Information
-
Patent Grant
-
6724289
-
Patent Number
6,724,289
-
Date Filed
Friday, August 17, 200123 years ago
-
Date Issued
Tuesday, April 20, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 336 65
- 336 90
- 336 92
- 336 96
- 336 107
- 336 192
- 336 198
- 123 634
- 123 635
-
International Classifications
-
Abstract
An ignition apparatus includes a high voltage (HV) terminal formed of stamped sheet metal configured to be disposed in a secondary winding spool, and to which a high voltage end of the secondary winding is attached and soldered. The ignition apparatus further includes an electrically conductive cup configured to surround the high voltage terminal when the secondary winding spool is inserted in the case. The high voltage terminal has one end that comes into engagement with an inner annular surface of the cup. The cup includes an annular sidewall that extends axially up to a winding flange where a HV end of the secondary winding exits a winding bay thereby surrunding the exiting HV secondary winding wire. The cup provides for a reduced electric field concentration.
Description
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates generally to an ignition apparatus for developing a spark firing voltage that is applied to one or more spark plugs of an internal combustion engine.
2. Discussion of the Background Art
Ignition coils are known for use in connection with an internal combustion engine such as an automobile engine, and which include a primary winding, a secondary winding, and a magnetic circuit. The magnetic circuit conventionally may comprise a cylindrical-shaped, central core extending along an axis, located radially inwardly of the primary and secondary windings and magnetically coupled thereto. The components are contained in a case formed of electrical insulating material, with an outer core or shield located outside of the case. One end of the secondary winding is conventionally configured to produce a relatively high voltage when a primary current through the primary winding is interrupted. In a common configuration, insulating resin or the like is introduced into the gap between the secondary winding and the case for insulating purposes. The high voltage end is coupled to a spark plug, as known, that is arranged to generate a discharge spark responsive to the high voltage. It is further known to provide relatively slender ignition coil configuration that is adapted for mounting directly above the spark plug—commonly referred to as a “pencil” coil.
One problem in the design of ignition coils, particularly pencil coils, involves a relatively high electrical field concentration at a location where the high voltage end of the secondary winding is terminated to a high voltage (HV) secondary terminal associated to a secondary winding spool. The relatively high electrical field concentration may be magnified by any burr, sharp edge, or solder icicle that may be formed on the terminal.
In addition, to connect the high voltage end of the secondary winding to the HV secondary terminal, the wire end must leave a so-called winding bay (i.e., the winding surface on the spool between upper and lower flanges). Outside the winding bay, the secondary winding wire creates a high density electric field therearound. As a consequence, the increased electrical field concentration, over time, may result in an electrical tree or dendrite forming off of the secondary winding, which may propagate through the insulating resin. After the dendrite grows far enough, for example toward ground potential (i.e., through the resin and case to the shield), the high voltage secondary winding will short to ground and the ignition coil will fail.
U.S. Pat. No. 6,208,231 issued to Oosuka et al. entitled “STICK-TYPE IGNITION COIL HAVING IMPROVED STRUCTURE AGAINST CRACK OR DIELECTRIC DISCHARGE,” discloses an ignition coil wherein a high voltage end of the secondary coil is electrically connected to a dummy coil, which is then electrically connected to a terminal plate. A high voltage connector configured for connection to a spark plug is then connected to the terminal plate. Oosuka et al. disclose the contention that since the secondary coil and the terminal plate are electrically connected through not a single connection but rather through the dummy coil, the surface area of the electrically connected portion between the secondary coil and the terminal plate is enlarged so as to avoid the concentration of electrical field. However, Oosuka et al. still disclose that the high voltage end of the dummy coil is electrically connected to the terminal plate by fusing or soldering. Additionally, the secondary winding wire as it leaves the winding bay still presents a relatively thin profile, wherein a high electric field is maintained. Accordingly, it is believed that the same problems described above continue to exist in the design of Oosuka et al.
Accordingly, there is a need for an improved ignition apparatus that minimizes or eliminates one or more of the problems as set forth above.
