U.S. patent application number 09/774928 was filed with the patent office on 2002-08-01 for ignition apparatus having built-in noise suppression.
Invention is credited to Gernert, Klaus, Hamer, Colin, Skinner, Albert Anthony.
Application Number | 20020101316 09/774928 |
Document ID | / |
Family ID | 25102724 |
Filed Date | 2002-08-01 |
United States Patent
Application |
20020101316 |
Kind Code |
A1 |
Hamer, Colin ; et
al. |
August 1, 2002 |
IGNITION APPARATUS HAVING BUILT-IN NOISE SUPPRESSION
Abstract
An ignition apparatus includes a suppression device comprising a
suppression winding that is in series with the secondary winding
and is further located outside of a magnetic circuit. The
suppression winding is made from the same wire as used in the
secondary winding and is wound on a reduced diameter portion of a
secondary winding spool. A carbon resistor is disposed in series
with the suppression winding in another embodiment. Nickel wire may
be substituted for the suppression winding and carbon resistor in
order to obtain both inductance and resistance characteristics for
the suppression device.
Inventors: |
Hamer, Colin; (Noblesville,
IN) ; Skinner, Albert Anthony; (Anderson, IN)
; Gernert, Klaus; (Konz, DE) |
Correspondence
Address: |
MARGARET A. DOBROWITSKY
DELPHI TECHNOLOGIES, INC.
Legal Staff Mail Code: 480-414-420
P.O. Box 5052
Troy
MI
48007-5052
US
|
Family ID: |
25102724 |
Appl. No.: |
09/774928 |
Filed: |
January 31, 2001 |
Current U.S.
Class: |
336/96 |
Current CPC
Class: |
F02P 3/02 20130101; Y10T
29/4902 20150115; H04B 15/025 20130101; F02P 13/00 20130101 |
Class at
Publication: |
336/96 |
International
Class: |
H01F 027/02 |
Claims
1. An ignition apparatus comprising: a magnetically-permeable
central core having a main axis; primary and secondary windings
outwardly of said core, said secondary winding being wound on a
secondary winding spool of magnetically non-permeable material,
said core and said windings being included in a magnetic circuit;
and a suppression device disposed outside of said magnetic circuit
comprising a suppression winding wound on said spool connected in
series with said secondary winding.
2. The ignition apparatus of claim 1 wherein said core has first
and second opposing ends with respect to said main axis, said
suppression winding being axially spaced from one of said ends.
3. The ignition apparatus of claim 1 wherein said suppression
winding comprises a continuation of a conductor used for said
secondary winding.
4. The ignition apparatus of claim 2 further comprising a
magnetically-permeable shield having a cylindrical shape disposed
radially outwardly of said central core and primary and secondary
windings and included in said magnetic circuit, said suppression
winding being axially spaced from an axial end of said shield.
5. The ignition apparatus of claim 3 wherein said secondary winding
spool includes a terminal formed of electrically conductive
material configured for connection to a high-voltage connector
assembly for providing a spark plug a firing voltage, a terminating
end of said suppression winding being connected to said
terminal.
6. The ignition apparatus of claim 3 wherein said secondary winding
spool includes a channel configured to allow passage of said
conductor.
7. The ignition apparatus of claim 1 wherein said suppression
winding is wound on said secondary winding spool.
8. The ignition apparatus of claim 7 wherein said secondary winding
is wound on a portion of said secondary winding spool having a
first diameter, said suppression winding is wound on a second
portion of said spool having a second diameter less than said first
diameter.
9. The ignition apparatus of claim 8 wherein an inductance of said
suppression winding is determined as a function of said second
diameter.
10. The ignition apparatus of claim 9 wherein said second diameter
is selected as a function of a desired suppression bandwidth.
11. The ignition apparatus of claim 10 wherein said suppression
bandwidth is at least one of a first bandwidth including a first
frequency of about 22 kHz and a second bandwidth including a second
frequency of about 100 MHz.
12. The ignition apparatus of claim 1 further including a resistor
in series with said secondary winding and said suppression
winding.
13. The ignition apparatus of claim 12 wherein said resistor
comprises a carbon resistor.
14. The ignition apparatus of claim 12 wherein said secondary
winding spool includes a first terminal, a second terminal and a
third terminal each formed of metal, said resistor being coupled
between said first and second terminals, said secondary winding
being coupled to said first terminal, said suppression winding
being coupled between said second and third terminals, and said
third terminal being coupled to a high-voltage connector assembly
configured for connection to a spark plug.
