DE4306327A1 - Reluctance motor - Google Patents

Abstract

An electric motor, preferably a DC motor without a commutator, having an auxiliary (reluctance) torque which is produced in a flat air gap by means of permanent magnets. The useful torque is produced in a cylindrical air gap of constant size. To this end, embodiments in accordance with a so-called reluctance motor (switched reluctance motor) and embodiments having permanent magnets in the operating air gap are provided. Eddy current losses are reduced by means of a coil core consisting of ferromagnetic sintered material. In one particular embodiment, this coil core is at the same time a sintered bearing for the rotor. <IMAGE>

Description

The invention relates to an electric motor, the overall rotation torque has at least one reluctance torque component.

Motors of this type of construction are, for example known from the boarding school. Patent application WO 90/11641.

It is an object of the invention to provide an engine that is suitable for driving fans and through distinguishes particularly low manufacturing costs.

This problem is solved by the characteristic part of claim 1.

The construction according to the invention is based on the knowledge that that at the current state of development of small engines a cost reduction is advantageously achieved in that the Number of switching elements required to the minimum number of one is reduced and the manufacture of the necessary Motor coils is carried out as simply as possible.  

Accordingly, the invention relates to the creation and Design of a particularly inexpensive to manufacture single-stranded, single-pulse motor.

The solution according to the invention has the following one after the other coordinated individual measures:

Stator design

A stator is provided which consists of a Flat coil consists of flat flux conductors on the bases elements are attached. Their basic form is essentially circular and has a number of eruptions on the Periphery, which in a simple case has the shape of a Have semicircle or are straight.

The Flußleitelemente serve the distribution of the Flat coil generated magnetic flux in predetermined Directions.

A similar principle is used in the construction of so-called Claw pole motors used.

The periphery of the flux guide acts on ferromagnetic Areas of the stator, which is when the coil is energized so moved that the magnetic resistance of the coil associated magnetic circuit assumes a minimum (reluctance principle).  

In this way, a positive or negative acting Torque can be generated for the rotor, depending on the rotor position. These torques are independent of the polarity of the Coil current, so that the motor in principle also with AC voltage can be operated.

In order to achieve a uniform direction of rotation for the rotor, is by means of suitable switching or commutation means for this ensured that only torque components with a uniform sign act on the rotor by energizing the coil.

To ensure a safe start in the desired direction of rotation cause is a for the motor according to the invention Device available, which is a reluctance auxiliary torque generated. This moves the rotor when there is no motor current in a rest position from which a safe motor start can take place. For this purpose, a disc is preferably used Shaped permanent magnet used on a circular Base of the rotor acts. The reluctance Auxiliary moments are thus caused by the action of the permanent magnet generated.

Rotor construction

The rotor construction consists of a ferromagnetic Hollow cylinder with slotted or crimped cylinder wall. The cylindrical base of the rotor is used to generate the reluctance auxiliary moments mentioned above also with breakouts  or beads. For the application of the engine in one An advantageous embodiment of the fan is that the rotor is made from a single stamped and bent sheet of iron is made and associated air blades as an integral Part of the rotor are to be considered.

These and other aspects of the invention are described in Drawing and the subclaims can be seen in more detail.

It shows:

Fig. 1 is an exploded view of the rotor and stator of the motor

Fig. 2 shows the course of proportional torques over the rotor angle of rotation during operation of the engine.

Fig. 3 shows a basic arrangement for a mechanical commutation device for the motor.

Fig. 4 is a circuit diagram for an engine according to the invention

Fig. 5 and Fig. 6 rotor surfaces of the motor with beads.

In Fig. 1, a preferred embodiment of the invention is illustrated, as is suitable in particular as a drive for a fan.

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

Furthermore, the rotor has a number of openings or beads with the edges 18 . These are even if particularly low manufacturing costs are aimed for. For motors that are as quiet as possible, however, a boundary is selected that provides or approximates a predefined course of the reluctance auxiliary torque.

In cooperation with the flat, cylindrical permanent magnet 11 , the openings or beads mentioned produce an alternating reluctance moment (permanent magnetic moment) M rel, prm.

This is due to the fact that the permanent magnet 11 has a number of magnetic poles on its surface, which are essentially distributed over individual sectors of the permanent magnet. For example, two north and two south poles are shown in FIG .

