Title: Electromagnetic drive device
Abstract: An electromagnetic drive device for lineally reciprocatilvely moving an operating member like a spool of a spool valve is reduced in the manufacturing cost without being degraded in its operational performance. In the electromagnetic drive device, a stator body is excited by an electromagnetic coil to axially move a plunger guided in an inner bore of the stator body, against the resilient force of a spring. The stator body is constituted by arranging a plurality of core portion annular plate elements made of a magnetic material, a plurality of yoke portion annular plate elements made of a magnetic material and a plurality of non-magnetic portion annular plate elements made of a non-magnetic material and placed between the core portion annular plate elements and the yoke portion annular plate elements and by piling up and bodily joining these annular plate elements in axial alignment with one another. Each of the annular plate elements is provided with plural embossed portions each of which is half-blanked to be prominent at one surface side and hollow at the other surface side. The embossed portions formed on each annular plate element are fit at the prominent surface sides thereof respectively in the hollow surface sides of the embossed portions formed on another annular plate element, so that all the annular plate elements can be bodily joined in axial alignment with one another.
Patent Number: 6,922,124 Issued on 07/26/2005 to Segi, et al.
| Inventors:
|
Segi; Masaya (Okazaki, JP);
Suzuki; Mikio (Hekinan, JP);
Takanishi; Koichi (Nishio, JP);
Suzuki; Masaru (Chiryu, JP);
Kaneda; Yoshinori (Okazaki, JP)
|
| Assignee:
|
Toyoda Koki Kabushiki Kaisha (Kariya, JP)
|
| Appl. No.:
|
781716 |
| Filed:
|
February 20, 2004 |
Foreign Application Priority Data
| Feb 21, 2003[JP] | 2003-044940 |
| Current U.S. Class: |
335/220; 335/281; 251/129.15 |
| Intern'l Class: |
H01F 007/08 |
| Field of Search: |
335/256,281-282,220-229,296
251/1291-12915
|
References Cited [Referenced By]
U.S. Patent Documents
| 4486053 | Dec., 1984 | Hawker et al.
| |
| 6420949 | Jul., 2002 | Umemoto et al.
| |
| 6588093 | Jul., 2003 | Emmerich et al.
| |
| 6601822 | Aug., 2003 | Tachibana et al.
| |
| 2003/0168619 | Sep., 2003 | Jansen.
| |
| Foreign Patent Documents |
| 0 133 858 | Mar., 1985 | EP.
| |
| 1 134 471 | Sep., 2001 | EP.
| |
| 1-242884 | Sep., 1989 | JP.
| |
| WO 99/1609/2 | Apr., 1999 | WO.
| |
Other References
"Materia Japan", vol. 36, No. 4(1997), pp. 358-360.
|
Primary Examiner: Donovan; Lincoln
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
Claims
1. An electromagnetic drive device having a stator body composed of a core portion
and a yoke portion serially arranged in axial alignment with a non-magnetic portion
placed therebetween, a plunger slidably received in an inner bore formed in at
least one of said yoke portion and said core portion in said stator body and resiliently
urged in one direction, and an electromagnetic coil for exciting said stator body
to move said plunger in the axial direction of the plunger against the resilient
force, wherein said stator body is constituted by piling up in the axial direction
and bodily joining a plurality of core portion annular plate elements made of a
magnetic material to form said core portion, a plurality of yoke portion annular
plate elements made of a magnetic material to form said yoke portion, and a plurality
of non-magnetic portion annular plate elements made of a non-magnetic material
to form said non-magnetic portion.
2. The electromagnetic drive device as set forth in claim 1, wherein:
each of said annular plate elements constituting said stator body is composed
of an annular body portion and plural embossed portions each half-blanked from
said annular body portion to be prominent at one surface side and hollow at the
other surface side; and
each of said annular plate elements is bodily joined with another annular plate
element, with prominent portions of said embossed portions at one surface side
of each annular plate element being fit respectively in hollow portions of said
embossed portions at the other surface side of said another annular plate element.
3. The electromagnetic drive device as set forth in claim 1, wherein said inner
bore of said stator body composed of said bodily joined annular plate elements
has a modified finish.
4. The electromagnetic drive device as set forth in claim 2, wherein said inner
bore of said stator body composed of said bodily joined annular plate elements
has a modified finish.
5. The electromagnetic drive device as set forth in claim 2, wherein each of
said embossed portions takes the form of an arc in section taken in the circumferential
direction of each annular plate element.
