JPS62265466A - Ignition device for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce a required break-down voltage to aim at miniaturizing an ignition coil, by providing a second ignition device for applying a high frequency a.c. voltage to the secondary side of the ignition coil during the period from a time which is before the generation of a high voltage on the secondary side of the ignition coil by a predetermined time, to the time of the generation of the high voltage. CONSTITUTION:An ignitor 5 as a first ignition device connected to an ECU 1 is connected to the primary side of a first ignition coil 6 whose secondary side is connected to spark plugs 81 in engine cylinders through a piezoelectric element 7 and a distributor 8. Further, a second ignitor 10 is connected to the ECU 1, and is also connected to the primary side of a second ignition coil 9 whose secondary side is connected to the secondary side of the first ignition coil 6. Further, the second ignitor 10 is arranged such that a high frequency voltage of a high value which does not cause spark plugs 81 to give spark discharge is applied to the spark plugs 81 during the period from the time which is before the generation of a high voltage on the secondary side of the first ignition coil 6 by a predetermined time, to the time of generation of the high voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ignition system for an internal combustion engine, and in particular, to an ignition system for an internal combustion engine, in addition to a regular ignition system for performing normal ignition, another ignition system for promoting discharge of a spark plug. The invention relates to an ignition device for an internal combustion engine that is connected to the secondary side of an ignition coil.

[Conventional technology]

Currently, the ignition coil used for internal combustion engines installed in automobiles is one with a battery voltage of 12V.
This method stores the secondary current as magnetic energy in the iron core, causes a voltage drop in the spark plug with the high voltage generated by the back electromotive force when the primary current is off, and then releases the magnetic energy stored in the iron core. It has become mainstream. In addition, many modern engines are equipped with superchargers (turbochargers and superchargers), and many engines are designed to have high compression to improve fuel efficiency. For this reason, the voltage that causes spark discharge between the spark plug gaps, ie, the required breakdown voltage, tends to increase.

[Problem that the invention aims to solve]

However, while the required breakdown voltage has increased, on the other hand, the performance of the ignition system, such as the generated voltage and withstand voltage of the ignition coil, the spark plug, high tension cord,
It is not possible to increase the voltage resistance of distributors, etc. For this reason, when the ignition device is exposed to adverse environments (for example, an environment where a high-tension cord gets wet), the stray capacitance on the secondary side increases and the secondary generated voltage of the ignition coil decreases. However, if the generated voltage is lower than the required breakdown voltage, there is a problem that spark discharge will not occur between the gaps of the spark plugs, resulting in a risk of engine misfire.

In addition, the battery voltage may become low (such as when starting at a low temperature), and at this time the voltage generated by the ignition coil decreases, potentially causing a misfire.And if a misfire occurs,
A problem arises in that drivability deteriorates.

[Means for solving problems]

The purpose of the present invention is to solve the problems that occur in the conventional ignition system of an internal combustion engine with a high compression ratio, to achieve a high compression ratio (and to lower the required breakdown voltage), and to reduce the size of the ignition coil. It is an object of the present invention to provide an excellent ignition system for an internal combustion engine, which can reduce the withstand voltage of ignition system parts other than the ignition coil, and reduce the cost of the entire ignition system.

An ignition device for an internal combustion engine according to the present invention that achieves the above object includes an ignition coil connected to a spark plug via a distributor, connected to the ignition coil, and energizing the primary side of the ignition coil for a predetermined period of time; a first ignition device that generates a high voltage on the secondary side of the ignition coil upon termination of energization;
Connected to the ignition coil, applying a high frequency voltage to the secondary side of the ignition coil from a predetermined time before the first ignition device generates a commercial voltage on the secondary side of the ignition coil until the cough high voltage is generated. The invention is characterized by comprising a second ignition device.

