Dynamic seal

Abstract

A dynamic seal has a surface adapted for dynamic sealing, at least the surface of the seal formed from an alloy having a composition, in weight percent, approximately: 0.22-0.26% C; 10.0-12.1% Ni; 1.40-3.10% Cr; 1.0-2.2% Mo; 12.0-16.0% Co; and balance Fe and impurities. A combustion seal of the above construction is also described. The combustion seal may be in the form of at least one of a piston ring for a reciprocating piston and an apex seal for a rotary piston.

Description

FIELD OF THE INVENTION

The presented invention is directed to devices, arrangements and associated methods for dynamic sealing.

BACKGROUND OF THE INVENTION

In the following discussion certain articles and methods will be described for background and introductory purposes. Nothing contained herein is to be construed as an “admission” of prior art. Applicant expressly reserves the right to demonstrate, where appropriate, that the articles and methods referenced herein do not constitute prior art under the applicable statutory provisions.

In multi-component systems technological advances in one area of the system are often limited, or even precluded, by the limitations of other components of the system. Multi-component systems comprising moving parts are one such example. Advances in such systems are often dependent upon the effectiveness of components that perform a sealing function. Such systems include, for example, combustion engines, pumps, and the like. Performance of such systems is often limited by the capabilities of the seals used therein.

Dynamic seals are often utilized under harsh operating conditions, and can be subjected to one or more of thermal loading, wear, and extreme mechanical loads and impacts. These conditions often cause seal failure, and resulting failure of the entire system or device. For example, it is reported that as early as 1924 Felix Wankel realized that sealing would be one of the biggest challenges in developing the rotary combustion engine. The development of diesel powered rotary engines, with their high operating temperatures, has been hindered by lack of adequate sealing technologies. Similarly, the implementation of alternative fuel technologies has been hampered by inadequate sealing solutions.

Material selection to satisfy a number of performance objectives represents a significant engineering problem. Existing seals utilize a number of different materials in an attempt to provide adequate performance, but to date these sealing materials have exhibited certain drawbacks and weaknesses.

One example is the use of cast iron provided with a hardened sliding or sealing surface. For instance, dynamic rotary piston apex seals formed from this material have not performed in an optimal manner under high temperatures and impact loads often experienced in rotary engine applications. These seals provide minimal self-lubricity and have failed under severe impact loads. Similarly constructed seals formed from a cast iron having a reduced hardness to improve ductility exhibit reduced toughness, resulting in accelerated and increased wear, and have not demonstrated the ability to handle cyclic impact loads in a reliable manner.

Another example is the use of silicon nitride ceramics to form rotary piston seals. While these materials exhibit an improved tolerance of high temperatures, these seals are relatively brittle making them susceptible to failures caused by high impact loads.

A number of other materials have been evaluated for performance under high thermal loading, high wear and severe mechanical loads and impacts, with less than optimal success. One such material is tungsten carbide. This material is very hard, resulting in excessive “break-in” periods, and damage to mating surfaces. This material also failed to perform as desired under high temperature oxygen rich environments.

Another material that has been evaluated is a cobalt-based refractory alloy (i.e., UNS R0016). This material, while exhibiting better overall toughness and ductility than cast iron, exhibited a longer break-in period. In addition, when utilized in a high-performance combustion environment, seals formed from this material exhibited wear that exceeded normal tolerances. These seals also appear to have left chatter marks on mating surfaces.

Seals formed from a super stainless steel (i.e., UNS S21800) exhibited break-in periods on par with cast iron seals, but again exhibited wear beyond normal tolerances in a high-performance combustion environment. In addition, at elevated temperatures (above approximately 1400° F.), seals formed from this material lost hardness and ability to resist wear. Coatings applied to such materials appear to improve wear performance, but not to an optimal level.

Another seal material comprises silicon carbide disposed in a carbon matrix. Seals formed from this material were coated on a wear surface thereof with silicon nitride (Si₃N₄) using a CVD process. These seals exhibited sporadic galling on mating surfaces and uneven wear.

In summary, the above-described sealing technologies lack one or more of the following desired sealing properties and characteristics:

• • Rapid break-in times;
  • Self-lubrication;
  • Resistance to high temperatures and thermal loading;
  • High wear resistance;
  • Wear properties compatible with mating surfaces; and
  • High resistance to impact loading and overall toughness.

