JPS61190152A - Air-tight device for combustion chamber of internal-combustion engine - Google Patents

Abstract

PURPOSE:To enable the area of a surface to which heat of a piston is transmitted to be ensured by forming a recess in one of contact surfaces of a piston ring and a crank chamber side wall of a piston ring groove and a wedge type of the groove sides having an opening diverging toward the crank chamber. CONSTITUTION:At least one of contact surfaces of a piston ring 21 and a crank chamber side wall 22a of a piston ring groove 22 is formed with a recess 29. And the sides of the piston ring groove 22 formed like a wedge having an opening diverging toward the crank chamber side. Thus, the area of piston ring surface contacting the side walls of the groove is ensured so that heat flow bundle flowing from a piston 8 to a cylinder through the piston ring 21 is sufficiently ensured to cool sufficiently the piston while the function of interrupting combustion gas can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to an airtight device for a combustion chamber of an internal combustion engine, in which a piston ring is disposed on a piston.

(Prior art) In general, the role of a piston ring is to adhere tightly to the cylinder inner wall surface with elastic force to maintain airtightness and prevent gas leakage.
Heat from the piston may be lost to the cylinder.

Modern engines tend to have higher compression ratios to improve performance and run with lean mixtures to save fuel, which causes the pistons to become hotter. As a result, the piston ring and the piston ring groove side wall tend to stick together.

On the other hand, Japanese Patent Application Laid-Open No. 54-125345 has a structure in which the side wall of the piston ring groove on the crank chamber side is formed flat, and a recess is formed in the piston ring surface in contact with the side wall, thereby reducing the cooling effect of the oil and the contact area of the piston ring. It has been disclosed that the piston ring and the piston ring groove side wall are prevented from sticking together by utilizing the temperature reduction caused by the reduction of the piston ring groove.

(Problems to be Solved by the Invention) However, simply forming a recess in the vehicle will impede the heat flux flowing from the piston through the piston ring and into the cylinder.

In other words, since the piston itself is not cooled sufficiently, there are problems such as a hole forming at the top of the piston and seizure between the piston and the cylinder.

Furthermore, the total length between the crank chamber side side wall of the piston ring groove and the piston ring surface in contact with the side wall is short, and the passage resistance between the cores is small, so the high pressure combustion gas after ignition and explosion can pass through the gap. There was a problem that it easily flowed into the crank chamber.

For this reason, even if the recess is formed to store the oil, the oil will be returned to the crank chamber from the recess due to the flow of combustion gas, and the piston ring and piston ring groove will not be connected to each other using the cooling effect of the oil. It was also difficult to fully utilize the effect of preventing adhesion to the side wall.

(Means for Solving the Problem) In an airtight device for an internal combustion engine combustion chamber, which includes a piston ring groove disposed in a piston and a piston ring fitted into the groove, the piston ring and the crank of the piston ring groove An airtight device for a combustion chamber of an internal combustion engine, characterized in that a recess is formed in at least one of the surfaces in contact with the chamber side wall, and the groove side surface has a wedge-shaped shape that widens toward the crank chamber side toward the mouth.

(Function) Even if the concave portion is formed, the contact area between the piston ring and the piston ring groove does not decrease, and the area of the heat transfer surface from the piston can be secured.

Furthermore, since a sufficient length of the contact portion between the piston ring and the piston ring groove can be ensured, the passage resistance between the piston ring and the piston ring groove is increased (thus, the blocking function against combustion gas is improved).

(Description of Embodiments) FIG. 1 is a partial cross-sectional view showing an engine portion of an outboard motor for marine propulsion, and FIG. 2 is a cross-sectional view of the cylinder portion taken along the line ■-■ in FIG.

The engine body 2 of the outboard motor 1 includes a cylinder head 3, a cylinder 4, a crankcase 5, a vertical crankshaft 6 sandwiched between the cylinder 4 and the crankcase 5, and a sleeve that fits into the cylinder 4. 7, a piston 8 housed therein, and a connecting rod 10 that connects the piston 8 and the crankshaft 6 via a piston pin 9.

Furthermore, the engine body 2 is formed by a carburetor 11, a reed valve 12 which is a check valve, a crank chamber 13 formed by a cylinder 4, a crank case 5, and a piston 8, a cylinder head 3, a piston 8, and a sleeve 7. combustion chamber 14
has.

The cylinder 4 is formed with an exhaust passage 15, an auxiliary scavenging passage 16, and two main scavenging passages 17a and 17b. Each exhaust boat 18 and sub-scavenging boat 1 open to the sleeve 7.
9. Main scavenging boat 20a.

20b, respectively.

The fresh air sucked into the crank chamber 13 passes through the sub-scavenging passage 16 or the main scavenging passages 17a and 17b while being subjected to compressive force as the piston 8 moves in the direction of the crankshaft 6.
It enters the combustion chamber 14 through each sub-scavenging boat 19 and main scavenging boats 20a and 20b.

FIG. 3 is a side view of the piston taken along the line 2 in FIG. 2. FIG.

