JPH0552168A - Capacitor discharging ignition device for internal combustion engine - Google Patents

Abstract

PURPOSE:To hold induced voltage to a fixed value from the time at a low speed to the time at a high speed in the case of inducing voltage for charging a capacitor by interrupting a short-circuit current of an exciter coil. CONSTITUTION:A boost control device 2A for controlling a base current of a transistor Tr1 of short-circuiting an exciter coil 1 and for controlling trigger timing of a thyristor S1, provided for interrupting the transistor Tr1, is provided. The boost control device 2A controls the base current of the transistor Tr1 so as to increase, when a short-circuit current of the exciter coil 1 is smaller than a reference value, and also the trigger timing of the thyristor S1 in accordance with a rotational speed so as to hold induced voltage of the exciter coil 1 to a preset value regardless of the rotational speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor discharge type ignition device for an internal combustion engine, which uses an exciter coil provided in a magnet generator as a power source.

[0002]

2. Description of the Related Art In a capacitor discharge type ignition device which has been widely used in the past, a positive half cycle output of an exciter coil provided in a magnet generator installed in an internal combustion engine is used as it is to store ignition energy. A high voltage for ignition is induced on the secondary side of the ignition coil by charging the capacitor and discharging the charge of the capacitor to the primary coil of the ignition coil at the ignition timing of the internal combustion engine.

Since it is necessary to charge the ignition energy storage capacitor to at least about 200V, when the capacitor is charged using the output voltage of the exciter coil itself, it is necessary to use a coil having a large number of turns as the exciter coil. Therefore, it was unavoidable that the generator became large-sized and that the space for winding another generator coil became small.

Therefore, a capacitor discharge type ignition device is provided in which a circuit for boosting the output voltage of the exciter coil is provided so that the ignition energy storage capacitor is charged with the output voltage of the exciter coil boosted by the booster circuit. Came to be. In this ignition device, when the exciter coil induces a positive half-cycle voltage, the transistor connected in parallel to the exciter coil is turned on to short-circuit the exciter coil, and the output voltage of the exciter coil reaches a certain level. At that time, the transistor is cut off to cut off the short-circuit current flowing through the exciter coil. When the short-circuit current flowing through the exciter coil is cut off, a high-polarity voltage that tends to keep the short-circuit current flowing is induced in the exciter coil. If the ignition energy storage capacitor is charged with this induced voltage, the number of turns of the exciter coil can be reduced and the capacitor can be charged to a sufficiently high voltage.

FIG. 5 shows an ignition device of this type proposed by the applicant of the present invention. This ignition device includes an exciter coil 1 and an exciter provided in a magnet generator attached to an internal combustion engine. A booster circuit 2 for boosting the induced voltage of the coil 1, an ignition coil 3, an ignition energy storage capacitor 4 and a capacitor discharging thyristor 5 provided on the primary side of the ignition coil 3, a voltage limiting circuit 6, and a direct current A power supply circuit 7, a signal coil 8 that induces a signal at a predetermined rotational position in synchronization with the rotation of the engine, and an ignition signal supply that supplies an ignition signal to the thyristor 5 at the ignition timing of the internal combustion engine using the output of the signal coil as an input. And a circuit 9.

The exciter coil 1 induces positive and negative half cycle voltages in synchronization with the rotation of the engine. DC power supply circuit 7
When an exciter coil induces a negative half-cycle voltage in the direction of the broken arrow in the figure, a power supply capacitor (not shown) is charged to a certain voltage to obtain a DC voltage across the power supply capacitor.

DC voltage obtained from the power supply circuit 7, power supply circuit 7 → resistor R1 → exciter shorting transistor Tr1
Base emitter → resistor R2 → power supply circuit 7 and power supply circuit 7 → resistor R1 → exciter short-circuit transistor Tr1 base emitter → transistor Tr2 emitter base → capacitor C1 → power supply circuit 7 Base current is applied to Tr1 and Tr2. Therefore, when the exciter coil 1 induces a positive half cycle voltage in the direction of the solid arrow, the transistor Tr1
Is conducted, and a short-circuit current of the exciter coil flows in the path of exciter coil 1 → transistor Tr1 → resistor R2 → exciter coil 1. Further, since the transistor Tr2 is conducting until the charging of the capacitor C1 is completed, the transistor Tr3 is in the cutoff state.