Description
INCORPORATION BY REFERENCE
This application is based on and claims priority under 35 U.S.C. sctn. 119 with
respect to Japanese Application No. 2003-044940 filed on Feb. 21, 2003, the entire
content of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electromagnetic drive device for linearly
reciprocatilvely moving an operating member such as, for example, a spool of a
spool valve.
2. Discussion of the Related Art
Heretofore, as electromagnetic drive device for reciprocatively moving
a spool of a spool valve, there has been known one described in Japanese unexamined,
published patent application No. 1-242884 (1989-242884). In the known electromagnetic
drive device, a first solenoid housing (i.e., core) and a second solenoid housing
(i.e., yoke) both made of a magnetic material are arranged serially in axial alignment
with a non-magnetic portion (i.e., air gap or non-magnetic member) placed therebetween,
thereby to constitute a stator, and a plunger is slidably guided in an inner bore
formed in the stator. By exciting the solenoid housings with a solenoid, the plunger
is axially moved against a spring, so that a spool in a spool or valve housing
attached to the first solenoid housing (i.e., core) is operated. Where the plunger
is slidably received in the inner bore of the stator in this manner, a strict alignment
is required between the internal surfaces of the yoke and the core. Therefore,
it is necessary to machine the internal surfaces of the yoke and the core after
they are inserted into and secured to a sleeve made of a non-magnetic material.
Further, there has also been known a technology described in U.S. Pat. No.
6,601,822 B2 to S. Tachibana et al. In this known technology, a stator for slidably
guiding a plunger is constituted as a cylindrical stationary core which is made
as one piece of a magnetic material, and a thin annular portion is formed by partly
cutting out the outer wall portion at the axial mid position of the stationary
core radially facing the plunger to the extent that the mechanical strength thereat
is not deteriorated. A plurality of radial through holes are formed in the thin
annular portion to decrease the area for magnetic path and thereby to increase
the magnetic resistance thereat so that a portion equivalent to a non-magnetic
portion can be formed at the thin annular portion.
Further, there is known a technology described in a technical journal "Materia
Japan", vol. 36, No. 4 (1997), pages 358-360. In this technology, a non-magnetic
pipe made of a quasi-austenite base stainless steel is first converted by a cold
roll process into a magnetic pipe, which is then partly processed by a selective
quenching, whereby a magnetic stator with a non-magnetic portion at its axial mid
portion can be made.
However, in the technology described in the aforementioned Japanese application,
problems are raised in that the number of parts constituting the electromagnetic
drive device increases and that many steps are needed for the machining of the
fitting portions, press-fittings, and the finish machining of the inner bore for
the plunger after the press-fittings, thereby resulting in an increase of the manufacturing
cost. On the other hand, the problem of an increase in the manufacturing cost can
be solved in the technology described in the aforementioned United States patent.
That is, in the second technology, the annular portion is made thin and is provided
with the plural radial through holes thereby to increase the magnetic resistance
thereat. However, since it is unavoidable that the magnetic flux leaks through
the annular portion, there is raised another problem that the magnetic attraction
force exerted on the plunger is weakened. Further, the last mentioned technology
for partly processing the magnetically converted stainless steel pipe by a selective
quenching process needs plural steps of special processing, which undesirably results
in an increase in the manufacturing cost.
SUMMARY OF THE INVENTION
Accordingly, it is a primary object of the present invention to provide
an improved electromagnetic drive device whose stator body is constituted by piling
up or laminating in axial alignment a plurality of annular plate elements which
can be formed by press-forming of a high productivity.
Briefly, according to the present invention, there is provided an electromagnetic
drive device having a stator body composed of a core portion and a yoke portion
serially arranged in axial alignment with a non-magnetic portion placed therebetween,
a plunger slidably received in an inner bore formed in at least one of the yoke
portion and the core portion in the stator body and resiliently urged in one direction,
and an electromagnetic coil for exciting the stator body to move the plunger in
the axial direction thereof against the resilient force. The stator body is constituted
by piling up in axial alignment and bodily joining a plurality of core portion
annular plate elements made of a magnetic material to form the core portion, a
plurality of yoke portion annular plate elements made of a magnetic material to
form the yoke portion, and a plurality of non-magnetic portion annular plate elements
made of a non-magnetic material to form the non-magnetic portion.
