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> o@ @a 1946-
F. x. RETTENMEYER
- 2,408,881
ULTRA HIGH FREQUENCY IGNITION SYSTEM
Filed May 29, '1942
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ßnventor
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2,408,881
Patented Oct. 8, 1946
UNITED vSTATES PATENT OFFICE
2,408,881
ULTRA HIGH FREQUENCY IGNITION
SYSTEl‘fI
v
Francis X. Rettenmeyer, Moorestown, N. J., as
signor to Radio Corporation of America, a cor
poration of Delaware
Application May 29, 1942, Serial No. 445,046
20 Claims. (Cl. 315-39)
l
This invention relates generally to ignition
systems for internal combustion engines and par
ticularly to ignition systems utilizing voltages of
ultra high frequency suitably coupled to spark
ing devices comprising resonant circuits includ
2
method of and apparatus for generating the re
quired potentials at ultra high frequency, trans
mitting these potentials over a low impedance
transmission line, and applying the ultra high
frequency potentials to a resonant circuit includ
ing a spark gap which is located within the com
bustion chamber of the internal combustion en
gine. A further object of the invention is to
provide an improved method of and means for
interference is generated by the high potentials
and comparatively low frequencies involved. Nu 10 pulsing the output of an ultra high frequency os~
cillator to provide extremely high instantaneous
merous ignition shielding devices are known for
power output with equipment of low continuous
decreasing the inherent radio interference in
power rating. Another object of the invention i's
such systems, but such devices have limited util
to provide an improved method of and means for
ity due to wide variations in moisture, pressure,
and temperature gradients encountered in air 15 coupling successively high potentials of ultra high
frequency to spark gaps within combustion cham
craft work. For example, when an airplane flies
bers by means of individual low impedance coax
through a cloud, considerable condensation may
ial cables suitably coupled to the equivalent of
occur within the shielding surrounding the high
any odd multiple of quarter~wave resonant de~
tension spark plug leads, resulting in reduced
vices, each including a spark gap. .Another ob
eilìciency of the ignition system. Moreover at
ject is to provide a new and improved spark plug.
low pressures spark-over may occur. Various
A further object is to provide an improved and
methods, including the use of air pumps, have
'simplified means for removing moisture accumu
been devised for exhausting the moisture, or in
lations within the ignition transmission lines.
creasing the air pressure, within the high tension
electrostatic shielding, but ‘the additional appa 25 The invention will be described by reference to
ratus required adds weight and has other serious - the drawing of which Figure 1 is a schematic cir
cuit diagram of one embodiment of the invention:
disadvantages.
Figure 2 is an elevational view of an improved
The instant system utilizes the advantages of
low impedance transmission line showing louvres
low inherent radiation from low impedance ul
tra high frequency transmission lines and, in ad~ 30 for exhausting moisture accumulations, and Fig~
ure 3 is a cros~s~sectional view of Figure 2. Sim~
dition, provides a simple and eflicient means, for
ilar reference numerals are app-lied to similar ele
removing continuously the moisture which ac
ments throughout the drawing.
cumulates within the outer shield of the trans
Referring to Fig. l., a power genera-ting source
mission line. Ey utilizing ignition voltages of
ultra-high frequency which are considerably 35 l which may be a suitable D.-C. generator driven
by the internal combustion engine is connected
above the normal frequencies used for radio
to a voltage divider 2, which is grounded at some
transmission, and by transmitting the ignition
intermediate point. If extremely high. anode
voltages over low impedance transmission lines
voltages are required, an A.-C. generator and
connecting an ultra high frequency generator to
the individual spark plugs of the internal com 40 transformer may be substituted for the 13.--C.
power supply and voltage divider. Potentials de",
bustion engine, radio interference is reduced to
rived from the voltage divider 2 are applied to
a practical operating level.
the electrodes of an ultra high frequency oscil
Various methods and apparatus well known in
lator tube 3 which includes an ultra high irc»
the art may be utilized for generating the ultra
quency oscillator circuit comprising a predetern
high frequency potentials required for satisfac
mined section of coaxial cable 4. However, the
tory ignition. It should be understood that the
oscillator circuit may be of any other type known
apparatus described herein is merely typical of
in the art. At extremely high frequencies, a mag~
the type of equipment which will provide sat
ing the spark gaps.
