ASSEMBLAGGIO_n119_MARZO_APRILE_2017

diversi vantaggi. Nei motori elettrici è previsto soprattutto
per tre applicazioni: per la giunzione tra i magneti e il
pacco di lamierini, tra l’albero e il rotore e tra lo statore
e l’alloggiamento. Oltre a compensare le tolleranze di
produzione più elevate ed evitare la corrosione da sfregamento
e da contatto, le colle sono anche resistenti
agli urti, caratteristica essenziale per contrastare gli effetti
delle elevate forze dinamiche in gioco nei motori
elettrici. Il loro effetto di smorzamento riduce i rumori
delle vibrazioni, apportando miglioramenti dal punto di
vista acustico. Grazie all’omogenea distribuzione delle
tensioni, sono in grado di bilanciare lo stress termico
che si può verificare, ad esempio, quando lo statore e
l’alloggiamento presentano coefficienti di dilatazione
termica diversi. Per quanto riguarda l’albero, esse sono
in grado di impedire il gioco e lo slittamento grazie alle
loro capacità di riempimento delle fessure.
Inoltre, in molti casi, l’utilizzo di colle consente anche
di diminuire i costi di produzione, in quanto, come già
accennato, sono consentite tolleranze del pezzo più
ampie. Infine, è possibile realizzare un’automazione
semplice e per elevate produzioni, anche senza apporto
di calore.
Tra le altre cose, la colla garantisce un bilanciamento delle tensioni tra lo statore
e l’alloggiamento (immagine: ebm-papst)
Adhesives provide for equalization of tensions between stator and housing
(figure: ebm-papst).
n TECHNIQUE
Adhesives for Electric Motors Manufacturing
As electric motors are becoming smaller and more efficient, they create new challenges for joining
technology. Bonding provides numerous advantages in terms of production and operation:
for instance, engineers designing motors can choose from a wide range of adhesives.
T
esla has been instrumental in establishing electric
cars as an ideal solution for efficient and sustainable
mobility of the future. However, electric motors are not
only used for emission-free driving, they are also found
in window regulators and seat adjusters. In fact, they
can be found everywhere – in electric bikes, in tools,
even in our kitchens.
All manufacturers of electric motors have one common
goal in mind: making them smaller and more powerful,
while increasing their efficiency. In the effort to achieve
this goal, engineers must consider many things: for
example, the lamination design, an optimal embedding
of the magnets into the lamination stack, and leaving
the smallest gap possible between magnet and coil.
Better joining with adhesives
Established methods of joining, like mechanical clamping
or bandaging of magnets, are reaching their limits in
terms of both motor function and production process.
For example, a progressive reduction in motor size leads
to tightened manufacturing tolerances, which drives up
costs. Manufacturers of efficient electric motors rely more
and more on rare earth magnets. Since they are prone to
corrosion, their surfaces are treated with a coating in the
form of passivation, nickel plating, or epoxy resin plating.
This coating may be damaged during assembly, openly
exposing the magnets to direct environmental influences.
Compared to these conventional methods, bonding
offers many advantages. It is a particularly suitable option
for three steps in the assembly of electric motors: joining
magnets and lamination stacks, joining shaft and rotor,
and joining stator and housing.
Adhesives not only compensate for higher manufacturing
tolerances and prevent fretting corrosion or contact
corrosion, but also provide impact resistance, which is
essential to withstand the high dynamic forces of electric
motors.
Their vibration-damping characteristics reduce noise
PubliTec
MARCH-APRIL 2017 91