Patent Description:
Permanent magnet motors typically include a number of magnets distributed around a rotor core. The magnets can be separated from one another by spacers located between them, the spacers also distributed around the rotor core. However, at high rotational speeds, centrifugal force can cause separation of the magnets, spacers, and/or other rotor components. Such designs can also be limited in electromagnetic performance and/or expensive to construct.

German publication <CIT> is directed to an electric machine including a multi-part shaft having a magnetic element, with a sleeve surrounding part of the multi-part shaft including the magnetic element.

<CIT> is directed to a rotor including magnets and spacers surrounded by a shield which is in turn surrounded by a sleeve.

Japanese publication <CIT> is directed to a rotor for an electric motor including a wire wound around the rotor and surrounded with resin, with circumferential grooves in which a part of the wire is wound.

This disclosure is directed to motors, particularly for use in compressors, having improved retention of components and/or improved electromagnetic properties.

Pre-tensioned carbon fiber sleeves and/or sleeves where the carbon fiber is particularly oriented can provide sufficient retention strength to keep rotor components in place during motor operation. Interlocking features such as keyways provided on magnets and/or spacers on a rotor for a motor can improve the retention of the magnets and/or spacers, reducing requirements for additional retention and thus lowering costs, simplifying manufacturing, and/or presenting opportunities for alternative materials to be used in any further retention features.

Shafts incorporating monolithic magnets can also reduce potential issues regarding retention by using different means of retention and having to secure the magnet between rotor ends, instead of having to secure multiple magnets to surfaces of a rotor core. Additionally, monolithic magnets experience the forces resulting from rotation in a balanced manner.

Eddy current shielding can improve the electromagnetic performance of a particular rotor design. The eddy current shielding can be provided on a rotor core, on the magnets, on the spacers, and/or located within a retention sleeve provided over the rotor. Such a shield can provide shunting and/or reduction of electromagnetic losses within the rotor. The thickness of the eddy current shielding can be optimized based on a computed skin depth resulting from stator slot and switching harmonics.

The size of an air gap between the stator and the rotor of the electric motor can be selected to improve electromagnetic properties of the motor as a whole, based on other motor parameters such as switching frequencies, eddy current shield location and thickness, and other parameters affecting the overall electromagnetic efficiency of the stator and rotor taken together.

In a claimed embodiment, a rotor for an electric motor includes a first rotor endpiece, a second rotor endpiece, and a permanent magnet, secured between the first rotor endpiece and the second rotor endpiece.

In a claimed embodiment, the first rotor endpiece is secured to the permanent magnet by an adhesive and the second rotor endpiece is secured to the permanent magnet by the adhesive.

a claimed embodiment, the rotor further includes an aperture passing through a center of the permanent magnet from a first rotor endpiece end of the permanent magnet to a second rotor endpiece end of the permanent magnet and a shaft extending through the aperture. The first rotor endpiece and the second rotor endpiece are joined by the shaft.

According to the invention, the rotor further includes a sleeve configured to surround a portion of the first rotor endpiece, a portion of the second rotor endpiece, and the permanent magnet.

According to the invention, the rotor further includes one or more first retention features provided on the first rotor endpiece and one or more second retention features provided on the second rotor endpiece. Each of the first retention features and the second retention features are configured to engage with the sleeve.

In a claimed embodiment, the sleeve includes a first flange configured to engage with the one or more first retention features and a second flange configured to engage with the one or more second retention features.

According to the invention, the sleeve comprises a plurality of first openings each configured to receive at least one of the first retention features and a plurality of second openings each configured to receive at least one of the second retention features.

In a claimed embodiment, the rotor further includes an eddy current shield located within the sleeve.

In a claimed embodiment, the rotor further includes an eddy current shield surrounding the permanent magnet.

In a claimed embodiment, the sleeve comprises carbon fiber.

<FIG> shows a perspective review of a rotor and a sleeve according to an embodiment. Rotor <NUM> includes rotor core <NUM>. Rotor core <NUM> includes projections <NUM>. Permanent magnets <NUM> and pole spacers <NUM> are disposed radially around rotor core <NUM>. In the embodiment shown in <FIG>, pole spacers <NUM> include recesses <NUM> configured to receive projections <NUM>. Rotor <NUM> further includes a retention sleeve <NUM> surrounding permanent magnets <NUM> and pole spacers <NUM>.

Rotor <NUM> is a surface permanent magnet (SPM) rotor for use in an electric motor. Rotor <NUM> is configured to be rotated by electromagnetic torque provided by a stator (see <FIG>) of the electric motor. Rotation of the rotor <NUM> resulting from the electromagnetic torque can be used to operate a device, for example a compressor such as a centrifugal compressor. Rotor <NUM> can be joined to or incorporated into a driveshaft to be rotated by operation of the electric motor. The driveshaft can be used, for example, to rotate an impeller such as an impeller of a centrifugal compressor. The rotor <NUM> can be used in, as a non-limiting example, hermetic or semi-hermetic centrifugal compressors used in chillers and/or heating, ventilation, air conditioning, and refrigeration (HVACR) systems having capacities of between <NUM> and <NUM> tons.

