Title:
ELECTRONIC IGNITION DEVICE FOR INTERNAL COMBUSTION ENGINES
United States Patent 3675635
Abstract:
An electronic ignition device for internal combustion engines comprises an ignition distributor having a distributor arm and an ignition circuit connected on the output side with the contact of the distributor arm. The ignition circuit is controlled without contacts by a magnetic pick-up having a rotating armature fixed for rotation with the distributor arm. The armature is formed by a disk carrying a number of permanent magnets corresponding to the number of permanent magnets corresponding to the number of cylinders of the internal combustion engine, the magnets being equally spaced in circumferential direction and disposed at the same radial distance from the axis of rotation of the disk. An induction coil with a soft iron core is disposed at one side of said disk. Upon rotation of the disk with the permanent magnets the exposed pole faces on said side of the disk pass across the end face of the soft iron core. This disposition allows the magnetic pick-up to be mounted within the usual ignition casing equipped with a conventional mechanical interrupter of existing internal combustion engines.


Inventors:
Graser, Toni (8340 Hinwil/Zurich, CH)
Hirs, Joseph (8621 Wetz.kon/Zurich, CH)
Application Number:
05/038340
Publication Date:
07/11/1972
Filing Date:
05/18/1970
Assignee:
TONI GRASER
JOSEPH HIRS
Primary Class:
International Classes:
F02P7/067; F02P7/077; F02B1/04; (IPC1-7): F02P1/00
Field of Search:
123/148E
View Patent Images:
US Patent References:
3587551N/A1971-06-28Harrow
3370190Electromagnetic pickup device1968-02-20Neapolitakis
3331362Internal combustion engine ignition systems1967-07-18Mitchell
3184653Switching circuits1965-05-18Hutson
3152281Transistor ignition system1964-10-06Robbins
2984695Electronic distributor1961-05-16Berdine
2353527N/A1944-07-11Touceda
Primary Examiner:
Goodridge, Laurence M.
Assistant Examiner:
Cox, Ronald B.
Claims:
We claim

1. In an ignition distributor for internal combustion engines of the type having an open housing with a rotatable shaft therein, a rotatable distributor arm having a lower stem portion for mounting on the end of said shaft, a mechanical interrupter arranged on an adjustable disc support positioned below said distributor arm, said interrupter being controlled by cam means fixed to said shaft, a cap for said housing carrying a plurality of contacts in sequential communication with said arm, the improvement comprising:

2. The improvement of claim 1 further including pulse shaper means incorporating a transistor amplifier means and an input means for connecting said input with said induction coil, said connecting means including a diode and a resistor for connecting one end of the induction coil with the base of a transistor of said transistor amplifier means of said pulse shaper means in order to deliver to said transistor the half-waves of the signals produced at said induction coil during rotation of the disc when the magnetic field collapses, and an ignition circuit electrically connected with said pulse shaper means and electrically connected at the output side with said distributor arm of said ignition distributor and controlled by output pulses of said pulse shaper means.

3. An ignition device according to claim 2, in which said transistor amplifier means connected to said induction coil, is controlled on the input side by the one half-waves of the control signals produced upon rotation of the magnet armature, and in which a controllable rectifier having a limiting resistor is connected to the outputs of the transistor amplifier means, and an RC-member consisting of a capacitor and series connected resistor is connected to the junction point of the limiting resistor and rectifier, said controllable rectifier being switched through by a reference voltage member having a lower reference voltage than the operating voltage of the transistor amplifier and connected in parallel with said rectifier and with a control electrode, when the output voltage of the amplifier attains the reference voltage, in order to produce via the RC-member, for each of the one half-waves of the control signal, a control pulse for said ignition circuit which is connected to the RC-member.

4. An ignition device according to claim 3, wherein said transistor of said transistor amplifier means comprises a n-p-n transistor in common-emitter circuit, said coil being wound in such manner as to produce half-waves with a negative amplitude upon a decaying magnetic field.

5. An ignition device according to claim 4, wherein said controllable rectifier is formed as a miniature thyristor having an anode connected by a limiting resistor to the collector of the n-p-n transistor, and a cathode connected to the emitter of said transistor.

