U.S. patent number 3,883,776 [Application Number 05/404,170] was granted by the patent office on 1975-05-13 for ignition circuit radiation suppression structure.
Invention is credited to Norman H. Berry.
United States Patent |
3,883,776 |
Berry |
* May 13, 1975 |
Ignition circuit radiation suppression structure
Abstract
A wire wound resistor for use in suppressing ignition circuit
radiation which has a very low resistance and a specified
inductance connected in an ignition circuit close to and in series
with the spark plug electrodes, as within the spark plug or between
the spark plug lead wire and the spark plug.
Inventors: |
Berry; Norman H. (Pleasant
Ridge, MI) |
[*] Notice: |
The portion of the term of this patent
subsequent to November 6, 1990 has been disclaimed. |
Family
ID: |
26920155 |
Appl.
No.: |
05/404,170 |
Filed: |
October 9, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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226042 |
Feb 14, 1972 |
3771006 |
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Current U.S.
Class: |
315/85; 313/118;
315/58; 338/66; 313/134; 315/62 |
Current CPC
Class: |
H01T
13/41 (20130101); H04B 15/025 (20130101); H01R
13/6616 (20130101); F02B 61/045 (20130101) |
Current International
Class: |
H01T
13/41 (20060101); H01T 13/00 (20060101); H01R
13/66 (20060101); H04B 15/02 (20060101); F02B
61/04 (20060101); F02B 61/00 (20060101); H01t
013/04 () |
Field of
Search: |
;315/41,54,57,58,62,71,85 ;313/118,134-136 ;338/66 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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891,357 |
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Dec 1943 |
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FR |
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942,973 |
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Nov 1963 |
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GB |
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898,971 |
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Jun 1962 |
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GB |
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Primary Examiner: Lawrence; James W.
Assistant Examiner: LaRoche; E. R.
Attorney, Agent or Firm: Whittemore, Hulbert &
Belknap
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of application Ser. No.
226,042, filed Feb. 14, 1972, now U.S. Pat. No. 3,771,006.
Claims
What I claim as my invention is:
1. An ignition circuit including a spark plug having a pair of
lower spaced apart electrodes, a spark plug lead wire connected in
series with the spaced apart electrodes of the spark plug, and a
wire wound ignition circuit radiation suppression resistor
connected in series with the series connected spark plug lead wire
and electrodes of the spark plug and positioned closely adjacent
the electrodes of the spark plug, which resistor has an inductance
of between 10 and 800 microhenries and a resistance of between 15
and 30 ohms.
2. Structure as set forth in claim 1 wherein the spark plug
includes an outer metallic body portion, and an inner ceramic
insulator core received within the outer body portion, and the
first of the lower electrodes extends through the insulator core,
the second of the lower electrodes is secured to the outer body
portion in spaced relation to the first lower electrode, and the
spark plug further includes an upper electrode secured to the
insulator core in spaced relation to the first lower electrode and
the wire wound radiation suppression resistor is positioned within
the insulator core and connected at opposite ends to the first
lower electrode and to the upper electrode.
3. Structure as set forth in claim 1, wherein an insulating spark
plug boot construction is provided between the spark plug lead wire
and the spark plug, the wire wound ignition circuit radiation
suppression resistor is positioned within the boot construction
which further includes terminals provided within the boot
construction for connecting one end of the radiation suppression
resistor to the end of the spark plug lead wire and connecting the
other end of the radiation suppression resistor to the spark plug
so that the radiation suppression resistor is connected in series
between the spark plug lead wire and spark plug.
4. Structure as set forth in claim 1 wherein the resistor has an
inductance of between 30 and 45 microhenries as measured on a
Techtronic L.C. 130 meter.
5. Structure as set forth in claim 4 wherein the spark plug
includes an outer metallic body portion, and an inner ceramic
insulator core received within the outer body portion, and the
first of the lower electrodes extends through the insulator core,
the second of the lower electrodes is secured to the outer body
portion in spaced relation to the first lower electrode, and the
spark plug further includes an upper electrode secured to the
insulator core in spaced relation to the first lower electrode and
the wire wound radiation suppression resistor is positioned within
the insulator core and connected at opposite ends to the first
lower electrode and to the upper electrode.
6. Structure as set forth in claim 4, wherein an insulating spark
plug boot construction is provided between the spark plug lead wire
and the spark plug, the wire wound ignition circuit radiation
suppression resistor is positioned within the boot construction
which further includes terminals provided within the boot
construction for connecting one end of the radiation suppression
resistor to the end of the spark plug lead wire and connecting the
other end of the radiation suppression resistor to the spark plug
so that the radiation suppression resistor is connected in series
between the spark plug lead wire and spark plug.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to ignition circuits of the type used on
automobiles having internal combustion engines and refers more
specifically to a wire wound resistor which has a very low
resistance and a specified inductance which is connected in series
with spark plug electrodes so as to be immediately adjacent the
sparking electrodes, which resistor is operable to suppress
radiation from the ignition circuit due to sparking of the spark
plugs.
