GB2625133A

GB2625133A - A rotor and a method of manufacture of a rotor

Info

Publication number: GB2625133A
Application number: GB2218449.3A
Authority: GB
Inventors: Bhartia Veral; Ananthanarayan Karthik; Negi Ayush; Prasad Praveen; Devara Prasad
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2022-12-08
Filing date: 2022-12-08
Publication date: 2024-06-12
Also published as: GB202218449D0

Abstract

A rotor 10 comprising first rotor laminae 12, each of the first rotor laminae having a slot therethrough, the slot of each of the first rotor laminae having a first slot width, wherein the slots of each of the first rotor laminae overlay each other, to form a rotor core 50 with a rotor slot 56 therethrough; a first support lamina 102 at a first end 104 of the stack of first rotor laminae, the first support lamina occluding, at least in part, the rotor slot to prevent the magnet 46 from moving in a first direction 58; a second support lamina 112 at a second end 114 of the stack of first rotor laminae, the second support lamina occluding, at least in part, the rotor slot to prevent the magnet from moving in a second direction 68 opposite the first direction; and a magnet positioned in the rotor slot. There may be multiple second rotor lamina stacked with the first, where the slot width of the second lamina is smaller than the slot width of the first lamina. A method of manufacturing a rotor and vehicle comprising a rotor are also claimed.

Description

A ROTOR AND A METHOD OF MANUFACTURE OF A ROTOR

TECHNICAL FIELD

The present disclosure relates to a rotor and a method of manufacturing a rotor. Particularly, but not exclusively, the present disclosure relates to an electric machine rotor and a method of manufacturing an electric machine rotor for use in an interior permanent magnet electric machine that can be used as a motor or a generator.

Aspects of the invention relate to a rotor, to a method of manufacturing a rotor, to an electric machine, and to a vehicle.

BACKGROUND

It is known to use one or more electric machine in a vehicle. Such electric machines may operate as motors or as generators. Electric machines may operate as traction motors for propelling a vehicle such as an automobile, van, truck, motorcycle, boat, or aeroplane. Electric machines may be used in place of, or in addition to, an internal combustion engine.

Such electric machines comprise a stator and a rotor. The stator and rotor may form part of a permanent magnet synchronous motor arrangement. An air gap is maintained between the rotor and the stator. The stator is a stationary element of the electric machine which may comprise a plurality of slots within which electrical windings are located. The rotor is a rotating element of the electric machine allowing a transfer of electrical energy input into the motor to a mechanical output, such as the rotation of a driveshaft of the vehicle.

The rotor may comprise a plurality of laminations, generally of a ferromagnetic material, stacked to form a rotor core or rotor iron. Magnets are embedded in slots through each of the laminations of the rotor to form a plurality of rotor poles, the number and position of slots being dependent upon the required rotor topology. In a permanent magnet synchronous motor, the embedded magnets are permanent magnets and generate a magnetic flux. A rotor pole has a direct axis, or d-axis, aligned to the permanent magnet flux, and quadrature axes, or q-axes, denoted as a +q-axis and a -q-axis, arranged transverse to the direction of the rotor pole (i.e. transverse to the d-axis). The angular extent of each rotor pole, which is the included angle between the +q-axis and the -q-axis, is referred to as a pole step.

Current methods of manufacturing rotors require each magnet to be inserted into a rotor slot through the rotor and retained in the rotor by the use of a wet process requiring the injection of an adhesive into the rotor slot whilst the magnet is located in position in the rotor slot. The adhesive retains the magnet and assists in conducting heat away from the magnet.

The vehicle may, for example, comprise a battery electric vehicle (BEV), a plug-in hybrid electric vehicle (PHEV) or a hybrid electric vehicle (HEV) where the electric machine is a traction motor for the vehicle. It is desirable to manufacture the rotor of the traction motor with a minimum number of manufacturing steps to minimise manufacturing complexity and cost, whilst maintaining motor performance and reliability.

It is an aim of the present invention to address one or more of the disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a rotor, a method of manufacturing a rotor, an electric machine, and a vehicle as claimed in the appended claims.

According to an aspect of the present invention there is provided a rotor comprising: a plurality of first rotor laminae, each of the first rotor laminae having a slot therethrough, the slot of each of the first rotor laminae having a first slot width, wherein the slots of each of the first rotor laminae overlay each other, to form a rotor core with a rotor slot therethrough; a first support lamina at a first end of the stack of first rotor laminae, the first support lamina occluding, at least in part, the rotor slot to prevent the magnet from moving in a first direction; a second support lamina at a second end of the stack of first rotor laminae, the second support lamina occluding, at least in part, the rotor slot to prevent the magnet from moving in a second direction opposite the first direction; and a magnet positioned in the rotor slot.

