GB2240664A

GB2240664A - Locating bobbin windings on stator

Info

Publication number: GB2240664A
Application number: GB9001360A
Authority: GB
Inventors: R S Boughton
Original assignee: Smith and Nephew PLC; Watson Marlow Ltd
Current assignee: Smith and Nephew PLC; Watson Marlow Ltd
Priority date: 1990-01-20
Filing date: 1990-01-20
Publication date: 1991-08-07
Also published as: GB9001360D0

Abstract

Coils (5), located on poles (3, 4, 13, 14, 3', 4', 13', 14') of the stator of an electric motor, are in the form of wire wound hobbins. Adjacent poles of the stator are different lengths, and the stator is constructed by firstly locating alternate bobbins on the poles, and secondly by locating the remaining bobbins interlocking with the first set before locating the bobbins in their final positions on the poles. The bobbins and the poles, on which they are to be located, are provided with cooperating formations allowing the bobbins to be located correctly. <IMAGE>

Description

ELECTRIC MOTORS This invention relates to electric motors and more particularly to the stator assemblies for electric motors such as reluctance motors.

Conventionally, the stator assembly or winding of a reluctance motor comprises a number of electromagnetic coils projecting radially inwards from the stator housing. The stator assembly surrounds a rotor, there being an air gap between the ends of the stator poles and the poles of the rotor.

The design of conventional stator assemblies, makes the provision of the coil windings a laborious and relatively expensive activity. Moreover, conventional design parameters have placed a limitation on the number of stator poles which can be accomodated in a stator housing of a given size. Thus improvements in motor performance have generally had to be accompanied by a concomitant increase in the motor price.

The present invention seeks to overcome the disadvantages of the prior art by the provision of means whereby such stator coils may be more economically produced.

In accordance with the present invention there is provided a stator for an electric motor comprising a stator housing having a plurality of radially inwardly extending poles and an associated coil for each pole wherein each coil comprises a wire wound bobbin adapted to be received and located on the stator pole.

The present invention also provides a reluctance motor comprising a stator and a rotor within the stator wherein the stator comprises a plurality of coil wound stator poles arranged radially around the rotor and wherein each coil is wound on a bobbin and each stator pole is adapted to receive and locate a respective coil wound bobbin.

The bobbin may comprise a separate carrier for the wire core and may be made of a suitable insulating material such as a plastics or ceramics material.

Alternatively the bobbin may be formed integrally with the coil windings. In the latter embodiment, a wire coil once wound may be coated with a setting material such as a resin or varnish and set, eg by baking.

Insulation between the coil and the pole metal can be provided by the use of inserts made of electrically insulating materials such as electrical quality fibre board. The insert may be of tubular configuration such as cylinder or may be a number of abutting or overlapping strips located against the inner surface of the wire coil.

The bobbins may be provided with detents lugs or ribs to engage with appropriately located detents lugs or ribs on the stator pole.

The use of bobbins enables the coils to be wound quickly and accurately and unhindered by the constructional arrangement of the stator housing and its associated poles. The wound bobbins may be readily located at the appropriate position on the stator pole.

In a preferred arrangement, the stator is constructed with adjacent poles of different length.

The length and circumferential spacing of the poles being such that the bobbin may be placed over the innner end of its associate pole without fouling the carrier end of the adjacent poles and may be located at a radial position on the pole in an interlocking relationship with a bobbin located at a different radial location on an adjacent pole.

The invention will be further described and illustrated by reference to the accompanying drawing which is a cross-sectional view of a stator for use in motors of the invention.

The stator 1 comprises a housing 2 from which a number of opposed pairs of projections 3,31, 4,41, 13, 131 and 14, 141 projecting inwardly. The projections define the stator poles and are arranged radially around a rotor (not shown) which is located in the central cylindrical region 20. The stator housing and poles are manufactured from magnetizable materials such as steel.

The poles 3,4 are provided with wire-wound coils 5, each coil being wound onto a bobbin 6.

The bobbins may be retained on the pole pieces by means of ribs (not shown) provided on the pole contacting surface of the bobbin and by means of detents or depressions on the corresponding surface of the pole.

As will be seen in the drawing each bobbin is interlocked with the adjacent bobbin. Thus, for example, in the construction of an eight pole stator the assembly 1, the wound bobbins 5 are first located on the pole pieces or limbs 4,41, 14 and 141. A further four bobbins are then located 3,31, 13 and 131. In the final assembly the coils on limbs 4,41, 14 and 141 are set back with respect to the coils on the alternating poles, thus providing a compact construction.

By the use of the present invention it is therefore possible to produce electric motors both economically and compactly.

Claims

1. A stator for an electric motor comprising a plurality of radially inwardly extending poles and an associated coil for each pole, wherein each coil comprises a wire wound bobbin adapted to be received and located on the stator pole.

2. A stator as claimed in claim 1, wherein the bobbin includes a separate carrier for the wire core.

3. A stator as claimed in claim 2, wherein the bobbin is made of a suitable insulating material.

4. A stator is claimed in claim 1, wherein the bobbin is formed integrally with the coil windings.

5. A stator as claimed in claim 4, wherein the wound wire coil is coated with a setting material such as a resin or varnish and set.

6. A stator as claimed in any preceding claim, wherein the bobbins are provided with detents lugs or ribs to engage with appropriately located detents lugs or ribs on the stator poles.

7. A stator as claimed in any preceding claim, wherein the stator is constructed with adjacent poles of different lengths, the lengths and circumferential spacing of the poles being such that each bobbin may be placed over the inner end of its associated pole without fouling the carrier end of the adjacent poles and may be located at a radial position on the pole in an interlocking relationship with a bobbin located at a different radial location on an adjacent pole.

8. An electric motor comprising a stator, as claimed in any preceding claim, and a rotor within the stator.

9. A method of construction of a stator for an electric motor, the method comprising the steps of: forming a plurality of radially inwardly extending, circumferentially spaced stator poles; forming a plurality of coils, each in the form of a wire wound onto a bobbin; locating respective bobbins on a first set of alternate stator poles; locating respective bobbins on a second set of alternate stator poles interleaved with the first set, such that each bobbin is interlocked with the bobbins on the adjacent poles; and finally locating the bobbins on the poles interlocked together, with bobbins on the first set of poles at a different radial distance from bobbins on the second set of poles.

10. A stator for an electric motor, substantially as herein described with reference to, and as shown in, the accompanying drawing.

11. A method of construction of a stator for an electric motor, substantially as herein described with reference to the accompanying drawing.