Patent Description:
In aircraft engines a generator can coupled to the engine to be driven by a spool shaft of the engine. There is always a need in the aerospace industry for improvements to drive shaft systems.

<CIT> discloses a generator having a disconnect mechanism.

<CIT> discloses a generator coupling for use with a gas turbine engine.

<CIT> discloses a connection for a generator in a gas turbine engine.

According to an aspect of the present invention, there is provided an aircraft drive shaft systemin accordance with claim <NUM>.

Optionally, the coupling includes 2n vertices corresponding to each vertex of each respective coupler mount. Each vertex of the coupling includes a bore operative to receive a fastener, such that the fastener extends through each respective bore of the coupling and corresponding coupler mount to fasten the respective coupler mount of the respective shaft to the coupling.

Optionally, the aircraft drive system includes a shaft drive having a front coupler mount at a second end of the shaft drive operative to fasten to the front coupler mount of the thru shaft operative to transmit torque from the shaft drive to the generator shaft through the thru shaft.

Optionally, a front coupling is included, where the front coupler mount of the shaft drive is fastened directly to the front coupling, and wherein the front coupler mount of the thru shaft is directly fastened to the front coupling.

Optionally, the shaft drive includes a splined section. In embodiments, a rotor is operatively connected to the generator shaft to rotate within a generator housing to generate electrical energy.

According to another aspect of the present invention, there is provided an aircraft system in accordance with claim <NUM>.

Optionally, a tail cone is included at an outlet of the turbine section, where the rotor and stator are mounted in the tail cone. In embodiments, the gas turbine engine can be selected from the group consisting of a turbojet, a turbofan, a turboprop, or a turboshaft.

Optionally, the spool shaft includes a front coupler mount at a second end of the spool shaft operative to fasten to the front coupler mount of the thru shaft operative to transmit torque from the spool shaft to the generator shaft through the thru shaft.

Optionally, the aircraft system further includes a front coupling, where the front coupler mount of the spool shaft is fastened directly to the front coupling, and the front coupler mount of the thru shaft is directly fastened to the front coupling.

According to another aspect of the present invention, there is provided an aircraft generator system in accordance with claim <NUM>.

Optionally, the generator system is integrally mounted in a tail cone of the gas turbine engine.

Optionally, the spool shaft is a low pressure turbine shaft of a dual spool gas turbine engine.

Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, an illustrative view of an embodiment of a system in accordance with the disclosure is shown in <FIG> and is designated generally by reference character <NUM>. Other embodiments and/or aspects of this disclosure are shown in <FIG>. Embodiments of the systems and methods provided herein can provide improved accommodation of misalignment of generator shafts for ease of installation and operation.

In aircraft engines, a generator can coupled to the engine to be driven by a spool shaft of the engine. Deflections between the fan shaft and generator shaft may arise due to tolerances and thermal defections which can result in excessive seal wear and coupler failure. One solution is to use a plastic coupler to isolate and allow angular mismatch between the shafts as well as axial deflections, but this can result in shaft shear based on deflection. The systems and methods provided herein provide improvements to drive systems for aircraft engine generators.

Referring to <FIG>, in accordance with at least one aspect of this disclosure, there is provided a drive shaft system <NUM>. In embodiments, the drive shaft system <NUM> includes a generator shaft <NUM> extending along a longitudinal axis A with a longitudinal bore <NUM> defined through the generator shaft <NUM>. A thru shaft <NUM> extends through the longitudinal bore <NUM> of the generator shaft <NUM>. In embodiments, the thru shaft <NUM> includes, a front coupler mount <NUM> at a first end <NUM> operative to receive torque input, and a rear coupler mount <NUM> at a second end <NUM> opposite the first end <NUM>.

The generator shaft <NUM> includes a rear coupler mount <NUM> at a second end <NUM> of the generator shaft configured to be coupled to the rear coupler mount <NUM> of the thru shaft <NUM> to transmit torque from the front coupler mount <NUM> of the thru shaft <NUM>, through the thru shaft <NUM>, and into the generator shaft <NUM>. A shaft drive <NUM> is operatively coupled to the thru shaft <NUM> on the first end <NUM> of the thru shaft <NUM> via a front coupler mount <NUM> at a second end <NUM> of the shaft drive <NUM> to transmit torque from the shaft drive <NUM> to the generator shaft <NUM> through the thru shaft <NUM>. The shaft drive <NUM> can be any suitable shaft drive, for example, the shaft drive <NUM> can be splined or include at least a splined section 120a.

