ENGINE HAVING ROTARY PISTONS

Abstract

The present invention relates to a mechanism (1) having rotary pistons (21), said mechanism comprising an outer enclosure (2) forming a stator in which a rotary assembly (20) forming a rotor moves, the rotary assembly (20) including: a plurality of pistons (21) forming a hinged polygon, each piston (21) defining a positive-displacement chamber (35) with the enclosure (2), and first guide (27, 27a, 27b) that are arranged so as to engage with second guide means (7a, 7b) comprising rolling surfaces (10a, 10b) so as to drive the polygon to carry out a predetermined movement, the mechanism (1) being characterized in that it comprises a drawback device (50) that maintains contact between the guide means (27, 27a, 27b) and the rolling surfaces (10a, 10b). The invention also relates to an engine and a pump including such a mechanism (1).

Description

TECHNICAL FIELD

The present invention relates to a rotary piston mechanism as well as an engine and pump using such a mechanism.

BRIEF SUMMARY OF RELATED ART

Rotary piston mechanisms, and in particular in their motor application, have been described in many documents, which define the geometric principles of the movement of a polygon articulated at the apices of the sides making it up; each of the sides all having the same length and each of the apices being in geometric contact with a stator shape.

In particular, documents WO 01/88341 A1, EP 1 295 012 B1 and US 2004/0089251 A1 propose different solutions for resolving the problems of sealing at the apices of the polygon, and transmission of the non-constant continuous movement of the pistons formed by the straight segments defined by the adjacent apices of the polygon.

All of these proposals more or less appropriately resolved all or some of the theoretical operating principles of this type of mechanism.

However, the feedback from tests done has shown difficulties for which no technical solution has yet been proposed.

The difficulties encountered during the exploitation of this type of mechanism first relate to mechanical tightening problems when it is hot as well as during assembly of the mechanism. The symptoms are blockages of the hinge assembly, which, despite a careful production, cannot pivot freely around the various axes making up its mechanism.

Possible compensations by excess play create knocking at the connecting rod assemblies, and pronounced wear of certain points of the mechanism, thereby limiting the lifetime of the pieces thus embrittled.

During analyses, it was also observed that the geometric and algebraic solutions were describing the ideal geometric locations, but with very small dimensions, i.e. solutions that are not very compatible with mechanical play tolerance accumulation phenomena.

Among the cited patents, some propose solutions that separate the sealing functions at the apices from the movement functions specific to the polygonal structure.

Thus, they propose a device having a movement specific to the polygon, independent of the profile of the stator enclosure inside which the apices of the polygon are in constant sliding contact.

This mechanical approach appears correct and therefore consists of determining the movement of the articulations of the polygons without action by the stator on the apex of the polygon.

In fact, one of the origins of tightening problems comes from imprecise machining of the stator profile. The decision to make the articulations of the rotary assembly independent of the stator shape helps resolve some of the defect problems.

Patent WO 01/88341 A1 proposes a solution describing the chaining of four pistons to one another using connecting rods also performing the appropriate transfer function between the pistons and the transmission shaft, as well as several mechanical solutions resolving the transfer function between the tangential speed variations of the pistons toward the central transmission shaft rotating at a constant speed, in particular using rollers traveling over a rolling surface installed on the lateral flanges.

However, after analysis, it was identified that the project as described was proposing a hyperstatic configuration that did not allow any play tolerance. In fact, the trapezoid described by the two connecting rods of the two adjacent pistons, the connecting point of the pistons and the connecting point on the driveshaft builds a hyperstatic connection. This trapezoid is undeformable and cannot allow any variation of the length of any one of its sides, as will be the case during the use of the mechanism, which will display expansion phenomena. The bearings of the articulations will be the embrittled members. These parts will wear prematurely while having created internal friction making the mechanism unsuitable for its purpose.

Furthermore, the shape of the connection between pistons does not appear capable of sustainably bearing the intense pulling, thrust, and centrifugal forces to which it will be subjected. These bowed collaborating movable interlocking forms are complex in terms of expansions, buttress formation, friction distribution, and their use is as difficult as it is unreliable. The sealing of such pieces is also more complex to achieve than the sealing of traditional axles and not very effective inasmuch as the stressed orientation of the sealing segment does not correspond to the forces undergone by that piece.

