DE2057520A1 - Electronic ignition switch for internal combustion engines - Google Patents

Description

ATES component! Elettronici SpA
Via Tempesta, 2, Milan / Italy

Electronic ignition circuit for internal combustion engines

Priority: March 13, 1970; Italy;
Registration no .: 21916 A / 70

■■ - ■ The invention relates to an electronic ignition circuit for internal combustion engines with a monostable multivibrator controlled by a mechanically operated switch, whose feedback transformer is connected to a storage capacitor via a tertiary winding, as well as to a controlled diode between the storage capacitor and the primary winding of an ignition transformer.

Electronic ignition circuits of this type are known. The monostable multivibrator is usually controlled in

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Dependent on the cam-controlled front flaps of the machine. When the transistor of the multivibrator is conductive, energy is stored in the feedback transformer, which is then transferred to a storage capacitor during the blocking phase of the transistor. The transfer of the energy from the capacitor to the secondary winding of the ignition transformer _}, which supplies the actual high voltage for the spark plugs, is controlled via an interconnected, controlled silicon diode, namely, " ¹ E *". control via an additional auxiliary winding provided on the feedback transformer. In the known circuits of this type, separate resistor-diode limiting elements are therefore required to protect the transformer and the controlled diode, and the known circuits are therefore relatively complex and expensive in construction and are not suitable for the standard equipment of motor vehicles.

The object of the invention is to create an electronic ignition circuit for internal combustion engines that is very simple and can be produced cheaply, and still works very safely and with good efficiency.

This task is based on an electronic ignition circuit of the type mentioned at the outset according to the invention in that the control circuit of the controlled diode with the control circuit of the transistor of the flip-flop ■

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this secondary winding of the feedback c transform format or s and a diode resistance limiting element has in common.

In the circuit according to the invention, the circuit consists of a diode and a V / resistor connected in parallel Limiting element in the control line for the monostable multivibrator at the same time in the control circuit of the controlled Diode is provided and thus protects both the transistor and the controlled · - = »Γ? Ode from reverse overvoltages. Which he- " circuit according to the invention can therefore be produced very simply and cheaply. Nevertheless, it has a good level of efficiency. It is particularly suitable for four-cylinder engines with around 7000 rpm.

The invention is explained in more detail below with reference to a schematic drawing of an exemplary embodiment.

In the illustrated ignition circuit, the voltage at terminal Vb | applied DC voltage by means of the monostable multivibrator OB, which in turn is controlled by the intermittent

opening /

the front flaps P of the machine, the feedback transformer Tr and the diodes D 3 and D 5 are converted into a high voltage of approx. 350 V at the storage capacitor C H. The energy stored in the storage capacitor C H is given to the primary winding of the ignition transformer THT when the diode D Ί, which is controlled in the rhythm of the front flaps P, is ignited.

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The high ignition voltage for the machine's spark plugs is then generated on the secondary winding of this ignition transformer.

The monostable multivibrator Ob consists of a switching transistor Ql and the feedback transformer Tr. The primary winding Np of this feedback transformer is located in series with the switching transistor Q 1 at the DC supply voltage Vb. The flip-flop is like a monostable Toggle circuit fed back positive via a resistor R 6.

When the front flaps P of the machine are closed, the transistor Q 1 of the monostable multivibrator remains when it is applied Supply voltage Vb blocked. When the front flaps P are open, the capacitor passes through the resistor R 1 C 1 and the diode D 1 an ignition pulse to the blocked trigger circuit Ob. The transistor Q 1 is turned on and the current in the primary winding N ρ increases linearly until the core of the transformer Tr is saturated. The current rises rapidly to a value

¹ C ^{= h} PE ^XX b

where I is the collector current and I, the base current of the transistor Q 1 and h _{pF is} the current gain coefficient for a grounded emitter for large signals.

The transistor is then blocked again, the collector-emitter voltage of transistor Q 1 increases, the voltage

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at the primary winding Np and the secondary winding coupled to it Nf decreases so that transistor Q 1 is quickly turned off.

If with I the in the winding Np during the conduction phase of the transistor Q 1 reached the maximum current value and L denotes the inductance of the winding Np, it is that in the core

1 ?

of the transformer Tr stored energy «L χ Γ ~.

When the transistor Q 1 is blocked, the energy is transferred to the capacitor C H via the tertiary winding NL of the feedback transformer and the diodes D 3 and D 5. If the losses are neglected, the electrostatic energy of the capacitor charge is equal to the inductive energy previously stored in the feedback transformer Tr. This energy arises immediately at the ends of the primary winding of the ignition transformer THT when the controlled diode D k becomes conductive.

The resistor R 4 is used to limit the base current of the Transistor Q 1. The resistor R 3 and the diode D 2 form a limiting element, through which the transistor Q 1 against excessively high blocking voltages in the base-emitter path are protected. The controlled diode D ^ is ignited via the capacitor C 2 with the same pulse that causes the transistor Q 1 to conduct. The resistance R 7 ensures during the conduction phase of the transistor Q 1 between

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see the cathode and the control electrode of the controlled diode D ^ a positive voltage, which is fed back to the winding Hf. With this positive voltage, the controlled diode D 4 remains switched on even in the event of possible oscillations in the output circuit, which would otherwise block it again after ignition. Such oscillations occur when the secondary winding of the ignition transformer TUT is open and there is no possibility of completely using up the energy stored in the capacitor C k. This energy deficit is unfavorable because it brings the voltage on the storage capacitor C 4 to undefined values during the subsequent charging phases. However, if the controlled diode D 4 can conduct for a certain time after the ignition, the complete energy output from the storage capacitor C 4 is achieved.

The controlled diode D 4 is ignited via the from the Diode D 2 and the resistor R 3 existing and provided to protect the transistor Q 1 limiting element. This limiter thus also serves to protect the controlled diode from excessively high reverse voltages.

Resistor R 5 biases the base of transistor Q 1. The capacitor C 3 delays the overturning of the transistor by having the maximum voltage values between collector and Emitter limited. With the diode D 5 the on the transformer THT transferred energy partially recovered by

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it extends the spark duration on the spark plugs.

With a circuit according to the invention, maximum voltage values of 2 ^ \ kV and more (measured at a resistance of 1MÄ between the electrodes of the spark plugs) can be generated _{on the secondary winding of the ignition transformer THT /} with a spark duration of 2OCUsec. The rising edge of the ignition pulses is about 20 / tsec. If the supply voltage fluctuates between 8 and 16 V, the energy only changes between 50 and 75 mjoule or the voltage on the storage capacitor C k between 320 and 390 V.

Claims

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Claims (2)

2U5V520 - 8 PATENT CLAIMS 1. J Electronic ignition circuit for internal combustion engines with a monostable multivibrator controlled by a mechanically operated switch, the feedback transformer of which is connected to a storage capacitor via a tertiary winding, and with a controlled diode between the storage capacitor and the primary winding of an ignition transformer, characterized in that the control circuit of the controlled diode (D 4) with the control circuit of the transistor (Q ί) of the flip-flop (Ob) has the secondary winding (Nf) of the feedback transformer (Tr) and a diode resistance limiting element (D2, R3) in common. 2. Ignition circuit according to claim 1, characterized in that that between the output of transistor (Ql) and the hot end of the secondary winding (Nf) of the feedback transformer a resistor (R6) is connected. 109 8 Λ 0/1007