Deceleration mechanism for an aviation propulsion system

Abstract

The invention relates to a reduction mechanism (19) for an aeronautical propulsion system, comprising a sun gear (19a), a ring gear (19b), a planet carrier (19d) and a series of planet gears (19c), the sun gear (19a) comprising a first pinion comprising a first toothing and each planet gear (19c) comprising a second pinion comprising a second toothing (19cd), the reduction mechanism comprising a lubrication circuit configured to transport a lubricant between the toothing, wherein at least one second pinion has a parameter, defined as:, wherein: is the rotation speed of the second pinion, intended to be reached by the second pinion in operation, is the distance between the point T2 and the point B, wherein T2 is the point of tangency between the line of action and the base circle of the second pinion, wherein the parameter is chosen so that:.

Description

Technical Field

[0001] This invention relates to the field of reduction gears or speed reduction mechanisms for aircraft propulsion systems. Therefore, this invention relates to reduction gears for aircraft propulsion systems, aircraft propulsion systems including such reduction gears, and methods for determining the dimensions of such reduction gears. Background Technology

[0002] An aerospace propulsion system typically includes, from upstream to downstream, a fan section, a compressor section that may include a low-pressure compressor and a high-pressure compressor, a combustion chamber, and a turbine section that may include a high-pressure turbine and a low-pressure turbine, along the direction of gas flow.

[0003] When the propulsion system is operating, the high-pressure compressor is driven to rotate by the high-pressure turbine via the high-pressure shaft. The fan, and, where appropriate, the low-pressure compressor, is driven to rotate by the low-pressure turbine via the low-pressure shaft.

[0004] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, states have already implemented, are implementing, or will implement various restrictions on carbon emissions. In particular, a progressive standard applies to new aircraft and those currently in circulation that require technological solutions to comply with existing regulations. For many years, civil aviation has been actively contributing to addressing climate change.

[0005] Technological research efforts have significantly improved the environmental performance of aircraft. The applicant considers all factors affecting the design and development phases to obtain aircraft components and products that are less energy-intensive, more environmentally friendly, and have a moderate environmental impact when integrated and used in civil aviation, with the aim of improving aircraft energy efficiency.

[0006] Therefore, the applicant is committed to reducing its negative climate impacts by using methods and benign development and manufacturing processes to minimize greenhouse gas emissions and reduce the environmental footprint of its activities.

[0007] These ongoing research and development efforts focus on next-generation aircraft engines, reducing machine weight (particularly through the materials used and lighter onboard equipment), developing the use of electrical technologies to ensure propulsion, and aviation biofuels as an integral part of technological advancements.

[0008] Therefore, one of the goals of technological research is to improve the environmental performance of aircraft. Relevant factors are considered in all design and development stages to obtain aircraft components and products that are less energy-intensive, more environmentally friendly, and whose integration and use in civil aviation have a moderate environmental impact, with the aim of improving the energy efficiency of aircraft.

[0009] For example, to improve the propulsion efficiency of an aircraft propulsion system and reduce its specific energy consumption, it has been found that increasing the rotational speeds of the low-pressure turbine and low-pressure compressor while decreasing the fan speed is advantageous. Similarly, to limit the drag and mass of an aircraft and thus reduce its fuel consumption, it has been found that making the propulsion system more compact (i.e., reducing the volume of all or some of its components) is advantageous.

[0010] However, in this process, it appears that the rotating components of the aerospace propulsion system (especially those in the compressor and turbine sections) are subjected to increased centrifugal forces while having smaller dimensions, which may degrade their mechanical strength and / or limit their lifespan.

[0011] Fans are typically driven to rotate at speeds lower than those of low-pressure turbines and compressors via a mechanical reduction mechanism (also known as a mechanical reduction gear). Examples of mechanical reduction gears are described in international application WO2010 / 092263A1 and French patent applications FR2987416A1, FR3008462A1, FR3008463A1, FR3041054A1, FR3095251A1, and FR3116096A1.

[0012] The function of mechanical reduction gears is to modify the speed and torque ratio between the input and output shafts of a mechanical system.

[0013] New-generation turbofan engines, especially those with high bypass ratios, include such mechanical reduction gears to drive the fan shaft. Typically, the reduction gears are designed to convert the rotational speed of the power turbine shaft (referred to as the high speed) into a lower speed used to drive the fan shaft, thus allowing independent control of both the fan speed and the power turbine speed.

[0014] This type of reduction gear comprises a central pinion called the sun gear, a ring gear, and planetary gears that mesh between the sun gear and the ring gear. The planetary gears are held in place by a frame called a planetary carrier. The sun gear, ring gear, and planetary carrier are star-shaped gears because their axes of rotation coincide with the longitudinal axis of the turbine. Each planetary gear has a different axis of rotation, which are evenly distributed around the axis of the star gear along the same operating diameter. These axes are parallel to the longitudinal axis.

[0015] There are various reduction gear architectures. In existing turbofan engine technology, reduction gears are either radial or planetary.

[0016] In other similar applications, there are architectures known as differential or composite architectures.

[0017] On the star-shaped reduction gear, the planetary gear carrier is fixed, and the gear ring forms the output shaft of the device, which rotates in the opposite direction to the sun gear.

[0018] On the planetary reduction gear, the gear ring is fixed, and the planetary gear set up the output shaft of the device that rotates in the same direction as the sun gear.

[0019] In a differential reduction gear, no components are rotatably fixed. The ring gear rotates in the opposite direction to the sun gear and planetary gear carrier.

[0020] A reduction gear can consist of one or more meshing stages. This meshing is achieved in various ways, such as contact, friction, or magnetic fields. There are several types of contact meshing, such as through straight teeth, helical teeth, or herringbone teeth.

[0021] In this application, "class" or "tooth" refers to a series of meshing teeth having a series of complementary teeth. The teeth can be internal or external.

[0022] Planetary gears may include one or two meshing stages. A single-stage planetary gear includes a tooth section, which may be a straight tooth section, a helical tooth section, or a herringbone tooth section, and the teeth of this tooth section are located on the same diameter. This tooth section mates with both the sun gear and the ring gear.

[0023] A two-stage planetary gear consists of two tooth sections or two series of teeth located on different diameters. The first tooth section meshes with the sun gear, and the second tooth section meshes with the ring gear.

[0024] The planetary gear carrier can be a single piece or include a cage that defines an inner housing for receiving the sun gear and planetary gears.

[0025] Furthermore, each planetary gear is centered and guided about its axis by bearings carried by the planetary gear carrier. Various bearing technologies exist for this application, such as rolling element bearings, sliding bearings, or hydrodynamic bearings, which offer higher load capacity and are therefore preferred in terms of size.

[0026] Therefore, the reduction gear includes multiple meshing portions formed between the planetary gear and the sun gear. In each meshing portion, the first pinion transmits rotational mechanical energy to the second pinion via a drive that occurs on the effective profile of the teeth.

[0027] To ensure high operating performance of reduction gears, it is necessary to ensure a proper supply of lubricant at the meshing point. This lubricant input (especially oil) improves power transmission efficiency, component cooling, and the mechanical strength and wear resistance of the effective profile of the teeth, which is the contact surface that meshes with the adjacent pinion.

[0028] Parameters have been defined in the prior art as the conditions under which lubricant is supplied to the meshing parts to meet the above requirements. In particular, references can be made to the articles "Elastohydrodynamic Lubrication," D. Dowson and G. G. Higginson, Pergman Press, Oxford, 1966; "Minimum Film Thickness in Elliptical Contacts with Different Fluid Film Lubrication States," B.J. Hamrock and D. Dowson, Proceedings of the Leeds-Lyon Tribology Symposium, 1979, pp. 22-27; and standards ISO 6336-22 and 21771-2014.

[0029] In particular, the thickness or height of the lubricant film (especially the oil film) is a parameter that best represents the lubrication system of the contact surfaces of the teeth.

[0030] Therefore, in order to improve the above performance, it is necessary to optimally control the lubricant film.

[0031] In particular, it is necessary to ensure the thickest or highest lubricant film to prevent metal-to-metal contact between the two effective tooth profiles. In fact, eliminating metal-to-metal contact reduces the risk of contact fatigue due to mixed lubrication of the micropitting type, as well as the risk of seizure, i.e., wear of two meshing pinions.

