Bevel gear arrangement for axial accessory gearbox

An accessory box for a gas turbine engine has an input gear to be driven by an input shaft. The input gear is engaged to drive a first driven gear on one radial side of a drive axis of the input gear. The first gear drives at least a second driven gear on one radial side of the drive axis, with at least one accessory driven by one of the first and second driven gears. The second driven gear drives a bevel gear arrangement to drive a third driven gear on an opposed side of the drive axis of the input gear. The third driven gear drives at least a second accessory. The accessories are associated with a gas turbine engine.

BACKGROUND OF THE INVENTION

This application relates to a drive arrangement for use in an accessory gearbox associated with a gas turbine engine.

Gas turbine engines are known, and typically include a compressor compressing air and delivering it into a combustion section. The air is mixed with fuel and combusted, and products of that combustion are driven over turbine rotors, driving the turbine rotors to rotate.

Any number of accessories are associated with a gas turbine engine, and will typically draw power from rotation of the turbine rotors through a tower shaft. The tower shaft drives the accessories at a location adjacent to the gas turbine engine. Historically, the accessory were spaced circumferentially about a central drive axis of the tower shaft. This sometimes resulted in an undesirably large radial envelope.

More recently it has been proposed to space the accessories axially along the drive axis of the tower shaft. In the proposed arrangements, a layshaft extends along an axial dimension, and the accessories are driven off of the layshaft at axially spaced locations.

SUMMARY OF THE INVENTION

In a featured embodiment, an accessory box for a gas turbine engine has an input gear to be driven by an input shaft. The input gear is engaged to drive a first driven gear on one radial side of a drive axis. The first gear drives at least a second driven gear on one radial side of the drive axis, with at least one accessory driven by one of the first and second driven gears. The second driven gear drives a bevel gear arrangement to drive a third driven gear on an opposed side of the drive axis. The third driven gear drives at least a second accessory. The accessories are associated with a gas turbine engine.

In an embodiment according to the previous embodiment, the first driven gear engages and drives an idler gear which in turn drives the second driven gear.

In an embodiment according to the previous embodiment, the first and second drive gears each drive an associated accessory.

In an embodiment according to the previous embodiment, at least one of the accessories is a starter for selectively driving the input gear.

In an embodiment according to the previous embodiment, the bevel gear arrangement includes a first bevel gear driven to rotate on one radial side. The first bevel gear drives a second bevel gear, and the second bevel gear drives a third bevel gear. The third bevel gear is on an opposed side of the drive axis, and with the first bevel gear being driven to rotate by the second driven gear, and the third bevel gear driving the third driven gear.

In an embodiment according to the previous embodiment, the second bevel gear is positioned on a remote side of a drive axis of the first and third bevel gears from the input gear.

In an embodiment according to the previous embodiment, the second bevel gear is positioned to be intermediate a drive axis of the first and third bevel gears and the input gear.

In an embodiment according to the previous embodiment, a gear fixed to rotate with the first bevel gear is driven by the second driven gear, and the third bevel gear is fixed to rotate with a gear that drives the third driven gear.

In an embodiment according to the previous embodiment, the gear fixed to rotate with the first bevel gear is directly driven by the second driven gear, and the gear fixed to rotate with the third bevel gear directly drives the third driven gear.

In an embodiment according to the previous embodiment, the third driven gear engages at least a fourth driven gear. The third and fourth driven gears are each associated to drive an accessory.

In an embodiment according to the previous embodiment, an outer diametric envelope of the input gear may be defined. The opposed side of the drive axis is outside the diametric envelope.

In an embodiment according to the previous embodiment, the input gear is a bevel gear driving a driven bevel gear associated with the first driven gear.

In another featured embodiment, a gas turbine engine has a compressor, a combustor and a turbine section. An accessory box has an input gear to be driven by an input shaft. The input gear is engaged to drive a first driven gear on one radial side of a drive axis of the input gear. The first gear drives at least a second driven gear on one radial side of the drive axis, with at least one accessory driven by one of the first and second driven gears. The second driven gear drives a bevel gear arrangement to drive a third driven gear on an opposed side of the drive axis of the input gear. The third driven gear drives at least a second accessory. The accessories are be associated with a gas turbine engine.

In an embodiment according to the previous embodiment, the bevel gear arrangement includes a first bevel gear driven to rotate on one radial side. The first bevel gear drives a second bevel gear, and the second bevel gear drives a third bevel gear, with the third bevel gear being on the opposed side of the drive axis. The first bevel gear is driven to rotate by the second driven gear, and the third bevel gear drives the third driven gear.

In an embodiment according to the previous embodiment, a gear fixed to rotate with the first bevel gear is driven by the second driven gear. The third bevel gear is fixed to rotate with a gear that drives the third driven gear.

