US1971497A - Ignition interference suppression - Google Patents

Description

Aug. 28, 1934. J. M. MILLER 1,971,497

IGNITION INTERFERENCE SUPPREE S ION Filed June 10. 1935 I 6. I I INVENTOR.

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the primary current by the pressing the interference Patented Aug. 28 1934 UN T-so STATES PATENT OFFICE 1.911.497 IGNITION mum-amen sUrrImssIoN John M. Miller,

Philadelphia, Pa, assignor to Atwater Kent Manufacturing Company, Philadolphin, Pa,

a corporation of Pennsylvania Application June It, 1933, Serial a... 675,293

3 Claims. (01. 123-148) 1 My invention relates to apparatus for supcaused by the ignition systems of motors to radio receivers,'particularly to receivers carried by. automobiles or'aircraft and located more or less adjacent their motors.

In accordance with my invention, the interfering oscillations generated in the ignition system are suppressed by the inclusion of radio frequency choke coils having low direct-current resistance and low distributed capacity in the hightension circuit of the ignition system. My invention also resides in the features of combination, construction and arrangement For an understanding of my invention, reference is to be had to the accompanying drawing,

in which:

Fig. 1 illustrates a typical ignition system utilizing my invention;

Fig. 2 is a sectional view on enlarged scale of one of the inductive suppressor units;

Fig. 3 is an end sectional view taken on line 3-3 of Fig. 2.

Referring to Fig. 1, the spark-plugs 1, havingcally interrupted by the breaker contacts 9 which a are shunted by the usual arcing. The current for the primary 10 of the spark coil is supplied by battery 11 which is charged by generator 12 when the contacts of the cut-out 13 condenser C to reduce are closed. Switch 14 is for manual closing or opening of the ignition circuit in starting or stopping of the motor generically represented by the cylinder heads 15.

Thus far described; the system is a typical ig-. nition system for an internal combustion motor, such as used in automobiles, aeroplanes, and in stationary installations. Each interruption of breaker contacts 9 induces a. high-voltage inthe secondary '1 which breaks down the gap of a spark-plug, the resulting spark igniting the charge of the associated cylinder. The current across the spark gap not only fulfils its intended purpose of ignition of the cylinder mixture but also sets'up'high frequency oscillations which seriously interfere with radio reception, particularly when the receiving apparatus is located near the ignition system which is pression is sometimes improved by necessarily true when the receiver is carried by an automobile or aircraft. a

I have found that the noises reproduced by the receiving apparatus which 'result from the interfering oscillations of the ignition system may do be suppressed by use of the inductive units L in the high-tension circuit. Usually, a coil unit L is included in each of the connections from the spark-plugs 1 to its distributor contact 4; the supthe inclusion of a suppressor unit in the lead contact 6; and in some cases, a single coil unit in this position suffices. v

In all cases, the unit should be a substantially pure inductance, i. c. it should have low resistance and low distributed capacity. If the resistance of the coil is high, it will adversely affect the performance of the motor because of the reduction of the high tension current.

Electrical disturbances arising from sparking of the generator commutator, of the cut-out contacts, etc., may be substantially eliminated by the by-pass condensers C1.

In Fig. 2 is shown an approved form of my inductive suppressor unit. The form 15 is of bakelite, hard rubber, or the deep grooves 16 which form winding slots for the coil which is wound, preferably from a continuous conductor, in sections or pies. When one section is wound, the conductor is passed through the slotl'! (Fig. 3) v until the coil is finished.

Winding of the coil in sections reduces the voltage per section to such extent that there is no likelihood of breakdown by the high voltage current from the spark-coil, and reduces the dis-' tributed capacity of the as a whole, to a minimum. A narrow, deep winding, as formed by each of the sectio greatly increases the insulation resistance to breakdown also reduces capacities between turns.

The coil unit shown in Fig. 2 is wound in twelve sections although it is to be understood that the umber of sections may be increased or decreased, and in some cases afford sufficient freedom from interference. The form may be wound, for example, with #34 double silk covered copper wire to have a direct-current resistance of about ohms and an inductance of the order of 10 miliihenries. The distributed capacity is negligible. The unit, therefore, offers to distributor If,the coil or wind- .ing has substantial distributed capacity, its eifecinto the next groove, and so on' potentials and a single section may.

like having a number of a5 little opposition to flow of the high-voltage direct current, and so does not have any appreciable effect upon the motor performance while it offers high impedance, of the order of many thousands of ohms, to the disturbing high frequency oscillations. Otherwise stated, .the unit is a substantially pure inductive, and exhibits high inductive reactance to the oscillations; the ratio of its inductive reactance to its resistance, and the ratio of its inductive reactance to its capacitative reactance, are both very high.

The terminals 18 and 19 suitably secured to opposite ends of the form are connected to opposite ends of the coil and are suitably formed for connection to a spark plug and its cable 3. Preferably one of them is suited for direct connection to the spark plug terminal for support thereby.

My invention is not limited to the specific system and inductive suppressor device described and illustrated, but is coextensive in scope with the appended claims.

What I claim is:

1. In an ignition system for an internal combustion motor including high-tension devices producing oscillations causing interference to radioreceiving apparatus, means for substantially eliminating said oscillations without appreciably affecting the performance of said motor comprising inductance units in series with said devices,

each unit having low direct-current resistance, low distributed capacity, actance to said oscillations.

2. In an ignition system for an internal combustion motor including high-tension devices producing oscillations causing interference to radioreceiving apparatus, means for substantially eliminating said oscillations without appreciably affecting the performance of said motor comprising inductance units in series with said devices, each unit comprising a coil of high inductive reactance to said oscillations and wound in .sections to reducev the distributed capacity and to decrease the possibility of high-voltage breakdown,

3. In an ignition system for an internal combustion motor including high-tension devices producing oscillations causing interference to radio-receiving apparatus, means for substantially eliminating said oscillations without appreciably afiecting the performance of said motor comprising inductance units in series with said devices, each unit comprising a core of non-magnetic material, and a plurality of serially connected coil sections, said sections being spaced axially substantially to reduce distributed capacity and to preclude high-voltage breakdown.

JOHN M. .LJILLER.

and high inductive re-

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