JPS5821107B2 - Ignition circuit for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an ignition circuit for an internal combustion engine mainly composed of transistors.

Conventionally, there has been a problem in that when starting an internal combustion engine, a particularly high secondary electromotive force must be applied to the spark plug in order to reliably ignite the cold compressed air-fuel mixture in the cylinder.

Therefore, reliable starting could not be achieved unless the primary breaking current was increased.

The purpose of this invention is to increase the primary breaking current value to increase the secondary electromotive force induced in the secondary winding of the magneto, by blocking the current flowing through the primary winding of the magneto's ignition coil. The goal is to ensure certainty.

The present invention will be explained below with reference to embodiments of the accompanying drawings.

T is a magneto ignition coil, which is constructed by winding a primary winding T1 and a secondary winding T2 around an iron core F, with the primary winding T1
The secondary winding T2 is wound with a small number of turns of thick conductive wire to increase the primary current during conduction, and the secondary winding T2 is wound with a large number of turns of extremely thin conductive wire to increase the secondary voltage.

One terminal of each of the primary winding T1 and the secondary winding T2 is both connected to ground G.

A spark plug P of the internal combustion engine is connected between both terminals of the secondary winding T2.

A transistor Qt −Q is connected between both terminals of the primary winding T1.
A three-stage current amplifier or a fixed bias circuit mainly consisting of a power transistor Q2 and a power transistor Q3, and a control circuit mainly consisting of a fourth transistor Q4 for controlling conduction/cutoff of this fixed bias circuit are connected.

The collector C2 and base B2 of a PNP transistor Q2 are connected to the emitter E1 and collector C1 of the NPN transistor Q, respectively, and a Bess stabilizing resistor Rs is inserted and connected between the base B2 and emitter 82 of the transistor Q2, and the transistor Q4 The emitter E1 of the transistor Q2 is connected to the base B3 of the NPN type power transistor Q3, and the other terminal of the bias resistor Rb whose one terminal is connected to the base B1 of the transistor Q1 is grounded to the earth G, and the emitter E2 of the transistor Q2 and the power transistor Q3 collector C
3 is grounded to the ground G, and the emitter E3 of the power transistor Q3 is connected to the terminal H of the primary winding T1 on the side opposite to the ground G side terminal to form the fixed bias circuit.

The base B1 of the transistor Q1 is connected to the collector C4 of the NPN transistor Q4, and a thermistor rt and a resistor r are connected between the base B4 and the emitter 84 of the transistor Q4.
Resistor r3 is connected in series with resistor r1 connected in parallel with 2.
A temperature compensating resistor R1 is inserted and connected in parallel, and 1
A voltage dividing resistor Rp is inserted and connected between the ground G side terminal of the secondary winding T1 and the base B4 of the transistor Q4, and the emitter of the transistor Q4 is connected to the terminal H opposite to the ground G side terminal of the primary winding T1.

The control circuit is constructed by connecting the ivy E4.

The power supply section of the magneto consists of an ignition coil T and a rotor (not shown), and the rotor consists of one or more magnets and a magnetic pole piece having one surface adhered to each pole of the magnet and the other surface disposed on the outer peripheral surface. It is made of non-magnetic material.

, the rotor is fastened to the crankshaft of the engine, and its outer magnetic pole face faces both end faces of the iron core F of the stationary ignition coil T with a small gap therebetween.

The rotation of the rotor causes a magnetic flux change in the iron core F, and this electromagnetic induction causes a primary induction in the primary winding T1 of the ignition coil T.

Generate electricity.

Due to this primary induced electromotive force, the transistors Qt and Q2
and power transistor Q3 are both conductive, and transistors Q1 . The current amplification factors of the common emitters of Q2 and power transistor Q3 are respectively β1. β2 and β3 are bias resistances.

Let the bias current that rarely flows be i, and the base stabilizing resistance Rs
If the electromagnetic current flowing in is n times this, then the emitter current of transistor Q is (β1 +1) i, and the collector current of transistor Q2 is β2 (β1 n)1, so the base current/current of power transistor Q3 is The current transferred as (β1β2+β1+1−nβ2)1×β2(β1−n)i, that is, approximately (β1
-n) becomes a sufficiently large value twice β, and the collector current (β1-n)β2β31 of the power transistor Q3 becomes a saturation current that cannot increase any further.

The base-emitter voltage of transistor Q1 is ■BE1
, the collector-emitter voltage of transistor Q2 is −■
.

If E2, Rbi +BEI -CR2 An equilibrium is established.

The voltage from the collector C1 of the transistor Q1 to the emitter E and the voltage from the emitter E2 of the transistor Q2 to the collector C2 are in opposite directions when viewed from the loop formed by them and Rs, and eliminate the respective collector-base losses. If the base stabilizing resistor Rs is short-circuited,
The operation of the transistor Q2 is stopped and collector-base loss remains, and the impedance (resistance) between the collector and emitter of the transistor Q2 disappears, so the equilibrium is broken and Rb i + VBEI> VCE2 (where -VC
E2 is the value at equilibrium of the bending.

Therefore, the terminal voltage of the primary winding T1 is this transistor Q1.
In the case of two-stage amplification with power transistor Q3 and power transistor Q3, the short-circuit effect is reduced and is higher than in the case of three-stage amplification of the present invention.

