JP2017150455A - Control device for plasma reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for a plasma reactor, the control device being capable of determining the abnormal adherence of PM (Particulate Matter) in the plasm reactor.SOLUTION: A power supply device for a plasma reactor is connected to a discharge electrode of the plasma reactor. The power supply device for the plasma reactor has a constitution of a flyback converter. After a primary voltage is applied to a boosting transformer (flyback type boosting transformer) of the power supply device for the plasma reactor for a certain time (S2), a determination integration current value which is changed according to a current flowing in the discharge electrode of the plasma reactor is acquired, and when the determination integration current value is a PM adhesion determination value or more (S3: YES), it is determined that PM abnormally adheres to the plasma reactor (S4).SELECTED DRAWING: Figure 4

Description

  The present invention relates to a control device used in a plasma reactor.

  Exhaust gas discharged from an engine, particularly a diesel engine, includes CO (carbon monoxide), HC (hydrocarbon), NOx (nitrogen oxide), PM (particulate matter), and the like.

  As a technique for removing PM contained in exhaust gas, a technique for removing PM contained in exhaust gas using a plasma reactor has been proposed. The plasma reactor includes a plurality of electrode panels. The electrode panel has, for example, a configuration in which an electrode is built in a dielectric, and the plurality of electrode panels are arranged to face each other with a gap in a direction orthogonal to the flow direction of the exhaust gas. When a voltage is applied between the electrodes from the power supply device for the plasma reactor, dielectric barrier discharge occurs, low temperature plasma (non-equilibrium plasma) is generated between the electrode panels, and PM in the exhaust gas flowing between the electrode panels is oxidized. Is removed.

  The plasma reactor power supply device includes a flyback step-up transformer. A switching element is connected in series to the primary coil of the flyback type step-up transformer, and a DC power source is connected to a series circuit of the primary coil and the switching element. The secondary coil of the flyback type step-up transformer is connected to the electrode of the plasma reactor.

  When the switching element is turned on, current flows through the primary coil of the step-up transformer, and energy is accumulated in the primary coil. Thereafter, when the switching element is turned off, the energy accumulated in the primary coil is released, an electromotive force is generated in the primary coil, and a secondary voltage corresponding to the turn ratio is generated in the secondary coil of the step-up transformer. By repeatedly turning on / off the switching element, a secondary voltage is generated in a pulsed manner, and a secondary voltage that changes in a pulse waveform is applied between the electrodes of the plasma reactor.

JP 2002-129949 A

  It is difficult to remove 100% of PM from the exhaust gas flowing through the plasma reactor in real time, and PM adheres to the surface of the electrode panel. When the adhesion amount of PM to the electrode panel increases, the discharge between the electrode panels does not uniformly occur, the discharge at a specific location becomes stronger, or the creeping discharge along the surface of the electrode panel occurs, PM removal rate decreases. Further, when the adhesion of PM further progresses, the resistance value between the power supply terminal of the electrode and the casing surrounding the electrode panel is lowered, and there is a risk of causing problems such as electric leakage.

  The objective of this invention is providing the control apparatus for plasma reactors which can determine abnormal adhesion of PM in a plasma reactor.

  In order to achieve the above object, a plasma reactor control device according to the present invention is a control device used in a plasma reactor for removing PM contained in exhaust gas discharged from an engine, and is a flyback type step-up transformer. A primary voltage applying means for applying a primary voltage over a predetermined time, a characteristic value acquiring means for acquiring a characteristic value that changes according to a current applied to an electrode of a plasma reactor from a flyback type step-up transformer, and a characteristic value acquiring means When the characteristic value acquired by the above is greater than or equal to a predetermined adhesion determination value, an abnormal adhesion determination unit that determines that PM is abnormally adhered to the plasma reactor is included.

  According to this configuration, the flyback type step-up transformer is connected to the electrode of the plasma reactor. After the primary voltage is applied to the flyback type step-up transformer, when the application of the primary voltage is stopped, a secondary voltage is generated in a pulsed manner on the secondary side of the flyback type step-up transformer. When this secondary voltage is applied between the electrodes of the plasma reactor, a discharge occurs between the electrodes, and a current flows through the electrodes.

  After the primary voltage is applied to the flyback type step-up transformer for a certain period of time, a characteristic value that changes according to the current flowing through the electrode of the plasma reactor (current applied to the electrode from the flyback type step-up transformer) is acquired. When the characteristic value is equal to or greater than a predetermined adhesion determination value, it is determined that PM is abnormally adhered to the plasma reactor.