An advantage of this aspect of the invention is that a direct mechanical engagement is provided between the magnet and the rotor laminae, reducing or eliminating the need for an additional wet process to retain magnets in the rotor slots, thus reducing the need for additional materials in the rotor construction and avoiding the need for specialised machinery for the injection of adhesive into the rotor slot. The invention may also improve rotor reliability and thermal performance over rotors which have been manufactured using a wet process.

The first support lamina may be planar. This provides an advantage of retaining the magnet with minimal mechanical forming of the first support lamina.

The second support lamina may be formed to have a projection into the rotor slot to engage with the magnet and prevent the magnet from moving in the second direction. The projection may be a flange or a blind flange. The projection may be formed by peening, punching, or drawing the second support lamina.

The rotor may comprise a plurality of second rotor lamina stacked with the plurality of first rotor laminae, each of the second rotor laminae having a slot therethrough, the slot of each of the second rotor laminae having a second slot width, the second slot width being smaller than the first slot width. The slots of the first rotor laminae may overlay the slots of the second rotor laminae, to form a rotor core with a rotor slot therethrough, the rotor slot having a varying width through the rotor core.

The second rotor laminae may be evenly distributed through the stack of first rotor laminae and second rotor laminae. This provides an advantage of avoiding rotor imbalance.

The second rotor laminae may comprise one in every n laminae of the stack of first rotor laminae and second rotor laminae, where n is a value between two and ten.

The magnet may engage with a first lengthwise edge of the slot of each of the second plurality of rotor laminae through the rotor core. The magnet may be engaged with a second lengthwise edge of the slot of each of the second plurality of rotor laminae through the rotor core. The engagement between the magnet and the first and second lengthwise edges of the slot of each of the second plurality of rotor laminae through the rotor core may be an interference engagement.

The magnet may be separated from a first lengthwise edge of the slot of each of the first plurality of rotor laminae through the rotor core.

The first lengthwise edge of the slot of each of the second plurality of rotor laminae may be deformed by the engagement between the magnet and the first lengthwise edge of the slot of each of the second plurality of rotor laminae through the rotor core. Each deformed first lengthwise edge of the slot of each of the second plurality of rotor laminae may exert a springback effect force on the magnet. This provides an advantage of helping to retain the magnet in-situ without the requirement of an adhesive to be applied between the magnet and the rotor laminae.

The rotor may be formed to comprise a plurality of rotor poles. Each rotor pole may comprise one or more slot therethrough in which a magnet may be positioned.

According to an aspect of the present invention there is provided a method of manufacturing a rotor, the rotor having a rotational axis, the method comprising: stacking a plurality of first rotor laminae, each of the first rotor laminae having a slot therethrough, the slot of each of the first rotor laminae having a first slot width, wherein the slots of each of the first rotor laminae overlay each other, to form a rotor core with a rotor slot therethrough; inserting a magnet into the rotor slot; securing a first support lamina at a first end of the stack of first rotor laminae, the first support lamina occluding, at least in part, the rotor slot, to prevent the magnet from moving in a first direction parallel to the rotational axis; securing a second support lamina at a second end of the stack of first rotor laminae, the second support lamina occluding, at least in part, the rotor slot, to prevent the magnet from moving in a second direction, opposite the first direction, parallel to the rotational axis.

An advantage of this invention is that wet processes for retaining magnets in rotor slots can be avoided, thus reducing the need for additional materials in the rotor construction and avoiding the need for specialised machinery for the injection of adhesive into the rotor slot. The invention may also improve rotor reliability over rotors manufactured using a wet process.

The method may comprise forming the second support lamina to have a projection into the rotor slot to engage with the magnet and prevent the magnet from moving in the second direction. The method may comprise forming the projection to be a flange or a blind flange.

The method may comprise forming the projection by peening, punching, or drawing the second support lamina.

The method may comprise stacking a plurality of second rotor lamina with the plurality of first rotor laminae, each of the second rotor laminae having a slot therethrough, the slot of each of the second rotor laminae having a second slot width, the second slot width being smaller than the first slot width, wherein the slots of the first rotor laminae overlay the slots of the second rotor laminae, to form a rotor core with a rotor slot therethrough, the rotor slot having a varying width through the rotor core.

The method may comprise evenly distributing the second rotor laminae through the stack of first rotor laminae and second rotor laminae.

The second rotor laminae may be distributed to comprise one in every n laminae of the stack of first rotor laminae and second rotor laminae, where n is a value between two and ten.

The method may comprise inserting the magnet into the rotor slot to engage the magnet with a first lengthwise edge of the slot of each of the second plurality of rotor laminae through the rotor core.

The inserted magnet may engage with a second lengthwise edge of the slot of each of the second plurality of rotor laminae through the rotor core. The engagement between the magnet and the first and second lengthwise edges of the slot of each of the second plurality of rotor laminae through the rotor core may be an interference engagement.

