Reduction mechanism for an aeronautical propulsion system

Abstract

The invention relates to a reduction mechanism (19) for an aeronautical propulsion system, the mechanism comprising a sun gear (19a), a ring gear (19b), a planet carrier (19d), and a series of planet gears (19c) rotatably mounted on the planet carrier (19d), wherein the sun gear (19a) comprises a first pinion that comprises a first toothing, and each planet gear (19c) comprises a second pinion that comprises a second toothing (19cd) that is capable of meshing with the first toothing of the first pinion, wherein the reduction mechanism (19) further comprises a lubrication circuit (36a) capable of conveying lubricant between the first toothing of the first pinion and the second toothing (19cd) of the second pinion, and wherein the first and second pinions have a relative sliding velocity Vg and a relative rolling velocity Vr between the two involute surfaces or active profiles in the transverse plane, wherein 0 < Vg < 30 m / s and: - if Vg < 5 m / s then Vr > 4 m / s, - if Vg 5 m / s then Vr / Vg > 1.15, and 2 < GR < 4.

Description

[0001]DESCRIPTION TITLE: REDUCTION MECHANISM FOR AERONAUTICAL PROPULSIVE SYSTEM FIELD OF THE INVENTION The invention relates to the field of reduction mechanisms, or reducers, for aeronautical propulsion systems. It thus relates to a reduction mechanism for an aeronautical propulsion system, an aeronautical propulsion system comprising such a reduction mechanism and a method for dimensioning such a reduction mechanism. STATE OF THE ART An aeronautical propulsion system generally comprises, from upstream to downstream in the direction of gas flow, a fan section, a compressor section which may comprise a low-pressure compressor and a high-pressure compressor, a combustion chamber and a turbine section which may comprise a high-pressure turbine and a low-pressure turbine.When the propulsion system is in operation, the high-pressure compressor is rotated by the high-pressure turbine via a high-pressure shaft. The fan and, if applicable, the low-pressure compressor are rotated by the low-pressure turbine via a low-pressure shaft. Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies both to new aircraft types and to those currently in operation, requiring the implementation of technological solutions to make them compliant with current regulations. Civil aviation has been mobilizing for several years now to make a contribution to the fight against climate change.Technological research efforts have already led to significant improvements in the environmental performance of aircraft. The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental consequences with the aim of improving the energy efficiency of aircraft. Consequently, the Applicant is constantly working to reduce its climate impact by using methods and operating virtuous development and manufacturing processes and limiting greenhouse gas emissions to the minimum possible to reduce the environmental footprint of its activity.This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, particularly through the materials used and lighter on-board equipment, the development of the use of electrical technologies to ensure propulsion, and, essential complements to technological progress, aeronautical biofuels. One of the objectives of technological research is thus to improve the environmental performance of aircraft, in all phases of design and development, the relevant factors are taken into account to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental consequences, with the aim of improving the energy efficiency of aircraft.For example, in order to improve the propulsive efficiency of an aeronautical propulsion system and reduce its specific consumption, it has been found that it is advantageous to increase the rotational speed of the low-pressure turbine and the low-pressure compressor, and to decrease the rotational speed of the fan. Similarly, in order to limit the drag and the mass of the aircraft, and thus reduce its fuel consumption, it has been found that it is advantageous to make the propulsion systems more compact, that is to say to reduce the size of all or part of their components. However, in doing so, it appears that the rotating components of the aeronautical propulsion systems, in particular those present within the compressor section and the turbine section, are subjected to increased centrifugal forces, while having smaller dimensions, which is likely to impair their mechanical strength and / or limit their service life.The rotational drive of the fan at a speed lower than the rotational speed of the low-pressure turbine and the low-pressure compressor is typically achieved by means of a mechanical reduction mechanism, also called a mechanical reducer. Examples of mechanical reducers are described in international application WO 2010 / 092263 A1 and French patent applications FR 2 987 416 A1, FR 3008 462 A1, FR 3 008 463 A1, FR 3 041054 A1, FR3 095 251 A1 and FR 3 116 096 A1. The role of a mechanical reducer is to modify the speed and torque ratio between the input shaft and the output shaft of a mechanical system. New generations of dual-flow turbomachines, particularly those with a high bypass ratio, include such a mechanical reducer to drive the fan shaft.Typically, the purpose of the reducer is to transform the so-called fast rotation speed of a power turbine shaft into a slower rotation speed for the shaft driving the fan, and thus allows the rotation speed of the fan and the rotation speed of the power turbine to be controlled independently. Such a reducer comprises a central pinion, called a sun gear, a crown gear and pinions called planet gears, which are meshed between the sun gear and the crown gear. The planet gears are held by a frame called a planet carrier. The sun gear, the crown gear and the planet carrier are planet gears because their axes of revolution coincide with the longitudinal axis of the turbomachine. The planet gears each have an axis of revolution, these axes being different and equally distributed over the same operating diameter around the axis of the planet gears. These axes are parallel to the longitudinal axis. There are several reducer architectures.In the state of the art of turbomachinery with double flow, the reducers are of the planetary or epicyclic type. In other similar applications, there are architectures called differential or "compound" in English. On a planetary reducer, the planet carrier is fixed and the ring constitutes the output shaft of the device which rotates in the opposite direction of the solar. On an epicyclic reducer, the ring is fixed and the planet carrier constitutes the output shaft of the device which rotates in the same direction as the solar. On a differential reducer, no element is fixed in rotation. The ring rotates in the opposite direction of the solar and the planet carrier. The reducers can be composed of one or more meshing stages. This meshing is ensured in different ways such as by contact, by friction or even by magnetic fields. There are several types of contact meshing such as with straight, helical or herringbone teeth.In the present application, the term "stage" or "teeth" means a series of meshing teeth with a series of complementary teeth. A toothing may be internal or external. A satellite may comprise one or two meshing stages. A single-stage satellite comprises a toothing which may be straight, helical or herringbone and whose teeth are located on the same diameter. This toothing cooperates with both the sun gear and the crown. A double-stage satellite comprises two teeth or two series of teeth which are located on different diameters. A first toothing cooperates with the sun gear and a second toothing cooperates with the crown. The planet carrier may be a single-piece or may comprise a cage defining an internal housing intended to receive the sun gear and the satellites. Furthermore, each satellite is centered and guided in rotation around an axis by a bearing which is carried by the planet carrier.There are several bearing technologies for this application such as rolling element bearings, or even plain or hydrodynamic bearings which have higher load capacities and are therefore preferable in terms of space requirements. A reducer thus has several meshes made between the planets and the solar. In each mesh, a first pinion transmits mechanical rotational energy to a second pinion by means of the drive carried out on the active profile of the teeth. In order to guarantee high operating performance of the reducer, it is necessary to ensure a necessary supply of lubricant on the meshing.This supply of lubricant, in particular oil, makes it possible to improve the efficiency of the power transmission, the cooling of the parts as well as the mechanical strength and wear resistance of the active profiles of the teeth, the active profile of a tooth being the contact surface meshing with the adjacent pinion(s). Parameters have been defined in the prior art in order to define conditions under which the meshing is supplied with lubricant so as to meet the needs stated above. We can notably cite the article “Elastohydrodynamic Lubrication”, D. Dowson, GR Higginson, Pergamon Press, Oxford, 1966, the article “Minimum Film Thickness in Elleptical Contacts for Different Regimes of Fluid Film Lubrication”, BJ Hamrock, D. Dowson, Proceedings of theLeeds-Lyon Symposium on Tribology, 1979, pages 22-27, and the standards ISO 6336-22 and 21771-2014.In particular, the thickness, or height, of the lubricant film, particularly the oil film, is the parameter best representing the lubrication system of the contact surfaces of the teeth. In order to improve the performance described above, it is therefore necessary to control the lubricant film as well as possible. In particular, it is necessary to ensure the thickest, or highest, lubricant film possible to avoid metal / metal contact between the two active tooth profiles. Indeed, the elimination of metal / metal contact makes it possible to limit the risk of contact fatigue due to mixed lubrication, such as micro-scaling (or "micropitting" in English), and the risk of seizure, namely the wear of two pinions which mesh together. Thus, it is necessary to guarantee a minimum height of the lubricant film during operation in order to ensure lubrication of the reducer to avoid metal / metal contact between the pinions.However, the minimum height of the lubricant