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Title:
DRIVING OR OPERATING MACHINE WITH BALANCING ARRANGEMENT
Document Type and Number:
WIPO Patent Application WO/2016/128926
Kind Code:
A1
Abstract:
A machine (1) comprises: - a rotor (10) exhibiting a preset number (n) of end zones (1 1); - a stator (20) exhibiting a recess (21) delimited by an inner surface (22a). The rotor (10) is eccentrically mounted internally of the recess (21) of the stator (20) and is movable relative to the stator (20) by performing a roto-orbital movement about an axis (A1) of the recess (21). Each end zone (1 1) of the rotor (10) is provided with a rolling element (16) suitable for rolling on the inner surface (22a) of the recess (21), in such a manner as to remain in contact with the inner surface (22a) of the recess (21 ), while the rotor (10) is roto-orbiting about the axis (A1) of the recess (21 ). The machine (1 ) is further provided with a balancing arrangement, so that pressurized fluid exerts axially balanced focus on the rotor (10).

Inventors:
MESSORI, Ledis (Via Rossini 10, Reggio Emilia, 42124, IT)
Application Number:
IB2016/050730
Publication Date:
August 18, 2016
Filing Date:
February 11, 2016
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
MESSORI, Ledis (Via Rossini 10, Reggio Emilia, 42124, IT)
International Classes:
F01C21/08; F01C1/22; F01C19/02; F01C19/08; F01C21/10; F04C2/22; F04C15/00
Foreign References:
US5391067A1995-02-21
DE3508072A11986-09-18
US20110209477A12011-09-01
US20140134035A12014-05-15
US3999905A1976-12-28
GB583035A1946-12-05
AT380636B1986-06-25
DE3519186A11986-12-04
US4072449A1978-02-07
Attorney, Agent or Firm:
COLO', Chiara (Bugnion S.p.A, Via Vellani Marchi 20, Modena, 41124, IT)
Download PDF:
Claims:
CLAIMS

A machine (1 ; 101) comprising:

- a rotor (10; 110) having a preset number (n) of end zones (11);

- a stator (20; 120) exhibiting a recess (21 ; 121 ) delimited by an inner surface (22a; 122a), the rotor (10; 110) being housed eccentrically inside said recess (21; 121) and being movable relative to the stator (20; 120) with a roto-orbital movement about an axis (A1) of the recess (21; 121);

- a shaft (30; 130) having an eccentric portion (32; 132), the rotor (10; 110) being provided with a hole (12; 112), in which said eccentric portion (32; 132) is engaged, the rotor (10; 110) being so installed as to be free to rotate and free to slide axially with respect to the eccentric portion (32; 132) of the shaft (30; 130),

wherein each end zone (11) of the rotor (10; 110) is provided with a rolling element (16; 116) suitable for rolling on said inner surface (22a; 122a), so as to remain in contact with said inner surface (22a; 122a) while the rotor (10; 110) is roto-orbiting about said axis (A1 ), and wherein the inner surface (22a; 122a) of the recess (21; 121) is defined, on a Cartesian plane perpendicular to said axis (A1), by a curve traced by a preset point when a rolling circumference is rolling on a base circumference, outside the base circumference, said curve having the following equations:

((n-1)R + R)sin - nEsin(n ) ((n-1 )R + R)cosa - Ecos(n ) + Rr cosarctg

((n-1)R + R)cosa- nEcos(n ) and

((n-1)R + R)sin - nEsin(n ) y = ((n-1 )R + R)sin - Esin(n ) + Rr sinarctg

((n-1 )R + R)cosa - nEcos(n ) wherein:

- n is an integer greater than or equal to one, equal to the number of end zones (1 1 ) of the rotor (10, 1 10);

- (n-1 ) R is the radius of the base circumference;

- R is the radius of the rolling circumference;

- Rr is the radius of each rolling element (16);

- a is an angle which indicates the angular position of the rolling circumference with respect to the base circumference, which coincides with the angular position of the rotor (10; 1 10) about the axis (A1 ) of the recess (21 ; 121 );

- E is the distance of said preset point from the center of the rolling circumference, measured along a segment joining the center of the rolling circumference with the center of the base circumference when said angle (a) is equal to zero, said distance (E) further expressing the eccentricity between the rotor (10; 1 10) and the stator (20; 120),

the rotor being delimited, transversely to said axis (A1 ), by a face and by a further face opposite to one another;

the machine (1 ;101 ) being provided with a balancing arrangement, configured for sending a pressurized fluid towards said face and towards said further face, so that the pressurized fluid exerts axially balanced forces on the rotor (10; 1 10).

A machine according to claim 1 , and further comprising a plurality of openings (23a, 23b; 123) for introducing the pressurized fluid between the rotor (10; 1 10) and the stator (20; 120) for discharging the pressurized towards the outside of the machine (1 ; 101 ).

A machine according to claim 2, wherein the openings (23a, 23b; 123) of said plurality are formed on a transverse wall (26; 180) which is fixed relative to the recess (21 ; 121 ) and arranged transversely to said axis (A1 ), so that the working fluid flows towards the rotor (10; 1 10) or alternatively towards the outside of the machine (1 ; 101 ) along a direction parallel to said axis (A1 ).

A machine according to claim 3, and further comprising a further transverse wall (181 ) extending transversely to said axis (A1 ), a plurality of balancing recesses (175) being obtained on the further transverse wall (181 ), each balancing recess (175) being in fluid communication with a respective opening (123) of said plurality of openings.

A machine according to claim 4, wherein each balancing recess (175) of said plurality of recesses is aligned, along a direction parallel to said axis (A1 ), with the respective opening (123) of said plurality of openings, each balancing recess (175) having a shape and dimensions corresponding to the shape and dimensions of the respective opening (123).

A machine according to claim 4 or 5, wherein said further face of the rotor (1 10) faces the transverse wall (180), said face of the rotor (1 10) facing the further transverse wall (181 ).

A machine according to any one of claims 2 to 6, wherein the number of openings (123) of said plurality is equal to 2(n-1 ).

A machine according to any preceding claim, which is configured as a hydraulic motor or a hydraulic pump.

A machine according to claim 2 or 3, wherein the number of openings (23a; 23b) of said plurality is equal to (n-1 ).

A machine according to claim 9, which is configured as an endothermic engine.

A machine according to claim 1 , and further comprising a plurality of sliding blocks (16b), each of which is at least partially housed in a seat (17) which is formed in an end zone (1 1 ) of the rotor (10), each sliding block (16b) supporting a rolling element (1 6), so that said rolling element (16) is free to rotate with respect to the corresponding sliding block (16b).

A machine according to claim 1 1 , and further comprising a feeding device for feeding the pressurized fluid between the rotor (10) and the stator (20), so that said pressurized fluid pushes the sliding blocks (16b) towards the stator (20), thereby keeping the rolling elements (16) pressed against the inner surface (22a) of the recess (21 ).

A machine according to claim 12, wherein on said face and on said further face of the rotor (10) respective channels (19) are formed which are suitable for receiving said pressurized fluid, each channel (19) being so conformed as to put the end zones (1 1 ) of the rotor (10) in fluid communication with one another, the channel (19) formed on said face of the rotor (10) being preferably symmetrical with respect to the channel (19) formed on said further face of the rotor (10).

A machine according to claim 13, wherein the channel (19) formed on said face of the rotor (10) communicates with the channel (19) formed on said further face of the rotor (10) through a groove (16f) which is obtained at the interface between a sliding block (16b) and its corresponding seat (17), so that the pressurized fluid which is flowing in the groove (16f) pushes the respective sliding block (16b) against the inner surface (22a) of the recess (21 ).

A machine according to claim 14, wherein each sliding block (16b) has at least one lubrication hole (16e) for allowing the pressurized fluid flowing in the corresponding groove (16f) to reach the rolling element (16) supported by the sliding block ( 16b), so that said rolling element (16) may be lubricated.

