JPS6336425B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a capacitor charge/discharge type ignition device,
In particular, the present invention relates to an ignition device equipped with a retardation device.

If the engine runs faster than necessary, it is not only dangerous but can also damage the engine.
Therefore, when the engine speed rises above a predetermined speed, countermeasures are taken such as stopping the engine or suppressing its rotation.
In particular, in the case of suppressing over-rotation, there are two types: one using a mechanical governor mechanism and the other using electrical retardation. The present invention provides a novel device that suppresses engine overspeed by electrically retarding the ignition timing when the engine speed increases.

That is, the present invention connects a series circuit of a retard switching element and a diode to the output terminal of a signal coil of a capacitor charge/discharge type ignition device, and connects a retard capacitor in parallel to this diode. The output end of this retard capacitor is connected to the control electrode of the ignition switching element. When the engine rotation speed exceeds a predetermined rotation speed, the output of the signal coil is bypassed by the series circuit of the retard switching element and the diode, and
This invention relates to a capacitor charge/discharge type ignition device in which an ignition switching element is retarded and made conductive through a retard capacitor that is charged by the voltage across the terminals of the diode.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below by way of example with reference to the drawings. FIG. 1 shows the circuit configuration of a capacitor charge/discharge type ignition device according to this embodiment. In this figure, an exciter coil 1 for obtaining an output for ignition is connected to a charging/discharging capacitor 3 via a diode 2. Furthermore, capacitor 3
is connected to the primary coil 6 of the ignition coil 5 via the thyristor 4. A secondary coil 7 of the ignition coil 5 is connected to a spark plug 8.

The gate of the ignition thyristor 4 is connected to the output end of the signal coil 9 via a series circuit of a diode 10 and a resistor 11. Further, the output end of the signal coil 9 is connected to the anode of the thyristor 4 via a diode 12. Further, a diode 13 is connected between the anode and cathode of the thyristor 4 to protect the thyristor. Also, between the gate and cathode of this thyristor 4, there is a resistor 14 for gate protection.
is connected.

Further, the circuit shown in FIG. 1 is provided with a retard circuit, as indicated by a dotted line 15. This retard circuit 15 has a capacitor 16 for detecting the engine speed, and both ends thereof are connected to both ends of the signal coil 9 via diodes 17 and 18, respectively. Note that the diodes 17 and 18 allow only the voltage on the negative side of the signal coil 9 to be applied to the capacitor 16. A variable resistor 19 is connected in parallel to the capacitor 16. Also, this capacitor 16
is connected to the gate of the retard thyristor 20.

The anode of the thyristor 20 is the diode 1 mentioned above.
0, and the cathode of this thyristor 20 is connected to the negative terminal of the signal coil 9 through a series circuit of three diodes 21, 22, and 23. There is. The series circuit of diodes 22 and 23 includes a resistor 24 and a light emitting diode 25 in parallel.
A series circuit with is connected. Further, the connection point between the diode 21 and the diode 22 is connected to an integrating circuit consisting of a variable resistor 26 and a capacitor 27. The output end of this capacitor 27 is connected to the gate of the ignition thyristor 4 via a diode 28.

Next, the operation of the ignition device having the above configuration will be explained. When the engine speed is low, the output shown by the solid line in FIG. 2 is obtained from the signal coil 9. Of these outputs, the minus side output of the signal coil 9 is applied to the capacitor 16. Therefore, the voltage between the terminals of the capacitor 16 becomes low as shown by the dashed line in FIG. As is clear from this figure, in order to quickly discharge the low voltage charge charged in the capacitor 16, the positive side of the coil ₉ is applied to the anode of the thyristor 20 to make the thyristor 20 conductive. The voltage across the terminals of the capacitor 16 applied to the gate of the thyristor 20 becomes equal to or lower than the gate trigger voltage _V3 of the thyristor 20 before the output becomes available. In this case, thyristor 20
is not conductive, and the retard circuit 15 does not operate.

