JPH08338298A - Burning state detecting device for internal combustion engine - Google Patents

Abstract

PURPOSE: To use the power source voltage of a battery power source mounted on a vehicle for ion current detection for detecting the burning state of an internal combustion engine, and stably detect the ion current. CONSTITUTION: A Zener diode 21 and a secondary current detecting resistor 32 are series-connected on the low voltage side of the secondary winding 1b of an ignition coil 1, a diode 36, an ion current detecting resistor 35 and a battery power source 34 are series-connected in parallel thereto. The voltage detected by the ion current detecting resistor 35 is directly inputted to a voltage follower 9 through a resistor 41, its output is inputted to a mask circuit 14, and the voltage from a battery power source 34 is directly applied during the period where a switching element Tr2 is ON by the output signal from a delay circuit 13. Thus, the residual magnetic noise is removed to allow a stable ion current detection (the output signal of a terminal D), and the knock signal can be detected by the terminal B of a band pass filter 10.

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 misfire from the combustion state of the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, as a prior art document relating to a combustion state detecting device for an internal combustion engine, Japanese Patent Laid-Open No. 4-179863.
The one disclosed in the publication is known. In this device, as shown in a typical ion current detection circuit of FIG. 6, a technique of detecting an ion current on the secondary high voltage side of an ignition coil is shown.

Further, those disclosed in JP-A-4-191465 and JP-A-4-194367 are known. In these devices, as shown in typical ion current detection circuits in FIGS. 7 and 8, a technique for detecting an ion current on the secondary low voltage side of the ignition coil is shown.

[0004]

FIG. 6 is a circuit diagram showing an ion current detecting circuit in a conventional combustion state detecting device for an internal combustion engine.

First, the ion current detection on the secondary high voltage side of the ignition coil 1 shown in FIG. 6 will be described.

In FIG. 6, the primary current I is applied to the ignition coil 1.
When the primary current I1 is cut off after 1 has been energized, the secondary current I2 flows through the ignition coil 1 through the high breakdown voltage diode 3. When the flame grows between the electrodes of the ignition plug 2, an ion current flows between the electrodes of the ignition plug 2 via the ion detection power source 4, the ion current detection resistor 5 and the high voltage rectification diode 6. Therefore, the ionic current flowing through the ionic current detecting resistor 5 can be measured at the terminal Vout. However, the high withstand voltage diode 3 and the high withstand voltage rectifier diode 6 in this configuration are required to withstand the maximum value of the discharge voltage of the ignition plug 2 of about 40 KV, which is very expensive and the detection of the ion current IION. Has a problem that it requires a high voltage (about 300 V) ion detection power source 4.

On the other hand, the ion current detection on the secondary low voltage side of the ignition coil 1 shown in FIGS. 7 and 8 will be described.

FIG. 7 is a circuit diagram showing another ion current detecting circuit in the conventional combustion state detecting apparatus for an internal combustion engine, and FIG. 8 is a circuit showing another ion current detecting circuit in the conventional combustion state detecting apparatus for an internal combustion engine. It is a figure.

7 and 8, the high withstand voltage diode 3 in FIG. 6 is not used and the high voltage ion detection power source 4 is replaced with the capacitor 8.

First, the operation of FIG. 7 will be described.

When the primary current I1 is supplied to the ignition coil 1 and then the primary current I1 is cut off, the ignition coil 1
Via diode 3'and Zener diode 7
The next current I2 flows. During this discharge, the ignition coil 1 operates as if it were a DC-DC converter, and the capacitor 8 is charged with a voltage corresponding to the Zener voltage of the Zener diode 7. When the flame grows between the electrodes of the spark plug 2 after the spark plug 2 is discharged, the amount of electricity charged in the capacitor 8 causes the ionic current detection resistor 5 and the secondary winding of the ignition coil 1 to cause An ion current IION flows between the electrodes. Therefore, the ion current detection resistor 5
It is possible to measure the ion current IION flowing through the terminal Vout, but this configuration requires a capacitor having a high withstand voltage or a capacitor having a large capacity, which is not practical.