A machine according to any one of claims 12 to 15, said machine being conformed as an endothermic engine, said feeding device being associated with a measurement and feedback system (60) for controlling pressure of said pressurized fluid, such that axially balanced forces act on said rotor (10).

A machine according to claim 16, wherein the rotor (10) is interposed between a transverse wall (26) of the stator (20) and a balancing plate (51 ), on a face (51 b) of the balancing plate (51 ) a balancing channel (57) being formed, the balancing channel (57) being suitable for receiving the pressurized fluid from the feeding device, the balancing channel (57) and the channels (19) formed on the rotor (10) having respective areas (Ar , Ap), in plan view, which are so dimensioned that the pressurized fluid acting on said areas (Ar, Ap) produces, in the recess (21 ), axial forces capable of balancing the further axial forces due to pressures generated during the compression and expansion steps of the endothermic engine.

A machine according to any preceding claim, wherein:

- said preset number (n) of end zones (1 1 ) of the rotor (10; 1 10) is an integer greater than, or equal to three;

- the end zones (1 1 ) of the rotor (10; 1 10) define corresponding vertices of a regular polygon;

- the recess (21 ; 121 ) of the stator (20; 120) exhibits a plurality of lobes (22; 122) comprising a number of lobes (22; 1 22) equal to said preset number (n) of end zones of the rotor (10; 1 10) reduced by one.

A machine according to claim 18, wherein each rolling element (16; 1 16) is a roller (16a) having a respective axis arranged at a vertex of said regular polygon.

Description:
DRIVING OR OPERATING MACHINE WITH BALANCING ARRANGEMENT

The invention relates to a driving motor or working machine which is able to convert the energy of a fluid into energy of the mechanical type or deliver energy, e.g. mechanical energy, to a fluid. For example, when referring to the driving motor, one can mention the endothermic engine or 5 the hydraulic motor whereas, when referring to the working machine, mention can be made of the hydraulic pump. The invention particularly relates to the geometric conformation of the driving motor or working machine.

The invention particularly refers to a driving motor or working machine of0 the rotary type, i.e. with its movable parts essentially moving according to a rotary movement, more precisely according to a roto-orbital movement, which provides at least a stationary part of the machine, termed stator, and a movable portion, called rotor which interacts with the stator.

The invention finds effective use in many different sectors providing use of5 an endothermic engine, i.e. a machine configured for conducting a fluid transformation thermodynamic process. The areas of greatest use are therefore the automotive and motorcycle industry, the electric generators actuation sector, or the sector concerned with professional implements provided with an endothermic engine and the like.

0 A further area of application of the present invention, by way of example, is that of the plants and/or industrial machinery, wherein use of hydraulic pumps or hydraulic motors is provided.

It is known a rotary endothermic engine called Wankel engine, which comprises a rotor and a stator chamber, which stator chamber is capable 5 of accommodating the rotor that is moving therein according to a roto- orbital movement.

To make a comparison with traditional reciprocating endothermic engines, the rotor of the Wankel engine is applicable to the pistons, while the stator chamber is applicable to the cylinders inside of which the pistons are 0 sliding alternately. In detail, the shape of the stator chamber of the Wankel engine is symmetrical relative to the two orthogonal barycentric axes and exhibits two lobed-shaped recesses capable of receiving the rotor during operation of the motor. The configuration of the two-lobes stator chamber is the most widespread and is known as epitrochoidal-shaped chamber.

The rotor is instead equilateral triangular in shape, with slightly convex and converging sides at the vertices of the triangle in three distinct apical zones. The contact between stator and rotor occurs at the apical segments placed relative to the vertices of the rotor which are sliding on the walls of the stator.

On the walls of the stator there are generally arranged openings for the suction of a fuel-air mixture and the discharge of the burnt gases. Seats are further provided which accomodate one or more mixture spark plugs. The rotor, turning inside the stator chamber according to a specific orbiting movement, forms three chambers, the volume of which varies cyclically : i.e. inside the three chambers, three with four-stroke provided Otto cycles occur simultaneously, which cycles are out of phase by 120°. Because for each revolution of the rotor, three with four-stroke provided Otto cycles are completed, it follows that at each revolution of the drive shaft a cycle becomes completed.

The rotor centrally exhibits a through hole inside of which a ring gear is arranged, which is predisposed for engaging with a pinion that is keyed on the stator of the Wankel engine. The drive shaft features a stationary axis of rotation about which the rotor is moving according to a roto-orbital movement, as already mentioned.

The combination of the rotary movement with the engagement of the rotor ring gear and the stator pinion, promotes transmission and conversion of the energy produced by the mixture combustion into energy of the mechanical type (torque on the drive shaft), besides acting as a gearbox between the rotor and the drive shaft. In other words, at each revolution of the rotor inside the stator chamber, the drive shaft makes three complete revolutions.

The technology of the Wankel endothermic engine is nowadays used for application to some car models and can further be applied in the aviation industry, or even in the dynamic model sector, proposed on a reduced scale but thoroughly working.

Uses of the Wankel engine are however rather limited in that this type of engine exhibits several drawbacks.

The main drawbacks of the Wankel engine are particularly due to the presence of apical segments, which are poorly reliable, breakable and tend to cause leaks. Further, because of the angular conformation of the rotor, the rotor is subject to sliding and to micro-impact shocks against the wall of the stator, the sliding track of which deteriorates quickly, thereby being tightness of the gaskets reduced with consequent reduction in efficiency.

US 5391067 discloses a fluid displacement rotary device free of any feed gears between the rotor and the corresponding crankshaft or the stator case.

DE 3508072 discloses a planetary compressor corresponding to a positive displacement pump for gases or liquids, which planetary compressor is provided with an elongated hole having an internal toothing, which may be regarded as an internal stationary gear wheel.

US 201 1/0209477 discloses a rotary displacement system which may be used to compress and/or expand compressible fluids.

US 2014/0134035 discloses a system comprising a trochoidal rotary device, provided with a rotor and a shaft which is eccentrically connected to the rotor, the shaft being stationary with respect to the rotor. US 3999905 discloses a rotary motor provided with a rotor having a plurality of apices. The apices are provided with sealings which are pushed against the walls of a chamber wherein the rotor is housed.

It is an object of the present invention to provide a driving motor or working machine, which is able to convert the energy of a fluid into mechanical energy or impart energy to a working fluid with a high efficiency and reliability of all mechanical components.

More specifically, in accordance with the present invention, the driving motor or working machine is so devised as to simplify the mechanical construction of the machine itself, thereby being the components number thereof simultaneously reduced.

According to a first aspect of the invention, there is provided a machine comprising:

- a rotor having a preset number of end zones;

- a stator exhibiting a recess defined by an inner surface;

wherein the rotor is eccentrically mounted internally of said recess and is movable relative to the stator with a roto-orbital movement about an axis of the recess;

characterized in that each end zone of the rotor is provided with a rolling element which is suitable to roll on said inner surface, so as to remain in contact with said inner surface while the rotor is roto-orbiting about said axis.

The invention allows to overcome the drawbacks previously mentioned in connection to the Wankel engine. The rotor indeed is interacting with the stator at the rolling elements, which rolling elements are rolling without sliding against the inner surface of the stator recess and remain in contact with such surface in any position assumed by the rotor, while the rotor is moving by rotating about the recess axis and rotating simultaneously about its own axis.

In this manner any sliding or micro-shocks of the rotor against the stator wall may be prevented.

In addition, the apical segments of the Wankel engine can be removed, which apical segments may result in tightness problems, poor reliability and fragility.

The profile of the stator's inner recess is indeed so designed as to ensure a tangency condition between the rolling elements and the inner surface of the stator in all positions taken on by the rotor during its rotary-orbital movement. This ensures that the rotor can move in contact with the inner surface of the stator recess, without the protrusions of the rotor sliding against this surface or becoming detached therefrom. It is further ensured that the rolling elements engage sealingly with the inner surface which defines the stator recess.

In a second aspect of the invention, there is provided a machine having the features of claim 1 .

