Pinion for a turbine engine reduction gear, reduction gear comprising such a pinion and turbine engine comprising such a reduction gear

Abstract

The invention relates to a pinion for a turbine engine reduction gear centred on an axis (X), comprising: a first annular hub (20A) on which a first set of teeth (22A) is formed, a second annular hub (20B) on which a second set of teeth (22B) is formed, an annular separating wall (30) spacing the first hub (20A) apart from the second hub (20B), a plurality of holes (26) formed in at least one of the first hub (20A) and the second hub (20B), wherein the first hub (20A) and the second hub (20B) each have a hole volume ratio equal to the total volume of the holes (26) in the hub divided by the total volume of the hub; and wherein the hole volume ratio in the first hub (20A) is greater than the hole volume ratio in the second hub (20B).

Description

Description Title of the invention: Pinion for a turbomachine reducer, reducer comprising such a pinion and turbomachine comprising such a reducer Technical Field

[0001] The present disclosure relates to a pinion for a turbomachine reducer, a reducer comprising such a pinion and a turbomachine comprising such a reducer. Prior art

[0002] Current high bypass ratio fan aircraft turbomachines include a mechanical transmission system, called a reduction gear, whose function is to drive the fan shaft (called a "fan" in English terminology) in rotation from the rotation of a power turbine in the low pressure line of the turbojet engine. The reduction gear thus makes it possible to transform the rotational speed of the power turbine shaft into a reduced rotational speed for the shaft driving the fan. Generally speaking, the reduction gear must transmit the motive power to the fan, while ensuring the required speed ratio, within strict space and mass constraints. Several architectures and technologies are possible for the reduction gear and the architecture chosen depends primarily on the speed reduction ratio.

[0003] Figure 1 shows a cross-sectional view of a conventional speed reducer structure. This figure illustrates an architecture in which the speed reducer 1 comprises a central sun gear 2 driven by an input shaft (not shown) rotatable about an axis A (perpendicular to the plane of the figure) as well as an external ring gear 3 coaxial with the sun gear 2. The reducer 1 further comprises planet gears 4 which are meshed with both the sun gear 2 and the external ring gear 3. The planet gears 4 are rotatably mounted on pivots 5 of a part called the planet carrier 7 of the reducer 1.

[0004] Three reducer configurations are possible: - planetary reducers in which the planet carrier 7 is fixed and the external crown 3 is free to rotate; - epicyclic reducers in which the external crown 3 is fixed and the planet carrier 7 is free to rotate; - differential reducers, in which no element is fixed in rotation and the external crown 3 rotates in the opposite direction to the sun pinion and the planet carrier 7.

[0005] By applying the engine torque to the reducer, the structural parts and interfaces of the reducer tend to deform, which can lead to a degradation of force distribution in a length direction of the reducer and therefore a degradation of the meshing.

[0006] There is therefore a need to provide a reducer that reduces performance losses associated with the application of engine torque. Statement of the invention

[0007] To this end, the present invention relates to a pinion for a turbomachine reducer centered on an axis, comprising: a first annular hub on which a first set of teeth is formed, a second annular hub on which a second set of teeth is formed, an annular separating wall distancing the first hub from the second means, a plurality of orifices formed in at least one of the first hub and the second means, the first hub and the second means each having an orifice void ratio which is equal to the total volume of the orifices in said hub divided by the total volume of said hub; wherein the orifice void ratio in the first hub is greater than the orifice void ratio in the second means.

[0008] Typically, the pinion extends around an axis of rotation.

[0009] In this presentation, the axis of rotation of the pinion is called the axis. The axial direction corresponds to the direction of the axis of rotation and a radial direction is a direction perpendicular to this axis and intersecting this axis. Similarly, an axial plane is a plane containing the axis of rotation of the pinion and a radial plane is a plane perpendicular to this axis, that is to say a plane transverse to the pinion. A circumference is understood as a circle belonging to a radial plane and whose center belongs to the axis of rotation of the pinion. A tangential or circumferential direction is a direction tangent to a circumference; it is perpendicular to the axis of rotation of the pinion but does not pass through this axis. A tangential or circumferential plane is a plane strictly parallel to the axis of rotation of the pinion, that is to say, not intersecting this axis and not including this axis. An axial or radial section corresponds respectively to a section along an axial plane or along a radial plane.

