Rotating electric machine comprising encapsulated coils and method of manufacturing a corresponding rotating electric machine

Abstract

The present disclosure relates to a rotating electric machine (100) in the form of an electric motor, comprising a stator (200), a rotor (300), a front bearing (400), a rear bearing (500), and an encapsulating structure (600), comprising a front region (610) and a rear region (620) interconnected and interlocked by means of at least one connecting rod (630). The present disclosure further relates to a method of manufacturing a corresponding rotating electric machine (100).

Description

ROTATING ELECTRIC MACHINE COMPRISING ENCAPSULATED COILS AND METHOD OF MANUFACTURING A CORRESPONDING ROTATING ELECTRIC MACHINEField of application

[0001] This disclosure pertains to the field of rotating electric machines, in particular a rotating electric machine without a housing, in which the external perimeter of the rotating electric machine is encapsulated by resin or has encapsulating portions needed to ensure casing.Background

[0002] Rotating electric machines are equipment used for transforming electric energy into mechanical energy, in the case of motors, and for transforming mechanical energy into electric energy, in the case of generators. Essentially, rotating electric machines comprise four main structures, which are the stator, rotor, housing, and bearings / caps.

[0003] The stator is the static active (energized) component responsible for transmitting the magnetic flux for rotating the rotor, in the case of motors, and for transmitting the energy generated by the rotor, in the case of generators, whereas the rotor is the active (energized) component of the rotating electric machine.

[0004] The rotor, in turn, basically comprises a shaft onto which one or more cages, coils, or permanent magnets are arranged, depending on the construction type and operating principle of the rotating electric machine.

[0005] The housing is a static element responsible for the integration and for enveloping the structures of the rotating electric machine,being typically manufactured in metallic and / or synthetic material, depending on the constructive type, dimensions, technical features and application of the rotating electric machine.

[0006] The bearings are the elements responsible for coupling the rotating parts to the static parts of a rotating electric machine, performing, for example, the coupling, bearing, and centralization of the (rotating) rotor in relation to the (static) stator, allowing for relative movement between rotor and stator, as well as transmitting forces therebetween, and may be arranged inside the caps or in other fixed elements of the housing.

[0007] The caps serve to close the front and back of the rotating electric machine, and may also, as mentioned above, support the bearings and, furthermore, provide constructive elements for fixing it to the housing and for the fixing other devices or components of the electric machine, such as deflector caps, pumps, turbines, pulleys and all sorts of accessories.

[0008] In addition to these elements, depending on the distinct features of each rotating electric machine, there may also be auxiliary systems such as cooling or air ventilation, responsible for increasing the heat exchange between the rotating electric machine and the environment in which it is located, complementing the cooling promoted by convection or conduction of the electric machine elements themselves.

[0009] In addition to the normal heating of a rotating electric machine, some applications subject the machines to additional stress that generates even more heat and, in either situation, an efficient heat exchange is essential. Thus, rotating electric machines demandhighly efficient cooling solutions to withstand the heating resulting from their operation.

[0010] Given that rotating electric machines operate under a myriad of different rotary conditions, mechanical loads, and temperatures, and given that the heat exchange in air-cooled electric machines increases according to the temperature differential and the volume of moved air, the cooling of rotating electric machines challenges and imposes limits on electric motor manufacturers beyond size and power limitations.[Oil] The restrictions also include the degree of protection and noise attenuation, since insulating against impurities, bad weather, and noise goes directly against the heat exchange between the electric machine and its surroundings, demanding a compromise between the variables which not always fully satisfies design requirements.

[0012] Another need is the construction of increasingly lighter and more compact electric machines, with a reduction in the number of components that need to be kept in stock by manufacturers.

[0013] Indeed, there remains the need of constructing of increasingly structurally resistant electric machine while at the same time reducing mass, which also results in the need to optimize its geometry to save material and also improve heat exchange, whilst also meeting the safety standards stipulated for this type of product.

[0014] The challenge thus lies in designing robust and light rotating electric machines which promote sufficient heat exchange for their operation and have the smallest possible number of structural pieces.

[0015] The electric machines must also be capable of withstanding the forces imposed onto the structure by the applications and a myriad of handling conditions (factory assembly, packaging, transport) and of operation of the electric machine (vibration, torque, variations in temperature, accidental physical contact and so on), whilst at the same time being simple to build and manufacture, optimizing both the use of raw materials and the manufacturing and mounting process.

[0016] There are several solutions in the state of the art for rotating electric machines with encapsulated coils.

[0017] An example is patent document EP 2975736, which discloses and describes a stator of a rotating electric machine and a method of producing the stator, where the stator comprises a stator winding having a winding head, the winding head being encapsulated with resin; and a closure assembly at the end of the stator.

