GB2248655A - Seal arrangement for a rotary engine - Google Patents

Abstract

In a rotary engine a rotor 14 rotatable within an oval chamber (10, Fig 1) has radial slots 19 receiving respective vanes 18 which are urged radially outwardly to make sealing engagement with the oval peripheral wall of the chamber (10). To ensure good sealing of the ends of each vane with respect to the end walls of the chamber (10), each vane 18 is of multi-part construction comprising end parts 50 for cooperation with the chamber end walls and an intermediate part 52. The end parts 50 and intermediate part 52 have mutually engaging surfaces which extend radially. Separately formed wedging members 66 are located in cavities 65 in the intermediate part 52 and act on the end parts 50 via lateral pins 84 to urge the end parts into sealing engagement with the end walls of the chamber (10), when the wedging members 66 are thrust radially outwardly by biassing springs or by centrifugal force. <IMAGE>

Description

DESCRIPTION OF INVENTION Title: "Seal Arrangement for a Rotary Engine" THIS INVENTION relates to engines, pumps, compressors and the like machines of the type in which a rotor rotates within a cavity in a stator and carries sealing elements which sealingly engage the walls of said cavity to divide the space defined between the rotor and the stator into a plurality of working spaces which, where the machine is an internal combustion engine, form the combustion chambers, the volume of each said working space or combustion space varying cyclically with rotation of the rotor in the stator for compression, expansion or displacement of the working fluid.

Machines of the above-noted kind are herein referred to as "rotary engines".

Rotary engines of many kinds have been proposed, but these have all suffered from disadvantages of one kind or another, particularly from gas-sealing problems, and complexity of seal structure.

It is an object of the invention, in one aspect, to provide a rotary engine, as herein defined, having improved sealing means for sealing the rotor with respect to the stator.

According to the invention, there is provided a rotary engine, as herein defined, wherein said cavity comprises' a peripheral wall extending around the rotor and opposing side walls between which the rotor is located and which connect with the peripheral wall at generally abrupt junction regions and wherein said rotor carries a plurality of sealing assemblies, each comprising at least two lateral parts mounted for independent displacement in the rotor, in directions parallel with the rotor axis, each said part including a portion engaging a respective said side wall of the said cavity and a portion supporting sealingly a further sealing element cooperating with the peripheral wall of the said cavity and at least one wedging element having a wedging surface inclined with respect to the axis of the rotor, the arrangement being such that, in operation, the or each said wedging element is thrust away from the rotor axis towards said peripheral wall so that each of said lateral parts of the sealing assembly is thrust against the respective side wall of the said cavity by the wedging action.

Preferably each said sealing assembly comprises said two lateral parts engaging respective said side walls of said cavity and an intermediate part, guide means guiding said lateral parts for linear motion relative to said intermediate part, parallel with the rotor axis, and wherein the or each said wedging element is accommodated within an internal cavity in said intermediate part.

An embodiment of the invention is described below by way of example with reference to the accompanying drawings in which: FIGURE 1 is a schematic sectional view of one form of rotary engine embodying the invention, more particularly an internal combustion engine, FIGURE 2 is a view in section along the line 2-2 in Figure 1, FIGURE 3 is an exploded perspective view showing the rotor and some of the seal assemblies of the engine of Figures 1 and 2, FIGURE 4 is a front elevation view of a seal assembly of the engine of Figures 1 to 3, FIGURE 5 is a view in section of the seal assembly of Figure 4, taken along the line V-V in Figure 4, FIGURE 6 is a view partly in end elevation and partly in section on the line VI-VI of Figure 4, and FIGURE 7 is a view similar to Figure 4 but partly in section and illustrating biasing means for the wedging elements.

Referring to Figure 1, a rotary internal combustion engine comprises a stator 9 affording an internal cavity or chamber 10 having a peripheral wall 12, which is elliptical as viewed in Figure 1 and has opposing side walls 13 (Figure 2) parallel with the plane of Figure 1. Mounted within the chamber 10 is a rotor 44 fixed to or integral with a shaft 16 extending from the chamber 10, perpendicular to the side walls 13 and rotatably journalled in the stator by bearings indicated at 17. The rotor 14 is generally cylindrical, concentric with the shaft 16 and is a close fit between the side walls 13 of the chamber 10. The rotor 14 is mounted centrally within chamber 10, i.e. with its rotary axis passing through the point of intersection of the major and minor axes of the ellipse defined by wall 17.The rotor 14 has lateral faces which cooperate closely with the side walls 13. Mounted in the rotor 14 at 900 intervals therearound are vanes 18 which are accommodated within respective radial slots 19 in the rotor and project therefrom to engage the peripheral wall 12. Each slot 19 extends from one lateral face of the rotor to the other and each vane 18 extends from one side wall 13 to the other.