With this configuration, the plurality of annular plate elements constituting
the stator body are obtained by being punched or blanked out by a press from a
plate member and therefore are at a low cost. Further, the non-magnetic portion
placed between the core portion and the yoke portion each made of a magnetic material
can be formed easily and completely only by placing and piling up the plural non-magnetic
portion plate elements between the plural core portion plate elements made of a
magnetic material and the plural yoke portion plate elements made of a magnetic
material, so that the magnetic leakage of magnetic flux from one of the yoke portion
and the core portion to the other can be prevented. Accordingly, since the cost
can be reduced in manufacturing the stator body having the core portion and the
yoke portion which are serially arranged in axial alignment with the non-magnetic
portion placed therebetween, the manufacturing cost for the electromagnetic drive
device can be reduced, and it does not occur that the magnetic attraction force
exerted on the plunger is weakened due to the leakage of the magnetic flux from
one of the yoke portion and the core portion to the other.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The foregoing and other objects and many of the attendant advantages of the present
invention may readily be appreciated as the same becomes better understood by reference
to the preferred embodiments of the present invention when considered in connection
with the accompanying drawings, wherein like reference numerals designate the same
or corresponding parts throughout several views, and in which:
FIG. 1 is a longitudinal sectional view showing the general construction of
an electromagnetic drive device in the first embodiment according to the present invention;
FIG. 2 is a sectional view of a stator body in the first embodiment shown in
FIG. 1;
FIG. 3 is an enlarged, fragmentary perspective view of one of embossed portions
formed on each of annular plate elements of the stator body for joining the annular
plate elements with one another;
FIG. 4 is a sectional view of the embossed portion taken along the line 4-4
in FIG. 3;
FIG. 5 is a sectional view of the embossed portion taken along the line 5-5
in FIG. 4; and
FIG. 6 is a sectional view of another stator body in the second embodiment used
in place of that shown in FIG. 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, an electromagnetic drive device in the first embodiment
according to the present invention will be described with reference to FIGS. 1
to
5. In this particular embodiment, the present invention is applied to
a solenoid-operated valve, and an electromagnetic drive device
10 of the
solenoid-operated valve in the embodiment is designed to linearly reciprocate a
spool (operating member)
24 of a valve section (operating device)
20
which is provided in axial alignment therewith.
As shown primarily in FIGS. 1 and 2, the electromagnetic drive device
10
is composed of a stator body
11 which is constituted by piling up or laminating
and bodily joining a plurality of annular plate elements
15a1
through
15a3,
15b,
15c in axial
alignment, a cover
16 made of a magnetic material which covers the stator
body
11 thereby to connect the axial opposite ends of the same magnetically
with each other, a plunger
17 and an electromagnetic coil
18. The
stator body
11 is composed of a core portion
12 and a yoke portion
13 which are serially arranged in axial alignment with a non-magnetic portion
14 provided therebetween. With respect to the outer shape thereof, the stator
body
11 extends in a predetermined diameter from the rear end of the yoke
portion
13 through the non-magnetic portion
14 up to the portion
close to the forward end portion of the core portion
12, and a flange portion
11d is formed at the forward end portion of the core portion
12.
Further, in the stator body
11, an inner bore
11a of another
predetermined diameter is formed to extend from the rear end of the yoke portion
13 through the non-magnetic portion
14 up to the axial mid position
of the core portion
12 in coaxial alignment with the axis of the stator
bore
11, and a center hole
11c which is smaller in diameter
than the inner bore
11a is formed from the axial mid position up
to the forward end of the core portion
12 in axial alignment with the inner
bore
11a.
The plunger
17 is made of a magnetic material in its entirety and is guided
and supported slidably in the inner bore
11a of the stator body
11.
The plunger
17 is movable between an advanced position (shown at the lower
half in FIG. 1) where its forward end surface
17a at the side of
the valve section
20 abuts on an inner end surface of the inner bore
11a
through a washer
19, and a retracted position (shown at the upper half
in FIG. 1) where its rear end surface
17b abuts on the inner bottom
surface of the cover
16. In the inner bore
11a, an electromagnetic
section fluid chamber (B) is defined between the forward end surface
17a
of the plunger
17 and the inner bore
11a of the stator
body
11, while a rear end fluid chamber (A) is defined between the rear
end surface
17b of the plunger
17 and the inner bottom surface
of the cover
16. The rear end fluid chamber (A) and the electromagnetic
section fluid chamber (B) are in communication with each other through a communication
hole
17c which is formed in the plunger
17 to pass through
axially of the same.
