JPS63306278A - Igniter for internal combustion engine - Google Patents

Abstract

PURPOSE:To protect power transistor from thermal breakdown by providing a closed condition anti-holding circuit for opening the power transistor upon elapse of predetermined time when ON-state of ignition signal is held in an input circuit. CONSTITUTION:A closed condition anti-holding circuit 28 is provided in an input circuit. Even if ON-state of ignition signal fed from an ignition signal generator continues, i.e. potential at terminal PS is held continuously at L level, a comparator 19 is inverted upon elapse of predetermined time, i.e. a time interval to be elapsed until the collector potential of NPN transistor 13 exceeds over the referential voltage of the comparator 19 through recharging of a capacitor 14, and the output thereof is brought to H level so as to bring the output of an inverting/amplifying circuit 25 to L level. Since the final stage power transistor 2 is turned OFF, excessive heating of the power transistor 2 is suppressed thus protecting the power transistor 2 and other circuitry from thermal breakdown.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an ignition device for an internal combustion engine that operates in response to an ignition signal from an ignition signal generator that generates an ignition signal in accordance with the rotation of the internal combustion engine. [Prior Art] Conventionally, as an ignition device for an internal combustion engine, a power transistor cuts off the primary current of an ignition coil in response to an ignition signal from an ignition signal generator that generates an ignition signal in accordance with the rotation of the internal combustion engine. There is a current interrupt type ignition device that induces a high voltage on the secondary side of the ignition coil.

FIG. 3 is a block diagram showing the configuration of a conventional ignition device for an internal combustion engine. In the figure, A is an amplifier circuit that amplifies an ignition signal from an ignition signal generator that generates an ignition signal according to the rotation of the internal combustion engine, and B is an amplifier circuit that limits the maximum current flowing through the primary side of the ignition coil 1 to below a certain level. A current limiting circuit 2 limits the current flowing to the primary side of the ignition coil 1 to 0N10FF.
3 is a spark plug; 4 is a current detection resistor that generates a voltage in response to the current flowing through the primary side of the ignition coil 1;

In the ignition device for an internal combustion engine having the above circuit configuration, the ignition signal from the ignition signal generator (not shown) is amplified by the amplification circuit A, and the amplified ignition signal turns off the power transistor 2, causing the ignition coil 1 to turn off. Cut off the primary current. As a result, a high voltage is generated at the secondary (ff+) of the ignition coil 1, and a spark is generated at the ignition plug 3. It was something to do.

[Problem that the invention seeks to solve]

However, in the ignition device for an internal combustion engine having the above circuit configuration, when the ignition signal from the ignition signal generator is held on, that is, the on state is maintained continuously, the ignition device is no longer energized, and the power transistor in the final output stage will remain closed. This causes a problem in that the power transistor generates too much heat, causing thermal damage to the power transistor and other circuits.

The present invention has been made in view of the above-mentioned points, and is intended for use in internal combustion engines, which eliminates the above-mentioned problems and prevents power transistors, etc. from being thermally destroyed even if the ignition signal from the ignition signal generator continues to be in the on state. The purpose is to provide an ignition device.

[Means for solving problems]

In order to solve the above problems, the present invention cuts off the primary QM flow of the ignition coil with a power transistor in response to an ignition signal from an ignition signal generator that generates an ignition signal in accordance with the rotation of an internal combustion engine. In a current interrupt type ignition system for an internal combustion engine that induces a high voltage on the secondary side of the ignition coil, when the ignition signal from the ignition signal generator remains on in the input circuit, the power transistor is opened after a predetermined period of time has elapsed. A closed state maintenance prevention circuit is provided.

[Effect]

By configuring the ignition device for an internal combustion engine as described above,
Even if the ignition signal from the ignition signal generator remains on, the closed state retention prevention circuit operates and opens the power transistor after a predetermined period of time, which prevents thermal damage to the power transistor and other circuits. .

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a circuit diagram showing a circuit configuration of an ignition device for an internal combustion engine according to the present invention. In this figure, parts given the same reference numerals as those in FIG. 3 indicate the same or equivalent parts.

As shown in FIG. 1, the ignition system for an internal combustion engine includes a resistor 21
a surge absorption circuit consisting of an energy diode 22;
Consisting of an amplifier circuit 23, an inverting amplifier circuit 25, a closed state maintenance prevention circuit 28, a current limiting circuit B1, a current detection resistor 4 for detecting the primary current of the ignition coil 1, a power transistor 2, an ignition coil 1, and a spark plug 3. be done.

Note that +■ indicates the voltage on the positive side of the battery (not shown).

In the ignition device for an internal combustion engine having the circuit configured as described above, an ignition signal is inputted to the terminal PS as an open collector input from the ignition signal generator, and when the ignition signal is at L (low) level, the inverting amplifier circuit 25 The output becomes H (high) level. As a result, the power transistor 2 is turned on, and the primary current of the ignition coil 1 flows.

When the terminal PS is input at H (high) level, the output of the inverting amplifier circuit 25 becomes L (low) level, and the power transistor 2 becomes O.
Becomes FF. When the power transistor 2 is turned off, the primary current of the ignition coil 1 is cut off, a high voltage is generated on the secondary side, and a spark discharge occurs at the ignition plug 3.

