JPH09236073A - Combustion state detector for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To certainly detect preignition information (premature ignition) based on the ion current of an internal combustion engine. SOLUTION: Reference voltage is applied to the gate terminal of an IGBT 3 by switching on an ignition signal IGt from an ECU (electronic control unit), and a primary current I1 is started to be led to flow in the primary winding 1a of an ignition coil 1. At this time, the comparative voltage value of the inversion (-) input terminal of a comparator 11 is gradually raised by a time constant of CR of a resistor 17 and a condenser 18. Therefore, the primary current 11 detected through a current detecting resister 4 is loosely reached to a predetermined upper limit by constant current control, and occurrence of a large noise during that time is prevented. Therefore, when preignition is generated in the middle of the raising of the primary current 11, and ion current I ION is led to flow out, the noise may not be superposed so that accurate preignition information can be detected on the basis of an output signal from a connection point (j).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion state detecting device for an internal combustion engine, which detects preignition from the combustion state of the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine, when the temperature of an ignition plug or the like rises abnormally, it becomes a hot point and starts to ignite and burn before ignition control by spark discharge, as if the ignition timing was advanced. Pre-Ignition (pre-ignition; hereinafter simply referred to as "pre-ignition") occurs in which the hot spot is further heated and the ignition timing is advanced. This plague increases the amount of work in the compression stroke and tends to rotate the internal combustion engine in the reverse direction, which causes the operating condition to malfunction, causing the combustion chamber to be exposed to abnormally high temperatures, causing problems such as piston seizure and knocking of the internal combustion engine. It was easy to become.

As a prior art document for coping with such a problem, the one disclosed in Japanese Patent Application Laid-Open No. 57-44768 is known. This document discloses a technique of detecting a plague due to such a hot spot based on the generation of an ion current and delaying the ignition timing to prevent a trouble from occurring in the internal combustion engine in advance.

[0004]

The ignition device for an internal combustion engine generally uses a constant current control circuit, and the primary current flowing through the primary winding of the ignition coil reaches a predetermined upper limit value. If there is a drastic change at the time, it is assumed that noise may be superimposed on the terminal for detecting the generation of the ionic current and erroneous detection of Plague.

Therefore, the present invention has been made in order to eliminate the predictability of such a problem, and provides a combustion state detecting device for an internal combustion engine capable of reliably detecting a plague based on the generation of an ion current of the internal combustion engine. Offering is an issue.

[0006]

According to another aspect of the present invention, there is provided a combustion state detecting apparatus for an internal combustion engine, wherein a switching element is driven by a current limiting circuit and flows through a primary winding of an ignition coil.
The secondary current is limited to a predetermined upper limit value, and the primary current is slowly reached to the predetermined upper limit value by the slow reaching control circuit. Therefore, generation of large noise due to electromagnetic induction on the secondary winding side of the ignition coil due to abrupt fluctuation of the primary current is suppressed. As a result, when a plague occurs during the rise of the primary current, the ion current detected by the ion current detection circuit does not have a large amount of superposition of noise, so that an accurate plague information can be detected.

In the current limiting circuit of the combustion state detecting device for the internal combustion engine according to the second aspect, the reference value for limiting the primary current flowing through the primary winding of the ignition coil detected by the primary current detecting circuit generates a reference value. Generated in the circuit. The reference value changed by the slow arrival control circuit and the primary current value are compared by the comparison drive circuit, and the switching element is turned on / off, so that the primary current reaches the predetermined upper limit value immediately after the start of energization. Is gradually increased. That is, since there is no abrupt change in the primary current, large noise induced on the secondary winding side of the ignition coil is suppressed, and superposition of a large noise signal on the ion current is suppressed. As a result, when plague is generated during the rise of the primary current and an ionic current flows, there is no superposition of large noises, so that there is an effect that accurate plague information can be detected.

