A method of manufacturing a stator of an AC generator for a vehicle

Abstract: A stator (2) of an ac generator for vehicle has a stator core (32) which is a lamination of steel sheets and has a plurality of slots (35) cut out in a cutout direction. A plurality of insulators (34) and, subsequently, electric conductors are respectively inserted into the plurality of slots (35) in the cutout direction. The insulators (34) are prevented from being damaged by sharp-edged burs (35a) formed when the plurality of conductor segments (33) are inserted in the cutout direction.

Description: The present invention relates to a method of manufacturing a stator of a vehicle ac generator according to claims 1 and 2. From PATENT ABSTRACTS OF JAPAN vol. 097, no. 011, 28 November 1997 (1997-11-28) & JP 09 191614 A (TAKAMORI:KK), 22 July 1997 (1997-07-22) a motor core, a method and engine for manufacturing the motor core is known. To prevent deterioration of dielectric strings by laminating a plurality of block segments, produced by punching a thin metal plate, such that the burs of outermost layer are not directed outward and then caulking the block segments integrally, an adverse effect of the burs on the painting performance is eliminated. Among the block segments, the block segment of the lowermost layer is punched. upward so that burs are directed upward and other block segments are punched downward so that burs are directed downward. A plurality of block segments having burs of different direction are laminated on the block segment of the lowermost layer and then they are caulked integrally. According to this known structure the effect of burs is eliminated at the comer part between the slots of core for winding an armature winding and insulating paint can be applied uniformly. Consequently, dielectric strength is ensured sufficiently and the reliability is enhanced with this known construction. From WO 97 40567 A a stator of an electric machine is known, which includes: a back iron region from which extend adjacent, radially inwardly projecting stator poles that define winding slots, a winding comprising a number of turns of lacquer coated wire which are looped around the stator poles and wherein the stator comprises a stack of laminations of magnetizable steel sheets provided with cutouts so as to create sharp edges at the rim portions of the cutouts, a plurality of insulation liners disposed between the winding and the inner walls of the slots to prevent abrasion of the insulation lacquer of the winding during assembly. It is further known that a plurality of conductor segments are welded to form a stator winding of a stator of an ac generator for a vehicle. For example, WO92/06527 discloses a stator whose stator winding is formed of a plurality of U-shaped conductor segments. The conductor segments are inserted from an end of the stator core and connected to one another at portions thereof on the other end of the stator core. The stator can have regularly disposed coils more easily than the stator having a stator winding of continuously wound magnet wires. In WO92/06527, there is no description about the insulator disposed between the conductor segment and the stator core. However, such electric insulators are necessary under some circumstances. It is preferable that such insulators are inserted into the slots easily together with the conductor segments. Such insulators are insulation layers known as insulation coatings of magnet wires, insulation sheets disposed between conductor segments and a stator core, or insulation layers covering inner surfaces of the slots of the stator. It is well-known that a stator core is a lamination of stamped-out steel sheets having a plurality of slots. When the sheets are cut by a stamping machine, burs having sharp edges are formed an the peripheral comers of the sheet. The outer and inner peripheral edges of the stator core can be lathed or squeezed easily to remove the burs, thereby providing accurate sizes and roundness. However, the burs an the peripheral edges of the slots are not removed. Therefore, if conductor segments are merely inserted into such slots as disclosed in WO 92/06527, the insulation coating of the conductor segments may be broken by the sharp edges of the burs an the peripheral edges of the slots. Therefore, a main object of the invention is to provide a method of manufacturing a stator of a vehicle ac generator, which method guarantees a good insulation structure for protecting the slot-insulation layer from damage, and to provide a stator manufactured according to such method. According to the present invention the above object is solved by the features of claim 1. A second inventive solution of the above object results from claim 2. The inventive method of manufacturing a stator of a vehicle ac generator, starts out from the steps of: (a) cutting a plurality of slots from steel sheets so that sharp edges are created at the cutout slots; (b) forming a lamination of steel