The present invention is related to a method for production of a ring-shaped permanent magnet structure, according to the preamble of claim 1.

Background

The challenge of production of ring-shaped permanent magnet structures is relevant for electric machines employing permanent magnets. The magnet pieces 10 (individual magnets) can either repulse or attract each other, depending on the direction of their magnetization, therefore, putting them together may be a challenging task. In Figure la it is shown that a pair of magnets 10 with magnetization along the same axis but in opposite direction experience mutual attraction force (F) when being located close to each other. In Figure lb it is shown that a pair of magnets 10 with magnetization along the same axis and in the same direction experience mutual repulsion force when being located close to each other. In Figure lc it is shown that a pair of magnets 10 with magnetization in perpendicular directions experience a more complex pattern of forces including turning forces (T) when being located close to each other. When the target is to make a structure consisting of several magnets 10, like shown in Figure Id and Figure le, the forces between the individual magnet pieces can either be favourable or not favourable for holding the structure together and in any case will make the installation process difficult and in the case of using large magnets even dangerous for those working on the assembly.

The permanent magnets 10 can form a self-supporting ring 30 like the one shown in Figure IF or can be attached to a carrying element 20 such as a ring made of steel as shown in Figures 1G and 1H. The structures in Figures If, lg and lh are so-called Halbach arrays 40, where the direction of magnetization of the neighbouring magnets can vary from the direction perpendicular to the surface of the carrying element 20 (support ring). Halbach arrays 40 provide stronger magnetic field than conventional magnet arrays. Assembly of Halbach arrays 40 is especially challenging since the force patterns within the array vary a lot depending on the direction of magnetization of the individual pieces and the spatial combinations of the pieces. Fig. lg is showing a Halbach array 40 on back iron for inner-rotor machine 50 and Fig. lh is showing a Halbach array 40 on back iron for outer-rotor machine 60. The prior art solutions to the problem of assembly of the interacting pieces of magnets into a structure can be divided into several groups.

The first group of solutions employ special temporary holding mechanisms to keep magnets in desired positions. For example, US7987579B2 discloses a method for mounting permanent magnets that form magnetic poles on a surface of a rotor which includes placement of a mold part against the support surface and inserting a permanent magnet into the mold so that the inserted permanent magnet is held in the mold in a desired position. CN105429411A discloses a rig for producing a magnetic pole made of three Halbach magnets. The rig comprises locking screws, magnetic anticollision pads, magnetic steel simulation blocks, mold sleeve and some other components. Individual magnets are inserted into their corresponding positions, then having the mold sleeve tightly fitted the magnet pieces and fixed by locking screws.

The drawback of the solutions from the first group is that they are time consuming and not easy to automate.

The second group of solutions employ special permanent holding, guiding or separation mechanisms that are integral part of the electric machine and are not removed after the magnet structure assembly. For example, CN109560634A discloses a solution for installing permanent magnets on the rotor, which comprises plurality of slots used for installing the permanent magnets and a plurality of locking insertion bars. CN204992963U discloses a mold body with plurality of barrier sheets/spacers to locate the permanent magnets.

The drawback of the solutions from the second group is that the holding elements occupy useful active space in the machine reducing its performance.

The third group of solutions is related to electric machines with so-called "buried" magnets. Such machines have slots where the magnets can be inserted. For example, JP2014220871A discloses a device for insertion of magnet pieces into holes in a rotor core using clamp mechanism for holding the magnets during the insertion process. JP2013162640A discloses a method of manufacturing a rotor, wherein a temporary magnet holder is formed with a plurality of slots at positions corresponding to the plurality of slots of the rotor core, and there is performed insertion from the holder's slots to the rotor slots. JP2017051058A discloses a magnet insertion device for a rotor iron core where permanent magnets are inserted into magnet insertion holes of the rotor iron core and where the axial centre of a rotor iron core main body is changed from a vertical state to a horizontal state by tilting means. Insertion into the holes/slots closed from all sides is relatively easy since individual magnets are not interacting with each other during the assembly. The drawback is that this method is not applicable for machines with surface-mounted magnets.