In case of expansion, in cases of temperature variation, this geometric solution is no longer respected, which results in a mechanical stress on the connection of the apex of the diamond without the possibility of absorbing that stress, which will result in a rupture of the connection between pistons, as well as stresses on the connecting rod assemblies, the latter not being able to transmit the expansions. This will irreversibly cause problems such as, for example, a rupture of a connecting rod bearing, or the destruction of the segment support device or the segment itself, which is already working in a cantilever, which may also result in deterioration of the stator profile by burring of its inner surface.

A machining anomaly, on the rolling surfaces, will result in a positioning error of the apex of the diamond, the sealing piece of which will be the only one to react this additional force. This piece will be stressed in its degree of freedom and may no longer pivot and will break; this stress may potentially be passed on to the connection between the pistons.

Patent EP 1 295 012 B1 and part of patent US 2004/0089251 A1 also propose determining the deformation of the polygon without bearing on the stator enclosure. This proposed solution uses a set of gears.

However, the sealing problem at the apices of the polygon does not appear to have been resolved.

Lastly, patent US 2004/0089251 A1 proposes a geometric solution accumulating the sealing function and a geometric function.

However, this solution does not resolve the problems of machining imprecisions and wear of certain parts of the mechanism as it is used.

BRIEF SUMMARY

The invention therefore aims to propose a technical solution making it possible to do away with these operating difficulties due to machining imprecisions, expansion phenomena due to the temperature or other factors, and wear phenomena of the pieces.

To that end, the present invention relates to a rotary piston mechanism comprising an outer enclosure forming a stator inside which a rotary assembly forming a rotor moves, the rotary assembly comprising a plurality of pistons forming an articulated polygon, each piston delimiting a volume chamber with the enclosure, and first guide means arranged to cooperate with second guide means comprising rolling surfaces, so as to stress the polygon to perform a predetermined movement, wherein the mechanism comprises a return device maintaining contact between the guide means and the rolling surfaces.

The first and second guide means allow the pistons to follow a predetermined direction so as to limit the action of the enclosure on the apices of the polygon while the return device makes it possible to offset the machining defects of the guide means as well as the expansion and wear of those elements occurring during operation of the mechanism.

According to one embodiment, the return device is supported by the rotary assembly.

According to one embodiment, the return device comprises a plurality of dampers positioned between a stationary point of each piston and a movable fastening point of each of the first guide means, such as the guide roller axis of rotation.

This arrangement makes it possible to offset the wear of each of the guide rollers individually.

Using several rollers makes it possible to distribute the forces applied on the guide surfaces. Furthermore, these rollers have a small bulk and limit the friction on the guide surfaces due to their degree of rotational freedom.

According to one embodiment, the guide rollers are conical.

It is easier to design guide rollers whereof the surfaces are parallel; however, a conical configuration of the guide rollers makes it possible to increase the bearing surface of the rollers relative to a flat configuration and prevents the guide rollers from deviating from their path.

According to this same embodiment, the second guide means are rolling surfaces with an equal slope.

According to another embodiment, the return device is supported by the outer enclosure.

This arrangement makes it possible to place the return device at stationary points and limit the number thereof.

According to one embodiment, the second guide means are supported by lateral flanges positioned coaxially to the outer enclosure and serving to close the latter part.

This arrangement makes it possible to take advantage of the ease of assembling and disassembling the flanges used to close the outer enclosure so as to position the second guide means therein. It is also possible to consider manually pre-adjusting the orientation of said second adjustment means using a suitable device before closing of the enclosure by the flanges.

According to one embodiment, the second guide means comprise two sectors, the first of which is secured to the stator enclosure and the second of which is translationally movable relative to the first, a return device being positioned between a stationary point of the first sector and a movable point of the second sector of each of the second guide means.

This arrangement makes it possible to be able to modify the eccentricity of the guide surfaces, which assume a substantially ellipsoidal form, and thus makes it possible to offset the general wear of the guide surfaces as well as their machining defects.

According to one embodiment, a segment support device is pivotably mounted along a single axis on each of the apices of the polygon.

This arrangement allows the segment support device to adapt to the shape of the enclosure and to present the segments at all times in a direction transverse to the wall of the stator in which they evolve, which reduces the wear of the segments and imparts better sealing to the volume chambers.

Advantageously, a segment support device comprises a device for pressing segments on the stator enclosure.

The purpose of this arrangement is to produce a continuous sliding contact of the segments on the inner surface of the single-piece body so as to offset the machining defects thereof and therefore further improve the sealing between the volume chambers.

According to one embodiment, at least one piston is connected by a single connecting rod (24) or by several connecting rods (241, 242) having the same hinge pins as the transmission shaft (40).

