JPH036867Y2 - - 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 induced by a magnet generator is short-circuited by a short circuit, and a transistor is used to short-circuit the voltage induced by a magnet generator. In an ignition device for an internal combustion engine that abruptly interrupts the circuit and applies ignition voltage to the ignition plug, a retard circuit is provided to delay the cutoff timing of the short circuit current of the short circuit, and the retard circuit is operated during normal rotation of the internal combustion engine. The short-circuit current is cut off near the peak value of the short-circuit current waveform of the short-circuit circuit without activation, and the above-mentioned retard circuit is activated during overspeed rotation to perform a large step retard, thereby adjusting the specified ignition timing of the spark plug. The present invention relates to an overspeed rotation prevention device for an internal combustion engine that operates to significantly delay and suppress overspeed rotation.

Conventionally, overspeed prevention devices for internal combustion engines stop the sudden interruption of the short-circuit current that induces high voltage in the secondary winding when the rotational speed of the internal combustion engine rises above a predetermined number of rotations, preventing the ignition plug from igniting. In this way, an increase in the rotational speed of the internal combustion engine is suppressed. Therefore, there is a problem that unburned raw gas is discharged from the internal combustion engine, and it is desired to prevent discharge of unburned raw gas. In order to solve this situation, the present inventor previously proposed in Japanese Patent Application No. 56-74141 that when the internal combustion engine rotates at low speed, it is set to shut off at the peak value of the short-circuit current waveform. When the speed rises to high speed, the ignition timing is advanced by a step advance, and the ignition timing is improved by natural retardation from medium to high speed speeds, and the retardation width is secured at the next retardation. Overspeed rotation for internal combustion engines, which prevents raw gas from being exhausted and suppresses overspeed rotation of the internal combustion engine by significantly retarding the ignition timing by significantly retarding the ignition timing when the engine reaches overspeed. Provided with prevention equipment. However, it has been confirmed that for small-output internal combustion engines, it is sufficient to provide a retard circuit with a relatively simple configuration. That is, in this type of ignition device, in order to control the ignition timing, for example, when the potential of the primary winding of the magnet generator reaches a peak point, the charging voltage of the capacitor for ignition control reaches a predetermined threshold value. It is configured as follows. In order to prevent overspeed rotation, in delaying the timing at which the charging voltage of the ignition control capacitor reaches the predetermined threshold value,
A configuration is adopted in which a charge in the opposite direction is applied in advance to the capacitor in a bias manner during overspeed rotation. However, in the case of the conventional configuration, it is necessary to correctly control the presence or absence of charge in the single capacitor for ignition control, making it difficult to adjust the circuit constants. In the present invention, since the output of the internal combustion engine is relatively small, the functions conventionally handled by a single capacitor for ignition control are separated, and the overspeed prevention function is handled separately. I'm trying to make the capacitor take care of it. Furthermore, the functions of the two capacitors mentioned above are combined by the SCR, which remains on during overspeed rotation, and this function can be applied to existing equipment that does not have an overspeed prevention function. can be easily added. This will be explained below with reference to the drawings.

Fig. 1 shows the circuit configuration of one embodiment of the present invention, Fig. 2 shows the ignition timing characteristic curve showing changes in the ignition timing of the invention, and Fig. 3 shows the induced energy in the primary winding of the magnet generator shown in Fig. 1. Examples of the no-load voltage waveforms shown in FIGS. 4 to 7 are waveform explanatory diagrams for explaining ignition timing.

In the circuit configuration of one embodiment of the present invention shown in FIG.
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,
7 is a transistor which is a switching transistor constituting the short circuit 6; 8 is a control transistor which controls the transistor 7 of the short circuit 6; 9 is a first pulser coil;
10 is a retard circuit, 11 is a second pulsar coil that induces a voltage in phase with the primary winding 3, 12
is a rotation speed detection circuit, 13 is a first SCR, 14 is a second SCR, 15 is a constant voltage diode, 16 to 21 are diodes, 22 is a variable resistor, 23 to 31 are resistors, 32 to 36 are capacitors,
37 represents a thermistor.

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

(1) Assume that the magnetic means 2 is rotated in accordance with the rotation of the internal combustion engine, and a forward voltage as indicated by arrow A in the figure is induced in the primary winding 3.

(2) The current generated by this voltage induced in the primary winding 3 is supplied as a base current to the transistor 7 via the resistor 30 for a while from the time of rise of the current, and the base current is supplied to the transistor 7 through the resistor 30.
A short-circuit current flows through the short-circuit 6 in a short-circuited state.

(3) During this time, part of the current flowing through the resistor 26 passes through the diode 19 and the resistor 29 to the capacitor 35.
to charge. When the charging voltage charged in the capacitor 35 reaches a predetermined threshold value, the control transistor 8 is turned on.

