Stator for electric motors having coil wound carriers mounted thereon

A stator for electric motors, includes a core having an upper and a lower portion and having teeth forming slots therebetween, first and second coil locking layers fixedly mounted on respective upper and lower portions of the core, and a plurality of preformed coil assemblies mounted on respective teeth of the core. Each coil wound carrier includes a winding section having an elongated opening configured to be adjusted around the corresponding tooth, and a first and a second winding carrier connected to opposite ends of the winding section. The first and second winding carriers include a projecting mating part, and the first and second coil locking rings include mating openings of complementary shape inside which are fitted the projecting mating part of respective first and second winding carriers of one of the preformed coil assemblies.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Application No. 19216436.6, filed in the European Patent Office on Dec. 16, 2019, which is expressly incorporated herein in its entirety by reference thereto.

FIELD OF THE INVENTION

The present invention relates to a stator for electric motors, including coil wound carriers mounted thereon. A plurality of preformed coil assemblies may be mounted on corresponding teeth of the stator. The present invention also relates to a rotary electric motor including such stator as well as a method for assembling a stator of a rotary electric motor.

BACKGROUND INFORMATION

During the manufacturing process of stators for rotary electric motors, the various components of the stator, such as coils, coil support, cables, and sensors, if needed, are assembled and all electrical connections are performed. The assembly is then potted in a specially adapted leak-tight enclosure, a so-called potting mold, by injection of synthetic resin, such as epoxy, at ambient pressure or under vacuum.

Potting is an important operation as it protects cabling, guarantees a minimum distance between conductive parts and humans/machines in order to comply with CE standards, improves thermal dissipation performances, and solidifies and fixes together all components of the stator, particularly the coils.

In some cases, however, e.g., for motors for low ambient temperatures, such as those used in aircraft, potting cannot be used in the motor because cracks could appear after a few temperature cycles. In this instance, other solutions to fix the coils to the stator may be required.

Winding carriers may be utilized to center the coils on the teeth of the stator in order to provide electrical insulation, to guarantee minimum distances to respect CE standards, and to help with orthocyclic winding of the coils.

Other approaches for centering and securing the coils on the teeth of the stator exist. U.S. Pat. No. 9,455,606, for example, discloses a winding carrier for a coil, that is configured to be mounted on a tooth of a stator for an electrical machine. The winding carrier is made of an electrically insulating material and includes a winding section around which a coil is wound.

However, U.S. Pat. No. 9,455,606 is silent on how winding carriers are reliably secured on the stator teeth.

SUMMARY

Example embodiments of the present invention provide a stator for electric motors that is, for example, configured to address the above disadvantages.

Example embodiments of the present invention provide a stator for electric motor, in which preformed coil assemblies are reliably secured to the stator teeth.

Example embodiments of the present invention provide a stator for electric motors that may be easy to assemble and cost-effective to manufacture.

Example embodiments of the present invention provide a method for securing each preformed coil assembly on the stator teeth.

According to an example embodiment of the present invention, a stator for electric motors includes a core having an upper and a lower surface and teeth forming slots therebetween, a first and a second coil locking layer fixedly mounted on respective upper and lower surfaces of the core, and a plurality of preformed coil assemblies mounted on respective teeth of the core. Each preformed coil assembly includes a winding section having an elongated opening configured to be fitted around the corresponding tooth, and first and second winding carriers connected to respective opposite ends of the winding section. The first and second winding carriers of each of the plurality of preformed coil assemblies include a projecting mating part while the first and second coil locking rings include a corresponding plurality of mating openings of complementary shape inside which are fitted the projecting mating part of respective first and second winding carriers of one of the preformed coil assemblies.

The stator may include a first supporting layer mounted between the upper surface of the core and the first coil locking layer, and a second supporting layer mounted between the lower surface of the core and the second coil locking layer.

The first and second winding carriers may each include a winding portion having a contacting surface resting against a corresponding surface of respective first and second supporting layers.

The first and second winding carriers may each include projecting walls extending on both sides of the contacting surface.

The projecting mating part of the first and second winding carriers may include a contacting surface resting on a lateral portion of respectively the first and second supporting layers.

The projecting mating part of each of the first and second winding carriers may be arranged as a T-shaped mating part fitted inside a corresponding T-shaped opening of a plurality of T-shaped openings arranged on the first and second coil locking layers.

The core may be arranged as a cylindrical core having teeth extending radially and inwardly from an inner surface of the cylindrical core. The first and second coil locking layers may be arranged as annular coil locking layers fixedly mounted on respective upper and lower annular surfaces of the core.

According to an example embodiment of the present invention, an electric rotary motor includes a stator as described above and a rotor rotatably mounted on the stator.

According to an example embodiment of the present invention, a method for assembling a stator of a rotary electric motor, includes: providing a cylindrical core having an upper and a lower annular surface and having teeth extending radially and inwardly from an inner surface of the cylindrical core, and forming slots therebetween; fixedly mounting a first supporting ring on the upper surface of the core and a second supporting ring on the lower surface of the core; providing a plurality of preformed coil assemblies each including a winding section having an elongated opening, and a first and a second winding carrier connected to respective opposite ends of the winding section, the first and second winding carriers including a projecting mating part having a contacting surface; adjusting the elongated opening of the winding section of each preformed coil assembly around a corresponding tooth of the cylindrical core such that the contacting surface of the projecting mating part of the first winding carrier of each preformed coil assembly rests against the first supporting ring, while the contacting surface of the projecting mating part of the second winding carrier of each preformed coil assembly rests against the second supporting ring; and fixedly mounting a first coil locking ring against the first supporting ring and a second locking ring against the second supporting ring, the first and second coil locking rings including a corresponding plurality of openings of complementary mating shape, thereby surrounding each projecting mating part of respective first and second winding carriers of each of the preformed coil assemblies.

