CA2110896C - Voltage modulation rotor/stator device, particularly for brushless electric motor - Google Patents

Abstract

<IMG> A current modulation device (1) comprises: a fixed stator (4) comprising at least one annular signal track (5) having an axis (ZZ) and whose potential varies circumferentially periodically and a a plurality of at least two collector tracks (6 and 7) each connected to a respective output terminal (A or B); and a rotor (3) adapted to be coupled to a rotary drive body rotating about the axis, having output brushes (10, 11) of the same number as the collector tracks and each adapted to scan a respective collector track , as well as input brushes (8, 9) of the same number as the output brushes, each input brush being electrically connected to a respective output brush and adapted to scan said annular signal track, these brushes input being arranged so as to take, during rotation of the rotor relative to the stator, potentials having a given electrical phase shift. </ SDOAB>

Description

i ~ VO 93/22621 P (. 'T / FR93 / 00391 Voltage modulation rotor / stator device, in particular for brushless electric motor.
The invention relates to the modulation of current in the phases of a brushless motor, and more generally to the modulation of at least two currents in function of the rotation of a rotor with respect to a stator.
S Generally, current switching in the phases of a brushless motor is driven.
- either by HALL sensors that provide logical signals (all or nothing) directly used for the switching phases, - either by a resolver or an absolute optical encoder provided the relative position of the motor rotor with respect to his stator. This much more accurate solution is well suitable for sinusoidal wave motors. She is in revenge much more expensive and cumbersome.
The invention aims to obtain information contiguous and precise of the relative rotor / stator position of a brushless motor, in order to generate the alternative signals intended to control the supply of the phases of this engine, thanks to a device that is not bulky and a price low, and which allows, moreover, by treatment of signals obtained, to have tachometric information of good quality on the speed of rotation of this engine.
More generally, it aims to achieve continuous and accurate information of the position or 2S relative speed of a rotor relative to a stator, thanks to a voltage modulation device which is not very

two brant and a moderate price.
To this end, it proposes a modulation device for voltage comprising:
a fixed stator comprising at least one annular track signal having an axis, connected at angular points alternatively distributed to the positive and negative terminals of a DC voltage source and having a resistivity such that its potential varies circumferentially periodically between a maximum value and a minimum value, as well as a plurality of at least two collector tracks centered on said axis and each connected to a respective terminal of output, each of these output terminals being connected to a respective one of said switching terminals, a rotor centered on said axis, adapted to be coupled to a rotary drive body rotating about the axis, having a plurality of at least two exit brushes same number as the plurality of collector tracks and adapted each to sweep a respective collector track, as well that a plurality of input brushes of the same number as the output brushes, each input broom being connected electrically to a respective output broom, each broom input being adapted to scan such an annular track of signal with periodic circumferential variation of potential carried by the stator, these input brushes being arranged in kind of sampling, when rotating the rotor with respect to the stator, potentials with an electrical phase shift given.
It will be appreciated that such a device is a potentiometer continuous rotation and with multiple brushes (that is to say multiple parallel outputs).
This potentiometer delivers in parallel P informations periodic during rotation of the rotating body P is equal to the number of output brushes.

2a When this potentiometer is used to control an engine polyphase brushless, having its rotor mated to that said engine, this number P is in principle equal to the number of phases of this engine (or multiple of it) and its ~;. ~ ~ ~~ UB

3 output terminals are each used to drive the current of one of the motor phases via a power electronics of any known type suitable.
If N is the number of pole pairs of this motor, the The above-mentioned periodic information has a frequency of preferably equal to N (or even a sub-multiple of N) times the motor rotation frequency. By electronic treatment appropriate format for the signals applied by the brooms to the collector tracks, we can adapt the forms periodic information from the potentiometer (Zig-zag shape, sinusoidal or trapezoidal shape, especially depending on the destination of this information periodicals (engine control, speed measurements, asser-things ...}.
Thanks to its simplicity, the device of the inven It has a small footprint and a reduced weight.
The formation of signal or collector tracks uses proven and robust technologies known manufacturers of potentiometers, where a great reliability of use; it is for example tracks called "tracks"
plastics "of conductive synthetic materials whose range of stability and temperature operation (typically -55 ° C, 200 ° C) allows a very large number applications.
According to other advantages of the invention.
- the device is precise and insensitive to variations in temperatures unlike Hall effect devices or Optical, - the device is insensitive to magnetic disturbances produced by the engine unlike the effects Lobby, the processing of the delivered signals makes it possible to obtain easily a tachometer information of good quality very useful for speed regulation or for servo functions, ..1 ..... 1 Y.-\. ..
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4 - the price of the sensor is low because of its accuracy if we.
According to preferred embodiments of the invention advantageously combined.
S - the stator comprises a single annular track of: .- signal swept by each entry broom, these entry brooms being angularly offset, - said collector tracks are two in number and input brushes have an angular offset equal to (i +, '- 4): cp, with i being an integer, if ~ p is the angular period with which varies circumferentially the potential of the track signal, said collector tracks are three in number, and the input brushes have angular offsets of 1 5 (i + ~ / ~). cp and (i + ~). c ~. with i being an integer, if cp is the angular period with which circumferentially varies the potential of the signal track, - the signal track is connected in four offset poets 90 ° alternately either to the positive terminal or to the negative terminal of the DC voltage source, thanks to which the angular period with which circumferential the potential of the signal track is n, said signal tracks and collectors, and said inlet and outlet brushes are arranged on faces transverse to the axis, - the entry brooms on the one hand and the exit brooms on the other hand, are provided on separate faces of the rotor and said signal track on the one hand, and the tracks collec on the other hand, are provided on distinct faces stator, all the brushes are formed on the same face of the rotor, and all the tracks are arranged on the same face of the stator, said signal tracks and collectors and said brushes inlet and outlet are formed on cylindrical surfaces stator and rotor respectively, ~ ..., WO 93/22621 ~ ~ ~ ~ ~ ~ ~ PCT / FR93 / 00391 a signal shaping element is connected between the collector tracks and the output terminals, said rotary drive body is the rotar of an engine brushless electric motor with each phase driven

