JPS6251761A - Ignition device - Google Patents

Abstract

PURPOSE:To enable an electric discharge to be restarted in a short time even if the discharge is interrupted by a blow-off during AC ignition, by providing a timer circuit in an ignition device of continuous AC discharge type for an internal-combustion engine. CONSTITUTION:An ignition device constitutes two closed circuits respectively containing primary coils 13, 14 of an ignition coil 11 and having switching elements 7, 8 to perform push-pull action by a control circuit comprising a discriminating circuit 40 and a logical circuit 3, generates a continuous AC discharge in a spark plug 30. Said control circuit connects a timer circuit 50 which measures an electrification time for one of the two closed circuits. And if said electrification time exceeds a preset value, the timer circuit 50, deciding the discharge to be interrupted, cuts off said one closed circuit while actuates the other closed circuit so as to immediately generate the discharge.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ignition device, and more particularly to an AC continuous discharge type ignition device that controls the primary coil current of an ignition coil.

[Conventional technology]

Conventionally, as an alternating current continuous discharge type ignition device for a spark-ignition internal combustion engine, for example, a system disclosed in Japanese Patent Laid-Open No. 56-34964 has been known. The duration can be made as long as necessary, and the average discharge current value is as high as 50mA or more.
High-energy single ignition is possible, and the mixture has excellent ignitability.

[Problem that the invention seeks to solve]

However, in the method disclosed in Japanese Patent Application Laid-Open No. 56-34964, the discharge tends to be interrupted due to the discharge spark blowing out when the internal combustion engine rotates at high speed or under high load, and once interrupted, it takes a long time until the discharge resumes. There was a problem that the ignitability was not good.

SUMMARY OF THE INVENTION In order to solve this problem, an object of the present invention is to provide an ignition device that controls to shorten the time until the discharge restarts even if the discharge spark is interrupted, and does not impair the ignitability of the internal combustion engine. do.

[Means for solving problems]

Therefore, the present invention provides a DC power source that generates a DC voltage; an ignition coil having a second primary coil and a secondary coil; a first switching element constituting a first closed circuit including the DC power source and the first primary coil; a second switching element constituting a second closed circuit including two primary coils, and a backflow prevention element that specifies the current direction of the first closed circuit and the second closed circuit to be one direction, respectively; first and second current detection elements that respectively detect the energizing currents of the first and second closed circuits, and operate according to an ignition instruction signal arriving from the outside;
Said 1st. With both current detection signals from the second current detection element as input, when the current flowing in one of the two closed circuits reaches a set value, a signal is sent to the two switching elements to cut off the energization of one of the closed circuits. and give it to one side,
A control circuit that applies a signal for starting energization of the other closed circuit to the other of the switching elements to cause the switching elements to perform a push-pull operation, and a energization time of one of the two closed circuits is set. and a timer circuit that cuts off the energization of one of the closed circuits and generates a signal that starts the energization of the other closed circuit when the value exceeds the value of the closed circuit.
The present invention provides an ignition device that periodically generates a trigger high voltage and a sustained discharge voltage such that the period is equal to or less than a set value.

[Effect]

As a result, even if discharge is interrupted due to blowout during AC ignition, if the energization time exceeds the set value due to the timer circuit, the first energizing current will reach the set value before the energizing current reaches the set value. The second closed circuit is switched to restart the discharge in a short time.

〔Example〕

The present invention will be explained below with reference to embodiments shown in the drawings.

FIG. 1 is an overall circuit diagram showing one embodiment of the present invention, which is partially different from the circuit diagram shown in Japanese Patent Laid-Open No. 56-34964.

In Figure 1, ■ is a DC power supply, which is an on-vehicle battery, and 2
3 is a signal generator that generates an ignition signal in synchronization with the rotation of the engine (not shown), and 3 is a logic circuit.