  The current flowing through the electrodes of the plasma reactor varies depending on the state of discharge between the electrodes. The state of discharge between the electrodes varies depending on the amount of PM attached to the plasma reactor (the electrode panel having a structure in which an electrode is built in a dielectric). Specifically, when the amount of PM deposition in the plasma reactor increases, the discharge at a specific location becomes stronger or creeping discharge occurs. Therefore, as shown in FIG. 5, when a predetermined amount or more of PM is attached to the plasma reactor (when PM is attached) and when the amount of PM attached to the plasma reactor is less than a predetermined amount (during normal discharge), Comparing the current flowing through the electrode of the plasma reactor after the primary voltage is applied to the flyback step-up transformer for a certain period of time, the current flowing through the electrode during PM deposition is larger than the current flowing through the electrode during normal discharge.

  Therefore, after the primary voltage is applied to the flyback type step-up transformer for a certain period of time, the characteristic value that changes according to the current applied to the electrode from the flyback type step-up transformer is equal to or greater than the adhesion determination value. It can be determined that PM is abnormally attached to the reactor. Since abnormal adhesion of PM in the plasma reactor can be determined, it is possible to take measures to suppress the occurrence of problems such as a decrease in PM removal rate and electric leakage.

  According to the present invention, it can be determined that PM is abnormally attached to the plasma reactor, and measures can be taken to suppress the occurrence of problems such as a decrease in PM removal rate and leakage.

It is sectional drawing which shows the structure of a plasma reactor schematically. It is a circuit diagram which shows the structure of the power supply device for plasma reactors. It is a block diagram which shows the functional structure of the control apparatus for plasma reactors concerning one Embodiment of this invention. It is a flowchart which shows the flow of an abnormal adhesion determination process. It is a graph which shows the waveform of the primary voltage and the electric current applied to a plasma reactor. It is a block diagram which shows the functional structure of the control apparatus for plasma reactors which concern on other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Plasma reactor>
FIG. 1 is a cross-sectional view schematically showing the configuration of the plasma reactor 1.

  The plasma reactor 1 is interposed in the middle of an exhaust pipe 2 such as an exhaust pipe in order to remove PM contained in exhaust gas discharged from a vehicle engine (not shown), for example.

The plasma reactor 1 is provided with discharge electrodes 3 and 4. The discharge electrodes 3 and 4 extend in the direction along the flow of the exhaust gas, and are alternately arranged in parallel with a space therebetween. An example of the material of the discharge electrodes 3 and 4 is tungsten. In addition, the discharge electrodes 3 and 4, for example, are built in a rectangular plate-like dielectric 5, thereby constituting an electrode panel 6 together with the dielectric 5. Between the electrode panels 6, the space | interval which can distribute | circulate waste gas is opened. As a material of the dielectric 5, Al ₂ O ₃ (alumina) can be exemplified.

  The power supply terminals T of the discharge electrodes 3 and 4 are drawn to the outside of the casing C that collectively surrounds the plurality of electrode panels 6, and the plasma reactor is interposed between the discharge electrodes 3 and 4 via the power supply terminals T. A high voltage in the form of a pulse wave output from the power supply device 7 is applied. When the output voltage of the plasma reactor power supply device 7 is applied between the discharge electrodes 3 and 4, a dielectric barrier discharge is generated between the electrode panels 6, and plasma is generated by the dielectric barrier discharge. Due to the generation of plasma, PM contained in the exhaust gas flowing between the electrode panels 6 is oxidized (burned) and removed.

<Power supply for plasma reactor>
FIG. 2 is a circuit diagram showing the configuration of the plasma reactor power supply device 7.

  The plasma reactor power supply device 7 has a flyback converter configuration. That is, the plasma reactor power supply device 7 includes a step-up transformer (flyback type step-up transformer) 11 and an energization control switching element 12. Further, the plasma reactor power supply device 7 includes a gate drive circuit 13.

  The step-up transformer 11 has a primary coil 21 and a secondary coil 22. One end of the primary coil 21 is connected to the wiring 23. A positive terminal of a battery 25 is connected to the wiring 23 via a fuse 24. The battery 25 is an in-vehicle battery that outputs a DC voltage of 12V, for example. The other end of the primary coil 21 is connected (grounded) to the ground via the energization control switching element 12. One end and the other end of the secondary coil 22 are connected to the discharge electrodes 3 and 4 of the plasma reactor 1, respectively.

