JPS5819339Y2 - Overspeed prevention circuit in non-contact ignition device for internal combustion engine - Google Patents

Description

[Detailed description of the invention] The present invention relates to an overspeed prevention circuit in a capacitive discharge type non-contact ignition device for an internal combustion engine. The purpose of this is to stop the trigger of the thyristor, thereby stopping the ignition operation of the ignition device and reducing the rotational speed of the internal combustion engine.

Various methods and configurations have been considered for overspeed prevention circuits in non-contact ignition devices for internal combustion engines.

Among these non-contact ignition devices, the electrical overspeed prevention means for capacitive discharge type non-contact ignition devices is to stop the ignition operation of the ignition device itself if the rotational speed of the internal combustion engine exceeds a set value. There are means for stopping the ignition, and means for delaying the ignition timing in the ignition device.

In the case of a means for stopping the ignition operation itself of the ignition device, the rotational speed of the internal combustion engine is monitored by an induced voltage proportional to the speed of the internal combustion engine in a generator coil or a trigger coil, and when this induced voltage value exceeds a predetermined value. If so, detect this by appropriate means and short-circuit both terminals of the primary winding of the ignition coil, or trigger a thyristor to discharge the charge stored in the capacitor to the primary winding. It was said to make it impossible.

In this way, when the internal combustion engine's rotational speed exceeds a set value, the induced voltage in the generator coil or trigger coil is monitored and a detection signal is issued, and the induced voltage in the generator coil or trigger coil is monitored. A circuit configuration is required for this purpose.

- Traditionally, the circuit configuration for this monitoring is to charge a capacitor with part of the forward voltage of the generator coil or part of the forward voltage of the trigger coil, and when the rotational speed of the internal combustion engine exceeds a set value. Therefore, the charge stored in this capacitor was discharged into a predetermined circuit to prevent the ignition device from igniting.

For this reason, conventional circuits of this type require some means to monitor the voltage charged to the capacitor, and when the charging voltage of the capacitor reaches a set value, the above-mentioned monitoring means activates the circuit. There must be a means to prevent the ignition device from igniting.

For this reason, the structure of the over-rotation prevention circuit naturally becomes complicated and, in some cases, extremely expensive.

In addition, in many cases, a capacitor for monitoring the rotational speed of an internal combustion engine is charged with a portion of the forward voltage of a generator coil or an I-trigger coil. In addition to power generation capacity,
The electricity that can be charged to this capacitor will also be required to be generated, and for this reason it is necessary to increase the ampere turns of the coil, so the generator coil or I/Riga coil used must be designed to prevent over-rotation. A large, expensive device with a higher rating than one without a circuit is to be used.

This means that when looking at the circuit as a whole, there is no change in the ignition performance itself, so the electrical efficiency of the entire circuit decreases, making it substantially inefficient.

The present invention was devised to solve the drawbacks and problems of the conventional example described above.If the charge charged to the capacitor is constant and the time constant of the discharge circuit of this capacitor is constant, the capacitor can be Although the time for discharging the charged electric charge is constant, the time interval between when the forward voltage is generated and when the reverse voltage is generated in the trigger coil becomes shorter as the rotational speed of the internal combustion engine increases. An embodiment of the present invention will be described below with reference to the drawings.

The ignition device to which the overspeed prevention circuit 4 according to the present invention is installed is a so-called capacitive discharge type ignition device, in which a rectifying diode D and a thyristor SCR in a forward direction are connected between both terminals of a generating coil GO. A series circuit is inserted in parallel between the anode and cathode of this thyristor SCR, a series circuit of a capacitor C and the primary winding T1 of the ignition coil T is inserted in parallel, and this thyristor is inserted between the gate and cathode of the thyristor SCR. A coil TC is inserted as a trigger for triggering the SCR at a predetermined timing.

It goes without saying that the secondary winding T2 of the ignition coil T
A spark plug P is connected to the ignition plug P.

The ignition operation of this general capacitive discharge type ignition device is performed as follows.

When a flywheel (not shown) in which a permanent magnet is embedded rotates and a forward voltage is induced in the generator coil GC, the forward voltage induced in the generator coil GC is transferred from the generator coil GC to the diode D to the capacitor C. →−Next winding T1→
The capacitor C is charged with the polarity shown in the diagram through the path of the generator coil GC.