The method may comprise inserting the magnet into the rotor slot to engage the magnet and the first lengthwise edge of the slot of each of the second plurality of rotor laminae through the rotor core and deforming the first lengthwise edge of the slot of each of the second plurality of rotor laminae, where each deformed first lengthwise edge of the slot of each of the second plurality of rotor laminae exerts a springback effect force on the magnet.

An advantage of this feature is that the springback effect force ensures that the magnet is well constrained against in-plane and axial movement of the magnet in the slot, as well as to ensure direct metal to metal contact for high conduction of heat away from the magnet.

The rotor may be formed to comprise a plurality of rotor poles. Each rotor pole may comprise one or more rotor slot therethrough for the insertion of a magnet.

According to an aspect of the present invention there is provided electric machine comprising a rotor according to any preceding aspect and a stator.

According to an aspect of the present invention there is provided a vehicle comprising an electric machine according to any preceding aspect.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 illustrates a section through a rotor according to an embodiment of the invention; Figure 2 illustrates a first rotor lamina of the rotor of Figure 1; Figure 3 illustrates a first support lamina according to an embodiment of the invention; Figure 4 illustrates a second support lamina according to an embodiment of the invention; Figure 5 illustrates a second rotor lamina of the rotor of Figure 1; Figure 6 illustrates the first rotor lamina of Figure 2 overlaying the second rotor lamina of Figure 5 in a rotor according to an embodiment of the invention; Figure 7 illustrates a section through a rotor according to an embodiment of the invention; Figure 8 illustrates an electric machine according to an embodiment of the invention; and Figure 9 illustrates a vehicle according to an embodiment of the invention.

DETAILED DESCRIPTION

Examples of the present disclosure relate to a rotor. In particular, examples of the present invention relate to an eight-pole rotor with a pole step of forty five mechanical degrees, although it will be understood that a different number of poles, such as four or six, may be provided. Non-limiting examples will now be described with reference to accompanying Figures 1 to 9, where the figures illustrate a rotor 10, an electric machine 100, and a vehicle 200.

The rotor 10 is intended for use in an electric machine 100, as illustrated in Figure 8, where the electric machine 100 comprises the rotor 10 and a stator 90. The rotor 10 has a rotational axis 70 about which the rotor 10 is arranged or configured to rotate. The stator 90 comprises a plurality of slots extending radially inwardly to support electrical windings. For example, the electric machine 100 may comprise forty-eight electrical winding slots in the stator 90 and eight rotor poles in the rotor 10. The electric machine 100 may provide the function of a motor and/or generator for operation in a vehicle 200. For example, the electric machine 100 may be a traction motor for an electric vehicle 200.

Figure 9 illustrates a vehicle 200 having a first electric machine 100-1 for driving one or more front wheel of the vehicle 200 and a second electric machine 100-2 for driving one or more rear wheel of the vehicle 200. In other embodiments the vehicle 200 may comprise only a single electric machine 100, arranged or configured to drive one of one or more front wheel of the vehicle 200 or one or more rear wheel of the vehicle 200. At a vehicle axle the electric machine 100 may be arranged to drive both wheels, either directly or through other transmission components. Other arrangements may have one electric machine 100 arranged or configured to drive each wheel of the vehicle 200.

With reference to Figure 1, there is shown a cut away side view of a portion of a rotor 10, the rotor comprising a plurality of first rotor laminae 12. The plurality of first rotor laminae are arranged in a stack of rotor laminae to form a rotor core 50. The rotor core 50 has a plurality of magnet slots, or rotor slots, 56 therethrough in which respective magnets 46 are positioned.

In the illustrated portion of the rotor 10 in Figure 1, there is shown a single rotor slot 56, through the rotor core 50, in which a magnet 46 is positioned.

The rotor 10 has a first support lamina 102 at a first end 104 of the stack of first rotor laminae 12, the first support lamina 102 occluding, at least in part, the rotor slot 56 to prevent the magnet 46 from moving in a first direction 58.

The rotor 10 has a second support lamina 112 at a second end 114 of the stack of first rotor laminae 12, the second support lamina 112 occluding, at least in part, the rotor slot 56 to prevent the magnet 46 from moving in a second direction 68 opposite the first direction 58.

The second support lamina 112 at the second end 114 of the stack of first rotor laminae 12 may be in contact with and further apply a frictional force the magnet 46 that reduces or prevents movement of the magnet in the plane of the first rotor laminae 12, that is, orthogonal to the first direction 58 and the second direction 68.

The rotor 10 is formed to comprise a plurality of rotor poles, which in this example comprises eight poles, each rotor pole comprising one or more rotor slots, or apertures, 56 therethrough in which a magnet 46 may be located or positioned. The rotor 10 may form part of an electric machine 100, as illustrated in Figure 8, which may be used, for example, as a traction motor for a vehicle 200, as illustrated in Figure 9.