15. The ignition apparatus of claim 12 wherein said secondary
winding spool includes a first terminal, a second terminal and a
third terminal, each formed of metal, said suppression winding and
said secondary winding being continuous and terminated on said
first terminal, said resistor being coupled between said first and
second terminals, said second terminal being coupled to said third
terminal that is connected to a high-voltage connector assembly
configured for connection to a spark plug.
16. The ignition apparatus of claim 1 wherein said secondary
winding comprises copper wire having an electrically insulating
coating, said suppression winding comprising nickel wire to thereby
introduce an inductance and resistance component.
17. An ignition apparatus comprising: a central core of
magnetically-permeable material having a main axis; a primary and a
secondary winding radially outwardly of said central core, said
secondary winding being wound on a secondary winding spool of
non-magnetically-permeable material; a shield radially outwardly of
said windings formed of magnetically-permeable material, said
central core, said windings and said shield forming a magnetic
circuit; and a suppression winding in series with said secondary
winding disposed outside of said magnetic circuit.
18. The ignition apparatus of claim 17, wherein said suppression
winding is axially spaced from respective axial ends of said core
and said shield.
19. A method of making an ignition apparatus comprising the step
of: winding a suppression coil on a secondary winding spool having
a main axis that is axially spaced from a secondary winding such
that the suppression coil is outside of a magnetic circuit.
20. The method of claim 19 further including the step of forming
the spool such that a portion thereof bearing the suppression
winding has a diameter selected to yield a preselected inductance
for the suppression winding so as be operative to suppress one of a
first bandwidth including 22 kHz and a second bandwidth including
100 MHz.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] The present invention relates generally to ignition coils
for developing a spark firing voltage that is applied to one or
more spark plugs of an internal combustion engine.
[0003] 2. Discussion of the Background Art
[0004] 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. 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. 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. The spark plug, however, operates as a noise generating
source when such spark events occur, which may result in radio
frequency interference (RFI). Separate mount ignition coils are
generally connected to the spark plug through a spark plug cable,
which has a minimizing effect on the RFI, due to its inherent
inductance characteristics. Some types of ignition coils do not use
ignition cables. For example, a relatively slender ignition coil
configuration is known that is adapted for mounting directly above
a spark plug--commonly referred to as a "pencil" coil. Such
ignition coils, therefore, do not utilize ignition cables.
Accordingly, the problem of RF noise presents particular challenges
in the design of "pencil" (i.e., direct mount) coils.
[0005] One approach taken in the art is disclosed in U.S. Pat. No.
5,603,307 issued to Morita et al. Morita et al. disclose a buffer
coil having an inductance that is much smaller than that of either
the primary winding or the secondary winding connected in series
with one of them. Morita et al., however, does not appear to
disclose that the buffer coil is outside of the magnetic circuit
described above, and is therefore not believed to be as effective
in suppressing RF noise as may be possible.
[0006] Another approach taken in the art involves connecting a wire
wound resistor in series with the secondary winding at the high
voltage end of the secondary winding. Incorporating the resistor
into the ignition coil adds complexity and introduces mechanical
stress inasmuch as the substrate on which such wire wound resistors
are available have a different coefficient of thermal expansion
that conventional encapsulants (e.g., epoxy potting material) used
in potting ignition coils. This mismatch causes the stresses during
operation (thermal cycling) of the ignition coil, which in turn may
lead to failure (i.e., failure of the encapsulant material, which
leads to imperfect insulation).
[0007] 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
[0008] 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 the conventional
ignition apparatus by including a suppression device disposed
outside of a magnetic circuit and comprising a suppression winding
wound on the spool connected in series with the secondary winding.
The foregoing approach eliminates thermal stresses associated with
the conventional ignition coils that include a wire wound resistor.
In addition, the present invention is less costly to implement
compared to the use of the wire wound resistor. Being outside of
the magnetic circuit allows the suppression device to present an
inductance that is electrically distinct from the inductance
associated with the secondary winding--this improves the
suppression device's ability to reduce RF noise.
[0009] An ignition apparatus according to the present invention
comprises a magnetically permeable central core having a main axis,
primary and secondary windings outwardly of the core. The secondary
winding is wound on a secondary winding spool formed of
magnetically non-permeable material. The core and the windings
being included in a magnetic circuit. The apparatus further
includes a suppression device disposed outside of the magnetic
circuit comprising a suppression winding also wound on the spool
and that is connected in series with the secondary winding.
