b of the cutouts 11,11 is
(See Fig. 2)
11a, 11a are formed substantially parallel to the tapered surface 7a.

On the other hand, a pin hole 12 is formed on the side wall of the piston main body 1a so as to overlap the ring groove 5.
12 is a tapered surface 7a of the piston ring 7 as shown in FIG.
The rotation preventing pin 9 press-fitted into the pin hole 12 also has the same shape as the piston ring 7.
Are arranged substantially parallel to the tapered surface 7a.

Thus, as shown in FIGS. 1 and 2, the tapered piston ring 7 has the cutout formed at the joint 10 thereof.
By engaging the detent pin 9 on 11,11,
In the present embodiment, the detent pin 9 is provided with the tapered surface of the piston ring 7 as described above.
Since the piston ring 7 is arranged substantially in parallel with the piston ring 7, the notch formed in the abutment portion 10 of the piston ring 7 even when the radial cross section of the piston ring 7 has a tapered shape inward in the radial direction.
Engagement allowance (hatched portion A in FIG. 1) between the 11, 11 and the detent pin 9 can be sufficiently ensured, and the detent in the circumferential direction of the piston ring 7 can be reliably performed. Can also be applied to a high horsepower internal combustion engine.

In this embodiment, since the upper portion of the ring groove 5 is machined substantially in parallel with the axis of the pit hole 12, the machining accuracy of the ring groove 5 below the detent pin 9 can be improved. Further, since the cross-sectional shape of the pin hole 12 in the ring groove 5 is uniform, the press-fitting operation of the rotation preventing pin 9 can be performed smoothly.

In the above embodiment, the notches 11 and 11 are formed not by partially cutting out the tapered surface 7a side of the abutment portion 10 of the piston ring 7 but by cutting out the entirety. Since the contact area of the outer peripheral surface of the piston ring 7 serving as the contact portion can be sufficiently secured, the sealing performance and durability of the piston ring 7 can be kept high.

By the way, the above is a taper type piston ring (keystone ring) with a tapered upper surface as the piston ring.
However, the present invention can be similarly applied to a case where a tapered piston ring having a tapered surface on the lower surface or both upper and lower surfaces is used.

(Effects of the Invention) As is apparent from the above description, according to the present invention, at least one of the upper and lower surfaces forms a tapered surface in the ring groove formed on the outer periphery of the side wall of the piston main body. A tapered piston ring having a radial cross section that tapers toward the other side is mounted, and a notch formed at an abutment portion on the tapered surface side of the tapered piston ring is formed around the side wall of the piston body. In a piston for an internal combustion engine that stops the tapered piston ring from rotating in the circumferential direction by engaging a locking pin, the locking pin is disposed substantially parallel to the tapered surface of the tapered piston ring. Engagement (lap allowance) between the notch formed at the abutment of the pin and the detent pin can be sufficiently ensured, and the detent in the circumferential direction of the piston ring can be reliably prevented. The effect that it can be performed is acquired.

[Brief description of the drawings]

1 is a front view of a detent portion of a piston according to the present invention, FIG. 2 is a sectional view taken along the line II-II of FIG. 1, FIG. 3 is a front view of a piston, and FIG. FIG. 5 is a plan view, and FIG. 5 is an enlarged sectional view taken along line VV of FIG. 1 ... Piston, 1a ... Piston body, 5,6 ... Ring groove, 7 ... Tapered piston ring, 7a ... Taper surface,
9 ... detent pin, 10 ... joint, 11 ... notch.

Claims (1)

(57) [Claims] An at least one of upper and lower surfaces of a ring groove formed on an outer periphery of a side wall of a piston body has a tapered surface, and has a radial cross-section tapering inward in a radial direction. By mounting a piston ring and engaging a detent pin implanted on the side wall of the piston body with a notch formed at the abutment on the tapered surface side of the tapered piston ring, In a piston for an internal combustion engine performing detent in the circumferential direction,
A piston for an internal combustion engine, wherein the detent pin is disposed substantially parallel to a tapered surface of the tapered piston ring.