When a primary current flows through the power transistor 2, a voltage responsive to the primary current of the ignition coil 1 is generated in the current detection resistor 4. When the voltage exceeds the voltage set by the current limiting circuit B, the current limiting circuit B is activated to reduce the base current of the power transistor 2 and control the primary current of the ignition coil 1 to the set value.

Next, the circuit configuration of the closed state maintenance prevention circuit 28 will be explained. First, the Zener diode 15 is connected to the positive probe V of the battery via the resistor 21 and the resistor 27 as a power source for the closed state maintenance prevention circuit 28. The reference potential of the comparator 19 is provided by dividing the potential, which has a constant voltage value by the Zener diode 15, by the resistor 17 and the resistor 18.

A diode 20 is inserted so that no current flows when the output of the comparator 19 is at L (low) level. Connect from the PS terminal to the base of the NPN transistor 13 via the resistor 11 and resistor 12, and from the collector of the NPNI-Rangemetal 130,
It is connected to the input terminal of a comparator 19 via a capacitor 14.

The operation of the ignition system for an internal combustion engine having the above circuit configuration will be explained using the waveform diagram shown in FIG. The potential of the PS terminal is as shown in Figure 2 (a
), and the 7tt position of the PS terminal becomes H (high).
When the level is on, the NPN transistor 13 is turned on, the capacitor 14 is not charged, and the output of the comparator 19 is at the L (low) level. The output is at L (low) level as shown in FIG. 2(c). Next, when the PS terminal becomes L (low) level, the NPN transistor 13 is turned off and charging of the capacitor 14 starts, and the collector potential of the NPN transistor 13 changes as shown in FIG. 2(b) and gradually rises. , normally zenadaode 15
Before it exceeds the reference potential set by resistors 17 and 18, the potential of the PS terminal becomes H (high) level and becomes NPN.
Since the transistor 13 is turned on, charging of the capacitor 14 is stopped and the capacitor 14 is discharged. When the potential of the PS terminal continues to maintain the L (low) level, the NPN l-transistor 13
The collector potential of P changes as shown in Figure 2(b), and P
When the S terminal becomes L (low) level and a certain period of time T has elapsed, the collector potential of the NPN transistor 13 becomes the reference potential set by the Zener diode 15 and the resistors 17 and 18, that is, the voltage shown in FIG. The score exceeds 78 points shown in (b). When the collector potential exceeds the reference potential, comparator 1
The output of 9 becomes H (high) level, and the output of inverting amplifier 25 becomes L (low) level. As a result, the power transistor 2 becomes 0FFL, and the power transistor 2 remains ONt until the PS terminal reaches H (high) level again. The above is the operation of the closed state maintenance prevention circuit 28. As explained above, according to the above embodiment, since the closed state maintenance prevention circuit 28 is provided in the input circuit, the ignition signal from the ignition signal generator continues to be in the on state, that is, the potential of the PS terminal is low. (low)
Even if the level continues, after a certain period of time, that is, the capacitor 14
After a period of time for the collector potential of the NPN transistor 13 to exceed the reference potential of the comparator 19 due to charging, the comparator 19 is inverted and its output becomes H (high) level, and the output of the inverting amplifier circuit 25 is Since the L (low) level is set, the power transistor 2 in the final output stage is turned off, thereby suppressing excessive heat generation in the power transistor 2 and preventing thermal damage to the power transistor 2 and other circuits.

The closed state maintenance prevention circuit described above is not limited to the configuration of the closed state maintenance prevention circuit 28 shown in FIG. Any circuit configuration may be used as long as it has a circuit configuration that opens the power transistor after a predetermined period of time has elapsed.

〔Effect of the invention〕

As explained above, according to the present invention, if the ignition signal from the ignition signal generator is kept in the on state, the input circuit is provided with a closed state retention prevention circuit that changes the power transistor from the closed state to the open state after a predetermined period of time. Therefore, even if the ignition signal from the ignition signal generator is kept in the on state for a long time, the power transistor that conducts and cuts off the primary current of the ignition coil will be in the open state after a predetermined time.
An excellent effect can be obtained in that excessive heat generation of the power transistor is suppressed, and thermal destruction of the power transistor and other circuits can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the circuit configuration of an ignition device for an internal combustion engine according to the present invention, FIG. 2 is a waveform diagram for explaining the operation of the ignition device for an internal combustion engine, and FIG. 3 is a conventional ignition device for an internal combustion engine. FIG. 2 is a block diagram showing the configuration of an ignition device. In the figure, 1...Ignition coil, 2...Power transistor, 3...Ignition plug, 4...E detection resistor, 23...Amplification circuit, 25... . . . Inverting amplifier circuit, 28. . . Closed state retention prevention circuit, B. . . Current limiting circuit. −? --- cs -α.

Claims (1)

[Claims] The input circuit is provided with an input circuit into which an ignition signal is input from an ignition signal generator that generates an ignition signal in accordance with the rotation of the internal combustion engine, and the primary current of the ignition coil is interrupted by a power transistor in response to the ignition signal, and the ignition is activated. In a current interrupt type ignition device for an internal combustion engine that induces a high voltage on the secondary side of a coil, when the ignition signal from the ignition signal generator is maintained in the on state in the input circuit, the An ignition device for an internal combustion engine, comprising a closed state maintenance prevention circuit that opens a power transistor.