[0018] Despite the stator described by the patent document EP 2975736 having encapsulated coils, it can be seen that this stator still has caps for closing its resin housing, which are fixed to the stator housing by means of screws, with no material savings or reduction of parts or mass.

[0019] Nonetheless, there is room for an encapsulating solution comprising coils encapsulated in synthetic material, without specific housing or casing, with overinjected bearings and that negates the requirement of using of caps and additional means of fastening.

[0020] The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentionedin the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may be inventions.Summary

[0021] A rotating electric machine comprising encapsulated coils is disclosed. The rotating electric machine further comprising: a stator, a rotor, a front bearing, and a rear bearing, wherein said rotating electric machine further comprises an encapsulating structure, comprising a front region and a rear region interconnected and interlocked by means of at least one connecting rod.

[0022] In another example embodiment, a method of manufacturing a rotating electric machine with encapsulated coils is disclosed, the method comprising: fixing said previously coiled stator in a cavity of a mold, wherein, said front bearing is positioned and fixed concentrically to said stator in said mold; insulating and sealing the holes and the rear and inside part of said stator; closing said mold and heating it in an oven; placing said mold in a vacuum chamber; inserting in said mold the load of thermoset material, wherein the incoming resin encapsulates said coil heads, both front and rear, in addition to encapsulating and incorporating said front bearing to said encapsulating structure, forming an encapsulated assembly; returning said mold to the oven to cure the thermoset material; removing the encapsulated assembly from the mold; mounting the front bearing in the housing of the front bearing; mounting said rotor on the front bearing; mounting the rear bearing in the housing of saidrear bearing; mounting said rear bearing on the shaft of said rotor; and closing said rotating electric machine through said rear bearing.Brief description of the drawings

[0023] For a better understanding and visualization of the subject of this disclosure, various example embodiments will now be described with reference to the accompanying figures, representing the obtained technical effect by means of exemplary embodiments without limiting the scope of this disclosure, in which, schematically: Figure 1 shows a perspective view of a rotating electric machine comprising an encapsulating structure in accordance with various example embodiments;Figure 2 shows a side view of the rotating electric machine in Figure 1, in accordance with various example embodiments;Figure 3: shows a front view of the rotating electric machine of Figure 1 with an A-A cross-section, in accordance with various example embodiments;Figure 4 shows a side view of A-A cross-section of the rotating electric machine in Figure 3, in accordance with various example embodiments;Figure 5: shows a perspective view of a rotating electric machine comprising an encapsulating structure, in accordance with various example embodiments;Figure 6: shows a front view of the rotating electric machine of Figure 5 with a B-B cross-section, in accordance with various example embodiments; andFigure 7: shows a side view of the B-B cross-section of the rotating electric machine in Figure 6, in accordance with various example embodiments.Detailed description

[0024] The present disclosure relates to a rotating electric machine (100), essentially comprising a stator (200), a rotor (300), a front bearing (400), a rear bearing (500), and an encapsulating structure (600).

[0025] The rotating electric machine (100), in accordance with various example embodiments, is preferably a conventional electric motor, more preferably an induction electric motor, single-phase or three-phase, which may comprise, in addition to the items and features mentioned and claimed herein, other typical and necessary items and features for the operation of a rotating electric machine.

[0026] The stator (200) comprises a stator package of plates (210), a stator winding (220) comprising a plurality of coils (221) and a plurality of coil heads (222), in addition to other elements known from state of electric motors as dealt with herein.

[0027] The rotor (300) comprises a shaft (310) on which one or more cages, coils, or permanent magnets (320) are arranged, in addition to other elements known from state of electric motors as dealt with herein.

[0028] The front bearing (400) comprises a main body, preferably formed in a single piece, comprising a housing (410) for a front bearing (420), in addition to a coupling interface region (430) comprising interface elements (431) such as holes, threaded holes, openings, cavities, shoulders, grooves and other constructive elements which allows for equipment and / or devices of the desired application to be coupled to the rotating electric machine (100), also allowing the use of static or dynamic sealing elements between the interfaces of the components in which such an element is needed.

[0029] The rear bearing (500) comprises a main body, preferably formed in a single piece, comprising a housing (510) for a rear bearing (520), in addition to an interface region (530) for direct coupling to the stator (200). In a preferred embodiment, the rear bearing (500)fits into the stator (200) by interference, negating the requirement of any additional fixing elements.

