Patent Description:
On featherable aircraft propeller systems, it is desirable to accurately measure the propeller blade pitch (or beta) angle to ensure that the blade angle is controlled according to the engine power set-point requested, such as in reverse and low pitch situations, also known as the beta operating region. For this purpose, some propeller feedback systems use a beta or feedback device, sometimes referred to as a phonic wheel, which rotates with the engine. The feedback device has multiple readable markers and a sensor can be used to measure the rotation of the feedback device via the markers, providing a proxy value for the rotational velocity of the engine, as well as measure blade angle. Existing feedback devices are however vulnerable to a so-called "edge-effect" that leads to an increase in reading error as the sensor approaches the edges of the feedback device.

A prior art blade angle feedback assembly having the features of the preamble of claim <NUM> is disclosed in <CIT>.

In accordance with an aspect of the present invention, there is provided a blade angle feedback assembly as claimed in claim <NUM>.

Further embodiments are as defined by the dependent claims <NUM>-<NUM>.

Features of the systems, devices, and methods described herein may be used in various combinations, in accordance with the embodiments described herein.

<FIG> depicts a gas turbine engine <NUM> of a type typically provided for use in subsonic flight. The engine <NUM> comprises an inlet <NUM> through which ambient air is propelled, a compressor section <NUM> for pressurizing the air, a combustor <NUM> in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section <NUM> for extracting energy from the combustion gases.

The turbine section <NUM> comprises a compressor turbine <NUM>, which drives the compressor assembly and accessories, and at least one power or free turbine <NUM>, which is independent from the compressor turbine <NUM> and rotatingly drives a rotor shaft (also referred to herein as a propeller shaft or an output shaft) <NUM> about a propeller shaft axis 'A' through a reduction gearbox (RGB) <NUM>. Rotation of the output shaft <NUM> is facilitated by one or more bearing assemblies (not illustrated), which can be disposed within the RGB <NUM> or at any other suitable location. Hot gases may then be evacuated through exhaust stubs <NUM>. The gas generator of the engine <NUM> comprises the compressor section <NUM>, the combustor <NUM>, and the turbine section <NUM>.

A rotor, in the form of a propeller <NUM> through which ambient air is propelled, is hosted in a propeller hub <NUM>. The rotor may, for example, comprise the propeller <NUM> of a fixed-wing aircraft, or a main (or tail) rotor of a rotary-wing aircraft such as a helicopter. The propeller <NUM> may comprise a plurality of circumferentially-arranged blades <NUM> connected to the hub <NUM> by any suitable means and extending radially therefrom. The blades <NUM> are also each rotatable about their own radial axes B through a plurality of blade angles, which can be changed to achieve modes of operation, such as feather, full reverse, and forward thrust.

With reference to <FIG>, a feedback sensing system <NUM> for pitch-adjustable blades of bladed rotors of aircraft will now be described. The system <NUM> may be used for sensing a feedback device (also referred to as a feedback ring or phonic wheel) <NUM> of an aircraft propeller. It should however be understood that, although the system <NUM> is described and illustrated herein with reference to an aircraft propeller, such as the propeller <NUM> of <FIG>, the system <NUM> may apply to other types of rotors, such as those of helicopters. The systems and methods described herein are therefore not limited to being used for aircraft propellers.

In some embodiments, the system <NUM> provides for detection and measurement of rotational velocity of one or more rotating elements of the engine <NUM> and of propeller blade angle on propeller systems, such as the propeller <NUM> of <FIG>. The system <NUM> may interface to existing mechanical interfaces of typical propeller systems to provide a digital detection for electronic determination of the propeller blade angle. It should be noted that although the present disclosure focuses on the use of the system <NUM> and the feedback device <NUM> in gas-turbine engines, similar techniques can be applied to other types of engines, including, but not limited to, electric engines and hybrid electric propulsion systems having a propeller driven in a hybrid architecture (series, parallel, or series/parallel) or turboelectric architecture (turboelectric or partial turboelectric).