sheets; (c) inserting insulators into said slots; and (d) inserting conductor segments into said slots, and is characterized in that (a 1) with said cutting step (a) burs are created; (b 1) with said forming step (b) the steel sheets are laminated such that said burs are all extending in the same direction (cutout direction); (c 1) with said inserting step (c) said insulators are inserted in a direction, which corresponds to the cutout direction; and (d 1) with said inserting step (d) said conductor segments are inserted into said slots in said cutout direction. According to another embodiment of the invention, a method of manufacturing a stator of a vehicle ac generator is composed of a first step of forming a lamination of steel sheets, a second step of cutting a plurality of slots from the lamination in a cutout direction, a third step of inserting insulators into the slots in the cutout direction, a fourth step of inserting conductor segments into the slots in the cutout direction; and a fifth step of connecting the conductor segments extending from the slots to one another. A stator, which is manufactured by the methods of the present invention, includes a stator core having a plurality of slots, a plurality of conductor segments disposed in the slots, and a plurality of insulation layers disposed between inner peripheries of the slots and the conductor members. The stator core is a lamination of steel sheets having the plurality of slots cut out in a cutout direction to provide burs projecting from each of the steel sheets in the cutout direction, and the conductor segments are inserted into the plurality of slots in the same direction as the cutout direction. Accordingly the insulation layers are inserted into the slots smooth and are not damaged when the conductor segments inserted into the plurality of slots. Each of the conductor segments can have a U-turn portion at the back end of the stator core in the cutout direction. The stator core is a lamination of steel sheets having the plurality of slots cut out in a cutout direction, and the electric conductors are inserted into the plurality of slots in the same direction as the cutout direction. Accordingly, the conductor segments can be inserted smooth into the slots. Each of the electric conductor segments can have a U-turn portion at the back end of the stator core in the cutout direction. Therefore, the insulators can be prevented from being damaged when the conductor segments are inserted. Each of the insulation layers can have a folded lip at the back end thereof in the cutout direction. As a result, the insulators can be prevented from being damaged when the conductor segments are inserted. Each of the insulation layers can have a folded lip at the front end thereof in the cutout direction. As a result, the insulator can be prevented from being damaged when the conductor segments are bent to form coil ends. Other objects, features and characteristics of the present invention as well as the functions of related parts of the present invention will become clear from a study of the following detailed description, the appended claims and the drawings. In the drawings: Fig. 1 is a cross-sectional view illustrating an ac generator for a vehicle according to an examplary embodiment; Fig. 2 is a perspective view of a conductor segment forming a part of stator winding of a stator according to a first examplary embodiment; Fig. 3 is a fragmentary side view of the stator according to the first examplary embodiment; Fig. 4 is a fragmentary cross-sectional view of the stator shown in Fig. 3; Fig. 5 is a cross-sectional view of the stator shown in Fig. 4 cut along line V-V; Fig. 6 is an illustration of forming laminated stator core of steel sheets according to a first embodiment of the invention; Fig. 7 is a perspective view illustrating an insulator being inserted into a slot of the stator according to the first embodiment of the invention, Fig. 8 is a perspective view illustrating coil ends at both ends of the stator according to the first examplary embodiment Fig. 9 is a fragmentary cross-sectional view of the stator according to the first examplary embodiment having an insulator with folded lip at an end thereof; Fig. 10 is a fragmentary cross-sectional view of a variation of the stator according to the first examplary embodiment having an insulator with folded lip at the other end thereof; Fig. 11 is a fragmentary cross-sectional view of a stator according to a second examplary embodiment; Fig. 12 is a fragmentary perspective view of the stator according to the second examplary embodiment; Fig. 13 is a perspective view illustrating a variation of conductor segment; Fig. 14 is a side view of a stator according to a third examplary embodiment having the conductor segments shown in Fig. 13; and Fig. 15 is a fragmentary cross-sectional view of a variation of the stator according to the first examplary embodiment. An examplary embodiment is described with reference to the appended