JPS59203874A - Superposed electric discharge type ignition device - Google Patents

Abstract

PURPOSE:To obtain superposed discharging time sufficiently and ensure the superposed electric discharge by a method wherein the operating period of time of a DC-DC converter for the superposed electric discharge type ignition device is controlled so as to be shortened in accordance with the increase of an engine speed. CONSTITUTION:When an ignition timing signal is generated in a pickup coil 2, a transistor T1 is conducted, a thyristor SCR is conducted, a part of the electric charge of a capacitor C4 flows into the primary coil 5a of an ignition coil 5 through the capacitor C5 and high voltage spark is generated. Impedance of an ignition plug 6 is reduced by the generation of this spark, the main electric charge of the capacitor C4 is discharged to the secondary coil 5b and high energy spark is generated by this superposed electric current. According to this method, a gap is compensated by auxiliary superpoed electric current after beginning of the electric discharge and the generation of ignition mistake may be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an internal combustion engine ignition system, and more particularly to a stacked discharge type ignition system that causes a stacked discharge to occur in an ignition coil.

[Background of the invention]

Generally, diesel engines perform self-ignition. That is, fuel is injected into the air at several hundred degrees centigrade, and the fuel is ignited by itself.

Therefore, it is easier to control combustion by self-igniting as quickly as possible, so diesel engines
A fuel with a high cetane number that self-ignites is required. The higher the rate at which this fuel is directly distributed into the air, the better the starting performance is. When the atmospheric temperature is 0° C. or higher, so-called normal temperature, the direct injection type has good startability and can be started without any starting aid device. However, when the temperature drops below -10C, starting performance becomes poor and some kind of starting aid device is required. Therefore, it has been conventional to use glow plugs. However, when the temperature drops below -20 tl:', there is a problem that the engine will not start.

Starting at this low temperature requires a different system than a gasoline engine.
It is necessary to ignite with a high energy of about 100 liters (J), so a capacitor discharge type high energy ignition device has conventionally been used. This capacitor discharge type high-energy ignition device charges a capacitor to about 1 to 1.5 KV using a DC-DC converter, and uses a portion of the charge in the capacitor to ignite a thyristor at a predetermined ignition timing, thereby discharging the ignition coil. The secondary voltage of the ignition coil generated at this time generates a high voltage spark in the ignition plug, causing a trigger current to flow. In this spark plug, the impedance decreases because the high-voltage spark ionizes between the two electrodes and becomes conductive.

Using this as a trigger, the main charge of the capacitor passes through the secondary coil of the ignition coil and is superimposed on the ignition plug to be discharged, thereby producing a high-energy spark. In order to create a high-energy spark that is effective for igniting an engine, that is, to grow a complete flame shell, the duration of the overlapped discharge, which is the main discharge, is approximately 1 to 1.5 m5ec. Therefore, in order to make the overlap discharge duration about 1 m (8), the secondary inductance of the ignition coil should be set as shown in Figure 2 Td (
It needs to be about 0.5 mH. However, when the secondary inductance of this ignition coil is increased, the rise time of the superimposed discharge current when the trigger is about to flow in is about 0.2m8eO as shown in Figure 1B, and this rise In some cases, the ionization between the poles of the spark plug due to the trigger current shown in FIG. 1A disappears by then, and no overlap discharge occurs.

Therefore, in order to ensure overlap discharge, it is necessary to accelerate the rise of the overlap discharge current, and to accelerate the rise, the secondary inductance of the ignition coil must be reduced. However, reducing the secondary inductance of the ignition coil has the disadvantage that the duration of the overlap discharge current is short and the multi-ignition performance is deteriorated.

On the other hand, in a gasoline engine, ignition occurs by turning on and off a power transistor in the spark plug, and maintaining this discharge for a certain period of time improves the stability of combustion in the engine, which is effective in improving fuel efficiency and output. Therefore, a stacked discharge circuit is added. However, DC-
If the operating time of the DC converter is not properly controlled, problems such as increased current consumption and erroneous ignition will occur.