(4) When the control transistor 8 is turned on, the base current that has been supplied to the transistor 7 is bypassed by the control transistor 8. As a result, transistor 7 is suddenly turned off. That is, the large short circuit current flowing through the short circuit 6 is abruptly cut off, and a high voltage is induced in the secondary winding 4.

(5) The control transistor 8 remains on until the charge in the capacitor 35 is discharged. That is, the charge of the capacitor 35 is transferred to the resistors 29, 28,
It is discharged via the base current circuit which is supplied via 27 to the control transistor 8.

(6) The no-load voltage induced in the primary winding 3 by the rotation of the magnetic means 2, that is, the induced voltage in the absence of the illustrated short circuit 6, control transistor 8, etc., will be described later in FIG. During the period in which the forward voltage in the direction of the arrow A in the drawing exists, the charge in the capacitor 35 continues to exist, and once the control transistor 8 is turned on, this state is maintained. While a voltage in the direction opposite to the arrow A shown in the figure is induced in the primary winding 3, the charge in the capacitor 35 is transferred to the resistor 29,
28 and 26, and the control transistor 8 has returned to its off state. That is, the control transistor 8 is returned to a state in which it can be turned on.

(7) Note that the diode 21 bypasses a reverse current while a voltage in the direction opposite to the arrow shown in the figure is induced in the primary winding 3.

During normal rotation of the configuration shown in FIG. 1, it operates as described above, and the timing for cutting off the short circuit current flowing through the short circuit 6 is set at the peak value of the short circuit current, as shown in FIG. 4A.

When the rotational speed of the internal combustion engine exceeds normal rotation and increases to a high rotational speed of 11,000 rpm or more, for example, the configuration shown in FIG. 1 operates as follows.

(8) When the rotational speed of the internal combustion engine increases to, for example, 11000rpm or higher, the first
The second SCR 14 of the retard circuit 10 operates so that the first SCR 13 is maintained in the firing state by the voltage supplied from the first pulser coil 9 via the diode 16.
is fired and the retard circuit 10 is activated.

(9) When the retard circuit 10 is activated, that is, when the second SCR 14 is fired, a part of the short circuit current flowing through the short circuit 6 flows through the parallel circuit of the resistor 25 and the capacitor 34 via the resistor 26, and then flows to the side. In order to be routed,
The time required to charge the capacitor 35 becomes longer, and the state in which the control transistor 8 is turned on becomes slower.

(10) Since the control transistor 8 is turned on later, the short-circuit current cutoff time of the transistor 7 is delayed.

In addition, in the present invention, the above capacitor 3
5, resistors 29 and 28, and diode 19 is called a first timing circuit, and a circuit including capacitor 34 and resistor 25 is called a second timing circuit. Only the first timing circuit is used during normal rotation, and both the first timing circuit and the second timing circuit are used during high speed rotation.

When the configuration shown in FIG. 1 rotates at high speed, that is, during overspeed rotation, the retard circuit 10 comes into operation as described above, and the timing for cutting off the short circuit current flowing through the short circuit 6 is determined as shown in FIG. 4B. The angle is retarded by α from the illustrated cutoff point. By significantly retarding the α angle, that is, the short circuit current cutoff timing, the ignition plug 5 of the internal combustion engine can be ignited after the specified ignition timing of the internal combustion engine, making it possible to suppress the increase in rotational speed. Become. Since the ignition plug 5 is used to ignite, the gas after combustion is always exhausted. FIG. 2 shows these changes in ignition timing.

FIG. 3 represents the no-load voltage induced in the primary winding of the magnet generator shown in FIG. That is, as the magnetic means 2 rotates, the third
As shown in the figure, a forward voltage pulse 46 and opposite voltage pulses 47 and 48 occur before and after it.
One voltage pulse 46 is generated every period T. This forward voltage pulse 46 corresponds to the voltage in the direction of arrow A shown in FIG.

In explaining the operation based on the voltage waveform or current waveform of the configuration shown in FIG. 1, the explanation should be based on the voltage pulses 46, 47, and 48 shown in FIG. Because the width is small, voltage pulse 4 will be used in the following explanation.
The following explanation assumes that pulse widths 6, 47, and 48 are relatively large. Accordingly, the pulse width of short-circuit current, etc., has also become relatively large.

FIGS. 4A and 4B are short-circuit current waveform explanatory diagrams illustrating an example of short-circuit current cutoff timing at each typical rotational speed of an internal combustion engine. Figure A shows the internal combustion engine when the rotation speed is normal, and Figure B shows the internal combustion engine when the rotation speed is high speed, that is, overspeed, and at this time the retard circuit 10 is activated. do. Compared to the short-circuit current waveform in A of the same figure, the cut-off timing is α.
This indicates that the angle is retarded.

