Patent ID: 12259031

DETAILED DESCRIPTION

Aspects of the disclosed embodiments will now be addressed with reference to the figures. Aspects in any one figure is equally applicable to any other figure unless otherwise indicated. Aspects illustrated in the figures are for purposes of supporting the disclosure and are not in any way intended on limiting the scope of the disclosed embodiments. Any sequence of numbering in the figures is for reference purposes only.

Turning toFIG.1, an aircraft5includes a control surface10, which may be a flap or slat of a wing20or other control surface of an aircraft, a motor30and a harmonic drive40coupled to the control surface10that receives rotational energy from the motor30and provides it to the control surface10.

As disclosed in greater detail below, the harmonic drive40has a housing50. As shown, the housing50is a split housing and includes first and second housing segments SOA, SOB. A harmonic gear70is disposed in the housing50. The gear70includes an input shaft60and an output shaft90. The input shaft60can include a wave generator profile65, discussed below. As shown, the output shaft90includes an output flange80. The output shaft90can either be coupled/connected to and driven by the input shaft60or de-coupled/disconnected from the input shaft as more fully explained below. The output flange80extends outwardly from the housing50.

A solenoid coil100can be disposed in the housing50such that it surrounds a portion of the input shaft.

When the solenoid100is powered a current passes through it and generates a magnetic field. The magnetic field can interact with the input shaft to move the input shaft and places the harmonic drive40in a disconnected state. When the solenoid coil100is not energized, the harmonic drive40is in a normal state, and the input shaft60and output shaft90are rotationally coupled. That is, the output shaft90rotates with rotation of the input shaft60. When the solenoid100is energized, the harmonic drive40is in the disconnect state, and the input shaft60and output shaft90are rotationally decoupled. That is, the output shaft90does not rotate with rotation of the input shaft60.

The harmonic drive also includes a flex spline110. The flex spline110illustrated inFIG.1can be a split spline having first and second spline segments110A,110B. Both the first and second spline segments110A,110B can be cup-shaped in one embodiment. The split configuration of the spline110and the housing50enables simplified assembly of the harmonic drive40but the spline need not always be split.

Turning toFIG.2, additional details of the harmonic drive40are explained. The housing50can be hollow in one embodiment. The housing50can include a housing outer wall120that extends axially from a first outer end130A of the housing50to a second outer end130B of the housing50. The inner side140B may define a channel140C.

A perimeter wall150A may be disposed within the channel140C, at the first outer end130A, which may define a first input shaft aperture160A. A partition wall150B may be disposed within the channel140C, between the first and second outer ends130A,130B of the housing50, and may define a second input shaft aperture160B. The partition wall150B may divide the channel140C into a first cavity170A is between the perimeter wall150A and the partition wall150B, and a second cavity170B between the partition wall150B and the second outer end130B. An output flange aperture180is defined in the housing outer wall120. The output flange aperture180extends into the first cavity170A. The output flange80, connected to the output shaft90, extends outwardly from the output shaft90, through the output flange aperture180.

The input shaft60is disposed within the first cavity170A. The shaft includes a first side190A that extends through the first input shaft aperture160A. The input shaft also includes a second side190B that extends through the second input shaft aperture160B. The input shaft60is configured so that in the first and second position of the input shaft60, e.g., regardless of whether the solenoid100is energized, a portion of the first side190A of the input shaft60is exterior to the first outer end130A of the housing50and a portion of the second side190B of the input shaft60is within or adjacent to the solenoid100.

The solenoid100is within the second cavity170B. The solenoid100is operable between a first mode and a second mode. In the first mode, the solenoid100is not energized, the input shaft60is in a first axial position (or first position) (FIG.2), and is rotationally coupled with the output shaft90. This corresponds to the normal state of the drive40. In the second mode, the solenoid100is energized, a magnetic field created by the solenoid draws the input shaft60to a second axial position (or second position) (FIG.1) so that the input shaft60is rotationally decoupled, or disconnected, from the output shaft90. This corresponds to the disconnect state of the drive40. That is, in the first mode (not energized) of the solenoid100(the normal state of the drive40), rotation of the input shaft60rotates the output shaft90. In the second mode (energized) of the solenoid100(the disconnect state of the drive40), rotation of the input shaft60does not rotate the output shaft90, because of the relative axial positioning of the input and output shafts60,90. The solenoid100may have a center aperture105that is configured to receive the second side190B of the input shaft60when the input shaft60is in the second position.

The input shaft60includes a shoulder200having a first side205A that faces the first outer end130A of the housing50and a second side205B that faces the second outer end130B of the housing50. The drive includes a spring210extending between the partition wall150B and the second side205B of the shoulder200of the input shaft60. The spring210biases the input shaft60from the second position to the first position, which is effective when the solenoid100is not energized. However, the solenoid100, when energized, is powerful enough to overcome the spring forces of the spring210and move the input shaft60to the second (disconnect) position.

The perimeter wall150A includes a perimeter wall arm220A. The perimeter wall arm220A extends axially into the first cavity170A to a first inner arm end230A. The partition wall150B includes a partition wall arm220B. The partition wall arm220B extends axially into the first cavity170A to a second inner arm end230B.

The drive40also includes a first thrust bearing240A disposed against the first inner arm end230A. The first thrust bearing240A engages the first side205A of the shoulder200when the input shaft60is in the first position. A second thrust bearing240B is disposed between the spring210and the second side205B of the shoulder200. The second thrust bearing240B engages the second inner arm end230B when the input shaft60is in the second position.

The drive40also includes a first input shaft bearing250A that engages the first side190A of the input shaft60and a second input shaft bearing250B that engages the second side190B of the input shaft60. The perimeter wall arm220A defines a first recess260A for seating the first input shaft bearing250A and the partition wall150B defines a second recess260B for seating the second input shaft bearing250B.