[0010] Typically, the first hub and / or the second hub has a cylindrical shape of revolution.

[0011] For the purpose of defining the void ratio, a structural and functional distinction is made between the hub and the set of teeth carried by the hub.

[0012] Naturally, a hub and the corresponding set of teeth can be formed from a single piece.

[0013] Typically, the gable can be formed in one piece.

[0014] The total volume of a hub is equal to the volume of the hub including the volume of the voids formed by the holes within it. For example, for a hub in the shape of a cylinder of revolution, the total volume of the hub is equal to the volume of the cylinder of revolution surrounding the hub.

[0015] The volume of the orifices is equal to the volume of the orifices delimited by the cylinder of revolution surrounding the hub.

[0016] Typically, the ratio between the orifice void rate of the second hub and the orifice void rate of the first hub is less than 90%, preferably less than 75%.

[0017] Typically, the orifice void rate of the first hub is between 10% and 50%, preferably between 15% and 33%.

[0018] Typically, the number of holes made in the first hub is equal to the number of teeth in the first set of teeth.

[0019] In addition or replacement, the number of holes in the second hub is less than or equal to the number of teeth in the second set of teeth, for example equal.

[0020] Typically, the orifices are arranged circumferentially around the axis, for example provided circumferentially on at least one common circumference.

[0021] Typically, the holes are provided circumferentially on a single common circumference.

[0022] By circumference common to orifices is meant a circumference passing through said orifices. In other words, seen in a transverse plane, the same virtual circle passes through the orifices of said common circumference.

[0023] Typically the common circumference passes through the centers of the cross sections of the holes provided on the common circumference.

[0024] Typically, the holes include blind holes and / or through holes.

[0025] Typically, the second hub has no holes.

[0026] Typically, holes of the plurality of holes have a cross-section that decreases axially. For example, the cross-section decreases toward an interior of the pinion.

[0027] By "inside the pinion" is meant a direction oriented radially towards the axis of rotation of the pinion or axially from a wheel towards the bearing, preferably both.

[0028] Typically, the variation in the cross-section of the orifices exhibits at least one discontinuity.

[0029] Discontinuity means a sudden variation in the section along the middle grain of an orifice, for example a counterbore.

[0030] Typically, orifices of the plurality of orifices have a frustoconical shape, for example piecewise frustoconical.

[0031] Typically, when viewed in cross-section, when viewed in cross-section, orifices of the plurality of orifices extend circumferentially about the axis according to an angular sector of an angle between 5° and 30°. In other words, each orifice individually extends according to an angular sector of an angle between 5° and 30°.

[0032] The present invention also relates to an aircraft turbomachine reducer, comprising an outer ring gear, a sun gear mounted inside the outer ring gear and at least one pinion according to the present invention mounted so as to mesh with the outer ring gear and the sun gear.

[0033] The present invention also relates to an aircraft turbomachine comprising an epicyclic gear train according to the present invention. Brief description of the drawings

[0034] The purpose of this presentation and its advantages will be better understood by reading the detailed description given below of different examples of embodiment given as non-limiting examples. For the purposes of readability of the figures, the numerical references will not designate all the occurrences of the same element. This description refers to the pages of figures attached, on which:

[0035] [Fig. 1] Figure 1 shows a schematic cross-sectional view of a conventional speed reducer;

[0036] [Fig. 2] Figure 2 represents a simplified and partial schematic view of an aircraft turbojet engine with fan in an axial section;

[0037] [Fig. 3] Figure 3 represents a schematic perspective view of a pinion according to an exemplary embodiment of the invention;

[0038] [Fig. 4] Figure 4 represents a schematic side view of the pinion according to an exemplary embodiment of the invention;