[For production]

According to the ignition device for an internal combustion engine of the present invention, during a predetermined period of time before high voltage is generated on the secondary side of the ignition coil by the first ignition device until the high voltage is generated, the second ignition device controls the spark plug. A high-frequency voltage having a voltage value that does not cause spark discharge to the spark plug is applied to promote the ionization of the air between the spark plug gaps, thereby increasing the required breakdown voltage when the spark plug spark discharges by the first ignition device. decreases.

Embodiments of the present invention will be described in detail below with reference to the drawings.

〔Example〕

FIG. 1 shows the structure of an embodiment of an ignition device for an internal combustion engine according to the present invention, and the ignition device of this embodiment is a full transistor type ignition device. In Figure 1, 1 is EC
This ECU 1 is connected to an intake pressure sensor 2, a rotation angle sensor 3, a water temperature sensor 4, etc., and data on engine operating state parameters are input manually from these sensors.

Further, an Eve knife 5 which is a first ignition device is connected to the ECU l, and this Eve knife 5 is connected to the primary side of the first ignition coil 6, and the secondary side of the first ignition coil 6 is connected to the ECU l. It is connected via the piezoelectric element 7 to a distributor 8 that distributes electricity to the spark plugs 81 of each cylinder.

Furthermore, the ECU 1 includes an oscillator 11 and an AND circuit 12.
, a transistor 13 , 14 , and an inverter 15 are connected to the second Eve knife 10 , which is connected to the primary side of the second ignition coil 9 . The next side is connected to the secondary side of the first ignition coil 6. 16 is a battery that supplies electricity to each of the above-mentioned parts.

FIG. 2 shows the tip of the spark plug 81, and the spark plug 81 is composed of a housing 82, a center electrode 83, an insulator 84, a ground electrode 85, and the like.

The housing 82 is used to support an insulator 84 and to attach the spark plug 81 to the engine.A ground electrode 85 is welded to the lower part of the housing 82, and a spark gap is formed between the housing 82 and the center electrode 83 connected to the distributor 8. 86 is formed.

In the above configuration, the ECU 1 calculates the ignition timing suitable for the operating condition based on the operating condition parameter signals input from each sensor, outputs the control signal rGTl to the first knife 5, and A control signal IGT2 is output to the second evening knife i0. From the first Eve knife 5, an ignition activation signal (fail signal) IGf generated from the collector voltage of a power transistor (not shown) that switches the primary current of the first ignition coil 6 is input to the ECU1. .

The timing diagram of the control signals IGTI and IGT2 is as shown in (at, (bl) in FIG. 3, and the control signal T
The breakdown waveform that appears on the spark plug 81 when only GTI is applied to the Eve knife 5 is shown in the same figure (gl).In the present invention, the off time L2 of the control signal IGTI
and the time t at which breakdown occurs in the spark plug 81.
3, but this is a time delay due to the capacitance of the piezoelectric element 7 inserted between the first ignition coil 6 and the distributor 8. Further, in the present invention, the control signal IGT2 is outputted from the ECU to the second Eve knife 10 at a time El (for example, 21Tl!1 time tl earlier) which is a predetermined time earlier than the ignition timing at time t3.

Since the output signal from the oscillator 11 which is oscillating with a waveform as shown in FIG. 3 (C1) is input to one terminal of the AND circuit 12 of the second Eve knife 10,
When the control signal IGT2 from Ul is input to the other terminal of the AND circuit 12, the output waveform of the AND circuit 2 becomes as shown in Fig. 3 (dl).The signal from the oscillator 11 becomes as shown in Fig. 1. This is to cause the shown piezoelectric element 7 to resonate at a resonant frequency, and the resonant period of this device is about 8 to 10 μs.

The signal passed through the AND circuit 12 turns on the transistor 13 when it is at a high level (5V), and goes to a low level (Ov).
At this time, the low level signal is converted to high level by the inverter I5, so the transistor 14 is turned on. When the transistor 13 is turned on, 1 (battery voltage 12 indicated by LV) is applied to the primary side of the second ignition coil 9.
A primary current of V flows, and as a result, a boosted high-voltage secondary current shown in the previous section flows on the secondary side.

