Patent Publication Number: US-2022234727-A1

Title: Brake assembly with contained brake environment

Description:
BACKGROUND 
     Magnetically levitated (“maglev”) transportation systems, such as Hyperloop vehicles, provide the potential to move passengers and cargo at faster speeds and with improved efficiency compared to currently utilized modes of transportation. These systems employ vehicles that include one or more pressurized capsules to carry passengers and/or cargo through evacuated, i.e., low pressure, tubes. When traveling at high speeds, the vehicles are levitated by magnetic fields, compressed air, or other suitable means. By reducing/eliminating the high-speed air resistance and the friction inherent in the wheels of known vehicles, maglev systems are able to provide greater travel speeds and improved efficiency. 
     When traveling at low speeds or stopped, the vehicles do not levitate, but are instead supported by a support system that includes a plurality of independently controlled landing gear assemblies. Like aircraft landing gear, the maglev support systems reciprocate between an extended (deployed) position and retracted (stowed) position by extending and retracting the individual landing gear assemblies. When the vehicles are levitated, the support system is retracted, and the wheels of the landing gear assemblies do not contact the ground. When the vehicles are traveling at low speeds or stopped, the support system is extended so that the wheels of the landing gear assemblies contact a ground surface to support the vehicles. 
       FIG. 1  shows a representative embodiment of a known landing gear assembly  20  suitable for use as part of one or more of the independently actuated landing gear assemblies of a maglev vehicle. The landing gear assembly  20  is described in U.S. Pat. No. 10,549,848 (“Klim et al.”), issued Feb. 4, 2020, and currently assigned to Safran Landing Systems Canada Inc., the disclosure of which is expressly incorporated herein. 
     The landing gear assembly  20  includes a wheel assembly  22  and a shock strut  38  that is extendable and retractable. The wheel assembly  22  is coupled to the shock strut  38 , which selectively drives extension and retraction of the landing gear assembly  20 . The wheel assembly  22  include a pair of wheels  24  rotatably mounted to an axle  32  that is positioned at one end of a trailing arm body  34 . A pivot pin  36  is positioned at the other end of the trailing arm body  34  to rotatably couple the trailing arm body to the vehicle (not shown), such as an aircraft or a maglev vehicle. 
     The shock strut  38  includes a housing  40  pivotably mounted to the vehicle. A drive screw  42  extends through an aperture in the housing  40  and includes an external screw thread  44  that engages an internal screw thread formed in the aperture of the housing  40 . A piston  48  extends from the drive screw  42  to operatively couple the drive screw  42  to the wheel assembly  22 . 
     A motor  46  is mounted to the housing  40  and is operably coupled to the drive screw  42  to selectively rotate the drive screw about a longitudinal axis. The drive screw  42 , housing  40 , and motor  46  cooperate to function as an actuator  50  that extends and retracts the landing gear assembly  20 . In this regard, the housing  40  functions as a ball nut so that selective rotation of the drive screw  42  by the motor  46  translates the drive screw and motor in an axial direction relative to the housing. This translation of the drive screw  42  rotates the wheel assembly  22  about its pivotal connection to the vehicle, thereby extending and retracting the landing gear assembly  20 . 
     One or more of the wheels assemblies  22  shown in  FIG. 1  includes a brake assembly to provide braking functionality when the landing gear assemblies  20  are extended and at least partially supporting the maglev vehicle.  FIG. 2  shows an embodiment of a known brake assembly  60  suitable for use with the wheel assemblies  22  shown in  FIG. 1 . The brake assembly  60  is disclosed in U.S. Pat. No. 8,839,918, issued to Thibault et al., (“Thibault”) and currently assigned to Safran Landing Systems, the disclosure of which is expressly incorporated herein. 
     Referring to  FIG. 2 , a portion of the wheel assembly  22  is shown. Each wheel  24  of the wheel assembly  22  includes a pneumatic tire  28  mounted to a rim  26 . The rim  26  is mounted to the axle  32  by a plurality of bearings  30  so that the wheel  24  is rotatably about the centerline  80  of the axle  32 . 
