JPS621421Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention is an overspeed rotation prevention device for an internal combustion engine, in particular, for example, a voltage generated by a magnet generator is short-circuited by a short circuit, and the short circuit is rapidly interrupted. In an ignition system for an internal combustion engine that applies an ignition voltage to the ignition system, opening of a mechanical contact existing in the short circuit when igniting a thyristor for preventing overspeed rotation that is connected in parallel to the short circuit. Before operation, a DC voltage is applied between the anode and cathode of the thyristor, and the opening position of the mechanical contact is separated from the position where it is determined whether or not the thyristor firing operation is possible, so that the mechanical contact is opened. The present invention relates to an overspeed rotation prevention device for an internal combustion engine that is less affected by timing adjustment.

Various devices for preventing overspeed rotation of internal combustion engines have been devised in the past, and one of them, as shown in FIG. A silicon controlled rectifying element (hereinafter simply referred to as SCR) provided in parallel with the mechanical contact is made conductive to form a short circuit, thereby suppressing overspeed rotation of the internal combustion engine. That is, in FIG. 1, 1 is a magnet generator, 2 is a magnetic means, 3 is a primary winding, 4 is a secondary winding, 5 is a spark plug, 6 is a short circuit, and 7 is a mechanical contact (point ) constituting the short circuit 6, 8 an SCR connected in parallel to the mechanical contact 7, 9 a capacitor for extinguishing the spark, 10 an SCR ignition circuit, 11
1 is a constant voltage circuit, 12, 13, and 14 are diodes that constitute the constant voltage circuit 11, 15 is a capacitor, 16 is a thermistor, 17 to 19 are resistors, 20 is a variable resistor, and 21 is a pulser coil. A diode 22 is wound on the same core as the primary winding 3 and the secondary winding 4.

The operation of the configuration shown in FIG. 1 will be roughly explained as follows.

It is assumed that the magnetic means 2 is rotated in accordance with the rotation of the internal combustion engine, and a forward voltage as indicated by the arrow x in the figure is induced in the primary winding 3 and the pulser coil 21. The electromotive force induced in the primary winding 3 causes a short circuit current to flow through the primary winding 3, the mechanical contact 7, and a closed circuit extending to the primary winding 3. The short circuit current is cut off by opening the mechanical contact 7 at a predetermined firing angle, inducing a high voltage in the secondary winding 4 and igniting the ignition plug 5.

On the other hand, the electromotive force induced in the pulsar coil 21 mainly flows through the diode 22 into the capacitor 15 of each of the diodes 12 to 14 of the constant voltage circuit 11. The maximum value of the voltage to which the capacitor 15 is charged depends on the rotational speed of the internal combustion engine and the air gap between the magnetic means 2 and the pulser coil 21.
Regardless of the magnitude of the electromotive force induced in the pulsar coil 21 based on the magnitude of , it is determined by the set voltage of the constant voltage circuit 11, so that the voltage is kept constant. For example, the capacitor 15 is set to a charging voltage of 2 to 3V. The charge charged in the capacitor 15 is transferred via the resistor 18.
It also flows into the gate of SCR8. This allows SCR
8 becomes conductive when a voltage is applied between the anode and the cathode, and a short circuit is formed between the primary winding 3, the SCR 8, and the primary winding 3. By the way, voltage is applied between the anode and cathode of the SCR 8 when the mechanical contact 7 is opened, and no voltage is applied between the anode and cathode of the SCR 8 until the mechanical contact 7 is opened.

Next, the operation of the configuration example shown in FIG. 1 during normal rotation and overspeed rotation will be explained based on the waveforms shown in FIGS. 3A and 3B.

Fig. 3A shows the state during normal rotation, and Fig. 3B shows the state during overspeed rotation. In the figure, A and B show the voltage waveform of the primary winding 3, the current waveform flowing through the mechanical contact 7, the voltage waveform of the pulsar coil 21, the voltage waveform of the capacitor 15, and the SCR
The current waveforms flowing through the circuits 8 and 8 are shown respectively.

