FIELD COIL WINDING

Abstract: A method and apparatus for winding field coils on in­ ternal poles of stator bodies, particularly for electric motors, have a magnet wire feeding needle or needles displaced eccentrically from the central armature axis of the stator body. The or each such feeding needle is disposed to reciprocate and partially rotate on an eccentric axis located between the central armature axis and the internal pole being wound. Due to this eccentricity, during the partial rotation of the feeding needle, the end turns of the coil are lifted above the end of the pole and laid more precisely in place. This enables the con­ ventional winding forms to be eliminated allowing a reduc­ tion in the length of the reciprocating stroke of the feeding needle and faster winding with reduction in "snap back" ef­ fect. A further cost saving occurs from a shorter length of the end turns resulting in less wire being used.

Description: FIELD OF THE INVENTION This invention relates to a method and apparatus for winding a field coil around an internal pole of a stator. BACKGROUND OF THE INVENTION Electric motors commonly have a hollow stator such as a laminated stator stack, having internal poles around which are wound field coils. Such field coils can be wound in pairs by a hollow wire feeding member having a pair of oppositely directed arms at its leading end from which two field coil wires are simultaneously fed. The wire feeding member reciprocates through the hollow stator on the central axis thereof, which is the rotational axis of the armature in the subsequently completed electric motor, and rotates through 180 degrees about this central axis at each end of each reciprocating stroke to wind two field coils on diametrically opposed internal poles. An integral part of this winding process is to first locate winding forms or horns at the outer ends of the poles to enable the magnet wires to be guided around the ends of the poles during the winding process; these winding forms then being removed after the field coils are wound. Such winding forms are disclosed, for example, in US Patent Nos. Reissue 28,831; 4,074,418; 3,648,938; and Reissue 25,281. The latter three patents also disclose and illustrate machines for winding field coils on internal poles. Further, Reissue 28,831 clearly illustrates the usual configuration of a pair of internal poles of a stator and also the filed coils when wound thereon. GB-A-2068787 discloses a method of winding a field coil around an internal pole of a stator having a passage therethrough defining an axis for rotation of an armature therein relative to said internal pole, said method comprising the steps of: feeding a field coil wire; oscillating the feeding of said field coil wire internally of said stator past said internal pole; and moving the feeding of said field coil wire transversely to said axis adjacent an end of said internal pole along a path which extends over the end of the internal pole, said oscillating and said moving effecting winding of the field coil around said internal pole without the employment of temporarily positioned winding forms. EP-A-0200236 published on November 5, 1986, thus falling under art. 54(3), discloses a method and a machine for forming windings on electric motor stators, comprising means for positioning a hollow stator having a central axis and at least one pole piece relative to a needle so that the longitudinal axis of the needle is excentric to said central axis of the stator; said longitudinal axis of said needle being maintained at a predetermined distance from said central axis of said stator and the end of the needle, from which the wire is delivered, projects outwardly alongside said pole piece at an end of said stator during rotation of said needle about said longitudinal axis; the machine and method enable the use of the traditional forming shoes and the relative tensioning devices to be dispensed with, so improving the winding quality and reducing the longitudinal reciprocating stroke of the needle. This invention is directed to a method of winding a field coil around a plurality of internal poles of a stator having a passage therethrough defining an axis for rotation of an armature therein relative to said internal poles. According to the invention the method comprising the steps of: feeding a plurality of field coil wires drawn from a plurality of wire feeding members ; reciprocating said wire feeding members along respective operating axes and partially rotating said wire feeding members on said respective operating axes when adjacent each end of said internal poles ; positioning the stator and said wire feeding members such that said armature axis is parallel to said axes and said operating axes are spaced apart on opposite sides of said armature axis ; said reciprocation and said partial rotation effecting winding of the field coil around said internal poles without employment of temporarily positioned winding forms. The present invention also provides an apparatus for winding a field coil a plurality of internal pole of a hollow stator which defines an armature axis for rotation thereon of an armature. Said apparatus comprises: a plurality of feeding members ; means for reciprocating said wire