The fourth group of solutions is related to use of powders or melt magnet materials and "in situ” magnetization. For example, JP2007180368A discloses a method of manufacturing a magnetic circuit component in which rare earth magnet powder and soft magnetic material powder parts are integrated, and where press moulding of the rare earth magnet powder takes place in an oriented magnetic field. JP2012050179A discloses a method using filling circumferential cavities of the assembly rig with a molten magnet manufacturing material and getting it magnetized by groups of permanent magnets that are permanent parts of the rig.

The drawback of the solutions from the fourth group is that they are complex to realize and the resulting permanent magnet structure often has weaker magnetization compared to structures made of pre-magnetized magnets.

Thus, the prior art solutions fail to disclose methods for production of active parts of electric machines including surface-mounted permanent magnets such as for example rotors with surfacemounted permanent magnets, wherein the methods would be time efficient, easy to automate and would result in high performance of the electric machines.

The disadvantage of the prior art solutions is that they are characterized by one or several of the following features:

- are not applicable for surface-mounted magnet arrays, such as for example Halbach arrays,

- are complex to realize,

- are not easy to automate,

- are time consuming,

- compromise performance of the magnet array.

Electric machines with permanent magnets are characterized by high power density compared to other machines, like induction machines or direct current machines. Such machines are enabling for emerging markets like drones, electric land transport, aerospace, etc., which will increase the need for methods for production of strong magnet arrays. Rotors with surface-mounted magnets is a common topology of permanent magnets machines. Permanent magnet machines with Halbach magnet arrays often display the best performance in terms of power density, torque density and efficiency, therefore there will be a need for methods for production of Halbach magnet arrays.

Thus, there will be a need for a method for production of a ring-shaped permanent magnet structure, especially surface-mounted permanent magnet arrays, such as Halbach arrays, which is:

- not complex to realize,

- easy to automate,

- time-efficient,

- safe,

- flexible/scalable,

- not compromising performance of the permanent magnet array.

Object

The main object of the present invention is to provide a method for production of a ring-shaped permanent magnet structure, partly or entirely solving the above-mentioned drawbacks of prior art and fulfilling the mentioned needs.

An object of the present invention is to provide a method for production of a ring-shaped permanent magnet structure for electrical machines that can be used in a wide range of applications.

It is an object of the present invention to provide a method for production of a ring-shaped permanent magnet structure resulting in high magnetic performance of the permanent magnet structure.

It is an object of the present invention to provide a method for production of a ring-shaped permanent magnet structure resulting in high mechanical quality, e.g., in terms of tolerance control between adjacent magnets, and at outer and inner surfaces of the ring-shaped structure.

It is an object of the present invention to provide a method for production of a ring-shaped permanent magnet structure facilitating magnet encapsulation with composite or a metal sleeve, or with epoxy infusion, in a later production step. It is further an object of the present invention to provide a method for production of a ring-shaped permanent magnet structure assembled of pre-magnetized permanent magnets.

An object of the present invention is to provide a method for production of a ring-shaped permanent magnet structure assembled by a combination of pre-magnetized permanent magnets and permanent magnets that are not pre-magnetized.

A further object of the present invention is to provide a method production of a ring-shaped permanent magnet structure assembled by using a simulation where all the permanent magnets are not pre-magnetized.

It is an object of the present invention to provide a method for production of a ring-shaped permanent magnet structure being safe, scalable, time-efficient and easy to automate.

It is further an object of the present invention to provide a method for production of a ring-shaped permanent magnet structure resulting in lower production costs, both for mass-production and low volume production.

An object of the present invention is to provide a method for production of a ring-shaped permanent magnet structure without compromising the performance of the permanent magnets.

Further objects of the present invention will appear from the following description, claims and attached drawings.

The invention

A method for production of a ring-shaped permanent magnet structure according to the present invention is defined by the technical features of claim 1. Preferable features of the method are described in the dependent claims.

The present invention is related to a method for production of a ring-shaped permanent magnet structure using permanent magnets divided into at least two groups, thus forming first and second groups of permanent magnets. The method according to the present invention comprises subsequent arrangement of the first and second groups of permanent magnets to form the ring-shaped permanent magnet structure.

