DE3432372C2 - Three-phase brushless DC motor - Google Patents

Description

The invention relates to a three-phase brushless DC motor according to the Preamble of claim 1.

A motor of this type in which the position sensors are located between the individual stators Poland are arranged is known from DE 29 40 637 A1. This occurs, in particular larger powers, the problem of influencing the magnetic field sensitive Position sensors through the field of stator windings. With such a leg the commutation times are unwanted from the pre optimal position shifted out, and the more, the larger the wick current is.

Furthermore, from US 39 88 654 a three-phase collectorless DC motor be knows that a permanent magnetic rotor magnet arrangement with a pair of poles like a three-strand stator winding connected in star. Three layers Desensors, for example Hall elements, are opposed to one another in the circumferential direction spaced around the rotor magnet assembly.

The invention has for its object a DC motor of the beginning ge named type so that a shift in the commutation times largely avoided under the influence of the currents flowing in the stator winding is.

According to the invention, this object is achieved in a surprisingly simple manner by that the position sensors in the stator circumferential direction with respect to the stator winding lungsstrands are arranged so distributed that that position report sensor, which commutates the winding current from one to another effect line is attached in the stator area, in which neither before nor after the commutation process is a current-carrying coil.  

In the motor according to the invention, the magnetic field-sensitive layers remain desensors unaffected during commutation by the stator winding field. Even with larger winding currents there are no undesirable publishers the commutation times.

While from VDI report No. 482, 1983 "DC motors with electronic commutator" a three-phase, three-strand, collectorless DC motor is known, in which the number of winding strands carrying stator poles is in a 3: 1 ratio to the number of pole pairs of the rotor magnet arrangement leads to a maximum stator pole width of 120 ° _el , is in a further embodiment of the invention the number of stator poles carrying the winding strands to the number of pole pairs of the rotor magnet arrangement in a ratio of 3: 2, each of these stator poles having a width at its pole face facing the air gap has essentially 180 ° _el and thus corresponds to the width of a rotor pole. This avoids longing. A particularly high degree of efficiency is achieved. The torque developed by the engine is largely constant. Nevertheless, pole gaps remain between the stator poles carrying the winding strands.

It turned out to be particularly favorable if the position sensors at the air gap in Gaps between the stator poles in the circumferential direction essentially in each case Center between the adjacent coils, between which the commutation of the Winding current takes place under the influence of the position sensor concerned.

According to a modified embodiment, the position sensors can also lie essentially on the radial symmetry axis of the stator pole Coil carries, which on the triggered by the relevant position reporting sensor Kom mutation process is not involved.

The engine can in a known manner (VDI report No. 482, 1983) as three-pulse eng engine or be designed as a six-pulse engine, he in the latter Case is preferably provided with at least four magnetic pole pairs.

Preferably, the gap remaining in the circumferential direction at the air gap between each two adjacent, preferably 180 ° _el wide stator poles is essentially filled by an unwrapped stator auxiliary pole carrying the position sensor. The auxiliary stator poles effectively avoid magnetic jerking because an approximately uniform induced voltage will be maintained over a relatively large angle, which means a uniform torque at a constant current. Without such auxiliary poles between 180 ° _el wide stator poles with a ratio of the stator poles to the rotor poles of 3: 4, the stator poles would functionally become wider than 180 ° _el because a large part of the magnetic rotor field occurring in the pole gaps would additionally be drawn onto the stator poles . It would undesirably have a longing effect.

The use of unwound stator auxiliary poles in gaps between two adjacent, pronounced stator poles carrying winding strands of a collector DC motor with permanent magnetic rotor magnet arrangement is in itself known from DE 30 37 724 A1.

In the engines described above, it is desirable, on the one hand, the slot openings to keep it small, but on the other hand to ensure that it can be wound according to production requirements len. This is achieved in further embodiments of the invention in that the Position sensor sensors carrying stator auxiliary poles manufactured as separate parts and after are sluggishly connected to the stator. During the winding process, the sta Torhilfspole omitted. This allows the winding to be easily inserted into the stator slots bring in. Only when the stator windings are formed are the auxiliary stator poles brought in.

