US2862150A

US2862150A - Ignition system

Info

Publication number: US2862150A
Authority: US
Publication date: 1958-11-25
Anticipated expiration: 1975-11-25

Description

Nov. 25, 1958 B. H. SHORT IGNITION SYSTEM Filed Jan. 8, 1954 .iilllmm mm- T1 YM EH 8.

INVENTOR. rooks H. Short %/I. His Attorney United States Patent ice IoNITIoN SYSTEM Brooks H. Short, Anderson, Ind., assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application January 8, 1954, Serial No. 402,910

Claims. (Cl. 315-224) This invention relates toan ignition apparatus and systems therefore and more particularly to an ignition system wherein unidirectional electronic switches control the charge and discharge of an ignition condenser.

It is an object of the present invention to provide a more efiicient ignition system for an internal combustion engine. This object is materialized by including two unidirectional electronic switches in circuit with an ignition condenser so that one of the electronic switches which is conductive in one direction of current flow only, will conduct a charge away from the condenser when the current flow passing therethrough is in a direction opposite to that passing through the other switch that is used as a triggering tube which is also conductive in one direction of current flow only and closes a circuit for discharging the condenser through an ignition coil.

It is a further object of the present invention to reduce the time and electrical energy required to charge an ignition condenser. This object is accomplished by including a unidirectional electronic switch in a circuit with the condenser that discharges through the windings of an ignition coil so that the charge induced on the condenser by the ignition coil will be discharged therefrom.

It is a further object of the present invention to connect a unidirectional electronic switch in parallel with a triggering tube of an electronic ignition system so that the switch will be conductive and permit current to pass in a reverse direction to the flow of current which passes through the triggering tube. This reversed flow of current will discharge the induced potential that is formed on an ignition condenser by the ignition coil after the triggering tube ceases to be conductive.

In carrying out the above object it is another object to vary the potential of an ignition system of an internal combustion engine inversely with the engine speed. This object is accomplished by including the variable resistance in the ignition circuit the ohmic value of whic varies inversely with the speed of the engine.

'It is a further object of the present invention to include a variable resistance, and a transformer, wherein the ohmic value of the resistance varies inversely with the speed of an internal combustion engine and thetransformer has both high and low voltage taps, in an ignition system of an internal combustion engine and connect the taps of the transformer through the contacts of a re- 2,862,150 Patented Nov. 25, 1958 lay so either the high or low voltage taps will be selectively connected in circuit with the variable resistance and a current rectifier for supply current of varying potential to the other electrical components at an ignition system.

Further objects and advantages of the present invention will be apparent from the following description reference being had to the accompanying drawings wherein a preferred embodiment of the present invention isclearly shown.

In the drawing:

Figure 1 is a wiring diagram of a portion of an ignition system for an internal combustion engine embodying the present invention.

Figure 2 shows a curve of the charging and discharging characteristics of a condenser in the ignition circuit of an internal combustion engine.

Figure 3 shows how the curve in Figure'2 is modified by the use of the present invention.

In the drawings the portions of an ignition system for an internal combustion engine shown represent improvements over the ignition system shown and described in application Ser. No. 402,912, now U. S. Patent No. 2,847,489, assigned to the assignee of the present invention, whereby the power consumption of that system is reduced to provide a highly efficient ignition system which will operate favorably during cranking periods when the engine is operating. 7 I

Referring now to the drawing, a transformer 20, rectifier tubes 22 and condensers 24 are connected with other parts of the electrical system, not shown, of an internal combustion engine and arranged as disclosed in Patent 2,536,143, as assigned by the patentees Brooks H. Short and Charles E. Buck to the assignee of the present invention so as to provide a voltage which normally varies between 600 and 1000 volts at a terminal 28 under various conditions set forth therein.

. The charging characteristics of the condenser 34 circuit which includes tube 30, inductance 32, and condenser 34 is shown in Figures 2 and 3 of thedrawings wherein the potential e as impressed on the condenser is plotted against time.

After condenser 334 is charged and the thyratron triggering tube 36 is caused to be conducting, in a manner to be hereinafter described, current will flow in the primary windings of a high frequency coil 38 to ground 42 and thereby induce current and voltage in the secondary windings of the coil 38 which is distributed through a suitable distributor 39 to the engine spark plugs, one of which is indicated as 40 on the drawing.

The main triggering condenser 44 has one of its plates connected to ground 42 and the other to a lead 48 to a junction 51 to the regulated potential across the voltage regulator circuit including regulator tube 50 and resistance 52 which are in series between the juncture 51 and ground 42. A regulating resistance 46 bridges the junction 51 with the terminal 28. The cold cathode voltage regulator tube 50 has its anode connected to junction 51 and its cathode connected through resistance 52 to ground.