6. An ignition device according to claim 5, wherein said reference voltage member comprises a Zener diode having an anode connected to the control electrode of said miniature thyristor and by a resistor to the emitter of the n-p-n transistor.

7. An ignition device according to claim 6, wherein said Zener diode is connected in parallel to the anode-control electrode gap, the Zener voltage of said diode not exceeding 70 percent of the operating voltage of the transistor.

8. An ignition device according to claim 6, wherein the collector of the n-p-n transistor is connected to an output terminal adapted for connection with an RPM counter by means of a matching circuit.

9. An electronic ignition device for an internal combustion engine having an ignition distributor and an ignition circuit electrically connected with the distributor arm of the ignition distributor on the output side, said ignition circuit being controlled without contacts by a magnetic pick-up having a rotatable armature and a stationary induction coil, wherein said armature of the magnetic pick-up comprises a disk of non-magnetic material mounted on said distributor arm for rotation therewith, a plurality of permanent magnets inserted in said disk, the number of magnets corresponding to the number of cylinders of the internal combustion engine, the magnets being uniformly spaced on the disk in circumferential direction and disposed at equal radial distances from the axis of rotation of said distributor arm, said magnets each having one of the pole faces exposed on the side of said disk remote of the distributor arm and situated in a plane at right angles to said axis of the distributor arm, and an induction coil having a soft iron core provided with an end face adjacent said side of the disk and arranged so that upon rotation of the disk said exposed pole faces move across said end face of the soft iron core, a transistor amplifier connected to said induction coil, said amplifier being controlled on the input side by the one half-waves of the control signals produced upon rotation of the magnet armature, and in which a controllable rectifier having a limiting resistor is connected to the outputs of the transistor amplifier, and an RC-member consisting of a capacitor and series connected resistor is connected to the junction point of the limiting resistor and rectifier, said controllable rectifier being switched through by a reference voltage member having a lower reference voltage than the operating voltage of the transistor amplifier and connected in parallel with said rectifier and with a control electrode, when the output voltage of the amplifier attains the reference voltage, in order to produce via the RC-member, for each of the one half-waves of the control signal, a control pulse for said ignition circuit which is connected to the RC-member, transistor amplifier comprising a n-p-n transistor in common-emitter circuit, the base of which is connected to one end of the induction coil by a resistor and a diode, the coil being wound in such manner as to produce half-waves with a negative amplitude upon a decaying magnetic field.

10. An ignition device according to claim 9, in which said controllable rectifier is formed as a miniature thyristor having an anode connected by a limiting resistor to the collector of the n-p-n transistor, and a cathode connected to the emitter of the transistor.

11. An ignition device according to claim 10, in which said reference voltage member comprises a Zener diode having an anode connected to the control electrode of said miniature thyristor and by a resistor to the emitter of the n-p-n transistor,

12. An ignition device according to claim 11 in which the Zener diode is connected in parallel to the anode-control electrode gap, the Zener voltage of said diode not exceeding 70 percent of the operating voltage of the transistor.

13. An ignition device according to claim 11, in which the collector of the n-p-n transistor is connected to an output terminal adapted for connection with an RPM counter by means of a matching circuit.

Description:
The invention relates to an electronic ignition device including an ignition distributor, for internal combustion engines, the device having an ignition circuit which is electrically connected on the side of the output with the distributor arm contact of the ignition distributor and controlled without contacts by a magnetic pick-up comprising a rotatable armature driven by the ignition distributor shaft, and a fixed induction coil.