After the charging of this capacitor C is completed, at an appropriate time, a forward voltage, that is, tonogami pressure, is induced in the latch coil TC, and this trigger voltage turns on the cynostar SCR, so that the capacitor C is charged. The charge is rapidly discharged to the primary winding T1 through this turned-on thyristor SCR.

Due to the discharge of the charging voltage in the capacitor C through the primary winding T1, a high voltage is induced in the secondary winding T2, which causes a spark discharge to occur in the plug P, thereby performing an ignition operation.

The overspeed prevention circuit A according to the present invention is assembled into an ignition circuit having the configuration and operation described above, and when the rotational speed of the internal combustion engine exceeds a set value, the thyristor S
It is configured as a kind of gate circuit for the thyristor SCR that makes the CR non-triggerable.

That is, in parallel with the trigger coil TC inserted between the gate and cathode of the thyristor SCR, a series circuit consisting of a diode D2 in the opposite direction and resistors R3 and R4 and a thyristor 5CR1 are connected, and both resistors R3 and R4 are connected in parallel. A capacitor C with a Zener diode ZD connected in parallel to set the charging voltage limit between the connection point and the negative terminal of the trigger coil TC when forward voltage is generated.
1 and a diode D1 in the opposite direction, and the positive electrode of this 4''/+fC1 is connected to the gate of the thyristor 5CR1 via an adjustment resistor R2. .

Note that the resistor R1 inserted between the gate and cathode of the thyristor 5CR1 is a resistor for stabilizing the operation of the thyristor SCR.

Since the circuit of the present invention has the above-described configuration, the reverse voltage -■ induced at the time ti (see Fig. 2) prior to the induction of the forward voltage 1 V in the trigger coil TC is
Trigger coil TC → diode D1 → capacitor C1 →
The capacitor C1 is charged with the indicated polarity through the path of resistor R3→diode D2→L/rega coil TC.

The reverse voltage -■ in the trigger coil TC charged to this capacitor C1 is determined by the voltage division ratio of resistors R3 and R4, but ultimately it is determined by the Zener diode connected in parallel to this capacitor C1. A voltage according to the Zener voltage Vz of ZD is charged.

Since the induced voltage Vt in the trigger coil TC increases in proportion to the rotational speed of the internal combustion engine, if the rotational speed of the internal combustion engine becomes normal rotation by appropriately setting the Zener voltage Vz, the capacitor C1 The charge charged to the internal combustion engine remains constant regardless of the increase in the rotational speed of the internal combustion engine.

The electric charge charged in the capacitor C1 is transferred from the capacitor C1→
Resistor R2 → Thyristor 5 Gate of CR1 → Thyristor 5
It is discharged through the path of cathode of CR1→resistance length 4→capacitor C1.

Therefore, the thyristor 5CR1 is kept in a triggerable state during the discharging period of the capacitor C1, that is, until the time t3 after a time determined by the capacitance of the capacitor C1 and the resistance values of the resistors R2 and R4. be.

Therefore, due to some reason, from the time t3 to t5
During the discharge period of the capacitor C1, the trigger coil T
If a forward voltage +■ is induced in C,
Thyristor 5CR1 is triggered and short-circuits between the gate and cathode of cynostar SCR.

By the way, as mentioned above, the voltage charged to the capacitor C1 becomes as follows when the rotational speed of the internal combustion engine exceeds a predetermined value.
Since it is always constant regardless of changes in the rotational speed of the internal combustion engine, the discharge time, that is, the time from time t3 to t5, is constant, whereas the reverse voltage -■ in the trigger coil TC is induced at time t1. The interval between the induction time t2 of the directional voltage 1 and 2 becomes shorter as the rotational speed of the internal combustion engine increases.

In other words, if time t□ is fixed, time t2
As the rotational speed of the internal combustion engine increases, the forward voltage +V induced at the forward voltage +V becomes closer to the time t1.

In this way, while the discharge time of the capacitor C1 is constant regardless of the rotational speed of the internal combustion engine, the time point t1 when the reverse voltage -V occurs and the time point when the forward voltage +V occurs depend on the rotational speed of the internal combustion engine. As the internal combustion engine increases, the distance between the forward direction voltage +V' and the forward direction voltage +V' is determined. ' At a time t, which is slightly delayed from the time t4 when `` occurs, the capacitor C
The circuit constants of the discharge circuit of the capacitor C1 are set so that the discharge of the capacitor C1 is completed.

