US3318515A

US3318515A - Wear resistant construction for rotary mechanisms

Info

Publication number: US3318515A
Application number: US461632A
Authority: US
Inventors: Jones Charles
Original assignee: Curtiss Wright Corp
Current assignee: John Deere Technologies International Inc
Priority date: 1965-06-07
Filing date: 1965-06-07
Publication date: 1967-05-09
Anticipated expiration: 1984-05-09

Description

May 9, 1967 c. JONES 3,318,515

WEAR RESISTANT CONSTRUCTION FOR ROTARY MECHANISMS Filed June 7, 1965 2 Sheets-Sheet 1 I NVENTOR.

EHARLEEI AGNES ATTEIRNEY C. JONES May 9, 1967 WEAR RESISTANT CONSTRUCTION FOR ROTARY MECHANISMS 2 Sheets-Sheet 2 Filed June 7, 1965 INVENTOR EHARLEE JBNEE ATTDHNEY' United States Patent 3,318,515 WEAR RESISTANT CONSTRUCTION FOR ROTARY MECHANISMS Charles Jones, Paramus, NJ., assignor to Curtiss-Wright Corporation, a corporation of Delaware Filed June 7, 1965, Ser. No. 461,632 7 Claims. (Cl. 230 23s This invention relates to rotary mechanisms and is :particularly directed to a wear resistant construction for the sealing surfaces of said mechanisms. Although the invention will be described in relation to rotary com bustion engines, it should be understood however, that the invention is equally applicable to other rotary mechanisms such as fluid motors and compressors.

Engines of the type described herein generally comprise an outer body having axially-spaced end walls interconnected with a peripheral wall to form a cavity therebetween and an inner body or rotor is received within said cavity between the cavity end walls. The inner surface of said peripheral wall preferably is parallel to the axis of said cavity and, as viewed in a plane transverse to said axis, said inner surface has a multi-lobed profile which preferably is an epitrochoid. The axis of said rotor is parallel to but spaced from the, axis of .the outer body cavity and said rotor has axially-spaced end faces disposed adjacent said outer body end walls and also has a plurality of circumferentially-spaced apex portions. The rotor is rotatable relative to the outer body and said apex portions continuously engage the-inner surface of said peripheral wall to form a plurality of working chambers between said rotor and said peripheral wall which vary in volume, during engine operation, as a result of relative rotation of said rotor and said outer body. A seal member is carried by each apex portion of the rotor for maintaining sealing contact between the rotor and the inner surface of the peripheral wall. Such engines also include an intake port for admitting a fuel-air mixture to said chambers, an exhaust port for said chambers and suitable ignition means such that, during operation of the engine, the working chambers of the engine each have a cycle operation which includes the four phases of intake, compression, expansion and exhaust. Preferably, the outer body is stationary while the rotor or inner body rotates relative to said outer body although other arrangements are possible such as both the inner and outer bodies rotating relative to one another.

During engine operation, the seal means carried by the rotor are in constant relative rubbing engagement with the inner surfaces of the peripheral wall and end walls. As will be apparent, the constant relative rubbing engagement between the seal members and the inner surface of the peripheral wall can result in serious wearing problems of these elements and can ultimately terminate the useful life of the engine. One common solution to the wear problem has been to provide a liner of a wear resistant material on the inner surface of the peripheral wall to increase the wear life of this surface. As explained in the prior Patent No. 3,155,313, issued on November 3, 1964 to the same assignee as the present application, the solution applied to reciprocating piston engines for solving such problems do not always satisfacton'ly apply to rotary combustion engines, particularly when using lightweight alloy materials as the base materials for the outer body. Due to the contact loading of the apex seals, the nonuniform heat dissipation, and gas loading characteristics of rotary comb-ustion engines, providing a wear resistant construction including a liner for the wearing surface of the peripheral Wall cannot be readily accomplished through the solutions found in the prior art since the prior art type liners tend to separate from the housing base material and do not provide satisfactory wearing characteristics. The above mentioned patent is drawn to an improvement in liners for rotary combustion engines which in itself was a significant advance over prior art type liners. The present invention is drawn to a further improvement in liners for the wearing surfaces of rotary combustion engines which is relatively more simple in construction than the above mentioned patent and has been found to have a greater wear life or less rate of wear than the construction shown in the above mentioned patent. The present invention is generally carried out by providing on the inner surface of a lightweight alloy peripheral wall a single relatively thin layer of a carbide composition material which is preferably flame sprayed onto said inner surface. The flame spraying technique of the carbide composition on the inner surface of the peripheral wall is carried out at substantially high temperatures and has been found to provide excellent bonding characteristics with the base material of the lightweight alloy peripheral wall thus eliminating the problems of separation of the layer from the base material. As will be explained hereinafter, the use of particular material compositions for the seal members of the engine in combination with the carbide composition layer on the peripheral wall has resulted in a substantial increase in the wear life of the sealing surfaces of the engine which therefore results in an extension of the useful life of the engine before which the engine must be torn down and rebuilt.

