REDUCTION GEAR FOR AIRCRAFT TURBOMACHINE AND CORRESPONDING TURBOMACHINE

Abstract

This gearbox for an aircraft turbomachine comprises a sun gear (14) intended to be rotationally fixed to a drive shaft (15) and a set of planet gears, the sun gear (14) comprising a central external peripheral toothing intended to mesh with said set of planet gears, the sun gear having at least one area of ​​increased flexibility at the location of the external peripheral toothing. Figure for the abbreviation: Fig 3

Description

Title of the invention: REDUCER FOR AIRCRAFT TURBOMACHINE AND CORRESPONDING TURBOMACHINE technical field

[0001] The invention relates, in general, to mechanical reducers for aircraft turbomachinery. Previous techniques

[0002] The role of a mechanical reducer is to modify the speed and torque ratio between the input shaft and the output shaft of a mechanical system.

[0003] With regard to aircraft turbomachinery, and in particular double-flow turbomachinery, especially those with a very high bypass ratio, the mechanical reducer has the role of driving the shaft of a fan by transforming the so-called high rotational speed of the shaft of a power turbine into a slower rotational speed for the shaft driving the fan.

[0004] Such a reducer includes a central pinion, called a solar pinion, which is driven by a drive shaft which receives the drive torque, a ring gear, which transmits the torque, at the output, to the blower shaft, and pinions called satellite gears which are meshed between the solar pinion and the ring gear.

[0005] The satellites are held by a chassis called a satellite carrier. The solar array, the corona, and the satellite carrier are planetary because their axis of revolution coincides with the longitudinal axis X of the turbomachine.

[0006] The satellites have different axes of revolution distributed over the same operating diameter around the axis of the planetary gears

[0007] These axes are parallel to the longitudinal axis X.

[0008] There are several reducer architectures.

[0009] In the state of the art of double-flow turbomachinery, the reducers are of the planetary or epicyclic type.

[0010] In other similar applications, there are so-called differential architectures.

[0011] On a planetary reducer, the planet carrier is fixed and the ring constitutes the output shaft of the device which rotates in the opposite direction to the solar.

[0012] On an epicycloidal reducer, the ring is fixed and the planet carrier constitutes the output shaft of the device which rotates in the same direction as the sun.

[0013] On a differential reducer, no element is fixed for rotation. The ring rotates in the opposite direction to the sun and the satellite carrier.

[0014] With reference to figures [Fig.1a] and [Fig.1b], during the operation of the reducer, the passage of the satellites is likely to cause a deformation of the solar S in due to the forces applied to its peripheral teeth, which has repercussions on the connection between the solar element and the drive shaft.

[0015] These deformations depend on the number of satellites and the torque passing through the satellites. For example, as can be seen in [Fig.lb], in the case of a three-satellite reducer, the solar element deforms by adopting a three-lobed shape.

[0016] These deformations create a radial slip on the link between the motor shaft and the solar panel, to the detriment of its proper functioning.

[0017] To overcome this drawback, it has been proposed to thicken the solar element to limit deformations. However, this solution entails an increase in the mass of the solar element and potentially an increase in the radial size of the reducer.

[0018] Another solution is to eliminate the splines, by making the drive shaft and the solar in a single block form, which, however, limits the modularity of the turbomachine. Description of the invention

[0019] In view of the foregoing, the object of the invention is to propose a reducer, and in particular a motor-solar shaft assembly for an aircraft turbomachine reducer, which overcomes this drawback and avoids the deformation of the solar element and its consequences.

[0020] The invention therefore relates to an aircraft turbomachine reducer, comprising a solar element intended to be rotationally fixed to a drive shaft and a set of satellites, the solar element comprising a median external peripheral toothing intended to mesh with said set of satellites.

[0021] The solar element includes at least one area of ​​increased flexibility at the location of the external peripheral teeth.

[0022] In one embodiment, the increased flexibility zone is formed by means of alveoli made in the middle zone of the peripheral dentition.

[0023] The cells are advantageously regularly distributed around the solar element.

[0024] For example, the increased flexibility zone is formed in a reduced thickness zone of the peripheral teeth and delimits in said peripheral teeth two half-teeth.

[0025] In one embodiment, the teeth are helical teeth.

[0026] Advantageously, the grooves are axially offset relative to the external peripheral teeth.

[0027] Preferably, sealing rings will be provided between the motor shaft and the solar element, on either side of the splines, so as to delimit lubricated areas in communication with a lubrication circuit.

[0028] The invention also relates to an aircraft turbomachine comprising a reducer as defined above. Brief description of the drawings

[0029] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example and made with reference to the accompanying drawings in which:

[0030] Figs [1a] and [1b], which have already been mentioned, schematically illustrate the effects of the forces applied by the satellites on the solar system;

[0031] Fig. 2 is a schematic axial cross-sectional view of a turbomachine equipped with a reducer having a motor-solar shaft assembly according to the invention;

[0032] Fig. 3 is a perspective view of a motor-solar shaft assembly according to the invention;

[0033] Fig. 4 is a cross-sectional view of the motor-solar shaft assembly of Fig. 3;

[0034] Figures 5 and 6 are respectively perspective and cross-sectional views of the solar system in Figures 3 and 4; and

[0035] Fig. 7 is a perspective view of the drive shaft of the assembly of Figures 3 and 4. Detailed description

[0036] Figure 2 shows a turbojet engine for an aircraft according to the invention, designated by the general numerical reference 1, with axis XX.