[0010] A method of making an ignition apparatus is also
presented.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The present invention will now be described by way of
example, with reference to the accompanying drawings, in which:
[0012] FIG. 1 is a simplified cross-sectional view of an ignition
apparatus according to the present invention;
[0013] FIG. 2 is a simplified schematic diagram illustrating a
suppression device used in the ignition apparatus of FIG. 1;
[0014] FIG. 3 is a simplified schematic diagram of a first
embodiment of the suppression device of FIG. 2;
[0015] FIG. 4 is a simplified schematic diagram of a second
embodiment of the suppression device of FIG. 2;
[0016] FIG. 5 is a simplified schematic diagram of a third
embodiment of the suppression device of FIG. 2;
[0017] FIG. 6 is a simplified schematic diagram of a fourth
embodiment of the suppression device of FIG. 2; and
[0018] FIG. 7 is a perspective view of a secondary winding spool
having the suppression device according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] 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 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, also as is well known, the relatively high
voltage produced by ignition apparatus 10 is provided to a spark
plug 14 (shown in phantom-line format) 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.
[0020] 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 vehicle, as known. Ignition apparatus 10
comprises a substantially slender high voltage transformer
including substantially, coaxially arranged primary and secondary
windings and a high permeability magnetic core.
[0021] FIG. 1 further shows a core 16, an optional first magnet 18,
an optional second magnet 20, 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 epoxy
potting material layer 32, a case 34, a shield 36, a low-voltage
(LV) connector body 38, and a high-voltage (HV) connector assembly
40. It should be understood that in conventional operation spark
plug 14, absent the improvement according to the present invention,
constitutes a source of radio frequency noise or interference when
producing sparks.
[0022] FIG. 2 is a schematic representation of an ignition
apparatus 10 according to the present invention. Ignition system
12, shown in block diagram form in FIG. 1, includes a control unit
70 and a switch 72. FIG. 2 further shows a suppression device 74
electrically connected in-series with secondary winding 30. As
further background, ccontrol unit 70 is configured generally to
perform a plurality of functions, including generation of an
ignition control signal EST (electronic spark timing). It should be
understood that the ignition control signal EST may be generated or
initiated by other control units not shown, such as a powertrain
control module (PCM) in accordance with known ignition control
strategies, and provided to control unit 70, such that control unit
70 responds by driving switch 72 to closure in response thereto. As
known, the ignition control signal defines the initial charging
time (e.g., duration), and the relative timing (e.g., relative to
cylinder top dead center) of when a spark is to occur. Switch 72 is
configured to selectively connect primary winding 24 to ground,
responsive to the ignition control signal. Such a connection to
ground, as is known generally in the art, will cause a primary
current I.sub.p to flow through primary winding 24. Switch 72 is
illustrated in the Figures as a block diagram; however, it should
be understood that switch 72 may comprise conventional components
known to those of ordinary skill in the art, such as, for purposes
of example only, an insulated gate bipolar transistor (IGBT). When
the ignition control signal is discontinued, switch 72 is opened up
thereby interrupting the primary current. A voltage rise occurs
across the secondary winding, a high voltage end of which is
coupled to spark plug 14. The spaced electrodes of plug 14
(defining a gap therebetween) are shown in diagrammatic form in
FIG. 2. The induced voltage continues to rise across this gap until
breakdown occurs, resulting in an electrical discharge across the
gap (i.e., the spark). As mentioned before, ordinarily this
discharge may lead to generation of radio frequency (RF) noise or
interference. According to the invention, however, suppression
device 74 is configured to suppress such RF noise.
[0023] FIGS. 3-6 illustrate various embodiments of suppression
device 74, respectively designated suppression devices 74a, 74b,
74c and 74d. Each will be described in turn, with coordinated
reference to FIG. 7.
[0024] FIG. 3 shows suppression device 74a that includes a
suppression winding 76 connected in series with secondary winding
30. Suppression winding 76 may comprise the same wire material used
for the main turns of secondary winding 30 and may also be
continuous therewith (i.e., no breaks).