feeding members along respective operating axes and partially rotating wire feeding members on said respective operating axes ; means for positioning the stator and said wire feeding members such that said armature axis is parallel to said operating axes and said operating axes are spaced apart on opposite sides of said armature axis. For a better understanding of the present invention reference will now be made, by way of example, to the accompanying drawings, in which:- FIGURE 1 shows an end view of a stator and depicts the concept on which the present invention is based; FIGURE 2 is a diagrammatic representation of the motion path of the feeding of the field coil wire using the concept of FIG. 1; FIGURE 3 is a diagrammatic elevational view, with a conveyor in section, of a coil winding machine according to the invention for carrying out an internal coil winding process of the invention; FIGURE 4 is a downward view on the line IV-IV of FIG. 3, with some parts omitted for simplicity, and the wire feeding members lowered from their position in FIG. 3; FIGURE 5 is a side representation of one end of a stator depicting the shape of one end of a field coil wound with the machine of FIGS. 4 and 5; FIGURE 6 is a similar representation to FIG. 5 but depicting one end of a conventionally wound field coil; FIGURE 7 is section on the line VII-VII of FIG. 4 of an individual pallet for supporting and positioning a stator (the stator being omitted); FIGURE 8 is a schematic representation of a stator assembly production flow line according to the invention; FIGURE 9 is a diagrammatic representation of the laying of end turns during the conventional winding of a field coil; and FIGURE 10 is a similar diagrammatic representation of the laying of the end turns of a field coil wound utilizing the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiment of the invention is shown in FIGS. 3, 4, 7 and 8. FIGS. 1, 2, 5, 6, 9 and 10 are diagrammatic representations to help understanding of the invention. The invention is particularly for winding field coils on internal poles of stators for electric motors; however, the invention can also be utilized for winding internal field coils for other electrodynamic machines. FIG. 1 shows an end field of an electric motor stator which is hollow having a central opening 12 extending therethrough for the length thereof. Two opposed internal poles 16, 18 extend into the central opening 12 and extend axially the length of the passage formed by the opening 12. Each pole 16, 18 has portions separated from the cylindrical body part of the stator 14 by a pair of slots 20 with a neck portion 22 therebetween connecting the internal pole to the stator. The whole stator is preferably formed as a laminated stator stack. The internal surfaces of the internal poles 16, 18 are cylindrical and are concentric with a central axis C of the stator 14. In the completed electric motor, an armature rotates about the axis C relative to the stator 14. A field coil is wound about each internal pole 16, 18, the turns of the coil passing lengthwise through the slots 20 on each side of the neck portion 22 with end turns passing around the outside of the neck portion 22 at each end of the stator. A wire feeding member having a rotatable arm 24 dispenses the wire from its outer end as it moves. This arm 24 would, if conventional, rotate about the central axis C to lay the end turns across the ends of the poles, and conventionally the arm would reciprocate along the central axis C to draw the wire through the length of the slots 20. In the embodiment shown, the arm 24 is rotatable about and reciprocates along an eccentric axis E, eccentrically displaced from the central axis C towards the internal pole 16 being wound. The eccentric arc Y swept by the dispensing end of the arm 24 starts adjacent the entrance to the lefthand side slot 20 and then sweeps up over the neck portion 22, that is well above the chord X across the neck portion 22 connecting the innermost ends of the somewhat tapered slots 20. The arc Y then finishes adjacent the entrance to the righthand slot. By having the centre E of this arc Y eccentric to the central armature axis C and located between the internal pole 16 and the axis C, the arc Y causes the wire being fed to lift up over the internal pole 16 instead of being initially drawn across the chord X. When the arc Y is completed in the direction of the arrow 26 and the arm 24 makes a reciprocating stroke through the central opening 12 along the eccentric axis E, the wire just laid by the arc Y will be drawn down across the chord X. Successive turns of the field coil are built up in this way with each end turn portion being lifted up over the internal pole 16 and then drawn down against previously wound end turns. The distance by which the end turns are lifted above the internal pole 16 can be selected by selecting the eccentricity of the axis E relative to the central axis C. The less the amount of this eccentricity, the tighter and flatter the end turns are wound; the greater this eccentricity, the higher the middle of the arc Y lifts the wire as it is wound above the internal pole, and any plastic coil support extending axially therefrom, and above previously wound end