Patent Application
20150210384
The present invention generally relates to taxi drive systems and more particularly, systems for transmitting torque to wheels of an aircraft.
A typical aircraft may taxi to and from runways with thrust force developed by its engines. A significant amount of fuel may be burned by the engines during a typical aircraft taxi profile before and after each flight. In many cases, the main engines may provide more motive force than is required to complete a successful taxi profile. In that regard, engine-thrust taxiing may be considered inefficient and may contribute to high fuel costs and ground level emissions.
Aircraft designers have sought a more efficient method for propelling an aircraft during taxiing. Electric taxi systems (ETS) have been proposed to provide higher efficiency. An ETS may be implemented by using electrical motors to provide the motive force for aircraft taxiing. While this general ETS concept holds promise for improved efficiency, there are practical application problems that need to be addressed in any successful ETS design. For example, it is desirable that an ETS should be selectively engageable with wheels of the aircraft so that the ETS does not impact normal take-off and landing procedures or aircraft performance. It is also desirable to construct an ETS with compact and lightweight components which may be retrofitted onto existing aircraft and may perform reliably even when exposed to varying environmental conditions that may be encountered by the aircraft at various airports.
The wheel rims of many commercial aircraft are designed to allow a limited amount of deflection of the wheel rims during taxiing and turning of the aircraft. For example, during taxiing, the load of the aircraft may cause the wheel to ovalize on each revolution. Moreover, the loads exerted on the wheel may cause deflections of the wheel rim with respect to the axle. For example, weight on the axle during a turn may cause flexure of the wheel rim radially or axially from the drive element as the drive element may not want to flex with the load forces.
Such deflections can be reduced by making aircraft wheels more stiff. But, wheel designs which allow for such deflections have been found to be less likely to experience metal fatigue failures. However, wheel deflections may present difficulties to designers of an ETS. The combination of wheel ovalization and axial deflections caused by wheel side load conditions and axle bending may compromise the structural integrity in the interface between the ETS drive and the wheel. For example, point loading of forces on drive elements may lead to wear issues over time, expediting failure of the connection between the ETS and the wheel
As can be seen, there is a need for a system in which an ETS drive may be reliably coupled to an aircraft wheel to transmit torque to the wheel. More particularly there is a need for such a system which does not add stiffness to the wheel and does not reduce the ability of the wheel to deflect as the aircraft taxies.
In one aspect of the present invention, an electric taxi system (ETS) for an aircraft may comprise an articulated driven sub-assembly coupled circumferentially with a wheel of the aircraft, the articulated driven sub-assembly being provided with a plurality of torque transmitting pockets; and a rotatable driver with a plurality of teeth, the driver being selectively engageable with the articulated driven sub-assembly so that successive ones of the teeth engage with successive ones of the torque transmitting pockets to transmit torque from a motor of the ETS to the wheel.
In another aspect of the present invention, apparatus for driving a wheel of an aircraft may comprise: a cylindrical wheel extension ring coupled to an inboard side of a wheel of the aircraft; an articulated driven-sub-assembly coupled circumferentially around the wheel extension ring; and a rotatable driver having a plurality of teeth, the driver positioned so that upon rotation of the driver, successive ones of the teeth engage with successive torque transmitting pockets of the articulated driven sub-assembly to transmit torque from the driver to the wheel.
In still another aspect of the present invention, a method for transmitting torque to an aircraft wheel may comprise the steps of: providing a circumferentially oriented articulated driven sub-assembly coupled with the wheel; selectively engaging a driver with the articulated driven sub-assembly; and rotating the driver with torque supplied from a motor of an electric taxi system (ETS) so that successive teeth of the driver engage with successive torque transmitting pockets of the articulated driven sub-assembly.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.
The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.
Various inventive features are described below that can each be used independently of one another or in combination with other features.
Broadly, embodiments of the present invention generally provide an apparatus and system to reliably transmit torque to an aircraft wheel while accommodating deflection of a wheel on an axle. Aspects of the subject technology may be useful in aircraft landing gear systems during taxiing of the aircraft
Referring now to
The driver 112 may be selectively engageable with the driven sub-assembly 114 through selective operation of an engaging and releasing device 106 that may be coupled to the gearbox 104. For example, the driver 112 may be engaged with the roller chain 118 during taxiing and then disengaged from the roller chain 118 during take-off, landing and flight of the aircraft.
Referring now to
Spaces between rollers 127 may be considered torque transmitting pockets 128. As the driver 112 rotates, successive ones of its teeth 129 may engage with successive ones of the pockets 128 and thus torque may be transmitted to the wheel 116. The rollers 127 may be internally lubricated so that the chain 118 may be employed on an exposed landing gear assembly without experiencing excessive wear.
Because the roller chain 118 is an articulated device, its presence on the wheel extension 120 may not increase stiffness of the wheel extension ring 120. Moreover, the wheel extension ring 120 may be constructed as a relatively thin cylinder which may not add substantial stiffness to the wheel 116. Thus, the wheel 116 may deflect in a normal manner during taxiing of the aircraft. In other words, the torque transmission assembly 110 may be retrofitted onto existing aircraft wheels without significantly altering the overall stiffness of the wheel 116.
Referring now to
In an exemplary embodiment, the driven sub-assembly 314 may comprise a chain with a plurality of torque transmitting pockets 316. The pockets 316 may be shaped to accommodate entry of internally-lubricated chain teeth 318 of the driver 312. The driven sub-assembly 314 may be constructed as a plurality of links 320 which may be attached to one another and/or attached to the wheel extension ring 120. For example, the driven sub-assembly 314 may be constructed with a dedicated one of the links 320 for each of the pockets 316. In an exemplary embodiment, each of the links 320 may be constructed from a plurality of stacked plates. In that case, the driven sub-assembly 314 may be considered to be a plate chain. In another exemplary embodiment, each of the links 320 may be formed as a monolithic element.
In another example shown in
Referring now to
It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.