The system <NUM> comprises an annular member <NUM> and one or more sensors <NUM> positioned proximate the annular member <NUM>. Annular member <NUM> (referred to herein as a feedback device) has a plurality of detectable features (also referred to as position markers or teeth) <NUM> disposed thereon for detection by sensor(s) <NUM>. In some embodiments, the feedback device <NUM> is mounted for rotation with propeller <NUM> and to move axially with adjustment of the blade angle of the blades (reference <NUM> in <FIG>) of the propeller <NUM>, and the one or more sensors <NUM> are fixedly mounted to a static portion of the engine <NUM>. In other embodiments, the one or more sensors <NUM> are mounted for rotation with propeller <NUM> and to move axially with adjustment of the blade angle of the blades <NUM> of the propeller <NUM>, and the feedback device <NUM> is fixedly mounted to a static portion of the engine <NUM>.

The system <NUM> also includes a controller <NUM> communicatively coupled to the one or more sensors <NUM>. The sensor(s) <NUM> are configured for producing a sensor signal which is transmitted to or otherwise received by the controller <NUM>, for example via a detection unit <NUM> thereof. The sensor signal can be an electrical signal, digital or analog, or any other suitable type of signal. In some embodiments, the sensor(s) <NUM> produce a signal pulse in response to detecting the presence of a position marker <NUM> in a sensing zone of the sensor <NUM>. For example, the sensor <NUM> is an inductive sensor that operates on detecting changes in magnetic flux, and has a sensing zone which encompasses a circular or rectangular area or volume in front of the sensor <NUM>. When a position marker <NUM> is present in the sensing zone, or passes through the zone during rotation of the feedback device <NUM>, the magnetic flux in the sensing zone is varied by the presence of the position marker <NUM>, and the sensor <NUM> can produce a signal pulse, which forms part of the sensor signal. Accordingly, the position markers <NUM> may be made of any suitable material (e.g., a ferromagnetic material, Mu-Metal, or the like) which would cause the passage of the position markers <NUM> near the sensor <NUM> to provide a change in magnetic permeability within the magnetic field generated by the sensor <NUM>.

In the example illustrated in <FIG>, a side view of a portion of feedback device <NUM> and sensor <NUM> is shown. The sensor (or sensors) <NUM> is mounted to a flange <NUM> of a housing of the reduction gearbox <NUM>, so as to be positioned adjacent the plurality of position markers <NUM>. In some embodiments, the sensor <NUM> is secured to the propeller <NUM> so as to extend away from the flange <NUM> and towards the position markers <NUM> along a radial direction, identified in <FIG> as direction 'R'. Sensor <NUM> and flange <NUM> may be fixedly mounted, for example to the housing of the reduction gearbox <NUM>, or to any other static element of the engine <NUM>, as appropriate.

In some embodiments, a single sensor <NUM> is mounted in close proximity to the feedback device <NUM> and the position markers <NUM>. In some other embodiments, in order to provide redundancy as well as dual-signal sources at multiple locations, one or more additional sensors, which may be similar to the sensor <NUM>, are provided. For example, an additional sensor <NUM> may be mounted in a diametrically opposite relationship, or at any angle, relative to the position markers <NUM>, which extend away from the feedback device <NUM> and towards the sensor(s) <NUM>. In yet another embodiment, several position markers <NUM> may be spaced equiangularly about the perimeter of the feedback device <NUM>. Other embodiments may apply.

With additional reference to <FIG>, in some embodiments the feedback device <NUM> is embodied as a circular disk which rotates as part of the engine <NUM>, for example with the propeller shaft <NUM> or with the propeller <NUM>. The feedback device <NUM> comprises opposing faces (not shown) having outer edges <NUM><NUM>, <NUM><NUM> and defines a root surface <NUM> which extends between the opposing faces and circumscribes them. Put differently, the root surface <NUM> of the feedback device <NUM> is the outer periphery of the circular disk which spans between the two opposing faces and the root surface <NUM> intersects the faces at the edges <NUM><NUM>, <NUM><NUM>. In these embodiments, the position markers <NUM> can take the form of projections which extend from the root surface <NUM>.

The position markers <NUM> may comprise a plurality of first projections (not shown) arranged along a direction substantially transverse to the opposing faces and substantially equally spaced from one another on the root surface <NUM>. The position markers <NUM> may also comprise one or more second projections (not shown) each positioned between two adjacent first projections. Each second projection is illustratively oriented along a direction, which is at an angle relative to the direction along which the first projections are arranged. The angle can be any suitable value between <NUM>° and <NUM>°, for example <NUM>°, <NUM>°, <NUM>°, or any other value, as appropriate. It should be noted, however, that in some other embodiments the second projection(s) can be co-oriented with the first projections. It should also be noted that in some embodiments, each second projection can be substituted for a groove or inward projection, as appropriate. In addition, in some embodiments, the feedback device <NUM> includes only a single second projection while, in other embodiments, the feedback device <NUM> can include more than one second projection. In the latter case, the second projections can be oriented along a common orientation or along one or more different orientations and each second projection can be located at substantially a midpoint between two adjacent first projections or can be located close to a particular one of two adjacent first projections.