SUMMARY OF THE INVENTION
An object of the present invention is to solve one or more of the problems as set forth above. An ignition apparatus according to the present invention overcomes shortcomings of conventional ignition apparatus by including an electrically conductive cup absent of sharp edges, burrs, or the like, which makes contact with a portion of a high voltage terminal. The cup also surrounds the high voltage terminal and the secondary winding wire as it exits the winding bay (i.e., it extends, in an axial direction, up to a lower winding flange). Because the cup is at the same voltage potential as the high voltage terminal, there will not be an electric field concentration in and around the area of the high voltage terminal. Additionally, since the cup extends up to the winding flange, the secondary connection wire is also surrounded, reducing the electric field in that region. The reduction in electric field concentration reduces or eliminates formation of dendrites which, as described in the Background, may over time result in ignition coil failures.
An ignition apparatus according to the present invention comprises a central core having a main axis, and primary and secondary windings outwardly of the central core. The secondary winding is wound on a secondary winding spool having a winding surface and at least one flange. The flange is provided to cooperate with the winding surface to receive the secondary winding. A high voltage end of the secondary winding is connected to a high voltage terminal located away from the winding surface. According to the invention, a cup formed of metal material engages the high voltage terminal on an inner surface thereof. The cup is configured to be contacted by a connector assembly that is itself suitable for connection to a spark plug. The cup surrounds the HV terminal, and, significantly, extends axially up to the winding flange also surrounding the secondary winding wire as it exits the winding surface. The cup being free of sharp edges and the like, as well as surrounding the secondary winding wire, reduces electrical field concentrations.
A method of making an ignition apparatus including the aforementioned conductive cup is also presented.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be described by way of example, with reference to the accompanying drawings.
FIG. 1
is a simplified cross-sectional view of an ignition apparatus having a conductive cup high voltage terminal arrangement according to the present invention.
FIG. 2
is a simplified cross-sectional view showing a portion of the cup of FIG.
1
.
FIG. 3
is a simplified perspective view of the apparatus of
FIG. 1
, with portions broken away, showing a connection to a HV terminal.
FIG. 4
is a simplified cross-sectional view taken substantially along lines
4
—
4
in
FIG. 3
showing the HV terminal contacting the conductive cup.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings wherein like reference numerals are used to identify identical components in the various views,
FIG. 1
is a simplified, cross-section view of an ignition apparatus or coil
10
in accordance with the present invention. As is generally known, ignition apparatus
10
may be coupled to, for example, an ignition system
12
, which contains primary energization circuitry for controlling the charging and discharging of ignition apparatus
10
. Further, the relatively high voltage produced by ignition apparatus
10
is provided to a spark plug
14
for producing a spark across a spark gap thereof, which may be employed to initiate combustion in a combustion chamber of an engine. Ignition system
12
and spark plug
14
perform conventional functions well known to those of ordinary skill in the art.
Ignition apparatus
10
is adapted for installation to a conventional internal combustion engine through a spark plug well onto a high-voltage terminal of spark plug
14
, which may be retained by a threaded engagement with a spark plug opening into the above-described combustion cylinder. The engine may provide power for locomotion of a self-propelled vehicle, such as an automotive vehicle.
FIG. 1
further shows a core
16
, an optional first magnet
18
, an optional second magnet
20
, an electrical module
22
, a primary winding
24
, a first layer of encapsulant such as an epoxy potting material layer
26
, a secondary winding spool
28
, a secondary winding
30
, a second layer
32
of encapsulant such as epoxy potting material, a case
34
, a shield assembly
36
, a first electrically conductive cup
37
, a low-voltage (LV) connector body
38
, and a high-voltage (HV) connector assembly
40
. Core
16
includes a top end
42
and a bottom end
44
. Connector assembly
40
may include an inductive resistor
41
, a second conductive cup
43
, and a spring
68
.
FIG. 1
further shows a rubber buffer cup
46
, a winding surface
47
of spool
28
, annular flange portions
48
,
50
, a high voltage (HV) secondary terminal
52
, a boot
54
, and a seal member
56
.
As described in the Background, a significant failure mode for conventional pencil coils results from a high electric field intensity where the high voltage end of the secondary winding is brought out of the winding bay and routed to the HV secondary terminal. Over time, with such conventional arrangements, dendrites form, and grow through the insulating epoxy and case toward ground potential (e.g., toward the shield element). Once the insulating resin and/or case material has been compromised, the high voltage secondary winding can short to ground, thus failing the ignition coil.