  The energization control switching element 12 is, for example, an enhancement type nMOSFET, and has a drain connected to the other end of the primary coil 21 of the step-up transformer 11 and a source connected to the ground.

  The gate drive circuit 13 is a circuit that outputs a signal (gate signal) for turning on / off the energization control switching element 12.

<Control device for plasma reactor>
In order to control the power supplied from the plasma reactor power supply device 7 to the plasma reactor 1, a plasma reactor control device 31 is connected to the plasma reactor power supply device 7.

  The plasma reactor control device 31 includes a CPU, a ROM, a RAM, and the like, and may be one of a plurality of ECUs (Electronic Control Units) mounted on the vehicle. It may be incorporated in one of these. A current sensor 32 is connected to the plasma reactor control device 31. The current sensor 32 detects an applied current applied to the discharge electrodes 3 and 4 of the plasma reactor 1, that is, an applied current output from the plasma reactor power supply device 7, and outputs a signal corresponding to the current value.

  The plasma reactor control device 31 controls the gate drive circuit 13 to switch output / stop of the signal from the gate drive circuit 13. That is, when an ON instruction signal is input from the plasma reactor control device 31 to the gate drive circuit 13, a signal is output from the gate drive circuit 13, and the signal is input to the energization control switching element 12. The control switching element 12 is turned on. When the off instruction signal is input from the plasma reactor control device 31 to the gate drive circuit 13, the output of the signal from the gate drive circuit 13 is stopped, and no signal is input to the gate of the energization control switching element 12. As a result, the energization control switching element 12 is turned off.

  When the energization control switching element 12 is turned on, the voltage of the battery 25 is applied as the primary voltage to the primary coil 21 of the step-up transformer 11, and energy is accumulated in the primary coil 21. Thereafter, when the energization control switching element 12 is turned off, the energy accumulated in the primary coil 21 is released, an electromotive force is generated in the primary coil 21, and the secondary coil 22 of the step-up transformer 11 has a 2 in accordance with the turn ratio. Next voltage is generated. By repeatedly turning on / off the energization control switching element 12, a secondary voltage is generated in a pulsed manner, and a secondary voltage that changes in a pulse waveform is applied between the discharge electrodes 3 and 4 of the plasma reactor 1.

  FIG. 3 is a block diagram showing a functional configuration of the plasma reactor control device 31 according to the embodiment of the present invention.

  The plasma reactor control device 31 includes a current integration unit 41, an applied voltage estimation unit 42, a target voltage setting unit 43, a subtraction unit 44, a signal output unit 45, and an abnormal adhesion determination unit 46.

  The current integrating unit 41 includes, for example, an integrating circuit that integrates the current value of the applied current detected by the current sensor 32, an inverting amplifier that amplifies the output of the integrating circuit and inverts its polarity, and an output of the inverting amplifier. And a peak hold / reset circuit that holds and outputs the maximum value. The peak hold / reset circuit is a combination of a general peak hold circuit and a reset circuit. The reset circuit is a circuit for turning on / off a reset switch provided in parallel with the hold capacitor of the peak hold circuit.

  Each time the ON instruction signal is output from the plasma reactor control device 31 to the gate drive circuit 13 (see FIG. 2), the reset circuit has a period from the output of the ON instruction signal to the output of the OFF instruction signal. A reset signal is input. Thereby, the current integration unit 41 outputs an integrated current value during a period in which the applied current value takes a positive value every time one pulse of the pulsed secondary voltage is output from the plasma reactor power supply device 7.

  An integrated current value is input from the current integrating unit 41 to the applied voltage estimating unit 42. The non-volatile memory (ROM, flash memory, EEPROM, etc.) of the plasma reactor control device 31 stores the relationship between the integrated current value and the applied voltage value in the form of a two-dimensional map. Based on the relationship, the applied voltage estimation unit 42 acquires an applied voltage value corresponding to the integrated current value input from the current integrating unit 41, and the applied voltage value is applied between the discharge electrodes 3 and 4. Estimated as an applied voltage value.

  The target voltage setting unit 43 sets a target value (target voltage value) of an applied voltage applied between the discharge electrodes 3 and 4 of the plasma reactor 1. Specifically, the target voltage setting unit 43 acquires the air-fuel ratio of the exhaust gas discharged from the engine (not shown), and obtains the PM amount contained in the unit volume of the exhaust gas from the air-fuel ratio. And the target voltage setting part 43 sets the target voltage value according to the calculated | required PM amount.

