JPS6141985Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a capacitor discharge type ignition device for an internal combustion engine that is equipped with an overspeed prevention circuit.

The overspeed prevention circuit used in this type of ignition device is designed to stop the ignition operation when the rotation speed is higher than the control speed. The engine's rotational speed is detected using the output of It was designed to prevent it. However, if the output of the positive half cycle of the exciter coil is short-circuited in this way, the rise of the negative direction output will be delayed due to armature action, so the overspeed prevention operation will start (misfire will start). There is a drawback that the difference between the rotational speed at which the rotational speed returns to the normal state becomes large and backup fire is likely to occur during the overspeed prevention operation.

An object of the present invention is to provide an ignition device for an internal combustion engine that eliminates the above-mentioned drawbacks by preventing armature reaction from occurring during overspeed prevention operation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below along with embodiments thereof with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In the figure, 1 is an ignition coil having a primary coil 1a and a secondary coil 1b, and 2 is an ignition coil attached to a cylinder of an engine, and a secondary coil 1b. A connected spark plug, 3 is an ignition control circuit that controls the primary current of the ignition coil 1 to generate a high voltage in the secondary coil 1b at the ignition position of the engine, and 4 is arranged in a magnet generator driven by the engine. An exciter coil 5 is an over-speed prevention circuit provided between the exciter coil 5 and the ignition control circuit 3.

The ignition control circuit 3 includes an ignition energy storage capacitor 3 whose one end is connected to one end of the primary coil 1a.
01, and the other end of this capacitor 301 is connected to each cathode of diodes 302 and 303 and the anode of a discharge control thyristor 304. The cathode of the thyristor 304 is connected to the anode of a diode 305 whose cathode is grounded, and a resistor 306 is connected in parallel between the gate and cathode of the thyristor 304. thyristor 30
The anode of a Zener diode 307 is connected to the gate of 4, and the cathode of the Zener diode 307 is connected to the anode of the diode 303. A resistor 30 is connected between the cathode of the Zener diode 307 and the cathode of the thyristor 304.
8 is connected, and a diode 309 whose anode is grounded is connected between the cathode of the Zener diode 307 and the ground. diode 302
The cathode of the diode 310 is connected to the anode of the thyristor 304 , and the anode of the diode 310 is connected to the cathode of the thyristor 304 . Further, a diode 311 is connected in parallel to both ends of the primary coil 1a with the anode facing the capacitor 301, and each part of the capacitor 301 to the diode 311 constitutes a capacitor discharge type ignition control circuit.

The over-rotation prevention circuit 5 includes an over-rotation prevention thyristor 501 whose anode is connected to the non-grounded terminal of the exciter coil 4.
A diode 502 having a direction opposite to that of the thyristor is connected in parallel to both ends of the thyristor. Thyristor 501
One end of a resistor 503 is connected to the anode of the resistor 503, and the other end of the resistor 503 is connected to the gate of the thyristor 501 through a resistor 504. Further, a resistor 505 is connected between the gate and cathode of the thyristor 501. In this embodiment, the resistor 503
and 504 constitute a circuit that provides a firing signal to the thyristor 501 with the output of the exciter coil 4 in one half cycle (the half cycle in which the output is generated in the direction of the solid arrow shown in the figure).

The anode of a ignition signal bypass thyristor 506 whose anode is grounded is connected to the connection point between the resistors 503 and 504, and a resistor 507 and a capacitor 50 are connected between the gate and cathode of this thyristor 506.
8 are connected in parallel. The gate of the thyristor 506 is connected to the anode of a Zener diode 509, and the cathode of the Zener diode 509 is connected to one end of each of a capacitor 510 and a resistor 511. capacitor 510 and resistor 51
1 are commonly connected to the cathode of a diode 512, and the anode of the diode 512 is connected to the non-grounded terminal of the exciter coil 4.
The cathode of the Zener diode 509 is also connected to the emitter of a PNP transistor 513 whose collector is grounded, and the base of the transistor 513 is connected to the drain of a field effect transistor (hereinafter referred to as FET) 514 whose source is grounded. A control rotation speed setting capacitor 515 and a resistor 516 that constitutes a discharge circuit that discharges this capacitor at a constant time constant are connected in parallel between the gate of the FET 514 and the ground.
A series circuit including a resistor 517 and a diode 518 with its cathode facing the exciter coil 4 is connected between the negative gate and the non-grounded terminal of the exciter coil 4.

