DE3432372A1 - DC motor without a commutator - Google Patents

Abstract

A three-phase DC motor without a commutator having a permanent-magnetic rotor-magnet arrangement (which has at least two pairs of poles) and having a star-connected, three-strand stator winding whose winding strands are arranged in a non-overlapping manner in slots of a slotted stator and whose currents are controlled, via at least three semiconductor elements, by means of at least three position-signalling sensors which are sensitive to magnetic fields and, for their part, are controlled by the rotor-magnet arrangement. The position-signalling sensors are arranged distributed in the stator circumferential direction with respect to the stator winding strands in such a manner that in each case that position-signalling sensor which causes the commutation of the winding current from one winding strand to another is fitted in the stator region in which there is no coil through which current flows either before or after the commutation process. <IMAGE>

Description

Brushless DC motor

The invention relates to a three-phase brushless direct current motor with a permanent magnetic rotor magnet arrangement having at least two pole pairs and a star-connected, three-phase stator winding, its winding phases are arranged non-overlapping in slots of a grooved stator and their currents through at least three semiconductor elements through at least three magnetic field sensitive Position sensors are controlled, which in turn by the rotor magnet assembly are controlled.

This type of control occurs with motors, especially with larger ones Achievements, the problem of influencing the position sensors sensitive to magnetic fields through the field of the stator windings. Be by such influencing the commutation times in an undesirable manner from the intended optimum Location. shifted out, and more so, the greater the winding current.

An object of the invention is therefore to provide a DC motor of designed so that a shift in the commutation times under the influence of the currents flowing in the stator winding to a large extent is avoided.

According to the invention, this object is achieved in a surprisingly simple manner solved in that the position sensors in the stator circumferential direction with reference to the stator winding phases are arranged distributed such that each one Position sensor, which commutates the winding current from one to one causes another winding phase, is attached in the stator area, in which neither before or after the commutation process there is a current-carrying coil.

In the motor according to the invention, the magnetic field-sensitive remain Position reporting sensors unaffected by the stator winding field during commutation. Even with larger winding currents, there is no undesired displacement the commutation times.

The number of stator poles is shown in a further embodiment of the invention to the number of rotor poles in a ratio of 3: 4, each of the stator poles having a width of essentially 1800 el. This will avoid a tendon.

A particularly high level of efficiency is achieved. The one developed by the engine Torque is largely constant.

It turned out to be particularly advantageous to position the position sensors in the circumferential direction each essentially in the middle between those adjacent coils place, between which the commutation of the winding current under the influence of the relevant position reporting sensor takes place.

According to a modified embodiment, the position reporting sensors also lie essentially on the axis of radial symmetry of the stator pole, the one Coil carries which on the commutation process triggered by the relevant position sensor is uninvolved.

The motor can be a three-pulse or six-pulse motor Engine be designed, in the latter case preferably with at least four magnetic pole pairs is provided.

The one remaining at the air gap in the circumferential direction is preferably Space between two adjacent, preferably 1800 el wide stator poles essentially filled by an unwound auxiliary stator pole. The auxiliary stator poles avoid magnetic jolting in an effective way, because over a relative an approximately uniform induced voltage is obtained at a large angle, which means an even torque with constant current. Without such auxiliary poles between 1800 el wide stator poles would be with a ratio of the stator poles to the rotor poles of 3: 4 the stator poles are functionally wider than 1800 el, because a large part of the magnetic rotor field occurring in the pole gaps would also be drawn onto the stator poles. It would turn out in an undesirable way adjust a longing effect.

