Patent Application
20160025152
The present invention relates generally to drive wheel clutches and clutch systems and specifically to a clutch designed for a non-engine powered drive wheel with a roller traction drive actuation system used to move an aircraft or other vehicles during ground travel.
Most vehicle drive systems include clutches that may be engaged and disengaged to actuate drive system components and control torque of these components as the vehicle is driven by the drive system. Providing a clutch able to effectively transfer torque in a vehicle drive system, particularly in a drive system powered by a non-engine drive means that is contained within the dimensions of a vehicle wheel, has presented challenges.
A wide range of different types of clutches suitable for transferring torque is known in the art. For example, in U.S. Pat. No. 8,333,272, Wheals et al disclose a dual clutch for automotive applications that includes a driving plate having a top hat type configuration with opposing engagement surfaces that engage axially aligned friction plates that are held in engagement with spring elements. In U.S. Patent Application Publication No. US2004/0256192, Hill et al describe an electromagnetic friction clutch with at least two components mounted to be rotatable relative to one another that may be pressed against each other by magnetic force. A magnetic friction clutch with friction discs that is stated to be capable of relatively high torque transfer is described by Shchokin et al in U.S. Patent Application Publication No. US2008/0142327. In U.S. Pat. Nos. 4,175,650 and 4,293,060, Miller discloses electromagnetic friction clutches that, respectively, prevent loss of torque between driven and driving means as friction material wears and provide a torque overload release arrangement. It is not suggested that any of the clutch arrangements described in the foregoing patents and published applications could be modified to effectively transfer torque in a vehicle drive wheel drive system located within the dimensions of a vehicle wheel that includes a non-engine drive means and a roller traction drive system operatively associated in torque transfer relationship with the drive means and a clutch.
Providing an electric motor within an aircraft nose wheel to drive an aircraft nose wheel and move the aircraft on the ground is described in U.S. Pat. No. 7,445,178 by McCoskey et al. This arrangement includes a dual cone activated mechanism that functions in combination with gearing to move a clutch laterally toward a rotor in the motor. It is not suggested that this clutch design could be adapted to transfer torque between a non-engine drive means and a roller traction drive system or other drive system to the aircraft nose wheel or to any other aircraft or vehicle wheel.
A need exists, therefore, for an effective clutch design that is capable of controlling the transfer of torque and transferring torque between a non-engine drive means, a roller traction drive or other drive system in torque transfer contact with the non-engine drive means, and a wheel in a vehicle wheel drive system contained within the dimensions of a vehicle wheel that operates to drive the vehicle at a desired ground travel speed and/or torque. A need also exists for an effective clutch design capable of controlling torque transfer and transferring torque between a non-engine drive means and a roller traction drive or other drive system and a wheel in an aircraft wheel drive system contained within the dimensions of an aircraft landing gear wheel that operates to drive an aircraft wheel and the aircraft at a desired taxi speed.
It is a primary object of the present invention therefore, to provide an effective clutch design that is capable of controlling torque transfer and transferring torque between a non-engine drive means, a drive system, and a wheel in a vehicle wheel drive system contained within the dimensions of a vehicle wheel that operates to drive the vehicle at a desired ground travel speed and/or torque.
It is another object of the present invention to provide an effective clutch design capable of controlling torque transfer and transferring torque between a non-engine drive means, a drive system, and a wheel in an aircraft wheel drive system contained within the dimensions of an aircraft landing gear wheel that operates to drive an aircraft wheel and the aircraft at a desired taxi speed.
It is an additional object of the present invention to provide a clutch configured with engaging surfaces having a geometry that, upon actuation of the clutch, causes the amplification of forces created as a result of the geometry of the engaging surfaces to transmit torque between a mechanical input and a mechanical output.
It is a further object of the present invention to provide a clutch for a vehicle drive wheel with a wheel drive system capable of driving the vehicle at a desired torque and/or speed by the transfer of torque between an electric drive motor, a roller traction drive system, and a vehicle wheel, wherein clutch components are configured to transmit torque to the vehicle wheel by a combination of circumferential and axial forces in response to external actuation.
It is a further object of the present invention to provide an electromagnetically activated clutch with a number of complementarily configured components that meshingly engage upon activation to produce sufficient circumferential and axial force to transfer torque to a vehicle wheel from a drive system.
It is yet an additional object of the present invention to provide a clutch useful for transferring torque in a drive wheel, wherein the geometry of meshing components of complementarily configured clutch elements may be selected to amplify the force required after clutch actuation to transmit a desired torque.
