WO1998016763A1

WO1998016763A1 - Gap-sealed piston ring

Info

Publication number: WO1998016763A1
Application number: PCT/US1997/018553
Authority: WO
Inventors: Dunhua Gao
Original assignee: Dunhua Gao
Priority date: 1996-10-14
Filing date: 1997-09-29
Publication date: 1998-04-23
Also published as: AU4902997A

Abstract

A one-piece piston ring (10) with fully sealed gap joint (24), having a pair of overlapping, slidable, and tapered ends (30, 32), separated by an axially parallel line (25) extended along a long arc (24). The arc starts from and forms a sharp angle with respect to the outer circumferential surface (22), and ends at the inner circumferential surface (20). Under the constraint of cylinder wall and by the resilience of the ring, the mutally contacting ends form a sealed joint which is pressed to close further by pressurized fluid and prevent the fluid from leaking. The enhanced seal efficiency and the build-in wear compensation allow multiple conventional compression rings in a piston to be replaced with single gap-sealed piston ring.

Description

GAP-SEALED PISTON RING

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to piston rings, particularly to a one-piece piston ring with a fully sealed gap joint to prevent fluids from leaking to the low pressure side.

2. Background Information

Piston rings are used in separating the low pressure and the high pressure compartment in internal combustion engines, fluid pumps, and other reciprocating mechanism that generates differentiated pressures. A conventional piston ring comprises a resilient C-shape element with spaced ends in the resting state. When such a ring is slipped over a piston and fitted into the piston ring groove, the circumferentially opposite ends move toward each other and form a gap joint with sufficient clearance allowing for thermal expansion. This gap joint, however, also permits undesirable leakage of pressurized fluid to the low pressure side. Leakage through the gap joint and other surfaces of a piston ring is generally referred as blow-by which reduces compression efficiency, leading to a lower fuel efficiency, a lower power output, a higher exhaust emission, and being harder to start in internal combustion engines. After significant wear, the resilient piston ring extends in circumference to fit the abraded cylinder wall with an enlarged gap which exacerbates the above problems.

To achieve the seal that yields the desirable compression ratio, two or more compression rings are often needed to install on a piston. Each supplementary ring adds more friction between the ring and the cylinder wall, which in turn increases the power dissipation. Multiple compression ring structure also increases the size and the weight of the piston head and does so to the entire engine as well.

In order to overcome the above problems, the prior art has proposed various designs aiming to seal the gap joint and eliminate the leakage. One types of proposals employed multiple member structure to seal the gap, including U.S. Pat. NO. 4,192,051 to Alfred Bergeron and U.S. Pat. NO. 5,618,048 to Maurice J. Moriarty. Another types of proposals described one-piece structure to partially or completely seal the gap joint. U.S. Pat. NO. 4,189,161 to Raymood L. Grimm and U.S. Pat. NO. 4,713,867 to Duke Fox disclosed piston rings defined by circumferential projections extended in opposite relationship from the ends of a parted annular member. Each projection defines an angled sealing surface contacting with that of the opposite end when the projections are overlapped in compressed state. U.S. Pat. NO. 4,449,721 to Kaxuo Tsuge improved this types of designs by providing resilient curved lips slidable along the seal surfaces on the axially overlapping stepping ends.

Whatever the precise merits, features and advantages of the above cited references, none of these prior arts have been widely adopted and manufactured in large scale, partially because that they are incomplete in sealing the gap joint, difficult to manufacture with low cost, fragile mechanically, or poor in wear resistance. None of these prior arts achieved or fulfills the following objects of the one-piece piston ring with a fully sealed gap joint in the present invention.

Accordingly, it is the principle object of the present invention to attain a fully sealed gap joint with such a low leakage so that not only above mentioned problems can be solved but also the number of the conventional compression rings, commonly 2-3, in a piston of an internal combustion engine can be comfortably replaced by one invented ring, yet such a one-compression ring engine achieves a better seal efficiency and a lower friction power dissipation.

Another principle object of this invention is to provide a design of a piston ring which can be manufactured with a relatively simple process in comparison with other seal-improved piston rings in prior arts, or even simpler than that of making the conventional piston rings. A further object of this invention is to provide a design of a piston ring that is able to adapt to extensive wears on both piston ring and cylinder wall without degradation in seal efficiency, thereby extending the engine life.

SUMMARY OF THE INVENTION

The above and other objects are achieved in a one-piece annular element having a pair of overlapping, relatively slidable, and tapered ends, separated by an axially parallel cut line extended along a long arc which is parallel to the upper or the lower surface of the ring. The long arc starts from and forms a sharp angle α with respect to the outer circumferential surface where α < 16°, and ends at the inner circumferential surface. The average length of the arc, equivalent to the length of two overlapping ends, is represented by a center angle θ > 0.6 (radian). Under the constraint of cylinder wall and by the resilience of the ring, the mutually contacting ends form a sealed gap joint which is forced to adjoin further by pressurized fluid and prevent the fluid from leaking to the low pressure compartment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an installed one-piece gap-sealed piston ring in accordance with the present invention.

FIG. 2 is a top plan view of the installed gap-sealed piston ring, illustrating the geometrical relationship of the long arc.

FIG. 3 is an enlarged fragmentally horizontal sectional view taken along the piston ring groove of a typical reciprocating mechanism, which includes a part of the installed piston ring, the piston, and the cylinder wall.

FIG. 4 is an enlarged partial vertical sectional view, taken along the line 4-4 in FIG.

3.