The resistor R2 is provided to detect the short circuit current of the exciter coil, and the resistor R4 is provided at both ends thereof.
And a voltage divider circuit consisting of R5 is connected. Resistance R5
The voltage obtained at both ends of is supplied as a trigger signal to the gate of a thyristor S1 provided to cut off the transistor Tr1. The resistance R
The voltage obtained at both ends of 5 does not reach the trigger level of thyristor S1.

When the output of the exciter coil 1 reaches its peak and the charging of the capacitor C1 is completed, the base current stops flowing through the transistor Tr2, so that the transistor Tr2 is turned off and the transistor Tr3 is turned on. Therefore, exciter coil 1 → collector emitter of transistor Tr1 → emitter collector of transistor Tr3 → resistor R3
→ Thyristor S1 gate cathode → Diode D1 →
A current flows through the path of the exciter coil 1 and the thyristor S
Trigger signal is given to 1. When the thyristor S1 is triggered, the base current of the transistor Tr1 is shunted from the transistor Tr1 so that the transistor Tr1 is cut off and the short-circuit current flowing through the exciter coil 1 is cut off. At this time, a high voltage (voltage having the same polarity as the voltage of the positive half cycle) that keeps flowing the short-circuit current that has been flowing until then is induced in the exciter coil 1.
Since this voltage is applied to the ignition energy storage capacitor 4 through the diodes 10 and 11, the capacitor 4 is charged to the polarity shown in the path of the exciter coil 1, the diode 10, the capacitor 4, the diode 11 and the exciter coil 1. When the ignition signal supply circuit 9 generates an ignition signal at the ignition timing of the internal combustion engine, the thyristor 5 becomes conductive, so that the charge of the capacitor 4 is discharged through the thyristor 5 and the primary coil 3a of the ignition coil 3. This causes a large magnetic flux change in the iron core of the ignition coil, so that a high voltage is induced in the secondary coil 3b of the ignition coil, and this high voltage is applied to the spark plug 12 attached to the cylinder of the engine. Therefore, sparks fly to the spark plug and the engine is ignited.

As described above, when the engine is operating at an extremely low speed,
The ignition operation is performed when the output voltage of the exciter coil 1 reaches a peak. As the engine speed increases,
Before the output voltage of the exciter coil 1 reaches its peak, the voltage across the resistor R5 (proportional to the short circuit current of the exciter coil) reaches the trigger level of the thyristor S1. Therefore, the trigger signal is applied to the thyristor S1 at a substantially fixed position set before the position where the output of the exciter coil 1 reaches the peak.

In the ignition device of FIG. 5, when the engine is running at low speed,
The waveform of the positive half-cycle voltage Vex induced in the exciter coil 1 at the medium speed and the high speed is shown in FIG. In FIG. 7, Va represents the level at which the short-circuit current is cut off, and Vb represents the set value of the charging voltage required to perform the predetermined ignition operation. The rate of change dV / dt of the voltage V with respect to time t increases as the engine speed increases, so that the induced voltage Vex increases as the engine speed N increases. Therefore, the charging voltage Vc of the ignition energy storage capacitor increases as the rotation speed N increases as shown by the broken line in FIG. 6, and the cutoff level Va is set so that the set voltage Vb is obtained when the engine is running at low speed. If set, it is inevitable that the charging voltage of the capacitor 4 becomes excessive in the medium speed region and the high speed region.

Therefore, in the conventional ignition device, a voltage dividing circuit composed of resistors R6 and R7, a Zener diode Z1 and
By providing a voltage limiting circuit 6 having a thyristor S2 for shorting the exciter coil, and applying a trigger signal to the thyristor S2 through the Zener diode Z1 when the induced voltage of the exciter coil 1 exceeds the specified value Vb, the thyristor S2 is provided. Is conducted to limit the voltage applied to the capacitor 4. The relationship between the charging voltage Vc of the capacitor and the rotation speed N when the voltage limiting circuit 6 is provided is as shown by the solid line in FIG.

