JPS6123661Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a capacitor discharge type internal combustion engine ignition system, and particularly for a capacitor discharge type internal combustion engine equipped with a circuit that controls the rotation speed by extinguishing the ignition spark when the engine overspeeds. This relates to an ignition device.

As a conventional device of this type, the one shown in FIG. 1 is known. In FIG. 1, reference numeral 1 denotes an exciter coil disposed within a magnet generator driven by an engine, and an alternating current voltage is induced in this exciter coil in synchronization with the rotation of the engine. One end of the exciter coil 1 is grounded, and the other end is connected to one end of the main capacitor 3 via a diode 2. 4 is an ignition coil having a primary coil 4a and a secondary coil 4b, one end of the primary coil 4a and the secondary coil 4b is grounded, and the other end of the primary coil 4a is connected to the other end of the main capacitor 3. There is. Secondary coil 4
A spark plug 5 attached to a cylinder of an engine (not shown) is connected in parallel to both ends of the primary coil 4a, and a diode 6 is connected in parallel to both ends of the primary coil 4a with its cathode on the ground side. A thyristor 7 is connected in parallel to both ends of the series circuit of the capacitor 3 and the primary coil 4a with its cathode being on the ground side, and a resistor 8 is connected in parallel between the gate and cathode of the thyristor 7. One end of a capacitor 9 is connected to the gate of the thyristor, and a series circuit of a diode 10 and a signal coil 11 disposed in a signal generator is connected between the other end of the capacitor 9 and ground.
A resistor 12 is connected in parallel to both ends of the capacitor 9, and the connection point between the cathode of the diode 10 and the capacitor 9 is connected to an over-rotation prevention thyristor 15 via a series circuit of a Zener diode 13 and a resistor 14.
connected to the gate. The thyristor 15 is connected in parallel to both ends of the exciter coil 1 with its cathode on the ground side, and a resistor 16 is connected in parallel between the gate and cathode of the thyristor 15. A diode 17 whose anode is connected to the ground side is also connected in parallel to both ends of the exciter coil 1.

In this ignition device, when a positive half-cycle voltage is induced in the exciter coil 1 in the direction of the arrow at time _t1 , the voltage from the exciter coil 1 to the diode 2, the main capacitor 3, and the primary coil 4a
A current flows through the charging circuit which returns to the exciter coil 1 through the , and the main capacitor 3 is charged. The waveform of the terminal voltage v _c of the main capacitor 3 is as shown in FIG. 5A. Next, when a signal voltage v _s (FIG. 5B) in the direction of the arrow shown in the figure is induced in the signal coil 11,
Diode 10, capacitor 9 and thyristor 7
The signal current i _s (fifth
Figure D) flows, and this signal current causes capacitor 9
is charged to the polarity shown. The signal current i _s is the time
When the trigger level of the thyristor 7 is reached at t ₂ , the thyristor 7 becomes conductive and the charge in the main capacitor 3 is discharged through the thyristor 7 and the primary coil 4a. As a result, a high voltage is induced in the secondary coil 4b, a spark is generated in the ignition plug 5, and the engine is ignited. The terminal voltage v _d of the capacitor 9 is as shown in FIG. 5C, and its maximum value corresponds to the peak value of the signal voltage v _s . While the rotational speed of the engine is low and the peak value of the output voltage of the signal coil 11 is low, the terminal voltage of the capacitor 9 does not reach a value that makes the Zener diode 13 conductive, so no firing signal is given to the thyristor 15. . Therefore, even if a positive half-cycle voltage is induced in the exciter coil 1, the thyristor 15 does not become conductive, and the main capacitor 3 can be charged without any problem. When the rotational speed of the engine increases to a certain degree and the peak value of the signal voltage V _s increases to a certain degree, the terminal voltage V _d of the capacitor 9 reaches a value that makes the Zener diode 13 conductive, and the capacitor 9
is charged at a constant time constant between the series circuit of the Zener diode 13 and the resistor 14, between the gate and cathode of the thyristor 15, through the parallel circuit of the resistor 16, and the resistor 8, and between the gate and cathode of the thyristor 15 is charged. A signal current i _g flows as shown in . When the terminal voltage of the capacitor 9 drops to a certain value and the voltage applied across the Zener diode 13 becomes lower than the Zener voltage, the signal current i
_g becomes zero and capacitor 9 charges through resistor 12. When the signal voltage _Vs is generated next, the capacitor 9 is recharged by the amount of charge it has lost. The period during which the signal current i _g flows between the capacitor 9 and the gate cathode of the thyristor 15 is constant regardless of the engine rotation speed, but the charging period of the main capacitor 3 becomes shorter as the engine rotation speed increases. . In the above ignition system, the period T during which the signal current i _g is equal to or higher than the trigger level of the thyristor 15 is the non-charging period T ₀ of the main capacitor 3 until the rotational speed of the engine reaches the set value.
The discharge time constant of the capacitor 9 is set so that it is shorter than . Therefore, while the rotational speed of the engine is lower than the set value, no firing signal is given to the thyristor 15 at time _t1 when a positive half-cycle voltage is induced in the exciter coil 1, and the thyristor 15 does not conduct. The main capacitor 3 is charged without any problem, and the ignition operation is performed without any problem.
When the rotational speed of the engine exceeds the set value, the time t1 at which a positive half-cycle voltage is induced in the exciter coil ₁ falls within the period T during which the signal current 1g exceeds the trigger level. At time _t1 , a positive half-cycle voltage is induced, and at the same time, thyristor 15 conducts, and main capacitor 3
charging is prevented. Therefore, the ignition operation is no longer performed, and the rotational speed of the engine decreases. When the rotational speed of the engine decreases, a positive half-cycle voltage is induced in the exciter coil 1 after the signal current i _g falls below the trigger level, and the main capacitor 3 is charged again and the ignition is activated. It will now be done normally. Thereafter, similar operations are repeated to control the rotational speed of the engine so as not to exceed the set value.