Rotor core <NUM> is a portion of rotor <NUM> towards a center of rotor <NUM>. Rotor core <NUM> can include one or more projections <NUM>. The projections <NUM> extend outwards from the surface of rotor core <NUM>. The projections <NUM> can be, for example, a bar shape, one or more studs or pins, or any other suitable projection from the rotor core that can interface with the recesses <NUM>. In embodiments, the projections <NUM> can extend a length of the pole spacers <NUM> along the axis of rotation of rotor <NUM>. In an embodiment, some or all of projections <NUM> extend less than the length of the pole spacers <NUM>. In an embodiment, each pole spacer <NUM> includes a recess <NUM>. In an embodiment, only some of pole spacers <NUM> include the recess <NUM>. While the recesses <NUM> are shown as being on pole spacers <NUM> in the embodiment shown in <FIG>, it is understood that in embodiments, at least some of permanent magnets <NUM> can include the recesses <NUM> and interface with corresponding projections <NUM> from rotor core <NUM>.

Permanent magnets <NUM> are a plurality of permanent magnets disposed on rotor core <NUM>. Permanent magnets <NUM> can be any suitable permanent magnet material such as SmCo or NdFeB or the like. Permanent magnets <NUM> can be distributed radially around the rotor core <NUM>. Pole spacers <NUM> can also be disposed on rotor core <NUM>, arranged in spaces between permanent magnets <NUM>. Pole spacers <NUM> combined with permanent magnets <NUM> define a plurality of magnetic poles that can respond to electromagnetic torque provided by the stator of the electric motor including rotor <NUM>. Pole spacers <NUM> can be any suitable material, such as for example stainless steel and the like. Permanent magnets <NUM> and pole spacers <NUM> can abut one another. In an embodiment, the permanent magnets <NUM> and pole spacers <NUM> surround the rotor core <NUM>. Permanent magnets <NUM> and pole spacers <NUM> can be included in any suitable number and configuration for providing magnetic poles allowing rotation of rotor <NUM>.

Recesses <NUM> are formed in at least some of the pole spacers <NUM>. Recesses <NUM> are configured to accommodate the projections <NUM>. Recesses <NUM> can be any suitable shape corresponding to projections <NUM>, such as a groove to accommodate bar-shaped projections <NUM>, holes to accommodate studs or pins, or the like. The interface between the recesses <NUM> and projections <NUM> can assist in retaining the pole spacers <NUM> and/or permanent magnets <NUM>, restricting slippage in a circumferential direction as rotor <NUM> turns. In embodiments, the interface between the recesses <NUM> and projections <NUM> can also restrict slippage of pole spacers <NUM> and/or permanent magnets <NUM> in an axial direction of the rotor <NUM>.

Retention sleeve <NUM> is a sleeve surrounding the rotor core <NUM>, permanent magnets <NUM>, and pole spacers <NUM>. The retention sleeve <NUM> can be any suitable material for retaining the permanent magnets <NUM> and pole spacers <NUM>. In an embodiment, retention sleeve <NUM> can be a composite material such as a carbon fiber or glass fiber composite. In an embodiment, retention sleeve <NUM> is a metallic material. Retention sleeve <NUM> can be a pre-tensioned material. When the retention sleeve <NUM> is a composite material including a fiber such as carbon fiber or glass fiber, the fiber orientation can be selected such that the strength is matched to the directional forces that retention sleeve <NUM> is configured to resist. For example, there may be axial stresses such as thrust or component separation, as well as radial forces such as centrifugal force driving rotor components such as the permanent magnets <NUM> and pole spacers <NUM> away from rotor core <NUM>. In embodiments, the fibers of a composite used for retention sleeve <NUM> can be such that at least a part of the fibers in the sleeve form a non-zero angle to the azimuth direction of the rotor <NUM>. In an embodiment, the non-zero angle may be an angle in a range between <NUM> degrees and <NUM> degrees from the azimuth direction of the rotor <NUM>. In an embodiment, the retention sleeve <NUM> can be assembled by wrapping the retention sleeve <NUM> directly to the rotor <NUM>, while applying a tensile force on the fibers. In another embodiment, the retention sleeve <NUM> can be produced by pre-wrapping the retention sleeve <NUM> onto a mandrel and then shrink fitting and/or press fitting the retention sleeve <NUM> onto the rotor <NUM>.

In an embodiment, retention sleeve <NUM> can be slid over the permanent magnets <NUM> and pole spacers <NUM>. In an embodiment, retention sleeve <NUM> is not press-fit onto the magnets <NUM> and pole spacers <NUM>. In an embodiment, retention sleeve <NUM> and the interface between recesses <NUM> and projections <NUM> are the sole sources of retention of the permanent magnets <NUM> and pole spacers <NUM> to the rotor core <NUM>. In an embodiment, no adhesive is included to retain permanent magnets <NUM> and/or pole spacers <NUM> to rotor core <NUM>.

<FIG> shows a sectional view of a rotor according to an embodiment. In the embodiment shown in <FIG>, rotor <NUM> includes rotor core <NUM> including recesses <NUM>, permanent magnets <NUM>, and pole spacers <NUM> including projections <NUM>.

In the embodiment shown in <FIG>, rotor core <NUM> includes recesses <NUM>, and the projections <NUM> are provided on pole spacers <NUM>.

Recesses <NUM> are formed in rotor core <NUM>. Recesses <NUM> can be any suitable shape corresponding to projections <NUM>, such as a groove to accommodate bar-shaped projections <NUM>, holes to accommodate studs or pins, or the like. The interface between the recesses <NUM> and projections <NUM> can assist in retaining the pole spacers <NUM> and/or permanent magnets <NUM>, restricting slippage in a circumferential direction as rotor <NUM> turns. In embodiments, the interface between the recesses <NUM> and projections <NUM> can also restrict slippage of pole spacers <NUM> and/or permanent magnets <NUM> in an axial direction of the rotor <NUM>. In embodiments, a recess <NUM> is included for each projection <NUM> provided on the pole spacers <NUM> of a particular rotor <NUM>. In embodiments, the recesses <NUM> can have straight sides so that the projections <NUM> on pole spacers <NUM> can be inserted directly into the recesses <NUM> as the pole spacers <NUM> are placed on the exterior of the rotor core <NUM>.