Conductive cup
37
is made so as to not have sharp edges, burrs, or the like. The cup is in electrical contact with the high voltage terminal, and is therefore at the same electrical potential or voltage. Significantly, the cup has annular sidewalls that extend axially up to the lower winding flange
50
. Accordingly, the aforementioned electric field concentration is reduced relative to the prior art.
FIG. 2
shows a portion of
FIG. 1
containing cup
37
in greater detail. The HV terminal
52
may be of the conventional stamped sheet metal type (e.g., 1008 steel) that is associated with secondary spool
28
, and to which a high voltage end of secondary winding
30
is terminated.
Cup
37
, generally, is configured in size and shape to be pressed or molded onto a lower axial portion of spool
28
. Cup
37
is manufactured in such a way so as to not have any sharp edges, burrs, or the like. These manufacturing approaches include but are not limited to machining and stamping, coupled with, for example, a vibratory finishing.
Cup
37
has a longitudinal axis associated therewith and is generally annular in shape. Cup
37
further includes a base
58
, and a first, generally annular side wall
59
extending therefrom in a first axial direction to a folded over (hemmed) edge
60
that defines an opening leading to an interior of the cup. The interior is configured to receive a lower longitudinal end of secondary winding spool
28
. The lower end of spool
28
is configured to receive the high voltage terminal
52
. The interior is defined, in-part, by an inner, generally annular surface of sidewall
59
. The axial extent of sidewall
59
is such that it extends all the way up to flange
50
when cup
37
is placed on spool
28
(so that base
58
engages spool
28
).
Cup
37
further includes a second annular side wall
61
extending from base
58
in a second axial direction opposite the first axial direction. In the illustrated embodiment, cup
37
includes an annular aperture
62
having a stop surface
63
. Aperture
62
is configured in size and shape to receive an end of resistor
41
in a press fit (interference fit).
Significantly, however, cup
37
is formed out of stamped sheet metal, which is subjected to a drawing and forming operation to arrive at the result shown in
FIGS. 1-4
. Fold
60
exhibits a relatively large radii, so as to maintain a reduced electric field (i.e., eliminate sharp edges). In addition, since sidewall
59
extends up to flange
50
, the cup surrounds the secondary winding
30
as it exits winding surface
47
. Cup
37
may be formed out of aluminum, brass, or other suitable electrically conductive material.
FIG. 3
is a perspective of ignition apparatus
10
, with portions broken away. Secondary winding
30
exits the winding bay through an axially extending passage
65
. In the illustrated embodiment, terminal
52
comprises a wire that is square shaped in cross-sectional. Terminal
52
is inserted in a bore
53
formed in spool
28
. A high voltage end of winding
30
, designated
30
HV
, is terminated on end
52
1
of terminal
52
, for example, via multiple turns, accompanied by a conventional soldering process.
With reference to
FIG. 4
, when secondary spool
28
is inserted and pressed longitudinally downwardly into case
34
, terminal
52
will go down into an interior portion of cup
37
. A first end
52
1
, is bent over after the high voltage end
30
HV
is terminated thereto. The second end
52
2
is also bent over; however, the shape and dimensions of spool
28
and cup
37
are selected so that end
52
2
engages cup
37
when cup
37
is placed over the bottom of spool
28
. The shape of spool
28
and dimensions are further selected so that end
52
1
does not touch cup
37
. Terminal end
52
2
and cup
37
will be in positive electrical contact. Because cup
37
is at substantially the same voltage potential as high voltage terminal
52
, and cup
37
surrounds terminal
52
, there will be a substantially reduced or eliminated electric field concentration at terminal
52
. Moreover, since cup
37
has sidewalls
59
that extend axially up to flange
50
(best shown in FIGS.
2
-
3
), the wire exiting the secondary winding bay is also surrounded. This has the advantage of reducing the concentrated electric field surrounding the thin wire.
As to additional advantages, solder tips and sharp edges that are present at the point where the secondary winding is terminated (e.g., end
52
1
), and which arise due to conventional manufacturing processes can now be tolerated. In addition, the design of an ignition apparatus according to the invention will also be robust as to the bend position of terminal
52
1
, so that the position of terminal
52
1
will now not have to be as controlled. In conventional arrangements, if high voltage terminal end
52
1
were not bent over far enough, the radially outermost portions thereof would be closer to case
34
, and would result in a higher electric field. As to cost advantages, an ignition apparatus according to the invention is less expensive to manufacture since certain manufacturing equipment can be eliminated, such as (i) that required to eliminate sharp solder points, (ii) that needed to measure the HV terminal bend position. Finally, in an internal combustion engine environment, the reduced electric field will result in lower ignition apparatus failures, and accordingly a lower warranty return rate. These improvements result by the substantial reduction or elimination of case punch-through failures (i.e., dendrite growth through insulating resin material, through case material, to ground potential, namely, the outer core or shield). The reduced electric field concentration will also extend the service life of the ignition apparatus.