The AND gate 4 in this circuit 3 is a circuit that takes an AND logic between the output signal of the signal generator 2 and the Q output signal of the flip-flop 26 in the discrimination circuit 40. During this period, the Q output signal of the flip-flop 26 is passed through, and when the signal generator 2 outputs an O level signal, it always outputs a 0 level signal. The AND gate 5 connects the output signal of the signal generator 2 and the flip-flop 26.
This circuit takes AND logic with the Q output signal of the flip-flop 26, and passes the Q output signal of the flip-flop 26 while the signal generator 2 is outputting a level signal, and when the signal generator 2 outputs an O level signal. Always outputs O level signal.

7.8 is a power transistor connected to perform push-pull operation by the outputs of AND gates 4 and 5; the base of transistor 7 is connected to the output terminal of AND gate 4, and the base of transistor 8 is connected to the output terminal of AND gate 5.
is connected to the output terminal of The collectors of the transistors 7.8 are each connected via a diode 9.10 to a primary terminal 16.18 of the ignition coil 11, and each collector is connected to the cathode of a diode 9, 10, respectively. The emitter of the transistor 7.8 is connected to the negative terminal of the common DC power supply 1 via a current detection resistor 22.24 having a minute resistance value.

The ignition coil 11 consists of a primary coil 13.14, a secondary coil 15, and an iron core 12 with a turns ratio of about 200 to 300.
are magnetically coupled via the primary coil 13.14.
Terminals 16 and 18 of the primary coil are connected to diodes 9 and 9.
10, and the intermediate terminal 17 is connected to the DC power supply 1.
It is connected to the positive terminal of. The output terminal 19 of the secondary coil 15 and the spark plug 30 are connected by a high voltage cable.

The determination circuit 40 determines the magnitude of the primary coil currents 1a and Ib of the ignition coil 11 by detecting the voltage drop across the current detection resistor 22.24. In this discrimination circuit 40, a current detection resistor 2 is connected to the positive input terminal of the comparator 27.
Since the voltage drop of 2 is applied and the comparison reference voltage Vref is applied to the negative input terminal, the comparator 27 compares both voltages and outputs a Lebel signal when the voltage drop is larger than the comparison voltage Vref. However, when the dropped voltage is smaller than the comparison voltage Vref, a signal at the θ level is output. On the other hand, regarding the comparator 28, the voltage drop of the current detection resistor 24 is applied to its positive input terminal, and the comparison voltage Vref is applied to its negative input terminal, so the voltage drop is larger than the comparison voltage V ref. When the voltage drop is smaller than the comparison voltage Vref, the comparator 28 outputs a level signal, and outputs a θ level signal when the voltage drop is smaller than the comparison voltage Vref. The flip-flop 26 is a D-type flip-flop (for example, Toshiba TC40138P), where the terminal S is a set input terminal, the terminal R is a reset input terminal, the terminal Q is an output terminal, the terminal Q is an inverted output terminal, and the terminal R is a data terminal. The input terminal, terminal CP, is a clock input terminal. The terminals S and R of this flip-flop 26 are connected to the output terminals of the comparators 28 and 27, respectively. When the comparator 27 outputs a level, the terminal Q outputs a 0 level, and when the comparator 28 outputs a level, the terminal Q outputs a level 0. Terminal Q outputs the level.

On the other hand, terminal Q outputs the inverted logic level of terminal Q.

Since the terminal of the flip-flop 26 is connected to the terminal δ, when the level of the terminal CP changes from 0 to 1 in the flip-flop 26, the level of the terminal Q is inverted.

The timer circuit 50 is a timer that operates using the rising and falling edges of the Q terminal output level of the flip-flop 26 in the discrimination circuit 40 as triggers. In this timer circuit 50, the +Tr terminal (rising edge detection terminal) of the one-shot multi 51 and the -Tr terminal (falling edge detection terminal) of the one-shot multi 52 are commonly connected to the Q terminal of the flip-flop 26. There is. Also, the Q terminal (output terminal) of one-shot multi 51.52
are respectively input to the input terminals of the OR gate 53, and the OR
The result of the logic is output from the output terminal of the OR gate 53. Therefore, the one-shot multi 51 detects the rise timing of the level of the Q terminal of the flip-flop 26, and the one-shot multi 52 detects the fall timing of the level, and a composite signal of trigger pulses corresponding to these timings is output from the OR gate 53. Output. These trigger pulse widths are determined by resistors 511, 521 . capacitor 512
．． 522 time constant.