Permanent magnets <NUM> and pole spacers <NUM> are provided around rotor core <NUM>. At least some of pole spacers <NUM> include projections <NUM>. Projections <NUM> can be, for example, bar-shaped projections, pins or studs, or any other suitable shape of projection that can interface with the recesses <NUM> of the rotor core <NUM> when the pole spacers are placed onto the rotor core <NUM>. While the embodiment shown in <FIG> shows projections <NUM> provided on each of pole spacers <NUM>, it is understood that projections <NUM> can be provided on only some of pole spacers <NUM> in other embodiments. It will also be appreciated that the projections may be on the rotor core and the recesses on the spacers.

<FIG> shows a sectional view of a rotor according to an embodiment. In the embodiment shown in <FIG>, rotor <NUM> includes rotor core <NUM> including keyways <NUM>, permanent magnets <NUM> each having shoulders <NUM>, and pole spacers <NUM> including key projections <NUM> and engagement projections <NUM>.

Rotor <NUM> is a surface permanent magnet rotor including rotor core <NUM>, permanent magnets <NUM>, and pole spacers <NUM> such that rotor <NUM> can be rotated by electromagnetic torque provided by a stator of an electric motor including rotor <NUM>.

Rotor core <NUM> is a rotor core on which permanent magnets <NUM> and pole spacers <NUM> are disposed. Rotor core <NUM> includes keyways <NUM>. Keyways <NUM> can be provided in rotor core <NUM>. Keyways <NUM> can be channels configured to accommodate key projections <NUM>. In an embodiment, keyways <NUM> have a portion within rotor core <NUM> that is wider than an opening of the keyway at the surface of the rotor core <NUM>. In an embodiment, each of keyways <NUM> has a trapezoidal shape, with a shorter of the parallel sides of the trapezoid being at a surface of the rotor core <NUM>. In an embodiment, the keyways <NUM> each extend at least a length of the key projections <NUM> provided on the pole spacers <NUM>. In an embodiment, the keyways <NUM> each extend in a straight line parallel to the axis of the rotor <NUM>. In an embodiment, the keyways <NUM> each allow the key projection <NUM> to be inserted straight into its respective keyway <NUM> during manufacture. In an embodiment, each keyway <NUM> in rotor core <NUM> has the same shape and/or dimensions.

Permanent magnets <NUM> are permanent magnets included to provide the magnetic poles allowing rotor <NUM> to be rotated by electromagnetic torque from the stator of a motor including rotor <NUM>. In the embodiment shown in <FIG>, shoulders <NUM> are provided on each side of each of the permanent magnets <NUM>. The shoulders <NUM> provide contact surfaces that can be contacted by the engagement projections <NUM> included in pole spacers <NUM>, such that engagement between the engagement projections <NUM> and the shoulders <NUM> can retain permanent magnets <NUM> to resist outwards movement of the permanent magnets <NUM> away from rotor core <NUM> when rotor <NUM> is being rotated.

Pole spacers <NUM> are included between permanent magnets <NUM>. The pole spacers <NUM> shown in <FIG> include key projections <NUM> and engagement projections <NUM>.

Key projections <NUM> are projections from a side of pole spacer <NUM> facing the rotor core <NUM> when rotor <NUM> is assembled. Key projections <NUM> each have a cross-section selected such that it can fit into one of keyways <NUM>, but that outwards movement away from rotor core <NUM> is limited by contact between the key projection <NUM> and keyway <NUM>. In an embodiment, key projections <NUM> include at least a portion having a trapezoidal shape in cross-section, with a longer side of the trapezoidal shape at an end of the key projection <NUM> that is away from the body of the pole spacer <NUM>. In an embodiment, a key projection <NUM> is provided on each of the pole spacers <NUM>. In an embodiment, each key projection <NUM> extends over a length that is shorter or equal to a length of the main body of the pole spacer <NUM>. In an embodiment, each key projection <NUM> maintains its cross-sectional shape over its entire length. Each key projection can be configured to be inserted straight into its corresponding keyway <NUM> when rotor <NUM> is assembled.

Engagement projections <NUM> extend from the sides of each pole spacer <NUM>. In an embodiment, engagement projections <NUM> can continue the outer surface of the pole spacers <NUM>. Engagement projections <NUM> are configured such that they can extend over the shoulders <NUM> of permanent magnets <NUM> adjacent the pole spacer <NUM>, such that outwards movement of the permanent magnets would be obstructed by contact with the engagement projections <NUM>.

While <FIG> each show a rotor <NUM>, <NUM> without a sleeve, sleeve assemblies such as the sleeve <NUM> shown in <FIG> and described above can be combined with embodiments including the features shown in <FIG>. In embodiments, the mechanical retention provided by the features shown in <FIG>, optionally along with a retention sleeve such as sleeve <NUM> shown in <FIG>, can be the only sources of retention force for retaining the permanent magnets <NUM>, <NUM> and pole spacers <NUM>, <NUM> to rotor cores <NUM>, <NUM>. In an embodiment, either of rotor <NUM> or rotor <NUM>, does not include adhesives retaining permanent magnets <NUM> or <NUM> and pole spacers <NUM> or <NUM> to the respective rotor core <NUM> or <NUM>.