The machine according to the second aspect of the invention is provided with a rotor which is freely sliding along the eccentric portion of the shaft on which the rotor is mounted. The rotor is axially balanced by hydraulic forces, i.e. by forces exerted by a pressurized fluid which is acting on two opposite faces of the rotor. In other words, the machine is configured such that the resultant of the forces which are acting on the rotor and following a direction parallel to the axis of the rotor, is substantially equal to zero. The pressurized fluid sent towards the two opposite faces of the rotor allows to provide a hydraulic floating of the rotor inside the stator.

It is thus provided an axial balancing system of the rotor particularly simple and effective.

As pressurized fluid, this balancing system uses the same working fluid to which the machine is configured for transferring energy or by which the machine is configured for receiving energy.

By balancing the rotor axially via hydraulic forces exerted by the pressurized fluid, one may avoid using bearings or other mechanical components which axially constrain the rotor relative to the stator.

Owing to the rotor in its floating condition in the pressurized fluid, assembly operations of the machine can be further simplified and mechanical efficiency can be improved.

Further characteristics and advantages will become more apparent from the detailed description of several embodiments provided by way of non- limiting example of a driving motor or a working machine which is suitable to convert the energy of a fluid into energy of a mechanical type or impart energy in accordance with the present invention. The dependent claims correspond to possible embodiments of the invention.

The description is provided with reference to the accompanying figures, which are in turn provided by way of non-limiting example, wherein:

Figure 1 a is a schematic sectional view of a machine in accordance with the present invention;

Figure 1 b is a schematic view of a stator case of the machine of Figure 1 a; Figure 1 c is a schematic view of a rotor of the machine of Figure 1 a wherein some parts are not visible;

Figure 2 is a partially exploded view of the rotor of Figure 1 c;

Figure 3a is a rear view of a plate of the machine of Figure 1 a;

Figure 3b is a front view of the plate of Figure 3a;

Figure 4 is a schematic view illustrating how a machine according to the invention can be axially balanced;

Figure 5a shows a different embodiment of the machine in accordance with the present invention;

Figure 5b illustrates a further and different embodiment of the machine in accordance with the present invention;

Figure 6 is a diagram illustrating some details of the axial balancing referenced in Figure 4;

Figure 7 is a schematic view showing some details relating to the manufacturing of a epitrochoid of a Wankel engine.

Figure 8 is a schematic front view showing a stator recess containing a rotor of a machine according to an alternative embodiment;

Figure 9 is a schematic front view showing a rear head, provided with a plurality of distribution openings of the machine of Figure 8;

Figure 10 is a schematic front view showing a front head, provided with a plurality of balancing recesses of the machine of Figure 8;

Figure 1 1 is a schematic front view showing a stator case or stator ring of the machine of Figure 8; Figure 12 is a schematic side view of the machine of Figure 8.

With reference to the attached figures, the machine in accordance with the present invention is generally referred to by the numeral 1 .

The machine 1 can be a driving motor or a working machine that is suitable to convert the energy of a fluid into energy of a mechanical type or to impart energy, for example mechanical energy, to a fluid and vice versa. In other words, the machine in accordance with the present invention may be a machine configured for transferring energy to a fluid, or a machine configured for receiving energy from a fluid.

In particular, the machine 1 may be an endothermic engine or a hydraulic engine, in the case where it is configured as a driving motor. Alternatively, the machine 1 can be a hydraulic pump, in the case where it is configured as a working machine.

As shown in Figure 1 a, the machine 1 comprises a rotor 10 having a preset n number of end zones or vertices 1 1 . The example referred to by Figures 1 a to 4, applies to the condition where n = 3, i.e. the rotor 10 has three vertices 1 1 .

More generally, the above mentioned number n is a positive integer greater than one, or equal to one, as better detailed below.

As shown, in Figure 1 c the rotor 10 is further provided with n sides 14 each of which is interposed between two vertices 1 1 . The sides 14 may be so configured as to confer a regular shape to the rotor 10. In particular, the sides 14 may be equal to one another and be, for example, convex- shaped.

As shown in Figures 1 c and 2, at each vertex 1 1 of the rotor 10 a rolling element 16 is disposed, which is particularly shaped as a roller. Each rolling element 16 is free to rotate about an axis passing through the corresponding vertex 1 1 .

The number of the rolling elements 16 of the rotor 10 is equal to the number of vertices 1 1 , i.e. it is equal to n.

It is possible to define a central axis A2 of the rotor 10. The vertices 1 1 are equidistant from the central axis A2. The central axis A2 is a barycentric axis of the rotor 10, i.e. it is passing through the barycenter of the rotor 10. As shown in Figures 1 a and 1 b, the machine 1 is further provided with a stator 20 comprising a stator case 25 inside of which a recess 21 is afforded. Within the recess 21 there are defined n-1 lobes 22, namely n-1 recesses separated from one another by respective protuberances 29. The number of lobes 22 of the stator 20 is therefore equal to the number of vertices 1 1 of the rotor 10, reduced by one.

In the example referenced by Figures 1 a to 4, the number of lobes 22 of the stator 20 is equal to two.

The lobes 22 of the stator 20 are regularly distributed about an axis A1 of the stator 20, which can be regarded as an axis of symmetry of the recess 21 .

As it will be better described further on, the axis A1 of the stator 20 coincides with the axis of the machine shaft 1 .

The rotor 10 is mounted eccentrically inside the recess 21 of the stator 20. In other words, the axis A1 of the stator 20 does not coincide with the central axis A2 of the rotor 10. The central axis A2 of the rotor 10 is placed at a distance E from the axis A1 of the stator 20. The distance E therefore defines the eccentricity of the rotor 10 relative to the stator 20. The rotor 10 is movable with a roto-orbital movement relative to the stator 20. In particular, the rotor 10 is rotating about its central axis A2, and is simultaneously orbiting about the axis A1 of the stator 20. Hence, while the rotor 10 is moving, a cylinder with radius E is described about the axis A1 of the stator 20 by the central axis A2 of the rotor.

As shown in Figure 1 a, in an operative configuration of the machine 1 , a plurality of working volumes 40 is defined between the stator 20 and the rotor 10. According to the type of machine 1 , the working volumes 40 may exhibit different pressure and temperature conditions, as well as different fluids.

The recess 21 of the stator 20 is defined by an inner surface 22a which is so conformed as to interact with the rolling elements 16 in such a manner that each rolling element 16 may roll without sliding against the inner surface 22a.

The inner surface 22a is so devised as to accommodate the rotor 10, which is provided with the rolling elements 16, so that the rolling elements 16 are steadily in contact with the inner surface 22a while the rotor 10 is moving about the axis A1 of the stator 20, thus orbiting about said axis and simultaneously rotating about its own central axis A2.

To understand how the inner surface 22a is devised, consider the example shown in Figures 1 a to 4, wherein - as already explained - the number of vertices 1 1 of the rotor 10 is n = 3, hence the number of lobes 22 of the stator 20 is equal to 2.

According to the example as described above, a traditional Wankel engine would be provided with a two-lobes stator having an inner recess defined by a curve termed epitrochoid, which curve is drawn by a generic point Q, placed at a distance E from the center of a circumference with radius R (rolling circumference), when the latter is rolling on a circumference with radius 2R (base circumference).

With reference to Figure 7, consider a Cartesian reference system having an origin O which coincides with the center of the base circumference. By O1 it is signified the center of the rolling circumference that is rolling on the base circumference. The X-axis of the Cartesian reference system is identified by the straight line passing through the centers O and O1 , respectively of the base circumference and the rolling circumference when the rolling circumference is in a position corresponding to a rotation angle equal to zero with respect to the base circumference.