However, according to the above conventional device, the thyristor 7
Since the thyristor 15 is required in addition to the thyristor 15, the circuit becomes complicated, and of the terminal voltage of the capacitor 9,
The amount exceeding the Zener voltage of Zener diode 13 (corresponding to the voltage drop across resistors 14 and 16)
Since only the thyristor 15 can be effectively used as an ignition signal for the thyristor 15, it is necessary to use a thyristor 15 with high gate sensitivity, and there is a risk that the thyristor 15 may malfunction due to noise.

The purpose of this invention is to simplify the circuit configuration by controlling the rotation speed using a thyristor that controls the discharge of the main capacitor, and to prevent malfunctions caused by noise. The purpose is to provide an ignition device.

In order to solve the above problems, in particular, the ignition device for an internal combustion engine of the present invention includes a rotation control capacitor,
A rotation control capacitor charging circuit that charges the rotation control capacitor with the output of the signal coil, and a discharge circuit that discharges the rotation control capacitor at a constant time constant through the thyristor when the thyristor is conductive to discharge the charge of the main capacitor. The discharging circuit is configured such that when the rotational speed of the internal combustion engine reaches the set value, the charging start time of the main capacitor falls within a period in which a current greater than the holding current is flowing from the rotation control capacitor to the thyristor. A constant is set.

The ignition device of the present invention will be explained in detail below with reference to the illustrated embodiments.

FIG. 2 shows a first embodiment of the present invention, in which parts equivalent to those in FIG. 1 are denoted by the same reference numerals. In this embodiment, the basic circuit configuration of the capacitor discharge type ignition device is completely the same as that shown in FIG. To control the rotation of the engine,
A rotation control capacitor 19 is connected in parallel to both ends of the signal coil 11 via a diode 18 whose anode is on the non-ground terminal side of the signal coil. Diode 2 on the 20 side
1 to the anode of the thyristor 7. And signal coil 11, diode 18
A capacitor charging circuit for rotation control is configured by the capacitor 19 and the capacitor 19, and the capacitor 19 and the resistor 2
0, the diode 21, and the thyristor 7 constitute a rotation control capacitor discharge circuit.

In the embodiment of FIG. 2, the terminal voltage v _c of the main capacitor 3, the signal voltage v _s , the terminal voltage v _d of the capacitor 9, the signal current i _s flowing into the gate of the thyristor 7, and the voltage from the capacitor 19 to the resistor 20, the diode 21, and the thyristor The waveforms of the discharge current i _a flowing through 7 are shown as shown in FIGS. 6A to 6E with respect to time t. When a positive half-cycle voltage is induced in the exciter coil ₁ at time t1, the main capacitor 3 is charged. When a signal voltage _Vs is induced in the signal coil 11, a _current Is flows to the gate of the thyristor 7 through the capacitor 9, and at the same time a charging current flows to the capacitor 19.
is charged to the polarity shown. When the signal current i _s reaches the trigger level of the thyristor 7 at time t ₂ , the thyristor 7 becomes conductive, the charge in the main capacitor 3 is discharged through the thyristor 7 and the primary coil 4a, and an ignition operation is performed. Further, when the thyristor 7 becomes conductive, the charge in the capacitor 19 is discharged through the resistor 20, the diode 21, and between the anode and cathode of the thyristor 7 at a constant time constant. Therefore, even after the discharge of the main capacitor 3 is completed, the thyristor 7 remains conductive. Since the discharge time constant of the capacitor 19 is substantially constant, the period T during which the thyristor 7 remains conductive is substantially constant. Here, the time constant of the discharge circuit of the capacitor 19 is such that when the rotational speed of the internal combustion engine reaches the set value, the charging start time of the main capacitor 3 is a period during which a current higher than the holding current flows from the capacitor 19 to the thyristor 7. It is set to go inside. Therefore, if the engine speed is lower than the set value, the thyristor 7 will shut off before the main capacitor 3 starts charging, and the main capacitor will be charged without any problem.
When the rotational speed of the engine reaches the set value, the thyristor 7 becomes conductive at the charging start time _t1 of the main capacitor 3, and as a result, the main capacitor 3
charging is blocked and ignition operation is hindered. Therefore, the rotational speed of the engine is reduced and controlled so that the rotational speed does not exceed the set value.