In the current limiting circuit of the combustion state detecting device for the internal combustion engine according to claim 3, a reference value for limiting the primary current flowing through the primary winding of the ignition coil detected by the primary current detecting circuit is generated as a reference value. Generated in the circuit. The primary current value changed by the slow-reaching control circuit is compared with the reference value by the comparison drive circuit, and the switching element is turned on / off, so that the primary current reaches a predetermined upper limit value immediately after the start of energization. Is gradually increased. That is, since there is no abrupt change in the primary current, large noise induced on the secondary winding side of the ignition coil is suppressed, and superposition of a large noise signal on the ion current is suppressed. As a result, when plague is generated during the rise of the primary current and an ionic current flows, there is no superposition of large noises, so that there is an effect that accurate plague information can be detected.

According to the combustion state detecting apparatus for the internal combustion engine of the fourth aspect, since the current limiting circuit functions before the ignition timing, the ion detecting the occurrence of the plague based on the ion current flowing during the rising of the primary current. By combining with the current detection device, an excellent effect of preventing false detection of plague can be obtained.

In the combustion state detecting device for the internal combustion engine according to the fifth aspect, the ionic current detecting device detects the ionic current generated during the detection period including the period during which the primary current is gradually increased by the slow arrival control circuit. Since no large noise is superposed during this detection period, it is possible to obtain an effect that the ion current detecting device can accurately determine that the detected ion current is Plague.

According to the combustion state detecting device of the internal combustion engine of claim 6, the driving of the switching element for limiting the current of the primary current in the current limiting circuit is started before the ion current detection period, and the detection is performed. Driving of the switching element is started during the period, and the change amount of the primary current is prevented from abruptly changing. For this reason, during the detection period, generation of large noise due to electromagnetic induction on the secondary winding side of the ignition coil due to abrupt fluctuation of the primary current is suppressed. This gives 1
When a plague occurs during the rise of the next current, the ion current detected by the ion current detection circuit does not have a large noise superposition, so that an accurate plague information can be detected.

In the combustion state detecting apparatus for an internal combustion engine according to a seventh aspect of the present invention, the driving of the switching element for the current limitation of the primary current, which is gradually increased toward the predetermined upper limit value in the current limiting circuit, is performed during the ion current detection period. Has started in front of
The driving of the switching element is started during the detection period, and the change amount of the primary current is prevented from abruptly changing. For this reason, during the detection period, generation of large noise due to electromagnetic induction on the secondary winding side of the ignition coil due to abrupt fluctuation of the primary current is suppressed. As a result, when a plague occurs during the rise of the primary current, the ion current detected by the ion current detection circuit does not have a large superposition of noise, so that an accurate plague information can be detected.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below based on Examples.

<First Embodiment> FIG. 1 is a circuit diagram showing a constant current control unit in an ignition circuit using a combustion state detecting device for an internal combustion engine according to a first embodiment of the present invention.

In FIG. 1, 1 is an ignition coil, and 1
a is the primary winding of the ignition coil 1 and 1b is 2 of the ignition coil 1.
It is the next winding. Reference numeral 2 is a spark plug arranged in a cylinder of an internal combustion engine (not shown). Primary winding 1 of ignition coil 1
One end of a is connected to the battery power supply terminal VB, and the other end is I
It is grounded via a series circuit of a GBT (Insulated Gate Bipolar Transistor) 3 and a current detection resistor 4. The IGBT 3 is a low breakdown voltage MOSFET whose gate circuit is a bipolar transistor.
It has a gate terminal, a collector terminal, and an emitter terminal. When the IGBT 3 is turned on, the primary current I1 flows from the battery power supply terminal VB to the ignition coil 1-1.
It flows to the ground side through the secondary winding 1a, the IGBT 3, and the current detecting resistor 4. The magnitude of the primary current I1 is converted into a voltage value by the current detecting resistor 4.

The gate terminal of the IGBT 3 is an ECU ignition signal output PNP transistor 5 and an igniter input protection resistor 6.
Is connected to the reference voltage terminal Vcc through a series circuit of a charge and discharge alleviating IGBT gate resistor 7. The PNP transistor 5 has its base terminal connected to an ECU (El
It is turned on when an ignition signal IGt is input from an ectronic Control Unit (electronic control unit) 8. This ignition signal I
Based on the ON operation of the PNP transistor 5 in response to Gt, the reference voltage + 5V (volt) is applied to the gate terminal of the IGBT 3 from the reference voltage terminal Vcc. ECU8
Is a logical operation circuit including a CPU as a well-known central processing unit, a ROM storing a control program, a RAM storing various data, an input / output circuit and a bus line connecting them.

