JPS6220705Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a capacitor charging/discharging type ignition system, and in particular, the ignition timing (angle) is set to obtain a constant angle ignition characteristic when the engine speed is below a set number, and In the above case, a simple ignition device is provided which can obtain ignition characteristics at a substantially constant angle advanced from the ignition angle. The present invention will be explained in detail below using the drawings. Figures 1, 2, and 3 are a circuit diagram of an embodiment of the present invention, an operation waveform diagram of each part, and an ignition characteristic diagram, respectively.
and PC is a power generation coil such as a magnetic generator rotated by the engine and an ignition signal generation coil (hereinafter referred to as a pulsar coil), D1 is a diode, C1 is an ignition power supply capacitor charged by the voltage generated by the power generation coil EXT, and IGC is an ignition signal generation coil. coil, n1n2
are its primary and secondary windings, SP is a spark plug, and SCR is a thyristor with a gate pole (hereinafter referred to as a thyristor) whose gate pole G is controlled to conduct through a switch circuit SC, which will be described later, based on the signal from the pulser coil PC.
As a result, the charge of the capacitor C1 is discharged to the primary winding n1 of the ignition coil Igc, and a spark is generated at the ignition plug SP via the secondary winding n2. SC is a switch circuit which constitutes the main part of the proposed device, and a resistor R is connected to both ends of the pulser coil PC.
A series circuit of a diode D2 and an ignition signal capacitor C2 connected through the ignition signal capacitor C2 is electrically conductive due to the potential difference between both ends (anode and cathode) of the diode D2, and its output is supplied to the gate electrode G of the thyristor SCR. A peak voltage detection circuit for the ignition signal includes a transistor Q1 connected as shown in FIG.
PD, a parallel circuit of a capacitor C3 and a discharge resistor R3 connected to both ends of the detection circuit PD, and a series circuit I of a constant voltage diode DZ.

(In addition, D4D5 in the figure are rectifier diodes, R2
is a current limiting resistor, R4 is a protective resistor, D6 is a backflow prevention diode, and SW is an engine stop switch. ) The circuit of the present invention is configured as described above.

Next, the circuit operation of the present device will be explained with reference to FIGS. 2 and 3. Note that the generated voltage of the generator coil EXT and the signal voltage of the pulser coil PC are 90° each other.
It is assumed that the phase difference is set in advance so that the phase difference is .degree.

In addition, in Fig. 2 a, b, and c, A is the charging voltage waveform of the capacitor C1, B is the constant voltage level of the constant voltage diode DZ, C is the voltage waveform of the pulser coil PC, and D is the voltage waveform of the ignition coil Igc. shows.

<Operation when the engine speed is below the set number> First, when the polarity of the generator coil EXT is on the upper side as shown in Figure 1, the capacitor C1 is connected to the generator coil.
It is charged to the polarity shown in the diagram through the path EXT → diode D1 → capacitor C1 → ignition coil primary winding n1 → EXT. When the polarity of the generator coil EXT is upper and lower, the capacitor C1
is blocked by the diode D1 and is not charged, and since a discharge circuit is not formed for the charge charged in the capacitor C1 during the previous cycle, the charged state shown in the figure is maintained. On the other hand, since the voltage generated by the pulsar coil PC is set to be out of phase with that of the generator coil EXT by 90 degrees, when the polarity of the generator coil EXT is on the upper side, the upper side of the PC becomes . Therefore, if the peak value (maximum wave height value) of the pulsar coil PC is below the setting level of the constant voltage diode DZ (Fig. 2 a), the capacitor C2 is connected to the pulsar coil during this time.
It is charged through the path of PC → resistor R1 → diode D2 → capacitor C2 → PC. and time t
2, when the signal voltage reaches its peak value (Fig. 2, a, c), the capacitor C2 is no longer charged, and in the process of the signal voltage decreasing from its peak, the cathode side potential of the diode D2 decreases. (that is, the charging level of capacitor C2) is higher than that on the anode side. When this potential difference exceeds the base-to-emitter voltage (VBE) of the transistor Q1 at time t3, the charge of the capacitor C2 changes from the capacitor C2 to the emitter of the transistor Q1.
It is discharged along the path of base → resistor R1 → pulser coil PC → capacitor C2 to make the transistor Q1 conductive, and the electric charge is transferred to capacitor C2 →
Emitter of transistor Q1, collector → diode D3 → gate G of thyristor, cathode → capacitor C2 is discharged and becomes thyristor SCR
is supplied as gate current. Therefore, at time t3, the thyristor SCR becomes conductive, and the charge in the ignition power supply capacitor C1 is rapidly discharged along the path of capacitor C1 → thyristor SCR → ignition coil primary winding n1 (Fig. 2 a). A spark is generated in the spark plug SP via the secondary winding n2. In other words, as the engine speed increases, the peak value of the ignition signal generated in the pulsar coil PC also increases, but the peak value (maximum peak value) is below the constant voltage level of the constant voltage diode (Figure 2 a, b). At the rotation speed, the thyristor is activated only by the operation of the peak voltage detection circuit PD in the switch circuit SC.
Since the SCR is always made conductive at the same ignition phase (point A) near the peak of the ignition signal, the third
As shown in the figure, an ignition characteristic of a constant angle (point A) can be obtained when the rotational speed is equal to or less than the set number N1.