Therefore, when the engine speed is low, normal ignition operation is performed and no retardation is performed. That is, the generated output taken out by the exciter coil 1 is charged to the capacitor 3 via the diode 2. An output waveform as shown by the solid line in FIG. 2 is obtained from the signal coil 9. Of this output waveform, the output on the positive side is connected to the diode 10 because the retard circuit 15 does not operate as described above.
and is supplied to the gate of the ignition thyristor 4 via the resistor 11. When the voltage applied to this gate reaches the gate trigger voltage indicated by V ₁ in FIG. It is suddenly supplied to the side coil 6. Therefore, a high voltage is taken out from the secondary coil 7, and this high voltage is supplied to the ignition plug 8, whereby the ignition plug 8 generates a spark and performs an ignition operation.

Next, the circuit operation when the engine speed increases and the engine is retarded will be described. Note that the charging of the capacitor 3 by the exciter coil 1 at this time is the same as in the case of the operation before the retardation. When the engine speed increases, the voltage on the negative side of the signal coil 9 applied to the capacitor 16 increases
In order to increase as shown by the solid line in the figure,
The voltage across the terminals of this capacitor 16 is applied to the _anode of the thyristor 20 as shown by the dashed line in FIG. , the gate trigger voltage V is maintained at a value greater than or equal to ₃ . Therefore, the gate of the thyristor 20 remains open until the positive output of the signal coil 9 reaches _V2 . Therefore, when the output of the signal coil 9 reaches _V2 as shown in FIG. 3, the thyristor 20 becomes conductive. For this purpose, the positive output of the signal coil 9 is connected to the thyristors 20 and 3.
It is bypassed to a series circuit of three diodes 21, 22, and 23. Therefore, the output of the signal coil 9 is no longer sufficiently supplied to the gate of the ignition thyristor 4, and the thyristor 4 is no longer conductive.

Thyristor 20 conducts and diodes 22,2
When current flows through diodes 3, a voltage drop occurs across diodes 22 and 23 due to this current. The voltage drop across these diodes 22 and 23 charges the capacitor 27 via the variable resistor 26, and the voltage of the capacitor 27 gradually increases. At this time, the voltage applied to the series circuit of diodes 22 and 23 and the voltage across the terminals of capacitor 27 are respectively shown by a dashed line and a dashed double dotted line in FIG. When the voltage across the terminals of the capacitor 27 reaches the gate trigger voltage _V4 of the thyristor 4 as shown in FIG. 4, this voltage opens the gate of the ignition thyristor 4 via the diode 28. Therefore, the thyristor 4 becomes conductive with a delay of the delay time shown in FIG. 4, and the capacitor 3
is supplied to the ignition coil 5. For this reason, the plug 8 is retarded by the ignition coil 5 to perform the ignition operation.

In addition, in the graph shown in FIG. 4, the trigger voltage V ₁ when the thyristor 4 is conductive when the retard operation is not performed and the trigger voltage V 1 when the thyristor 4 is conductive by the capacitor 27 when the retard operation is performed. The difference between the trigger voltage V ₄ and each other is as follows:
This is because the resistor 11 is connected between the positive terminal of the signal coil 9 and the gate of the thyristor 4. That is, this resistance 11 causes the signal coil 9
, the thyristor 4 becomes conductive when the high trigger voltage V ₁ is output when the retarding operation is not performed. Since there is an apparent difference in the trigger voltage of the thyristor 4 before and after the retard,
The retard angle range can be widened.

Furthermore, when this retarding operation is performed, the current bypassed through the thyristor 20 flows to the light emitting diode 25 via the diode 21 and the resistor 24. Therefore, this light emitting diode 25 emits light. Therefore, the light emitting diode 25 provides an indication that the retarding operation is being performed.

As described above, according to the ignition system of this embodiment, when the engine speed exceeds a predetermined speed, the retardation operation is automatically performed, thereby suppressing engine overspeed. It turns out. Since the engine speed when the retarding operation is performed is determined by the time constant of discharging the capacitor 16, the resistance value of the variable resistor 19 connected in parallel with the capacitor 16 is changed. Therefore, the set rotation speed can be changed freely. Furthermore, by changing the resistance value of the variable resistor 26, which together with the capacitor 27 constitutes an integrating circuit, the voltage rise characteristics of the capacitor 27, that is, the voltage rise characteristics shown by the two-dot chain line in FIG. 4, can be changed. . Therefore, by adjusting the resistance value of the variable resistor 26, the retard angle can be adjusted. Since the trigger voltage V ₄ of the thyristor 4 during retard is lower than the trigger voltage V ₁ before retard, as is clear from FIG. 4, the resistance value of the variable resistor 26 must be changed. Therefore, the delay time can be freely changed within the range from when the output of the coil 9 reaches V ₁ until the voltage applied to the series circuit of the diodes 22 and 23 falls. That is, according to this embodiment, the retard angle range can be made very wide.