With the engines described above, but also generally with Brushless DC motors with a permanent magnet rotor magnet arrangement and a grooved stator carrying a non-overlapping wound stator winding, the one sequence of one-piece with each other connected, e.g. in usually punched out of dynamo sheet, having poles, it is desirable on the one hand to keep the slot openings small, but on the other hand to make them suitable for production Ensure windability. According to the invention, this problem is solved by that between the poles a sequence of additional poles is inserted, which are called separate Parts can be connected to the stator at a later date. During the wrapping process the additional poles are omitted. This allows the winding to be easily inserted into the stator slots bring in. Only when the stator windings are formed do the additional poles become brought in. These subsequently attachable additional poles can expediently be the above form called unwound auxiliary poles.

In a further embodiment of the invention, the additional poles are in recesses of the stator winding core can be used.

While the latter is conveniently in a conventional manner If a laminated core is involved, each additional pole is preferably a one-piece pole body educated. In particular, the additional poles can be made of solid material or as a sintered body be trained. Because the additional poles correspond to their relatively small circumferential extent take up only a relatively small magnetic flux, namely eddy current losses remain low even with massive additional poles. The production from sintered iron has the Advantage that very precise shapes can be produced by powder metallurgy can without the need for subsequent machining. Furthermore also present suitable types of siliconized iron for electrotechnical applications available, for example from the company Vakuumschmelze under the trade name "Trafoperm" be put on the market.

The additional poles can advantageously be equipped with cutouts, which are suitable for receiving position reporting sensors., which are particularly Hall generators, Hall IC1s or similar magnetic sensors. In the Using sintering technology, such recesses can be designed in a particularly simple manner will.

The invention is described below on the basis of preferred exemplary embodiments explained in more detail. In the accompanying drawings: Fig. 1 shows schematically a Partial view of a direct current motor according to the invention, Fig. 2 is a view similar Fig. 1 for a modified embodiment of the invention, Fig. 3 is a partial section by an auxiliary pole corresponding to the line III-III of Fig. 2, and Fig. 4 different Curves to explain the preferred mode of operation of the engine according to FIG.

The three-phase brushless DC motor of Fig. 1 has a rotor 10, which is rotatably mounted in a manner that is not detailed, and has a permanent magnet Rotor magnet assembly 11 on. The rotor magnet assembly 11 is preferably of a Rubber magnetic strips formed i.e.

a one-piece strip made of a mixture of hard ferrite, e.g. Barium ferrite, and elastic material. The magnetic stripe is on the pole pitch trapezoidal or approximately trapezoidal with a relatively small pole gap magnetized radially. In the illustrated embodiment, it forms four pairs of poles, on the outer one Represent the circumferential surface alternately magnetic north poles 12 and magnetic south poles 13. It goes without saying that other magnetic materials can also be used and that the rotor magnet assembly is alternatively also composed of individual magnetic plates can be.

The rotor 10 is of a stator 15, preferably in the form of a laminated one Laminated core, with the formation of a cylindrical air gap 16 includes. From the stator 15 only one half is shown; the other half corresponds to this symmetrically formed. The stator 15 has six T-shaped main poles 17. Every that of the pole faces 18 of the main poles 16 facing the air gap 16 extends over an angle of 1800 el, i.e. the width of each of the six main poles at the air gap 16 is equal to the width of each of the eight rotor poles 12, 13. In this way between the main poles 17 at the air gap 16 gaps which are each 600 el wide. These gaps are essentially filled by auxiliary poles 19, i.e. the pole faces 20 of the auxiliary poles 19 extend over a width of almost 600 el; they end in the circumferential direction at a short distance from the respective adjacent main pole face 18. Each of the main poles 17 carries a stator coil, three of which are shown in FIG Stator coils 22, 23, 24 are shown. Corresponding stator coils with the each diametrically opposed stator coil 22 or 23 or 24 connected in series can be sitting on the three main poles not illustrated. The stator coils together form a star-connected, three-strand stator winding, whose winding parts do not overlap one another. This will make them special get short winding heads, which is not only advantageous for reasons of space, but also leads to low winding resistance. The star point of the stator winding is in the arrangement according to FIG. 1 via a line 25 to the positive side + UB one Supply voltage source connected, he stands with one end of the coils 22, 23, 24 in connection, while the other end of these coils each have one Semiconductor switches 26, 27 or 28 with the negative side UB of the supply voltage source can be connected. Each of the semiconductor switches 26, 27, 28 is used for the commutation process each controlled by a magnetic field-sensitive position reporting sensor 30, 31, 32. The position reporting sensors can in particular be Hall generators or Hall ICs act, which in turn are controlled by the rotor magnet assembly 11.