A connection point a between the emitter terminal of the IGBT 3 and the current detecting resistor 4 is connected to a non-inverting (+) input terminal of a comparator 11 through a series circuit of a resistor 9 and a resistor 10. It is connected. Further, the connection point b between the resistors 9 and 10 is grounded via the resistor 12, and the connection point b is connected to the connection point c between the resistors 6 and 7 and the oscillation prevention resistor 13. Has been done. The oscillation preventing resistor 13 divides the voltage between the gate and the emitter of the IGBT 3 and applies positive feedback to the comparator 11. Between the gate and the emitter, a series resistor of a resistor 4 and a resistor 9 and a resistor 12 in parallel are provided. The voltage is divided by the resistance value of the resistor and the resistance value of the resistor 13.

The connection point d between the PNP transistor 5 and the resistor 6 is grounded through the series circuit of the resistance 14, the resistance 15 and the resistance 16, and the connection point e between the resistance 15 and the resistance 16 is. It is grounded via a series circuit of a resistor 17 and a capacitor 18. Then, the resistor 17 and the capacitor 18
The connection point f between and is connected to the inverting (-) input terminal of the comparator 11. Therefore, in the comparator 11, the voltage value according to the voltage between both terminals of the current detection resistor 4 at the connection point a, that is, the voltage value according to the primary current I1 flowing through the primary winding 1a of the ignition coil 1 The voltage divided by the resistors 15 and 16 by the simple reference voltage generating Zener diode 20 is compared with the voltage value at the connection point f when the capacitor 18 is charged via the resistor 17. From this comparator 11, L (Low:
A low level signal or an H (High: high) level signal is output.

The connection point g between the resistor 6 and the resistor 7
Is grounded through the NPN transistor 19, and the base terminal of the NPN transistor 19 is connected to the output terminal of the comparator 11. The NPN transistor 19 is turned off when the L level signal is input from the comparator 11 and is turned on when the H level signal is input.

Further, one end of the secondary winding 1b of the ignition coil 1 is grounded via the ignition plug 2 and the other end is grounded via the Zener diodes 21 and 22. Here, the Zener diode 21 is connected in the reverse direction and the Zener diode 22 is connected in the forward direction with respect to the direction in which the secondary current I2 flows. A connection point i between the secondary winding 1b of the ignition coil 1 and the Zener diode 21 is connected to a capacitor 23 as an ion current detection power source and an ion current detection resistor 2
It is grounded via a series circuit with 4. Further, a connection point j between the capacitor 23 and the ion current detecting resistor 24
Is connected to the ion current detector 25, and is also connected to a connection point k between the Zener diode 21 and the Zener diode 22.

The voltage value applied to the ion current detecting resistor 24 according to the ion current IION flowing through the secondary winding 1b of the ignition coil 1 at the connection point j is input to the ion current detecting device 25. The ion current detection device 25 monitors the voltage value of the connection point j only for a preset detection period (while a window signal described later is on), and during that period, the ion current signal SIIO corresponding to the ion current IION.
When the occurrence of N is detected, it is determined that a plague has occurred, and a control signal for increasing the air-fuel ratio to the internal combustion engine to make it into a lean fuel state, a control signal to temporarily stop fuel, or a control to delay the ignition timing. It has a function of outputting a signal or the like to the ECU 8 side and returning the operating state of the internal combustion engine to a normal state.

Next, regarding the operation of the constant current control unit in the ignition circuit thus constructed, the characteristic diagram of FIG. 2 and the characteristic diagram of FIG. 3 showing the relationship between the primary current I1 and the energization time T using the battery voltage as a parameter. This will be described with reference to the timing chart. For comparison, the capacitor 18 is shown in FIG.
The relationship between the primary current I1 of the constant current control unit and the energization time T in the conventional ignition circuit without the above will be described with reference to the characteristic diagram of FIG. 5 showing the battery voltage as a parameter and the timing chart of FIG.

