Patent Description:
An electric motor may be used by aircraft as a power source for various functions, such as supplying rotational energy in an aircraft propulsion system. In aircraft propulsion systems that utilize only a single motor, the lack of a backup motor increases the likelihood of a crash or other catastrophic condition should the motor fail. A single motor propulsion system also may not meet the power demands required by the propulsion system in the most efficient manner. Using two or more motors in a propulsion system addresses these concerns but may give rise to other issues.

<CIT> discloses a propulsion system assembly is provided including a driveshaft and a plurality of electric motor modules, wherein the plurality of electric motor modules are in axially stacked relationship with one another with respect to the drive axis.

<CIT> discloses a motorized aircraft controlled by a drive control means that rotationally drives a propulsion system propeller. The propulsion system propeller is driven by a plurality of electric motors.

<CIT> discloses a hybrid propulsion system for an aircraft comprising one or more turboshaft engines that provide shaft power and are capable of providing thrust; and one or more electrical generators and/or one or more hydraulic pumps.

<CIT> discloses an electrical redundant drive system for a propulsion means of an aircraft and a method for driving the propulsion means. The drive system has two or more separate electric motors which are connected to the propulsion means via a common transmission.

<CIT> discloses electrically powered Vertical Takeoff and Landing (VTOL) aircraft that can include one or more electrical energy stores capable of delivering electrical power to one or more electric motors disposed within one or more rotor housings.

An aspect of the invention is set out according to appended claim <NUM>. Embodiments of the invention are set out according to the appended dependent claims.

To provide a more complete understanding of the present disclosure and features and advantages thereof, reference is made to the following description, taken in conjunction with the accompanying figures, in which like reference numerals represent like elements:.

The following disclosure describes various illustrative embodiments and examples for implementing the features and functionality of the present disclosure. While particular components, arrangements, and/or features are described below in connection with various example embodiments, these are merely examples used to simplify the present disclosure and are not intended to be limiting. It will of course be appreciated that in the development of any actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, including compliance with system, business, and/or legal constraints, which may vary from one implementation to another. Moreover, it will be appreciated that, while such a development effort might be complex and time-consuming; it would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

In the Specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present disclosure, the devices, components, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as "above", "below", "upper", "lower", "top", "bottom", or other similar terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components, should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the components described herein may be oriented in any desired direction. When used to describe a range of dimensions or other characteristics (e.g., time, pressure, temperature, length, width, etc.) of an element, operations, and/or conditions, the phrase "between X and Y" represents a range that includes X and Y.

Additionally, as referred to herein in this Specification, the terms "forward", "aft", "inboard", and "outboard" may be used to describe relative relationship(s) between components and/or spatial orientation of aspect(s) of a component or components. The term "forward" may refer to a spatial direction that is closer to a front of an aircraft relative to another component or component aspect(s). The term "aft" may refer to a spatial direction that is closer to a rear of an aircraft relative to another component or component aspect(s). The term "inboard" may refer to a location of a component that is within the fuselage of an aircraft and/or a spatial direction that is closer to or along a centerline of the aircraft (wherein the centerline runs between the front and the rear of the aircraft) or other point of reference relative to another component or component aspect. The term "outboard" may refer to a location of a component that is outside the fuselage of an aircraft and/or a spatial direction that farther from the centerline of the aircraft or other point of reference relative to another component or component aspect.

Further, the present disclosure may repeat reference numerals and/or letters in the various examples. Example embodiments that may be used to implement the features and functionality of this disclosure will now be described with more particular reference to the accompanying.

Embodiments described herein are a design for an electric motor stack and gearbox unit. In accordance with features of embodiments described herein, the electric motor stack includes three radial flux motor cores with an integral one-piece drive shaft housed within a shared housing. The drive shaft is supported through forward (or front) and rear (or back) endplates of the housing by bearings. The housing is sealed by an o-ring around the endplate mating surfaces and by a dynamic lip seal around the drive shaft in the front and back of the housing. The forward end of the drive shaft plugs into the gearbox to drive the gearbox rotors.