film depends on numerous parameters linked to the gear teeth, including: the normal module; the normal pressure angle; the helix angle; the number of teeth; the total reduction ratio, among others. SUMMARY OF THE INVENTION One of the aims of the present invention is to determine the values ​​of the parameters conditioning a minimum height of lubricant film between the pinions of a reduction mechanism so as to be able to size the lubricant film to meet the needs stated above. To this end, the invention is the result of technological research aimed at significantly improving the performance of aircraft and, in this sense, contributes to reducing the environmental impact of aircraft.For this purpose, the invention relates to a reduction mechanism for an aeronautical propulsion system, comprising a sun gear, a ring gear, a planet carrier and a series of planets rotatably mounted on the planet carrier, the sun gear comprising a first pinion comprising a first toothing and each planet comprising a second pinion comprising a second toothing suitable for meshing with the first toothing of the first pinion, the reduction mechanism further comprising a lubrication circuit suitable for conveying lubricant between the first toothing of the first pinion and the second toothing of at least one second pinion, in which the first pinion has, with respect to at least one second pinion, a relative sliding speed ^^, in meters per second (m / s), and a relative rolling speed ^. ^ , in meters per second (m / s), between the two developing surfaces or active profiles, defined as a function of the parameters ^1 and ^2 comme : ^^ = |^2 − ^1|et : ^^ = |^1 + ^2| avec : et : ^2 = ^2^ × Ω^ et : ^2^ = ^^ × sin ^^ − ^1^ et : et : ^1 = ^2 ^^ et : et : et : et : et : ^ = ^ × ^1 cos ^^ ^^ ^ × cos ^ et : où : Oh ^is a rotational speed of the first pinion, in radians per second (rad / s), intended to be reached by the first pinion in operation, is a rotational speed of the second pinion, in radians per second (rad / s), intended to be reached by each second pinion in operation,^2^ is the distance between points T2 and B, in meters (m), T2 being the point of tangency between the line of action and the base circle of the second pinion,^2 is the number of teeth of the second pinion,^^ is the operating center distance, in meters (m),^ is a center distance variation, in meters (m), between 0 mm and 0.8 mm,^^ is the total reduction ratio,^1^ is the distance between points T1 and B, in meters (m), B being a characteristic point of the meshing which corresponds to the transition from N-1 to N teeth in mesh (N being the maximum number of teeth in mesh according to the driving ratio), and T1 being the point of tangency between the line of action and the base circle of the first gable,^^^^ is the active head diameter of the first gear at point B, in meters (m), ^, ^^ is the diameter of the base circle of the first pinion, in meters (m),^^ is the normal module, in millimeters (mm),^1 is the number of teeth of the first pinion,^ is the helix angle or primitive inclination angle, in degrees (°), ℎ ^ ∗ is the projection height corresponding to the active head diameter for the first toothing, ^ ^ is the transverse or apparent pressure angle, in degrees (°),^^ is the normal pressure angle, in degrees (°), in which the relative sliding speed ^ ^ is chosen such that: 0 < ^^ < 30 ^ / ^ and in which the relative rolling speed ^^ and the total reduction ratio ^^ are chosen such that: - if ^^ < 5 ^ / ^ then ^^ > 4 ^ / ^, - if ^^ > 5 ^ / ^ then 1,15, and 2 < ^^ < 4, et : is chosen so that 20 ^^^ / ^ ≤ 1000 ^^^ / ^Ω^ is chosen such that 200 ^^^ / ^ ≤ Ω^ ≤ 1000 ^^^ / ^,^^ is chosen such that 2.5 ^^ ≤ ^^ ≤ 5 ^^,^1 is chosen such that 20 ≤ ^^ ≤ 60,ℎ ∗ ^ is chosen such that 0.7 × ^ ∗^ ≤ ℎ^ ≤ 1.3 × ^^,^ is chosen such that 12° ≤ ^ ≤ 35°,^^ is chosen such that 15° ≤ ^^ ≤ 28°.The reduction mechanism may have one or more of the following features:In one embodiment, the relative sliding speed ^ ^ is chosen so that: 0 < ^^ < 10 ^ / ^ and the relative rolling speed ^^ and the total reduction ratio ^^ are chosen so that: - if ^^ < 5 ^ / ^ then ^^ > 4 ^ / ^, - if ^^ > 5 ^ / ^ then 1,15,and 2 < ^^ < 4.In one embodiment, the relative rolling speed ^^ is chosen such that: 4^ / ^ < ^^ < 50 ^ / ^and the relative sliding speed ^^ is chosen such that:- if ^^ > 4 ^ / ^ then ^^ < 5 ^ / ^.In one embodiment, the relative rolling speed ^ ^ is chosen so that: ^^ > 30 ^ / ^and the relative sliding speed ^ ^is chosen such that:- if ^^ > 4 ^ / ^ then ^^ < 5 ^ / ^.In one embodiment, the parameter ^1 is chosen such that:0 < ^1 < 40 ^ / ^,or even 0.5 ^ / ^ < ^1 < 40 ^ / ^,or even 2 ^ / ^ < ^1 < 40 ^ / ^.In one embodiment, the parameter ^2 is chosen such that: 0 < ^2 < 45 ^ / ^In one embodiment, the parameter ^1 is chosen such that: 0 < ^1 < 0.5 ^ / ^and the parameter ^2 is chosen such that: ^2 < 5 − ^1In one embodiment, the parameter ^1 is chosen such that: ^1 > 0.5 ^ / ^and the parameter ^2 is chosen such that: ^2 < 14 × ^1In one embodiment, for the first pinion and at least one second pinion, a minimum height parameter ^^, in meters (m), or minimum thickness, of the lubricant film, in particular of the oil, between the active profiles of the first toothing of the first pinion and the second toothing of the second pinion is defined as: ^^ = ^ × [^^ × 0, ^,^ ^,^ ^^,^^^ 985 × ^ × ^ × ^ ]. avec : 1 − 13,2 ^^ = 1+ 0.213 × (1 + 2.23 × ^^,^^) × ^^,^^ et : ^ = ^^ × ^ et : et : et : où :^ is the linear load of the teeth, in Newton per meter (N / m),^^ is the Hertz pressure, in megapascal (MPa),^ is a dimensionless thermal parameter,^ is the Young's modulus of the first or second teeth, designated E1 for the first teeth and E2 for the second teeth, in pascal (Pa),^′ is the reduced modulus of elasticity, in pascal (Pa),^ ^ is the initial Poisson's ratio, ^ ^ is the Poisson's ratio of the first tooth, ^ ^ is the Poisson's ratio of the second toothing, ^ ^ is the piezoelectricity coefficient of the lubricant (Pa -1 ), ^ ^ is the radius of curvature at the point of contact B, in meters (m), in which the minimum height ^^ of the lubricant film is chosen such that que : 0.02 × 10^^ ^ < ^^ < 0.4 × 10^^ ^ et :^ is chosen such that 200 ^ / ^^ ≤ ^ ≤ 1600 ^ / ^^,^^ is chosen such that 500 ^^^ ≤ ^^ ≤ 1800 ^^^,^ is chosen such that 1.3 × 10^^ ≤ ^ ≤ 2 × 10^^,^ is chosen such that 200 ^^^ ≤ ^ ≤ 230 ^^^,^^ is chosen such that 1 × 10^^ ^^^^ ≤ ^^ ≤ 1.8 × 10 ^^ ^^ ^^,^^ is chosen such that 0.5 ^^ < ^^ < 60 ^^,^^ is chosen such that 0.25 ^^. ^ ≤ ^^ ≤ 0.32 ^^. ^,^^ is chosen such that 0.25 ^^. ^ ≤ ^^ ≤ 0.32 ^^. ^,^ is chosen such that 8 × 10 ^^. ^ ≤ ^^ ≤ 2 × 10 ^^. ^.In one embodiment, the minimum height ^^ of the lubricant film is chosen such that:0.07 × 10^^ ^ < ^^ < 0.2 × 10^^ ^In one embodiment, the first toothing of the first pinion and the second toothing of each second pinion comprise straight, helical or herringbone teeth. In one embodiment:- each satellite comprises one or two meshing stages, and / or- the planet carrier is in one piece or comprises a cage defining an internal housing for receiving the solar and the satellites, and / or- each satellite is centered and guided in rotation around an axis by a bearing carried by the planet carrier, each bearing being of the rolling element type or of the hydrodynamic type. Furthermore,the invention also relates, according to another of its aspects, to an aeronautical propulsion system comprising:- a power turbine, in particular a low pressure turbine, and a turbine drive shaft, in particular a low pressure shaft, driven in rotation by the power turbine about a longitudinal axis, - a fan rotor and a fan shaft, the fan rotor being coupled in rotation to the fan shaft, - a reduction mechanism as defined above, comprising an inlet connected to the turbine drive shaft and an outlet connected to the fan shaft, capable of driving the fan rotor in rotation about the longitudinal axis by means of the turbine drive shaft and the fan shaft at a rotational speed lower than that of the power turbine. Furthermore, the invention also relates, according to another of its aspects, toa method for dimensioning a reduction mechanism of an aeronautical propulsion system comprising a power turbine, in particular a low-pressure turbine, and a turbine drive shaft, in particular a low-pressure shaft, driven in rotation by the power turbine about a longitudinal axis, and a fan rotor and a fan shaft, the fan rotor being rotationally coupled to the fan shaft, the reduction mechanism comprising an inlet intended to be connected to the turbine drive shaft, and an outlet intended to be connected to the fan shaft, and being capable of driving the fan rotor in rotation about the longitudinal axis by means of the turbine drive shaft and the fan shaft at a rotational speed lower than that of the power turbine, the reduction mechanism comprising a sun gear, a crown,a planet carrier and a series of satellites rotatably mounted on the planet carrier, the solar comprising a first pinion having a first toothing and each satellite comprising a second pinion having a second toothing suitable for meshing with the first toothing of the first pinion, the reduction mechanism further comprising a lubrication circuit suitable for conveying lubricant between the toothing of the first pinion and the toothing of at least one second pinion, in which the first pinion has, with respect to at least one second pinion, a relative sliding speed ^^, in meters per second (m / s), and a relative rolling speed ^, ^ , in meters per second (m / s), between the two developing surfaces or active profiles, defined as a function of the parameters ^1 and ^2 comme : ^^ = |^2 − ^1| et : ^^ = |^1 + ^2| avec : et : ^2 = ^2^ × Ω^ et : ^2^ = ^^ × sin ^^ − ^1^ et : et : ^2 = ^1 ^^ et : et : et : et : et : ^ cos ^^ ^^ = ^^ × ^1 × cos ^ et : où : Oh ^is a rotational speed of the first pinion, in radians per second (rad / s), intended to be reached by the first pinion in operation, is a rotational speed of the second pinion, in radians per second (rad / s), intended to be reached by each second pinion in operation,^2^ is the distance between points T2 and B, in meters (m), T2 being the point of tangency between the line of action and the base circle of the second pinion,^2 is the number of teeth of the second pinion,^^ is the operating center distance, in meters (m),^ is a center distance variation, in meters (m), between 0 mm and 0.8 mm,^^ is the total reduction ratio,^1^ is the