NL2025414B1 - AC synchronous motor - Google Patents

Abstract

The present invention relates to a method for manufacturing one of a rotor and stator for an alternating current, ’AC’, synchronous motor. 5 According to the present invention, a holder used for defining the distance between adjacent magnets is left in place and is, similar to the magnets themselves, covered by a protective synthetic resin. FIG. 3A 10

Description

AC synchronous motor The present invention relates to a method for manufacturing one of a rotor and stator for an alternating current, ° AC’, synchronous motor. This motor may be a linear motor or may have the more common rotating form. The present invention further relates to a part of an AC synchronous motor, the part being either a stator or a rotor, wherein the part has been obtained by applying this method. In addition, the present invention relates to an AC synchronous motor comprising the part.

Figure 1 illustrates an iron-core AC synchronous linear motor 1 known from the prior art. It comprises a primary part 2 and a secondary part 3. Secondary part 3 comprises a plurality of spaced apart magnets 4 that are mounted to a closing plate 5 made of iron or steel. Although not shown, magnets 4 are typically covered by a protective synthetic resin.

Primary part 2 comprises a housing 6 in which a plurality of electrical coils are provided. Electrical wiring 7 is passed through housing 6 to allow the electrical coils to be energized for the purpose of causing a relative motion between primary part 2 and secondary part 3 along a direction indicated by arrow M.

In figure 1, primary part 2 constitutes the moving part of the motor, i.e. the rotor, and the secondary part 3 constitutes the stationary part of the motor, i.e. the stator. However, in other embodiments the roles are reversed.

By energizing the electrical coils, a Lorentz force directed along the direction indicated by arrow W will be generated that acts on primary part 2. This force causes a relative motion between primary part 2 and secondary part 3. Primary part 2 is typically configured for three-phase systems. The plurality of electrical coils are then grouped into three groups, each group corresponding to a different phase Pi, P2, P3, of the three-phase system. A phase offset of 120 degrees exists between each pair of phases. Moreover, in a typical case, electrical coils belonging to a different phase are adjacently arranged.

Figures 2A and 2B illustrate a known method by which magnets 4 can be arranged on closing plate 5. As a first step (I), magnets 4 are coupled to a mesh-like non-magnetic holder 10 that comprises a plurality of openings 11. Holder 10 is held against a magnetic plate 13. Near plate 13, holder 10 is provided with shoulders 12 to prevent magnets 4 from getting into direct contact with magnetic plate 13. Consequently, after magnets 4 become coupled to magnetic plate 13, shown as step (II), a clearance 14 exists between magnets 4 and magnetic plate 13.

As a next step (111), holder 10 with magnets 4 and magnetic plate 13 are brought into close proximity with closing plate 5 that is also magnetic. Due to clearance 14, the magnetic force exerted by closing plate 5 onto magnets 4 will be larger than the magnetic force exerted by magnetic plate 13. Consequently, magnets 4 will move relative to holder 10 towards closing plate 5, which is shown as step (IV). This relative motion can be further stimulated by increasing clearance 14 by moving away magnetic plate 13. Prior to coupling with closing plate 5, magnets 4 are provided with an adhesive (not shown) to allow magnets 4 to be fixedly attached to closing plate 5.

After the adhesive has sufficiently cured, magnetic plate 13 and holder 10 are removed from magnets 4, which is shown as steps (V) and (VI). It is noted that holder 19 and magnetic plate 13 may be fixedly attached to each other in which case holder 10 and magnetic plate 13 are removed as a single unit.

As a final step, shown as step (VII), a protective synthetic resin 15 is applied to cover magnets 4.

To obtain smooth motion of primary part 2 over secondary part 3, it is important that the magnets are regularly spaced relative to each other. More in particular, the interval between adjacent magnets should preferably be identical for each pair of adjacent magnets. If the intervals are different, the resulting force and/or motion will display unwanted disturbances referred to as cogging or ripple.

An object of the present invention is to provide a method for manufacturing one of a rotor and stator for an AC synchronous motor in which the abovementioned disturbances are reduced.

