GB2152765A

GB2152765A - Bobbin assembly for use in electric motors

Info

Publication number: GB2152765A
Application number: GB08421183A
Authority: GB
Inventors: Hatsuo Kitahara
Original assignee: Sankyo Seiki Manufacturing Co Ltd
Current assignee: Nidec Instruments Corp
Priority date: 1984-01-10
Filing date: 1984-08-21
Publication date: 1985-08-07
Also published as: GB8421183D0; JPS60114559U

Abstract

A bobbin assembly usable as a stator for a small electric motor or the like has a pair of complementary separate multi-part structures 1, 2 mounted together. Each structure 1, 2 is composed of a plastics bobbin component 2 with a central aperture 2a containing metal strips 1b forming core pole teeth adjoined by a flange 1a of a core component 1. The flanges 1a of the cores 1 are sandwiched between flanges or walls 2b of the bobbins and interengageable projections and recesses 2d, 2e on these walls 2b locate through the flanges 1a to positively locate the structures together. <IMAGE>

Description

SPECIFICATION Bobbin assembly for use in electric motors The present invention relates to a bobbin assembly for use as a stator in a small electric motor, particularly a stepping or synchronous motor, or generator.

A conventional form of bobbin assembly described in detail hereinafter has a pair of bobbin structures mounted side-by-side. Each such structure is itself composed of an annular bobbin onto which wire is wound and an annular core with metal strips forming pole teeth within the bobbin. Hitherto, various problems arise in the construction and subsequent processing of the assembly and a general object of the present invention is to provide an improved bobbin assembly.

In its broadest aspect the present invention provides a bobbin assembly for use in electric motors; said assembly comprising a pair of bobbin structures each composed of an annular bobbin onto which a coil can be wound and an annular metallic core provided with an array of axially extending teeth engaging within the associated bobbin; wherein the bobbin structures are provided with interengageable projection and recess means serving to locate the bobbin structures relative to one another to prevent misalignment and to inhibit relative rotation between the bobbin structures.

In a preferred embodiment, a bobbin assembly constructed in accordance with the invention comprises a pair of bobbin structures side-by-side, each bobbin structure being composed of an annular bobbin made from synthetic plastics and having a portion between spaced-apart flanges onto which a coil is wound and an annular metallic core with a plurality of axially extending pole teeth projecting from a flange which engage within the associated bobbin; wherein the bobbins have complementary interengageable projections and recesses which project through the flanges of the cores which abut one another thereby to positively locate the bobbin structures together to prevent misalignment and inhibit relative rotation.

Conveniently, projections and recesses characterising the invention may be provided on only one side wall or flange of each of the otherwise symmetrical bobbins. Each projection may be a simple pin while each recess may itself be formed in another projection resembling a small stud or boss. The boss and pin are then located in diametrically opposed positions and engage through holes or slots in the abutting flanges of the cores.

The invention may be understood more readily, and various other features of the invention may become apparent, from consideration of the following description in conjunction with the accompanying drawings wherein: Figure 1 is a sectional side view of a conventional bobbin assembly; Figure 2 is a sectional side view of a bobbin assembly constructed in accordance with the invention; Figure 3 is an exploded perspective view of the assembly shown in Fig. 2; and Figure 4 is an end view of a modified core for use in the bobbin assembly shown in Figs.

2 and 3.

As shown in Fig. 1, a known bobbin assembly designed for use in small electric motors is composed of a pair of symmetrical annular bobbins 2 and a pair of complementary annular cores 1. Each bobbin 2 is a onepiece synthetic plastics, e.g. resin, component with walls or flanges 2b, 2c defining therebetween a reduced central cylindrical region 10 onto which a coil is wound as generally designated at 11. Each core is a one-piece electrically-conductive metal component with a single end wall or flange 1a adjoining a circular array of axially projecting parallel teeth 1 b. The teeth 1 b of each core 1 engage within a central aperture 2a in an associated bobbin 2 and the structures or sub-assemblies composed of the bobbins 2 with the cores 1 therein are fitted together with the flanges 1 a abutting one another as shown.Misalignment between the structures 1, 2 and/or between the teeth 1 b of the cores 1 and the bobbins 2 - as exemplified by gap "g" in Fig. 1 gives rise to difficulties in subsequent processing not the least when wire is wound onto the bobbins 2. If the teeth 1 b of the cores 1 are made to engage within the apertures 2a in the bobbins 1 with a tight press fit to avoid axial misalignment between the teeth 1 b and the bobbin 2 there is a danger that the teeth 1 b, which are relatively fragile may become deformed. This can also occur quite easily after the structures 1, 2 of the conventional assembly have been united.Another problem which can occur if the teeth 1 b are forced into the aperture 2a of the bobbin 2 is that slivers or shards of plastics can be stripped from the periphery wall of the aperture 2a and if not removed these slivers can adversely affect the operation of the subsequently constructed motor or the like.