SUMMARY OF THE INVENTION

According to the present invention there is provided a dynamic seal that provides unexpectedly superior sealing performance relative to conventional dynamic seals.

The present invention provides a dynamic seal and preferably a dynamic seal that exhibits at least one of rapid break-in times, self lubrication, resistance to high temperatures and thermal loading, high wear resistance, wear properties compatible with mating surfaces, and high resistance to impact loading and high overall toughness. According to one embodiment, a seal constructed according to the present invention exhibits a combination of the above-listed properties. According to a further embodiment, a seal constructed according to the principles of the present invention provides a combination of all of the above listed properties. According to another aspect of the present invention, a seal formed according to the present invention provides at least one, or a combination of some or all, of the above listed properties when utilized in a dynamic sealing environment under high friction, high temperatures and high mechanical loads and stresses. According to another aspect of the present invention, a seal formed according to the present invention provides at least one, or a combination of some or all, of the above listed properties when utilized in combustion sealing environment. According to another aspect of the present invention, a seal formed according to the present invention provides at least one, or a combination of some, or all, of the above listed properties when utilized as at least one of a piston ring for a reciprocating piston and as an apex seal for a rotary combustion engine piston.

According to one aspect of the present invention, there is provided a dynamic seal formed, at least in part, from an alloy comprising, consisting essentially of, or consisting of (in weight %) about: 0.22-0.26% C; 10.0-12.1% Ni; 1.40-3.10% Cr; 1.0-2.2% Mo; 12.0-16.0% Co; and balance Fe, with minor amounts of impurities normally associated with modern steel making processes. According to the present invention there is provided a combustion seal formed, at least in part, from an alloy comprising, consisting essentially of, or consisting of (in weight %) about: 0.22-0.26% C; 10.0-12.1% Ni; 1.40-3.10% Cr; 1.0-2.2% Mo; 12.0-16.0% Co; and balance Fe, with minor amounts of impurities normally associated with modern steel making processes. According to the present invention there is also provided an apex seal for a rotary combustion engine formed, at least in part, from an alloy comprising, consisting essentially of, or consisting of (in weight %) about: 0.22-0.26% C; 10.0-12.1% Ni; 1.40-3.10% Cr; 1.0-2.2% Mo; 12.0-16.0% Co; and balance Fe, with minor amounts of impurities normally associated with modern steel making processes. According to one embodiment of the present invention, at least the surface of the seal in dynamic contact with at least one mating sealing surface is formed from the above-described material. According to an alternative embodiment, the entire seal is formed from the above-described material.

According to the present invention all ranges identified herein are intended to include the identified end points. In addition, the terms “approximately” and “about” are intended to encompass minimal variation from the identified values, such as standard deviations associated with common measurement techniques utilized to quantify the content of such alloy constituents.

According to one aspect, the present invention provides an apex seal for a rotary piston comprising a surface adapted for dynamic sealing contact, at least the surface formed from an alloy having a composition comprising, in weight %, approximately: 0.22-0.26% C; 10.0-12.1% Ni; 1.40-3.10% Cr; 1.0-2.2% Mo; 12.0-16.0% Co; and balance Fe and impurities.

According to a further aspect, the present invention provides a method of improving combustion sealing, the method comprising: forming at least a surface of a seal adapted for dynamic sealing contact from an alloy having a composition comprising, in weight %, approximately: 0.22-0.26% C; 10.0-12.1% Ni; 1.40-3.10% Cr; 1.0-2.2% Mo; 12.0-16.0% Co; and balance Fe and impurities; and installing the seal at a location such that at least a portion of the seal is exposed to combustion.

According to yet another aspect, the present invention provides a dynamic seal comprising a surface adapted for dynamic sealing, at least the surface of the seal formed from an alloy having a composition comprising, in weight percent, approximately: 0.22-0.26% C; 10.0-12.1% Ni; 1.40-3.10% Cr; 1.0-2.2% Mo; 12.0-16.0% Co; and balance Fe and impurities.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments are illustrated in the drawings in which like reference numerals refer to the like elements and in which:

FIG. 1 is a sectional schematic illustration of a dynamic seal formed according to the principles of the present invention.

FIG. 2 is a sectional view of a combustion seal formed according to the principles of the present invention.