     The brake assembly  60  includes an annular bracket  70  fixedly coupled to the axle  32 . The bracket  70  is configured to provide mounting interfaces for brake components that remain fixedly positioned relative to the axle  32 . In some embodiments, several brackets are utilized to fixedly mount the brake components to the axle  32 . In some embodiments, one or more brake components are fixedly mounted other landing gear components to maintain a fixed position relative to the axle  32 . 
     The illustrated brake assembly  60  is a multi-disc brake assembly that includes a stack  64  of discs. More specifically, the stack  64  includes a series of alternating rotors  66  and stators  68 . Each of the rotors  66  is keyed to the rim  26  of the wheel  24  so that the rotors rotate in unison with the wheel. Each of the stators  68  is keyed to the axle  32  and remains rotationally fixed relative to the axle. Thus, when the aircraft wheels  24  rotate, e.g., when the maglev vehicle is supported by the landing gear assembly  20  and the vehicle is in motion, the rotors  66  rotate with the wheels relative to the stators  68 . 
     A plurality of actuators  62  are mounted to the bracket  70  and are spaced circumferentially around the axle  32 . The actuators  62  are linear actuators that selectively extend and retract in unison. Extension of the actuators  62  clamps the stack  64  between the actuators and a torque plate  72  mounted to or integrally formed with the bracket  70  opposite the actuators. As the actuators  62  compress the stack  64 , adjacent stators  68  and rotors  66  engage each other. With the stack  64  compressed and the rotors  66  rotating with the wheels  24 , friction between the rotors  66  and the stators  68  generate a resistive braking force that is reacted to the wheels through the stators. When the actuator is retracted, the rotors  66  and stators  68  disengage from each other, and the restive braking force ceases. 
     Materials developed for use in conventional braking systems are generally designed for use in standard atmospheric operating conditions. Utilizing these materials in a low-pressure braking environment can affect performance and operational lifetime of a braking system. Further, known braking systems, such as those that employ friction braking, produce particulate matter (dust) from the abrasion of braking friction materials. Dust produced from braking within a confined space can cause contamination of the operational environment, which can negatively affect other equipment and systems within the operational environment. 
     SUMMARY 
     In accordance with an embodiment of the present disclosure, a brake assembly is provided. The brake assembly is suitable for use in conjunction with a wheel having a rim rotatably mounted to an axle. The brake assembly includes a brake stack and an actuation assembly that is configured to selectively apply a force to the brake stack. A cover sealingly engages with the rim of the wheel to at least partially define a fluidic barrier between a brake cavity and an ambient environment. The brake stack is disposed within the sealed brake cavity in fluidic isolation from the ambient environment. 
     In any embodiment, the actuation assembly is mounted to the cover. 
     In any embodiment, the cover is sealingly engaged with the axle. 
     In any embodiment, the brake assembly further comprises a brake control unit in fluid connection with the brake cavity. 
     In any embodiment, the brake control unit is configured to provide an input flow of gas to the brake cavity through an inlet formed in the cover. 
     In any embodiment, the brake control unit comprises a pump. 
     In any embodiment, the gas is an inert gas. 
     In any embodiment, the brake control unit is configured to receive an output flow of gas from the brake cavity through an outlet formed in the cover. 
     In any embodiment, the input flow of gas flows through a first conduit in fluid connection at a first end with the brake control unit, the first conduit being in fluid connection at a second end with the inlet formed in the cover. 
     In any embodiment, an output flow of gas flows from the brake cavity to the brake control unit through a second conduit in fluid connection at a first end with the brake control unit and at a second end with an outlet formed in the cover. 
     In any embodiment, the brake assembly further comprises a filter configured to remove particulate matter from the output flow of gas. 