The operation of the SCR8 during normal rotation is as follows. That is, a short-circuit current flows through the mechanical contact 7 in the same phase as the voltage induced in the primary winding 3. Parsa・
The electromotive force induced in the coil 21 is connected to the primary winding 3 so that it is in reverse phase, and as the voltage induced in the pulsar coil 21 increases, the capacitor 15 increases as shown in FIG. It is charged from A to B. When the voltage induced in the pulsar coil 21 increases further, the constant voltage circuit 11 operates and is maintained at its set voltage. This is the part BC in Figure A. When the voltage induced in the pulsar coil 21 drops to a predetermined voltage, the electric charge stored in the capacitor 15 is mainly discharged through the variable resistor 20, and the voltage of the capacitor 15 increases as shown by CD in FIG. The voltage drops. When the electromotive force induced in the primary winding 3 reaches the maximum positive value H (a in the figure), the mechanical contact 7
is adjusted so that it is open, and when the electromotive force of the primary winding 3 rises to its maximum positive value H,
Mechanical contacts 7 are opened. At this time, the electromotive force induced in the primary winding 3 is applied between the anode and cathode of the SCR 8, but as shown in FIG. Since the voltage level is below L, the SCR 8 cannot be ignited, and the short circuit current in the short circuit 6 is cut off. As a result, a high voltage is induced in the secondary winding 4 and the spark plug 5
ignite.

Next, the operation of the SCR 8 during overspeed rotation is as follows. That is, due to the high speed rotation, a high voltage with a short period is induced in the primary winding 3 as shown in FIG. The voltages charged in the capacitor 15 are as shown in A', B', and C' in the figure, and the constant voltage parts B' and C' set by the constant voltage circuit 11 are the part BC during normal operation. held at the same potential.
When the voltage induced in the pulsar coil 21 drops to a predetermined voltage, the charge charged in the capacitor 15 starts discharging mainly through the variable resistor 20, but this discharge characteristic depends on the circuit constants. Since the circuit constant (time constant) during the normal rotation and the overspeed rotation are the same, they have discharge characteristics with the same slope as shown in C' and D' in the same figure. There is. On the other hand, the mechanical contact 7 is opened at H' (FIG. 7B) when the electromotive force induced in the primary winding 3 is at its maximum value, and this causes a gap between the anode and the cathode of the SCR 8 to be applied to the primary winding 3. An electromotive force induced in is applied. At this time, when the mechanical contact 7 is open (H'), the discharge voltage of the capacitor 15 is at a potential higher than the voltage level L that causes a gate current sufficient to ignite the SCR 8 to flow, as shown in FIG. Eventually, the SCR 8 becomes conductive, and the short circuit current flowing through the short circuit 6 continues to flow from the mechanical contact 7 to the SCR 8 instead. The FGH section in the same figure shows this situation. This causes short circuit 6
The short circuit current flowing through the secondary winding 4 is not interrupted, and the high voltage that causes the spark plug 5 to ignite cannot be induced in the secondary winding 4. Consequently, the increase in rotation of the internal combustion engine is suppressed.

In this way, the conventional overspeed rotation prevention device for an internal combustion engine is configured such that a voltage is applied between the anode and the cathode of the SCR 8 after the mechanical contact 7 is opened. By adjusting the (ignition position), for example, the set rotation speed of the overspeed rotation prevention device of the internal combustion engine changes by 600 rPm or more when the open position of the mechanical contact 7 changes by 1 degree in rotation angle. Therefore, there is a drawback that the set rotational speed of the overspeed rotation prevention device of the internal combustion engine changes significantly due to wear and tear of the mechanical contacts 7, etc.

The present invention is aimed at solving the above-mentioned drawbacks, and the above-mentioned pulser coil is further provided with another reverse winding, and a voltage is previously applied between the anode and cathode of the SCR. When the rotational speed of the internal combustion engine reaches an overspeed rotation exceeding a specified set value, current is applied to the gate of the SCR via the SCR ignition circuit based on the electromotive force induced in the pulsar coil, causing a short circuit. The SCR is made conductive before the mechanical contacts of the circuit are opened. That is, the short circuit current of the short circuit is bypassed to the SCR, and even when the mechanical contact reaches a predetermined ignition angle and is opened, the short circuit current continues to flow through the SCR and prevents the ignition plug from igniting. This eliminates the influence of fluctuations in overspeed rotation speed due to adjustment of the open position of the mechanical contact. This will be explained below with reference to the drawings.