`
Present ignition 'systems for aircraft use have
the distinct disadvantage that considerable radio
netron circuit provides satisfactory power out
isfactory operation, and that the invention is not
50 put. Pulsing of the oscillations generate-d in the
limited t0 the specific apparatus disclosed.
thermionic tube circuit is accomplished by means
Among the objects of the invention are to pro
vide a new and improved method of and appa
of a suitable commutator device 5 connected in
series with the vacuum tube anode power lead
ratus for ultra high frequency ignition in inter
connected to the voltage divider 2. In practice,
nal combustion engines. Another object of the
invention is to provide a new and improved 55 the pulsing commutator may be driven by the
2,408,881
3
interna1 combustion engine, and synchronized
with the engine cylinder ñring. High potentials
of ultra. high frequency, derived by suitable cou
pling to the oscillatory circuit 4, are applied to
the rotating element 8 of a contact or capacity
type distributor which may be also driven by the
4
the transmission cable. The openings 54 may be
arranged at desired intervals around the sheath
5| or, if desired, may be limited to the lower sur
faces thereof. Fig. 3 illustrates more clearly the
louvre formation.
The term “transmission line” as used in t-he
internal combustion engine and the switching
appended claims is intended to include all known
rate of which is synchronized with the switching
types of lines, such as for example, coaxial lines,
of the pulsing commutator device 5 described
balanced lines, single and multi-conductor lines,
heretofore. The stationary elements l and 'l' lO and Wave guides. Any suitable known means may
of the distributor are connectedihrough a plu
be provided for coupling the spark gaps and the
rality of individual low impedance transmission
distributor to the particular type of transmission
lines 8 and B’ which may be conventional co
line utilized.
axial cable, to a plurality of special spark plug
I claim as my invention:
devices 9 and 9'. The spark plug
have
1. An ignition system including a source of
a length which is the equivalent or any cdd mul~
ultra-high frequency oscillations, means for puls
tiples of quarter-wave linesl which terminate in
ing said oscillations, at least one spark gap de
the spark gaps I0 and I0’. The ends of the outer
vice comprising a resonant line including one of
conductors 9, 9’ of the plugs remote from the
said gaps and upon which standing waves may
spark gaps. Il), l0', respectively, are short~cir- 20 be established at said ultra high frequency, and
cuited to the respective inner conductors ll, Il’
means including separate low impedance trans
to provide voltage maxima at the spark
due
mission lines alternately connecting said source
to standing waves thereby provided in the plugs.
to each of said spark gap devices at a point inter
The short-circuited conductors are preferably
mediate a voltage node and voltage loop of said
entirely closed to provide a gas seal. It should 25 standing waves on said resonant line.
he understood that wave guides may be used as
transmission lines, and that they may be coupled
2. An ignition system including a source of
ultra-high frequency oscillations, means ior puls
to the distributor and spark plugs in any well
ing said oscillations, at least one spark gap de
known manner. The connection from the low
vice comprising an odd multiple of a quarter
impedance transmission line 8 passes through. the
wave line including one ci said gaps, and means
gas tight gasket I3 to the quarter-wave line ll,
including separate low impedance `transmission
and should preferably be made at a point on the
lines successively connecting said source to each
line II to obtain maximum power transfer when
of said spark gaps.
a spark occurs at the spark gap lll. The gasket
3. An ignition system including a source of
I3 may be either conductive or insulation, dem
ultra-high frequency oscillations, means for puls
pending upon whether .it is located at a voltage
ing said oscillations, a plurality of spark gap de
node, or at some other point. It should be unn
vices each comprising an odd multiple of quarter
derstood that the mechanical construction of the
wave lines including one oi said gaps, low im
quarter»\vave spark plug is not a limiting factor
pedance transmission lines connected to each of
of this invention and that any arrangement other 40 said devices, and switching means for selectively
than that shown which provides the equivalent
connecting said source to each of said low im
of an odd multiple of a quarter-wave load circuit
will be equally satisfactory. The plug construc
tion should preferably be adapted to he readily
demountable from the cylinder head
may
include the conventional yscrew type spark plug
supporting means.
The pulsing of the oscillator output by the
pulsing commutator will provide an oscillator
output of extremely high instantaneous power »
characteristics from an oscillator tube of low
pedance transmission lines.
4. Apparatus of ,the type described in claim 3
including means for synchronizing the operation
f ` of said pulsing means and said switching means.
5. Apparatus of the type described in cla-im 3
characterized by the fact that the frequency o_î
said oscillations is in excess of 500 megacycles.