The valve section
20 is composed of a valve sleeve
21 and the aforementioned
spool
24 slidably received in a valve hole
22 which is formed coaxially
in the valve sleeve
21. The valve sleeve
21 is secured to the stator
body
11 in axial alignment therewith by caulking the opening end portion
of the cover
16 with its flange portion at the rear end portion being in
abutting contact with the flange portion at the forward end portion of the stator
body
11. The spool
24 is resiliently urged toward the electromagnetic
drive section
10 by means of a spring (not shown), which is interposed between
itself and a plug member (not shown) screwed into a forward end portion (not shown)
of the valve sleeve
21. A rod portion
24a which is formed
to protrude from the rear end of the spool
24 extends passing through the
center hole
11c of the stator body
11 and abuts on the forward
end surface
17a of the plunger
17. Thus, in the inoperative
state, the plunger
17 is kept at the aforementioned retracted position where
the rear end surface
17b thereof abuts on the inner bottom surface
of the cover
16. An intermediate fluid chamber (C) formed at the mid position
between the stator body
11 and the valve sleeve
21 communicates,
on one hand, with the electromagnetic section fluid chamber (B) through an annular
clearance which is formed between the center hole
11c of the stator
body
11 and the rod portion
24a of the spool
24 and,
on the other hand, with the external of the solenoid-operated valve through a labyrinth
supply/drain passage
23 composed of an annular groove
23a and
cutouts
23b,
23c.
As shown in FIGS. 1 and 2, the stator body
11 is composed of the core
portion
12 and the yoke portion
13 which are arranged serially in axial alignment
with each other with the non-magnetic portion
14 placed therebetween. Each
of the core portion
12, the yoke portion
13 and the non-magnetic
portion
14 is constituted by piling up or laminating in axial alignment
and bodily joining a plurality of annular plate elements
15 which are formed
by being punched or blanked out from a thin metal plate of the thickness of e.g.,
0.5 millimeter.
The non-magnetic portion
14 denoted as a zone (F) in FIG. 2 is constituted
by piling up a plurality of non-magnetic portion annular plate elements
15c
made of a non-magnetic material (e.g., austenite-base stainless steel) one
after another. The inner and outer diameters of each non-magnetic portion annular
plate element
15c coincide respectively with the diameter of the
inner bore
11a and the outer diameter of the portion of the stator
body
11 excepting for the flange portion
11d. As shown in
FIGS. 3 to
5, at three positions circumferentially spaced at equiangular
intervals on an annular body portion (S) thereof, each non-magnetic portion annular
plate element
15c is provided with embossed portions (T) which are
formed by half-blanking each to take an arc shape of a predetermined width. The
thickness (d) between the front surface (Ta) and the reverse surface (Tb) of each
embossed portion (T) in a direction normal to the surface of the body portion (S)
is almost the same as the thickness of the body portion (S). The half-blanking
for the embossed portions (T) can be performed simultaneously of blanking or punching
out the body portion (S). The prominent front surfaces (Ta) of the embossed portions
(T) formed on each non-magnetic portion annular plate element
15c are
respectively fit in the corresponding hollow reverse surfaces (Tb) of the embossed
portion (T) formed on another non-magnetic portion annular plate element
15c
which is to be piled thereon, so that all the non-magnetic portion annular
plate elements
15c are joined bodily in axial alignment thereby to
form the non-magnetic portion
14.
The yoke portion
13 denoted as a zone (E) in FIG. 2 is constituted by
piling up or laminating a plurality (larger in number than the non-magnetic portion
annular plate elements
15c) of yoke portion annular plate elements
15b made of a magnetic material (e.g., cold rolled steel plate desirably
of a high fineness) one after another. The shape and dimension of each yoke portion
annular plate element
15b are the same as those of each non-magnetic
portion annular plate element
15c. In the same manner as the non-magnetic
portion annular plate elements
15c, each yoke portion annular plate
element
15b is piled or laminated on another yoke portion annular
plate element
15b with the prominent front surfaces (Ta) of the embossed
portions (T) on one element (
15b) being respectively fit in the hollow
reverse surfaces (Tb) of those on another element (
15b), so that
all the yoke portion annular plate elements
15b are joined bodily
in axial alignment thereby to form the yoke portion
13. Further, the prominent
front surfaces (Ta) or the hollow reverse surfaces (Tb) of the annular plate element
15b of the yoke portion
13 which element is closest to the
side of the non-magnetic portion
14 is fit in the hollow reverse surface
(Tb) or the prominent upper surface (Ta) of the annular plate element
15c
of the non-magnetic portion
14 which element is closest to the side
of the yoke portion
13, so that the yoke portion
13 and the non-magnetic
portion
14 are joined bodily in axial alignment.
