JP2013124545A - Ion current detecting device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ion current detecting device for an internal combustion engine that can detect properly an ion current generated at combustion in the internal combustion engine allowing SI combustion and HCCI combustion.SOLUTION: When an electrification signal for a discharge ignition time is supplied to an ignition coil 1 in the SI combustion, a capacitor 2b for an ion current detecting electric power source of an ion current detecting circuit 2 is charged, by discharge ignition of an ignition plug, to a voltage V1 limited by a charge voltage controlling Zener diode 2a, but a capacitor 2e for the ion current detecting electric power source is blocked by a high-pass filter circuit 22 not to be charged, and ion current detection by the power source voltage V1 is carried out therein. When an electrification signal for a dischargeless ignition time is supplied to the ignition coil 1 in the HCCI combustion, a high-voltage high-frequency signal generated in a secondary side is passed through the high-pass filter circuit 22, the capacitor 2e for the ion current detecting electric power source is charged to a voltage V2e, and an ion current is detected by an electric power source voltage (V1+V2e).

Description

  The present invention relates to an ion current detection device for an internal combustion engine mounted on a motor vehicle, particularly an internal combustion engine capable of dealing with two different combustion systems such as combustion by HCCI (premixed compression ignition) and SI combustion by normal spark ignition. The present invention relates to an improvement of an ion current detector for an engine.

  Conventionally, in an internal combustion engine ignition device, the state of combustion is determined by detecting an ionic current generated during combustion, and by detecting the misfire and knocking by grasping the combustion and operating state of the internal combustion engine, various combustions are performed. A technique for appropriately performing control is applied to an internal combustion engine of a motor vehicle. As such an ion current detection device for an internal combustion engine, a spark plug is used as an ion probe, and a capacitor charged by the discharge current of the spark plug is provided without preparing a separate power source for ion current detection. An ion current detection apparatus using a capacitor as a power source for ion current detection has been proposed (see, for example, Patent Document 1).

  A conventional ion current detector is shown in FIG. This is applied to a combustion control mechanism of a gasoline engine, and an ignition coil 1 to which an energization signal (pulse signal) is input from an engine control unit ECU that comprehensively controls a combustion process includes an ignition switching element 1c. By opening and closing by the energization signal, a high voltage is generated in the secondary coil 1b when the primary current of the primary coil 1a to which the ignition power supply VB + is applied is cut off, thereby causing a discharge current via the discharge gap g of the spark plug. Flows. An ion current detection power supply capacitor 2b is provided in the ion current detection device 2 provided in the discharge current flow path, and a charge sufficient for ion current detection is stored by the discharge current.

  The ion current detection device 2 includes a charge voltage control Zener diode 2a for controlling the charge voltage of the ion current detection power supply capacitor 2b, an ion current detection resistor 2c that causes a voltage drop due to the ion current, and an ion current. Since an ion signal amplification circuit 21 that detects and amplifies the voltage drop due to the detection resistor 2c and outputs an ion current detection signal is provided, the fuel in the internal combustion engine is discharged by the discharge of the ignition plug every combustion cycle. Is properly burned, the ion current detection power supply capacitor 2b is properly charged, and the ion generated by the combustion causes an ion current to flow between the discharge gaps g of the spark plug, and the ion signal amplification circuit 21 outputs an ion current detection signal. Will be. Based on this ion current detection signal, appropriate control of the internal combustion engine can be performed.

  In recent years, HCCI (premixed compression ignition) combustion has attracted attention as an internal combustion engine with good combustion efficiency and low emission of nitrogen oxides. In the HCCI combustion, the air-fuel mixture in the combustion chamber of the cylinder is compressed to a high temperature, thereby generating self-ignition of the air-fuel mixture and combusting the air-fuel mixture. Since HCCI combustion is difficult to control combustion such as the timing of ignition, unlike normal SI combustion in which ignition is performed by sparks, it is important to grasp the combustion state by detecting ionic current in the same manner as in normal SI combustion. . In addition, in the case of an HCCI gasoline engine, the sweet spot that can be operated by HCCI combustion is limited, and in order to operate the engine in other regions, it is considered to mix a normal SI combustion region where ignition by discharge is mixed. It has been.