5 by the signal provided by one, respectively, of the terminals of exit, - The rotor of this dispositïf comprises a hollow hitch coupled in rotation with the shaft of said motor, the resistivity of the collector tracks is lower than least two orders of magnitude at the resistivity of the track of signal.
Objects, features and benefits of the invention is apparent from the description which follows, given in As a non-limitative example, with reference to the attached drawings on which ones .
FIG. 1 is a view in axial section of a voltage modulation device according to the invention, according to the line IT of FIG. 5, FIG. 2 is a view of one of the faces transverse internals of the stator, FIG. 3 is a view of the other of the faces transverse internals of the stator, FIG. 4 is a view of that of the faces transverse external rotor facing the face represented in FIG.
FIG. 5 is a view of the other of the faces transverse external rotor, - Figure 6 is a graph showing the evolution over time of the UA and UB signals generated by the with Figures 1 to 5, FIG. 7 is a view similar to that of FIG.
Figure 5, but with three collectors, according to a variant of production, - Figure 8 is a similar graph showing the signals generated by the device of FIG.

WO 93/22621 - Pf, "FR93 / 0 ~.
..
s - Figure 9 is another similar graph showing the signals generated by the device of FIGS.
to 5 with electronic shaping treatment, and FIG. 10 is a sectional view of still another other variant of a voltage modulation device, integrated with a two-phase motor.
Figures 1 to 5 show a device for voltage modulation for controlling the phases of a brushless motor, designated by reference 1 in its i0 together.
This device comprises a hollow sleeve 2 coupled in rotation, for example by keying, to a tree of 50, a rotor 3 secured to this sleeve 2 and a fixed stator 4, + and - power terminals and terminals output A and B.
More precisely the shaft 50 causing in rotation the sleeve 2 and thus the rotor 3 is here the tree of output of a two-phase rotary motor 51 having a housing 52 to which the stator 4 is fixed by any appropriate known means, while the output terminals A and B of the device are connected to switching control terminals 53 and 54 of the two-phase motor.
The power supply terminals - ~ and - of the device 1 are connected to the terminals of a stabilized voltage source continuous 55 of any known type appropriate (for example a source -10 V, + 10 V).
In a classical way, the control terminals of switching (or steering) 53 and 54 are connected to a electronic block of power schematized in 56 (of any type known appropriate), adapted according to the control signals, to apply appropriately to phases (not shown) of the motor, current supplied by a voltage source 57 (here continues).
The stator 4 comprises on the one hand a track annular signal 5 (here unique), on the other hand two tracks annular rings 6 and 7, these various tracks annu W ~ 93/22621 ~~ ~. ~. 0 ~ ~ ~ PCT / FIt93 / 0039i lair being centered; the zZ axis of the drive shaft 50.
The rotor 3 comprises two input brushes 8 and 9 both adapted to scan the annular signal track 5, S and two output brushes 10 and 11, respectively connected to the two input brushes 8 and 9 within the rotor 3 by links 12 and 13, and adapted to sweep respectively the two annular collector tracks 6 and 7.
In this example, the annular tracks S, 6 and 7 are provided on transverse faces 14 and 15 of the stator 4, while the brooms 8 to 11 are arranged on transverse faces 76 and 17 of the rotor, the brushes entering 8 and 9 being at the same distance from the zZ axis, but angularly offset from each other by an angle cx no null, while the output brushes 10 and 11 are located at different distances with respect to the Zz axis, with a any angular offset here equal to 0.
The layout of the tracks and brooms on transverse faces has the advantage of allowing to give the device 1 a very small axial size.
In a variant not shown, the tracks and the brushes can be arranged on cylindrical surfaces in stator and rotor respectively, which has the advantage of allowing a very small radial size.
This annular signal track is connected in a plurality of first points 20 at the power terminal + and in a plurality of second points 21 of the same number as the first points 20 to the power terminal. The first points 20 and the second points 21 are placed in alternation by being regularly distributed angularly;
the first and second points are two in number and two, and therefore alternate with a shift of 90 °. The resistor of the annular signal track is sufficiently high so that the potential of this track varies circumferentially-between the maximum values Vmax and the minimum Vmin potential of the direct current source 55 without dissipation i WO 93/22621,. , ~ PL ° f / ~ R93 / 0 ~ 1., ~~~ .1 notable power. This potential varies linearly in function of the angle from which one deviates from a point to a point 21 and vice versa, with here an angular period of not.
Of course, in variant not shown, there can have as many continuous sources as there are couples of first / second points.
The input brushes are arranged so to take potentials presenting, during the rotation of the rotor with respect to the stator, an electrical phase shift of n / 2. C ° is why compared to the angular period n, the angular offset α between these is (i + ~ 4) n, i being any integer between 0 and 3. In the example represented a is 225 ° (see FIG. 5).
The annular collector tracks 6 and 7 are they are also conductive, avE.c preferably a resistivity much lower (for example in a ratio 100 to 1000) than that of the signal track. They are respectively connected to output terminals A and B.