FIG. 2 shows a circuit configuration of an embodiment of the present invention, and reference numerals 1 to 22 in the figure correspond to those in FIG. 1. 23 is a reverse winding and is a pulsar coil 21
24 and 25 represent diodes wound on the same core as .

The configuration shown in FIG. 2 and the configuration shown in FIG. They have the same configuration except that the voltage is applied between them.

The reverse winding 23 is connected in a reverse phase relationship with the pulsar coil 21 and in phase with the primary winding 3.

Next, the operation of the configuration example shown in FIG. 2 during normal rotation and overspeed rotation will be explained based on the waveforms shown in FIGS. 4A and 4B.

FIG. 4A shows the state of normal rotation, and FIG. 4B shows the state of overspeed rotation. In the figure, A and B show the voltage waveform of the primary winding 3, the current waveform flowing through the mechanical contact 7, the voltage waveform of the pulsar coil 21, the voltage waveform of the capacitor 15, and the voltage of the reverse winding 23. The waveforms indicate the current waveforms flowing through the SCR 8.

The operation of the SCR8 during normal rotation is as follows. That is, a short circuit current flows through the mechanical contact 7 in phase with the voltage induced in the primary winding 3. Parsa・
The electromotive force induced in the coil 21 is connected to the primary winding 3 so that it is in reverse phase, and as the power induced in the pulsar coil 21 increases, the capacitor 15 increases as shown in FIG. It is charged from A to B. When the voltage induced in the pulsar coil 21 increases further, the constant voltage circuit 11 operates and is maintained at its set voltage. This is the part BC in Figure A. When the voltage induced in the pulsar coil 21 drops to a predetermined voltage, the electric charge stored in the capacitor 15 is mainly discharged through the variable resistor 20, and the primary winding as shown in CD in FIG. The line 3 is almost completely discharged near zero potential, where the voltage induced in the line 3 changes from negative to positive. This discharge characteristic is a characteristic obtained by setting the variable resistor 20 to have the above characteristic. When a positive voltage is induced in the primary winding 3, a forward voltage is applied between the anode and cathode of the SCR 8 via the diode 24 by the reverse winding 23 in which a voltage in the same phase as this is induced. begins to be At this time, as shown in Figure A, the voltage of the capacitor 15 is already below the voltage level L that causes a gate current sufficient to ignite the SCR 8 to flow, so a forward voltage is applied between the anode and cathode of the SCR 8. SCR even if
8 cannot be fired. When the electromotive force induced in the primary winding 3 reaches the maximum positive value H, the mechanical contact 7 is opened and the short circuit current in the short circuit 6 is interrupted. As a result, a high voltage is induced in the secondary winding 4, causing the ignition plug 5 to ignite.

Next, the operation of the SCR 8 during overspeed rotation is as follows. That is, due to the high speed rotation, a high voltage with a short period is induced in the primary winding 3 as shown in FIG. The voltages charged in the capacitor 15 are as shown in A', B', and C' in the figure, and the constant voltage parts B' and C' set by the constant voltage circuit 11 are the part BC during normal rotation. held at the same potential. When the voltage induced in the pulsar coil 21 drops to a predetermined voltage, the capacitor 1
The charges charged in the variable resistor 20 start discharging mainly through the variable resistor 20. This discharge characteristic is determined by the circuit constant, and since the circuit constant (time constant) during the normal rotation and the overspeed rotation are the same, the same circuit constant as shown in C' and D' The slope discharge characteristics
The SCR firing circuit 10 has. Although the time constant of the discharge characteristic is constant, the period of the electromotive force induced in the primary winding 3 is becoming shorter, so the electromotive force induced in the primary winding 3 changes from negative to positive. In the vicinity of the changing zero voltage, the charge charged in the capacitor 15 is not completely discharged, and is higher than the voltage level L that causes a gate current sufficient to fire the SCR 8 to flow. At this time, the electromotive force induced in the reverse winding 23 which is in phase with the voltage induced in the primary winding 3 is applied as a forward voltage between the anode and cathode of the SCR 8 via the diode 24. As a result, the SCR 8 is ignited, and a short circuit current flows into the SCR 8 as well. This is E′ in the same figure.
Corresponds to part F′. Eventually, when the electromotive force induced in the primary winding 3 reaches its highest voltage value, the mechanical contact 7 is opened at H', but the short circuit current in the short circuit 6 begins to flow to the SCR 8, which is already in a conductive state. .
Sections F', G', and H' in the same figure show this situation. As a result, the short-circuit current flowing through the short-circuit circuit 6 is not interrupted, and the high voltage that causes the ignition plug 5 to ignite cannot be induced in the secondary winding 4, and the increase in rotation of the internal combustion engine is suppressed.