JP-A-4-194367

  However, due to the characteristics of the combustion gas in the combustion chamber, the ionic current value at the time of HCCI combustion is extremely smaller than that at the time of SI combustion, so that it is optimal for measurement during SI combustion as in the invention described in Patent Document 1. When the ion current detection power source generated by the charging voltage control Zener diode and the ion current detection power source capacitor set to the value is used, the ion current can be detected well during SI combustion, but it is detected during HCCI combustion. The value is too small and measurement is impossible or accuracy is low. Therefore, in the conventional ion current detection circuit for SI combustion, it is very difficult to detect the ion current during HCCI combustion, grasp the combustion state, and control HCCI combustion.

  If the circuit constant of the ion current detection circuit is set to an optimum value for measurement during HCCI combustion, the ion current can be detected during HCCI combustion. If this is done, the detected value becomes too large to be measured, and engine control during SI combustion becomes difficult.

  In order to realize a control system that mixes the HCCI combustion region and the SI combustion region, for example, as a power source for ion current detection used during HCCI combustion and a power source for ion current detection used during SI combustion, a Zener diode for charging voltage control and an ion It is conceivable to prepare two combinations of capacitors for current detection power supply and switch the voltage of the power supply for ion current detection suitable for SI combustion and HCCI combustion.

  However, when configuring an ion current detection device in which an ion current detection power source for HCCI combustion and an ion current detection power source for SI combustion are configured in advance, the transition from HCCI combustion to SI combustion and from SI combustion to HCCI When switching to combustion, it is necessary to automatically switch to an ion current detection power source corresponding to each combustion mode, so a circuit for instructing switching to the ion current detection power source according to the determination mode of the combustion mode, etc. Is required. If these functions are provided in the ion current detection device, the cost increases, and the size of the device becomes large, and securing the installation space becomes a problem. When these functions are provided outside the ion current detection device, In addition to the necessity of securing the arrangement space of the control device provided with the mode determination circuit, the switching instruction circuit, etc., wiring and terminals for guiding the instruction signal from the control device to the ion current detection device are also required.

  Therefore, the present invention can appropriately detect ion current generated during combustion of an internal combustion engine capable of SI combustion with discharge ignition and HCCI combustion that does not require discharge ignition, and suppresses increase in size and cost of the device itself. An object of the present invention is to provide an ion current detection device for an internal combustion engine.

  In order to solve the above problems, the invention according to claim 1 is directed to the secondary coil when the switching element cuts off the primary current flowing through the primary coil based on the energization signal for discharge ignition, which is a pulse having a required length. The generated high voltage is supplied to the ignition plug of the combustion chamber and connected to the secondary coil side of the ignition coil that causes a discharge current to flow in the discharge gap of the ignition plug, and is charged by the discharge current at the ignition plug and retains the charge. A discharge ignition ion current detection circuit comprising an ion current detection power supply capacitor and a charging voltage control Zener diode for limiting a voltage applied to the ion current detection power supply capacitor; By applying the charged voltage of the charged ion current detection power supply capacitor to the spark plug after discharge, the ignition plug In an ion current detection device for an internal combustion engine that detects an ion current generated between a pole and a combustion chamber and detects a combustion state of the internal combustion engine, a discharge composed of the charging voltage control zener diode and the ion current detection power supply capacitor A non-discharge ignition additional ion current detection circuit comprising a charge voltage control Zener diode connected in series with an ignition ion current detection circuit and an ion current detection power supply condenser is provided on the ignition coil side, and is used for the discharge ignition. A high-frequency secondary generated on the secondary side of the ignition coil by applying a non-discharge ignition energization signal that repeats an energization signal shorter than the energization signal to the switching element of the ignition coil so that the ignition coil functions as a step-up transformer. Pass the frequency of the voltage, but do not pass the frequency of the ignition cycle based on the energization signal for discharge ignition. A pass filter is provided in a charging path from the charging voltage control Zener diode of the additional ionic current detection circuit for non-discharge ignition to the ionic current detection power supply capacitor, and when ignited by discharge ignition by the ignition plug, the ignition coil The high voltage generated on the secondary side by supplying the discharge ignition energization signal to the secondary ignition cannot pass through the high-pass filter, and the ion current detection power supply capacitor of the additional ion current detection circuit during no discharge ignition is not charged. The ionic current generated between the electrode of the ignition plug and the combustion chamber during combustion of the internal combustion engine by discharge ignition is detected only by the charging voltage of the capacitor for the ionic current detection power source of the ionic current detection circuit for discharge ignition, and the ignition During combustion that does not require discharge ignition by a plug, a non-discharge ignition energization signal is supplied to the ignition coil for ignition. The high-frequency secondary voltage generated on the secondary side of the coil charges the ion current detection power supply capacitor of the additional ion current detection circuit for non-discharge ignition through the high-pass filter. An internal combustion engine that is not accompanied by discharge ignition by the power supply voltage for ion current detection in which the charge voltage for the capacitor for ion current detection power supply of the additional ion current detection circuit for non-discharge ignition is added to the charge voltage of the capacitor for ion current detection power supply An ion current generated between the electrode of the spark plug and the combustion chamber during combustion is detected.

