JP2002303238A - Ignition device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an ignition device securely perform the ignition when an energy charging system is broken. SOLUTION: In the ignition device 10, a battery 11, an energy accumulation coil 12 and a transistor 13 are connected in series, and the primary side coil 16a of an ignition coil 16 and a transistor 17 are connected in series between the energy accumulation coil 12 and the transistor 13. Further, a transistor 19 and a diode 20 are connected in series between the battery 11 and the primary side coil 16a of the ignition coil 16. An ECU 30 turns on/off the transistors 13 and 17 alternately in the discharge period of a spark plug 21 for implementing the so-called multiple discharge. Moreover, the ECU 30 turns on/off the transistors 17 and 19 at high speed to generate the corona discharge at an electrode part of the spark plug 16 when a trouble occurs in the energy charging system including the energy accumulation coil 12 and the transistor 13, and after that, to execute the ignition with prescribed ignition signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ignition device for an internal combustion engine.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open Publication No.
There is a multiple discharge ignition device disclosed in Japanese Patent No. 5659, in which an energy storage coil and a capacitor for storing discharge energy are provided in addition to a normal ignition coil. Multiple discharges have been made possible by alternately using the energies.

[0003]

However, in the above prior art, if a failure occurs in the energy charging system including the energy storage coil and the capacitor, the energy stored in the energy storage coil and the capacitor cannot be used as ignition energy. . Therefore, sufficient ignition energy could not be secured, and there was a risk that the ignition operation would be hindered. In particular, when the battery voltage drops, the ignition energy may not reach the discharge breakdown voltage, and ignition may not be possible.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an ignition device for an internal combustion engine that can reliably perform ignition when a failure occurs in an energy charging system. It is to be.

[0005]

According to the first aspect of the present invention, the first and second switching elements are alternately turned on / off during a discharge period immediately after the ignition timing, and a multiple discharge is performed accordingly. That is, when the first and second switching elements are alternately turned on (conducting), the energy stored in the energy storage coil and the energy stored in the ignition coil are discharged alternately as discharge energy, and the discharge ignites the ignition plug. A spark is generated to ignite. this is,
This is a multiple ignition operation when the energy charging system is normal.

On the other hand, when a failure occurs in the energy charging system due to, for example, failure of the energy storage coil or the first switching element, the DC power supply is directly connected to the primary coil of the ignition coil. At the same time, the second switching element is turned on / off at high speed. After that, ignition is performed by a predetermined ignition signal. in this case,
By turning on / off the second switching element at high speed immediately before ignition, corona discharge is generated in the electrode portion of the ignition plug. In general, it is known that the discharge breakdown voltage decreases immediately after the occurrence of corona discharge, and the reduction in the discharge breakdown voltage increases the probability of causing discharge breakdown. As a result, ignition at the time of failure of the energy charging system can be reliably performed.

More specifically, as described in claim 2, when the energy charging system fails, it is preferable to output a high-frequency fail-safe signal to the second switching element immediately before ignition. In this case, the output of the fail-safe signal causes corona discharge to occur in the electrode portion of the ignition plug as described above, and the discharge breakdown voltage decreases.

According to the third aspect of the present invention, a third switching element is provided for bypassing the energy storage coil and connecting the DC power supply to the primary coil of the ignition coil. In the event of a failure, the third switching element is switched from off to on. In this case, by turning on the third switching element, power can be supplied from the DC power supply even when a failure occurs in the energy charging system.

According to the third aspect of the present invention, as described in the fourth aspect, when the energy charging system fails, the third switching element may be operated in the same manner as the second switching element.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an electrical configuration of an ignition control device for an internal combustion engine according to the present embodiment. The control device is mounted on an automobile,
An LI (Distributor Less Ignition) type ignition device is provided. For convenience, FIG. 1 shows a configuration for one cylinder, but actually, a configuration for the number of cylinders of the internal combustion engine is provided.

In the ignition device 10 shown in FIG. 1, an energy storage coil 12 and a transistor 13 are connected in series between a plus terminal of a battery 11, which is a DC power supply, and a ground. A capacitor 15 is connected via a diode 14 to a point A between the energy storage coil 12 and the transistor 13. Transistor 13 is EC
It is turned on / off by a signal SG1 from U30, and energy is stored in the energy storage coil 12 by energization accompanying turning on of the transistor 13. The capacitor 15 is charged in advance with the energy stored in the energy storage coil 12. Note that the current flowing through the transistor 13 is i0.

At a point B between the diode 14 and the capacitor 15, a primary coil 16a of the ignition coil 16 is provided.
And the transistor 17 are connected in series. An OR gate circuit 18 is connected to the base of the transistor 17. In this case, the signal SG2 from the ECU 30 is O
The voltage is applied to the base of the transistor 17 via the R gate circuit 18, and the transistor 17 is turned on / off. When the transistor 17 is turned on / off, the energy stored in the capacitor 15 and the coils 12, 16 is sequentially released, and a primary current i1 flows through the primary coil 16a.