distance between points T1 and B, in meters (m), B being a characteristic point of the meshing which corresponds to the transition from N-1 to N teeth in mesh (N being the maximum number of teeth in mesh according to the driving ratio), and T1 being the point of tangency between the line of action and the base circle of the first gable,^^^^ is the active head diameter of the first gear at point B, in meters (m), ^, ^^ is the diameter of the base circle of the first pinion, in meters (m),^^ is the normal module, in millimeters (mm),^1 is the number of teeth of the first pinion,^ is the helix angle or primitive inclination angle, in degrees (°), ℎ ^ ∗ is the projection height corresponding to the active head diameter for the first toothing, ^ ^ is the transverse or apparent pressure angle, in degrees (°),^^ is the normal pressure angle, in degrees (°),the method comprising a step of dimensioning the reduction mechanism during which the relative sliding speed ^ ^ is chosen such that: 0 < ^^ < 30 ^ / ^ and in which the relative rolling speed ^^ and the total reduction ratio ^^ are chosen such that: - if ^^ < 5 ^ / ^ then ^^ > 4 ^ / ^, - if ^^ > 5 ^ / ^ then 1,15, and 2 < ^^ < 4, et :Ω^ is chosen such that 20 ^^^ / ^ ≤ 1000 ^^^ / ^is chosen such that 200 ^^^ / ^ ≤ Ω^ ≤ 1000 ^^^ / ^,^^ is chosen such that 2.5 ^^ ≤ ^^ ≤ 5 ^^,^1 is chosen such that 20 ≤ ^^ ≤ 60,ℎ ∗ ^ is chosen such that 0.7 × ^ ∗^ ≤ ℎ^ ≤ 1.3 × ^^,^ is chosen such that 12° ≤ ^ ≤ 35°,^^ is chosen such that 15° ≤ ^^ ≤ 28°.In one embodiment, the method comprises a step of dimensioning the reduction mechanism during which the relative sliding speed ^^ is chosen such that:0 < ^^ < 10 ^ / ^and the relative rolling speed ^^ and the total reduction ratio ^^ are chosen such that:- if ^^ < 5 ^ / ^ then ^^ > 4 ^ / ^,- if ^^ > 5 ^ / ^ then ^ ^ ^ ^ > 1,15, and 2 < ^^ < 4. In one embodiment, the method comprises a step of dimensioning the reduction mechanism during which the relative rolling speed ^ ^is chosen so that: 4^ / ^ < ^^ < 50 ^ / ^and the relative sliding speed ^ ^ is chosen such that:- if ^^ > 4 ^ / ^ then ^^ < 5 ^ / ^.In one embodiment, the method comprises a step of dimensioning the reduction mechanism during which the relative rolling speed ^ ^ is chosen so that: ^^ > 30 ^ / ^and the relative sliding speed ^ ^is chosen such that:- if ^^ > 4 ^ / ^ then ^^ < 5 ^ / ^.In one embodiment, the method comprises a step of dimensioning the reduction mechanism during which the parameter ^1 is chosen such that:0 < ^1 < 40 ^ / ^,or even 0.5 ^ / ^ < ^1 < 40 ^ / ^,or even 2 ^ / ^ < ^1 < 40 ^ / ^.In one embodiment, the method comprises a step of dimensioning the reduction mechanism during which the parameter ^2 is chosen such that:0 < ^2 < 45 ^ / ^In one embodiment, the method comprises a step of dimensioning the reduction mechanism during which the parameter ^1 is chosen such that:0 < ^1 < 0.5 ^ / ^and in which the parameter ^2 is chosen such that:^2 < 5 − ^1In one embodiment, the method comprises a step of dimensioning the reduction mechanism reduction in which the parameter ^1 is chosen such that: ^1 > 0,5 ^ / ^and in which the parameter ^2 is chosen such that:^2 < 14 × ^1 In one embodiment, for the first pinion and at least one second pinion, a minimum height parameter ^^ is defined, in meters (m), or minimum thickness, of the lubricant film, in particular of the oil, between the active profiles of the first toothing of the first pinion and the second toothing of the second pinion, defined as:^^ = ^ × [^^ × 0 ^,^ ^,^ ^^,^^^ ,985 × ^ × ^ × ^ ], avec : 1 − 13,2 ^^ = 1+ 0.213 × (1 + 2.23 × ^^,^^) × ^^,^^ et : ^ = ^^ × ^ et : et : et : où : ^ ^is the radius of curvature at the point of contact B, in meters (m),^ is the linear load of the teeth, in Newton per meter (N / m),^^ is the Hertz pressure, in megapascal (MPa),^ is a thermal parameter, dimensionless,^ is the Young's modulus of the first tooth or the second tooth, designated E1 for the first tooth and E2 for the second tooth, in pascal (Pa),^′ is the reduced modulus of elasticity, in pascal (Pa),^ ^ is the initial Poisson's ratio, ^ ^ is the Poisson's ratio of the first tooth, ^ ^ is the Poisson's ratio of the second toothing, ^ ^ is the piezoelectricity coefficient of the lubricant (Pa -1 ), the method comprising a step of dimensioning the reduction mechanism during which the minimum height ^^ of the lubricant film is chosen such that: 0.02 × 10^^ ^ < ^^ < 0.4 × 10^^ ^ et :^ is chosen such that 200 ^ / ^^ ≤ ^ ≤ 1600 ^ / ^^,^^ is chosen such that 500 ^^^ ≤ ^^ ≤ 1800 ^^^,^ is chosen such that 1.3 × 10^^ ≤ ^ ≤ 2 × 10^^,^ is chosen such that 200 ^^^ ≤ ^ ≤ 230 ^^^,^^ is chosen such that 1 × 10^^ ^^^^ ≤ ^^ ≤ 1.8 × 10 ^^ ^^ ^^,^^ is chosen such that 0.5 ^^ < ^^ < 60 ^^,^^ is chosen such that 0.25 ^^. ^ ≤ ^^ ≤ 0.32 ^^. ^,^^ is chosen such that 0.25 ^^. ^ ≤ ^^ ≤ 0.32 ^^. ^,^ is chosen such that ^^ ^^^ 8 × 10 ^^. ^ ≤ ^^ ≤ 2 × 10 ^^. ^.In one embodiment, the method comprises a step of dimensioning the reduction mechanism during which the minimum height ^^ of the lubricant film is chosen such that: 0.02 × 10^^ ^ < ^^ < 0.4 × 10^^ ^Furthermore, the invention also relates, according to another of its aspects, to a reduction mechanism manufactured from a dimensioning method as defined above. PRESENTATION OF THE DRAWINGS Other characteristics and advantages will emerge from the following description, which is purely illustrative and non-limiting, and must be read with reference to the appended figures, among which: - figure 1 schematically represents an aircraft comprising propulsion systems,-figure 2 schematically represents, in partial view and in section, an example of a propulsion system in which the fan section is ducted, -figure 3 schematically represents, in partial view and in section, an example of a propulsion system in which the fan section is unducted, -figure 4 schematically represents a first example of a planetary reduction mechanism, -figure 5 schematically represents a first example of an epicyclic reduction mechanism, -figure 6 schematically represents a first example of a differential reduction mechanism, -figure 7 schematically and partially represents an axial section of an example of an epicyclic reduction mechanism, -figure 8 schematically and partially represents,the lubricating film formed between the active profiles of a first toothing of a first pinion of the sun gear of a reduction mechanism according to the invention and a second toothing of a second pinion of a satellite of a series of satellites of the reduction mechanism according to the invention, - figure 9 represents, schematically and partially, the highlighting of the relative sliding between the first and second pinions of the reduction mechanism according to the invention, and - figures 10 to 15 illustrate, schematically and partially, parameters used in the definition of a reduction mechanism according to the invention. DETAILED DESCRIPTION OF EMBODIMENTS In the example illustrated in figure 1, the aircraft is an airplane 100 comprising a fuselage 101 and two wings 102. In this example, the aircraft comprises two propulsion systems 1,each propulsion system 1 being attached to a respective wing 102 of the aircraft 100 via a pylon. In another embodiment, the aircraft could comprise one or more propulsion systems attached to the fuselage 101. Figure 2 schematically represents, in partial view and in section, a first example of a propulsion system 1. In this example, the propulsion system 1 is a double-spool gas turbine engine with a ducted fan. In Figure 2, the propulsion system 1 has a main direction extending along a longitudinal axis X. The propulsion system 1 comprises a fan section 2 and a primary body 3,often referred to as a "gas generator". The blower section 2 includes a blower 22 and a blower housing 12. The blower 22 includes a blower rotor 9. The blower housing 12 surrounds the blower rotor 9. The blower rotor 9 is rotatably mounted relative to the blower housing 12. The blower rotor 9 includes a blower hub 13 and blower blades 14 extending radially from the hub 13. The blower blades 14 may be fixed relative to the blower hub 13 or have variable pitch. In the latter case,each of the fan blades 14 is pivotally mounted relative to the fan hub 13 along a pitch axis and is connected to a pitch change mechanism (not shown) mounted in the propulsion system 1. The pitch change mechanism makes it possible to adjust the pitch angle of the fan blades 14 according to the flight phases. The fan rotor 9 comprises at least fourteen fan blades 14 and at most twenty-four fan blades 14, preferably at least sixteen fan blades 14 and at most twenty-two fan blades 14. In addition, in this example, the fan section 2 also comprises a fan stator 16 fixedly mounted on the fan casing 12. The fan stator 16 comprises fixed blades 17 generally referred to as “outlet blades” (or “OGVs”,for "Outlet Guide Vane" in English). This set of fixed vanes has the function of straightening and regulating the airflow flowing downstream of the fan rotor 9 to contribute to the engine thrust. This set of fixed vanes also plays a noise reduction role. Alternatively, the outlet vanes 17 could have a variable pitch. If necessary, and similarly to the fan blades 14 of the fan rotor 9, the root of the outlet vanes 17 is pivotally mounted along a pitch axis and is connected to a pitch change mechanism (not shown), the pitch being adjusted according to the flight phases by the pitch change mechanism. The number of outlet vanes 17 depends on the acoustic criteria defined for the propulsion system 1 and is at least equal to the number of fan blades 14. The primary body 3 comprises a compressor section 29,a combustion chamber 6 and a turbine section 30. The compressor section 29 comprises a low pressure compressor 4 and a high pressure compressor 5. The low pressure compressor 4 comprises a rotor 41 adapted to be driven in rotation relative to the casing 31 of the propulsion system 1 and a stator 42 fixedly mounted on the casing 31. The rotor 41 of the low pressure compressor 4 comprises movable wheels 4a and the stator 42 of the low pressure compressor 4 comprises fixed wheels 4b. The movable wheels 4a are arranged alternately with the fixed wheels 4b, thus forming a succession of low pressure compressor stages. Similarly,the high pressure compressor 5 comprises a rotor 51 suitable for being driven in rotation relative to the casing 31 of the propulsion system 1 and a stator 52 fixedly mounted on the casing 