POWER TRANSMISSION GEARBOX AND AN AIRCRAFT

Abstract

A power transmission gearbox having at least one driving gear with spur teeth presenting a large radius. The gearbox includes at least one mechanical outlet drive system suitable for driving an accessory, the mechanical outlet drive system having a gear with face teeth referred to as an accessory pinion, the accessory pinion presenting a small radius (R2) lying orthogonally between each face tooth and its axis of rotation, the small radius (R2) being smaller than the large radius (R1).

Claims

1. A power transmission gearbox having at least one gear referred to as a driving gear that is movable in rotation about an axis of rotation (AX1), the driving gear being a gear with spur teeth presenting a minimum radius referred to as the large radius (R1) lying orthogonally between each spur tooth of the driving gear and the axis of rotation (AX1), wherein the gearbox includes at least one mechanical outlet drive system suitable for driving an accessory, the mechanical outlet drive system comprising a driven gear having face teeth referred to as an accessory pinion, the accessory pinion being movable in rotation about a drive axis (AX2) that intersects the axis of rotation (AX1), at least one face tooth of the accessory pinion being engaged with at least one spur tooth of the driving gear, the accessory pinion presenting a minimum radius referred to as the small radius (R2) lying orthogonally between each face tooth of the accessory pinion and the drive axis (AX2), the small radius (R2) being less than the large radius (R1).

2. A gearbox according to claim 1, wherein the gearbox includes at least one speed reduction stage, and the driving gear is a gear for setting the speed reduction stage into motion via at least one power transmission shaft.

3. A gearbox according to claim 1, wherein the gearbox includes at least one mechanical inlet member engaged with a gear referred to as a drive gear, the drive gear setting a speed reduction stage into motion via at least one power transmission shaft, each mechanical inlet member being suitable for being driven by an engine, the driving gear being represented either by the drive gear, or by a gear of the mechanical inlet member and referred to as an inlet gear, or by a gear constrained to rotate with the drive gear and referred to as a complementary gear.

4. A gearbox according to claim 1, wherein at least one mechanical outlet drive system has a drive shaft secured to the accessory pinion of the mechanical outlet drive system, the drive shaft being suitable for engaging with an accessory.

5. A gearbox according to claim 4, wherein the drive shaft projects outside a casing of the gearbox.

6. A gearbox according to claim 1, wherein the gearbox includes a plurality of mechanical outlet drive systems distributed in azimuth around the driving gear.

7. A gearbox according to claim 6, wherein the mechanical outlet drive systems are uniformly distributed in azimuth around the driving gear.

8. A gearbox according to claim 1, wherein at least two accessory pinions of two mechanical outlet drive systems are offset from each other in elevation, one accessory pinion rotating in a counterclockwise direction and the other accessory pinion rotating in a clockwise direction.

9. A power transmission architecture having a gearbox and at least one accessory, wherein the gearbox is according to claim 1, at least one accessory being connected to a mechanical outlet drive system.

10. A power transmission architecture according to claim 9, wherein the gearbox includes a casing referred to as the gearbox casing, each driving gear and each accessory pinion being arranged in the gearbox casing, at least one accessory including a casing referred to as an accessory casing fastened to the gearbox casing.

11. A power transmission architecture according to claim 9, wherein each accessory is connected to its own mechanical outlet drive system, which is dedicated to that accessory.

12. An aircraft including a rotor, wherein the aircraft includes a power transmission architecture according to claim 9, the rotor being driven in rotation by the gearbox.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0075] The invention and its advantages appear in greater detail from the context of the following description of examples given by way of illustration and with reference to the accompanying figures, in which:

[0076] FIG. 1 is a diagram showing an aircraft of the invention;

[0077] FIGS. 2 and 3 are diagrams showing spur gears respectively with straight teeth and with helical teeth;

[0078] FIGS. 4 and 5 are diagrams showing face pinions respectively with straight teeth and with helical teeth;

[0079] FIG. 6 is a diagram showing a driving gear with face teeth that is set into motion by a driving gear with spur teeth;

[0080] FIG. 7 is a diagram showing accessory pinions uniformly distributed in azimuth around a driving gear; and

[0081] FIG. 8 is a diagram showing two accessory pinions that are offset vertically.

DETAILED DESCRIPTION OF THE INVENTION

[0082] Elements present in more than one of the figures are given the same references in each of them.

[0083] FIG. 1 shows an aircraft 1 of the invention. This aircraft includes a power transmission architecture 6.

[0084] In particular, the power transmission architecture 6 is set into motion by at least one engine 2. Under such circumstances, the power transmission architecture 6 drives a rotor 3 in rotation. Such a rotor 3 may have a hub 4 carrying blades 5 serving at least to participate in providing the aircraft 1 with lift and/or propulsion.