In FIG. 1, the PNP transistor 5 has an E
When the ignition signal IGt is input from the CU 8, the PNP transistor 5 is turned on. Then, the reference voltage terminal Vcc
Then, the reference voltage + 5V is applied to the resistor 7 via the resistor 6, and the IGBT 3 is turned on. When the IGBT 3 is turned on, a primary current I1 flows from the battery power supply terminal VB to the ground side through the primary winding 1a of the ignition coil 1, the IGBT 3, and the current detecting resistor 4.

Here, since the primary winding resistance of the ignition coil 1 is relatively large, as shown in FIGS. 2 and 5, the higher the battery voltage connected to the battery power supply terminal VB, the larger the primary current I1. It can flow to the primary winding 1a side. The primary current I1 flowing through the primary winding 1a is limited to a predetermined upper limit value I1 max by constant current control to protect the circuit elements when the battery voltage is high, and does not depend on the constant current control when the battery voltage is low. It will be decided by itself.

By the way, as shown in FIG.
The higher the battery voltage and the steeper the primary current I1, the more rapid the change when reaching the predetermined upper limit value I1 max. On the other hand, in the present embodiment shown in FIG. 2, the predetermined upper limit value I1 max is gently reached even when the battery voltage is high and the primary current I1 rises steeply.

In FIG. 1, the comparator 11 determines the voltage value at the connection point a and the voltage value at the connection point f at which the current value of the primary current I1 is converted into a voltage value by the current detecting resistor 4. Be compared. When the voltage value at the connection point a is lower than the voltage value at the connection point f, the comparator 11 outputs an L level signal to the base terminal of the NPN transistor 19. The NPN transistor 19 is off when its base terminal is at L level. When the primary current I1 flowing through the primary winding 1a of the ignition coil 1 rises and reaches the voltage value at the connection point f, the comparator 11 outputs an H level signal to the base terminal of the NPN transistor 19. The NPN transistor 19 is in the ON state when its base terminal is at the H level. Then, the predetermined upper limit value I
Comparator 1 until the voltage value corresponding to 1 max is reached
The NPN transistor 19 is repeatedly turned on / off based on the comparison result of 1.

That is, the voltage value of the connection point f connected to the inverting (-) input terminal of the comparator 11 is the ECU 8
Even if the PNP transistor 5 is turned on by the ignition signal IGt from, the comparison voltage value at the connection point e (corresponding to a predetermined upper limit value I1 max for limiting the primary current I1 flowing through the primary winding 1a of the ignition coil 1) The voltage value of the connection point e is gradually increased based on the CR time constant of the resistor 17 and the capacitor 18. Therefore, as shown in FIG. 2, in the comparator 11, the voltage value of the connection point a,
That is, the current value of the primary current I1 is controlled from the initial stage of rising and gradually reaches the predetermined upper limit value I1 max. By adding a resistor between the capacitor 18 and the ground, the rise of the current value of the primary current I1 can be controlled from the middle to gradually reach the predetermined upper limit value I1 max. Also, the battery voltage is low and the resistance is 1.
1 than the CR time constant given by 7 and capacitor 18
When the next current I1 rises slowly, the waveform becomes equivalent, as is apparent from the characteristic diagrams of FIGS.

As described above, the NPN transistor 19
Is repeatedly turned on / off by the output signal from the comparator 11 to adjust the gate voltage of the IGBT 3,
The primary current I1 flowing through the BT3 is gradually reduced to a predetermined upper limit value I.
1 max is reached and held. At this time, the gate voltage of the IGBT 3 is applied to the comparator 1 by the oscillation prevention resistor 13.
1 is fed back to the non-inverting (+) input terminal side and IG
Oscillation of the primary current I1 flowing through BT3 is prevented. Further, the resistance 7 reduces the charging / discharging speed with respect to the stray capacitance of the gate terminal of the IGBT 3 which is pulled out by the NPN transistor 19. This prevents oscillation of the current value of the primary current I1 flowing through the primary winding 1a of the ignition coil 1,
It is possible to realize constant current control in which there is no abrupt change when reaching the predetermined upper limit value I1 max and large noise is prevented.