A conventional stack discharge type ignition device for a gasoline engine has a configuration as shown in FIG. That is, the battery 100 supplies current to each part of the ignition device via the key switch 102. An ignition device 103 is constituted by a pickup coil 103a that detects a signal synchronized with the engine, a control circuit (not shown), and a final stage power transistor 103b, and an ignition coil 104 is driven by this ignition device 103. Also, Site Norag 105b
, l:l-105a, and spark plugs 106, 107, 108, 109 installed in each cylinder.
A power distribution section is constructed.

Also, resistors 117, 118, 119, 120°121.
122, 123, 124 and Zener diode 130
, co/capacitors 132 and 139, and comparator 136
, transistor 133°134, and diode 129
, 138 and a step-up transformer 137 constitute a DC-DC converter, and resistors 110, 111, 11
2゜113, 114, 115, 116 and diode 1
25, 126, 128, a comparator 135, and a capacitor 131 constitute a control section (2).

The ignition device 103 detects an alternating current signal as shown in FIG. The on-time of the transistor 103b is controlled. When this power transistor 103b is turned on, a part of current 1 flows through the primary coil of the ignition coil 104 as shown in FIG. On the secondary side of the multi-ignition coil 4, a negative secondary voltage V as shown in FIG.
2 occurs. This negative secondary voltage v2 causes the power distributor 5 to
is applied to the ignition plug, for example, the ignition plug 106, through the rotor 1058% side plug 105b, and breaks the insulation between the electrodes of the ignition plug 106. Normally, a high voltage of -IOKV to -20KV is required to break the insulation between the electrodes of a spark plug.

When the insulation between the electrodes of this spark plug 106 is broken, the GN
D→Spark plug 106→Side plug 10 in power distributor 105
5b→rotor 105a→secondary coil of ignition coil 104→DC-DC converter capacitor 139→GND, a secondary current 2 flows as shown by the solid line in FIG. 4(G).

Moreover, when the DC-DC converter is not used, that is, the ignition plug 10 is operated only by the ignition device 103 and the ignition coil 104.
6,107,108,109, the discharge duration (t1 time shown in Figure 4 (Q, (to)) is approximately 1m5eC and 6D, and the discharge ends at point A in Figure 4 (CI). The peak value (
(not including capacitive discharge) is approximately 40 mA.

The ignition device 103 is connected to the point Otake 106, 107° 108.
109, the voltage required to sustain the discharge of the ignition plug is approximately -LKv to -2KV (see Fig. 4 (Q)), as described above. If a medium-high voltage of IKV to -2KV is superimposed on the secondary side of the ignition coil 104 after the insulation breakdown between the electrodes of the ignition plug, the discharge will continue! l), DC-D
If the C converter output voltages are superimposed with appropriate timing control from the time of startup to the time of high speed, it will lead to improved fuel efficiency and engine efficiency.

Therefore, the DC-DC converter will be explained next.

The power supply line of the p comparator 136 is stabilized by the resistor 122 and the Zener diode 130. Further, an oscillator (2) is constituted by resistors 117, 118, 119, 120° 121, a capacitor 132, and a comparator 136. The output signal of the oscillator H is applied to the base of the transistor 1330 via the resistor 23, so the transistor 133 repeats the switching operation. When this transistor 133 is off, a base current flows to the power transistor 134 via the resistor 24, the power transistor 134 is turned on, and current flows to the primary coil of the step-up transformer 137. When the transistor 133 is turned on, the power transistor 134 is turned off, the negative coil current is cut off, and the energy stored in the step-up transformer 137 generates a negative voltage on the cathode side of the high voltage diode 1380 on the secondary side, and the voltage is changed from GND to the capacitor 139. →Diode 138
The capacitor 139 is charged through the route → secondary coil of the step-up transformer 137 → GND. Since the power transistor 134 is switched by the oscillator ■, the charging voltage of the capacitor 139 (capacitor 139 and diode 1
The contact voltage of the anode of 38) is -1KV to -2KV.

In this way, with the ignition device 3, the ignition plugs 106, 107°10
8. When the insulation between the electrodes of 109 is broken, GND → ignition plug → Otakeki side plug → rotor → ignition coil 104
Discharge current ■2 flows in the path from the secondary coil of The current is superimposed on the discharge current (2), and the discharge current of the spark plugs 106 to 109 as a whole continues until point B where the oscillator (2) stops operating, as shown by the dotted line in FIG. The discharge of the secondary voltage v2 shown in FIG.