In this position of the rolling circumference with respect to the base circumference, a segment having a length E (where E<R) lying on the axis X along the segment joining the centers O and O1 , identifies a point Q, which point Q, while the rolling circumference is rolling on the base circumference, describes an epitrochoid with the following equations: Xtr = Tcosoc - Ecos3a

Ytr = Tsina - Esin3a

wherein:

T = 2R + R;

2R is the radius of the base circumference;

R is the radius of the rolling circumference that is rolling on the base circumference and externally of the latter;

a is an angle which indicates the angular position of the rolling circumference with respect to the base circumference while the rolling circumference is rolling externally of the base circumference. The angle a further indicates the angular position of the rotor of the Wankel engine about an axis of the stator recess;

E is the distance of the point Q generating the epitrochoid from the center of the rolling circumference, which is measured along the segment joining the center of the base circumference with the center of the rolling circumference when a = 0. The distance E further expresses the eccentricity between rotor and stator, i.e. the radius of the circumference along which the rotor is orbiting.

The epitrochoid having the equations mentioned above, defines a stator recess capable of housing a rotor whose vertices identify an equilateral triangle with side 2Tcosn / 6.

In order that the recess 21 of the stator 20 is capable of housing, under constant contact conditions, a rotor 10 provided with three vertices defining an equilateral triangle, at which vertices there are provided respective rolling elements 16 being shaped as rollers of radius Rr, the epitrochoid equations of the Wankel engine are modified as follows:

x = Tcosoc - Ecos3a + Rr cosarctg(-dXtr/dYtr)

y = Tsina - Esin3a + Rr sinarctg(-dXtr/dYtr)

Wherefrom the following is obtained: Tsina - 3Esin3a

x = Tcosa - Ecos3a + Rr cosarctg

Tcosa - 3Ecos3a Tsina - 3Esin3a

y = Tsina - Esin3a + Rr sinarctg

Tcosa - 3Ecos3a

The above equations apply to those values of the angle a that meet the following condition:

0 < α < π/2

As for π/2 <α <2π, the shape of the curve which defines the inner surface 22a of the recess 21 can be derived from the equations which were previously reported by symmetry.

It is thus possible to define an inner surface 22a that defines the stator recess 21 and is able to ensure that, during the roto-orbital movement of the rotor 10 relative to the stator 20, the rolling elements 16 are constantly in contact with the inner surface 22a while rolling without sliding on the latter.

The equations referred to above can be generalized as follows in the case of a rotor 10 provided with n vertices which are so arranged as to define a regular polygon, to each vertex being associated a corresponding rolling element 16:

((n-1 )R + R)sina - nEsin(na) x = ((n-1 )R + R)cosa - Ecos(na) + Rr cosarctg

((n-1 )R + R)cosa - nEcos(na)

((n-1 )R + R)sina - nEsin(na) y = ((n-1 )R + R)sina - Esin(na) + Rr sinarctg

((n-1 )R + R)cosa - nEcos(na) wherein:

- n is an integer and positive which expresses the number of vertices 1 1 of the rotor 10 corresponding to the number of the rolling elements 16;

- (n-1 ) * R is the radius of the base circumference; - R is the radius of the rolling circumference that is rolling on the base circumference;

- E is the eccentricity between rotor and stator, i.e. the radius of the circumference along which the rotor is orbiting, wherein E<R and E is sufficiently small in order that any double points of the curve generated by the equations in question can be prevented;

- Rr is the radius of the rolling elements 16;

- a is an angle which indicates the angular position of the rotor 10 about the axis A1 of the stator 20.

The above equations apply to values of the angle a falling within the following range:

0 < α < π/(η-1 )

For the values of the angle a which differ from those of the range referred to above, the curve which defines the stator recess 21 can be derived by symmetry with respect to the axis A1 from the one already obtained by exploiting above equations.

The above equations apply for n > 3, i.e. for those cases which are the most interesting from an industrial viewpoint. Theoretically it is however also possible to provide for cases in which n = 1 and n = 2.

In particular, if n = 1 the rotor is conformed, on a plane, as a segment whose only "vertex" coincides with an end of the segment itself, at which end there is provided a rolling element. The stator is in this case provided with a recess defined by an inner surface having a circular cross section. On the other hand, if n = 2 the rotor is conformed, on a plane, as a segment which is provided with two rolling elements positioned at the "vertices" or end zones of the segment.

In order that any case is included wherein n is a positive integer, greater than, or equal to one, the above equations may be modified as follows:

((n-1 )R + R)sin - nEsin(n ) x = ((n-1 )R + R)cosa - Ecos(n ) + Rr cosarctg

((n-1 )R + R)cosa - nEcos(n ) ((n-1 )R + R)sina - nEsin(n ) y = ((n-1 )R + R)sin - Esin(n ) + Rr sinarctg

((n-1 )R + R)cosa - nEcos(n ) In the two previous equations, the sign "+" shall be selected with reference to y rising values, whilst the sign "-" shall be selected for y decreasing values.

The two above equations are valid solely for a values between 0 and 2π.

Such equations identify a curve whose points ensure a constant tangency condition between the curve itself and a circumference with a radius Rr, the center of which is lying at a preset point Q, placed at a distance E from the center of the rolling circumference. In the position corresponding to a = 0, the preset point Q is lying on the x axis along the segment which joins the center of the base circumference and the center of the rolling circumference.

The above equations are obtained by choosing a Cartesian reference system in which the origin coincides with the center of the base circumference and the x-axis is lying along the segment joining the center of the base circumference with that of the rolling circumference, in the position corresponding to a = 0. In this position, the preset point Q is lying inside the segment which joins the center of the base circumference with the center of the rolling circumference.

Of course, in the event that the Cartesian reference system is modified, for example by translating and/or rotating the x-axis and the y-axis, the equations of the curve would change despite the curve remaining geometrically unchanged. Indeed, the same curve may be described by different equations, depending on how the reference system is chosen.

In summary, on a Cartesian plane perpendicular to the axis A1 of the stator 20 and to the central axis A2 of the rotor 10, the recess 21 of the stator 20 is defined by a perimetric edge 24, whose x and y coordinates are defined by the above equations, wherein there are present four parameters that can be chosen arbitrarily, i.e. n, R, E, Rr. Once set such parameters, the shape of the stator recess 21 is uniquely defined, as well as the main geometric and dimensional characteristics of the rotor 10 associated therewith.

The equations previously mentioned do not define the shape of the sides 14 of the rotor 10, which shape can be chosen arbitrarily while taking care to ensure that, during rotation of the rotor 10, the sides 14 do not come into contact with the inner surface 22a of the stator recess 21 . In particular, the sides 14 may be curve-shaped and may for example be shaped in plan view, as circumferential arcs.

The shape of the sides 14 helps to define the shape of the working volumes 40, particularly at the upper dead point. Where the machine 1 is an endothermic engine, the shape of the sides 14 defines the compression ratio.

The number of working volumes 40 is equal to n, i.e. equal to the number of vertices 1 1 of the rotor 10.

As shown in Figure 1 a, the stator 20 exhibits a plurality of openings situated within the recess 21 , which openings particularly comprise an inlet opening 23a and an outlet opening 23b. The functioning of the openings 23a, 23b depends on the type of configuration of the machine 1 and shall be detailed more fully herein below.

Where the machine 1 is an endothermic engine, the number of openings 23a, 23b is generally equal to (n-1 ), where n was previously already defined. This condition is particularly applicable to the case in which n is an even number.

As shown in Figure 1 a, the machine 1 further comprises a shaft 30, which is rotatable about an axis of rotation which coincides with the axis A1 of the stator 20. The shaft 30 is provided with an eccentric portion 32, configured to be received internally of a hole 12, which hole 12 is formed within the rotor 10 coaxially with the central axis A2 of the rotor 10.

In particular, the rotor 10 is mounted in such a manner as to be neutral, i.e. free to rotate with respect to the eccentric portion 32 of the shaft 30. Furthermore, the rotor 10 is axially free relative to the shaft 30, i.e. it is free to slide axially along the eccentric portion 32. This means that the eccentric portion 32 is not provided with fastening elements capable of constraining the movement of the rotor 10 along the central axis A2.

By way of example, the coupling between the eccentric portion 32 of the shaft 30 and the rotor 10 can be realized by means of a suitably lubricated bushing.