A front end coupling <NUM> operatively connects the front coupler mount <NUM> of the shaft drive <NUM> to the front coupler mount <NUM> of the thru shaft <NUM>. A rear end coupling <NUM> operatively connects the rear coupler mount <NUM> of the thru shaft <NUM> to the rear coupler mount <NUM> of the generator shaft <NUM>. Each of the front coupler mounts <NUM>, <NUM> and the rear coupler mounts <NUM>, <NUM> are fastened directly to the respective coupling <NUM>, <NUM> such that there is no direct connection between the shaft drive <NUM> and the thru shaft <NUM> or between the thru shaft <NUM> and the generator shaft <NUM>.

Each of the front coupler mounts <NUM>, <NUM> and the rear coupler mounts <NUM>, <NUM> has n vertices (labeled V in <FIG>), wherein each vertex V includes a bore <NUM> operative to receive a fastener <NUM>. Each coupler mount can have any suitable shape and number n of vertices V, such as a triangular shape having three vertices (e.g. as shown n=<NUM>), or multiples thereof. In certain such embodiments, each coupling <NUM>, <NUM> thus can include 2n vertices corresponding to each vertex V of each respective coupler mount <NUM>, <NUM>, <NUM>, <NUM> (e.g. as shown, each coupling <NUM>, <NUM> therefore includes six vertices). Each vertex of the couplings <NUM>, <NUM> also includes a corresponding bore <NUM> operative to receive the fastener <NUM> to mount the respective coupler mounts <NUM>, <NUM>, <NUM>, <NUM> to the respective coupling <NUM>, <NUM>. When inserted, the fastener <NUM> extends through each respective bore <NUM> of the coupling <NUM>, <NUM> and corresponding coupler mount <NUM>, <NUM>, <NUM>, <NUM> to fasten the respective coupler mount <NUM>, <NUM>, <NUM>, <NUM> of the respective shaft <NUM>, <NUM>, <NUM> to the couplings <NUM>, <NUM>.

Referring now to <FIG>, in accordance with another aspect of this disclosure, there is provided an aircraft system <NUM>. For brevity, the description of common elements with respect to the drive system <NUM> that have been described above are not repeated. In certain embodiments, the drive system <NUM> as presented herein can be included in an aircraft <NUM> implementing the aircraft system <NUM>. In certain embodiments, the aircraft <NUM> can include an engine <NUM>, where the engine <NUM> can be a propulsive energy engine (e.g. creating thrust for the aircraft <NUM>), or a non-propulsive energy engine. As described herein, the engine <NUM> is a turbofan engine, although the present disclosure may likewise be used with other engine types, for example turbojet, turboprop, or turboshaft.

In embodiments, the gas turbine engine <NUM> includes a compressor section <NUM>, a turbine section <NUM>, and a spool shaft <NUM> operatively connecting the compressor section <NUM> to be driven by the turbine section <NUM> and the drive shaft system <NUM>. In the aircraft system <NUM>, the shaft drive <NUM> is the spool shaft <NUM> of the gas turbine engine <NUM>, such that the thru shaft <NUM> is operatively connected to the spool shaft <NUM> in any suitable manner as described herein (e.g. via coupler mounts <NUM>, <NUM>). In certain embodiments, the spool shaft <NUM> can be a low pressure turbine shaft of a dual spool gas turbine engine.

A rotor <NUM> is operatively connected to the generator shaft <NUM> to rotate within a generator housing <NUM> to generate electrical energy, and a stator <NUM> is operatively connected to the generator housing <NUM> radially outward of the rotor <NUM>. In certain embodiments, a tail cone <NUM> is included at an outlet <NUM> of the turbine section <NUM>, where the generator housing <NUM> and elements included therein (e.g. generator shaft <NUM>, rotor <NUM>, and stator <NUM>) are mounted in the tail cone <NUM>.

