Method for producing a stator of an alternating-current dynamo-electric machine

[0002] 1. Field of the Invention

[0003] The present invention relates to a method for producing a stator of an alternating current dynamo-electric machine, for example, an alternating current generator for automobiles, which is driven by an automobile engine, or the like.

[0004] 2. Description of the Related Art

[0005] FIG. 4 is a cross-sectional view showing an example of an alternating current generator for automobiles to which the present invention can be applied. In this figure, a rotor 1 includes a rotating shaft 11, a pair of claw pole field cores 12 mounted to the rotating shaft 11, and a field coil 13 fixed within the pair of field cores 12. The rotating shaft 11 is rotated by transmitting a driving force of an automobile engine through a belt (not shown).

[0006] A stator 2 surrounding the rotor 1 includes a stator core 21 and a stator coil assembly 22 fixed to the stator core 21. The inner peripheral surface of the stator 2 is opposed to the outer peripheral surface of the rotor 1 through a gap. The stator 2 is held in place between a front bracket 3 and a rear bracket 4. Furthermore, the rotor 1 is supported by the front bracket 3 and the rear bracket 4 through bearings 31 and 41 respectively.

[0007] A conventional method for producing the stator 2 will now be described in conjunction with FIG. 5. First, a strip 20 having a plurality of slots is cut from a long, narrow steel plate as shown in FIG. 5. At this time, two strips 20 can be cut from one steel plate. Next, one strip 20 is wound into a ring to produce the stator core 21 having a prescribed semi-diameter as shown in FIG. 6. A plurality of slots 21aare provided on the inner peripheral surface of the stator core 21.

[0008] On the other hand, the stator coil assembly 22 is formed into a cylindrical shape as shown in FIG. 7. The cylindrical stator coil assembly 22 is brought into the inside of the cylindrical stator core 21 along a guide (not shown) by an assembling apparatus (not shown) while bending its end portion, and thereafter inserted into the slots 21aof the stator core 21 to obtain the stator 2 as shown in FIG. 8.

[0009] Further, methods disclosed, for example, in U.S. Pat. No. 416,033 and Japanese Patent Laid-Open No. 52-34301 are known as methods for producing the cylindrical stator core 21.

[0010] In the conventional method for producing the stator 2 as described above, the stator coil assembly 22 is inserted into the slots 21aafter being pre-formed into the cylindrical shape so as to correspond to slots 21adisposed cylindrically. This assembly operation is complicated and the stator coil assembly 22 is sometimes damaged. Therefore, a production efficiency is reduced. Further, the stator coil assembly 22 cannot be inserted into the slots 21aat a higher density, so output cannot be improved.

[0011] The present invention has been achieved with a view toward solving the problems described above, and further, it is an object of the present invention to provide a method for producing a stator of an alternating current dynamo-electric machine which is capable of easily disposing a stator coil assembly in slots of a stator core at a higher density and which also is preventing damage to conductors of the stator coil assembly.

[0012] To this end, according to an aspect of the present invention, there is provided a method for producing a stator of an alternating current dynamo-electric machine, comprising the steps of: laminating a plurality of magnetic strips together to produce a laminated core assembly with a rectangular parallelopiped shape having a plurality of slots; disposing a stator coil assembly in the slot; and bending the laminated core assembly together with the stator coil assembly to produce a cylindrical stator.

[0013] FIG. 1 is a perspective view showing an example of an alternating current generator for automobiles as produced by a method of this invention;

[0014] FIG. 2 is a perspective view showing the stator core of FIG. 1 before being formed;

[0015] FIG. 3 is a perspective view showing a laminated assembly of FIG. 2 after disposing a stator coil assembly;

[0016] FIG. 4 is a cross-sectional view showing an example of an alternating current generator for automobiles;

[0017] FIG. 5 is a plan view showing strips which compose a stator core;

[0018] FIG. 6 is a perspective view showing a cylindrical stator core;

[0019] FIG. 7 is a perspective view showing a cylindrical stator coil assembly; and

[0020] FIG. 8 is a perspective view showing the stator core of FIG. 6 after fixing the stator coil assembly of FIG. 7 thereto;

[0021] FIG. 9 shows an embodiment of a laminated assembly; and

[0022] FIG. 10 shows the laminated assembly of FIG. 9 in a bent state.

[0023] The embodiments according to the present invention will now be described with reference to the accompanying drawings. FIG. 1 is a perspective view showing an example of an alternating current generator for automobiles as produced by a method of this invention. In this figure, a stator 5 includes a cylindrical stator core 51 having a plurality of slots 51a,and a stator coil assembly 52 disposed in the slots 51a. Further, the stator core 51 has a single welded portion 51bsomewhere on its circumference. The construction of the whole alternating current generator is the same as FIG. 4.

[0024] A method for producing the stator 51 will now be described. First, strips 20 shown in FIG. 5 are cut into a prescribed length. The strips 20 may have, for example, a width of 30 mm and a thickness of 1 mm. Thereafter, a plurality of cut strips 20 are laminated together to produce a laminated assembly 50 with a roughly rectangular parallelopiped shape as shown in FIG. 2.

[0025] On the other hand, the stator coil assembly 52 is preformed into a shape which is generally flat and which needs not be further formed within the slots 51aof FIG. 2, and thereafter inserted into the slots 51aas shown in FIG. 3. In other words, the stator coil assembly 52 is preformed before it is inserted into the slots 51aso as to be ready for the insertion. Next, the laminated assembly 50 is bent into a cylindrical shape by a forming machine (not shown) to produce the stator core 51. After the bending process, both ends of the laminated assembly 50 are welded together along the welding portion 51bof FIG. 1.

[0026] In the method for producing the stator 5 as described above, when the stator coil assembly 52 is to be inserted into the slots 51a,the stator coil assembly 52 is required to be moved only in one direction relative to the straight stator core 51, so that the stator coil assembly 52 is easily disposed in the slots 51aat a higher density. Further, since no excess bending force is applied to the stator coil assembly 52, damage to the conductors of the stator coil assembly 52 is prevented. Additionally, since it is not necessary to pre-form the stator coil assembly 52 into the cylindrical shape, production of the stator coil assembly 52 is facilitated. Therefore, production efficiency of the stator is increased.

[0027] Moreover, as shown in FIG. 9, it is also possible that slits 60 be provided on the bottom portion of the slots 51aof the laminated assembly 50, making the laminated assembly 50 easier to be bent. As shown in FIG. 9 the size of each of the slits 60 is set so that the slits 60 are compressed to disappear when forming the stator core 51 cylindrically, thus the slits 60 have no negative influence upon the magnetic field.

[0028] While in the above embodiment, one stator core 51 is made from one laminated assembly 50, it is also possible that a cylindrical stator core is made by assembling a plurality of stator cores bent into circular arc shapes respectively.

[0029] Further, a method for producing a stator of this invention is applicable to alternating current dynamo-electric machines other than alternating current generators for automobiles.