Based on the above operation, when the gate voltage is applied to the IGBT 3 by the ignition signal IGt at the time t0 as shown in FIG. 3 (a), the primary current I1 is simultaneously increased as shown in FIG. 3 (b). Ascending starts, and as shown in FIG.
A signal is input to the ion current detection device 25 from the connection point j in FIG. As shown in FIG. 3C, at time t0, the primary current I1 starts to flow in the ignition coil 1 and at the same time, the ignition on-noise signal SNon is generated, and at time t4, the primary current I1 in the ignition coil 1 ends. After that, at time t5, residual magnetic noise SNRM is generated due to the residual magnetism remaining in the iron core of the ignition coil 1. In response to this input signal, in the ion current detector 25, as shown in FIG. 3 (d), a detection period in which the window signal is turned on only during the time t1 to t3 during which the primary current I1 is rising is set. As a result, as shown by the chain double-dashed line in FIG. 3C, only a large signal exceeding the predetermined threshold value Vref is detected among the output signals from the connection point j in FIG.

Conventionally, as shown in FIG. 6, from time t01 onward.
Even if the window signal during t03 is turned on and the detection period is set, at time t02 during that period,
A large noise signal SNVC was generated due to the abrupt fluctuation of the primary current I1. On the other hand, as shown in FIG. 3, in the detection period in which the window signal is on between the times t1 and t3 of this embodiment, the primary current I1 is gently changed and a large noise signal is generated. Because there is no
The large signal detected during this period is the ion current signal S
IION can be identified, and when this ion current signal SIION is detected as shown at time t2 in FIG. 3C, it can be accurately determined that plague is occurring.

As described above, the combustion state detecting apparatus for the internal combustion engine according to the present embodiment is configured so that the primary coil 1a of the ignition coil 1 has a flow rate of 1
IGB as a switching element for interrupting the next current I1
The primary current I of the ignition coil 1 is driven by driving T3 and the IGBT3.
1 for limiting 1 to a predetermined upper limit value I1 max, current detecting resistor 4, comparator 11, resistors 14, 15, 16 and NPN
A current limiting circuit achieved using transistor 19,
Ion current IION flowing through the secondary winding 1b of the ignition coil 1
Zener diodes 21, 22 and capacitor 2 for detecting
3. An ion current detecting circuit achieved by using the ion current detecting resistor 24, and a resistor 17, which is connected to the current limiting circuit and allows the primary current I1 of the ignition coil 1 to slowly reach the upper limit I1 max. And a slow arrival control circuit achieved by a delay circuit using 18.

Therefore, the primary winding 1a of the ignition coil 1 is
The primary current I1 flowing through the
Will be reached. Then, the abrupt fluctuation of the primary current I1 disappears, the generation of large noise induced on the secondary winding 1b side of the ignition coil 1 is suppressed, and the superposition of the large noise signal on the ion current IION is suppressed. That is, the primary current I1
When the plague is generated during the ascent of the ion current and the ion current IION flows, accurate plague information can be detected because there is no superposition of large noise.

Further, the current limiting circuit of the combustion state detecting apparatus for the internal combustion engine of this embodiment is specifically achieved by using the current detecting resistor 4 for detecting the primary current I1 of the ignition coil 1. Current detecting circuit and resistors 14, 1 for generating a reference value as a voltage value for limiting the primary current I1 of the ignition coil 1.
5, a reference value generation circuit achieved by using
Using a comparator 11 and an NPN transistor 19 which turn on / off the IGBT 3 based on the result of comparison between the current value of the primary current I1 detected by the next current detection circuit and the reference value generated by the reference value generation circuit. A slow drive control circuit including a comparison drive circuit achieved and using a resistor 17 and a capacitor 18 changes the reference value generated by the reference value generation circuit.

Therefore, the primary winding 1a of the ignition coil 1
Immediately after the start of the energization of the primary current I1 flowing through the capacitor until the reference value as the target value of the current limit reaches the predetermined upper limit value I1 max, the resistance 17 and the capacitor 18 gradually increase the delay time due to the CR time constant. To be done. With such a simple structure, abrupt fluctuation of the primary current I1 is eliminated, generation of large noise induced on the secondary winding 1b side of the ignition coil 1 is suppressed, and a large noise signal is superposed on the ion current IION. Is suppressed. As a result, when plague is generated during the rise of the primary current I1 and the ion current IION flows, there is no superposition of large noise, and accurate plague information can be detected.