[0039] [Fig. 5] Figure 5 represents a schematic view in radial section of a quadrant according to the section plane V of Figure 4;

[0040] [Fig. 6] Figure 6 represents a schematic view in radial section according to a first alternative of Figure 5;

[0041] [Fig. 7] Figure 7 represents a schematic view in radial section according to a second alternative of Figure 5;

[0042] [Fig. 8A] [Fig. 8B] [Fig. 8C] [Fig. 8D] Figures 8A, 8B, 8C and 8D represent simplified schematic views along the axial section plane VIII of Figures 5 to 7 according to different embodiments of orifices 26. Description of the embodiments

[0043] Figure 2 shows an example of a mixed-flow turbojet engine 10 having a main axis A shown in chain-dotted lines. The air flow in the turbojet engine 10 is shown in the diagram from left to right. The inlet of the turbojet engine 10 has a fan 11 driving the air inside the turbojet engine 10. The air flow is then divided into a primary air flow and a secondary air flow. The primary air flow is compressed successively by a low-pressure compressor 12 and a high-pressure compressor 13, driven respectively by a low-pressure turbine 16 and a high-pressure turbine 15. Between the compressors 12, 13 and the turbines 15, 16 is a combustion chamber 14 receiving the air compressed by the compressors 12, 13 and into which the fuel is injected in order to carry out combustion.The combustion gases exit the combustion chamber 14, driving the turbines 15 and 16, and join the secondary air flow at the outlet, the latter passing through the turbojet engine 10 on the radial periphery of the primary air flow. The combustion gases exiting the turbines 15, 16 are then ejected from the turbojet engine 10 through the nozzle 17, at the distal end of the turbojet engine 10.

[0044] A speed reducer 1 may be provided to transmit motive power from the turbine shaft 15, 16 to the shaft driving the fan 11.

[0045] The planet gears 4 are also also engaged, i.e. meshed, with an external crown (not shown but similar to the crown 3 in FIG. 1) coaxial with the sun gear 2. These planet gears 4 are rotatably mounted on pivots of a planet carrier part, not shown, of the reducer 1. Figure 1 illustrates a possible configuration for the speed reducer 1, except for the number of planet gears 4 which is likely to vary.

[0046] In the speed reducer 1 the planet carrier 7 is fixed and the crown 3 is free to rotate (planetary reducer).

[0047] Depending on the reduction ratio envisaged, the planetary gearbox 1 can be configured as one stage or two stages.

[0048] Figures 3 and 4 show two views of a planetary gear pinion extending around its axis of rotation X. The pinion may for example be a planetary gear 4 or a sun gear 2.

[0049] The pinion 2,4 comprises a first hub 20A on which a first set of teeth 22A is formed, and a second hub 20B on which a second set of teeth 22B is formed.

[0050] The first hub 20A has a length L1 A along the axis of rotation A. Typically, L1 A is between 20 mm and 100 mm.

[0051] The second hub 20B has a length L1 B along the axis of rotation A. Typically, L1 B is between 20 mm and 100 mm.

[0052] Typically, L1 A can be equal to L1 B.

[0053] In the example of the present embodiment, the teeth are chevron-shaped, the first set of teeth 22A and the second set of teeth 22B together forming a chevron. However, it will be understood that the invention is compatible with any other type of teeth, in particular straight or helical teeth.

[0054] The first hub 20A and / or the second hub 20B typically has the shape of a cylindrical sleeve, that is to say having the shape of the volume formed between two coaxial cylinders of revolution of the same length and different diameters.

[0055] The first set of teeth (or first toothing) 22A and the second set of teeth (or second toothing) 22B may be separated by an annular separating wall 30, for example a smooth separating wall 30, i.e. without teeth. For example, the separating wall 30 may be a cylindrical sleeve. In other words, the separating wall 30 axially distances the first set of teeth 22A from the second set of teeth 22B.

