JP6008189B2 - Ion current detection device for internal combustion engine - Google Patents

Description

  The present invention relates to a grounding probe and a conductive probe projectingly provided in a combustion chamber of an internal combustion engine in order to determine a combustion state for determining an ignition timing of an internal combustion engine mounted on a motor vehicle and controlling a combustion process thereafter. (In general, it is a device that detects the ionic current that is obtained between the vehicle and the earth). In particular, even in gasoline engines, not only fuel ignition by the usual SI (Spark Ignition) system As with diesel engines, HCCI (Homogeneous-Charge Compression), which causes a chemical reaction to proceed due to a temperature rise due to fuel compression in the cylinder (combustion chamber) and auto-ignites the premixed gas compressed near the compression top dead center Ignition: Pre-mixed compression ignition) Ion for internal combustion engines that can be used in either combustion mode when switching between combustion modes depending on engine operating conditions The present invention relates to an improvement in providing a current detection device.

  Conventionally, an ignition device for an internal combustion engine, particularly the SI system described above, that is, the switching element is turned off at the ignition timing of the fuel in the combustion chamber of the internal combustion engine to cut off the primary current of the ignition coil. In an ignition device that ignites fuel by generating a high voltage on the secondary side and blowing a discharge spark into the discharge gap of a spark plug provided in the combustion chamber by this high voltage, fuel combustion (explosion) in the combustion chamber Accordingly, a technique has been proposed in which the current combustion state is discriminated in real time by detecting the cation generated in the combustion chamber as an ionic current in real time, and measures such as misfire and knocking are taken.

  As a specific ion current detection device for this purpose, various ideas have been repeated. For example, as recognized in Patent Document 1 below, instead of providing a dedicated conductive plug for ion current detection, an ignition plug is used. Is also used as an ion current detection probe, and a capacitor that is charged by the discharge current at the spark plug is not provided separately to provide a power source necessary to detect and detect positive ions as ion current. Some batteries are inserted into a path and charged, and this is used as a power source for ion detection. Incidentally, it has been found that at least a similar temporal detection waveform profile can be obtained for the ion current regardless of the position of the ion current detection probe. Therefore, no problem occurs even if the spark plug is used as an ion current detection probe.

  On the other hand, in recent years, there is a need to provide a gasoline engine that performs fuel ignition by the HCCI method, which is more efficient than the SI method and emits less nitrogen oxides. However, in the HCCI method, since combustion starts by self-ignition of the fuel, the combustion start timing (corresponding to the ignition timing in the SI method) cannot be directly controlled from the outside. For this reason, the HCCI method is a more essential requirement than the fact that it is important to reliably grasp the combustion state by the above-described ion current detection.

  However, in order to satisfy this, two more problems must be taken into consideration. One is that it is difficult to provide a gasoline engine that covers the entire combustion area using only the HCCI system, considering various operating conditions. It is said that it is necessary to use an engine that can be switched according to the vehicle driving situation by mixing SI systems. And if you have to accept this, a second problem arises.

  That is, even when a gasoline engine that selectively uses the HCCI method and the SI method for starting combustion is provided, of course, it is desirable that the ion current detection device can be used for both SI and HCCI combustion methods. In other words, it is almost impossible to assemble one for each system, considering that it will be offered to the market as a product. However, it is known that the ionic current value in the HCCI method is extremely smaller than that in SI combustion due to the characteristics of the combustion gas in the combustion chamber. One of the causes of this current level difference is that the ion current is associated with chemical ionization and thermoelectricity in the SI method, but is only governed by chemical ionization in the HCCI method. For this reason, the ion current cannot be detected with the same detection sensitivity regardless of which of the two combustion systems is used because of the fixed circuit characteristics of the same ion current detection circuit. If it is a high-sensitivity detection circuit, the sensitivity is too high for the SI method, making it impossible to measure, or conversely, if the detection circuit has the optimum sensitivity for the SI method, the sensitivity will be greatly insufficient for the HCCI method, making measurement impossible. Or the accuracy drops significantly. Therefore, a means for switching the circuit characteristics of the ion current detection circuit to the optimum characteristics (substantially the optimum effective detection sensitivity) for the SI method and the HCCI method is required. In fact, an ion current detection circuit itself capable of switching circuit characteristics has already been proposed.