In one embodiment, the position markers <NUM> are integrally formed with the feedback device <NUM> so that the feedback device <NUM> may have a unitary construction. In another embodiment, the position markers <NUM> are manufactured separately from the feedback device <NUM> and attached thereto using any suitable technique, such as welding or the like.

It should also be noted that, although the present disclosure focuses primarily on embodiments in which the position markers <NUM> are projections, other embodiments are also considered. The position markers <NUM> may, for example, comprise one or more of protrusions, teeth, walls, voids, recesses, and/or other singularities. For instance, in some embodiments, the position markers <NUM> may be embedded in the circular disk portion of the feedback device <NUM>, such that the feedback device <NUM> has a substantially smooth or uniform root surface <NUM>. A position marker <NUM> can then be a portion of the feedback device <NUM> which is made of a different material, or to which is applied a layer of a different material. The position markers <NUM> may then be applied to the root surface <NUM>, for instance as strips of metal or other material for detection by the sensor <NUM>, which can be an inductive sensor capable of sensing changes in magnetic flux (as discussed above) or any other suitable sensor such as a Hall sensor or a variable reluctance sensor. Still other embodiments are considered.

The signal pulses produced by the sensor <NUM>, which form part of the electrical signal received by the control system <NUM>, can be used to determine various operating parameters of the engine <NUM> and the propeller <NUM>. The regular spacing of the first projections can, for example, be used to determine a speed of rotation of the feedback device <NUM>. In addition, the second projection(s) can be detected by the sensor <NUM> to determine a blade angle of the propeller <NUM>.

With continued reference to <FIG>, the feedback device <NUM> is supported for rotation with the propeller <NUM>, which rotates about the longitudinal axis 'A'. The feedback device <NUM> is also supported for longitudinal sliding movement along the axis A, e.g. by support members, such as a series of circumferentially spaced feedback rods <NUM> that extend along the axis A. A compression spring <NUM> surrounds an end portion of each rod <NUM>.

As depicted in <FIG>, the propeller <NUM> comprises a plurality of angularly arranged blades <NUM>, each of which is rotatable about a radially-extending axis B through a plurality of adjustable blade angles, the blade angle being the angle between the chord line (i.e. a line drawn between the leading and trailing edges of the blade) of the propeller blade section and a plane perpendicular to the axis of propeller rotation. In some embodiments, the propeller <NUM> is a reversing propeller, capable of operating in a variety of modes of operation, including feather, full reverse, and forward thrust. Depending on the mode of operation, the blade angle may be positive or negative: the feather and forward thrust modes are associated with positive blade angles, and the full reverse mode is associated with negative blade angles.

Referring now to <FIG> in addition to <FIG>, the feedback device <NUM> illustratively comprises position markers <NUM>, which, in one embodiment, can take the form of projections which extend from the root surface <NUM>. As the feedback device <NUM> rotates, varying portions thereof enter, pass through, and then exit the sensing zone of the sensor <NUM>. From the perspective of the sensor <NUM>, the feedback device <NUM> moves axially along axis A and rotates about direction F. However, as the sensor <NUM> is positioned adjacent to the edges <NUM><NUM>, <NUM><NUM> of the feedback device <NUM> as a result of movement of the feedback device <NUM>, a drop in magnetic flux occurs. This results in a so-called "edge-effect" that leads to an increase in reading error (also referred to herein as beta error) at the edges <NUM><NUM>, <NUM><NUM>, particularly as the feedback device <NUM> moves away from the sensor <NUM>. In order to permit the sensor <NUM> to accurately detect the passage of the position markers <NUM> without any edge-related effects, it is proposed herein to surround the sensor <NUM> with a magnetic shield (not shown) that extends laterally away from the exterior of the housing <NUM> and over the position markers <NUM> so as to cover (i.e. span) a distance of axial displacement (i.e. translation) of the feedback device <NUM> (and accordingly of the position markers <NUM>) along axis A, as will be discussed further below.