The auxiliary stator poles are expediently inserted into recesses in the stator winding core puts. While the latter is expedient in a conventional manner Is a laminated core, each of the stator auxiliary poles is preferably a one-piece pole body educated. In particular, the stator auxiliary poles made of solid material or as Be sintered body. Because the stator auxiliary poles are relatively small NEN circumferential extent absorb only a relatively small magnetic flux, lead ben eddy current losses even with massive auxiliary stator poles low. The Her position made of sintered iron has the advantage that very ge by powder metallurgy exact forms can be produced without it having to be subsequently machined Processing required. For the rest, are also available for electrical engineering applications Suitable siliconized iron grades are available, such as z. B. from the company Va vacuum melt launched under the trade name "Trafoperm" will.  

The auxiliary stator poles can advantageously be provided with cutouts for receiving the position melts be provided with sensors, which are in particular Hall generators, Hall ICs or similar magnetic sensors can act. When using the sintering technique such recesses can be made particularly simple.

The invention is described in more detail below on the basis of preferred exemplary embodiments explained. In the accompanying drawings:

Fig. 1 shows schematically a partial view of a DC motor dung after OF INVENTION,

Fig. 2 is a view similar to FIG. 1 for a modified embodiment of the invention,

Fig. 3 is a partial section through an auxiliary pole along the line III-III of Fig. 2, and

Fig. 4 different curves illustrating the preferred operation of the motor of FIG. 1.

The three-phase collectorless DC motor of FIG. 1 has a rotor 10 , which is rotatably mounted in a manner that is not illustrated in greater detail, with a permanent-magnet rotor magnet arrangement 11 . The rotor magnet arrangement 11 is preferably formed by a rubber magnetic strip, ie a one-piece strip made of a mixture of hard ferrite, e.g. B. barium ferrite, and elastic material. The magnetic stripe is radially magnetized via the pole pitch trapezoidal or approximately trapezoidal with a relatively small pole gap. In the exemplary embodiment illustrated, it forms four pole pairs, which alternately represent magnetic north poles 12 and magnetic south poles 13 on their outer peripheral surface. It goes without saying that other magnetic materials can also be used and that the rotor magnet arrangement can alternatively also be composed of individual magnetic plates.

The rotor 10 is surrounded by a stator 15 , preferably in the form of a laminated Blechpa kets, forming a cylindrical air gap 16 . Only one half of the stator 15 is shown; the other half is accordingly formed out symmetrically. The stator 15 has six T-shaped salient stator poles (main poles) 17 . Each of the pole faces 18 of the main stator poles 7 facing the air gap 16 extends over an angle of 180 ° _el , ie the width of each of the six main stator poles at the air gap 16 is equal to the width of each of the eight rotor poles 12 , 13 . In this way, there are 16 gaps between the main poles 17 at the air gap, each of which is 60 ° _el wide. These gaps are essentially filled by stator auxiliary poles 19 , ie the pole faces 20 of the stator auxiliary poles 19 facing the air gap extend over a width of almost 60 ° _el ; they end in the circumferential direction at a short distance from the respective adjacent main pole face 18th Each of the main stator poles 17 carries a stator coil, of which the three stator coils 22 , 23 , 24 are shown in FIG. 1. Ent speaking stator coils, which can be connected in series with the diametrically opposite stator coil 22 or 23 or 24 , sit on the three main poles, not shown. The stator coils form a three-strand stator winding connected in a star, the winding parts of which do not overlap each other. This results in particularly short end windings, which is not only advantageous for reasons of space, but also leads to low winding resistance. In the arrangement according to FIG. 1, the star point of the stator winding is connected via a line 25 to the positive side + U _{B of} a supply voltage source; it is connected to one end of each of the coils 23 , 23 , 24 , while the other end of these coils can be connected to the negative side -U _{B of} the supply voltage source via a respective semiconductor switch 26 , 27 or 28 . Each of the semiconductor switches 26 , 27 , 28 is controlled for the commutation process by a magnetic field-sensitive position sensor 30 , 31 , 32, respectively. The Lagemel desensors can in particular be Hall generators or Hall ICs, which in turn are controlled by the rotor magnet arrangement 11 .

