DE4345599B4 - electric motor - Google Patents

Abstract

The present invention relates to an electric motor with reluctance auxiliary torque, comprising a stator and a rotor, which is designed as an external rotor with a cup-shaped, ferromagnetic Rückschlussteil and a cylindrical, at least 8-pin, mounted inside the Rückschlussteils permanent magnet, wherein the stator at least one coaxial coil and a coaxial iron core with flux guides on both sides of the coil; the flux guides each have outer edge boundaries, which face over a circumferential angle of 180 ° el. the permanent magnet of the rotor with a small, substantially constant air gap and have over another 180 ° el. Recesses, which represent a substantially enlarged air gap with respect to the permanent magnet; the recesses of the two flux guides are not arranged substantially rotated against each other; the permanent magnet has two axially adjacent rows of poles having the same number of poles, with two axially adjacent poles of these rows of poles having opposite polarity and at least one permanent magnet for generating the reluctance auxiliary torque being arranged on the flux conductor facing the bottom of the rotor.

Description

The The present invention relates to an electric motor whose total torque has at least one Reluktanzmoment share.

From the US 4,775,812 A a brushless DC motor is known in which the rotor is brought by a mounted in the region of the bearing plate magnet system in cooperation with a mounted on the opposite axial end of the rotor magnetic ring in the rest position in a preferred position.

From the DE 35 02 284 A1 is also a brushless DC motor known ( 1 - 5 and associated text). This has a stator and a rotor, which is designed as an external rotor with a cup-shaped, ferromagnetic return part and an 8-pole, mounted inside the return part permanent magnet. The stator comprises two coaxial coils and coaxial iron cores with flux guides on both sides of the coils. The flux guides each have outer edge boundaries, which over a circumferential angle of about 180 ° el. facing the permanent magnet of the rotor with a small, substantially constant air gap and over about 180 ° el. Have recesses, which represent a substantially enlarged air gap relative to the magnet. In contrast to the subject matter of claim 1, the recesses of the individual flux guide are by 120 ° el. arranged offset from one another.

It It is the object of the invention to provide an engine which is to the drive for Fans is suitable and characterized by particularly low production costs distinguished.

These Task is solved by an electric motor with the features of claim 1.

The inventive construction starts from the realization that at the current state of development of small engines a cost reduction advantageous thereby succeed that by a double pole arrangement by increasing the effectiveness of each used magnetic materials more efficient use of these Magnetic materials, so that for a given power of Motors are reduced the total amount of magnetic material can.

Accordingly The invention relates to the creation and design of a particular economical producible single-stranded, one-pulse motor.

The solution refers to the following concerted individual measures:

stator:

It a stator is provided, which consists of a flat coil, at their bases flat flux guide elements are attached. Their basic form is essentially circular and has a number of outbreaks on the periphery, which in a simple case about the shape have a semicircle or are rectilinear.

The Flux guiding elements are used to distribute the generated by the flat coil magnetic flux in predetermined directions.

A similar Principle is used in the construction of so-called claw pole motors.

The Periphery of the flux guiding elements acts on ferromagnetic areas of the stator, which is at energized coil so moved that the magnetic resistance belonging to the coil Magnetic circuit assumes a minimum (reluctance principle).

On this way can be a positive or negative torque for the Rotor can be generated, depending on the rotor position. These torques are independently from the polarity of the coil current, so that the Motor can be operated in principle with AC voltage.

Around a uniform direction of rotation for to cause the rotor, by suitable switching or commutation ensured, that only Torque components with a uniform sign due to the current supply the coil act on the rotor.

Around a safe start in the desired direction of rotation to effect is for the engine has a device which has a reluctance auxiliary torque generated. This moves in the absence of motor current, the rotor in one Rest position from which a safe engine start can take place. For this purpose, a preferably disc-shaped permanent magnet is used, the on a circular Footprint of the Rotor interacts. The said reluctance auxiliary moments are thus generated by the action of the permanent magnet.

Rotor design:

The rotor construction consists of a ferromagnetic hollow cylinder, which is designed as a pot-shaped return part, on the inner wall of an at least 8-pin Permanentmag net is arranged.

For the application the electric motor in a fan is an advantageous embodiment in that the Rotor made of a single stamped and bent sheet iron is and related See air blades as an integral part of the rotor are.

These and further aspects of the invention will become more apparent from the drawing seen.

It shows:

1 an exploded view of the rotor and stator of an electric motor, which operates on the reluctance principle;

2 the course of proportional torques on the rotor rotation angle during operation of the electric motor;

3 a basic arrangement for a mechanical commutation device for the electric motor;

4 a circuit diagram for an electric motor;

5 and 6 Rotor surfaces of the engine with beads;

7 a plan view of a stator and an associated rotor in cross-sectional view;

8th a schematic representation of a rotor of an electric motor according to the invention; and

9 in a schematic representation of a settlement of the magnetic pole pairs of in 8th represented rotor.