turns. Depending on the shape, size, and number of turns in the field coil, the eccentricity of the eccentric axis E may remain constant throughout winding or may be stepwise or continuously increased or decreased during the winding of each field coil. After each partial rotation of the wire feed through the arc Y, the arm moves to the opposite end of the stator 14 and another arc Y, only in the opposite direction of rotation to the arrow 26, is performed, the arm 24 returning along the eccentric axis E to the position shown in FIG. 1 to complete one turn of the coil. It will be noted that due to the eccentricity of the eccentric axis E, the arm 24 can be longer than if it were centred at the central axis C. Also, the arc Y can subtend different angles about the eccentric axis E, although for shallow lift the angle subtended about eccentric axis E may be less than 180 degrees, for greater lift it should be greater than 180 degrees. It will also be noted that the arc Y increases in distance from the central axis C as it passes over the pole being wound. FIG. 2 illustrates the motion path of the feeding of the wire, which in FIG. 1 is the radial extremity of the arm 24. The path is turned through 180 degrees downwards from the orientation in FIG. 1. The arc Y is shown at the top, followed by a stretch Z which extends through the righthand slot 20 of the internal pole 16 in FIG. 1, then through a reverse arc y at the other end of the stator, and finally returning along the stretch z through the slot 20 on the lefthand side of the internal pole 16, as indicated by the arrows. It is preferable to start the reciprocation strokes along stretches Z, z before the wire feed completes the arc Y, y and to commence the wire feed along the arcs y, Y before the wire feed completes the strokes along stretches Z, z. Thus, the wire feed passes through a three dimensional curve as the arm 24 swings through the arcs Y and y, as depicted in FIG. 2, although such three dimensional curves will essentially be concentric to the eccentric axis E and eccentric to the central axis C. With the arrangement of FIG. 1, a single field coil is wound at a time, the stator 14 being rotated through 180 degrees after the field coil is completed around the internal pole 16 in order to wind a field coil on the opposite internal pole 18. Preferably, however, two wire feeding members, one on each side of the central axis C, are employed and simultaneously operated to wind field coils on both internal poles 16 and 18 at the same time. The arms of the two wire feeding members may reciprocate axially through the central opening 12 in unison or 180 degrees out of phase. The preferred field coil winding apparatus of FIGS. 3, 4 and 7 will now be described. FIG. 3 shows in section flanged side rails 28 of a conveyor system having a pair of endless belts 30 movable over the bottom flanges 32. A square base portion 34 of a pallet 36 is supported by the endless belts 30, an upper cylindrical portion 38 of the pallet 36 receiving therein the lower part of a vertically orientated stator assembly 40. A locating pin 42, actuated by an air cylinder 44, engages in a vertical bore 46 in the square base portion 34 of the pallet 36 to accurately index the pallet 36 below the coil winding machine. A second such locating pin (not shown) engages another vertical bore in the square base portion 34 of the pallet 36. Also the stator assembly 40 is accurately orientated in the upper cylindrical portion 38. Extending upwardly from the square base portion 34 on the opposite sides of the upper cylindrical portion 38 are posts 48, each having on the top a wire clamping clip 50, there being a pair of such posts on each side (see FIG. 4). The upper end of the stator assembly 40 has a plastic end ring 52, with terminal posts 54, attached to the stator 56. A plastic coil support 58 extends axially from each internal pole (see also FIG. 4). A wire feeding member 60, in the form of a tube, extends vertically downwards from a drive mechanism 62, the lower end of the wire feeding member being curved outwards to form an arm 64 from an outlet at the outer end of which a field coil wire 66 is dispensed. A second similar wire feeding member 68, behind the wire feeding member 60, similarly extends downwardly from the drive mechanism 62 and has an outwardly curved but oppositely directed arm 70 from an end outlet of which is dispensed a second field coil wire 72. A pair of air cylinders 74 operate push rods 76 to clamp down on the top of the stator assembly 40 to firmly hold it in place during coil winding. The drive mechanism 62 reciprocates and partially rotates the wire feeding member 60 in the same manner as described previously in relation to FIGS. 1 and 2. The drive mechanism 62 simultaneously operates the other wire feeding member 68. Wire gripping and locating arms 78, operated by drives 80, take the ends of the field coil wires 66 and 72 and inserts them in the respective wire clamping clips 50 before returning to their inoperative positions shown. FIG. 4 shows a downward view of the line IV-IV of FIG. 3 (with some parts omitted) clearly showing the square base portion 34 of the pallet 36 and the upper cylindrical portion 38 having a bore 82 in which snugly engages