In this manner, it is not necessary to couple the rotor to the stator by using gears such as the stator pinion and the ring gear solidly constrained with the rotor, as employed in the Wankel engine. In fact, the rotor 10 is drawn and induced to roto-orbital movement via the rolling elements 16 which strike against the inner surface 22a of the recess 21 .

By indicating with ο«ν the angle based on which the shaft 30 is rotating about the axis A1 , and with ocrot the net rotation angle of the rotor 10, the following condition applies:

OCriv = Π x OCrot

In other words, in order that the rotor 10 makes a full revolution on itself, it is required that the shaft 30 performs n revolutions.

This concept can be further expressed by stating for example that, in the case shown wherein n=3, one complete revolution of the shaft 30 corresponds to a 120° rotation of the rotor 10 on itself.

As shown in Figure 2 (wherein a rolling element 16 has been illustrated on purpose disassembled from the rotor 10 to better make visible more details otherwise hidden), there is formed a seat 1 7 in proximity of each vertex 1 1 of the rotor 10, which seat 17 is suitable to accommodate at least partially a corresponding rolling element 16.

In the example shown, each seat 17 is symmetrical with respect to a radial half-line 18 having its origin in the central axis A2 of the rotor 10 and passing through a respective vertex 1 1 . Each seat 17 is formed as a prismatic-shaped recess, which prismatic-shaped recess is defined by two guide surfaces 17a that are planar and parallel to the respective radial half-line 18.

Each rolling element 16 comprises a roller 16a, which in the example shown is supported by a sliding block 16b which is received internally of a corresponding seat 17. Each roller 16a is free to rotate with respect to the sliding block 16b supporting it.

As already mentioned, during operation of the machine 1 , each roller 16a is so configured as to be in contact with the inner surface 22a of the recess 21 and to rotate about an own axis so as to move on this surface according to a rolling movement.

Each sliding block 16b has a prismatic shape, so as to engage in shape- coupling within the respective seat 17. Each sliding block 16b exhibits a recess 16c in its own outer portion, the recess 16c being suitable for housing at least partially the respective roller 16a. The recess 16c is such as to allow the roller 16a to freely rotate while promoting containment thereof, preferably by carrying on a lateral containment of the roller 16a. For the sake of full disclosure, the outer portion 16b of the sliding blocks is to be meant as the sliding block portion 16b facing radially outwards, i.e. away from the central axis A2 of the rotor 10.

Each sliding block 16b further exhibits an inner portion opposite to the outer portion, i.e. facing towards the central axis A2 of the rotor 10.

Within its own inner portion, i.e. at the side opposite to the roller 16a, each sliding block 16b is defined by a thrust surface 16d the function of which will be better described hereinafter.

On the thrust surface 16d a groove 16f is formed which extends between a front face and a rear face of the sliding block 16b. The front face and the rear face of the sliding block 16b define the sliding block 16b transversely, in particular perpendicularly, to the central axis A2. In the example shown, the groove 16f extends parallel to the central axis A2.

Each sliding block 16b is finally provided with one or more lubrication holes 16e, which are conformed as through holes that bring into fluid communication the notch 16c with the groove 16f. Where each sliding block 16b comprises a plurality of lubrication holes 16e, the lubrication holes 16e may be conformed as radial holes parallel to one another starting from the groove 16f and flowing into the notch 16c. In the example shown, each sliding block 16b exhibits three lubrication holes 16e.

The rotor 10 exhibits channels 19 which are capable of receiving a fluid for the reasons that will be described in detail below.

In the example shown, the channels 19 are two in number and are disposed symmetrically relative to a transverse plane of symmetry of the rotor 10, i.e. relative to a plane which extends perpendicularly to the central axis A2. In other words, there is provided a channel 19 on a front face of the rotor 10 and a further channel 19 on a rear face of the rotor 10. The front face and the rear face of the rotor 10 define the rotor 10 transversely, in particular perpendicularly with respect the central axis A2. In the example shown, the front face and the rear face of the rotor 10 are equal to each other.

In the example shown, each channel 19 has an inner edge 19a having for example a circular shape coaxial to the central axis A2. Each channel 19 further exhibits an outer edge 19b which diverges from the inner edge 19a in proximity to the vertices 1 1 . Thus, each channel 19 widens towards the vertices 1 1 , so that the seats 17 of the rotor 10 are put in fluid communication with one another.

The channel 19 formed on the front face of the rotor 10 is in fluid communication with the channel 19 formed on the rear face of the rotor 10 through the grooves 16f. As better disclosed hereinafter, the grooves 16f of the sliding blocks 16b allow the fluid to flow from one side to the opposite side of the rotor 10, so that any decompensation in the fluid pressure is balanced from one side to the other of the assembly comprising the rotor 10 and the stator 20 in an operating configuration of the machine 1 .

A pressurized fluid coming for example from an inner flow device of the machine (as for example a mechanical pump, not shown) is sent into a channel 19 of the rotor 10, for example into the channel 19 formed on the rear face of the rotor 10. From the channel 19, the pressurized fluid reaches the seats 17 of the rotor 10, wherefrom it flows into the channel through the grooves 16f, which channel is afforded on the other face of the rotor 10, e.g. on the front face.

The pressurized fluid circulating in the channels 1 9 exerts, on the thrust surfaces 16d of the sliding block 16b, a thrust which is radially directed outwardly of the rotor 10. The rollers 16a are thus pressed against a portion of the inner surface 22a of the recess 21 in an operating configuration the machine 1 .

It is thus ensured the sealing between the working volumes 40 defined between the rotor 10 and the stator 20 during operation of the machine 1 . Through the lubrication holes 16e, the pressurized fluid circulating in the grooves 16f further reaches the rollers 16a.

The lubrication holes 16e can therefore be regarded as lubricating means which allow the pressurized fluid to lubricate the rollers 16a. Owing to the lubrication holes 16e, a thin layer of fluid, for example a lubricating oil, can be particularly supplied and deposited both on the outer surface of the rollers 16a and on the inner surface 22a of the stator 20, via the rolling of the rollers 16a along the inner surface 22a.

As shown in Figures 4 and 6, the recess 21 of the stator 20 in which the rotor 10 is received, is defined anteriorly and laterally by the stator case 25, and is closed at the rear by a plate 51 . The plate 51 is arranged transversely, in particular perpendicularly to the axis A1 of the stator 20 and the central axis A2 of the rotor 10. The plate 51 is defined by a rear face 51 b, shown in Figure 3a and facing the opposite side with respect to the rotor 10, and by a front face 51 a, shown in Figure 3b and facing the rotor 10.

The plate 51 is defined by an outer edge having the same shape of the inner surface 22a that delimits the stator recess 21 .

The plate 51 exerts a sealing action on the pressurized fluid contained within the stator case 25, so that any unwanted fluid releases are prevented. The plate 51 is preferably made of a metal with high resistance to wear due to the fact that during operation of the machine 1 the plate 51 is facing the rotor 10 and all the components related thereto.

The plate 51 exhibits a central hole 53 for passage of the shaft 30. In one embodiment, the machine 1 is an engine, particularly an endothermic engine, during the operation of which, a fuel and comburent mixture in a gaseous state is present within the working volumes 40. The pressurized fluid that circulates in the channels 19 is instead a lubricating oil, preferably a mineral and/or synthetic oil.

In this case, the machine 1 is so configured as to exhibit an n-vertices piston, namely the rotor 10, which is rotating eccentrically about the motor shaft, or the shaft 30, thereby generating working chambers 40 through its movement, inside of which chambers there are performed cyclically the four typical steps, i.e. the steps of suction - compression - combustion - and exhaust of the gasoline Otto cycle.

In the above configuration of the machine 1 , the plate 51 , the rotor 10 and the stator case 25 are configured in order that a compensation between the pressures acting inside the machine 1 is achieved, so that the rotor 19 is axially balanced. These components therefore define a balancing arrangement, owing to which the pressurized fluid is sent towards two opposite faces of the rotor 10, so that the rotor 10 is axially balanced.

