JPH0639097Y2 - Ignition device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a capacitor discharge type ignition device for an internal combustion engine.

[Prior Art] Recently, as a capacitor discharge type ignition device for an internal combustion engine, a so-called pulsarless type ignition device which does not use a pulsar coil that outputs a signal for determining an ignition timing has been widely used.

FIG. 4 shows a circuit configuration of a conventional ignition device of this type. In FIG. 4, 1 is an ignition coil, 2 is an exciter coil provided in a magnet generator driven by an internal combustion engine, and 3 is ignition energy. Storage capacitor, 4 is a discharge control thyristor, 5 to 8 are diodes, 9 is a resistor,
Reference numeral 10 is a spark plug attached to a cylinder of an engine (not shown). In this example, exciter coil 2 → diode 5
→ capacitor 3 → primary coil of ignition coil 1 → diode 6 → exciter coil 2 circuit constitutes a capacitor charging circuit that charges the capacitor 3 with the positive half cycle output of the exciter coil 2 to the polarity shown in the figure. The circuit of 2 → diode 7 → resistor 9 → diode 8 → exciter coil 2 constitutes a trigger circuit that supplies a trigger signal to the thyristor 4 with the negative half cycle output of the exciter coil.

In the above ignition device, the exciter coil 2 induces an AC voltage in synchronization with the rotation of the engine. Exciter coil 2
When a positive half-cycle voltage in the direction of the solid arrow is induced, exciter coil 2 → diode 5 → capacitor 3 → primary coil of ignition coil 1 → diode 6 → exciter coil 2 When the exciter coil 3 induces a negative half-cycle voltage in the direction of the dashed arrow shown in the figure, the exciter coil 2 →
A current flows through the path of diode 7 → resistor 9 → diode 8 → exciter coil 2 to generate a voltage across resistor 9. When the voltage generated across the resistor 9 becomes equal to or higher than a predetermined threshold level, the thyristor 4 is triggered and becomes conductive, and the charge of the capacitor 3 is discharged to the primary coil of the ignition coil. As a result, a high voltage for ignition is induced in the secondary coil of the ignition coil, and the high voltage causes a spark in the spark plug 10 to ignite the engine.

[Problems to be Solved by the Invention] In the above ignition device, when the peak value of the output of the exciter coil rises as the engine speed increases, the negative half-cycle output voltage of the exciter coil causes the thyristor 4 to output. The ignition timing advances because the phase reaching the trigger level advances, and conversely, when the output voltage of the exciter coil decreases with the increase of the rotation speed, the ignition timing is delayed. In general, the output voltage of the magneto generator tends to increase in the low and medium speed range of the engine as the rotation speed increases, and in the high speed range, the output voltage tends to decrease due to the armature reaction. The ignition characteristic obtained by the ignition device is as shown by a curve a shown by a broken line in FIG. 3, and the ignition timing is advanced in the low and medium speed regions of the engine and delayed in the high speed region.

As described above, in the conventional ignition device, the ignition timing advances when the engine is running at low speed, so the Ketchin phenomenon occurs at the start of a two-cycle engine, making it difficult to start the engine. Particularly, in the kick start type engine, the Ketchin phenomenon occurs. At that time, there is a risk that the driver may be injured due to the reaction that acts on the kick pedal.

In this case, it is possible to set the ignition timing at the start to a position that is sufficiently delayed so that the Ketchin phenomenon does not occur even if the ignition timing advances at low speed. It becomes impossible to set the ignition timing in the region to a sufficiently advanced position, and it becomes impossible to secure the output of the engine.

The purpose of the present invention is to set the ignition timing at a low speed to a delayed position, and to advance the ignition timing in the middle and high speed range to secure the output of the engine. To provide a device.

[Means for Solving the Problems] The present invention is directed to an ignition coil, an exciter coil provided in a magnet generator driven by an internal combustion engine, and an ignition energy storage capacitor provided on the primary side of the ignition coil. And a capacitor charging circuit that charges the ignition energy storage capacitor to one polarity with the positive half cycle output of the exciter coil, and discharges the charge of the ignition energy storage capacitor through the primary coil of the ignition coil when conducting. In an internal combustion engine ignition device comprising a thyristor thus provided, a trigger capacitor connected in series to an ignition energy storage capacitor,
By flowing a current from the exciter coil through the trigger capacitor and the current limiting element during the negative half cycle of the exciter coil in a direction that discharges the electric charge charged in the trigger capacitor during the positive half cycle. A trigger circuit for generating a voltage for triggering across the current limiting element, and a voltage generated across the triggering capacitor during the positive half cycle of the exciter coil or the current during the negative half cycle of the exciter coil. A trigger signal input circuit that supplies a trigger signal to the thyristor when the voltage generated across the limiting element exceeds a predetermined level is provided, and the trigger capacitor of the trigger capacitor when the rotation speed of the internal combustion engine exceeds a set value. Set the capacitance of the trigger capacitor so that the voltage across both ends is above the specified level. Those was boss.