For example, the device 1 has a diameter outer diameter of 45 mm, thickness of 10 mm and diameter internal of the sleeve is 10 mm. The signal track has a diameter of 35 mm, width of 3 mm, thickness of 0.3 mm, a resistance seen from the terminals of the voltage source of About 10kS2. These tracks had been carried out by the Company EUROFARAD according to a classical technology of plastic tracks charged with conductive particles.
It will be understood that terminal A connected to the track collector ring 7 is at the same potential as the broom 10, so at the same potential as the broom 8, and therefore at potential of the portion of runway 5 with which the broom 8 is in contact at the moment considered. Similarly terminal B is, by track 5, the broom 11 and the broom 9, to the potential of the portion of track 5 with which the broom 9 is in contact at the moment considered.
The signal track is with the brooms WO 93122621 PG ° f / FHt93 / 00391 input an annular series of potentiometric dividers (in number equal to the number of track sections separated by points 20 and 21.
If we denote by ~ the angular position of the rotor relative to the stator, taking as a position the origin of Figure 5, then the evolution of terminal voltages A and B is given in FIG.
variations between Vmin and Vmax In a variant, the tracks 6 and 6 are 7 and the terminals A and B an implementation processing element signal form 100 adapted to convert alternating signals linear variations in sinusoidal AC signals "
(for example a signal generator integrated circuit of the type AD 639 by margue ANALOG DEVICES). we then obtain the curves of figure 9. This allows to control the current in a two-phase multipole motor (N pairs of poles) to sinusoidal field, for example of the type described in EP-0,312,464. According to yet another variant of realization not shown, it is interposed between the tracks 6 and 'i and the terminals A and B a signal clipper, in which case curves similar to those of FIG.
this is because, due to the fact of the clipping, these curves are trapezoidal. Other forms of shape conversion signal can be chosen.
According to yet another variant embodiment, the resistivity of the signal track can be varied along its circumference thanks to what one can get without shaping treatment between lanes 6 and 7 and the terminals A and B, nonlinear variations of the potentials UA
and UB depending on the angle 8.
It will be appreciated that the U ~ and Ug voltages delivered in A and B are usable to feed the two phases of motor 51 whose output shaft 50 drives the rotor 3.
Preferably, the annular signal track 5 is unique; the input brushes, the exit brushes, the collector tracks and output terminals are in one and the same WO 93/22521 ~ P0f / FR93 / Oi,! ~ "" ~~ ,!
. ~~ The ~ .U ~~~
number equal to the number of engine phases that we want feed, and the number of first points (or seconds points) is equal to the number of pairs of motor poles (other numbers are possible subject to treatment 5 appropriate electronic output signals).
This is how to order a three-phase motor with two pairs of poles, preferably three tracks are provided collectors, three exit brooms, and three brooms entry 30, 31 and 32 placed in the arrangement of the figure 10 7, with, for the associated signal track, first two points connected to Vmax, two second points connected to Venom, arranged at 45, 135, 225 and 31 S ° (positioned on the figure 7 for a good understanding), the entry brooms being angularly positioned at positions 0, 60 and 120 °, that is (i + ~ h) .n and (i + y3) .r ~, where i is an integer whatever, it being specified that the angular period of the potential variation along the signal path is n, as in Figure 2. After clipping, we obtain the curves UA, UB and UC shown in FIG.
spawning at the potentials taken by the brushes 30, 31 and 32 respectively, with an electrical phase shift of 120 °.
Figure 10 shows an alternative embodiment and implementing a voltage modulation device according to the invention.
There is shown a two-phase motor 60 compliant to the aforementioned document ~ P-0.312.464 with two floors 61 and 62 of polar parts ~ - coils, corresponding to the two phases at feed. The voltage modulation device 63 is disposed between these two floors. To minimize clutter axial direction of this device, the rotor 64 and the stator 65 are L-section rings respectively fixed to the rotor 66 and the stator 67 of the engine, having only two faces in look, namely a single stator transverse face 68 on which are provided the signal track 69 that the collector tracks 70 and 71 and a single face r ~~~~~ Q ~~~
VO 93/22621. '~. ~ PC1 '/ FR93 / 0 ~ 391 transverse rotor 72 carrying the various input brushes and output.
The processing of the signals UA and UB makes it possible to obtain nach tachometric information by signal derivation and demodulation. For example, with type signals of those of Figure 9, we have, Vmin and Vmax symmetrical by zero value can be written -Vref and + Vref LA - Vref INS 2 6 UB - Vref COS 2 8 1p by derivation. U'A - 2 Vref 6 COS 2 8 U'B - -2 Vref 8 INS 2 8 and. V (8) - U'A UB - U'B UA ~ 2 (Vref) 28 It goes without saying that the foregoing description has not proposed as a non-limitative example and that many variants can be proposed by the man of art without leaving the framework of inventioa. For example the number of phases or couples of first points and sec ~ nds points 20 and 21 can be different from two or three (eg 1, 4, etc ...).
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Claims (13)

