DE19704576A1 - Switched reluctance motor e.g. as automobile windscreen wiper motor - Google Patents

Abstract

The reluctance motor includes a metallic rotor (11) revolving around an axis (13), which is structured on its outer surface area, and a stator (12) surrounding the rotor, which comprises at least one controllable electromagnet (14). A north- and south-pole (14a, 14b) of the stator is arranged in a small distance to the structured outer surface area of the rotor. The north- and the south-pole of the electromagnet are arranged side-by-side, in a predetermined distance in direction of te rotor. The electromagnet is preferably formed by an U-shaped excitation coil which includes an individual coil metal or a packet of stratified, congruent coil metals.

Description

The invention relates to a reluctance motor with a metallic rotor that can be rotated around an axis its peripheral surface is structured, and one Outside rotor surrounding stator, the at least one Controllable electromagnet, the north and South Pole a short distance from the structured Um catch surface of the rotor are arranged.

Such a motor is included as an electric drive high efficiency and high speed to be achieved since known for some time. The term is often used for this "Switched reluctance motor" or "switched reluctance" or SR used.

A reluctance motor uses the attraction of a place fixed electromagnets versus one made of metal or Iron existing rotor, which has the endeavor that Position of least magnetic resistance, d. H. minimal reluctance to ingest. Owns for this purpose  the engine is a metallic one, usually for formation of poles distributed over the circumference with a set of teeth trained rotor that runs over a central central axis is rotatably mounted, and a stationary stator, the surrounds the rotor at a short distance. The stator owns several poles of excitation spore distributed over the circumference len, with diametrically opposite poles for formation a north and south pole pair are interconnected. If a current flows through one of the excitation coils, an electromagnetic field between the opposite poles. The rotor tries the position to take minimal reluctance, being a torque experiences. The excitation coil remains excited until the Poles of the rotor out relative to the poles of the stator are aimed. A sequential, all-round excitement of the poles of the excitation coils distributed over the circumference a continuous rotation of the rotor.

A disadvantage of such a reluctance motor the relatively complex construction with proven correspondingly complicated control electronics.

The invention has for its object a Reluk to create dance engine of the type mentioned, the constructive is simple and inexpensive to manufacture.

According to the invention, this object is achieved with a reluctance Motor solved in that the north and south poles of the Electromagnets in the circumferential direction of the rotor the right distance apart. In which Reluctance motor according to the invention is the electromagnetic table field not between diametrically opposite Poles built up, but the poles are in circumferential direction right next to each other. So the advantage is one  limited, precisely defined magnetic field ver bound. Furthermore, it is not necessary to use the rotor to be made entirely of metal or iron, as single Lich the edge areas of the rotor are in the magnetic field. In this way it can be provided that the rotor one Has plastic core of a metal, outside sided ring is surrounded, with which the further Advantage of excellent rotor running properties connected is.

With the engine mentioned, it was possible to get the advantageous principles of common synchronous, asynchronous, Combine DC and three-phase motors. Because the engine it has neither brushes nor permanent magnets universally applicable and accordingly good for each adapt current requirement profiles. Since the rotor with the motor is not in direct contact with the stator essentially wear-free and in its lifetime limited only by the design of the bearings of the axis. The engine is characterized by a simple construction and allows a flat design, which makes it especially in the automotive industry, for example is well usable as a wiper motor. The motor achieves relatively high speeds and is insensitive against liquid media, so that no complex sealing tion, for example splash protection is necessary.

Since the motor works essentially without contact, it can no disruptive sparking occur, so that it is in total together with very good electromagnetic compatibility owns. In addition, the engine can be easily be recycled because it has no pole magnets contains. The motor is preferably equipped in such a way that its control electronics directly to a computer or  another computing unit can be connected.

In a development of the invention it is provided that the Electromagnet formed by a U-shaped excitation coil is, whose thighs each with wire evenly around are wound and thus form the poles. To the pathogen Manufacture coil in a simple manner and to the respective to be able to adapt to structural conditions a single coil sheet or a package story ter, similarly trained and thus more congruent Coil sheets are formed. By layering a belie number of coil sheets can packets and thus Excitation coils of any thickness in a simple manner be put.