6. Apparatus of the type described in claim 3
characterized by the fact that said source of oscil
lations includes a thermionic tube and a section
continuous power rating. Any other well known
of coaxial cable of predetermined dimensions,
pulsing means, which may be suitably synchro
7. An ignition system for an internal combus
nized, would be equally satisfactory. As ex
tion engine including power generating means,
plained heretofore, ‘the -low impedance transmisn 55 ultra-high frequency generating means including
sion line 8 will provide minimum radiation. The
a thermionic tube and a resonant section of co
entire generator system including the oscillator,
axial cable, pulsing means, means including said
the resonant circuit, the pulsing commutator, the
pulsing means for connecting said power generat
distributor and the power generator should prei
ing means to said ultra~high frequency generat»
erably be enclosed within an electrostatic shield 60 ing means, a plurality of spark gap devices each
i2. The sheaths 8 and 8' of the low impedance
comprising an odd multiple oi quarter wave lines
transmission line should preferably be gounded to
including one of said gaps, low impedance trans~~
the electrostatic shield and to the common ground
mission lines connected to each of said devices,
of the internal combustion engine.
switching means for connecting selectively said
Referring to Fig. 2, a modiñcation of »the low
ultra-high frequency generating means to each
impedance transmission cable includes an inner
conductor 52 connected at a suitable point to the
quarter-wave transmission line l l comprising a
spark plug. The outer concentric sheath 5| in
cludes a plurality of louvres 53 having openings
54. If a column of air is directed coaxially along
the transmission line in the direction indicated
by the arrow, low pressure areas will occur in the
vicinity of each of the openings 54, providing
satisfactory exhaustion of the moisture Within
of said low impedance lines, and means for syn~
chronizing the opera-tion of said pulsing means
and said switching means.
8. Apparatus of »the type described in claim 'l
characterized by the fact that said ultra-high
frequency is in excess of 500 megacycles.
9. Apparatus of the 4type described in claim 7
including grounded electrostatic shielding means
enclosing said system.
10. Apparatus of the type described in claim 3
2,408,881
5
6
including grounded electrostatic shielding means
enclosing said system.
11. In an ultra-high frequency ignition system
for internal combustion engines including a plu
including means for connection to a transmission
rality of spark gap devices each comprising an
odd multiple of quarter Wave lines including said
gaps, the method including generating oscilla
tions in excess of 500 megacycles, pulsing said
line, characterized by .the fact that said yconnect
ing means is connected to said center electrode
at a point providing effective impedance match
ing between said transmission line and said spark
gap.
16. Apparatus of the type described in claim 14
including means for connection to a transmission
oscillations, switching said pulsed oscillations,
line, 4characterized by the fact that said connect
successively transmitting said switched oscilla
tions at low potential to each of said spark gap
devices and successively applying said low poten
ing means is connected to said center electrode
at a point providing effective impedance matching
between said transmission line and said spark
tial oscillations to each of said devices at a point
gap.
intermediate a voltage loop and a voltage node
17. Apparatus of the type described in claim 13
of said quarter wave line~
15 including threaded mounting means for support
12. In an ultra Ihigh frequency ignition system
ing said cylindrical electrode.
including an ultra high frequency generator, a
18. An ignition system including a source of
plurality of sparking devices and individual low
ultra-high frequency oscillations, a plurality of
impedance coaxial lines connecting said generator
ignition devices each comprising a resonant struc
`to said sparking devices, spaced apertures in said 20 ture upon which standing Waves may be estab
coaxial lines, air deflecting means in operable re
lished at said ultra-high frequency to raise sub
lation to said apertures, and means including said
stan-tially the temperature at a predetermined
deflecting means for varying the air pressure
point in said device, :and means -including separate
within said coaxial lines.
low impedance transmission lines connecting said
13. A tuned Spark plug for ultra-high frequency
source to each of said ignition devices.
ignition voltages including an elongated center
19. An ignition system including a source of
electrode, a -coaxially disposed :cylindrical elec
ultra-high frequency oscillations, means for puls
trode surrounding said center electrode, means
ing said oscillations, at least one ignition device
connecting one end of said center electrode to
comprising a resonant structure upon which
the proximate end of said cylindrical electrode, 30 standing waves may be established at said ultra
means forming a Spark gap between the remain
high frequency to raise substantially the temper
ing ends of said electrodes, and .connecting means
ature at a predetermined point in said device, and
for said ultra-high frequency voltages interme
means including separate loW impedance trans
diate the ends of said center electrode and to said
mission lines connecting said source to each of
cylindrical electrode.
35 said devices.
14. A tuned spark plug for ultra-high frequency
20. A resonant ignition plug for ultra-high fre
ignition voltages including an elongated center
quency voltages including an elongated cen-ter
electrode of length equivalent to some odd mul
electrode of length equivalent to some odd mul
tiple of one quarter wavelength of said voltages.
tiple of one-quarter Wavelength of said voltages.
1'5. Apparatus of the type described in claim 13 40
FRANCIS X. RETTENMEYER.
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