US3291109A

US3291109A - Electronic system

Info

Publication number: US3291109A
Application number: US388640A
Authority: US
Inventors: Nicholas T Neapolitakis
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 1964-08-10
Filing date: 1964-08-10
Publication date: 1966-12-13
Anticipated expiration: 1983-12-13

Description

Dec. 13, 1966 N. T. NEAPOLITAKIS 3,291,109

ELECTRONIC SYSTEM Filed Aug. 10, 1964 FIG. 1

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- lnvenrbr:

N/CHOL/LS Z' NEAPOL/TAK/S mm (Lu, K Mek United States Patent 3,291,109 ELECTRONI SYSTEM Nicholas T. Neapolitakis, Chicago, Ill., assignor to Motorola, Inc., Franklin Park, Ill., a corporation of Illinois Filed Aug. 10, 1964, Ser. No. 388,640 4 Claims. (Cl. 123-148) This invention relates generally to ignition systems for internal combustion engines and more particularly to an improved ignition system utilizing an encapsulated magnetically actuated reed switch and a switching circuit including semiconductor devices.

Internal combustion engines, as used in automobiles and other vehicles, include an ignition system for firing the combustible charges in the cylinders thereof. Such systems are controlled by a switching mechanism, usually referred to as breaker points, which operates in synchronism with the engine. The breaker points are connected in a circuit and actuate the same to provide high voltage pulses, and these are applied to the various spark plugs or other ignition devices in the cylinders of the engine through a distributor device. The distributor device also operates in synchronism with the engine to apply the pulses to particular cylinders. In systems commonly in use wherein the breaker points interrupt the current supplied to the primary of an ignition coil, it is necessary for the breaker points to interrupt a current sufficiently large that arcing and pitting takes place at the contacts. This results in poor operation after a period of time, and the points must be replaced at regular intervals. This results in objectionable maintenance of the engines.

In order to reduce the current through the breaker points, ignition systems have been used including transistors for interrupting the current supplied to the ignition coil. A smaller current for triggering the transistor circuit is then switched by the breaker points. These systems have reduced the wear at the breaker points but have not been entirely satisfactory as faulty operation may still take place when the breaker point contacts are contaminated by foreign particles. The mechanical cam structure and the breaker point rubbing block, for actuating the breaker points, wear and must be periodically adjusted for proper dwell time. Further the switching action in the breaker points, particularly at low speeds such as during starting, has not provided the desired action in the ignition system.

It is, therefore, an object of this invention to provide an improved ignition system for an internal combustion engine which is reliable in operation and requires a minimum of maintenance.

Another object of the invention is to provide a transistorized ignition switch system including a switching device which provides extremely rapid switching action.

A feature of the invention is the provision of an ignition system for an internal combustion engine including a circuit switched by an encapsulated magnetic reed device, with a magnetic circuit therefor which provides rapid reversal of the magnetic field through the reed, and rapid switching action thereof.

Another feature of the invention is the provision of a transistor ignition system controlled by a reed device positioned in a magnetic circuit having a rotating magnetic member and pole pieces cooperating therewith so that the flux through the reed device changes sharply and reverses to provide rapid switching action. The rotating member may be a disc of magnetic material with discrete radial poles, or an axially magnetized disc with pole "ice plates on the opposite faces thereof having interleaved pole pieces to provide alternate poles about the periphery. The reed device includes encapsulated magnetic contacts having portion extending therefrom and engaging pole pieces through which the reed device is intermittently coupled to poles of opposite polarity of the rotating member. The magnetic reed may be positioned horizontally, vertically, or at an angle, to provide the desired action in the space which may be available.

The invention is illustrated in the drawings wherein:

FIG. 1 is a circuit diagram of the ignition system of the invention;

FIG. 2 is a cross sectional view showing the magnetic structure in a distributor housing;

FIG. 3 illustrates an alternate magnetic structure for the system of FIG. 1;

FIG. 4 is a cross sectional view along the line 4-4 of FIG. 3;

FIG. 5 shows the sealed reed device and the coupling to the magnetic pole; and

FIG. 6 shows an alternate embodiment with the reed device positioned vertically.

