Note: Descriptions are shown in the official language in which they were submitted.
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The prs~ent invent:lon r~lata~ to ~ ~tep b~ tep
motor comprl~ine a multlpolar rotor9 a ~tator a~ociatad
with the rotor and mean~ for producin~" ~or each pha~3a9
a magnetomo~ive ~oroo .
~ o~m motor3 of -thi~ type gen~rall;sr comprl~,
coaxially a~sociated with the ro-tor, an annular ~tator
hou~lng contalning the ~n~rgizing coil, ~or cach pha~o,
and compri~ing 0, plurality o~ pol~r teeth or tongue8 qrhich
are possibly imbricat0d snd adaptod to cooperate~ magn~tl~
10 cally Nith th~ rotorO
Tha number o~ ~tep~ that may be made by the rotor o~
such ~ motor i~ the course OI ~ complete revolution being
a functio~ o~ the rlumber o~ polar teeth oX the 3tator,
therfl aro n~nerouo applicationo, particularly in the
domain of ~rvo-control and automatio devices where, to
obtain the great~t po~ible preci~ion in the po~itioning
o~ certain ~ervo-controlled member~ (measuring ~y~tem~, ~
printersD eto.), the greate~t po~ible angular reaolution,
i.e. motor~ whLch ean make ~ largo n~nbsr of atep~ per
re~olution o~ the rotor~ mu~t be available~
~ o obtaLn th:L~ h~h re~olution, oonvvn-tionnl prao-
tlc~ ¢on~:L~t~ in inGrea~ing a~ much a~ po~.~lble the number
o~ polflr ~e~th o~ th~ ~tator and oorr~lati~ly~ o~ cour~
th~ numb~r o~ rotor dipol~.
Howaver~ ~or a given motor o~ ~hloh tho eeomatric
polar o-tructur~ ha~ bver~ adQpted optimall~ ~ith th~ charac-
teristlc~ o~ the magnetomotive ~ouroe, it i~ observed that
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th~ operation consl~tlng ln increa~ing the number o~
~tator pol0s oan only be carricd out to the d~trim~nt o~
th~ motiv~ power a~ailable on the rotor, l~e~ wlth a~
appraoiablo decrea~e oi the motor torqu~ e~en though it
~ought~ within the tolerable limlt~ o~ heat~ng ~d o-~ dema~
gnetization o~ tho rotor, to comp~n~a-te thi~ lo~ o~ motlv~
power by an increace in the eleotrical energizing power~
In ~aot9 the incraa~e in the number o~ ~tep~9 and
con~aqu~ntly the decrea~3 o~ the angular value o~ each o~
the~e ~tep~, nece~arily brings about a decrea~ o~ the
- wldth oP aach ~tator polar toothg a~ ~ell a~ a reduct~on
in the ~pace ~eparatine t~o con~eoutivs teeth~ Thu~ the
polar t~eth being o~ eupposedly unchanged thic~nees and
height 9 their mutually oppo~ita lateral edge~ con~equently
remaining idantlcal, tha rsluctanc0 o~ the stator cLrcuit
docrea~es in proportion to the ~paca between toeth to th~
point that th~ increa~e in the leakage ~lu~ re~Lting
there~rom bring~ about magnetio ~atur~tion o~ th~ teeth o~
~hioh the ~eotion ha~ bcen r~dueod.
Thia phenomenon o~ ~aturatlon oi the etator polar
teeth there~or~ constitute~ a limit to tha increa~e in the
moti~e power of a given motor oP ~hlch it i~ de~ired to
i~orea~e tha number o~ ~tsp~.
When, de~p:Lte ~hie Limlk~ ib i~ do~irod that the
~iLabl~ motiv~ power be gr~ster th~n t~t ~hich it allow~
to be attairl~d ~or a determined numb~r o~ ~tep~, it i~ then
neoe~ary~ in known mQnner~ in tho ~lr~t place, to raduce
the haiBh~ o~ the ~tator polar t~eth o~ the givan motor in
ordar to po~tpone the appearance o~ the detrim~nt~l phano~
~0 menon o~ ~a-turntlon then, .tn the ~econd plao0y thi~
.0 2
reduction in polar height allowing the decrease in -the axial
height of -the mo-tor, to compensate for the loss of available
motive power by coupling on the same shaft as many identic,al
motors as are necessary for obtaining the desired torque.