In one embodiment (illustrated in <FIG>), the position markers <NUM> include a plurality of projections <NUM> which are arranged along a direction 'D', which is substantially transverse to the opposing edges <NUM><NUM>, <NUM><NUM>. Although only two projections <NUM> are illustrated in <FIG>, it should be understood that any suitable number of projections <NUM> may be present across the whole of the root surface <NUM>. The projections <NUM> can be substantially equally spaced from one another on the root surface <NUM>. In addition, the projections <NUM> are of substantially a common shape and size, for example having a common volumetric size. In some embodiments, only some of the projections <NUM> may have extensions whereas others may not and the projections <NUM> may not always be equally spaced around the root surface <NUM>.

The feedback device <NUM> also includes at least one supplementary projection <NUM> which is positioned between two adjacent ones of the projections <NUM>. In the embodiment depicted in <FIG>, the projection <NUM> is oriented along a direction 'E', which is at an angle relative to direction 'D'. The angle between directions 'D' and 'E' can be any suitable value between <NUM>° and <NUM>°, for example <NUM>°, <NUM>°, <NUM>°, or any other value, as appropriate. It should be noted, however, that in some other embodiments the supplementary projection <NUM> can be co-oriented with the projections <NUM>, for instance along direction 'D'.

In some embodiments, the feedback device <NUM> includes only a single supplementary projection <NUM>. In other embodiments, the feedback device <NUM> can include two, three, four, or more supplementary projections <NUM>. In embodiments in which the feedback device <NUM> includes more than one supplementary projection <NUM>, the supplementary projections can all be oriented along a common orientation, for instance direction 'E', or can be oriented along one or more different orientations. The projection <NUM> can be located at substantially a midpoint between two adjacent projections <NUM>, or, as shown in <FIG>, can be located close to a particular one of two adjacent projections <NUM>.

As shown in <FIG>, and <FIG>, the sensor <NUM> illustratively comprises a housing <NUM> having a generally cylindrical shape with a sensor axis SA. In some embodiments, the sensor axis SA may be a radial line relative to the axis of rotation (reference A in <FIG>) of the feedback device (reference <NUM> in <FIG>). In some embodiments, the housing <NUM> may have a circular outer cross-sectional profile (as illustrated in <FIG>). The sensor <NUM> may have a single-channel configuration and accordingly may have a single coil 504A disposed inside of housing <NUM>. The coil 504A may be configured to generate one or more sensor signals in response to variations in the magnetic field caused by the movement of position markers <NUM> relative to the sensor <NUM>. In other embodiments, the sensor <NUM> may have a multi-channel configuration wherein sensor signals are acquired in a redundant manner. In this case, the sensor <NUM> may have a two-channel configuration (as shown in <FIG>) with two electrically-isolated coils 504A and 504B. In response to the variations in the magnetic field, coil 504A may be configured to generate first sensor signal(s) on a first channel and coil 504B may be configured to generate second sensor signal(s) on a second channel.

Sensor <NUM> comprises a magnet <NUM> disposed inside housing <NUM>. The magnet <NUM> has two opposite (i.e. North and South) poles. The magnet <NUM> may be a permanent magnet. The magnet <NUM> may be stationary and mounted adjacent the feedback device <NUM>. In some embodiments, the sensor <NUM> may comprise pole piece <NUM>, which is configured to direct the magnetic field generated by the magnet <NUM> radially inwardly (or outwardly) along sensor axis SA and toward the feedback device <NUM> at a location expected to be occupied by position marker(s) <NUM>. The magnetic flux exiting the distal end of the pole piece <NUM> may then intersect the position marker(s) <NUM> as the position marker(s) <NUM> move past the sensor <NUM>. The magnetic field may therefore include a first magnetic flux intersecting the location that the position marker(s) <NUM> are expected to occupy and a second magnetic flux (also referred to herein as leakage magnetic flux) not intersecting the location that the position marker(s) <NUM> are expected to occupy. The leakage magnetic flux may be present substantially around sensor axis SA (e.g., in a substantially axisymmetric manner). Coils 504A and 504B may be wound around pole piece <NUM>, with coil 504A being a radially-inner coil and coil 504B being a radially-outer coil that surrounds coil 504A. Coils 504A, 504B may be stationary relative to magnet <NUM> and mounted in the magnetic field of magnet <NUM>. The coils 504A, 504B may be of different sizes and/or positions.