[0025] With particular reference to FIG. 7, there is shown a
perspective view of secondary winding spool 28 carrying a plurality
of turns of wire on a main body portion thereof defining secondary
winding 30. In the illustrated embodiment, spool 28 may be formed
with a channel 78 configured to allow axial routing of the wire
that forms secondary winding 30. FIG. 7 also shows a first terminal
80 and a second terminal 82, in addition to a high-voltage terminal
52 that connects to high-voltage connector assembly 40 (best shown
in FIG. 1). In the first embodiment, the main turns of secondary
winding 30 are made, then, in a continuous fashion (e.g., on the
same winder), further turns are made to form suppression winding
76. The end of the suppression winding 76 is then connected to
high-voltage terminal 52. In the illustrative embodiment, the
diameter of the turns of suppression winding 76 is reduced relative
to the diameter of the turns of secondary winding 30. However, the
respective circular patterns of the secondary winding 30 and
suppression winding 76 are substantially coaxial, although axially
offset or spaced apart, one from another. The value of the
inductance sought for suppression winding 76 will vary depending on
the overall design of the ignition apparatus and the desired
suppression bandwidth ranges. For example purposes only, however,
the secondary winding 30 may comprise between about 10,000-30,000
turns of 40-46 AWG polyester coated copper wire, and may more
preferably be between about 15,000-25,000 turns, while the
suppression winding 76 may comprise approximately 20 turns of the
same wire at about a 16 mm diameter (e.g., which yields about 15 to
20 .mu.H).
[0026] In addition, suppression winding 76 (as well as winding 86
described below) is disposed outside of a magnetic circuit
comprising core 16, windings 24 and 30, and shield 36. This is
preferred since is presents the inductance provided by suppression
winding 76 as distinct from the inductance provided by secondary
winding 30, which improves the suppression effectiveness of
suppression device 74. Referring to FIG. 1, the lowermost axial
extent of any of the components in the magnetic circuit is
illustrated by the line designated "B", which corresponds to a
lowermost axial edge or bottom of shield 36. As further
illustrated, shield 36, core 16 and magnets 18, 20 (if present)
generally extend about the same axial length. While magnetic flux
may exist in areas below the line designated "B", "outside" of the
magnetic circuit herein means that the suppression winding is
axially spaced from line "B", or, in other words, below the
lowermost portion of any one of the core, magnets (if present),
primary and secondary windings, or shield.
[0027] FIGS. 4 and 5 show suppression devices 74b and 74c,
respectively, each including a suppression winding 76 connected in
series with a resistor 84. The embodiments of FIGS. 4 and 5 may be
used when a resistance is desirable or required in order to obtain
a predetermined suppression effect (i.e., to obtain a certain level
of suppression over a certain bandwidth on or around a nominal
center frequency). Resistor 84 may comprise a carbon resistor,
which is much less expensive than wire wound resistor referred to
in the Background (e.g., $0.01 versus $0.12-$0.20). Again,
suppression winding 76 may comprise the same wire material used for
the main turns of secondary winding 30.
[0028] Referring to FIGS. 4 and 7, and regarding suppression device
74b, when resistor 84 is placed intermediate the secondary winding
30 and suppression winding 76, it provides a measure of isolation
therebetween. In this embodiment, secondary winding 30 is wound and
the high voltage end thereof is routed through channel 78 and is
terminated on metal terminal 80. The ends of resistor 84 are
respectively coupled to metal terminals 80 and 82. Resistor 84 may
be disposed on the exterior of spool 28 or may alternatively be
molded into it. Suppression winding 76 may be wound as described
above on the reduced diameter portion of spool 28. One end of
suppression winding 76 is connected to metal terminal 82 while the
other end is connected to high-voltage terminal 52. Regarding
suppression device 74c, suppression winding 76 is wound,
preferably, in a continuous fashion on the reduced diameter portion
of spool 28, and is terminated on terminal 80. Resistor 84 is
coupled between terminals 80, 82 as described above. Finally, a
connector is made between terminals 82 and 52.
[0029] FIG. 6 shows a fourth embodiment of the present invention,
namely suppression device 74d. Suppression device 74d includes a
suppression winding 86 connected in series with secondary winding
30. Suppression winding 86 comprises a wire conductor that includes
a relatively high resistance, such as nickel wire, various types of
which are known in the art. Suppression winding 86 may be wound as
described above on the reduced diameter portion of spool 28. The
winding 86 may be uncoated and the turns spaced, or, preferably,
the winding 86 may be of the coated type (i.e., insulated type)
having a coating similar to that used on the secondary winding 30.
Suppression winding 86 may be wound first with its ends connected
to terminals 80 and 52. Next, the secondary winding 30 may be
wound, with the high voltage end thereof being routed through
channel 78 and connected to terminal 80.
[0030] The foregoing embodiments of suppression device are
operative to reduce RF interference. One bandwidth of interest
(medium wave) may be centered about 22 kHz, while a second
bandwidth of interest may be centered about 100 MHz. Of course, the
suppression device may be configured to suppress other bandwidths
of interest, for example, in the gigahertz range (e.g., of concern
to cell phones). It should be appreciated that the inductance of
the suppression winding is established in part as a function of the
diameter of the spool 28 in the reduced diameter area.
