Interconnect drive system

An interconnect drive system for an aircraft has a driveline and clutch control system. The driveline comprises a shaft for each propulsion assembly, each shaft for transferring torque to and from the associated propulsion assembly, and a clutch operably coupling the shafts and configured for selective engagement. The clutch is capable of transferring a first amount of torque between the shafts while engaged and a second amount of torque between the shafts while disengaged. The system also has a clutch control system, comprising a computer operably connected to the clutch for controlling operation of the clutch and sensors for sensing torque applied to the driveline, output from the sensors being communicated to the computer. The computer commands operation of the clutch in response to the output from the sensors, the clutch being commanded to disengage to relieve a transient torque imbalance in the driveline.

BACKGROUND

Tiltrotor aircraft, such as the Bell Boeing V-22 Osprey and Bell V-280 Valor, have proprotors on opposing sides of the aircraft that are selectively pivotable between a vertical orientation for rotor-borne flight (helicopter mode) and a horizontal orientation for wing-borne flight (airplane mode). Typically, each proprotor is driven in rotation by an associated propulsion assembly, comprising an engine, a gearbox, and a transmission. The transmissions of the propulsion assemblies are connected with an interconnect driveshaft to allow the engine of one propulsion assembly to drive rotation of both proprotors, thus providing redundancy and allowing for continued flight if the engine of either propulsion assembly becomes inoperative.

DETAILED DESCRIPTION

This disclosure divulges an interconnect drive system configured to minimize flight-maneuver-induced loads in an interconnect driveline that couples multiple proprotors of a tiltrotor aircraft. However, this drive system may be configured for use with other types of aircraft having an interconnect driveline operably coupling multiple rotors or propellers.

FIG. 1illustrates tiltrotor aircraft11having an interconnect drive system according to this disclosure,FIG. 2illustrates a portion of the system, andFIG. 3schematically illustrates the system.

Referring toFIGS. 1 and 2, aircraft11comprises fuselage13, wing15, and tail section17. An electronic flight-control system19is shown located in fuselage13. Nacelles21,23are each pivotally mounted on opposing sides of fuselage13and, in this embodiment, on opposing ends of wing15. Nacelle21houses propulsion assembly25, and nacelle23houses propulsion assembly27, each propulsion assembly25,27comprising an engine29, a gearbox31, and a transmission33. Gearbox31is configured for transferring torque from the associated engine29to a mast35for rotating an attached proprotor39, each proprotor39being an assembly having multiple blades41. Each mast35also transfers torque to the associated transmission33. Each nacelle21,23is pivotable relative to wing15for selectively moving propulsion assemblies25,27and proprotors39between a vertical orientation in helicopter mode and a horizontal orientation in airplane mode. All propulsion assemblies according to this disclosure may alternatively be configured with electric motors to produce torque for driving proprotors39, and electric versions may eliminate some components, such as, for example, gearbox31.

Transmissions33are operably connected to each other by an interconnect driveline43, comprising driveshafts45,47,49, mid-wing gearbox51, and clutch53. Interconnect driveline43is configured to transmit engine torque from transmission33of one of propulsion assemblies25,27to transmission33of the other propulsion assembly25,27, allowing one engine29to drive both proprotors39for continued flight during one-engine inoperative conditions. Torque transmitted by driveline43through mid-wing gearbox51also supplies power to operate auxiliary systems. In this embodiment, clutch53is positioned between driveshaft45and driveshaft47for operably coupling propulsion assembly25to mid-wing gearbox51, although clutch53could alternatively be positioned in driveline43between propulsion assembly27and mid-wing gearbox51.

In addition to transferring torque from engines29, interconnect driveline43directly couples proprotors39for maintaining a selected phasing of proprotors39relative to each other. As shown and described in the '004 application, clutch53may be used to asymmetrically index, or “phase,” proprotors39for minimizing vibrations during operation of propulsion assemblies25,27. As they counterrotate in airplane-mode flight, proprotors39may be phased relative to each other to an asymmetric, out-of-phase positioning or returned to symmetric, in-phase positioning. This is described in the '004 application as being accomplished by disengaging clutch53for a predetermined amount of time to achieve a selected phasing angle, which is preferably, for example, 0 degrees or 60 degrees for three-blade proprotors39, 0 degrees or 45 degrees for four-blade proprotors (not shown), etc. An out-of-phase positioning causes each blade41of one of proprotors39to pass fuselage13at a different time than each blade41of the other proprotor39passes fuselage13.