[0085] The power transmission architecture 6 is thus provided with a gearbox 10 set into motion by at least one engine 2. The gearbox 10 is also mechanically connected to the rotor 3 that is to be driven.

[0086] Under such circumstances, the gearbox comprises, within a gearbox casing 90, a drive gear 15 setting into motion at least one speed reduction stage 20. For example, the speed reduction stage comprises a sun gear 21 constrained to rotate with the drive gear 15 by a power transmission shaft 16. The sun gear meshes with at least one planet gear 22 running along a peripheral ring gear 24. Each planet gear is also carried by a planet carrier 23. The planet carrier may be mechanically connected to the rotor that is to be driven, as shown in FIG. 1, or it may be connected to another speed reduction stage.

[0087] The drive gear 15 may also be driven in rotation indirectly about an axis of rotation by each engine. Thus, the gearbox is provided with one mechanical inlet member 25 for each engine. Each mechanical inlet member 25 is provided with at least one inlet gear 26 that meshes with the drive gear 15. The mechanical inlet member may also have an overrunning clutch or freewheel 100.

[0088] Furthermore, the mechanical inlet member 25 may include at least one shaft 27 suitable for being mechanically connected to an engine 2. A shaft 27 may be secured to an inlet gear or it may mesh with an inlet gear, e.g. via gearing having conical spur teeth.

[0089] Each inlet gear 26 is then received in the gearbox casing 90, the shaft 27 projecting from the gearbox casing 90 in order to be connected to an engine 2.

[0090] Furthermore, the gearbox 10 may possess at least one additional gear referred to as a complementary gear 30 that is arranged in the gearbox casing 90. The complementary gear is then constrained to rotate with the drive gear 15 by a link shaft 31.

[0091] A complementary gear may also drive mechanically an auxiliary gearbox BTA, in particular a tail gearbox of a rotorcraft.

[0092] In addition, the power transmission architecture 6 includes at least one accessory 7 that is set into motion via a rotary member of the gearbox 10. These accessories may in particular include lubrication pumps, hydraulic pumps, compressors, alternators, and fans.

[0093] In order to enable each accessory 7 to operate, the gearbox 10 has one outlet mechanical drive system 50 for each accessory 7. Each accessory 7 is then set into motion by a single mechanical outlet drive system 50, each mechanical outlet drive system 50 setting a single accessory 7 into motion.

[0094] Each mechanical outlet drive system 50 meshes with a gear referred to as the driving gear 40. In the example of FIG. 1, the drive gear 15, an inlet gear 26 and/or also the complementary gear 30 may be driving gears setting into motion at least one mechanical outlet drive system 50.

[0095] With reference to FIGS. 2 and 3, each driving gear 40 is a gear with spur teeth 45 that is movable in rotation about an axis of rotation AX1.

[0096] Under such circumstances, a driving gear 40 comprises a block of material presenting a top disk 41, possibly parallel to a bottom disk 42. In addition, the driving gear has an edge face 43 that extends in elevation along the axis of rotation AX1 from the bottom disk 42 to the top disk 41.

[0097] Teeth 45, known as spur teeth, are then arranged on the edge face 43 of the driving gear 40.

[0098] As shown in FIG. 2, the spur teeth 45 may be straight. Each spur tooth 45 is then contained in a plane containing the axis of rotation AX1.

[0099] As shown in FIG. 3, the spur teeth 45 may be helical teeth.

[0100] Whatever the variant, a driving gear presents a minimum radius referred to as the large radius R1. The large radius R1 of a driving gear represents the smallest radius of a disk between a tooth and the axis of rotation AX1. Consequently, the large radius R1 is the radius of the bottom disk 42 or of the top disk 41.

[0101] With reference to FIG. 1, a mechanical outlet drive system 50 also comprises an accessory pinion 55 meshing with a driving gear 40.

[0102] An accessory pinion 55 is a face tooth gear 60 movable in rotation about a drive axis AX2. This drive axis AX2 intersects the axis of rotation AX1 of the corresponding driving gear.

[0103] With reference to FIGS. 4 and 5, an accessory pinion 55 comprises a block of material presenting a top face 56 optionally parallel to a bottom face 57. Furthermore, an accessory pinion 55 includes an edge face 58 that extends in elevation along the drive axis AX2 from the bottom face 57 to the top face 56 of the accessory pinion 55.

[0104] Teeth referred to as face teeth 60 are then provided on one face. In the example shown, face teeth extend in elevation from the top face 56. These face teeth 60 also present a surface that is ruled.

