US2260331A - Ignition system fob internal - Google Patents

Description

Oct. 28, 1941. M. F. PETERS EIAL 2,260,331

IGNITION SYSTEM FOR INTERNAL COMBUSTION ENGINES Filed Nov. 20, 1940 INVENTOR NELVILLE F. PETERS BY GEORGE F. BLACKBURN Patented Oct. 28, 1941 S' PATENT OFFICE IGNITION SYSTEM FOR INTERNAL COMBUSTION ENGINES Melville F. Peters, Beltsville, Md., and George F. Blackburn, Washington, D. C.

Application November 20, 1940, Serial No. 366,430

19 Claims.

(Granted under the act of amended April 30, 1928; 3'70 0.

This invention relates generally to electrical ignition systems for internal combustion engines, and particularly to circuits for reducing primary breaker point contact arcing in such ignition systems.

An object of our invention is to provide an im-' proved ignition circuit for internal combustion engines in which the current flow through the primary breaker point contacts never exceeds a small value, and is only a small part of the total primary current.

Another object of our invention is to provide an improved ignition system for internal com bustion engines which includes a discharge tube means to carry the greater part. of the primary current.

Another object of our invention is to provide an improved ignition system for internal combustiomengines in which the primary breaker point contacts make and break only a small current initiating the discharge of an electron tube means, the latter providing an interruptible path for the greater portion of the primary current.

A further object of our invention is 'to provide an improved ignition system for internal combustion engines which permits a reduction in the contact area oi the primary breaker point contacts and in which the arcing at such contacts is reduced.

Our invention is a modification and improvement of the ignition system claimed and described in U. S. Patent No. 2,184,315, granted to us on December 26, 1939. In the system described in this patent, advantage was taken of the discharge of one primary circuit capacitor and the substantially simultaneous charge of another in the production of the secondary high voltage, and the primary circuit breaker point contacts were not opened until the current flow through them had reached zero or a low value.

However, when using the system described in the aforementioned patent in connection with certain internal combustion engines operating at very high speeds, it has been found, especially in circuits not having a low time constant, that the primary breaker point contacts are opened while there is still an appreciable current flow thrcugh them, there not being sufficient time for the capacitors to become fully chargedand/or discharged before the breaker point contacts are opened at such speeds. Such results in arcing and consequent wearing away of the contacts, necessitating frequent adjustment or renewal thereof. Arcing of these contacts also occurs,

I but toa lesser extent, when they are closed. b-

March 3, 1883, as

viously, these contacts must have a suficient contact area to carry the high though momentary peak discharge and charging currents of the primary capacitors.

Our present invention overcomes this undesirable excessive arcing contacts in installations where it occurs, by providing a parallel electron dischargetube path for the far greater part of the primary current, the primary breaker point contacts carrying and breaking only the very small current for initiating the electron discharge through the tubes, and having resistors in series therewith which limit the current through the contacts to a very low value.

With the above and other objects in view, our invention will be described in connection with the accompanying drawing which is an electrical and mechanical schematic diagram incorporating our invention in its preferred form.

Referring to the drawing, the positive supply line 2 from a conventional engine driven generator or other direct current source oi electrical energy (not shown) is connected to one'terminal o! capacitor 3 and of a resistor i, and is further connected to fixed breaker point contact 5 and to the anode 6 of a cold-cathode discharge tube 3. The negative supply line 8 from the same direct current source is connected to one terminal of capacitor 9, to the cathode it of a second coldcathodedischarge tube it, and is further connected to grids it, it: of tube it through resistors ill and ii, respectively. Grid it is also connected to movable breaker point contact 35 through resistor il A storage capacitor 2' is preferably connected across the positive supply line 2 and the negative supply line 8, but it the source has a sumciently low internal resistance this capaci tor will not be required for satisfactory operation.

of our invention. The remaining terminals of capacitors 3, 9 and resistcr are connected togeth'er and are further connected to one terminal of the primary winding it of iron core step-up transformer or induction coil it. The other terminal of primary winding it is connected to fixed breaker point contact 29, to the cathode 28 of. tube '6, to the anode 22 of tube ia'and is further connected to grids 23 and 24 of tube 1 through resistors 25 and 25, respectively. Grid it is also connected to movable breaker point contact El through resistor 28. One terminal '29 of the secondary or high voltage winding 35 of transformer i9 is connected to ground, the other terminal 30 being connectedto a conventional at the primary breaker point i type distributor (not shown) of the engine, or to a spark plug (not shown) thereof.