In this case, if the boost ratio of the ignition coil 9 is set to about 40 times, the battery voltage of 12V will be boosted to about +0.5KV. When the transistor 14 is turned on, a primary current of voltage 12V indicated by LLV flows through the primary side of the ignition coil 9, and a boosted current of approximately -0.5KV indicated by Ll flows through the secondary side.
A high voltage secondary current flows. The output waveform of this ignition coil 9 is shown in FIG. 3 (el).

The voltage of ±0.5KV generated by the ignition coil 9 in this way is input to the piezoelectric element 7, and since the step-up ratio of the piezoelectric element 7 is approximately 10 times, the final voltage is as shown in Fig. 3 (). It is possible to obtain an alternating voltage of +/-5KV.

The reason why the output of the piezoelectric element 7 does not immediately reach the maximum output due to the input signal, but gradually increases and takes a certain amount of time to reach a certain voltage is because the resonance phenomenon of the piezoelectric element is utilized, and the alternating This is because even if a voltage is applied to the piezoelectric element 7, the piezoelectric element 7 does not immediately vibrate to the maximum amplitude.

The frequency of the alternating voltage passing through the piezoelectric element 7 is 100 to 12
0 KHz (because the period is 8 to 10 μs), and the output voltage decreases to about ±3 KV by passing through the distributor 8 (this is because the voltage of about 2 ν is lost in the discharge gap of the distributor 8). ). Then, a voltage of approximately ±3 KV is applied to the ignition gap 86 of the ignition plug 81 before the first Eve knife 5 normally discharges.

Note that this voltage of approximately ±3 KV is less than the breakdown voltage of the spark plug 81, and no spark discharge occurs in the spark gear 86 of the spark plug 81 due to this voltage.

In this way, a high-frequency alternating voltage (frequency D100-120 K11z, "= 3 KV
) is applied to the spark plug 81, no spark discharge occurs between the center electrode 83 and the ground electrode 85, but the ionization of the air in the spark gap 86 is promoted. and,
As the ionization of the air in the spark gap 86 progresses, the voltage at which a spark discharge occurs between the center electrode 83 and the ground electrode 85, ie, the required breakdown voltage, decreases.

This is known from literature, etc., which states that when a discharge is caused between a certain gap, applying a high-frequency alternating voltage across the gap is more effective than applying a low-frequency alternating voltage. Therefore, the breakdown voltage will be lower. In fact, applying a high-frequency alternating voltage across the gap promotes ionization of the air between the gears, and the ions facilitate discharge.

In addition, according to the inventor's experiments, when the required breakdown voltage was compared with a conventional ignition system under the same conditions using the device shown in Figure 1, it was found that a high frequency alternating voltage was applied across the plug gap before regular discharge. Results showed that the required breakdown voltage was approximately 20% lower for the device of the present invention than for the conventional ignition device.

If the required breakdown voltage can be lowered in this way, 13
Ignition coil performance (generated voltage) can be lowered,
At the same time, it is possible to reduce the cost of the ignition coil, and at the same time reduce the cost of ignition system parts other than the ignition coil, such as the distributor,
The withstand voltage of high tension cords and spark plugs can be lowered. Furthermore, if the withstand voltage of the entire ignition system can be lowered, the cost of the entire ignition system can also be reduced.

The specific effects for each component are as follows: 1. Distributor Franchover voltage can be lowered than before, so the diameter of the distributor can be made smaller, which not only reduces costs, but also makes it easier to install it in the engine. Improves sex.

■The rubber camp that connects the high tension cord coil, distributor, and spark plug is made of inexpensive rubber, such as EPDM.
It is possible to change to rubber caps, reducing costs (conventionally, rubber caps made of silicone rubber were often used to improve voltage resistance).

