JP3178290B2 - Magneto ignition device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto ignition device using a high-pressure magneto system as an ignition system for an engine, and more particularly to a switching device for interrupting the induced current based on the induced current flowing through its primary coil. The present invention relates to a DC power supply circuit that supplies DC power to a control circuit.

[0002]

2. Description of the Related Art In general-purpose, small-sized engines, a high-pressure magneto system excellent in high-speed rotation performance is generally employed as an ignition system. This high-speed magneto system integrates an ignition coil and an interrupter into a magnet-type alternator, closes the contacts and induces an induced current (induced current) in the primary coil.
As a short-circuit current, and near the point where the short-circuit current is maximum, the contact is opened to generate a high voltage in the secondary coil, thereby causing a spark in the spark plug. The interrupter for interrupting the induction current of the primary coil is generally a semiconductor switching element such as a power transistor, and a control circuit is required to control the opening and closing of the semiconductor switching element. Therefore, in order to energize the control circuit with a DC power supply without using a separate winding or batteries, a DC power supply circuit (forward conversion circuit) using an induced current is generally attached to the magneto ignition device.

FIG. 4 is a circuit diagram showing a magneto ignition device having a conventional rectifier circuit disclosed in Japanese Patent Publication No. 61-39508. In FIG. 4, since an induced electromotive force is generated by rotation of a flywheel with magnet (not shown), the output of the magneto coil 1 is an AC output, and the potential at point a is positive (forward voltage) with respect to point b. In the case of (1), the main transistor 2 is turned on by the base current ib flowing into the main transistor (switching element) 2 from the control circuit 3, the collector current ic flows, and the induced current becomes a short-circuit current. Thereafter, when the collector current ib as shown in FIG. 5B reaches the maximum value P, the control circuit 3 detects this and shuts off the base current ib. As a result, the main transistor 2 is turned off. As shown in FIG. 5 (a), a spike-like high voltage (for example, 300 to 400 V) is generated in the coil 1, and a spark flies in the ignition gap 6 of the spark plug. The potential at point a is b
If the point is negative (reverse voltage), the main transistor 2
The reverse current ie hardly flows until the reverse breakdown voltage V _ECO (about 20 V) is reached, and when the reverse voltage between a and b exceeds V _ECO , the avalanche current ie flows and is consumed as heat energy. . At the time of the reverse voltage, a part of the reverse current ie is charged to the first capacitor C1 via the resistor 7 and the diode 8. Thus, the terminal voltage V _C1 of the first capacitor C1 changes as shown in FIG. Next, when the potential at the point a becomes positive again with respect to the point b, the potential of the negative electrode of the capacitor C1 is raised, and the accumulated charge is transferred to the second capacitor C2 via the diode 9 and the resistor 20 to be charged. . At this time, the charge of the second capacitor C2 is the sum of the charge of the capacitor C1 and the charge from the magneto coil 1, and the terminal voltage V _C2 is as shown in FIG. This voltage V _C2 is used as a DC power supply to supply power to the control circuit 3 via the regulator circuit 11. The resistor 7 is selected so that the reverse current does not flow significantly, and the resistor 20 is selected so that the load energy of the main transistor 2 is not excessively consumed.

As described above, the first capacitor C1 is charged by the magneto-reverse voltage, and the charge is diverted to the capacitor C2 at the time of forward voltage and used as a DC power supply for the control circuit. There is no need to provide batteries, and conventionally, wastefully consumed energy can be effectively used. Further, heat loss due to the reverse current flowing through the main transistor 2 is reduced, so that reliability can be improved and the heat radiation structure can be downsized.

[0005]

However, the conventional magneto ignition device shown in FIG. 3 has the following problems.

Since the charge of the first capacitor 1 once charged at the time of the reverse voltage is transferred to the second capacitor 2 at the time of the forward voltage, the first capacitor 1 for commutation is required, and as a result, the circuit configuration And the number of parts increases.

