Title:
MAGNETO IGNITION SYSTEM FOR INTERNAL COMBUSTION ENGINES
United States Patent 3861373
Abstract:
To provide for better uniformity of ignition pulses in capacitor discharge ignition systems, the magneto armature is formed with two windings of different numbers of turns which are both coupled to the charge circuit for the ignition capacitor, but uncoupled from each other by diodes, and a further control winding is wound on one of the cores associated with each one of the windings, connected in opposite phase with respect to the winding on the associated core, and electrically connected to trigger discharge of the capacitor through an ignition coil.


Inventors:
Allwang, Heribert (Rothenbach, DT)
Haubner, Georg (Berg, DT)
Hofer, Walter (Schwabach, DT)
Application Number:
05/449288
Publication Date:
01/21/1975
Filing Date:
03/08/1974
Assignee:
Robert, Bosch G. M. B. H. (Gerlingen-Schillerhohe, DT)
Primary Class:
Other Classes:
315/209CD
International Classes:
F02P3/08; F02P1/08; F23Q3/00; (IPC1-7): F02D1/00
Field of Search:
123/148E 315
View Patent Images:
US Patent References:
3753429INTERNAL COMBUSTION ENGINE IGNITION SYSTEM1973-08-21Imhof et al.
3736914ELECTRONIC IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE1973-06-05Schmuldienst et al.
3461851IGNITION SYSTEM AND MAGNETO THEREFOR1969-08-19Stephens
Primary Examiner:
Antonakas, Manuel A.
Assistant Examiner:
Cranson Jr., James W.
Attorney, Agent or Firm:
Flynn & Frishauf
Claims:
We claim

1. Magneto ignition system for internal combustion engines comprising

2. System according to claim 1, wherein the cores (13, 14; 37, 38) have different cross-sectional area, the control winding (25x) and one of the armature windings (15x) being located on the core of greater cross-sectional area.

3. System according to claim 2, wherein the cores form the leg parts (37, 38) of a U-shaped core structure (36) in which the leg parts are of different cross-sectional area.

4. System according to claim 1, wherein the magnet (41, 42) is located at the inner surface of a hollow rotating structure (40);

5. System according to claim 4, wherein the armature cores are separate core elements;

6. System according to claim 4, wherein the armature cores are separate core elements (13, 14) located magnetically in parallel with respect to the magnet (41, 42).

7. System according to claim 1, wherein the control winding (25) is located on the core (14) carrying the winding (16) with the smaller number of turns.

8. System according to claim 1, wherein the cross-sectional area of the cores is different and the control winding (25) is located on the core with the smaller cross-sectional area.

9. System according to claim 1, wherein one, terminal, each, of both windings (15, 16) of the armature windings, and of the control winding (25) are commonly connected to ground, or chassis of the engine.

10. System according to claim 1, wherein the engine has a fly-wheel (40) having a cylindrical, hollow portion;

11. System according to claim 10, wherein the cores are located adjacent and parallel to each other, spanning a chord of the cylindrical portion, and the attachment means comprises axially extending pins (43) passing through said cores, separating said cores from each other, while attaching both said cores to the carrier;

12. System according to claim 1, wherein the cores (13, 14) are of different cross-sectional area, and the winding (16) having the smaller number of turns, as well as the control winding (25) are located on the core (14) having the smaller cross-sectional area.

Description:
The present invention relates to an ignition system for internal combustion engines, and more particularly to a magneto ignition system in which an armature circuit is connected to a diode to charge an ignition capacitor which is triggered to be discharged by means of an electronic triggering element, the discharge being connected through an ignition coil to provide an output spark at a spark plug connected to the secondary of the coil.

Capacitor discharge ignition systems have been proposed in which an ignition capacitor is first charged by a half wave derived from the magneto armature, for example during the occurrence of the positive half wave. During the subsequent negative half wave, the capacitor is discharged through an ignition coil or transformer. Discharge of the capacitor is controlled by a trigger circuit including a semiconductor switch, such as a transistor, a thyristor, or the like, the conduction of which is, in turn, controlled from a control winding connected in phase opposition to the charge winding of the armature of the magneto. When a pulse is obtained from the control winding, the thyristor, or similar switching element is rendered conductive to discharge the capacitor.

Circuits of this kind, which have been proposed, have the disadvantage that upon increasing speed of the internal combustion engine, the armature winding of the armature is highly loaded. The capacitor must be charged during shorter time intervals as the speed increases. This loading results in an armature reaction which prevents complete charging of the ignition capacitor when the engine operates at its upper speed ranges; further, the armature reaction influences the voltage available from the control winding. The positive voltage half wave derived from the control winding is attenuated at increasing speed due to the counter-acting flux due to armature reaction and, further, retarded in phase. In higher ranges of speeds of the internal combustion engine, the control winding will therefore provide a control pulse only at a later instant in time, resulting in, effectively, retardation of the spark, which decreases the efficiency of the internal combustion engine. If the ignition capacitor cannot be charged completely, the voltage at the spark plug will decrease, which limits the upper speed which can be obtained by the internal combustion engine.