In an embodiment according to the previous embodiment, the gear fixed to rotate with the first bevel gear is directly driven by the second driven gear, and the gear fixed to rotate with the third bevel gear directly drives the third driven gear.

In an embodiment according to the previous embodiment, an outer diametric envelope of the input gear may be defined. The opposed side of the drive axis is outside the diametric envelope.

In an embodiment according to the previous embodiment, accessories include at least a starter for selectively starting the gas turbine engine.

In an embodiment according to the previous embodiment, the accessories also include a generator for generating electricity from rotation of the turbine section.

In an embodiment according to the previous embodiment, the accessories also include a lube pump and a fuel pump for supplying lubrication and fuel to the gas turbine engine.

These and other features of this application will be best understood from the following specification and drawings, the following of which is a brief description.

DETAILED DESCRIPTION

A gas turbine engine10is illustrated inFIG. 1having a fan section20delivering air into a compressor section16, and for bypass air, as known. Air from the low pressure compressor section16passes into a high pressure compressor section26, and then into a combustor section30. From the combustor section30, products of combustion pass downstream over a high pressure turbine section28, and a low pressure turbine section18. A gear reduction17is shown transmitting rotation from a shaft driving the low pressure compressor16, and the fan section20, such that the two can rotate at different speeds relative to each other. While one exemplary gas turbine engine is illustrated in this Figure, the teachings of this application would extend to other gas turbine engines for any number of other applications and arrangements.

An accessory gearbox60is mounted to a case structure44generally parallel to the engine axis of rotation A. The accessory gearbox60may include accessory components such as an Air Turbine Starter (ATS), a deoiler (D), a hydraulic pump (HP), an oil pump (OP), an integrated drive generator (IDG), a permanent magnet alternator (PMA), a fuel pump module (FMP), and others. It should be understood, that any number and type of accessory components may alternatively or additionally be provided.

In theFIG. 1arrangement, a tower shaft is driven by the turbine shaft to drive a number of accessories.

FIG. 2shows an embodiment of an axial gearbox200wherein the tower shaft70drives a bevel gear72, which may be known as an input gear for purposes of this application. The bevel gear72engages another bevel gear74. The bevel gear74drives a gear75, and drives an accessory76. In fact, the accessory76may be a starter, which can alternatively be driven to drive the gear74, and hence the tower shaft70. It is known in the prior art that a starter can be arranged within such an accessory gearbox to selectively drive the tower shaft to start rotation of the turbines, fans, and compressors, and start the gas turbine engine.

The gear75may drive an idler gear78which in turn drives another gear79. Gear79may drive an accessory80, which may be an integrated drive generator for generating electricity from rotation of the turbine rotors.

A bevel gear82rotates with the gear79and engages another bevel gear84which drives an accessory, which may be lube pump shown at86. The bevel gear84in turn drives another bevel gear83which then drives a gear90, and drives an accessory88. The accessory88may be a fuel pump. The combination of the three bevel gears82,84,83“turns” the rotation from one side of a centerline C of the tower shaft70, across a diametrical envelope R of the bevel gear72, such that rotation is now transmitted back toward the tower shaft70by gear90being driven, and driving a gear92, which rotates with a gear94, which then ultimately drives a gear96. Gears92/94drive accessory98, which may be a permanent magnet alternator. Gear94drives gear96to drive accessory100, which may be a hydraulic pump.

The compound gears on each shaft (83/90or92/94, for example) allows a speed change between the rotation speed of the drive for the accessories driven by the associated drive shafts.

The overall arrangement of the drive that passes axially along one radial side of the tower shaft70, crosses the centerline of the tower shaft70, and then comes back axially toward the tower shaft70, results in a tighter axial dimension for the overall gearbox200. In this manner, the gearbox may be positioned in a smaller axial space, such that it is associated with cooler locations on the gas turbine engine, such as the compressor case.

FIG. 3shows an alternative embodiment300, wherein much of the accessory drive is common to theFIG. 2embodiment. However, the lube pump86is driven with a bevel gear112which is positioned to be axially closer to the tower shaft70then the bevel gear110that drives it, and the bevel gear114that it drives. That is, in theFIG. 2embodiment, the bevel gear84is on an opposed side of drive axes of the gears82and83relative to the tower shaft70, while in theFIG. 3embodiment, the bevel gear112is intermediate the drive axes of the gears110and114in the tower shaft70. While the bevel gears as all shown with their axes of rotation at right angles to each other, other arrangements may be utilized. All that is required is the use of the bevel gears allows the drives to cross the axis of rotation of the tower shaft, and move axially along in an opposed direction.