[0032] Therefore, it is necessary to ensure a minimum lubricant film height during operation to guarantee the lubrication of the reduction gears and thus prevent metal-to-metal contact between the pinions. However, the minimum lubricant film height depends on many parameters related to the teeth of the reduction gears: normal modulus; normal pressure angle; helix angle; number of teeth; overall reduction ratio, etc. Summary of the Invention

[0033] One of the objectives of this invention is to determine the parameter value of the minimum lubricant film height between the pinions of the adjustment reduction mechanism, thereby enabling the determination of the lubricant film size to meet the aforementioned requirements.

[0034] Therefore, this invention is the result of technical research aimed at significantly improving aircraft performance and in this respect helps to reduce the environmental impact of aircraft.

[0035] Therefore, the present invention relates to a reduction gear for an aircraft propulsion system, comprising a sun gear, a ring gear, a planetary gear carrier, and a series of planetary gears rotatably mounted on the planetary gear carrier. The sun gear includes a first pinion with a first tooth portion, and each planetary gear includes a second pinion with a second tooth portion configured to mesh with the first tooth portion of the first pinion. The reduction mechanism also includes a lubrication circuit containing lubricant, the lubrication circuit being configured to deliver lubricant between a first tooth of a first pinion and a second tooth of at least one second pinion. Among them, at least one second pinion has parameters , is defined as:

[0036] in:

[0037] and:

[0038] and:

[0039] and:

[0040] and:

[0041] and:

[0042] and:

[0043] and:

[0044] and:

[0045] in: It is the rotational speed of the second pinion, measured in radians per second (rad / s), intended to be achieved by at least one second pinion during operation. It is the distance between point T2 and point B, in meters (m), where T2 is the point of tangency between the line of action and the base circle of the second pinion. It refers to the number of teeth on the second pinion. This is the distance between the work centers, expressed in meters (m). This refers to the change in center distance, measured in meters (m), ranging from 0 mm to 0.8 mm. It is the overall reduction ratio. This is the distance between point T1 and point B, in meters (m). B is the characteristic point of meshing, corresponding to the transition from N-1 meshing teeth to N meshing teeth (N is the maximum number of meshing teeth determined by the contact ratio). T1 is the point of tangency between the line of action and the base circle of the first pinion. It is the effective tooth tip diameter of the first pinion at point B, in meters (m). It is the diameter of the base circle of the first pinion, in meters (m). It is the normal modulus, and the unit is millimeters (mm). It is the number of teeth on the first pinion. It is the helix angle or reference lead angle, in degrees (°). It is the tooth tip height, corresponding to the effective tooth tip diameter of the first tooth. It is the end face pressure angle or apparent pressure angle, and the unit is degrees (°). It is the normal pressure angle, and the unit is degrees (°). Among them, parameters Chosen to make:

[0046] and: Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as .

[0047] The speed reduction mechanism may have one or more of the following characteristics.

[0048] In one embodiment, the first pinion has parameters , is defined as:

[0049] in: It is the rotational speed of the first pinion, measured in radians per second (rad / s), and is intended to be achieved by the first pinion during operation. Among them, the rotational speed of the first pinion Chosen to make: .

[0050] In one embodiment, parameters Chosen to make: .

[0051] In one embodiment, parameters Chosen to make: , or even: .

[0052] In one embodiment, parameters Chosen to make:

[0053] And parameters Chosen to make: .

[0054] In one embodiment, parameters Chosen to make:

[0055] And parameters Chosen to make: .

[0056] In one embodiment, parameters Chosen to make: .

[0057] In one embodiment, the first pinion has a relative sliding speed with respect to at least one second pinion between two involute surfaces or effective profiles, measured in meters per second (m / s). And relative rolling speed in meters per second (m / s) The relative sliding speed and the relative rolling speed are used as parameters. and The function is defined as:

[0058] and:

[0059] Among them, relative sliding speed Chosen to make:

[0060] And among them, relative rolling speed and total reduction ratio Chosen to make: -if :but , -if :but , and .

[0061] In one embodiment, relative sliding speed Chosen to make:

[0062] And relative rolling speed and total reduction ratio Chosen to make: -if :but , -if :but , and .

[0063] In one embodiment, the first pinion has a relative sliding speed with respect to at least one second pinion between two involute surfaces or effective profiles, measured in meters per second (m / s). And relative rolling speed in meters per second (m / s) The relative sliding speed and the relative rolling speed are used as parameters. and The function is defined as:

[0064] and:

[0065] Among them, relative rolling speed Chosen to make:

[0066] And among them, relative sliding speed Chosen to make: -if :but .

[0067] In one embodiment, relative scrolling speed Chosen to make:

[0068] And relative sliding speed Chosen to make: -if ,but .

[0069] In one embodiment, for a first pinion and at least one second pinion, the minimum height parameter of the lubricant film, particularly the oil, in meters (m) between the effective profile of the first tooth of the first pinion and the effective profile of the second tooth of the second pinion. Or the minimum thickness is defined as:

[0070] in:

[0071] and:

[0072] and:

[0073] and:

[0074] and:

[0075] and:

[0076] and:

[0077] and:

[0078] and:

[0079] and:

[0080] in: It is the radius of curvature at the contact point B, in meters (m). It is the linear load on the teeth, and the unit is Newtons per meter (N / m). It is Hertz pressure, and the unit is megapascal (MPa). It is a dimensionless thermal parameter. It is the Young's modulus of the first or second tooth portion, denoted by E1 for the first tooth portion and E2 for the second tooth portion, with the unit being Pascals (Pa). It is the reduced modulus of elasticity, and its unit is Pascal (Pa). These are the initial Poisson coefficients. It is the Poisson's coefficient of the first tooth. It is the Poisson's coefficient for the second tooth. It is the piezoelectric coefficient (Pa) of the lubricant. -1 ), It is the rotational speed of the second pinion, measured in radians per second (rad / s), intended to be achieved by at least one second pinion during operation. It is the distance between point T2 and point B, in meters (m), where T2 is the point of tangency between the line of action and the base circle of the second pinion. It refers to the number of teeth on the second pinion. This is the distance between the work centers, expressed in meters (m). This refers to the change in center distance, measured in meters (m), ranging from 0 mm to 0.8 mm. It is the overall reduction ratio. It is the rotational speed of the first pinion, measured in radians per second (rad / s), and is intended to be achieved by the first pinion during operation. Among them, the minimum height of the lubricant film Chosen to make:

[0081] and: Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as .

[0082] In one embodiment, the minimum height of the lubricant film Chosen to make: .

[0083] In one embodiment, the first tooth portion of the first pinion and the second tooth portion of each second pinion include straight teeth, helical teeth, or herringbone teeth.

[0084] In one embodiment: - Each planetary gear includes one or two meshing stages, and / or - The planetary gear carrier may be a single piece or include a cage defining an inner housing to receive the sun gear and planetary gears, and / or - Each planetary gear is centered and guided to rotate about its axis by a bearing carried by a planetary gear carrier. Each bearing is of the rolling element type or the hydrodynamic type.

[0085] Furthermore, according to another aspect of the present invention, the present invention also relates to an aviation propulsion system, comprising: - A power turbine, particularly a low-pressure turbine; and a turbine drive shaft, particularly a low-pressure shaft, said turbine drive shaft being driven by the power turbine to rotate about a longitudinal axis; - Fan rotor and fan shaft, the fan rotor being rotatably connected to the fan shaft; - The reduction mechanism as defined above includes an inlet connected to the turbine drive shaft and an outlet connected to the fan shaft, and is configured to drive the fan rotor to rotate about the longitudinal axis at a speed lower than the power turbine speed via the turbine drive shaft and the fan shaft.

