WO2000057027A1

WO2000057027A1 - Rotary engine with overexpanded cycle

Info

Publication number: WO2000057027A1
Application number: PCT/PT1999/000007
Authority: WO
Inventors: Virgílio DOS REIS CARDOSO IGREJA
Original assignee: Servotrol - Sistemas De Comando Automático, Lda.
Priority date: 1999-03-23
Filing date: 1999-03-23
Publication date: 2000-09-28

Abstract

A radial vaned combustion rotary engine enclosing a longitudinal cavity has rotatably mounted thereinto a rotor with a plurality of radially extended slots equally disposed along its periphery wherein a plurality of vanes are slidable. Means for guiding the vanes in pure circular pathways are provided on both inner flat surfaces of the housing's tops. These pathways are two secant circular tracks of equal or different radii. Air alone or a mixture of air and fuel is drawn by the induction/compression vanes from the intake port and compressed in recesses alternately located along the periphery of the rotor. The after ignition hot gases power the expansion/exhaust vanes and the rotor and are exhausted through the exhaust port. If the maximum volume between the expansion/exhaust vanes is larger than the maximum volume between induction/compression vanes, the engine's operation cycle is the so-called Atkinson or Miller cycle.

Description

ROTARY ENGINE WITH OVEREXPANDED CYCLE

Field of the Invention and Background

This invention relates to internal combustion engines, and more particularly, to rotary vaned engines having enlarged expansion cycles.

It is well known that the efficiency of spark-ignition (SI) or compression- ignition (Cl) reciprocating-piston conventional engines increases if the hot gases expand to a larger volume than the initial volume of compression. Within the cylinder of an ordinary four-stroke engine, for instance, the gas pressure at exhaust valve opening is greater than the exhaust pressure. The existing energy of the cylinder gases at this point in the cycle is then dissipated in the exhaust blowdown process. Additional expansion within the engine cylinder would increase the area of the conventional pressure- volume p-v diagram, for the same fuel input, thereby increasing the engine's efficiency. The resulting cycle is known as Atkinson cycle or Miller cycle. Many crank and valve mechanisms combined with turbochargers have been proposed to achieve this additional expansion in reciprocating- piston engines. These are, in general, complex and costly systems.

It is also well known that rotary engines have advantages over reciprocating-piston engines, like higher power-to-weight and power-to- volume ratios, fewer moving parts, and operation with decreased noise and vibration. The Wankel engine is one type of a rotary engine. A single- rotor Wankel engine has two rotating parts: the triangular-shaped trochoidal rotor and the output shaft with its integral eccentric. The rotor rotates and orbits around the shaft axis in a chamber house internally configured to place the apexes of the rotor in constant engagement with its inner eperitrochoid wall. This constant engagement causes a comparatively rapid wear on the apex seals and the inner wall of the rotor house. Efforts to minimize this wear process continue. Breathing is through ports located at optimal points of the chamber house. Induction, compression, expansion and exhaust phases follow the Otto cycle, like in a conventional reciprocating-piston engine, however without moving valves. Means as the above mentioned mechanisms or other which could turn the Otto cycle into a Miller cycle in a Wankel engine are not known to date.

Vaned rotary engines are other type of rotary engines. Rather than using a trochoidal rotor, this type of engine is characterized by a cylindrical rotor, mounted within a housing, having a plurality of radially-extending slots which support a plurality of vanes. These vanes may have a radial motion or an axial motion with respect to the rotor. Each combustion chamber is defined between a pair of successive vanes, the portion of the rotor between them, and the inner surface of the housing enclosing the chamber. As the combustion chamber revolves around the inside of the housing, it continuously changes in volume, expanding and contracting, due to the radial or axial motion of the vanes in cooperation with radial vane guides or cams disposed on the housing at each side of the rotor. Wear can be substantially decreased by retaining means which prevent the working ends of the vanes to press the inner surface of the housing or the cam surfaces of the housing. Intake and exhaust ports are adequately located within the rotor housing. Examples of such engines are U.S. Patent 5,277,158 to Pangman, U.S. Patent 5,524,587 to Mallen, and U.S. Patent 4,401 ,070 to McCann. The same phases of the Otto cycle are present during the operation of these engines. To date, practical means to turn the Otto cycle into the Miller cycle in this type of engines were not achieved.

Although the known rotary type engines yield an increase in power-to- weight and power-to-volume ratios and a smoother operation over reciprocating-piston engines, they are still unable to follow the Miller cycle. On the other hand the inner surface of the rotor housing of these engines has in general a non simple profile which turn its construction dificult and therefore costly. For instance, the Wankel engine shows a complex inner profile following an epitrochoid curve; the known vaned engines have in general oval or elliptical shaped profiles. Besides this fact, also the orbital movement of the rotor in the Wankel engine, and the reciprocating movement of the vanes, in the known vaned engines, originate inertial forces which must be counterbalanced to avoid noise and vibration of the engine. This fact implies additional necessary parts of the engine which contribute to increase the costs of construction.

