Coil-forming wire material and method of manufacturing such material

Abstract: A coil-forming wire material which can be efficiently arranged in slots of a motor core so as to down-size coil ends, thereby making the coil and a motor compact. The coil-forming wire material comprises a plurality of flexible thin wires (11). The thin wires are stuck at given portions (12) such that they have a predetermined cross sectional shape. The stuck portions serve as rigid portions, i.e. coil sides. The coil-forming wire material also has flexible connecting portions (13) where the wires are loose. The coil-forming wire material has the flexible connecting portions and the rigid portions which are arranged in an alternate manner. The flexible connecting portions serve as coil ends. The coil ends extend from the core with a small curvature due to the flexibility thereof.

Description: This invention relates to a coil-forming wire material according to the preamble of claim 1 and to a method of manufacturing such a coil-forming wire material. In a motor, a stator generally comprises a core 102 and an enamel-insulated coil-forming wire material 101 (called "wire material 101") wound around the core 102 as shown in Fig. 1 of the accompanying drawings. Referring to Fig. 2, the core 102 is made of a plurality of laminated annular metal plates 102a. Further, the core 102 has a plurality of axially formed slots 103 on its inner surface. The wire material 101 is wound around the core 102 through optional slots, thereby forming a coil. When current is applied to the wire material 101, a magnetic flux is generated through the coil, so a motor is driven. In the coil, a portion of the wire material 101 passing through the slot 103 is called "a coil side 101a" while a portion of the wire material connecting coil sides 101a is called "a coil end 101b". In the motor using such a stator, it is required to effectively arrange the wire material in the slots so as to enable the motor to produce a high output and to be made compact. To meet such a demand, proposals have been made to cause a wire material to have a rectangular cross section instead of a conventional circular cross section such that adjacent turns of the wire material can be in close contact with one another at flat portions thereof. This can reduce spaces present between the adjacent turns of the wire material, and enables the wire material to be efficiently arranged in the slots. However, such a rectangular wire material tends to become more rigid, which means that a coil end would have a large curvature, and project extensively from the stator core. Thus, the coil itself would become larger, enlarging a motor as a whole. Further, a greater force is required to wind the wire material around the core, which would lengthen the time taken to manufacture coils. In another motor, it has been proposed to flatten a wire material at coil sides thereof passing through slots. The flat portions of the wire material can be efficiently and closely arranged in the slots. However, there is a difference of height at a border between the flattened and non-flattened portions of the wire material. In order to arrange the flattened portions tightly in the slots, it is necessary that such a border should be far from ends of the slots. This means that the coil ends extensively project from the stator core, enlarging the motor as well as the coil. The prior art according to document US-A-4 635 350 shows a coil forming wire material which is woundable around a core of a motor through slots of the core. The coil-forming wire is a single bar with a predetermined cross-section comprising rigid portions to be arranged in the slots and serving as coil sides, and comprising a plurality of connecting portions for connecting these rigid portions and serving as coil ends projecting from the slots. Furthermore, the prior art according to the DE-B-1 489 900 shows a coil forming wire material comprising a plurality of loosely bound portions serving as coil ends and a plurality of rigid portions pressed together so as to adopt a predetermined cross-sectional shape for the arrangement in the stator slots to serve as coil sides. Further, the wire of the rigid portions are pressed together so that they are stuck together to give the rigid portions a specific cross-section. It is an object of the present invention to provide an improved coil-forming wire material and an improved manufacturing method thereof, which results in a more compact motor. This object is achieved by a coil-forming wire according to claim 1 and by a manufacturing method according to claim 2. In this arrangement, the rigid portions are made of a single wire, which can be efficiently arranged in the slots. Further, the rigid portions are joined by the connecting portions made of a plurality of thin members, which are flexible enough to be curved in accordance with the shape of the core. Thus, the connecting portions do not extensively project from the core, which is effective in making the motor compact. The rigid portions may preferably have a rectangular cross section, and can be efficiently arranged in the slots with their wide surfaces facing one another, enabling the motor to produce a high output and be made compact. The connecting portions are formed by partially dividing the single wire into a plurality of threads. Since the single wire is processed so as to have the rigid portions and the connecting portions, the rigid portions can be efficiently arranged in the slots, and the flexible connecting portions do not extensively project from the core, which can down-size not only the coil but also the motor. The connecting portions are joined to the single wire. The rigid portions and the connecting portions can be easily formed. Further, the rigid portions made of the single wire can be efficiently arranged in the slots, and the flexible connecting portions do not extensively project from the core, which can down-size not only the coil but also the motor. The method as claimed in claim 2 is effective in manufacturing the coil-forming wire material having the rigid portions which can be efficiently arranged in the slots and the flexible connecting portions. The wire material can be easily wound around the core of the motor. Brief Description of the Drawings An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Fig. 1 is a schematic view of a conventional coil-forming wire material wound around a stator core of a motor; Fig. 2 is a top view of the stator core; Fig. 3 is an external view of a coil-forming wire material according to an embodiment of the invention; Fig. 4 schematically shows a method of manufacturing the coil-forming wire material; Fig. 5A schematically shows a coil-forming wire material before it is processed by a method according to the present invention; Fig. 5B shows that the coil-forming wire material is rolled and flattened so as to obtain a flexible connecting portion; and Fig. 5C shows that the flattened portion of the coil-forming wire material is cut into thin threads. Description of the Preferred Embodiment In an embodiment shown in Fig. 3, a wire material 20 includes a number of rigid portions 21 and a number of flexible connecting portions 22, i.e. the rigid portions 21 and the flexible connecting portions 22 are alternately arranged. The wire material 20 is wound around a stator core with the rigid portions 21 passing through the slots. The rigid portions 21 are packed in the slots with reduced spaces therebetween. However, when each rigid portion 21 is a single enamel-insulated wire having a prismatic cross section joined by welding or by crimping to the flexible connecting portion 22 made of cylindrical thin wires in a bundle of the same thickness as the rigid portions 21 (cf. Fig. 4), the cross-sectional area of the flexible connecting portions 22 is less than that of the rigid portions 21, because of the spaces between the wires. It is therefore necessary to increase the cross-sectional area of the flexible connecting portions 22 until it equals that of the rigid portions 21. However, this causes the flexible connecting portions 22 to become bulkier than the rigid portions 21. If the flexible connecting portions 22 are longitudinally superimposed with respect to the rigid portions 21, it is impossible to keep the rigid portions 21 tightly stacked in the slot. Therefore, the cylindrical thin wires of the flexible connecting portions 22 are arranged in a flattened bundle, creating a roughly oval cross-section. When the wire material 20 is wound around the core, the rigid portions 21 are tightly stacked in the slots, and the flexible connecting portions 22 are not taller than the rigid portions 21, making it possible to avoid the problem of the coil end projecting out from the stator core. When the wire material 20 is wound around the stator core, the flexible connecting portions 22 constitute coil ends. The flexible coil ends allow a small curvature, and do not project extensively, which reduces the sizes of a coil and a motor. The wire material 20 of Fig. 3 is manufactured by a method shown in Figs. 5A to 5C. In this case, a single enamel-insulated wire 30 is used, which has a rectangular cross section and is somewhat rigid. The wire material 30 is marked out into rigid portions 30a and flexible connecting portions 30b in accordance with positions of the slots of the stator core, as shown in Fig. 5A. Referring to Fig. 5B, the wire material 30 is rolled and flattened at the flexible connecting portions 30b. Thereafter, the flattened flexible connecting portions 30b are cut, by a laser beam machine or the like, into thin threads 31, as shown in Fig. 5C. The foregoing process is repeated for the remaining flexible connecting portions 30b, thereby obtaining the wire material 20 of a desired length. The coil-forming wire materials according to the invention can be wound not only around the stator core of the motor but also around a rotor core of a motor having slots on its outer surface.