In 1 an embodiment of an electric motor is shown, as it is particularly suitable as a drive for a fan.

The rotor 8th consists of a stamped and bent sheet iron part 20 , This optionally has fan blades 19 on, furthermore cylindrically bent Reluktanzbleche 9 with the borders 16 and 17 , The number of reluctance sheets is not up 4 limited.

Furthermore, the rotor has a number of openings or beads with the edges 18 on. These are even, if particularly low production costs are desired. For quiet engines, however, a boundary is selected, which provides or approximates a predefined course of the Reluktanzhilfsmomentes.

The mentioned breakthroughs or beads generate in interaction with the flat, cylindrical permanent magnet 11 an alternating reluctance torque (permanent magnetic moment) M rel, prm.

This is because the permanent magnet 11 has on its surface a number of magnetic poles, which are distributed substantially magnets on individual sectors of the permanent magnets. In 1 For example, two north and two south poles are shown.

These poles are oriented advantageously to the contour of the stator, as in 1 is shown so that a pole is near an extension 12 located. The rotor is due to the interaction of permanent magnet poles of the permanent magnet 11 and the breakthroughs 18 or the beading 61 turned to certain locking positions. These are characterized by a magnetic circuit for the permanent magnet, in which the magnetic resistance assumes a minimum value. If the rotor is rotated by external torques, the interaction of permanent magnet causes 11 with the openings, breakouts or beads of the rotor part an alternating reluctance torque (permanent magnetic moment).

This alternating reluctance torque is substantially out of phase with the torque which is present when the coil is energized 15 by means of the stator laminations 12 and 14 acting on the rotor. When energizing the coil 15 practice the tongues of Statorbleche (flux guides) on the peripheral areas 121 and 141 attractive and tangential forces on the reluctance sheets 9 of the rotor. This creates an electromagnetically caused torque.

The sink 15 can be applied to the stator in the simplest winding technique. Coil start or end are with the connection points 13 Mistake.

The coil comprises in an advantageous embodiment, not shown in detail bearing tube for receiving spherical or plain bearings. These carry a rotatable shaft, which coincides with the center 64 is fixed to the rotor, as is known in the art and is therefore not specified in detail in the drawing.

The sink 15 is energized at appropriate commutation times to apply a uniform sign torque to the rotor for rotation in a desired direction of rotation. It is therefore important according to the invention by a suitable single-phase commutation device 29 to ensure that a current to the coil 15 only given torques with uniform sign to the rotor. Repetitive electromagnetically generated torques are thus prevented by the coil is de-energized, that is switched off, as for example 2 and 3 is apparent.

A simple solution with mechanical commutator (collector) shows 3 (developed representation).

A switching contact 41 contacted a reluctance sheet 9 if and only if this has taken an angular position at which a Spulenbestromung leads to a desired torque.

The coil energization through the switching contact 41 is interrupted before an opposite torque occurs.

2 shows the relationship of the involved torques of the motor over the rotation angle phi of the rotor.

With uninterrupted energization of the coil 15 with a constant current, the rotor exerts over an angular range greater than 180 deg. el., is a positive torque. This is through the section 1 represented the electromagnetically generated reluctance torque. For the to 360 deg. el. complementary angle range is at energized coil 15 generates a negative moment (curve section 2 ). However, due to the provision of the commutation device, the electromagnetically generated negative reluctance torque becomes between the zero crossings 6 and 7 suppressed and then has no share of the total torque of the rotor.

To bridge this torque gap, the above-described permanent magnetically generated reluctance torque is used, which is represented by curves 3 and 4 is pictured. This torque component is constantly acting on the rotor, but has changing sign. - In an advantageous embodiment of the invention, the positive portion of the permanent magnetically generated reluctance torque extends over an angular range, which is also greater than 180 °. el. is. Permanent magnetically and electromagnetically generated torque components are therefore essentially in phase opposition. The effective electromagnetically generated reluctance torque is about twice the magnitude of the permanent magnetically generated reluctance torque.

With connection of the commutation device 29 to the coil 15 Thus, a curve of the total torque on the rotation angle of the rotor, as he is in essence by the curve 5 (M tot) is played.

In the 3 shown commutation circuit with mechanical Kommutatorkontakt will be described in more detail below.

The front ends 121 of the stator plate 12 form when current is applied to the coil with direct current z. B. North Pole, while the front pages 141 of the stator plate form common south poles. The contact 41 is mechanically arranged so that a contact at the contact point 42 takes place once a tongue 9 of the reluctance sheet in the area of action of the end faces 121 and 141 located.