Referring again to
FIG. 1
, further details concerning ignition apparatus
10
will now be set forth configured to enable one to practice the present invention. It should be understood that portions of the following are exemplary only and not limiting in nature. Many other configurations are known to those of ordinary skill in the art and are consistent with the teachings of the present invention. Central core
16
may be elongated, having a main, longitudinal axis “A” associated therewith. Core
16
includes an upper, first end
42
, and a lower, second end
44
. Core
16
may be a conventional core known to those of ordinary skill in the art. As illustrated, core
16
, in the preferred embodiment, takes a generally cylindrical shape (which is a generally circular shape in radial cross-section), and may comprise compression molded insulated iron particles or laminated steel plates, both as known.
Magnets
18
and
20
may be optionally included in ignition apparatus
10
as part of the magnetic circuit, and provide a magnetic bias for improved performance. The construction of magnets such as magnets
18
and
20
, as well as their use and effect on performance, is well understood by those of ordinary skill in the art. It should be understood that magnets
18
and
20
are optional in ignition apparatus
10
, and may be omitted, albeit with a reduced level of performance, which may be acceptable, depending on performance requirements.
A rubber buffer cup
46
may be included.
Module
22
may be configured to perform a switching function, such as connecting and disconnecting an end of primary winding to ground.
Primary winding
24
may be wound directly onto core
16
in a manner known in the art. Primary winding
24
includes first and second ends and is configured to carry a primary current I
P
for charging apparatus
10
upon control of ignition system
12
of module
22
. Winding
24
may be implemented using known approaches and conventional materials. Although not shown, primary winding
24
may be wound on a primary winding spool (not shown) in certain circumstances (e.g., when steel laminations are used). In addition, winding
24
may be wound on an electrically insulating layer that is itself disposed directly on core
16
.
Layers
26
and
32
comprise an encapsulant suitable for providing electrical insulation within ignition apparatus
10
. In a preferred embodiment, the encapsulant comprises epoxy potting material. The epoxy potting material introduced in layers
26
, and
32
may be introduced into annular potting channels defined (i) between primary winding
24
and secondary winding spool
28
, and, (ii) between secondary winding
30
and case
34
. The potting channels are filled with potting material, in the illustrated embodiment, up to approximately the level designated “L” in FIG.
1
. In one embodiment, layer
26
may be between about 0.1 mm and 1.0 mm thick. Of course, a variety of other thicknesses are possible depending on flow characteristics and insulating characteristics of the encapsulant and the design of the coil
10
. The potting material also provides protection from environmental factors which may be encountered during the service life of ignition apparatus
10
. There is a number of suitable epoxy potting materials well known to those of ordinary skill in the art.
Secondary winding spool
28
is configured to receive and retain secondary winding
30
. In addition to the features described above, spool
28
is further characterized as follows. Spool
28
is disposed adjacent to and radially outwardly of the central components comprising core
16
, primary winding
24
, and epoxy potting layer
26
, and, preferably, is in coaxial relationship therewith. Spool
28
may comprise any one of a number of conventional spool configurations known to those of ordinary skill in the art. In the illustrated embodiment, spool
28
is configured to receive one continuous secondary winding (e.g., progressive winding) on an outer winding surface thereof, between upper and lower flanges
48
and
50
(“winding bay”), as is known. However, it should be understood that other configurations may be employed, such as, for example only, a configuration adapted for use with a segmented winding strategy (e.g., a spool of the type having a plurality of axially spaced ribs forming a plurality of channels therebetween for accepting windings) as known.