DETAILED DESCRIPTION

Referring toFIG.1, an upper and a lower supporting ring18a,18bmade of an insulating material are fixedly mounted against respective upper and lower annular surfaces12a,12bof a cylindrical iron core12made of a laminated stack and including teeth14extending radially and inwardly from an inner surface of the iron core12to form slots16therebetween (see alsoFIG.2). The upper and lower supporting rings18a,18bmay be affixed against their respective annular surface12a,12b, for example, by glue or an adhesive tape. This affixing can, however, be temporary, because the supporting rings18a,18bwill be maintained in place by the preformed coil assemblies after insertion. The thickness of the supporting rings18a,18bis selected to prevent axial displacement of preformed coil assemblies30when they are inserted in their respective tooth14, as illustrated inFIGS.2to4.

Referring toFIG.6, each preformed coil assembly30includes an elongated opening34lined with insulation paper33and a first and a second winding carriers35a,35b(see alsoFIG.5a) mounted at the two ends of a preformed rectangular coil31to form a winding section32. As illustrated inFIGS.5aand5b, each of the first and second winding carriers35a,35bincludes a winding portion36and a projecting mating part40extending from one side of the winding portion36. A contacting surface37, adjacent the projecting mating part40, extends across the width of each first and second winding carriers35a,35bof the preformed coil assembly30. The projecting mating part may be arranged as, for example, a T-shaped mating part40having a contacting surface41, as illustrated inFIG.5b, which is adapted to rest against a surface of the upper or lower supporting ring18a,18b. However, the projecting mating part40may have different shapes, as described below.

The first and second winding carriers35a,35bof each preformed coil assembly30further include projecting walls38extending on both sides of the contacting surface37in order to provide for an orthocyclic winding of the rectangular coil31and to provide additional electrical insulation.

Referring toFIG.2, the preformed coil assemblies30are fitted around their respective teeth14such that the contacting surface41of the T-shaped mating part40extends radially on the corresponding supporting ring18a,18bwhile the contacting surface37rests against an inner portion of the supporting ring18a,18b. The rectangular opening34may, for example, be slightly larger than the dimensions of the tooth14to provide mounting tolerances in the order of, e.g., 100 microns in both orthogonal directions.

Once all preformed coil assemblies30are mounded on their respective teeth14, upper and lower coil locking rings19a,19bare affixed respectively against the upper and lower supporting rings18a,18b, as illustrated inFIGS.3and4. Each coil locking ring19a,19bincludes a plurality of mating through-openings20regularly spaced apart from each other around the ring. The mating through-openings20may have a corresponding T-shaped configuration to receive respective T-shaped mating part40of each winding carrier35a,35bof the preformed coil assembly30. The mating through-opening may, however, have different shapes that are complementary to the shapes of the projecting mating part40of the first and second winding carriers35a,35bof the preformed coil assembly30.

As illustrated, for example, inFIG.3, each of the upper and lower supporting rings18a,18band each of the upper and lower coil locking rings19a,19binclude non-threaded through-holes18c,19cfor their permanent affixation to the upper and lower supporting rings18a,18bby, e.g., self-tapping screws.

In summary, when coil carriers30are fitted around their respective tooth14, the coils are locked such that: i) axial movement is prevented by the upper and lower supporting rings18a,18b; ii) radial movement is prevented by the upper and lower coil locking rings19a,19b; and iii) tangential movement is prevented by the respective radial tooth14.

Although potting is not suitable for aircraft applications, the motor stator may undergo an impregnation process using varnish and curing to glue all parts together and prevent long-term damage, for example, due to vibration.

The stator10for electric motors as described herein may be readily assembled and cost-effective to produce, since expensive components are not required. For example, the supporting rings18a,18band coil locking rings19a,19bmay be cut out of a sheet of raw material, e.g., with water jet cutting. PA, LCP, or other non-conductive materials may be used. Coil locking rings19a,19bmay be segmented to decrease the amount of wasted material.

Assembling the stator may entail the following steps. An initial step includes fixedly mounting the upper supporting ring18aon the upper surface12aof the core12and the lower supporting ring18bon the lower surface12bof the core by, for example, glue or an adhesive layer. A subsequent step includes adjusting the elongated opening34of the winding section32of each preformed coil assembly30around a corresponding tooth14of the cylindrical core12such that the contacting surface41of the projecting mating part40of the first winding carrier35aof each preformed coil assembly30rests against the upper supporting ring18a, while the contacting surface41of the projecting mating part40of the second winding carrier35bof each preformed coil assembly30rests against the lower supporting ring18b. A further step includes fixedly mounting the upper coil locking ring19aagainst the upper supporting ring18aand the lower locking ring19bagainst the lower supporting ring18bby, for example, glue or an adhesive layer. A subsequent step includes ensuring permanent affixation of the supporting and coil locking rings against the upper and lower surfaces12a,12bof the core12by, for example, self-tapping screws. The stator winding may be optionally impregnated thereafter with varnish and cure as required.

LIST OF REFERENCE NUMERALS