Japanese Unexamined Patent Publication No. 4-194367

  However, the previous proposal was found to be flawed in determining what is the current SI system or the HCCI system and issuing an instruction to switch the circuit characteristics to the ion current detection circuit. For example, in the method that has been proposed previously, for example, an engine control unit (ECU: Engine Control Unit) mounted on a vehicle is used as illustrated in FIG. ) To switch the circuit characteristics with an external signal obtained from), or to feed back the output of the ion current detection circuit, and from the magnitude of the output, determine which system is the combustion method and switch the circuit characteristics. It was. None of this is desirable. In the former case, additional members such as signal lines and terminals for external signal transmission are increased, which is disadvantageous in terms of cost and space. In the latter case, it is actually set at that time. Since it is necessary to make a judgment based on the balance between the detection sensitivity and the output level obtained, an erroneous judgment may be caused depending on which combustion method is used.

  In order to solve this problem, the present invention can reliably determine whether the combustion method in the internal combustion engine is currently the SI method or the HCCI method, and issue an instruction to switch the circuit characteristics accurately to the ion current detection circuit. An ion current detection device for an internal combustion engine that can be used and can also use an existing wiring path is provided.

In order to achieve the above object, the present invention
By turning off the switching element at the timing of ignition of fuel in the combustion chamber of the internal combustion engine, the primary current of the ignition coil is cut off, and a high voltage is generated on the secondary side of the ignition coil. Select both the SI method that ignites the fuel by throwing a discharge spark in the discharge gap of the installed spark plug, and the HCCI method that self-ignites the fuel by the temperature rise due to fuel compression without generating a discharge spark. An ionic current detector that can be assembled into an internal combustion engine ignition device capable of operation;
As an ion current detection power source necessary for flowing positive ions generated in the combustion chamber after fuel combustion as an ion current, it is charged with the discharge current accompanying the generation of discharge sparks when operating with the SI method, while operating with the HCCI method Sometimes the above switching element is turned on and off at a predetermined frequency as a switching element of a DC-DC converter so that an output in a voltage range that does not cause a discharge spark on the secondary side of the ignition coil is generated. A power supply capacitor which is used as a switching transformer of a DC converter and is charged by a DC-DC converter output current obtained by rectifying a pulse voltage output appearing on the secondary side of the ignition coil by a rectifier diode;
When detecting the above ion current, the instruction signal issued by the circuit characteristic switching circuit is received, and the ion current can be switched to the circuit characteristics suitable for ion current detection in each of the SI method and HCCI methods. A detection circuit;
The circuit characteristic switching circuit has a current SI method according to a determination result of a frequency determination circuit that determines a frequency of an on / off signal applied to a switching element that turns on / off the primary current of the ignition coil. To determine whether the operation is in HCCI or HCCI, and issue the above instruction signal;
An ionic current detector for an internal combustion engine is proposed.

  In addition to satisfying the above basic configuration, in the present invention, as a subordinate configuration, the ion current detection circuit includes an ion current detection resistor circuit that converts the ion current into a voltage dimension, and the converted ion current. Switching of the circuit characteristics of the ion current detection circuit upon receiving an instruction signal from the circuit characteristics switching circuit includes (a) a charging voltage of the power supply capacitor, and (b) the ion current detection. An ion current detection device for an internal combustion engine, characterized in that it is made by switching any one, two, or all of the circuit constants of the resistor circuit for use, and (c) the amplification degree of the amplifier circuit. suggest.

  Further, according to the present invention, in the ion current detection device in the above-described subordinate configuration, the charging voltage of the power supply capacitor is controlled by the Zener voltage of the Zener diode circuit in parallel with the power supply capacitor, and the SI of the frequency determination circuit is used. A configuration is proposed in which the circuit characteristic switching circuit generates an instruction signal for switching the zener voltage as one of the circuit characteristics according to the determination result of whether the operation is based on the system or the HCCI system.

  In addition, regarding the switching of the circuit constants of the resistor circuit, the circuit characteristic switching circuit may be configured according to the determination result of whether the operation is performed in the SI method or the HCCI method using the frequency determination circuit. It is also proposed that an instruction signal for switching the resistance value of the path through which the ion current flows as one of the above is generated.

  As for the above-mentioned amplifier, this is constituted by an operational amplifier, and the circuit characteristic switching circuit has a circuit characteristic according to the determination result of whether the operation is the SI method or the HCCI method by the frequency determination circuit. A configuration is proposed in which an instruction signal for switching the amplification degree is generated by switching the feedback resistance value of the operational amplifier as one.