[0013]

In the proposed capacitor discharge type ignition device shown in FIG. 5, a voltage limiting circuit is provided to short-circuit the exciter coil at medium speed and high speed, so that the charging voltage of the capacitor becomes excessive. Since it has been set so as not to occur, extra energy is consumed at the middle speed and the high speed, and there is a problem that a large amount of heat is generated.

It is also possible to limit the short-circuit current of the exciter coil in order to limit the induced voltage of the exciter coil at medium speed and high speed of the engine, but in such a case, at the time of low speed of the engine. There is a problem that the induced voltage of the exciter coil is insufficient.

An object of the present invention is to ensure the induced voltage of the exciter coil required at a low speed by controlling the voltage boosted by the booster circuit according to the number of revolutions, and also to control the voltage of the exciter coil at a medium speed and a high speed. An object of the present invention is to provide a capacitor discharge type internal combustion engine ignition device that prevents an induced voltage from becoming excessive.

[0016]

SUMMARY OF THE INVENTION The present invention is an exciter coil provided in a magneto generator driven by an internal combustion engine, and an ignition energy storage capacitor charged with a positive half cycle output voltage of the exciter coil. A capacitor discharge circuit that discharges the electric charge of the capacitor to the primary coil of the ignition coil when the ignition signal is given, and an ignition signal supply circuit that supplies the ignition signal to the capacitor discharge circuit at the ignition timing of the internal combustion engine. The present invention relates to a capacitor discharge type internal combustion engine ignition device.

In the present invention, an exciter short-circuit transistor having a collector-emitter circuit connected in parallel to the exciter coil, and a cut-off control circuit for turning off the exciter short-circuit transistor when a trigger signal is applied. , When the exciter coil generates a positive half cycle output voltage, it supplies the base current to the exciter short-circuit transistor, and the cut-off control circuit is activated at the set trigger timing within the period when current is flowing through the exciter short-circuit switch. And a boost control device for providing a trigger signal.

The boost controller increases the base current of the exciter-shorting transistor when the short-circuit current flowing through the exciter-shorting transistor is less than the reference value, and increases the exciter-shorting transistor when the short-circuit current exceeds the reference value. Base current control means for controlling the base current of the exciter short-circuit transistor so as to reduce the base current of the exciter short circuit, and induced in the exciter coil when the exciter short-circuit transistor is cut off from the rotation speed of the internal combustion engine and the output voltage of the exciter coil. The trigger timing required to make the voltage to be equal to the set value the time from the reference time to the trigger timing, and the trigger timing calculated by measuring the time from the reference time. And a trigger signal supplying means for giving a trigger signal to the cutoff control circuit when It is provided.

In the present invention, the capacitor is charged by the positive half cycle output of the exciter coil. However, it is optional which of the two half cycles of the exciter coil output is the positive half cycle. is there.

[0020]

As described above, the base current of the exciter short-circuit transistor is increased when the short-circuit current flowing through the exciter short-circuit transistor is less than the reference value, and the exciter short-circuit transistor is increased when the short-circuit current exceeds the reference value. By controlling the base current of the exciter short-circuit transistor so as to reduce the base current, it is possible to induce a relatively high voltage in the exciter coil even when the engine is operating at an extremely low speed, and to perform ignition operation. Can be lowered to facilitate starting the engine.

As described above, the voltage induced in the exciter coil when the exciter short-circuiting transistor is cut off is made equal to the set value based on the rotation speed of the internal combustion engine and the output voltage of the exciter coil (dV / dt is constant. Do)
If the trigger time required for this is calculated and the exciter short-circuit transistor is cut off at the calculated trigger time, the induced voltage of the exciter coil can be made almost constant from low speed to high speed. There is no need for a voltage limiting circuit to short the extra output voltage of the coil. Therefore, since wasteful energy is not consumed, energy efficiency can be improved and heat generation can be reduced.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention. In FIG. 1, 1 is an exciter coil provided in a magnet type AC generator installed in an internal combustion engine (not shown), 2 is a booster circuit, and 3 is Ignition coil, 4 is an ignition energy storage capacitor, 5 is a discharge thyristor, 8 is a signal coil, and 9 is an ignition signal supply circuit.

