Note: Descriptions are shown in the official language in which they were submitted.
lQ77688
This invention relates to a method for producing a
pole piece for use as a component of a rotor of a generator
of the type referred to as an alternator in the automobile
industry, i.e. a pole piece for a generator which is adapted
to produce alternating current and to supply the current as
direct current.
In generators of the above type, two pole pieces are
mounted on a generator rotor shaft in a spaced relationship
to each other. In the prior art, such pole piece have been
produced by mechanically cutting a slug or workpiece of a
predetermined length off a round steel bar mate-rial and
mechanically processing the workpiece. This has required a
relatively high capacity press line including various
mechanical cutting means, resulting in high production costs.
Therefore, the purpose of the present invention is to
provide a method for producing a pole piece of the above type
which can perform all the processing steps without requiring
any mechanical cutting means, except in the initial step in
which the workpiece is cut off a round steel bar material,
which can employ a relatively low capacity press line for
performing the processing steps preferably at room
temperature, which can attain a high yield rate.
According to the invention there is provided a method
for producing a pole piece for a generator comprising the
steps of (a) extruding one end of a cylindrical steel
workpiece to form an annular projection of reduced diameter
at one end of said workpiece; (b) upsetting said workpiece so
as to cause the main portion adjacent said annular projection
to bulge radially outwardly, (c) deforming said bulged main
portion into a central disc portion with said annular
projection integrally formed on one face thereof and said
-- 2 --
~ .
1077688
disc portion having at the periphery thereof a plurality of
- radial projections integrally formed therewith, said
projections being of substantial length relative to the
radius of the original workpiece, (d) punching a hole through
the center of said disc portion and coincident with said
annular projection, and (e) bending the outer portions of
said radial projections in the direction of said annular
projection to form teeth members having peripheral portions
parallel to the axis of the central hole and radially spaced
from said annular projection.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings show a workpiece in various
stages of formation according to a preferred method of the
present invention as described in detail in the following.
In the drawings:-
Fig. 1 is an isometric view of a slug formed by
cutting a section of a suitable length off a round steel bar
material in a first method step;
Fig. 2A is an end elevational view of one half portion
of said workpiece processed in a second method step and cut
across the longitudinal axis of the workpiece;
Fig. 2B is a vertically sectional view of said
workpiece shown in Fig. 2A taken along the longitudinal axis
of said workpiece;
Fig. 3A is a plan view of one half portion of said
workpiece processed in a third method step and cut across the
longitudinal axis of the workpiece;
Fig. 3B is a vertically sectional view of said
workpiece of Fig. 3A taken along the longitudinal axis of the
workpiece. ~
- 3 -
1C~77688
Fig. 4A is a plan view of one half portion of said
workpiece processed in a fourth method step and cut across
the longitudinal axis of the workpiece;
Fig. 4B is a vertically sectional view of said
workpiece of Fig. 4A taken along the longitudinal axis of the
workpiece;
Fig. 5A is a plan view of one half portion of said
workpiece processed in a fifth method step and cut across the
longitudinal axis of the workpiece;
Fig. 5B is a vertically sectional view of said
workpiece
- 3a -
~,,
1077688
of Fig. 5A taken along the longitudinal axis of the workpiece;
Fig. 6A is a plan view of one half portion of said
workpiece processed in a sixth method step and cut across the
longitudinal axis of the workpiece;
Fig, 6B is a vertically sectional view of said workpiece
of Fig. 6A taken along the longitudinal axis of the workpiece;
Fig. 7A is a plan view of one half portion of said
workpiece processed in a seventh method step and cut across the
longitudinal axis of the workpiece;
Fig. 7B is a vertically sectional view of said workpiece
of Fig. 7A taken along the longitudinal axis of the workpiece,
Fig. 8A is a plan view of one half portion of said
workpiece processed in an eighth method step and cut across the
longitudinal axis of the workpiece;
Fig. 8B is a vertically sectional view of said workpiece
of Fig. 8A taken along the longitudinal axis of the workpiece;
and
Fig. 9 is a cross-sectional view which shows a pair
of pole pieces assembled on the rotor of a generator with the
20 annular projections of the pole pieces abutting against each
other.