A magnetic shield <NUM> is mounted to the sensor <NUM> and may have a generally cylindrical shape and be disposed externally to the sensor housing <NUM>. For example, the magnetic shield <NUM> may be mounted to the exterior of housing <NUM> by any suitable means (as illustrated in <FIG>, and <FIG>). Alternatively, the magnetic shield <NUM> may be mounted to the interior of housing <NUM> by any suitable means. In one embodiment, the magnetic shield <NUM> may be configured as a sealed enclosure that surrounds the sensor <NUM> on all sides. In another embodiment, the magnetic shield <NUM> may be configured as an unsealed enclosure, which comprises apertures and which does not surround the sensor <NUM> in its entirety.

The magnetic shield <NUM> may be made from one or more materials of relatively high magnetic permeability to readily support the formation of a magnetic field within itself. In some embodiments, the magnetic shield <NUM> is made from Mu-metal or any suitable material(s) exhibiting a relatively high relative magnetic permeability. In some embodiments, the material(s) of the magnetic shield <NUM> may have a relative magnetic permeability value between <NUM>,<NUM> and <NUM>,<NUM>. In other embodiments, the material(s) of the magnetic shield <NUM> may have a relative magnetic permeability value between <NUM>,<NUM> and <NUM>,<NUM>. Other embodiments may apply.

As will be understood by a person skilled in the art and still referring to <FIG>, a given position marker <NUM> comprises two opposite axial ends (also referred to as edges or terminations) 202A, 202B, the axial end 202A, 202B being the ends where the position marker <NUM> terminates in the axial direction relative to rotation axis A. When no magnetic shield <NUM> is used, as an axial end (e.g., axial end 202A) of the position marker <NUM> approaches the sensor <NUM>, the different amounts of material from the position marker <NUM> positioned adjacent either sides of the sensor <NUM> can result in asymmetric permeability and skew the magnetic field of an unshielded sensor (i.e. offset line M from sensor axis SA). This edge-related effect may in turn cause some error in the sensor signals provided by coils 504A, 504B. For instance, error(s) in the determined axial position of the feedback device <NUM> and/or discrepancies between signals obtained from separate coils 504A, 504B of different channels may be experienced. In some situations, the error increases exponentially as the axial end 202A moves away from the unshielded sensor <NUM> and can therefore limit the amount of useable axial movement available for a given length of position markers <NUM>. The magnetic shield <NUM> may be used to provide one or more low-reluctance return paths for guiding leakage magnetic flux (from the pole piece <NUM> or the magnet <NUM>). This may in turn reduce the edge-related effect otherwise exhibited using an unshielded sensor, consequently decreasing the likelihood of errors.

In particular, the magnetic shield <NUM> may provide controlled and predictable magnetic return path(s) for the leakage magnetic flux <NUM> so that effects of such leakage on coils 504A, 504B may be reduced. It should be understood that, for the sake of clarity, only a few magnetic flux lines for the magnetic flux <NUM> are illustrated in <FIG>. The illustrated magnetic flux lines are not to scale but are merely shown for illustrative purposes. Magnetic shield <NUM> may shunt most of the leakage magnetic flux (which does not intersect with the location that the position markers <NUM> are expected to occupy) back toward the opposite magnetic pole of magnet <NUM>, thereby isolating such leakage magnetic flux from external influences (e.g., position markers <NUM>). In other words, the magnetic shield <NUM> efficiently closes the magnetic circuit between the two opposite (i.e. North and South) poles of magnet <NUM> for leakage magnetic flux. In some embodiments, the magnetic shield <NUM> may be symmetric across sensor axis SA to define two or more (e.g., symmetric) return paths that are angularly distributed about the sensor axis SA in an axisymmetric manner. It should however be understood that the magnetic shield <NUM> need not be symmetric across sensor axis SA and the magnetic shield <NUM> may have any other suitable configuration.