Also in the reluctance motor according to the invention, the Stator several distributed over the circumference of the rotor Have excitation coils, which preferably each have the structure mentioned. The arrangement of the excitation track len about the circumference of the rotor is from the structural Conditions dependent. For the individual excitation coils should have different orientations relative to the The rotor is structured or interlocked in order to in all relative positions between the rotor and stator sufficient, as uniform a torque as possible receive. This offset of the excitation coils can either by their non-uniform arrangement in the circumferential direction tion and / or by appropriate choice of the number of Erre coils and the rotor teeth can be reached. If more the quotient should be provided as an excitation coil none from the number of rotor teeth and the number of excitation coils be an integer, so that for each coil in each Position of the rotor different operating states surrender. The smaller the quotient mentioned, the  Limit value goes towards 1, the better there is start-up and Torque behavior of the reluctance motor.

As already mentioned, it is advantageous for the rotor to form this outside with a toothing, wherein in practice as the ratio of the tooth width to the Width of the formed between successive teeth deten tooth gap has advantageously 1: 1. However, other relationships can also be provided.

The rotor can also be manufactured and attached in a simple manner desired structural conditions are adjusted if he from a single rotor plate or a package stratified, congruent rotor plates is formed, such as this in connection with the design of the pathogen coils was explained.

To create a rotating magnetic field that the rotor lagging behind is a progression of the individual pathogens winding necessary. During an acceleration time only one of all available excitation coils activated. Switching to activate the next one Excitation coil can then be either synchronous and / or asyn chronological. In the first case, the excitation coils or the strength of the magnetic field generated by them To be able to control the alignment of the teeth of the Rotors known relative to the respective excitation coil be. This is achieved in that the Stator at least one detect the orientation of the rotor the sensor is assigned to a corresponding posi tion signal to control electronics for the exciters dispenses coil. An induc tiv encoder, a Hall sensor or any other non-contact Detector used, the number of the sensor  passing teeth of the rotor detected and a ent speaking counting signal to the control electronics averages. Because of this count signal, the exciters spool through power oil at exactly the right time sistors switched through. By simply switching the Coil order, for example by counting down or partial swapping of the order can be done more easily change the direction of rotation of the motor. Because the said Control on the underperforming tax side of the Electronics happens, can be complex and expensive lei No need for a switch.

In the asynchronous mode of operation, the motor is turned on rotating magnetic field specified by an external clock generator and the engine tries to to run after the magnetic field.

In both cases it is simple and pronounced Cost-effective speed control through voltage regulation on the power side and / or by clock frequency ben, for example from an Eprom, a generator, etc. possible. In addition, it can be specified, only everyone to process the nth pulse of the sensor, whereby the Engine a predetermined changed performance experiences.

In a further development of the invention it can be provided that on the axis, d. H. on the same axle shaft in ver different axial planes, several identical or different like rotors with a mutual offset in rotation direction are arranged, each of which at least one Stator is assigned. This way, on the one hand an excessive surface area of only one rotor increasing number of excitation coils avoided, others  on the one hand, the synchronism properties of the engine are through the now wandering, effective in three dimensions Magnetic field significantly improved. Another advantage it follows that by changing the design and the number of rotors and excitation coils Allow engine parameters to vary within wide limits, where only standardized components are used the one that enables cost-effective series production. This is due to the structure of the rotors and / or Excitation coils each of at least one, preferably several rotor or coil plates are still supported. At Using multiple rotors does not have to be one rotor o.g. Position sensor to be assigned if the opposite angular offset of the rotors in the direction of rotation is known is.

The rotors preferably have different dimensions solutions, especially a different number of teeth and / or different tooth widths and / or under different gap widths and you can one under different number of excitation coils with if necessary be assigned to different offsets. To this Direct evaluation and control is possible in this way and there is a safe start-up behavior in everyone Position, a higher torque with an increased number of steps or sensor pulse frequency, a fast, uniform Acceleration and a structurally simple control.

It should be noted that the characteristics of the engine both a synchronous operation, an asynchronous operation and mixed operation is also permitted. Furthermore can synchronize any number of motors in parallel operation achieved through mutual control of the motors will.  