Next, the control unit (2) that controls the operating time of the oscillator (2) will be explained.

Resistors 110, 111, 112, 113, 114.
-115, capacitor 131, and diode 125
126 and a comparator 135 constitute a one-shot multi. This one-shot multiple trigger is generated when the power transistor 103b at the final stage of the ignition device 103 has a collector voltage (1) with a waveform as shown in FIG. The fly voltage is divided by the resistor 111 via the resistor 1101 and the diode 125, and is applied to the (e) input terminal of the comparator 135. That is, the final stage power transistor 103b of the ignition device 103
In synchronization with the turning off of the comparator 135, the output terminal of the comparator 135 becomes HIGH for a certain period of time. The output terminal voltage waveform of this comparator 135 is shown in FIG. 4 [F].

Further, while the output terminal of the comparator 135 is HIGH, the diode 128 is non-conductive, so the capacitor 132 of the oscillator (1) repeats charging and discharging, the DC-DC converter operates, and the capacitor 139 is charged.

Further, when the output terminal of the comparator 135 becomes LOW, the (c) input terminal of the comparator 136 becomes approximately 0.7V, and the ffl input terminal voltage becomes higher, so that the output of the comparator 136 is always HIGH, and the transistor 13
3 is turned on and the power transistor 134 is turned off, so the DC-DC converter stops operating. This DC
-The collector voltage waveform of the transistor 133 during a DC current is as shown in FIG.

In such an ignition device shown in FIG.
The operating time of the converter is controlled for a certain period of time using a one-shot multi-function device, etc., but the time when the rotor and side plug face each other in the power distribution device decreases as the engine speed increases. The DC-DC converter continues to operate even if the opposing circuit disappears, causing a spark out. When this spark burnout occurs, the DC-DC converter is no longer in a no-load state, and the residual voltage of the capacitor 139 increases. For this reason, it has the disadvantage that it discharges at the next power distribution timing, causing premature ignition. Also, when the rotor and side plug are not facing each other, D
Since the C-DC converter is in operation, it has the disadvantage of causing energy loss.

[Purpose of the invention]

A first object of the invention is to provide a repeated discharge type ignition device that can ensure repeated discharge and provide a sufficient repeated discharge time.

A second object of the invention is to provide a stack discharge type ignition device that does not cause premature ignition.

[Summary of the invention]

The first invention is achieved by inserting and connecting a series circuit of a high voltage diode and a resistor in parallel with the secondary coil of the ignition coil.
The aim is to ensure repeated discharge and to allow sufficient repeated discharge time.

The second invention provides means for setting the operating time of the DC-DC converter so that the overlap time decreases according to the rotation speed, and overlap discharge is performed during the time when the rotor of the power distribution device and the side plug face each other. The aim is to prevent premature ignition by terminating the fuel.

[Embodiments of the invention]

Examples of the present invention will be described below.

FIG. 5 shows an embodiment of the first invention.

In the figure, 1 is a reluctor, 2 is a pickup coil, and the pickup coil 2 generates an ignition timing signal at a predetermined ignition timing. 3 is an oscillator, approximately 10KHz
The primary current of the primary coil 4a of the step-up transformer 4 is intermittent by the transistor T2, and a high voltage of 1 to 1.5 KVO is generated in the secondary coil 4b of the step-up transformer, which is then passed through the diode D2 to the capacitor C4 at 1 to 1.5 KV. to charge.

Further, in the figure, 5 is an ignition coil, 5a is a primary coil, and 5b is a secondary coil. One end of this secondary coil 5a is connected to a capacitor C5, and the other end is connected to a secondary coil 5b. The other end of this secondary coil 5b is connected to a spark plug 6.

Further, both ends of the secondary coil 5b are connected to high voltage diodes D4.
It is bridged through a series circuit of D5 and resistor R, 15.

Furthermore, in the figure, 7 is a switch, and 8 is a battery.