the stator 56. The relative disposition of the pairs of posts 48 and pairs of terminal posts 54 can be seen. The internal poles 16, 18 are identical to those described in FIG. 1, however only the neck portion 22 of each internal pole can be seen, the ends of the internal poles being covered by the plastic coil supports 58 extending axially therefrom. The arms 64, 70 of the wire feeding members 60, 68 extend in opposite directions, and the wire feeding members 60, 68 reciprocate and rotate, as indicated by the arrows, about eccentric axes 84, 86, respectively. The eccentric axes 84, 86 are diametrically and equally spaced eccentrically on opposite sides of the central axis C of the stator 56, each eccentric axis 84, 86 being located between the central axis C and the mid-point of the cylindrically curved surface of the respective internal pole. FIG. 7 shows a cross-section of the pallet 36 on the line VII-VII of FIG. 4 and shows a pair of posts 48 and the wire clamping clips 50 thereof extending up above the upper cylindrical portion 38 of the pallet 36. A step-like shoulder 88 is formed, on opposite sides of the vertical bore 82 through the pallet 36, at the junction between the square base portion 34 and the upper cylindrical portion 38 of the pallet 36, these shoulders 88 supporting the lower end of the stator assembly 40 when inserted. In operation the pallet 36 is indexed below the drive mechanism 62, wire feeding members 60, 68 etc., by the pair of locating pins 42, the push rods 76 clamp the stator assembly 40 in place in the pallet 36, and the wire gripping and locating arms 78 are operated to clamp the free ends of the field coil wires 66, 72 in the appropriate wire clamping clips 50. The wire feeding members 60, 68 are then lowered so that their arms 64, 70 are disposed just above the upper edge of the plastic coil support 58. The drive mechanism 62 then reciprocates the wire feeding members 60, 68 down and up through the central opening 12 of the stator 14 with the wire feeding members being partially rotated, as indicated by the arrows 90, when adjacent each end of the poles. The successive strokes of this oscillatory motion end just beyond the outer ends of the plastic coil supports 58 extending axially from each end of each internal pole 16, 18. The feeding of each field coil wire 66, 72 follows paths as shown in FIG. 2, but one being effectively the mirror image of the other, to simultaneously wind field coils on the two internal poles 16, 18. When the winding is completed the wire feeding members retract upwardly to their position in FIG. 3, the wire gripping and locating arms 78 are actuated to clamp the upwardly extending ends of the field coil wires 66, 72 in the pair of wire clamping clips 50, and the wires are then cut. The push rods 76 move upwardly, the locating pins 42 retract and the pallet 36 is moved onwards by the endless belts 30, the next stator assembly to be wound then being moved into position and indexed by the locating pins 42. The field coil wires are fed from the arms 64, 70 by being drawn therefrom as the arms 64, 70 move. By laying the end turns of each field coil closely over the ends of the plastic coil supports 58, the amount of "snap back" conventionally experienced, as the wire in the end turn being formed is tensioned during the immediately subsequent reciprocating stroke, is substantially reduced. This "snap back" may be even further reduced by shortening the length of the plastic coil supports 58 - or even eliminating them altogether, this being possible due to the tighter, more controlled and accurately formed end turns that are possible with the preferred embodiment. FIG. 5 diagrammatically represents end turns 94 that can be formed by the preferred embodiment, and FIG. 6 diagrammatically represents end turns 96 obtained when conventionally employing winding forms at the axial ends of the coil supports. Turning first to FIG. 6, due to the length of the conventionally used winding forms - as long as again or longer than the coil supports - the wire feeding extends a substantial distance past the ends of the internal poles before returning on the next reciprocating stroke. This not only creates substantial "snap back" (that may at times even break the wire), but caused control of the shaping and positioning of the end turn to be lost as the wire feeding point returns a substantial way back through the stator before the excess length of wire of the end turn is "snapped" tight. This results in end turns 96 shaped as in FIG. 6, and as can be seen, these tend to extend some distance beyond the end of the internal pole and also desirably require a retaining tab 92 as shown. Now turning to FIG. 5, due to the shorter reciprocating stroke as a result of the elimination of the winding forms, and due to the eccentricity of the axis about which the wire feeding member partially rotates, the end turns 94 are more precisely and tightly laid across the end of the internal pole resulting in a somewhat rectangular formation of these end turns 94. It will be appreciated that due to this tighter rectangular formation, which has reduced axial extension, less wire is employed in the field coil, so saving cost and increasing the power of the field coil as less