In practicing the invention, an ignition system is provided which includes an ignition coli, and one or more switching transistors connected in series with the coil across a source of potential for interrupting the current through the coil to produce firing pulses. The conduction of the switching transistor (or transistors) is determined by a magnetically actuable encapsulated reed switch which is placed adjacent a rotating magnetic structure, and which may be provided in a distributor housing. The rotating magnetic structure produces a fluctuating field which opens and closes the reed switch in synchronism with the internal combustion engine to provide properly timed firing pulses. The rotating magnetic 'structure includes discrete poles which move past pole pieces of amagnetic structure including the reed device. This causes abrupt changes in the reluctance so that the flux through the reed device changes quite sharply. The alternate poles are of opposite polarity so that the flux through the reed device reverses and this acts to provide positive movement of the reeds so that extremely rapid switching action takes place. The rotating magnetic structure may be a toothed wheel with alternate teeth magnetized to opposite polarities, or may be an axially magnetized disc with pole plates on either side having teeth extending therefrom and interleaved with each other to provide alternatepoles of opposite polarity. The reed switch may be positioned in various manners as may be required to meet space requirements.

Referring now more particularly to FIG. 1, there is shown an ignition system for an internal combustion engine 11 having eight cylinders. Engine 11 has a plurality of spark plugs 12 for igniting the fuel mixture in the cylinders thereof. High voltage firing pulses are supplied to spark plugs 12 by a distributor 13 which has a plurality of fixed contacts 14 connected to respective ones of spark plugs 12. The high voltage pulse is developed in the secondary winding of a high voltage ignition coil 16, and applied to the moving contact 15 which moves into proximity with the fixed contacts 14.

As shown in FIG. 1, ignition coil 16 is of the well known auto-transformer type. However, a double winding transformer may also be used within the scope of the invention. When current flowing through the primary of ignition coil 16 is suddenly interrupted, a high voltage spike will be induced in the secondary thereof. It is this spike that is applied to moving contact 15 of distributor 13, and from the fixed contacts 14 thereof to the spark Ca plugs 12 of internal combustion engine 11. The primary of ignition coil 16 is connected to the source of current, namely storage battery 17, by a pair of

transistors

18 and 19. Battery 17 may be charged by an alternator or generator 21, the output of which may be regulated by regulator 23 in a well known manner. Also connected in series with the primary of coil 16 and

transistors

18 and 19, are ignition switch 25 and ballast resistor 27.

As previously stated,

transistors

18 and 19 control the conduction of current to the primary of ignition coil 16. Upon interruption of current in coil 16, a high reverse voltage occurs.

Zener diodes

28 and 29 are connected across the emitter and collector portions of

transistors

18 and 19 respectively to prevent the reverse voltage across these portions from exceeding their breakdown voltage. A resistor 31 is connected between the emitter and base portions of transistor 18, and the base portion of transistor 18 is connected through an isolating diode 33 to resistor 35. Resistor 37 connects the base portion of transistor 19 to its emitter portion, and the base portion is also connected to resistor 36. A control transistor 41 V has its emitter portion connected to the junction between

resistors

36 and 35, and has its collector portion grounded.

Upon conduction of transistor 41, transistor 19 will be forward biased through resistor 36, whereas transistor 18 will be forward biased through resistor and diode 33. This will cause current to flow in coil 16. When transistor 41 is cut otf, the potential on the base portions of both

transistors

19 and 18 will rise quickly toward their respective emitter potentials due to the connection through

resistor

37 and 31, cutting these transistors off. This interrupts current through coil 16 producing a firing pulse therein.

The conduction of control transistor 41 is controlled by a circuit responsive to the speed and timing of engine 11. A resistor 43 connects the base portion of transistor 41 to battery 17 through ignition switch 25. The base portion of transistor 41 is also connected to ground through resistor 44 and magnetically actuable reed switch 45. Resistor 44 may be very small and can have a value as low as 1 ohm. This protects the reed from excessive current in the event that the collector portion of transistor 41 is not well grounded. Resistor 44 also reduces the current spike through the reed contacts when the reeds close initially as the system starts. This is because at this time v the voltage applied through

resistors

37 and 36 to the emitter portion of transistor 41 is almost the full supply voltage because of the inductance of coil 16.

Reed switch 45 comprises a pair of

reeds

47 and 48 which are normally open. Reed switch 45 is encapsulated and placed adjacent a rotating magnet member 50 which, during the course of its rotation, will align poles 51 of op posite polarity adjacent to

pole pieces

52 and 53 which are magnetically connected to

reeds

47 and 48 respectively. This causes the reeds to attract one another and therefore to close. The discrete poles 51 are shaped to match the

pole pieces

52 and 53 so that as the poles move into and out of registry with the pole pieces a sudden change in flux takes place. This provides a fast snap switch action.