[Advantage of the Invention] With the configuration described above, the terminal voltage of the trigger capacitor does not reach the level that triggers the thyristor when the engine is running at low speed. Therefore, in the negative half cycle of the exciter coil, both ends of the current limiting element of the trigger circuit are connected. The resulting voltage triggers the thyristor to ignite. When the engine speed increases and enters the medium-high speed region, the terminal voltage of the trigger capacitor reaches a level that can trigger the thyristor in the positive half cycle of the exciter coil, so during the positive half cycle of the exciter coil. The ignition operation is started. As described above, in the present invention, the ignition operation is performed during the negative half cycle of the exciter coil when the engine is operating at low speed, and the ignition operation is performed during the positive half cycle of the exciter coil when operating at high speed. It is possible to make a large difference between the ignition timing of the engine and the ignition timing at the time of medium and high speeds, and even if the ignition timing at the time of low speed is set to a position sufficiently delayed from the top dead center of the engine, the ignition timing at the time of high speed is sufficient. It can be set in the advanced area. Therefore, it is possible to prevent the occurrence of the Ketchin phenomenon at low speed and to secure the output at medium and high speeds.

[Embodiment] An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the present invention. In FIG. 1, parts that are the same as the parts of the conventional example shown in FIG. In this embodiment, the ignition coil 1
One ends of the primary coil 1a and the secondary coil 1b are grounded, and one end of the ignition energy storage capacitor 3 is connected to the other end of the primary coil 1a. The cathode of the diode 5 is connected to the other end of the capacitor 3, and one end of the exciter coil 2 is connected to the anode of the diode 5. The anode of the thyristor 4 is connected to the connection point between the diode 5 and the capacitor 3, and the cathode of the thyristor 4 is grounded. One end of a trigger capacitor 11 is connected to the other end of the exciter coil 2, and the other end of the capacitor 11 is connected to the cathode of a diode 12 whose anode is grounded. The cathode of the Zener diode 13 is connected to the connection point between the capacitor 11 and the diode 12, and the anode of the Zener diode is connected to the gate of the thyristor 4. At both ends of the capacitor 11 are a diode 14 and a resistor whose anode is directed to the exciter coil side.
Series circuit with 15 connected in parallel, Zener diode
A resistor 16 is connected between the cathode of 13 and ground. The cathode of the diode 8 is also connected to one end of the exciter coil 2, and the anode of the diode is connected to the cathode of the thyristor 4. An ignition plug 10 is connected to the secondary coil of the ignition coil.

In this embodiment, the exciter coil 2 → diode 5 →
The capacitor 3 → primary coil 1a → diode 12 → trigger capacitor 11 → exciter coil 2 circuit constitutes a capacitor charging circuit for charging the ignition energy storage capacitor, and the trigger capacitor 11 ignites in the charging circuit of this capacitor. It is inserted in series with respect to the energy storage capacitor 3.

Further, in this embodiment, the exciter coil 2 → the capacitor 11
And a series circuit of a diode 14 and a resistor 15 → a resistor 16 → a diode 8 circuit, a positive half through the exciter coil through the trigger capacitor 11 and the resistor (current limiting element) 16 during the negative half cycle of the exciter coil 2. A trigger circuit is configured to generate a voltage for triggering across the resistor 16 by flowing a current in the direction for discharging the electric charge charged in the triggering capacitor during a half cycle.
Here, the electrostatic capacity of the trigger capacitor 11 is set to be sufficiently larger than the electrostatic capacity of the ignition energy storage capacitor 3, and the engine speed is set to a set value (rotation speed at which the engine moves from the low speed rotation range to the medium speed rotation range). The ratio of the electrostatic capacity of the ignition energy storage capacitor 3 to the electrostatic capacity of the trigger capacitor 11 is set so that the voltage across the trigger capacitor 11 reaches a level at which the Zener diode 13 conducts when the above is reached. ing.

Further, the Zener diode 13 causes the voltage generated across the trigger capacitor 11 during the positive half cycle of the exciter coil or the voltage across the resistor 16 during the negative half cycle of the exciter coil to reach a predetermined level or higher. A trigger signal input circuit is provided for supplying a trigger signal to the thyristor 4 when the trigger signal is input.

In the above embodiment, the exciter coil 2 induces an alternating voltage as shown in FIG. 2 (A) in synchronization with the rotation of the engine. FIG. 2B shows the waveform of the voltage Vr applied between the cathode of the Zener diode 13 and the ground at the rotation speed N1 in the low speed region and the rotation speed N2 in the medium and high speed regions.
Shows the waveform of the voltage Vgk between the gate and cathode of the thyristor 4. When the exciter coil 2 induces a positive half cycle voltage Ve, the exciter coil 2 → diode 5
→ Capacitor 3 → Primary coil 1a of ignition coil → Diode 12 → Capacitor 11 → Exciter coil 2 causes current to flow, and capacitors 3 and 11 are charged to the polarity shown in the figure. The voltage Vr is applied between the cathode of the Zener diode 11 and the ground by the voltage across the capacitor 11,
At low engine speeds (for example, when the engine speed is N1), the voltage Vr
Does not reach the level Vz for making the Zener diode 13 conductive, the thyristor 4 is not triggered by the voltage across the trigger capacitor 11.