Fig. 4 is a detailed cross-sectional view of the piston ring groove, Fig. 5 is a detailed cross-sectional view of the piston ring, and Fig. 6 is an external view of the main parts of the piston ring as seen along the arrow ■ line in Fig. 5. .

The two common piston rings 21 are in the piston ring groove 2.
2, and the locking pin 23 of the piston ring 21 is press-fitted into the piston 8.

Two circumferential recesses 24 are formed in the piston ring 21.

FIG. 7 is a diagram showing the situation around the recess 24.

During the ignition explosion in (a), the pressure in the combustion chamber 14 rises rapidly. At this time, as shown in (a), the high-pressure combustion gas 25 in the combustion chamber 14 enters the piston ring groove 22 and attempts to escape into the crank chamber 13 through the clearance C3.

However, the crank chamber side side wall 22 of the piston ring groove 22
Since a is inclined and long in the radial direction, the resistance of the pipe becomes large. Therefore, the oil that accumulates in the recess 24 is not washed away.

When the clearance decreases from 03 to 04 due to the pressing force 26 of the combustion gas 6-1 in the expansion stroke after the ignition explosion in (b), the oil accumulated in the recess 24 is transferred to the contact surface between the side wall 22a and the piston ring 21. 27.

Even if the recess 24 is formed, since the side wall 22a is inclined and long in the radial direction, the contact area between the piston ring 21 and the piston ring groove 22 is not reduced (and the heat transfer 28 from the piston 8 is not sufficiently reduced). In addition, due to the lubricating action of the oil, it is possible to reliably prevent the piston ring 21 and the piston ring groove side wall 22a from sticking together.

Abrasion particles from the piston 8 or cutting particles from cylinder machining may enter the piston ring groove 22 and weld the aluminum, resulting in sticking.

Furthermore, the outboard motor in this example is used at full throttle more often than land-based engines, so ensuring sufficient heat transfer and preventing stalemate are particularly effective in ensuring engine durability. be.

At low speeds, the scavenging flow rate is generally slow, so the mixed fuel that cannot be atomized adheres to the wall around the crank chamber 13.

In this embodiment, since the main scavenging passage 17a is arranged at the bottom, when the piston ring 21 passes through the main scavenging boat 20a, the oil is heated through the circumferential recess 24 more than in other arrangements. Can be supplied to the exhaust boat side, which has a large load.

FIG. 8 is a sectional view of the main part around the side wall of the piston ring groove of the second embodiment, and FIG. 9 is a sectional view of the main part around the side wall of the piston ring groove of the third embodiment.

The second embodiment has four parts 29 on the side wall 22a of the piston ring groove.
The third embodiment has a wedge-shaped shape different from that of the first embodiment, and the side wall 22b of the piston ring groove 22 on the combustion chamber side.
is also inclined and radially long.

(Effect of the invention) Since the total length between the crank chamber side side wall of the piston ring groove and the piston ring surface in contact with the side wall is long (and four parts are provided between the cores), the piston travels from the piston through the piston ring to the cylinder. Sufficient heat flux can be secured.Furthermore, it prevents the oil from returning to the crank chamber from the recess due to the flow of combustion gas, and prevents the piston ring from sticking to the side wall of the piston ring groove using the lubricating action of the oil. It is also possible to fully utilize the preventive effect.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing an engine portion of an outboard motor for propulsion of a marine vessel. FIG. 2 is a cross-sectional view of the cylinder portion taken along the line ■-■ in FIG. FIG. 3 is a side view of the piston taken along the line 2 in FIG. 2. FIG. FIG. 4 is a detailed sectional view around the piston ring groove 22. FIG. 5 is a detailed sectional view of the piston ring 21. FIG. 6 is an external view of the main parts of the piston ring 21, taken along the arrow line 2 in FIG. 5. FIG. FIG. 7 is a diagram showing the situation around the recess 00. FIG. 8 is a sectional view of the main part around the side wall of the piston ring groove of the second embodiment, and FIG. 9 is a sectional view of the main part around the side wall of the piston ring groove of the third embodiment. Cylinder...4 Piston...8 Crank chamber...13 Combustion chamber...14 Exhaust passage...15 Main scavenging passage... ...17a Main scavenging boat...20B Piston ring...21 Piston ring groove...22 Side wall...22a Recess...29 Patent applicant Sanshin Kogyo Co., Ltd. Company -1〇- Rod 3 Figure 7 (A) (B) (I) (B) Figure 8 Figure 9

Claims (1)

[Claims] In an airtight device for a combustion chamber of an internal combustion engine, comprising a piston ring groove disposed in a piston and a piston ring fitted into the groove, at least one of the contact surfaces between the piston ring and a side wall of the piston ring groove on the crank chamber side. An air sealing device for a combustion chamber of an internal combustion engine, characterized in that a recess is formed in the groove, and the side surface of the groove has a wedge-shaped shape that widens toward the crank chamber side toward the mouth.