The one-shot multi 54 is a retriggerable one-shot multi (for example, Toshiba TC40478P), and +T
The r terminal (rising edge detection terminal) and the ReTr terminal (retrigger terminal) are commonly connected to the output terminal of the OR gate 53. Further, the Q terminal of the one-shot multi 54 is connected to the CP terminal of the flip-flop 26. The output pulse width (timer one hour) Tt of the one-shot multi 54 when there is no retrigger is determined by the number of time points of the resistor 541 and capacitor 542. Therefore, OR gate 53
The trigger pulse interval Tp output from the timer is one hour T.
When it is smaller than t, that is, when 'rp<'rtO, the Q terminal of the one-shot multi 54 outputs O level, and 'r
When p<'rt, output the rubel.

Next, the operation of the above configuration will be explained.

During operation of the internal combustion engine, a signal generator 2 which generates an ignition signal in synchronization with the rotation of the engine outputs a square wave pulse signal as shown in FIG. 2(a). That is, the signal generator 2 outputs the level signal only during the spark discharge period.

On the other hand, the discrimination circuit 40 outputs a square wave pulse signal at a natural frequency of about 2 to 5 KHz, which is determined by the circuit design including the ignition coil 11. Therefore, the AND gate 4 is the second
A pulse signal as shown in figure (b) is output, and the other AND
The gate 5 outputs a pulse signal as shown in FIG. 2(C). Transistors 7□8 are connected to AND gates 4.
Since it is turned on and off according to the output of 5, the period T in Fig. 2
In this case, pulse signals having mutually opposite phases are applied to the bases of both transistors 7.8, thereby causing the transistors 7.8 to alternately turn on and off.

FIG. 3 is an enlarged view of the time axis of the waveforms of various parts during the period T, and FIG.

Then, as shown in FIG. 3 (fl), the flip-flop 26
Since the Q output of is Lebel, the output of the AND gate 4 rises to Lebel, the transistor 7 is turned on from the off state, and the current Ia flowing through the primary coil 13 is increased as shown in Fig. 3(b).
), it increases with time. When the current 1a of the primary coil 13 reaches 20A at time t2, a voltage corresponding to the current 20A is generated at the terminal 23 due to the voltage drop across the current detection resistor 22, and this voltage and the comparison reference voltage Vref
Vref is determined so that they are the same.

Therefore, after time t2, terminal 2 corresponding to current 1a
3 becomes larger than the comparison reference voltage Vref, the output of the comparator 27 changes from the O level to the level at time t2 as shown in FIG. As shown in FIG. 3(f), the output of the terminal Q changes from the level to the O level at time t2, and the transistor 7 changes from the on state to the off state, so that the current in the primary coil 13 changes. 1a rapidly decreases immediately after reaching the maximum value of 20 A as shown in Fig. 3 (bl). Therefore, a back electromotive force is generated in the primary coil 13 in the direction of the arrow x in Fig. 1, and the secondary As shown in FIG. 3 (kl), a trigger high voltage of -30 kV is generated at the terminal 19 of the coil 15, and the spark plug 3
0 can be sparked. After the start of discharge, a constant voltage of -2 is outputted at approximately -2, and a discharge current flows through the secondary coil 15 as shown in FIG. 3 (1).

Further, the output of the comparator 27 changes from the 0 level to the level at time t2, and then the current of the primary coil 13
a decreases and becomes smaller than the current 20A, and the voltage drop at the terminal 23 becomes smaller than the comparison reference voltage Vref, so the output of the comparator 27 changes from level to O level. Therefore, as shown in FIG. 3(d), the comparator 27 generates a short pulse waveform immediately after time t2.

