GB2174252A

GB2174252A - Brushless synchronous machine with axial air gap

Info

Publication number: GB2174252A
Application number: GB08604738A
Authority: GB
Inventors: Helmut Harer; Helmut Kreuzer; Siegfried Schustek; Ludger Verstege
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1985-03-21
Filing date: 1986-02-26
Publication date: 1986-10-29
Also published as: JPS61224851A; ES553244A0; ES8703067A1; FR2579385B1; DE3510228A1; GB2174252B; GB8604738D0; FR2579385A1

Abstract

In a brushless synchronous machine with axial air gap and comprising a disc rotor 14 carrying permanent magnet segments 15, and two annular laminated stator cores 19, 20 which are held on both sides of the disc rotor 14 in the machine housing 10 and which in each case carry a three-phase armature winding 23, 24 wound of insulated wire, each laminated stator core 19, 20 is constructed as slotless sheet-steel coil 21, 22 of steel tape and each armature winding 23, 24 is constructed as self-supporting two- layer wave winding for the purpose of eliminating interfering detent torques and magnet tooth noises and of facilitating production. The armature windings 23, 24 are bonded to the face of the respective associated sheet-steel coil 21 or 22 by means of a casting compound. <IMAGE>

Description

SPECIFICATION Brushless synchronous machine with axial air gap State of the Art The invention sets out from a brushless synchronous machine with air gap of the generic type of Claim 1.

In a known synchronous machine of this type, the armature winding is wound on the laminated stator cores provided with radial slots, in such a manner that the coil section sides are lying in one or more layers in the slots and the end turns joining the coil section sides are arranged at the inner and outer edges of the laminated stator cores and are preferably bent in the axial direction. The known synchronous machine is used as a drive motor for robots since it has a high overload capacity due to the large heat capacity of its laminated stator cores into which the armature windings are directly inserted.

However, due to the slotted laminated stator cores unwanted detent torques occur and due to the fact that the teeth are magnetically excitable, this machine tends to develop noise to a greater or lesser extent depending on its speed of revolution and natural resonance.

Advantages of the Invention In comparison, the synchronous machine with axial air gap according to the invention, having the characterising features of Claim 1, has the advantage that the normal, very distinct detent torques have been eliminated by the slotless laminated stator cores whilst the machine retains its high overload capacity without reduction. Magnetic noices are also avoided. The synchronous machine according to the invention can be very simply manufactured from the point of view of production engineering, both with respect to its stator and to its rotor. Armature windings and laminated stator cores are separately prefabricated and joined to each other by simple bonding.

The elaborate production of the slotting and winding of the laminated stator cores can be dispensed with. The casting compound also ensures good heat conduction from the armature winding, which is constructed as a socalled air gap winding, to the laminated stator core.

The synchronous machine according to the invention can be equally advantageously used both as a robot motor and as a motor vehicle generator. The greater cross-sections of efficiency required for the motor vehicle generator, which must be constructed as a low-voltage machine, can be obtained by connecting partwindings in parallel without changing the overall axial height of the armature winding. The synchronous machine according to the invention has the low rotating masses required for both cases of application and has a sufficiently high overload capacity due to good air cooling, even at a high ambient temperature.

The synchronous machine according to the invention is largely vibration-proof and suitable for motor vehicle operation. When used as a motor vehicle generator, the necessary rectifiers are integrated into the machine housing and arranged in the cooling air stream. It is possible to construct the machine as a liquidcooled machine without constructional change of the electric part.

Advantageous developments and improvements of the synchronous machine with axial air gap, specified in Claim 1, are possible by means of the measures listed in the further claims.

In this connection, an advantageous embodiment of the invention is found in Claim 2. As as result of this construction, the air gap winding has a constant axial thickness of only two wire thicknesses, with the exception of the inner end turns. As a result, the outer end turns can still be partially arranged inside the front face of the laminated stator cores in accordance with the embodiment according to Claim 3. Keeping the power of the synchronous machine unchanged, smaller outside diameters of the stators are obtained or, conversely, if the outside diameter of the stator is kept constant, greater electric power is achieved.

An advantageous embodiment of the invention is also obtained from Claim 11. By these measures, radial air ducts are created between the permanent magnet segments, through which ducts, during the rotation of the disc rotor, air is thrown outwards and, in turn, causes increased cooling of the armature windings and of the laminated stator cores.