The tube 50 because of the arrangement in the circuit acts as a voltage regulator tube and Will conduct current and will serve as a by-pass whenever the potential at junction 51 exceeds a predetermined value and thus limits the potential of capacitor 44 to a certain value, for example 300 volts. The breaker points of an ignition timer, diagrammatically shown as contact points 54 on the drawing, are so arranged in the circuit that When the points 54 are closed, a second triggering condenser 56 is charged from the potential of condenser 44. This charge of condenser 56 is impressed on the grid of the thyratron triggering tube 36 through resistance 58, to make tube 36 conductive and thereby cause current to flow in the primary of coil 38 in the manner heretofore set forth.

When the contacts 54 close, condenser 56 is charged from condenser 44 through ground 42, tube 36, and resistance 58. The charging of condenser 56 causes the tube .36 to be ionized or conducting. This ionization causes condenser 34 to be discharged through the primary of coil 38 thereby producing ignition voltages. Resistance with one end connected between condenser 56 and resistance 58 and the other end connected to ground 42 limits the discharging of condenser 56 when points 54 are opened. When points 54 are open, condenser 56 will discharge through

resistors

62 and 60. This circuit during discharge of condenser 56 places a negative voltage on grid of tube 36. Upon the opening of contacts 54, this negative potential removes all possibility of the ionization of tube 36 and'thereby renders the tube nonconductive when the points 54 are opening.

As indicated in application Serial No. 402,912, now U. S. Patent No. 2,847,489, the condenser 34, because of the characteristics of the charging circuit which includes the tube 30 and inductance 32, will be charged with a polarity, indicated for purposes of illustration only as positive and negative on the drawings, until the charge as represented by point b in the drawings is reached. When ignition is called for and the triggering tube 36 is caused to be conducting by an impulse in the grid circuit thereof, the condenser 34 sends current through the tube to ground and back through the primary of coil 38 to the other side of the condenser. This current flows until all the energy stored in the capacitor has been consumed and at that instant the current is at a maximum and causes potential in the condenser to rapidly drop along the line of be indicated in Figure 2. The maximum current flow at this time represents an appreciable energy stored in the primary inductance of 38 which then becomes available to induce a current and cause it to continue to flow even though the capacitor has become discharged. The current continues to flow in the original direction to the end that the capacitor becomes charged with a reverse polarity as indicated by the portion from c to d on Figure 2. When all the available energy appears across the capacitor, but with reversed polarity, the tube 36 will not conduct this current as the current will pass therethrough in one direction only. The net effect of the foregoing is that a reverse charge is imposed on capacitor 34 which must be removed before it can be charged to the full potential through tube 30 and inductance 32. Such charging requires more energy than would be required to accumulate the same charge on capacitor 34 from a vzero voltage.

So that the reversed polarity charge on condenser 34 will be reduced, a unidirectional electronic switch such as a thyratrontube 100 is placed in parallel with the triggering tube 36. When the voltage on condenser 34 reaches its negative reversed peak as shown on lines to d of Figure 3, the tube 100 Will become conducting, as it is connected in reverse in the circuit, and thus permits the reverse charge imposed on condenser 34 to send current through the circuit and cause the condenser 34 to be discharged as represented by the line d'e'. The charge placed on condenser 34 through tube 30 and inductance 32 will not pass through tube 100 as the tube will not be conducting for the current which flows in that direction.

Further after tube has permitted a current to pass therethrough, this current will induce lines of flux in the inductance of coil 38 and the flux will cause the current to continue to flow in the same direction to charge the condenser along line ef. This charge will be relieved through tube 36 and the subsequent charges on condenser 34 will be relieved until the point of zero voltage is reached as indicated by point g wherefrom the condenser 34 may be charged along line gh through inductance 32 and tube 30 as heretofore set forth. From the above it is apparent that the combination of a tube 100 with tube 36 will effect a greater ignition duration as Well as lower the power input current to the system.

The transformer 20 has the secondary winding 102 thereof arranged to provide a low voltage tap 104, a higher voltage tap 106 and a common terminal tap 108. The common tap 108 is connected through a lead 110 to one of the terminals 112 of the rectifier circuit, heretofore described. The low voltage tap 104 is connected by a lead 114 to a second fixed contact 116 of relay 118. Contacts 116 and 122 are spaced from each other and have a movable armature 124 of the relay located therebetween so that the armature 124 will alternately make contact with one or the other and thereby close a circuit therebetween. The fixed end of the armature 124 is suitably connected through lead 236 to a second terminal 27 of the rectifier unit. The armature 124 of relay 118 is normally biased by a spring 128 so that it is in contact with contact 116 and thereby normally supply the lower voltage to the rectifier unit.