[0037] This turbojet 1 is a twin-flow turbojet which has at the front, considering the direction of the airflow admitted into the turbojet, a fan 2 which is connected to a reducer 3 which drives in rotation a low pressure compressor 4, then a high pressure compressor 5.

[0038] The turbomachine 1 also includes a combustion equipment comprising an annular combustion chamber 6, and downstream, a high-pressure turbine 7 and a low-pressure turbine 8.

[0039] The hot gases from the combustion pass through the high-pressure turbines 7 and the low-pressure turbine 8, the latter driving the blower before escaping through an exhaust nozzle 9.

[0040] The low-pressure compressor and the low-pressure turbine are connected by a low-pressure shaft 10. The high-pressure compressor and the high-pressure turbine are connected by a high-pressure shaft 11. The blower is driven by a blower shaft 12 which is driven by the low-pressure shaft 10 by means of the reducer 3. This reducer is generally of the planetary or epicyclic type.

[0041] The following description relates essentially to the reducer, in particular the drive shaft which receives the drive torque from the low pressure turbine and the solar which meshes with the satellites.

[0042] Figures 3 and 4 show a motor-solar shaft assembly of a gearbox for an aircraft turbomachine, designated by the general numerical reference 13.

[0043] This assembly 13 includes a solar 14, illustrated in figures 5 and 6, intended to mesh with a set of satellites of the reducer and a drive shaft 15, illustrated in figures 7 and 8, which receives the drive torque delivered by the low pressure turbine and which supplies this drive torque to the blower via the satellites, the ring gear and the blower shaft 12.

[0044] The solar element 14 has a general cylindrical shape and extends around the X axis and the drive shaft 15.

[0045] It includes an external median peripheral toothing 16 intended to mesh with the satellites of the reducer, as well as internal female grooves 17.

[0046] The drive shaft 15 also has a generally elongated and tubular shape and extends around the axis X inside the solar 14. It has at one of its free ends a flange B for connecting the assembly 13 to the low-pressure shaft 10.

[0047] Externally, the drive shaft 15 has male splines 18 coupled to the internal splines 17 of the solar element. On either side of the splines, the drive shaft-solar element assembly has a set of sealing rings 19 delimiting lubricated areas at the locations of the splines 17 and 18, these lubricated areas being connected to a lubrication circuit (not shown).

[0048] As can be seen in particular in [Fig. 7], the splines 18 of the drive shaft are provided at the end areas of the drive shaft. This is also the case for the splines 17 of the solar panel, which are provided at the mutually opposite ends of the solar panel, opposite the splines 18 of the drive shaft.

[0049] The teeth 16 are located in the middle zone so that the splines 17 and 18 are offset from the teeth. The splines and the teeth are therefore made in different sections of the drive shaft and the solar element.

[0050] This axial offset helps to reduce the deformation of the solar cross-section, under the effect of the forces which pass through the reducer.

[0051] As can be seen in particular in [Fig. 5], the solar element 14 is further provided with at least one area of ​​increased flexibility at the location of the external peripheral teeth. This area of ​​increased flexibility is notably formed in the middle zone of the peripheral teeth.

[0052] In one embodiment, these areas of increased flexibility are made up of radial through-holes 22, regularly distributed in the periphery of the solar 14.

[0053] In addition or as an alternative, these zones of increased flexibility can be formed by a zone of reduced thickness. Advantageously, as shown, the zones of increased flexibility are formed by recesses 22 made in a zone 23 of reduced thickness. These zones of increased flexibility thus delineate, in the solar element 14, and in particular in the toothing 16, two half-teeth 24 and 25, each having helical teeth.

[0054] These areas of increased flexibility allow localized deformation of the solar panel under the action of the forces applied by the satellites, instead of deforming the grooves and improve the thermomechanical and dynamic behavior of the power transmission line between the low pressure turbine and the blower shaft.

[0055] Furthermore, the splines can subsequently realign themselves with respect to the drive shaft 15 by having balanced loads.

[0056] It should be noted that the double helix gears of the solar array also allow the load to be distributed between the upstream and downstream gears. In this respect, it is desirable to provide for an overlap of the solar array's gears with those of the satellites, for example, by having the solar array's gears wider than those of the satellite.

Claims

Demands

1. Aircraft turbomachine reducer, comprising a solar element (14) intended to be rotationally fixed to a drive shaft (15) and a set of satellites, the solar element (14) comprising a median external peripheral toothing (16) intended to mesh with said set of satellites, characterized in that the solar element has at least one area of ​​increased flexibility at the location of the external peripheral toothing.

2. Reducer according to claim 1, wherein the increased flexibility zone is formed by means of alveoli (22) made in the middle zone of the peripheral teeth.

3. Reducer according to claim 2, in which the cells are regularly distributed around the solar element (14).

4. Reducer according to any one of claims 1 and 2, wherein the increased flexibility zone (22) is formed in a reduced thickness zone of the peripheral teeth (16) and delimits in said peripheral teeth two half-teeth (24, 25).

5. Reducer according to any one of claims 1 to 4, wherein the teeth (16) are helical teeth.

6. A gearbox according to any one of claims 1 to 5, wherein the splines (17, 18) are axially offset relative to the external peripheral teeth (16).

7. A gearbox according to any one of claims 1 to 6, comprising sealing rings (19) between the drive shaft (15) and the solar element, on either side of the splines (17, 18), so as to delimit lubricated areas in communication with a lubrication circuit.

8. An aircraft turbomachine comprising a gearbox according to any one of claims 1 to 7.