[0105] As shown in FIG. 4, the face teeth 60 may be straight teeth. Each tooth extends along a straight line, which straight line does not necessarily intersect the drive axis AX2.

[0106] As shown in FIG. 5, the face teeth 60 may be helical teeth.

[0107] Whatever the variant, an accessory pinion 55 presents a minimum radius referred to as the small radius R2. The small radius R2 of an accessory pinion 55 represents the smallest radius between a tooth and the drive axis AX2.

[0108] With reference to FIG. 1, at least one face tooth of an accessory pinion then comes into contact with at least one spur tooth of a driving gear.

[0109] Furthermore, the small radius R2 of an accessory pinion 55 is smaller than the large radius R1 of the driving gear that meshes with the accessory pinion 55.

[0110] With reference to FIG. 6, a driving gear 40 having spur teeth 45 meshes with an accessory pinion 55 having face teeth, thereby constituting a gear set that increases speed of rotation.

[0111] Each accessory pinion may then be used directly or indirectly to set an accessory into motion.

[0112] For example, a mechanical outlet drive system 50 comprises a drive shaft 65 constrained to rotate with the accessory pinion 55 of the mechanical outlet drive system 50. The drive shaft 65 may be carried by a bearing 69 that may be a smooth bearing or a rolling bearing.

[0113] The drive shaft 65 of a mechanical outlet drive system 50 then extends from a first end 66 secured to the accessory pinion 55 to a second end 67. The second end 67 may include a straight or conical pinion 68 to set an accessory 7 into motion. Nevertheless, an accessory does not necessarily include mechanical take-off means.

[0114] The drive shaft of a mechanical outlet drive system 50 may extend entirely inside the gearbox casing 90 in order to engage an accessory. For example, such a mechanical outlet drive system 50 may mesh with the complementary gear 30 in order to drive an accessory 7 of the type comprising a lubrication pump 200, for example.

[0115] Nevertheless, the drive shaft of a mechanical outlet drive system 50 may project out from the gearbox casing 90 to reach an accessory referred to as an external accessory 8 situated outside the gearbox. By way of example, such an accessory may be a fan in the example of FIG. 1.

[0116] For example, the drive shaft passes for this purpose through an opening in the gearbox casing 90. Such an opening may also provide an operator with access to the inside of the gearbox.

[0117] Furthermore, at least one accessory may be fastened to the gearbox.

[0118] Specifically, mechanical outlet drive systems 50 make it possible to arrange accessories close to the gearbox. Under such circumstances, an accessory casing 9 for an accessory may be fastened by conventional means 95 to the gearbox casing 90. By way of example, such means 95 may comprise reversible fastener means, such as screw fasteners, in particular.

[0119] FIG. 7 shows an embodiment of a gearbox.

[0120] The gearbox has a drive gear 15. The drive gear 15 is set into rotation jointly by two mechanical inlet members 25 that are connected respectively to two engines 2. Each mechanical inlet member 25 comprises at least one inlet gear 26 and a shaft 27, for example.

[0121] Independently of the way in which the drive gear 15 is driven in rotation about its axis of rotation AX1, a driving gear may engage with a plurality of mechanical outlet drive systems 50.

[0122] In the embodiment of FIG. 7, three mechanical outlet drive systems 50 mesh with the drive gear 15 for the purpose of setting three respective accessories 7 into motion.

[0123] Under such circumstances, the mechanical outlet drive system 50 may optionally be uniformly distributed in azimuth around the drive gear 15. Two adjacent mechanical outlet drive systems 50 are then spaced apart by an angle 300 of 120 degrees. More precisely, two drive shafts 65 of two adjacent mechanical outlet drive systems 50 extend respectively on two axes that are spaced apart by an angle 300.

[0124] Furthermore, and as shown in FIG. 8, the direction of rotation of an accessory pinion may be adjusted by positioning the accessory pinion above or below the driving gear that is meshing with the accessory pinion.

[0125] An accessory pinion is positioned above such a driving gear when the drive axis AX2 about which the accessory pinion 55 rotates overlies the driving gear A. Conversely, an accessory pinion is positioned below such a driving gear when the driving gear overlies the drive axis AX2 about which the accessory pinion 55 rotates.

[0126] Consequently, when two accessory pinions 55 of two mechanical outlet drive systems 50 are offset relative to each other in elevation, one accessory pinion 55 rotates in a counterclockwise direction and the other accessory pinion 55 rotates in a clockwise direction.

[0127] Naturally, the present invention may be subjected to numerous variations as to its implementation. Although a plurality of embodiments are described, it will readily be understood that it is not conceivable to identify exhaustively all possible embodiments. It is naturally possible to envisage replacing any of the means described by equivalent means without going beyond the ambit of the present invention.