PISTON ASSEMBLY FOR AN ENGINE

Abstract

In an engine piston assembly of the present invention, a piston structure, together with a piston ring set matched to the piston structure and an inner wall of a cylinder bore body, forms a crevice passage having at least two annular expansion chambers and also having a function of multistage throttling and expansion. The engine piston assembly of the present invention can not only greatly and effectively reduce the intra-cylinder carbon deposition and the hydrocarbon emissions in the exhaust gas emissions of the engine, but also significantly improve the engine efficiency and the overall performance of the engine, so that the present invention is suitable for wide applications.

Claims

1-10. (canceled)

11. A piston assembly for an engine, comprising: a cylinder bore body with an inner wall; a piston body; a first compression piston ring; a second compression piston ring; and an oil ring assembly; wherein, the first compression piston ring, the second compression piston ring and the oil ring assembly each contacts with the inner wall of the cylinder bore body; a top land, a first compression ring groove, a second land, a second compression ring groove, a third land, and an oil ring groove are disposed in turn on the periphery of the piston body from top to bottom; more than one annular expansion chamber is disposed between the second land and the inner wall of the cylinder bore body, and the more than one annular expansion chamber is defined by the region between more than one annular expansion groove disposed on the periphery of the second land and the inner wall of the cylinder bore body; so that a crevice passage with a multistage throttling and expansion is formed, which has a function of multistage throttling and expansion.

12. A piston assembly for an engine, the engine comprising: a cylinder bore body with an inner wall; a piston body; a first compression piston ring; a second compression piston ring; and an oil ring assembly; wherein, the first compression piston ring, the second compression piston ring and the oil ring assembly each contacts with the inner wall of the cylinder bore body; a top land, a first compression ring groove, a second land, a second compression ring groove, a third land, and an oil ring groove are disposed in turn on the periphery of the piston body from top to bottom; at least one annular expansion chamber is disposed between the second land and the inner wall of the cylinder bore body, the at least one annular expansion chamber is defined by the region between at least one annular expansion groove disposed on the periphery of the second land and the inner wall of the cylinder bore body, and at least one annular expansion chamber is also disposed between the third land and the inner wall of the cylinder bore body, and the at least one annular expansion chamber is defined by the region between the at least one annular expansion groove disposed on the periphery of the third land and the inner wall of the cylinder bore body; so that a crevice passage with a multistage throttling and expansion is formed, which has a function of multistage throttling and expansion.

13. A piston assembly for an engine, the engine comprising: a cylinder bore body with an inner wall; a piston body; a first compression piston ring; a second compression piston ring; and an oil ring assembly; wherein, the first compression piston ring, the second compression piston ring and the oil ring assembly each contacts with the inner wall of the cylinder bore body; a top land, a first compression ring groove, a second land, a second compression ring groove, a third land, and an oil ring groove are disposed in turn on the periphery of the piston body from top to bottom; at least one annular expansion chamber is disposed between the third land and the inner wall of the cylinder bore body, and the at least one annular expansion chamber is defined by the region between the at least one annular expansion groove disposed on the periphery of the third land and the inner wall of the cylinder bore body; so that a crevice passage with a multistage throttling and expansion is formed, which has a function of multistage throttling and expansion.

14. The piston assembly of claim 11, wherein one of the annular expansion chambers is disposed in a crevice region between the second compression piston ring and the second compression ring groove, so that a crevice passage with a multistage throttling and expansion is formed, which has a function of multistage throttling and expansion.

15. The piston assembly of claim 14, wherein the depth of the second compression ring groove is greater than the radial thickness of the second compression piston ring, and a ratio of the radial thickness of the second compression piston ring to the depth of the second compression ring groove is 0.66 to 0.69.

16. The piston assembly of claim 11, wherein the first compression piston ring and the second compression piston ring have equal or unequal radial thicknesses, and a ratio of the radial thickness of the first compression piston ring to the radial thickness of the second compression piston ring is 0.8 to 0.9.

17. The piston assembly of claim 11, wherein the first compression piston ring and the second compression piston ring have equal or unequal axial thicknesses, and a ratio of the axial thickness of the first compression piston ring to the axial thickness of the second compression piston ring is 0.6 to 1.0.

18. The piston assembly of claim 11, wherein there is a difference in the ring gap size between the first compression piston ring and the second compression piston ring, and a ratio of the ring gap of the first compression piston ring to the ring gap of the second compression piston ring is 0.28 to 0.55.