<FIG> and <FIG> illustrate an example tiltrotor aircraft <NUM> that includes ducted rotors (or fans). The tiltrotor aircraft <NUM> is convertible between a helicopter mode (shown in <FIG>), which allows for vertical takeoff and landing, hovering, and low speed directional movement, and an airplane mode (shown in <FIG>), which allows for forward flight as well as horizontal takeoff and landing. Aircraft <NUM> includes a fuselage <NUM>, wings <NUM>, and a plurality propulsion assemblies <NUM> each comprising a ducted fan <NUM> rotatably coupled to fuselage <NUM> or wings <NUM>. As best shown in <FIG>, each ducted fan <NUM> includes a rotor assembly <NUM>, a flow-straightening stator assembly <NUM>, and a duct <NUM> surrounding rotor assembly <NUM> and stator assembly <NUM>. Rotor assembly <NUM> includes a plurality of rotor blades <NUM> configured to rotate about a mast axis <NUM>. Rotation of rotor blades <NUM> about mast axis <NUM> generates lift while operating in helicopter mode and thrust while operating in airplane mode. Stator assembly <NUM> is positioned downstream of rotor blades <NUM> and includes a stator hub <NUM> centrally located within duct <NUM> and a plurality of stator vanes <NUM> coupled between duct <NUM> and stator hub <NUM>. Stator hub <NUM> may house an electric motor therein configured to produce rotational energy that drives the rotation of rotor assembly <NUM>. Alternatively, stator hub <NUM> may house a gearbox therein that drives the rotation of rotor assembly <NUM>, wherein the gearbox receives rotational energy from a drive shaft passing through an attachment post <NUM> and the adjacent stator vane <NUM>.

Rotor blade assemblies <NUM> can be collectively manipulated to selectively control direction, thrust, and lift of tilting ducted fan aircraft <NUM>. Indeed, the collective pitch of rotor blade assemblies <NUM> may be independently controlled from one another to allow for differential thrust output by ducted fans <NUM>. For example, the collective pitch of the rotor blade assembly of one ducted fan may be higher or lower than the collective pitch of rotor blade assembly of another ducted fan such that the thrust generated by each ducted fan differs from each of the others.

Ducted fans <NUM> are each convertible, relative to fuselage <NUM>, between a horizontal position, as shown in <FIG>, and a vertical position, as shown in <FIG>. Ducted fans <NUM> are in the horizontal position during vertical takeoff and landing mode. Vertical takeoff and landing mode may be considered to include hover operations of tilting ducted fan aircraft <NUM>. Ducted fans <NUM> are in the vertical position during forward flight mode, in which tilting ducted fan aircraft <NUM> is in forward flight. In forward flight mode, ducted fans <NUM> direct their respective thrusts in the aft direction to propel tilting ducted fan aircraft <NUM> forward. Tilting ducted fan aircraft <NUM> is operable to fly in all directions during the vertical takeoff and landing mode configuration of <FIG>, although faster forward flight is achievable while in the forward flight mode configuration of <FIG>. Ducted fans <NUM> may be tiltable between the vertical and horizontal positions by a rotatable shafts (not shown) extending through wings <NUM> and which are rotatable in response to commands originating from a pilot and/or a flight control system.

As shown in <FIG>, and as will be described in detail below, each of the propulsion assemblies <NUM> utilize an electric motor stack and gear box unit <NUM> disposed within a respective rotatable pylon <NUM> as a power source to rotate the respective rotor hub assembly <NUM> via a rotor mast <NUM>.