These poles are advantageously oriented on the contour of the stator, as shown in FIG. 1, so that a pole is located in the vicinity of an extension 12 . The rotor is rotated due to the interaction of permanent magnet poles of the permanent magnet 11 and the openings 18 or the beads 61 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 11 with the openings, breakouts or beads of the rotor part causes an alternating reluctance moment (permanent magnetic moment).

According to the invention, this alternating reluctance torque is substantially in phase opposition to the torque which acts on the rotor when the coil 15 is being charged by means of the stator plates 12 and 14 . When the coil 15 is energized, the tongues of the stator plates (flux guide pieces) on the periphery regions 121 and 141 exert attractive and tangential forces on the reluctance plates 9 of the rotor. This creates an electromagnetic torque.

The coil 15 can be applied to the stator using the simplest winding technique. The beginning and end of the coil are provided with the connection points 13 .

In an advantageous embodiment, the coil comprises a bearing tube (not shown) for receiving ball or plain bearings. These carry a rotatable shaft which is fastened to the center 64 of the rotor, as is known from the prior art and is therefore not shown in the drawing.

The coil 15 is fed at suitable commutation times or phases in order to apply a torque with a uniform sign to the rotor so that it rotates in a desired direction of rotation. According to the invention, it is therefore important to ensure, by means of a suitable single-phase commutation device 29 , that energizing the coil 15 only gives the rotor torques with a uniform sign. Back-driving electromagnetically generated torques are prevented by the coil being de-energized, ie switched off, as z. B. from Fig. 2 and 3 can be seen.

A simple solution with a mechanical commutator (collector) is shown in FIG. 3 (developed view).

A switch contact 41 contacts a reluctance sheet 9 precisely when it has assumed an angular position in which a current supply to the coil leads to a desired torque. The coil energization through the switch contact 41 is interrupted before an opposite torque occurs.

Fig. 2 shows the relationship between the torques involved in the motor via the angle of rotation phi of the rotor.

When the coil 15 is continuously energized with a constant current, the rotor exercises over an angular range which is greater than 180 °. is a positive torque. This is represented by section 1 of the electromagnetically generated reluctance torque. For the 360 deg. Complementary angular range is generated with energized coil 15, a negative moment (curve section 2 ). However, the commutation device provided suppresses the electromagnetically generated negative reluctance torque between the zero crossings 6 and 7 and then has no share in the total torque of the rotor.

To bridge this torque gap, the above-described, permanently magnetically generated reluctance torque is used, which is represented by curves 3 and 4 . This torque component constantly acts on the rotor, but has a changing sign. - In an advantageous embodiment of the invention, the positive portion of the permanent magnet reluctance moment extends over an angular range that is also greater than 180 degrees. el.

Permanent magnet and electromagnetically generated Torque components are therefore essentially against phase. The effective electromagnetically generated reluctance moment is about twice the amount Reluctance torque generated by permanent magnet.

When the commutation device 29 is connected to the coil 15, there is therefore a profile of the total torque over the angle of rotation of the rotor, as it is essentially represented by the curve 5 (M tot).

The commutation circuit with mechanical commutator contact shown in FIG. 3 is described in more detail below.

The end faces 121 of the stator plate 12 form z when the coil is energized with direct current. B. north poles, while the end faces 141 of the stator plate form common south poles. The contact 41 is mechanically arranged so that contact is made at the contact point 42 as soon as a tongue 9 of the reluctance sheet is in the effective area of the end faces 121 and 141 .

This closes a circuit which starts from the first connection terminal V1, is passed through the reluctance plate 9 and is passed on to the permanent contact grinder 43 at a contact point 44 to a connection point 13 of the coil 15 .

The second connection point 13 of the coil is connected to the second connection terminal V0 of the circuit.

During the closing phase of contact 41 , the reluctance sheets 9 experience a force that is both radial and tangential, because when they move in the direction of the arrow shown, the energy of the magnetic circuit of the coil 15 is reduced.

After moving the reluctance sheets by 180 deg. el., which corresponds to a sheet width in the example shown, contact 41 is opened. The reluctance sheets 9 move on the one hand due to their kinetic energy. In addition, the permanently magnetically generated reluctance torque continues to act in a driving manner until the next contact 41 is made with the subsequent reluctance plate 9 . The game described is then repeated again.