The known electronic ignition devices mostly are subsequently built into automobiles equipped with conventional ignition systems controlled by mechanical interrupters. In automobiles having rotating piston- and Otto-engines the ignition point is controlled automatically in dependence of the number of revolutions, in order to obtain the greatest output at all operating conditions. The ignition timing device is assembled together with the interrupter and the ignition distributor in a casing, so that it is convenient for saving costs to use these already available parts also with electronic built-in ignition circuits, i.e. to lay out the circuit in such manner that it may be connected to the mechanical interrupter and the ignition distributor. The advantages of electronic ignition devices, however, become fully apparent only when these devices are not controlled by contacts, e.g. mechanically by means of the interrupter, but in contactless manner by a suitable pick-up. For a contactless control preferably magnetic pick-ups are used, several types of which are known and suitable for insertion into the ignition distributor casing. Such known magnetic pick-ups consist for example of a rotating armature fixed to the distributor shaft having a number of permanent magnet poles corresponding to the number of cylinders, the pole surfaces of which are situated in a cylindrical surface coaxial with the distributor shaft. The magnet armature rotates in an annular stator having a coil connected to the electronic ignition circuit. In all known distributor constructions, the individual components, particularly the distributor arm and the mechanical interruptor are assembled in a restricted space, so that the interrupter must be dismantled when a magnetic pick-up is built-in, and besides, a certain type of pick-up can only be used with a definite distributor or with a few types of distributors. This is uneconomical and considerably increases the cost of the electronic ignition device. A reduction of the size of such pick-up structures practically is impossible since the permanent magnets must have a definite minimum volume in order to guarantee a safe operation at the lower speed ranges (starting speed).

In conventional electronic ignition devices the primary circuit of the ignition coil comprises a storage capacitor and a controllable rectifier, preferably a thyristor, as an electronic switching element. The storage capacitor is charged by a commutator transformer and the thyristor is controlled by a pulse transformer. With a through-connected thyristor the storage capacitor will be discharged by the primary winding of the ignition coil, and the high tension pulse induced in the secondary winding is fed to the distributor. The ignition circuit is controlled by control pulses supplied to the pulse transformer. For generating the control pulses either the mechanical interrupter or another transmitter is used. A magnetic pick-up supplies substantially sine-shaped control signals from which there are formed control signals in a pulse shaper. The control pulses shall have steep sides, i.e. practically they shall represent rectangular pulses, and their pulse duration possibly should be shorter than the disconnection time of the thyristor of the ignition circuit. For generating such pulses the sine-shaped control signals of the pick-up may be highly amplified in order to obtain the desired steepness of the sides. Such amplification, however, results in a considerable liability to interference in the ignition device, since together with the control signals also interference signals are amplified which can lead to an undesired through connection of the thyristor of the ignition circuit. An electronic ignition device to be added to an existing device can be produced economically and operate safely only when the ignition characteristic destined for the respective internal combustion engine is so to say taken over by the electronic device. With the inductive generation of pulse signals, however, phase displacements will occur the magnitude of which depends of the ohmic load. For such taking-over of the existing ignition characteristic it is a condition that the control signals supplied by the pick-up are loaded as little as possible in the pulse shaping stage for generating the control pulses.

Known electronic ignition devices with a magnetic pick-up accordingly are relatively expensive and often susceptible to trouble, and their use for subsequent combination with existing ignition systems is limited, the building-in of a magnetic pick-up into a distributor casing being complicated and the original ignition system controlled by the mechanical interrupter being completely put out of operation. The replacement of an already existing ignition device by a new electronic ignition device not only means double expenditure but also the abandonment of an additional safety. Electronic ignition devices having a magnetic pick-up do not require attendance or servicing and are safe in operation. However, should trouble occur, it cannot be dealt with actually by the ordinary service stations. For such cases it would be advantageous when the original ignition device could be used again.

It is an object of the invention to provide an electronic ignition device with a magnetic pick-up which can be economically produced, in which the magnetic pick-up can be built later on into an existing distributor casing without having to remove any parts therefrom, and which can be mounted with a few manipulations and operates without disturbance.

According to the invention, said armature of the magnetic pick-up comprises a disk of non-magnetic material mounted on said distributor arm for rotation therewith, a plurality of permanent magnets inserted in said disk, the number of magnets corresponding to the number of cylinders of the internal combustion engine, the magnets being uniformly spaced on the disk in circumferential direction and disposed at equal radial distances from the axis of rotation of said distributor arm, said magnets each having one of the pole faces exposed on the side of said disk remote of the distributor arm and situated in a plane at right angles to said axis of the distributor arm, and an induction coil having a soft iron core provided with an end face adjacent said side of the disk and arranged so that upon rotation of the disk said exposed pole faces move across said end face of the soft iron core.