[0031] Referring again to FIG. 1, further details concerning an
exemplary ignition apparatus 10 will now be set forth configured to
enable one to practice the present invention. It should be
understood that the following is 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. 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.
[0032] Magnets 18 and 20 are 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.
[0033] 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.sub.p
for charging apparatus 10 upon control of ignition system 12.
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).
[0034] 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. 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.
[0035] Secondary winding spool 28 is configured to receive and
retain secondary winding 30. In addition to the features described
above in connection with FIG. 7, spool 28 is also characterized by
the following. 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), 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.
[0036] 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.
[0037] 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.
[0038] Spool 28 may further include a first annular feature 48 and
a second annular feature 50 formed at axially opposite ends
thereof. Features 48 and 50 may be 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.
[0039] In addition, the body portion of spool 28 tapers on a lower
end thereof to a reduced diameter, generally cylindrical outer
surface sized to provide an interference fit with respect to a
corresponding through-aperture at the lower end of case 34. In
addition, the spool body includes a blind bore or well at the spark
plug end configured in size and shape to accommodate the size and
shape of HV connector assembly 40. In connection with this
function, spool 28 includes an electrically conductive (i.e.,
metal) high-voltage (HV) terminal 52 disposed therein configured to
connect suppression device 74 to the HV connector assembly 40.
[0040] 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. 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 is connected to suppression
device 74 is a manner described above. Winding 30 may be
implemented using conventional approaches and material known to
those of ordinary skill in the art.
[0041] Case 34 includes an inner, generally cylindrical surface 54,
an outer surface 56, a first annular shoulder 58, a flange 60, an
upper through-bore 62, and a lower through bore 64.
[0042] Inner surface 54 is configured in size to receive and retain
the core 16/primary winding 24/spool 28/secondary winding 30
assembly. The inner surface 54 of case 34 may be slightly spaced
from spool 28, particularly the annular spacing features 48, 50
thereof (as shown), or may engage the spacing features 48, 50.
[0043] Annular shoulder 58 and flange 60 are located near the
lower, and upper ends of case 34, respectively. Shoulder 58 is
formed in size and shape to engage and support a bottommost
circumferential edge of shield 36. Likewise, flange 60 is
configured in size and shape to engage and support an uppermost
circumferential edge of shield 36.
[0044] Bore 62 is configured in size and shape to receive the
combined assembly of core 16/primary winding 24/spool 28/secondary
winding 30.
[0045] Bore 64 is defined by an inner surface thereof configured in
size and shape (i.e., generally cylindrical) to provide an
interference fit with an outer surface of spool body 28 (i.e., a
lowermost portion thereof), as described above. When the lowermost
body portion of spool 28 is inserted in bore 64, therefore, a seal
is made.
[0046] 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).
[0047] Shield 36 is generally annular in shape and is disposed
radially outwardly of case 34, and, preferably, engages outer
surface 56 of case 34. The shield 36 is 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 nominally
be about 0.50 mm thick, in one embodiment. 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.
[0048] Low voltage connector body 38 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 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, in
a manner known to those of ordinary skill in the art, and are
thereafter connected to various parts of apparatus 10, also in a
manner generally know to those of ordinary skill in the art.
[0049] HV connector assembly 40 may include a spring contact 68 or
the like, which is electrically coupled to HV terminal 52 disposed
in a blind bore portion formed in a lowermost end of spool 28.
Contact spring 68 is configured to engage 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.
[0050] An ignition apparatus in accordance with the present
invention includes a suppression device connected in series with
the secondary winding and is disposed outside of the magnetic
circuit. In a preferred embodiment, the same wire that is used to
wind the secondary winding is used to form the suppression winding
but is wound on a reduced diameter portion of the secondary winding
spool. In a further embodiment, a carbon resistor is further
connected in series with the suppression winding. In a still
further embodiment, nickel wire is used for the suppression winding
in lieu of the standard wire and the carbon resistor. The invention
suppresses RFI while reducing or eliminating complexities and part
costs associated with conventional approaches taken in the art.
[0051] It is to be understood that the above description is merely
exemplary rather than limiting in nature, the invention being
limited only by the appended claims. Various modifications and
changes may be made thereto by one of ordinary skill in the art,
which embody the principles of the invention and fall within the
spirit and scope thereof.
* * * * *