When configured as in the above embodiment, the rotation can be controlled using the thyristor that controls the discharge of the main capacitor 3, so there is no need to use an extra thyristor, and the circuit configuration can be simplified. Furthermore, since the rotation control capacitor 19 is discharged to almost zero volts, its capacity can be reduced. Furthermore, since the capacitor 9 only needs to have a small capacity, the cost can be reduced. Furthermore, since the thyristor 7 may have low gate sensitivity, malfunctions due to noise can be prevented. Further, since the rotation control capacitor discharges through the thyristor, the discharge can be stably performed, and the discharge duration can be easily and reliably set.

Next, FIG. 3 shows a second embodiment of the present invention, in which the rotation control capacitor 1
9 is connected in series to the gate of thyristor 7. One end of capacitor 19 is connected to diode 2.
A resistor 12 is connected in parallel to both ends of this capacitor 19. A diode 23 is connected between the connection point between one end of the capacitor 19 and the diode 22 and the ground, with the anode on the ground side.
A series circuit of a signal coil 11 and a diode 10 is connected between the other end of the signal coil 9 and ground. The other end of the capacitor 19 is connected to the anode of the thyristor 7 through a resistor 20 and a diode 21.

In the embodiment shown in FIG. 3, the output voltage of the signal coil 11 charges the capacitor 19 to the polarity shown. At the same time, a signal current is applied to the thyristor 7,
When this signal current reaches the trigger level, the thyristor 7 becomes conductive and ignition is performed. Furthermore, when the thyristor 7 becomes conductive, the charge in the capacitor 19 is transferred to the resistor 2.
0, the diode 21, the thyristor 7, and the diode 23 are discharged at a constant time constant, and the thyristor 7 is kept in a conductive state for a certain period of time.

In the embodiment shown in FIGS. 2 and 3,
Since the thyristor 7 becomes conductive during the charging of the capacitor 19, the capacitor 19 is only charged to a voltage corresponding to the voltage drop across the resistor 20, and the output current of the signal coil 11 increases. In addition, since the initial value of the discharge current of the capacitor 19 is large and the current value decreases as time passes, the capacitor 19
At the end of the discharge, the conduction of the thyristor 7 becomes unstable, and there is a risk that the set rotational speed may vary, albeit slightly. In order to improve these points, it is necessary to connect the gate G of the field effect transistor FET to a resistor R instead of the resistor 20 as shown in FIG.
A constant current circuit connected to the source S via the capacitor 19 may be connected to keep the discharge current of the capacitor 19 substantially constant.

In the embodiment shown in FIG. 2, the signal current is limited by supplying a signal to the gate of the thyristor 7 via a bias circuit consisting of a capacitor 9 and a resistor 12. The same operation can be achieved by replacing the parallel circuit with another current limiting circuit, for example, a constant current circuit as shown in FIG.

As described above, according to the present invention, when the rotational speed of the internal combustion engine reaches a set value, a current greater than the holding current flows from the rotation control capacitor to the thyristor that controls the main discharge, thereby charging the main capacitor. Since the rotation of the engine is controlled by preventing the rotation of the engine, the rotation of the engine can be controlled with a simple configuration. Further, since a thyristor for controlling discharge of the main capacitor is used as a switch means for preventing charging of the main capacitor, a thyristor with low gate sensitivity can be used, and malfunctions due to noise can be prevented.

[Brief explanation of the drawing]

Figure 1 is a connection diagram showing a conventional example, Figures 2 and 3
The figures are connection diagrams showing different embodiments of the present invention, and FIG. 4 is a connection diagram showing an example of a constant current circuit that can be used in the embodiments of FIGS. 2 and 3.
5A to 5E are diagrams showing signal waveforms at various parts of the apparatus shown in FIG. 1, and FIGS. 6A to 6E are diagrams showing signal waveforms at various parts in the embodiment shown in FIG. 1...Exciter coil, 2...Diode,
3... Main capacitor, 4... Ignition coil, 5...
Spark plug, 7... Thyristor, 10, 18, 2
1...Diode, 11...Signal coil, 19...
...Rotation control capacitor.

Claims (1)

[Scope of utility model registration request] an ignition coil, a main capacitor provided on the primary side of the ignition coil, and a charging circuit that charges the main capacitor to one polarity with the output of an exciter coil that induces a voltage in synchronization with the rotation of the internal combustion engine; A thyristor is provided to discharge the electric charge of the main capacitor through the primary coil of the ignition coil when conductive, and a signal coil that generates a signal in synchronization with the rotation of the internal combustion engine is used as a signal source to control the ignition timing. A rotation control capacitor; a rotation control capacitor charging circuit that charges the rotation control capacitor with the output of the signal coil; and a discharge circuit that discharges the rotation control capacitor at a constant time constant between the anode and cathode of the thyristor when the thyristor is conductive, and when the rotation speed of the internal combustion engine reaches a set value, the main capacitor is discharged. An ignition device for an internal combustion engine, characterized in that the time constant of the discharge circuit is set so that the charging start time falls within a period in which a current greater than a holding current is flowing from the rotation control capacitor to the thyristor. .