JP2009221850A - Igniter with ion current detection function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an igniter having ion current detection function can generate a failure determination signal for surely detecting a failure. <P>SOLUTION: The igniter 20 includes a first threshold Vth1 indicating that current normally flows in a coil primary side 11 of an ignition coil 10, and second threshold Vth2 larger than the first threshold Vth1, and is provided with an IGf signal circuit 28 generating failure determination fail safe signal indicating whether primary current flowing in the coil primary side 11 of the ignition coil 10 exceeds the first threshold Vth1 and the second threshold Vth2. Consequently, since the fail safe signal indicating whether primary current normally flows, namely whether the igniter 20 normally operates can be generated, a failure of the igniter 20 can be surely detected by using the fail safe signal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an igniter with an ion current detection function.

  Conventionally, for example, Patent Literature 1 proposes an ignition system abnormality detection device that detects an igniter failure from an ionic current generated with combustion of an air-fuel mixture in a combustion chamber of an internal combustion engine. Specifically, Patent Document 1 discloses that an ion current detection circuit is used as means for detecting an ignition system abnormality.

When the coil primary current is energized, the secondary current I2 is supplied through the ion current detection circuit and the coil secondary winding to charge the coil secondary side stray capacitance, and the ion output signal is supplied as an energization monitor signal. Output. The failure of the igniter is detected by monitoring the time when the ion output signal of the energization monitor signal exceeds the threshold value. The time during which the secondary current flows (energization monitor signal width) is determined by the decay time constant due to the resistance in the ion detection circuit and the coil secondary side stray capacitance.
JP 2006-336535 A

  However, in the above conventional technique, the ion current waveform changes greatly depending on the resistance value of the ion current detection resistor. Specifically, if the ion current detection resistance is too large, the energization monitor signal may be pulse broken without the ion current waveform ending indefinitely. Further, if the ion current detection resistance is too small, the secondary current may be attenuated immediately and the energization monitor signal width may be shortened.

  In addition, the ion current waveform varies depending on the environment in which the ignition system abnormality detection device is used. On the other hand, when the power supply voltage increases when the ignition system abnormality detection device is incorporated in the vehicle, the decay time of the ion current is shortened or the current waveform is broken. On the other hand, an abrupt change in the power supply voltage may cause a change in the current waveform of the ionic current, resulting in erroneous output of an energization monitor signal. Further, when the ignition coil secondary side stray capacitance is small, the charging time is shortened, so that the decay time of the ion current is also shortened and the energization monitor signal width is shortened.

  Therefore, when the ion current waveform is used as a failure determination signal, when the ion current waveform is abnormal due to the above causes and a normal ion current waveform cannot be obtained, it is impossible to accurately determine the igniter failure. There is a problem that it ends up.

  In view of the above-described points, an object of the present invention is to provide an igniter with an ion current detection function capable of generating a failure determination signal for reliably detecting a failure.

  In order to achieve the above object, according to the first aspect of the present invention, a primary current is passed through the coil primary side (11) of the ignition coil (10) to the coil secondary side (12) of the ignition coil (10). A current is induced to cause a discharge in the gap of the spark plug (30). When the fuel is burned by the discharge, the combustion ions generated on the secondary side (12) of the ignition coil (10) are ionized. An igniter with an ion current detection circuit including an ion current detection circuit (27) that detects ignition and misfire in a gap portion of the spark plug (30) by detecting the current as a current, and includes an ignition coil (10) A primary current that flows through the coil primary side (11) of the ignition coil (10) has a first threshold value (Vth1) indicating that the current is normally flowing through the coil primary side (11). Is the first threshold Characterized in that it comprises a fail-safe signal generating circuit (28) for generating a fail-safe signal for failure determination indicating whether exceeds the value (Vth1).

  Thus, as long as the primary current normally flows to the coil primary side (11) of the ignition coil (10), the fail-safe signal generation circuit (28) has the primary current set to the first threshold value (Vth1). A fail-safe signal can be generated to indicate that it has been exceeded. Conversely, if the primary current does not exceed the first threshold value (Vth1), the failsafe signal generation circuit (28) indicates that the primary current does not exceed the first threshold value (Vth1). Can be generated. The primary current is a current that flows to the coil primary side (11) if the igniter is operating normally, and it is determined using the first threshold value (Vth1) whether or not the primary current has flowed. Thus, it is possible to generate a fail-safe signal for failure determination for reliably detecting an igniter failure.