1. Phase power supply control device of a brushless electric motor comprising terminals of switching comprising:
- a fixed stator comprising at least one annular track signal having an axis connected at points angularly distributed alternately across the positive and negative terminals of a DC voltage source and having a resistivity such that its potential varies circumferentially periodically between a maximum value and a minimum value, as well as a plurality of at least two collector tracks centered on said axis and each connected to a respective terminal of output, each of these output terminals being connected to a respective one of said switching terminals, - a rotor centered on said axis, adapted to be coupled to a rotary drive body rotating around the axis, comprising a plurality of at least two output brushes in same number as the plurality of collector tracks and adapted each to scan a respective collector track, as well as that a plurality of input brushes in the same number as the output brushes, each input brush being connected electrically to a respective output brush, each brush input being adapted to scan such an annular track of signal with periodic circumferential variation of potential carried by the stator, these input brushes being arranged in sort of taking, during the rotation of the rotor relative to the stator, potentials exhibiting an electrical phase shift given. 2. Device according to claim 1, characterized in that that said rotating drive body is the rotor of said brushless electric motor. 3. Device according to claim 2, characterized in that that the rotor of this device comprises a coupled cruex sleeve in rotation to a shaft of said brushless electric motor. 4. Device according to any one of claims 1 to 3, characterized in that the stator comprises a single track signal ring swept by each input brush, these input brushes being angularly offset (.alpha.). 5. Device according to claim 4, characterized in that that said collector tracks are two in number and the input brushes have an angular offset equal to (i + 1/4). .PHI., with i being an integer, if .PHI. is the angular period with which circumferentially varies the potential of the track signal. 6. Device according to claim 4, characterized in that that said collector tracks are three in number, and the input brushes have angular offsets of (i + 1/3).
.PHI. and (i + 2/3).cndot. .PHI., with i being an integer, if .PHI. is here period angle with which varies circumferentially the potential of the signal path. 7. Device according to any one of claims 4 to 6, characterized in that the signal track is connected in four points offset by 90°, alternately, either at the terminal positive or to the negative terminal of the voltage source continues, whereby the angular period with which circumferentially varies the potential of the signal track is .pi.. 8. Device according to any one of claims 1 to 7, characterized in that said signal tracks and collectors, and said input and output brushes are provided on faces transverse to the axis. 9. Device according to claim 8, characterized in that as the input brushes on the one hand and the output brushes on the other hand, are provided on separate faces of the rotor and said signal track on the one hand, and the tracks collectors on the other hand, are provided on faces distinct from the stator. 10. Device according to claim 8, characterized in that all the brushes are provided on the same face of the rotor, and all the tracks are provided on the same face of the stator. 11. Device according to any one of the claims 1 to 7, characterized in that said signal tracks and collectors and said input and output brushes are provided on cylindrical surfaces of the stator and the rotor respectively. 12. Device according to any one of the claims 1 to 11, characterized in that a shaping element of signal is connected between the collector tracks and the output terminals. 13. Device according to any one of the claims 1 to 12, characterized in that the resistivity of the tracks manifolds is at least two orders of magnitude lower to the resistivity of the signal path.