US3155311A

US3155311A - Housing construction for rotary mechanisms

Info

Publication number: US3155311A
Application number: US211997A
Authority: US
Inventors: Jones Charles
Original assignee: Curtiss Wright Corp
Current assignee: Curtiss Wright Corp
Priority date: 1962-07-24
Filing date: 1962-07-24
Publication date: 1964-11-03
Anticipated expiration: 1981-11-03
Also published as: GB1044917A; DE1451702A1

Description

Nov. 3, 1964 c. JONES 3,155,311

HOUSING CONSTRUCTION FOR ROTARY MECHANISMS Filed July 24, 1962 s Sheets-Sheet 1 INVENTOR. CHARLES IJEINEEJ ATTORNEY Nov. 3, 1964 c, JONES HOUSING CONSTRUCTION FOR ROTARY MECHANISMS Filed July 24, 1962 3 Sheets-She t 2 ATTORNEY Nov. 3, 1964 c. JONES 3,155,311

HOUSING CONSTRUCTION FOR ROTARY MECHANISMS Filed July 24, 1962 3 Sheets-Sheet 3 INVENTOR. EHARLEEI LJDNEEI ATTORNEY axis portion. eral Wallis exposed to greater temperature than its outer United States Patent 3,155,311 HQUSING CGNSTRUQTIQN FUR RU'IARY MECI-IAPJHSMS Chariesilones, Paramus, NJ, assignor to Curtiss-Wright orporation, a corporation of Delaware Filed July 24, 1962, Ser. No. 211,997 4 Claims. (til. flail-445) preferably is basically an epitrochoid. Mounted within the cavity'on an axis parallel and spaced from the outer body axis is a rotor whose outer wall forms a plurality of circumferentially-spaced apex portions which engage the inner surface of the outer body to form working chambers which, upon relative rotation of the outer body and rotor, vary in volume. On one side of the housing or outer body there is provided an intake port --for admitting air or a fuel-air mixture and an exhaust port for expelling the burnt gases produced during combustion. An ignition means may be provided on the opposite side of the housing for ignition of the fuel-air mixture.

Because of the construction and operation of combustion engines of this type, each of tie cycles of intake,

compression, expansion and exhaust always takes place in the same relative areas of the housing. As a result,

a large amount of heating-up. occurs in the area of combustion and expansion while in the area wherein the intake stage takes place the housing remains relatively cool.

.So, it can be seen that there is a large variation in the heat flux produced in said housing. This heating up of the housing produces thermal stresses which result in bending moments that tend to act around the housing causing its peripheral wall to expand or grow around its major Also, since the inner surface of the periphsurface, the inner surface tends to expand at a greater "rate than the outer surface and said inner surface tends ,to droop inward or when viewed in a plane, including the engine axis the shape of the inner surface becomes convex. This changing of shape of the inner surface is commonly referred to as crowning. In addition to the thermal stresses acting on thehousing during operation, the expansion of the gases tends to produce bending stresses around the housing which also tend to alter the ,shape of the housing and if not properly compensated for will affect the desired housing shape, and hence, performance, and may lead to fatigue, creep or other stress Previous embodiments of rotary combustion engines of the type described may also be subject to chipping of the plating or wear resistant covering normally used ou the inner surface of the peripheral wall. Another commonproblem sometimes present in these embodiments :isthe deterioration of the gasket or gas seal used between Patented Nov. 3, 1 964 ice effects on the housing. The invention contemplates providmg an arrangement between the main housing or eripheral wall and the end walls which will minimize thermal distortion and will provide for a more consistent trochoid bore profile from assembly to assembly. The invention further substantially eliminates the problems of plating chipping on the peripheral wall inner surface and minimizes deterioration of the gas seal.

The invention is generally carried out by extending the main housing or peripheral wall axially substantially beyond the width of the rotor to form a female pilot section on each side of the rotor housing whose inner surface conforms to the inner surface of the rotor housing. The end walls each have a male pilot formed thereon whose outer surface corresponds to the shape of the female pilot and which extends therein to both sides of the rotor and fits in substantially close contact with the female pilot. As will be explained, in greater detail below, this construction leads to a substantially more sturdy engine housing, and gives more flexibility in design.

Accordingly, it is one object of the invention to provide a novel and improved housing for a rotary combustion engine.

It is also an object of the invention to provide a novel and unique pilot arrangement for the mating parts of the rotary combustion engine housing.