In addition, since commutation occurs during the magneto forward voltage period, the terminal voltage V _C2 of the second capacitor 2 exhibits a ripple as shown in FIG. 5D during this period. Therefore, if the terminal voltage V _C2 is used as it is as the DC power supply of the control circuit 3, there is power supply instability. Therefore, the control of the control circuit 3 which detects the maximum value P of the collector current ib and cuts off the base current ib during the magneto forward voltage period. Reliability matters. In order to avoid this problem, the regulator circuit 11 shown in FIG.
Therefore, the addition of the regulator circuit 11 necessitates an increase in the number of components of the DC power supply circuit.

In the magneto forward voltage period, the charge once charged in the first capacitor C1 is transferred to the second capacitor C2 at the time of the reverse voltage, and a part of the forward current is transferred to the first and second capacitors C1. , C2, the value of the collector current ic flowing through the main transistor 2 is slightly reduced during the magneto forward voltage period, and the value of the high voltage generated when the main transistor 2 is cut off is also slightly reduced. for that reason,
Increasing the resistance value of the resistor 20 reduces the load energy consumption of the main transistor 2, but conversely increases the time constant of the charge commutation, so that the charging efficiency of the second capacitor C2 is not good. Bringing problems.

In view of the above problems, it is an object of the present invention to provide a DC power supply circuit for obtaining a DC current for a control circuit from a part of a reverse current flowing through a primary coil of a magneto ignition device. To achieve cost reduction by simplifying the circuit configuration and reducing the number of parts, and to stabilize the power supply voltage during the forward voltage period in which the switching element is cut off.

[0010]

Means for Solving the Problems To solve the above problems, the means adopted in the present invention is to charge the storage means with a reverse current at the time of reverse voltage, do not charge at the time of forward voltage, and use a constant voltage as a DC power supply. It is characterized by a long discharge.
That is, the present invention provides a primary coil that generates an AC induced voltage by rotation of a magnet, an intermittent unit that short-circuits the primary coils when a forward voltage is generated from the induced voltage, and induces a high voltage by the short circuit. In a magneto ignition device comprising a secondary coil, control means for controlling the opening and closing of the intermittent means, and DC power supply means for supplying a DC current to the control means, the DC power supply means includes a reverse of an induced voltage. Rectifying means for rectifying only the reverse current generated at the time of voltage, power storage means interposed in a rectification path of the rectification means, and a series circuit connected in parallel to the power storage means and comprising a constant voltage rectification means and a current limiting means. And the voltage between the terminals of the constant voltage rectification means is used as a DC power supply of the control means.

Here, the rectifying means is a reverse current inflow junction diode and a reverse current outflow junction diode, the storage means is a single capacitor, the constant voltage rectification means is a single constant voltage diode, and the current limiting means is a single resistor. It is desirable that

[0012]

When a reverse voltage is generated in the primary coil, a reverse current flows through the rectifier before the value of the reverse voltage reaches the breakdown voltage of the intermittent means, and the power storage means is charged. When the reverse voltage increases, a reverse current flows through the path due to breakdown of the intermittent means or the like, but continues to flow even through the rectifying means. Here, since a series circuit composed of the constant voltage rectification means and the current limiting means is connected in parallel to the power storage means and connected in parallel to the power storage means, a part of the reverse current is bypassed through the series circuit. The power storage means is protected from overcurrent. In addition, since the series circuit includes the current limiting means, the residual voltage value of the constant voltage rectifying means and the residual voltage value of the reverse voltage value can be taken, and the destruction of the constant voltage rectifying means can be prevented. At the same time, the voltage between the terminals of the power storage means is substantially a reverse voltage value, and a rich amount of stored power can be secured even during one reverse voltage period. For this reason, in the latter half of one reverse voltage period, the storage voltage value is close to the reverse voltage, so even if the power is discharged from the power storage means as a power supply in the forward voltage period, it is gradual until the storage voltage falls below the constant voltage value. Draw a descent curve. Therefore, during the period until the forward current (short-circuit current) reaches the maximum value, the constant voltage of the rectifier is supplied to the controller as a DC power supply, so that the DC power supply is stabilized.

[0013]

Next, an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a circuit diagram showing a circuit configuration of a magneto ignition device according to an embodiment of the present invention.