  The subtracting unit 44 subtracts the applied voltage value estimated by the applied voltage estimating unit 42 from the target voltage value set by the target voltage setting unit 43.

  The signal output unit 45 controls the input of the on instruction signal and the off instruction signal to the gate drive circuit 13 so that the subtraction value calculated by the subtraction unit 44 approaches 0, and turns on / off the switching element 12 for energization control. Control off.

  The abnormal adhesion determination unit 46 inputs, to the signal output unit 45, a command for applying a primary voltage to the primary coil 21 of the step-up transformer 11 for a certain period of time in order to determine abnormal PM adhesion in the plasma reactor 1. In response to this, the signal output unit 45 inputs an ON instruction signal to the gate drive circuit 13 for a certain time, and turns on the energization control switching element 12 for a certain time. After the OFF instruction signal is input from the signal output unit 45 to the gate drive circuit 13, the integrated current value of the applied current is input from the current integrating unit 41 to the abnormal adhesion determining unit 46 as the determining integrated current value. The abnormal adhesion determination unit 46 determines the abnormal adhesion of PM in the plasma reactor 1 based on the determination integrated current value input from the current integration unit 41. When the abnormal adhesion determination unit 46 determines that PM is abnormally adhered to the plasma reactor 1, for example, the target voltage setting unit 43 increases the target voltage value in order to suppress a decrease in the PM removal rate. Enter the command to be executed.

<Abnormal adhesion determination processing>
FIG. 4 is a flowchart showing the flow of the abnormal adhesion determination process.

  The abnormal adhesion determination unit 46 performs an abnormal adhesion determination process shown in FIG. 4 in order to determine abnormal PM adhesion to the plasma reactor 1 (electrode panel 6).

  In the abnormal adhesion determination process, first, it is determined whether or not the vehicle has traveled more than a certain distance (for example, 50 km) since the integrated current value for determination was previously measured (acquired) (step S1).

  If the vehicle has not traveled a certain distance (NO in step S1), the subsequent processing is not executed.

  If the vehicle has traveled more than a certain distance since the previous determination integrated current value was acquired (YES in step S1), the primary voltage is constant in the primary coil 21 of the step-up transformer 11 when a certain condition is satisfied. Applied over time (step S2). The certain condition may be, for example, a condition that the engine of the vehicle is started, or a condition that the engine is stopped by the idling stop function.

  After the primary voltage is applied to the primary coil 21 of the step-up transformer 11 for a certain period of time, when the application of the primary voltage is stopped, the secondary voltage is generated in the secondary coil 22 of the step-up transformer 11 in a pulsed manner. By applying this secondary voltage between the discharge electrodes 3 and 4 of the plasma reactor 1, a dielectric barrier discharge is generated between the electrode panels 6, and a current flows through the discharge electrodes 3 and 4. At this time, the current integration unit 41 integrates the current value flowing through the discharge electrodes 3, 4, that is, the current value of the applied current detected by the current sensor 32, and the integrated current value obtained thereby is the integrated current value for determination. Is input to the abnormal adhesion determination unit 46.

  Then, the abnormal adhesion determination unit 46 determines whether or not the determination integrated current value input from the current integration unit 41 is greater than or equal to a preset PM adhesion determination value (step S3).

  If the determination integrated current value is not greater than or equal to the PM adhesion determination value, that is, if the determination integrated current value is less than the PM adhesion determination value (NO in step S3), the process returns to step S1, and the previous determination integrated current value is reached. Whether or not the vehicle has traveled more than a certain distance is determined again.

  On the other hand, when the integrated current value for determination is equal to or greater than the PM adhesion determination value (YES in step S3), it is determined that PM is abnormally adhered to the plasma reactor 1 (step S4), and the abnormal adhesion determination process is performed. Is terminated.

<Effect>
As described above, the plasma reactor power supply device 7 is connected to the discharge electrodes 3 and 4 of the plasma reactor 1. After the primary voltage is applied to the step-up transformer 11 of the plasma reactor power supply device 7 for a certain period of time, a determination integrated current value that changes in accordance with the current flowing through the discharge electrodes 3 and 4 of the plasma reactor 1 is acquired. When the integrated current value is equal to or greater than a predetermined PM adhesion determination value, it is determined that PM is abnormally adhered to the plasma reactor 1.