[0030] The rear bearing (500) may also comprise interface elements (531) such as holes, threaded holes, openings, cavities, shoulders, grooves, and other constructive elements that allow coupling to the stator (200). Optionally, the rear bearing (500) may also receive a rear fan (700), and the rear fan (700) can be fixed / coupled / fitted permanently or otherwise, without requiring any modification to the rear bearing (500). Furthermore, the rear bearing (500) is configured to facilitate the use of static or dynamic sealing elements between the components' interfaces, in which such element is necessary. It should be noted that other accessories, e.g., encoders, brakes, etc., can be attached to the rear bearing (500).

[0031] The encapsulating structure (600) is a synthetic material structure, preferably but not limited to a thermoset resin, more preferably an epoxy or silicone resin, constructed in a single piece, comprising a front region (610) and a rear region (620) interconnected and interlocked by means of at least one connecting rod (630). In an example embodiment, the resin may be introduced between the stator wires and grooves.

[0032] The encapsulating structure (600) is applied by molding to the rotating electric machine (100). In the context of this disclosure, the term "molding" broadly refers to encapsulation, by means of a molten material applied to the intended surfaces of one or more components and / or groups of components and / or regions of a rotating electric machine so as to envelop the target surfaces totally or partially.

[0033] In the context of this disclosure, the term "molding" refers more specifically to any smelting technique capable of smelting an encapsulating material and applying it by transfer onto the intended surfaces dimensionally limited by one or more molds and preferably suited to the encapsulating material, electric machine dimensions, expected production scale, etc., which can be chosen, without restricting the scope of this disclosure, from the group consisting of overmoulding, overinjection, gravity casting, injection molding, blow molding, etc.

[0034] Preferably but without limiting this disclosure, the application by molding of the encapsulating structure (600) takes place through transfer molding by resin casting, in which the previously coiled stator (200) is fixed in a cavity of a mold, in which, in said mold, the front bearing (400) is positioned and concentrically fixed to the stator (200). The holes and, in particular, the rear and internal part of the stator (200) are insulated and sealed. The mold is then closed, heated in an oven, placed in a vacuum chamber, then finally receives the thermoset material load by gravity, returning thereafter to the oven for curing.

[0035] The cast resin encapsulates the front and rear coil heads (222), grooves and wires, and forms at least one connecting rod (630), in addition to encapsulating and incorporating the front bearing (400) into the encapsulating structure (600).

[0036] After removal from the mold, the front bearing (420) is mounted onto the housing (410) of the front bearing (400), a fixation ring or another locking method can be used in this step, the rotor (300), with its axis (310) is mounted onto the front bearing (400), therear bearing (520) is mounted on the shaft (310) of the rotor (300), so that the housing (510) of the rear bearing (500) as well as the rear bearing (500) itself are positioned onto the shaft (310) of the rotor (300). At this stage, it is possible to use static or dynamic sealing elements so as to promote the closing of the rotating electric machine (100), which is done through the rear bearing (500), which is preferably but not limited to fitted by interference in the internal diameter of the stator (200) and allows for the use of sealing between the rear bearing (500) assembly and the resin of the rear region (620). It should be noted that the rear bearing (500) may be fitted to the internal diameter of the stator (200) and secured by threading, screwing, etc.

[0037] Thus, the rotating electric machine (100) is closed by means of an O-Ring (not shown) mounted between the rear bearing (500) and the internal diameter of the stator (200), which are fitted by interference, and a fixing ring (not shown) which seals the rear bearing (500) to form an enclosure.

[0038] In a preferred embodiment of this disclosure, the front region (610) fully encapsulates the front coil heads (222) and incorporates the front bearing (400), the rear region (620) fully encapsulates the rear coil heads (222), wherein the at least one connecting rod (630) interconnects and interlocks the front (610) and rear regions (620), only partially covering the stator package of plates (210), leaving the stator (200) exposed and thus favoring the heat exchange between the rotating electric machine (100) and its surroundings.

[0039] A method of manufacturing a rotating electric machine with encapsulated coils, the method comprising:I) fixing the previously coiled stator (200) in a cavity of a mold, wherein, the front bearing (400) is positioned and fixed concentrically to the stator (200) in said mold;II) insulating and sealing a plurality of holes and, in particular, a rear and inside part of the stator (200);III) closing the mold and heating it in an oven;IV) placing the mold in a vacuum chamber;V) inserting in the mold a load of thermoset material, wherein an incoming resin encapsulates the coil heads (222), both front and rear, in addition to encapsulating and incorporating the front bearing (400) to the encapsulating structure (600), forming an encapsulated assembly;VI) returning the mold to the oven to cure the thermoset material;VII) removing the encapsulated assembly from the mold;VIII) mounting the front bearing (420) in the housing (410) of the front bearing (400);IX) mounting the rotor (300) on the front bearing (400);X) mounting the rear bearing (520) in the housing (510) of the rear bearing (500);XI) mounting the rear bearing (500) on the shaft (310) of the rotor (300);XII) closing the rotating electric machine (100) through the rear bearing (500), which fits by interference in the internal diameter of the stator (200) and seals the assembly by means of the rear bearing (500) and the resin of the rear region (620) and optionally;XIII) attaching / coupling / fitting a rear fan (700) and / or any other accessory available for the rear bearing on the rear bearing (500).