FIG. 3 is a partial perspective view of a portion of an arrangement illustrated in FIG. 2.

FIG. 4 is a cross sectional view of a combustion seal formed according to one embodiment of the present invention.

FIG. 5 is a cross sectional view taken along lead line 5-5 of FIG. 4.

FIG. 6 is a sectional view of a combustion seal formed according to an alternative embodiment of the present invention.

FIG. 7 is a perspective view of a portion of arrangement illustrated in FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

Devices, arrangements and their associated methods are structured to comprise one or more of the following characteristics.

The dynamic seal formed according to a first embodiment of the present invention is illustrated in FIG. 1. As illustrated in FIG. 1, a seal 10 is provided with at least one surface 12 adapted for dynamic sealing contact with a mating surface 14. According to the present invention, the seal 10 is not limited to the illustrated geometry. Numerous alternative geometries are contemplated by the present invention. In addition, the seal 10 may be provided with one or more surfaces adapted for dynamic seal contact which differ from that of the illustrated embodiment. As alluded to above, the mating surface and the dynamic seal 10 are relatively movable. This relative movement can take a number of forms. For example, the relative movement may be rotary, reciprocal, sliding, oscillating, and the like. According to a further optional aspect, at least a portion of the seal 10 is exposed to a combustion environment.

According to the present invention, at least the surface 12 of the seal 10 which is adapted for dynamic sealing contact is formed from an alloy having a composition which is described below. Thus according to the present invention, the seal 10 may be provided with a coating formed from the alloy. Alternatively, the seal 10 may be in the form of a composite, wherein a portion of the seal 10 is formed from the alloy, and the remaining portion of the seal 10 is formed from a different material. According to a further alternative, the entire seal 10 is formed from the alloy.

According to the present invention, the seal 10 is at least formed in part, from an alloy having a composition comprising, consisting essentially of, or consisting of (in weight %) approximately: 0.22-0.26% C; 10.0-12.1% Ni; 1.40-3.10% Cr; 1.0-2.2% Mo; 12.0-16.0% Co; and balance Fe, with minor amounts of impurities normally associated with modern steel making processes (e.g., sulphur, phosphorus, and silicon). According to an alternative embodiment, the alloy is formed from a composition comprising, consisting essentially of, or consisting of, in weight %, approximately: 0.023% C; 11.1% Ni; 3.10% Cr; 1.2% Mo; 13.0% Co; and balance Fe and normal amounts of impurities normally associated with modern steel making processes (e.g., sulphur, phosphorus, and silicon). According to a further alternative embodiment, the above described alloys may contain Fe amounts from (in weight %) 68.95%-72.37%.

According to the present invention, alloys of the above described composition may be subjected to a number of suitable heat treatments in order to impart beneficial properties thereto. For example, a dynamic seal 10 formed according to the principles of the present invention may be formulated from an alloy having any of the above described compositions, and alternatively, subjected to one or more of the following heat treatment processes: decarburization; normalizing (e.g., heating to 1650° F. and holding for one hour, followed by air cooling to room temperature); annealing (e.g., heating to 1250° F. for 16 hours); solution treatment (e.g., heating to 1625° F.+/−20° F. for 1 hour); quenching (e.g., cooling from the solution treatment to 150° F. in 1 to 2 hours); cold treatment (cooling from room temperature to −150° F., and holding for 1 hour); aging (heating to 900° F.+/−10° F. and holding for 5 hours). Alloys of the above type may be custom formulated. Alternatively, such alloys may be acquired from commercial sources. For example, the AerMet® 100 alloy, sold by Carpenter Specialty Alloys may be utilized to form the dynamic seal 10 of the present invention.

A suitable surface finish may also be applied to the dynamic seal 10 of the present invention, preferably to at least one surface 12 adapted for dynamic sealing contact. For example, a suitable surface finishing procedure may be utilized to provide at least one surface of a dynamic seal 10 with a surface roughness on the order of near 0-36 RMS, preferably 8-20 RMS. Suitable surface finish techniques including conventional ball end milling, wire EDM, grinding with a formed grinding wheel, polishing, etc.

According to an alternative embodiment of the present invention, the previously described dynamic seal 10 may be in the form of a combustion seal. In the following description, the combustion seal described herein may be provided with any features and/or characteristics previously described in connection with the dynamic seal 10 of the present invention.