The magneto ignition device of the present embodiment includes a primary coil 1a of a magneto coil 1 which generates an AC induced voltage by rotation of a flywheel 10 with a magnet, and a primary coil 1a when a forward voltage is generated from the AC induced voltage. A switching unit 12 for short-circuiting between the two, a secondary coil 1b of the magneto coil 1 for inducing a high voltage by the short-circuit, a control circuit 14 for opening and closing the switching unit 12, and a DC current to the control circuit 14. And a DC power supply circuit (forward conversion circuit) 16 for supplying power. Here, the switching unit 12
Is a power transistor Q connected between both ends (points a and b) of the primary coil 1a and interrupts a short-circuit current, a voltage dividing resistor r connected between the points a and b, and a base current of the transistor Q. Thyristor TH for shutting off the thyristor. Further, the control circuit 14 generates a gate signal of the thyristor TH and controls turn-on and turn-off of the thyristor TH.

The DC power supply circuit 16 includes an inflow-side junction diode D1 and an outflow-side junction diode D2 for rectifying only a reverse current generated at the time of a reverse voltage among the induced voltages, and a rectification path between the diodes D1 and D2. It has a provided polar storage capacitor C and a series circuit which is connected in parallel to the storage capacitor C and includes a 6V constant voltage rectifier diode (Zener diode) ZD and a resistor R. The voltage between the terminals of the constant voltage rectifier diode (Zener diode) ZD is supplied to the control circuit 14 as a DC power supply voltage.

The forward voltage V ⁺ and the reverse voltage as between both ends of the primary coil 1a of magneto coils 1 (a point and point b) shown in FIG. 3 by the rotation of the flywheel 10 V ^- is repeated alternately induced A voltage V _ab is induced. When the potential at the point a is positive with respect to the point b (forward voltage V ⁺ ), the switching unit 12 is in the ON state under the control of the control circuit 3, and the induced current flows through the switching unit 12 as the short-circuit current Ia.
When the short circuit current Ia as shown in FIG. 3B reaches the maximum value P, the control circuit 14 detects this and turns on the thyristor TH, so that the base current of the power transistor Q is cut off. , The transistor Q is turned off. As a result, as shown in FIG.
Is applied to the secondary coil 1b at a spike-like high voltage (for example, 300 to
400 V), and sparks fly into the ignition gap 6 of the spark plug.

[0018] Negative (reverse voltage V ^-) with respect to potential point b at the point a in the case of the reverse breakdown voltage V _ECO transistor Q
(About 20 V), the reverse current hardly flows through the transistor Q.
The reverse current Ib shown in FIG. When the reverse voltage exceeds V _ECO , an avalanche current flows through the transistor Q,
It is consumed as heat energy and the DC power supply circuit 1
6, the reverse current Ib also flows. Therefore, the capacitor C is charged by the reverse current Ib, the terminal voltage V _C is reversed voltage approximately instantaneously as shown in FIG. After the disappearance of the reverse current Ib, the discharge current I _C changes as shown in FIG. 3, and the inter-terminal voltage V _C gradually decreases with a gentle time constant. Until the Zener voltage of the constant voltage diode ZD falls to 6 V, as shown in FIG. 3, the terminal voltage V _ZD of the constant voltage diode ZD remains at 6 V. In order to lengthen the period of the constant voltage 6V, the capacity of the capacitor C may be increased, and a large amount of charge and a long time constant may be set. When the rotation speed of the flywheel 10 increases and the period of the negative pulse decreases,
Inevitably, the period during which the inter-terminal voltage V _ZD becomes 6 V or less disappears.

The reverse current Ib charges the capacitor C and flows through a series circuit including a constant voltage diode ZD and a resistor R. Since a part of the reverse current is bypassed through this series circuit, the capacitor C is protected from overcurrent. Further, since the series circuit includes the resistor R, the voltage drop causes the constant voltage diode Z
D is protected from overvoltage. Since the stored voltage value is close to the reverse voltage in the latter half of one reverse voltage period, a gradual falling curve is drawn until the voltage becomes equal to or lower than the constant voltage value in the forward voltage period. For this reason, the point in time when the forward current (short-circuit current) reaches the maximum value falls within the constant voltage period, and the operation reliability of the control circuit 14 can be guaranteed by stabilizing the DC power supply.