According to a first aspect of the present invention, this object is achieved using the method as defined in claim 1. This method comprises the steps of a) providing a plurality of permanent magnets, and b) providing a first plate of magnetic material onto which the magnets need to be mounted, and a second plate of magnetic material.

The method according to the invention further comprises the steps of c) providing a holder having openings at well defined, e.g. identical, intervals and with a size that is substantially identical to a size of the magnets, and d) arranging the magnets into the openings of the holder such that the magnets become fitted to the holder while the holder is supported by a supporting surface.

In addition, the method of the invention comprises the steps of e) magnetically coupling the holder with the magnets to the second plate via spacing means, wherein the spacing means are physically separated from the holder and are configured to lower a strength of the magnetic coupling between the magnets and the second plate. In addition, the method of the invention further comprises f) bringing the second plate, the holder, and the magnets in close proximity of the first plate causing the magnets to become more magnetically coupled to the first plate than they are coupled to the second plate, wherein the magnets, prior to be being coupled to the first plate, are provided with an adhesive, and wherein the magnets, after being coupled to the fust plate, contact the first plate via the adhesive.

As final steps, the method of the invention comprises g) decoupling the second plate from the magnets by moving the second plate away from the magnets and the holder, h) allowing the adhesive to cure thereby fixating the magnets, while being coupled to the holder, onto the first plate, and i) covering the magnets and holder with an synthetic resin. For example, the synthetic resin may comprise epoxy or polyurethane, The magnets are coupled to the holder in such a manner that the magnets do not or hardly move relative to the holder during at least steps e)-i). This could be achieved by optimizing the tolerances on the openings in the holder to create the tightest tolerances on the positioning of the magnets in these openings. For example, the sizes of the magnets and openings can be such that, during step d, the magnets can be snugly and/or tightly fitted in the openings of the holder.

Contrary to the method described in connection with figures 2A and 2B, the magnets IO remain coupled to the holder in the final product.

The Applicant has found that irregular intervals between adjacent magnets in the known AC synchronous motor manufactured using the method illustrated in figures 2A and 2B can be attributed to the relative motion between holder 10 and magnets 4.

The Applicant has found that openings 11 must be somewhat larger than magnets 4 to facilitate the relative motion required for coupling magnets 4 to closing plate 5 in step (IV) and to allow holder 10 to be removed from magnets 4 in step (VI). In addition, openings 11 cannot be too small as this complicates removal of holder 10 without disturbing the placement of magnets 4 on closing plate 5. However, openings 11 cannot be too large with respect to magnets 4 as this would impede accurate placement of magnets 4.

By allowing the holder to remain coupled to the magnets, the abovementioned problems can be mitigated.

Furthermore, in the known method, shoulders 12, which form a part of holder 10, are used to keep magnets 4 separated from magnetic plate 13 such that the latter can more easily be removed when magnets 4 become coupled to closing plate 5. In this sense, shoulders 12 constitute spacing means for lowering a strength of the magnetic coupling between the magnets and the magnetic plate. According to the invention however, the spacing means are physically separated from the holder which means that the spacing means can be removed after the magnets are magnetically coupled to the second plate, e.g. the closing plate. In this manner, there are little to no protruding elements that extend beyond the magnets. This allows the primary part to pass by the magnets at a relatively close distance, thereby increasing the maximum force that can be generated by the motor.

The method may further comprise providing a supporting element such as a further plate. In this case, step d) may comprise arranging the holder on the supporting element such that the holder is supported by the supporting element during said arranging the magnets into the openings of the holder. Here, the supporting element merely has a mechanical supporting function and need not be made of magnetic material.

Further to the above, the magnets can be arranged into the openings of the holder with a side of the magnets facing the supporting element, wherein step e) may comprise bringing the second plate into close proximity of the magnets at an opposite side of the magnets. When using a supporting element, the spacing means may comprise a preferably non- magnetic spacer element, such as a foil. Step e) may then comprise arranging the spacer element in between the holder and the second plate before coupling the magnets to the second plate. Alternatively, the spacing means may comprise a plurality of recesses in the second plate corresponding to the plurality of magnets. Step e) may then comprise aligning the recesses with the magnets prior to coupling the magnets to the second plate.

