Core sheet, core and method of manufacturing an armature

Details Core sheet, core and method of manufacturing an armature Core sheet, core and method of manufacturing an armature

1999-02-25

2001-06-05

Tamai, I. E. (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S216006

Reexamination Certificate

active

06242835

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATION
This application relates to and incorporates herein by reference Japanese Patent Application No.
10-55154
filed on Mar. 6, 1998.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a core sheet, core and method of manufacturing an armature using the core sheet.
2. Related Art
In a conventional electric motor, as shown in
FIGS. 19
,
20
,
21
, an armature
20
has a rotary shaft SH at its radial center. A core
21
wound with armature windings C is fixed to the rotary shaft SH together with commutator SG. The core
21
comprises a plurality of stacked core sheets
22
, each of which is a thin magnetic steel plate. The core
21
has on its outer peripheral surface a plurality of slits
23
, each of which extends in parallel with the rotary shaft SH. The slit
23
has a slit width d in the circumferential direction of the core
21
.
The core sheet
22
has a plurality of T-shaped teeth
24
extending in the radial direction from its radial central part. The core sheet
22
also has a through hole
25
at its central part so that the rotary shaft SH passes therethrough in the axial direction. The teeth
24
are spaced apart in the circumferential direction to provide a plurality of slots
26
.
Each armature winding C is wound around each tooth
24
through slits
23
. Specifically, the armature winding C is wound in the slots
26
from the radial central part toward the outer peripheral part of the core
21
in generally the fixed width d.
In this armature
20
, there remains in each slot
26
space at a location other than the space corresponding to the slit width d, because the space for disposing the armature winding C is limited by the slit width d. Thus, the space in the slot
26
is not used effectively.
It is possible to wind the armature winding in more turns in the slot
26
by widening the slit width. However, the widened slit is likely to cause cogging in the torque of the motor, because each slit
23
extends in the axial direction as a continuous line thereby causing reluctance changes at the same time. Further, the slipping out of the armature winding c is likely to occur in the radially outward direction from the slot
26
through the slit. Thus, the width of the slot should not be widened too much.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved core sheet and a core for an armature of an electric motor.
It is another object of the present invention to provide an armature of an electric motor, which has a high space factor in each slot, less cogging in the torque and less slipping out of the armature windings.
It is a further object of the present invention to provide an improved method of manufacturing an armature of an electric motor, which increases efficiency of winding operation.
According to the present invention, an armature for a motor has a core, which comprises a plurality of core sheets stacked together in an axial direction. Each sheet has a plurality of teeth having an extended protrusion, which covers an armature winding fitted in slots. The extended protrusion is a pair of bendable long protrusion pieces on each tooth of one sheet, and a pair of bendable short protrusion pieces on each tooth of another sheet stacked adjacently to the one sheet. Alternatively, the extended protrusion is a pair of long protrusion piece and short protrusion piece on each tooth. The protrusion pieces are bent to cover the armature winding after winding operation, leaving only a narrow slit between the two extended protrusions. Thus, the slit is provided discontinuously in an axial direction of the core, so that cogging in torque of the motor is reduced.


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