[0086] Furthermore, according to another aspect of the invention, the invention also relates to a method for determining the dimensions of a reduction gear for an aerospace propulsion system, the aerospace propulsion system comprising: a power turbine, particularly a low-pressure turbine; and a turbine drive shaft, particularly a low-pressure shaft, the turbine drive shaft being driven by the power turbine to rotate about a longitudinal axis; and a fan rotor and a fan shaft, the fan rotor being rotatably coupled to the fan shaft. The reduction gear includes an inlet intended for connection to the turbine drive shaft and an outlet intended for connection to the fan shaft, and is configured to drive the fan rotor to rotate about a longitudinal axis at a speed lower than the power turbine speed via the turbine drive shaft and the fan shaft. The reduction mechanism includes a sun gear, a ring gear, a planetary gear carrier, and a series of planetary gears rotatably mounted on the planetary gear carrier. The sun gear includes a first pinion with a first tooth portion, and each planetary gear includes a second pinion with a second tooth portion configured to mesh with the first tooth portion of the first pinion. The reduction mechanism also includes a lubrication circuit containing a lubricant, the lubrication circuit being configured to deliver the lubricant between the teeth of a first pinion and the teeth of at least one second pinion. Among them, at least one second pinion has parameters , is defined as:

[0087] in:

[0088] and:

[0089] and:

[0090] and:

[0091] and:

[0092] and:

[0093] and:

[0094] and:

[0095] and:

[0096] in: It is the rotational speed of the second pinion, measured in radians per second (rad / s), intended to be achieved by at least one second pinion during operation. It is the distance between point T2 and point B, in meters (m), where T2 is the point of tangency between the line of action and the base circle of the second pinion. It refers to the number of teeth on the second pinion. This is the distance between the work centers, expressed in meters (m). This refers to the change in center distance, measured in meters (m), ranging from 0 mm to 0.8 mm. It is the overall reduction ratio. This is the distance between point T1 and point B, in meters (m). B is the characteristic point of meshing, corresponding to the transition from N-1 meshing teeth to N meshing teeth (N is the maximum number of meshing teeth determined by the contact ratio). T1 is the point of tangency between the line of action and the base circle of the first pinion. It is the effective tooth tip diameter of the first pinion at point B, in meters (m). It is the diameter of the base circle of the first pinion, in meters (m). It is the normal modulus, and the unit is millimeters (mm). It is the number of teeth on the first pinion. It is the helix angle or reference lead angle, in degrees (°). It is the tooth tip height, corresponding to the effective tooth tip diameter of the first tooth. It is the end face pressure angle or apparent pressure angle, and the unit is degrees (°). It is the normal pressure angle, and the unit is degrees (°). The method includes the step of determining the dimensions of the reduction mechanism (19), in which parameters... Chosen to make:

[0097] and: Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as .

[0098] In one embodiment, the first pinion has parameters , is defined as:

[0099] in: It is the rotational speed of the first pinion, measured in radians per second (rad / s), and is intended to be achieved by the first pinion during operation. The method includes the step of determining the dimensions of the reduction mechanism, in which the rotational speed of the first pinion is... Chosen to make: .

[0100] In one embodiment, the method includes the step of determining the dimensions of the speed reduction mechanism, in which parameters... Chosen to make:

[0101] And parameters Chosen to make: .

[0102] In one embodiment, the method includes the step of determining the dimensions of the speed reduction mechanism, in which parameters... Chosen to make:

[0103] And parameters Chosen to make: .

[0104] In one embodiment, the method includes the step of determining the dimensions of the speed reduction mechanism, in which parameters... Chosen to make: , Or even: , Or even: .

[0105] In one embodiment, the first pinion has a relative sliding speed with respect to at least one second pinion between two involute surfaces or effective profiles, measured in meters per second (m / s). And relative rolling speed in meters per second (m / s) The relative sliding speed and the relative rolling speed are used as parameters. and The function is defined as:

[0106] and:

[0107] The method includes the step of determining the dimensions of the speed reduction mechanism, in which the relative sliding speed... Chosen to make:

[0108] And relative rolling speed and total reduction ratio Chosen to make: -if :but , -if :but , and .

[0109] In one embodiment, the method includes the step of determining the dimensions of the speed reduction mechanism, in which the relative sliding speed... Chosen to make:

[0110] And relative rolling speed and total reduction ratio Chosen to make: -if :but , -if :but , and .

[0111] In one embodiment, the first pinion has a relative sliding speed with respect to at least one second pinion between two involute surfaces or effective profiles, measured in meters per second (m / s). And relative rolling speed in meters per second (m / s) The relative sliding speed and the relative rolling speed are used as parameters. and The function is defined as:

[0112] and:

[0113] The method includes the step of determining the dimensions of the speed reduction mechanism, in which the relative rolling speed... Chosen to make:

[0114] And relative sliding speed Chosen to make: -if :but .

[0115] In one embodiment, the method includes the step of determining the dimensions of the speed reduction mechanism, in which the relative rolling speed... Chosen to make:

[0116] And relative sliding speed Chosen to make: -if ,but .

[0117] In one embodiment, for a first pinion and at least one second pinion, the minimum height parameter of the lubricant film, particularly the oil, in meters (m) between the effective profile of the first tooth of the first pinion and the effective profile of the second tooth of the second pinion. Or the minimum thickness is defined as:

[0118] in:

[0119] and:

[0120] and:

[0121] and:

[0122] and:

[0123] and:

[0124] and:

[0125] and:

[0126] and:

[0127] and:

[0128] in: It is the radius of curvature at the contact point B, in meters (m). It is the linear load on the teeth, and the unit is Newtons per meter (N / m). It is Hertz pressure, and the unit is megapascal (MPa). It is a dimensionless thermal parameter. It is the Young's modulus of the first or second tooth portion, denoted by E1 for the first tooth portion and E2 for the second tooth portion, with the unit being Pascals (Pa). It is the reduced modulus of elasticity, and its unit is Pascal (Pa). These are the initial Poisson coefficients. It is the Poisson's coefficient of the first tooth. It is the Poisson's coefficient for the second tooth. It is the piezoelectric coefficient (Pa) of the lubricant. -1 ), It is the rotational speed of the second pinion, measured in radians per second (rad / s), intended to be achieved by at least one second pinion during operation. It is the distance between point T2 and point B, in meters (m), where T2 is the point of tangency between the line of action and the base circle of the second pinion. It refers to the number of teeth on the second pinion. This is the distance between the work centers, expressed in meters (m). This refers to the change in center distance, measured in meters (m), ranging from 0 mm to 0.8 mm. It is the overall reduction ratio. It is the rotational speed of the first pinion, measured in radians per second (rad / s), and is intended to be achieved by the first pinion during operation. The method includes the step of determining the dimensions of the speed reduction mechanism, in which the minimum height of the lubricant film is determined. Chosen to make:

[0129] and: Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as .

[0130] In one embodiment, the method includes the step of determining the dimensions of the speed reduction mechanism, wherein the minimum height of the lubricant film is determined. Chosen to make: .

[0131] Furthermore, according to another aspect of the invention, the invention also relates to a deceleration mechanism manufactured by a dimensional determination method as defined above. Attached Figure Description

[0132] Other features and advantages will become apparent from the following description, which is purely illustrative and non-limiting and should be read with reference to the accompanying drawings, in which: - Figure 1 The diagram schematically illustrates an aircraft including its propulsion system. - Figure 2 The partial cross-sectional view schematically illustrates an example of a propulsion system in which the fan section is a ducted fan section. - Figure 3 A partial cross-sectional view schematically illustrates an example of a propulsion system in which the fan section is a ductless fan section. - Figure 4 The first example of a star-shaped reduction gear is schematically shown. - Figure 5 The first example of a planetary deceleration mechanism is schematically shown. - Figure 6 A first example of a differential reduction mechanism is schematically shown. - Figure 7 An example of a planetary reduction mechanism is schematically shown in partial axial section. - Figure 8 The effective profile of the first tooth portion of the first pinion of the sun gear in the reduction mechanism according to the invention is schematically partially shown between the effective profile of the second tooth portion of the second pinion of the planetary gear in a series of planetary gears of the reduction mechanism according to the invention. - Figure 9 The diagram schematically shows, in part, a prominent depiction of the relative sliding between the first and second pinions of the reduction mechanism according to the invention, and... - Figures 10 to 15 The parameters used to define the deceleration mechanism according to the invention are shown schematically in partial form. Detailed Implementation

[0133] exist Figure 1In the example shown, the aircraft is an airplane 100 comprising a fuselage 101 and two wings 102. In this example, the aircraft includes two propulsion systems 1, each propulsion system 1 being attached to a corresponding wing 102 of the airplane 100 by means of a pylon. In another embodiment, the aircraft may include one or more propulsion systems attached to the fuselage 101.

[0134] Figure 2 A first example of the propulsion system 1 is schematically shown in a partial cross-sectional view.

[0135] In this example, propulsion system 1 is a dual-shaft ducted fan gas turbine engine.

[0136] exist Figure 2 In this system, the propulsion system 1 has a main direction extending along the longitudinal axis X. The propulsion system 1 includes a fan section 2 and a main body 3, which is commonly referred to as a "gas generator".

[0137] Fan section 2 includes a fan 22 and a fan housing 12. Fan 22 includes a fan rotor 9. Fan housing 12 surrounds fan rotor 9. Fan rotor 9 is rotatably mounted relative to fan housing 12.

[0138] The fan rotor 9 includes a fan hub 13 and fan blades 14 extending radially from the hub 13. The fan blades 14 may be fixed relative to the fan hub 13 or have a variable setting. In the latter case, each fan blade 14 is pivotally mounted relative to the fan hub 13 along a set axis and connected to a pitch changing mechanism (not shown) installed in the propulsion system 1. The pitch changing mechanism allows adjustment of the set angle of the fan blades 14 according to the flight phase.

