US2984766A

US2984766A - Ignition system

Info

Publication number: US2984766A
Application number: US862929A
Authority: US
Inventors: Harold K Moore
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1959-12-30
Filing date: 1959-12-30
Publication date: 1961-05-16
Anticipated expiration: 1978-05-16

Description

H. K. MOORE IGNITION SYSTEM May 16, 1961 Filed Dec. 50, 1959 HAROLD K. MOORE INVENTOR.

BY W

AT RNEYS tea IGNITION SYSTEM Filed Dec. 30, 1959, Ser. No. 862,929

9 Claims. (Cl. 315-214) [his invention relates to an ignition system for an internal combustion engine and more particularly to a transistorized ignition system for an internal combustion engine.

In conventional internal combustion engine ignition systems, full battery voltage is applied across the primary Winding of the ignition coil through a set of distributor breaker points. As a result, a heavy current flows in the primary winding and through the contact points. When the contact points are opened, arcing occurs across the points since current through the primary winding continues to flow because of the collapsing magnetic field of the ignition coil. This causes pitting and corrosion of the distributor breaker points, and experience shows that the breaker points have to be periodically replaced because of this pitting and corrosion.

In conventional ignition systems, the average value of the primary current is quite high since heavy primary current flows continuously in one direction when the breaker points are closed. This heavy average primary current causes substantial power losses which must be dissipated in the form of heat. Care must be taken, therefore, to design the ignition coil to withstand this heat and also to limit the average primary current to a value compatible with the coil construction so that damage to the coil does not occur from overheating.

The present invention provides an ignition system in which the pitting and corrosion of the breaker points is substantially eliminated and in which high peak output voltages from the secondary winding of an ignition coil can be achieved. This is accomplished by the provision of a positive feedback transistor oscillator with the primary winding of the ignition coil being positioned in the output or load circuit of the oscillator. An oscillating output from the secondary winding of the coil is thus achieved which is sequentially applied to the spark plugs of an internal combustion engine through a distributor. The breaker points of the distributor are employed to substantially reduce the energy output of the oscillator during periods when the secondary winding of the ignition coil is not connected to any of the spark plugs. To accomplish this, the breaker points may be positioned in the base circuit of the transistor or they may be positioned in series with a capacitor which shunts the primary winding of the ignition coil. In either case, the breaker points switch only a small amount of current compared to the current flowing in the primary winding of the coil, thereby reducing pitting and corrosion of the breaker points.

The primary current oscillates during the period when the secondary winding is connected to the spark plugs, and falls substantially to zero during periods when the secondary coil is not connected to the spark plugs. This produces a low average current while simultaneously providing large peak currents and voltages in the primary winding. It has been found that the output voltages of the secondary winding obtainable from this system may be 25 %35% higher than that obtainable with a conventional system using the same size ignition coil, since the 2,984,765 Patented May iii, 196i average primary current is smaller and consequently the heat produced as a result of the PR losses is reduced. These high secondary output voltages are particularly important under engine starting conditions.

An object of the present invention is the provision of an ignition system for an internal combustion engine in which the breaker points have a long life.

Another object of the invention is the provision of an ignition system which is capable of producing high output voltages.

Other objects and attendant advantages of the present invention will become more readily apparent as the specification is considered in connection with the accompanying drawings in which:

Fig. l is a circuit diagram of one embodiment of the invention, and

Fig. 2 is a circuit diagram of another embodiment of the invention.

Referring now to the drawing in which like reference numerals designate like parts throughout the views thereof, there is shown in Fig. l a transistor generally desig nated by the numeral 10. The emitter ll of the transistor is connected to the positive terminal or" a battery 12 through an ignition switch 13. The negative terminal of the battery 12 is grounded. The collector 14 of the transistor is connected to the primary winding 15 of an ignition coil which is generally designated by the numeral 16. The base l7 of the transistor is connected to a feedback winding 18 of the ignition coil 16 through a resistor 21. One terminal of the primary winding and one terminal of the feedback winding are grounded, as shown.

The ignition coil 16 includes a secondary winding 22 having one terminal grounded and the other terminal connected to a rotating arm 23 of distributor 2d. The rotating arm of the distributor sequentially makes contact with a plurality of

distributor cap contacts

25, 26, 27 and 28 to energize

spark plugs

31, 32, 33 and 34.

A capacitor 35 is connected to the collector 14 of the transistor and to the ungrounded terminal. of the primary winding 15. The capacitor is also connected to ground through a set of conventional distributor breaker points designated by the numeral 36. The breaker points are operatedopened and closed-by a cam 37 which is rotated in timed relationship with the rotating arm 23 of the distributor 24.

The transistor it the primary winding 15, and the feedback winding 13 of the ignition coil 16, together with the power supply or battery 12, form a positive feedback transistor oscillator.