One end of the exciter coil 1 is grounded, and both ends of the exciter coil 1 are connected in parallel with a diode 13 with its anode facing the ground side. The exciter coil 1 induces an AC voltage in synchronization with the rotation of the engine, but the output voltage of the negative half cycle in the direction of the broken line arrow in the figure is short-circuited by the diode 13.

The ignition coil 3 has a primary coil 3a and a secondary coil 3b. One ends of the primary coil 3a and the secondary coil 3b are grounded, and the cathodes of both ends of the primary coil 3a are directed to the ground side. The diode 11 is connected.
An ignition plug 12 attached to a cylinder of the engine is connected to the secondary coil of the ignition coil.

One end of the ignition energy storage capacitor 4 is connected to the specific ground side terminal of the primary coil 3a of the ignition coil, and the thyristor 5 is connected between the other end of the capacitor and the ground. Further, a cathode of a diode 10 having an anode connected to a non-grounded side terminal of the exciter coil 1 is connected to a connection point between the capacitor 4 and the thyristor 5, and the capacitor 4 is shown by a positive half cycle induced voltage of the exciter coil 1. It is designed to be charged with polarity. A resistor 14 is connected in parallel to both ends of the thyristor 5, and a resistor 15 and a capacitor 16 are connected in parallel between the gate and cathode of the thyristor.

In this example, capacitor 4 → thyristor 5
→ Primary coil 3a of ignition coil → Capacitor 4 circuit constitutes a capacitor discharge circuit. When an ignition signal is applied to the gate of thyristor 5, the thyristor becomes conductive and charges of capacitor 4 are transferred to the ignition coil 1. Next coil 3
a is discharged.

The booster circuit 2 is provided with an exciter-shorting transistor Tr1 composed of a composite transistor in which NPN transistors are connected in Darlington connection, and the collector of this transistor is connected to the non-grounded side terminal of the exciter coil 1. The base of the transistor Tr1 is connected to the boost controller 2A through the resistor R1, and the emitter of the transistor is grounded through the small resistor R2 for current detection.
The emitter of the transistor Tr1 is a PNP transistor T
The emitter of r2 and the emitter of the PNP transistor Tr3 are connected, and the base of the transistor Tr3 is the transistor T.
It is connected to the collector of r2. A resistor R10 is connected between the collector of the transistor Tr2 and ground, and
A diode D2 and a capacitor C1 are connected between the base and emitter of r2 and between the base and ground, respectively.

A thyristor S1 is connected between the base of the transistor Tr1 and the ground, and a resistor R11 is connected between the gate and cathode of the thyristor. The gate of the thyristor S1 is connected to the boost controller 2A, and the resistor R12
Through the collector of the transistor Tr3. A diode D3 is connected between the base and collector of the transistor Tr1. In this example, the thyristor S1 constitutes a cut-off control circuit that cuts off the exciter short-circuit transistor Tr1 when a trigger signal is applied.

The step-up control device 2A is composed of a microcomputer and controls the base current of the transistor Tr1 and the trigger timing of the thyristor S1 (interruption control circuit) according to the control algorithm shown in the flow chart of FIG.

In the conventional ignition device, a DC power supply circuit using an exciter coil as a power supply was used, but in this embodiment, a 12V battery is used as the power supply for the boost control device 2A and the ignition signal supply circuit 9. There is.

Although not shown, in the present embodiment,
There are provided a rotation speed detecting means for detecting the engine speed N and a short circuit current detecting means for detecting a short circuit current ic (average value) of the exciter coil. The rotation speed N is the signal coil 8
It is detected from the cycle of and the frequency of the output of the exciter coil. The short circuit current ic is detected from the voltage across the resistor R2.