In Figure 2, which illustrates a first rotor lamina 12, the poles are illustrated as segments 141, 14-2, 14-3, 14-4, 14-5, 14-6, 14-7, 14-8 of the first rotor lamina 12, each segment being identical to each other segment. Each of the segments 14-1, 14-2, 14-3, 14-4, 14-5, 14-6, 14- 7, 14-8 of the first rotor lamina 12 of rotor 10 are bounded by a first quadrature axis, or +q axis, 74 and a second quadrature axis, or -q axis, 76. For simplicity, these axes are only shown for a first segment 14-1. For the first segment 14-1, the +q-axis 74 and the -q-axis 76 define the lateral boundaries of the first segment 14-1. Each of the segments 14-1, 14-2, 143, 14-4, 14-5, 14-6, 14-7, 14-8 comprises a respective identical slot 16 therethrough. In some embodiments, the slots 16 may be of different forms depending on lamination and magnet topology. The orientation of the magnet slots with respect to the rotation axis may differ from that shown in Figure 2. Additionally, it will be understood that each segment 14-1, 14-2, 143, 14-4, 14-5, 14-6, 14-7, 14-8, may comprise multiple slots 16 each of which may vary in form and orientation depending on lamination and magnet topology.

In the illustrated arrangement of Figure 2, first segment 14-1 comprises a slot 16 within which a first permanent magnet arrangement 46 may be positioned or retained. The slot 16 has a first slot width 18. In some embodiments, the first permanent magnet arrangement 46 may be substantially orthogonal to a direct axis, or d-axis, 72 of the segment 14-1. The slot 16 within which the first permanent magnet arrangement 46 is positioned, or is to be positioned during manufacture of the rotor 10, may be symmetrically disposed about the d-axis 72. In other embodiments, the slot 16 within which the first permanent magnet arrangement 46 is positioned, or is to be positioned during manufacture of the rotor 10, may be offset from the d-axis and/or may be oriented at an angle to the d-axis. In some embodiments, each of the segments 14-1, 14-2, 14-3, 14-4, 14-5, 14-6, 14-7, 14-8 may comprise more than one slot 16 within which a respective permanent magnet arrangement 46 may be positioned or retained.

In some embodiments multiple slots 16 may be provided symmetrically about the d-axis, and in some of those embodiments at least some of the slots 16 may be oriented at an angle to the d-axis, for example to form a U or V shaped arrangement of slots 16 about the d-axis. In some embodiments there may be multiple layers of slots 16, that is, slots 16 which are radially separated from other slots 16 within each of the segments 14-1, 14-2, 14-3, 14-4, 14-5, 14-6, 14-7, 14-8. For simplicity, the arrangement illustrated and described in the following embodiments provides a single slot 16 centred on the d-axis and orthogonal thereto.

As illustrated in Figure 2 for the slot 16 in the first segment 14-1, the slot 16 has a first slot width 18 along the d-axis 72 orthogonal to the rotational axis 70 of the rotor 10, between a first lengthwise edge 20 of the slot 16 of the first rotor lamina 12 and a second lengthwise edge 22 of the slot 16 of the first rotor lamina 12. The first lengthwise edge 20 of the slot 16 of the first rotor lamina 12 may be a radially inner edge of the slot 16 of the first rotor lamina 12 and the second lengthwise edge 22 of the slot 16 of the first rotor lamina 12 may be a radially outer edge of the slot 16 of the first rotor lamina 12. The slot 16 has a first slot length 19 orthogonal to the d-axis 72 and the first slot width 18. It will be understood that the width 18 is the shortest side of the slot 16 and the length 19 is the longest side of the slot 16, orthogonal to the shortest side of the slot 16. Each of the segments of the first rotor lamina 12 comprises a slot 16 within which a permanent magnet arrangement 46 may be positioned and disposed symmetrically within. Of course, in arrangements where the slot 16 is not oriented orthogonal to the d-axis, the first lengthwise edge 20 may not necessarily be a radially inner edge of the slot 16 and the second lengthwise edge 22 of the slot 16 may not necessarily be a radially outer edge of the slot 16, for example where the slot 16 is oriented parallel to the d-axis.

The rotor 10 comprises a plurality of first rotor laminae 12, which are stacked to overlay each other. Each of the plurality of first rotor laminae 12 is oriented in the stack of first rotor laminae 12 such that the slots 16 of each of the plurality of first rotor laminae 12 are aligned to form the rotor slot 56.

Once the plurality of first rotor laminae 12 are formed into the stack of first rotor laminae 12, a first support lamina 102 can be positioned at a first end 104 of the stack of first rotor laminae 12 before a first permanent magnet arrangement 46, which may be in the form of a single magnet 46, or segmented magnets 46, is inserted or positioned in the rotor slot 56.