In all known ignition distributors the distributor arm comprises a stem for plugging on the distributor shaft. The disk of the magnet armature can be pushed on the stem of the distributor arm and can be connected, for example by means of screws, for rotation therewith. The disc together with the distributor finger can form a structural unit made of plastics. In any case the magnet armature of the ignition device according to the invention only requires a space which hitherto was present without being utilized. In a distributor having a mechanical interrupter the induction coil with a soft iron core can be fixed to the interrupter disk without having to remove parts therefrom; thus the mechanical interrupter remains fully operative. The induction coil can be formed by a cylindrical coil and contain a simple straight core which can carry a pole shoe having a usual rectangular end face. The adjustment of the point of ignition preferably is effected by regulating the coil on the interrupter disk. For this purpose the induction coil with the soft iron core can be mounted on a flat clamping plate of suitable shape which, when the position of the coil is correctly adjusted, can be clamped fast by means of screws to the interrupter plate. This also enables a particularly simple mounting of the magnetic pick-up upon subsequent introduction into an interrupter casing. The induction coil and the permanent magnets can be uniformly dimensioned for all types of ignition distributors. Only the disks of non-magnetic material, e.g. of plastics, are different, which, according to the number of cylinders of the respective motor must be equipped with four, six or eight permanent magnets. Such disks which can be fixed to distributor arms preferably are formed as annular disks, the internal diameter thereof corresponding to the stem diameter of the distributor arm. It has shown that a set of a few different disks will suffice for all current distributor types. The magnetic pick-up of the ignition device accordingly can be manufactured cheaply in series production, its individual components, magnet armature with or without distributor arm, induction coil with core and clamping plate being assembled to structural units made available in commerce for subsequent building in.

In a modification of the invention a transistor amplifier is connected to the induction coil and is controlled on the input side by the one half-waves of the control signal produced when the magnet armature rotates, while a controllable rectifier having a limiting resistor is connected to the outputs of the transistor amplifier and an RC-member consisting of a capacitor and series connected resistor is connected to the junction point of the limiting resistor and rectifier, said controllable rectifier being switched through by a reference voltage member having a lower reference voltage than the operating voltage of the transistor amplifier and connected in parallel with said rectifier and with a control electrode, when the output voltage of the amplifier attains the reference voltage, in order to produce via the RC-member, for each of the one half-waves of the control signal, a control pulse for an ignition circuit connected to the RC-member.

The invention will now be described with reference to the accompanying drawings, in which

FIG. 1 diagrammatically shows an ignition distributor of conventional construction with the cover removed and with a built-in magnetic pick-up of an ignition device according to the invention;

FIG. 2 is a circuit diagram of the electronic ignition device according to the invention, equipped with the magnetic pick-up of FIG. 1.

The diagrammatic representation of FIG. 1 shows a conventional arrangement of an ignition distributor, only the distributor arm 1 thereof being shown, of a mechanical interrupter and of a centrifugal force ignition point distributor or timer 9 arranged in a common casing 10. The distributor shaft 11 which is rotatably mounted in the casing 10 carries at its upper end the distributor arm 1, the stem 1a of which is engaged over the end of the shaft 11. The interrupter cam 12 arranged on the shaft 11 below the distributor arm 1 is shifted in the direction of rotation in known manner by the centrifugal force ignition point timer 9. The interrupter disk 8 extending transversely through the casing 10 and carrying the interrupter 13 is situated between the interrupter cam 12 and the ignition point timer 9.

A magnetic pick-up for contactless control of an electronic ignition circuit is additionally built into the distributor casing 10. The represented magnetic pick-up comprises a plane circular ring disk 2 of plastic having a number of openings corresponding to the number of cylinders of the respective internal combustion engine, in which openings the permanent magnets 3 are inserted. The permanent magnets 3 have a uniform radial distance from the center of the disk and are equally spaced on the disk in circumferential direction. The disk 2 is engaged on the stem 1a of the distributor arm or finger 1 and is fixed to the stem, e.g. by screws, for rotation with the shaft. The thickness of the disk is so chosen that upon rotation and locally acting magnetic forces no oscillations will occur.