Capacitor 1 for igniting SCR8 explained above
It is clear that the discharge characteristics of No. 5 can be arbitrarily set by changing the variable resistor 20.

As explained above, according to the present invention, a forward voltage is applied between the anode and cathode of the SCR before the opening operation of the mechanical contact, and the opening position of the mechanical contact and the firing operation of the SCR are Since the short circuit is controlled by separating the position from which it is determined whether the mechanical contact is open or not, it is not affected by the adjustment of the position at which the mechanical contact is opened. For this reason,
The set rotational speed can be held almost constant, and since the setting is made using a variable resistor, handling becomes easy.

[Brief explanation of the drawing]

Figure 1 is an example of the circuit configuration of a conventional overspeed rotation prevention device for an internal combustion engine, Figure 2 is an example circuit configuration of an overspeed rotation prevention device for an internal combustion engine according to the present invention, and Figures 3A and 3B are Figure 1 is an explanatory diagram of waveform operation to explain the operation during normal rotation and overspeed rotation for the configuration example shown in Figure 1, and Figure 4 A and B are for the configuration example shown in Figure 2 during normal rotation and overspeed rotation. A waveform operation explanatory diagram illustrating the operation with. In the figure, 1 is a magnet generator, 2 is a magnetic means, and 3 is 1
Next winding, 4 is a secondary winding, 5 is a spark plug, 6 is a short circuit, 7 is a mechanical contact, 8 is an SCR, 9 is a capacitor, 10 is an SCR ignition circuit, 11 is a constant voltage circuit,
12, 13, 14 are diodes, 15 is a capacitor, 16 is a thermistor, 17 to 19 are resistors,
20 is a variable resistor, 21 is a pulser coil, 22 is a diode, 23 is a reverse winding, and 24 and 25 are diodes.

Claims (1)

[Scope of utility model registration request] magnetic means for generating a moving magnetic field in response to rotation of the internal combustion engine; ignition coil means having a primary winding magnetically coupled to the magnetic means; and a pulsar coil magnetically coupled to the magnetic means. A coil, a mechanical contact arranged to short-circuit the voltage induced in the primary winding and determining the ignition position of the ignition device, a thyristor provided in parallel with the mechanical contact, and the pulsar. A diode that half-wave rectifies the voltage induced in the coil to create a positive voltage during the negative half-wave period of the voltage induced in the primary winding, and a peak value of the output side voltage of the diode to a predetermined level. A constant voltage circuit for clipping, a capacitor charged with a trapezoidal wave voltage clipped by the constant voltage circuit, a gate control circuit for supplying the terminal voltage of the capacitor to the gate of the thyristor, and charging of the capacitor. It is equipped with a discharge circuit that discharges electric charge, and during normal rotation, the mechanical contact is opened to forcibly cut off the current flowing to the primary winding to ignite, and during overspeed rotation, the electrical current is discharged from the capacitor. An internal combustion engine in which a voltage supplied to the gate of the thyristor via the gate control circuit prevents the thyristor from interrupting the current flowing to the primary winding regardless of whether the mechanical contact is opened. The overspeed rotation prevention device includes a reverse winding that is magnetically coupled to the magnetic means and wound with a polarity that pre-applies a voltage to the thyristor, so that the rotational speed of the internal combustion engine is at a set value. An overspeed rotation prevention device for an internal combustion engine, characterized in that when the above-mentioned overspeed rotation is reached, a thyristor is fired before the above-mentioned mechanical contact is operated.