It is further an object of the invention to provide a more stable housing for a rotary combustionengine by substantially reducing thermal distortion and stress deviation in said housing. 7

Other objects and advantages of the invention will be apparent upon reading the following detailed description with the accompanying drawingswherein:

FIGURE 1 is a sectional view of a rotary combustion engineembodying the present invention,

FIGURE 2 is a sectional view of FIGURE 1 taken along line 22 of FIGURE 1 and,

FIGURE 3 is an exploded perspective view of a portion of a rotary combustion engine embodying the present invention.

In previous embodiments of rotary combustion engines of the type described in the above-mentioned United States Patent 2,988,865 the housing is designed so that the purpose to aid in aligning the above-mentioned parts of the housing and is also required to absorb the effects of the thermal distortion and bending stresses produced by the expansion and compression of the gases and to carry, in shear of the dowel pins, the gas load on the rotor housing which attempts to displace the housing out of its proper axial position. It has been found,

however, that the dowel arrangement does not always adequately absorb the forces placed upon the dowel pins so that substantial distortion of the housing may occur such that when the engine is disassembled the housing must be remachined before it can be reassembled since the dowels no. longer align. This isnotonly costly but in eifect results in weakeningthe housing. Furthermore, if the distortion of the housing is not adequately c ontrolled the sealing of the rotor apex portion against the inner surface of the peripheral wall may gradually become less efficient and thereby result in a poorly operating engine since the working chambers will no longer properly be sealed off from one another. Further, the peripht 3 eral wall in response to thermal stresses produced in the high heat flux zones tends to crown inwardly, as viewed in a plane including the engine axis, as explained above, and therefore, may further interfere with the line engagement of the apex seal members with the inner surface of the peripheral wall.

It also has been the practice in previous embodiments of rotary combustion engines to attempt to increase the life of the inner surface of the peripheral wall, which is constantly being rubbed by the apex seals during operation, by plating this surface with a high wear-resistant material. For example, when using an aluminum housing, a chromium plating may be bonded on said surface. This plating usually extends the entire width of the inner surface and abuts the mating end wall of the housing to form a corner therebetween. It has been found that, when the engine is in Operation the plating sometimes tends to chip at the above-mentioned corners causing deformation in the inner surface and damaging the seals. One attempt at correcting this problem may be made by chamfering the ends of the plating but this may result in an undesirable loss of compression.

The present invention has for its purpose substantially minimizing the above-mentioned problems if not completely eliminating at least some of them, as will be apparent from the following detailed description.

Referring to the figures, there is shown in FIGURES 1 and 3 a rotary combustion engine having a hollow outer body or housing generally designated at it the housing generally comprising a main rotor housing formed by a peripheral wall 12 and a pair of

end walls

14 and 16 connected thereto forming a cavity therebetween. A shaft 18 is rotatably supported in the housing It by suitable bearings 20 and has an eccentric portion 22 formed thereon upon which is rotatably mounted a rotor 24 said rotor being disposed in said housing cavity and being rotatably supported on the shaft eccentric 22 by a suitable bearing such as plain sleeve type bearing 26. As seen in FIG- URES 2 and 3, the outer wall of the rotor forms three circumferentially-spaced apex portions in each of which there is mounted a radially-movable seal strip member 28 which engages the inner surface 29 of the peripheral wall to form working chambers 30 which, upon relative rotation of the rotor 24 and the housing 10, vary in volume. The shape of the inner surface 29 of the peripheral wall 12 preferably is basically a two-lobed epitrochoid as shown in FIGURES 2 and 3. A suitable wear-resistant plating indicated at 32 in FIGURE 1 may be suitably bonded on the inner surface 29 of the peripheral wall 12 for engagement by the seal strips 28 to ensure better wearing characteristics between the contacting surfaces of the seal strip members 28 and the peripheral wall 12. For example, the plating material may be composed of chromium or steel, although it is not limited to these particular materials.

The rotor 24 has an internally-toothed gear 34 mounted thereon through mating bosses 36 on the rotor and 38 on the gear and fastened to the rotor 24 by suitable screws 40. Co-axially supported about shaft 18 is an externally toothed gear 42 which meshes with gear 34, said gear 42 having a radially-extending flange portion 44 for fastening said gear to the end wall 16 by suitable screws 46. The gear 42 has a cylindrical extension which provides a supporting bearing surface for the shaft in the housing 10. The

gears

34 and 42 serve to rotatably guide the rotor 24 in following the epitrochoidal path during its rotation. An intake port 48 (FIGURE 2) is provided on one side of the housing for admitting air or a fuel-air mixture along with an exhaust port 50 for expelling the burnt gases and on an opposite side of the housing an ignition means 52 may be provided.