In accordance with the present invention, the assembly shown in Figs. 2 and 3, in which like reference numerals are used to denote like parts to Fig. 1, has one of the flanges 2a of each bobbin 2 provided with two axial projections 2d, 2f. The projection 2d is a simple rod or pin while the projection 2f is a boss with an aperture 2e adapted to receive the projection 2d. The projections 2d, 2f are located in diametrically opposed positions so that the projections and recesses 2d, 2e can inter-engage. The flanges 1 a of the cores are provided with through bores 1 c also in diametrically opposed positions and posi tioned to receive the inter engaging projections 2f, 2d. The provision of the projections and recesses 2d, 2e serves to positively locate the structures 1, 2.This measure also inhibits relative rotation between the core and bobbin components, prevents misalignment and protects the teeth 1 b against deformation. Moreover, when an associated rotor is located within the core teeth 1 b of the finished assembly, the improved location with the cores 1 concentric with the bobbins 2 thus equalizing the gap "g" as shown in Fig. 2 provides the motor with more reliable operating characteristics. Since the inter-engaging projections and recesses 2d, 2e are made from the same materiai, i.e. synthetic plastics, there is no danger that shards or scraps will be stripped off as in the case of metal/plastics engagement.The fact that the respective structures 1, 2 are locked together against relative rotation means that the coil winding operation can be performed on both bobbins simultaneously providing uniformity and facilitating subsequent soldering work.

Instead of using bores 1c in the flanges 1, U-shaped slots or recesses 1 c can be adopted as shown in Fig. 4.

In other modifications, not illustrated, one projection and recess 2d, 2e or more than two projections and recesses 2e, 2d can be provided on the flanges 2a. In some cases this renders the individual structures 1, 2 nonsymmetrical.

Normally the cores 1 would be assembled to the bobbins 2 separately and then the structures 1, 2 would be mated together. In an alternative however, the cores 1 are fixed or located together as a separate step prior to mounting the bobbins 2. To fix the cores 1 together their flanges 1 a can be positively located as through at least one further projection and recess or by spot-welding for example.

Claims

1. A bobbin assembly for use in electric motors; said assembly comprising a pair of bobbin structures mounted side-by-side, each bobbin structure being composed of an annular bobbin made from synthetic plastics and having a portion between spaced-apart flanges onto which a coil is wound and an annular pole teeth projecting from a flange which erigaye within the associated bobbin; wherein the bobbins have compler,1entary interengageable projections and recesses which project though tie f::anges of the cores which abut one another thereby to positiveiy locate the bobbin structures t-ogiler to prevent misalignment and inhibit relative rotation.

2. An assembly according to claim 1, wherein projeitions and recesses are provided on one flange of each bobbin.

3. An assembly according to claim 1, wherein one projection and one recess are provided on one flange of each bobbin in diametrically-opposed positions.

4. An assembly according to claim 1, 2 or 3, wherein each projection takes the form of a pin and each associated recess is located in a usher projection.

5. An assembly according to any one of claims 1 to 4, wherein the flanges of the cores have apertures for receiving the projections and recesses.

6. An assembly according to any one or claims 1 to 4, wherein the flanges of the cores have slots for receiviny the projectiol)s and recesses.

7. A bobbin assembly according to any one of claims 1 to 6, wherein the abutting flanges of the cores are also fixed or located one to another.

8. A bobbin assembly for use in electric motors; said assembly comprising a pair of bobbin structures each composed of an annular bobbin onto which a coil can be wound and an annular metallic core provided with an array of axially extending teeth engaging within the associated bobbin; wherein the bobbin structures are provided with interengageable projection and recess means serving to locate the bobbin structures relative to one another to prevent misalignment and to inhibit relative rotation between the bobbin structures.

9. A bobbin assembly substantially as described with reference to, and as illustrated in, Figs. 2 and 3 of the accompanying drawings or Figs. 2 and 3 as modified by Fig. 4 of the accompanying drawing.

1 0. An electric motor or generator employing as a stator a bobbin assembly in accordance with any one of the preceding claims.