[0139] The fan rotor 9 includes 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.

[0140] Additionally, in this example, the fan section 2 also includes a fan stator 16 fixedly mounted on the fan housing 12. The fan stator 16 includes blades 17 commonly referred to as outlet guide vanes (OGVs). These blades have the function of straightening and regulating the airflow flowing downstream of the fan rotor 9 to contribute to the engine's thrust. These blades also serve to reduce noise.

[0141] Alternatively, the outlet guide vane 17 may have a variable setting. Where appropriate, similar to the fan blades 14 of the fan rotor 9, the root of the outlet guide vane 17 is pivotally mounted along a setting axis and connected to a pitch changing mechanism (not shown), which is adjusted by the pitch changing mechanism according to the flight phase.

[0142] The number of outlet guide 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.

[0143] The main body 3 includes a compressor section 29, a combustion chamber 6, and a turbine section 30.

[0144] The compressor section 29 includes a low-pressure compressor 4 and a high-pressure compressor 5.

[0145] The low-pressure compressor 4 includes a rotor 41 configured to rotate relative to the housing 31 of the propulsion system 1, and a stator 42 fixedly mounted on the housing 31.

[0146] The rotor 41 of the low-pressure compressor 4 includes a movable wheel 4a, and the stator 42 of the low-pressure compressor 4 includes a fixed wheel 4b. The movable wheel 4a and the fixed wheel 4b are arranged alternately to form a series of low-pressure compressor stages.

[0147] Similarly, the high-pressure compressor 5 includes a rotor 51 configured to be rotated relative to the housing 31 of the propulsion system 1, and a stator 52 fixedly mounted on the housing 31.

[0148] The rotor 51 of the high-pressure compressor 5 includes a movable wheel 5a, and the stator 52 of the high-pressure compressor 5 includes a fixed wheel 5b. The movable wheel 5a and the fixed wheel 5b are arranged alternately to form a series of high-pressure compressor stages.

[0149] The turbine section 30 includes a high-pressure turbine 7 and a low-pressure turbine 8.

[0150] The high-pressure turbine 7 includes a rotor 71 configured to rotate relative to the housing 31 of the propulsion system 1, and a stator 72 fixedly mounted on the housing 31.

[0151] The rotor 71 of the high-pressure turbine 7 includes a movable wheel 7a, and the stator 72 of the high-pressure turbine 7 includes a fixed wheel 7b. The movable wheel 7a and the fixed wheel 7b are arranged alternately to form a series of high-pressure turbine stages.

[0152] Similarly, the low-pressure turbine 8 includes a rotor 81 configured to rotate relative to the housing 31 of the propulsion system 1, and a stator 82 fixedly mounted on the housing 31.

[0153] The rotor 81 of the low-pressure turbine 8 includes a movable wheel 8a, and the stator 82 of the low-pressure turbine 8 includes a fixed wheel 8b. The movable wheel 8a and the fixed wheel 8b are arranged alternately to form a series of low-pressure turbine stages.

[0154] The propulsion system 1 includes a low-pressure shaft 11 that connects the rotor 41 of the low-pressure turbine 4 to the rotor 81 of the low-pressure compressor 8. The low-pressure shaft 11 is rotatably mounted relative to the housing 31 about the longitudinal axis X.

[0155] When the propulsion system 1 is in operation, the rotor 81 of the low-pressure turbine 8 drives the rotor 41 of the low-pressure compressor 4 to rotate via the low-pressure shaft 11.

[0156] The propulsion system 1 also includes a fan shaft 20 and a reduction gear 19. The fan rotor 9 is rotatably connected to the fan shaft 20. The reduction gear 19 has an inlet and an outlet. The inlet of the reduction gear 19 is connected to the low-pressure shaft 11, and the outlet of the reduction gear 19 is connected to the fan shaft 20. Therefore, when the propulsion system 1 is operating, the rotor 81 of the low-pressure turbine 8 drives not only the rotor 41 of the low-pressure compressor 4 to rotate via the low-pressure shaft 11, the reduction gear 19, and the fan shaft 20, but also drives the fan rotor 9 to rotate.

[0157] With the aid of the reduction gear 19, the fan rotor 9 is driven to rotate at a speed lower than that of the rotor 41 of the low-pressure turbine 4.

[0158] Therefore, the reduction gear 19 allows for independent control of the speed of the fan 22 as well as the speed of the low-pressure turbine 8 and the low-pressure compressor 4.

[0159] The low-pressure turbine 8, low-pressure shaft 11, low-pressure compressor 4, fan shaft 20, reduction gear 19 and fan 22 together constitute the "low-pressure body" of propulsion system 1.

[0160] The propulsion system 1 also includes a high-pressure shaft 10 that connects the rotor 51 of the high-pressure turbine 5 to the rotor 71 of the high-pressure compressor 7. The high-pressure shaft 10 is rotatably mounted relative to the housing 31 about a longitudinal axis X. The high-pressure shaft 10 is coaxial with and extends about a low-pressure shaft 11.

[0161] 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 to rotate via the low-pressure shaft 11.

[0162] The high-pressure turbine 7, the high-pressure shaft 10, and the high-pressure compressor 4 together constitute the "high-pressure body" of the propulsion system 1.

[0163] The low-pressure shaft 11 and the high-pressure shaft 10 can rotate together, that is, they are driven in the same direction of rotation about the longitudinal axis X. As a variation, the low-pressure shaft 11 and the high-pressure shaft 10 can rotate in opposite directions, that is, they are driven in opposite directions of rotation about the longitudinal axis X.

[0164] The dual-shaft propulsion system 1 may specifically include a single-stage high-pressure turbine 7 (i.e., including exactly one stage), or a two-stage high-pressure turbine 7 (i.e., including exactly two stages, such as...). Figure 2 (as shown in the example).

[0165] High-pressure compressor 5 includes at least eight stages (e.g. Figure 2 (as shown in the example) and up to eleven levels.

[0166] The low-pressure turbine 8 includes at least three stages (such as...) Figure 2 (as shown in the example) and up to seven levels.

[0167] The low-pressure compressor 4 includes at least two stages and at most four stages.

[0168] When the propulsion system is operating, the airflow F entering the propulsion system 1 passes through the fan 22 and is then divided into a primary airflow F1 and a secondary airflow F2. The primary airflow F1 and the secondary airflow F2 flow from upstream to downstream in the propulsion system 1.

[0169] The secondary airflow F2 (also known as the "bypass airflow") flows in the secondary flow path surrounding the main body 3. The secondary airflow F2 enables the cooling of the outer periphery of the main body 3 and is used to generate most of the thrust provided by the propulsion system 1.

[0170] The main airflow F1 flows in the main path inside the main body 3, passing sequentially through the compressor section 29 (low-pressure compressor 4 and high-pressure compressor 5), the combustion chamber 6 (in which the main airflow F1 mixes with fuel to act as an oxidant), and the turbine section 30 (high-pressure turbine 7 and low-pressure turbine 8). The main airflow F1 causes the movable wheels 7a and 8a of the turbine section 30, which receive energy from the combustion chamber 6, to rotate. The rotation of the movable wheels 7a and 8a then drives the movable wheels 4a and 5a of the compressor section 29 and the fan rotor 9 to rotate.

[0171] To improve the propulsion efficiency of propulsion system 1 and reduce its specific energy consumption and noise from fan section 2, propulsion system 1 has a high bypass ratio. A "high" bypass ratio is defined as a bypass ratio greater than or equal to 10, for example, between 10 and 80 (inclusive), preferably between 10 and 35 (inclusive), and more preferably between 10 and 18 (inclusive). The bypass ratio is defined as the ratio between the mass flow rate of the secondary airflow F2 and the mass flow rate of the primary airflow F1, measured at sea level when propulsion system 1 is stationary, not installed, in standard atmosphere (as defined by the International Civil Aviation Organization (ICAO) manual, Doc 7488 / 3, 3rd edition). "Not installed" means that measurements are performed when propulsion system 1 is on a test stand (and not installed on the aircraft), as this makes measurements easier to perform.