The operation of this positive feedback transistor oscillator and the ignition system of the present invention is explained below. When the ignition switch 13 is closed, the emitter 11 will rise to a positive potential, and the base 17 will be biased negatively with respect to the emitter through the feedback winding 18 and the resistor 21. The collector 14 will also be biased negatively with respect to the emitter 11 through the primary winding 15. Thus, the transistor will be turned on and current will flow from the battery through the transistor, from emitter to collector, and through the primary winding 15 of the ignition coil. The primary winding 15 and the feedback winding 18 have the relative polarities, as shown by the dot convention. Thus, as current increases in the primary winding 15, a negative pulse will be applied to the base 17 from the feedback winding 18. This negative pulse together with the bias applied will cause the transistor to reach saturation conditions. When saturation is reached, the current no longer increases in the primary winding 15, and the negative pulse disappears from the base 17 of the transistor, thereby reducing the current flow through the transistor. When this happens, the flux in the ignition coil starts to decrease, thereby inducing a positive pulse at the unmarked terminal of the feedback winding 18. This positive pulse is applied to the base of the transistor through the base resistor 21, and is of suflicient magnitude to bias the transistor to cut ofi. When the transistor is cut off, current no longer flows in the winding 15, and the positive pulse disappears from the base of the transistor. When the positive pulse disappears from the base of the transistor, the transistor is again biased to conduct through the action previously described and the cycle repeats.

There is thus provided a positive feedback transistor oscillator with the primary winding of the ignition coil being positioned in the output circuit thereof, and with the feedback winding 18 of the ignition coil being positioned in the input circuit thereof.

The oscillator produces an oscillating current in the primary winding of the ignition coil which causes an oscillating high voltage output in the secondary winding 22 which is sequentially applied to the spark plugs by the rotating arm 23 of distributor 24. The capacitor and the breaker points 36, when closed, provide a shunt path for the high frequency electrical energy produced by the oscillator so that substantially no alternating electrical energy is present in the primary winding 15. Thus, with breaker points closed, substantially no energy will be applied to the rotating arm of the distributor.

The rotating arm of the distributor and the cam 37 are arranged so that the breaker points are closed during the time that the rotating arm is between the

contacts

25, 26, 27 and 28 of the distributor cap, and are open when the distributor arm makes electrical connection to these contacts. From this description, it can be appreciated that the ignition coil applies energy to the rotating arm of the distributor only during the time when the arm is capable of transmitting this energy to the spark plug. Such action insures positive spark timing for the engine, and provides minimum average primary current in the primary winding 15.

Fig. 2 discloses an embodiment of the invention which is similar to that shown in Fig. 1, except that the breaker points 36 are positioned in the base circuit of the transistor. These breaker points are operated in timed relationship with the distributor arm 23, and are closed when the rotating arm 23 of the distributor makes contact with each of the

distributor head contacts

25, 26, 27 and 28. When the breaker point contacts are closed, the embodiment shown in Fig. 2 is identical in operation to the embodiment shown in Fig. 1 with the breaker points shown in that figure in the open position. The breaker points 36 shown in Fig. 2 are opened by the cam 37 when the rotating arm 23 of the distributor is positioned between the

distributor head contacts

25, 26, 27 and 23. It can be appreciated that when distributor breaker points 36 of Fig. 2 are open, the base circuit is opened and the oscillatory output will no longer occur.

With the circuit shown in Fig. 1, a conventional distributor which has the breaker points grounded may be employed. With the embodiment shown in Fig. 2, however, a conventional distributor must be modified to insulate the breaker points from the normal ground connection.

The ignition systems shown in Figs. 1 and 2 may employ the same components, and the following description of these components is given by way of example only:

Transistor 1G Delco DTlOO transistor.

Resistor 21 100 ohms.

Battery 12 Standard 12 volt automotive battery.

Primary winding 15 100 turns of No. 22 copper wire.

Feedback winding 18 100 turns of No. 22 copper wire.

Secondary winding 22 28,000 turns of No. 38

copper wire. Capacitor 35 of Fig. 1 100 id.

The above listed number of turns for the primary, feedback and secondary windings are applicable for an open core which is standard in the conventional automotive vehicle ignition system. It has been found that with a closed type core, the feedback and primary windings may be reduced to 25 turns, and that the secondary winding may employ 28,000 turns of No. 40 copper wire.

The transistorized ignition system of this invention will produce high peak voltages in the secondary winding of the ignition coil, since a high peak primary current may be employed without causing the coil to overheat. Althrough the peak primary current is high, the average current may be quite low due to the oscillations in the primary current, and due to the fact that the current is interrupted by the action of the breaker points. It also can be appreciated that this ignition system will provide a long life for the distributor breaker points since, in both Figs. 1 and 2, only a small amount of current, compared to the current in the primary, need be switched. Thus, the present invention provides an ignition system for an internal combustion engine in which the breaker points have a long life and which is capable of producing high output voltages.

Although the invention is shown employing PNP type transistors the invention is in no way limited to this type of transistor. It will be readily apparent to those skilled in the art how the circuit of the present invention may be connected to employ other types of transistors, for example, NPN type transistors.

It will be understood that the invention is not to be limited to the exact construction shown and described and that various changes and modifications may be made without departing from the spirit and scope of the invention, as defined in the appended claims.