Due to the geometric conditions, the position sensor 30 can be arranged on the gate along the air gap 16 at eight different positions, of which four positions are labeled 30 a, 30 b, 30 c and 30 d in FIG. 1. The four other possible positions are diametrically opposite to the illustrated positions. It has been found that an influence on the position detection sensors by the field of the stator coils and an undesirable shift in the commutation times caused thereby can be avoided in a simple manner by distributing the position detection sensors 30 , 31 , 32 at the air gap 16 in the stator circumferential direction with respect to the stator winding strands are arranged that the position indicator sensor which causes the commutation of the winding current from one winding phase to another is mounted in the stator area in which there is neither a current-carrying coil before nor after the commutation process. The position report sensor 30 effects the commutation from the stator coil 22 to the stator coil 23 by blocking the semiconductor switch 26 and opening the semiconductor switch 27 . The condition mentioned above is fulfilled for the position report sensor 30 if it is arranged at positions 30 a or 30 c; on the other hand, it is not fulfilled at positions 30 b and 30 d. The position 30 a lies on the radial axis of symmetry of the main pole 17 , which carries the coil 24 , ie the coil which is not involved in the commutation process triggered by the position sensor 30 . The second favorable Po sition 30 c for the position indicator sensor 30 is located below that Statorhilfspol 19, which is located between the adjacent stator coils 22, 23, between which the winding is commutated lung current under the influence of the position indicator sensor 30th In contrast, according to the above condition, positions 30 b and 30 d for position sensor 30 are excluded. B at position 30 of the position indicator sensor would be applied to 30 after commutation of the magnetic field of coil 23, while at position 30 d a pressurization of the sensor 30 from the spool 22 before the commutation process would take place approximately.

The same applies to the two other position-sensing sensors 31 , 32 , the positions of which are possible in principle within the illustrated range of 180 ° _mech with 31 a, 31 b, 31 c, 31 d and 32 a, 32 b, 32 c, 32 d . From these positions, in turn, only the positions 31 a, 31 c and 32 a, 32 c meet the conditions provided here.

The above explanation of FIG. 1 is based on a three-pulse operation, that is to say the switching on of only one of the three winding strands, each winding strand being traversed by current in the same direction. The stator coils 22 , 23 , 24 and the semiconductor switches 26 , 27 , 28 form a circuit arrangement which can be referred to as a half bridge. However, the motor described can also work with a full-bridge circuit that allows the direction of the winding currents to be reversed (such a full-bridge circuit is known, for example, from FIG. 6B in DE 30 44 027 A1), and the motor can be operated in six pulses, in which case each time at the same time two windings are energized. With reference to FIG. 1 one can clearly make, but that only the positions c in a six-pulse operation 30, 31 c, 32 the condition c suffice that the position indicator sensor which causes the commutation from one to another phase winding, in the Statorbe rich should be attached, in which neither before nor after the commutation process is a current-carrying coil.

The use of at least eight permanent magnet poles also has the advantage that the forces acting on the rotor shaft are symmetrical with respect to the motor axis are.