  The current flowing through the discharge electrodes 3 and 4 of the plasma reactor 1 varies depending on the state of discharge between the discharge electrodes 3 and 4. The state of discharge between the discharge electrodes 3 and 4 varies depending on the amount of PM attached to the plasma reactor 1 (electrode panel 6). Specifically, when the PM adhesion amount in the plasma reactor 1 increases, the discharge at a specific location becomes strong or creeping discharge occurs. Therefore, as shown in FIG. 5, when a predetermined amount or more of PM adheres to the plasma reactor 1 (at the time of PM attachment) and when the amount of PM adhesion in the plasma reactor 1 is less than a predetermined amount (at the time of normal discharge). In FIG. 4, when the primary voltage is applied to the step-up transformer 11 of the plasma reactor power supply device 7 and the current flowing through the discharge electrodes 3 and 4 of the plasma reactor 1 is compared, the current flowing through the discharge electrodes 3 and 4 when PM is deposited. Becomes larger than the current flowing through the discharge electrodes 3 and 4 during normal discharge.

  Therefore, after the primary voltage is applied to the step-up transformer 11 of the plasma reactor power supply device 7 for a certain period of time, the integrated current value that changes according to the current applied from the plasma reactor power supply device 7 to the discharge electrodes 3 and 4. Is equal to or greater than the PM adhesion determination value, it can be determined that PM is abnormally adhered to the plasma reactor 1. Since abnormal adhesion of PM in the plasma reactor 1 can be determined, it is possible to take measures to suppress the occurrence of problems such as a decrease in PM removal rate and leakage.

<Modification>
As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form.

  For example, the case where the characteristic value that changes according to the current applied to the discharge electrodes 3 and 4 of the plasma reactor 1 from the plasma reactor power supply device 7 is an integrated current value is taken as an example, but the configuration shown in FIG. Is applied, and the current applied to the discharge electrodes 3 and 4 from the plasma reactor power supply 7 by the peak detector 47 after the primary voltage is applied to the step-up transformer 11 of the plasma reactor power supply 7 for a certain period of time. The peak value may be acquired as the characteristic value. When the peak value acquired by the peak detection unit 47 is equal to or greater than a preset PM adhesion determination value, the abnormal adhesion determination unit 46 determines that PM is abnormally adhered to the plasma reactor 1. Good.

  The peak detection unit 47 is, for example, a high-pass filter circuit that passes a high-frequency component of the current value of the applied current detected by the current sensor 32, an inverting amplifier that amplifies the output of the high-pass filter circuit and inverts its polarity, It can be constituted by an analog circuit including a peak hold / reset circuit that holds and outputs the maximum value of the output of the inverting amplifier. The peak hold / reset circuit is a combination of a general peak hold circuit and a reset circuit. The reset circuit is a circuit for turning on / off a reset switch provided in parallel with the hold capacitor of the peak hold circuit.

  Each time the ON instruction signal is output from the plasma reactor control device 31 to the gate drive circuit 13 (see FIG. 2), the reset circuit has a period from the output of the ON instruction signal to the output of the OFF instruction signal. A reset signal is input. As a result, the peak detector 47 outputs a peak current value during a period in which the applied current value takes a positive value every time one pulse of the pulsed secondary voltage is output from the plasma reactor power supply device 7.

  In addition, various design changes can be made to the above-described configuration within the scope of the matters described in the claims.

1 Plasma reactor 3 Discharge electrode (electrode)
4 Discharge electrode (electrode)
7 Power supply for plasma reactor 11 Step-up transformer (flyback type step-up transformer)
31 Control Device for Plasma Reactor 32 Current Sensor 41 Current Integration Unit (Characteristic Value Acquisition Unit)
46 Abnormal adhesion determination unit (abnormal adhesion determination means)
47 Peak detector (characteristic value acquisition means)

Claims (1)

A control device used in a plasma reactor for removing PM (Particulate Matter) contained in exhaust gas discharged from an engine,
Primary voltage application means for applying a primary voltage over a predetermined time to a flyback type step-up transformer connected to the electrode of the plasma reactor;
Characteristic value acquisition means for acquiring a characteristic value that changes according to the current applied to the electrode;
An apparatus for controlling a plasma reactor, comprising: an abnormal adhesion determination unit that determines that PM is abnormally adhered to the plasma reactor when the characteristic value acquired by the characteristic value acquisition unit is equal to or greater than a predetermined adhesion determination value.

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