Breaker point contacts 5, 21 and i6, 29 are mounted on spring arms which tend to close the electrical circuits including these respective pairs of contacts. A rotatable engine-driven cam 32 operates to break the circuit at these contacts in accordance with the timing of the engine.

Secondary winding 3| iswound with many times the number of turns l9, and is disposed in inductive relationship therewith, such that the secondary voltage will be sufllcient to jump the spark gap within 9. cylinder of the engine. Capacitors 3, 9 are preferably, though not necessarily, of equal capacity. Resistors I 0, 25 serve as biasing resistors for grids I4, 23, respectively, and as such assist in fixing the breakdown operating points of tubes 7 and I3.

In operation, assuming the engine at rest with contacts 5, 2'! closed and contacts I I, 20 open, with voltage applied across capacitor 2' of polarity as indicated, capacitor 9 will be charged to substantially the terminal voltage of the source through the circuit including closed contacts 5,

as primary winding 2'1, resistors 28 and 26, and primary coil I 9. Due

to the presence of resistors 28, 23 in series in this circuit, the current flow through contacts 5, 21 will never exceed a small value. If now the engine be started, the rotation of cam 32 in the direction shown will first open the circuit at contacts 5, 21, and will immediately afterwards permit contacts I8, 20 to close. Capacitor 9 having previously been charged in the manner explained below, the closing of contacts i5, 20 applies a sufliciently positive voltage to grid i 5 of tube I3 by means of resistors 11 and Ii, to cause this tube to become conductive. a low resistance electron discharge path being formed between the anode and the cathode thereof. Capacitor 9 then discharges rapidly through the circuit including the primary coil l8 of transformer i9 and this low resistance electron path between the anode and cathode of tube H, such discharge being accompanied by the substantially simultaneous charge of capacitor 3, also through pri mary coil I9 and tube I 3, the charging current of capacitor 3 and the discharge current of capacitor 9 flowing through primary coil l8 in the same direction. This charging current for capacitor 3 is supplied by storage capacitor 2', ii

used, or from the direct potential source, and capacitor 3 is charged to substantially the terminal potential of the source. As cam 32 rotates further in the direction shown, contacts I9, 29 are opened and contacts 5, 21 are permitted to close immediately thereafter. Such imposes a sumciently positive voltage on grid 24 of tube 1, through resistors 29 and 29, to cause this tube to become conductive, whereupon capacitor 3 immediately discharges through the circuit including the primary coil I9 of transformer 19 and the conductive electron path through tube 1, such being accompanied by the substantially simultaneous charge of capacitor 9, also through a circuit including primary coil l9 and tube 1. Here also the discharge current of capacitor 3 and the charging current of capacitor 9 flow through primary coil ii in the same direction. capacitor 9 again being charged from capacitor 2' or the source to substantially the terminal voltage of the latter.

As cam 32 continues to rotate in the direction shown, the above described cycle is repeated.

The circuit including contacts 5, 21 and resistors 23, 29 may be called the trigger circuit for tube 1, and these elements plus cam 32 may be referred to as the trigger means for this tube. Similarly, the circuit including contacts is, 20 and resistors II, I! may be called the triggering circuit of tube l3, and these elements plus cam 32 may be referred to as the trigger means for tube i3.

The discharge of one capacitor and the charge of the other occurring substantially simultaneously through the primary winding i8 of transformer I9, the current surges due to these respective discharges and charges also occur practically simultaneously, resulting in a cumulative effect thereof in the production of the secondary high voltage. cumulative effect in the aforementioned patent, which contains a more complete exposition thereof.

Our present invention has other advantages in common with our aforementioned patented invention, one of which is that the flow of current from the source is more nearly uniform.

than in the case of systems employing a single capacitor, since, except for brief interruptions rent may be employed.

Our present invention preferably employs a transformer l9 having a single primary winding i8 through which the charging and discharging current of both capacitors 3, 9 flows. It is obvious that a dual primary transformer of the type used in the aforementioned patent could also be employed in our present invention, one such primary winding being connected in the circuit shown at point a, the other primary winding being connected at point 22, in which case the current flow through each primary winding would always be uni-directional.