Alternatively, once the plurality of first rotor laminae 12 are formed into the stack of first rotor laminae 12, the magnet 46 can be inserted into the rotor slot 56 and retained in position before the first support lamina 102 is positioned at the first end 104 of the stack of first rotor laminae 12.

The first support lamina 102 can be of planar form, as illustrated in Figure 3, or it may comprise projections configured to project into respective rotor slots 56 to engage with the respective magnets 46 and prevent the magnets 46 from moving in the first direction 58.

Once the first support lamina 102 is in position to prevent the magnet 46 from moving in the first direction 58, a second support lamina 112 can be positioned at a second end 114 of the stack of first rotor laminae 12 to engage with the magnet 46 and prevent the magnet 46 from moving in the second direction 68. The magnet 46 may have an axial length, that is, a length in an axis parallel to the rotational axis 70 of the rotor 10, which is less than the axial length of the rotor slot 56 through the plurality of first rotor laminae 12.

As illustrated in Figure 4, the second support lamina 112 is formed to have a projection 116 into the rotor slot 56 to engage with the magnet 46 and prevent the magnet 46 from moving in the second direction 68. The projection 116 may be an open flange with an opening through to the magnet 46. Alternatively, the projection 116 may be a blind flange. The projection can be formed in various mechanical operations, such as by peening, punching, or drawing the second support lamina 112 in the locations corresponding to the slot 16 in the first rotor laminae 12. The projection has a width 118 smaller than the first slot width 18 of the slot 16 in the first rotor laminae 12 and a length 119 smaller than the first slot length 19 of the slot 16 in the first rotor laminae 12. The projections 116 can thereby be inserted into the respective slots 16 of a first rotor lamina 12, against which the second support lamina 112 is positioned or abutted.

In some embodiments, the rotor 10 also comprises a plurality of second rotor laminae 32, where each of the second rotor laminae 32 has a slot 36 therethrough, the slot 36 of each of the second rotor laminae 32 having a second slot width 38, the second slot width 38 being smaller than the first slot width 18. The arrangement and function of the first rotor laminae 12 and second rotor laminae 32 in various rotors 10 is described in more detail below with respect to Figures 6, 7, and 8.

In Figure 5, which illustrates a second rotor lamina 32, different to the first rotor lamina 12, the poles are illustrated as segments 34-1, 34-2, 34-3, 34 4, 34-5, 34-6, 34-7, 34-8, of the second rotor lamina 32, each segment being identical to each other segment. Each of the segments 34-1,34-2, 34-3, 34-4, 34-5, 34-6, 34-7, 34-8 of second rotor lamina 32 of rotor 10 are bounded by a first quadrature axis, or +q axis, 74 and a second quadrature axis, or -q axis, 76. For simplicity, these axes are only shown for a first segment 34-1. For the first segment 34-1, the +q-axis 74 and the -q-axis 76 define the lateral boundaries of the first segment 34-1. Each of the segments 34-1, 34-2, 34-3, 34-4, 34-5, 34-6, 34-7, 34-8 comprising a respective identical slot 36 therethrough, although in some embodiments the slots 36 may be of different forms depending on lamination and magnet topology. The orientation of the magnet slots with respect to the rotation axis may differ from that shown in Figure 5. Additionally, it will be understood that each segment 34-1, 34-2, 34-3, 34-4, 34-5, 34-6, 34-7, 34-8, may comprise multiple slots 36 each of which may vary in form and orientation depending on lamination and magnet topology.

In the arrangement illustrated in Figure 5, first segment 34-1 comprises a slot 36 within which the first permanent magnet arrangement 46 may be positioned or retained. The first permanent magnet arrangement 46 may be substantially orthogonal to a direct axis, or d-axis, 72 of the segment 34-1, as illustrated in Figure 5 and described further below. The slot 36 within which the first permanent magnet arrangement 46 is positioned, or is to be positioned during manufacture of the rotor 10, may be symmetrically disposed about the d-axis 72. As illustrated in Figure 5 for the slot 36 in the first segment 34-1, the slot 36 has a first slot width 38 along the d-axis 72 orthogonal to the rotational axis 70 of the rotor 10, between a first lengthwise edge 40 of the slot 36 of the second rotor lamina 32 and a second lengthwise edge 42 of the slot 36 of the second rotor lamina 32. The first lengthwise edge 40 of the slot 36 of the second rotor lamina 32 may be a radially inner edge of the slot 36 of the second rotor lamina 32 and the second lengthwise edge 42 of the slot 36 of the second rotor lamina 32 may be a radially outer edge of the slot 36 of the second rotor lamina 32. Each of the segments of the second rotor lamina 32 comprises a slot 36 within which a permanent magnet arrangement 46 may be positioned or retained, and disposed symmetrically within. Of course, in arrangements where the slot 36 is not oriented orthogonal to the d-axis, the first lengthwise edge 40 may not necessarily be a radially inner edge of the slot 36 and the second lengthwise edge 42 of the slot 36 may not necessarily be a radially outer edge of the slot 36, for example where the slot 36 is oriented parallel to the d-axis.