[0040] It should be noted that the molding process may also be carried out by injection, transfer, vacuum-assisted or any other type depending on the encapsulating material, sizing of the electric machine, provided, naturally, that the necessary adaptations are carried out during the molding / unmolding process of the encapsulating structure (600).

[0041] The rotating electric machine (100) uses resin to close its front region (610) and its rear region (620). As such, said rotating electric machine (100) negates the requirement of caps, screws (with the exception of the front fixing ring), and housing, and may or may not have external cooling.

[0042] Furthermore, to ensure mounting strength, in an example embodiment, a connecting rod (630) is configured to interconnect the front region (610) and the rear region (620). Thus, in an example embodiment, the stator body (200) is configured to be exposed, without housings. Exposing the stator body (200) ensures other benefits for the solution, as it reduces mass, volume, and manufacturing cost of the rotating electric machine (100), simplifies the demolding process, and does not affect the heat exchange capacity of the assembly.

[0043] It should be noted that the stator (200) should preferably but without limitation be at least 30% exposed or more preferably still at least 70% exposed.

[0044] Furthermore, due to the fact that the coils (221) are encapsulated in resin, the protection of the stator winding (220) is ensured with an IP55 protection degree, in addition to ensuring goodheat dissipation, given that the resins have a good heat transfer coefficient.

[0045] Finally, even after a full mounting of the electric rotating machine, internal components, e.g. bearings, may be easily replaced in cases of breakdown / maintenance by removing the rear bearing (500). The process of replacing the internal components of the rotating electric machine is feasible in terms of process simplicity and economy, even in cases where the rear bearing (500) needs to be replaced as a result of damage due to its removal.Conclusion

[0046] It will be easily understood by one skilled in the art that modifications may be made to the present disclosure without departing from the concepts set out in the description above. Such modifications should be considered as included within the scope of the present disclosure. Consequently, the particular embodiments previously described in detail are illustrative and exemplary only and are non-restrictive as to the scope of the present disclosure, which should be given the full extent of the appended claims and any and all equivalents thereof.

Claims

CLAIMS1. A rotating electric machine comprising encapsulated coils: the rotating electric machine comprising: a stator, a rotor, a front bearing, and a rear bearing, wherein said rotating electric machine further comprises an encapsulating structure, comprising a front region and a rear region interconnected and interlocked by means of at least one connecting rod.

2. The rotating electric machine according to claim 1, wherein said rotating electric machine is an electric motor.

3. The rotating electric machine according to claim 1, wherein said encapsulating structure is applied by casting to said rotating electric machine.

4. The rotating electric machine according to claim 1, wherein said front region fully encapsulates one or more front coil heads and incorporates said front bearing, wherein said rear region fully encapsulates one or more rear coil heads, wherein said connecting rod only partially covers a stator package of plates.

5. The rotating electric machine according to claim 1, wherein said stator is exposed.

6. The rotating electric machine according to claim 5, wherein said stator is at least 30% exposed.

7. The rotating electric machine according to claim 1, wherein said encapsulating structure is constructed as a single piece.

8. The rotating electric machine according to claim 1, wherein a rear fan is fixed / coupled / fitted in said rear bearing permanently or otherwise.

9. A method of manufacturing a rotating electric machine with encapsulated coils according claim 1, wherein the method comprises the steps of:I) fixing a previously coiled stator in a cavity of a mold, wherein, saidfront bearing is positioned and fixed concentrically to said stator in said mold;II) insulating and sealing a plurality of holes and a rear and inside part of said stator;III) closing said mold and heating it in an oven;IV) placing said mold in a vacuum chamber;V) inserting in said mold a load of thermoset material, wherein an incoming resin encapsulates coil heads, both front and rear, in addition to encapsulating and incorporating said front bearing to said encapsulating structure, forming an encapsulated assembly;VI) returning said mold to the oven to cure the thermoset material;VII) removing the encapsulated assembly from the mold;VIII) mounting a front bearing in a housing of the front bearing;IX) mounting said rotor on the front bearing;X) mounting a rear bearing in a housing of said rear bearing;XI) mounting said rear bearing on a shaft of said rotor; andXII) closing said rotating electric machine through said rear bearing.

10. The method according to claim 9, wherein the method further comprises the step of:XIII) attaching / coupling / fitting a rear fan or any other accessory available for the rear bearing on said rear bearing.

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