Bearing assembly

A gear box includes a housing, an actuator coupled to the housing, and a bearing assembly pivotably coupled to the actuator. The bearing assembly including an outer raceway, a cylindrical housing positioned within the outer raceway, and an annular bearing positioned between the outer raceway and the housing. The cylindrical housing has a first end and a second end opposite the first end. A sensor is coupled to the first end of the cylindrical housing and configured to monitor an operating condition of the annular bearing. A linkage couples the actuator to the second end of the cylindrical housing and an output shaft is rotatably coupled to the bearing assembly.

BACKGROUND

Exemplary embodiments relate to the art of rotary wing aircraft, and more particularly, to a sensor for detecting a failure of a bearing in a tail rotor assembly.

In a typical rotary wing aircraft, such as a helicopter for example, a tail rotor system converts tail driveshaft rotary power into the aerodynamic forces necessary to control the direction of flight and to counteract main rotor torque. However, component failures can cause additional torque to be introduced into the helicopter's mechanical system. The added torque can damage system components at unpredictable points in the system.

SUMMARY

In one aspect, the disclosure provides a gear box comprising a housing, an actuator coupled to the housing, and a bearing assembly pivotably coupled to the actuator. The bearing assembly including an outer raceway, a cylindrical housing positioned within the outer raceway, the cylindrical housing having a first end and a second end opposite the first end, an annular bearing positioned between the outer raceway and the housing, a sensor coupled to the first end of the cylindrical housing, the sensor configured to monitor an operating condition of the annular bearing, and a linkage coupling the actuator to the second end of the cylindrical housing. An output shaft rotatably coupled to the bearing assembly.

In another aspect, the disclosure provides a bearing assembly for a gear box of an aircraft. The bearing assembly comprising an outer raceway, a housing positioned within the outer raceway, the housing having first end face and a second end face opposite the first end face, an annular bearing positioned between the outer raceway and the housing, and a sensor coupled to the first end face of the housing, the sensor configured to monitor an operating condition of the annular bearing.

In another aspect, the disclosure provides a gear box comprising a housing, an actuator coupled to the housing, a linkage having a first end pivotably coupled to the actuator and a second end opposite the first end, and a bearing assembly coupled to the second end of the linkage. The bearing assembly including an outer raceway, a cylindrical housing positioned within the outer raceway, an aperture formed in an end of the cylindrical housing, and an annular bearing positioned between the outer raceway and the housing. An output shaft coupled to the bearing assembly. The second end of the linkage is positioned within the aperture and pivotably coupled to the cylindrical housing.

DETAILED DESCRIPTION

Before any embodiments are explained in detail, it is to be understood that the disclosure is not intended to be limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. Embodiments are capable of other configurations and of being practiced or of being carried out in various ways.

A plurality of hardware and software-based devices, as well as a plurality of different structural components may be used to implement various embodiments. In addition, embodiments may include hardware, software, and electronic components or modules that, for purposes of discussion, may be illustrated and described as if most of the components were implemented solely in hardware. However, one of ordinary skill in the art, and based on a reading of this detailed description, would recognize that, in at least one embodiment, the electronic based aspects of the invention may be implemented in software (for example, stored on non-transitory computer-readable medium) executable by one or more electronic processors. For example, “control units” and “controllers” described in the specification can include one or more electronic processors, one or more memory modules including non-transitory computer-readable medium, one or more input/output interfaces, one or more application specific integrated circuits (ASICs), and various connections (for example, a system bus) connecting the various components.

It also should be understood that although certain drawings illustrate hardware and software located within particular devices, these depictions are for illustrative purposes only. In some embodiments, the illustrated components may be combined or divided into separate software, firmware and/or hardware. For example, instead of being located within and performed by a single electronic processor, logic and processing may be distributed among multiple electronic processors. Regardless of how they are combined or divided, hardware and software components may be located on the same computing device or may be distributed among different computing devices connected by one or more networks or other suitable communication links.