The use of connecting rods is geometrically easier to design than a set of gears, for example, and will be a source of less play due to the reduced number of elements and connections.

In this embodiment with connecting rods, the invention consists of keeping only one connecting rod per piston, for example that defined as rear in patent WO 01/88341 A1 in the case of rotation in the indirect trigonometric direction or in the clockwise direction.

The transfer function between the pistons and the engine shaft is kept; the expansions are no longer problematic, as an expansion will only create an imperceptible rotation of the rotary assembly relative to a reference position.

According to one embodiment, two adjacent pistons are connected to one another by a pivot link with an axis parallel to the axis of rotation of the rotary assembly.

This configuration makes it possible to obtain a connection of two adjacent pistons that is both very solid and flexible, and is also easy to produce, as it only comprises a single pin fitted into both ends of the two pistons.

According to one embodiment, the rolling surfaces are turned toward the axis of rotation of the rotary body.

According to one embodiment, the rotary assembly comprises a lubrication circuit mounted in a closed circuit.

This arrangement makes it possible to use a so-called “dry sump” lubrication system with all of the advantages thereof, in particular more significant and targeted lubrication at the critical locations, a lowered center of gravity of the mechanism due to the lack of an oil pan under the mechanism, a reservoir outside the mechanism that is not very bulky, and the possibility of incorporating a heat exchanger for cooling oil in the lubrication circuit.

According to one embodiment, the distance between the connecting pin between two adjacent pistons and the hinge pin of the segment support device is constant.

This arrangement makes it possible to define a particular stator profile corresponding to this geometric constraint that will only give the segment holders and segments their sealing function between volume chambers.

According to one embodiment, the distance between the connecting pin between pistons and the hinge pin of the segment support device is variable.

This arrangement makes it possible to obtain maximal volume ratios between chambers to the extent that the segment support devices and segments still perform their sealing function.

According to this embodiment, the segment support device comprises a complementary device for pressing segments on the stator, such as a hydraulic piston.

This arrangement offers the possibility of being able to still further increase the volume ratios between chambers by offering the segment supports and segments the possibility of ensuring sealing of the volume chambers despite substantial spacing of the wall of the stator for certain positions of the pistons.

The present invention also relates to a pump comprising a mechanism as described above as well as an engine using the same mechanism in its use for producing mechanical energy.

BRIEF DESCRIPTION OF THE DRAWINGS

In any event, the invention will be well understood using the following description, done in reference to the appended diagrammatic drawings, showing, as non-limiting examples, several embodiments of a mechanism according to the invention.

FIG. 1 shows a summary projection diagram of the profile of the mechanism according to the invention.

FIG. 2 shows a summary projection diagram of the profile of the mechanism with a first embodiment of the arrangement of the play compensating device.

FIG. 3 shows a summary projection diagram of the profile of the mechanism with a second embodiment of the arrangement of the play compensating device.

FIG. 4 shows the arrangement of three pistons in perspective view positioned outside the stator enclosure.

FIG. 5 is a perspective view of a second guide means with its play compensating device according to the embodiment illustrated in FIG. 3.

FIG. 6 is a perspective view of the inner portion of a flange incorporating the second guide means with its play compensating device illustrated in FIG. 5.

FIG. 7 is a perspective view of the outer portion of the flange illustrated in FIG. 6.

FIG. 8 shows a cross-sectional and profile view of the mechanism according to the invention.

FIG. 9 shows a cross-sectional view of a hydraulic damper of the mechanism according to the invention.

DETAILED DESCRIPTION

As illustrated in FIGS. 1, 2, 3 and 8, a rotary piston 21 mechanism 1 includes an outer enclosure 2 forming a stator inside which a rotary assembly 20 forming a rotor moves.

All of the reasoning described hereafter is valid for a polygon with n apices. The following reasoning is based on an embodiment with a polygon having four apices, or with four pistons forming an articulated deformable diamond, this example not being limiting.

The outer enclosure 2 in the embodiment illustrated in FIGS. 1, 2, 3 and 8 includes a single-piece body 3 generally made from steel, forming a volume with two identical ellipsoidal bases, in which an ellipsoid-shaped through cavity 5 is bored. The inner surface 4 of said cavity 5 is advantageously glazed so as to give it a surface state satisfactory for the applications of the mechanism 1.