It should also be understood that the magnetic shield <NUM> may have different configurations in order to achieve different types and amounts of magnetic flux guiding in different applications. For example, the geometry of the magnetic shield <NUM> may vary based on the specific configurations of the sensor <NUM> and of the feedback device <NUM>. In the embodiment shown in <FIG>, the magnetic shield <NUM> comprises a top wall 510A, at least one side wall 510B, and a bottom wall 510C, cooperatively defining a receptacle within which part of the sensor housing <NUM> and/or other internal components of the sensor <NUM> may be received. In particular, magnetic shield <NUM> may have a receptacle configuration within which coils 504A and 504B are partially or entirely received. In this manner, coils 504A and 504B may be shielded by magnetic shield <NUM>. Part of or the entirety of pole piece <NUM> may be received inside the receptacle defined by the magnetic shield <NUM>. The magnetic shield <NUM> may have a single-piece unitary construction wherein top wall 510A, side wall(s) 510B, and bottom wall 510C are integrally formed. It should however be understood that top wall 510A, side wall(s) 510B, and bottom wall 510C may comprise separate components (e.g., washer and sleeve) that are subsequently assembled together to permit magnetic coupling therebetween.

Bottom wall 510C is illustratively disposed between coils 504A, 504B and feedback device <NUM>. In some embodiments, the bottom wall 510C may comprise two spaced wall members 512A, 512B defining an aperture <NUM> extending through bottom wall 510C. The aperture <NUM> may permit some of the magnetic flux that is guided by pole piece <NUM> to pass through the magnetic shield <NUM> via the aperture <NUM>. In some embodiments, the aperture <NUM> is centrally located within bottom wall 510C. In some embodiments, sensor axis SA passes through the aperture <NUM>. In some embodiments, a distal portion of pole piece <NUM> extends into or through the aperture <NUM>. The aperture <NUM> may be sized and positioned to provide an air gap between the magnetic shield <NUM> and the pole piece <NUM>.

As shown in <FIG>, the bottom wall 510C of the magnetic shield <NUM> extends laterally away from an exterior of the sensor housing <NUM>, over the position markers <NUM>. This extension of the magnetic shield <NUM> (also referred to herein as a magnetic shield extension) may be made of the same material as the magnetic shield <NUM>, i.e. of Mu-metal or any other suitable material(s) exhibiting a relatively high relative magnetic permeability. In one embodiment, the magnetic shield extension is integral with the magnetic shield <NUM>, whereby the extension is machined from solid, leaving overhung material extensions. In another embodiment, the magnetic shield extension is added to the magnetic shield <NUM> by a suitable assembly method (e.g., welding). Other embodiments may apply that include manufacturing methods such as additive manufacturing, casting, forging, extrusion, powder metallurgy, blanking, broaching, milling, grinding, brazing, and other suitable methods.

The magnetic shield extension spans the distance of axial displacement of the feedback device <NUM>. In particular, the magnetic shield <NUM> is configured to extend laterally away from the sensor housing <NUM> so as to fully cover the position markers <NUM> (i.e. span the distance over which the position marker(s) are displaced) as they travel along the axis A, from a minimum axial translation position to a maximum axial translation position, respectively labelled "Min Position" and "Max Position" in <FIG>. As a result, the magnetic shield extension allows for inductive coupling to be increased as the position markers <NUM> pass nearby the sensor <NUM>. The magnetic shield extension therefore provides a permeable material extension which reroutes the path of the magnetic flux lines <NUM> and increases the magnetic flux density at the edges (references <NUM><NUM>, <NUM><NUM> in <FIG>) of the feedback device <NUM>, as the feedback device <NUM> moves axially along axis A. The presence of the added material will make detection possible even when the axial position of the feedback device <NUM> is farthest away from the sensor <NUM> (i.e., at the minimum and maximum axial translation positions). In this manner, the magnetic flux path is continuous when the feedback device <NUM> moves axially away from the sensor <NUM>. In other words, the magnetic shield extension results in an extension of the magnetic flux path and the magnetic path extension provides a low reluctance magnetic return path (for some magnetic flux of the magnetic field exiting the pole piece <NUM> from one pole of the magnet <NUM> toward the opposite pole) to close the magnetic circuit and reduces the loss of magnetic flux density at the edges <NUM><NUM> and <NUM><NUM>. This increases the sensor signal and may in turn mitigate (i.e. reduce) edge-related effects, thereby allowing accurate detection of the position markers <NUM>. The beta error experienced by the feedback system is thus decreased, particularly as the feedback device <NUM> moves away from the sensor <NUM>.

It should be understood that the geometry of the magnetic shield extension and/or the distance by which the magnetic shield extension projects away from the sensor housing <NUM> may be optimized for a given application, the parameters (e.g. engine configuration) specific to that application, the distance of the sensor <NUM> relative to the feedback device <NUM>, the geometry of the feedback device <NUM>, and the beta error experienced by the feedback system. In particular, the thickness, size, and shape of the magnetic shield extension is determined to ensure optimal detection of the position markers <NUM>, depending on the application and/or specific configurations of the sensor <NUM> and of the feedback device <NUM>. In one embodiment, the magnetic shield extension is configured to extend only as far away from the sensor housing <NUM> as required to eliminate the beta error.