The battery 11 and the ignition coil 16
A transistor 19 and a diode 20 are connected in series between the secondary coil 16a. Transistor 1
9 is ON / OFF by a signal SG3 from the ECU 30
When the transistor 19 is ON, the primary coil 16a
Is directly connected to the battery 11. This signal SG3 corresponds to a “fail-safe signal”, and the signal SG3 is also output to the transistor 17 via the OR gate circuit 18. In the present embodiment, the transistor 13 is the “first
Transistor 17 corresponds to a “second switching element”, and the transistor 1
9 corresponds to a “third switching element”.

An ignition plug 21 is connected to one end of the secondary coil 16b of the ignition coil 16. When the primary coil 16a is energized, the secondary coil 16b
, A secondary current i2 flows.

On the other hand, the ECU 30 detects the state of the internal combustion engine (intake air amount, rotation speed, cooling water temperature, etc.) by inputting signals from various sensors and optimizes ignition according to the state of the internal combustion engine at each time. Decide when. The above-described transistors 13, 17, and 19 are connected to the ECU 30.
The CU 30 outputs drive signals SG1 to SG3 to the transistors 13, 17, and 19, respectively. Also, E
The high side of the capacitor 15 is connected to the CU 30. The ECU 30 monitors the state of charge of the capacitor 15 and, based on the monitoring result,
A failure of the energy charging system including the transistor 13 and the capacitor 15 is determined.

Next, the operation of the ignition control device configured as described above will be described with reference to the time charts of FIGS. In the device of the present embodiment, the transistors 13 and 17 are alternately turned on / off during the discharge period immediately after the ignition timing.
FIG. 2 shows a multiple ignition operation when the energy charging system is normal. FIG. 3 shows a fail-safe ignition operation when the energy charging system fails. 2 and FIG. 3, the driving signals SG1 to SG3 and the current i flowing through the transistor 13 are shown.
0, the primary current i1 of the ignition coil 16, and the secondary current i2
And the secondary voltage V2.

In FIG. 2, at time t1, the H level drive signal SG1 is output from the ECU 30 to the transistor 13. The transistor 13 is turned on by the same signal SG1, the current i0 gradually increases, and energy is stored in the energy storage coil 12 (t1 to t1).
2 period). The period from t1 to t2 is about several milliseconds, and the H level signal during the same period corresponds to a so-called ignition signal.

On the other hand, during the discharge period from t2 to t5, the transistors 13 and 17 are alternately turned ON / OFF to perform multiple discharges of the spark plug 21. That is, at the timing t2, which is the ignition timing (falling time of the ignition signal), the drive signal SG1 = L and the drive signal SG2 = H
, The transistor 13 is turned off and the transistor 17 is turned on. As a result, the electrostatic energy of the capacitor 15 and the magnetic energy stored in the energy storage coil 12 are simultaneously
The secondary current i2 is supplied to the secondary coil 16a and flows through the transformer. Then, the discharge at the ignition plug 21 is started. In the period from t2 to t3, the transistor 17
Is ON (SG2 = H), magnetic energy is stored in the ignition coil 16.

Thereafter, at the timing t3, the transistor 13 is turned on and the transistor 17 is turned off by switching between the drive signal SG1 = H and the drive signal SG2 = L. At this time, when the transistor 17 is turned off, the magnetic energy stored in the ignition coil 16 is released as discharge energy of the ignition plug 21. Further, during the period from t3 to t4, since the transistor 13 is ON, magnetic energy is stored again in the energy storage coil 12.

Further, at the timing of t4, the transistor 13 is turned off and the transistor 17 is turned on again. Thereby, the magnetic energy stored in the energy storage coil 12 is released as discharge energy of the spark plug 21. At this time, energy is again stored in the ignition coil 16. Since then, each transistor 1
3 and 17 are alternately turned on, and the energy of the energy storage coil 12 and the ignition coil 16 are used alternately, and the discharge of the ignition plug 21 is repeated. As a result, the spark discharge of the ignition plug 21 is continued within the discharge period (the period from t2 to t5). Note that when the energy charging system shown in FIG. 2 is normal, the drive signal SG3 is held at the L level throughout the entire period.

On the other hand, when the energy charging system fails due to the failure of the energy storage coil 12, the transistor 13, the capacitor 15, and the like, as shown in FIG. 3, the drive signals SG1 and SG2 are held at the L level throughout the entire period. Then, instead of the drive signals SG1 and SG2, the drive signal SG
3 is output in the form shown in the figure, and the transistors 17 and 19 are turned on / off by this signal SG3.