Each vane 18 is reciprocable radially in its respective slot 19 and is biassed resiliently outwardly by spring means indicated schematically at 21 in Figures 1 and 2. It will be noted that the space defined between the rotor 14 and the peripheral wall 12 is thus divided, by the vanes 18, into four working chambers and that, as the rotor 14 rotates, the volume of each such working chamber alternately increases and decreases. In order to maximise the nominal compression ratio associated with these working chambers, the diameter of the rotor 14 is made only slightly smaller than the minor axis of the ellipse defining the peripheral wall 12.

An inlet port 24 and an exhaust port 26 are formed in the stator wall at spaced-apart locations therearound. In the position illustrated in Figure 1, working spaces 10a and 10d are separated from each other by a vane 18 which is instantaneously engaged with a portion of the peripheral wall 12 between the inlet and exhaust ports 24, 26 and, given that the rotor is rotating in the direction indicated by the arrow 28 in Figure 1, the chamber 10a is shown in the phase in which it is expanding to draw fuel/air mixture in through the inlet port 24, whilst the chamber 10b is shown in the phase in which it is being reduced in volume to compress a charge of fuel/air mixture therein, the chamber 10c is shown in the phase in which it is increasing in volume during expansion therein of hot combustion gases resulting from burning of a previously compressed fuel/air charge, the charge having been ignited by means of a spark plug 30 having a spark gap exposed within the chamber 10c (the spark gap not being shown in the drawings). The chamber lOd is shown in Figure 1 in the phase in which it is being reduced in volume to expel combustion products from the chamber 10d to the exhaust port 26. It will be appreciated that, at the particular instant in the working cycle illustrated in Figure 1, the expansion of the combustion gases in chamber lOc is supplying work to the engine. The engine illustrated thus operates under a "fourstroke cycle, with each space 10a, lOb, 10c, 10d cycling repeatedly through an intake phase, a compression phase, a combustion phase and an exhaust phase.Each chamber 10a to 10d has its largest volume when it is symmetrically disposed with respect to and bisected by the major axis of the ellipse defining the wall 12 and has its smallest volume when it is symmetrically disposed with respect to and bisected by the minor axis of said ellipse, a situation which, for the chambers 10b and 10d respectively, occurs after a further 450 rotation of the rotor from the position shown in Figure 1. Preferably in the position after such further 450 rotation, the chamber 10d opposite that in which the spark plug 30 is exposed is in communication, temporarily, with both the inlet port 24 and the exhaust port 26, providing an appropriate degree of "overlap" between exhaust and intake phases.In Figure 2, the reference 32 denotes a conventional pulley secured to the shaft 16 driving a water pump and generator (not shown) in known manner and the reference 34 indicates a fan secured to the shaft 16 to draw air through a cooling radiator (not shown). The reference 37 indicates a flywheel.

In Figures 3 to 5, in which parts corresponding to parts in Figures 1 and 2 have the same references, the form of a sealing vane 18 is shown in more detail than indicated in Figures 1 and 2. Each vane 18 is actually formed of a plurality of discrete parts and is herein also referred to as a sealing assembly.

As shown in Figure 3, each slot 19 in the rotor 40 extends from one side of the rotor to the other and is of uniform width, measured in the circumferential direction, i.e. perpendicular to the radius passing mid-way through the slot and perpendicular to the direction of the rotor axis, each slot 19 affording smooth flat parallel opposing side walls within which the respective sealing assembly 18 fits closely. Each sealing assembly 18 comprises three main body parts, preferably lightweight parts of aluminium alloy or the like, these parts comprising two lateral parts 50, located at axially opposite ends of the respective slot 19 and an intermediate part 52 which is located between the parts 50 and is sealingly engaged therewith. Each of the parts 50, 52, occupies the full width of the slot 19 and each is of substantially the same dimension measured radially of the rotor.As illustrated in Figure 4, in the assembled engine, the parts 50, 52, fit together, end to end, to form a composite generally rectangular block. Each lateral part 50 has a generally planar end face 56 substantially perpendicular to the direction in which the rotor axis extends and which end face 56 engages the opposing side wall of the stator cavity and has an opposite surface which cooperates with an opposing end surface of the part 52. As shown in Figure 5, said opposite surface of each lateral part 50 may comprise co-planar outer faces 58 extending parallel with the end face 56 and a central tongue 59 projecting from the plane of said co-planar outer faces towards and into the parts 52, said tongue 59 extending longitudinally along a radius from the rotor axis and having flanks parallel with the sides of the respective slot 19.