When the armature 124 of relay 118 is moved by the energization of windings 130, it will move from the contacting position with contact 116 and move into contact with contact 122 and thereby close a circuit with contact 122 and thereby connect the terminal 106 of transformer 20 with terminal 27 of the rectifier circuit so as to supply a higher voltage potential thereto. The winding 130 of relay 118 is circuited with the starting circuit, not shown, of the internal combustion engine so that during periods of starting the winding 130 will be energized and thus move the armature 124 so as to break the circuit through contact 116 and make the circuit through contact 122 and thus provide the high potential available to the ignition system so as to insure a better starting.

It has been found that the ignition system of an internal combustion engine requires less voltage at higher speeds than it does at lower speeds. For that reason a ballast lamp 132 is included in circuit with the primary windings 134 of the transformer 20. This lamp acts as a variable resistance the ohmic value of which increases proportionately with the value of the current passing therethrough. Further it is known that as the speed of the internal combustion engine increases, the output of the generator also increases and thus supplies increased energy to primary 134 of transformer 20. This increase in electrical energy will correspondingly increase the induced current and voltage in the secondary windings 102 and correspondingly increase the voltage potential delivered to

terminals

104 and 106. This increased potential is partially compensated for by the increase in the ohmic value of variable resistance 132 and thus provides a more constant potential to the remainder of the ignition system.

Manifestly the variable resistance or ballast lamp 132 may be of any of the well known types as for example, a lamp having a tungsten filament that has a resistance which varies directly as the value of the current passing therethrough and further the lamp might be connected in the secondary circuit, not shown, of the system between terminal 108 and terminal 112 of the rectifier so as to accomplish the same purpose but in this event the ohmic value, to be hereinafter disclosed preferably will have to vary directly with the engine speed.

Satisfactory operation has been obtained by using elements having the following model designations or electrical characteristics:

Transformer 20 primary.. 76 turns of #22 /2 wire. Transformer 20 secondary between

taps

108 and 104 2450 turns of #36 wire. Transformer 20 secondary between

taps

108 and 106 4500 turns of #36 wire. Rectifier tubes 22 Model DT-264.

Grid resistances 25 Mohms.

Condenser 24 .68 mfd. Inductance 32 55 henrys. Condenser 34 .044 mfd. Condenser 44 .01 mfd. Resistance 46 47 K' ohms. Resistance 52 51 K ohms. Condenser 56 .002 mfd. Resistance 58 22 K ohms. Resistance 60 400 K ohms. Resistance 62 150 K ohms. Grid condenser 138 .0005 mfd. Resistance 135 5000 ohms. Condenser 136 .006 mfd. Tube 30 DT-264. Tube 50 DT-263 cold cathode voltage regulator.

Tubes

36 and 100 Model DT-265. Resistance lamp 132 Rated at .60 HM at 3.4

amperes.

Tubes 22 and tube 30 known as cold cathode tubes because they do not have heated cathode filaments, become conducting by electrostatic field created by application of voltage from the transformer secondary and once ionized they are kept ready for conduction by keep alive electrode. Condenser 136 in combination with resistance 135 is known as a bufier condenser which absorbs transient voltages when the vibrator contacts not shown open.

Tube 30 having a model designation of DT264 is known as a rectifier tube as previously set forth is of the type that will conduct increasing values of voltages in one direction of current flow only.

Tube 36 and tube 100 are cold cathode types which require a positive potential on its grid in order to be conducting and once having been conducting will continue to conduct as long as the plate voltage is above the ionizing voltage, for example, 300 volts.

The inductance 32 because of its arrangement with condenser 34 makes possible the charging of condenser 34 to a value of twice the voltage of terminal 28 so the condenser 34 when fully charged has a potential twice the maximum potential of terminal 28. When tube 36 and tube 100 become conducting due to the charge placed on condenser 56, the condenser will be discharged faster than it is charged from terminal 28. When this happens the potential of the plates of the tubes will fall below the voltage required to maintain ionization and the tubes will cease to conduct, as the inductance 32 operates to prevent a rapid increase in voltage on the plate of condenser 34.

Tube 50, of the cold cathode voltage regulator type, becomes conductive when the voltage on the plate exceeds a predetermined value. Thus the condenser will be charged only to that value and the tube will be conductive only when the voltage at junction 51 exceeds that amount.

The high frequency ignition coil 38 is constructed in a manner disclosed in the patent of Short and Tynan 2,463,123, granted March 1, 1949, as assigned to the assignee of the present invention.