Resistor 4 is used in the circuit to insure that capacitor 9 is charged to substantially the full terminal voltage of the supply source when the ignition system is turned on, when the engine has been stopped in such position that both pairs of contacts 5, 21 and i9, 20 are open. If resistor l were not employed and the ignition system were turned on after the engine had been stopped for a considerable period with both sets of breaker point contacts open, the voltage of the supply source would be distributed across capacitors) and 9 in series. Then if an attempt were made to start the engine, the reduced voltage across either capacitor 3, 9 would not be sufflcient, in some installations, to cause either tube 1, l3 to discharge. The previous charge on either condenser 3, 9 as well as that on capacitor 2', would leak oil during the period while the engine was idle. in most installations.

While the use of cold-cathode discharge tubes is preferable in our present invention, it is obvious that hot cathode types could be employed Advantage was also taken of this.

their peak charging curlimit ourselves to such. we have found tubes of the Strobotron type 631:P-1,"manufactured by the Hygrade Sylvania'Corp, to be satisfactory for use as tubes I, I2. with tubes of the latter type employed, we have found that currents of the'order of five milliampcres or less through the circuits including contacts 5, 21 and IS, 2|! will provide a sufficient voltage on grids 24 and I! to cause these tubes to become conductive, as described above.

With contacts 5,11 and i6, 20 breaking only currents of the order mentioned above, arcing troubles at these contacts are completely eliminated. Further, since these contacts never carry currents greater than those mentioned above, their size and contact area may be reduced correspondingly.

The following specific values have been found satisfactory for use in the circuit shown. We

emphasize that these are only suggested values that have produced satisfactory operation, and we do not limit ourselves to such, or even to values of the order of those listed below. In the circuit shown, capacitor 2' may have a capacity of 8 microfarads. Capacitors 3, '9, have a capacity of 2 microfarads each. Resistor 4 may have a resistance of 1 me'gohm; resistors i1, 28- 10,000 ohms each; resistors ll, 26l00,000 ohms each; resistors i0, 25-250,000 ohms each.

It will be understood that the above description and accompanying drawing comprehend only the general and preferred embodimentof' our invention and that various minor changes in detail of construction, proportion and arrangement of parts may be made within the scope of the appended claims without sacrificing any of the advantages of our invention. 4 The invention herein described may be manufactured and used by or for the Government of the United States for government purposes witha first capacitor and a second capacitor electrically connected in series across said source, a step-up transformer, having a primary winding and a secondarywinding, a first space discharge means and a second space discharge means each having a grid, a first common circuit including said primary winding and said first discharge means for chargingsaid first capacitor and discharging said second capacitor, a second common circuit including said primary winding and said second discharge means for discharging said first capacitor and charging said second capacitor, means including a cam actuated contact means cylically operable to apply a sufiicient voltage to said grids to cause said discharge means to become alternately conductive, a charging resistor connected across said first capacitor, and a storage capacitor connected across said source, the current flowing through said contact means .being of a relatively low value, said first capacitor being charged and said second capacitor being simultaneously discharged through said first common circuit, said first capacitor being discharged and said second capacitor 'being simultaneously charged through said second common circuit.

3. In combination, a source of electrical ener y, a first capacitor and a second capacitor out the payment of any royalties thereon or I therefor.

We claim:

1. In combination, a source of electrical energy of substantially constant potential, a first capacitor and a second capacitor electrically connected in series across said source, a step-up transformer having a primary winding and a secondary winding, a first space discharge means and a second space discharge means each having a grid, a first common circuit including said primary winding and said first discharge means for charging said first capacitor and discharging said second capacitor, a second common circuit ineluding said primary winding and said second discharge means for discharging said first capacitor and charging said second capacitor, means including a cam actuated contact means cyclically operable to apply 'a sufficient volta e to said grids to cause said discharge means to become alternately conductive, a charging resistor connected across said first capacitor, and a storage capacitor connected across said source,

the current flowing through said contact means being of the order of a few milliamperes, the

flow of charging current from saidsource being substantially uninterrupted, said first capacitor being charged and said second capacitor being simultaneously discharged through said first common circuit, saidfirst capacitor being discharged and said second capacitor being simultaneously charged through said'secondcommon circuit. 2. In combination, a source of electrical energy.