  According to the ionic current detection device for an internal combustion engine according to claim 1, for charge voltage control connected in series with an ion current detection circuit for discharge ignition comprising the Zener diode for charge voltage control and the capacitor for ion current detection power supply. A non-discharge ignition energization signal that repeats an energization signal shorter than the discharge ignition energization signal by providing a non-discharge ignition additional ion current detection circuit comprising a Zener diode and an ion current detection power supply capacitor on the ignition coil side. Is applied to the switching element of the ignition coil to allow the ignition coil to function as a step-up transformer, thereby passing the frequency of the high-frequency secondary voltage generated on the secondary side of the ignition coil. A high-pass filter that does not pass the frequency of the ignition cycle is added to the additional ion current detection circuit for non-discharge ignition. Provided in the charging path from the voltage control Zener diode to the capacitor for the ion current detection power supply, and when the ignition is burned by the spark plug, the discharge ignition energization signal is supplied to the ignition coil and generated on the secondary side The high voltage that has passed is not able to pass through the high-pass filter, and the ion current detection power supply capacitor of the additional ion current detection circuit for non-discharge ignition is not charged, so that the ion current detection power supply capacitor for the discharge ignition ion current detection circuit The ionic current generated between the electrode of the spark plug and the combustion chamber during combustion of the internal combustion engine due to discharge ignition is detected only by the charging voltage of the spark ignition, and when the combustion does not require discharge ignition by the spark plug, An energization signal for discharge ignition is supplied, and the high-frequency secondary voltage generated on the secondary side of the ignition coil is By charging the ion current detection power supply capacitor of the additional ion current detection circuit for non-discharge ignition through the battery, it is added to the charge voltage of the ion current detection power supply capacitor of the ion current detection circuit for discharge ignition during no discharge ignition. Generated between the spark plug electrode and the combustion chamber during combustion of an internal combustion engine without discharge ignition by the ion current detection power supply voltage to which the charge voltage of the ion current detection power supply capacitor of the ion current detection circuit is added Since the current is detected, the ion current detection at the time of discharge ignition and the ion current detection at the time of no discharge ignition can be performed with a power supply voltage of an appropriate value. Moreover, there is no need to provide an ion current detection function at the time of discharge ignition and an ion current detection function at the time of no discharge ignition, and an ion current detection function at the time of discharge ignition and no discharge ignition by an energization signal to the ignition coil. Since the ion current detection function at the time can be automatically switched, an increase in size and cost of the apparatus itself can be suppressed.

It is a schematic block diagram which shows embodiment of the ion current detection apparatus which concerns on this invention. It is a schematic block diagram of the conventional ion current detection apparatus.

  Next, an embodiment of an ion current detection device according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a schematic configuration of an ion current detection device according to an embodiment in which the present invention is applied to a gasoline engine, and is similar to the configuration of the conventional ion current detection device described above (see FIG. 2). The ignition coil 1 to which an ignition signal (discharge ignition energization signal) is input from the engine control unit ECU or the like, and the ignition switching element 1c are opened and closed by the ignition signal, so that the primary power supply VB + for ignition is applied. An ignition plug that applies a high voltage generated in the secondary coil 1b when the primary current of the coil 1a is interrupted, and an ion current detection circuit 2 provided in a discharge current flow path that flows through the discharge gap g of the ignition plug. Is provided.

  Similar to the conventional apparatus, the ion current detection circuit 2 includes an ion current detection power supply capacitor 2b, a charge voltage control Zener diode 2a for controlling the charge voltage, and an ion current that causes a voltage drop due to the ion current. A detection resistor 2c and an ion signal amplifier circuit 21 that detects and amplifies and outputs a voltage drop caused by the ion current detection resistor 2c as an ion signal is provided. If the battery is properly charged, an ion current flows between the discharge gaps g of the spark plug due to the ions generated by the SI combustion, and an ion current detection signal is output from the ion signal amplification circuit 21.

