Robert Boschgmbh

Jiri Podrapsky

Josef Orova

To suppress negative half-waves derived from a magneto armature and not used for ignition without use of external damping networks, the semiconductor switch controlling current flow, and abrupt turn-off to initiate an ignition event, is formed as a monolithic semiconductor element, and the inherent inverse diode of the monolithic element is utilized to pass the reverse voltage half-waves. To prevent damage to the inherent diodes due to over-voltage or current overloading, a damping resistance element is connected in series with the main current carrying path of the monolithic circuit elements, preferably a Darlington transistor, which, preferably, is a semiconductor resistor having a preferred current passage characteristic in the same direction as the current flow through the Darlington transistor, for example a Zener diode, a resistor, or a series of diodes polarized like the inverse diode, bridged by a diode conducting in the same direction as the Darlington transistor, or the like.

Magneto-semiconductor ignition system

To prevent reverse-direction operation of an internal combustion (IC) engine to which the ignition system is connected which, possibly, may lead to dangerous conditions if the IC engine is used, for example in a chain saw, lawn mower, or the like, a diode (35) is connected across a second, ignition instant modifying R/C circuit (34, 33) in the control network (29) of the magneto ignition system, which includes a first R/C circuit (30, 31) to provide for immediate conduction of a control transistor (27) and hence blocking of a controlled ignition transistor (21) and disconnection of the ignition system in case of reverse rotation. This system is a further development of the basic ignition system described in U.S. Pat. No. 4,188,929, to which reference is made.

Magneto ignition system for an internal combustion engine

Speed limiting in an ignition system utilizing a magneto generator is accomplished by increasing the damping of the half wave not utilized for ignition. This is accomplished by switching in additional resistance in parallel with the damping circuit resistance when the speed of the engine exceeds the speed to which it is to be limited. The additional damping during the half wave which is not utilized causes a decrease in the current and voltage wave utilized for ignition because of armature reaction. The decrease, in turn, causes a sudden change in ignition timing in the direction of late ignition and therefore an additional damping or complete suppression of ignition.

System for limiting the speed of internal combustion engine having an

On-off oscillations immediately following the initiation of the spark in a magneto ignition system are prevented by a timing circuit the capacitor of which is charged continually even during the spark time and whose discharge time constant exceeds 10 .mu.s. The capacitor is discharged through the emitter-base circuit of a control transistor and keeps the control transistor in a saturated state throughout the desired spark duration. While the control transistor is in the saturated state, it shortcircuits the emitter-base circuit of the ignition transistor, thereby blocking the ignition transistor continuously. Since the capacitor of the timing circuit is continually charged, the actual spark duration greatly exceeds the 10 .mu.s time constant of the timing circuit and may be as high as 1.2 ms.

Magneto ignition system with increased spark energy

To provide for electronically controlled spark advance of the ignition instant in a transistorized magneto ignition system, the ignition instant is controlled by a threshold switch responsive to voltage generated by the magneto, the threshold being connected to a timing circuit which includes a resistance network therein, the resistance value of which is variable with respect to operating speed of the engine. The resistance network includes a R/C timing circuit which, as the speed of the engine increases, presents a respectively smaller resistance value to rapidly recurring signals from the magneto so that, effectively, the resistance value of the timing circuit controlling current flow through the threshold circuit is decreased, causing a shift in the ignition instant, the circuit being arranged to advance the spark with respect to upper dead center (UDC) position of the piston of the engine.

Internal combustion engine magneto-type ignition system with

In an ignition system having a magneto, the ignition timing is advanced when the engine speed exceeds a predetermined speed, by abruptly changing the voltage applied to the base of a transistor having an emitter-collector circuit connected in series with the primary winding of the ignition coil. The change in base voltage is such that the primary current flowing before the ignition time is decreased, increasing the primary voltage and thereby advancing the ignition time when the speed of the engine reaches the predetermined speed. The abrupt change is generated by opening or closing a switch which connects a resistor in series or parallel, respectively, with a resistor connected to the base of the transistor. The speed dependent switch may be a transistor whose conductive or non-conductive state is determined by the charge and discharge of a capacitor which, in turn, varies as a function of engine speed.

Speed-dependent ignition time advancement apparatus in magneto generator

To provide for ignition advance as the speed of the engine increases, a frequency-dependent circuit formed by a series RC circuit is connected in parallel with the control path of a switch in series with the primary of the magneto ignition coil so that the switch will be controlled to cut off or to open earlier as the speed increases.

At higher engine speeds the ignition time is advanced by decreasing the time between the breakdown of a threshold element which breaks down for a predetermined amplitude of voltage across the primary winding of the ignition coil and the furnishing of the signal which causes interruption of the primary current. The time is shortened either by decreasing the time constant of the timing circuit connected to the threshold element, or by switching a second timing circuit having a shorter time constant into the circuit at higher engine speeds.

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Buchschwabach, Germany

Jiri Podrapsky