It is yet another object of the present invention to provide an electromagnetically activated clutch in a vehicle drive wheel drive system that includes an electric drive means and a roller traction drive system coupled to the clutch with clutch components configured to facilitate torque transfer from the electric drive means to a vehicle wheel.
It is yet an additional object of the present invention to provide a method for controlling torque transfer in a vehicle wheel drive system that includes a non-engine drive means, a roller traction drive system, and a clutch designed to transfer torque between these wheel drive system components and a vehicle drive wheel to move the vehicle on a ground surface at a desired speed and/or torque.
It is yet a further object of the present invention to provide a method for controlling torque transfer in an aircraft landing gear wheel drive system that includes a non-engine drive means, a roller traction drive system, and a clutch designed to transfer torque between these wheel drive system components and an aircraft landing gear drive wheel to move the aircraft on a ground surface at taxi speeds.
In accordance with the aforesaid objects, a clutch is provided that is designed to effectively transfer torque between wheel drive system components in a vehicle drive wheel drive system and move the vehicle on a ground surface. The wheel drive system components include a non-engine drive means and a roller traction drive or other drive system in torque transmission contact with the clutch and with the vehicle drive wheel. The clutch may include a number of complementarily configured clutch elements designed to mesh into engagement when actuated by an electromagnetic or other engagement means and to produce and amplify circumferential and axial forces that facilitate the transfer of torque to a vehicle wheel. Geometry of meshing components of complementarily configured clutch elements may be selected to amplify the force required after clutch actuation to transmit a desired torque. The clutch elements may disengage when electromagnetic actuation is removed or may remain engaged without operation of the electromagnetic engagement means. Spring elements may bias and maintain the clutch components out of engagement when not activated by the electromagnetic engagement means. A high friction coating may be applied to interfaces between clutch elements and the vehicle wheel. In the presence of selected overspeed parameters, the clutch may be designed to overrun and cease torque transmission. Elements functionally equivalent to a centrifugal brake may be provided to prevent clutch engagement when drive wheel speed exceeds a selected limit. The preferred application of the clutch of the present invention is to control the transfer of torque between a non-engine drive means and a roller traction drive system to drive an aircraft landing gear wheel to move the aircraft during taxi.
Other objects and advantages will be apparent from the following description, drawings, and claims.
Using a non-engine powered drive wheel to drive a vehicle normally driven by an engine on a ground surface can provide significant fuel savings. When the vehicle is an aircraft, the potential savings that accompany moving the aircraft on the ground with drive means other than the aircraft's main engines extend well beyond saving fuel. Efficiently controlling a vehicle drive wheel to move the vehicle requires effectively controlling the transfer of torque through the drive components of the drive wheel drive system. Providing a clutch that is capable of effectively transferring torque and controlling the transfer of torque between a drive means and a roller traction drive or other drive system and a wheel to move the vehicle drive wheel at a desired torque and ground speed has presented challenges. The clutch of the present invention successfully addresses these challenges.
The clutch of the present invention is discussed primarily as it may be used in an aircraft landing gear drive wheel. It is understood, however, that the present clutch design will be useful for controlling torque transmission in any vehicle with a drive wheel driven by a drive means which is a source of power other than the vehicle's main power source in a wheel drive system that includes at least a drive means and a roller traction drive or other drive system for moving the vehicle wheel and, therefore, the vehicle, on a ground surface at a desired torque and speed. The number of drive wheels on a vehicle may vary. For example, without limitation, the clutch design of the present invention may be effectively employed to transmit torque to drive an automobile with one or more electric drive wheel motors in drive wheels that are used to propel the automobile without operation of an internal combustion engine. Other kinds of vehicles and uses are also contemplated to be within the scope of the present invention. Additional applications of the clutch of the present invention in systems other than vehicles are also contemplated.
Referring to the drawings,
In the wheels of a conventional aircraft landing gear, movement of the wheels and, therefore, ground movement of the aircraft are presently controlled by controlling the amount of thrust from the aircraft main engines and applying the aircraft's brakes. In a wheel drive system with the clutch of the present invention, movement of the drive wheel 14 is controlled by the operation of a non-engine drive means 20 that is not powered by the aircraft's main engines, but may be powered by the aircraft's auxiliary power unit (APU) or another suitable source of electric, hydraulic or pneumatic power. In another type of vehicle, for example without limitation, one or more drive wheels may be powered entirely by battery-powered electric motors.
