JPS6149155A - Piston of internal-combustion engine - Google Patents

Abstract

PURPOSE:To suppress gas from leaking and reduce a number of rings, by providing an annular groove on the peripheral surface, opposed to the ceramic coating internal wall surface of a cylinder in its top dead center side, of a piston and fitting the plural piston rings to be mounted to the bottom half of the peripheral surface of the piston. CONSTITUTION:A piston 3 in an internal-combustion engine provides on the peripheral surface in a side of the top dead center a plurality of stripes of annular grooves 19 to be opposed to the internal wall surface of a ceramic coating 18 in a cylinder 1 in a side of the top dead center over almost a half stroke. While the piston is constituted such that a plurality of piston rings 21 are fitted into ring grooves 20 on the peripheral surface in a side of the bottom dead center of the piston and opposed to a non-ceramic coating internal wall surface of the cylinder 1 over the full stroke of the piston. In this way, the piston, dropping the pressure of gas in a combustion chamber due to diffusion in the annular groove and reducing a leak of the gas from the piston ring, enables a number of piston rings to be decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a piston of a reciprocating piston type internal combustion engine, and more particularly to a structure for preventing gas leakage from between the piston and the cylinder.

[Prior art]

The combustion section of a marine diesel engine, etc. has a nine cylindrical cylinder whose head is closed by a cylinder head, and the combustion gas pressure in the combustion chamber of the cylinder head and the intake and exhaust gas move back and forth within the cylinder and connect to the crankshaft via a connecting rod. It is made up of a rotating piston. Each of the plurality of ring grooves provided on the outer circumferential surface of the piston is fitted with a piston ring that has a slightly larger diameter than the piston diameter, has an expansion force, and fits tightly against the inner wall surface of the cylinder. The piston is configured to transmit high-temperature heat received by the piston to the cylinder to prevent the piston from overheating, reduce gas leakage to the outside of the combustion chamber, maintain compression pressure, and perform good combustion.

However, in the conventional combustion section -C, it was not always possible to expect a satisfactory effect in preventing gas leakage by the piston ring.

In other words, there is a gap in the thickness direction and a gap in the circumferential direction due to expansion between the piston ring and the ring groove.
In addition, the piston ring has a gap created by cutting one point in the circumferential direction, and if these gaps are made too small, the piston ring will break due to thermal expansion and the cylinder wall will wear out, so please make sure that the gap is appropriate. Therefore, it was impossible to completely prevent gas leakage. Conventionally, in order to minimize gas leakage, the number of piston rings was unavoidably increased in the 7ζ, but the cylinder wall was prone to wear, and the friction between the piston ring and the cylinder wall caused damage. υThe disadvantage was that mechanical loss increased.

[Summary of the invention]

The present invention is based on the above-mentioned points, and includes a plurality of annular grooves and a plurality of piston rings on the outer circumferential surface,
By configuring the combustion gas to diffuse into the annular groove during approximately half a stroke on the top dead center side, this works together with the action of the piston rings to block gas leakage from the combustion chamber, reducing the number of piston rings. To provide a piston for an internal combustion engine that prevents cylinder wear by reducing the amount of wear.

Embodiments of the present invention will be described in detail below with reference to the drawings.

〔Example〕

1 to 6 show an embodiment of a piston for an internal combustion engine according to the present invention, and FIG. 1 is a longitudinal cross-sectional view of this piston, with the right half and left half shifted in phase by 900 degrees in the circumferential direction. , Fig. 2 is a sectional view taken along the line AA in Fig. 1, Fig. 3 is a top view of Fig. 1 viewed from the direction of arrow B, Fig. 4 is a partially cutaway front view of the spherical head of the connecting rod, and Fig. 5. is a CC sectional view of FIG. 4, and FIG. 6 is an enlarged sectional view of the annular groove. In the figure, cylinder 1
The piston is provided with a cylindrical liner 2 fitted on the inner circumferential surface of the piston, and a piston, generally designated by reference numeral 3, is slidably fitted on the inner circumferential surface of the liner 2.