Further, FIG. 8 shows a configuration in which the Zener diode 7 and the capacitor 8 of FIG. 7 and the diode 3'and the ion current detecting resistor 5 are arranged in the opposite positional relationship, and a high voltage is not applied to the ion current detecting resistor 5. The detection voltage is 0V
There was a problem that it became smaller.

Therefore, the present invention has been made to solve such a problem, and the power source voltage of a battery power source mounted on a vehicle for detecting an ion current for detecting a combustion state of an internal combustion engine can be used and stabilized. It is an object of the present invention to provide a combustion state detection device for an internal combustion engine, which can detect an ion current by using an internal combustion engine.

[0014]

A combustion state detecting device for an internal combustion engine according to a first aspect of the present invention is a first combustion device for detecting a combustion state of an internal combustion engine in which a secondary winding of an ignition coil for generating an ignition spark is connected in series to a low voltage side. A diode, an ion current detection resistor and a battery power source are connected, and the ignition coil is generated in parallel with the first diode, the ion current detection resistor and the battery power source on the low voltage side of the secondary winding of the ignition coil. The current path for passing the secondary current is connected via the second diode. According to a second aspect of the present invention, in addition to the configuration of the first aspect, the combustion state detecting device for an internal combustion engine further comprises the step of flowing the ion current detection resistor after a secondary current flows through the secondary winding of the ignition coil. The voltage corresponding to the ion current from the battery power source is directly input to the operational amplifier via the protection resistor.

According to a third aspect of the present invention, in addition to the configuration of the first or second aspect, the combustion state detecting device for an internal combustion engine is arranged such that the battery voltage of the battery power source is lowered before starting the internal combustion engine. A predetermined amount of electricity is stored in a capacitor connected in parallel with the battery power source via a third diode from the battery power source.

According to a fourth aspect of the present invention, in addition to the structure of any one of the first to third aspects, the combustion state detecting device for an internal combustion engine is arranged in parallel with the primary winding of the ignition coil. A fourth diode for rectifying a current generated in a direction opposite to the primary current flowing through the primary winding of the ignition coil and a current flowing through the fourth diode when a switching element connected in series to the ignition coil is turned on. Is connected to a current reducing means for reducing.

A combustion state detecting device for an internal combustion engine according to a fifth aspect of the present invention is, in addition to the configuration according to any one of the first to fourth aspects, further connected in series to the output of the operational amplifier. A mask circuit for directly applying the battery voltage of the battery power source through the second switching element and the fifth diode is provided.

According to a sixth aspect of the present invention, in addition to the structure of the fifth aspect, the combustion state detecting device for an internal combustion engine is provided with a moderating means for moderating the transition state of the ion current after the mask circuit finishes the masking. Is.

[0019]

According to the present invention, the first diode, the ion current detecting resistor and the battery power source are connected to the low voltage side of the secondary winding of the ignition coil, and the ignition coil is connected in parallel with them. A second diode is arranged in the current path for passing the generated secondary current. In this configuration, the first diode and the second diode do not have to have high withstand voltage.

In the combustion state detecting device for the internal combustion engine of claim 2, after the secondary current flows through the secondary winding of the ignition coil,
The voltage corresponding to the ion current from the battery power source that flows through the ion current detection resistor is directly input to the operational amplifier via the protection resistor. That is, since the power supply voltage from the battery power supply is used for the ion current detection and the voltage applied to the ion current detection resistor is low, it can be directly input to the operational amplifier.

In the internal combustion engine combustion state detecting device of the third aspect, the capacitor is connected in parallel to the battery power source, and a predetermined amount of electricity is stored in the capacitor from the battery power source through the third diode. Therefore, even if the battery voltage of the battery power supply drops at the time of starting the internal combustion engine, the capacitor serves as a backup power supply and the power supply voltage is stabilized.

In the combustion state detecting device for the internal combustion engine according to the fourth aspect, the fourth diode and the current reducing means are connected in parallel to the primary winding of the ignition coil. Therefore, the current generated in the opposite direction to the primary current flowing through the primary winding of the ignition coil is rectified by the fourth diode, and when the switching element connected in series to the ignition coil is turned on by the current reducing means, the fourth current is generated. The current flowing through the diode is reduced, and the plurality of residual magnetic noise voltage pulses generated on the secondary side of the ignition coil are consumed as the current on the primary side to be reduced to one shot.