     In any embodiment, the brake assembly further comprises a sensor disposed within the brake cavity, wherein the sensor is configured to sense at least one of a temperature, a pressure, and a humidity within the brake cavity, the sensor being configured to transmit a signal to the brake control unit corresponding to the sensed at least one of the temperature, the pressure, and the humidity. 
     In accordance with an embodiment of the present disclosure, a brake assembly is provided. The brake assembly is suitable for use in conjunction with a wheel having a rim rotatably mounted to an axle. The brake assembly includes a brake stack and an actuation assembly that is configured to selectively apply a force to the brake stack. The brake assembly further includes a sealed brake cavity in fluid isolation from the ambient environment. The brake cavity comprises a cover sealingly engaged with the rim to at least partially define a fluidic barrier between the brake cavity and the ambient environment. The brake stack is disposed within the brake cavity. 
     In any embodiment, the brake assembly further comprises a ventilation assembly in fluid communication with the brake cavity, the ventilation assembly being configured to provide a flow of gas through the brake cavity. 
     In any embodiment, the ventilation assembly comprises a filter configured to remove particulate matter from the flow of gas. 
     In any embodiment, the ventilation assembly comprises a sensor configured to sense a temperature within the brake cavity, the ventilation assembly controlling the flow of gas at least in part in response to the sensed temperature. 
     In any embodiment, the ventilation assembly comprises a sensor configured to sense a humidity within the brake cavity, the ventilation assembly controlling the flow of gas at least in part in response to the sensed humidity. 
     In any embodiment, the ventilation assembly comprises a filter configured to remove particulate matter from the flow of gas. 
     In any embodiment, the ventilation assembly further comprises a sensor configured to sense a pressure within the brake cavity, the ventilation generating a signal to service the filter in response to the sensed pressure exceeding a predetermined maximum threshold. 
     In any embodiment, the ventilation assembly generates a signal to perform a ventilation assembly check in response to the sensed pressure dropping below a predetermined minimum threshold. 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and many of the attendant advantages of the disclosed subject matter will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  shows an isometric view of a known landing gear assembly; 
         FIG. 2  shows a cross sectional view of a known brake assembly suitable for use with the landing gear assembly of  FIG. 1 ; 
         FIG. 3  shows cross-sectional view of a brake assembly according to a first representative embodiment of the present disclosure, wherein the brake assembly is suitable for use with the landing gear assembly of  FIG. 1 ; 
         FIG. 4  shows cross-sectional view of a brake assembly according to a second representative embodiment of the present disclosure, wherein the brake assembly is suitable for use with the landing gear assembly of  FIG. 1 ; 
         FIG. 5  shows cross-sectional view of a brake assembly according to a third representative embodiment of the present disclosure, wherein the brake assembly is suitable for use with the landing gear assembly of  FIG. 1 ; and 
         FIG. 6  shows a schematic diagram of a representative embodiment of a ventilation assembly suitable for use with any of the brake assemblies of  FIGS. 3-5 . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of a sealed brake assembly are provided. The brake assemblies are suitable for use with maglev vehicles or other applications in which it is advantageous to isolate the brake assembly environment from the operating (ambient) environment. The described brake assemblies may include a ventilation assembly that purges particulate matter and other contaminates from the brake assembly environment. The ventilation assembly also provides control of various conditions within the brake assembly environment in order to improve performance and reduce wear of brake assembly components. 
       FIGS. 3-5  show various representative embodiments of brake assemblies according to the present disclosure. The brake assemblies are shown in conjunction with a wheel assembly  22  and an axle  32  similar to those shown in  FIG. 2 . To avoid repetition, descriptions of the various brake assembly embodiments are made with the understanding that unless otherwise noted, the wheel assembly  22 , axle  32 , actuators  62 , and brake stack  64  (including rotors  66  and stators  68 ) are as described with reference to  FIG. 2 . 