The cooperating outer surface of the part 50 is of complementary form, affording co-planar outer faces 60 parallel with or mating with the opposing outer faces 58 and a central groove or channel 61 which receives the tongue 59 as a close sliding fit.

The part 50 has two internal cavities 65 extending radially outwardly from the radially inner face of the part 52 and accommodating respective wedge elements 66 for radial movement therein, the cavities 65 having internal lateral walls 70 parallel with the sides of the respective slot 19 and slidably engaging the opposing parallel side faces 72 of the respective wedging element 66. Each cavity 65 terminates at its side nearer to the adjacent part 50 in a side wall 74 extending radially with respect to the rotor axis and perpendicularly to said lateral wall 70 and each cavity terminates, at its side further from the adjacent part 50, in a side wall 76 which is perpendicular to the lateral walls 70 but is inclined with respect to the side wall 74 so that the cavity 65 narrows from its radially inner end to its radially outer end.Each wedging element 66 likewise has a side face 80 which opposes and is parallel with the respective side wall 74 and has a face 82 which is inclined with respect to the face 80 and mates with and is slidable on the inclined side face 76 of the cavity.

Each part 52 has a peg 84 projecting from its rib 59 parallel to the rotor axis and extending through an aligned bore 86 in the part 50 into the adjacent cavity 65, the free end of the peg 84 in the assembled engine engaging the face 80 of the element 66.

Extending along the radially outer end of the composite block formed by the parts 50, 52, is a rectangularsection groove or channel 62 which receives, as a close sealing fit, a generally rectangular-section seal support bar 64 which in turn supports a sealing bar 68. The support bar 64 and the sealing bar 68 extend substantially from one end of the composite block formed by parts 50, 52 to the other and thus, in the assembled engine, closely adjoin the opposing side walls of the stator cavity. The support bar 64 is urged radially outwardly from the channel 62 by resilient biassing elements (not shown) mounted in the parts 50 and 52.

A bore 36 extends radially with respect to the rotor axis, into the part 52 from the radially inner end of part 52. Extending into the bore 36 from the central region of the rotor and fixed to the rotor is a radially extending tubular support 38. An axial oil-way through the shaft 16 communicates with an internal passage provided through the support 38 whereby lubricating oil can be supplied through oil-ways in the parts 52 and 50 to the channel 62, the cooperating faces of the parts 50 and 52, the walls of the slots 19 and so on.

Each sealing bar 68 is externally cylindrical, apart from a surface of substantially lesser curvature which engages the wall 12. The bar 68 is located within a partcylindrical groove or channel 41 extending along the radially outer face of the support bar 64 parallel with the rotor axis, such channel receiving, as a close rotating fit, the correspondingly cylindrical part of the surface of the bar 68. This arrangement allows the bar 68 to pivot about the axis of curvature of its cylindrical surface, relative to the bar 64, as the latter travels around the wall 12 during rotation of the rotor. The curvature of the surface of lesser curvature of the bar 68 is intermediate the maximum and minimum curvature of the wall 12, so as to fit as closely as possible with the wall 12.Each end part 50 has, in its end face 56, slots 67, for example, of -"U"shape, with legs extending radially with respect to the rotor axis, which receive correspondingly shaped sealing bars (not shown) backed by appropriate biassing springs, (not shown) which seal the laterally outer ends of the parts 50 relative to the side walls 13. The lateral faces of the rotor 14 may also be sealed with respect to the side walls 13 by means of an arrangement of annular sealing rings, for example accommodated in annular grooves in the side walls 13.

As shown in Figure 7, a biasing spring fitted around the support 38 acts, via a yoke, illustrated schematically at 73, on the radially inner surfaces of wedging elements 66 to urge the latter radially outwardly with respect to the intermediate parts 52, 50 (the latter being restrained by engagement, via the sealing bar 68 and sealing support bar 64, with the peripheral wall 12), the consequent wedging action between the inclined mating surfaces 82, 76 of the wedge elements 66 and the cavities 65, respectively, on the one hand, and between the surfaces 80 of the wedge elements 66 and the free ends of pegs 84, on the other hand, serving to urge the parts 50 outwardly from the part 52 into firm sealing engagement with the side walls 13 of the stator cavity.