In the combustion state detecting apparatus for an internal combustion engine according to a fifth aspect, the output of the operational amplifier is directly supplied to the battery of the battery power source via the second switching element and the fifth diode connected in series with the mask circuit. A voltage is applied. Therefore, during the operation of the mask circuit, the output of the operational amplifier remains stuck to the battery voltage, and noise during that time is removed.

According to another aspect of the combustion state detecting apparatus for an internal combustion engine of the present invention, the moderating means makes the transition state of the ion current moderate after the masking by the masking circuit. For this reason,
No noise is generated in the ion current after the mask is finished.

[0025]

EXAMPLES The present invention will be described below based on specific examples.

FIG. 1 is a circuit diagram showing an overall configuration of a combustion state detecting device for an internal combustion engine according to an embodiment of the present invention, and FIG. 2 is a time chart showing signal waveforms of terminals and the like in the circuit diagram of FIG. Is. It should be noted that the same reference numerals and symbols are given to those having the same configurations or corresponding portions as those of the above-mentioned conventional example.

In FIG. 1, reference numeral 1 is an ignition coil, and
a is a primary winding and 1b is a secondary winding. Reference numeral 2 is a spark plug arranged in a cylinder of an internal combustion engine (not shown). The primary winding 1a of the ignition coil 1 has a
A diode 11 for rectifying a current generated in a direction opposite to the primary current I1 flowing through the secondary winding 1a and a resistor 12 for reducing the current flowing through the diode 11 when the switching element Tr1 is turned on are connected in parallel.

On the low voltage side of the secondary winding 1b of the ignition coil 1, a Zener diode 31 and a secondary current detecting resistor 3 are provided.
2 are connected in series. These Zener diodes 3
A diode 36 in parallel with the primary and secondary current detection resistor 32,
The ion current detection resistor 35 and the battery power source 34 are connected in series. The diode 3 is provided in the battery power source 34 so that the applied voltage can be kept higher than a certain voltage even when the voltage of the battery power source 34 drops at the time of starting.
A capacitor 38 is connected in parallel via 7. Further, in order to cancel the influence of the secondary inductance of the ignition coil 1 on the frequency of the ion current detecting resistor 35 and keep the gain constant, a capacitor 39 is connected in parallel to the ion current detecting resistor 35.

Since the detection voltage by the ion current detection resistor 35 is in the range of 0V to the battery voltage VB, the voltage follower as an operational amplifier is directly connected through the resistor 41 as the impedance matching protection resistor without converting the reference level. 9 has been entered. The detected current by the secondary current detection resistor 32 is a well-known delay circuit 13 including a switching element, a capacitor and a resistor.
Has been entered in. The output signal from the voltage follower 9 (the output signal of the terminal A) is input to the mask circuit 14 including the switching element Tr2, the capacitor 141, the diode 142 and the resistor 143 via the resistor 42 for impedance matching, and the switching element Tr2. The voltage is directly applied from the battery power source 34 during a period in which is turned on by the output signal from the delay circuit 13 (the output signal from the terminal C).

An output signal from the mask circuit 14 (an output signal from the terminal D) is input to a voltage follower 15 which is an operational amplifier via a resistor 43 as a protection resistor for impedance matching. The output signal from the voltage follower 15 is input to the well-known bandpass filter 10 via the resistor 44 for impedance matching, and the output signal that has passed through the bandpass filter 10 is output from the terminal B.

Here, a basic circuit for ion current detection in the combustion state detecting apparatus for an internal combustion engine according to one embodiment of the present invention will be described with reference to FIG.

FIG. 3 is a circuit diagram showing a basic circuit for ion current detection in a combustion state detecting apparatus for an internal combustion engine according to an embodiment of the present invention, and FIG. 4 is a circuit showing another basic circuit for ion current detection in FIG. It is a figure.