During flight of aircraft11, transient torque, or “cross-talk,” may be experienced from one proprotor39to the other proprotor39due to certain maneuvers, such as, for example, turns. These maneuvers can cause forces on proprotors39that would cause one proprotor39to rotate faster than the other proprotor39, but this is prevented by proprotors39being connected to each other by interconnect driveline43and forced to turn at a synchronous rotational speed. When these transient forces are encountered, a torque imbalance exists within driveline43between assemblies25,27, and significant torsional loads can be imparted on proprotors39, mast35, transmissions33, and interconnect driveline43, including spring-like torsional reactions in driveline43. This requires components to be designed to handle these high loads, which are in addition to those normally experienced at maximum continuous power, and this typically requires components to have a larger size, higher mass, or both. The interconnect drive systems according to this disclosure are configured to reduce the load and torque experienced by interconnect drivelines, allowing the components to be designed for lower torsional load levels.

Referring now also toFIG. 3, a schematic illustration of interconnect drive system55of aircraft11is shown. Drive system55couples propulsion assemblies25,27and comprises driveline43and a clutch control system57.

As shown and described above, driveline43operably couples transmissions33of propulsion assemblies25,27through driveshafts45,47,49, mid-wing gearbox51, and clutch53. Clutch53is a selectively engaged coupling between driveshafts45and47, with clutch53coupling driveshafts45,47when engaged. All clutches in this disclosure can be one or a combination of several types, such as, for example, non-slip friction clutches (with dry or wet friction materials), slipper friction clutches, and positive engagement clutches (with interlocking components when engaged). Clutches according to this disclosure may also include a ratchet system. In addition, all clutches in this disclosure can be operated by one or a combination of pneumatic, hydraulic, or electromechanical systems and configured to have one or multiple plates or other coupling components. For example, clutch53may be a dry, slipper friction clutch that, while engaged and capable of continuously transferring torque, passively allows for a limited amount of slipping to occur between driveshafts45,47when a selected transient torque load is exceeded. All clutches of this disclosure are preferably configured to fail to engagement (i.e., remain engaged after failure or move to engagement after failure), ensuring that the propulsion assemblies remain coupled together for providing proper phasing and continued flight.

Clutch control system57is an electronic system for operating clutch53in response to measured or calculated transient torque values. In the embodiment shown, system57comprises at least an electronic computer59, torque/load sensors61, and attitude/motion sensors63. Data connection65provides for data transmission between sensors61and computer59and data connection67provides for data transmission between sensors63and computer59, data connections65,67allowing for measured values to be communicated to computer59and for computer59to operate sensors61,63. Data connection69provides for data transmission between computer59and clutch53of driveline43, allowing computer59to send commands for operation of clutch53and to receive data communications from clutch53. All data connections according to this disclosure can be wired or wireless. Computer59may be a standalone device or may be an integral component of flight control system19(FIG. 1). Torque/load sensors61may be, for example, strain gauges affixed to one or more of driveshafts45,47,49or torque sensor components installed between components of driveline43. Attitude/motion sensors63may be, for example, one or more of a combination of gyroscopes, accelerometers, inertial guidance components, or similar devices for determining the attitude and motion of aircraft11.

During flight, engine29of each propulsion assembly25,27produces torque that is transferred to the associated mast35through gearbox31. This torque is also transferred from transmission33of assembly25into driveshaft45and from transmission33of assembly27into driveshaft49. During ideal operating conditions, the torque output in driveshafts45,49is substantially balanced and proprotors39are continuously symmetrically indexed, at 0 degrees blade offset, or continuously phased relative to each other, for example, at 60 degrees out-of-phase. However, when one of proprotors39experiences a transient torque that would cause that proprotor39to turn faster, that torque is transferred through driveline43to the other proprotor39and would cause the other proprotor39to also turn faster. Due to mechanical, mass, and aerodynamic properties opposing the acceleration of the other proprotor39, the net result is a high torque experienced by driveline43and components of propulsion assemblies25,27. Without a system to alleviate at least some of this torque imbalance, the propulsion assemblies25,27and driveline43must be designed to accommodate these additional transient loads, resulting in a heavier and more costly aircraft11. Limiting the transient torque loads within driveline43may allow driveline43to be designed for smaller loads and result in a lighter and less expensive aircraft11.

When flight maneuvers induce a transient torque on one of proprotors39, as measured by torque/load sensors61, or is expected to induce a transient torque, as calculated by computer59based on data from attitude/motion sensors63, clutch53permits faster rotation of one of proprotors39relative to the other proprotor39to lessen the transient torque transmitted through driveline43. This is accomplished by allowing driveshafts45,47, which normally rotate at the same speed, to rotate relative to each other about their axis of rotation as driveshafts45,47continue to rotate. As driveshaft47is coupled to driveshaft49through mid-wing gearbox51, this allows for rotation of driveshafts45,49relative to each other and phasing of proprotors39. This relative rotation occurs at clutch53by allowing a “break” in driveline43, and this may occur as limited, passive slippage between friction components or through active disengagement of clutch53as commanded by computer59. As used herein, “disengagement” is a separation of coupling components within clutch53or allowing slippage by reducing the pressure applied to friction components within clutch53. The allowed amount of relative rotation of driveshafts45,47will be based on the amount and duration of the transient torque, and this is unlike the predetermined relative rotation of driveshafts45,47when using clutch53to phase proprotors39by a selected angle solely for vibration attenuation, as described in the '004 application.