As shown in FIG. 2, the core portion
12 is partitioned into three (i.e.,
first to third) zones D
1, D
2 and D
3, and each of core portion
annular plate elements
15a1,
15a2 and
15a3 in the zones D
1, D
2 and D
3 is made
of a magnetic material. Each first core portion annular plate element
15a1
takes the quite same configuration as each yoke portion annular plate element
15b
inclusive of the embossed portions (T). Except that the inner diameter is that
of the center hole
11c, each second core portion annular plate element
15a2 takes the same configuration as each first core potion
annular plate element
15a1 inclusive of the embossed portions
(T). Further, except that the outer diameter is that of the flange portion
1d,
each third core portion annular plate element
15a3 takes the
same configuration as each second core portion annular plate element
15a2
inclusive of the embossed portions (T). In the same manner as the yoke portion
annular plate elements
15b and the non-magnetic annular plate elements
15c, the first through third core portion annular plate elements
15a1,
15a2,
15a3
are joined bodily in axial alignment each by being fit in another to be piled thereon
at the embossed portions (T) thereof. The embossed portions (T) of the first core
portion annular plate element
15a1 at an end in the zone (D
1)
and the embossed portions (T) of the non-magnetic portion annular plate element
15c at the facing side of the non-magnetic portion
14 are
brought into fitting engagement, so that the core portion
12 and the non-magnetic
portion
14 are joined bodily in axial alignment with each other.
As described above, the stator body
11 which is composed of the non-magnetic
portion
14 and the core portion
12 and the yoke portion
13
serially arranged in axial alignment at the axial opposite ends of the non-magnetic
portion
14 and which has the inner bore
11a and the center
hole
11c is formed by piling up and bodily joining the plural annular
plate elements
15c,
15b and
15a1 to
15a3
in axial alignment with one another. In this particular embodiment, in order to
make the sliding movement of the plunger
17 smooth and to make the clearance
relative to the plunger
17 minimum for stronger magnetic attraction force,
the inner bore
11a and the outer surface of the stator body
11
formed in this way are finished and improved in precision. Either one or both of
the internal surface of the inner bore
11a of the stator
11
and the outer or external surface of the plunger
17 are coated with a thin
non-magnetic film (e.g., plating of a nickel-phosphorus film in the depth of 20
to 50 micrometers, painting or coating of a resin of Teflon® or the like),
whereby it can be obviated that two magnetic bodies are directly contacted with
each other thereby to impede the smooth relative sliding movement therebetween.
When electric current is applied to the electromagnetic coil
18 of the
electromagnetic drive device
10, the stator body
11 is excited in
proportion to the magnitude of the electric current applied thereto thereby to
make the plunger
17 attracted toward the core portion
12, and thus,
the spool
24 of the operating device
20 is moved against the resilient
force of the spring (not shown), as depicted at the lower half in FIG.
1.
With movement of the plunger
17, the rear end fluid chamber (A) varies in
volume, and the oil around the solenoid-operated valve within an oil pan (not shown)
containing the same is charged into the rear end fluid chamber (A) or discharged
therefrom through the labyrinth supply/drain passage
23, the intermediate
fluid chamber (C), the clearance between the center hole
11c and
the rod portion
24a, the electromagnetic section fluid chamber (B),
and the communication node
17c.
In the foregoing embodiment, the non-magnetic portion
14 between the core
portion
12 and the yoke portion
13 each made of a magnetic material
can be formed easily and completely by piling up or laminating the plural non-magnetic
portion annular plate elements
15c made of a non-magnetic material
between the plural core portion annular plate elements
15a1,
15a2
and
15a3 made of a magnetic material and the plural yoke portion
annular plate elements
15b made of a magnetic material. Thus, the
magnetic flux can be prevented from leaking from the yoke portion
13 directly
to the core portion
12 without passing through the plunger
17, and
it is ensured that the magnetic flux passes from the yoke portion
13 reliably
through the plunger
17 to the core portion
12, as indicated by a
loop line with arrow in FIG.