It is an object of the present invention to provide an ignition system which is simple, and effective over the entire speed range of the internal combustion engine and provides an essentially uniform ignition voltage throughout the speed range of the engine and which, preferably, increases the ignition pulse timing towards spark advance as the speed of the engine increases.

Subject Matter of the Present Invention

Briefly, the armature is formed to have two windings of different numbers of turns, located on individual cores, which are connected to the capacitor charging circuit through individual coupling diodes, so that the windings are uncoupled from each other. The control winding is wound on one of the cores, for example on the core having the smaller number of turns of the armature winding thereon, and connected in phase opposition with respect to the winding on the respective core.

The two charge windings of the armature are so matched to the charge capacitor that the winding having the greater number of turns charges the capacitor in the lower range of speed; the winding having the lower number of turns charges the capacitor in the upper range of speed of the engine. This optimum charge of the capacitor permits full control voltage to appear across the control winding, since the positive half wave of the control voltage is not attenuated by armature reaction. As the speed of the engine rises, the rate of change of the voltage, with respect to time, appearing in the control winding will likewise rise, so that the triggering voltage for the discharge circuit is reached sooner and the ignition timing is changed to advance the spark.

The invention will be described by way of example with reference to the accompanying drawings, wherein:

FIG. 1 is a schematic circuit diagram of a capacitor discharge system with a magneto generator, to generate both a charge voltage as well as a control voltage;

FIG. 2 is a schematic side view of an armature winding with a U-shaped core; and

FIG. 3 is a perspective view, partly broken away, of a fly-wheel utilized, simultaneously, as the rotating magnet of a magneto in which the armature is arranged on cores which are located in chords of the internal circumference of the fly-wheel.

An internal combustion engine, not shown, is connected to a magneto generally shown at 10 (FIG. 1). The internal combustion engine drives a magnetic ring 11, which is in magnetic circuit relationship with an armature 12. Armature 12 is wound on two separate cores 13, 14, each of which has an armature winding 15, 16, respectively, wound thereon. The number of turns of the windings 15 and 16 is different. One terminal 15a of the armature winding 15, being the winding with the higher number of turns, is connected to the anode of a diode 17. A corresponding terminal 16a of the armature winding 16, that is, the winding with the smaller number of turns, is connected to the anode of a diode 18. The cathodes of the two diodes 17, 18 are connected together and to a supply line 19 which is connected to one terminal of the charging ignition capacitor 20. The other terminal of ignition capacitor 20 is connected to the primary 21a of an ignition coil 21. The secondary 21b of the ignition coil 21 is connected by means of an ignition cable 22 to a spark plug 23. The other terminals of the primary and secondary windings of the ignition coil 21, as well as the terminals 15b, 16b of the armature windings 15, 16 are connected to chassis or ground. A diode 28 bridges the primary winding 21a. The series circuit formed of capacitor 20 and the primary 21a of the ignition coil 21 is bridged by the main current path of a thyristor 24, having a gate or trigger contact 24a.

The core 14, carrying the winding with the smaller number of turns has a control winding 25 applied thereto, phased oppositely to the winding 16. One terminal 25b is connected to the common ground or chassis line. The other terminal 25a is connected through a diode 26 with the gate electrode 24a of the thyristor 24. A resistor 27 bridges the gate electrode 24a to chassis.

Operation: Upon starting of the internal combustion engine, the magnet wheel 11 is rotated in the direction of the arrow. Upon such rotation, an alternating voltage is induced in the windings 15, 16. The negative half waves which are induced are blocked by the diodes 17, 18. The positive half waves are transmitted over diodes 17, 18 to the ignition capacitor 20. The charge circuit is closed over the primary winding 21a of the ignition coil 21 and over the ground or chassis return line to the armature windings 15, 16. In lower ranges of speed, the voltage induced in winding 15 (with the larger number of turns) rises rapidly, so that it can charge the ignition capacitor 20 almost to its upper limit. As the speed of the engine increases, however, the voltage in winding 15 decreases due to armature reaction. Charge in the capacitor 20 is applied from the winding 16 having a lesser number of turns, since the armature reaction due to current flow in winding 16 is much smaller. The charge windings 15, 16 are so matched to the capacity of the capacitor 20 that, even in upper speed ranges, the entire positive voltage half wave is not required to completely charge the ignition capacitor 20. After the ignition capacitor 20 is charged, armature reaction in the windings 15, 16 drops to zero, so that the subsequent negative voltage half wave occurs without time delay and phase retardation.