One preferred embodiment of the method of the present
invention will be now described with reference to the accompanying
drawings.
First of all, a round steel bar material is provided
and a section is cut off having a length suitable for forming
the desired pole piece by means of a suitable cutter to obtain
a slug or workpiece 1 as shown in Fig. 1.
The slug or workpiece 1 is extruded in a press so as
30 to form a reduced diameter annular projection 2 at one end of `-
the workpiece 1 a~ shown in Figs. 2A and 2B.
- 4
., ~' ,.
1~:)7768l5
After the extruding step, the workpiece i8 upset 80
as to cause the main portion of the workpiece to bulge radially
outwardly so as to form a bulge 1' as shown in Figs. 3A and 3B.
The workpiece is then subjected to a fourth step in
which it is processed so as to deform the bulge 1' into a disc
portion 3, coaxial with the annular projection 2 and having a
diameter greater than and a thickness smaller than that of the
bulge l', and spiders 3' integral with and extending radially
outwardly from the outer periphery of the disc portion as shown
in Figs. 4A and 4B.
The thus processed workpiece is then subjected to a
fifth step in the method in which the spiders 3' are shaped
or trimmed as shown in Figs. 5A and 5B.
After the fifth step, the thus processed workpiece
is turned upside down to locate the disc portion 3 at the bottom
and an axial hole 4 is punched through the disc portion 3 in
communication with the opening defined by the annular projection
2, as shown in Figs. 6A and 6B. In forming the hole 4 in the
workpiece, it is necessary only to punch through the disc
portion 3 which is of reduced thickness as a result of the
second step. Thus~ it will be understood that the service life
,, of the punch die employed in the punching step may therefore be
quite long.
After the sixth step, the workpiece is subjected to a
bending step in a press to bend the spiders 3' on the sides of
' the annular projections 2 of the workpiece in a direction
parallel to the common axis of the center or axial hole 4 and
the annular projection 2 as shown in Figs. 7A and 7B.
Finally, the workpiece is subjected to a sizing step
to obtain a complete product or pole piece 5 as shown in Figs.
8A and 8B.
- 5 -
1077~;88
As shown in Fig. 9, in practice, a pair of pole
pieces 5, 5 produced by the method as mentioned hereinabove
are mounted on a rotary shaft 6 of a generator by means of
the axial holes 4, 4 with the annular projections 2, 2 of the
pole pieces 5, 5 abutting against each other to thereby form
the rotor assembly of the generator.
All the steps in the method from the first step to
the last step can be performed at room temperature. Since the
annular projection 2 is formed by extrusion in the second step,
the centering of the workpiece in the succeeding steps can be
easily achieved. In the sixth step of the method for forming
the axial hole 4, since it is necessary to punch through only
the reduced thickness disc portion 3, the service life of the
punch die is increased and the hole 4 can be precisely formed
with a smooth hole surface. If the entire thickness of the
workpiece including the annular pro~ection 2 had to be punched,
the service life of the die employed in the punching of the
center hole 4 would be reduced. Moreover, if the center hole
forming operation were performed by means of a lathe or other
turning means~ there would be the problem that, when the pole
piece is fitted on the rotary shaft, so-called "biting" would
occur because of the presence of traces of metal on the hole
surface scored by the cutting tool. This can be effectively
avoided by the present invention. The method of the present
invention can also be made automatic by a press line directly
connected to an assembly line.
The load applied to the presses employed is relatively
small and a relatively small amount of scrap material is gener-
ated, thereby increasing the yield rate. Furthermore, the pole
pieces may be made o~ less expensive rimmed steel rather than
expensive killed stePl as conventionally used in the prior art
1~77688
methods for producing pole pieces. Thus, the overall productlon
cost can be reduced and labor expense can be saved,
While one embodiment of the invention has been shown
and described in detail, it will be understood that the same
is for illustration purpose only and not to be taken as a
definition of the invention, reference being had for this
purpose to the appended clai.ms.
- 10