Next, the operation of the retard circuit 10 will be explained based on voltage and current waveforms.

FIGS. 5A to 5C are explanatory diagrams of current and voltage waveforms when the internal combustion engine rotates at a normal rotational speed. In the figure, numeral 49 is the short circuit current, and 50 is the first pulsar current.
The voltage induced in the coil 9 is in phase with the voltage induced in the primary winding 3, that is, the short circuit current 49, and 51 is the voltage induced in the second pulsar coil 11. Reference numeral 52 represents the voltage of the capacitor 32, which is in a reverse phase relationship with the voltage 50 induced in the first pulsar coil 9.

When the rotational speed of the internal combustion engine is low (eg, 0 to 3000 rpm), a voltage 50 induced in the first pulser coil 9 is supplied to the first SCR 13 as shown in FIG. 5B. On the other hand, as shown in _FIG . Therefore, the retard circuit 10 does not operate. In this way, when the retard circuit 10 does not operate at low speed rotation, the timing of cutting off the short circuit current 49 flowing through the short circuit 6 depends on the charging voltage charged in the capacitor 35, and the short circuit as shown in FIG. Circuit constants are set so that the current is cut off at the peak value of the current 49.

FIGS. 6A to 6D are explanatory diagrams of current and voltage waveforms when the internal combustion engine rotates at a medium speed. In the figure,
Reference numbers 49 to 52 correspond to those in FIG.

When the rotation speed of the internal combustion engine is medium speed rotation, that is, normal rotation (3000 to 11000 rpm), the voltage 50 induced in the first pulser coil 9 is supplied to the first SCR 13 as shown in FIG. 6B. . However, in the retard circuit 10, the second pulsar coil 1
The voltage 51 induced in the first SCR 1 rises as shown in C of the same figure, and the voltage 52 of the capacitor 32 also increases as shown in the first SCR 1.
3 exceeds the voltage level _L1 of the capacitor 32 required to fire the first SCR 13, and the first SCR 13 fires.
The voltage 52 of the capacitor 32 is applied to the constant voltage diode 1 in the interval between t ₁ and t ₂ , as shown in the enlarged diagram of figure D.
5, it is maintained at a constant voltage. The charge accumulated in the capacitor 32 as the voltage 51 induced in the second pulsar coil 11 drops is transferred to the variable resistor 22, the diode 18, and the first SCR.
13 and a circuit via the gates of the second SCR 14 and a series circuit of resistors 23 and 24. This discharge characteristic is as shown in the section between t ₂ and t ₃ in Figure D, and the voltage of the capacitor 32 is
At the time of t ₀ , the voltage level of the capacitor 32 has already fallen below _L2 , which is necessary to apply a voltage sufficient to flow the holding current of the first SCR 13 to the first SCR 13, and until t ₀ , The first SCR 13 is extinguished. Therefore, after t ₀ , the first pulsa・
Voltage 50 from coil 11 is applied to the first SCR1
3, even if the first SCR1
3, the gate current is applied to the gate of the first SCR.
The voltage of the capacitor 32 has been discharged and dropped below the voltage level _L1 of the capacitor 32 necessary for firing the first SCR 13, and the first SCR 13 will not be fired again. Note that the voltage levels L ₁ and L ₂ correspond to a threshold level for turning on the SCR and a threshold level for turning it off, respectively. Therefore, when the rotation speed of the internal combustion engine is medium speed, the retard circuit 1
0 does not work. In this case, the first SCR
will be fired at t ₄ .

FIGS. 7A to 7D are explanatory diagrams of current and voltage waveforms when the internal combustion engine rotates at a high speed. In the figure,
Reference numerals 49 to 52 correspond to those in FIG.