A preferred non-engine drive means 20 may include a rotating element, such as a rotor 22, and a stationary element, such as a stator 24. The rotor 22 may be located externally of the stator 24, as shown, but other drive means component arrangements may also be used. For example, the positions of the rotor 22 and stator 24 could be reversed so that the rotor is internal to the stator.
A drive means 20 preferred for use in a drive wheel drive system with the clutch of the present invention may be an electric motor assembly that is capable of operating at high speed and could be any one of a number of suitable designs. An example of one type of drive means that may be used effectively is an inside-out electric motor in which the rotor can be internal to or external to the stator, such as that shown in
A wheel drive system in which the clutch of the present invention is designed to function optimally preferably includes a roller traction drive system 26, which is shown only in a location superior to the axle 12a, but, in actuality, extends circumferentially around the wheel axle 12a. The roller traction drive system 26 is not shown in the location it would occupy inferior to the axle 12a so that the wheel drive system housing 28 can be seen more clearly. The roller traction drive system 26 performs essentially the same functions that would be performed by gearing or a gear system. The replacement of gearing by a roller traction drive system in an aircraft drive wheel drive system, or another similar drive system, presents many advantages.
A roller traction drive system designed to actuate a non-engine drive means capable of moving a commercial sized aircraft or other vehicle on the ground not only has a low profile and is light weight, but also provides the high torque and high speed change ratio required to optimally operate the non-engine drive means to move an aircraft on the ground. Unlike a gear system, a roller traction drive system has substantially zero backlash and can be made of dry running components that do not require lubrication. Planetary and other gear systems are capable of only limited gear ratios, while an infinite gear ratio is possible with a preferred roller traction drive system. A roller traction drive system may be, in addition, self-energizing, which requires the maintenance of an optimum coefficient of friction (CF) and traction angle between rollers and a motive surface contacted by the rollers.
One preferred roller traction drive system 26 may employ a series of rollers (not shown), preferably arranged in two rows and positioned within opposed motive surfaces or “races,” for example 30 and 32, so that a respective inner or outer row of rollers contacts an inner or outer race. The roller traction drive system 26 may be positioned within a roller box 34, as shown in
Ideally, a roller traction drive 26 is designed to achieve the torque and reduction ratios required for optimal operation of a vehicle drive wheel drive system. During high speed operation of the roller traction drive, moreover, the non-engine drive means rotor 22 must be kept in alignment and at a reliably consistent radial distance with respect to the roller traction drive. Additional parameters that maximize the service life and safety of a roller traction drive as it operates in conjunction with a non-engine drive means as described herein to move an aircraft or other vehicle on the ground may also be important considerations in the effective and efficient transfer of torque with the clutch of the present invention. When the roller traction drive system 26 is engaged, torque is transmitted to the drive means 20 through rolling friction, which is approximately equal to the applied torque, although this can be affected by the specific configuration of the roller traction drive system.
A roller box 34 of the roller traction drive system 26 may include a contact element 36 in torque transmitting contact with the rotor element 22 of the non-engine drive means 20. The contact element 36 enables transmission of torque between the roller traction drive system 26 and the drive means rotor element 22 to change the speed of the rotor element as necessary. This arrangement may additionally function as a bearing for the drive means rotor 22. A surface 38 on the opposite side of the roller box 34 from the contact element 36 may be in torque transmitting contact with a clutch, as discussed below.
The clutch 40 of the present invention is shown in a preferred location relative to the roller box 34 and non-engine drive means 20 in the aircraft wheel drive system of
An external actuator of the clutch embodiment shown in
In the embodiment shown in
A clutch capable of effectively transmitting torque as described herein may have a range of different configurations and may include different numbers of clutch elements. For example, without limitation, the clutch 40 shown in the clutch embodiment of
The central clutch element 50 in this embodiment may be mechanically linked to the roller traction drive system roller box 34, preferably along roller box surface 38 by a flexible coupling (not shown) that provides moderate play to the clutch. Other suitable connections may also be employed. The central clutch element 50 has a surface 52 that is correspondingly configured to engage surface 38 of the roller box 34.