This known method obviously presents the drawback
of high production costs since the number of the technologi-
cal elements constituting the step-by-step motor unit
procuring the desired motive power must be multiplled by as
many times as it is desired for example to double the number
of s-teps.
It is precisel~ an object of the present invantion
to eliminate this drawback by providing a technological.ly
simple and economical means for maintaining at its original
value the available motive power of a step-by-step motor with
multipolar magnetized rotor whose resolution it is desired to
increase by multiplication of the number of polar steps.
More particularly, according to the present inven-
tion, there is provided a step-by-step motor comprising:
a stator having an energizing coil for producing a
magnetomotive force;
a rotor surrounded by the stator and having an axis
about whieh the rotor is rotatable, this ro-tor havincJ a
cl.rcum~erentlal periphery and a succession oE altcrnate
ma~netic dipoles dispoc;ed a].oncJ its circumferential periphery
and ko wh:Lch the macJne-tomotive force o the coil ls applied;
a bearin~ which :Is pos:ltlonally Elxed wlth rcspect
ko -the stator ancd through wh;i.ch the c,lxls o:E the rotor passes;
wherein the stator includes an lnner cyllnd:r:lcal
wall adapted Eor d:lviding the ma~netomotive force of l,he coll
appli.ed -to the magnetic dlpoles oE the rotor and eomprislny
two end rings having polar teeth in a number equal to that oE
the magnetic dipoles of the rotor, and at least an i.nter-
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rnedia-te ring disposed between the two end rings and made of
ferromagnetic material, this intermediate ring being secured
to an inner wall of the coil and comprising two annular rows
of polar -teeth, the teeth o~ each row beinc; angularly of~set
between the teeth in the other row; the number oE the -teeth
of each row being e~ual to the number of the teeth of the end
rings and to the number of the dipoles of the rotor.
The invention will be more readily understood up on
reading of -the foLlowing non-restrictive description given
L0 for the purpose of exemplification only with reference to the
accompanying drawings t in which:
- Fig. 1 shows the diametrical section through a
step-by-step motor which, according to the known technique,
comprises a double stator.
- Figs. 2 and 3 show how, on a developed diagram of
stator multipolar system, the reluctance and section of the
polar teeth of a known motor evolve when the angular value of
a step is reduced by half.
- Fig. ~, which is disposed on the same shee-t oE
drawings as Figure 1, shows, par-tly in perspective, a pre-
ferred embodiment o -the structure of the stator multipolar
.system associated with the rotor of a step-by-step motor
:Lmproved ac~cordi.rlcJ to the :Lnvention.
Re~errincJ now to the drawings, the step-by-step
motor o~ Fig. 1, whose struct~lre :i.s we:Ll known, comprises a
cylindxiccll xo~ox 1 whose sha~t 2 to which it is connected
by a r:Lm 3, pivots in the bearincJ 4 fast with a support 5.
The rotor, which is ~or example rnade o~ hard
~err.Lte, is magnetized so as to presen-t, along -the peripheral
~eneratrices, a succession oE alternat~-3 magnetic dipoles. The
rotor 1 is surrounded by a first stator housing 6, generally
annular in ~orm, which is fast with the support 5 and which
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- 4
contains an energizing coil 7 with multiple windings to
allow supply from a generally polyphased electrical source.