A cylindrical induction coil 5 having a straight soft iron core 4 is arranged in upright position on the interrupter disk 8 opposite the interrupter 13. The coil 5 and the core 4 are fixed on a flat clamping plate 14 which itself can be clamped by means of screws 15 to the interrupter disk 8. The clamping plate 14 is provided with slots through which pass the screws 15, so that the coil 5 and the soft iron core 4 may be shifted over a certain range on the interrupter disk 8 and clamped in a definite position with respect to the contact of the distributor arm 1. Conveniently the clamping plate 14 is provided with a circular arc-shaped slot the mean radius of which is equal to the distance of the center of a permanent magnet 3 from the axis of rotation of the distributor arm or of the disk 2 and the axis of the coil is in alignment with the middle axis of the slot, so that upon adjustment of the coil with correspondingly arranged clamping screws 15, a radial shifting of the coil is not necessary and the end faces 4a of the iron core are aligned with the path of the rotating permanent magnets 3.

For a satisfactory operation of the ignition device it is necessary that the permanent magnets have a certain minimum volume. On the other hand, it is advantageous in such pick-ups when the pole facing the iron core of the coil has a narrow pole surface with parallel longitudinal edges, or edges directed radially towards the axis of rotation. For this reason, blanks of magnet bodies are used which are exactly machined and finished on one pole only. The openings of the disk 2 will be correspondingly shaped and the magnet bodies are so inserted into the openings and cemented therein that the finished pole surfaces are exposed and situated in a plane at right angles to the axis of the disk.

Conducting wires 6 are connected to the ends of the induction coil 5 and are introduced through a cable passage 16 in the casing 10 and connected with their other ends to the electrical part of the ignition device. The electrical part comprises a pulse shaper stage 17 on the input side, which produces control signals of defined edge steepness from the practically sine-shaped signals supplied from the induction coil 5. The control pulses are fed to the proper ignition circuit 18. The ignition circuit 18 is transistorized and any suitable type of the various known circuits can be used.

When the above described ignition device is incorporated in the existing ignition system having a mechanical interrupter, the following three modes of operation are possible: Operation with the mechanical interrupter and the originally existing ignition system, operation with the mechanical interrupter controlled electronic ignition circuit, and operation with electronic ignition circuit controlled without contacts by the magnetic pick-up. The switching-over from one mode of operation to the other can be effected in a few manipulations by reversing of connections; when operating with the electronic ignition device the interrupter 13 conveniently will be lifted off and clamped in place.

FIG. 2 shows the circuit diagram of the ignition device according to the invention. As has been described already, the magnetic pick-up consists of a disk 2 of non-magnetic material which is mounted for rotation with the stem of the distributor arm 1. A number of permanent magnets 3 corresponding to the number of cylinders of the internal combustion engine on which the device is mounted, is inserted in the disk 2. For example the south poles of the magnets 3 comprise pole faces 3a which are exposed on the bottom side of the disk turned away from the distributor arm 1, and which, upon rotation of the disk 2, travel across the end face 4a of a soft iron core 4 of an induction coil 5 disposed stationary below the disk 2. One end of the induction coil 5 is connected to the input I of a pulse shaper stage 17. The output A of the pulse shaper stage 17 is connected with the control input E of an ignition circuit 18 known per se. The ignition circuit 18 includes a conventional ignition coil 20, across the primary winding of which a capacitor controlled by a thyristor S2 is discharged. The secondary winding of the ignition coil 20 is connected by an ignition conductor 22 with the contact of the distributor arm 1. Since ignition circuits of this type are well known in the art, details thereof are not represented.

The pulse shaper stage 17 as shown in the diagram comprises as an amplifier a n-p-n type transistor T1 in common emitter circuit. The negative pole of the battery B is connected by a resistor R2 with the base and by a resistor R4 with the emitter of the transistor T1. The positive pole of the battery B is connected to the base by an ignition switch 19 and a resistor R3, and by a resistor R5 with the collector of the transistor T1. The base of the transistor T1 is connected by a resistor R1, a diode D1 and the input terminal I of the pulse shaper stage with one end of the inductor coil 5, the other end of which is grounded.