The depth of the secondary winding in the illustrated embodiment may decrease from the top of spool
28
(i.e., near the upper end
42
of core
16
), to the other end of spool
28
(i.e., near the lower end
44
) by way of a progressive gradual flare of the spool body. The result of the flare or taper is to increase the radial distance (i.e., taken with respect to axis “A”) between primary winding
24
and secondary winding
30
, progressively, from the top to the bottom. As is known in the art, the voltage gradient in the axial direction, which increases toward the spark plug end (i.e., high voltage end) of the secondary winding, may require increased dielectric insulation between the secondary and primary windings, and, may be provided for by way of the progressively increased separation between the secondary and primary windings.
Spool
28
is formed generally of electrical insulating material having properties suitable for use in a relatively high temperature environment. For example, spool
28
may comprise plastic material such as PPO/PS (e.g., NORYL available from General Electric) or polybutylene terephthalate (PBT) thermoplastic polyester. It should be understood that there are a variety of alternative materials that may be used for spool
28
known to those of ordinary skill in the ignition art, the foregoing being exemplary only and not limiting in nature.
Features
48
and
50
may be further configured so as to engage an inner surface of case
34
to locate, align, and center the spool
28
in the cavity of case
34
and providing upper and lower defining features for a winding surface therebetween.
As described above, spool
28
has associated therewith an electrically conductive (i.e., metal) high-voltage (HV) terminal
52
disposed therein configured to engage cup
37
, which cup is in turn electrically connected to the HV connector assembly
40
. The body of spool
28
at a lower end thereof is configured so as to be press-fit into the interior of cup
37
(i.e., the spool gate portion).
FIG. 1
also shows secondary winding
30
in cross-section. Secondary winding
30
, as described above, is wound on spool
28
, and includes a low voltage end and a high voltage end
30
HV
. The low voltage end may be connected to ground by way of a ground connection through LV connector body
38
in a manner known to those of ordinary skill in the art. The high voltage end
30
HV
is connected to HV terminal
52
as shown in FIG.
3
. Winding
30
may be implemented using conventional approaches and material known to those of ordinary skill in the art.
Case
34
includes an inner, generally enlarged cylindrical surface, an outer surface, a first annular shoulder, a flange, an upper through-bore, and a lower through bore.
The inner surface of case
34
is configured in size to receive and retain spool
28
which contains the core
16
and primary winding
24
. The inner surface of case
34
may be slightly spaced from spool
28
, particularly the annular features
48
,
50
thereof (as shown), or may engage the features
48
,
50
.
Lower through-bore
64
(best shown in
FIG. 2
) is defined by an inner surface thereof configured in size and shape (i.e., generally cylindrical) to accommodate an outer surface of cup
37
at a lowermost portion thereof as described above. When the lowermost body portion of spool
28
is inserted in the lower bore containing cup
37
, a portion of HV terminal
52
2
engages an inner surface of cup
37
(also via a press fit) as best shown in FIG.
4
.
Case
34
is formed of electrical insulating material, and may comprise conventional materials known to those of ordinary skill in the art (e.g., the PBT thermoplastic polyester material referred to above).
Shield
36
is generally annular in shape and is disposed radially outwardly of case
34
, and, preferably, engages an outer surface of case
34
. The shield
36
preferably comprises electrically conductive material, and, more preferably metal, such as silicon steel or other adequate magnetic material. Shield
36
provides not only a protective barrier for ignition apparatus
10
generally, but, further, provides a magnetic path for the magnetic circuit portion of ignition apparatus
10
. Shield
36
may be grounded by way of an internal grounding strap, finger or the like (not shown) well know to those of ordinary skill in the art. Shield
36
may comprise multiple, individual sheets
36
, as shown.
Low voltage connector body
38
via module
22
is configured to, among other things, electrically connect the first and second ends of primary winding
24
to an energization source, such as, the energization circuitry (e.g., power source) included in ignition system
12
. Connector body
38
is generally formed of electrical insulating material, but also includes a plurality of electrically conductive output terminals
66
(e.g., pins for ground, primary winding leads, etc.). Terminals
66
are coupled electrically, internally through connector body
38
to module
22
and other portions of apparatus
10
, in a manner known to those of ordinary skill in the art.
HV connector assembly
40
is provided for establishing an electrical connection to spark plug
14
. Assembly
40
may include an inductive resistor
41
, a second conductive cup
43
and a spring contact
68
or the like. Resistor
41
may be provided to combat electromagnetic interference (EMI). Second cup
43
provides for a transition spring
68
. Cup
43
includes an annular projection
70
configured allow spring
68
to be coupled thereto. Contact spring
68
is in turn configured to engage in a high-voltage connector terminal of spark plug
14
. This arrangement for coupling the high voltage developed by secondary winding
30
to plug
14
is exemplary only; a number of alternative connector arrangements, particularly spring-biased arrangements, are known in the art.