In FIG. 3, the primary winding 1 of the ignition coil 1
In a, an ECU (Electronic Control Unit: not shown) is shown.
An ignition signal IGt from the electronic control unit) energizes the primary current I1 from the battery power source VB. At the same time as the primary current I1 flowing through the primary winding 1a of the ignition coil 1 is cut off, a secondary current I2 flows through the zener diode 31 through the spark plug 2 and the secondary winding 1b of the ignition coil 1. The secondary current I2 causes the spark plug 2 to fly and ignite the fuel. At this time, the ion current detection resistor 35
A diode 36 for rectifying the secondary current I2 so as not to flow is provided on the side.

When the flame grows on both ends of the spark plug 2 after the negative discharge of the spark plug 2 is completed, both ends of the spark plug 2 are in a so-called ionized state and become a resistor of several hundred MΩ. The negative discharge current of the spark plug 2 is in the opposite direction to the Zener diode 31. Then, the ion current IION from the battery power source 34 (+ voltage application) flows through the ignition plug 2 through the ion current detection resistor 35, the diode 36, and the secondary winding 1b of the ignition coil 1.
Then, the ion current I flowing through the ion current detection resistor 35
The voltage corresponding to ION is detected at the terminal Vout.

In this circuit configuration, the secondary current I2 is connected in series with the Zener diode 31 for the purpose of preventing an on-discharge current in the opposite direction to the secondary current I2 when the ignition coil 1 is on.
It goes without saying that the same operation is performed even if a diode for passing a current in the same direction is inserted.

Another embodiment of the basic circuit for ion current detection will be described with reference to FIG.

In FIG. 4, the primary winding 1 of the ignition coil 1
A primary current I1 from the battery power source VB is supplied to a by an ignition signal IGt from an ECU (not shown). Primary current I1 flowing through the primary winding 1a of the ignition coil 1
At the same time, the secondary current I2 flows through the secondary winding 1b of the ignition coil 1 and the ignition plug 2 via the diode 31a. The secondary current I2 causes the spark plug 2 to fly and ignite the fuel. At this time, a diode 36 is provided on the side of the ion current detecting resistor 35 to rectify so that a resonance current or the like generated in a direction opposite to the secondary current I2 does not flow.

After the + discharge of the spark plug 2 is completed, when the flame grows on both ends of the spark plug 2, both ends of the spark plug 2 become ionized and become a resistor of several hundred MΩ. The + discharge current of the spark plug 2 is in the same direction as the diode 31a. Then the spark plug 2
Is the ion current I from the battery power source 34 (+ voltage application)
ION flows through the ion current detection resistor 35, the diode 36, and the secondary winding 1b of the ignition coil 1. Then, the voltage corresponding to the ion current IION flowing through the ion current detection resistor 35 is detected at the terminal Vout.

Next, the circuit operation of FIG. 1 in which the basic circuit of FIG. 3 is adopted will be described with reference to the time chart of FIG. 2 showing the signal waveform of each terminal and the like. Note that FIG.
The ignition signal IGt is shown in (a), the primary current I1 flowing through the primary winding 1a of the ignition coil 1 in FIG. 2 (b), and the secondary winding 1b flowing in the ignition coil 1 in FIG. 2 (c). Secondary current I2,
FIG. 2D shows the waveforms of the output signal of the terminal A of FIG. 1 when the internal combustion engine is at low speed, and FIG. 2E shows the waveforms of the output signal of the terminal A of FIG. 1 when the internal combustion engine is at high speed. . 2 (f), FIG. 2 (g), and FIG. 2 (h), the terminal C of FIG. 1 corresponding to FIG. 2 (e), which is the waveform of the output signal of the terminal A when the internal combustion engine is rotating at high speed. , D and B output signals are shown.

At time t1, when the ignition signal IGt from the ECU becomes H (High) level (see FIG. 2A), the switching element Tr1 is turned on and the ignition coil 1
The primary current I1 begins to flow in the current (see FIG. 2 (b)). At the same time, the ignition on-noise signal SNon is superimposed on the raw ion current output signal (output signal of the terminal A) (FIGS. 2D and 2).
(E)). Then, the noise signal SN1 is generated in the output signal from the terminal B of the bandpass filter 10 (see FIG. 2).
(See (h)).

