Multilayered coil structure
This is a continuation, of Application Ser. No. 945,836, filed Sept. 26, 1978 now abandoned. 
    
    
     The present invention relates to a multilayered coil structure adapted for use in coreless motors. 
     In an ordinary coreless motor shown in FIG. 1, a cylindrical cup-shaped yoke 1 is provided at the center of its bottom portion with an insulating central support member 2, on which mounted is a cylindrical permament magnet 3 disposed coaxially within the yoke 1. In a center hole of the support member 2, a rotary shaft 5 is rotatably supported as born by insulating bearings 4 so that the shaft 5 will extend axially through the magnet 3, and a cylindrically wound rotor coil 6 is coupled to an inner end of the shaft 5 by means of an insulating disk 7 so that the coil 6 is disposed coaxially and rotatably in a cylindrical magnetic gap between the cup-shaped yoke 1 and the cylindrical magnet 3. The disk 7 secures on one surface opposite to the shaft 5 a plurality of commutator segments 8 arranged radially and connected to the coil 6, and brushes 9 for supplying a source power to the commutator segments 8 are brought into contact with them as supported by an insulative closure disk 10 of opened edge of the yoke 1. 
     For the rotor coil of the motors having the above structure, there has been usually employed a multilayered coil specifically in the case when it is desired to increase the motor torque. FIG. 2 shows schematically an example of the multilayered coil such as disclosed in the U.S. Pat. No. 3,360,668, wherein 11 is an inner coil forming the first layer and 12 is an outer coil forming the second layer and these first and second layer coils are wound sequentially. For the purpose of mutually connecting the separately wound coils of the first and second layers, the first layer coil 11 is provided with, for example, three intermediate taps 13, 14 and 15 while the second layer coil 12 is provided similarly with three intermediate taps 16, 17 and 18, and these taps are respectively cut into two portions, that is, for example, the tap 13 is cut into tap portions 13&#39; and 13&#34; as shown in FIG. 3 and these portions are mutually connected to form connections 13&#39;-16&#34;, 13&#34;-17&#39;, 14&#39;-17&#34;, 14&#34;-18&#39; and so on. Such coil structure requires, therefore, combersome steps of forming the taps, cutting them in two and mutually connecting the cut tap portions, and the respective steps must be repeated depending on the number of the taps which corresponds to the number of the commutator segments, so that the manufacture of the coil as well as the motor of the kind referred to has to become complicated and expensive. The present invention has been suggested to remove these drawbacks of the conventional multilayered coil. 
     According to the present invention, the above-mentioned drawbacks has been successfully removed by a provision of a cylindrical coil of a multilayer structure wherein an inner coil and an outer coil are continuously wound for each coil section corresponding to each commutator segment, namely for each circumferential length of πd/n of the cylindrical coil, wherein n being the number of commutator segments so that the entire coil structure will be wound continuously as a whole. 
     Principal object of the present invention is, therefore, to provide a multilayered coil structure which is easy to manufacture. 
     Another object of the present invention is to provide a multilayered coil structure wherein the order of coil winding is less perturbed in the vicinity of crossing parts of coil wire connecting between the respective layers of respective coil sections. 
     Still another object of the present invention is to provide a multilayered coil structure allowing a high-density winding. 
    
    
     Other objects and advantages of the present invention will be made apparent from the following detailed description of preferred embodiments thereof shown in accompanying drawings, in which: 
     FIG. 1 is a schematic sectioned view of an exemplary structure of general coreless motors; 
     FIG. 2 is perspective view showing schematically an example of conventional multilayered coil; 
     FIG. 3 is a diagram showing the manner in which the respective coil sections are connected between the respective layers in the case of FIG. 2; 
     FIG. 4 is a diagram for explaining the connection in a coil according to an embodiment of the present invention as shown in FIG. 5; 
     FIG. 5 is a perspective view showing schematically a coil according to an embodiment of the present invention; 
     FIG. 6 is a developed view of a coil according to another embodiment of the present invention for showing schematically its winding manner; 
     FIG. 7 is a perspective view of the coil according to the embodiment of FIG. 6; and 
     FIG. 8 is a developed view of a coil according to a further embodiment of the present invention for showing schematically its winding manner. 
    