Further details and features of the invention are from the following description of exemplary embodiments with reference to the drawing. It demonstrate:

FIG. 1a to 1d, the basic function as the reluctance motor in a schematic representation;

Fig. 2 is a schematic representation of a reluctance motor with two exciting coils,

Fig. 3 shows a reluctance motor having three excitation coils,

Fig. 4 shows a reluctance motor with five excitation coils and sensors and sen

Fig. 5 shows a section through a rotor with a plastic core.

Figs. 1a to 1d show a reluctance motor, which has a group consisting of metal and in particular iron rotor 11 that is mounted on a not shown axis 13 and rotatably supported on this. On its circumferential surface the rotor is provided with evenly spaced teeth 15 11, wherein the width Eg of the teeth 15 of the width of the ZL formed between successive teeth tooth spaces corresponding to 15 a.

Arranged near the circumferential surface of the rotor 11 is an excitation coil 14 , which forms a stator 12 and has a U-shaped shape, its free legs 14 a and 14 b facing the rotor 11 . The legs 14 a and 14 b are wrapped in a manner not shown and thus form coils. When the windings of current flow through, a magnetic field is established, one of the legs forming the north pole and the other leg forming the south pole. The strength of the possible magnetic field is indicated by the line width of the schematically represented magnetic field line M.

As shown in Fig. 1a, the rotor 11 is relative to the excitation coil 14 not in the "magnetic Gleichge weight", since the teeth 15 are not aligned symmetrically to the legs 14 a and 14 b. The rotor 11 tends to assume the position of minimal reluctance, which is why a torque acts on it, which is symbolically indicated in FIG. 1a by an arrow. To illustrate the rotation of the rotor 11 , one of the teeth is marked with a dot.

In the position shown in FIG. 1b, the rotor 11 is in the magnetic equilibrium position. The magnetic field comes into its own here most, since the greatest possible amount of the ferromagnetic material of the rotor lies in the direct magnetic flux. In order not to brake the motor, the excitation coil and thus the magnetic field is switched off in this position.

The rotor 11 runs due to its inertia and / or the effect of other, not shown excitation gerspulen until it reaches the position shown in FIG. 1c, in which a tooth is arranged centrally between the legs 14 a and 14 b of the excitation coil 14 . In this position, the magnetic field does not work or only to a very small extent, since the surface of the rotor is very small. Here the magnetic field is still switched off since the rotor still has sufficient momentum. As soon as the rotor 11 has passed the central position shown in FIG. 1c, the excitation coil 14 is reactivated, so that a magnetic field builds up, which exerts a torque on the rotor, as explained in connection with FIG. 1a. The cycle then begins again, as shown in FIGS . 1a to 1d.

In order to keep the rotor running as evenly as possible, several excitation coils should be arranged distributed over the circumference. As shown in FIG. 2, two excitation coils are provided in the exemplary embodiment shown here, the structure of which has already been explained in connection with FIG. 1. It must be ensured that the excitation coils 14 assume different positions relative to the teeth of the rotor facing them in each position of the rotor 12 . In the exemplary embodiment shown, in which the rotor has an even number of teeth, this would not be the case if the two excitation coils were arranged diametrically opposite one another. It is therefore envisaged to provide a slight offset which deviates from the diametrical 180 ° position between the two excitation coils. The offset is not necessary if the quotient of the number of rotor teeth and the number of excitation coils is an integer. The mode of operation of the reluctance motor shown in FIG. 2 corresponds to that of the motor according to FIGS. 1a to 1d.

The excitation coils 14 have a geometric offset relative to the rotor 18 . The control electronics switches the first excitation coil at the point in time explained in connection with FIGS. 1a to 1d. The flashback voltage induced negatively by switching off the first excitation coil is diverted into the second excitation coil and used for further acceleration of the rotor 11 .

The embodiment shown in Fig. 3 differs from the aforementioned exemplary embodiment only in that three excitation coils 14 are distributed over the circumference of the rotor 11 , and here, too, is ensured by corresponding mutual offset of the excitation coils 14 that these each have different relative positions to the teeth facing them in a considered state of the rotor. In this case, too, the offset is not necessary if the quotient of the number of rotor teeth and the number of excitation coils is an integer.