31. The rotor 51 of the high pressure compressor 5 comprises movable wheels 5a and the stator 52 of the high pressure compressor 5 comprises fixed wheels 5b. The movable wheels 5a are arranged alternately with the fixed wheels 5b, thus forming a succession of high pressure compressor stages. The turbine section 30 comprises a high pressure turbine 7 and a low pressure turbine 8. The high pressure turbine 7 comprises a rotor 71 suitable for being driven in rotation relative to the casing 31 of the propulsion system 1 and a stator 72 fixedly mounted on the casing 31. The rotor 71 of the high pressure turbine 7 comprises movable wheels 7a and the stator 72 of the high pressure turbine 7 comprises fixed wheels 7b. The movable wheels 7a are arranged alternately with the fixed wheels 7b,thus forming a succession of high-pressure turbine stages. Similarly, the low-pressure turbine 8 comprises a rotor 81 suitable for being driven in rotation relative to the casing 31 of the propulsion system 1 and a stator 82 mounted fixedly on the casing 31. The rotor 81 of the low-pressure turbine 8 comprises movable wheels 8a and the stator 82 of the low-pressure turbine 8 comprises fixed wheels 8b. The movable wheels 8a are arranged alternately with the fixed wheels 8b, thus forming a succession of low-pressure turbine stages. The propulsion system 1 comprises a low-pressure shaft 11 connecting the rotor 41 of the low-pressure turbine 4 to the rotor 81 of the low-pressure compressor 8, the low-pressure shaft 11 being rotatably mounted relative to the casing 31 around the longitudinal axis X. When the propulsion system 1 is in operation,the rotor 81 of the low-pressure turbine 8 rotates the rotor 41 of the low-pressure compressor 4 via the low-pressure shaft 11. The propulsion system 1 further comprises a fan shaft 20 and a reduction mechanism 19. The fan rotor 9 is rotatably coupled to the fan shaft 20. The reduction mechanism 19 has an inlet and an outlet. The inlet of the reduction mechanism 19 is connected to the low-pressure shaft 11 and the outlet of the reduction mechanism 19 is connected to the fan shaft 20. Thus, when the propulsion system 1 is in operation, the rotor 81 of the low pressure turbine 8 drives in rotation not only the rotor 41 of the low pressure compressor 4, but also the fan rotor 9, by means of the low pressure shaft 11, the reduction mechanism 19 and the fan shaft 20. Thanks to the reduction mechanism 19,the fan rotor 9 is rotated at a speed lower than the rotational speed of the rotor 41 of the low-pressure turbine 4. The reduction mechanism 19 thus makes it possible to independently control the rotational speed of the fan 22 and the rotational speed of the low-pressure turbine 8 and the low-pressure compressor 4. The low-pressure turbine 8, the low-pressure shaft 11, the low-pressure compressor 4, the fan shaft 20, the reduction mechanism 19 and the fan 22 together form the “low-pressure body” of the propulsion system 1. The propulsion system 1 further comprises a high-pressure shaft 10 connecting the rotor 51 of the high-pressure turbine 5 to the rotor 71 of the high-pressure compressor 7,the high pressure shaft 10 being rotatably mounted relative to the casing 31 about the longitudinal axis X. The high pressure shaft 10 is coaxial with the low pressure shaft 11 and extends around the low pressure shaft 11. When the propulsion system 1 is in operation, the rotor 81 of the low pressure turbine 8 drives the rotor 51 of the low pressure compressor 5 in rotation via the low pressure shaft 11. The high pressure turbine 7, the high pressure shaft 10 and the high pressure compressor 4 together form the “high pressure body” of the propulsion system 1. The low pressure shaft 11 and the high pressure shaft 10 may be co-rotating, that is to say, driven in the same direction of rotation about the longitudinal axis X. Alternatively, the low pressure shaft 11 and the high pressure shaft 10 may be counter-rotating,that is to say be driven in opposite directions of rotation around the longitudinal axis X. The double-spool propulsion system 1 may in particular comprise a single-stage high-pressure turbine 7, that is to say comprising exactly one stage, or a two-stage high-pressure turbine 7, that is to say comprising exactly two stages (as illustrated in the example of Figure 2). The high-pressure compressor 5 comprises at least eight stages (as illustrated in the example of Figure 2) and at most eleven stages. The low-pressure turbine 8 comprises at least three stages (as illustrated in the example of Figure 2) and at most seven stages. The low-pressure compressor 4 comprises at least two stages and at most four stages. When the propulsion system is in operation, an air flow F entering the propulsion system 1 passes through the fan 22 and is then divided between a primary air flow F1 and a secondary air flow F2,which circulate from upstream to downstream in the propulsion system 1. The secondary air flow F2, also called "bypass air flow", flows in the secondary vein, around the primary body 3. The secondary air flow F2 makes it possible to cool the periphery of the primary body 3 and is used to generate the majority of the thrust provided by the propulsion system 1. The primary air flow F1 flows in a primary vein inside the primary body 3, passing successively through the compressor section 29 (low pressure compressor 4 and high pressure compressor 5), the combustion chamber 6 where it is mixed with fuel to serve as an oxidizer, and the turbine section 30 (high pressure turbine 7 and low pressure turbine 8). The passage of the primary air flow F1 through the turbine section 30 receiving energy from the combustion chamber 6 causes rotation of the moving wheels 7a, 8a of the turbine section 30,which in turn drive the moving wheels 4a, 5a of the compressor section 29 and the fan rotor 9 in rotation. In order to improve the propulsive efficiency of the propulsion system 1 and to reduce its specific consumption as well as the noise emitted by the fan section 2, the propulsion system 1 has a high dilution ratio (or "bypass ratio" in English). By "high" dilution ratio, it is meant a dilution ratio greater than or equal to 10, for example between 10 and 80 inclusive, preferably between 10 and 35 inclusive, preferably between 10 and 18 inclusive. The bypass ratio is defined as a ratio between the mass flow rate of the secondary air flow F2 and the mass flow rate of the primary air flow F1, these mass flow rates being measured when the propulsion system 1 is stationary, uninstalled, in take-off mode in a standard atmosphere (as defined by the International Civil Aviation Organization (ICAO) manual, Doc 7488 / 3,3rd edition) and at sea level. By "not installed" it is meant that the measurements are carried out when the propulsion system 1 is on a test bench (and not installed on an aircraft), the measurements then being simpler to carry out. In a propulsion system including a reduction mechanism 19 such as that illustrated in FIG. 2, the decoupling between the rotational speed of the fan 22 and the rotational speed of the low pressure turbine 8 makes it possible to reduce the rotational speed and the pressure ratio of the fan rotor 9 while increasing the power extracted by the low pressure turbine 8. Indeed, the overall efficiency of the propulsion system 1 is conditioned to the first order by the propulsive efficiency, which is favorably influenced by a minimization of the variation in kinetic energy of the air passing through the propulsion system 1. In a propulsion system with a high bypass ratio,the majority of the flow rate generating the propulsive force is constituted by the secondary air flow F2 of the propulsion system 1, the kinetic energy of the secondary air flow F2 being mainly affected by the compression that the secondary air flow F2 undergoes when passing through the fan section 2. The propulsive efficiency and the pressure ratio of the fan section 2 are therefore linked: the lower the pressure ratio of the fan section 2, the better the propulsive efficiency. In order to improve the propulsive efficiency of the propulsion system 1, the pressure ratio of the fan, which corresponds to the ratio between the average pressure at the outlet of the fan stator 16 (or, in the absence of stator 16, of the fan rotor 9) and the average pressure at the inlet of the fan rotor 9, is less than or equal to 1.70, preferably less than or equal to 1.50, for example between 0.90 and 1,45. The average pressures are measured here over the height of at least one of the fan blades 14, that is to say the surface which radially delimits on the inside the air flow vein at the inlet of the fan rotor 9 at the tip 21 of the fan blade 14. The peripheral speed at the tip 21 of the fan blades 14 can also be between 260 meters per second (ms-1) and 400 meters per second (ms, -1) included. The fan pressure ratio can then be between 1.20 and 1.45. In a direct-drive propulsion system, the fan rotor 9 can, alternatively, be directly coupled to the low-pressure shaft 11, i.e. without a reduction mechanism. The low pressure shaft 11 is then merged with the fan shaft 20 so that the fan rotor 9 is driven by the low pressure shaft 11 at the same rotational speed as the rotor 81 of the low pressure turbine 8. The propulsion system 1 is configured to provide a thrust of between 18,000 lbf (80,068 N) and 51,000 lbf (226,859 N), preferably between 20,000 lbf (88,964 N) and 35,000 lbf (155,688 N). The diameter D of the fan rotor 9 may be between 80 inches (203.2 cm) and 185 inches (469.9 cm) inclusive.When the fan rotor 9 is ducted, the diameter D is preferably between 85 inches (215.9 cm) and 120 inches (304.8 cm) inclusive, for example of the order of 90 inches (228.6 cm), which allows the integration of the propulsion system 1 in a conventional manner, in particular under a wing of the aircraft 1. Figure 3 schematically represents, in partial view and in section, a second example of propulsion system 1. In Figure 3, the components identical or similar to those of the propulsion system of Figure 2 are designated by identical references. In the example illustrated in Figure 3, the propulsion system 1 is a twin-spool gas turbine engine with an unducted fan. It may be a gas turbine engine of the “Open Rotor” or “Unducted Single Fan” type in English terminology.Unlike the first example of Figure 2, the fan rotor 9, which can also be referred to as a "propeller", is not surrounded by a fan