The output signals of the amplifier are picked up at the outputs L and M, one output L being connected to the collector and the other output M to the emitter of the transistor T1. The collector-to-emitter space is bridged by a limiting resistor R6 connected to the output L and by a thyristor S1 connected in series with the resistor R6, the cathode of the thyristor being connected to the output M. The anode of the thyristor, i.e. the junction point N of the limiting resistor R6 and the thyristor S1 is connected with the one electrode of a capacitor C1 the other electrode of which is connected by a charging resistor R9 with the negative pole of the battery B. In the represented example the RC member formed by the capacitor C1 and the resistor R9 is shown as a part of the input stage of the electronic ignition circuit 18. The input stage comprises a pulse amplifier having a n-p-n transistor T2 in known circuit arrangement. The base of the transistor T2 is connected to the junction point P of the capacitor C1 and the resistor R9 of the RC member. A resistor R8 forms together with the resistor R9 of the RC member the base voltage divider for the transistor of the pulse amplifier stage.

A Zener diode Z1 with an operating resistor R7 is connected in parallel with the thyristor S1 of the pulse shaper stage 17. The cathode of the Zener diode Z1 is applied to the junction point N of the thyristor S1 and the limiting resistor R6, and the anode of the Zener diode is connected to the control electrode G of the thyristor S1. A Zener diode is used having a Zener voltage with a lower value than the operating voltage of the transistor amplifier T1, R2 . . . R5. Preferably, the Zener voltage shall not exceed 70 percent of the operating voltage. When the disk 2 rotates, an essentially sine-shaped signal voltage is induced in the induction coil 5, however, in contradistinction with known magnetic pick-ups no reversal of polarity of the magnetic field occurs. The one half-waves of the signal voltage are formed when the magnetic field in the iron core is created, and the other half-waves are formed when the magnetic field collapses or decays. The load dependent phase shift already mentioned occurs when the magnetic field sets up. For producing signal pulses the front sides of the half-waves are used. The direction of winding of the induction coil and the polarity of the permanent magnets is so chosen that the half-waves with positive amplitude are formed when the magnetic field sets up and when the magnetic field decays the half-waves with negative amplitude are formed. The negative half waves are then practically independent of the value of the ohmic load. The positive half-waves are suppressed by the diode D1 and the negative half-waves are supplied via the resistor R1 of the base of the transistor T1. At each half-wave the voltage at the collector of the transistor T1 rises. When this signal voltage reaches the value of the Zener voltage of the Zener diode Z1, i.e. the value of the reference voltage, then the Zener diode Z1 becomes conductive and the thyristor S1 is switched through by the control electrode G, so that the capacitor C1 of the RC member rapidly discharges and a short negative pulse, for example of a duration of 2μ sec, will occur at the junction point P of the RC member which pulse is supplied to the base of the transistor T2 of the input pulse amplifier of the ignition circuit 18. When the amplitude of the input signal voltage at the transistor T1 decreases, also the signal voltage at the collector drops to a minimum, so that the thyristor S1 is switched off into non conducting condition and the circuit is ready for producing a control pulse from the subsequently arriving signal half-wave.

The Zener voltage, as already mentioned, does not exceed 70 percent of the operating voltage of the transistor amplifier. This guarantees that even at smallest RPM of the engine, particularly when starting, ignition sparks will be safely produced.

A further advantage of this ignition device consists in that a revolution counter can be connected to the pulse-shaper stage 17. For this purpose the collector of the transistor T1 is connected to an output terminal F. A commercially available revolution counter RPM can be connected to the output terminal F by a matching circuit 21. This matching circuit may comprise a n-p-n transistor T3 which produces at each control signal a pulse for the RPM counter by discharging of a capacitor.

The above described pulse shaper renders the electronic ignition device fully insensitive to interference pulses, so that a safe ignition is guaranteed at low as well as high speed of rotation. Moreover, the pulse shaper is of simple construction and can be manufactured at moderate cost.

While there is shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims. Accordingly,