  Further, the ionic current detection circuit 2 includes a non-discharge ignition additional ion current detection circuit connected in series with a discharge ignition ion current detection circuit comprising a charging voltage control zener diode 2a and an ion current detection power supply capacitor 2b. As shown, a zener diode 2d for charging voltage control and a capacitor 2e for ionic current detection power supply are provided on the ignition coil 1 side. In addition, a high-pass filter circuit 22 is provided in the charging path from the charging voltage control Zener diode 2d to the ion current detection power supply capacitor 2e. Note that the threshold value of the high-pass filter circuit 22 is set to be higher than at least the period of the energization signal during SI combustion (a few hundred Hz at the maximum), and may be about several kHz, for example.

  As described above, in the ion current detection circuit 2 in which the discharge ignition ion current detection circuit and the non-discharge ignition addition ion current detection circuit are connected in series, during SI combustion accompanied by discharge by the spark plug, only during discharge Although the voltage of the charging voltage control Zener diode 2a and the voltage of the charging voltage control Zener diode 2d (Vl + V2) are generated but are blocked by the high-pass filter circuit 22, the ionic current in the additional ionic current detection circuit during no-discharge ignition The detection power supply capacitor 2e is not charged, and only the ion detection power supply capacitor 2b is charged through the charging rectifier diode 2i. As a result, the voltage (Vl) controlled by the charging voltage control Zener diode 2a, which is an appropriate voltage for detecting the ionic current during SI combustion after the end of the discharge, becomes the first ionic current detecting resistor 2f, the second ionic current. An ionic current is detected by being applied to the spark plug via the detection resistor 2g and the ionic current detection diode 2h.

  On the other hand, at the time of combustion without discharge ignition such as HCCI, it is not necessary to control the ignition coil 1 to supply a discharge ignition energization signal and generate a discharge spark in the ignition coil. To function as. In order to do so, a short energization signal may be repeatedly applied to the switching element 1c of the ignition coil 1 from the ECU or a dedicated oscillation circuit.

  That is, if a non-discharge ignition energization signal that repeats an energization signal shorter than the discharge ignition energization signal is supplied to the switching element 1c of the ignition coil 1 as a DC-AC drive signal, the ignition coil functions as a step-up transformer. The secondary coil 1b of the ignition coil 1 generates a high frequency secondary voltage.

  The high frequency secondary voltage of several hundred volts generated in the secondary coil 1b as described above has a high frequency of several kHz to several tens kHz and satisfies the passage condition of the high pass filter circuit 22. Passing the circuit 22, the ion detection power supply capacitor 2e is charged through the charging rectifier diode 2k. At the same time, the ion detection power supply capacitor 2b is also charged through the charging rectifier diode 2i. The ion current detection power supply capacitor 2b is charged up to the voltage V1, and the ion detection power supply capacitor 2e is charged up to the voltage V2e (a voltage lower than the voltage V2 by the voltage drop caused by the high-pass filter 22 and the charging rectifier diode 2k). After that, the exciting current from the ignition coil 1 is regenerated to the secondary coil 1b side through the exciting current resetting diode 2j, and the exciting energy is reset.

  Therefore, when the supply of the non-discharge ignition energization signal is stopped and the generation of the secondary voltage of the ignition coil 1 is stopped, the ion detection power supply capacitor 2b that is voltage-limited by the charging voltage control Zener diode 2a has the voltage V1. Since the ion detection power supply capacitor 2e charged by the charging voltage control Zener diode 2d is charged to the voltage V2e, the voltage of the two power supply capacitors is added to the voltage (Vl + V2e). Current detection can be performed.

  As described above, according to the ion current detection device of this embodiment, the discharge ignition ion current detection circuit including the charge voltage control Zener diode 2a and the ion current detection power supply capacitor 2b, and the charge voltage control Zener diode 2d. And the ion current detection circuit for the non-discharge ignition and the ion current for the non-discharge ignition by using the ion current detection circuit 2 in series connected to the non-discharge ignition additional ion current detection circuit consisting of the capacitor for the ion current detection power supply 2e. Detection can be performed with an appropriate power supply voltage.

  In addition, the ion current detection power source capacitor 2e of the additional ion current detection circuit for non-discharge ignition is charged instead of separately providing the ion current detection function for discharge ignition and the ion current detection function for non-discharge ignition. By controlling the conditions by the high-pass filter circuit 22, it is possible to obtain a power supply voltage for ion current detection suitable for SI combustion and HCCI combustion, and contribute to downsizing of the apparatus that can be stored in a narrow space.