Instead of using a supporting element, the second plate can be configured to support the holder during step d). In this case, the step of coupling the magnets to the holder and the step of magnetically coupling the holder with the magnets to the second plate are performed substantially simultaneously. Moreover, in this case, the spacing means may comprise a preferably non- magnetic spacer element, such as a foil, and the method may further comprise arranging the spacer element in between the holder and the second plate prior to arranging the magnets in the openings of the holder. Alternatively, the spacing means may comprise a plurality of recesses in the second plate corresponding to the plurality of magnets, and step d) may comprise aligning the openings with the recesses in the second plate prior to arranging the magnets in the openings of the holder.

The holder can be planar and mesh-shaped and can be made from non-magnetic material.

For example, the holder can be made from acrylonitrile butadiene styrene, ‘ABS’, polyether ether ketone ‘PEEK’, nylon, ultra-high-molecular-weight polyethylene, ‘HMPE’, aluminum, titaniam and/or carbon fiber.

After coupling the holder with the magnets to the second plate, a first side of the magnets can be facing the second plate. After coupling the magnets to the first plate, a second side of the magnets, opposite to the first side, can be facing the first plate, wherein the magnets, prior to be being coupled to the first plate, are provided with said adhesive on the second side of the magnets.

The magnets may lie flush with or slightly above the holder on the second side of the magnets prior to performing step 1). In this manner, physical contact of the magnets with the first plate, albeit via the adhesive, can be guaranteed.

Additionally or alternatively, the magnets may lie flush with the holder on the first side of the magnets after performing step d). In this manner, no protruding elements will extend beyond the magnets that would prevent the coils and the magnets to pass at close range.

Step d) may comprise using an adhesive to further fixate the magnets to the holder. As stated before, the magnets are fitted into the openings to prevent the magnets from moving relative to the holder during the process of attaching the magnets to the first plate, for example by means of a tight or snug fit. This fixation may be further aided by the application of an adhesive between the magnets and the holder.

According to a second aspect, the present invention provides a part of an AC synchronous motor, the part being either a stator or a rotor, and being obtained by the method as described 5 above.

According to a third aspect, the present invention provides a part of an AC synchronous motor, the part being either a stator or a rotor. This part comprises a first plate of magnetic material, a plurality of permanent magnets fixedly attached to the first plate using an adhesive, a holder comprising a plurality of openings into which the magnets are fitted, preferably in a snugly or tightly fit manner, at predefined intervals, and a resin covering the first plate, the magnets, and the holder.

According to a fourth aspect, the present invention provides an AC synchronous motor comprising the part described above.

Next, the present invention is explained further by referring to the appended drawings wherein: Figure 1 illustrates an iron-core AC synchronous motor known from the prior art; Figures 2A-2B illustrate a known method for manufacturing the secondary part of the motor of figure 1; Figures 3A-3B illustrate a first method for manufacturing the secondary part of an AC synchronous motor in accordance with the present invention; Figures 4A-4B illustrate a second method for manufacturing the secondary part of an AC synchronous motor in accordance with the present invention; and Figures 5A-5B illustrate a third method for manufacturing the secondary part of an AC synchronous motor in accordance with the present invention.

In the description of the figures that will follow next, the coupling between the first plate and the magnets, between the second plate and the magnets, and between the magnets and the supporting element, will be illustrated by indicating a particular direction in which these elements are coupled, e.g. top to bottom or vice versa. It is however noted that such coupling direction is provided for illustrative purposes only. The invention is not limited to a particular coupling direction.

Figures 3A-3B illustrate a first method for manufacturing the secondary part of an AC synchronous motor in accordance with the present invention. This method starts with a step (1) of coupling magnets 4 with their first sides 4A facing second plate 13 into openings 101 of a holder 100 while a non-magnetic foil 102 is being arranged in between holder 100 and second plate 13.

