JPH07269451A - Ignition device for internal combustion engine - Google Patents

Abstract

PURPOSE:To shorten the converter stopping time to prolong the charging time, and thereby improve the ignition performance by keeping impedance between the gate and the cathode or the earth of a thyristor lower for the period of time from the trigger signal terminated time of the thyristor up to the converter stopping signal terminated time, and thereby increasing the holding current of the thyristor. CONSTITUTION:When a switch 1 is closed, a transistor 5 is turned ON/OFF, and a capacitor 8 is charged. At this time, when the output of a pulser coil 10 is inputted to a trigger circuit 11, a thyristor 12 is triggered to a set ignition timing to ignite a fuel-air mixture. In this case, a transistor 22 is turned ON only for the period of time from the trigger signal terminated time up to the converter stopping signal terminated time, namely only when the output of the trigger circuit 11 is L by a gate circuit 21, and the output of a converter stopping circuit 17 is H. Thus, a resistance 23 is inserted between the gate and the cathode of the thyristor 12 to decrease impedance between the gate and the cathode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge thyristor target.
The present invention relates to an ignition device for an internal combustion engine with a reduced on / off time.

[0002]

2. Description of the Related Art Conventionally, as an ignition device for an internal combustion engine, a capacitor (3) charged in advance to several hundreds of volts is discharged to a primary side of an ignition coil by a thyristor at a required ignition timing of the internal combustion engine, and a secondary coil of the ignition coil is discharged. There is known a capacitor discharge type ignition device (hereinafter, referred to as CDI) that generates a high voltage on a side to perform ignition. And in this kind of ignition device, in order to charge the capacitor to several hundred volts, DC
A method is known in which a battery voltage is boosted by using a DC converter to charge a capacitor.

FIG. 1 shows an example of a conventional CDI of this type. The conventional technique will be described below with reference to FIG. In this type of CDI, when the switch 1 is closed, power is supplied from the battery-2 and the power supply circuit 3 of the CDI operates. As a result, the astable multivibrator 4 starts oscillating and the transistor 5 starts ON / OFF operation. The collector of the transistor 5 is connected to the primary winding of the step-up transformer 6, and the other end of the step-up transformer 6 is connected to the battery-2 via the switch 1. Therefore, the step-up transformer 6 is excited by the operation of the transistor 5. A high voltage is generated on the secondary side of the step-up transformer 6.

The current on the secondary side flows through diode 7 → capacitor 8 → diode 9 to charge capacitor 8. At this time, the transistor 5 generally operates at several tens to several hundreds of kHz, and the capacitor 8 is charged to a preset voltage of several hundreds of volts according to the time according to the circuit time constant. At this time, when the capacitor 8 is charged to the set value, the voltage detection circuit (not shown) stops the operation of the transistor 5 and controls the charging voltage to a constant value.

Next, when an internal combustion engine (not shown) rotates, the pulser coil 10 generates a pulse signal in synchronization with the rotation of the engine. The signal of the pulsar coil 10 is the trigger circuit 11
Is input to the thyristor 12 at the required ignition timing of the internal combustion engine with reference to the signal of the pulser coil 10.
A trigger signal is applied to the gate.

As a result, the thyristor 12 is turned on, and the electric charge of the capacitor 8 is discharged through the primary side of the ignition coil 13 (4). On the secondary side of the ignition coil 13, a high voltage of several tens of kV is generated due to this short-circuit current, and the spark plug 14 is discharged to ignite the internal combustion engine.

At this time, the time required for the capacitor 8 to discharge depends on the circuit time constant, but since it is generally about 100 μs, the output signal of the trigger circuit 11 is generally set to several hundreds of μs. This time (t1) is a preset time.

When the capacitor 8 is discharged, the discharge energy of the capacitor 8 is temporarily stored on the primary side of the ignition coil 13, and this energy is connected to the diode 9 connected in parallel to the ignition coil 13. Is short-circuited and disappears gradually. Therefore, the capacitor 8 is charged in the reverse direction only by the forward voltage drop (about 1 V) of the diode 9. Therefore, during the output signal pulse width (t1) of the trigger circuit 11, the capacitor 8 finishes discharging and the current flowing through the thyristor 12 disappears. Therefore, the thyristor 12 turns off when the signal of the trigger circuit 11 ends.

However, at this time, the DC-DC converter 16
Is operating, the output current flows through the thyristor 12, the thyristor 12 cannot be turned off, the capacitor 8 is not recharged, and therefore the internal combustion engine cannot be ignited. Therefore, the converter stop circuit 1 is included in the CDI.
When the output signal of the trigger circuit 11 is generated, the converter stop circuit 17 is a DC-DC converter.
The operation of the data 16 is stopped.

However, if the DC-DC converter 16 is operating just before the thyristor 12 is turned on, the DC-DC converter 16 operates.
Energy is output until the output of the converter 16 is short-circuited by the thyristor 12 and the thyristor 12 can be turned off.
It takes about 1 ms to disappear. At high temperatures, this time is extended. In addition, the current continues to flow due to the dielectric absorption of the capacitor 8 and the thyristor 12 becomes OF.
F (5) is no longer possible, and it takes about 1.5 ms for the thyristor 12 to turn off at low temperatures.