Referring now to the figures,FIG.1illustrates a rotary wing aircraft10according to some embodiments. The aircraft10includes an airframe12with an extending tail14, which mounts a tail rotor assembly16. The aircraft10includes a main rotor assembly18that rotates about an axis A through a main rotor gearbox20by one or more engines22. The airframe12includes a cockpit15having one or more seats for flight crew (e.g., pilot and co-pilot) and optional passengers.

The engines22generate the power available for flight operations and couple such power is transmitted to the main rotor assembly18and the tail rotor assembly16through the main rotor gearbox20. The main rotor assembly18includes a plurality of rotor blades28supported by a rotor hub32. Although a particular helicopter configuration is illustrated and described in the disclosed embodiment, other configurations and/or machines, such as high speed compound rotary-wing aircraft with supplemental translational thrust systems, dual contra-rotating, coaxial rotor system aircraft, turbo-props, tilt-rotors tilt-wing aircraft and non-aircraft applications such as wind turbines or any application with a critical bearing of the configuration described herein will also benefit here from.

The tail rotor assembly16includes a plurality of tail rotor blades36located at the extending tail14and converts the tail driveshaft rotary power into aerodynamic forces necessary to control the direction of flight of the aircraft10. Similarly, in some embodiments, the propeller blades36may be mounted in a static configuration with respect to the aircraft10as illustrated inFIG.1. However, in other embodiments, the tail rotor blades36may have a variable position, which allows the tail rotor blades36to provide yaw control in addition to translational thrust. Also, in some embodiments, the aircraft10may include more than one sets of propeller blades36, such as, for example, one positioned on the back left of the aircraft10and one positioned on the back right of the aircraft10.

With reference toFIG.2, a tail rotor gear box40is operably coupled to the tail rotor assembly16. The tail rotor assembly16provides a mounting point for the tail rotor blades36(schematically illustrated inFIG.2) and for a blade pitch change mechanism42. The gear box40includes a housing44, a first shaft or actuator52(e.g., a hydraulic actuated servo) statically mounted to the housing44, a bearing assembly56pivotably coupled to the actuator52by a linkage64(e.g., at a clevis), and a rotating output shaft60coupled to the bearing assembly56. The actuator52is connected to the output shaft60of the tail rotor assembly16through the bearing assembly56that allows the output shaft60to rotate about a longitudinal axis68while the actuator52extends and retracts only and does not spin.

For example, when the actuator52moves the adjustment shaft66inboard, a pitch walking beam and pitch change control links69(schematically illustrated together inFIG.2) associated with each of the tail rotor blades36twist the tail rotor blades36about internal elastomeric bearings (not shown) to increase blade pitch. Conversely, when the actuator52moves the adjustment shaft66outboard, the pitch walking beam and pitch change control links associated with each of the tail rotor blades36twist the tail rotor blades36about the internal elastomeric bearings to decrease blade pitch. An increase in blade pitch will turn the aircraft10to the left and a decrease in pitch will turn the aircraft10to the right.

The adjustment shaft66also rotates with and moves linearly within the output shaft60. The bearing assembly56supports the adjustment shaft66within the output shaft60and allows the adjustment shaft66and the output shaft60to rotate independently of the actuator52. As will be described below, an outer raceway84of the bearing assembly56rotates with the adjustment shaft66and output shaft60, while an inner raceway is non-rotating and coupled to the actuator52by way of the linkage64and thereby moves linearly with the actuator52.

As also illustrated inFIG.1, the aircraft10includes an electronic controller70. The electronic controller70includes a plurality of electrical and electronic components that provide power, operation control, and protection to the components and modules within the electronic controller70. The electronic controller70can include an electronic processor72(such as a programmable electronic microprocessor or similar device) that executes software to control operation of the main rotor assembly18and the tail rotor assembly16. In the example illustrated inFIG.1, the electronic controller70also includes memory74(for example, non-transitory, machine-readable memory, such as, for example, a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a ROM, a programmable read-only memory (PROM), an EEPROM, an erasable programmable read-only memory (EPROM), and a Flash memory) and an input-output interface76.