19. The piston assembly of claim 12, wherein, one of the annular expansion chambers is disposed in a crevice region between the second compression piston ring and the second compression ring groove, so that a crevice passage with a multistage throttling and expansion is formed, which has a function of multistage throttling and expansion.

20. The piston assembly of claim 19, wherein, a fourth expansion chamber is defined by the crevice region between the oil ring groove and the oil ring assembly; the depth of the oil ring groove is greater than the radial thickness of the oil ring assembly; and a ratio of the radial thickness of the oil ring assembly to the depth of the oil ring groove is 0.66 to 0.69; so that a crevice passage with a multistage throttling and expansion is formed, which has a function of multistage throttling and expansion.

21. The piston assembly of claim 19, wherein the depth of the second compression ring groove is greater than the radial thickness of the second compression piston ring, and a ratio of the radial thickness of the second compression piston ring to the depth of the second compression ring groove is 0.66 to 0.69.

22. The piston assembly of claim 19, wherein the first compression piston ring and the second compression piston ring have equal or unequal radial thicknesses, and a ratio of the radial thickness of the first compression piston ring to the radial thickness of the second compression piston ring is 0.8 to 0.9.

23. The piston assembly of claim 12, wherein the first compression piston ring and the second compression piston ring have equal or unequal axial thicknesses, and a ratio of the axial thickness of the first compression piston ring to the axial thickness of the second compression piston ring is 0.6 to 1.0.

24. The piston assembly of claim 12, wherein there is a difference in the ring gap size between the first compression piston ring and the second compression piston ring, and a ratio of the ring gap of the first compression piston ring to the ring gap of the second compression piston ring is 0.28 to 0.55.

25. The piston assembly of claim 13, wherein one of the annular expansion chambers is disposed in a crevice region between the second compression piston ring and the second compression ring groove, so that a crevice passage with a multistage throttling and expansion is formed, which has a function of multistage throttling and expansion.

26. The piston assembly of claim 25, wherein the depth of the second compression ring groove is greater than the radial thickness of the second compression piston ring, and a ratio of the radial thickness of the second compression piston ring to the depth of the second compression ring groove is 0.66 to 0.69.

27. The piston assembly of claim 13, wherein the first compression piston ring and the second compression piston ring have equal or unequal radial thicknesses, and a ratio of the radial thickness of the first compression piston ring to the radial thickness of the second compression piston ring is 0.8 to 0.9.

28. The piston assembly of claim 13, wherein the first compression piston ring and the second compression piston ring have equal or unequal axial thicknesses, and a ratio of the axial thickness of the first compression piston ring to the axial thickness of the second compression piston ring is 0.6 to 1.0.

29. The piston assembly of claim 13, wherein there is a difference in the ring gap size between the first compression piston ring and the second compression piston ring, and a ratio of the ring gap of the first compression piston ring to the ring gap of the second compression piston ring is 0.28 to 0.55.

30. The piston assembly of claim 25, wherein, an expansion chamber is defined by the crevice region between the oil ring groove and the oil ring assembly; the depth of the oil ring groove is greater than the radial thickness of the oil ring assembly; and a ratio of the radial thickness of the oil ring assembly to the depth of the oil ring groove is 0.66 to 0.69; so that a crevice passage with a multistage throttling and expansion is formed, which has a function of multistage throttling and expansion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] To describe the technical solutions in the embodiments of the present invention more clearly, the accompanying drawings to be used in the description of the embodiments will be briefly described below. Apparently, the accompanying drawings described hereinafter are some of the embodiments of the present invention, and a skilled person in the art can acquire other drawings according to these drawings without any creative effort, in which:

[0017] FIG. 1 is a sectional view of a engine piston assembly according to an embodiment of the present invention;

[0018] FIG. 2 is a sectional view of a piston body of FIG. 1;

[0019] FIG. 3 is a partially enlarged sectional view of the ring gap of a first compression piston ring of FIG. 1;

[0020] FIG. 4 is a partially enlarged sectional view of the ring gap of a second compression piston ring of FIG. 1; and

[0021] FIG. 5 is a sectional view of a engine piston assembly according to another embodiment of the present invention,

[0022] in which: [0023] 1: cylinder bore body; [0024] 2: piston body; [0025] 3: first compression piston ring; [0026] 4: second compression piston ring; [0027] 5: oil ring assembly; [0028] 201: top land; [0029] 202: first compression ring groove; [0030] 203: second land; [0031] 204: second compression ring groove; [0032] 205: third land; [0033] 206: oil ring groove; [0034] 207: piston skirt; [0035] 208: first annular expansion groove; [0036] 209: second annular expansion groove; [0037] 301: ring gap of the first compression piston ring; and [0038] 401: ring gap of the second compression piston ring.