The outer enclosure 2 also includes two lateral ellipsoid-shaped flanges 6a, 6b, shown in FIGS. 6 and 7, closing the through cavity 5 at each of the two ellipsoidal bases of the single-piece body 3. Each of said flanges 6a, 6b is screwed to the single-piece body 3 of the enclosure 2 and incorporates sealing means such as an O-ring positioned in a groove situated on the joint of the flanges 6a, 6b with the single-piece body 3.

Each of the flanges 6a, 6b comprises a bearing 8a, 8b centered to allow the rotation of the transmission shaft 40 along the axis 30 of the bearings 8a, 8b.

Each of these bearings 8a, 8b is respectively secured by screws 18a to each of the flanges 6a, 6b and comprises two cushions on the inner contour 18b thereof as well as an oil seal flush on the outer surface 18c of each of the bearings 8a, 8b so as to perform oil sealing between the barriers 8a, 8b in the transmission shaft 40.

As illustrated in FIG. 6, guide means 7a, 7b having a volume shape with substantially ellipsoidal bases 19a generating a first rolling surface 10a and a second rolling surface 10b of revolution on the outer contour 19b of these same substantially ellipsoidal bases 19a, are positioned coaxially to the alignment axis 30 of the two flanges 6a, 6b and oriented towards the inside of the enclosure 2. They are fastened using screws 9a passing through each of the bearings 8a, 8b from the outside towards the inside of the flanges 6a, 6b and being screwed on threaded bores 9b positioned opposite the screws 9a on each of the guide means 7a, 7b.

The substantially ellipsoidal guide means 7a, 7b are coaxial and have a slight rotational offset along their axis 30. Each of said guide means 7a, 7b has an ellipsoidal central opening 11 whereof the small axis has a size larger than the diameter of the bearings 8a, 8b so as not to bother the rotation of the transmission shaft 40.

According to one embodiment, these guide means 7a, 7b are made in a single piece having a predefined shape not evolving during use of the mechanism 1.

According to another embodiment illustrated in FIG. 5, these guide means 7a, 7b comprise two sectors 71 and 72 separating the substantially ellipsoidal volume into two volumes at the small axis thereof, thereby creating four coplanar and distinct cutting surfaces 12a, 12b, 12c and 12d on each of the sectors 71 and 72, each of the surfaces of a same sector 71 being opposite a surface of the other sectors 72 while being parallel thereto.

The sector 71 is fastened to the bearings 8a, 8b using screws 9a tightening in the threaded bores 9b, the second sector 72 is slidingly mounted in translation relative to the sector 71. The two sectors 71 and 72 have a first mechanical link 13 formed by a pin positioned between two first surfaces 12a, 12b opposite the sectors 71 and 72. This pin 13 is secured on the surface 12a and slides translationally in a bore positioned on the surface 12b.

A second mechanical link 14 is formed in the same way between the other two opposite surfaces 12c, 12d. However, the axis 14 of this link is surrounded by conical washers 15 acting in compression, such as a spring, and acting as a play compensating device 50.

In order to ensure the continuity of the deformable rolling surfaces 10a and 10b to adapt to the relative translational movements of the two adjacent edges of the two sectors 71 and 72, positioned on each of the edges of the two sectors 71 and 72 of each of the guide means 7a and 7b is a joint 16 of the cantilever comb expansion type. These joints 16 are made up of a set of identical parallelepiped teeth 17a, spaced apart by a same distance and coming transversely from the cutting surfaces 12a, 12c of the sector 71, and by another set of teeth 17a coming transversely from the cutting surfaces 12b, 12d of the sector 72 respectively located opposite the cutting surfaces 12a, 12c of the sector 71, each set of teeth 17a fitting into the spaces 17b between teeth 17a created by the other set of teeth 17a.

The rotary assembly 20 forming a rotor is made up of four pistons 21 forming a deformable diamond. The pistons 21 have a convex shape on the outer surface 21 a thereof and a planar shape on the inner surface 21 b thereof.

Each of the adjacent pistons 21 is solidly connected using a pivot link made up of a pin 22 passing transversely through the ends of two adjacent pistons 21.

Each piston 21 has a parallelepiped recess 23 whereof two walls 23a, 23b are positioned transversely to the pins 22 ensuring the connection of the adjacent pistons 21.

In this recess 23 and between these two walls 23a, 23b, a connecting rod 24 is positioned here made up of two connecting rods 241, 242 positioned side-by-side and separated by a space 24c. These two connecting rods 241, 242 are maintained by a pivot link formed by a pin 25 passing transversely through the two walls 23a, 23b as well as the head 24a of each of the two cylindrical connecting rods 241, 242. This pin 25 is thus positioned parallel to the pins 22, linking the adjacent pistons 21 to one another.