In order to shorten the stop time (t2), the value of the resistor 18 may be set small.
If is smaller, the output of the trigger circuit 11 must be larger, and the drive circuit of the thyristor 12 becomes larger. Further, since the problem that the thyristor 12 cannot be turned on when the battery voltage is low, etc. occurs, the resistance 18 must be set to about several kΩ. Therefore, the stop time (t2) of the converter stop circuit 17 must be set to about 2 ms.

By the way, in consideration of the maximum operating speed of the internal combustion engine, generally in a motorcycle or the like, 12000 rpm to 150 rpm.
00 rpm and the time (t0) of one rotation is 5 ms to 4
ms. Therefore, at the maximum operating speed of the internal combustion engine,
Although the time required for ignition is several hundreds of μs, the converter stop time (t2) must be about 2 ms, and the charging time (t4) of the capacitor 8 becomes 3 ms to 2 ms. Therefore, when a small DC-DC converter is used, there is a drawback that the charging voltage drops at high speed.

[0013]

The present invention has been made in order to solve the drawback of the conventional CDI in that the charging voltage is lowered at the time of high rotation, and shortens the converter stop time to extend the charging time. It is an object of the present invention to provide an ignition device for an internal combustion engine, which secures a charging voltage and improves ignition performance.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 3 shows an embodiment of the present invention. FIG. 3 shows a part of the circuit block 20 of FIG. 1, and the other parts are the same as those of FIG. (6) The operation of the present invention will be described below with reference to FIG.

In this circuit, when the switch 1 is closed as in the conventional CDI, the power supply circuit 3 operates, the transistor 5 turns on and off, and the DC-DC converter 16 operates to charge the capacitor 8. When the output of the pulsar coil 10 is input to the trigger circuit 11, the thyristor 12 is triggered and ignition is performed at a preset required ignition timing of the internal combustion engine.

At this time, the discharge time (t
1) is about 100 μs as in the conventional circuit. By the way, the converter stop circuit 17 has the same structure as the conventional DC-D.
It is provided to stop the C converter and turn off the thyristor.

In the gate circuit 21, the output of the trigger circuit 11 is LOW (in a non-triggered state), and
The output of the inverter stop circuit 17 is high (a state in which the converter is stopped) for the time (t3), the transistor 22
Turn on.

As a result, the resistor 23 is inserted between the gate and the cathode of the thyristor 12, and the impedance between the gate and the cathode of the thyristor 12 is lowered. Generally, the holding current (IH) of a thyristor has a characteristic that it becomes larger as the gate impedance is lower. Therefore, the thyristor 12 is controlled by the operation of the transistor 22.
When the impedance decreases, the holding current increases.
Therefore, the DC stopped by the converter stop circuit 17
-Emission current of DC converter 16 or capacitor 8
At a low current such as the current due to dielectric absorption at low temperature,
The thyristor 12 cannot continue to be turned on, and the thyristor 12 is turned on almost at the same time when the transistor 22 is turned on.
FF.

Therefore, the converter stop time (t2) may be set to be longer than the trigger time (t1) by several hundreds of μs, and the converter stop time (t2) can be significantly shortened as compared with the conventional circuit (7). For this reason, the capacitor charging time (t4) at the same rotation speed is relatively extended as compared with the conventional circuit. As a result, even if a small DC-DC converter is used, the capacitor charging voltage can be increased at high rotation speed.

According to the present invention, while the thyristor is being triggered, the gate impedance of the thyristor 12 is only the resistor 18 because the transistor 22 is OFF.
You can set the dance high. Therefore, since the thyristor can be triggered by the same trigger circuit as the conventional one, it is not necessary to upsize the trigger circuit.

Further, in the present invention, the capacitor charging time (t
In the case of 4), the gate impedance can be set high as in the conventional case, so that a gate voltage detection circuit used for a false firing prevention circuit or the like when the VBO of the thyristor 12 deteriorates can be connected.

By the way, the transistor 22 is turned off up to this point.
As described above, the thyristor 12 is set to O for the time (t3) for N.
Since it may be several hundreds of μs or more before FF, a timer circuit 24 such as a single multivibrator is inserted in the output stage of the gate circuit 21 as shown in FIG.
Pre-set capacitor charging time (t4) regardless of 2)
It is also possible to set a shorter time (t3).

Further, in the case of such a configuration, in order to connect the gate voltage detection circuit of the thyristor at the time of charging,
The maximum value of the time (t3) for turning on the transistor 22 is limited to the time (t2) before the start of operation of the converter, and the time (t3) for turning on the transistor 22 is set at an arbitrary shorter time. It is natural that things are possible.