Turning now to <FIG>, in accordance with yet another aspect of this disclosure, there is provided a generator system <NUM>, for example for use in an aircraft engine <NUM>. For brevity, the description of common elements with respect to the drive system <NUM> and aircraft system <NUM> that have been described above are not repeated. In certain embodiments, the drive system <NUM> as shown and described herein can be included in the aircraft generator system <NUM> (e.g. as a tail cone generator). In certain embodiments of the generator system <NUM>, the thru shaft <NUM> is operatively connected to the spool shaft <NUM> of a gas turbine engine <NUM> on a first end <NUM>, and the thru shaft <NUM> is operatively connected to the generator shaft <NUM> on a second end <NUM>, so that the generator shaft <NUM> is driven by the spool shaft <NUM> through the thru shaft <NUM>. It is noted that for clarity purposes, the rotor <NUM> and stator <NUM> are omitted from <FIG>. A generator end cap <NUM> can be fastened to the generator housing <NUM> for covering the rear end coupling <NUM> during operation.

In accordance with another aspect of this disclosure, there is provided a method of assembling the generator system <NUM> into an aircraft engine (e.g. engine <NUM>). The method includes mounting the front coupling <NUM> to the spool shaft <NUM> (e.g. via front coupler mount <NUM>), mounting the first end <NUM> of the thru shaft <NUM> to the front coupling <NUM> (e.g. via front coupler mount <NUM>), and assembling the generator housing <NUM> around the thru shaft <NUM> and spool shaft <NUM>. The method can next include mounting the rear coupling <NUM> to the second end <NUM> of the thru shaft <NUM> (e.g. via rear coupler mount <NUM>), mounting the rear coupling <NUM> to the second end <NUM> of the generator shaft <NUM> (e.g. via rear coupler mount <NUM>), and mounting the rear cover <NUM> to the generator housing <NUM>.

Assembly of the generator system <NUM> to the engine <NUM> in such a manner allows for improved assembly over previous systems and methods in that there is no blind assembly of a long shaft into its mating feature, for example how a typical low pressure spool shaft may be done. Without blind assembly, assembly can be made easier, assembly mistakes can be avoided, as well as damage to parts during assembly may be prevented.

In embodiments (e.g. as shown in <FIG> ), by driving the generator with a thru shaft, the pivot point of the thru shaft can be moved away from the spool shaft coupler (e.g. front end coupling). Increasing the distance between the spool shaft coupler and the thru shaft pivot point can therefore reduce the influence of shaft offset and thermal deflections on the angularity between the two shafts and the amount of misalignment the coupler has to compensate for. The front and rear end couplings can also compensate for any axial movement due to thermal influence.

Embodiments can be advantageous over typical generator shafts by reducing the risk of spool shaft/generator dynamic instability, which in some instances may impact engine vibrations level and/or durability degradation of engine seals/coupling and/or the generator over time. Moreover, in embodiments, the thru shaft can also allow the generator to be moved forward (e.g. closer to the turbine section in a tail cone generator) which can reduce the overhung mass and subsequently the loading on the engine mounts and overall engine structure.

Claim 1:
An aircraft drive shaft system (<NUM>) comprising:
a generator shaft (<NUM>) extending along a longitudinal axis (A) with a longitudinal bore (<NUM>) defined through the generator shaft (<NUM>);
a thru shaft (<NUM>) extending through the longitudinal bore (<NUM>) of the generator shaft (<NUM>), the thru shaft (<NUM>) having:
a front coupler mount (<NUM>) at a first end (<NUM>) of the thru shaft (<NUM>) operative to receive torque input; and
a rear coupler mount (<NUM>) at a second end (<NUM>) of the thru shaft (<NUM>) opposite the first end (<NUM>), wherein the generator shaft (<NUM>) includes a rear coupler mount (<NUM>) at a second end (<NUM>) of the generator shaft (<NUM>) that is coupled to the rear coupler mount (<NUM>) of the thru shaft (<NUM>) operative to transmit torque from the front coupler mount (<NUM>) of the thru shaft (<NUM>), through the thru shaft (<NUM>), and into the generator shaft (<NUM>); and
a coupling (<NUM>), wherein the rear coupler mount (<NUM>) of the thru shaft (<NUM>) is fastened directly to the coupling (<NUM>), and wherein the rear coupler mount (<NUM>) of the generator shaft (<NUM>) is fastened directly to the coupling (<NUM>),
characterised in that:
each of the front coupler mount (<NUM>) of the thru shaft (<NUM>) and the rear coupler mount (<NUM>, <NUM>) of each of the thru shaft (<NUM>) and the generator shaft (<NUM>) has n vertices (V),
wherein each vertex (V) includes a bore (<NUM>) operative to receive a fastener (<NUM>).