q~
The magneti¢ circuit, con~titutted by the ~tator
houslng 6" is interrupted on it~ inner cylindrlcal ~all
~o as to preaent a multlpol~r ~ystem 60 con~t~tuted by a
plurality oî teeth o~ which the alte~nate, generally
imbricated arrangement determine~ along the generatrice~
air ~pace~ ~rhioh Qra the seat of a leakage ~lwc produced
by ths ma~;netomotivs force o~ the coll and peripherallyr
oriented by the direction oi~ the energizln~ current9 ~o
~ to eoop0rat0 ~ith the P~ oP the magnetized dipole~
o~ the rotor 11,
Thi~ known arrEmgement, which i~ illuetratod in Fig~ O
2 and 3, doe~ not make it pos~ible, a~ will be ~3een her~
inafter, to increas~ the number o~ ~tep~ o~ Q g:Lven motor
without lo~ o~ torque~ ~his i~ ~hy~ ~hen it i~ d~ired
~or a:~ample to double the numb~r oi~ step~ o~ a motor of
giveIl size, the elementary ~tator fitructurc ~8tator hou-
~ing 6'" cnergiz.ing coil 7') mu~t al~o be doubled Q~3 well
a~ , o~ cour~e " the length o~ th~ rotor 1, in the
proportion, ao 0hown in ~
~o e:~plain thie nec~sity, FigE3o 2 and 3 mu~t bo
referred to, which ~ho,r howf in the multipolar syetem~ 60
Fl,nd 60 ~ ~ the reluctanc~ and tho ~ectlon o~ th~ ~t~tor
polar t~th o~ ~ g:l~en motor evo~ ~rhon the ~tep :l0 r~
duced, f or a~nmple ~ by ha~ .
~h~ lelk.~e reluct~nco ~ o~ th~ ~ t;ator olrouît i~
qu~Mtion (Flg. 2) l~ invar~ely proportional to the ~cou-
mulated ~u~ce~ OI the ~ide~ oll~ opposite polnr teeth ~nd
proportlonal to the di~t~nc~ l 8epEIrating thea0 ~ldeG.,
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For an ~delltical radial th.ickne~ o-~ tha ~tator
polar piec0~, the opposit~ aoe~ e~ the polar tie~th
~idos are ~ub~tE~tiallg proportio~ to the l~ngth~ ~ oi
the~e ~lde~ . -
On the ether h~d (Figo 3~ ~rhen th~ number o~ step0i~ doubl~?d, by reducing th~ wldth o~ the polar lteeth bg
hal~, the u~a~ul lron s~ctilon ~ 0,t tihe bace o:~ theoe teeth
i.s con~equently 1~180 reduc~d by hale7 a~ ~ell a~ th~ lnt~
mediate dif~tanco ~2 ~
It ~ollowa that~ the len~th ~ o:~ the oppo~it~ teeth
sidet3 remaining ~qu0.l, th0 ~tator reluotanoe dacr~a~e~
sub~tarltl~lly by hali. Thue,, the increa~ in the induoed
~lwl: ~, ~vers01y proportional to the r~luctano~, proYo
kes the incre~3~ in the induction B - ~ and th~r~or~
saturation at the level o~ th~ ba~0 of tha polar taeth o~
reduced ~eotio~ ~ andJ by the limitation o:~ th0 leakag0
flu:1c between teeth whlch results thereIrom, a limitatlon
OI the ma~ne-tic torque e:~certe~ on the rotor.