The piston 3 is made up of a piston crown 4, a skirt 5, and a connecting rod support metal fitting 6. Of these, the piston crown 4 is made of a ceramic material in the shape of a disk, and its outer periphery is made of heat-resistant steel. A plurality of screw fittings 7 formed of
is included during molding. Further, a concave portion 8 is provided on the upper end surface of the piston crown 4 in order to avoid interference with an intake/exhaust valve (not shown) and improve combustion. The piston crown 4, which is fixed to the skirt 5 by a bolt 9 inserted into a screw fitting 7 and screwed into a threaded hole in the skirt 5, may be made of heat-resistant cast iron and coated with ceramic. The skirt 5 has the same diameter as the piston crown 4, and has a hemispherical surface 5a formed on its inner circumference il/2, and a cylindrical surface 5b formed on the remaining approximately 1/2. Numeral 10 is a positioning pin for centering the piston crown 4 and skirt 5 when they are fixed with bolts 9, and is screwed into a screw hole 50 provided in the hemispherical surface 5& from the hemispherical surface 5&. The bottle-shaped part at the tip is the pin hole of the piston crown 4.
The connecting rod support fitting 6, which is tightly fitted, is fitted into the cylindrical surface 5b of the skirt 5, and a plurality of bolts 11 are screwed into the threaded holes in the end face of the skirt 5 from the flange thereof.
It is fixed to the skirt 5 by. The connecting rod support hardware 6 is fixed to the skirt 5 and has a spherical head surface 6a that forms a spherical surface together with the hemispherical surface 5q. 0 in which a pair of opposing sliding surfaces 6b, half of which are enclosed by diagonal lines, and a large-diameter hole 6c are formed in a continuous manner is designated by the reference numeral 12.
A connecting rod consisting of a spherical head 15 and a rod-shaped portion 16 whose seven flange portions are joined by a bolt 13 and a double nut 14. The connecting rod 12 has a spherical head 15 rotatably fitted to the spherical surface consisting of the hemispherical surfaces 5m and 6a, and a sliding surface 17 fitted to the sliding surface 6b.
The other end of the rod-shaped portion 16 is fitted into an eccentric portion of a crankshaft (not shown). With this structure, the piston 3 which compresses air and is at the top dead center shown in FIG. It descends inside the cylinder 1 and rotates the crankshaft via the connecting rod. The rotation of the crankshaft causes the piston 3 to move up and down during exhaust and intake, and the rising of the piston compresses the air, after which the above-mentioned process is repeated. Note that the chain 12A in FIG. 1 shows a connecting rod that is tilted due to the crank action while the piston 3 is being raised and lowered.

Therefore, a structure for preventing gas leakage during combustion will be explained. On the top dead center side of the inner circumferential surface of the liner 2 of the cylinder 1, there is a line approximately 1/2 the length of the stroke T of the piston 3 and 0.4 m.
A ceramic coating 18 having a thickness of about m is applied by thermal spraying), while the skirt 5 of the piston 3
A plurality of annular grooves 19 facing the ceramic coating 18 are provided in parallel in the axial direction on the outer peripheral surface.

This annular groove 19 generates a vortex flow in the annular groove 19 to diffuse the gas that is trying to move downward in the gap between the cylinder 1 and the piston 3 in FIG. The position of the stone 3 is set on the top dead center side so that it faces the ceramic ding 18 in a part of the half-stroke movement on the top dead center side. Further, as shown in an enlarged view in FIG. 6, the cross-sectional shape of the annular groove 1S is formed by an upper inclined surface, a lower horizontal surface, and a vertical surface. The clearance between the cylinder 1 and the cylinder 1 is approximately twice as large.