When the transient torque experienced by a proprotor39has subsided below a selected level and driveshafts45,47are again rotating together with no relative motion, proprotors39will likely be at an undesired phase angle relative to each other. In order to return proprotors39to a desired phasing, clutch53will be commanded by computer59to disengage to cause a break in driveline43until proprotors39re-index to the desired phasing. The current rotational position and rotational speed of each proprotor39will be communicated to computer59from position sensors (not shown) for each proprotor39or each mast35, allowing computer59to calculate the required duration of the disengagement of clutch53and providing a feedback loop for phase adjustment. A ratcheting mechanism may be used in clutch53to allow relative rotation of driveshafts45,47in only one direction.

FIG. 4is a schematic illustration of an alternative embodiment of an interconnect drive system according to this disclosure. System71is configured for use with aircraft11for coupling propulsion assemblies25,27. System71is similar to system55, as shown and described above, and comprises an interconnect driveline73and clutch control system57. Driveline73comprises the components of driveline43, with the exception of driveshaft49being replaced by a second clutch75and driveshafts77,79that operably couple propulsion assembly27to mid-wing gearbox51. Driveshaft77couples clutch75to gearbox51, and driveshaft79couples clutch75to transmission33(not shown) of propulsion assembly27. A wired or wireless data connection81provides for data transmission between computer59and clutch75, and data connections69,81allow computer59to communicate commands for operation of clutches53,75and to receive data communications from clutch53,75. Similarly to the operation of system55, during operation of interconnect drive system71, one or both of clutches53,75may passively slip or be commanded to disengage in response to a transient torque on one of proprotors39, as measured by torque/load sensors61, or a transient torque-causing event, as calculated by computer59based on data from attitude/motion sensors63. One or both of clutches53,75can be disengaged to permit faster rotation of one of proprotors39relative to the other proprotor39for lessening the transient torque transmitted through driveline73. This is accomplished by allowing driveshafts45,47to rotate relative to each other and/or allowing driveshafts77,79to rotate relative to each other in the manner described above. Clutches53,75are preferably disengaged one at a time, which is all that is required to create a break in driveline73. Though clutches53,75may be disengaged simultaneously, it is preferred that at least a slip coupling is maintained in at least one clutch53,75to provide for torque to be continuously transferred to mid-wing gearbox51. Clutches53,75may be operated in an equal or unequal alternating basis, though one of clutches53,75may be designated as primary and the other clutch53,75designated as backup, with the primary clutch53,75being used exclusively until specified operating conditions are exceeded (e.g., excessive heat buildup), routine maintenance is required, or disengagement components fail. As noted above, clutches53,75are configured to fail to engagement.

FIGS. 5 and 7illustrate tiltrotor aircraft, each comprising an alternative embodiment of an interconnect drive system according to this disclosure. The systems are shown schematically for these aircraft, respectively, inFIGS. 6 and 8.

Referring now toFIGS. 5 and 6, a quad-tiltrotor aircraft83(QTR) comprises fuselage85, forward wing87, and aft wing89. Propulsion assemblies91,93are pivotally mounted at opposing ends of forward wing87, and propulsion assemblies95,97are pivotally mounted at opposing ends of aft wing89, each propulsion assembly91,93,95,97having similar components as, and being configured similarly to, propulsion assemblies25,27of aircraft11. As described above for propulsion assemblies25,27, propulsion assemblies91,93,95,97are each configured for driving an attached proprotor (not shown) in rotation.

An interconnect driveline99operably couples transmissions of propulsion assemblies91,93,95,97for allowing torque transfer between assemblies91,93,95,97and for maintaining a selected relative phasing of the proprotors of aircraft83. A forward portion of driveline99is located within wing87and comprises driveshafts101,103,105, mid-wing gearbox107, mid-wing transmission109, and clutch111. Driveshaft101couples propulsion assembly91to clutch111, driveshaft103couples clutch111to gearbox107(which is directly coupled to transmission109), and driveshaft105couples propulsion assembly93to transmission109. An aft portion of driveline99is located within wing89and comprises driveshafts113,115,117, mid-wing gearbox119, mid-wing transmission121, and clutch123. Driveshaft113couples propulsion assembly95to clutch123, driveshaft115couples clutch123to gearbox119(which is directly coupled to transmission121), and driveshaft117couples propulsion assembly97to transmission121. A driveshaft125extends longitudinally between wings87,89and couples transmissions109,121, thereby providing a torque path from each of propulsion assemblies91,93,95,97to all other assemblies91,93,95,97. Though shown configured for a QTR, interconnect driveline99can be modified for use with aircraft having additional wings and/or propulsion assemblies.