After magnets 4 are coupled to holder 100, shown as step (11), a second side 4B of magnets 4 lies flush with a top-side of holder 100.

Holder 100 is a planar mesh-like structure having a thickness, i.e. dimension perpendicular to second plate 13, which is at least approximately the same as a thickness of magnets 4. Openings 101 are provided at well-defined and preferably identical intervals. Foil is generally a thin foil having a thickness of about 1 mm and is made from acrylonitrile butadiene styrene, ‘ABS’ ultra-high-molecular-weight polyethylene, ‘HMPE’, and/or polytetrafluoroethylene, ‘PTFE’.

In step (IID), first plate 5, i.e. the closing plate, is brought into close proximity with magnets 4. At a given distance, the magnetic force exerted onto magnets 4 by first plate 5 will exceed that magnetic force that is exerted onto magnets 4 by second plate 13. It is noted that the magnetic force exerted by second plate 13 is reduced due to the presence of foil 102, which effectively increases a distance between second plate 13 and magnets 4.

As a result of moving first plate 5 towards magnets 4, magnets 4 and holder 100 will move as an entity towards first plate 5. This situation is shown as step (IV). This allows second plate 13 and foil 102 to be moved away from magnets 4 as shown in step (V). As a final step (VI), magnets 4 and holder 100 can be covered using a protective synthetic resin 15.

Figures 4A-4B illustrate a second method for manufacturing the secondary part of an AC synchronous motor in accordance with the present invention. As a first step (I), magnets 4 are moved towards a non-magnetic supporting plate 202 on which a holder 200 with openings 201 is arranged. After arranging magnets 4 in openings 201, as shown in step (Il), a magnetic second plate 205 with recesses 205A is moved towards magnets 4. As shown in the figure, recesses 205A are aligned with magnets 4. After moving second plate 205 sufficiently close to magnets 4, magnets 4 and holder 200 to which they are coupled, become magnetically coupled to second plate 205 as shown as step (IV). Recesses 205A reduce the strength of the magnetic coupling that would have otherwise existed between second plate 205 and magnets 4 if the magnets 4 would have been arranged completely against second plate 205.

As a next step (V), supporting plate 202 is moved away from magnets 4. Thereafter, as step (VD), a first plate 5, e.g. closing plate, is brought into contact with magnets 4. As the magnetic force exerted by plate 5 is much higher than that of second plate 205, magnets 4 become magnetically coupled allowing second plate 205 to be moved away in step (VII) without displacing magnets 4 relative to first plate 5. Prior to coupling magnets 4 to first plate 5, an adhesive such as glue is provided between magnets 4 and first plate 5. As a final step (VI), a protective synthetic resin 15 is applied over magnets 4 and holder 200. This step is performed after the applied adhesive has sufficiently or fully cured.

In steps (D-(I1I) of figure 4A, a non-magnetic supporting element 202 was used during the process of coupling, e.g. pressing, magnets 4 into openings 201 of holder 200. Alternatively, holder 200 can be first aligned relative to second plate 205. More in particular, openings 201 can be aligned relative to recesses 205A. Thereafter, magnets 4 can be arranged in openings 201 without the use of supporting element 202. Put differently, second plate 205 functions as supporting element.

Similarly, in step (I) of figure 3A, second plate 13 acted as supporting element during the process of arranging magnets 4 in openings 101 of holder 100. Alternatively, the coupling of magnets 4 could equally have been performed using a non-magnetic supporting plate on which holder 100 would be arranged. After arranging magnets 4 in openings 101, foil 102 could then be arranged over magnets 4. Thereafter, second plate 13 could be brought into close proximity with magnets 4 allowing them to be magnetically coupled to second plate 13. Once coupled, the supporting plate could be removed easily thereby arriving at a similar situation as depicted in step IO (I) of figure 3A.

In the above, the present invention has been explained using detailed embodiments thereof. However, various modifications can be made to these embodiments without departing from the scope of the invention which is defined by the appended claims and their equivalents.