On the other hand, a plurality of (three in this embodiment) rings m2a are provided on the outer peripheral surface of the lower part of the skirt 5, and in this ring groove 2o, one place on the circumference is cut and an expansion force is applied. A conventionally known piston ring 21 is fitted into the inner circumferential surface of the liner 2.This piston ring 21 is inserted into the liner 2, which is not coated with the ceramic coating 18, at the top dead center shown in FIG. The position and length of the ceramic coating 18 are set so that it faces the inner circumferential surface during the entire stroke of the piston 3, and as the piston 3 moves up and down, the inner circumferential surface of the liner 2 The annular groove 19 is configured to slide smoothly and to block the passage of gas whose pressure has decreased due to diffusion in the annular groove 19.

Next, the circulation path of lubricating oil will be explained. The connecting rod 12 is provided with an oil hole 22 (through the shaft core) for raising the lubricating oil pumped from the lubricating oil pump side from the shaft side, and its upper end is located between the positioning pin 10 and the locating pin 10. It opens into the space.

Further, from the upper part of the oil hole 22, a plurality of oil holes 24 are connected by an annular groove 23 on the circumferential surface of the spherical part 15 and branched off.
A part of the oil rising inside the oil hole 22 is spouted out to form the spherical part 15.
It is configured to lubricate the 0 circumferential surface. Furthermore, the positioning bottle 10 is provided with a hole 25 that also serves as a spanner insertion hole and a plurality of oil holes 26 branching from this hole, and a plurality of oil grooves 27 are formed in the upper end surface of the skirt 5. The grooves are provided radially from the annular groove 28 connecting the openings of the grooves. 29 is an annular oil groove connecting the ends of the oil groove 27;
Vertical holes 30 that penetrate the skirt 5 in the axial direction are bored at multiple locations in the circumferential direction, and each vertical hole 30 connects to an annular oil passage 31 that is a space surrounding the center of the spherical portion 15. It is opened.

Reference numeral 32 denotes an oil groove provided on the hemispherical surface 5& of the skirt 5 for good oil lubrication, and 33 is provided at two locations in the circumferential direction of the connecting rod support metal fitting 6 as shown in FIG. This is an oil groove along the spherical portion 15 and is open downward from the spherical portion. With this configuration, the hemispherical surfaces 5m, 6a
The oil that lubricates the fitting surfaces of the spherical part 15 and the annular oil passage 31
It passes through the oil groove 32 and is discharged downward toward the crankshaft.

The operation of the piston configured as above will be explained. When the piston 3 rises to the top dead center position shown in the figure and fuel is injected into the compressed high temperature and high pressure air, the combustion gas expands, the piston 3 descends, and its skirt 5
The connecting rod 12, in which the hemispherical surfaces 5a and 6a and the spherical portion 15 are fitted, is lowered.

In this case, since the lower end of the connecting rod 12 is connected to the eccentric portion of the crankshaft, the connecting rod 12 can be rotated by bringing its sliding surface 17 into sliding contact with the sliding surface 6b of the connecting rod support fitting 6. The crankshaft is rotated while swinging as shown by the chain line 12A in FIG. In addition, the oil that has been pressure-fed from the crankshaft side of the lubricating oil pump 9 and ascended through the oil hole 22 of the connecting rod 12 flows through the opening of the oil hole 22 and the oil hole 24.
A part of the oil flows out from the opening of the annular oil passage 31, lubricating the spherical surface 5a and flowing down into the annular oil passage 31. In addition, the remaining oil passes through the oil hole 26 and the oil groove 27 to the annular oil groove 29, and flows inside the vertical hole 30.
It flows down toward the T-shaped oil passage 31. When this oil passes through the oil groove 27 and the annular oil groove 29, it cools the back surface of the piston crown 4, and when flowing down the vertical hole 3o, it cools the annular groove 19 and the ceramic coating 18, which are the outer periphery of the skirt 5. cooling the sliding surfaces. The oil collected in the annular oil passage 31 flows into the oil groove 32.
is emitted toward the crankshaft. In this way, the piston 3, which has descended due to the expansion of the combustion gas, moves up and down due to the rotation due to the inertia of the crankshaft, during which air is exhausted and taken in. When the piston 3 rises again, the air is compressed, thereby completing one cycle. After that, the cycle repeats.