Due to the geometric conditions, the position reporting sensor 30 on the stator along the air gap 16 in eight different positions, of which in Fig. 1 four positions are designated by 30a, 30b, 30c and 30d. the four other possible positions correspond to the positions illustrated, respectively diametrically opposite. It has been found that the position sensors are influenced due to the field of the stator coils and an undesired displacement caused by it the commutation times can be avoided in a simple manner that the position reporting sensors 30, 31, 32 so arranged at the air gap 16 are that in each case that position reporting sensor, which the commutation of the winding current caused by one strand of winding to another, is attached where neither before or after the commutation process there is a current-carrying coil.

The position reporting sensor 30 causes the commutation of the stator coil 22 to the stator coil 23 by locking the semiconductor switch 26 and turning on the Semiconductor switch 27. The above condition is for the position reporting sensor 30 satisfied when this is arranged at positions 30a or 30c; she is however, not satisfied at positions 30b and 30d. The position 30a is on the axis of radial symmetry of the main pole 17 which carries the coil 24, i.e. that Coil which is involved in the commutation process triggered by the position reporting sensor 30 is uninvolved. The second favorable position 30c for the position reporting sensor 30 is located under that auxiliary pole 19, which is located between the adjacent stator coils 22, 23 is between which the winding current under the influence of the position sensor 30 is commutated. On the other hand, the positions are divided according to the above condition 30b and 30d for the position reporting sensor 30. The position reporting sensor would be at position 30b 30 acted upon by the magnetic field of the coil 23 after the commutation process, while at the position 30d an application of the sensor 30 from the coil 22 before the Commutation process would take place.

The same applies to the other two position reporting sensors 31, 32, their possible positions within the illustrated area from 1800 mech with 31a, 31b, 31c, 31d and 32a, 32b, 32c, 32d, respectively are. Of these positions, only positions 31a, 31c and 32a meet, 32c the condition provided here.

The above explanation of FIG. 1 is based on a three-pulse Operation, i.e. switching on only one of the three winding phases, each winding strand is always traversed by electricity in the same direction. The stator coils 22, 23, 24 and the semiconductor switches 26, 27, 28 form one Circuit arrangement that can be referred to as a half bridge.

However, the invention is not limited to this. The illustrated engine Rather, it can also work with a full bridge circuit, which is a reversal of the Direction of the winding currents allowed (such a full bridge circuit is, for example from Fig. 6B of DE-OS 30 44 027 known), and the motor can be operated with six pulses are, in which case two winding phases are energized at the same time. Based 1 can be made clear that in a six-pulse operation, however only positions 30c, 31c, 32c meet the condition that the position reporting sensor, which causes the commutation from one strand of the winding to another, in should be attached to the stator area, in which neither before nor after the commutation process a current-carrying coil is located.

