Gearbox of aircraft turbine engine

A gearbox for an aircraft turbine engine has a casing defining an enclosure for housing rotating elements lubricated by oil. At least one tubular sleeve is coupled to the rotating elements and configured to rotate a shaft. The sleeve includes splines configured to cooperate with complementary splines of said shaft. The gearbox further includes means for recovering lubricating oil from the rotating elements and conveying the recovered oil by streaming to the splines to lubricate the splines.

TECHNICAL FIELD

The present invention relates to a gearbox for an aircraft turbine engine.

BACKGROUND OF THE INVENTION

The state of the art in particular comprises document EP-A1-2,711,505, U.S. Pat. No. 3,621,937 and GB-A-2,488,142.

A gearbox for an aircraft turbine engine, in particular for an airplane or helicopter turbojet engine or turboprop, may consist of an accessory gearbox (AGB), which is used to drive equipment of the turbine engine, such as pumps, electricity generators, etc. The accessory gearbox transmits mechanical power originating from the turbine engine to the equipment via a kinematic chain made up of rotating elements such as pinions or rolling bearings. A gearbox for an aircraft turbine engine may also consist of a transfer gearbox (TGB), for example to kinematically connect an accessory gearbox to a turbine shaft of the turbine engine by using two transfer shafts optionally forming an angle and connected to one another by the transfer gearbox.

Such a gearbox, in particular an accessory gearbox such as a transfer gearbox, comprises a casing defining an enclosure for housing rotating elements that are lubricated by oil, this oil further being able to serve to cool the casing. The gearbox comprises at least one tubular sleeve meshing with at least one rotating element and configured to be coupled to and rotate a shaft, for example a transfer shaft or the shaft of a piece of equipment of the turbine engine. This sleeve includes a female nesting part including splines configured to cooperate with splines of a male nesting part of the shaft.

The splines of the female nesting part of the sleeve and those of the male nesting part of the shaft must be lubricated. However, this lubrication requires only a very small amount of oil. It in fact suffices to ensure an oil level in the splines to lubricate the coupling. In the current technique, a continuously operating spray nozzle is generally used to lubricate these splines. The diameter of the spray nozzle may not be too small, which means that the splines are quite often over-lubricated. This results in needless oil consumption.

Document U.S. Pat. No. 5,119,905 illustrates a specific prior art relative to an accessory gearbox in which a spray nozzle is used intermittently. The jet of oil projected by the spray nozzle passes through a hole of the sleeve, when the engine is stopped. This technology has a drawback related to the fact that the filling of an annular reservoir supplying oil to the splines only occurs when the engine is stopped. The renewal of the oil allocated to lubricating the splines therefore only occurs particularly discontinuously over time.

The present invention in particular aims to provide a simple, effective and inexpensive solution to at least part of the aforementioned problems.

BRIEF DESCRIPTION OF THE INVENTION

The invention proposes a gearbox for an aircraft turbine engine, comprising a casing defining an enclosure for housing rotating elements lubricated by oil, and at least one tubular sleeve coupled to the rotating elements and configured to rotate a shaft, this sleeve including female splines configured to cooperate with male splines of said shaft, the box further comprising means for recovering lubricating oil from the rotating elements and conveying recovered oil by streaming to the splines to lubricate them, said recovery and conveying means comprising at least one inner wall collecting oil from said casing, the gearbox being configured to cause the oil to stream over said at least one collecting inner wall during the operation of the turbine engine, characterized in that said recovery and conveying means comprise a channeling member that extends at least partially inside said sleeve, and at least one gutter configured to convey the oil that streams over said at least one collecting inner wall to the channeling member, in which said channeling member and said at least one gutter are supported by or formed with a flange of the casing, this flange defining said at least one collecting inner wall and serving as a support for rolling bearing of the sleeve, the flange comprising at least one radial opening allowing oil flowing on said collecting inner wall to reach said channeling member.

The splines are thus lubricated by recovered oil lubricating the rotating elements and not by oil dedicated exclusively to lubricating the splines. At least part of lubricating oil of the rotating elements is thus recovered and conveyed to the splines without a direct contribution of oil from a spray nozzle. This makes it possible to limit the lubricating oil consumption of the gearbox. Furthermore, the recovery and conveyance of the oil can be done continuously during the operation of the engine, which is advantageous relative to the prior art.

The invention makes it possible to optimize the bulk of the gearbox. The recovery and conveying means do not hinder the rotational guiding of the sleeve, since the bearing near the recovery and conveying means is perfectly integrated in this configuration owing in particular to the radial opening provided in the cylindrical support wall of the bearing.