The positions of the position detection sensors 30 , 31 , 32 discussed above are of particular importance when the motor of FIG. 1 is operated in the manner illustrated in FIG. 4, although it is understood that other and equivalent applications are also possible. Fig. 4A shows the output voltage of one of the three Lagemeldesenso ren of the engine, for example when using Hall generators as Lagemeldesen sensors. This voltage is a cyclic voltage with a period of 360 ° _el . The voltage of FIG. 4A is applied to a comparator or a conventional pulse-shaping at more complete, the more precisely defined voltage waveform shown in FIG. 4B to obtain whose pulses each have a pulse width of 180 ° _el. The same applies to the other two position sensors, the pulse trains of which, however, are preferably out of phase with each other by 120 ° _el , which is due to the positions of these three position sensors and which is indicated schematically in FIG. 4C for the three position sensors. The group of the three pulse trains according to FIG. 4C is fed to a logic circuit arrangement in order to generate three different pulse trains, which in turn are schematically illustrated in FIG. 4D. The impulses of each of these sequences have a duration of 120 ° _el and a period of 360 ° _el . The three pulse sequences are mutually shifted by 120 ° _el phases. Each of the three pulse sequences is used to make one of the three semiconductor switches (e.g. transistors) 26 , 27 , 28 live, so that FIG. 4D also shows the corresponding conductivity durations of these three semiconductor switches. In the Fig. 4E1, 4E2 and 4E3 and the potential are illustrated (in the hatched areas) the actual torque contributions of the three coil groups. If the associated semiconductor switch of one of these coil groups were always live, the associated torque contribution would be at certain times in the intended direction of rotation (positive) and at other times in the unintended direction of rotation (negative). As a result, this embodiment ensures that the semiconductor switches 26 , 27 , 28 are never made conductive at times that would lead to the generation of torque in the unintended direction.

If one considers only the positive half-waves of the torque (each of which has a duration of 180 ° _el ), it can be seen that the torque has a relatively uniform value only within a range of approximately 120 ° _{el of} the half-period of 180 ° _el . For about 30 ° _el at the beginning and at the end of each half-period, the potential torque contribution is anything but constant. As a result, only the 120 ° _el intervals are actually used, as indicated by the hatched areas. In other words, corresponding to the conductivity durations of the semiconductor switches 26 , 27 , 28 shown in FIG. 4D, the coils of the three coil groups are supplied with current only at the times during which their torque contributions have a substantially constant amount.

It should be noted that the mode of operation illustrated in FIG. 4 is only to be seen as an example and applies in the event that the engine is operated with three partial torque pulses of 360 ° _el . It goes without saying, however, that the motor could, for example, provide six such pulses if the coil group were supplied with current in the opposite direction, for example, for each coil group during the time interval shifted by 180 ° _el from the hatched ready by 120 ° _el is fed to the three coil groups via three further semiconductor switches or in another way.

The extensive closure of the cylindrical air gap 16 Statorflä surface by the stator auxiliary poles 19 is highly desirable because if the stator auxiliary poles 19 were omitted, a large part of the magnetic rotor field passing over to the auxiliary stator poles in the illustrated construction would also be drawn to the main poles 17 . In terms of function, this would act as if the pole faces 18 of the main poles 17 were substantially wider than 180 ° _el , which would amount to a chord. In addition, strong jerking would occur. Both are avoided by the stator auxiliary poles 19 . On the other hand, the stator auxiliary poles 19 hinder the introduction of the coils 22 , 23 , 24 , which do not overlap one another, into the relevant stator slots 34 .

In order to keep the slot openings between the main pole faces 18 small on the one hand, but on the other hand to ensure that the stator can be wound in accordance with production requirements, the stator auxiliary poles are not included in the three-phase collectorless DC motor according to FIG. 2 (where the rotor is not shown for the sake of simplicity) the main poles punched out of the sheets of the stator core, but formed as a separate pole body 36 , which can be used subsequently in corresponding recesses 37 of the sta tor core 38 . The main poles 17 are in this imple mentation form with the stator coils 22 , 22 ', 23 , 23 ' and 24 , 24 'wound while the stator auxiliary poles 19 forming pole body 36 are not yet used. Only after loading the main poles 17 , the pole bodies 36 are inserted into the recesses 37 in order to essentially close the slot openings 39 . The pole body 36 are preferably made of non-laminated, solid material. Since the auxiliary poles absorb only a relatively small magnetic flux corresponding to their relatively small circumferential extent of 60 ° _el compared to the circumferential extent of 180 ° _{el of} the main pole faces 18 , pole bodies 36 made of solid material do not lead to substantial eddy current losses. The pole body 36 can advantageously also be made of sintered material, in particular iron. The sintering process enables the production of dimensionally accurate shapes without subsequent processing. Also suitable for the polar body 36 are silicic iron types, such as those brought under the name "Trafoperm" by the company vacuum melt on the market.

