AU636441B2

AU636441B2 - Commutator for an electric motor

Info

Publication number: AU636441B2
Application number: AU70307/91A
Authority: AU
Inventors: Franz Armbruster; Paul Borrmann; Helmut Braun; Klaus Gohde; Reinhard Henkel; Hans-Juergen Kessler; Uwe Kroeger; Juergen Seeliger; Juergen Soellick; Heinz Wagner; Hans Wuerth
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1990-01-25
Filing date: 1991-01-09
Publication date: 1993-04-29
Anticipated expiration: 2011-01-09
Also published as: WO1991011837A1; DE4002106A1; DE59101617D1; EP0511972B1; AU7030791A; ES2054486T3; JP2859438B2; BR9105957A; EP0511972A1; JPH05504018A

Description

R.23217 Commutator for an elect.ic machine Prior art The invention relates to commutator for electric machines, having a multiplicity of segments which, at their rear ends, are connected by welding to winding ends of a rotor winding, composed of round wire, of the machine, at least two winding ends being arranged one lying on top of the other in the radial directioin on each segment.

Different embodiments for the arrangement and connection of the winding ends of a rotor winding of an electric marhine to segments of a commutator are known.

German Offenlegungsschrift DE-OS 19 05 733 shows commutator line ends composed of round wire which are attached to one another by resistance welding. Subsequently, one winding end is shortened so that the other protrudes. This protruding end is radially inserted into a slit of a commutator lug. Subsequently, the lug is radially deformed with heat in such a way that the protruding free winding end is electrically connected to the lug and thus to the associated commutator lamina.

This method is relatively complicated; also lugs which are specially provided with a slot are required on the commutator laminas.

German Offenlegungsschrift DE-OS 35 30 652 discloses a commutator for electric machines which has radially extending insulating laminas between its segments, which laminas broaden outwards in a wedge shape. They form chambers between each other, into which chambers winding ends, composed of round wire, of the rotor winding of the electric machine are placed. Two winding ends are provided which lie one on top of the other and in this position are attached to one another and to the floor of the chamber by welding. In order to provide better overspeed protection, in addition a rotor band can close off the chambers from the outside. The insulating laminas required to form the chambers make the design relatively complicated and thus cost intensive.

-2- Japanese Patent 55-10816 discloses a commutator for an electric motor which also has segments provided with slots. The wire ends of the rotor winding which are composed of round wire are provided with a zigzag profile which interacts with the slot walls.

Finally, German Offeniegungsschrift DE-OS 31 28 626 shows a commutator for electric machines in which special profile wires are inserted. The winding ends of the rotor winding are placed in slots of the commutator segments and pressed with a special tool die so that the winding ends which lie one on top of the other are brought into close contact with one another and at the same time a segment area is plastically deformed in such a way that an electric and also mechanically secure connection is produced at the lamina lug.

Specifically profiled rotor winding wires are also used in German Offenlegungsschrift DE-OS 27 39 730. These wires can have for example a rectangular-shaped cross-section. The winding ends are butt-welded to one another and to the corresponding commutator lamina by means of welding. Here, the winding ends can rest on top of one another with their narrow sides or also with their broad sides.

Summary of the Invention The present invention provides a commutator connection to the rotor winding of an electric machine, said rotor winding having a multiplicity of segments which, at their rear ends, are connected by welding to winding ends of the rotor winding, each winding being composed of round wire, at least two winding ends being arranged one lying on top of the other in the radial direction on each segment, and being laterally exposed and being welded to one another in a planar fashion via die stamped/machined surfaces resting one on top of the other the, support surface, associated with the lower winding end, and commutator segment have heat accumulation channels for assisting in welding operations.

Advantages of the Invention The commutator according to the invention has, in contrast with the t d I' -3prior art, the advantage that in spite of the use of round wire for the rotor winding exact positioning during the welding of the winding ends is possible without a slotted commutator design and without insulating laminas of the commutator, without this leading to slipping or the like. Despite the absence of receiving chambers for the winding ends, simple handling and precise arrangement during welding is possible. Since the winding ends associated with each segment are exposed, the commutator is of very simple construction. The winding ends can be welded to one another over a large surface and without displacement since they have die stamped/machined surfaces formed by circular section-shaped material displacement/removal as a result of which appropriately sized support surfaces are produced. In addition, these relatively large die stamped/machined surfaces ensure electrical connections with only a very small contact resistance. In addition, or alternatively, the lower winding end can be connected in a planar fashion to the segment by welding via a die stamped or machined surface of this kind.

During the welding process, the two wires are acted upon radially so that they weld to one another at their die stamped/machined surfaces. Since the wire support surface has the aforesaid heat accumulation channels, in each case a particularly large welding current density is produced at the channels which ensures satisfactory welding.

It is advantageous if the heat accumulation channels run in the circumferential direction of the commutator.