An ignition apparatus in accordance with the present in invention includes a conductive cup used in establishing a high voltage connection between the secondary winding/HV terminal and the spark plug (perhaps via additional components such as resistor
41
, cup
43
and via spring
68
) which significantly reduces the electric field intensity in the area of the connection. Particularly, the cup
37
has a sidewall that extends axially up to the flange. This extension surrounds the HV end portion of secondary winding
30
as it leaves the winding bay, which is operative to reduce the electric field concentration. The reduction in the electric field intensity substantially minimizes or eliminates a significant failure mode for pencil ignition coils, namely, the grounding out of the secondary winding through an arcing via a dendrite formed in the insulating material (e.g., to a ground such as the outer core or shield). This reduction of the occurrence of this failure mode leads to lower warranty returns, as well as increasing the product's expected service life.
Claims
- 1. An ignition apparatus comprising:a central core having a main axis; a primary winding; a spool having a winding surface and a flange; a terminal; a secondary winding wound on said surface and having a high-voltage end thereof connected to said terminal; and a cup formed of metal material engaging said terminal and configured to be contacted by a connector assembly for connection to a spark plug, wherein said cup defines a first cup having a base and a generally annular side wall, said side wall extending from said base to said spool flange in a generally axial direction relative to said main axis, said side wall having an interior surface facing said spool and terminal, said interior surface of said first cup engaging said terminal; said connector assembly including a second conductive cup, a resistive element between said first cup and said second cup, and a spring coupled to said second cup.
- 2. The apparatus of claim 1 wherein said resistive element comprises a ceramic resistor, said spring being configured to be connected to the spark plug.
- 3. The apparatus of claim 1 wherein said flange extends radially outwardly relative to said winding surface, said flange including an axially extending passage configured to allow said high voltage end of said secondary winding to pass therethrough to said terminal.
- 4. The apparatus of claim 1 wherein said sidewall is a first side wall and said axial direction is a first axial direction, said cup having a second annular side wall extending from said base in a second axial direction opposite said first axial direction, said second annular side wall terminating in a closed end of said cup.
- 5. The apparatus of claim 4 wherein said first annular wall has a first diameter associated therewith and said second annular side wall has a second diameter associated therewith smaller than said first diameter.
- 6. The apparatus of claim 1 wherein said up comprises one of aluminum, brass material, and steel.
- 7. The apparatus of claim 1 wherein said cup is configured to surround said terminal and said high voltage end of said secondary winding.
- 8. The apparatus of claim 1 wherein said cup is formed of stamped sheet metal, a fold region defined at an end of said first annular wall.
- 9. The apparatus of claim 1 wherein said terminal is configured to present a resilient arrangement for engaging an inner surface of said cup.
- 10. An ignition coil comprising:a central core formed of magnetically permeable material having a main axis; a primary winding disposed radially outwardly of said core; a secondary winding spool having a winding surface and a flange; a high-voltage terminal; a secondary winding wound on said surface and having a high-voltage end thereof connected to said high-voltage terminal; a case formed of electrical insulating material disposed outwardly of said core, said spool and said primary and secondary windings; an outer core formed of magnetically permeable material located radially outwardly of said case; and a cup formed of metal contacting said high-voltage terminal configured to be contacted by a connector assembly for connection to a spark plug, wherein said cup has a base and a generally annular side wall extending radially along said main axis around said terminal and extending axially to said flange thereby providing an interior surface to engage said terminal.
- 11. The apparatus of claim 10 wherein said flange includes at least one axially extending passage for allowing said high-voltage end of said secondary winding to pass therethrough for connection to said terminal.
US Referenced Citations (4)
Number |
Name |
Date |
Kind |
5714922 |
Suzuki et al. |
Feb 1998 |
A |
6023215 |
Sakamaki et al. |
Feb 2000 |
A |
6094121 |
Sakamaki et al. |
Jul 2000 |
A |
6208231 |
Oosuka et al. |
Mar 2001 |
B1 |
Foreign Referenced Citations (1)
Number |
Date |
Country |
0837481 |
Apr 1998 |
EP |