The alternate poles marked N, S, N, etc. around the periphery of the annular magnet 50 are uniformly spaced to operate the reed switch at regular angular positions of the magnet. As the magnet 50 continues rotation, the alternate polesproduce fields which are in opposite directions to open the reeds at the half way point and then close them again once the field is completely reversed. It should be noted that the field may actually force the reeds apart in the event that they tend to stick together due to magnetic retentivity, moisture, or foreign particles.

With reed switch 45 closed, the base portion of transistor 41 will be grounded and hence transistor 41 will be driven into conduction to ground the juncture between

resistors

36 and 35. This causes the

transistors

18 and 19 to conduct and current to flow through coil 16. When reed switch 45 opens, the base portion of transistor 41, which is connected to battery 17 through resistor 43, will rise to battery potential, actually reverse biasing the transistor 41 to insure rapid cut off. This cuts

ofl transistors

18 and 19 and interrupts current through coil 16 so that a high voltage is developed thereacross. This is applied through distributor 13 to the spark plugs 12, as previously described.

Magnetically actuable reed switches of the type suitable for use as switch 45 are commercially available. One source for such switches is Hamlin, Inc. of Lake Mills, Wisconsin, and the switches are designated MRR-Z. The reeds are glass encapsulated in a tube which may be ap proximately Vs of an inch in diameter and less than 1 inch long. The reeds may be made of nickel'iron alloy and rhodium plated. Other contact structures may be used, such as gold diffused or nickel plated contacts. Suitable reed switches are also available from other sources.

As the reed switch and the magnetic poles connected thereto will be supported by insulated members it is not necessary that either of the reeds be grounded as shown in the circuit of FIG. 1. This provides full latitude of use of ignition systems in various circuit arrangements in vehicles having either the positive or the negative terminal of the electrical supply grounded.

In FIG. 2 the reed switch and magnetic structure are shown in a distributor housing with the distributor switch 13. The distributor housing includes a base 71 and a cover or cap 72. The distributor shaft '73 extends upwardly into the housing and actuates drive plate 75. Drive plate 75 is connected through the spring biased fiy weight mechanism 77 and drive pin 78 to the centrifugal advance plate 79. Advance plate 79 drives rotor shaft 81 on which insulating rotor 83 is mounted. Rotor 83 carries the moving contact 15 of the distributor, which was described in connection with FIG. 1. The fixed contacts 14 of the distributor, which are connected to the spark plugs, are mounted in the cap 72 and extend down wardly therefrom. The moving contact 15 engages a cen= ter contact 60 which is connected to ignition coil 16, to complete the circuit therefrom to one of the fixed contacts 14.

The rotating magnetic member 50 may be mounted on the rotor shaft 81, which in the standard distributor structure carries a cam for operating mechanical breaker points. The encapsulated reed switch 45 is placed adjacent the periphery of the member 50 and may be supported by pole pieces 52 and 53 (see FIG. 1), which are in turn supported by non-magnetic insulating member 85 mounted on vacuum advance cup 86 of the distributor. The breaker points are commonly supported in a similar way from the vacuum advance cup. The

magnetic reeds

47 and 48 extend from the encapsulated reed device and 'iIJre mounted on the

pole pieces

52 and 53 as shown in The system which has been described operates to provide high voltage firing pulses in response to actuation of the reed switch in synchronism with operation of an internal combustion engine having a plurality of cylinders with a spark plug in each cylinder. Although an eight cylinder engine has been illustrated, it will be apparent that the ignition system can be used with an engine having any number of cylinders. The system can also be used for providing ignition pulses in response to actuation of the reed switch which may be independent of the engine operation, for use in a turbine or jet engine.

FIGS. 3, 4 and 5 shown an alternate form of the rotating magnetic structure. This structure includes a disc shaped magnet 90 (FIG. 4), which is magnetized in the axial direction, so that the upper surface provides one polarity and the lower surface provides the other polarity.

Pole plates

91 and 92 are secured to the two faces of the disc magnet 90. The two

pole plates

91 and 92 may be of identical configuration, with the teeth or

projections

93 and 94 thereon opposing each other, and positioned at angles of 45 with respect to each other. The teeth therefore provide discrete poles, with alternate poles being of opposite polarity and equally spaced around the circumference of the structure.