The enabling element of the present invention is a multi-component assembly tool, wherein the components thereof are movable, removable and/or reconfigurable for performing the different steps of the production of the ring-shaped permanent magnet structure. According to the present invention, the mentioned components of the multi-component assembly tool in different configurations, by assembly or movement in relation to each other, form channels for insertion of the mentioned first and second groups of permanent magnets.

The final positions of the mentioned permanent magnets from the two groups are defined such that a ring-shaped permanent magnet structure is formed, wherein the permanent magnets from the two groups are located interchangeably in circumferential direction thereof. Accordingly, the method according to the present invention comprises arranging each permanent magnet from the second group in between two permanent magnets from the first group and each permanent magnet from the first group between two permanent magnets from the second group.

The method for production of the ring-shaped permanent magnet structure according to the present invention involves the same main steps or actions independently of realization. According to the present invention, the method may comprise one or more additional steps or actions that may vary.

The method according to the present invention comprises assembling the multi-component assembly tool into an initial configuration forming first channels corresponding to final positions of the permanent magnets of the first group in the ring-shaped permanent magnet structure. At the same time, parts of the multi-component assembly tool temporary occupy final positions of the permanent magnets of the second group between the permanent magnets of the first group in the ring-shaped permanent magnet structure.

The method, in the initial configuration of the multi-component assembly tool, further comprises inserting the first group of permanent magnets into the first channels formed during the assembling of the multi-component assembly tool.

The method according to the present invention further comprises inserting the permanent magnets of the second group into second channels of the multi-component assembly tool and arranging the second group of permanent magnets into their final position by reconfiguration of the multicomponent assembly tool by extracting the parts of the multi-component assembly tool occupying the final position at the same time as moving the permanent magnets of the second group into the final position of the ring-shaped permanent magnet structure.

According to one embodiment of the method according to the present invention it comprises using a multi-component assembly tool comprising at least one outer tool component and inner slotted tool component, wherein, during forming of the first channels, the inner slotted tool component forms at least sides of the first channels and the outer tool component forms at least a part of the periphery of the first channels.

According to one embodiment of the method according to the present invention it comprises using a multi-component assembly tool comprising at least one outer tool component and inner slotted tool component, wherein, during forming of the first channels, the slotted outer tool component forms at least sides of the first channels and the inner slotted tool component forms at least a part of the periphery of the first channels.

In accordance with one embodiment of the method according to the present invention, the method comprises moving the inner slotted tool component out of the outer tool component creating free space in the form of the second channels between the permanent magnets of the first group.

In accordance with one embodiment of the present invention, the method comprises producing a ring-shaped permanent magnet structure being self-supporting.

According to a further embodiment of the present invention, the method comprises arranging or fixation of the ring-shaped permanent magnet structure to a support structure. A support structure, which the ring-shaped permanent magnet structure is to be arranged adjacent to or fixed to, is according to the present invention arranged to the multi-component assembly tool before or after the insertion of the permanent magnets of the first group in the multi-component assembly tool. According to one embodiment of the present invention, the support structure can comprise only a rotor ring separated from the rest of a carrying structure or the rotor ring together with a part of a carrying structure.

In accordance with a further embodiment of the method according to the present invention, the method comprises using a support structure wherein a part or parts thereof is rotor back iron.

According to a further embodiment of the present invention, at least some of the above described assembly steps or actions are performed in an automated manner. In accordance with a further embodiment of the present invention, the method comprises forming a ring-shaped permanent magnet structure in the form of a Halbach array.

According to a further embodiment of the present invention, the method comprises assembly by a combination of pre-magnetized permanent magnets and permanent magnets that are not premagnetized.

In accordance with one embodiment of the present invention, the method comprises simulation where all the permanent magnets are not pre-magnetized, wherein, underthis scenario, the present invention facilitate the post-assembly magnetization of a ring-shaped permanent magnet structure in one magnetization step or in multiple magnetization steps.

Further preferable features and advantageous details of the present invention will appear from the following example description, claims and attached drawings.