Accordingly it is one object of the invention to provide a novel and improved construction for increasing the Wear life of the sealing surfaces of a rotary mechanism.

It is another object of the invention to provide a novel and improved construction for the sealing surfaces of a rotary combustion engine which is relatively simple in construction.

It is a further object of the invention to provide a novel and improved liner construction for a rotary combustion engine.

It is an additional object of the invention to provide a novel and improved liner construction for the inner surface of a lightweight alloy housing in a rotary combustion engine which liner has good bonding characteristics with said inner surface and is relatively simple in construction.

It is still a further object of the invention to provide a novel and improved liner construction for a lightweight alloy housing in a rotary combustion engine which provides for increased life of said inner surface over that of prior constructions for said housings.

It is still another object of the invention to provide a wear resistant construction for the sealing surfaces of a rotary combustion engine including a hard wear resistant liner securely bonded to the inner surfaces of the rotor housing of said engine and including seal members composed of an alloy material whose major constituent is iron.

It is still a further object of the invention to provide a flame sprayed carbide composition liner for the inner surface of the outer body of a rotary combustion engine.

Other objects and advantages of the invention will be best understood upon reading the following detailed description with the accompanying drawings in:

FIG. 1 is a sectional view of a rotary combustion engine embodying the present invention, and

FIG. 2 is a sectional view taken along line 22 of FIG. 1.

Referring to FIGS. 1 and 2 of the drawings, a rotary combustion engine generally designated at 10 as shown therein comprises an outer body formed by a peripheral wall 12 interconnecting with

end walls

14 and 16 to form a cavity. As viewed in FIG. 2, the contour of the inner surface of the peripheral wall 12 has a multi-lobe profile which preferably is'basically a two-lobed epitrochoid. A shaft 18 is supported for rotation within the outer body by suitable bearings 20 which shaft 18 has an eccentric portion 22 formed thereon. A rotor 24 is supported for rotation on the eccentric portion 22 by a suitable bearing 26 and said rotor has a plurality of circumferentially-spaced apex portions which are disposed for sealing engagement with the inner surface of the peripheral wall 12. An apex seal strip 28 is disposed in. a groove in each of the rotor apex portions for radial movement relative to the rotor and the outer body for maintaining sealing engagement with the inner surface of said peripheral wall 12. The rotor 24 shown in FIG. 2' has three lobes joined together to form three apex portions of the rotor. It is of course to be understood that the invention is not limited to a two-lobed cavity and a rotor having three apex portions and it is intended that other combinations may be used, for example, a threelobed cavity with a rotor having four apex portions.

Side face seals 30 are provided within each of the side faces of the rotor for sealing engagement with the inner surfaces of the

end housings

14 and 16, respectively, which side face seals 30 mate with intermediate seal bodies 32 which also aid in supporting the apex seal strips 28 in each of the apex portions. The apex seal strips 28, the side face seals and the intermediate seal body 32 form a V continuous seal for each of the working chambers 34 defined between the rotor and the inner surface of the peripheral Wall 12. As the rotor and outer body rotate 7 relative to one another, the working chambers 34 vary in volume.

An internally toothed gear 36 is mounted on the rotor and is in meshing engagement With an externally-toothed gear 38 for aiding the rotor in tracing its epitrochoidal path. An intake port 40 is provided in the peripheral wall 12 for admitting air or a fuel-air mixture in order to 1 supply the combustiou zone of the engine. An exhaust port 42 is provided in a region adjacent to the intake port 40 for expelling the burnt gases from the engine and an ignition means 44 is provided in still another region of the outer body for ignition of the fuel-air mixture, which may be eliminated if the engine is run on a diesel cycle. It will be apparent that during rotation of the rotor 24 relative to the outer body 12 that the stages of intake, compression, expansion and exhaust may be carried out. Axially-spaced cooling fins 46 are provided on the region of the outer body wherein the greatest heat is generated that being in the portion between the ignition means 44 and the exhaust port 42 in the direction of rotor rotation. Structural reinforcing ribs 38 are provided in the region of the outer body between the intake port and the ignition means 44 which reinforcing ribs aid in maintaining the peripheral wall rigid during engine operation.