casing. Since the fan section 2 is not shrouded, the fan blades 14 have a variable pitch. Thus, each of the fan blades 14 is pivotally mounted relative to the fan hub 13 along a pitch axis and is connected to a pitch change mechanism 15 mounted in the propulsion system 1. The pitch change mechanism makes it possible to adjust the pitch angle of the fan blades 14 as a function of the flight phases. Similarly, the outlet blades 17 have a variable pitch, the root of the outlet blades 17 being pivotally mounted along a pitch axis and connected to a pitch change mechanism 15, the pitch being adjusted as a function of the flight phases by the pitch change mechanism.Alternatively, the propulsion system 1 could comprise two unducted, counter-rotating fan rotors 9. Such a propulsion system 1 is known, in English terminology, by the acronym "CROR" for "Contra-Rotating Open Rotor" or "UDF" for "Unducted Double Fan". The fan rotors 9 may be placed at the rear of the primary body 3 so as to be of the pusher type or at the front of the primary body 3 so as to be of the puller type. The absence of fairing around the fan rotor 9 makes it possible to increase the bypass ratio significantly without the propulsion system 1 being penalized by the mass of the casings 12 or nacelles intended to surround the fan section 2. The bypass ratio of the propulsion system 1 comprising an unfairly faired fan section 2 is thus greater than or equal to 40, for example between 40 and 80 inclusive.The peripheral speed at the tip 21 of the fan blades 14 of the fan rotor(s) 9 may furthermore be between 210 meters per second (ms-1) and 260 meters per second (ms-1) inclusive. The fan pressure ratio may then preferably be between 0.90 and 1.20 inclusive. The diameter D of the fan rotor 9 may be between 80 inches (203.2 cm) and 185 inches (469.9 cm) inclusive. When the rotor 9 is unducted, the diameter D is preferably greater than or equal to 100 inches (254 cm), for example between 120 inches (304.8 cm) and 156 inches (396.2 cm). The diameter of the fan rotor 9 is measured here in a plane normal to the longitudinal axis X, which is the axis of rotation of the fan rotor 9, at an intersection between a tip 21 and a leading edge 22 of the fan blades 14. It should be noted that, since Figure 2 and Figure 3 are partial views, the diameter D is only partially visible.The reduction mechanism 19 may comprise an epicyclic, planetary or differential reduction mechanism, single-stage, also called monostage, or multi-stage, in particular two-stage, also called two-stage. For example, Figure 4 illustrates a reduction mechanism 19 of the planetary (or “star” type in English).The reduction mechanism 19 comprises a sun gear 19a (input of the reduction mechanism 19), centered on an axis of rotation of the reduction mechanism 19 generally coincident with the longitudinal axis X and configured to be driven in rotation by the low pressure shaft 11, a ring gear 19b (output of the reduction mechanism 19) coaxial with the sun gear 19a and configured to drive in rotation the fan shaft 20 about its axis X of rotation, and a series of satellites 19c distributed circumferentially about the axis X of rotation of the rotor 9 of the fan section2, between the sun gear 19a and the ring gear 19b, each satellite 19c being meshed internally with the sun gear 19a and externally with the ring gear 19b. The series of satellites 19c is mounted on a planet carrier 19d which is fixed relative to a stator part 19e of the propulsion system 1, for example relative to a casing of the compressor section 4, 5.In another example, Figure 5 illustrates a reduction mechanism 19 of the epicyclic type (or "planetary" in English), in which case the crown 19b is fixedly mounted on the stator part 19e of the propulsion system 1 and the fan shaft 20 is driven in rotation by the planet carrier 19d. In yet another example, Figure 6 illustrates a reduction mechanism 19 of the differential type (or "differential" in English), in which case no element is fixed in rotation.The set of satellites 19c is held by a satellite carrier 19d which is connected to a first fan shaft 20a, each satellite 19c driving the ring gear 19b attached to a second counter-rotating fan shaft 20b. Whatever the configuration of the reduction mechanism 19, the diameter of the ring gear 19b and of the satellite carrier 19d are greater than the diameter of the sun gear 19a, so that the rotational speed of the rotor 9 of the fan section 2 is lower than the rotational speed of the low-pressure shaft 11. The reduction ratio of the reduction mechanism 19 is greater than or equal to 2.5 and less than or equal to 11. In the case of a propulsion system 1 with a ducted fan, the reduction ratio may be greater than or equal to 2.7 and less than or equal to 3.5, typically around 3.0. In the case of a propulsion system 1 with an unducted fan, the reduction ratio can be between 9.0 and 11.0.Figure 7 schematically and partially represents, in axial section, an example of a mechanical reducer 19 of the epicyclic type, the planet carrier 19d and the sun gear 19a of which are mobile in rotation, the crown 19b of the reducer 19 being fixed in the frame of reference of the motor. At the input, the reducer 19 is connected to the low pressure shaft 11, for example by means of internal splines 77a. Thus, the low pressure shaft 11 drives the sun gear 19a. The sun gear 19a, the axis of rotation of which coincides with the longitudinal axis X, drives a series of planet gears 19c, which are equally distributed over the same diameter around the axis of rotation X. This diameter is equal to twice the operating center distance between the sun gear 19a and the planet gears 19c. The number of planet gears 19c is generally defined between three and seven for this type of application. The set of 19c satellites is held by a chassis formed by the 19d satellite carrier.Each planetary gear 19c rotates about its own rotation axis Y, and meshes with the ring gear 19b. At the output, in this configuration shown in Figure 7, the set of planetary gears 19c rotates the planet carrier 19d about the longitudinal axis X. The ring gear 19b is fixed to the motor casing or stator via a ring gear carrier 23 and the planet carrier 19d is fixed to the fan shaft 20. In another planetary configuration, the set of planetary gears 19c is held by a planet carrier 19d which is fixed to the motor casing or stator. Each satellite 19c drives the crown 19b which is connected to the fan shaft 20 via a crown carrier 23. In another differential configuration, all of the satellites 19c are held by a planet carrier 19d which is connected to a first fan shaft 20a. Each satellite drives the crown 19b which is connected to a second counter-rotating fan shaft 20b via a crown carrier 23.Each planet gear 19c is mounted to rotate freely using a bearing 24, for example of the rolling bearing type or of the hydrodynamic type. Each bearing 24 is mounted on one of the axes 25a of the planet carrier 19d and all the axes are positioned relative to each other using one or more structural frames 25b of the planet carrier 19d. There are a number of axes 25a and bearings 24 equal to the number of planet gears 19c. For reasons of operation, assembly, manufacturing, control, repair or replacement, the axes 25a and the frame 25b can be separated into several parts. For the same reasons as those mentioned above, the toothing of a planet gear 19c can be separated into several helices or teeth each having a median plane P, P'. In this example, the operation of a reducer 19, each satellite 19c of which comprises two series of chevron teeth cooperating with a crown 19b separated into two half-crowns, is detailed below.An upstream half-crown 26 consisting of a rim 26a and a half-fixing flange 26b. On the rim 26a is the front propeller meshed with a propeller of the toothing 19cd of each satellite 19c. The propeller of the toothing 19cd also meshes with that of the sun 19a. A downstream half-crown 27 consisting of a rim 27a and a half-fixing flange 27b. On the rim 27a is the rear propeller meshed with a propeller of the toothing 19cd of each satellite 19c. The helix of the 19cd toothing also meshes with that of the sun gear 19a. If the helix widths vary between the sun gear 19a, the satellites 19c and the crown 19b because of the tooth overlaps, they are all centered on a median plane P for the upstream teeth and on another median plane P' for the downstream teeth. Figure 7 thus illustrates the case of a single-stage gear reducer, that is to say that the same 19cd toothing of each satellite 19c cooperates with both the sun gear 19a and the crown 19b.Even if the toothing 19cd comprises two sets of teeth, these teeth have the same average diameter and form a single toothing called a chevron. The fixing half-flange 26b of the upstream crown 26a and the fixing half-flange 27b of the downstream crown 27a form the fixing flange 28 of the crown 19b. The crown 19b is fixed to a crown carrier 23 by assembling the fixing flange 28 of the crown 19b and the fixing flange 35 of the crown carrier 23 using a bolted assembly for example. The arrows FH in Figure 7 describe the routing of the oil in the reducer 19. The oil arrives in the reducer 19 from the stator part in a distributor 36 by different means which will not be specified in this view because they are specific to one or more types of architecture. The distributor 36 comprises injectors 36a and arms 36b. The injectors 36a have the function of lubricating the teeth and the arms 36b have the function of lubricating the bearings.The oil is brought to the injector 36a to exit through the end 36c in order to lubricate the teeth. The oil is also brought to the arm 36b and circulates via the supply mouth 36d of the bearing. The oil then circulates through the axis in one or more buffer zones 25c to then exit through the orifices 25d in order to lubricate the bearings 24 of the planet gears 19c. A reduction mechanism 19 thus comprises several meshes formed between the sun gear 19a and the planet gears 19c. In each mesh, a first pinion Pi1 transmits mechanical rotational energy to a second pinion Pi2 by means of the drive carried out on the active profile of the teeth.Figure 8 schematically represents the lubricant film, in particular oil, formed between the active profiles of a first toothing of a first pinion Pi1 of the sun gear 19a of a reduction mechanism 19 and a second toothing 19cd of a second pinion Pi2 of a satellite 