    
     Referring to a first embodiment of the present invention with reference to FIGS. 4 and 5, respective coil sections L 11 , L 12 , L 13 , L 14  and L 15  disposed along an internal circular position form a first layer L 1 , and other coil sections L 21 , L 22 , L 23 , L 24  and L 25  disposed along an outer circular position form a second layer L 2 . A coil wire is wound to run diagonally from an axial end edge to the other of a cylindrical shape and sequentially side to side as folded back at each of the edges as seen in FIG. 5 which illustrates a case of five commutator segment, i.e. n=5 as an example. 2a is the start point of the entire coil from which the coil section L 11  of the first layer L 1  extends a circumferential length of πd/5 and then, via a crossing part 2b, the coil forms the outer layer from a point corresponding to the start point 2a to extend a circumferential length of πd/5 outside along the section L 11  so as to form the section L 21  of the second layer L 2 . The coil further continues, via a crossing part 2c, to form the inner first layer section L 12  which extends a circumferential length of π/5, the terminating end of which is connected, via a crossing part 2d, to the outer second layer section L 22 . The inner first layer sections L 11  -L 15  and outer second layer sections L 21  -L 25  are wound in this manner over the entire circumference of the coil&#39;s cylindrical shape. Thus, the multilayered coil of the present invention is formed in a remarkably simplified continuous manner as readily seen in FIG. 5, without requiring the conventional formation of intermediate taps and connection of cut parts of the taps. The crossing parts, except for crossing part 2a-2e which constitutes the interconnection between the ends of the coil wire, are thus integrally continuous in the sense that they have never been broken and reconnected. 
     In FIGS. 6 and 7, there is shown a second embodiment which provides a multilayered coil having smoothly formed end edges of the coil&#39;s cylindrical shape. In FIG. 6 showing the manner of coil winding in a developed view of the coil, respective solid lines represent respective turns of the coil wire in the first or inner layer while broken lines represent respective turns of the coil wire in the second or outer layer. The initial turn of the inner layer extends diagonally in alternate directions between the both edges in the order of 21→22→23→24 . . . , while the initial turn of the outer layer extends diagonally in the order of turns 21&#39;→22&#39;→23&#39;→24&#39; . . . In this structure, a wire turn 21&#39;-22&#39; of the second layer, for example, is located adjacent to and between wire sections turns 21-22 and 24-25 of the first layer, and such turns are arranged as if rods are piled in two layers. In this case, the crossing part of the wire between the final turn 31-32 33-b of the first layer and the initial turn c-33&#39;-34&#39;-22&#39; of the outer layer defines a path b-A 1  -c as shown with broken line in FIG. 6. In this structure, the crossing part b-A 1  -c includes a first portion b-A, extending parallel to a wire turn 31-32-33 of the first layer. The crossing part is again folded back at a point A 1  in the vicinity of the intersection of turns 21-22 and 31-32 to form a second portion extending parallel to turn 21-22. The wire is then folded back again at the edge point c to be shifted into the initial turn of the next section of the second layer. The folding point c is located between the points a and 22 on the same edge and is displaced from the point 22 by a distance equal to a half of the wire diameter. 
     It will be appreciated that the turns of the coil extend diagonally and completely circumferentially since each turn extends along opposite sides of the coil. The coil comprises a plurality of coil sections, each section including an inner layer and an outer layer. Each inner and outer layer includes an initial turn and a final turn. The crossing part of a given coil section interconnects a termination point of the final turn of the inner layer with the initial turn of the outer layer such that the initial and final turns of the outer layer are disposed adjacent to the initial and outer turns, respectively, of the inner layer. For example, in the embodiment described in connection with FIG. 6, the inner layer of the first coil section has an initial turn 21→22→23→24 and a final turn 31→32→33-b. The crossing part b-A 1  -c interconnects the termination point b of that final turn with the initial turn c-33&#39;→21&#39;→22&#39; of the outer layer of the same coil section. The crossing part is located axially inwardly of the associated axial end of the coil and is positioned in between the inner and outer layers. 
     FIG. 7 shows in a perspective view the coil formed in the above described manner, wherein broken B indicates the thrus-formed crossing parts. In the case of, for example, n=5, there will be provided five of such crossing parts. 
     FIG. 8 shows a further embodiment in which the folded crossing parts are provided along the other edge of the cylindrical coil. Other arrangements of the wire turns are the same as those shown in FIG. 6. 
     According to the embodiments of FIGS. 6 to 8, there are provided such advantages that: 
     (1) Smooth formation of the entire coil can be easily achieved as the crossing parts of the wire are not disposed out of the axial end edge of the coil. 
     (2) Any accident resulting from a rare arrangement of turns, shortcircuit specifically between the crossing parts and wire breakage can be prevented, as the wound coil turns are less perturbed at the crossing parts. 
     (3) Axial length or height of the coil can be stabilized to be uniform over the entire axial edge. 
     (4) The same winding manner can be applied equally to the multilayered coils of more than two layers.