  In the invention described in claim 2, the fail-safe signal generation circuit (28) has a second threshold value (Vth2) larger than the first threshold value (Vth1), and the primary current is the first. A fail-safe signal including rising and falling edges is generated when the threshold value (Vth1) and the second threshold value (Vth2) are exceeded.

  In this way, by generating a fail-safe signal including rising and falling edges, it is possible to easily determine whether or not a failure has occurred in the igniter. Further, the time between the rising edge and the falling edge of the fail safe signal can also be used as one of the igniter failure determination materials, and the igniter failure determination can be performed more reliably.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram of an ignition system including an igniter with an ion current detection circuit according to an embodiment of the present invention. In FIG. 1, in the system, an igniter 20 with an ion current detection circuit (hereinafter referred to as an igniter) is connected to the coil primary side 11 of the ignition coil 10, and a spark plug 30 is connected to the coil secondary side 12. It is shown.

  One end side of the coil primary side 11 of the ignition coil 10 is connected to an in-vehicle battery outside the igniter 20, and the other end side is connected to the igniter 20. Further, one end side of the coil secondary side 12 of the ignition coil 10 is connected to the igniter 20, and the other end side is connected to the spark plug 30.

  As shown in FIG. 1, the igniter 20 includes a waveform shaping circuit 21, an overvoltage protection circuit 22, a drive circuit 23, a transistor 24, a lock prevention circuit 25, an overcurrent protection circuit 26, an ion current detection circuit 27, and an IGf signal circuit. 28.

  The waveform shaping circuit 21 is a circuit that shapes the waveform of an ignition input signal (IGt signal) input from an engine ECU outside the igniter 20. The waveform shaping circuit 21 inputs the waveform shaped signal to the lock prevention circuit 25 and the drive circuit 23.

  The engine ECU outputs the above ignition input signal to each igniter 20 attached to each cylinder in order to cause combustion in each cylinder of the engine.

  The overvoltage protection circuit 22 inputs the battery voltage applied from the vehicle-mounted battery to the drive circuit 23. Further, the overvoltage protection circuit 22 stops the application of the battery voltage to the drive circuit 23 and prevents an excessive voltage from being input to the drive circuit 23 when the constant voltage applied from the in-vehicle battery exceeds a certain value. Also plays a role.

  The drive circuit 23 drives the transistor 24 ON / OFF according to the ignition input signal input from the waveform shaping circuit 21.

  The transistor 24 is a switching element for energizing the coil primary side 11 of the ignition coil 10. The primary side 11 of the ignition coil 10 is connected to the collector of the transistor 24, and the shunt resistor 29 is connected to the emitter. The shunt resistor 29 is connected to the ground outside the igniter 20. Note that a diode 24a for current return is connected between the emitter and collector of the transistor 24, so that the transistor 24 can be prevented from being destroyed due to current concentration during recovery.

  When the transistor 24 is turned on, a current path including the in-vehicle battery, the coil primary side 11, the transistor 24, the shunt resistor 29, and the ground is formed, and the primary current flows from the in-vehicle battery to the coil primary side 11.

  The lock prevention circuit 25 inputs an ignition input signal from the waveform shaping circuit 21 and forcibly turns off the transistor 24 when it is determined that the ignition input signal is to turn on the transistor 24 for a predetermined time or more. . That is, the lock prevention circuit 25 plays a role of preventing in advance that the primary current continues to flow through the coil primary side 11 for a specified time or longer when the drive circuit 23 is turned on.

  When the primary current flowing between the transistor 24 and the shunt resistor 29 exceeds a certain value, the overcurrent protection circuit 26 controls the drive circuit 23 to drive the transistor 24 and causes the coil primary side 11 to have an excessive primary. It plays a role of preventing current from flowing.

  The ion current detection circuit 27 detects combustion ions generated in the gap portion of the coil secondary ignition plug 30 as an ion current when the fuel is combusted by discharge in the ignition plug 30. The ion current detection circuit 27 is connected to the coil secondary side 12 of the ignition coil 10, and an ion current flowing through the coil secondary side 12 is input.

  The ion current detected by the ion current detection circuit 27 is output to the engine ECU as an ion output signal for determining a combustion state such as normal combustion, misfire, and smoldering detection of a pre-ignition (early ignition) plug. . Then, the engine ECU determines the combustion state based on the ion output signal.