[0056] The partition wall 30 has a length L3 along the axis A. Typically, L3 is between 40 mm and 500 mm.

[0057] For the purposes of this disclosure, a virtual plane P is defined that is transverse relative to the axis of rotation X and intersecting the separating wall 30 in its middle. The separating wall 30 may, for example, be a bearing, in particular a plain bearing.

[0058] The plane P may be a plane of symmetry of the assembly formed by the first hub 20A, the separating wall 30 and the second hub 20B, independently or not of the orifices 26 described below.

[0059] The plane P can also be a plane of symmetry of the first set of teeth 22A and the second set of teeth 22B.

[0060] The structure of the pinion will be described in more detail in the radial sectional views of the quadrants of Figures 5 to 7, in particular the distribution of the orifices 26, and the axial sectional views of Figures 8A to 8D, in particular the structure of the orifices 26.

[0061] For ease of representation, only quadrants are shown in Figures 5-7, and only a half-section is shown in Figures 8A-8D. Naturally, it is understood that the features to be shown in connection with these figures may similarly extend to the entire first hub 20A and / or the entire second hub 20B. In other words, the sprocket may comprise four quadrants as described below.

[0062] The first hub 20A has an inner radius r1 and an outer radius r2. The inner radius r1 can be between 20 mm and 250 mm. The outer radius r2 can be between 25 mm and 275 mm. In other words, the thickness of the cylindrical sleeve is equal to r2-r 1 .

[0063] The first set of teeth 22A may be included in a cylindrical sleeve with an inner radius equal to the outer radius r2 of the first hub 20A and an outer radius r3. The outer radius r3 may be between 35 mm and 300 mm.

[0064] In other words, the first set of teeth 22A may extend radially from the first hub 20A and have a tooth height equal to r3-r2.

[0065] The second hub 20B has an inner radius and an outer radius whose values ​​are respectively included in the value ranges of the inner radius r1 and the outer radius r2 of the first hub 20A defined above.

[0066] Typically, the inner radius of the second hub 20B may be equal to r1.

[0067] Typically, the outer radius of the second hub 20B may be equal to r2.

[0068] The second set of teeth 22B may be included in a cylindrical sleeve with an internal radius equal to the external radius of the second hub 20B, and an external radius whose value is included in the range of values ​​of the external radius r3 described above.

[0069] Typically, the outer radius of the cylindrical sleeve comprising the second set of teeth 22B may be equal to r3.

[0070] In other words, the second set of teeth 22A may extend radially from the second hub 20B and have a tooth height equal to r3-r2.

[0071] Holes 26 may be formed in the first hub 20A and / or the second hub 20B.

[0072] The orifices 26 may typically extend axially, i.e., have a non-zero axial component. For example, the orifices 26 may extend strictly parallel to the axial direction.

[0073] In addition or as a replacement, the orifices 26 may typically extend radially, i.e. have a non-zero radial component. For example, the orifices 26 may extend strictly in a radial direction.

[0074] The first hub 20A and the second hub 20B each have a void ratio which is equal to the total volume of the orifices 26 in said hub divided by the total volume of said hub.

[0075] In the present disclosure, the void ratios differ from one hub to another and, for example, the void ratio of the first hub 20A is greater than the void ratio of the second hub 20B.

[0076] In other words, the proportion of orifices 26 in the first hub 20A is greater than the proportion of orifices 26 in the second hub 20B.

[0077] Such a structure results in a difference in flexibility of the pinion between the first hub 20A and the second hub 20B, in particular following the application of force by gearing with the respective sets of teeth 22A, 22B. The first hub 20A is thus more flexible than the second hub 20B.

[0078] This results in particular in a reduction in the torsional rigidity of the pinion, and thus makes it possible to reduce the risks of misalignment between the first set of teeth 22A carried by the first hub 20A and the teeth with which the first set of teeth 22A meshes and / or to reduce the risks of misalignment at the level of the separating wall 30 and / or the associated bearings.