At time t2, the ignition signal IGt becomes L
At the (Low) level (see FIG. 2A), the switching element Tr1 is turned off and the primary current I1 flowing through the ignition coil 1 is cut off (see FIG. 2B). For this reason,
At the same time as the secondary current I2 begins to flow in the ignition coil 1, 2
The secondary current I2 is detected by the secondary current detection resistor 32 (see FIG. 2C). At this time, the ignition off noise signal SNoff is superposed on the raw ion current output signal (output signal of the terminal A) (see FIGS. 2D and 2E). Further, the delay circuit 13 is operated by the secondary current I2, and the mask signal (output signal of the terminal C) becomes L level (see FIG. 2 (f)). The masking signal turns on the switching element Tr2 of the mask circuit 14, and the masking circuit 14 starts charging the smoothing capacitor 141. Therefore, the ion current masked signal (output signal of the terminal D) remains stuck to the voltage VB of the battery power source 34 until time t4 (see FIG. 2 (g)).

At time t3, when the secondary current I2 of the ignition coil 1 has finished flowing, the residual magnetic noise in the raw ion current output signal (the output signal of the terminal A) is caused by the residual magnetism remaining in the iron core of the ignition coil 1. Signal SNRM is superimposed (Fig. 2
(D), see FIG. 2 (e)). This residual magnetic noise signal S
The NRM has three high-frequency pulses in the figure, but can be reduced to one by inserting the diode 11 and the resistor 12 on the primary side of the ignition coil 1.

In this state, since the residual magnetic noise pulse is consumed by the primary side current of the ignition coil 1, the Zener voltage of the secondary side Zener diode 31 of the ignition coil 1 is increased to some extent to perform ignition. It is essential that the secondary side of the coil 1 be in a state close to open immediately after the end of discharge. The method of reducing the residual magnetism by inserting the diode 11 and the resistor 12 into the primary side of the ignition coil 1 is not limited as long as the secondary side of the ignition coil 1 has a detection resistor for detecting an ion current. It can be easily inferred that it is also effective for

At time t3, the mask signal (the output signal of the terminal C) remains L level due to the delay action of the delay circuit 13 (see FIG. 2 (f)). It should be noted that the ignition-on noise signal SNon and the ignition-off noise signal SNof superposed on the ion current raw output signal (output signal of the terminal A) are superposed.
The ion current IION is obtained by removing f and the residual magnetic noise signal SNRM.
The ION is shown in Fig. 2 (d) and Fig. 2 (e).

At time t4, the mask signal (output signal of terminal C) becomes H level, and the ion current masked signal (output signal of terminal D) becomes the ion current raw output signal (terminal A).
Output signal) (FIG. 2 (f), FIG. 2).
(See (g)). At this time, the ion current masked signal (output signal of the terminal D) gradually falls due to the discharging action of the anneal capacitor 141 (see FIG. 2 (g)).
Therefore, noise does not occur in the output signal from the terminal B of the bandpass filter 10 (see FIG. 2 (h)).

At time t5, if the knock signal SINOCK of the internal combustion engine is superimposed on the ion current signal SIION of the raw ion current output signal (output signal of the terminal A), the output signal from the terminal B of the bandpass filter 10 Knock signal S
NOCK can be detected (see FIG. 2 (h)).

When the internal combustion engine as shown in FIG. 2 (d) is running at low speed, the residual magnetic noise signal SNRM waveform and the ion current signal SIION waveform superimposed on the raw ion current output signal (the output signal of the terminal A) are generated. They do not overlap at time t4. In such a case, the knock signal SINOCK of the internal combustion engine, which is superposed on the raw ion current output signal (output signal of the terminal A), can be detected by the output signal from the output terminal B of the bandpass filter 10 without any problem (illustration). Omitted).

As described above, the combustion state detecting apparatus for the internal combustion engine according to the present embodiment is arranged such that the first coil is connected in series to the low voltage side of the secondary winding 1b of the ignition coil 1 for generating an ignition spark in the ignition plug 2 of the internal combustion engine. While connecting the diode 36 as a diode, the ion current detection resistor 35 and the battery power source 34,
The diode 3 on the low voltage side of the secondary winding 1b of the ignition coil 1
6. A Zener diode 31 as a second diode is provided with a current path for passing the secondary current I2 generated in the ignition coil 1 in parallel with the ion current detection resistor 35 and the battery power source 34.
Connection is made through the above, and this can be the embodiment of claim 1.