In other words, the connection of transistor Q2 in the circuit shown in the figure has the effect of lowering the terminal voltage of primary winding T1 and increasing the primary current.

The terminal voltage of the primary winding T1 is applied across both terminals of the series connection of the voltage dividing resistor Rp and the temperature compensating resistor Rt, and the divided voltage corresponding to the temperature compensating resistor Rt is the base-emitter voltage V of the transistor Q4. B becomes E4.

Therefore, the collector current (β
1-n) At the moment when β2β31 reaches its maximum value, the corresponding transistor Q of the terminal voltage of the primary winding T1
By setting the temperature compensation resistor R1 to the voltage dividing resistor Rp in advance so that the base-emitter voltage VBE4 of the transistor Q4 slightly exceeds the base knee voltage at the ambient temperature at that time, the transistor Q4 immediately becomes conductive.
The sum of the base-emitter voltage VBEI of power transistor Q3 and the base-emitter voltage VBE3 of power transistor Q3 is the collector-emitter voltage of transistor Q4, which is vcE4.
Then, VBEI+VBE3"VCE4.

Therefore, both the transistor Q1 and the power transistor Q3 cut their base knee voltages, and the bias current i disappears, and are in the cutoff state. At the same time, the transistor Q2 also loses its base current, and becomes the cutoff state, and the 1 flowing through the primary winding T1. The secondary current is cut off at its maximum value, and the induced electromotive force in the secondary winding T2 due to this mutual induction causes the secondary winding T2 itself to be flooded with iron at the same time as the primary winding T1 is opened, and the magnetic flux within F changes. A secondary high voltage sufficient to perform the most effective spark discharge is supplied to the spark plug P by superimposing it on the induced electromotive force induced by the spark plug P.

The temperature compensating resistor Rt is always connected to the transistor Q4 with respect to the voltage dividing resistor Rp which remains unchanged even when the ambient temperature of the transistor Q4 changes.
A resistor rl is applied so as to provide a voltage between the base B4 and the emitter 84 to compensate for the changing base knee voltage of B4.
r2. The respective values of r3 and thermistor ri are determined and obtained as their combined resistance.

Regardless of the change in ambient temperature, if the accuracy of this determined Rt is the same, the primary winding T
This ensures that the maximum value of the primary current of 1 is interrupted.

Note that in the illustrated embodiment, the transistor Q1. Q3 and Q
4 is shown as an NPN type, and the transistor Q2 is shown as a PNP type, but the present application is not limited to these.
It goes without saying that the transistor Q3 can be configured as an NPN type.

As described above, in the ignition circuit of the present invention, the current amplification rate of the three-stage current amplifier or fixed bias circuit is approximately the product of the current amplification rates of each transistor, and the first stage transistor The final stage power transistor and 2
By making the polarity different from that of the transistor in the first stage, the voltage flowing from the emitter to the collector of the first stage transistor and 2
The voltages from the collectors of the transistors in the third stage to the emitters are faced in a loop to reduce the collector loss, and the impedance (resistance) between the bases of the transistors in the third stage is reduced. 1 of the ignition coil by reducing the impedance (resistance).
It is possible to increase the short-circuit effect to the next winding and reduce its terminal voltage, making it possible to cut off the maximum value of the primary current close to the point of short-circuit (G), and to generate sufficiently high discharge energy in the spark plug. .

[Brief explanation of the drawing]

The figure is an electrical circuit diagram showing an embodiment of the present invention.・T...Ignition coil, T...Primary winding, T2...
...Secondary winding, P...Spark plug, Ql + Q2
+ Q4...Transistor, Q3...Power transistor, Rh-bias resistor, R5...Base stabilizing resistor, Rp...Voltage dividing resistor, Rt...Temperature compensation resistor, C
a... Capacitor.

Claims (1)

[Claims] 1 Insert a transistor Q3 between the ground terminal G and terminal H of the primary winding fm T of the magneto's ignition coil T so that the collector C3 is connected to the ground terminal G and the emitter E3 is connected to the terminal H, and The collector C1 and emitter E1 of the transistor Q1 are connected between the terminal G and the base B3 of the transistor Q3 via the base stabilizing resistor Rs, and the control transistor Q4 is connected between the terminals G and H so that the collector C4 is biased. The emitter E4 is connected to the ground terminal G via a resistance wire so that the emitter E4 becomes the terminal H, and the base B1 of the transistor Q1 is connected to the collector C4 of the transistor Q4, and the base B4 and emitter of the control transistor Q4 are connected to each other. In the ignition circuit for an internal combustion engine, a temperature compensation resistor Rt is connected between the control transistor Q4 and the ground terminal G, and a voltage dividing resistor Rp is connected between the base B4 of the control transistor Q4 and the ground terminal G. The base B2 of the transistor Q2 with the polarity opposite to that of Qs is connected to the collector C1 of the transistor Q1, and the collector C1 of the transistor Q2 is connected to the base B of the transistor Q3.
3, and the emitter E2 of the transistor Q2 is connected to the ground terminal G, and the transistors Qh, Q2 . Q3
An ignition circuit for an internal combustion engine, characterized in that it is equipped with a three-stage current amplifier.