The control winding 25 is wound in phase opposition to the charge winding 16. During the negative half wave in the charge winding 16, a positive half wave will be induced in the control winding 25, which is applied over diode 26 to the control electrode 24a of the thyristor 24. Thyristor 24 has a certain response threshold level. When the voltage has reached this threshold or triggering level, the thyristor is rendered conductive and the capacitor 20 can rapidly discharge over a discharge circuit formed by the ignition capacitor 20, thyristor 24, chassis connection and the primary 21a of ignition coil 21. This rapid suddenly occurring pulse, having a high rate of change of current, results in a high voltage pulse in the secondary 21b of ignition coil 21 to provide the spark at spark plug 23. The charge and discharge cycle repeats on the ignition capacitor 20 upon each half rotation of the magnetized or magnet wheel 11. The control winding 25 operates practically without loading. The rate of voltage rise thus increases as the speed of the engine increases, so that the triggering level of the thyristor is reached earlier and earlier as the speed increases, and so that the discharge of the capacitor 20 is likewise advanced, thus changing the timing of the ignition of the internal combustion engine in the direction to advance the spark as the speed of the engine itself increases.

FIG. 2 shows a magneto generator 30 in which a permanent magnet 32, having pole shoes 33, 34 at the sides thereof, is located on the circumference of a fly-wheel 31 of the internal combustion engine. The fly-wheel 31 is driven by the internal combustion engine from a shaft, not shown. The permanent magnet 32 cooperates with an armature 35 on the engine, which is stationary. It includes a U-shaped iron core 36 with two projecting legs 37, 38, on which the windings 15x, 16x and the control winding 25x are wound. The windings 15x, 16x, 25x correspond to the windings 15, 16, 25 of FIG. 1. The cross-sectional areas of the legs 37, 38 are different. The control winding 25x and the armature winding 15 are located on the core leg 37 which has the larger cross-sectional area. The winding 16, having the smaller number of windings, is located on core leg 38 having a smaller cross-sectional area. The three windings have one terminal, each, connected to the core 36, and hence to chassis of the machine; the other terminals are brought out at terminals 15a, 16a, 25a, respectively, and connect to the corresponding terminals 15a , 16a, 25a of FIG. 1.

Operation: Basically, the operation of the magneto generator 30 of FIG. 2 is essentially the same as that described in connection with FIG. 1. The different cross-sectional area of the two core legs 37, 38 provides for relatively great leakage of the flux derived from the permanent magnet 32, as it passes with its pole shoes between the ends of the core legs 37, 38. This, then, effectively de-couples the windings 15x and 16x from each other, so that a counter-flux in one of the windings does not adversely effect the induced voltage in the other winding.

The control winding 25x is connected in phase opposition with respect to the winding 15x. In operation of the engine, the ignition capacitor is first charged by the windings 15x or 16x, respectively, and then discharged, at the ignition instant, by the positive voltage half wave arising in the control winding 25x, thereby rendering thyristor 24 conductive and discharging capacitor 20. The charge and discharge cycle with respect to ignition capacitor 20 and the resulting ignition of spark plug 23 of the internal combustion engine only occurs once upon each rotation of the fly-wheel 31. If more frequent ignition is desired, more than one magnetic structure 32, 33, 34 can be located around the circumference of fly-wheel 31.

The magneto generator generally shown at 10 in FIG. 1 may be associated also with hollow fly-wheels. Referring to FIG. 3, a pot-shaped, cylindrical, hollow fly-wheel 40 has located therein four segment-shaped permanent magnets 41, of alternating polarity. The cut-away portion of the fly-wheel makes visible the magneto structure 12a which includes cores 13, 14 formed as chords with respect to the circumference of the cylindrical fly-wheel 40. The permanent magnets 41 are supplied with pole shoes 42. The chord-located cores 13, 14 are magnetically in parallel, and located axially staggered in the cylindrical fly-wheel - armature combination. Non-magnetic spacer pins 43 space the cores 13, 14 from each other and additionally secure the cores on an armature plate 44, which is stationary. The lower, or inner core 14 has a smaller cross sectional area than the outer, or upper core 13. Space utilization is particularly efficient when the control winding 25 is wound together with the winding 16, having the lesser number of turns on one common core 14 (which is the core of smaller cross-sectional area). The other main winding 15, with the larger number of turns, is then located on core 13 having the larger cross-sectional area.

Various changes and modifications may be made within the inventive concept. It is possible, for example, to locate the cores 13, 14 not axially staggered, as shown in FIG, 3, but rather axially aligned and offset with each other by 90°, or 180° electrical. The main windings 15, 16 must, however, have different numbers of turns, and the control winding 25 must be located on one of the cores associated with one of the main windings, and connected in phase opposition with respect thereto.

Typical dimensions for a magneto generator, of the type of FIG. 1 may be:

coil 15: 7000 turns coil 16: 1500 turns coil 25: 100 turns cross section of armature core 13: 4.0 cm2 cross section of core 14: 2.5 cm2 charge capacitor 20: 2.0 μF.

The foregoing is merely an example and various changes and modifications may be made within the inventive concept.