As explained in US. Patent 3,155,313, issued on November 3, 1964 to. the same assignee as the present application, the life of the inner surface of the peripheral Wall may be effected by the constant rubbing and variable loading of the seal strips which may cause substantial wearing of the inner surface as well as of the seal: strips. Also, the varying gas loads present acting on the peripheral Wall inner surface and on the apex seal strips, to vary their engagement with the inner surface, and the variations in heat flux produced during operation tend to distort the inner surface and may cause a separation of the liner from the main housing. The varying states of engine operation which occur adjacent the same regions of the outer body during the working cycle lead to a large changing of gas pressures and variation incentrifugal forces in the engine which result in the apex seal strips being forced against the inner surface of the peripheral wall in response to large gas pressures and centrifugal forces at one point While at another point relatively small gas pressures and centrifugal forces are forcing the apex ner surface engaged by the seals and of the seal strips themselves which problems are not normally found in reciprocating combustion engines. The above cited patent provides one solution for overcoming some of the problems faced in rotary combustion engines.

A primary purpose of the present invention is to provide an improved wearing surface structure for the sealing surfaces of a rotary combustion engine which has an increased wear life even over the solution provided in the previously mentioned patent and which construction 7 is relatively simple in structure. As also previously stated,

the invention 'is particularly applicable to outer bodies formed of lightweight alloy materials such as aluminum and magnesium wherein due to the high rate of thermal expansion and due to the fact that these materials are relatively soft, the problems encountered in relation to Wearing of the sealing surfaces are even greater than as for example using cast iron outer bodies.

In accordance withthe present invention a peripheral wall 12 is provided with a relatively thin single layer liner 50 on the inner surface thereof which liner 50 substantially conforms to the multi-lobed profile of peripheral:

wall 12 and also substantially covers the entire inner surface thereof (FIGS. 1 and 2). As stated above, the material of the peripheral wall 12 is preferably a lightweight alloy material such as aluminum or magnesium, and the liner is preferably applied thereto by a flame spraying technique, as will be explained in greater detail below. The material of the liner 50 is preferably formed from a carbide composition ceramic coating which is a known material having relatively high hardness characteristics. As defined in the Metals Handbook, volume 1, eighth edition by the American Society of Metals, a carbide is defined as a compound of carbon with one or more metallic compounds. The carbide compounds preferably used in the present invention are tungsten carbide and titanium carbide although other carbide compounds are intended to come within the scope of the ine vention. As stated above, carbide composition material is preferably applied to the base material or lightweight alloy housing by a flame spraying or flame plating technique. However, it should be understood that the material may be applied course on the characteristics of the material. Preferably, the particular flame spraying technique used is one known as detonation-gun flame spraying in which controlled detonations of acetylene and oxygen melt and propel particles of the material to be coated onto the substrate material. The acetylene and oxygen are supplied to a flame spraying gun along with material to be coated wherein the acetylene and oxygen are ignited and the coating particles then emerge from the gun at supersonic speeds to coat the substrate material. .This technique is particularly adapted to most carbide composition materials in that these materials have very high melting points some of which are in excess of 5,000 F. as, for example, tungsten carbide. The coating or liner canbe made relatively thin by this technique and after suitable grinding and honing the layer has a thickness which is a relatively small percentage of the thickness of the peripheral wall. In a peripheral wall having a thickness of approximately /8 to A of an inch the liner has a proportional thickness which is preferably in the range of 2.5% to 4.17% of the wall thickness. It should be understood, however, that the thickness of the peripheral wall is not intended by other processes depending of' to be-limited to these values. Due to the relative hardness of coatings such as tungsten carbide, a proper surface finish is necessary. With a liner of the type thus far described a mirror surface finish within the range of 2-8 micro. inches is desirable. It has been found that the use of a liner composed of a carbide composition material has substantial wear superiority over prior liners such as for example chromium plated liners, and further have the advantage of reduced friction at the wearing surface thus minimizing the requirement for lubrication at the sealing surfaces. Even with the use of prior known seal materials it has been found that the wear after substantial testing approaches ,4 or less in carbide composition liner than previously used liner materials.

In addition to the above advantages the liner of the invention offers substantial increased bond strength with the base lightweight alloy material so that the problem of liner separation is not present as was the case in some of the prior art type of liner materials. Further one of the more significant advantages found in using the carbide composition materials as liners for a rotary combustion engine lies in the fact that substantially no seal chatter has been found to occur when using these materials. As is well known in this art, many patents and solutions have been directed to the elimination of chatter in engines of this type. Chatter for purposes discussed herein may be defined as the occurrence of ridge-like indentations in the inner surface of the peripheral wall which tend to be found in localized regions of said inner surface. Chatter is known to be detrimental to engine operation in that, if the surface engaged by the seal means is not substantially smooth, the seal members will wear at an increased rate. Therefore, the elimination of chatter in engines of this type is a substantial contribution to the advancement of the art and is a significant factor in increasing the life of the seal members.