In such a configuration, when an ignition timing signal is generated in the pickup coil 2 at a predetermined ignition timing, the transistor T1 becomes conductive, and the thyristor SCR passes through the resistor R13.
A gate current flows through the gate of the thyristor SCR, and the thyristor SCR becomes conductive. At this time, part of the charge in the capacitor C4 flows into a part of the coil 5a of the ignition coil 5 through the capacitor C5, and a high voltage of 30 to 40 KV is generated in the secondary coil 5b.

A high voltage spark is generated in the multiple spark plug 6 due to this high voltage, and a trigger current flows between both electrodes of the spark plug 60. By the generation of this high voltage spark, the two electrodes of the ignition glove 6 are ionized and conductive, resulting in a drop in diimpedance. Therefore, the main charge of capacitor C4 is
Discharge occurs along the path of spark plug 6 → secondary coil 5b, and this overlapping current generates a high-energy spark. At this time, in order to maintain ionization between the two poles of the spark plug 6, a series circuit of diodes D4 and D5 and a resistor R15 is provided to flow an auxiliary overlapping current.

The path of this auxiliary overlap current does not have an inductance component, so there is no delay in the rise time of the current, so the ionization between the two poles of the spark plug 6 by the trigger current continues instantaneously and is completely completed until the arrival of the main overlap current. Since the ionization is maintained and the impedance between the two poles of the spark plug 6 is maintained, the overlapped discharge can be performed satisfactorily. The relationship between this overlapping current and trigger current is shown in FIG. That is, A indicates a trigger current, B indicates a main overlapping current, and C indicates an auxiliary overlapping current. This causes a trigger current to flow,
After the discharge is started, the gap with the main overlap current is compensated by the auxiliary overlap current.

Therefore, according to this embodiment, ignition errors will not occur.

FIG. 7 shows an embodiment of the second invention.

In the figure, the same reference numerals as in the conventional example shown in FIG. 3 indicate the same parts and the same functions. This embodiment differs from the conventional example shown in FIG.
The point where the connection point between 1 and the resistor 116 and the output terminal of the comparator 135 are connected via the diode 127, and the resistance value of the resistor 16, which was conventionally about 30Ω to 50Ω, was changed to about 3MΩ. The point is that the resistance is high.

Therefore, when the voltage (1) output from the power transistor 103b as shown in FIG. 8 (4) is applied to the resistor 110, the flyback voltage will be
A trigger waveform as shown in FIG. 8 is applied to the (g) input terminal 5. Since the trigger waveform as shown in FIG. 80 is higher than the (→input terminal voltage) of the comparator 135, the output of the comparator 135 becomes HIGH.
6 and is charged with a time constant determined by resistors 115, 114, 111 and capacitor 131. At this time, as the capacitor 131 is charged up, the voltage V5 decreases, and while the voltage v11 generated at the resistor 111 is larger than the input terminal V4 (V5
>V4), the output terminal of the comparator 135 is); f
Sustain IGH. The waveform of this voltage Vs, V4 is the 8th waveform.
It is shown in FIG.

When the capacitor 131 is charged up, the potential v5 at the connection point between the diode 125 and the resistor 111 becomes V5 < V4
fx'), the output terminal of the comparator 135 becomes LOW. When the output terminal of the comparator 135 is LOW, a current flows to the output terminal of the p comparator 135 via the resistor 115, and a current flows via the resistor 116 to the capacitor 1.
31 and the current flowing through the diode 128 from the (c) input terminal of the comparator 136 of the oscillator 1 of the DC-DC comparator. At this time, the charges on the capacitor 131 are as follows:
It is discharged with a time constant determined by the resistor 116, but at low speeds, the ignition period is longer than the discharge time, so the contact voltage V3 of the cathode of the capacitor 131 and the diode 127 is as shown in Fig. 8 (Q
As shown in the figure, the voltage decreases to oV.

However, in the high speed range, the multiple ignition period becomes shorter than the discharge time of the capacitor 131, and the contact voltage v3 between the cathode of the capacitor 131 and the diode 127 does not fall to 0■ as shown in FIG.
is always charged with a certain charge proportional to the engine speed.