It would, therefore, be an advancement in the art to provide a rotary internal combustion engine able to, by itself, follow the so called Atkinson or Miller cycles, substantially increasing the thermal efficiency of this type of engines.

Another advancement in the art would be to provide a rotary internal combustion engine of the vane type with a inner profile of the rotor housing composed only by pure circular arcs, turning its construction easier and decreasing, therefore, the corresponding cost.

Still another advancement in the art woud be to provide a rotary internal combustion vaned engine with vane guidance pathways which follow pure circles, eliminating, in this way, the reciprocating movements of the vanes.

Yet another advancement in the art would be to provide a rotary internal combustion engine of the vane type with vanes only dedicated to the induction/compression phases and equal or different vanes only dedicated to the expansion/exhaust phases, which contribute to the optimization of the operation cycle of the engine.

Object and Advantages of the Invention

The object of the present invention is to provide a single rotor vaned rotary internal combustion engine with: i) an expansion volume of the hot gases larger than the compression volume of the intake gases; ii) an inner profile of the rotor housing composed by pure circular arcs; iii) pure circular vane retention guides; iv) vanes dedicated only to the induction/compression phases and vanes dedicated only to the expansion/exhaust phases; v) self-lubrication of the vanes. The corresponding advantages of the invention are: i) higher thermal efficiency; ii) simpler construction; iii) less noise and vibration; iv) additional means of optimization of the engine's cycle; iv) easier lubrication of the vanes.

Summary of the Invention

In accordance with the above referred object, this invention provides a single rotor radial vane internal combustion rotary engine comprising a housing enclosing a longitudinal cavity with an internal cross section internally limited by two pairs of circular arcs. The first pair, formed by two arcs of equal radius, is symetric in relation to an axis where the centers of the second pair are located. This one is formed by two arcs of equal or different radius. A cylindrical rotor with the radius of the arcs of the first pair is installed into the cavity and supported on both sides of the housing by adequate bearings. The rotor has a plurality of radially extended slots equally disposed along its periphery wherein a plurality of vanes having retention ends and working ends are slidable. Means for guiding the vanes in pure circular pathways are provided on both top sides of the housing. These pathways are two secant circular tracks of equal or different radius, made on both inner flat surfaces of the housing's tops. They are eccentric in relation to the longitudinal axis of the housing and are aligned with the above referred second pair of arcs of equal or different radius. Pins in the retention ends of the vanes pivot in the holes of slide members which are formed by curved pieces which can slide smoothly in the tracks.

Half of the vanes (involved in the induction/compression phases) are guided by the slides which move along one of the circular tracks; those of the other half (involved in the expansion/exhaust phases) are guided by the slides which move along the second circular track without, however, interfering with the first ones. In this way, when the rotor rotates, the working end of each vane slides over the corresponding cylindrical inner surfaces of the cavity, without pressure, therefore without wear. On the other hand, the cylindrical outer surface of the rotor also slides over the inner cylindrical surfaces of equal radius of the cavity. At half-lenght of the outer surface of the rotor, between slots, are alternately located recesses whereinto the intake gases are compressed and burned when the engine is in operation. Intake and exhaust ports as well as a sparkplug (in the case of a SI engine) or a fuel injector (in the case of Cl engine) for ignition are properly located along the housing. In rotation, the induction/compression vanes draw and compress simultaneously into the recesses air alone or air and fuel mixture. This mixture or air with the injected fuel is then ignited and the hot gases act upon the expansion/exhaust vanes which power the rotor and simultaneously evacuate the burned gases through the exhaust port. Both types of vanes, guided along the independent secant circular tracks, partially emerge from, and immerge into, the slots. When immersed they are lubricated by the oil in circulation inside the rotor. The volume of gases drawn or evacuated is that between two emersed vanes, one vane between them being immersed. If the volume between two emerged expanding vanes is larger than the one between two emerged compressed vanes, as it happens if the independent circular tracks have different radii or/and different eccentricies, then the engine is able to follow a Miller cycle.

Brief Description of the Drawings

The above mentioned objects and advantages will be better understood from the following detailed description of a preferred embodiment of the invention depicted by the following drawings:

FIG.1 is a top view of the central body of the engine showing in particular the inner profile formed by circular arcs. Cutaways of the location of the sparkplug and the intake and exhaust ports are also shown.

FIG.2 is a top view of the rotor showing the slots as well as the passageway holes for the internal circulation of lubricate oil. The peripheral recesses are shown in dashed lines.

FIG.3 shows the inner faces of the top members of the engine's housing where the circular secant guiding tracks of the vanes can be seen.

FIG.4 shows the front view and the profile view of a induction/compression vane.