This closes a circuit, which starts from the first terminal V1, via the reluctance sheet 9 and at the permanent contact grinder 43 , at a contact point 44 to a connection point 13 the coil 15 is forwarded.

The second connection point 13 the coil is connected to the second terminal V o of the circuit. During the closing phase of contact 41 experience the reluctance sheets 9 a force directed both radially and tangentially, because when moving in the direction of the arrow, the energy of the magnetic circuit of the coil 15 reduced.

After a movement of the reluctance sheets by 180 °. el., which corresponds to a sheet width in the example shown, is in contact 41 open. The reluctance sheets 9 move on the one hand due to their kinetic energy on. In addition, elsewhere the permanently magnetically generated reluctance torque continues to drive in a driving manner until a next contact of the contact 41 with the subsequent reluctance sheet 9 he follows. Hereupon the described game repeats itself again.

The described device for mechanical contact is special inexpensive produced. The invention provides in another advantageous Execution form However, electronic switching elements before. The contact wear is eliminated at that solution completely.

Such an arrangement shows 4 ,

Instead of contact 41 is an electronic switch 26 present, that of a sensor element 29 driven. This may be, for example, a light barrier passing through the reluctance sheets 9 is opened or interrupted. A preferred sensor element consists of an integrated circuit with Hall sensor (Hall IC).

This is done by an auxiliary permanent magnet 56 driven, whose field lines through the reluctance plates 9 be redirected in phase. Only in case of temporary absence of the reluctance sheets 9 they act on the Hall IC, so that the desired in-phase energization of the coil 15 via the electronic switch 26 entry. The sink 15 is advantageous with a freewheeling diode 25 bridged.

5 gives the surface of a rotor with beads.

This has a cylinder bottom surface 60 with breakthroughs 53 , The contour of the cylinder bottom is determined by inner diameter 51 and outer diameter 52 limited. Accordingly, the cylinder jacket of the rotor has outer beads 54 or inner beads 55 on. A rotor mold of this kind can be produced in the usual way by deep drawing and pressing.

In a further embodiment of the rotor according to 6 also beads are used instead of breakouts. The top view of the cylinder base has on the one hand the piercing point Z, reference numeral 64 , the axis of rotation through the plane of the paper.

Lower lying areas 60 of the cylinder bottom alternate with higher lying areas 61 , The higher-lying areas are defined by edges 62 limited, while edges 63 the deeper border of the shown beads reflects.

For special inexpensive Motors are provided with simple beads or breakouts, while motors with more even Torque behavior, i. comparatively reduced alternating momentum components, have specially contoured beads, breakthroughs or breakouts.

A Another embodiment of the electric motor also comes from the knowledge from that so-called Reluctance motors with permanently magnetically generated auxiliary torque this and an associated electromagnetic Useful moment not necessarily combined in one either only cylindrical or alternatively produce in a flat air gap have to. Rather, it is useful the generation of said moments, namely useful moment and auxiliary torque, to separate, in such a way that the Useful moment using a cylindrical (more precisely: a hollow cylindrical) air gap is generated while providing a permanent magnetic Aid moment a flat, plane air gap is used. A Construction of this kind is especially for such electric motors of Advantage that as drive for a fan or Fan are provided, since these in the manner of a propeller more or less flat front side without further storage devices exhibit. At the rear surface of this Front side can be with simple means a plane air gap for generating an auxiliary torque provide.

An electric motor according to such aspect is in 7 shown. This is a view of a stator 70 and associated rotor 69 , which is shown in a cross-sectional view for ease of understanding.

The rotor 69 is rotated by means of a conventional shaft and conventional bearing means (both not shown) about an axis which the paper plane of the drawing in the piercing point 78 vertical cuts.

The rotor 69 consists of a hollow cylindrical iron yoke 71 , on which permanent magnets 72 . 73 are mounted in a conventional manner. At the hollow cylinder of the rotor is followed by a substantially circular, flat iron back surface (rotor lid) with recesses or beads, as in similar form in 5 and 6 will be shown.

The construction of the stator 70 similar to that of the stator 10 out 1 , but has further simplifications. Instead of a one-piece permanent magnet are now two smaller, such as circular permanent magnets 77 . 81 provided, which are cheaper. Also, the upper Flußleitblech the stator has a simpler periphery, consisting of circular arc pieces 75 and straight sections 79 composed, which is also cheaper.