The machine 1 comprises a feeding device for feeding the pressurized fluid previously mentioned, particularly oil, towards the rotor 10. As shown in Figures 4 and 6, the feeding device may comprise an inlet conduit 54, which is afforded for example within a closing element 55 tightened against the stator case 25 in order to close the stator case 25, particularly via N threaded connection elements extending along respective axes AN shown in Figure 6. The closing element 55 is positioned in such a manner that the plate 51 comes to be interposed between the closing element 55 and the rotor 10. The latter is in turn interposed between the plate 51 and a transverse wall 26 of the stator case 25. Between the plate 51 and the closing element 55 there are interposed one or more sealing elements 101 , which are capable of exerting a static sealing action.

Even between the plate 51 and the stator case 25 there is interposed at least one static sealing element 102.

The pressurized fluid, having a pressure equal to p1 , is sent towards the rear face 51 b of the plate 51 through the inlet conduit 54. As shown in Figure 3a, on the rear face 51 b of the plate 51 a balance channel 57 is formed, which penetrates through a thickness portion of the plate 51 and has a ring-closed plan shape extending about the axis A1 of the stator 20. Two through holes 56 are facing the balance channel 57 through which holes, the pressurized fluid contained inside the balance channel 57 can reach the rotor 10. The through holes 56 are arranged diametrically opposite to one another.

The balance channel 57 has a zone Ap, in plan view, indicated by a plurality of dots as illustrated in Figure 3a. The pressurized fluid pressure p1 is acting on the zone Ap, which pressurized fluid is coming from the inlet conduit 54. The pressurized fluid thus exerts on the plate 51 a force F1 which is directed toward the rotor 10 resulting from the following condition:

F1 = p1 x Ap

As shown in Figure 3b, the front face 51 a of the plate 51 is substantially smooth, i.e., free of any channel balancing. On the front face 51 a of the plate 51 , two slots 52 can be identified into each of which slots 52, a through hole 56 is passing.

In the example shown, the slots 52 are arranged symmetrically with respect to an axis of the plate 51 which axis, in an operative configuration of the machine 1 , coincides with the axis A1 of the stator 20. The slots 52 are dimensioned in such a manner that at least one of them is steadily facing the channel 19, which channel 19 is formed on the rear face of the rotor 10 whatever the angular position of the rotor 10. Hence, the pressurized fluid coming from the inlet conduit 54 and passing through the plate 51 , can always flow through the rotor 10 in order to reach the front face thereof, i.e. the farthest face from the plate 51 .

As shown in Figure 1 b, on the transverse wall 26 of the stator case 25 there are provided two cavities 27 having, in plan view, the same shape of the slots 52 of the plate 51 . The cavities 27 are shaped as grooves, and are in mutual communication via a communication conduit which is formed within the stator casing 25 and is not shown.

When the machine 1 is operating as a motor, a fluid with pressure p1 is present inside the cavities 27. This allows to balance the axial force due to the presence of fluid inside the slots 52 of the plate 51 , which also has a pressure p1 .

Going into detail of the axial forces developing inside the machine 1 , the pressurized fluid flowing through the plate 51 , exerts a force Fr on the rear face of the rotor 10, i.e. on the side facing the plate 51 , which force Fr is directed towards the transverse wall 26 of the stator case 25, given by the following condition:

Fr = p1 x Ar

Based on the above condition, p1 - as previously already mentioned - signifies the fluid pressure acting on the rotor 10 by flowing through the plate 51 , whilst Ar indicates the area, in plan view, of the channel 19, which channel 19 is afforded on the rear face of the rotor 10, shown with a plurality of dots in Figure 2.

An equal and opposite force is acting on the front face 51 a of the plate 51 . Because the channel 19 obtained on the front face of the rotor 10 has the same shape and same dimensions of the channel 19 formed on the rear face thereof, a force having an intensity equal to Fr is acting on the front face of the rotor 10, which force is pushing the rotor 10 towards the plate 51 .

Finally, a force having an intensity equal to Fr is further acting on the transverse wall 26 of the stator case 25, in a direction that is guided by the rotor 10 towards the wall.

In addition to the force generated by the pressure p1 , axial forces are further acting inside the stator 20, which arise during operation of the motor defined by the machine 1 due to the pressure generated in the working volumes 40 during the expansion and compression steps.

If "pc" indicates the axial pressure generated during the compression step, which axial pressure is acting on an overall area Ac of the plate 51 (or respectively of the transverse wall 26 of the stator case 25), while "pe" signifies the axial pressure generated during the expansion step, which axial pressure is acting on an overall area Ae of the plate 51 (or respectively of the transverse wall 26 of the stator case 25), the pressures pc and pe shall generate an overall force Fee on the plate 51 , which force Fee is addressed from the rotor 10 to the plate 51 with an intensity equal to :

Fee = (pc x Ac) + (eg χ Ae)

An equal and opposite force is acting on the transverse wall 26 of the stator case 25.

Since during operation of the motor, the pressures pc and pe vary, which are generated during the compression and expansion steps respectively, and so do the areas Ac and Ae, one may consider to provide a balancing of the axial forces acting on the rotor 10 by varying the pressure p1 of the inlet fluid, so that the following condition is met:

p1 x Ap > (pc x Ac) + (pe χ Ae) + (p1 χ Ar)

This forces balancing allows a hydrostatic floatability of the rotor 10 within the stator 20 during operation of the machine 1 as a motor.

Figure 6 illustrates diagrammatically how the forces are distributed which allow to obtain the balancing previously mentioned.

In order that the pressure p1 is suitably varied, the machine 1 comprises a measuring and/or feedback system 60 which is configured for varying and adjusting the pressure p1 , so that the condition previously mentioned is met. Figure 4 shows schematically, by way of example, the measuring and/or feedback system 60, which comprises a pressure regulating valve 61 , preferably with electronic control, for adjusting the pressure p1 . Such pressure is preferably given by a mechanical pump connected with the machine 1 in the endothermic motor configuration.

It may be appropriate to work in safety conditions so as to prevent the plate 51 from becoming detached from the rotor 10 due to the axial forces generated within the machine 1 . To this end, p1 shall be selected such that the following condition is met:

p1 x Ap > (pc x Ac) + (pe χ Ae) + (p1 χ Ar)

The sign > as indicated in the above condition, is to be meant as slightly >, wherein the concept of "slightly" may be quantified smoothly by the skilled person from time to time.

In order to prevent the plate 51 from becoming detached by the rotor 10 with the machine 1 stopped, there may be further provided one or more preloading elastic elements 100, shown in Figure 4, which are capable of acting on the plate 51 with the machine 1 both at rest and in the operating configuration thereof. The preloading elastic elements 100 may comprise cup springs or elastic elements of different kind, which are so configured as to exert a constant pressure on the plate 51 towards the inner portion of the machine 1 , namely where the rotor 10 is housed.

In a further embodiment, the machine 1 can be shaped as a hydraulic motor, wherein the working fluid is a non-compressible fluid distributed within the working volumes 40, in particular an oil for mechanical transmissions.

Where the machine 1 is shaped as a hydraulic motor, it may be convenient to not use an axial forces balancing system.

Furthermore, use is not required of thrust means for pushing the rolling elements 16 towards the inner surface 22a of the stator recess 21 . The accuracy generally characterizing mechanical workings is indeed sufficient to ensure occurrance of a minimum leakage, which is admissable for hydrostatic components. If need be, at a time of mounting the hydraulic motor, rectifications can be made by inserting calibrated spacers between the seats 17 and the sliding blocks 16b.

Where the machine 1 is a hydraulic motor, the stator 20 may comprise a pair of inlet openings 23a and a pair of outlet openings 23b, for example, arranged crosswise with respect to the axis A1 of the stator 20.

In a further and different embodiment, the machine 1 is configured as a pump, particularly a hydraulic pump wherein the working fluid is a non- compressible fluid distributed within the working volumes 40. The examples shown so far include a rotor 10 provided with three vertices 1 1 defining an equilateral triangle, whereas the stator 20 is provided with two lobes 22.