The overspeed prevention circuit 5 is constituted by each part of the thyristor 501 to the diode 518, and in this circuit a Zener diode 509, a capacitor 51
0, resistor 511, diode 512, transistor 513, and FET 514 generate an ignition signal when the output of the one half cycle of the exciter coil rises during a period in which the terminal voltage of the control rotation speed setting capacitor is equal to or higher than the set value. By supplying an ignition signal to the bypass thyristor 506, the thyristor 5
A thyristor control circuit 500 that makes 06 conductive is configured.

Next, the operation of the above embodiment will be explained. In FIG. 1, when the engine rotates, the exciter coil 4 generates an AC voltage V _e with a no-load waveform as shown in FIG. 2A in synchronization with the engine rotation. Incidentally, time t [sec] is plotted on the horizontal axis of FIGS. 2A to 2E. While this exciter coil 4 is generating an output for one half cycle in the direction of the solid arrow shown in the figure (hereinafter referred to as positive direction output), the over-rotation prevention thyristor 501 is biased in the forward direction, and in this state, the resistor 503 and When an ignition signal is applied through 504, this thyristor 501 becomes conductive and ignition energy is supplied to the ignition control circuit 3.

In the present invention, a firing signal is given to the thyristor 501 only when the engine rotational speed is within a steady rotational speed range below the control rotational speed. That is, when the exciter coil 4 generates the other half-cycle output in the direction of the dashed arrow shown in the figure (hereinafter referred to as negative direction output), the control rotation speed setting capacitor 515 is charged to the polarity shown in the figure through the resistor 517 and the diode 518. Ru. When the negative direction output of the exciter coil 4 exceeds the Zener level V _a of the Zener diode 307, the Zener diode 307 becomes conductive, and the exciter coil 4 is almost short-circuited through the diode 309, the Zener diode 307, and the gate cathode of the thyristor 304. state, the capacitor 515
is approximately the resistance 51 after being charged to the Zena level V _a
6, and the waveform of the terminal voltage V _c becomes as shown in FIG. 2E. Further, the waveform of the negative direction output of the exciter coil 4 is as shown in FIG. 2B. During the period _T1 in which the voltage _Vc across the control rotational speed setting capacitor 515 is equal to or higher than a certain level _VF , the FET 514 is in a state where it cannot conduct, so the transistor 513 is also in a state where it cannot conduct. When the positive direction output of the exciter coil 4 rises in this state, an ignition signal is given from the exciter coil 4 to the thyristor 506 through the diode 512, the resistor 511, and the Zener diode 509. Also, there is a period T ₂ during which the terminal voltage V _c of the capacitor 515 is less than a certain level V _F
During this period, the FET 514 is in a state where it can conduct.
When the positive direction output of the exciter coil 4 occurs in this state, the FET 514 and the transistor 513
conducts and diverts all firing signals to thyristor 506 from the thyristor 506.

In the present invention, when the engine rotation speed is in a steady rotation speed range below the control rotation speed, the second
As shown in the figure, the terminal voltage V _c of the capacitor 515
It is set so that the positive direction output of the exciter coil 4 does not rise within a period T ₁ during which V _F is equal to or higher than a certain level V F . Therefore, in the steady rotation region below the control rotation speed, the FET 514 and the transistor 513 become conductive at the same time as the positive direction output rises to the exciter coil 4, thereby blocking the supply of the firing signal to the firing signal bypass thyristor 506. and prevents the thyristor 506 from conducting. At this time, the ignition signal is supplied to the over-rotation prevention thyristor 501 without any problem, and the thyristor 501 becomes conductive at the same time as the positive output of the exciter coil 4 rises. When the thyristor 501 becomes conductive, the diode 302
Through this, capacitor 301 is charged to the polarity shown, and its terminal voltage _Vcc rises as shown in FIG. 2C. Next, when the negative direction output of the exciter coil 4 reaches the Zener level V _a , the Zener diode 307 becomes conductive and a firing signal is given to the thyristor 304, causing the thyristor 304 to become conductive. At this time, the electric charge of the capacitor 301 is transferred to the thyristor 304.
It is discharged through the secondary coil 1a, causing a large magnetic flux change in the iron core of the ignition coil. This causes a high voltage V _h to be applied to the secondary coil 1b (see Figure 2D).
occurs, a spark is generated in the ignition plug 2, and the engine is ignited.