FIG. 4 shows a reluctance motor 10 with five excitation coils 14 , which are evenly distributed over the circumference of the rotor 12 and each have a mutual offset of 720. Between the excitation coils, a sensor 17 is provided in the form of, for example, a reflected light barrier, which detects the light reflected on the rotor teeth 15 and thus provides precise information about the current orientation of the rotor 12 . In order to clearly distinguish the reflection behavior of the teeth 15 from that of the tooth gaps 15 a, the rotor teeth 15 are painted white or reflective on their outside, while the tooth gaps are provided with an absorbent coating, in particular a matt black coating. The sensors 17 give a control signal to a control electronics, not shown, which controls the excitation and thus the magnetic flux in the excitation coils 14 .

Alternatively, all of the position and Appropriate identification of the individual rotor teeth Sensors are used, which the freedom of choice Functional safety sensors depending on the serves the respective requirement profile.

Fig. 5 shows an alternative embodiment of a ro tor. While in the previously mentioned Ausführungsbei play the rotor consists entirely of metal and is formed in particular by layering a plurality of metal sheets to form a package, a plastic core 18 is provided in the embodiment shown in Fig. 5, the outside of a metal, toothed th Ring 19 is surrounded, the verbun at schematically illustrated attachment points 16 with the plastic core 18 is the. The external, relatively larger mass of the toothed ring 19 relative to the plastic core 18 gives the rotor very good running properties. The plastic core 18 is penetrated by the axis 13 , which also consist of plastic and can be integrally connected to the plastic core 18 .

Claims (14)

1. Reluctance motor with a metallic rotor ( 11 ) rotatable about an axis ( 13 ), which is structured on its circumferential surface, and a stator ( 12 ) surrounding the rotor ( 11 ) on the outside, which has at least one controllable electromagnet ( 14 ) has, whose north and south poles ( 14 a, 14 b) are arranged at a short distance from the structured circumferential surface of the rotor ( 11 ), characterized in that the north and south poles ( 14 a, 14 b) of the Electromagnets ( 14 ) are arranged next to one another in the circumferential direction of the rotor ( 11 ) at a predetermined distance. 2. Reluctance motor according to claim 1, characterized in that the electromagnet ( 14 ) is formed by a U-shaped excitation coil. 3. Reluctance motor according to claim 2, characterized records that the excitation coils a single Spu lenblech or a package of layered, congruent Coil sheets includes. 4. Reluctance motor according to claim 2 or 3, characterized in that the stator ( 12 ) has a plurality of excitation coils distributed over the circumference of the rotor ( 11 ). 5. reluctance motor according to one of claims 1 to 4, characterized in that the rotor ( 11 ) has circumferential teeth ( 15 ). 6. reluctance motor according to claim 5, characterized records that the ratio of the tooth width (ZB) to the width (ZL) of between successive Teeth formed tooth gaps is about 1: 1. 7. Reluctance motor according to one of claims 1 to 6, characterized in that the rotor ( 11 ) is formed by a single rotor plate or a package of layered, congruent rotor plates. 8. reluctance motor according to one of claims 1 to 7, characterized in that the rotor ( 11 ) has a plastic core ( 18 ) which is surrounded by a metal lenen, externally toothed ring ( 19 ). 9. Reluctance motor according to one of claims 1 to 8, characterized in that the stator ( 12 ) at least one of the orientation of the rotor ( 11 ) is assigned to the sensor ( 17 ) which is a corresponding signal to a control electronics for releases the excitation coil. 10. reluctance motor according to one of claims 1 to 9, characterized in that on the axis ( 13 ) a plurality of rotors ( 11 ) are arranged with a mutual Ver set in the direction of rotation, each of which is assigned at least one stator ( 12 ). 11. Reluctance motor according to claim 10, characterized records that the rotors are of the same design  are. 12. Reluctance motor according to claim 10, characterized records that the rotors trained differently det. 13. Reluctance motor according to claim 12, characterized records that the rotors have a different Number of teeth and / or different tooth widths and / or have different gap widths. 14. Reluctance motor according to one of claims 10 to 13, characterized in that the rotors one under different number of excitation coils assigned is.