The electronic processor72is communicatively connected to the memory74and the input-output interface76. In some embodiments, the memory74stores software75executable by the electronic processor72to perform the control functionality and associated methods described herein. It should be understood that the electronic controller70can include other components, and the configuration illustrated inFIG.1is provided as one example. For example, in some embodiments, the electronic controller70includes one or more for example, microprocessors, digital signal processors, customized processors and field programmable gate arrays (FPGAs) and unique stored program instructions (including both software and firmware) that control the one or more processors to implement, in conjunction with certain non-processor circuits, the functionality described herein or a portion thereof. Alternatively, the functionality described herein, or a portion thereof, could be implemented by a state machine that has no stored program instructions, or in one or more application specific integrated circuits (ASICs), in which functionality is implemented as custom logic. Of course, a combination of the two approaches could be used.

The bearing assembly56also includes a sensor80(schematically illustrated inFIGS.1and4-6). The sensor80generates a signal representing an operating condition (e.g., vibration, temperature, or the like) of the bearing assembly56and transmits the signal to the electronic controller70(directly or indirectly). Further, since the bearing assembly56is isolated from any oil sump of the gear box40, the sensor80may be coupled to the controller70through a wired connection. The electronic controller70receives such signals via the input-output interface76and these signals can be used as part of the control functionality performed by the electronic processor72(through execution of the software75). These received signals (or data derived therefrom) can also be stored in the memory74. The interface76may provide a message to the operator indicating a defect (e.g., failure or near failure) of the bearing assembly56. For example, the controller70may be configured to detect a first threshold of the operating condition corresponding to a first state of the bearing assembly56and a second threshold of the operating condition corresponding to a second state of the bearing assembly56. When the controller70detects the first threshold, the processor72may initiate a message to alert the operator that maintenance of the bearing assembly56is required, but the aircraft10can still be operated for a predetermined amount of time (e.g., to allow the operator to get to a service center). When the controller70detects the second threshold, the processor72may initiate a message to alert the operator that replacement of the bearing assembly56is required while also restricting operation of the aircraft10.

Now with reference toFIGS.3-6, the bearing assembly56includes an outer housing or outer raceway84, a cylindrical housing88positioned within the outer raceway84, and an annular bearing92(e.g., an annular duplex ball bearing) (FIG.4) positioned between the outer raceway84and the cylindrical housing88. The bearing assembly56also includes a sleeve94mounted on an outer diameter of the cylindrical housing88, which is secured to the cylinder housing88by a securing member95(e.g., a nut, a compression member, etc.). The sleeve94engages a shoulder96of the cylindrical housing88and preloads the annular bearing92in between the outer raceway84and the cylindrical housing88. An outer diameter of the cylindrical housing88or the sleeve94may define the inner raceway of the bearing assembly56. The output shaft60and the adjustment shaft66surrounds the cylindrical housing88and are coupled to the outer raceway84of the bearing assembly56. In the illustrated embodiment, the shoulder96is positioned proximate a first end (e.g., left end from the reference point ofFIG.6) of the outer raceway84.

In other embodiments, the shoulder96may be formed in the cylindrical housing88proximate a second end (e.g., right end from the reference point ofFIG.6) of the outer raceway84. Moving the shoulder96proximate the second end allows more room for seals and ball races to be properly located. In addition, the shoulder96may have a larger contact area when the shoulder96is located proximate the second end, which increases a load capacity of the bearing assembly56. In addition, extension forces from the actuator52(e.g., from a right-side of the bearing assembly56with reference toFIG.4) on the bearing assembly56reacts against the shoulder96and retraction forces (from a left-side of the bearing assembly56with reference toFIG.4) from the actuator52causes the sleeve94to react against the securing member95.