Claims (17)

MODIFIED CONCLUSIONS L A method of manufacturing a rotor and stator for an AC synchronous motor, comprising the steps of: a) providing a plurality of permanent magnets; b) providing a first plate of magnetic material on which the magnets are to be mounted, and a second plate of magnetic material; c) providing a container with openings at well-defined intervals and having a size substantially identical to a size of the magnets; d) placing the magnets in the openings of the container so that the magnets fit into the container while the container is supported by a support surface; e) magnetically coupling the holder with the magnets to the second plate; f) bringing the second plate, the holder and the magnets into close proximity to the first plate causing the magnets to be magnetically coupled to the first plate more than they are coupled to the second plate, the magnets before being coupled provided with an adhesive to the first plate, and wherein the magnets, after being coupled to the first plate, contact the first plate through the adhesive; ) disconnecting the second plate from the magnets by moving the second plate away from the magnets and the holder; and h) allowing the adhesive to set thereby fixing the magnets to the first plate while coupled to the holder; characterized in that the method further comprises the step of i) covering the magnets and the holder with a synthetic resin, and in that the magnets are coupled to the holder such that the magnets do not or hardly move with respect to the holder for at least least steps e)-1), and that said magnetically coupling the holder with the magnets to the second plate is via spacers physically separated from the holder and arranged to decrease a strength of the magnetic coupling between the magnets and the second plate. A method according to claim 1, further comprising providing a support element such as a further plate, and wherein step d) comprises placing the holder on the support element such that the holder is supported by the support element during placement of the magnets in the support element. openings of the container. A method according to claim 2, wherein the magnets are placed in the openings of the holder with one side of the magnets facing the support element, step e) comprising bringing the second plate into close proximity to the magnets on an opposite side. of the magnets. A method according to claim 2 or 3, wherein the spacer means comprise a preferably non-magnetic spacer element, such as a foil, wherein step e) comprises placing the spacer element between the holder and the second plate prior to coupling the magnets to the second plate. A method according to claim 2 or 3, wherein the spacer means comprises a plurality of recesses in the second plate corresponding to the plurality of magnets, step e) comprising aligning the recesses with the magnets prior to coupling the magnets to the second plate. The method of claim 1, wherein the second plate is adapted to support the container during step d). Method according to claim 6, wherein the spacer means comprise a preferably non-magnetic spacer element, such as a foil, the method further comprising placing the spacer element between the holder and the second plate prior to placing the magnets in the openings of the holder. A method according to claim 6, wherein the spacer means comprises a plurality of recesses in the second plate corresponding to the plurality of magnets, step d) comprising aligning the openings with the recesses in the second plate prior to placing the magnets into the openings of the container. A method according to any one of the preceding claims, wherein the container is flat and mesh-shaped and is preferably made of non-magnetic material. A method according to any one of the preceding claims, wherein: after coupling the holder with the magnets to the second plate, a first side of the magnets faces the second plate; and after coupling the magnets to the first plate, a second side of the magnets, opposite to the first side, faces the first plate, wherein the magnets, prior to being coupled to the first plate, are provided with the adhesive on the second side of the magnets. The method of claim 10, wherein the magnets are flush with or slightly above the container on the second side of the magnets prior to performing step f). A method according to claim 10 or 11, wherein the magnets are flush with the holder on the first side of the magnets after performing step €). A method according to any one of the preceding claims, wherein step d) comprises using an adhesive to further secure the magnets to the holder. A method according to any one of the preceding claims, wherein the predetermined intervals are identical intervals. Part of an AC synchronous motor, the part being a stator or a rotor, and obtained by the method according to any one of the preceding claims. A part of an AC synchronous motor, the part being a stator or a rotor, comprising: a first plate of magnetic material; a plurality of permanent magnets fixedly attached to the first plate by an adhesive: a container including a plurality of openings into which the magnets are fitted at predetermined intervals; a resin covering the first plate, the magnets and the holder. An AC synchronous motor comprising the part of claim 15 or 16.