<FIG> shows a sectional view of a rotor and sleeve assembly according to an embodiment. Rotor and sleeve assembly <NUM> includes rotor <NUM> and sleeve <NUM>. Rotor <NUM> includes first end piece <NUM>, second end piece <NUM>, and permanent magnet <NUM>. In an embodiment, an eddy current shield <NUM> can be included between rotor <NUM> and sleeve <NUM>.

Rotor <NUM> is a rotor of an electric motor. Rotor <NUM> is configured to rotate in response to application of electromagnetic torque, for example by a stator (see <FIG>) of an electric motor including the rotor <NUM>.

Sleeve <NUM> can be any suitable sleeve for use with the rotor <NUM>. Sleeve <NUM> can include an eddy current shield, as described below and shown in <FIG>. Sleeve <NUM> can be sized such that it can be slid onto the rotor <NUM>. Sleeve <NUM> is configured such that it can retain rotor <NUM> and eddy current shield <NUM> within the range of rotational speeds for rotor <NUM> during operation of an electric motor. In some embodiments, sleeve <NUM> can be a composite material such as a carbon fiber composite or a glass fiber composite. Sleeve <NUM> can include the pre-tension and/or the fiber orientation as in retention sleeve <NUM> described above and shown in <FIG>. In embodiments, the pre-tension and/or fiber orientation can be selected to provide axial force for retaining first end piece <NUM>, permanent magnet <NUM>, and second end piece <NUM> to one another. In embodiments, the fiber orientation in sleeve <NUM> can be such that at least a part of the fibers in the sleeve form a non-zero angle to the azimuth direction of the rotor <NUM>. In an embodiment, the non-zero angle may be an angle in a range between <NUM> degrees and <NUM> degrees from the azimuth direction of the rotor <NUM>. In an embodiment, the sleeve <NUM> can be assembled by wrapping the sleeve <NUM> directly to the rotor <NUM>, while applying a tensile force on the fibers. In another embodiment, the sleeve <NUM> can be produced by pre-wrapping the sleeve onto a mandrel and then shrink fitting and/or press fitting the sleeve <NUM> onto the rotor <NUM>.

First end piece <NUM> forms one end of the rotor <NUM>. First end piece <NUM> is provided on a first side of the permanent magnet <NUM>. Second end piece <NUM> forms an opposite end of the rotor from first end piece <NUM>, on an opposite side of permanent magnet <NUM>. At least one of first end piece <NUM> and/or second end piece <NUM> can be joined to or included in a driveshaft to be rotated by operation of the motor including rotor <NUM>. The driveshaft can be used to operate, for example, an impeller. Each of first end piece <NUM> and second end piece <NUM> can be joined to permanent magnet <NUM> by any suitable means that allows rotation of permanent magnet <NUM> to be transferred to first end piece <NUM> and second end piece <NUM>. Examples for joining first end piece <NUM>, second end piece <NUM>, and/or permanent magnet <NUM> to one another can include features on the sleeve <NUM>, axial mechanical fasteners, radial mechanical fasteners, threading, shrink-fitting, press-fitting, adhesives, and/or interlocking retaining features, or the like. In an embodiment, axial thrust forces can contribute to the first end piece <NUM>, second end piece <NUM>, and/or permanent magnet <NUM> being retained to one another. Central axes of each of first end piece <NUM>, second end piece <NUM>, and permanent magnet <NUM> can be collinear when the rotor <NUM> is assembled. First and second end pieces can be made of any suitable materials, such as for example steel materials and the like. The first end piece <NUM> and/or the second end piece <NUM> can be made of a non-magnetic material, for example aluminum, titanium, austenitic stainless steel, carbon fiber composites, nickel-chromium alloys, or any other suitable non-magnetic material, or the like.

Permanent magnet <NUM> can be a single permanent magnet or composed of multiple magnets bonded to one another. Permanent magnet <NUM> can include any suitable permanent magnet materials such as SmCo or NdFeB or the like.

Eddy current shield <NUM> can optionally be provided on the rotor <NUM> or between rotor <NUM> and sleeve <NUM>. Optionally, the eddy current shield can instead be located within sleeve <NUM>, for example as described below and shown in <FIG>.

<FIG> shows a sectional view of a rotor and sleeve assembly according to an embodiment. Rotor and sleeve assembly <NUM> includes rotor <NUM> and sleeve <NUM>. Rotor <NUM> includes first end piece <NUM> including first channel <NUM>, second end piece <NUM> including second channel <NUM>, and permanent magnet <NUM> having third channel <NUM>. A shaft <NUM> extends through the first channel <NUM>, second channel <NUM>, and third channel <NUM>. The shaft <NUM> is secured to first end piece <NUM> and second end piece <NUM>, for example by flanges <NUM> provided towards opposite ends of the shaft <NUM>.

Sleeve <NUM> can be any suitable sleeve for use with the rotor <NUM>. Sleeve <NUM> can include an eddy current shield, as described below and shown in <FIG>. Sleeve <NUM> can be sized such that it can be slid onto the rotor <NUM>. In some embodiments, sleeve <NUM> can be a composite material such as for example a carbon fiber composite or a glass fiber composite or the like. Pre-tensioning, fiber orientation, and/or assembly of sleeve <NUM> can be according to the description of sleeve <NUM> provided above.