FIG.5 shows the same views of an expansion/exhaust vane.

FIGS.6 and 7 show the top views of the curved slides for the induction/compression and expansion/exhaust vanes guidance, respectively. FIG.8 is a top view of the engine's housing showing the rotor, vanes and slides duly mounted. Cutaways of the ports and the location of the sparkplug as well as the circular tracks and rotor's recesses (in dashed lines) are also shown.

FIG.9 is a cross-sectional front view of the engine, taken along the axis AA' of the preferred embodiment illustrated in FIG.8

Detailed Description of the Preferred Embodiment

Reference will now be made in detail to a preferred embodiment of the invention, however not to be limiting of its scope, an exemple of which is illustrated in the accompanying drawings. Figures 1 to 6 present the engine's members one by one; figures 7 and 8 show the same members associated, forming the preferred embodiment.

FIG.1 shows the central body 1 of the engine with its inner profile formed by two pairs of pure circular arcs: the first one 2-2' with the same center O and the second one 3-3' with centers O' and O" on the axis AA'. The intake port 4, the exhaust port 5 and the threaded hole 6 for the sparkplug are located at the half lenght of the body. A plurality of threaded holes 7 at both sides of this central member allow the fixing of the top members, not shown in this figure.

FIG. 2 shows the rotor 8 with a diameter practically equal to the arcs 2-2'. With the same length of the central body, the rotor has a plurality of slots 9, a plurality of passageway holes 10 for the internal circulation of the lubricate oil and a central hole 11. The diameter of this hole is just the necessary one to pass the central shaft, not shown in this figure, to which the rotor is attached by a slot key. The recesses 12 distributed alternately along the periphery of the rotor at its half lenght are shown by dashed lines.

FIG.3 shows the inner faces of the top members 13 with the circular guiding tracks 14 and 15 of the vanes. Track 14 corresponds to the induction/compression vanes; track 15 corresponds to the expansion/exhaust vanes. It is noticed that the diameter of track 15 is bigger than the diameter of track 14 so that the Miller cycle could be followed. Holes 16 are necessary as passgeways for the internal circulation of the lubricate oil. Bores 17 allow the fixing, by screws, of the top members to the central body 1.

FIGS.4 and 5 show the front view and the profile view of the induction/compression vane 18 and expansion/exhaust vane 19 respectively. Pins 20 at the retention ends of the vanes pivot in the central holes 21 of the curved slides 22 and 23 shown in FIGS.6 and 7 respectively. Adjustable thin blades 24 are sandwiched at the working ends of the vanes and secured by screws 25. Their function is to permit the adjustment of the clearance between working ends of the vanes and the inner surfaces corresponding to circular arcs 3-3' of the central body to a minimum. Slides 22 and 23 match exactly with the internal geometry of the guiding tracks and can move into them along their circular lubricated path-ways without significant friction.

FIG.8 is a top view of the engine without one top member where all the previously described members can be seen assembled. Cutaways show the intake and exhaust ports as well as the sparkplug for the ignition of the compressed mixture of air and fuel. As illustrated, rotor 8 rotates in a counterclockwise direction. Vanes 18-18'-18"-18'" are involved in the induction/compression phases. Vanes 19-19'-19"-19'" are involved in the expansion/exhaust phases. Once the rotation is initiated, and after at least one complete turn of the rotor, the volume 27 is progressively filled by the intake gases due to the negative pressure created in front of the intake port 4 by the movement of vane 18. At the same time, the volume 28, already filled with gases, progressively decreases to the volume of recess 12, where the compressed gases are trapped. Thereupon they are ignited by the sparkplug 26 and the hot gases rapidly expand forcing the vane 19 and rotor 8 to move in the same counterclockwise direction. Volume 29 progressively increases during this power phase until vane 19 occupies the position of vane 19'. At the same time the expanded gases in volume 30 are exhausted due to the movement of vane 19. Phases induction/compression and expansion/exhaust are in this way completed and are continuously repeated during the continued engine's operation. If the maximum value of volume 30 is larger than the maximum value of volume 27, a Miller cycle is followed; should these volumes be equal the correspondent cycle would be a Otto cycle.

FIG.9 is a cross sectional view taken along A-A' of the embodiment illustrated in FIG.8. Finnes for the engine's air cooling are shown in the central member but other conventional cooling system could be considered. The circulation of the lubricate oil through the interior of the engine is also supposed to be done by conventional means, 33 being the inlet and 34 the outlet of the oil. Rotor 8 is secured to the shaft 32 by the key-bolt 31.

It must be noticed that arcs 3 and 3' shown in FIG.1 are pure circular arcs.