[0172] Including the deceleration mechanism 19 (e.g.) Figure 2In the propulsion system of the reduction gear shown, the decoupling between the rotational speed of fan 22 and the rotational speed of low-pressure turbine 8 allows for a reduction in the speed and pressure ratio of fan rotor 9, while increasing the power extracted by low-pressure turbine 8. In fact, the overall efficiency of propulsion system 1 is primarily regulated by propulsion efficiency, which is advantageously influenced by minimizing the change in kinetic energy of air passing through propulsion system 1. In propulsion systems with high bypass ratios, most of the flow generating propulsion force consists of the secondary airflow F2 of propulsion system 1, the kinetic energy of which is primarily affected by the compression experienced by the secondary airflow F2 as it passes through fan section 2. Therefore, propulsion efficiency and the pressure ratio of fan section 2 are correlated: the lower the pressure ratio of fan section 2, the better the propulsion efficiency. To improve the propulsion efficiency of propulsion system 1, the fan pressure ratio, corresponding to the ratio between the average pressure at the outlet of fan stator 16 (or, in the absence of stator 16, fan rotor 9) and the average pressure at the inlet of 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. Here, the average pressure is measured at the height of at least one fan blade 14, that is, from the surface that radially defines the airflow path at the inlet of the fan rotor 9 to the tip 21 of the fan blade 14.

[0173] The circumferential speed at the tip 21 of the fan blade 14 can also be between 260 m / s (ms). -1 ) to 400 m / s (ms) -1 The fan pressure ratio can then be between 1.20 and 1.45 (including the endpoint).

[0174] In a direct-drive propulsion system, instead, the fan rotor 9 is directly connected to the low-pressure shaft 11, i.e., without a reduction gear. The low-pressure shaft 11 then coincides with the fan shaft 20, such that the fan rotor 9 is driven by the low-pressure shaft 11 at the same speed as the rotor 81 of the low-pressure turbine 8.

[0175] The propulsion system 1 is configured to provide thrust 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).

[0176] The diameter D of the fan rotor 9 can 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, about 90 inches (228.6 cm), which allows for the integration of the propulsion system 1 in a conventional manner, particularly under the wings of the aircraft 1.

[0177] Figure 3 A second example of propulsion system 1 is schematically shown in a partial cross-sectional view.

[0178] exist Figure 3 In, with Figure 2 Components of the propulsion system that are identical or similar are indicated by the same reference numerals.

[0179] exist Figure 3 In the example shown, propulsion system 1 is a dual-shaft, ductless fan gas turbine engine. This can be an open rotor or a ductless single-fan type gas turbine engine.

[0180] and Figure 2 Unlike the first example, the fan rotor 9 (also known as the "propeller") is not surrounded by a fan housing.

[0181] Since the fan section 2 is ductless, the fan blades 14 have a variable setting. Therefore, each fan blade 14 is pivotally mounted relative to the fan hub 13 along a setting axis and connected to a pitch changing mechanism 15 installed in the propulsion system 1. The pitch changing mechanism allows adjustment of the setting angle of the fan blades 14 according to the flight stage. Similarly, the outlet guide vanes 17 have a variable setting; the root of the outlet guide vanes 17 is pivotally mounted along a setting axis and connected to the pitch changing mechanism 15, which adjusts the setting according to the flight stage.

[0182] Alternatively, the propulsion system 1 may include two ductless, counter-rotating fan rotors 9. This propulsion system 1 is widely known by the acronym "CROR" (counter-rotating open rotor) or "UDF" (ductless dual fan). The fan rotors 9 may be placed at the rear of the body 3 as a propeller type, or at the front of the body 3 as a tractor type.

[0183] The absence of a fairing around the fan rotor 9 allows for a significantly increased bypass ratio, while the propulsion system 1 is unaffected by the mass of the casing 12 or nacelle intended to surround the fan section 2. Therefore, the bypass ratio of the propulsion system 1, including the ductless fan section 2, is greater than or equal to 40, for example, between 40 and 80 (inclusive). Furthermore, the circumferential velocity at the tip 21 of the fan blades 14 of the fan rotor 9 can be between 210 m / s. -1 Up to 260 m / s (ms) -1 The fan pressure ratio can then preferably be between 0.90 and 1.20 (inclusive).

[0184] The diameter D of the fan rotor 9 can 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). Here, the diameter of the fan rotor 9 is measured in a plane perpendicular to the longitudinal axis X (the axis of rotation of the fan rotor 9), at the intersection between the tip 21 and the leading edge 22 of the fan blade 14.

[0185] It should be noted that, due to Figure 2 and Figure 3 It is a partial view, so the diameter D is only partially visible.

[0186] The reduction mechanism 19 may include a planetary, star, or differential reduction mechanism, having a single stage, also known as a single-stage mechanism, or having multiple stages, particularly two stages (also known as a two-stage mechanism).

[0187] For example, Figure 4 A star-shaped reduction gear 19 is shown. The reduction gear 19 includes: a sun gear 19a (the inlet of the reduction gear 19), which is centered on the rotational axis of the reduction gear 19 (which coincides approximately with the longitudinal axis X) and configured to be driven to rotate by the low-pressure shaft 11; a ring gear 19b (the outlet of the reduction gear 19), which is coaxial with the sun gear 19a and configured to drive the fan shaft 20 to rotate about its rotational axis X; and a series of planetary gears 19c, which are circumferentially distributed about the rotational axis X of the rotor 9 of the fan section 2 and located between the sun gear 19a and the ring gear 19b, each planetary gear 19c meshing internally with the sun gear 19a and externally with the ring gear 19b. The series of planetary gears 19c are mounted on a planetary gear carrier 19d, which is fixed relative to the stator portion 19e of the propulsion system 1, for example, fixed relative to the housing of the compressor sections 4 and 5.

[0188] In another example, Figure 5 A planetary reduction gear 19 is shown, in which the gear ring 19b is fixedly mounted on the stator portion 19e of the propulsion system 1, and the fan shaft 20 is driven to rotate by the planetary gear carrier 19d.

[0189] In yet another example, Figure 6 A differential reduction gear 19 is shown, in which no component is rotatably fixed. The set of planetary gears 19c is held by a planetary gear carrier 19d connected to the first fan shaft 20a, and each planetary gear 19c drives a ring gear 19b added to the second counter-rotating fan shaft 20b.

[0190] Regardless of the configuration of the reduction mechanism 19, the diameters of the gear ring 19b and the planetary gear carrier 19d are larger than the diameter of the sun gear 19a, which makes the rotational speed of the rotor 9 of the fan section 2 lower than the rotational speed of the low-pressure shaft 11.

[0191] 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 the ducted fan propulsion system 1, the reduction ratio can be greater than or equal to 2.7 and less than or equal to 3.5, typically around 3.0. In the case of the non-ducted fan propulsion system 1, the reduction ratio can be between 9.0 and 11.0.

[0192] Figure 7 An example of a planetary mechanical reduction gear 19 is schematically shown in partial axial section, wherein the planetary gear carrier 19d and the sun gear 19a are rotatable, and the gear ring 19b of the reduction gear 19 is fixed in the reference frame of the engine.

[0193] At the inlet, the reduction gear 19 is connected to the low-pressure shaft 11, for example, via an internal spline 77a. Therefore, the low-pressure shaft 11 drives the sun gear 19a. The axis of rotation of the sun gear 19a coincides with the longitudinal axis X, and the sun gear 19a drives a series of planetary gears 19c, which are evenly distributed around the axis of rotation X on the same diameter. This diameter is equal to twice the distance between the working centers of the sun gear 19a and the planetary gears 19c. For this type of application, the number of planetary gears 19c is typically limited to between three and seven.

[0194] The set of planetary gears 19c is held in place by a frame formed by a planetary gear carrier 19d. Each planetary gear 19c rotates about its own axis of rotation Y and meshes with a ring gear 19b.

[0195] At the exit, Figure 7 In the configuration shown, the planetary gear 19c drives the planetary gear carrier 19d to rotate about the longitudinal axis X. The ring gear 19b is fixed to the engine housing or stator via the ring gear carrier 23, and the planetary gear carrier 19d is fixed to the fan shaft 20.

[0196] In another star configuration, the set of planetary gears 19c is held by a planetary gear carrier 19d fixed to the engine housing or stator. Each planetary gear 19c drives a ring gear 19b, which is added to the fan shaft 20 via a ring gear carrier 23.

[0197] In another differential configuration, the set of planetary gears 19c is held by a planetary gear carrier 19d connected to the first fan shaft 20a. Each planetary gear drives a ring gear 19b, which is added to the second counter-rotating fan shaft 20b via a ring gear carrier 23.

[0198] Each planetary gear 19c is mounted to rotate freely using a bearing 24 of, for example, rolling or hydrodynamic type. Each bearing 24 is mounted on one of the shafts 25a of the planetary gear carrier 19d, and all shafts are positioned relative to each other using one or more structural frames 25b of the planetary gear carrier 19d. The number of shafts 25a and bearings 24 is equal to the number of planetary gears 19c. The shafts 25a and frames 25b may be divided into multiple parts for reasons of operation, installation, manufacture, inspection, repair, or replacement.