By the way, as shown in FIG. 4, the trigger circuit 11,
Resistor 19, gate circuit 21, transistor 22, resistor 2
Although the explanation has been given using the drive circuit of the thyristor 12 according to No. 3 (8), the transistors 22 and 25 and the resistor 2 as shown in FIG.
It is also possible to use a drive circuit having a configuration such as 3, 26.

The resistor 23 used for the impedance conversion of the present invention may of course be 0Ω.

[0026]

As described above, the time until the thyristor is turned off can be shortened by reducing the gate impedance of the thyristor for a certain period of time after the termination of the thyristor trigger, and a small DC-DC can be obtained. Even if the converter is used, the charging voltage of the ignition capacitor can be increased until the internal combustion engine rotates at high speed. Therefore, it is possible to provide an ignition device for an internal combustion engine having improved ignition performance. Also at the same time VBO
It is possible to have an erroneous firing prevention circuit or the like due to deterioration, so that the effect is great.

[Brief description of drawings]

FIG. 1 is an example of a conventional circuit

FIG. 2 is a time chart of each part of FIGS. 1 and 3.

FIG. 3 One embodiment of the present invention

FIG. 4 is another embodiment of the present invention.

FIG. 5 shows another embodiment of the drive circuit configuration of the present invention.

[Explanation of symbols]

 Switch 1 Battery-2 Power supply circuit 3 (9) Astable multivibrator 4 Transistor 5, 22, 25 Step-up transformer 6 Diode 7, 9, 15 Capacitor 8 Pulser coil 10 Trigger circuit 11 Thyristor 12 Ignition coil 13 Spark plug 14 DC-DC converter 16 Converter stop circuit 17 Resistors 18, 19, 23, 26 Control circuit block 20 Gate circuit 21 Monostable multivibrator 24

Claims (5)

[Claims] 1. A DC-DC converter connected to a power source and comprising a series circuit of a transformer and a switching element, a capacitor charged by the output of the DC-DC converter, and a primary side of the capacitor, An ignition coil having a secondary side connected to an ignition plug, a thyristor connected to discharge the electric charge of the capacitor through the primary side of the ignition coil, and a pulser coil that generates a pulse signal in synchronization with the operation of the internal combustion engine, A trigger circuit that triggers the thyristor at the required ignition timing of the internal combustion engine by the signal of the pulsar coil, and the D circuit when the thyristor is conductive.
In an ignition device for an internal combustion engine, comprising a converter stop circuit for stopping a C-DC converter for a predetermined time, from the end of the trigger signal of the trigger circuit to the end of the stop signal of the converter stop circuit. The ignition device for an internal combustion engine is provided with an impedance conversion circuit for reducing the impedance between the gate and the cathode of the thyristor or between the gate and the ground of the thyristor. 2. A DC-DC converter which is connected to a power supply and which is composed of a series circuit of a transformer and a switching element, a capacitor charged by the output of the DC-DC converter, and a primary side of which is connected to the capacitor. An ignition coil having a secondary side connected to an ignition plug, a thyristor connected to discharge the electric charge of the capacitor through the primary side of the ignition coil, and a pulser coil that generates a pulse signal in synchronization with the operation of the internal combustion engine, A trigger circuit that triggers the thyristor at the required ignition timing of the internal combustion engine by the signal of the pulsar coil, and the D circuit when the thyristor is conductive.
In an ignition device for an internal combustion engine, comprising a converter stop circuit for stopping a C-DC converter for a predetermined time, an arbitrary time shorter than the time when the trigger signal of the trigger circuit ends and the time when the trigger signal of the next cycle occurs. , Between the gate and the cathode of the thyristor, or between the gate and the ground.
Internal combustion engine characterized by being equipped with an impedance conversion circuit for reducing dance (2) Ignition device. 3. A DC-DC converter connected to a power supply, comprising a series circuit of a transformer and a switching element, a capacitor charged by the output of the DC-DC converter, and a primary side connected to the capacitor. An ignition coil having a secondary side connected to an ignition plug, a thyristor connected to discharge the electric charge of the capacitor through the primary side of the ignition coil, and a pulser coil that generates a pulse signal in synchronization with the operation of the internal combustion engine, A trigger circuit that triggers the thyristor at the required ignition timing of the internal combustion engine by the signal of the pulsar coil, and the D circuit when the thyristor is conductive.
In an ignition device for an internal combustion engine, comprising a converter stop circuit for stopping a C-DC converter for a predetermined time, from the end of the trigger signal of the trigger circuit to the end of the stop signal of the converter stop circuit. Ignition of an internal combustion engine provided with an impedance conversion circuit for reducing the impedance between the gate and the cathode or between the gate and the ground of the thyristor for a short arbitrary time. apparatus. 4. A gate voltage detecting circuit for detecting a gate voltage of the thyristor during charging of the capacitor, wherein the gate voltage detecting circuit is provided. Ignition device for internal combustion engine. 5. The breakdown voltage deterioration prevention circuit for preventing reverse rotation of an internal combustion engine due to erroneous firing when the breakdown voltage (VBO) of the thyristor is deteriorated, according to any one of claims 1 and 3. Ignition device for internal combustion engine.