Also the median circles of tracks 14 and 15 illustrated in FIG. 3 are pure circles. However arc 3 must not be concentric with the median of track 14 and the same must happen in relation to arc 3' and the median of track 15. This must be so because the vanes rotate in relation to the center of the rotor and not in relation to the centers of the circular tracks. Therefore it is upon the radii of the rotor that it is necessary to grant constant distances between the medians of the tracks 14 and 15 and the corresponding arcs 3 and 3' and not upon the radii of the circular tracks. These constant distances correspond to the constant lenghts of the vanes. It is possible, however, to grant a practical constant distance between arc 3 and the median of track 14, just within the limited angular amplitude of arc 3, with a negligible error, if the center of arc 3 is properly deviated from the center of track 14 along axis AA'. The same applies to the centers of arc 3' and track 15. This procedure turns the construcion of the engine very easy particularly in what concerns the inner surface of the central body without significantly jeopardizing the sealing tightness of the vanes. Thin blades 24 secured by screws 25 illustrated in FIGS. 4 and 5 allow the adjustment and readjustment, whenever necessary, of the minute resulting gap between the working tips of the vanes and the inner surface of the central body.

It must be also noticed that, as the tracks are pure circular pathways, the vanes rotate but do not reciprocate at all in relation to the centers of the circular tracks when the rotor rotates. Therefore no corresponding inertial forces result. However, as the vanes are inside the slots of the rotor and this is eccentric in relation to the tracks, they have a movement in relation to the rotor along the slots. Due to this fact, a force by effect of Coriolis is created in each vane, acting upon the rotor. The resultant of all forces corresponding to the plurality of the vanes is, however, negligible. This means that the engine is practically exempt of vibrations when in operation.

It must be further noticed that in each revolution of the rotor all vanes alternately immerge into the slots and are bathed in the lubricant oil which circulates internally to the rotor. This fact ensures a permanent lubrication of the vanes during the operation of the engine and aids in carrying to the outside the internally produced heat.

The above described embodiment is to be considered in all respects only as an illustrative example and not as a restrictive one. Thus, the scope of the invention should be determined not by the illustrated embodiment but by the appended claims.

LIST OF THE PARTS

1 Housing -2' First pair of circular arcs of equal radii -3' Second pair of circular arcs of equal or different rad

Intake port

Exhaust port

Threaded hole for the sparkplug

Threaded holes for fixing the top members

Rotor

Slots

10 Passageway holes in the rotor

1 1 Central hole

12 Recesses

13 Top members

14 Track for compression vanes

15 Track for expansion vanes

16 Passageway holes in the top members

17 Top members' bores for fixing

18 Induction/compression vanes

19. Expansion/exhaust vanes

20 Vane pins

21 Holes in the curved slides

22 Curved slides for induction/compression vanes

23 Curved slides for expansion/exhaust vanes

24 Adjustable thin blades

25 Screws in the vanes

26 Sparkplug

27 Induction volume

28 Compression volume

29 Expansion volume

11 /1 Exhaust volume Key bolt Shaft Lubricate oil inlet Lubricate oil outlet

11/2

Claims

A single rotor radial vaned internal combustion rotary engine having conventional means for the internal circulation of lubricate oil, for the ignition of gases and for the air or water cooling system, being, however, characterized by comprising:

1 ) a housing enclosing a longitudinal cavity with an internal cross section limited by two pairs of circular arcs, the first one being formed by two arcs (2-2^') of equal radius symetric in relation to an axis (AA') where the centers (O'O") of the second pair (3-3^') are located, this one being formed by two arcs of equal or different radii, and having intake (4) and exhaust (5) ports as well a sparkplug (26) or fuel injector properly located.

2) a cylindrical rotor (8) with the radius of the first pair of arcs and the lenght of the cavity whereinto is rotatably mounted, said rotor having a plurality of radially extended slots, (9) equally disposed along its periphery, and recesses (12) at half-length of its outer surface, located alternately between slots, the number of recesses being half of that of vanes.

3) a plurality of vanes (18-19) slidable into the slots with the lenght of the rotor and equal or different widths, having retention ends provided by pins (20) and working ends equipped with sandwiched secured, though adjustable, thin blades (24) half of the vanes being involved only in the induction/compression phases, the other half being involved only in the expansion/exhaust phases of the engines' cycle.

4) two top (13) members enclosing the cavity, having each, at its inner flat

12 surfaces, two pure circular secant tracks (14-15) of equal or different radii, eccentric in relation to the longitudinal axis of the cavity and aligned with the pair of equal or different radii referred above in 1), each circular track being responsible for the guidance of each half of the vanes.

5) a plurality of curved slide members (22-23) with cross sections matching the cross section of the tracks, which can slide smoothly along the tracks, half of them assigned to the guidance of one half of the vanes, sliding along one track, the other half assigned to the guidance of the second half of vanes, sliding along the second track, all curved slides having central holes (21) wherein the pins (20) of the retention ends of the vanes can pivot.

13