  According to the present invention, there is no risk of misjudgment whether it is the SI method or the HCCI method, and the circuit characteristics relating to the ion current detection of the ion current detection circuit are completely synchronized with the timing of switching the combustion method in the ECU. Can be automatically switched to the appropriate circuit characteristics for each method of SI method and HCCI method, and no external switching signal is required, and no separate wiring or terminals can be required. And cost reduction.

1 is a schematic configuration diagram of a preferred embodiment of an ion current detection device for an internal combustion engine according to the present invention.

  FIG. 1 shows a schematic configuration of an ion current detector for an internal combustion engine according to a preferred embodiment of the present invention.

  The ignition device for an internal combustion engine in which the present ion current detection device is incorporated can be assembled to an ignition device assembled so as to operate as a classic primary current interruption type discharge ignition device during operation in the SI system, The ion current detection circuit 20 can be inserted and used in the path of the discharge current when the discharge spark for fuel ignition flies at the discharge gap g of the spark plug disposed in the combustion chamber. In addition, the ignition mechanism in the SI method, the ignition mechanism in the HCCI method, and the ion current detection mechanism itself in each case may be known in the past, and the present invention does not change this basic mechanism. Absent. In other words, the ion current detection device of the present invention described here has other circuit configurations other than those shown in the figure that perform similar operations with respect to the ignition operation and the operation of the ion current detection circuit 20 that is a main part related to ion current detection. It can also be applied to.

  When the illustrated ignition device first operates in the classic SI system, the primary current flowing by connecting to the vehicle-mounted battery Vb (not shown) in the primary winding 11 of the ignition coil 10 is also illustrated. However, if the switching element 13 is turned off by the ignition signal Si from the ECU that is almost always installed in modern vehicles, a high voltage is generated in the ignition coil secondary winding 12 and combustion occurs. One electrode that forms a discharge gap g provided in the room, in the case shown, from the ground electrode that normally becomes chassis earth, the discharge gap g, ignition coil secondary winding 12, diode 31, ion current detection circuit A discharge current returning to the ground flows through the capacitor 21 (hereinafter simply referred to as a power supply capacitor), which is a power source for detecting the ionic current in 20, and the forward diode 25, and this occurs in the discharge gap g. Ignited fuel (gasoline) in a spark, a combustion of fuel (blast) make. The power supply capacitor 21 is charged by the discharge current at this time. However, at the time of combustion in this SI system, the above-described diode 31 is merely inserted as a diode that enters the forward direction with respect to the discharge current. However, at the time of combustion in the following HCCI system, this diode 31 functions as a rectifier diode 31 provided in the rectifier circuit 30 of the DC-DC converter in order to divert the ignition coil 10 as a switching transformer of the DC-DC converter. The power capacitor 21 is charged. As will be described later, the forward diode 25 relating to the discharge current inserted between the power supply capacitor 21 and the ground becomes a reverse diode when an ionic current flows, and the ionic current detection resistor circuit described later is more reliably connected. The diode 32 that is forward and viewed from the ground side is a diode for resetting the exciting current of the secondary winding of the ignition coil as normally provided in this type of ignition device. .

  Unlike the above-described SI method, when the combustion is performed in the HCCI method, naturally, since the discharge current does not flow, the power supply capacitor 21 cannot be charged. Therefore, as conventionally devised, the switching element 13 for turning on and off the primary current of the ignition coil 10 is turned on and off at a predetermined frequency as a switching element of the DC-DC converter (this drive in the figure). The signal waveform is indicated by a symbol Sd), and the ignition coil 10 is connected to a DC-DC converter while generating a voltage output in a voltage range (generally several hundred volts) that does not cause the discharge spark on the secondary side of the ignition coil. Used as a switching transformer. As a result, a pulse voltage output in an appropriate voltage range appears on the secondary side of the ignition coil, and this is rectified by the rectifier diode 31 to charge the power supply capacitor 21. At this time, the discharge gap g is in an open state, but stray capacitance is also expected in the wiring path between the ignition coil and the secondary winding, so that a sufficient charge charge flow can be secured.

  One of the circuit characteristics related to the ionic current detection of the ionic current detection circuit is how much the charging voltage of the power supply capacitor 21 is set. It may be relatively lower than that required. This is because, as described above, the ion current value is relatively large compared to that obtained in the HCCI method. If the charging voltage is fixed for one of the systems, it will not work well for the other system. Therefore, during combustion in the SI method, a Zener diode circuit is generally connected in parallel as a charging voltage control circuit to the power supply capacitor 21 so that the Zener voltage is relatively low in the SI method and high in the HCCI method. To be.