DETAILED DESCRIPTION OF THE INVENTION

[0039] To enable a further understanding of the present invention content of the invention herein, refer to the detailed description of the invention and the accompanying drawings below. Apparently, the embodiments described herein are a part of but not all of the embodiments of the present invention. All other embodiments obtained based on the embodiments in the present invention by one person of ordinary skill in the art without any creative effort shall fall into the protection scope of the present invention.

[0040] FIGS. 1-2 show a preferred embodiment of the present invention.

[0041] An engine piston assembly, comprises a cylinder bore body 1 with an inner wall, a piston body 2, a first compression piston ring 3, a second compression piston ring 4 and an oil ring assembly 5; the first compression piston ring 3, the second compression piston ring 4 and the oil ring assembly 5 each contacts with the inner wall of the cylinder bore body 1; a top land 201, a first compression ring groove 202, a second land 203, a second compression ring groove 204, a third land 205, an oil ring groove 206 and a piston skirt 207 are disposed in turn on the periphery of the piston body 2 from top to bottom; the first compression ring groove 202 and the second compression ring groove 204 have unequal depths, and a ratio of the depth of the first compression ring groove 202 to the depth of the second compression ring groove 204 is less than 1.0; a first annular expansion groove 208 is formed on the periphery of the second land 203, and a first annular expansion chamber is defined by the region between the first annular expansion groove 208 and the inner wall of the cylinder bore body 1; the first compression piston ring 3 and the second compression piston ring 4 have unequal radial thicknesses, and a ratio of the radial thickness of the first compression piston ring 3 to the radial thickness of the second compression piston ring 4 is less than 1.0; the depth of the second compression ring groove 204 is greater than the radial thickness of the second compression piston ring 4; and a second expansion chamber is defined by the crevice region between the second compression ring groove 204 and the second compression piston ring 4.

[0042] As described above, an angle formed by intersecting the surface of the second land 203 with the first compression ring groove 202 or the second compression ring groove 204 has a small chamfer.

[0043] Wherein, the first expansion chamber is arranged between the second land 203 and the inner wall of the cylinder bore body 1, and the first annular expansion groove 208 is located in the middle of the second land 203. An upper corner angle and a lower corner angle, which are formed by the surface of intersecting the first annular expansion groove 208 with the outer circumferential face of the second land 203, are kept sharp, without any chamfer or fillet.

[0044] Further, a ratio of the radial thickness of the second compression piston ring 4 to the depth of the second compression ring groove 204 is less than 1.0, preferably 0.66 to 0.69.

[0045] Still further, the first compression piston ring 3 and the second compression piston ring 4 have unequal radial thicknesses, and a ratio of the radial thickness of the first compression piston ring 3 to the radial thickness of the second compression piston ring 4 is less than 1.0, preferably 0.8 to 0.9; and the first compression piston ring 3 and the second compression piston ring 4 have equal or unequal axial thicknesses, and a ratio of the axial thickness of the first compression piston ring 3 to the axial thickness of the second compression piston ring 4 is less than or equal to 1.0, preferably 0.6 to 1.0.

[0046] As shown in FIG. 3-4, there is a difference in the ring gap size between the first compression piston ring 3 (301) and the second compression piston ring 4 (401), and a ratio of the ring gap 301 of the first compression piston ring 3 to the ring gap 401 of the second compression piston ring 4 is less than 1.0, preferably 0.28 to 0.55.

[0047] As shown in FIG. 5, in a case where an engine is running under a high cylinder pressure, the present invention further provides another engine piston assembly. The engine piston assembly comprises a cylinder bore body 1 with an inner wall, a piston body 2, a first compression piston ring 3, a second compression piston ring 4 and an oil ring assembly 5; the first compression piston ring 3, the second compression piston ring 4 and the oil ring assembly 5 each contacts with the inner wall of the cylinder bore body 1; a top land 201, a first compression ring groove 202, a second land 203, a second compression ring groove 204, a third land 205, an oil ring groove 206 and a piston skirt 207 are disposed in turn on the periphery of the piston body 2 from top to bottom; the first compression ring groove 202 and the second compression ring groove 204 have unequal depths, and a ratio of the depth of the first compression ring groove 202 to the depth of the second compression ring groove 204 is less than 1.0; a first annular expansion groove 208 is formed on the periphery of the second land 203, and a first annular expansion chamber is defined by the region between the first annular expansion groove 208 and the inner wall of the cylinder bore body 1; the first compression piston ring 3 and the second compression piston ring 4 have unequal radial thicknesses, and a ratio of the radial thickness of the first compression piston ring 3 to the radial thickness of the second compression piston ring 4 is less than 1.0; the depth of the second compression ring groove 204 is greater than the radial thickness of the second compression piston ring 4; a second expansion chamber is defined by the crevice region between the second compression ring groove 204 and the second compression piston ring 4; and a second annular expansion groove 209 is formed on the periphery of the third land 205, and a third expansion chamber is defined by the region between the second annular expansion groove 209 and the inner wall of the cylinder bore body 1, which is located in the middle of the third land 205.