drawings. As shown in Fig. 1, ac generator 1 includes stator 2, rotor 3, frame 4, rectifier 5 and so on. Stator 2 is composed of stator core 32, a plurality of conductor segments 33 forming a stator winding and a plurality of insulators 34. Stator core 32 is a lamination of steel sheets, which has a number of slots formed inside thereof. The plurality of conductor segments project from opposite ends of stator core 32 to form coil ends 31 and are connected to one another to form a stator winding. Rotor 3 has field coil 8, a pair of front and rear pole cores 7 and shaft 6. Front and rear pole cores 7 respectively have six claw pole pieces extending axially to enclose field coil 8. Field coil 8 has a cylindrical body covered by an insulating coating. Axial flow type cooling fan 11 is welded to the front side pole core 7. Cooling fan 11 blows cooling air in the radial and axial direction from the front side thereof. Centrifugal cooling fan 12 is welded to the rear side pole core 7 to blow cooling air radially outward from the rear side thereof. Frame 4 accommodates stator 2 and rotor 3 and supports rotor 3 to rotate with shaft 6. Stator 2 is fixed to frame 4 around the pair of pole cores 7 at a certain gap therefrom. Frame 4 has air discharge vents 42 at portions opposite coil ends 31 of stator 2 and air intake vents 41 at the axial ends thereof. AC generator 1 described above is rotated in a certain direction by an engine (not shown) via a belt and a pulley 20. When field coil 8 is energized by an outside power source, each of the pole pieces of pole cores 7 is excited, so that the stator winding can provide a three-phase ac voltage. Thus, rectifier 5 provides a certain amount of dc current at the output terminals. As illustrated in Fig. 2, conductor segments 33 is a U-shaped member made of conductive metal (e.g. copper) bar or plate which has U-turn portion 33c. Conductor segment 33 has inner conductor portion 33a, outer conductor portion 33b and U-turn portion 33c between inner and outer conductor portions 33a, 33b. Each of inner conductor portions 33a has straight inner portion disposed in the radially inner layer of the winding and each of outer conductor portions 33b has straight outer portion disposed in the radially outer layer of the winding. As illustrated in Fig. 3, U-turn portions 33c are disposed at one axial end of stator core 32, and slant portions 33e forming coil ends 31 are disposed at the other axial end of stator core. Slant portions 33e of conductor segments 33 in the outer layer extend in one direction and slant portion 33e of conductor segment 33 in the inner layer extend in the other direction. Straight ends 33d of conductor segments 33 are welded to one another by an ultrasonic wave welder or an arc welder, or are soldered or mechanically connected to one another. A pair of conductor segments 33 is disposed in each one of slots 35 and is connected to one another. As illustrated in Fig. 4, inner and outer conductor portions 33a, 33b of each of conductor segments 33 has rectangular cross-section with circumferential sides being longer than its radial sides. Conductor segments 33 are coated with insulation film to insulate one segment from another. Insulators 34 insulate each of conductor segments from the inner surface of slots 35. Stator core 32 is a lamination of a spirally-wound belt-like steel sheet 36 as shown in Fig. 6. A plurality of concavities 37 are cut out from the belt-like steel sheet in the same direction to form a plurality of slots with sharp edges or burs 35a projecting in the cutout direction. In Fig. 5, U-turn portions 33c are disposed on the back axial end of the stator core in the cutout direction. Each of conductor segments 33 has side surfaces in parallel with the inner wall of slot 35, thereby providing a high space factor of conductor segments 33. Insulator 34 is made from an insulation sheet. As shown in Fig. 7, the insulation sheet is formed to fit the inner periphery of slot 35. Preferably, each of insulators 34 is inserted into one of slots 35 from the back end of the stator core in the cutout direction. Therefore, insulators 34 can be inserted smooth into slots 35. After insulator 34 is inserted into each of slots 35, a number of U-shaped conductor segments 33 are lined up so that U-turn portions 33c can be disposed at the back end of stator core 32 in the cutout direction or in the same direction as the burs extend. As shown in Fig. 4, outer conductor portions 33b are inserted into the inside portion of slots 35, and inner conductor portions 33a are inserted into the outside portion of slots 35. Each of conductor segments 33 is made of a U-shaped copper plate, which is press-fitted into one of slots 35 so that opposite surfaces of outer and inner conductor portions 33b, 33a can fit the parallel walls of slot 35 via insulators 34. Thereafter, two straight ends 33d of each of conductor segments 33 are bent in the opposite directions respectively to connect to respective