As indicated, the input shaft60includes a center portion270that is axially centered on the shoulder200and defines the wave generator profile65. A wave generator bearing set280is disposed against the center portion270of the input shaft60and extends axially from a first side290A to a second side290B. When the input shaft60is in the first position, the wave generator bearing set280is axially aligned with the output shaft90. When the input shaft60is in the second position, the wave generator bearing set280is axially offset from the output shaft90.

A first thrust washer340A is disposed radially against the first side205A of the shoulder200and axially against the first side290A of the wave generator bearing set280. A second thrust washer340B is disposed radially against the second side205B of the shoulder200and axially against the second side290B of the wave generator bearing set280.

A first containment washer (or clip)350A is disposed radially against the first side205A of the shoulder200and axially against the first thrust bearing240A, to prevent movement of the first thrust bearing240A against the input shaft60. A second containment washer350B is disposed radially against the second side205B of the shoulder200and axially against the second thrust bearing240B to prevent relative movement of the second thrust bearing240B against the input shaft60.

By utilizing the first and second containment washers350A,350B, when the input shaft60moves from the first position (FIG.2) to the second position (FIG.1), the thrust washers340A,340B move the wave generator bearing set280with the input shaft60. This decouples the wave generator bearing set280from the spline380B of the flex spline110. As a result, the spline380B will not be engaged by the input shaft60and will not engage the gear set380A of the output shaft90.

With the disclosed embodiments, the input shaft60will not drive, and will also not prevent free rotation, of the output shaft90and output flange80when the solenoid coil100is energized. As a result, energizing the solenoid100enables free rotation of the output flange80, and thus free movement of a control surface10coupled to the output flange80. In operation of an aircraft5, for example, if the motor30should fail to function properly, energizing the solenoid100will allow the control surface10to freely rotate to a position that minimizes air resistance.

The output shaft90has a center portion300, a first output shaft arm310A that extends toward the first outer end130A of the housing50from the center portion300of the output shaft90. A second output shaft arm310B extends toward the second outer end130B of the housing50from the center portion300of the output shaft90. A first output shaft bearing320A is disposed between the first output shaft arm310A and the housing50. A second output shaft bearing320B is disposed between the second output shaft arm310B and the housing50.

The housing50also defines an output shaft recess330that seats the center portion300of the output shaft90. This axially secures the output shaft90withing the housing50.

The housing50defines the split housing with the first housing segment50A extending from the first outer end130A to a first inner end360A. The second housing segment50B extends from the second outer end130B of the housing50to a second inner end360B of the second housing segment50B. The first and second inner ends360A,360B of the housing segments50A,50B are within the first cavity170A.

The output flange aperture180is defined between the first and second inner ends360A,360B of the housing segments50A,50B. The output shaft recess330is defined at the second inner end360B of the second housing segment50B.

The flex spline110is disposed within the first cavity170A. The flex spine110has a first outer end370A located at the perimeter wall150A, between the inner side140B of the housing50and the perimeter wall arm220A The flex spine also includes a second outer end370B is disposed at the partition wall150B, between the inner side140B of the housing50and the partition wall arm220B. The output shaft90defines an inner facing gear set380A and the flex spline110defines an outer facing spline380B that meshes with the inner facing gear set380A in each operable mode of the solenoid100. This is because the output shaft90does not move axially with the input shaft60. However, the spline380B only engages the gear set380A when the solenoid100is not energized, the input shaft60is in the first position, and the wave generator bearing set280is axially aligned with the spline380B during rotation of the input shaft60. That is, when the solenoid100is energized, the input shaft60is in the second position, and the wave generator bearing set280is axially offset from the spline380B during rotation of the input shaft60, and the spline380B does not engage the gear set380A.

The flex spline110includes two spine segments110A,110B. The first spline segment110A is cup-shaped, defined by a first spline base (or flange)390A at the first outer end370A of the flex spline110and a first spline wall (or tube)400A that extends from the first spline base390A to a first splined end410A. The first spline segment110A surrounds a portion of the first side190A of the input shaft60and the first thrust bearing240A. The second spline segment110B is also cup-shaped, having a second spline base390B at the second outer end370B of the spline110and a second spline wall400B that extends from the second spline base390B to a second splined end410B. That is, the spline segments110A,110B face each other within the first cavity170A. The second spline segment110B surrounds a portion of the second side190B of the input shaft60and the second thrust bearing240B.

The first spline base390A defines a first center aperture430A that is configured to receive the perimeter wall arm220A so that the perimeter wall arm220A separates the first spline base390A and the first input shaft bearing250A. The second spline base390B defines a second center aperture430B that is configured to receive the partition wall arm220B so that the partition wall arm220B separates the second spline base390B and the spring210. The first inner end410A of the first spline segment110A and the second inner end420B of the second spline segment110B are disposed at an axial center440of the output shaft90.

It is to be appreciated that the split configuration of the housing enables the installation of the split cup-type flex spline. As a result, the embodiments provide a cup-type harmonic drive. The cup-type harmonic drive has a higher operational efficiency than, for example, a strait or pancake style harmonic drive. However, such other configurations are within the scope of the disclosure.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof.

Those of skill in the art will appreciate that various example embodiments are shown and described herein, each having certain features in the particular embodiments, but the present disclosure is not thus limited. Rather, the present disclosure can be modified to incorporate any number of variations, alterations, substitutions, combinations, sub-combinations, or equivalent arrangements not heretofore described, but which are commensurate with the scope of the present disclosure. Additionally, while various embodiments of the present disclosure have been described, it is to be understood that aspects of the present disclosure includes only some of the described embodiments. Accordingly, the present disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.