In one embodiment illustrated in <FIG>, the magnetic shield extension is created by extending the bottom wall members 512A, 512B outwardly and away from the housing <NUM>, along a direction C. In other words, each bottom wall member 512A, 512B projects laterally away from the side wall 510B by a predetermined distance. It should however be understood that the magnetic shield <NUM> may be extended by providing a plurality of magnetic shield extension members. The magnetic shield extension members may not all extend along a same direction C but may extend in multiple directions. <FIG> and <FIG> illustrate one embodiment where the direction C is substantially parallel to the direction of axial translation (i.e. axis A of <FIG>). Still, the magnetic shield extension may extend along other directions. <FIG> illustrates an embodiment where the direction C along which the magnetic shield extension (illustrated by bottom wall members 512A, 512B) extends is at an angle θ to the axis A. The angle θ may be selected such that axis C is substantially parallel to the direction (reference D in <FIG>) along which the angled projection(s) (reference <NUM> in <FIG>) extend. Other embodiments may apply. For example, the direction C may be substantially aligned with the direction of radial movement (labelled as direction R shown in <FIG>), and be accordingly substantially transverse to the axis A.

<FIG> show an embodiment where the magnetic shield extension is bilateral, i.e. created on either side of the sensor axis SA (by extending both bottom wall members 512A, 512B), such that the magnetic shield <NUM> is extended in both the minimum axial translation position and the maximum axial translation position. However, it should be understood that the magnetic shield extension may alternatively be unilateral (i.e. created on one side of the sensor axis SA), such that the magnetic shield <NUM> is extended in either the minimum axial translation position or the maximum axial translation position. This is shown in <FIG>, where only bottom wall member 512A' is extended beyond the sensor housing <NUM>. Bottom wall member 512B' does not project outwardly away from the housing <NUM> and is substantially flush therewith. In the embodiment of <FIG>, the magnetic shield <NUM> is therefore only extended in the minimum axial translation position.

The determination as to the side(s) of the sensor axis SA on which the magnetic shield extension is created illustratively depends on the location (i.e. the distance) of the sensor <NUM> relative to the feedback device <NUM>. Indeed, it is desirable to provide the magnetic shield extension adjacent the edge(s) <NUM><NUM>, <NUM><NUM> of the feedback device <NUM> furthest away from a location where the sensor <NUM> is positioned. For example, for a feedback device assembly having a sensor <NUM> located adjacent a given one of the edges (e.g., edge <NUM><NUM>), it may be desirable to extend the magnetic shield <NUM> beyond the opposite edge (e.g., edge <NUM><NUM>). If the sensor <NUM> is positioned between the edges <NUM><NUM>, <NUM><NUM>, e.g., substantially halfway, it may in turn be desirable to extend the magnetic shield <NUM> beyond both edges <NUM><NUM>, <NUM><NUM>. Additional factors, such as the amount of beta error, may also come into play when determining the geometry of the magnetic shield extension. For example, if a higher beta error is exhibited on one side of the feedback device <NUM>, material extension may be added to the magnetic shield <NUM> in order to balance the readings or eliminate the beta error all together. Available space according to clearances and tolerance stackup of the feedback system may also impact the determination as to which side(s) (i.e. bottom wall member 512A, 512B) of the magnetic shield <NUM> to extend. Additionally, the determination of which side(s) to extend may be related to the accuracy required by the feedback system and the magnetic shield extension may be employed as a means of achieving the required accuracy.

The length (or span) of the magnetic shield extension (e.g., along direction C) may also be varied according to the application. The magnetic shield extension(s) may indeed be configured to exceed, precede, or match the minimum or maximum axial positions of the position markers <NUM>. In the embodiment shown in <FIG>, bottom wall member 512A is configured to exceed the minimum position by a distance d1. In other words, in this embodiment, the bottom wall member 512A extends beyond axial end 202A of the position marker <NUM> by distance d1. In the embodiment shown in <FIG>, the bottom wall member 512A is configured to precede the minimum position by a distance d2. In other words, in this embodiment, the axial end 202A of the position marker <NUM> extends beyond the edge of the bottom wall member 512A by distance d2. In the embodiment shown in <FIG>, bottom wall member 512A is configured to match the axial end 202A of the position marker <NUM>. In other words, in this embodiment, the edge of the bottom wall member 512A and the axial end 202A of the position marker <NUM> are substantially flush (i.e. terminate in the same plane and are aligned along axis G).