straight ends 33d extending from different layers of different slots 35 as shown in Fig. 8. As a variation such as shown in Fig. 9, insulators 34a can have a folded lip 38 at one end. Folded lip 38 is disposed at the end of stator core 32 toward U-turn portion 33c or the back end of the stator core 32 in the cutout direction. The insulators 34a are inserted into slots 35 so that folded lips 38 can engage the back end of stator core 32 in the cutout direction, and conductor segments 33 are subsequently inserted in to slots 35. Accordingly, the insulators 34a can be held by folded lips 38 at the correct axial position. As another variation as shown in Fig. 10, insulator 34b are inserted from the front end of stator core 32 with folded lips 38 on the front end in the cutout direction. Therefore, the insulators 34b can be prevented by folded lips 38 from being damaged when segment ends 33d are bent to form coil ends as illustrated in Fig. 10. Folded lip 38 can be substituted by other equivalent expanded structure for positioning the insulator such as a flared lip. A stator according to a second examplary embodiment is shown in Fig. 11. The stator according to the second embodiment has four conductor segments 133, which are lined up in the radial direction in each of slots 135. Conductor segments 133 are connected in the manner illustrated in Fig. 12. Each of four conductor segments 133 extends from one of slots 135 in an alternately different direction. Conductor segments 133 on this side of Fig. 12 extend clockwise and those on the opposite side extend counterclockwise. End portion 133d of one conductor segment 133 is connected to end portion 133d of another conductor segment 133 spaced apart at a certain pitch. Conductor segments 133 in the innermost layer are connected to those in the second inner layer, and conductor segments in the third layer are connected to those in the outermost layer. A stator according to a third embodiment has a pair of I-shaped or J-shaped conductor segments 233 instead of U-shaped conductor segments 33 as shown in Fig. 13. Each of conductor segments 233 has straight inner conductor portion 233h and two straight outer conductor portions 233i extending outward from the opposite ends of inner conductor portion 233h. One of outer conductor portions 233i is bent as shown in Fig. 13. As shown in Fig. 14, opposite and portions 233d of one conductor segment 233 are connected to end portions 233d of other conductor segments 233 to form a stator winding. Conductor segments 233 are simple in shape and easy to manufacture. Because each of conductor segments 233 corresponds to one of insulators 34, it is easy to insert insulators 34 and conductor segments 233 into slots 35. As shown in Fig. 15, insulation resin coating 40 can be coated on the inner surface of slots 35 instead of insulators 34 made of insulation sheets. The coating can be prevented from being damaged if conductor segments 33 are inserted in the same direction as the burs extending, thereby ensuring good insulation between conductor segments 33 and stator core. In the foregoing description of the present invention, the invention has been disclosed with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made to the specific embodiments as defined by the appended claims.

Claims: A method of manufacturing a stator (2) of a vehicle ac generator, comprising the subsequent steps of: (a) cutting a plurality of slots from steel sheets so that burs (35a) are created at the cutout slots (35); (b) forming a lamination of steel sheets; (c) inserting insulators (34) into said slots (35); and (d) inserting conductor segments (33) into said slots (35), characterized in that (bl) with said forming step (b) the steel sheets are laminated such that said burs (35a) are all extending in the same cutout direction; (c1) with said inserting step (c) said insulators (34) are inserted in a direction, which corresponds to the cutout direction; and (d1) with said inserting step (d) said conductor segments (33) are inserted into said slots (35) in said cutout direction. A method of manufacturing a stator (2) of a vehicle ac generator comprising the following steps: (1) forming a lamination of steel sheets; (2) cutting a plurality of slots (35) from said lamination in a common cutout direction so that burs (35a) are created extending in a common cutout direction; and characterised by the steps of: (3) inserting insulators (34) into said slots (35) in said cutout direction; (4) inserting conductor segments (33) into said slots in said cutout direction; and (5) connecting said conductor segments (33) extending from said slots (35) to one another.

Inventors: KUSASE SHIN, SHIGA TSUTOMU, UMEDA ATSUSHI, KUSASE, SHIN, SHIGA, TSUTOMU, UMEDA, ATSUSHI, Kusase, Shin, c/o Denso Corporation, Shiga, Tsutomu, c/o Denso Corporation, Umeda, Atsushi, c/o Denso Corporation
Applicants: DENSO CORP, DENSO CORPORATION
Application year: 1999
Main classification: H02K3
IPC codes: H02K15, H02K3, H02K1