Therefore, the diode 36, the ion current detecting resistor 35, and the battery power source 34 are connected to the ignition coil 1 in the two positions.
Secondary current 1b generated in the ignition coil 1 connected to the low voltage side of the secondary winding 1b and connected in parallel with them.
A Zener diode 31 is arranged in the current path for passing the current. In the circuit configuration for detecting the ion current, since the battery power source 34 can be used, it is not necessary to provide a special power source or the like, and the diode 36 and the zener diode 31 do not have to have a high withstand voltage, so that the cost is low.

Further, in the combustion state detecting apparatus for the internal combustion engine of this embodiment, after the secondary current I2 flows through the secondary winding 1b of the ignition coil 1, the battery power source 34 flowing through the ion current detecting resistor 35 supplies the secondary current I2. The voltage corresponding to the ion current IION is directly input to the operational amplifier composed of the voltage follower 9 through the protection resistor 41, which can be the embodiment of claim 2.

Therefore, the secondary winding 1b of the ignition coil 1
After the secondary current I2 flows through the
The voltage corresponding to the ion current IION from the battery power source 34 flowing through the battery 5 is directly input to the voltage follower 9 via the protection resistor 41. That is, since the power supply voltage VB from the battery power supply 34 is used for the ion current detection and the voltage applied to the ion current detection resistor 35 is low, it can be directly input to the voltage follower 9 without level conversion. Therefore, it is possible to detect the ion current itself while preventing a minute decrease in the ion current due to the additional circuit.

The combustion state detecting apparatus for the internal combustion engine according to the present embodiment is arranged so that the battery power source 34 supplies the battery via the third diode 37 before the battery voltage VB of the battery power source 34 drops at the time of starting the internal combustion engine. The capacitor 38 connected in parallel to the power source 34 stores a predetermined amount of electricity, and this can be the embodiment of claim 3.

Therefore, the capacitor 38 is connected in parallel to the battery power source 34, and a predetermined amount of electricity is stored in the capacitor 38 from the battery power source 34 via the third diode 37. Therefore, even when the battery voltage VB of the battery power source 34 drops at the time of starting the internal combustion engine, the capacitor 38 functions as a backup power source and the power source voltage is stabilized.

Further, the combustion state detecting apparatus for the internal combustion engine of this embodiment is arranged in parallel with the primary winding 1a of the ignition coil 1 in the direction opposite to the primary current I1 flowing through the primary winding 1a of the ignition coil 1. The fourth diode 11 for rectifying the generated current and the current reducing means achieved by the resistor 12 for reducing the current flowing through the fourth diode 11 when the switching element Tr1 connected in series to the ignition coil 1 are turned on. They are connected, and this can be the embodiment of claim 4.

Therefore, the current reducing means achieved by the fourth diode 11 and the resistor 12 is 1 of the ignition coil 1.
It is connected in parallel to the next winding 1a. Therefore, the current generated in the opposite direction to the primary current I1 flowing through the primary winding 1a of the ignition coil 1 is rectified by the fourth diode 11, and the resistor 12
Switching element T connected in series with ignition coil 1 at
The current flowing through the fourth diode 11 is reduced when r1 is turned on, and a plurality of residual magnetic noise pulses generated on the secondary side of the ignition coil 1 are consumed as the primary side current of the ignition coil 1. Can be reduced to 1 shot.

In addition, the combustion state detecting apparatus for the internal combustion engine of the present embodiment, via the second switching element Tr2 and the fifth diode 142 connected in series to the output of the operational amplifier composed of the voltage follower 9. Mask circuit 1 for directly applying the battery voltage VB of the battery power source 34
4 is provided, which can be the embodiment of claim 5.

Therefore, in the mask circuit 14, the battery voltage VB of the battery power source 34 is directly applied to the output of the voltage follower 9 through the second switching element Tr2 and the fifth diode 142 which are connected in series. . Therefore, while the mask circuit 14 is in operation, the output of the voltage follower 9 remains stuck to the battery voltage VB, and the residual magnetic noise corresponding to the set Zener voltage is removed by the high frequency superimposed on the ion current during that period.