Drawing In the description which follows, the invention is explained in greater detail with the aid of an illustrative embodiment shown in the drawing, in which: Figure 1 shows a longitudinal section of a synchronous machine with axial air gap, used as a robot motor, Figure 2 shows a largely diagrammatic representation of a three-phase two-layer wave winding for the 6-pole synchronous machine with axial air gap according to Fig. 1, restricted to one winding phase and to an indication of the two other winding phases.

Description of the Illustrative Embodiment The synchronous machine with axial air gap, which can be seen in longitudinal section in Fig. 1, has a two-part machine housing 10, comprising two end shields 11, 12 in which a rotor shaft 13 is rotatably supported. The rotor shaft 13 is joined to rotate with a disc rotor 14 which carries the exciter system of permanent magnet segments 15. In the present illustrative embodiment, six permanent magnet segments 15 are arranged to be uniformly distributed over the circumference of the disc rotor 14. The permanent magnet segments 15 are embedded between two reinforcing layers 16, 17. As can be seen in the lower half of the disc rotor 14 in Fig. 1, the reinforcing layers 16, 17 are pulled inwards in the pole gaps to such an extent that they rest against each other. This creates radial air ducts 28 for improved guidance of the cooling air.To absorb centrifugal forces, the disc rotor 14 is bandaged on the outside with a winding 18 of high-strength material. Such a winding 18 consists of several layers of glass rovings which are wound with pretension over the permanent magnet segments 15. The material used for the reinforcing layer is either glass-fibre reinforced plastic (FRP) or non-magnetic steel (V2A).

On both sides of the disc rotor 14, an annular laminated stator core 19 or 20 is held, in each case with axial spacing, in the machine housing 10. Each laminated stator core 19, 20 is constructed as a slotless sheet-steel coil 21, 22 of constant-width steel tape. The sheet-steel coils 21, 22 are held by push fit in the machine housing 10 and secured against axial displacement by securing means, not shown, such as radial pins or spring elements.

Each laminated stator core 19, 20 and each sheet-steel coil 21, 22 carries a three-phase armature winding 23, 24 wound of insulated wire and having radially extending coil section sides 25 and outer and inner end turns 26, 27 which join the coil section sides. As can be seen from Fig. 2, each armature winding 23, 24 is constructed as a self-supporting two-layer wave winding. The pre-fabricated armature windings 23, 24 are placed as air gap windings on the face of the associated sheetsteel coil 21 or 22 and are bonded to the latter by means of a heat-conducting casting compound.

As can be seen in detail from Fig. 2, the coil section sides 25 and the outer end turns 26 of the respective armature winding 23, 24 are arranged in only two winding layers lying on top of each other, in which arrangement the radially extending coil section sides 25 in each individual winding layer rest close against each other at the bending points of the inner end turns 27. In Fig. 2, only one winding phase of the three-phase two-layer wave winding, the start of which is designated by U and the end of which is designated by X, is completely shown whilst the other two winding phases, having winding starts V and W and winding ends Y and Z, can only be seen with a little more than one coil section of the winding. Fig. 2 also shows the coil section sides 25 lying in the lower winding layer as dashes and the coil section sides 25 lying in the upper winding layer as continuous lines.

During the production of the wave winding according to Fig. 2, the insulated wire is guided in the course of the winding of each winding phase from the phase start U and V and W to the phase end X and Y and Z, respectively, in such a manner that it extends exclusively in the area of the wire cover of the winding layer which is the lower one in the course of the winding in the winding layer which is the upper one in the course of the winding. The layer change-overs from the lower winding layer to the upper winding layer are exclusively located in the area of the outer end turns 26. In this arrangement, the three winding phases are continuously wound in, each winding phase occupying about a third of one pole division. The three winding phases can also be separately prefabricated and subsequently interleaved in the manner described.

The two-layer wave winding shown in Fig. 2 has a constant axial thickness of only two thicknesses of insulated wire, with the exception of the inner end turns 27. As a result, a part of the outer end turns 26 can be arranged inside the face of the annular sheetsteel coils 21 and 22 as can be seen from Fig. 1.

As could only be indicated in Fig. 2, the outer end turns 26 are run preferably in the shape of an arc in such a manner that adjacent end turns 26 located in the same winding layer and belonging to different winding coil sections are in contact at least along a section of an end turn. The coil section sides 25 in both winding layers are located in two planes which extend perpendicularly to the axis of the disc rotor 14 and in parallel with each other. The layer change-overs present in the outer end turns 26, from the lower winding layer to the upper winding layer, are placed in such a manner that they are located outside the laminated stator core 19, 20 and of the sheet-steel coil 21, 22 in the case of a two-layer wave winding 23, 24 bonded to the laminated stator core 19, 20 or to the sheetsteel coil 21, 22.

