Classifications

• • Y02T10/125—

Definitions

• the present invention relates to a piston assembly for an internal combustion engine. More particularly, the invention relates to a piston assembly for an internal combustion engine which prevents air from an air source for an internal combustion engine like an air cleaner or a turbo charger from leaking into the inside of the piston assembly and prevents lubrication oil leak from a crankcase into a combustion chamber of the engine thereby reducing lubrication oil loss and incomplete combustion.
• An internal combustion engine comprises one or more cylinders and pistons, which move reciprocally in the cylinders.
• a two-cycle internal combustion engine includes a piston assembly 10, and a cylinder liner 12, which surround the piston assembly 10, and fits into a cylinder (not shown).
• a cylinder liner 12 In the middle part of the cylinder liner 12, is formed an air intake port 14.
• the piston assembly 10 includes a piston 16, a plurality of grooves 18 formed at the outer periphery of the upper part of the piston 16, and compression rings 17 inserted into the grooves 18 to keep sealing between the piston 16 and the cylinder liner 12.
• the piston assembly 10 has also two grooves 20, 22 formed at the outer periphery of the lower part of the piston 16, an oil ring 24 inserted into the groove 22 and another oil ring, or an oil-scraping ring 26 inserted into the groove 20, which in positioned above the groove 22.
• the oil ring 24 collects lubrication oil and returns it to the crankcase of the engine.
• the oil-scraping ring 26 scrapes down lubrication oil spread on the cylinder liner 12.
• the entire outer periphery or a portion of the periphery of the oil scraping ring 26 contacts the cylinder liner 12, and adjusts the thickness of the lubrication oil film by scraping down excess oil.
• An oil passage 28 is formed between the grooves 20, 22 to communicate the inside of the piston 16 and the gap between the outer cylindrical wall of the piston 16 and the liner wall of the cylinder liner 12.
• Figs. 2 through 4 show the oil-scraping ring 26.
• the oil-scraping ring 26 has an upper rail 30 and a lower rail 32. Diameters of the rails are the same.
• a plurality of evenly spaced scallops 34 is formed on the lower rail 32. The scallops 34 pass the oil collected by the upper rail 30 to the crankcase via the oil passage 28.
• This reverse flow forces oil spread on the cylinder liner 12 or on the outer wall of the piston 16 to be sprayed onto the portion of the cylinder liner 12 near the air intake port 14.
• the sprayed oil is flowed into the combustion chamber together with the intake air and burned together with the fuel.
• an object of the invention is to provide an enhanced sealing mechanism for a piston assembly for an internal combustion engine.
• Another object of the invention is to prevent air leak into the inside of the piston assembly. Still another object of the invention is to prevent oil leak into a combustion chamber of the engine.
• Still another object of the invention is to prevent excessive pressure buildup in a crankcase of the engine. Still another object of the invention is to prevent formation of gaps around the oil ring in its assembled state.
• the present invention provides a piston assembly for an internal combustion engine comprising a piston that has a shape of a cylinder and has an outer cylindrical wall and a top portion on one end of the cylinder; an oil ring that is pressed against a cylinder liner of the internal combustion engine; and a circular groove that is formed in the outer cylindrical wall of the piston and holds the oil ring.
• the groove has an upper wall, a sidewall, and a lower wall and the upper wall is positioned toward the top portion of the piston.
• the piston assembly further includes a circular recess that is formed in the upper wall of the groove and a sealing member that is inserted into the recess and contacts the oil ring.
• the sealing member may be an elastic member and in the assembled state within the circular groove, the sealing member is compressed to provide sealing between the groove and the oil ring.
• the sealing member is an O-ring.
• the invention provides a piston assembly for an internal combustion engine comprising a piston that has a shape of a cylinder and has an outer cylindrical wall and a top portion on one end of the cylinder, and oil ring that has an upper projection and a lower projection that are formed on an outer periphery of the oil ring, a circular groove that is formed in the outer cylindrical wall of the piston and holds the oil ring.
• the upper projection of the oil ring is positioned toward the top portion of the piston. Both of the projections of the oil ring have tapered edges, and the outer diameter of the upper projection is greater than the outer diameter of the lower projection.
• the groove has an upper wall, a sidewall, and a lower wall and the upper wall is positioned toward the top portion of the piston.
• the piston assembly further includes a circular recess that is formed in the upper wall of the groove and a sealing member that is inserted into the recess and contacts the oil ring.
• the difference between the outer diameters of the upper projection and the lower projection is from about 0.2 cm to about 0.6 cm. More preferably, the difference is about 0.4 cm.
• the thickness of the edge of the upper projection is greater than the thickness of the edge of the lower projection.
• the present invention provides a piston assembly for an internal combustion engine comprising a piston that has a shape of a cylinder and has an outer cylindrical wall and a top portion on one end of the cylinder, an oil ring, and a circular groove that is formed in the outer cylindrical wall of the piston and holds the oil ring.
• the oil ring has an outer periphery, an inner periphery, a top portion, a bottom portion, a recess that is formed along the inner periphery, an upper edge that connects the top portion and the recess, a lower edge that connects the bottom portion and the recess, and an elastic member that is inserted into the recess of the oil ring and presses the oil ring against a cylinder liner of the internal combustion engine.