DETAILED DESCRIPTION OF THE PREFERED EMBODYMENTS

Referring the drawings, wherein referencing numerals in each figure represent the same element. The preferred embodiment of the one-piece gap- sealed piston ring in accordance with the present invention is illustrated in FIG. 1. The piston ring 10 is a one-piece annular member 12 concentric to a reference axis 14. This annular member 12 is defined by an upper surface 16, a lower surfacelδ, an inner circumferential surface 20, and an outer circumferential surface 22.

To allow a piston ring to be slipped over a piston head and fit into a piston ring groove, a ring must be extendible to a slightly larger diameter. For a ring made with hard enough material, at least one cut has to be made to open the ring. In the present invention, this is accomplished preferably by an axially parallel cut line 25 extended smoothly along a long arc 24 which is parallel to the upper surface 16 or the lower surface 18. The long arc 24 starts from the outer circumferential surface 22 and ends at the inner circumferential surface 20.

Two overlapping and tapered ends including the outer end 30 on the circumferentially outer side and the inner end 32 on the circumferential inner side, are separated by the cut line 25 extended along the long arc 24. It should be noted that the ring 10 is made of resilient material preferably steel or other metals, so that when the ring 10 is in the resting state, the two ends 30 and 32 remain mutually contact and slidable to allow the ring 10 extends to a relax state. Alternatively in the resting state, there may be an open clearance between two ends 30 and 32. Throughout the illustrations in this disclosure, the ring 10 is displayed in the installed or working state, in which the two ends 30 and 32 remain mutually contacted and slidable along the arc 24 under different conditions.

FIG. 2 illustrates a more detailed geometrical relations of the long arc 24 which forms a sharp angle α with respect to the outer circumferential surface 22. Theoretically, the smaller this angle is, the perfect annular outer circumferential surface it can maintain in order to seal the interface between piston ring and cylinder wall. Constrained by the strength of the material chosen for ring constructions and operation parameters, the preferred angle α is chosen to be less than 16°. After extensive experimentation, the sharp angle has been optimized in the range of 3° < α < 10°. The length of the overlapping ends equivalent to the average length of the long arc is represented by a central angle θ which is largely determined by the dimensions of the ring, the choice of α, and the working environment. In the optimized range of α, θ is generally larger than 0.6 (radian).

FIG. 3 shows the piston ring 10 placed in the piston ring groove 36 in a piston 38, where the outer circumferential surface 22 is in contact with the cylinder wall 34. The 4 - 4 section of FIG. 3 is illustrated in FIG. 4. After the piston ring 10 is installed, the resilient member 12 presses the outer circumferential surface 22 against cylinder wall 34, providing an initial seal. During the compression stroke, the pressurized fluid 40 applies a radial force further pressing the ring 10 against the cylinder wall 34, resulting a tighter seal. The same medium 40 also exerts an axial force to the ring 10, sealing the interface of the lower ring surface 18 and the lower piston ring groove surface 36. The critical element of this invention is the seal of the joint 24. Two mutually contacting ends 30, 32 relatively slide to completely seal the joint without retaining any gap in all working conditions.

The seal efficiency of the invented ring 10 has been tested in the internal combustion engines. When two conventional compression rings on a piston in the engine are replaced with just one invented ring, the cylinder pressure increased 10- 15% over the control; And the fuel consumption, friction dissipation, and local over heating are all reduced. Therefore, multiple conventional compression rings on a piston can now be comfortably reduced to one invented ring, yet providing an enhanced engine performance. In addition, since the friction induced power dissipation by piston rings accounts for about 40% of the total power dissipation in a typical internal combustion engine, one-compression ring engine can significantly reduce the total power dissipation. Furthermore, such a one-compression ring engine is relatively easy to start.

The simple structure of ring 10 allows multiple ring stacking, preferably two, installed in a piston ring groove. The stacking configuration further improves the seal efficiency and further reduces the friction dissipation due to less pressure applied to the cylinder wall 34 as a result of less resilient force exerted by each thin ring. As the piston ring 10 and cylinder wall wear, the resilient member 12 will gradually extend to compensate the lost part with a consequent smaller center angle θ. The gap-joint seal and the seal between the circumferential surface of the ring and cylinder wall remain effective.

Claims

What is claimed is:

1. A piston ring comprising a one-piece annular member having axially opposing upper and lower surfaces, radially opposing inner and outer circumferential surfaces, and a pair of overlapping, tapered, and mutually slidable ends which specifically comprise a circumferential ly outer end and a circumferentially inner end, said ends having mutual contact surfaces when installed in a piston ring groove, said contact surfaces being maintained by resilience of said annular member and by the constraint of the cylinder wall, said contact surfaces being separated by an axially parallel cut line extended smoothly from said outer circumferential surface to said inner circumferential surface following a long arc parallel to said upper and lower surfaces, said long arc forming a sharp angle α with respect to said outer circumferential surface where α < 16°, whereby said contact surfaces form a sealed joint pressed radially by pressurized fluid to adjoin further and prevent the fluid from leaking.

2. A piston ring as defined in claim 1 wherein said sharp angle α is optimized in the range of 3° < α < 10°.

3. A piston ring as defined in claim 1 wherein the average length of said long arc represented by central angle θ is optimized in the range of θ > 0.6 (radian) depending on the selection of said sharp angle α and other geometrical and working parameters of the ring.

4. A piston ring as defined in claim 1 wherein said overlapping and slidable ends remains intimately contacted and sealed through circumferentially extending the resilient ring, in response to wears of the cylinder wall and said outer circumferential surface of the ring.

5. A piston ring comprising a plurality of stacked rings defined in claim 1 , whereby the fluid leakage is further reduced and the friction power dissipation by the ring and the cylinder wall is reduced.

6. A method for using one piston ring defined in claim 1 to replace a plurality of conventional compression rings on a piston to reduce said friction power dissipation and to reduce the size and weight of a structure containing the reciprocal mechanism.