  The IGf signal circuit 28 generates a fail-safe signal indicating whether or not the primary current normally flows, that is, whether or not the igniter 20 is operating normally. Specifically, the IGf signal circuit 28 has a first threshold value Vth1 indicating that a current is normally flowing through the coil primary side 11 of the ignition coil 10, and a second threshold value greater than the first threshold value Vth1. A failure determination that has a threshold value Vth2 and indicates whether or not the primary current flowing through the coil primary side 11 of the ignition coil 10 has exceeded the first threshold value Vth1 and the second threshold value Vth2 during discharge. Generate fail-safe signals for use.

  In the present embodiment, the IGf signal circuit 28 generates a fail-safe signal that falls when the primary current exceeds the first threshold value Vth1 and rises when the primary current exceeds the second threshold value Vth2. To do. The fail safe signal generated by the IGf signal circuit 28 is output to the engine ECU. And engine ECU will perform failure determination of the igniter 20 based on this fail safe signal.

  The IGf signal circuit 28 is connected to the path so as to detect a primary current flowing through the path between the emitter of the transistor 24 and the shunt resistor 29. In this case, the IGf signal circuit 28 only needs to be able to detect the primary current, and may be connected to a path in the igniter 20 that can detect the primary current.

  The above is the configuration of the ignition system and the igniter 20 according to the present embodiment. In the above configuration, the IGf signal circuit 28 corresponds to the fail-safe signal generation circuit of the present invention.

  Next, the operation of generating a fail-safe signal in the igniter 20 will be described with reference to FIG. FIG. 2 is a timing chart showing an ignition input signal, a primary current flowing in the coil primary side 11 of the ignition coil 10, and a fail-safe signal. Among these, FIG. 2A shows a case where the igniter 20 is normal, and FIGS. 2B and 2C show a case where the igniter 20 has failed.

  First, the case where the igniter 20 is normal will be described. When an ignition input signal (IGt signal) is input from the engine ECU to the waveform shaping circuit 21 of the igniter 20, the ignition input signal is waveform-shaped and input to the drive circuit 23. Thus, when the transistor 24 is turned on by the drive circuit 23, a primary current flows from the vehicle-mounted battery to the coil primary side 11. Thereby, as shown in FIG. 2A, while the IGt signal is ON, the primary current flows to the coil primary side 11 of the ignition coil 10, and magnetic energy is stored in the ignition coil 10.

  In addition, when a primary current flows through the coil primary side 11, a current flows based on the stray capacitance existing on the coil secondary high-voltage side as the coil secondary side 12. This current is detected as an ion current by the ion current detection circuit 27 and is output to the engine ECU as an ion output signal shown in FIG.

  As the primary current increases, the primary current exceeds the first threshold value Vth1. As a result, the signal output to the engine ECU at the Hi level falls and becomes a Low level signal. Thereafter, when the primary current increases and exceeds the second threshold value Vth2, the signal output to the engine ECU that was at the Lo level rises and becomes a Hi level signal.

  If the igniter 20 is operating normally, the primary current continues to increase while the IGt signal is ON. Therefore, if the primary current exceeds the first threshold value Vth1, the signal falls and the second threshold value is reached. Since the signal falls when Vth2 is exceeded, a fail-safe signal in which the rise and fall of the signal are set is generated. That is, the fail safe signal waveform shown in FIG. 2A indicates that the igniter 20 is operating normally.

  In the present embodiment, the width between the fall and rise of the fail safe signal is 0.5 ms or more. This fail safe signal is input to the engine ECU, and a failure determination of the igniter 20 is performed. In the engine ECU, for example, the failure of the igniter 20 is determined by monitoring the falling and rising edges of the fail-safe signal and the time from the falling edge to the rising edge of the signal. As shown in FIG. 2A, the primary current increases at a constant rate, and a fail-safe signal including falling and rising edges is generated exceeding the first threshold value Vth1 and the second threshold value Vth2. In this case, the engine ECU determines that the igniter 20 is normal.

  Then, ignition occurs at the spark plug 30 at the timing when the IGt signal falls. In other words, the magnetic energy stored in the ignition coil 10 is induced to the coil secondary side 12 by suddenly interrupting the current flowing through the coil primary side 11, and in the gap between the coil secondary side 12 and the spark plug 30. It is discharged as a discharge current, and ignition is performed. The high voltage generated on the secondary side of the coil at the time of discharging is charged to an ion detection power supply unit formed by paralleling a capacitor in the ion current detection circuit 27 and a Zener diode. When ignition is performed, combustion ions of fuel flame ions and NO thermally dissociated ions are generated in the combustion chamber of the engine. In order to detect the combustion ions, the voltage accumulated in the ion detection power supply unit posted in the ion current detection circuit 27 is applied to the spark plug 30 via the secondary coil winding so that the combustion ions are converted into the ion current. , And output to the engine ECU as an ion output signal, the engine ECU can make a misfire determination.