The microcomputer constituting the boost controller 2A first reads the output voltage Vex of the exciter coil 1 and detects the zero point of the voltage just before the positive half cycle output voltage Vex of the exciter coil rises. Vex
When a zero point is detected, a short circuit current is supplied to the exciter coil by supplying a base current to the transistor Tr1 to make the transistor Tr1 conductive, and the engine speed N and the short circuit current ic of the exciter coil are read. .. At this time, the count value corresponding to the trigger time of the thyristor S1 is set in the counter and the counter is started.

The trigger time of the thyristor S1 is calculated as the time from a predetermined reference time to the trigger time.
In this example, the time of the zero point immediately before the output of the positive half cycle of the exciter coil rises is used as the reference time.

After the count value corresponding to the trigger time of the thyristor S1 (time to shut off the short-circuit current of the exciter coil) is set in the counter and the counter is started, the magnitude relationship between the read short-circuit current ic and the reference value io is set. To judge. As a result, when the short-circuit current ic is smaller than the reference value io, the base current of the transistor Tr1 is increased, and when the short-circuit current ic is larger than the reference value io, the base current of the transistor Tr1 is decreased. In FIG. 2, the base current control means for controlling the base current of the exciter short-circuit transistor is realized by the process of determining the magnitude relation between the currents ic and io and the process of increasing or decreasing the base current.

After the base current of the transistor Tr1 is controlled, the voltage induced in the exciter coil 1 when the exciter shorting transistor Tr1 is cut off is set based on the rotational speed N of the internal combustion engine and the output voltage Vex of the exciter coil. Is calculated (the dV / dt is made constant) as the time from the reference time to the trigger time.

Next, when the counter counts the count value corresponding to the trigger timing (when the trigger timing is measured), a trigger signal is given to the gate of the thyristor S1.
Reset the counter and go back to the beginning.

When the thyristor S1 is triggered and becomes conductive, the transistor Tr1 is turned off, so that a high voltage is induced in the exciter coil 1. This voltage charges the capacitor 4 through the diodes 10 and 11 to the polarity shown. When an ignition signal is given to the gate of the thyristor 5 at the ignition timing of the internal combustion engine, the thyristor 5 becomes conductive, and the charge of the capacitor 4 is discharged through the thyristor 5 and the primary coil 3a of the ignition coil, so that the ignition coil 2 A high voltage is induced in the secondary coil 3b. Since this high voltage is applied to the spark plug 12, a spark is generated in the spark plug 12,
The engine is ignited.

In the above embodiment, when the program is first executed when the engine is started, the trigger time is not calculated, so the counter does not set the count value corresponding to the trigger time, and the trigger time is not set. Is not measured. In this case, when the output voltage of the exciter coil reaches a peak and charging of the capacitor C1 is completed, and the transistor Tr2 is cut off and the transistor Tr3 is turned on, a trigger signal is given to the thyristor S1 through the resistor R12. Therefore, in this case, the short-circuit current of the exciter coil is cut off at the peak position of the output voltage of the exciter coil.

When the trigger timing of the cutoff control circuit (thyristor S1) is controlled according to the number of revolutions so as to keep dV / dt constant as in the above embodiment, as shown in FIG. The higher the voltage, the higher the cutoff level becomes Va → Va
It becomes lower as ′ → Va ″, and the induced voltage of the exciter coil is set to the set value Vb from low speed to high speed of the engine.
Kept in.

If the base current of the transistor Tr1 is controlled to increase when the short-circuit current of the exciter coil is smaller than the reference value as described above, the voltage induced in the exciter coil is increased when the engine is started or when the engine speed is extremely low. can do.

In the above embodiment, the relationship between the charging voltage Vc of the capacitor 4 and the engine speed N is shown in FIG. 3, and the charging voltage Vc of the capacitor 4 is low even if the voltage limiting circuit is not provided. It is almost constant from time to high speed.