Claims: Coil-forming wire material continously woundable around a core (102) of a motor through slots (103) of the core, said coil-forming wire material comprising a single wire (10, 20, 30) having a predetermined cross-section and including rigid portions (21, 30a) to be adapted for arranging in the slots (103) and serving as coil sides, and a plurality of connecting portions (22, 30b) for connecting said rigid portions (21, 30a), said connecting portions (22, 30b) are made of a plurality of thin members, and serve as coil ends being adapted to be projectable from the slots, characterized in that said connecting portions are formed by partially dividing said single wire into a plurality of threads. Method of manufacturing a coil-forming wire material continously woundable around a core (102) of a motor through slots (103) of the core, said method comprising the steps of: (a) forming rigid portions (21, 30a) in a single wire, said rigid portions to be arranged in slots (103) and serving as coil sides; and (b) rolling and flattening portions of said single wire between said rigid portions (21, 20a); and (c) cutting said flattened portions into a plurality of threads and forming connecting portions as coil ends extending from the slots. A coil-forming wire material according to claim 1, characterized in that said rigid portions have a rectangular cross-section.

Inventors: MIYAZAKI HIROSHI, MIYAZAKI, HIROSHI, MIYAZAKI, HIROSHI, C/O TOYOTA JIDOSHA K.K.
Applicants: TOYOTA MOTOR CO LTD, TOYOTA JIDOSHA KABUSHIKI KAISHA
Application year: 1996
Main classification: H02K15
IPC codes: H02K3, H02K15