The device described for mechanical contacting is particularly inexpensive to manufacture. The invention sees in another advantageous embodiment, however electronic switching elements. The contact wear is completely eliminated with that solution.

Such an arrangement is shown in FIG. 4.

Instead of the contact 41 there is an electronic switch 26 which is controlled by a sensor element 29 . This can be a light barrier, for example, which is opened or interrupted by the reluctance plates 9 . A preferred sensor element consists of an integrated circuit with a Hall sensor (Hall IC).

This is controlled by an auxiliary permanent magnet 56 , the field lines of which are diverted in phase by the reluctance plates 9 . Only when the reluctance sheets 9 are temporarily absent do they act on the Hall IC, so that the desired in-phase energization of the coil 15 occurs via the electronic switch 26 . The coil 15 is advantageously bridged by a free-wheeling diode 25 .

Fig. 5 shows the surface of a rotor according to the invention with beads.

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

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

Lower regions 60 of the cylinder base alternate with higher regions 61 . The higher areas are delimited by edges 62 , while edges 63 represent the lower edge of the beads shown.

According to the invention are particularly inexpensive Motors provided simple beads or breakouts, while motors with more even torque behavior, d. H. comparatively reduced alternating torque components, specially contoured beads, openings or breakouts exhibit.

Another embodiment of the invention is also based on the knowledge that so-called reluctance motors with permanent magnet generated auxiliary torque this and a associated electromagnetic useful torque is not necessary wise combined in one either cylindrical or old natively in an only flat air gap. Much more it is useful according to the invention to generate the genann separate moments, namely useful torque and auxiliary torque, in such a way that the useful torque using a cylindrical (more precisely: a hollow cylindrical) air gap is generated while providing a permanent mag a flat, flat air gap is pulled. A construction of this kind is special advantageous for such electric motors that drive as a fan or ventilator are provided, since this after Kind of a propeller a more or less flat end face  without additional storage devices. At the back The hard surface of this face can be removed with simple Averaging a flat air gap to generate an auxiliary torque provide.

An engine according to such another aspect of the invention is shown in FIG. 7. This is a top 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) around an axis which perpendicularly intersects the paper plane of the drawing at the penetration point 78 .

The rotor 69 consists of a hollow cylindrical iron yoke 71 , to which permanent magnets 72 , 73 are attached in a manner known per se. To the hollow cylinder of the rotor is a substantially circular, flat back iron area (rotor cover) connects with recesses or corrugations, as shown in similar form in Fig. 5 and Fig. 6.

The construction of the stator 70 is similar to that of the stator 10 from FIG. 1, but has further simplifications. Instead of a one-piece permanent magnet, two smaller, z. B. circular permanent magnets 77 , 81 are provided, which are cheaper. The upper flux guide plate of the stator also has a simpler periphery, which is composed of circular arc pieces 75 and straight sections 79 , which is also less expensive.

To avoid eddy currents, the flow guide pieces have a plurality of slots 74 . The permanent magnets 77 , 81 are glued to the flux guide piece next to the slots 74 or via these. On the back of the flux guide piece, as shown in FIG. 1, there is also a single-layer or multi-layer coil of essentially circular or hollow cylindrical shape. It comprises a bearing tube, also not shown, for receiving bearing means and preferably a ferromagnetic coil core of hollow cylindrical shape, which extends between the upper flux guide with the peripheral lines 75 , 79 and the lower flux guide with the peripheral line 80 . As can be seen from the drawing, the upper and lower flux guide are of the same shape, but in the stator at an angle of 90 degrees. mech. twisted arranged. However, the lower flux guide plate is not equipped with permanent magnets, since it does not face any end face of the rotor.

The peripheral lines 75 , 80 define the cylindrical air gap between the rotor 69 and the stator 70 . When the coil between the flux guide pieces, which is not shown, is energized, the latter are magnetized, with opposite poles. A north pole 72 of the rotor is therefore attracted to 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 the permanent magnets 77 and 81 - a preferred detent position, which, however, causes a stable or unstable moments constellation when the coil is energized, so that the rotor stands under order despite the coil being energized would not move.