  Although there are various specific circuit configurations of the Zener diode circuit, for example, in the case shown in the figure, the Zener diode circuit is composed of a pair of Zener diodes z1 and z2, and only one Zener diode z1 is used in the SI system. Is connected in parallel with the power supply capacitor 21 and the charging voltage is kept at a relatively low voltage value, the contact C1 is closed by the instruction signal S1 from the circuit characteristic switching circuit 40, so that the other zener diode z2 is short-circuited. It has come to be. Conversely, in the HCCI system, the contact C1 is opened, and the charging voltage of the power supply capacitor 21 is controlled to be increased by a relatively high zener voltage in which both zener diodes z1 and z2 are in series. The contact C1 can be said to be the same for the other contacts C2 and C3 described later, but may be an electromechanical contact such as a relay or a solid-state contact using a semiconductor switching element. There may be.

  From another viewpoint, switching the charging voltage of the power supply capacitor 21 as one of the circuit characteristics means that the “effective detection sensitivity” of the ion current detection circuit 20 is substantially different between the SI method and the HCCI method. It will also be switching. That is, it can be said that one specific example of the circuit characteristic switching means which is the effective sensitivity switching means is the charging voltage switching means of the power supply capacitor 21 constituted by Zener diodes z1 and z2. Even when the charging voltage control circuit is assembled using the zener diodes z1 and z2 in this way, instead of connecting them in series, the zener voltages that are different from each other are provided in parallel to switch the contacts. Therefore, the lower zener voltage may be selected for the SI method, and the higher zener voltage for the HCCI method, and each zener diode z1 and z2 may actually be composed of a plurality of zener diodes. It may be configured.

  As described above, if the power supply capacitor 21 is charged to a sufficient power supply voltage in both the SI method and the HCCI method, as described above, if positive ions are generated in the combustion chamber during combustion, the power supply capacitor The ionic current flows in the direction opposite to the discharge current due to the power supply voltage 21. This ionic current then flows through a resistor circuit consisting of a pair of series resistors R1, R2 through a diode 22 and one of which is also selectively short-circuited by a contact C2, and through a bypass resistor 33. Since it flows to the ignition coil secondary winding 12 side, in the case of the illustrated configuration, the ionic current according to the circuit constant of the voltage dividing circuit with the input impedance of the amplifier circuit 23 configured by an operational amplifier Is converted and detected in the voltage dimension.

  Here, the ionic current is considerably larger when burning in the SI method than that required when burning in the HCCI method, so the resistance value of the resistance circuit in series in this ionic current path may be relatively small, At the time of combustion in the SI system, the circuit constant of the resistance circuit as one of the circuit characteristics related to the ion current detection of the ion current detection circuit 20, in this case, the resistance value is switched to be relatively small.

  Various configurations of this resistance circuit are also conceivable, but as shown in the figure, when configured from a pair of resistors R1 and R2, only one of the resistors R1 enters the ion current path in series during the SI system, and the resistance value The other resistor R2 is short-circuited by closing the contact C2 by the instruction signal S2 from the circuit characteristic switching circuit 40 so as to be relatively small. On the contrary, in the HCCI method, the contact C2 is opened, the added resistance value of the pair of resistors R1 and R2 is selected, and the value of the ion current detection signal converted into the voltage dimension is kept at a sufficient value. As before, when a resistor circuit is assembled with a pair of resistors R1 and R2, those with different resistance values are provided in parallel, and by switching the contact point, the lower resistance value during SI method is In the HCCI method, a higher resistance value may be selected, and each of the resistors R1 and R2 may actually be composed of a plurality of resistors.

  In any case, switching the circuit constants of the ion current detection resistor circuit (R1, R2) also means that the “effective detection sensitivity” of the ion current detection circuit 20 is substantially different between the SI method and the HCCI method. It will also be switching. That is, another specific example of the circuit characteristic switching means that is also an effective sensitivity switching means is a resistance value switching means of a resistance circuit.

  The ion current detection voltage converted into the voltage dimension by the resistor circuit is amplified and output by the amplifier circuit 23, and is given to an ECU (not shown) to be used for grasping the combustion state. However, as in the SI method, the HCCI method is used. In order to obtain a sufficient output even in times, it is preferable to switch the amplification degree between large and small. Of course, a large amplification is required for the HCCI method. In the illustrated case, the amplifier circuit 23 is configured by an operational amplifier, and is configured such that a feedback resistance value that determines the amplification degree is switched by an instruction signal S3 from the circuit characteristic switching circuit 40.

