Electronically Commutated Collectorless Direct-Current Motor

1. Technical Field

The present invention pertains to an electronically commutated, collectorless direct-current motor.

2. Background Art

Such a direct-current motor is known from DE-OS 34 38 747. The stator winding of the known electronically commutated, collectorless direct-current motor comprises an insulating body which consists of a disk-shaped ring and a plurality of axially extending slotted portions annularly arranged thereon. The slotted portions are supported by a tubular section. The individual phase windings of the stator winding are located outside the slotted portions, the ends of the windings being connected to a circuit board. The ends are commonly soldered directly to the circuit board.

The disadvantage of the known direct-current motor is that during production, the ends of the winding must be soldered to the circuit board by hand.

It is the object of the present invention to provide an electronically commutated, collectorless direct-current motor which can be produced in a more cost-effective manner.

This object is achieved in a direct-current motor of the above kind in which ends of the stator coil are secured to eyehooks which are connected with a cylindrical plastic body. The plastic body is concentric with the stator coil, and has a front end having a rim. The rim has a plurality of recesses which contain the eyehooks.

An embodiment of the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a longitudinal section of an embodiment of the electronically commutated, collectorless direct-current motor in accordance with the invention;

FIG. 2 is a section of a plastic body with eyehooks;

FIG. 3 is an end view of the plastic body of FIG. 2;

FIG. 4 is a side view of the stator coil with the plastic body and the eyehooks, and

FIG. 5 is a front view of a lamination shape of the external magnetic yoke.

An electronically commutated, collectorless direct-current motor 1 in accordance with the invention is shown in FIG. 1. It comprises an external magnetic yoke 2, a stator 3, a multipolar rotor 4, and two end shields 5, 6. Together with an outer casing 35, the two end shields 5, 6 form a frame 36 of the direct-current motor 1.

A shaft 7 of the rotor 4 is connected with the end shields 5, 6 via two bearings 8, 9. The rotor 4 comprises a steel cylinder or a cylinder 11 built up of laminations 10 supporting a multipolar magnetic system 12 which consists of several annular magnets subdivided in the axial direction, or of embedded magnetic bars. Furthermore, a bipolar annular magnet 13 is located on the shaft 7 to permit position determination. The cylinder 11 consisting of the laminations 10 serves as an internal magnetic yoke.

The stator 3 consists of a multipolar stator coil 14, a plastic body 15, several eyehooks 16, and a circuit board 17. The stator coil 14 has a number of phase windings 29 which are equal to a multiple of the number of poles and which are wound to form a ring circuit. The plastic body 15 is shown in FIGS. 2 and 3. It consists of a hollow cylinder 19 with a rim 20 which is provided on the front end. The rim 20 has a number of recesses 21 equal to the number of phase windings and which contain the eyehooks 16. The hollow cylinder 19 and the rim 20 are of one-piece construction and have an inner cylindrical surface. However, the outside diameter of the rim 20 exceeds that of the hollow cylinder 19. In addition, in the area of the recesses 21, the rim 20 has outer projections 23. Arranged at the front end of the rim 20 between the recesses 21 are pin-shaped spacers 24. Slots 25 for receiving Hall-effect sensors 26 are located in two areas between two pairs of recesses 21 instead of the spacers 24. In these slots 25, the Hall-effect sensors 26 are protected against shock and require no adjustment.

Each end 18 of the stator coil 14 is brought along about half the circumference of the hollow cylinder 19, then around the projections 23, through the eyehooks 16 and again along about half the circumference of the hollow cylinder in such a manner that the plastic body 15 is surrounded by the end 18 of the stator coil, thus being fixed in position. Each of the ends 18 of the stator coil are welded to a corresponding one of the eyehooks 16.

Each eyehook 16 is U-shaped and consists of two legs 27, 28 of different lengths. When the eyehooks 16 are arranged in the rim 20, the shorter leg 27 is bent outside the recess 21, thus forming a hook. After the corresponding end 18 of the stator coil has been brought between the legs 27 and 28, the shorter leg 27 is bent towards the longer leg 28 and welded. The longer leg 28 of the eyehook 16 forms a pin for connection to an electrical socket, and extends beyond the spacers 24 by about 4 mm, so that it can be inserted into the circuit board 17 and soldered. The shorter leg 27 primarily serves to fix the ends 18 of the stator coil within the eyehook 16 and does not extend beyond the spacers 24.

The stator coil 14 ends 18 of the are firmly soldered to the circuit board 17 via the eyehooks 16, with the circuit board 17 resting against the spacers 24. Furthermore, the Hall-effect sensors 26 disposed in the slots 25 are electrically connected to the circuit board 17 via wires 40 and 41 (shown in FIG. 1) which are soldered to the circuit board 17. In addition, other elements are located on the circuit board 17. Thus, for example, several connectors which are electrically connected to the corresponding eyehooks 16 are soldered to the circuit board 17 so as to protrude from the frame 36 and are accessible from the outside. The circuit board 17, on the other hand, is firmly connected with the end shield 5 by a suitable snap connection (not shown).

The stator coil 14 is a self-supporting drum winding (FIG. 4). It is wound on a winding support and receives its shape by a thermal treatment using self-bonding lacquer. The latter insulates the coil 14 and bonds the individual wires, thus ensuring the dimensional stability after the winding support has been removed. The principle of the arrangement of the phase windings is already disclosed in DE-OS 34 38 747 without the self-supporting shape of the stator coil 14 having been mentioned therein and without the electric connection of the ends of the stator coil shown therein being made in the fashion described herein above. The stator coil 14 has an inside radius R.sub.1 at the first winding head 30 and an inside radius R.sub.2 at the second winding head 31, where R.sub.1 <R.sub.2. In the area between the winding heads 30, 31, the phase windings 29 are arranged predominantly axially and in a circle with the radius R.sub.2. Only in the area of the first winding head 30 does the circle formed by the phase windings decrease to the radius R.sub.1. The outside radius R.sub. 3 of the first winding head 30 is smaller than the inside radius R.sub.2 of the second winding head 31. The stator coil 14 has slot-shaped free spaces 32.

The external magnetic yoke 2 is constituted by a laminated-sheet plate. The lamination shape is shown in FIG. 5. It has a round cutout 34 with teeth 33.

The electronically commutated, collectorless direct-current motor in accordance with FIG. 1 is assembled by inserting the stator coil 14, with the plastic body 14 attached thereto adjacent the first winding head 30, into the laminated-sheet plate constituting the external magnetic yoke 2 so that the slot-shaped free spaces 32 of the stator coil 14 are filled by the teeth 33 of the laminated-sheet plate. The stator coil 14 is inserted into the laminated-sheet plate until it projects about an equal length from each side end of the laminated-sheet plate. The circuit board 17 is then soldered to the eyehooks 16 and the Hall-effect sensors 26. The end shield 5, which has a suitable device for fixing the circuit board 17, is then slipped on the stator 3 which is formed as above. The rotor 4 is inserted through the stator 3 on the bearing 8 of the end shield 5 and finally, the end shield 6 with the bearing 9 is placed on the rotor 4. In the assembled condition, the Hall-effect sensors 26 are then arranged a region adjacent the surface of the annular magnet 13.