     Referring now to  FIG. 3 , a first representative embodiment of a brake assembly  100  is shown. The brake assembly  100  includes a bracket  110  fixedly positioned relative to the axle  32 . In the illustrated embodiment, the bracket  110  has an annular shape that includes a central aperture  132  through which the axle  32  extends. The bracket  110  has a Z-shaped cross section with a first end  112  that extends radially inward and is coupled to the axle  32 . A second end  114  of the bracket  110  extends radially outward and acts as a torque plate that reacts actuating forces applied to the brake stack  64 . A central portion  116  of the bracket  110  extends parallel to the axis  80  of the axle  32 . The central portion  116  engages the stators  68  of the brake stack  64  and fixes the stators in rotation relative to the axle  32 . 
     An annular cover  130  extends around the axle  32  and is fixedly coupled to the first end  112  of the bracket. A plurality of brake actuators  62  is mounted to the cover and positioned such that extension of the actuators compresses the brake stack  64  against the second end  114  of the bracket  110  to provide a resistive braking force. 
     An annular seal  138 , such as labyrinth seal, is disposed between the cover  130  and the rim  26  of the wheel  24  to provide sealing engagement between the cover and the rim. Similarly, an annular seal  138  engages the cover  130  and the axle  32  to provide a sealed interface therebetween. Another annular seal  138  provides a sealed interface between the axle  32  and the rim  26  of the wheel  24  so that the axle  32 , the rim  26 , and the cover  130  cooperate to define a sealed brake cavity  140  in which the brake stack  164  is located. In this regard, the brake cavity  140  and the components contained therein are in fluidic isolation from the ambient environment  150  of the landing gear assembly  20 . It will be appreciated that the number, type, and location of the seals is exemplary only, and any suitable sealing configuration may be used to provide a sealed brake cavity  140 . 
     At least one inlet aperture  134  and at least one outlet aperture  136  are formed in the cover  130 . The inlet and outlet apertures  134  and  136  are in fluid connection with an inlet conduit  402  and an outlet conduit  404 , respectively. 
     Referring now to  FIG. 6 , the brake assembly  100  includes a ventilation system  400  configured to monitor and control the environment within the sealed brake cavity  140 . The ventilation system  400  includes a brake control unit  406  operatively coupled to various components of the brake assembly. The brake control unit  406  includes an electronic control unit (ECU)  408  communicatively coupled to a number of components of the brake assembly  100  to control various aspects of the brake assembly operation. In some embodiments, the ECU  408  includes a processor and memory. The memory may include computer readable storage media in read-only memory (ROM), random-access memory (RAM), and keep-alive memory (KAM), for example. The KAM may be used to store various operating variables or program instructions while the processor is powered down. The computer-readable storage media may be implemented using any of a number of known memory devices such as PROMs (programmable read-only memory), EPROMs (electrically PROM), EEPROMs (electrically erasable PROM), flash memory, or any other electric, magnetic, optical, or combination memory devices capable of storing data, instructions, programs, modules, etc. 
     As used herein, the term processor is not limited to integrated circuits referred to in the art as a computer, but broadly refers to a microcontroller, a microcomputer, a microprocessor, a programmable logic controller, an application specific integrated circuit, other programmable circuits, combinations of the above, among others. Therefore, as used herein, the term “processor” can be used to generally describe these aforementioned components, and can be either hardware or software, or combinations thereof, that implement logic for carrying out various aspects of the present disclosure. Similarly, the terms “module” and “unit” can include logic that may be implemented in either hardware or software, or combinations thereof. 
     The brake control unit includes a flow generator  410 , such as a pump, in fluid communication with the brake cavity  140  through the inlet conduit  402  and the outlet conduit  404 . The flow generator  410  provides a flow of gas to the brake cavity  140  through the inlet conduit  402 . In some embodiments, the gas is an inert gas, such as argon or nitrogen, to prevent oxidation of the brake system components. In some embodiments, the gas has a high thermal capacity to provide improved cooling of the brake system components. In some embodiments, the gas is chosen based on the brake component materials to maintain or improve performance of the brake system. 