[0199] For the same reasons mentioned above, the teeth of planetary gear 19c can be divided into multiple propellers or teeth, each propeller or tooth having a central plane P, P'. In this example, the operation of reduction gear 19 is described in detail below, wherein each planetary gear 19c includes two series of herringbone teeth that mate with a gear ring 19b divided into two half-gear rings.

[0200] The upstream semi-gear ring 26 consists of an edge 26a and a fixed semi-flange 26b. The front propeller, which meshes with the propeller of the tooth 19cd of each planetary gear 19c, is located on the edge 26a. The propeller of the tooth 19cd also meshes with the propeller of the sun gear 19a.

[0201] The downstream semi-gear ring 27 consists of an edge 27a and a fixed semi-flange 27b. The rear propeller, which meshes with the propeller of the tooth 19cd of each planetary gear 19c, is located on the edge 27a. The propeller of the tooth 19cd also meshes with the propeller of the sun gear 19a.

[0202] Although the propeller width varies between the sun gear 19a, planet gear 19c and gear ring 19b due to tooth overlap, the propeller width is centered on the intermediate plane P for the upstream tooth and on another intermediate plane P' for the downstream tooth.

[0203] therefore, Figure 7 The case of a single meshing stage reduction gear is shown, where the same tooth portion 19cd of each planetary gear 19c meshes with both the sun gear 19a and the ring gear 19b. Although the tooth portion 19cd comprises two series of teeth, these teeth have the same average diameter and form a single tooth portion known as a herringbone tooth portion.

[0204] The fixed half-flange 26b of the upstream gear ring 26a and the fixed half-flange 27b of the downstream gear ring 27a form the fixed flange 28 of the gear ring 19b. The gear ring 19b is fixed to the gear ring frame 23 by assembling the fixed flange 28 of the gear ring 19b and the fixed flange 35 of the gear ring frame 23 using, for example, bolt mounting.

[0205] Figure 7Arrow FH describes the delivery of oil in the reduction gear 19. Oil reaches the reduction gear 19 from the stator portion in the distributor 36 via various devices, which are not detailed in this view as they are specific to one or more types of architectures. The distributor 36 includes an injector 36a and an arm 36b. The injector 36a functions to lubricate the teeth, and the arm 36b functions to lubricate the bearings. Oil is delivered to the injector 36a and discharged through the end 36c to lubricate the teeth. Oil is also delivered to the arm 36b and circulates via the bearing supply port 36d. The oil then circulates through the shaft into one or more buffer areas 25c and is discharged through the orifice 25d to lubricate the bearing 24 of the planetary gear 19c.

[0206] Therefore, the reduction mechanism 19 includes a plurality of meshing portions formed between the sun gear 19a and the planet gear 19c. In each meshing portion, the first pinion Pi1 transmits rotational mechanical energy to the second pinion Pi2 via a drive that occurs on the effective profile of the teeth.

[0207] Figure 8 The effective profile of the first tooth portion of the first pinion Pi1 of the sun gear 19a in the reduction mechanism 19 is schematically shown between the effective profile of the second tooth portion 19cd of the second pinion Pi2 of the planetary gear 19c in the series of planetary gears 19c of the reduction mechanism 19.

[0208] The lubricant film is obtained via the lubrication circuit 36a of the reduction mechanism 19, which allows the lubricant to be delivered between the first tooth of the first pinion Pi1 and the second tooth 19cd of the second pinion Pi2.

[0209] Figure 8 The minimum height of the lubricant film is shown. Or minimum thickness. This is the minimum distance between the effective profile of the first tooth of the first pinion Pi1 and the effective profile of the second tooth 19cd of the second pinion Pi2 projected in the radial plane relative to the first pinion Pi1 and the second pinion Pi2, or the minimum normal distance between the effective profile of the first tooth of the first pinion Pi1 and the effective profile of the second tooth 19cd of the second pinion Pi2.

[0210] To ensure the high operational performance of the reduction gear 19, a controlled supply of lubricant to the meshing parts must be maintained. Therefore, the minimum height of the lubricant film must be controlled. The value should be controlled to be optimal.

[0211] In particular, a thick lubricant film (and therefore a significantly smaller height) (While it remains under control during operation) This allows for the prevention of metal-to-metal contact between two effective tooth profiles, and thus allows for limiting the risk of contact fatigue of the micropitting type, as well as the risk of jamming, i.e., wear in the pinion mesh.

[0212] Minimum height of the lubricant film between the effective profile of the first tooth of the first pinion Pi1 and the effective profile of the second tooth of the second pinion Pi2 (19cd). (Expressed in meters (m)) is defined as:

[0213] in:

[0214] and:

[0215] and:

[0216] and:

[0217] and:

[0218] and:

[0219] and:

[0220] and:

[0221] and:

[0222] and:

[0223] and:

[0224] and:

[0225] and:

[0226] and:

[0227] and:

[0228] and:

[0229] in: It is the radius of curvature at the contact point B, in meters (m). It is the linear load on the teeth, and the unit is Newtons per meter (N / m). It is Hertz pressure, and the unit is megapascal (MPa). It is a dimensionless thermal parameter. It is the Young's modulus of the first or second tooth portion, denoted by E1 for the first tooth portion and E2 for the second tooth portion, with the unit being Pascals (Pa). It is the reduced modulus of elasticity, and its unit is Pascal (Pa). These are the initial Poisson coefficients. It is the Poisson's coefficient of the first tooth. It is the Poisson's coefficient for the second tooth. It is the piezoelectric coefficient (Pa) of the lubricant. -1 ), This refers to the rotational speed of the first pinion Pi1, measured in radians per second (rad / s), which is intended to be achieved by the first pinion Pi1 during operation. This refers to the rotational speed of the second pinion Pi2, measured in radians per second (rad / s), which is intended to be achieved by the second pinion Pi2 during operation. It is the distance between point T2 and point B, in meters (m), where T2 is the point of tangency between the line of action and the base circle of the second pinion Pi2. It is the number of teeth on the second pinion Pi2. This is the distance between the work centers, expressed in meters (m). This refers to the change in center distance, measured in meters (m), ranging from 0 mm to 0.8 mm. It is the overall reduction ratio. This is the distance between point T1 and point B, in meters (m). B is the characteristic point of meshing, corresponding to the transition from N-1 meshing teeth to N meshing teeth (N is the maximum number of meshing teeth determined by the contact ratio). T1 is the point of tangency between the line of action and the base circle of the first pinion Pi1. It is the effective tooth tip diameter of the first pinion Pi1 at point B, in meters (m). It is the diameter of the base circle of the first pinion Pi1, in meters (m). It is the normal modulus, and the unit is millimeters (mm). Let Pi1 be the number of teeth of the first pinion. It is the helix angle or reference lead angle, in degrees (°). It is the tooth tip height, corresponding to the effective tooth tip diameter of the first tooth. It is the end face pressure angle or apparent pressure angle, and the unit is degrees (°). It is the normal pressure angle, and the unit is degrees (°).

[0230] Figure 9 The geometric parameters associated with the relative sliding between the first pinion Pi1 and the second pinion Pi2 of the reduction mechanism 19 according to the invention are schematically shown.

[0231] In particular, Figure 9 The meshing of a pair of conjugate profiles of the teeth of the first pinion Pi1 and the second pinion Pi2 is shown, with their line of action L. AC At points T1 and T2, the diameter of the first pinion Pi1 is d. b1 The base circle Cb1 and the diameter of the second pinion Pi2 are d. b2 The base circle Cb2 is tangent to each other. According to the definition of conjugate profiles, these conjugate profiles roll over each other and remain constantly tangent. Similarly, in this… Figure 9 In the diagram, the first and second segments of the circle are represented by circles with diameters d and d, respectively. y1 Cy1 and having a diameter d y2 Cy2.

[0232] Point B is the characteristic point of meshing, corresponding to the transition from N-1 to N meshing teeth (N is the maximum number of meshing teeth obtained from the contact ratio).

[0233] also, Figures 10 to 15 It also allows for the definition of other parameters used to define the deceleration mechanism according to the present invention.

[0234] Tooth D is shown separately. Figure 10 In the attached diagram, Ft and Fp represent the tooth flank and tooth root, respectively. Ha and hf represent the addendum (corresponding to the tooth tip diameter) and dedendum, respectively. The numeral h is the height of tooth D.

