Robert Boschgmbh

Bernd W Kalkhof

Bernd Bodig

Karl Nagel

Gerd Hohne

Werner Jundt

Gerhard Sohner

Helmut Schmied

Georg Pfaff

Horst Lohmuller

Uwe Gunther

The invention relates to an ignition device for combustion engines. The ignition device has a switching transistor (7) which, when a trigger is energized, is current-conductive, further an ignition coil (6), the primary winding (5) of which forms with the transistor (7) a series circuit, and, further, a signal transducer (10) connected in advance of the trigger (11) to supply a capacitor-charging current, after a lapse of a time period of its control signal (a, b) reaching a peak value. The threshold of the trigger (11) can be shifted relative to the control signal (a,b) by use of an electrical storage device (30) which can be charged and discharged, and in which the charge is dependent on the predetermined current value in the primary winding (5). In accordance with the invention, the storage device (30) can be charged by the control signal (a,b) and can be discharged over a shunt circuit branch (32) with high resistance value (resistor 33) as well as over a shunt circuit branch (34) with low resistance value (resistor 37). Upon reaching of a primary current value of predetermined level, the charging of the storage device (30) is stopped and the shunt circuit branch (34) with low resistance value is completed when transistors (36,38) become conductive.

Ignition device for combustion engines

The temperature sensing circuit includes a source of constant current I.sub.S, a voltage divider R.sub.1, R.sub.2 and an output transistor T.sub.1 whose base collector circuit is connected parallel to the first resistor and whose base emitter circuit is connected parallel to the second resistor. An auxiliary source of current having a positive temperature coefficient is connected in series with the first resistor of the voltage divider to cause a voltage drop thereon having an opposite temperature coefficient than the output voltage U.sub.S generated at the collector-emitter circuit of the output transistor.

Temperature sensing semiconductor circuit

In order limit the rate of rise of current when the final stage transistor T8 is switched, the base current of the final stage transistor is supplied by a first current-controlled current source when the final stage transistor switches on an inductive load. The final stage transistor in this circuit can be given an integrating behavior with a very small MOS negative feedback capacitor, leading to the control current input of the first controlled current source, to which a diode-connected switching transistor T4 supplies a constant current when a driver transistor T7 is blocked by an input signal U.sub.E. When the driver transistor T7 is made conducting, the constant current is diverted to the driver transistor and the base current of the final stage transistor T8 is cut off except for the dynamic contribution of feedback capacitor, while the reverse peak diode D provides protection against voltage spikes. A second current-controlled current source is inteposed between a constant current source and the diode-connected switching transistor in order to provide voltage decoupling between the constant current source and the switching transistor.

Electronic final stage for switching electro-magnetic valve with the

To limit the current through the emitter-collector path of an output transistor, typically a Darlington transistor pair (T7, T8) to a load, in case of short circuit or malfunction of the load (L), in which a control circuit path resistor (R1) is serially connected with the emitter-collector path of the output transistor and the load, a reference current source is provided, connected to have current flow additionally through the resistor (R1) and providing control current to the output transistor at a control terminal (2) thereof, thereby permitting self-regulation of output current to a safe level regardless of reflected load resistance.

Transistor-controlled-load, short-circuit-protected current-supply

A timing wave generator 26 provides the same input to two threshold switches that switch on at approximately the same time but have different switching hysteresis. The switch with the smaller hysteresis can affect ignition timing only through a delay circuit while the other can do so directly. If the engine stalls the delay circuit will assure that the primary current is shut off in a short time. In normal operation the large hysteresis of one of the threshold switches is in control and provides insensitivity to disturbance, but during startup the characteristics of the delay circuit can provide the appropriate ignition timing.

Ignition system for an internal combustion engine

The voltage across a capacitor is changed in a first direction while the current in the primary winding of the ignition coil increases to a predetermined value less than the value required for ignition and is thereafter changed in a second direction until ignition takes place. The voltage across the capacitor is applied to the inverting input of a difference amplifier constituting a threshold stage controlling the initiation and termination of current flow through the ignition coil. The two changes are symmetrical when the engine speed remains constant. The residual voltage across the capacitor at the end of the second change is maintained until the start of the next subsequent first change, so that the time at which the threshold stage switches in, that is the time at which primary current starts to flow in the ignition coil changes as a function of the residual voltage in the capacitor.

Ignition system with improved temperature and voltage compensation

The voltage in the secondary of an ignition coil is prevented from reaching an amplitude at which a spark might be created by a Zener diode connected in parallel with the series transistor acting as a switch which interrupts the current through the primary winding of the coil. Upon breakdown of the Zener diode, the series transistor is switched to the conductive state briefly, thereby preventing further voltage build-up in the secondary. When the engine is in operation, a transistor which forms part of a voltage divider is switched to the conductive state, connecting the voltage divider between the secondary winding and the Zener diode. The voltage divider is so dimensioned that the Zener diode will respond to a voltage slightly less than the breakdown voltage of the emitter-collector circuit of the series transistor, but higher than the voltage required for creating a spark.

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Reutlingen, Germany

Bernd W Kalkhof