Each of the pistons 21 also comprises two through openings 26a, 26b, which are also parallel to the axes 22, and made on the lower portion of the piston 21 on either side of the recess 23. These two openings 26a, 26b are intended each to receive a first guide means 27, illustrated in FIGS. 1, 2, 3 and 8 by rollers 27.

Each of the pistons 21 only comprises two rollers 27 each positioned on the lateral surfaces 21c, 21d of the piston 21. In the direction of rotation of the rotary assembly 20, a front guide roller 27a and a rear guide roller 27b are distinguished whereof the axes of rotation are on either side of the recess 23 coaxial to each the openings 26a, 26b. The piston 21 has a suitable profile on either side allowing the rotation of each of said two rollers 27a and 27b.

On the same end of their outer surface 21a, each piston 21 has a semicircular transverse notch 28 on the width of the piston 21. Inside that notch 28, there is a segment support device 29 having, like the notch 28, a semicircular shape allowing it pivot in the notch 28 along the hinge pin 32 of the segment support device 29.

On said segment support device 29, two radial segments 31 are positioned protruding from the convex surface 21 a of the piston 21. Each of these segments 31 is pushed toward the outside of the device 29 by the action of a spring 33 positioned in the device 29.

In the embodiment illustrated in FIGS. 1, 2, 3 and 8, the distance between the linking pin 22 of two adjacent pistons 21 and the hinge pin 32 of the segment support device 29 is constant.

As illustrated more precisely in FIG. 8, each of the connecting rods 24 is, as already mentioned above, made up of two connecting rods 241, 242 positioned side-by-side and separated by a space 24c. Each of these two connecting rods 241, 242 is connected to a transmission shaft 40 by means of the pivot link made by a pin 34 passing transversely through the foot 24b of each of the cylindrical connecting rods 241, 242 on the one hand, and on the other hand, a hub 41 of the transmission shaft 40 passing in the space 24c positioned between the feet 24b of the two connecting rods 241, 242.

It is understood that these two connecting rods 241, 242 could be connected to one another to form a single mechanical part.

According to the embodiment illustrated in FIG. 2, the two guide rollers 27a and 27b present on the lateral surfaces 21c, 21d of each piston 21 are connected thereto by means of a return device 50 or play compensating device such as hydraulic dampers 50, illustrated in FIG. 9.

A hydraulic damper 50 is made up of a piston-cylinder assembly whereof the internal leaks are calibrated. The piston 51 is pierced at the center thereof with a calibrated diameter and the ball 53, provided with a spring 54 acting as a check valve, imposes the passage direction of the oil through the calibrated space 55 between the piston 51 and the cylinder 52.

In this embodiment, a stationary connection by means of a screw (not shown) is made between the piston 21 and the first fastener 56 of the hydraulic damper 50 and a pivot link is made by means of a pin (not shown) between the second link 57 of the hydraulic damper 50 and the axis of rotation 27c of a roller 27.

Once the rotary assembly 20 is assembled, it is inserted inside the single-piece body 3 and enclosed inside the stator enclosure 2 during mounting of the lateral flanges 6a, 6b.

Once mounted, the rotary assembly 20 delimits, with the stator enclosure 2, volume chambers 35.

A closed oil circuit (not shown) is arranged in the various parts of the rotary assembly 20 so as to lubricate the contact areas between the different moving pieces relative to one another, as is the case for the pins 25 and 34 respectively maintaining the head 24a and the foot 24b of the connecting rods 24. This so-called dry sump circuit includes an oil pump as well as an oil reservoir, which are both positioned outside the stator enclosure 2. A heat exchanger is also arranged in the oil circuit so as to cool it.

It should be noted that the embodiment comprising arranging a hydraulic damper 50 between each piston 21 and roller 27 of the rotary assembly 20 and positioning guide means 7a, 7b in two sectors 71 and 72 capable of moving in translation relative to one another does not prohibit embodiments comprising using only the hydraulic dampers 50 between each piston 51 and roller 27 of the rotary assembly 20 or the guide means 7a, 7b.

Once the mechanism 1 is mounted, it can be used as an engine so as to produce torque on its transmission shaft 40, or as a pump by driving that same transmission shaft 40 using a coupling connecting it to an external engine.