First end piece <NUM> forms one end of the rotor <NUM> and includes first channel <NUM>. First channel <NUM> is a channel extending from a side of first end piece <NUM> configured to face the permanent magnet <NUM> through at least a portion of first end piece <NUM>. The first channel <NUM> can have any suitable cross-sectional shape to allow shaft <NUM> to pass through the first channel <NUM>. The first channel <NUM> can be concentric with the first end piece <NUM>. The first channel <NUM> can extend along a central axis of the rotor <NUM>.

Second end piece <NUM> forms a second end of rotor <NUM>, opposite first end piece <NUM>. At least one of first end piece <NUM> and second end piece <NUM> can connect to or be incorporated in a driveshaft to be rotated by the motor including rotor <NUM>. Second end piece <NUM> includes second channel <NUM>. Second channel <NUM> is a channel extending from a side of second end piece <NUM> configured to face the permanent magnet <NUM> through at least a portion of second end piece <NUM>. The second channel <NUM> can have any suitable cross-sectional shape to allow shaft <NUM> to pass through the second channel <NUM>. The second channel <NUM> can have the same shape and/or dimensions as first channel <NUM>. The second channel <NUM> can be concentric with the second end piece <NUM>. The second channel <NUM> can extend along a central axis of the rotor <NUM>.

Permanent magnet <NUM> includes third channel <NUM>. Third channel <NUM> is a channel extending all the way through permanent magnet <NUM> along an axis of the permanent magnet <NUM>. Third channel <NUM> can be sized to allow shaft <NUM> to pass through permanent magnet <NUM>. The third channel <NUM> can be concentric with the permanent magnet <NUM>. Third channel <NUM> can have any suitable cross-sectional shape for accommodating shaft <NUM>.

Shaft <NUM> is a shaft sized such that it can extend through first channel <NUM>, second channel <NUM>, and third channel <NUM> such that it extends from first end piece <NUM> though permanent magnet <NUM> to second end piece <NUM>. In some embodiments, shaft <NUM> can be a stud or a bolt. Shaft <NUM> can be sized and have any suitable cross-sectional shape for passing through each of first channel <NUM>, second channel <NUM>, and third channel <NUM>. In an embodiment, shaft <NUM> can be formed integrally with one of first end piece <NUM> or second end piece <NUM>. In this embodiment, the end piece <NUM>, <NUM> in which shaft <NUM> is formed integrally, the corresponding first or second channel <NUM>, <NUM> is not formed in that end piece <NUM>, <NUM>.

Flanges <NUM> can be provided on shaft <NUM> such that the combination of first end piece <NUM>, second end piece <NUM>, and permanent magnet <NUM> can be retained together. Flanges <NUM> can extend from shaft <NUM> at or near opposite ends of shaft <NUM>. The flanges <NUM> can be sized such that they cannot pass through any of first channel <NUM> or second channel <NUM>. In an embodiment, at least one of flanges <NUM> can be integral with shaft <NUM>. In an embodiment, at least one of flanges <NUM> can be removably incorporated into shaft <NUM>, for example by being included in a nut or a washer secured by a nut that can be applied to a threaded end provided on shaft <NUM>. Flanges <NUM> can retain first end piece <NUM>, second end piece <NUM>, and permanent magnet <NUM> together such that the first end piece <NUM> and second end piece <NUM> squeeze the permanent magnet <NUM>.

<FIG> shows a sectional view of a rotor and sleeve assembly according to an embodiment. Rotor and sleeve assembly <NUM> includes rotor <NUM> and sleeve <NUM>. Rotor <NUM> includes first end piece <NUM> including a first shoulder <NUM>, second end piece <NUM> including a second shoulder <NUM>, and permanent magnet <NUM>. The sleeve <NUM> includes flanges <NUM> at opposing ends of sleeve <NUM> such that each flange engages with one of first shoulder <NUM> and second shoulder <NUM> to secure first end piece <NUM>, permanent magnet <NUM>, and second end piece <NUM> together.

Rotor <NUM> includes first end piece <NUM> at a first end, second end piece <NUM> at an opposite end, and permanent magnet <NUM> located between the first end piece <NUM> and the second end piece <NUM>. At least one of first end piece <NUM> and second end piece <NUM> can be connected to or included in a driveshaft to be driven by rotation of the rotor <NUM>. Rotor <NUM> is retained together by engagement of the sleeve <NUM> with the first end piece <NUM> and second end piece <NUM>.

Sleeve <NUM> can be used to retain first end piece <NUM>, permanent magnet <NUM>, and second end piece <NUM> together. In some embodiments, sleeve <NUM> can be a composite material such as for example, a carbon fiber composite or a glass fiber composite or the like. The sleeve can include flanges <NUM> at or near each respective end that are configured to engage with features formed in the first and second end pieces <NUM>, <NUM> such as first shoulder <NUM> and second shoulder <NUM>. Sleeve <NUM> can be sized and/or flanges <NUM> positioned with respect to the sizes of first end piece <NUM>, second end piece <NUM>, and permanent magnet <NUM>, or the positions of shoulders <NUM>, <NUM> such that the flanges <NUM> press first end piece <NUM> and second end piece <NUM> towards permanent magnet <NUM>. Pre-tensioning, fiber orientation, and/or assembly of sleeve <NUM> can be according to the description of sleeve <NUM> provided above.