As shown inFIGS.4and6, the linkage64further includes a first end100pivotably coupled to the actuator52via a fastener102and a second end104pivotably coupled to the cylindrical housing88of the bearing assembly56via a second fastener106. In the illustrated embodiment, a first bearing108(e.g., a first spherical pivot bearing) is positioned adjacent the first end100of the linkage64and a second bearing112(e.g., a second spherical pivot bearing) is spaced from the first bearing108and positioned adjacent the second end104. The first and second bearings108,112enable the bearing assembly56to adapt or self-align when there is an offset between the actuator52and the output shaft60in response to movement of the actuator52. The self-alignment of the bearing assembly56reduces significant moment loading of the annular bearing92.

With reference toFIGS.4-6, a first aperture116is formed in a first end of the cylindrical housing88and a second aperture120is formed in a second end of the cylindrical housing88. The first aperture116extends partially along the length of the cylindrical housing88and is sized to receive the sensor80. The sensor80may be press fit into the aperture116, threaded or the like. It should be appreciated that the sensor80is coupled to the first end of the cylindrical housing88. The construction of the aperture116allows the sensor80to be positioned proximate the annular bearing92to detect an operating condition (e.g., vibration, temperature, or the like) of the annular bearing92. In addition, the second spherical pivot bearing112is positioned approximately centrally within the outer raceway84, which allows the sensor80to positioned proximate the outer raceway84without the linkage passing through or beyond the outer raceway84. The position of the second spherical pivot bearing112ensures the second spherical pivot bearing112and the sensor80are within a load zone of the bearing assembly56. In particular, positioning the sensor80proximate the load zone to detect overheating or vibration of the annular bearing92.

Now with reference toFIGS.5and7, the cylindrical housing88further includes a wire passage124in communication with the first aperture116. In other words, the wire passage124is formed in the first end of the cylindrical housing88and extends through the cylindrical housing88to the second end. The wire passage124provides space for a wired connection between the sensor80and the controller70(FIG.1). In the illustrated embodiment, the aperture116is parallel to a longitudinal axis126of the cylindrical housing88and the wire passage124extends at an angle relative to the aperture116and the longitudinal axis126. The wire passage124also extends to a recess132that is formed an outer surface of the cylinder housing88(FIG.7). The recess132extends through the shoulder96of the cylindrical housing88to allow the wired connection to exit the bearing assembly56.

The second aperture120extends partially along the length of the cylindrical housing88and defines an integral clevis121(FIGS.4and5) that is configured to receive the second bearing112and the second end104of the linkage64. The second aperture120allows the second bearing112and the pivot point of the linkage64to be positioned proximate a center point of the annular bearing92. The cylindrical housing88further includes a through hole128(FIG.6) perpendicular to first aperture116, the second aperture120, and the longitudinal axis126of the cylindrical housing88. The through hole128is sized to receive the fastener106that secures the second bearing112and the second end104of the linkage64to the cylindrical housing88. In the illustrated embodiment, the fastener106is recessed within the cylindrical housing88(e.g., positioned below an outer diameter surface of the cylindrical housing88). Further, the sleeve94surrounds the through hole128to restrict access to the through hole128when the bearing assembly56is assembled.

FIGS.8-13illustrate a second embodiment of a bearing assembly156, with like components and features as the embodiment of the bearing assembly56shown inFIGS.1-7being labeled with like reference numerals plus “100”. The bearing assembly56is utilized for a tail rotor gear box in an aircraft similar to the tail rotor gear box40for the aircraft10ofFIGS.1and2and, accordingly, the discussion of the aircraft10and tail rotor gear box40above similarly applies to the bearing assembly156and is not re-stated. Rather, only differences between the bearing assembly56ofFIGS.3-7and the bearing assembly156ofFIGS.8-13are specifically noted herein.

The bearing assembly156includes an outer housing or outer raceway184, a cylindrical housing188positioned within the outer raceway184, and an annular bearing192(e.g., an annular duplex ball bearing) (FIG.9) positioned between the outer raceway184and the cylindrical housing188. The bearing assembly156also includes a shoulder196that preloads the annular bearing192in between the outer raceway184and the cylindrical housing188. An outer diameter of the cylindrical housing188defines the inner raceway of the bearing assembly156.