[0235] In addition, Figure 11 In the figure, the reference numeral d corresponds to the diameter of the pitch circle, where d / 2 is the radius of the pitch circle, and the reference numeral d... b Corresponding to the diameter of the base circle, where d b / 2 is the radius of the base circle.

[0236] Therefore, in the cross-section, the end face pressure angle or apparent pressure angle It is the involute d in the tooth section v The acute angle formed between the tangent at the point where it intersects the pitch circle and the radius passing through that point.

[0237] Normal pressure angle It is the end face pressure angle The projection onto a plane perpendicular to the tooth. The normal pressure angle is determined by... Defined. In the case of straight teeth, the angle and They are the same.

[0238] In addition, Figure 12 The effective tooth tip diameter of the first pinion Pi1 is shown in the figure. Effective tooth tip diameter of the second pinion Pi2 Similarly, the base circle diameter of the first pinion Pi1 is shown. The base circle diameter of the second pinion Pi2 .

[0239] Figure 13 The tooth tip height corresponding to the effective tooth tip diameter is also shown. ,Should Figure 13 In the attached figure, reference d corresponds to the pitch circle diameter, and reference d... a Corresponding to the tooth tip diameter.

[0240] Figure 14 The distance between the working centers of the two axes O1 and O2 passing through the two pinions is partially shown. .

[0241] also, Figure 15 Allowed helix angle (as shown in the diagram) The helix angle is referenced to the helical surface H. r tangent t a Reference cylinder L with the point of contact through the tangent e The angle between the envelopes. Figure 15In the diagram, PN represents the normal plane, and AX represents the central axis of the pinion.

[0242] It should be noted that the parameters described in this application are well known to those skilled in the art and are specifically mentioned in the above-cited documents, particularly standards ISO 6336-22 and 21771-2014.

[0243] Advantageously, the minimum height listed above and used for calculating the lubricant film... The parameters make: Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as .

[0244] Furthermore, according to the present invention, the first pinion Pi1 and the second pinion Pi2 have parameters It is chosen such that: .

[0245] In addition, the first pinion Pi1 and the second pinion Pi2 have parameters It was chosen to make And parameters Chosen as .

[0246] According to a particular embodiment, parameters Chosen as And parameters Chosen as .

[0247] In addition, parameters It can be selected to make .

[0248] Furthermore, the first pinion Pi1 and the second pinion Pi2 have a relative sliding speed in meters per second (m / s) between the two involute surfaces or effective profiles. And relative rolling speed in meters per second (m / s) Relative sliding speed and relative rolling speed are used as parameters. and The function is defined as:

[0249] and:

[0250] Among them, relative sliding speed Chosen as And among them, relative rolling speed and total reduction ratio Chosen to make: -if ,but , -if ,but , and .

[0251] In particular, relative sliding speed Chosen as And relative rolling speed and total reduction ratio Chosen to make: -if ,but , -if ,but , and .

[0252] As a variation, relative rolling speed It can be selected to make and relative sliding speed It can be chosen such that: if ,but .

[0253] According to a particular embodiment, relative rolling speed Chosen as and relative sliding speed Chosen as such that: if ,but .

[0254] In addition, the minimum height of the lubricant film It can be selected such that: More specifically, this makes: .

[0255] The selection of parameters proposed in this invention advantageously allows for a sufficient lubricant film to be obtained, thereby particularly limiting any metal-to-metal contact between the tooth profiles of the first pinion Pi1 and the tooth profiles of the second pinion Pi2.

Claims

1. A reduction gear (19) for an aircraft propulsion system (1), comprising a sun gear (19a), a ring gear (19b), a planetary gear carrier (19d), and a series of planetary gears (19c) rotatably mounted on the planetary gear carrier (19d), wherein the sun gear (19a) includes a first pinion (Pi1) having a first tooth portion, and each planetary gear (19c) includes a second pinion (Pi2) having a second tooth portion (19cd) configured to mesh with the first tooth portion of the first pinion (Pi1). The reduction mechanism (19) further includes a lubrication circuit (36a) containing lubricant, the lubrication circuit being configured to deliver lubricant between a first tooth of the first pinion (Pi1) and a second tooth (19cd) of at least one second pinion (Pi2). in, At least one second pinion (Pi2) has parameters , is defined as: in: and: and: and: and: and: and: and: and: in: It is the rotational speed of the second pinion (Pi2), measured in radians per second (rad / s), intended to be achieved by at least one second pinion (Pi2) during operation. It is the distance between point T2 and point B, in meters (m), where T2 is the point of tangency between the line of action and the base circle of the second pinion (Pi2). It is the number of teeth on the second pinion (Pi2). This is the distance between the work centers, expressed in meters (m). It is the overall reduction ratio. This is the distance between point T1 and point B, in meters (m), where B is the characteristic point of meshing, corresponding to the transition from N-1 to N meshing teeth, N is the maximum number of meshing teeth determined by the contact ratio, and T1 is the point of tangency between the line of action and the base circle of the first pinion (Pi1). It is the effective tooth tip diameter of the first pinion (Pi1) at point B, in meters (m). It is the diameter of the base circle of the first pinion (Pi1), in meters (m). It is the normal modulus, and the unit is millimeters (mm). It is the number of teeth on the first pinion (Pi1). It is the helix angle or reference lead angle, in degrees (°). It is the tooth tip height of the effective tooth tip diameter of the first tooth portion. It is the end face pressure angle or apparent pressure angle, and the unit is degrees (°). It is the normal pressure angle, and the unit is degrees (°). Among them, parameters Chosen to make: and: Chosen as , This refers to the change in center distance, measured in meters (m), ranging from 0 mm to 0.8 mm. Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as .

2. The deceleration mechanism (19) according to claim 1, wherein, The first pinion (Pi1) has parameters , is defined as: in: It is the rotational speed of the first pinion (Pi1), measured in radians per second (rad / s), which is intended to be achieved by the first pinion (Pi1) during operation. Wherein, the rotational speed of the first pinion Chosen as .

3. The deceleration mechanism (19) according to claim 2, wherein, parameter Chosen to make: And among them, the parameters Chosen to make: 。 4. The deceleration mechanism (19) according to claim 2, wherein, parameter Chosen to make: And among them, the parameters Chosen to make: 。 5. The reduction mechanism (19) according to claim 2 or 4, wherein, parameter Chosen to make: 。 6. The reduction mechanism (19) according to any one of claims 2 to 5, wherein, The first pinion (Pi1) has a relative sliding speed in meters per second (m / s) between at least one second pinion (Pi2) on two involute surfaces or effective profiles. And relative rolling speed in meters per second (m / s) The relative sliding speed and the relative rolling speed are used as parameters. and The function is defined as: and: Wherein, the relative sliding speed Chosen to make: And therein, the relative rolling speed and the total reduction ratio Chosen to make: -if ,but , -if ,but .

7. The deceleration mechanism (19) according to claim 6, wherein, The relative sliding speed Chosen to make: 。 8. The reduction mechanism (19) according to any one of claims 2 to 7, wherein, The first pinion (Pi1) has a relative sliding speed in meters per second (m / s) between at least one second pinion (Pi2) on two involute surfaces or effective profiles. And relative rolling speed in meters per second (m / s) The relative sliding speed and the relative rolling speed are used as parameters. and The function is defined as: and: Wherein, the relative rolling speed Chosen to make: And therein, the relative sliding speed Chosen to make: 。 9. The deceleration mechanism (19) according to claim 8, wherein, The relative rolling speed Chosen to make: 。 10. The deceleration mechanism (19) according to any one of the preceding claims, wherein, For the first pinion (Pi1) and at least one second pinion (Pi2), the minimum height parameter in meters (m) of the lubricant film, particularly the oil, between the effective profile of the first tooth portion of the first pinion (Pi1) and the effective profile of the second tooth portion (19cd) of the second pinion (Pi2). Or the minimum thickness is defined as: in: and: and: and: and: and: in: It is the radius of curvature at the contact point B, in meters (m). It is the linear load on the teeth, and the unit is Newtons per meter (N / m). It is Hertz pressure, and the unit is megapascal (MPa). It is a dimensionless thermal parameter. It is the Young's modulus of the first tooth or the second tooth, denoted by E1 for the first tooth and E2 for the second tooth, with the unit being Pascal (Pa). It is the reduced modulus of elasticity, and its unit is Pascal (Pa). These are the initial Poisson coefficients. It is the Poisson's coefficient of the first tooth. It is the Poisson's coefficient of the second tooth. It is the piezoelectric coefficient (Pa) of the lubricant. -1 ), It is the rotational speed of the first pinion (Pi1), measured in radians per second (rad / s), which is intended to be achieved by the first pinion (Pi1) during operation. Among them, the minimum height of the lubricant film Chosen to make: and: Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as .