Since the capacitor 515 is charged to a constant voltage and discharged at a constant time constant, as the rotational speed of the engine increases, the rise time of the positive direction output of the exciter coil 4 becomes equal to the terminal voltage V _c of the capacitor 515.
As the engine rotation speed approaches the period T ₁ in which V _F is above a certain level, and the engine rotation speed exceeds the control rotation speed, as shown in _FIG . The output will start rising.
At this time, when the square output of the exciter coil 4 rises, the FET 514 is not conductive, so the transistor 513 is not conductive, and a firing signal is applied from the exciter coil 4 to the thyristor 506 through the diode 512, the resistor 511, and the Zener diode 509. Therefore, at the same time as the positive direction output of the exciter coil 4 rises, the thyristor 506 becomes conductive, and all firing signals to the thyristor 501 are bypassed from the thyristor 501 and the thyristor 506 is turned on.
1 is prevented from conducting. When conduction of the thyristor 501 is prevented in this way, the capacitor 301
Since the fuel is not charged, ignition will not occur and the engine will misfire. Therefore, the rotational speed of the engine is reduced and overspeeding is prevented. When the engine rotation speed becomes less than the control rotation speed, thyristor 5 is activated again.
Since the supply of the ignition signal to 01 is now allowed, the ignition operation is restarted.

In the above embodiment, the signal circuit that supplies the firing signal to the thyristor 304 is configured using the diode 305.
and 309, Zener diode 307, and resistor 3
06 and 308, and the negative direction output of the exciter coil is used to give the ignition signal to the thyristor 304, but it is also possible to give the ignition signal to the thyristor 304 by the output of a separately provided signal coil. good. In that case, a separate circuit is provided to charge the capacitor 515 with a constant voltage using the negative output of the exciter coil 4.

As described above, according to the present invention, the exciter coil is not short-circuited during the overspeed prevention operation, so no armature reaction occurs, and the rotation speed can be accurately detected and the control rotation speed and return rotation speed can be adjusted. This has the advantage of being able to reduce the difference between

[Brief explanation of drawings]

Fig. 1 is a connection diagram showing an embodiment of the present invention, and Figs. 2 A to E and Figs. 3 A to E show the parts shown in Fig. 1 in the rotation range below the control rotation speed and in the rotation range above the control rotation speed, respectively. FIG. 1...Ignition coil, 3...Ignition control circuit, 4...
...Exciter coil, 5...Over-rotation prevention circuit.

Claims (1)

[Scope of utility model registration request] A discharge control thyristor that discharges the electric charge of the capacitor through the primary coil of the ignition coil when electrically connected to an ignition energy storage capacitor provided on the primary side of the ignition coil; and a discharge control thyristor that ignites the thyristor at the ignition position of the engine. an ignition control circuit having a signal circuit for providing a signal; an exciter coil disposed in a magnetic alternator driven by the engine to provide ignition energy to be stored in the capacitor at the output of one half cycle; An ignition device for an internal combustion engine, comprising: an overspeed prevention circuit that prevents overspeed of the engine by blocking the ignition operation by the ignition control circuit when the rotation speed of the engine reaches a set value, wherein the overspeed prevention circuit prevents the engine from overspeeding. The circuit includes an overspeed prevention thyristor connected in series with the exciter coil so as to turn on and off the charging current of the ignition energy storage capacitor, and an overspeed prevention thyristor connected in series with the exciter coil to turn on and off the charging current of the ignition energy storage capacitor; A circuit that provides an ignition signal to the rotation prevention thyristor, a control rotation speed setting capacitor that is charged to a substantially constant voltage by the output of the other half cycle of the exciter coil, and a control rotation speed setting capacitor that supplies the control rotation speed setting capacitor at a constant time. A discharge circuit that discharges at a constant rate,
The ignition signal bypass thyristor is provided to bypass the ignition signal to the over-rotation prevention thyristor, and the exciter coil is connected to the exciter coil during a period when the terminal voltage of the control rotation speed setting capacitor is equal to or higher than a set value. and a thyristor control circuit that supplies an ignition signal to the ignition signal bypass thyristor to make the ignition signal bypass thyristor conductive when the output of the one half cycle of the ignition signal bypass thyristor rises. Characteristics of the ignition system for internal combustion engines.