When a trigger waveform as shown in FIG. 8 [F] is applied in this state, the capacitor 131 starts charging again from a state where it has been charged with a certain charge, so the charging time until charge-up is reduced to a low speed range. It is shortened in comparison. This charging current is mainly supplied to the capacitor 131 via the diode 27. Therefore, the time for which V5 > V4 is shortened, as shown in FIG. 80. That is, the operating time of the DC-DC converter is shortened in the high speed range.

In this way, the charging time is determined by providing a diode 127 and a resistor 1.
Regardless of the resistor 116, the same time as the conventional one can be secured, and since the resistor 116 has a high resistance, the discharge time takes a correspondingly longer time. Therefore, as the engine speed increases, the electric charge stored in the capacitor 131 increases. Therefore, the operating time of the DC-DC converter in the high speed range is controlled according to the engine speed.

FIG. 9 shows an example of shortening the operating time of the DC-DC converter of this embodiment. In the figure, A is a conventional DC
- DC converter operating time, B is the DC converter operating time of this example.
- DC converter operating time, C indicates rotor facing time, and D indicates pre-ignition region.

Therefore, according to this embodiment, the overlap discharge time is shortened in advance as the engine speed increases so that the DC-DC converter is stopped and overlap discharge is terminated while the rotor and side plug are facing each other. DC-DC
Since the operating time of the converter is set, pre-ignition can be prevented.

Further, according to this embodiment, the DC-DC converter does not continue to operate when the rotor and the side plugs are not opposed to each other, and energy loss can be reduced compared to conventional ignition devices.

Furthermore, according to this embodiment, the operating time of the DC-DC converter can be shortened by using a high-resistance resistor 116 and using a simple circuit that only requires one additional diode.

〔Effect of the invention〕

As explained above, according to the first invention, overlap discharge can be ensured and sufficient overlap discharge time can be taken, and according to the second invention, premature ignition can be prevented. It can be done.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the waveforms of the trigger current and overlap current, Fig. 2 is a diagram showing the rise time and overlap discharge duration of the secondary inductance and overlap current, and Fig. 3 is a conventional example of the second invention. FIG. 4 is a waveform diagram of each part of FIG. 3, FIG. 5 is a circuit diagram showing an embodiment of the first invention, and FIG. 6 is a trigger current and auxiliary overlap current according to the embodiment shown in FIG. FIG. 7 is a circuit diagram showing the embodiment of the second invention, FIG. 8 is a main waveform diagram of the embodiment shown in FIG. 7, and FIG. 9 is based on the embodiment shown in FIG. 7. It is a characteristic diagram. 4...Step-up transformer, SCR...Thyristor, D4
゜D5...Diode, R5...Resistor, 104...
・Ignition coil, 105...Distributor, 110, 111,
115゜116...Resistance, 135...Comparator, 127...th/Fast 2 mouth o 05/, 0/, divination secondary inctance (m H) (empty S) Kaya name OV□th 9 Mouth Ha

Claims (1)

[Claims] 1. A DC-DC converter is used to charge a capacitor, and at a predetermined ignition timing, a portion of the charged charge of the capacitor is applied to a portion of the ignition coil, and the high voltage generated at this time is applied to the ignition plug. In a stack discharge type ignition device that generates a voltage spark and, after the generation of the high voltage spark, supplies the main charge of the capacitor to the spark plug via the secondary coil of the ignition coil to sustain discharge, the secondary coil of the ignition coil The stacked discharge type 2 is characterized by inserting and connecting a series circuit of a resistor and a high-voltage diode in parallel to the next coil, which is necessary to break down the insulation between a power distributor equipped with a mechanical power distribution mechanism and a spark plug electrode. After causing dielectric breakdown between the ignition device that generates a high voltage pulse and the ignition plug electrode, a one-shot multiple is used to supply a stacked discharge current for a predetermined period of time to further sustain the discharge current. In a stacked discharge type ignition system equipped with a medium-high voltage DC-DC converter, the HIGH output time of the one-shot multi, which controls the operation time of the DC-DC converter that determines the stacked discharge time, is set to a predetermined number of revolutions. A stacked discharge type ignition device characterized by being provided with means for controlling the length to decrease as the height increases.