GB2220802A

GB2220802A - Connecting armature windings

Info

Publication number: GB2220802A
Application number: GB8816050A
Authority: GB
Inventors: Patrick Shui-Chung Wang
Original assignee: Johnson Electric Industrial Manufactory Ltd
Current assignee: Johnson Electric Industrial Manufactory Ltd
Priority date: 1988-07-06
Filing date: 1988-07-06
Publication date: 1990-01-17
Also published as: GB8816050D0; DE8908266U1; JPH0279166U

Abstract

The armature comprises a winding, a plurality of commutator segments (11), each having an integral terminal portion (12), a commutator base (10) having a plurality of housings (15) which are formed with housing recesses for said terminal portions (12), and an electrical connector (25) supported with respect to each of the housings. Each connector (25) has a first part (25a) disposed within and preferably extending across the housing and a second part (25b) disposed externally of the housing. The second part (25b) has a sharp edge (28) around which a portion (29) of the winding is wound and each terminal portion has a slot (21) which straddles and grips the first part of a connector (25) in a respective housing (15). <IMAGE>

Description

An armature for an electric motor This invention relates to an armature for an electric motor and a motor having such an armature.

In our British Patent No. 2128818B, for example, we described a connection between an armature winding and a commutator segment which avoids the application of heat to effect the connection and which utilises the principle of insulation displacement in which a wire having an insulating cover is forced into a slot narrower than the wire diameter to form a clean metal to metal contact between the wire and a terminal portion of the commutator segment.

Some motor armatures have windings of very thin wire. This very thin wire is flimsy and hence prone to breakage. Moreover, it is difficult to manufacture commutator segments with slots narrow enough to form a clean metal to metal contact with this very thin wire.

The present invention seeks to mitigate this drawback.

According to the present invention there is provided an armature for an electric motor, comprising a winding, a plurality of commutator segments each having an integral terminal portion, a commutator base having a plurality of housings which are respectively formed with housing recesses for said terminal portions, and an electrical connector supported with respect to each of the housings, each connector having a first part disposed within the housing and a second part disposed externally of the housing, the second part of each connector having a sharp edge around which a portion of the winding is wound and each terminal portion having a slot which straddles and grips the first part of a connector in a respective housing.

Preferably, the electrical connectors are rigid.

Preferably, the first part of each connector extends across a respective housing recess.

Other preferred and/or optional features of the invention are set forth in claims 4 to 7, inclusive.

The invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Figure 1 is an exploded perspective view of a commutator forming part of an armature according to the invention, Figure 2 is a longitudinal section through the commutator of Figure 1 when assembled, Figure 3 is a plan view of one embodiment of a commutator segment in blank form, and Figure 4 is a side view of the rose-like terminal support with one of the housings shown in section.

Referring first to Figures 1 and 2 of the drawings, there is shown therein a commutator base 10 and a commutator segment 11. The segment 11 has an integral terminal portion 12 at one end and an integral lug 13 at its other end with a brush contacting portion 9 therebetween. The base 10 comprises a rose-like terminal support 14 including five housings 15, each of which has a recess 15a receiving a terminal portion 12 of a commutator segment 11, and a cylindrical support 16 on which the brush contacting portions 9 of the commutator segments 11 are seated.

The terminal portion 12 of the commutator segment blank shown in Figure 3 is generally rectangular with its minor axis coincident with the longitudinal axis of the brush contacting portion 9 of the commutator segment. The terminal portion 12 comprises a central part 18 and two end parts 19 and 20. The central part 18 has a central cut out portion 17 which reduces from its largest width at the centre to two elongate slots 21 which terminate either end of the cut out.

The closed end of each slot 21 is enlarged to ensure that the edges of the slot 21 have a certain resilience to separation.

A triangular barb 22 is provided on either side of the minor axis of the central part 18 along the edge furthest from the brush contacting portion 9 of the commutator segment. These barbs 22 grip the housing 14 (Figures 1 and 2) and therefore retain the terminal portion 12 in the housing 14, as will be explained hereinafter.

The brush contacting portion 9 of the commutator segment 11 is of arcuate form to conform to the external radius of the support 16. The terminal portion 12 is bent upright from the commutator segment 11 and the central part 18 of the terminal portion is bent at 900 in areas 23 to form the arms 24 (Figure 1) which extend parallel to each other and to the longitudinal axis of the commutator segment 11, and forward along the length thereof.

The commutator segments 11 are seated on the support 16 and located thereon by the lugs 13 which extend into respective recesses in the end of the support 16 remote from the terminal support 14.