Example

The present invention will below be described in further detail with references to the attached drawings of non-limiting example embodiments, where:

Fig. la-c are principle drawings of the physics of magnet forces,

Fig. ld-h are principle drawings of the use of magnet arrays in practical applications,

Fig. 2a-c are principle drawings of components of a multi-component assembly tool according to one embodiment of the present invention,

Fig. 3 is principle drawing of arrangement of a support structure according to the present invention,

Fig. 4 is a principle drawing of insertion of a first group of permanent magnets,

Fig. 5a-b are a principle drawing of locking the first group of permanent magnets in the multicomponent assembly tool,

Fig. 6 and 7 are principle drawings of insertion and arrangement of permanent magnets of a second group in final position, Fig. 8 is a principle drawing showing separation of parts of the multi-component assembly tool,

Fig. 9 is a principle drawing of the ring-shaped permanent magnet structure in an outer tool component,

Fig. 10 is a principle drawing of a multi-component assembly tool according to a second embodiment of the present invention,

Fig. 11 is a principle drawing showing insertion of permanent magnets of the first group,

Fig. 12 is a principle drawing showing arrangement of a magnet slide tool component to the multicomponent assembly tool,

Fig. 13 is a principle drawing showing insertion of permanent magnets of the second group into the permanent magnet slide tool,

Fig. 14a-b are principle drawing of an inner slotted stop disc and a center plug, respectively, according to the present invention,

Fig. 15a-b are principle drawings of the use of the center plug and inner slotted stop disc for final arrangement of the permanent magnets of the second group,

Fig. 16a-b are principle drawings of locking the permanent magnets, and

Fig. 17 is a principle drawing of arrangement of the ring-shaped permanent magnet structure to a support structure.

Reference is now made to Fig. la-h showing principle drawings of physics of magnetic forces and the use of magnet arrays in practical applications, illustrating the complexity of the challenge the present invention is solving. The details of the prior art solutions are described above in the background section.

Reference is now made to Figures 2-9 describing a first embodiment of realization of method for production of a ring-shaped permanent magnet structure 100.

For realization of the method for production of a ring-shaped permanent magnet structure 100, the present invention makes use of a multi-component assembly tool 200. According to the first embodiment of the present invention, the multi-component assembly tool 200 comprises mainly tubular components adapted to be arranged to each other and/or into each other. Figure 2a-c show principle drawings of the respective components 210-230 of the multicomponent assembly tool assembly 200 according to the first embodiment of the present invention. The multi-component assembly tool 200 according to the first embodiment comprises an outer tool component 210, a magnet slide tool component 220 and an inner slotted component 230. According to the first embodiment, the magnet slide tool component 220 is provided with through channels 221, further described below. In accordance with the first embodiment, the inner slotted component 230 is formed by a mainly ring-shaped main body 231, provided with protruding parts 232 distributed in circumferential direction thereof, wherein the protruding parts 232 extend in a mainly perpendicular direction of the ring-shaped main body 231. In the shown embodiment the protruding parts 232 are mainly L-shaped and extends with a first leg thereof from the inner circumference of ring-shaped main body 231 and a distance towards the center thereof and ending in the second leg mainly perpendicular to the ring-shaped main body 231. In this manner the protruding parts 232 forms a narrower slotted inner diameter of the inner slotted component 230, adapted for receiving a first group of permanent magnets 250, further described below.

Reference is now made to Figure 3 showing the mentioned components 210-230 assembled together to form the multi-component assembly tool 200. The mentioned protruding parts 232 are adapted to be partly received in the mentioned channels 221 of the magnet slide tool component 220, such that the when the mentioned components 210-230 are assembled together the components are rotationally locked together. Figure 3 further shows a ring-shaped support structure 240, such as a rotor ring, which can also comprise back iron. According to the present invention, the ring-shaped support structure 240 can be received and accommodated in the mentioned inner slotted component 230, as shown in Fig. 4.

As Fig. 4 shows, after arrangement of the ring-shaped support structure 240 in the inner slotted component 230, first channels 201 are formed in the slots of the inner slotted component, restricted by the inner surface of the outer tool component 210 and the exterior diameter of the ring-shaped support structure 240 at upper and lower sides, which first channels 201 are adapted to receive and accommodate a first group of permanent magnets 250, as shown in Fig. 5a.