As can be seen from FIGURE 2 the expansion and exhaust phases always take place in the same relative positions in the housing and will result in a substantial heatingup of this area while in the area of the intake port, the

housing will remain relatively cool, due in part to the introduction of a fresh supply of fuel and air in the intake area. As a result the heating-up in the housing is not uniform and distortion may occur around the housing due to the thermal stresses produced in the heated-up area. Furthermore, since the heat input is at the inner surface of the rotor housing a steep temperature gradient is produced in the radial direction, which contributes to the thermal stresses. Also, in the area of the expansion phase bending stresses will be produced around the housing due to the sudden expansion of the gases from combustion. The stresses produced as a result of heating-up of the housing and the gas expansion may have serious effects upon the engine if not properly compensated for, as was pointed out above. As further shown in FIGURE 1, when the engine is assembled, the end walls are connected to the peripheral wall by suitable axially extending bolts 54, and a suitable gas seal 56, for example an asbestos packing compound or an 0 ring, may be interposed between the end Walls to eliminate any gas leakage from the housing which might result in compression losses. Axially-spaced supporting ribs 58 may be provided on the peripheral wall 12 in the region of the intake port to give said peripheral wall more rigid support and in the region of combustion and expansion where higher heat flux is produced, axiallyspaced cooling fins 6t may be provided for use in aircooling the engine and for supporting the peripheral wall 12. However, it should be understood, that although axially-spaced cooling fins are preferred, circumferentially spaced cooling fins could also be used.

In accordance with the invention the main rotor housing, substantially formed by the peripheral wall 12, differs from the previous embodiments in that the wall 12 and its inner plating 32 extend axially beyond the width of the rotor 24 on both sides thereof as clearly shown in FIG- URES 1 and 3, where in FIGURE 3 the fin structure has not been shown for purposes of more clearly illustrating the invention. This axial extending of the peripheral wall brings about the formation of

female pilot sections

62 and 64 on each side of the main rotor housing the inner surfaces of which have the identical multi-lobed shape and form an extension of the surface 29. The

end walls

14 and 16 are each formed with

male pilot sections

66 and 68 respectively, which are designed to extend axially into the main rotor housing female pilots on each side thereof to a position adjacent the end faces of the rotor 24. Suitable side seals 69 are provided in each end wall of the rotor 24 which bear against the inner faces of the

male pilot sections

66 and 68 respectively, to seal any compression leakage at the radially inward portion of the working chambers. The outer contour of the male pilot sections is substantially the same as the inner contour of the female pilot, that is, basically a two-lobed epitrochoid. The outer portions 7a and 72 of the

end walls

14 and 16 respectively extend radially outward beyond the male pilot sections to abut the peripheral wall at its axial end faces. At the outer periphery of the end walls the

outer portions

70 and 72 on

walls

14 and 16, respectively, have bolts 54 which pass through these portions to securely clamp the

housing sections

12, 14 and 16 together.

During operation of the engine, thermal stresses are produced, because of the heating up of the engine, which tend to distort the housing. In the present invention, due to the fact that the peripheral wall extends beyond the width of the rotor and the end walls extend into the rotor housing from outside of said housing and thereby forming the pilot sections, these

end sections

62 and 64 of the peripheral wall beyond the rotor Width remain relatively cold compared to the intermediate portion of the peripheral wall between said end sections. In this way these relatively cold end sections of the peripheral wall substantially counteract the thermal stresses in the intermediate portion of the peripheral wall thereby substantially minimizing any distortion of said peripheral wall. This was not possible in the previous embodiments since the ing toproduce distortion can be minimized, which in this xthe perip-heral Wall as thin as possible so that maximum "heat transfer may be obtained. to be made relatively thick because the heat produced in In the past this wall had the engine would cause theperipheral wall to droop or crown and, as described above, this crowning is undesirable. In the present invention, crowning is substantially eliminated and at the same time the peripheral wall can be made relatively thin. This is so because the

male pilot sections

66 and 68 which fit tightly into the

female pilot sections

62 and 64 form a relatively cold area as compared to the inter-mediate portion of the rotor housing which counterbalances the themnal stresses and therefore substantially eliminates crowning. Another advantage realized from this internal support of the male pilot sections is the direct absorption of the bending stresses produced in the engine resulting from the compression and combustion of the gases. These bending stresses normally travel in a direction around the housing or peripheral wall in varying intensity tending to distort the housing and also cause fatigue or other over-stressed phenomenon in the metal. Due tothe fact that the pilot of the present invention fits snugly against the inner surface of the peripheral wall, and because the pilot arrangement is an inherently rigid structure these bending stresses will be shouldered or absorbed in the supporting male sections of the pilot and the peripheral wall remains very close to the desired engine geometric shape during operation.