     Gas is returned from the brake cavity  140  to the flow generator  410  of the brake control unit  406  through the outlet conduit  404 . An inline particle filter  416  filters particulate matter, such as brake dust, out of the returning gas before the gas reaches the brake control unit  406 . The particulate matter is collected in a particle collector  418  that may be replaced or serviced as needed. 
     As shown in  FIGS. 3 and 6 , the brake assembly  100  includes one or more sensor(s)  420 . These sensor(s)  420  may include brake assembly state sensors capable of generating values that represent states including, but not limited to, the temperature of various brake assembly components, including the gas within the brake cavity  140 . The sensors(s)  420  may also generate signals corresponding to the pressure and/or humidity of the gas inside the brake cavity  140 . The sensor(s)  420  are communicatively coupled to the ECU  408 , and values generated by the sensor(s)  420  may be transmitted to the ECU. It will be appreciated that the number, type and location of the sensor(s) may vary from the disclosed embodiment. In this regard, the sensor(s) may be placed in any suitable location for sensing particular conditions within the brake system. 
     In some embodiments, additional copies of the ECU  408 , and/or other components may be provided for redundancy. Further, the components of brake assembly  100  may be communicatively coupled via any suitable communication technique, including but not limited to serial wired communication, wireless communication (via Bluetooth, Wi-Fi, or other wireless communication techniques), and/or networked wired communication (via USB, Ethernet, CANBUS, or other wired communication techniques). 
     In some embodiments, the brake control unit  406  includes a temperature control module  412  communicatively coupled to the ECU  408 . The ECU  408  receives signals from a sensor  420  indicating a sensed temperature within the brake cavity  140  and may signal the temperature control module  412  to control the temperature of the gas supplied to the brake cavity  140  improve brake performance In some embodiments, when a sensed temperature exceeds a predetermined threshold, the ventilation system  400  provides a flow of gas (or increases an existing flow) to the brake cavity  140  to cool the brake stack  64 , thereby improving performance and decreasing wear of the brake components. Similarly, in some embodiments the brake control unit  406  includes a humidity control module  414  communicatively coupled to the ECU  408 . The ECU  408  receives signals from a sensor  420  indicating a sensed humidity within the brake cavity  140  and may signal the humidity control module  414  to control the humidity of the gas supplied to the brake cavity  140  to improve brake performance and longevity. 
     In some embodiments, a sensor  420  senses a pressure within the brake cavity  140  and sends a corresponding signal to the ECU  408 . In some embodiments, when the sensed pressure exceeds a predetermined maximum threshold value, the ECU  408  may generate a signal indicating that the particle filter  416  should be serviced, as increase pressure may result from a clogged filter. In some embodiments, when the sensed pressure is below a predetermined minimum threshold value, the ECU  408  may generate a signal that the brake system should be checked for a possible leak. 
     Still referring to  FIGS. 3 and 6 , the disclosed brake assembly  100  isolates the brake assembly components from the ambient environment. In embodiments utilized on maglev vehicles, the brake assembly  100  prevents particulate matter produced by braking operations from contaminating the low-pressure environments in which the vehicles operate. In other embodiments, such as brakes used on lunar rovers, the brake assembly  100  isolates the brake components from environmental contaminates that could cause undue wear or premature failure of the brake components. The disclosed brake assembly  100  also provides a controlled environment for the brake components, and in particular, the brake stack. By controlling the temperature, humidity pressure, and any other suitable operating conditions or combinations of conditions, brake performance and longevity can be improved. 
     In operation, the ventilation system  400  provides a flow of gas to the brake cavity  140 . More specifically, the brake control unit  406  controls the flow generator  410  to provide a flow of gas to the brake cavity  140  through the inlet aperture  134  of the cover  130 . The gas flows through the brake cavity  140  and then returns to the brake control unit  406  through the outlet aperture  136 . As the gas flows through the brake cavity  140 , the gas impinges on the rotors  66  and stators  68  to cool the brake components. The flow of gas through the brake cavity  140  also purges the brake cavity of particulate matter and collects the particulate matter to ensure that the ambient environment  150  is not contaminated. In some embodiments, the gas flow also allows for additional temperature and/or humidity control within the brake cavity  140 . 