19c of a series of satellites 19c of the reduction mechanism 19. The lubricant film is obtained by means of a lubrication circuit 36a of the reduction mechanism 19 allowing the conveyance of the lubricant between the first toothing of the first pinion Pi1 and the second toothing 19cd of the second pinion Pi2. The minimum height Hm, or minimum thickness, of the lubricant film is shown in Figure 8.This is the minimum distance, projected in a radial plane relative to the first pinion Pi1 and the second pinion Pi2, between the active profiles of the first toothing of the first pinion Pi1 and the second toothing 19cd of the second pinion Pi2, or the normal minimum distance between the active profiles of the first toothing of the first pinion Pi1 and the second toothing 19cd of the second pinion Pi2. In order to guarantee high operating performance of the reduction mechanism 19, it is essential to ensure a controlled supply of lubricant to the meshing. For this, the value of the minimum height Hm of the lubricant film must be controlled as well as possible.In particular, a thick lubricant film, therefore with a significant minimum height Hm, which remains controlled during operation, can prevent metal / metal contact between the two active tooth profiles, and therefore limit the risk of contact fatigue, of the micro-scaling type (or "micropitting" in English), and the risk of seizure, namely wear in the meshing of the pinions. The minimum height Hm, expressed in meters (m), of the lubricant film between the active profiles of the first tooth of the first pinion Pi1 and the second tooth19cd of the second pinion Pi2 is defined as: ^^ = ^ ^,^ ^,^ ^^,^^^ × [^^ × 0.985 × ^ × ^ × ^ ]. avec : 1 − 13,2 ^^ = 1+ 0.213 × (1 + 2.23 × ^^,^^) × ^^,^^ et : ^ = ^^ × ^ et : et : et : et : et : ^2 = ^2^ × Ω^ et : ^2^ = ^^ × sin ^^ − ^1^ et : et : et : et : et : et : et : ^ = ^ × cos ^^ ^^ ^ ^1 × cos ^ et : où : ^ is the linear load of the teeth, in Newton per meter (N / m),^^ is the Hertz pressure, in megapascal (MPa),^ is a dimensionless thermal parameter,^ is the Young's modulus of the first or second teeth, designated E1 for the first teeth and E2 for the second teeth, in pascal (Pa),^′ is the reduced modulus of elasticity, in pascal (Pa),^ ^ is the initial Poisson's ratio, ^ ^ is the Poisson's ratio of the first tooth, ^ ^ is the Poisson's ratio of the second toothing, ^ ^ is the piezoelectricity coefficient of the lubricant (Pa -1 ), ^ ^ is the radius of curvature at the point of contact B, in meters (m), Ω ^is a rotational speed of the first pinion Pi1, in radians per second (rad / s), intended to be reached by the first pinion Pi1 in operation, is a rotational speed of the second pinion Pi2, in radians per second (rad / s), intended to be reached by each second pinion Pi2 in operation,^2^ is the distance between points T2 and B, in meters (m), T2 being the point of tangency between the line of action and the base circle of the second pinion Pi2,^2 is the number of teeth of the second pinion Pi2,^^ is the operating center distance, in meters (m),^ is a center distance variation, in meters (m), between 0 mm and 0.8 mm,^^ is the total reduction ratio,^1^ is the distance between points T1 and B, in meters (m), B being a characteristic point of the meshing which corresponds to the passage from N-1 to N teeth in mesh (N being the maximum number of teeth in mesh according to the driving ratio),and T1 being the point of tangency between the line of action and the base circle of the first pinion Pi1,^^^^ is the active head diameter of the first pinion Pi1 at point B, in meters (m), ^, ^^ is the diameter of the base circle of the first pinion Pi1, in meters (m),^^ is the normal module, in millimeters (mm),^1 is the number of teeth of the first pinion Pi1,^ is the helix angle or primitive inclination angle, in degrees (°),ℎ ^ ∗ is the projection height corresponding to the active head diameter for the first toothing, ^ ^is the transverse or apparent pressure angle, in degrees (°),^^ is the normal pressure angle, in degrees (°).Figure 9 schematically represents the geometric parameters associated with the relative sliding between the first Pi1 and second Pi2 pinions of the reduction mechanism 19 according to the invention. In particular, Figure 9 represents the meshing of the pair of conjugate profiles of the teeth of the first Pi1 and second Pi2 pinions whose line of action L AC is tangent at T1 and T2 to the base circles Cb1, of diameter d b1 , and Cb2, of diameter db2, of the first pinion Pi1 and of the second pinion Pi2. By the very definition of conjugate profiles, these roll on each other and are constantly tangent. In this figure 9 also, the first and second primitive circles are respectively noted Cy1, of diameter dy1, and Cy2, of diameterd y2. Point B is a characteristic point of the meshing which corresponds to the transition from N-1 to N meshing teeth (N being the maximum number of meshing teeth according to the driving ratio). Furthermore, Figures 10 to 15 also make it possible to define other parameters used for the definition of a reduction mechanism according to the invention. In Figure 10, which represents a tooth D in isolation, the references Ft and Fp designate the tooth flank and the root respectively. The references ha and hf designate the projection height, corresponding to the head diameter, and the recess height respectively. The reference h is the height of the tooth D. Furthermore, in Figure 11, the reference d corresponds to the diameter of the pitch circle, d / 2 being the radius of the pitch circle, and the reference db corresponds to the diameter of the base circle, db / 2 being the radius of the base circle. In a cross-section, the transverse or apparent pressure angle ^ ^is thus the acute angle formed between the tangent to the involute d v of the toothing at its point of intersection with the pitch circle and the radius passing through this point. The normal pressure angle ^ ^ is the projection of the transverse pressure angle ^^ in a plane normal to the teeth. It is defined by the fact that tan ^^ =tan ^^ × cos ^. In the case of straight teeth, the angles ^^ and ^^ are identical. Furthermore, in Figure 12, the active head diameter ^^^^ of the first pinion Pi1 and the active head diameter ^^^^ of the second pinion Pi2 are shown. Similarly, the diameter of the base circle ^^^ of the first pinion Pi1 and the diameter of the base circle ^^^ of the second pinion Pi2 are shown. The projection height corresponding to the active head diameter ℎ ^ ∗is also shown in Figure 13, the reference d in this Figure 13 corresponding to the pitch diameter and the reference da corresponding to the head diameter. Figure 14 illustrates the operating center distance ^^ between the two axes passing through O1 and O2 of the two pinions. In addition, Figure 15 illustrates the helix angle ^ which is the angle between a tangent ta to a reference helix Hr and the envelope line of the reference cylinder Le passing through the tangent contact point. In this Figure 15, PN designates a normal plane and AX designates the central axis of the pinion. It should be noted that the parameters described in the present application are well known to those skilled in the art and are notably mentioned in the literature cited above, in particular the ISO 6336-22 and 21771-2014 standards.Advantageously, the parameters listed above and entering into the calculation of the minimum height Hm of the lubricant film are such that:^ is chosen such that 200 ^ / ^^ ≤ ^ ≤ 1600 ^ / ^^,^^ is chosen such that 500 ^^^ ≤ ^^ ≤ 1800 ^^^,^ is chosen such that 1.3 × 10^^ ≤ ^ ≤ 2 × 10^^,^ is chosen such that 200 ^^^ ≤ ^ ≤ 230 ^^^,^^ is chosen such that 1 × 10^^ ^^^^ ≤ ^^ ≤ 1.8 × 10. ^^ ^^ ^^ ,Ω^ is chosen such that 20 ^^^ / ^ ≤ Ω^ ≤ 1000 ^^^ / ^Ω^ is chosen such that 200 ^^^ / ^ ≤ Ω^ ≤ 1000 ^^^ / ^,^^ is chosen such that 2.5 ^^ ≤ ^^ ≤ 5 ^^,^1 is chosen such that 20 ≤ ^^ ≤ 60,ℎ ∗^ is chosen such that 0.7 × ^ ∗^ ≤ ℎ^ ≤ 1.3 × ^^,^ is chosen such that 12° ≤ ^ ≤ 35°,^^ is chosen such that 15° ≤ ^^ ≤ 28°,^^ is chosen such that 0.5 ^^ < ^^ < 60 ^^,^^ is chosen such that 0.25 ^^. ^ ≤ ^^ ≤ 0.32 ^^. ^,^^ is chosen such that 0.25 ^^. ^ ≤ ^^ ≤ 0.32 ^^. ^,^ is chosen such that ^^ ^^^ that 8 × 10 ^^. ^ ≤ ^^ ≤ 2 × 10 ^^. ^,^^ is chosen such that 2.5 ≤ ^^ ≤ 3.5.Furthermore, in accordance with the invention, the first Pi1 and second Pi2 pinions have a relative sliding speed ^^, in meters per second (m / s), and a relative rolling speed ^ ^ , in meters per second (m / s), between the two involute surfaces or active profiles, defined as a function of the parameters ^1 and ^2 as:^^ = |^2 − ^1| et : ^^ = |^1 + ^2|in which the relative sliding speed ^ ^is chosen such that: 0 < ^^ < 30 ^ / ^ and in which the relative rolling speed ^^ and the total reduction ratio ^^ are chosen such that: - if ^^ < 5 ^ / ^ then ^^ > 4 ^ / ^, - if ^^ > 5 ^ / ^ then 1,15, and 2 < ^^ < 4.According to a particular embodiment, the relative sliding speed ^ ^ is chosen so that 0 < ^^ < 10 ^ / ^ and the relative rolling speed ^^ and the total reduction ratio ^^ are chosen so that:- if ^^ < 5 ^ / ^ then ^^ > 4 ^ / ^,- if ^^ > 5 ^ / ^ then 1,15,and 2 < ^^ < 4. Furthermore, according to a particular embodiment, the relative rolling speed ^^ is chosen such that 4 ^ / ^ < ^^ < 50 ^ / ^ and the relative sliding speed ^^ is chosen such that if ^^ > 4 ^ / ^ then ^^ < 5 ^ / ^. The relative rolling speed ^^ can also be chosen such that ^^ > 30 ^ / ^ and the relative sliding speed ^^ can be chosen such that if ^^ > 4 ^ / ^ then ^^ < 5 ^ / ^. Furthermore, the parameter ^1 can be chosen such that 0.5 ^ / ^ < ^1 <40 ^ / ^, or even 0.5 ^ / ^ < ^1 < 40 ^ / ^, or even 2 ^ / ^ < ^1 < 40 ^ / ^. Similarly, the parameter ^2 can be chosen such that 0 < ^2 < 45 ^ / ^. In particular, the parameter ^1 is chosen such that 0 < ^1 < 0.5 ^ / ^ and the parameter ^2 is chosen such that ^2 < 5 − ^1. According to a particular embodiment, the parameter ^1 is chosen such that ^1 > 0.5 ^ / ^ and the parameter ^2 is chosen such that ^2 < 14 × ^1.Furthermore, the minimum height Hm of the lubricant film can be chosen such that 0.02 × 10^^ ^ < ^^ < 0.4 × 10^^ ^, and in particular such that 0.07 × 10^^ ^ < ^^ < 0.2 × 10^^ ^. The choice of parameters as proposed in the present invention advantageously allows the obtaining of an adequate lubricant film, in particular making it possible to limit any metal / metal contact between the tooth profiles of the first Pi1 and second Pi2 pinions.