That is, in FIG. 3, t12 to t13 correspond to the output period of the ignition signal, and during this period, the drive signal SG3
Are held at the H level. In a predetermined period (period t11 to t12) immediately before the ignition signal at t12 to t13,
The driving signal SG3 has a sufficiently high frequency (for example, 10 kHz).
z). Thereby, t11 to t1
In the period of 2, the transistors 17 and 19 are turned ON /
It is turned off. In this case, the transistors 17 and 19
Since N time is short, the energy stored in the ignition coil 16 is relatively small. Therefore, a voltage at a level that does not cause discharge breakdown is applied to the ignition plug 21, and corona discharge occurs in the electrode portion of the ignition plug 21.

Thereafter, the ignition signal is output from t12 to t12.
In the period of 13, the ON time of the transistors 17 and 19 is sufficiently long, so that sufficient energy is stored in the ignition coil 16. Then, a high voltage is applied to the ignition plug 21 at the fall of this ignition signal (timing at t13).
At this time, the discharge breakdown voltage is lowered by the corona discharge described above, and reliable discharge breakdown is obtained. In short, after the corona discharge occurs, the discharge breakdown voltage decreases, and the probability of the discharge breakdown due to the decrease in the discharge breakdown voltage increases.

As described above, immediately before ignition, the high-frequency drive signal S
By outputting G3, a predetermined voltage is applied to the spark plug 21 before the discharge, and FIG. 4 shows an experimental result regarding the applied voltage before the discharge and the discharge breakdown voltage in that case. According to FIG. 4, it can be confirmed that, for example, when the applied voltage immediately before the discharge is about 500 V, the discharge breakdown voltage is reduced by about 10% as compared with the case where the voltage is not applied before the discharge. The pre-discharge applied voltage is the amplitude of one side of the secondary voltage V2 during the period from t11 to t12 in FIG.

According to the present embodiment described above, when a failure occurs in the energy charging system, corona discharge is generated immediately before ignition to reduce the discharge breakdown voltage. It can be performed reliably. That is, a fail-safe operation at the time of occurrence of a failure can be suitably performed. Further, ignition can be performed even when the battery voltage is low at the time of failure of the energy charging system.

In the above embodiment, the same drive signal SG3 was output to the transistors 17 and 19 when the energy charging system failed, but this configuration is changed. For example, when the energy charging system fails, the transistor 19
Is maintained in the ON state, and the battery 11 and the primary coil 16 are
a is always directly connected. In contrast, transistor 17
Outputs the same signal as the above-described drive signal SG3 (see FIG. 3). That is, different drive signals are output to the transistors 17 and 19, and these are individually driven. Also in this configuration, corona discharge occurs in the electrode portion of the ignition plug 21, and as described above, ignition at the time of failure of the energy charging system can be reliably performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an outline of an ignition control device for an internal combustion engine according to an embodiment of the invention.

FIG. 2 is a time chart for explaining a multiple ignition operation.

FIG. 3 is a time chart for explaining a fail-safe operation when a failure occurs in the energy charging system.

FIG. 4 is a diagram showing a relationship between a pre-discharge applied voltage and a discharge breakdown voltage.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Ignition device, 11 ... Battery, 12 ... Energy storage coil, 13 ... Transistor, 16 ... Ignition coil, 16
a: Primary coil, 16b: Secondary coil, 17: Transistor, 19: Transistor, 21: Spark plug, 3
0 ... ECU.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinichi Okabe 14 Iwatani, Shimowasukamachi, Nishio City, Aichi Prefecture Inside the Japan Auto Parts Research Institute (72) Inventor Seiko Watanabe 14 Iwatani, Shimotsukamachi, Nishio City, Aichi Prefecture Stock Company (72) Inventor Tetsuya Miwa 1-1-1, Showa-cho, Kariya-shi, Aichi F-term (reference) in Denso Corporation 3G019 BA01 BB02 BB09 BB16 CA13 EC02 FA11 KC03

Claims (4)

[Claims] A DC power supply, an energy storage coil and a first switching element are connected in series, and a primary coil of an ignition coil and a second switching element are provided between the energy storage coil and the first switching element. Elements are connected in series, and further, an ignition plug is connected to the secondary coil of the ignition coil.
And an ignition device for an internal combustion engine for performing multiple discharges by alternately turning on / off a second switching element, wherein when a failure occurs in an energy charging system including an energy storage coil and a first switching element, ignition is performed. An ignition device for an internal combustion engine, wherein the DC power supply is directly connected to a primary coil of the coil, the second switching element is turned on / off at a high speed, and then ignition is performed by a predetermined ignition signal. 2. An ignition device for an internal combustion engine according to claim 1, wherein a high-frequency failsafe signal is output to said second switching element immediately before ignition when said energy charging system fails. 3. A third switching element bypassing the energy storage coil and connecting a DC power supply to a primary coil of an ignition coil, wherein the third switching element is provided when the energy charging system fails. 3. The ignition device for an internal combustion engine according to claim 1, wherein the ignition device is switched from off to on. 4. The ignition device for an internal combustion engine according to claim 3, wherein the third switching element operates in the same manner as the second switching element when the energy charging system fails. .