In addition, the combustion state detecting apparatus for the internal combustion engine of the present embodiment is provided with an annealing means which is achieved by the capacitor 141 which makes the transition state of the ion current IION after masking by the mask circuit 14 gentle. The present invention can be an embodiment of claim 6.

Therefore, the smoothing means achieved by the capacitor 141 moderates the transition state of the ion current IION after the mask circuit 14 finishes masking.
Therefore, it is possible to obtain a stable ion current IION after the mask is finished without noise superposition.

By the way, in the above embodiment, the zener diode 31 is provided in order to make the spark plug 2 negatively discharged in FIG. 1, but the present invention is not limited to this. However, as described in the basic circuit of FIG. 4, if the spark plug 2 is positively discharged, it may be a diode. In addition, the battery power source 34 by + discharge
If the voltage VB is applied to the positive side, the ignition plug 2 is driven by the voltage when the ignition coil 1 is turned on, which is normally generated when the ignition plug 2 is turned off, at the time t1 shown in FIG.
Can be configured so that it does not erroneously ignite.

Further, in the above embodiment, if only the presence or absence of combustion of the internal combustion engine is to be detected, then FIG.
It should be recognized that the ionic current is superposed on the waveform of the output signal of the terminal A shown in (e) or the output signal of the terminal D shown in FIG.

Further, a modification of the combustion state detecting device for the internal combustion engine in the above embodiment will be described with reference to FIG. FIG. 5 is a circuit diagram showing a detection portion of the output signal of the terminal A in the circuit diagram of FIG. 1, that is, the output signal based on the generation of the ion current. It should be noted that the same reference numerals and symbols are given to those having the same configurations or corresponding portions as those of the above-described embodiment, and detailed description thereof will be omitted.

In FIG. 1, the ion current detecting resistor 35 is used.
The voltage detected by is input to the voltage follower 9, which is an operational amplifier, through the resistor 41 as a protection resistor for impedance matching. The voltage follower 9 is replaced by a differential amplifier circuit 9'in the circuit of FIG. 5, and the voltage across the ion current detection resistor 35 is differentially amplified via resistors 41 and 45 as impedance matching protection resistors. The voltage detected by the ionic current detection resistor 35 is amplified based on the differential output that is input to the operational amplifiers OP1 and OP2 that form the circuit 9 '. Here, the differential amplifier circuit 9 '
The resistance values of the resistors 46 and 47 in the inside are respectively set as R1 and R2. Then, the voltage detected at both ends of the ion current detecting resistor 35 becomes (1 + R1 / R2) times and is output from the terminal A. Therefore, by using this circuit, the voltage value corresponding to the ion current output can be amplified to an arbitrary size by using the minimum necessary elements without using a capacitor or the like.

[0064]

As described above, according to the combustion state detecting device for the internal combustion engine of the first aspect, the first diode, the ion current detecting resistor and the battery power source are provided on the low voltage side of the secondary winding of the ignition coil. A second diode is arranged in the current path for passing the secondary current generated in the ignition coils connected to and connected in parallel with them. As a result, the first diode and the second diode do not have to have a high withstand voltage, and since a battery power source can be used and a special power source is not required, an ion current for detecting the combustion state of the internal combustion engine can be obtained. The detection can be achieved with an inexpensive configuration.

According to the combustion state detecting device for an internal combustion engine of claim 2, in addition to the effect of claim 1, the secondary current of the ignition coil flows, and then the ion current detecting resistor flows. The voltage corresponding to the ion current from the battery power source is directly input to the operational amplifier via the protection resistor. That is,
The power supply voltage from the battery power supply is used for ion current detection, and since the voltage applied to the ion current detection resistor is low, it can be directly input to the operational amplifier. As a result, it is possible to prevent a minute decrease in ion current due to the additional circuit.

According to the combustion state detecting device for an internal combustion engine of claim 3, in addition to the effect of claim 1 or claim 2, the capacitor is connected in parallel to the battery power source, and the third diode from the battery power source is connected. A predetermined amount of electricity is stored in the capacitor via the. As a result, when the battery voltage of the battery power supply drops at the time of starting the internal combustion engine, the capacitor serves as a backup power supply and can stabilize the power supply voltage.