Referring now to <FIG>, the magnetic shield extension may be configured to have a geometry that matches that of the position markers <NUM>. Indeed, although the magnetic shield extension has thus far been illustrated and described as being a linear extension that extends axially (along direction C in <FIG>) and outwardly away from the sensor housing <NUM>, the magnetic shield extension may be a radial curvilinear extension (as shown in the embodiment of <FIG>) where both bottom wall members 512A" and 512B" are shaped so as to follow the curvilinear shape of the feedback device <NUM> (see from the front in <FIG>) in order to maintain a substantially constant air gap between the feedback device <NUM> and the magnetic shield <NUM>.

It should however be understood that, depending on the configuration of the feedback device <NUM>, only one of the bottom wall members (e.g. bottom wall member 512A") may be curvilinear while the other bottom wall member (e.g. bottom wall member 512B") remains axial and linear (as shown in <FIG> for instance). In this manner, the magnetic shield extension of the magnetic shield <NUM> may be configured to extend both axially and radially. Other embodiments may apply.

As shown in <FIG>, in order to increase the magnetic flux path at the edges <NUM><NUM>, <NUM><NUM> of the feedback device <NUM>, the magnetic shield extension may also extend downwards on the peripheral sides of the feedback device <NUM>. In one embodiment, bottom wall members 512A‴ and 512B‴ may be substantially L-shaped so as to extend downwards towards the axial ends 202A, 202B of the position markers <NUM>. However, it should for example be understood that the shape of the magnetic shield extension need no match the geometry of the position markers <NUM> (as shown in <FIG> for instance). Indeed, the shape of the magnetic shield extension is illustratively designed to increase magnetic flux density and optimize magnetic couple. As such, even if the position markers <NUM> are rectangular-shaped, the magnetic shield extension may not be rectangular in shape.

From the above description, it can be seen that, in one embodiment, the feedback device <NUM> may be configured to allow for the sensor <NUM> to be positioned near or at the edges <NUM><NUM>, <NUM><NUM> of the feedback device <NUM> while accurately detecting the passage of the position markers <NUM>, thereby mitigating any edge-related effects that may influence the sensor <NUM>.

Claim 1:
A blade angle feedback assembly (<NUM>) for a variable-pitch aircraft propeller rotor (<NUM>), the rotor (<NUM>) rotatable about a longitudinal axis (A) and having an adjustable blade pitch angle, the assembly (<NUM>) comprising:
a feedback device (<NUM>) having at least one position marker (<NUM>) provided thereon;
at least one sensor (<NUM>) mounted adjacent the feedback device (<NUM>), one of the feedback device (<NUM>) and the at least one sensor (<NUM>) configured to be coupled to rotate with the rotor (<NUM>) about the axis (A) and to be displaced axially along the axis (A) with adjustment of the blade pitch angle, the at least one sensor (<NUM>) configured to detect a relative passage of the at least one position marker (<NUM>) as the one of the feedback device (<NUM>) and the at least one sensor (<NUM>) rotates about the axis (A), the at least one sensor (<NUM>) comprising a housing (<NUM>) and a magnet (<NUM>) having a first pole and a second pole opposite the first pole, the magnet (<NUM>) having a magnetic field; and
a magnetic shield (<NUM>) mounted to the at least one sensor (<NUM>) and configured to define a magnetic return path for some magnetic flux of the magnetic field exiting from the first pole of the magnet (<NUM>) toward the second pole, the magnetic shield (<NUM>) comprising at least one wall member (510A, 510B, 510C) positioned adjacent the at least one position marker (<NUM>), the at least one wall member (510A, 510B, 510C) comprising a bottom wall (510C),
characterised in that:
the bottom wall (510C) comprises at least one extension member that extends laterally away from the exterior of the housing (<NUM>) and spans the distance over which the at least one position marker (<NUM>) is configured to be displaced relative to the at least one sensor (<NUM>) with axial displacement of the one of the feedback device (<NUM>) and the at least one sensor (<NUM>) along the axis (A) with adjustment of the blade pitch angle.