Referring now to <FIG>, illustrated therein is an electric motor stack and gearbox unit <NUM> that may be used as a power source to rotate a rotor hub assembly, such as rotor hub assembly <NUM> (<FIG> and <FIG>), and that may be used to implement electric motor stack and gear box unit <NUM> (<FIG>). <FIG> is a cutaway view of the electric motor stack and gearbox unit <NUM>. As shown in <FIG> and <FIG>, the unit <NUM> includes a gear box <NUM> and an electric motor stack comprising a plurality of electric motors <NUM> and associated power electronics <NUM>. In embodiments, electric motors <NUM> are implemented as radial flux motors.

As best shown in <FIG>, the motors <NUM> of the electric motor stack <NUM> collectively drive (i.e., provide rotational power to) an integral drive shaft <NUM>. Each of the motors <NUM> is connected to the drive shaft <NUM> via a respective one of overrunning clutches <NUM>, each of which transmits torque in one direction only and permits the drive shaft <NUM> to "freewheel," or continue to rotate, when the respective one of the motors <NUM> is stopped (e.g., upon failure of the motor). As will be described in greater detail hereinbelow, a forward end of drive shaft <NUM> is received within a receptacle <NUM> of the gearbox <NUM> for providing rotational power to a second drive shaft <NUM> disposed within gearbox <NUM> for driving gearbox gears <NUM>. Gearbox gears <NUM> operate to transfer torque to a rotor shaft <NUM> connected to rotor assembly (<FIG>). It will be noted that, although motor stack <NUM> is illustrated as including three motors, more or fewer motors may be included without departing from the scope of the appended claims.

<FIG> is a perspective view of an exterior of the electric motor stack <NUM> illustrating details of a housing <NUM> thereof. <FIG> is a cutaway view of the electric motor stack <NUM> as shown in <FIG>. Housing <NUM> includes a forward endplate <NUM> and a rear endplate <NUM> through which ends of drive shaft <NUM> extend. As will be described in greater detail hereinbelow, mechanisms are provided in forward endplate <NUM> and rear endplate <NUM> for securely supporting ends of drive shaft <NUM>. A forward end <NUM> of drive shaft <NUM> extends through an opening in approximately a center of forward endplate <NUM> and is splined for interconnecting with receptacle <NUM>, which is splined in a complementary manner such that the drive shaft <NUM> imparts rotational energy to the second drive shaft <NUM> of gearbox <NUM>.

As best shown in <FIG>, a rear end <NUM> of drive shaft extends through the rear endplate <NUM> of housing <NUM>. As previously noted, forward end <NUM> of drive shaft <NUM> is splined to mate with a splined receptacle disposed within gearbox <NUM> (not shown in <FIG>) to drive second drive shaft <NUM> (not shown in <FIG>).

<FIG> is an exploded view of the electric motor stack <NUM> as shown in <FIG> and <FIG>. Referring to <FIG>,in addition to housing <NUM> including front endplate <NUM> and rear endplate <NUM>, motors <NUM>, motor controller electronics <NUM>, drive shaft <NUM>, and overrunning clutches <NUM>, motor stack <NUM> includes a rear bearing <NUM> and a rear main seal <NUM> associated with a shaft opening <NUM> disposed in rear endplate <NUM> and a forward main seal <NUM> and a forward bearing <NUM> associated with a shaft opening <NUM> disposed in forward endplate <NUM>. As shown in <FIG>, drive shaft <NUM> includes splined portions <NUM>, which are engaged by motors <NUM> for applying rotational power to drive shaft <NUM>.

The drive shaft <NUM> is supported through forward (or front) endplate <NUM> and rear (or back) endplates <NUM> of the housing <NUM> by forward bearing <NUM> and rear bearing <NUM>, respectively. Seals <NUM>, <NUM>, for sealing the housing <NUM> around the openings <NUM>, <NUM>, may be implemented with o-rings around the mating surfaces of endplates <NUM>, <NUM>, and dynamic lip seals around the drive shaft <NUM> in the front and back of the housing <NUM>.