According to the combustion state detecting device of the internal combustion engine of claim 4, in addition to the effect of any one of claims 1 to 3, the fourth diode and the current reducing means are the primary of the ignition coil. Connected in parallel to the winding. Therefore, the current generated in the opposite direction to the primary current flowing through the primary winding of the ignition coil is rectified by the fourth diode, and when the switching element connected in series to the ignition coil is turned on by the current reducing means, the fourth current is generated. The current flowing through the diode is reduced. As a result, the period during which the residual magnetic noise generated on the secondary side of the ignition coil resonates can be significantly reduced.

According to the combustion state detecting device for the internal combustion engine of claim 5, in addition to the effect of any one of claims 1 to 4, the mask circuit is connected in series to the output of the operational amplifier. The battery voltage of the battery power source is directly applied via the second switching element and the fifth diode. As a result, the output of the operational amplifier remains stuck to the battery voltage during operation of the mask circuit, and residual magnetic noise superimposed on the ion current during this period can be removed.

According to the combustion state detecting device for an internal combustion engine of claim 6, in addition to the effect of claim 5, the moderation means makes the transition state of the ionic current gentle after the mask circuit finishes the masking. As a result, the ion current waveform after masking can be made stable without noise superposition.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an overall configuration of a combustion state detection device for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a time chart showing signal waveforms of respective terminals and the like in the circuit diagram of FIG.

FIG. 3 is a circuit diagram showing a basic circuit for ion current detection in a combustion state detection device for an internal combustion engine according to an embodiment of the present invention.

FIG. 4 is a circuit diagram showing another basic circuit for detecting the ion current of FIG.

FIG. 5 is a circuit diagram showing a modification of the internal combustion engine combustion state detection apparatus according to one embodiment of the present invention.

FIG. 6 is a circuit diagram showing an ion current detection circuit in a conventional combustion state detection device for an internal combustion engine.

FIG. 7 is a circuit diagram showing another ion current detection circuit in a conventional combustion state detection device for an internal combustion engine.

FIG. 8 is a circuit diagram showing still another ion current detection circuit in a conventional combustion state detection device for an internal combustion engine.

[Explanation of symbols]

 1 Ignition coil 1a Primary winding 1b Secondary winding 2 Spark plug 9,15 Voltage follower 10 Bandpass filter 13 Delay circuit 14 Mask circuit

Claims (6)

[Claims] 1. A first diode, an ion current detection resistor, and a battery power source are connected in series to the low-voltage side of a secondary winding of an ignition coil for generating an ignition spark in an ignition plug of an internal combustion engine, and the ignition coil of the ignition coil is connected. On the low voltage side of the secondary winding, a current path for passing a secondary current generated in the ignition coil in parallel with the diode, the ion current detection resistor, and the battery power source is connected via a second diode. An internal combustion engine combustion state detecting device. 2. An operational amplifier which supplies a voltage corresponding to an ion current from the battery power source, which flows through the ion current detection resistor after a secondary current flows through the secondary winding of the ignition coil, through a protection resistor. The combustion state detecting device for the internal combustion engine according to claim 1, wherein 3. Before the battery voltage of the battery power source at the time of starting the internal combustion engine drops, a predetermined amount of electricity is stored in a capacitor connected in parallel to the battery power source from the battery power source via a third diode. The combustion state detection device for an internal combustion engine according to claim 1 or 2, wherein the combustion state detection device is charged. 4. A fourth diode for rectifying a current generated in a direction opposite to a primary current flowing through the primary winding of the ignition coil in parallel with the primary winding of the ignition coil and the ignition coil. The internal combustion engine according to any one of claims 1 to 3, wherein a switching element connected in series is connected to a current reducing unit that reduces a current flowing through the fourth diode when the switching element is turned on. Combustion state detection device. 5. A mask circuit for applying a battery voltage of the battery power source to the output of the operational amplifier via a second switching element and a fifth diode connected in series to the output of the operational amplifier. The combustion state detection device for an internal combustion engine according to any one of claims 1 to 4. 6. The combustion state detecting device for an internal combustion engine according to claim 5, further comprising an averaging means for grading a transition state of the ion current after the mask circuit finishes masking.