It will be understood that the d-axis 72, +q axis 74 and -q axis 76 are radial axes, extending radially outwards from the rotational axis 70 of the rotor in the plane of the laminae, shared between the first rotor laminae 12 of the rotor 10 and the second rotor laminae 32 of the rotor 10.

Figure 6 illustrates overlaying of a first rotor laminae 12 on a second rotor laminae 32 to form a rotor 10. Whilst only the uppermost two laminae are observed in Figure 6, it will be understood that there will be a plurality of first rotor laminae 12 and a plurality of second rotor laminae 32 that form the rotor 10, as illustrated in Figure 7. The second rotor laminae 32 are interspersed within the first rotor laminae 12 in the stack of plurality of first rotor laminae 12 and plurality of second rotor laminae 32. The plurality of first rotor laminae 12 and the plurality of second rotor laminae 32 are stacked such that the slots 16 of the first rotor laminae 12 overlay the slots 36 of the second rotor laminae 32, to form a rotor core 50 comprising a stack of first rotor laminae 12 and second rotor laminae 32 with a magnet slot, or rotor slot, 56 therethrough, the rotor slot 56 having a varying width through the rotor core 50.

It will be understood that the segments 14-1, 14-2, 14-3, 14-4, first rotor laminae 12 overlay respective segments 34-1, 34-2, 14-5, 14-6, 14-7, 14-8 of the 34-3, 34-4, 34-5, 34-6, 34-7, 34-8, of the second rotor laminae 32, in the stack of rotor laminae forming the rotor core 50, that is, in the rotor 10 the first segments 14-1, 14-2, 14-3, 14-4, 14-5, 14-6, 14-7, 14-8 of the first rotor laminae 12 overlay the first segments 34-1, 34-2, 34-3, 34-4, 34-5, 34-6, 34-7, 34-8 of the second rotor laminae 32, along an axis parallel to the rotational axis 70 of the rotor 10.

A first permanent magnet arrangement 46 which may be in the form of a single magnet 46, or segmented magnets 46, is positioned in the rotor slot 56. The magnet 46 is engaged with a first lengthwise edge 40 of the slot 36 of each of the second plurality of rotor laminae 32 through the rotor core 50.

In order to retain the magnet 46 in-situ in the rotor slot 56, the magnet 46 is engaged with a second lengthwise edge 42 of the slot 36 of each of the second plurality of rotor laminae 32 through the rotor core 50, wherein the engagement between the magnet 46 and the first and second lengthwise edges 40, 42 of the slot 36 of each of the second plurality of rotor laminae 32 through the rotor core 50 is an interference engagement. The function of the interference engagement is to ensure that the magnet 46 is constrained against planar and axial movement in the slot 36. The interference engagement also ensures direct contact between the magnet 46 and the second plurality of rotor laminae 32 through the rotor core 50 for conduction of heat away from the magnet 46.

The second lengthwise edge 22 of the slot 16 of the first rotor laminae 12 and the second lengthwise edge 42 of the slot 36 of the second rotor laminae 32 may be aligned along the rotor slot 56, in other words aligned along an axis parallel to the rotational axis 70 of the rotor 10. In this arrangement, the stack of first rotor laminae 12 and second rotor laminae 32 provide a rotor slot 56 where one lengthwise wall of the rotor slot 56 is planar. A magnet 46 inserted into such a rotor slot 56 will have an engagement with both the second lengthwise edge 22 of the slot 16 of the first rotor laminae 12 and the second lengthwise edge 42 of the slot 36 of the second rotor laminae 32 through the rotor core.

An embodiment of a rotor 10 is partly illustrated in Figure 7, which shows a single rotor slot 56 of the rotor 10. The magnet 46 is separated from a first lengthwise edge 20 of the slot 16 of each of the first plurality of rotor laminae 12 through the rotor core 50. This provides lower insertion stresses on the magnet 46, and reduced surface damage to the magnet 46 compared to having a plurality of the first plurality of rotor laminae 12 in an interference engagement.

A plurality of first rotor laminae 12 and a plurality of second rotor laminae 32 are stacked to form a stack of first rotor laminae 12 and second rotor laminae 32, each of the first rotor laminae 12 having slots 16 therethrough, the slots 16 of each of the first rotor laminae 12 each having a first slot width 18, and each of the second rotor laminae 32 having slots 36 therethrough, the slots 36 of each of the second rotor laminae 32 each having a second slot width 38, the second slot width 38 being smaller than the first slot width 18.