To avoid eddy currents, the Flußleitstücke several slots 74 on. The permanent magnets 77 . 81 Be next to the slots 74 or glued over this on the Flußleitstück. At the back of said flux guide also closes, as in 1 shown, a single or multilayer coil of substantially annular or hollow cylindrical shape. It also includes a bearing tube, not shown, for receiving bearing means, and preferably a ferromagnetic coil core of hollow cylindrical shape extending between the upper flux guide and the peripheral lines 75 . 79 and the lower flux guide with the peripheral line 80 extends. As can be seen from the drawing, upper and lower flux guide are indeed of the same shape, but in the stator at an angle of 90 °. mech. arranged twisted. However, the lower Flußleitblech is not equipped with permanent magnets, since it faces no face of the rotor.

The peripheral lines 75 . 80 define the cylindrical air gap between the rotor 69 and stator 70 , When energizing the coil, not shown between the flux guides they are magnetized, namely opposite polarity. A North Pole 72 Therefore, the rotor is attracted by a flux guide with a magnetic south pole and vice versa. The drawn position of the rotor 69 relative to the stator 70 is - in the absence of permanent magnets 77 and 81 - A preferred detent position, however, when energized the coil causes either a stable or unstable torque constellation, so that the rotor would not move under circumstances energized coil.

To avert this problem, the permanent magnets 77 and 81 provided, which are located within said plane air gap and thanks to the surface shape of the rotor cover exert not only axially directed forces on the rotor, but also upon rotation of the rotor 69 cause an auxiliary torque, which as described above possesses alternating sign over the rotation angle and can not be suppressed.

It is important to note that as in 1 Also, the correct angular position of the openings or beads of the rotor lid in relation to the position of the permanent magnets 72 . 73 is maintained, so that the auxiliary torque the rotor 69 of the stationary, de-energized motor can rotate in a starting angular position and energizing the coil rotates the rotor.

The construction according to 7 differs from that of the 1 in essence, that the useful torque of the engine according to 1 is generated as reluctance torque in a cylindrical air gap, while the useful torque of a motor according to 7 is generated by an electromagnetic moment using permanent magnets, wherein the permanent magnets are located on a circular cylindrical surface. This means at the same time that in the latter case, the current direction through the coil depending on the rotor position must be set (commutated), or the coil must be divided into two coils and the coil halves must be energized depending on the rotor position with DC predetermined polarity, as is known from Motor technology is known in principle.

The construction acc. 7 is therefore advantageous in comparison to known motors, because when using modern, highly remanent magnetic materials, the cylindrical magnets with poles 72 . 73 be kept comparatively thin. As a result, however, it is necessary to keep the air gap of the magnetic circuit for the useful moment as small as possible. It is therefore advantageous according to the invention to dispense with the usual contours of the stator poles with variable air gap dimension and to keep the air gap as small as possible and of constant size as indicated in the drawing.

In a special embodiment for smaller ones Motors with an outer diameter from about 3 inches it is cheap the ferromagnetic iron core for the motor coil of sintered iron material to manufacture. This reduces on the one hand the otherwise always to be considered Eddy current losses, if necessary through radially directed slots have to be reduced. On the other hand, such a core is at the same time the bearing (sintered bearing) for the Rotor shaft, without further devices.

In one embodiment of the invention according to 8th is also provided for the rotor, a cylindrical air gap for generating a useful torque, and a cylindrically oriented arrangement of a plurality of magnetic pole pairs, as in the settlement according to 9 is shown.

The arrangement according to 8th So has a stator construction according to those as in 1 drawn and a permanent magnetbestückten rotor. The permanent magnets of the rotor according to 8th and 9 However, they differ from those of 7 shown in that over an angular range of 360 °. el. a quadrupole arrangement according to 9 is provided. Also for the solution according to 8th and 9 is provided that a reluctance auxiliary torque is generated with additional, fixed to the stator permanent magnet in the flat, frontal air gap of the engine.

Claims (1)

Electric motor with reluctance auxiliary torque, with a stator and a rotor, which is designed as an external rotor with a cup-shaped, ferromagnetic Rückschlussteil and a cylindrical, at least 8-pin, mounted inside the Rückschlussteils permanent magnet, wherein • the stator at least one coaxial coil and a coaxial iron core with flux guides on both sides of the coil; • The flux guides each have outer edge boundaries, which over a circumferential angle of 180 ° el. facing the permanent magnet of the rotor with a small, substantially constant air gap and over another 180 ° el. Having recesses, which represent a substantially enlarged air gap relative to the permanent magnet; • The recesses of the two flux guides are not arranged substantially rotated against each other; • The permanent magnet has two axially adjacent rows of poles of the same number of poles, with two each axially adjacent poles of these rows of poles have opposite polarity; and • at least one permanent magnet for generating the reluctance auxiliary torque is arranged on the flux guide piece facing the bottom of the rotor.