At time t2, the Q output of the flip-flop 26 changes from level 0 to level 0 as shown in FIG.
As shown in g), the level changes from O level to level.

Subsequently, after time t2, transistor 8 and diode 1
0 is conductive, and the current 1b of the primary coil 14 is as shown in Fig. 4 (C).
increases over time as shown in .

At time t, the current 1b of the primary coil 14 becomes the current 20
When the voltage reaches A, a voltage corresponding to the current 20A is generated at the terminal 25 due to a voltage drop across the current detection resistor 24, and Vref is determined so that this voltage and the comparison reference voltage Vref are the same. Therefore, after the time t3, the voltage drop at the terminal 25 corresponding to the current 1b becomes larger than the comparison reference voltage Vref, so that the voltage drop at the terminal 25 corresponding to the current 1b becomes larger than the comparison reference voltage V ref, so that the voltage drop at the terminal 25 becomes larger than the comparison reference voltage V ref, so that the voltage drop at the terminal 25 corresponding to the current 1b becomes larger than the comparison reference voltage V ref.
At this point, the output of the comparator 28 changes from 0 level to level. Therefore, since this level signal is input to the terminal S of the flip-flop 26, the output of the terminal Q changes from the O level to the level at the time shown in FIG. 3(f), and the transistor 8 is turned on. Since the current 1b of the primary coil 14 reaches the maximum value of 20 A as shown in FIG. A back electromotive force is generated in the Y direction, and a voltage is generated at the terminal 19 of the secondary coil 15 whose polarity instantly switches from a negative voltage of -2 kV to a positive voltage of +2 kV, as shown in Figure 3 (k). Figure 3 [J!
) continues without interruption.

Immediately after the output of the comparator 28 changes from the θ level to the level at time t, the current 1b of the primary coil I4 decreases and becomes smaller than the current 20A, and the terminal 25
Since the voltage drop becomes smaller than the comparison reference voltage Vref, the output of the comparator 28 changes from level to O level. Therefore, as shown in FIG. 3(e), the output signal of the comparator 28 generates a short pulse waveform immediately after time t3. After time t3, transistor 7 and diode 9
conducts, and the current 1a increases again as shown in FIG. 3(b).

Here, in this embodiment, the diode 10 is the transistor 8.
Since the negative pulse high voltage is not absorbed in order to prevent conduction between the base and collector of the Trigger high voltage occurs.

On the other hand, since the diode 9 prevents conduction between the base and collector of the transistor 7 and therefore does not absorb the negative pulse high voltage, the Y generated in the primary coil 14 at time t3
When the back electromotive force in the direction is stably generated and the discharge of the spark plug 30 is interrupted, a positive trigger high voltage is generated in the secondary coil I5, and when the discharge is not interrupted, the voltage polarity changes instantly. The spark plug 30 continues to discharge.

Thereafter, the above-mentioned operation is repeated, and the result is shown in FIG. 3(k).

By generating the voltage and current waveforms shown in (i) in the secondary coil 15, it is possible to cause the ignition plug 30 to perform continuous alternating current discharge.

Next, a case in which the discharge is blown out and interrupted due to an air current or the like near the ignition plug 30 will be described in comparison with a case in which it is not interrupted.

Roughly speaking, the difference between when the discharge is interrupted and when it is not interrupted is that the timer circuit 50 operates and generates a signal in order to shorten the non-discharge period from the interruption to the discharge again. Forced to flip Flon 126
It is to invert the . Therefore, the operation of the timer circuit 50 will be mainly explained.

The timer circuit 50 is shown in FIG. 3 (fl, (h), (1)
As shown in FIG. 2, the rising and falling edges of the Q output of the flip-flop 26 are detected, a trigger signal is generated, and this signal is input to the +Tr terminal of the one-shot multi 54 connected to enable retrigger operation.

The interval Tp of this trigger signal (for example, about 200μ5e
c) and the output pulse width (timer one hour) Tt of the one-shot multi 54 are set to satisfy the relationship 'rp<'rt (for example, Tt=400μ5ec). Therefore, Fig. 3 (
''), after the Q output of the one-shot multi 54 changes from the level to the O level at time t2, it remains at the 0 level until time t because it is retriggered.