11. The deceleration mechanism (19) according to claim 10, wherein, Minimum height of the lubricant film Chosen to make: 。 12. The deceleration mechanism (19) according to any one of the preceding claims, wherein, The first tooth portion of the first pinion (Pi1) and the second tooth portion (19cd) of each second pinion (Pi2) include straight teeth, helical teeth or herringbone teeth.

13. The deceleration mechanism (19) according to any one of the preceding claims, wherein, - Each planetary gear (19c) includes one or two meshing stages, and / or - The planetary gear carrier (19d) is either a single piece or includes a retainer defining an inner housing to receive the sun gear (19a) and the planetary gears (19c), and / or - Each planetary gear (19c) is centered and guided to rotate about an axis by a bearing carried by the planetary gear carrier (19d), each bearing being of the rolling element type or the hydrodynamic type.

14. An aircraft propulsion system (1), comprising: - Power turbine (8), especially low-pressure turbine; And a turbine drive shaft (11), particularly a low-pressure shaft, which is driven by the power turbine (8) to rotate about a longitudinal axis (X); - Fan rotor (9) and fan shaft (20), the fan rotor (9) being rotatably connected to the fan shaft (20); - The deceleration mechanism (19) according to any one of the preceding claims includes an inlet connected to the turbine drive shaft (11) and an outlet connected to the fan shaft (20), the deceleration mechanism being configured to drive the fan rotor (9) to rotate about the longitudinal axis (X) at a speed lower than that of the power turbine (8) via the turbine drive shaft (11) and the fan shaft (20).

15. A method for determining the dimensions of a reduction gear (19) for an aircraft propulsion system (1), the aircraft propulsion system comprising: Power turbines (8), especially low-pressure turbines; And a turbine drive shaft (11), particularly a low-pressure shaft, which is driven by the power turbine (8) to rotate about a longitudinal axis (X); and a fan rotor (9) and a fan shaft (20), which are rotatably connected to the fan shaft (20). The reduction mechanism (19) includes an inlet intended to connect to the turbine drive shaft (11) and an outlet intended to connect to the fan shaft (20), and the reduction mechanism is configured to drive the fan rotor (9) to rotate about the longitudinal axis (X) at a speed lower than that of the power turbine (8) via the turbine drive shaft (11) and the fan shaft (20). The reduction mechanism (19) includes a sun gear (19a), a ring gear (19b), a planetary gear carrier (19d), and a series of planetary gears (19c) rotatably mounted on the planetary gear carrier (19d). The sun gear (19a) includes a first pinion (Pi1) having a first tooth portion, and each planetary gear (19c) includes a second pinion (Pi2) having a second tooth portion (19cd) configured to mesh with the first tooth portion of the first pinion (Pi1). The reduction mechanism (19) further includes a lubrication circuit (36a) containing a lubricant, the lubrication circuit being configured to deliver the lubricant between the teeth of the first pinion (Pi1) and the teeth of at least one second pinion (Pi2). Among them, at least one second pinion (Pi2) has parameters , is defined as: in: and: and: and: and: and: and: and: and: in: It is the rotational speed of the second pinion (Pi2), measured in radians per second (rad / s), intended to be achieved by at least one second pinion (Pi2) during operation. It is the distance between point T2 and point B, in meters (m), where T2 is the point of tangency between the line of action and the base circle of the second pinion (Pi2). It is the number of teeth on the second pinion (Pi2). This is the distance between the work centers, expressed in meters (m). It is the overall reduction ratio. This is the distance between point T1 and point B, in meters (m), where B is the characteristic point of meshing, corresponding to the transition from N-1 to N meshing teeth, N is the maximum number of meshing teeth determined by the contact ratio, and T1 is the point of tangency between the line of action and the base circle of the first pinion (Pi1). It is the effective tooth tip diameter of the first pinion (Pi1) at point B, in meters (m). It is the diameter of the base circle of the first pinion (Pi1), in meters (m). It is the normal modulus, and the unit is millimeters (mm). It is the number of teeth on the first pinion (Pi1). It is the helix angle or reference lead angle, in degrees (°). It is the tooth tip height of the effective tooth tip diameter of the first tooth portion. It is the end face pressure angle or apparent pressure angle, and the unit is degrees (°). It is the normal pressure angle, and the unit is degrees (°). The method includes the step of determining the dimensions of the reduction mechanism (19), in which parameters... Chosen to make: and: Chosen as , This refers to the change in center distance, measured in meters (m), ranging from 0 mm to 0.8 mm. Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as .

16. The size determination method according to claim 15, wherein, The first pinion (Pi1) has parameters , is defined as: in: It is the rotational speed of the first pinion (Pi1), measured in radians per second (rad / s), which is intended to be achieved by the first pinion (Pi1) during operation. The method includes the step of determining the dimensions of the reduction mechanism (19), in which the rotational speed of the first pinion is determined. Chosen to make: .

17. The size determination method according to claim 16, comprising the step of determining the size of the reduction mechanism (19), wherein in the step, parameters Chosen to make: And among them, parameter Chosen to make: 。 18. The size determination method according to claim 16, comprising the step of determining the size of the reduction mechanism (19), wherein in the step, parameters Chosen to make: And among them, parameter Chosen to make: 。 19. The size determination method according to claim 16 or 18, comprising the step of determining the size of the reduction mechanism (19), wherein in the step, parameters Chosen to make: 。 20. The method for determining dimensions according to any one of claims 16 to 19, wherein, The first pinion (Pi1) has a relative sliding speed in meters per second (m / s) between at least one second pinion (Pi2) on two involute surfaces or effective profiles. And relative rolling speed in meters per second (m / s) The relative sliding speed and the relative rolling speed are used as parameters. and The function is defined as: and: The method includes the step of determining the dimensions of the deceleration mechanism (19), in which the relative sliding speed... Chosen to make: And therein, the relative rolling speed and the total reduction ratio Chosen to make: -if ,but , -if ,but .

21. The size determination method according to claim 20, comprising the step of determining the size of the deceleration mechanism (19), wherein the relative sliding speed... Chosen to make: 。 22. The method for determining dimensions according to any one of claims 16 to 21, wherein, The first pinion (Pi1) has a relative sliding speed in meters per second (m / s) between at least one second pinion (Pi2) on two involute surfaces or effective profiles. And relative rolling speed in meters per second (m / s) The relative sliding speed and the relative rolling speed are used as parameters. and The function is defined as: and: The method includes the step of determining the dimensions of the reduction mechanism (19), in which the relative rolling speed... Chosen to make: And the relative sliding speed Chosen to make: 。 23. The size determination method according to claim 22, comprising the step of determining the size of the deceleration mechanism (19), wherein the relative rolling speed... Chosen to make: 。 24. The method for determining dimensions according to any one of claims 15 to 23, wherein, For the first pinion (Pi1) and at least one second pinion (Pi2), the minimum height parameter in meters (m) of the lubricant film, particularly the oil, between the effective profile of the first tooth portion of the first pinion (Pi1) and the effective profile of the second tooth portion (19cd) of the second pinion (Pi2). Or the minimum thickness is defined as: in: and: and: and: and: and: in: It is the radius of curvature at the contact point B, in meters (m). It is the linear load on the teeth, and the unit is Newtons per meter (N / m). It is Hertz pressure, and the unit is megapascal (MPa). It is a dimensionless thermal parameter. It is the Young's modulus of the first tooth or the second tooth, denoted by E1 for the first tooth and E2 for the second tooth, with the unit being Pascal (Pa). It is the reduced modulus of elasticity, and its unit is Pascal (Pa). These are the initial Poisson coefficients. It is the Poisson's coefficient of the first tooth. It is the Poisson's coefficient of the second tooth. It is the piezoelectric coefficient (Pa) of the lubricant. -1 ), It is the rotational speed of the first pinion (Pi1), measured in radians per second (rad / s), which is intended to be achieved by the first pinion (Pi1) during operation. The method includes the step of determining the dimensions of the reduction mechanism (19), in which the minimum height of the lubricant film is determined. Chosen to make: and: Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as , Chosen as .

25. The size determination method according to claim 24, comprising the step of determining the size of the reduction mechanism (19), wherein the minimum height of the lubricant film is determined in the step. Chosen to make: 。 26. A speed reduction mechanism (19) manufactured by the dimensional determination method according to any one of claims 15 to 25.

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