length of wire results in a lower coil resistance with consequential higher amperage. Additionally, the plastic coil support 58 can be axially reduced in length and the end retaining tab eliminated. Additionally, due to the better winding control, the turns of the field coil can be more densely packed in the slots on each side of the pole. FIGS. 9 and 10 illustrate a further difference between the preferred embodiment and conventional internal coil winding employing winding forms. FIG. 9 shows a longitudinal section through a plastic coil support 98 and an abutting winding form 100 (in broken lines) in position. After each end turn is drawn over the winding form 100, it is drawn along the plastic coil support 98. Consequently, consecutively wound end turns 102, 104, 106 tend to want to lie side by side transversely across the plastic coil support 98 as the coil is built. On the other hand, as illustrated in FIG. 10, with the preferred embodiment, due to the eccentricity of the rotational axis of the wire feeding member, consecutively wound end turns 103, 105, 107 tend to want to lie on top of the other as the coil is built, each successive end turn tending to be lifted upon the previous end turn to the limit of the eccentric displacement of the axis of the wire feeding member from the central axis of the stator. FIG. 8 shows schematically according to an aspect of the invention a preferred manner of incorporating the coil winding of the present invention into a production line with online operating stations. Pallets 36 are successively moved through the production line on a conveyor system as indicated by the arrows. At the first station 110 a fan end ring followed by a stack of laminations are dropped into an awaiting pallet, and the laminations welded together to form a stator with the fan end ring being attached thereto. At the next station 112, slot insulating liners are inserted in the slots on each side of each pole. At the next station 114, a commutator end ring is loaded on the upper end of the stator. The conveyor system then moves successive pallets to four coil winding stations 116 as shown in FIG. 3, these four coil winding stations effectively being in parallel and can conveniently all be simultaneously operated from the same drive mechanism 62. As the pallets 36 leave the coil winding stations 116 they are coupled in pairs and moved through a terminating station 118 at which the two pairs of wire ends clamped in the four wire clamping clips 50 on the pallet are removed and crimped in four respective terminal posts 54 in the plastic end ring 52, any excess length of wire being trimmed as necessary during this operation. The pairs of pallets 36 are then moved through a bonding station 120 at which a current is passed through the field coils to bond together the resin coating on adjacent turns of the field coil wire. After testing, the stator assemblies are ready for assembly into electric motors. In conventional production of stator assemblies, the coil winding is the slowest operation and forms a bottleneck tending to limit the production rate of the line. Such conventional coil winding usually requires time for handling, positioning and removing the winding forms, time to terminate the ends of the coil wire to the stator before and after coil winding, and time to wind the field coils. This total time is typically 22 to 24 seconds. With the preferred embodiment, by eliminating the winding forms, shortening the strokes of the wire feeding members, and simplifying wire end securing (with actual termination at a separate faster downstream station), total time at the coil winding station should be reduced to the order of 9 to 10 seconds. All other stations in the production line of FIG. 8 have a total operating time of the order of 3 to 4 seconds except the bonding station 120 with an operating time of 5 to 6 seconds. Thus by using the coil winding process of the preferred embodiment and the production line of FIG. 8 as modified by the present invention, the production rate of stator assemblies can be approximately doubled from the 500 to 600 per hour of conventional production lines to about 1000 to 1200 per hour. For example, when winding field coils in stators having end rings without coil supports, or even without end rings, a coil support or supports may be incorporated in the coil winding machine and moved next to the ends of the internal poles before coil winding to temporarily support the radially innermost end turn as these are wound. These supports, which may be somewhat like cylinders with axes parallel to the stator armature axis, may then be moved away from internal poles towards the armature axis after coil winding before the wire feeding members are withdrawn, together with these support cylinders, upwards above the wound stator. Further, the coil winding machine may be located below the conveyor in FIG. 3 and the wire feeding members inserted upwardly through the pallet into the stator which would be differently supported and clamped in the pallet. Also, the length of the reciprocating strokes of the wire feeding members may be varied during the coil winding, e.g. , may be stepwise lengthened, particularly with smaller eccentric displacement of the axes 84, 86.