In order to avoid this problem, the permanent magnets 77 and 81 are provided, which are located within the plane air gap mentioned and, due to the surface shape of the rotor cover, not only exert axially directed forces on the rotor, but also cause an auxiliary torque when the rotor 69 rotates, which is how has the above-mentioned alternating sign about the angle of rotation and cannot be suppressed.

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

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

The construction acc. Fig. 7 is therefore advantageous in in comparison to known engines, because the cylindrical magnets with poles 72, 73 are comparatively kept thin by using modern, hochremanenter magnetic materials. However, this makes it necessary to keep the air gap of the magnetic circuit as small as possible for the useful torque. It is therefore advantageous according to the invention to dispense with the usual contours of the stator poles with variable air gap dimensions 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 motors with an outside diameter of about 3 centimeters it favorable according to the invention, the ferromagnetic Iron core for the motor coil made of sintered iron material to manufacture. On the one hand, this always reduces the otherwise take eddy current losses into account if necessary radially directed slots must be reduced. To the others, such a core is also the bearing (sinter bearings) for the rotor shaft, without further devices.

In a further embodiment of the invention according to FIG. 8, a cylindrical air gap for generating a useful torque is also provided for the rotor, as well as a cylindrically oriented arrangement of several magnetic pole pairs, as shown in the development according to FIG .

The arrangement according to FIG. 8 thus has a stator construction according to that as drawn in FIG. 1 and a permanent magnet-equipped rotor. The permanent magnets of the rotor according to FIG. 8 and FIG. 9 differ from those of the one shown in FIG. 7 in that over an angular range of 360 degrees. el. a quadrupole arrangement according to FIG. 9 is provided. Also for the solution according to FIGS. 8 and 9 it is provided that a reluctance auxiliary torque is generated with additional permanent magnets attached to the stator in the flat, frontal air gap of the motor.

Claims (8)

1. Single-strand reluctance motor, with a stator (10) and with a rotor ( 8 ), characterized by the following features:

• - the motor is powered in single-pulse mode,
• the stator has a substantially flat coil ( 15 ), the normal of which runs parallel to the motor axis,
• - The stator has two essentially flat flux guide pieces ( 12 , 14 ) which are provided with recesses ( 21 ), the coil ( 15 ) is located between the flux guide pieces ( 12 , 14 ),
• - The stator has a flat permanent magnet ( 11 ),
• the rotor has the basic shape of a hollow cylinder which is open on one side and which is provided on the cylinder jacket and / or on the cylinder base surface with recesses, cutouts or beads,
• - The motor has a single-phase mechanical or electronic commutation device ( 31 ) for energizing the coil ( 15 ).

2. Motor according to claim 1, characterized in that the permanent magnet ( 11 ) generates a reluctance auxiliary torque which has a phase shift with respect to a useful reluctance torque of the motor. 3. Motor according to claim 2, characterized in that the ratio of electro magnetically generated reluctance torque too permanent magnetic generated reluctance torque is 2 to 10. 4. Motor according to claim 1 or 2 for use in one Axial fan. 5. Fan according to claim 4, characterized by a rotor-wing unit, which consists of is made in one piece. 6. Electric motor with auxiliary torque generated by permanent magnet, with a stator and with a rotor characterized by the following features:

• - The motor is powered in two-pulse mode.
• the stator has a substantially flat coil, the normal of which runs parallel to the motor axis,
• - The stator has two substantially flat flux guide pieces ( 12 , 14 ), which are provided with recesses ( 79 '), the coil is located between the flux guide pieces ( 12 , 14 ),
• - The stator has two flat permanent magnets ( 77 , 81 ),
• the rotor has the basic shape of a hollow cylinder which is open on one side and which is provided with recesses, cutouts or beads on the base of the cylinder,
• the motor has an at least single-phase electronic commutation device for energizing the coil,
• - The motor has a cylindrical air gap to generate a useful torque.

7. Electric motor according to claim 6, characterized in that a ferromagnetic core made of sintered material is provided within the coil between the flux guide pieces ( 12 , 14 ), the core having a bore which serves as a sintered bearing for the rotor shaft of the electric motor. 8. Electric motor with a magnet arrangement for generating a Auxiliary torque in a flat air gap, characterized in that an additional, cylindrical Working air gap available to generate a useful torque  is, the gap width over a mechanical angle of approximately 180 deg. el. of substantially constant Size is.