First shoulder <NUM> and second shoulder <NUM> are each recesses in an end of the outer perimeter of first end piece <NUM> and second end piece <NUM>, respectively. Each of first shoulder <NUM> and second shoulder <NUM> are configured to provide contact surfaces configured to engage with flanges <NUM> provided on sleeve <NUM>, such that the contact of the flanges <NUM> with first shoulder <NUM> and second shoulder <NUM> provides pressure that pushes the first end piece <NUM> and second end piece <NUM> towards permanent magnet <NUM>. In an embodiment, grooves can be provided in place of first shoulder <NUM> and second shoulder <NUM> to receive the flanges <NUM> of sleeve <NUM> to retain the rotor <NUM> together. In an embodiment, the first shoulder <NUM> and/or second shoulder <NUM> can include roughened surfaces for contacting the flanges <NUM>.

<FIG> shows a sectional view of a rotor and sleeve assembly according to an embodiment. Rotor and sleeve assembly <NUM> includes rotor <NUM> and sleeve <NUM>. Rotor <NUM> includes first end piece <NUM>, second end piece <NUM>, and permanent magnet <NUM>. Each of first end piece <NUM> and second end piece <NUM> include a plurality of projections <NUM> radially distributed around a circumference of that respective end piece <NUM> and <NUM>. Sleeve <NUM> includes a plurality of slots <NUM> configured to receive the projections <NUM> and positioned correspondingly to the projections <NUM>. An eddy current shield <NUM> can surround permanent magnet <NUM> and portions of first and second end pieces <NUM>, <NUM>.

Rotor <NUM> includes first end piece <NUM> at a first end, second end piece <NUM> at an opposite end, and permanent magnet <NUM> located between the first end piece <NUM> and the second end piece <NUM>. At least one of first end piece <NUM> and second end piece <NUM> can be connected to or included in a driveshaft to be driven by rotation of the rotor <NUM>. Rotor <NUM> is retained together by engagement of the sleeve <NUM> with projections <NUM> provided on each of first end piece <NUM> and second end piece <NUM>. Projections <NUM> are radially distributed around the outer surfaces of each of first end piece <NUM> and second end piece <NUM>.

Sleeve <NUM> includes a plurality of slots <NUM> provided near the opposite ends of sleeve <NUM>. In some embodiments, sleeve <NUM> can be a composite material such as for example a carbon fiber composite or a glass fiber composite or the like. Each of the slots <NUM> is positioned and sized such that it receives one or more of the projections <NUM>. In an embodiment, the slots <NUM> are configured to accommodate all of the projections <NUM> provided on the first and second end pieces <NUM>, <NUM>. In an embodiment, the projections <NUM> and slots <NUM> are each respectively sized and positioned such that a snap fit is formed to secure each of the first end piece <NUM> and the second end piece <NUM> to the sleeve <NUM>. Projections <NUM> and slots <NUM> can have any suitable shapes for interfacing with one another, such as the rectangular shapes for each shown in <FIG>.

The size of sleeve <NUM> and the respective positions of projections <NUM> and slots can be such that when each of first and second end pieces <NUM>, <NUM> are engaged with sleeve <NUM>, each of the first and second end pieces <NUM>, <NUM> are pressed together towards permanent magnet <NUM>. The rotor <NUM> can be held together primarily or entirely by the fit of the projections <NUM> with the slots <NUM> on sleeve <NUM>. In an embodiment, adhesive may or may not be included between permanent magnet <NUM> and either of first end piece <NUM> and/or second end piece <NUM>. Pre-tensioning, fiber orientation, and/or assembly of sleeve <NUM> can be according to the description of sleeve <NUM> provided above.

<FIG> shows a close-up view of the rotor and sleeve assembly of <FIG>. <FIG> allows the plurality of projections <NUM> to be seen where they are received in the plurality of slots <NUM> that are formed in sleeve <NUM>.

<FIG> shows a close-up perspective view of the rotor of <FIG>, with the sleeve <NUM> removed. In <FIG>, an eddy current shield <NUM> surrounding permanent magnet <NUM> is visible, as is first end piece <NUM>. The plurality of projections <NUM> can be seen extending from the surface of the first end piece <NUM>, radially distributed about the surface of the first end piece <NUM>.

<FIG> shows a schematic of a motor according to an embodiment. Motor <NUM> includes a stator <NUM> and a rotor <NUM>. Stator <NUM> has an interior diameter ID. Rotor <NUM> has an outer diameter OD. The difference between ID and OD is the air gap AG. Motor <NUM> can be a high-speed permanent magnet motor. In an embodiment, motor <NUM> can be included in a centrifugal HVAC system, as shown in <FIG> and described below. Motor <NUM> can be for a centrifugal HVAC system having a capacity in a range from at or about <NUM> tons to at or about <NUM> tons.

Stator <NUM> is a stator configured to generate electromagnetic torque capable of rotating rotor <NUM>. Stator <NUM> can include a core and a winding. The core can include multiple slots having a slot pitch. Stator <NUM> can be energized using a variable-frequency drive (VFD). Switching by the VFD can lead to losses at the rotor by way of harmonics, particularly eddy current iron losses at the rotor <NUM>.

Losses at rotor <NUM> can cause heating that can in turn lead to issues with the rotor such as exceeding a glass transition temperature for polymer components included therein, such as composite retention sleeves, heating-based elongation of the rotor, remanent flux in permanent magnets, or affecting demagnetization margins. Providing sufficient cooling to remedy or prevent these heating effects can lead to additional expense and inefficiency in designs of motors <NUM> and devices including such motors. While losses at rotor <NUM> can be controlled at the stator by way of filters, increased switching frequencies, or the like, this can lead to similar losses instead occurring at the stator <NUM>, or requiring costly additional electronic controls.