Further, in the combustion state detecting apparatus for the internal combustion engine of the present embodiment, the ions detected by the ion current detecting circuit realized by using the Zener diodes 21, 22 and the capacitor 23 and the ion current detecting resistor 24 are further detected. An ion current detection device 25 for inputting an ion current signal SIION based on the voltage value of the ion current detection resistor 24 as a detection signal corresponding to the current IION and detecting generation of plague based on this ion current signal SIION Is.

Therefore, when the plague is generated while the primary current I1 is rising and the ion current IION flows, the ion current detection device 25 can detect accurate plague information based on the ion current detection signal SIION.

Further, the ion current detecting device 25 of the combustion state detecting device for the internal combustion engine of the present embodiment is based on the driving of the IGBT 3 as a switching element in the slow reaching control circuit achieved by using the resistor 17 and the capacitor 18. After the primary current I1 of the ignition coil 1 is gently increased, before the cutoff of the primary current I1 is performed, the pre-ignition is performed based on the ion current signal SIION as the detection signal of the ion current IION in the detection period set by the window signal. It is something to detect.

Therefore, noise is not superposed on the ion current IION detected during the detection period set before the cutoff of the primary current I1 which is gently increased by the capacitor 18 of the slow-arrival control circuit. Therefore, when the ion current detection device 25 detects the ion current signal SIION within the detection period, it can be accurately determined to be Plague.

Furthermore, the combustion state detecting apparatus for an internal combustion engine of this embodiment is an IGBT as a switching element for connecting and disconnecting the primary current I1 flowing through the primary winding 1a of the ignition coil 1.
3 and the primary current I1 of the ignition coil 1 for driving the IGBT 3
Current detection resistor 4, which limits the current to a predetermined upper limit value I1 max,
A current limiting circuit achieved by using the comparator 11, resistors 14, 15, 16 and NPN transistor 19, Zener diodes 21, 22 for detecting the ion current IION flowing through the secondary winding 1b of the ignition coil 1, a capacitor 23,
The ion current detection circuit achieved by using the ion current detection resistor 24 and the ion current IION detected by the ion current detection circuit during the detection period set by the window signal before the ignition timing are input to the internal combustion engine. And an ion current detector 25 for determining the combustion state of the ion current detector 25.
The GBT 3 is driven to limit the primary current I1 of the ignition coil 1.

Therefore, the drive of the IGBT3 for current limitation in the current limiting circuit is started before the detection period of the ion current IION, and the drive of the IGBT3 is started during the detection period to reduce the variation of the primary current I1. Rapid fluctuations are prevented. As a result, the primary current I1 during the detection period
Of the primary current I1 is suppressed, the large noise induced on the secondary winding 1b side of the ignition coil 1 is suppressed, and the large noise signal is superposed on the ion current IION. Suppressed. As a result, the primary current I
When a plague is generated during the ascent of 1 and the ion current IION flows, accurate plague information can be detected because there is no superposition of large noise.

The specific implementation method is not limited to the one in which the current limiting operation is started immediately after the start of energization as in the above embodiment, and the primary current I1 is a predetermined upper limit value I1max or less. The current limiting operation may be started for the first time within the range, or the current limiting operation may be started for just before the detection period of the ion current IION. In any case, the ion current detection period is set so as to include the period during which the primary current of the ignition coil is gradually increased by the slow arrival control circuit.

Further, even if the detection period of the ion current detecting device is made variable so as to start the detection of the ion current IION after the start of the current limiting operation, it is possible to prevent the erroneous detection of Plague due to noise.

In addition, the current detecting resistor 4, the comparator 11 and the resistor 1 of the combustion state detecting device for the internal combustion engine according to the present embodiment.
The current limiting circuit realized by using 4, 15, 16 and NPN transistors 19 drives the IGBT 3 and gradually increases the primary current I1 of the ignition coil 1 toward a predetermined upper limit value I1 max.