  In the case of the figure, the feedback resistor circuit is composed of a pair of resistors R3 and R4 in parallel with each other, and in order to lower the amplification relatively so as not to produce an excessive output voltage in the SI system, a circuit characteristic switching circuit The contact C3 is closed by the instruction signal S3 from 40, the feedback resistance value is relatively reduced by the combined parallel resistance value of the resistors R3 and R4, the amplification degree is relatively lowered, and conversely, the contact C3 is used in the HCCI method. Is opened, and a feedback resistor circuit is configured only by the resistor R4 to increase the amplification degree. Here, as before, when a resistor circuit is assembled with a pair of resistors R3 and R4, those with different resistance values are provided in parallel, and the lower resistance value is used during SI mode by switching contacts. In the HCCI method, a higher resistance value may be selected, or each of the resistors R1 and R2 may actually be composed of a plurality of resistors.

  Here again, switching the amplification degree of the amplification circuit as one of the circuit characteristics related to the ion current detection in the ion current detection circuit 20 is also substantially different between the SI method and the HCCI method. This also means that the “effective detection sensitivity” of the detection circuit 20 is switched.

  For these reasons, in the above-described place, three circuit characteristic switching means for effectively switching the ion current detection sensitivity have been shown. There are three types: (a) switching the charging voltage of the power supply capacitor 21, (b) switching the circuit constant of the ion current detection resistor circuit, and (c) switching the amplification degree of the amplifier circuit. However, in practice, there is no restriction that all of these means (a), (b), and (c) must be used. There may be cases where any one or only two may be present. The present invention includes such a case. Further, if other circuit characteristic switching means can be configured, the configuration of the present invention can be applied to such a case. In short, when detecting an ion current, an ion that can be switched to an appropriate circuit characteristic in the SI method and the HCCI method in response to an instruction signal (S1, S2, S3) issued by the circuit characteristic switching circuit 40. If there is a current detection circuit, the configuration of the present invention for determining the switching of the circuit characteristics, in particular, the configuration for determining the combustion method at that time described below is equally applicable to such an ion current detection circuit. is there.

  The particular focus of the present invention is on what information the circuit characteristic switching circuit 40 issues an instruction signal (S1, S2, S3) for switching based on what information. Although the method considered before reaching the present invention was mentioned a little earlier, as shown by the phantom line in FIG. 1, first, from the engine control unit (ECU: Engine Control Unit) mounted on the vehicle. In this method, an external signal St is given to the circuit characteristic switching circuit 40, thereby issuing a circuit characteristic switching instruction (switching signals S1 to S3). However, this increases the number of additional members such as signal lines and terminals for transmitting the external signal St, which is disadvantageous in terms of cost and space.

  In addition, the output of the ion current detection circuit 20, in this case, a part of the output of the operational amplifier 23 is fed back, and the level determination circuit 70 determines the combustion method from the current output level. A method for determining whether or not to issue a switching signal transmission command to the circuit characteristic switching circuit 40 has also been proposed. This configuration eliminates the need for separate wiring and terminals for signals from the outside, and can be modularized around the igniter and the ion current detection circuit, making it possible to reduce the cost and size. Since the determination is based on the current detection output itself, there is a high possibility that accurate combustion control cannot be performed due to a difference between the actual combustion method and circuit setting depending on the combustion state.

  Therefore, the present invention focuses on the frequency of the drive signal applied to the switching element 13 that selectively cuts off the primary current of the ignition coil 10. In other words, in the SI system that should function as a current interrupting ignition device, the ON / OFF signal as the ignition signal Si applied to the switching element 13 is at most several hundred Hz, whereas the ignition is performed in the HCCI system. When the coil 10 is used as a switching transformer of a DC-DC converter, the frequency of the drive signal Sd applied to the switching element 13 to interrupt the primary current is usually from several KHz to several tens KHz, SI system The frequency is very different from the time.

  Based on this knowledge, the present invention provides a frequency determination circuit 50 for determining the frequency of the on / off signal applied to the switching element 13, and the determination result indicates that if the circuit characteristic switching circuit 40 is the SI system, The instruction signals (S1, S2, S3) for switching are issued so that the circuit characteristics are suitable for the HCCI system. If the frequency is so different between the SI method and the HCCI method, there is no risk of misjudgment as to which combustion method is used at that time.