However, as already described in detail, the number of vertices 1 1 (and consequently the number of lobes 22) can be chosen arbitrarily. By way of example, in Figure 5a there is shown a configuration in which the rotor is provided with four vertices 1 1 which define a square, while the stator comprises three lobes 22 distributed uniformly about the axis A1 . In Figure 5b it is instead represented an example in which the rotor includes five vertices 1 1 defining a regular pentagon, while the stator comprises four lobes 22 separated by angles of 90°.

The invention has attained the preset aims.

During operation, the stator is in contact only with the rolling elements placed within the vertices of the rotor, regardless of the number n of vertices of the rotor and the number (n-1 ) of the lobes of the stator. This allows to eliminate the apical segments of traditional Wankel engines, and at the same time to reduce friction and avoid the risk of jamming between rotor and stator.

The invention further allows to avoid coupling between the stator pinion and the rotor ring gear of the Wankel engine, which implies a considerable mechanical simplification and lightening, as well as a reduction of manufacturing costs in accordance with the present invention. Where the machine 1 is an endothermic engine, the radial sealing between rotor and stator is ensured by the auxiliary pressure p1 through which the rollers are pressed against the surfaces of the stator recess in a regular and constant manner. The axial sealing is ensured by the hydrostatic balancing.

Owing to the constructive and mechanical simplicity of the machine of the present invention, considerable advantages were obtained in terms of inertia forces of the movable elements for the benefit of higher efficiency with respect to the known solutions.

Figures 8 to 1 1 show a machine 101 according to an alternative embodiment, particularly a machine of the hydraulic type such as a hydraulic motor or hydraulic pump. The parts of the machine 101 common to those of the machine 1 previously disclosed, shall be referenced by the numerals used in Figures 1 to 7 preceded by the digit "1 " and shall not be further described in detail.

As shown in Figure 8, the machine 101 comprises a stator 120 exhibiting a recess 121 defined by an inner surface 122a. The inner surface 122a is defined by a curve having the same equations previously mentioned. Inside the stator 120 there is disposed a rotor 1 10, movable with a roto- orbital movement about the axis A1 of the recess 121 . The rotor 1 10 has a plurality of vertices, within each of which a rolling element 1 16 is mounted, which is suitable to roll on the inner surface 122a, so as to remain in constant contact with the inner surface 122a while the rotor 1 10 is roto- orbiting about the axis A1 .

The rolling elements 1 16 are supported directly by the rotor 1 10 without any interposition by the sliding blocks.

The example shown refers to a rotor 1 10 provided with n = 3 vertices, however what is being disclosed hereinafter, generally applies to any integer and positive n value greater than or equal to 1 .

Internally of the stator 120, a plurality of lobes or recesses 122 is defined.

The number of lobes or recesses 122 of the stator 120 is equal to the number of vertices n of the rotor 1 10, reduced by one.

Between the rotor 1 10 and the stator 120 a plurality of chambers or working volumes 140 is defined, which are suitable for receiving a pressurized fluid or working fluid, e.g. oil. In the example shown, the number of working volumes 140 is equal to 3. More generally, the number of working volumes 140 is equal to the vertices number n of the rotor 1 10. A hole 1 12 is obtained inside the rotor 1 10, through which hole an eccentric portion 132 of a shaft 130 (see Figure 12) of the machine 101 is passing. The shaft 130 extends along the axis A1 , while the eccentric portion 132 is centered on the central axis A2. The rotor 1 10 is so mounted as to freely rotate relative to the eccentric portion 132. In addition, the rotor 1 10 may freely slide axially with respect to the eccentric portion 132.

The recess 121 is formed internally of a stator case 125 shown in Figure 1 1 , which is ring-shaped in the example illustrated. This ring extends around the axis A1 . As visible in Figure 12, the stator case 125 is interposed between a first head or rear head 180, shown in Figure 9, and between a second head or front head 181 shown in Figure 10. The rear head 180 and front head 181 respectively define a transverse wall and a further transverse wall defining the recess 121 transversely to the axis A1 . The rear head 180, the stator case 125 and the front head 181 are assembled in such a manner as to be stationary one to another. This may occur, for example, by using a plurality of fixing screws not shown, passing through a plurality of through holes 172, which through holes 172 are formed in the rear head 180 and a plurality of further through holes 173 formed in the stator case 125, the fixing screws becoming then engaged in respective threaded holes 174 of the front head 181 .

The machine 101 shown in Figures 8 to 12 differs from the machine 1 disclosed above, basically due to the fact that the rotor 1 10 is balanced axially, i.e., it is balanced with respect to the forces acting thereon in a direction parallel to the central axis A2. The rotor 1 10 is acting as a distributor element for distributing the pressurized fluid or working fluid within the working volumes 140, i.e. in order that the quantities and the time may be determined for the working fluid to respectively enter and exit from each working volume 140 at each revolution of the shaft 130 of the machine 101 . To this end, the machine 101 is provided with a plurality of passages or distribution openings 123, which allow the working fluid to respectively enter or exit from each working volume 140 along an axial direction, i.e. parallel to the axis A1 . As shown in Figure 9, the distribution openings 123 are afforded on the rear head 180. The distribution openings 123 comprise a plurality of inlet openings 123a, through which the working fluid can enter the working volumes 140, and a plurality of outlet openings 123b, through which the working fluid can exit from the working volumes 140. As shown in Figure 8, the inlet openings 123a and the outlet openings 123b are distributed alternatively around the axis A1 .

The arrangement of the inlet openings 123a and outlet openings 123b shown in Figure 8 applies where the rotor 1 10 is rotating counterclockwise. By reversing the sense of rotation of the rotor 1 10, the inlet openings 123a previously mentioned become outlet openings, whereas the outlet openings 123b referred to previously, become inlet openings.

In the case where the machine 101 is an engine, the inlet openings 123a are acting as delivery openings. On the other hand, if the machine 101 is a pump, the inlet openings 123a are acting as intake openings.

The distribution openings 123 are alternately opened and closed by the rotor 1 10 while the latter is rotating. In fact, during rotation of the rotor 1 10, the rotor is passing in front of each inlet opening 123, so that a certain time interval is defined during which each distribution opening 123 is thoroughly covered, i.e. closed, by the rotor 1 10. A further time interval may be defined during which each distribution opening 123 is left partially or completely uncovered by the rotor 1 10, so that the working fluid may cross this opening. Hereinafter a distribution opening 123 is defined as inactive or passive during the time in which it is completely covered, i.e. closed by the rotor 1 10. On the other hand, each distribution opening 123 will be defined as active during the time in which the rotor 1 10 is leaving that distribution opening 123 partially or completely uncovered.

The NL number of distribution openings 123 is equal to twice the number of lobes 122 of the stator 120. Thus, the following condition applies: NL = 2 (n-1 ).

Since, as already stated above, the number of working volumes 140 is equal to n (i.e. to the number of vertices of the rotor 1 10), the NLA number of distribution openings 123 which are active at same time, shall be equal to n as well, namely:

NLA = n

Therefore, the number NLP of distribution openings 123 being simultaneously passive or obscured at each revolution of the shaft of the machine 101 , is given by:

N L p = NL - NLA = 2(n-1 ) - n = n-2

In other words, a machine 101 which is provided with 2 (n-1 ) openings, has n active openings and (n-2) passive openings in every instant of its operation.

As previously already widely disclosed with reference to Figures 1 to 7, a complete cycle of the machine 101 is carried out in a complete rotation of the shaft 130, namely in a 2π rotation of the shaft 130 of the machine 101 . In addition, the reduction ratio between the shaft 130 and the rotor 1 10 is equal to 1 /n, i.e., n revolutions of the shaft 130 are needed in order that the rotor 1 10 makes a complete revolution on itself. Consequently, a machine cycle 101 corresponds to an RR rotation of the rotor 1 10 equal to 2π / n.

For each distribution opening 123, a PA activity period may be defined, i.e. a rotation angle of the rotor 1 10 in which the distribution opening 123 is active for each revolution of the shaft 130. Similarly, for each distribution opening 123, a Pp passivity period can be defined, i.e. a rotation angle of the rotor 1 10 in which the distribution opening 123 is inactive for each revolution of the shaft 130.