However, at time t8, as shown in FIG. 3 (1-), when the current in the secondary coil 15 becomes O due to discharge cut-off,
The current Ta of the primary coil 13 shown in FIG. The period Tt' from the time t when the i/13 starts energizing to the time tl+ is considerably larger than 'rp in FIG. 3, and also larger than the timer one hour Tt.

That is, Tp < Tt <Tt'. (For example, Tt'=
800μ5ec).

Therefore, since the one-shot multi 54 is not retriggered for a period of Tt', from time t to Tt (for example, 400
It operates at time t, after which time has elapsed by μ5ec), and changes from 0 level to level as shown in FIG. 301. This level change is input to the CP terminal of the flip-flop 26, and the Q output is output as shown by the solid line in FIG. 3(f) and (g).
The level of the Q output is inverted.

Then, at time t, a trigger high voltage is generated as shown by the solid line in FIG. It will be done.

What is important here is that if the timer circuit 50 is not provided, the discharge will be interrupted for a period of t to t (approximately 700 μ5 ec), but with the timer circuit provided,
The period during which the discharge is interrupted is t, ~t.

(approximately 300 μ5 ec).

From the above explanation, the spark plug 30 can be capacitively discharged by the trigger high voltage, and then can be discharged for a long time by continuous AC discharge, but if the discharge of the spark plug 30 is temporarily interrupted due to the airflow in the combustion chamber of the internal combustion engine. However, the operation of the timer circuit 50 quickly restarts the discharge and shortens the time it takes for the discharge to stop.

〔Effect of the invention〕

As described above, in the present invention, a timer circuit is added to the AC continuous discharge type ignition device disclosed in Japanese Patent Application Laid-Open No. 56-34964, and when the switching period of a pair of power transistors becomes larger than a set value, Since the timer circuit works and forces the pair of power transistors to switch, even if the spark plug stops discharging, it can immediately resume discharging, so the spark plug can be turned on almost continuously for a long time. It becomes possible to discharge,
This has the excellent effect of improving the fuel efficiency of combustion discharge from an engine, etc., and reducing the amount of harmful components emitted from the exhaust gas.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing one embodiment of the device of the present invention, and FIG.
3 and 3 are waveform diagrams of various parts for explaining the operation of the apparatus shown in FIG. 1. DESCRIPTION OF SYMBOLS 1... Vehicle-mounted battery that generates a direct current, 2... Signal generator, 3.40... Discrimination circuit and logic circuit forming a control circuit, 7, 8... Each of the first. A power transistor serving as a second switching element, 9.10... A diode serving as a backflow prevention element, 11... An ignition coil, 1
3.14...Primary coil, 15...Secondary coil, 2
2.24...Respectively 1st. A current detection resistor forming a second current detection element, 30... Spark plug, 50... Timer circuit.

Claims (1)

[Claims] a DC power source that generates a DC voltage; an ignition coil having first and second primary coils and a secondary coil; and a first closed circuit that includes the DC power source and the first primary coil. a second switching element constituting a second closed circuit including the DC power source and the second primary coil; and a current direction of the first closed circuit and the second closed circuit. a backflow prevention element that respectively defines one direction, first and second current detection elements that respectively detect the energizing current of the first and second closed circuits, and operate according to an ignition instruction signal received from the outside, Using both current detection signals from the first and second current detection elements as input, a signal is generated to cut off the current flow to one of the closed circuits when the current flowing in one of the closed circuits reaches a set value. a control circuit that applies a signal to one of the switching elements and starts energizing the other closed circuit to cause the switching element to perform a push-pull operation; When the energization time of one of the closed circuits exceeds a set value, the timer circuit cuts off the energization of one of the closed circuits and generates a signal that starts energization of the other closed circuit. An ignition device that periodically generates a sustained discharge voltage such that the period is less than or equal to a set value.