  In addition, the frequency determination circuit 50 can be integrated with the peripheral module in the actual device configuration, and there is no need for separate wiring and terminals, thereby reducing the size and cost, and the timing of combustion switching in the ECU. The characteristics of the ion current detection circuit can be automatically switched to desired characteristics from time to time in complete synchronization.

  The preferred embodiment of the apparatus of the present invention has been described above. However, any modification is free as long as it conforms to the gist of the present invention.

10 Ignition coil
11 Ignition coil primary winding
12 Ignition coil secondary winding source
13 Switching element
20 Ion current detection circuit
21 Power supply capacitor
23 Amplifier circuit (operational amplifier)
30 Rectifier circuit
31 Rectifier diode
40 Circuit characteristics switching circuit
50 Frequency judgment circuit g Discharge gap
z1, z2 Zener diode
R1, R2, R3, R4 resistors
S1, S2, S3 Instruction signal for switching circuit characteristics
C1, C2, C3 contact
Si ignition signal
Sd DC-DC converter drive signal

Claims (5)

By turning off the switching element at the timing of ignition of the fuel in the combustion chamber of the internal combustion engine, the primary current of the ignition coil is cut off, a high voltage is generated on the secondary side of the ignition coil, and the high voltage causes the combustion chamber to Select both the SI method that ignites the fuel by blowing a discharge spark in the discharge gap of the spark plug provided in the HCCI method that self-ignites the fuel by the temperature rise due to fuel compression without generating the discharge spark An ionic current detection device that can be assembled to an internal combustion engine ignition device that can be operated as
As an ion current detection power source necessary for flowing positive ions generated in the combustion chamber after fuel combustion as an ion current, the HCCI is charged with the discharge current accompanying the generation of the discharge spark when operating in the SI system. During operation in the system, the switching element is turned on / off at a predetermined frequency as a switching element of a DC-DC converter, and an output in a voltage range that does not cause the discharge spark is generated on the secondary side of the ignition coil. A power supply capacitor charged by a DC-DC converter output current obtained by using the ignition coil as a switching transformer of a DC-DC converter, thereby rectifying a pulse voltage output appearing on the secondary side of the ignition coil by a rectifier diode;
When detecting the ion current, the instruction signal generated by the circuit characteristic switching circuit is received, and the ion can be switched to a circuit characteristic suitable for ion current detection in each of the SI method and the HCCI method. A current detection circuit;
The circuit characteristic switching circuit is currently based on a determination result of a frequency determination circuit that determines a frequency of an on / off signal applied to the switching element that turns on and off a primary current of the ignition coil. Determine whether the operation is in SI mode or the HCCI mode and issue the instruction signal;
An ionic current detection device for an internal combustion engine. An ion current detection device for an internal combustion engine according to claim 1,
The ion current detection circuit includes an ion current detection resistor circuit that converts the ion current into a voltage dimension and an amplification circuit that amplifies the converted ion current detection voltage, and the instruction signal of the circuit characteristic switching circuit The switching of the circuit characteristics of the ion current detection circuit in response to (a) the charging voltage of the power supply capacitor, (b) the circuit constant of the resistance circuit for ion current detection, and (c) the amplification degree of the amplification circuit , Any one, two, or all by switching between them;
An ionic current detection device for an internal combustion engine. An ion current detection device for an internal combustion engine according to claim 2;
The charging voltage of the power supply capacitor is controlled by a Zener voltage of a Zener diode circuit in parallel with the power supply capacitor, and the operation of the SI method or the operation of the HCCI method is performed by the frequency determination circuit. The circuit characteristic switching circuit issues the instruction signal for switching the zener voltage as one of the circuit characteristics in accordance with a determination result;
An ionic current detection device for an internal combustion engine. An ion current detection device for an internal combustion engine according to claim 2;
The circuit characteristic switching circuit causes the ion current to flow as one of the circuit characteristics according to the determination result of whether the operation is performed in the SI method or the operation in the HCCI method by the frequency determination circuit. Issuing an instruction signal for switching the resistance value of the path;
An ionic current detection device for an internal combustion engine. An ion current detection device for an internal combustion engine according to claim 2;
The amplifier is configured by an operational amplifier, and the circuit characteristic switching circuit has one of the circuit characteristics according to the determination result of whether the operation is the SI method or the HCCI method by the frequency determination circuit. Generating an instruction signal for switching the amplification degree by switching the feedback resistance value of the operational amplifier as one;
An ionic current detection device for an internal combustion engine.

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