JPH05231237A - Piston for internal combustion engine - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] Reducing the consumption of oil for lubricating internal combustion engines is a constant theme. The present invention aims to further reduce oil consumption. [Structure] The oil escape hole 6 is a tapered hole 6 having a diameter (a) of the opening on the ring groove 4 side larger than the diameter (b) of the opening on the piston inner side, and above the hole (crown side). ) Is provided on the inner wall 7 of the piston.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston for an internal combustion engine that ensures oil return.

[0002]

2. Description of the Related Art A piston that reciprocates in a cylinder is a sliding friction surface such as a piston ring and an inner circumferential surface of the cylinder, a bearing surface between a piston pin and a piston, and a bearing surface between a piston pin and a connecting rod. Oil supply is essential. Therefore, the oil in the oil pan may be scattered to the inner peripheral surface of the cylinder and the inside of the piston, or
Oil is pumped from the camshaft to the inner surface of the cylinder and the inside of the piston.

The oil supplied to the inner peripheral surface of the cylinder and the inside of the piston reduces the anti-friction resistance of the sliding friction surface,
It works to cool high temperature parts. Further, the piston has a pressure ring for preventing the air-fuel mixture, combustion gas, and exhaust gas in the cylinder from leaking to the crank chamber side, and oil for replenishing the inner peripheral surface of the cylinder to reduce the friction of the pressure ring. Equipped with an oil ring that scrapes off excess oil from the inner peripheral surface of the cylinder.

The ring groove in which the oil ring is mounted has a plurality of oil escape holes spaced apart so as to open into the groove bottom and the piston. This window or hole serves to escape the oil scraped off to the inner wall surface side of the piston and return the oil to the oil pan.

[0005]

The oil escape hole is a drill hole having the same inside and outside diameters. further,
The inner wall surface of the piston has a cylindrical shape flush with the ring groove portion for the oil ring to the ring groove portion for the pressure ring to enhance the cooling effect by the oil supplied to the inner wall surface.

In such a conventional piston for an internal combustion engine, oil scraped from the inner peripheral surface of the cylinder can be released to the inside of the piston through an oil escape hole by the oil ring. The inventor has noticed that the oil thus leaked to the inner peripheral surface side of the cylinder through the oil escape hole, resulting in a large amount of oil consumption. Therefore, it is an object of the present invention to solve the above-mentioned problems of the conventional technology.

[0007]

In order to solve the above-mentioned problems, the present inventor has focused on improving the shapes of the oil escape hole and the inner wall surface of the piston in which the hole opens. That is, the present invention basically provides means for using an oil escape hole for reducing the diameter inside the piston and providing a step portion extending to the center side of the piston on the upper side of the opening of the hole to the inside of the piston. adopt.

Specifically, according to the present invention, in a piston for an internal combustion engine which reciprocates in a cylinder and has a ring groove having an oil escape hole, the diameter of the oil escape hole is large outside and is small inside. A piston for an internal combustion engine, characterized in that it has a step portion projecting toward the center of the piston at the upper part of the inner wall surface inside the piston in which the oil escape hole is opened.

Preferably, the downward surface of the step portion is a circular arc surface, and the oil on the upper side of the step portion is directed toward the center of the piston.

[0010]

[Operation] The tapered oil escape hole promotes the escape of oil from the ring groove to the inside of the piston, but resists the reverse flow of oil from the inside of the piston to the ring groove, and minimizes the reverse flow. .. The stepped portion on the inner wall surface of the piston above the oil escape hole serves to prevent the oil scattered or pressure-fed to the inner wall of the crown portion from being directed toward the oil escape hole. That is, the oil on the inner wall of the crown portion of the piston should not be directed as much as possible in the direction of the oil escape hole, and the scattered or pressure-fed oil that is about to enter the hole must enter the small-diameter opening and the hole is tapered. Therefore, the flow resistance is large and the backflow of oil to the ring groove is minimized.

[0011]

EXAMPLE Referring to FIG. The internal combustion engine piston 1 is
A ring-shaped groove 3 for the pressure ring and a ring-shaped groove 4 for the oil ring are provided on the outer peripheral surface of the body 2 of the cast aluminum alloy. The boss 10 for the piston pin opens on the outer peripheral surface of the piston body. In the bottom groove 5 of the ring groove 4 for the oil ring, a plurality of oil escape holes 6 are provided separately.

As shown in FIG. 2, the oil escape hole 6 opens in the ring groove bottom wall 5 and the inner wall surface 7 of the piston body 2. The oil escape hole 6 is a tapered hole having a large opening (a) on the ring groove bottom wall 5 side and a small opening 6 on the inner wall surface 7 side. That is, the relationship of a> b is established. This facilitates the escape of oil from the ring groove 4 into the piston and provides resistance to the reverse oil flow.

On the inner wall surface 7 of the piston body 2 and above the opening of the oil escape hole 7, there is provided a step portion 8 which is slightly arcuate and is directed toward the piston center. Step 8
Is connected to the inner wall 9 side of the piston crown. This inner wall 9
Directs the oil scattered or pumped into the piston body 2 to the vicinity of the center of the inside of the piston body 2 as shown by the arrow. Therefore, the oil sprayed on the inner wall 9 does not return to the oil escape hole 6, and there is almost no oil backflow to the ring groove 4.

In forming the step portion 8, the piston body 2
The inner wall of the may be cut by the dimension l ₁ and the dimension l ₂
Alternatively, the ring body may be cast with only the wall thickness. In the illustrated example, the center of the oil escape hole 6 is orthogonal to the center of the piston, but it may be directed downward. The ratio of the diameter (a) of the opening on the ring groove bottom wall 5 side of the oil escape hole to the diameter (b) of the opening on the piston inner side is preferably 2 to 1. a
= 3 mmφ, b = 1.5 mmφ, l ₁ = 3 mm and the conventional piston were compared and tested under the same conditions. As a result, the example of the present invention was able to reduce the oil consumption by about 20% compared with the conventional example. .. Further, even if the step portion 8 is installed, there is almost no difference in the cooling effect between the present invention and the conventional example.

[0015]

[Effect] In the present invention, since only the oil escape hole and the inner wall of the piston are improved, the manufacturing process need not be largely changed. In addition to reducing oil consumption, the cooling effect and oil return can be maintained as before.

[Brief description of drawings]

FIG. 1 is a partially sectional front view of a piston according to an example of the present invention.

FIG. 2 is a partial sectional view showing an oil escape hole and a step portion.

[Explanation of symbols]

 2 Piston body 4 Ring groove 5 Bottom wall 6 Oil escape hole 8 Step

Claims (2)

[Claims] 1. A piston for an internal combustion engine having a ring groove that reciprocates in a cylinder and has an oil escape hole, wherein the oil escape hole has a tapered shape with a large outside diameter and a small inside diameter. A piston for an internal combustion engine, comprising a step portion projecting toward a center of the piston at an upper portion of an inner wall surface inside the opened piston. 2. The downward surface of the step portion is a circular arc surface.
Piston ring for internal combustion engine.