According to a first, non-limiting example, a combustion seal formed according to the principles of the present invention is illustrated in FIG. 2. A rotary combustion engine 20 is illustrated in FIG. 2. The rotary combustion engine 20 generally comprises a housing 22 having an inner surface 24 defining a chamber. A rotary piston 26 is contained, and revolves within housing 22. One or more apex seals 28 are provided in the rotary piston 26, and form a dynamic seal along the inner surface 24 of the housing 22. Apex seals 28 also form a combustion seal during normal operation of the rotary combustion engine 20.

The various sealing components associated with the rotary piston 26 are illustrated in greater detail in FIG. 3. As illustrated therein, the rotary piston 26 is also provided with one or more corner seals 30, which are adapted to seal the juncture of an end plate (not shown) and housing 22. Similarly, a side seal 32 is provided along the perimeter of the rotary piston 26 for forming a seal with an opposing face of an end plate (not shown) typically provided in the rotary combustion assembly. An outer oil seal 34, and an inner oil seal 36 may also be provided on an end surface of the rotary piston 26, as illustrated in FIG. 3. A dynamic seal formed according to the principles of the present invention will be especially useful for sealing functions in rotary combustion engines, where extreme operating conditions may exist that promote failure of conventional seal designs. Dynamic seals of the present invention exhibited the ability to provide an effective and reliable seal in environments of the type described above, providing unexpectedly superior results when compared with conventional sealing technologies.

According to one embodiment of the present invention, an apex seal 28 for a rotary piston 26 is formed from an alloy having any of the previously described compositions, heat treatments, and surface finish properties. Such an apex seal 28 is illustrated, in greater detail, in FIGS. 4-5. As illustrated in FIG. 4, the apex seal 28 is generally in the form of a rectangular strip. The particular shape of the apex seal 28 can be similar to that of conventionally produced apex seals. The apex seal 28 is optionally formed with a separate corner piece 38. According to one embodiment, the separate comer piece 38 is also formed from the alloy having a composition, heat treatment, and surface finish properties, such as that previously described. According to a further embodiment, the corner piece 38 is formed from a material having a composition, heat treatment, or surface finish properties, which differ from that of the remainder of the body of the apex seal 28.

According to a further alternative embodiment, the apex seal 28 is split, horizontally, along the entire length thereof, not including the comer seal, thereby forming a 3-piece design (not shown). The cross sectional width 40 of the generally rectangular strip apex seal 28 is illustrated in FIG. 5. The apex seal 28 may be formed having any suitable width 40. For example, the cross sectional width 40 may be on the order of 2 mm-3 mm. However, it should be understood, that the apex seal 28 of the present invention is not limited to these widths.

According to a further, non-limiting example, a combustion seal formed according to the principles of the present invention is illustrated FIG. 6-7. According to this embodiment, a piston ring 66 is formed from an alloy having a composition, heat treatment, and/or surface finish properties of the type previously described. Illustrated in FIG. 6, a reciprocating piston engine 60 generally includes a combustion chamber defined by a cylinder wall 62 within which a reciprocating piston 64 travels. At least one piston ring 66 is mounted to the reciprocating piston 64, forming a dynamic seal along the cylinder wall 62. As illustrated in FIG. 7, the piston ring 66 comprises a generally annular shape, having a split end 68 in order to enable mounting over the piston 64.

It should be understood that a number of different seals may be formed according to the principles of the present invention. Mainly, a seal having a combination of the above described composition, heat treatments, and/or surface finishes may be beneficially utilized in a number of applications. Such applications include, for example, jet aircraft engines, marine engines, compressors, pumps, and the like. In general, principles of the present invention may be utilized to provide sealing solutions in environments in which high temperatures, poor lubrication, high friction, and/or high impact loading are present.