The spring 21 acting on the wedge elements 66 indirectly urges the intermediate part 52, and thus, by the pegs 84, the parts 50 radially outwardly from the rotor to urge the sealing bar 64, 68 against the peripheral wall 12.

When the engine is running at a normal operating speed, of course, the centrifugal force acting on the members 50, 52, is sufficient to maintain these parts in the outermost positions in which they urge the sealing bar 68 via the bar 64 against the peripheral wall 12 of the stator cavity.

Centrifugal force acting on the wedge elements 66 is likewise sufficient, at normal running speeds, to produce the desired wedging action referred to above. The spring 21 merely serves to urge the elements 66 and thus the parts 50, 52, radially outwardly and to produce the necessary wedging action, when the engine is stationary or rotating at low speed (e.g. during starting).

The lateral faces of the parts 50, 52 of each vane are sealed with respect to the opposing side walls of the respective slots 19 by further sealing bars, indicated at 90 in Figure 4 but not shown in Figure 3, accommodated in longitudinal grooves, parallel with the rotor axis, in said lateral faces of the parts 50 and 52. Thus, each straight lateral sealing bar 90 has its major portion, intermediate its ends, accommodated within a rectangular-section groove in the lateral face of the intermediate part 52 and has its end portions accommodated in respective grooves formed in the respective lateral parts 52, the last-mentioned grooves being of the same cross section as and formed as extensions of the corresponding groove in the lateral face of part 50.

Spring biasing arrangements, known per se and not shown, act to urge the lateral sealing bars against the opposing side walls of the slots 19. It will be appreciated that movement of the lateral portion 50 away from the intermediate portion and towards the respective side walls of the stator cavity is not interfered with by the sealing bars 90 since the end portions of the latter merely move longitudinally in the respective grooves in the parts 50, whilst radial movement of the parts 50 relative to the parts 52 is prevented by the pegs 84 so that there is no risk of breakage of the sealing bars 90.

It will be appreciated that various modifications are possible. Thus, for example, it would be possible for a single wedging element to be provided within the intermediate part 52, the single wedging element having opposite wedging faces engaging the ends of the pegs 84, the support 38 being replaced by some other guiding and lubricating arrangement. In another possible arrangement, the cavities accommodating the wedging element 66 may open into and be continuous with the grooves 61 receiving the tongues 59 of the lateral parts 50, with the outer faces of the wedging elements 66 directly engaging the opposing end surfaces of the tongues 59, with locating pegs or other locating formations, fulfilling the locating functions of the pegs 80, being provided at locations compatible with such modified arrangements.

Claims (5)

1. A rotary engine, as herein defined, wherein said cavity comprises a peripheral wall extending around the rotor and opposing side walls between which the rotor is located and which connect with the peripheral wall at generally abrupt junction regions and wherein said rotor carries a plurality of sealing assemblies, each comprising at least two lateral parts mounted for independent displacement in the rotor, in directions parallel with the rotor axis, each said part including a portion engaging a respective said side wall of the said cavity and a portion supporting sealingly a further sealing element cooperating with the peripheral wall of the said cavity and at least one wedging element having a wedging surface inclined with respect to the axis o the rotor, the arrangement being such that, in operation, the or each said wedging element is thrust away from the rotor axis towards said peripheral wall so that each of said lateral parts of the sealing assembly is thrust against the respective side wall of the said cavity by the wedging action.

2. A rotary engine according to claim 1 wherein each said sealing assembly comprises said two lateral parts engaging respective said side walls of said cavity and an intermediate part, guide means guiding said lateral parts for linear motion relative to said intermediate part, parallel with the rotor axis, and wherein the or each said wedging element is accommodated within an internal cavity in said intermediate part.

3. A rotary engine according to claim 2 wherein each said sealing assembly is accommodated in a respective radial slot in the rotor, extending from said side wall to said side wall of the cavity and of uniform width measured perpendicular to the respective radius and the rotor axis, and wherein said intermediate part and said lateral parts of the respective sealing assembly each occupy the whole width of the respective slot and cooperate sealingly with the opposing walls of the slot, and wherein said further sealing element comprises a sealing bar accommodated in a slot extending longitudinally along the radially outer edges of said lateral parts and said intermediate part.

4. A rotary engine substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

5. Any novel feature or combination of features described herein.