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

The positions of the position sensors discussed above are of particular importance when the engine of FIG. 1 is illustrated in that of FIG It is operated wisely, although si.ch understands that other and equivalent Applications come into consideration. Figure 4A shows the output voltage of one of the three Position sensors of the engine, for example when using Hall generators as position reporting sensors. At. this voltage is a cyclical voltage with a period of 360 ° el. The voltage of Fig. 4A is applied to a comparator or another conventional pulse shaper stage applied to the more precisely defined L3 voltage waveform according to Fig. 4B, for example, whose pulses each have a pulse width by i6O0el. to have. The same applies to the other two position sensors, their pulse trains, however, preferably against each other by 120 ° el. are out of phase, what on the positions of these three. Position reporting sensors and what in Fi.g. 4C is indicated schematically for the three position reporting sensors. The group the three pulse trains according to FIG. 4C are fed to a logic circuit arrangement, in order to generate three different pulse sequences, which are again shown schematically in FIG. 4D are illustrated. The impulses of each of these sequences have a duration of i2.00el. and a period of 360 el. The three pulse trains are against each other by each 120 ° el. phase shifted. Each of the three pulse trains is used to create one each. of the three semiconductor switches (e.g. transistors) 26, 27, 28 are live. close, so that FIG. 4D also shows the corresponding conductivity periods of these three semiconductor switches represents. In FIGS. 4E1, 4EZ and 4E3 are the potential ones as well. (in the hatched Areas) illustrates the actual pre-torque contributions of the three coil groups. When the associated semiconductor switch of one of these coil groups is always live the associated torque contribution would be at certain times in the intended Direction of rotation (positi. v) and at other times in the unintended Direction of rotation (negative). As a result, in this embodiment ensured that the semiconductor switches 26, 27, 28 are never conductive made to generate torque in the unintended direction would lead. If one only considers the positive half-waves of the torque (from each of which has a duration of 180 ° el. has), it can be seen that the torque has a relatively uniform value only within a range of about 120 ° el. the half-period from 180 ° el. Has. For about 300, at the beginning and at the end of each half-period the potential torque contribution is anything but constant, as a result, as indicated by the hatched areas, actually only the 120 ° el. intervals utilized. In other words, corresponding to the conductivity times shown in FIG. 4D the semiconductor switch will only supply the coils of the three coil groups with electricity applied to the times during which their torque contributions a substantially have a constant amount.

It should be noted that the mode of operation illustrated in FIG is only to be regarded as an example and applies in the event that the engine with three Partial torque pulses each 36O0el. is being worked on. It is understood, however, that for example, the motor could provide six such pulses, if for each Coil group during the opposite hatched area by 180 ° el. shifted, 120 ° el.

wide time interval the coil group with current in opposite Direction would be applied, for example, the three coil groups over three further semiconductor switch or is supplied in some other way.

The extensive closure of the cylindrical air gap 16 delimiting The stator surface through the auxiliary poles 19 is highly desirable because it is omitted the auxiliary pole 19 a large part of the illustrated construction on the Auxiliary poles transferring magnetic rotor field additionally to the main poles 17 would be drawn. In terms of function, this would act as if the pole faces were 18 of the main poles 17 are much wider than 1800 el, which equates to a stretch would. In addition, severe jerking would occur. Both are made possible by the auxiliary poles 19 avoided. On the other hand, the auxiliary poles 19 hinder the introduction of each other non-overlapping coils 22, 23, 24 in the relevant stator slots 34.

On the one hand, the groove openings between the main pole faces 18 are small to keep, on the other hand, for a production-ready winding of the stator are to be taken care of with the three-phase brushless direct current motor according to FIG. 2 (where the rotor is not shown for the sake of simplicity), the auxiliary poles are not punched out together with the main poles from the laminations of the stator core, but designed as a separate pole body 36, which is subsequently inserted into corresponding recesses 37 of the laminated stator core 38 can be used. The main pole will be 17- wound in this embodiment with the stator coils 22, 22 ', 23, 23' and 24, 24 ', while the pole bodies 36 forming the auxiliary poles 19 have not yet been inserted. Only after the main poles have been wound are the pole bodies 36 into the recesses 37 inserted to the slot openings 39 essentially close. The pole bodies 36 are preferably made of non-laminated, solid material. There the auxiliary poles according to their relatively small circumferential extent of 600 el opposite the circumferential extent of 1800 el of the main pole faces 18 is only a relatively small one Take up magnetic flux, do not lead to pole bodies 36 made of solid material substantial eddy current losses. The pole bodies 36 can advantageously also be made from Sintered material, in particular sintered iron, be manufactured. The sintering process allows the production of dimensionally accurate shapes without subsequent processing.