As shown in Figures 1, 2 and 3, an electrical connector 25 is supported by each housing 15 of the terminal support 14. The connectors 25 are L-shaped pins each having a first limb 25a which extends across the housing 15 at a tangent to an imaginary circle centered on the axis 26 of the support 14 and which is located in an aligned pair of slots 27 in the housing 15, and a second limb 25b which extends parallel to the axis 26. The limb 25a of the connector 25 is generally cylindrical and has a diameter slightly greater than the width of each slot 21 in a respective terminal portion 12. The second limb 25b is flat and has sharp edges 28 around which is wound a connector portion 29 of a thin wire armature winding, the sharp edges 28 breaking through insulation on the wire.

The armature is assembled as follows.

A lamination stack (not shown) is first mounted fast on an armature shaft. The rose-like terminal support 14, having a connector 25 extending across each housing 15, is then mounted fast on the armature shaft against the lamination stack. The armature is then wound in conventional manner and connector portions 29 of the winding are wound around the respective second limbs 25b of the connectors 25 a multiplicity of times to guarantee the integrity of each joint and ensure that the electrical resistance between each connector portion 29 and the respective connector 25 is low.

The commutator segments 11 are pre-assembled on the cylindrical support 16 and after the armature has been wound the support 16 is mounted on the armature shaft.

The commutator segments 11 are mounted on the support 16 in angularly spaced apart relationship with the brush contacting portions 9 seated on the peripheral surface of the support 16. The segments 11 are located with respect to the support 16 by the lugs 13 which are press fitted into respective recesses in one end of the support 16.

When mounting the cylindrical support 16 on the armature shaft, the support 16 is moved towards the rose-like terminal support 14 and the terminal portions 12 enter respective housings 15. As each terminal portion 12 enters its respective housing 15 the first limb 25a of the connector 25 enters the slots 21 in the terminal portion 12 to establish and maintain electrical contact between the connector 25 and the commutator segment 11. Also the barbs 22 bite into the housing 15 to firmly secure the terminal portion 12 in the housing 15.

With such an arrangement it is possible on the one hand to assemble the commutator segments 11 on the support 16 and on the other hand wind the armature in remote locations and to then connect the commutator segments 11 to the armature winding by a sliding mechanical connection between the terminal portions 12 and the electrical connectors 25.

Moreover, by making the circumferential extent of each housing recess 15a greater than the circumferential extent of a respective terminal portion 12 the angular positions of the commutator segments 11 with respect to the terminal housings 15 can be selected during assembly of the armature to provide for a desired commutation angle. In this case the first limbs 25a of the electrical connectors 25 may be of arcuate shape to facilitate connection between the terminal portion 12 and the electrical connector 25 in a desired angular relationship.

Instead of slots 27 each housing could be provided with a pair of aligned holes to locate the respective connector 25.

The connectors 25 need not be L-shaped but may be of other appropriate form. For example, each connector 25 could be T-shaped with a first limb extending across the housing recess 15a and a second limb extending through the base of the housing 15 for connection to a connector portion of the armature winding.

The above embodiment is given by way of example only and various other modifications will be apparent to persons skilled in the art without departing from the scope of the invention as defined by the appended claims.

Claims

1. An armature for an electric motor, comprising a winding, a plurality of commutator segments, each having an integral terminal portion, a commutator base having a plurality of housings which are respectively formed with housing recesses for said terminal portions, and an electrical connector supported with respect to each of the housings, each connector having a first part disposed within the housing and a second part disposed externally of the housing, the second part of each connector having a sharp edge around which a portion of the winding is wound and each terminal portion having a slot which straddles and grips the first part of a connector in a respective housing.

2. An armature as claimed in claim 1, wherein the electrical connectors are rigid.

3. An armature as claimed in claim 1 or claim 2, wherein the first part of each connector extends across a respective housing recess.

4. An armature as claimed in any one of the preceding claims, wherein each terminal portion has at least two spaced parallel arms each comprising a slot which straddles and grips a first part of a connector.

5. An armature as claimed in any one of the preceding claims, wherein each terminal portion has a barb for retaining the terminal portion in a respective housing.

6. An armature as claimed in any one of the preceding claims, wherein the commutator base comprises a first part which includes said housings and a second part on which brush contacting portions of the commutator segments are seated.

7. An armature as claimed in any one of the preceding claims, wherein the circumferential extent of each housing recess is greater than the circumferential extent of a respective terminal portion so that the angular position of the commutator segments with respect to the terminal housings can be selected during assembly of the armature.

8. An armature substantially as hereinbefore described with reference to the accompanying drawings.

9. An electric motor equipped with an armature as set forth in any one of the preceding claims.