As shown inFIGS.9and10, the linkage164further includes a first end200pivotably coupled to the actuator52(FIG.2) (e.g., via a fastener) and a second end204pivotably coupled to the cylindrical housing188of the bearing assembly156via a fastener206. In the illustrated embodiment, a first bearing208(e.g., a first spherical pivot bearing) is positioned adjacent the first end200of the linkage164and a second bearing212(e.g., a second spherical pivot bearing) is spaced from the first bearing208and positioned adjacent the second end204. The first and second bearings208,212enable the bearing assembly156to adapt or self-align when there is an offset between the actuator152and the output shaft60in response to movement of the actuator52. The self-alignment of the bearing assembly156reduces significant moment loading of the annular bearing192.

With reference toFIGS.12and13, a sensor180is coupled to a first end face216of the cylindrical housing188and an aperture220is formed in a second end of the cylindrical housing188. In some embodiments, the sensor180may be directly coupled to (e.g., threaded into) the cylindrical housing188. In other embodiments, the sensor180may be coupled to the cylindrical housing188via a bracket or the like. Coupling the sensor180to the first end face216allows the sensor180to be positioned proximate a loading zone of the annular bearing192to detect an operating condition (e.g., vibration, temperature, or the like) of the annular bearing192. In addition, the cylindrical housing188further includes a wire passage224formed in the first end face216and extending through the cylindrical housing188to the second end of the cylindrical housing188. The wire passage224provides space for a wire182to connect between the sensor180and the controller70(FIG.1). In the illustrated embodiment, the wire passage224extends parallel to a longitudinal axis226. Further, the wire182extends from the sensor180and makes a 180 degree bend and enters through the wire passage224in the cylindrical housing188. Further, the bearing assembly156includes a bracket185coupled to the cylindrical housing188via one or more fasteners187(FIG.13) and configured to secure the wire182in the wire passage224. For example, the wire182may have a crimped-on seal that will seat inside the bracket185and the wire passage224.

With reference toFIGS.10and11, the aperture220extends partially along the length of the cylindrical housing188and defines an integral clevis221that is configured to receive the second bearing212and the second end204of the linkage164. The aperture220allows the second bearing212and the pivot point of the linkage164to be positioned proximate a center point of the annular bearing192. The cylindrical housing188further includes a through hole228(FIG.10) perpendicular to the aperture220, and the longitudinal axis226of the cylindrical housing188. The through hole228is sized to receive the fastener206that secures the second bearing212and the second end204of the linkage164to the cylindrical housing188. In the illustrated embodiment, the fastener206is recessed within the cylindrical housing188(e.g., positioned below an outer diameter surface of the cylindrical housing188). Further, the annular bearing192and outer raceway184surrounds the through hole228to restrict access to the through hole228when the bearing assembly156is assembled.

In contrast to the bearing assembly56, the arrangement of the sensor180of the bearing assembly156allows a larger size annular bearing192to be used, and allows the through hole228to receive a larger diameter fastener206. The larger diameter fastener allows for the bearing assembly156to handle significantly greater loads. In the illustrated embodiment, the fastener206is clearance fit in the through hole228of the cylindrical housing188and seated against a shoulder236. The fastener206is further secured within the through hole228with a first retaining member240and a second retaining member244. The first retaining member240extends through the shoulder236and engages the fastener206. The second retaining member244may be a plug (FIG.13) that is press-fit into the through hole228. The bearing assembly156further includes a pair of washers248,252positioned between the second bearing212and the aperture220. The pair of washers248,252create an additional standoff between the linkage164and the aperture220, which allows the linkage164to swivel over a larger angle while retaining a tight tolerancing of the second bearing212and the aperture220.

Various features and advantages are set forth in the following claims.