Silicate iron types are also suitable for the pole bodies 36, for example, under the name "Trafoperm" from the company Vakuumschmelze be put on the market.

The pole bodies provided for forming the unwound auxiliary poles 19 36 can advantageously be provided with recesses 40 (FIG. 3) for receiving the position reporting sensors 30, 31, 32 be provided. In particular when manufacturing the pole bodies 36 using the sintering process this practically does not require any additional manufacturing effort.

It is understood that in the arrangement of FIG. 2, the rotor in the may be designed in the same way as in the case of FIG. While FIGS. 1 and 2 illustrate internal rotor motors, it is also understood. that the above explained measures in the same way also with external rotor motors with advantage can be provided.

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Claims (14)

Claims 1. Three-phase brushless DC motor with a at least two pole pairs having permanent magnetic rotor magnet arrangement and a star-connected, three-phase stator winding, its winding phases are arranged non-overlapping in slots of a grooved stator and their currents through at least three semiconductor elements through at least three magnetic field sensitive Position sensors are controlled, which in turn by the rotor magnet assembly are controlled, characterized in that the position reporting sensors (30, 31, 32) in Stator circumferential direction with respect to the stator winding strands arranged so distributed are that in each case that position reporting sensor, which the commutation of the winding current caused from one to another winding phase, in the stator area (30a, 30c, 31a, 31c, 32a, 32c) is attached, in which neither before nor after the commutation process a current-carrying coil (22, 23, 24) is located. 2. DC motor according to claim 1, characterized in that the Number of stator poles (17) to the number of rotor poles (12, 13) in a ratio of 3: 4 and each of the stator poles has a width of substantially 1800 el. 3. DC motor according to claim 1 or 2, characterized in that that the position reporting sensors in the circumferential direction each essentially in the middle (at 30c, 31c, 32c) lie between the adjacent coils, between which the Commutation of the winding current under the influence of the relevant position sensor he follows. 4. DC motor according to claim 1 or 2, characterized in that that the position reporting sensors (30, 31, 32) are essentially on the axis of radial symmetry (at 30a, 31a, 32a) of the stator pole (17) which carries the coil which is not involved in the commutation process triggered by the relevant position signaling sensor is. 5. DC motor according to one of the preceding claims, characterized characterized in that the motor is designed as a three-pulse motor. 6. DC motor according to claim 3, characterized in that the Motor designed as a six-pulse motor with at least four magnetic pole pairs (12, 13) is. 7. DC motor according to one of claims 2 to 6, characterized in that that the space remaining in the circumferential direction at the air gap (16) between each two adjacent, preferably 1800 el wide stator poles (17) from an unwound Stator auxiliary pole (19) is essentially filled. 8. Brushless DC motor with a permanent magnet Rotor magnet arrangement and a non-overlapping wound stator winding supporting, grooved stator, which is a series of poles that are integrally connected to one another has, in particular according to one of the preceding claims, characterized in that that between the poles (17) a sequence of additional poles (19) is inserted, which as separate parts can be subsequently connected to the stator. 9. DC motor according to claims 7 and 8, characterized in that that the additional poles (19) form the unwound auxiliary poles. 10. DC motor according to claim 8 or 9, characterized in that that the additional poles (19) can be inserted in recesses (37) of the stator (38). 11. DC motor according to one of claims 8 to 10, characterized in that that each additional pole (19) is designed as a one-piece pole body (36). 12. DC motor according to claim 11, characterized in that the additional poles (19) are made of solid material. 13. DC motor according to claim 12, characterized in that the additional poles (19) are designed as sintered bodies. 14. DC motor according to one of claims 8 to 13, characterized in that that the additional poles (19) with recesses (40) to accommodate Position reporting sensors (30, 31, 32) are provided.