According to one embodiment of the invention, the flange has a planar part and a hollow cylindrical part that extends substantially perpendicular to the planar part and that supports the rolling bearing, said channeling member extending inside the cylindrical part from the planar part, and said at least one radial opening being arranged in the cylindrical part at the junction with the planar part such that the streaming oil passes through said at least one radial opening to be collected in said at least one gutter.

Preferably, the splines extend in a longitudinal annular cavity of the sleeve that is defined at one longitudinal end by an annular seal configured to cooperate with said shaft, and an opposite longitudinal end by an annular dam preferably formed by a leveling seal whereof the outer periphery defines the maximum oil level in said annular cavity.

Advantageously, the annular dam extends in a transverse plane that is traversed by the recovery and conveying means.

Advantageously, said flange comprises two gutters together forming a V with an angle of about 120-160°. The or each gutter can have a substantially U-shaped section. The or each gutter can extend substantially radially relative to the axis of said cylindrical part of the flange. The or each gutter can be situated in an axial space extending between said planar part of the flange and an end of the sleeve guided by said bearing. The channeling member can have a substantially U-shaped section.

The present invention also relates to a turbine engine, such as an aircraft turbojet engine or turboprop, characterized in that it comprises a gearbox as described above.

DETAILED DESCRIPTION OF THE INVENTION

Reference will first be made toFIG. 1, which shows an example of an accessory gearbox10for driving equipment12of a turbine engine, such as an aircraft turbojet engine or turboprop. Such an accessory gearbox is in particular described in document FR-A1-2,941,744.

This gearbox10is intended to withdraw mechanical power originating from the turbine engine and transmit it to the pieces of equipment, which are pumps, electricity generators, etc. The transmission is done by a kinematic chain made up of rotating elements meshing with one another to form lines of gears or accessories.

The accessory gearbox10comprises a casing14defining an enclosure housing rotating elements that for example comprise pinions and rolling bearings. The kinematic chain is connected to a driveshaft16that is a radial shaft of the turbine engine or an intermediate shaft, the chain also being connected to movement shafts18of the pieces of equipment. The accessory gearbox10is fastened to the turbine engine and the pieces of equipment are generally in turn fastened to the accessory gearbox10.

FIG. 2shows one embodiment of the invention. References10,14and18are also used to designate the accessory gearbox, its casing and the shaft of a piece of equipment, respectively. The example gearbox according to the invention described in reference toFIGS. 2 to 4relates to an accessory gearbox, but it is understood that the embodiment described herein is also applicable to a transfer gearbox.

The coupling of the shaft18to the kinematic chain of the accessory gearbox10is done using splines24,26. The shaft18comprises a male end part28intended to be nested in a sleeve30making up a tubular part of the rotating element or a pinion of the accessory gearbox, this end part28including outer or male splines24that are preferably rectilinear splines extending substantially parallel to the rotation axis A of the shaft18.

The accessory gearbox10comprises one or several pinion sleeves30, each sleeve being used to rotate a shaft18of a piece of equipment and to transmit the power from the kinematic chain to this shaft.

The sleeve30comprises a female end part32intended to receive the end part28of the shaft18, this end part32including inner or female splines26that are substantially complementary to the splines24. They are therefore preferably rectilinear, extending substantially parallel to the rotation axis A of the shaft18.

The splines24,26here extend in an inner longitudinal cavity34of the sleeve30that is defined at one end, situated on the side of the shaft18, by an annular seal36, and at the opposite end by an annular dam38. The annular seal36is supported by the sleeve30and is intended to cooperate with the shaft18to provide sealing against the oil between the sleeve30and the shaft18. Alternatively, the seal36could be supported by the shaft18and cooperate with the sleeve30. The annular dam38is preferably formed by an annular leveling seal. The cavity34makes it possible to store a predetermined volume of oil in which the splines24,26bathe. The leveling seal (dam38) is configured to define a maximum oil level40in the cavity34, the excess oil then being discharged from the cavity34while flowing through the leveling seal.

The sleeve30rotates and is rotated by at least one rotating element of the accessory gearbox, for example another pinion. To that end, the sleeve can comprise a toothed wheel at its outer periphery suitable for meshing with the toothed wheel of another pinion. The sleeve30and its toothed wheel constitute a pinion.

The rotating elements of the accessory gearbox10are lubricated by oil, which can be brought into the inner enclosure of the casing14by spray nozzles, for example.

According to the invention, the accessory gearbox10comprises means for recovering lubricating oil from the rotating and conveying elements by streaming of the recovered oil to the splines24,26. These means here comprise a wall or flange42of the casing14on which at least part of the oil that was used to lubricate the rotating elements flows. This flange42, which serves as a sealing cover for the casing, comprises or bears at least one inner wall48collecting lubricating oil of the rotating elements and a channeling member44that has an elongated shape and extends partially inside the sleeve30such that its free longitudinal end is situated as close as possible to the cavity34of the sleeve30and the oil can be conveyed and is discharged simply by streaming and gravity to this cavity34(arrow46). The leveling seal (annular dam38) thus extends in a transverse plane P that is traversed by the channeling member44. Advantageously, the streaming by the member44is provided to be sufficient to compensate any minor oil leak at the seal36.