2. Description of the Prior Art
In the past, suppression of radiation from ignition circuits of
automobiles on firing of the spark plugs therein has often been
accomplished by inclusion of wire wound resistors in the spark
plugs between an upper and lower electrode or connecting such
resistors in series between a spark plug lead wire and the spark
plug as shown in U.S. Pat. No. 3,212,044 and U.S. Pat. No.
3,529,273, respectively. Such wire wound resistors of the past have
usually been of relatively high ohmic value of, for example, 5,000
or 10,000 ohms. These prior wire wound resistors have been
specified generally by their resistance value and physical size.
Any inductance in the wire wound resistors has been considered
irrelevant in the past. Such resistors are necessarily wound of
fine wire spaced close together so that at the usual ignition
circuit voltages flashover between the turns of the wire wound
resistors has been a problem limiting the minimum physical size of
the resistors. A compromise has therefore been reached in the past
between the flashover point of the wire wound resistors and the
length of the resistors and therefore the size of the spark plugs
and boots in which they have been installed.
SUMMARY OF THE INVENTION
It has been found that the inductance of the wire wound resistors
is of particular importance in suppression of radiation from
ignition circuits, especially when the wire wound resistors are
placed close to sparking electrodes as, for example, within or
closely adjacent to the spark plugs of the ignition circuits. On
the other hand, it appears that the actual resistance of the wire
wound resistors is of little importance in suppressing radiation in
ignition circuits. Therefore, the radiation suppressing resistors
according to the invention have a very low resistance and a
predetermined inductance.
The low resistance of the resistors of the invention prevents
flashover even though the resistors are made relatively short in
comparison to prior resistors. The inductance in the wire wound
resistors in accordance with the invention provides radiation
suppression in the ignition circuits at least as good as that
previously supplied by the higher ohmic value resistors of the
past.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partially broken away view of spark plug construction
including an ignition circuit radiation suppression resistor
therein constructed in accordance with the invention.
FIG. 2 is a partly broken away view of ignition circuit
construction including an ignition circuit radiation suppression
resistor constructed in accordance with the invention connected in
a boot between a spark plug lead wire and a terminal adapted to be
connected to a spark plug.
FIG. 3 is a graph illustrating ignition circuit radiation
suppression permissible under the Society of Automotive Engineers
recommendations and that obtained by the resistor of the invention,
as illustrated in FIGS. 1 and 2 in three separate
installations.
DESCRIPTION OF THE PREFERRED EMBODIMENT
As shown in FIG. 1, the spark plug 10 includes an outer metallic
body member 12, an inner ceramic insulating core 14, a pair of
lower electrodes 16 and 18 and an upper electrode 20. The wire
wound resistor 22 of the invention is electrically connected
between the lower electrode 16 and the upper electrode 20 within
the insulating core 14 of the spark plug 10 by the springs 25 and
27.
The spark plug structure 10 as shown is well known and will not be
considered in detail herein. Further, it is known to place a wire
wound resistor 22 between electrodes 16 and 20 to suppress
radiation in an ignition circuit, in which the spark plug 10 is
connected, on sparking between the lower electrodes 16 and 18.
It is also known to place a wire wound radiation suppression
resistor 22 in an insulating boot construction 34 between a spark
plug lead wire 32 and an upper spark plug electrode 20. One such
boot constructure 34 is illustrated in FIG. 2.
As shown in FIG. 2, the ends of a wire wound radiation suppression
resistor 22 are electrically engaged with the terminals 36 and 38.
The terminal 36 is electrically connected to the spark plug lead
wire 32, while the terminal 38 is open to provide a slip fit over
an electrode 20 of a spark plug. Inner insulation 40 is provided
surrounding the radiation suppression resistor 22, the terminal 36
and a portion of the terminal 38. The outer insulation 42 then
encompasses the entire structure including the inner insulation 40,
radiation suppression resistor 22, terminals 36 and 38 and the end
of the spark plug lead wire 32 as shown.
Again, it is not new to place radiation suppression resistors in
either spark plugs or spark plug boot constructions.
However, in the past it has been considered that the wire wound
resistors must necessarily be of a resistive value such as 5,000 or
10,000 ohms to effectively suppress radiation on sparking between
the electrodes 16 and 18 occurring in an ignition circuit.
Accordingly, the wire wound resistors of the past have been so
specified and limited and have thus been restricted in minimum
length due to the possibility of flashover occurring in the wire
wound resistors due to the voltage impressed between the electrodes
20 and 16 and the relatively large resistance of the wire wound
resistors. In the past, the inductance of the wire wound resistors
has been generally ignored by those interested in radiation
suppression in ignition circuits.