FIG. 5 shows the state of change in the retard angle by the ignition device according to this embodiment. As is clear from this figure, the ignition angle is almost constant before the retardation, but when the ignition angle is retarded, the ignition angle is delayed in steps, and thereafter it is continuously retarded. The reason why the angle is retarded in steps and then further retarded continuously is as follows.
That is, the voltage for charging the capacitor 27 is the voltage between the terminals of the series circuit of the diodes 22 and 23. Therefore, even if the engine speed increases and the output voltage of the signal coil 9 increases, The voltage between the terminals of the series circuit of diodes 22 and 23 is clamped to a substantially constant value. Therefore, if the resistance value of the variable resistor 26 is kept constant, the time required for the capacitor 27 to reach the predetermined voltage _V4 will always be constant, regardless of the engine speed. Therefore, the time delayed by this capacitor 27 is constant. On the other hand, as the engine speed increases, the period of one rotation becomes gradually shorter. Therefore, if the retard time is constant, the retard angle becomes relatively large. That is, according to this embodiment, the higher the engine speed, the more effectively the retardation operation is performed, thereby making it possible to prevent the engine from overspeeding.

Further, in this embodiment, when the retard operation is performed as described above, a part of the current passing through the thyristor 20 passes through the light emitting diode 25, which causes the light emitting diode to light up and perform the retard operation. It will be displayed. Therefore, by notifying the user that the retardation operation is being performed, there is an advantage that psychological anxiety can be removed. Moreover, this display can be achieved by a simple configuration in which the light emitting diode 25 is simply connected to the retard circuit 15. Needless to say, the light-emitting diode 25 does not display the retard angle when the thyristor 20 is not conductive, that is, when the retard operation is not performed.

As described above, according to the present invention, since the retard angle is retarded using the retard angle capacitor, the retard angle can be freely changed by controlling the charging characteristics of this capacitor. can.
Further, according to the present invention, since the retarding capacitor is charged by the clamp voltage of the diode, the voltage rise time becomes a substantially constant value. Therefore, as the engine speed increases, the retard angle can be made to continuously increase accordingly. Therefore, the higher the engine speed is, the more effectively the retardation operation is performed, thereby effectively preventing overspeeding of the engine.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a capacitor charge/discharge type ignition device according to an embodiment of the present invention, and Fig. 2 shows the output waveform of the signal coil when the engine speed is low and no retard operation is performed. Graphs, Figure 3 is a graph showing the output waveform of the signal coil when the engine speed is high and retard operation is being performed, Figure 4 is a graph showing the charging characteristics of the retard capacitor, and Figure 5 is a graph showing the charging characteristics of the retard capacitor. The figure is a graph showing the ignition angle with respect to the engine rotation speed of the ignition system of this embodiment. In the symbols used in the drawings, 1... exciter coil, 3... charging capacitor, 4... ignition thyristor, 5... ignition coil, 9... signal coil, 20... retard thyristor, 22 ,2
3...Diode, 25...Light emitting diode, 2
7...This is a retardation capacitor.

Claims (1)

[Claims] 1. The output of the exciter coil is stored in a charging capacitor, and the ignition switching element is made conductive by the output of the signal coil, thereby discharging the electric charge of the charging capacitor and igniting. In such an ignition system, a series circuit of a retard switching element and a diode is connected to the output terminal of the signal coil, and a retard capacitor is connected in parallel to this diode, and the retard The output terminal of the ignition switching element is connected to the control electrode of the ignition switching element, and when the engine speed exceeds a predetermined rotation speed, the output of the signal coil is controlled by the series circuit of the retard switching element and the diode. is bypassed, and the ignition switching element is made conductive with a retard through a retard capacitor charged by the voltage across the terminals of the diode. Capacitor charge/discharge type ignition device. 2. The device according to claim 1, characterized in that a display means is connected in series with the retard switching element so that a display is displayed when retardation is performed. Capacitor charge/discharge type ignition device.