Although the application of the liner invention has been found to increase the seal life inner surface of the invention irrespective of the sealing means or composition used, it has been found that certain compositions of material for seal members in combination with the carbide composition of the inner surface provides for even greater wear life of the seal means. It has not thus far been accurately determined why only certain compositions for the seal members cooperate with the liner of the invention to produce such advantageous results and it can only be stated that these combinations produce superior unexpected increased wear life of the seal members. The following materials listed below have been found to afford substantial increases in seal life when used with the carbide composition liner of the invention:

(1) A material known as Clevite 300 and having the following composition:

Percent Carbon 0.050 Silicon 0.50 Cobalt 15.00 Molybdenum 15 .00 Iron Balance (2) A material known as Goetze-Ika and having the following composition:

departing from the spirit or scope thereof.

Percent 6 (3) A material known as Pearlitic Malleable Iron and having the following composition:

. Percent Carbon 2.35-25 Silicon 1.0-1.5 Manganese 0.28-0.48 Phosphorus 0.06-0.10 Sulphur 0.16-0.20 Iron Balance (4) A material known as Nodular Iron and having the following composition:

Balance The above detailed description has set forth a novel and improved wear surface construction for a rotary combustion engine which has proved to have substantial increased operating life over constructions heretofore found in the art. The construction is relatively simple in structure and may 'be manufactured with known techniques. A further improvement in the art has been found by combining with the novel and improved liner construction of the invention particular composition seal materials which, when used with the novel and improved liner of the invention, provide for even greater increase in the operating life of the wearing surfaces of the engine and an accompanying minimum permissible oil consumption. It should be further understood that, although the detailed description herein has been directed primarily to the construction of the peripheral wall liner and apex seals, the invention is equally applicable to the sealing surfaces of the end Walls and rotor side face seals and it is intended that the latter construction be included within the scope of the invention.

While I have described my invention in detail in its preferred embodiment, it will be obviou to those skilled in the art, after understanding my invention that various changes and modifications may be made therein without I aim in the appended claims to cover all such modifications.

I claim as my invention:

1. In a rotary mechanism having an outer body comprising a pair of axially-spaced end walls and a peripheral wall interconnecting said end walls to form a cavity with the inner surface of said peripheral wall having a multilobe profile; a rotor supported for relative planetary rotation within said cavity, a plurality of circumferentiallyspaced radially movable seal members carried by said rotor for sealing engagement with the multi-lobe inner surface of said peripheral wall thereby forming a plurality of working chambers which upon relative rotation of said outer body and said rotor vary in volume; a wear resistant construction for the sealing surfaces of said seal members and the inner surface of said peripheral wall wherein each said seal member is comprised of an alloy metal whose major constituent is iron and said multilobe inner surface of said peripheral wall has a relatively thin layer liner securely bonded thereto and conforming to the multi-lobe profiles of said inner surface, said liner comprising a carbide composition material.

2. In a rotary mechanism, as recited in claim 1, wherein the material of said seal members has approximately the following composition:

Percent Carbon 0.050 Silicon 0.50 Cobalt 15.00 Molybdenum 15.00 Iron Balance 3. In a rotary mechanism as recited in claim 1 wherein said liner is made of a material selected from the group consisting of tungsten carbide and titanium carbide.

4. In a rotary mechanism as recited in claim 1 wherein said peripheral wall is formed from a material selected from the group consisting of aluminum, .magnesium, aluminium alloy and magnesium alloy.

5. In a rotary mechanism as recited in claim 4 wherein the thickness of said liner ranges from 2% to 4.5% of the peripheral wall thickness.

6. In a rotary mechanism as recited in claim 1, comprising means for urging said seal member against said peripheral wall.

7. A wear resistant construction for the sealing surfaces of a rotary combustion engine comprising an outer body having axially-spaced end walls and a peripheral wall interconnecting said end walls to form a cavity therebetween, the inner surface of said peripheral wall having a multilobe profile; a rotor mounted for planetary rotation within said cavity and having a plurality of circumferentiallyspaced apex portions for engagement with the inner surface of said peripheral wall to form a plurality of working chambers between said rotor and said peripheral wall which vary in volume upon relative rotation of said rotor and said outer bodyya plurality of seal members carried by said rotor for rubbing sealing contact with the inner surface of said peripheral wall, there being at least one said seal member carried by each apex portion of said rotor; said wear resistant construction including said seal members being composed of an alloy metal whose major constituent is iron and said peripheral wall being composed of a lightweight alloy material with said inner surface of said peripheral wall having a relatively thin layer securely bonded thereto for relative rubbing contacting engagement with said seal members, said layer comprising a tungsten carbide material with the thickness of said layer ranging from 2 percent to 4.2 percent of the'thickness of said peripheral wal-l'.

References Cited by the Examiner i UNITED STATES PATENTS 1,831,411 1l/1931 Dietz 92169 X 3,033,180 5/1962 Bentele 1238 3,155,311 11/1964 Jones 230-145 3,155,313 11/1964 Bentele 230238 ROBERT M. WALKER, Primary Examiner.