Among the strokes of the piston 3 that moves up and down during the above-described cycle, in the Y half stroke on the top dead center side, the annular groove 19 and the ceramic coating 18 face each other, and the piston ring 21 is connected to the liner 2 without the ceramic coating. The piston 3 moves up and down while facing the inner circumferential surface of the piston 3. Also, at approximately half a stroke toward the bottom dead center, is it annular?
The piston 3 moves up and down while #19 and the piston ring 21 both face the inner peripheral surface of the liner 2. Therefore, during approximately half a stroke toward the top dead center where the gas pressure is high, the combustion gas in the combustion chamber attempts to leak toward the piston ring 21 through the gap between the piston 3 and the cylinder 1, but the annular groove Since there is one day, the gas flows into the annular groove 19.
The pressure is diffused while generating excess flow within the annular groove 1.
Since it is possible to lower the number of piston rings 21 to 173 or less compared to the case without 9, gas leakage can be minimized even if the number of piston rings 21 is reduced. Ceramic coating 18 is applied to the inner wall surface on the top dead center side of the cylinder 1, which is broken, so it has excellent heat resistance and
It can suppress heat dissipation and reduce heat loss. Furthermore, since it does not come into contact with the piston 3, it will not wear out. Furthermore, by forming the piston crown 4 from a ceramic material, it is possible to provide a heat insulating effect against combustion gas.

In this embodiment, an example in which the present invention is applied to a 4-stroke diesel engine is shown, but the invention can be similarly applied to a 2-stroke diesel engine, a 4-stroke gasoline engine, and a 2-stroke gasoline engine.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a plurality of annular grooves are provided on the outer circumferential surface of the piston of an internal combustion engine on the top dead center side, and the annular grooves on the top dead center side are inserted between s4 strokes. A plurality of piston rings t[i are placed in the ring groove on the outer circumferential surface on the bottom dead center side so as to face the ceramic-coated inner wall surface of the cylinder during the entire stroke of the piston. By configuring it so that the gas that is about to leak from the combustion chamber is reduced in pressure (by diffusion in the annular groove) and there is less leakage from the piston rings, the number of piston rings can be reduced compared to the conventional one. This reduces mechanical loss due to friction in the piston sliding parts, improving engine efficiency, and reducing cylinder wear and improving durability. Furthermore, since the inner wall surface of the cylinder on the top dead center side is coated with ceramic coating, it is possible to suppress heat dissipation from the cylinder and reduce heat loss.

[Brief explanation of the drawing]

Figures 1 to 6 show an embodiment of a piston for an internal combustion engine according to the present invention, and Figure 1 is a longitudinal cross-section of this piston cut with the right half and left half shifted in phase by 90° in the circumferential direction. Figure 2 is a sectional view taken along line AA in Figure 1, Figure 3 is a top view of Figure 1 viewed from the direction of arrow B, Figure 4 is a partially cutaway front view of the spherical head of the connecting rod, and Figure 5 is a partially cutaway front view of the spherical head of the connecting rod. The figure is a CC sectional view of FIG. 4, and FIG. 6 is an enlarged sectional view of the annular groove. 1. Fist cylinder, 2. Liner, 3. Piston, 12. Connecting rod, 18. Fist ceramic coating, 19. Annular groove, 20. Ring. Groove, 21---piston ring.

Claims (1)

[Claims] A plurality of annular grooves for combustion gas diffusion are provided on the circumferential surface facing the ceramic coating inner wall surface on the cylinder top dead center side during approximately half a stroke on the top dead center side, and the ceramic coating on the cylinder bottom dead center side during the entire stroke. A piston for an internal combustion engine, characterized in that a plurality of piston rings that come into sliding contact with an uncoated inner wall surface are fitted into an outer ring groove.