The wire wound resistors 22 in accordance with the invention may be
similar to the usual wire wound resistors in that the wire itself
may be, for example, 0.001 inch or 0.0015 inch in diameter and
approximately 18 feet long wound on a ceramic core which is, for
example, 1/8 inch .+-. 1/16 inch in diameter and 3/8 to 3/4 inch
long. The wire wound resistor 22 of the invention, however, differs
from the usual wire wound resistors in that the wire wound
resistors 22 have very low resistance as, for example, 15 to 30
ohms in contrast to the relatively large resistance of 5,000 to
10,000 ohms of previous wire wound resistors.
In addition, the resistor 22 is designed to have a known inductance
as, for example, between 10 and 800 microhenries inductance when
calculated in accordance with the known formula: ##EQU1## where: L
= inductance in .mu. h
R = radius of the coil
N = number of turns in the coil
l = length of the coil
The low resistance of the wire wound resistor 22 prevents flashover
from occurring in the wire wound resistor even though the resistor
may be shorter and have the same number of turns thereon since the
voltage drop across the resistor of between 15 and 30 ohms will be
considerably less than the voltage drop across the previously used
high ohmic value resistors.
Further, the specified inductance of the wire wound resistor 22
which is between 10 and 800 microhenries within the scope of the
invention as set forth above and which is preferably between 30 and
45 microhenries as measured on a Tektronix LC 130 meter, provides
the radiation suppression desired and previously considered
obtainable only with wire wound resistors of higher ohmic value.
The Tektronix meter is available as an off-the-shelf item from
Tektronix in Beaverton, Oregon.
Thus, by providing a wire wound resistor of predetermined
inductance rather than predetermined resistance, shorter resistors
are possible with less chance of a flashover and the resistors may
be made of less exotic alloy wire and will produce equivalent
radiation suppression in ignition circuits.
The following chart shows actual tests of different wire wound
resistors having the indicated radiation suppression in standard
ignition circuits:
Db Attenuation ______________________________________ Frequency 20
50 100 150 200 250 MHz Standard Plug 16 16 16 16 16 16 Resistor
Plug 10 0 0 0 0 0 30 Ohm .112 diameter .605 length 30-45.mu.h
Resistor Plug 16 0 0 0 0 0 15 Ohm .112 diameter .385 length
30-45.mu.h Resistor Plug 12 0 0 0 0 0 15 Ohm .147 diameter .380
length 30-45.mu.h Resistor Plug 4 0 0 0 0 0 5,000 Ohm .112 diameter
.685 length 70.mu.h ______________________________________
Further, in FIG. 3 the radiation suppression provided in standard
ignition circuits using the low ohmic value wire wound resistor 22
having an inductance of 30 to 45 h, as measured on a Tektronix L.C.
130 meter, as compared against the Society of Automotive Engineers'
recommended standards is presented. The line 24 shows the Society
of Automotive Engineers' recommended standard, while the lines 26,
28 and 30 illustrate the equivalent results obtained by placing
wire wound resistors 22 in the spark plugs 10 as shown in FIG. 1 in
standard ignition circuits.
In the test producing line 28 on the graph of FIG. 3, the ignition
circuit was a Ford Galaxie 1971, 351 cubic inch combustion engine
ignition circuit having plain wire plug leads of 39 ohms
resistance. The test for line 30 on the graph was conducted on a
Chrysler 105 horsepower, 4-cylinder outboard marine engine as was
the test for line 26. Both the Chyrsler engine circuits had 39 ohms
resistance in the spark plug lead. In the case of line 30 there was
a coiled wire lead while in the case of line 26 the lead was a
plain metallic wire. All ignition circuits had a carbon core lead
from the distributor to the ignition coil and resistors such as
resistor 22 were used in the spark plugs in the ignition
systems.
From the above indicated results it will be obvious that the low
resistance, specified inductance wire wound resistor 22 of the
invention is at least as efficient in suppression of ignition
circuit radiation as the higher resistance resistors thought
necessary in the past.
It is hypothesized that the inductance of the resistor 22,
especially when place within the spark plug or in the spark plug
boot closely adjacent the sparking electrodes provides a back
electromotive force which tends to dampen oscillations set up in
the ignition circuit on sparking of the spark plugs, which
oscillations produce the objectional radiation. The radiation is
thus suppressed providing the inductance is sufficient even though
the resistance value of the resistors 22 is particularly low.
While one embodiment of the present invention has been considered
in detail, it will be understood that other embodiments and
modifications thereof are contemplated by the inventor. It is
therefore the intention to include within the scope of the
invention all embodiments and modifications as are defined by the
appended claims.
* * * * *