In this way, by setting the discharge time of the capacitor C1, as long as the rotational speed of the internal combustion engine is within the normal rotational speed range, a forward voltage +■ will be induced after the time t3 when the discharge of the capacitor C1 is completed. Therefore, the thyristor 5CR1 is not triggered by this forward voltage +V, and therefore, the thyristor SCR is triggered by this forward voltage +■, and an ignition operation is performed.

From this state, when the rotational speed of the internal combustion engine increases for some reason and reaches the set value before overspeeding, the forward direction that gradually approaches time t1 as the rotational speed of the internal combustion engine increases. The point at which voltage +V occurs is time t
4, the discharge of capacitor C1 is finally completed at time t3
thyristor 5CR1 which is ready to be triggered by the discharge of capacitor C1.
A forward voltage +V' is applied between the anode and cathode of.

Therefore, the thyristor 5CR1 is triggered and remains conductive until the forward voltage +V' disappears.

Due to the triggering of the thyristor 5CR1, the gate and cathode of the thyristor SCR are short-circuited, so that the thyristor SCR becomes incapable of being triggered, and as a result, the ignition circuit is unable to perform the ignition operation, and the rotational speed of the internal combustion engine increases no further. It is not possible to do so and it deteriorates.

In this way, when the rotational speed of the internal combustion engine decreases due to the ignition operation of the ignition circuit not being performed, this decrease in the rotational speed of the internal combustion engine causes the capacitor C1 to
The generation of the forward voltage +■ is delayed with respect to the discharge completion time t3, and the ignition circuit returns to a state in which it can perform the ignition operation.

As described above, the overspeed prevention circuit A according to the present invention has a trigger coil TC that increases and changes in proportion to the rotational speed of the internal combustion engine.
Rather than monitoring the induced voltage value of the trigger coil TC
While the discharge time for discharging a certain amount of the reverse voltage -V induced in the trigger coil TC is constant, the interval between the time when the reverse voltage - Since it takes advantage of the fact that it changes according to the rotational speed of the internal combustion engine, there is no need for a special circuit to monitor the induced voltage of the trigger coil TC, which allows for a simpler circuit configuration and reliable operation. Furthermore, since what is charged to the capacitor C1 is the reverse induced voltage in the trigger coil TC, which has not been used at all, the ampere turns of the trigger coil TC is increased in order to charge this capacitor C1. On the contrary, since the reverse induced voltage, which has never been used before, is used, the electrical efficiency of the ignition circuit as a whole is improved, and the overspeed of the internal combustion engine is eliminated. It has many excellent effects as a prevention circuit.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a capacitive discharge type ignition circuit to which an embodiment of the overspeed prevention circuit according to the present invention is connected. FIG. 2 is a voltage waveform diagram for explaining the operation of the circuit of the present invention. FIG. 2a shows the induced voltage waveform in the trigger coil, and FIG. 2 shows the discharge voltage waveform of the capacitor. Explanation of symbols GC: Generating coil, T: Ignition coil, T1
;Primary winding, T2;Secondary winding, P;Plug, C9C1;
Capacitor, 5CR9SCR1; Thyristor, D. DI, D2; diode, TC; trigger coil, R1
゜R2, Ra, R4: Resistance, ZD: Zener diode, A: Overspeed prevention circuit, vt: Trigger voltage, -V: Reverse voltage, +v, -1-v': Forward voltage, Vz: Zener voltage, tl, t2. t3. t4. t5; Time point.

Claims (1)

[Scope of utility model registration request] The forward voltage induced in the generator coil GC is charged to a capacitor C, and the charge charged to the capacitor C is transferred to the primary winding T in the ignition coil T through a thyristor SCR triggered at a predetermined timing by a trigger coil TC.
The secondary winding T2 of the ignition coil T by discharging to 1
An over-speed prevention circuit connected to a capacitive discharge type ignition circuit that generates a spark discharge to a plug P connected to the thyristor SCR, which is in a reverse direction parallel to the trigger coil TC between the gate and cathode of the thyristor SCR. A series circuit of a diode D2 and resistors R3 and R4 is connected to the thyristor 5CR1, and a terminal connected to the cathode of the thyristor SCR, which becomes a positive terminal when a reverse voltage is generated in the trigger coil TC, and a resistor for dividing both voltages. A series circuit with a capacitor C1 in which a diode D1 in the opposite direction and a Zener diode ZD for charging voltage limitation are connected in parallel is inserted between the connection point of R3 and R4, and the positive side electrode of the capacitor C1 is connected to the capacitor C1. is connected to the gate of a thyristor 5CR1 via a resistor R2.