Claims

CLAIMS 1. Mécanisme de réduction (19) d’un système propulsif aéronautique (1), comportant un solaire (19a), une couronne (19b), un porte-satellites (19d) et une série de satellites (19c) montés rotatifs sur le porte-satellites (19d), le solaire (19a) comprenant un premier pignon (Pi1) comportant une première denture et chaque satellite (19c) comprenant un deuxième pignon (Pi2) comportant une deuxième denture (19cd) propre à engrener avec la première denture du premier pignon (Pi1), the reduction mechanism (19) further comprising a lubrication circuit (36a) propre à acheminer du lubrifiant entre la première denture du premier pignon (Pi1) et la deuxième denture (19cd) d’au moins un deuxième pignon (Pi2), dans lequel le premier pignon (Pi1) présente par rapport à au moins un deuxième pignon (Pi2) une vitesse de glissement relatif ^^, en mètres par seconde (m / s), et a relative rolling speed ^ ^ , in meters per second (m / s), between the two involute surfaces or active profiles, defined according to the parameters ^1 et ^2 comme : ^^ = |^2 − ^1| et : ^^ = |^1 + ^2| avec : et : ^2 = ^2^ × Ω^ et : ^2^ = ^^ × sin ^^ − ^1^ et : et : et : et : et : et : et : ^ = ^ × ^ cos ^^ ^^ ^ 1 × cos ^ et : où : Ω ^is a rotational speed of the first pinion (Pi1), in radians per second (rad / s), intended to be reached by the first pinion (Pi1) in operation, is a rotational speed of the second pinion (Pi2), in radians per second (rad / s), intended to be reached by each second pinion (Pi2) in operation, ^2^ est la distance entre les points T2 et B, en mètres (m), T2 étant le point de tangency between the line of action and the base circle of the second gable (Pi2), ^2 est le nombre de dents du deuxième pignon (Pi2), ^^ est l’entraxe de fonctionnement, en mètres (m), ^ est une variation d’entraxe, en mètre (m), comprise entre 0 mm et 0,8 mm, ^^ est le rapport de réduction total, ^1^ est la distance entre les points T1 et B, en mètres (m), B étant un point characteristic of the meshing which corresponds to the passage from N-1 to N teeth in mesh (N being the maximum number of teeth in mesh depending on the driving ratio), and T1 being the point of tangency between the line of action and the base circle of the first pinion (Pi1), ^^^^ est le diamètre actif de tête du premier pignon (Pi1) au niveau du point B, en meters (m), ^ ^^ is the diameter of the base circle of the first gable (Pi1), in meters (m), ^^ est le module normal, en millimètres (mm), ^1 est le nombre de dents du premier pignon (Pi1), ^ est l’angle d’hélice ou angle d’inclinaison primitive, en degrés (°), ℎ ^ ∗ is the height of the active head diameter for the first toothing, ^ ^is the transverse or apparent pressure angle, in degrees (°), ^^ est l’angle de pression normal, en degrés (°), in which the relative sliding speed ^ ^ is chosen such that: 0 < ^^ < 30 ^ / ^ et dans lequel la vitesse de roulement relatif ^^ et le rapport de réduction total ^^ are chosen so that: - si ^^ < 5 ^ / ^ alors ^^ > 4 ^ / ^, - si ^^ > 5 ^ / ^ alors 1,15, et 2 < ^^ < 4, et : est choisi de telle sorte que 20 ^^^ / ^ ≤ 1000 ^^^ / ^ Ω^ est choisi de telle sorte que 200 ^^^ / ^ ≤ Ω^ ≤ 1000 ^^^ / ^, ^^ est choisi de telle sorte que 2,5 ^^ ≤ ^^ ≤ 5 ^^, ^1 est choisi de telle sorte que 20 ≤ ^^ ≤ 60, ℎ ∗ ^ est choisi de telle sorte que 0,7 × ^ ∗ ^ ≤ ℎ^ ≤ 1,3 × ^^, ^ est choisi de telle sorte que 12° ≤ ^ ≤ 35°, ^^ est choisi de telle sorte que 15° ≤ ^^ ≤ 28°.

2. Mécanisme de réduction (19) selon la revendication 1, dans lequel la vitesse de glissement relatif ^^ est choisie de telle sorte que : 0 < ^^ < 10 ^ / ^.

3. Mécanisme de réduction (19) selon la revendication 1 ou 2, dans lequel la vitesse relative rolling ^ ^ is chosen so that: 4 ^ / ^ < ^^ < 50 ^ / ^ et dans lequel la vitesse de glissement relatif ^^ est choisie de telle sorte que : ^^ < 5 ^ / ^.

4. Mécanisme de réduction (19) selon la revendication 3, dans lequel la vitesse de relative bearing ^ ^ is chosen so that: ^^ > 30 ^ / ^.

5. Reduction mechanism (19) according to any one of the claims précédentes, dans lequel le paramètre ^1 est choisi de telle sorte que : 0 < ^1 < 40 ^ / ^ 6. Reduction mechanism (19) according to any one of the claims précédentes, dans lequel le paramètre ^2 est choisi de telle sorte que : 0 < ^2 < 45 ^ / ^ 7. Mécanisme de réduction (19) selon la revendication 5 ou 6, dans lequel le paramètre ^1 est choisi de telle sorte que : 0 < ^1 < 0,5 ^ / ^ et dans lequel le paramètre ^2 est choisi de telle sorte que : ^2 < 5 − ^18. Mécanisme de réduction (19) selon la revendication 5 ou 6, dans lequel le paramètre ^1 est choisi de telle sorte que : ^1 > 0,5 ^ / ^ et dans lequel le paramètre ^2 est choisi de telle sorte que : ^2 < 14 × ^1 9. Mécanisme de réduction (19) selon l’une quelconque des revendications previous, in which for the first pinion (Pi1) and at least a second pignon (Pi2) est défini un paramètre de hauteur minimale ^^, en mètres (m), ou épaisseur minimale, du film de lubrifiant, notamment de l’huile, entre les profils assets of the first toothing of the first pinion (Pi1) and of the second toothing (19cd) du deuxième pignon (Pi2) défini comme : ^^ = ^ × [^^ × 0 ^,^ ^,^ ^^,^^ ^ ,985 × ^ × ^ × ^ ] avec : 1 − 13,2 ^^ = 1 + 0,213 × (1 + 2,23 × ^^,^^) × ^^,^^ et : ^ = ^^ × ^ et : et : et : où : ^ est la charge linéique des dentures, en Newton par mètres (N / m), ^^ est la pression de Hertz, en mégapascal (MPa), ^ est un paramètre thermique, adimensionné, ^ est le module de Young de la première denture ou de la deuxième denture, désigné E1 for the first toothing and E2 for the second toothing, in pascal (Pa), ^′ est le module d’élasticité réduit, en pascal (Pa), ^ ^ is the initial Poisson's ratio, ^ ^ is the Poisson's ratio of the first tooth, ^ ^ is the Poisson's ratio of the second toothing, ^ ^ is the piezoelectricity coefficient of the lubricant (Pa -1 ), ^ ^is the radius of curvature at the point of contact B, in meters (m), dans lequel la hauteur minimale ^^ du film de lubrifiant est choisie de telle sorte que : 0,02 × 10^^ ^ < ^^ < 0,4 × 10^^ ^ et : ^ est choisi de telle sorte que 200 ^ / ^^ ≤ ^ ≤ 1600 ^ / ^^, ^^ est choisi de telle sorte que 500 ^^^ ≤ ^^ ≤ 1800 ^^^, ^ est choisi de telle sorte que 1,3 × 10^^ ≤ ^ ≤ 2 × 10^^, ^ est choisi de telle sorte que 200 ^^^ ≤ ^ ≤ 230 ^^^, ^^ est choisi de telle sorte que 1 × 10^^ ^^^^ ≤ ^^ ≤ 1,8 × 10 ^^ ^^ ^^ , ^^ est choisi de telle sorte que 0,5 ^^ < ^^ < 60 ^^, ^^ est choisi de telle sorte que 0,25 ^^. ^ ≤ ^^ ≤ 0,32 ^^. ^, ^^ est choisi de telle sorte que 0,25 ^^. ^ ≤ ^^ ≤ 0,32 ^^. ^, ^ est chois ^^ ^^ ^ i de telle sorte que 8 × 10 ^^. ^ ≤ ^^ ≤ 2 × 10 ^^. ^.

10. Mécanisme de réduction (19) selon la revendication 9, dans lequel la hauteur minimale ^^ du film de lubrifiant est choisie de telle sorte que : 0,07 × 10^^ ^ < ^^ < 0,2 × 10^^ ^ 11. Mécanisme de réduction (19) selon l’une quelconque des revendications previous, in which the first toothing of the first pinion (Pi1) and the second denture (19cd) de chaque deuxième pignon (Pi2) comportent des dents de type droites, hélicoïdales ou en chevron.

12. Mécanisme de réduction (19) selon l’une quelconque des revendications précédentes, dans lequel : - chaque satellite (19c) comporte un ou deux étages d’engrènement, et / ou - le porte-satellites (19d) est monobloc ou comporte une cage définissant un logement interne pour recevoir le solaire (19a) et les satellites (19c), et / ou - chaque satellite (19c) est centré et guidé en rotation autour d’un axe par un palier porté par le porte-satellites (19d), chaque palier étant de type à éléments roulants or hydrodynamic type.

13. Système propulsif aéronautique (1) comportant : - une turbine de puissance (8), notamment une turbine basse pression, et un arbre d’entraînement de turbine (11), notamment un arbre basse pression, entraîné en rotation par la turbine de puissance (8) autour d’un axe longitudinal (X), - un rotor de soufflante (9) et un arbre de soufflante (20), le rotor de soufflante (9) étant accouplé en rotation à l’arbre de soufflante (20), - un mécanisme de réduction (19) selon l’une quelconque des revendications précédentes, comportant une entrée raccordée à l’arbre d’entraînement de turbine (11) et une sortie raccordée à l’arbre de soufflante (20), propre à entraîner le rotor of fan (9) rotating around the longitudinal axis (X) by means of the shaft d’entraînement de turbine (11) et de l’arbre de soufflante (20) à une vitesse de rotation lower than that of the power turbine (8).