electrically connected in series across said source, a step-up transformer having a primary winding and a secondary winding, a first space discharge means and a second space discharge means each having a grid, a first common circuit including said primary winding and said first discharge means for charging said first capacitor and discharging said second capacitor, a second common circuit including said primary winding and said second discharge means for discharging said first capacitor and charging said second capacitor, meansincluding a cam actuated contact means cyclically operable to apply a sufficient voltage to said grids to cause said discharge means to become alternately conductive, and a charging resistor connected across said first capacitor, said first capacitor being charged and said second capacitor being simultaneously discharged through said first common circuit, saidfirst capacitor being discharged and said second capacitor being simultaneously charged through said second common circuit.

4. In combination, a source of electrical energy, a first capacitor and a second capacitor electrically connected in series ac oss said source, a step-up transformer having a primary winding and a secondary winding, a first space discharge means and a second space discharge means each' having a grid, 9. first common circuit including said primary winding and said first discharge means for charging said first capacitor and discharging said second capacitor, a second common circuit including said primary winding and said second discharge means for discharging said first capacitor and charging said second capacitor, means including a cam actuated contact means cyclically operable to apply a suilicient voltage to said grids to cause said discharge means to become alternately conductive, and

a charging resistor connected across said first capacitor.

5. In combination, a source of electrical energy of substantially constant "potential, a first ca,-

pacitor and a second capacitor electrically connected in series across said source, two space discharge means, a step-up transformer having a primary winding and a secondary winding, a

. being discharged first circuit for charging said first capacitor and discharging said second capacitor including said primary winding and one said discharge means, a second circuit for discharging said first capacitor and charging said second capacitor in: cluding said primary winding and the other said nately conductive, said first capacitor being charged and said second capacitor being simultaneously discharged through said first circuit and alternately said first capacitor being discharged and said second capacitor being simultaneously charged through said second circuit, a charging resistor connected across said first capacitor, and a storage capacitor connected across said source, the current flow through said contact means being limited to a very small value. I

6. In combination, a source of electrical energy, a first capacitor and a second capacitor electrically connected in series across said source, two space discharge means, a step-up transformer having a primary winding and a secondary winding, a first charging said first capacitor and charging said second capacitor including said primary winding and the other said discharge means, a trigger means including a cam actuated contact means cyclically operable to cause said discharge means to become alternately conductive, said first ca-, pacitor being charged and said second capacitor being simultaneously discharged -through said first circuit and alternately said first capacitor and said second capacitor being simultaneously charged through said second circuit, and a charging resistor connected across said first capacitor, the current fiow through said contact means being limited to a very small value.

7. In combination, a source of electrical energy, a first winding and one capacitor and simultaneously space dischar e charging said second capacitor including said primary winding and the other said discharge means, means including a cam actuated contact means cyclically operable to cause said discharge means to become alternately conductive, and a charging resistor connected across said first capacitor.

9. In combination, a source of electrical energy of substantially constant potential, two capacitors electrically connected in series across said source, a step-up transformer having a primary winding and a secondary winding, two space discharge means, trigger means including a cam actuated contact means cyclically operable to cause said discharge means to'become alternately conductive, circuit means responsive to said trigger means for charging one said capacitor and simultaneously discharging the othersaid capacitor through said primary winding and one said discharge means, and for alternately discharging the previously charged capacitor and simultaneously charging the previously discharged capacitor through said primary winding and the other said discharge means, a charging resistor connected across one said capacitor, and a storage capacitor connected across said source, the current flowing through said trigger means being only a small proportion of the total primary current. I

10. In combination, a source of electrical energy, two capacitors electrically connected in series across said source, a step-up transformer having a primary winding and a secondary winding, two space discharge means, trigger means including a cam actuated contact means cyclically operable to cause said discharge means to become alternately conductive, circuit means responsive to said trigger means for charging one said capacitor and simultaneously discharging the other said capacitor through said primary said discharge means, and for alternately discharging the previously charged charging the previously discharged capacitor through said primary winding and the other said discharge means, and a charging resistor connected, across one said capacitor, the current fiowing through said trigger means being only a small proportion of H the total primary current. 7