In the manufacture of the rotor 10 the slots 16 of the first rotor laminae 12 are configured to overlay the slots 36 of the second rotor laminae 32, to form a rotor core 50 with rotor slots 56 therethrough, the rotor slots 56 being formed from the combination of slots 16 of the first rotor laminae 12 and the slots 36 of the second rotor laminae 32. Since the slot width 18 of the slots 16 of the first rotor laminae 12 are larger than the slot width 38 of the slots 36 of the second rotor laminae 32, the rotor slots 56 comprise varying width slots through the rotor core 50 in an area 60 encompassing the first lengthwise edges 20 of the slots 16 of each of the first plurality of rotor laminae 12 and the second lengthwise edges 40 of the slots 36 of each of the second plurality of rotor laminae 32 through the rotor core 50.

Once the plurality of first rotor laminae 12 and second rotor laminae 32 are formed into the stack of first rotor laminae 12 and second rotor laminae 32 and are correctly positioned relative to each other, a first support lamina 102 can be positioned at a first end 104 of the stack of first rotor laminae 12 before a first permanent magnet arrangement 46, which may be in the form of a single magnet 46, or segmented magnets 46, is inserted or positioned in each of the rotor slots 56.

Alternatively, once the plurality of first rotor laminae 12 and second rotor laminae 32 are formed into the stack of first rotor laminae 12 and second rotor laminae 32 and are correctly positioned relative to each other, the magnets 46 can be inserted into the rotor slots 56 in a first direction 58 to engage with a first lengthwise edges 40 of the slots 36 of each of the second plurality of rotor laminae 32 through the rotor core 50. The magnets 46 are then retained in position before the first support lamina 102 is positioned at the first end 104 of the stack of first rotor laminae 12 and second rotor laminae 32.

In Figure 7, the magnet 46, in one rotor slot 56, is illustrated fully inserted into the rotor slot 56. When the magnet 46 is inserted into the rotor slot 56, the first lengthwise edge 40 of the slot 36 of each of the second plurality of rotor laminae 32 is deformed, or bent, by the interference engagement between the magnet 46 and the first and second lengthwise edges 40, 42 of the slot 36 of each of the second plurality of rotor laminae 32 through the rotor core 50.

Each deformed first lengthwise edge 40 of the slot 36 of each of the second plurality of rotor laminae 32 exerts a springback effect force on the magnet 46. The springback effect force is created by resilient deformation of the material of the second plurality of rotor laminae 32.

Therefore, when the first lengthwise edge 40 of the slot 36 of each of the second plurality of rotor laminae 32 is deformed to provide a springback effect force, the deformation is predominantly out of the plane of the respective rotor lamina 32 resulting in bending of the rotor lamina 32 to provide a springback load. The function of the springback effect from the overhanging first lengthwise edge 40 of the slot 36 of each of the second plurality of rotor laminae 32 is to ensure that the magnet 46 is constrained or prevented from moving in planar and axial directions. The engagement of the deformed, or bent, first lengthwise edge 40 of the slot 36 of each of the second plurality of rotor laminae 32 with the magnet 46 also provides for direct metal to metal contact allowing conduction of heat away from the magnet 46.

Once the first support lamina 102 is in position to prevent the magnet 46 from moving in the first direction 58, a second support lamina 112 can be positioned at a second end 114 of the stack of first rotor laminae 12 and second rotor laminae 32 to engage with the magnet 46 and prevent the magnet 46 from moving in the second direction 68. The engagement of the open or blind flange 116 with the magnet 46 also serves to restrain the magnet 46 from moving in a direction orthogonal to the direction 68 by its frictional engagement with the magnet.

As shown in Figures 2 and 5, in segments 14-1 and 34-1, the slot 16 of each of the first rotor laminae 12 has a first slot length 19, in a lengthwise direction, orthogonal to the first slot width 18, and the slot 36 of each of the second rotor laminae 32 has a second slot length 39, in the lengthwise direction, orthogonal to the second slot width 38. Alternatively, or in addition, to the embodiments described above, the second slot length 39 may be smaller than the first slot length 19, and the magnet 46 is engaged with a first widthwise edge 41 of the slot 36 of each of the second plurality of rotor laminae 32 through the rotor core 50. The magnet 46 may be separated from a first widthwise edge 21 of the slot 16 of each of the first plurality of rotor laminae 12 through the rotor core 50.

For example, in one embodiment, the first slot width 18 of the first rotor laminae 12 is the same as the second slot width 38 of the second rotor laminae 32, and the first slot length 19 of the first rotor laminae 12, orthogonal to the first slot width 18, is larger than the second slot length 39 of the second rotor laminae 32, orthogonal to the second slot width 38. In such an arrangement a similar magnet engaging or retaining arrangement can be provided as described above, but, upon insertion of the magnet 46 into the rotor slot 56, the engagement or retention of the magnet 46 is in an axis orthogonal to the axis of engagement presented in the embodiments above, that is, the engagement with an inserted magnet 46 is by a first widthwise edge 41 of the slot 36 of each of the second plurality of rotor laminae 32 through the rotor core 50.