• the radii of the upper and lower edges of the oil ring are less than the inner radius of the elastic member.
• the difference between the radii of the upper and lower edges of the oil ring and the inner radius of the elastic member of the oil ring is about 0.5 mm.
• Fig. 1 is a cross-sectional view showing a piston assembly and a cylinder liner by prior art
• Fig. 2 is a plan view of an oil ring by prior art
• Fig. 3 is a cross-sectional view taken along a line HI -HI in Fig. 2;
• Fig. 4 is a cross-sectional view taken along a line IV -IV in Fig. 2;
• Fig. 5 is a cross-sectional view showing a piston, oil rings, and a cylinder liner by prior art
• Fig. 6 is a cross-sectional view showing a piston assembly according to the present invention.
• Fig. 7 is a cross-sectional view showing a piston, an oil ring, and a cylinder liner according to the present invention
• Fig. 8 is a plan view showing an oil ring according to the present invention.
• Fig. 9 is a cross-sectional view taken along a line IX- IX in Fig. 7;
• Fig. 10 is a cross-sectional view taken along a line X - X in Fig. 7.
• a piston assembly 40 for an internal combustion engine includes a piston 42, a plurality of grooves 44 formed at an outer periphery of the upper part of the piston 42, compression rings 46 inserted into the grooves 44 to keep sealing between the piston 42 and a cylinder liner (112 : See Fig. 7).
• the piston assembly 40 further has two grooves 48, 50 formed at an outer periphery of the lower part of the piston 42, an oil ring 52 inserted into the groove 48 and another oil ring, or an oil-scraping ring 54 inserted into the groove 50, which is positioned above the groove 48.
• the groove 50 holding oil ring 54 has an upper wall 56, a sidewall 58, and a lower wall 60.
• a circular recess 62 is formed on the upper wall 56 of the groove 50.
• a sealing member 64 is inserted into the recess 62 such that it should contact the oil ring 54.
• the sealing member 64 blocks a gap between the upper wall 56 of the groove 50 and an upper surface of the oil ring 54, and provides a tight seal eliminating leak of oil or air.
• the sealing member 64 is made of elastic material so that it is compressed against an upper surface of the oil ring 54.
• the sealing member 64 is preferably, an O-ring.
• FIG. 8-10 show the oil ring 54 in detail.
• a recess 66 is formed along an inner periphery of the oil ring 54.
• An elastic member or pressing member 68 is inserted into the recess 66 to force the oil ring 54 radially outward, that is, toward the cylinder liner 112.
• the pressing member 68 is formed of a coil spring. Since the pressing member 68 presses an outer periphery of the oil ring 54 against the cylinder liner, the outer periphery of the oil ring tightly contacts the cylinder liner and a gap between them is eliminated.
• the oil ring 54 further has a top portion 70, a bottom portion 72, and upper edge 74 connecting the top portion 70 and the recess 66, and a lower edge 76 connecting the bottom portion 72 and the recess 66.
• the recess 66 is extended to the edges 74, 76 such that the radii of the edges are less than the inner radius of the pressing member 68. All of the radii are measured from the center of the oil ring 54. This increases the area that the oil ring 54 contacts the groove 50 thereby enhancing sealing effect.
• the difference s between the radii of the edges and the inner radius of the pressing member is 0.5 mm.
• the oil ring 54 further has an upper projection or rail 78 and a lower projection or rail 80 formed on the outer periphery of the oil ring.
• the outer diameter of the upper rail 78 is greater than that of the lower rail 80.
• a plurality of evenly-spaced scallops 82 are formed on a periphery of the lower rail 80 to pass oil scraped by the upper rail 78 to a crankcase via an oil passage 84 positioned between the grooves 48, 50.
• the upper rail 78 is tapered and has an edge 86 at the end of the taper.
• the lower rail 80 is tapered and has an edge 88 at the end of the taper.
• the upper rail 78 is formed bigger than the lower rail 80 considering that the portion of the cylinder around the air intake port is machined to have an increasing size to compensate thermal expansion.
• the difference r between the outer diameters of the upper rail 78 and the lower rail 80 is in the range form 0.2 cm to 0.6 cm, and more preferably about 0.4 cm.
• the difference between the radius of the edge 86 of the upper rail 78 and the radius of the edge 88 of the lower rail 80 is in the range from 0.1 cm to 0.3 cm, and more preferably about 0.2 cm.
• the radii are measured from the center of the oil ring 54.
• the thickness tl of the edge 86 of the upper rail 78 is preferably greater than the thickness t2 of the edge 88 of the lower rail 80.
• the air supplied from an air cleaner or a turbo charger (not shown) via the air intake port 114 is prevented from leaking into the inside of the piston 42.
• the air flowing between the cylinder liner 112 and the piston assembly 40 is prevented from leaking into the inside of the piston assembly via a gap between the oil ring 54 and the groove 50 because the sealing member 64 seals the gap.
• the sealing of the gap is further enhanced by the increased contact area of the oil ring 54 and the groove 50 that is provided by the extended edges 74, 76 of the oil ring 54.

Landscapes

• Pistons, Piston Rings, And Cylinders (AREA)
• Cylinder Crankcases Of Internal Combustion Engines (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=34373992

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Country Status (4)

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• 2003
  • 2003-01-27 BR BR0318056-5A patent/BR0318056A/pt not_active IP Right Cessation
  • 2003-01-27 AU AU2003206189A patent/AU2003206189A1/en not_active Abandoned
  • 2003-01-27 EP EP03703432A patent/EP1599666A1/de not_active Withdrawn
  • 2003-01-27 JP JP2004567574A patent/JP2006513358A/ja active Pending

Non-Patent Citations (1)

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