Pole pieces

95 and 96, generally similar to the

pole pieces

52 and 53 of FIG. 1, are positioned so that they are intermittently aligned with the

pole teeth

93 and 94 as the magnetic structure rotates. The

pole pieces

95 and 96 may support an encapsulated reed switch 98, similar to the switch 45 as previously described. The magnetic structure of FIGS. 3, 4 and 5 may be easier to provide than that shown in FIGS. 1 and 2 as the permanent magnet is a simple ring. The pole plates can be easily constructed or soft iron.

In the event that the spacing between the pole pieces is not sufiicient for the reed switch which is to be used to be positioned horizontally therebetween, or that it is preferable to mount the reed switch in a vertical direction, the reed switch may be supported as shown in FIG. 6. The

pole pieces

95 and 96 may be positioned as shown in FIG. 3. The

reeds

100 and 101 of the reed switch, which extend from the capsule, have portions shaped to engage the pole pieces. Alternatively, brackets of magnetic material may be used to connect the reeds to the pole pieces.

Reeds

100 and 101 may be similar to the

reeds

47 and 48 of FIG. 1 and may be used in the circuit described in FIG. 1.

The ignition system described has been found to provide eifective operation of internal combustion automotive engines, both for starting and at high speed. The sealed reed contacts carry small currents and have long life. The magnetic structure used provides very rapid switching action. The circuit is protected so that excessive current cannot be applied to the contacts of the sealed reed contacts as the system starts operation, or due to poor grounding of transistor 41 (FIG. 1).

I claim:

1. An ignition system for an internal combustion engine including in combination, an ignition coil for providing high voltage firing pulses for the internal combustion engine, semiconductor switching means having a portion providing a conductive path and a control portion for selectively rendering said path conductive, means connecting said conductive path portion of said semiconductor switching means in series with at least a part of said ignition coil across potential supply means, and control means connected to said control portion of said semiconductor switching means for controlling the conduction thereof, said control means including magnetic reed switch means and a magnetic structure for operating the same, said magnetic reed switch means including first and second magnetic reed elements having portions with contacts adapted to engage each other to complete a circuit therethrough and a sealed enclosure about said portions, said reed elements having portions extending outside said enclosure, said magnetic structure including pole pieces connected to said portions of said magnetic reed elements extendingoutside said enclosure, and a rotor having a permanent magnet and discrete magnetic poles with alternate poles being of opposite polarity, said rotor being movable to align adjacent ones of said poles thereof with said pole pieces and then displace said poles from said pole pieces, whereby the flux through said magnetic reed switch means changes suddenly and reverses in polarity to provide rapid switching action.

2. An ignition system for an internal combustion engine including in combination, an ignition coil for providing high voltage firing pulses for the internal combustion engine, semi-conductor switching means having a portion providing a conductive path and a control portion for selectively rendering said path conductive, means connecting said conductive path portion of said semiconductor switching means in series with at least a part of said ignition coil across potential supply means, and control means connected to said control portion of said semiconductor switching means for controlling the conduction thereof, said control means including switch means having first and second magnetic reeds with portions having contacts for closing a circuit and a magnetic structure for operating the same, said switch means including an enclosure about said portions of said reeds having contacts and said reeds having portions extending from said enclosure, said magnetic structure including a rotor having a permanent magnet and discrete magnetic poles with alternate poles being of opposite polarity, and first and second pole pieces connected respectively to said portions of said first and second magnetic reeds extending outside said enclosure and supporting the same so that said reeds extend substantially parallel to the axis of said rotor, said rotor being movable to align adjacent ones of said poles thereof with said pole pieces and then displace said poles from said pole pieces, whereby the flux through said magnetic reed switch means changes suddenly and reverses in polarity to provide rapid switching action.

3. An ignition system for an internal combustion engine including in combination, an ignition coil for providing high voltage firing pulses for the internal combustion engine, semi-conductor switching means having a portion providing a conductive path, means connecting said conductive path portion in series with at least a part of said ignition coil across potential supply means, said switching means including a semiconductor device having a collector portion connected to a reference potential and a base portion connected to the potential supply means, and control means connected to said base portion of said semiconductor device for controlling the conduction in said conductive path in synchronism with operation of the internal combustion engine, said control means including magnetic reed switch means and a magnetic structure for operating the same, said magnetic switch means including first and second magnetic reed elements having portions with contacts adapted to engage each other to complete a circuit therethrough and an enclosure about said portions, said reed elements having portions extending outside said enclosure, means including resistance connecting said reed switch means between said base portion and the reference potential, with said resistance limiting the current flowing through said reed switch means, said magnetic structure including pole pieces coupled to said portions of said magnetic reed elements extending outside said enclosure and a rotor having a permanent magnet and discrete magnetic poles with alternate poles being of opposite polarity, said rotor being movable to align adjacent ones of said poles thereof with said pole pieces and then displace said poles from said pole pieces, whereby the flux through said magnetic reed switch means changes suddenly and reverses polarity to provide rapid switching action.