In some embodiments of the rotor 10, the second rotor laminae 32 are evenly distributed through the stack of first rotor laminae 12 and second rotor laminae 32. The second rotor laminae 32 may comprise one in every n laminae of the stack of first rotor laminae 12 and second rotor laminae 32, where n is a value between two and ten. For example, Figure 7 illustrates an example rotor 10 where n is 6. In other examples n may be 2, 3, 4, 5, 7, 8, 9, or 10. A larger value of n allows for a rotor arrangement 10 with a smaller second slot width 38, such that upon insertion of a magnet 46 into the rotor slot 56, the deformation of the first lengthwise edge 40 of the slot 36 of each of the second plurality of rotor laminae 32 may be larger, with the deformed first lengthwise edge 40 of one lamina of the second plurality of rotor lamina 32 not interfering with a neighbouring lamina of the second plurality of rotor laminae 32. It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

CLAIMS1. A rotor comprising: a plurality of first rotor laminae, each of the first rotor laminae having a slot therethrough, the slot of each of the first rotor laminae having a first slot width, wherein the slots of each of the first rotor laminae overlay each other, to form a rotor core with a rotor slot therethrough; a first support lamina at a first end of the stack of first rotor laminae, the first support lamina occluding, at least in part, the rotor slot to prevent the magnet from moving in a first direction; a second support lamina at a second end of the stack of first rotor laminae, the second support lamina occluding, at least in part, the rotor slot to prevent the magnet from moving in a second direction opposite the first direction; and a magnet positioned in the rotor slot.
2. A rotor according to claim 1, wherein the first support lamina is planar.
3. A rotor according to any preceding claim, wherein the second support lamina is formed to have a projection into the rotor slot to engage with the magnet and prevent the magnet from moving in the second direction.
4. A rotor according to claim 3, where the projection is an open flange or a blind flange.
5. A rotor according to claim 3 or claim 4, where the projection is formed by peening, punching, or drawing the second support lamina.
6. A rotor according to any preceding claim, comprising a plurality of second rotor lamina stacked with the plurality of first rotor laminae, each of the second rotor laminae having a slot therethrough, the slot of each of the second rotor laminae having a second slot width, the second slot width being smaller than the first slot width, wherein the slots of the first rotor laminae overlay the slots of the second rotor laminae, to form a rotor core with a rotor slot therethrough, the rotor slot having a varying width through the rotor core.
7. A rotor according to claim 6, wherein the second rotor laminae are evenly distributed through the stack of first rotor laminae and second rotor laminae.
8. A rotor according to claim 7, wherein the second rotor laminae comprise one in every n laminae of the stack of first rotor laminae and second rotor laminae, where n is a value between two and ten
9. A rotor according to any of claims 6 to 8, wherein the magnet engages with a first lengthwise edge of the slot of each of the second plurality of rotor laminae through the rotor core.
10. A rotor according to claim 9, wherein the magnet is separated from a first lengthwise edge of the slot of each of the first plurality of rotor laminae through the rotor core.
11. A rotor according to claim 9 or claim 10, wherein the first lengthwise edge of the slot of each of the second plurality of rotor laminae is deformed by the engagement between the magnet and the first lengthwise edge of the slot of each of the second plurality of rotor laminae through the rotor core, each deformed first lengthwise edge of the slot of each of the second plurality of rotor laminae exerting a springback effect force on the magnet.
12. A method of manufacturing a rotor, the rotor having a rotational axis, the method comprising: stacking a plurality of first rotor laminae, each of the first rotor laminae having a slot therethrough, the slot of each of the first rotor laminae having a first slot width, wherein the slots of each of the first rotor laminae overlay each other, to form a rotor core with a rotor slot therethrough; inserting a magnet into the rotor slot; securing a first support lamina at a first end of the stack of first rotor laminae, the first support lamina occluding, at least in part, the rotor slot, to prevent the magnet from moving in a first direction parallel to the rotational axis; securing a second support lamina at a second end of the stack of first rotor laminae, the second support lamina occluding, at least in part, the rotor slot, to prevent the magnet from moving in a second direction, opposite the first direction, parallel to the rotational axis.
13. A method of manufacturing a rotor according to claim 12, the method comprising: stacking a plurality of second rotor lamina with the plurality of first rotor laminae, each of the second rotor laminae having a slot therethrough, the slot of each of the second rotor laminae having a second slot width, the second slot width being smaller than the first slot width, wherein the slots of the first rotor laminae overlay the slots of the second rotor laminae, to form a rotor core with a rotor slot therethrough, the rotor slot having a varying width through the rotor core.
14. An electric machine comprising a rotor according to any of claims 1 to 11 and a stator.
15. A vehicle comprising an electric machine according to claim 14.