FIG. 6is a schematic illustration of interconnect drive system127, comprising interconnect driveline99and clutch control system57(as shown and described above for systems55,71). A wired or wireless data connection129provides for data transmission between computer59(not shown) of system57and clutch111, and wired or wireless data connection131provides for data transmission between computer59and clutch123. As described above for systems55,71, data connections129,131allow computer59to communicate commands for operation of clutches111,123and to receive data communications from clutch111,123. One or both of clutches111,123may passively slip or be commanded to disengage in response to transient torque on one of the proprotors of aircraft83, as measured by torque/load sensors61, or to a maneuver calculated, based on data from attitude/motion sensors63, by computer59to cause a transient torque imbalance. Clutch111allows for the proprotor of one of propulsion assemblies91,93to rotate faster than the proprotor of the other propulsion assembly91,93by allowing driveshafts101,103to rotate relative to each other in the manner described above. Clutch123allows for the proprotor of one of propulsion assemblies95,97to rotate faster than the proprotor of the other propulsion assembly95,97by allowing driveshafts113,115to rotate relative to each other in the manner described above. It should be noted that this configuration does not provide for a break in the torque path between propulsion assemblies93,97, though assemblies93,97will likely encounter similar transient-torque events due to being on the same side of aircraft83. Clutches111,123may be disengaged simultaneously, as propulsion assemblies93,97are always coupled to mid-wing gearboxes107,119. As shown in broken lines in the figure, optional components include additional forward clutch133coupling propulsion assembly93to mid-wing transmission109, additional aft clutch135coupling propulsion assembly97to mid-wing transmission121, and central clutch137coupling transmissions109,121to each other. Optional data connections139,141,143are used to provide data communication between computer59and clutches133,135,137, respectively. Clutches111,123,133,135,137may be operated separately or in any combination to achieve the result of driving proprotors associated with propulsion systems91,93,95,97while allowing for phasing of the proprotors to alleviate loads in driveline99caused by transient torque experienced by the proprotors during flight.

Referring now toFIGS. 7 and 8, a tiltrotor aircraft145comprises fuselage147, wing149, and tail section151. Propulsion assemblies152,153(not visible inFIG. 7) are mounted at opposing ends of wing149, each assembly152,153comprising similar components to propulsion assemblies25,27of aircraft11and described above. However, the engine and gearbox (not visible) of each assembly152,153are carried in a fixed nacelle155,157, with only an associated mast (not visible) and attached proprotor159pivoting together on an associated pylon161,163relative to wing149. A pusher propeller165is mounted at the aft end of fuselage147for providing additional longitudinal thrust.

As shown in the schematic view ofFIG. 8, an interconnect drive system167comprises interconnect driveline169and clutch control system57(as shown and described above for systems55,71,127). Driveline169operably couples the transmissions of propulsion assemblies152,153for allowing torque transfer between assemblies152,153and propeller165and also for maintaining a selected relative phasing of proprotors159. Driveline169comprises driveshafts171,173,175,177, mid-wing gearbox179, mid-wing transmission181, and clutch183. Driveshaft171couples propulsion assembly152to clutch183, driveshaft173couples clutch183to gearbox179(which is directly coupled to transmission181), and driveshaft175couples propulsion assembly153to transmission181. Driveshaft177extends longitudinally and couples mid-wing transmission181to propeller165, thereby providing a torque path from each one of propulsion assemblies152,153to the other assembly152,153and to propeller165.

A wired or wireless data connection185provides for data transmission between computer59(not shown) of system57and clutch183. As described above for systems55,71,127, data connection185allows computer59to communicate commands for operation of clutches183and to receive data communications from clutch183. As shown in broken lines in the figure, optional components include additional forward clutch187coupling propulsion assembly153to mid-wing transmission181and central clutch189coupling transmissions181to propeller165. Optional data connections191,193are used to provide data communication between computer59and clutches187,189, respectively. Clutches183,187,189may be operated separately or in any combination to achieve the result of driving proprotors of propulsion assemblies152,153while allowing for phasing of the proprotors to alleviate an imbalance of torque loads in driveline169caused by transient torque experienced by the proprotors during flight.

Although in the foregoing illustrations, the clutch has been shown and described as a separate component, in some embodiments, one or more clutches may be incorporated into a mid-wing gearbox, a mid-wing transmission, or a transmission of a propulsion assembly.