Motor manufacturing technology using a spiral type core

Akira Hashimoto, Nobuaki Miyake,
Yuji Nakahara, Yasuyuki Nakanishi,
Hideto Nishimura,
Mitsubishi Electric Corp.

As spindle motors for information devices are mass-produced in large volumes, high productivity is required and the parts handling procedures have to be simplified.  For instance, when 5 core sheets are stacked by a press at the punching speed of 300 strokes per minute, the core is finished in 1 second.  However, there are other procedures such as the removal of the cores from the press, forming the insulation layer and coil winding, and these procedures are carried out for every stator core fabrication.  Therefore, it is required plural motor stators are fabricated collectively like the flow of a river.

Motor manufacturing technology using a spiral type core consists of the following processes as shown in Fig. 1.
 1. Core stacking using press machine (for example, 50 stator cores sets are stacked)
 2. Insulation layer forming (electrical plating)
 3. Development in straight  line/separation at connected area
 4. Coil winding  (three teeth are wound simultaneously)
 5. Folding cores cylindrically/assembly
Finally, the stator is fixed on a printed circuit board, and the coil ends are connected automatically.  The spiral type core can be developed in straight line and separated, and consists of three kinds of cores a - c which have the slits in different separation positions as shown in Fig. 2.  These cores are stacked and caulked simultaneously during pressing.  Core c is connected to another stator core via connected portion, that is, core c is located between two stator cores. Fig. 3 is a photograph of the spiral type core.  This core does not have a simple cylindrical shape, and can be developed  and separated easily.

The motor design was reviewed from the viewpoints of the core structure and coil winding method, and an original manufacturing technology using a spiral type core was created.  Using the proposed manufacturing process, the working hours required for insulation layer forming and core attachment for the winding machine were shortened to less than 1/3 and 1/10 respectively. 


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