Rotor <NUM> can include an eddy current shield such as, as non-limiting examples, the eddy current shields <NUM>, <NUM>, or <NUM> described below and shown in <FIG>. Rotor <NUM> can be sized in relation to stator <NUM> such that air gap AG is sized based on the resulting rotor losses from the design including rotor <NUM>. This can be determined based on a predicted skin depth of the stator slot harmonics along with the presence, thickness, and location of an eddy current shield included in rotor <NUM>. In embodiments, the size of air gap AG can be a determined magnetic air gap between the stator <NUM> and the outermost of the eddy current shield or the permanent magnets and/or pole spacers of the rotor <NUM>. The sizing of the rotor can be based on, for example, modeling of the motor <NUM> when operating at a full load, and/or modeling of the motor <NUM> when operating at a partial load. In an embodiment, the sizing of rotor <NUM> can be designed for improvement to integral part load value (IPLV) for a compressor including motor <NUM>. IPLV can be reflective of the cost of operation of a compressor when it is at a partial load, providing a cost function for such operations. In an embodiment, the sizing of air gap AG can be based on the speed of the motor, for example being significantly larger for high-speed motors compared to lower-speed motors. Reduction of losses in rotor <NUM> by the eddy current shield and the sizing of the air gap AG can reduce cooling demands, improving efficiency and reducing design constraints on the motor <NUM> as a whole or systems including said motor.

The air gap AG can be based at least in part on the rotor surface speed for rotor <NUM>. The rotor surface speed is a function of the diameter of rotor <NUM> and the design rotational speed for rotor <NUM> in motor <NUM>. For example, in a high-speed motor embodiment where the surface speed of rotor <NUM> is between <NUM> and <NUM>/s, the air gap AG can be, for example, between at or about <NUM> and at or about <NUM>. In this embodiment, the air gap AG can vary in length by at or about <NUM> to at or about <NUM> per <NUM>/s of change to the surface speed of rotor <NUM>. It is understood that these are nominal design measurements and can vary, for example, according to manufacturing tolerances or other similar deviations in dimensions of the rotor <NUM> and an optional sleeve on said rotor. In an embodiment, the sizing of the air gap AG can further be based on the type of rotor, such as an SPM rotor such as those shown in <FIG> and <FIG> and described above, or a monolithic permanent magnet such as those shown in <FIG>. In an embodiment, the size of air gap AG can be slightly larger for monolithic permanent magnet embodiment, for example having an air gap AG that is from at or about <NUM> to at or about <NUM>. The air gap AG determined based on the rotor surface speed can be a magnetic air gap based on the outermost magnetic component of rotor <NUM> including any sleeve provided on the rotor. The magnetic air gap may not include portions of the sleeve that are non-magnetic such as carbon fiber composite portions. In an embodiment, both the physical air gap and a thickness of a non-magnetic sleeve can be combined to find the magnetic air gap for motor <NUM>.

<FIG> shows a sectional view of a rotor and sleeve assembly including an eddy current shield according to an embodiment. Rotor and sleeve assembly <NUM> includes rotor <NUM> and sleeve <NUM>. The rotor <NUM> includes rotor core <NUM>, permanent magnets <NUM>, and pole spacers <NUM>. Eddy current shield <NUM> is provided on an outer surface of permanent magnets <NUM> and pole spacers <NUM>.

Rotor <NUM> is a rotor of an electric motor. While rotor <NUM> is shown as a surface permanent magnet (SPM) rotor having multiple permanent magnets applied to a rotor core in <FIG>, it is understood that rotor <NUM> can be any suitable type of rotor, also including the single permanent magnet such as the rotors <NUM>, <NUM>, <NUM>, or <NUM> described above and shown in <FIG>. Sleeve <NUM> is a sleeve used to retain components of the rotor <NUM>. Sleeve <NUM> can be made of a non-conductive material such as, for example, composites such as carbon fiber or glass fiber composites or the like. Sleeve <NUM> can be, for example, any of the sleeves discussed above and shown in <FIG> such as, for example, retention sleeve <NUM>. Sleeve <NUM> can be pre-tensioned and have sufficient mechanical density, density, and thermal conductivity properties for use with rotor <NUM> under the operational conditions for the motor including rotor and sleeve assembly <NUM>.

The SPM rotor design of rotor <NUM> as shown in <FIG> includes rotor core <NUM>, permanent magnets <NUM>, and pole spacers <NUM>.

Rotor and sleeve assembly <NUM> further includes eddy current shield <NUM>. Eddy current shield <NUM> is a conductive material configured to provide electromagnetic shunting. The electromagnetic shunting provided by eddy current shield <NUM> can reduce rotor losses that result from the circulation of high frequency currents caused by the power electronics switching harmonics in alternating current (AC) electric motors. Eddy current shield <NUM> can include a conductive material such as copper or any other suitable metal having similarly high conductivity. While the eddy current shield <NUM> is shown as incorporated into a surface permanent magnet type rotor in the embodiment of <FIG>, it is understood that the eddy current shield <NUM> can be provided on an outer surface of any rotor, also including permanent magnet rotors such as those shown in <FIG>, <FIG>, or <FIG> and described above. In those embodiments, the eddy current shield <NUM> can be located between the outer surface of the rotor <NUM> and the inner surface of sleeve <NUM>. In embodiments, eddy current shield <NUM> may not possess sufficient mechanical properties to retain components of rotor <NUM> by itself, for example eddy current shield <NUM> may be subject to deformation allowing displacement of permanent magnets <NUM> and pole spacers <NUM> when the rotor <NUM> is rotated at operational speeds. As such, while eddy current shield <NUM> surrounds the permanent magnets <NUM> and pole spacers <NUM>, sleeve <NUM> can be used to provide the retention for those components. This can allow the use of more conductive materials to be used in eddy current shield <NUM> when compared to typical metallic materials that can be used for retention. Eddy current shield <NUM> may include discontinuities along its surface such that there are some openings or portions of rotor <NUM> not covered by eddy current shield <NUM>, for example for stress relief or manufacturability.