11. In combination, a source or electrical energy, two capacitors electrically connected in series across said source, a step-up transformer having a primary winding and a secondary windtwo space discharge means, trigger means including a cam actuated cally operable to cause said discharge means to become alternately conductive, circuit means responsive to said trigger means for charging one said capacitor and simultaneously disc the other said capacitor through said primary winding and one said discharge means, and for alternately discharging the previously charged capacitorand simultaneously charging ously discharged winding and 12. In combination, a source at electrical energy or substantially constant potential, two capacitors electrically connected in series across said source, a step-up transtormer having a priding and a secondary winding, two means, means including a cam actuabd contact means cyclically operable to charge one said capacitor and to discharge the other said capacitor through said primary winding and one said discharge means, and alternately to discharge the previously charged capacitor and to simultaneously charge the previously discharged capacitor through said primary winding and the other said discharge means, a charging resistor connected across'one said capacitor, and a storage capacitor connected across said source, the current flowing through said contact means being limited to a very small value.

13. In combination, a source of electrical energy, two capacitors electrically connected in series across said source, a step-up transformer 1 having a primary winding and a secondary winding, two space discharge means, means including a cam actuated contact means cyclically operable to charge one said capacitor and to simultaneously discharge the other said capacitor through said primary winding and one said discharge means, and alternately to discharge the previously charged capacitor and to simultaneously charge the previously discharged capacitor through said primary winding and the other said discharge means, and a charging resistor corrnected across one said capacitor, the current flowing iinough said contactv means being limited to a very small. value.

14. In combination, a source of electrical energy, two capacitors electrically connected in series across said source, a step-up transformer having a primary winding, 8. space discharge means, a trigger means including a. cam actuated contact means cyclically operable to cause said discharge means to become conductive, means including said discharge means responsive to said trigger means for charging one said capacitor and simultaneously discharging the other said capacitor through said primary winding, and alternately for discharging the previously charged capacitor and charging the previously discharged capacitor through said primary winding, and a charging resistor connected across one said capacitor. I

17. In combination, a source of electrical energy, a first capacitor and a second capacitor elec-' trically connected in series across said source, a

having a primary winding and a secondary winding, two space discharge means,-means including a cam actuated contact means cyclically operable to charge one said capacitor and to simultaneously discharge the other said capacitor through said primary winding and one said discharge means, and alternately to discharge the previously charged capacitor and to simultaneously charge the previously discharged capacitor through said primary winding and the other said discharge means, and a charging resistor connected across one said capacitor. 1

15. In combination, a source of electrical energy of substantially constant potential, two capacitors electrically connected in series across said source, a step-up transformer having a primary winding, 9. space discharge means, a trigger means including a cam actuated contact means cyclically operable to cause said discharge means means including said disergy, a pair of capacitors connected in series to become conductive, charge means responsive to said trigger means for charging one said capacitor and simultaneously discharging the other said capacitor through said primary winding, and alternately for discharging the previously charged capacitor and charging the previously discharged capacitor through said primary winding, a charging resistor connected across one said capacitor, and a charging capacitor connected across said source.

16. In combination, a source of electrical energy, two capacitors electrically connected in series across said source, a step-up transformer step-up transformer having a primary winding, a space discharge means, a triggering means for said discharge means, a charging and discharging means for said capacitors including said primary winding and said discharge means, said triggering means being cyclically operable to cause said first capacitor to become charged and said second capacitor to simultaneously become discharged through said charging and discharging means, and alternately to cause said second capacitor to become.charged and said first capacitor to simultaneously become discharged through said charging and discharging means, a charging resistor connected across said first capacitor, and a storage capacitor connected across said source.

18. In combination, a source of electrical energy, a first capacitor and a second capacitor electrically connected in series across said source, a step-up transformer having a primary winding, a space discharge means, a triggering meansfor said discharge means, a charging and discharging means for said capacitors including said primary winding and said discharge means, said triggering means being cyclically operable to means, and alternately to cause said second capacitor -to become charged and said first capacitor to simultaneously become discharged through said charging and discharging means. and a charging resistor connected across said first capacitor.

19. In combination, a source of electrical erracross said source, a'step-up transformer having aprimary winding, a space discharge device connected in parallel with each of said capacitors through the primary winding of said transformer,

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