When the rotational speed of the internal combustion engine increases to high speed rotation, that is, overspeed rotation (11000 rpm or more), the voltage 51 induced in the second pulsar coil 11 increases as shown in Figure C, and the voltage 52 of the capacitor 32 also increases. Exceeds the voltage level L ₁ of the capacitor 32 necessary to ignite the first SCR 13, and the first SCR 1
3 fires. and the voltage 52 of capacitor 32
As shown in the enlarged view of FIG. D, the voltage is maintained at a constant voltage in the interval between t ₁ and t ₂ by the constant voltage diode 15 . The charge accumulated in the capacitor 32 as the voltage 51 induced in the second pulsar coil 11 drops is transferred to the variable resistor 22 and the diode 1.
8. Discharge occurs in a circuit via the gates of the first SCR 13 and second SCR 14 and a series circuit of resistors 23 and 24. Since this discharge circuit is always the same regardless of the rotational speed of the internal combustion engine, the discharge characteristics charged in the capacitor 32 from t ₂ to t ₃ are determined by the circuit constants of the discharge circuit, and The discharge characteristics at the time of rotation and the discharge characteristics at high speed rotation have the same slope. Moreover, the voltage 5 induced in the second pulsar coil 11 rotating at high speed
Since the period of 1 is smaller than the period during medium-speed rotation, the discharge curve during high-speed rotation is t ₂ and t ₃ shown in D of the same figure.
The discharge starts as shown in the interval t0, and the discharge starts at a time closer to _t0 . Then, the charging voltage of the capacitor 32 is discharged, and the voltage is discharged to the voltage level L ₂ of the capacitor 32 necessary to keep the voltage sufficient to flow the holding current of the first SCR 13 applied to the first SCR 13. Before (at t ₅ in Figure D), the voltage 50 of the first pulser coil 9 has already risen steeply compared to when rotating at medium speed.
It works to maintain the firing state of SCR13. The first SCR 13, which is thus ignited, is not extinguished. That is, at the same time that a forward voltage indicated by arrow A in FIG. 1 is induced in the primary winding 3, the retard circuit 10 is activated. The operation when the retard circuit 10 is activated is explained in the above operation explanations (8) to (10).

The thermistor 37 functions to prevent the voltage supplied to the gate of the first SCR 13 from varying due to ambient temperature, thereby stabilizing the engine speed at which the retard circuit 10 operates.

As explained above, according to the present invention, it is possible to retard the ignition timing when a relatively small internal combustion engine, such as that used in a chain saw, reaches an overspeed rotation state, thereby causing a spark to fly to the ignition plug. In addition, overspeed rotation can be suppressed, making it unnecessary to exhaust unburned raw gas. The circuit structure is much simpler than that of the previously filed Japanese Patent Application No. 1983-74141, and has the following advantages. That is, for example, the time constant of the second timing circuit can be adjusted independently, and the setting of the timing in which both circuits cooperate becomes simple and stable. Furthermore, for example,
In the cases shown in No. 41658 and Utility Model Application Publication No. 54-176033, if there is a variation in the amount of reverse bias charge applied to the capacitor that sets the delay time, the effect directly affects the delay time, but this application does not apply. In the case of the invention, the capacitors in both timing circuits are charged from a zero state. Therefore, in the case of the present invention, the delay time is not affected by the residual charge in the capacitor, and no error occurs in setting the delay time.

Note that in a small internal combustion engine, overspeed rotation can be suppressed only by the retardation circuit because the inertia of the mechanical system is small.

[Brief explanation of the drawing]

Fig. 1 shows the circuit configuration of one embodiment of the present invention, Fig. 2 shows the ignition timing characteristic curve showing changes in the ignition timing of the invention, and Fig. 3 shows the induced energy in the primary winding of the magnet generator shown in Fig. 1. No-load voltage waveforms shown in Figures 4 to 7
The figure shows a waveform explanatory diagram for explaining ignition timing. 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 transistor, 8 is a control transistor,
9 is the first pulsar coil, 10 is the retard circuit, 1
1 is the second pulsar coil, 12 is the rotation speed detection circuit, 13 is the first SCR, 14 is the second SCR, 1
5 is a constant voltage diode, 16 to 21 are diodes, 22 is a variable resistor, 23 to 31 are resistors,
32 to 36 represent capacitors, and 37 represents a thermistor, respectively.

Claims (1)

[Claims for Utility Model Registration] Magnetic means for generating a moving magnetic field in response to the rotation of an internal combustion engine, a power generation winding magnetically coupled to the magnetic means, and control for controlling the voltage and current of the power generation winding. An ignition device for an internal combustion engine, comprising a means and an ignition means, wherein the voltage and current induced in the power generation winding by the magnetic means are controlled by the control means to ignite the ignition means, A first timing circuit is provided that determines conduction timing of a control transistor that controls a transistor of a short circuit that short-circuits a predetermined forward current of the voltage induced in the power generation winding, and conduction of the control transistor is provided. a retard circuit that retards the cut-off timing of the transistor of the short circuit by delaying the timing, the retard circuit comprising: a second pulsar coil magnetically coupled to the magnetic means; a rotation speed detection circuit that detects the rotation speed of the internal combustion engine based on the voltage output from the pulsar coil; a second timing circuit connected in parallel to the first timing circuit; and the rotation speed detection circuit. The second above mentioned
Equipped with an SCR that controls the timing circuit of
and the SCR is controlled when overspeed rotation is detected in the rotation speed detection circuit, and the ignition state of the SCR is maintained during overspeed rotation,
The second timing circuit is configured to enable the second timing circuit, and during overspeed rotation, the timing of conduction of the control transistor is delayed by a time constant of the first timing circuit and the second timing circuit. An overspeed rotation prevention device for an internal combustion engine, characterized in that the overspeed rotation prevention device is configured to