Fig. 5a further shows arrangement of a further component of the multi-component assembly tool 200 according to the present invention in the form of a slotted outer stop disc 260 according to a first embodiment, adapted the slotted upper surface of the inner slotted component 230, adapted for locking the first group of permanent magnets 250 in place in the mentioned first channels 201. Fig. 5b show the state where the slotted outer stop disc 260 is installed as a part of the multicomponent assembly tool 200.

Reference is now made to Figure 6 showing the multi-component assembly tool 200 from the other direction than the Figures 1-5. According to the present invention, it comprises inserting a second group of permanent magnets 251 in the mentioned channels 221 of the magnet slide tool component 220.

The present invention further comprises pushing the second group of permanent magnets 251 from the magnet slide tool component 220 into the outer tool component 210 and pushing the inner slotted component 230 out of the outer tool component 210 until the second group of permanent magnets 251 are positioned in the outer tool component 210.

As shown in Fig. 7 and 8 the components of the multi-component assembly tool 200 are now separated and the outer tool component 210 is accommodating the first and second group of permanent magnets 250, 251 surrounding the ring-shaped support structure 240 as shown in Fig. 9.

Reference is now made to Figures 10-17 showing another variant of realization of the same method, wherein the support structure 240, such as a rotor ring, is installed at one of the last assembly steps and wherein the support structure is a part of the carrying structure. In the shown embodiment, the multi-component assembly tool 200 comprises an outer tool component 210 enclosing an inner slotted component 230 and a slotted outer stop disc 270 according to a second embodiment of the present invention. The inner slotted component 230 is in this embodiment comprising a ring-shaped main body 231 provided with exterior protruding parts 232 extending with longitudinal direction thereof in transversal direction of the main body 231, except for a distance at one side thereof corresponding to the width of the mentioned slotted outer stop disc 270. The mentioned slotted outer stop disc 270 exhibits an exterior circumference adapted the exterior circumference of the outer tool component 210 and an inner circumference adapted the exterior circumference of the main body 231 of the inner slotted component 230, and is provided with slots 271 (Fig. 16a) extending from the inner circumference adapted the spacing between the mentioned protruding parts 232 and height thereof. In this manner, when the inner slotted component 230 is arranged in the outer tool component 210, and the slotted outer stop disc 270 is arranged to the inner slotted component 230 and outer tool component 210, at one side thereof, wherein the slotted outer stop disc 270 is arranged such that the slots coincide with the exterior protruding parts 232 and able to receive these in a sliding manner, further described below. First channels 201 is formed by the spacing between the protruding parts 232 restricted by the outer tool component 210 at upper side and by the slotted outer stop disc 270 at rear end, as shown in Fig. 10.

As for the first embodiment, also the second embodiment comprises a step of inserting a first group of permanent magnets 250 into the mentioned first channels 201 and into contact with the slotted outer stop disc 270, as shown in Fig. 11.

According to the present invention, it further comprises adding a magnet slide tool component 220 having channels 221 formed by slots extending from inner circumference thereof. According to the present invention, the magnet slide tool component 220 is adapted to be received and accommodated in a recess 211 in the outer tool component 210, and wherein the channels 221 are adapted the protruding parts 232 of the inner slotted component 230 and wherein the teeth formed between the channels 221 are adapted for engagement with the permanent magnets 250 of the first group, as shown in Fig. 12.

According to the present invention it comprises inserting a second group of permanent magnets 251 into the mentioned channels 221 of the magnet slide tool component 220 until they reach the inner slotted component 230, as shown in Fig. 13, and the second group of permanent magnets 251 is thus positioned alternatively between the mentioned first group of permanent magnets 250, and wherein the second group of permanent magnets 251 coincides with the protruding parts 232 of inner slotted component 230 and the slots 271 of the slotted outer stop disc 270.

Reference is now made to Figures 14a and 14b which shows an inner slotted stop disc 280 and a center plug 290 which are parts used/added during the next steps. The center plug 290 is mainly tubular and formed by two parts with different exterior circumference, wherein a first and smallest exterior circumference is adapted the interior circumference of the outer stop disc 270 and the second and largest exterior circumference is adapted the interior circumference of the magnet slide tool component 220, wherein the part with the largest exterior circumference has a length that corresponds to the length of the outer tool component 210.