Next, the exciter coil 2 has a negative half cycle voltage Ve ′.
When induced, current flows in the path of exciter coil 2 → capacitor 11 → resistor 16 → diode 8 → exciter coil 2 and exciter coil 2 → diode 14 → resistor 15 → resistor 16 → diode 8 → exciter coil 2,
A voltage Vr is generated across the resistor 16. When this voltage reaches a predetermined level at the angle θ1, the Zener diode 13 becomes conductive and a trigger signal is given to the thyristor 4, and the thyristor 4
Conducts. When the thyristor 4 becomes conductive, the electric charge of the capacitor 3 is discharged through the thyristor 4 and the primary coil 1a. Due to this discharge, a large magnetic flux change occurs in the iron core of the ignition coil, and a high voltage for ignition is induced in the secondary coil 1b.
Since this high voltage is applied to the spark plug 10, a spark is generated in the spark plug and the engine is ignited.

Next, when the rotation speed of the engine exceeds the set rotation speed Ns (for example, when the rotation speed becomes N2), the voltage across the capacitor 11 charged in the positive half cycle of the exciter coil 2 becomes high, and the positive voltage of the exciter coil 2 increases. Since the voltage Vr applied between the cathode of the Zener diode 13 and the ground exceeds the predetermined level Vz at the angle θ2 during the half cycle of, the Zener diode 13 becomes conductive at the position of the angle θ2 and the trigger signal is sent to the thyristor 4. Is given and the ignition operation is performed.

As described above, in the device of the present invention, the ignition operation is performed in the negative half cycle of the exciter coil when the engine is at a low speed, and the ignition operation is performed in the positive half cycle period of the exciter coil in the region of the set rotational speed or higher. Therefore, the characteristic of the ignition timing θi with respect to the rotation speed N is as shown by the curve b in FIG. 3, and the advance angle α can be widened. Therefore, even if the ignition timing in the low speed region near the starting rotation speed is set to a position that is sufficiently delayed so as not to cause the Ketchin phenomenon, the advance amount of the ignition timing in the medium and high speed regions can be made sufficiently large. It is possible to secure the output of the engine in the high speed range.

[Effect of the Invention] As described above, according to the present invention, the ignition operation is performed during the negative half cycle of the exciter coil at the constant speed of the engine, and during the positive half cycle of the exciter coil at the middle and high speeds. Since the ignition operation is performed, the difference between the ignition timing at low speed and the ignition timing at medium and high speed can be made large, and the ignition timing at low speed can be set at a position sufficiently delayed from the top dead center of the engine. Even if it is set, the ignition timing at the time of high speed can be set in a sufficiently advanced region. Therefore, there is an advantage that the Ketchin phenomenon can be prevented from occurring at low speed and the output at medium to high speed can be secured.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG.
FIG. 3 is a diagram showing the voltage waveform of each part of the figure, FIG. 3 is a diagram showing the ignition characteristics obtained by the conventional device and the ignition characteristic obtained by the device of the present invention, and FIG. 4 is the conventional device. It is a circuit diagram. 1 ... Ignition coil, 2 ... Exciter coil, 3 ... Ignition energy storage capacitor, 4 ... Thyristor, 5,
8,12,14 …… Diode, 11 …… Trigger capacitor, 1
6 ... Resistor (current limiting element).

Claims (1)

[Scope of utility model registration request] 1. An ignition coil, an exciter coil provided in a magnet generator driven by an internal combustion engine, an ignition energy storage capacitor provided on the primary side of the ignition coil, and a positive electrode of the exciter coil. A capacitor charging circuit for charging the ignition energy storage capacitor to one polarity with a half cycle output, and a capacitor charging circuit for discharging the electric charge of the ignition energy storage capacitor through the primary coil of the ignition coil when conducting. In the ignition device for an internal combustion engine including a thyristor, a trigger capacitor connected in series to the ignition energy storage capacitor, and a trigger capacitor from the exciter coil for the trigger during a negative half cycle of the exciter coil. Through the capacitor and the current limiting element during the positive half cycle A trigger circuit that causes a voltage for triggering across the current limiting element by causing a current in a direction to discharge the charge stored in the capacitor for rigging; and a triggering capacitor during a positive half cycle of the exciter coil. A trigger signal input circuit that supplies a trigger signal to the thyristor when the voltage across the current limiting element or the voltage across the current limiting element during a negative half cycle of the exciter coil exceeds a predetermined level. The capacitance of the trigger capacitor is set so that the voltage across the trigger capacitor becomes equal to or higher than the predetermined level when the rotation speed of the internal combustion engine exceeds a set value. Ignition device for internal combustion engine.