<Operation when the engine speed is higher than the set number> Next, as described above, when the capacitor C1 is holding the charge from the first half cycle and the polarity of the pulsar coil PC is on the upper side, the engine speed will change. exceeds the set number, and as a result, the signal voltage increases around its peak value (at time t
In 2), when the setting level of the constant voltage diode DZ (Fig. 2 b) is exceeded, the pulser coil PC → diode D4 → constant voltage diode DZ = resistor R3
Capacitor C3 → Gate G of thyristor SCR,
The gate current of the thyristor SCR flows in the path from cathode to pulser coil PC, and the thyristor SCR
conduction. Therefore, the ignition phase of the thyristor, that is, the ignition timing changes (advances) to point B shown in FIG. 2b. On the other hand, the charge of the capacitor C3 (the polarity shown) is discharged through the resistor R3 when the upper side of the pulser coil PC is OFF, and is prepared for the next cycle.
Furthermore, as the rotational speed further increases, the signal voltage increases as shown in Fig. 2 c-c, and when it reaches the set level (Fig. 2 c-b) at time t1, it becomes more advanced than the above.
A spark is generated at C. The above operation means that the thyristor SCR becomes conductive at times t2 and t1 when the signal voltage reaches the set level of the voltage regulator diode DZ. The firing angle of becomes almost constant.

That is, in the parallel circuit of capacitor C3 and resistor R3, the charging voltage of capacitor C3 increases correspondingly as the peak value of the signal voltage increases, but the discharge time constant of capacitor C3 is set constant. Furthermore, as the rotational speed increases, the period of the pulsar coil PC becomes shorter, so its discharge period becomes shorter. Therefore, the capacitor C3 maintains a high residual voltage with the polarity shown in the next cycle in proportion to the increase in the rotational speed. Therefore, at a predetermined rotation speed, for example, N3 and N7 in Fig. 3 (ignoring diode D4 and resistor R2 of series circuit I), the signal voltage reaches or exceeds the sum of the voltage of constant voltage diode DZ and the residual voltage of capacitor C3. When the thyristor
Make SCR conductive. Therefore, the rotational speed N3 and N
7, the peak values of the pulser coil PC reach the same value, but the residual voltage of the capacitor C3 also differs in proportion to this, and the thyristor SCR
conduction occurs at a nearly constant firing angle.

In summary, according to the present invention, the switch circuit
In SC, when the number of revolutions is below the set number, the peak detection circuit PD is used, and when the number of revolutions is more than the set number, the series circuit I is used.
As a result, as shown in Fig. 3, when the number of settings is N1 or less, a constant angle ignition characteristic as shown by point A is obtained, and when the number of settings is N1 or more, the thyristor is made conductive. The ignition characteristic is made to have a substantially constant angle as points D and E, which are advanced in steps from point A to points B and C.

As is clear from the above explanation, according to the present invention, when the engine speed is less than or equal to the set number, an ignition characteristic of a constant angle is obtained, and when it is greater than or equal to the set number, the ignition angle changes in steps. Since a constant (advanced) ignition characteristic can be obtained, it is particularly suitable for ignition of general-purpose engines, and has great practical effects.

[Brief explanation of the drawing]

FIGS. 1, 2, and 3 are a circuit diagram of an embodiment of the present invention, operation waveform diagrams of various parts, and ignition characteristic diagrams. In the figure, EXT is a power generation coil, PC is an ignition signal generation (pulsar) coil, C1 is a capacitor for ignition power supply, SCR is a thyristor with a gate pole, G is a gate electrode, IGC is an ignition coil, SP is a spark plug, and SC is a switch circuit. , PD is a peak voltage detection circuit, I is a series circuit, Q1 is a transistor, C2 is a capacitor for ignition signal, D2 is a diode, DZ is a constant voltage element, C3 is a capacitor, R3 is a discharge resistor, SW is an engine stop switch. .

Claims (1)

[Claims for Utility Model Registration] (1) A capacitor is charged by the voltage generated by a power generation coil, and the charge in the capacitor is discharged to the ignition coil via a thyristor which is conducted by an ignition signal from an ignition signal generation coil. In the capacitor charging/discharging type ignition device configured,
A switch circuit consisting of a peak voltage detection circuit for the ignition signal, a parallel circuit of a capacitor and a resistor, and a series circuit of a constant voltage element connected to both ends of the detection circuit is provided, whereby the thyristor is made conductive, and the switch circuit is connected to both ends of the detection circuit. When the number of revolutions is below a set number, an ignition characteristic of a constant angle is obtained, and when the number of revolutions is above a set number, an ignition characteristic of a constant angle is obtained, which is advanced in steps from the above-mentioned ignition angle. A capacitor charge/discharge type ignition device. (2) A peak that includes a series circuit of a diode and a capacitor connected across the ignition signal generating coil and a transistor connected to conduct due to the potential difference between the ends of the diode and supply its output to the gate of the thyristor. A capacitor charge/discharge type ignition device according to claim 1, characterized in that a voltage detection circuit is used.