The present invention comprises, as in the first embodiment, pushing the second group of permanent magnets 251 out of the magnet slide tool component 220 and into the outer tool component 210, and into alignment with the first group of permanent magnets 250. This is enabled by the use of the mentioned center plug 290 and inner slotted stop disc 280, wherein the inner slotted stop disc 280 enables force application to the second group of permanent magnets 251 directly. According to the present invention, the center plug 290 is first pressed into the multi-component assembly tool 200, i.e. received in the inner slotted tool component 230 and magnet slide tool component 220 and will hold the first group of permanent magnets 250 against the inner surface of the outer tool 210.

When the center plug 290 is inserted as described, the inner slotted stop disc 280 is arranged to one end of the center plug 290 so that teeth 281 thereof align with the permanent magnets 251 of the second group, as shown in Fig. 15a, wherein the permanent magnets 251 of the second group is partly inserted into the outer tool component 210. Then the permanent magnets 251 of the second group are moved into the outer tool component 210 by means of pushing the inner slotted stop disc 280 to a state where the second group of magnets 251 are fully inserted in the outer tool component 210 at the same time as the center plug 290 pushes the inner slotted tool component 230 out of the outer tool component 210, as shown in Fig. 15b.

The present invention further comprises as step of exchanging the slotted outer stop disc 270, as shown in Fig. 16a, with a full outer stop disc 300, as shown in Fig. 16b. By changing to a full outer stop disc 300, all the permanent magnets 250, 251 are locked inside the outer tool component 210 at their final position.

For a self-supported ring-shaped permanent magnet structure, the removing of the central plug 290 and full outer stop disc 300 and pushing the ring-shaped permanent magnet structure 100 out of the outer tool component 210 would be the final steps. However, for the ring-shaped permanent magnet structure 100 on a support structure 240, such as rotor back iron and carrying structure more steps are required.

Reference is now made to Figure 17 showing installation of a ring-shaped permanent magnet structure 100 according to the present invention to a rotor. According to the present invention, a rotor support structure 400 is inserted from one side of the ring-shaped permanent magnet structure 100 and pushes on one side of the center plug 290 and is received interior of the permanent magnets 250, 251 and the outer tool component 210. In this manner, as the rotor slides in, the center plug 290 slides out.

According to one embodiment of the present invention, the components of the multi-component assembly tool 200 are molded components shaped to exhibit a desired shape.

In accordance with one embodiment of the present invention, at least the parts 210-230, 260-280 used to assemble the permanent magnets 250, 251, are made of non-magnetic material. Many of the steps described above require pushing or pulling forces applied to the parts involved.

The above-described embodiments can be combined and modified to form other embodiments being within the scope of the attached claims. Modifications

The present invention is applicable for arrays with radially-magnetized permanent magnets and all kinds of Halbach magnet structures.

In a further modification, the present invention is also applicable for surface-mounted permanent magnet structures for conventional permanent magnet machines and special topologies like permanent magnet ring in pseudo-direct drives.

In a further modification, the present invention is also applicable for self-supported or mounted on the support structure.

In a further modification, the present invention is also applicable for rotary or linear electrical machines.

List of designations

10 - individual magnet (piece)

20 - carrying element for magnet array

30 - self-supporting magnet ring Halbach array

40 - Halbach array

50 - Halbach array on back iron for inner-rotor machine

60 - Halbach array on back iron for outer-rotor machine

100 - permanent magnet structure

200 - multi-component assembly tool

201 - first channels

210 - outer tool component

211 - recess of outer tool component

220 - magnet slide tool component

221 - channels in the magnet slide tool component

230 - inner slotted tool component

231 - main body inner slotted tool component

232 - protruding parts of inner slotted tool component

240 - support structure

250 - permanent magnets of first group

251 - permanent magnets of second group

260 - slotted outer stop disc according to a first embodiment

270 - slotted outer stop disc according to a second embodiment

271 - slots of slotted outer stop disc

280 - inner slotted stop disc

281 - teeth of inner slotted stop disc

290 - center plug

300 - full outer stop disc

400 - rotor support structure