As can also be seen in FIGURE 1, the plating 32 of the inner surface of the peripheral wall does not form any corners with the end wall in the high heat zone. The plating 32 extends continuously beyond the rotor width to the outer portions 70 and '72 of the end walls and can readily absorb the stresses placed upon it by the heat produced and the rubbing of the seal members 28 without any chipping resulting since the corners at the ends of the plating are now located beyond the width of the rotor apex seals.

The gas seal or gasket between the end and peripheral walls of the housing in previous embodiments is subject to deterioration because in these embodiments the peripheral wall was only as wide as the width of the rotor and the gas seal which was placed between the end faces of the peripheral wall and the inner faces of the end walls, was therefore located in a region of high heat flux. In the present invention, however, the gas seal or gasket 56 (FIGURE 1) is located outside of the high heat zone by virtue of the fact that the peripheral Wall end faces are located substantially beyond the width of the rotor. Thus, the heat fluctuations produced in the rotor housing have little effect on the gas seal 5d and gas seal deterioration is therefore substantially eliminated.

The present invention further facilitates a relatively simple cooling fin arrangement when providing air cooling for an engine of the type described above. As viewed in FIGURE 1, cooling fins 69 may be formed on the pe ripheral wall axially beyond the width of the rotor housing which provides for cooling area for the peripheral wall and beyond the rotor housing ends without requiring the addition of any complicated or relatively bulky structure. This is a highly desirable feature since, because of the high local heat input in engines of this type, cooling fins should be provided beyond the axial width of the rotor housing in any event to help carry away the .heatfrom the localized heat areas. tion the provision of cooling fins in this region is relatype of engine.

In the present inventively simple to machine, does not provide for a relatively bulky structure and the peripheral wall may be made relatively thin because of the supporting characteristics of the male pilot sections 66 and '68. It is of course desirable from a cooling standpoint in particular to be able to make the peripheral Wall as thin as possible since the heat trans- .fer across a thinner wall is better than across a' thick wall since the temperature drop across a thin wall is less and therefore the temperature difference between the inner surface and the outer surface can be more readily stabilized. 'As discussed above, the peripheral wall can be made relatively thin with no danger of the wall buckling and without any rippling of the cooling fins provided thereon since the peripheral wall is supported internallyby the

male pilot sections

66 and 68.

It has been found that keeping a tight fit-between-the mating pilot sections provides the best support and absorption of stresses in the housing. Therefore, the

male pilot sections

66 and 68 are formed with outer dimensions so as to tightly fit within the

female pilot sections

62 and 64 respectively, and, if desired, an interference fit may be provided between the mating pilot sections to ensure an even tighter fit which would also provide a desirable prestress condition since the tensile assembly stresses will cancel out the predominantly compressive inside surface stresses at the worst temperatures and operating conditions.

From the foregoing it can be seen that a sturdy and relatively simple housing construction is provided for a rotary combustion engine which overcomes troublesome deflects sometimes encountered in prior housings of this The housing is economical to produce and requires little alteration in the basic construction of the rotary combustion engine itself. Due to the sturdiness and simplicity of construction of the housing in the present invention a more reliable operating engine and more commercially feasible engine can be produced. Further, the housing of the present invention is readily adaptable for use in multi-unit engines wherein more than one rotor housing is used. Also, the invention is equal- 13 applicable to liquid cooled engines as well as those of the air-cooled type.

While the invention has been set forth in detail in the above description, it is to be understood that the invention is not to be so limited thereby and various modifications and alterations may be made by those skilled in the art without departing from the spirit and scope of the invention defined in the following claims.