The pole body 36 provided to form the unwound stator auxiliary poles 19 can advantageously be provided with cutouts 40 ( FIG. 3) for receiving the position detection sensors 30 , 31 , 32 . In particular in the manufacture of the pole body 36 in the sintering process, this requires practically no additional manufacturing outlay.

It is understood that in the arrangement according to FIG. 2 the rotor can be designed in the same way as in the case of FIG. 1. While FIGS. 1 and 2 internal rotor motor ren illustrate, it is further understood that the measures described above measures may also be provided at an external rotor motor with advantage in the same way.

Claims (13)

1. Three-phase collectorless DC motor with a permanent magnet's rotor magnet arrangement ( 11 ) having at least two pole pairs and a star-connected, three-stranded stator winding, the winding strands of which are arranged without overlap on at least three pronounced stator poles ( 17 ) and whose currents over at least three semiconductor elements by at least Three magnetic field-sensitive position sensors are controlled, which in turn are controlled by the rotor magnet arrangement ( 11 ), characterized in that the position sensors ( 30 , 31 , 32 ) are distributed in the stator circumferential direction with respect to the stator winding strands in such a way that the position sensor, wel cher causes the commutation of the winding current from one to another winding phase, in the Sta torbereich ( 30 a, 30 c, 31 a, 31 c, 32 a, 32 c) is attached, in which neither before nor after the commutation process current-carrying coil ( 22 , 23 , 24 ). 2. DC motor according to claim 1, characterized in that the number of the stator poles carrying the winding strands ( 17 ) to the number of pole pairs of the rotor magnet arrangement ( 11 ) is in a ratio of 3: 2 and each of these stator poles ( 17 ) on its pole face facing the air gap ( 18 ) has a width of essentially 180 ° _cl and thus corresponds to the width of a rotor pole ( 12, 13 ). 3. DC motor according to claim 1 or 2, characterized in that the position sensors ( 30, 31, 32 ) at the air gap ( 16 ) in gaps between the stator poles ( 17 ) in the circumferential direction in each case substantially in the middle (at 30 c, 31 c , 32 c) lie between the adjacent coils ( 22, 23, 24 ), between which the commutation of the winding current takes place under the influence of the position sensor ( 30, 31, 32 ) in question. 4. DC motor according to claim 1 or 2, characterized in that the position sensors ( 30 , 31 , 32 ) are substantially on the radial axis of symmetry (at 30 a, 31 a, 32 a) of the stator pole ( 17 ), which coil ( 22, 23, 24 ), which is not involved in the commutation process triggered by the relevant position reporting sensor ( 30, 31, 32 ). 5. DC motor according to one of the preceding claims, characterized in that the engine as a three-pulse Engine is designed. 6. DC motor according to claim 3, characterized in that the motor is designed as a six-pulse motor with at least four pole pairs in the rotor magnet arrangement ( 11 ). 7. DC motor according to claim 3, characterized in that the circumferential direction at the air gap ( 16 ) remaining gap between two adjacent, preferably 180 ° _cl wide, stator poles ( 17 ) from a position-bearing sensor ( 30 , 31 , 32 ), unwound stator auxiliary pole ( 19 ) is essentially filled. 8. DC motor according to claim 7, characterized in that the Lagemel desensoren ( 30 , 31 , 32 ) carrying stator auxiliary poles ( 19 ) are manufactured as separate parts and are subsequently connected to the stator ( 38 ). 9. DC motor according to claim 8, characterized in that the stator auxiliary poles ( 19 ) in recesses ( 37 ) of the stator ( 38 ) are used. 10. DC motor according to claim 8 or 9, characterized in that each of the auxiliary stator poles ( 19 ) is designed as a one-piece pole body ( 36 ). 11. DC motor according to claim 10, characterized in that the stator auxiliary poles ( 19 ) are made of solid material. 12. DC motor according to claim 11, characterized in that the stator auxiliary poles ( 19 ) are designed as sintered bodies. 13. DC motor according to one of claims 8 to 12, characterized in that the stator auxiliary poles ( 19 ) with recesses ( 40 ) for receiving the Lagemeldesenso ren ( 30 , 31 , 32 ) are provided.