[0079] This makes it possible in particular to reduce the sizing constraints on the micro-geometry of the teeth of the sets of teeth 22A, 22B as well as the bearings and rollers.

[0080] This also makes it possible to reduce the occurrence of overloads caused by such defects, for example misalignment, so that the first hub 20A is able to receive a comparatively greater load than the second hub 20B, without significantly increasing the risks of degradation or malfunction.

[0081] Furthermore, modifying the flexibility of the first hub 20A makes it possible to adjust the dynamic behavior of the first set of teeth 22A, and thus ensure good dynamic sizing for the desired use of the pinion.

[0082] Finally, these orifices 26 make it possible to reduce the mass of the pinion.

[0083] Naturally, such effects are also obtained for the second hub 20B, possibly to a lesser extent depending on the void ratio in the second hub 20B.

[0084] The number of holes 26 in the first hub 20A may be less than or equal to the number of teeth in the first set of teeth 22A.

[0085] In addition or as a replacement, the number of holes 26 in the second hub 20B may be less than or equal to the number of teeth in the second set of teeth 22B.

[0086] Such a number of orifices makes it possible in particular to locally adjust the rigidity of the first hub 20A and / or of the second hub 20B, in particular by associating an orifice with each tooth of the first set of teeth 22A or of the second set of teeth 22B.

[0087] Typically, the void ratio of the first hub is between 10% and 50%, preferably between 15% and 33%.

[0088] Typically, the ratio between the void rate of the second hub 20B and the void rate of the first hub 20A is less than 90%, for example less than 75%.

[0089] It will be noted that the void rate of the second hub 20B may be 0%. In other words, the second hub 20B may be devoid of orifices 26. In such a case, the ratio between the void rate of the second hub 20B and the void rate of the first hub 20A is also 0%.

[0090] An orifice means a blind hole opening out at one end, a through hole at two ends, or a pocket, that is to say a hole formed in the mass and not opening out.

[0091] It is understood that a through hole formed in the first hub 20A and in the second hub 20B contributes to the void ratio of the first hub 20A and the second hub 20B in their relative proportions.

[0092] By orifice, we mean here a removal of material in the mass of a hub. It is understood, however, that the orifices 26 can also comprise a material called filler material having a Young's modulus lower than the Young's modulus of the hub material.

[0093] Typically, the pinion may comprise a metallic material, for example steel. The Young's modulus of such materials is typically between 150 and 230 GPa.

[0094] The filler material may comprise an elastomer-type material, for example polyetheretherketone. The Young's modulus of such materials is typically between 2000 and 10000 MPa.

[0095] In particular, the orifices 26 may comprise a plug formed in the filling material.

[0096] For example, in the case of a blind orifice or a through orifice, the presence of a plug makes it possible to reduce turbulence formed by air entering the orifices 26 when the pinion is rotating, which turbulence could in particular lead to energy losses and the generation of vibrations and noise.

[0097] The orifices 26 may have a circular cross-section, as shown in the embodiments of Figures 5 and 6. Such a structure can easily be obtained using standard machining tools.

[0098] The orifices 26 may be circumferentially distributed. For example, the orifices 26 may be circumferentially equally distributed, as shown in Figures 5 and 6.

[0099] The orifices 26 can be distributed over the same circumference C.

[0100] The orifices 26 can be distributed axisymmetrically around the axis of rotation A.

[0101] The angle 01 between the centers of two consecutive orifices 26 can be between 5° and 20°, where 61 is measured in a transverse plane.

[0102] The orifices 26 may have an oblong cross-section. Typically, the orifices 26 may have a cross-section extending over an arc of a circle, as shown in Figure 7. Typically, the orifice shape of Figure 7 may be obtained by running a conventional machining tool along a portion of the circumference.

[0103] In other words, the orifices 26 extend circumferentially and continuously along an angular sector of angle 02 between 5° and 45°, for example between 5° and 30°.

[0104] Consecutive orifices 26 may be separated by a portion devoid of orifices having an angle 03 of between 5° and 20°.