EXAMPLE

A plurality of apex seals were formed from an alloy composition comprising: 0.25% C; 1.40% Mo; 2.40% Cr; 15.0% Co; 11.0% Ni; and 69.95% Fe. The apex seals were installed into a rotary piston of a 6 poit 1986 Mazda Rx7 engine. The engine was operated to effect break-in of the seals. A total running time of 8-9 hours, and approximately 520 road miles, were used to accomplish this objective. Thus, the break-in time was comparable to original equipment manufacture (OEM) apex seals. The engine was being tested in a vehicle equipped with a nitrous oxide (NOS) injection system. The first test was then preformed under conditions in which the car was backfiring due to incorrectly set carburetor jets. Such backfiring or detonation conditions place extreme stress on apex seals in rotary combustion engines. Three runs were made in the above-described vehicles using 100 hp fuel NOS jets. All three runs were “unclean”, in other words backfiring or detonation occurred on each of the runs. After removing the engine, disassembling it, and examining the apex seals, the following observations were made. The apex seals were not fractured, distorted or bowed, and were not galled, beyond normal break-in wear. The rotor-housing surface was minimally affected by the seals. Mainly, a few very light gall marks appeared on the housing.

While this invention is satisfied by embodiments in many different forms, as described in detail in connection with preferred embodiments of the invention, it is understood that the present disclosure is to be considered as exemplary of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated and described herein. Numerous variations may be made by persons skilled in the art without departure from the spirit of the invention. The scope of the invention will be measured by the appended claims and their equivalents. The abstract and the title are not to be construed as limiting the scope of the present invention, as their purpose is to enable the appropriate authorities, as well as the general public, to quickly determine the general nature of the invention. In the claims that follow, unless the term “means” is used, none of the features or elements recited therein should be construed as means-plus-function limitations pursuant to 35 U.S.C. §112, ¶6.

Claims

1. An apex seal for a rotary piston comprising a surface adapted for dynamic sealing contact, at least the surface formed from an alloy having a composition comprising, in weight %, approximately: 0.22-0.26% C; 10.0-12.1% Ni; 1.40-3.10% Cr; 1.0-2.2% Mo; 12.0-16.0% Co; and balance Fe and impurities.

2. The seal of claim 1, wherein the seal is formed entirely of the alloy.

3. The seal of claim 1, wherein the surface is provided with a finish resulting in a surface roughness of near 0-36 RMS.

4. The seal of claim 1, comprising a substantially rectangular shaped strip.

5. The seal of claim 1, comprising a separate corner piece.

6. The seal of claim 1, comprising a cross-sectional width of about 2 mm.

7. The seal of claim 1 comprising a cross-sectional width of about 3 mm.

8. The seal of claim 1, wherein the composition comprises, in weight %, approximately: 0.23% C; 11.1% Ni; 3.10% Cr; 1.2% Mo; 13.0% Co; and balance Fe and impurities.

9. A method of improving combustion sealing, the method comprising: forming at least a surface of a seal adapted for dynamic sealing from an alloy having a composition comprising, in weight %, approximately: 0.22-0.26% C; 10.0-12.1% Ni; 1.40-3.10% Cr; 1.0-2.2% Mo; 12.0-16.0% Co; and balance Fe and impurities; and installing the seal at a location such that at least a portion of the seal is exposed to combustion.

10. The method of claim 9, further comprising forming the seal entirely from the alloy.

11. The method of claim 9, further comprising providing the surface with a finish resulting in a surface roughness of near 0-36 RMS.

12. The method of claim 9, wherein the seal is formed as a substantially rectangular strip, and is installed at an apex of a rotary piston of a rotary combustion engine.

13. The method of claim 12, wherein the seal is formed with a separate corner piece.

14. The method of claim 9, wherein the composition comprises, in weight percent, approximately: 0.23% C; 11.1% Ni; 3.10% Cr; 1.2% Mo; 13.0% Co; and balance Fe and impurities.

15. A dynamic seal comprising a surface adapted for dynamic sealing, at least the surface of the seal formed from an alloy having a composition comprising, in weight percent, approximately: 0.22-0.26% C; 10.0-12.1% Ni; 1.40-3.10% Cr; 1.0-2.2% Mo; 12.0-16.0% Co; and balance Fe and impurities.

16. The seal of claim 15, wherein the seal is formed entirely of the alloy.

17. The seal of claim 15, wherein the surface is provided with a surface finish resulting in a surface roughness of near 0-36 RMS.

18. The seal of claim 15, wherein the seal comprises a combustion seal.

19. The seal of claim 18, wherein the combustion seal comprises at least one of a piston ring for a reciprocating piston and an apex seal for a rotary piston.

20. The seal of claim 15, wherein the composition comprises, in weight percent, approximately: 0.023% C; 11.1% Ni; 3.10% Cr; 1.2% Mo; 13.0% Co; and balance Fe and impurities.