  In addition, an ion current detection function at the time of discharge ignition and an ion current detection function at the time of non-discharge ignition are automatically switched by an energization signal to the ignition coil 1 (an energization signal for discharge ignition or an energization signal for no discharge ignition). Therefore, it is not necessary to provide a switch circuit for switching the ion current detection function provided separately in the ion current detection circuit 2, and it is not necessary to control the switch circuit in accordance with the switching timing of the ion current detection function.

  As mentioned above, although embodiment of this invention was described based on the accompanying drawing, this invention is not limited to these embodiment, You may implement by diverting well-known existing equivalent technical means. Absent.

DESCRIPTION OF SYMBOLS 1 Ignition coil 1a Primary coil 1b Secondary coil 1c Switching element 2 Ion current detection circuit 2a Charging voltage control Zener diode 2b Ion detection power supply capacitor 2c Ion current detection resistor 2d Charging voltage control Zener diode (for HCCI)
2e Ion detection power supply capacitor (for HCCI)
2f First ion current detection resistor 2g Second ion current detection resistor 2h Ion current detection diode 2i Charging rectifier diode 2j Excitation current reset diode 2k Charging rectifier diode (for HCCI)
21 Ion signal amplifier circuit 22 High-pass filter circuit g Spark discharge discharge gap

Claims (1)

A high voltage generated in the secondary coil when the switching element cuts off the primary current flowing in the primary coil based on the discharge ignition energization signal, which is a pulse of the required length, is supplied to the ignition plug of the combustion chamber for ignition. Connected to the secondary coil side of the ignition coil that flows the discharge current through the discharge gap of the plug,
An ion current detection power supply capacitor that is charged by a discharge current at the spark plug and retains an electric charge, and a charge voltage control Zener diode that limits the voltage applied to the ion current detection power supply capacitor, for discharge ignition Ion current detection circuit
Ion current generated between the electrode of the spark plug and the combustion chamber during combustion of the internal combustion engine by applying the charging voltage of the capacitor for the ion current detection power source charged by the discharge current of the spark plug to the spark plug after discharge In the internal combustion engine ion current detection device for detecting the combustion state of the internal combustion engine,
A charge voltage control Zener diode connected in series with an ion current detection circuit for discharge ignition consisting of the Zener diode for charge voltage control and the capacitor for ion current detection power supply and a non-discharge ignition added consisting of a capacitor for ion current detection power supply connected in series An ion current detection circuit is provided on the ignition coil side,
By applying a non-discharge ignition energization signal, which repeats an energization signal shorter than the discharge ignition energization signal, to the switching element of the ignition coil, the ignition coil functions as a step-up transformer on the secondary side of the ignition coil. A high-pass filter that passes the frequency of the generated high-frequency secondary voltage but does not pass the frequency of the ignition cycle based on the energization signal for discharge ignition, and a Zener diode for charging voltage control of the additional ion current detection circuit for non-discharge ignition Provided in the charging path from the ion current detection power supply capacitor to
During combustion by discharge ignition by the spark plug, a high voltage generated on the secondary side by supplying a discharge ignition energization signal to the ignition coil cannot pass through the high-pass filter, and additional ion current for non-discharge ignition When the capacitor for the ionic current detection power supply of the detection circuit is not charged, only the charging voltage of the capacitor for the ionic current detection power supply of the ionic current detection circuit for discharge ignition causes only the ignition plug electrode and combustion during combustion of the internal combustion engine due to discharge ignition. Detects the ion current generated between the chambers,
During combustion that does not require discharge ignition by the spark plug, a no-discharge ignition energization signal is supplied to the ignition coil, and the high-frequency secondary voltage generated on the secondary side of the ignition coil passes through the high-pass filter and discharges without discharge. By charging the ion current detection power supply capacitor of the additional ion current detection circuit, the charge current of the ion current detection power supply capacitor of the discharge ignition ion current detection circuit is added to the charge voltage of the non-discharge ignition additional ion current detection circuit. The ion current generated between the spark plug electrode and the combustion chamber during combustion of the internal combustion engine without discharge ignition is detected by the ion current detection power supply voltage to which the charging voltage of the ion current detection power supply capacitor is added. An ionic current detection device for an internal combustion engine, characterized in that

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