Around the sheet-steel coils 21, 22 forming the laminated stator cores 19, 20, housing material can also be partially sprayed to provide support in the machine housing 10.

The two armature windings 23, 24 are cooled as follows: During the rotation of the disc rotor 14, air is thrown radially outwards through the radial air ducts 28, and passes inward again through cooling slits 29 between the laminated stator cores 19 and 20 and the machine housing which is closely ribbed on the inside. Two inside ribs 30 of the inside ribbing can be seen in Fig. 1. Another portion of the heat passes from the armature winding via the heat-conductive casting compound into the laminated stator cores 19,20 to the machine housing 10 which is also closely ribbed on the outside.

The invention is not restricted to the illustrative embodiment of a synchronous machine with axial air gap, provided for use as a robot motor, as described above. Thus, the synchronous machine with axial air gap can also be used as an on-board power generator in a motor vehicle. Such on-board power generators are designed as low-voltage machines.

The larger conductor cross-sections required for this can be achieved by connecting partwindings of a winding phase in parallel which does not give the winding a greater overall axial height. The rectifiers required with onboard power generators are integrated in the machine housing and arranged in the cooling air stream. In addition, it is possible to construct the on-board power generator with liquid cooling. In this arrangement, the cooling liquid is carried in ducts on the surface of the machine housing. The heat from the armature windings is partially removed via the air in the internal space of the synchronous machine via the machine housing, which is closely ribbed on the inside, to the ducts carrying the cooling liquid.

Claims

1. Brushless synchronous machine with axial air gap, comprising a disc rotor carrying permanent magnet segments and two annular laminated stator cores which are held on both sides of the disc rotor in the machine housing and which in each case carry a three-phase armature winding wound of insulated wire and comprising radially extending coil section sides and inner and outer end turns joining the coil section sides, characterised in that each laminated stator core (19,20) is constructed as a slotless steel-sheet coil (21, 22) of constantwidth steel tape and each armature winding (23, 24) is constructed as a self-supporting two-layer wave winding which is bonded onto the face of the sheet-steel coil (21,22) by means of a casting compound.

2. Synchronous machine according to Claim 1, characterised in that the coil section sides (25) and the outer end turns (26) of the wave winding (23, 24) are arranged in only two winding layers lying on top of each other, and that, in the course of winding, the wire is guided from the start of the winding to the end of the winding in such a manner that the wire runs exclusively in the area of the wire cover of the winding layer which is the lower one in the course of the winding in the winding layer which is the upper one in the course of the winding and the layer change-overs are located in the area of the outer end turns (26).

3. Synchronous machine according to Claim 2, characterised in that the radially aligned coil section sides (25) extend inward to such an extent that coil section sides (26) which are located next to each other in a winding layer and belong to different winding coil sections are at least almost in contact at the bending points of the inner end turns (27).

4. Synchronous machine according to Claim 2 or 3, characterised in that the outer end turns (26) are run preferably in the shape of an arc in such a manner that adjacent end turns (26) located in the same winding layer and belonging to different winding coil sections are in contact at least along an end turn section.

5. Synchronous machine according to one of Claims 2-4, characterised in that the coil section sides (25) in both winding layers are located in two planes which extend perpendicularly to the axis of the disc rotor (14) and in parallel with each other.

6. Synchronous machine according to one of Claims 2-5, characterised in that the outer end turns (26) rest at least partially against the face of the sheet-steel coils (21, 22).

7. Synchronous machine according to Claim 6, characterised in that the layer change-overs from the lower winding layer to the upper winding layer, which are present in the area of the outer end turns (26), are located outside the sheet-steel coils (21,22).

8. Synchronous machine according to one of Claims 2-7, characterised in that the winding phases of the wave winding (23, 24) are continuously wound.

9. Synchronous machine according to one of Claims 2-7, characterised in that the three winding phases of the wave winding (23, 24) are separately prefabricated and subsequently interleaved.

10. Synchronous machine according to one of Claims 1-9, characterised in that the sheetsteel coils (21, 22) are held by push fit in the machine housing (10) and are secured against axial displacement by securing means such as radial pins or spring elements.

11. Synchronous machine according to one of Claims 1-10, characterised in that the permanent magnet segments (15) of the disc rotor (14) are embedded between two reinforcing layers (16, 17) and that the reinforcing layers (16, 17) are pulled inward in the pole gaps to such an extent that they rest against each other and form radial air ducts (28).

12. A brushless synchronous machine substantially as herein described with reference to the accompanying drawings.