14. Procédé de dimensionnement d’un mécanisme de réduction (19) d’un système propulsif aéronautique (1) comportant une turbine de puissance (8), notamment une turbine basse pression, et un arbre d’entraînement de turbine (11), notamment un low pressure shaft, driven in rotation by the power turbine (8) around a axe longitudinal (X), et un rotor de soufflante (9) et un arbre de soufflante (20), le rotor de soufflante (9) étant accouplé en rotation à l’arbre de soufflante (20),the reduction mechanism (19) comprising an inlet intended to be connected to l’arbre d’entraînement de turbine (11), et une sortie destinée à être raccordée à l’arbre de soufflante (20), et étant propre à entraîner le rotor de soufflante (9) en rotation around the longitudinal axis (X) by means of the drive shaft of turbine (11) et de l’arbre de soufflante (20) à une vitesse de rotation inférieure à that of the power turbine (8), le mécanisme de réduction (19) comportant un solaire (19a), une couronne (19b), un porte-satellites (19d) et une série de satellites (19c) montés rotatifs sur le porte- satellites (19d), le solaire (19a) comprenant un premier pignon (Pi1) comportant une première denture et chaque satellite (19c) comprenant un deuxième pignon (Pi2) comportant a second toothing (19cd) suitable for meshing with the first toothing of the first pinion (Pi1), the reduction mechanism (19) further comprising a lubrication circuit (36a) propre à acheminer du lubrifiant entre la denture du premier pignon (Pi1) et la toothing of at least one second pinion (Pi2), in which the first pinion (Pi1) has, with respect to at least one second pignon (Pi2) une vitesse de glissement relatif ^^, en mètres par seconde (m / s), et a relative rolling speed ^ ^ , in meters per second (m / s), between the two involute surfaces or active profiles, defined according to the parameters ^1 et ^2 comme : ^^ = |^2 − ^1| et : ^^ = |^1 + ^2| avec : et : et : ^2^ = ^^ × sin ^^ − ^1^ et : et :^1 = ^2 ^^ et : et : ^^^ = ^^ × π × cos ^^ et : ^ ^ ^ ^ = cos ^ et : et : ^ = cos ^^ ^^ ^^ × ^1 × cos ^ et : où : Ω ^ is a rotational speed of the first pinion (Pi1), in radians per second (rad / s), intended to be reached by the first pinion (Pi1) in operation, is a rotational speed of the second pinion (Pi2), in radians per second (rad / s), intended to be reached by each second pinion (Pi2) in operation, ^2^ est la distance entre les points T2 et B, en mètres (m), T2 étant le point de tangency between the line of action and the base circle of the second gable (Pi2), ^2 est le nombre de dents du deuxième pignon (Pi2), ^^ est l’entraxe de fonctionnement, en mètres (m), ^ est une variation d’entraxe, en mètre (m), comprise entre 0 mm et 0,8 mm, ^^ est le rapport de réduction total, ^1^ est la distance entre les points T1 et B, en mètres (m), B étant n pointcharacteristic of the meshing which corresponds to the passage from N-1 to N teeth in mesh (N being the maximum number of teeth in mesh depending on the driving ratio), and T1 being the point of tangency between the line of action and the base circle of the first pinion (Pi1), ^^^^ est le diamètre actif de tête du premier pignon (Pi1) au niveau du point B, en meters (m), ^ ^^ is the diameter of the base circle of the first gable (Pi1), in meters (m), ^^ est le module normal, en millimètres (mm), ^1 est le nombre de dents du premier pignon (Pi1), ^ est l’angle d’hélice ou angle d’inclinaison primitive, en degrés (°), ℎ ^ ∗ is the height of the active head diameter for the first toothing, ^ ^ is the transverse or apparent pressure angle, in degrees (°), ^^ est l’angle de pression normal, en degrés (°), the method comprising a step of sizing the reduction mechanism (19) au cours de laquelle la vitesse de glissement relatif ^^ est choisie de telle sorte that: 0 < ^^ < 30 ^ / ^ et dans lequel la vitesse de roulement relatif ^^ et le rapport de réduction total ^^ are chosen so that: - si ^^ < 5 ^ / ^ alors ^^ > 4 ^ / ^, - si ^^ > 5 ^ / ^ alors 1,15, et 2 < ^^ < 4, et : est choisi de telle sorte que 20 ^^^ / ^ ≤ 1000 ^^^ / ^ Ω^ est choisi de telle sorte que 200 ^^^ / ^ ≤ Ω^ ≤ 1000 ^^^ / ^, ^^ est choisi de telle sorte que 2,5 ^^ ≤ ^^ ≤ 5 ^^, ^1 est choisi de telle sorte que 20 ≤ ^^ ≤ 60, ℎ ∗ ^ est choisi de telle sorte que 0,7 × ^^ ≤ ℎ∗ ^ ≤ 1,3 × ^^, ^ est choisi de telle sorte que 12° ≤ ^ ≤ 35°, ^^ est choisi de telle sorte que 15° ≤ ^^ ≤ 28°.

15. Procédé de dimensionnement selon la revendication 14, comportant une étape of sizing of the reduction mechanism (19) during which the speed de glissement relatif ^^ est choisie de telle sorte que : 0 < ^^ < 10 ^ / ^.

16. Procédé de dimensionnement selon la revendication 14 ou 15, comportant une step of sizing the reduction mechanism (19) during which the relative rolling speed ^ ^ is chosen so that: 4 ^ / ^ < ^^ < 50 ^ / ^ et dans lequel la vitesse de glissement relatif ^^ est choisie de telle sorte que : ^^ < 5 ^ / ^.

17. Procédé de dimensionnement selon la revendication 16, comportant une étape of sizing of the reduction mechanism (19) during which the relative rolling speed ^ ^ is chosen so that: ^^ > 30 ^ / ^.

18. Procédé de dimensionnement selon l’une quelconque des revendications 14 à 17, comprising a step of sizing the reduction mechanism (19) during de laquelle le paramètre ^1 est choisi de telle sorte que : 0 < ^1 < 40 ^ / ^ 19. Procédé de dimensionnement selon l’une quelconque des revendications 14 à 18, comprising a step of sizing the reduction mechanism (19) during de laquelle le paramètre ^2 est choisi de telle sorte que : 0 < ^2 < 45 ^ / ^ 20. Procédé de dimensionnement selon la revendication 18 ou 19, comportant une étape de dimensionnement du mécanisme de réduction (19) au cours de laquelle le paramètre ^1 est choisi de telle sorte que : 0 < ^1 < 0,5 ^ / ^ et dans lequel le paramètre ^2 est choisi de telle sorte que : ^2 < 5 − ^1 21. Procédé de dimensionnement selon la revendication 18 ou 19, comportant une étape de dimensionnement du mécanisme de réduction (19) au cours de laquelle le paramètre ^1 est choisi de telle sorte que : ^1 > 0,5 ^ / ^ et dans lequel le paramètre ^2 est choisi de telle sorte que : ^2 < 14 × ^1 22. Procédé de dimensionnement selon l’une quelconque des revendications 14 à 21, dans lequel pour le premier pignon (Pi1) et au moins un deuxième pignon (Pi2) estdefined a minimum height parameter ^^, in meters (m), or minimum thickness, of the lubricant film, in particular oil, between the active profiles of the first toothing of the first pinion (Pi1) and the second toothing (19cd) of the second pignon (Pi2) défini comme : ^^ = ^ × [^^ × 0,985 × ^^,^ × ^^,^ ^^,^^ ^ × ^ ] avec : 1 − 13,2 ^^ = 1 + 0,213 × (1 + 2,23 × ^^,^^) × ^^,^^ et : ^ = ^^ × ^ et : et : et : où : ^ est la charge linéique des dentures, en Newton par mètres (N / m), ^^ est la pression de Hertz, en mégapascal (MPa), ^ est un paramètre thermique, adimensionné, ^ est le module de Young de la première denture ou de la deuxième denture, désigné E1 for the first toothing and E2 for the second toothing, in pascal (Pa), ^′ est le module d’élasticité réduit, en pascal (Pa), ^ ^ is the initial Poisson's ratio, ^ ^ is the Poisson's ratio of the first tooth, ^ ^ is the Poisson's ratio of the second toothing, ^ ^ is the piezoelectricity coefficient of the lubricant (Pa -1 ), ^ ^is the radius of curvature at the point of contact B, in meters (m), the method comprising a step of dimensioning the reduction mechanism (19) au cours de laquelle la hauteur minimale ^^ du film de lubrifiant est choisie de telle sorte que : 0,02 × 10^^ ^ < ^^ < 0,4 × 10^^ ^ et : ^ est choisi de telle sorte que 200 ^ / ^^ ≤ ^ ≤ 1600 ^ / ^^, ^^ est choisi de telle sorte que 500 ^^^ ≤ ^^ ≤ 1800 ^^^, ^ est choisi de telle sorte que 1,3 × 10^^ ≤ ^ ≤ 2 × 10^^, ^ est choisi de telle sorte que 200 ^^^ ≤ ^ ≤ 230 ^^^, ^^ est choisi de telle sorte que 1 × 10^^ ^^^^ ≤ ^^ ≤ 1,8 × 10 ^^ ^^ ^^ , ^^ est choisi de telle sorte que 0,5 ^^ < ^^ < 60 ^^, ^^ est choisi de telle sorte que 0,25 ^^. ^ ≤ ^^ ≤ 0,32 ^^. ^, ^^ est choisi de telle sorte que 0,25 ^^. ^ ≤ ^^ ≤ 0,32 ^^. ^, ^ est choisi de te ^^ ^^ ^ lle sorte que 8 × 10 ^^. ^ ≤ ^^ ≤ 2 × 10 ^^. ^.

23. Procédé de dimensionnement selon la revendication 22, comportant une étape de dimensionnement du mécanisme de réduction (19) au cours de laquelle la hauteur minimale ^^ du film de lubrifiant est choisie de telle sorte que : 0,07 × 10^^ ^ < ^^ < 0,2 × 10^^ ^ 24. Mécanisme de réduction (19) fabriqué à partir d’un procédé de dimensionnement selon l’une quelconque des revendications 14 à 23.

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