FIGS. 3 and 4show a more concrete example embodiment of the accessory gearbox10according to the invention, and in particular its flange42bearing the oil recovery and conveying means.

The flange42here is formed in a single piece and in particular comprises a planar part on the inner face of which at least one recess is formed defining a collecting inner wall48as described in the preceding.

The flange42also comprises a hollow cylindrical part54that extends substantially perpendicular to the planar part and that supports a rolling bearing52of the sleeve. The collecting inner wall48is substantially perpendicular to the axis of this cylindrical part54. The rolling bearing52comprises an outer ring mounted in a free end part of the cylindrical part54and an inner ring mounted around an end part of the sleeve30, opposite the splines26. The sleeve50is thus partially engaged, by an end part, in the cylindrical part54of the flange42. This end part is, however, at an axial distance from the planar part of the flange42in order to allow oil to flow between them (arrow46), as will be described below.

The cylindrical part54here is formed by a boss of the flange that comprises outer radial extensions in which tapped screwing orifices49are provided for screws fastening the outer ring of the bearing52to the flange42.

The cylindrical part54comprises a radial opening56at the junction with the wall48of the planar part of the flange42. Oil can thus stream over the wall48to the inside of the cylindrical part54, while passing through the opening56.

The flange42further comprises, radially inside the cylindrical part54, the aforementioned channeling member44as well as two gutters50that serve to collect the oil passing through the radial opening56and convey it to the longitudinal end of the member44connected to the planar part of the flange42.

Each gutter50has a substantially U-shaped section and extends substantially radially relative to the axis of the cylindrical part54, substantially from this axis to the cylindrical part54. The gutters50together form a V with an angle of about 120-160°. The gutters50are situated substantially in the axial space extending between the planar part of the flange42and the end of the sleeve30guided by the bearing52.

The channeling member44has a substantially U-shaped section and extends partially inside the sleeve30to be able to discharge the recovered oil into the inner cavity34of the sleeve. The cavity34is defined by the leveling seal (dam38) and by the aforementioned sealing gasket (seal36inFIG. 2), which here is supported by the shaft and is therefore not shown. This sealing gasket is intended to cooperate with an inner cylindrical surface of the sleeve30.

The end part of the sleeve30including the splines26is guided by another bearing60and is further surrounded by a dynamic sealing gasket62, the bearing60and the seal62being mounted in a cylindrical wall64of the casing14.

The sleeve30is further secured to an outwardly toothed wheel66so as to form a pinion.

The flange42ofFIGS. 3 and 4can be made by foundry for example, or by machining.

As diagrammatically shown by arrow46inFIG. 3, the oil that is sprayed or discharged during operation on the collecting wall48streams to the opening56and penetrates the cylindrical wall54to be collected in the gutters50, which convey this oil to the channeling member44. This oil next flows into the inner cavity34of the sleeve30for lubrication of the splines26as well as those of the corresponding equipment shaft. Because the channeling member44traverses the transverse plane in which the leveling seal (annular dam38) extends, the oil that flows by gravity to the free end of this channeling member necessarily falls into the inner cavity34of the sleeve30.

The oil contained in the inner cavity34is thus continuously renewed. Indeed, during the operation of the turbine engine, the entire annular space of the inner cavity34is filled with oil under the effect of the centrifugal force due to the rotation of the sleeve30. The oil flowing in the sleeve30from the channeling member44mixes with the oil of the inner cavity34. The excess oil in the inner cavity34overflows above the leveling seal38to return into the casing, or also to participate in lubricating bearing52.

The channeling member44is advantageously arranged to extend substantially horizontally once the accessory gearbox is installed in the turbine engine, or to form a slight slope relative to the horizontal in most flight attitudes so as to favor the flow of the oil by gravity. The flow of the oil in the inner cavity34is thus not interrupted, except during exceptional and short flight attitudes. It may for example be provided that the opening of the sleeve30on the side of the leveling seal38is oriented toward the front of the aircraft, such that during the flight, the flow of the oil in the inner cavity34from the channeling member44can be interrupted only during any flight phase with a strong downward incline (in particular in case of nose-down acceleration).

Furthermore, the leveling seal38advantageously has a sufficient radial height so that, when the turbine engine is stopped, i.e., when the rotating elements of the accessory gearbox are no longer rotating, part of the splines of the sleeve and the shaft dabble in the oil retained in the bottom of the inner cavity34. When the turbine engine is restarted, all of splines are quickly lubricated by this retained oil.