Therefore, the drive of the IGBT3 for the current limitation of the primary current I1 which is gradually increased toward the predetermined upper limit value I1 max in the current limitation circuit is started before the detection period of the ion current IION, IGB during the detection period
The driving of T3 is started to prevent the change amount of the primary current I1 from abruptly changing. As a result, 1 during the detection period
Since the abrupt fluctuation of the secondary current I1 is suppressed and the abrupt fluctuation of the primary current I1 does not occur, the large noise induced on the secondary winding 1b side of the ignition coil 1 is suppressed, and the large noise signal to the ion current IION is suppressed. Is suppressed. This allows
When plague is generated while the primary current I1 is rising and the ion current IION flows, accurate plague information can be detected because there is no superposition of large noise.

In order to achieve the purpose of preventing the noise which affects the detection of the plague, it is important to suppress the rapid change of the primary current during the plague detection period. Is less than a predetermined value depending on the transformer performance such as the primary / secondary winding ratio of the ignition coil and the sensitivity of the circuit / device that detects the signal indicating the pre-play by distinguishing it from noise. Suppressed to.

<Embodiment 2> FIG. 4 is a circuit diagram showing a constant current controller in an ignition circuit using a combustion state detecting apparatus for an internal combustion engine according to a second embodiment of the present invention.
In the figure, components having the same configuration or corresponding parts as those in the above-described embodiment are denoted by the same reference numerals and symbols, and detailed description thereof is omitted.

In FIG. 4, the capacitor 18 connected between the connection point f and the ground in FIG.
The only difference is that capacitors 26 are connected in parallel at both ends of the. The operation of the constant current control unit configured as described above that is different from the above embodiment will be described.

In FIG. 4, the reference voltage e by the simple reference voltage generating Zener diode 20, the resistor 15 and the resistor 16 is input to the inverting (-) input terminal of the comparator 11. This reference voltage e is a preset fixed value, unlike the above-mentioned embodiment. Meanwhile, the resistor 26 and the capacitor 26
Are connected in parallel, the IGBT 3 is turned on and the voltage value detected by the current detection resistor 4 corresponding to the current value of the primary current I1 flowing through the primary winding 1a of the ignition coil 1 is It is quickly input to the non-inverting (+) input terminal of the comparator 11 as it is charged. Then, as the primary current I1 flowing through the primary winding 1a of the ignition coil 1 approaches a predetermined upper limit value I1 max, the capacitor 26 that has been completely charged suppresses large fluctuations in the primary current I1.
As a result, the primary current I1 flowing through the primary winding 1a of the ignition coil 1 exhibits a steep rise at the first rise and becomes gentle as it reaches the predetermined upper limit value I1 max. It is possible to prevent the generation of noise at the connection point j of the detection circuit.

As described above, the current limiting circuit of the combustion state detecting device for the internal combustion engine according to the present embodiment specifically includes the ignition coil 1
Primary current detection circuit achieved by using the current detection resistor 4 for detecting the primary current I1 of the above, a Zener diode 20 for limiting the primary current I1 of the ignition coil 1, resistors 15 and 16
Based on the result of comparison between the reference value generated by the reference current generating circuit and the current value of the primary current I1 detected by the primary current detecting circuit and the reference value generated by the reference value generating circuit. On / off driven comparator 11, N
A comparison drive circuit achieved by using a PN transistor 19 and a capacitor 26 connected in parallel to the resistor 9;
The slow reaching control circuit achieved by the differentiating circuit using is to change the primary current value detected by the primary current detection circuit.

Therefore, the primary winding 1a of the ignition coil 1 is
The primary current I1 flowing in the comparator drive circuit is obtained by differentiating the detection value of the current detection resistor 4 in the slow-arrival control circuit which is connected to the primary current detection circuit and is achieved by using the capacitor 26 as the advance element. Therefore, the detected value is apparently large immediately after the start of the energization of the primary current I1, and the detected value gradually and gradually rises with respect to the actual detected value and converges. With such a simple structure, abrupt fluctuations of the primary current I1 are eliminated, generation of large noise induced on the secondary winding 1b side of the ignition coil 1 is suppressed, and a large noise signal to the ion current detection signal SIION is suppressed. Is suppressed. As a result, when plague is generated during the rise of the primary current I1 and the ion current IION flows, there is no superposition of large noise, and accurate plague information can be detected based on the ion current detection signal SIION.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a constant current control unit in an ignition circuit using a combustion state detecting device for an internal combustion engine according to a first example of an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the relationship between the primary current and the energization time of the constant current control unit in the ignition circuit of FIG. 1 using the battery voltage as a parameter.