What is claimed is:

1. A transistorized ignition system for an automotive vehicle comprising a plurality of spark plugs, a distributor including a rotating arm, said rotating arm being sequentially connected to and disconnected from said spark plugs, an ignition coil including a primary and a secondary winding, said secondary winding being connected to the rotating arm of said distributor, a transistor oscillator having an output circuit, said primary winding being positioned in the output circuit of said transistor oscillator, and means connected to said output circuit of said transistor oscillator for reducing the energy output thereof during operating periods when the rotating arm of said distributor is not connected to any of said spark plugs. V

2. A transistorized ignition system for an automotive vehicle comprising a plurality of spark plugs, a distributor including a rotating arm, said rotating arm being sequentially connected to and disconnected from said spark plugs, an ignition coil including a primary and a secondary winding, said secondary winding being connected to the rotating arm of said distributor, a transistor oscillator having an output circuit, said primary winding being positioned in the output circuit of said transistor oscillator, and means connected across said primary winding for shunting said primary winding during operating periods when the armof said distributor is disconnected from said spark plugs.

3. A transistorized ignition system for an automotive Vehicle comprising a plurality of spark plugs, a distributor including a rotating arm, said rotating arm being sequentially connected to and disconnected from said spark plugs, an ignition coil including a primary and a secondary winding, said secondary winding being connected to the rotating arm of said distributor, a transistor oscillator having an output circuit, said primary winding being positioned in the output circuit of said transistor oscillator, said transistor oscillator having an input circuit, switch means positioned in the input circuit of said transistor oscillator, and means operated in timed relationship with the rotating arm of said distributor for opening said switch means during operating periods when said rotating arm is disconnected from said spark plugs.

4. A transistorized ignition system for an automotive vehicle comprising a plurality of spark plugs, a distributor connected to sequentially supply electrical energy to said spark plugs, an ignition coil including a primary winding, a secondary winding and a feedback winding, said secondary winding being connected to said distributor, a transistor having an input circuit and an output circuit, said primary winding of said ignition coil being positioned in the output circuit of said transistor and said feedback winding being positioned in the input circuit of said transistor, said transistor with its input and its output circuit forming an inductively coupled positive feedback oscillator, and means for shunting said primary winding of said ignition coil including a set of contact points which are opened sequentially in timed relationship with the distributor connection to each of the spark plugs.

5. A transistorized ignition system for an automotive vehicle comprising a plurality of spark plugs, a distributor connected to sequentially supply electrical energy to said spark plugs, an ignition coil including a primary winding, a secondary winding and a feedback winding, said secondary winding being connected to said distributor, a transistor having an input circuit and an output circuit, the primary winding of said ignition coil being positioned in the output circuit of said transistor and the feedback winding being positioned in the input circuit of said transistor, said transistor with its output circuit and its input circuit forming an inductively coupled positive feedback transistor oscillator, and means operated in timed relationship with said distributor for opening said input circuit during periods between successive connections of said distributor to said spark plugs.

6. A transistorized ignition system for an automotive vehicle comprising, a plurality of spark plugs, a distributor connected to sequentially supply electrical energy to said spark plugs, an ignition coil including a primary and a secondary winding, said secondary winding being connected to said distributor, a transistor oscillator having an output circuit, said primary Winding being positioned in the output circuit of said transistor oscillator, and means for shunting said primary winding in timed relationship with the disconnection of said distributor from each of said spark plugs.

7. A transistorized ignition system for an automotive vehicle comprising, a plurality of spark plugs, a distributor connected to sequentially supply electrical energy to said spark plugs, an ignition coil including a primary and a secondary winding, said secondary winding being connected to said distributor, a transistor oscillator having an output circuit and an input circuit, said primary winding being positioned in the output circuit of said transistor oscillator, and means for opening the input circuit of said transistor oscillator in timed relationship with the disconnection of said distributor from each of said spark plugs.

8. An ignition system for an internal combustion engine comprising, a plurality of electrical ignitor means, a distributor connected to sequentially supply electrical energy to each of said electrical ignitor means, an ignition coil including a primary and a secondary winding, said secondary winding being connected to said distributor, a semi-conductor device oscillator having an output circuit, said primary winding being positioned in the output circuit of said semi-conductor device oscillator, and means for shunting said primary winding in timed relationship with the disconnection of said distributor from each of said electrical ignitor means.

9. An ignition system for an internal combustion engine comprising, a plurality of electrical ignitor means, a distributor connected to sequentially supply electrical energy to each of said electrical ignitor means, an ignition coil including a primary and a secondary winding, said secondary winding being connected to said distributor, a semi-conductor device oscillator having an output circuit, said primary winding being positioned in the output circuit of said semi-conductor device oscillator, and means for opening the input circuit of said semiconductor device oscillator in timed relationship with the disconnection of said distributor from each of said electrical ignitor means.

References Cited in the file of this patent UNITED STATES PATENTS 1,589,489 SnOOk June 22, 1926 1,968,930 Cotter et a1. Aug. 7, 1934 2,816,230 Lindsay Dec. 10, 1957 2,857,518 Reed Oct. 21, 1958 FOREIGN PATENTS 1,137,949 France Jan. 21, 1957