It should be appreciated that aircraft illustrated herein, such as ducted rotor aircraft <NUM>, is merely illustrative of a variety of aircraft that can implement the embodiments disclosed herein. Indeed, the various embodiments of the electric motor stack and gearbox unit described herein may be used on any aircraft that utilizes motors. Other aircraft implementations can include hybrid aircraft, tiltrotor aircraft, quad tiltrotor aircraft, unmanned aircraft, gyrocopters, airplanes, helicopters, commuter aircraft, electric aircraft, hybrid-electric aircraft, ducted fan aircraft having any number of ducted fans, tiltwing aircraft, including tiltwing aircraft having one or more interwing linkages, more or fewer ducted fans or non-ducted rotors and the like. As such, those skilled in the art will recognize that the embodiments described herein for an electric motor stack and gearbox unit can be integrated into a variety of aircraft configurations. It should be appreciated that even though aircraft are particularly well-suited to implement the embodiments of the present disclosure, examples of non-aircraft vehicles and devices which are not covered by the appended claims can also implement the embodiments.

The components of rotor assembly <NUM> may comprise any materials suitable for use with an aircraft rotor. For example, rotor blades <NUM> and rotor hub may comprise carbon fiber or aluminum; and rotor mast may comprise steel or titanium. While rotor hub assembly <NUM> are shown with four rotor blades <NUM>, respectively, it should be understood that they may have as few as two rotor blades and may have more than four rotor blades.

Alternative embodiments that result from combining, and/or integrating features of the embodiment(s) are also within the scope of the disclosure. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about <NUM> to about <NUM> includes, <NUM>, <NUM>, <NUM>, etc.; greater than <NUM> includes <NUM>, <NUM>, <NUM>, etc.). For example, whenever a numerical range with a lower limit, Rl, and an upper limit, Ru, is disclosed, any number falling within the range is specifically disclosed. In particular, the following numbers within the range are specifically disclosed: R=Rl +k * (Ru-Rl), wherein k is a variable ranging from <NUM> percent to <NUM> percent with a <NUM> percent increment, i.e., k is <NUM> percent, <NUM> percent, <NUM> percent, <NUM> percent, <NUM> percent,. <NUM> percent, <NUM> percent, <NUM> percent,. , <NUM> percent, <NUM> percent, <NUM> percent, <NUM> percent, <NUM> percent, or <NUM> percent. Moreover, any numerical range defined by two R numbers as defined in the above is also specifically disclosed. Use of the term "optionally" with respect to any element of a claim means that the element is required, or alternatively, the element is not required, both alternatives being within the scope of the claim. Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of. Accordingly, the scope of protection is not limited by the description set out above but is defined by the claims that follow. Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment(s) of the present invention. Also, the phrases "at least one of A, B, and C" and "A and/or B and/or C" should each be interpreted to include only A, only B, only C, or any combination of A, B, and C.

Claim 1:
An electric motor stack and gearbox unit (<NUM>) comprising:
a gearbox (<NUM>); and
a motor assembly comprising:
a shared housing (<NUM>) having a forward endplate (<NUM>) and a rear endplate (<NUM>);
a plurality of electric motors (<NUM>) disposed within the shared housing (<NUM>), wherein the plurality of motors (<NUM>) comprises a motor stack (<NUM>), wherein each of the motors (<NUM>) comprises a radial flux motor core; and
a drive shaft (<NUM>) driven by the plurality of motors (<NUM>) and having a first end (<NUM>) extending through the forward endplate (<NUM>) of the shared housing (<NUM>) and a second end (<NUM>) extending through the rear endplate (<NUM>) of the shared housing (<NUM>), wherein the first end (<NUM>) of the drive shaft (<NUM>) is configured to engage with the gearbox (<NUM>); wherein
the forward endplate (<NUM>) and the rear endplate (<NUM>) are formed separately from the main body of the shared housing (<NUM>); wherein
the first end (<NUM>) of the drive shaft (<NUM>) is splined to mate with a splined receptacle (<NUM>) disposed within the gearbox (<NUM>).