[0105] Figures 8A to 8D show axial sectional views according to different embodiments of orifices 26.

[0106] As discussed above, the orifices 26 may be blind holes, for example in the embodiments of Figures 8A and 8C, or through holes, for example in the embodiments of Figures 8B and 8D.

[0107] The orifices 26 may have a decreasing cross-section, for example decreasing towards an interior of the pinion, that is to say a decreasing surface cross-section, in particular towards an interior of the pinion.

[0108] By "inside the pinion" is meant a direction oriented radially towards the axis of rotation A of the pinion or axially from a wheel towards the bearing, preferably both.

[0109] Typically, by "inside the pinion" we can mean a direction towards the point of intersection O between the axis of rotation A of the pinion and the plane P.

[0110] Typically, for blind or through holes, the cross-section has a decreasing area from one (or the, if applicable) end of the hole, as shown in the embodiment of Figures 8C and 8D, and Figure 8B where the decrease is not a strict decrease.

[0111] The cross-section of the orifices 26 may have at least one discontinuity. For example, the cross-section may have an abrupt change in diameter, as shown in the embodiment of FIG. 8B.

[0112] The orifices 26 may have a shape of a cylinder of revolution, a truncated cone, or any other geometric shape that can be obtained by conventional machining tools. The orifices 26 may be formed in pieces by a combination of these geometric shapes.

[0113] Such shapes of orifices 26 make it possible in particular to create a flexibility gradient, in other words a stiffness gradient, in a length direction of the pinion.

[0114] It is understood that the pinion described above can be provided with a single-stage or multi-stage, epicyclic, planetary or differential reducer 1.

[0115] The reducer 1 may comprise any type of planet carrier, in particular a single-piece, or comprising an assembly of a cage and a cage carrier.

[0116] The reducer 1 can be provided with any type of satellite bearing, in particular comprising rolling elements or a hydrodynamic bearing.

[0117] Although the present invention has been described with reference to specific embodiments, it is obvious that modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims

Claims

1. Pinion for a turbomachine reducer centered on an axis (X), comprising: a first annular hub (20A) on which a first set of teeth (22A) is formed, a second annular hub (20B) on which a second set of teeth (22B) is formed, an annular separation wall (30) distancing the first hub (20A) from the second hub (20B), a plurality of orifices (26) formed in the first hub (20A), the second hub (20B) being devoid of orifices.

2. A sprocket according to claim 1, wherein a void rate of holes in the first hub (20A) is between 10% and 50%, preferably between 15% and 33%, the void rate of holes in the first hub (10A) being equal to the total volume of the holes (26) in the first hub (20A) divided by the total volume of the first hub (20A).

3. A sprocket according to claim 1 or 2, wherein the number of holes (26) made in the first hub (20A) is equal to the number of teeth in the first set of teeth (22A).

4. A sprocket according to any one of claims 1 to 3, wherein the orifices (26) are arranged circumferentially around the axis (X).

5. A pinion according to any one of claims 1 to 4, wherein the orifices (26) comprise blind holes and / or through holes.

6. A sprocket according to any one of claims 1 to 5, wherein orifices (26) of the plurality of orifices (26) have an axially decreasing cross-section.

7. A sprocket according to claim 6, wherein the variation in cross-section of the orifices (26) has at least one discontinuity.

8. A sprocket according to claim 6 or 7, wherein holes (26) of the plurality of holes (26) have a frustoconical shape, for example piecewise frustoconical.

9. A pinion according to any one of claims 1 to 8, wherein viewed in cross-section, orifices (26) of the plurality of orifices (26) extend circumferentially around the axis (X) along an angular sector of angle between 5° and 30°.

10. Reducer (1) for an aircraft turbomachine, comprising an outer ring (3), a sun gear (2) mounted inside the outer ring (3) and at least one pinion (4) according to any one of claims 1 to 9 mounted so as to mesh with the outer ring (3) and the sun gear (2).

11. Aircraft turbomachine (10) comprising a reducer (1) according to claim 10.

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