<FIG> shows a sectional view of a rotor and sleeve assembly including an eddy current shield according to an embodiment. Rotor and sleeve assembly <NUM> includes rotor <NUM> and sleeve <NUM>. The rotor <NUM> includes rotor core <NUM>, permanent magnets <NUM>, and pole spacers <NUM>. In the embodiment shown in <FIG>, eddy current shield <NUM> is provided between rotor core <NUM> and the permanent magnets <NUM> and pole spacers <NUM>, for example being located on an outer surface of rotor core <NUM>.

Sleeve <NUM> can be any suitable retention sleeve for the rotor <NUM>. Sleeve <NUM> can be made of a non-conductive material such as, for example, composites such as carbon fiber or glass fiber composites or the like. Sleeve <NUM> can be, for example, any of the sleeves discussed above and shown in <FIG> such as, for example, retention sleeve <NUM>.

Eddy current shield <NUM> is disposed between the rotor core <NUM> and permanent magnets <NUM> and pole spacers <NUM>. Eddy current shield <NUM> can include a conductive material such as copper or any other suitable metal having similarly high conductivity. Eddy current shield can be secured to the rotor core <NUM> by any suitable method, such as mechanical fasteners, adhesives, or the like. Each of permanent magnets <NUM> and pole spacers <NUM> can be secured to the eddy current shield by suitable means such as mechanical fasteners, adhesives, or the like. Eddy current shield <NUM> may include discontinuities along its surface such that there are some openings or portions of rotor core <NUM> not covered by eddy current shield <NUM>, for example for stress relief or manufacturability.

<FIG> shows a sectional view of a rotor and sleeve assembly including an eddy current shield according to an embodiment. Rotor and sleeve assembly <NUM> includes rotor <NUM> and sleeve <NUM>. Sleeve <NUM> includes an eddy current shield <NUM> located between an inner layer <NUM> and an outer layer <NUM>. Rotor <NUM> includes rotor core <NUM>, permanent magnets <NUM>, and pole spacers <NUM>.

Sleeve <NUM> includes inner layer <NUM>, eddy current shield <NUM>, and outer layer <NUM>. Inner layer <NUM> and outer layer <NUM> can each be, for example, composite materials such as carbon fiber or glass fiber composites or the like. Each of inner layer <NUM> and outer layer <NUM> can be configured to have particular fiber directions and/or be pre-tensioned when applied. In embodiments, inner layer <NUM> assembled by wrapping the inner layer <NUM> directly to the rotor <NUM>, while applying a tensile force on the fibers, then placing the eddy current shield <NUM> on an outer surface of inner layer <NUM>, then wrapping the outer layer <NUM> onto the eddy current shield <NUM> and optionally a portion of inner layer <NUM>. In another embodiment, the sleeve <NUM> can be produced by pre-wrapping the inner layer <NUM> onto a mandrel, placing the eddy current shield <NUM> on an outer surface of inner layer <NUM>, then wrapping the outer layer <NUM> onto the eddy current shield <NUM> and optionally a portion of inner layer <NUM> and then shrink fitting and/or press fitting the full sleeve <NUM> onto the rotor <NUM>. The eddy current shield <NUM> can be attached to the inner layer <NUM> in pieces joined to the inner layer <NUM> by adhesive, as one or more pieces wrapped around inner layer <NUM>, as a ring press-fit or shrink fit to the inner layer <NUM>, included as one or more fibers in a layer wrapped around inner layer <NUM>, or sprayed onto inner layer <NUM>.

Rotor <NUM> is shown as being an SPM rotor including rotor core <NUM>, permanent magnets <NUM>, and pole spacers <NUM>. While the embodiment shown in <FIG> shows an SPM rotor, it is understood that the sleeve <NUM> including the eddy current shield <NUM> can be used in any sleeved rotor including permanent magnet rotors such as those shown in <FIG>, <FIG>, or <FIG> and described above. The sleeve <NUM> can provide the retention force keeping the components of rotor <NUM> in place. In an embodiment, sleeve <NUM> is configured to retain permanent magnets <NUM> and pole spacers <NUM> in place while the rotor <NUM> is being rotated during operation of a motor.

Claim 1:
A rotor (<NUM>) for an electric motor, comprising:
a first rotor endpiece (<NUM>);
a second rotor endpiece (<NUM>);
a permanent magnet (<NUM>), secured between the first rotor endpiece and the second rotor endpiece; and
a sleeve (<NUM>) configured to surround a portion of the first rotor endpiece, a portion of the second rotor endpiece, and the permanent magnet; characterized in that the rotor further includes:
one or more first retention features (<NUM>) provided on the first rotor endpiece; and
one or more second retention features (<NUM>) provided on the second rotor endpiece, wherein each of the first retention features and the second retention features are configured to engage with the sleeve, characterised in that
the sleeve comprises a plurality of first openings (<NUM>) each configured to receive at least one of the first retention features and a plurality of second openings (<NUM>) each configured to receive at least one of the second retention features.