■It is possible to omit the pressure-resistant insulator that is conventionally used in spark plugs, reducing costs.

In addition, if you increase the high-frequency alternating voltage applied across the spark plug gap, there is a risk of spark discharge occurring before proper ignition, and if discharge occurs before proper ignition, sparks may occur. , there is a risk of engine damage. In order to prevent this, in the embodiment described above, the value of the high frequency alternating voltage applied to the spark plug 81 is suppressed to approximately ±3 KV, but this applied voltage value may be set to a value suitable for each engine. For this purpose, the ignition coil 9 may be provided with a tap for changing the boost ratio so that the boost voltage value of the second ignition coil 9 can be adjusted.

FIG. 4 shows the structure of another embodiment of the ignition device of the present invention. In the apparatus of this embodiment, the same components as those in the embodiment of FIG.

The device shown in FIG. 4 differs from the device shown in FIG. 1 in that the second ignition coil and the first large ignition coil are integrated into a composite ignition coil 20. This composite ignition coil 2
0 is when the number of turns between the primary coil 21 and the secondary coil 22 of the ignition coil of a normal full transistor ignition system is, for example, 100 turns on the primary side and 10,000 turns on the secondary side. (turns ratio 100), this can be realized by using the secondary coil 22 in common and adding another coil 23 with the number of turns 250 to the primary side (second
(Because the turns ratio of the boost coil for the ignition system is 40).

Also in this embodiment, another coil 23 may be provided with a tap for changing the boost ratio so that the boost voltage value of the composite ignition coil 20 can be adjusted.

In this way, by combining the ignition coils of the first ignition device and the second ignition device into one, the volume occupied by the ignition coil is reduced when this is mounted on a heavy vehicle, which improves mountability. Compared to the case where there are two ignition coils, there is no need for a wired OR connection, preventing a decrease in productivity due to the figure-7 structure of the high-voltage line, and increasing the reliability of the joint.

As a modification of the embodiment shown in FIG. 4, it is also possible to combine the first igniter 5 and the second igniter 10 into one. By combining two igniters into one in this manner, it is possible to further reduce the cost of the entire ignition system, and it is expected that the ease of mounting on a vehicle will be further improved.

〔Effect of the invention〕

As explained above, according to the present invention, the required breakdown voltage of the spark plug can be lowered, so the cost of the ignition coil can be reduced, and at the same time, the withstand voltage of the ignition system components other than the ignition coil can be reduced. This has the effect of reducing the cost of the entire ignition system.

Further, when the required breakdown voltage of the ignition plug is lowered, gap wear of the ignition plug is reduced and the life of the ignition plug can be extended.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of the ignition system for an internal combustion engine according to the present invention, FIG. 2 is a partially enlarged sectional view of the tip of the spark plug shown in FIG. 1, and FIG. FIG. 4 is a waveform diagram showing signal waveforms at various parts of the device. FIG. 4 is a schematic diagram showing the configuration of another embodiment of the ignition device for an internal combustion engine according to the present invention. ■... ECU, 5... First igniter, 6... Ignition coil, 7... Piezoelectric element,
8... Distributor, 9... Second ignition coil, 10... Second igniter, 11... Oscillator, 12... AND circuit, 20...
...Composite ignition coil, 81...Spark plug. b Figure 1

Claims (1)

[Claims] 1. An ignition coil connected to a spark plug via a distributor; energizing the primary side of the ignition coil for a predetermined period of time; a first ignition device that generates a high voltage on the next side; and a first ignition device connected to the ignition coil, from a predetermined time before the first ignition device generates a high voltage on the secondary side of the ignition coil until the time when the high voltage is generated. An ignition device for an internal combustion engine, comprising: a second ignition device that applies a high-frequency voltage to the secondary side of the ignition coil during the ignition process. 2. The ignition device for an internal combustion engine according to claim 1, wherein the ignition coil is an ignition coil of the second ignition device.