The above-mentioned DC power supply circuit 16 charges only a single storage capacitor C with a reverse current at the time of reverse voltage, does not charge at all at the time of forward voltage, and eliminates ripples in the power supply voltage at the time of forward voltage. Further, since the entire reverse voltage is applied to the storage capacitor C by utilizing the voltage drop of the resistor, and the charging voltage is set to a high value at the time of the reverse voltage, the constant voltage of the constant voltage diode ZD discharges a long time at the time of the forward voltage. In this way, the power supply voltage is stabilized. Further, in this example, the diode D
1 and D2, the reverse current is actively rectified from the transistor Q at the time of reverse voltage.
The effect of suppressing the avalanche current flowing through the transistor Q is larger than before, the heat loss in the transistor Q is reduced, the reliability can be improved, and the heat radiation structure can be downsized.

[0021]

As described above, the present invention is characterized in that the storage means is charged with a reverse current at the time of reverse voltage, is not charged at the time of forward voltage, and is discharged at a constant voltage as a DC power supply for a long time. I do. Therefore, the following effects are obtained.

Since a capacitor for charge transfer is not required, simplification of the circuit configuration and reduction in the number of components contribute to cost reduction.

In the forward voltage period, the power storage means is not charged,
Also, since no charge commutation is performed, no ripple occurs during the forward voltage period of the DC power supply voltage. Therefore, control reliability of the control means can be secured by stabilizing the power supply voltage.

Since the short-circuit current flowing through the intermittent means during the forward voltage period is not consumed by the DC power supply means, the value of the high voltage does not decrease, and the DC power supply circuit can be used without impairing the ignition characteristics.

Since the reverse current is actively rectified and taken out at the time of the reverse voltage by the rectifying means, the effect of suppressing the reverse current flowing through the intermittent means becomes more remarkable and the heat generation of the intermittent means can be suppressed. This contributes to improvement in element reliability and downsizing of the heat dissipation structure.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a circuit configuration of a magneto ignition device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a specific example of a switching unit in the embodiment.

FIG. 3 is a waveform chart showing voltage and current waveforms of respective parts in the embodiment.

FIG. 4 is a circuit diagram showing a magneto ignition device having a conventional rectifier circuit disclosed in Japanese Patent Publication No. 61-39508.

FIG. 5 is a waveform diagram showing voltage and current waveforms of respective parts in the magneto ignition device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Magneto coil 1a ... Primary coil 1b ... Secondary coil 6 ... Ignition gap 10 ... Flywheel with a magnet 12 ... Switching part 14 ... Control circuit 16 ... DC power supply circuit D1 ... Inflow side junction diode D2 ... Outflow side junction diode ZD ... constant voltage diode C ... storage capacitor R ... resistor Q ... power transistor r ... voltage dividing resistor TH ... thyristor.

Claims (2)

(57) [Claims] 1. A primary coil for generating an AC induced voltage by rotation of a magnet, an intermittent means for short-circuiting between the primary coils when a forward voltage is generated among the induced voltages, and a high voltage is induced by the short-circuit. In a magneto ignition device comprising: a secondary coil; control means for controlling opening and closing of the intermittent means; and DC power supply means for supplying a DC current to the control means. Rectifying means for rectifying only the reverse current generated at the time of voltage, power storage means interposed in the rectification path of the rectification means, and a serial circuit connected in parallel to the power storage means and comprising a constant voltage rectification means and a current limiting means Wherein the voltage between the terminals of the constant voltage rectifying means is used as a DC power supply for the control means. 2. The magneto-ignition device according to claim 1, wherein the rectifier is a reverse current inflow junction diode and a reverse current outflow junction diode, the power storage means is a sole capacitor, The magnet igniter according to claim 1, wherein the voltage rectifying means is a single constant voltage diode, and the current limiting means is a single resistor.