     Referring now to  FIG. 4 , another embodiment of a brake assembly  200  will be described. The brake assembly  200  is similar to the brake assembly  100  of  FIG. 3 , wherein components of the brake assembly  200  designated with a reference number  2 XX correspond to components of the brake assembly  100  designated with a reference number  1 XX. The brake assembly  200  will be described with the understanding that components of the brake assembly  200  are similar to the corresponding components of the previously described brake assembly  100  except as otherwise noted. 
     The cover  230  of brake assembly  200  includes a plurality of inlet apertures  134  and outlet apertures  136 , wherein the outlet apertures are positioned radially outward of the inlet apertures. The middle portion  216  of the bracket  210  includes a plurality of apertures  218  extending radially therethrough. The illustrated configuration directs gas flow from a radially inward portion of the brake cavity  240 , outward through the apertures  218  in the bracket  210 , between the stators  68  and rotors  66 , and then out through the outlet apertures  236 . In this manner, the disclosed configuration provides more direct flow of gas over the stators  68  and rotors  66 , which results in greater cooling of the brake components and a more thorough purging of particulate matter within the brake cavity  240 . 
     In order to seal the brake cavity  240 , seals  238  are positioned between the rim  26  and the cover  230 , between the axle  32  and the cover  230 , between the axle  32  and the bracket  210 , and on both sides of the inboard roller bearing  30  between the rim  26  and the axle  32 . It will be appreciated that the number and location of seals  238  in this and other disclosed embodiments is exemplary only. Other embodiments using seals of different numbers, types, and positions to seal the brake cavity  240  are possible and should be considered within the scope of the present disclosure. 
     Referring now to  FIG. 5 , another embodiment of a brake assembly  300  will be described. The brake assembly  300  is similar to the brake assembly  200  of  FIG. 4 , wherein components of the brake assembly  300  designated with a reference number  3 XX correspond to components of the brake assembly  200  designated with a reference number  2 XX. The brake assembly  300  will be described with the understanding that components of the brake assembly  300  are similar to the corresponding components of the previously described brake assembly  200  except as otherwise noted. 
     In the illustrated embodiment, the first end  312  of the bracket  310  includes a return flange  320  that extends in an outboard direction. The return flange  320  sealingly engages the rim  26  with a seal  338 . The brake assembly  300  further includes seals  338  positioned between the rim  26  and the cover  330  and between the axle  32  and the cover  330 . Thus, the illustrated embodiment may utilize fewer seals than other contemplated embodiments. 
     It will be appreciated that the disclosed embodiments are exemplary only and should not be considered limiting. In some embodiments, various configurations are employed to provide a sealed brake cavity. Further, the present disclosure is not limited to a particular type of brake configuration. In some embodiments, different brake actuators, brake stack configurations, and/or other brake components may be utilized. These and other variations are contemplated and should be considered within the scope of the present disclosure. 
     The present application may reference quantities and numbers. Unless specifically stated, such quantities and numbers are not to be considered restrictive, but exemplary of the possible quantities or numbers associated with the present application. Also, in this regard, the present application may use the term “plurality” to reference a quantity or number. In this regard, the term “plurality” is meant to be any number that is more than one, for example, two, three, four, five, etc. The terms “about,” “approximately,” “near,” etc., mean plus or minus 5% of the stated value. For the purposes of the present disclosure, the phrase “at least one of A, B, and C,” for example, means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C), including all further possible permutations when greater than three elements are listed. 
     The principles, representative embodiments, and modes of operation of the present disclosure have been described in the foregoing description. However, aspects of the present disclosure which are intended to be protected are not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. It will be appreciated that variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present disclosure. Accordingly, it is expressly intended that all such variations, changes, and equivalents fall within the spirit and scope of the present disclosure, as claimed.