In accordance with a particular embodiment of the invention, it is provided for the wire support surface to form the basis of a fixing groove which runs in the direction of the longitudinal extent of the winding ends. The circular contour of the lower winding end is provided with multipoint support in the fixing groove so, a multipoint support in the fixing groove, so that the lower winding wire cannot slip during the welding process. Of course, the base of the fixing groove can also be provided with heat accumulation channels.

ro 3a Drawing The drawings illustrate the invention with reference to a plurality of exemplary embodiments; specifically in ,he drawing: 4 Figure 1 shows a cross-section through a section of a commutator of an electric machine, Figure 2 shows a view in accordance with Figure 1 according to a further embodiment, Figure 3 shows a further embodiment of a design in accordance with Figure 2 and Figure 4 shows a view of a wire support surface of the commutator in the direction of the arrow A in Figures 1 and 2.

Description of exemplary embodiments Figure 1 shows a cross-section through a portion of a commutator 1 in the region of a segment 2 which is composed of conductive material. Both sides of the segment 2 are adjoined by further segments (not illustrated) which are insulated from one another by means of insulating webs 3. Outside the area of the commutator 1 which interacts with carbon brushes, the winding ends 4, 5 of a rotor winding of an electric machine which has the commutator 1 are connected to the segment 2. For this purpose, the winding ends 4, composed of round wire are provided in their connecting area with die stamped/machined surfaces 6, 7 formed by circular section-shaped material displacement/removal.

In this way, the winding ends 4, 5 are arranged one lying on top of the other in planar fashion at the rear end of the segment 2 and are acted upon radially with an electrode in order to weld them to one another and to the segment 2 without them slipping relatively to one another. The winding ends 4 and 5 are thus arranged exposed on the commutator i.

As can be seen from Figure 1, there can also be a die stamped/machined surface 8 on the lower side of the lowest winding end 5, which surface is also formed by circular section-shaped material displacement/removal.

The same can also apply to the top of the winding end 4; that is to say a die stamped/machined surface 9 is also present here. Depending on the design of the commutator/

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5 rotor, further winding ends can thus be connected to the die stamped/machined surface 9 by welding.

A broken line 10 shows in Figure 1 that the wire support surface 11 of the commutator 1, that is to say the outside of the segment 2, is provided with heat accumulation channels 12. The heat accumulation channels 12 run in the circumferential direction of the commutator 1. Their concrete design emerges from Figure 4. They form a trapezoidal curve, that is to say they are provided with edges which run at oblique angles. The height of the web is preferably 0.3 mm and each of the upper web surfaces has approximately a width of 0.2 mm. The heat accumulation channels 12 can also be attached, if appropriate, to the winding ends 5 instead of to the segments 2.

Figure 2 shows a further exemplary embodiment in which in contrast with the exemplary embodiment in Figure 1 die stamped/machined surfaces 6 and 7 are only constructed in the contact area between the winding end 4 and the winding end The exemplary embodiment in Figure 3 shows a design like that in Figure 2, in which case however the wire support surface 11 is formed by the base 13 of a fixing groove 14 which runs in the direction of the longitudinal extent of the winding ends 4, 5. In this way, the position of the graduated circle-shaped underside of the winding end 5 is fixed so that it cannot slip relative to the segment 2 during the welding process.

Claims

1. Commutator connection to the rotor winding of an electric machine, said rotor winding having a multiplicity of segments which, at their rear ends, are connected by welding to winding ends of the rotor winding, each winding being composed of round wire, at least two winding ends being arranged one lying on top of the other in the radial direction on each segment, and being laterally exposed and being welded to one another in a planar fashion via die stamped/machined surfaces resting one on top of the other, the support surface, associated with the lower winding end, and commutator segment have heat accumulation channels for assisting in welding operations.

2. Commutator connection according to Claim 1, wherein the heat accumulation channels are arranged on the commutator segments and run in the circumferential direction of the commutator.

3. Commutator connection according to any one of the preceding claims, wherein the support surface is located on the base of a fixing groove at the end of each segment which fixing groove runs in the direction of the longitudinal extent of the winding ends.

4. Commutator connection according to any one of the preceding claims, wherein the lower winding end is connected in planar fashion to the segment via a die stamped/machined surface by welding. A commutator connection to the rotor winding of an electric machine substantially as hereinbefore described with reference to the accompanying drawings. D A T E D this 19th day of February 1993. ROBERT BOSCH GmbH By their Patent Attorneys: f 'CALLINAN LAWRIE V w 7 The invention relates to a commutator for electric machines, having a multiplicity of segments which are connected by welding to winding ends 5) of a rotor winding, composed of round wire, of the machine, at least two winding ends being arranged one lying on top of the other in the radial direction on each segment. For the sake of manufacture with secure contacts, it is provided, with a simple design, that the winding ends associated with each segment are exposed and are connected to one another in a planar fashion via die stamped/machined surfaces 7, 8, 9) formed by means of circular segment-shaped material displacement/removal. (Figure 1) RSL 1 7>,