It ~ill there~ore be neces~ary, in order be~t to
20 eliminate the detrimental phenomenon oi caturation and to
:Lmpro~0 the ~nerge~ic y~eld O:e the motor~ ~o recluce the
height o~ th~ teeth ~ welï an the heigh t o:f the ro tor
~or ~ elv~n ma~snetomotiv~ :eorce ~urnl~hed by tho ~ame vo~
lum~ o:f cop~r o~ the co~l~
Thl~ ïowarine~ o~ the hei~ht o~ the mo-tor i~ lna~ta
bly tr~n~31ated b~ an ~ppreciabl~ r~duction o:~ th~ motor
torqu~,, partioularly :e~motion o~ thi~ hoi~lt (~bout 50 %
3~V~
~or a doubling o~ th0 number of ~-t~p~) which l~ad~ to
oompen~atlng ~ lo~ by the additio~ o~ the ~ame ~ha~ o~
a ~upplementary motor e~h tim~ ~t i~ de0ired to doubl~
the number o~ ~tep~
It is preci~aly to avoid thi~ e2pensi~0 and ~ompli
ca-tad multiplicatlon o~ tho elem~rlt~ oon~ltuting ~ gr~up
o~ a plurality of motor~ with a l~rge number oP ~t~p~ that
the invention pro~ido~ ho~m in Fig. 4, th~ interpo~l-
tion, betwe~n two end ringB 60l 9 602 o~ ~tator polar te~th
o~ a ~tep~ t~p motor with ~ing~.~ coil (not ~hown~9 o~
an intermediat~ ring 603 mad0 o~ ~erromagn~ti~ ~aterlal
con~titut~d by a double ~eri~ oi polar teeth oppo~it~ by
the ba~e and ln a number e~ual to that of the pole~ o~ th3
rotor and o~ tha ~-tatorO Each ~eriee o~ polar teeth o~ the
intermediat~ pol~r pi~c~ has relati~ an~r e~ttin~
col~ciding with the ~ngular aettin~ oi tha dipole~ o~ the
rotor, a~ well a~ w1th th~t o~ the and polar teeth oppo;
~ite the ~tator.
Thi~ in~ermediate rlng, who~e ~unction e~sentiall~
consi~ta in ~ubdi~iding the maenetic potential a.nd to ~ome
extent in relaying b~tween the end polar t~eth o* the ~tator
tho ~lux produced by th~ ~ouree o~ ma~ne-tomotl~ ~orce or,
ln othar ~ord~l, ln dividin~ the magnetomoti~0 ~oI~oe ~pplied
to the po~ o:~ the rotor, mnko~ it po~ibl~, by optimn~
ll7.1ng the rala~lve l~ngth and ~idth of th0 polar t~eth9
~ ha~ been explalnod hervin~bove~ to aliMin~t~ the phono-
monon o~ ~a~llration d0trlmental to m~lntain~ng the motor
~orque nt it~ maximum value.
~8~3
The ~ntermediate ring 603 i~ mechanlcallg malntained
ln po~ition between thc ~nd ring~ on th~ lnner wall o~ th~
31n~1e coil by an appropriat0~ conv~ntional technologioal
mean~ ~u¢h a~ ior e~ample by iorc~-iittlng, adhe~ion or
inoert~on by oa~ting o~ the pla~tic~ mQterial con~titutln~
the 0hell oi the coil.
Theoretically, there i~ no llmit to the multiplica
tion in coa~ial ~eri~ o~ th~ lnte~mediate ~tator ring~
603 in order to incr~a~e the torqu~ at the ~ame tim~ a~ the
length oi the motor and it3 constituent ~le~ento (~ingl~
coil, multipolar rotor7 otator hou~ing), increa~e~,
Flnally, it mu~t b~ coneidered that each lntermediat~
ring 60~ ~ith doublc sorieo oi polar teeth (who~e ~hape and
relative angular 8ett~ng are det~rmined only by th~ lncli
natio~ or ~ngular o~tting o~ tho rotor dipolar generatrice8)
conatitutea an au~iliary 0tator encrgized in ~oriea bg ~he
ma&netomotivo ~orce o~ the oingle coil.
Thie arraneemcnt ~orming the subject matter o~ the
invention, assentially make~ it po~ible to avoid the oatu-
ratlon o~ the polar teeth o~ reducad ~e¢tlon by the leakageflux circulating in ~he spaces between teeth.
Undor the~e condition~, it 1~ pos~ibl~ ~imply and
aconomically to lnorea~ the re~olution oP a ctep~by-~tep
mo~or o~ gl~n type with doublo directlon o~ rotation, by
increQ~:In the number oP it~ ~ta~or polar teeth, without
a~eçtlng the el00tr.0mechanlo~1 oharacteri~tico thereo
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