4. An ignition system for an internal combustoin engine including in combintion, an ignition coil for providing high voltage firing pulses for the internal combustion engine, semi-conductor switching means having a portion providing a conductive path, means connecting said conductive path portionin series with at least a part of said ignition coil across potential supply means, said switch-- ing means including a transistor having a collector electrode connected to a reference potential and a base electrode connected to the potential supply means, and control means connected to said base electrode of said transistor for controlling the conduction in said conductive path, said control means including magnetic reed switch means and a magnetic structure for operating the same, said switch means including first and second reed elements having portions with contacts thereon for completing a circuit therethrough and a sealed enclosure about said portions, means including resistance connecting said reed switch means betwen said base electrode and the reference potential, with said resistance limiting the current flowing through said reed switch means, said magnetic structure including a rotor having magnetic poles movable with respect to said magnetic reed switch means, whereby the flux through said magnetic reed switch means changes to provide switching action.

OTHER REFERENCES Specifications for the Heathkit, Heath Company, June 28, 1963. References Cited by the Exammer 1. C. Norris: Delcotronic Transistor Ignition System,

UNITED STATES PATENTS 5 Iuly1963.

3;; rlrognola- References Cited by the Applicant aynes. 2/1957 Mike 123 148 UNITED STATES PATENTS 9/1959 Holthouse 123-148 10 2, 2 1947 C06 et 1. 1/1963 Straub 123 -148 2,878,298 3/1959 Giacoletto. 5/1964 Vriens 315--209 2,999,914 9/1961 Stanaway.

FOREIGN PATENTS MARK NEWMAN, Primary Examiner.

Great Britain. LAURENCE M. GOODRIDGE, Examiner.

Claims

1. AN IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE INCLUDING IN COMBINTION, AN IGNITION COIL FOR PROVIDING HIGH VOLTAGE FIRING PULSES FOR THE INTERNAL COMBUSTION ENGINE, SEMICODUCTOR SWITCHING MEANS HAVING A PORTION PROVDING A CONDUCTIVE PATH AND A CONTROL PORTION FOR SELECTIVELY RENDERING SAID PATH CONDUCTIVE, MEANS CONNECTING SAID CONDUCTIVE PATH PORTION OF SAID SEMICONDUCTOR SWITCHING MEANS IN SERIES WITH AT LEAST A PART OF SAID IGNITION COIL ACROSS POTENTIAL SUPPLY MEANS, AND CONTROL MEANS CONNECTED TO SAID CONTROL PORTION OF SAID SEMICONDUCTOR SWITCHING MEANS FOR CONTOLLING THE CONDUCTION THEREOF, SAID CONTROL MEANS INCLUDING MAGNETIC REED SWITCH MEANS AND A MAGNETIC STRUCTURE FOR OPERATING THE SAME, SAID MAGNETIC REED SWITCH MEANS INCLUDING FIRST AND SECOND MAGNETIC REED ELEMENTS HAVING PORTIONS WITH CONTACTS ADAPTED TO ENGAGE EACH OTHER TO COMPLETE A CIRCUIT THERETHROUGH AND A SEALED ENCLOSURE ABOUT SAID PORTIONS, SAID REED ELEMENTS HAVING PORTION EXTENDING OUTSIDE SAID ENCLOSURE, SAID MAGNETIC STRCTURE INCLUDING POLE PIECES CONNECTED TO SAID PORTIONS OF SAID MAGNETIC REED ELEMENTS EXTENDING OUTSIDE SAID ENCLOSURE, AND A ROTOR HAVING A PERMANENT MAGNET AND DISCRETE MAGNETIC POLES WITH ALTERNATE POLES BEING OF OPPOSITE POLARTIY, SAID ROTOR BEING MOVABLE TO ALIGN ADJACENT ONES OF SAID POLES THEREOF WITH SAID POLE PIECES AND THEN DISPLACE SAID POLES FROM SAID POLE PIECES, WHEREBY THE FLUX THROUGH SAID MAGNETIC REED SWITCH MEANS CHANGES SUDDENLY AND REVERSES IN POLARITY TO PROVIDE RAPID SWITCHING ACTION.