I claim as my invention:

1. In a rotary combustion engine having an outer body composed of a pair of end walls and a peripheral wall connected together to form a. cavity therebetween, the inner surface of said peripheral wall having a plurality of lobes therein giving said cavity a multi-lobed configuration, a rotor rotatably mounted within said cavity, said rotor having sealing cooperation with said end walls and having a plurality of ciIcum-ferentially spaced apex portions for sealing engagement with the inner surface of said peripheral wall forming working chambers therebetween which upon relative rotation of said rotor and said outer body vary in volume, an intake means for admitting air to said chambers for combustion therein, and an exhaust means for expelling the burnt gases from said chambers, said peripheral wall having a width substantially greater than that of said rotor so that said peripheral wall projects beyond the rotor and said outer body end walls each having a central portion projecting inwardly to a position adjacent said rotor and extending within the adjacent portion of said peripheral wall projecting beyond said rotor with each said end wall central portion having a flat end face and the peripheral surface of each said end wall central portion having a multilobed configuration substantially identical with that of the inner surface of the peripheral wall and being dimensioned so that each central portion of said outer body end walls is in tight fitting engagement with the entire inner surface of the adjacent projecting portion of said peripheral Wall.

2. In a rotary combustion engine as recited in claim 1 wherein the inner surface of said peripheral wall has a wear-resistant layer securely bonded thereon, said layer extending axially across the entire width of said peripheral wall inner surface and having a rnulti-lobe configuration conforming to the entire inner surface of said peripheral wall.

3. In a rotary combustion engine as recited in claim 1 wherein the configuration of said peripheral wall inner surface and the peripheral surface of said inwardly projecting central portion is basically a two-lobed epitrochoid and said rotor has three circumferentially-spaced apex portions.

4. In a rotary combustion engine as recited in claim 1 wherein the outer surface of said peripheral wall has a plurality of axially-spaced circuinferentially extending cooling fins provided thereon said cooling fins being spaced across substantially the entire Width of said peripheral wall so that at least some of said cooling fins extend over said projecting central portions of said end Walls.

References Cited in the file of this patent UNITED STATES PATENTS 2,816,513 Watson Dec. 17, 1957 2,847,157 Nilsson Aug. 12, 1958 2,876,948 Hockel Mar. 10, 1959 2,988,065 Wankel June 13, 1961

Claims

1. IN A ROTARY COMBUSTION ENGINE HAVING AN OUTER BODY COMPOSED OF A PAIR OF END WALLS AND A PERIPHERAL WALL CONNECTED TOGETHER TO FORM A CAVITY THEREBETWEEN, THE INNER SURFACE OF SAID PERIPHERAL WALL HAVING A PLURALITY OF LOBES THEREIN GIVING SAID CAVITY A MULTI-LOBED CONFIGURATION, A ROTOR ROTATABLY MOUNTED WITHIN SAID CAVITY, SAID ROTOR HAVING SEALING COOPERATION WITH SAID END WALLS AND HAVING A PLURALITY OF CIRCUMFERENTIALLY SPACED APEX PORTIONS FOR SEALING ENGAGEMENT WITH THE INNER SURFACE OF SAID PERIPHERAL WALL FORMING WORKING CHAMBERS THEREBETWEEN WHICH UPON RELATIVE ROTATION OF SAID ROTOR AND SAID OUTER BODY VARY IN VOLUME, AN INTAKE MEANS FOR ADMITTING AIR TO SAID CHAMBERS FOR COMBUSTION THEREIN, AND AN EXHAUST MEANS FOR EXPELLING THE BURNT GASES FROM SAID CHAMBERS, SAID PERIPHERAL WALL HAVING A WIDTH SUBSTANTIALLY GREATER THAN THAT OF SAID ROTOR SO THAT SAID PERIPHERAL WALL PROJECTS BEYOND THE ROTOR AND SAID OUTER BODY END WALLS EACH HAVING A CENTRAL PORTION PROJECTING INWARDLY TO A POSITION ADJACENT SAID ROTOR AND EXTENDING WITHIN THE ADJACENT PORTION OF SAID PERIPHERAL WALL PROJECTING BEYOND SAID ROTOR WITH EACH SAID END WALL CENTRAL PORTION HAVING A FLAT END FACE AND THE PERIPHERAL SURFACE OF EACH SAID END WALL CENTRAL PORTION HAVING A MULTILOBED CONFIGURATION SUBSTANTIALLY IDENTICAL WITH THAT OF THE INNER SURFACE OF THE PERIPHERAL WALL AND BEING DIMENSIONED SO THAT EACH CENTRAL PORTION OF SAID OUTER BODY END WALLS IS IN TIGHT FITTING ENGAGEMENT WITH THE ENTIRE INNER SURFACE OF THE ADJACENT PROJECTING PORTION OF SAID PERIPHERAL WALL.