[0048] In a case where an engine is running under a high cylinder pressure, the present invention further provides another engine piston assembly. The engine piston assembly comprises a cylinder bore body 1 with an inner wall, a piston body 2, a first compression piston ring 3, a second compression piston ring 4 and an oil ring assembly 5; the first compression piston ring 3, the second compression piston ring 4 and the oil ring assembly 5 each contacts with the inner wall of the cylinder bore body 1; a top land 201, a first compression ring groove 202, a second land 203, a second compression ring groove 204, a third land 205, an oil ring groove 206 and a piston skirt 207 are disposed in turn on the periphery of the piston body 2 from top to bottom; the first compression ring groove 202 and the second compression ring groove 204 have unequal depths, and a ratio of the depth of the first compression ring groove 202 to the depth of the second compression ring groove 204 is less than 1.0; a first annular expansion groove 208 is formed on the periphery of the second land 203, and a first annular expansion chamber is defined by the region between the first annular expansion groove 208 and the inner wall of the cylinder bore body 1; the first compression piston ring 3 and the second compression piston ring 4 have unequal radial thicknesses, and a ratio of the radial thickness of the first compression piston ring 3 to the radial thickness of the second compression piston ring 4 is less than 1.0; the depth of the second compression ring groove 204 is greater than the radial thickness of the second compression piston ring 4; a second expansion chamber is defined by the crevice region between the second compression ring groove 204 and the second compression piston ring 4; a second annular expansion groove 209 is formed on the periphery of the third land 205, and a third expansion chamber is defined by the region between the second annular expansion groove 209 and the inner wall of the cylinder bore body 1, which is located in the middle of the third land 205; a fourth expansion chamber (not shown) is defined by the crevice region between the oil ring groove 206 and the oil ring assembly 5; the depth of the oil ring groove 206 is greater than the radial thickness of the oil ring assembly 5; and a ratio of the radial thickness of the oil ring assembly 5 to the depth of the oil ring groove 206 is less than 1.0, preferably 0.66 to 0.69.

[0049] In the engine piston assembly of the present invention, from the combustion chamber to the crankcase, at least two stages of suddenly-converged throttling mechanism and suddenly-enlarged expansion mechanism for capturing the blow-by gas leakage are provided. Those mechanisms, together with the inner wall of the cylinder bore body 1, form a special crevice passage that has a function of multistage throttling and expansion. The crevice passage will generate high enough flow resistance and great energy dissipation effect in the compression, ignition and expansion processes of the fuel-air mixture of an engine cycle, and thus can effectively prevent the unburned high-pressure fuel-air mixture and the burned high-temperature and high-pressure gas from blow-by leaking out from the combustion chamber and the cylinder to the crankcase of the engine; and, in the exhaust process, the crevice passage can ensure that only few hydrocarbon emissions may escape from the crevices.

[0050] In conclusion, in the engine piston assembly of the present invention, a piston structure, together with a piston ring set and an inner wall of a cylinder bore body both matched to the piston structure, forms a crevice passage having at least one annular expansion chamber and also having a function of multistage throttling and expansion. The crevice passage will generate high enough flow resistance and great energy dissipation effect in the compression, ignition and expansion processes of the mixed fuel-air mixture of an engine cycle, and thus can effectively prevent the unburned high-pressure fuel-air mixture and the burned high-temperature and high-pressure gas from blow-by leaking out from the combustion chamber and the cylinder to the crankcase of the engine; and, in the exhaust process, the crevice passage can ensure that only few hydrocarbon emissions may escape from the crevices. The present engine piston assembly of the present invention can not only greatly and effectively reduce the intra-cylinder carbon deposition and the hydrocarbon emissions in the exhaust gas emissions of the engine, but also significantly improve the engine efficiency and the overall performance of the engine, so that the present invention is suitable for wide applications.

[0051] The protection scope of the present invention is not limited to each of embodiments described in this description. Any changes and replacements made on the basis of the scope of the present invention patent and of the description shall be included in the scope of the present invention patent.