1. Therefore, it does not occur that such magnetic
leakage causes the magnetic attraction force on the plunger
17 to be weakened.
Further, the plural annular plate elements
15 (
15a1,
15a2,
15a3,
15b,
15c) which constitute the
stator body
11 of the electromagnetic drive device
10 can be obtained
by being blanked out from a plate member on a press, so that the electromagnetic
drive device
10 can be reduced in the manufacturing cost.
Also in the foregoing embodiment, the plural embossed portions (T) each of which
is prominent at the side of the front surface (Ta) and hollow at the side of the
reverse surface (Tb) are formed on the body portion (S) of each annular plate member
15, and the prominent front surface (Ta) of the embossed portion (T) on
each annular plate element
15 is fit in the hollow reverse surface (Tb)
of the embossed portion (T) on another annular plate element
15 to be piled
thereon, and in this way, all the annular plate elements
15 are joined one
after another. Thus, it becomes quite easer to join all the annular plate elements
15 bodily in axial alignment with one another. In addition, since the embossed
portions (T) can be formed at the same time when each annular plate element
15
is formed by being blanked out on a press, the forming of the embossed portions
(T) can be practiced without incurring a substantial extra cost, so that the manufacturing
cost for the annular plate elements
15 does not increase.
Although in the foregoing embodiment, each embossed portion (T) is predetermined
in width and arc in cross-section, it is not limited to the shape. Rather, each
embossed portion (T) may take the cross-section of a shallow trapezoid or any arbitrary
shape. Or, the embossed portion (T) may be formed by practicing half-blanking process
at each designated positions on the body portion (S) of each annular plate member
15 with a round punch and a die with a die hole of the same diameter, and
all the annular plate elements
15 may be joined by fitting the prominent
front surfaces (Ta) of the embossed portions (T) of each annular plate element
15 in the corresponding hollow reverse surfaces (Tb) of the embossed portions
(T) of another plate element
15 to be piled thereon.
Also in the aforementioned embodiment, the inner bore
11a of the
stator body
11 constituted by joining the plural annular plate members
15
is finished thereby to smoothen the sliding movement of the plunger
17 in
the inner bore
11a, and the clearance between the plunger
17
and the inner bore
11a is minimized to increase the magnetic attraction
force, so that the performance of the electromagnetic drive device
10 can
be enhanced, In this particular embodiment, since the half-blanking for the embossed
portions (T) is carried out simultaneously of the punching-out of the body portion
(S), high precision can be attained as to the relative position between the inner
bore
11a and each of the embossed portions (T), and the internal
surface of each annular plate element
15 which can be obtained by a punching-out
operation on a press is kept at a certain degree of preciseness as a matter of
course. Accordingly, the punched-out internal surfaces of the plural annular plate
elements
15 which are joined at the embossed portions (T) thereof each fit
in another have a high concentricity, and thus, a small allowance is sufficient
for finishing the inner bore
11a, so that the machining cost for
such finish process can be restrained from increasing.
Further, in the foregoing embodiment, the stator body
11 is provided
with the flange portion
11d only at the forward end portion serving
as the core portion
12. However, in the second embodiment, as shown in FIG.
6, there may be used another stator body
11A which is provided with another
flange portion
11a also at the rear end portion serving as the yoke
portion
13 in addition to the flange portion
11d provided
at the forward end portion. Therefore, in the second embodiment, the yoke portion
13 is composed of two zones E
1 and E
2, and first yoke portion
annular plate elements
15b1 in the zone E
1 take the same configuration
as the yoke portion annular plate elements
15b shown in FIG. 2, while
second yoke portion annular plate elements
15b2 in the zone E
2
take the same configuration as the third core portion annular plate elements
15a3
shown in FIG. 2 except for the difference in the diameter of the internal surface.
Further, joining all the annular plate elements
15 at the embossed portions
(T) thereof can be done in the same manner as those shown in FIG. 3 through 5.
Since the laminated stator body
11A can be easily separated into two or
more laminated blocks at any desired potions within any of the zones D
1,
D
2, E
1 and E
2 by disengaging the embossed portions (T), any
difficulty does not arise in assembling the electromagnetic coil
18.
Obviously, numerous modifications and variations of the present invention
are possible in light of the above teachings. It is therefore to be understood
that within the scope of the appended claims, the present invention may be practiced
otherwise than as specifically described herein.
*