FIG. 3 is a timing chart showing transition states of various signals in the ignition circuit of FIG.

FIG. 4 is a circuit diagram showing a constant current control unit in an ignition circuit using a combustion state detecting device for an internal combustion engine according to a second example of the embodiment of the present invention.

FIG. 5 is a characteristic diagram showing a relationship between a primary current and a conduction time of a constant current control unit in a conventional ignition circuit using a battery voltage as a parameter.

FIG. 6 is a timing chart showing transition states of various signals in the conventional ignition circuit.

[Explanation of symbols]

1 Ignition Coil 1a Primary Winding 1b Secondary Winding 2 Spark Plug 3 IGBT (Switching Element) 4 Current Detection Resistor 5 (ECU Ignition Signal Output) Transistor 6 (Ignite Input Protection) Resistance 7 (Charge / Discharge Mitigation) IGBT Gate resistance 8 ECU (electronic control unit) 9, 10, 12, 13 (for current feedback) resistance 11 Comparator 14, 15, 16, 17 (for reference voltage) Resistance 18 Capacitor 19 NPN transistor 20 (for simple reference voltage generation) Zener diode 21,22 Zener diode 23 Capacitor 24 Ion current detection resistor 25 Ion current detection device 26 Capacitor

Claims (7)

[Claims] 1. A switching element for connecting and disconnecting a primary current flowing through a primary winding of an ignition coil;
A current limiting circuit for limiting a secondary current to a predetermined upper limit value, an ion current detecting circuit for detecting an ion current flowing through a secondary winding of the ignition coil, and a current limiting circuit connected to the current limiting circuit,
A combustion state detection device for an internal combustion engine, comprising: a slow arrival control circuit that gently causes the next current to reach the upper limit value. 2. The current limiting circuit includes a primary current detection circuit that detects the primary current of the ignition coil, and a reference value generation circuit that generates a reference value that limits the primary current of the ignition coil. A comparison drive circuit that turns on / off the switching element based on a comparison result between the primary current value detected by the primary current detection circuit and the reference value generated by the reference value generation circuit. The combustion state detecting device for an internal combustion engine according to claim 1, further comprising: the slowly reaching control circuit changes the reference value generated by the reference value generating circuit. 3. The current limiting circuit includes a primary current detection circuit that detects the primary current of the ignition coil, and a reference value generation circuit that generates a reference value that limits the primary current of the ignition coil. A comparison drive circuit that turns on / off the switching element based on a comparison result between the primary current value detected by the primary current detection circuit and the reference value generated by the reference value generation circuit. The combustion state detection device for an internal combustion engine according to claim 1, further comprising: the slow-movement control circuit changes the primary current value detected by the primary current detection circuit. 4. An ion current detection device is further provided, which receives a detection signal corresponding to the ion current detected by the ion current detection circuit and detects the occurrence of preignition based on the detection signal. The combustion state detection device for an internal combustion engine according to any one of claims 1 to 3, characterized in that: 5. The ion current detection device performs preignition based on a detection signal of the ion current in a detection period including a period in which the primary current of the ignition coil is gradually increased by the slow arrival control circuit. It detects, The combustion state detection apparatus of the internal combustion engine of Claim 4 characterized by the above-mentioned. 6. A switching element for connecting and disconnecting a primary current flowing through a primary winding of an ignition coil;
A current limiting circuit for limiting the secondary current to a predetermined upper limit value, an ion current detecting circuit for detecting an ion current flowing through the secondary winding of the ignition coil, and an ion current detecting circuit for detecting a period set before ignition timing. The ion current detected by the circuit is input, and an ion current detection device for determining the combustion state of the internal combustion engine is provided, and the switching element is used in the current limiting circuit before the detection period by the ion current detection device. A combustion state detection device for an internal combustion engine, which is driven to limit the primary current of the ignition coil. 7. The internal combustion engine according to claim 6, wherein the current limiting circuit drives the switching element to gradually increase the primary current of the ignition coil toward a predetermined upper limit value. Combustion state detection device.