Claims: A method of winding a field coil around a plurality of internal poles (16, 18) of a stator (14, 56) having a passage (12) therethrough defining an axis (C) for rotation of an armature therein relative to said internal poles (16, 18) said method comprising the steps of: feeding a plurality of field coil wires (66, 72) drawn from a plurality of wire feeding members (60, 68); reciprocating said wire feeding members (60, 68) along respective operating axes (E) and partially rotating said wire feeding members (60, 68) on said respective operating axes (E) when adjacent each end of said internal poles (16, 18); positioning the stator (14, 56) and said wire feeding members (60, 68) such that said armature axis (C) is parallel to said axes (E) and said operating axes (E) are spaced apart on opposite sides of said armature axis (C); said reciprocation and said partial rotation effecting winding of the field coil around said internal poles (16, 18) without employment of temporarily positioned winding forms. A method according to claim 1, characterized in that each of said internal poles (16, 18) comprises a neck portion (22), and a portion which extends transversely away from said neck portions (22) on each side of said neck portions (22) to define circumferential slots (20) on each side of said neck portions (22) between said internal poles (16, 18) and a main body portion of said stator (14, 56) and said rotation of each of said wire feeding members (60, 68), when adjacent each end of said internal poles (16, 18) commences in said passage (12), adjacent the entrance to one slot (20), passes radially beyond said neck portion (22) and returns to said axial passage (12) adjacent the entrance to the slot (20) on the other side of said neck portion (22). A method according to claim 1 characterized in that it comprises the step of securing an end of said field coil wires (66, 72) relative to said stator (14, 56) before winding said field coil, and wherein said emitting step comprises drawing said field coil wires (66, 72) from said wire feeding members (60, 68) by movement of the latter. A method according to claim 3, characterized in that it comprises the step of supporting said stator (14, 56) on a pallet (36), and performing said securing by attaching said end to said pallet (36). A method according to claim 4, characterized in that it comprises the step of removing said end from said pallet (36) after said field coils have been wound, and then securing said end to a terminal of said stator (14, 56). A method according to claim 4, characterized in that it comprises the step of mounting a terminal end ring (52) on an end of said stator (14, 56) and wherein said terminal is supported by said end ring (52). A method according to claim 5, characterized in that it comprises the step of mounting a brush and bearing support structure at an end of said stator (14, 56) before said field coil is wound, and wherein said terminal is on said brush and bearing support structure. A method accrding to claim 1, characterized in that two wire feeding members (60, 68) are reciprocated along respective axes parallel to but displaced to opposite sides of said stator (14, 56) axis (C). A method according to claim 8, characterized in that said two wire feeding members (60, 68) are simultaneously partially rotated in such way that one is effectively the mirror image of the other, to simultaneously wind field coils on the two internal poles (16, 18). An apparatus for winding a field coil on a plurality of internal poles (16, 18) of a hollow stator (14, 56) which defines an armature axis (C) for rotation thereon of an armature, said apparatus comprising: a plurality of feeding members (60, 68); means for reciprocating said wire feeding members (60, 68) along respective operating axes (E) and partially rotating wire feeding members (60, 68) on said respective operating axes (E); means for positioning the stator (14, 56) and said wire feeding members (60, 68) such that said armature axis (C) is parallel to said operating axes (E) and said operating axes (E) are spaced apart on opposite sides of said armature axis (C). An apparatus according to claim 10 characterized in that said operating axis are disposed on diametrically opposite sides of the armature axis (C), and further comprising common drive means (62) for reciprocating and partially rotating both said wire feeding members (60, 68) together. An apparatus according to claim 10 characterized in that each wire feeding member (60, 68) comprises a hollow tube with a single transversely extending arm (64, 70) at one end and from which wire is drawn as the arm moves. An apparatus according to any of claims 10 to 12, characterized in that said positioning means comprises conveyor means (30) for conveying a pallet (36) containing said stator (14, 56) to a location adjacent said wire feeding members (60, 68), and indexing means (42) for indexing said pallet (36) to correctly position the armature axis (C) of said stator (14, 56).

Inventors: WHEELER, DALE K.
Applicants: AXIS S.P.A.
Application year: 1985
Main classification: H02K15
IPC codes: H02K15