  Next, a case where a failure has occurred in the igniter 20 will be described. As shown in FIG. 2B, no primary current flows through the coil primary side 11 even though the IGt signal is ON. In this case, an ion output signal due to the rising edge of the IGt signal is not generated. Further, since the primary current does not flow, the primary current does not exceed the first threshold value Vth1 and the second threshold value Vth2, so that the fail-safe signal is a flat signal as shown in FIG. Is generated into a simple signal. Therefore, the engine ECU determines that the igniter 20 has failed, assuming that the fail-safe signal does not include falling and rising edges.

  In addition, as shown in FIG. 2C, when the IGt signal is turned on and then turned off before the specified period elapses, the ion output signal is generated because the IGt signal is turned on. However, since the primary current decreases as the IGt signal is turned OFF, the first threshold value Vth1 is not exceeded. Therefore, as in the case shown in FIG. 2B, a flat fail-safe signal is generated, and the engine ECU determines that the igniter 20 has failed.

  As described above, in the present embodiment, the IGf signal circuit 28 generates a fail-safe signal based on the primary current flowing in the coil primary side 11 of the ignition coil 10 while the IGt signal is ON. It is characterized by generating.

  That is, by comparing the primary current with the first threshold value Vth1 and the second threshold value Vth2 in the IGf signal circuit 28, a fail-safe signal for failure determination can be generated. This fail safe signal is obtained by monitoring the primary current flowing through the coil primary side 11 and is a signal indicating whether or not the primary current normally flows. Can be used as a signal for detection.

  Also, the rise and fall are set by comparing the primary current with the two first threshold values Vth1 and Vth2 and generating a fail-safe signal including the rise and fall of the signal. The fail-safe signal can be generated, and the failure determination can be easily performed. In addition, information such as the width of the rising and falling edges of the failsafe signal can be used as a material for determining the failure of the igniter 20, so that more detailed failure determination of the igniter 20 can be performed.

(Other embodiments)
In the above embodiment, the IGf signal circuit 28 detects the primary current using the two first threshold values Vth1 and Vth2, but even one threshold value for the primary current is available. I do not care. That is, the IGf signal circuit 28 may only generate a fail-safe signal for failure determination indicating whether or not the primary current flowing through the coil primary side 11 of the ignition coil 10 has exceeded the first threshold value Vth1. If the igniter 20 is operating normally, the rise or fall of the signal can be obtained, and if the igniter 20 is malfunctioning, the rise or fall of the signal cannot be obtained. By monitoring the trigger as a trigger, a fail-safe signal for determining a failure of the igniter 20 can be generated.

  In the above embodiment, the engine ECU determines the failure of the igniter 20 only by the failsafe signal. However, the failure of the igniter 20 may be determined by combining the ion output signal and the failsafe signal.

It is a figure of the ignition system containing the igniter with an ion current detection function which concerns on one Embodiment of this invention. It is the timing chart which showed the ignition input signal, the primary current which flows into the coil primary side of an ignition coil, and a fail safe signal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Ignition coil 11 Coil primary side 12 Coil secondary side 27 Ion current detection circuit 28 Fail safe signal generation circuit 30 Spark plug Vth1 1st threshold value Vth2 2nd threshold value I2 Coil secondary side current C2 Coil secondary side Stray capacitance

Claims (2)

By passing a primary current through the coil primary side (11) of the ignition coil (10) and inducing a current through the coil secondary side (12) of the ignition coil (10), the gap is formed in the spark plug (30). That causes a discharge,
An ion current detection circuit that detects combustion and misfire of the engine by detecting combustion ions generated in the gap portion of the coil secondary ignition plug (30) as an ion current when the fuel is burned by the discharge. 27) an igniter with an ion current detection function,
The coil primary side (11) of the ignition coil (10) has a first threshold value (Vth1) indicating that a current normally flows, and the coil primary side of the ignition coil (10) A fail-safe signal generation circuit (28) for generating a fail-safe signal for failure determination indicating whether or not the primary current flowing in (11) exceeds the first threshold value (Vth1); An igniter with ion current detection feature. The fail safe signal generation circuit (28) has a second threshold value (Vth2) larger than the first threshold value (Vth1), and the primary current is the first threshold value (Vth1). ) And the second threshold value (Vth2), a fail-safe signal including a rising edge and a falling edge is generated. Igniter.

Images