As described above, according to the present invention, since it is not necessary to provide a voltage limiting circuit for short-circuiting an excessive output of the exciter coil, it is possible to prevent wasteful energy consumption and reduce heat generation.

[0043]

As described above, according to the present invention, when the short-circuit current flowing through the exciter-shorting transistor is below the reference value, the base current of the exciter-shorting transistor is increased so that the short-circuit current exceeds the reference value. Since the base current of the exciter shorting transistor is controlled so as to reduce the base current of the exciter shorting transistor when the engine is operating, it is possible to induce a relatively high voltage in the exciter coil even when the engine is operating at an extremely low speed to perform the ignition operation. Can
There is an advantage that the starting rotation speed of the engine can be set low.

Further, according to the present invention, the trigger timing required for making the voltage induced in the exciter coil equal to the set value when the exciter short-circuit transistor is cut off from the rotational speed of the internal combustion engine and the output voltage of the exciter coil. Since the exciter short-circuit transistor is cut off at the calculated trigger time, the induced voltage of the exciter coil can be made substantially constant from low speed to high speed. Therefore, since a voltage limiting circuit for short-circuiting the excessive output voltage of the exciter coil is not required, it is possible to prevent wasteful energy consumption and reduce heat generation.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart showing a control algorithm of the boost control device used in the embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between the induced voltage of the exciter coil and the rotation speed in the example of the present invention.

FIG. 4 is a waveform diagram schematically showing a waveform of an output voltage of an exciter coil obtained at a low speed, a medium speed, and a high speed in an embodiment of the present invention.

FIG. 5 is a circuit diagram showing a configuration of an already proposed ignition device.

6 is a diagram showing the relationship between the induced voltage of the exciter coil of the ignition device of FIG. 5 and the rotation speed.

7 is a waveform diagram schematically showing waveforms of induced voltages of an exciter coil obtained at low speed, medium speed, and high speed in the ignition device of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Exciter coil, 2 ... Booster circuit, 2A ... Booster control device, 3 ... Ignition coil, 4 ... Ignition energy storage capacitor, 5 ... Thyristor, 8 ... Signal coil, 9 ... Ignition signal supply circuit, 10 ... Diode, Tr1 ... Exciter short-circuit transistor, S1 ... Thyristor that constitutes a cutoff control circuit.

Claims (1)

[Claims] 1. An exciter coil provided in a magnet generator driven by an internal combustion engine, an ignition energy storage capacitor charged with a positive half cycle output voltage of the exciter coil, and an ignition signal are provided. A capacitor discharge internal combustion engine equipped with a capacitor discharge circuit for discharging the electric charge of the capacitor to the primary coil of the ignition coil and an ignition signal supply circuit for supplying an ignition signal to the capacitor discharge circuit at the ignition timing of the internal combustion engine. In an ignition device for an exciter short circuit transistor, wherein a collector-emitter circuit is connected in parallel to the exciter coil,
A shut-off control circuit that shuts off the exciter short-circuit transistor when a trigger signal is applied, and supplies a base current to the exciter short-circuit transistor when the exciter coil generates a positive half-cycle output voltage. A boosting control device for applying a trigger signal to the cutoff control circuit at a trigger timing set within a period in which a current flows through the exciter short-circuiting switch, wherein the boosting control device includes the exciter shorting transistor. The exciter short circuit is configured to increase the base current of the exciter short-circuit transistor when the flowing short-circuit current is equal to or less than a reference value and decrease the base current of the exciter short-circuit transistor when the short-circuit current exceeds a reference value. Current control hand for controlling the base current of the transistor A trigger time necessary to make the voltage induced in the exciter coil equal to the set value when the exciter short-circuit transistor is cut off from the rotation speed of the internal combustion engine and the output voltage of the exciter coil, from the reference time. Trigger timing calculation means for calculating the time up to the trigger timing, and trigger signal supply means for giving the trigger signal to the cutoff control circuit when the trigger timing calculated by measuring the time from the reference time is measured. An ignition device for a capacitor discharge type internal combustion engine, comprising: