US2421790A

US2421790A - Ultra high frequency ignition device

Info

Publication number: US2421790A
Application number: US499294A
Authority: US
Inventors: Nathaniel I Korman
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1943-08-19
Filing date: 1943-08-19
Publication date: 1947-06-10
Anticipated expiration: 1964-06-10

Description

N. l. KORMAN ULTRA-HIGH FREQUENCY GNLTIoN DEVICE June 10, 1947,

Filed Aug. 19, 1945 nventor Gttomeg Patented June 10, 1947 ULTRA HIGH FREQUENCY IGNITION DEVICE Nathaniel I. Korman, Camden, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application August 19, 1943, Serial No. 499,294

'I'his invention relates generally to ignition systems for internal combustion engines and particularly to ignition plugs forsystems employing ultra-high frequency energy suitably applied to said plugs for establishing ignition temperatures.

Present ignition systems for aircraft use have the distinct disadvantage that considerable radio interference is generated by the high potentials, bythe wave form thereof, and by comparatively low frequencies involved. Numerous ignition shielding devices are known for decreasing the inherent radio interference set up by said systems, but such devices have limited utility due to Wide variations in moisture, pressure and temperature gradients encountered in radio aircraft operation. For example, When an airplane flies through a cloud, considerable condensation may occur within the shielding surrounding the high tension spark plug leads, resulting in reduced eiiiciency of the ignition system and objectionable radio interference. Moreover, at loW pressures experienced at extremely high altitudes, sparkover may occur in the ignition distribution system thereby causing engine failure. Various methods, including the use of air pumps, have been devised for exhausting the moisture or increasing the air pressure Within the high tension electrostatic ignition shielding, but the additional apparatus required adds Weight and has other serious disadvantages.

The instant invention is an improvement upon the system described in the copending U. S. application of Francis X. Rettenmeyer Ser. No. 445,046 led May 29, 1942, entitled Ultra high frequency ignition system. That copending application discloses and claims an ultra-high frequency ignition system which utilizes the advantages of low inherent radiation from low impedance high frequency transmission lines or from Wave guides. The Wave guides couple an ultra-high frequency pulse generator to tuned sparking devices which comprise quarter wave sections of concentric transmission line. The system thus described, by utilizing ignition voltages of ultra-high frequency considerably above the normal frequencies used for radio transmission, and by employing low impedance ignition energy transmission lines, greatly reduces radio interference and provides efficient ignition under normally adverse conditions.

The instant invention comprises several embodiments and modifications thereof of ignition plugs adapted for use with wave-guide ultrahigh frequency ignition distribution systems. Briefly, the various embodiments of the inven- 7 Claims. (Cl. 315-39) tion each comprise a cylindrical conductive member'formed to receive a waveguide distribution element, and threaded to engage a threaded spark plug port in an internal combustion engine. An insulating member is disposed Within a constricted portion of the cylindrical conductive member which extends into the spark plug port to provide an effective gas seal. A conductive element which is resonant at the operating ultra-high frequency is raised in temperature, or forms a spark discharge, in response to the ultrahigh frequency energy of the field impressed thereon.

One embodiment of the invention includes a conductive disc including a resonant aperture of predetermined shape and dimensions to provide a spark discharge at a restricted portion of said aperture in response to impressed ultra-high frequency energy. A second modification of the invention includes a section of wave guide having a length equivalent to one half wavelength at the operating frequency and having conductive portions at each end to provide spark gaps for the ultra-high frequency energy impressed thereon. A third embodiment of the invention comprises a resonant conductive ring supported by a suitable insulating spider transversely of the constricted Wave guide portion which extends into the cylinder spark plug port. Ultra-high frequency energy generates circulating currents on the surface of the resonant conductive ring which heat the surface of the ring to ignition temperatures. When the ultra-high frequency energy is not impressed upon the ring the mass thereof provides suiiicient cooling by conduction from the surface portions to the interior portions thereof.

Among the objects of the invention are to provide an improved method of and means for providing ultra-high frequency ignition in an internal combustion engine. Another object of the invention is to provide an improved ultra-high frequency ignition plug for use with a wave guide type ignition distribution system. An additional object of the invention is to provide an improved ultra-high frequency ignition plug for use with a wave guide distribution system wherein a spark discharge is provided across a restricted portion of a resonant conductive element forming a portion of said plug. An additional object of the invention is to provide an improved ultrafurther object of the invention is to provide an ultra-high frequency ignition plug for use with a wave guide type ignition distribution system wherein the surface of a resonant conductive element is heated to ignition temperatures by circulating currents induced therein, and wherein cooling of the heated conductive element is provided by conduction from the surface portions to the interior portions thereof.

rIhe invention will be further described by reference to the accompanying drawing of which Figure l is an elevational cross-sectional view of one embodiment thereof, Figures 2 and 3 are cross-sectional views of different modifications of Figure l taken along the section line II-II; Figure 4 is a cross-sectional elevational view of a second embodiment of the invention; Figure 5 is a sectional view of the embodiment illustrated in Figure 4 taken along the section line V-V; Figure 6 is a cross-sectional elevational view of a third embodiment of the invention and Figure 7 isV a sectional View of Figure 6 taken along the section line VII- VIL Similar reference characters are applied to similar elements throughout the drawing.

Referring to Figure l, a cylindrical conductive ignition plug I includes an enlarged portion 2 having slots 3' adapted to provide spring contact surfaces for receiving an ultra-high frequency ignition distribution wave guide d. A constricted portion 5 of the ignition plug I includes a threaded sleeve 6 adapted to engage the threads of a conventional spark plug port of an internal combustion engine. A portion 1 of the threaded sleeve 6 may be flattened to receive a Wrench for tightening the plug into the spark plug port. An

insulating plug 8 is sealed within the constricted portion 5 of the ignition plug I to provide an effective gas seal for the internal combustion engine cylinder.

Adjacent the end of the constricted plug portion 5, remote from the enlarged plug portion 2, a conductive ignition element 9 is disposed transversely of the constricted portion 5 of the wave guide plug. A spark discharge is caused to occur across a gap Iii when the conductive element S is subjected to ultra-high frequency energy through the Wave guide system. The ultra-high frequency energy may be pulsed and commutated to provide suitably timed pulses of ignition en- A ergy in the manner described in the aforementioned copending application.

Figure 2 illustrates the details of a typical conductive sparking element 9 as employed in the device described in Figure 1. The conductive disc 9 disposed transversely of the constricted ignition plug portion 5 includes a "resonant aperture formed by two circular holes II, II connected by a narrow slot Iii. Ultra-high frequency energy in the form of an electric field in the wave guide induces circulating currents in the conductive disc 9 which provides suiiicient voltage between the adjacent sides of the narrow slot ID to provide a spark discharge across said slot in response to the pulsed and commutated ultrahigh lfrequency energy.

Figure 3 is similar to Figure 2 with the exception that the conductive disc 9 includes two parallel disposed slots I2, I2' interconnected by a narrow slot Ii). The spark discharge occurs between the closely spaced sides of the narrow slot or aperture Il) in response to voltages induced therein by circulating currents caused by ultra-high frequency energy applied thereto.

Figure 4 is similar in all respects to Figure 1 with the exception that the constricted portion of the ignition plug has a length of the order of 1/2 wavelength at the operating frequency. Conductive elements I3, I3', forming spark gaps I4, I4', are disposed adjacent the ends of the constricted plug portion 5. Ultra-high frequency energy applied to the constricted plug portion induces voltages between the spaced conductive elements forming the gaps I4, I4 to provide a spark discharge across the gaps which may loe employed for internal combustion ignition. Preferably, the gap I4 is shorter than .fthe gap III in order to insure that sparking always will occur at the gap I4 which is disposed Within the engine cylinder.

Figure 5 is a section of the device described in Figure 4 taken along the section line V-V to illustrate the conformation of the spark gap employed.

Referring to Figures 6 and '7, the device described is similar to Figures 1 andl 4 with the eX- ception that a relatively short insulating plug 8r is employed, and ignition is accomplished byheating a metallic element instead of by a sparkdischarge. An insulating spider I5 disposed transversely of the constricted portion 5V of the ignition plug I adjacent the end thereof remote from the enlarged portion 2, supports a conductive ring I6. The conductive ring I6 is resonant at the operating ignition frequency, and the surface portions thereof are heated to ignition temperatures by circulating currents induced therein by the ignition energy field within the constricted portion of the ignition plug.

At operating frequencies of the order o-f 10,000 megacycles, the circulating currents penetrate the metallic ring only a few microns, thereby providing extremely high-surface temperatureswith relatively low power. Also, as soon as the ignition energy is interrupted by the distributing device in the ignition pulse generator, the surfaceV be in any convenient form and of any material V providing suitable resistance to corrosion and carbon accumulation. Likewise, the conductivel discs providing sparking electrodes in the devices described in Figures 1 to 5 inclusivemay be varied in size and shape and constructed of suitable materials to minimize wear and carbon accumulation. It should further be understood that the enlarged portion of the ignition plug may be circular, square or rectangular in cross-section, or of any other shape adapted to receive the particular type of wave guide employed for ignition distribution from the ignition pulse generator.

I claim as my invention:

1. A tuned gas ignition device for ultra-high frequency ignition energy derived from a Wave guide energy distribution system comprising a hollow conductive dielectric guide element having a first portion formed to engage said wave guide and having a second portion formed to engage a complementarily shaped utilization device, and conductive ignition means tuned to said frequency and disposed transversely ofV said device at the end thereof remote from` and in op'- erative relation with respect to said' hollow, conduct-ive element whereby ignition currents are induced in said means in response to ultra-high frequency energy derived from said wave guide.

2. A tuned gas ignition device for ultra-high frequency ignition energy derived from a wave guide energy distribution system comprising a hollow conductive dielectric guide element having a iirst portion formed to engage said wave guide and having a second portion formed to engage a complementarily shaped utilization device, and conductive ignition means defining a resonant aperture tuned to said frequency and disposed transversely of said device at the end thereof remote from said hollow conductive element to induce in said means an ignition current in response to ultra-high frequency energy derived from said wave guide.

3. A tuned gas ignition device for ultra-high v frequency ignition energy derived from a wave guide energy distribution system comprising a hollow conductive dielectric guide element having a iirst portion formed to engage said wave guide and having a second portion formed to engage a complementarily shaped utilization device, and conductive ignition means tuned to said frequency and disposed transversely of said device at the end thereof remote from said hollow conduc tive element whereby ignition currents are induced in said means in response to ultra-high frequency energy derived from said wave guide.

4. Apparatus of the type described in claim 1 comprising an ignition plug for an internal combustion device, and including a dielectric element providing a gas seal between said portions of said conductive element to prevent gas leakage from said combustion device through said ignition plug.

5. A tuned gas ignition device for ultra-high frequency ignition energy derived from a Wave guide energy distribution system comprising a hollow conductive dielectric guide element having a first portion formed to engage said wave guide and having a second portion formed to engage a complementarily shaped utilization device, and a pair of conductive means spaced an even multiple of one-quarter wavelength and tuned to said frequency andV disposed transversely of said device at the end thereof remote from said hollow conductive element to induce in said means an ignition current in response to ultrahigh frequency energy derived from said wave guide.

6. Apparatus of the type described in claim 5 comprising an ignition plug for an internal combustion device, and including dielectric means interposed between said conductive means and providing a gas seal between said portions of said conductive element to prevent gas leakage from said combustion device through said ignition plug.

7. A tuned gas ignition device for ultra-high frequency ignition energy derived from a Wave guide energy distribution system comprising a hollow conductive dielectric guide element having a first portion formed to engage said Wave guide and having a second portion formed to engage a complementarily shaped utilization device, and conductive ignition means dening a current discharge path tuned to said frequency and disposed transversely of said device at the end thereof remote from said hollow conductive element to induce in said means an ignition current in response to ultra-high frequency energy derived from said wave guide.

NATHANIEL I. KORMAN.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,106,771 Southworth Feb. 1, 1938 2,129,711 Southworth Sept. 13, 1938 2,129,713 Southworth Sept. 13, 1938 2,190,668 Llewellyn Feb. 20, 1940 2,372,429 Jones Mar. 27, 1945