The PA activity period is the same for all distribution openings 123.

This occurs if the following condition is met:

PA = (RR X NLA) / NL = [(2π/η) x n] / 2(n-1 ) = π/(η-1 )

Similarly, the Pp passivity period is the same for all distribution openings

123. This occurs if the following condition is met:

PP = (R R X NLP) / NL = [(2π/η) x (n-2)] / [2(n-1 )] = [π(η-2)] / [n(n-1 )]

In the example of Figures 8 to 10, wherein n = 3, i.e. the rotor 1 10 is substantially triangular and the stator 120 has two lobes 122, the following conditions apply:

N L = 2(n-1 ) = 4

NLA = n = 3

NLP = n-2 = 1

RR = 2π/η = 2π/3 = 120°

PA = π/(η-1 ) = π/2 (corresponding to a 90°rotation of the rotor 1 10)

Pp = [π(η-2)] / [n(n-1 )] = π/6 (corresponding to a 30°rotation of the rotor 1 10).

In other words, during a complete revolution of the shaft 130 of the machine 101 around the axis A1 , the rotor 1 10 is rotating by 120°. Each distribution opening 123 remains active for the time necessary for the rotor 1 10 to perform a 90° rotation, whilst it is passive for the time necessary for the rotor 1 10 to perform a 30° rotation.

Where n = 4, that is, the rotor 1 10 is substantially quadrangular and the stator 120 has three lobes 122, the following conditions apply:

N L = 2(n-1 ) = 6

NLA = n = 4

NLP = n-2 = 2

RR = 2π/η = 2π/4 = 90° PA = π/(η-1 ) = π/3 (corresponding to a 60°rotation of the rotor 1 10)

Pp = [π(η-2)] / [n(n-1 )] = π/6 (corresponding to a 30°rotation of the rotor

1 10) .

On the other hand, if n = 5, that is, the rotor 1 10 is substantially pentagonal and the stator 120 has four lobes 122, the following conditions apply:

N L = 2(n-1 ) = 8

NLA = n = 5

NLP = n-2 = 3

RR = 2π/η = 2π/5 = 72°

PA = π/(η-1 ) = π/4 (corresponding to a 45° rotation of the rotor 1 10)

Pp = [π(η-2)] / [n(n-1 )] = 3π/20 (corresponding to a 27° rotation of the rotor

1 10).

During the Pp passivity period, each distribution opening 123 is completely obscured, that is covered, by the rotor 1 10. This means that the pressure of the working fluid existing within the distribution opening 123 generates a force which is directed in the axial direction (i.e. parallel to the axis A1 ), which force is entirely applied to the rotor 1 10. It follows that the rotor 1 10 is axially unbalanced, i.e. it is subject to axial forces the resultant of which differs from zero.

Likewise, during the PA activity period, each distribution opening 123 may be partially obscured, i.e. covered by the rotor 1 10. This helps to axially unbalance the rotor 1 10, since the working fluid present within the obscured portion of the distribution opening 123 exerts a direct force on the rotor 1 10 which direct force is parallel to the axis A1 .

In summary, the rotor 1 10 (as well as the rotor 10 of Figures 1 to 7) has a dual function. Firstly, the rotor 1 10 is acting as an expansion/compression organ, i.e. it determines the volume change of the working volumes or chambers 140, similarly to a piston of a reciprocating machine. Secondly, the rotor 1 10 is acting as a distributor element, that is, it allows the working fluid to be distributed within each chamber 140. In the case where the machine 101 is an engine, an active inlet or delivery opening 123a is associated to this chamber 140 when an expansion step is occurring within the chamber 140, so that the working fluid is allowed to enter the chamber 140 in question. If instead, a contraction step is occurring within a chamber 140, to that chamber 140 an active outlet opening 123b is associated so that the working fluid is allowed to exit the chamber 140. When a distribution opening 123 is passive, that opening is isolated from all 140 chambers.

If, on the other hand, the machine 101 is a pump, when the volume of a chamber 140 is increasing, to that chamber 140 an active inlet or intake opening 123a is associated, so that the working fluid is allowed to enter the chamber 140 in question. If instead the volume of a chamber 140 is decreasing, to that chamber 140 an active delivery opening 123b is associated, so that the working fluid is allowed to exit the chamber 140. When a distribution opening 123 is passive, that opening is isolated from all 140 chambers.

In order to ensure an axial balancing of the rotor 1 10, i.e. in order to ensure that the resultant of the direct forces acting on the rotor 1 10 and parallel to the axis A1 , is substantially zero, the following measures may be taken.

On the front head 181 , a plurality of balancing recesses 175 - i.e. non- through cavities - is obtained, which are arranged in a position facing to the distribution openings 123.

The number of balancing recesses 175 corresponds to the number of distribution openings 123, namely it is equal to 2 (n-1 ). Each balancing recess 175 is disposed in an axially opposite position with respect to a corresponding distribution opening 123. In other words, each balancing recess 175 is aligned with the corresponding distribution opening 123 along a direction parallel to the axis A1 .

The shape in plan of each balancing recess 175 is equal to the shape in plan of the corresponding distribution opening 123. In addition, on a plane perpendicular to the axis A1 , each balancing recess 175 has the same dimensions of the corresponding distribution opening 123.

Each balancing recess 175 is in fluid communication with the corresponding distribution opening 123. To this end, in the example shown, each distribution opening 123 is in fluid communication with a transverse conduit 176, which extends transversely to the rear head 180, in particular perpendicularly to the axis A1 . Each transverse conduit 176 is in fluid communication with a longitudinal conduit 177, which extends parallel to the axis A1 by passing through the stator case 125. Each longitudinal conduit 177 is in fluid communication with a further transverse conduit 178 which is formed within the thickness of the front head 181 and directed transversely, in particular perpendicularly, to the axis A1 . Each additional transverse conduit 178 is flowing in turn into a balancing recess 175.

By placing each balancing recess 175 in fluid communication with the corresponding distribution opening 123, it is ensured that in each balancing recess 175 the same working fluid is present, and thus the same pressure, which pressure is present in the corresponding distribution opening 123. Since each balancing recess 175 is axially opposite to the corresponding distribution opening 123, as well dimensioned such as that distribution opening, when the rotor 1 10 is closing a distribution opening 123 completely or partially, the corresponding balancing recess 175 is closed with the same closing level of the distribution opening 123. The working fluid present within a balancing recess 175 therefore exerts, on a face of the rotor 1 10, a force which is equal and opposite to the force that the working fluid, present in the corresponding distribution opening 123, is exerting on a further face of the rotor 1 10. In this way, the rotor 1 10 is axially balanced.

The face and the further face of the rotor 1 10 mentioned above are opposite one to another and arranged transversely, in particular perpendicularly, to the axis A1 . In an alternative embodiment not shown, the distribution openings 123 may be placed in fluid communication with the corresponding balancing recesses 175 via conduits formed within the rotor 1 10 rather than within the stator case 125.

The distribution openings 123, the transverse conduits 176, the longitudinal conduits 177, the additional transverse conduits 178 and balancing recesses define, within the machine 101 , a balancing arrangement which allows the pressurized fluid to be sent on two opposite faces of the rotor 1 10, said opposite faces being arranged transversely to the axis A1 . In this way, the pressurized fluid is exerting equal and opposite axial forces on the opposite faces of the rotor 1 10 so that the rotor 1 10 results balanced in the axial direction.

Thus, both in the examples shown in Figures 1 to 7, as well as in the example shown in Figures 8 to 12, the rotor is axially balanced by means of hydraulic forces, i.e. by means of forces exerted by a pressurized fluid on two opposite faces of the rotor. Thus, the rotor appears in a floating condition within the stator, in that the rotor, inside the stator, is surrounded by a fluid, which fluid is exerting equal and opposite forces on axially opposite faces of the rotor. This allows to axially balance the rotor in a particularly simple and effective manner.