Of course, both of these applications require developments of the single-piece body 3 so as to create intake and exhaust pathways therein for pump, external combustion engine, or steam expansion engine applications, as well as lighting for internal combustion engine applications.

During the rotation of the rotary assembly 20 inside the stator enclosure 2, the front rollers 27a of each of the pistons 21 follow the trajectory of the rolling surface 10a of the guide means 7a, while the rear rollers 27b of each of the pistons 21 follow the trajectory of the rolling surface 10b of the guide means 7b.

The apices of the diamond formed by the four pistons 21 thus follow the trajectory of the inner surface 4 of the single-piece body 3 of the stator enclosure 2 without bearing on that same surface 4.

The segments 31 by means of the spring 33 present in the segment support device 29 ensure continuous sliding contact on the inner surface 4 of the single-piece body 3 of the stator enclosure 2.

The connection of the segment support device 29 in its notch 28 guarantees the segments 31 radial contact with the inner surface 4 of the single-piece body 3 of the stator enclosure 2, which makes it possible to reduce the wear thereof and preserve good sealing of the volume chambers 35.

During the operation of the mechanism 1, expansion phenomena may appear, the transfer function between the pistons 21 and the transmission shaft 40 is preserved and the expansions will only create an imperceptible rotation of the transmission shaft 40 relative to a reference position.

During extended operation with poor lubrication capable of causing wear of one of the rolling surfaces 10a, 10b or several rollers 27, the hydraulic dampers 50 arranged on each of the rollers 27 will offset that wear at all times by providing continuous contacts between the rollers 27 and the two rolling surfaces 10a and 10b.

In the case of overall wear of the rollers 27, the rolling surfaces 10a and 10b in the embodiment thereof with two sectors 71 and 72 will increase the perimeter of their rolling surface 10a, 10b so as to compensate the wear of the rollers 27.

The invention is of course not limited to only the embodiments of this mechanism 1 described above as examples, but on the contrary encompasses all alternatives thereof. The segment support device 29 can comprise a complementary device for pressing the segments 31 on the inner surface 4 of the single-piece body 3 of the outer stator enclosure 2 so as to make it possible to use a different stator profile and increase the volume ratio between the volume chambers 35, and the return device 50 illustrated here by the dampers 50 may be of any type, on the condition it provides contact between the guide means (27, 27a, 27b) and the rolling surfaces (10a, 10b).

Claims

1. A rotary piston mechanism comprising;

an outer enclosure forming a stator inside which a rotary assembly forming a rotor moves, the rotary assembly comprising: a plurality of pistons forming an articulated polygon, each piston delimiting a volume chamber with the enclosure, and first guide means arranged to cooperate with second guide means comprising rolling surfaces, so as to stress the polygon to perform a predetermined movement, and

wherein the mechanism comprises a return device maintaining contact between the guide means and the rolling surfaces.

2. The mechanism according to claim 1, wherein the return device is supported by the rotary assembly.

3. The mechanism according to claim 1, wherein the return device comprises a plurality of dampers positioned between a stationary point of each piston and a movable fastening point of each of the first guide means comprising a guide roller axis of rotation.

4. The mechanism according to claim 1, wherein the return device is supported by the outer enclosure.

5. The mechanism according to claim 1, wherein the second guide means are supported by lateral flanges positioned coaxially to the outer enclosure and serving to close the latter part.

6. The mechanism according to claim 1, wherein the second guide means comprise two sectors, a first of which is secured to the stator enclosure and a second of which is translationally movable relative to the first, a return device being positioned between a stationary point of the first sector and a movable point of the second sector of each of the second guide means.

7. The mechanism according to claim 1, wherein a segment support device is pivotably mounted along a single axis on each apice of the polygon.

8. The mechanism according to claim 7, wherein the segment support device comprises a device for pressing segments on the stator enclosure.

9. The mechanism according to claim 7, wherein the segment support device comprises a complementary device for pressing segments on the stator.

10. The mechanism according to claim 1, wherein at least one piston is connected by a single connecting rod or by several connecting rods having same hinge pins as the transmission shaft.

11. The mechanism according to claim 1, wherein two adjacent pistons are connected to one another by a pivot link with an axis parallel to an axis of rotation of the rotary assembly.

12. The mechanism according to claim 1, wherein the second guide means are turned toward a axis of rotation of the rotary assembly.

13. The mechanism according to claim 1, wherein the rotary assembly comprises a lubrication circuit mounted in a closed circuit.

14. A pump comprising a mechanism according to claim 1.

15. An engine comprising a mechanism according to claim 1.