The system is operative when the potential at terminal 28 ranges between 600 to 1000 volts. 600 volts, for example, is that which is obtained when the voltage of the partly charged battery is low but yet sufficient to efiect operation of the cranking motor. During the 6 starting periods the value of this low voltage is increased when the relay which is actuated by the starting circuit of the engine places a greater number of turns on the secondary winding 102 of the transformer 20 in circuit with the rectifier so as to increase the potential supplied to the various other portions of the ignition apparatus. 1000 volts, for example, is generally realized when the battery is fully charged when operating the cranking motor or when the current is applied by the generator for ignition battery charging. In order to provide for adequate charging of condenser 34 when terminal voltage is 600 volts and not subject the condenser 34 to excessive voltage when the terminal 28 potential is higher than 1000 volts, the voltage regulator tube 50 is provided.

The present system is operative the instant the ignition switch, not shown, closes since the cold cathode type rectifier tubes 22 and the cold cathode thyratron tubes 36 and are used. These tubes require high voltage for current operation which is in the capabilities of a storage battery of an internal combustion engine if a suitable voltage step-up system such as the vibrator, transformer rectifier tubes are employed.

It is apparent that from the foregoing that the ignition device disclosed represents a highly efficient ignition system for an internal combustion engine as power loss through all of the tubes and inductance is small and the energy which is pressed upon the system during the periods when the engine is operating is regulated so that it varies inversely to engine speed.

Further the use of the reversed electronic switch limits the impression of the charged opposite polarity on the main ignition condenser so as to effect a highly eflicient system as is manifest by the fact that the operating current utilized in the present system is approximately 2.6 amps. for an ordinary internal combustion engine compared to 8 amperes when other systems are employed.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. An electronic ignition circuit, comprising: an ignition condenser, a current source for charging said condenser, an ignition coil having primary and secondary windings wherein the primary is in circuit with said condenser and current source, a spark plug in circuit with said secondary winding, a distributor in circuit with said spark plug for making and breaking the circuit between said spark plug and said winding, a unidirectional electronic switch in circuit with said condenser and the primary winding of said coil for controlling the discharging of said condenser through said coil in one direction of current flow only and a second unidirectional electronic switch in circuit with said condenser and the primary winding of said coil for discharging said condenser through said coil when the current flow therethrough is in the reverse direction.

2. An electronic ignition system comprising; an ignition condenser, a current source for charging said condenser with a charge of predetermined polarity, an ignition coil having primary and secondary windings wherein the primary winding is in circuit with said condenser, a spark plug in circuit with said secondary winding, a distributor for making and breaking the said spark plug circuit, a unidirectional electronic switch connected in circuit with said condenser and the primary windings of said coil for discharging said condenser through said primary winding when the charge on said condenser is of one polarity, and a second electronic switch connected in circuit with said condenser and primary winding for discharging said condenser when the charge on said condenser is of the opposite polarity.

3. An electric ignition system having; an ignition condenser, a current source for charging said condenser, an ignition coil including a primary winding and a secondary winding, a unidirectional electronic switch in circuit with 7 and adapted to close said circuit between said primary winding and condenserf'or one direction of c'u'rrentfl'o'w only, a second unidirectional 'e'lectr'onic switch connected in circuit with and adapted to close said circuit between said primary Winding and condenser when the current flow therebetwe'en is in the reverse direction.

4. The electronic ignition system as set forth in claim 1, wherein the current source includes a transformer having a high and low voltage tap, a current rectifier, and a switch connected-in circuit with said transformer and rectifier and selectively operable 'to connect either the high or low voltage taps with said rectifier.

SVAn ignition system for an internal combustion engine, comprising; 'a transformer having a high and low voltage tap, a current rectifier, a relay connected in circuit with said transformer and rectifier and normally adapted to close a circuit between said low voltage tap and one terminal of said current rectifier, said relay being connected to be energized by a current from an external source and arranged for connecting the high and disconnecting the lo'w voltage tap'skws'lith said one "terminal of said current rectifier when said rel'ayis energized, and a variable resistance element connected in circuit with another terminal of said rectifier and thehig h and low voltage taps of said transformer'and having the ohmic value thereof varying directly with the current flow therethrough.

References Cited in the file of this patent UNITED STATES PATENTS 1,469,582 Buresch 001. 2, 1923 2,222,498 Bychinsky Nov. 19, "1940 2,309,629 Dawson Feb. 2, 1 943 2,365,610 White D60. 19, 1 944 2,536,143 Short et al. Jan. 2, 1951 2,662,202 Short Dec. 8, 1 953 was."