The opposed edges 54 and 56 of the central clutch element 50 may additionally be formed with a geometric pattern, such as the contoured or toothed pattern shown in
The respective axial edges 57 and 59 of first and second clutch elements 46 and 48 that do not have geometric patterns may form contact surfaces with other clutch and/or wheel structures. Consequently, the edge surfaces 57 and 59 optimally have a shape that allows the clutch elements 46 and 48 to rotate freely relative to adjacent structures, such as a surface 45 on the engagement ring 44 or a surface 71 on a wheel interface ring 70, and/or each other, as described below. The clutch elements 46 and 48 may be conical, curved, or have any other suitable symmetry that allows them to rotate freely relative to the wheel axle 12a when not engaged so that the vehicle wheel can also spin freely. The surfaces 57 and 59 may also be slightly uneven, provided that they are sufficiently smooth to avoid contact with adjacent surfaces during rotation. A surface 72 on the wheel interface ring 70 opposite surface or edge 71 may contact the wheel 14 (
A high friction coating material, such as, for example without limitation, a diamond coating or a coating of a material with frictional properties equivalent to diamond, may be applied to contact surface 59 on the second clutch element 48 and/or on the surfaces 71 and 72 of the wheel interface ring 70. Such coatings are known in the art.
The clutch of the present invention may be designed to be coaxial with a non-engine drive means 20 and a roller traction drive system 26 and mounted radially outwardly of these drive system components completely within a vehicle wheel as shown in
A number of spring elements, such as the springs 66 and 68 shown in
In an additional embodiment 80 of the clutch of the present invention, shown schematically in
A different design of electromagnetic engagement means is employed in the
In operation, the clutch of the present invention may require an external actuator which brings together two rotating clutch elements that may be rotating at different speeds, thereby creating drag. Angled surfaces, for example, teeth, on patterned edges or surfaces of the rotating clutch elements are caused to interact by this drag so that the angled surfaces transform circumferential force caused by the drag into axial force, which pushes the rotating clutch elements securely together, thereby locking the clutch. Additionally, when an “Engage Clutch” command has been received by the clutch in the wheel drive system described herein, the electromagnets 42 or 98 are energized. An “Engage Clutch” command may be instituted manually or, preferably, automatically when wheel drive system sensors and/or software determine that the control of torque transfer provided by the clutch is required during operation of the wheel drive system. A variety of actuation systems for clutches actuated by electromagnetic energization means are available and could be incorporated into a vehicle wheel drive system that uses the clutch of the present invention.
In the
Once the clutch 40 is engaged, frictional forces may enable the clutch elements 46, 48 and 50 to remain engaged without assistance from the electromagnets 42. De-energization of the electromagnets 42 may be used to disengage the clutch so that the engagement ring 44 moves out of contact with the clutch elements and the springs 66 and 68 bias and maintain the clutch elements out of meshing contact with each other and, thus in a disengaged condition. In an overspeed condition, which may be detected with respect to established operating parameters, the clutch is intended to overrun so that torque transmission is stopped.
In the
In both the
Torque transmission can be controlled by controlling the kinds of friction surfaces used in the present clutch and by selecting an optimum clutch element tooth slope angle. This enables the clutch to be designed so that a relatively weak magnetic actuation force is amplified to a force level sufficient to transmit a desired torque. If it is desired for the clutch not to be self-energizing, these parameters may be adjusted so that the clutch will release as soon as electromagnetic actuation is stopped, which could be done automatically in response to selected conditions or manually.
The clutch of the present invention may be designed for bi-directional engagement, primarily when the wheel drive system is moving in reverse. A suitable force, such as that described above with respect to the movement of engagement ring 44, may be applied to the edge 59 of the second clutch element 48 or to the edge 57 of the first clutch element 46 to move the clutch elements 46, 48 and 50 into meshing engagement to transmit torque between wheel drive system components and the vehicle wheel. For torque to be applied by the present clutch in both directions, the arrangement of clutch elements in
Although not specifically shown, clutch elements, such as those in
To enhance safe operation of the wheel drive system, the clutch of either the
While the present invention has been described with respect to preferred embodiments, this is not intended to be limiting, and other orientations, arrangements and structures that perform the required functions are contemplated to be within the scope of the present invention.
The clutch design of the present invention will find its primary applicability where is desired to provide effective torque transfer and control over torque transfer in a wheel drive system that includes a non-engine drive means and a roller traction drive system within the dimensions of a vehicle wheel and is designed to move the vehicle wheel to move the vehicle on a ground surface at a desired speed and torque. A preferred use of the present clutch design is to transfer and control torque within a wheel drive system in an aircraft landing gear wheel operated by the wheel drive system to move the aircraft on the ground at taxi speeds.
